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The doVersion Number: 7.0
Copyright (c) 1981-2008 by Aspen Technology, Inc. All rights reserved. 
Aspen HYSYS, Aspen HYSYS Petroleum Refining, Aspen Flare System Analyzer, Aspen Energy Analyzer, 
Aspen HYSYS Refining CatCracker, Aspen HYSYS Pipeline Hydraulics, Plantelligence and Enterprise 
Optimization and the aspen leaf logo are trademarks or registered trademarks of Aspen Technology, 
Inc., Burlington, MA.
All other brand and product names are trademarks or registered trademarks of their respective 
companies.
This manual is intended as a guide to using AspenTech’s software. This documentation contains 
AspenTech proprietary and confidential information and may not be disclosed, used, or copied without 
the prior consent of AspenTech or as set forth in the applicable license agreement. Users are solely 
responsible for the proper use of the software and the application of the results obtained.
Although AspenTech has tested the software and reviewed the documentation, the sole warranty for the 
software may be found in the applicable license agreement between AspenTech and the user. 
ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, 
WITH RESPECT TO THIS DOCUMENTATION, ITS QUALITY, PERFORMANCE, 
MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE.
Aspen Technology, Inc.
200 Wheeler Road
Burlington, MA 01803-5501
USA
Phone:  (781) 221-6400
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ThTechnical Supportv
  Online Technical Support Center ........................................................ vi
  Phone and E-mail .............................................................................. vii
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ThOnline Technical Support 
Center
AspenTech customers with a valid license and software 
maintenance agreement can register to access the Online 
Technical Support Center at:
http://support.aspentech.com
You use the Online Technical Support Center to: 
• Access current product documentation
• Search for technical tips, solutions, and frequently asked 
questions (FAQs)
• Search for and download application examples
• Search for and download service packs and product 
updates
• Submit and track technical issues
• Send suggestions
• Report product defects
• Review known deficiencies and defects 
Registered users can also subscribe to our Technical Support e-
Bulletins. These e-Bulletins proactively alert you to important 
technical support information such as:
• Technical advisories
• Product updates and releasesvi
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ThPhone and E-mail
Customer support is also available by phone, fax, and e-mail for 
customers who have a current support contract for their 
product(s). Toll-free charges are listed where available; 
otherwise local and international rates apply. 
For the most up-to-date phone listings, please see the Online 
Technical Support Center at: 
http://support.aspentech.comvii
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Thviii
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The doTable of Contents
Technical Support..................................................... v
Online Technical Support Center ............................vi
Phone and E-mail................................................ vii
Aspen HYSYS Thermodynamics .............................. vii
1  Components .........................................................1-1
1.1 Introduction .................................................... 1-2
1.2 Component List Property View ........................... 1-4
2  Fluid Package .......................................................2-1
2.1 Introduction .................................................... 2-2
2.2 Fluid Packages Tab........................................... 2-3
2.3 Adding a Fluid Package - Example ...................... 2-5
2.4 Aspen HYSYS Fluid Package Property View........... 2-7
2.5 COMThermo Property View ...............................2-95
2.6 References ...................................................2-121
3  Hypotheticals .......................................................3-1
3.1 Introduction .................................................... 3-3
3.2 Hypo Manager ................................................. 3-4
3.3 Adding a Hypothetical - Example ........................ 3-5
3.4 Creating a Hypo Group ....................................3-13
3.5 Hypothetical Component Property View ..............3-26
3.6 Solid Hypotheticals..........................................3-36
3.7 Cloning Library Components .............................3-42
3.8 Hypo Controls.................................................3-44
3.9 References .....................................................3-45
4  Aspen HYSYS Oil Manager ....................................4-1
4.1 Introduction .................................................... 4-3
4.2 Oil Characterization .......................................... 4-4ix
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The do4.3 Petroleum Fluids Characterization Procedure ........ 4-9
4.4 Oil Characterization Property View.....................4-14
4.5 Characterizing Assays ......................................4-17
4.6 Hypocomponent Generation..............................4-59
4.7 User Property .................................................4-76
4.8 Correlations & Installation ................................4-81
4.9 TBP Assay - Example .......................................4-88
4.10 Sulfur Curve - Example ..................................4-107
4.11 References ...................................................4-115
5  Reactions .............................................................5-1
5.1 Introduction .................................................... 5-2
5.2 Reaction Component Selection ........................... 5-3
5.3 Reactions........................................................ 5-6
5.4 Reaction Sets .................................................5-36
5.5 Generalized Procedure .....................................5-46
5.6 Reactions - Example ........................................5-48
6  Component Maps ..................................................6-1
6.1 Introduction .................................................... 6-2
6.2 Component Maps Tab ....................................... 6-2
6.3 Component Map Property View........................... 6-4
7  User Properties ....................................................7-1
7.1 Introduction .................................................... 7-2
7.2 User Properties Tab .......................................... 7-3
7.3 User Property Property View .............................. 7-5
A  Property Methods & Calculations..........................A-1
A.1 Introduction .................................................... A-3
A.2 Selecting Property Methods ............................... A-4
A.3 Property Methods ........................................... A-10
A.4 Enthalpy & Entropy Departure Calculations ........ A-56
A.5 Physical & Transport Properties ........................ A-64
A.6 Volumetric Flow Rate Calculations .................... A-74
A.7 Flash Calculations .......................................... A-81
A.8 References .................................................... A-91x
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The doB  Oil Methods & Correlations ...................................B-1
B.1 Introduction .................................................... B-2
B.2 Characterization Method.................................... B-2
B.3 References .................................................... B-11
C  Amines Property Package.....................................C-1
C.1 Amines Property Package .................................. C-2
C.2 Non-Equilibrium Stage Model ............................. C-5
C.3 Stage Efficiency ............................................... C-7
C.4 Equilibrium Solubility ........................................ C-9
C.5 Phase Enthalpy .............................................. C-19
C.6 Simulation of Amine Plant Flowsheets ............... C-20
C.7 Program Limitations ....................................... C-24
C.8 References .................................................... C-25
D  Glycol Property Package.......................................D-1
D.1 Introduction ....................................................D-2
D.2 Pure Component Vapor Pressure ........................D-4
D.3 Mixing Rules....................................................D-4
D.4 Phase Equilibrium Prediction ............................ D-12
D.5 Enthalpy/Entropy Calculations.......................... D-13
D.6 References .................................................... D-13
 Index.................................................................... I-1xi
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xii
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ThAspen HYSYS 
Thermodynamics
To comprehend why Aspen HYSYS is such a powerful 
engineering simulation tool, you need look no further than its 
strong thermodynamic foundation. The inherent flexibility 
contributed through its design, combined with the unparalleled 
accuracy and robustness provided by its property package 
calculations leads to the representation of a more realistic 
model. 
Not only can you use a wide variety of internal property 
packages, you can use tabular capabilities to override specific 
property calculations for more accuracy over a narrow range or 
use the functionality provided through ActiveX to interact with 
externally constructed property packages. Through the use of 
Extensibility, you can extend Aspen HYSYS so that it uses 
property packages that you created within the Aspen HYSYS 
environment.
The built-in property packages provide accurate 
thermodynamic, physical, and transport property predictions for 
hydrocarbon, non-hydrocarbon, petrochemical, and chemical 
fluids. 
The Thermodynamics development group at AspenTech has 
evaluated experimental data from the world’s most respected 
sources. Using this experimental data, a database containing in 
excess of 1500 components and over 16,000 fitted binaries has 
been created. If a library component cannot be found within the 
database, a comprehensive selection of estimation methods is 
available for creating fully defined hypothetical components.
Aspen HYSYS also contains a powerful regression package that 
may be used in conjunction with its tabular capabilities. 
Experimental pure component data, which Aspen HYSYS 
provides for over 1,000 components, can be used as input to the 
regression package. Alternatively, you can supplement the vii
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Thexisting data or supply a complete set of your own data. 
The regression package fits the input data to one of the 
numerous mathematical expressions available in Aspen HYSYS. 
This allows you to obtain simulation results for specific 
thermophysical properties that closely match your experimental 
data.
As new technology becomes available to the market place, 
AspenTech welcomes the changes. Aspen HYSYS was designed 
with the foresight that software technology is ever-changing and 
that a software product must reflect these changes. Aspen 
HYSYS has incorporated COMThermo which is an advanced 
thermodynamic calculation framework based on Microsofts COM 
(Component Object Model) technology. The COMThermo 
framework is fully componentized which makes it possible to 
develop independent, extensible, customizable, and 
encapsulated thermodynamic calculation modules. It acts like a 
thermodynamic calculation server which allows users to utilize, 
supplement, or replace any of its components. 
The framework also encompasses a wide variety of property 
calculations, flash methods, databases, etc. The calculation 
methods cover all of the thermodynamic calculation packages in 
Aspen HYSYS. In future releases of Aspen HYSYS, the old Aspen 
HYSYS thermodynamic engine will gradually be replaced by 
COMThermo.
Simulation Basis Manager
One of the important concepts upon which Aspen HYSYS is 
based is that of environments. The Basis Environment allows 
you to input or access information within the Simulation Basis 
Manager while the other areas of Aspen HYSYS are put on hold. 
This helps to maintain peak efficiency by avoiding unnecessary 
flowsheet calculations. Once you return to the Build 
Environment, all changes that were made in the Basis 
Environment take effect at the same time. Conversely, all 
thermodynamic data is fixed and is not changed as 
manipulations to the flowsheet take place in the Build viii
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ThEnvironment.
Use the Hot Key CTRL B to re-enter the Basis Environment 
from any Environment.ix
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ThAnother advantage of the Simulation Basis Environment is the 
assurance that all the basic thermodynamic requirements are 
provided before a simulation case is built. The minimum 
information required before leaving the Simulation Basis 
Manager is as follows:
• At least one installed fluid package with an attached 
Property Package.
• At least one component in the fluid package.
• A fluid package specified as the Default fluid package. 
This is automatically done by Aspen HYSYS after the first 
fluid package is installed.
The Simulation Basis Manager can be accessed at any stage 
during the development of a simulation case. When a New Case 
is created, the first property view that appears is the Simulation 
Basis Manager. You can also return to the Basis Environment 
from the Main or Sub-Flowsheet Environment at any time to 
make changes to the thermodynamic information.
You can create as many fluid packages as you like in the 
Simulation Basis Manager. This functionality makes it possible 
for each flowsheet in the case to be associated with an individual 
fluid package, thus allowing it to have its own particular 
property package and set of components. The Default fluid 
package is assigned to each new Sub-Flowsheet that is created 
while in the Build Environment. If a different fluid package is 
desired, you can re-enter the Basis Environment to perform the 
required change.
Provided that changes are made in the Basis Environment, 
Aspen HYSYS displays a message box each time you re-enter 
the Main Build Environment. 
 Figure 1.1x
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ThThis provides a means of leaving Aspen HYSYS in HOLDING 
mode so that you can perform complimentary changes (for 
example, new stream compositions or column specifications) to 
the flowsheet prior to the Basis modifications taking effect.
The Simulation Basis Manager property view allows you to 
create and manipulate fluid packages in the simulation. 
Whenever you create a New Case, Aspen HYSYS opens to the 
Components tab of the Simulation Basis Manager.  
The tabs available on the Simulation Basis Manager property 
view are described in the table below: 
If Aspen HYSYS is left in HOLDING mode, calculations can be 
activated by clicking the Solver Active icon in the Toolbar.
 Figure 1.2
Tab Description
Components Allows access to a component list which is associated 
with a fluid package. When adding a new component 
list or editing a current list, the Component List 
property view opens. This property view is designed to 
simplify adding components to the case.
Fluid Pkgs Allows you to create and manipulate all fluid packages 
for the simulation case. Also, you can assign a fluid 
package to each flowsheet that exists within the case 
and select a Default fluid package, which is 
automatically used for all new flowsheets.
Solver Active icon
For more information, 
refer to the section on 
the Simulation Basis 
Manager in the Aspen 
HYSYS User Guide.xi
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ThHypotheticals Allows individual Hypotheticals and Hypothetical 
Groups to be defined for installation into any fluid 
package.
Oil Manager Allows access to the Oil Environment where you can 
input assay data, cut/blend an oil and define pseudo 
components for installation in any existing fluid 
package.
Reactions Allows you to install reaction components, create 
reactions, create reaction sets, attach reactions to 
reaction sets and attach reaction sets to any existing 
fluid package.
Component Maps Allows you to specify composition across fluid package 
(sub-flowsheet) boundaries.
User Properties Create and make user properties available to any fluid 
package.
The Enter Simulation Environment button can be accessed 
from any of the tabs on the Simulation Basis Manager 
property view.
Tab Descriptionxii
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Components 1-1
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Th1  Components1-1
1.1  Introduction................................................................................... 2
1.2  Component List Property View....................................................... 4
1.2.1  Adding Library Components ....................................................... 5
1.2.2  Selecting Library Components.................................................... 8
1.2.3  Manipulating the Selected Components List................................ 14
1.2.4  Adding Electrolyte Components ................................................ 26
1.2.5  Adding Hypothetical Components ............................................. 28
1.2.6  Adding Components from Existing Component Lists .................... 30
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1-2 Introduction
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Th1.1 Introduction
The Components Manager provides a location where sets of 
chemical components being modeled may be created, retrieved 
and manipulated. These component sets are stored in the form 
of Component Lists which may be a collection of library pure 
components or Hypothetical components. The Components 
Manager is accessed by selecting the Components tab from the 
Simulation Basis Manager. 
The Components Manager always contains a Master Component 
List that cannot be deleted. The Master Component List contains 
every component available from “all” component lists. If you 
add components to any other Component List, they are 
automatically added to the Master Component List. Also, if you 
delete a component from the master, it is deleted from any 
other Component List that is using it.
When working with the Fluid Package Manager, components are 
associated with Fluid Packages through Component Lists. A 
Component List must be selected for each Fluid Package 
created.
 Figure 1.1
For further details 
regarding to the use of 
Component Lists with 
Fluid Packages, see 
Chapter 2 - Fluid 
Package.1-2
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Components 1-3
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ThThe Components tab of the Simulation Basis Manager property 
view contains six buttons which allow you to organize all 
component lists for the current case. Each button is described in 
the following table:
You cannot associate the Master Component List to a fluid 
package. Add a component list and associate it to a fluid 
package.
Button Description
View Opens the Component List property view for the selected 
Component List. From this property view, you can add, 
modify, or remove individual components from the current 
list. 
Add Allows you to add a new Component List into the case. 
When clicked, the Component List property view appears 
and components associated with the case may be added. 
New components may be added to the component list by 
highlighting the component list name and clicking the View 
button. 
Delete Allows you to delete a Component List from the case. No 
warning message is provided before deleting a list and a 
deleted Component List cannot be recovered.
Copy Makes a copy of the selected (highlighted) Component List. 
The copied version is identical to the original, except for the 
name. This command may be useful for modifying 
Component Lists while keeping the original list intact.
Import Allows you to import a pre-defined Component List from a 
disk. When the Import button is selected, the location 
dialog window for the component list file appears. 
Component Lists have a file extension of (*.cml).
Export Allows you to export the selected Component Lists (*.cml) 
to disk. The exported list file can be retrieved in another 
case by using the Import function detailed above. 
Refresh Allows you to reload component data from the database. 
For example, if you have a case from a previous version, 
the data is updated from the older version to the latest 
version.
Re-Import Updates the properties and parameters of an imported list  
if the properties have changed after they were imported 
into the case.1-3
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1-4 Component List Property View
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Th1.2 Component List 
Property View
When adding or viewing an existing Component List from the 
Components tab of the Simulation Basis Manager property view, 
the Component List property view is opened.
The Component List property view is designed to simplify adding 
components to a Component List. Access is provided to all 
Library components within Aspen HYSYS, which include the 
traditional components, electrolytes, defined Hypotheticals, and 
other existing lists. The property view consists of the following 
tabs: 
• The Selected tab allows you to add components and 
view their properties. The Components page varies 
according to the tree browser selection in the Add 
Component group. 
 Figure 1.2
The Name cell displays the name of 
the component list being viewed.
The Add Component tree browser allows you to 
filter through alternative component lists.1-4
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Components 1-5
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Th• The Component by Type tab displays all components 
selected for the component list by its particular type 
(traditional, electrolytes, hypotheticals, etc.) as shown 
below. 
1.2.1 Adding Library 
Components
The Component List property view shown previously is 
encountered when you are adding Library components to a 
Component List. Use the tree browser in the Add Components 
group to filter the library components for each group listed. 
The Selected tab has three main groups: 
• Add Component
• Selected Components
• Components Available in the Component Library
Each group is described separately in the following sections.
 Figure 1.31-5
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1-6 Component List Property View
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ThAdd Component Group
The Add Component group contains a tree browser that enables 
you to filter components by type. Selecting components from 
the component tree browser determines the type of components 
that are displayed in the Components Available in Component 
Library group. A different property view appears depending on 
whether you are adding Traditional, Electrolytes, Hypothetical, 
or Other components.
Selected Components Group
The Selected Components group shows the list of components 
that have been added. 
The various functions that allow you to manipulate the list of 
selected components are listed in the following table: 
 Figure 1.4
Object Description
Selected 
Component List
Contains all the currently installed components for a 
particular component list.
Add Pure Adds the highlighted component(s) from the 
Components Available group to the Selected 
Component List.
Substitute Swaps the highlighted selected components with the 
highlighted available component.
Remove Comp Deletes the highlighted component from the Selected 
Component List.
Add Component tree 
browser1-6
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Components 1-7
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ThComponents Available in the 
Component Library Group
The Components Available in the Component Library group 
displays library components depending on the filtered method 
used. 
Sort List Accesses the Move Components property view, where 
you can change the order of the selected component 
list.
View Comp Accesses the selected component’s identification 
property view. 
When substituting components, Aspen HYSYS replaces the 
component throughout the case (i.e., all specifications for 
the old component are transferred to the new component). 
However, the substitution function does not automatically 
handle components that are part of a Reaction.
 Figure 1.5
Object Description1-7
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1-8 Component List Property View
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ThThe group has several features designed to make the selection 
of components as efficient and convenient as possible. 
1.2.2 Selecting Library 
Components
As mentioned previously, library components are selected from 
the Components Available in the Component Library group, and 
placed in the Selected Components group. There are many ways 
in which you can select components for a component list. Once 
you become familiar with the available methods for component 
selection, you can select the procedure that you find most 
convenient.
The process of adding components from the component library 
to the Selected Components list can be divided into three sub-
processes. By visualizing the process of component selection in 
this way, you are made aware of all the available possibilities 
Object Description
Match As you type in this cell, Aspen HYSYS filters the 
component list to locate the component that best 
matches your current input. This depends on the radio 
button selected.
View Filter 
button
This button opens the Filters floating property view 
which contains a range of property packages and 
component filtering options to assist in your 
component selection process. 
SimName\ 
FullName 
Synonym\ 
Formula
These three radio buttons determine the context of 
your input in the Match cell.
Show Synonyms When this checkbox is selected Aspen HYSYS includes 
known synonyms for each component in the list.
Cluster This checkbox is available only when the Show 
Synonyms checkbox is selected. By selecting the 
Cluster checkbox, all synonyms are indented and 
listed below the component name. Otherwise, the 
synonyms are listed alphabetically throughout the list.
Whenever a component(s) is highlighted in the Available 
List, click the Add Pure button to move it to the Selected 
Component List.
For further details, refer 
to Filter Options for 
Traditional 
Components.1-8
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Components 1-9
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Thoffered by Aspen HYSYS. You can then adopt the most logical 
and efficient approach to use each time you build a case.
For component addition to the component list, the following 
methods are recommended:
1. Filter the library list.
2. Select the desired component(s).
3. Transfer the component(s) to the Selected Components list.
Filtering the Component List for 
Traditional Components
A recommended practice for component selection is the use of 
the available tools which Aspen HYSYS provides for filtering the 
component library. This narrows the selection range and allows 
you to apply one of the various methods for transferring the 
selection(s) to the Selected Components list. 
Filtering options for electrolytes and hypotheticals are different 
and available in Section 1.2.4 - Adding Electrolyte 
Components and Section 1.2.5 - Adding Hypothetical 
Components, respectively.
There are four tools available for filtering the list in the 
Components Available in the Component Library group. The 
filtering tools can be used independently or in combination and 
are described in the table below:
Filtering Tool Description
Property Package & 
Family Type Filters
Filters the list according to your selection of 
property package and/or component families.
Show Synonyms Component synonyms appear alphabetically 
throughout the list when this checkbox is selected.
Cluster The Cluster checkbox is available only when the 
Show Synonyms checkbox is selected and 
Match input field is empty. By selecting the 
Cluster checkbox, all synonyms are indented and 
listed below the component name.
Match This input cell allows type-matching of the 
component simulation name, full name, synonym 
or formula.
Refer to previous Filter 
Options for Traditional 
Components for further 
details.1-9
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1-10 Component List Property View
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ThWhen trying to Match a component, Aspen HYSYS searches the 
component column in the list for whichever radio button is 
selected:
By using the Match input cell, you can access any component 
within the Aspen HYSYS library that is accessible under the 
currently selected Property Package. You can make the Match 
field active by selecting it or by using the ALT M hot key.
The Match input cell accepts keyboard input, and is used by 
Aspen HYSYS to locate the component in the current list which 
best matches your input. The first character of the filtered 
component names must agree with first character of the listed 
component name. Subsequent characters in the Match cell must 
appear somewhere in each listed component name. Other than 
the first character, any number of unmatched characters can 
appear within the names of the listed components.
Radio Button Description
SimName This option matches the text entered into the Match input 
to the name used within the simulation.
Full Name/
Synonym
This option may match the components full name or a 
synonym of the SimName. It is typically a longer name.
Formula Use this option when you are not sure of the library name, 
but know the formula of the component.1-10
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Components 1-11
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ThIf the component you want to add is Water, type H2 in the Match 
cell. Aspen HYSYS filters the list of available Library Components 
to only those that match your current input string. The first 
component in the list, H2, is an exact match of your current 
input and therefore, is highlighted. Notice that H2O is available 
in the list even though you have entered only H2.
Since Hydrogen is not the component of choice, you can 
continue to reduce the list of available library component 
options by typing in the character O after the H2 in the Match 
cell.
 Figure 1.61-11
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1-12 Component List Property View
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ThFilter Options for Traditional 
Components
The floating Filter property view is accessed by clicking the 
View Filters button from Component List property view. It 
allows access to the Property Package filter and Family Type 
filter options.
The Property Package Filter group filters components based on 
their compatibility with the selected property package. Once a 
property package is selected, the Recommended Only checkbox 
works as follows:
• If the Recommended Only checkbox is selected, Aspen 
HYSYS only displays (in the component library list) 
components that are recommended with the chosen 
property package.
• If the Recommended Only checkbox remains un-
selected, all the components in the Aspen HYSYS library 
are displayed in the component library list. An ‘x’ is 
shown beside each component that Aspen HYSYS does 
not recommend for the selected property package, 
however, you may still select these components if you 
want.
The Family Type Filter group allows Aspen HYSYS to filter the list 
of available components to only those belonging to a specific 
family. The Use Filter checkbox, when selected, toggles the 
Family Type Filter options On and Off. By default, all checkboxes 
in the Family Filter group are cleared. You can identify which 
families should be included in the list of available components by 
selecting the desired checkbox(es). The All button selects all 
checkboxes, and the Invert button toggles the status of each 
checkbox individually. For example, if you select all of the 
checkboxes, and then want to quickly clear them, simply click 
the Invert button. If you only had the Hydrocarbons and the 
Solids options activated and you clicked the Invert button, 
these two options are deactivated and the remaining options are 
The Property Package Filter is only a component selection 
filtering tool and does not associate a Fluid Package with the 
component list (this is accomplished within the Fluid 
Package Manager). 1-12
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Components 1-13
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Thactivated.1-13
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1-14 Component List Property View
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ThSelecting the Component(s)
After the list of Library Components are filtered, you can see the 
desired component among the displayed components. Use one 
of the following available methods to highlight the component(s) 
of choice described in the following table:
Whenever the list of components is filtered, the highlight is 
placed on the first component in the reduced list. If you use the 
keyboard commands to access the list of components, you may 
have to move the highlight if the first component is not desired.
To move through the Components Available in the Component 
Library group, use one of the following methods:
Transferring the Component(s)
After the Library Component list is filtered and the desired 
component(s) highlighted, transfer the selection(s) to the 
Selected Components list. Use one of the following methods:
• Click the Add Pure button
• Press the ENTER key
• Double-click on the highlighted item. This option only 
works for a single component selection.
Selection Method Description
Mouse Place the cursor over the desired component and press 
the primary mouse button.
Keyboard Use the TAB key or SHIFT TAB combination to move 
the active location into the list of components.
Method Description
Arrow Keys Move the highlight up or down one line in the 
component list.
Page Up/Page 
Down
Use these keyboard keys to move through the list an 
entire page at a time.
Home/End The HOME key moves to the start of the list and the 
END key moves to the end of the list.
Scroll Bar With the mouse, use the scroll bar to navigate through 
the list.1-14
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Components 1-15
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ThThe methods are the same whether you are adding traditional 
components, electrolytes, hypotheticals, or other components.
1.2.3 Manipulating the 
Selected Components List
After adding the components to the Selected Components list, 
you can substitute, remove, sort, and view components. These 
methods apply to traditional library components, electrolytes, 
hypotheticals, and other components.
To demonstrate the manipulation functions, the Selected 
Components group shown below is used for reference purposes. 
Removing Selected Components
You can remove any component(s) from the Selected 
Components list by the following steps:
1. Highlight the component(s) you want to delete. 
2. Click the Remove button, or press the DELETE key.
For Library components, Aspen HYSYS removes the 
component(s) from the Selected Components list and places 
back in the Components Available in the Component Library list. 
Since Hypothetical components are shared among Fluid 
 Figure 1.7
Refer to Chapter 3 - 
Hypotheticals for 
detailed information on 
Hypothetical 
components.1-15
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1-16 Component List Property View
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ThPackages, there is no actual transfer between the lists. (i.e., The 
Hypo always appears in the Available group, even when it is 
listed in the selected Components list.)
Substituting Components
When substituting components, Aspen HYSYS replaces the 
component throughout the case (i.e., all specifications for the 
old component are transferred to the new component). 
However, the substitution function does not automatically 
handle components which are part of a Reaction.
You can substitute a component in the selected Component List 
with one in the Components Available in the Component Library 
list by using the following procedure:
1. From the selected Component List, highlight the component 
you want to remove.
2. In the Available Component list, highlight the component to 
be substituted. 
3. Click the Substitute button.
4. The removed component is returned to the Available 
Component list and the substituted component is placed in 
the Selected Component List.
You can only substitute one component at a time. Even 
though Aspen HYSYS allows you to highlight multiple 
components, the substitution only involves the first 
highlighted component.1-16
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Components 1-17
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ThSorting a Component List
When there are components in the Selected Components group 
you can use the Sort List button to rearrange the component 
order.
Using the property view shown in Figure 1.8, the sorting 
procedure is illustrated below:
1. Click the Sort List button, and the Move Components 
property view appears.
2. From the Component(s) to Move group, select the 
component you want to move. In this example, Methane is 
selected. 
3. From the Insert Before group, highlight the component 
before which Methane is to be inserted. In this case, 
Propane is highlighted.
4. Click the Move button to complete the move. Methane is 
inserted before Propane in the component list, and Ethane is 
forced to the top of the list, followed by Methane, Propane, 
and n-Butane.
You can select and highlight multiple components for 
moving.
5. When you have completed the sorting, click the Close 
button to return to the Components tab.
 Figure 1.81-17
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1-18 Component List Property View
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ThViewing Components
Once a component is added to the Selected Components list, the 
View Component button becomes active. The View 
Component button accesses the Pure Component property 
view allowing you to view and edit properties of the specified 
component.
The property views are different and are specific to the type of 
component selected. Pure library components and hypothetical 
components share the first type of property view. The difference 
between the two is that you cannot “directly” modify the 
properties in the pure components Property View, whereas, in 
the hypotheticals you can. The Edit Properties feature allows 
you to edit pure component and solid properties.  
The second property view is shared by pure component solids 
and hypothetical solids. Again you cannot “directly” modify the 
pure component solid properties, whereas, hypotheticals can be 
edited directly. 
The electrolytes property view is the same as the edit properties 
feature for library components. Although, the electrolyte 
properties are set by OLI systems and cannot be modified like 
traditional components. 
Each property view consists of five tabs. Throughout the tabs 
the information is displayed in red, blue and black. Values 
displayed in red are estimated by Aspen HYSYS. Values 
displayed in blue are user supplied. Black values represent 
calculated values or information that is provided by Aspen 
HYSYS.
You can also examine the property view for any component 
in the Selected Component List by double-clicking on the 
component.
For more information on 
hypotheticals, refer to 
Chapter 3 - 
Hypotheticals.
For more information on 
electrolytes, refer to 
Section 1.2.4 - Adding 
Electrolyte Components.1-18
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Components 1-19
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ThPure Component Property View
In this example, Methane and Carbon are used by clicking the 
View Component button, which opens the following traditional 
pure component and Solid pure component property views, 
respectively: 
ID Tab
The ID tab is the first tab in the property view. The black values 
in the Component Identification group represent information 
that is provided by Aspen HYSYS. The User ID Tags are used to 
identify your component by a user specified tag number. You 
can assign multiple tag numbers to each component.
 Figure 1.9
You can also view a component by right-clicking on the 
component and selecting View command from the object 
inspect menu.1-19
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1-20 Component List Property View
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ThCritical Tab & Props Tab
The Critical Tab displays Base and Critical Properties. The 
properties for pure components are supplied by Aspen HYSYS 
and are read-only. However, you can edit these properties using 
the Edit Properties button. 
The Component Property view for solid components does not 
have critical properties and therefore does not require the 
Critical tab. An alternate tab called the Props tab which displays 
default values for Solid properties and Coal Analysis is included. 
These properties can also be edited using the Edit Properties 
button.
Point Tab
Additional Point properties are given by Aspen HYSYS for the 
Thermodynamic and Physical Props and the Property Package 
Molecular Props. The pure component properties differ from the 
solid properties. 
The solid properties depend only on the Heat of Formation and 
Combustion. These properties may be altered by selecting Point 
properties in the Edit Properties property view. 
TDep Tab
The temperature Dependent Properties for pure components are 
shown in this tab. Aspen HYSYS provides the minimum 
temperature, maximum temperature and coefficients for each of 
the three calculation methods.
The difference between pure components and solid pure 
components is that solids do not participate in VLE calculations. 
Their vapour pressure information is, by default, set to zero. 
However, since solid components do affect Heat Balances, the 
Specific Heat information is used. The properties may be edited 
by selecting the Edit Properties button.1-20
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Components 1-21
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ThUserProp & PSD Tabs
The UserProp tab displays user specified properties. User 
properties must be specified on the UserProperty tab in the 
Simulation Basis Manager property view. Once a user property 
is specified there, you can view and edit UserProp on this 
component property view. 
The PSD tab displays the particle size distribution for solids. It 
allows the user to specify PSDs and calculate various mean and 
modal diameters for the entered PSD. 
To edit a PSD, click the Edit Properties button to open the 
Editing Properties for Component property view, select Type 
radio button in the Sort By group, and select Particle Size 
Distribution from the tree browser. The options available for edit 
the PSD appears on the right side of the Editing Properties for 
Component property view.
 Figure 1.10
See Chapter 7 - User 
Properties for more 
information.1-21
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1-22 Component List Property View
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ThA PSD can be specified in three ways: 
The input information required for each Input PSD are as 
follows:
The user has the choice between using the User-Defined 
Discrete or one of the statistical distribution methods. The 
statistical methods (Log Probability & Rosin-Rammler) may be 
preferred over the discrete method if any of the following 
occurs:
• A number of particle size measurement devices give the 
distribution as a statistical fit.
• Certain physical process tend to give rise to distributions 
that are described well by a statistical distribution. For 
example, processes involving high shear (e.g. crushing 
Input PSD Group Description
User-Defined 
Discrete
Allows the user to enter particle diameter vs 
distribution values over the range of the distribution. 
To enter the distribution, Select the Edit Discrete 
PSD button. The entered distribution can be a 
Composition Basis with mass percent or number 
percent data and can be InSize, cumulative Undersize 
or cumulative Oversize as an Input Basis. Once a 
discretized PSD is entered, the user can have other 
types of PSD fitted to it. These fits are displayed in the 
Fit Type group. The selected fit can be changed by 
regenerating the fit at any time.
Log-probability Is a two-parameter statistical representation which 
allows the user to specify the mean and standard 
deviation of the PSD. 
Rosin-Rammler Is a two-parameter statistical representation which 
allows the user to specify the Rosin-Rammler model 
diameter and spread parameter of the PSD.
Input PSD Group Input Information Required
User-Defined 
Discrete
The PSD requires PSD name, basis, particle density 
and number of points to use in fitted PSDs. The 
distribution requires particle diameters (including 
minimum diameter) and either InSize, Undersize or 
Oversize distribution points.
Log-probability The PSD requires PSD name, basis, particle density 
and number of points to use in generating the PSD. 
The distribution requires mean diameter and standard 
deviation.
Rosin-Rammler The PSD requires PSD name, basis, particle density 
and number of points to use in generating the PSD. 
The distribution requires modal diameter and spread 
parameter.1-22
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Components 1-23
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Thof coal, atomization of liquids in a two-fluid nozzle) tend 
to give size distributions that can be readily described by 
a Rosin-Rammler distribution.
• By using a statistical distribution, it is easier to extend 
the distribution to lower and higher size ranges. For 
many design processes involving size distributions, it is 
the values of the distribution at these 'tails' that have 
most influence when trying to optimize the design. 
Therefore, the accuracy with which these 'tails' can be 
described is important.
The Fit Type group for the User-Defined Discrete Input allows 
users to fit a distribution to the entered discrete data. The fitting 
improves the accuracy of any calculations made by it.
• It increases the number of discrete steps over which a 
size distribution can be described. The more steps, mean 
smaller steps which means more accuracy when 
interpolating, etc.
• It provides more data at the extremes (‘tails’) of the 
distribution, again improving accuracy.
The fit type used is based on which provides the closest fit to the 
data. The fitting alogorithm displays a dialog with six fits to the 
data. The AutoFit selects one fit for the data automatically, and 
the NoFit does not fit the data. The Standard and Probability fit 
types are lagrangian interpolations on the entered data, but one 
works on the raw data while one works on a probability 
transformation of the data. That is, the distribution values are 
transformed to the linear equivalents used in plotting against a 
probability axis. 
The other two fits are a log-probability and a Rosin-Rammler 
distribution. For these two fits, the value of R2 (the fit 
coefficient) is given and the closer this is to 1 the better the fit. 
Ultimately, it is up to the user to choose the best fit and is often 
based on the visual appearance of the fitted distibutions 
compared to the entered one. One limitation to PSD is that the 
particle diameters cannot be specified as sieve mesh sizes.1-23
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1-24 Component List Property View
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ThEdit Properties
The Edit Properties button allows the user the flexibility of 
viewing and modifying properties for traditional and hypothetical 
components. Electrolyte component properties are specified by 
OLI Systems which may only be viewed. The Edit Properties 
property view can be accessed on three different levels and are 
shown below:
• Component level. Double-click on any component or 
right-click and select View in the object inspect menu. 
Click the Edit Properties button.
• Fluid Package level. Click the Edit Properties button on 
the Fluid Package property view.
• Stream level. Select a stream which is not a product 
stream. Click the Edit Properties button on the 
Composition page.
The Component level Edit Properties property view is shown 
below for methane.
 Figure 1.111-24
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Components 1-25
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ThThe properties can be sorted using the Sort By group on any 
level. 
The edit Properties feature is flexible in that it allows you to edit 
properties on the component, fluid package, or stream levels. 
The component level is the highest and allows you to edit 
properties throughout your case. Any changes at this level 
correspond to a global change to all fluid packages using the 
particular component. The initial value stored at this level for 
any given component is considered the 'default' property value. 
At the component level, the reset options are described below.
The second level is the fluid package level which allows you to 
edit properties specific to a fluid package. This allows the 
flexibility of having different property values for different fluid 
packages throughout the case. Any changes at this level 
corresponds to a change for any flowsheet using this fluid 
package.
Sort By Description
Property Name Sort through properties by Property Name.
Group Sort through properties by Groups. This includes 
Thermo, Prop Pkg, Physical, Cold, Solid, etc.
Type Sort through Point, Curve, Distribute, PSD, and 
Hydrate properties.
Modify Status Sort through properties which are modified in the 
specific Component, Fluid Pkg, or Stream.
Component Level Reset Description
Reset selected property 
to library default
Resets the selected property to the library or 
original default value for this component. This 
button is active only if a component is 
modified on the component level.
Reset all properties to 
library default
Resets all properties to library or original 
default values for this component. This button 
is active only if a component is modified on 
the component level.
Reset selected property 
for all users of this 
component
Clears local changes to the selected property 
for all users of this component. Users are 
defined by changes in the Fluid pkg and 
stream levels.
Reset all properties for 
all users of this 
component
Clears local changes to all properties for all 
users of this component. Users are defined by 
changes in the Fluid pkg and stream levels.1-25
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1-26 Component List Property View
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ThThe reset options for the fluid pkg level are described below:
The stream level allows you to edit properties specific to input 
streams of the case. Changes made at this level enable one to 
modify a particular component's property for a particular 
stream. This allows the flexibility of properties to dynamically 
change across the flowsheet. 
The reset options are listed below and are active if you modify a 
property value at the stream level.
The properties for the stream are accessible from the stream 
level editor. However, only the feed stream properties are 
modifiable. 
Keep in mind that any property vector changes at the Stream 
level supercede changes at the fluid package level. For example, 
if a stream is trying to access a particular component's 'Point' 
property value and the property vector is contained in the 
stream's local property slate, the local value is used. If the 
property vector does not exist locally, then it calls up to the fluid 
package's property state for the particular property vector and 
Fluid Pkg Level Reset Description
Reset selected prop 
vector to 
components default
Clears the selected property vector within this fluid 
package and resets it to the component level 
value.
Reset all props to 
components default
Clears all changed property vectors within this 
fluid package and resets them to the component 
level values.
Reset selected 
property for all users 
of this fp
Clears local changes to selected property vector 
for all users of this fluid package. The user is 
defined as the stream level property selected, 
which is overwritten with current fluid package 
value.
Reset all properties 
for all users of this fp
Clears local changes to all properties for all users 
of this fluid package. The users are defined as the 
stream level properties, which are overwritten 
with current fluid package values.
Stream Level Reset Description
Reset Selected Prop 
Vector to FP Default
Clears selected property vector and reset it to the 
fluid package level value for this stream.
Reset All Props to FP 
Default
Clears all changed property vectors and reset 
them to the fluid package values for this stream.1-26
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Components 1-27
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Thuses this value if it exists. If the property vector does not exist 
at the fluid package level, then the initial Component level value 
is used. 
1.2.4 Adding Electrolyte 
Components
Electrolytes can be added to the component list in the 
Component List property view. In the Add Component group of 
the Selected tab, select the Electrolyte page located as the 
subgroup of the Components configuration. 
The property view is filled with information on electrolytes as 
shown below.
OLI Alliance Suite for Aspen HYSYS and OLI Analyzer must 
be installed in order for the Electrolyte page to appear. 
 Figure 1.121-27
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1-28 Component List Property View
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ThThe methods for adding, substituting, removing, and sorting 
components are common for all components on the selected 
tab. The filtering options for Electrolytes which are described in 
the following table:
You can select or provide additional electrolyte component 
databases to simulate special aqueous-based chemical systems. 
Aspen HYSYS supports three special databases: GEOCHEM, 
LOWTEMP, and REDOX.
You can access those special databases by clicking on the 
Additional Database button, and select the desired special 
databases from the Special Databank group in the 
OLI_Electrolyte Additional Database property view. The use of 
GEOCHEM, LOWTEMP, and REDOX databases must combine 
with the choice of Full Databank. You can also supply your own 
OLI private databank to suit the need of your simulation case.
To get a comprehensive list of the Full, and GEOCHEM database 
components, refer to:
• Appendix A.1 - List of Full HYSYS OLI Interface 
Database, of the Aspen HYSYS OLI Interface 
Reference Guide.
• Appendix B.1 - List of HYSYS OLI Interface 
GEOCHEM Database, of the Aspen HYSYS OLI 
Interface Reference Guide.
Filter Description
Match This input cell allows type-matching of the component 
simulation name, full name / synonym, or formula based on 
the ratio button selected.
None No electrolyte components exist or match your selection in 
the property view. You need to acquire an additional license 
to view the electrolyte database.
Full The full database contains thousands of species in water 
based on the OLI system database.
Limited This database contains approximately 1,000 components 
which are of most interest to process industries.
Refer to Filtering the 
Component List for 
Traditional 
Components for 
additional information on 
using the Match field to 
filter the component list 
for traditional 
components.
Refer to the following 
sections in the Aspen 
HYSYS OLI Interface 
Reference Guide for 
more information on the 
OLI databases: 
• Section 1.8.1 - Full 
Database
• Section 1.8.2 - 
Limited Database
• Section 1.8.3 - 
Special Databases
• Section 1.8.4 - 
Private User 
Databases - OLI 
Data Service1-28
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Components 1-29
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Th1.2.5 Adding Hypothetical 
Components
Hypotheticals can be added to a component list through the 
Components List property view. In the Add Components group 
of the Selected tab, select the Hypothetical branch from the 
tree browser. The Components List property view is filled with 
information appropriate to the addition of Hypothetical 
components.
Some of the features from the Selected tab are common to both 
the selection of Hypotheticals and Library components. Items 
specific to Hypotheticals are described in the following table:   
Refer to Section 3.5 - 
Hypothetical 
Component Property 
View for details on the 
various Component 
property view tabs.
 Figure 1.13
Object Description
Add Group Adds all the Hypothetical components in the Selected 
selection in the Hypo Group list current to the current 
component list. 
Add Hypo Adds the currently selected Hypothetical in the Hypo 
Component list to the Current Component List. 
Hypo Group Displays all the Hypo Groups available to the current 
component list.
Refer to Chapter 3 - 
Hypotheticals for more 
detailed information to 
Add and modify 
Hypothetical components.1-29
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1-30 Component List Property View
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ThHypo 
Components
Displays all the Hypothetical components contained in 
the currently selected Hypo Group.
Hypo Manager Accesses the Hypotheticals tab of the Simulation Basis 
Manager, from which you can create, view, or edit 
Hypotheticals.
Quick Create a 
Hypo Comp
A short-cut for creating a regular Hypothetical 
component and adds it to the currently selected Hypo 
Group and opens its property view.
Quick Create a 
Solid Hypo 
component
A short-cut for creating a solid Hypothetical component 
and adds it to the currently selected Hypo Group and 
opens its property view.
While you can add Hypos to a Component List from the 
Selected tab, this is merely a short-cut. To access all features 
during the creation of Hypotheticals and Hypothetical 
groups, you should access the Hypotheticals tab of the 
Simulation Basis Manager.
Object Description1-30
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Components 1-31
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Th1.2.6 Adding Components 
from Existing Component 
Lists
Components can be added from other component lists by using 
the Other List option. In the Add Components group, select the 
Other list. The Components tab is redrawn with information 
appropriate to accessing components from alternate component 
lists.
The Existing Components group displays a list of all available 
component lists loaded into the current case. Highlighting a 
component list name displays its associated group of 
components in the Components in Selected Component List.
To transfer a component from an existing component list, simply 
highlight the component name in the list and click the Add 
button. The highlighted component is added to the Selected 
Components list.
 Figure 1.141-31
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1-32 Component List Property View
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Th1-32
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Fluid Package 2-1
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Th2  Fluid Package2-1
2.1  Introduction................................................................................... 2
2.2  Fluid Packages Tab ........................................................................ 3
2.3  Adding a Fluid Package - Example.................................................. 5
2.4  HYSYS Fluid Package Property View .............................................. 7
2.4.1  Set Up Tab .............................................................................. 8
2.4.2  Parameters Tab ...................................................................... 25
2.4.3  Binary Coefficients Tab............................................................ 51
2.4.4  Stability Test Tab.................................................................... 62
2.4.5  Phase Order Tab..................................................................... 66
2.4.6  Reactions Tab ........................................................................ 68
2.4.7  Tabular Tab............................................................................ 69
2.4.8  Notes Tab.............................................................................. 94
2.5  COMThermo Property View .......................................................... 95
2.5.1  Set Up Tab ............................................................................ 96
2.5.2  Parameters Tab .....................................................................109
2.5.3  Binary Coefficients Tab...........................................................111
2.5.4  Stability Test Tab...................................................................116
2.5.6  Reactions Tab .......................................................................120
2.5.8  Notes Tab.............................................................................120
2.6  References................................................................................. 121
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2-2 Introduction
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Th2.1 Introduction
In Aspen HYSYS, all necessary information pertaining to pure 
component flash and physical property calculations is contained 
within the Fluid Package. This approach allows you to define all 
the required information inside a single entity. The four key 
advantages to this approach are:
• All associated information is defined in a single location, 
allowing for easy creation and modification of the 
information.
• Fluid Packages can be exported and imported as 
completely defined packages for use in any simulation.
• Fluid Packages can be cloned, which simplifies the task of 
making small changes to a complex Fluid Package.
• Multiple Fluid Packages can be used in the same 
simulation; however, they are all defined inside the 
common Simulation Basis Manager.
In this chapter, all information concerning the fluid package is 
covered. This includes the basic procedure for creating a fluid 
package by using both traditional Aspen HYSYS and COMThermo 
thermodynamics. Finally, information on the Fluid Package 
property view is provided for each of the following tabs:
• Set Up
• Parameters
• Binary Coefficients
• Stability Test
• Phase Order
• Reactions (Rxns)
• Tabular
• Notes
It should be noted that individual components are not added 
within the Fluid Package Manager. Instead, component selection 
is handled independently in the Basis Manager through the 
Components tab. The Components Manager provides a general 
location where sets of chemical components being modeled may 
be retrieved and manipulated. 
Refer to Chapter 1 - 
Components for further 
details on the 
Components Manager.2-2
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Th2.2 Fluid Packages Tab
The second tab of the Simulation Basis Manager property view is 
the Fluid Packages (Fluid Pkgs) tab. When you create a New 
Case, Aspen HYSYS displays the Fluid Pkgs tab, as shown below:
In the Current Fluid Packages group, you can organize all Fluid 
Packages for the current case.
The following table lists and describes each button:
 Figure 2.1
You must define at least one fluid package prior to entering 
the Simulation Environment.
When a New Case is created, only the Add and Import 
buttons are available.
Button Description
View This is only active when a fluid package exists in the 
case. It allows you access the property view for the 
selected fluid package.
Add Allows you to install a new fluid package into the case.
Refer to Section 2.4 - 
HYSYS Fluid Package 
Property View for 
details on what 
information you can edit 
by clicking the View 
button.2-3
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2-4 Fluid Packages Tab
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ThThe Flowsheet - Fluid Pkg Associations group lists each 
Flowsheet in the current simulation along with its associated 
Fluid Package. You can change the associations between 
Flowsheets and which Fluid Pkg To Use in this location. You can 
also specify a default fluid package by selecting a package in the 
Default Fluid Pkg drop-down list. Aspen HYSYS automatically 
assigns the Default Fluid Package to each unit operation, 
SubFlowsheet or columns using the default fluid package in the 
simulation. 
Selecting an alternative fluid package from the Basis Manager 
property view allows you to transition or switch between fluid 
pkgs anywhere in the flowsheet with the addition of the stream 
cutter object.
The Fluid Pkg for New Sub-FlowSheets group allows you to 
select the default fluid package that is associated to a 
subflowsheet, when the subflowsheet is created.
• Use Default Fluid Pkg radio button associates the 
default fluid package of the entire simulation case to the 
subflowsheet.
• Use Parent’s Fluid Pkg radio button associates the 
default fluid package of the parent flowsheet to the 
subflowsheet.
Delete Allows you to delete a fluid package from the case. When 
you delete a fluid package, Aspen HYSYS displays a 
warning, and asks you to verify that you want to delete 
the package. You must have at least one fluid package 
for your case at all times.
Copy Makes a copy of the selected fluid package. Everything is 
identical in this copied version, except the name. This is a 
useful tool for modifying fluid packages.
Import Allows you to import a pre-defined fluid package from 
disk. Fluid packages have the file extension *.fpk.
Export Allows you to export the selected fluid package (*.fpk) 
to disk. The exported fluid package can be retrieved into 
another case, by using its Import function.
Changing the default package only changes those fluid pkgs 
that are currently set to use the default fluid package. That 
is, any operation or stream which is not set to the default 
fluid package is not modified.
Button Description
For details concerning 
the importing and 
exporting functionality, 
refer to Section 7.23.7 
- Exporting/
Importing Workbook 
Tabs in the Aspen 
HYSYS User Guide.
Refer to Chapter 5 - 
Logical Operations in the 
Aspen HYSYS 
Operations Guide for 
detailed information on the 
stream cutter object and 
fluid package transitioning.2-4
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Th2.3 Adding a Fluid Package 
- Example
When you click the Add button from the Simulation Basis 
Manager property view, Aspen HYSYS opens the Fluid Package 
property view to the Set Up tab. The Fluid Package property 
view is based on the traditional Aspen HYSYS Thermodynamics.  
The order of the tabs in the Fluid Package property view are tied 
to the sequence of defining a Fluid Package using Aspen HYSYS 
thermodynamics.
• On the Set Up tab, select a Property Package for the case 
from the Property Package Selection group. You can filter 
the list of Property Packages by selecting a radio button 
in the Property Package Filter group. You must also select 
a Component List for the case from the Component List 
Selection group. Component Lists are built in the 
Simulation Basis Manager and may contain library, 
hypothetical, and electrolyte components. 
• Depending on the Property Package selected, you may 
need to specify additional information, such as the 
Enthalpy and Vapour Model, Poynting Correction factor, 
etc.
• Depending on the Property Package selected, you may 
need to supply additional information based on the 
selected components. This is done on the Parameters 
tab.
 Figure 2.2
A complete description of 
each page of the Fluid 
Package property view is 
given in Section 2.4 - 
HYSYS Fluid Package 
Property View.
For further details relating 
to Component Lists and 
component selection, 
refer to Chapter 1 - 
Components.2-5
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2-6 Adding a Fluid Package - Example
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Th• If necessary, specify the binary coefficients on the Binary 
Coeffs tab. As an alternative to supplying binaries, you 
may want to have estimates made for the selected 
components.
• If necessary, instruct Aspen HYSYS how to perform 
Phase Stability tests as part of the flash calculations on 
the Stab Test tab.
• Define any reactions and reaction sets for the fluid 
package or access the Reaction Manager on the Rxns 
tab.
• On the Tabular tab, you can access the Tabular Package 
for the equation based representation of targeted 
properties.
• The final tab on the Fluid Package property view is the 
Notes tab, where you can supply descriptive notes for the 
new Fluid Package. 
If you select the COMThermo package from the Property 
Package Selection list, Aspen HYSYS opens the COMThermo 
Setup view. On the COMThermo Setup view, you can chose 
Model cases for the vapor and liquid phases. Depending on the 
model selected, you can specify additional information. For 
example, in the Model Options group, select the calculation 
methods for Enthalpy and Entropy and Cp, using the drop-down 
list.  
 Figure 2.3
Refer to Chapter 5 - 
Reactions for 
information on the 
Reaction Manager.2-6
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ThSelecting the COMThermo package makes a few changes in the 
Fluid Package property view tabs:
• Depending on the Model selected, you might need to 
supply additional information based on the selected 
components on the Parameters tab.
• If necessary, specify the binary coefficients on the Binary 
Coeff tab. As an alternative to supplying binaries, you 
can have estimates made for the selected components.
• If necessary, instruct Aspen HYSYS-COMThermo how to 
perform Phase Stability tests as part of the flash 
calculations on the Stab Test tab.
2.4 Aspen HYSYS Fluid 
Package Property View 
The Fluid Package property view consists of eight tabs and is 
based on the traditional Aspen HYSYS thermodynamics. All the 
information pertaining to the particular Fluid Package is on these 
tabs.
 Figure 2.4
Removes the Fluid 
Package from the 
case. You must 
confirm that you want 
to delete the Fluid 
Package
You can input a name 
for the Fluid Package 
in this field.
The selected base 
Property Package type is 
shown in this status bar.2-7
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2-8 Aspen HYSYS Fluid Package 
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Th2.4.1 Set Up Tab
The Set Up tab is the first tab of the Fluid Package property 
view.
When you create a new Fluid Package, the Fluid Package 
property view appears as shown in the above figure.
The Set Up tab contains the Property Package Selection, 
Component List Selection, Property Package Filter, and Launch 
Property Wizard button. The Property Wizard offers you a guide 
to help you choose the appropriate property package in Aspen 
HYSYS based on your process.
After a Property Package has been selected, additional 
information and options might be displayed to the right of the 
Property Package Selection group. The information that is 
displayed is dependent on the selected Property Package.
The following sections provide an overview of the various 
Property Packages, as well as details on the various groups that 
appear on the Set Up tab.
 Figure 2.5
Refer to Section 2.5 - 
COMThermo Property 
View for more 
information on Advanced 
Thermodynamics group.
Additional information is displayed in 
this space depending on the Property 
Package selection.
Select a Component List here. It is not recommended 
to use the Master Component List.
Select a property package 
for the fluid package using 
the property package filter.2-8
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ThProperty Package Selection Group
In the Property Package Selection group, you have access to the 
list of all the Property Package/Property Methods available in 
Aspen HYSYS and to the Property Package Filter group.
The Property Package Filter allows you to filter the list of 
available property methods, based on the following criteria:
Equations of State (EOS)
For oil, gas, and petrochemical applications, the Peng-Robinson 
Equation of State is generally the recommended property 
package. Enhancements to this equation of state enable its 
accuracy for a variety of systems over a wide range of 
conditions. It rigorously solves most single-phase, two-phase, 
and three-phase systems with a high degree of efficiency and 
reliability. 
 Figure 2.6
Filter Description
All Types All the Property Packages appear in the list.
EOSs Only Equations of State appear in the list.
Activity Models Only Liquid Activity Models appear in the list.
Chao Seader 
Models 
Only Chao Seader based Semi Empirical methods 
are displayed.
Vapour Pressure 
Models 
Vapour pressure K-value models are shown in the 
list.
Miscellaneous Models that do not fit into any of the above 4 
categories (i.e., excluding All) are displayed.
For more detailed 
information about the 
property packages 
available in Aspen HYSYS, 
refer to Appendix A - 
Property Methods & 
Calculations.2-9
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2-10 Aspen HYSYS Fluid Package 
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ThAll equation of state methods and their specific applications are 
described below:
EOS Description
BWRS This model is commonly used for compression 
applications and studies. It is specifically used for gas 
phase components that handle the complex 
thermodynamics that occur during compression and is 
useful in both upstream and downstream industries. 
GCEOS This model allows you to define and implement your own 
generalized cubic equation of state including mixing rules 
and volume translation.
Glycol PPkg Glycol property package contains the TST (Twu-Sim-
Tassone) equation of state to determine the phase 
behaviour more accurately and consistently for the TEG-
water mixture.
Kabadi Danner This model is a modification of the original SRK equation 
of state, enhanced to improve the vapour-liquid-liquid 
equilibria calculations for water-hydrocarbon systems, 
particularly in dilute regions.
Lee-Kesler 
Plocker
This model is the most accurate general method for non-
polar substances and mixtures.
MBWR This is a modified version of the original Benedict/Webb/
Rubin equation. This 32-term equation of state model is 
applicable for only a specific set of components and 
operating conditions.
Peng-Robinson This model is ideal for VLE calculations as well as 
calculating liquid densities for hydrocarbon systems. 
Several enhancements to the original PR model were 
made to extend its range of applicability and to improve 
its predictions for some non-ideal systems. However, in 
situations where highly non-ideal systems are 
encountered, the use of Activity Models is recommended.
PR-Twu This model is based on Peng-Robinson and incorporates 
the Twu EoS Alpha function for improved vapor pressure 
prediction of all Aspen HYSYS library components. 
PRSV This is a two-fold modification of the PR equation of state 
that extends the application of the original PR method for 
moderately non-ideal systems.
Sour PR Combines the PR equation of state and Wilson's API-Sour 
Model for handling sour water systems.
Sour SRK Combines the Soave Redlich Kwong and Wilson's API-
Sour Model.
SRK In many cases it provides comparable results to PR, but 
its range of application is significantly more limited. This 
method is not as reliable for non-ideal systems.
SRK-Twu This model is based on SRK and incorporates the Twu 
EoS Alpha function for improved vapor pressure 
prediction of all Aspen HYSYS library components.
For more information on 
the package see 
Appendix D - Glycol 
Property Package.2-10
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ThActivity Models
Although Equation of State models have proven to be very 
reliable in predicting the properties of most hydrocarbon based 
fluids over a wide range of operating conditions, their 
application is limited to primarily non-polar or slightly polar 
components. Highly non-ideal systems are best modeled using 
Activity Models.
The following Activity Model Property Packages are available:
Twu-Sim-
Tassone
This model uses a new volume function for improved 
liquid molar volume predictions for mid range and heavy 
hydrocarbons and incorporates the Twu EoS Alpha 
function for improved vapor pressure prediction of all 
Aspen HYSYS library components.
Zudkevitch 
Joffee 
Modification of the Redlich Kwong equation of state. This 
model has been enhanced for better prediction of 
vapour-liquid equilibria for hydrocarbon systems, and 
systems containing Hydrogen.
Activity Model Description
Chien Null Provides a consistent framework for applying existing 
Activity Models on a binary by binary basis. It allows you 
to select the best Activity Model for each pair in your 
case.
Extended NRTL This variation of the NRTL model allows you to input 
values for the Aij, Bij, Cij, Alp1ij and Alp2ij parameters 
used in defining the component activity coefficients. 
Apply this model to systems:
• with a wide boiling point range between 
components.
• where you require simultaneous solution of VLE and 
LLE, and there exists a wide boiling point range or 
concentration range between components.
General NRTL This variation of the NRTL model allows you to select the 
equation format for equation parameters:  and . 
Apply this model to systems:
• with a wide boiling point range between 
components.
• where you require simultaneous solution of VLE and 
LLE, and there exists a wide boiling point or 
concentration range between components.
Margules This was the first Gibbs excess energy representation 
developed. The equation does not have any theoretical 
basis, but is useful for quick estimates and data 
interpolation.
EOS Description
τ α2-11
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2-12 Aspen HYSYS Fluid Package 
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ThChao Seader & Grayson Streed Models
The Chao Seader and Grayson Streed methods are older, semi-
empirical methods. The Grayson Streed correlation is an 
extension of the Chao Seader method with special emphasis on 
hydrogen. Only the equilibrium data produced by these 
correlations is used by Aspen HYSYS. The Lee-Kesler method is 
used for liquid and vapour enthalpies and entropies.
NRTL This is an extension of the Wilson equation. It uses 
statistical mechanics and the liquid cell theory to 
represent the liquid structure. It is capable of 
representing VLE, LLE, and VLLE phase behaviour.
UNIQUAC Uses statistical mechanics and the quasi-chemical theory 
of Guggenheim to represent the liquid structure. The 
equation is capable of representing LLE, VLE, and VLLE 
with accuracy comparable to the NRTL equation, but 
without the need for a non-randomness factor.
 van Laar This equation fits many systems quite well, particularly 
for LLE component distributions. It can be used for 
systems that exhibit positive or negative deviations from 
Raoult's Law, however, it cannot predict maxima or 
minima in the activity coefficient. Therefore it generally 
performs poorly for systems with halogenated 
hydrocarbons and alcohols.
Wilson First activity coefficient equation to use the local 
composition model to derive the Gibbs Excess energy 
expression. It offers a thermodynamically consistent 
approach to predicting multi-component behaviour from 
regressed binary equilibrium data. However the Wilson 
model cannot be used for systems with two liquid 
phases.
Model Description
Chao Seader Use this method for heavy hydrocarbons, where the 
pressure is less than 10342 kPa (1500 psia), and 
temperatures range between -17.78 and 260°C (0-500°F).
Grayson 
Streed
Recommended for simulating heavy hydrocarbon systems 
with a high hydrogen content.
Activity Model Description2-12
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ThVapour Pressure Models
Vapour Pressure K-value models may be used for ideal mixtures 
at low pressures. Ideal mixtures include hydrocarbon systems 
and mixtures such as ketones and alcohols, where the liquid 
phase behaviour is approximately ideal. The models may also be 
used as first approximations for non-ideal systems. The 
following vapour pressure models are available:
Miscellaneous Types
The Miscellaneous group contains Property Packages that are 
unique and do not fit into the groups previously mentioned.
Models Description
Antoine This model is applicable for low pressure systems that 
behave ideally.
Braun K10 This model is strictly applicable to heavy hydrocarbon 
systems at low pressures. The model employs the Braun 
convergence pressure method, where, given the normal 
boiling point of a component, the K-value is calculated at 
system temperature and 10 psia (68.95 kPa).
Esso Tabular This model is strictly applicable to hydrocarbon systems at 
low pressures. The model employs a modification of the 
Maxwell-Bonnel vapour pressure model.
Property Package Description
Amine Pkg Contains thermodynamic models developed by 
D.B. Robinson & Associates for their proprietary 
amine plant simulator, AMSIM v. 7.0 plus some 
enhancements from v. 7.1 for BTX absorption. You 
can use this property package for amine plant 
simulations with Aspen HYSYS.
Amines is an optional Property Package. Contact 
your AspenTech representative for further 
information.
ASME Steam Restricted to a single component, namely H2O. 
Uses the ASME 1967 Steam Tables.
Clean Fuels Pkg Designed specifically for systems of thiols and 
hydrocarbons. 
For more information on 
the Amines package see 
Appendix C - Amines 
Property Package.2-13
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2-14 Aspen HYSYS Fluid Package 
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ThAdditional Property Package Options
Depending on the Property Package you have selected, 
additional information and options might be displayed on the 
right side of the Set Up tab. Note that not all EOSs or Activity 
models include the specifications indicated.
DBR Amine Package Similar to the Amine Pkg, but independently coded 
and maintained by DBR; can be updated anytime 
AMSIM thermo features and capabilities are 
updated. Features include advanced solving and 
flowsheet-composing capabilities through Aspen 
HYSYS, physical solvent simulation capability by 
DEPG, and improved thermodynamic model 
predictions based on newly available experimental 
data.
Infochem Multiflash Contains comprehensive library of thermodynamic 
and transport property models, a physical 
preoperty databank, methods for characterizing 
and matching the properties of petroleum fluids, 
and multiphase flashes capable of handling any 
combination of phases. This package requires a 
Aspen HYSYS Upstream license.
NBS Steam Restricted to a single component, namely H2O. 
Utilizes the NBS 1984 Steam Tables.
Neotec BlackOil Uses methods developed by Neotechnology 
Consultants, Ltd. and can be used when oil and 
gas data is limited. This package requires an 
Aspen HYSYS Upstream license.
OLI_Electrolyte Developed by OLI Systems Inc. and used for 
predicting the equilibrium properties of a chemical 
system including phase and reactions in a water 
solution.
Property Packages Specifications and Options
Equation of States EOS Enthalpy Method Specification (for most 
EOS, this option is located on the Parameters 
tab)
Activity Models Activity Model Specifications
Amine Pkg Amine Options: 
• Thermodynamic Models for Aqueous Amine 
Solutions
• Vapour Phase Model
OLI_Electrolyte OLI_Electrolyte Options:
• Initialize and View Electrolytes
• Phase and Solid options
Property Package Description
For more information on  
Infochem Multiflash, 
refer to the Aspen 
HYSYS Upstream 
Option Guide.
For more information on  
Neotec Black Oil, refer 
to the Aspen HYSYS 
Upstream Option 
Guide.
For more information on  
OLI_Electrolyte, refer to 
the Aspen HYSYS OLI 
Interface Reference 
Guide.2-14
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ThEOS Enthalpy Method Specification
The Lee-Kesler Plocker (LKP) and Zudkevitch Joffee (ZJ) 
property packages both use the Lee-Kesler enthalpy method. 
You cannot change the enthalpy method for either of these 
Equations of State. With any other Equation of State, you have a 
choice for the enthalpy method:
Activity Model Specifications
The Activity Model Specification group appears for each activity 
model. There are three specification items within this group as 
shown in the following figure.
Activity Models only perform calculations for the liquid phase, 
thus, you are required to specify the method to be used for 
solving the vapour phase. The first field in the Activity Model 
Specifications group allows you to select an appropriate Vapour 
Model for your fluid package.
Enthalpy Method Description
Equation of State With this radio button selection, the enthalpy method 
contained within the Equation of State is used.
Lee-Kesler The Lee-Kesler method is used for the calculation of 
enthalpies. 
This option results in a combined Property Package, 
employing the appropriate equation of state for 
vapour-liquid equilibrium calculations and the Lee-
Kesler equation for the calculation of enthalpies and 
entropies. 
This method yields comparable results to Aspen 
HYSYS' standard equations of state and has identical 
ranges of applicability.
Lee-Kesler enthalpies may be slightly more accurate 
for heavy hydrocarbon systems, but require more 
computer resources because a separate model must be 
solved.
 Figure 2.72-15
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2-16 Aspen HYSYS Fluid Package 
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ThThe list of vapour phase models are accessed through the drop-
down list and are described below.
The second field in the Activity Model Specifications group is the 
UNIFAC Estimation Temp. This temperature is used to estimate 
interaction parameters using the UNIFAC method. By default, 
the temperature is 25°C, although better results are achieved if 
you select a temperature that is closer to your anticipated 
operating conditions.
The third field in this group is a checkbox for the Poynting 
Correction. This checkbox toggles the Poynting correction factor, 
which by default, is selected. The correction factor is only 
available for vapour phase models. The correction factor uses 
each component's molar volume (liquid phase) in the calculation 
of the overall compressibility factor.
Models Description
Ideal The Aspen HYSYS default. It is applied for cases in which 
you are operating at low or moderate pressures.
RK The generalized Redlich Kwong cubic equation of state is 
based on reduced temperature and reduced pressure, and is 
generally applicable to all gases.
Virial Enables you to better model the vapour phase fugacities of 
systems that display strong vapour phase interactions. 
Typically this occurs in systems containing carboxylic acids, 
or other compounds that have the tendency to form stable 
hydrogen bonds in the vapour phase.
PR Uses the Peng Robinson EOS to model the vapour phase. 
Use this option for all situations to which PR is applicable.
SRK Uses the Soave Redlich Kwong EOS to model the vapour 
phase. Use this option for all situations to which SRK is 
applicable.2-16
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ThAmine Options
The following Amine options are available when the Amine pkg 
is selected.
The Thermodynamic Models for Aqueous Amine Solutions group 
contains radio buttons that enable you to select between the 
Kent-Eisenberg and Li-Mather models. 
The Vapour Phase Model group contains radio buttons that 
enable you to select between Ideal and Non-Ideal models.
DBR Amine Options
When the DBR Amine Package is selected, Aspen HYSYS will 
prompt you to launch DBR Amine.
 Figure 2.8
 Figure 2.9
Refer to the Appendix 
C.4 - Equilibrium 
Solubility for detailed 
information on each 
thermodynamic model.2-17
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2-18 Aspen HYSYS Fluid Package 
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ThClick the Launch DBRAmine button and the Model Selection 
dialog box will display. This dialog box allows you to choose 
Kent-Eisenberg, Li-Mather, or Physical Solvent.
After the Model Selection is chosen and the DRB Amine dialog 
box is closed, the COMThermo Setup displays.
DBRAmine and DBRAmineFlash are automatically selected in the 
Model Selection group for both vapor and liquid phases. Using 
DBRAmineFlash with the DBRAmine allows for better handling of 
the flash calculations of amine or DEPG cases.
The Model options group shows each property and what 
calculation method is used for that property.
 Figure 2.10
 Figure 2.112-18
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ThOLI_Electrolyte Options
If the OLI_Electrolyte property package is selected for the fluid 
package, the following electrolyte options appear on the right 
side of the property view.
After selecting electrolyte components for a component list from 
the database, a electrolyte system is established. 
The Initialize Electrolytes Environment button is used for 
the following:
• Generating a group of additional components based on 
the selected components and the setting in Phase Option 
and Solid Option below.
• Generating a corresponding Chemistry model for 
thermodynamic calculation.
The View Electrolyte Reaction in Trace Window button is 
active when the Electrolytes Environment is initialized. It allows 
you to view what reaction(s) are involved in the Thermo flash 
calculation in the trace window.
Phase Option Group
The Phase Option includes the following four phases: vapour, 
organic, solid, and aqueous. The checkboxes allow you to select 
the material phases that are considered during the flash 
calculation. 
• The vapour, organic, and solid phases may be included or 
excluded from calculations. 
 Figure 2.12
Refer to the Aspen 
HYSYS OLI Interface 
Reference Guide for 
detailed information on 
electrolytes.2-19
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2-20 Aspen HYSYS Fluid Package 
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Th• The aqueous phase must be included in all electrolyte 
simulations and is not accessible. 
By default, the vapour and solid phases are selected with the 
organic phase cleared.
The flexibility of selecting different phase combinations and the 
procedure for phase mixing used by the flash calculation is 
described in the following table:
Solid Option Group
The Solid Option group contains two checkboxes and the 
Selected Solid button. 
• Aspen HYSYS allows you to exclude all solids in your case 
by selecting the Exclude All Solids checkbox. 
• You can exclude solid components individually when the 
solid phase is included, by disabling solid components 
that are not of interest in the simulation. 
To do this, you must invoke Initialize Electrolytes 
Environment option first, and then click the Selected 
Solid button. When you click the button, you can select 
any component that you want to be included or excluded 
in all of the Electrolyte streams from the case. When the 
solid components are excluded, you have to re-initialize 
the Electrolytes Environment.
Phases Included Description of the Flash Action
Vapour and Solid Generates vapour and solid phases when they exist. If 
an organic phase appears, it is included in the vapour 
phase.
Organic and 
Solid
Generates the organic and solid phase when they exist. 
If a vapour phase appears, it is included in the organic 
phase.
Vapour and 
Organic
Generates the vapour and organic phase when they 
exist. If a solid phase appears, it is included in the 
aqueous phase.
Vapour only Generates the vapour phase when it exists. If an 
organic phase appears, it will be included in the vapour 
phase and if a solid phase appears, it is included in the 
aqueous phase.
Organic Only Generates the organic phase when it exists. If a vapour 
phase appears, it will be included in the organic phase 
and if a solid phase appears, it is included in the 
aqueous phase.
Solid Only An electrolyte case with no organic or vapour phase is 
impossible and is not be accepted.
Refer to Section 1.6.6 - 
Disabling Solid 
Components in the 
Aspen HYSYS OLI 
Interface Reference 
Guide for more 
information on including 
and excluding solids.2-20
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Th• If you select the All Scaling Tendency checkbox, all 
solids are excluded from the case. The Scaling Tendency 
Index is still calculated in the flash calculation.
Redox Options Group
The Redox Options group contains features that enable you to 
access the REDOX database. The REDOX database supports 
calculations involving the reduction and oxidation of pure metals 
and alloys to simulate the corrosion process in aqueous system.
• The Included checkbox enables you to toggle between 
including or ignoring the selected REDOX sub-system for 
the active property package.
• The Redox Subsystem Selection... button enables you 
to access the Redox Sub-Systems property view. This 
property view enables you to select the REDOX sub-
system you want to apply to the property package. 
 Figure 2.13
By default, OLI REDOX selects the redox subsystems that 
contain metals of engineering importance. This default is 
motivated by corrosion applications, for which redox 
transformations of engineering metals are important.
Refer to Section 1.6.7 - 
Scaling Tendencies of 
the Aspen HYSYS OLI 
Interface Reference 
Guide for more 
information.
Refer to REDOX section 
from Section 1.8.3 - 
Special Databases in 
the Aspen HYSYS OLI 
Interface Reference 
Guide for more 
information.2-21
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2-22 Aspen HYSYS Fluid Package 
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ThComponent List Selection Group
You must also select a Component List to associate with the 
current Fluid Package from the Component List Selection drop-
down list. 
Component Lists are stored outside of the Fluid Package 
Manager in the Components Manager and may contain 
traditional, hypothetical, and electrolyte components.
Aspen HYSYS provides a warning message when you attempt to 
associate a Component List containing incompatible and/or not 
recommended components, with your property package.
Also, if you switch between property packages, and any 
components are incompatible or not recommended for use with 
the current property package, a property view appears 
providing further options (see the following Warning Messages 
section).
Warning Messages
There are two different warning property views that you may 
encounter while modifying a Fluid Package. These situations 
arise when a Component List is installed into the Fluid Package 
and you want to select a new property package. Some 
components from the selected Component List may either not 
be recommended or are incompatible with the new property 
package selection.
 Figure 2.14
It is not recommended for users to attach the Master 
Component List to any Fluid Package. If only the master list 
exists, by default a cloned version of the Master Component 
List is created (called Component List -1). This list is 
selected initially when a new Fluid Package is created.2-22
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ThThe first property view involves the use of Non-Recommended 
components. In Aspen HYSYS, you can select components that 
are not recommended for use with the current property 
package. 
If you try to switch to another property package for which the 
components are not recommended, the following property view 
appears: 
The objects from the Components Not Recommended for 
Property Package property view are described below:
 Figure 2.15
Object Description
Not 
Recommended
The non-recommended components are listed in this 
group.
Desired Prop Pkg This field initially displays the Property Package for 
which the listed components are Not Recommended.
This field is also a drop-down list of all available 
Property Packages so you may make an alternate 
selection without returning to the Fluid Package 
property view.
Action This group box contains two radio buttons:
• Delete Components. This removes incompatible 
components from the Fluid Package.
• Keep Components. This keeps the components 
in the Fluid Package.
OK Accepts the Desired Prop Pkg with the appropriate 
Action.
Cancel Return to the Prop Pkg tab without making changes.2-23
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ThThe second dialog involves the use of Incompatible components. 
If you try to switch to a property package for which the 
components are incompatible, the following property view 
appears: 
The Objects from the Components Incompatible with Property 
Package property view are described below:
 Figure 2.16
Object Description
Incompatible 
Components
The incompatible components are listed in this group.
Desired Prop Pkg This field initially displays the Property Package for 
which the listed components are Incompatible.
This field is also a drop-down list of all available 
Property Packages so you may make an alternate 
selection without returning to the Fluid Package 
property view.
OK This button accepts the Desired Prop Pkg with the 
appropriate Action (i.e., delete the incompatible 
components).
Cancel Press this button to keep the current Property Package2-24
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Th2.4.2 Parameters Tab
The information and options displayed on the Parameters tab is 
dependent on the Property Package selection. Some Property 
Packages have nothing on the Parameters tab, while others 
display additional information required. Those Property 
Packages which have information on the Parameters tab are 
mentioned in this section.
If a value is estimated by Aspen HYSYS, it is indicated in red and 
can be modified.
GCEOS (Generalized Cubic EOS)
The Generalized Cubic Equation of State (GCEOS) is an 
alternative to the standard equation of state property packages. 
It allows you to define and customize the cubic equation to your 
own specifications.
 Figure 2.172-25
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ThGeneralized Cubic Equation of State
To gain an understanding of how to specify the GCEOS property 
package Parameters tab, you must first consider the general 
cubic equation of state form: 
where:
(2.1)
OR
(2.2)
(2.3)
(2.4)
(2.5)
P RT
v b–
----------- a T( )
v2 ubv wb2+ +
------------------------------------–=
Z3 C1Z2 C2Z C3+ + + 0=
C1 Bu B– 1–=
C2 B2w B2u– Bu– A+=
C3 B3w B2w AB+ +( )–=
Z Pv
RT
------=
A
amixP
R2T 2
--------------=2-26
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ThMRij = the mixing rule
To calculate the values of bi and ac, the cubic equation, 
Equation (2.12), is solved to find a value for . 
The value of ai in Equation (2.9) requires you to use the  
(2.6)
(2.7)
(2.8)
(2.9)
(2.10)
(2.11)
(2.12)
B
bmixP
RT
--------------=
amix xixj ai T( )aj T( ) MRij×∑∑=
bmix xibi∑=
ai T( ) acα=
ac
3 u w–( )ξ2+
3 u 1–( )ξ+
-------------------------------- uξ+⎝ ⎠
⎛ ⎞ RTcVc=
bi ξVc=
u w u+( ) w–[ ]ξ3 3 w u+( )ξ2 3ξ 1–+ + 0=
ξ
α
2-27
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2-28 Aspen HYSYS Fluid Package 
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Thterm. 
 in turn is made up of the  term.The parameter  is a 
polynomial equation containing five parameters: . 
The parameter  is also represented by a polynomial equation 
consisting of 4 parameters (A, B, C and D).
The Parameters tab for the GCEOS consists of three group 
boxes:
• GCEOS Pure Component Parameters
• GCEOS Parameters
• Initialize EOS
GCEOS Pure Component Parameters Group
This group allows you to define  by specifying the values of 
.
To specify the value of , select the kappa0 radio button and a 
property view similar to the one shown in Figure 2.18 should 
appear. The group consists of a matrix containing 4 parameters 
of Equation (2.15): A, B, C, and D for each component 
(2.13)
(2.14)
(2.15)
α T( ) 1 κ 1 TR
0.5–( )+[ ]
2
=
α κ κ
κ0 κ1 κ2 κ3 κ4 κ5,,,,,
κ0
κ κ0 κ1 κ2 κ3TR–( ) 1 TR
κ4–( )+[ ] 1 TR
0.5+( ) 0.7 TR–( ) T
κ5××+=
κ0 A Bω Cω2 Dω3+ + +=
α
κ0 to κ5
κ02-28
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Thselected in the Fluid Package. 
 Figure 2.182-29
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2-30 Aspen HYSYS Fluid Package 
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ThTo specify the remaining kappa parameters (in other words, 
), select the kappa1-5 radio button. A new matrix 
appears in the GCEOS Pure Component Parameters group. 
This matrix allows you to specify the  values for each 
component in the Fluid Package.
Volume Translation
The GCEOS allows for volume translation correction to provide a 
better calculation of liquid volume by the cubic equations of 
state. The correction is simply a translation along the volume 
axis, which results in a better calculation of liquid volume 
without affecting the VLE calculations. Mathematically, this 
volume shift is represented as:
 Figure 2.19
(2.16)
(2.17)
κ0 to κ5
κ
ṽ v xici
i 1=
n
∑+=
b̃ b xici
i 1=
n
∑+=2-30
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Thwhere:  
= translated volume
 = is the translated cubic equation of state parameter
ci = the pure component translated volume
xi = the mole fraction of component i in the liquid phase. 
The resulting equation of state appears as shown in Equations 
(2.4), (2.5) and (2.6) with b and v replaced with the 
translated values (  and ).
To specify the value of the pure component correction volume, 
ci, select the Vol. Translation radio button. A property view 
similar to the one shown in Figure 2.20 will appear. 
The GCEOS Pure Components Parameters group now contains a 
matrix containing the volume correction constants for each 
component currently selected. The matrix should initially be 
empty. You can enter your own values into this matrix or click 
the Estimate button and have Aspen HYSYS estimate values for 
you. ci is estimated by matching liquid volume at normal boiling 
point temperature with that of the liquid volume obtained from 
an independent method (COSTALD).
Aspen HYSYS only estimates the correction volume constant for 
those components whose cells have no value (i.e., they contain 
0.000). If you specify one value in the matrix and click the 
 Figure 2.20
ṽ
b̃
ṽ b̃2-31
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2-32 Aspen HYSYS Fluid Package 
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ThEstimate button, you are only estimating those empty cells. 
GCEOS Parameters Group
The GCEOS Parameters group allows you to specify the u and w 
parameters found in Equations (2.3) to (2.15).
The following table lists the u and w values for some common 
equations of state:
Equation Status Bar
The GCEOS Parameter group also contains the Equation Status 
Bar. It tells you the status of the equation definition. There are 
two possible messages and are described as follows:
To estimate a cell containing a previously entered value, 
select the cell, delete the current value and click the 
Estimate button.
EOS u w
van der Waals 0 0
Redlich-Kwong 1 0
Peng-Robinson 2 -1
Message Description
This message appears if poor values are chosen for u 
and w.
If the values selected for u and w are suitable this 
message appears. 2-32
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ThInitialize EOS
The Initialize EOS drop-down list allows you to initialize GCEOS 
Parameters tab with the default values associated with the 
selected Equation of State.
The four options available are as follows:
• van der Waals Equation
• SRK Equation
• PR Equation
• PRSV Equation
Glycol Property Package
The following options appear on the Parameters tab when the 
Glycol property package is selected:
• Enthalpy
• Density
• Use Water Gas kij2-33
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ThEnthalpy
The Peng-Robinson package offers two options for Enthalpy,
Density
The two options for Density are Use EOS Density and 
COSTALD (default).
COSTALD
When COSTALD is selected, the Smooth Liquid Density 
checkbox will appear in the Parameters area. This checkbox is 
selected as the default.
In previous versions to Aspen HYSYS 3.0, these property 
packages used the Costald liquid density model. This method 
was only applied when the reduced temperature (Tr) was less 
than unity. When the reduced temperature exceeded unity, it 
switched to the EOS liquid density. Hence, at Tr=1 there is a 
sharp change (discontinuity) in the liquid density causing 
problems especially in dynamics mode. 
Enthalpy Method Description
Equation of State The enthalpy method contained within the Equation of 
State is used.
Lee-Kesler Lee-Kesler method is used for calculating enthalpy, 
resulting in a combined Property Package, employing 
the appropriate equation of state for vapour-liquid 
equilibrium calculations and the Lee-Kesler equation 
for the calculation of enthalpies and entropies. 
This method yields comparable results to the Aspen 
HYSYS standard equations of state and has identical 
ranges of applicability.
Lee-Kesler enthalpies may be slightly more accurate 
for heavy hydrocarbon systems, but require more 
computer resources because a separate model must be 
solved.2-34
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Fluid Package 2-35
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ThFor older cases including HYSIM cases, the density smoothing 
option is not selected. This means that liquid densities in cases 
using the smoothing option may differ from those cases in the 
past.
By default, new cases have COSTALD and the Smoothing 
Liquid Density option selected, so that Aspen HYSYS 
interpolates the liquid densities from Tr=0.95 to Tr=1.0, giving 
a smooth transition. It should be noted that the densities differ 
if the option is not selected.
If both the Use EOS Density and Smooth Liquid Density boxes 
are not selected, the behaviour and results are the same as 
before (previous to Aspen HYSYS 3.0) and can cause problems 
as discussed earlier.
Kabadi Danner
The Kabadi Danner Property Package uses Group Parameters 
that are automatically calculated by Aspen HYSYS. The values 
are generated from Twu's method. 
Costald typically gives better liquid densities and smoothing 
near Tr=1 is common.
 Figure 2.212-35
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2-36 Aspen HYSYS Fluid Package 
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ThPeng-Robinson
The following options appear on the Parameters tab when the 
Peng-Robinson package is selected:
• Enthalpy
• Density
• Modify H2 Tc and Pc
• Indexed Viscosity
• Peng-Robinson Options
 Figure 2.222-36
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ThEnthalpy
The Peng-Robinson package offers two options for Enthalpy,
Density
The two options for Density are Use EOS Density and 
COSTALD (default).
COSTALD
When COSTALD is selected, two options appear on the 
Parameters tab:
• Smooth Liquid Density
• Pressure Correction
The Smooth Liquid Density checkbox is selected as the 
default.
In previous versions to Aspen HYSYS 3.0, these property 
packages used the Costald liquid density model. This method 
was only applied when the reduced temperature (Tr) was less 
than unity. When the reduced temperature exceeded unity, it 
switched to the EOS liquid density. Hence, at Tr=1 there is a 
sharp change (discontinuity) in the liquid density causing 
problems especially in dynamics mode. 
Enthalpy Method Description
Equation of State The enthalpy method contained within the Equation of 
State is used.
Lee-Kesler Lee-Kesler method is used for calculating enthalpy, 
resulting in a combined Property Package, employing 
the appropriate equation of state for vapour-liquid 
equilibrium calculations and the Lee-Kesler equation 
for the calculation of enthalpies and entropies. 
This method yields comparable results to the Aspen 
HYSYS standard equations of state and has identical 
ranges of applicability.
Lee-Kesler enthalpies may be slightly more accurate 
for heavy hydrocarbon systems, but require more 
computer resources because a separate model must be 
solved.2-37
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2-38 Aspen HYSYS Fluid Package 
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ThFor older cases including HYSIM cases, the density smoothing 
option is not selected. This means that liquid densities in cases 
using the smoothing option may differ from those cases in the 
past.
By default, new cases have COSTALD and the Smoothing 
Liquid Density option selected, so that Aspen HYSYS 
interpolates the liquid densities from Tr=0.95 to Tr=1.0, giving 
a smooth transition. The densities differ if the option is not 
selected.
If both the Use EOS Density and Smooth Liquid Density boxes 
are not selected, the behaviour and results are the same as 
before (previous to Aspen HYSYS 3.0) and can cause problems 
as discussed earlier.
The Pressure Correction drop down menu offers two options:
• Chueh-Prausnitz’s Equation
• Tait’s Equation
The Chueh-Prausnitz equation is:
where:
 = molar density
Vs = saturated molar volume at T by COSTALD model
B = functions of (P, Ps, T, , Tc, Pc)
P = systems pressure
Ps = saturated pressure at T
n = constant
Costald typically gives better liquid densities and smoothing 
near Tr=1 is common.
(2.18)ρ 1 Vs⁄( ) 1 B+( )n=
ρ
ω
2-38
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ThTait’s equation is
Vs  = the saturated volume at T by COSTALD model
P = the system pressure
Ps  = the saturated pressure at T
C and B  are funtions of (T, , Tc, Pc)
EOS Density and Volume Translation
When Use EOS Density is selected, Volume Translation 
information appears in the Parameters area. Volume Translation 
is a widely used empirical method to improve the accuracy of 
the liquid density calculated by the EOS.
The matrix contains the volume correction constants for each 
component currently selected. The default value for each 
component is zero. You can enter your own values into this 
matrix, or you can click the Estimate Vol. Trans. button and 
have Aspen HYSYS estimate all the missing values for you.
Aspen HYSYS offers two methods of estimating the volume 
translation parameter: COSTALD (default) and RACKETT. The 
RACKETT model incorporates temperature dependence, whereas 
the COSTALD model includes both temperature and pressure 
dependence.
(2.19)V Vs 1 C B P+
B Ps+
---------------⎝ ⎠
⎛ ⎞ln–=
ω
2-39
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2-40 Aspen HYSYS Fluid Package 
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ThFor COSTALD, the liquid volume model is: 
where:
 and  are functions of  for  
The mixing rules for COSTALD are:
where:
The RACKETT model calculates liquid molar volume as a 
function of temperature.
The equation for the RACKETT model is:
(2.20)
(2.21)
(2.22)
(2.23)
(2.24)
(2.25)
Vmsat VmCTDVmR 0, 1 ωVmR δ,–( )=
VmR 0, VmR δ, Tr 0.25 T< r 1.0≤2-40
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Thwhere:
R = the universal gas constant
Tc = the critical  temperature, 
Pc = the critical pressure
Zm
RA = the RACKETT parameter,  
Vcm = the critical molar volume, 
The binary interaction parameter kij is estimated automatically 
using the following equation: 
(2.26)
Tc
Pc
----- xi
Tci
Pci
------
i
∑=
xiVci
i
∑
Tr
T
Tc
----=2-41
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2-42 Aspen HYSYS Fluid Package 
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ThModify H2 Tc and PC
When Modify H2 Tc and PC is selected, the critical 
temperature and pressure of hydrogen is modified as a function 
of temperature. This feature produces better results for 
simulation systems containing hydrogen.
Indexed Viscosity
The Indexed Viscosity option enables you to toggle between two 
methods/rules used to calculate the blended liquid viscosity.
When you select Indexed Viscosity, the Viscosity Index 
Parameters property view that is associated to the active fluid 
package appears.
In the Viscosity Index Parameters group, you specify the value 
for each of the three parameters used in the linearized viscosity 
calculation. The equation below the table displays how each 
parameter is used in the Twu and Bulls (1981)2 calculation.
Theory
Viscosity cannot be blended linearly, so a methodology is 
adopted that substitutes a function of the measured viscosity 
that is approximately linear with temperature. A linearized 
equation for viscosity is given by Twu and Bulls (1981)2:
Description
Aspen HYSYS 
Viscosity
Provides an estimate of the apparent liquid viscosity of 
an immiscible hydrocarbon liquid-aqueous mixture 
using only the viscosity and the volume fraction of the 
hydrocarbon phase
Indexed 
Viscosity
Uses a linearized viscosity equation from Twu and Bulls
(2.27)
For more information on 
viscosity mixing rules, 
refer to Indexed 
Viscosity Mixing Rule in 
Section 2.4.1 - Set Up 
Tab
10 10log(( ) v 0.7+( ) )log m 10T b+log=2-42
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Thwhere:  
T = absolute temperature °R
v = kinematic viscosity in cSt
The above equation can be simplified to the following 
expression:
where:  
a = constant at a fixed temperature
v = kinematic viscosity in cSt
c = adjustable parameter
b = constant
This expression is linearly blended for the mixture. From there,  
the kinematic viscosity is calculated.
Pure Component
Aspen HYSYS calculates the viscosity of a pure compound based 
on the component class designation as well as the phase in 
which the component is present as well as a temperature range:
Each viscosity model is based on the corresponding states 
principle. A complete description of the corresponding stages 
NBS model used for viscosity prediction used by Ely and Hanely 
is given in the NBS publication3. This model was modified to 
eliminate the iterative procedure for calculating the system 
shape factors. The generalized Leech-Leland shape factor 
models have been replaced by component specific models. 
Although the modified NBS models handles most hydrocarbons 
(2.28)
System Vapor Liquid
Light HCs (NBP<155F) Modified Ely and Hanley Ely and Hanely
Heavy HCs Modified Ely and Hanley Twu
Modified Letsou-Stiel Modified Ely and Hanely Modified Letsou-Stiel
a 10 10log(( ) v c+( ) )log b+2-43
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Thwell, the Twu method is known to do a better job of predicting 
the viscosity of heavy hydrocarbon liquids. The Twu model is 
also based on the corresponding states principle and uses a 
viscosity correlation for n-alkanes as its reference fluid instead 
of methane. 
Experimental viscosity curves can be supplied via hypothetical 
properties or user data in Aspen HYSYS directly by mapping the 
library component as a hypothetical.
Peng-Robinson Options
The Peng-Robinson package has two options.
PR-Twu
Parameter tab options for the PR-Twu package are essentially 
the same as for the Peng-Robinson package with the following 
exceptions:
• Modify H2 Tc and Pc option is not available
• User Water Gas Kij option is available
• No Volume Translation options are available if Use EOS 
Density is selected
Estimations for viscosity can be further improved over 
internal estimation routines by supplying the experimental 
viscosity for a hypothetical component.
Option Description
Aspen 
HYSYS
The Aspen HYSYSPR EOS is similar to the PR EOS with several 
enhancements to the original PR equation. It extends its range 
of applicability and better represents the VLE of complex 
systems.
Standard This is the standard Peng Robinson (1976) equation of state, a 
modification of the RK equation to better represent the VLE of 
natural gas systems accurately.
For more information on 
property packages, refer 
to Appendix A.3.1 - 
Equations of State.2-44
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ThPeng-Robinson Stryjek Vera (PRSV)
In the Options grouping, PRSV offers two option for calculating 
enthalpy.
In the Parameters grouping, PRSV uses an empirical factor, 
Kappa, for fitting pure component vapour pressures.
Sour PR and Sour SRK
Parameter tab options for the Sour PR and Sour SRK packages 
are essentially the same as for the Peng-Robinson package, with 
the following exceptions:
• The Peng-Robinson Option is not available
• No Volume Translation options are available if Use EOS 
Density is selected
Enthalpy Method Description
Equation of State The enthalpy method contained within the Equation of 
State is used.
Lee-Kesler The Lee-Kesler method is used for the calculation of 
enthalpies. 
This option results in a combined Property Package, 
employing the appropriate equation of state for 
vapour-liquid equilibrium calculations and the Lee-
Kesler equation for the calculation of enthalpies and 
entropies. 
This method yields comparable results to the Aspen 
HYSYS standard equations of state and has identical 
ranges of applicability.
Lee-Kesler enthalpies may be slightly more accurate 
for heavy hydrocarbon systems, but require more 
computer resources because a separate model must be 
solved.
 Figure 2.232-45
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ThSRK
Parameter tab options for the Sour PR, Sour SRK, and SRK 
packages are essentially the same as for the Peng-Robinson 
package, with the exception that the Peng-Robinson Option is 
not available.
SRK-Twu and Twu-Sim-Tassone
Parameter tab options for the SRK-Twu and Twu-Sim-Tassone 
packages are essentially the same as for the SRK package with 
the following exceptions:
• Modify H2 Tc and Pc option is not available
• Use Water Gas Kij option is available
• No Volume Translation options are available if Use EOS 
Density is selected
Zudkevitch Joffee
This Property Package uses a b zero Parameter. Aspen HYSYS 
sets the b zero parameter of the ZJ equation to be zero.
 Figure 2.242-46
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ThChien Null
The Chien Null model provides a consistent framework for 
applying different activity models on a binary by binary basis. 
On the Parameters tab, you can specify the Activity Model to be 
used for each component pair, as well as two additional pure 
component parameters required by the model.
The two groups on the Parameters tab for the Chien Null 
property package are:
• Chien Null Component Parameters
• Chien Null Binary Component Parameters
Component Parameters
Values for the Solubility and Molar Volume are displayed for 
each library component and estimated for hypotheticals.
The Molar Volume parameter is used by the Regular Solution 
portion of the Chien Null equation. The Regular Solution is an 
Activity Model choice for Binary pair computations.
 Figure 2.252-47
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ThBinary Component Parameters
All of the components in the case, including hypotheticals, are 
listed in the matrix. You can view the details for the liquid and 
vapour phase calculations by selecting the appropriate radio 
button: 
• Liq Activity Models
• Virial Coefficients
By selecting the Liq Activity Models radio button, you can specify 
the Activity Model that Aspen HYSYS uses for the calculation of 
each binary. The matrix displays the default property package 
method selected by Aspen HYSYS for each binary pair. 
The choices are accessed by highlighting the drop-down list in 
each cell. If Henry's Law is applicable to a component pair, 
Aspen HYSYS selects this as the default property method. When 
Henry's Law is selected by Aspen HYSYS, you cannot modify the 
model for the binary pair.
In the previous property view, NRTL was selected as the default 
property package for all binary pairs. You can use the default 
selections, or you can set the property package for each binary 
pair. Remember that the selected method appears in both cells 
representing the binary. Aspen HYSYS may filter the list of 
options according to the components involved in the binary pair.
 Figure 2.26
The Property Packages available in the drop-down list are:
• None Required
• Henry
• van Laar
• Margules
• NRTL
• Scatchard
• Reg Soln
• General2-48
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ThBy selecting the Virial Coefficients radio button, you can view 
and edit the virial coefficients for each binary. Values are only 
shown in this table when the Virial Vapour model is selected on 
the Set Up tab. You can use the default values suggested by 
Aspen HYSYS or edit these values. Virial coefficients for the pure 
species are shown along the diagonal of the matrix table, while 
cross coefficients, which are mixture properties between 
components, are those not along the diagonal.
Wilson
The Molar Volume for each library component is displayed, as 
well as those values estimated for hypotheticals.
Chao Seader & Grayson Streed
The Chao Seader and Grayson Streed models also use a Molar 
Volume term. Values for Solubility, Molar Volume, and 
Acentricity are displayed for library components. The 
parameters are estimated for hypotheticals.
 Figure 2.27
 Figure 2.282-49
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ThAntoine
Aspen HYSYS uses a six term Antoine expression, with a fixed F 
term. For library components, the minimum and maximum 
temperature and the coefficients (A through F) are displayed for 
each component. The values for Hypothetical components are 
estimated.
Benedict-Webb-Rubin-Starling 
(BWRS)
The Benedict-Webb-Rubin-Starling property package uses 11 
pure-component parameters.
 Figure 2.29
The BWRS pure-component parameters are:
• B0
• A0
• C0
• gamma
• b
• a
• alpha
• c
• D0
• d
• E02-50
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ThFor 15 compounds, the pure-component parameters are built-in 
to the property package and stored in the database. For other 
compounds, these parameters are automatically calculated 
using Tc, Vc, and acentric factor by Aspen HYSYS. The values 
are generated from Han-Sterling correlations.
2.4.3 Binary Coefficients Tab
The Binary Coefficients (Binary Coeffs) tab contains a matrix 
table which lists the interaction parameters for each component 
pair. Depending on the property method selected, different 
estimation methods may be available and a different property 
view may be shown. You have the option of overwriting any 
library value.
The cells with unknown interaction parameters contain dashes (-
--). When you exit the Basis Manager, unknown interaction 
parameters are set to zero.
For all matrices on the Binary Coeffs tab, the horizontal 
components across the top of the matrix table represent the "i" 
component and the vertical components represent the "j" 
component.
Compounds with Built-in parameters are:
• Methane
• Ethane
• Propane
• I-Butane
• n-Butane
• I-Pentane
• n-Pentane
• n-Hexane
• n-Heptane
• n-Octane
• Ethylene
• Propylenen
• N2
• CO2
• H2S
Note: The Binary Cooeffs tab for the Glycol Property package 
contains a page for both EOS and Activity Model Interaction 
Parameters.2-51
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ThGeneralized Cubic Equation of State 
Interaction Parameters
When GCEOS is the selected property package on the Set Up 
tab, the Binary Coeffs tab appears as shown below. 
The GCEOS property package allows you to select mixing 
methods used to calculate the equation of state parameter, aij. 
Aspen HYSYS assumes the following general mixing rule:
where:  
MRij = the mixing rule parameter. 
 Figure 2.30
(2.29)aij aiajMRij=2-52
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ThThere are seven methods to choose for MRij:
Equation
(2.30)
(2.31)
(2.32)
(2.33)
where: 
(2.34)
MRij T( ) 1 Aij BijT CijT
2
+ +–( )=
MRij T( ) 1 Aij BijT Cij T⁄+ +–( )=
MRij T( ) 1 xi Aij BijT CijT
2
+ +( )– xj Aji BjiT CjiT
2
+ +( )–=
MRij T( ) 1 xi Aij BijT Cij T⁄+ +( )– xj Aji BjiT Cji T⁄+ +( )–=
MRij T( ) 1
kij kji×( )
xikij xjkji+
--------------------------–=
kij Aij BijT CijT
2+ +=2-53
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ThEach mixing rule allows for the specification of three 
parameters: Aij, Bij, and Cij, except for the Wong Sandler mixing 
rule which has the Aij and Bij parameter and also requires you to 
provide NRTL binary coefficients. 
The parameters are available through the three radio buttons in 
the upper left corner of the tab: Aij, Bij, and Cij/NRTL. By 
selecting a certain parameter’s radio button you may view the 
associated parameter matrix table. 
Wong Sandler Mixing Rule
The Wong Sandler1 mixing rule is a density independent mixing 
rule in which the equation of state parameters amix and bmix of 
any cubic equation of state are determined by simultaneously 
solving: 
where: 
(2.35)
Wong Sandler Mixing Rule - Refer to Wong Sandler Mixing Rule 
section for more information.
When selecting the Cij/NRTL radio button you are specifying 
the Cij parameter unless you are using the Wong Sandler 
mixing rule. In this case you are specifying NRTL binary 
coefficients used to calculate the Helmholtz energy.
Equation
MRij T( ) 1
kij kji×( )
xikij xjkji+
--------------------------–=
kij Aij BijT
Cij
T
------+ +=2-54
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Th• the excess Helmholtz energy at infinite pressure.
• the exact quadratic composition dependence of the 
second virial coefficient. 
To demonstrate this model, consider the relationship between 
the second viral coefficient B(T) and the equation of state 
parameters a and b:
Consider the quadratic composition dependence of the second 
virial coefficient as:
Substitute B with the relationship in Equation (2.36):
To satisfy the requirements of Equation (2.38), the 
relationship for amix and bmix are:
with:
(2.36)
(2.37)
(2.38)
(2.39)
(2.40)
B T( ) b a
RT
------–=
Bm T( ) xixjBij T( )
j
∑
i
∑=
bmix
amix
RT
----------– xixj b a
RT
------–⎝ ⎠
⎛ ⎞
i jj
∑
i
∑=
bmix
xixj b a
RT
------–⎝ ⎠
⎛ ⎞
i jj
∑
i
∑
1 F x( )
RT
----------–
------------------------------------------------=
amix bmixF x( )=2-55
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Thwhere:  
F(x) = is an arbirtrary function
The cross second virial coefficient of Equation (2.8) can be 
related to those of pure components by the following 
relationship:
The Helmholtz free energy departure function is the difference 
between the molar Helmholtz free energy of pure species i and 
the ideal gas at constant P and T. 
The expression for Ae is derived using lattice models and 
therefore assumes that there are no free sites on the lattice. 
This assumption can be approximated to the assumption that 
there is no free volume. Thus for the equation of state: 
bmix can be approximated by the following:
(2.41)
(2.42)
(2.43)
(2.44)
b a
RT
------–⎝ ⎠
⎛ ⎞
ij
bi
ai
RT
------–⎝ ⎠
⎛ ⎞ bj
aj
RT
------–⎝ ⎠
⎛ ⎞+
2
---------------------------------------------------- 1 Aij– BijT–( )=
Ai T P,( ) Ai
IG T P,( )– P vd
v ∞=
vi
∫–
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎛ ⎞ RT
v
------ vd
v ∞=
RT
P
------
∫–
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎛ ⎞
–=
viP ∞→
lim bi=
vmixP ∞→
lim bmix=
bmix
xixj b a
RT
------–⎝ ⎠
⎛ ⎞
ijj
∑
i
∑
1
A∞
e x( )
RT
--------------
⎝ ⎠
⎜ ⎟
⎛ ⎞
xi
ai
biRT
-----------⎝ ⎠
⎛ ⎞
i
∑–+
-----------------------------------------------------------------=2-56
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Ththerefore amix is:
and F(x) is:
The Helmholtz free energy, , is calculated using the NRTL 
model. You are required to supply the binary coefficient values 
on the parameters matrix when the Cij/NRTL radio button is 
selected.
(2.45)
(2.46)
 term is equal to 0.3.
amix
bmix
---------- xi
ai
bi
--- A∞
e x( )–
i
∑=
F x( ) xi
ai
bi
--- A∞
e x( )–
i
∑=
A∞
e x( )
α
2-57
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ThEquation of State Interaction 
Parameter
The Equation of State Interaction Parameters group for a 
selected EOS property package is displayed on the Binary Coeffs 
tab.. 
The numbers displayed in the table are initially calculated by 
Aspen HYSYS, but you can modify them. All known binary 
interaction parameters are displayed, with unknowns displayed 
as dashes (---). You have the option of overwriting any library 
value.
 Figure 2.31
This information applies to the following Property Packages:
• Kabadi Danner
• Lee-Kesler Plocker
• Glycol
• PR
• PRSV
• Soave Redlich Kwong, SRK
• Sour PR
• Sour SRK
• Zudkevitch Joffee
• BWRS
These two radio buttons only 
appear for the PR and SRK based 
Equations of State.
This is equivalent to no Kij2-58
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ThFor all Equation of State parameters (except PRSV), Kij = Kji, so 
when you change the value of one of these, both cells of the pair 
automatically update with the same value. In many cases, the 
library interaction parameters for PRSV do have Kij = Kji, but 
Aspen HYSYS does not force this if you modify one parameter in 
a binary pair.
If you are using PR or SRK (or one of the Sour options), two 
radio buttons are displayed at the bottom of the tab.
Activity Model Interaction 
Parameters
The Activity Model Interaction Parameters group, as displayed 
on the Binary Coeffs tab when an Activity Model is the selected 
property package, is shown in the figure below. 
Radio Button Description
Estimate HC-HC/
Set Non HC-HC 
to 0.0
This radio button is the default selection. Aspen HYSYS 
provides the estimates for the interaction parameters 
in the table, setting all non-hydrocarbon pairs to 0.
Set All to 0.0 When this is selected, Aspen HYSYS sets all interaction 
parameter values in the table to 0.0.
 Figure 2.32
The numbering and naming of the radio buttons selections 
vary according to the selected Activity Model.2-59
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ThThe interaction parameters for each binary pair are displayed; 
unknown values will show as dashes (---). You can overwrite 
any value or use one of the estimation methods. The estimation 
methods are described in the following section.
To display a different coefficient matrix (i.e., Bij), select the 
appropriate radio button.
Estimation Methods
When using Activity Models, Aspen HYSYS provides three 
interaction parameter estimation methods. Select the 
estimation method by selecting one of the following radio 
buttons and then invoke the estimation by selecting one of the 
available buttons:  
This information applies to the following property packages:
• Chien Null
• Extended NRTL
• General NRTL
• Glycol
• Margules
• NRTL
• UNIQUAC
• Wilson
You may reset the binary parameters to their original library 
values by clicking the Reset Params button.
Button Description
 UNIFAC 
VLE 
Aspen HYSYS calculates parameters using the UNIFAC VLE 
model.
UNIFAC 
LLE 
Aspen HYSYS calculates all parameters using the UNIFAC LLE 
model.
Immiscible The three buttons used for the UNIFAC estimations are 
replaced by the following:
• Row in Clm Pair. Use this button to estimate the 
parameters such that the row component (j) is 
immiscible in the column component (i).
• Clm in Row Pair. Use this button to estimate 
parameters such that the column components (j) are 
immiscible in the row components (i).
• All in Row. Use this button to estimate parameters 
such that both components are mutually immiscible.
Alphaij = Alphaji, but Aij  Aji.≠2-60
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ThIf you have selected either the UNIFAC VLE or UNIFAC LLE 
estimation method, you can apply it in one of the following 
ways, by selecting the appropriate button:
Since the Wilson equation does not handle three phase 
systems, the Coeff Estimation group does not show the 
UNIFAC LLE or Immiscible radio buttons when this property 
package is used.
UNIFAC estimations are by default performed at 25°C, unless 
you change this value on the Set Up tab.
Button Description
Individual 
Pair
This button is only visible when UNIFAC VLE is selected. It 
calculates the parameters for the selected component pair, 
Aij and Aji. The existing values in the matrix are 
overwritten. 
Unknowns 
Only
If you delete the contents of cells or if Aspen HYSYS does 
not provide defaults values, you can use this option and 
have Aspen HYSYS calculate the activity parameters for all 
the unknown pairs.
You may reset the binary parameters to their original library 
values by clicking the Reset Params button.
All Binaries Recalculates all the binaries in the matrix. If you had 
changed some of the original Aspen HYSYS values, you can 
use this to have Aspen HYSYS re-estimate the entire 
matrix.2-61
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Th2.4.4 Stability Test Tab
The stability test can be thought of as introducing a "droplet" of 
nucleus into the fluid. The droplet then either grows into a 
distinctive phase or is dissolved in the fluid.
For multi-phase fluids, there exist multiple false calculated 
solutions. A false solution exists when convergence occurs for a 
lower number of phases than exists in the fluid. For example, 
with a three-phase fluid, there is the correct three-phase 
solution, at least three false two-phase solutions and multiple 
false single-phase solutions. A major problem in converging the 
flash calculation is arriving at the right solution without a prior 
knowledge of the number of equilibrium phases.
The Stability Test allows you to instruct Aspen HYSYS on how to 
perform phase stability calculations in the Flowsheet. If you 
encounter situations where a flash calculation fails or you are 
suspicious about results, you can use this option to approach 
the solution using a different route.
The strategy used in Aspen HYSYS is as follows: unless there is 
strong evidence for three phases, Aspen HYSYS first performs a 
two-phase flash. The resulting phases are then tested for their 
stability.
 Figure 2.332-62
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ThDynamic Mode Flash Options Group
Aspen HYSYS enables you to modify the flash calculation 
methods to be used. There are three setting options available:
If the IOFlash option is selected, the Pressure Flow Solver group 
on the Dynamics page of the Preferences options allows the 
flash to be solved simultaneously with heat transfer equations. 
The option can result in a further significant speed increase, but 
should only be used if the case is stable using IO.
Flash Option Description
Try IOFlash 
first
This activates an alternative optimized Inside-Out flash 
algorithm that may provide a significant speed 
improvement in many cases. It is aimed at dynamics 
mode, but operates in steady state mode as well. The flash 
can handle rigorous three phase calculations using the 
Stability Test Parameters settings, although it is not tested 
as well as the default flash algorithms and does not work 
with all property packages. If you experience problems 
that are flash related, try selecting or deselecting the 
option. For maximum speed in two phase systems, you can 
also set the Maximum Phases Allowed for the fluid package 
to two in the Stability Test Parameters group, or set the 
Method to none to disable the test.
If the IOFlash fails, Aspen HYSYS will immediately go to 
method selected in the Secant Flash Options group. 
The remaining options are for the dynamic mode secant flash 
options.
Flash3 This is the default secant flash algorithm used in dynamics 
mode. It is fast, but does not perform rigorous phase 
stability tests based on the option set in the Stability Test 
Parameters group. Hence, it may not always detect a 
second liquid phase when it is present.
Multi Phase This is a secant flash algorithm that performs phase 
stability testing according to the settings in the Stability 
Test Parameters group. This option is typically slower than 
the flash3 option. It can be used when multiple liquid 
phases are important or in rare cases where using the 
flash3 option results in instabilities due to the second liquid 
phase not being detected consistently.
Use Multi 
Phase 
Estimates
The checkbox becomes available when you select Multi 
Phase as the Secant Flash Option. If the case consist of 
three phases, estimates are passed to the flash which 
speeds up some flashes.
COMThermo is not optimized for dynamics mode and may 
result in performance issues if used in dynamics mode.
 
2-63
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ThIf a dynamics case has more than one liquid phase (or if a single 
liquid phase is aqueous or a hydrocarbon), it is recommended 
that you use the Phase Sorting Method for the fluid package on 
the Section 2.4.5 - Phase Order Tab. By default, phases are 
sorted on density and phase types. If the phase type changes, 
instabilities may result. The Phase Sorting Methods allow you to 
clearly define the order in which phases should be defined so 
that they are consistent.
Stability Test Parameters Group
You can specify the maximum number of phases allowed (2 or 
3) in the Maximum Phases Allowed input cell. If this value is set 
to 2, the stability test quits after 2-phase flashes. Occasionally, 
you may still get 3 phases, as the flash may attempt to start 
directly with the 3-phase flash.
The Stability scheme used is that proposed by Michelson. In the 
Method group, you can select the method for performing the 
stability test calculations by selecting one of the following radio 
buttons:
Radio Button Description
None No stability test is performed.
Low Uses a default set of Phases/Components to Initiate the 
Stability Test. This method includes the Deleted phases (if 
they exist), the Wilson's Equation initial guess and the 
Water component (if it exists) in the fluid.
Medium In addition to the options used for the Low method, this 
method also includes the Average of Existing phase, the 
Ideal Gas phase and the heaviest and lightest components 
in the fluid.
All All available Phases and Components are used to initiate 
the test.2-64
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ThPhases to Initiate Test
There are four choices listed within the Phase(s) to Initiate Test 
group. These checkboxes are selected according to the radio 
button selection in the Method group. If you change the status 
of any option, the radio button in the Method group is 
automatically set to User. 
If any one of these initiating nuclei (initial guesses) forms a 
distinctive phase, the existing fluid is unstable and this nucleus 
provides the initial guess for the three-phase flash. If none of 
these initial guesses shows additional phases, it can only be said 
that the fluid is likely to be stable.
One limitation with the stability test is the fact that it relies on 
the property package chosen rather than physical reality. At 
best, it is as accurate as the property package. For instance, the 
NRTL package is known to be ill-behaved in the sense that it 
could actually predict numerous equilibrium phases that do not 
exist in reality. Thus, turning on all initial guesses for NRTL may 
not be a good idea.
User Allows you to activate any combination of checkboxes in 
the Phase(s) to Initiate Test and Comp(s) to Initiate Test 
groups. If you make changes when a default Method radio 
button (i.e., Low, Medium) is selected, the method will be 
changed to User automatically.
HYSIM Flash This is the flash method used in HYSIM. If this choice is 
selected, Aspen HYSYS will use the same flash routines as 
in HYSIM and no stability test will be performed. This option 
allows comparison of results between HYSIM and Aspen 
HYSYS. This stability option is not recommended for 
dynamics mode. Use the default flash3 option with the 
stability parameter set to none.
Checkboxes Description
Deleted If a phase is removed during the 2-phase flash, a droplet of 
the deleted fluid is re-introduced.
Average of 
Existing
The existing equilibrium fluids are mixed in equal portions; 
a droplet of that fluid is introduced.
Ideal Gas A small amount of ideal gas is introduced.
Wilson's 
Equation
A hypothetical fluid is created using the Wilson's K-value 
and is used to initiate the stability test.
Radio Button Description2-65
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ThTemperature Limits
The temperature limits are intended to be used in dynamics 
mode and are set to stop the flash when the limits are attained. 
If the limits are reached, then dynamics will extrapolate 
thereafter. The limits avoid potential problems with some 
property packages at low temperatures and during severe 
process upsets where you would get numerical errors and heat 
exchanger convergence problems.
Components to Initiate Test
When a droplet of nucleus is introduced into the fluid, the 
droplet either grows into a distinctive phase or is dissolved in 
the fluid. Another obvious choice for the droplet composition is 
one of the existing pure components. For example, if the fluid 
contains hexane, methanol and water, one could try introducing 
a droplet of hexane, a droplet of methanol or a droplet of water. 
The choices for the pure component droplets are listed in the 
Comp(s) to Initiate Test group.
2.4.5 Phase Order Tab
The Phase order feature is intended for dynamics. Aspen HYSYS 
dynamics always uses three phases for streams and fluids in the 
stream property view. For each unit operation, dynamics also 
assumes that the same material is in the same phase slot for all 
of the connected streams. The order of the first phase is always 
vapour and the second phase is liquid. The third phase may be 
aqueous or it can be a second liquid phase. 
By default, Aspen HYSYS sorts these phases based on their Type 
(liquid or aqueous) and Phase Density. However, subtle changes 
to the stream properties may change the order. Stream 
properties displayed as a liquid phase in one instance may be 
displayed as an aqueous phase in another. For example, inside a 
tray section the composition of a phase may change so that 
instead of being aqueous it is a liquid phase. The phase moves 
to a different slot in the fluid. This can cause disturbances in 
Refer to Section 12.2 - 
Material Stream 
Property View of the 
Aspen HYSYS 
Operations Guide for 
more information on 
stream properties.2-66
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Thdynamics mode. 
The Phase Sorting Method includes two options and is shown 
below.
Use Phase Type and Density
This option can cause instabilities in dynamics. In practice if 
small spikes are identified and an examination of the flowsheet 
reveals that some material appears in different phase slots in 
different parts of the flowsheet (where the spikes originate) 
than the user specified option is recommended.
Use User Specified Primary 
Components
The Use User Specified Primary Components option displays the 
Select Primary Phase Components group that allows you to 
specify which components should be in phase slot 1 and which 
components should be in phase slot 2. These checks are used to 
determine the phase order wherever the fluid package in 
question is used.
 Figure 2.34
This option changes the order of phases in steady state as 
well. Although in steady state many of the calculations 
depend on the phase type and not the order, and hence 
should not have any significant impact. 2-67
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ThIf there is only one non-vapour phase present and the mole 
fractions of the primary component adds up to more than the 
specified threshold, it is considered to belong in phase slot 1 and 
of type “liquid 1”. Otherwise the ratio of primary component for 
the two choices is examined.
This option is recommended when:
• a simulation is performed and it has more than one liquid 
phase.
• the densities of the two liquid phases may be close.
• one or more phases is close to being labelled either 
aqueous or liquid.
2.4.6 Reactions Tab
Within the Basis Environment, all reactions are defined through 
the Reaction Manager (Reactions tab of the Simulation Basis 
Manager). On the Rxns tab of the Fluid Package property view, 
you are limited to attaching/detaching reaction sets.
Changing this option does not resolve the case or 
immediately update the affected streams. The changes occur 
while the integrator is running, which minimizes 
disturbances.
 Figure 2.35
See Chapter 5 - 
Reactions for more 
information.2-68
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ThThe objects for the Rxns tab within the Fluid Package property 
view are described below. 
2.4.7 Tabular Tab
The Tabular Package can regress the experimental data for 
select thermophysical properties such that a fit is obtained for a 
chosen mathematical expression. The Tabular Package is utilized 
in conjunction with one of the Aspen HYSYS property methods. 
Your targeted properties are then calculated as replacements for 
whatever procedure the associated property method would have 
used.
Although the Tabular Package can be used for calculating every 
property for all components in the case, it is best used for 
matching a specific aspect of your process. A typical example 
would be in the calculation of viscosities for chemical systems, 
where the Tabular Package will often provide better results than 
the Activity Models.
Object Description
Current 
Reactions Sets
This lists all the currently loaded reactions set in this 
Fluid Package.
Associated 
Reactions
There are two Associated Reactions list boxes. Both 
boxes displays all the reactions associated with the 
respective selected Reaction Set. 
Add Set This button attaches the highlighted Available Reaction 
Set to the Fluid Package and displays it in the Current 
Reactions Sets group.
Remove This button removes the highlighted Current Reaction 
Set from the Fluid Package.
Available 
Reactions Sets
This list-box displays all the Available Reactions Sets in 
the case.
Simultaneous 
Basis Mgr
Click this button to access the Reaction Manager.2-69
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ThTabular Package calculations are based on mathematical 
expressions that represent the pure component property as a 
function of temperature. The values of the property for each 
component at the process temperature are then combined, 
using the stream composition and mixing rule that you specify.
The Tabular provides access to a comprehensive regression 
package. This allows you to supply experimental data for your 
components and have Aspen HYSYS regress the data to a 
selected expression. Essentially, an unlimited number of 
expressions are available to represent your property data. There 
are 32 basic equation shapes, 32 Y term shapes, 29 X term 
shapes, as well as Y and X power functions. The Tabular 
provides plotting capabilities to examine how well the selected 
expression predicts the property. You are not restricted to the 
use of a single expression for each property. Each component 
can be represented using the best expression.
You may not need to supply experimental data to use the 
Tabular. If you have access to a mathematical representation for 
a component/property pair, you can simply select the correct 
equation shape and supply the coefficients directly. Further, 
Aspen HYSYS provides a data base for nearly 1,000 library 
components, so you can use this information directly within the 
Tabular without supplying any data whatsoever. 
Aspen HYSYS contains a default library containing data for 
over 1,000 components.
Whenever experimental data is supplied, it is retained in the 
memory by Aspen HYSYS and stored in the case.2-70
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ThIn addition, Aspen HYSYS can directly access the information in 
the PPDS database for use in the Tabular. This database is 
similar to that provided with Aspen HYSYS in that the properties 
for the components are represented using a mathematical 
expression.
Requirements for Using the Tabular
There are only two requirements on the usage of the Tabular 
package. First, most properties require that all components in 
the case have their property value calculated by the Tabular. 
Second, enthalpy calculations require that the Tabular be used 
for both the liquid and vapour phase calculations. Similarly, you 
may use only one enthalpy type property for each phase. For 
example, liquid enthalpy and liquid heat capacity cannot both be 
selected. An extension to this occurs when the latent heat 
property is selected. When this property is activated, only one 
enthalpy type property or one heat capacity property may be 
selected.
The PPDS database is an optional tabular feature. Contact 
your Hyprotech representative for further information.
The Heat of Mixing property can be applied in one of two 
manners. For Activity Models that do not have Heat of Mixing 
calculations built in, this allows you to supply data or have 
the coefficients estimated, and have Heats of Mixing applied 
throughout the flowsheet. Equations of State do account for 
Heat of Mixing in their enthalpy calculations, however, in 
certain instances predict the value incorrectly. You can use 
this route to apply a correction factor to the Equation of 
State. 
In the cases where the Equation of State is predicting too 
high a value, implementing a negative Heat of Mixing can 
correct this.2-71
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ThLimits in the Tabular Option
In enthalpy extrapolation, if the upper temperature limit (Tmax) 
is less than the critical temperature (Tc) Aspen HYSYS Tabular 
option continues to extrapolate the data based on the original 
curve up to the critical point. At this point, an internal 
extrapolation method is used to calculate the liquid enthalpy. 
Due to the internal extrapolation method, there may be a huge 
discontinuity and poor extrapolation results from Tmax to Tc. The 
poor calculated values cause problem with the PH flash 
calculation.
There are two methods to avoid this problem:
• Increase the Tmax value of the original enthalpy curve. 
However, as mentioned above the curve itself does not 
extend above Tmax very well and produces poor results. 
You will have to be responsible for changing the curve 
shape to extrapolate in a better manner.
• User the Enthalpy Model Tr Limit option. This option 
allows you to control the starting temperature at which 
the extrapolation method is implemented. So instead of 
Tc, the extrapolation will start at a certain Tr (the default 
value is 0, which tells Aspen HYSYS to use the default 
method) typically 0.7 to 0.99.
Extrapolating accurate/adequate data is important, especially 
for enthalpy values approaching the critical point, as the values 
can change in odd manner and may require special 
extrapolation. 
If you are not using PPDS mixing rules (PPDS extrapolation 
methods) Aspen HYSYS supplies a very simple extrapolation 
based on constant Cp calculated from the original tabular 
enthalpy curve. This method keeps everything monotonically 
increasing through the critical point and into the dense phase.2-72
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ThUsing the Tabular Package
When using the Tabular package a general sequence of steps is 
shown below: 
1. Enable the Configuration and Notes pages (under the 
Options branch) by selecting the Enable Tabular 
Properties check box.
2. Select the Basis for Tabular Enthalpy by clicking the 
appropriate radio button on the Configuration page.
3. Select the checkboxes for the desired target properties from 
the All Properties, Physical, and Thermodynamic pages 
in the Options branch.
 Figure 2.36
To view all pages under the Options branch, use the Plus icon 
 to expand the tree browser.2-73
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ThThe All Properties page is shown below. 
As properties are added, the Information branch also 
becomes expandible. To expand the branches in the tree 
browser, click the Plus icon  that appears in front of a 
branch. 
Expanding the Information branch displays all of the active 
target properties selected on the pages under the Options 
branch. If the Heat of Mixing property is activated on the All 
Properties or Thermodynamics page, a new expandible 
branch for Heat of Mixing appears in the Tabular Package 
group.
4. If you have the PPDS database, select the check box for the 
database.
5. Once a target property is selected on one of the three pages 
under the Options branch, you can select the Mixing Basis 
by using the drop-down list. 
The Parameter value may also be changed on this page.
 Figure 2.372-74
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Th6. To view the existing library information, you must first select 
the desired page from the expandible Information branch. 
Click the desired property from the tree browser.
7. To plot the existing library information, click the Cmp Plots 
button. Click a component using the drop-down list in the 
Curve Selection group to change the components being 
plotted. The variables, Enthalpy vs. Temperature are plotted 
from the Variables group and shown in the figure below.
 Figure 2.38
 Figure 2.392-75
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Th8. Return to the Information page of the property by closing 
the plot property view. To view the PropCurve property view 
for a selected component, highlight a value in the column of 
the desired component and click the Cmp Prop Detail 
button.
9. Set the Equation Form and supply data. You can view this 
same format of data for library components.
The Tabular tab of the fluid package property view contains a 
tree browser which controls the options displayed in the tab. The 
options depend on the branches selected in the tree browser, 
these branches are:
• Configuration
• Options
• Information
• Heat of Mixing (appears only when Heat of Mixing is 
activated in the Options)
• Notes
 Figure 2.402-76
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ThConfiguration Branch
The Configuration page consists of two groups, the Global 
Tabular Calculation Options, and the Basis for Tab. Enthalpy 
(ideal gas).
Global Tabular Calculation Behaviour Group
The Global Tabular Calculation Behaviour Group contains two 
checkbox options:
 Figure 2.41
Checkbox Description
Enable 
Calculation 
of Active 
Properties
If this is activated, all the selected Active Properties are 
calculated via the Tabular Package. If this check box is 
cleared, all properties are calculated by the Property 
Package. This provides a master switch to enable/disable 
the Tabular Package while retaining the Active Property 
selections.
Enable 
Tabular 
Properties
Toggles the Tabular Properties on or off. If the check box is 
toggled off, no other pages are available and none of the 
previously inputted data is stored. 
Selecting the Enable Tabular Properties check box 
activates the Options, Information, and Notes branch.2-77
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Th Basis for Tabular Enthalpies
This group becomes active after the Enable Tabular Properties 
checkbox is clicked. It allows you to select between the enthalpy 
basis for tabular calculations:
• H = 0 K, ideal vapour (HYSIM basis)
• H = Heat of formation at 25 °C, ideal vapour
Options Branch
You can target a property through the three sub-branches 
available in the Options branch. 
The difference between the Enable Calculation of Active 
Properties and the Enable Tabular Properties checkboxes:
The Enable Calculation of Active Properties check box 
toggles between the properties regressed from the data 
supplied on the Tabular tab and the default values calculated 
by the Property Package. While clearing the checkbox 
returns to the default Property Package values, the tab 
retains all inputted data for the active property selections.
The Enable Tabular Properties checkbox makes the other 
pages active for specification. Clearing this checkbox purges 
the tab of any tabular property data it might have previously 
contained.
 Figure 2.422-78
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ThTo expand the branch, click the Plus icon  in front of the 
Options label in the Tabular Package group. This displays the All 
Properties, Physical, and Thermodynamics pages. Each one 
of these pages consists of a five column matrix table.
Property Type
The All Properties page consists of seventeen properties which 
include both the Physical and Thermodynamic properties. These 
properties have then been subdivided into two groups and 
displayed again on either the Physical or Thermodynamics 
page. These properties are listed in the table below, along with 
the subgroup that they belong to:
• K-value (V/L1) [Thermodynamic]
• K-value (V/L2) [Thermodynamic]
• K-value (L1/L2) [Thermodynamic]
• Enthalpy(L) [Thermodynamic]
• Enthalpy(V) [Thermodynamic]
• Latent Heat [Thermodynamic]
• Heat Capacity(L) [Thermodynamic]
• Heat Capacity(V) [Thermodynamic]
• Heat of Mixing [Thermodynamic]
• Viscosity (L) [Physical]
• Viscosity (V) [Physical]
• Thermal Cond (L) [Physical]
• Thermal Cond (V) [Physical]
• Surface Tension [Physical]
• Density (L) [Physical]
• Entropy(L) [Thermodynamic]
• Entropy(V) [Thermodynamic]
Use Aspen HYSYS/Use PPDS 
The checkboxes in the Use Aspen HYSYS and Use PPDS columns 
allow you to select between the Hyprotech and the PPDS 
libraries. Depending on the property type selected, the PPDS 
library may not be available. When the PPDS library is available, 
the checkbox changes from light grey to white.2-79
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ThComposition Basis
The Composition Basis allows you to select the Basis (mole, 
mass, or liq volume) on which the mixing rule is applied. When 
you select a property type the Composition Basis becomes 
active for that property. The available options can be accessed 
from the drop-down list within the cell of each property 
selected.
The default mixing rule which is applied when calculating the 
overall property is shown in the following form:
Mixing Parameter
The last column in the matrix table is the Mixing Parameter. This 
allows you to specify the coefficient (f) to use for the mixing rule 
calculations. Notice that the default value is 1.00. The value that 
Aspen HYSYS uses as the default is dependent on the property 
selected. For instance, if you select Liquid Viscosity as the 
property type, Aspen HYSYS uses 0.33 as the default for the 
Mixing Parameter.
If you are using the PPDS database, you can modify the mixing 
rule parameters for any property with the exception of the 
vapour viscosity and vapour thermal conductivity. The 
parameters for these properties are set internally to the 
appropriate PPDS mixing rule.
The PPDS database is an optional tabular feature. Contact 
your Hyprotech representative for further information.
(2.47)Propertymix xiPropertyi
f
i
∑
1
f
--
=
2-80
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ThInformation Branch
After properties are activated on one of the three pages in the 
Options branch, the property appears in the Information branch. 
This branch can be expanded by clicking the Plus icon  in 
front of the Information label in the Tabular Package group. 
A component may be targeted by clicking in any cell in the 
component’s column. For example, if Propane was the 
component of interest, click in any cell in the third column. Once 
the component is targeted, select the Cmp Prop Detail button to 
access the PropCurve property view. Most of the information 
contained in the PropCurve property view is displayed on the 
Information pages and can also be changed there.
 Figure 2.43
The Heat of Mixing property does not create a page in the 
Information branch. Instead it will create a unique branch in 
the Tabular Package group.
See Supplying Tabular 
Data for further 
information on the 
PropCurve property view. 2-81
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ThCmp Plots Button
The Cmp Plot button accesses the plot of Temperature vs. the 
selected Property Type. The Variables group shows the property 
used for the X and Y axis (Enthalpy in this case). 
Aspen HYSYS can only plot four curves at a time. The Curve 
Selection group lists the components which are plotted on the 
graph. The default is to plot the first four components in the 
component list. You can replace the default components in the 
Curve Selection group with other components by using the 
drop-down list in each cell.
Select the component you want to add to the Curve Selection 
group. The new component replaces the previously selected 
component in the Curve Selection group, and Aspen HYSYS 
redraws the graph, displaying the data of the new component.
Aspen HYSYS uses the current expressions to plot the graphs, 
either from the Aspen HYSYS library or your supplied regressed 
data.
 Figure 2.44
Object inspect the plot area to access the Graph Control 
property view.
Refer to Section 10.4 - 
Graph Control of the 
Aspen HYSYS User 
Guide for more 
information.2-82
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ThHeat of Mixing Branch
When the Heat of Mixing property is activated on either the All 
Properties or the Thermodynamic page in the Options 
branch, a new branch gets added to the root of the tree browser 
in the Tabular Properties group. This branch can be expanded by 
clicking the Plus icon  in front of the Heat of Mixing label in 
the Tabular Package group. The pages in the branch correspond 
to the components in the fluid package.
Heat of Mixing Page
This page is only visible when Heat of Mixing is selected on the 
All Properties or Thermodynamic pages. It consists of the 
following objects:
 Figure 2.45
Object Description
UNIFAC VLE Aspen HYSYS uses the UNIFAC VLE estimation method to 
calculate the binary coefficients. This overwrites any 
existing coefficients.
UNIFAC LLE Same as UNIFAC VLE, except the LLE estimation methods 
are used.
Temperature The reference temperature at which the UNIFAC 
parameters are calculated.2-83
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ThComposition Pages
The Composition pages in the Heat of Mixing branch are very 
similar to the pages contained in the Information branch. Click 
the View Details button to access a modified PropCurve 
property view. 
The only difference is that there is no Coeff tab. Most of the 
information contained in the PropCurve property view is 
displayed on the Information pages, where it can be modified.
Notes Page
Any comments regarding the tabular data or the simulation in 
general may be displayed here.
 Figure 2.46
See Supplying Tabular 
Data for further 
information on the 
PropCurve property view. 2-84
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ThSupplying Tabular Data
When you have specified the flowsheet properties for which you 
want to use the Tabular Package, you can change the data 
Aspen HYSYS uses in calculating the properties. Aspen HYSYS 
contains a data file with regressed coefficients and the 
associated equation shape, for most components.
To illustrate the method of supplying data, use Methane as a 
component and Liquid Enthalpy as the Property. From the 
Enthalpy (L) Tabular Package group, select the Methane cell as 
the component and click the Cmp. Prop. Detail button. 
The Variables tab of the PropCurve property view is displayed as 
shown below: 
If Heat of Mixing is used, you can access the Prop Curve by 
selecting the component and then click the View Details 
button. Although it should be noted that this property view 
does not include the Coeffs tab.
 Figure 2.472-85
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ThThe PropCurve property view contains the following tabs:
Variables Tab
The Variables tab is the first tab of the PropCurve property view. 
It contains four groups, X-Variable, Y-Variable, Q-Variable, and 
Equation Form. The Variables tab is shown in the previous 
figure.
X-Variable Group
This group contains information relating to the X-Variable and is 
described below.
Tab Description
Variables Specify the equation shapes and power functions for the 
property.
Coeff Displays the current coefficients for the selected equation.
Table Current tabular data for the property (library or user 
supplied).
Plots Plots of the property using the tabular data and the 
regressed equation.
Notes User supplied descriptive notes for the regression.
Cells Description
X Since all properties are measured versus Temperature, this 
cell always shows Temperature when using the Tabular 
Package.
Unit Displays the units for the temperature values. You cannot 
change the units here. The Aspen HYSYS internal units for 
Temperature, K, are always used.
Shape This is the shape of the X variable. The choices for the X 
Shape can be accessed using the drop-down list in the cell. 
There are 29 available shapes. Use the scroll bar to move 
through the list. In this case, the shape selected is Xvar:x. 
This means that the X variables in the equation are equal to 
X, which represents temperature. If LogX:log10(x) is 
selected as the X Shape, then the X variables in the 
equation are replaced by log10(x).
 Shape Norm This is a numerical value used in some of the X Shapes. In 
the drop-down list for X Shape, notice that the second 
choice is Xreduced:x/norm. The x/norm term, where norm 
= 190.70, replaces the X variable in the equation. You can 
change the numerical value for Norm in the cell.2-86
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ThY-Variable Group
This group contains all information relating to the Y-Variable.
Exponent Allows you to apply a power term to the X term, for 
example, X0.5.
Eqn 
Minimum
Defines the minimum boundary for the X variable. When a 
flowsheet calculation for the property is outside the range, 
Aspen HYSYS uses an internal method for extrapolation of 
the curve. This method is dependent on the Property being 
used. See the Equation Form section.
Eqn 
Maximum
Defines the maximum boundary for the X variable. When a 
flowsheet calculation for the property is outside the range, 
Aspen HYSYS uses an internal method for extrapolation of 
the curve. This method is dependent on the Property being 
used. See the Equation Form section.
Cells Description
Y This is the property chosen for Tabular calculations.
Unit Displays the units for the Y variable. You cannot change the 
units here, it must be done through the Basis Manager 
(Preferences option).
Shape This is the shape of the Y variable. The choices for the Y Shape 
are available using the drop-down list within the cell. There 
are 32 shapes selected. Use the scroll bar to move through the 
list. In this case, the shape chosen is Yvar:y. This means that 
the Y variables in the equation are equal to Y, which represents 
enthalpy. If LogY:log10(y) is chosen as the Y Shape, then the 
Y variables in the equation are replaced by log10(y).
Shape 
Norm
This is a numerical value used in some of the Y Shapes. In the 
drop-down list for Y Shape, notice that the second choice is 
Yreduced:y/norm. The Y variable in the equation is replaced 
by the y/norm value. This numerical value can be changed 
within the cell.
Exponent Allows you to apply a power term to the Y term, for example, 
Y0.5.
Cells Description2-87
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ThQ-Variable Group
This group contains all information relating to the Q Variable. 
This Variable is used in some of the X and Y Variable equations. 
Coefficients Group
This group is only visible in the Heat of Mixing page when it is an 
active property. 
The Coefficients group contains the coefficient values either 
obtained from the Aspen HYSYS database, or regressed from 
data supplied in the Table tab.
Equation Form
Depending on which property you have selected, Aspen HYSYS 
selects a default Equation Shape. You have the option of using 
this equation or an alternative one. You can select a different 
equation from the drop-down list associated with this cell. The 
drop-down list contains 33 available equations to choose from.
Cell Description
Q Represents the Q variable which is always Pressure.
Unit Displays the units for the Q Variable, which are always the 
default internal units of pressure, kPa.
Default This is the default numerical value given to the Q Variable 
which can be modified within the cell.
 Figure 2.482-88
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ThWhen Aspen HYSYS cannot regress the data to produce 
equation coefficients for the selected equation shape, the 
message Non-Regressable appears on the right of the drop-
down list. You can still use the equation shape, but you have to 
manually input the coefficients. 
Coeff Tab
This tab displays the current coefficients for the specified 
equation. Notice that this property view also contains the 
Equation Form group, allowing you to change the equation from 
this tab. 
 Figure 2.49
 Figure 2.50
Some equation shapes only allow you to supply coefficients 
directly. You are informed if the equation shape cannot have 
tabular data regressed to it.
The X, Y, and Q variables and their units are displayed for 
reference only. They can not be modified.2-89
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ThThe Coefficients group contains the coefficient values either 
obtained from the Aspen HYSYS database, or regressed from 
data supplied in the Table tab.
The checkboxes supplied next to each coefficient value allow you 
to instruct Aspen HYSYS not to regress certain coefficients, they 
will remain at the fixed value (default or user supplied) during 
regression.
Table Tab
You can supply your tabular data before or after selecting the 
Equation Shape. To enter data, select the Table tab.
 Figure 2.51
 Figure 2.522-90
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ThIf the component is from the Aspen HYSYS library, 20 points are 
generated between the current Min and Max temperatures. If 
you need to supply data, click the Clear Data button. You can 
also add your data to the Aspen HYSYS default data and have it 
included in the regression.
Supplying Data
If you are going to supply data, select the unit cell under the X 
and Y variable columns and press any key to open the drop-
down list. From the list you can change to the appropriate units 
for your data. 
The procedure for supplying data is as follows:
1. Select the appropriate units for your data.
2. Clear the existing data with the Clear Data button, or move 
to the location that you want to overwrite. 
3. Supply your data.
Coefficients calculated using the deleted data are still 
present on the Coeff tab until the Regress button is clicked.
4. Supply Net Weight Factors if desired.
Q-Column
This column contains the Pressure variable. The presence of this 
extra variable helps in providing better regression for the data. 
As with the X and Y variables, the units for pressure can be 
changed to any of the units available in the drop-down list.
Wt Factor
You can apply weighting to individual data points. When the 
regression is performed, the points with higher weighting factors 
are treated preferentially, ensuring the best fit through that 
region.
To delete a particular data point, highlight the data point and 
press the DELETE key.2-91
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ThRegressing the Data
After you have provided the data, you need to update the 
equation coefficients. Click the Regress button to have Aspen 
HYSYS regress your data, generating the coefficients based on 
the current shapes. If you then change any of the equation 
shapes, the data you supplied is regressed again. You can re-
enter the regression package and select a new shape to have 
your data regressed. 
Data Retention
Whenever experimental data is supplied, it is retained by Aspen 
HYSYS in memory and is stored in the case. At a later date, you 
can come back into the Tabular Package and modify data for the 
Property, and Aspen HYSYS regresses the data once again.
Plot Tab
To examine how the current equations and coefficients 
represent the property, select the Plots tab to view the plot. 
 Figure 2.53
Use the Plot button on the Tabular tab to display up to four 
component curves on the same graph.2-92
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ThOnly the selected component (in this case Methane) is 
displayed. The plot contains two curves, one plotted with the 
regressed equation and the other with the Table values. If the 
Tabular values supplied on the Table tab are in different units, 
they are still plotted here using the Aspen HYSYS internal units. 
This provides a means for gauging the accuracy of the 
regression. In this example, the two curves overlap each other, 
such that it appears to only show one curve.
Besides displaying the component curve, this property view also 
displays the number of points used in determining the tabular 
equation (in this case 20). As well, the x-Axis group displays the 
Min (91.7) and Max (169) x-values on the curve.
You can change the Min and Max x-axis values and have Aspen 
HYSYS extend the curve appropriately. Place the cursor in the 
Min cell and type in a new value. For example, type 70. This 
replaces 91.7, and Aspen HYSYS extends the curve to include 
this value. Similarly, you can change the Max value, and have 
Aspen HYSYS extend the curve to include this new value. Type 
180 to replace the Max value of 169.00.
The new curve is shown below.
 Figure 2.542-93
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2-94 Aspen HYSYS Fluid Package 
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ThNotes Page
The Notes page is used for supplying a description to associate 
with the Tabular Data just entered.
When you have finished providing all necessary data, close the 
PropCurve property view and return to the Tabular tab of the 
Fluid Package property view. You can now continue to supply 
data for the other components, if you want. The properties that 
you have specified to be calculated with the Tabular package 
carry through into the Flowsheet.
2.4.8 Notes Tab
The Notes tab allows you to provide documentation that is 
stored with the Fluid Package. When you export a Fluid Package, 
any Notes associated with it are also exported. When you want 
to import a Fluid Package at a later date, the Notes tab allows 
you to view information about the Fluid Package.
To review all notes within 
the fluid package, refer to 
Section 7.19 - Notes 
Manager of the Aspen 
HYSYS User Guide.2-94
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Th2.5 COMThermo Property 
View
The Fluid Package COMThermo property view can be accessed 
by selecting COMThermo Pkg in the Property Package Selection 
list on the Set Up tab of the Fluid Package property view. Like 
the basic Fluid Package property view, the property view for 
COMThermo consists of eight tabs and is based on the 
COMThermo thermodynamics framework. These tabs include 
information pertaining to the particular fluid package selected 
for the case. 
When you create a new fluid package and select the 
COMThermo from the list, the COMThermo Setup view appears. 
 Figure 2.552-95
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Th2.5.1 Set Up Tab
When the COMThermo Package is selected from the Property 
Package selection list, the COMThermo Setup link appears in the 
right hand side of the property view.
COMThermo Setup Window
The COMThermo Setup window automatically appears when you 
select the COMThermo Property package from the Property 
Package Selection list. This window displays
• Model Selection
• Model Phase
• Model Options
• Extended Setup
• Advanced Thermodynamics
After a Model is selected in this window, Properties and Method 
options are displayed in the Model Options group. The properties 
and methods that are displayed are dependent on the selected 
Model.
 Figure 2.56
Information on Property and 
calculation Methods depending on 
the Model selected. Use the drop-
down list to select alternative 
calculation methods.
Select the 
Vapor or Liquid 
Model Phase 
using the radio 
buttons.
Additional Information on the Model selected.
Select a flash calculation 
method here. The buttons 
below are used to setup the 
extended custom property 
package and extended flash.
Select a 
property model 
for the vapor 
and liquid 
phase.2-96
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ThThe following sections provide an overview of the various 
models.
Model Selection
In the Model Selection group, you have access to the list of 
default property models that are available in Aspen HYSYS-
COMThermo. The availability of the models depends on the 
Vapour or Liquid Model Phase selected for your system. Using 
the radio buttons, the models are filtered for vapor and liquid 
models. A model for the vapor and liquid phase is required and 
displayed in the Property Pkg status bar.
* Described in the following sections.
Equations of State
Equations of state are used to model the behaviour of single-, 
two-, and three-phase systems. For oil, gas, and petrochemical 
applications, the Peng Robinson Equation of State is generally 
the recommended property model. It rigorously solves most 
single-, two-, and three-phase systems with a high degree of 
efficiency and reliability. 
Object Description
Vapor Phase The Vapor Phase contains a list of Equations of State* 
used to model the vapor phase in the Model Selection 
Group.
Liquid Phase The Liquid Phase contains a list of the various Equations 
of State*, Activity Models*, and semi-empirical methods 
(Chao Seader & Grayson Streed) to characterize the 
liquid phase of a chemical system.
To create or add property packages and properties, refer to 
the COMThermo online help in the development kit.
For detailed information 
on COMThermo Models 
that are available in 
Aspen HYSYS, refer to the 
Aspen COMThermo 
Reference Guide.
Refer to the Aspen 
COMThermo Reference 
Guide for more detailed 
information on the 
available Equations of 
State.2-97
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ThEnhancements to this equation of state (Aspen HYSYSPR) 
enable it to be accurate for a variety of systems over a wide 
range of conditions. The equation of state methods and their 
specific applications are described below:
EOS Description Available for
Ideal Gas PV=nRT can be used to model the Vapor Phase but 
is only suggested for ideal systems under 
moderate conditions.
Vapor Phase only
PR
Peng-
Robinson
This model is ideal for VLE calculations as well as 
calculating liquid densities for hydrocarbon 
systems. However, in situations where highly non-
ideal systems are encountered, the use of Activity 
models is recommended.
Vapor and Liquid 
Phase
Aspen 
HYSYSPR
The Aspen HYSYSPR EOS is similar to the PR EOS 
with several enhancements to the original PR 
equation. It extends the range of applicability and 
better represents the VLE of complex systems.
Vapor and Liquid 
Phase
PRSV
Peng-
Robinson 
Stryjek-Vera
This is a two-fold modification of the PR equation 
of state that extends the application of the original 
PR method for moderately non-ideal systems. It 
provides a better pure component vapor pressure 
prediction as well as a more flexible mixing rule 
than Peng robinson.
Vapor and Liquid 
Phase
SRK
Soave-
Redlich- 
Kwong
In many cases it provides comparable results to 
PR, but its range of application is significantly 
more limited. This method is not as reliable for 
non-ideal systems.
Vapor and Liquid 
Phase
KD
Kabadi 
Danner
This model is a modification of the original SRK 
equation of state, enhanced to improve the vapor-
liquid-liquid equilibrium calculations for water-
hydrocarbon systems, particularly in dilute 
regions.
Vapor and Liquid 
Phase
Lee-Kesler-
Plocker
This model is the most accurate general method 
for non-polar substances and mixtures.
Vapor and Liquid 
Phase
Redlich-
Kwong
The Redlich-Kwong equation generally provides 
results similar to Peng-Robinson. Several 
enhancements are made to the PR as described 
above which make it the preferred equation of 
state.
Vapor Phase only
Sour Peng-
Robinson
Combines the PR equation of state and Wilson's 
API-Sour Model for handling sour water systems.
Vapor and Liquid 
Phase2-98
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ThActivity Models
Although Equation of State models have proven to be reliable in 
predicting the properties of most hydrocarbon based fluids over 
a wide range of operating conditions, their application is limited 
to primarily non-polar or slightly polar components. Non-ideal 
systems at low to moderate pressure are best modeled using 
Activity Models. Activity models only perform calculations for the 
liquid phase. This requires you to specify a calculation method 
for the modeling of the vapor phase.
The following Activity Models are available for modelling the 
liquid phase of a system:
Virial This model enables you to better model vapor 
phase fugacities of systems displaying strong 
vapor phase interactions. Typically this occurs in 
systems containing carboxylic acids, or 
compounds that have the tendency to form stable 
hydrogen bonds in the vapor phase. In these 
cases, the fugacity coefficient shows large 
deviations from ideality, even at low or moderate 
pressures.
Vapor only
Zudkevitch-
Joffee
This is a modification of the Redlich Kwong 
equation of state, which reproduces the pure 
component vapor pressures as predicted by the 
Antoine vapor pressure equation. This model is 
enhanced for better prediction of vapor-liquid 
equilibrium for hydrocarbon systems, and systems 
containing Hydrogen.
Vapor and Liquid 
Phase
Model Description
Ideal Solution Assumes the volume change due to mixing is zero. This 
model is more commonly used for solutions comprised 
of molecules not too different in size and of the same 
chemical nature.
Regular 
Solution
This model eliminates the excess entropy when a 
solution is mixed at constant temperature and volume. 
The model is recommended for non-polar components in 
which the molecules do not differ greatly in size. By the 
attraction of intermolecular forces, the excess Gibbs 
energy may be determined.
NRTL This is an extension of the Wilson equation. It uses 
statistical mechanics and the liquid cell theory to 
represent the liquid structure. It is capable of 
representing VLE, LLE, and VLLE phase behaviour.
EOS Description Available for
Refer to the Aspen 
COMThermo Reference 
Guide for more detailed 
information on the 
available Activity models.2-99
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ThGeneral NRTL This variation of the NRTL model uses five parameters 
and is more flexible then the NRTL model. The following 
equation format is used for the equation parameters 
( ):
Apply this model to systems:
• with a wide boiling point range between 
components.
• where you require simultaneous solution of VLE 
and LLE, and there exists a wide boiling point or 
concentration range between components.
UNIQUAC Uses statistical mechanics and the quasi-chemical 
theory of Guggenheim to represent the liquid structure. 
The equation is capable of representing LLE, VLE, and 
VLLE with accuracy comparable to the NRTL equation, 
but without the need for a non-randomness factor.
Wilson First activity coefficient equation to use the local 
composition model to derive the Gibbs Excess energy 
expression. It offers a thermodynamically consistent 
approach to predicting multi-component behaviour from 
regressed binary equilibrium data. However the Wilson 
model cannot be used for systems with two liquid 
phases.
Chien-Null Provides consistent framework for applying existing 
Activity Models on a binary by binary basis. It allows you 
to select the best Activity Model for each pair in your 
case.
Margules This was the first Gibbs excess energy representation 
developed. The equation does not have any theoretical 
basis, but is useful for quick estimates and data 
interpolation.
Van Laar This equation fits many systems quite well, particularly 
for LLE component distributions. It can be used for 
systems that exhibit positive or negative deviations from 
Raoult’s Law; however, it cannot predict maxima or 
minima in the activity coefficient. Therefore it generally 
performs poorly for systems with halogenated 
hydrocarbons and alcohols.
UNIFAC VLE/
LLE
Both UNIFAC VLE and UNIFAC LLE use the solution of 
atomic groups model in which existing phase equilibrium 
data for individual atomic groups is used to predict the 
phase equilibria of system of groups for which there is 
no data. The group data is stored in specially developed 
interaction parameter matrices for both VLE and LLE 
property packages.
Model Description
τ and α
τi j Aij
Bij
T
------
Cij
T2
------ FijT Gij Tln+ + + +=
αij α1ij α2i jT+=2-100
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ThVapor Pressure Models
Vapor pressure K-value models may be used for ideal mixtures 
at low pressures. Ideal mixtures include hydrocarbon systems 
and mixtures such as ketones and alcohols, where the liquid 
phase behaviour is approximately ideal. The Vapour Pressure 
models may also be used as a first approximation for non-ideal 
systems.
Chao Seader & Grayson Streed Models
The Chao Seader and Grayson Streed methods are older, semi-
empirical methods. The Grayson Streed correlation is an 
extension of the Chao Seader method with special emphasis on 
hydrogen. Only the equilibrium data produced by these 
correlations is used by Aspen HYSYS. The Lee-Kesler method is 
used for liquid and vapor enthalpies and entropies.
Extended Property Package & Extended Flash
The Extended Property Package model allows the user to 
incorporate existing external property packages with minimum 
modifications to them. You may setup a number of different 
Models Description
Antoine This model is applicable for low pressure systems that 
behave ideally.
Braun K10 This model is strictly applicable to heavy hydrocarbon 
systems at low pressures. The model employs the Braun 
convergence pressure method, where, given the normal 
boiling point of a component, the K-value is calculated at 
system temperature and 10 psia (68.95 kPa).
Esso Tabular This model is strictly applicable to hydrocarbon systems 
at low pressures. The model employs a modification of 
the Maxwell-Bonnel vapor pressure model.
Model Description
Chao Seader Use this method for heavy hydrocarbons, where the 
pressure is less than 10342 kPa (1500 psia), and 
temperatures range between -17.78 and 260 °C (0-500 
°F).
Grayson Streed Recommended for simulating heavy hydrocarbon 
systems with a high hydrogen content.2-101
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2-102 COMThermo Property View
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Thproperty packages using extended methods, which perform 
different thermodynamic calculations, handle different 
databases for pure compound properties and/or interaction 
parameters. 
Unlike default COMThermo methods, which are stateless, 
Extended Property Packages can keep and carry state 
information. State information refers to data such as pure 
compound and mixture information. In the implementation of an 
Extended Property Package, the calls between different property 
calculation routines can be made directly without a need to use 
COM interfaces. You can mix and match Extended Property 
methods with COMThermo default property calculation methods. 
This can be set up in the XML model file.
To set up an Extended Property Package two XML model files are 
required, one for vapor phase and one for liquid phase. Both 
XML model files must contain the same package name. When 
selecting an extended package for calculations, the same 
extended package must be selected for both vapor and liquid 
phase.
The Extended PropPkg Setup button is accessed by selecting the 
appropriate extended package for both the vapor and liquid 
model phases. The Extended PropPkg property view is shown 
below for an example package with ExtPkg as the name of the 
The COMThermo online help is located in the COMThermo DK 
(development kit). You need to setup the COMThermo DK 
from the installation disk.
To set up an Extended Property Package for calculations, you 
must select the same extended package for both the vapor 
and liquid phases.
Refer to Extended 
Property Packages and 
Flash section in the 
Aspen COMThermo 
Programmers Guide for 
detailed information on 
how to add extended flash 
and extended property 
packages.2-102
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ThXML model file.
The Extended Property Package Setup includes a description of 
the package and the setup files. The Add button allows you to 
browse Setup files for the Extended Property package. The On 
View button allows you to see and configure the associated 
property views of your selected extended method.
The Extended Flash model provides the user with the capability 
to use custom flash calculation methods. COMThermo also 
allows the user to mix and match different flash methods. For 
example, the user can implement a PV (pressure-vapor fraction) 
flash in an Extended Flash package and use the existing 
COMThermo PT flash (pressure-temperature). The flash option 
can be setup through the Flash Family, which is located in the 
Model and Flash XML section of the COMThermo online help.
A Extended Flash also requires a flash XML model file to setup 
the flash family name. The Extended Flash Setup button is 
accessed by selecting the appropriate XML model filename. The 
Extended Flash Setup property view is shown below for an 
example flash with ExtendedFlash as the name of the XML 
model file.
 Figure 2.57
FIF2-103
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ThExtended Property Package and Extended Flash can be used 
together or separately.
Model Options
When you have selected a Model, additional property and option 
methods are displayed in the Model Options group on the right 
side of the COMThermo Setup window. This information is 
directly related to the Model and phase selected.
The Model options group shows each property and what 
calculation method is used for that property. 
 Figure 2.58
A model must be selected for both the vapor and liquid 
phases.2-104
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ThFor example, the Peng-Robinson Model Options for the vapor 
phase are shown below:
The Enthalpy property uses the Peng-Robinson Enthalpy 
calculation method. The method options which are displayed in 
red have alternative calculation methods. By placing your cursor 
on the drop-down list, you have a choice to select the Lee-Kesler 
calculation method for Enthalpy.
The Entropy and Cp properties may also be altered to use the 
Lee-Kesler calculation methods for the Peng-Robinson EOS. If 
the property method is altered, it appears in blue. The 
information in black are default methods for Aspen HYSYS-
COMThermo. Methods are added in the XML file and then can be 
seen in the method group for the property selected. Refer to the 
Wizards & Add-Ins section of the COMThermo online help 
located in the COMThermo Development Kit to help in adding 
new properties, property packages, and flash.
 Figure 2.59
 Figure 2.602-105
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ThEOS Enthalpy, Entropy & Cp Method Specification
With most of the Equations of States, you may have two or 
three alternative calculation methods for enthalpy, entropy, and 
Cp. The property calculation methods that are available include: 
the EOS selected, and the Lee-Kesler method.
Once the vapor phase is selected, the liquid phase needs to 
defined.
Activity Model Specifications
The Activity Models perform calculations for the liquid phase 
only. Once a Liquid phase model is selected, the model options 
group is filled with property methods. The UNIQUAC activity 
model options are shown below.
With most of the activity models, you have a choice for the 
calculation method for the standard Ln Fugacity Poynting 
Correction. By default, the ideal standard Ln Fugacity is set 
without the Poynting correction and may be changed using the 
Methods Description
Equation of 
State
With this selection, the enthalpy, entropy, and Cp 
calculation methods contained within the Equation of 
State are used.
Lee-Kesler The Lee-Kesler method may be used for the calculation of 
enthalpies, entropies and Cp values. This option results in 
a combined Property Model, employing the appropriate 
equation of state for vapor-liquid equilibrium calculations 
and the Lee-Kesler equation for the calculation of 
enthalpies and entropies. This method yields comparable 
results to Aspen HYSYS standard equations of state and 
has identical ranges of applicability.
Lee-Kesler enthalpies may be slightly more accurate for 
heavy hydrocarbon systems, but require more computer 
resources because a separate model must be solved.
 Figure 2.612-106
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Thdrop-down list. The Poynting factor uses each component’s 
molar volume (liquid phase) in the calculation of the overall 
compressibility factor. 
Advanced Thermodynamics
The Advanced Thermodynamics group, located on the lower 
right-side of the COMThermo Setup window, allows you to 
model the fluid package based on the COMThermo framework.
The Advanced Thermodynamics group contains the following 
buttons:
• Import. Allows you to import an existing COMThermo 
property package.
• Export. Allows you to export a COMThermo based 
property package.
• Regression. Allows you to export the fluid package 
directly into COMThermo Workbench where the fluid 
package can be manipulated by a broad selection of 
estimation methods and data regression. Once the 
regression is complete in the COMThermo Workbench, 
the regressed fluid package can be imported back to 
Aspen HYSYS.
To aid you in adding customized properties to the model 
options group.
 Figure 2.62
The imported/exported COMThermo Property package can 
be used in Aspen HYSYS, DISTIL, and COMThermo 
Workbench.
You must have the Conceptual Engineering Suite installed 
with COMThermo Workbench licensing in order to apply the 
Regression feature in Aspen HYSYS.
Refer to Wizards & Add-
Ins section of the Aspen 
COMThermo Reference 
Guide.
Refer to the 
Thermodynamics 
Workbench guide of the 
Conceptual Engineering 
Suite for more 
information on 
COMThermo Workbench.2-107
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2-108 COMThermo Property View
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ThWhen you click the Regression button the following property 
view appears:  
 Figure 2.63
Regression Description
Start Regression This button is similar to exporting a fluid package. It 
allows you to select a file to be opened up in 
COMThermo Workbench for regression analysis.
Load Regression This button is similar to importing a fluid package. A 
menu of existing packages appear, allowing you to 
retrieve information from a previously regressed 
package.
Writing Fluid 
Package
A status indicator to indicate that a new fluid package 
is being generated.
Starting 
COMThermo 
Workbench
A status indicator to indicate that COMThermo 
Workbench is starting after the fluid package is 
generated.
The regressed fluid package is saved with *.ctf extension 
along with two default tag files, cc.XML, and pm.XML. You 
must have all three files saved in the same directory to 
access the regressed fluid package.2-108
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ThComponent List Selection
You must select a Component List to associate with the current 
Fluid Package from the Component List Selection drop-down list 
on the Set Up tab. Component Lists are stored outside of the 
Fluid Package Manager in the Components Manager and may 
contain library, hypothetical, and electrolyte components. To 
view the Component List property view, click on the View 
button.
2.5.2 Parameters Tab
The information and options displayed on the Parameters tab is 
dependent on the selection of the Property Model. Property 
models which require additional parameters are displayed here, 
while others are not. For example, the Chein-Null activity model 
requires parameters to specify alternative models for binary 
interaction parameters. The Chien-Null property package is 
mentioned in this section.
Chien Null
The Chien Null model provides a consistent framework for 
applying different activity models on a binary by binary basis. 
On the Parameters tab, you can specify alternative activity 
models to be used for each component pair.
It is not recommended for users to attach the Master 
Component List to any Fluid Package. If only the master list 
exists, by default a cloned version of the Master Component 
List is created (called Component List -1). This list is 
selected initially when a new Fluid Package is created.2-109
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ThBinary Component Parameters
To view the Chein-Null activity models table, CN must be 
selected as the liquid phase model and the IP Model Name on 
the binary coefficients tab. All components in the case, including 
hypotheticals are listed in the table as shown below:
The table displays the default property methods provided by 
COMThermo for each binary pair. The methods are accessed by 
highlighting a cell and opening the drop-down list. From the list 
you can specify an Activity Model that COMThermo uses for the 
calculation of each binary. If Henry's Law is applicable to a 
component pair, COMThermo selects this as the default property 
method. When Henry's Law is selected by Aspen HYSYS, you 
cannot modify the model for the binary pair.
By default, the Henry and NRTL activity models are selected for 
the binary pairs in the above property view. You may use the 
default selections, or set the property package for each binary 
pair. Remember that the selected method appears in both cells 
representing that binary.
 Figure 2.64
The Activity Models available in the drop-down list are:
• None Required
• Henry
• van Laar
• Margules
• NRTL
• Scatchard
• Reg Soln
• General2-110
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ThCOMThermo may filter the list of options according to the 
components involved in the binary pair.
2.5.3 Binary Coefficients Tab
The Binary Coefficients (Binary Coeffs) tab contains a table 
which lists the interaction parameters for each component pair. 
Depending on the property method selected, different 
estimation methods are available and therefore a different 
property view may be displayed. 
All known binary interaction parameters are shown and the 
unknown interaction parameters are displayed with dashes (---
). When you exit the Basis Manager, unknown interaction 
parameters are set to zero. You have the option of overwriting 
any library interaction parameter values.
For all tables on the Binary Coeffs tab, the horizontal 
components across the top of the table represent the "i" 
component and the vertical components represent the "j" 
component.2-111
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2-112 COMThermo Property View
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ThEquation of State Interaction 
Parameter (IP)
When you select an EOS model using the IP Model Name drop-
down list, the Interaction Parameter model information is 
displayed on the Binary Coeffs tab as shown in the figure below.      
The property view contains a table of cells commonly referred to 
as the Matrix Pane displaying binary interaction coefficients. The 
top of the property view contains the IP Model Name and 
Coefficients drop-down lists. 
 Figure 2.65
This information applies to the following Property Models:
• Kabadi Danner
• Lee-Kesler Plocker
• PR
• PRSV
• Soave Redlich Kwong, SRK
• Sour PR
• Virial
• Zudkevitch Joffee
These two radio buttons only appear for the 
PR and SRK based Equations of State.
This is equivalent 
to no Kij2-112
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ThThe drop-down lists determine which binary iteration 
coefficients are shown in the table:
The list of options for both the Model Name and Coefficients are 
dependent on the property model (EOS and Activity) selected 
for the vapor and liquid phase. For example, if you select the 
Virial EOS as the vapor model, it appears in the IP Model Name 
drop-down list. You can view and/or edit the virial coefficients 
for each binary. The following IP model list represents the vapor 
(Virial) and liquid models (Chien-Null) chosen for the example. 
Values are only shown in the matrix when the Virial Vapor Phase 
model is selected on the Set Up tab. You can use the default 
values suggested by Aspen HYSYS or edit these values. Virial 
coefficients for the pure species are shown along the diagonal of 
the matrix, while cross coefficients, which are mixture 
properties between components, are those not along the 
diagonal.
Drop-Down List Description
IP Model Name This drop-down list shows all of the binary interaction 
coefficient matrices associated with the property 
package selected. Ordinarily there is one, two, or three 
binary interaction coefficient matrices per property 
package. Equations of state typically have one matrix, 
and activity coefficient models typically have two IP 
matrices, one for ordinary condensable components 
and the other for non-condensible components The 
selected Model is displayed in the Matrix Pane.
Coefficients This drop-down list shows the type of binary 
interaction coefficients that are displayed in the Matrix 
Pane. The naming convention for each binary 
interaction coefficient type is A1i,j, A2i,j, and so on. 
This resembles the "aij", "bij" form where i and j are 
the column and row in the binary interaction coefficient 
matrix, respectively.
Reset COM 
Parameters
This button resets all binary interaction coefficients in 
the matrix pane to the original Aspen HYSYS estimated 
parameters.
Matrix Pane contains a list of the binary interaction 
coefficients for all binary component pairs in the Fluid 
Package. The naming convention is as follows:
• i  column
• j  row
=
=
2-113
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ThThe numbers that appear in the table are initially calculated by 
Aspen HYSYS and are modifiable. All known binary interaction 
parameters are displayed, with unknowns displayed as dashes 
(---). You have the option of overwriting any library value.
For all Equation of State parameters (except PRSV), Kij = Kji. If 
the value is modified for one of the parameters, both cells of the 
pair automatically update with the same value. In many cases, 
the library interaction parameters for PRSV do have Kij = Kji, but 
Aspen HYSYS does not force this if you modify one parameter in 
a binary pair.
If you are using PR, SRK or the PR Sour EOS, two radio buttons 
appear below the Interaction parameters table. 
Radio Button Description
Estimate HC-HC/
Set Non HC-HC to 
0.0
This radio button is the default selection. Aspen 
HYSYS provides the estimates for the interaction 
parameters in the table, setting all non-hydrocarbon 
pairs to 0.
Set All to 0.0 When this is selected, Aspen HYSYS sets all 
interaction parameter values in the table to 0.0.2-114
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ThActivity Model Interaction 
Parameters
The IP activity model displayed in the IP Model drop-down list is 
the corresponding liquid phase model selected on the Set Up 
tab. When you select an Activity Model in the IP Model Name 
list, the Interaction Parameter model information is displayed on 
the Binary Coeffs tab, as shown in the figure below. 
The activity models display the appropriate set of Coefficients 
for each component pair. For example, Chien-Null allows for 3 
sets of coefficients for each component pair, where (A1i,j = ai,j, 
A2i,j = bi,j and A3i,j = ci,j). 
 Figure 2.66
This information applies to the following liquid property models:
• Chien Null
• General NRTL
• Margules
• NRTL
• UNIQUAC
• van Laar
• Wilson
 Figure 2.67
Refer to the Aspen 
COMThermo Reference 
Guide for more 
information.2-115
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2-116 COMThermo Property View
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ThThe interaction parameters for each binary pair are displayed; 
unknown values show as dashes (---). You can overwrite any 
value.
To display a different coefficient matrix pane (i.e., Bij = A2i,j), 
select the appropriate coefficient using the drop-down list.
2.5.4 Stability Test Tab
The StabTest tab allows you to control how phase stability and 
flash calculations are performed. If you encounter situations 
where the flash fails or you are suspicious about the results, you 
can use this option to approach the solution using a different 
scheme.
For multi-phase fluids, there exist multiple false calculated 
solutions. A false solution exists when convergence occurs for a 
lower number of phases than exists in the fluid. For example, 
with a three-phase fluid, there is the correct three-phase 
solution, at least three false two-phase solutions and multiple 
false single-phase solutions. A major problem in converging the 
flash calculation is arriving at the right solution without a prior 
knowledge of the number of equilibrium phases.
Aspen HYSYS initially performs a two-phase flash, unless there 
is strong evidence for three phases. The resulting phases are 
then tested for their stability. 
You may reset the binary parameters to their original library 
values by clicking the Reset COM Parameters button.
COMThermo is not optimized for dynamics mode and may 
result in performance issues if used in dynamics mode.2-116
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ThThe StabTest property view is shown in the figure below.
Flash Settings
The following options are available in the Flash Settings table: 
 Figure 2.68
Flash Settings Description of Setting
MaximumNo. 
Iterations
You can set the maximum number of iterations executed 
in the flash calculations. The algorithm terminates after it 
reaches the maximum number of iterations.
Absolute 
Tolerance
This is the convergence tolerance of the governing flash 
equilibrium equations. If the equilibrium equation error is 
less than the Absolute Tolerance, the flash algorithm is 
assumed to have converged.
Relative 
Tolerance
In addition to the above condition, if the change in the 
error between iterations is less than the Relative 
Tolerance, the flash is assumed to have converged.
Ignore 
Composition
This is used to detect convergence to the trivial solution 
(where the compositions in the two phases are identical). 
If the differences in the compositions of the two phases 
are all less than the Trivial Composition Tolerance, the 
result is assumed to be trivial. 
To avoid discarding azeotropic results, the 
compressibility (Z) factors for the two phases are 
computed and compared in the case where the two 
phases involved are modelled using the same Property 
Methods (Equation of State Methods).2-117
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2-118 COMThermo Property View
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ThStability Test Parameters
The Stability Test Parameters group is described in the following 
sections.
Maximum Phases Allowed
You can specify the maximum number of phases allowed. If the 
maximum is set to 2, the stability test terminates after a 2-
phase flash. Occasionally, you may still get three phases, as the 
algorithm may attempt to start directly with the 3-phase flash.
Note that if the true solution has two phases and the maximum 
phases allowed is set to two, there is still no guarantee that the 
correct solution is reached. For instance, for binary mixtures 
around the azeotropic point, the correct solution may be liquid-
liquid equilibrium, but the algorithm may incorrectly converge to 
vapor-liquid equilibrium.
The Stability scheme used is proposed by Michelson(1980a). In 
the Method group, you can choose the method for performing 
the stability test calculations by selecting one of the radio 
buttons:
Radio Button Description
None No stability test is performed.
Low Uses a default set of Phases/Components to Initiate the 
Stability Test. The following methods are used: Deleted 
Phase, Wilson’s Equation and Component Initiation 
(Water). Only the water component (if it is part of your 
Fluid Package) is "introduced".
Medium In addition to those methods used for the Low method, 
the Average of Existing and Ideal Gas methods are also 
included. As well, the heaviest and the lightest 
components in the fluid are "introduced" using the 
Component Initiation method.
All All Phase Initiation methods are utilized, and all 
components are introduced using the Component 
Initiation method.2-118
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ThSecant Method Flash Setting
The Secant Method Flash Setting group is shown below.
The settings that are available for the Secant Method Flash are 
shown in the following table.
Phase Mole Fraction Tolerance
The phase fraction tolerance is used whenever a vapor fraction 
is given along with a temperature or pressure for the secant 
method flash. Aspen HYSYS guesses a temperature or pressure 
depending on which variable is required and predicts a new 
vapor fraction. The calculation terminates when the vapor 
fraction is within the tolerance range and the flash is converged.
 Figure 2.69
Temperature & 
Pressure Settings
Description
Default The default or initial value.
low_bound The lower or minimum bound for the secant 
method search.
up_bound The upper or maximum bound for the secant 
method search.
maxInc The maximum increment or initial step size for the 
secant temperature search. The logarithm of 
pressure is used as the primary variable for the 
pressure search, thus an initial pressure multiplier 
is used as the pressure increment.
tolerance The tolerance during the secant temperature and 
pressure search. It is used mainly by the backup 
flashes.2-119
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2-120 COMThermo Property View
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ThEnthalpy Tolerance
Different combinations may be used to flash. If the enthalpy is 
given, Aspen HYSYS guesses a temperature or pressure 
depending on which one is required and predicts a new enthalpy 
until the flash is converged within the tolerance specified.
Entropy Tolerance
Different combinations may be used to flash. If the entropy is 
given, Aspen HYSYS guesses a temperature or pressure 
depending on which one is required and predicts a new entropy 
until the flash is converged within the tolerance specified.
2.5.5 Phase Order Tab
The COMThermo Phase Order tab is the same as the traditional 
Aspen HYSYS property view. See Section 2.4.5 - Phase Order 
Tab.
2.5.6 Reactions Tab
The COMThermo Rxns tab is the same as the traditional Aspen 
HYSYS property view. See Section 2.4.6 - Reactions Tab.
2.5.7 Tabular Tab
The COMThermo Tabular tab is the same as the traditional 
Aspen HYSYS property view. See Section 2.4.7 - Tabular Tab.
2.5.8 Notes Tab
See traditional Aspen HYSYS thermodynamics Section 2.4.8 - 
Notes Tab.2-120
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Th2.6 References
 1 Wong, D. S. H., Sandler, S. I., “A Theoretically Correct Mixing Rule for 
Cubic Equations of State”, A.I.Ch.E. Journal, 38, No. 5, p.671 
(1992)
 2 Twu, H.C. and Bulls, J.W., "Viscosity Blending Tested", Hydrocarbon 
Processing, April 1981.
 3 Ely, J.F. and Hanley, H.J.M., "A Computer Program for the Prediction 
of Viscosity and Thermal Conductivity in Hydrocarbon Mixtures", 
NBS Technical Note 1039.2-121
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2-122 References
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Th2-122
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Hypotheticals 3-1
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Th3  Hypotheticalsw.cadfamily.com    EMa
e document is for study 3.1  Introduction................................................................................... 3
3.2  Hypo Manager................................................................................ 4
3.3  Adding a Hypothetical - Example ................................................... 5
3.3.1  Creating the Ethanol Hypo......................................................... 6
3.3.2  Hypo/Library Component Comparison ....................................... 11
3.4  Creating a Hypo Group................................................................. 13
3.4.1  Hypo Group Property View....................................................... 13
3.4.2  Supplying Basic Information .................................................... 17
3.4.3  UNIFAC Structure ................................................................... 23
3.5  Hypothetical Component Property View....................................... 26
3.5.1  ID Tab .................................................................................. 28
3.5.2  Critical Tab ............................................................................ 29
3.5.3  Point Tab............................................................................... 30
3.5.4  TDep Tab .............................................................................. 32
3.6  Solid Hypotheticals ...................................................................... 36
3.6.1  ID Tab .................................................................................. 36
3.6.2  Props Tab .............................................................................. 37
3.6.3  Point Tab............................................................................... 39
3.6.4  TDep Tab .............................................................................. 40
3.6.5  PSD Tab ................................................................................ 41
3.7  Cloning Library Components ........................................................ 42
3.7.1  Converting a Library Component to a Hypo ................................ 433-1
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3-2 Hypotheticals 
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The document is for study 3.8  Hypo Controls ...............................................................................44
3.8.1  Viewing Groups ......................................................................44
3.8.2  Moving Hypos.........................................................................45
3.9  References....................................................................................453-2
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Th3.1 Introduction
Aspen HYSYS allows you to create non-library or Hypothetical 
components from the Hypo Manager. Hypothetical components 
can be pure components, defined mixtures, undefined mixtures, 
or solids. You can also convert/clone Aspen HYSYS library 
components into Hypotheticals, which allow you to modify the 
library values. 
The Hypo Manager is located on the Hypotheticals tab of the 
Simulation Basis Manager. It can also be accessed via the Hypo 
manager button from the Components tab under hypothetical 
components.
A wide selection of estimation methods are provided for the 
various Hypo groups (hydrocarbons, alcohols, etc.) to ensure 
the best representation of behaviour for the Hypothetical 
component in the simulation. In addition, methods are provided 
for estimating the interaction binaries between hypotheticals 
and library components. You can also use Hypotheticals with the 
Tabular Package, as well as in Reactions.
In Aspen HYSYS, Hypothetical components exist independent of 
the Fluid Package. When a Hypothetical is created, it is placed in 
a Hypo Group. From the Hypo Manager, you can create new 
Hypo Groups and move Hypothetical components within the 
Hypo Groups. Hypo Groups can also be imported and exported, 
thus making them available to any simulation case.
Since Hypothetical components are not exclusively associated 
with a particular Fluid Package, it is possible for multiple Fluid 
Packages to share Hypotheticals. In other words, you only need 
to create a Hypothetical once, and it can be used in any Fluid 
Package throughout the case.3-3
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3-4 Hypo Manager
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Th3.2 Hypo Manager
By selecting the Hypotheticals tab from the Simulation Basis 
Manager, the following property view appears:
The left side of the property view is the Hypothetical Groups 
group.
The lists all the Hypothetical groups currently installed in the 
simulation. The available commands for this group (accessed 
using the associated buttons) are as follows:
 Figure 3.1
You can Import and Export Hypothetical groups, allowing 
you to use defined hypotheticals in any future simulation
Hypothetical groups and individual hypothetical components 
can be installed in more than one Fluid Package.
Button Description
View Accesses the Hypo Group property view for the selected 
group.
Add Adds a Hypothetical Group to the present case.
Delete Deletes the selected Hypothetical Group from the case.3-4
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ThThe right side of the property view displays the Hypothetical 
Quick Reference group. This group includes all Hypotheticals 
currently installed in the Basis Environment (Hypo Name 
column) along with their associated Hypo Groups (Group Name 
column). The available buttons within this group are described 
below:
3.3 Adding a Hypothetical 
- Example
In this example, a hypothetical Ethanol component is defined, 
and the results to the library Ethanol component using the 
Wilson property package are compared. The ethanol 
hypothetical component is defined as having a boiling point of 
78.25 °C and a specific gravity of 0.789.
Translocate Searches through all of the hypothetical components in the 
case and if there are duplicates Aspen HYSYS replaces 
them and puts all the duplicates in a separate Hypo group 
which then can be deleted.
This is intended for use when large cases have had large 
numbers of templates/fluid packages imported and there 
are lots of repeated hypotheticals in the case.
Import Imports a Hypothetical Group from disk.
Export Exports the selected Hypothetical Group and saves it to a 
file, so that it can be retrieved at a later time.
Button Description
View Hypo Access the property view for the highlighted Hypothetical.
View Group Access the Hypo Group property view for the highlighted 
Hypothetical.
Move Hypos Move Hypotheticals from one Hypo Group to another.
Clone Comps Use a copy of a selected library components as the basis for 
defining a Hypothetical.
Button Description3-5
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3-6 Adding a Hypothetical - Example
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Th3.3.1 Creating the Ethanol 
Hypo
To create a ethanol hypo, follow the steps outlined below:
1. Open a new case in Aspen HYSYS.
2. Select Tools | Preferences in the menu bar to open the 
Session Preferences property view.
3. In the Session Preferences property view, click the 
Variables tab and select the Units page.
4. Select SI as the units for this example case.
5. In the Simulation Basis Manager property view, select the 
Hypotheticals tab.
6. From the Hypothetical Groups group, click the Add button to 
create a new Hypothetical Group. Aspen HYSYS 
automatically names this group HypoGroup1. You can 
change the name later, if desired.
When you add a new Hypothetical Group, Aspen HYSYS 
automatically opens the Hypo Group property view, where 
you add and define the Hypothetical component(s) for the 
group. 
You must install a Hypothetical Group before you can install 
a Hypo component.3-6
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Th7. On the Hypo Group property view, enter HypoAlcohol as 
the new Group Name.
Notice that the Aspen HYSYS default in the Component 
Class list is Hydrocarbon. 
8. In the Component Class drop-down list, select Alcohol.
9. Now, install a Hypothetical component. From the Individual 
Hypo Controls group, click the Add Hypo button. This adds 
a Hypothetical component and automatically names it 
Hypo20000*.
10. Enter a new name for this component by selecting the Name 
cell typing HypoEtoh.
11. In the NBP cell, enter the normal boiling point of the 
component as 78.25°C.
12. The specific gravity for the hypothetical component is 0.789. 
In the Liq Density cell, enter 0.789 and select the 
SG_H2O60api units. A liquid density of 787.41 kg/m3 is 
calculated by Aspen HYSYS.
 Figure 3.2
 Figure 3.33-7
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3-8 Adding a Hypothetical - Example
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Th13.Although Aspen HYSYS could estimate the unknown 
properties for HypoEtoh with only the NBP and Liquid 
Density, more accurate results are obtained if the 
component structure is supplied. Click the UNIFAC button to 
access the UNIFAC Component Builder.
14. The chemical formula of ethanol is C2H5OH, and it is 
comprised of the groups CH3, CH2, and OH. Highlight CH3 
in the Available UNIFAC Groups list. It is the first 
selection in the list.
15.Click the Add Group(s) button. 
Notice that a “1” is displayed under Sub Group in the 
UNIFAC Structure group. By default, Aspen HYSYS assigns 
the value “1” to the How Many cell. The number is valid, 
since this is the number of CH3 groups required. The 
number of Free Bonds has increased to 1 with the addition of 
the CH3 Sub Group.
16. To add the CH2 group, highlight it in the Available UNIFAC 
Groups list (it is the second in the list) and click the Add 
Group(s) button. Again, only 1 Sub Group is required, so 
the default is acceptable.
 Figure 3.43-8
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Th17.Since the OH group is not immediately visible in the list of 
Available UNIFAC Groups, a different approach is taken. 
In the UNIFAC Structure input field, type OH at the end of 
the existing structure (CH3CH2) and press ENTER. 
Once the UNIFAC Structure is complete, Aspen HYSYS 
calculates the UNIFAC Base and Critical Properties. 
18.Click the Close icon  to close the property view and return 
to the Hypo Group property view.
Aspen HYSYS can now use the existing information (NBP, 
Liquid Density and UNIFAC structure) to estimate the 
remaining properties for the Hypothetical component. 
 Figure 3.5
Notice that the Incomplete status message is replaced with 
Complete when there are 0 Free Bonds.
Property Estimation 
Methods are explained in 
Section 3.4.2 - 
Supplying Basic 
Information.3-9
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3-10 Adding a Hypothetical - Example
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Th19.We will now examine the Estimation Method that Aspen 
HYSYS uses. Click the Estimation Methods button to 
access the Property Estimation property view.
If you want, you can change the estimation method for any 
property. In this example, all properties use the Default 
Method. 
20.Click the Close icon  to return to the Hypo Group property 
view.
21.Click the Estimate Unknown Props button and Aspen 
HYSYS uses the currently specified methods to estimate the 
unknown properties for the component. The molecular 
weight for the hypothetical is the same as the molecular 
weight for ethanol, 46.07, since the UNIFAC structure is 
used for the Hypo component. 
 Figure 3.6
 Figure 3.7
Remember that specified values are displayed in blue, and 
Aspen HYSYS estimated values are displayed in red.3-10
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Th22.You can examine all properties for the Hypo through its 
property view. Double-click on the Hypothetical component 
name, HypoEtoh, to access the Component property view. 
23.Click the Close icon  to return to the Hypo Group property 
view.
24.Click the Close icon  and Aspen HYSYS returns you to the 
Hypotheticals tab of the Simulation Basis Manager. The 
Ethanol Hypothetical has is created.
3.3.2 Hypo/Library Component 
Comparison
To conclude, compare the ethanol hypothetical to the ethanol 
library component. Go to the Simulation Basis Manager:
1. On the Fluid Pkgs tab, click the Add button to install the 
new Fluid Package. 
2. On the Set Up tab, select Wilson as the Property Package 
and close the fluid package property view.
3. Move to the Components tab and add Ethanol to the 
Selected Component List by highlighting the Components 
page in the Add Component group.
 Figure 3.8
For further information 
regarding the Property 
View, refer to Section 
3.5 - Hypothetical 
Component Property 
View.3-11
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3-12 Adding a Hypothetical - Example
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Th4. From the Available Hypo Components group, highlight the 
HypoEtoh* component and click the Add Hypo button from 
the Hypothetical page.
5. Move to the Binary Coeffs tab in the fluid package property 
view and click the Unknowns Only button in the Coeff 
Estimation group.
6. Close the Fluid Package property view.
7. Click the Enter Simulation Environment button to enter 
the Main Environment.
8. In the Workbook, create the stream Pure. Enter a vapour 
fraction of 0 and a pressure of 1 atm for the stream on the 
Material Streams tab of the workbook. Move to the 
Compositions tab an enter 1 for the mole fraction of Ethanol, 
and 0 for HypoEtoh*.
9. Now create a second stream, Hypo. Enter a vapour fraction 
of 0 and a pressure of 1 atm for the stream. The mole 
fraction of HypoEtoh* is 1, and that for Ethanol is 0.
When you have specified these two streams, Aspen HYSYS 
calculates the bubble point temperature for each stream. 
The Conditions tab of the property view for each stream is 
shown below.
 Figure 3.93-12
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Th3.4 Creating a Hypo Group
When defining a hypothetical, there is no set procedure. The 
following is a suggested sequence in which you can follow:
1. Create the Hypo Group. 
2. Select the Component Class for the Hypo Group.
3. Set the Estimation Methods for the Group (optional). 
4. Install the Hypotheticals.
5. Supply all information that you have for the Hypo.
6. Supply a UNIFAC structure for the Hypo (optional). 
7. Estimate the Properties for the Hypo.
3.4.1 Hypo Group Property 
View
As mentioned in the Hypothetical example, you add a Hypo 
Group by clicking the Add button from the Hypotheticals tab of 
the Simulation Basis Manager. This opens the Hypo Group 
property view, which contains two groups (Hypo Group Controls 
and Individual Hypo Controls), and a table of estimated or 
known property values.
 Figure 3.10
For more information, 
refer to Section 3.4.1 - 
Hypo Group Property 
View.
For more information, 
refer to Section 3.4.2 - 
Supplying Basic 
Information.
For more information, 
refer to Section 3.4.3 - 
UNIFAC Structure.3-13
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3-14 Creating a Hypo Group
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ThHypo Group Controls
The Hypo group contains the following options: 
Option Description
Group Name Displays the current name for the Hypothetical Group. 
Aspen HYSYS provides a default name, but you can change 
this to a more descriptive name. Individual Hypothetical 
components must reside inside of a Hypothetical group.
Component 
Class
Every component in a Hypo Group must be of a common 
Component Class. The options are accessed using the drop-
down list attached to the input cell. There is a wide 
selection of available Classes, which allows for better 
estimation of the component properties. Aspen HYSYS, by 
default, selects the Component Class to be Hydrocarbon. 
Prior to installing any components, select the Component 
Class.
Estimation 
Methods
Access the Property Estimation property view, from which 
you can select an estimation method for each property. The 
selected estimation methods apply to all Hypotheticals in 
the Hypo Group.
Estimate 
Unknown 
Props
This button estimates the unknown properties for all 
Hypothetical components within the Hypo Group, using the 
methods chosen on the Property Estimation property view. 
Clone Library 
Comps
Aspen HYSYS allows you to convert library components into 
hypothetical components. For more information, refer to 
Section 3.7 - Cloning Library Components.
Notes Allows you to supply Notes and Descriptions for the 
Hypothetical Group. This is useful when exporting Hypo 
groups, because when you import them later, the 
description appears along with the Hypo group name.
For the Component Class, there are varying levels of 
specificity. For example, under Alcohol, you can specify sub-
classes of alcohols, such as Aliphatic, Aromatic, Cyclo and 
Poly. Using a stricter degree of component type assists 
Aspen HYSYS in choosing appropriate estimation methods; 
however, it forces all components to be calculated using the 
same method. If you want to mix component classes (i.e., 
both Aliphatic and Aromatic inside the same Hypo Group), 
select the more general Component Class of Alcohol.
For more information, 
refer to Section 3.4.2 - 
Supplying Basic 
Information.3-14
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ThIndividual Hypo Controls
The Individual Hypo Controls group at the bottom of the Hypo 
Group property view contains buttons for manipulating the 
Hypotheticals within the Hypo Group and two radio buttons for 
switching between Base Properties and Vapour Pressure data.
The table displayed in the middle section of the Hypo Group 
property view, displays either the Base Properties or the Vapour 
Pressure properties, depending on which radio button is 
selected. You can add a new Hypo component in either the Base 
Properties or Vapour Pressure property view. 
Button Description
View Displays the Property View for the highlighted hypothetical 
component.
The View button will not be available unless a hypothetical 
is present in the case. 
Add Hypo Automatically adds a new hypothetical component to the 
group. Aspen HYSYS places the new Hypo in the table, and 
names it according to the default naming convention (set in 
the Session Preferences). 
Add Solid Automatically adds a new solid hypothetical component to 
the group. Aspen HYSYS places the new Hypo in the table, 
and names it according to the default naming convention 
(set in the Session Preferences).
Delete Deletes the highlighted hypothetical component from the 
case. After deleting a Hypo it cannot be recovered.
The Delete button will not be available unless a 
hypothetical is present in the case. 
UNIFAC Opens the UNIFAC Component Builder, from which you can 
provide the UNIFAC Structure for the highlighted 
hypothetical component.
The UNIFAC button will not be available unless a 
hypothetical is present in the case. 3-15
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3-16 Creating a Hypo Group
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ThBase Properties
The Base Properties for each Hypothetical are shown on the 
Hypo Group property view when the Base Properties radio 
button is selected. 
The table lists each Hypothetical along with the following Base 
Properties: 
 Figure 3.11
These properties are the same as those shown on the Critical 
tab of the Hypo component property view.
Base Property Description
NBP Normal boiling point
MW Molecular weight
Liq Density Liquid density
Tc Critical temperature
Pc Critical pressure
Vc Critical volume
Acentricity Acentric factor
Individual Base Properties are supplied by selecting the 
appropriate cell. Use the drop-down list to select the units 
within the cell. 3-16
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Hypotheticals 3-17
ww
ThVapour Pressure Properties
The Vapour Pressure table displays the temperature range and 
Antoine Coefficients for the hypothetical components. Also 
shown are the pressure and temperature units on which the 
equation is based and the form of the equation.
The values shown on this property view are also available on the 
TDep tab of the individual Hypo property view. 
Use the horizontal scroll bar to view Coeff E and Coeff F.
3.4.2 Supplying Basic 
Information
Before Aspen HYSYS can estimate the properties for a 
hypothetical, some information about the Hypo must be 
provided. For the estimation, you must supply a minimum 
amount of information and select the estimation methods to be 
used.
 Figure 3.123-17
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3-18 Creating a Hypo Group
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ThMinimum Information Required
If the hypothetical component is defined as a hydrocarbon, the 
appropriate default correlations can be used to calculate its 
critical properties or any other missing information. Its 
interaction parameters are also calculated by Aspen HYSYS 
based on the estimated critical properties. For Aspen HYSYS to 
estimate the component's critical properties, a minimum 
amount of information must be supplied, as shown in the 
following table. 
Estimation Methods
Prior to installing any Hypotheticals into a Hypo group, examine 
the Estimation Methods which Aspen HYSYS uses to calculate 
the unknown properties for a hypothetical component. You can 
specify a estimation method for each property. Click the 
Estimation Methods button on the Hypo Group property view.
Normal Boiling Point Minimum Required Information
<  700 °F (370 °C) Boiling Point
> 700 °F (370 °C) Boiling Point and Liquid Density
Unknown API & Molecular Weight
The more information you can supply, the more accurate the 
estimations are.
 Figure 3.133-18
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Hypotheticals 3-19
ww
ThThe Estimation Methods that you choose for the Hypo Group 
apply to all Hypotheticals in that group.
There are three groups in the Property Estimation property view 
and are described below:
Group Description View
Property to Set 
Methods For
This group lists all the available 
properties. From the list, choose the 
property for which you want to set the 
Estimation Method. Use the scroll bar to 
move through the list. Initially, Aspen 
HYSYS sets all the properties to the 
Default Method.
Estimation 
Method For 
Selected 
Property
This drop-down list displays all the 
available estimation methods for the 
highlighted property. Depending on the 
property, the drop-down list differs. The 
list shown here is a partial display of 
estimation methods for Critical 
Temperature.
Variables 
Affected by this 
Estimate
This group lists all the variables that are 
affected by the selected estimation 
method. The list changes depending on 
the property selected. For example, when 
you select an estimation method for 
Critical Temperature, you are not only 
affecting the critical temperature, but 
also the properties which use critical 
temperature in their estimation or 
calculation.3-19
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3-20 Creating a Hypo Group
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ThThe following table individually lists each Property, its Default 
Method, its Available Estimation Methods and the Variables 
Affected by estimating the Property. It is understood that each 
property can have Do Not Estimate selected as its Estimation 
Method, so this option does not appear in the Available Methods 
list.
Property Default Method Available Methods Variables Affected
Critical 
Temperature
• if ρLIQ > 1067 kg/m3 or 
NBP > 800 K, Lee-
Kesler is used
• if NBP < 548.16 K and  
ρLIQ<850 kg/m3, 
Bergman is used
• all other cases, Cavett 
is used 
Aspen, Bergman, Cavett, 
Chen Hu, Eaton Porter, 
Edmister, Group 
Contribution, Lee Kesler, 
Mathur, Meissner Redding, 
Nokay, Riazi Dauber, Roess, 
PennState, Standing, Twu
• Critical 
Temperature
• Standard Liquid 
Density
• COSTALD 
Variables 
• Viscosity Thetas
Critical 
Pressure
• if ρLIQ > 1067 kg/m3 or 
NBP > 800 K, Lee-
Kesler is used
• if NBP < 548.16 K and  
ρLIQ <850 kg/m3, 
Bergman is used
• all other cases, Cavett 
is used 
Aspen, Bergman, Cavett, 
Edmister, Group 
Contribution, Lee Kesler, 
Lydersen, Mathur, 
PennState, Riazi Daubert, 
Rowe, Standing, Twu
• Critical Pressure
• Standard Liquid 
Density
• COSTALD 
Variables
• Viscosity Thetas
Critical 
Volume
• Pitzer Group Contribution, Pitzer, 
Twu
• Critical Volume
• Standard Liquid 
Density
• COSTALD 
Variables
• Viscosity Thetas
Acentricity • for Hydrocarbon, Lee-
Kesler is used
• all other cases, Pitzer 
is used
Bergman, Edmister, Lee 
Kesler, Pitzer, Pitzer Curl, 
Robinson Peng, Twu
• w
• ωGs
• Standard Liquid 
Density
• COSTALD 
Variables
• Viscosity Thetas
Molecular 
Weight
• if NBP < 155 °F, 
Bergman is used
• all other cases, Lee-
Kesler is used
API, Aspen, Aspen Leastq, 
Bergman, Hariu Sage, Katz 
Firoozabadi, Katz Nokay, 
Lee Kesler, PennState, Riazi 
Daubert, Robinson Peng, 
Twu, Whitson
• Molecular Weight
Normal 
Boiling Point
• Hyprotech proprietary 
method
• Normal Boiling 
Point
• Viscosity Thetas
Vapour 
Pressure
• for Hydrocarbon, Lee-
Kesler is used
• all other cases, Riedel 
is used
Gomez Thodos, Lee Kesler • Antoine 
Coefficient
• PRSV_kappa3-20
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Hypotheticals 3-21
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ThLiquid 
Density
• Yen-Woods Bergman, BergmanPNA, 
Chueh Prausnitz, Gunn 
Yamada, Hariu Sage, Katz 
Firuzabadi, Lee Kesler, Twu, 
Whitson, Yarborough, Yen 
Woods
• Standard liquid 
Density
• COSTALD 
Variables
Ideal Gas 
Enthalpy
• Cavett Cavett, Fallon Watson, 
Group Contribution, Lee 
Kesler, Modified Lee Kesler, 
• Ideal H Coefficient
Heat of 
Formation
• for chemical structure 
defined in UNIFAC 
groups, Joback is 
used
• all other cases, this 
formula is used:
Group Contribution • Heat of Formation
• Heat of 
Combustion
Ideal Gas 
Gibbs Energy
• Hyprotech proprietary 
method
Group Contribution • Gibbs Coefficient
Heat of 
Vapourizatio
n
• Two Reference Fluid 
(using benzene and 
carbazole)
Chen, Pitzer, Riedel, Two 
Reference1, Vetere
• Cavett Variables
Liquid 
Viscosity
• for non-Hydorcarbon 
or NBP < 270 K 
Letsou Stiel is used
• for Hydorcarbon and 
NBP < 335 K, NBS 
viscosity is used
• all other cases, Twu is 
used
Hyprotech Proprietary, 
Letsou Stiel
• Viscosity Thetas
Surface 
Tension
• Brock Bird Brock Bird, Gray, Hakin, 
Sprow Prausnitz
• Tabular Variables
Radius of 
Gyration
• Hyprotech proprietary 
method
Default Only • Critical 
Temperature
• Critical Pressure
• Normal Boiling 
Point
• Molecular Weight
• Standard Liquid 
Density
Property Default Method Available Methods Variables Affected
Hform octane( ) MW⋅
MW octane( )
-------------------------------------------------3-21
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3-22 Creating a Hypo Group
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ThIn defining Hypothetical components, there are some properties 
for which you cannot select the estimation method. Aspen 
HYSYS determines the proper method based on information you 
have provided. The following table lists these properties and 
their respective default methods:
Property Default Estimation Method
Liquid Enthalpy • The previously calculated Liquid Heat 
Capacity is used.
Vapour Enthalpy • Liquid Enthalpy + Enthalpy of Vapourization
Chao Seader Molar 
Volume
• If Tc > 300 K, Molar Volume from 
COSTALD @ 25 °C and 1 atm is used
• all other cases, ρLIQ @ 60 °F is used
Chao Seader 
Acentricity
• component acentric factor is used
Chao Seader 
Solubility Parameter
• If Tc > 300K, Watson type Enthalpy of 
Vaporization is used
• all other cases, values of 5.0 are used
Cavett Parameter • Two Reference Fluid1 method (using 
benzene and carbazole)
Dipole Moment • No estimation method available, sets value 
equal to zero.
Enthalpy of 
Combustion
• No estimation method available, sets value to 
.
COSTALD 
Characteristic 
Volume
• If NBP < 155 °F, Bergman is used
• all other cases, Katz-Firoozabadi is used
Liquid Viscosity 
Coefficients A and B
• For non-Hydrocarbon or NBP < 270 K, 
Letsou Stiel is used
• for Hydrocarbon and NBP < 335 K, NBS 
viscosity is used
• all other cases, Twu is used.
Vapour Viscosity • Chung
PRSV Kappa1 • Vapour Pressure from Antoine’s 
Equation
Kfactor1 • Vapour Pressure from Antoine’s 
Equation3-22
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Hypotheticals 3-23
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Th3.4.3 UNIFAC Structure
Most of the estimation methods require a UNIFAC structure for 
some aspect of the estimation. It may be that either the 
property itself, or some other property that is affected by the 
estimation procedure requires the chemical structure.
The UNIFAC structure is supplied through the UNIFAC 
Component Builder. This can either be accessed by clicking the 
UNIFAC button in the Hypo Group property view, or by clicking 
the Structure Builder button on the ID tab of the Hypothetical 
component property view. Whichever route is taken, the 
following property view appears:
The UNIFAC Component Builder property view is made up of the 
following objects:
 Figure 3.14
Objects Description
UNIFAC Structure 
Group
Displays the Type and Number of Sub Groups in 
the UNIFAC Structure.
This group makes reference to both the UNIFAC 
Structure group (the table of cells) and the 
UNIFAC Structure entry field. 
Add Group(s) Adds the currently selected Sub Group from the 
Available UNIFAC Groups list box to the UNIFAC 
Structure group.
Delete Group Deletes the currently selected Sub Group in the 
UNIFAC Structure group.3-23
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3-24 Creating a Hypo Group
ww
ThThe procedure for supplying the UNIFAC structure is to highlight 
the Sub Group(s) in the Available UNIFAC Groups column and 
select the Add Group(s) button. Additional sub groups can be 
accessed in the list by using the Scroll Bar.
As you add sub groups, Aspen HYSYS displays the number of 
Free Bonds available. This is zero when the UNIFAC structure is 
complete. When you have supplied enough groups to satisfy the 
bond structure, the status message changes to Complete (with 
a green background).
As you specify groups, the UNIFAC Calculated Base Properties 
and UNIFAC Calculated Critical Properties are automatically 
updated based on the new structure.
Free Bonds Displays the number of free bonds available in the 
present UNIFAC Structure. This is 0 when the 
structure is complete.
Status Bar This bar is found in the centre of the property 
view. It indicates the present status of the UNIFAC 
Structure. You see either Incomplete in red, 
Complete in green, or Multi-Molecules in yellow.
Available UNIFAC 
Groups
Contains all the available UNIFAC component sub 
groups.
UNIFAC Structure
field
Displays the chemical structure of the molecule 
you are building.
UNIFAC Calculated 
Base Properties
Displays properties such as Molecular Weight, the 
UNQUAC R parameter, and the UNIQUAC Q 
parameter for a UNIFAC Structure with at least 1 
sub group.
UNIFAC Calculated 
Critical Properties
Displays the critical properties for a UNIFAC 
Structure with at least 1 sub group.
Objects Description3-24
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Hypotheticals 3-25
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ThThere are three methods available for adding Sub Groups to the 
UNIFAC Structure:
Aspen HYSYS automatically calculates Base Properties and 
Critical Properties using the currently supplied structure.
Sub Group Description
Highlighting 
the Sub 
Group
The list of Available UNIFAC Groups displays all the sub 
groups. Notice that CH3 is the first selection in this list. You 
can use the scroll bars to move through the list until you 
find the group you need. When you find the correct Sub 
Group, highlight it, and click the Add Group(s) button. 
The sub group now appears in the UNIFAC Structure group.
You can highlight more than one sub group, and add all at 
the same time.
Using the 
Sub Group 
Number
Each sub group has a number associated with it. If you 
know the number for the sub group you want to add to the 
UNIFAC Structure, move the active location to the Sub 
Group column of the UNIFAC Structure group. Enter the 
number of the Sub Group. Aspen HYSYS does not 
automatically fill in the number of sub groups. Move the 
active location to the How Many column and type in the 
number of sub groups required.
Notice the difference between the UNIFAC Structure group 
(the table of cells) and the UNIFAC Structure entry field.
Typing in the 
UNIFAC 
Structure 
input field
Notice the UNIFAC Structure input field near the bottom of 
the property view. Any sub groups already installed are 
listed here. Place the cursor after the last group, and type 
in the group to install. For example, if we want to add an 
OH group, type in OH. When you type the sub group in this 
box, Aspen HYSYS automatically adds it to the UNIFAC 
Structure group.
You can add multiples of a Sub Group in the UNIFAC 
Structure box. Type the number of Sub Groups and the Sub 
Group name, separated by a space. For example, type 3 CH2 
to add three CH2 groups to the UNIFAC structure. NOTE: You 
cannot add Sub Groups in this way to an existing UNIFAC 
structure.3-25
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3-26 Hypothetical Component Property 
ww
Th3.5 Hypothetical 
Component Property 
View
Hypotheticals, like library components, have their own property 
view. Once inside, you can add or modify information, or 
examine the results of the estimations.
You can access the property view for the Hypo component from 
different property views:
View Method of Accessing Hypo
Simulation Basis 
Manager, 
Hypotheticals Tab
All the hypothetical components are displayed in 
the Hypothetical Quick Reference group. You can 
either double-click on the component name, or 
highlight it and click the View Hypo button.
Hypo Group All the hypothetical components in the Hypo Group 
you have chosen to view, are displayed. Either 
double-click on the Hypo component you want to 
view, or highlight it and click the View button.
Simulation Basis 
Manager, 
Components Tab
After adding a hypothetical to the Selected 
Component List group, highlight it and click the 
View Component button or object inspect its 
name and select View.3-26
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Hypotheticals 3-27
ww
ThThe Hypothetical property view is made up of five tabs and are 
shown below. Some of the tabs have radio buttons for switching 
between the various properties. When a different radio button is 
selected, Aspen HYSYS redraws the property view with the 
information appropriate to the item. 
After you have entered adequate estimation parameters, you 
can click the Estimate Unknown Properties button to 
complete the hypothetical estimation. The Edit Properties 
button allows you to edit properties within the hypocomponent 
at the component level. The Edit Visc Curve button allows you 
to recalculate the viscosity coefficients based on the 
temperature and dynamic viscosity data provided by the user. 
Throughout the tabs of the property view, information is 
displayed in red, blue, and black. Values displayed in red are 
estimated by Aspen HYSYS and values displayed in blue are user 
supplied. Black values represent calculated values or 
information that you cannot modify (in other words, Family/
Class on the ID tab).
 Figure 3.15
Refer to Edit Properties 
in Section 1.2.3 - 
Manipulating the 
Selected Components 
List for more information.3-27
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3-28 Hypothetical Component Property 
ww
Th3.5.1 ID Tab
The ID tab is the first tab in the Hypo property view. If it is the 
first time you are entering a Property View, Aspen HYSYS places 
you on this tab.
You can supply values directly for any of the component 
properties, or overwrite values estimated by Aspen HYSYS. 
If you change a specified value, all properties previously 
estimated using that specification are forgotten. Click the 
Estimate Unknown Props button to have the properties 
recalculated.
 Figure 3.16
If a Structure is 
already entered, 
it is displayed 
here. You can 
also enter the 
Structure 
directly into this 
cell.
Use this button 
to access the 
UNIFAC 
Component 
Builder and 
supply the 
structure of the 
Hypo.3-28
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Hypotheticals 3-29
ww
Th3.5.2 Critical Tab
The Critical tab of the property view displays the base and 
critical properties. This is the same information displayed on the 
Hypo Group when the Base Properties radio button is selected.
You can supply or change the Base Properties on this tab. The 
property views, shown in Figure 3.17, display the Critical tab 
before and after the Estimate Unknown Props button is clicked. 
Notice that since the Normal Boiling Point was less that 370 °C, 
only the Molecular Weight value was required for this 
estimation. 
 Figure 3.17
For more information on 
the Minimum 
Information required for 
Property Estimation see 
Section 3.4.2 - 
Supplying Basic 
Information3-29
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3-30 Hypothetical Component Property 
ww
Th3.5.3 Point Tab
The Point tab displays Additional Point Properties for the 
hypothetical. There are two radio buttons on the property view, 
which allow you to toggle between two tables of information are 
the:
• Thermodynamic and Physical Properties
• Property Package Molecular Properties
Thermodynamic & Physical 
Properties
This property view displays the Thermodynamic and Physical 
properties for the Hypo. Aspen HYSYS estimates these values, 
based on the base property data entered and the selected 
estimation methods.
Notice that the Heat of Comb field is . This indicates 
that Aspen HYSYS cannot estimate this value with the given 
information. Aspen HYSYS allows you to input a value for this 
property.
 Figure 3.183-30
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Hypotheticals 3-31
ww
ThThe viscosity coefficients of A and B are first estimated by Aspen 
HYSYS based on the initial specifications from the Hypo Group 
property view. If you want to calculate these coefficients, you 
can override the estimation by clicking the Edit Visc Curve 
button. This allows you to enter a set of data points of 
temperature versus dynamic viscosity. 
There are three buttons available in the Edit Viscosity Curve 
property view:
Aspen HYSYS will recalculate the values of the viscosity 
coefficients based on the data points you just entered. The 
values of the viscosity coefficients A and B will then change from 
red to black indicating that they are calculated values.
 Figure 3.19
Buttons Descriptions
OK Allows Aspen HYSYS to accept the data to perform the 
calculations.
Delete Clears all the data points in the data table and closes the 
property view automatically.
Cancel Cancels the operation and exit the property view. The data 
points you entered will not be used in the calculations but 
these points will be saved in the data table without being 
cleared so you can make modification later. 3-31
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3-32 Hypothetical Component Property 
ww
ThProperty Package Molecular Props
This property view displays the Molecular properties for the 
Hypo. The values estimated are dependent on the selected 
estimation method for each property.
Some of the fields in this property view are . This 
indicates that Aspen HYSYS cannot estimate these values with 
the information given. However, you can specify values for 
these properties.
3.5.4 TDep Tab
The TDep tab displays Temperature Dependent Properties for 
the hypothetical. There are three radio buttons on the property 
view, which allow you to toggle between the three different 
displays of information. The property views available are:
• Vapour Enthalpy
• Gibbs Free Energy
• Vapour Pressure
 Figure 3.203-32
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Hypotheticals 3-33
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ThVapour Enthalpy
The Vapour Enthalpy calculation is performed on a Mass Basis. 
The reference point for the equation is an ideal gas at 0 K. The 
units for Mass Vapour Enthalpy and Temperature are kJ/kg and 
degrees Kelvin, respectively.
When required, the Vapour Enthalpy equation is integrated by 
Aspen HYSYS to calculate entropy. Note that if enthalpy 
coefficients are entered, a constant of integration, g, should be 
supplied along with the other coefficients. Specify this value in 
the g coefficient field.
Notice that Aspen HYSYS has estimated the Minimum and 
Maximum Temperatures. 
Below the temperature range are values for the Vapour Enthalpy 
equation coefficients (from a to g). Aspen HYSYS estimates the 
coefficients, but you may change any of the values.
 Figure 3.213-33
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3-34 Hypothetical Component Property 
ww
ThVapour Pressure
The Vapour Pressure is calculated using the Modified Antoine 
equation. Aspen HYSYS estimates the Minimum and Maximum 
Temperature values based on the supplied properties and 
estimation methods.
The units used for Pressure and Temperature are kPa, and 
degrees Kelvin, respectively.
The bottom section of this property view displays the values for 
each of the Antoine equation coefficients (from a to f). Aspen 
HYSYS estimates the coefficients, however you can modify these 
values.
 Figure 3.223-34
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Hypotheticals 3-35
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ThGibbs Free Energy
The Gibbs Free Energy calculation uses Enthalpy as its property 
type and is performed on a Molar Basis. The basis for the 
equation is ideal gas at 25 °C. Aspen HYSYS estimates the 
Minimum and Maximum Temperature values.
The units for Molar Enthalpy and Temperature are kJ/kg mole 
and degrees Kelvin, respectively.
The bottom section of the property view displays the values for 
each of the Gibbs Free Energy equation coefficients (from a to 
c).
Aspen HYSYS estimates the Gibbs Free Energy coefficients if you 
supply the UNIFAC structure and enter the Ideal Gas Gibbs Free 
Energy at 25 °C in the a coefficient cell.
 Figure 3.233-35
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3-36 Solid Hypotheticals
ww
Th3.6 Solid Hypotheticals
Solid Hypotheticals can be added to any Hypo Group, regardless 
of the Group Type. In the Individual Hypo Controls group of the 
Hypo Group property view, click the Add Solid button.
When you install a solid hypo, you notice that the Base 
Properties cells on the Hypo Group property view are displayed 
as .
3.6.1 ID Tab
To define the Solid Hypo, access its property view by 
highlighting the component name on the Hypo Group property 
view and clicking the View button.
The ID tab of the Solid Component property view is the same as 
that for other Hypo components except that the User Props tab 
is replaced by the PSD tab. Note that in this case, the Family/
Class is Alcohol. The Class type has no effect on the values 
calculated for the solid component.
Solids do not take part in VLE calculations, but they do have 
an effect on heat balance calculations.3-36
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Hypotheticals 3-37
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Th3.6.2 Props Tab
The Props tab displays the basic properties of the component in 
two groups: 
• Solid Properties where bulk properties are entered
• Coal Analysis where data can be entered on a possible 
Coal Analysis
 Figure 3.243-37
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3-38 Solid Hypotheticals
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ThSolid Properties
The minimum information that must be supplied includes the 
Molecular Weight and the Density. The appropriate units can 
also be specified within the cell as shown below. 
The other Solid Properties are described below: 
Coal Analysis
You can also provide the results of a Coal Analysis on a 
percentage basis for the listed components.
 Figure 3.25
Solid Property Description
Diameter Particle diameter, if not supplied this defaults to 1 mm 
when the remaining properties are estimated.
Sphericity Value between zero and one, with one being perfectly 
spherical.
Area/Unit 
Volume
Measure of the surface area of the particle as a 
function of the particle volume.3-38
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Hypotheticals 3-39
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Th3.6.3 Point Tab
The only information on the Point tab that is relevant to the 
Solid is the Heat of Combustion and Heat of Formation. 
This information is only required if you plan on using a Solid 
component as part of a reaction.
 Figure 3.263-39
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3-40 Solid Hypotheticals
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Th3.6.4 TDep Tab
Since Solid Hypos do not participate in VLE calculations, their 
vapour pressure information is, by default, set to zero. However, 
since solid components do affect Heat Balances, the Specific 
Heat information can either be estimated by Aspen HYSYS, or 
supplied. 
 Figure 3.27
While other Hypotheticals use the Ideal Gas Enthalpy 
coefficients, solids use the Specific Heat Capacity.3-40
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Th3.6.5 PSD Tab
The PSD tab displays the particle size distribution for solids. It 
allows you to specify PSD’s and calculate various mean and 
modal diameters for the entered PSD. The PSD tab is shown 
below.
Refer to Section 1.2.3 - Manipulating the Selected 
Components List and see UserProp & PSD Tabs for more 
information on Particle Size Distribution.
 Figure 3.283-41
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3-42 Cloning Library Components
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Th3.7 Cloning Library 
Components
You can convert Aspen HYSYS library components into 
Hypotheticals through the Clone Library Comps button on the 
Hypo Group property view. When you click this button, the 
Convert Library Comps to Hypothetical Comps property view is 
displayed. Any of the library components present in the current 
Fluid Package can be converted to a Hypothetical. 
This property view is made up of two sections, the Source 
Components group and the Hypo Groups.
 Figure 3.29
By using the Add New Hypo Group button, you do not have to 
return to the Simulation Basis Manager to create a Hypo 
Group.
Object Description
Component Lists Allows you to select the component list that contains the 
library component you want to clone.
Available Library 
Comps
Selects the component you want to convert into a 
hypothetical.
Replace ALL 
Instances
If you want to replace the library component with the Hypo 
in every Fluid Package that contains the library component, 
select this checkbox. If you only want to replace the library 
components in the highlighted Fluid Package, do not select 
the checkbox.3-42
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Th3.7.1 Converting a Library 
Component to a Hypo
When converting a library component to a Hypo, follow the 
procedure outlined below. Figure 3.29 is used as a reference.
1. Select the Component List which contains the target library 
component. In this case, Component List - 1 is the 
selected component list. 
2. From the Available Library Comps group, select the 
component to clone. In this case, 1-Propanol is selected.
3. Select the Target Hypo Group, where the new Hypo is to 
be placed. HypoAlcohol is selected.
4. Decide if you want to replace all instances of the source 
component (1-Propanol) with the new Hypo. Select the 
Replace All Instances checkbox to do this. In Figure 3.29 
the checkbox is selected.
5. To complete the conversion, click the Convert to Hypo(s) 
button.
6. The new Hypo appears in the Hypo Components group, and 
has an asterisk (1-Propanol*) after its name, signifying 
that it is a hypothetical. 
7. Close the property view to return to the Hypo Group 
property view.
Hypo Group Selects the Hypothetical Group in which you want the 
converted library component placed.
Hypo 
Components
Displays all the hypothetical components present in the 
selected hypothetical group. When a library component is 
converted into a hypothetical, it is listed here.
Object Description3-43
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Th3.8 Hypo Controls
The manipulation commands for hypotheticals are contained on 
the Hypotheticals tab of the Simulation Basis Manager. The Hypo 
Controls are the buttons contained within the Hypothetical Quick 
Reference group as shown below:
3.8.1 Viewing Groups
Notice that the Hypothetical Quick Reference group displays the 
names of hypothetical groups and components. The components 
are listed in the Hypo Name column and the group to which each 
component belongs is listed in the Group Name column.
From the Group Name column, select the Group that you want 
to view, and click the View Group button. Aspen HYSYS 
displays the Hypo Group property view for that Hypo Group. All 
the Hypo components that are part of the group appear on this 
property view.
 Figure 3.303-44
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Th3.8.2 Moving Hypos
When hypothetical components are created in Aspen HYSYS, 
they are created within a Hypo Group, and become part of the 
group. After adding a hypothetical component to a certain 
group, you may want to move it to another existing group. You 
can accomplish this through the Hypo Controls. From the 
Hypothetical Quick Reference group, click the Move Hypo 
button. This produces the following property view: 
Follow this procedure to move a Hypo to a different Hypo Group:
1. From the Hypo Components group, select the Hypo that you 
want to move.
2. Select the Target Hypo Group to which the Hypo is being 
moved.
3. Click the Switch to Group button, which becomes available 
when a selection is made in both the Hypo Components 
group and Target Hypo Group. 
4. When you are finished moving groups, close the property 
view and return to the Hypotheticals tab of the Simulation 
Basis Manager.
3.9 References
 1 Reid, R.C., Prausnitz, J.M., Poling, B.E., The Properties of Gases & 
Liquids, 4th edition, McGraw-Hill, 1987.
 Figure 3.31
By clicking the Add New Hypo Group button, Aspen HYSYS 
allows you to add a new Hypo Group while this property view 
has focus.3-45
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Th3-46
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Aspen HYSYS Oil Manager 4-1
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Th4  Aspen HYSYS Oil 
Managerw.cadfamily.com    EMa
e document is for study 4.1  Introduction................................................................................... 3
4.2  Oil Characterization ....................................................................... 4
4.2.1  Laboratory Data ....................................................................... 4
4.2.2  Conventional Distillation Data .................................................... 5
4.2.3  Data Reporting Basis ................................................................ 7
4.2.4  Physical Property Assay Data ..................................................... 7
4.2.5  Property Curve Basis ................................................................ 9
4.2.6  Common Laboratory Data Corrections ......................................... 9
4.2.7  Default Correlations................................................................ 10
4.3  Petroleum Fluids Characterization Procedure .............................. 10
4.3.1  Initialization .......................................................................... 10
4.3.2  Step One - Characterize Assay ................................................. 13
4.3.3  Step Two - Generate Hypocomponents ...................................... 13
4.3.4  Step Three - Install Oil............................................................ 14
4.3.5  User Property ........................................................................ 14
4.3.6  Correlations........................................................................... 14
4.4  Oil Characterization Property View .............................................. 15
4.5  Characterizing Assays.................................................................. 18
4.5.1  Input Data Tab....................................................................... 23
4.5.2  Calculation Defaults Tab .......................................................... 53
4.5.3  Working Curves Tab................................................................ 56
4.5.4  Plots Tab ............................................................................... 57
4.5.5  Correlations Tab ..................................................................... 58
4.5.6  User Curves Tab..................................................................... 60
4.5.7  Notes Tab.............................................................................. 614-1
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4-2 Aspen HYSYS Oil Manager 
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The document is for study 4.6  Hypocomponent Generation .........................................................62
4.6.1  Data Tab................................................................................63
4.6.2  Correlations Tab......................................................................71
4.6.3  Tables Tab..............................................................................73
4.6.4  Property Plot Tab ....................................................................74
4.6.5  Distribution Plot Tab ................................................................76
4.6.6  Composite Plot Tab..................................................................77
4.6.7  Plot Summary Tab...................................................................78
4.6.8  Notes Tab ..............................................................................79
4.7  User Property ...............................................................................79
4.7.1  User Property Tab ...................................................................80
4.7.2  User Property Property View.....................................................81
4.8  Correlations & Installation............................................................85
4.8.1  Correlation Tab .......................................................................85
4.8.2  Correlation Set Property View ...................................................86
4.8.3  Install Oil Tab .........................................................................92
4.9  TBP Assay - Example ....................................................................93
4.9.1  Initialization ...........................................................................95
4.9.2  Step 1 - Input Assay Data ........................................................97
4.9.3  Step 2 - Cut Assay into Hypocomponents .................................106
4.9.4  Step 3 - Transfer Information to Flowsheet ...............................109
4.9.5  Fluid Package Association.......................................................111
4.10  Sulfur Curve - Example .............................................................112
4.10.1  Fluid Package .....................................................................112
4.10.2  Install a User Property .........................................................113
4.10.3  Install the Assay .................................................................114
4.10.4  Create the Blend .................................................................117
4.10.5  Results ..............................................................................118
4.11  References................................................................................1204-2
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Th4.1 Introduction
The Oil Characterization environment can be accessed from the 
Oil Manager tab of the Simulation Basis manager or by clicking 
the Oil Environment icon on the toolbar. To enter the Oil 
Characterization environment, at least one fluid package must 
exist in the case. Hypothetical (pseudo) components must be 
compatible with the property method being used by the fluid 
package.
Also on the Oil Manager tab, you can view all flowsheets that 
exist in the current case and the fluid package associated with 
each. All hypocomponents that are defined within the Oil 
Characterization environment are assigned to a Hypo group and 
installed in an associated fluid package. Since Light End 
calculations for an oil require information from the property 
method being used by the associated fluid package, the 
hypocomponent cannot be shared among different fluid 
packages as regular hypothetical components can. However, 
you can still use the same hypocomponent in the non-associated 
fluid packages by adding them as hypotheticals, via the Add 
Hypo or Add Group button on the Selected tab of the 
Component List property view.
The Oil Characterization environment provides a location where 
the characteristics of a petroleum fluid can be represented by 
using discrete hypothetical components. Physical, critical, 
thermodynamic and transport properties are determined for 
each hypothetical component using correlations that you select. 
The fully defined hypocomponent can then be installed in a 
stream and used in any flowsheet.
Aspen HYSYS defines the hypocomponent by using assay data 
which you provide. The features available for the input of assay 
data minimize the time required for data entry. For instance, 
defined assays can be cloned, imported and exported. Exported 
assays can be used in other fluid packages or in other cases 
altogether.
Some of the features exclusive to the oil environment include:
• Providing laboratory assay data
Oil Environment icon
Refer to Chapter 3 - 
Hypotheticals for 
more information on 
hypo controls.4-3
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4-4 Oil Characterization
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Th• Cutting a single assay
• Blending multiple assays
• Assigning a user property to hypocomponents
• Selecting correlation sets to determine properties
• Installing hypocomponent into a stream
• Viewing tables and plots for your input and for the 
characterized fluid
4.2 Oil Characterization
The petroleum characterization method in Aspen HYSYS 
converts your laboratory assay analyses of condensates, crude 
oils, petroleum cuts, and coal-tar liquids into a series of discrete 
hypothetical components. These petroleum hypocomponents 
provide the basis for the property package to predict the 
remaining thermodynamic and transport properties necessary 
for fluid modeling.
Aspen HYSYS produces a complete set of physical and critical 
properties for the petroleum hypocomponent with a minimal 
amount of information. However, the more information you can 
supply about the fluid, the more accurate these properties are, 
and the better Aspen HYSYS predicts the fluid's actual 
behaviour.
4.2.1 Laboratory Data
Accurate volatility characteristics are vital when representing a 
petroleum fluid in your process simulation. Aspen HYSYS 
accepts five standard laboratory analytical assay procedures:
• True boiling point distillation (TBP)
• ASTM D86 and ASTM D1160 distillations (Separately or 
Combined)
• ASTM D2887 simulated distillation
• Equilibrium flash vapourization (EFV)
• Chromatographic analysis4-4
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ThThe characterization procedure performs its calculations based 
on an internally calculated TBP curve. If you supply an ASTM or 
EFV distillation curve, it is converted to a TBP curve using 
standard methods described in the API Data Book. If you do not 
supply any distillation data, then an average TBP distillation 
curve is generated for you based on the overall molecular 
weight, density, and Watson (UOP) K factor of your fluid.
4.2.2 Conventional Distillation 
Data
The five primary types of assay data accepted by the Petroleum 
Characterization Procedure in Aspen HYSYS are listed here and 
explained in the following sections.
• True Boiling Point analysis
• ASTM D86 and 1186 Distillations
• ASTM D2887
• Equilibrium Flash Vaporization
• Chromatrographic analysis
True Boiling Point (TBP) Analysis
A TBP analysis is performed using a multi-stage batch 
fractionation apparatus operated at relatively high reflux ratios 
(15 - 100 theoretical stages with reflux ratios of 5 to 1 or 
greater). TBP distillations conducted at either atmospheric or 
vacuum conditions are accepted by the characterization 
procedure. 
The Watson (UOP) K factor is an approximate index of 
paraffinicity, with high values corresponding to high degrees 
of saturation:
where the mean average boiling point is in degrees Rankine.
K Mean Avg. BP( )
1
3
--
sp gr 60F / 60F
-----------------------------------------=4-5
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4-6 Oil Characterization
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ThThe petroleum fluid's bubble point is a multi-component 
equilibrium condition such that there is an incipient vapour 
phase forming. This would, in effect, be a single-stage of 
fractionation as opposed to the highly refluxed operation of a 
TBP analysis.
ASTM D86 and D1160 Distillations
ASTM D86 and ASTM D1160 distillations also employ batch 
fractionation apparatus, but they are conducted using non-
refluxed Engler flasks. Two standard ASTM distillations are 
supported: ASTM D86, used for light to medium petroleum 
fluids, and ASTM D1160, carried out at varying vacuum 
conditions and used for heavier petroleum fluids. For ASTM D86 
distillation, Aspen HYSYS can correct for barometric pressure or 
cracking effects.
ASTM D2887
ASTM D2887 is a simulated distillation curve generated from 
chromatographic data. The resulting boiling point curve is 
reported on a weight percent basis.
Equilibrium Flash Vaporization
An EFV curve is generated by a series of experiments conducted 
at constant pressure (1 atm). The results relate the temperature 
versus volume percent of liquid distilled, where the total vapour 
is in equilibrium with the unvaporized liquid.
The initial boiling point (IBP) of a TBP curve does not 
correspond to the bubble point temperature of the petroleum 
fluid at atmospheric pressure.4-6
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ThChromatographic Analysis
A Chromatographic analysis is a simulated distillation performed 
by passing a small amount of totally vaporized sample through a 
packed gas chromatograph column. The relative amounts of the 
sample that appear in each standard "chromatographic" 
hydrocarbon group (paraffinic, aromatic and naphthaline 
groups, ranging from C6 to C30) are then detected and 
reported.
4.2.3 Data Reporting Basis
All of the distillation analyzes described above are reported 
using one of the following fractional bases (assay basis):
• Liquid volume percent or liquid volume fractions
• Mole percent or mole fractions
• Mass percent or mass fractions
Aspen HYSYS accepts TBP and Chromatographic analyzes in any 
one of the three standard bases. However, due to the form of 
the API Data Book conversion curves, EFV, ASTM D86 and ASTM 
D1160 distillations must be supplied on a liquid volume basis, 
and ASTM D2887 are only reported on a weight basis.
4.2.4 Physical Property Assay 
Data
As you supply more information to Aspen HYSYS, the accuracy 
of the Petroleum Characterization increases. Supplying any or 
all of bulk molecular weight, bulk density or bulk Watson (UOP) 
K factor increases the accuracy of your hypocomponent 
properties. Appropriately, if you supply laboratory curves for 
molecular weight, density and/or viscosity, the accuracy 
increases further.
Refer to Appendix B - 
Oil Methods & 
Correlations for 
information on the 
correlations used in the 
Oil Environment.4-7
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4-8 Oil Characterization
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ThIf you cannot supply property curve data, Aspen HYSYS 
generates internal curves using the available information. This 
information is applied using correlations. You can change the 
default set of property correlations as required.4-8
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Th4.2.5 Property Curve Basis
Physical property analyzes are normally reported by a 
laboratory using one of the following two conventions:
• An Independent assay basis where the property assay 
volume fractions do not correspond on a one-to-one 
basis with the distillation assay fractions.
• A Dependent assay basis, where a common set of assay 
fractions are utilized for both the distillation curve and 
the physical property curves.
Physical properties are average values for the given range, and 
hence are midpoint values. Distillation data reports the 
temperature when the last drop of liquid boils off for a given 
assay range; therefore distillation is an endpoint property. Since 
all dependent input property curves are reported on the same 
endpoint basis as the distillation curve, they are converted by 
Aspen HYSYS to a midpoint basis. Independent property curves 
are not altered in any manner before being used in the 
characterization, since they are already defined on a midpoint 
basis.
4.2.6 Common Laboratory 
Data Corrections
With ASTM D86 data, correction procedures are available to 
modify the laboratory results for both barometric pressure and 
thermal cracking effects, which result in the degradation of the 
sample at high distillation temperatures. These corrections are 
sometimes performed by the laboratory. If the corrections have 
not already been applied, the Characterization procedure has 
options available to apply the necessary corrections before 
commencing calculations.4-9
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4-10 Petroleum Fluids Characterization 
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Th4.2.7 Default Correlations
When you begin a petroleum characterization session, Aspen 
HYSYS already has a set of default correlations for generating 
physical and critical properties of the hypocomponent. You may 
change any of the correlations at any time.
4.3 Petroleum Fluids 
Characterization 
Procedure
4.3.1 Initialization
Before entering the Oil Characterization environment, you are 
required to create a fluid package with a specified Property 
Package at the very minimum. The Associated Property Package 
must be able to handle hypothetical components (i.e., a Steam 
Package is not allowed).
If you want to use library components to represent the Light 
Ends portion of your assay, it is best to select the components 
prior to entering the Oil Characterization environment (if you 
forget to do this, you can return later to the Components tab 
and select the components).
Refer to Section 4.8.2 - 
Correlation Set 
Property View for a 
listing of available 
correlations or Appendix 
B - Oil Methods & 
Correlations for a 
description of each 
correlation.4-10
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ThThe Oil Manager tab of the Basis Manager property view is 
shown below:
The Associated Fluid Package for the Oil serves two primary 
functions:
• Provides the light end components.
• Identifies to which Fluid Package the Hypo group (oil) is 
being installed.
When you install the oil into a stream, Aspen HYSYS always 
places this stream in the main flowsheet. For this reason, the 
associated Fluid Package must be the fluid package used by the 
main flowsheet.
If you want to install the hypocomponent into a subflowsheet, 
this must be done on the Components tab of the Sub-Flowsheet 
fluid package (Hypothetical page, Add Group or Add Hypo 
button). If the sub-flowsheet uses the same fluid package as the 
main flowsheet, then this action is not necessary, as the 
hypocomponent is added to the fluid package once an oil stream 
is installed.
 Figure 4.1
The fluid package that is used in the Oil Characterization 
environment is displayed in the Associated Fluid Package 
drop-down list on the Oil Manager tab of the Simulation 
Basis Manager property view.4-11
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4-12 Petroleum Fluids Characterization 
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ThIf you are going to transfer an oil stream between flowsheets 
with different fluid packages, ensure that the hypocomponent is 
installed in each flowsheet fluid package. 
If you have not defined the same components in each fluid 
package, Aspen HYSYS will transfer only the compositions for 
those components that are available, and will normalizes the 
remaining compositions.
The fluid package that is used in the Oil Characterization 
environment can be selected from the Associated Fluid Package 
drop-down list. To enter the Oil environment, select the Enter 
Oil Environment button as shown in Figure 4.1, or select the Oil 
Environment button from the toolbar. The following figure 
illustrates the make-up of a typical oil:
 Figure 4.2
OIL 
(blend)
Assay 1
Assay 3
Bulk 
Properties
Boiling Point 
Curve
Property Curves 
Dependent/
Independent
• Molecular Weight
• Mass Density
• Watson (UOP) K
• Viscosity
• TBP
• ASTM D86
• ASTM D1160
• ASTM D86-D1160
• ASTM D2887
• EFV
•  Chromatograph
• Molecular Weight
• Mass Density
• Viscosity
Assay 24-12
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ThAn Oil or Blend is comprised of any number of Assays. Each 
individual Assay contains specific information with respect to the 
Bulk Properties, Boiling Point Curve and Property Curves. For 
the Bulk Properties, you may supply Molecular Weight, Mass 
Density, Watson (UOP) K factor, and/or Viscosity. You can 
provide the Boiling Point curve in any one of the formats 
displayed in the Figure 4.2. During calculations, Aspen HYSYS 
automatically converts all curves to a TBP basis. You also have 
the option of supplying Molecular Weight, Mass Density, and/or 
Viscosity curves.
There are three general steps you must follow when creating an 
oil:
1. characterize assay
2. generate hypocomponent
3. install oil in flowsheet
4.3.2 Step One - Characterize 
Assay
Enter the petroleum assay data into Aspen HYSYS via the Assay 
tab of the Oil Characterization property view. Aspen HYSYS uses 
the supplied Assay data to generate internal TBP, molecular 
weight, density and viscosity curves, referred to as Working 
Curves. 
4.3.3 Step Two - Generate 
Hypocomponents
Hypocomponents are generated from the Working Curves via 
the Cut/Blend tab of the Oil Characterization property view. 
It is a good idea to open the Trace Window before you start 
the characterization, since it displays important information 
during Oil Characterization calculations.
Refer to Section 4.5 - 
Characterizing Assays 
for more details.4-13
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4-14 Petroleum Fluids Characterization 
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ThThis process is explained in Appendix B - Oil Methods & 
Correlations. See Section 4.6 - Hypocomponent 
Generation for the procedure.
4.3.4 Step Three - Install Oil
Once the Blend is characterized satisfactorily, install 
hypocomponent into your Aspen HYSYS case via the Install Oil 
tab of the Oil Characterization property view. You can install the 
oil as a defined stream by providing a Stream name. The 
hypocomponent is also added to a distinct Hypo group and to 
the associated fluid package. 
4.3.5 User Property
In addition to the three basic steps required to characterize an 
oil in Aspen HYSYS, user properties can be added, modified, 
deleted, or cloned. User Properties can be created from the Oil 
Manger or in the Basis Environment. A user property is any 
property that can be calculated on the basis of composition. 
4.3.6 Correlations
Correlations can be selected via the Correlation tab of the Oil 
Characterization property view. Aspen HYSYS allows you to 
select from a wide variety of correlations used in both the 
determination of working curves and in the generation of 
hypocomponent.
All of the information used in generating your 
hypocomponent is stored with the case. This includes: 
Assays and their associated Options, Property Curves and 
Bulk Properties, User Properties, the Correlations used for 
generating the pseudo-components, the Constituent oils 
(with flow rates) for blends, and the flowsheet stream in 
which each oil was installed. This information is available the 
next time you open the case.
Refer to Section 4.8.3 - 
Install Oil Tab for more 
details.
Refer to Section 4.7 - 
User Property for more 
information.
Refer to Section 4.8.1 - 
Correlation Tab for 
more information.4-14
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Th4.4 Oil Characterization 
Property View
When you enter the Oil Characterization environment, the 
following property view appears:
This property view is the Oil Characterization environment. 
There are five tabs which represent the main areas of the 
environment and are described below:
 Figure 4.3
Tab Description
Assay Add, edit, delete, clone, import or export Assays (see 
Section 4.5 - Characterizing Assays).
Cut/Blend Add, edit, delete or clone Blends (see Section 4.6 - 
Hypocomponent Generation).
User 
Property
Add, edit, delete or clone User Properties (see Section 4.7 
- User Property).
Correlation Add, edit, delete or clone Correlation Sets (see Section 
Section 4.8.1 - Correlation Tab).
Install Oil Install hypocomponent into a stream in a Aspen HYSYS 
case (see Section 4.8.3 - Install Oil Tab).4-15
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4-16 Oil Characterization Property View
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ThThe Clear All, Calculate All, and Oil Output Settings... buttons 
are available on any tab of the Oil Characterization property 
view. 
• If you select the Calculate All button, Aspen HYSYS 
calculates all Assays and Blends. This option is useful if 
you have several Assays and/or Blends and you want to 
see the global effect of a change in the correlation.
• If you select the Clear All button, Aspen HYSYS displays 
the following warning:
If you want to delete all Oil Characterization information 
select Yes.
• Selecting the Oil Output Settings... button results in 
the Oil Output Settings property view.
Oil Output Settings Property View
On this property view, you can set the initial boiling point (IBP) 
and final boiling point (FBP) cut points on a liquid volume, mole 
or mass percentage basis. These values are used to determine 
the initial and final boiling temperatures of the TBP working 
curve. The default values are 1% for the IBP and 98% for the 
FBP.
 Figure 4.4
 Figure 4.54-16
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ThIf for example, an IBP value of 1% is specified, the initial boiling 
point becomes the weighted average boiling temperature of all 
components that boil off in the first volume percent. The final 
boiling point is determined in a similar manner. If 98% is used 
for the FBP, the final boiling temperature becomes the weighted 
average boiling temperature of all the components that boil off 
in the last 2 volume percent. The ends of the curve are 
'stretched' to fill the assay range of 0 to 100%.
On the Oil Output Settings property view, you can select the 
default ASTM D86 Interconversion Method TBP conversion type 
from the Default D86 Curve Type drop-down list:
• API 19741 
• API 19872 
• API 19943 
• Edmister-Okamoto 19594 
You can also select the ASTM D2887 Interconversion method 
from the following:
• API 19875
• API 1994 Indirect6
• API 1994 Direct7
The Oil Output Settings are saved along with your simulation 
case. They can be accessed either within the Oil manager or 
through the Simulation menu bar option in the Main Simulation 
environment. 
Changing the IBP and FBP in the Oil Output Settings will affect 
the following calculations:
• Blend Properties Table and Plots
• Boiling Point Utility
• Cold Properties Utility
• Column specs (Cut Point, Gap Cut Point, Flash Point, RON 
Point)
• Column Profiles
When IBP and FBP changes are made, all necessary calculations 
are automatically performed.
Oil Input settings are accessed through the Session 
Preferences property view.4-17
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4-18 Characterizing Assays
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Th4.5 Characterizing Assays
The Assay tab of the Oil Characterization property view is shown 
below:
The Available Assays are listed in the left portion of the property 
view. The following Assay manipulation buttons are available:
The ASTM D86 and ASTM D2887 interconversion methods do 
not affect column specifications, since each related 
columnspec has its own independent setting. If you want to 
change the column specifications, click the Change 
Interconversion Methods for Existing Column Specs button. 
Aspen HYSYS asks you to confirm that you want to globally 
impose these changes.
 Figure 4.6
C
Button Description
View Edit the currently highlighted Assay.
Add Create a new Assay.
Delete Erase the currently highlighted Assay.
Aspen HYSYS does not prompt for confirmation when 
deleting an assay, so be careful when you are using this 
command. However, Aspen HYSYS does not delete an 
assay that is being used by a blend.
Refer to Section 4.9 - 
TBP Assay - Example 
for characterizing 
assays.4-18
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ThFor a highlighted Assay, you can edit the name in the Name field 
and provide a description in the Description textbox found in 
Assay Information group.
To create a new assay or edit an existing assay you can click the 
Add or View button, respectively. This opens the Assay 
property view for the new or existing assay.
Importing PIMS in .csv Format
You can import a PIMS-generated assay file in .csv format to the 
Oil Environment. Since many commercial assay generator tools 
convert their assay format to PIMS' .csv format, Aspen HYSYS 
can now import assays from these other sources via this format. 
Aspen HYSYS does not support detailed petroleum properties - 
such as Sulphur, RON etc., so these properties from PIMS assay 
are stored as user curves.
If you are importing a PIMS Assay, follow the additional steps 
described in the next section.
PIMS Assay Import Additional Steps 
If you are importing PIMS assay, there are more steps to follow:
1. After selecting the PIMS file, the Import PIMS Data property 
view appears.
All the data shown initially in the table of the Import PIMS 
Data property view are default values not related to the csv 
file previously selected.
To map the PIMS variable data to the RefSYS variable data, 
you must browse to and select the PIMS String Table.
Clone Create a new Assay with the same properties as the 
currently highlighted Assay. Aspen HYSYS immediately 
opens a new Assay view.
Import Import a previously saved assay file in .oil format or a PIMS 
generated assay file in .csv format.
Export Save an assay to disk so that it can be used in other cases.
Imported and Exported assays have a filename form *.oil.
Button Description4-19
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4-20 Characterizing Assays
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Th2. In the Import PIMS Data property view, click Import Data 
String.
3. Select the PIMS String Table file (*.sdb extension) to map 
the PIMS variable tag with RefSYS variable tag and click 
Open. (The default name and location for the data string file 
is: \[install location]\paks\PIMSAssay.sdb)
The PIMS String Table file (*.sdb) consists of 3 sections:
• The Property Tag section, where the text used to for the 
PIMS petroleum property variables is mapped to the text 
of the RefSYS property description.
Below is a sample of the PIMS tag (left) and associated 
RefSYS tag (right):
- ISPG =  "Standard Liquid Density" 
- IFVT =  "Boiling Temperature"
- VBAL =  "Volume Fraction"
- IMWT =  "Molecular Weight"
- IACD =  "Acidity"
• The Component Tag section, where the text used to 
represent PIMS components is mapped to the text of the 
RefSYS components:
Below is a sample of the PIMS tag (left) and associated 
RefSYS tag (right):
- NC1 =  "Methane"
- NC2 =  "Ethane"
- NC3 =  "Propane"
- IC4 =  "I-Butane"
- NC4 =  "N-Butane"
- IC5 =  "I-Pentane"
• The Unit Tag section. The Unit Tag section is optional. It 
maps PIMS unit abbreviations to RefSYS units if the PIMS 
Assay was stored using unit syntax other than that which 
RefSYS recognizes.
You can add this section by appending a line for each 
“foreign” unit in the following format:
UNIT_{PIMS property tag} = "{unit name}" 
for example: 
UNIT_IFVT = "C" 
means the PIMS property tag "IFVT" has units in C 
(Celcius).4-20
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Th4. Click the Import PIMS Data button.  
RefSYS reads in all the data from the assay table using the 
mapping instructions from the string table, and populates 
the list in the Import PIMS Data property view.
When the Oil Input Preferences button under the Assay 
Information group is selected, the Session Preferences property 
view opens to the Oil Input tab. From here you can set the input 
defaults for your case. 
When a new case is created, the methods specified in the Oil 
Input settings initialize the Oil Output settings. However, any 
changes made afterwards to either settings group are 
independent.
Assay Property View
The Assay property view is shown below: 
 Figure 4.7
The appearance of the Assay property view depends on how 
you define the assay in the Assay Definition group and which 
radio button is selected in the Input Data group.4-21
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4-22 Characterizing Assays
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ThThe Assay property view consists of seven tabs, which are 
described below: 
There are four objects found at the bottom of the property view 
and are described below:
The following sections outline each of the tabs contained within 
the Assay view (accessed via the View or Add button).
Tab Description
Input Data Allows you to define and specify the Assay.
Calculation 
Defaults
Allows you to set the calculation methods and 
extrapolation methods for the assay and assay 
property curves.
Working Curves Displays a table of Assay Working curves.
Plots Allows you to view any of the input assay curves in 
graphical form.
Correlations Allows you to edit the individual property conversion 
methods used.
User Curves Allows you to attach available user properties to the 
assay.
Notes Allows you to attach relevant comments to the assay.
Object Description
Name You can provide the name of the Assay in the Name cell 
(maximum 12 characters).
Assay Status The status bar is displayed at the bottom of the screen:
• Assay Was Not Calculated. You have not provided 
enough Assay information to determine a solution (or 
you have enough information and have not clicked the 
Calculate button).
• Assay Was Calculated. You have provided Assay 
information, clicked the Calculate button, and 
obtained a solution.
• An Error Was Found During Calculation. The Trace 
Window usually shows a description of the type of 
Error.
Calculate Select this button to calculate the Assay.
Delete Select this buttons to delete the current Assay.
There is no confirmation when you delete an assay, unless 
it is being used by a blend, in which case you cannot delete 
it.4-22
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Th4.5.1 Input Data Tab
The minimum amount of information that Aspen HYSYS requires 
to characterize a petroleum fluid is either:
• a laboratory distillation curve
• two of the following three bulk properties: Molecular 
Weight, Density, or Watson (UOP) K factor.
However, any additional information such as distillation curves, 
bulk properties and/or property curves, should be entered if 
possible. With more supplied information, Aspen HYSYS 
produces a more accurate final characterization of your oil.
The Watson (UOP) K factor is an approximate index of 
paraffinicity, with high values corresponding to high degrees 
of saturation:
where the mean average boiling point is in degrees Rankine.
When you open the Assay view to the Input Data tab, all that 
is displayed is the Assay Data Type and Bulk Properties drop-
downs. New input fields are added as you specify the 
information for your oil.
K Mean Avg. BP3
sp gr 60F / 60F
--------------------------------------=4-23
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4-24 Characterizing Assays
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ThThe Input Data tab is shown below:    
The Input Data tab is split into two groups: the Assay Definition 
and Input Data groups. The Assay Definition group is where the 
assay type and use of property curve, light ends data and bulk 
properties are defined. The Input Data group is where the 
distillation, property curve, light ends and property data is 
actually inputted. 
 Figure 4.8
Specify which 
individual Input 
Data curves are to 
be included.
Depending on the specifications made in the 
Assay Definition group. These radio buttons 
become visible. Each radio button makes a 
different entry field visible.
The layout of Input Data 
group depends largely on 
the settings you choose in 
this group.
Options related to 
the Assay Data 
Type are 
displayed in this 
area.
The entry fields displayed in this table depend on which 
radio button is selected.
For each of the three property curves, Molecular Weight, 
Density and Viscosity, you have the following options: Not 
Used, Dependent, or Independent. If you switch the status 
to Not Used after you have entered assay data, all your data 
for that property curve is lost when you return your selection 
to Dependent or Independent.4-24
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ThLight Ends Handling & Bulk Fitting
If you have a light-ends analysis along with light-ends free input 
curves and total bulk properties or light-ends free bulk 
properties you can use the Aspen HYSYS oil manager to 
combine the light-ends analysis with the light-ends free input 
curves to match the specified bulk properties. This functionality 
is clearly seen in the case of chromatographic input, where you 
may want to input the light-ends along with the C6+ as the 
chromatographic data groups. Because of the nature of the 
analysis, the chromatographic data is light-ends free.
Light Ends Analysis Versus Calculated TBP 
Curve
Ideally, for the light-ends free distillation input curve, the TBP at 
0% should coincide with the highest NBP in the light-ends 
components with non-zero compositions, see Case B in Figure 
4.9. However, due to imperfect input data or extrapolation, the 
calculated TBP at 0% may be lower than the top NBP for light 
ends (Case A in Figure 4.9) or higher than the top NBP for light 
ends (Case C in Figure 4.9). To avoid overlapping or 
discontinuity, these two cases must be properly handled.4-25
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4-26 Characterizing Assays
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ThIn Case A, the highest temperature of the non-zero component 
in light ends is above the TBP at 0%. In this case, we need to 
eliminate the points having TBP lower than the top light-ends 
temperature. After the elimination, the remaining portion of the 
light-ends free TBP curve are re-scaled to 100%, and then a 
new set of standard 51 points calculation tables are regenerated 
from the remaining portion of the corresponding curves.
In Case C, the top light-ends temperature is below the TBP at 
0%. Since the extrapolation may not be accurate, more trust is 
put on the light-ends analysis and hence assign the top light-
ends temperature as the TBP at 0%. To avoid a sudden jump in 
the distillation curve, the first 20% of the distillation curve is 
also smoothed.
 Figure 4.94-26
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ThCurve Partition for Bulk Property Fitting
To allow piece-wise fitting for a bulk property, a property curve 
is divided into three sections: head, main, and tail. The ending 
% of the head section and beginning % of the tail section can be 
specified. Each section can have an independent adjusting 
weight factor as shown in the figure below.
For piecewise bulk property fitting there are two concerns to be 
addressed. First, since each section can have an independent 
adjusting weight factor, there may be a discontinuity at the 
boundary of the two sections. Second, how to ensure relatively 
fast convergence with uneven adjustment of the property 
concerned. For the first concern, discontinuity is avoided by 
using linear interpolation between two sections. For the second 
concern, the weight factor is normalized first and then the 
following equation is used to calculate the new point property 
value from the old point property value:
where:  
New[i] = the new property value at point i
Wt[i] = the normalized weight factor at point i
Ratio = the calculated uniform adjusting ratio
Old[i] = the old property value at point i
 Figure 4.10
(4.1)New i[ ] 1 Wt i[ ] Ratio 1–( )×+[ ] Old i[ ]×=4-27
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4-28 Characterizing Assays
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ThAspen HYSYS allows you to specify if a given curve contains 
light-ends contributions, set if a specified bulk property contains 
light-ends and partition a property curve so that some sections 
can be adjusted more than others.
The Light Ends Handling & Bulk Fitting Options property view is 
accessed by clicking the Light Ends Handling & Bulk Fitting 
Options button.
The light ends handling and bulk fitting options are described 
below:
The last five columns are used for piece-wise bulk property 
fitting. When fitting a given bulk property value the internal 
calculation curve, either based on the input curve or calculated 
from a correlation, is divided into three sections. Each of the 
three sections can be independently adjusted.
 Figure 4.11
Column Description
Input Curve Displays all the possible input curves, including user 
property curves.
Curve Incl L.E. Specifies if the corresponding input curve includes light 
ends. If an input curve is not used, the corresponding 
checkboxes are grayed out.
Bulk Value Specifies the bulk value for the corresponding input 
curve.
Bulk Value Incl 
L.E.
Specifies if a given bulk value contains the 
contributions of light ends. If no light end compositions 
are given these checkboxes are grayed out.4-28
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ThWhen fitting a given bulk value, at least one section must be 
adjustable. Therefore, at least one section must have a non-
zero percentage range and a non-zero adjusting weight factor. 
Since the adjusting weight factors are relative, it is the weight 
factor ratios among the three sections that matter.
The Apply smart bulk fitting on molecular weight and 
mass density checkbox allows you to achieve the best bulk 
fitting on mass density and molecular weight input curves. If the 
checkbox is selected, the mass density and molecular weight 
rows are disabled and the values appear in black.
In situations when either a full light ends analysis is not 
available or you do not want to identify part of the analyzed 
light ends components (in other words, only partial light ends 
analysis data is available), Aspen HYSYS can generate 
overlapping hypothetical components to compensate the 
missing portion of the light ends, making the output stream 
matching both the partial light ends input and the other input 
curves. To activate this option, select the Allow Partial Light 
Ends Input checkbox. Once selected, Aspen HYSYS identifies 
the need and generate the needed hypothetical components to 
compensate the missing portions of the light ends, leading to a 
much better fit between the generated curves and the input 
curves.
Column Description
Head% Specifies the ending percent for the head section on 
the input basis.
Head Adj Wt Specifies the corresponding relative bulk fit adjusting 
weight factor from 0 to 10, where 0 means no 
adjusting at all.
Main% Specifies the ending percent for the main section of the 
input basis.
Main Adj Wt Specifies the corresponding relative bulk fit adjusting 
weight factor from 0 to 10, where 0 means no 
adjusting at all.
Tail Adj Wt Specifies the corresponding relative bulk fit adjusting 
weight factor from 0 to 10, where 0 means no 
adjusting at all.4-29
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4-30 Characterizing Assays
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ThIf the input for either molecular weight or mass density curves is 
less than 95% on a user defined basis, only the extrapolated tail 
is adjusted to match the user specified bulk value. If the input is 
more than or equal to 95% on the user defined basis, the entire 
curve will be adjusted to match the bulk value specified. 
The user input data is the most reliable data available, and 
hence should not be adjusted to match the bulk value as long as 
there is enough extrapolated data to adjust.
When only the tail is adjusted, it is ensured that the upper end 
point is no lower than the linear extrapolation of the last two 
points. This means that in most cases, the extrapolated portion 
of the curve is concave, i.e., the curvature is positive. If the bulk 
value is given such that the extrapolated values are below the 
linear extrapolation values, the whole curve is adjusted and the 
following warning message is displayed: “Curve is normalized 
due to the inconsistency between the supplied curve and bulk 
data.” 
If the upper limit value is reached when adjusting the molecular 
weight or density curve and the specified bulk value is still not 
matched, no adjustment is made and the following message 
appears: “No exact match, upper limit reached”. For molecular 
weight, the upper limit value is ten times that of the bulk value. 
For mass density, the upper limit is three times that of the bulk 
value.
If a bulk molecular weight or mass density is given without a 
corresponding input curve, the whole calculated curve will be 
adjusted.
The 95% input is an artificial dividing line to decide if only the 
tail is adjusted or the whole curve is adjusted. If the user input 
curve crosses the dividing line, there is a chance to have a 
sudden change in the behaviour. If this occurs, you can 
overcome the problem by manually setting the bulking fitting 
options without using the smart option. To achieve similar 
results manually, you can set the Head Adj Wt and Main Adj Wt 
to zero, set the Main % to the desired tail starting percent, and 
leave the Tail Adj Wt to its default value of 1.0. 4-30
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ThBulk Properties Definition
These bulk properties are optional except when distillation data 
is not available (you have selected None as the Data Type). If 
you do not supply any distillation data, you must supply two of 
the three initial bulk properties (Molecular Weight, Mass Density 
or Watson (UOP) K factor) for Aspen HYSYS to create a "typical" 
TBP curve. This TBP curve is generated based on a Whitson 
molar distribution model.
If you are supplying property curves and you supply a bulk 
molecular weight, density, or Watson K factor, Aspen HYSYS 
smoothes and adjusts the corresponding curves to match the 
supplied bulk properties. This procedure is performed whether 
you supply property curves or they were internally generated by 
Aspen HYSYS.
Assay Definition Group
The Assay Definition group contains only one object involved in 
the specification of Bulk Properties: the Bulk Properties drop-
down. The Bulk Properties drop-down list has two options:
Option Description
Used If an Assay Data Type is not selected, the Input Data group 
displays the Bulk Prop table along with the Molecular 
Weight of lightest component field. However, if an Assay 
Data Type is selected, a Bulk Props radio button appears in 
the Input Data group. When this radio button is active the 
Bulk Prop table is displayed.
Not Used No bulk properties are considered in the oil characterization 
calculations.4-31
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4-32 Characterizing Assays
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ThInput Data Group
The Input Data group that appears when Used is selected for 
bulk properties is shown in the figure below: 
It consists of two objects: the Bulk Properties table and 
Molecular Weight of lightest component field.
The Bulk Properties table has several fields:
 Figure 4.12
The Molecular Weight of lightest component field is only 
visible when the Assay Data Type selected is None.
Bulk Properties Description
Molecular 
Weight
The Molecular Weight must be greater than 16.
Standard Density The mass density must be between 250 and 2,000 kg/
m3 (units can be mass density, API, or specific gravity, 
chosen from the drop-down list).4-32
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ThDefining Assay Types
Assay Definition Group
To define Assay types, select a type in the Assay Definition 
group using the drop-down list.
Watson (UOP) K 
factor 
This factor must be between 8 (highly aromatic or 
naphthenic) and 15 (highly paraffinic). Only field units 
are used here.
The Watson (UOP) K factor is an approximate index of 
paraffinicity, with high values corresponding to high 
degrees of saturation:
where:
Mean Avg. BP = the mean average boiling point 
is in degrees Rankine.
Bulk Viscosities The bulk viscosity type and the temperature at two 
reference points.
 Figure 4.13
Bulk Properties Description
K Mean Avg. BP3
sp gr 60F / 60F
--------------------------------------=4-33
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4-34 Characterizing Assays
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ThAssay types that are available are described in the table below:
Assay Type Description
TBP True boiling point distillation data at atmospheric pressure. 
Once you have selected this option, the TBP Distillation 
Conditions group is displayed. 
The default distillation conditions are atmospheric, 
however, you can enable Vacuum Distillation for sub-
atmospheric conditions by selecting the Vacuum radio 
button. The default pressure in this case is 10 mmHg 
(ASTM standard). When you supply sub-atmospheric data, 
it is automatically corrected from vacuum to atmospheric 
conditions using procedure 5A1.13 (without K-correction) 
from the API Data Book.
ASTM D86 Standard ASTM D86 distillation data at atmospheric 
pressure. 
You must provide data on a liquid volume basis.
You can specify the ASTM D86/TBP Interconversion Method 
(API 19741, API 19872, API 19943 or Edmister-Okamoto 
19594) on the Calculation Defaults tab. With the ASTM D86 
Assay type you can also correct for thermal cracking as well 
as for elevation.
ASTM D1160 ASTM D1160 distillation data. After you have selected this 
option, the ASTM D1160 Distillation Conditions group is 
displayed. By default, the Vacuum radio button is selected 
and the Vacuum Distillation Pressure is set to 10 mmHg 
(ASTM standard). When ASTM D1160 Vacuum data is 
supplied, Aspen HYSYS will first convert it to TBP vacuum 
data, and then convert this to TBP data at 760 mmHg using 
procedure 5A1.13 of the API Data Book.
You must provide data on a liquid volume basis.
ASTM D86-
D1160 
This is the combination of the ASTM D86-D1160 data types. 
The options for ASTM D86 and ASTM D1160 are similar to 
the descriptions above. You must provide data on a liquid 
volume basis.
ASTM D2887 Simulation distillation analysis from chromatographic data, 
reported only on a weight percent basis at atmospheric 
pressure. On the Calculation Defaults tab, you have the 
choice of conversion method (API 19875, API 1994 
Indirect6, API 1994 Direct7).
Chromatogra
ph
A gas chromatograph analysis of a small sample of 
completely vaporized oil, analyzed for paraffin, aromatic 
and naphthenic hydrocarbon groups from C6 to C30. 
Chromatographic analyses may be entered on a mole, 
mass, or liquid volume basis. With this option, you enter 
Light Ends, Bulk and Chromatographic analysis data.
Refer to 
Chromatographic 
Assay Input for more 
information.4-34
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ThInput Data Group
The Input Data group displayed when the Distillation radio 
button is selected depends on the Assay type you have selected 
in the Assay Definition group.
Distillation Data
For Assay Type options TBP, ASTM D86, ASTM D1160, ASTM 
D2887 and EFV, the procedure for entering boiling temperature 
information is essentially the same - you are required to enter at 
least five pairs of Assay Percents and boiling Temperatures. The 
Distillation input table is exactly the same for each of these 
options.  
EFV Equilibrium flash vaporization curve; this involves a series 
of experiments at constant atmospheric pressure, where 
the total vapour is in equilibrium with the unvaporized 
liquid.
None No distillation data is available; Aspen HYSYS generates a 
TBP curve from bulk property data. With this option, you 
only enter bulk data.
The conversion procedure from various assay types to a TBP 
curve is based on Figure 3-0.3 of the API Data Book.
You can view and edit the assay boiling Temperature input 
table by selecting the Distillation radio button and clicking 
the Edit Assay button.
Assay Type Description4-35
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4-36 Characterizing Assays
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ThFor the ASTM D86-D1160 characterization procedure, you are 
required to enter boiling temperature information for both the 
ASTM D86 and ASTM D1160 data types. This procedure 
averages the ASTM D86 curve and ASTM D1160 curve in the 
area where they overlap. 
 Figure 4.144-36
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ThFor example, in the combined ASTM D86-D1160 input form 
shown on the figure below, the last recorded ASTM D86 assay 
point is at 30 vol%, and the first reported ASTM D1160 data 
point is at 10 vol%. 
Therefore, the resulting TBP curve will represent the average of 
the two curves between 10 vol% and 30 vol%. Each curve must 
contain a minimum of 5 data points.
Chromatographic Assay Input
This distillation option allows you to enter a standard laboratory 
chromatographic analysis directly. The only required input is the 
assay fraction for each chromatographic hydrocarbon group in 
the paraffin, aromatic, and naphthenic families. The required 
minimum of five points can be any combination of points from 
the three PNA groups. The normal boiling point of each 
hydrocarbon group is displayed in the PNA tables.
Chromatographic analyses may be entered on either a mole, 
mass, or liquid volume basis, with the best results obtained 
when the input fractions are on a mole fraction basis. 
 Figure 4.154-37
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4-38 Characterizing Assays
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ThA typical C6+ liquids chromatographic analysis is shown in the 
chromatographic input form below.
Chromatographic analyses are typically performed after the light 
ends of the original sample are removed. If you have a Light 
Ends analysis in this case, refer to Light Ends Handling & 
Bulk Fitting for details.
Assay Input - No Distillation Data Available
When a distillation analysis is not available, Aspen HYSYS 
generates a typical TBP curve based on supplied bulk properties 
(molecular weight, mass density, and Watson (UOP) K factor). 
You have the option of specifying the molecular weight of the 
lightest component in the mixture, which may help in generating 
more accurate TBP curves for heavy petroleum fluids.
 Figure 4.16
You may also supply bulk 
property data (see Bulk 
Properties in Section 
4.5.1 - Input Data Tab 
for details).4-38
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Th 
Although accurate enough for heat balance applications, caution 
should be exercised when the Whitson option is used to produce 
hypocomponent for fractionation calculations. This method 
realistically supplies accuracy sufficient only for preliminary 
sizing calculations.
For condensate with only bulk data available for the C7+ 
fraction, experience has shown a considerable increase in 
accuracy by representing the fraction with several 
hypocomponent as opposed to a single hypothetical component 
with the bulk properties. 
Refer to Bulk Properties Definition (earlier in this Section) for 
details on entering bulk property data, particularly in regards to 
Bulk Viscosities.
Aspen HYSYS uses the Whitson Molar Distribution model that 
requires at least two of the three bulk properties (not 
including bulk viscosities) to produce an average TBP 
distribution.
 Figure 4.174-39
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4-40 Characterizing Assays
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ThGeneral Guidelines
Some general guidelines are provided below:
• There is no limit to the number of assay data points that 
you may enter for TBP, ASTM D86, ASTM D1160, ASTM 
D86-D1160 ASTM D2887 or EFV analyses. Data points 
may be input in any order, as Aspen HYSYS 
automatically sorts your input data.
• Aspen HYSYS requires a minimum of 5 data points for all 
assays. Depending on the shape of the input curve, 
intermediate values for Aspen HYSYS' internal TBP 
working curve are interpolated using either a third or 
fourth order LaGrange polynomial fit. The points outside 
your data are extrapolated using the extrapolation 
method which you select on Calculation Defaults tab: 
Least Squares, Lagrange or Probability.
• Each time you change the Basis or Extrapolation method, 
the Assay needs to be recalculated.
• TBP, EFV, and Chromatographic laboratory assay values 
may be entered on a liquid volume, mole or weight basis. 
Liquid volume is the default basis for TBP and EFV input, 
and mole is the default basis for Chromatographic input. 
Due to the form of the conversion curves in the API Data 
Book, you must supply your ASTM D86 and ASTM D1160 
distillation data on a liquid volume basis. ASTM D2887 is 
only reported on a weight percent basis.
• If you are editing an assay, redefining the Basis does not 
alter your supplied assay values. For example, consider 
an assay curve with 10, 30, 50, 70 and 90 liquid volume 
percent points. If you change the Basis to mass percent, 
the assay percents and temperature are not changed. 
The temperature you supplied for 10% liquid volume is 
retained for 10% mass.
Aspen HYSYS generates all of its physical and critical 
properties from an internally generated TBP curve at 
atmospheric conditions. Regardless of what type of assay 
data you provide, Aspen HYSYS always converts it to an 
internal TBP curve for the characterization procedure. The 
internal TBP curve is not stored with the assay.4-40
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ThLight Ends Definition
Light Ends are defined as pure components with low boiling 
points. Components in the boiling range of C2 to n-C5 are most 
commonly of interest. Generally, it is preferred that the portion 
of the oil's distillation assay below the boiling point of n-C5 be 
replaced with discrete pure components (library or 
hypothetical). This should always yield more accurate results 
than using hypocomponent to represent the Light Ends portion.
Assay Definition Group
Aspen HYSYS provides three options to account for Light Ends, 
which are as follows:
Option Description
Ignore Aspen HYSYS characterizes the Light Ends portion of your 
sample as hypocomponents. This is the least accurate 
method and as such, is not recommended.
Auto 
Calculate
Select this when you do not have a separate Light Ends 
analysis but you want the low boiling portion of your assay 
represented by pure components. Aspen HYSYS only uses 
the pure components you selected in the fluid package.
Input 
Composition
Select this when you have a separate Light Ends assay and 
your petroleum assay was prepared with the light ends in 
the sample. Aspen HYSYS provides a form listing the pure 
components you selected in the fluid package. Input your 
data on a non-cumulative basis.
To correctly employ the Auto Calculate or Input Composition 
options, you should either pick library components, or define 
hypothetical components to represent the Light Ends before 
entering the Oil Characterization environment. If you have 
selected the Auto Calculate method without specifying light 
ends, Aspen HYSYS calculates the oil using only 
hypocomponent, just as if you had selected Ignore. If you 
selected Input Composition, there are no light end 
components for which you can supply compositions. You can 
go back to the Fluid Package property view at any time and 
define your light components.4-41
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4-42 Characterizing Assays
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ThThe following sections provide a detailed explanation of Light 
Ends, how the laboratory may account for them, how they are 
reported and how Aspen HYSYS utilizes this information. It is 
recommended that you read this information to ensure that you 
are selecting the right options for your assay.
Laboratory Assay Preparation
During TBP and ASTM laboratory distillations, loss of some of 
the Light Ends components from the sample frequently occurs. 
To provide increased accuracy, a separate Light Ends assay 
analyzed using chromatographic techniques may be reported.
Regardless of whether a separate light ends analysis was 
provided, your overall assay is either Light Ends Included or 
Light Ends Free. The way in which your sample was analyzed 
affects both the results and the method you should use to input 
the information for your characterization.
Light Ends Portion Included in Assay
In this case, your assay data was obtained with the light ends 
components in the sample; i.e., the assay is for the whole 
sample. The IBP temperature for your assay is lower than the 
boiling point of the heaviest pure light end component. This 
corresponds to an IBP approximately equal to the weighted 
average boiling point of the first 1% of the overall sample. For 
example, if the lightest component is propane and it makes up 
more than 1% of the total sample, the IBP of the assay is 
approximately -45°F (the normal boiling temperature of 
propane).4-42
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ThIf the Light Ends were included in your overall assay, there are 
two possibilities:
Assay is Light Ends Free
Your assay data was analyzed with the Light Ends components 
removed from the sample, or the assay was already adjusted for 
the Light Ends components. The IBP temperature for your assay 
is higher than the boiling point of the heaviest pure light end 
component - typically your assay is for the C6+ fraction only and 
the IBP temperature is somewhat above 95°F (36°C).
If your distillation data is light-ends free and you have separate 
light-ends analysis data, you can use Aspen HYSYS oil 
characterization to combine the two. The advantage of doing 
this is that the bulk properties, if available, will be fitted and 
matched accurately. To do the combining, you need to input the 
distillation data and light ends data as usual and then click the 
Light Ends Handling & Bulk Fitting Options button 
accessible from Input Data or User Curves tab. In the Light-
Ends Handling & Bulk Fitting Options property view, clear the 
Curve Incl L.E. checkbox for distillation. If you have bulk 
properties to fit, you need to indicate if the bulk values include 
light ends by selecting or clearing the Bulk Value Incl L.E. 
checkboxes.
Option Description
Light Ends 
Analysis 
Supplied
If you know that light ends are included in your assay, 
select the Input Composition option from the Light 
Ends group, and enter the composition data directly 
into the Light Ends composition property view.
No Light Ends 
Analysis 
Available
If you do not have a laboratory analysis for the light 
ends portion of your assay, then you should use the 
Auto Calculate option. Aspen HYSYS represents the 
light ends portion of your assay as discrete pure 
components, automatically assigning an appropriate 
assay percentage to each. If you do not do this (you 
select Ignore), Aspen HYSYS represents the Light Ends 
portion of the assay as petroleum hypocomponent.4-43
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4-44 Characterizing Assays
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ThInput Data Group
When you have selected Input Composition as the Light Ends 
option and you select the Light Ends radio button in the Input 
Data group, the following property view appears.  
There are three objects associated with the Light Ends Input and 
are described below: 
 Figure 4.18
Object Description
Light Ends Basis Allows you to select the basis for the Light Ends 
analysis on a mole, mass, or liquid volume basis. The 
way in which you enter the rest of the light ends data 
depends on whether you select a percent or flow basis:
• Percent. Enter the percent compositions for the 
Light Ends on a non-cumulative basis. Aspen 
HYSYS calculates the total Light Ends percentage 
by summing all of the Light Ends assay data. If 
the sum of the light ends assay values is equal to 
100 (you have submitted normalized data), you 
must enter the Percent of light ends in the Assay. 
This value must be on the same basis as the 
distillation data. 
If the sum of the light ends is equal to 1.0000, 
Aspen HYSYS assumes that you have entered 
fractional data (rather than percent), and you are 
required to enter the Percent of light ends in the 
Assay.
• Flow. Enter the flows for each component, as 
well as the percent of light ends in the assay.4-44
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ThAuto Calculate Light Ends
The Auto Calculate extraction procedure internally plots the 
boiling points of the defined Light Ends components on the TBP 
working curve and determine their compositions by 
interpolation. Aspen HYSYS adjusts the total Light Ends fraction 
such that the boiling point of the heaviest Light End is at the 
centroid volume of the last Light Ends component. The results of 
this calculation are displayed in Light Ends Composition matrix. 
If a fluid package contains a large number of hydrocarbons, 
especially heavy ones, Aspen HYSYS may allocate a very large 
portion of the assay input to light ends, leading to undesired 
results. The checkboxes under the Use column allows you to 
decide which components are used in the light ends auto 
allocation. This option gives you more control on the light ends 
to be used, and allows the use of any fluid package to be 
associated with the oil manager, even with very heavy 
hydrocarbons.
Light Ends 
Composition 
matrix
The matrix consists of the three fields:
• Light Ends. Displays all pure components or 
hypotheticals you selected in the associated fluid 
package.
• Composition. The composition value of the 
associated component is either entered (when 
Light Ends drop-down is set to Input 
Composition) or automatically calculated (when 
the Light Ends drop-down is set to Automatically 
Calculated)
• NBP. The Normal Boiling Point of the associated 
component or hypothetical.
Percent of lights 
ends in Assay
The total percentage of light ends in the Assay. If the 
Light Ends Basis selected is percentage (i.e., 
LiquidVolume%, Mole% or Mass%), then this is 
automatically calculated. If the Basis selected is flow 
based (i.e., Liquid Flow, Mole Flow or Mass Flow), you 
are required to provide this value.
Object Description
Refer to Appendix B - 
Oil Methods & 
Correlations for a 
graphical representation 
of the Auto Calculate 
Light Ends removal 
procedure.4-45
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4-46 Characterizing Assays
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ThUnlike when setting the Input Composition, the matrix is not 
editable.
Physical Property Curves 
Specification
Physical property analyzes are normally reported from the 
laboratory using one of the following two conventions:
• An Independent assay basis, where a common set of 
assay fractions is not used for both the distillation curve 
and physical property curve.
• A Dependent assay basis, where a common set of assay 
fractions is used for both the distillation curve and the 
physical property curves.
Physical properties are average values for the given range, and 
hence are midpoint values. Distillation data reports the 
temperature when the last drop of liquid boils off for a given 
assay range, and therefore distillation is an endpoint property. 
Since all dependent input property curves are reported on the 
same endpoint basis as the distillation curve, they are converted 
by Aspen HYSYS to a midpoint basis. Independent property 
curves are not altered in any manner as they are already 
defined on a midpoint basis.
 Figure 4.194-46
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ThAs with distillation curves, there is no limit to the number of 
data points you provide. The order in which you input the points 
is not important, as Aspen HYSYS sorts the input data. A 
minimum of five data points is required to define a property 
curve in Aspen HYSYS. It is not necessary that each property 
curve point have a corresponding distillation value.
If a bulk molecular weight or mass density is going to be 
supplied, then the corresponding Molecular Weight or Density 
working curve generated from your input is smoothed to ensure 
a match. If you do not enter bulk properties, then they are 
calculated from the unsmoothed working curves.
Assay Definition Group
Each property curve type (i.e., Molecular Wt., Density and 
Viscosity) has its own drop-down list in the Assay Definition 
group. 
Entering the 0 vol% point of a dependent curve contributes 
to defining the shape of the initial portion of the curve, but 
has no physical meaning since it is a midpoint property 
curve.
 Figure 4.204-47
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4-48 Characterizing Assays
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ThEach drop-down list contains the same three options and are 
described below:
Input Data Group
Defining Molecular Weight and Density property curves as either 
Independent or Dependent adds the corresponding radio button 
to the Input Data group. However, defining a Viscosity property 
curve as Independent or Dependent, Aspen HYSYS accepts 
viscosities for assay values at two specified temperatures, with 
the default temperatures being 100 and 210°F. Selecting the 
Molecular Wt., Density, Viscosity1, or Viscosity2 radio 
buttons brings up the objects associated with the specification of 
the respective property curve. 
To enter the property curve data, simply select the radio button 
for the property curve you want to input and click the Edit Assay 
button.
Option Description
Not Used No property data is considered in the assay calculation.
Dependent A common set of assay fractions is used for both the 
distillation curve and the physical property curves.
Independent A common set of assay fractions is not used for both the 
distillation curve and physical property curve.4-48
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ThMolecular Wt. Curve
An example of a Molecular Weight assay is shown below: 
The assay data is entered into the Assay Input Table property 
view which is opened when the Edit Assay button is selected. 
The form of this property view is the same regardless of whether 
you have specified Independent or Dependent data. However, if 
you specified Dependent data, the Assay Percents that you 
defined for the distillation data are automatically entered in the 
table.
Depending on the shape of the curve, intermediate values for 
Aspen HYSYS' internal working curve are interpolated using 
either a third or fourth order Lagrange polynomial fit of your 
input curve, while points outside your data are extrapolated. 
You can select the extrapolation method for the fit of your input 
curve on the Calculation Defaults tab: Least Squares, Lagrange 
or Probability.
 Figure 4.21
In Dependent Curves, making a change to an Assay Percent 
value automatically changes this value in all other 
Dependent curves (including the Boiling Point curve).4-49
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4-50 Characterizing Assays
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ThDensity Curve
An example of a Density assay is shown below:
The assay data is entered into the Assay Input Table property 
view which is opened when the Edit Assay button is selected. 
The form of this property view is the same regardless of whether 
you have specified Independent or Dependent data. However, if 
you specified Dependent data, the Assay Percents that you 
defined for the distillation data are automatically entered in the 
table.
Depending on the shape of the curve, intermediate values for 
Aspen HYSYS' internal working curve are interpolated using 
either a third or fourth order Lagrange polynomial fit of your 
input curve, while points outside your data are extrapolated. 
You may select the extrapolation method for the fit of your input 
curve on the Calculation Defaults tab: Least Squares, Lagrange 
(default) or Probability.
 Figure 4.224-50
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ThViscosity Curves
Aspen HYSYS accepts viscosities for assay data at two specified 
temperatures and therefore provides two radio buttons, 
Viscosity1 and Viscosity2, in the Input Data group.
You can input data for one or both of the viscosity curves. Each 
radio button brings up identical sets of objects, specific to assay 
data at the designated temperature. Temperatures are entered 
in the Temperature field with default values being 100 and 
210°F. This implies that you have determined the viscosity at 
100 or 210°F for each of your assay portions (10%, 20%, etc.). 
In the Viscosity Curves group box, you can specify which curve 
(or both) you want to use by selecting the appropriate radio 
button. 
The Assay Input Table property view, which is opened when the 
Edit Assay button is selected, is filled in with the assay data. The 
form of this property view is the same regardless of whether you 
have specified Independent or Dependent data. However, if you 
specified Dependent data, the Assay Percents that you defined 
for the distillation data are automatically entered in the table.
 Figure 4.234-51
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4-52 Characterizing Assays
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ThYou may also define the viscosity unit  type. The Units Type can 
be one of the following:
Depending on the shape of the curve, intermediate values for 
Aspen HYSYS' internal working curve are interpolated using 
either a third or fourth order Lagrange polynomial fit of your 
input curve, while points outside your data are extrapolated. 
You may select the extrapolation method for the fit of your input 
curve on the Calculation Defaults tab: Least Squares, Lagrange 
or Probability. 
The defaults for a new assay may be modified by clicking the Oil 
Input Preferences… button on the Assay tab of the Oil 
Characterization property view. The same property view may 
also be accessed from the Simulation environment by the 
following sequence: 
1. Select Tools-Preferences command from the menu bar.
2. On the Session Preferences property view, go to the Oil 
Input tab.
3. Select the Assay Options page.
Unit Type Description
Dynamic Conventional viscosity units (e.g., - cP)
Kinematic Ratio of a fluid's viscosity to its density (e.g.,- stoke, m2/s)4-52
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Th4.5.2 Calculation Defaults Tab
The Calculation Defaults tab is shown below:
The internal TBP curve is not stored with the assay. The 
Calculation Defaults tab contains three main groups: 
• Conversion Methods
• Corrections for Raw Lab Data
• Extrapolation Methods
Conversion Methods Group
Aspen HYSYS generates all of its physical and critical properties 
from an internally generated TBP curve at atmospheric 
conditions. Regardless of what type of assay data you provide, 
Aspen HYSYS always converts it to an internal TBP curve for the 
characterization procedure. For ASTM D86 and ASTM D2887 
assays types, you may specify the inter-conversion or 
conversion methods used in the Conversion Methods group. 
 Figure 4.244-53
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ThThe group consists of the following two drop-down lists:
Corrections for Raw Lab Data Group
In this group, two correction methods are available for 
previously uncorrected laboratory data:
Field Description
D86-TBP 
(Interconversion)
There are four interconversion methods available:
• API 19741
• API 19872
• API 19943
• Edminster Okamoto 19594
D2887-TBP 
(Interconversion)
There are three interconversion methods 
available:
• API 19875
• API 1994 Indirect6
• API 1994 Direct7
Correction Description
Apply Lab 
Barometric 
Pressure 
Correction
ASTM D86 data that is generated above sea level 
conditions must be corrected for barometric pressure. 
If this is not done by the laboratory, select the Yes 
radio button from the subgroup and Aspen HYSYS 
performs the necessary corrections. Enter the ambient 
laboratory barometric pressure in the Lab Barometric 
Pressure field and Aspen HYSYS corrects your ASTM 
distillation data to 1atm before applying the API Data 
Book conversions for ASTM D86 to TBP distillation.
Apply ASTM D86 
API Cracking 
Correction
API no longer recommends using this correction:
The ASTM cracking correction is designed to correct for 
the effects of thermal cracking that occur during the 
laboratory distillation. If this is not done by the 
laboratory, select the Yes radio button, and Aspen 
HYSYS performs the necessary corrections. This 
correction is only applied to ASTM D86 temperatures 
greater than 485°F (250°C). 
The API cracking correction should not be applied to 
ASTM D86 distillations that extend beyond 900°F 
(500°C), due to the exponential nature of the 
correction.4-54
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ThExtrapolation Methods Group
Aspen HYSYS allows you to choose the extrapolation method 
used for the different Assays (i.e., Distillation and the Molecular 
Weight, Density and Viscosity property curves). There are three 
methods available:
This group also allows you to specify which end of the curve to 
apply the extrapolation method. There are three choices 
available:
• Upper end
• Lower end
• Both ends
Extrapolation 
Method
Uses
Lagrange For assays representing cuts (i.e., naphtha) or assays 
for properties other than Boiling Temperature. 
Least Squares The Least Squares method is a lower order Lagrange 
method. For this method, the last five input points are 
used to fit a second order polynomial. If the curvature 
is negative, a straight line is fit.
Probability Use the Probability extrapolation method in cases 
when your Boiling Temperature assay represents a full 
range crude and the data is relatively flat. For 
instance, the data in the distillation range of your 
assay (i.e., 10% to 70%) may be relatively constant. 
Instead of linearly extending the curve to the IBP and 
FBP, the Probability method only considers the steep 
rise from the FBP.
Te
m
p
er
at
u
re
Assay%
Known Part 
of Curve 
Extrapolated 
Part 4-55
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4-56 Characterizing Assays
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Th4.5.3 Working Curves Tab
The third tab of the Assay view is the Working Curves tab. 
After the Assay is calculated, you can view the Assay Working 
Curves:
Recall that the working curves are interpolated using either a 
third or fourth order Lagrange polynomial fit of your input curve, 
while the method used to extrapolate points outside your data 
depends on the type of curve (Mass Density, Viscosity, 
Molecular Weight). You select the method for the fit of your 
input curve: Least Squares, Lagrange or Probability.
Aspen HYSYS always uses 50 points in the calculation of the 
working curves, but the molar distribution varies depending on 
the data you provide. In cases where there is a region with a 
steep gradient, Aspen HYSYS moves more points to that region, 
but still uses 50 points.
 Figure 4.254-56
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Th4.5.4 Plots Tab
Following the Working Curves tab is the Plots tab, on which you 
can view any of the input data curves in a graphical format.
The Property drop-down list, shown above, displays the options 
available for the y-axis of the plot. The Distillation option shows 
the boiling temperature input according to the Assay Type 
chosen (i.e., TBP, ASTM D86, etc.). The x-axis displays the 
Assay% on a basis consistent with the format of your input.
An example of a distillation boiling point curve is shown in the 
figure below. All of the entered data point pairs and the 
interpolated values are drawn on the plot.
 Figure 4.26
 Figure 4.27
The User Property option is 
only available if a User 
Property is created and a 
User Curve is defined in the 
Assay.4-57
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ThTo make changes to the appearance of the plot, object inspect 
the plot area. From the menu that appears, select Graph 
Control.
4.5.5 Correlations Tab
The Correlations tab of the Assay property view is shown below:
The correlations tab consists of the following objects:
 Figure 4.28
Object Description
Selected 
Correlation 
Set
By default, this is Default Set (if you have changed the 
name of the default set, that name is displayed). You can 
select another correlation set from the Selected drop-down 
list, but first you must define one on the Correlation tab of 
the Oil Characterization property view.
You can define new correlations sets via the Correlation 
tab, accessible from the main Oil Characterization property 
view.
Low and 
High End 
Temperature
This is the range for which the Correlations are applied. If 
you split the range, then more than one temperature range 
is displayed. 
You can edit the temperature of defined splits for custom 
Correlation Sets on this tab.
MW The MW correlation is displayed. You cannot change the 
correlation in this property view; this can be done from the 
Correlation tab accessible from the main Oil 
Characterization property view or by clicking the Edit 
button.
You can change only the name of the default set. If you 
want to change any correlations, you must create a new 
correlation set.
For details on the various 
Graph Control options, 
refer to Section 10.4 - 
Graph Control of the 
Aspen HYSYS User 
Guide.
Refer to Section 4.8.1 - 
Correlation Tab for 
more information. 4-58
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ThOnly the molecular weight and specific gravity correlations are 
required in the calculation of the working curves. The critical 
pressure, critical temperature, acentricity, and ideal enthalpy 
correlations are also displayed on the Assay property view, as 
these are applicable only in the calculation of the 
hypocomponent properties.
If you supply molecular weight or density curves, then their 
respective correlations are not required. You do not have a 
choice of correlations for calculating the viscosity curves.
 SG The specific gravity (density) correlation is displayed. You 
cannot change the correlation in this property view; this 
can be done from the Correlation tab accessible from the 
main Oil Characterization property view or by clicking the 
Edit button.
Tc, Pc, Acc. 
Factor, Ideal 
H
The critical temperature, critical pressure, acentricity and 
Ideal Enthalpy correlations are displayed. You cannot 
change correlations on this tab; this can be done in the 
Correlation property view accessible from the main Oil 
Characterization property view. To edit the Selected 
Correlation Set from this tab, click the Edit button. This 
takes you to the Correlation property view.
Although a Correlation set contains methods for all 
properties, the Correlation tab, as seen on the Assay and 
Blend property views, displays only the properties 
appropriate to that step in the Characterization process.
Object Description4-59
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Th4.5.6 User Curves Tab
The User Curves tab of the Assay property view is shown below:
The available and selected User Properties are displayed in the 
left portion of the property view. User Properties are defined on 
the User Property tab of the Oil Characterization property view.
There are two elements to a User Curve:
• The definition of how the property value is calculated for 
a stream (mixing rule).
• The assay/property value information that is supplied for 
a given assay.
The property definition (see Section 4.7 - User Property for 
details) is common to all assays.
After a User Property is defined, you can add it to the Assay by 
highlighting it and selecting the Add button. To remove a User 
Property from the current Assay, highlight it and select the 
Remove button. Double-clicking on a User Property name in the 
selection list opens the User Property property view as described 
in Section 4.7.2 - User Property Property View.
 Figure 4.29
See Light Ends 
Handling & Bulk Fitting 
for details on the Light 
Ends Handling & Bulk 
Fitting Options button.4-60
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ThAfter adding a User Property, you can edit the User Curve Data:
4.5.7 Notes Tab
Aspen HYSYS provides a tab where you can enter a description 
of the Assay for your own future reference. This can also be 
accessed through the notes manager.
User Curve Data Description
Table Type This is either Dependent or Independent. If you select 
Dependent, the Assay Percents are automatically set to 
the values you specified for the Boiling Temperature 
assay (Input Data tab). 
If the table type is Dependent and you change the 
assay percents on this tab, this also changes the assay 
percents in the Distillation boiling temperature matrix 
and for any other dependent curve.
Bulk Value Specify a Bulk Value. If you do not want to supply a 
bulk value for the user property, ensure that this cell 
reads  by placing the cursor in that cell and 
pressing the DELETE key.
Extrapolation 
Method
This field allows you to choose the extrapolation 
method used for the selected user property in the 
current assay. The available choices are: 
• Least Squares
• Lagrange
• Probability
Apply To This field allows you to choose which end of the curve 
to apply the extrapolation method to. There are three 
choices available:
• Upper end
• Lower end
• Both ends
User Property 
Table
Provide the Assay percents and User Property Values in 
this table. At least five pairs of data are required.4-61
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4-62 Hypocomponent Generation
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Th4.6 Hypocomponent 
Generation
The Cut/Blend tab of the Oil Characterization property view is 
shown below: 
The Available Blends are listed in the left portion of the property 
view. The following Blend manipulation buttons are available:
 Figure 4.30
For a highlighted Blend, you can edit the name and provide a 
description in the Blend Information group.
Button Description
View Edit the currently highlighted Blend.
Add Create a new Blend.
Delete Erase the currently highlighted Blend. Aspen HYSYS does 
not prompt for confirmation when deleting a Blend, so be 
careful when you are using this command.
Clone Create a new Blend with the same properties as the 
currently highlighted Blend. Aspen HYSYS immediately 
opens a new Blend property view.4-62
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ThAs described in the Oil Characterization property view section, 
the general buttons at the bottom of the property view are:
• The Clear All button is used to delete all Oil 
Characterization information.
• The Calculate All button re-calculates all Assay and 
Blend information.
• The Oil Output Settings... button allows you to change 
IBP, FBP, ASTM D86, and ASTM D2887 interconversion 
methods for output related calculations.
In the following sections, each tab of the Blend property view 
(accessed through the View or Add buttons) is described.
4.6.1 Data Tab
The Cut/Blend characterization in Aspen HYSYS splits internal 
working curves for one or more assays into hypocomponents. 
Once your assay information is entered through the Assay view, 
you must Add a Blend and transfer at least one Assay to the Oil 
Flow Information table to split the TBP working curve(s) into 
discrete hypocomponent. The first tab of the Blend property 
view is shown below: 
 Figure 4.31
All Boiling Point information supplied in an assay is 
converted to TBP format.4-63
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4-64 Hypocomponent Generation
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ThAssay Selection
A list of the available Assays is shown in the left portion of the 
property view. You can choose an assay by highlighting it and 
clicking the Add button. It is removed from the Available Assays 
list and added to the Oil Flow Information table, which displays 
the following information: 
You can remove an Assay from the Oil Flow Information table by 
highlighting it and selecting the Remove button.
Oil Flow 
Information
Description
Oil The name of the Assay is displayed in this column. There is 
no limitation to the number of assays that can be included 
in a single blend or to the number of blends that can 
contain a given assay. Each blend is treated as a single oil 
and does not share hypocomponent with other blends or 
oils.
Flow Units You can select the Flow Basis (Mole, Mass or Liquid 
Volume) here. 
If you have several Assays, it is not necessary that they 
have the same Flow Basis.
Flow Rate Enter the flow rate; you can use any units (with the same 
basis); they are converted to the default.
You are allowed to define a flowsheet stream for each 
constituent assay in a blend.
To view an Assay, double-click on the Assay name, either in 
the Available Assays list, or in the Oil column of the Oil Flow 
Information table.4-64
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ThBulk Data
The Bulk Data button becomes available when more than one 
assay is present in the Oil Flow Information table.
Aspen HYSYS allows you to provide the following bulk data for a 
blend on the Bulk Values property view:
• Molecular Weight
• Mass Density
• Watson (UOP) K
• Viscosities at 2 temperatures
The Bulk Data feature is particularly useful for supplying the 
bulk viscosities of the blend, if they are known.
Cut Ranges
You have three choices for the Cut Option Selection: 
These methods are described in detail later in this section.
 Figure 4.32
Cut Options Description
Auto Cut Aspen HYSYS cuts the assay based on internal values.
User Ranges You specify the boiling point ranges and number of cuts per 
range.
User Points You specify only how many hypocomponent you require. 
Aspen HYSYS proportions the cuts according to an internal 
weighting scheme.4-65
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ThYou can specify as many components as you want, within the 
limitations of the available memory. Whether specified or 
calculated internally, each cut point is integrated to determine 
the average (centroid) boiling point. The centroid is always 
determined using Aspen HYSYS' internally generated TBP curve 
on a weight basis.
Although the external procedure for blending assays is almost 
identical with that for cutting a single assay, Aspen HYSYS' 
internal procedure is somewhat different. After Aspen HYSYS 
has converted each assay to a TBP vs. weight percent curve, all 
of the individual curves are combined to produce a single 
composite TBP curve. This composite curve is then used as if it 
were associated with a single assay; hypocomponents are 
generated based on your instructions.
These hypocomponents are now common to the blended oil and 
all the constituent oils. For each of the constituent oils, Aspen 
HYSYS back calculates the compositions that correspond to 
these hypocomponents.
When you re-cut an oil, Aspen HYSYS will automatically 
update the associated flowsheet streams with the new 
hypocomponents when you leave the Basis Environment.
Caution should be exercised when blending some 
combinations of analyses. An inherent advantage, as well as 
limitation, of blending is that all constituent oils share a 
common set of hypocomponent and therefore physical 
property characteristics. Any analyses that have large 
overlapping TBP curves and very different physical property 
curves should not be blended (for example, hydrocracker 
recycles and feedstocks have similar TBPs but very different 
gravity curves). The physical properties of components for 
overlapping areas represent an average that may not 
represent either of the constituent assays.4-66
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ThThis procedure is recommended whenever recombining product 
oils or fractions to produce a single inlet stream, for example in 
generating a feed for an FCCU main fractionator from analyzes 
of the product streams. The major advantage to blending is that 
fewer hypocomponents are used to represent a given feed 
because duplicate components for overlapping TBP curves are 
eliminated. 
A second advantage is that the composite TBP curve tends to 
smooth the end portions of the individual assay curves where 
they may not be as accurate as the middle portions of the 
curves.
Recommended Boiling Point Widths
The following table is a guideline for determining the number of 
splits for each boiling point range. These are based upon typical 
refinery operations and should provide sufficient accuracy for 
most applications. You may want to increase the number of 
splits for ranges where more detailed fractionation is required.
Regardless of your input data, it is recommended that you limit 
your upper boiling range to 1650°F (900°C). All of the critical 
property correlations are based on specific gravity and normal 
boiling points and thus, NBPs above this limit may produce 
erroneous results. The critical pressure correlations control this 
limit. There is no loss in accuracy by lumping the heavy ends 
because incremental changes in solubility of lighter components 
are negligible and this range is generally not be fractionated.
Aspen HYSYS allows you to assign the overall blend 
composition and/or individual assay compositions to 
streams via the Install Oil tab (Section 4.8.3 - Install Oil 
Tab).
Cutpoint Range Boiling Point Width Cuts/100°F
IBP to 800°F (425°C) 25°F (15°C) per cut 4
800°F to 1200°F (650°C) 50°F (30°C) per cut 2
1200°F to 1650°F (900°C) 100°F (55°C) per cut 14-67
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4-68 Hypocomponent Generation
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ThAuto Cut
If you select the AutoCut option, Aspen HYSYS performs the 
cutting automatically. Aspen HYSYS uses the boiling point width 
guidelines, as shown previously: 
User Points
If you select User Points from the Cut Option Selection drop-
down list, Aspen HYSYS performs the cutting process depending 
on the number of cuts you specify. Enter the total number of 
cuts you want to use for the oil in the appropriate field. All splits 
are based upon TBP temperature, independent of the source or 
type of assay data. Aspen HYSYS proportions the cuts according 
to the following table:
The internal weighting produces more hypocomponents per 
100°F range at the lower boiling point end of the assay. For 
example, given a TBP temperature range of 100°F to 1400°F 
and 38 components requested, Aspen HYSYS produces 28 
components for the first range, eight components for the second 
range and two components for the last range:
(800 - 100) / 100 * 4 = 28
(1200 - 800) / 100 * 2 = 8
Range Cuts
100 - 800°F 28
800 - 1200°F 8
1200 - 1600°F 4
Cutpoint Range Internal Weighting
IBP - 800°F (425°C) 4 per 100°F 
800°F - 1200°F (650°C) 2 per 100°F 
1200°F to FBP 1 per 100°F 4-68
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Th(1400 - 1200) / 100 * 1 = 2
User Ranges
If you want to define cutpoint ranges and specify the number of 
hypocomponent in each range, select User Ranges and Aspen 
HYSYS displays the Ranges Selection information as shown in 
the figure below.
The IBP and FBP are shown above and these values correspond 
to the initial boiling point and the final boiling point of Aspen 
HYSYS' internal TBP working curve. At this point all light ends 
are removed (if requested) and the IBP presented is on a light 
ends free basis. 
The IBP and FBP of the internal TBP curve used for the column 
operation's cutpoint specifications and the boiling point tables 
are determined in this manner. If the first or last 
hypocomponent has a volume fraction larger than that defined 
by the endpoints for the IBP or FBP respectively, the TBP curve 
is extrapolated using a spline fit.
You may supply the Initial Cut Point; however, if this field is left 
blank, Aspen HYSYS uses the IBP. Aspen HYSYS combines the 
material boiling between the IBP and the initial cutpoint 
temperature with the material from the first cut to produce the 
first component. This component has an NBP centroid 
approximately half way between these boundaries.
 Figure 4.33
Refer to the Boiling 
Ranges Section 4.4 - Oil 
Characterization 
Property View for 
definitions of the IBP and 
FBP.4-69
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4-70 Hypocomponent Generation
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ThThe next parameters that you must supply are the upper 
cutpoint temperature and the number of cuts for the first 
cutpoint range. As shown in Figure 4.33, the upper cutpoint 
temperature for the first range also corresponds to the lower 
boiling point of the second cutpoint range, so it does not have to 
be re-entered. After the first cut range is defined, only the upper 
cutpoint temperature and the number of cuts need to be 
supplied for the remaining ranges. If the final cutpoint 
temperature is not equal to or greater than the FBP, Aspen 
HYSYS combines the material between the FBP and the last cut 
temperature with the material in the last component.
For example, assume that the IBP and FBP are 40 and 1050°F 
respectively, the initial cut temperature is 100, the upper limit 
for the first cut is 500 degrees, and the number of cuts in the 
first range is eight.
Since the boiling width for each component in the first cut range 
is 50°F (i.e., [500-100]/8), the first component's NBP is at the 
centroid volume of the 40 to 150 cut, in this case approximately 
95°F. The remaining components have NBP values of 
approximately 175, 225, 275, 325, 375, 425 and 475°F. The 
upper temperature for the second range is 1,000 and the 
number of cuts is equal to 5. Since the FBP is 1050, the material 
in the boiling range from 1,000 to 1,050 is included with the last 
component.4-70
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Th4.6.2 Correlations Tab 
The Correlations tab of the Blend property view is shown in the 
figure below: 
The Correlations tab consists of the following objects: 
 Figure 4.34
As in the Assay Oil characterization, you can only change the 
name of the default set. If you want to change any 
correlations, you must create a new correlation set.
Object Description
Selected 
Correlation 
Set
By default, this is Default Set (if you have changed the 
name of the default set, that name is displayed). You can 
select another correlation set from the Selected drop-down 
list, but first you must define one on the Correlation tab of 
the Oil Characterization property view.
You can define new correlations sets via the Correlation 
tab, accessible from the main Oil Characterization property 
view. See Section 4.8.1 - Correlation Tab.
Low and 
High End 
Temperature
This is the range for which the Correlations are applied. If 
you split the range, then more than one temperature range 
is displayed. 
You can edit the temperature of defined splits for custom 
Correlation Sets on this tab.4-71
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4-72 Hypocomponent Generation
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ThThe critical pressure, critical temperature, acentricity and ideal 
enthalpy correlations are required in the Blend calculation (or 
more specifically, in the calculation of hypocomponent 
properties). In the calculation of hypocomponent properties, the 
molecular weight and specific gravity (and viscosity) are 
estimated from their respective working curves.
MW The MW correlation is displayed. You cannot change the 
correlation in this property view; this can be done from the 
Correlation tab accessible from the main Oil 
Characterization property view or by clicking the Edit 
button.
You can change only the name of the default set. If you 
want to change any correlations, you must create a new 
correlation set.
 SG The specific gravity (density) correlation is displayed. You 
cannot change the correlation in this property view; this 
can be done from the Correlation tab accessible from the 
main Oil Characterization property view or by clicking the 
Edit button.
Tc, Pc, Acc. 
Factor, Ideal 
H
The critical temperature, critical pressure, acentricity and 
Ideal Enthalpy correlations are displayed. You cannot 
change correlations on this tab; this can be done in the 
Correlation property view accessible from the main Oil 
Characterization property view. To edit the Selected 
Correlation Set from this tab, click the Edit button. This 
takes you to the Correlation property view.
Object Description4-72
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Th4.6.3 Tables Tab
After calculating a Blend, you can examine various property and 
flow summaries for the generated hypocomponent that 
represent a calculated oil.
From the Table Type drop-down list, you can select any one of 
the following:
 Figure 4.35
Table Type Description
Component 
Properties
With this Table Type selection, you can select one of the two radio 
buttons in the Table Control group:
• Main Properties. Provides the normal boiling point, molecular 
weight, density and viscosity information for each individual 
component in the oil.
• Other Properties. Provides the critical temperature, critical 
pressure, acentric factor, and Watson K factor for each 
individual hypocomponent.
Component 
Breakdown
Provides individual liquid volume%, cumulative liquid volume%, 
volume flows, mass flows and mole flows, for the input light ends 
and each hypocomponent in the oil.
Molar 
Compositions
Provides the molar fraction of each light end component and each 
hypocomponent in the oil.4-73
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4-74 Hypocomponent Generation
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Th4.6.4 Property Plot Tab
Aspen HYSYS can plot various properties versus liquid volume, 
mole or mass percent distilled. The x-axis choice is made from 
the Basis drop-down list. Any of the following options may be 
plotted on the y-axis by making a selection from the Property 
drop-down list:
• Distillation. A table appears in which you can select 
which boiling point curves to examine. Select the 
checkbox of each curve you want displayed. The options 
include: TBP, ASTM D86, D86(Crack Reduced), ASTM 
D1160(Vac), ASTM D1160(Atm) and ASTM D2887.
• Molecular Weight
• Density
• Viscosities at 100 and 210°F (or the input temperature)
• Critical Temperature
• Critical Pressure
• Acentric Factor
Oil Properties For this selection, you can select the Basis (liquid volume, molar or 
mass) in the Table Control group box. There are also three radio 
buttons, each producing a different table:
• Distillation. Provides TBP, ASTM D86, D86 Crack Reduced, 
ASTM D1160 (Vac), ASTM D1160 (Atm), and ASTM D2887 
temperature ranges for the oil.
• Other Properties. Provides critical temperature, critical 
pressure, acentric factor, molecular weight, density and 
viscosity ranges for the oil.
• User Properties. Provides all user property ranges for the oil.
Oil Distributions Provides tabular information on how your assay would be roughly 
distributed in a fractionation column. Examine the End 
Temperatures of the various ranges as well as the Cut Distributions. 
You can select the basis for the Cut Distribution Fractions (Liquid 
Volume, Molar, Mass) in the Table Control group. The radio buttons 
provide the option of standard fractionation cuts or user defined 
cuts: 
• Straight Run. Lists crude column cuts: Off gas, LSR Naphtha, 
Naphtha, Kerosene, Light Diesel, Heavy Diesel, Atmos Gas Oil 
and Residue.
• Cycle Oil. Lists Cat Cracker cycle oils: Off Gas, LC Naphtha, HC 
Naphtha, LCGO, ICGO, HCGO, Residue 1 and Residue 2.
• Vacuum Oil. Lists vacuum column cuts: Off Gas, LVGO, HVGO 
and 5 VAC Residue ranges.
• User Custom. Allows for the definition of customized 
temperature ranges. If changes are made to the information in 
any of the standard fractionation cuts, the radio button will 
automatically switch to User Custom.
Table Type Description4-74
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Th• User Property. A table appears to allow you the choice of 
which user property to plot.
Click the Clone and shelf this plot button to store the current 
plot. Aspen HYSYS automatically names the plot with the 
following format: 'the name of the active blend'-'number of plots 
created'. For instance, the first plot created for Blend-1 would be 
named Blend-1-0, and any subsequent plots would have the 
number after the dash incrementally increased.
To edit plot labels, you must clone the plot using the Clone and 
shelf this plot button. The BlendPlot appears and is stored in the 
Plot Summary tab.
An example of a TBP curve on a liquid volume basis for an oil is 
shown below.
Plot labels can not be modified within the Property Plot tab 
Blend property view.
 Figure 4.36
Refer to the Section 
4.6.7 - Plot Summary 
Tab section for 
information concerning 
the Plot Summary tab.4-75
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Th4.6.5 Distribution Plot Tab
Aspen HYSYS can also plot a distribution bar chart so you can 
study how your assay would be roughly distributed in a 
fractionation column. Straight Run, Cycle Oil, Vacuum Oil and 
User Custom TBP cutpoints are available distribution options, as 
shown by the radio buttons in the Cut Input Information group. 
You can choose the Basis for the Cut Distribution Fractions 
(Liquid Volume, Molar, Mass) in the Plot Control group.
Click the Clone and shelf this plot button to store the current 
plot. Aspen HYSYS automatically names the plot with the 
following format: ‘the name of the active blend'-'number of plots 
created'. 
For example, the first plot created for Blend-1 is named Blend-
1-0, and any subsequent plots would have the number after the 
dash incrementally increased. All stored plots are listed on the 
Plot Summary tab.
 Figure 4.37
Refer to the Section 
4.6.7 - Plot Summary 
Tab for information 
concerning the Plot 
Summary tab.4-76
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ThTo edit plot labels, you must clone the plot using the Clone and 
shelf this plot button. The BlendPlot appears and is stored in the 
Plot Summary tab.
If changes are made to the names or end temperatures in any 
of the standard fractionation cuts, the radio button 
automatically switches to User Custom.
An example distribution plot is shown in the following figure.
4.6.6 Composite Plot Tab
The Composite Plot tab allows you to visually check the match 
between the input assay data and the calculated property 
curves. The choice for the graphical comparison is made from 
the Property drop-down list:
• Distillation
• Molecular Weight
• Density
• Viscosity
• User Property
Plot labels can not be modified within the Distribution tab 
Blend property view. 
 Figure 4.384-77
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4-78 Hypocomponent Generation
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ThClick the Clone and shelf this plot button to store the current 
plot. Aspen HYSYS automatically names the plot with the 
following format: 'the name of the active blend'-'number of plots 
created'. 
For example, the first plot created for Blend-1 is named Blend-
1-0, and any subsequent plots have the number after the dash 
incrementally increased. All stored plots are listed on the Plot 
Summary tab.
To edit plot labels, you must clone the plot using the Clone and 
shelf this plot button. The BlendPlot appears and is stored in 
the Plot Summary tab.
An example molecular weight curve comparison is shown in the 
following figure. 
The calculated molecular weight lies above the input curve 
(instead of over-laying it) because the calculated curve has 
been shifted to match an input bulk MW.
Plot labels can not be modified within the Composite tab 
Blend property view.
 Figure 4.39
Refer to the Section 
4.6.7 - Plot Summary 
Tab for information 
concerning the Plot 
Summary tab.4-78
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Th4.6.7 Plot Summary Tab
On this tab, you can view the list of stored plots for the current 
blend. From the Created Plots group you can access any stored 
plots or remove plots from the list. The list of created plots are 
generated from the Property, Distribution, and Composite Plots 
tabs and shown on the left. 
Access a plot by double-clicking on its name or by right-clicking 
its name and selecting View from the object inspect menu. 
From the BlendPlot property view, you can edit plot labels by 
right-clicking and selecting the graph control option. This 
method of modifying plots is preferable, since you can plot what 
you want and that there is a single location for viewing them.
The cloned plots are independent, thus the labels can be 
modified and are not overwritten. The plotted data for the 
cloned plots is also updated as the blend changes.
Click the Remove button to remove a selected plot from the 
list. Only one plot can be removed from the list at a time.
4.6.8 Notes Tab
Aspen HYSYS provides a tab where you can enter a description 
of the Blend for your own future reference.
There is no confirmation message when you click the 
Remove button.4-79
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4-80 User Property
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Th4.7 User Property
A User Property is any property that can be defined and 
subsequently calculated on the basis of compositions. Examples 
for oils include R.O.N. and Sulfur content. During the 
characterization process, all hypocomponents are assigned an 
appropriate property value. Aspen HYSYS then calculates the 
value of the property for any flowsheet stream. This enables 
User Properties to be used as Column specifications. 
After User Properties are installed, you can then supply assay 
information as for Viscosity, Density or Molecular Weight 
Curves.
Refer to Section 4.5.6 - 
User Curves Tab for an 
explanation of attaching 
User Properties to 
existing Assays.4-80
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Th4.7.1 User Property Tab
The User Property tab of the Oil Characterization property view 
is shown below:
The Available User Properties are listed in the left portion of the 
property view. The following User Property manipulation buttons 
are available:
The general buttons at the bottom of the property view are:
• The Clear All button is used to delete all Oil 
Characterization Information.
• The Calculate All button re-calculates all Assay and 
Blend information.
 Figure 4.40
Button Description
View Edit the currently highlighted User Property.
 Add Create a new User Property (see the following section, 
User Property Property View).
Delete Erase the currently highlighted User Property. Aspen HYSYS 
does not prompt for confirmation when deleting a User 
Property.
Clone Create a new User Property with the same properties as the 
currently highlighted User Property. Aspen HYSYS 
immediately opens a new User Property property view.4-81
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4-82 User Property
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Th• The Oil Output Settings... button allows you to change 
IBP, FBP, ASTM D86, and ASTM D2887 interconversion 
methods for output related calculations.
For a highlighted User Property, you can edit the name and 
provide a description.
4.7.2 User Property Property 
View
When you first open this property view, the Name field has 
focus. The name of the User Property must be 12 characters or 
less.
 Figure 4.41
Refer to Chapter 7 - 
User Properties for 
detailed information on 
User Properties.4-82
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ThEquation Parameters
The following options are available for the Basic user prop 
definition group:
Parameter Description
Mixing Basis You have the following options: Mole Fraction, Mass 
Fraction, Liquid Volume Fraction, Mole Flow, Mass 
Flow, and Liquid Volume Flow. 
All calculations are performed using compositions in 
Aspen HYSYS internal units. If you have specified a 
flow basis (molar, mass or liquid volume flow), Aspen 
HYSYS uses the composition as calculated in internal 
units for that basis. For example, a User Property with 
a Mixing Basis specified as molar flow is always 
calculated using compositions in kg mole/s, regardless 
of what the current default units are.
The choice of Mixing Basis applies only to the basis 
that is used for calculating the property in a stream. 
You supply the property curve information on the same 
basis as the Boiling Point Curve for your assay.4-83
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4-84 User Property
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ThMixing Rule  Select from one of three mixing rules:
where: 
Pmix = total user property value 
P(i) = input property value for component 
x(i) = component fraction or flow, depending on 
the chosen Mixing Basis 
f1, f2 = specified constants
Mixing 
Parameters 
The mixing parameters f1 and f2 are 1.00 by default. 
You may supply any value for these parameters.
Unit Type This option allows you to select the variable type for 
the user property. For example, if you have a 
temperature user property, select temperature in the 
unit type using the drop-down list.
Parameter Description
Refer to Chapter 7 - 
User Properties for 
more detail on the Mixing 
Rules.
Pmix( )f 1 f 2 x i( )P i( )f 1( )
i 1=
N
∑=
Pmix( )f 1 f 2 x i( ) P i( )( )f 1ln( )
i 1=
N
∑=
f1 Pmix• 10
f2 Pmix•
+
x i( ) f1 P i( )• 10f2 P i( )•+( )
i 1=
N
∑
=
4-84
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ThComponent User Property Values
If you want, you may provide a Property value for all of the 
Light End components you defined in the Property Package. This 
is used when calculating the property value for each 
hypocomponent (removing that portion of the property curve 
attributable to the Light Ends components).
On this property view, you do not provide property curve 
information. The purpose of this property view is to instruct 
Aspen HYSYS how the User Property should be calculated in all 
flowsheet streams. Whenever the value of a User Property is 
requested for a stream, Aspen HYSYS uses the composition in 
the specified basis, and calculate the property value using your 
mixing rule and parameters.
Notes Tab
Aspen HYSYS provides a tab where you can enter a description 
of the User Properties for your own future reference.
Once you have calculated a Blend which includes an Assay 
with your User Property information, the value of the User 
Property for each hypocomponent is displayed in the 
Component User Property Values group.4-85
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4-86 Correlations & Installation
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Th4.8 Correlations & 
Installation
4.8.1 Correlation Tab
Aspen HYSYS allows you to choose from a wide variety of 
correlations to determine the properties of the generated 
hypocomponent. From the Correlation tab of the Oil 
Characterization property view, you can create customized 
Correlation Sets.
The Available Correlation Sets are listed on the left side of the 
property view. The following Correlation manipulation buttons 
are available:
 Figure 4.42
Buttons Description
View Edit the currently highlighted Correlation Set.
Add Create a new Correlation Set (see the following section, 
Correlation Set Property View).
Correlation sets can also 
be viewed through the 
Assay tab - 
Correlations and Cut/
Blend tab - 
Correlations tab.4-86
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ThFor a highlighted Correlation Set, you can edit the name and 
provide a description.
The general buttons at the bottom of the property view are:
• The Clear All button is used to delete all Oil 
Characterization Information.
• The Calculate All button re-calculates all Assay and 
Blend information.
• The Oil Output Settings... button allows you to change 
IBP, FBP, ASTM D86, and ASTM D2887 interconversion 
methods for output related calculations.
4.8.2 Correlation Set Property 
View
When you create or edit a Correlation Set, the following 
property view appears:
Delete Erase the currently highlighted Correlation Set. Aspen 
HYSYS does not prompt for confirmation when deleting a 
Correlation Set.
Clone Create a new Correlation Set with the same properties as 
the currently highlighted Correlation Set. Aspen HYSYS 
immediately opens a new Correlation Set property view. 
 Figure 4.43
Buttons Description
Refer to Section 4.8.2 - 
Correlation Set 
Property View, for more 
information4-87
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4-88 Correlations & Installation
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ThWhen you first open this property view, the Name field has 
focus. The name of the Correlation Set must be 12 characters or 
less.
Correlations and Range Control
Changes to the Molecular Weight or Specific Gravity correlations 
are applied to the curve (Assay), while the critical temperature, 
critical pressure, acentric factor and heat capacity correlations 
apply to the Blend's hypocomponent properties. Changes to the 
Assay correlations have no effect when you have supplied a 
property curve (e.g., Molecular Weight); they only apply in the 
situation where Aspen HYSYS is estimating the properties.
• The Working Curves are calculated from the Assay data, 
incorporating the Molecular Weight and Specific Gravity 
correlations. 
• The Hypocomponents are generated based on your cut 
option selections.
• Finally, the hypocomponent properties are generated:
• The NBP, molecular weight, density and viscosity are 
determined from the Working curves.
• The remaining properties are calculated, incorporating 
the critical temperature, critical pressure, acentric factor 
and heat capacity correlations.
To change a correlation, position the cursor in the appropriate 
column and select a new correlation from the drop-down list.
You cannot change the correlations or range for the Default 
Correlation Set. If you want to specify different correlations 
or temperature ranges, you must create a new Correlation 
Set.4-88
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ThThe table below shows the Aspen HYSYS defaults and available 
options for these properties.
Property
Default 
Correlation
Optional Correlations
MW Twu • Lee-Kesler
• Aspen
• Penn State
• Katz-Firoozabadi
• Hariu-Sage
• API
• Robinson-Peng
• Whitson
• Riazi-Daubert
• Bergman
• Katz-Nokay
• Modified Kesler-
Lee
• Aspen least-
squares
• Twu
Pc Lee-Kesler • Rowe
• Standing
• Lyderson
• Penn State
• Mathur
• Twu
• Cavett
• Riazi-Daubert
• Edmister
• Bergman
• Aspen
Tc Lee-Kesler • Rowe
• Standing
• Nokay
• Penn State
• Mathur
• Spencer-Daubert
• Chen-Hu
• Meissner-Redding
• Cavett
• Riazi-Daubert
• Edmister
• Bergman
• Aspen
• Roess
• Eaton-Porter
• Twu
SG Constant Watson 
K
• Bergman
• Yarborough
• Lee-Kesler
• Bergman-PNA
• Hariu-Sage
• Katz-Firoozabadi
Ideal 
Enthalpy
Lee-Kesler • Cavett
• Fallon-Watson
• Modified Lee-
Kesler
Acentric 
Factor
Lee-Kesler • Edmister
• Robinson Peng
• Bergman
The Riazi-Daubert correlation has been modified by Whitson. 
The Standing correlation has been modified by Mathews-
Roland-Katz. The default correlations are typically the best 
for normal hydrocarbon systems. An upper limit of 1250°F 
(675°C) is suggested for the heaviest component. Although 
the equations have been modified to extend beyond this 
range, some caution should be exercised when using them 
for very heavy systems. Highly aromatic systems may show 
better results with the Aspen correlations. 
Detailed discussions 
including the range of 
applicability for the 
correlations is found in 
Appendix B - Oil 
Methods & 
Correlations.4-89
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4-90 Correlations & Installation
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ThYou have the choice of changing a property correlation over the 
entire range, or making a certain correlation valid for a 
particular boiling point range only. To split correlations over 
several boiling ranges click the Add New Range button and the 
following property view appears.
Enter the temperature where you want to make the split into the 
New Temp cell (in this case 400°C), and select the Split Range 
button. The temperature is placed in the correlation set, and the 
Correlation table is split as shown below:
You can now specify correlations in these two ranges. 
• You can add more splits.
 Figure 4.44
 Figure 4.454-90
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Th• You can also delete a split (merge range) by selecting 
the Remove Range button as shown in Figure 4.45.
Highlighting the appropriate temperature in the Temperature 
Range list and selecting the Merge Temp Range button removes 
or merges the temperature range. When you merge a range, 
any correlations you chose for that range is forgotten.
 
Assay & Blend Association
The different components of the Assay and Blend Association 
group are described below:
When you merge a range, you delete the correlations for the 
range whose Low End Temperature is equal to the range 
temperature you are merging.
Any changes to the correlations for an Input Assay results in 
first the assay being recalculated, followed by any blend 
which uses that assay. For an existing oil, it will be 
automatically recalculated/re-cut using the new 
correlations, and the new components are installed in the 
flowsheet.
Object Description
New Assays/Blends If you select this checkbox, all new Assays and 
Blends that are created use this Correlation Set.
Available Assays/
Available Blends 
These radio buttons toggle between Assay or 
Blend information.
Assay/Blend Table This table lists all Assays or Blends with their 
associated Correlation Sets, depending on which 
radio button is selected. You can select the Use 
this Set checkbox to associate the current 
Correlation Set with that Assay or Blend. 
You can also select the Correlation Set for a 
specific Assay on the Correlation tab of that Assay 
view.4-91
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4-92 Correlations & Installation
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ThNotes Tab
Aspen HYSYS provides a tab where you can enter a description 
of the Correlations for your own future reference.4-92
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Aspen HYSYS Oil Manager 4-93
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Th4.8.3 Install Oil Tab
The Install Oil tab of the Oil Characterization property view is 
shown below:
You may install a calculated Blend into your Aspen HYSYS case; 
it appears in the Oil Name column of the table. Simply provide a 
Stream name for that Blend, and ensure that the Install 
checkbox is selected. You may use an existing stream name, or 
create a new one. If you do not provide a name or you cleared 
the Install checkbox(es), the hypocomponent is not attached to 
the fluid package. You can install an oil to a specific 
subflowsheet in your case by specifying this in the Flow Sheet 
column. 
 Figure 4.46
If you want to install the hypocomponent into a non-
Associated Fluid Package, Add the Oil Hypo group from the 
Components tab of that Fluid Package property view.4-93
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4-94 TBP Assay - Example
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ThEach installed Oil appears in the component list as a series of 
hypocomponents named NBP[1] ***, NBP[2] ***, with the 1 
representing the first oil installed, 2 the second, etc.; and *** 
the average boiling point of the individual Oil components. 
Aspen HYSYS also assigns the Light Ends composition, if 
present, in the flowsheet stream.
When a Blend is installed in a stream, the relative flow rate of 
each constituent Assay is defined within the Oil Characterization 
and cannot be changed. However, if you install each of the 
constituent Assays (represented by Blends with a single Assay) 
into their own flowsheet stream, various combinations can be 
examined using Mixer or Mole Balance operations. The flow and 
composition for each constituent oil is transferred to your 
designated flowsheet streams. The flow rate of any specified Oil 
stream (as opposed to the constituents of a Blend) can be 
changed at any time by re-specifying the stream rate in the 
flowsheet section.
4.9 TBP Assay - Example
In this example, a crude oil with a TBP assay curve extending 
from 100°F to 1410°F is characterized. Associated with this TBP 
assay are:
• A dependent molecular weight curve
• An independent API gravity curve
• Two independent viscosity curves, one at 100°F and the 
other at 210°F
• The bulk molecular weight and bulk API gravity
• A liquid volume Light Ends assay for the crude oil
It is desired to split the assay into 38 hypocomponents, with 
25°F cuts between 100 and 800°F, 50°F cuts between 800 and 
1200°F, and the remaining portion of the crude assay into two 
components.
For Blends that contain more than one Assay - each 
individual Assay is automatically displayed in the Oil Install 
Information table.4-94
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ThThe following assay information is available:    
Bulk Crude Properties
MW 300
API Gravity 48.75
Light Ends Liquid Volume%
Propane 0.0
i-Butane 0.19
n-Butane 0.11
i-Pentane 0.37
n-Pentane 0.46
TBP Distillation Assay
Liquid Volume% Temperature (F) Molecular Weight
0.0 80.0 68.0
10.0 255.0 119.0
20.0 349.0 150.0
30.0 430.0 182.0
40.0 527.0 225.0
50.0 635.0 282.0
60.0 751.0 350.0
70.0 915.0 456.0
80.0 1095.0 585.0
90.0 1277.0 713.0
98.0 1410.0 838.0
Dependent property curves have values at the same 
distillation percentage as the Boiling Temperature assay, but 
does not need to have values at every percentage.
API Gravity Assay
Liq Vol% Distilled API Gravity 
13.0 63.28
33.0 54.86
57.0 45.91
74.0 38.21
91.0 26.014-95
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4-96 TBP Assay - Example
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Th4.9.1 Initialization
Before you can start the actual characterization process, you 
must:
1. Begin a new Aspen HYSYS case.
2. Select an appropriate property package.
3. Add any non-oil components, including the Light Ends that 
are to be used in the characterization process, to the 
component list.
In this case, use the Peng-Robinson equation of state, and 
select the following components: C3, i-C4, n-C4, i-C5, and n-C5. 
After you have selected the Light End components, click the Oil 
Environment icon on the toolbar to enter the Oil 
Characterization environment.
Prior to the input of assay data, a customized Unit Set is created 
such that the default units used by Aspen HYSYS correspond to 
the assay data units. Create a customized unit set by cloning the 
Field unit set. Select API as the new unit for both Mass Density 
and Standard Density and leave all other Field default units as 
they are.
You can view a display of important messages related to the 
progress of the characterization in the Trace Window. If you 
want, open the Trace Window at the bottom of the Desktop.
Viscosity Assay
Liq Vol% Distilled Visc. (cP) 100°F Visc. (cP) 210°F
10.0 0.20 0.10
30.0 0.75 0.30
50.0 4.20 0.80
70.0 39.00 7.50
90.0 600.00 122.30
Refer to Chapter 2 - 
Fluid Package for 
details on installing a 
fluid package.
Oil Environment icon
Refer to the Section 
12.3.1 - Units Page of 
the Aspen HYSYS User 
Guide for details on 
creating a customized 
unit set.
For more information 
concerning the Trace 
Window, refer to Section 
1.3 - Object Status & 
Trace Windows of the 
Aspen HYSYS User 
Guide.4-96
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Aspen HYSYS Oil Manager 4-97
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ThThe main property view in the Oil Environment is the Oil 
Characterization property view, as shown below:
The tabs are organized according to the general procedure 
followed in the characterization of an oil. Completing the 
characterization requires the following three steps:
1. Access the Assay view by selecting the Add button on the 
Assay tab of the Oil Characterization property view. Input 
all of the assay data on the Input Data tab of the Assay 
view and click the Calculate button.
2. Access the Cut/Blend property view (which also gives you 
cutting options) by selecting the Add button on the Cut/
Blend tab of the Oil Characterization property view. Cut the 
assay into the required number of hypocomponent using the 
cut points outlined previously.
3. Install the calculated oil from the Oil Environment into the 
flowsheet by accessing the Install Oil tab of the Oil 
Characterization property view.
Although you can access the User Property tab and the 
Correlation tab from the Oil Characterization property view, 
neither of these tabs are used in this example.
 Figure 4.474-97
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4-98 TBP Assay - Example
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Th4.9.2 Step 1 - Input Assay 
Data
On the Assay tab of the Oil Characterization property view, 
select the Add button. This opens the Assay view and places the 
active location in the Name cell of the Input Data tab. For this 
example, change the name of the Assay to Example. The Assay 
tab is shown below. 
The first time you enter this property view, it is blank, except for 
the Bulk Properties field and the Assay Data Type field. 
 Figure 4.48
The layout of this property view depends on:
1. Which Data Type you have selected. This mainly affects what Data Type 
options are available (Distillation, Light Ends, etc.)
2. Which Input Data radio button you have selected. When you specify that 
you have Independent or Dependent Molecular Weight, Density or 
Viscosity data, a new radio button is added to the property view. In this 
property view, the TBP Data Type is selected and the Distillation radio 
button is selected.4-98
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ThDefining the Assay
The Input Data tab is split into two groups: Assay Definition and 
Input Data. As its name implies, the Assay Definition group is 
where the properties of the assay are defined. Since bulk 
property data is provided, select Used from the Bulk Properties 
drop-down list. The bulk properties appears in the Input Data 
group. Next from the Assay Data Type drop-down list, select 
TBP. The Bulk Props and Distillation radio buttons are now 
visible.
Light ends can be Auto Calculated by Aspen HYSYS, however 
since you are provided with the light ends data, select Input 
Compositions from the Light Ends drop-down list.
Now, set the Molecular Weight, Density and Viscosity curve 
options in each of the respective drop-down lists. The Molecular 
Weight curve is Dependent, the Density curve is Independent, 
and the Viscosity curves are also Independent. As you specify 
these options, radio buttons corresponding to each curve are 
added to the Input Data group box. Now that the Assay is 
sufficiently defined, you can begin entering assay data.
Specifying Assay Data
Specification of the Assay occurs in the Input Data group. The 
field and options visible inside the group are dependent on 
which radio button is selected in the Input Data group.
Aspen HYSYS calculates internal working curves using the 
supplied property curve data. For each property curve, you can 
select the method used for the Extrapolation of the working 
curve. The Extrapolation method for each working curve is 
specified in the Curve Fitting Methods group of the Calculation 
Defaults tab.4-99
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4-100 TBP Assay - Example
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ThBulk Props
Select the Bulk Props radio button. Input a Bulk Molecular 
Weight (300) and Bulk Mass Density (48.75 API_60) as shown 
in the figure below. 
No bulk viscosity information is available, so leave the Viscosity 
cells blank. It is not necessary to delete the Viscosity 
Temperatures as these are ignored if you do not provide bulk 
viscosities.
Light Ends
Next, select the Light Ends radio button. The Input Data group 
displays a Light Ends Basis drop-down list and a Light Ends 
Composition table. From the drop-down list, select LiquidVolume 
as the Light Ends Basis and enter the Light Ends composition as 
shown below:
 Figure 4.49
 Figure 4.504-100
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Aspen HYSYS Oil Manager 4-101
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ThDistillation
Select the Distillation radio button to view the TBP Distillation 
assay. To enter the data, click the Edit Assay button. The Assay 
Input Table property view appears and enter the following assay 
data: 
Molecular Weight
Select the Molecular Weight radio button to view the Molecular 
Weight data. 
 Figure 4.51
As you enter values into the table, the cursor automatically 
moves down after each entry, making it easier to supply all 
values in each column.
Since the Molecular Weight assay is Dependent, the Assay 
Percentage values that you entered for the Boiling Point 
Temperature assay are automatically displayed.4-101
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4-102 TBP Assay - Example
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ThYou need only enter the Molecular Weights as shown below:
Density
Select the Density radio button to view (or edit) the Density 
assay. The default density units are displayed, in this case API. 
The completed API gravity curve input is shown below:
 Figure 4.52
 Figure 4.534-102
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Aspen HYSYS Oil Manager 4-103
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ThViscosity
Select the Viscosity1 and Viscosity2 radio buttons to view (or 
edit) the Viscosity assays. When either of these buttons are 
selected, an additional input box is displayed, which allows you 
to supply the viscosity temperatures. Make sure the Use Both 
radio button is selected in the Viscosity Curves group box. The 
required viscosity input is shown below: 
 Figure 4.54
Ensure that the Viscosity Units Type is Dynamic, and that the 
two temperatures entered are 100°F and 210°F.4-103
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4-104 TBP Assay - Example
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ThCalculating the Assay
After entering all of the data, go to the Calculation Defaults tab. 
The extrapolation methods displayed in the Curve Fitting 
Methods group. 
The default extrapolation methods for the working curves are 
adequate for this assay. To begin the calculation of the assay, 
press the Calculate button. The status message at the bottom of 
the Assay view shows the message Assay Was Calculated. 
 Figure 4.554-104
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ThAfter the Assay is calculated, the working curves are displayed 
on the Working Curves tab.
The working curves for the normal boiling point, molecular 
weight, mass density and viscosity are regressed from your 
input curves. Aspen HYSYS uses 50 points in the calculation of 
the working curves, but the molar distribution varies depending 
on the data you provide. Aspen HYSYS moves more points to a 
region with a steep gradient. The calculation of the Blend is 
based on these working curves.
You can examine graphical representations of your assay data 
on the Plots tab. Open the Property drop-down list and select 
the curve that you would like to view. The default plot is the 
Boiling Point Temperature (Distillation) curve. Because input 
data for the boiling temperature, molecular weight, density and 
viscosity were provided, all of these options are shown in the 
drop-down list.
 Figure 4.56
The options available in the Property drop-down list 
correspond to the property curve data specified on the Input 
Data tab. If only bulk data is provided, there are no plots 
available.
Refer to Section 4.5 - 
Characterizing Assays 
for information on the 
characterization 
procedure, working curves 
and extrapolation 
methods.4-105
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4-106 TBP Assay - Example
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Th Figure 4.57
If multiple assays are 
blended, repeat the steps 
outlined in Section 4.9.2 
- Step 1 - Input Assay 
Data.4-106
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Aspen HYSYS Oil Manager 4-107
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Th4.9.3 Step 2 - Cut Assay into 
Hypocomponents
You can now cut the Assay into individual hypocomponents. On 
the Cut/Blend tab of the Oil Characterization property view, 
select the Add button. This takes you to the Blend property view 
with the list of available assays. 
From the Available Assays group, select Example and click the 
Add button. This adds the Assay to the Oil Flow Information 
table, and a Blend (Cut) is automatically calculated. 
The Blend is calculated because the default Cut Option, Auto 
Cut, appears as soon as a Blend is added. Since the Cut Option 
was not changed prior to the addition of the Available Assay to 
the Blend, Aspen HYSYS realizes enough information is available 
to cut the oil and the calculations occur automatically.
 Figure 4.58
If you have only one Assay, it is not necessary to enter a 
Flow Rate in the Oil Flow Information table.4-107
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4-108 TBP Assay - Example
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ThInstead of using the default Cut Option, the cut points are 
defined. From the Cut Option drop-down list, select User 
Ranges. Enter a Starting Cut Point Temperature of 100°F and fill 
out the Cut Point table as shown on the left. Click the Submit 
button to calculate the Blend.
The results of the calculation can be viewed on the Tables tab of 
the Blend property view. The default Table Type is the 
Component Properties table with the Main Properties radio 
button selected in the Table Control group. 
 Figure 4.59
 Figure 4.604-108
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Aspen HYSYS Oil Manager 4-109
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ThFrom the drop-down list, you can also view a Component 
Breakdown, Molar Compositions, Oil Properties, and Oil 
Distributions.
All of the data that is found on the Tables tab can be viewed 
graphically from the following three tabs: 
• Property Plot
• Distribution Plot
• Composite Plot
On the Distribution Plot tab, select Liquid Volume fraction from 
the Basis drop-down list. The following plot is displayed:
 Figure 4.61
 Figure 4.62
Refer to Section 4.6.3 - 
Tables Tab for details 
on the information 
available on the Tables 
tab.4-109
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4-110 TBP Assay - Example
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ThThe Cut Distribution Plot, as shown above, displays the volume 
fraction of the oil that would be recovered in various products. 
This graph is particularly useful in providing estimates for 
distillation products.
4.9.4 Step 3 - Transfer 
Information to Flowsheet
The final step of the characterization is to transfer the 
hypocomponent information into the flowsheet. 
On the Install Oil tab of the Oil Characterization property view, 
enter the Stream Name Example Oil, to which the oil 
composition is being transferred.
Aspen HYSYS assigns the composition of your calculated Oil and 
Light Ends into this stream, completing the characterization 
procedure. Also, the hypocomponent is placed into a Hypo group 
named Blend1 and installed in the fluid package. When you 
leave the Oil Characterization environment, you are placed in 
the Basis environment. It is here that you can examine 
individual hypothetical components that make-up your oil.
 Figure 4.63
Refer to the tab 
subsections in Section 
4.6 - Hypocomponent 
Generation for 
information on the 
available plots.4-110
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ThEnter the Simulation Environment and move to the Workbook to 
view the stream you just created. The Compositions page 
displaying the stream Example Oil is shown below.
If you decide that some of the hypocomponent parameters need 
to be recalculated, you can return to the Oil Environment at any 
time to make changes. To edit an Assay, highlight it on the 
Assay tab of the Oil Characterization property view, and click 
the Edit button. If you want to see the effect of using a different 
correlations on your oil, you can access this information on the 
Correlation tab of the Oil Characterization property view.
 Figure 4.644-111
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4-112 TBP Assay - Example
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Th4.9.5 Fluid Package 
Association
In the example shown in Figure 4.65, there is only one fluid 
package for the flowsheet. Specifying the stream name 
(Example Oil) not only creates the stream in the flowsheet, but 
adds the Hypo group (which contains all of the individual 
hypocomponents) to the fluid package.
When there are multiple fluid packages in the simulation, you 
can specify the one with which the Oil is to be associated 
(accessed through the Oil Manager tab of the Simulation Basis 
Manager property view). This serves two functions: first, it 
identifies which pure components are available for a light ends 
analysis, and second, it identifies the fluid package to which the 
Hypo group is being installed.
If you do not want to associate the oil to the fluid package, clear 
the appropriate Associate checkbox.
 Figure 4.65
In this case, the Oil is Associated with Fluid Package Basis-14-112
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Th4.10 Sulfur Curve - 
Example
The User Property option in the Oil Characterization 
environment allows you to supply a property curve and have 
Aspen HYSYS characterize it with an Assay. Each 
hypocomponent is assigned a property value when the Blend is 
characterized. You can specify the basis upon which the 
property should be calculated (mole, mass or liquid volume, and 
flows or fractions), as well as which mixing rule should be used.
In this example, a TBP curve with an associated Sulfur Curve is 
installed. There is no Light Ends analysis available, so the Auto 
Calculate Light Ends option is used.
4.10.1 Fluid Package
Prior to entering the Oil Characterization environment, create a 
Fluid Package with Peng-Robinson as the property method and 
C1, C2, C3, i-C4, and n-C4 as the components. The choice of the 
Light Ends components is influenced by the Sulfur Curve data 
(refer to Section 4.10.3 - Install the Assay section).4-113
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Th4.10.2 Install a User Property
Enter the Oil Environment by clicking the Oil Environment icon 
on the toolbar. To supply a User Curve for an assay, you must 
first add a User Property. On the User Property tab of the Oil 
Characterization property view, select Add to access the User 
Property property view as shown below. 
The default options are used for the Equation Parameters except 
for the Mixing Basis field. Sulfur is quoted on a w/w basis so, 
select Mass Fraction from the drop-down list. Aspen HYSYS 
automatically names and numbers the User Properties. You can 
provide a descriptive Name for the property, such as Sulfur.
 Figure 4.66
You can also add a User Property via the User Property tab in 
the Simulation Basis Manager. 
Oil Environment icon4-114
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ThAspen HYSYS gives you the option of providing a Component 
User Property Value for each Light End component. If, for 
example, this was a Heating Value Property, you would supply 
each component value at this point. These components do not 
have a “Sulfur value", so they can be left at 0.
4.10.3 Install the Assay
Create an Assay by clicking the Add button on the Assay tab of 
the Oil Characterization property view. Select TBP as the Assay 
Data Type, specify a Liquid Volume% as the Assay Basis, and 
leave the TBP Distillation Conditions group at the default 
settings.
Since no Light Ends analysis is provided, select the Auto 
Calculate from the Light Ends drop-down list. The Auto Calculate 
procedure replaces the portion of the TBP curve which is 
covered by the Boiling Point range of the Light Ends 
components. In this way, the initial boiling point of the TBP 
working curve is slightly higher than the normal boiling point of 
the heaviest Light End component.
The TBP curve starts at -25°C. Taking this information into 
account, Light End components with boiling points that lie within 
the first two percent of the TBP assay were chosen. In this way, 
the benefits of the Auto Calculate procedure are gained without 
losing a significant portion of our property curve.
There is no Molecular Weight, Density, or Viscosity data, so you 
can leave the curve options as Not Used. On the Calculation 
Defaults tab, the extrapolation method for the Distillation curve 
can be left at its default, Probability. There are no bulk 
properties for the assay. Provide the boiling temperature data, 
as tabulated below:
TBP Data
Assay% Temp (C) Assay% Temp (C) Assay% Temp (C)
0.02 -25 20.73 180 71.43 500
0.03 -20 24.06 200 73.86 520
0.05 -10 27.55 220 76.22 5404-115
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ThThe Assay view with the TBP Data is shown below: 
0.31  0 30.93 240 78.46 560
0.52  10 34.32 260 80.57 580
0.55  20 37.83 280 82.55 600
1.25  30 41.21 300 84.41 620
2.53  40 44.51 320 86.16 640
2.93  50 48.01 340 87.79 660
3.78  60 51.33 360 89.32 680
4.69  70 54.58 380 90.67 700
5.67  80 57.73 400 93.48 750
7.94 100 60.65 420 95.74 800
10.69 120 63.39 440 98.78 900
13.84 140 66.16 460
17.28 160 68.90 480
 Figure 4.67
TBP Data
Assay% Temp (C) Assay% Temp (C) Assay% Temp (C)4-116
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ThSulfur Curve
On the User Curves tab of the Assay property view, select the 
Available User Property Sulfur and click the Add button. In the 
User Curve Data group, select Independent as the Table Type 
and ensure that the Bulk Value cell displays . Click the 
Edit button and enter the Sulfur Curve Data shown below in the 
Assay Input Table.
After this data is entered, click the Calculate button found at the 
bottom of the Assay property view.
Sulfur Curve Data
Assay% Sulfur Value Assay% Sulfur Value
0.90 0.032 54.08 2.733
7.38 0.026 55.85 2.691
11.48 0.020 57.17 2.669
16.42 0.083 60.00 2.670
22.40 0.094 64.47 2.806
26.68 0.212 68.40 3.085
31.78 0.616 72.09 3.481
36.95 1.122 75.66 3.912
42.04 1.693 78.99 4.300
47.14 2.354 82.05 4.656
48.84 2.629 84.85 4.984
50.52 2.786 87.38 5.286
52.22 2.796 90.33 5.6464-117
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Th4.10.4 Create the Blend
A Blend is created using the Auto Cut option. On the Cut\Blend 
tab of the Oil Characterization property view, select the Add 
button. On the Data tab of the Blend property view, highlight 
Assay-1 from the list of Available Assays and click the Add 
button. The assay is now added to the Oil Flow Information 
table. The Blend is immediately calculated, as the default Cut 
Option is Auto Cut.
 Figure 4.684-118
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Th4.10.5 Results
Finally, the user property is defined and needs to be installed. 
On the Install Oil tab of the Oil Characterization property view, 
specify the Stream Name as Example Oil to which the oil 
composition is transferred.
Aspen HYSYS assigns the composition of your calculated Oil and 
Light Ends into this stream, completing the characterization 
procedure for the User Property. 
 Figure 4.694-119
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ThYou can return to the User Property tab of the Oil 
Characterization property view and click the View button to 
display the Sulfur User Property property view.
In the Component User Property Values group, the Property 
Value is calculated for all the hypocomponents for the blend. 
You can scroll through the table to view the Property Value for 
each hypocomponent.
 Figure 4.704-120
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ThFrom the Composite Plot tab of the Blend property view, you can 
view a plot of the Calculated and Inputted values for the User 
Property. Select User Property from the Property drop-down 
list and select the Sulfur checkbox to view the following figure.
4.11 References
 1 Figure 3A1.1, Chapter 3, API Technical Data Book, Fourth Edition 
(1980).
 2 Procedure 3A1.1, Chapter 3, API Technical Data Book, Fifth Edition 
(1987).
 3 Procedure 3A1.1, Chapter 3, API Technical Data Book, Sixth Edition 
(1994).
 4 Edmister, W.C., and Okamoto, K.K., “Applied Hydrocarbon 
Thermodynamics, Part 12: Equilibrium Flash Vaporization 
Correlations for Petroleum Fractions”, Petroleum Refiner, August, 
1959, p. 117. 
 5 Procedure 3A3.1, Chapter 3, API Technical Data Book, Fifth Edition 
(1987).
 6 Procedure 3A3.2, Chapter 3, API Technical Data Book, Sixth Edition 
(1994).
 7 Procedure 3A3.1, Chapter 3, API Technical Data Book, Sixth Edition 
(1994).
 Figure 4.714-121
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Th4-122
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Reactions 5-1
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Th5  Reactions5-1
5.1  Introduction................................................................................... 2
5.2  Reaction Component Selection....................................................... 3
5.2.1  Adding Components from Basis Manager ..................................... 4
5.2.2  Selections Within the Reaction Manager ...................................... 4
5.2.3  Library Reaction Components..................................................... 5
5.3  Reactions ....................................................................................... 6
5.3.1  Manipulating Reactions ............................................................. 7
5.3.2  Conversion Reaction ................................................................. 8
5.3.3  Equilibrium Reaction ............................................................... 13
5.3.4  Kinetic Reaction ..................................................................... 20
5.3.5  Heterogeneous Catalytic Reaction............................................. 26
5.3.6  Simple Rate Reaction.............................................................. 33
5.4  Reaction Sets ............................................................................... 36
5.4.1  Manipulating Reaction Sets ...................................................... 37
5.4.2  Reaction Set Property View...................................................... 38
5.4.3  Exporting/Importing a Reaction Set .......................................... 44
5.4.4  Adding a Reaction Set to a Fluid Package................................... 45
5.4.5  Reactions in the Build Environment........................................... 45
5.5  Generalized Procedure................................................................. 46
5.6  Reactions - Example..................................................................... 48
5.6.1  Add Components to the Reaction Manager ................................. 48
5.6.2  Create a Reaction................................................................... 48
5.6.3  Add the Reaction to a Reaction Set ........................................... 49
5.6.4  Attach the Reaction Set to a Fluid Package................................. 50
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Th5.1 Introduction
Reactions within Aspen HYSYS are defined inside the Reaction 
Manager. The Reaction Manager, which is located on the 
Reactions tab of the Simulation Basis Manager, provides a 
location from which you can define an unlimited number of 
reactions and attach combinations of these reactions in Reaction 
Sets. The Reaction Sets are then attached to Unit Operations in 
the Flowsheet.
The Reaction Manager is a versatile, time-saving feature that 
allows you to do the following:
• Create a new list of components for the Reactions or 
simply use the fluid package components.
• Add, Edit, Copy, or Delete Reactions and Reaction Sets.
• Attach Reactions to various Reaction Sets or attach 
Reaction Sets to multiple Fluid Packages, thus 
eliminating repetitive procedures.
• Import and Export Reaction Sets.
 Figure 5.15-2
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Th5.2 Reaction Component 
Selection
On the Reactions tab of the Simulation Basis Manager, there are 
three main groups which are described below:
Each of the main groups within the Reaction Manager are 
examined in more detail. In this section, the Rxn Components 
group is described. The features in the Reactions group and 
Reaction Sets group are detailed in subsequent sections.
There are three distinct ways in which components can be made 
accessible to Reactions in the Reaction Manager:
• You can add components on the Component tab of the 
Simulation Basis Manager. The components are added to 
the component list and are available in the Rxn 
Components group to be attached to the Reaction Set. 
These components are also included in the fluid package 
depending on the component list selected for the 
package.
• You can install components directly in the Reaction 
Manager without adding them to a specific component 
list by clicking the Add Comps button. The Component 
List property view appears and you can add reaction 
components for the reaction. These components appear 
automatically in the master component list, but not in 
the component list selected for the fluid package. 
When a Reaction Set (containing a Reaction which uses 
the new components) is attached to a fluid package, the 
components which are not present in the fluid package 
are automatically transferred.
• You can select an Equilibrium Reaction from the Library 
tab of the Equilibrium Reactor property view. All 
components used in the reaction are automatically 
installed in the Reaction Manager. Once the Reaction Set 
Group Description
Rxn 
Components
Displays all components available to the Reaction Manager 
and the Add Comps button.
Reactions Displays a list of the defined reactions and four buttons 
available to help define reactions.
Reaction 
Sets
Displays the defined reactions sets, the associated fluid 
packages and several buttons that help to define reaction 
sets and attach them to fluid packages.
Refer to Chapter 1 - 
Components for more 
information on adding 
components.
Refer to Section 5.4 - 
Reaction Sets for details 
on attaching a fluid 
package.5-3
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5-4 Reaction Component Selection
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Th(containing the Library reaction) is attached to a fluid 
package, the components are automatically transferred 
to the fluid package.
5.2.1 Adding Components 
from Basis Manager
With this method of component selection, components are 
selected on the Components tab from the Simulation Basis 
Manager. Add a component list by clicking the Add button. From 
the Component List property view, select the components which 
are required for the reaction. This is similar to adding 
components to a component list for a particular fluid package or 
case. All components that are selected are displayed and 
available in the Rxn Components group of the Reaction Manager.
5.2.2 Selections Within the 
Reaction Manager
Components can be made available prior to the creation of 
Reactions by directly selecting them within the Reaction 
Manager. By selecting the components within the Reaction 
Manager, you are not required to transfer component 
information from the fluid package. The components appear in 
the Master Component list, but not in the component list. Once 
a Reaction Set is attached to a fluid package, Aspen HYSYS 
automatically transfers all of the components contained within 
the Reaction(s) to the fluid package.
The components listed in the Selected Reaction Components 
group are available to any Reaction that you create.
Hypocomponents created using the Oil Manager can be used 
in Reactions. They are listed as Associated Components if 
they are installed in a fluid package. 
At least one fluid package must exist before components can 
be transferred from the Reaction Manager.
Refer to Chapter 4 - 
HYSYS Oil Manager for 
details on 
hypocomponent.5-4
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ThThe following procedure demonstrates the steps required when 
beginning with a new case:
1. Create a new case by clicking the New Case icon on the 
toolbar.
2. On the Fluid Pkgs tab of the Simulation Basis Manager, click 
the Add button. A new fluid package is created and its 
property view opens. Close the Fluid Package property view.
3. Move to the Reactions tab. Click the Add Comps button in 
the Rxn Components group and the Component List property 
view is displayed.
4. Select either traditional or hypothetical components. The 
procedure for selecting components is similar to the 
selection of components for the fluid package.
5. Return to the Reaction Manager to create the Reaction(s) 
and install the Reaction(s) within a Reaction Set. 
6. Attach the Reaction Set to the fluid package created in Step 
#2. 
7. All components used in the Reaction(s) that are contained 
within the Reaction Set are now available in the fluid 
package.
5.2.3 Library Reaction 
Components
When a Library Equilibrium Reaction is selected, all of its 
constituent components are automatically added to the Reaction 
Manager. You can then use the components in the Rxn 
Components group of the Reaction Manager to define other 
reactions. Library reactions can be installed prior to the addition 
of components to the case. You are not required to add 
components using the Component List property view or Reaction 
Manager.
To add a Library reaction, do the following:
1. From the Reaction Manager, click the Add Rxn button in the 
Reactions group.
2. Highlight Equilibrium from the Reactions property view and 
click the Add Reaction button.
New Case icon
See Section 5.3 - 
Reactions, and Section 
5.4 - Reaction Sets for 
details.
See Section 5.4.4 - 
Adding a Reaction Set 
to a Fluid Package for 
details.5-5
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5-6 Reactions
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Th3. Move to the Library tab of the Equilibrium Reaction property 
view and select a reaction from the Library Equilibrium Rxns 
group.
4. Click the Add Library Rxn button. All library information 
concerning the reaction is transferred to the various tabs of 
the Equilibrium Reaction property view. The components 
used by the reaction are now shown in the Rxn Components 
group of the Reaction Manager.
5.3 Reactions
In Aspen HYSYS, a default reaction set, the Global Rxn Set, is 
present in every simulation. All compatible reactions that are 
added to the case are automatically included in this set. A 
Reaction can be attached to a different set, but it also remains 
in the Global Rxn Set unless you remove it. To create a 
Reaction, click the Add Rxn button from the Reaction Manager.
The following table describes the five types of Reactions that can 
be modeled in Aspen HYSYS:
 Figure 5.2
Reaction Type Requirements
Conversion Requires the stoichiometry of all the reactions and the 
conversion of a base component in the reaction.
Equilibrium Requires the stoichiometry of all the reactions. The 
term Ln(K) may be calculated using one of several 
different methods, as explained later. The reaction 
order for each component is determined from the 
stoichiometric coefficients.
Refer to Section 5.4 - 
Reaction Sets for 
information on Reaction 
Sets.5-6
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ThEach of the reaction types require that you supply the 
stoichiometry. To assist with this task, the Balance Error tracks 
the molecular weight and supplied stoichiometry. If the reaction 
equation is balanced, this error is equal to zero. If you have 
provided all of the stoichiometric coefficients except one, you 
may select the Balance button to have Aspen HYSYS determine 
the missing stoichiometric coefficient.
Reactions can be on a phase specific basis. The Reaction is 
applied only to the components present in that phase. This 
allows different rate equations for the vapour and liquid phase in 
same reactor operation.
5.3.1 Manipulating Reactions
From the Reaction Manager, you can use the four buttons in the 
Reactions group to manipulate reactions. The buttons are 
described below: 
Heterogeneous 
Catalytic
Requires the kinetics terms of the Kinetic reaction as 
well as the Activation Energy, Frequency Factor, and 
Component Exponent terms of the Adsorption kinetics.
Kinetic Requires the stoichiometry of all the reactions, as well 
as the Activation Energy and Frequency Factor in the 
Arrhenius equation for forward and reverse (optional) 
reactions. The forward and reverse orders of reaction 
for each component can be specified.
Simple Rate Requires the stoichiometry of all the reactions, as well 
as the Activation Energy and Frequency Factor in the 
Arrhenius equation for the forward reaction. The 
Equilibrium Expression constants are required for the 
reverse reaction.
Button Command
View Rxn Accesses the property view of the highlighted reaction.
Add Rxn Accesses the Reactions property view, from which you 
select a Reaction type.
Delete Rxn Removes the highlighted reaction(s) from the Reaction 
Manager.
Copy Rxn When selected, the Copy Reactions property view appears 
where you can select an alternate Reaction Type for the 
reaction or duplicate the highlighted reaction.
Reaction Type Requirements5-7
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Th5.3.2 Conversion Reaction
The Conversion Reaction requires the Stoichiometric Coefficients 
for each component and the specified Conversion of a base 
reactant. The compositions of unknown streams can be 
calculated when the Conversion is known.
Consider the following Conversion reaction:
where:  
a, b, c, d = the respective stoichiometric coefficients of the 
reactants (A and B) and products (C and D)
A = the base reactant
B = the base reactant not in a limiting quantity
In general, the reaction components obey the following reaction 
stoichiometry:
When you right-click a reaction in the Reactions group, you 
can select View or Delete from the object inspect menu.
By default, conversion reactions are calculated 
simultaneously. However you can specify sequential 
reactions using the Ranking feature.
(5.1)
(5.2)
Refer to Section 5.4 - 
Reaction Sets for more 
information.
A b
a
--B c
a
--C d
a
--D+→+
NA NAo
1 XA–( )=
NB NBo
b
a
--N
Ao
X
A
–=
NC NCo
c
a
-- NAo
XA( )+=
ND NDo
d
a
-- NAo
XA( )+=5-8
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Thwhere:  
N* = the final moles of component * (*= A, B, C and D)
N*o = the initial moles of component *
XA = the conversion of the base component A
The moles of a reactant available for conversion in a given 
reaction include any amount produced by other reactions, as 
well as the amount of that component in the inlet stream(s). An 
exception to this occurs when the reactions are specified as 
sequential.
When you have supplied all of the required information for 
the Conversion Reaction, the status bar (at the bottom right 
corner) will change from Not Ready to Ready.5-9
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ThStoichiometry Tab
The Stoichiometry tab of a conversion reaction is shown in 
thefollowing figure: 
For each Conversion reaction, you must supply the following 
information:
 Figure 5.3
Input Field Information Required
Reaction Name A default name is provided which may be changed. The 
previous property view shows the name as Rxn-1.
Components The components to be reacted. A minimum of two 
components are required. You must specify a minimum 
of one reactant and one product for each reaction you 
include. Use the drop-down list to access the available 
components. The Molecular Weight of each component 
is automatically displayed.
Stoichiometric 
Coefficient 
Necessary for every component in the reaction. The 
Stoichiometric Coefficient is negative for a reactant 
and positive for a product. You may specify the 
coefficient for an inert component as 0, which, for the 
Conversion reaction, is the same as not including the 
component in the table. The Stoichiometric Coefficient 
does not have to be an integer; fractional coefficients 
are acceptable.
The Reaction Heat value is calculated and displayed 
below the Balance Error. A positive value indicates that 
the reaction is endothermic.5-10
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ThBasis Tab
The Basis tab of a conversion reaction is shown in the figure 
below:
On the Basis tab, you must supply the following information:
 Figure 5.4
Required Input Description
Base Component Only a component that is consumed in the reaction (a 
reactant) may be specified as the Base Component 
(i.e., a reaction product or an inert component is not a 
valid choice). You can use the same component as the 
Base Component for a number of reactions, and it is 
quite acceptable for the Base Component of one 
reaction to be a product of another reaction. 
You have to add the components to the reaction before 
the Base Component can be specified.5-11
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5-12 Reactions
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ThRxn Phase The phase for which the specified conversions apply. 
Different kinetics for different phases can be modeled 
in the same reactor. Possible choices for the Reaction 
Phase are:
• Overall. Reaction occurs in all Phases.
• Vapour Phase. Reaction occurs only in the 
Vapour Phase.
• Liquid Phase. Reaction occurs only in the Light 
Liquid Phase.
• Aqueous Phase. Reaction occurs only in the 
Heavy Liquid Phase.
• Combined Liquid. Reaction occurs in all Liquid 
Phases.
Conversion 
Function 
Parameters
Conversion percentage can be defined as a function of 
reaction temperature according to the following 
equation:
This is the percentage of the Base Component 
consumed in this reaction. The value of Conv.(%) 
calculated from the equation is always limited within 
the range of 0.0 and 100%.
The actual conversion of any reaction is limited to the 
lesser of the specified conversion of the base 
component or complete consumption of a limiting 
reactant.
Reactions of equal ranking cannot exceed an overall 
conversion of 100%.
Sequential Reactions may be modelled in one reactor 
by specifying the sequential order of solution. 
To define a constant value for conversion percentage, enter 
a conversion (%) value for Co only. Negative values for C1 
and C2 means that the conversion drops with increased 
temperature and vice versa.
Required Input Description
Conv Co C1 T C2 T2⋅+⋅+=
See Reaction Rank, in 
Section 5.4 - Reaction 
Sets.5-12
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Th5.3.3 Equilibrium Reaction
The Equilibrium Reaction computes the conversion for any 
number of simultaneous or sequential reactions with the 
reaction equilibrium parameters and stoichiometric constants 
you provide.
The Equilibrium constant can be expressed as follows: 
where:
K = Equilibrium constant
[BASE]ej = Basis for component j at equilibrium
vj = Stoichiometric coefficient for the jth component
Nc = Number of components
The equilibrium constant ln(K) may be considered fixed, or 
calculated as a function of temperature based on a number of 
constants:
where:
Alternatively, you may supply tabular data (equilibrium constant 
versus temperature), and Aspen HYSYS automatically calculates 
(5.3)
This equation is only valid when BASE (i.e., concentration) is 
at equilibrium composition.
(5.4)
K BASE[ ]ej
( )
vj
j 1=
Nc
∏=
Ln Keq( ) a b+=
a A B
T
--- C T( )ln⋅ D T⋅+ + +=
b E T2 F T3 G T4 H T5⋅+⋅+⋅+⋅=5-13
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Ththe equilibrium parameters for you. Ln(K) may also be 
determined from the Gibbs Free Energy.
Stoichiometry Tab
The Stoichiometry tab for a equilibrium reaction is shown in the 
figure below: 
For each reaction, you must supply the following information:
When you have supplied all of the required information for 
the Equilibrium Reaction, the status bar (at the bottom right 
corner) changes from Not Ready to Ready.
 Figure 5.5
Input Required Description
Reaction Name A default name is provided, which may be changed by 
simply selecting the field and entering a new name.
Components A minimum of two components is necessary. You must 
specify a minimum of one reactant and one product for 
each reaction you include. The Molecular Weight of 
each component is automatically displayed.
Stoichiometric 
Coefficient 
For every component in this reaction. The 
Stoichiometric Coefficient is negative for a reactant 
and positive for a product. You may specify the 
coefficient for an inert component as 0. The 
Stoichiometric Coefficient need not be an integer; 
fractional coefficients are acceptable.5-14
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ThBasis Tab
The Basis tab for an equilibrium reaction contains two groups, 
the Basis and the Keq Source, which are shown in the figure:
The Basis group requires the following information:
The Keq Source group contains four radio buttons and a 
checkbox. 
• By selecting the appropriate radio button, you can select 
one of four options as the Keq Source for the equilibrium 
reaction.
• If the Auto Detect checkbox is selected, Aspen HYSYS 
automatically changes the Keq Source, depending on the 
Keq information you provide. For example, if you enter a 
fixed equilibrium constant, the Fixed Keq radio button is 
 Figure 5.6
Input Required Description
Basis From the drop-down list in the cell, select the Basis for 
the reaction. For example, select Partial Pressure or 
Activity as the basis.
Reaction Phase The possible choices for the Reaction Phase, accessed 
from the drop-down list, are the Vapour and Liquid 
Phases.
Minimum 
Temperature 
and Maximum 
Temperature 
Enter the minimum and maximum temperatures for 
which the reaction expressions are valid. If the 
temperature does not stay within the specified bounds, 
a warning message alerts you.
Basis Units Enter the appropriate units for the Basis, or make a 
selection from the drop-down list.5-15
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Thautomatically selected. If you later add data to the Table 
tab, the Keq vs. T Table radio button is automatically 
selected.
Keq Tab
Depending on which option was selected in the Keq Source 
group (from the Basis tab), the Keq tab will display the 
appropriate information.
The following table outlines each of the Keq source options and 
the respective information on the Keq tab.
Option Description View on Keq Tab
Ln(Keq) 
equation
Ln(Keq), assumed to be a function of temperature 
only, is determined from the following equation:
where:
A, B, C, D, E, F, G, H = the constants defined 
on the Keq tab.
Gibbs 
Free 
Energy 
The equilibrium constant is determined from the 
default Aspen HYSYS pure component Gibbs Free 
Energy (G) database and correlation.
The correlation and database values are valid/
accurate for a temperature (T) range of 25°C to 
426.85°C.
If a wider range of G-T correlation is required, the 
user can clone the library component and input 
the components Gibbs Free Energy correlation to 
temperatures beyond the default temperature 
limit.
Ln Keq( ) a b+=
a A B
T
--- C T( )ln⋅ D T⋅+ + +=
b E T2 F T3 G T4 H T5⋅+⋅+⋅+⋅=5-16
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ThApproach Tab
Under certain process conditions, an equilibrium reaction may 
not, actually reach equilibrium. The Equilibrium reaction set 
uses two types of approach, Fractional and Temperature, to 
simulate this type of situation. You may select either one or both 
types of approaches for use in the simulation.
Fixed K In this case, the equilibrium constant Keq is 
considered to be fixed, and is thus independent of 
temperature. You may specify either Keq or 
Ln(Keq) on the Keq tab. Select the Log Basis 
checkbox to specify the equilibrium constant in the 
form Ln(Keq).
K vs. T 
Table 
On the Keq tab, you can provide temperature and 
equilibrium constant data. Aspen HYSYS estimates 
the equilibrium constant from the pairs of data 
which you provide and interpolates when 
necessary. For each pair of data that you provide 
Aspen HYSYS calculates a constant in the Ln(K) 
equation. If you provide at least 4 pairs of data, all 
four constants A, B, C and D are estimated.
The constants may be changed even after they are 
estimated from the pairs of data you provide, 
simply by entering a new value in the appropriate 
cell. If you later want to revert to the estimated 
value, simply delete the number in the appropriate 
cell, and it is recalculated.
The term R2 gives an indication of the error or 
accuracy of the Ln(K) equation. It is equal to the 
regression sum of squares divided by the total 
sum of squares, and is equal to one when the 
equation fits the data perfectly.
You can also provide the maximum (T Hi) and 
minimum (T Lo) temperatures applicable to the 
Ln(K) relation. The constants are always 
calculated based on the temperature range you 
provide. If you provide values in the K Table which 
are outside the temperature range, the calculation 
of the constants is not affected.
Option Description View on Keq Tab5-17
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ThThe Approach tab contains two groups, the Fractional Approach 
and Temperature Approach. 
Both the Fractional Approach and Temperature Approach 
methods can be used to simulate an Equilibrium reaction that is 
a departure from equilibrium. 
For the Temperature Approach method, the Aspen HYSYS 
reaction solver will take into account the heat of reaction 
according to the equations listed. The direction of non-
equilibrium departure depends on whether the reaction is 
endothermic or exothermic.
The Fractional Approach method is an alternative to the 
Temperature Approach method and is defined according to the 
following equation:
Equation (5.5) could be interpreted as defining the “actual” 
reaction extent of the equilibrium as only a percentage of the 
equilibrium reaction extent of the reaction. In the solver, the 
value of Approach % is limited between 0 and 100%.
 Figure 5.7
Temperature Approach is not relevant for a fixed Keq source 
and thus the group does not appear when Fixed Keq is 
selected from the Basis tab.
(5.5)Feed Product– Approach% Feed Product–( )equilibrium⋅=5-18
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ThLibrary Tab
The Library tab allows you to add pre-defined reactions from the 
Aspen HYSYS Library. The components for the selected Library 
reaction are automatically transferred to the Rxn Components 
group of the Reaction Manager.
When you select a reaction, all data for the reaction, including 
the stoichiometry, basis, and Ln(K) parameters, are transferred 
into the appropriate location on the Equilibrium Reaction 
property view. To access a library reaction, highlight it from the 
Library Equilibrium Rxns group and click the Add Library Rxn 
button.
 Figure 5.8
When K Table contains data input, the library reaction 
selection will be blocked. You must click the Erase Table 
button on the Keq tab and before you can add a library 
reaction.5-19
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Th5.3.4 Kinetic Reaction
To define a Kinetic Reaction, it is necessary to specify the 
forward Arrhenius Parameters (the reverse is optional), the 
stoichiometric coefficients for each component, and the forward 
(and reverse) reaction orders. An iterative calculation occurs, 
that requires the Solver to make initial estimates of the outlet 
compositions. With these estimates, the rate of reaction is 
determined. A mole balance is then performed as a check on the 
rate of reaction. If convergence is not attained, new estimates 
are made and the next iteration is executed.
Equation (5.6) relates the rate of reaction rA with the reaction 
rate constants and the basis (e.g. - concentration). Equation 
(5.7) is a mole balance on the unit operation; for steady state 
solutions, the right side is equal to zero.
(5.6)
(5.7)
When you have supplied all of the required information for 
the Kinetic Reaction, the status bar (at the bottom right 
corner) changes from Not Ready to Ready.
rA k f BASIS( ) k' f ' BASIS( )⋅–⋅=
FAo FA– rA VdV
∫+
dNA
dt
---------=5-20
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ThStoichiometry Tab
When the Kinetic Reaction is selected, the following property 
view is displayed:
For each reaction, you must supply the following information:
 Figure 5.9
Input Required Description
Reaction Name A default name is provided, which may be changed at 
any time.
Components You must specify a minimum of one reactant and one 
product for each reaction you include. Access the 
available components using the drop-down list. The 
Molecular Weight of each Component is automatically 
displayed.5-21
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ThThermodynamic Consistency
Crucial to the specification of the reverse reaction equation is 
maintaining thermodynamic consistency so that the equilibrium 
rate expression retains the form of Equation (5.3). Failure to 
do so may produce erroneous results from Aspen HYSYS.
Consider the previously mentioned reaction:
with the forward kinetics following the relationship:
Stoichiometric 
Coefficient
Necessary for every component in the reaction. The 
Stoichiometric Coefficient is negative for a reactant 
and positive for a product. The Stoichiometric 
Coefficient need not be an integer; fractional 
coefficients are acceptable. You may specify the 
coefficient for an inert component as 0, which in most 
cases is the same as not including the component in 
the list. However, you must include components that 
have an overall stoichiometric coefficient of zero and a 
non-zero order of reaction (i.e., a component that 
might play the role of a catalyst). The Kinetic Reaction, 
which allows you to specify the Stoichiometric 
Coefficient and the order of reaction, makes it possible 
to correctly model this situation. 
Forward and 
Reverse Orders 
These are reaction orders. Aspen HYSYS initially fixes 
the orders of reaction according to the corresponding 
stoichiometric coefficient. These may be modified by 
directly entering the new value into the appropriate 
cell. For instance, in the following reaction:
the kinetic rate law is
When the stoichiometric coefficients are entered for 
the reaction, Aspen HYSYS sets the forward orders of 
reaction for CO and Cl2 at 1. Simply enter 1.5 into the 
Forward Order cell for Cl2 to correctly model the 
reaction order.
(5.8)
Input Required Description
CO Cl2+ COCl2→
rCO k CO[ ] Cl2[ ]3 2⁄=
CO Cl2 COCl2↔+
rateforward kf CO[ ] Cl2[ ] 3 2⁄=5-22
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ThNow suppose you want to add the reverse kinetic reaction. Since 
the forward reaction is already known, the order of the reverse 
reaction has to be derived in order to maintain thermodynamic 
consistency. Suppose a generic kinetic relationship is chosen:
where:  
 = the unknown values of the order of the three 
components
Equilibrium is defined as the moment when:
The equilibrium constant K is then equal to:
To maintain the form of the equilibrium equation seen in 
Equation (5.3), K is also equal to:
Now combining the two relationships for K found in Equation 
(5.10) and Equation (5.11):
To maintain thermodynamic consistency:  must be 0,  must 
be 0.5 and  must be equal to 1.
(5.9)
(5.10)
(5.11)
(5.12)
ratebackward kr CO[ ]α Cl2[ ]β COCl2[ ]γ=
α β γ, ,
rateforward ratebackward– 0=
K
kf
kr
----
CO[ ]α Cl2[ ]β COCl2[ ]γ
CO[ ] Cl2[ ]3 2⁄
---------------------------------------------------------= =
K
COCl2[ ]
CO[ ] Cl2[ ]
--------------------------=
CO[ ]α Cl2[ ]β COCl2[ ]γ
CO[ ] Cl2[ ]3 2⁄
---------------------------------------------------------
COCl2[ ]
CO[ ] Cl2[ ]
--------------------------=
α β
γ
5-23
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ThBasis Tab
The Basis tab for a kinetic reaction is shown below:
On the Basis tab, the following parameters may be specified:
 Figure 5.10
Input Required Description
Basis View the drop-down list in the cell to select the Basis 
for the reaction. If, for instance, the rate equation is a 
function of the partial pressures, select Partial Pressure 
as the Basis.
Base Component Only a component that is consumed in the reaction (a 
reactant) may be specified as the Base Component 
(i.e., a reaction product or an inert component is not a 
valid choice). You can use the same component as the 
Base Component for a number of reactions, and it is 
quite acceptable for the Base Component of one 
reaction to be a product of another reaction.
Reaction Phase The phase for which the kinetic rate equations apply. 
Different kinetic rate equations for different phases can 
be modeled in the same reactor. Possible choices for 
the Reaction Phase, available in the drop-down list, 
are: Overall, Vapour Phase, Liquid Phase, Aqueous 
Phase, and Combined Liquid.
Minimum 
Temperature and 
Maximum 
Temperature 
Enter the minimum and maximum temperatures for 
which the forward and reverse reaction Arrhenius 
equations are valid. If the temperature does not 
remain within these bounds, a warning message alerts 
you during the simulation.
Basis Units Enter the appropriate units for the Basis, or make a 
selection from the drop-down list.
Rate Units Enter the appropriate units for the rate of reaction, or 
make a selection from the drop-down list.5-24
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ThParameters Tab
On the Parameters tab, you may specify the forward and reverse 
parameters for the Arrhenius equations. These parameters are 
used in the calculation of the forward and reverse reaction 
constants.
The reaction rate constants are a function of temperature 
according to the following extended form of the Arrhenius 
equation:
where:  
k = forward reaction rate constant
k' = reverse reaction rate constant
 Figure 5.11
(5.13)
(5.14)
A, E, , are the Arrhenius Parameters for the forward 
reaction. A', E', and  are the Arrhenius Parameters for the 
reverse reaction.
Information for the reverse reaction is not required.
k A E
RT( )
-----------–
⎩ ⎭
⎨ ⎬
⎧ ⎫
Tβ⋅exp⋅=
k' A' E′
RT
------–
⎩ ⎭
⎨ ⎬
⎧ ⎫
Tβ′⋅exp⋅=
β
β′5-25
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ThA = forward reaction Frequency Factor
A' = reverse reaction Frequency Factor
E = forward reaction Activation Energy
E' = reverse reaction Activation Energy
 = forward extended reaction rate constant
 = reverse extended reaction rate constant
R = Ideal Gas Constant (value and units dependent on the 
units chosen for Molar Enthalpy and Temperature)
T = Absolute Temperature
5.3.5 Heterogeneous Catalytic 
Reaction
Aspen HYSYS provides a heterogeneous catalytic reaction 
kinetics model to describe the rate of catalytic reactions 
involving solid catalyst. The rate equation is expressed in the 
general form according to Yang and Hougen (1950):
Since these types of reactions involve surface reaction together 
with adsorption (and desorption) of reactants and products, the 
resulting rate expression will be strongly mechanism dependent.
Consider the following the simple reaction:
If the Arrhenius coefficient, A is equal to zero, there is no 
reaction. If Arrhenius coefficients E and  are zero, the rate 
constant is considered to be fixed at a value of A for all 
temperatures.
(5.15)
β
β′
β
r– kinetic term( ) potential term( )
adsorption term( )
-----------------------------------------------------------------------=
aA bB cP→+5-26
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ThDepending on the reaction mechanism, its reaction rate 
expression (ignoring reverse rate of reaction) could be:
where:  
K* = the adsorption rate constant for component *
k+ = the forward reaction rate constant
k = reaction rate constant for oxidation of hydrocarbon
k* = reaction rate constant for surface re-oxidation
Aspen HYSYS has provided a general form, as follows, to allow 
user to build in the form of rate expression they want to use.
where:  
kf and kr = the Rate Constants of the forward and reverse 
kinetic rate expressions
K = the absorption rate constant
M = number of absorbed reactants and products plus 
absorbed inert species
Langmuir-
Hinshelwood Model
(5.16)
Eley-Rideal Model (5.17)
Mars-van Krevelen 
Model (5.18)
(5.19)
r
k+KAKBCACB
1 KACA KBCB KPCP+ + +( )2
------------------------------------------------------------------------=
r
k+KBCACB
1 KBCB KPCP+ +( )
-------------------------------------------------=
r
kCA
1 a b⁄( ) k k∗⁄( )CACB
n–+
----------------------------------------------------------=
r
kf Ci
αi
i 1=
Reactants
∏ kr Cj
βj
j 1=
Products
∏–
1 Kk Cg
γkg
g 1=
M
∏
⎩ ⎭
⎪ ⎪
⎨ ⎬
⎪ ⎪
⎧ ⎫
k 1=
M
∑+
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎛ ⎞ n
-------------------------------------------------------------------=5-27
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ThThe rate constants kf, kr and Kk are all in Arrhenius form. You 
are required to prove the Arrhenius parameters (pre-
exponential factor A and activation energy E) for each of these 
constants.
You may have to group constants, for example in Equation 
(5.16), kf = k+ KAKB. You must take care in inputting the 
correct values of the Arrhenius equation. Also note that no 
default values are given for these constants.
The Heterogeneous Catalytic Reaction option can be used in 
both CSTR and PFR reactor unit operations. A typical Reaction 
Set may include multiple instances of the Heterogeneous 
Catalytic Reaction.
Stoichiometry Tab
When the Heterogeneous Catalytic Reaction is selected, the 
following property view appears:
 Figure 5.125-28
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ThFor each catalytic reaction, you must supply the following 
information:
Basis Tab
The Basis tab for a catalytic reaction is shown below:
Input Required Description
Reaction Name A default name is provided, which may be changed.
Components You must specify a minimum of one reactant and one 
product for each reaction you include. Open the drop-
down list in the cell to access all of the available 
components. The Molecular Weight of each component 
is automatically displayed.
Stoichiometric 
Coefficient 
Necessary for every component in this reaction. The 
Stoichiometric Coefficient is negative for a reactant 
and positive for a product. The Stoichiometric 
Coefficient need not be an integer; fractional 
coefficients are acceptable. You may specify the 
coefficient for an inert component as 0, which in this 
case is the same as not including the component in the 
list.
 Figure 5.135-29
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ThOn the Basis tab, the following parameters may be specified: 
Input Required Description
Basis Open the drop-down list in the cell to select the Basis 
for the reaction. For example, select Partial Pressure or 
Molar Concentration as the basis.
Base Component Only a component that is consumed in the reaction (a 
reactant) may be specified as the Base Component 
(i.e., a reaction product or an inert component is not a 
valid choice). You can use the same component as the 
Base Component for a number of reactions, and it is 
acceptable for the Base Component of one reaction to 
be a product of another reaction.
Reaction Phase The phase for which the kinetics apply. Different 
kinetics for different phases can be modeled in the 
same reactor. Possible choices for the Reaction Phase 
(available in the drop-down list) are Overall, Vapour 
Phase, Liquid Phase, Aqueous Phase, and Combined 
Liquid.
Minimum 
Temperature and 
Maximum 
Temperature 
Enter the minimum and maximum temperatures for 
which the forward and reverse reaction Arrhenius 
equations are valid. If the temperature does not 
remain in these bounds, a warning message alerts you 
during the simulation.
Basis Units Enter the appropriate units for the Basis, or make a 
selection from the drop-down list.
Rate Units Enter the appropriate units for the rate of reaction, or 
make a selection from the drop-down list.5-30
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ThNumerator Tab
The Numerator tab is specified in much the same way as you 
would specify a typical Aspen HYSYS Kinetic Reaction. The 
Numerator tab is shown below:
You must supply the forward and reverse parameters of the 
extended Arrhenius equation. The forward and reverse reaction 
rate constants are calculated from these values. In addition to 
the rate constants, you must also specify the reaction order of 
the various components for both the forward and reverse 
reactions. This is done by selecting the Components field of the 
Reaction Order cell matrix, and selecting the appropriate 
component from the drop-down list and entering values for the 
Forward and/or Reverse orders.
When specifying Forward and Reverse relationships it is 
important to maintain thermodynamic consistency. For more 
information on thermodynamic consistency see Section 5.3.4 - 
Kinetic Reaction, Thermodynamic Consistency.
 Figure 5.14
For more information on 
Kinetic reaction 
specifications see Section 
5.3.4 - Kinetic 
Reaction.5-31
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ThDenominator Tab
The Denominator tab for a catalytic reaction is shown in the 
following figure:
The Denominator tab contains the Component Exponents matrix 
in which each row represents a denominator term. The A and E 
columns are for the pre-exponential factor and the activation 
energy, respectively for the adsorption term (K). 
The remaining columns are used to specify the exponents ( ) 
of the absorbed components (Cg). In order to add a term to the 
denominator of the kinetic expression, you must activate the 
row of the matrix containing the  message and add the 
relevant equation parameter values. The Delete Term button is 
provided to delete the selected row (or corresponding term) in 
the matrix. The overall exponent term n is specified in the 
Denominator Exponent field.
 Figure 5.15
(5.20)1 Kk Cg
γkg
g 1=
M
∏
⎩ ⎭
⎪ ⎪
⎨ ⎬
⎪ ⎪
⎧ ⎫
k 1=
M
∑+
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎛ ⎞ n
γkg5-32
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Th5.3.6 Simple Rate Reaction
The Simple Rate Reaction is also similar to the Kinetic Reaction, 
except that the reverse reaction rate expression is derived from 
equilibrium data.
Stoichiometry Tab
When the Simple Rate Reaction is selected the following 
property view appears. 
For each reaction, supply the following information:
When you have supplied all of the required information for 
the Simple Rate Reaction, the status bar (at the bottom right 
corner) will change from Not Ready to Ready.
 Figure 5.16
Field Description
Reaction Name A default name is provided, which may be changed.
Components You must specify a minimum of one reactant and one product for 
each reaction you include. Open the drop-down list in the cell to 
access all of the available components. The Molecular Weight of 
each component is automatically displayed.
Stoichiometric 
Coefficient 
Necessary for every component in this reaction. The Stoichiometric 
Coefficient is negative for a reactant and positive for a product. The 
Stoichiometric Coefficient need not be an integer; fractional 
coefficients are acceptable. You may specify the coefficient for an 
inert component as 0, which in this case is the same as not including 
the component in the list.5-33
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ThBasis Tab
The Basis tab for the simple rate reaction is shown below:
On the Basis tab, the following parameters may be specified:
 Figure 5.17
Parameter Description
Basis Open the drop-down list in the cell to select the Basis 
for the reaction. For example, select Partial Pressure or 
Molar Concentration as the basis.
Base Component Only a component that is consumed in the reaction (a 
reactant) may be specified as the Base Component 
(i.e., a reaction product or an inert component is not a 
valid choice). You can use the same component as the 
Base Component for a number of reactions, and it is 
acceptable for the Base Component of one reaction to 
be a product of another reaction.
Reaction Phase The phase for which the kinetics apply. Different 
kinetics for different phases can be modeled in the 
same reactor. Possible choices for the Reaction Phase, 
available in the drop-down list, are Overall, Vapour 
Phase, Liquid Phase, Aqueous Phase and Combined 
Liquid.
Minimum 
Temperature and 
Maximum 
Temperature 
Enter the minimum and maximum temperatures for 
which the forward and reverse reaction Arrhenius 
equations are valid. If the temperature does not 
remain in these bounds, a warning message alerts you 
during the simulation.
Basis Units Enter the appropriate units for the Basis, or make a 
selection from the drop-down list.
Rate Units Enter the appropriate units for the rate of reaction, or 
make a selection from the drop-down list.5-34
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ThParameters Tab
The Parameters tab for the rate reaction is shown below:
The forward reaction rate constants are a function of 
temperature according to the following extended form of the 
Arrhenius equation:
where:  
k = forward reaction rate constant
A = forward reaction Frequency Factor
E = forward reaction Activation Energy
 = forward extended reaction rate constant
R = Ideal Gas Constant
T = Absolute Temperature
 Figure 5.18
(5.21)
If Arrhenius coefficient A is equal to zero, there is no 
reaction. If Arrhenius coefficients E and  are equal to zero, 
the rate constant is considered to be fixed at a value of A for 
all temperatures.
k A E
RT
------– Tβ⋅exp⋅=
β
β
5-35
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ThThe reverse equilibrium constant K' is considered to be a 
function of temperature only:
where:  
A', B', C', D' = the reverse equilibrium constants
You must supply at least one of the four reverse equilibrium 
constants.
5.4 Reaction Sets
All Reaction Sets created within the Reaction Manager become 
available for attachment to your reactor operations in the 
flowsheet. Reaction Sets may contain more than one reaction. 
There is limited flexibility for the mixing of reaction types within 
a Reaction Set. You can have Equilibrium and Kinetic reactions 
within a single Reaction Set, but you must have a distinct 
Reaction Set for conversion reactions.
Aspen HYSYS provides the Global Rxn Set, which contains all 
compatible reactions that you have defined in the case. If you 
only add Kinetic and Equilibrium reactions, or exclusively 
Conversion reactions to the case, all reactions are active within 
the Global Rxn Set. However, if you add an incompatible mix of 
reactions (i.e., Conversion and Kinetic), only the type of 
reactions that are compatible with the first installed reaction are 
active in the Global Rxn Set.
The same reaction can be active in multiple reaction sets. A new 
set can be added from the Reaction Manager by selecting the 
Add Set button.
(5.22)
If only one type of reaction is used, all reactions are active in 
the Global Rxn Set, thereby eliminating the need to explicitly 
define a new Reaction Set.
K′ln A′ B′
T
---- C′ T( )ln D′T+ + +=5-36
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Th5.4.1 Manipulating Reaction 
Sets
All Reaction Set manipulations are conducted in the Reaction 
Sets group of the Reactions tab of the Basis Manager. The 
following buttons are available in the Reaction Sets group to 
manipulate reaction sets: 
Button Description
View Set Displays the property view for the highlighted reaction set.
Add Set Adds a reaction set to the list of reaction sets and opens its 
property view.
Delete Set Removes the highlighted reaction set(s) from the Reaction 
Manager. You must confirm your action to delete a reaction 
set.
Copy Set Duplicates the highlighted reaction set(s).
Import Set Opens a reaction set from disk into the current case.
Export Set Saves a reaction set to disk for use in another case.
Add to FP Accesses the Add 'Reaction Set Name' view, from which 
you attach the highlighted reaction set(s) to a fluid 
package. This button is available only when a Reaction Set 
is highlighted in the Reaction Sets group.
When you right-click a Reaction Set in the Reaction Sets 
group, you can select View or Delete from the object inspect 
menu.5-37
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Th5.4.2 Reaction Set Property 
View
When you add a new set, or view an existing one, the Reaction 
Set property view appears as shown below.
The following table describes the features contained within this 
property view.
 Figure 5.19
Feature Description
Name A default Reaction Set name is provided, which can be 
changed.
Set Type Aspen HYSYS determines the Set Type from the reaction 
types in the Active List. This field cannot be modified. The 
Reaction Set types are Conversion, Kinetic, Equilibrium, 
and Mixed. A Mixed Set Type corresponds to a Reaction Set 
containing both Kinetic and Equilibrium reactions.5-38
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ThSolver 
Method 
The Solver method is available when dealing with Kinetic 
reaction sets. Several Solver Methods are available from 
the drop-down list and explained below:
• Default. The Reaction Solver attempts to calculate 
the solution using Newton's Method. If this is not 
successful, it then uses the Rate Iterated and Rate 
Integrated Methods. For most cases, it is best to use 
the Default Solver Method.
• Newton's Method. This method usually converges 
quickly by taking the derivative of the function using 
the current estimates, and uses these results to obtain 
new estimates.
• Rate Iterated. This method is a partial Newton's 
method, and assumes that the off-diagonal elements 
of the Jacobian matrix are equal to zero. The Rate 
Iterated Method works well when there is very little 
interaction between reactions.
• Rate Integrated. This method integrates the 
reaction equations until all time derivatives are zero. 
The Rate Integrated method is stable, but slow.
• Auto Selected. Same as Default.
Active List Reactions may be added to the Active List by positioning 
the cursor in the Active List column and selecting an 
existing Reaction from the drop-down list. You may also 
type the name of an existing reaction directly in the cell 
that shows .
You can open the property view for any reaction in the 
Active List by highlighting it and clicking the View Active 
button. Alternatively, you may double-click on the reaction 
to view it.
A reaction in the Active List may be transferred to the 
Inactive List simply by selecting the reaction and clicking 
the Make Inactive button.
Inactive List Existing reactions may be added to the Inactive List by 
positioning the cursor in the Inactive List column and 
selecting a Reaction from the drop-down list.
You can access the property view for any reaction in the 
Inactive List by highlighting it and clicking the View 
Inactive button. You may also double-click on the reaction 
to view it.
A reaction in the Inactive List may be transferred to the 
Active List by selecting the reaction and clicking the Make 
Active button. If this reaction is not independent of other 
reactions in the Active List, an error message is displayed, 
and the reaction remains in the Inactive List.
You cannot have two versions of the same reaction with 
different rate constants in the Active List.
Operations 
Attached 
All operations to which the Reaction Set is attached are 
listed in this column.
Feature Description5-39
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ThAdvanced Features
By clicking the Advanced button, you can view the Advanced 
reaction options. 
Within the Volume Continuation Parameters group, the following 
options are available:
 Figure 5.20
Object Description
Volume 
Continuation 
For most cases, it is not necessary to select this option. 
In situations where convergence is not easily attained 
(e.g., high reaction rates), select the Volume 
Continuation checkbox to enable Aspen HYSYS to 
more easily reach a solution. For Volume Continuation 
calculations, Aspen HYSYS “ramps” the volume starting 
from the initial volume fraction to the final volume 
fraction in the specified number of steps. For each 
successive step, the previous solution is used as the 
initial estimate for the next step.
Initial Volume 
Fraction 
The default value is 1.0000e-06. This is the Volume 
Fraction at the start of the calculations.
Number of Steps The default value is 10. If the solution does not 
converge, increase this value and re-run the 
simulation.
Current Parm 
Value 
This field displays the current parameter value.
Current Step 
Number 
This field displays the current step number.5-40
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ThThe parameters within the Initial Estimate Generation 
Parameters group are generally used with Reactions that have a 
high degree of interaction. You can also use these parameters to 
give some assistance in obtaining the final solution when the 
reactor operation fails to converge or when you have a large 
number of components and reactions. The parameters are 
described in the following table:
The Reaction Solver Option group allows you to set the number 
of iterations and the tolerance level. The option depends on the 
boundary condition of the reactor operation which is using the 
reaction set. For example, when a reactor operation is used to 
determine the outlet temperature, the number of iterations and 
tolerance level are used in the reaction solver to search for a 
solution.
Trace Level Provides a trace output of the calculations in the Trace 
Window. The trace level value corresponds to the level 
of detail that you see in the Trace Window. You are 
limited to the values 0, 1, 2, or 3.
Prev Solution as 
Estimates 
It is necessary to make an initial estimate of the outlet 
compositions to obtain the proper solution. Select this 
checkbox if you want to use the previous solution as 
the initial estimate. This does not apply to the 
conversion reaction, since the specified conversion 
determines the outlet compositions.
Use Iso and Adia 
Temp as Adia Est 
If you calculate a heat flow given a specific 
temperature, and then use this heat flow as a spec 
(deleting the temperature specification), Aspen HYSYS 
uses the previously calculated temperature as an 
estimate for the Adiabatic calculation.
Parameter Description
Damping 
Factor 
Default is 1.0, indicating that there is no damping. You can 
change this value. With a lower the damping factor, Aspen 
HYSYS uses smaller steps (slower and more stable) in 
converging towards the solution.
Tolerance This is the tolerance set for the Estimate Generation. By 
default, this is set to 0.001. You are able to change this 
value. 
Maximum 
Iterations 
Maximum number of iterations Aspen HYSYS uses. There is 
no default value, and so you can set whatever value is 
desired.
Object Description5-41
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ThReaction Rank
The Ranking button is visible only when the Reaction Set type is 
Conversion. This option automatically handles most situations 
where reactions are sequential:
allowing the three reactions to be modeled in a single reactor.
In this case the Rank would be:
However in situations where there are competing reactions:
you can use the Ranking factor to specify which conversion 
value should be applied first. For example, if Rxn-4 was ranked 
first, the specified conversion for Rxn-5 would only be applied to 
the amount of component B remaining after Rxn-4 had run to its 
specified conversion.
Option Description
Max Numb of 
Iteration
Controls the maximum number of iterations specified 
before the reaction solver stops searching for a solution. By 
default, the value is 200.
Tolerance The specified tolerance level is the relative error between 
the energy balance equation and the calculated value by 
the reaction solver in the iteration. By default, the value is 
0.00001.
A B→
Rxn 1–
B C→
Rxn 2–
C D→
Rxn 3–
A B 1→
B C 2→
C D 3→
A B+ C→
Rxn 4–
B D+ E→
Rxn 5–5-42
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Th  
To specify the Ranking, you must do so from the Reaction Ranks 
property view, which contains the following fields: 
 Figure 5.21
Aspen HYSYS assigns default ranks to multiple conversion 
reactions by examining the reactants and products. For 
example, you may have a reaction set containing the 
following:
1.CH4+H2O  CO+3H2 
2.CH4+2H2O  CO2+4H2
3.CH4+2O2  CO2+2H2O
Aspen HYSYS notices that a product of Reaction 3, H2O, is 
used as a reactant in both Reactions 1 and 2. Since H2O may 
not be available until Reaction 3 has occurred, it is assigned 
a rank of 0 and the other reactions are each given the default 
Rank of 1. The feed composition is not taken into account, as 
Reaction Ranks are assigned prior to entering the Build 
Environment.
Object Description
Reaction This column shows all of the reactions to be ranked.
Rank Shows the rank for each reaction, which is an integer value. 
The minimum value is 0 and the maximum is equal to the 
number of Reactions ranked. Thus, when ranking three 
sequential reactions, you may rank them 0-1-2 or 1-2-3; 
both methods give the same results. You may override the 
default values through the input of new values in the 
appropriate cells.
You can set two or more reactions to have the same Rank; 
for instance, the ranks for Rxn-1 and Rxn-2 may be 1, and 
the rank for Rxn-3 may be 2.
User 
Specified
If you specify the Rank of the reaction, this checkbox is 
selected.
→
→
→
5-43
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ThThe buttons along the bottom of the Reaction Ranks property 
view have the following functions:
5.4.3 Exporting/Importing a 
Reaction Set
After a Reaction Set is customized with reactions, it can be 
exported to a file. The same Reaction Set can then be used in 
another simulation case by importing the file and attaching it to 
a fluid package. Highlight a Reaction Set in the Reaction Sets 
group of the Reaction Manager and click the Export Set button.
Select a file path (the default is usually satisfactory) and enter a 
filename with the extension *.rst. Click the Save button to 
export the reaction set to a file.
The Import Set button allows you to introduce an exported 
Reaction Set into a simulation case. Choose the Reaction Set file 
(with the extension *.rst) from the list and select the Open 
button. If the file is not listed in the File Name field, an alternate 
File Path may be needed.
Button Description
Cancel Closes the property view without accepting any changes 
that were made.
Reset Resets the Reaction Ranks to the internal default.
Accept Closes the property view, accepting the changes that were 
made.
 Figure 5.225-44
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Th5.4.4 Adding a Reaction Set to 
a Fluid Package
To make a Reaction Set available inside the flowsheet, attach it 
to the fluid package which is associated with the flowsheet. 
Highlight a reaction set in the Reaction Sets group of the 
Reaction Manager and click the Add to FP button. The Add 
'Reaction Set Name' view appears, where you can highlight a 
fluid package and click the Add Set to Fluid Package button.
5.4.5 Reactions in the Build 
Environment
When you are inside the Main or Column Environment you can 
access the Reaction Package property view without having to 
return to the fluid package. Under Flowsheet in the Main Menu, 
select Reaction Package.
When a Reaction Set is attached to a unit operation, you can 
access the Reaction Set property view or the property view(s) 
for the associated Reaction(s) directly from the property view of 
the operation. Some of the unit operations that support 
reactions include the Reactor operation (conversion, equilibrium, 
or kinetic), the PFR, the Separator, and the Column.
 Figure 5.23
Refer to Section 5.3 - 
Reaction Package of the 
Aspen HYSYS User 
Guide for more details.
Refer to the Aspen 
HYSYS Operation 
Guide for more 
information on the 
individual unit operations.5-45
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5-46 Generalized Procedure
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Th5.5 Generalized Procedure
The following procedure outlines the basic steps for creating a 
reaction, creating a reaction set, adding the reaction to the 
reaction set and then making the set available to the flowsheet. 
Refer to the Reaction Package property view, shown in Figure 
5.1, as you follow the procedure:
1. Select Reaction Package under Flowsheet in the menu 
bar.
2. On the Reaction Package property view, click the Add Rxn 
button to create a new Reaction.
3. A Reactions property view appears, from which you must 
select the type of reaction to create. Select a reaction type 
and click the Add Reaction button.
4. The property view for the reaction type you selected is 
displayed. Complete the input for the reaction until Ready 
appears as the status message. You can close the Reaction 
property view, if desired.
 Figure 5.245-46
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Reactions 5-47
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Th5. On the Reaction Package property view, click the New Set 
button to create a Reaction Set. The Reaction Set property 
view appears.
6. If desired, change the Name of the Reaction Set to better 
identify it.
7. To attach the newly created reaction to the Reaction Set, 
place the cursor in the  cell of the Active List 
column. Open the drop-down list in the cell and select a 
reaction. The reaction becomes attached to the Reaction Set, 
as indicated by the selected checkbox in the OK column.
8. Click the Close button on the Reaction Set property view.
9. In the Available Reaction Sets group of the Reaction 
Package property view, highlight the name of the newly 
created Reaction Set. Notice that the attached reaction is 
listed in the Associated Reactions group.
10.Click the Add Set button to make the Reaction Set, and thus 
the Reaction, available to unit operations in the flowsheet. 
The new Reaction Set is displayed in the Current Reaction 
Sets group.
 Figure 5.255-47
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5-48 Reactions - Example
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Th5.6 Reactions - Example
The following procedure demonstrates the minimum steps 
required for:
• The addition of components to the Reaction Manager.
• The creation of a reaction.
• The addition of the reaction to a reaction set.
• The attachment of the reaction set to a fluid package.
5.6.1 Add Components to the 
Reaction Manager
For this example, it is assumed that a New Case is created and a 
fluid package is installed. 
1. Within the fluid package, the Peng Robinson property 
package is selected.
2. Within the component list, the following set of components 
are selected: H2O, CO, CO2, H2, O2, and CH4.
3. Go to the Reactions tab of the Simulation Basis Manager. 
The selected components are present in the Rxn 
Components group.
5.6.2 Create a Reaction
1. To install a reaction, click the Add Rxn button.
2. From the Reactions property view, highlight the Conversion 
reaction type and click the Add Reaction button. The 
Conversion Reaction property view appears.
3. On the Stoichiometry tab, select the first row of the 
Component column in the Stoichiometry Info table. 
4. Select Methane from the drop-down list. The Mole Weight 
column automatically provides the molar weight of methane.
5. In the Stoich Coeff field, enter -3 (i.e., 3 moles of methane 
is consumed).
Refer to Section 2.4 - 
HYSYS Fluid Package 
Property View for 
details on installing a fluid 
package.
Refer to Section 5.3 - 
Reactions for 
information concerning 
reaction types and the 
addition of reactions.5-48
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Th6. Now define the rest of the Stoichiometry tab as shown in the 
figure below and click the Balance button. 
7. Go to the Basis tab and set Methane as the Base 
Component and Conversion to 60%. The status bar at the 
bottom of the property view now shows a Ready status. 
Close the property view.
5.6.3 Add the Reaction to a 
Reaction Set
By default, the Global Rxn Set is present within the Reaction 
Sets group when you first display the Reaction Manager. 
However, for this procedure, a new Reaction Set is created:
1. Click the Add Set button. Aspen HYSYS provides the name 
Set-1 and opens the Reaction Set property view.
2. To attach the newly created Reaction to the Reaction Set, 
place the cursor in the  cell under Active List.
3. Open the drop-down list and select the name of the Reaction 
(Rxn-1). The Set Type corresponds to the type of Reaction 
which you have added to the Reaction Set. 
 Figure 5.26
Refer to Section 5.4 - 
Reaction Sets for details 
concerning Reactions 
Sets.5-49
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5-50 Reactions - Example
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ThThe status is now Ready.
4. Close the property view to return to the Reaction Manager.
5.6.4 Attach the Reaction Set 
to a Fluid Package
1. To attach the reaction set to the fluid package, highlight Set-
1 in the Reaction Sets group and click the Add to FP button.
When a Reaction Set is attached to a Fluid Package, it 
becomes available to unit operations within the Flowsheet 
using that particular Fluid Package.
2. The Add 'Set-1' property view appears, from which you 
highlight a fluid package and click the Add Set to Fluid 
Package button.
 Figure 5.27
 Figure 5.285-50
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Th3. Close the property view. Notice that the name of the fluid 
package appears in the Assoc. Fluid Pkgs group when the 
Reaction Set is highlighted in the Reaction Sets group.5-51
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5-52 Reactions - Example
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Th5-52
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Component Maps 6-1
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Th6  Component Maps6-1
6.1  Introduction................................................................................... 2
6.2  Component Maps Tab..................................................................... 2
6.2.1  Component Mapping Group ....................................................... 3
6.2.2  Collections Group ..................................................................... 3
6.2.3  Maps for Collection Group.......................................................... 3
6.3  Component Map Property View ...................................................... 4
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6-2 Introduction
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Th6.1 Introduction
On the Component Maps tab of the Simulation Basis Manager, 
you can map fluid component composition across fluid package 
boundaries. Composition values for individual components from 
one fluid package can be mapped to a different component in an 
alternate fluid package. This is usually done when dealing with 
hypothetical oil components.
Two previously defined fluid packages are required to perform a 
component mapping which is defined as a collection. One fluid 
package becomes the target component set and the other 
becomes the source component set. Mapping is performed using 
a matrix of source and target components. The transfer basis 
can be performed on a mole, mass, or liquid volume basis.
6.2 Component Maps Tab
The Component Maps tab of the Simulation Basis Manager is 
shown below.
 Figure 6.16-2
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Component Maps 6-3
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Th6.2.1 Component Mapping 
Group
The Component Mapping group defines the source and target 
fluid packages to be mapped. Once two distinct fluid packages 
are selected, the Create Collection button creates a collection in 
the Collections group. 
6.2.2 Collections Group
The Collections group lists all the component mapping 
collections currently available. You can change the collection 
name by selecting the name you want to edit and typing in the 
new name.
6.2.3 Maps for Collection 
Group
The Maps for Collection group allows you to manage your 
Component Maps for each collection. The Collection drop-down 
list lets you select the collection maps that you want to add, 
edit, or delete. A default collection map is added to this list and 
cannot be deleted. To add a Component Map based on the 
currently selected collection, click the Add button. To view a 
Component Map, select it from the list and click the View 
button. Both the Add and View buttons open the Component 
Map Property view. To delete a Component Map, select the map 
from the list and click the Delete button.6-3
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6-4 Component Map Property View
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Th6.3 Component Map 
Property View
Each time a Component Map is created or viewed via the 
Component Maps tab of the Simulation Basis Manager, the 
Component Map property view opens as shown below:
The Component Map property view allows you to map the 
source components to the target components in the component 
matrix. Within the matrix, you can map all Specifiable (in red) 
component mapping values. The following table describes all of 
the options found in this property view.
 Figure 6.2
Object Description
Name Displays the name of the component map. The name 
can be modified within the cell.
View Options The View Options group provides you with three 
options in which to view the component matrix.
• View All. Displays all of the source and target 
components in the matrix.
• View Specifiable. Displays only the components 
that require values.
• Transpose. Transposes the component matrix.6-4
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ThComponent 
Transfer Options
The Component Transfer Options group provides two 
options.
• Unlock all Components. Unlocks all of the 
component values, allowing you to specify your 
own values.
• Transfer Like Hypotheticals. Automatically 
maps like hypotheticals.
• Transfer Hypos by NBP. Automatically maps 
hypos by NBP. This option is available when  the 
Transfer Like Hypotheticals checkbox is 
selected. 
Transfer Basis The Transfer Basis group provides three options that 
allow you to define the composition mapping basis:
• Mole 
• Mass 
• Liq Volume 
Multiple Specify Allows you to specify a value to one or more 
components at a time.
Clone from 
another Map
Allows you to import values into the mapping matrix 
from another map.
Clear All Removes all of the user defined information from the 
matrix.
Normalize Normalizes the mapping matrix.
Object Description6-5
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Th6-6
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User Properties 7-1
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Th7  User Properties7-1
7.1  Introduction................................................................................... 2
7.2  User Properties Tab ....................................................................... 3
7.2.1  Adding a User Property ............................................................. 4
7.3  User Property Property View.......................................................... 5
7.3.1  Data Tab ................................................................................. 5
7.3.2  Notes Tab................................................................................ 9
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7-2 Introduction
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Th7.1 Introduction
On the User Properties tab of the Simulation Basis Manager, you 
can create an unlimited number of user properties for use in the 
Build Environment. A User Property is any property that can be 
defined and subsequently calculated on the basis of 
composition. 
When User Properties are specified, they are used globally 
throughout the case. You can supply a User Property value for 
each component. User properties can be modified for a specific 
component, fluid package, or stream using the property editor.
Specifying a User Property is similar to supplying a value at the 
component level in that it is globally available throughout the 
case, unless it is specified otherwise. It is the initial user 
property value for the component in the master component list. 
By selecting the mixing basis and mixing equation, the total 
User Property can be calculated.
After a User Property is defined, Aspen HYSYS is able to 
calculate the value of the property for any flowsheet stream 
through the User Property utility. User Properties can also be set 
as Column specifications.
Refer to Edit Properties 
from Section 1.2.3 - 
Manipulating the 
Selected Components 
List for more 
information on the 
property editor.7-2
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User Properties 7-3
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Th7.2 User Properties Tab
The User Properties tab of the Simulation Basis Manager is 
shown below:
The available User Properties are listed in the User Properties 
group. The following User Property manipulation buttons are 
available:
In the User Property Parameters group, all information 
pertaining to the highlighted property in the User Property group 
is displayed. You can edit the User Property parameters directly 
on the Simulation Basis property view or click the View button 
for the User Property property view.
 Figure 7.1
Button Description
View Edit the currently highlighted User Property.
A User Property can also be added or viewed through the 
Oil Characterization - User Property tab.
Add Create a new User Property.
Delete Erase the currently highlighted User Property. Aspen HYSYS 
will not prompt for confirmation when deleting a User 
Property, so be careful when you are using this command.
Refer to Section 7.3 - 
User Property Property 
View for descriptions of 
the User Property 
Parameters.7-3
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Th7.2.1 Adding a User Property
To add a user property, follow the steps below:
1. On the User Properties tab of the Simulation Basis Manager, 
click the Add button. The User Property property view 
appears.
2. Provide a descriptive Name for the user property on 
Simulation Basis property view.
3. In the User Property Parameters group, select a Mixing 
Basis using the drop-down list within the cell.
4. Select a Mixing Rule.
5. You can modify the two Mixing Parameters (F1 and F2) to 
more accurately reflect your property formula.
6. Select a Unit Type from the filtered drop-down list.
7. Input initial property values for each component.7-4
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User Properties 7-5
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Th7.3 User Property Property 
View
Each time a User Property is created through the User Property 
tab of the Simulation Basis Manager, the User Property property 
view is displayed. The User Property property view has two tabs, 
the Data tab and the Notes tab. All information regarding the 
calculation of the User Property is specified on the Data tab.
7.3.1 Data Tab
On the Data tab, the Basic user prop definition, and the Initial 
user property value groups are displayed.
 Figure 7.27-5
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ThBasic User Property Definition Group
The following options are available for Process type properties:
Parameter Description
Mixing Basis You have the following options: Mole Fraction, Mass 
Fraction,  and Liquid Volume Fraction. 
All calculations are performed using compositions in 
Aspen HYSYS internal units. If you have specified a flow 
basis (molar, mass or liquid volume flow), Aspen HYSYS 
uses the composition as calculated in internal units for 
that basis. 
For example, a User Property with a Mixing Basis 
specified as molar flow is always calculated using 
compositions in kg mole/s, regardless of what the current 
default units are.
Mixing Rule Select from one of three mixing rules:
(7.1)
(7.2)
(7.3)
where:
Pmix = total user property value 
P(i) = user property value for component 
x(i) = component page value which should be a 
dimensionless value (fraction) 
Index = blended (total) index value 
f1 and f2 are specified constants
Mixing 
Parameters 
The mixing parameters f1 and f2 are 1.00 by default. You 
may supply any value for these parameters.
Unit Type This option allows you to select the variable type for the 
user property. 
For example, if you have a temperature user property, 
select temperature in the unit type using the drop-down 
list.
Pmix( )f 1 f 2 x i( )P i( )f 1( )
i 1=
N
∑=
Pmix( )f 1 f 2 x i( ) P i( )( )f 1ln( )
i 1=
N
∑=
Index x i( ) f 1 P i( )⋅ 10f 2 P i( )⋅+( )
i 1=
N
∑=7-6
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ThMixing Rules
As listed previously, there are three mixing rules available when 
you are defining a user property. Equation (7.1) and Equation 
(7.2) are relatively straightforward. The index mixing rule, 
Equation (7.3), is slightly more complex.
With the index mixing rule, Aspen HYSYS allows you to combine 
properties that are not inherently linear. A property is made 
linear through the use of the index equation.
Equation (7.3) can be simplified into the following equations: 
You supply the individual component properties (Pi) and the 
index equation parameters (i.e., f1 and f2). Using Equation 
(7.4), Aspen HYSYS calculates an individual index value for 
each supplied property value. The sum of the index values, 
which is the blended index value, is then calculated using the 
Mixing Basis you have selected (Equation (7.5)). 
The blended index value is used in an iterative calculation to 
produce the blended property value (P in Equation (7.6)). The 
blended property value is the value which will be displayed in 
the user property utility.
(7.4)
(7.5)
(7.6)
The form of your index equation must resemble the Aspen 
HYSYS index equation such that you can supply the f1 and f2 
parameters. Some common properties which can make use 
of the Index equation include R.O.N., Pour Point and 
Viscosity.
Indexi f 1 P i( )⋅ 10f 2 P i( )⋅+=
Index x i( ) Indexi⋅
i 1=
N
∑=
Index f1 P 10f 2 P⋅+⋅=7-7
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ThInitial User Property Values for All 
Components Group
The purpose of this property view is to instruct Aspen HYSYS 
how the User Property should be initialized throughout the case. 
Whenever the value of a User Property is requested by the User 
Property utility or by the column specification, Aspen HYSYS 
uses the composition in the specified basis, and calculate the 
User Property value using your mixing rule and parameters.
The values for pure components are always used for the 
property and are not overwritten by the synthesis. The values 
for hypocomponents are only used if the synthesis of the 
property can not be achieved. For example, if there are 
insufficient number of data points. To specify a Property Value, 
click on the Edit component user property values button.
Edit Component User Property 
Values
This property view allows you to edit initial user property values 
for components in the master component list.
 Figure 7.3
User Property values can 
be assigned to 
hypocomponent during 
the characterization of an 
oil. Refer to Section 
7.2.1 - Adding a User 
Property for more 
information.
Refer to Chapter 14 - 
Utilities of the Aspen 
HYSYS Operations 
Guide for more 
information on the User 
Property utility.
Refer to Chapter 2 - 
Column Operations of 
the Aspen HYSYS 
Operations Guide for 
information on the User 
Property specification.7-8
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ThOnce property values are entered or edited, click the Submit 
button which allows all values to be modified at one time. The 
changes are reflected on the User Property property view for 
each component.
7.3.2 Notes Tab
Aspen HYSYS provides a tab where you can enter a description 
of the User Properties for your own future reference.7-9
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Th7-10
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Property Methods & Calculations A-1
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ThA  Property Methods & 
CalculationsA-1
A.1  Introduction .................................................................................. 3
A.2  Selecting Property Methods ........................................................... 4
A.3  Property Methods ........................................................................ 10
A.3.1  Equations of State.................................................................. 11
A.3.2  Activity Models ...................................................................... 23
A.3.3  Activity Model Vapour Phase Options......................................... 45
A.3.4  Semi-Empirical Methods.......................................................... 47
A.3.5  Vapour Pressure Property Packages .......................................... 48
A.3.6  Miscellaneous - Special Application Methods............................... 52
A.4  Enthalpy & Entropy Departure Calculations ................................. 56
A.4.1  Equations of State.................................................................. 56
A.4.2  Activity Models ...................................................................... 59
A.4.3  Lee-Kesler Option................................................................... 61
A.5  Physical & Transport Properties................................................... 64
A.5.1  Liquid Density........................................................................ 65
A.5.2  Vapour Density ...................................................................... 66
A.5.3  Viscosity ............................................................................... 66
A.5.4  Liquid Phase Mixing Rules for Viscosity...................................... 68
A.5.5  Thermal Conductivity.............................................................. 70
A.5.6  Surface Tension ..................................................................... 73
A.5.7  Heat Capacity ........................................................................ 74
A.6  Volumetric Flow Rate Calculations............................................... 74
A.6.1  Available Flow Rates ............................................................... 75
A.6.2  Liquid & Vapour Density Basis .................................................. 76
A.6.3  Formulation of Flow Rate Calculations ....................................... 78
A.6.4  Volumetric Flow Rates as Specifications..................................... 80
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A-2 Property Methods & Calculations 
A-2
A.7  Flash Calculations.........................................................................81
A.7.1  T-P Flash Calculation ...............................................................82
A.7.2  Vapour Fraction Flash ..............................................................83
A.7.3  Enthalpy Flash........................................................................85
A.7.4  Entropy Flash .........................................................................85
A.7.5  Electrolyte Flash .....................................................................85
A.7.6  Handling of Water ...................................................................86
A.7.7  Supercritical Handling..............................................................88
A.7.8  Solids....................................................................................89
A.7.9  Stream Information.................................................................90
A.8  References ...................................................................................91
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ThA.1 Introduction
This appendix is organized such that the detailed calculations 
that occur within the Simulation Basis Manager and within the 
Flowsheet are explained in a logical manner.
• In the first section, an overview of property method 
selection is presented. Various process systems and their 
recommended property methods are listed.
• Detailed information is provided concerning each 
individual property method available in Aspen HYSYS. 
This section is further subdivided into equations of state, 
activity models, Chao-Seader based semi-empirical 
methods, vapour pressure models, and miscellaneous 
methods.
• Following the detailed property method discussion is the 
section concerning enthalpy and entropy departure 
calculations. The enthalpy and entropy options available 
within Aspen HYSYS are largely dependent upon your 
choice of a property method.
• The physical and transport properties are covered in 
detail. The methods used by Aspen HYSYS in calculating 
liquid density, vapour density, viscosity, thermal 
conductivity, and surface tension are listed.
• Aspen HYSYS handles volume flow calculations in a 
unique way. To highlight the methods involved in 
calculating volumes, a separate section is provided.
• The next section ties all of the previous information 
together. Within Aspen HYSYS, the Flash calculation uses 
the equations of the selected property method, as well as 
the physical and transport property functions to 
determine all property values for Flowsheet streams. 
After a flash calculation is performed on an object, all of 
its thermodynamic, physical and transport properties are 
defined. The flash calculation in Aspen HYSYS does not 
require initial guesses or the specification of flash type to 
assist in its convergence.
• A list of References is included at the end of the 
Appendix.A-3
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A-4 Selecting Property Methods
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ThA.2 Selecting Property 
Methods
The property packages available in Aspen HYSYS allow you to 
predict properties of mixtures ranging from well defined light 
hydrocarbon systems to complex oil mixtures and highly non-
ideal (non-electrolyte) chemical systems. Aspen HYSYS provides 
options for:
• Enhanced equations of state (PR and PRSV) for rigorous 
treatment of hydrocarbon systems
• Semi-empirical and vapour pressure models for the 
heavier hydrocarbon systems
• Steam correlations for accurate steam property 
predictions
• Activity coefficient models for chemical systems
All of these equations have their own inherent limitations and 
you are encouraged to become more familiar with the 
application of each equation.
The following table lists some typical systems and 
recommended correlations. However, when in doubt of the 
accuracy or application of one of the property packages, contact 
AspenTech to receive additional validation material or our best 
estimate of its accuracy.
Type of System Recommended Property Method
TEG Dehydration PR
Sour Water Sour PR
Cryogenic Gas Processing PR, PRSV, TST
Air Separation PR, PRSV, TST
Atm Crude Towers PR, PR Options, GS, TST
Vacuum Towers PR, PR Options, GS (<10 mm Hg), 
Braun K10, Esso K, TST
Ethylene Towers Lee Kesler Plocker
High H2 Systems PR, ZJ, GS (see T/P limits), TST
Reservoir Systems PR, PR Options, TST
Steam Systems Steam Package, CS or GS
Hydrate Inhibition PR
Chemical systems Activity Models, PRSVA-4
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ThA.2.1 Activity Models
The Activity Model options in Aspen HYSYS are Chien Null, 
Extended NRTL, General NRTL, Margules, NRTL, UNIQUAC, Van 
Laar, and Wilson.
Activity Models, which handle highly non-ideal systems, are 
much more empirical in nature when compared to the property 
predictions in the hydrocarbon industry. Polar or non-ideal 
chemical systems are traditionally handled using dual model 
approaches. In this type of approach, an equation of state is 
used for predicting the vapour fugacity coefficients and an 
activity coefficient model is used for the liquid phase. Since the 
experimental data for activity model parameters are fitted for a 
specific range, these property methods cannot be used as 
reliably for generalized application.
A.2.2 Chao Seader Models
The Chao Seader Model options in Aspen HYSYS are Chao 
Seader and Grayson Streed.
The Chao Seader Models, though limited in scope, may be 
preferred in some instances. For example, they are 
recommended for problems containing mainly liquid or vapour 
H2O because they include special correlations that accurately 
represent the steam tables. 
• The Chao Seader method can be used for light 
hydrocarbon mixtures. 
HF Alkylation PRSV, NRTL (Contact AspenTech)
TEG Dehydration with Aromatics PR (Contact AspenTech)
Hydrocarbon systems where H2O 
solubility in HC is important
Kabadi Danner
Systems with select gases and light 
hydrocarbons
MBWR
Type of System Recommended Property MethodA-5
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A-6 Selecting Property Methods
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Th• The Grayson-Streed correlation is recommended for use 
with systems having a high concentration of H2 because 
of the special treatment given H2 in the development of 
the model. This correlation may also be slightly more 
accurate in the simulation of vacuum towers.
The Chao Seader and Grayson Streed packages can also be used 
for three-phase flashes, but are restricted to the use of pure 
H2O for the second liquid phase.
A.2.3 Equations of State (EOS)
The Equation of State (EOS) models include BWRS, GCEOS, 
Glycol Package, Kabadi-Danner, Lee-Kesler-Plocker, MBWR, 
Peng-Robinson, PR-Twu, PRSV, Sour PR, Sour SRK, SRK, SRK-
Twu, Twu-Sim-Tassone, and Zudkevitch-Joffee.
Peng-Robinson (PR)
For oil, gas, and petrochemical applications, the Peng-Robinson 
EOS (PR) is generally the recommended property package. 
Enhancements to this equation of state enable it to be accurate 
for a variety of systems over a wide range of conditions. It 
rigorously solves any single-, two-, or three-phase system with 
a high degree of efficiency and reliability and is applicable over a 
wide range of conditions, as shown in the following table.
The PR EOS is enhanced to yield accurate phase equilibrium 
calculations for systems ranging from low-temperature 
cryogenic systems to high-temperature, high-pressure reservoir 
systems. The same EOS satisfactorily predicts component 
distributions for heavy oil, aqueous glycol, and CH3OH systems. 
Method Temp (°F) Temp (°C) Pressure (psia) Pressure (kPa)
PR > -456 > -271 < 15,000 < 100,000
The range of applicability in many cases is more indicative of 
the availability of good data rather than on the actual 
limitations.A-6
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ThThe PR EOS perform rigorous three-phase flash calculations for 
aqueous systems containing H2O, CH3OH or glycols, as well as 
systems containing other hydrocarbons or non-hydrocarbons in 
the second liquid phase.
The PR can also be used for crude systems, which have 
traditionally been modeled with dual model thermodynamic 
packages (an activity model representing the liquid phase 
behaviour, and an EOS or the ideal gas law for the vapour phase 
properties). These earlier models are suspect for systems with 
large amounts of light ends or when approaching critical 
regions. Also, the dual model system leads to internal 
inconsistencies. The proprietary enhancements to the PR 
method allow it to correctly represent vacuum conditions and 
heavy components (a problem with traditional EOS methods), 
as well as handle the light ends and high-pressure systems.
Soave-Redlich-Kwong (SRK)
The Soave-Redlich-Kwong (SRK) equation also provides 
comparable results to the PR in many cases. However, the SRK 
range of application is significantly limited and it is not as 
reliable for non-ideal systems. For example, it should not be 
used for systems with CH3OH or glycols.
The SRK can also be used for crude systems, which have 
traditionally been modeled with dual model thermodynamic 
packages (an activity model representing the liquid phase 
behaviour, and an equation of state or the ideal gas law for the 
vapour phase properties). These earlier models are suspect for 
systems with large amounts of light ends or when approaching 
critical regions. Also, the dual model system leads to internal 
inconsistencies. The proprietary enhancements to the SRK 
method allow it to correctly represent vacuum conditions and 
heavy components (a problem with traditional EOS methods), 
as well as handle the light ends and high-pressure systems.
Method Temp (°F) Temp (°C) Pressure (psia) Pressure (kPa)
PR > -456 > -271 < 15,000 < 100,000
SRK > -225 > -143 <  5,000 < 35,000A-7
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A-8 Selecting Property Methods
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ThAs an alternate, the PRSV EOS should also be considered. It can 
handle the same systems as the PR equation with equivalent, or 
better accuracy, plus it is more suitable for handling moderately 
non-ideal systems.
Peng-Robinson Stryjek-Vera (PRSV)
The PRSV equation of state can handle the same systems as the 
PR equation with equivalent, or better, accuracy. PRSV is also 
more suitable for handling moderately non-ideal systems.
The advantage of the PRSV equation is that not only does it 
have the potential to more accurately predict the phase 
behaviour of hydrocarbon systems, particularly for systems 
composed of dissimilar components, but it can also be extended 
to handle non-ideal systems with accuracies that rival traditional 
activity coefficient models. The only compromise is increased 
computational time and the additional interaction parameter 
that is required for the equation.
The PRSV equation of state performs rigorous three-phase flash 
calculations for aqueous systems containing H2O, CH3OH, or 
glycols, as well as systems containing other hydrocarbons or 
non-hydrocarbons in the second liquid phase. 
Twu-Sim-Tassone (TST)
The Twu-Sim-Tassone (TST) cubic equation of state (CEOS) 
model is another alternative property package for crude 
systems. TST uses the Twu alpha function and TST excess Gibbs 
energy mixing rules for the accurate prediction of K-values. TST 
also allows the EOS to describe both van der Waals fluids and 
highly non-ideal mixtures in a consistent and unified framework. 
TST is generalized as a linear function of acentric factor to allow 
the extension of its use to lower reduced temperatures and 
heavy hydrocarbons. The generalized EOS accurately represents 
the vapour pressure over the entire range of temperatures for 
both light and heavy hydrocarbons. Compared to SRK and PR, 
the TST EOS predicts similar accuracy in the vapor-liquid A-8
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Thequilibria of highly non-ideal systems over a wide range of 
temperature and pressure.
A.2.4 Vapour Pressure Models
The Vapour Pressure models include Antoine, Braun K10, and 
Esso Tabular.
The Vapour Pressure models are designed to handle heavier 
hydrocarbon systems at lower pressures. These equations are 
traditionally applied for heavier hydrocarbon fractionation 
systems and consequently provide a good means of comparison 
against rigorous models. They should not be considered for VLE 
predictions for systems operating at high pressures or systems 
with significant quantities of light hydrocarbons.
A.2.5 Miscellaneous Types
Property packages that do not fit into the other categories are 
listed as Miscellaneous Types. These models include Amine Pkg, 
ASME Steam, Aspen Properties, DBR Amine Package, Infochem 
Multiflash, NBS Steam, Neotec Black Oil, and OLI Electrolyte.
• Amine Pkg and DBR Amine Package are recommended 
for simulating the removal of acid gases (hydrogen 
sulphide and carbon dioxide) in natural gas plants and oil 
refineries
• ASME Steam and NBS Steam are recommended for 
steam systems.
• Neotec Black Oil is recommended for modeling the 
behaviour of a petroleum fluid downstream of the well 
and flowlines (systems where the liquid phase is a non-
volatile oil).
• Infochem Multiflash is recommended for modeling the 
properties of gases, liquids, and solids (characterize and 
match the properties of petroleum fluids, and multiphase 
flashes capable of handling any combination of phases).
• OLI Electrolyte is recommended for aqueous electrolyte 
systems.A-9
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A-10 Property Methods
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ThA.3 Property Methods
Details of each individual property method available in Aspen 
HYSYS are provided in this section, including equations of state, 
activity models, Chao-Seader based empirical methods, vapour 
pressure models, and miscellaneous methods.
The following table provides a summary of the available 
methods of VLE and Enthalpy/Entropy calculation for each of the 
Property Methods. 
Property Method VLE Calculation
Enthalpy/Entropy 
Calculation
Equations of State
PR PR PR
PR LK ENTH PR Lee-Kesler
SRK SRK SRK
SRK LK ENTH SRK Lee-Kesler
Kabadi Danner Kabadi Danner SRK
Lee Kesler Plocker Lee Kesler Plocker Lee Kesler
PRSV PRSV PRSV
PRSV LK PRSV Lee-Kesler
Sour PR PR & API-Sour PR
SOUR SRK SRK & API-Sour SRK
Zudkevitch-Joffee Zudkevitch-Joffee Lee-Kesler
Activity Models
Liquid
Chien Null Chien Null Cavett
Extended and General 
NRTL
NRTL Cavett
Margules Margules Cavett
NRTL NRTL Cavett
UNIQUAC UNIQUAC Cavett
van Laar van Laar Cavett
Wilson Wilson Cavett
Vapour
Ideal Gas Ideal Ideal Gas
RK RK RK
Virial Virial Virial
Peng Robinson Peng Robinson Peng Robinson
SRK SRK SRK
Please refer to Section 
A.4 - Enthalpy & 
Entropy Departure 
Calculations, for a 
description of Enthalpy 
and Entropy calculations.A-10
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ThA.3.1 Equations of State
Aspen HYSYS currently offers the following equations of state:
• Peng-Robinson14 (PR)
• Soave-Redlich-Kwong19 (SRK) 
• Twu-Sim-Tassone (TST) 
In addition, Aspen HYSYS offers several methods which are 
modifications of these property packages, including PRSV, 
Zudkevitch Joffee (ZJ), and Kabadi Danner (KD). Lee Kesler 
Plocker12 (LKP) is an adaptation of the Lee Kesler equation for 
mixtures, which itself was modified from the BWR equation. Of 
these, the PR EOS supports the widest range of operating 
conditions and the greatest variety of systems. The Peng-
Robinson and Soave-Redlich-Kwong EOSs generate all required 
equilibrium and thermodynamic properties directly. Although the 
forms of these EOS methods are common with other commercial 
simulators, they have been significantly enhanced by AspenTech 
to extend their range of applicability. 
Semi-Empirical Models
Chao-Seader CS-RK Lee-Kesler
Grayson-Streed GS-RK Lee-Kesler
Vapour Pressure Models
Mod Antoine Mod Antoine-Ideal Gas Lee-Kesler
Braun K10 Braun K10-Ideal Gas Lee-Kesler
Esso K Esso-Ideal Gas Lee-Kesler
Miscellaneous - Special Application Methods
Amines Mod Kent Eisenberg 
(L), PR (V)
Curve Fit
Steam Packages
ASME Steam ASME Steam Tables ASME Steam Tables
NBS Steam NBS/NRC Steam Tables NBS/NRC Steam Tables
MBWR Modified BWR Modified BWR
The properties predicted by the Aspen HYSYS PR and SRK 
equations of state do not necessarily agree with those 
predicted by the PR and SRK of other commercial simulators.
Property Method VLE Calculation
Enthalpy/Entropy 
CalculationA-11
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A-12 Property Methods
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ThThe Peng-Robinson property package options are PR, Sour PR, 
and PRSV. Soave-Redlich-Kwong equation of state options are 
the SRK, Sour SRK, KD, and ZJ.
PR & SRK
The PR and SRK packages contain enhanced binary interaction 
parameters for all library hydrocarbon-hydrocarbon pairs (a 
combination of fitted and generated interaction parameters), as 
well as for most hydrocarbon-nonhydrocarbon binaries.
For non-library or hydrocarbon hypocomponent, HC-HC 
interaction parameters are generated automatically by Aspen 
HYSYS for improved VLE property predictions.
The PR EOS applies a functionality to some specific component-
component interaction parameters. Key components receiving 
special treatment include He, H2, N2, CO2, H2S, H2O, CH3OH, 
EG, DEG, and TEG. For further information on application of 
equations of state for specific components, contact AspenTech.
The PR or SRK EOS should not be used for non-ideal 
chemicals such as alcohols, acids, or other components. They 
are more accurately handled by the Activity Models (highly 
non-ideal) or the PRSV EOS (moderately non-ideal).A-12
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ThThe following page provides a comparison of the formulations 
used in Aspen HYSYS for the PR and SRK equations of state. 
Soave Redlich Kwong Peng Robinson
  
where:
b=
 
bi=
a=
ai=
aci=
=
mi=
When an acentric factor > 0.49 is present Aspen 
HYSYS uses following corrected form:
A=
B=
P RT
V b–
------------ a
V V b+( )
---------------------–=
Z3 Z2– A B– B2–( )Z AB–+ 0=
P RT
V b–
------------ a
V V b+( ) b V b–( )+
------------------------------------------------–=
Z3 1 B–( )– Z2 A 2B– 3B2–( )Z AB B2– B3–( )–+ 0=
xibi
i 1=
N
∑ xibi
i 1=
N
∑
0.08664
RTci
Pci
---------- 0.077796
RTci
Pci
----------
xixj aiaj( )0.5 1 kij–( )
j 1=
N
∑
i 1=
N
∑ xixj aiaj( )0.5 1 kij–( )
j 1=
N
∑
i 1=
N
∑
aciαi aciαi
0.42747
RTci( )2
Pci
------------------ 0.457235
RTci( )2
Pci
------------------
αi
0.5 1 mi 1 Tri
0.5–( )+ 1 mi 1 Tri
0.5–( )+
0.48 1.574ωi 0.176ωi
2–+ 0.37464 1.54226ωi 0.26992ωi
2–+
0.379642 1.48503 0.164423 0.016666ωi–( )ωi–( )ωi+
aP
RT( )2
-------------- aP
RT( )2
--------------
bP
RT
------ bP
RT
------A-13
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A-14 Property Methods
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ThTwu-Sim-Tassone (TST)
The TST EOS model incorporates:
• Twu alpha function, which can accurately represent the 
vapor pressure of pure components
• Advanced zero-pressure mixing rules, which can 
accurately represent phase equilibria of complex non-
ideal systems
The required parameters for the Twu alpha function have been 
determined for the components in the Aspen HYSYS database. 
Binary interaction parameters for components typically 
encountered in the TEG hydration process have also been 
determined. Please refer to Section D.3.1 – TST Mixing Rules 
for a more thorough description of the TST EOS and its mixing 
rules.
Kabadi Danner (KD)
This KD10 model is a modification of the original SRK EOS, 
enhanced to improve the vapour-liquid-liquid equilibria 
calculations for H2O-hydrocarbon systems, particularly in the 
dilute regions.
The model is an improvement over previous attempts which 
were limited in the region of validity. The modification is based 
on an asymmetric mixing rule, whereby the interaction in the 
water phase (with its strong H2 bonding) is calculated based on 
both the interaction between the hydrocarbons and the H2O, 
and on the perturbation by hydrocarbon on the H2O-H2O 
interaction (due to its structure).A-14
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ThLee Kesler Plöcker Equation
The Lee Kesler Plöcker equation is an accurate general method 
for non-polar substances and mixtures.
Plöcker et al.3 applied the Lee Kesler equation to mixtures, 
which itself was modified from the BWR equation.
The compressibility factors are determined as follows:
The Lee Kesler Plöcker equation does not use the COSTALD 
correlation in computing liquid density. This may result in 
differences when comparing results between equation of 
states.
(A.1)
(A.2)
(A.3)
z z o( ) ω
ω r( )
--------- z r( ) z o( )–( )+=
z pv
RT
------
prvr
Tr
--------- z Tr vr Ak, ,( )= = =
z 1 B
vr
---- C
vr
2
---- D
vr
5
---- C4
Tr
3vr
2
---------- β γ
vr
2
----+ γ–
vr
2
-----exp+ + + +=A-15
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A-16 Property Methods
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Thwhere:
Mixing rules for pseudocritical properties are as follows:
(A.4)
vr
pcv
RTc
---------=
C c1
c2
Tr
----–
c3
Tr
2
-----+=
ω o( ) 0=
B b1
b2
Tr
----–
b3
Tr
2
-----–
b4
Tr
3
-----–=
D d1
d2
Tr
----–=
ω r( ) 0.3978=
Tcm
1
Vcm
η
---------
⎝ ⎠
⎜ ⎟
⎛ ⎞
xixjvcij
j
∑
i
∑=
Tcij
Tci
Tcj
( )1 2⁄= Tcii
Tci
= Tcjj
Tcj
=
vcm
xixjvcij
j
∑
i
∑=
vcij
1
8
-- vci
1 3⁄ vcj
1 3⁄+( )
3
=
vci
zci
RTci
pci
----------=
zci
0.2905 0.085ωi–=A-16
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Thpcm
zcm
RTcm
vcm
-----------=
zcm
0.2905 0.085ωm–=
ωm xiωi
i
∑=A-17
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A-18 Property Methods
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ThPeng-Robinson Stryjek-Vera
The Peng-Robinson Stryjek-Vera (PRSV) EOS is a two-fold 
modification of the PR EOS that extends the application of the 
original PR method for moderately non-ideal systems. It is 
shown to match vapour pressures curves of pure components 
and mixtures more accurately than the PR method, especially at 
low vapour pressures. 
It is successfully extended to handle non-ideal systems giving 
results as good as those obtained using excess Gibbs energy 
functions like the Wilson, NRTL, or UNIQUAC equations.
One of the proposed modifications to the PR equation of state by 
Stryjek and Vera was an expanded alpha ( ) term that became 
a function of acentricity and an empirical parameter ( ) used 
for fitting pure component vapour pressures. 
where:  
 = characteristic pure component parameter
 = acentric factor
The  parameters  for a large number of compounds are stored in 
the Aspen HYSYS database. These s are determined using the 
equation in A.5  instead of the original PRSV equation. This equation 
better fits the data over the entire T range because the experimental 
vapor pressure data generally covers the entire range of the saturation 
curve (generally from Tb up to the critical point: Tr = 1). If the original 
PRSV equation is used, only vapor pressure data up to Tr = 0.7  
have an effect on .
The adjustable ( ) term allows for a much closer fit of the pure 
component vapour pressure curves. This term is regressed 
(A.5)
α
κi
αi 1 κi 1 Tr
0.5–( )+[ ]
2
=
κi κ0i κ+ 1i 1 Tri
0.5+( ) 0.7 Tri
–( )=
κ0i 0.378893 1.4897153ωi 0.17131848ωi
2– 0.0196554ωi
3+ +=
κ1i
ωi
κ1 i
κ1i
κ1i
κ1iA-18
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Property Methods & Calculations A-19
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Thagainst the pure component vapour pressure for all components 
in Aspen HYSYS library.
For hypocomponents that are generated to represent oil 
fractions, Aspen HYSYS automatically regresses the  term for 
each hypocomponent against the Lee-Kesler vapour pressure 
curves. For individual user-added hypothetical components,  
terms can either be entered or they are automatically regressed 
against the Lee-Kesler, Gomez-Thodos or Reidel correlations.
The second modification consists of a new set of mixing rules for 
mixtures. Conventional mixing rules are used for the volume 
and energy parameters in mixtures, but the mixing rule for the 
cross term, aij, is modified to adopt a composition dependent 
form. Although two different mixing rules were proposed in the 
original paper, Aspen HYSYS has incorporated only the Margules 
expression for the cross term.
where:  
Although only a limited number of binary pairs are regressed for 
this equation, our limited experience suggests that the PRSV 
can be used to model moderately non-ideal systems such as 
H2O-alcohol systems, some hydrocarbon-alcohol systems. You 
can also model hydrocarbon systems with improved accuracy. 
Also, due to PRSV's better vapour pressure predictions, 
improved heat of vaporization predictions should be expected.
(A.6)
If kij =kji, the mixing rules reduce to the standard PR 
equation of state. 
Different values can be entered for each of the binary 
interaction parameters.
κ1i
κ1i
aij aiiajj( )0.5 1.0 xikij– xjkji–( )=
kij kji≠A-19
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A-20 Property Methods
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ThSour Water Options
Sour Water options in Aspen HYSYS take into account the 
presence of caustic (NaOH) and carboxylic acids (such as formic 
acid, acetic acid, acrylic acid, maleic acid, succinic acid, and 
benzoic acid).  These components affect the chemical 
equilibrium calculations to determine the concentration of ions 
(such as OH-, H+, HS-), which are then used to compute pH and 
solubility of CO2, H2S, and NH3.
The Sour option is available for both the PR and SRK equations 
of state. The Sour PR option combines the PR equation of state 
and Wilson's API-Sour Model for handling sour water systems, 
while Sour SRK uses the SRK equation of state with the Wilson 
model. 
The Sour options use the appropriate equation of state for 
calculating the fugacities of the vapour and liquid hydrocarbon 
phases as well as the enthalpy for all three phases. The K-values 
for the aqueous phase are calculated using Wilson's API-Sour 
method. This option uses Wilson's model to account for the 
ionization of the H2S, CO2, and NH3 in the aqueous water phase. 
The aqueous model employs a modification of Van Krevelen's 
original model with many of the key limitations removed. The K-
value of water is calculated using an empirical equation, which is 
a function of temperature only. More details of the model are 
available in the original API publication 955 titled "A New 
Correlation of NH3, CO2, and H2S Volatility Data from Aqueous 
Sour Water Systems."
The original model has the following ranges: 
• Temperatures between 20°C (68°F) and 140°C (285°F)
• Pressures up to 50 psi
• Composition range of 1 ppm to about 30% weight of 
dissolved ammonia, carboxylic acid, salts, and caustic
• pH range: 2 to 14
Use of either the PR or SRK equation of state to correct vapour 
phase non idealities extends this range, but due to lack of 
experimental data, exact ranges cannot be specified. The 
acceptable pressure ranges for the Aspen HYSYS model vary 
depending upon the concentration of the acid gases and H2O. A-20
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ThThe method performs well when the H2O partial pressure is 
below 100 psi.
This option may be applied to sour water strippers, hydrotreater 
loops, crude columns, or any process containing hydrocarbons, 
acid gases, and H2O.
Zudkevitch Joffee
The Zudkevitch Joffee model is a modification of the Redlich 
Kwong equation of state. This model is enhanced for better 
prediction of vapour liquid equilibria for hydrocarbon systems, 
and systems containing H2. The major advantage of this model 
over the previous version of the RK equation is the improved 
capability of predicting pure component equilibria, and the 
simplification of the method for determining the required 
coefficients for the equation. 
Enthalpy calculations for this model are performed using the Lee 
Kesler model. 
EOS Enthalpy Calculation
With any the Equation of State options except ZJ and LKP, you 
can specify whether the Enthalpy is calculated by either the 
Equation of State method or the Lee Kesler method. The ZJ and 
LKP must use the Lee Kesler method in Enthalpy calculations. 
Selection of an enthalpy method is done by selecting radio 
buttons in the Enthalpy Method group. 
The flash calculation is much slower than the standard EOS, 
because the method performs an ion balance for each K-
value calculation.
 Figure A.1A-21
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A-22 Property Methods
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ThSelecting the Lee Kesler Enthalpy option results in a combined 
property package employing the appropriate equation of state 
(either PR or SRK) for vapour-liquid equilibrium calculations and 
the Lee-Kesler equation for calculation of enthalpies and 
entropies.
The LK method yields comparable results to Aspen HYSYS' 
standard equations of state and has identical ranges of 
applicability. As such, this option with PR has a slightly greater 
range of applicability than with SRK.
Zero Kij Option
Aspen HYSYS automatically generates hydrocarbon-
hydrocarbon interaction parameters when values are unknown if 
the Estimate HC-HC/Set Non HC-HC to 0.0 radio button is 
selected. 
The Set All to 0.0 radio button turns off the automatic 
calculation of any estimated interaction coefficients between 
hydrocarbons. All binary interaction parameters that are 
obtained from the pure component library remain.
The Set All to 0.0 option may prove useful when trying to match 
results from other commercial simulators which may not supply 
interaction parameters for higher molecular weight 
The Lee-Kesler enthalpies may be slightly more accurate for 
heavy hydrocarbon systems, but require more computer 
resources because a separate model must be solved.
This option is set on the Binary Coeffs tab of the Fluid 
Package property view.
 Figure A.2
For information on the 
differences between EOS 
and LK methods, refer to 
the Section A.4 - 
Enthalpy & Entropy 
Departure 
Calculations.A-22
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Thhydrocarbons.
A.3.2 Activity Models
Although equation of state models have proven to be reliable in 
predicting properties of most hydrocarbon based fluids over a 
large range of operating conditions, their application is limited to 
primarily non-polar or slightly polar components. Polar or non-
ideal chemical systems are traditionally handled using dual 
model approaches. In this approach, an equation of state is 
used for predicting the vapour fugacity coefficients (normally 
ideal gas assumption or the Redlich Kwong, Peng-Robinson or 
SRK equations of state, although a Virial equation of state is 
available for specific applications) and an activity coefficient 
model is used for the liquid phase. Although there is 
considerable research being conducted to extend equation of 
state applications into the chemical arena (e.g., the PRSV 
equation), the state of the art of property predictions for 
chemical systems is still governed mainly by Activity Models. 
Activity Models are much more empirical in nature when 
compared to the property predictions (equations of state) 
typically used in the hydrocarbon industry. For example, they 
cannot be used as reliably as the equations of state for 
generalized application or extrapolating into untested operating 
conditions. Their tuning parameters should be fitted against a 
representative sample of experimental data and their 
application should be limited to moderate pressures. 
Consequently, more caution should be exercised when selecting 
these models for your simulation. 
Activity Models produce the best results when they are 
applied in the operating region for which the interaction 
parameters were regressed.A-23
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A-24 Property Methods
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ThThe phase separation or equilibrium ratio Ki for component i, 
defined in terms of the vapour phase fugacity coefficient and the 
liquid phase activity coefficient is calculated from the following 
expression:
where:  
 = liquid phase activity coefficient of component i
fi° = standard state fugacity of component i
P = system pressure
 = vapour phase fugacity coefficient of component i
Although for ideal solutions the activity coefficient is unity, for 
most chemical (non-ideal) systems this approximation is 
incorrect. Dissimilar chemicals normally exhibit not only large 
deviations from an ideal solution, but the deviation is also found 
to be a strong function of the composition. To account for this 
non-ideality, activity models were developed to predict the 
activity coefficients of the components in the liquid phase. The 
derived correlations were based on the excess Gibbs energy 
function, which is defined as the observed Gibbs energy of a 
mixture in excess of what it would be if the solution behaved 
ideally, at the same temperature and pressure. 
For a multi-component mixture consisting of ni moles of 
component i, the total excess Gibbs free energy is represented 
by the following expression:
where:  
 = activity coefficient for component i
(A.7)
(A.8)
Ki
yi
xi
---=
γi fi°
Pφi
---------=
γi
φi
GE RT ni γiln( )∑=
γiA-24
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Property Methods & Calculations A-25
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ThThe individual activity coefficients for any system can be 
obtained from a derived expression for excess Gibbs energy 
function coupled with the Gibbs-Duhem equation. The early 
models (Margules, van Laar) provide an empirical 
representation of the excess function that limits their 
application. The newer models such as Wilson, NRTL and 
UNIQUAC utilize the local composition concept and provide an 
improvement in their general application and reliability. All of 
these models involve the concept of binary interaction 
parameters and require that they be fitted to experimental data.
Since the Margules and van Laar models are less complex than 
the Wilson, NRTL and UNIQUAC models, they require less CPU 
time for solving flash calculations. However, these are older and 
more empirically based models and generally give poor results 
for strongly non-ideal mixtures such as alcohol-hydrocarbon 
systems, particularly for dilute regions. The Chien-Null model 
provides the ability to incorporate the different activity models 
within a consistent thermodynamic framework. Each binary can 
be represented by the model which best predicts its behaviour. 
The following table briefly summarizes recommended models for 
different applications (for a more detailed review, refer to the 
texts “The Properties of Gases & Liquids”17 and “Molecular 
Thermodynamics of Fluid Phase Equilibria” 16). 
A = Applicable; N/A = Not Applicable;? = Questionable; G = Good; LA = Limited Application
Vapour phase non-ideality can be taken into account for each 
activity model by selecting the Redlich-Kwong, Peng-Robinson, 
or SRK equations of state as the vapour phase model. When one 
Application Margules van Laar Wilson NRTL UNIQUAC
Binary Systems A A A  A A
Multicomponent 
Systems
LA LA A  A A
Azeotropic Systems A A A  A A
Liquid-Liquid Equilibria A A N/A  A A
Dilute Systems ? ? A A A
Self-Associating 
Systems
? ? A A A
Polymers N/A N/A N/A N/A A
Extrapolation ? ? G G GA-25
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A-26 Property Methods
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Thof the equations of state is used for the vapour phase, the 
standard form of the Poynting correction factor is always used 
for liquid phase correction. If dimerization occurs in the vapour 
phase, the Virial equation of state should be selected as the 
vapour phase model. 
The binary parameters required for the activity models are 
regressed based on the VLE data collected from DECHEMA, 
Chemistry Data Series12. There are over 16,000 fitted binary 
pairs in the Aspen HYSYS library. The structures of all library 
components applicable for the UNIFAC VLE estimation are also 
in the library. The Poynting correction for the liquid phase is 
ignored if ideal solution behaviour is assumed. 
If you are using the built-in binary parameters, the ideal gas 
model should be used. All activity models, with the exception of 
the Wilson equation, can automatically calculate three phases 
given the correct set of energy parameters. The vapour 
pressures used in the calculation of the standard state fugacity 
are based on the pure component coefficients in Aspen HYSYS' 
library using the modified form of the Antoine equation.
When your selected components exhibit dimerization in the 
vapour phase, the Virial option should be selected as the vapour 
phase model. Aspen HYSYS contains fitted parameters for many 
carboxylic acids, and can estimate values from pure component 
properties if the necessary parameters are not available. 
All of the binary parameters in the Aspen HYSYS library are 
regressed using an ideal gas model for the vapour phase.
Aspen HYSYS internally stored binary parameters are NOT 
regressed against three phase equilibrium data.
Refer to Section A.3.3 
- Activity Model 
Vapour Phase Options 
for a detailed description 
of the Virial option.A-26
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ThGeneral Remarks
The dual model approach for solving chemical systems with 
activity models cannot be used with the same degree of 
flexibility and reliability that the equations of state can be used 
for hydrocarbon systems. However, some checks can be devised 
to ensure a good confidence level in property predictions:
• Check the property package selected for applicability for 
the system considered and see how well it matches the 
pure component vapour pressures. Although the 
predicted pure component vapour pressures should 
normally be acceptable, the parameters are fitted over a 
large temperature range. Improved accuracies can be 
attained by regressing the parameters over the desired 
temperature range.
• The automatic UNIFAC generation of energy parameters 
in Aspen HYSYS is a very useful tool and is available for 
all activity models. However, it must be used with 
caution. The standard fitted values in Aspen HYSYS likely 
produce a better fit for the binary system than the 
parameters generated by UNIFAC. As a general rule, use 
the UNIFAC generated parameters only as a last resort.
• Always use experimental data to regress the energy 
parameters when possible. The energy parameters in 
Aspen HYSYS are regressed from experimental data, 
however, improved fits are still possible by fitting the 
parameters for the narrow operating ranges anticipated. 
The regressed parameters are based on data taken at 
atmospheric pressures. Exercise caution when 
extrapolating to higher or lower pressure (vacuum) 
applications. 
• Check the accuracy of the model for azeotropic systems. 
Additional fitting may be required to match the azeotrope 
with acceptable accuracy. Check not only for the 
temperature, but for the composition as well.
• If three phase behaviour is suspected, additional fitting 
of the parameters may be required to reliably reproduce 
the VLLE equilibrium conditions.
• An improvement in matching equilibrium data can be 
attained by including a temperature dependency of the 
energy parameters. However, depending on the validity 
or range of fit, this can lead to misleading results when 
extrapolating beyond the fitted temperature range.
By default, Aspen HYSYS regresses ONLY the aij parameters 
while the bij parameters are set to zero, i.e., the aij term is 
assumed to be temperature independent. A temperature 
dependency can be incorporated by supplying a value for the bij A-27
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A-28 Property Methods
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Thterm. The matrix for the bij values are displayed by selecting the 
Bij radio button to switch matrices (note the zero or blank 
entries for all the binary pairs).
When using the NRTL, General NRTL or Extended NRTL 
equations, more than two matrices are available. In general, the 
second matrix is the Bij matrix, and the third matrix is the  
parameter where . Any component pair with an aij value 
has an associated  value.
Immiscible
This option is included for modeling the solubility of solutes in 
two coexisting liquid phases that are relatively immiscible with 
one another, such as a H2O-hydrocarbon system. In this system, 
the hydrocarbon components (solutes) are relatively insoluble in 
the water phase (solvent) whereas the solubility of the H2O in 
the hydrocarbon phase can become more significant. The limited 
mutual solubility behaviour can be taken into account when 
using any activity model with the exception of Wilson.
This feature can be implemented for any single component pair 
by using the Immiscible radio button. Component i is insoluble 
with component j, based on the highlighted cell location. 
Alternatively, you can have all j components treated as insoluble 
with component i. Aspen HYSYS replaces the standard binary 
parameters with those regressed specifically for matching the 
solubilities of the solutes in both phases.
The activities for the unknown binaries are generated at pre-
selected compositions and the supplied UNIFAC reference 
temperature.
The Wilson equation does not support LLE equilibrium.
Both the aij and bij parameters are regressed with the 
immiscible option.
αij
αij αji=
α
A-28
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ThThese parameters were regressed from the mutual solubility 
data of n-C5, n-C6, n-C7, and n-C8 in H2O over a temperature 
range of 313 K to 473 K.
The solubility of H2O in the hydrocarbon phase and the solubility 
of the hydrocarbons in the water phase are calculated based on 
the fitted binary parameters regressed from the solubility data 
referenced above.
Chien-Null
The Chien Null model provides a consistent framework for 
applying existing activity models on a binary by binary basis. In 
this manner, the Chien Null model allows you to select the best 
activity model for each pair in the case.
The Chien Null model allows three sets of coefficients for each 
component pair, accessible through the A, B and C coefficient 
matrices. Please refer to the following sections for an 
explanation of the terms for each of the models.
Chien Null Form
The Chien-Null generalized multi-component equation can be 
expressed as follows:
Each of the parameters in this equation are defined specifically 
for each of the applicable activity methods. 
(A.9)
2 Γi
Lln
Aj i,  xj
j
∑⎝ ⎠
⎜ ⎟
⎛ ⎞
Rj i,  xj
j
∑⎝ ⎠
⎜ ⎟
⎛ ⎞
Sj i,  xj
j
∑⎝ ⎠
⎜ ⎟
⎛ ⎞
Vj i,  xj
j
∑⎝ ⎠
⎜ ⎟
⎛ ⎞
------------------------------------------------------- xk
Aj k,   xj
j
∑⎝ ⎠
⎜ ⎟
⎛ ⎞
Rj k,   xj
j
∑⎝ ⎠
⎜ ⎟
⎛ ⎞
Sj k,  xj
j
∑⎝ ⎠
⎜ ⎟
⎛ ⎞
Vj k,  xj
j
∑⎝ ⎠
⎜ ⎟
⎛ ⎞
------------------------------------------------------------  ⋅
k
∑+=
Ai k,  
Aj k,  xj
j
∑
----------------------
Ri k,  
Rj k,  xj
j
∑
----------------------
Si k,  
Sj k,  xj
j
∑
---------------------–
Vi k,  
Vj k,  xj
j
∑
----------------------–+A-29
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ThDescription of Terms
The Regular Solution equation uses the following:
 is the solubility parameter in (cal/cm3)½ and vi
L is the 
saturated liquid volume in cm3/mol calculated from:
The van Laar, Margules and Scatchard Hamer use the following:
For the van Laar, Margules and Scatchard Hamer equations:
where:  
T = temperature unit must be in K
(A.10)
(A.11)
Ai j,
vi
L δi δj–( )2
RT
---------------------------= Ri j,
Ai j,
Aj i,
--------= Vi j, Ri j,= Si j, Ri j,=
δi
vi
L vω i, 5.7 3Tr i,+( )=
Model Ai,j Ri,j Si,j Vi,j
van Laar
Margules
Scatchard Hamer
γi j,
∞ln Ai j,
Aj i,
--------
Ri j, Ri j,
2 γi j,
∞ln
1
γi j,
∞ln
γj i,
∞ln
----------------
⎝ ⎠
⎜ ⎟
⎛ ⎞
+
-------------------------------
Ai j,
Aj i,
--------
1 1
2 γi j,
∞ln
1
γi j,
∞ln
γj i,
∞ln
----------------
⎝ ⎠
⎜ ⎟
⎛ ⎞
+
-------------------------------
Ai j,
Aj i,
-------- vi
∞
vj
∞
-----
vi
∞
vj
∞
-----
(A.12)γi j,
∞ln ai j,
bi j,
T
------- cijT+ +=A-30
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ThThe NRTL form for the Chien Null uses:
The expression for the  term under the Chien Null incorporates 
the R term of Aspen HYSYS' NRTL into the values for aij and bij. 
As such, the values initialized for NRTL under Chien Null are not 
the same as for the regular NRTL. When you select NRTL for a 
binary pair, aij is empty (essentially equivalent to the regular 
NRTL bij term), bij is initialized and cij is the  term for the 
original NRTL, and is assumed to be symmetric. 
The General Chien Null equation is:
In all cases:
With the exception of the Regular Solution option, all models 
can utilize six constants, ai,j, aj,i, bi,j, bj,i, ci,j and cj,i for each 
component pair. For all models, if the constants are unknown 
they can be estimated internally from the UNIFAC VLE or LLE 
methods, the Insoluble option, or using Henry's Law coefficients 
for appropriate components. For the general Chien Null model, 
The Equation (A.12) is of a different form than the original 
van Laar and Margules equations in Aspen HYSYS, which 
uses an a + bT relationship. However, since Aspen HYSYS 
only contains aij values, the difference should not cause 
problems.
If you have regressed parameters using HYPROP for any of 
the Activity Models supported under the Chien Null, they are 
not read in.
(A.13)Ai j, 2τi j, Vi j,= Ri j, 1= Vi j, ci j,– τi j,( )exp= Si j, 1= τi j, ai j,
bi j,
T K( )
-----------+=
(A.14)
(A.15)
τ
α
Ai j, ai j,
bi j,
T K( )
-----------+= Ri j,
Ai j,
Aj i,
--------= Vi j, Ci j,= Si j, Ci j,=
Ai i, 0= Ri i, Si i, Vi i, 1= = =A-31
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A-32 Property Methods
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Ththe cij's are assumed to be 1.
Extended & General NRTL
The Extended and General NRTL models are variations of the 
NRTL model. More binary interaction parameters are used in 
defining the component activity coefficients. You may apply 
either model to systems:
• with a wide boiling point range between components.
• where you require simultaneous solution of VLE and LLE, 
and there exists a wide boiling point range or 
concentration range between components.
You can specify the format for the Equations of  and  to be 
any of the following: 
Options
where:
T = temperature in K
t = temperature in °C
τij αij
τij Aij
Bij
T
------
Cij
T2
------ FijT Gij T( )ln+ + + +=
αij Alp1i j Alp2ijT+=
τij
Aij
Bij
T
------+
RT
-------------------=
αi j Alp1ij=
τij Aij
Bij
T
------ FijT Gij T( )ln+ + +=
αij Alp1ij Alp2i jT+=
τij Aij Bijt
Cij
T
------+ +=
αij Alp1ij Alp2ijT+=
τij Aij
Bij
T
------+=
αi j Alp1ij=A-32
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ThDepending on which form of the equations that you have 
selected, you are able to specify values for the different 
component energy parameters. The General NRTL model 
provides radio buttons on the Binary Coeffs tab which access the 
matrices for the Aij, Bij, Cij, Fij, Gij, Alp1ij and Alp2ij energy 
parameters.
The Extended NRTL model allows you to input values for the Aij, 
Bij, Cij, Alp1ij and Alp2ij energy parameters by selecting the 
appropriate radio button. You do not have a choice of equation 
format for  and . The following is used:
where:  
T = temperature in K
t = temperature in °C
Margules
The Margules equation was the first Gibbs excess energy 
representation developed. The equation does not have any 
theoretical basis, but is useful for quick estimates and data 
interpolation. Aspen HYSYS has an extended multicomponent 
Margules equation with up to four adjustable parameters per 
binary.
The four adjustable parameters for the Margules equation in 
Aspen HYSYS are the aij and aji (temperature independent) and 
The equations options can be viewed in the Display Form 
drop-down list on the Binary Coeffs tab of the Fluid Package 
property view.
(A.16)
The equation should not be used for extrapolation beyond 
the range over which the energy parameters are fitted.
τij αij
τij Aij Bijt
Cij
T
------+ +⎝ ⎠
⎛ ⎞=
αij Alp1i j Alp2i j+=A-33
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A-34 Property Methods
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Ththe bij and bji terms (temperature dependent). The equation 
uses parameter values stored in Aspen HYSYS or any user 
supplied value for further fitting the equation to a given set of 
data. 
The Margules activity coefficient model is represented by the 
following equation: 
where:  
 = activity coefficient of component i
xi = mole fraction of component i
Ai = 
Bi = 
T = temperature (K)
n = total number of components
aij = non-temperature dependent energy parameter between 
components i and j
bij = temperature dependent energy parameter between 
components i and j [1/K]
aji = non-temperature dependent energy parameter between 
components j and i
bji = temperature dependent energy parameter between 
components j and i [1/K]
NRTL
The NRTL (Non-Random-Two-Liquid) equation, proposed by 
Renon and Prausnitz in 1968, is an extension of the original 
Wilson equation. It uses statistical mechanics and the liquid cell 
(A.17)γiln 1.0 xi–[ ]2 Ai 2xi Bi Ai–( )+[ ]=
γi
xj
aij bijT+( )
1.0 xi–( )
--------------------------
j 1=
n
∑
xj
aji bjiT+( )
1.0 xi–( )
--------------------------
j 1=
n
∑
A-34
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Ththeory to represent the liquid structure. These concepts, 
combined with Wilson's local composition model, produce an 
equation capable of representing VLE, LLE and VLLE phase 
behaviour. 
Like the Wilson equation, the NRTL is thermodynamically 
consistent and can be applied to ternary and higher order 
systems using parameters regressed from binary equilibrium 
data. It has an accuracy comparable to the Wilson equation for 
VLE systems.
The NRTL equation in Aspen HYSYS contains five adjustable 
parameters (temperature dependent and independent) for 
fitting per binary pair. The NRTL combines the advantages of the 
Wilson and van Laar equations.
• Like the van Laar equation, NRTL is not extremely CPU 
intensive and can represent LLE quite well. 
• Unlike the van Laar equation, NRTL can be used for dilute 
systems and hydrocarbon-alcohol mixtures, although it 
may not be as good for alcohol-hydrocarbon systems as 
the Wilson equation.
The NRTL equation in Aspen HYSYS has the following form:
where:  
 = activity coefficient of component i
Gij = 
 = 
Due to the mathematical structure of the NRTL equation, it 
can produce erroneous multiple miscibility gaps. 
(A.18)γiln
τjixjGji
j 1=
n
∑
xkGki
k 1=
n
∑
---------------------------
xjGij
xkGkj
k 1=
n
∑
----------------------- τij
τmjxmGmj
m 1=
n
∑
xkGkj
k 1=
n
∑
-----------------------------------–
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎛ ⎞
j 1=
n
∑+=
γi
τijαij–[ ]exp
τij
aij bijT+
RT
---------------------A-35
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A-36 Property Methods
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Thxi = mole fraction of component i
T = temperature (K)
n = total number of components
aij = non-temperature dependent energy parameter between 
components i and j (cal/gmol)
bij = temperature dependent energy parameter between 
components i and j (cal/gmol-K)
 = NRTL non-randomness constant for binary interaction 
note that  for all binaries
The five adjustable parameters for the NRTL equation in Aspen 
HYSYS are the aij, aji, bij, bji, and  terms. The equation uses 
parameter values stored in Aspen HYSYS or any user supplied 
value for further fitting the equation to a given set of data.
UNIQUAC
The UNIQUAC (UNIversal QUAsi Chemical) equation proposed 
by Abrams and Prausnitz in 1975 uses statistical mechanics and 
the quasi-chemical theory of Guggenheim to represent the liquid 
structure. The equation is capable of representing LLE, VLE and 
VLLE with accuracy comparable to the NRTL equation, but 
without the need for a non-randomness factor. The UNIQUAC 
equation is significantly more detailed and sophisticated than 
any of the other activity models. Its main advantage is that a 
good representation of both VLE and LLE can be obtained for a 
large range of non-electrolyte mixtures using only two 
adjustable parameters per binary. The fitted parameters usually 
exhibit a smaller temperature dependence which makes them 
more valid for extrapolation purposes. 
The UNIQUAC equation utilizes the concept of local composition 
as proposed by Wilson. Since the primary concentration variable 
is a surface fraction as opposed to a mole fraction, it is 
applicable to systems containing molecules of very different 
sizes and shape, such as polymer solutions. The UNIQUAC 
equation can be applied to a wide range of mixtures containing 
H2O, alcohols, nitriles, amines, esters, ketones, aldehydes, 
halogenated hydrocarbons and hydrocarbons. 
αij
αij αji=
αijA-36
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ThAspen HYSYS contains the following four-parameter extended 
form of the UNIQUAC equation. The four adjustable parameters 
for the UNIQUAC equation in Aspen HYSYS are the aij and aji 
terms (temperature independent), and the bij and bji terms 
(temperature dependent). 
The equation uses parameter values stored in Aspen HYSYS or 
any user supplied value for further fitting the equation to a 
given set of data.
where:  
 = activity coefficient of component i
xi = mole fraction of component i
T = temperature (K)
n = total number of components
Lj = 0.5Z(rj-qj)-rj+1
 = 
 = 
 = 
(A.19)γiln
Φi
xi
-----⎝ ⎠
⎛ ⎞ln 0.5Zqi
θi
Φi
-----⎝ ⎠
⎛ ⎞ Li
Φi
xi
-----⎝ ⎠
⎛ ⎞ Ljxj qi 1.0 θjτji
j 1=
n
∑ln–
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎛ ⎞
qi
θjτi j
θkτkj
k 1=
n
∑
----------------------
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎜ ⎟
⎛ ⎞
j 1=
n
∑–+
j 1=
n
∑–+ln+=
γi
θi
qixi
qjxj
j
∑
---------------
τij
aij bijT+
RT
---------------------–exp
Φi
rixi
rjxj
j
∑
---------------A-37
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A-38 Property Methods
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ThZ = 10.0 co-ordination number
aij = non-temperature dependent energy parameter between 
components i and j (cal/gmol)
bij = temperature dependent energy parameter between 
components i and j (cal/gmol-K)
qi = van der Waals area parameter - Awi /(2.5e9)
Aw = van der Waals area
ri = van der Waals volume parameter - Vwi /(15.17)
Vw = van der Waals volume
Van Laar 
The van Laar equation was the first Gibbs excess energy 
representation with physical significance. The van Laar equation 
in Aspen HYSYS is a modified form of that described in “Phase 
Equilibrium in Process Design” by H.R. Null. This equation fits 
many systems quite well, particularly for LLE component 
distributions. It can be used for systems that exhibit positive or 
negative deviations from Raoult's Law, however, it cannot 
predict maxima or minima in the activity coefficient. Therefore, 
it generally performs poorly for systems with halogenated 
hydrocarbons and alcohols. Due to the empirical nature of the 
equation, caution should be exercised in analyzing multi-
component systems. It also has a tendency to predict two liquid 
phases when they do not exist. 
The van Laar equation has some advantages over the other 
activity models in that it requires less CPU time and can 
represent limited miscibility as well as three phase equilibrium. 
Aspen HYSYS uses the following extended, multi-component 
form of the van Laar equation.
The van Laar equation also performs poorly for dilute 
systems and cannot represent many common systems, such 
as alcohol-hydrocarbon mixtures, with acceptable accuracy.
(A.20)γiln Ai 1.0 zi–[ ]2 1.0 Eizi+( )=A-38
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Thwhere:  
 = activity coefficient of component i
xi = mole fraction of component i
Ai = 
Bi = 
Ei = -4.0 if Ai and Bi < 0.0, otherwise 0.0
zi = 
T = temperature (K)
n = total number of components
aij = non-temperature dependent energy parameter between 
components i and j
bij = temperature dependent energy parameter between 
components i and j [1/K]
aji = non-temperature dependent energy parameter between 
components j and i
bji = temperature dependent energy parameter between 
components j and i [1/K]
The four adjustable parameters for the van Laar equation in 
Aspen HYSYS are the aij, aji, bij, and bji terms. The equation will 
use parameter values stored in Aspen HYSYS or any user 
supplied value for further fitting the equation to a given set of 
data. 
Wilson
The Wilson equation, proposed by Grant M. Wilson in 1964, was 
the first activity coefficient equation that used the local 
composition model to derive the Gibbs Excess energy 
expression. It offers a thermodynamically consistent approach 
to predicting multi-component behaviour from regressed binary 
γi
xj
aij bijT+( )
1.0 xi–( )
--------------------------
j 1=
n
∑
xj
aji bjiT+( )
1.0 xi–( )
--------------------------
j 1=
n
∑
Aixi
Aixi Bi 1.0 xi–( )+[ ]
------------------------------------------------A-39
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Thequilibrium data. Our experience also shows that the Wilson 
equation can be extrapolated with reasonable confidence to 
other operating regions with the same set of regressed energy 
parameters. 
Although the Wilson equation is more complex and requires 
more CPU time than either the van Laar or Margules equations, 
it can represent almost all non-ideal liquid solutions 
satisfactorily except electrolytes and solutions exhibiting limited 
miscibility (LLE or VLLE). It performs an excellent job of 
predicting ternary equilibrium using parameters regressed from 
binary data only. 
The Wilson equation gives similar results as the Margules and 
van Laar equations for weak non-ideal systems, but consistently 
outperforms them for increasingly non-ideal systems.
The Wilson equation in Aspen HYSYS requires two to four 
adjustable parameters per binary. The four adjustable 
parameters for the Wilson equation in Aspen HYSYS are the aij 
and aji (temperature independent) terms, and the bij and bji 
terms (temperature dependent). Depending upon the available 
information, the temperature dependent parameters may be set 
to zero. 
Although the Wilson equation contains terms for temperature 
dependency, caution should be exercised when extrapolating. 
The Wilson activity model in Aspen HYSYS has the following 
The Wilson equation cannot be used for problems involving 
liquid-liquid equilibrium.
Setting all four parameters to zero does not reduce the 
binary to an ideal solution, but maintains a small effect due 
to molecular size differences represented by the ratio of 
molar volumes.A-40
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Thform:
where:  
 = activity coefficient of component i
Aij = 
xi = mole fraction of component i
T = temperature (K)
n = total number of components
aij = non-temperature dependent energy parameter between 
components i and j (cal/gmol)
bij = temperature dependent energy parameter between 
components i and j (cal/gmol-K)
Vi = molar volume of pure liquid component i in m3/kgmol 
(litres/gmol)
The equation uses parameter values stored in Aspen HYSYS or 
any user supplied value for further fitting the equation to a 
given set of data. 
(A.21)γiln 1.0 xjAij
xkAki
xjAkj
j 1=
n
∑
---------------------
k 1=
n
∑–
j 1=
n
∑ln–=
γi
Vj
Vi
----
aij bijT+( )
RT
--------------------------–expA-41
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A-42 Property Methods
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ThHenry’s Law
Henry's Law cannot be selected explicitly as a property method 
in Aspen HYSYS. However, Aspen HYSYS uses Henry's Law when 
an activity model is selected and "non-condensable" 
components are included within the component list.
Aspen HYSYS considers the following components "non-
condensable":
The extended Henry's Law equation in Aspen HYSYS is used to 
model dilute solute/solvent interactions. "Non-condensable" 
components are defined as those components that have critical 
temperatures below the temperature of the system you are 
modeling. The equation has the following form:
Component Simulation Name
CH4 Methane
C2H6 Ethane
C2H4 Ethylene
C2H2 Acetylene
H2 Hydrogen
He Helium
Ar Argon
N2 Nitrogen
O2 Oxygen
NO NO 
H2S H2S 
CO2 CO2 
CO CO
(A.22)Hijln A B
T
--- C T( ) DT+ln+ +=A-42
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Thwhere:  
i = solute or "non-condensable" component
j = solvent or condensable component
Hij = Henry's coefficient between i and j in kPa
A = A coefficient entered as aij in the parameter matrix 
B = B coefficient entered as aji in the parameter matrix 
C = C coefficient entered as bij in the parameter matrix
D = D coefficient entered as bji in the parameter matrix
T = temperature in degrees K
An example of the use of Henry's Law coefficients is illustrated 
below. The NRTL activity model is selected as the property 
method. There are three components in the Fluid Package, one 
of which, ethane, is a "non-condensable" component. On the 
Binary Coeffs tab of the Fluid Package property view, you can 
view the Henry's Law coefficients for the interaction of ethane 
and the other components. 
By selecting the Aij radio button, you can view/edit the A and B 
coefficients. Select the Bij radio button to enter or view the C 
and D coefficients in the Henry's Law equation.A-43
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ThIf Aspen HYSYS does not contain pre-fitted Henry's Law 
coefficients and Henry's Law data is not available, Aspen HYSYS 
estimates the missing coefficients. To estimate a coefficient (A 
or B in this case), select the Aij radio button, highlight a binary 
pair and press the Individual Pair button. The coefficients are 
regressed to fugacities calculated using the Chao-Seader/
Prausnitz-Shair correlations for standard state fugacity and 
Regular Solution. To supply your own coefficients you must 
enter them directly into the Aij and Bij matrices, as shown 
previously. 
No interaction between "non-condensable" component pairs is 
taken into account in the VLE calculations.
 Figure A.3
Aspen HYSYS does 
not contain a pre-
fitted Henry's Law 
A coefficient for 
the ethane/ethanol 
pair. You can 
estimate it or 
provide your own 
value.
Henry's 
Law A 
coefficient 
for the 
interaction 
between C2 
and H2O.
Normal binary 
interaction 
coefficient for 
the H2O/
Ethanol pair.
C2 is a "non-condensable" 
component. Henry's Law 
is used for the interaction 
between C2 and the other 
components in the Fluid 
Package. 
Henry's Law B 
coefficient for the 
interaction 
between C2 and 
H2O.
Henry's Law D 
coefficient for the 
interaction between 
C2 and H2O.
Henry's Law C 
coefficient for 
the interaction 
between C2 and 
H2O.A-44
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ThA.3.3 Activity Model Vapour 
Phase Options
There are several models available for calculating the Vapour 
Phase in conjunction with the selected liquid activity model. The 
selection depends on specific considerations of your system. 
However, in cases when you are operating at moderate 
pressures (less than 5 atm), selecting Ideal Gas should be 
satisfactory. The choices are described in the following sections.
Ideal
The ideal gas law is used to model the vapour phase. This model 
is appropriate for low pressures and for a vapour phase with 
little intermolecular interaction.
Peng Robinson, SRK, or RK
To model non-idealities in the vapour phase, the PR, SRK, or RK 
options can be used in conjunction with an activity model. The 
PR and SRK vapour phase models handle the same types of 
situations as the PR and SRK equations of state.
When selecting one of these options (PR, SRK, or RK) as the 
vapour phase model, you must ensure that the binary 
interaction parameters used for the activity model remain 
applicable with the selected vapour model. You must keep in 
mind that all the binary parameters in the Aspen HYSYS Library 
are regressed using the ideal gas vapour model.
For applications where you have compressors or turbines being 
modeled within your Flowsheet, PR or SRK is superior to either 
the RK or ideal vapour model. You obtain more accurate 
horsepower values by using PR or SRK, as long as the light 
components within your Flowsheet can be handled by the 
selected vapour phase model (i.e., C2H4 or C3H6 are fine, but 
alcohols are not modeled correctly).
For more information, 
refer to Section A.3.1 - 
Equations of State.A-45
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ThVirial
The Virial option enables you to better model vapour phase 
fugacities of systems displaying strong vapour phase 
interactions. Typically this occurs in systems containing 
carboxylic acids or compounds that have the tendency to form 
stable H2 bonds in the vapour phase. In these cases, the 
fugacity coefficient shows large deviations from ideality, even at 
low or moderate pressures.
Aspen HYSYS contains temperature dependent coefficients for 
carboxylic acids. You can overwrite these by changing the 
Association (ii) or Solvation (ij) coefficients from the default 
values.13
If the virial coefficients need to be calculated, Aspen HYSYS 
contains correlations using the following pure component 
properties:
• critical temperature
• critical pressure
• dipole moment
• mean radius of gyration
• association parameter
• association parameter for each binary pair
Aspen HYSYS recommends you use the Virial option for 
organic acid components (like formic acid, acetic acid, 
propionic acid, butyric acid, and heptonic acid).
If one of the mentioned acid is present in the stream, the 
entire mixture is treated using Chemical Theory of 
dimerization. The degrees of dimerization for each 
component is dependent on its association parameter as well 
as the cross association with other components.A-46
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ThThis option is restricted to systems where the density is 
moderate, typically less than one-half the critical density. The 
Virial equation used is valid for the following range:
A.3.4 Semi-Empirical Methods
The Chao-Seader3 and Grayson-Streed6 methods are older, 
semi-empirical methods. The GS correlation is an extension of 
the CS method with special emphasis on H2. Only the 
equilibrium results produced by these correlations is used by 
Aspen HYSYS. The Lee-Kesler method is used for liquid and 
vapour enthalpies and entropies as its results are shown to be 
superior to those generated from the CS/GS correlations. This 
method is also adopted by and recommended for use in the API 
Technical Data Book. 
The following table gives an approximate range of applicability 
for these two methods, and under what conditions they are 
applicable. 
(A.23)
Method Temp (°F) Temp (°C) Press (psia) Press (kPa)
CS 0 to 500 -18 to 260 <1,500 <10,000
GS 0 to 800 -18 to 425 <3,000 <20,000
Conditions of Applicability
For all hydrocarbons (except 
CH4):
• 0.50.5
P T
2
--
yiPci
i 1=
m
∑
yiTci
i 1=
m
∑
--------------------≤A-47
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ThThe GS correlation is recommended for simulating heavy 
hydrocarbon systems with a high H2 content, such as 
hydrotreating units. The GS correlation can also be used for 
simulating topping units and heavy ends vacuum applications. 
The vapour phase fugacity coefficients are calculated with the 
Redlich Kwong equation of state. The pure liquid fugacity 
coefficients are calculated using the principle of corresponding 
states. Modified acentric factors are included in Aspen HYSYS' 
GS library for most components. Special functions are 
incorporated for the calculation of liquid phase fugacities for N2, 
CO2 and H2S. These functions are restricted to hydrocarbon 
mixtures with less than five percent of each of the above 
components. 
As with the Vapour Pressure models, H2O is treated using a 
combination of the steam tables and the kerosene solubility 
charts from the API Data Book. This method of handling H2O is 
not very accurate for gas systems. Although three phase 
calculations are performed for all systems, it is important to 
note that the aqueous phase is always treated as pure H2O with 
these correlations.
A.3.5 Vapour Pressure 
Property Packages
Vapour pressure K value models may be used for ideal mixtures 
at low pressures. This includes hydrocarbon systems such as 
mixtures of ketones or alcohols where the liquid phase behaves 
approximately ideal. The models may also be used for first 
approximations for non-ideal systems. 
The Lee-Kesler model is used for enthalpy and entropy 
calculations for all vapour pressure models and all 
components with the exception of H2O, which is treated 
separately with the steam property correlation.
All three phase calculations are performed assuming the 
aqueous phase is pure H2O and that H2O solubility in the 
hydrocarbon phase can be described using the kerosene 
solubility equation from the API Data Book (Figure 9A1.4).A-48
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ThVapour pressures used in the calculation of the standard state 
fugacity are based on Aspen HYSYS' library coefficients and a 
modified form of the Antoine equation. Vapour pressure 
coefficients for hypocomponent may be entered or calculated 
from either the Lee-Kesler correlation for hydrocarbons, the 
Gomez-Thodos correlation for chemical compounds or the Reidel 
equation. 
The Vapour Pressure options include the Modified Antoine, 
BraunK10, and EssoK packages.
Approximate ranges of application for each vapour pressure 
model are given below:
Modified Antoine Vapour Pressure 
Model 
The modified Antoine equation assumes the form as set out in 
the DIPPR data bank. 
where:  
A, B, C, D, E and F = fitted coefficients
Pvap = the pressure in kPa
T = the temperature in K
These coefficients are available for all Aspen HYSYS library 
components. Vapour pressure coefficients for hypocomponent 
Because all of the Vapour Pressure options assume an ideal 
vapour phase, they are classified as Vapour Pressure Models.
Model Temperature Press (psia) Press (kPa)
Mod. Antoine <1.6 Tci <100 <700
BraunK10 0°F (-17.78°C) <1.6 Tci <100 <700
EssoK <1.6 Tci <100 <700
(A.24)Pvapln A B
T C+
------------- D T ETF+ln+ +=A-49
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A-50 Property Methods
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Thmay be entered or calculated from either the Lee-Kesler 
correlation for hydrocarbons, the Gomez-Thodos correlation for 
chemical compounds, or the Reidel equation. 
This model is applicable for low pressure systems that behave 
ideally. For hydrocarbon components that you have not provided 
vapour pressure coefficients for, the model converts the Lee-
Kesler vapour pressure model directly. As such, crude and 
vacuum towers can be modeled with this equation. 
When using this method for super-critical components, it is 
recommended that the vapour pressure coefficients be replaced 
with Henry's Law coefficients. Changing Vapour Pressure 
coefficients can only be accomplished if your component is being 
installed as a Hypothetical.
Braun K10 Model 
The Braun K10 model is strictly applicable to heavy hydrocarbon 
systems at low pressures. The model employs the Braun 
convergence pressure method, where, given the normal boiling 
point of a component, the K value is calculated at system 
temperature and 10 psia. The K10 value is then corrected for 
pressure using pressure correction charts. The K values for any 
components that are not covered by the charts are calculated at 
10 psia using the modified Antoine equation and corrected to 
system conditions using the pressure correction charts. 
Accuracy suffers with this model if there are large amounts of 
acid gases or light hydrocarbons. All three phase calculations 
assume that the aqueous phase is pure H2O and that H2O 
solubility in the hydrocarbon phase can be described using the 
kerosene solubility equation from the API Data Book (Figure 
All enthalpy and entropy calculations are performed using 
the Lee-Kesler model.A-50
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Property Methods & Calculations A-51
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Th9A1.4). 
Esso K Model
The Esso Tabular model is strictly applicable to hydrocarbon 
systems at low pressures. The model employs a modification of 
the Maxwell-Bonnel vapour pressure model in the following 
format:
where:
Ai = fitted constants
Tb
i = normal boiling point corrected to K = 12
T = absolute temperature
K = Watson characterisation factor
For heavy hydrocarbon systems, the results are comparable to 
the modified Antoine equation since no pressure correction is 
applied. For non-hydrocarbon components, the K value is 
calculated using the Antoine equation. Accuracy suffers if there 
is a large amount of acid gases or light hydrocarbons. All three 
phase calculations are performed assuming the aqueous phase 
is pure H2O and that H2O solubility in the hydrocarbon phase 
can be described using the kerosene solubility equation from the 
The Lee-Kesler model is used for enthalpy and entropy 
calculations for all components with the exception of H2O 
which is treated with the steam tables.
(A.25)Pvaplog Aix
i
∑=
xi
Tb
i
T
----- 0.0002867Tb
i–
748.1 0.2145Tb
i–
-------------------------------------------=A-51
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A-52 Property Methods
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ThAPI Data Book (Figure 9A1.4). 
A.3.6 Miscellaneous - Special 
Application Methods
Amines Property Package
The amines package contains the thermodynamic models 
developed by D.B. Robinson & Associates for their proprietary 
amine plant simulator, called AMSIM. Their amine property 
package is available as an option with Aspen HYSYS giving you 
access to a proven third party property package for reliable 
amine plant simulation, while maintaining the ability to use 
Aspen HYSYS' powerful flowsheeting capabilities.
The chemical and physical property data base is restricted to 
amines and the following components:
The equilibrium acid gas solubility and kinetic parameters for the 
aqueous alkanolamine solutions in contact with H2S and CO2 are 
incorporated into their property package. The amines property 
package is fitted to extensive experimental data gathered from 
a combination of D.B. Robinson's in-house data, several 
The Lee-Kesler model is used for enthalpy and entropy 
calculations for all components with the exception of H2O 
which is treated with the steam tables.
For the Amine property method, the vapour phase is 
modeled using the PR model.
Component Class Specific Components
Acid Gases CO2, H2S, COS, CS2 
Hydrocarbons CH4   C7H16 
Olefins C2=, C3=
Mercaptans M-Mercaptan, E-Mercaptan
Non Hydrocarbons H2, N2, O2, CO, H2OA-52
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Property Methods & Calculations A-53
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Thunpublished sources, and numerous technical references.
This method does not allow any hypotheticals.A-53
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A-54 Property Methods
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ThThe following table gives the equilibrium solubility limitations 
that should be observed when using this property package:  
* The amine mixtures, DEA/MDEA and MEA/MDEA are assumed to be primarily MDEA, so 
use the MDEA value for these mixtures.
The absorption of H2S and CO2 by aqueous alkanolamine 
solutions involves exothermic reactions. The heat effects are an 
important factor in amine treating processes and are properly 
taken into account in the amines property package. Correlations 
for the heats of solution are set up as a function of composition 
and amine type. The correlations were generated from existing 
published values or derived from solubility data using the Gibbs-
Helmholtz equation. 
The amines package incorporates a specialized stage efficiency 
model to permit simulation of columns on a real tray basis. The 
stage efficiency model calculates H2S and CO2 component stage 
efficiencies based on the tray dimensions given and the 
calculated internal tower conditions for both absorbers and 
strippers. The individual component stage efficiencies are a 
function of pressure, temperature, phase compositions, flow 
rates, physical properties, mechanical tray design and 
dimensions as well as kinetic and mass transfer parameters. 
Since kinetic and mass transfer effects are primarily responsible 
for the H2S selectivity demonstrated by amine solutions, this 
must be accounted for by non unity stage efficiencies.
Alkanolamine
Alkanolamine 
Concentration (wt%)
Acid Gas Partial 
Pressure (psia)
Temperature 
(°F)
Monoethanolamine, MEA 0 - 30 0.00001 - 300 77 - 260 
Diethanolamine, DEA 0 - 50 0.00001 - 300 77 - 260 
Triethanolamine, TEA 0 - 50 0.00001 - 300 77 - 260 
Methyldiethanolamine, MDEA* 0 - 50 0.00001 - 300 77 - 260 
Diglycolamine, DGA 50 - 70 0.00001 - 300 77 - 260 
DIsoPropanolAmine, DIsoA 0 - 40 0.00001 - 300 77 - 260 
The data is not correlated for H2S and CO2 loadings greater 
than 1.0 mole acid gas/mole alkanolamine.
See Chapter 2 - Column 
Operations of the Aspen 
HYSYS Operations 
Guide for details on how 
to specify or have Aspen 
HYSYS calculate the stage A-54
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Property Methods & Calculations A-55
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ThSteam Package
Aspen HYSYS includes two steam packages:
• ASME Steam
• NBS Steam
Both of these property packages are restricted to a single 
component, namely H2O.
ASME Steam accesses the ASME 1967 steam tables. The 
limitations of this steam package are the same as those of the 
original ASME steam tables, i.e., pressures less than 15,000 
psia and temperatures greater than 32°F (0°C) and less than 
1,500°F. 
The basic reference is the book “Thermodynamic and Transport 
Properties of Steam” - The American Society of Mechanical 
Engineers - Prepared by C.A. Meyer, R.B. McClintock, G.J. 
Silvestri and R.C. Spencer Jr.11
Selecting NBS_Steam uses the NBS 1984 Steam Tables, which 
reportedly has better calculations near the Critical Point. 
MBWR
In Aspen HYSYS, a 32-term modified BWR equation of state is 
used. The modified BWR may be written in the following form:
where:
(A.26)P RTρ NiXi
i 1=
32
∑+=
X1 ρ2T= X9 ρ3 T2⁄= X17 ρ8 T⁄= X25 ρ7F( ) T3⁄=
X2 ρ2T1 2⁄= X10 ρ4T= X18 ρ8 T2⁄= X26 ρ9F( ) T2⁄=
X3 ρ2= X11 ρ4= X19 ρ9 T2( )⁄= X27 ρ9F( ) T4⁄=A-55
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ThF = exp (-0.0056 r2) 
The modified BWR is applicable only for the following pure 
components: 
X4 ρ2 T⁄= X12 ρ4 T⁄= X20 ρ3F( ) T2( )⁄= X28 ρ11F( ) T2⁄=
X5 ρ2 T2⁄= X13 ρ5= X21 ρ3F( ) T3( )⁄= X29 ρ11F( ) T3⁄=
X6 ρ3T= X14 ρ6 T⁄= X22 ρ5F( ) T2⁄= X30 ρ13F( ) T2⁄=
X7 ρ3= X15 ρ6 T2⁄= X23 ρ5F( ) T4⁄= X31 ρ13F( ) T3⁄=
X8 ρ3 T⁄= X16 ρ7 T⁄= X24 ρ7F( ) T2⁄= X32 ρ13F( ) T4⁄=
Component Temp (K) Temp (R) Max Press (MPa) Max Press (psia)
Ar 84 - 400 151.2 - 720 100 14,504
CH4 91 - 600 163.8 - 1,080 200 29,008
C2H4 104 - 400 187.2 - 720 40 5,802
C2H6 90 - 600 162. - 1,080 70 10,153
C3H8 85 - 600 153. - 1080 100 14,504
i-C4 114 - 600 205.2 - 1,080 35 5,076
n-C4 135 - 500 243. - 900 70 10,153
CO 68 - 1,000 122.4 - 1,800 30 4,351
CO2 217 - 1,000 390.6 - 1,800 100 14,504
D2 29 - 423 52.2 - 761.4 320 46,412
H2 14 - 400 25.2 - 720 120 17,405
o-H2 14 - 400 25.2 - 720 120 17,405
p-H2 14 - 400 25.2 - 720 120 17,405
He 0.8 - 1,500 1.4 - 2,700 200 29,008
N2 63 - 1,900 113.4 - 3,420 1,000 145,038
O2 54 - 400 97.2 - 720 120 17,405
Xe 161 - 1,300 289.8 - 2,340 100 14,504
The mixtures of different forms of H2 are also acceptable. 
The range of use for these components is shown in the above 
table.A-56
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ThA.4 Enthalpy & Entropy 
Departure Calculations
The Enthalpy and Entropy calculations are performed rigorously 
by Aspen HYSYS using the following exact thermodynamic 
relations:
where:  
Ideal Gas Enthalpy basis ( ) used by Aspen HYSYS is equal 
to the ideal gas Enthalpy of Formation at 25°C
Ideal Gas Entropy basis ( ) used by Aspen HYSYS is equal 
to the ideal gas Entropy of Formation at 25°C and 1 
atm
With semi-empirical and vapour pressure models, a pure liquid 
water phase is generated and the solubility of H2O in the 
hydrocarbon phase is determined from the kerosene solubility 
model.
A.4.1 Equations of State
For the Peng-Robinson Equation of State, the enthalpy and 
entropy departure calculations use the following relations:
(A.27)
(A.28)
(A.29)
H H ID–
RT
------------------- Z 1– 1
RT
------ T T∂
∂P
⎝ ⎠
⎛ ⎞
V
P– Vd
∞
V
∫+=
S S°
ID–
RT
------------------ Zln P
P°
-----ln– 1
R
--
T∂
∂P
⎝ ⎠
⎛ ⎞
V
1
V
--– Vd
∞
V
∫+=
H ID
S°
ID
H H ID–
RT
------------------- Z 1– 1
21.5bRT
------------------- a T td
da– V 20.5 1+( )b+
V 20.5 1–( )b+
------------------------------------
⎝ ⎠
⎜ ⎟
⎛ ⎞
ln–=A-57
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Thwhere:  
Ideal Gas Enthalpy basis (HID) used by Aspen HYSYS changes 
with temperature according to the coefficients on the 
TDep tab for each individual component
For the SRK Equation of State:
A and B term definitions are provided below:
(A.30)
(A.31)
(A.32)
(A.33)
Peng-Robinson Soave-Redlich-Kwong
bi
ai
aci
mi
S S°
ID–
R
------------------ Z B–( )ln P
P°
-----ln– A
21.5bRT
------------------- T
a
--
td
da V 20.5 1+( )b+
V 20.5 1–( )b+
------------------------------------
⎝ ⎠
⎜ ⎟
⎛ ⎞
ln–=
a xixj aiaj( )0.5 1 kij–( )
j 1=
N
∑
i 1=
N
∑=
H H ID–
RT
------------------- Z 1– 1
bRT
---------- a Tda
dt
-----– 1 b
V
---+⎝ ⎠
⎛ ⎞ln–=
S S°
ID–
RT
------------------ Z b–( )ln P
P°
-----ln– A
B
-- T
a
-- da
dt
----- 1 B
Z
--+⎝ ⎠
⎛ ⎞ln+=
0.077796
RTci
Pci
---------- 0.08664
RTci
Pci
----------
aciαi aciαi
0.457235
RTci( )2
Pci
------------------ 0.42748
RTci( )2
Pci
------------------
αi 1 mi 1 Tri
0.5–( )+ 1 mi 1 Tri
0.5–( )+
0.37646 1.54226ωi 0.26992ωi
2–+ 0.48 1.574ωi 0.176ωi
2–+A-58
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Thwhere:  
R = Ideal Gas constant
H = Enthalpy
S = Entropy
subscripts:
ID = Ideal Gas
o = reference state
PRSV
The PRSV equation of state is an extension of the Peng-
Robinson equation using an extension of the  expression as 
shown below: 
This results in the replacement of the  term in the definitions 
of the A and B terms shown previously by the  term shown 
above.
(A.34)
a xixj aiaj( )0.5 1 kij–( )
j 1=
N
∑
i 1=
N
∑=
κ
αi 1 κi 1 Tr
0.5–( )+[ ]
2
=
κi κ0i 1 Tri
0.5+( ) 0.7 Tri–( )=
κ0i 0.378893 1.4897153ωi 0.17131848ωi
2– 0.0196554ωi
3+ +=
αi
αiA-59
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A-60 Enthalpy & Entropy Departure 
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ThA.4.2 Activity Models
The Liquid enthalpy and entropy for Activity Models is based on 
the Cavett Correlation as shown below:
for Tri < 1:
for Tri  1:
where:
a1, a2, a3 = functions of the Cavett parameter, fitted to 
match one known heat of vaporization 
The Gas enthalpies and entropies are dependent on the model 
chosen to represent the vapour phase behaviour:
• Ideal Gas: 
(A.35)
(A.36)
(A.37)
(A.38)
(A.39)
(A.40)
HL HID–
Tci
---------------------- max
Hi°Δ L sb( )
Tci
-------------------------
Hi°Δ L sb( )
Tci
-------------------------,
⎝ ⎠
⎜ ⎟
⎛ ⎞
=
≥
HL HID–
Tci
---------------------- max
Hi°Δ L sb( )
Tci
-------------------------
Hi°Δ L sp( )
Tci
-------------------------,
⎝ ⎠
⎜ ⎟
⎛ ⎞
=
Hi°Δ L sb( )
Tci
------------------------- a1 a2 1 Tri
–( )
1 a3 Tri
0.1–( )–
+=
Hi°Δ L sp( )
Tci
------------------------- max 0 b1 b2Tri
2 b3Tri
3 b4Tri
4 b5Tri
2+ + + +,( )=
H H ID=
S S°
ID Cv Td
T
------------
T1
T2
∫ R
V2
V1
-----ln+= =A-60
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Th• Redlich-Kwong:
• Virial Equation:
where:  
B = second virial coefficient of the mixture
(A.41)
(A.42)
(A.43)
(A.44)
H HID–
RT
------------------- Z 1– 1.5
bRT
---------- 1 b
V
---+⎝ ⎠
⎛ ⎞ln–=
S S°
ID–
RT
------------------ Z b–( )ln P
P°
-----ln– A
2B
------ 1 B
Z
---+⎝ ⎠
⎛ ⎞ln+=
H HID–
RT
------------------- T
V B–
------------ dB
dt
------– Z 1–( )+=
S S°
ID–
R
------------------ RT
V B–
------------ dB
dT
------– R V
V B–
------------ln– R V
V°
-----ln+=A-61
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ThA.4.3 Lee-Kesler Option
The Lee and Kesler method is an effort to extend the method 
originally proposed by Pitzer to temperatures lower than 0.8 Tr. 
Lee and Kesler expanded Pitzer's method expressing the 
compressibility factor as:
where:  
Z o = the compressibility factor of a simple fluid
Z r = the compressibility factor of a reference fluid
They chose the reduced form of the BWR equation of state to 
represent both Z o and Z r:
where:  
The constants in these equations were determined using 
experimental compressibility and enthalpy data. Two sets of 
constants, one for the simple fluid ( ) and one for the 
reference fluid ( ) were determined. 
(A.45)
(A.46)
The SRK and PR are 
given in Section A.3.1 
- Equations of State.
Z Z° ω
ωr
----- Zr Z°–( )+=
Z 1 B
Vr
----- C
Vr
2
----- D
Vr
5
----- D
Tr
3
Vr
3
----------- β γ
Vr
2
-----–
⎝ ⎠
⎜ ⎟
⎛ ⎞
e
γ
Vr
2
-----
⎝ ⎠
⎛ ⎞–
+ + + +=
Vr
VPc
RTc
---------=
B b1
b2
Tr
----–
b3
Tr
2
-----–
b4
Tr
4
-----–=
C c1
c2
Tr
----–
c3
Tr
3
-----+=
D d1
d2
Tr
----+=
ω° 0=
ωr 0.3978 n C8–,=A-62
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ThThe Enthalpy and Entropy departures are computed as follows:
For mixtures, the Critical Properties are defined as follows:
(A.47)
(A.48)
(A.49)
H HID–
RTc
------------------- Tr Z 1–
b2 2
b3
Tr
---- 3
b4
Tr
2
-----+ +
TrVr
------------------------------------–
c2 3
c3
Tr
2
-----–
2TrVr
2
--------------------–
d2
5TrVr
5
--------------– 3E+
⎩ ⎭
⎪ ⎪
⎪ ⎪
⎨ ⎬
⎪ ⎪
⎪ ⎪
⎧ ⎫
=
S S°
ID–
R
------------------ Zln P
P°
-----⎝ ⎠
⎛ ⎞ln–
b1
b3
Tr
2
----- 2
b4
Tr
3
-----+ +
Vr
---------------------------------–
c1 3
c3
Tr
2
-----–
2Vr
2
--------------------–
d1
5Vr
2
--------– 2E+=
E
c4
2Tr
3γ
----------- β 1 β 1 γ
Vr
2
-----+ +
⎝ ⎠
⎜ ⎟
⎛ ⎞
e
γ
Vr
----⎝ ⎠
⎛ ⎞–
–+
⎩ ⎭
⎪ ⎪
⎨ ⎬
⎪ ⎪
⎧ ⎫
=
ω xiωi
i 1=
N
∑=
zci
0.2905 0.0851ωi–=
Vci
Zci
RTci
Pci
-----------------=
Vc
1
8
-- xixj Vci
1
3
--
Vcj
1
3
--
+
⎝ ⎠
⎜ ⎟
⎛ ⎞
3
j 1=
N
∑
i 1=
N
∑=
Tc
1
8Vc
-------- xixj Vci
1
3
--
Vcj
1
3
--
+
⎝ ⎠
⎜ ⎟
⎛ ⎞
3
Tci
Tcj
( )0.5
j 1=
N
∑
i 1=
N
∑=
Pc 0.2905 0.085ω–( )
RTc
Vc
---------=A-63
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ThFugacity Coefficient
The fugacity coefficient calculations for SRK and Peng Robinson 
models is shown below.
Soave-Redlich-Kwong
Peng Robinson
(A.50)φiln Z Pb
RT
------–⎝ ⎠
⎛ ⎞ln– Z 1–( )
bi
b
--- a
bRT
---------- 1
a
-- 2ai
0.5 xjaj
0.5 1 kij–( )
j 1=
N
∑
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎛ ⎞ bi
b
---– 1 b
V
---+⎝ ⎠
⎛ ⎞ln–+=
(A.51)φiln Z Pb
RT
------–⎝ ⎠
⎛ ⎞ln– Z 1–( )
bi
b
--- a
21.5bRT
------------------- 1
a
-- 2ai
0.5 xjaj
0.5 1 kij–( )
j 1=
N
∑
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎛ ⎞ bi
b
---– V 20.5 1+( )b+
V 20.5 1–( )b–
------------------------------------ln–+=A-64
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ThA.5 Physical & Transport 
Properties
The physical and transport properties that Aspen HYSYS 
calculates for a given phase are viscosity, density, thermal 
conductivity, and surface tension. The models used for the 
transport property calculations are all pre-selected to yield the 
best fit for the system under consideration. For example, the 
corresponding states model proposed by Ely and Hanley is used 
for viscosity predictions of light hydrocarbons (NBP<155), the 
Twu methodology for heavier hydrocarbons, and a modification 
of the Letsou-Stiel method for predicting the liquid viscosities of 
non-ideal chemical systems.
 A complete description of the models used for the prediction of 
the transport properties can be found in the references listed in 
each sub-section. All these models are modified by Hyprotech to 
improve the accuracy of the correlations. 
In the case of multiphase streams, the transport properties for 
the mixed phase are meaningless and are reported as 
, although the single phase properties are known. 
There is an exception with the pipe and heat exchanger 
operations. For three-phase fluids, Aspen HYSYS uses empirical 
mixing rules to determine the apparent properties for the 
combined liquid phases.A-65
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ThA.5.1 Liquid Density
Saturated liquid volumes are obtained using a corresponding 
states equation developed by R. W. Hankinson and G. H. 
Thompson7 which explicitly relates the liquid volume of a pure 
component to its reduced temperature and a second parameter 
termed the characteristic volume. This method is adopted as an 
API standard. The pure compound parameters needed in the 
corresponding states liquid density (COSTALD) calculations are 
taken from the original tables published by Hankinson and 
Thompson, and the API Data Book for components contained in 
Aspen HYSYS' library. 
The parameters for hypothetical components are based on the 
API gravity and the generalized Lu equation. Although the 
COSTALD method was developed for saturated liquid densities, 
it can be applied to sub-cooled liquid densities, i.e., at pressures 
greater than the vapour pressure, using the Chueh and 
Prausnitz correction factor for compressed fluids. It is used to 
predict the density for all systems whose pseudo-reduced 
temperature is below 1.0. Above this temperature, the equation 
of state compressibility factor calculates the liquid density. 
Hypocomponents generated in the Oil Characterization 
Environment have their densities either calculated from internal 
correlations or generated from input curves. Given a bulk 
density, the densities of the hypocomponent are adjusted:
The characteristic volume for each hypocomponent is calculated 
using the adjusted densities and the physical properties. The 
calculated characteristic volumes are then adjusted such that 
the bulk density calculated from the COSTALD equation matches 
the density calculated using the above equation. This ensures 
that a given volume of fluid contains the same mass whether it 
is calculated with the sum of the component densities or the 
COSTALD equation.
(A.52)
ρbulk
1.0
xi
ρi°
------∑
-------------=A-66
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ThA.5.2 Vapour Density
The density for all vapour systems at a given temperature and 
pressure is calculated using the compressibility factor given by 
the equation of state or by the appropriate vapour phase model 
for Activity Models. 
A.5.3 Viscosity
Aspen HYSYS automatically selects the model best suited for 
predicting the phase viscosities of the system under study. The 
model selected is from one of the three available in Aspen 
HYSYS: a modification of the NBS method (Ely and Hanley), 
Twu's model, or a modification of the Letsou-Stiel correlation. 
Aspen HYSYS selects the appropriate model using the following 
criteria:
All of the models are based on corresponding states principles 
and are modified for more reliable application. Internal 
validation showed that these models yielded the most reliable 
results for the chemical systems shown. Viscosity predictions for 
light hydrocarbon liquid phases and vapour phases were found 
to be handled more reliably by an in-house modification of the 
original Ely and Hanley model, heavier hydrocarbon liquids were 
more effectively handled by Twu's model, and chemical systems 
were more accurately handled by an in-house modification of 
the original Letsou-Stiel model. 
Chemical System Vapour Phase Liquid Phase
Lt Hydrocarbons (NBP<155°F) Mod Ely & Hanley Mod Ely & Hanley
Hvy Hydrocarbons (NBP>155°F) Mod Ely & Hanley Twu
Non-Ideal Chemicals Mod Ely & Hanley Mod Letsou-StielA-67
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ThA complete description of the original corresponding states 
(NBS) model used for viscosity predictions is presented by Ely 
and Hanley in their NBS publication. The original model is 
modified to eliminate the iterative procedure for calculating the 
system shape factors. The generalized Leech-Leland shape 
factor models are replaced by component specific models. Aspen 
HYSYS constructs a PVT map for each component using the 
COSTALD for the liquid region. The shape factors are adjusted 
such that the PVT map can be reproduced using the reference 
fluid.
The shape factors for all the library components are already 
regressed and included in the Pure Component Library. 
Hypocomponent shape factors are regressed using estimated 
viscosities. These viscosity estimations are functions of the 
hypocomponent Base Properties and Critical Properties.
Hypocomponents generated in the Oil Characterization 
Environment have the additional ability of having their shape 
factors regressed to match kinematic or dynamic viscosity 
assays. 
The general model employs CH4 as a reference fluid and is 
applicable to the entire range of non-polar fluid mixtures in the 
hydrocarbon industry. Accuracy for highly aromatic or 
naphthenic crudes is increased by supplying viscosity curves 
when available, since the pure component property generators 
were developed for average crude oils. The model also handles 
H2O and acid gases as well as quantum gases. 
Although the modified NBS model handles these systems very 
well, the Twu method was found to do a better job of predicting 
the viscosities of heavier hydrocarbon liquids. The Twu model16 
is also based on corresponding states principles, but has 
implemented a viscosity correlation for n-alkanes as its 
reference fluid instead of CH4. A complete description of this 
model is given in the paper entitled “Internally Consistent 
Correlation for Predicting Liquid Viscosities of Petroleum 
Fractions”21. A-68
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ThFor chemical systems the modified NBS model of Ely and Hanley 
is used for predicting vapour phase viscosities, whereas a 
modified form of the Letsou-Stiel model is used for predicting 
the liquid viscosities. This method is also based on 
corresponding states principles and was found to perform 
satisfactorily for the components tested.
The shape factors contained in the Aspen HYSYS Pure 
Component Library are fit to match experimental viscosity data 
over a broad operating range. Although this yields good 
viscosity predictions as an average over the entire range, 
improved accuracy over a narrow operating range can be 
achieved by using the Tabular features.
A.5.4 Liquid Phase Mixing 
Rules for Viscosity
The estimates of the apparent liquid phase viscosity of 
immiscible Hydrocarbon Liquid - Aqueous mixtures are 
calculated using the following "mixing rules":
• If the volume fraction of the hydrocarbon phase is 
greater than or equal to 0.5, the following equation is 
used22:
where:  
 = apparent viscosity
 = viscosity of Hydrocarbon phase
 = volume fraction Hydrocarbon phase
• If the volume fraction of the hydrocarbon phase is less 
than 0.33, the following equation is used5:
(A.53)
(A.54)
For more information on 
the Tabular features, refer 
to Chapter 2 - Fluid 
Package.
μeff μoile
3.6 1 νoil–( )
=
μeff
μoil
νoil
μeff 1 2.5νoil
μoil 0.4μH2O+
μoil μH2O+
-----------------------------------
⎝ ⎠
⎜ ⎟
⎛ ⎞
+ μH2O=A-69
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Thwhere:  
 = apparent viscosity
 = viscosity of Hydrocarbon phase
 = viscosity of Aqueous phase
 = volume fraction Hydrocarbon phase
• If the volume of the hydrocarbon phase is between 0.33 
and 0.5, the effective viscosity for combined liquid phase 
is calculated using a weighted average between 
Equation (A.53) and Equation (A.54). 
The remaining properties of the pseudo phase are calculated as 
follows:
(A.55)
μeff
μoil
μH2O
νoil
MWeff xiMWi∑=
ρeff
1
xi
ρi
----⎝ ⎠
⎛ ⎞∑
-----------------=
Cpeff
xiCpi∑=
(molecular weight)
(mixture density)
(mixture specific heat)A-70
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ThA.5.5 Thermal Conductivity
As in viscosity predictions, a number of different models and 
component specific correlations are implemented for prediction 
of liquid and vapour phase thermal conductivities. The text by 
Reid, Prausnitz and Poling18 was used as a general guideline in 
determining which model was best suited for each class of 
components. 
For hydrocarbon systems the corresponding states method 
proposed by Ely and Hanley4 is generally used. The method 
requires molecular weight, acentric factor and ideal heat 
capacity for each component. These parameters are tabulated 
for all library components and may either be input or calculated 
for hypothetical components. It is recommended that all of 
these parameters be supplied for non-hydrocarbon 
hypotheticals to ensure reliable thermal conductivity coefficients 
and enthalpy departures. 
The modifications to the method are identical to those for the 
viscosity calculations. Shape factors calculated in the viscosity 
routines are used directly in the thermal conductivity equations. 
The accuracy of the method depends on the consistency of the 
original PVT map.
For vapour phase thermal conductivity predictions, the Misic 
and Thodos, and Chung et al.16 methods are used (except for 
H2O, C1, H2, CO2, NH3 which use a polynomial for pure 
components). The effect of higher pressure on thermal 
conductivities is taken into account by the Chung et al. method.
For liquid phase thermal conductivity predictions, the following 
methods are used:
• For pure water, the Steam Tables is used.
• For water, C1, C2, C3, 3M-3Epentane, propene, DEG, 
TEG, EG, He, H2, Ethylene, Ammonia, a proprietary 
polynomial correlation is used. 
If both water and DEG are present in the mixture, 
additional corrections are made for these two 
compounds.
• For Hydrocarbons with MW > 140 and TR < 0.8, a 
modified Missenard & Reidel method16 is used.A-71
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Th• For Alcohol, Ester, and other Hydrocarbons not included 
in the previous categories, the Latini method16 is used.
• For all other compounds, the Sato-Reidel method is 
used.
The liquid phase thermal conductivity is calculated using the 
following mixing rule:
where:
 = liquid thermal conductivity of the mixture
 = liquid thermal conductivity of component i
 = mole fraction of component i
As with viscosity, the thermal conductivity for two liquid phases 
is approximated by using empirical mixing rules for generating a 
single pseudo liquid phase property. The thermal conductivity 
for this pseudo liquid phase is calculated by the following 
equation15:
where:  
 = liquid thermal conductivity of the combined two liquid 
phases
 = liquid thermal conductivity of liquid phase i at 
temperature T
(A.56)
(A.57)
λmix xiλi
1 3⁄
i
∑⎝ ⎠
⎜ ⎟
⎛ ⎞ 3
=
λmix
λi
xi
λLmix
φLi
φLj
λLij
j
∑
i
∑=
λLmix
λLij
2
1 λLi
⁄( ) 1 λLj
⁄( )+
-------------------------------------------=
λLiA-72
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Th = liquid thermal conductivity of liquid phase j at 
temperature T
 = molar phase fraction of liquid phase i
 = molar volume of liquid phase i
 = molar phase fraction of liquid phase k
 = molar volume of liquid phase k
For a two liquid phase system the equation simplifies to:
(A.58)
λLj
φLi
xLi
VLi
xLk
VLk
k 1=
∑
-------------------------=
xLi
VLi
xLk
VLk
λLmix
φL1
2λL1
2φL1
φL2
λ12 φL2
2λL2
+ +=A-73
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ThA.5.6 Surface Tension
Surface tensions for hydrocarbon systems are calculated using a 
modified form of the Brock and Bird equation17. The equation 
expresses the surface tension ( ) as a function of the reduced 
and critical properties of the component. The basic form of the 
equation was used to regress parameters for each family of 
components.
where:  
 = surface tension (dynes/cm2)
TBR = reduced boiling point temperature (Tb/Tc)
a = parameter fitted for each chemical class
b =  (parameter fitted for each chemical 
class, expanded as a polynomial in acentricity)
For aqueous systems, Aspen HYSYS employs a polynomial to 
predict the surface tension.
(A.59)
Aspen HYSYS predicts only liquid-vapour surface tensions.
σ
σ Pc
2 3⁄ Tc
1 3⁄ Q 1 TR–( )a b×=
σ
Q 0.1207 1
TBR Pcln×
1.0 TBR–
--------------------------+⎝ ⎠
⎛ ⎞ 0.281–=
co c1ω c2ω2 c3ω3+ + +A-74
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ThA.5.7 Heat Capacity
Heat Capacity is calculated using a rigorous Cv value whenever 
Aspen HYSYS can. The method used is given by the following 
equations:
However, when ever this equation fails to provide an answer, 
Aspen HYSYS falls back to the semi-ideal Cp/Cv method by 
computing Cp/Cv as Cp/(Cp-R), which is only approximate and 
valid for ideal gases. Examples of when Aspen HYSYS uses the 
ideal method are:
• Equation (A.60) fails to return an answer
• The stream has a solid phase
• abs(dV/dP) < 1e-12
• Cp/Cv < 0.1or Cp/Cv > 20 - this is outside the range of 
applicability of the equation used so Aspen HYSYS falls 
back to the ideal method
A.6 Volumetric Flow Rate 
Calculations
Aspen HYSYS has the ability to interpret and produce a wide 
assortment of flow rate data. It can accept several types of flow 
rate information for stream specifications as well as report back 
many different flow rates for streams, their phases and their 
components. One drawback of the large variety available is that 
it often leads to some confusion as to what exactly is being 
specified or reported, especially when volumetric flow rates are 
involved. 
In the following sections, the available flow rates are listed, each 
corresponding density basis is explained, and the actual 
formulation of the flow rate calculations is presented. For 
volumetric flow rate data that is not directly accepted as a 
stream specification, a final section is provided that outlines 
(A.60)Cp Cv– T– dV dT⁄( )2 dV dT⁄( )⁄⋅=A-75
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Thtechniques to convert your input to mass flow rates.
A.6.1 Available Flow Rates
Many types of flow rates appear in Aspen HYSYS output. 
However, only a subset of these are available for stream 
specifications.
Flow Rates Reported in the Output
The flow rate types available through the numerous reporting 
methods - property views, workbook, PFD, specsheets, and so 
forth are:
• Molar Flow
• Mass Flow 
• Std Ideal Liq Vol Flow
• Liq Vol Flow @Std Cond
• Actual Volume Flow 
• Std Gas Flow
• Actual Gas Flow
Flow Rates Available for 
Specification
The following flow rate types are available for stream 
specifications:
• Molar Flows
• Mass Flows
• Std Ideal Liq Vol Flow
• Liq Vol Flow @Std CondA-76
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ThA.6.2 Liquid & Vapour Density 
Basis
All calculations for volumetric stream flows are based on 
density. Aspen HYSYS uses the following density basis:
Calculation of Standard & Actual 
Liquid Densities
The Standard and Actual liquid densities are calculated 
rigorously at the appropriate T and P using the internal methods 
of the chosen property package. Flow rates based upon these 
densities automatically take into account any mixing effects 
exhibited by non-ideal systems. Thus, these volumetric flow 
rates may be considered as "real world".
Density Basis Description
Std Ideal Liq 
Mass Density 
This is calculated based on ideal mixing of pure 
component ideal densities at 60°F.
Liq Mass Density 
@Std Cond 
This is calculated rigorously at the standard reference 
state for volumetric flow rates.
Actual Liquid 
Density 
This is calculated rigorously at the flowing conditions of 
the stream (i.e., at stream T and P).
Standard Vapour 
Density 
This is determined directly from the Ideal Gas law.
Actual Vapour 
Density 
This is calculated rigorously at the flowing conditions of 
the stream (i.e., at stream T and P).
The volumetric flow rate 
reference state is defined 
as 60°F and 1 atm when 
using Field units or 15°C 
and 1 atm when using SI 
units.
Actual Densities are 
calculated at the stream 
Temperature and 
Pressure.A-77
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ThCalculation of Standard Ideal Liquid 
Mass Density
Contrary to the rigorous densities, the Standard Ideal Liquid 
Mass density of a stream does not take into account any mixing 
effects due to its simplistic assumptions. Thus, flow rates that 
are based upon it do not account for mixing effects and are 
more empirical in nature. The calculation is as follows:
where:  
xi = molar fraction of component i
 = pure component Ideal Liquid density
Aspen HYSYS contains Ideal Liquid densities for all components 
in the Pure Component Library. These values are determined in 
one of three ways, based on the characteristics of the 
component, as described below:
• Case 1 - For any component that is a liquid at 60°F and 1 
atm, the data base contains the density of the 
component at 60°F and 1 atm.
• Case 2 - For any component that can be liquified at 60°F 
and pressures greater than 1 atm, the data base 
contains the density of the component at 60°F and 
Saturation Pressure.
• Case 3 - For any component that is non-condensable at 
60°F under any pressure, i.e., 60°F is greater than the 
critical temperature of the component, the data base 
contains GPA tabular values of the equivalent liquid 
density. These densities were experimentally determined 
by measuring the displacement of hydrocarbon liquids by 
dissolved non-condensable components.
(A.61)
Ideal DensityStream
1
xi
ρi
Ideal
-------------∑
---------------------=
ρi
IdealA-78
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ThFor all hypothetical components, the Standard Liquid density 
(Liquid Mass Density @Std Conditions) in the Base Properties is 
used in the Ideal Liquid density (Std Ideal Liq Mass Density) 
calculation. If a density is not supplied, the Aspen HYSYS 
estimated liquid mass density (at standard conditions) is used. 
Special treatment is given by the Oil Characterization feature to 
its hypocomponent such that the ideal density calculated for its 
streams match the assay, bulk property, and flow rate data 
supplied in the Oil Characterization Environment.
A.6.3 Formulation of Flow Rate 
Calculations
The various procedures used to calculate each of the available 
flow rates are detailed below, based on a known molar flow.
Molar Flow Rate
Mass Flow
Std Ideal Liq Vol Flow
This volumetric flow rate is calculated using the ideal density of 
the stream and thus is somewhat empirical in nature.
(A.62)
(A.63)
(A.64)
Total Molar Flow Molar FlowStream=
Mass Flow Total Molar Flow MWStream×=
Even if a stream is all 
vapour, it still has a Liq 
Volume flow, based upon 
the stream's Standard 
Ideal Liquid Mass density, 
whose calculation is 
detailed in the previous 
section. LiqVolFlow
Total Molar Flow MWStream×
Ideal DensityStream
--------------------------------------------------------------------------=A-79
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ThLiq Vol Flow @Std Cond
This volumetric flow rate is calculated using a rigorous density 
calculated at standard conditions, and reflects non-ideal mixing 
effects.
Actual Volume Flow
This volumetric flow rate is calculated using a rigorous liquid 
density calculation at the actual stream T and P conditions, and 
reflects non-ideal mixing effects.
Standard Gas Flow
Standard gas flow is based on the molar volume of an ideal gas 
at standard conditions. It is a direct conversion from the 
stream's molar flow rate, based on the following:
• Ideal Gas at 60°F and 1 atm occupies 379.46 ft3/lbmole
• Ideal Gas at 15°C and 1 atm occupies 23.644 m3/kgmole
Actual Gas Flow
This volumetric flow rate is calculated using a rigorous vapour 
density calculation at the actual stream T and P conditions, and 
reflects non-ideal mixing and compressibility effects.
(A.65)
(A.66)
(A.67)
Std Liquid Volume Flow Molar Flow MW×
 Std Liq Density
--------------------------------------------=
Actual Volume Flow Molar Flow MW×
Density
--------------------------------------------=
Actual Gas Flow Molar Flow MW×
 Density
--------------------------------------------=A-80
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ThA.6.4 Volumetric Flow Rates as 
Specifications
If you require that the flow rate of your stream be specified 
based on actual density or standard density as opposed to 
Standard Ideal Mass Liquid density, you must use one of the 
following procedures:
Liq Vol Flow @Std Cond 
1. Specify the composition of your stream. 
2. Use the Liq Vol Flow @Std Cond and calculate the 
corresponding mass flow rate either manually or in the 
SpreadSheet.
3. Use this calculated mass flow as the specification for the 
stream.
Actual Liquid Volume Flow 
1. Specify the composition and the flowing conditions (T and P) 
of your stream.
2. Use the density reported for the stream and calculate the 
corresponding mass flow rate either manually, or in our 
spreadsheet.
3. Use this calculated mass flow as the specification for the 
stream. A-81
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ThA.7 Flash Calculations
Rigorous three phase calculations are performed for all 
equations of state and activity models with the exception of 
Wilson's equation, which only performs two phase vapour-liquid 
calculations. As with the Wilson Equation, the Amines and 
Steam property packages only support two phase equilibrium 
calculations.
Aspen HYSYS uses internal intelligence to determine when it can 
perform a flash calculation on a stream, and then what type of 
flash calculation needs to be performed on the stream. This is 
based completely on the degrees of freedom concept. Once the 
composition of a stream and two property variables are known, 
(vapour fraction, temperature, pressure, enthalpy or entropy) 
one of which must be either temperature or pressure, the 
thermodynamic state of the stream is defined. When Aspen 
HYSYS recognizes that a stream is thermodynamically defined, 
it performs the correct flash automatically in the background. 
You never have to instruct Aspen HYSYS to perform a flash 
calculation.
Property variables can either be specified by you or back-
calculated from another unit operation. A specified variable is 
treated as an independent variable. All other stream properties 
are treated as dependent variables and are calculated by Aspen 
HYSYS.
In this manner, Aspen HYSYS also recognizes when a stream is 
overspecified. For example, if you specify three stream 
properties plus composition, Aspen HYSYS prints out a warning 
message that an inconsistency exists for that stream. This also 
applies to streams where an inconsistency is created through 
Aspen HYSYS calculations. 
For example, if a stream Temperature and Pressure are 
specified in a flowsheet, but Aspen HYSYS back-calculates a 
different temperature for that stream as a result of an enthalpy 
balance across a unit operation, Aspen HYSYS generates an 
Inconsistency message.
Specified variables can 
only be re-specified by 
you or through Recycle 
Adjust, or SpreadSheet 
operations. They do not 
change through any heat 
or material balance 
calculations.
If a flash calculation is 
performed on a stream, 
Aspen HYSYS knows all 
the property values of 
that stream, i.e., 
thermodynamic, 
physical and transport 
properties.A-82
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ThA.7.1 T-P Flash Calculation
The independent variables for this type of flash calculation are 
the temperature and pressure of the system, while the 
dependent variables are the vapour fraction, enthalpy, and 
entropy.
With the equations of state and activity models, rigorous 
calculations are performed to determine the co-existence of 
immiscible liquid phases and the resulting component 
distributions by minimization of the Gibbs free energy term. For 
vapour pressure models or the semi-empirical methods, the 
component distribution is based on the Kerosene solubility data 
(Figure 9A1.4 of the API Data Book). 
If the mixture is single-phase at the specified conditions, the 
property package calculates the isothermal compressibility (dv/
dp) to determine if the fluid behaves as a liquid or vapour. Fluids 
in the dense-phase region are assigned the properties of the 
phase that best represents their current state.
Aspen HYSYS automatically performs the appropriate flash 
calculation when it recognizes that sufficient stream 
information is known. This information is either specified by 
the user or calculated by an operation.
Depending on the known stream information, Aspen HYSYS 
performs one of the following flashes: T-P, T-VF, T-H, T-S, P-
VF, P-H, or P-S.
The material solids appear in the liquid phase of two-phase 
mixtures, and in the heavy (aqueous/slurry) phase of three-
phase systems. Therefore, when a separator is solved using 
a T-P flash, the vapour phase is identical regardless of 
whether or not solids are present in the feed to the flash 
drum.
Use caution in specifying solids with systems that are 
otherwise all vapour. Small amounts of non-solids may 
appear in the "liquid" phase.
See Section 2.4.4 - 
Stability Test Tab for 
options on how to 
instruct Aspen HYSYS to 
perform phase stability 
tests.A-83
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ThA.7.2 Vapour Fraction Flash
Vapour fraction and either temperature or pressure are the 
independent variables for this type of calculation. This class of 
calculation embodies all fixed quality points including bubble 
points (vapour pressure) and dew points. 
To perform bubble point calculation on a stream of known 
composition, simply specify the Vapour Fraction of the stream 
as 0.0 and define the temperature or pressure at which the 
calculation is desired. For a dew point calculation, simply specify 
the Vapour Fraction of the stream as 1.0 and define the 
temperature or pressure at which the dew point calculation is 
desired. Like the other types of flash calculations, no initial 
estimates are required. 
The vapour fraction is always shown in terms of the total 
number of moles. For example, the vapour fraction (VF) 
represents the fraction of vapour in the stream, while the 
fraction, (1.0 - VF), represents all other phases in the stream 
(i.e., a single liquid, 2 liquids, a liquid and a solid).
Dew Points 
Given a vapour fraction specification of 1.0 and either 
temperature or pressure, the property package calculates the 
other dependent variable (P or T). If temperature is the second 
independent variable, Aspen HYSYS calculates the dew point 
pressure. Likewise, if pressure is the independent variable, then 
the dew point temperature is calculated. Retrograde dew points 
may be calculated by specifying a vapour fraction of -1.0. It is 
important to note that a dew point that is retrograde with 
respect to temperature can be normal with respect to pressure 
and vice versa.
All of the solids appear in the liquid phase.A-84
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ThBubble Points/Vapour Pressure
A vapour fraction specification of 0.0 defines a bubble point 
calculation. Given this specification and either temperature or 
pressure, the property package calculates the unknown T or P 
variable. As with the dew point calculation, if the temperature is 
known, Aspen HYSYS calculates the bubble point pressure and 
conversely, given the pressure, Aspen HYSYS calculates the 
bubble point temperature. For example, by fixing the 
temperature at 100°F, the resulting bubble point pressure is the 
true vapour pressure at 100°F. 
Quality Points
Bubble and dew points are special cases of quality point 
calculations. Temperatures or pressures can be calculated for 
any vapour quality between 0.0 and 1.0 by specifying the 
desired vapour fraction and the corresponding independent 
variable. If Aspen HYSYS displays an error when calculating 
vapour fraction, then this means that the specified vapour 
fraction doesn't exist under the given conditions, i.e., the 
specified pressure is above the cricondenbar, or the given 
temperature lies to the right of the cricondentherm on a 
standard P-T envelope.
Vapour pressure and bubble point pressure are synonymous.
Aspen HYSYS calculates the retrograde condition for the 
specified vapour quality if the vapour fraction is input as a 
negative number.A-85
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A-86 Flash Calculations
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ThA.7.3 Enthalpy Flash
Given the enthalpy and either the temperature or pressure of a 
stream, the property package calculates the unknown 
dependent variables. Although the enthalpy of a stream cannot 
be specified directly, it often occurs as the second property 
variable as a result of energy balances around unit operations 
such as valves, heat exchangers and mixers.
If Aspen HYSYS responds with an error message, and cannot 
find the specified property (temperature or pressure), this 
probably means that an internally set temperature or pressure 
bound was encountered. Since these bounds are set at quite 
large values, there is generally some erroneous input that is 
directly or indirectly causing the problem, such as an impossible 
heat exchange.
A.7.4 Entropy Flash
Given the entropy and either the temperature or pressure of a 
stream, the property package calculates the unknown 
dependent variables.
A.7.5 Electrolyte Flash
The electrolyte stream flash differs from the Aspen HYSYS 
material stream flash to handle the complexities of speciation 
for aqueous electrolyte systems.
The Aspen HYSYS OLI Interface package is an interface to the 
OLI Engine (OLI Systems) that enables simulations within Aspen 
HYSYS using the full functionality and capabilities of the OLI 
Engine for flowsheet simulation.
If a specified amount of energy is to be added to a stream, 
this may be accomplished by specifying the energy stream 
into either a Cooler/Heater or Balance operation.
Refer to the Aspen 
HYSYS OLI Interface 
Reference Guide for 
detailed information on 
electrolyte flash and 
aqueous 
thermodynamics.A-86
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ThWhen the OLI_Electrolyte property package is associated with 
material streams, the streams exclusively become electrolyte 
material streams in the flowsheet. That is, the stream conducts 
a simultaneous phase and reaction equilibrium flash. For the 
model used and the reactions involved in the flash calculation, 
refer to the Aspen HYSYS OLI Interface Reference Guide.
An electrolyte material stream in Aspen HYSYS can perform the 
following type of flashes:
• TP Flash
• PH Flash
• TH Flash
• PV Flash
• TV Flash
Due to the involvement of reactions in the stream flash, the 
equilibrium stream flash may result in a different molar flow and 
composition from the specified value. Therefore, mass and 
energy are conserved for an electrolyte material stream against 
the Aspen HYSYS stream for mass, molar and energy balances.
Limitations exist in the Aspen HYSYS OLI Interface package in 
the calculation of the stream flash results. The calculation for 
the electrolyte flash results must fall within the following 
physical ranges to be valid.
• composition of H2O in aqueous phase must be > 0.65.
• Temperature must be between 0 and 300°C.
• Pressure must be between 0 and 1500 atm.
• Ionic strength must be between 0 and 30 mole/kg-H2O.
A.7.6 Handling of Water
Water is handled differently depending on the correlation being 
used. The PR and PRSV equations are enhanced to handle H2O 
rigorously whereas the semi-empirical and vapour pressure 
models treat H2O as a separate phase using steam table 
correlations. 
Refer to Section 1.7 - 
Range of Applicability 
of the Aspen HYSYS OLI 
Interface Reference 
Guide for more 
information on the 
limitations of the HEO 
models.A-87
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A-88 Flash Calculations
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ThIn these correlations, H2O is assumed to form an ideal, partially-
miscible mixture with the hydrocarbons and its K value is 
computed from the relationship:
where:  
p° = vapour pressure of H2O from Steam Tables
P = system pressure
xs = solubility of H2O in hydrocarbon liquid at saturation 
conditions.
The value for xs is estimated by using the solubility data for 
kerosene as shown in Figure 9A1.4 of the API Data Book2. This 
approach is generally adequate when working with heavy 
hydrocarbon systems. However, it is not recommended for gas 
systems.
For three phase systems, only the PR and PRSV property 
package and Activity Models allow components other than H2O 
in the second liquid phase. Special considerations are given 
when dealing with the solubilities of glycols and CH3OH. For acid 
gas systems, a temperature dependent interaction parameter 
was used to match the solubility of the acid component in the 
water phase.
The PR equation considers the solubility of hydrocarbons in H2O, 
but this value may be somewhat low. The reason for this is that 
a significantly different interaction parameter must be supplied 
for cubic equations of state to match the composition of 
hydrocarbons in the water phase as opposed to the H2O 
composition in the hydrocarbon phase. For the PR equation of 
state, the latter case was assumed more critical. The second 
binary interaction parameter in the PRSV equation allows for an 
improved solubility prediction in the alternate phase.
With the activity coefficient models, the limited mutual solubility 
of H2O and hydrocarbons in each phase can be taken into 
account by implementing the insolubility option (please refer to 
(A.68)Kω
p°
xsP( )
------------=A-88
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ThSection A.3.2 - Activity Models). Aspen HYSYS generates, 
upon request, interaction parameters for each activity model 
(with the exception of the Wilson equation) that are fitted to 
match the solubility of H2O in the liquid hydrocarbon phase and 
hydrocarbons in the aqueous phase based on the solubility data 
referred to in that section. 
The Peng-Robinson and SRK property packages will always force 
the water rich phase into the heavy liquid phase of a three 
phase stream. As such, the aqueous phase is always forced out 
of the bottom of a three phase separator, even if a light liquid 
phase (hydrocarbon rich) does not exist. Solids are always 
carried in the second liquid phase.
A.7.7 Supercritical Handling
Aspen HYSYS reports a vapor fraction of zero or one, for a 
stream under supercritical conditions. Theoretically, this value 
doesn’t have any physical meaning for a supercritcial fluid, since 
there is no distinction of liquid or vapor phases in a supercritical 
region. However, it is important to determine if a supercritical 
fluid is liquid-like or a vapor-like fluid. This is because some of 
the properties reported in Aspen HYSYS are calculated using 
certain sets of specific phase models. In other words, phase 
identification has to be carried out in order to decide which 
model to use to calculate these properties.
In Aspen HYSYS, all flash results go through a phase order 
function to identify the phase type. Different packages have 
their own different order.
For example, the following criteria are used to identify phase 
types for the PR, SRK, SourPR, and Sour SRK cubic equations of 
state at supercritical region:
1. If the compressibility factor (Z) is greater than 0.3, and the 
isothermal compressibility factor (beta) is greater than 0.75, 
a vapor fraction of 1.0 is assigned to the stream.
2. If Z is greater than 0.75 and the sum of composition of light 
compounds (NBP<230K) is greater than the sum of 
composition of heavy compounds, a vapor fraction of 1.0 is 
assigned to the stream.A-89
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ThOtherwise, vapor fraction of 0 is assigned to the stream and 
liquid correlations are used.
A.7.8 Solids
Aspen HYSYS does not check for solid phase formation of pure 
components within the flash calculations, however, incipient 
solid formation conditions for CO2 and hydrates can be predicted 
with the Utility Package.
Solid materials such as catalyst or coke can be handled as user-
defined, solid type components. The Aspen HYSYS property 
package takes this type of component into account in the 
calculation of the following stream variables: stream total flow 
rate and composition (molar, mass and volume), vapour 
fraction, entropy, enthalpy, specific heat, density, molecular 
weight, compressibility factor, and the various critical 
properties. Transport properties are computed on a solids-free 
basis. Note that solids are always carried in the second liquid 
phase, i.e., the water rich phase.
Solids do not participate in vapour-liquid equilibrium (VLE) 
calculations. Their vapour pressure is taken as zero. However, 
since solids do have an enthalpy contribution, they have an 
effect on heat balance calculations. Thus, while the results of a 
Temperature flash are the same whether or not such 
components are present, an Enthalpy flash is affected by the 
presence of solids.
A solid material component is entered as a hypothetical 
component in Aspen HYSYS.
For more information on 
utilities, refer to Chapter 
14 - Utilities of the 
Aspen HYSYS 
Operations Guide.
Refer to Chapter 3 - 
Hypotheticals for more 
information on 
Hypotheticals.A-90
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Property Methods & Calculations A-91
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ThA.7.9 Stream Information
When a flash calculation occurs for a stream, the information 
that is returned depends on the phases present within the 
stream. The following table shows the stream properties that 
are calculated for each phase:
Steam Property Applicable PhasesA
Vapour Phase Mole Fraction F V L S
Vapour Phase Mass Fraction F V L S
Vapour Phase Volume Fraction F V L S
Temperature F V L S
Pressure F V L S
Flow F V L S
Mass Flow F V L S
Liquid Volume Flow (Std, Ideal) F V L S
Volume Flow F V L S
Std. Gas Flow F V L S
Std. Volume Flow F L S
Energy F V L S
Molar Enthalpy F V L S
Mass Enthalpy F V L S
Molar Entropy F V L S
Mass Entropy F V L S
Molar Volume F V L S
Molar Density F V L S
Mass Density F V L S
Std. Liquid Mass Density FD L S
Molar Heat Capacity F V L S
Mass Heat Capacity F V L S
CP/CV F V L S
Thermal Conductivity FB,D V L
Viscosity FB,D V L
Kinematic Viscosity FB,D V L
Surface Tension FB L
Molecular Weight F V L S
Z Factor FB V L S
Air SG FB V
Watson (UOP) K Value F V L S
Component Mole Fraction F V L S
AStream phases:
F - Feed
V - Vapour
L - Liquid
S - SolidA-91
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A-92 References
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ThBPhysical property queries are allowed on the feed phase of single phase streams.
CPhysical property queries are allowed on the feed phase only for streams containing vapour 
and/or liquid phases.
DPhysical property queries are allowed on the feed phase of liquid streams with more than one 
liquid phase.
A.8 References
 1 API Publication 955, A New Correlation of NH3, CO2 and H2S 
Volatility Data From Aqueous Sour Water Systems, March 1978.
 2 API Technical Data Book, Petroleum Refining, Fig. 9A1.4, p. 9-15, 5th 
Edition (1978).
 3 Chao, K. D. and Seader, J. D., A.I.Ch.E. Journal, pp. 598-605, 
December 1961.
 4 Ely, J.F. and Hanley, H.J.M., "A Computer Program for the Prediction 
of Viscosity and Thermal Conductivity in Hydrocarbon Mixtures", 
NBS Technical Note 1039.
 5 Gambill, W.R., Chem. Eng., March 9, 1959.
 6 Grayson, H. G. and Streed, G. W., "Vapour-Liquid Equilibria for High 
Temperature, High Pressure Systems", 6th World Petroleum 
Congress, West Germany, June 1963.
 7 Hankinson, R.W. and Thompson, G.H., A.I.Ch.E. Journal, 25, No. 4, 
p. 653 (1979).
Component Mass Fraction F V L S
Component Volume Fraction F V L S
Component Molar Flow F V L S
Component Mass Flow F V L S
Component Volume Flow F V L S
K Value (y/x)
Lower Heating Value
Mass Lower Heating Value
Molar Liquid Fraction F V L S
Molar Light Liquid Fraction F V L S
Molar Heavy Liquid Fraction F V L S
Molar Heat of Vapourization FC V L
Mass Heat of Vapourization FC V L
Partial Pressure of CO2 F V L S
Steam Property Applicable PhasesAA-92
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Property Methods & Calculations A-93
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Th 8 Hayden, J.G. and O’Connell, J.P., Ind. Eng. Chem., Process Des. Dev. 
14, 209 (1975).
 9 Jacobsen, R.T and Stewart, R.B., 1973. "Thermodynamic Properties 
of Nitrogen Including Liquid and Vapour Phases from 63 K to 2000K 
with Pressure to 10 000 Bar." J. Phys. Chem. Reference Data, 2: 
757-790.
 10Kabadi, V.N., and Danner, R.P. A Modified Soave-Redlich-Kwong 
Equation of State for Water-Hydrocarbon Phase Equilibria, Ind. 
Eng. Chem. Process Des. Dev. 1985, Volume 24, No. 3, pp 537-
541.
 11Keenan, J. H. and Keyes, F. G., Thermodynamic Properties of Steam, 
Wiley and Sons (1959).
 12Knapp, H., et al., "Vapor-Liquid Equilibria for Mixtures of Low Boiling 
Substances", Chemistry Data Series Vol. VI, DECHEMA, 1989.
 13Passut, C. A.; Danner, R. P., “Development of a Four-Parameter 
Corresponding States Method: Vapour Pressure Prediction”, 
Thermodynamics - Data and Correlations, AIChE Symposium 
Series; p. 30-36, No. 140, Vol. 70.
 14Peng, D. Y. and Robinson, D. B., "A Two Constant Equation of State", 
I.E.C. Fundamentals, 15, pp. 59-64 (1976).
 15Perry, R. H.; Green, D. W.; “Perry’s Chemical Engineers’ Handbook 
Sixth Edition”, McGraw-Hill Inc., (1984).
 16Prausnitz, J.M., Lichtenthaler, R.N., Azevedo, E.G., "Molecular 
Thermodynamics of Fluid Phase Equilibria", 2nd. Ed., McGraw-Hill, 
Inc. 1986.
 17Reid, C.R., Prausnitz, J.M., and Sherwood, T.K., "The Properties of 
Gases and Liquids", McGraw-Hill Book Company, 1977.
 18Reid, R.C., Prausnitz, J.M., and Poling, B.E., "The Properties of Gases 
& Liquids", McGraw-Hill, Inc., 1987.
 19Soave, G., Chem Engr. Sci., 27, No. 6, p. 1197 (1972).
 20Stryjek, R., Vera, J.H., J. Can. Chem. Eng., 64, p. 334, April 1986.
 21Twu, C.H., I.E.C. Proc Des & Dev, 24, p. 1287 (1985).
 22Woelflin, W., "Viscosity of Crude-Oil Emulsions", presented at the 
spring meeting, Pacific Coast District, Division of Production, Los 
Angeles, Calif., Mar. 10, 1942.
 23Zudkevitch, D., Joffee, J. "Correlation and Prediction of Vapor-Liquid 
Equilibria with the Redlich-Kwong Equation of State", AIChE 
Journal, Volume 16, No. 1, January pp. 112-119.A-93
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A-94 References
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ThA-94
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Oil Methods & Correlations B-1
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ThB  Oil Methods & 
CorrelationsB-1
B.1  Introduction .................................................................................. 2
B.2  Characterization Method................................................................ 2
B.2.1  Generate a Full Set of Working Curves ........................................ 3
B.2.2  Light Ends Analysis................................................................... 4
B.2.3  Auto Calculate Light Ends.......................................................... 7
B.2.4  Determine TBP Cutpoint Temperatures ........................................ 8
B.2.5  Graphically Determine Component Properties............................... 9
B.2.6  Calculate Component Critical Properties ...................................... 9
B.2.7  Correlations........................................................................... 10
B.3  References................................................................................... 11
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ThB.1 Introduction
This appendix is a supplement to Chapter 4 - HYSYS Oil 
Manager. Included in this appendix is the general procedure 
used by Aspen HYSYS to characterize an oil and a list of 
correlations used in the Oil Manager.
B.2 Characterization 
Method
The procedure Aspen HYSYS uses to convert your assay data 
into a series of petroleum hypocomponent involves four major 
internal characterization steps:
1. Based on your input curves, Aspen HYSYS calculates a 
detailed set of full range Working Curves that include the 
true boiling point (TBP) temperature, molecular weight, 
density and viscosity behaviour.
2. Next, by using either a default or user-supplied set of 
cutpoint temperatures, the corresponding fraction for each 
hypocomponent is determined from the TBP working curve.
3. The normal boiling point (NBP), molecular weight, density 
and viscosity of each hypocomponent are graphically 
determined from the working curves.
4. For each hypocomponent, Aspen HYSYS calculates the 
remaining critical and physical properties from designated 
correlations, based upon the component's NBP, molecular 
weight, and density.
Knowledge of the four phases of the characterization process 
provide a better understanding of how your input data 
influences the final outcome of your characterization. The 
following sections detail each step of the calculation.B-2
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ThB.2.1 Generate a Full Set of 
Working Curves
To ensure accuracy, a true boiling point (TBP) curve and 
associated molecular weight, density, and viscosity property 
curves are required for the characterization calculations. Aspen 
HYSYS takes whatever input curves you have supplied, and 
interpolates and extrapolates them as necessary to complete 
the range from 0 to 100%. These full range curves are referred 
to as the working curves.
If you supply an ASTM D86, ASTM D1160, or EFV distillation 
curve as input, it is automatically converted to a TBP distillation 
curve. On the other hand, if you do not have any distillation 
data, supplying two of the three bulk properties (molecular 
weight, density, or Watson (UOP) K factor) allows Aspen HYSYS 
to calculate an average1 TBP distillation curve.
Physical property curves that were not supplied are calculated 
from default correlations designed to model a wide variety of 
oils, including condensates, crude oils, petroleum fractions, and 
coal-tar liquids. If you supply a bulk molecular weight or bulk 
density, the corresponding physical property curve (either user-
supplied or generated) is smoothed and adjusted such that the 
overall property is matched. A typical TBP curve is illustrated 
below. 
 Figure B.1
Percent Distilled0 100
Te
m
p
er
at
u
re
IBP
FBPB-3
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B-4 Characterization Method
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ThB.2.2 Light Ends Analysis
Aspen HYSYS uses your Light Ends data to either define or 
replace the low boiling portion of your TBP, ASTM D86 or ASTM 
D1160 curve with discrete pure components. Aspen HYSYS does 
not require that you match the highest boiling point light-end 
with the lowest boiling point temperature on the TBP curve. 
Using the sample Light Ends analysis shown here, Aspen HYSYS 
replaces the first portion of the TBP working curve to the assay 
percentage just past the boiling point of n-pentane 
(approximately 95°F or 36°C) or 11.3 vol% (the cumulative 
light ends total), whichever is greater. The new TBP curve would 
include the Light Ends Free portion of the original sample 
beginning at 0% distilled with the associated IBP representing 
the remaining portion of the original sample.
Three possible Light Ends/Assay situations can exist as depicted 
in the next three figures. In the following figures:
• Point A represents the boiling point of the heaviest light-
end, n-Pentane in this example.
• Point B represents the temperature at which the total 
Light Ends percentage intersects the TBP working curve.
Default values of the IBP and FBP can be changed on the 
Boiling Ranges property view.
Refer to Section 4.4 - 
Oil Characterization 
Property View for more 
information.B-4
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ThIf points A and B coincide exactly as shown in Figure B.2, 
Aspen HYSYS assigns the TBP working curve's IBP equal to the 
boiling point of the heaviest light end and normalizes the 
remaining portion of the TBP curve with the light ends removed. 
All points that lie below point B on the curve are eliminated.
Figure B.3 depicts the situation that may arise from 
inconsistent data or from a poor extrapolation of the IBP. 
These situations are corrected by assuming that the Light Ends 
analysis is correct and that the error exists in the internal TBP 
curve. In the figure, Point A (boiling point of the heaviest light 
end component) lies below Point B (internal TBP curve 
temperature associated with your cumulative light ends 
percentage) on the internal TBP working curve. Aspen HYSYS 
replaces point B (the Light Ends free IBP) by a point that uses 
the cumulative light ends percentage and the normal boiling 
 Figure B.2
 Figure B.3
Percent Distilled0 100
Te
m
p
er
a
tu
re
IBP
FBP
NBP 
nC5
Portion of Original Assay that will 
be Renor-malized to be on a Light 
Ends Free Basis
Cumulative Light 
Ends % Distilled
A B
Percent Distilled0 100
Te
m
p
er
at
u
re
IBP
FBP
NBP 
nC5
Portion of Original Assay that will 
be Renor-malized to be on a Light 
Ends Free Basis
Cumulative Light Ends % Distilled
B
A
B-5
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B-6 Characterization Method
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Thpoint of the heaviest light ends component. The Light Ends free 
portion of the curve is smoothed before normalizing.
Figure B.4 shows the boiling point of the heaviest light-end 
occurring at an assay percentage greater than the cumulative 
Light Ends total. Aspen HYSYS corrects this situation by 
successively eliminating TBP working curve points from point B 
up to the first temperature point greater than the heaviest light 
end temperature (Point A).
For example, if in the above figure Point B represents 5% and 
Point A represents 7%, the new TBP curve (which is light ends 
free) is stretched, i.e., what was 93% of the assay (determined 
from point A) is now 95% of the assay. As in the previous case, 
Point A's temperature is assigned to the new TBP curve’s IBP, 
and the Light Ends free portion is smoothed and normalized.
 Figure B.4
Percent Distilled0 100
Te
m
p
er
a
tu
re
IBP
FBP
NBP 
nC5
Portion of Original Assay that 
will be Renor-malized to be 
on a Light Ends Free Basis
Cumulative Light Ends % Distilled
A
B
Portion of TBP that is eliminated due to 
inconsistencies between the Distillation 
and Light-Ends AnalysesB-6
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Oil Methods & Correlations B-7
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ThB.2.3 Auto Calculate Light 
Ends
Aspen HYSYS' Auto Calculate Light Ends procedure internally 
plots the boiling points of the defined components on the TBP 
working curve and determines their compositions by 
interpolation. Aspen HYSYS adjusts the total Light Ends fraction 
such that the boiling point of the heaviest light end is at the 
centroid volume of the last Light Ends component. The figure 
below illustrates the Auto Calculate Light Ends removal 
procedure.
 Figure B.5
Te
m
p
er
at
u
re
IBP
FBP
NBP nC5
nC4
iC5
iC4
0 100
iC4 iC5
nC5nC4
Percent Distilled
Cumulative 
Light Ends 
% Distilled
Portion of Original Assay that will be 
Renormalized to be on a Light Ends Free Basis
New IBP point for the TBP curve
Centroid Volume of the Last 
Light-End ComponentB-7
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B-8 Characterization Method
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ThB.2.4 Determine TBP Cutpoint 
Temperatures
You may specify the hypocomponent breakdown by supplying a 
number of cutpoint temperatures and the corresponding number 
of cuts for each temperature range, or you may let Aspen 
HYSYS calculate an optimal set of cutpoints for you based upon 
the overall number of hypocomponent you have designated. The 
characterization process then uses its TBP working curve and 
the specified set of TBP cutpoints to determine the fraction of 
each hypocomponent on the input curve basis. 
In Figure B.6, four components are generated from the TBP 
curve using five TBP cutpoints of equal temperature increment. 
Refer to Section 4.6 - Hypocomponent Generation for more 
details.
 Figure B.6
Percent Distilled0 100
Te
m
p
er
at
u
re
T4
CUT1
CUT2 CUT3
CUT4
IBP
T3
T2
T1B-8
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Oil Methods & Correlations B-9
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ThB.2.5 Graphically Determine 
Component Properties
After the cutpoints and the fraction of each hypocomponent are 
known, the average boiling point may be determined. This is the 
normal boiling point (NBP), which is calculated for each 
component by equalizing the areas between the TBP curve and a 
horizontal line representing the NBP temperature. This is shown 
in the figure below, with the grey areas representing the 
equalized areas. The average molecular weight, density, and 
viscosity of each hypocomponent are subsequently calculated 
from the corresponding smoothed working curves for molecular 
weight, density and viscosity.
B.2.6 Calculate Component 
Critical Properties
Knowing the normal boiling point, molecular weight, and density 
enables Aspen HYSYS to calculate the remaining physical and 
thermodynamic properties necessary to completely define the 
petroleum hypocomponent. These properties are estimated for 
each hypocomponent using default or user-selected correlations 
as outlined in Section B.2.7 - Correlations.
 Figure B.7
Te
m
p
er
at
u
re
T4
IBP
T3
T2
T1
Percent Distilled
0 100
CUT1 CUT2 CUT3 CUT4B-9
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B-10 Characterization Method
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ThB.2.7 Correlations
The range of applicability for the critical property correlations 
are explained below:
Critical Property 
Correlation
Range of Applicability
Lee-Kesler These equations yield nearly identical results to those obtained using the 
graphical correlations found in the API Data Book for boiling temperatures 
below 1250°F (677°C). The equations are modified to extend beyond this 
range, but an upper limit is not given by the authors.
Cavett The author does not present any reference as to which data were used for 
the development of the correlations or their limitations. Experience has 
proven these correlations to produce very good results for fractions whose 
API gravity is greater than zero or for highly aromatic and naphthenic 
fractions such as coal tar liquids.
Riazi-Daubert In the boiling point range 0 - 602°F (-18 - 317°C), these correlations 
perform slightly better than other methods. Their most serious drawback 
is the limitation of the boiling point to 855°F (457°C) for the calculation of 
critical pressure and molecular weight.
Nokay Limitations for these correlations are not presented in the original 
publications. The critical temperature and molecular weight correlations 
are particularly good for highly aromatic or naphthenic systems as shown 
in a paper by Newman, "Correlations Evaluated for Coal Tar Liquids".
Roess The main limitation of these correlations is that they should not be used 
for fractions heavier than C20 (650°F, 343°C). They highly underestimate 
critical temperatures for heavier fractions and should not be used for 
heavy oil applications.
Edmister These equations are very accurate for pure components, but are restricted 
to condensate systems with a limited amount of isomers. Edmister 
acentric factors tend to be lower than Lee-Kesler values for fractions 
heavier than C20 (650°F, 343°C). It is recommended that application of 
the Edmister equation be restricted to the range below C20.
Bergman These correlations were developed for lean gases and gas condensates 
with relatively light fractions, thereby limiting their general applicability to 
systems with carbon numbers less than C15.
Spencer-Daubert This family of correlations is a modification of the original Nokay equations 
with a slightly extended range of applicability.
Rowe These equations were presented for estimating boiling point, critical 
pressure and critical temperature of paraffin hydrocarbons. Carbon 
number, which is used as the only correlating variable, limits the range of 
applicability to lighter paraffinic systems.
Standing The data of Matthews, Roland and Katz was used to develop these 
correlations. Molecular weight and specific gravity are the correlating 
variables. Although Standing claims the correlations are for C7+ fractions, 
they appear to be valid for narrower boiling point cuts as well. The 
correlations should be used with caution for fractions heavier than C25 
(841°F, 450°C).B-10
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ThB.3 References
 1 Whitson, C. H., “Characterizing Hydrocarbon Plus Fractions”, Society 
of Petroleum Engineers Journal, August 1983.
Lyderson These correlations are based on the PNA (Paraffin/Napthene/Aromatic) 
concept similar to Peng-Robinson PNA.
Bergman This method is limited to components whose gravity does not exceed 
0.875 because of the form of the PNA equations. Acentric factors for 
fractions heavier than C20 are considerably higher than those estimated 
from either the Edmister or Lee-Kesler equation. These correlations are 
included primarily for completeness and should not be used for fluids 
containing fractions heavier than C20.
Yarborough This method is only for use in the prediction of specific gravity of 
hydrocarbon components. Carbon number and aromaticity are the 
correlating variables for this equation. The Yarborough method assumes 
that the C7+ molecular weight and specific gravity are measured. It also 
assumes that the mole fractions are measured from chromatographic 
analysis (paraffin molecular weights are assumed to convert weight to 
mole fractions).
Katz-Firoozabadi These correlations are only available for the prediction of molecular weight 
and specific gravity. Normal boiling point is the only correlating variable 
and application should be restricted to hydrocarbons less than C45.
Mathur Limitations for these correlations are not published by the author. These 
equations produce excellent results for highly aromatic mixtures such as 
coal-tar liquids, but are not rigorously examined for highly paraffinic 
systems.
Penn State These correlations are similar to Riazi-Daubert correlations and should 
have approximately the same limitations.
Aspen These correlations yield results quite close to the Lee-Kesler equations, 
but tend to produce better results for aromatic systems. Limitations for 
these equations are not available, but the Lee-Kesler limitations should 
provide a good guide.
Hariu Sage These correlations were developed for estimating molecular weight from 
boiling point and specific gravity utilizing the Watson Characterization 
Factor, Kw. It provides reasonable extrapolation to boiling points greater 
than 1500°F (816°C) and is more accurate than the Lee-Kesler molecular 
weight correlation.
Critical Property 
Correlation
Range of ApplicabilityB-11
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ThB-12
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Amines Property Package C-1
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ThC  Amines Property 
PackageC-1
C.1  Amines Property Package .............................................................. 2
C.2  Non-Equilibrium Stage Model......................................................... 5
C.3  Stage Efficiency ............................................................................. 7
C.3.1  Non-Equilibrium Stage Model ..................................................... 8
C.4  Equilibrium Solubility..................................................................... 9
C.4.1  Kent & Eisenberg Model ............................................................ 9
C.4.2  Li-Mather Electrolyte Model ..................................................... 13
C.5  Phase Enthalpy ............................................................................ 19
C.6  Simulation of Amine Plant Flowsheets ......................................... 20
C.6.1  Solving the Columns............................................................... 20
C.6.2  Converging the Contactor........................................................ 21
C.6.3  Converging the Regenerator .................................................... 22
C.6.4  Recycle Convergence .............................................................. 22
C.6.5  Operating Conditions .............................................................. 23
C.7  Program Limitations .................................................................... 24
C.7.1  Range of Applicability ............................................................. 24
C.8  References................................................................................... 25
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ThC.1 Amines Property 
Package
The removal of acid gases such as hydrogen sulphide (H2S) and 
carbon dioxide (CO2) from process gas streams is often required 
in natural gas plants and in oil refineries. There are many 
treating processes available. However, no single process is ideal 
for all applications. The initial selection of a particular process 
may be based on feed parameters such as composition, 
pressure, temperature and the nature of the impurities, as well 
as product specifications. 
Final selection is ultimately based on process economics, 
reliability, versatility, and environmental constraints. The 
selection procedure is not a trivial matter; any tool that provides 
a reliable mechanism for process design is highly desirable. 
Acid gas removal processes using absorption technology and 
chemical solvents are popular, particularly those using aqueous 
solutions of alkanolamines. The Amines Property Package is a 
special property package designed to aid in the modeling of 
alkanolamine treating units in which H2S and CO2 are removed 
from gas streams. The Property Package contains data to model 
the absorption/desorption process which use the following:
• aqueous solutions of single amines – monoethanolamine 
(MEA), diethanolamine (DEA), methyldiethanolamine 
(MDEA), triethanolamine (TEA), 2,2'-hydroxy-
aminoethylether (DGA), or diisopropanolamine (DIPA)
• aqueous solutions of blended amines – MEA/MDEA or 
DEA/MDEA
• a physical solvent – dimethyl ethers of polyethylene 
glycol (DEPG) also known as Coastal AGR
Any combination of two amines can be used for the Li-Mather 
model. 
The Amines Property Package is a special option available 
for Aspen HYSYS. For more information on this option or get 
information on other Aspen HYSYS additions please contact 
your AspenTech Agent.C-2
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ThFigure C.1 shows the conventional process configuration for a 
gas treating system that uses aqueous alkanolamine solutions. 
The sour gas feed is contacted with amine solution counter-
currently in a trayed or packed absorber. Acid gases are 
absorbed into the solvent that is then heated and fed to the top 
of the regeneration tower. Stripping steam produced by the 
reboiler causes the acid gases to desorb from the amine solution 
as it passes down the column. A condenser provides reflux and 
the acid gases are recovered overhead as a vapour product. 
Lean amine solution is cooled and recycled back to the absorber. 
A partially stripped, semi-lean amine stream may be withdrawn 
from the regenerator and fed to the absorber in the split-flow 
modification to the conventional plant flowsheet. A three-phase 
separator or flash tank may be installed at the outlet of the 
absorber to permit the recovery of dissolved and entrained 
hydrocarbons and to reduce the hydrocarbon content of the acid 
gas product.
 Figure C.1C-3
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ThThe design of amine treating units involves the selection of the 
following:
• the process configuration
• the amine type and concentration
• the solution circulation rate
• the reboiler heat requirements
• the operating pressures and temperatures. 
The mechanical tray design and the number of stages in the 
contactor are known to affect the process performance and are 
particularly important in selective absorption applications.
Amine treating units were designed in the past using hand 
calculations and operating experience. Design conditions were 
typically chosen within a conservative range to cover the 
deficiencies in the data used in the hand calculations. Simulation 
is one means of obtaining values for the key design variables in 
the process, and is generally used to confirm the initial design 
obtained by the above methods. 
Rules-of-thumb do not exist for the design of selective 
absorption applications since operating experience is limited. 
Furthermore, the process is generally controlled by reaction 
kinetics and cannot be designed on the basis of chemical 
equilibrium alone. The simulation program must be relied upon 
as a predictive tool in these cases. 
The AMSIM program uses technology developed by DB Robinson 
& Associates Ltd. to model the equilibrium solubility of acid 
gases in aqueous amine solutions. 
A new nonequilibrium stage model which is based on the stage 
efficiency concept is used to simulate the performance of 
contactors and regenerators. A list of reference articles on the 
research leading to the development of AMSIM can be found at 
the end of this section. The best data known to exist is used to 
determine the component properties in the AMSIM databank.
Currently Aspen HYSYS uses AMSIM version 7.2. AMSIM has 
also been integrated with COMThermo.C-4
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Th 
C.2 Non-Equilibrium Stage 
Model
A non-equilibrium stage model developed to simulate the multi-
component multistage mass transfer process encountered in an 
amine treating unit is used in the Amines Property Package. 
The generalized stage model shown in Figure C.2 gives the flow 
geometry and nomenclature for an individual stage in a column. 
The fundamental concept used is that the rate of absorption/
desorption of acid gases to/from the amine solution must be 
considered as a mass-transfer rate process. This rate process 
depends on the equilibrium and kinetic parameters that describe 
the acid gas/amine system.
The model incorporates a modified Murphree-type vapour 
efficiency to account for the varying mass-transfer rates of 
individual acid gas components. The acid gas stage efficiencies 
are, in turn, functions of mass-transfer coefficients and the 
mechanical design of the tray. 
The AMSIM models is designed for one amine or two amines. 
When two amines are selected, the Amines property package 
expects both amines to have a composition or both amines 
to be zero. You cannot specify one amine composition to be 
greater than zero and the other to be equal to zero. It is 
suggested that instead of specifying one amine to be zero, 
input a very small composition value for said amine.C-5
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ThWhen the generalized stage model is extended to the multistage 
case, the resulting column flow geometry and nomenclature is 
shown in Figure C.2. The resulting set of balance equations 
that characterize the multistage unit are given in Section C.4 - 
Equilibrium Solubility. This set of equations must be solved 
for each column in the flowsheet. A modified Newton-Raphson 
method is used to solve the rigorous non-linear stage equations 
simultaneously for temperature, composition and phase rates on 
each stage in a column.
 Figure C.2C-6
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ThC.3 Stage Efficiency
The stage efficiency as defined under the Amines property 
package option is given by:
where:  
 = Stage efficiency
i = Component number
j = Stage number
K = Equilibrium ratio
V = Molar flow rate of vapour
X = Mole fraction in liquid phase
Y = Mole fraction in vapour phase
The stage efficiency is a function of the kinetic rate constants for 
the reactions between each acid gas and the amine, the 
physico-chemical properties of the amine solution, the pressure, 
temperature and the mechanical tray design variables such as 
tray diameter, weir height and weir length. 
You may specify the stage efficiencies or have them calculated 
in Aspen HYSYS.
(C.1)
If the Amines option is selected, Aspen HYSYS always uses 
stage-component efficiencies. Note that the efficiencies used 
are only for H2S and C02 components. If the efficiencies are 
not specified for the column, Aspen HYSYS calculates 
efficiencies based on the tray dimensions specified in the 
Amines page of the Column property view. If no tray 
dimensions are specified, Aspen HYSYS uses the default tray 
dimensions to calculate the stage efficiencies. These are real 
stages, not ideal stages.
η
Vj SVj+( )Yj Vj 1+ Yij 1+–
Vj SVj+( )K1jXij Vj 1+ Yij 1+–
------------------------------------------------------------------------=
η
C-7
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ThC.3.1 Non-Equilibrium Stage 
Model
Overall Material Balance
Component Material Balance
Energy Balance
Equilibrium Relationship
Summation Equation
(C.2)
(C.3)
(C.4)
(C.5)
(C.6)
Fj Lj 1– Lj SLj+( )– Vj SVj+( )–+ 0=
Fjzij Lj 1– xij 1– Vj 1+ Yij 1+ Lj SLj+( )xij– Vj SVj+( )yij–+ + 0=
FjHFj Qj Lj 1– hj 1– Vj 1+ Hj 1+ Lj SLj+( )hj– Vj SVj+( )Hi–+ + + 0=
ηi jKijxij Vj SVj+( ) Vj SVj+( )yij– 1 ηij–( )Vj 1+ yij 1++ 0=
yij 1.0–∑ 0=C-8
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ThC.4 Equilibrium Solubility
C.4.1 Kent & Eisenberg Model
A model based on the Kent and Eisenberg approach is used to 
correlate the equilibrium solubility of acid gases in the amine 
solutions. The reference articles contain experimental data that 
were used to validate the solubility model. Additional 
unpublished data for DEA, MDEA, MEA/MDEA, and DEA/MDEA 
systems have also been incorporated. 
Improvements were made to the model to extend the reliable 
range to mole loadings between 0.0001 and 1.2. A proprietary 
model was developed to predict the solubility of acid gas 
mixtures in tertiary amine solutions. Solubilities of inert 
components such as hydrocarbons are modelled using a Henry's 
constant adjusted for ionic strength effects. 
The prediction of equilibrium ratios or K-values involves the 
simultaneous solution of a set of non-linear equations that 
describe the chemical and phase equilibria and the 
electroneutrality and mass balance of the electrolytes in the 
aqueous phase. These equations are provided below. The model 
is used to interpolate and extrapolate the available experimental 
solubility data in the Amines Property Package. For tertiary 
amines that do not form carbamate, the equations involving that 
ionic species are eliminated from the model.
These equations are shown as follows:  
Chemical Reactions
(C.7)
(C.8)
(C.9)
R1R2NH H2O R1R2NH2
+ OH-+⇔+
R1R2R3N H2O R1R2R3NH+ OH-+⇔+
R1R2NH CO2 R1R2NCOO- H++⇔+C-9
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Th    
(C.10)
(C.11)
(C.12)
(C.13)
(C.14)
Equilibrium Relations
(C.15)
(C.16)
(C.17)
(C.18)
(C.19)
(C.20)
(C.21)
(C.22)
Chemical Reactions
H2O H+⇔ OH-+
H2S H+⇔ HS-+
CO2 H2O+ H+⇔ HCO3
-+
HS- H+⇔ S=+
HCO3
- H+⇔ CO3
=+
K1
H+[ ] R1R2NH[ ]
R1R2NH2
+[ ]
--------------------------------------=
K2
H+[ ] R1R2R3N[ ]
R1R2R3NH+[ ]
----------------------------------------=
K3
HCO3
-[ ] R1R2NH[ ]
R1R2NCOO-[ ]
-----------------------------------------------=
K4
H+[ ] OH-[ ]
H2O[ ]
---------------------------=
K5
H+[ ] HS-[ ]
H2S[ ]
--------------------------=
K6
H+[ ] HCO3
-[ ]
CO2[ ] H2O[ ]
--------------------------------=
K7
H+[ ] S=[ ]
HS-[ ]
----------------------=
K8
H+[ ] CO3
=[ ]
HCO3
-[ ]
----------------------------=C-10
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Th 
Phase Equilibria
(C.23)
(C.24)
Charge Balance
(C.25)
Mass Balance
(C.26)
(C.27)
(C.28)
(C.29)
yH2SφH2S
V P HH2S H2S[ ]=
yCO2
φCO2
V P HCO2
CO2[ ]=
H+[ ] R1R2NH2
+[ ] R1R2R3NH+[ ]+ +
OH-[ ] R1R2NCOO-[ ] HCO3
-[ ] HS-[ ] 2 CO3
=[ ] 2 S=[ ]+ + + + +
=
C1 2 amine–, R1R2NH[ ] R1R2NH2
+[ ] R1R2NCOO-[ ]+ +=
C3 amine– R1R2R3N[ ] R1R2R3NH+[ ]+=
CCO2
C1 2 amine–, C3 amine–+( )αCO2
CO2[ ] R1R2NCOO-[ ] HCO3
-[ ] CO3
=[ ]+ + +
= =
CH2S C1 2 amine–, C3 amine–+( )αH2S
H2S[ ] HS-[ ] S=[ ]+ +
= =C-11
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C-12 Equilibrium Solubility
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ThThe fugacity coefficient of the molecular species is calculated by 
the Peng-Robinson equation of state:
where:  
The temperature-dependent quantity  has the following form.
The parameters  and  are substance-dependent and are 
determined through rigorous regressions against reliable data.
For mixtures, equation parameters a and b are estimated by the 
following mixing rules.
(C.30)
(C.31)
(C.32)
(C.33)
(C.34)
(C.35)
p RT
v b–
----------- a T( )
v v b+( ) b v b–( )+
---------------------------------------------–=
a α 0.45724( )R2Tc
2 Pc⁄=
b 0.07780( )RTc Pc⁄=
α
α1 2⁄ 1 α1 1 Tr–( ) α2 1 Tr–( ) 0.7 Tr–( )+ +=
α1 α2
a i j xixj aiaj( )0.5 1 kij–( )∑∑=
b i j xixj
bi bj+
2
--------------⎝ ⎠
⎛ ⎞ 1 lij–( )∑∑=C-12
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ThC.4.2 Li-Mather Electrolyte 
Model
The Amines property package is modified to simulate three 
phase behaviour. For the three phase simulation, the K values 
from the Peng-Robinson property package were combined with 
the K values from the Amines LLE and VLE package. 
The Li-Mather model shows a strong predictive capability over a 
wide range of temperatures, pressures, acid gas loadings, and 
amine concentrations. AMSIM is capable of simulating processes 
with blended solvents made up of any two of six principle 
amines (MEA, DEA, MDEA, TEA, DGA and DIPA).
The framework of the thermodynamic model is based on two 
types of equilibria: vapour-liquid phase equilibria and liquid-
phase chemical equilibria.
Phase Equilibria
The vapour-liquid equilibria of the molecular species is given by:
where:  
Hi = Henry’s constant
P = system pressure
xi, yi = mole fraction of molecular specied i in the liquid and 
gas phase
 = fugacity coefficient on the gas phase
 = activity coefficient in the liquid phase
(C.36)yiΦi
VP Hixiγi
L=
Φi
V
γi
L
C-13
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C-14 Equilibrium Solubility
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ThThe fugacity coefficient is calculated by the Peng-Robinson 
equation of state (Peng and Robinson, 1976):
Where the parameters are obtained from the EQUI-PHASE 
EQUI90TM program library. The activity coefficient is calculated 
by the Clegg-Pitzer equation that is described later in this 
section.
Chemical Equilibria
In case of single amine-H2S-CO2-H2O systems, the important 
chemical dissociation reactions are as follows:
The chemical equilibrium constants in the acid gas - amine 
systems play an important role in the prediction of the 
equilibrium solubilities of acid gases in the aqueous amine 
solutions. The equilibrium constant K can be expressed by:
(C.37)
Chemical Dissociation Reactions
(C.38)
(C.39)
(C.40)
(C.41)
(C.42)
(C.43)
(C.44)
P RT
V b–
------------ a T( )
V V b+( ) b V b–( )+
------------------------------------------------–=
Amine+ Amine H++⇔
H2S HS- H++⇔
CO2 H2O HCO3
- H++⇔+
H2O OH- H++⇔
HCO3
- CO3
= H++⇔
HS- S= H++⇔
K Πi xiyi( )
βi=C-14
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ThThe equilibrium constant is expressed as a function of 
temperature:
Henry’s constant has the same function of temperature as that 
in equation (C.45). In the liquid phase, there are four molecular 
species, Amine, H2O, CO2, H2S and seven ionic species, Amine+, 
HCO3
-, HS-, H+, OH-, CO3
=, S= for the amine-H2S-CO2-H2O 
system. In the gas phase, there are only four molecular species, 
Amine, H2O, CO2 and H2S.
The determination of the compositions of all molecular and ionic 
species in both vapour and liquid phases involves the 
simultaneous solution of a set of non-linear equations that 
describe the phase equilibria and chemical equilibria, 
electroneutrality (charge balance) and mass balance of the 
electrolytes in the aqueous solution.
The Clegg-Pitzer Equation
The original Pitzer equation (Pitzer, 1973) did not consider the 
solvent molecules in the system as interacting particles. Thus it 
is not suitable for the thermodynamic description of the mixed-
solvent systems. In the Clegg-Pitzer model, all the species in the 
system were considered as interacting particles. The long-range 
electrostatic term and the short-range hard-sphere-repulsive 
term deduced from the McMillan-Mayer's statistical osmotic-
pressure theory remained unchanged. The excess Gibbs free 
energy, gex consists of the long-range Debye-Huckel 
electrostatic interaction term, gDH and the short-range Margules 
expansions with two- and three-suffix, gs:
(C.45)
(C.46)
(C.47)
Kln C1 C2 T C3 T C4T+ln+⁄+=
gex gDH gs+=
gDH
RT
---------
4AxIx
ρ
------------- 1 ρIx
1 2⁄+( ) xcxaBacg αIx
1 2⁄( )
a
∑
c
∑+ln=C-15
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Thwhere:
The expressions of activity coefficient for solvent N and ion M+ 
are as follows:
(C.48)
(C.49)
gs
RT
------ aijxixj aijkxixjxk
k
∑
j
∑
i
∑+
a
∑
c
∑=
gs
RT
------ xI xn FcFaWnca xnxn' Ann'xn' An'nxn+( )
n""
∑
n
∑+
a
∑
c
∑
n
∑=
Ann' 2ann' 3an'n+=
Ann' 2ann' 3ann'n''+=
Wnca 2wnc 2wna wca– 2unc 2una+ + +( ) 4⁄=
wij 2aij 3 2 aiij aijj+( )⁄+=
uij 3 2 aiij aijj–( )⁄=
γNln
2AxIx
3 2⁄
1 ρIx
1 2⁄+
---------------------- xcxaBca αIx
1 2⁄–( ) xI 1 xN–( ) FcFaWNca
xI ′xn FcFaWnca ′xn ANnxn 1 2xN–( ) 2AnNxN 1 xN–( )+[ ]
2 ′ ′xnxn' Ann'xn' An'nxn+( )
n'
∑
n
∑–
n
∑+
a
∑
c
∑
n
∑–
a
∑
c
∑+exp
a
∑
c
∑–=C-16
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ThWhere subscripts c, a, n and n’ represent cation, anion and 
molecular species, respectively. The subscript 2 in equation 
(C.50) stands for water. the total mole fraction of ions (xI) is 
given by:
The cation and anion fractions Fc and Fa are defined for fully 
symmetrical electrolyte systems by
The mole fraction ionic strength Ix is defined as
(C.50)
(C.51)
(C.52)
(C.53)
(C.54)
γ
M+ln zM
2 Ax
2
ρ
-- 1 ρIx
1 2⁄+( )
Ix
1 2⁄ 1 2Ix zM
2⁄–( )
1 ρIx
1 2⁄+
-----------------------------------------+ln– xaBmag αIx
1 2⁄( )
xcxaBca
zM
2 g αIx
1 2⁄( )
2Ix
---------------------------- 1 zM
2 2Ix⁄–( ) αIx
1 2⁄–( )exp+ 2 xn FaWnMa
xn 1 xI+( ) FcFaWnca 2 FaW2Ma FcFaW2ca
2 xnxn' Ann'xn' An'nxn+( )
n'
∑
n
∑–
a
∑
c
∑+
a
∑–
a
∑
c
∑
n
∑–
a
∑
n
∑+
a
∑
c
∑–
a
∑+=
xI 1 xn∑–=
Fc 2xc xI⁄=
Fa 2xa xI⁄=
Ix 1 2 zi
2xI∑⁄=C-17
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C-18 Equilibrium Solubility
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ThThe function of g(x) is expressed by
where:  
Ax is the Debye-Huckel parameter on a mole fraction basis:
where:  
Ci, Cn = molar concentrations of the ion i and solvent n, 
respectively
I = ionic strength in molar concentration
 = Debye-Huckel parameter, which is a function of 
temperature, density and dielectric constant of the 
mixed solvents
 = related to the hard-core collision diameter, or distance of 
closest approach between ions in solution
An'n and Ann' = interaction parameters between and among 
the molecular species, respectively
Bca = hard sphere repulsion parameter between ions
Wnca = the interaction parameter between ions and between 
ion and solvent
Parameters An'n, Ann', Bca and Wnca share the same function 
of temperature:
(C.55)
(C.56)
(C.57)
g x( ) 2 1 1 x+( ) x–( )exp–[ ] x2⁄=
x αIx
1 2⁄ 2I1 2⁄= =
I 1 2⁄ zi
2Ci∑=
Ax Aφ Cn∑( )
1 2⁄
=
Aφ
ρ
Y a b T⁄+=C-18
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Amines Property Package C-19
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ThThe Clegg-Pitzer equations appear to be uncompromisingly long 
and contain many terms and parameters. However, it should be 
pointed out that only a few parameters were used and many 
terms, such as the quaternary terms in the original Clegg-Pitzer 
equations were omitted in this model. It can be seen that only 
Ann', An'n, Bca and Wnca appear in the expressions and are 
treated as adjustable parameters. 
In this model, both water and amine are treated as solvents. 
The standard state of each solvent is the pure liquid at the 
system temperature and pressure. The adopted reference state 
for ionic and molecular species is the ideal and infinitely dilute 
aqueous solution.
C.5 Phase Enthalpy
Vapour phase enthalpy is calculated by the Peng-Robinson 
equation-of-state which integrates ideal gas heat capacity data 
from a reference temperature. Liquid phase enthalpy also 
includes the effect of latent heat of vaporization and heat of 
reaction.
The absorption or desorption of H2S and CO2 in aqueous 
solutions of alkanolamine involves a heat effect due to the 
chemical reaction. This heat effect is a function of amine type 
and concentration, and the mole loadings of acid gases. The 
heat of solution of acid gases is obtained by differentiating the 
experimental solubility data using a form of the Gibbs-Helmholtz 
equation. 
The heat effect which results from evaporation and 
condensation of amine and water in both the absorber and 
regenerator is accounted for through the latent heat term which 
appears in the calculation of liquid enthalpy. Water content of 
the sour gas feed can have a dramatic effect on the predicted 
temperature profile in the absorber and should be considered, 
particularly at low pressures.C-19
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C-20 Simulation of Amine Plant 
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ThC.6 Simulation of Amine 
Plant Flowsheets
The key to solving an amine treating system lies in the 
simulation of the contactor and the regenerator. In both 
columns, rigorous non-equilibrium stage efficiency calculations 
are used. In addition, the contactor efficiency incorporates 
kinetic reaction and mass transfer parameters. Only the Amines 
Property Package can effectively simulate this system, and only 
components included in this package should be used. 
C.6.1 Solving the Columns
Follow these general guidelines:
• Ensure that the gas to the Contactor is saturated with 
water.
• Use actual, not ideal, stages.
• Change stage efficiencies for CO2 and H2S from their 
default values of 1.0 to fractions for the regenerator and 
the initial absorber run.
• Use calculated efficiencies for subsequent absorber runs 
as detailed below.
• Change the damping factor from a default value of 1.0 to 
a fraction as recommended in the following section. This 
may be necessary to prevent oscillation during 
convergence.C-20
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ThC.6.2 Converging the 
Contactor
Convergence is most readily achieved by first solving with 
estimated efficiencies (suggested values are 0.3 for CO2 and 0.6 
for H2S), then requesting calculated efficiencies and restarting 
the column. To do this, you must first specify three dimensions 
for each tray: tray diameter, weir length and weir height. 
Specify these parameters in the Amines page of the Parameters 
tab in the Column property view.
For an existing column, use the actual dimensions. For a design 
situation (or when the tray dimensions are unknown) use the 
Tray Sizing utility to estimate these parameters. Input the 
calculated tray dimensions and select Run. Aspen HYSYS will 
calculate the individual component efficiencies (H2S, CO2) based 
on the tray dimensions. Only single pass trays can be modeled 
with the Amines Property Package. If the trays in your column 
are multipass, you must estimate the dimensions based on a 
single pass tray.
After the tray dimensions are specified, the column is 
recalculated. Note that efficiencies can be calculated only when 
using the Amines Property Package. These values apply 
specifically to CO2 and H2S. Damping factors in the range 0.4 - 
0.8 usually give the fastest convergence. 
Temperatures around the contactor should be as follows:
Contactor  Temperature Range
Feed Gas 65 - 130 °F
Lean MEA, DEA, TEA, MDEA 100 - 120 °F
Lean DGA 140 °F 
(lean amine minimum 10 °F > feed gas)
Absorber Bottoms 120 - 160 °FC-21
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C-22 Simulation of Amine Plant 
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ThC.6.3 Converging the 
Regenerator
As with the Contactor, efficiencies can be either specified by the 
user, or calculated by the program. For the condenser and 
reboiler, values of 1.0 must be used. For the remaining trays, 
efficiencies of 0.15 for CO2 and 0.80 for H2S are suggested 
initial estimates.
The easiest specifications to converge are the stage 1 
(condenser) temperature and the reboiler duty. Following is a 
guideline for typical duties.
The reboiler temperature should not exceed 280 F to avoid 
physical degradation of the amines into corrosive by-products. 
Regenerators usually converge best with reflux ratio estimates 
of 0.5 - 3.0 and damping factors of 0.2 - 0.5.
C.6.4 Recycle Convergence
The remaining unit operations in the flowsheet are 
straightforward. Note that you need a water makeup stream, as 
indicated in Figure C.1. Since the lean amine concentration 
may vary due to water carryover in the product from the 
vessels, a water makeup is required to maintain a desired 
concentration. 
Amine losses in the contactor overhead are usually negligible 
and the makeup stream replaces any water lost so the amine 
concentration in the recycle does not change significantly during 
the recycle convergence. Thus, you can quite easily make an 
excellent initial estimate for the lean amine recycle. The phase, 
of course, is liquid and the temperature, pressure, total flow rate 
Amine Duty, BTU/US Gallon
TEA, MDEA 800
DEA 1,000
MEA 1,200
DGA 1,300C-22
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Thand composition are known. Although the composition of CO2 
and H2S is unknown, these sour components have only a very 
minor impact on the recycle and can initially be specified to be 
zero in the recycle stream.
C.6.5 Operating Conditions
The Amines property package contains data for the following 
alkanolamines and mixtures of alkanolamines.
Many different amine system designs can be modelled. However, 
for both good tower convergence and optimum plant operation, 
the following guidelines are recommended:
* Amine mixtures are assumed to be primarily MDEA.
Amine
Aspen HYSYS 
Name
Monoethanolamine MEA
Diethanolamine DEA
Triethanolamine TEA
Methyldiethanolamine MDEA
Diglycolamine DGA
Diisopropanolamine DIPA
Monoethanolamine/Methyldiethanolamine Blend MEA/MDEA
Diethanolamine/Methlydiethanolamine Blend DEA/MDEA
Amine
Lean Amine 
Strength
Maximum Acid Gas Loading 
(Moles Acid Gas/ Mole Amine)
Weight % CO2 H2S
MEA 15 - 20 0.50 0.35
DEA 25 - 35 0.45 0.30
TEA, MDEA 35 - 50 0.30 0.20
DGA 45 - 65 0.50 0.35
DEA/MDEA* 35 - 50 0.45 0.30
MEA/MDEA* 35 - 50 0.45 0.30C-23
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C-24 Program Limitations
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ThC.7 Program Limitations
The Amines property package contains correlations of data 
which restrict its use to certain conditions of pressure, 
temperature, and composition. These limitations are given 
below.
The chemical and physical property data base is restricted to 
amines and the following components:  
C.7.1 Range of Applicability
The following table displays the equilibrium solubility limitations 
that should be observed when using this property package. 
Available Components with Amines Property Package
Acid Gases CO2, H2S, COS, CS2
Hydrocarbons CH4 to C12
Olefins C2=, C3=, C4=, C5=
Mercaptans M-Mercaptan, E-Mercaptan
Non-Hydrocarbons H2, N2, O2, CO, H2O
Aromatic C6H6, Toluene, e-C6h6, m-Xylene
This method does not allow for the use of any hypotheticals.
Amine
Alkanolamine 
Concentration
Acid Gas Partial 
Pressure
Temperature
Range (Wt%) psia oF
MEA 0 – 30 0.00001 – 300 77 – 260
DEA 0 – 50 0.00001 – 300 77 – 260
TEA 0 – 50 0.00001 – 300 77 – 260
MDEA 0 – 50 0.00001 – 300 77 – 260
DGA 50 – 70 0.00001 – 300 77 – 260
DIPA 0 – 40 0.00001 – 300 77 – 260
DEPG 90 – 100 0.01 – 600 -4 – 212
For amine mixtures, use the values for MDEA (assumed to be 
the primary amine).C-24
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ThC.8 References
 1 Atwood, K., M.R. Arnold and R.C. Kindrick, "Equilibria for the System, 
Ethanolamines-Hydrogen Sulfide-Water", Ind. Eng. Chem., 49, 
1439-1444, 1957.
 2 Austgen, D.M., G.T. Rochelle and C.-C. Chen, "Model of Vapour-Liquid 
Equilibria for Aqueous Acid Gas Alkanolamine Systems", Ind. Eng. 
Chem. Res., 03, 543-555, 1991.
 3 Bosch, H., "Gas-Liquid Mass Transfer with Parallel Reversible 
Reactions-III. Absorption of CO2 into Solutions of Blends of 
Amines", Chem. Eng. Sci., 44, 2745-2750, 1989.
 4 Chakravarty, T., "Solubility Calculations for Acid Gases in Amine 
Blends", Ph.D. Dissertation, Clarkson College, Potsdam, NY, 1985.
 5 Danckwerts, P.V., and M.M. Sharma, "The Absorption of Carbon 
Dioxide into Solutions of Alkalis and Amines", The Chemical 
Engineer, No.202, CE244-CE279, 1966.
 6 Deshmukh, R.D. and A.E. Mather, "A Mathematical Model for 
Equilibrium Solubility of Hydrogen Sulfide and Carbon Dioxide in 
Aqueous Alkanolamine Solutions",
 7 Chem. Eng. Sci., 36, 355-362, 1981.
 8 Dingman, J.C., "How Acid Gas Loadings Affect Physical Properties of 
MEA Solutions", Pet. Refiner, 42, No.9, 189-191, 1963.
 9 Dow Chemical Company, "Alkanolamines Handbook", Dow Chemical 
International, 1964.
 10Isaacs, E.E., F.D. Otto and A.E. Mather, "Solubility of Mixtures of H2S 
and CO2 in a Monoethanolamine Solution at Low Partial Pressures", 
J. Chem. Eng. Data, 25, 118-120, 1980.
 11Jou, F.-Y., A.E. Mather, and F.D. Otto, "Solubility of H2S and CO2 in 
Aqueous Methyldiethanolamine Solutions", Ind. Eng. Chem. Process 
Des. Dev., 21, 539-544, 1982.
 12Jou, F.-Y., F.D. Otto and A.E. Mather, “Solubility of H2S and CO2 in 
Triethanolamine Solutions”, Presented at the AIChE Winter National 
Meeting, Atlanta, Georgia, March 11-14, 1984.
 13Jou, F.-Y., F.D. Otto and A.E. Mather, "Solubility of Mixtures of H2S 
and CO2 in a Methyldiethanolamine Solution", Paper 140b, 
Presented at the AIChE Annual Meeting, Miami Beach, Florida, 
Nov.2-7, 1986.C-25
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C-26 References
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Th 14Jou, F.-Y., A.E. Mather and F.D. Otto, "The Solubility of Mixtures of 
Hydrogen Sulfide and Carbon Dioxide in Aqueous 
Methyldiethanolamine Solutions", Submitted to The Canadian 
Journal of Chemical Engineering, 1992.
 15Kahrim, A. and A.E. Mather, "Enthalpy of Solution of Acid Gases in 
DEA Solutions", Presented at the 69th AIChE Annual Meeting, 
Chicago, Illinois, Nov.28-Dec.2, 1976.
 16Katz, D.L., D. Cornell, R. Kobayashi, F.H. Poettmann, J.A. Vary, J.R. 
Elenbaas and C.F. Weinaug, "Handbook of Natural Gas 
Engineering", McGraw-Hill, New York, 1959.
 17Kent, R.L., and B. Eisenberg, "Better Data for Amine Treating", 
Hydrocarbon Processing, 55, No.2, 87-90, 1976.
 18Kohl, A.L. and F.C. Riesenfeld, "Gas Purification", 4th Ed., Gulf 
Publishing Co., Houston, Texas, 1985. 
 19Lal, D., E.E. Isaacs, A.E. Mather and F.D. Otto, "Equilibrium Solubility 
of Acid Gases in Diethanolamine and Monoethanolamine Solutions 
at Low Partial Pressures", Proceedings of the 30th Annual Gas 
Conditioning Conference, Norman, Oklahoma, March 3-5, 1980.
 20Lawson, J.D., and A.W. Garst, "Gas Sweetening Data:Equilibrium 
Solubility of Hydrogen Sulfide and Carbon Dioxide in Aqueous 
Monoethanolamine and Aqueous     Diethanolamine Solutions", J. 
Chem. Eng. Data, 21, 20-30, 1976.
 21Lawson, J.D., and A.W. Garst, "Hydrocarbon Gas Solubility in 
Sweetening Solutions: Methane and Ethane in Aqueous 
Monoethanolamine and Diethanolamine", J. Chem Eng. Data, 21, 
30-32, 1976. 
 22Lee, J.I., F.D. Otto, and A.E. Mather, "Solubility of Carbon Dioxide in 
Aqueous Diethanolamine Solutions at High Pressures", J. Chem. 
Eng. Data, 17, 465-468, 1972. 
 23Lee, J.I., F.D. Otto, and A.E. Mather, "Solubility of Hydrogen Sulfide in 
Aqueous Diethanolamine Solutions at High Pressures", J. Chem. 
Eng. Data, 18, 71-73, 1973a.
 24Lee, J.I., F.D. Otto, and A.E. Mather, "Partial Pressures of Hydrogen 
Sulfide over Aqueous Diethanolamine Solutions", J. Chem. Eng. 
Data, 18, 420, 1973b.
 25Lee, J.I., F.D. Otto, and A.E. Mather, "The Solubility of Mixtures of 
Carbon Dioxide and Hydrogen Sulphide in Aqueous Diethanolamine 
Solutions", Can. J. Chem. Eng., 52, 125-127, 1974a.C-26
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Amines Property Package C-27
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Th 26Lee, J.I., F.D. Otto and A.E. Mather, "The Solubility of H2S and CO2 in 
Aqueous Monoethanolamine Solutions", Can. J. Chem. Eng., 52, 
803-805, 1974b.
 27Lee, J.I., F.D. Otto and A.E. Mather, "Solubility of Mixtures of Carbon 
Dioxide and Hydrogen Sulfide in 5.0 N Monoethanolamine 
Solution", J. Chem. Eng. Data, 20, 161-163, 1975.
 28Lee, J.I., F.D. Otto and A.E. Mather, "Equilibrium in Hydrogen Sulfide-
Monoethanolamine-Water System", J.Chem. Eng. Data, 21, 207-
208, 1976a.
 29Lee, J.I., F.D. Otto and A.E. Mather, "The Measurement and Prediction 
of the Solubility of Mixtures of Carbon Dioxide and Hydrogen 
Sulphide in a 2.5 N 
 30 Monoethanolamine Solution", Can. J. Chem. Eng., 54, 214-219, 
1976b.
 31Lee, J.I., F.D. Otto and A.E. Mather, "Equilibrium Between Carbon 
Dioxide and Aqueous Monoethanolamine Solutions", J. Appl. Chem. 
Biotechnol., 26, 
 32541-549, 1976c.
 33Lee, J.I. and A.E. Mather, "Solubility of Hydrogen Sulfide in Water", 
Ber. Bunsenges z. Phys. Chem., 81, 1020-1023, 1977.
 34Mason, D.M. and R.Kao, "Correlation of Vapor-Liquid Equilibria of 
Aqueous Condensates from Coal Processing" in Thermodynamics of 
Aqueous Systems with Industrial Applications, S.A. Newman, ed., 
ACS Symp. Ser., 133, 107-139, 1980.
 35Murzin, V.I., and I.L. Leites, "Partial Pressure of Carbon Dioxide Over 
Its Dilute Solutions in Aqueous Aminoethanol", Russian J. Phys. 
Chem., 45, 230-231, 1971.
 36Nasir, P. and A.E. Mather, "The Measurement and Prediction of the 
Solubility of Acid Gases in. Monoethanolamine Solutions at Low 
Partial Pressures", Can. J. Chem. Eng., 55, 715-717, 1977.
 37Otto, F.D., A.E. Mather, F.-Y. Jou, and D. Lal, "Solubility of Light 
Hydrocarbons in Gas Treating Solutions", Presented at the AIChE 
Annual Meeting, Paper 21b, San Francisco, California, November 
25-30, 1984.
 38Peng, D.-Y., and D.B. Robinson, "A New Two-Constant Equation of 
State", Ind. Eng. Chem. Fundam., 15, 59-64, 1976.
 39Rangwala, H.A., B.R. Morrell, A.E. Mather and F.D. Otto, "Absorption 
of CO2 into Aqueous Tertiary Amine/MEA Solutions", The Canadian 
Journal of Chemical Engineering, 70, 482-490, 1992. C-27
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C-28 References
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Th 40Tomcej, R.A. and F.D. Otto, "Computer Simulation and Design of 
Amine Treating Units", Presented at the 32nd Canadian Chemical 
Engineering Conference, Vancouver, British Columbia, Oct.3-6, 
1982.
 41Tomcej, R.A., F.D. Otto and F.W. Nolte, "Computer Simulation of 
Amine Treating Units", Presented at the 33rd Annual Gas 
Conditioning Conference, Norman, 
 42Oklahoma, March 7-9, 1983.
 43Tomcej, R.A., "Simulation of Amine Treating Units Using Personal 
Computers", Presented at the 35th Canadian Chemical Engineering 
Conference, Calgary, Alberta, Oct.5-8, 1985.
 44Tomcej, R.A. and F.D. Otto, "Improved Design of Amine Treating 
Units by Simulation using Personal Computers", Presented at the 
World Congress III of Chemical Engineering, Tokyo, Japan, 
September 21-25, 1986. 
 45Tomcej, R.A., D. Lal, H.A. Rangwala and F.D. Otto, "Absorption of 
Carbon Dioxide into Aqueous Solutions of Methyldiethanolamine", 
Presented at the AIChE Annual Meeting, Miami Beach, Florida, 
Nov.2-7, 1986.
 46Tomcej, R.A., F.D. Otto, H.A. Rangwala and B.R. Morrell, "Tray Design 
for Selective Absorption", Presented at the 37th Annual Laurance 
Reid Gas Conditioning Conference, Norman, Oklahoma, March 2-4, 
1987.
 47Union Carbide Corporation, "Gas Treating Chemicals", Union Carbide 
Petroleum Processing, Chemicals and Additives, 1969.
 48Versteeg, G.F., J.A.M. Kuipers, F.P.H. Van Beckum and W.P.M. Van 
Swaaij, "Mass Transfer with Complex Reversible Chemical Reactions 
- I. Single Reversible Chemical Reaction", Chem. Eng. Sci., 44, 
2295-2310, 1989.
 49Winkelman, J.G.M., S.J. Brodsky and A.A.C.M. Beenackers, "Effects 
of Unequal Diffusivities on Enhancement Factors of Reversible 
Reactions: Numerical Solutions and Comparison with Decoursey's 
Method", Chem. Eng. Sci., 47, 485-489, 1992.
 50Zhang, Dan D., Gordon X. Zhao, H.-J. Ng, Y.-G. Li and X.-C. Zhao, “An 
Electrolyte Model for Amine Based Gas Sweetening Process 
Simulation”, Preceeding of the 78th GPA Annual Convention, p25, 
1999.
 51Zhange, Dan D., H.-J. Ng and Ray Vledman, “Modeling of Acid Gas 
Treating Using AGR Physical Solvent”, Proceeding of the 78th GPA 
Annual Convention, p62, 1999.C-28
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Glycol Property Package D-1
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ThD  Glycol Property 
PackageD-1
D.1  Introduction .................................................................................. 2
D.2  Pure Component Vapor Pressure ................................................... 4
D.3  Mixing Rules .................................................................................. 4
D.3.1  TST Mixing Rules ..................................................................... 4
D.3.2  Zero-Pressure CEOS/AE Mixing Rules.......................................... 7
D.3.3  Liquid GE Model ..................................................................... 11
D.4  Phase Equilibrium Prediction ....................................................... 12
D.5  Enthalpy/Entropy Calculations .................................................... 13
D.6  References................................................................................... 13
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D-2 Introduction
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ThD.1 Introduction
In the gas processing industry, it is necessary to dehydrate/
remove water vapour present in the natural gas stream. In 
nature, impurities like water vapor are mixed in the natural gas. 
Water vapor in the gas stream can cause the following 
problems:
• Hydrate formation, at low temperature conditions, that 
can plug valves and fittings in gas pipelines.
• React with hydrogen sulfide or carbon dioxide to form 
weak acids that can corrode gas pipelines.
The standard method to remove water vapor from natural gas 
stream is to use triethylene glycol (TEG) to absorb the water. 
Aspen HYSYS provides the Glycol property package for use in 
modeling glycol dehydration process using TEG.  This property 
package is based on the TST (Twu-Sim-Tassone) equation of 
state. The property package contains the necessary pure 
component and binary interaction parameters for components 
commonly encountered in natural gas dehydration process. The 
property package is tuned to represent accurately, the phase 
behaviour of these components, especially that for the TEG-
water binary system.
The TST equation of state can accurately predict:
• activity coefficients of the TEG-water solutions within the 
average absolute deviation of 2%
• dew point temperatures within an average error of 
• water content of gas within the average absolute 
deviation of 1%
The Glycol property package should be applicable over the range 
of temperatures, pressures, and component concentration 
encountered in a typical TEG-water dehydration system: 
between 15°C to 50°C and between 10 atm to 100 atm for the 
gas dehydrator, and between 202°C to 206°C and 1.2 
atmospheres for the glycol regenerator.
1°C±D-2
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Glycol Property Package D-3
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ThThe table below displays the prediction of equilibrium water 
content in lbH2O/MMSCF for a gas stream in contact with 99.5 
weight percent TEG, using the Glycol property package.
The figure below displays the predicted equilibrium water dew 
point vs. contact temperature at various TEG concentrations in 
weight %. 
The BIP databank for the Glycol property package will be 
updated in future releases of Aspen HYSYS. Currently, there 
The accuracy of predicted solubility of hydrocarbons in 
aqueous phase is expected to be within the experimental 
uncertainty.
T dew (K)
Reported by: Predicted from TST (EOS):
McKetta2 Bukacek1 Water Content Pressure (Pa)
277.59 390 396 393 838
266.48 170 176 174 370
255.37 70 72 71 151
244.26 28 27 26 56.1
233.15 9.2 9.1 9 18.7
222.04 2.4 2.8 2.6 6
 Figure D.1D-3
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D-4 Pure Component Vapor Pressure
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Thmay be some limitations or missing BIP for certain component 
pairs. For example, heavy hydrocarbons or hypothetical 
components which may not have any interaction parameters 
available. For assitance in using this property package, please 
contact Technical Support.
D.2 Pure Component 
Vapor Pressure
For the Glycol property package, three alpha function 
parameters are used to correlate the vapor pressure of the 
component in the Aspen HYSYS component database. The alpha 
function parameters are:
• L in Equation (D.6) 
• M in Equation (D.6)
• N in Equation (D.6)
D.3 Mixing Rules
For Glycol property package, three adjustable parameters are 
used to correlate Vapor-Liquid-Equilibrium (VLE) mixture data. 
The parameters corresponding to the TST (Twu-Sim-Tassone) AE 
mixing rules are:  binary interaction parameters in 
Equations (D.30) and (D.31).
D.3.1 TST Mixing Rules
The TST (Twu et al. 20025) cubic equations of state is:
where:  
a, b = parameters values that correspond to the critical 
temperature of the component
(D.1)
Aij Aji αij,,,
P RT
v b–
----------- a
v 3b+( ) v 0.5b–( )
--------------------------------------------–=D-4
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ThThe critical temperature are found by setting the first and 
second derivatives of pressure with respect to volume to zero at 
the critical point:
where:
c = indicates the variable at the critical point
The parameter a is a function of temperature. The value of a(T) 
at temperatures other than the critical temperature is calculated 
using the following equation:
where:
 = function of the reduced temperature 
• For vapor pressure prediction, the Twu  correlation 
(Twu et al., 19913) is used:
(D.2)
(D.3)
(D.4)
(D.5)
where:
L,M,N = parameters that are unique for each component
(D.6)
ac 0.470507R2Tc
2
Pc
-----=
bc 0.0740740R
Tc
Pc
-----=
Zc 0.296296=
a T( ) α T( )ac=
α T( ) Tr T Tc⁄=
α T( )
α T( ) Tr
N M 1–( )e
L 1 Tr
NM–( )
=
D-5
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D-6 Mixing Rules
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Th• For non-library components, the generalized alpha 
function, , is expressed as a function of two 
variables: the reduced temperature and the acentric 
factor.
• For non-library and petroleum fractions, the generalized 
alpha function, , is:
Each  is a function of the reduced temperature only.
where:  
L,M,N = databank values corresponding to subcritical and 
supercritical conditions
For :
(D.7)
where:
 = corresponds to 
 = corresponds to 
(D.8)
(D.9)
(D.10)
L 0.196545 0.704001
M 0.906437 0.790407
N 1.26251 2.13086
α T( )
α α Tr ω,( )=
α T( )
α α 0( ) ω α 1( ) α 0( )–( )+=
α 0( ) ω 0=
α 1( ) ω 1=
α
α 0( ) Tr
N 0( ) M 0( ) 1–( )e
L 1 Tr
NM 0( )
–⎝ ⎠
⎛ ⎞
=
α 1( ) Tr
N 1( ) M 1( ) 1–( )e
L 1 Tr
NM 1( )
–⎝ ⎠
⎛ ⎞
=
Tr 1≤
α 0( ) α 1( )D-6
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ThFor :
D.3.2 Zero-Pressure CEOS/AE 
Mixing Rules
The zero-pressure mixing rules for the cubic equation of state 
mixture a and b parameters are as given:
where:  
 = equation of state a and b parameters which are 
evaluated from the van der Waals mixing rule
 = excess Helmholtz energies at zero pressure
 = function of reduced liquid volume at zero pressure 
L 0.358826 0.0206444
M 4.23478 1.22942
N -0.200000 -8.00000
(D.11)
(D.12)
The mixing rules given by Equations (D.11) and (D.12) are 
volume-dependent through .
(D.13)
Tr 1>
α 0( ) α 1( )
a∗ b∗
avdw∗
bvdw∗
------------- 1
Cv0
-------
A0
E
RT
------
A0vdw
E
RT
--------------
bvdw
b
----------⎝ ⎠
⎛ ⎞ln––
⎝ ⎠
⎜ ⎟
⎛ ⎞
+=
b∗
bvdw∗ avdw∗–
1
avdw∗
bvdw∗
------------- 1
Cv0
-------
A0
E
RT
------
A0vdw
E
RT
--------------
bvdw
b
----------⎝ ⎠
⎛ ⎞ln––
⎝ ⎠
⎜ ⎟
⎛ ⎞
+–
----------------------------------------------------------------------------------------------------------=
avdw bvdw,
A0
E A0vdw
E,
Cv0
Cv0
v0∗ v0 b⁄=
Cv0
1
w u–( )
-----------------–
v0∗ w+
v0∗ u+
-----------------
⎝ ⎠
⎜ ⎟
⎛ ⎞
vdw
ln=D-7
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D-8 Mixing Rules
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Th = zero pressure liquid volume is calculated from the 
cubic equation of state using the van der Waals mixing 
rule for its a and b parameters by setting pressure 
equal to zero and selecting the smallest root:
The mixing rule for the parameter b as given by Equation 
(D.12) forces the mixing rule to satisfy the quadratic 
composition dependence of the second virial coefficient. 
Alternatively, the conventional linear mixing rule could be 
chosen for the b parameter, in other words, ignoring the second 
virial coefficient boundary condition.
To omit the need for the calculation of  from the equation of 
state, the zero-pressure liquid volume of the van der Waals 
fluid, , is made a constant, r.
Thus Equation (D.13) becomes:
where:  
 = constant replacing  and signifies that  is no longer 
a density dependent function
(D.14)
Equation (D.14) has a root as long as:
(D.15)
(D.16)
(D.17)
v0∗vdw
v0∗ 1
2
-- a∗
b∗
----- u w––⎝ ⎠
⎛ ⎞ u w a∗
b∗
-----–+⎝ ⎠
⎛ ⎞ 2
4 uw a∗
b∗
-----+⎝ ⎠
⎛ ⎞–
1
2
--
–
⎩ ⎭
⎪ ⎪
⎨ ⎬
⎪ ⎪
⎧ ⎫
=
a∗
b∗
----- 2 u w+ +( ) 2 u 1+( ) w 1+( )+≥
b xixj
1
2
-- bi bj+( )
j
∑
i
∑=
v0∗
v0∗vdw
Cr
1
w u–( )
-----------------– r w+
r u+
------------⎝ ⎠
⎛ ⎞ln=
Cr Cv0
CrD-8
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ThThus Equations (D.11) and (D.12) become:
 is derived from the equation of state by assuming a fixed 
reduced liquid molar volume r for a van der Waals fluid at zero 
pressure:
where:  
 = equation of state a and b parameters which are 
evaluated from the conventional van der Waals mixing 
rules
The excess Helmholtz energy is much less pressure-dependent 
than the excess Gibbs energy. Therefore, the excess Helmholtz 
energy of the van der Waals fluid at zero pressure can be 
approximated by the excess Helmholtz energy of van der Waals 
fluid at infinite pressure.
(D.18)
(D.19)
(D.20)
(D.21)
(D.22)
a∗ b∗
avdw∗
bvdw∗
------------- 1
Cr
-----
A0
E
RT
------
A0vdw
E
RT
--------------
bvdw
b
----------⎝ ⎠
⎛ ⎞ln––
⎝ ⎠
⎜ ⎟
⎛ ⎞
+=
b∗
bvdw∗ avdw∗–
1
avdw∗
bvdw∗
------------- 1
Cr
-----
A0
E
RT
------
A0vdw
E
RT
--------------
bvdw
b
----------⎝ ⎠
⎛ ⎞ln––
⎝ ⎠
⎜ ⎟
⎛ ⎞
+–
--------------------------------------------------------------------------------------------------------=
A0vdw
E
A0vdw
E
RT
------------- xi
bi
bvdw
----------⎝ ⎠
⎛ ⎞ln Cr
avdw∗
bvdw∗
------------- xi
ai∗
bi∗
------
i
∑–
⎝ ⎠
⎜ ⎟
⎛ ⎞
+
i
∑=
avdw bvdw,
avdw xixj aiaj 1 kij–( )
j
∑
i
∑=
bvdw xixj
1
2
-- bi bj+( )
j
∑
i
∑=D-9
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D-10 Mixing Rules
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Thwhere:  
 = constant
For algebraic simplicity, the following development is limited to a 
binary mixture, in order to obtain the following expression for 
the excess Helmholtz energy of a van der Waals fluid from 
Equation (D.23):
where:  
 = characteristic parameter of interaction between 
molecules 1 and 2
Extending these relations to a multi-component 
mixture,Equations (D.24) and (D.25) become:
(D.23)
(D.24)
(D.25)
(D.26)
(D.27)
(D.28)
A0vdw
E
RT
-------------
A∞vdw
E
RT
-------------- C1
avdw∗
bvdw∗
------------- xi
ai∗
bi∗
------
i
∑–
⎝ ⎠
⎜ ⎟
⎛ ⎞
= =
C1
1
w u–( )
----------------- 1 w+
1 u+
------------⎝ ⎠
⎛ ⎞ln–=
A0vdw
E
RT
-------------
x1x2b1b2δ12
x1b1 x2b2+( )
--------------------------------=
δ12
δ12
C1
RT
------
a1
b1
---------
a2
b2
---------–
⎝ ⎠
⎜ ⎟
⎛ ⎞
2
2k12
a1
b1
---------
a2
b2
---------+–=
A0vdw
E
RT
------------- 1
2
-- bδij( )ΦiΦj
j
∑
i
∑=
δij
C1
RT
------
ai
bi
--------
aj
bj
--------–
⎝ ⎠
⎜ ⎟
⎛ ⎞
2
2kij
ai
bi
--------
aj
bj
--------+–=
Φi
xibi
b
--------=D-10
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ThD.3.3 Liquid GE Model
A general multi-component equation for a liquid activity model is 
now proposed for incorporation in the zero-pressure mixing 
rules as:
Equation (D.29) is similar to the NRTL equation but not the 
same. The NRTL assumes  are the parameters of the 
model, but the excess Gibbs energy model assumes  are 
the binary interaction parameters. For example, to obtain the 
NRTL model,  are calculated from the NRTL parameters 
:
Equation (D.29) can recover the conventional van der Waals 
mixing rules when the following expressions are used for :
The above two equations are expressed in terms of the cubic 
equation of state parameters,  and the binary interaction 
parameter . 
(D.29)
(D.30)
(D.31)
(D.32)
(D.33)
GE
RT
------ xi
xjτj iGji
j
n
∑
xkGki
k
n
∑
------------------------
i
n
∑=
Aij Aji αij,,
τij Gij,
τij Gij,
Aij Aji αij,,
τji
Aji
T
------=
Gji αji– τji( )exp=
τij Gij,
τji
1
2
--δi jbi=
Gji
bj
bi
---=
ai bi,
kijD-11
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D-12 Phase Equilibrium Prediction
ww
ThBy substituting Equations (D.32) and (D.33) into Equation 
(D.29), Equation (D.26) is obtained. 
Subsequently, the mixing rules, Equations (D.18) and (D.16), 
are reduced to the classical van der Waals one-fluid mixing 
rules. 
D.4 Phase Equilibrium 
Prediction
The following equations are the TST (Twu-Sim-Tassone) zero 
pressure mixing rules used for phase equilibrium prediction in 
the Glycol property package:
(D.1)
(D.16)
(D.18)
(D.23)
(D.29)
P RT
v b–
----------- a
v 3b+( ) v 0.5b–( )
--------------------------------------------–=
b xixj
1
2
-- bi bj+( )
j
∑
i
∑=
a∗ b∗
avdw∗
bvdw∗
------------- 1
Cr
-----
A0
E
RT
------
A0vdw
E
RT
--------------
bvdw
b
----------⎝ ⎠
⎛ ⎞ln––
⎝ ⎠
⎜ ⎟
⎛ ⎞
+=
A0vdw
E
RT
-------------
A∞vdw
E
RT
-------------- C1
avdw∗
bvdw∗
------------- xi
ai∗
bi∗
------
i
∑–
⎝ ⎠
⎜ ⎟
⎛ ⎞
= =
GE
RT
------ xi
xjτj iGji
j
n
∑
xkGki
k
n
∑
------------------------
i
n
∑=D-12
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Glycol Property Package D-13
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ThD.5 Enthalpy/Entropy 
Calculations
The Glycol property package uses the Cavett model for enthalpy 
and entropy calculations.
D.6 References
 1 Bukacek, R.F., “Equilibrium Moisture Content of Natural Gases”, 
Research Bulletin 8, Institute of Gas Technology, Chicago, IL, 1955.
 2 McKetta, J.J. and Wehe, A.H., cited by GPA Engineering Data Book, 
Fig. 15-10, Ninth Edition, Fourth Revision, Gas Processors Suppliers 
Associations, Tulsa, OK, 1979.
 3 Twu, C.H., Bluck, D., Cunningham, J.R., and Coon, J.E., “A Cubic 
Equation of State with a New Alpha Function and a New Mixing 
Rule”, Fluid Phase Equilib. 1991, 69, 33-50.
 4 Twu, C.H., Tassone, V., Sim, D.W., and Watanasiri, S., “Advanced 
Equation of State Method for Modeling TEG-Water for Glycol Gas 
Dehydration”, Fluid Phase Equilibria, 2005 (in press).
 5 Twu, C.H., Sim, W.D., and Tassone, V., “A Versatile Liquid Activity 
Model for SRK, PR, and A New Cubic Equation of State TST”, Fluid 
Phase Equilibria, 2002, 194-197, 385-399.D-13
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ThD-14
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Index
www.c
The doA
Activity Models 2-11, A-5, A-23
 See models - Chien Null, Margules, NRTL, 
NRTL Options, UNIQUAC, van 
Laar, and Wilson
additional specifications 2-15, 2-106
binary interaction parameters 2-59, 2-
115
choosing vapour phase model 2-16, A-25, 
A-45
departure calculations A-59
estimating interaction parameters 2-60
immiscible liquid phases A-28
Amines Property Package 2-13, A-52
Antoine
modified vapour pressure model A-49
parameters tab 2-50
vapour pressure model 2-13, 2-101
ASME Steam A-54
property package 2-13
Assay and Blend Association 4-86
Assay Data
general guidelines 4-37
no distillation data available 4-32, 4-35
physical properties 4-28
standard input 4-32
Assays
characterizing 4-14, 4-17
correlations 4-55
inputting 4-20
light ends 4-38
analysis B-4
auto calculating 4-42, B-7
included 4-39
inputting 4-41
light ends free 4-40
notes 4-58
plotting 4-54
selecting 4-61
types of 4-53
user curves 4-57
working curves 4-53
ASTM D1160. See Laboratory Assay 
Procedures
ASTM D2887. See Laboratory Assay 
Procedures
ASTM D86. See Laboratory Assay Procedures
Auto Cut 4-65
B
Basis Environment 1-viii
Basis Manager
component maps tab 6-2
fluid package tab 2-3
hypotheticals tab 3-4
oil manager tab 4-10
reactions tab 5-3
user properties tab 7-3
Blends
auto cutting 4-65
bulk data 4-62
composite plots 4-74
correlations 4-68
cut ranges 4-62
distribution plots 4-73
information 4-70
notes 4-76
oil distributions 4-71
plots summary 4-75
property plots 4-71
Braun K10 2-13, 2-101, A-50
Bubble Point A-84
Bulk Properties 4-28
BWR Equation A-15
C
Cavett Correlation A-59
Chao Seader A-5, A-47
models 2-12, 2-101
parameters tab 2-49
semi-empirical method 2-12, 2-101
Chien Null A-25, A-29
activity model 2-11
parameters tab 2-47, 2-109
Chromatographic Analysis. See Laboratory 
Assay Procedures
Chromatographic Assay Input 4-34
Coal Analysis 3-38
Collection (Component Maps) 6-2
Component List Selection 2-22, 2-104
Component Selection 1-13
family filter 1-12
family type filter 1-12
filter options 1-12
general procedure 1-9
property package filter 1-12
tips 1-8I-1
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The dowarning messages 2-22
Components
adding 1-5
cloning. See Hypotheticals, cloning library 
components
creating custom. See Hypotheticals, 
adding
filtering 1-9
hypotheticals quick access 1-28
incompatible 2-24
manager 1-2
mapping 6-2
master component list 1-2
name format 1-8, 1-10
non recommended 2-23
parameters tab 2-25, 2-109
removing 1-6, 1-14
selected components group 1-6
selection 1-8, 1-13
sorting 1-7, 1-16
substituting 1-6, 1-15
synonyms 1-8
transferring 1-13
viewing 1-7, 1-17
Components Manager 1-2
Conversion Reactions 5-6, 5-8–5-12
rank 5-42
Correlations
assay 4-55
blend 4-68
critical property B-10
oil characterization 4-81
Cubic EOS
mixing rules D-7
Cut 4-62
Cut/Blend. See Blends or Oil Characterzation
Cutpoint B-8
D
D86 Interconversion Methods 4-16
D86. See Laboratory Assay Procedures
Density.See  Liquid Density or Vapour Density
Dew Point A-83
E
EFV (Equilibrium Flash Vapourization). See 
Laboratory Assay Procedures
Eley-Rideal Model 5-27
Enthalpy Basis A-56
tabular 2-85
Enthalpy Departure Calculations A-56
Enthalpy Flash A-85
Entropy Flash A-85
Equations of State (EOS) 2-9, A-11
additional information 2-15, 2-106
departure calculation A-56
enthalpy calculation A-21
interaction parameters 2-58, 2-112
See models - GCEOS, Kabadi Danner, 
Lee-Kesler Plocker, Peng 
Robinson, PRSV, Peng Robinson 
Options, SRK, SRK Options, 
Zudkevitch Joffee.
TST CEOS D-4
Equilibrium Reactions 5-6, 5-13–5-19
fractional approach 5-18
temperature approach 5-18
Esso Tabular A-51
vapour pressure model 2-13, 2-101
Extended NRTL. See NRTL Options
F
Flash Calculations A-81
handling water A-86
temperature-pressure (TP) A-82
vapour fraction A-83
Flow Rate
actual gas A-79
actual volume A-79
as a specification A-80
available A-74
densities, liquid and vapour A-76
liquid volume A-78
mass A-78
molar A-78
standard gas A-79
standard liquid volume A-79
volumetric A-74
Fluid Package
activity models 2-11
adding 2-3
adding - quick start 2-5
adding notes 2-94
advantages 2-2
associated flowsheet 2-4
base property selection 2-9
copy 2-4
delete 2-4I-2
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The doequations of state 2-9
export 2-4
import 2-4
property package selection 2-8
property view 2-7, 2-95
reactions 2-68
stability test 2-64, 2-118
tabular 2-69
 See also Tabular Package
Fugacity Coefficients A-63
G
GCEOS
binary coeffs tab 2-52
Generalized Cubic Equation of State 2-10
Generalized Cubic Equations of State 2-25
interaction parameters 2-52
parameters tab 2-25
General NRTL. See NRTL Options
Glycol Property Package D-2
enthalpy calculation D-13
entropy calculation D-13
liquid activity model D-11
mixing rules D-4
phase equilibrium prediction D-12
pure component vapor pressure D-4
Grayson Streed A-6, A-47
parameters tab 2-49
semi-empirical method 2-12, 2-101
H
Henry's Law A-42
Heterogeneous Catalytic Reactions 5-7, 5-26–
5-32
Eley-Rideal 5-27
Langmuir-Hinshelwood 5-27
Mars-van Krevelen Model 5-27
Hypothetical Components. See Hypotheticals
Hypothetical Group
controls 3-14
creating 3-4, 3-13
deleting 3-4
exporting 3-5
group name 3-14
importing 3-5
moving 3-45
moving between 3-5
viewing 3-4, 3-44
Hypotheticals
adding 1-28, 3-15
adding a hypothetical - quick start 3-5
adding hypothetical group 1-28
base properties 3-16
cloning library components 3-5, 3-14, 3-
42
critical properties 3-29
deleting 3-15
estimating properties 3-14, 3-30
estimation methods 3-14, 3-18
individual controls 3-15
minimum information required 3-18
moving 3-5
property view 3-26
quick reference 3-5
solid hypotheticals 3-15, 3-36
temperature dependent properties 3-32
UNIFAC structure builder 3-15, 3-23
vapour pressure properties 3-17
viewing 3-5, 3-15
viewing group. See Hypothetical Group, 
viewing
I
Ideal Gas Law A-45
departure calculations A-59
Installing
oils 4-14
reaction set 5-45
Interaction Parameters
activity models 2-59, 2-115, A-26
equations of state 2-58, 2-112
estimating A-22
Henry’s Law A-43
K
K/ln(K) Equilibrium Constant 5-16
Kabadi Danner A-11, A-14
equation of state 2-10
parameters tab 2-35
Kinetic Reactions 5-20–5-26
requirements 5-7
L
Laboratory Assay Procedures
ASTM D1160 4-6, 4-31
ASTM D2887 4-6, 4-31
ASTM D86 4-6, 4-31
ASTM D86 and D1160 4-31I-3
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The dochromatographic analysis 4-6, 4-31
assay input 4-34
D2887 interconversion method 4-16
D86 interconversion method 4-16
equilibrium flash vapourization 4-6, 4-32
preparation 4-39
TBP analysis 4-5, 4-31
Langmuir-Hinshelwood Model 5-27
Lee Kesler Plocker 2-10, A-11, A-15
Lee-Kesler Enthalpy A-22, A-47, A-61
Liquid Density A-65
actual A-76
ideal A-77
standard A-76
M
Mapping
collection 6-2
components 6-1
target 6-2
transfer options 6-5
Margules A-25, A-33
activity model 2-11
Mars-van Krevelen Model 5-27
MBWR A-54
property package 2-10
N
NBS Steam A-54
property package 2-14
NRTL (Non Random Two Liquid) A-25, A-28, 
A-34
activity model 2-12
NRTL Options A-28
Extended NRTL 2-11, A-32
General NRTL 2-11, A-32
O
Oil Characterization
analysis methods. See Laboratory Assay 
Procedures
bulk blending data 4-62
component critical properties B-9
composite plots 4-74
correlations 4-9, 4-14, 4-55, 4-81
cutting/blending 4-14, 4-59
deleting 4-15
density curves 4-47
determining TBP cutpoints B-8
distribution plots 4-73
FBP 4-15
IBP 4-15
installing oil 4-87
laboratory data corrections 4-8
light ends 4-38–4-39, 4-41, B-4
method B-2
molecular weight curves 4-46
notes 4-86
output settings 4-15
physical property curves 4-8, 4-34
procedure 4-9
property plots 4-71
property view 4-14
purpose 4-3
user properties 4-14, 4-76
viscosity curves 4-48
working curves 4-53
P
Peng Robinson A-6–A-7, A-12
departure calculations A-56
equation of state 2-10
fugacity coefficient A-63
modelling vapour phase A-45
Peng Robinson Options A-12
PRSV 2-10
Sour PR 2-10, A-20
Physical Properties A-64
Poynting Correction 2-16, A-26
PPDS 2-79, 2-81
Property Package
selecting a A-4
Property Packages
See Amines Property Package, Braun K10, 
Chao Seader, Esso Tabular, 
Grayson Streed, Lee Kesler 
Plocker, Margules, MBWR, PRSV, 
Peng Robinson,
Peng Robinson Options, SRK, SRK 
Options, Steam Packages, 
UNIQUAC, van Laar and Wilson.
PRSV (Peng Robinson Stryjek Vera) A-8, A-18
equation of state 2-10
parameters tab 2-45
Pseudo Component Generation 4-59
Q
Quality Pressure A-84I-4
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The doR
Reaction Package
adding 5-46
Reaction Rank 5-42
Reaction Sets 5-36
adding 5-37
adding to fluid package 5-37, 5-45
advanced features 5-40
attaching to unit operations 5-45
copying 5-37
deleting 5-37
exporting 5-37, 5-44
importing 5-37, 5-44
quick access 2-69
solver method 5-39
viewing 5-37
Reactions
activating 5-39
adding 5-7
components 5-3–5-4
conversion. See Conversion Reactions
copying 5-7
deactivating 5-39
deleting 5-7
equilibrium. See Equilibrium Reactions
heterogeneous catalytic. See 
Heterogeneous Catalytic 
Reactions
kinetic. See Kinetic Reactions
library reactions 5-5
quick start 5-48
selecting components 5-3–5-4
sets. See Reaction Sets
simple rate. See Simple Rate Reactions
thermodynamic consistency 5-22
viewing 5-7
Redlich Kwong (RK) A-45
departure calculations A-60
S
Simple Rate Reactions 5-33–5-36
requirements 5-7
Solids A-89
Sour PR. See Peng Robinson Options
Sour SRK. See SRK Options
Sour Water Options A-20
See SRK Options and Peng Robinson 
Options
SRK (Soave Redlich Kwong) A-7, A-11–A-12
departure calculations A-57
equation of state 2-10
fugacity coefficient A-63
modelling vapour phase A-45
SRK Options A-12
See Kabadi Danner and Zudkevitch Joffee
Sour SRK 2-10, A-20
Stability Test 2-62, 2-116
parameters 2-64, 2-118
Steam Packages A-54
See ASME Steam and NBS Steam
Stream Information A-90
Surface Tension A-73
T
Tabular Package 2-69
active properties selection 2-77
data 2-78
enthalpy basis 2-85
library 2-79, 2-81
plotting 2-82
regression 2-86
requirements 2-71
supplying data 2-85
using 2-73
viewing selection 2-81
Target (Component Maps) 6-2
TEG D-2
Thermal Conductivity A-70
Transport Properties A-64
triethylene glycol D-2
TST
mixing rules D-4
U
UNIFAC LLE
interaction parameter estimation 2-60
UNIFAC Property Estimation A-27
UNIFAC Structure Builder 3-23
UNIFAC VLE
interaction parameter estimation 2-60
UNIQUAC (Universal Quasi Chemical 
Parameters) 2-12, A-25, A-36
User Points 4-65
User Properties 4-57, 4-76, 7-2–7-9
adding 7-3
deleting 7-3
mixing rules 7-7I-5
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The donotes 7-9
viewing 7-3
User Ranges 4-66
V
van Laar A-25, A-38
activity model 2-12
Vapour Density A-66
Vapour Pressure A-84
Vapour Pressure Models 2-13, A-9, A-48
Antoine 2-13, 2-101
Braun K10 2-13, 2-101
Esso Tabular 2-13, 2-101
Virial Equation A-26
departure calculations A-60
modelling vapour phase A-46
Viscosity A-66
liquid phase mixing rules A-68
W
Water A-86
Wilson 2-12, A-25, A-39
parameters tab 2-49
Working Curves B-3
Z
Zudkevitch Joffee A-11, A-21
equation of state 2-11
parameters tab 2-46I-6
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