Multiflash Command

Reference

KBC Advanced Technologies ltd.

Version 6.2
2017

KBC Advanced Technologies ltd

42-50 Hersham Road
Walton on Thames
Surrey
KT12 1RZ
UK
T +44 (0) 1932 242 424
e-mail: software@kbcat.com
 This manual and the information contained within is the copyright of Infochem / KBC Advanced Technologies
ltd.

KBC Advanced Technologies ltd.

42-50 Hersham Road
Walton on Thames
Surrey
KT12 1RZ
UK
T +44 (0) 1932 242 424

Disclaimer
While every effort has been made to ensure that the information contained in this document is
correct and that the software and data to which it relates are free from errors, no guarantee is given
or implied as to their correctness or accuracy. Neither Infochem / KBC Advanced Technologies ltd
nor any of its employees, contractors or agents shall be liable for direct, indirect or consequential
losses, damages, costs, expenses, claims or fee of any kind resulting from any deficiency, defect or
error in this document, the software or the data.
Contents
Introduction...............................................................................................................1

Changes from previous versions...................................................................2

Using Multiflash......................................................................................................5
Entering commands...................................................................................................5
Specifying a problem.................................................................................................5
Units............................................................................................................................10
Changing the problem.............................................................................................10
Error messages and diagnostics...........................................................................10
Output........................................................................................................................11
Model configuration files.......................................................................................11
Example Calculation................................................................................................12

Databanks and components...........................................................................13

Commands for setting component databanks..................................................13
Loading components from a databank...............................................................14
Data entry for a normal component....................................................................15
Petroleum fractions.................................................................................................28
PVT analysis..............................................................................................................30
Black oil analysis......................................................................................................35
Inhibitor calculator..................................................................................................36
Salinity........................................................................................................................37

Model definition....................................................................................................39
Introduction..............................................................................................................39
Equation of state models.......................................................................................39
Activity models.........................................................................................................50
Other thermodynamic models for fluids............................................................64
Thermodynamic models for solids......................................................................65
Viscosity models......................................................................................................70
Thermal conductivity models................................................................................73
Surface tension models..........................................................................................75

Binary interaction parameters......................................................................79

BIPDATA.....................................................................................................................79
BIPSET.........................................................................................................................80
Troubleshooting - BIPs............................................................................................82

Phase descriptors and stream types.........................................................83

The PD command.....................................................................................................83
The streamtype command.....................................................................................84
The KEYS component command...........................................................................85
PVT Experiment Data.........................................................................................89
Storing PVT Experiment data................................................................................89

Conditions................................................................................................................91
Commands for setting conditions.......................................................................91

Matching wax data...............................................................................................93

Wax+Oil viscosity.................................................................................................94

Matching asphaltene deposition point.....................................................95

PVT table files........................................................................................................96

Pipesim PVT files......................................................................................................96
OLGA table generator..............................................................................................97
Prosper table generator..........................................................................................97

Other commands..................................................................................................99
The TITLE command................................................................................................99
Setting Enthalpy and Entropy bases....................................................................99
Commands for changing units...........................................................................100
The SET command................................................................................................102
The REMOVE command........................................................................................103
The INCLUDE command.......................................................................................104

Alphabetical list of selected commands...............................................105

Introduction

Multiflash is an advanced software package for performing

complex equilibrium calculations quickly and reliably. The
main utility is a multiple phase equilibrium algorithm which
is interfaced to Infochem / KBC’s package of
thermodynamic models and a number of physical property
data banks.
This document describes the Multiflash command language
which can be used to configure and drive the software.
Multiflash itself can be used and accessed in many different
ways (see below) but the command language is common to
all implementations. An overview of the Multiflash software
structure is given in the diagram on the following page.
The command-line version of Multiflash is largely machine
independent. It can be run by typing in all the necessary
instructions at the command line or by reading in files of
commands. The software is also available as an interactive
Microsoft Windows program (see the User’s Guide for
Multiflash for Windows) and as an add-in for use with the
Microsoft Excel spreadsheet program (see the User’s Guide
for Multiflash Excel Interface).
For application developers Multiflash can be used as a set of
procedures callable from Microsoft Visual Basic (see the
Programmer’s Guide for the Multiflash Visual Basic
Interface), C and C++ (see the Programmer’s Guide for the
Multiflash C Language Interface) and Fortran. The low-level
application interface is descried in the Multiflash
Programmer’s Guide.

1
Changes from previous
versions

Since Multiflash 6.0, the command processor, which is used to read

MFL files, has been redesigned for efficiency and for flexibility. This
had to take into account the new Graphical User Interface (GUI), in
which there is no output window to send command outputs to.
As such these are the fundamental changes:
• All the SHOW/LIST/WRITE commands have been disabled.
• HELP command as been disabled as there is no output for
messages. The Error messages help file will provide all the
necessary information.
• All MATCH commands have been disabled:
◦ The new matching facilities available in the PVT Lab tests
tool in Multiflash do not make use of commands, hence
there are no commands available to drive the model
tuning.
• Error messages do not appear in the main window. If any
error occurs in the “send commands” tool in the GUI will show
an error dialog box.
• Calculation commands have been disabled
◦ Calculations are solely driven by the GUI, hence
commands like PTF, PFRACF, FRACPHENV, PHENV,
FIXEDPHASE, etc, have been disabled.
◦ Wax appearance temperature and wax precipitation curve
are disabled.
• Delump/blend commands has been disabled. All
delumping/blending operations are done without using the
command processor.
• PVT tables command have been disabled are only needed to
store PVT table information.
• SET commands are disabled. Any calculation modes or
property output are set in the GUI.

2
 Applications
programming
interfaces - Visual
Basic, C, Fortran

Command Microsoft Microsoft Other

driven Windows Excel applications
Interactive Interactive interface e.g. Process
interface interface simulators

Multiflash
Multiphase equilibrium

MODELS
Equations of state
Activity models
Group contribution models
Solids
Hydrates
Transport properties

DATA
MANAGER

User- User
INFODATA DIPPR
entered data
data files
Petroleum fractions Other databanks

Multiflash Software Structure

Using Multiflash

This section gives an overview of how the command language can be

used to set up and run a problem.

Entering commands
In the Multiflash GUI, the command dialog box all commands may be
entered to perform tasks not supported by the GUI. The other
interfaces have different ways of accepting commands, e.g. in the
Excel interface commands can be entered on a spreadsheet. An
alphabetical list of commands is given on page 105.
Most commands need to be followed by extra information to
complete their action, e.g.
PUREDATA INFODATA;
The PUREDATA command is followed by the INFODATA keyword to
instruct Multiflash to use the infodata data bank to load component
properties. Commands may be entered in upper- or lower-case and
may be abbreviated to the shortest unique character string.
In all versions commands may be read in from existing input files, the
MFL files. Input files can be read in using the INCLUDE command, e.g.
INCLUDE c4c5.mfl;
Include files can have any name that is acceptable on your computer
system. The sample files supplied with Multiflash use the file
extensions .mfl.

Specifying a problem
A phase or chemical equilibrium problem is specified using the
sequence of operations described below.

Source of pure component data

The data source (databank) for normal components is set using the
command PUREDATA, followed by the databank name. E.g.
PUREDATA INFODATA;
sets the databank to be the standard Infochem fluids databank. More
than one databank may be used to set up a problem but only one can
be active at any time. For more details see Commands for setting
component databanks on page 13.

5
Components in a mixture
Normal components are added to the mixture using the command
COMPONENTS followed by a list of component names. The maximum
number of components is currently 200. If the component name
includes punctuation or spaces then it should be put in double
quotation marks. Each name must be a valid component name for the
databank in force. E.g.
components methane butane water "carbon dioxide ";
An alternative form of the components command allows a
component to be defined in a particular place in the sequence of
components. For example, to define component 4 without,
necessarily, defining components 1 to 3
components 5 methanol;
When defining components from more than one databank,
components are added to the end of the existing list of components
unless you specify otherwise, e.g.
PUREDATA DIPPR;
COMPONENTS methanol hydrogen "carbon monoxide";
PUREDATA Infodata;
COMPONENTS oxygen;
makes oxygen the fourth component.
For more details see Commands for setting component databanks on
13. Information on how to define components that are petroleum
fractions is given in the section on page 28.

Source of binary interaction parameter data

Binary interaction parameters (BIPs) are required by most of the
mixture models in Multiflash. BIP data may be taken from a databank
or entered directly on the command line. If BIP data are not defined
the models will use their internal default values. The default BIPs may
or may not lead to reasonable predictions of mixture properties. The
behaviour depends on the model and mixture.
BIP databanks are defined by the command BIPDATA followed by the
bank name. E.g.
BIPDATA infobips oilandgas;
The oilandgas bank provides BIP values for components typical of oil
and gas mixtures for cubic eos. And the infobips databank provides
the interaction parameters for VLE and refrigerants.
The command BIPSET is used to define BIPs directly. This is a
somewhat complex and, potentially, error-prone process. It is
recommended that the necessary commands are entered in a problem
setup file which can then be included, checked and revised as
necessary.
For more details see Binary interaction parameters on page 79.

6
Mixture models
A complete description of the available models and how they are
defined is are given in the section starting on p.39. It is necessary to
set up models that Multiflash can use to calculate (at least) fugacity
coefficients in phase equilibrium calculations. If other properties such
as enthalpy or volume are of interest then the appropriate models
must be made available.
A model is specified using the command MODEL, followed by a user-
defined model identifier, a Multiflash model keyword and any further
model-dependent information. For example, the following command
sets up the PR eos with the name MPR
MODEL MPR PR PRBIP;
The model identifier can be any unique name assigned by the user. It
is used subsequently to refer to the model, e.g. when defining a phase
descriptor (see below).
The MODEL command also allows a set of BIPs defined with the
BIPSET command to be associated with a model. For example, the
following command defines the Wilson A activity equation as a model
called MWILSONMPR using the PR eos ( MPR ) as the vapour phase
model and taking BIPs from a bipset called Wilson1:
MODEL MWILSONMPR wilson a MPR Wilson1;
Note that the MODEL command is also used to define transport
property mixture models. The following command sets up a viscosity
model called MLBCMPR (which uses a previously-defined MPR ).
MODEL MLBCMPR LBC LFIT MPR;

Phase descriptors
The idea of a phase descriptor (PD) is central to the operation of
Multiflash. The phase descriptor contains all the information required
to identify a phase and to retrieve its thermodynamic and transport
properties. A PD must be specified for each possible phase that
Multiflash is to consider. It is possible that only a subset of the list of
possible phases will actually be present at equilibrium. The maximum
number of PDs that may be defined is currently 20 and the maximum
number of phases that may be present at equilibrium is 7.
Multiflash is designed to allow the use of different thermodynamic
models for different phases and for different properties of a given
phase. The solution methods used do not make any assumptions
about thermodynamic consistency between fugacity coefficients,
volumetric properties and thermal properties.
The phase descriptor for each phase is defined using the PD (or
phasedescriptor) command (see p. 83). The command sets up a
user-defined identifier for the phase; the phase type (e.g. liquid), plus
a list of model identifiers for fugacities, volume, enthalpy/ entropy,
viscosity, thermal conductivity and surface tension. The PD identifier
can be any unique name assigned by the user, it is simply used as a
label, e.g. in the output, and does not have any other significance.
The list of models may be terminated at any point by the end marker
; and any models not specified will be taken as undefined. A * in
place of a model identifier denotes ‘use the last named model’ or
‘undefined’ if the last model is unsuitable for that property.
If the volume model is not defined then it is set to the fugacity model,
if the enthalpy/entropy model is not defined then it is set to the
volume model. If you need to calculate viscosity, thermal conductivity

7
or surface tension then a model must be defined for each property
required.
For example,
PD hc_liquid liquid MPR;
defines a PD called hc_liquid. The phase type is liquid and all the
thermodynamic properties (fugacities, volume, enthalpy and entropy)
will be calculated with the model MPR. No transport property models
are defined.
In the following example the thermodynamic properties will be
calculated using the model MPR (as no other models are defined for
volume or enthalpy/entropy - note the use of *) and, in addition, the
viscosity will be calculated using the viscosity model MLBCMPR. The
thermal conductivity and surface tension remain undefined.
PD hc_liquid liquid MPR * * MLBCMPR;
The example below adds a thermal conductivity model MCLSMPR and a
surface tension model MMCSMPR
PD hc_liquid liquid MPR * * MLBCMPR MCLSMPR MMCSMPR;

Key components
For phase equilibrium calculations involving more than one liquid
phase the user may wish to define a set of key components which are
associated with a phase descriptor. This is done by using the
command KEYS, followed by the PD name, followed by the name or
the CARN number of the key component,s e.g.
KEYS liquid2 water methanol;
Or
KEYS liquid2 007732-18-5 000067-56-1;
where liquid2 is a phase descriptor that has previously been defined.
For more details see p. 85.
Similarly the keyword “not” can also be used to indicate that a
component should not be present (or present in the smallest amount)
in a phase. For example, to identify the non-aqueous liquid phase in a
hydrocarbon/water/methanol problem the following command could
be used:
KEYS liquid1 not water not methanol;
Or
KEYS liquid1 not 007732-18-5 not 000067-56-1;
For many calculations it is not necessary to define key components.
Multiflash will allocate the phase descriptors for multiple liquid
phases in the order in which the phases are found. However this
means that the same phase may appear in different columns of the
output as conditions change, e.g. Liquid2 may become Liquid1.
For fixedphase calculations, when the fixed phase is one of the
liquid phases, key components must be defined because Multiflash
has no other way of distinguishing between multiple liquid phases.
In versions previous to Multiflash 4.4 only one key component could
be defined per phase descriptor, this was done by using the command
KEY. Although, from MF 4.4 onwards the use of KEY (as opposed to
KEYS) is no longer recommended Multiflash still recognises it for
compatibility reasons.

8
From version 4.4 onwards a new keyword can be used to define
aqueous phases: AQUEOUS:
KEYS water AQUEOUS;
This keyword will automatically add the following list o components
as aqueous components to the list of key components:
• water
• methanol
• ethanol
• MEG
• DEG
• TEG
• Glycol
• Propylene glycol
• Propylene glycol monomethyl ether
• dipropylene glycol
• dipropylene glycol monomethyl ether

Composition
The compositions (or amounts of each component) are defined by the
AMOUNTS command. The default units for amounts are mole numbers
but they may be changed using the units and/or inputunits and
outputunits commands (see p.99). The AMOUNTS command is
followed by a list of values for all components, e.g.
AMOUNTS .3 .3 .4 0.;
An alternative form of the command allows the amount of an
individual component to be changed or entered. The components for
which the amount is to be changed can be identified by name or serial
number. Because the serial number is an integer, the amount must
contain a decimal point, e.g.
AMOUNTS methanol 2.0;
or (if methanol is the third component)
AMOUNTS 3 2.0;
For more details see Amounts of components on p. 91.

Calculation conditions
Calculation conditions are defined with the commands TEMPERATURE,
PRESSURE, ENTHALPY, ENTROPY, INTERNALENERGY and VOLUME (or
DENSITY), followed by the numerical value. The volume and density
commands are equivalent - the value is interpreted as a volume or a
density depending on the input units set for volume/density. The
default units for all quantities are SI, i.e. temperature in K, pressure in
Pa, energy in J/mol and volume in mol/ m3.
For example, the following command sets the temperature and
enthalpy
TEMPERATURE 350 ENTHALPY -28.575;

9
 All input conditions must be defined before they are used. Once
defined they will remain in force until changed. For more details see
Commands for setting conditions on p. 91.

Doing a calculation
All the calculation commands are listed in the section starting on p.
91. In general commands ending with the suffix FLASH are phase
equilibrium. A typical example would be PTFLASH for an isothermal
flash. Before using a calculation command the amounts and other
input quantities must be specified.

Units
The default units for input and output are SI. They may be changed by
the commands INPUTUNITS and OUTPUTUNITS respectively.
Alternatively the UNITS command sets both input units and output
units to the same unit. The commands are followed by the keyword
for the property for which the units are to be changed, e.g.
TEMPERATURE, followed by the unit setting. Where the unit relates to
more than one property e.g. enthalpy and internal energy, then the
units for both will be changed if any one of them is altered. For more
details see Commands for changing units on page 100.
The following example sets the input units for temperature to degrees
Celsius, the output (display) units for pressure to mm of mercury, and
both input and output units for density to kg/m3:
INPUTUNITS TEMPERATURE C;
OUTPUTUNITS PRESSURE mmHg;
UNITS density kg/m3;

Changing the problem

Once a problem has been set up any of the specifications may be
changed by use of the commands already described. All specifications
remain fixed until changed or reset.
The command REMOVE is used to remove (or undefined) related
groups of specifications which may be all, bipsets , models,
components, pds, streamtypes . Remove all removes all BIP data,
models, components, phase descriptors and stream types and resets
the units back to the values they had when Multiflash was started, i.e.
any units set in the mfconfig.dat file are kept. For more details see
p. 103.

Error messages and diagnostics

When errors occur an error number will appear followed by a single
line description of the error, e.g.
*** ERROR 210 ***
Loading component from data bank has failed - Diagnostic = component number
DIAGNOSTIC 1

For further information HELP followed by the error number will

usually provide more information. e.g.
help 210;

*** ERROR 210 ***

10
 Module: Multiflash command processor
Subprogram: MFCOMP
Error: 210
Multiflash has tried to load the data for a component from the data
files/data bank into the pure-component data system. The load procedure
has failed.
Diagnostics: (1) Component number

The ‘module’ is the section of Multiflash in which the error occurred.

The ‘subprogram’ name is intended for use by Infochem technical
support. The final line of the above example shows a ‘diagnostics’
message which identifies further information that is printed out after
the error message. In this case it shows that component number 1
caused the problem.
The diagnostic level setting (not related to the diagnostics mentioned
above) provides a way of getting more information about the progress
of a calculation. The diagnostic information is primarily for use by
Infochem in tracking down errors and is not intended to be
meaningful in general use. The normal level is 0, higher levels, up to
5, give more information, lower levels, down to -2, give less. These are
set using the command SET diagnostics followed by an integer
value for the diagnostic level, e.g.
SET diagnostics 3;
Diagnostics are switched off by SET nodiagnostics;

Output
The command-line version of Multiflash produces output on the
screen and in the log file (see below). Other interfaces provide output
in the most appropriate form, e.g. the Visual Basic programming
interface can return output in a character string or via function
arguments.
Output is produced in response to a calculation command, now only
in the VBA interface.
Multiflash provides several levels of physical property output,
specified by SET physprops followed by a code, which is made up of
the numbers 0, 1 or 2, optionally followed by the letters A,D,E,F & T
(or VCS) depending on what outputs are required.. The zero setting
produces minimum output of phases and compositions, 1 adds
thermal/volumetric properties and 2 adds derivatives such as Cp and
Cv and also the speed of sound. The A adds the activity coefficients of
the components in each phase. The D adds the diffusivity. The E code
adds thermal properties calculated relative to elements in their
standard states (at 298K and 1atm) which are useful for chemical
reaction studies. The F adds the fugacity coefficients. The T code adds
all transport properties. For transport properties selection use instead
V for viscosities, C for thermal conductivity and S for surface tension.
In all cases output will only be produced if the relevant models have
been defined. For example, to list all thermodynamic and transport
properties
SET physprops 2VCS;

Model configuration files

Problem definition can be viewed as falling into two broad categories,
those parts which usually remain fixed and those which can vary
frequently. Examples of the former would be the sources of data, the

11
 models used and the phase descriptors. On the other hand
specifications which may change are the components, the
compositions and the calculation conditions.
In order to minimise effort for the user Infochem has set up a series
of model configuration files (suffix .mfl), which define the more
static elements of the problem. Each model configuration file
corresponds to a model or group of models with a particular set of
model variants. For example rks.mfl defines the RKS model. The
.mfl files are supplied as part of the software distribution.

Example Calculation
The following example sets up the models and phase descriptors for
investigating hydrate formation.
remove all;
units temperature K pressure Pa enthalpy J/mol
entropy J/mol/K volume m3/mol amounts mol viscosity
Pas thcond W/m/K;
puredata infodata;
bipset RKSABIP3 3 constant eos none ;
bipdata INFOBIPS OILANDGAS4 ;
model MRKSANRTL RKSA PSAT LDEN NRTL RKSABIP3;
model MHYD1MRKSANRTL HYDRATE I MRKSANRTL;
model MHYD2MRKSANRTL HYDRATE II MRKSANRTL;
model MICEMRKSANRTL FREEZEOUT 007732-18-5#WATER#
MRKSANRTL;
pd GAS gas MRKSANRTL;
pd LIQUID1 liquid MRKSANRTL;
pd HYDRATE1 hydrate MHYD1MRKSANRTL;
pd HYDRATE2 hydrate MHYD2MRKSANRTL;
pd ICE condensed MICEMRKSANRTL;
pd WATER liquid MRKSANRTL;
keys WATER AQUEOUS;
keys LIQUID1 *;
The components and their amounts are now specified. A series of
isothermal flashes is performed at varying temperatures taking a
fixed pressure "slice" across the phase diagram. The onset of hydrate
formation at a given pressure is predicted as well as the temperature
at which a fixed amount of hydrate will form. Calculation of the ice
point at the given pressure is shown.
components methane butane water;
amounts .49 .49 .02;
pressure 1e5;
# Change T at fixed pressure to cross phase diagram
temperature 250;ptflash;
temp 200; ptf;
temp 220; ptf;
temp 290; ptf;
temp 300; ptf;
# use the fixedphase flash to look for the
# temperature at which hydrate first forms
fixedphase hydrate2 0.0;pfracf;
# repeat the calculation to look for the formation
# of 1% (molar) hydrate
fixedphase hydrate2 0.01;pfracf;
# use the same fixedphase option to look for the
# ice line at 1 bar
fixedphase ice 0.0;pfracf;

12
Databanks and components

Commands for setting component databanks

PUREDATA
The PUREDATA command sets the default databank for pure
component properties for components that may be present.
The command has the following format
PUREDATA databank_name;
databank_name may be one of the following:

databank_name Meaning
INFODATA Infochem fluids databank
DIPPR DIPPR data compilation of pure
compound properties, from AIChE.
Requires separate licence. See separate
documentation.
ERASE erases (removes) currently defined
databank

Other databanks, typically containing users’ own data, in one of the

standard formats may be specified as follows:
PUREDATA databank_type file_name1 file_name2;
The databank_type, associated file_name1 and file_name2 are
defined in the following table.
Databank_type required files Notes
OWNINFODATA 1. databank index files must
2. databank (.bin) correspond to the
file Infodata structure

13
Loading components from a databank

COMPONENTS
The COMPONENTS command loads normal components that may be
present in mixed fluid and solid phases. Each component name is
searched for in the currently defined fluid components databank (see
PUREDATA command).
The command has the following format:
COMPONENTS entry_mode n name_1 name_2 name_3 ….;
entry_mode may be either insert, overwrite or amend. If omitted
the default mode is overwrite.
n is an integer serial number that defines the position of the first
component (name_1) in the component list. If n is omitted it is taken
as the last component currently defined. The current version of
Multiflash allows up to 200 components to be defined.
Name_1 name_2 etc. must be valid component names for the
databank currently defined with the puredata command. If a name
has embedded spaces or commas then it should be enclosed in
inverted commas, e.g. “carbon dioxide” .
In insert mode each new component causes the component to be
inserted in the existing list of components at position n (or at the end
if n is omitted) without deleting any of them. This is done by
incrementing the numbers of existing components as necessary.
In overwrite mode, any existing component of the same component
number will be replaced by the newly defined component.
In amend mode, the component is left unaltered except its name
and/or physical properties will be overwritten by any new value
entered by the user (see below).
For example, the following commands load three components from
the DIPPR databank and the fourth component from the Infodata
databank.
PUREDATA DIPPR;
COMPONENTS methanol hydrogen “carbon monoxide”;
PUREDATA Infodata;
COMPONENTS oxygen;

IONS
This command is like the COMPONENTS command except that it
defines an ion as a component in the fluid mixture, for example:
PUREDATA Infodata;
IONS Ca++ Cl-;

SEGMENTS
This command is used to define a segment from which a polymer is
constituted. It is used for the PC-SAFT model. A segment is not a true
component, so it is not normally read from a databank. See below for
an example.

14
Data entry for a normal component

Defining a new component

The usual (and recommended) way of defining pure components is to
use the PUREDATA command to define a databank and then to use the
COMPONENTS command to select components from that databank. Any
number of databanks may be used by repeating this sequence for
each databank. The PETROFRACS command (p.29) is provided for
defining petroleum fraction pseudocomponents. In addition, the user
may define components by entering data directly into Multiflash. This
technique can be used to define all the necessary data for a
compound or to overwrite selective data items for a component
already defined from a databank.
Direct data entry can be quite complex and requires a detailed
understanding of the way the data are used by the mixture models
and of the correlating equations used to represent pure component
properties. It is not recommended that you attempt to define
components in this way unless there is no alternative. However, if you
do wish to proceed, the best method is to prepare the data in the
form of an problem setup file which can then be corrected as
necessary.
Data items are entered using the COMPONENTS command as follows.
COMPONENTS entry_mode n component_name DATA
property_name1 property_value1
property_name2 property_value2…. ;;
To create a new component entry_mode should be either overwrite
or amend (see above).
N is an integer serial number that defines the position of the
component in the component list. If n is omitted it is taken as the last
component currently defined.
Component_name. Is the user-defined name for the new component. It
may be a string up to 72 characters in length. If it contains embedded
spaces or commas then it should be enclosed in inverted commas.
The DATA keyword marks the start of data entry for the compound.
The end of data for a component is denoted by a semi-colon. A
second semi-colon is needed to terminate the COMPONENTS command.
The Property_name must be one of the keywords listed in the
sections Pure component constant properties (p.17 ) and Pure
component temperature-dependent properties (p.20). The
Property_value is one or more numbers that define a simple
constant property such as the critical temperature or the coefficients
in a correlation for a temperature-dependent property such as the
vapour pressure.

Example
The following is a description of a typical data entry sequence. The
command PUREDATA erase cancels any current data source and
allows a new, non-databank, component to be defined. All
components loaded prior to this remain defined. The new component
is then defined using the COMPONENTS command.
For any constant property the data entry is relatively straightforward,
e.g. Pcrit 40.5e5. The situation is a little more complex for
temperature dependent properties. It is necessary to define the
property name, equation number and correlation coefficients. The

15
information given in Pure component temperature-dependent
properties (p.20) defines the relevant property names, equation
numbers and details of the coefficients required.
For some quantities, e.g. for parachor or dipole moment, there are
fixed units; for other quantities units are assumed to be as the
current input units setting. There is no unit conversion when entering
coefficients of temperature dependent pure component properties;
these are all in standard SI units.
For example, to add a component:
PUREDATA erase;
COMPONENTS 3 naphthalene data
mw 128.175
tboil 491.14
tmelt 353.15
pcrit .4051e07
tcrit 748.4
acentricfactor .303
cpideal 1 4.0 52.0 160 1.80665 -6.0491 17.8647
-15.4058 0 10000
lden 4 616.74 0.25473 748.35 0.27355 333.15 748.35
psat 3 -7.19879 .75005 -2.23858 -3.78919 353.15
748.4; ;
Note that two end markers are needed. The first defines the end of
the data command, the second the end of the components command.

Amending data for an existing component

The procedure is similar to setting up a new component except that
the some data for the component must already have been entered.
This is done either by loading the component from a databank or by
defining some data as described above.
Data items are entered or overwritten using the COMPONENTS
command as follows.
COMPONENTS entry_mode n component_name DATA
property_name1 property_value1
property_name2 property_value2…. ;;
The command parameters are as described for the case of creating a
new component.

Example
To change the critical temperature for a component as it is loaded
from a databank;
PUREDATA Infodata;
COMPONENTS hydrogen data tcrit 30;;
The following example is equivalent to the first one. Several
components are loaded and then the properties of component 1 are
changed:
PUREDATA Infodata;
COMPONENTS hydrogen, ethane, methane;
COMPONENTS amend 1 data tcrit 30;;

16
Pure component constant properties
The property units are given in parentheses where applicable. Units
for other properties may be set by the UNITS or INPUTUNITS
commands.

17
Keyword Property description
CARNUMBER Chemical abstracts registry number. The format is: 6
digits -2 digits-1 digit. E.g. 007440-37-1
FORMULA Chemical formula ( up to 20 character )
FAMILYCODE Chemical family code ( up to 20 character )
UNIFAC UNIFAC subgroups and abundance
MOLECULARWEIGHT OR relative molar mass (molecular weight in g/mol)
MW
TCRIT critical temperature
PCRIT critical pressure
VCRIT critical volume
ACENTRICFACTOR acentric factor defined as
  1  log 10 pr at Tr  0.7 , where Tr  T / Tc
and pr  p sat / pc

TBOIL normal boiling point

HFORMATION standard enthalpy change on formation in the perfect
gas state at 298.15K
SSTANDARD standard entropy in the perfect gas state at 298.15K
and 1bar
TMELT normal melting point
HMELT enthalpy change on fusion at the melting point
SMELT entropy change on fusion at the melting point
CPMELT solid/liquid difference in Cp at the melting point
VMELT solid/liquid difference in molar volume at the melting
point
RUNIQUAC UNIQUAC r parameter
QUNIQUAC UNIQUAC q parameter
THLWATER characteristic temperature for Henry’s Law correlation
for component in water (K )
VHLWATER characteristic volume for Henry’s Law correlation for
solubility of a component in water ( m3/mol )
DIPOLEMOMENT dipole moment (debye)
POLARIZABILITY Polarizability of component in Å3
QUADRUPOLEMOMENT Quadrupole moment in Debye Å
PARACHOR parachor ( (dyne/cm)¼ cm3/mol )
RADGYR radius of gyration (m)
HOCASS Hayden O’Connell self association parameter
GFORMATION Gibbs energy of formation in the perfect gas state at
298.15K and 1 bar
TTRIPLE triple point temperature
PTRIPLE triple point pressure
HCOMBUSTION enthalpy of combustion
V25 molar volume at 298.15K for use with solubility
parameters
SOLUPAR liquid phase solubility parameter
SOLIDSOLUPAR solid solution phase solubility parameter
ZCRIT critical compressibility factor
REFRACTINDEX refractive index
TFLASH flash temperature
TAUTO autoignition temperature
FLAMLOWER lower flammability limit (volume % in air)

18
Keyword Property description
FLAMUPPER upper flammability limit (volume % in air)
SPGRAVITY OR SG specific gravity at 60 ºF
EXPANSIVITY Thermal expansivity of liquid at 1 atm and 60 F (K-1)
OMASCALE Scaling factor to give conventional value of Ωa for
cubic EOS
OMBSCALE Scaling factor to give conventional value of Ωb for
cubic EOS
OMARKS Scaling factor to give conventional value of Ωa
specific to RKS model.
OMBRKS Scaling factor to give conventional value of Ωb
specific to RKS model.
OMAPR Scaling factor to give conventional value of Ωa
specific to PR model.
OMAPR Scaling factor to give conventional value of Ωb
specific to PR model.
CNUMBER Carbon number for petroleum fractions
REFVISCOSITY reference viscosity for liquid at the boiling point
REFVISST reference viscosity for liquid at the boiling point for
SUPERTRAPP viscosity model
REFVISPD reference viscosity for liquid at the boiling point for
Pedersen viscosity model
REFVISTW reference viscosity for liquid at the boiling point for
Two model
REFVISLB reference viscosity for liquid at the boiling point for
LBC model
LJEVISC Lennard-Jones σ parameter (m)
LJBVISC Lennard-Jones ε/k parameter for viscosity ( K )
VCLBC Critical volume for the LBC model (m3)
EOSC Corresponding states reference equation code
TYPE The type of components.
HDATUM Options for calculating enthalpy
1 for compound
2 for elements
3 for standard enthalpy ( 298.15K )
SDATUM Options for calculating entropy
1 for compound
2 for elements
3 for standard entropy ( 298.15K, 1 bar )
COMPREFNO The component reference number
HYDOC Hydrate cavity occupation codes
HYD1 Hydrate parameter 1
HYD2 Hydrate parameter 2
HYD3 Hydrate parameter 3
ASSBETA CPA β parameter
ASSEPSILON CPA ε AB parameter ( J / mol )
ASSGAMMA CPA γ AB parameter
ASSDELTA
CPA δ AB parameter ( K −1 )
ASSFF Number of association sites ( CPA )
ASSAC
CPA ac parameter ( Jm 3 /mol 2 )

ASSBC CPA b parameter ( m 2 / mol )

19
Keyword Property description
ASSKAPPA CPA κ parameter
SAFTKAPPA PC-SAFT κ parameter
SAFTEPSILON PC-SAFT ε AB parameter
SAFTGAMMA PC-SAFT γ AB parameter
SAFTFF Number of association sites ( PC-SAFT )
SAFTEK PC-SAFT  /k parameter
SAFTSIGMA PC-SAFT  parameter
SAFTLAMBDA PC-SAFT  parameter
SAFTM PC-SAFT m parameter
MCRKS1 First Mathias Copeman parameter with RKSA model
MCRKS2 Second Mathias Copeman parameter with RKSA model
MCRKS3 Third Mathias Copeman parameter with RKSA model
MCPR1 First Mathias Copeman parameter with PRA model
MCPR2 Second Mathias Copeman parameter with PRA model
MCPR3 Third Mathias Copeman parameter with PRA model
VSRKS1 The first volume shift parameter ( m3/mol ) with eos
RKSA
VSRKS2 The second volume shift parameter ( m3/mol K ) with
eos RKSA
VSRKS3 The third volume shift parameter ( m3 K/mol )
VSPR1 The first volume shift parameter ( m3/mol ) with eos
PRA
VSPR2 The second volume shift parameter ( m3/mol K ) with
eos PRA
VSPR3 The third volume shift parameter ( m3 K/mol ) with
eos PRA
CPIDLIQ Set to 1 to use the pure liquid enthalpy as reference
for excess energy models. Set to 2 to also use pure
liquid enthalpy as reference for gas phase.
MWEST Mw parameter used to tune the SuperTRAPP viscosity
model
MWEPD Mw parameter used to tune both variants of Pedersen
viscosity model
TBOTW Boiling point parameter used to tune the Two
viscosity model

Pure component temperature-dependent

properties
The form of each correlation is defined below. Property units are
given in parentheses. They are fixed and are not affected by the UNITS
or INPUTUNITS command.
The format require for each property correlation is
property_name equation_number coefficients Tmin Tmax;
property_name is one of the keywords from the following table.
equation_number identifies the correlation.
coefficients are the numerical values of the correlation
coefficients. The number of coefficients required depends on the
equation number.

20
 Tmin and Tmax are the minimum and maximum temperature limits
for the correlation in K.

Keyword Equation Additional information

number
CPIDEAL ideal gas Cp correlation (J/mol K)
0 data unknown; 0 coefficients
1 Harmens method, 9 coefficients
a3, a4, a5, a6, a7, a8, a9, Tmin, Tmax
C p / R  a3  a4  a3  y 2 1   y  1 F ( y )
T
where F ( y )  a 6  a 7 y  a8 y 2  a9 y 3 , y 
T  a5
2 DIPPR equation 107, 7 coefficients
a3, a4, a5, a6, a7, Tmin, Tmax
2 2
 a5 / T   a7 / T 
C p  a3  a 4    a6  
 sinha5 / T    cosh a 7 / T  
5 DIPPR equation 100, 7 coefficients
a3, a4, a5, a6, a7, Tmin, Tmax
C p  a 3  a 4 T  a 5T 2  a 6 T 3  a 7 T 4

21
CPLIQUID liquid Cp correlation (J/mol K)
0 data unknown, 0 coefficients
1 DIPPR equation 114, 9 coefficients
a1, a2, a3, a4, a5, a6, a7, Tmin, Tmax
C p  a1 /   a2  a3  a4 2  a5 3  a6 4  a7 5
where   1  T / Tc

5 DIPPR equation 100, 7 coefficients

a1, a2, a3, a4, a5, Tmin, Tmax
C p  a1  a2T  a3T 2  a4T 3  a5T 4
CPSOLID solid Cp correlation (J/mol K)
0 data unknown, 0 coefficients
5 DIPPR equation 100, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
C p  a1  a2T  a3T 2  a 4T 3  a5T 4
PSAT saturated vapour pressure (Pa)
0 data unknown, 0 coefficients
1 Wagner (form 1) 5 coefficients
a1, a2, a3, Tmin, Tmax
a1  a 2 2  a3 3
ln p  ln pc 
Tr
where Tr  T / Tc ,   1  Tr
2 Antoine equation, 9 coefficients
a1, a2, a3, a4, a5, a6, a7, Tmin, Tmax
a2 a
ln p  a1   a 4T a6  a5 ln T  72
T  a3 T
Note that if the third term is unused a4 should be set to 0 and
a6 must be set to a positive value such as 1.0.
3 Wagner (form 2), 6 coefficients
a1, a2, a3, a4, Tmin, Tmax
3
a1  a 2  a3 3  a 4 6
2
ln p  ln pc 
Tr
where Tr  T / Tc ,   1  Tr

4 Wagner (form 3), 6 coefficients

a1, a2, a3, a4, Tmin, Tmax
3 5
a1  a 2  a 3  a 4 5
2 2
ln p  ln pc 
Tr
where Tr  T / Tc ,   1  Tr

5 DIPPR equation 100, 7 coefficients

a1, a2, a3, a4, a5, Tmin, Tmax
p  a1  a2T  a3T 2  a4T 3  a5T 4

22
HVAP enthalpy of vaporisation correlation (J/mol)
0 data unknown, 0 coefficients
1 Watson/DIPPR 106 equation, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
H  a1 Y
where Y  a 2  a3Tr  a 4 Tr  a5Tr , Tr  T / Tc ,
2 3

Tr  T / Tc ,   1  Tr
2 Wagner type equation for enthalpy of
vaporisation, 9 coefficients
a1, a2, a3, a4, a5, a6, a7, Tmin, Tmax

H / RTc  a1 1 / 3  a 2 2 / 3  a3  a 4 4 / 3  a5 5 / 3

 a6 2  a 7 6
where   1  T / Tc
5 DIPPR equation 100, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
H  a1  a2T  a3T 2  a4T 3  a5T 4

LDENS saturated liquid density correlation (mol/m3)

0 data unknown, 0 coefficients
1 Infochem equation, 5 coefficients
a1, a2, a3, Tmin, Tmax
  a1  a 2 a3
where   1  T / Tc
2 Hankinson and Thompson equation
(modified), 6 coefficients
a1, a2, a3, a4, Tmin, Tmax
1 2 4
  1 / Vc  a1 3  a 2 3  a3  a 4 3
where   1  T / Tc

Note that in the above equation  is the mass density and Vc

is the critical volume per unit mass
3 Rackett equation (modified), 5 coefficients
a1, a2, a3, Tmin, Tmax
1 /   a1 a 2  a3 
Y

2
where
Y  1  7 ,   1  T / Tc
4 DIPPR equation 105, 6 coefficients
a1, a2, a3, a4, Tmin, Tmax
1 /   a 2 Y / a1
Y  1  1  T / a3 
a4
where

5 DIPPR equation 100, 7 coefficients

a1, a2, a3, a4, a5, Tmin, Tmax
  a1  a 2T  a3T 2  a4T 3  a5T 4
SDENS solid density correlation (mol/m3)
0 data unknown, 0 coefficients
5 DIPPR equation 100, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
  a1  a 2T  a3T 2  a4T 3  a5T 4

23
24
LTHCOND liquid thermal conductivity correlation (W/m K)
0 data unknown, 0 coefficients
1 Jamieson equation, 6 coefficients
a1, a2, a3, a4, Tmin, Tmax
 1 2

  a1 1  a 2  a3 3  a 4 
3
 
where   1  T / Tc

2 DIPPR equation 101, 7 coefficients

a1, a2, a3, a4, a5, Tmin, Tmax
ln   a1  a 2 / T  a3 ln T  a 4T a5
5 DIPPR equation 100, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
  a1  a2T  a3T 2  a4T 3  a5T 4
VTHCOND vapour thermal conductivity correlation (W/m K)
0 data unknown, 0 coefficients
1 DIPPR equation 102, 6 coefficients
a1, a2, a3, a4, Tmin, Tmax
a1 T a2

1  a3 / T  a4 / T 2
2 Reduced correlation, 6 coefficients
a1, a2, a3, a4, Tmin, Tmax
Tr

a1  a 2Tr  a3Tr2  a 4Tr3
where Tr  T / Tc

3 Monatomic ideal gas, 2 coefficients, Tmin, Tmax

  3750 0 R / M
5 DIPPR equation 100, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
  a1  a2T  a3T 2  a4T 3  a5T 4
LVISC liquid viscosity correlation (Pa s)
0 data unknown, 0 coefficients
1 Reid, Prausnitz and Poling equation 1,
4 coefficients a1, a2, Tmin, Tmax
  a1T a2
2 DIPPR equation 101, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
ln   a1  a 2 / T  a3 ln T  a 4T a5
3 Reduced correlation, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
1 4
ln / a5   a1 X  a 2 X
3 3

a3  a 4
where X  1
T  a4
4 Reid, Prausnitz and Poling equation 2/3, 6
coefficients a1, a2, a3, a4, Tmin, Tmax
ln   a1  a 2 / T  a3T  a 4T 2

25
 5 DIPPR equation 100, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
  a1  a2T  a3T 2  a4T 3  a5T 4
VVISC vapour viscosity correlation (Pa s)
0 data unknown, 0 coefficients
1 DIPPR equation 102, 6 coefficients
a1, a2, a3, a4, Tmin, Tmax
a1T a2

1  a3 / T  a 4 / T 2
2 Reichenberg equation, 5 coefficients
a1, a2, a3, Tmin, Tmax
a1Tr
 1

1  a T T  1
2 r
a3
r
6

where Tr  T / Tc
3 Chapman-Enskog equation, 5 coefficients
a1, a2, a3, Tmin, Tmax
1
26.69  10 7  MT  2


a12  2, 2 T * , a3 
where

   
 2, 2  AT * B  C exp  DT *  E exp  FT *  0.2a32 / T *
T  T / a 2 , A  116145
*
. , B  014874
. , C  0.52487 ,
D  0.77320 , E  216178
. , F  2.43787
5 DIPPR equation 100, 7 coefficients
a1, a2, a3, a4, a5, Tmin, Tmax
  a1  a2T  a3T 2  a4T 3  a5T 4
STENSION surface tension correlation (N/m)
0 data unknown, 0 coefficients
1 DIPPR equation 106, 7 coefficients
a1, a2, a3, a4, a5 Tmin, Tmax
  a1 1  Tr 
Y

where Y  a2  a3Tr  a4Tr2  a5Tr3 , Tr  T / Tc

2 Extended Sprow and Prausnitz equation, 5
coefficients a1, a2, a3, Tmin, Tmax
  a1 a2 1  a3 
where   1  T / Tc

5 DIPPR equation 100, 7 coefficients

a1, a2, a3, a4, a5, Tmin, Tmax
  a1  a 2T  a3T 2  a 4T 3  a5T 4
VIRIALCOEFF second virial coefficient correlation (m3/mol)
0 data unknown, 0 coefficients
1 DIPPR equation 104, 7 coefficients
a1, a2, a3, a4, a5 Tmin, Tmax
B  a1  a 2  a3 3  a 4 8  a5 9
where   Tc / T

5 DIPPR equation 100, 7 coefficients

a1, a2, a3, a4, a5, Tmin, Tmax

26
 B  a1  a2T  a3T 2  a4T 3  a5T 4
DIELECTRIC relative permittivity/dielectric constant correlation
0 data unknown, 0 coefficients
1 Maryott-Smith equation 1, 6 coefficients
a1, a2, a3, a4, Tmin, Tmax
  a1  a 2T  a3T 2  a 4T 3
2 Maryott-Smith equation 2, 4 coefficients
a1, a2, Tmin, Tmax
  expa1  a 2T 
3 Infochem equation, 6 coefficients
a1, a2, a3, a4, Tmin, Tmax
  1  a1 exp a 2T  a3T 2  a 4T 3 

Pure component Unifac subgroup structure

The specification of Unifac subgroup structure is more complex as it
requires a sequence of subgroup identifiers followed by molecular
abundances. The abundances are normally integers, but Multiflash can
accept non-integer values. Multiflash allows up to 10 different
subgroups to be specified in any one component. Multiflash uses a set
of generic subgroups that are used to define subgroups structures for
all variants of Unifac; details are given in the section of the Unifac
model. If the user refers to a subgroup by a name that is not
recognised by Multiflash, it is taken to be a new user-defined
subgroup. Multiflash allows up to 10 user-defined subgroups to be
defined at any one time.

Example
COMPONENTS “1,3-butanediol” data unifac CH3 1 CH2 2
CH 1 OH 1 s-OH 1;;

Defining polymers using segments

It is useful to define polymers for the PC-SAFT model, especially
copolymers, from polymer segments. So initially a number of
segments are defined, for example for monomeric groups of the
polyethylene and polypropylene polymers:
SEGMENTS SegPE data saftsigma 4.0217e-10 saftek 252.0
mw 38.023; SegPP data saftsigma 4.1000e-10 saftek
217.0 mw 43.384;
Each segment must be given values for its SAFTSIGMA and SAFTEK
parameters as well as its molecular weight. A copolymer of
polyethylene and polypropylene can now be defined using the
SAFTBOND property and the molecular weight.
COMPONENTS PEP47 data saftbond SegPE 0.125 SegPP
0.875 0 mw 236000 tcrit 10000 pcrit 10000
acentricfactor 2.5;
The SAFT bond fractions are the lower left triangle of a matrix
defining the bond fractions in the polymer chain between the named
segments. The critical temperature, critical pressure and acentric
factor are only used to provide starting estimates for phase
equilibrium calculations, and have no impact on the converged results
given by the PC-SAFT model. Note that in the fluid composition, the

27
 amounts of the segments must all be set to zero, as the segments are
not real components of the mixture.
For a discussion of the copolymer method, see Modeling of polymer
phase equilibria using Perturbed-Chain SAFT by Tumakaka, Gross and
Sadowski in Fluid Phase Equilibria, 194-197, 541, (2002). The
definition of the bond fractions is given by Tumakaka, Gross and
Sadowski, (although their examples of actual values of bond fractions
are not realistic).

Minimum data requirements

The minimum data required to perform any phase equilibrium
calculation with Multiflash using the basic equations of state is the
critical temperature, critical pressure and acentric factor for each
component. The data requirements are model dependent and models
other than the equations of state require additional data. Isenthalpic
and isentropic calculations also require coefficients for the ideal-gas
Cp values for each component. To work in mass units rather than in
molar units the molecular weight is required.
Chemical equilibrium calculations using the basic equations of state
require the critical temperature, critical pressure, acentric factor, Cp
values, enthalpy of formation, standard entropy and chemical formula
for each component. Again, other models require additional data.

Petroleum fractions
Petroleum fractions or pseudo components are commonly used in
modelling oil and gas processing operations. A petroleum fraction
may be used to represent the aggregate properties of complex
mixtures that are split into fractions of roughly constant boiling point
by gas chromatography or standard tests such as ASTM distillation.

Characterisation methods
The CHARDATA command sets the characterisation methods that will
be used when defining petroleum fractions (PETROFRAC and
PVTANALYSIS commands). In this context the characterisation method
refers to the set of correlations that are used to estimate the
properties of a petroleum fraction based on the information supplied,
e.g. molecular weight and specific gravity. The correlations are used
to estimate all the properties that are normally required for equations
of state and basic transport property models. These properties
include: molecular weight, boiling point, critical temperature, critical
pressure, critical volume, parachor, dipole moment, solubility
parameter, enthalpy of formation, standard entropy, perfect gas Cp,
vapour pressure, enthalpy of vaporisation, saturated liquid density,
saturated liquid viscosity, saturated liquid Cp and saturated surface
tension. Any property values supplied in the PETROFRAC command
are used in preference to estimated values.
The CHARDATA command has the following format:
CHARDATA method_id TB_variant ;
The possible values for command parameters are defined in the
following table

28
parameter Value comments
method_id INFOCHAR The default set of correlations
recommended by Infochem.
TB/MW/SG are related by the Soereide
correlation (see below) and critical
properties are estimated by the Lee-
Kesler correlations: Kesler, M.G., and Lee,
B.I., Improve predictions of enthalpy of
fractions, Hydrocarbon Proc., 55(3), 153
(1976)
TB_variant TBSOEREIDE The default variant for infochar.
Specifies the Soereide correlation form
TB in terms of MW and SG. See: Brule,
M.R. and Whitson, C.H., SPE Phase
behaviour monograph, (1996).
Only valid for infochar.
TBAPI Specifies the API Technical Data Book
Procedure 2B2.2 procedure for MW in
terms of TB. and SG.
Only valid for infochar.

Defining petroleum fractions

To define a petroleum fraction the user must supply some basic
information using the PETROFRACS command. It has the following
format:
PETROFRACS entry_mode component_no component_name
petroleum_type DATA property_name1 value1
property_name2 value2 … ;;
entry_mode may be either insert, overwrite or amend. If omitted
the default mode is insert (see description of COMPONENTS
command).
component_no is an integer that determines where the petroleum
fraction is placed in the list of components used by Multiflash. It may
be omitted in which case it is taken to be the last component in the
current list.
component_name is a user-defined name for the petroleum fraction.
Petroleum_type is a keyword for marking whether the petroleum
fraction is normal fraction or asphaltene or resin or normal paraffin
or iso-paraffin. This keyword is optional and may be omitted. If it is
omitted, the default setting is normal fraction. It becomes important
when asphaltene association model is used. For the Coutinho wax
model, the normal paraffins are required in the calculations.
The DATA keyword sets the information on the physical properties of
the petroleum fraction. It must be followed by a series of
property_name keywords and the corresponding property values.
The most useful property keywords are listed below.

Keyword Detailed information

MOLECULARWEIGHT OR MW molecular weight (g/mol)
SPGRAVITY OR SG SG60/60, i.e. specific gravity at
60F relative to water at 60F
TBOIL Normal boiling point
TCRIT Critical temperature
PCRIT Critical pressure
ACENTRICFACTOR Pitzer acentric factor
VISCOSITY Viscosity at true boiling point

29
 It is not necessary to supply all of the properties listed. The more data
provided the better, but the minimum input sets are a carbon number
or any two of molecular weight, specific gravity and boiling point or
all three of: critical temperature, critical pressure and acentric factor.
The specific gravity, molecular weight and boiling point are usually
available for heavy fractions. The alternative of defining critical
properties and the acentric factor allows direct transfer of
pseudocomponents from a process simulator into Multiflash.
Although it is not usual, any of the constant or temperature-
dependent properties stored in the INFODATA databank could be
specified in the data list.
The units of the boiling point, critical temperature and critical
pressure are set by the UNITS or INPUTUNITS commands.
The command sequence must be terminated by two end markers. The
first ends the DATA keyword and the second ends the PETROFRACS
command.

Example
The following example defines a petroleum fraction called C7PLUS as
Multiflash component number 3.
PETROFRACS 3 C7PLUS
data mw 329 sg .881 tboil 648;;

PVT analysis
Experimental PVT analysis data can be directly used to specify an
input stream for Multiflash using the PVTANALYSIS command. The
PVT analysis typically consists of compositions for identifiable
discrete components and for single carbon number fractions (SCN) or
petroleum cuts. The compositions may be for a complete reservoir
fluid or may be separated into gas compositions and liquid
compositions. In the latter case it is necessary to supply a separator
gas-oil ratio (GOR) so that the streams may be recombined.
The available PVT characterisation method in Multiflash is called
Infoanal2. Any the information in a MFL file created by the original
method will be loaded properly, you should re-characterise the fluid
with the revised method.
The command format for the fluid with n-Paraffin distribution is in
the following order.
PVTANALYSIS
Infoanal2
mw type_id x_1
sg type_id x_1 APISG
components name_x_1 name_x_2 name_x_3...
C6, C7, ... & Plusfraction;
totamounts x_1 x_2 x_3 ...;
cutlbound x_1 x_2 x_3 ...;
cutlbunits cut_unit
cutmw x_1 x_2 x_3 ...;
cutsg x_1 x_2 x_3 ...;
D86

30
 stoamounts/nfractions x_1 x_2 x_3 ...;
gasamounts x_1 x_2 x_3 ...;
units amountunit (fluid/liquid)
npunits amountunit (n-paraffins)
gasunits amountunit
nplus n
npnplus n
startsplit n or name (e.g. C6 )
npstartsplit n or name (e.g. N6 )
pluslbound x_1 x_2 x_3 ...;
nppluslbound x_1 x_2 x_3 ...;
sara wpsat wparo wpres wpasp
estimatesara
gorvalue x_1
gorunits gor_unit
wax x_1
estimatewax
watercut x_1
includewater
total x_1;

Infoanal2 is the keyword for specifying the revised PVT

characterisation method. This keyword is optional.
mw - allowed values of type_id are: fluid, sto or fraction. This
should be followed by the appropriate value x_1 of the molecular
weight in g/mol.
Type_ID Value of MW ( x_1 )
fluid the value for the whole fluid
sto the value of total stock tank oil
fraction the value for the heaviest cut

The mw keyword is optional. If not entered the value is estimated from

the specific gravity or from the hydrocarbon distribution.
sg - allowed values of type_id are: fluid , sto or fraction. This
should be followed by the appropriate value x_1 of the specific
gravity (SG).
Type_ID Value of SG ( x_1 )
fluid the value for the whole fluid
sto the value of total stock tank oil
fraction the value for the heaviest cut

The sg keyword is optional. If not entered the value is estimated from

the molecular weight or from the hydrocarbon distribution.
If the value of SG is to be specified in API degrees, the keyword APISG
should be added.

31
components - followed by the discrete component names name_x_1,
name_x_2, name_x_3, etc, and the range of the petrofractions
ending with a ; terminator. The range of the petrofractions must be
specified to be the starting single carbon number of the
petrofractions (e.g. C6 ), followed by & and then the plusfraction ( the
last petrofraction ). The discrete components which can be handled by
PVT analysis are listed below. If you have some components which are
not listed here, you can always add them to your final component list
from a databank after PVT analysis is done. Please note that the
keyword components must be used before any of the amounts
keywords given below.

1 Nitrogen 11 n-pentane
2 Hydrogen sulphide 12 Methylcyclopentane
3 carbon dioxide 13 Benzene
4 Methane 14 Cyclohexane
5 Ethane 15 Methylcyclohexane
6 Propane 16 Toluene
7 Isobutane 17 Ethylbenzene
8 n-butane 18 m-xylene
9 Isopentane 19 o-xylene
10 Neopentane 20 p-xylene

Amounts/totamounts - followed by the amounts x_1, x_2, x_3

etc. of the discrete components and the amounts of all the cuts in the
total fluid or the separator liquid stream, ending with the amount of
the plusfraction and a ; terminator.
cutlbound – followed by the amounts x_1, x_2, x_3 etc. of the
user-defined lower carbon-number boundaries for the petroleum cuts.
This keyword is only available with Infochem revised characterisation
method. This keyword is optional.
cutlbunit – units used to define the carbon-number boundaries after
keyword cutlbound. The boundaries can be defined as a true boiling
point equivalent to the carbon number, hence the permitted units are
either keyword cnumber or a temperature unit. This keyword is only
available with Infochem revised characterisation method. This
keyword is only required if keyword cutlbound is used.
cutmw – followed by the amounts x_1, x_2, x_3 etc. of the user-
defined molecular weights for the petroleum cuts. This keyword is
only available with Infochem revised characterisation method. This
keyword is optional.
cutsg – followed by the amounts x_1, x_2, x_3 etc. of the user-
defined specific gravities for the petroleum cuts. This keyword is only
available with Infochem revised characterisation method. This
keyword is optional.
D86 – indicates that the characterisation has been measured by the
ASTM D86 method. This keyword is optional.
stoamounts - followed by the amounts x_1, x_2, x_3 etc. of the
mass or mole percent of all the n-paraffin in STO and a ; terminator.
Please note that all the amounts for discrete components have to go
to the total fluid/liquid stream.
nfractions - followed by the fractions x_1, x_2, x_3 etc. of all
the n-paraffin in each cut and a ; terminator. Please note that all the
amounts for discrete components have to go to the total fluid/liquid
stream.
Only one of the keywords namounts and nfractions is allowed to
be used to specify the information of the n-paraffins.

32
gasamounts - followed by the amounts x_1, x_2, x_3 etc. of the
discrete components and the amounts of all the cuts in the gas
stream ending with a ; terminator. The number of amount values
must not exceed the number of the disrcete and the liquid cuts
specified. This keyword is optional.
If a discrete component is present without knowing its value, its value
should be entered as a star * to denote undefined in these cases
amounts, totamounts, namounts, nfractions and gasamounts.
n-Paraffin distribution always starts from N6. If some of the n-
Paraffins are not known, their values should be entered as a star * to
denote undefined.
units - specifies the type of input units for the liquid discrete
components, petroleum cuts and total amounts. This keyword can
only be used after the keywords amounts/totamounts,
namounts/nfractions and gasamounts. Allowed values for
amountunit are: mol or mole (default), kmol, kg, g, lbmol, lb. This
keyword is optional.
npunits - specifies the amount units in which the amount values are
given by namounts or nfractions. Allowed values for amountunit
are: mole or g. If this keyword is missing, it takes the default value
from units. This keyword is optional.
gasunits - specifies the amount units in which the amount values
are given by gasamounts. Allowed values for amountunit are: mol or
mole (default), kmol, kg, g, lbmol, lb. This keyword is optional.
nplus - the integer number of pseudocomponents that the
plusfraction will be split into. The default value is 1. The nplus value
generated by the PVTANALYSIS command will be greater than the
input value if asphaltenes and resins are present and specified by
SARA. This keyword is optional.
npnplus - the integer number of normal paraffin pseudocomponents
that will be created. This value is required for characterising the
normal paraffin distribution which is associated with the coutinho
wax model; the default value is 15 if the keyword is omitted.
startsplit - the cut sequence number or name (e.g. C20 etc.) at
which the split is to start which can only be in the range 1 to (number
of cuts + 1); the default is the latter value if this keyword is omitted.
If the number of normal and non-normal cuts are different, then the
smaller value will be used to calculate the default value of startsplit.
This keyword is optional.
npstartsplit - the normal paraffin cut sequence number or name
(e.g. N20 etc.) at which the normal paraffin split is to start; the default
is the value used for N6 if this keyword is omitted.
pluslbound – followed by the amounts x_1, x_2, x_3 etc. of the
user-defined lower carbon-number boundaries for the
pseudocomponents. This keyword is optional.
nppluslbound – followed by the amounts x_1, x_2, x_3 etc. of the
user-defined lower carbon-number boundaries for the normal paraffin
pseudocomponents. This keyword is optional.
sara - indicates the presence of a saturates/aromatics/resins/
asphaltenes (SARA) analysis and must be followed by four values: the
wt% of saturates, the wt% of aromatics, the wt% of resins and the wt%
of asphaltenes. If the values are unknown, the symbol * should be
specified. This keyword is optional.
estimatesara – indicates that the SARA analysis will be estimated by
Multiflash. This keyword is optional.

33
gorvalue - specifies the gas-oil ratio x_1 at standard conditions (1
bar and 15ºC) as a pure volume ratio. The value must be in the units
set by the gorunits keyword. The value is used to recombine the gas
stream amounts with the liquid amounts in the correct proportion to
obtain the composition of the recombined fluid. This keyword is
optional.
gorunits - specifies the units in which the gorvalue is given..
Allowed values for gor_unit are: m3/m3 (default), or scf/stb .
The unit conversion factor from scf/stb to m3/m3 is 0.1801175. This
keyword is optional.
Wax – specifies the wax content (UOP) value which is used by
Multiflash to estimate the normal paraffin distribution in association
with the Coutinho wax model. This keyword is optional.
estimatewax – indicates that the wax content will be estimated by
Multiflash. This keyword is optional.
watercut - specifies the water cut x_1 as the volume fraction of the
total liquid. It is used to calculate how much water to add to the
hydrocarbon fluid. This keyword is optional.
includewater – indicates that water is to be included as one of the
components present in the fluid mixture. This keyword is optional. If
the watercut keyword is used, water must be present whether or not
includewater is used.
total - specifies the total amount x_1 of hydrocarbon fluid the user
wants to have present in current input units. This keyword is
optional.
Note that the minimal specification requires only the keyword
components and amounts and one or more values. The keywords
units, gasunits, startsplit, nplus, gorunits, gorvalue,
watercut and total may only be used after the keywords
amounts, namounts and gasamounts.

Example
The following example creates a complete input stream from the
experimental PVT analysis data which includes well defined
components (N2, H2S, CO2, methane ethane, propane, isobutane,
butane, isopentane, neopentane, n-pentane), a group of cuts and the
heavy end cut with a molecular weight of 515 and a specific gravity of
0.935. The cuts and heavy end will be split into 15
pseudocomponents starting at C6. A SARA analysis is provided so
resin and asphaltene components will also be generated.
PVTanalysis infoanal2
mw fraction 515.0
sg fraction 0.935
components N2 H2S CO2 methane ethane propane
isobutane butane isopentane neopentane n-pentane C6 &
C30;
amounts 0.02 0.03 0.5 8.37 3.97 3.73 0.68 2.5 1.11 * 1.80
3.0 3.45 4.02 4.19 4.32 3.83 3.45 3.37 3.18 2.95 2.65 2.72
2.44 2.02 2.22 2.04 1.85 1.69 1.56 1.46 1.43 1.32 1.29 1.24
15.60;
units g
nplus 15
startsplit C6
sara 64 23 12.2 0.8;

34
Black oil analysis
Experimental black oil analysis data can be directly used to specify an
input stream for Multiflash using the BLACKOIL command. The
minimum input for the Blackoil analysis consists of Specific gravity of
stock tank oil and residual GOR ( Rs ). The oil properties such as Gas
Gravity, Watson characterisation K factor and the Gas analysis are
optional in the input but they are quite useful information to make
the calculated bubblepoint or dewpoint more accurate.
The command format is in the following order.
BLACKOIL
gasanalysis x_1, x_2, x_3, x_4, x_5, x_6, x_7,
x_8 ;
gorvalue x_1
gorunits gor_unit
gasgravity x_1
sg x_1
nplus n
npnplus n
startsplit n or name (e.g. C6 )
npstartsplit n or name (e.g. N6 )
pluslbound x_1 x_2 x_3 ...;
nppluslbound x_1 x_2 x_3 ...;
sara wpsat wparo wpres wpasp
estimatesara
wax x_1
estimatewax
watercut x_1
total x_1;
gasanalysis – is followed by eight values for the fixed eight
discrete components. The eight discrete components are Nitrogen,
H2S, CO2, methane, ethane, propane, I-butane, n-butane. The
information about the gas analysis is optional but it is useful to make
the calculated bubblepoint or dewpoint more accurate.
gorvalue - specifies the gas-oil ratio x_1 at standard conditions (1
bar and 15ºC) as a pure volume ratio. The value must be in the units
set by the gorunits keyword. This keyword is required in the input
in order to make the blackoil analysis method work correctly.
gorunits - specifies the units in which the gorvalue is given..
Allowed values for gor_unit are: m3/m3 (default), or scf/stb .
The unit conversion factor from scf/stb to m3/m3 is 0.1801175. This
keyword is required in the blackoil input.
sg – specifies the specific gravity of the stock tank oil at standard
condition. This keyword is required in the input of the blackoil
analysis.
nplus - the integer number of pseudocomponents that the
plusfraction will be split into. The default value is 1. The nplus value
generated by the BLACKOIL command will be greater than the input

35
 value if asphaltenes and resins are present and specified by SARA.
This keyword is optional.
npnplus - the integer number of normal paraffin pseudocomponents
that will be created. This value is required for characterising the
normal paraffin distribution which is associated with the coutinho
wax model; the default value is 15 if the keyword is omitted. This
keyword only works with the Blackoil analysis method or the
Infochem resvied characterisation method ( Infoanal2 ).
startsplit - the cut sequence number or name (e.g. C20 etc.) at
which the split is to start which can only be in the range 1 to (number
of cuts + 1); the default is the latter value if this keyword is omitted.
If the number of normal and non-normal cuts are different, then the
smaller value will be used to calculate the default value of startsplit.
This keyword is optional.
npstartsplit - the normal paraffin cut sequence number or name
(e.g. N20 etc.) at which the normal paraffin split is to start; the default
is the value used for N6 if this keyword is omitted.
pluslbound – followed by the amounts x_1, x_2, x_3 etc. of the
user-defined lower carbon-number boundaries for the
pseudocomponents. This keyword is optional.
nppluslbound – followed by the amounts x_1, x_2, x_3 etc. of the
user-defined lower carbon-number boundaries for the normal paraffin
pseudocomponents. This keyword is optional.
sara - indicates the presence of a saturates/aromatics/resins/
asphaltenes (SARA) analysis and must be followed by four values: the
wt% of saturates, the wt% of aromatics, the wt% of resins and the wt%
of asphaltenes. This keyword is optional.
EstimateSARA – indicates that the SARA will be estimated by
Multiflash. This keyword is optional.
Wax – specifies the wax content (UOP) value which is used by
Multiflash to estimate the normal paraffin distribution in association
with the coutinho wax model. This keyword is optional.
Estimatewax – indicates that the wax content will be estimated by
Multiflash. This keyword is optional.
watercut - specifies the water cut x_1 as the volume fraction of the
total liquid. It is used to calculate how much water to add to the
hydrocarbon fluid. This keyword is optional.
total - specifies the total amount x_1 of hydrocarbon fluid the user
wants to have present in current input units. This keyword is
optional.

Inhibitor calculator
The inhibitor calculator can be used to add the content of inhibitors
(methanol, MEG, DEG, TEG and ethanol), the salt content of aqueous
streams to mixtures. This converts the measured compositions of the
inhibitors, salts in aqueous streams into an equivalent amount to that
of water in the mixture for hydrate inhibition calculations. The
command for adding Inhibitors is INHIBITOR. To use the INHIBITOR,
it is necessary to define water and inhibitors into the stream from any
databank first and then input amount of water in correct unit. The
command format for adding the four inhibitors at the same time is:
INHIBITOR BASIS inhibitor_name1 inhibitor_value1
inhibitor_name2 inhibitor_value2 ...;

36
 BASIS is used to specify fractions of inhibitors in either mass or mole
or volume fraction. The keywords are MASSFRACTION,
MOLEFRACTION and VOLUMEFRACTION respectively.
The inhibitor_name means the name of the inhibitors which
includes methanol, MEG, DEG, TEG and ethanol and
inhibitor_value is the fractions of the inhibitors. Note that the
total of the fractions entered must be less than 1.

Salinity
The ion ratio and salt content of aqueous streams can be entered
using the SALINITY command which converts the measured salt
compositions into an equivalent amount of a salt pseudocomponent
or ion ratios for freezing point depression or hydrate inhibition
calculations. The properties have been tuned for use only with the
RKSA model with Infochem mixing rules (see p. 43).
To use the SALINITY command it is first necessary to include water
and saltcomponent (the salt pseudocomponent) or ions such as Na+
and Cl- in the components list. Water may be loaded from any
databank. Saltcomponent or Na+, K+, Ca++, Cl- and Br- ions are
defined in the INFODATA databank. There are three ways of entering
the salt compositions or ions which are described in the following
sections. In each case the amount of saltcomponent and ions
equivalent to the salt composition is estimated and added to the
input amounts.

Ion analysis
The concentrations of the following ions may be entered: Na+, Ca++ ,
Mg++ , K+ , Sr++ , Ba++ , Fe++ , Cl– , SO4–– , HCO3– and Br–.
The command format is:
SALINITY model_selector ionconcentrations
Na x Ca x Mg x K x Sr x Ba x Fe x
Cl x SO4 x HCO3 x Br x
spgravity sg;
The keyword model_selector is given as follows. If the
model_selector is omitted, the default setting is saltcomp.
model_selector Comments
saltcomp For calculating the amount of a salt
pseudocomponent proportional to the
amount of water in the component list.
electrolyte For calculating ion ratios of salt
compositions proportional to the amount of
water in the component list.
elecNaCl For calculating ion ratios of salt
compositions proportional to the amount of
water in the component list. For this option
to components introduced are restricted to
Na+ and Cl- ions which are added on a
sodium chloride equivalent basis.

The ionconcentrations keyword sets the input mode for entering

the salinity as ion concentrations in mg/l. There is no choice of units.
The concentration of each ion follows the ion name (in any order).
Only those ions with non-zero concentrations need to be listed.

37
If the specific gravity of the solution is known it may be entered using
the spgravity keyword. If omitted it is estimated.

Total dissolved solids

The command format is:
SALINITY model_selector tds x spgravity sg;
The model_selector selections are the same as described above. If
model_selector is omitted, the default setting is saltcomp.
The tds keyword sets the input mode for entering the salinity as total
dissolved solids in mg/l. There is no choice of units.
If the specific gravity of the solution is known it may be entered using
the spgravity keyword. If omitted it is estimated.

Salt analysis
The concentrations of the following salts may be entered: NaCl, NaBr,
CaCl2, MgCl2 , KCl , SrCl2 , BaCl2 , FeCl2 , Na2SO4 and NaHCO3

The command format is:

SALINITY model_selector analysis_type
NaCl x NaBr x CaCl2 x MgCl2 x KCl x SrCl2 x
BaCl2 x FeCl2 x Na2SO4 x NaHCO3 x ;
The model_selector selections are the same as described above. If
the model_selector is omitted, the default setting is saltcomp.
The analysis_type keyword sets the input mode for entering the
salinity as a salt analysis. There are three options for the units:
saltmassfractions, saltmolalities and saltmolefractions.
The concentration of each salt in the units selected follows the salt
name (in any order). Only those salts with non-zero concentrations
need to be listed.

Example
The following example enters the amount of saltcomponent
equivalent to a 13% by mass solution of NaCl.
PUREDATA Infodata;
units amounts g;
COMPONENTS water saltcomponent;
Amounts water 1.0;
SALINITY saltcomp saltmassfractions NaCl 0.13;

38
Model definition

Introduction
The thermodynamic and transport property models in Multiflash and
their applicability are described in more detail in the Models and
Physical Properties Manual.
The MODEL command is used to define a model. It has the format:
MODEL model_id MF_model_name [Model_options]... ;
model_id is a user-defined name that will be used to refer to the
particular combination of the property model and options specified.
MF_model_name is the Multiflash name for the basic model. The list
of recognised models is given below together with the applicable
options.
Model_options are additional keywords that describe model
variants, references to other, previously-defined, models or references
to the source of binary interaction parameters.
For example,
MODEL MPR PR PRBIP;
defines the identifier MPR for the Peng-Robinson equation of state
with the set of BIPs called PRBIP.

Equation of state models

Ideal gas equation of state

NRT
p
V
part of model Multiflash
definition keyword Comments
Model name IDG

The following example defines the ideal gas eos model and gives it
the identifier MIDG
model MIDG idg;

39
 Benedict-Webb-Rubin-(Starling) equation of state
RT  B C D C'  2   2 
p N   2  5  2 1  2  exp  2  
V  V V V V 
  V   V 
Reference: Starling, Fluid thermodynamic properties for light
petroleum systems, Gulf Publishing Co., Houston (1973).

part of model Multiflash

definition keyword Comments
Model name BWRS
model variant * or BWRS BWRS equation
SH BWRS equation using parameters from
Starling and Han correlations
BWR BWR equation with parameters from
Orye and others
BIP data Bip_set optional, Bip_set is the name for a
set of BIPs defined by the BIPSET
command.

The following example defines the BWRS eos model and BIP taken
from a (previously defined) bipset called BWRSBIP and gives it the
identifier MBWRS
model MBWRS bwrs bwrs BWRSBIP;

Hayden-O’Connell gas phase model

This treats each component in the gas phase as forming a monomer-
dimer equilibrium. For most components that deviate only slightly
from ideal behaviour, the model reduces to the volume-explicit virial
equation:

RT
V  B
p
The second virial coefficient B is estimated for each component from
a generalised correlation (J.G. Hayden and J.P. O’Connell, Ind. Eng.
Chem.. Proc. Des. Dev, 14, 209 (1975)). This correlation accounts for
non-polar, polar and chemical association effects. The pure
component properties required by the model are: critical temperature,
critical pressure, radius of gyration, dipole moment and an empirical
association parameter. Values for these quantities are stored in the
Infodata databank.
A second virial coefficient model such as HOC can account for gas
phase non-idealities up to pressures of about 5 to 10 bar. The
implementation of the HOC model in Multiflash allows the vapour
phase association of substances such as acetic acid to be represented.

part of model Multiflash

definition keyword Comments
Model name HOCONNELL

The following example defines the Hayden-O’Connell model and gives

it the identifier MHOC
model MHOC hoconnell;

40
 Lee-Kesler-(Plöcker) equation of state
This is a 3-parameter corresponding states model based on
interpolating the reduced properties of a mixture between those of
two reference substances, one spherical and the other non-spherical.
The equation for each property is of the form

 (1)
z mix  z ( 0 ) 
 (1)z  z ( 0) 
The method is rather slow and complex compared with cubic eos but
can yield accurate predictions of density and enthalpy for non-polar
mixtures. It is not particularly recommended for phase equilibrium
calculations. The model definition is

part of model Multiflash

definition keyword Comments
Model name LKP
model variant * or LKP Lee-Kesler Plöcker mixing rule
LK original Lee-Kesler mixing rule
BIP data Bip_set optional, Bip_set is the name for a
set of BIPs defined by the BIPSET
command. The model can accept one
temperature-independent BIP (per pair
of components)

The following example defines the LKP eos model and gives it the
identifier MLKP
model MLKP lkp;

Peng-Robinson equation of state

NRT a
p  2
V  b V  2bV  b 2

part of model Multiflash

definition keyword Comments
Model name PR
BIP data Bip_set optional, Bip_set is the name for a
set of BIPs defined by the BIPSET
command

The following example defines the PR eos model and gives it the
identifier MPR
model MPR pr;

Advanced Peng-Robinson equation of state

The enhanced Infochem version of the PR eos offers a wide range of
options for various aspects of the eos

41
part of model Multiflash
definition keyword Comments
Model name PRA
method for * or PR standard PR method
calculating eos a PR78 PR78 method
parameter PSAT fit parameter to reproduce saturated
vapour pressure using correlation
from databank
PSAT78 as above but for PR78 method
MC use Mathias-Copeman parameters
method for * or PR standard PR method
calculating eos b LDEN fit parameter to reproduce saturated
parameter liquid density at 298K or Tr=0.7
(Peneloux method)
Mixing rules * or VDW standard VDW 1-fluid
GEX excess Gibbs energy MHV2
HV Huron-Vidal
NRTL Infochem modified NRTL
HVPSM Huron-Vidal-Pedersen (HVP)
Excess Gibbs energy Gex_model required for GEX and HV, must be the
model model identifier for an activity
coefficient model
BIP data Bip_set optional, Bip_set is the identifier for
a set of BIPs defined by the BIPSET
command

The following example first defines a liquid phase activity model

MNRTLVLE using the NRTL equation. It then defines an equation of
state model MPRA based on PR with the a parameter fitted to the
vapour pressure and the b parameter fitted to the liquid density. The
mixing rule is MHV2 which uses the excess Gibbs energy model
defined for MNRTLVLE, i.e. NRTL.
model MNRTLVLE nrtl vle;
model MPRA pra psat lden gex MNRTLVLE;
The following example defines the PR78 eos model and gives it the
identifier MPR78
model MPR78 pra pr78 lden vdw PR78BIP;
For the PRA78 model,
model MPRA78 pra psat78 lden vdw PR78BIP;
For the PR-HVP model.
model MPRHVP pra pr lden hvpsm PRHVPBIP3;

Redlich-Kwong-(Soave) equation of state

NRT a
p 
V  b V (V  b)

42
part of model Multiflash
definition keyword Comments
Model name RKS
method for * or RKS Soave modification of RK
calculating eos a API API modification of RKS
parameter RK original RK
BIP data Bip_set optional, Bip_set is the name for a
set of BIPs defined by the BIPSET
command

The following example defines the RKS eos model with the API
modification and BIP taken from a (previously defined) bipset called
RKSBIP and gives it the identifier MRKS
model MRKS rks api RKSBIP;

Advanced RKS equation of state

The enhanced Infochem version of the RKS eos offers a wide range of
options for various aspects of the eos

part of model Multiflash

definition keyword Comments
Model name RKSA
method for * or RKS Soave modification of RK
calculating eos a API API modification of RKS
parameter RK original RK eos
PSAT fit parameters to reproduce saturated
vapour pressure using correlation
from databank
MC use Mathias-Copeman parameters
method for * or RKS standard RKS method
calculating eos b LDEN fit parameter to reproduce saturated
parameter liquid density at 298K or Tr=0.7
(Peneloux method)
Mixing rules * or VDW standard VDW 1-fluid
GEX excess Gibbs energy MHV2
HV Huron-Vidal
NRTL Infochem modified NRTL
HVPSM Huron-Vidal-Pedersen (HVP)
Excess Gibbs energy Gex_model required for GEX and HV, must be the
model model identifier for an activity
coefficient model
BIP data Bip_set optional, Bip_set is the identifier for
a set of BIPs defined by the BIPSET
command

The following example sets up the version of the RKS eos

recommended for modelling the fluid phases in hydrate calculations.
model MRKSANRTL rksa psat lden nrtl;

PSRK equation of state

This model consists of the RKSA equation of state with vapour
pressures fitted using Mathias-Copeman parameters (if available), the
Peneloux volume correction and the PSRK type mixing rules. The
excess Gibbs energy is provided by the PSRK variant of the Unifac
method. This is the same as the normal VLE Unifac model except that
the group table has been extended to include a large number of
common light gases.

43
 The PSRK model is an extension of the Unifac method. It is intended
to predict the phase behaviour of a wide range of polar mixtures
using the solution of groups concept as embodied in Unifac. The main
benefit of PSRK is that it is able to handle mixtures containing gases
much better than Unifac and unlike a normal equation of state it can
handle polar liquids. This is because (a) it uses an equation of state
with an excess Gibbs energy mixing rules thereby avoiding problems
of how to handle supercritical components in an activity coefficient
equation; (b) the Unifac group parameter table has been extended in
PSRK to include 32 common light gases.

part of model Multiflash

definition keyword Comments
Model name UNIFAC
Model variant PSRK the PSRK type mixing rules, extension
of the Unifac method
Model name RKSA
method for PSAT fit parameters to reproduce saturated
calculating eos a vapour pressure using correlation
parameter from databank
method for LDEN fit parameter to reproduce saturated
calculating eos b liquid density at 298K or Tr=0.7
parameter (Peneloux method)
Mixing rules PSRK the PSRK type mixing rules, extension
of the Unifac method.
Excess Gibbs energy Gex_model must be the PSRK Unifac model
model identifier

The following example sets up the version of the PSRK eos

recommended for modelling the fluid phases.
model MUNIFACPSRK UNIFAC PSRK;
model MRKSAPSRK RKSA MC LDEN PSRK MUNIFACPSRK;
Consult the section on Unifac for details of how to use more options
for the definition of the Unifac groups and subgroups used, etc.

PSRK-NRTL equation of state

This model is the same as the PSRK model except that the excess
Gibbs energy is provided by the NRTL equation. So unlike the PSRK
equation, the PSRK-NRTL variant requires that BIPs are provided for
the NRTL equation in order to give accurate results. The model
definition is set out in the following table.

44
part of model Multiflash
definition keyword Comments
Model name NRTL
type of phase * or VLE Vapour-liquid equilibrium default for
behaviour alpha parameter
vapour phase model * Leave undefined as not required for
role as Gex model
BIP data Bip_set Optional, Bip_set is the name for a
set of BIPs defined by the BIPSET
command; requires 3 BIPs Aij , A ji
and  ij
Model name RKSA
method for PSAT fit parameters to reproduce saturated
calculating eos a vapour pressure using correlation
parameter from databank
method for LDEN fit parameter to reproduce saturated
calculating eos b liquid density at 298K or Tr=0.7
parameter (Peneloux method)
Mixing rules PSRK the PSRK type mixing rules, extension
of the Unifac method.
Excess Gibbs energy Gex_model must be the PSRK Unifac model
model identifier

Example
model MNRTL nrtl vle * NRTLBIP3;
model MRKSAPSRK RKSA MC LDEN PSRK MNRTL;

Cubic plus association (CPA) model

The CPA model consists of the Redlich-Kwong-Soave equation plus an
additional term based on Wertheim’s theory that represents the effect
of chemical association.
The CPA model also uses the Peneloux density correction to match
the liquid density calculated from the equation of state to that stored
in the chosen physical property data system at a reduced temperature
of 0.7 or at 298.15K, whichever temperature is the lower.
The CPA model may be used for hydrate calculations with methanol,
MEG and salt inhibition, as these are the only cases for which
parameters are currently provided. This will be extended in future
versions.
part of model Multiflash
definition keyword Comments
Model name ASSOC
method for PSAT fit parameters to reproduce saturated
calculating eos a vapour pressure using correlation
parameter from databank.
Bipdata bipset BIP values for association model –
physical term.
Bipdata bipset BIP values for association model –
association term.

The following example sets up the CPA association model. BIP values
are taken from the bipset ASSOCBIP and ASSOCBIP-2.

45
 bipset ASSOCBIP 1;
bipset ASSOCBIP-2 1;
model MASSOC ASSOC PSAT ASSOCBIP ASSOCBIP-2;

Zudkevitch Joffee model

The ZJ eos is based on the original version of Redlick-Kwong (RK)
eos.
For the original version of RK, the “a” and “b” parameters are
expressed explicitly in terms of the critical temperature and pressure
For the ZJ eos, the ai and bi parameters are defined by simultaneously
solving the equations of fugacity coefficients along the saturation line
and the RKS equation for both vapour and saturated liquid phase,
where the required saturation vapour pressure and saturated liquid
density are obtained from the correlation of the pure components.

part of model Multiflash

definition keyword Comments
Model name ZJ
Variant ZJ The ai and bi parameters are fitted to
match vapour and saturated liquid
density
Bipdata bipset BIP values for ZJ physical term.

PC-SAFT model
The PC-SAFT equation is a development of the SAFT model that has
been shown to give good results for a wide range of polar and non-
polar substances including polymers. Polymers are one of the most
important areas of application of PC-SAFT. The model appears to be
one of the most accurate and realistic equations of state currently
available for modelling polymer systems.
PC-SAFT stands for the Perturbed Chain Statistical Associating Fluid
Theory and it incorporates current ideas of how to model accurately
the detailed thermodynamics of fluids within the framework an
equation of state. The mathematical structure is very complex and
cannot be conveniently described in a manual. Users are referred to
Appendix A of the reference given in the Models and Physical
Properties Manual.
It is a development of the SAFT model that has been shown to give
good results for a wide range of polar and non-polar substances
including polymers. The model appears to be one of the most
accurate and realistic equations of state currently available for
modelling polymer systems.
Two version of PC-SAFT models are available in the latest version of
Multiflash.

46
part of model Multiflash
definition keyword Comments
Model name SAFT
Model variant PC The model variant identifier for the
original PC-SAFT model.
Model variant ORIGINAL The second model variant for PC-SAFT
model
Bipdata bipset BIP values for PC-SAFT model –
attraction term
Bipdata bipset BIP values for PC-SAFT model –
association term

The following example sets up the original PC-SAFT model. BIP values
are taken from the bipsets SAFTBIP and SAFTBIP-2.
bipset SAFTBIP 1 constant eos none ;
bipset SAFTBIP-2 1 constant association J/mol ;
model MPCSAFT SAFT PC ORIGINAL SAFTBIP SAFTBIP-2;
The simplified version of PC-SAFT is a simplified version of PC-SAFT
by the Danish Technical University ( which is located at Lyngby in
Denmark ).
part of model Multiflash
definition keyword Comments
Model name SAFT
Model variant LYNGBY The model variant identifier for the
simplified version of PC-SAFT model.
Model variant ORIGINAL The second model variant for the
simplified version of PC-SAFT model
Bipdata bipset BIP values for PC-SAFT model –
attraction term
Bipdata bipset BIP values for PC-SAFT model –
association term

The following example sets up the simplified version of PC-SAFT

model.
bipset SAFTBIP 1 constant eos none ;
bipset SAFTBIP-2 1 constant association J/mol ;
model MPCSAFTLB SAFT LYNGBY ORIGINAL SAFTBIP SAFTBIP-
2;

Multi-reference fluid corresponding states

(CSMA) model
The CSMA model is based on a collection of very accurate equations
of state for a number of reference fluids. It will provide accurate
values of properties for any of the reference fluids (see below for a
list) and it uses a 1-fluid corresponding states approach to estimate
mixture properties. It is formulated so that mixture properties will
reduce to the (accurate) pure component values as the mixture
composition approaches each of the pure component limits. In
Multiflash 4.0, the GERG-2004 mixing rule is also available.
The model definition can be considered in two distinct parts: the
definition of pseudo-critical properties for a mixture (mixing rules),
and the prescription for combining the properties of the reference
substances to give the total mixture properties (combining rules).
The current model implementation includes reference equations of
state for the following substances: ammonia, argon, n-butane, iso-

47
 butane, 1-butene, cis-2-butene, trans-2-butene, cyclohexane, CO, CO2,
COS, ethane, ethanol, ethylene, fluorine, helium, heptane, hexane, iso-
hexane, hydrogen, H2S, krypton, methane, neon, nitrogen, NF3, octane,
oxygen, n-pentane, iso-pentane, neo-pentane, propane, propylene, SF6,
SO2, toluene, water (IAPSW 95), xenon, R11, R113, R114, R115, R116,
R12, R123, R124, R125, R13, R134a, R14, R143a, R152a, R22, R227fa,
R23, R245fa, R32 and RC318. The equations of state are taken from
various sources and do not all have the same quality or range of
applicability. Other hydrocarbons and petroleum fractions are
included using a generalised equation of state.

part of model Multiflash

definition keyword Comments
Model name CSMA
Mixing rules VDW or GERG standard VDW 1-fluid or the GERG-
2008 mixing rule.
BIP data bipset BIP values for the mixing rules for the
critical temperature
BIP data bipset BIP values for the mixing rules for the
critical molar volume. Default value is
set to 1.
BIP data bipset With the GERG-2008 mixing rule, the
binary weighting factor for the
departure function contribution in the
mixture is required that is defined in
the INFOBIPS databank.

The following example sets up the advanced version of CSM model

with VDW mixing rule and the definition of the fluid phases.
model MCSMA CSMA VDW CSMABIP;
bipset CSMABIP 1 constant eos none ;
bipset CSMABIP-2 1 constant eosv none ;
bipdata INFOBIPS ;
model MCSMA CSMA VDW CSMABIP CSMABIP-2;
pd GAS gas MCSMA;
pd LIQUID1 liquid MCSMA;
With the GERG-2004 mixing rule, the example sets up the advanced
version of CSM model and the definition of the fluid phases are:
bipset CSMABIP 1 quadratic gergt none ;
bipset CSMABIP-2 1 quadratic gergv none ;
bipset CSMABIP-3 1 constant gergf none ;
bipdata INFOBIPS ;
model MCSMA CSMA GERG CSMABIP CSMABIP-2 CSMABIP-3;
pd GAS gas MCSMA;
pd LIQUID1 liquid MCSMA;

In Multiflash 4.1, the CSMA model also includes the GERG-2008

natural gas model. This is an industry-standard high-accuracy model
for mixtures of natural gas components: methane, nitrogen, C02,
ethane, propane, n-butane, iso-butane, n-pentane, iso-pentane, hexane,
heptane, octane, nonane, decane, argon, oxygen, hydrogen, hydrogen
sulphide, CO, water, helium. The model includes appropriate BIPs for
all components in the list.
The model is fully described in the publications:
• O. Kunz, R. Klimeck, W. Wagner, M. Jaeschke, The GERG-2004
wide-range equation of state for natural gases and other
mixtures, GERG Technical Monograph 15 (2007)

48
 • Kunz, O., Wagner, W. The GERG-2008 wide-range equation of
state for natural gases and other mixtures: An expansion of
GERG-2004. To be submitted to J. Chem. Eng. Data (2011)
The model is very accurate for pure substances that are included in
the above list of reference substances. It is also applicable to near-
ideal mixtures such as air but for the best results it is necessary to fit
values of the binary interaction parameters to match experimental
data. For the natural gas mixtures or non-ideal mixtures such as
water + CO2, the GERG-2008 model should be used.

part of model Multiflash

definition keyword Comments
Model name GERG
Mixing rules GERG GERG-2004 model for natural gas
mixtures.
BIP data bipset BIP values for the mixing rules for the
critical temperature
BIP data bipset BIP values for the mixing rules for the
critical molar volume. Default value is
1.
BIP data bipset The binary weighting factor for the
departure function contribution in the
mixture.

The following example sets up the GERG-2008 model with BIPs and
the definition of the fluid phases.
bipset GERGBIP 1 quadratic gergt none ;
bipset GERGBIP-2 1 quadratic gergv none ;
bipset GERGBIP-3 1 constant gergf none ;
bipdata INFOBIPS ;
model MGERG GERG GERG GERGBIP GERGBIP-2 GERGBIP-3;
pd GAS gas MGERG;
pd LIQUID1 liquid MGERG;

Steam Tables (IAPWS-95)

The international standard formulation for the properties of water is
made up from the following components. The thermodynamic
properties are obtained from the IAPWS95 formulation. The viscosity,
thermal conductivity and surface tension are based on the latest
IAPWS release. The references can be found in the Models and Physical
Properties Manual.

part of model Multiflash

definition keyword Comments
Model name IAPWS95

The following example sets up the model.

model MSTEAM IAPWS95;

CO2 high-accuracy model

This is a model for pure carbon dioxide using the most accurate
correlations currently available. The model is based on the high
accuracy equation of state published by Span and Wagner (1996). The
viscosity is described by the correlation of Fenghour et al (1998) and
the thermal conductivity uses the correlation of Scalabrin et al. (2006).

49
 The references can be found in the Models and Physical Properties
Manual.

part of model Multiflash

definition keyword Comments
Model name HACO2

The following example sets up the model.

model MCO2 HACO2;
pd GAS gas MCO2;
pd LIQUID1 liquid MCO2;

Water/Amonia high-accuracy model

The high accuracy corresponding state model for water-ammonia
binary system is based on the work developed by Beiner Tillner-Roth
and Daniel G . Friend. The references can be found in the Models and
Physical Properties Manual.

part of model Multiflash

definition keyword Comments
Model name WAMM
Model variant WAMM Only variant available
Bipdata Bipset
Bipdata Bipset
Bipdata Bipset

The following example sets up the model.

bipset WAMMBIP 1 quadratic gergt none ;
bipset WAMMBIP-2 1 quadratic gergv none ;
bipset WAMMBIP-3 1 constant gergf none ;
bipdata INFOBIPS ;
model MWAMM WAMM WAMM WAMMBIP WAMMBIP-2 WAMMBIP-3;pd
GAS gas MWAMM;
pd LIQUID1 liquid MWAMM;
keys LIQUID1 *;
pd WATER liquid MWAMM;
keys WATER AQUEOUS;

Activity models

Ideal solution liquid activity method

GE
0
RT

50
part of model Multiflash
definition keyword Comments
Model name IDL
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

The following example first defines the ideal gas eos model and then
sets up the ideal liquid model with the identifier MIDLMIDG
model MIDG idg;
model MIDLMIDG idl MIDG POYNTING;
Or if the Poynting correction is not required
model MIDG idg;
model MIDLMIDG idl MIDG NOPOYNTING;
The default is to include the Poynting correction in which case the
keyword can be omitted, which is done in subsequent examples of
activity models.
model MIDG idg;
model MIDLMIDG idl MIDG;

Regular solution method

Regular solution theory can be used for vapour-liquid calculations for
mixtures of non-polar or slightly polar components. The theory is
applicable to systems which exhibit negligible entropies and volumes
of mixing. However, it has been largely superseded by equations of
state
Flory-Huggins theory is able to describe systems which include some
long chain molecules. It has consequently applied to model polymer
systems but it has been largely superseded by other models such as
PC-SAFT.

part of model Multiflash

definition keyword Comments
Model name REGULAR
Model Variant REGULAR or The model variants identifier for
FH either the regular solution or Flory
Huggins regular solution model.
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

The following example first defines the ideal gas eos model and then
sets up the ideal liquid model with the identifier MREGULARMIDG

51
 bipset REGULARBIP 1 constant eos none ;
model MIDG idg;
model MREGULARMIDG REGULAR REGULAR MIDG REGULARBIP;
For the Flory Huggins regular solution model:
bipset REGULARBIP 1 constant activity J/mol ;
model MIDG IDG; model
MFHMIDG REGULAR FH MIDG REGULARBIP;

NRTL liquid activity method

This model may be used for vapour-liquid, liquid-liquid and vapour-
liquid-liquid equilibrium calculations. The VLE option should be used
for VLLE. It is necessary to supply BIP values to obtain accurate
predictions.

∑ n j A ji G ji
G = ∑ ni
E j

i ∑ n j G ji
j
α ij Aij
G ij =exp (− )
RT

part of model Multiflash

definition keyword comments
Model name NRTL
type of phase * or VLE Vapour-liquid equilibrium or liquid-
behaviour LLE liquid equilibrium; sets default for
alpha parameter
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
BIP data Bip_set Optional, Bip_set is the name for a
set of BIPs defined by the BIPSET
command; requires 3 BIPs Aij , A ji
and  ij
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

The following example first defines the rk eos model and then sets up
the vle version of the NRTL activity model with the identifier
MNRTLMRKS. BIP values can be taken from the databank INFOBIPS.BIN
for VLE or INFOLLBIPS.BIN for LLE by defining the BIP databank as
bipdata infobips;
Then set the BIP values using the command, for example
bipset NRTLBIP3 3 constant activity J/mol;
followed by model definitions.
model MRKS rks rk;
model MNRTLMRKS nrtl vle MRKS NRTLBIP3;

52
 UNIQUAC liquid activity method
This model may be used for vapour-liquid, liquid-liquid and vapour-
liquid-liquid equilibrium calculations. It is necessary to supply BIP
values to obtain accurate predictions.

 ri  j n j  z
   q n ln i  j j j    q n ln i  j ji j j 
GE q rn  q G q n 
  ni ln
RT   rj n j  2 i i i
 ri  q j n j  i i
  q jnj 
i  j   j  i  j 
 Aij 
Gij  exp   , z  10
 RT 
part of model Multiflash
definition keyword Comments
Model name UNIQUAC
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
BIP data Bip_set Optional, Bip_set is the name for a
set of BIPs defined by the BIPSET
command; requires 2 BIPs Aij and A ji
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

The following example first defines the RKS eos model and then sets
up the UNIQUAC activity model with the identifier MUNIQUACMRKS. BIP
values can be taken from the databank INFOBIPS.BIN for VLE or
INFOLLBIPS.BIN for LLE by defining the BIP databank as
bipdata infobips;
Then set the BIP values using the command, for example
bipset UNIQUACBIP2 2 constant activity J/mol;
followed by model definitions.
model MRKS rks rks;
model MUNIQUACMRKS uniquac MRKS UNIQUACBIP2;

Wilson activity method: A variant

This model may be used for vapour-liquid equilibrium calculations
but it is not capable of predicting liquid-liquid immiscibility. It is
necessary to supply BIP values to obtain accurate predictions.

GE   j Aij n j 
  ni ln  
 j j 
RT i
 n 

53
part of model Multiflash
definition keyword Comments
Model name WILSON
variant A The variant determines the way in
which BIPs are defined
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
BIP data Bip_set Optional, Bip_set is the name for a set
of BIPs defined by the BIPSET
command; requires 2 BIPs, Aij and Aji
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

The following example first defines the rk eos model and then sets up
the Wilson-A activity model with the identifier MWILSONAMRKS. BIP
values are taken from the (previously defined) bipset WILSONBIP2
model MRKS rks rk;
model MWILSONAMRKS Wilson A MRKS WILSONBIP2;

Wilson activity method: E variant

This model may be used for vapour-liquid equilibrium calculations
but it is not capable of prediction liquid-liquid immiscibility. It is
necessary to supply BIP values to obtain accurate predictions.

GE   j Gij n j 
  ni ln  
RT   nj 
i  j 
V j*  Aij 
Gij  exp  
Vi*
 RT 
part of model Multiflash
definition keyword Comments
Model name WILSON
variant * or E the variant determines the way in
which BIPs are defined
vapour phase V_model model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
BIP data Bip_set Optional, Bip_set is the name for a
set of BIPs defined by the BIPSET
command; requires 2 BIPs, Aij and
A ji , plus pure component saturated
*
liquid volume Vi
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

54
 The following example first defines the rk eos model and then sets up
the Wilson-E activity model with the identifier MWILSONEMRKS. BIP
values can be taken from the databank INFOBIPS.BIN by defining the
BIP databank as
bipdata infobips;
Then set the BIP values using the command, for example
bipset WILSONBIP2 2 constant activity J/mol;
followed by model definitions.

model MRKS rks rk;

model MWILSONEMRKS Wilson E MRKS WILSONBIP2;

UNIFAC liquid activity method

The UNIFAC method is similar to UNIQUAC but interaction
parameters are predicted based on the molecular group structure of
the components in a mixture. The model is completely predictive and
does not require any BIPs.

part of model Multiflash

definition keyword Comments
Model name UNIFAC
type of phase * or VLE Vapour-liquid equilibrium or liquid-
behaviour LLE liquid equilibrium; determines which
group interaction parameters are used
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

Using the more comprehensive UNIFACA keyword, the definitions are:

part of model Multiflash

definition keyword Comments
Model name UNIFACA
Model Variant ORIGINAL Three model variant identifiers for
*, VLE or selecting the form of the
LLE combinatorial term and the residual
term; the third variant keyword is
ORIGINAL currently not used
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

55
 The following example first defines the rk eos model and then sets up
the VLE version of the UNIFAC activity model with the identifier
MUNIFACVLEMRKS.
model MRKS rks rk;
model MUNIFACVLEMRKS UNIFAC VLE MRKS;
Or,
model MRKS rks rk;
model MUNIFACVLEMRKS UNIFACA ORIGINAL VLE ORIGINAL
MRKS;

UNIFAC for the PSRK equation

This version of Unifac has been extended to include a number of
common gases and is designed for use in the Gex mixing rules of the
PSRK equation of state. Although the user can define a vapour phase
model as for all versions of Unifac, it is unnecessary when the model
is used as part of the PSRK equation. In Multiflash, the PSRK model is
taken to include the correction for hydrocarbons defined in Prediction
of vapor-liquid equilibria for asymmetric systems at low and high
pressures with the PSRK model by Li, Fischer and Gmehling from Fluid
Phase Equilibria, 143, 71, (1998). Using the simpler UNIFAC keyword,
the definition follows.

part of model Multiflash

definition keyword Comments
Model name UNIFAC
Model Variant PSRK Selects the PSRK variant
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

With the UNIFACA keyword, the definition is:

part of model Multiflash

definition keyword Comments
Model name UNIFACA
Model Variant ORIGINAL Three model variant identifiers for
PSRK selecting the form of the
combinatorial term and the residual
ORIGINAL term; the third variant keyword is
currently not used
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state

With the UNIFACA keyword, it is also possible to specify the PSRK

model without the hydrocarbon correction of Li, Fischer and
Gmehling:

56
part of model Multiflash
definition keyword Comments
Model name UNIFACA
Model Variant ORIGINAL Three model variant identifiers for
PSRKNOHCC selecting the form of the
combinatorial term and the residual
ORIGINAL term; the third variant keyword is
currently not used
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

The following example defines PSRK Unifac without a gas phase

model.
model MUNIFACPSRK UNIFAC PSRK;
Or,
model MUNIFACPSRK UNIFACA ORIGINAL PSRK ORIGINAL;
Or without the hydrocarbon correction,
model MUNIFACPSRK UNIFACA ORIGINAL PSRKNOHCC
ORIGINAL;

Dortmund Modified UNIFAC method

The Dortmund modified UNIFAC is a variant of UNIFAC that is better
able to represent the simultaneous vapour-liquid equilibria, liquid-
liquid equilibria and excess enthalpies of polar mixtures. Like original
UNIFAC, however, it does not allow for the presence of light gases in
the mixture.

part of model Multiflash

definition keyword Comments
Model name UNIFACA
Model Variant DORTMUND Three model variant identifiers for
DORTMUND selecting the form of the
combinatorial term and the residual
ORIGINAL term; the third variant keyword is
currently not used
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties; not
needed if the model is only used as
the Gex_model in one of the advanced
equations of state
Poynting POYNTING or Optionally selects if Poynting
correction NOPOYNTING correction should be added to activity
coefficients (default) or not.

The following example first defines the ideal gas eos model and then
sets up the ideal liquid model with the identifier MUNIFACADMMIDG
model MIDG idg;
model MUNFACADMMIDG UNIFACA DORTMUND DORTMUND
ORIGINAL MIDG;

57
 UNIFAC groups and subgroups
In Multiflash, all variants of UNIFAC are handled using the same set of
generic groups and subgroups. The current complete list of groups
and subgroups which cover all the latest public-domain versions of
original UNIFAC, PSRK and Dortmund modified UNIFAC are shown in
the following table. The q and r values used in Multiflash are given for
original UNIFAC and PSRK UNIFAC in columns 3 and 4, while values
for Dortmund modified UNIFAC are given in columns 5 and 6. Entries
marked not applicable (n/a) denote subgroups that are not part of the
particular variant of UNIFAC. When two main group names are given,
the first is the main group assignment for original and PSRK UNIFAC
while the second is for Dortmund modified UNIFAC.

Subgroup Main r q r q
group Dortmund Dortmund
CH3 CH2 0.9011 0.848 0.6325 1.0608
CH2 0.6744 0.54 0.6325 0.7081
CH 0.4469 0.228 0.6325 0.3554
C 0.2195 0 0.6325 0
CH2=CH C=C 1.3454 1.176 1.2832 1.6016
CH=CH 1.1167 0.8670 1.2832 1.2489
CH=C 0.8886 0.676 1.2832 0.8962
CH2=C 1.1173 0.988 1.2832 1.2489
C=C 0.6605 0.485 1.2832 0.4582
H2C=CH2 1.3564 1.3098 n/a n/a
ACH ACH 0.5313 0.4 0.3763 0.4321
AC 0.3652 0.12 0.3763 0.2113
ACCH3 ACCH2
1.2663 0.968 0.91 0.949
ACCH2
1.0396 0.66 0.91 0.7962
ACCH
0.8121 0.348 0.91 0.3768
OH OH
1.0 1.2 1.2302 0.8927
s-OH
n/a n/a 1.063 0.8663
t-OH
n/a n/a 0.6895 0.8345
CH3OH CH3OH
1.4311 1.432 0.8585 0.9938
H2O H2O
0.92 1.4 1.7334 2.4561
ACOH ACOH
0.8952 0.68 1.08 0.975
CH3CO CH2CO
1.6724 1.488 1.7048 1.67
CH2CO
1.4457 1.18 1.7048 1.5542
CH3O CHO
0.998 0.948 0.7173 0.771
CH2COO CCOO
1.9031 1.728 1.27 1.6286
CH3COO
1.6764 1.42 1.27 1.4228
CH3O CH2O
1.145 1.088 1.1434 1.6022
CH2O
0.9183 0.78 1.1434 1.2495
CH-O
0.6908 0.468 1.1434 0.8968
FCH2O
0.9183 1.1 n/a n/a
CH3NH2 CNH2
1.5959 1.544 1.6607 1.6904
CH2NH2
1.3692 1.236 1.6607 1.3377
CHNH2
1.1417 0.924 1.6607 0.985
m-CNH2
n/a n/a 1.6607 0.985
CH3NH CNH
1.4337 1.244 1.368 1.4332
CH2NH
1.207 0.936 1.368 1.0805
CHNH
0.9795 0.624 1.368 0.7278

58
Subgroup Main r q r q
group Dortmund Dortmund
ACNH2 ACNH2
1.06 0.816 1.1849 0.8067
CH3CN CCN
1.8701 1.724 1.5575 1.5193
CH2CN
1.6434 1.416 1.5575 1.1666
COOH COOH
1.3013 1.224 0.8 0.9215
HCOOH COOH/
1.528 1.532 0.8 1.2742
m-COOH
CH2CL CCL
1.4654 1.264 0.9919 1.3654
CHCL
1.238 0.952 0.9919 1.0127
CCL
1.0106 0.724 0.9919 0.66
CH2CL2 CCL2
2.2564 1.988 1.8 2.5
CHCL2
2.0606 1.684 1.8 2.1473
CCL2
1.8016 1.448 1.8 1.7946
CHCL3 CCL3/
2.87 2.41 2.45 2.8912
m-CCL3
CCL3 CCL3
2.6401 2.184 2.65 2.3778
CCL4 CCL4
3.39 2.91 2.618 3.1836
ACCL ACCL
1.1562 0.844 0.5365 0.3177
CH3NO2 CH3NO2
2.0086 1.868 2.644 2.5
CH2NO2
1.7818 1.56 2.5 2.304
CHNO2
1.5544 1.248 2.887 2.241
ACNO2 ACNO2
1.4199 1.104 0.4656 0.3589
CS2 CS2
2.057 1.65 1.24 1.068
CH3N (C)3N
1.1865 0.94 1.0746 1.176
CH2N
0.9597 0.632 1.0746 0.824
HCOO HCOO
1.242 1.188 1.9 1.8
I I
1.264 0.992 1.076 0.9169
BR BR
0.9492 0.832 1.209 1.4
CH3SH CH3SH
1.877 1.676 1.289 1.762
CH2SH
1.651 1.368 1.535 1.316
CHSH
1.425 1.06 n/a n/a
CSH
1.199 0.752 n/a n/a
CH2CH2OH CCOH
1.8788 1.664 n/a n/a
CHOHCH3
1.878 1.66 n/a n/a
CHOHCH2
1.6513 1.352 n/a n/a
CH3CH2OH
2.1055 1.972 n/a n/a
CHCH2OH
1.6513 1.352 n/a n/a
FURFURAL FURFURAL
3.168 2.484 1.299 1.289
C5H5N PYRIDINE
2.9993 2.113 2.5 2.1477
C5H4N
2.8332 1.833 2.8882 2.2496
C5H3N
2.667 1.553 3.2211 2.5
AC2H2N
n/a n/a 1.4578 0.9022
AC2HN
n/a n/a 1.2393 0.633
AC2N
n/a n/a 1.0731 0.353
r1-AC2H2N
n/a n/a 1.4578 0.9022
r2-AC2H2N
n/a n/a 1.4578 0.9022
r1-AC2HN
n/a n/a 1.2393 0.633
(CH2OH)2 DOH
2.4088 2.248 2.088 2.4
CH***C C***C
1.292 1.088 0.9214 1.3
C***C

59
Subgroup Main r q r q
group Dortmund Dortmund
CH***CH
1.0613 0.784 1.303 1.132
0.791 0.72 n/a n/a
DMSO DMSO
2.8266 2.472 3.6 2.692
ACRY ACRY
2.3144 2.052 1.0 0.92
CL-(C=C) CLCC
0.791 0.724 0.5229 0.7391
ACF ACF
0.6948 0.524 0.8814 0.7269
DMF-1 DMF
3.0856 2.736 2.0 2.093
DMF-2
2.6322 2.12 2.381 1.522
CF3 CF2
1.4060 1.38 1.284 1.266
CF2
1.0105 0.92 1.284 1.098
CF
0.615 0.46 0.8215 0.5135
COO COO
1.38 1.2 1.6 0.9
SIH3 SIH2
1.6035 1.263 n/a n/a
SIH2
1.4443 1.006 n/a n/a
SIH
1.2853 0.749 n/a n/a
SI
1.047 0.4099 n/a n/a
SIH2O SIO
1.4838 1.062 n/a n/a
SIHO
1.303 0.764 n/a n/a
SIO
1.1044 0.465 n/a n/a
NMP NMP
3.981 3.2 n/a n/a
CCL3F CCLF
3.0356 2.644 n/a n/a
CCL2F
2.2287 1.916 n/a n/a
HCCL2F
2.406 2.116 n/a n/a
HCCLF
1.6493 1.416 n/a n/a
CCLF2
1.8174 1.648 n/a n/a
HCCLF2
1.967 1.828 n/a n/a
CCLF3
2.1721 2.1 n/a n/a
CCL2F2
2.6243 2.376 n/a n/a
CONH2 CON
1.4515 1.248 n/a n/a
CONHCH3
2.1905 1.796 1.5 1.08
CONHCH2
1.9637 1.488 1.5 1.08
CON(CH3)2 CON/
2.8589 2.428 2.4748 1.9643
CONCH3CH2 m-CON
2.6322 2.12 2.2739 1.5754
CON(CH2)2
2.4054 1.812 2.0767 1.1866
C2H5O2 OCCOH
2.1226 1.904 n/a n/a
C2H4O2
1.8952 1.592 n/a n/a
CH3S CH2S
1.613 1.368 n/a n/a
CH2S
1.3863 1.06 n/a n/a
CHS
1.1589 0.748 n/a n/a
MORPH MORPH
3.474 2.796 n/a n/a
C4H4S THIOPHEN
2.8569 2.14 n/a n/a
C4H3S
2.6908 1.86 n/a n/a
C4H2S
2.5247 1.58 n/a n/a
CO2† CO2
1.3 0.982 n/a n/a
CH4† CH4
1.1292 1.124 n/a n/a
N2† N2
0.856 0.93 n/a n/a
H2S† H2S
1.235 1.202 n/a n/a

60
Subgroup Main r q r q
group Dortmund Dortmund
H2† H2
0.416 0.571 n/a n/a
CO† CO
0.711 0.828 n/a n/a
NH3† NH3
0.851 0.778 n/a n/a
AR† AR
1.177 1.116 n/a n/a
O2† O2
0.733 0.849 n/a n/a
H2COCH2† EPOXY
1.5926 1.32 n/a n/a
H2COCH†
1.3652 1.008 n/a n/a
H2COC†
1.1378 0.78 n/a n/a
HCOCH† 1.1378 0.696 n/a n/a
HCOC† 0.9104 0.468 n/a n/a
COC† 0.6829 0.24 n/a n/a
HF† HF
1.016 1.216 n/a n/a
HI† HI
1.393 1.208 n/a n/a
COS† COS
1.6785 1.316 n/a n/a
SO2† SO2
1.343 1.164 n/a n/a
NO† NO
0.716 0.62 n/a n/a
N2O† N2O
0.98 0.888 n/a n/a
SF6† SF6
2.374 2.056 n/a n/a
HE† HE
0.885 0.985 n/a n/a
NE† NE
0.886 0.986 n/a n/a
KR† KR
1.12 1.12 n/a n/a
XE† XE
1.13 1.13 n/a n/a
HCL† HCL
1.056 1.256 n/a n/a
HBR† HBR
1.058 1.258 n/a n/a
F2† F2
0.75 0.88 n/a n/a
CL2† CL2
1.53 1.44 n/a n/a
BR2† BR2
1.9 1.66 n/a n/a
HCN† HCN
1.2 1.19 n/a n/a
NO2† NO2
1.0 1.1 n/a n/a
CF4† CF4
1.78 1.82 n/a n/a
O3† O3
1.1 1.27 n/a n/a
CLNO† CLNO
1.48 1.34 n/a n/a
C2H6 C2H6
n/a n/a n/a n/a
c-CH2 c-CH2
n/a n/a 0.7136 0.8635
c-CH
n/a n/a 0.3479 0.1071
c-C
n/a n/a 0.347 0
c-CH2OCH2 c-CH2O
c-CH2OC/2H n/a n/a 1.7023 1.8784
c-C/2HOC/2H n/a n/a 1.4046 1.4
n/a n/a 1.0413 1.0116
c-CONCH3 c-CONC
n/a n/a 3.981 3.2
c-CONCH2
n/a n/a 3.7543 2.892
c-CONCH
n/a n/a 3.5268 2.58
c-CONC
n/a n/a 3.2994 2.252

61
Subgroup Main r q r q
group Dortmund Dortmund
AC2H2S ACS
n/a n/a 1.7943 1.34
AC2HS
n/a n/a 1.6282 1.06
AC2S
n/a n/a 1.4621 0.78
r1-AC2H2S
n/a n/a 1.7943 1.34
r2-AC2H2S
n/a n/a 1.7943 1.34
r1-AC2HS
n/a n/a 1.6282 1.06
Notes on the table: the identifiers shown are as used in Multiflash;
they are not case-sensitive. If the user introduces an identifier for a
subgroup or group which is not present in the table, it is taken to be a
new user-defined subgroup or group. Multiflash allows up to 10 user-
defined subgroups and 10 user-defined groups to be present at any
time. Subgroups shown in italics are not generic identifiers and
should be avoided. Subgroups marked with a † symbol only occur in
PSRK UNIFAC; if they are present when other variants of UNIFAC are
used, they will cause an error to occur.
When a particular variant of UNIFAC is invoked, the generic UNIFAC
subgroups are translated to other subgroups within the actual
UNIFAC model. The translation rules for original UNIFAC and PSRK
UNIFAC are as follows.
c-CH2CH2
c-CHCH
c-CC
s-OHOH
t-OHOH
c-CH2OCH2CH2 + FCH2O
c-CH2OC/2H½ CH2 + FCH2O
c-C/2HOC/2HFCH2O
AC2H2SC4H4S – 2 ACH
r1-AC2H2SC4H3S – ACH – AC
r2-AC2H2SC4H2S – 2 AC
AC2HSC4H3S – 2 ACH
r1-AC2HNC4H3S – 2 ACH
AC2SC4H2S – 2 ACH
AC2H2NC5H5N – 3 ACH
r1-AC2H2NC5H4N – 2 ACH – AC
r2-AC2H2NC5H3N – ACH – 2 AC
AC2HNC5H4N – 3 ACH
r1-AC2HNC5H3N – 2 ACH – AC
AC2NC5H3N – 3 ACH
C2H62 CH3
For Dortmund modified UNIFAC the translation table is:
NMPc-CONCH3 + 3 c-CH2
r1-AC2H2SAC2H2S
r2-AC2H2SAC2H2S
r1-AC2HSAC2HS
r1-AC2H2NAC2H2N
r2-AC2H2NAC2H2N
r1-AC2HNAC2HN
C2H62 CH3

User-modified UNIFAC groups and subgroups

For each definition of a UNIFAC model the user can amend the
subgroup and group definitions using the UNIFACA keyword in
combination with the data keyword. For example,

62
model MUNIFAC UNIFACA ORIGINAL VLE ORIGINAL MIDG
POYNTING DATA
SUBGROUP HCOOH 1.528 1.532 HCOOH
SUBGROUP S-CH3 0.89 0.84 CH2
SUBGROUP CH3 0.91 0.85 CH2
GROUP HCOOH CH2 330 –0.1 0
GROUP CH2 HCOOH 570 0.2 0
;;
Note that if a gas phase model is not required, the 6th keyword can be
replaced by a * to indicate it is undefined.
After the data keyword repeated SUBGROUP and GROUP keywords
can be used to modify the subgroup and group definitions used in the
instance of UNIFAC referred to by the MUNIFAC identifier. The
keyword SUBGROUP must always be followed by four further
keywords giving the name of the subgroup in question, its r value, its
q value and the name of the main group to which the subgroup
belongs. The keyword GROUP must always be followed by the name of
the first and second groups to which it applies followed by three
coefficients a, b, c defining the group interaction parameter according
to the relation,

Aij =a+ b T + c T 2
where T is the absolute temperature in kelvin. Note that group
interactions between any pair of groups requires two GROUP
keywords for a complete definition of Aij and Aji.
In the UNIFAC example above, the user has decided that the formic
acid subgroup should have its own main group which will be called
HCOOH. The r and q values are in fact set to the normal values for
subgroup HCOOH. Because there is no standard main group called
HCOOH, Multiflash will create a new user-defined main group of this
name with group interaction parameters between HCOOH and all
other main groups set to zero. Next the user has decided to introduce
a new subgroup S-CH3 to denote a secondary methyl group which is
defined as belonging to the existing CH2 main group. The existing
CH3 subgroup is amended to have non-standard r and q values of
0.91 and 0.85 respectively. Finally the user has defined the group
interaction parameters between HCOOH and CH2 to be linear
functions of temperature.
It is possible to add approximately 100 SUBGROUP and GROUP
keywords to a Unifac model definition before Multiflash’s internal
storage limits are reached.

Activity coefficient model for gas phase

The ACG (activity coefficient model for gas phase model) model has
been added to make it possible to calculate enthalpy, entropy and
heat capacity from the liquid heat capacity and heat of vaporisation
instead of from the perfect gas heat capacity. The ACG model
depends on a gas phase model and an activity coefficient model for
the liquid phase. It is also necessary to set the pure component
property CPIDLIQ = 2 for any component for which this method
should be used.

63
 part of model Multiflash
definition keyword Comments
Model name ACG
vapour phase V_model Model name for an equation of state
model model that is used to obtain the
reference state vapour properties.
liquid phase Gex_model Model name for an activity coefficient
model model that is used to obtain liquid
enthalpy, entropy and heat capacity.

Other thermodynamic models for fluids

Electrolyte model
The new electrolyte model is designed to be added on to any equation
of state. The models selection form allows it to be selected for use
with the Advanced RKS equation and the CPA model. It represents
salts as equivalent mixtures of sodium, potassium, calcium, chloride
and bromide ions.
The following example sets up models MHYD1MRKSANRTLand
MHYD2MRKSANRTL for hydrate structures I and II using the
Electrolyte model.
model MRKSANRTL RKSA PSAT LDEN NRTL RKSABIP3;
model MDH LRELECTROLYTE DH BORN VIRIAL ELECBIP
ELECBIP-2 ELECBIP-3;
model MTEST LREPHCHECK;
model MADDMRKSANRTLMDH ADD ZANAL MTEST MRKSANRTL MDH;
model MHYD1MRKSANRTL HYDRATE I MRKSANRTL;
model MHYD2MRKSANRTL HYDRATE II MRKSANRTL;
The following example sets up models MHYD1MASSOC and
MHYD2MASSOC for hydrate structures I and II using the Electrolyte
and CPA model .
bipset ASSOCBIP 1 constant;
bipset ASSOCBIP-2 1 constant;
bipset ELECBIP 1 constant;
bipset ELECBIP-2 1 constant;
bipset ELECBIP-3 1 constant;
model MASSOC ASSOC PSAT ASSOCBIP ASSOCBIP-2;
model MDH LRELECTROLYTE DH BORN VIRIAL ELECBIP
ELECBIP-2 ELECBIP-3;
model MTEST LREPHCHECK;
model MADDMASSOCMDH ADD ZANAL MTEST MASSOC MDH;
model MHYD1MASSOC HYDRATE I MASSOC;
model MHYD2MASSOC HYDRATE II MASSOC;

COSTALD liquid density model

The COSTALD model is a corresponding states method for predicting
the density of liquid mixtures. It is valid for liquids on the saturation
line and for compressed liquids up to a reduced temperature of 0.9.
The volume of a liquid on the saturation line is defined by:

V sat
V * 
 V R( 0) 1  V R(1) 

64
 where V sat is the saturated liquid volume, V * is a characteristic
volume for each substance,  is the acentric factor and V R( 0) and
V R(1) are generalised functions of reduced temperature. In the
Infochem implementation V * is obtained by matching the saturated
liquid volume stored in the databank at 298 K or a reduced
temperature of 0.7, whichever is the lower.
The volume of a compressed liquid is given by:

V   B  p  
sat  1  C ln 
V   B   p sat  
where B is a generalised function of reduced temperature and ,C
is a generalised function of  , and p sat
is the saturation pressure at
the given temperature.

part of model Multiflash

definition keyword Comments
Model name COSTALD
BIP data bipset optional, bipset is the name for a set
of BIPs defined by the BIPSET
command; requires 1 BIP, kij

Henry’s law model for water

A specialised model for predicting solubility of light gases in water at
low concentrations.

part of model Multiflash

definition keyword Comments
Model name HLW
liquid phase model L_model model name for a model that is used
to obtain the properties of pure water
in the liquid phase

Thermodynamic models for solids

Gas hydrate model

The original Infochem model uses a modification of the RKS equation
of state for the fluid phases plus the van der Waals and Platteeuw
model for the hydrate phases. The model introduced in Multiflash 2.9
uses the CPA model for the fluid phases. The hydrate models have
also been extended to include hydrate structure H in addition to
structures I and II. The model can explicitly represent all the effects of
the presence of inhibitors, although parameters for the CPA model
are only provided for methanol, MEG and salt. CPA parameters for
additional thermodynamic inhibitors will be added in future versions.

The hydrate model can be used in conjunction with either the RKSA
equation of state or CPA model and the OILANDGAS BIP correlations.

65
part of model Multiflash
definition keyword Comments
Model name HYDRATE
structure type * or II hydrate structure II
I hydrate structure I
H hydrate structure H
liquid phase model L_model model name for a model that is used
to obtain the properties of pure water
in the liquid phase

The following example sets up models MHYD1MRKSANRTL and

MHYD2MRKSANRTL for hydrate structures I and II using the RKSA
eos with Infochem mixing rules to get the properties of the liquid
phase.
model MRKSANRTL RKSA PSAT LDEN NRTL RKSABIP3;
model MHYD1MRKSANRTL HYDRATE I MRKSANRTL;
model MHYD2MRKSANRTL HYDRATE II MRKSANRTL;
The following example sets up models MHYD1MASSOC and
MHYD2MASSOC for hydrate structures I and II using the CPA model.
There are two sets of BIPs required by CPA model which have to be
defined before the model specification.
bipset ASSOCBIP 1 constant;
bipset ASSOCBIP-2 1 constant;
model MASSOC ASSOC PSAT ASSOCBIP ASSOCBIP-2;
model MHYD1MASSOC HYDRATE I MASSOC;
model MHYD2MASSOC HYDRATE II MASSOC;

Nucleation model
This model is an extension of the existing thermodynamic model for
hydrates described above. In order to extend the nucleation model
into the Multiflash program, the following enhancements to the
nucleation model were made:
 The model was extended to cover the homogeneous
nucleation of ice and fitted to available ice nucleation
data.
 The model was generalised to cover in principle
nucleation from any liquid or gas phase.
 A correction for heterogeneous nucleation was included
that was matched to available hydrate nucleation data.
 An improved expression was adopted for fluid diffusion
rates.
 More robust numerical methods were introduced into the
program.
The nucleation model provides an estimate of the temperature or
pressure at which hydrates can be realistically expected to form. The
model is based on the statistical theory of nucleation in
multicomponent systems. Although there are limitations and
approximations involved in this approach it has the major benefit
that a practical nucleation model can be incorporated within the
framework of a traditional thermodynamic hydrate modelling
package.
With the existing Infochem hydrate model and the nucleation model,
the hydrate formation and dissociation boundaries can be predicted
between which is the hydrate formation risk area.
The following example sets up the nucleation model in association
with the hydrate model MHYD1MRKSANRTL and MHYD2MRKSANRTL

66
 described above for hydrate structures I and II and the MRKSNRTL for
the fluid phases.
model MNUCL1MHYD1MRKSANRTL BPNUC MHYD1MRKSANRTL;
model MNUCL2MHYD2MRKSANRTL BPNUC MHYD2MRKSANRTL;

Solid freezeout model

This model is used to calculate the thermodynamic properties of solid
phases formed by freezing one or more of the components in the
fluid mixture. It may be applied to any component where this may be
a consideration. The freeze-out model in general is defined by:

ln ϕi=α ln ϕliq
i − ( Δ H −T ref Δ C p
R )( 1
−
1
T T ref )
S
+ corr +
R
ΔCp
R
ln
T
( )
T ref
−
( p− p atm )Δ V
RT
For the freeze-out of pure solids, the parameters are as follows: ϕi is
the fugacity coefficient of pure solid component i, liq
i is the
fugacity coefficient of the same component as a pure liquid at the
same pressure p and temperature T (calculated from the liquid
phase model associated with the freeze-out model),   1 , H ,
C p and V are the changes in molar enthalpy, molar heat
capacity and molar volume respectively on fusion at the melting
point, Tref is a reference temperature which corresponds to the
normal melting point when S corr  0 which is assumed in this case.
patm is atmospheric pressure. H , C p and V are constants,
which are normally obtained from the chosen data source.
Solid freeze-out can be used to model the solidification of
compounds such as water, carbon dioxide or methane, for example in
natural gases. It can also be used to model eutectics. In its general
form, the freeze-out model can be applied to any solid phase of fixed
composition, which must be defined. The model can for example be
applied to hydrated salts such as monoethylene glycol (MEG)
monohydrate or to crystalline mineral salts, i.e. scales. If   1 , the
solid fugacity coefficient is defined relative to the liquid phase of the
same composition whereas, if   0 , the solid fugacity coefficient is
an absolute value. S corr is a molar enthalpy correction factor that
allows the reference temperature Tref to be different from the
normal melting point. For solid phases that are not pure substances,
the parameters H , C p V , S corr and Tref must be
defined specifically for the phase in question.
The basic pure component form of the model can be defined as
follows.

part of model Multiflash

definition keyword Comments
Model name FREEZEOUT
solid component comp_name name or serial number (in order of
comp_no component definition) of the
component in the pure solid phase
liquid phase model L_model model name for a model that is used
to obtain the properties of the pure
component in the liquid phase

67
 The following example sets up a model for an ice phase (
MICEMRKSANRTL ) using the RKSA eos with Infochem mixing rules to
get the properties of the liquid phase.
model MRKSANRTL rksa psat lden nrtl;
model MICEMRKSANRTL FREEZEOUT water MRKSANRTL;
The advanced form of the model is defined as follows:

part of model Multiflash

definition keyword Comments
Model name FRZA
reference state LIQUID or =1
ACTIVITY =0
liquid phase model L_model Model name for a model that is used
to obtain the properties of the pure
component(s) in the liquid phase.
variants keyword DATA Used to specify model parameters
for freeze-out phase.
model variants COMPONENT Model parameter keywords each
repeated (order VMELT followed by appropriate values.
optional) HMELT
SMELT
CPMELT
TMELT

Each model variant must be followed by associated values as given in

the following table.

Multiflash Associated value(s)

keyword
COMPONENT Name or CAR number of
component followed by
its abundance
V
VMELT
H
HMELT
Scorr
SMELT
Cp
CPMELT
Tref
TMELT

This example defines a solid phase of calcium chloride dihydrate:

model MRKSANRTL rksa psat lden nrtl;
model MNACL.2(H2O) FRZA ACTIVITY MRKSANRTL DATA
COMPONENT Ca++ 1 COMPONENT Cl- 2 COMPONENT water 2
VMELT 1.4e-4 HMELT –34745 SMELT 103.32 CPMELT –264.89
TMELT 298.15;

Wax model
The model can be used to predict the wax appearance temperature
and the wax deposition from crude oils. The Coutinho wax model has
to be used in associated with the normal-paraffin pseudocomponents
and can predict the wax appearance temperature and deposition more
accurately.
Waxes are mainly formed from normal paraffins but isoparaffins and
naphthenes are also present. Some waxes also have an appreciable

68
 aromatic content. Waxes phase formation shows a very complex range
of behaviour. When waxes form from crude oils, the individual
fractions do not form a solid solution but they individually freeze out
to form a mixture of solids, defined as a multi-solid phase.

Part of model Multiflash

definition keyword Comments
Model name coutinho Infochem new wax model, called
Multisolution ( coutinho) wax model.
variant Wilson or Used together to define the couthino
uniqac wax model, which can be wilson or
unifac.
liquid phase model L_model model name for a model that is used
to model the fluid phase

The following example for Coutihno wax model sets up a model for a
wax phase using RKSA eos to get the properties of the liquid phase.
Model MRKSA RKSA PSAT LDEN VDW RKSABIP;
model MWAXMRKSA COUTINHO WILSON MRKSA;

Asphaltene model
Asphaltenes, heavy aromatic residues of the oil are another type of
solid deposition that can occur from crude oils. They are thought to
be polycyclic aromatics of very high molecular weight. They also
contain nitrogen and sulphur. Asphaltenes are polar compounds and
they are stabilised in crude oil by the presence of resins which are
also polar compounds and have a strong tendency to associate with
asphaltenes.

Part of model Multiflash

definition keyword Comments
Model name RAEQUIL
variants keyword DATA Used to specify model parameters by
users for asphaltene phase.
model variants AAP Model parameter keywords each
repeated (order AAE followed by appropriate values.
optional)
RAP
RAE

The following example sets up a model for gas and liquid phases
using RKSA model and a model for a asphaltene phase using
asphaltene association model and default model parameters. Then
combine those two models together to create a general model for the
phase equilibrium calculations.
model MREFFLUID RKSA PSAT LDEN VDW ASPHALTBIP;
model MREFASPHALTENE RAEQUIL;
model MADD ADD ZANAL MREFFLUID MREFASPHALTENE;
There are four model parameters. The following is the example to
change and modify the model parameters.
model MREFASPHALTENE RAEQUIL DATA AAP value_aap
AAE value_aae RAP value_rap RAE value_rae;
where AAP and AAE are the keywords for asphaltene-asphaltene
interaction parameters, followed by the corresponding values, their
positions indicated in italics; RAP and RAE are for those for resin-
asphaltene interactions. DATA marks the start of model parameters
entry and must be present if model parameters are entered directly.

69
Viscosity models

SuperTRAPP viscosity model

The SuperTRAPP method is a predictive extended corresponding
states model that uses propane as a reference fluid. It can predict the
viscosity of petroleum fluids and well-defined components over a
wide range of thermodynamic states from the dilute gas to the dense
fluid. The basic idea behind this model is that the viscosity of a
mixture can be equated to the viscosity of a hypothetical pure fluid
which is then related to the viscosity of a reference fluid at a
corresponding-state point (ρ0 ,T0). In order to improve the viscosity
prediction for cycloalkanes and highly branched alkanes, the concept
of mass shape factor in introduced in this method. In order to apply
the method, the following are required:
 An equation of state for the reference fluid,
 Correlation for the viscosity of the reference fluid,
 The critical parameters, acentric factor and molecular weight
of the fluid of the interest or for each component of the
mixture of the interest.
The original method is not applicable to aqueous mixtures of
alcohols, glycols or salts. The Infochem implementation of Super
TRAPP model includes modification to ensure that the viscosity of
aqueous solutions of methanol, ethanol MEG, DEG and TEG or salts
and ions are predicted reasonably well.
Two variants of the SuperTRAPP model are implemented:
 Standard SuperTRAPP model as described above.
 Liquid viscosity fitting. An internal model parameter is
adjusted to match the experimental measurements.
Overall the SuperTRAPP method is the most versatile method for
viscosity predictions and its performance is generally better than the
other methods available in Multiflash. We would recommend this
method for oil and gas application. It is the default viscosity model
for use with equations of state.
Reference: Huber, M. L. & Hanley, H.J.M. (1996) The corresponding-
states principle: Dense Fluids. In J. Millat, J. H. Dymond & C. A. Nieto
(Eds.), Transport properties of Fluids: Their correlation, Prediction and
Estimation. Cambridge University Press.

part of model Multiflash

definition keyword Comments
Model name SPVISC
model variant * or SPVISC Standard SuperTRAPP method
LFIT Fits SuperTRAPP parameters to match
reference viscosity for each
component

Pedersen model
This is a predictive corresponding states model originally developed
for oil and gas systems. It is based on accurate correlations for the
viscosity and density of the reference substance which is methane.
The model is applicable to both gas and liquid phases. The Infochem

70
 implementation of the Pedersen model includes modifications to
ensure that the viscosity of liquid water, methanol, ethanol, MEG, DEG
and TEG and aqueous solutions of these components or salt are
predicted reasonably well. We would recommend this method for oil
and gas applications.
Multiflash includes two variants of the PDV model. The first uses the
Infochem implementation of the original PDV method. The second
variant fits parameters in the model to reproduce the saturated liquid
viscosity of each component at its boiling point.
Reference: Pedersen, Fredenslund and Thomassen, Properties of Oils
and Natural Gases, Gulf Publishing Co., (1989).

part of model Multiflash

definition keyword Comments
Model name PDVISC
model variant * or PDVISC Standard PDV method
LFIT Fits PDV parameters to match
reference viscosity for each
HEAV component
Heavy fluids variant

Twu model
This is a predictive model suitable for oils. It is based on a correlation
of the API nomograph for kinematic viscosity plus a mixing rule for
blending oils. It is only applicable to liquids.
Multiflash includes two variants of the TWV model. The first uses the
Infochem implementation of the original PDV method. The second
variant fits parameters in the model to reproduce the saturated liquid
viscosity of each component at its boiling point.
Reference: Twu, Generalised method for predicting viscosities of
petroleum fractions, AIChE Journal, 32, 2091, (1986).

part of model Multiflash

definition keyword Comments
Model name TWVISC
model variant * or TWVISC Standard TWV method
LFIT Fits TWV parameters to match
reference viscosity for each
component

Lohrenz-Bray-Clark viscosity model

The LBC method is a predictive model for gas or liquid viscosity. It is
mainly applicable to the types of components in oil and gas
processing operations.
This model is a predictive model which relates gas and liquid
densities to a fourth degree polynomial in reduced density.
r   c :

     10 
1/ 4
* 4
 a1  a 2  r  a 3  2r  a 4  3r  a5  4r

where a1 , a 2 , a 3 , a 4 and a5 are constants. For pure components

the viscosity reducing parameter  is defined by

71
   Tc1/ 6 MW 1/ 2 pc2 / 3
where Tc and pc are respectively the critical temperature and critical
pressure and MW is the component molecular weight. For a mixture
these properties are calculated using mole fraction averages.
In Multiflash the fluid densities are derived from any chosen equation
of state, rather than the correlations proposed by Lohrenz et al. This
has the advantage that there is no discontinuity in the dense phase
region when moving between liquid-like and gas-like regions.
Multiflash also allows two variants of the LBC model. The first uses
the original LBC method to estimate the critical volume of petroleum
fractions and takes the critical volume of other components from the
chosen data source. The second variant fits the critical volume of each
component to reproduce the liquid viscosity at the boiling point.

It is also possible to specify a critical volume specifically for the LBC

model by setting the pure component property VCLBC.

part of model Multiflash

definition keyword Comments
Model name LBC
model variant * or LBC Standard LBC method
LFIT Fits LBC parameters to match
reference viscosity for each
component
fluid phase model fluid_model model name for a model that is used
to obtain the density of the mixture in
a fluid phase
Variant keyword DATA Used to specify LBC model parameters
Model variant A1 Model parameter keywords each
repeated A2 followed by appropriate values.
(order optional) A3
A4
A5

This example sets up an eos model (MRKSA) and then defines the LBC
viscosity model using MRKSA to calculate the density.
model MRKSA rksa psat lden;
model MLBCMRKSA LBC * MRKSA;
There are five model parameters. The following is an example of how
to modify these model parameters.
model MLBCMRKSA LBC * MRKSA DATA A1 value_a1 A2
value_a2 A3 value_a3 A4 value_a4 A5 value_a5;

Liquid viscosity mixing rule

This method obtains the liquid mixture viscosity by applying a simple
mixing rule to the pure component saturated liquid viscosities
obtained from a databank. The databank specified for each
component must contain a liquid viscosity correlation.
 i ni ln  i
ln  
 i ni
where  i is the and pure liquid viscosity for component i and ni is
the number of moles of component i in the mixture.

72
 part of model Multiflash
definition keyword Comments
Model name LVS1

Vapour viscosity mixing rule

This method obtains the vapour mixture viscosity by applying a
simple mixing rule to the pure component vapour viscosities at zero
density obtained from a databank. The databank specified for each
component must contain a gas viscosity correlation.

 i ni M i  i

 i ni M i

where Mi and i are the molecular weight and pure gas viscosity for
component i and ni is the number of moles of component i in the
mixture.

part of model Multiflash

definition keyword Comments
Model name VVS1

Thermal conductivity models

Chung-Lee-Starling model
The CLS method is a predictive model for gas or liquid thermal
conductivity. It is mainly applicable to the types of components in oil
and gas processing operations.
     p

 1 
   0   Bi Y 
 H2 
where 0 is a generalised function of reduced temperature, Bi is a
generalised function of  , H2 is a generalised function of  r and Y
is a function of volume.

part of model Multiflash

definition keyword Comments
Model name CLS
fluid phase model fluid_model Model name for a model that is used
to obtain the density of the mixture in
a fluid phase

SuperTRAPP thermal conductivity model

The STRAPP method is an extended corresponding states model that
can be used for petroleum fluids, well-defined components and pure
substances.

73
 In general the thermal conductivity is defined as the sum of the
internal contribution and the translational contribution. The
translational contribution can be defined as three parts: the dilute gas
contribution, the residual and critical enhancement contribution.
int dilute −gas res Crit
λ x (T , ρ ,{x })=λ x (T , {x })+ λ x (T ,{x })+ λ x ( T , ρ , {x})+ λ x (T , ρ , {x})
int
For a mixture, the internal contribution λx can be estimated from
the empirical mixing and combining rules using the modified Eucken
correlation for the individual components.
For the dilute gas term, the expression for the translational
contribution is formulated as

15 Rηox (T )
λ dilute− gas
x (T , {x })=
4M x
in units of mW/m/K. R is the molar gas constant in units of
J /mol / K and Mx is the molecular weight for the mixture in unit
of g/mol and the expression of η ox (T ) for a mixture is given as
follows.
n
∑ x i ηio( T ) M 1/2
i n
i=1
η ox ( T )= n
and M x=∑ xi M i
i =1
∑ x x M 1i /2
i=1

Where ηio is the dilute gas viscosity given by Lucas correlation in

unit of μP .
The expression of the residual contribution term is evaluated using
the extended corresponding state method and is related to the
thermal conductivity of a reference fluid of propane at a
corresponding state, ( ρo ,T o ) .
res res
λ x ( T , ρ)=λo (T o , ρo ) F λ
where the F λ calculation requires mixing and combining rules for
the mixtures.
In the current version of STRAPP in Multiflash 3.9, the critical
Crit
enhancement term, λx is omitted since the critical enhancement
for mixtures is usually very small.

part of model Multiflash

definition keyword Comments
Model name SPTHCOND

Liquid thermal conductivity mixing rule

This method obtains the liquid mixture thermal conductivity by
applying a simple mixing rule to the pure component saturated liquid
thermal conductivities obtained from a databank. The databank
specified for each component must contain a liquid thermal
conductivity correlation.

74
 1
 i ni M i
1 2i

2  i ni M i
where Mi and i are the molecular weight and pure saturated liquid
thermal conductivity of component i and ni is the number of moles
of component i in the mixture..

part of model Multiflash

definition keyword Comments
Model name LTC1

Vapour thermal conductivity mixing rule

This method obtains the vapour mixture thermal conductivity by
applying a simple mixing rule to the pure component vapour thermal
conductivities at zero density obtained from a databank. Requires
that the databank specified for each component contains a gas
thermal conductivity correlation.

 i ni M i  i

 i ni M i

where Mi and i are the molecular weight and pure gas thermal
conductivity of component i and ni is the number of moles of
component i in the mixture.

part of model Multiflash Comments

definition keyword
Model name VTC1

Surface tension models

Linear Gradient Theory

This method predicts the interfacial tension between
two phases. The possible pairs of phases are: Liquid /
Gas and Liquid / Liquid.

The model uses the difference in densities between

the two phases and the energy gradient that arrives
from the fact that the phases are immiscible to predict
the interfacial tension.
II
ρref

σ = ∫ 2c
ρref
I
√ (∑ ρ ( μ ( ρ)− μ )−( P ( ρ )−P )) dρ
i
i i
eq
i
eq
ref

Where ρ is the density, μ is the chemical potential, P is

the pressure and σ is the interfacial tension. The
parameter c is called the influence parameter and is a
function of temperature.

75
part of model Multiflash
definition keyword Comments
Model name LGST
liquid phase model EOS_model Model name for an equation of state
model that is used to obtain the
density and thermodynamic properties
of the mixture.

Macleod-Sugden surface tension method

The MCS method is a predictive model for surface tension based on
the parachor stored in the databank. It is mainly applicable to the
types of components in oil and gas processing operations.

 1/ 4   Pi (  l xi   v yi )
where:
Pi is the parachor for component i
l is the liquid molar density

v is the vapour molar density

xi is the liquid mole fraction

yi is the vapour mole fraction

part of model Multiflash

definition keyword Comments
Model name MCS
liquid phase model liquid_model Model name for a model that is used
to obtain the density of the mixture in
the liquid phase

The MCS model cal also be used in 2 phase mode, where the vapour
phase is also calculated by the Equation of State rather than the ideal
gas equation.

part of model Multiflash

definition keyword Comments
Model name MCSA
Variant MCS1P Equivalent to the MCS model
MCS2P 2 phase variant
Equation of state EOS_model Model name for a model that is used
model to obtain the density of the mixture in
the liquid phase and gas phase, if
using the 2 phase variant

Sutton
The Sutton method predicts the interfacial tension between an
aqueous phase and a gas or a liquid hydrocarbon phase. The method
uses the density difference between the phases and the critical
pressure of the hydrocarbon phase.

76
 c3

[( ) ]
c1 (ρw −ρh ) + c 2
σ hw = a 2 + a3 T + a4 T 2
T
Tc
where
σ hw is the surface tension between water and a hydrocarbon
phase
T is the temperature

Tc is the critical temperature of the hydrocarbon phase

ρw is the density of the aqueous phase
ρh is the density of the hydrocarbon phase
It is mainly applicable to the type of components found in the oil and
gas processing including hydrate inhibitors.

part of model Multiflash

definition keyword Comments
Model name SUT
Variant SUT
liquid phase model liquid_model Model name for a model that is used
to obtain the density of the mixture in
the liquid phase

Surface tension mixing rule

This method obtains the surface tension of a liquid mixture by
applying a simple mixing rule to the pure component saturated liquid
surface tensions obtained from a databank. Requires that the
databank specified for each component contains a liquid surface
tension correlation.
1
 i ni
1 i

  i ni
where i is the surface tension of the pure saturated liquid for
component i and ni is the number of moles of component i in the
mixture.

part of model Multiflash

definition keyword Comments
Model name ST1

77
Binary interaction parameters

BIPDATA
The BIPDATA command sets the default databank (or correlation) for
binary interaction parameter data for use by thermodynamic and/or
transport property models for mixtures.
The command has the following format
BIPDATA datasource_name1 datasource_name2;
Or
BIPDATA datasource_name1;
datasource_names may be two of the following:

datasource_name Meaning
OILANDGAS4 latest version of Infochem correlations for BIPs for
cubic eos models (PR, PRA, RKS, RKSA) and LGST
model for components in oil and gas mixtures.
Components included are: hydrocarbons,
petroleum fractions, water, methanol, glycols, H2S,
CO2 , N2, and saltcomponent (for RKSA)

OILANDGAS3 old version of correlations superseded by

oilandgas4 to version 2.9 in January 2000
(included for backwards compatibility).
OILANDGAS2 old version of correlations superseded by
oilandgas3 in November 1997 (included for
backwards compatibility)
OILANDGAS1 old version of Infochem correlations superseded
by oilandgas2 in June 1994 (included for
backwards compatibility)
OILANDGAS synonym for oilandgas4
INFOBIPS BIPs databank for VLE with NRTL and UNIQUAC
models and refrigerants.
INFOLLBIPS BIPs databank for LLE with NRTL and UNIQUAC
models.
ERASE erases (removes) currently defined datasource

The following example sets up a model called MRKS that uses the RKS
equation of state with the OILANDGAS correlations for BIPs.
BIPDATA INFOBIPS OILANDGAS;
MODEL MRKS RKS;

79
 Other binary interaction parameter data, typically containing users’
own data, in one of the standard formats may be specified as follows:
BIPDATA datasource_name file_name.idx
file_name.bin;
The databank_type, associated file_name are defined in the
following table.

Dataresource_name File_name Notes

OWNINFOBIPS 1. databank index Files must correspond
(.idx) to the structure and
2. databank (.bin) format used in
file Multiflash

BIPSET
The BIPSET command defines an identifier for a collection of BIP
values and sets the numerical values of the BIPs. The BIPs may
subsequently be associated with a mixture model for thermodynamic
or transport properties.
The command has the following format
BIPSET bipset_id no_of_bips T_dependence
Bipset_function_type bip_unit component_1
component_2 bip_values ....
The following table gives the valid options and settings:

80
command Description Notes
parameter
bipset_id user-defined name that will be used to any unique alphanumeric string, e.g.
refer to the collection of BIP values bipuser
no_of_bips the number of BIP values that will be See the information on model
defined per binary pair of components. definition for the number of BIPs
The number required is model-dependent required for each model
and also depends on whether the BIPs are
temperature-dependent
T_dependence a keyword describing the T-dependence The normal function used to describe
model used. May be: temperature dependence is:
constant 2
linear
B=a 0 + a 1 T + a 2 T
quadratic where B is the BIP and T is the
(constant is assumed if omitted). temperature in K
Bipset_Functio a keyword for describing the type of bip Eos for EOS models
n_Type sets. May be: activity for activity models
Eos association for CPA association
activity models
association
Bip_unit a keyword giving the dimensions of the The BIPs may have units depending on
BIPs. The available units for BIPs for the models specified. If it is omitted,
activity models are J/mol, cal/mol, K, the BIPs will be treated as
Aspen or none (denoting dimensionless). dimensionless (or association units).
The units for eos models are all
dimensionless. For association, the units
are fixed as dimensionless, molar energy
and molar heat capacity units
respectively.
component_1 component identifiers for the BIP These may be names or serial
component_2 numbers.
the number of BIP values entered
bip_values BIP values (real numbers) must agree with the number specified
above
The component identifiers and BIP
values may be repeated as many times
as required to specify all BIPs

The following example defines a BIP dataset called WILSONBIP2 and

sets the values of two BIPs for the component pair methanol and
isobutene. Because the temperature-dependence keyword is omitted
the parameters are assumed to be constants.

bipset WILSONBIP2 2 constant activity J/mol methanol

isobutene 1.16 2.5;
If both BIPSET and BIPDATA are used, then the BIPSET data will be
used first, then BIPs will be taken from the defined BIPDATA source
and the remainder will be set to the default value(s) for the model.
Remember that the user identifier for any defined BIPSET must be
attached to the definition of the model.
Regarding activity methods, for the dimensionless and Aspen units
options note that the actual temperature function becomes
b=a 0 + a 1 /T + a 2 T
as the dimensionless BIP is actually b=B/RT. For the Aspen units, the
NRTL  parameter is defined as a quadratic function of the Celsius
temperature t:

81
 2
α=a 0 + a1 t+ a 2 t
It is possible to use the same BIP set for more than one model,
provided the models use the same number of parameters. For
instance if an RKS BIP set is provided then it could also be used with
the Peng-Robinson EOS if the values are appropriate.

Troubleshooting - BIPs

Order of components
Equations of state with standard mixing rules usually have a single
symmetric BIP. This means that the BIP is the same regardless of the
order of components. However, activity coefficient models usually
have two asymmetric BIPs. It is important that you enter both BIPs
and in the correct cells so that the binary pair is consistent with BIPs
supplied.

Number of BIPs for the model

If you are supplying BIPs in a .mfl file it is important that you define
and supply the correct number of BIPs.
Wilson A, Wilson E and UNIQUAC require 2 BIPs. If you only specify 1
after the bipset name a warning message will appear;
Model has the wrong no. of BIPs for the existing
set
A similar message will appear if you only specify 2 BIPs for NRTL
which requires 3.
The other possibility is that you specify the correct number of BIPs for
the model, but fail to supply them all. The result will depend on the
model and the default BIPs set.
If you specify NRTL with 3 BIPs and only supply 2 the default is to set
the third parameter to 0.3, for NRTL VLE and to 0.2 for NRTL LLE. For
other BIP sets the default value is 0. If no BIPs are specified the BIPs
are read from the databank. If the databank does not hold any values
the BIPs will be set to the default values.
For example if you specify UNIQUACBIP to have 2 constant BIPs and
supply only one BIP value, the second BIP will be set to 0.0, and no
warning message will be issued. We recommend that you always
check your supplied BIPs using the Tools/BIPs option.

Naming the components

If you forget to enter the component names for a binary pair in a file
before the BIP values you will upset the expected sequence of the
command and the likely error message will be
MFL Syntax error.

82
Phase descriptors and stream
types

The PD command
The PD command is used to define a phase descriptor (PD). The PD is a
user-defined name that is used to refer to a phase. It is necessary to
define a PD for all the phases that you wish Multiflash to consider
when doing a flash calculation.. To exclude the formation of a
particular phase type, e.g. gas, the corresponding PD should be
omitted or erased. The phasedescriptor command is a synonym for
pd.
The maximum number of PDs that may be defined is currently set at
20. The maximum number of phases that can coexist at equilibrium is
limited to 7.
The command for defining a phase has the format:
PD pd_id phase_type model_identifiers;
And the command for deleting an existing phase is:
PD pd_id erase;
The following table gives the valid options and settings:

command Description notes

parameter
pd_id user-defined name that will be used any unique alphanumeric string, e.g.
to refer to the particular instance of liquid1
phase type and associated models
phase_type a keyword that defines the phase 1. gas, vapor and vapour are
type, valid settings are: synonyms.
condensed 2. condensed means a pure solid
gas phase.
hydrate 3. Multisolid and solidsolution mean a
liquid mixed solid phase.
multisolid
solidsolution
vapor
vapour

83
model_identifiers identifiers for up to six models that 1. the model identifiers are the user-
will be used to evaluate the defined names associated with the
thermodynamic and transport models (see description of MODELS
properties of the phase. Models for command)
the following properties may be 2. at least one thermodynamic model
specified in the order given: must be defined (the same model is
1. fugacity (K-values) then used for all thermodynamic
2. Volume/density (optional) properties)
3. Enthalpy/entropy (optional) 3. transport property models need only
4. Viscosity (optional) be defined if output of these
5. Thermal conductivity (optional) properties is required
6. surface tension (optional)
7. Nucleation model
8. Diffusivity model
Erase erases (removes) the PD from the list 1. the pd_id must have been previously
of PDs available for Multiflash defined
2. all information associated with the
PD is lost

The streamtype command

The streamtype command is used to define a stream type in
association with the phase descriptors (PDs) and components. The
streamtype command is a synonym for st.
The command has the format:
ST st_id composition nmol_1 nmol_2 …; components
comp_1&comp_alias_1 comp_2&comp_alias_2 … ; pds
pd_id_1&pd_alias_1 pd_id_2&pd_alias_2 …; ;
In the command there is an end-marker for keywords composition,
components and pds, and the last end-marker must be present for
terminating the streamtype command. If no phase descriptors are
currently defined and you try to define a stream type using the
command described above, you will see an error message on the
screen:
*** ERROR 555 ***
Unrecognised entry - No phase descriptor of this name
has been defined
The composition field provides the flexibility to define multiple feeds
into one MFL file. The amounts are assigned using the same order as
the components are listed in the MFL file. If no composition is
defined, the amounts for the components are taken from the amounts
command.
The components are identified using either their names or component
numbers comp_1 … . If the components keyword is omitted, all
defined components are included in the stream type. For each
component, an alias can be defined which is the name by which the
component must be referred to when the stream type is set to be the
current operative stream type. The alias can be omitted for any or all
components, for example:
components comp_1 comp_2 … ;
in which case the components will be referred to by their normal
names.
The phases are designated by their phase identifiers pd_id_1 … . If the
pds keyword is omitted, all defined phases are included in the stream
type. For each phase, an alias can be defined which is the name by

84
 which the phase must be referred to when the stream type is set to be
the current operative stream type. The alias can be omitted for any or
all phases, for example:
pds pd_id_1 pd_id_2 … ;
in which case the phases will be referred to by their normal names.
The command to remove a stream type has the format:
ST st_id erase;
The following table gives the valid options and settings:

command Description Notes

parameter
st_id user-defined name that will be used any unique alphanumeric string, e.g.
to refer to a stream type stream1
composition Keyword that defined compositions
for the stream
nmol_1 Component amount Real or integer
components keyword that defines the optional
components for a stream type
comp_1 component name or number alphanumeric or integer
comp_alias_1 user-supplied component alias
phasedescriptors keyword that defines the phase optional
or pds descriptors for a stream. type

pd_id_1 phase identifier

pd_alias_1 user-supplied phase alias
Erase erases (removes) the stream type 1. the st_id must have been
from the list of those available for previously defined
Multiflash 2. all information associated with the
stream type is lost

The KEYS component command

The KEYS command is used to associate a set of key components to a
PD. A key component helps identifying a particular phase when two
or more PDs would otherwise be indistinguishable. It is not necessary
to define key components unless a flash calculation needs to identify
phases uniquely (e.g. a search for a particular phase fraction). The
command has the format:
KEYS pd_id key_component_id1
key_component_id2 ... ;
or:
KEY pd_id not key_component_id1
not key_component_id2 ... ;
pd_id is a previously-defined phase descriptor name.
key_component_id(i) is the name of the ith component used to
identify the phase. The user can associate as many key components to
a given PD as the maximum number of components allowed in
Multiflash.

85
In general, the rule used is that the key components should represent
a large (mass) fraction of the given phase. If the a given component
name is preceded by the keyword not , this means that this
component should be present in the minimum mass fraction.
For more flexibility, it is possible to combine “positive” and “negative”
key components. For example,
KEY pd_id not key_component_id1
key_component_id2 ;
would identify phases that simultaneously have a large mass fraction
of “key component 2” and low mass fraction of “key component 1”.
When a set of “positive” key components is defined, two criteria need
to be met for a phase to be allocated to the associated phase
descriptor: (1) The given phase must be the one with the highest mass
fraction of the key components among all the eligible phases (i.e.,
phases using the same fugacity model, in the same state of matter,
etc.) (2) The total mass fraction of key components must be above a
given threshold which has a default value of 0.65 but that can vary
when special name keywords are used for the key components.
Five special name keywords are available: ASPHALTENE , AQUEOUS , *
, LIGHTEST and HEAVIEST. Only a special name keyword can be used
for a given PD, and it cannot be used in combination with additional
key components.
The ASPHALTENE keyword is used to identify asphaltene phases. It
requires the asphaltene component to be present in a large fraction
while the rest of the components in negligible fractions.
The AQUEOUS keyword includes as positive key components water as
well as the most common components soluble in water (e.g.,
methanol, MEG, salts, etc.). In addition, it requires that the total mass
fraction of aqueous components is greater than 0.5.
The * keyword is used to denote a phase which has negligible
amounts of the positive key components of all the other phase
descriptors. It is equivalent to specifying all the positive key
components of the other phase descriptors but with the keyword not
in front of each one of them. This keyword is useful to represent
generic hydrocarbon liquids.
The keywords LIGHTEST and HEAVIEST select the lightest or heaviest
component in the mixture as the single key component. The criterion
used is that the heaviest component is the one with the largest
acentric factor and the lightest is the one with the smallest acentric
factor. Since this keyword is meant to identify the phase where the
lightest(heaviest) component tends to preferentially go to, when these
keywords are used the phase with the largest mass fraction of the
lightest(heaviest) component is always identified with this phase
descriptor as long as the total mass fraction of the key component
exceeds 0.01.
Allocation of PDs with key components is always attempted before
PDs with no key components. However, if when trying to allocate a PD
with positive key components the requirement of minimum mass
fraction is not met, then phase descriptors with no key components
will be attempted to allocate. If after allocating the PDs with no key
components there are still unallocated phases, Multiflash will try to
use the PDs with positive key components even if the minimum mass
fraction requirement is not met. Hence, note that when an insufficient
number of PDs has been defined phases might be allocated to
inadequate phase descriptors.

86
In versions previous to Multiflash 4.4, only a single key component
could be associated to a PD. This was done using the command KEY.
The use of this command is no longer recommended but it is still
supported for compatibility reasons. However, when the KEY
command is used Multiflash assumes the following: (1) If the key
component is water, MF assumes that the keyword AQUEOUS was
intended. (2) If the key component is preceded by the command NOT
then it is assumed that the user intended the keyword * .

87
PVT Experiment Data

Storing PVT Experiment data

Since version 6.0, Multiflash stores experimental data that can be used
for model tuning, in a different way. The exceptions were Wax and
Asphaltenes experimental data, where the Match command is still
used.
The new PVT experimental data command can store data for these
experiments:
• Saturation points (dew and bubble points)
• Viscosity (liquid and gas)
• Constant Mass Expansion (CME)
• Constant Volume Depletion (CVD)
• Differential Liberation Experiment (DLE)
• Multi-stage separator test.
The entries for PVT experimental data are defined as follows:

PVTEXP exp_type [TEMPERATURE [units] value]

[STREAM steam_name]
{property [units] x_1 x_2 … ;} ; ;

The TEMPERATURE field is mandatory for experiments carried out at a

fixed temperature: CME, CVD and DLE.
The units for each quantity are optional but recommended to avoid
The STREAM keyword tells Multiflash for which stream is the
experiment referring to. It is only valid for MFL files that define
multiple streams.
The property field can be repeated as many times as necessary to
store all the data. It can take the following values:
• pressures: list of pressures in experiment
• saturation: list of saturation pressures.
• OilDensity: liquid density measurements
• gasDensity: gas density measurements.

89
 • RelVol: relative volume defined as V/Vtot
• LiqVolFrac: liquid volume fraction defined as Vliq/Vsat
• YFAC: Y factor for CME
• ZFAC: Z factor for gas phase
• Compressibility
• gas_Depleted: gas depleted in CVD experiments
• Cum_gas_Depleted: cumulative gas depleted in CVD
• TWOPHASEZ: 2 phase Z factor measured in CVD
• gasVISC: gas viscosity values.
• GasGravity: gas gravity defined as Mw gas / Mw air
• GASCOMP: defined the gas composition measured in the
several stages in the separator test and in DLE. Each stage is
marked with the STAGE keyword.
• BO: oil volume formation factor
• BG: gas volume formation factor.
• GOR: is used for both Rs in DLE and GOR in separator test
• TLIST: list of temperatures. This is valid in saturation,
viscosity and separator test experiments. Note: this keyword
must be place instead of the TEMPERATURE keyword.

When an MFL created from a previous version of Multiflash is opened

in version 6.0, the old experimental data commands are converted
into new PVTEXP commands:
• viscosity: the old data is assumed to be liquid viscosity and
viscosity experiment commands are created.
• Bubble/dew points: saturation experiment commands are
created
• GOR: the GOR data is converted in a single stage separator
test.
• Density: converted into CME experiments, one for each
detected temperature, with density data only.

90
Conditions

Commands for setting conditions

State quantities
Each of the following keywords must be followed with the value of
the quantity in the current input units:
keyword notes
DENSITY used as synonym for volume
ENTHALPY
ENTROPY
INTERNALENERGY internal energy
PRESSURE
TEMPERATURE
VOLUME

Amounts of components
The AMOUNTS command enters the amounts of each component in the
current input units.
The command has the following format
AMOUNTS x_1 x_2 x_3 ....
Where x_i is the amount of each component entered as a real number
(with a decimal point). The amounts are defined in the order specified
starting with the amount of the first component.
There are two alternative forms of the command.
AMOUNTS component_id x_n
This form defines amounts of components by name, i.e.
component_id must be a valid component name and x_n is the
amount of the component.
AMOUNTS n x_n
This form defines amounts of components by number, i.e. n must be
an integer serial number and x_n is the amount of the nth
component.

91
TOLAMOUNTS - amounts of components in
second mixture for tolerance calculation
The TOLAMOUNTS keyword is used to set the amounts of components
in a second mixture which is combined with the main mixture
composition in a tolerance calculation with the FRACTOLERANCE
command. The command has the same format as the AMOUNTS
command except AMOUNTS is replaced by TOLAMOUNTS.

92
Matching wax data

The MATCH command can be used to store the wax data of wax
precipitation curve or wax appearance temperatures by tuning
melting temperature of petroleum fractions. The command format for
matching the amount of wax phase at a T and P to the total fluid is:
match table waxpc overall temperatures x_1 x_2
x_3 ...;pressures x_1 x_2 x_3 ...; molefractions x_1
x_2 x_3;;;
If the wax data are in massfraction, the keyword molefractions
should be replaced by massfractions.
Keyword molefractions, followed by mole fractions of the wax
phase to either the total amount of the fluid or the amount of the
liquid plus wax phase. If the data of the wax phase are related to the
total liquid plus wax phase, the keyword overall should be replaced
by liquid in the command.
The units for the temperatures and pressures in the command can be
set by using units command shown below and have to be set before
using the match command so that the values for the temperature and
pressure are consistent with the units specified.
Units temperature unit_name_temp ;
Units pressure unit_name_press;
For the wax appearance temperature matching, the fractions for the
wax phase at a T and P should be set to zero.
Three semicolons are required in the end of the commands.
No active matching is possible without using the GUI.

93
Wax+Oil viscosity

The WAXVISCOSITY command is used to store the Wax+Oil viscosity

data with shear rate and temperature. The Multiflash GUI will read
from this information.

Waxviscosity units pressure p_units temperature t_units

viscosity vis_units pressure exp_pressure temperatures
t_1 t_2 … ; shear s_1 s_2 … ; data vis_1 vis_2 vis_3 … ;
WAXparameters D E F ;

All the keywords above are mandatory. The units of the data are
defined by the string in p_units, t_units and vis_units for pressure,
temperature and viscosity, respectively. For units commands, see the
Units section.

The value for exp_pressure is the pressure at which the experiment is

carried out. It follows the units defined in the waxvissotiy command.
T_1, t_2, etc define the list of temperatures in the experiment and s_1,
s_2 define the shear rates used. The viscosity data is disposed in a
linear form where alue are stored by temperatures.

The Waxparameters keyword is used to store the D, E and F

multipliers for the model used. (see the Model reference manual for
more information)
Example command for 2 temperatures and 1 shear rate:
WAXVISCOSITY UNITS PRESSURE bar TEMPERATURE degC
VISCOSITY Pas PRESSURE 1 TEMPERATURES 10 20 SHEAR 50 ;
DATA 5 5 ; WAXPARAMETERS 1 1.5 1 ;

94
Matching asphaltene
deposition point

The MATCH command can be used to store asphaltene experimental

data model parameters to match the asphaltene deposition point or
reservoir condition or get the default model parameters or match
asphaltene titration. The command format is:
Fixedphase asphaltene unspecified .0 molefraction;
match asphaltene ADE;
The temperature and pressure to be matched are taken from the
specified input conditions, i.e. they must have been set using the
temperature and pressure commands.
If the temperature and pressure are not given from the specified
input condition, the alternative way to use the MATCH the command
which includes temperature and pressure. The command for
matching one set of ADE is:
match asphaltene ADE temperature t_1 t_2 … pressure
p_1 p_2 ;
The match asphaltene command now accepts any number of
temperature/pressure pairs for the ADE values. Any matching is done
using the GUI.
The commands for storing reservoir condition or getting the default
model parameters or asphaltene titration are:
match asphaltene reservoir temperature x_1 pressure
x_2;
Storing the mass fraction of heptanes in asphaltene titration under
stock tank condition is available. This is an alternative way to tune the
asphaltene model parameters. The command format is:
match asphaltene titration x_1;
The value x_1 is the mass fraction of heptanes required to
precipitate asphaltenes from oils.

95
PVT table files

Pipesim PVT files

Pipesim is a general purpose simulator for modelling fluid flow in oil
and gas wells, flowlines and pipeline systems. It is a product of Baker
Jardine & Associates Ltd.
Multiflash can produce a PVT data file for use by Pipesim. The file
contains all the physical property information required by Pipesim. It
consists of a series of flash calculations on a grid of pressure and
temperature values. The information stored includes the stream
composition and for each grid point: liquid volume fraction, watercut
volume fraction, liquid density, gas density, gas compressibility
factor, gas molecular weight, liquid viscosity, total enthalpy, total
entropy, liquid heat capacity, gas heat capacity and liquid surface ten-
sion. For a complete definition of PVT files see the Pipesim
documentation.
Before generating a PVT file it is necessary to define the components,
compositions, models and phase descriptors. Note that models for
viscosity and surface tension must be defined in addition to the usual
thermodynamic models.
The command to store information needed to generate a PVT file is:
TABLE PIPESIM file_name
PRESSURES pressure_list;
TEMPERATURES temperature_list;
TITLE “title_text” ;
where:
file_name is the name of the PVT file to be written. The
usual file extension is ‘.pvt’. If a file name has been entered
previously then entering * means that it should be reused.
Pressure_list is a list of pressure values at which
properties will be generated. Note that a ; is needed to end
the list.
Temperature_list is a list of temperature values at which
properties will be generated. Note that a ; is needed to end
the list.
Title_text is the title that is written to the PVT file. It is
optional. If present, it should be enclosed in quotation
marks. No end marker is needed, but

96
 A final end marker ; is necessary to terminate the complete
TABLE command.
For example:
TABLE PIPESIM pipe5.pvt
PRESSURES 1e5, 5e5 10e5;
TEMPERATURES 350 400 450;
TITLE “Riser simulation”;

OLGA table generator

Olga is a general purpose transient simulator for modelling fluid flow
in flowlines and pipeline systems. It is a product of Scandpower A/S.
Multiflash version 3.4 onwards can produce a PVT data file for use by
Olga. The command to store information needed to generate a PVT
data file is:
table Olga mode “File_name” title "Title_PVTData"
hydratefile “Hydrate_file_name” waxfile
“Wax_file_name” pressures x_1 x_2 x_3 . . .;
temperatures x_1 x_2 x_3 . . .;;
mode is now ignored. It will be set by the GUI.
“File_name”, the file name is used to save the calculated PVT data
from Multiflash which should be quoted by double quotes. It can
include the full path where the file is saved.
"Title_PVTData" is used to specify the title of the data, can be
omitted. If it is specified, it should be quoted by double quotes.
hydratefile is an optional keyword to signal that Multiflash should
write out an Olga hydrate file. It is followed by
“Hydrate_file_name”, the name of the file used to save the hydrate
data. “Hydrate_file_name” should be quoted by double quotes and
can include the full pathname where the file is saved.
waxfile is an optional keyword to signal that Multiflash should
write out an Olga wax file. It is followed by “Wax_file_name”, the
name of the file used to save the wax data. “Wax_file_name” should
be quoted by double quotes and can include the full pathname where
the file is saved.
pressures, followed by the values of pressure at which the physical
properties are calculated.
temperatures, followed by the values of temperature at which the
physical properties are calculated.

Prosper table generator

Prosper is a well performance, design and optimisation program for
modelling the well configurations for the oil and gas industry. It is a
product of the Petroleum Experts.
Multiflash 3.9 can produce a PVT data file for use by Prosper. The
command to store information to generate a PVT data file is:
table prosper “File_name” title "Title_PVTData"
properties PRES GOR OFVF OVIS ODEN OCOM GFVF GVIS
ZFAC GDEN CGR WVIS WCOM; units temperature temp_unit
pressure pres_unit; temperature x_T1 pressure

97
 x_value_p11, x_value_p12, x_value_p13…; temperature
x_T2 pressure x_value_p21, x_value_p22, x_value_p23…;
“File_name”, the file name is used to save the calculated PVT data
from Multiflash which should be quoted by double quotes. It can
include the full path where the file is saved.
"Title_PVTData" is used to specify the title of the data, can be
omitted. If it is specified, it should be quoted by double quotes.
properties is a keyword to signal what properties are required for
the output and should be ended with a semicolon. The maximum
number of the properties in the output is 13 but the number can be
less. For each property a unique keyword should be used and are
listed as follows.

Keywords Description
GOR GOR in unit of scf/sbl
PRES The pressure in unit of psi.
OFVF Oil FVF in unit of RB/sbl
OVIS Oil viscosity in unit of cPoise
ODEN Oil density in unit of lb/ft3
OCOM Oil compressibility in unit of 1/psi
GFVF Gas FVF in unit of ft3/scf.
GVIS Gas viscosity in unit of cPoise.
ZFAC Gas Z factor
GDEN Gas density in unit of lb/ft3.
CGR Reservoir condensate-gas ratio in unit of
bbl/MMscf.
WVIS Water viscosity in unit of cPoise.
WCOM Water compressibility in unit of 1/psi.
Units are used for specifying the units for both temperature and
pressure, followed by a keyword, temperature with a unit,
temp_unit or pressure with a unit, pres_unit. And it should be
ended with a semicolon, ;.
temperatures, followed by the values of temperature at which the
physical properties are calculated.
pressures, followed by the values of pressure at which the physical
properties are calculated, should be finished with a semicolon. For
each isotherm at a temperature, maximum of 15 different pressure
values can be specified.

98
Other commands

The TITLE command

The TITLE command sets a descriptive title. This would typically be
used to record some details or background for the problem
definition stored in a Multiflash command file. The title command
has the following format:
title “title text”;
The title text up to 256 characters is stored by Multiflash and can be
displayed using the show title; command. If the title text is split
over several lines, quotation marks are only needed in the beginning
and the end of text as in the following example.
title “title text line 1
title text line 2
title text line 3”;

Setting Enthalpy and Entropy bases

The enthalpy and entropy can be calculated on different bases. By
default Multiflash will calculate the enthalpy and entropy on the
compound basis (see below for definition). For both properties It is
also possible to use the elements basis and for the entropy the
standard basis.
The following command can be used to set the options required:
Datum enthalpy h_basis entropy s_basis;
where h_basis is the identifier for the enthalpy basis and s_basis
is the identifier for the entropy basis.
basis identifier meaning
compound enthalpy or entropy is set to zero for each
compound in its perfect gas state at 298.15K and
1 bar
elements enthalpy or entropy is set to zero for each
element in its perfect gas state at 298.15K and 1
bar
standard entropy is set to zero for each compound in the
perfect crystal state at 0K

99
 For example, the following command sets the compound basis for
enthalpy and the standard basis for entropy:
Datum enthalpy compound entropy standard;

Commands for changing units

Multiflash uses separate sets of units for entering quantities (input
units) and for displaying results of calculations (output units).
The commands for setting units have the following formats:
UNITS property_name unit_name
INPUTUNITS property_name unit_name
OUTPUTUNITS property_name unit_name
UNITS sets both input and output units for a property. The following
table lists the property and unit name keywords. For some properties,
e.g. thermal conductivity, the keyword recognised by Multiflash is
different from the property name and is given in parentheses.

100
Property Units notes
temperature K
degC
degF
degR
pressure Pa all values absolute except
kPa where indicated
Mpa
bar
barg gauge
atm
atmg gauge
psi
psig gauge
mmHg
inwg inches water gauge
at
atg
amount mol or mole
kmol
kg
g
lbmol
lb
volume or mol/m3
density kg/m3
lb/ft3
lbmol/ft3
mol/cm3
g/cm3
kmol/m3
m3/mol
m3/kg
ft3/lb
ft3/lbmol
cm3/mol
cm3/g
m3/kmol
enthalpy J/mol the calorie unit
internal energy kJ/mol is the thermo-chemical
(internalenergy) MJ/mol calorie defined as 4.184J
Gibbs energy kJ/kg exactly
(gibbs) cal/mol
kcal/mol
kcal/lbmol
BTU/lbmol
cal/g
kcal/lb
BTU/lb
entropy J/mol/K heat capacity units are
heat capacity kJ/kmol/K always the same as the
MJ/mol/K entropy units
GJ/kmol/K
J/kg/K
kJ/kg/K
cal/mol/K
kcal/lbmol/F
BTU/lbmol/F
kcal/lb/F
BTU/lb/F
speed of sound m/s unit setting cannot be
changed
viscosity Pas
cP centiPoise

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 Property Units notes
thermal W/m/K
conductivity kW/m/K
(thcond) kJ/hr/m/K
BTU/hr/ft/F
kcal/hr/ft/F
cal/s/cm/K
kcal/hr/cm/K
mW/cm/K
W/cm/K
mW/m/K
surface tension N/m
mN/m
dyne/cm
Diffusivity m2/s
Coefficients cm2/s

The SET command

The SET command is used to set a number of options that control the
operation of Multiflash. The command has the format:
SET option_name option_setting
The following table gives the valid options and settings:

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option name operation option settings
Amounts displays output compositions as
amounts (moles or mass). See
fractions
Fractions displays output compositions as
moles fractions or mass
fractions. See amounts
Physprops calculation and display of The setting may be made up of a
physical properties of phases numeric value followed by the
following equilibrium characters A, E, F and/or T.
calculation 2 phases present, phase
compositions and amounts
1 the above plus:
volume, enthalpy,
entropy, internal
energy, Gibbs energy, average
molecular weight (default)
2 adds Cp, Cv, speed of sound
A adds activity coefficients
E adds H/S/G/U relative to
elements in standard states
E adds fugacity coefficients
Transport properties
C adds thermal conductivity,
V adds viscosity
S add surface/interfacial tension
Nophysprops equivalent to level 0
Streamtype Set the current stream type for Streamtype_id, the stream type
any flash calculations. identifier previous defined using
streamtype command.

The REMOVE command

The REMOVE command is used to remove or undefine all or part of the
current problem specification. The command has the format:
REMOVE remove_option;
The following table gives the valid options:
option Action
all removes all databanks, components, bipsets,
models, phase descriptors, and input quantities.
The input and output units are redefined to the
initial settings they had following processing of
the mfconfig.dat file.
bipsets removes all defined bipsets
components removes all components and amounts
models removes all models
pds removes all phase descriptors
streamtypes removes all stream types

Other related commands are:

PUREDATA ERASE;
COMPONENTS comp_no ERASE;

103
 PETROFRACS comp_no ERASE;
BIPDATA ERASE;
BIPSET bipset_id ERASE;
MODEL model_id ERASE;
PD pd_id ERASE;
STREAMTYPE streamtype_id ERASE;

The INCLUDE command

The INCLUDE command reads in a file of Multiflash commands and
processes each command. The command has the format:
INCLUDE file_name;
the file_name must be a valid file access string for the computer
system in use. The command may be abbreviated to INC . The default
file extension is .mfl

104
Alphabetical list of selected
commands

105
COMMAND Purpose definition
on page
AMOUNTS specify or change composition 9, 91
BIPDATA specify the source databank for binary interaction 6, 79
parameters.
BIPSET set binary interaction parameters. 79
CHARDATA Specify petroleum fraction correlations. 28,
COMPONENTS specify components. 6, 14
DENSITY set the input volume condition for fixed volume 9, 91
calculations.
DATUM Set the option for calculation of enthalpy and 99
entropy.
ENTHALPY set the input enthalpy condition i.e. for isenthalpic 9, 91
flash.
ENTROPY set the input entropy condition i.e. for isentropic 9, 91
flash.
INCLUDE read in a file of Multiflash commands 5, 104
INHIBITOR add the content of inhibitors (methanol, MEG, DEG, 36
TEG and ethanol), the salt content of aqueous streams
to mixtures.
INPUTUNITS change the input units 10, 99
INTERNALENERGY set the input internal energy condition for 9, 91
calculations at constant internal energy
KEYS define the key component for a phase descriptor 8, 85
MODEL define a model for a thermodynamic or transport 7, 39
property of a mixture.
OUTPUTUNITS change the output units 10, 99
PD set up a phase descriptor for any phase 7, 83
(abbreviation for PHASEDESCRIPTOR)
PETROFRACS define a petroleum fraction pseudocomponent 29
PHASEDESCRIPTOR set up a phase descriptor for any phase c.f. PD 83
PRESSURE set the pressure 9, 91
PUREDATA specify the data source for pure component data for 5, 13
components.
PVTANALYSIS Allows the entry of experimental PVT analysis data to 30,
specify an input stream.
REMOVE removes (part of) the current problem and allows the 10, 103
user to specify a new problem
SALINITY converts the measured salt compositions into an 37
equivalent amount of a salt pseudocomponent or ion
ratios for freezing point depression or hydrate
inhibition calculations.
SET set a configuration option for the program 102
STREAMTYPE Define a stream type 84
TABLE specify a group of calculations 96
TEMPERATURE set the temperature 9, 91
TITLE store descriptive title 99
TOLAMOUNTS specifies component amounts for a second stream for 92
use in a tolerance calculation
UNITS sets both input and output units 10, 99
VOLUME set the input volume condition for fixed volume 9, 91
calculations.
, the comma can be used is used to separate keywords
as an alternative to a space.

106
COMMAND Purpose definition
on page
; the semicolon is the end-of-command marker. It
terminates a command or separates multiple
commands.
# comment character for input files. Any text following
the comments character is disregarded.

107