Decision Making Thermodynamic Models ASPEN

Guidelines for Choosing a Property Method The following diagrams show the process for choosing a property method. Note: For a more detailed way of choosing a property method, including consideration of process type, use the Property Method Selection Assistant. Assistant. Non-electrolyte

*

Polar

Electrolyte

ELECNRTL

Real

PENG-ROB, RK-SOAVE, LK-PLOCK, PR-BM, RKS-BM > 1atm

Nonpolar

CHAO-SEA, GRAYSON, BK10 Pseudo & Real

Vacuum

*

BK10, IDEAL

Polarity

Electrolyte

Real or Pseudocomponents

Pressure

See the next figure to continue.

See Also Guidelines for Choosing a Property Method for Polar Non-Electrolyte Systems Guidelines for Choosing an Activity Coefficient Property Method

Guidelines for Choosing a Property Method for Polar Non-Electrolyte Systems Y

NRTL, UNIQUAC, and their variances

Y N

P < 10 bar

Y

WILSON, NRTL, UNIQUAC, and their variances UNIF-LL

N Polar non-electrolyte

N

Y (correlative models) P > 10 bar N (predictive models)

Pressure

UNIFAC, UNIF-LBY, UNIF-DMD SR-POLAR, PRWS, RKSWS, PRMHV2, RKSMHV2

PSRK, RKSMHV2

Liquid-Liquid

Interaction parameters available (in databanks or user-specified)

* See the next figure to continue. See Also Guidelines for Choosing an Activity Coefficient Property Method

Guidelines for Choosing an Activity Coefficient Property Method

Hexamers

WILS-HF

DP?

Y WILSON NRTL UNIQUAC UNIFAC

Dimers

WILS-NTH, WILS-HOC NRTL-NTH, NRTL-HOC UNIQ-NTH, UNIQ-HOC UNIF-HOC

VAP?

N

Vapor phase association

Degrees of polymerization

WILSON, WILS-RK, WILS-LR, WILS-GLR, NRTL, NRTL-RK, NRTL-2 UNIQUAC, UNIQ-RK, UNIQ-2, UNIFAC, UNIF-LL, UNIF-LBY, UNIF-DMD

Using the Property Method Selection Assistant to Choose a Property Method The Property Method Selection Assistant helps you to select the most appropriate property method for modeling your system. To open the Property Method Selection Assistant wizard: 

On the Tools menu, select Property method selection assistant.

– or – 

Click sheet.

next to the Property method field on the Properties | Specifications | Global

The Property Method Selection Assistant wizard guides you step-by-step by enquiring a series of questions about the type of process or component involved in your system. Then it suggests one or more property methods that are most suitable to use with relevant links on each suggested methods.

Links do not function. To access the original, with functioning links, do the following while in Aspen Plus. Help, Contents, Accessing Other Help, click on the Aspen Physical Properties System Help link, in the Contents select Aspen Physical Property System Reference, Physical Property Methods and Models Reference Manual, Chapter 3 Property Model Description, Thermodynamic Property Models, Overview.

Thermodynamic Property Models This section describes the available thermodynamic property models in the Aspen Physical Property System. The following table provides a list of available models, with corresponding Aspen Physical Property System model names. The table provides phase types for which the model can be used and information on use of the model for pure components and mixtures. Aspen Physical Property System thermodynamic property models include classical thermodynamic property models, such as activity coefficient models and equations of state, as well as solids and electrolyte models. The models are grouped according to the type of property they describe. Thermodynamic Property Models Equation-of-State Models Property Model

Model Name(s)

Phase(s) Pure

Mixture

ASME Steam Tables

ESH2O0,ESH2O

VL

X

—

BWR-Lee-Starling

ESBWR0, ESCSTBWR

VL

X

X

Benedict-Webb-Rubin-Starling

ESBWRS, ESBWRS0

VL

X

X

Hayden-O'Connell

ESHOC0,ESHOC

V

X

X

HF equation-of-state

ESHF0, ESHF

V

X

X

Ideal Gas

ESIG

V

X

X

Lee-Kesler

ESLK

VL

—

X

Lee-Kesler-Plöcker

ESLKP0,ESLKP

VL

X

X

NBS/NRC Steam Tables

ESSTEAM0,ESSTEAM

VL

X

—

Nothnagel

ESNTH0,ESNTH

V

X

X

Peng-Robinson

ESPR0, ESPR

VL

X

X

Standard Peng-Robinson

ESPRSTD0,ESPRSTD

VL

X

X

Peng-Robinson-Wong-Sandler

ESPRWS0,ESPRWS

VL

X

X

Peng-Robinson-MHV2

ESPRV20,ESPRV2

VL

X

X

Predictive SRK

ESRKSV10, ESRKSV1

VL

X

X

Redlich-Kwong

ESRK0, ESRK

V

X

X

Redlich-Kwong-Aspen

ESRKA0,ESRKA

VL

X

X

Standard Redlich-Kwong-Soave

ESRKSTD0,ESRKSTD

VL

X

X

Redlich-Kwong-Soave-Boston-Mathias ESRKS0,ESRKS

VL

X

X

Redlich-Kwong-Soave-Wong-Sandler

ESRKSWS0, ESRKSWS

VL

X

X

Redlich-Kwong-Soave-MHV2

ESRKSV20, ESRKSV2

VL

X

X

Schwartzentruber-Renon

ESRKU0,ESRKU

VL

X

X

Soave-Redlich-Kwong

ESSRK, ESSRK0

VL

X

X

VPA/IK-CAPE equation-of-state

ESVPA0, ESVPA

V

X

X

Peng-Robinson Alpha functions

—

VL

X

—

RK-Soave Alpha functions

—

VL

X

—

Huron-Vidal mixing rules

—

VL

—

X

MHV2 mixing rules

—

VL

—

X

PSRK mixing rules

—

VL

—

X

Wong-Sandler mixing rules

—

VL

—

X

Property Model

Model Name

Phase(s) Pure

Mixture

Bromley-Pitzer(Chien-Null)

GMPT2

L

—

X

Chien-Null

GMCHNULL

L

—

X

Constant Activity Coefficient

GMCONS

S

—

X

Electrolyte NRTL

GMELC

L L1 L2

—

X

Ideal Liquid

GMIDL

L

—

X

NRTL(Non-Random-Two-Liquid)

GMRENON

L L1 L2

—

X

Pitzer

GMPT1

L

—

X

Polynomial Activity Coefficient

GMPOLY

S

—

X

Redlich-Kister

GMREDKIS

LS

—

X

Scatchard-Hildebrand

GMXSH

L

—

X

Three-Suffix Margules

GMMARGUL

LS

—

X

UNIFAC

GMUFAC

L L1 L2

—

X

UNIFAC (Lyngby modified)

GMUFLBY

L L1 L2

—

X

UNIFAC (Dortmund modified)

GMUFDMD

L L1 L2

—

X

UNIQUAC

GMUQUAC

L L1 L2

—

X

van Laar

GMVLAAR

L

—

X

Wagner interaction parameter

GMWIP

S

—

X

Wilson

GMWILSON

L

—

X

Wilson model with liquid molar volume

GMWSNVOL

L

—

X

Activity Coefficient Models

Vapor Pressure and Liquid Fugacity Models Property Model

Model Name

Phase(s) Pure

Mixture

Extended Antoine/Wagner

PL0XANT

L L1 L2

X

—

Chao-Seader

PHL0CS

L

X

—

Grayson-Streed

PHL0GS

L

X

—

Kent-Eisenberg

ESAMIN

L

—

X

Maxwell-Bonnell

PL0MXBN

L L1 L2

X

—

Solid Antoine

PS0ANT

S

X

—

Property Model

Model Name

Phase(s) Pure

Mixture

Watson / DIPPR / IK-CAPE

DHVLWTSN

L

X

—

Clausius-Clapeyron Equation

DHVLWTSN

L

X

—

Heat of Vaporization Models

Molar Volume and Density Models Property Model

Model Name

Phase(s) Pure

Mixture

API Liquid Volume

VL2API

L

—

X

Brelvi-O'Connell

VL1BROC

L

—

X

Clarke Aqueous Electrolyte Volume

VAQCLK

L

—

X

Costald Liquid Volume

VL0CTD,VL2CTD

L

X

X

Debije-Hückel Volume

VAQDH

L

—

X

Rackett / DIPPR / IK-CAPE Liquid Volume

VL0RKT,VL2RKT

L

X

—

Rackett Mixture Liquid Volume

VL2RKT

L

X

X

Modified Rackett

VL2MRK

L

X

X

Solids Volume Polynomial

VS0POLY

S

X

—

Property Model

Model Name

Phase(s) Pure

Mixture

Aqueous Infinite Dilution Heat Capacity Polynomial

—

L

—

X

Criss-Cobble Aqueous Infinite Dilution Ionic Heat Capacity

—

L

—

X

DIPPR / IK-CAPE Liquid Heat Capacity HL0DIP

L

X

—

Ideal Gas Heat Capacity / DIPPR

—

V

X

X

Solids Heat Capacity Polynomial

HS0POLY

S

X

—

Property Model

Model Name

Phase(s) Pure

Mixture

Henry's constant

HENRY1

L

—

X

Water solubility

—

L

—

X

Property Model

Model Name

Phase(s) Pure

Mixture

Cavett Liquid Enthalpy Departure

DHL0CVT, DHL2CVT

L

X

X

BARIN Equations for Gibbs Energy, Enthalpy, Entropy and Heat Capacity

—

SLV

X

—

Electrolyte NRTL Enthalpy

HAQELC, HMXELC

L

—

X

Electrolyte NRTL Gibbs Energy

GAQELC, GMXELC

L

—

X

Liquid Enthalpy from Liquid Heat Capacity Correlation

DHL0DIP

L

X

X

Enthalpies Based on Different Reference Status

DHL0HREF

LV

X

X

Heat Capacity Models

Solubility Correlation Models

Other Models

Recommended Property Methods for Different Applications See the following topics to see a table showing the recommended property methods for a simulation of that type. Oil and gas production Refinery Gas processing Petrochemicals Chemicals Coal processing Power generation Synthetic fuel Environmental Water and steam Mineral and metallurgical processes

Gas Processing Application

Recommended Property Methods

Hydrocarbon separations Demethanizer C3-splitter

PR-BM, RKS-BM, PENG-ROB, RK-SOAVE

Cryogenic gas processing Air separation

PR-BM, RKS-BM, PENG-ROB, RK-SOAVE

Gas dehydration with glycols

PRWS, RKSWS, PRMHV2, RKSMHV2, PSRK, SR-POLAR

Acid gas absorption with Methanol (RECTISOL) NMP (PURISOL)


Acid gas absorption with Water Ammonia Amines Amines + methanol (AMISOL) Caustic Lime Hot carbonate

ELECNRTL

Claus process


Petrochemicals Application


Ethylene plant Primary fractionator

CHAO-SEA, GRAYSON

Light hydrocarbons Separation train Quench tower

PENG-ROB, RK-SOAVE

Aromatics BTX extraction

WILSON, NRTL, UNIQUAC and their variances

Substituted hydrocarbons VCM plant Acrylonitrile plant

PENG-ROB, RK-SOAVE

Ether production MTBE, ETBE, TAME


Ethylbenzene and styrene plants

PENG-ROB, RK-SOAVE –or– WILSON, NRTL, UNIQUAC and their variances

Terephthalic acid

WILSON, NRTL, UNIQUAC and their variances (with dimerization in acetic acid section)

See Guidelines for Choosing a Property Method for Polar Non-Electrolyte Systems to see diagrams for recommendations based on pressure and vapor phase association.

Chemicals Application


Azeotropic separations Alcohol separation


Carboxylic acids Acetic acid plant

WILS-HOC, NRTL-HOC, UNIQ-HOC

Phenol plant


Liquid phase reactions Esterification


Ammonia plant

PENG-ROB, RK-SOAVE

Fluorochemicals

WILS-HF

Inorganic Chemicals Caustic Acids Phosphoric acid Sulphuric acid Nitric acid Hydrochloric acid

ELECNRTL

Hydrofluoric acid

ENRTL-HF

See Guidelines for Choosing a Property Method to see recommendations based on pressure and vapor phase association.

Parameter Requirements for Thermodynamic Reference State The reference state for thermodynamic properties is the constituent elements in an ideal gas state at 298.15 K and 1 atm. To calculate enthalpies, entropies, and Gibbs free energies, Aspen Plus uses: 

Ideal gas heat of formation (DHFORM)



Ideal gas Gibbs free energy of formation (DGFORM)

For systems that do not involve chemical reaction, you may allow DHFORM and DGFORM to default to zero. Values of

Must be available for all components

DHFORM

Participating in chemical reactions

DGFORM

Involved in equilibrium reactions modeled by the RGibbs reactor model

See Also Reference State for Conventional Solid Components Reference State for Ionic Species

Decision Making Thermodynamic Models ASPEN

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