Fenomenos de transporte

Chapter 7

7

Physical Property Methods
Choosing the appropriate property method is often the key decision in determining the accuracy of your simulation results. This chapter provides guidelines for choosing appropriate property methods and models including:  What is a property method  Available property methods  Choosing a property method  Creating new property methods Specifying the global property method  Specifying a property method for a flowsheet section  Specifying a local property method  Defining supercritical components  Specifying properties for the free-water phase  Special method for K-value of water in the organic phase  Specifying electrolyte calculations  Modifying property methods  Property methods for nonconventional components

WhatIs a Property Method?
A property method is a collection of methods and models that Aspen Plus uses to compute thermodynamic and transport properties.

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Physical Property
Methods

The thermodynamic properties are:  Fugacity coefficient (K-values)  Enthalpy  Entropy  Gibbs free energy  Volume The transport properties are:  Viscosity Thermal conductivity  Diffusion coefficient  Surface tension Aspen Plus includes a large number of built-in property methods that are sufficient for most applications. However, you can create new property methods to suit your simulation needs.

Available Property Methods
You must select one or more Property Methods to model the properties of specific systems in your flowsheet. Eachproperty method has a unique approach to representing K-values. The following tables list all of the property methods available in Aspen Plus. You can modify these existing methods or create new methods. For more information, see Modifying Property Methods on page 7-18.

Property Methods
Ideal Property Methods

Ideal Property Method
IDEAL

K-Value Method

Ideal Gas/Raoult's law/Henry's lawRelease 8 version of Ideal Gas/Raoult's law

SYSOP0

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Equation-of-State Property Methods

Equation-of-State Property Method

K-Value Method

BWR-LS
LK-PLOCK

BWR Lee-Starling Lee-Kesler-Plöcker Peng-Robinson Peng-Robinson
with Boston-Mathias alpha function

PENG-ROB PR-BM PRWS
PRMHV2

Peng-Robinson with Wong-Sandler mixingrules Peng-Robinson
with modified Huron-Vidal mixing rules

PSRK RKSWS
RKSMHV2

Predictive Redlich-Kwong-Soave Redlich-Kwong-Soave with Wong-Sandler mixing rules Redlich-Kwong-Soave
with modified Huron-Vidal mixing rules

RK-ASPEN RK-SOAVE
RKS-BM

Redlich-Kwong-ASPEN

Redlich-Kwong-Soave Redlich-Kwong-Soave
with Boston-Mathias alpha function

SR-POLAR

Schwartzentruber-RenonActivity Coefficient Property Methods
Activity Coefficient

Liquid Phase Activity
Coefficient Method

Vapor Phase Fugacity
Coefficient Method

Property Method
B-PITZER ELECNRTL ENRTL-HF ENRTL-HG

Bromley-Pitzer Electrolyte NRTL Electrolyte NRTL Electrolyte NRTL

Redlich-Kwong-Soave Redlich-Kwong HF Hexamerization model Redlich-Kwong Ideal gas Hayden-O'Connell NothnagelRedlich-Kwong Ideal gas Redlich-Kwong-Soave Redlich-Kwong-Soave

NRTL
NRTL-HOC NRTL-NTH NRTL-RK

NRTL NRTL NRTL NRTL
NRTL (using dataset 2)

NRTL-2 PITZER
PITZ-HG

Pitzer Pitzer

continued

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Physical Property
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Activity Coefficient

Liquid Phase Activity Coefficient

Vapor Phase Fugacity
Coefficient Method

Property Method
UNIFACUNIF-DMD UNIF-HOC UNIF-LBY UNIF-LL UNIQUAC UNIQ-HOC UNIQ-NTH UNIQ-RK UNIQ-2 VANLAAR VANL-HOC VANL-NTH VANL-RK VANL-2

Method
UNIFAC Dortmund-modified UNIFAC UNIFAC Lyngby-modified UNIFAC UNIFAC for liquid-liquid systems UNIQUAC UNIQUAC UNIQUAC UNIQUAC UNIQUAC (using dataset 2)

Redlich-Kwong Redlich-Kwong-Soave Hayden-O'Connell Ideal gas Redlich-Kwong Ideal gas Hayden-O'Connell Nothnagel...