CHEN 4460 – Process Synthesis, Simulation and Optimization

Dr. Mario Richard EdenDepartment of Chemical Engineering

Auburn University

Lab Lecture No. 4 – Selection of Property Models

October 2, 2012

Contains Material Developed by Dr. Daniel R. Lewin, Technion, Israel

Choosing Property Models

Importance of Selection

• Correct predictions of physical properties of the mixture as function of temperature and pressure.

• Each method is suitable only for particular types of components and limited to certain operating conditions.

• Choosing the wrong method may lead to incorrect simulation results.

• Particularly important for reliable computations associated with separation operations (distillation, LL extraction, etc.).

Principal Selection Steps

Choosing the most suitable model/thermo method.

Comparing the obtained predictions with data from the literature.

Adding estimates for components not available in the chosen thermo package. Can they be neglected?

Generation of lab data if necessary to check the thermo model.

Sources of Information

• Publications and professional literature that deal with the process in question or with the components that participate in the process.

• Simulator reference manual (HELP).

• DATABANKS

• Rules of thumb.

Types of Models

EOS Models Activity Coefficient ModelsLimited ability to represent non-ideal liquids Can represent highly non-ideal liquids

Consistent in critical region Inconsistent in critical region

Can represent both vapor and liquid phases Can represent liquid phase only. Gas phase must still be described by an EOS model

Parameters extrapolate well with temperature Binary parameters are highly dependent on temperature

Do you have any POLARcomponents in your system?

NO YES

YESUse EOS ModelAre the operating conditions

near the CRITICAL region of themixture?

Do you have LIGHT gases orSUPERCRITICAL components

in your system?

NO

NO YES

Use Activity CoefficientModel

Use Activity CoefficientModel with Henry’s law

Recommendations

• Eric Carlson, “Don’t gamble with physical properties for simulations,” Chem. Eng. Prog. October 1996, 35-46.

• Prof J.D. (Bob) Seader, University of Utah

• Aspentech Recommendations

Eric Carlson

E?

R?

P?

Polar

Real

Electrolyte

Pseudo & Real

Vacuum

Non-electrolyte

Braun K-10 or ideal

Chao-Seader,Grayson-Streed or Braun K-10

Electrolyte NRTLOr Pizer

See Figure 2

Polarity

R?Real or pseudocomponents

P? Pressure

E? Electrolytes

All Non-polar

Figure 1

Peng-Robinson,Redlich-Kwong-SoaveLee-Kesler-Plocker

Eric Carlson

P?

ij?

ij ?

LL?

(See alsoFigure 3)

P < 10 bar

(See alsoFigure 3)

P < 10 bar

P > 10 barP > 10 bar

PSRKPR or SRK with MHV2

Schwartentruber-RenonPR or SRK with WSPR or SRK with MHV2

UNI FAC and itsextensions

UNI FAC LLE

PolarNon-electrolytesPolarNon-electrolytes

NoNo

YesYes

YesYes

LL?NoNo

NoNo

YesYes

YesYes

NoNo

WI LSON, NRTL,UNI QUAC and their variances

NRTL, UNI QUACand their variances

LL? Liquid/ Liquid

P? Pressure

ij ? I nteraction ParametersAvailable

Figure 2

VAP?

DP?YesYes

NoNoWilson, NRTL,UNI QUAC, or UNI FAC* with ideal Gas or RK EOS

Wilson NRTLUNI QUACUNI FAC

Wilson NRTLUNI QUACUNI FAC

HexamersHexamers

DimersDimersWilson, NRTL, UNI QUAC,UNI FAC with Hayden O’Connellor Northnagel EOS

Wilson, NRTL, UNI QUAC,or UNI FAC with special EOS f or Hexamers

VAP? Vapor Phase Association

Degrees of PolymerizatiomDP?UNI FAC* and its Extensions

Eric Carlson

Figure 3

Bob Seader

LG?

E?

PC?

HC?

YesYes

YesYes

NoNo

YesYes

See Figure 5

Special: e.g., Sour Water (NH3, CO2, H2S, H2O)Aqueous amine solution with CO2 and H2S

PC?

NoNo

Modifi ed NRTL

NoNo

NoNo

PSRKYesYes

NoNoSee Figure 5

See Figure 6

HC? Hydrocarbons

LG? Light gases

PC? Organic Polar Compound

E? Electrolyte

YesYes

Bob Seader

Figure 4

Bob Seader

Figure 5

T?

P?

BP?

Narrow orwideNarrow orwide

PR

LKP

Cryogenic Cryogenic

Non- Cryogenic Non- Cryogenic

Critical Critical

Non-CriticalNon-Critical

SRK, PR

PR, BWRS

Very wideVery wide

HC and/ or LGHC and/ or LG

P? Pressure region

T? Temperature region

BP? Boiling point range of compound

Bob Seader

Figure 6

PPS?

BI P?

AvailableAvailable

UNI FAC

Yes Yes

NoNoWilson

NRTL, UNI QUAC

Not AvailableNot Available

PC with HCPC with HC

PPS? Possible PhaseSplitting

BI P? Binary I nteractionParameters

Aspentech

Example: 1-Propanol/Water

• Find the best thermodynamic package for 1-Propanol , H2O mixture.

• Eric Carlson, “Don’t gamble with physical properties for simulations,” Chem. Eng. Prog. October 1996, 35-46.

• Prof J.D. (Bob) Seader, University of Utah

Carlson: 1-Propanol/Water

E?Polar

Non-electrolyteSee Figure 2

Polarity

R?Real or pseudocomponents

P? Pressure

E? Electrolytes

Figure 1

Carlson: 1-Propanol/Water

P?

ij?

LL?

(See alsoFigure 3)

P < 10 bar

UNIFAC and its extensions

PolarNon-electrolytes

Yes

LL?No

No

No

WILSON, NRTL,UNIQUAC and their variances

LL? Liquid/Liquid

P? Pressure

ij? Interaction Parameters Available

Figure 2

Seader: 1-Propanol/Water

LG?

HC?

Yes

No PC?

See Figure 6

HC? Hydrocarbons

LG? Light gases

PC? Organic Polar Compound

E? Electrolyte

Yes

Figure 4

Seader: 1-Propanol/Water

Figure 6

PPS?

BIP?

Available

UNIFAC

Yes NRTL, UNIQUAC

Not Available

PC with HC

PPS?Possible PhaseSplitting

BIP? Binary Interaction Parameters

Solution: 1-Propanol/Water

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 182

84

86

88

90

92

94

96

98

100

1-Propanol mol. frac.

T [o

C]

TXY diagram f or 1-Propanol, H2O

Perry NRTL PRSV UNIQUAC Van-Laar (Built-inVan-Laar(Perry)