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Chemical Process Simulation - ChemCAD
Thermodynamic
Thermodynamic
• Type of solutions/Classification of solution
• Recommendations for selection of thermodynamics model
- Equations of state (Hydrocarbons)
- Activity coefficients model (Chemicals)
- Electrolyte model (Electrolyte)
- Special models
• Workshop
Type of Solutions
IDEAL
Uniform-sized molecules are randomly located.
REGULAR
Different sized molecules are randomly located.
NON-IDEAL (POLAR)
Molecules are segregated by type in very strong
clusters.
ELECTROLYTES
Molecules may ionize in solution.
H H
Cl-
H+
H H
Cl-
H H
H+
H H
Thermodynamic Model Selection
◎ IDEAL Solution
- Vapor Pressure
- Equation of State
◎ REGULAR Solution
- Equation of State
◎ POLAR Solution
- Activity Coefficient Model
◎ ELECTROLYTES Solution
- Electrolytes Model
◎ POLYMER Solution
- Polymer Model
K-Value Options
◎ IDEAL Solution — Pure component
Vapor Pressure
Pure component
◎ REGULAR Solution — Hydrocarbons ---- Equation of State
Soave-Redlich-Kwong
High-moderate P& T’s Hydrocarbon
Chao-Seader
High-moderate P& T’s Hydrocarbon
Peng-Robinson
High-moderate P& T’s Hydrocarbon
API Soave
High-moderate P& T’s Hydrocarbon
Grayson Streed
Moderate P& T’s Hydrocarbon
Maxwell-Bonnell K-Charts
Low Pressure, Heavy Hydrocarbon
K-Value Options
◎ NON-IDEAL (POLAR) Solution — Chemicals
UNIFAC
UNIQUAC
NRTL
Wilson
T. K. Wilson
Hiranuma(HRNM)
Wilson Salt
Margules
Van Laar
Regular Solution
T=275-475K, P=0-4 atm VLE,LLE,Predictive
Highly non-ideal VLE,LLE
Highly non-ideal, VLE,LLE
Highly non-ideal, VLE
Highly non-ideal, VLE,LLE
Highly non-ideal, VLE,LLE
Non-ideal solutions with salts dissolved
Highly non-ideal, VLE,LLE (4 suffix)
Moderately non-ideal
Moderately non-ideal (Predictive)
Modified SRK (4 parameters)
Predictive SRK
Polar compounds in regular solutions
Polar components in non-ideal solutions.
better than UNIFAC at high pressures
EDC, SAFT
K-Value Options
◎ ELECTROLYTES Solution
Amines (MEA, DEA)
Gas sweetening
Sour Water
Acid Gases and NH3 dissolved in H2O
PPAQ
General, but electrolyte system is most common
application (HCl, NH3, HNO3)
Ideal
Pitzer
NRTL for electrolyte 1982
NRTL for electrolyte 1986
K-Value Options
◎ SPECIAL TECHNIQUES
Henry's Law
TSRK
TEG
FLOR
UPLM
ACTX
Polynomials
K Tables
User-Added Subroutine
Gases dissolved in Water
Methanol system; particularly with light gases
Dehydration of hydrocarbon streams using
tri-ethylene-glycol
Flory-Huggins method for polymers
UNIFAC for polymers
User specified activity coefficients
User K's
User K's
User K's
K-Value Options
Hydrocarbons
System
K-model
H-model
Ordinary
SRK
SRK
Cryogenics
PR
Crude
CS, GS
PR
LK
ESSO
LK
SRK
SRK
Vacuum Crude
Power Combustion
Acids, Bases, Electrolytes
Chemicals
Electrolytes Models
SRK, HTSL
Activity Coeff.
Latent Heat
Activity Coefficient Models
Van Laar
Margules
UNIFAC
NRTL
UNIQUAC
Wilson
VLE
Yes
Yes
Yes
Yes
Yes
Yes
LLE
No
Yes
Yes
Yes
Yes
No
Accuracy
Good
Good
Good
Very Good
Very Good
Best
Simplicity
Simple
Simple
Complex
Complex
Complex
Complex
Calculation
Fast
Fast
Slow
Slow
Slow
Slow
BIPs
-
-
-
Need
Need
Need
H-Value Options
K-value
H-value
K-value
H-value
SRK
SRK
VANL
LATE
PR
PR
MARG
LATE
BWRS
BWRS
REGU
SRK
APIS
SRK
AMMI
AMMI
Grayson-Streed
Lee-Kesler
SOUR
SRK
MSRK
SRK
TEG
SRK
PSRK
LATE
TSRK
SRK
ESSO
Lee-Kesler
PPAQ
SRK or LATE
VAP
LATENT
FLOR
LATENT
NRTL
LATENT
UPLM
LATENT
UNIF
LATENT
T.K. Wilson
LATENT
UNIQ
LATENT
Hiranuma(HRNM)
LATENT
WILS
LATENT
ACTX
LATENT
Thermodynamics Wizard
Define components, and set
max. amd min. pressures,
and temperatures, respectively
Bip data threshold : For activity
coeff. Model reference
Start
P< 1 atm
Check Class
No
H=Latent
Chemicals
K=VAP
K=GS
K=ESSO
H=LEEK
H=LEEK
NC=1
No
No
Crude Oil
H=SRK
No
Amine
K=Amine
H-Amine
No
Sour
No
Polymer
No
Electrolytes
No
Chemical
P<200psi
No
Chemical
No
T<100F
No
K=Sour
K=LPLM
K=PPAQ, E-NRTL
Check BIPs
K=PSRK, ESD, SAFT
K=PR
K=SRK
H=Sour
H=Latent
H=SRK
K=NRTL,Wilson,
UNIQ, UNIF
H=Latent
H=PR
H=SRK
HTSL
H=Latent
K Model Selection and Option
H Model Selection and Option
Workshop : Phase Equil. with Fugacity Correction
System:
Methanol/Water, Fugacity correction (Y/N)
Results:
Low pressure(1 atm)
High pressure(30atm)
Comment: Fugacity correction may be important at
relatively high pressure.
1 atm without fugacity correction
1 atm with fugacity correction
30 atm without fugacity correction
30 atm with fugacity correction
Workshop : Vapor Phase Association
System: Acetic Acid/Water, Vapor Phase Association(Y/N)
Results: With Vapor Phase Association and without
Vapor Phase Association
Conclusion: Organic acids in gas phase (forming dimer) needs
vapor phase association
Water and Acetic Acid
No Vapor Phase Association
With Vapor Phase Association