Chemical Process Simulation - ChemCAD. Thermodynamic

Transcription

1 Chemical Process Simulation - ChemCAD Thermodynamic

2 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

3 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 Cl - H H H+ H H Cl- H+ H H H

4 Thermodynamic Model Selection IDEAL Solution REGULAR Solution POLAR Solution ELECTROLYTES Solution POLYMER Solution - Vapor Pressure - Equation of State - Equation of State - Activity Coefficient Model - Electrolytes Model - Polymer Model

5 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

6 K-Value Options NON-IDEAL (POLAR) Solution Chemicals UNIFAC T= K, P=0-4 atm VLE,LLE,Predictive UNIQUAC Highly non-ideal VLE,LLE NRTL Highly non-ideal, VLE,LLE Wilson Highly non-ideal, VLE T. K. Wilson Highly non-ideal, VLE,LLE Hiranuma(HRNM) Highly non-ideal, VLE,LLE Wilson Salt Non-ideal solutions with salts dissolved Margules Highly non-ideal, VLE,LLE (4 suffix) Van Laar Moderately non-ideal Regular Solution Moderately non-ideal (Predictive) Modified SRK (4 parameters) Predictive SRK EDC, SAFT Polar compounds in regular solutions Polar components in non-ideal solutions. better than UNIFAC at high pressures

7 K-Value Options ELECTROLYTES Solution Amines (MEA, DEA) Sour Water PPAQ Gas sweetening Acid Gases and NH 3 dissolved in H 2 O General, but electrolyte system is most common application (HCl, NH3, HNO3) Ideal Pitzer NRTL for electrolyte 1982 NRTL for electrolyte 1986

8 K-Value Options SPECIAL TECHNIQUES Henry's Law Gases dissolved in Water TSRK Methanol system; particularly with light gases TEG Dehydration of hydrocarbon streams using tri-ethylene-glycol FLOR Flory-Huggins method for polymers UPLM UNIFAC for polymers ACTX User specified activity coefficients Polynomials User K's K Tables User K's User-Added Subroutine User K's

9 K-Value Options System K-model H-model Hydrocarbons Ordinary Cryogenics Crude Vacuum Crude Power Combustion Acids, Bases, Electrolytes Chemicals SRK PR CS, GS ESSO SRK Electrolytes Models Activity Coeff. SRK PR LK LK SRK SRK, HTSL Latent Heat

10 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

11 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

12 Thermodynamics Wizard Define components, and set max. amd min. pressures, and temperatures, respectively Bip data threshold : For activity coeff. Model reference

13 Start Check Class P< 1 atm No H=Latent Chemicals K=VAP NC=1 K=GS K=ESSO No No H=LEEK H=LEEK H=SRK Crude Oil No Amine No K=Amine H-Amine No No No Chemical No No No Sour Polymer Electrolytes Chemical T<100F P<200psi K=Sour K=LPLM K=PPAQ, E-NRTL Check BIPs K=PSRK, ESD, SAFT K=PR K=SRK H=Sour H=Latent H=SRK HTSL K=NRTL,Wilson, UNIQ, UNIF H=Latent H=PR H=SRK H=Latent

14 K Model Selection and Option

15 H Model Selection and Option

16 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.

17 1 atm without fugacity correction 30 atm without fugacity correction 1 atm with fugacity correction 30 atm with fugacity correction

18 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

19 Water and Acetic Acid No Vapor Phase Association With Vapor Phase Association