Presentation on theme: "CHEN 4460 – Process Synthesis, Simulation and Optimization Dr. Mario Richard Eden Department of Chemical Engineering Auburn University Lab Lecture No."— Presentation transcript:
CHEN 4460 – Process Synthesis, Simulation and Optimization Dr. Mario Richard Eden Department 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 ModelsActivity Coefficient Models Limited ability to represent non-ideal liquidsCan represent highly non-ideal liquids Consistent in critical regionInconsistent in critical region Can represent both vapor and liquid phasesCan represent liquid phase only. Gas phase must still be described by an EOS model Parameters extrapolate well with temperatureBinary parameters are highly dependent on temperature
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 NRTL Or Pizer See Figure 2 Polarity R? Real or pseudocomponents P? Pressure E? Electrolytes All Non-polar Figure 1 Peng-Robinson, Redlich-Kwong-Soave Lee-Kesler-Plocker
Example: 1-Propanol/Water Find the best thermodynamic package for 1- Propanol, H 2 O 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-electrolyte See Figure 2 Polarity R? Real or pseudocomponents P? Pressure E? Electrolytes Figure 1
Carlson: 1-Propanol/Water P? ij? LL? (See also Figure 3) P < 10 bar UNIFAC and its extensions Polar Non-electrolytes Yes LL? No WILSON, NRTL, UNIQUAC and their variances LL? Liquid/Liquid P? Pressure ij? Interaction Parameters Available Figure 2