Effects And Applications Of Thermodynamic Model Parameters For The Phase Behavior Prediction Of Some Binary Azeotropes Containing Lower Alcohols

The chemical process simulation based on the thermodynamic model can calculate the basic performance and equipment costs of the distillation process theoretically,but the calculation results are strongly dependent on the selected thermodynamic model and parameters.In this paper,we take the example of the lower alcohol binary azeotrope systems as example to study the effects of different thermodynamic models and the same model with different parameters on the azeotrope phase behavior.Accurate simulation and high-efficiency separation of binary azeotrope containing lower alcohols can be achieved based on the aspects of vapor-liquid equilibrium experiments,data regression,thermodynamic model selection,and design of separation schemes.Taking n-propanol and water as the research object,the experimental data were fitted with the data predicted by the thermodynamic model parameters built-in Aspen plus,which proved that the built-in parameters cannot predict the phase behavior of the mixture correctly.The isostatic data included in the NIST-TDE database,which could pass the thermodynamic consistency test,were regressed by different thermodynamic models to get the parameters.The parameters with the smallest deviation between the predicted and experimental data were brought into the extractive distillation simulation for n-propanol and water.N-methyl-2-pyrrolidone(NMP)and ethylene glycol were used as solvents to implement the separation,and the processes using built-in and regressed binary interaction parameters were compared to illustrate the effect of accurate model parameters.The economic deviation between the regression and built-in parameters is more than 10%,which indicates that the same thermodynamic model with different parameters have a great influence on the azeotrope phase behavior and distillation design.Isobutanol and benzene binary system were used to study the effect of different parameters for different and same models on the prediction applicability of azeotrope phase behavior and the influence of distillation design.The vapor-liquid equilibrium data of isobutanol-benzene was measured by the vapor-phase condensation cycle method.The experimental data in this paper and experimental data under different pressures were regressed by different thermodynamic models,respectively.The most accurate models and parameters under different pressures were selected by fitting with the experimental data.The results show that the mixture was non-azeotropic below 0.64 atm,and the most accurate model is the Wilson based on the atmospheric pressure data regression.And the mixture is a minimum azeotrope at 1 to 3.4 atm,and the most accurate model is the UNIQUAC based on high pressure data regression.On the basis of the special phase behavior,different models and parameters were selected in different pressure zones to achieve accurate calculation of different distillation processes.For binary azeotropes containing lower alcohols,the different parameters for different and same models have a great influence on prediction of phase behavior and the design of distillation.Therefore,the selected thermodynamic model parameters must be able to predict the phase behavior of the separation system accurately within the operating parameters of the distillation design.In other words,the applicability of the thermodynamic model to the various operating parameters for the distillation colums must be considered in the process design,especially the pressure applicability.