The Research Of A New Activity Coefficient Models Based On Elements And Chemical Bonds

This article described two methods to solve the phase equilibrium problem:the equation of state and activity coefficient method, as well as their advantages and disadvantages, and introduced the group contribution method in detail:its development and the shortages. Through the analysis of the existing problems of the group contribution method, a new activity coefficient prediction model based on elements and chemical bonds was proposed by combining with UNIQUAC and ASOG model.In this paper, based on72binary systems vapor-liquid equilibrium data including alkanes, olefins, aromatics, alcohols and ketones (2702data points), the interaction energy parameters of C, H, O elements as well as C-C, C=C, C-O, C=O, O-H, C-H, benzene ring chemical bond were regressed using the new elements and chemical bonds activity coefficient prediction model.Vapor-liquid equilibrium of10binary systems (167data points) that was not included in data base was predicted by the new model. The average absolute error of vapor composition and the bubble point were0.010,1.48%respectively.The results were compared with existing group contribution method, such as UNIFAC,UNIFAC(Dortmund),UNIFAC(Larsen),ASOG. The results shows that:for the binary system, the predicted results of the new activity coefficient model was better than the original UNIFAC initial model and UNIFAC latest fixesextended, close to UNIFAC (Dortmund), UNIFAC (Larsen) and ASOG model.In order to verify the accuracy of prediction of vapor-liquid equilibrium of multi-system using the new model, vapor-liquid equilibrium of12ternary systems (507data points) was predicted. The average absolute error of vapor composition and the average relative error of the bubble point were0.0162,1.52%respectively. The results were compared with existing group contribution method as well. The result shows that for the ternary system, the activity coefficient model based on elements and chemical bonds was better than the original UNIFAC initial model, close to the others.In summary, the accuracy for the vapor-liquid equilibrium prediction new activity coefficient prediction model based on elements and chemically bonds is good. Compared with the existing group contribution model, the new model has fewer parameters, the group split more convenient, and can provided quantitative estimate of the vapor-liquid equilibrium for the design of chemical process separation unit.