Multicomponent VLE calculations by UNIQUAC and UNIFAC

Abstract

Vapor-liquid equilibrium data is essential and fundamental for design of separation equipment. If available, experimental data are of course the best, but when such data are not available, the engineer has to apply thermodynamic relations to phase equilibrium calculations. In this ,study, since the equations for phase equilibria are complex and require trial and error methods, a computer program was prepared for this purpose. The program uses UNIQOAC and UNIFAC equations for liquid phase nonidea1ity and Peng-Robinson equation for vapor phase nonidea1ity. The program can also perform calculation for systems containing noncondensab1e components at infinite dilution. Totally 1500 data points of thirty-three binary systems and four ternary systems were studied. The results calculated using UNIQt}AC and UNIFAC equations were compared against experimental results. For comparison purposes,the systems were also simulated using Raoult's law. As a result, it is observed that UNIQUAC and UNIFAC equations are in good agreement with experimental data, mostly much better than those by Raoult's law. Also, it can be seen that Peng-Robinson equation gives good results for vapor phase nonideality. Unfortunately, the results for condensable noncondensable systems were not encouraging.