Phase Equilibria and Simulation Method for Heterogeneous Azeotropic Distillation

Abstract

This paper discusses how to predict the VLE and VLLE of heterogeneous azeotropic distillations more accurately and proposes a three-phase distillation algorithm. Many studies have been published on the simulation of heterogeneous azeotropic distillations. Their results, however, were highly dependent on the use of phase equilibrium models and distillation calculation algorithms. We investigated the phase equilibrium models and related parameters which were used in published papers and found that their accuracy was not sufficient. To improve the accuracy of VLE and VLLE prediction we propose a combination method in which two sets of NRTL parameters for VLE and LLE are used. Also proposed is a stage-by-stage simulation algorithm for three-phase distillation with the characteristics of rapid and reliable determination of the phase number on each stage and robust convergent stability. The effectiveness of the proposed method and algorithm is illustrated by examples using the ethanol/benzene/water system. © 1993, The Society of Chemical Engineers, Japan. All rights reserved.