A Modified "inside-out" algorithm for simulation of multistage multicomponent separation processes using the UNIFAC group-contribution method

Abstract

A computational procedure using Boston and Sullivan's "insideout" multistage multicomponent separation algorithm is proposed and implemented in this thesis. The multicomponent systems simulated with this computational procedure were polar systems in which the activity coefficients were calculated using the UNIQUAC model with parameters obtained from the UNIFAC group-contribution method. To improve convergence for multicomponent systems of this type, the "inside-out" procedure was modified by incorporating a local two-parameter liquid-phase compositional-dependence model within the component material balance calculations. The proposed algorithm was implemented in a FORTRAN 77 program and executed on the Honeywell DPS 8/70M computer at the University of Calgary. This program was tested for a wide variety of nonideal systems. The separation process units simulated were distillation columns (including azeotropic and extractive cases), absorption columns and reboiled absorption columns. In general, inclusion of the liquid-phase model resulted in improved convergence for systems in which the original Boston-and- Sullivan method failed to converge.