Optimal Design and Multicriteria Comparison of Extractive Distillation Processes for Separating of a Quaternary Low-Boiling Solvent Mixture

Abstract

This article mainly explores the eco-efficient separation of a quaternary mixture of methanol, n-hexane, ethyl acetate and ethanol from a pharmaceutical enterprise via extractive distillation, in which the removal of five binary azeotropes is involved. To this end, two candidate entrainers, aniline (AN) and ethylene glycol (EG) are selected through analyzing the influence of adding extractant on the volatility curve. The optimal conventional processes with AN and EG (AN-CED and EG-CED) are developed by minimization of total annual costs (TAC) using simulated annealing algorithm. The side-stream extractive distillation process with AN (AN-SSED) and the dividing-wall extractive distillation process with EG (EG-EDWC) are also proposed to reduce total operating cost (TOC) and total capital cost (TCC). Finally, the proposed four processes are compared in multiple criteria. The results show that the AN-SSED process is the best among all processes from the aspects of economy, CO2 emissions and inherent safety. The EG-EDWC process is also able to reduce TAC and CO2 emissions compared to the two conventional processes, but is the worst in terms of intrinsic safety.

Keywords: Side-stream extractive distillation, Extractive dividing-wall column, Optimal design, Multicriteria comparison, Low-boiling solvent azeotropes