Combining the preconcentration column and recovery column for the extractive distillation of ethanol dehydration with low transition temperature mixtures as entrainers

Abstract

Extractive distillation using low transition temperature mixtures (LTTMs) is a promising technology to separate ethanol and water azeotrope. In this work, the separation of water and ethanol by extractive distillation using LTTMs (choline chloride/urea 1:2) as entrainer was designed and simulated in Aspen Plus. Firstly, database of ChCl/urea = 1:2 (Reline) was established in Aspen Plus. Secondly, the simulation and optimization of the conventional extractive distillation process for ethanol dehydration with Reline or ethylene glycol as entrainer were worked out. The results showed that the TAC (total annual cost) of the process with Reline as entrainer was reduce by 14.61% than that of the process with EG as entrainer. In addition, in order to reduce energy consumption in distillation, an energy-efficient extractive distillation process which combining the preconcentration section and entrainer recovery section in one column was developed. The results showed that the proposed process with Reline as entrainer could save 29.48% and 17.42% of TAC compared with the conventional extractive distillation with EG and Reline as entrainer, respectively.