Dual-objective optimization and energy efficiency enhancement of natural decantation assisted extractive distillation process for n-butanol/isobutanol/water separation

Abstract

Isobutanol (i-BuOH) and n-butanol (n-BuOH) are widely used as solvents and organic raw materials in fine chemical and pharmaceutical fields. Hence the recovery of high-purity products from chemical industrial effluent containing i-BuOH and n-BuOH is of great significance to improve economic and environmental benefits. In this article, two extractive distillation processes with or without natural decantation are developed with 1,4-butanediol as entrainer, namely CED and NDED. In order to obtain the optimal process parameters under the trade-off between economic and environmental benefits, the two processes are optimized with total annual cost (TAC) and CO2 emissions as objective functions by a non-sorting genetic algorithm. Further, a heat integrated extractive distillation process with natural decantation and vapor recompressed heat pump is designed and investigated, namely HI-NDED-VRHP. Finally, a fair multi-criteria evaluation is conducted on all three optimal processes in terms of TAC, CO2 emissions, and total energy consumption (TEC). The results show that the HI-NDED-VRHP process is highly eco-efficient, which can reduce TAC by 18.9%, CO2 emissions 44.2% and TEC 44.7% than the CED process and decrease TAC by 12.4%, CO2 emissions 36.7% and TEC 37.1% than the NDED process.