Economic, environmental, energy, exergy (4E) and inherent safety analysis of hybrid extractive-heteroazeotropic distillation for sustainable treatment of crude n-butanol waste liquor

Abstract

During the 1,4-butanediol (BDO) production by maleic anhydride direct hydrogenation method, large amounts of crude n-butanol liquor containing a small amount of methanol, tetrahydrofuran, and water is generated. This article proposes four processes based on extractive distillation and heteroazeotropic distillation for the first time, including conventional extractive distillation process with single extractant of ethylene glycol (SCED), conventional extractive distillation process with double extractants of dimethyl sulfoxide and BDO (DCED), and two hybrid extractive-heteroazeotropic distillation processes (CED1-HAD, CED2-HAD). Furthermore, these processes are optimized with total annual costs (TAC) and CO2 emissions as objectives by non-dominated sorting genetic algorithm. Finally, their performance is compared comprehensively through multiple evaluation metrics related to economy, environment, energy, inherent safety and exergy. The results show that among these CED2-HAD is much superior to other three processes except that the safety index is slightly lower than the CED1-HAD process, while SCED has the worst performance. As compared to CED1-HAD, CED2-HAD can reduce TAC by 31.6%, CO2 emissions by 29.6%, total energy consumption (TEC) by 33.0% and exergy loss by 32.4%, and increase PRI by 16.4%. As compared to SCED, DCED can reduce TAC by 33.2%, CO2 emissions by 35.7%, TEC by 37.8% and exergy loss by 35.1%, and increase PRI by 12.7%. Aiming at the problem of efficiently separating complex quaternary mixtures with multiple azeotrope components, this study provides a solid theoretical basis and practical contribution for the effective separation of such mixtures in real-world industry.