Design and comparison of energy-saving double column and triple column reactive-extractive hybrid distillation processes for ternary multi-azeotrope dehydration

Complex multi-azeotrope and multi-boundary lead to immense challenges of solvent selection for the separation of the ternary multi-azeotrope system. In principle, integrating reactive distillation (RD) with extractive distillation (ED) is fundamental to achieve higher energy efficiencies and to reduce process expenses and environmental impacts. However, these hybrid distillation processes that can overcome the challenges have not been fully investigated. To this end, this article developed and compared the energy-saving reactive-extractive hybrid distillation processes for purification and recovery of the high-value ethyl acetate and EtOH from the wastewater containing multi-azeotrope. The proposed hybrid distillation processes include triple-column reactive-ED (TCRED), double-column reactive-ED (DCRED). In the hybrid processes, ethylene glycol (EG) and dimethyl sulfoxide (DMSO) are adopted as solvents in the ED, while ethylene oxide is introduced as reactant to perform the hydration reaction in the RD process. These separation schemes are optimized with the objective of the minimum total annual costs (TAC) via genetic algorithm procedure to obtain the optimal design parameters. Subsequently, environmental assessment indicator (CO2 emissions) is also calculated to perform the comprehensive analysis for the presented separation processes. The results demonstrate that the hybrid distillation processes coupled with RD can significantly reduce process costs as well as CO2 emissions compared to the conventional TCED process, especially for the DCRED process. The DCRED scheme with EG as solvent has the lowest TAC and CO2 emissions, with a reduction of 43.29%/35.10% TAC and 38.06%/24.73% CO2 emissions compared with the TCRED configurations with EG or DMSO as solvents, respectively. The major contributions of this work are to facilitate the future development for conceptual design of the hybrid distillation processes containing RD.

Automated summary

This study developed energy-saving reactive-extractive hybrid distillation processes for the purification and recovery of ethyl acetate and EtOH from wastewater containing a multi-azeotrope. Through optimization, the results showed that the hybrid processes significantly reduced process costs and CO2 emissions compared to traditional methods.