Novel energy-efficient design of side-stream extractive distillation process with intermediate reboiler for separating multi-azeotropic mixture based on multi-objective optimization

Side-stream extractive distillation is extensively employed to separate azeotropic mixtures since its energyefficient benefits. Nevertheless, its economic effect is not always obvious due to the introduction of expensive high-pressure steam. In this article, a conventional triple-column extractive distillation process is firstly researched for separating n-hexane/ethyl acetate/acetonitrile mixture. To effectively decrease the requirement for high-pressure steam and achieve a reduction in economic costs of side-stream extractive distillation, three innovative side-stream extractive distillation processes with intermediate reboiler are proposed. A multiobjective genetic method is applied to optimize the four processes with total annual cost (TAC) and entropy production as two objective functions. Additionally, due to the presence of intermediate reboiler, heat integration design is implemented to the three side-stream extractive distillation processes with intermediate reboiler. Compared to the triple-column extractive distillation process, the heat integration of the three sidestream extractive distillation processes with intermediate reboiler exhibit better performance considering economy, energy-efficient, and entropy production. It indicates that the heat integration of the double sidestream extractive distillation process with intermediate reboiler can reduce 20.10% of TAC, 29.65% of energy consumption, and 35.63% of entropy production, respectively.