Design and optimization of extractive distillation for separating methyl ethyl ketone/isopropanol/n-heptane ternary azeotropes

In pharmaceutical manufacturing, there is a widespread presence of industrial waste liquids containing methyl ethyl ketone, isopropanol, and n-heptane. This work employs extractive distillation to separate this multi-azeotropic system. Firstly, the conventional extractive distillation process (CED) is designed, and the optimal parameters of the three-objective trade-off are obtained by multi-objective optimization. Then, the side-stream distillation, intermediate reboiler and heat integration enhancement methods are introduced to reduce energy consumption and costs. The results demonstrate that the double side-stream extractive distillation with intermediate reboiler and heat integration process (DSSEDIR-HI) shows the best economic and environmental performance. Compared to the CED process, the total annual cost is reduced by 23.9 %, CO₂ emissions are decreased by 42.5 %, and thermodynamic efficiency is improved by 68.4 %. This study provides a sustainable pathway for the separation of methyl ethyl ketone/isopropanol/n-heptane mixture.