Energy-Efficient Mixed-Solvent Extractive Distillation with Bottom-Liquid Flash Heat Pump and Heat Integration Technologies for Separating Methyl Ethyl Ketone/Ethanol/Water Multicomponent Azeotropes

The methyl ethyl ketone (MEK)/ethanol (EtOH)/water (H2O) multicomponent system is characterized by multiple azeotropes, thereby limiting the recovery of high-purity products by conventional distillation. However, separation procedures for this system remain relatively underexplored. In this study, EG/GLY-based conventional extractive distillation (EG/GLY-CED) and an energy-saving intensified configuration are developed and evaluated for separating this multicomponent azeotropic mixture. Relative volatility, σ-profile, electrostatic potential penetration analysis (ESPP), and independent gradient model based on hirshfeld partition analysis (IGMH) are first used to screen the mixed entrainer and elucidate its separation mechanism. Subsequently, three procedures are established: EG-based conventional extractive distillation (EG-CED), EG/GLY-based conventional extractive distillation (EG/GLY-CED), and heat-integrated heat pump-assisted extractive distillation (HI-HPAD). Subsequently, Pareto frontiers are generated using NSGA-II, with total annual cost (TAC), gas emissions, and total energy consumption (TEC) minimized as objective functions, and the optimal solution is identified using TOPSIS. The results show that, compared with EG-CED, EG/GLY-CED reduces TAC, gas emissions, and TEC by 64.23%, 65.30%, and 65.29%, respectively. With the further integration of bottom-liquid flash heat pump and heat integration technologies, TAC, gas emissions, and TEC are reduced by 38.61%, 62.16%, and 59.27%, respectively, relative to EG/GLY-CED. Exergy analysis indicates that although the intensified procedure shows slightly lower thermodynamic efficiency than the conventional mixed-solvent procedure due to the additional compression and heat-exchange equipment, it exhibits the optimal overall economic, environmental, and energy performance. This study demonstrates that the EG/GLY mixed entrainer significantly improves the separation performance of the MEK/EtOH/H2O system.