Energy-Saving Exploration of Mixed Solvent Extractive Distillation Combined with Thermal Coupling or Heat Pump Technology for the Separation of an Azeotrope Containing Low-Carbon Alcohol

Abstract

Ternary extractive distillation (TED) is an effective and sustainable separation process for treating pharmaceutical wastewater containing ethyl acetate/isopropanol/water, corresponding to three binary azeotropes, to realize the recovery of ethyl acetate and isopropanol. Visual Basic software was used to optimize the extractive distillation process using a single solvent and mixed solvent in different proportions based on a sequential iterative optimization method, and the optimal mixture proportion (30% DMSO+70% EG) of the mixed solvent was determined. The economic and environmental performance of the extractive distillation process with a mixed solvent combined with partial thermal coupling technology was studied. The heat recovery within the separation process was further improved by the energy-efficient heat exchanger network synthesis (HENs) option. The economic and environmental performance of the mixed solvent extractive distillation process combined with heat pump technology was also explored. The results show that for the ternary extractive distillation process, the use of mixed solvent can significantly reduce energy consumption, which can lead to lower total annual cost (TAC) and CO2 emission. Compared with a conventional separation process with mixed solvent, the extractive distillation process combined with partial thermal coupling and heat pump technology further improves the economic and environmental performance. The TAC and CO2 emission of the mixed solvent separation process combined with partial thermal coupling technology were reduced by 12.183% and 19.869%, respectively. The TAC and CO2 emission of the mixed solvent separation process combined with heat pump distillation technology were reduced by 34.782% and 37.156%, respectively, which indicates the feasibility of using these two energy-saving processes for continuously updated cleaner production.