Heat integration and heat pump intensified extractive distillation for isopropanol-water separation using deep eutectic solvents as entrainer

As a new type of environment-friendly solvent, deep eutectic solvents （DESs） have great potential in extractive distillation. In this study, the separation of isopropanol and water by extractive distillation using DESs （ChCl/TEG, molar ratio was 1∶3） as entrainer was designed and optimized by Aspen Plus. Targeting minimization of total annual cost （TAC）, sequential iterative optimization was applied to key variables including feed stage location, entrainer flow rate, entrainer temperature, number of theoretical stages, and reflux ratio. Compared with the process using traditional solvent ethylene glycol （EG） as entrainer, the proposed process required significantly fewer theoretical stages and lower reflux ratio, reducing TAC by 20.95%. To achieve further energy saving, two processes combined with heat integration and heat pump were established. A comprehensive comparative analysis demonstrated that the heat integration and heat pump intensified extractive distillation process achieves significant reductions of 46.35% in energy consumption, 31.10% in TAC, and 39.33% in exergy loss compared to the conventional process using EG as the solvent. The results indicate that DESs exhibit considerable potential to replace conventional solvents due to their superior economic and environmental benefits.