Energy-efficient recovery of tetrahydrofuran/n-butanol via pressure-swing and heterogeneous azeotropic distillation: Design, optimization, and comprehensive performance evaluation

The recovery of organic substances from industrial wastewater holds significant importance for environmental governance, efficient resource utilization, and sustainable development. This research proposes a synergistic separation technology combining pressure-swing distillation and heterogeneous azeotropic distillation (PS-HAD) for the recovery of tetrahydrofuran (THF) and n-butanol (BuOH) from multicomponent waste mixtures generated during γ-butyrolactone production. Furthermore, to reduce energy consumption during the separation process, three energy-saving strategies were implemented: heat pump-assisted distillation (HP-PS-HAD), heat integration (HI-PS-HAD), and heat pump-heat integration (HP-HI-PS-HAD). The proposed schemes were comprehensively evaluated in terms of total annual cost (TAC), thermodynamic efficiency (η), CO2 emissions, and total energy consumption (TEC). The findings indicate that the enhanced processes can markedly decrease energy usage and improve economic efficiency. The HP-HI-PS-HAD process exhibits the best performance, achieving a 31.84 % reduction in TAC, a 52.38 % decrease in CO2 emissions, a 46.25 % reduction in TEC, and a 44.74 % improvement in thermodynamic efficiency. Based on this, to further optimize the separation process, the NSGA-II algorithm was employed for multi-objective parameter optimization of the HP-HI-PS-HAD process with the best energy-saving performance. This optimization achieved a 1.56 % reduction in TEC and a 0.77 % reduction in TAC. This research is of significant guiding importance for the efficient recovery of THF/BuOH in industrial wastewater and the promotion of clean production in the chemical industry.