Reduction of the energy demand and multi-performance evaluation of the pressure-swing and extractive distillation separation of the ethanol/benzene/ cyclohexane azeotropic system

Appropriate process and energy-saving enhancements are crucial for the separation of established systems. The feasibility and separation principle of pressure-swing distillation separation process for ethanol/benzene/cyclohexane azeotropic system were analyzed through residue curve maps, and the pressure-swing distillation process was proposed. Efficient extractants for separating binary azeotropic systems were screened based on relative volatility, and an extractive distillation process was proposed. The non-dominated sorting genetic algorithms-Ⅱ was used to optimize the pressure-swing distillation and extractive distillation process with the goal of achieving the annual minimum TAC and gas emissions. Enhancement strategies such as heat-integrated pressure-swing distillation, vapor recompression assisted extractive distillation, and heat-integrated extractive distillation are proposed based on the process characteristics of pressure-swing distillation and extractive distillation. Finally, a comprehensive evaluation was conducted on the economic, energy-saving, environmental and exergy aspects of the five processes. The results indicate that heat-integrated extractive distillation has the best process performance. Compared with pressure-swing distillation and extractive distillation, TAC decreased by 76.72 % and 22.3 %, energy consumption decreased by 84.22 % and 30.13 %, gas emissions decreased by 84.22 % and 30.13 %, and exergy efficiency increased by 13.21 % and 7.04 %.