Multi-objective optimisation and energy-saving design of pressure-swing extractive distillation for separating ethanol/acetonitrile/water azeotropic system

Extractive distillation has been widely used in the separation and purification of azeotropes generated in downstream chemical processes. However, the limitations of extractive distillation leave much to be desired in terms of energy savings. In this work, a new pressure-swing extractive distillation (PSED) considering the pressure sensitivity of azeotropes is proposed in separating ethanol/acetonitrile/water system. Special attention is given to the entrainer selection with the surface charge density analysis. The multi-objective optimisation is further facilitated using NSGA-II, including the objectives of capital cost, operating cost, and CO2 emissions. The energy-saving strategy considering the heat pump and heat exchanger network is integrated along with the optimal PSED solution provided by the TOPSIS analysis. Results reveal the proposed energy-efficient process presents a 64.65% decrease in total annual cost, a 65.30% reduction in CO2 emissions and a significant improvement in thermodynamic efficiency, compared with a recent work of pressure-swing distillation.