Process simulation of a pressure-swing distillation-heat pump for the separation of dimethyl carbonate/methanol azeotropes

The separation of dimethyl carbonate/methanol azeotropes using traditional pressure-swing distillation suffers from the problem of high energy consumption. Aspen Plus software was used to simulate the conventional heat integration process of the pressure-swing distillation process, the coupling process of intermediate reboiler heat pump distillation and conventional heat integration, conventional heat pump distillation, and the coupling process of conventional heat pump distillation and intermediate reboiler. The improvements resulting from different processes were evaluated with the total annual cost (TAC) and carbon dioxide emissions as indicators. The results show that when the depreciation period of the equipment is three years, the heat-integrated coupling process with an intermediate reboiler added to the 16th plate affords the most economic benefits, and the TAC is 22.73×10⁶ yuan/a, which is 43.06% lower than that of the original pressure-swing distillation process. When the depreciation period of the equipment is five years, the coupling of two-stage compression conventional heat pump distillation and an intermediate reboiler has the best economic benefit. The TAC is 21.02×10⁶ yuan/a, which is 47.34% lower than that of the original pressure-swing distillation process. The carbon dioxide emission is 3.01 t/h, which is 76.13% lower than that of the original pressure-swing distillation process. When the equipment depreciation period is eight years, the TAC of the coupling of two-stage compression conventional heat pump distillation and an intermediate reboiler is the smallest (17.50×10⁶ yuan/a), which is 56.16% lower than that of the original pressure-swing distillation process.