Efficient extractive distillation design for separating binary azeotrope via thermodynamic and dynamic analyses

Efficient and stable separation of ethyl acetate/cyclohexane mixture in an economic way is significant for the pesticide industries. The economy of the extractive distillation (ED) process performs and the pressure-swing distillation (PSD) process was compared based on total annual cost (TAC). Thermodynamic analysis was used to further modify the ED process. Two-stage preheating was applied to improve the energy use efficiency and further reduce the costs. The results show that the TAC of the ED process is lower than that of PSD process by 58.2% and the cost of the two-stage preheating extractive distillation process is 9.3% lower than traditional ED process. To separate the mixture steadily, an improved multi-proportion control structure was developed. The proportion elements change their output signals based on the initial ratios when the input signals change. The improved control structure can separate the components to 99.9 mol%. Both the economy and controllability of the modified process perform well.