Comprehensive analysis on the economy and energy demand of pressure-swing distillation and pervaporation for separating waste liquid containing multiple components

A large amount of waste liquids containing methanol/acetone/water mixtures are produced in the synthesis of methyl methacrylate(MMA). Under the advocacy of green chemical industry, it is urgent to develop an efficient, economic and energy-saving mixture separation process. Through thermodynamic azeotropic behavior and pressure sensitivity analysis, pressure-swing distillation was determined and the optimal separation pressure of each column in the process was obtained. Due to the composition of waste liquids produced were quite different in MMA production, the pressure-swing distillation separation process was designed to fully achieve the accurate waste liquids treatment. Taking the total annual cost(TAC) as the target, the sequential iteration method was used to optimize the process, and the impact of composition on economy was compared. In order to further realize the energy-saving of the separation process, the pervaporation membrane module was introduced to pretreat the waste liquid in the pressure-swing distillation. The results showed that the TAC of the coupling process was 46% higher than that of the pressure-swing distillation process, and the thermodynamic efficiency was 30% higher. This study provides waste liquid treatment technology for enterprises and analyzes its economic and energy efficiency, which has reference significance for the development of coupled separation technology.