Optimization of Pressure-Swing Batch Distillation with and without Heat Integration for Separating Dichloromethane/Methanol Azeotrope Based on Minimum Total Annual Cost

Pressure-swing batch distillation was investigated to separate the binary azeotrope of dichloromethane/methanol. Based on the robust control of a composition flow rate cascade control structure, minimum total annual cost, instead of conventional energy consumption, was studied to optimize the process. Different cooling mediums of cooling water and refrigerated water were applied and compared based on a 323 K reflux-drum criterion. Heat integration was also studied to realize further reduction of total annual cost. The results show that the difference of the costs is small when the lower-pressure column was operated at 1 and 1.6 atm. However, heat integration reduces the cost by 11.3% and shows advantage in energy consumption, which is 53.8% lower than that of the process without heat integration.