Design and Control of Distillation System for Methylal/Methanol Separation. Part 1: Extractive Distillation Using DMF as an Entrainer

A method for methylal/methanol separation using extractive distillation with N,N-dixnethylformamide as an entrainer is presented. Rigorous steady state and dynamic simulations for this process are implemented on commercial simulators (Aspen Plus and Aspen Dynamics). On the basis of global economic optimization, a design with optimized operation conditions for this process is developed. For dynamic simulations, feed flow rate and feed composition disturbances are used to evaluate the dynamic performance of several control structures. The dynamic simulation results reveal that the control structure with fixed reflux ratio can handle all disturbances well, except one kind of composition disturbance. An improved control structure with R/F (the reflux flow rate/the feed flow rate) ratio scheme is used to maintain the two products' purity requirements. Dynamic simulation results reveal that this control structure can handle feed flow rate and composition disturbances quite effective.