Design and Control of Distillation System for Methylal/Methanol Separation. Part 2: Pressure Swing Distillation with Full Heat Integration

A new method for methylal/methanol separation is presented by using fully heat-integrated pressure swing distillation. Rigorous steady state and dynamic simulations for this neat operation are implemented on commercial simulators (Aspen Plus and Aspen Dynamics). On the basis of the proposed partial optimization and global economical optimization, an optimized configuration for this fully heat-integrated pressure swing distillation is developed. From the simulation results, it is found that this process is more competitive than the one via extractive distillation from the economical view. Several control structures for this system are presented. The dynamic simulation results reveal that the proposed basic control structure is unable to maintain the two bottom products at their quality specification. This problem can be resolved by using a pressure-compensated temperature control scheme. The dynamic responses of this pressure-compensated temperature control show that this control structure works pretty well for this fully heat-integrated pressure swing distillation, even for large feed flow rate and composition disturbances. Contrast between the dynamic controllabilities of extractive distillation process and pressure swing distillation process is also made. Results show that the dynamic performances of the two alternative processes are somewhat similar.