Effective Control of Vapor Recompression-Assisted Dividing Wall Column with a Middle Partition

Vapor recompression-assisted dividing wall columns (VRC-DWCs) with a middle partition have been shown to have a higher energy efficiency compared to conventional DWCs. However, the controllability of this highly integrated process remains as a challenging issue since all of the benefits of a VRC-DWC are reasonable only under good dynamic controllability. Compared to the control of the vapor recompression-assisted dividing wall column with an upper or a lower partition, the control for this kind of process is more difficult since it has less degree of freedom. Hence, this paper develops three novel and effective control structures for VRCDWCs with upper middle, lower middle, and center middle partitions, respectively. In the proposed control structures, the compressor work is selected to control the main column's bottom purity and the flowrate of vaporized bottom liquid is selected to control the temperature of the outlet compressed vapor. The dynamic simulation results for three separation cases reveal that the disturbances in feed flowrate and compositions quite well with fairly small integral absolute error proposed structures can handle (IAE) values. This work provides novel control strategy of the VRC-assisted DWC processes and offers a choice for the energy-efficient distillation applications from the standpoint of dynamic controllabilities.