Insight into controllability and operation of extractive dividing-wall column

Abstract

The extractive dividing-wall column (E-DWC) as process intensification can achieve more sustainable chemical process with economic and safe performance. However, the operation and controllability are in question and are biggest obstacle to the industrialization of extractive dividing-wall column. The coupling effect of E-DWC improves the thermal efficiency significantly but loses one control freedom and enhance interaction behavior compared with the conventional process. In this paper, we investigate the interaction behavior in E-DWC and illuminate the necessary of the extra control freedom to address the interaction behavior although the number of control freedom degrees are just enough for holding purity specification of three products.To solve the coupling effect and interaction behavior, in this paper, the intermediate heating is used to add one control freedom to change the vapor split through directly increasing the flowrate of vapor. We use two systems-acetone and methanol, and bioethanol dehydration as cases to explore the controllability and operation of E-DWC. The results of dynamic simulation prove that the interaction behavior and coupling effect indeed cause poor controllability of E-DWC. Moreover, the intermediate heating strategy indeed is valid and can improve controllability of E-DWC significantly. The integral of squared error and deviation of product purity are reduced significantly both for two cases. Especially for acetone and methanol, the setting time and integral of squared error in the presence of +20% composition disturbance is reduced significantly.