Energy and Economic Evaluation of Wall Placement for Divided Wall Distillation Columns

Abstract

Divided wall columns (DWC) implemented as a form of process intensification for conventional distillation configurations for azeotropic systems normally use an entrainer for breaking the azeotrope. By contrast, this study uses water/isopropanol/acetone as a model chemical system with the goal of having a water/isopropanol azeotropic composition as one of the products. The direct conventional and indirect conventional sequences and middle wall DWC, top wall DWC, and bottom wall DWC were investigated by Aspen Plus simulations, which allowed for product composition, economic, and energy usage comparison between the distillation configurations. The effect of wall placement on economics and energy usage was evaluated for the model chemical system. All of the distillation configurations produced the same product compositions with the middle wall DWC having the lowest associated economic and energy cost. The middle wall DWC had at least 8% fixed capital investment and 14% energy savings compared to the conventional sequences. The location of the dividing wall affected the economic and energy costs, with the middle wall DWC still having the lowest associated costs.