Optimization of Dividing Wall Distillation Columns

Abstract

The dividing wall distillation column (DWC) is an energy efficient configuration, capable of a high purity tertiary separation within a single column.1 DWC’s are an alternative to the standard two distillation column configuration. A DWC includes additional degrees of freedom, making modeling and optimization more complex than standard distillation columns.1 This study compiles results from previous DWC pilot columns into a process simulation to validate the method. Three pilot DWC columns were studied - the results of the three DWC column configurations (one four-product DWC and two three-product DWCs) were reconstructed using Aspen PlusTM and the product streams from the resulting simulations were compared to those provided in the authors’ papers.10-12 Each model is optimized using HEEDS®, a multidisciplinary optimization software that tests hundreds of design cases and analyze their results. From a base case simulation, the optimization software varied the DWC design parameters (number of stages, feed location, reboiler duty, etc.) across a specified range. Using the SHERPA optimization method, the objective function of HEEDS® was set to minimize/maximize the key process parameters used to design a DWC. From the simulations, the “best” design is determined, heat transfer is implemented, and a scale-up for each optimized design is conducted. HEEDS® in combination with Aspen PlusTM forms a powerful and efficient tool for the optimization of DWC simulations and designs and the reduction in time and simple user interface allows for many opportunities to test the various complicated design characteristics of the DWC.