Optimization of EB/SM Distillation Processes Based on Divided Wall Columns in a PO/SM Process with a Chaos Differential Evolution Algorithm

Abstract

As an important chemical raw material, styrene has a high price because of its high energy consumption for separation. This article focuses on the styrene separation unit in a practical propylene oxide/styrene monomer process, and divided wall columns (DWC) are used for process optimization. Four DWC models are evaluated in terms of both economics based on the minimum total annual cost (TAC) and operability based on degrees of freedom. Differential evolutionary (DE) algorithms are used to optimize the parameters for each case study. In the process of finding the minimum TAC, the traditional DE often falls into local solutions and has low efficiency. In order to solve this problem, we propose chaotic sequences in DE algorithms to generate variables with ergodicity, which improves the optimization efficiency. Compared with the conventional process, Wright’s fully thermally coupled DWC (FTC) and Agrawal’s liquid-only transfer DWC (ALT) can save 21.36 and 10.14% TAC, respectively, but ALT has 2 more degrees of freedom than FTC. The FTC has the best economic efficiency, while the ALT strikes a balance between operability and economics.

Energy-Efficient Design Sequences for the Purification of Styrene Monomer from the Pyrolysis Oil of Waste Polystyrene

“…This highlights the need for precise determination of the column pressure based on the desired purity of the SM product. This study assumed a target purity of at least 99.7 wt % for the industrial-grade SM product, , indicating that the column should operate at pressures of 0.45 bar or below.…”