Extractive Divided-Wall Column for Organic Recovery from Wastewater: 4E-Safety-Control Assessment

In the synthesis of liquid crystal monomers and the industrial production of norgestrel in the pharmaceutical industry, wastewater containing tetrahydrofuran and ethanol is generated, necessitating the recovery and reuse of these high-value organic compounds. This study identified dimethyl sulfoxide (DMSO) as the entrainer with optimal separation performance and sustainability through phase diagram analysis and ecotoxicity assessment. The mechanism by which DMSO enhances the separation of the ternary azeotrope was investigated via quantum chemical calculations. A three-column extractive distillation (TCED) process and an extractive dividing-wall column (EDWC) process were designed. Using the total annual cost, carbon dioxide emissions, and process route index as objective functions, both processes were optimized separately using the second-generation nondominated sorting genetic algorithm. The results indicate that the EDWC process exhibits a superior performance. The sustainability of the EDWC process was further demonstrated using the Eco-indicator 99 method based on a life cycle assessment. Exergy analysis results show that the exergy loss of the EDWC process is reduced by 25.77% compared with the TCED process. Finally, three control structures were designed for the EDWC process, and subsequent dynamic control performance tests revealed that the model predictive control scheme delivered the best control performance. The main contribution of this work lies in providing a multiscale analysis ranging from intermolecular interactions to process optimization and control, offering valuable insights for the practical industrial application of the EDWC process.