Sustainable and efficient-saving process synthesis design for separating methanol-water-toluene via extractive distillation based on multi-objective optimization

Reducing production costs and energy consumption has always been the focus of industrial production today, which is driving the chemical industries from this old model towards developing sustainable processes with high efficiency and environmental protection. In this paper, three energy-saving and environment-friendly extractive distillation processes were designed and optimized to separate the methanol/water/toluene mixture. The extractive distillation process was improved by preheating the feed stream using a solvent circulation stream, the thermal energy utilization efficiency has been enhanced. Meanwhile, the process parameters were optimized by multi-objective genetic algorithm (MOGA) taking total annual cost (TAC), CO2emission (ECO2), and separation efficiency of extractive section (Eext) as objective functions. Compared with the existing process, the best separation process can reduce the TAC by up to 20.0 % and the ECO2by up to 30.0 %. In addition, the validity and rationality of the separation processes were verified by analyzing the influence of sensitive variables and exergy losses. This study provides a reference for the separation and energy saving of wastewater containing methanol and toluene.