Assessment of Conventional and Intensified Extractive Distillation Processes from Economic, Sustainability, and Inherent Safety Considerations

An analysis of the intensification of homogeneous azeotropic distillation systems based on extractive distillation into dividing wall columns (DWCs) is presented. The effect of the intensification task is combined with the solvent selection for the separation of azeotropic mixtures. The approach is based on a multiobjective optimization model that includes economic, sustainability, and inherent safety components. Four solvents with different properties, namely, dimethyl sulfoxide, cyclohexanol, diethylene glycol, and dimethylformamide, were tested for the separation of a dichloromethane/methanol mixture taken as a case study. It was found that the intensification of extractive distillation into DWCs turned out to be economically adverse under the use of three of the four solvents considered, while inherent safety was favored for two of the four solvents under analysis. It is shown that the economic behavior of intensified units can be related to the boiling temperature of the entrainer. An index for the screening of solvents from inherent safety considerations was also developed. The results from this application showed that diethylene glycol can be rated as the best option for the separation of azeotropic dichloromethane/methanol mixtures from economic and inherent safety components, while dimethylformamide was the best from sustainability considerations.