Design and optimization for the separation of cyclohexane-isopropanol-water using mixed extractants with thermal integration based on molecular mechanism

Abstract

With the improvement of people's living standards, higher requirements are put forward for food safety, variety and quality. Edible oil is essential in people's life, but the production and processing process will produce a lot of waste, it is necessary to develop efficient and energy-saving treatment technology. Taking the wastewater containing ternary azeotropic system of cyclohexane-isopropanol-water produced in rapeseed oil production as an example, cyclohexane and isopropanol were separated and recovered by extractive distillation. Through the analysis of relative volatility, density functional theory and molecular mechanism, the suitable extractants of DMSO and EG were selected from the perspective of action mechanism. Aiming at the lowest economic cost, optimize the parameters of the process with single solvent and the mixed solvents by sequential iterative method, and further to determine the optimal process parameters and the optimal ratio of mixed extractant. In addition, the effects of single extractant and mixed extractant on the azeotropic system of extractive distillation were compared in terms of thermodynamic efficiency and environmental impact. The results shown that, compared with the single extractant, the extractive distillation process using the mixed extractant can save 30.71% and 16.71%, the thermodynamic efficiency was increased by 24.13% and 16.72%, GWP was reduced by 19.32% and 3.77%, AP was decreased by 19.26% and 3.43%. Combined with thermal integration technology, the economic cost was further reduced by 28.12%, the thermodynamic efficiency was increased by 10.49%, GWP and AP were reduced by 51.72% and 51.78% respectively on the basis of the optimal extractive distillation process with mixed extractants. The results shown that cyclohexane and isopropanol can be effectively recovered from the wastewater produced in rapeseed oil production by using mixed extractant and heat integrated energy-saving technology in extractive distillation process, which is of great significance for food safety, resource saving and environmental protection, and has guiding significance for the separation of other similar azeotropes.