Analysis and intensification of energy saving process for separation of azeotrope by ionic liquid extractive distillation based on molecular dynamics simulation

N-heptane and ethyl acetate are important solvents for chemical intermediates such as hexanitrohexaazaisowurtzitane. Based on molecular dynamics simulation, the interaction between mixed extractant and azeotrope was discussed through microscopic mechanism, and the optimal mixing ratio was determined. Based on the process, the influence of different ratio on the separation effect was further verified. It is found that the increase of the proportion of organic solvents can effectively promote the interaction between ionic liquids and esters. In addition, the separation processes of common distillation, extractive dividing wall column distillation and vapor recompression assisted extractive distillation were studied. Based on the sequential iterative algorithm, the process was optimized with the minimum annual total cost as the objective function, and the economy of vapor recompression assisted extractive distillation with mixed entrainers was the best. Compared with traditional organic solvent extractive distillation, the annual total cost can be reduced by 10.81%. According to the optimization results, the economic performance of carbon dioxide, nitrogen oxides and sulfur dioxide emissions was calculated. Through calculation, the technology of vapor recompression assisted extractive distillation with mixed entrainer is significantly better than other processes, and the gas emission can be reduced by 21.03%. In conclusion, the use of mixed entrainer in extractive distillation process can greatly improve the energy-saving effect than a single entrainer. This provides some guidance for industrial separation of other azeotropes.