New single-column extractive distillation with heavy entrainer to separate binary azeotropic mixtures

Abstract

Extractive distillation with heavy entrainer is widely used in the separation of binary azeotropic mixtures. While a large amount of energy is always consumed in conventional two-column processes. A new flash tank-assisted single-column extractive distillation with heavy entrainer (FT-SCED) is proposed in this paper. The side vapor-phase stream with high heavy component content is withdrawn from the extractive column, and then it is partly condensed in a flash tank. By this means, the high-purity light and heavy products can be achieved from the overheads of column and flash tank, respectively. To obtain the proposed process, an initial single column extractive distillation with heavy entrainer is designed firstly. Then the flash tank is added into the process on the basis of the thermodynamic feasibility analysis. Genetic Algorithm procedure is employed to optimize the independent variables of the obtained process. Two case studies show that the proposed process has lower annual total cost compared with conventional extractive distillation and extractive dividing wall column. PI control strategies are established for the proposed processes in two cases. The dynamic control results show that these control strategies handle feed flowrate and composition disturbances excellently.