Contribution to the study of minimum extractor agent flow rate

Abstract

The extractive distillation is the most common used alternative when the mixture to separate has an azeotropic point or its components have close boiling points. Although most liquid separations are performed in the industry by distillation, the energy consumption of the distillation columns is very high, so any improvement achieved in that means energy and economic saving. Shortcut methods have an important role in the conceptual design of distillation processes because they rapidly provide constraints for important design parameters such as minimum reflux ratio, number of stages, process feasibility, possible splits, and, specifically for extractive distillation, minimum solvent feed ratio and maximum reflux ratio. In this work, a simplified method using reversible distillation models has been applied to the conceptual design of double feed extractive distillation columns. As previously found by other authors, it is observed that these extractive distillation pinch curves, in addition to determining the feasibility region, are also useful for calculating an approximate mínimum entrainer feed ratio independent of other parameters, as well as accurately pinpointing the minimum and maximum reflux ratios. Applications to example extractive distillation systems allow us to conclude that the method is reliable, fast, and much easier to implement than other methods.