EXTENDING CONTINUOUS CONVENTIONAL AND EXTRACTIVE DISTILLATION FEASIBILITY INSIGHTS TO BATCH DISTILLATION

Researchers have begun to study a batch column with simultaneous top and bottom products, sometimes called a middle vessel column. The column is similar to a continuous column in that it has both a rectifying and a stripping section. However, instead of a feed tray, the middle vessel column has a tray with a large holdup that acts like the still pot. Using ternary diagrams, we show that one can identify the feasible products and possible column profile regions for the batch rectifier, the stripper, and the middle vessel columns using methods developed for continuous distillation. Using insights developed for continuous distillation, we also compare extractive distillation using the batch rectifier and middle vessel column and show that these columns can theoretically recover all of the pure distillate product from an azeotropic feed. However, the batch rectifier requires a still pot of infinite size. It is possible to ''steer'' the still pot composition in the middle vessel column by adjusting column parameters such as the product and extractive agent flow rates. Theoretically, it thus becomes possible to recover all of the distillate Product without the need for an infinite still pot.