Technology Type

Extractive Distillation (ED) is performed in the presence of a miscible, high-boiling, relatively non-volatile component, the solvent, that forms no azeotrope with the other components in the mixture.

The method is used for mixtures of substances with similar boiling points by adding a third substance to change the boiling point of one of the compounds, thus making them easier to separate. For example a mixture of components (A + B) is introduced into a first distillation column and a solvent (S) is separately introduced in the same column. The solvent and B interact in such a way as to change the boiling point of B. The distillate from the first column (A) can then be effectively separated from (B). Now that (A) has been separated from (B), the mixture of solvent and (B) is pumped to a solvent recovery column in order to separated (S) from (B), whereas (S) is recirculated back into the first column and the process starts again.
 

Source: How Extractive Distillation is like Getting Gum out of your Hair, EPIC PROCESS SYSTEMS