Distillation is based on the fact that the vapour of a boiling mixture will be richer in more volatile components and the original will have less volatile components. Distillation columns help separate the two effectively. It a process in which a liquid or vapour mixture of two or more substances is separated into its component fractions of desired purity, by the application and removal of heat.

The two basic columns are batch and continuous.

Batch Columns - In batch operation, the feed is introduced in batches. The distillation is carried to get the desired product, released and then the next batch is introduced.

Continuous Columns - In continuous columns a continuous uninterrupted feed stream is present. They can handle high throughputs and are the more common of the two types.

Continuous columns can further be of different types depending various things:

• Number of components of the feed (Binary and Multi Component)
• Number of product streams (Multi Product)
• Exit of the extra feed (Extractive and Azeotropic)
• Type of column internals (Tray and Packed)