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an introduction
© Copyright 1997-2023 by M.T. Tham and R.C. Costello
There are many types of distillation columns, each designed to perform specific types of separations, and each design differs in terms of complexity.

Batch and Continuous Columns

One way of classifying distillation column type is to look at how they are operated. Thus we have:
batch and
continuous columns.
Batch Columns

In batch operation, the feed to the column is introduced batch-wise. That is, the column is charged with a 'batch' and then the distillation process is carried out. When the desired task is achieved, a next batch of feed is introduced.

Continuous Columns

In contrast, continuous columns process a continuous feed stream. No interruptions occur unless there is a problem with the column or surrounding process units. They are capable of handling high throughputs and are the most common of the two types. We shall concentrate only on this class of columns.

Types of Continuous Columns

Continuous columns can be further classified according to:

the nature of the feed that they are processing,

binary column - feed contains only two components
multi-component column - feed contains more than two components
the number of product streams they have
multi-product column - column has more than two product streams
where the extra feed exits when it is used to help with the separation,
extractive distillation - where the extra feed appears in the bottom product stream
azeotropic distillation - where the extra feed appears at the top product stream
the type of column internals
tray column - where trays of various designs are used to hold up the liquid to provide better contact between vapour and liquid, hence better separation
packed column - where instead of trays, 'packings' are used to enhance contact between vapour and liquid