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TYPES OF DISTILLATION COLUMNS
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There
are many types of distillation columns, each designed to perform
specific types of separations, and each design differs in terms
of complexity.
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Batch and Continuous Columns
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One
way of classifying distillation column type is to look at how
they are operated. Thus we have:
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batch
and
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continuous
columns.
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Batch
Columns
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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.
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Continuous
Columns
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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.
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Types of Continuous Columns
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Continuous
columns can be further classified according to:
the
nature of the feed that they are processing,
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binary
column - feed contains only two components
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multi-component
column - feed contains more than two components
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the
number of product streams they have
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multi-product
column - column has more than two product streams
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where
the extra feed exits when it is used to help with the separation,
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extractive
distillation - where the extra feed appears in the bottom product
stream
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azeotropic
distillation - where the extra feed appears at the top product
stream
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the
type of column internals
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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
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packed
column - where instead of trays, 'packings' are used to enhance
contact between vapour and liquid
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