TYPES OF DISTILLATION COLUMNS
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
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