Distillation columns separate liquid mixtures based on boiling points, utilizing either batch or continuous processes. Essential components include a vertical shell, column internals (like trays/plates), a reboiler, a condenser, and a reflux drum. The operation involves generating vapour in the reboiler, with the reflux ratio determining the amount of liquid recycled versus removed as product.

1. DISTILLATION COLUMN
• A distillation column, or tower, is used to
separate liquid mixtures into individual
constituents based on their boiling points.
• The liquid is heated to produce vapours
which are then condensed, by cooling, back
into liquid form.
• The liquids are then collected in trays or
plates positioned at different heights inside
the column, their position based on the
boiling point of each separate component.

2. Batch Column
• 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

3. Main Components of Distillation Columns
• a vertical shell where the separation of liquid components is carried
out
• column internals such as trays/plates and/or packings which are used
to enhance component separations
• a reboiler to provide the necessary vaporisation for the distillation
• a condenser to cool and condense the vapour leaving the top of the
column
• a reflux drum to hold the condensed vapour from the top of the
column so that liquid (reflux) can be recycled back to the column

5. Basic Operation
• Heat is supplied to the reboiler to generate vapour
• The liquid removed from the reboiler is known as the bottoms
product or simply, bottoms
• The vapour moves up the column, and as it exits the top of the unit, it
is cooled by a condenser. The condensed liquid is stored in a holding
vessel known as the reflux drum.
• Some of this liquid is recycled back to the top of the column and this
is called the reflux. The condensed liquid that is removed from the
system is known as the distillate or top product.

12. Reflux Ratio
• The reflux ratio in a distillation column is the ratio of the amount of
liquid returned to the column as reflux to the amount of liquid
removed as product.
• The formula for reflux ratio is R = Lc/D, where R is the reflux ratio,
Lc is the liquid returned to the column, and D is the liquid removed as
product.

14. Batch Columns
• In batch columns, the feed to the column is introduced batchwise and
the distillation is carried. When the desired quality is reached or when
the desired quantity is distilled out, the operation is stopped and next
batch of feed is introduced.

15. • Continuous ColumnsThese columns have a continuous feed stream and are capable of handling
Throughputs. These are further classified on the basis of,
The nature of the feed they are further processing
• Binary columns—Feed has only two components
• Multicomponent column—Feed has more than two components
The number of product streams they have
• Two product streams
• Multi product streams
The use of additional components in distillation
• Extractive distillation—use of solvent
• Azeotropic distillation—use of entrainer
The type of columns:
• Tray columns—use of sieve plate columns/Bubble cap trays/Valve
trays for better vapour–liquid contacting
• Packed towers—use of packings in columns for better vapour—liquid
contacting.

16. STEAM DISTILLATION
• Some systems have very high boiling points and some of these
substances are unstable at high temperatures. Especially when such
systems are completely insoluble with each other, steam distillation
can be a useful method of separating such mixtures.