Distillation columns are given first priority in separation techniques and mostly for multicomponent separations. When a feed mixture having more than two components or compounds in it than it is termed as a multicomponent mixture. So for obtaining the individual compounds from the mixture a technique of volatility or difference in vapour pressure and their boiling points can be used for developing a separation technique by supplying heat.

If the components in the mixture have different boiling points at constant pressure than by maintaining those temperatures at the different location in the distillation column, that particular component can be separated from fixed temperature plate location. The products can be separated into side streams from the distillation column.

Multicomponent distillation becomes difficult for azeotropic and close boiling component mixtures. The purity of the distillate product is disturbed during continuous operations and difficult to control. But a packed and sieve tray design is mixed to develop a multi-component distillation column so that the components can be separated by controlling the temperature of the packed bed and providing enough contact area and time for separation. 
model diagram of distillation column PID

Distillation column