When a mixture is to be separated into individual pure components, and if it contains components with wide difference in their boiling points than the mixture can be separated using a distillation column. The mixtures with two components called as binary mixture, and this type of mixture can be fed to the distillation column at five different conditions like it may be in liquid state, vapor or combination of liquid/ gas state. We commonly use distillation column for liquid and liquid/gas state feeds, has when the mixture is fed to the column at feed plate high boiling or less volatile component in liquid form flow down to the bottom of the column along with the equilibrium composition which mean that some of the low boiling or more volatile component exist just in equilibrium condition.
Distillation column stripping section operation:
By supplying the latent heat to the liquid mixture it transforms into vapors and starts to rise up to first plate of the column. To supply heat continuously a reboiler is used at the bottom of the column, liquid from the bottom liquid hold up flow into the shell side of the reboiler while steam is passed into the tube section of shell and tube heat exchanger. Vapors produced from the reboiler are passed into bottom plate and this process continuous. Distillation column equipment is stabilized with constant heat flow to the liquid mixture and simultaneously removing heat from the distillate at the top of the column.
Distillation column stripping section description:
A manhole is provided at the bottom just above the mechanical supports, in most designs man hole are provided opposite side of the leader. Hexagonal bolting are well fitted to the supports and piping of the column. Centrifugal pump is used for circulation of the liquid through the circuits of liquid holder, shell tube reboiler. View glass with about 2 meters are used with pressure fitting gaskets so that they can with stands high temperature fluctuations and pressure shocks in the column.
Cost estimation of the distillation column depends on the steam consumption and circulation rate of the centrifugal pump. Basement of the column which counts about 10 percent of the column cost and increase as per the height of the column increases and it material of construction determines the maintenance cost of the supports of the column. Due to the wind force at top of the column it swing at its position this effect should be absorbed and supported by the basement of the column.
The same column set up which is shown in the isometric figure is arranged for most of the unit operation during separation of the components in petroleum, solvent recovery, purification sections. This set up is well designed and established as standard for particular operations, with new research on heat exchangers advanced plate and frame heat exchangers and hot boxes are used to supply heat energy effectively and less loss.
With the help of the control valves at steam inlet line the temperature of the shell and tube reboiler is maintained constant through the operation and controls the flow rate of the steam based on the load of the feed and compositions. Bottom product is withdrawn through the outlet control valve which maintains the required level in the column bottom liquid hold up so that circulating pump could get enough volume of liquid flow to it suction.