Column's arrangement

If we have a three-component mixture and we want to separate them into their pure products respectively, we need at least two columns. It is however possible to use only one column for this kind of mixture. The only disadvantage is that the purity of the intermediate-boiling component will always be low!

One simple equation is available to be used in order to know how many columns are needed:

Number of columns needed = Number of components - 1

So in case of having three different components, as mentioned we need 2 columns (3-1 = 2).

There are however many ways to rearrange these two columns. The number of rearrangement also can be easily calculated using one simple equation:

Number of sequence = (2(p-1)!)/p!(p-1)!

with p = number of component

Hence for a ternary mixture, we have 5 different ways to arrange the two columns needed. In this entry 3 of them will be shown. There are also known as:

1) A-path
2) C-path
3) A/C-path

A-path: where the separation is done in a descending order of relative volatility

 C-path: where the separation is done in an ascending order of relative volatility

A/C-path: Separation of the B  from A and C is done first.

This type of sequence consumes a lot of energy as it has 6 heat exchangers compared to only 4 in A-path and C-path respectively.