McCabe-Thiele Method

The McCabe-Thiele Method is a method of solving systems related to a common liquid-liquid separation method in chemical engineering: distillation. It is used to solve for the number of stages needed for a distillation column in order to achieve a desired result from this separation process. The system to be solved for this problem is given below:

A rectification column is fed 100 kg mol/h of a mixture of 50 mol % benzene and 50 mol % toluene at 101.32 kPa abs pressure. The feed is liquid at the boiling point. The distillate is to contain 90 mol % benzene and the bottoms 10 mol % benzene. The reflux ratio is 4.52:1.

The McCabe-Thiele Method is used to take advantage of material balances and process variables to "step-off stages" in order to find the theoretical number of stages to achieve the given separation. The specification of the molar outlet flows is also calculated. The first image below shows the formation of various lines graphed in the second image, which is used to "step-off stages" to count theoretical stages.