Plotting McCabe-Thiele Diagrams in Microsoft Excel for Non-Ideal Systems
John L. Gossage · 2016
McCabe-Thiele diagrams are an indispensable aid to teaching distillation, as they graphically demonstrate key concepts (number of stages, feed location, minimum reflux ratio, etc.) related to operability of a distillation column.Their drawback is that they are difficult to draw freehand, and this difficulty is aggravated when the vapor-liquid equilibrium data for the system is represented by a set of equilibrium data points, as then the necessary first step is to construct the equilibrium curve.In this paper, a method is presented to automate the process of fitting binary equilibrium data to a smooth curve (using a cubic B-spline algorithm implemented via Visual Basic for Applications, or VBA) and then drawing the McCabe-Thiele diagram in Microsoft Excel.In this way, the effect of changes to the operating conditions can be easily demonstrated.Furthermore, the method will locate the azeotrope if the system has one.