McCabe–Thiele method

The McCabe–Thiele method is a technique that is commonly employed in the field of chemical engineering to model the separation of two substances by a distillation column.

[1][2][3] It uses the fact that the composition at each theoretical tray is completely determined by the mole fraction of one of the two components.

The assumption of constant molar overflow requires that: The method was first published by Warren L. McCabe and Ernest Thiele in 1925,[4] both of whom were working at the Massachusetts Institute of Technology (MIT) at the time.

A McCabe–Thiele diagram for the distillation of a binary (two-component) feed is constructed using the vapor-liquid equilibrium (VLE) data—which is how vapor is concentrated when in contact with its liquid form—for the component with the lower boiling point.

For example, if the feed is a saturated liquid, q = 1 and the slope of the q-line is infinite (drawn as a vertical line).

Figure 1: Typical McCabe–Thiele diagram for distillation of a binary feed
Figure 2: Examples of q-line slopes