## Review Of Binary Distillation – McCabe-Thiele By Computer

For many years the McCabe-Thiele graphical method (1) has been the accepted procedure for determining the number of theoretical trays in a binary distillation when constant molal overflow prevails throughout the column. For close boiling separations such as in an ethane-ethylene or propane-propylene splitter, constant molal overflow is very closely attained. However, in the rectifying sections of these columns, relative volatilities are close to one. As a result, the equilibrium curve and upper operating line are very close together, especially in the region of the overhead product composition x_{D. }This situation makes it very difficult to graphically step-off theoretical stages, which can be great in number in this region.

The difficulties described above can be circumvented if one is able to solve the McCabe-Thiele method analytically or by numerical methods on the computer or on a PC. Here a BASIC computer program is presented for doing just that. This program should be especially useful, for example, to a process engineer, working on an ethylene plant proposal, who needs to make a quick size (height) estimate for a C_{2} or C_{3} splitter column. Use of the program is illustrated for a specific example involving a C_{3} splitter.

Finally, a brief discussion is presented for estimating the effect of errors in relative volatility on the calculation of the number of theoretical stages.

Steve brownHi, Chuck someone mentioned John Lenoir as their teacher and I thought of you. How is everything. It’s been a long time.

Steve Brown

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