Masters Theses

Date of Award

8-1986

Degree Type

Thesis

Degree Name

Master of Science

Major

Chemical Engineering

Major Professor

F. E. Weber

Committee Members

George C. Frazier, John M. Holmes

Abstract

A computer code was written to compare the Ponchon-Savarit and McCabe-Thiele methods for three binary systems with varying degrees of chemical nonideality. The purpose of the research was to determine the effects of chemical nonideality on the assumption of constant molal overflow. These effects might cause differences between the two methods.

The binary system chosen to represent ideal behavior was benzenetoluene. The ethanol-water system was selected for moderate nonideal behavior. For strong nonideal behavior, the chosen system was propanol-water.

All three binary systems compared well with respect to the number of trays. However, there were some differences in predicted minimum reflux ratios between the design methods. The operating lines for the McCabe-Thiele method were not very sensitive to these difference in minimum reflux ratios.

The main conclusion of the study was the effects of chemical nonideality were minimal on the McCabe-Thiele method for operating pressures less than 5 atmospheres. However, for prediction of minimum reflux ratios for nonideal systems, the McCabe-Thiele method gave different values from the Ponchon-Savarit method. This difference was especially large on a percent difference basis for systems with small minimum reflux ratios (less than 0.1). If an accurate estimation of the minimum reflux ratio is needed in this situation it is recommended that the Ponchon-Savarit method be used.

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