Document Type


Date of Award


Degree Name

Master of Science in Chemical Engineering - (M.S.)


Chemical Engineering and Chemistry

First Advisor

Edward Charles Roche, Jr.

Second Advisor

John E. McCormick

Third Advisor

Deran Hanesian


One of the most important factors to know in the design of distillation columns is the minimum reflux ratio. Numerous procedures have been developed for the determination of the value of the minimum reflux ratio for multicomponent mixtures requiring various degrees of computational effort. Shortcut techniques are obviously advantageous with respect to computation time. After reviewing the available methods, those by Underwood, Colburn, Scheibel and Montross, Murdoch and Holland, and Shiras et al. were selected for further evaluation, mainly on the basis of practical potential.

Comparison of these procedures was accomplished by calculating the minimum reflux ratio for a large number of systems with widely varying conditions. Considerable differences were found between the results of these methods; the spread between the lowest and highest value varying from less than 10% for a 4-component system with adjacent keys to over 100% for an 8-component mixture with one split key. It was established that these deviations stem mainly from differences in the relative volatilities.

The reliability and usefulness of the methods investigated would have to be determined by comparison of the results with those from a rigorous calculation. For general application, only the techniques by Underwood and Shiras et al. can be considered since they contain a feature for determining the product composition. Scheibel and Montross' procedure is the only one which can be used to carry out a hand calculation within a reasonable length of time.



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