"Fugacity coefficients of gases in binary mixtures" by David W. H. Roth

Document Type

Thesis

Date of Award

6-30-1960

Degree Name

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

Department

Chemical Engineering

First Advisor

Joseph Joffe

Second Advisor

C. L. Mantell

Third Advisor

George C. Keeffe

Abstract

Fugacity coefficients of components in gaseous mixtures have been calculated by a method proposed by Joffe which is based on the use of generalized thermodynamic functions, and on Kay's rule for definition of the pseudocritical points of a gaseous mixture. The method should be applicable to compounds which can be correlated by the theory of corresponding states.

The method was tested by application to 255 experimental points comprised of four gaseous systems, and included Argon-Ethylene, Hydrogen - Nitrogen, Methane - Ethane, and Methane n Butane. Thermodynamic functions from two recent generalized correlations, that of Pitzer et al., and that of Lydersen, Greenkorn, and Hougen, were used in the Joffe method to calculate fugacity coefficients. These two recent correlations involve the use of a third parameter and extend the theory of corresponding states to include a wider range of compounds. The results from each of these correlations were compared to results obtained by Engleman using the Joffe method and older correlations then in existence in 1956, and were also compared to the experimental values.

The Pitzer correlation gave results which were significantly better than those obtained with the other correlations. The results obtained by the combination of the Joffe method and the Pitzer correlation approached the method of Edmister and Ruby, tested by Engleman, in accuracy.

An equation was derived for the fugacity of components in binary gas mixtures based on Joffe's method and Joffe's proposal for definition of the pseudocritical points of a binary mixture. This equation was tested on 21 experimental points and resulted in some improvement over the Joffe method based on Kay's rule. The equation is recommended for systems composed of components differing greatly in critical temperature, for finding the fugacity of a component in low molecular concentration, or for systems in the two phase region. (damson derived this equation for n components in a gaseous mixture; this equation is presented, with a slight modification to one of the summation terms.

Equations are given which will correct fugacity coefficients calculated by the Joffe method, using the Pitzer correlation, to agree more closely with the experimental values. These equations are not recommended for use in any systems other than those tested.

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