Document Type


Date of Award


Degree Name

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


Chemical Engineering

First Advisor

Joseph Joffe

Second Advisor

George C. Keeffe

Third Advisor

Michael Frederick


A method is presented for calculation of fugacity coefficients in gas mixtures. This work is based on a recent paper by Leland, Gamson, and Chappelear, wherein they presented a new method for evaluation of ideal K values. The information required for the method presented here includes pure component physical properties, and generalized tables or equations for compressibility factors, fugacity coefficients, and real gas enthalpy departure terms. Pseudo-critical temperatures and pressures for the mixture are calculated using the expressions presented by Leland and Mueller.

Five different binary systems consisting of paraffin hydro-carbon and CO2 mixtures containing 318 separate points were used to test this method. The results were compared with fugacity coefficients calculated from experimental data. For mixtures containing molecules of small size, this work predicts fairly accurate coefficients. For mixtures containing molecules with an appreciable difference in molecular size, the component with the larger molecule displays substantial deviations from the experimental fugacity coefficient. The one-non-hydrocarbon molecule studied, carbon dioxide, was accurately treated by this method. For binary systems containing two parraffinic components, this method will predict fugacity coefficients higher than experimental data for both components.

By comparison of this method with Pitser's for the same set of data, it was established that the Pitzer method was more accurate, but does require experimental data on equimolal mixtures. The method considered here requires further study to determine what modifications can be made so systems with large differences in molecular size can be accurately treated.



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