COMPARISON OF 8 EQUATIONS OF STATE TO PREDICT GAS-PHASE DENSITY AND FUGACITY

In recent years a number of new equations of state, many of them modifications of the original Redlich-Kwong equation, have been proposed. Eight different equations, some of them generalized and others more specific, are evaluated here for their ability to predict gas-phase density and fugacity. Both pure components and mixtures are considered. Polar systems, including aqueous-gas and sour-gas mixtures, are emphasized. Included in the study are the original Redlich-Kwong, the Redlich-Kwong-Chueh, the Redlich-Kwong-Soave, the Barner-Adler-Joffe, the virial, the Nakamura-Breedveld-Prausnitz, the Redlich-Kwong-deSantis, and the Redlich-Kwong-Guerreri equations of state. In terms of its predictive ability for gas-phase density, the original Redlich-Kwong equation is found to be as reliable as some of its modifications. At low and moderate pressures polar systems are adequately represented by the virial equation; however, at high pressures, none of the equations is in general reliable. © 1979, American Chemical Society. All rights reserved.