Limitations of the Grayson-Streed

Grayson and Streed modified the Chao-Seader correlation in 1963 by fitting data over a wider range of conditions and hence deriving different constants for the equations that give the fugacity coefficients of the pure liquids. This method supplies special coefficients for hydrogen and methane because typical application temperatures are far above the critical points of these two components. Grayson and Streed's modifications have extended the application range for hydrocarbon systems up to 800°F and 3000 psia, but the lower limits imposed by Chao and Seader still apply:

• Pressure: Up to 3000 psia, but not exceeding 0.8 of the critical pressure of the system.

• Temperature: - 100°F to 800°F, and pseudo-reduced temperature, Tr, of the equilibrium liquid mixture less than 0.93. The pseudo-reduced temperature is based on the molar average of the critical temperatures of the components.

• Concentration: Up to 20 mole percent of other dissolved gases in the liquid.