The Johnson-Grayson method (JG) may be used to predict enthalpies for hydrocarbon liquids and vapors. It is essentially an ideal enthalpy correlation, using saturated liquid at - 200 degrees F as the datum. Vapor phase corrections are computed with the Curl-Pitzer method. Pressure effects on the liquid phase are ignored.
The method is useful for heavy hydrocarbons over the temperature range 0 - 1200 degrees F. It can be extrapolated with reasonable results. The method should not be used for mixtures lighter than carbon number five.
See "Johnson-Grayson (JG)" under "Generalized Correlation Methods" in Chapter 2, Volume 1, of the PRO/II Reference Manual for more information.
Application Guidelines
Refinery heavy ends systems such as vacuum systems. Synthetic fuel applications with heavy oils.