This model (GPSWATER) was developed for the Gas Processors Association in 1990 for sour water systems containing NH3, H2S, CO2, CO, CS2, MeSH, EtSH and H2O. The SWEQ method developed by Grant Wilson for a joint project of API and EPA was extended to a temperature of 600 degrees F. See Sour for a description of the SWEQ model.
The total pressure was extended to 2000 psia by incorporating vapor phase non-idealities and by addition of the Poynting correction for the liquids. The chemical reactions for all reactions of the above mentioned chemicals in water are considered. The chemical equilibrium constants are correlated as functions of temperature and composition. The effects of light gases such as N2 and H2 are considered and electrostatic effects are incorporated into the liquid activity coefficients.
Phase equilibria for other components present in the system are calculated with the SRK-Modified Panagiotopoulos-Reid (SRKM) method.
Other thermodynamic properties calculated with the SRKM method include the vapor enthalpy, liquid and vapor entropies and the vapor density. The liquid density and liquid enthalpy are calculated with the Ideal method.
See "GPA Sour Water Package (GPSWATER)" under "Special Packages" in Chapter 2, Volume 1, of the PRO/II Reference Manual for more information.
Application Guidelines
Sour water systems which contain NH3, H2S and CO2 at pressures less than 2000 psia and temperatures in the range 68 - 600 degrees F. The weight fraction of NH3 must be less than 0.40 and the partial pressure of the CO2 and H2S must not exceed 1200 psia.
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