Prediction of the solubility and gas-liquid equilibria for gas-water and light hydrocarbon-water systems at high temperatures and pressures with a group contribution equation of state

A group contribution equation of state has been proposed. The model is based on the Weidlich-Gmehling modified UNIFAC and Soave-Redlich-Kwong equation of state, in which the modified Huron-Vidal excess Gibbs free energy mixing rule is used, the residual term of the modified UNIFAC is changed a little and the combinatorial term is improved. Nine interaction parameters between gas groups CO2, CO, N-2, H-2, H2S, CH4, C2H6, C3H8, C4H10 and water are fitted. The model parameters have been used to predict solubility and gas-liquid equilibria for seven gas-water, and thirty-nine light hydrocarbon-water data sets in large temperature and pressure ranges (278-637 K, 1-1972 bar). The predicted results are in good agreement with the experiments, which makes it possible that the real phase behavior at high temperatures and pressures for gas-water and light hydrocarbon-water systems which are of interest to petroleum and natural gas exploitation industries, can be predicted reliably. (C) 1997 Elsevier Science B.V.