Abstract: The aim of this work is to apply cubic equations of state (EOS) to vapor-liquid equilibria calculations of gas-
heavy hydrocarbon systems, which are asymmetric in molecular size and are usually found in natural gases. Investigation has
been done to test the validity of the original PSRK and the cubic simplified perturbed hard-chain (CSPHC) models for global
phase diagrams. The calculation results show that both equations overpredict vapor pressure in the near critical region. In
the prediction of the solubilities of high molecular weight (MW) hydrocarbons in the natural gas, the PSRK model gives good
agreement for the dew point pressure-vapor composition diagrams. Adjustment of the pure component parameters of the CSPHC EOS
for heavy components to fit the vapor-liquid equilibrium (VLE) data has been proved to give significant promoting in
prediction accuracy. However, further improvement of a van der Waals EOS, such as SRK, PT and DG models for the asymmetric
systems by adjusting the three pure component properties, Tc, pc and ω, did not achieve satisfactory results for heavy
components.

Key words: equation of state, natural gas, vapor-liquid equilibria, asymmetric systems

摘要： The aim of this work is to apply cubic equations of state (EOS) to vapor-liquid equilibria calculations of gas-
heavy hydrocarbon systems, which are asymmetric in molecular size and are usually found in natural gases. Investigation has
been done to test the validity of the original PSRK and the cubic simplified perturbed hard-chain (CSPHC) models for global
phase diagrams. The calculation results show that both equations overpredict vapor pressure in the near critical region. In
the prediction of the solubilities of high molecular weight (MW) hydrocarbons in the natural gas, the PSRK model gives good
agreement for the dew point pressure-vapor composition diagrams. Adjustment of the pure component parameters of the CSPHC EOS
for heavy components to fit the vapor-liquid equilibrium (VLE) data has been proved to give significant promoting in
prediction accuracy. However, further improvement of a van der Waals EOS, such as SRK, PT and DG models for the asymmetric
systems by adjusting the three pure component properties, Tc, pc and ω, did not achieve satisfactory results for heavy
components.

关键词: equation of state;natural gas;vapor-liquid equilibria;asymmetric systems