Amir Abbas Izadpanah

In this study, the dispersion term of perturbation hard chain theory (PHCT) presented by Nasrifar and Jalali is used instead of dispersion term in the perturbed chain statistical association fluid theory dimmer (PC-SAFT-D). The parameters of this equation of state were obtained for alkanes from methane to eicosane, nitrogen, carbon dioxide and hydrogen sulfide. The average absolute deviation in vapor pressure and saturated liquid density obtained from this equation of state was 6.77%and 3.39%. This equation of state was developed into binary systems: hydrocarbons-hydrocarbons, nitrogen-alkanes, hydrogen sulfide-alkanes and carbon dioxide-alkanes. To describe the phase equilibrium of some binary systems, propane-decane, hydrogen sulfide-heptane, nitrogen-alkanes, propane-carbonic oxide, ethane-propane, binary interaction parameter ( kij ) is required. This parameter was calculated by fitting the equation of state to experimental vapor-liquid equilibrium data for these systems. The results of this model for hydrocarbon-hydrocarbon binary systems were compared with the PC-SAFT-D equation of state and the results showed that for light hydrocarbons it performs better than the PC-SAFT-D equation of state. Finally, the model was used to predict the dew point pressure of natural gas mixtures, and for these systems the error of model prediction was greater than the PR equation of state