Phase behavior of sour natural gas systems using classical and statistical thermodynamic equations of states

Vapor-liquid equilibrium (VLE) of natural gas systems containing light hydrocarbons, water, carbon dioxide (CO₂), hydrogen sulfide (H₂S), nitrogen (N₂), monoethylene glycol (MEG), triethylene glycol (TEG), benzene (C₆H₆), toluene (C₇H₈), methanol (CH₃OH) and ethanol (C₂H₅OH) are predicted in this work. A performance comparison between Peng-Robinson equation of state (PR EoS) and the perturbed chain form of the statistical associating fluid theory (PC-SAFT EoS) is made based on their predictability power in modeling such systems at different conditions. Data on saturated liquid densities and vapor pressures are used to optimize pure component PC-SAFT parameters for MEG and TEG. Experimental VLE data is used to fit both temperature dependent and independent binary interaction parameters (k_ij) in the PC-SAFT framework. Peng-Robinson EoS shows better results in predicting phase behavior of dry natural gas systems. However, PC-SAFT EoS exhibits superiority for systems containing water and/or methanol.