Application of Peng–Rabinson equation of state for CO2 freezing prediction of hydrocarbon mixtures at cryogenic conditions of gas plants

Carbon dioxide freezing problem is studied at cryogenic condition of NGL production gas plants. The Peng–Rabinson equation of state is used for predicting the CO2 freezing points of hydrocarbon liquid and vapor mixtures. A quadratic temperature dependent correlation is presented for the proper description of a binary interaction parameter of methane and carbon dioxide at low temperatures. The overall average absolute relative deviation between the experimental and predicted CO2 freezing temperatures for this binary system is 0.26%. The proposed model is then used for equilibrium calculations of a gas plant demethanizer column, and the CO2 freezing points of the vapor and liquid hydrocarbon mixtures at the cold top trays of the demethanizer are predicted.