Modeling of Vapor-Liquid Equilibrium of Carbon Dioxide -Hydrocarbon, Nitrogen-Hydrocarbons, and Natural Gas Mixtures Using the Simplified PC-SAFT-D Equation of State

Simplified hard dimer chain theory combined with the perturbed chain statistical association fluid theory (PC-SAFT), which is used for binary systems of normal alkanes by Nasrifar, was developed to carbon dioxide-hydrocarbon, nitrogen-hydrocarbon, and natural gas systems. The parameters m, σ, and ε / k for carbon dioxide, nitrogen, isobutane, and isopentane were calculated. The results showed that for these components, the average absolute error obtained using this equation for the vapor pressure of carbon dioxide, nitrogen, isobutane, and isopentane was 2.7, 0.3, 2.1, and 2.2; and for the saturated liquid volume was 1.2, 1.1, 3.1 and 1.5, respectively. Using kij for correction of dispersion interactions, vapor-liquid equilibrium of carbon dioxide- hydrocarbon and nitrogen-hydrocarbon systems were investigated and the results of this equation were compared with the SAFT and PC-SAFT equations, respectively. The results showed that the model has better performance than these two equations of state. Finally, the model was used to predict the dew point temperature of natural gas mixtures, and for these systems, the error obtained from the prediction of the model was lower than the PR78 equation.