Vapor - liquid equilibrium of the carbon dioxide/methane mixture at three isotherms

Abstract

Experimental vapor – liquid equilibrium data for the CO2/CH4 mixture have been measured at 293.13 K, 298.14 K and 303.15 K, with emphasis on the mixture critical area. The maximum estimated standard uncertainties are 3 mK in temperature, 2 kPa in pressure and 0.0008 in mole fraction. The scaling law of statistical thermodynamics has been fitted to the critical region data of each isotherm and very good estimation of the critical point is achieved with a maximum uncertainty of 10 kPa in critical pressure and 0.0009 in critical molar composition. The measurements have been validated against experimental data taken from the literature, where available, and against the prediction of the GERG-2008 model. The Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) Equations of State using the classic van der Waals one fluid mixing rules, the perturbed chain statistical association fluid theory (PC-SAFT) and the Universal Mixing Rule – Peng Robinson (UMR-PRU) model have been fitted to the data of each isotherm with very satisfactory results. UMR-PRU yields the lowest deviation, especially concerning the critical point area, with an overall absolute average deviation (AAD) of 0.18% in bubble point pressure and 0.43% in CO2 mole fraction of the vapor phase. In the critical points, UMR-PRU results in an average % AAD equal to 1.55 in critical pressure and 0.99 in the critical point composition.