Adsorption of methane, nitrogen, carbon dioxide and their mixtures on wet Tiffany coal

Gas adsorption was measured for methane, nitrogen, CO2 and their binary and ternary mixtures on a wet Tiffany coal sample. The measurements were conducted at 327.6 K (130.0 F) at pressures to 13.8 MPa (2000 psia). The expected uncertainties in the amounts adsorbed vary with pressure and composition. In general, average uncertainties are about 5% (0.01–0.08 mmol/g) for the total adsorption; however, the expected percentage uncertainties in the amount of individual-component adsorption are significantly higher for the lesser-adsorbed gas at lower molar feed concentrations (e.g. nitrogen in the 20/80 nitrogen/CO2 system). ngmuir/loading ratio correlation (LRC) and the Zhou–Gasem–Robinson (ZGR) two-dimensional equation of state (EOS) are capable of representing the total adsorption for the pure, binary and ternary systems within their expected experimental uncertainties. However, the quality of fit for the individual-component adsorption varies significantly, ranging from 3% (0.01 mmol/g) for the more-adsorbed methane or CO2 to 32% (0.01 mmol/g) for the lesser-adsorbed nitrogen. Further, the LRC and ZGR EOS predict binary adsorption isotherms, based solely on pure-fluid adsorption parameters, within twice their experimental uncertainties.