Competitive adsorption/desorption of CO2/CH4 mixtures on anthracite from China over a wide range of pressures and temperatures

Abstract

The adsorption/desorption of CO₂/CH₄ mixtures with three different volume fractions was investigated at 294 K, 311 K, 333 K, and 353 K with pressures of up to 70 bar on anthracite from China using a high-pressure volumetric analyzer (HPVA II-200). For the mixtures, the total excess adsorbed amount decreased as the temperature rose. In addition, it displayed an upward tendency with an increase in the CO₂ fraction in the feed gas. The excess adsorbed amounts of the component gases were calculated on the basis of the composition of the gas phase measured by gas chromatography. For a mixture with a CO₂ fraction of 50%, relatively good adsorptivity for CO₂ was displayed at low pressures (<30 bar), whereas better adsorptivity for CH₄ was displayed at high pressures. When the CO₂ fraction in the feed gas increased from 20% to 50%, the excess adsorbed amount of CO₂ increased dramatically, whereas the excess adsorbed amount of CH₄ decreased slightly (6.3%). When the CO₂ fraction increased from 50% to 80%, the excess adsorbed amount of CO₂ increased substantially, whereas the excess adsorbed amount of CH₄ decreased drastically (42.4%). On the basis of the experimental data, the total excess adsorbed amount can be well simulated by the Ono–Kondo (OK) lattice thermodynamic model with an average deviation of 6.4%. Moreover, the excess adsorbed amounts of the individual components have also been predicted using the OK model.