Experimental comparison of CO ₂ , CH ₄ , and N ₂ adsorption capacity on typical Chinese coals at different temperatures

Competitive adsorption of CO2/N2/CH4 on coals is important to evaluate potential application of CO2- or N2 – ECBM, which is not fully addressed in previous studies. In this paper, CH4, CO2, and N2 adsorption behaviors are experimentally compared at different reservoir temperatures (307 K, 318 K, and 333 K) and pressure up to 9 MPa. It is found that adsorption capacities all decrease with increasing temperature for CH4, CO2, and N2, while the differences in maximum adsorption capacity at different temperatures is not significant. Maximum adsorption capacity of anthracite coal is much larger than those of bituminous coals, while the maximum adsorption capacities of two selected bituminous coal are close to each other. The maximum adsorption capacity of CO2 is 1.93 mmol/g，which is significantly higher than that of CH4 and N2 with exactly 1.80 mmol/g and 1.11 mmol/g respectively. However, for a given coal sample, gas type does not affect the thermal-stimulated desorption capacities significantly.