Influence of Supercritical CO2 Fluid on CH4 and CO2 Diffusion in Vitrinite-Rich Coals and Inertinite-Rich Coals

Coal maceral composition has a great effect on gas adsorption and diffusion. The interaction between supercritical CO2 (SCCO2) fluid will affect diffusion behavior in coals. Thus, the diffusivity derived from kinetics of CH4 vitrinite- inertinite-rich coals with low-violate bituminous rank collected Hancheng mine Weibei coalfield pre- post-SCCO2 exposure (SFE) were tested at conditions 45 °C 0.9 MPa. In combination pore distribution functional group content, possible mechanism alterations characteristics various compositions was addressed. results show that for vitrinite-rich coals, SFE increases macropore apparent coefficient CH4, while this treatment decreases micropore CH4. However, reverse trend is found diffusion–adsorption rate. For post-SFE, rate increases, an increase decrease occur micropore, respectively. Generally, shows stronger impact than suggest different selectivity to SCCO2 fluid. reason can be attributed changes structure surface content. causes macro/mesopore volume all samples. induces reduction oxygen-containing species content opposite occurs account difference compositions. With regard CO2, superior volume. favor but go against transport. This accounts aforementioned Overall, during CO2-ECBM process requires further attention.