Influence of components on methane micropore filling capacity of low-rank coal

Abstract

N2/CO2 adsorption methods were used to measure pore characteristics of low-rank coal, and methane isothermal adsorption experiments were conducted for further evaluation. Results from N2 adsorption experiments reveal that the pore size ranges from 1.03 to 3.26 nm, with pore volumes (PVs) of 0.006–0.013 cm3/g The CO2 adsorption experiments reveal that the micropore size distribution is 0.479–0.548 nm, with PVs of 0.026–0.056 cm3/g. The methane isothermal adsorption experiments shows that the maximum adsorption volume is 12.82–28.68 cm3/g. The micropore filling theory developed for medium to high-rank coals shows that over 94.71 % of methane is stored in micropores, validating its applicability to low-rank coal. Through theoretical analysis and calculations, a dimensionless expression has been derived for the relationship between the micropore filling capacity of methane in low-rank coal and the content of its various components. This study offers a theoretical foundation for outburst prevention of gas in low-rank coal mining regions.