Experimental meso scale study on the distribution and evolution of methane adsorption in coal

To reveal the nature of methane storage in coal under different adsorption pressures, a method combining scanning electron microscopy and energy dispersive spectrometry (SEM-EDS) with infrared thermal imaging is used to observe meso structures, methane distribution, and evolution characteristics in coal. The results indicate that the different meso structures of coal have different methane adsorption characteristics, leading to a non-uniformity of the methane distribution and evolution. In other words, compared with the cavity pores and meso fractures in telocollinite, which are compactly filled with clay minerals, the cell cavity pores and meso fractures in telinite, which are non-compactly filled with clay minerals, have more inter-gravel pores and broken coal structures at different scales, and can store great amounts of methane owing to a larger surface area and greater number of adsorption sites for methane molecules. Therefore, the methane content in coal increases sharply in these meso structures with increasing adsorption pressure, resulting in a centralization of the adsorption locations and increasing inhomogeneity of methane storage at different locations. In addition, owing to the shallower potential wells for methane adsorption, the coverage rate of the adsorption sites in these meso structures increases more slowly during an increase in pressure, leading to a decreased aggregation of methane storage in coal.