Evolution characteristics of coal microstructure and its influence on methane adsorption capacity under high temperature pyrolysis

The ability of coal to absorb gas is one of the most important factors affecting the prevention and control of mine gas-related disasters and safe exploitation of coal seam gas. In this paper, high gas content coal samples from the Pingdingshan mining area are selected as the research object. The micro molecular structure of coal is altered by pyrolysis, combined with experimental methods such as infrared spectroscopy, isothermal adsorption and liquid nitrogen adsorption. The evolution characteristics of functional groups of coal during high temperature pyrolysis and the variation of gas adsorption capacity of coal after pyrolysis at different temperatures were studied from a micro level. The results show that when the pyrolysis temperature increased from 20 degrees C to 750 degrees C, the methane adsorption capacity of coal samples decreased with the increase of pyrolysis temperature. C=C, -OH, C=O, -CH2 in coal molecules gradually decreased. In terms of the effect of functional groups and the pore structure on methane adsorption, the methane adsorption capacity in descending order is: C=C > -OH > C=O > -CH2. The results of this study provide theoretical guidance for the development of new technologies for the development of coalbed methane thermal injection mining technology. (c) 2022 Published by Elsevier Ltd.