Temperature Reduction Characteristics of Coal with Different Moisture Contents During Cryogenic Treatment

To investigate the effect of moisture content on coal in cryogenic treatment, based on a gas-containing coal cryogenic treatment simulation testing system and an automated mercury intrusion porosimeter, temperature changes, strains, and characteristic parameters of the pore structure of coal after cryogenic treatment were determined. In addition, a thermal–water–mechanical coupling theoretical model was established using COMSOL software to simulate the changes in temperature and volume of coal. It was observed that moisture content was correlated negatively with the rate of temperature drop of coal and correlated positively with the frost heave strain. After cryogenic treatment, the final volume of coal decreased and the pores increased. The experiment revealed that frost heave heat extended the temperature stabilization time by an average of 27%, while methane adsorption heat had almost no effect. It is recommended to control the moisture content of coal at around 5% when using cryogenic treatment for anti-outburst, while for frozen coring, the moisture content should be controlled below 3%. The research results provide significant understanding of changes caused by cryogenic treatment on coal and supply practical information for optimizing the industrial production application of cryogenic treatment on coal.