Effects of added moisture on methane adsorption of coal with different degrees of metamorphism: An experimental and molecular dynamics simulation studies

This article combines physical experiments and molecular simulations to explore the influence of added water on CH 4 adsorption in different metamorphism grade coal. Specifically, under different pressures, when the added water content increases from 0% to 6.26%, the CH 4 adsorption amount in high metamorphic coal decreases by approximately 76.72%, 63.82%, 59.53%, 56.10%, and 50.94%. However, the decrease in adsorption amount of gas fat coal and long flame coal is lower than that of anthracite, indicating that the effect of adding water on CH 4 adsorption is most significant in high metamorphic coal, while the effect on medium and low metamorphic coal is relatively small. The average adsorption heat of CH 4 molecules in anthracite is 1.66 times of that of gas fat coal and 2.40 times of that of long flame coal, and the higher the added moisture content, the lower the adsorption heat of CH 4 , the more significant the inhibitory effect of added moisture on CH 4 adsorption by coal.