Simulated study on CH₄ adsorption by Shanxi gas-fat coal at different moisture contents

Context To investigate the impact of moisture on gas adsorption in gas-fat coal, Shanxi gas-fat coal was chosen as the research subject. The Adsorption module within molecular simulation software was utilized to construct gas-fat coal models with moisture contents of 0%, 1.14%, 2.26%, and 3.72%. The results revealed that the isothermal adsorption curves of gas-fat coal under different moisture contents all followed the Langmuir adsorption curve (Type Ι), wherein the Langmuir volume of gas-fat coal was most sensitive to changes in moisture content within the range of 0 to 1.14%. A linear equation was found to better characterize the influence of moisture on gas content in Shanxi gas-fat coal, represented by the formula η = 1/(1 + 1.98078w), where, η represents the moisture impact coefficient; w is the moisture content; 1.98078 is the coefficient of moisture influence of Shanxi gasifier coal. Coupled with changes in the surface free energy of gas-fat coal, the pressure exerted a positive effect on the adsorption of gas on the coal surface, enhancing the adsorption space of methane within gas-fat coal.Methods Using Materials Studio software, the adsorption capacity and adsorption heat of methane were computed at various temperatures (323 K, 333 K, 343 K) and pressures (0.5-8 MPa). Furthermore, a comparative analysis was conducted to assess the applicability of classical linear equations, linear equations, power function equations, and exponential function equations in quantitatively characterizing the influence of moisture.