Study on heterogeneous characteristics of methane adsorption by natural coal

Abstract

In order to find a method for accurately evaluating the methane adsorption capacity of coal with non-uniform potential wells, this paper based on the Langmuir adsorption kinetic process, carried out theoretical analysis and experimental research on the characteristics of methane adsorption by natural coal with non-uniform potential wells, and obtained the following conclusion: in the equilibrium state of coal and methane adsorption, the methane molecules in coal tend to be adsorbed on the deeper adsorption sites of the potential well, and the coverage of potential wells at different depths conforms to the Logistic(S-type) curve law with adsorption pressure and temperature as parameters. The Langmuir parameter a of natural coal samples all increase with the increase of adsorption pressure, and the Langmuir parameter b decreases with the increase of adsorption pressure. The difference in the distribution of the adsorption potential wells of different types of natural coal samples leads to the different Langmuir parameters a and b under different adsorption pressures. The calculated value of methane adsorption in natural coal based on the Langmuir equation is higher at low adsorption pressure, and lower at high adsorption pressure. The calculation method of the non-uniform potential well isotherm adsorption capacity can greatly reduce the calculation error of the methane adsorption capacity in coal.

Keywords

• adsorption potential well
• non-uniform
• adsorption pressure
• methane adsorption capacity
• calculation accuracy