Study on the impact of moisture on methane storage and transport characteristics in coking coal based on molecular simulation

Coalbed methane (CBM), as a kind of unpolluted source, has been extensively used on the global scope. However, extracting CBM could encounter some problems. For instance, gas adsorption (GA) and migration may be constrained by moisture content. This study, based on molecular simulation methods, investigates the impact of moisture content on methane (CH 4 ) adsorption and diffusion characteristics in Shenyang coking coal (CC). The macromolecular model of CC was established by component analysis, Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and solid-state 13C Nuclear Magnetic Resonance (NMR) techniques. The adsorption, as well as the diffusion behavior of methane within fluctuating moisture content, was comprehensively analyzed. The conclusions illustrate that as moisture content rises, methane’s adsorption capacity, adsorption heat, and diffusion coefficient (DC) significantly decline. Moisture weakens methane’s storage and migration abilities by competing for adsorption sites and altering the pore structure of coal. Furthermore, the study introduces the concept of critical moisture saturation , providing a theoretical basis for optimizing dewatering strategies in CBM extraction. Finally, based on the multiscale model results, a “pre-dewatering plus staged pumping” process optimization is proposed, offering quantitative guidance for the production of CBM from high-moisture coal seams.