Lattice Boltzmann Simulation of the Kinetics Process of Methane Diffusion with the Adsorption–Desorption Hysteresis Effect in Coal

[Image: see text] The occurrence of coalbed methane adsorption–desorption hysteresis has been widely observed, but a unified understanding of its mechanism is lacking, and the factors affecting its degree are unclear. This study introduces a microscale LB model for gas diffusion–adsorption–desorption in porous media that also accounts for the adsorption–desorption hysteresis effect. The accuracy of the model has been validated using previous experimental data, and the primary controlling factors of adsorption–desorption hysteresis were analyzed. The findings are as follows: (1) In the process of methane diffusion–adsorption–desorption, Knudsen diffusion dominates in micro- and mesopores, while viscous flow prevails in macropores; our model can adaptively adjust gas transport regimes across a broad range of pore sizes and pressures. (2) The desorption amount and rate are close relative to the correction factors α and β. A higher α value corresponds to greater initial adsorption as well as longer desorption time, whereas a lower β value implies weaker desorption capacity and a slower desorption rate. (3) Pore size can affect gas diffusion–adsorption–desorption kinetics, where larger pore size corresponds to efficient gas diffusivity; when r < 10 nm, the desorption process is mainly controlled by the desorption rate. Overall, this study has offered new insights into the mechanism behind methane adsorption–desorption hysteresis at the microscale, identified primary controlling factors of methane diffusion–adsorption–desorption process, and provided a foundation for numerical simulations and experiments related to the adsorption–desorption hysteresis.