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Abstract It is of great significance for coal mining and utilization to study the adsorption process of mixed gas in coal. In this paper, the Monte Carlo method (MC) is employed to study the competitive saturation adsorption of oxygen and water vapor inside coal particles, and then the convection, diffusion and adsorption inside and between particles are studied by lattice Boltzmann method (LBM). In addition, this study examines the impacts of porosity, average particle size, and gas concentration on the process of adsorption in coal porous media. The research results show that oxygen and water vapor present in the mixed gas experience increased permeability, diffusion rate, and saturated adsorption capacity as the porosity and average particle size of the coal porous medium increase. However, the time required to achieve saturated adsorption decreases. Under the condition of maintaining the proportion of gas components and altering the initial gas concentrations from 4.087 to 53.131 mol/m3, saturated adsorption capacity of both gases remains nearly unchanged. Yet, the effective diffusivity of gases declines with increasing initial concentration. Additionally, it is also found that water vapor diffuses more quickly than oxygen in the mixed gas and achieves adsorption saturation faster.

The issue of coal spontaneous combustion greatly threatens the production safety of coal mining, storage, and transportation. It is significant to study oxygen adsorption understand the mechanism of coal spontaneous combustion. In this paper, based on the fractal dimension of coal and the self-similar fractal geometry, the internal pore structure of coal is modeled. Then, the lattice Boltzmann method is employed to conduct the numerical simulation of oxygen adsorption in coal. Compared with the existing experimental data and numerical simulation, the lattice Boltzmann method is verified to be correct. The numerical results indicate that in the process of oxygen adsorption in coal, the preferential flow occurs when the large pores connect to the channel. In the meantime, the large diffusion coefficient leads to an early time for adsorption equilibrium. The oxygen adsorption increases with an increased adsorption rate constant. Pore structure plays a significant role in the adsorption behavior of oxygen in coal. The results can provide theoretical support for reducing coal spontaneous combustion and ensuring coal mine safety in production. [ABSTRACT FROM AUTHOR]