Investigation of adsorption-diffusion behaviors of elementary O2, CO2, and N2 in coal particles: influence from temperature

Adsorption–diffusion behaviors of gases (i.e., O2, CO2, and N2) in coal are directly related to the coal spontaneous combustion (CSC), in which the temperature is the key factor affecting the gas migration process in coal. In this work, isothermal adsorption experiments of O2, CO2, and N2 under different temperatures were carried out on bituminous coal and anthracite coal samples at 0.5 MPa, respectively. Based on the free gas density gradient diffusion (FDGD) model, the microchannel diffusion coefficients of different gases at different temperatures were calculated, and the effects from temperature were quantitatively evaluated. The results acquired from the experiment and simulation show that (i) the adsorption capacity of these three gases decreases as the temperature increases, and the adsorption capacity at the same temperature satisfies CO2 > O2 > N2; (ii) the FDGD model is verified to be still applicable at different temperatures, indicating that the adsorption-diffusion behavior of O2, CO2, and N2 in coal particles at different temperatures is still consistent with the FDGD diffusion; (iii) the microchannel diffusion coefficient Km of the three gases gradually increases when the temperature goes up. The present work contributes to the understanding of the gases migration process in the development of CSC.