Study on CO₂ adsorption and diffusion law of coal under different temperatures and pressures

In order to overcome the difficulty of gas mining when coal mining depth increased, the adsorption and diffusion laws of CO₂ molecules at different temperatures and pressures were simulated by using the simulation software Materials Studio; the relationship between CO₂ mean square displacement and time was simulated based on molecular dynamics. The results showed that in the isothermal adsorption curves of 15 ℃, 25 ℃, 30 ℃ and 35 ℃, the adsorption capacity of CO₂ decreased gradually when temperature increased. It showed that CO₂ was conducive to geological storage at low temperatures; the values of self-diffusion coefficient, corrected diffusion coefficient and transfer diffusion coefficient of CO₂ in coal increased when temperature and pressure increased. The maximum value was reached at 35 ℃ and 3.5 MPa.