Study on the dynamics mechanism of methane diffusion in coal under microwave heating

To study the effects of microwave on the methane desorption characteristics of coal, the structural parameters of Pingdingshan coal were obtained through X-ray diffraction (XRD) and mercury intrusion test. Then the coal molecular structure models were established. The adsorption of CH4 was simulated using Materials Studio. Finally, the combination of methane desorption experiments and molecular simulations were adopted to investigate the effects of microwave on the methane desorption characteristics, and the microscopic mechanism was analyzed. The results show that: the effect of microwave on the structure of coal is mainly reflected in the change of crystallite diameter (La). For the macro perspective, the average pore diameter, total pore volume, porosity and permeability of the coal increase and the total specific surface area decreases after microwave heating. Microwave heating leads to the decrease in adsorption pores, the increase in percolation pores and microfractures, and the enhancement of inter-pore connectivity. The simulated transport diffusion coefficients were in good accordance with the methane desorption experimental results, indicating that microwave heating helps methane to diffuse out of the coal.