Abstract:
To addresses issues such as coal dust generated and coal body damage leading to excessive gas emission during coal mining. By combining experiments and molecular dynamics simulations, it explores how polyacrylamide (PAM) enhances coal wettability and suppresses gas adsorption and desorption. Surface tension and contact angle experiments were conducted on PAM solutions of varying concentrations. Results show that at a 0.2% PAM mass fractions, both surface tension and contact angle were minimized. Coal samples treated with 0.2% PAM exhibite significantly better wettability than raw coal and water-treated samples. Methane adsorption and desorption experiments were conducted on coal samples subjected to different treatments within a pressure range of 0−2 MPa. The results indicated that the adsorption and desorption capacities of the coal samples followed the order: water-treated coal > raw coal > PAM-solution-treated coal. Furthermore, under varying pressures, both adsorption and desorption capacities ranked from highest to lowest corresponding to the pressures of 2.0, 1.5, 1.0, and 0.5 MPa, respectively. Based on the results from low-temperature nitrogen adsorption and Fourier transform infrared spectroscopy (FTIR) experiments, it is found that PAM treatment blocks or covers the pore structure of the coal, while enhancing the competitive adsorption of water molecules on methane molecules, thereby weakening the coal’s adsorption capacity. This also leads to the formation of stable structures between coal and methane molecules through hydrogen bonding, increasing the energy barrier for methane desorption and blocking desorption paths, ultimately reducing the adsorption and desorption capacity of the coal. Molecular dynamics simulations showe that in the coal-PAM system, more water molecules infiltrated the coal-water interface, suggesting improved wettability. Diffusion coefficient simulations indicate that, under the same pressure, the order of diffusion coefficients was: coal-water system > coal-PAM system > raw coal system. Additionally, within the same system, the diffusion coefficients ranked from highest to lowest corresponding to the pressures of 2.0, 1.5, 1.0, and 0.5 MPa, respectively. Finally, an integrated gas and dust control technology based on PAM solutions is proposed, providing significant theoretical support and practical guidance for coal mine gas and dust management.