Study on Characteristic Parameters of Particulate Coal Gas Desorption and Diffusion Under Negative Pressure Environment

In order to study the characteristic parameters of particulate coal gas desorption and diffusion within a negative pressure environment, a self-made particulate coal gas desorption experimental system was used to simulate the law of gas desorption and diffusion in the initial negative pressure stage of the negative pressure sampling process, and to study the particulate coal at different adsorption equilibrium pressures (0.5 MPa, 0.74 MPa and 1 MPa) and different negative pressures (-40 kPa, -50 kPa and -60 kPa) gas desorption and diffusion laws, and based on the classical diffusion model of the third kind of boundary conditions, the characteristic parameters of gas desorption and diffusion are analyzed. The research result shows that the ultimate gas desorption capacity of particulate coal increases with the increase of the negative pressure value of the environment, and the ultimate gas desorption capacity increases with the increase of the adsorption equilibrium pressure and rate of increase becomes smaller; under the same adsorption equilibrium pressure, with the increase of the negative pressure value, the mass transfer Biotherm and the mass transfer Fourier increase accordingly. The larger the negative pressure value, the smaller the external convective mass transfer resistance of particulate coal, the depth of the disturbance of the diffusion field goes deeper into the coal particles; the diffusion coefficient increases with the increase of the negative pressure value under the same adsorption equilibrium pressure, and decreases with the increase of the adsorption equilibrium pressure under the same negative pressure value, and the