Abstract: To study the gas diffusion characteristic and dynamic parameters change after water injection in coal mass, the desorption process of different water injection rates in coal samples under 0.5MPa adsorption equilibrium pressure were experimented on the homemade high-pressure water injection mixing plant. The experimental results show that the relation curves between time and desorption quantities of coal samples with different water injection rates have similar shape of Langmuir’s adsorption isotherm. In addition, all the coal samples with different water injection rates have limitation desorption quantities, and the variation of limitation desorption quantity with moisture is belong to exponential function. When the moisture increases from 0.05% to 12.04%, the limitation gas desorption amount decreases from 7.3383 mL/g to 2.7749 mL/g. Moreover, under the same adsorption pressure, the greater the moisture rate is, the smaller the gas desorption velocity of 1st minute (V1) is, and the change of gas desorption velocity of 1st minute with moisture is belong to logarithmic function. After water injection, Biot’s criterion of mass transmission increases, and the diffusion coefficient and Fourier’s criterion of mass transmission reduce, that is, the water injection have changed the diffusion kinetic parameters of coal mass.

Key words: water injection, limitation desorption quantity, gas desorption velocity, irradiation parameters