Experimental study on desorption and oxidation characteristics and pore response of gas-bearing coal under the coupling effect of temperature and pressure
摘要
With the increase of coal mining depth, high gas pressure, high ground temperature, and high osmotic pressure have significantly changed the characteristics of coal and rock, promoting the evolution of low-gas non-spontaneous combustion coal seams to high-gas spontaneous combustion-prone coal seams. In this paper, through building a physical simulation experimental platform, conducting low-temperature liquid nitrogen and scanning electron microscope experiments, the influence law of adsorbed gas on the pore structure and oxidation characteristics of coal under the coupling effect of temperature and pressure was systematically studied. The research shows that: (1) The increase of pre-adsorption temperature inhibits adsorption, while the increase of pre-adsorption pressure promotes adsorption, and the two have a synergistic effect on the adsorption performance of coal. (2) The adsorption isotherms of raw coal samples and coal samples pre-adsorbed with gas belong to type Ⅱ, and the adsorption hysteresis loops belong to type H3. Adsorbed gas regulates the structural evolution by occupying pore space and supporting. The increase of temperature promotes desorption and softening of the pore wall, and the increase of pressure causes coal compression or fracture. Gas temperature, pressure and adsorbed gas jointly control the dynamic evolution of the pore structure. (3) Adsorbed gas significantly inhibits the spontaneous combustion process of coal through diluting the oxygen concentration and endothermic effect. At the same time, during the heating and oxidation process of coal with low adsorbed gas content, the concentrations of CO and C2H4 are higher, and the risk of spontaneous combustion is greater. This study innovatively reveals the variation laws of the pore structure and oxidation characteristic parameters of coal samples in different temperature and pressure gas environments, providing an optimization direction for the prevention and control measures of the combined disasters of gas and coal spontaneous combustion in goafs.