Variation characteristics of expansion energy of desorption gas in process of stepwise decompression and desorption

Coal and gas outburst is a process of energy release. Gas expansion energy is the energy produced by the expansion of free gas and desorbed gas in the coal seam. It is the main source of energy for coal and gas outburst. When coal and gas outburst occurs, the gas inside the coal seam is desorbed under a reduced pressure environment. In order to explore the change characteristics of gas expansion energy under stepwise pressure reduction and desorption, the anthracite coal in the Jincheng Mining Area is used as the research object and the gas adsorption-desorption experimental device is used. Two desorption experiments of stepwise decompression and desorption and atmospheric desorption were carried out, and the change characteristics of desorption gas expansion energy under stepwise decompression and desorption were analyzed. The research results show that the greater the adsorption equilibrium pressure, the greater the internal energy of the adsorbed gas in the coal, and the worse the stability of the system. Coal and gas outburst accidents are prone to occur under external disturbances; when the adsorption equilibrium pressure is the same, the desorption gas will expand under normal pressure. The energy is higher than the desorption gas expansion energy under reduced pressure desorption, and as the adsorption equilibrium pressure increases, the difference between the two gradually increases. Under 2.5 MPa adsorption equilibrium pressure, the desorption gas expansion energy under normal pressure environment is higher than that under reduced pressure environment. The gas expansion energy is 28.6% higher; the ambient pressure in a reduced pressure environment can inhibit the desorption gas expansion to a certain extent, and the higher the ambient gas pressure, the more obvious the suppression effect; reducing the desorption gas expansion energy can be used as a way to prevent coal and gas technical means of gas highlighting.