Experimental study on cooling law of spontaneous combustion by liquid CO₂ injection in coal bunker

As a large coal storage yard, coal bunker is prone to spontaneous combustion due to air leakage and chimney effect. In order to study the disposal effect of liquid CO₂ on spontaneous combustion of coal bunker, a liquid CO₂ cooling test bench was built to simulate the structure of coal bunker. The temperature variation laws of the coal bunker during the injection of liquid CO₂ and after the injection was stopped were tested, and the variation of the temperature field in the high-temperature area was analyzed. The results show that during the injection of liquid CO₂ into the coal bunker, the main cooling areas are concentrated at the liquid CO₂ release port and the seepage passage area; the average temperatures of the a, b, and d planes decreased by 22.7 ℃, 33.0 ℃, and 10.2 ℃ respectively. The cooling areas are the phase change cooling area, seepage cooling area, and convection cooling area respectively. After the injection was stopped, compared with the temperature before the injection, the temperatures in the upper and lower high-temperature areas decreased by 22.3 ℃ and 16.8 ℃ respectively. The temperature change of the coal body in the coal bunker mainly relied on the heat transfer through the temperature difference conduction of the coal body and the heat absorption by the sublimation of low-temperature dry ice. At the same time, it indicates that during the fire extinguishing process in the coal bunker.