A comprehensive method to prevent top-coal spontaneous combustion utilizing dry ice as a fire extinguishing medium: test apparatus development and field application.

There is a high potential for coal spontaneous combustion (CSC) above the roof beams of supports during the mining-stopped period. Early detection of temperature abnormal zones and corresponding measures are necessary to prevent CSC. In this work, a top-coal temperature measurement method was proposed, combining the coal surface temperature detection and the drilling temperature observation. Furthermore, an apparatus was developed that dramatically increases the rate of dry ice sublimation, resulting in the rapid release of cryogenic carbon dioxide gas. The device utilizes water from firefighting pipes in underground coal mines as a heat source for dry ice sublimation without electrical energy and has been applied and validated taking Silaogou Coal Mine in China as a field test site. Specifically, we found that during the stoppage period, the coal above the supports near the air inlet tunnel is more likely to appear hot spots; the carbon dioxide gas generated by the dry ice phase change device can quickly reduce the hot spots temperature, and the coal temperature does not rebound after the gas injection is stopped. Based on the above analysis, this work can effectively prevent the early top-coal spontaneous combustion during the stop mining period.