Study on the evolutions of temperature and oxygen in the goaf of nearly vertical coal seam after low-temperature nitrogen injection

The near vertical coal seam adopts a segmented mining method to form a layered composite goaf, and its spontaneous combustion law is more complex. In order to understand the evolution law of temperature and oxygen after injecting low-temperature nitrogen into the goaf, the changes in oxygen and temperature before and after injecting low-temperature nitrogen into the goaf were analyzed through on-site observation and CFD numerical simulation. The results showed that after injecting low-temperature nitrogen into the goaf, the oxidation zone decreased by 10.7 m, and the return air corner temperature of this layer and the upper layer decreased by 16.6 K and 12 K, respectively, CO decreased to 0 mg/L; As the injection time of low-temperature nitrogen gas increases, the influence range of low-temperature nitrogen gas gradually increases, and the temperature and oxygen concentration in the goaf continue to decrease to below 283 K. The highest oxygen concentration in this layer's goaf is about 6%, while the upper layer's goaf is less affected by low-temperature nitrogen gas than this layer's goaf, and the oxygen concentration decreases to 6.8%. This study provides theoretical support for the prevention and control of coal spontaneous combustion in goaf areas near vertical coal seams.