## 3 Results and Discussion
### Formation Mechanism of Low Oxygen in Return Air Corner of Working Face
According to the field test, the oxygen concentration changes in the return air corner before and after the pressure air belt device is added, as shown in Figure 16. As shown in Figure 16, the oxygen concentration in the return air corner before the pressure air belt device is added is lower than 18% and the lowest is 16.8%. After adding pressure air belt equipment, the oxygen concentration in the corner of return air increased rapidly and stabilized above 19%. By adopting the upper and lower corner plugging and increasing the pressure air equipment, the oxygen concentration in the corner of the return air increased by 2\(\sim\)3% and stabilized at more than 19%, achieving the effect of low oxygen treatment. Figure 14: Effect of the pressure air belt. Figure 15: Installation position of a pressure air belt device. The upper and lower corner of the wind wall  
The upper and lower corners of the working face are spaced at a certain distance, and the wind wall is constructed at the same time to reduce the air leakage facing the goat of the coal seam. Before the coal bag wall is built in the lower corner of the 5106 working surface, rapid oxidation of leftover coal appears in the goat at the inlet side. According to the goat measuring point (J3) in the air inlet roadway, the change of carbon monoxide concentration in the goat monitored is shown in Figure 17. On 20 May 2021, a coal bag wall was built on the working surface and lower corner of 5106 to reduce air leakage in the goat, and the surface of the coal bag wall was sprayed (as shown in Figure 18). As can be seen from Figure 16, carbon monoxide was detected from 12 May before the construction of the coal bag wall, with a concentration of 15 ppm. Subsequently, the concentration of carbon monoxide increased rapidly and the rate of increase gradually  
Figure 16: Oxygen concentration in the return air corner before and after adding a pressure air belt. Figure 17: Carbon monoxide concentration at J3 monitoring point in the goat. accelerated. On 20 May, after the construction of the coal bag wall at the lower corner of the 5106 work surface, the concentration of carbon monoxide reached its maximum and then rapidly decreased until it dropped to zero. It shows that after the coal bag wall is built in the upper and lower corner, the goat pressure is improved by increasing the resistance at both ends of the working face, which plays an effect of plugging the air leakage and inhibits the oxidation of the coal left in the goat. (3) Analysis of oxidation prevention and control effect of goat residual coal  
As can be seen from Figure 19, the oxidation of coal left in goat has been effectively controlled by taking measures such as nitrogen injection, grouting, construction of pressure air belt and plugging of air leakage in upper and lower corners. Nitrogen injection is carried out in the buried pipe on the air inlet side of 5106 working face, and the nitrogen injection amount is 864 m\({}^{3}\)/h. Grouting is carried out in the buried pipe on the return air side of 5106 working face, and the grouting amount is 67.39 m\({}^{3}\)/h. The concentration of carbon monoxide in goat has been maintained at a relatively low level, while the O\({}_{2}\) concentration in the return air corner has been stable at more than 19%. The risk of natural combustion and low oxygen in the corner of return air in the goat of 5106 working face are improved.