Simulation Study on Continuous Nitrogen Injection in Goaf based on COMSOL Dynamic Model

In order to clarify the feasibility and advantages of dynamic continuous nitrogen injection in goaf, taking fully mechanized working face of Rui’an Company as an example, a COMSOL simulation software was used to establish a dynamic continuous nitrogen injection model in goaf, numerical simulation studies were carried out to analyze the dynamic distribution of N₂ in goaf, the change law of maximum temperature, the width of oxidation zone in goaf, the dynamic change law of volume fraction of gas and CO in the working face and goaf. The continuous distribution effect of high concentration N₂ can be improved under the condition that the dynamic nitrogen injection port is 20 m away from the cutting top line and the nitrogen injection amount is 360 m³/h, the growth rate of goaf temperature, temperature and width of oxidation zone were significantly reduced, and fraction of gas and CO volume in goaf and working face can be effectively reduced. Dynamic continuous nitrogen injection can not only effectively prevent coal spontaneous combustion under the condition of small amount of nitrogen injection, but also control the overlimit of gas and CO volume fraction in working face.