Effect Investigation And Optimization Of Nitrogen Injection In The Goaf Of Yuandian No.1 Coal Mine

Coal spontaneous combustion will not only cause a lot of loss of coal resources and environmental pollution,but also may cause other coal mine accidents,which will threaten the life safety of underground personnel.The 822 working face of Yuandian No.1 coal mine adopts the fully mechanized top coal caving mining technology.There are many left in the goaf and the risk of spontaneous combustion is great,which brings a major threat to the safety production of the coal mine.At present,nitrogen injection fire prevention technology is mainly used to prevent the spontaneous combustion of the coal in the goaf.Therefore,the investigation of nitrogen injection effect and the study of the best nitrogen injection process parameters to prevent the spontaneous combustion of the coal are of great significance for the safe mining of the mine.Based on the 822 working face of Yuandian No.1 coal mine as the engineering background,the oxygen concentration and temperature change in the goaf of 822working face are measured by the buried pipe monitoring system.According to this,the"three zones"of goaf spontaneous combustion are divided and the effect of nitrogen injection is analyzed.The results show that the nitrogen injection can effectively reduce the oxygen concentration in the goaf of 822 working face and reduce the possibility of spontaneous combustion in the goaf.However,the decrease of oxygen concentration in the goaf at the side of the roadway has not achieved the expected effect.Based on the analysis of the roof overburden condition and nitrogen injection technology of the working face,it is precisely because the overburden in the goaf is insufficient and the nitrogen injection technology is unreasonable that the effect of nitrogen injection fire-fighting measures is not ideal.FLAC^3D software is used to simulate the evolution process of overburden stress field in working face 822.Based on the analysis of the plastic area distribution of the strike and tendency of the goaf,the"three areas"of the horizontal caving zone in the goaf are divided.Through comparative analysis,it can be seen that there is a basic corresponding relationship between the"three zones"of goaf spontaneous combustion and the"three zones"of horizontal caving zone.The simulation results show that the gob at one side of the machine lane is within 70m from the working face and the caving is not real,which also explains that the oxygen concentration in the gob at the side of the machine lane near 822 working face does not drop to less than 20%until 70m later.The distribution rule of oxygen concentration in the goaf of no.822 working face of Yuandian No.1 coal mine under the condition of nitrogen injection is simulated by Fluent software,and the same nitrogen injection quantity is simulated at different positions of goaf.The influence of different nitrogen injection positions on the distribution of oxygen concentration in the goaf of no.822 working face of Yuandian No.1 coal mine is compared and analyzed,and the goaf 40 m away from no.822working face is determined as the best nitrogen injection position by analyzing the nitrogen injection quantity 1400m³/h is the best nitrogen injection quantity.Through the above research,in view of the existing problems of the nitrogen injection process adopted in 822 working face of Yuandian No.1 coal mine at present,the paper puts forward measures to prevent air leakage,such as increasing the nitrogen injection amount,increasing the buried depth of nitrogen injection port,building the air inlet side wind wall,hanging the wind curtain,etc.The technology of non interval nitrogen injection in the goaf of Yuandian No.1 coal mine is designed to provide guidance for the fire prevention and extinguishing work in the later mining process of this coal seam.There are 27 figures,11 tables and 97 references in this paper.