Study On Flow Characteristics And Application Of Nitrogen-fine Water Mist Flow In Goaf

Goaf fire is one of the main types of mine fire.Fire in goaf is usually caused by spontaneous combustion of residual coal,which needs heat accumulation in a certain process and is difficult to find in time.Therefore,the prevention of spontaneous combustion of residual coal is particularly critical.Once the spontaneous combustion occurs,the residual coal will cause harm,and it is also very important for its control.Therefore,it is necessary to use efficient and convenient fire-fighting technology.Nitrogen-fine water mist fire-fighting technology is a kind of fire-fighting method with low hazard to personnel and equipment,good fire-fighting technology effect and friendly environment.The mechanism of fire-fighting of nitrogen-fine water mist flow was analyzed in the paper.The effectiveness of nitrogen and water mist was verified.The fire-fighting technology of nitrogen-fine water mist flow was improved.The theory of nitrogen-fine water mist flow was analyzed,and on this basis,the effects of velocity on the flow characteristics in goaf of nitrogen-fine water mist flow and the effects of injector on the flow characteristics in goaf of nitrogen-fine water mist flow were simulated by FLUENT,respectively.Application of fire-fighting technology of nitrogen-fine water mist flow was studied.The main results of the paper were:(1)Based on the mechanism of coal combustion,the ability of nitrogen-fine water mist flow to cool down and block oxygen to reduce combustion was analyzed in the four stages of combustion.The fire-fighting mechanism of nitrogen-fine water mist flow mainly cooled,insulated oxygen,reduced heat radiation,and also destroyed the flame structure by stretching flame and destructive expansion.(2)With the increase of nitrogen velocity,the velocity of nitrogen-fine water mist flow increases,and the velocity distribution of nitrogen-fine water mist flow is uniform,showing a symmetrical distribution.With the increase of fine water mist velocity,the velocity of nitrogen-fine water mist flow decreases,and the velocity distribution of nitrogen-fine water mist flow is uniform.With the increase of nitrogen content,the velocity of nitrogen-fine water mist flow increases,and the velocity distribution in goaf is more uniform.(3)The velocity of nitrogen-fine water mist flow decreases as the nozzle position deepens along the length of goaf.When the nozzle is placed at the end of the working face,there are large areas of low speed and high speed,and the velocity distribution is not uniform.When the nozzle is arranged at 10 m and 20 m away from the end of the working face,there is a small area of low speed and high speed,and the velocity distribution is uniform.With the increase of the number of nozzles,the velocity of nitrogen-fine water mist flow increases,the area of low-speed area in the four corners of the goaf increases,the area of highspeed area on both sides of the goaf increases,and the velocity distribution in the goaf is uneven.(4)The pipeline was optimized and the pipeline configuration was studied;the suitable method of nitrogen-fine water mist flow was studied,the process flow was designed;the prevention and control measures of nitrogen and water mist leakage was put forward.