Study On Division Of "Three Zones" And Fire Prevention And Extinguishing Technology In Goaf Of Inclined Coal Seam Working Face

Fire is one of the five major disasters in coal mines in China,and the coal spontaneous combustion in goaf is the top priority of coal mine fire prevention and control.The accurate acquisition of the distribution characteristics of “three zones” of spontaneous combustion is the basis and rpemise for reasonably determining the fire prevention and extinguishing technology in goaf.The average dip angle of NO.8+10coal seam in Ruilong Mine is 25°,the natural tendency grade in II,and the shortest spontaneous combustion period is 89 days.The W-shaped ventilation system is used in8115 working face,and the distribution characteristics of “three zones” of spontaneous combustion in goaf need to be discussed,so as to provide a theoretical basis for selecting the fire prevention and extinguishing technology suitable for inclined coal seam and W-shaped ventilation working face.Therefore,this paper adopts the method of combining theoretical analysis,numerical simulation and field test to study the distribution law of “three zones” in goaf of inclined coal seam working face and fire prevention and extinguishing technology.Based on the actual production demand of Ruilong Coal Mine,the 8115 working face was taken as the main research object.Firstly,the bundle tube method was used to measure the “three zones” of spontaneous combustion with the oxygen concentration was taken as the division index in the goaf;Secondly,based on ANSYS FLUENT software,the numerical model of working face goaf is constructed and solved,which verifies the accuracy of field measurement results and numerical model;After that,the working face air supply and ventilation system,coal seam angle three kinds of factors on distribution characteristics of “three zones” of spontaneous combustion in goaf were discussed one bye one;Finally,taking nitrogen injection fire extinguishing technology as an example,based on numerical simulation method,the influence of different nitrogen injection positions on the distribution of “three zones” of spontaneous combustion was discussed,and the optimal nitrogen injection position was determined.Through the above research,the main conclusions are as follows :(1)Through the mutual verification of field measurement and numerical simulation,the maximum safe oxidation width of 8115 working face is 192.24 m,the limit advancing speed is 0.29m/d,and the width of spontaneous combustion zone in goaf is 35 m;(2)The air leakage rate and the width of spontaneous combustion zone in goaf increase with the increase of wind speed and coal seam dip angle,and the boundary of spontaneous combustion zone extends to the deep part of goaf;(3)Under the condition of the same air volume,the air leakage rate and the width of spontaneous combustion zone in goaf of W-shaped,U-shaped and Y-shaped ventilation systems increase in turn,and the W-shaped ventilation system should be preferred in spontaneous combustion coal seam;(4)In the numerical simulation of ’ spontaneous combustion ’ three zones in goaf,the distribution law of oxygen concentration and gas concentration in goaf should be taken into account,and the working face ventilation system suitable for disaster prevention should be selected according to the severity of coal seam disasters;(5)It is suggested that the mine should simultaneously adopt the buried pipe nitrogen injection fire prevention and control measures on both sides of the inlet and return airway of the working face to comprehensively control the spontaneous combustion zone in the goaf.Figure 34,table16,reference 87.