The Study Of Forecast Of Tunnel Fire Source Based On Infrared Detection Technology

The coal spontaneous combustion in underground coal mine is located in the goaf formed by the air inflow trough and the return air trench after mining,and the coal wall which has been in contact with air for a long time in the mining roadway.This paper focuses on these two situations.Spontaneous combustion of coal roadway often occurs within a certain depth from the coal body inside the coal wall surface.Based on the roof pressure on both sides of the coal pillar after the excavation of the roadway,the opening and development of the inner fissure in the coal wall is intensified,and the air leakage of the coal wall increases.By establishing the calculation model of surrounding rock loosening circle,the range of surrounding rock plastic loosening circle in coal wall is calculated theoretically,about 1.42m;And the inversion calculation model of high temperature point in coal wall is established.The temperature of coal wall surface is scanned by YRH700 infrared thermal imager,and the specific position of high temperature point and the temperature value of high temperature point in the range of plastic loose circle are further calculated.Combined with the selected sample-Fenxi Ruitai Coal Mine,Zhengming Coal Industry Co.,Ltd.,roof fall,monitoring of gas of CO?CO₂ in roadway the working face advance speed of 0409 face,the coal wall in the range of 13.1 m⁶7 m from the working face to the end of the working face is studied.In view of the spontaneous combustion in the goaf of the working face,combined with the redivision of the three zones in the theory of"U-type spontaneous combustion zone",the spontaneous combustion zone is determined,and the model of the spontaneous combustion coal pile in the goaf is established.The effect of spontaneous combustion of coal pile is studied by infrared thermal imager.The influence of particle size on the heat transfer of coal pile and the effect of water content of coal sample on the heat transfer of coal pile were studied respectively.The maximum effective detection results of YRH700 infrared thermal imager and the maximum effective heat transfer thickness of coal pile were tested.It lays a certain theoretical reference value for the practical operation of this technology in the coal mine.Finally,the heat radiation trend of the high temperature heat source inside the coal pile is studied,in order to provide the direction for the fire extinguishing work after spontaneous combustion in the goaf.Through the above experiments,the following conclusions are drawn:?1?The range of loose zone of 0 409 roadway is 4.34 m,the range of plastic zone of coal is 1.42 m;?2?In the range of 13.1 m⁶7 m from the end of the trench,40 m⁵0 m is the highest temperature value and the depth of the position is also within the range of loose circle.The depth of its position is also within the range of loosening circle,about 1.5 m and the maximum temperature is about 32?.These two places should be regarded as the key sections of fire prevention in the roadway of working face 0409;?3?The heat transfer rate of coal pile is the fastest when the diameter of coal sample is more than 30mm,and the heat transfer rate is positively correlated with the size of coal sample when the porosity of coal pile is within a certain range;?4?The maximum effective detection range of the domestic YRH700intrinsically safe infrared thermal imager is 6 m.When the detection distance is greater than 6 m,the temperature difference between the high temperature region and the surrounding low temperature region will still be shown in the instrument.However,it can not provide the accurate temperature in the high temperature region,and can not judge the stage of spontaneous combustion;?5?Through the water experiment,it is concluded that the moisture content in the pore of coal pile has influence on the heat transfer effect and heat transfer rate of coal body,and when the moisture content meets certain extreme range conditions,that is,water content will not vaporize and endothermic.The moisture content is negatively correlated with the heat transfer effect/heat transfer rate of coal pile;?6?Through three kinds of coal samples with different thickness,the optimal fitting equation is established,which takes the distance?thickness?of the internal heat source from the coal pile as the independent variable and the maximum temperature of the coal pile as the dependent variable.The maximum effective detection depth of the infrared thermal imager for coal wall is 33.628 cm;?7?Through the experiment of heat radiation trend of high temperature heat source,it is concluded that after the air around the coal pile is heated,the moving track of the heated gas in the transverse direction is"flattened",that is,the heat first diffuses to the horizontal direction,which causes the temperature of the surrounding cold air to rise.At the same time,in the vertical direction,the heat expands outwards in the form of temperature gradient,which is similar to the isotherm model.Therefore,the key direction of fire prevention and extinguishing after spontaneous combustion of coal in goaf should be directly above the residual coal,and the inert gas or yellow mud and other substances can be added to the area of non-spontaneous combustion in this area to prevent further expansion of the scope of spontaneous combustion.This experiment provides directional guidance for the implementation of fire prevention measures after spontaneous combustion of coal in goaf.All the experiments in this paper are carried out on the basis of infrared detection technology,which has a certain theoretical guidance and reference significance for practical production or industrial testing.