Research On Key Temperature Sensing Technology Of Optical Fiber In Spontaneous Combustion Coal Seam Of Goaf For Intelligent Coal Mining Face

Intelligent fire monitoring in goaf is an important part of intelligent mining.Optical fiber temperature sensing technology can be applied to the complex underground environment due to its unique properties.It has been widely used in coal mine intelligent mining fire monitoring in recent years In order to ensure the safe mining of coal seam,this thesis studies the key technology of temperature optical fiber sensing in goaf based on the project of’110 working method of spontaneous combustion coal seam fire prevention equipment and technology in Pan Nan Xiang Shui Coal Mine,Guizhou Province.This research mainly adopts the research methods of theoretical analysis,numerical simulation and field practice,and carries out the research on the spontaneous combustion characteristics of residual coal in No.120519 intelligent working face,the numerical simulation of the temperature field change in goaf,and the field application of the key technology of optical fiber temperature sensing,which provides a reference for the fire monitoring of intelligent mining goaf.The coal samples of 120519 intelligent working face were tested for the characteristic gas of spontaneous combustion of residual coal,and the spontaneous combustion characteristics of residual coal in goaf were studied.The results show that CO,CO₂,CH4,C₂H₆ and C₃H₈ exist in the whole process of coal-oxygen reaction from30°C.The formation rate of CO and CO₂ and the consumption rate of oxygen are exponentially developed.The appearance of C₂H₄ at 120°C is a sign that the oxidation of residual coal enters an accelerated stage.The appearance of C₂H₂ is at 260°C,which is a sign of residual coal combustion.At 70°C,the content of each generated gas is very low.The temperature change of goaf in 120519 intelligent working face under different conditions was studied by means of numerical simulation.The temperature field changes of goaf with different construction methods,different propulsion distances and different wind speeds were simulated.The results show that the length of oxidation zone and the range of high temperature area in goaf can be reduced by sealing the roof cutting roadway.The advancing distance of the mining face will have a great influence on the oxygen concentration field and temperature field on the inlet side,and have little effect on the goaf on the return side.With the increase of wind speed,the heat dissipation zone and oxidation zone in the goaf increase greatly.In Xiangshui Coal Mine,the fire monitoring system of 120519 intelligent working face was designed and built to solve the urgent need of 120519 intelligent working face for intelligent early warning of fire hidden danger in goaf.The equipment of the system was selected and applied on site.The layout scheme of underground monitoring system was designed,and the demand of 120519 intelligent working face for fire monitoring system was completed,which achieved good field effect.The field practice research was carried out by using optical fiber as the main temperature monitoring method and beam tube as the means to judge the three zones of spontaneous combustion in goaf,and the general variation law of temperature in goaf of 120519 intelligent working face was studied.It is found that the highest temperature on the side of the return airway is about 30°C,and the three zones of spontaneous combustion in the goaf are 35-80m behind the working face.The judgment of the three zones of spontaneous combustion in goaf monitored by beam tube and optical fiber is roughly the same,and the optical fiber temperature measurement technology is more reliable.At the same time,the optical fiber temperature sensing technology is used to establish the goaf temperature prediction model based on the existing goaf temperature and BP neural network.The average absolute error between the predicted value and the true value of the model is 0.47°C,and the accuracy of the model is 98%,which can better guide the field practice.There are 47 figures,15 tables and 78 references in this thesis.