Study On The Temperature Field Evolution Law Of Spontaneous Combustion In Geting Mine

Fire is one of the major hazards in coal mines in China.According to incomplete statistics,it is estimated that there are approximately 4000 fire hazards in coal mines in China every year.Among these,spontaneous combustion accidents in goafs account for over 60%of all accidents.Because of real challenges,such as the impossibility of constant monitoring of the temperature field in coal mine sites and of large-scale simulation in laboratory studies of spontaneous combustion in coal mine goafs,numerical simulation has become the main means of studying spontaneous combustion in goafs.On the basis of previous numerical simulations of the temperature field in coal mine goafs,the present paper reveals the distribution pattern of thermal energy in a goaf.By taking into account the effect of atmospheric pressure on the temperature field in the goaf and adding an atmospheric pressure boundary condition to the numerical simulation of the temperature field in the goaf,an atmospheric pressure factor is proposed and determined;software for simulating the temperature field in the goaf under the impact of atmospheric pressure is designed and realized.In addition,the software is promoted and applied to the Geting Mine of the Oriental Energy Co.,Ltd.in Shangdong,China.A comparison of the experimental data and the simulation results are conducted and the temperature field evolution law of spontaneous combustion in Geting Mine is analyzed.The applying of the above achievements will provide new methods for hidden fire detection and early warning in coal mines.This research work is conducted on basis of a coal mine using the method of theoretical analysis,numerical simulation,experimental analysis,and field test.The specific research contents and conclusions are as follows.First,a novel theory for the distribution of thermal energy in a goaf is proposed from the perspective of the thermal energy exchange and equilibrium.On basis of the oxygen concentration,the air flow field and the autoxidation of coal,the theory includes the thermal energy loss zone,the thermal energy storage zone,the thermal energy equilibrium zone,the thermal energy release zone,and the micro-thermal energy migration zone.It can better explain the thermal energy distribution in a goaf than existing three-zone categorization scheme and,thereby,provide a new thought process for investigating the evolution of spontaneous combustion.Second,in the numerical simulation of the spontaneous combustion temperature field in a goaf,the effect of atmospheric pressure on the law governing the temperature field distribution is proposed and analyzed for the first time.On the basis of the large amount of real,on-site data,the least-squares method is used to identify the parameters of the atmospheric pressure.Four important factors—Sm1,Sm2,Sm1,and Sm2—are obtained and incorporated into the boundary conditions.This result was awarded a patent.Third,based on the numerical simulation of Fluent,software for simulating the temperature field in a mining goaf that is applicable to coal mines is designed and realized.By setting basic parameters,the distribution of the temperature field in a coal mine goaf can be intuitively and accurately revealed,which supports for the detection of the high-temperature points in coal mine goafs.Fourth,an experimental platform for spontaneous combustion simulation of different coal inclination angles is developed,and an atmospheric pressure simulation system is established in underground tunnels.By changing the pressure in the experimental tunnels,the change laws of the temperature distribution are measured and analyzed.The change laws are consistent with the Fluent simulation,indicating that the temperature field model is correct and reliable.Fifth,research results are successfully applied to the 2308 working faces of Geting Mine.After accurate hidden fire detection and early warning,an obvious effect is obtained by using various fire prevention measures,such as fixed-point and longitudinal two-way injection of nitrogen.