Study On The Thermal Effect Of Coal Oxidation Self-ignition And The Period Of Adiabatic Spontaneous Combustion

The coal mining process is severely affected by coal spontaneous combustion disasters,and there are various indicators for evaluating the degree of coal spontaneous combustion at home and abroad.The theory of coal-oxygen recornbination and quantum chemistry believes that the thermal effect of coal oxidation spontaneous combustion is a comprehensive characterization parameter of heat during the spontaneous combustion of coal,and is the root cause of spontaneous combustion.The time that the oxidative heat effect accumulates to spontaneous combustion is the natural ignition period of coal.When the loose coal body does not accumulate oxidative heat and the heat transfer occurs outside,the shortest time is the coal adiabatic natural ignition period.The latter is the only definitive solution to evaluate the danger of coal spontaneous combustion under certain experimental conditions.Therefore,it is of great significance to scientifically and reliably evaluate the danger of coal spontaneous combustion by conducting research on the thermal effects of coal oxidation spontaneous combustion and coal adiabatic spontaneous combustion.Based on the theory of coal-oxygen recombination and quantum chemistry,this paper proposes a theoretical test method for the physical similarity reference of coal oxidation spontaneous combustion and adiabatic natural ignition period.A physical similarity reference test experimental system was constructed,and the experimental conditions such as physical reference materials and experimental air supply were quantitatively determined.The coal samples of spontaneous combustion seam(Pansan Coal Mine)and easily spontaneous combustion coal seam(Zhaoxian Mine)under different leading temperature differences were tested experimentally,and the relationship between the natural ignition period of the experiment and the temperature difference and adiabatic spontaneous ignition period were obtained by curve fitting.Based on the test data of coal samples and reference samples,the thermal effect of coal oxidation spontaneous combustion was calculated using the heat formula method,and the natural ignition period of coal experiments under different leading temperature differences was calculated.Through error analysis,the errors of coal oxidative heat effect and natural ignition period were less than 5.08%and 1.1%,respectively,which verified the reliability and stability of the experimental system,the rationality and scientificity of the method.Based on the analysis of the thermal effect and the crossover point of the spontaneous combustion time,the temperature range at which the crossover point appears is summarized,and the main factor affecting the spontaneous combustion period of the coal experiment is the oxidation spontaneous combustion heat effect before the critical temperature.Using COMSOL numerical simulation software,a mass and heat transfer model of a sample tank in a physical similar reference test system was constructed.With the help of parameters such as the oxygen consumption rate and heat release intensity of the coal sample obtained by the test,the distribution pattern of temperature field in the coal sample under the conditions of leading heating and heat dissipation was analyzed.The natural ignition period of coal samples under the conditions of adiabatic and positive temperature difference and negative temperature difference(-1,-2,-3℃)were obtained,and the correctness of the physical similarity reference test method for coal experimental ignition period was verified.At the same time,the correction coefficients of the experimental measurement results were determined,and the thermal effects of coal oxidation spontaneous combustion and the adiabatic spontaneous ignition period can be calculated.The physical similar reference experimental system and test theory method constructed in this paper can realize the rapid determination of coal adiabatic self-ignition heat effect and coal adiabatic spontaneous ignition period.The research on the determination of spontaneous combustion tendency has certain theoretical guiding significance.