Research On Characteristics Of Porous Media And Model Of Spontaneous Combustion Of Residual Coal In Goaf

The spontaneous combustion of residual coal in the goaf is one of the major disasters in coal mines.The spontaneous combustion of residual coal in the goaf is due to the physical adsorption,chemical adsorption and chemical reaction of the oxygen in the goaf and the air leakage.The nature of coal spontaneous combustion can be seen as a heat transfer problem in the porous medium.This paper examines the following:Firstly,through the analysis of the theory of coal spontaneous combustion theory and porous media,this paper constructs the regularization model of the pore network of residual coal in the goaf area.According to the heat and mass transfer theory of porous media,and based on the law of conservation of energy,the law of conservation of mass,Darcy's law and Fourier law,etc.,the mechanism of heat and mass transfer in the spontaneous combustion of the goaf is analyzed,and the difference equations for mass transfer,heat transfer,and momentum transfer the spontaneous combustion of residual coal in the goaf is established.The main influencing factors of heat and mass transfer in porous media include particle size distribution,porosity and thermal conductivity of porous media.Therefore,these influencing factors need to be analyzed.In this paper,the fractal dimension theory is used to analyze the particle size mass distribution of the coal samples of Fusheng coal mine and Liuhe coal mine,and the fractal dimension is obtained.The porosity between coal particles was analyzed without considering the porosity inside the coal particles.Firstly,a single particle size ball accumulation model was established to obtain the porosity under theoretical analysis.At the same time,the porosity of coal particles under a single particle size was determined experimentally,and the porosity was analyzed;by establishing an idealized goaf model with a certain size,and according to the spherical filling theory,the model is filled with a single particle size,and the small particle size coal particles are gradually filled according to the pore diameter,and the porosity under the mixed particle size is obtained.According to the comparison of the fractal dimension and porosity of the particle size mass distribution,the qualitative relationship between them is obtained.Finally,by measuring the thermal conductivity of five different coal samples at different particle sizes and different temperatures,a linear relationship between thermal conductivity and particle size and temperature was obtained.An idealized thermal conductivity porous media model was established.The relationship between thermal conductivity and porosity was established by the thermal resistance network method.The cause of the error was analyzed by comparing the calculation results with experimental results.