A mathematical model of low-temperature oxidation of a coal heap

Abstract

Present methods for predicting endogenous fires are insufficiently effective and planning organizations and coal enterprises do not have reliable methods for assessing fire hazard. Further perfection of measures for fire prevention requires a more accurate quantitative assessment of physical, technological, and ventilation parameters. A knowledge of the laws governing spontaneous combustion of coal in the worked-out area will enable us to investigate the influence exerted on it by individual factors and to regulate the temperature conditions by varying the quantitative values of these factors. Previous investigations of thermochemical processess of spontaneous combustion of coal concentrated on the evolution of heat at a constant rate of filtration of air within the reaction medium, no account being taken of convective removal or of the effect of diffusion of air on the change in the heat balance. The higher frequency of fires in thick steep seams is due to the fact that the coal left in the worked-out area is concentrated in crushed form in the lower sector of the panel. Our aim is to solve the problem of temperature determination along the horizontal axis in the center of a coal heap shaped like a parallelepiped in the presence of a predominant airmore » current in the reacting medium of the caving zone along the strike of the seam. We assume ideal heat exchange with the ambient medium, the temperature of which is constant, and linear initial distribution from the oxygen concentration limits and air density. For a mathematical representation of processess of self-heating of coal with transition to combustion we selected the model of thermophysical processes in coking materials.« less