Eliminating scale effect: Development and attenuation of coal spontaneous combustion

Low temperature oxidation can occur in coal and coal piles, which can lead to severe fires in coal fields, storage rooms, and goaf areas. An important feature of these coal fire disasters is their large scale, providing a favorable environment for the inoculation of coal fires. A new method for studying coal oxidation reactions, which combines theoretical analysis with multi physical field numerical models, has been proposed to eliminate the influence of scale effects. Based on the theoretical analysis, the reliable numerical simulation conditions are obtained, and the results are compared with those of large coal spontaneous combustion experiment. The temperature, gas and reaction rate of coal oxidation have been analyzed and verified. The attenuation characteristics of coal oxidation reaction under sealed and nitrogen retarding measures have also been analyzed with emphasis. The research results indicate that the proposed new simulation method has been proven to be effective through multiple results validation. Sealing measures can weaken coal oxidation reactions, but heat elimination is slower. The measure of injecting nitrogen can quickly control local coal oxidation reactions and remove heat. The greater the flow rate of inert gas, the better the retarding effect on coal. The development process of coal oxidation will form "quasi spherical" and "crescent shaped", which are prominent characteristics of slow oxidation and rapid propagation, respectively.