Low-temperature oxidation of coal .3. Modelling spontaneous combustion in coal stockpiles

In the first two papers of this series, a reaction-diffusion model for low-temperature oxidation of coal was developed and used to extract kinetic rate parameters for a Wyoming subbituminous coal. In this paper, this model is incorporated in a two-dimensional model for spontaneous combustion of open coal stockpiles where the influence of moisture migration can be neglected. Wind-driven forced convection is found to be the dominant mechanism for how of air within the open stockpile. The model calculations are in excellent qualitative agreement with observations reported from large-scale tests. The roles of bed porosity, side slope, wind velocity, coal reactivity and bed particle size are examined in detail. A correlation is also developed for long-term safe storage of coal in open stockpiles.