Effects of Wind Flow on Self-Heating Characteristics of Coal Stockpiles

The oxidation process occurring in stockpiles of reactive materials, such as coal, induces a natural convection flow field within the pile. Due to porosity of the stockpile, this flow field is affected by the wind flow in the surrounding air. The wind sets up pressure variation around the pile and, therefore, builds up a forced gas advection field within the pile. The present work studies the effects of such a wind-driven flow field on self-heating characteristics of typical coal stockpiles. For this purpose, the calculations of the heat and mass transfer processes within a realistically shaped coal stockpile have been coupled to a wind flow model in which the wind is assumed to blow in a fixed direction relative to the pile. The calculations have been performed using the computational fluid dynamics packaged FLUENT. The calculations indicate that the wind flow significantly alters the dynamics of the flow field inside the pile and thereby affects the self-heating process. In particular, the external ‘fixed direction’ wind instigates non-symmetrical heating/concentration profiles within the pile.