SELF-IGNITION AND CONVECTION PATTERNS IN AN INFINITE COAL LAYER

Abstract

Abstract Spontaneous combustion can occur in a coal stockpile if the heat generated by oxidation cannot be dissipated at near ambient temperature. Determination of conditions for which combustion occurs is of great importance in designing coal stockpiles. An approximate analysis is used to obtain natural convection patterns in a laterally-unbounded layer of coal. Down-hexagons and two-dimensional rolls appear to be the stable flow planforms. A continuation procedure gives a simple criterion for the point of ignition in the layer in terms of easily measurable parameters. This criterion can be used to determine ignition points in the interior of a large coal stockpile and complements earlier work in which a similar criterion was developed for the edge of a stockpile.