Determination of Critical Self-Ignition Temperature of Low-Rank Coal Using a 1 m Wire-Mesh Basket and Extrapolation to Industrial Coal Piles

Abstract

Spontaneous combustion of coal stockpiles can occur when the environment temperature exceeds the critical self-ignition temperature (CSIT), which strongly depends on the pile volume. Measurements of the self-heating rates of a low-rank coal were carried out at various ambient air temperatures using pile heights of 2.5 to 10 cm (laboratory-scale) and 25 to 100 cm (large-scale), simulated using cubic wire-mesh baskets of different sizes. The experimental results demonstrated the feasibility of using the established Frank–Kamenetskii model in prediction of coal pile self-ignition. The larger-scale experiments showed quite different temperature variations during the heating process compared with the laboratory-scale experiments. Gas emissions and height changes of the piles revealed characteristics of the different stages of heating. Analysis of data obtained from the larger-scale tests demonstrated that prediction of CSIT based on laboratory experiments is reliable and useful. Relationships for CSIT and safe...