Propagation of Smouldering in Wood Dust Deposits Ignited by Embedded Hot Bodies

Combustible dust poses a hazard to industry in two ways, i.e., reactive as a cloud or reactive as a pile. This paper deals with the smouldering behaviour of wood dust deposits initiated by hot bodies. Effects of embedded depth and airflow condition are investigated. Two sizes of wood dust are selected as test samples, namely wood powder and wood chip. The results indicate that under the same hot bodies embedded depth, wood chip combustion propagates faster than wood powder in general due to its unique flocculent structure. Due to the increased insulation effect of the wood dust layer, the temperature at the same measuring point is higher than that of the wood chip layer. In addition, under airflow conditions, the smouldering propagation of wood deposits is significantly higher than that without airflow (2.42 and 4.34 m/s) for both wood powder and wood chip samples. However, the deposited wood powder has a lower minimum ignition temperature than wood chip. Accumulated wood dust in considered to have a greater fire risk in powder form.