An experimental investigation on the effect of convection on the ignition behaviour of single coal particles under various O₂ concentrations

An experimental study on the convection effect on the ignition behavior of single coal particles with size of ∼1.5 mm was carried out in an electrically heated vertical tube furnace under various O₂ concentrations and temperatures ranging from 873 K to 1123 K. Under all test conditions, anthracite particles ignited heterogeneously. However, the ignition mechanism of the bituminous coal particles was conditionally changed by the convention. For both coals, the ignition delay time decreased and then increased with the increasing convection intensity, and the variation trends were insignificant under strong convections or high furnace temperatures. Under O₂-enriched conditions, convection is in favor to coal ignition at low furnace temperatures and even cause asymmetrical hetero-homogeneous ignition. The ignition temperature of bituminous coal decreased and then increased with increasing convection intensity. It slightly decreased with the increasing O₂ concentration at a weak convection and remained nearly constant when convection was rather strong. The influencing mechanisms of convection on coal particle ignition were discussed.