Ignition and combustion behaviors were observed for pulverized coal particles which were suspended in a laminar upward flow and were heated by a single pulse Nd : YAG laser. The surface temperature of the particles was estimated to increase at a rate of about 106K/s. For a bituminous coal, observations with high-speed video revealed that the coal particles ignited heterogeneously 1-2ms after the laser pulse operation and this was followed by the evolution of volatile materials and their combustion in the gas phase. A rate constant of surface oxidation reaction of the bituminous coal at a temperature range between 800K and 1400K was calculated by an analysis of the ignition temperatures of the particles. The reaction order for oxygen partial pressure was 1.0 and the activation energy was 50KJ/mol, which coincide with published values determined by heterogeneous reaction theory. Ignition temperature varied several hundred degrees for the same coal and experimental conditions due to the difference of chemical characteristics of particles. This corresponded to a three-times variation in the frequency factors.


Mechanical Engineering



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