The structural changes of bituminous coal particles during the initial stages of pulverized-coal combustion

Abstract

The effect of the chemical composition of pulverized bituminous coal particles on their physical transformation during the initial stages of combustion has been investigated. The results suggested that cenosphere formation does not require extensive thermal decomposition of the coal particles. The vitrinites in the bituminous coal softened earlier and developed larger cenospheres than the other macerals. The coal particles swelled to a higher extend during combustion than in pyrolysis; however, the cenospheres formed in the former process experienced a higher extent of fragmentation. The formation of micropores in char particles appeared to be related to the thermoplasticity and secondary devolatilization. The increase in microporosity occurred predominantly during the shrinkage of the cenospheres. Inertinite-rich samples developed higher microporosity than liptinite-rich particles during both pyrolysis and combustion for a given extent of weight loss.