Reactivity distributions and extinction phenomena in coal char combustion

Based on in situ optical measurements and off-line analyses for four coals, the basic features of single-particle pulverized coal char combustion have been elucidated as a function of carbon conversion. Two regimes can be clearly defined: one at low carbon conversion, where the reacting particle populations have properties that are nearly time invariant and a second regime at higher carbon conversion where the distribution properties change dramatically. At low carbon conversion, there is a broad distribution of single-particle combustion rates, reflecting the heterogeneity in the parent fuel. Particle-to-particle reactivity differences are shown to be the primary cause of the broad temperature distribution for Pocahontas coal char