COMBUSTION IN THE BURNOUT STAGE - THE FATE OF INERTINITE

The paper reports on the fate of inertinite-type chars during high tem perature combustion. The aim is assessing the extent to which inertini te macerals affect combustion efficiency as measured from percentage b urn-out. Char samples from three medium to high-inertinite coals varyi ng in burn-off between 20% and 99.7% were taken from the KEMA 1 MW com bustion test facility. The samples were analyzed by classical microsco py. Char particles were identified as inertinite-type by visual observ ation. The concentration of inertinite-type particles in char does not change significantly at intermediate stages of combustion, between 30 % and 98% burnoff. When less than 2% of the original coal is left unbu rnt, there is a shift in char composition. Higher concentrations of la rge (>8 mu m) fusinoid and inertoid particles are found in the last st age of burn-out for two of three coals. During most of the time solid chars from inertinite burn at the same rate as porous chars. In the fl y char, the percentage unburnt from inertinite is only slightly higher than the average unburnt from the whole coal.