COMBUSTION CHAR MORPHOLOGY RELATED TO COMBUSTION TEMPERATURE AND COALPETROGRAPHY

The morphology of chars sampled from various laboratory-scale reactors operating at temperatures from 800 to > 1400 degrees C, together with chars collected directly in the flame zone in a full-scale pulverized fuel combustion experiment, was examined. A coal and coal blend domin ated by vitrinite-rich microlithotypes together with four coals domina ted by inertinite-rich microlithotypes were used to produce the combus tion chars. Char samples produced at temperatures above similar to 130 0 degrees C have a morphotype composition very similar to the composit ion of the full-scale char samples, whereas the morphotype composition s of those produced at similar to 1150 degrees C or lower are signific antly different. Correlation between coal petrography and char morphol ogy and determination of char reactivity should thus be attempted only using chars produced at temperatures comparable with those for the in tended use of the coal. A clear distinction between the high-temperatu re char samples (burnout 50-60 wt% daf) emerges which is related mainl y to the parent coal petrography and probably secondarily to the rank. Vitrite, clarite and vitrinertite V may be correlated with the porous tenuisphere and crassisphere morphotypes, whereas inertite, durite, v itrinertite I, duroclarite and clarodurite may be correlated with the crassinetwork-mixed-network-mixed morphotype group. Copyright (C) 1996 Elsevier Science Ltd.