PYROLYSIS OF COAL MACERAL CONCENTRATES UNDER PF-COMBUSTION CONDITIONS(I) - CHANGES IN VOLATILE RELEASE AND CHAR COMBUSTIBILITY AS A FUNCTION OF RANK

The pyrolytic behaviour of sets of maceral concentrates have been exam ined under conditions similar to those of pf-combustion. Relative comb ustion reactivities of chars prepared during the pyrolysis experiments have been compared by standard methods. As expected, for samples of s imilar elemental C-content, total volatile release decreased as: lipti nite > vitrinite > inertinite. The data indicates the absence of syner gistic effects between vitrinite and inertinite during pyrolysis. The sensitivity of pyrolysis yields to inertinite content was found to dim inish with increasing coal sample rank. In marked contrast to the orde r established for volatile release, combustion reactivities of maceral chars (of similar carbon content) may be ranked in the order: inertin ite > vitrinite > liptinite. A direct comparison with maceral concentr ates from the same coal was undertaken. Vitrinite/inertinite graded sa mples of a South African coal were pyrolysed at 1500 degrees C: these chars exhibited increasing reactivity with increasing inertinite conce ntration, but observed differences in reactivity between samples from the same coal were not large. Furthermore, for a higher rank coal, cha r reactivities were found to be essentially independent of original in ertinite concentration. It is clearly possible for chars from low vola tile coals to be relatively reactive. However, there appears to be no reason to suggest that 'reactive inertinites' might release volatile m atter in quantities comparable to those of vitrinites from the same co al. (C) 1998 Elsevier Science Ltd. All rights reserved.