ASPECTS OF COMBUSTION BEHAVIOR OF COALS FROM SOME NEW-ZEALAND LIGNITE-COAL REGIONS DETERMINED BY THERMOGRAVIMETRY

Thermogravimetric analysis of five Late Cretaceous and Cenozoic New Ze aland lignites demonstrate that their combustion behaviour is distinct from that of subbituminous coals and may be characterised by peak tem perature (T-6 = 377-416 degrees C), maximum rate of combustion (R-C = 25-31%wt min(-1)), and temperature of char burnout (T-8 = 421-497 degr ees C). These parameters reflect variation in thermal behaviour associ ated with both the organic and inorganic constituents of the coal. The information obtained is additional to that found by proximate analysi s; the latter alone proves insufficient to predict the combustion beha viour of the coals relative to one another. A post-combustion thermal event, T-9, is seen among the lignites as in other low-rank coals comb usting below 600 degrees C, which appears to be related to the organic sulphur content of the coal. (C) 1997 Elsevier Science B.V.