Combustion characteristics of naturally weathered (in situ) bituminous coals

The relative combustion behavior of five companion outcrop bituminous coals (naturally weathered) and five deep-mined (unoxidized) coals was determined. Chemical and structural differences between the weathered and fresh coals and the extent of oxidation were also determined. The combustion behavior was evaluated in terms of ignition temperature, char reactivity and combustion efficiency (carbon burnout). The relative ignition temperatures of the crop coals were less than those of the corresponding fresh coals in all cases. Devolatilization of the crop coals began at a lower temperature and extended over a wider temperature range than for the fresh coals. The reactivity and the combustion efficiency of the chars produced from the crop coals were higher than those of the corresponding fresh coals. Consequently, the "ease of combustion" was greater for the crop coals than their fresh companions.