THERMOGRAVIMETRIC ANALYTICAL PROCEDURES FOR DETERMINING REACTIVITIES OF CHARS FROM NEW-ZEALAND COALS

Tightly constrained thermogravimetric experimental procedures (particl e size < 212 mu m, sample mass 15.5 mg, CO2 reactant gas, near isother mal conditions) allow the reactivity of chars from high volatile New Z ealand coals to be determined to a repeatability of +/-0.07 h(-1) at 9 00 degrees C and +/-0.5 h(-1) at 1100 degrees C. The procedure also pr ovides proximate analyses information and affords a quick (< 90 min) c omparison between different coal types as well as indicating likely op erating conditions and problems associated with a particular coal or b lend. A clear difference is evident between reactivities of differing New Zealand coal ranks. Between 900 and 1100 degrees C, bituminous coa ls increase thirtyfold in reactivity compared with fourfold for subbit uminous, with the latter being three to five times greater in reactivi ty at higher temperature. (C) 1997 Elsevier Science B.V.