ESTIMATION OF KINETIC RATE PARAMETERS FOR COAL COMBUSTION FROM MEASUREMENTS OF THE IGNITION TEMPERATURE

Combustion reactivity plays a significant role in the development of o ptimal strategies for the efficient utilization of coal. A promising t echnique for characterization of combustion reactivity involves measur ement of the gas temperatures which lead to the ignition of coal parti cles of different sizes, and the use of classical ignition theory to e xtract the relevant reaction rate parameters. This paper examines the influence of the modeling assumptions, within the framework of heterog eneous ignition theory, on the combustion rate parameters calculated f rom experimental data. It is shown that unequivocal determination of r eaction order from ignition data is difficult. Further, the manner in which the rate constant is defined-whether it is based on the external or the internal surface area-exerts a significant influence on the re activity parameters. The effect of radiation is included in the energy balance and shown to influence the results substantially, for larger particles in particular. Finally, it is shown that combustion reactivi ty determined from ignition measurements does not differ significantly from other measurement techniques if the effects of radiation and mas s transport limitations are accounted for. (C) 1998 Elsevier Science L td. All rights reserved.