The char combustion reactivities of a western subbituminous coal and an eastern hv bituminous coal were measured in Sandia's Char Combustion Laboratory. Coal particles ranging from 90 to 106 μm in diameter were injected into an entrained flow reactor. The gas flow was provided by a Hencken burner, combusting a mixture of methane, hydrogen, and oxygen, with a nitrogen diluent. In situ measurements of particle temperature, size, and velocity were made using a two-color optical sizing pyrometer. The oxygen content of the gases ranged from 6 to 37 mole-%, while the gas temperature was approximately 1600 K. Char reactivity was determined from the optical data using an energy balance and gas-particle transport model. Data were fitted to a simple wth-order reaction model of the form n_c~"= A p_(o_2,s)~n e~(-E/RT_p) using a non-linear least squares method. Most of the particles were burning close to the diffusion limit under the conditions of this study, making it difficult to determine precise values for the kinetic coefficients. Approximate best-fit values were E = 80 kJ/mol and n = 0.1 for both sets of data, with A = 2230 mol/m~2-s-atm~n for the subbituminous coal and A = 1940 mol/m~2-s-atm~n for the hv bituminous coal. The simple single-film model appears to be a suitable representation of the char combustion under the conditions of this study.
展开▼
