A REDUCED KINETIC-MODEL FOR NOX REDUCTION BY ADVANCED REBURNING

Advanced reburning technology, which makes use of natural gas injectio n followed by ammonia injection, has proven to be an effective method for the removal of up to 85-95% of the NO in pulverized, coal-fired fu rnaces;: This paper reports the development of a seven-step, Ii-specie s reduced mechanism for the prediction of nitric oxide concentrations using advanced reburning from a 312-step, 50-species full mechanism. T he derivation of the reduced mechanism is described, including the sel ection of the full mechanism, the development of the skeletal mechanis m, and the selection of steady-state species. The predictions of the s even-step reduced mechanism are in good agreement with those of the fu ll mechanism over a wide range of parameters, applicable to coal-based , gas-based, and oil-based combustion cases. Comparisons with three in dependent sets of experimental laminar data indicate that the reduced mechanism correctly predicts the observed trends, including the effect s of temperature, the ratio of(NH3/NO)(in), and concentrations of CO, CO2, O-2, and H2O on NO reduction. The observed effects of CO on NH3 s lip were also reliably predicted. Mechanistic considerations provide a n explanation for the roles of the important radicals and species. Als o, parametric studies of the effects of CO2 and H2O have been performe d with the reduced mechanism. A maximum in NO reduction exists, which strongly depends on the concentrations of NOin, CO, and O-2, the ratio of (NH3/NO)(in), and temperature.