NOx emissions from intermediate-temperature combustion of steel-industry by-product gases

A study of NOx emissions from the combustion of coke-oven gas and blast-furnace gas (steel industry by-product gases) was undertaken using detailed kinetic modeling to elucidate the pathways for NOx formation. The study was performed at the intermediate temperatures (1200-1400K) and 1 atm, which represent conditions found in a commercial, ultra-low NOx burner. Simulation results indicated that nitric oxide is formed exclusively in the radical-rich flame zone under these conditions. The traditionally-accepted pathway of Fenimore 'prompt' NO formation, through methylidene and methylene attack on nitrogen molecules, was found to play no role under the conditions of our simulations. In light of this finding, kinetic pathways for NO formation were re-examined. It was found that, according to currently available kinetic parameters, the NO formation is controlled by the H + N 2 reaction. Recently published studies on this reaction, as well as on the rate for the products-set-corrected spin-conserved pathway for the CH + N2 reaction, agree with our finding that the H + N2 channel will be the dominant initiation reaction to NO formation from nitrogen molecule. The NOx emissions from our simulations were found to consist almost exclusively of nitric oxide.