| OCR Text |
Show Burner Concept Air Staging American Flame Research Committee 1992 Fall International Symposium October 19-21, 1992 NOx Reduction Strategy for the High performance StAB Burner The key features of the StAR burner include: • Staged combustion: quasi adiabatic fuel-rich pyrolysis zone in a refractory lined precombustion chamber . • Aue gas recirculation (FOR): flue gas recirculated into the fuel-rich pyrolysis stage of the flame by jet pump action • Multiple secondary air jets to penetrate the flow of pyrolysis products and complete the ' , '- combustion process Staged combustion, which is effective in reducing NO, emission from combustion of organically bound nibUgen bearing fuels. can also be used for hydrocarbon fuels that do not contain fuel-N compounds. Under these latter conditions, however. the reaction paths of NO formation and destruction are different. In fuel-rich hydrocarbon flames. the source of NO is the fixation of annospheric nittogen (NJ by hydrocarbon fragments, in reactions such as: CH + N2 = HCN + N CH1 + Nl = HCN + NH The N atom from the first reaction can then participate in the following fast reaction: N+OH=NO+H However. the other products. HeN and NH will be partially converted in the fuel-rich flame to molecular nibUgen. (NJ. provided that the temperature is sufficiently high (f ~ 1400 K) and there is sufficient residence time for these reactions to go to completion. The NO fonned by the reaction of N2 with hydrocarbon radicals or inttoduced through external FGR can also be convened back to N2 through a "rebum" route in the fuel-rich flame. This process is initiated by reactions producing HCN, e.g.: CH + NO = HCN + 0 , I J .--~ |
