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Show (2) W h e n propane afterburning was conducted through the burner, a higher N 2 0 reduction could be achieved with a lower air flow rate to the burner, especially if the thermal input to the burner was limited. (3) O n the basis of thermal input, methane is the least effective secondary fuel, while ethane and propane have a similar ability, in reducing N 2 0 emissions. (4) N 2 0 reduction by afterburning is usually accompanied by a comparatively small increase in N O x emissions. Methane injection results in the largest increase in N O x emissions compared with it's N 2 0 reduction. (5) The difficulty in complete combustion in the afterburning zone, under conditions of this study (ca. 1123 K, 6 % initial oxygen and 0.3 s), also indicates that methane is not a good secondary fuel to be injected to reduce N 2 0 emissions. If methane is to be used as an afterburning fuel, the configuration with the burner, rather than direct fuel injection, is preferred so that both low N 2 0 emissions and complete combustion of methane can be achieved. However, this remains to be experimentally confirmed. (6) Gas phase modeling shows that thermal decomposition of N 2 0 plays only a minor role in reducing N 2 0 emissions, compared with gas phase radical reactions. In addition, the modeling also confirms that methane is less effective than ethane in reducing N 2 0 emissions even if both fuels are completely consumed in the afterburning zone. ACKNOWLEDGEMENT The authors would like to acknowledge the financial support from the E P S R C (UK) for the research work presented in this paper. Technical help from Mr. E. Woodhouse is also acknowledged. |