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Show 40-50 percent reduction in the amount of fuel NO produced. On the other hand, x Muzio's experiment (8) produced only 25-30 percent reduction. From these results it would appear that staged combustion was more effective for fuels containing volatile nitrogen than for those with refractory nitrogen. Volatile nitrogen was suspected to undergo more complete reduction in the rich first stage, a condition necessary for reduction of NO via two-staged combustion. Evidence x ° for this effect was found by Gerhold and co-workers (28). The distinction between volatile and refractory nitrogen, which has permitted past researchers (2,11,28) to gain a somewhat better understanding of the mechanism and effectiveness of NO control via staged combustion for residual x ° oils (2,28) and coal (11), is now applied to coal-derived liquid fuels. ROLE OF VOLATILITY OF FUEL-NITROGEN Nitrogenous fuel species will most likely undergo some thermal decomposition prior to entering the combustion zone. Some intermediate species or precursors to NO formation are formed as a result of the thermal decomposition. These x intermediate species are, in general, low molecular weight nitrogen containing compounds or radicals (HCN, NH^, NH-, NH, N). Even though investigators disagree as to the importance of the different individual species in the fuel nitrogen chemistry, there is consensus on the basic reaction path in the premixed flames, namely: . NO FUEL-N * HCN ) W\ ^ ^ N 2 The data presented by Foster and Keck (30) also support this scheme for turbulent diffusion flames. For the staged combustion to yield low NO levels, there must /C -8- |