Reactions of fuel-nitrogen in rich flame gases

Abstract

Fuel-nitrogen fed as ammonia or as pyridine to rich flames is mainly present in the burnt gas in the forms HCN, NH 3, NO and N 2. The HCN decays in this region to form more NH 3, and the NH 3(or species equilibrated with NH 3)undergoes two types of reactions: an oxidation to NO at rate R 1, reaction with NO to form N 2 at rate R 2. The total remaining fuel-N not yet converted to NO or N 2, i.e. RN = HCN + NH 3, therefore decays in accordance with -d[RN] dt =R1 + R2 , and the simultaneous change in NO is -d[NO] dt =R1 − R2 , Empirically, these rates can be epxressed R 1 5×10 12[ H 2 O] 2[ NH 2] [ H 2 e −20 kcal/RT mole cc,sec , R 2= 9×10 12 [ NO] [ NH 2 . R 1 is not readily interpreted in terms of elementary reactions; R 2 is the rate of NO + NH 2 → N 2 + H 2O. The findings are not necessarily valid in the primary reaction zone where other processes also occur. To the extent that all the fuel-N added to rich flames attains NO and N 2 in accordance with R 1 and R 2, however, the yield of NO is predictable a priori. The prediction agrees roughly with the yields observed.