OCR Text |
Show energy, a the oxygen reaction order, and [Fuel N] is the fuel-nitrogen concentration of the fuel. Values for the pre-exponential factor and activation energy depends on the assumption that all the fuel nitrogen can be converted to either HeN or NH~ De-Soete suggested values for Aa' Ab,E oxid ' and Ered of 4.10 6 , 1.8.10 , 16, and 13, respectively, if th fuel nitrogen is converted to NH3 initially and 1.10 10 , 3.10 12 , 33 .5, and 30, respectively, if it is assumed that all fuel nitrogen is converted to HCN. Equation (13) shows that the rate of NO formation increases with oxygen concentration but reduces with increasing fuel-nitrogen content. It is interesting to note that NO formed, from fuel nitrogen will behave like any other fuel-nitogen species which will react with CH . This is an important key process during staged x combustion where the presence of fuel NO in the secondary oxidation zone with high CH radical concentrations would lead to its x destuction. (2) In the present model, the fuel NO produced from residual fuel oils or solid fuels (e. g. coal) is predicted using the approach adopted by Smoot et.al. (25). The kinetic mechanism of fuel-NO formation and destruction is represented by a sequence of global reactions which in addition to gas-phase kinetics considers th effect of solid carbon (e .g. char or cenospheres) on NO mlS 1 n C + 0 < --> N 2 + CO. R22 Based on the reduced mechanism RM) th v r all r ti n rates for NO and HeN can be repr s nt d (16) |