OCR Text |
Show (7) The rate of change of NH3 was determined from the following nitrogen balance: = - d(NO) dt d(HCN) _ 2 d(N2 ) (8) dt dt The decay of OH was based on OH + H + M --> H20 + M recombination reaction, with H in partial equilibrium with H20 and H2. This gave the following expression for OH decay rate: d(OH) = dt (9) All functions fi can be expressed as follows (see Table I): N B .. (OH)mjj I; = L A ij T II exp ( T'l) X j (H20)"J This mechanism differs from that reported earlier10 in the inclusion of NO + NH as an N2 forming reaction in the overall mechanism. The previous analysis allowed for the formation of N20, which would introduce an error in the nitrogen balance (Equation 8), since N20 was not included in the balance. Furthermore, the modified analysis allows the evaluation of N20 concentrations, which can be utilized to test the validity of the nitrogen balance. The following reactions are proposed as the dominant reactions affecting N 20 formation and destruction: NH + NO --> N20 + H N20 + H --> N2 + OH A pseudo steady state assumption of N20 gives the following expression: (N 0) = t. (NH3 ) (NO) 2 9 (H 2 ) The values of the parameters of functions fi are listed in Table 1. (10) (11) (12) Simultaneous solution of Equations 3, and 6-9 can give predictions of all nitrogenous species (NO, HeN, and NH3), provided initial values of these species are known. The initial 7 |