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Show 1.6.4 to the findings of Sahmian and Hansen [163 and others that [OH] actually may vary with time. Sec. IV of the present paper considers *: extended model in which the value of [OH] is determined by a kinetic process involving reactions (2) and (3) as sinks. The model includes a net production term for [OH], the branching coefficient oc, the reaction NH3 • H -> NH2 • H2, and a destruction term for H. It is believed that the extended model incorporates all of the essential features of the Thermal De-NOx process, while retaining much of the simplicity of the Seery-Zabielski-Fenimore model. The extended model is used in Sec. V to analyze the possibility of applying the Thermal De-NOx process to gas turbine combustors. II. THE SEERY-ZABIELSKI-FENIMORE MODEL An important step in the Seery-Zabielski-Fenimore model is the conversion of NH3 into NH2 by reaction (3). Upon assuming that equilibrium is maintained in this reaction, as well as in the reactions between OH, H20 and 02, it is possible to calculate the NO and NH3 concentrations as a function of time after injection. To this purpose, use can be made of the values for k^, k 2 and k3 listed in [25] and [121 The results can be compared with the experimental data obtained by Muzio, Arand and Teixeira [4] and by Fenimore [121 The predicted rate of NO reduction is found to be much larger than observed; at temperatures near 1200 K, the difference is a factor on the order of 100. This difference implies that reaction (3) is slow, and hence is rate-determining in the model of [11] and [121 Consequently, it is useful to write the rate equations governing the NO destruction process in the form edx/dr = -z(x - xc) (5) dy/dT = -y (6) edz/dr = -z(x + xc) • ey (7) where e = k3COH]/(kiCNO]0), and where x = [NO]/[NO]0 is the nondimensionalized NO-concentration, xc = [NOJC/WOIQ the nondimensionalized critical NO-concentration, y = [NH3]/ [NO]0 the nondimensionalized NH3-concentration, z = [NH2]/[NO]Q the nondimensionalized NH2-concentration, while [NO]0 is the initial NO concentration and T - k3[OH]t = t/tc the nondimensionalized time. It is assumed that c « 1, the validity of this assumption can be verified from experimental data (see Sec. III). Furthermore, it is assumed that the temperature T is constant in the zone where the NO reduction is taking place. Eq. (6) has the immediate solution |