Two Simple Models for the Noncatalytic Reduction of NO with NH3

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1.6.1 TWO SIMPLE MODELS FOR THE NONCATALYTIC REDUCTION OF NO WITH NH3 P.C.T. de Boer* Sibley School of Mechanical and Aerospace Engineering Cornell University Ithaca, New York 14853 ABSTRACT A detailed investigation is made of two simple models for the noncatalytic reduction of NO by NH3 in oxygen-rich postflame gases (the "Thermal DeNOx" process). The first model is that proposed by Seery and Zabielski, and by Fenimore. It is based on the reactions (1) NH2 + NO -+ N2 + H20; (2) NH2 * OH -» -> NO; and (3) NH3 + OH -> NH2 + H20. As noted previously by Fenimore, reactions (1) and (2) lead to the existence of a critical concentration CN03C, below which CN03 cannot be reduced. The nondimensionalized rate equations for reactions (l)-(3) are solved analytically for the case of constant OH-concentration. The solution is compared with the experimental data of Muzio, Arand and Teixeira; it is found that the corresponding OH-concentrations are well below their equilibrium values. This is taken into account in an extended model, where the replenishment of OH is rate-limiting. The results of the extended model can be fitted quite well to available experimental data. The model is applied to conditions typical of gas turbine combustors. * Part of this work was done while the author was on leave at the General Electric Company, Schenectady, N.Y. 12345.