Effects of Mixing and Thermal Quenching on NO Reduction by Selective Non-Catalytic Reduction in the Presence of CO

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co + OH -> CO2 + H, while the second effect is due to chain branching reactions that result from the H produced in this reaction. This enhancement of SNCR chemical rates leads to the shifting and narrowing of the temperature window for SN CR and also explains why increased jet momentum leads to higher reductions in the presence of CO. The chemical kinetics are faster in the presence of CO such that the increased mixing caused by higher injection momentum was beneficial. In the absence of CO, increases of injection momentum with the accompanying diluent nitrogen lead to reductions in efficiency as the reactants pass through the temperature window before they can react. Figure 12 compares measurement to predictions for two injection temperatures at high and low quench rates. The fully detailed chemical kinetics, applied to homogeneous, · thennally quenched conditions, consistently over-predicts NO reduction by a large margin. The coupled turbulent mixing and chemical kinetic model, however, predicts both the magnitude and trends of the experimental data. Notice that as the injection temperature is decreased from 1303K to 1267 K NOp'N0i more than doubles in both the model and the experiment. Also, as the quench rate increases from 418 to 2420 K/s, NOfNOi more than doubles. The model also captures the effect of ~njection momentum as accomplished by increasing the diruent nitrogen flow. As shown in Figure 12, increases of injection momentum consistently result in higher NOfNOj in the absence of CO. Effect ofCa FigUre 13 presents the measurements and predictions of NOfINOi for the cases with and without CO for a reagent injection temperature of 1267 K, and high and low quench rates. In all cases the JASPER model captures the magnitude and trend of the NO reduction efficiency. The model even predicts the changing dependence of NO reduction on the momentum ratio depending upon the presence of CO. Notice that in all cases a lower quench rate is better than a higher quench rate. Also, the addition of CO is always beneficial for the higher quench rate cases but is not beneficial for the lower quench rate conditions except at high reagent jet injection momentum. These data and predictions indicate the complex interaction of the turbulent mixing and chemical reaction processes present tin the ASR process that are accurately predicted by the JASPER model. Conclusions Selective NO reduction involves the competition between two chemical kinetic pathways: the oxidation of selective reducing agent producing NO, and the selective reduction of NO by reactants produced as the reducing agent decomposes. Although these chemical processes have been modelled successfully, it is difficult to integrate this relatively complex mechanism into a mixing model to quantify the effects of reactant contact under thermal quenched conditions, especially in the presence of CO. The fully coupled CFD/chemical kinetic model described above has been used to determine how the competing pathways interact under mixing limited, thermally quenced conditions in the presence of CO, and how they affect SNCR performance. Pilot scale results of selective non-catalytic reduction of NO by ammonia have indicated that high reduction efficiencies are possible with rapid mixing and nearly isothermal conditions Page 8