| OCR Text |
Show 60 17Ju/y 1990 3.9x IiJ6Btu/hr Ll 0 Pilot ON 50 ~ Pilot OFF ~ () Pilot ON, FGR 15 40 .d 18Ju/y 1990 3.9 x lOS Btu/hr ~ 0 Pilot ON fI. M (J Pilot ON, FGR 15 ~30 E • Pilot ON, FGR 30 D. D. 0 ~ Pilot ON, FGR 50 Z 20 ~ 4.4 X 106etu/hr, Pilot 6.6 x 106 Btu/hr .Ll Pilot ON ~ Pilot ON, FGR 15 10 ~ Pilot ON, FGR 30 ~ Pilot ON, FGR 50 0 0 2 3 4 5 6 7 8 9 10 ~%(d) WJS100SA.DAO Figure 5 The Influence of Oxygen on NOx Emissions. minimum level of NOx which could be achieved was 12 ppm (d, 3% 02). The decrease in NOx with increase in O2 concentration for a premixed flame is the opposite of that which occurs for a diffusion flame. In the premixed flame, additional air reduces the flame temperature which has a larger influence on NOx production than the increase in oxygen concentration. Addition of flue gas results in further reduction of the flame temperature. The amount of NOx reduction which can be achieved by addition of flue gas recirculation is reduced at higher levels of flue gas recirculation. In fact, 12 ppm (d, 3%) NOx appears to be the limit which can be achieved by diluting the flame with either air or flue gas. The implication of this limit is that NOx emissions is insensitive to changes in temperatures at this level. 12 WJSlOO5APAO / AFRC-90-25 |
