| OCR Text |
Show A second flammability limit graph (Figure 4) is provided that shows the flammability limits for the six mixtures of hydrogen and carbon dioxide tested. In addition, a constant temperature line of 1900°F is shown. The fact that the burner flamed out at an operating condition for which the adiabatic flame temperature was slightly below 1900°F might suggest that this temperature may be an absolute minimum operating temperature. If this is the case, then the limits of burner operation with respect to air flow are much narrower than the flammability limit curve might suggest. For example, for the 31 % hydrogen fuel the upper limit is approximately 17 % hydrogen while the lower limit is 14 % hydrogen or the oxygen limits are 9% and 12%. VIll. Correlation of NOx vs. O2 vs. % Inerts Significant data has been obtained relating NOx emissions from the Callidus internal recirculation staged fuel burner to variations in thermal input, excess air and the proportion of low heating value (LHV) off gas frred. The NOx levels resulting from these trials are shown in Figure 5 through Figure 12. To examine the effect of combining NOx minimizing techniques, in this case low excess air frring and the utilization of a low heating value gas as a fuel, on the burner emissions it was assumed that the relationship between NOx emissions, O2, and % LHV could be modeled as linear functions. The gradient of these linear functions can then be interpreted as the sensitivity the NOx production to altering the excess air levels or the proportion of LHV off gas frred. This provides a means of representing any NOx vs. O2 curve or NOx vs. percentage of LHV off gas fired curve as a single point, and by combining these points in a plot of the effect of varying amounts of LHV off gas in the fuel on the sensitivity of NOx to O2 or the effects of varying excess air levels on the sensitivity of NOx to percentage of LHV off gas frred can be made. These plots are shown for data relating to frring rates of 25 %, 50%, 75 %, and 100% of design heat release, Figure 13 and Figure 14. The analysis shown as Figure 13 shows that the addition of LHV off gas caused a reduction in NOx emissions at all excess air frring levels and all burner heat release rates (all data is 11 |
