OCR Text |
Show Results The air staging research program involves several sets of ongoing experiments. First, the standard burner was benchmarked for later comparison. The subsequent experiments involved different methods for introducing secondary combustion air independent of the vortex. The basic burner showed a remarkable pattern when the primary air was reduced below stoichiometric conditions. The normal NOx emission on the order of 100 ppmv was demonstrated for lean fuel conditions, while a previously undiscovered ultra-low NOx plateau less than 10 ppmv prevailed for rich fuel conditions (see figure 2). The transition between the two plateaus was abrupt. A two plateau pattern also emerged for the CO, one for lean conditions at 11 ppmv, and the other for rich conditions at over 2000 ppmv. It was not possible to attain experimental conditions where both NO and Co would be below their high plateaus at the same time. Further testing will be done to optimize the burner's performance. The numbers and locations of secondary air ports will be considered. It is also possible that another group of experiments will be conducted to test the performance of an annular shell around the combustion block to introduce the secondary air. Conclusions The experimental results form rich combustion with a high intensity burner raise important questions about the relative importance of flame chemistry and flame temperature in NOx formation. The recirculating vortex of the AECOmetric High Intensity Burner creates a unique environment of almost perfectly mixed air, fuel, and exhaust gases which is usually found only in laboratory experiments. The abrupt transition between the "high" NOx and ultralow NOx operating modes of the burners do not favour an explanation based upon temperature. The effort to oxidize CO independent of the furnace is not a serious limitation on applications of the AECOmetric High Intensity Burner in ultralow NOx applications. The oxidizing environment downstream of the burner is extremely important in determining the ultimate CO emissions form the combustion system as a whole. If a chamber downstream of the burner can maintain temperatures in excess of 1400 degrees Fahrenheit for a residence times on the order of one second, then the CO emissions from the burner are not significant. However, the research will benefit finding the widest number of applications for the new technology and will continue. Page 4 |