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Show accomplished by removing three out of the four bumer segments. The bumer was fired on natural gas first, then casing gas was introduced. The flow of natural gas was then reduced to a minimum value necessary to keep the bumer ignited. Casing gas flows varied from 8,000 scfh to 26,200 scfh. This is equivalent to FGR rates of 5% to 350/0. Figure 8 shows the NOx results for these tests. NOx emissions below 9 ppm were achieved for FGR rates greater than 20% which compares closely with data collected in the laboratory. Since the steamer was operating at less than 1/4 capacity (due to the limited amount of casing gas available), slightly higher NOx emissions would be expected at higher capacities. In general, CO emissions were well below 100 ppm for all test pOints. 3.3 CONCEPT OPTIMIZATION After completing the field demonstration, additional tests were conducted at laboratory scale. New fuel injection manifolds were fabricated to study the effects of injection angle, injected gas velocity and injector location relative to the main (surface) burner. Methods of further increasing the effectiveness of staged fuel injection were also investigated. The results of these tests are shown in Figure 9 for NOx emissions and Figure 10 for CO emissions. There is considerable scatter in the NOx emissions from the various injection geometries with NOx values ranging from 6 ppm to almost 40 ppm (corrected to 3% O2, dry). There are several different injection geometries that satisfy the project goal of a sub-9 ppm burner. The CO emissions were usually higher and more scattered than the NOx emissions. Given the small dimensions of our laboratory boiler, we knew that completely oxidizing the CO before the flame enters the convective section would be the greatest challenge. However, in larger and hotter systems, complete oxidation of the CO would be easier. Using the laboratory data, NOx emissions were correlated to an entrainment factor based on turbulent jet theory. The entrainment factor is given by the following equation. 11 |