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Show Currently available burners can reduce NOx by up to 60 percent or can achieve NOx emissions of 60-80 ppm (d, 3% 02)' Newly developed burners can reduce the level of NOx emissions to 30-40 ppm (d, 3% 02) without flue gas recirculation (FGR) and to values approaching 15 ppm (d, 3% 02) with high levels of FGR (Figure 2) (4). The cost of reducing NOx using low NOx burners without FGR can be less than $200/ton N02 removed. Use of FGR can increase the cost of NOx removal to $300-400/ton N02 removed. This work was initiated to determine the NOx emissions levels which can be achieved using different burner design concepts. The approach was to use equilibrium, kinetic, and simple aerodynamic calculations to determine the configurations and geometry which would result in low emissions of nitrogen oxide (5). These results were then used to design a versatile burner which could operate in a number of configurations which produce low levels of NOx emissions. The results of the calculations and the burner design were reported by Pohl (5). This paper reports the results from testing the premixed configuration of the burner between 3.9 and 6.6 x 106 Btu/hr. EXPERIMENTAL The premixed configuration of the burner is shown in Figure 3. Natural gas is reduced from a pipeline in Hsinchu, Taiwan, metered through a rotameter and fed to the back of the burner. Flue gas, if used, is drawn by a fan from the exit of the furnace, cooled to 150°C (300 OF) by a water spray, measured with an orifice meter, and fed radially into a shroud surrounding the natural gas chamber in the rear of the burner. The water spray will increase the water content and heat capacity of the flue gas. The shroud has holes around the natural gas chamber which evenly distributes the flue gas into the natural gas. The rear natural gas chamber is isolated from the air chamber by two layers of 1 mm opening screen to help prevent flashbacks. The mixed natural gas and air exits into a second chamber where air is fed through a perforated shroud. The face of the burner is covered with two layers of 1 mm opening screens to prevent flashback from the furnace. The burner is set within a cast refractory quad which has inside diameter of 381 mm, an outside diameter of 576 mm, a total depth of 271 mm, a throat depth of 220 mm (half angle. 5 WJSlOO5A.PAO / AFRC90-25 |