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Show gas rates that can be achieved at those high air temperatures (Figure 6). This feature makes the StAR burner attractive for both operations that use ambient air and operations that use high levels of air preheat. Fmally, the performance of the StAR II burner at turndown was investigated. The optimized burner showed an improvement in NOx emissions at turndown (Figure 7), partly because the lower thennalloading lowers the flame temperatures, but also because the relative recirculated flue gas rate increased as the burner was turned down (to as much as 36% at 4:1 turndown). The efficiency of a jet-pump is a strong function of the mass-flow rates and velocities in the jet-pump. In the design of the jet-pump, advantage can be taken of this feature to match the recirculation rates with the needs of the burner at any firing rate. The optimization and detailed characterization of the StAR II burner at the BERL allowed several significant improvements to be made to the StAR burner and provided valuable insights into its operation. Firs~ the NOx emissions from the StAR prototype were reduced by 5 - 10 ppm compared to the original configuration. Second, the turndown performance of the burner w~ improved so that very low NOx emissions were achievable at flring rates as low as 20% of design. Finally, the stability of the flame when operated with cold air was improved. Application of the StAR Burner to an Indusbial Furnace Schlosser Forge in Cucamonga, California was selected for the initial field trial of the StAR II burner. Schlosser is a market leader in the production of nickel-based alloy and titanium aircraft turbine rings. Being situated in the Los Angeles area, they are subject to the SCAQMD's RECLAIM regulations governing NOx emissions. Thus, they are faced with the need to signiflcantly reduce total NOx emissions from their plant over the next 9 years. This situation is exacerbated by their plans to add additional furnace capacity. Two StAR II burners were installed on a new box-type forge furnace as shown in Figures 8 and 9. This unit operates in a batch mode with charging cycles of 15 to 120 minutes. Depending on the material being heated, the furnace temperature ranges from 1090 - 1505 K (1500 - 2250°F). The furnace is equipped with two radiationtype recuperators capable of preheating the combustion air to 700 - 755 K (800 - 900<>p). This furnace has now been in operation for about one year. Over this period, the StAR II burners have achieved very low NOx and CO emissions. Using 730 K (850°F) combustion air, NOx levels are 25 - 35 ppm across the entire load range. In all cases, CO emissions are below 30 ppm. At this combustion air temperature, the NOx levels achieved are 80 - 90% below emissions from companion furnaces at Schlosser that employ conventional self-recuperative burners. 11 |
