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Show INTRODUcnON Emissions regulations are forcing the replacement of conventional fast mixinglhigh-NOx emitting pulverized coal burners with 10w-NOx designs. Therefore, it is crucial to minimize the potentially adverse effects associated with such retrofits. For example, longer flames and higher unburned carbon levels of low-NOx burners could hamper the boiler performance and create fly ash recycling and disposal problems, particularly in single-wall fired units with shallow depth furnaces. Burning lower volatile and less reactive coals can further exacerbate the situation. In a continuing effort to improve the combustion and emissions performance of lowNOx PC burners, Babcock & Wilcox has conducted research and development programs to address such issues. This investigation is aimed at evaluating innovative mixing devices in the burner coal nozzle to improve combustion efficiency while minimizing NOx emissions. Earlier pilot-scale screening tests [1,2] at 5 million Btulhr in the B&W Small Boiler Simulator facility led to the selection of coal nozzle mixing devices that could potentially reduce the flame length and unburned carbon levels of existing 10w-NOx burners, without increasing the NOx emissions appreciably. Following the pilot-scale screening tests, full-size performance of the most promising configurations was evaluated in a newly commissioned 100 MBtu/hr state-of-the-art research facility. This paper describes the test facility, burner hardware, and the experimental results and conclusions. CLEAN ENVIRONMENT DEVEWPMENT FACILITY General Facility Description Figure 1 shows a schematic of the single burner firing configuration of B&W's Clean Environment Development Facility (CEDF) in Alliance, Ohio. Numerical modeling played a key role in guiding the CEDF design efforts [3] to replicate the thermal environment and flow characteristics of a "hot" utility boiler. The geometry of the tunnel section accommodates a single 1 ()() 1vffitulhr burner and maintains proper furnace flow patterns. The inside surface of the CEDF furnace is refractory lined to yield average gas temperatures of around 2800°F just above the tunnel section, and 2250° at the furnace exit, when fIring high volatile PC at full load. 2 |