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Show NOx REDUCTION AND AERODYNAMICALLY AIR PRECOMBUSTOR BURNER J P SMART and R WEBER BURNOUT OPTIMISATION STAGED BURNER AND AN The International Flame Research Foundation SUMMARY Paper No. 15 USING AN AIR STAGED Recently, a significant body of work has been undertaken at the IFRF to develop low-NOx pulverised-coal burners. The majority of the work has focused on the design and evaluation of internal air staged burners at the 2.5 MW semi-i~dustrial scale. Specific emphasis has been given to retrofitting the burner designs to wall-fired combustion units. Two burner concepts have been evaluated, an aerodynamically air staged burner (AASB) and an air staged precombustor burner (ASPB). The dominant design feature of all air-staged burners is the creation of a fuel-rich zone in which volatile coal-nitrogen species react to molecular N2 in prefernce to NOx. The two burners create this fuel rich zone in fundamentally different ways. The AASB relies on optimisation of the near-burner field aerodynamics whereas the ASPB utilises a prechamber operating under sub-stoichiometric conditions. Both burner were fired with a high volatile and a medium volatile bituminous coal. Relatively low NOx emissions and acceptable burnout levels were achieved for both coals, however a coal type dependence was observed. Results of the two burners have been compared to an externally air staged burner firing the same coals. 1 INTRODUCTION Currently, manufacturers and users of coal combustion equipment are making a significant effort to design and operate coal combustion systems to reduce NOx emissions. Recently, the development has been particularly rapid as many governments begin to enact strict air quality legislation. In pulverized coal combustion, NOx is formed from two sources, the coal and the combustion air. Coal-bound nitrogen is apportioned to volatile matter and the residual char during pyrolysis and combustion. The formation of NOx from the coal is predominantly from the 1 |