Importance

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Abstract

To minimize NO.sub.x emissions in an intermediate size industrial boiler furnace having two vertically spaced rows of burners, each upper burner has a central fuel nozzle and a main air opening adjacent to the nozzle and communicating with a wind box associated with the furnace. In addition, each upper burner has a plurality of air delivery ports through the wall surrounding said upper burner, such air delivery ports also communicating with the wind box. The air delivery ports can be of different sizes and shapes and can be at different angles with respect to the vertical plane of the wall through which the air delivery ports extend. Control of the air through the main air opening adjacent to the nozzle of each upper burner is achieved by one or more shiftable registers or dampers which operate to close the air flow from the wind box to the air opening. Each lower burner has the same construction as each upper burner except that the lower burner does not have the air delivery ports through the wall surrounding the nozzle and its adjacent main air opening. Typically, each lower burner is fired off-stoichiometrically with only about 70% theoretical air and each upper burner is fired with about 90% theoretical air, the make-up air for each upper burner coming through the air delivery ports arranged around it. The air delivery ports also provide the makeup air for the excess fuel through the lower burners. The air pressure of the air across the air delivery ports has a higher pressure than the air pressure across the main air openings adjacent to the fuel nozzles. This assures that the make-up air through the surrounding air delivery ports will penetrate deeply into the combustion chamber of the furnace.

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First Claim