B&W pioneered the development and application of NOx ports and air staging as a NOx emissions control technique.
Air staging involves removing a portion of the air from the burners to reduce oxygen availability early in the combustion process and reintroducing it later in the combustion process. Often the physical arrangement dictates replacing the staged air through ports located above the combustion zone; hence the name overfire air (OFA) is commonly applied to such systems. The layout of a combustion system and furnace, however, may necessitate supplying staged air at the same elevation or below the burner zone, such that OFA is something of a misnomer. OFA is used here, in its generic sense, to refer to any air staged system. The ports through which the OFA is injected are called OFA ports or NOx ports.
Combined with B&W's other low NOx technologies, such as burners and selective catalytic reduction systems, overfire air systems are part of an overall NOx reduction strategy.
B&W overfire air port features and specifications.
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