A low NOx burner (2) includes a primary air and fueldischarge assembly which, in turn, includes a burner plate (6)having a plurality of slots (32) from which fuel gas jets andcombustion air are discharged. The slots are arranged suchthat the width of the recirculation zones between adjacentslots substantially varies between the central region of theburner plate and its perimeter. With this construction, thelocal ignition patterns vary such that local oscillations offlame front occur at different frequencies so that vibrationsare greatly dampened and resonance problems in the furnaceminimized or eliminated. In applications where high excessair is not desirable, such as boiler applications, the burneris modified by providing a secondary fuel and flue gasinjection assembly (80) to form a two stage burner (2'). Inthe preferred embodiment, the secondary injection assemblyincludes a plurality of discrete fuel and flue gas injectiontubes (82, 94) arranged around the primary air and fuel gasdischarge assembly (50). The secondary fuel and flue gases aredirected radially inward and downstream from the burner plateso that they mix with the combustion air entering through theburner plate slots (32) in a secondary combustion zone. Theresulting delay in the combustion of the secondary fuel gas andthe need for heating the flue gas lowers the overall combustiontemperature, which in turn reduces the NOx formation in thesecond or downstream combustion zone.
展开▼
