Low no.sub.x fuel gas burner

Abstract

An industrial fuel gas burner fired with a mixture of combustion air having up to about 45% flue gas which flows in a downstream direction along an annular combustion air conduit disposed about an axially movable core of the burner that terminates in an end cone that faces the combustion chamber of the furnace. Within the conduit and upstream of a discharge end thereof is a fuel gas discharge header formed by concentric, radially inner and outer tubular ring-shaped fuel gas headers which are concentrically disposed about an axis of the burner and in fluid communication with a source of pressurized fuel gas. The headers have a multiplicity of fuel gas discharge orifices which form three-dimensionally oriented gas streams directed into the combustion air-flue gas flow in the annular conduit. The orifices have a diameter of at least about 0.1 inch. The fuel gas has a pressure so that the fuel gas streams have sufficient energy to flow portions of the gas to a vicinity of the annular conduit walls to intimately mix the fuel gas with the combustion air and form a substantially uniform combustion air-flue gas-fuel gas mixture at a discharge end of the annular conduit. The end cone periphery mounts a number of blades that create enhanced, non-repetitively irregular turbulence in the flow discharged from the conduit, which causes irregular turbulence along the boundary between the flow and combustion gas which recirculate in the wake of the cone. The core of the burner including the blades can slide along a guide so that the discharge area between the throat and the cone can be varied with the firing rate, and the blades can be moved away from the conduit when the burner operates at full load.