High capacity/low NOx radiant wall burner

A burner assembly for a radiant burner includes a burner tube structure in the form of an elongated burner conduit having spaced inlet and outlet ends. The conduit is adapted and arranged for directing a fuel lean gaseous mixture comprising a portion of the total fluid fuel to be combusted and oxygen therealong from the inlet end to the outlet end. The assembly also includes a main burner nozzle at the outlet end of the conduit, which nozzle has a central axis, a wall extending around a centrally located chamber therein, and a downstream end spaced from the outlet end of the conduit. The main burner nozzle is arranged and adapted for receiving the mixture from the conduit in the chamber and redirecting the same through a plurality of apertures in the wall and into a combustion zone in a direction transverse to the axis and at a velocity which is greater than the flame speed of the gaseous mixture. The apertures are distributed circumferentially around the wall, whereby the mixture is directed without substantial recirculation and with minimal pressure drop through said apertures and into the combustion zone in the form of a generally round flat pattern which is detached from the nozzle, surrounds the wall and extends outwardly across a radiant surface of a burner tile. The burner also includes an elongated fuel tube extending in a direction generally parallel to the axis, and the fuel tube has a downstream end portion. A secondary fuel nozzle includes a secondary fuel port on the downstream end portion of the fuel tube, which secondary fuel port is located and arranged so as to deliver secondary fuel to a position which is on the opposite side of the fuel pattern from the radiant surface and sufficiently remote from the combustion zone to permit the same to become intermixed with flue gases before entering said combustion zone.