Vibration-resistant low no.sub.x burner

Abstract

A low NO.sub.x burner includes a refractory lined plate with a refractory side facing a combustion chamber. A multiplicity of combustion air passages extend through the plate toward the combustion chamber. A multiplicity of spaced-apart primary fuel nozzles each have a discharge opening being surrounded by one of the combustion air passages for directing fuel therethrough to mix with combustion air passing through the air passages. A multiplicity of anchor fuel nozzles project through the plate for directing fuel into the combustion chamber. The anchor fuel nozzles are spaced apart from each other and from the combustion air passages. The flows of fuel and combustion air through the primary and anchor nozzles and the air passages into the combustion chamber are controlled to generate a flame. In applications that require low excess air, such as boiler applications, the burner is modified by providing a secondary fuel and flue gas injection assembly to form a two-stage burner. In the preferred embodiment, the secondary injection assembly includes a plurality of discrete fuel and flue gas injection nozzles arranged around the primary and anchor fuel nozzles and combustion air passages. By varying the percentage and actual pattern of secondary fuel injection and by varying the configuration of the array of primary and anchor nozzles and the spacing between the nozzles, the flame shape may be easily tailored to the size and shape of practically any furnace. The flame can thus be optimized to achieve lower NO.sub.x and improved efficiency.