Abstract: Primary fuel and preheated oxidant are injected into a combustion zone to produce a flame with a predetermined adiabatic flame temperature. The preheated oxidant is injected at a target rate of oxidant injection. The primary fuel is injected at a first reduced rate which is less than a corresponding target rate of fuel injection. Secondary fuel is simultaneously injected into the combustion zone separately from the flame at a second reduced rate which is equal to the difference between the first reduced rate and the target rate of fuel injection. In this manner, combustion of the fuel with the preheated oxidant provides the amount of heat expected from the target rates of injection, while maintaining an adiabatic flame temperature that is lower than it might otherwise be if the target rate of fuel injection were provided entirely at the flame. The lower adiabatic flame temperature provides a correspondingly lower rate of NOx production.

Abstract: A low NOx burner and related method are disclosed including the steps of supplying a first reactant stream and introducing a second reactant stream into the first reactant stream at a first point so as to produce co-flowing streams. This resulting fuel/oxidant stream is discharged into a furnace environment having inert combustion products substantially equilibrated to furnace temperature, so as to entrain the combustion products and mix them together with the co-flowing stream. The temperature of the co-flowing stream is increased by the entrained products until it ignites in a combustion region displaced from the first point. Thus ignition cannot occur until the reactant stream has been diluted by inert products of combustion, reducing both oxygen concentration and peak flame temperature, so as to suppress NOx production.

Abstract: A flat flame burner is disclosed having flow passages for admitting fuel and air to a burner tile. A structure for producing a rotational flow cooperates with a divergent burner tile in order to produce a radially-divergent flame with a very small axial component and a high degree of entrainment of inert combustion products in a furnace. A portion of the fuel is injected into the entrained furnace products, in order to suppress the rate of combustion, so as to produce an ultra low NOx flat flame burner. The present invention also permits greater versatility and improved operability over previous flat flame burners.