Abstract: A low NO.sub.x burner includes a primary air and fuel discharge assembly which, in turn, includes a burner plate having a plurality of slots from which fuel gas jets and combustion air are discharged. The slots are arranged such that the width of the recirculation zones between adjacent slots substantially varies between the central region of the burner plate and its perimeter. With this construction, the local ignition patterns vary such that local oscillations of flame front occur at different frequencies so that vibrations are greatly dampened and resonance problems in the furnace minimized or eliminated. In applications where high excess air is not desirable, 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 tubes arranged around the primary air and fuel gas discharge assembly.

Abstract: A low NO.sub.x burner includes a burner plate having a plurality of slots from which fuel gas jets and combustion air are discharged. A plurality of fuel tubes are aligned with the slots for discharging the fuel gas therethrough. The fuel tubes are spaced from the slots so that combustion air, provided by a wind box, also can flow through the slots. The fuel gas and combustion air are discharged at high velocity, thereby generating very high turbulence in the combustion chamber downstream from the burner. The slots are arranged such that the width of the recirculation zones between adjacent slots substantially varies between the central region of the burner plate and its perimeter. With this construction, the local ignition patterns vary such that local oscillations of flame front occur at different frequencies and are not synchronized so that vibrations are greatly dampened and resonance problems in the furnace minimized or eliminated.

Abstract: A burner especially adapted for use with pulverized fuel slurries, such as pulverized coal-water slurries. The burner has an atomizing nozzle which disperses the slurry in the form of multiple, diverging spray cones issuing from a corresponding number of atomizing orifices. Each orifice is formed by a central atomizing air flow. The slurry is brought into contact with the air flow and is atomized thereby. Before the atomized air flow is discharged, it is enveloped by a rotating auxiliary air flow and constricted to generate a venturi effect which facilitates the formation of the diverging, cone-shaped discharge pattern. A combustion air spinner surrounds the nozzle and is constructed of multiple vanes which have circularly arcuate shapes and a length, in the direction of the air flow, which is least proximate the nozzle and greatest at the periphery of the vanes. This assures an even combustion air flow rate over the entire radial extent of the spinner.

Abstract: A system for marginally adjusting the fuel flow to a burner to maintain the proper oxygen content in the exhaust from the burner is disclosed. The burner is of the type where both the fuel and air flow rates are adjusted in a substantially fixed ratio in response to load changes on the system with the fuel being adjusted by a fuel control valve mounted in a fuel supply line. A self-operating pressure regulating valve having an actuator responsive to the differential pressure across the fuel control valve is mounted in the fuel line upstream of the fuel control valve. A set point adjustment mechanism is mounted on the regulating valve actuator to adjust the set point of the regulating valve in response to an oxygen controller which senses the oxygen content in the stack gases. The set point adjustment mechanism has a cam assembly which continously adjusts the set point of the regulator actuator by varying the compression on a spring loaded diaphragm therein.