摘要:
A method and apparatus retrofitted to a multiple-intertube pulverized-coal burner to reduce NO.sub.x emissions of roof fired boilers. An internal two stage process controls the amount of secondary air which flows to the burner. The first stage includes a secondary air damper and air flow station to regulate the amount of air which flows into a windbox of the burner. A baffle plate assembly which includes a plurality of baffle plates further limits the amount of air which flows to the core of the burner for combustion of the fuel. The baffle plates create a pressure drop within the windbox which forces or diverts a quantity of air to the periphery of the burner. The second stage includes an outlet formed in the hot primary air duct, an air plenum which communicates therewith, and a plurality of interjectory air ports which correspond with the burners in number and position along a front wall of the boiler and which communicate with the air plenum. The interjectory air ports inject interjectory air into a combustion chamber of the boiler at a substantially 90 degree angle to the direction of a plurality of burner tips of each burner and supplies the balance of the required theoretical combustion air needed to complete combustion of the fuel. A plurality of probes measure the amount of primary air, secondary air and interjectory air and signal a command loop circuit to adjust the secondary air dampers and interjectory air ports accordingly.
摘要:
A method is disclosed for reducing NOx pollutants in the combustion of hydrocarbon fuels in a two stage burner. A first stage of combustion is established and maintained passing a stream of combustion air and first stage products of combustion down a centerline of the burner to a second stage downstream therefrom. This second stage is established by arranging an array of fuel tips around the first stage burner, each fuel tip having a fuel jet with a nominal trajectory angled toward the burner centerline and an inert gas jet placed between the burner and the fuel jet which is angled to cross the trajectory of the fuel jet. Fuel is injected into the second stage of the burner through the fuel jet and the inert gas, e.g. steam, is injected through the inert gas jet such that it influences the trajectory of the fuel to a modified fuel trajectory which is moved away from the centerline of the burner. Controlling the injection of the inert gas as a function of the firing rate for the burner allows the modified fuel trajectory to be moved progressively outward from the centerline of the burner across a range of increasingly higher firing rates. This reduces NOx production by moving the introduction of second stage combustion to a cooler and less oxygen rich area of the furnace as the furnace is progressively fired to greater heat outputs. Another aspect of the present invention is a low NOx burner.
摘要:
The invention relates to a process and apparatus for reducing pollutant gas emissions in the combustion of fuel, which utilize oxygen or oxygen-enriched air while avoiding the resulting disadvantages of high flame temperature and low gas momentum resulting in high NO.sub.x emissions. The invention provides a process of burning fuel, which simultaneously injects two jets of heated oxidant gas such as recirculated furnace gases and mixing such recirculated furnace gases with the oxidant into the furnace.
摘要:
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. The secondary fuel and flue gases are directed radially inward and downstream from the burner plate so that they mix with the combustion air entering through the burner plate slots in a secondary combustion zone. The resulting delay in the combustion of the secondary fuel gas and the need for heating the flue gas lowers the overall combustion temperature, which in turn reduces the NO.sub.x formation in the second or downstream combustion zone.
摘要:
A burner flame stabilizer which circumferentially stages the air to form circumferentially-spaced fuel rich and fuel lean zones for lowering of NO.sub.x is described. A circumferential solid fuel stager is described, which operates with a fuel stabilizer to provide increased dwell time for coal particles volatilization in a recirculation zone established by the flame stabilizer. Various embodiments are described.
摘要:
A gas-fired burner incorporating an air driven jet pump for mixing air, fuel, and recirculated flue gas with reduced heat loss from the recirculated flue gas is disclosed. The burner is configured for the staged introduction of combustion air to provide a fuel-rich combustion zone and a fuel-lean combustion zone. Internal flue gas channels deliver cooled flue gas to the primary fuel-rich combustion zone. A valve assembly may be provided to control the flow of flue gas. Secondary air channels concentrically arranged within the flue gas channels deliver superheated, staged air to the secondary fuel-lean combustion zone. Heat is transferred from the hot flue gas to the counterflowing cooler secondary air. The burner achieves reduced NO.sub.x emission levels in high temperature applications which use preheated combustion air with no or minimal loss in thermal efficiency from flue gas recirculation.
摘要:
A forced draft burner apparatus and method providing extremely low NO.sub.x, CO and hydrocarbon emissions, while maintaining the desirable features of a nozzle mix burner. This is accomplished by injecting the fuel gas in a position that would be typical for a nozzle mix burner, while generating such rapid mixing that, effectively, premixed conditions are created upstream of the ignition point.
摘要:
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. Preferably a gas nozzle is arranged at the center of the burner plate and is provided with fuel gas discharge ports to direct fuel gas in a direction tangential to the nozzle so as to induce gas exiting therefrom to swirl downstream from the burner plate. A spinner also is arranged around this central gas nozzle to cause combustion air channeled around the nozzle to swirl downstream from the nozzle. In this way, flame stability without air preheat is achieved with up to 110% excess air.
摘要:
A burner for burning fuel in an oxidant having a fuel nozzle sandwiched between upper and lower oxidant nozzles. The fuel nozzle and upper and lower oxidant nozzles produce fuel and oxidant jets of outwardly divergent, fan-shaped configuration to provide a wide uniform flame and thus the elimination of hot spots. Upper and lower secondary oxidant nozzles can be provided in staged combustion such that fuel is burned and oxidant supplied by the upper and lower oxidant nozzle means in the substoichiometric ratio and then combustion is completed by oxidant supplied by the secondary upper and lower oxidant nozzles. In another aspect, a nozzle is provided in which a passageway is divided in a lengthwise direction and thus the flow of oxidant flowing through the passageway is divided into a plurality of subflows of equal velocity and of gradually divergent configuration to prevent the decay of a fan-shaped flow of oxidant from the nozzle.