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  Dynamic burner reconfiguration and combustion system for process heaters and boilersUSPTO Application #: 20060275724Title: Dynamic burner reconfiguration and combustion system for process heaters and boilers Abstract: A furnace combustion system includes a plurality of burners adapted to generate a plurality of flames and an oxidant port disposed between and surrounded by at least two of the burners. Each burner is spaced apart from another burner and adapted to combust a stream of a first fuel or an other fuel with a stream of a first oxidant or an other oxidant and to generate a flame. The oxidant port is adapted to transmit at least one jet of the first oxidant or the other oxidant axially between at least two of the flames. The at least one jet is transmitted from the oxidant port at a controlled flow rate. At least a portion of the first oxidant or the other oxidant in the jet is required to complete combustion of at least a portion of at least one stream of the first fuel or the other fuel. (end of abstract) Agent: Air Products And Chemicals, Inc. Patent Department - Allentown, PA, US Inventors: Mahendra Ladharam Joshi, Xianming Jimmy Li Related Keywords: burner, combustion, fuel, furnace, jet, oxidant, port, stream USPTO Applicaton #: 20060275724 - Class: 431181000 (USPTO) Related Patent Categories: Combustion, Fuel Disperser Installed In Furnace, Plural Feed Means Extending To Common Wall Opening Of Furnace The Patent Description & Claims data below is from USPTO Patent Application 20060275724. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates to combustion systems and methods for reducing nitrogen (NOx) and carbon monoxide (CO) emissions, and in particular to such systems and methods which produce global (overall) reductions in NOx, as opposed to localized NOx reductions (such as those produced by staging techniques). [0002] Many process heaters and boilers have NOx emissions compliance problems for various reasons. For example, many vertical cylindrical process heaters produce more than 100 ppm NOx on average. Most of these heaters are of older design and operate at a very high firing intensity (>500,000 Btu/Hr-ft2). Multiple burners in the heaters typically are clustered in a tight burner circle and individual flames merge in the center which creates a high-temperature, fuel-rich region. The unified flames produce both thermal and prompt NOx due to the coalescing fuel-rich region in the center of the heater. [0003] Whereas in cylindrical heaters the burners generally are installed in a circular geometry, in wall-fired boilers, multiple burners usually are installed as a matrix on a side wall of the furnace of the boiler. The spacing of the burners in both applications is reduced to the minimum for deriving the maximum heat flux per unit volume. However, the arrangement of tightly packed burners leads to merging of individual flames, an increase in peak flame temperatures, formation of fuel-rich regions, and an increase in NOx emissions. [0004] Typical coal-fired burners in wall-fired boilers produce on average about 400 ppmv NOx or 200 mg/MJ NOx emissions. Most low-NOx burners today have incorporated some sort of air staging process, but the limitations of air staging are clear due to undesirable flame merging created by close proximity of burners installed on a firing wall and poor flame stability (at higher staging levels). Highly staged burners have a flame stability issue due to fuel-rich primary flame stoichiometry (.phi.>1.3). [0005] There are many prior art applications involving low-NOx burners fitted with ports for individual staged air jets. However, these jets are dedicated to altering the combustion process for a particular burner. The goal of such air staging is to create a primary flame deficient of combustion air (oxidant), or producing a fuel-rich flame which has a lower adiabatic flame temperature and thus lower thermal NOx formation rates. The resulting fuel-rich mixture from the primary flame is then combusted downstream using the staged air jet(s). Thus, air staging is a two-step process involving 1) fuel-rich primary combustion, and 2) destruction of CO and HCs in a second step using staged air jet(s). The main drawbacks of such air staging processes are set forth below. [0006] 1) The first step, or primary fuel-rich combustion, leads to significant prompt NOx formation due to formation of CH type bonds, which leads to HCN and NO formation. [ NO ] = k .function. [ N 2 ] .times. .intg. .times. [ C x .times. H y ] .times. d .theta. C x .times. H y CH + C x - 1 .times. H y - 1 [0007] 2) The staged air jets are designed for secondary combustion of HCs and CO produced from a particular burner and not from neighboring burners. CH+N.sub.2.fwdarw.HCN+N HCN+O.sub.2.fwdarw.NO+. . . [0008] 3) The staged air jets dedicated to individual burners do not alter the negative process effects (fuel-rich flame, higher peak temperatures, higher NOx emissions) produced by merging of multiple flames. The combined effect of merging or coalescing flames actually amplify the NOx emissions by creating hot spots due to lack of heat transfer and lack of oxidant availability in the central flame region. [0009] 4) The individual staged air jets dedicated to each burner are not designed in the flow rate, velocity, swirl, or other flow characteristics to match proper mixing and performance requirements of the merged or unified flame. The resulting process is not adequate to address the NOx reduction objectives. In fact, a unified flame could wipe out the individual NOx reduction benefits produced by each burner fitted with air staging jets. [0010] In summary, the individual burner air staging processes of the prior art are "localized" low-NOx processes, whereas the present invention provides for a "global" low-NOx process and furnace combustion system. [0011] It is desired to have a system and method to lower NOx and CO emissions from process heaters, boilers, and other such combustion equipment which use multiple burners. [0012] It is further desired to have a system and a method to reduce the flame merging effect of multiple burners, the associated peak flame temperatures, and the resulting NOx emissions in such process heaters, boilers, and combustion equipment. [0013] It is still further desired to have an improved process heater having lower NOx and CO emissions, higher overall heat transfer, higher heater turndown, and improved draft management for natural draft heaters. [0014] It is still further desired to have an improved furnace in a boiler or process heater having reduced hot spots, improved heat transfer profile, increased fuel efficiency, and an extension of tube life due to lowered peak flame temperatures. [0015] It also is desired to have a system and a method for combusting fuels in process heaters and boilers which afford better performance than the prior art, and which also overcome many of the difficulties and disadvantages of the prior art to provide better and more advantageous results. BRIEF SUMMARY OF THE INVENTION [0016] The present invention is a furnace combustion system and a method for combusting a fuel in a furnace. The invention also includes a method and a system for reducing nitrogen oxide emissions from a plurality of products of combustion generated during combustion of a fuel in a furnace. [0017] A first embodiment of the furnace combustion system includes a plurality of burners adapted to generate a plurality of flames, including a first burner and a second burner, and an oxidant port disposed between and surrounded by at least two of the plurality of burners, including the first burner and the second burner. The first burner is adapted to combust a first stream of a fuel with a first stream of a first oxidant and to generate a first flame. The second burner is spaced apart from the first burner and adapted to combust a second stream of the fuel, or a stream of an other fuel, with a second stream of the first oxidant, or a first stream of a second oxidant, and to generate a second flame. The oxidant port is adapted to transmit at least one jet of the first oxidant, the second oxidant, or an other oxidant, axially between at least two of the plurality of flames, including the first flame, and the second flame. The at least one jet is transmitted from the oxidant port at a controlled flow rate. At least a portion of the first oxidant, or the second oxidant, or the other oxidant in the at least one jet is required to complete combustion of at least a portion of at least one of the first stream of the fuel and the second stream of the fuel, or the stream of the other fuel. [0018] There are many variations of the first embodiment of the furnace combustion system. In one variation, the controlled flow rate is controlled at least in part by a damper. In another variation, the oxidant port is substantially equidistant from the first burner and the second burner. In yet another variation, the at least one jet includes a swirling stream. In a variant of this variation, the swirling stream has a swirl number in the range of about 0.2 to about 0.6. [0019] In another variation, the at least one jet has an oxygen concentration in a range of about 5 vol. % to about 50 vol. %. In yet another variation, the at least one jet provides about 5% to about 50% of a total oxidant required to operate a furnace operated with the furnace combustion system. In still yet another variation, the at least one jet has a velocity in a range of about 20 ft/sec. to about 1,000 ft/sec. [0020] In another variation, at least one of the first flame and the second flame is fuel-rich. In yet another variation, the first flame merges with the second flame. In still yet another variation, at least one of the first burner and the second burner is adapted to transmit a variable distribution of at least one of the fuel and the other fuel. [0021] A second embodiment of the furnace combustion system includes a plurality of burners adapted to generate a plurality of flames and an oxidant port disposed between and surrounded by at least two of the plurality of burners. Each burner is spaced apart from another burner and adapted to combust a stream of a first fuel or an other fuel with a stream of a first oxidant or an other oxidant to generate a flame. The oxidant port is adapted to transmit at least one jet of the first oxidant or the other oxidant axially between at least two of the plurality of flames. The at least one jet is transmitted from the oxidant port at a controlled flow rate. At least a portion of the first oxidant or the other oxidant in the at least one jet is required to complete combustion of at least a portion of at least one stream of the first fuel or the other fuel. [0022] A third embodiment of the furnace combustion system, the system being in a furnace having an interior and a longitudinal axis, includes a plurality of burners adapted to generate a plurality of flames and an oxidant port disposed in the interior of the furnace between and surrounded by the plurality of burners. Each burner is spaced apart from another burner and adapted to combust a stream of a first fuel or an other fuel with a stream of a first oxidant or an other oxidant and to generate a flame. The plurality of burners is disposed in the interior of the furnace in a substantially circular pattern spaced around the longitudinal axis of the furnace. The oxidant port is substantially equidistant from each burner and adapted to transmit at least one jet of the first oxidant or the other oxidant axially between at least two of the plurality of flames. The at least one jet is transmitted from the oxidant port at a controlled flow rate. At least a portion of the first oxidant or the other oxidant in the at least one jet is required to complete combustion of at least a portion of at least one stream of the first fuel or the other fuel. Continue reading... Full patent description for Dynamic burner reconfiguration and combustion system for process heaters and boilers Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Dynamic burner reconfiguration and combustion system for process heaters and boilers patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Dynamic burner reconfiguration and combustion system for process heaters and boilers or other areas of interest. ### Previous Patent Application: Apparatus for producing spherical powder, burner for treaitng powder, method for producing spherical powder, spherical oxide powder, and oxide powder Next Patent Application: Gas burner having means for reversibly fixing the cover Industry Class: Combustion ### FreshPatents.com Support Thank you for viewing the Dynamic burner reconfiguration and combustion system for process heaters and boilers patent info. IP-related news and info Results in 0.35429 seconds Other interesting Feshpatents.com categories: Tyco , Unilever , Warner-lambert , 3m |
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