Low NOx burner with bypass duct

Abstract

A burner and a method of using the burner. The burner utilizes a bypass conduit to separate combustion air being delivered to a primary combustion zone into two or more portions. The two portions are injected into the primary combustion zone at different points to reduce flame temperature. A NOx reduction medium may be mixed with the combustion air in the bypass conduit. The NOx reduction medium may be flue gas from a combustion chamber having a primary combustion zone.

Description

Technical Field

[0001] (Priority Claim) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 170,139, filed Apr. 2, 2021, which is hereby incorporated by reference in its entirety.

[0002] (Field of the Invention) The present invention generally relates to gas burners, and more specifically, to gas burners having lower NOx generation.

Background Art

[0003] Petroleum refining processes and petrochemical processes often involve heating process streams in furnaces. The interior chamber of the furnace includes tubes that contain the process stream. The interior chamber is heated by a plurality of gas burners that receive fuel which combusts to generate heat.

[0004] One area of interest regarding gas burners is the generation of NOx gas. As understood, NOx refers to nitrogen oxides mainly composed of nitric oxide NO and nitrogen dioxide NO2. In combustion processes, at least three major NOx formation mechanisms are thought to exist, specifically, thermal NOx, fuel NOx, and prompt NOx. See “Nitrogen Oxides(NOx), What and How They are Controlled” EPA Technical Bulletin November 1999 (available at https: / / www3.epa.gov / ttncatc1 / dir1 / fnoxdoc.pdf).

[0005] It is known that NOx formation in a gas burner can be reduced by staging the fuel and air and creating a primary combustion (flame) zone and a secondary combustion (flame) zone. Staged air burners and staged fuel burners are mainly effective in the thermal NOx and prompt NOx formation processes. The highest flame temperature, and thus the greatest potential for thermal NOx formation, is brought about when the gas fuel and combustion air are completely mixed and burned rapidly at or near the stoichiometric ratio.

[0006] Therefore, staged air burners and staged fuel burners attempt to lower the flame temperature and thereby reduce NOx generation. A typical staged fuel burner or staged air burner creates two combustion zones for non-stoichiometric combustion.

[0007] In the case of a staged fuel burner, all of the combustion air passes through the primary combustion zone and enters the secondary combustion zone along with the partially burned products of the primary combustion zone. In this case, the primary combustion zone is lean and has an excess amount of combustion air. Lean combustion allows the mass of the combustion air to rapidly absorb heat from the flame and transfer it outside the primary combustion zone, thus giving time (measurable in milliseconds) for heat to radiate from the primary combustion zone to the surrounding environment, including the heater, boiler, or furnace process tubes, thereby partially lowering the flame temperature. The completely and / or partially burned (reacted) combustion products move from the primary combustion zone to the secondary combustion zone or the staged combustion zone. Such movement gives time (also measurable in milliseconds in this case) for the primary combustion zone products to further radiate heat to the surrounding environment and the process tubes. Therefore, the somewhat cooled combustion products from the primary combustion zone conduct heat from the secondary combustion zone and act to cool the secondary combustion zone. Furthermore, the combustion reaction in the secondary combustion zone generally occurs under relatively lean conditions because typical process heaters, boilers, or furnaces operate under lean conditions with 5% - 25% excess combustion air. Thereby, the combustion process is completed to a considerable extent (at an industrially acceptable level of efficiency, with 5% - 25% excess air).

[0008] A typical staged air burner, operating in reverse of the staging process, introduces all of the fuel gas for combustion and only a portion of the combustion air into the primary combustion zone. In the case of a staged air burner, the primary combustion zone can operate stoichiometrically as reactants and products pass through the secondary combustion zone, achieving industrially acceptable excess air levels (5% - 25% excess air). In a staged air burner, the reactants must pass through a region near stoichiometric ratio where the flame temperature (and thus thermal NOx formation) is high, and thus, a staged air burner can have difficulty delivering very low NOx emissions.

[0009] In a more recent example, an internal flue gas recirculation burner utilizes flue gas in a heater or furnace combustion chamber that is driven by fuel gas and introduced into the primary and secondary combustion zones. This flue gas, which is relatively low temperature and a large amount of combustion products (flue gas), enters and passes through the combustion zone, thereby further cooling the combustion zone and reducing thermal NOx formation. The water vapor in the flue gas also serves to reduce NOx formed via the prompt NOx mechanism by solvating hydrocarbon combustion and catalyzing, by means of the recently understood water gas shift reaction (WGSR) mechanism as described in "A Paradigm Shift in Steam Assisted Elevated Flare Systems" International Flame Research Foundation, July 2020, by Jan De Ren, Kurt Kraus and Chris Ferguson. Such WGSR mechanisms also exist to some extent in typical or conventional staged fuel burners or staged air burners since the combustion products from the primary combustion zone to the secondary combustion zone contain some water vapor.

[0010] Both staged air burners and staged fuel burners require and can generate large, substantial flames in order to achieve low NOx emissions. Modern heater and furnace designs need to be designed larger and more expensively for the combustion chamber to allow for the larger, lower NOx emission burner flames of staged fuel burners and staged air burners.

[0011] Accordingly, there is still a need for burners having low NOx production that are not plagued by these drawbacks. SUMMARY OF THE INVENTION

[0012] A novel burner and method of using the same have been invented. According to the present invention, the novel burner utilizes one or more bypass conduits to separate the combustion air sent to the primary combustion zone into two or more portions. Non-stoichiometric combustion (either rich or lean) is known to lower the flame temperature and change the formation of intermediate products of combustion, thereby reducing the formation when formed by various known or theorized mechanisms including thermal NOx and prompt NOx formation. These portions are injected into the primary combustion zone at different points to facilitate the design control of the stoichiometric ratio at various locations within the flame. Accordingly, the flame temperature and the nature of the intermediate products of combustion can be designed for various locations within the flame, thereby reducing NOx production.

[0013] By using a bypass conduit, NOx generation is reduced, but it has further been found that NOx gas generated by the flame can be further reduced by mixing a NOx reduction medium with the combustion air in the bypass conduit. The NOx reduction medium can be mixed with the fuel gas, the combustion air injected into the bypass conduit, along the bypass conduit, or outside the bypass conduit, or any combination of the above. The present invention contemplates various sources of the NOx reduction medium, but one specifically contemplated source is the flue gas generated by the flame in the burner. Other NOx reduction media include steam, nitrogen, carbon dioxide, and various process off-gases, waste gases, or synthesis streams that may contain various amounts of these listed gaseous components or other gaseous components. One process off-gas is typically a pressure swing absorber (PSA) off-gas that may contain various amounts of nitrogen, carbon dioxide, water vapor, methane, and other light hydrocarbons. These NOx reduction media containing water vapor such as steam and flue gas also drive the water gas shift reaction process. By minimizing the amount of NOx reduction medium required to achieve the desired level of NOx emissions, the operating cost of delivering the medium is reduced. On the other hand, an excessive amount of NOx reduction medium can interfere with the combustion process, destabilize the burner, or even extinguish the burner flame. The various control methods described herein adjust or control the amount of NOx reduction medium delivered to various locations within the burner to reduce NOx formation to the desired level while maintaining safe and stable continuous combustion and heat transfer.

[0014] Accordingly, the NOx reduction medium can be injected at various locations within a single burner. Further, the NOx reduction medium may be injected at any one location of any single burner.

[0015] Accordingly, in at least one aspect, the present invention can be characterized as providing a process for a specified predetermined mixing of fuel, air, and a NOx reduction medium at a plurality of locations within a burner and a flame zone. The directed injection of the various components, as well as the resulting controlled mixing and reaction rates, minimize the amount of NOx reduction medium required to achieve the maximum NOx reduction effect within the combustion process. The NOx reduction medium can be specifically directed and mixed not only at specific locations that are clearly designed to operate in a rich or stoichiometric manner, but also at those locations that are in a stoichiometric state. Similarly, at lean and super-stoichiometric locations, different proportions and compositions of the NOx reduction medium are directed to affect NOx reduction. For example, the locations of the burner bluff body or stabilization cavity are known to be areas of high NOx formation. Accordingly, these locations are the targets for non-stoichiometric operation and directed flue gas reduction medium.

[0016] Accordingly, the present invention can be broadly characterized as providing a burner having a plenum, a burner tile, the burner tile being arranged such that a first portion of combustion air from the plenum flows from the plenum through the burner tile to a primary combustion zone, at least one conduit having an outlet configured to inject a fuel stream including fuel gas into the primary combustion zone, and a bypass conduit having an outlet configured to inject a second portion of combustion air from the plenum into the primary combustion zone. The second portion of combustion air is injected downstream of the first portion of combustion air. The burner may include a plurality of bypass conduits each having an outlet configured to inject a portion of the second portion of combustion air from the plenum into the primary combustion zone. The bypass conduits from the plurality of bypass conduits may be concentric. The bypass conduits from the plurality of bypass conduits may each have a different length with respect to the distance from the burner tile to the outlet of each bypass conduit. The bypass conduits from the plurality of bypass conduits may be arranged in a parallel arrangement. The burner may also include a premixer configured to mix fuel gas and a portion of combustion air upstream of the combustion zone such that the fuel stream further includes combustion air. The bypass conduit has an inlet, and the inlet may have either an increasing inner dimension for increasing the proportion of combustion air entering the bypass conduit from the plenum or a decreasing inner dimension for decreasing the proportion of combustion air entering the bypass conduit from the plenum. The burner may further include at least one conduit configured to send a NOx reduction medium to the combustion zone.

[0017] In another aspect, the present invention generally can be characterized as providing a burner having a plenum, a burner tile, at least one conduit having an outlet configured to inject a fuel stream including fuel gas into a primary combustion zone, a bypass conduit having an outlet configured to inject a second portion of combustion air from the plenum into the primary combustion zone, and at least one conduit configured to send a NOx reduction medium into the bypass conduit, the passageway within the burner tile, or both. The second portion of combustion air is injected downstream of the first portion of combustion air. The NOx reduction medium may be recirculated flue gas generated in the primary combustion zone. The burner may include a fan configured to draw flue gas from the primary combustion zone into a recirculation conduit. Additionally, the burner may include a heat exchanger configured to recover heat from the recirculated flue gas to cool the recirculated flue gas before the recirculated flue gas is returned to the primary combustion zone. The burner may include a premixer configured to mix fuel gas and a portion of combustion air upstream of the combustion zone such that the fuel stream further includes combustion air. The NOx reduction medium may be injected into the premixer. The NOx reduction medium may be mixed with the fuel gas before the fuel gas is injected into the premixer. The NOx reduction medium may be mixed with combustion air within the plenum.

[0018] In some aspects, the present invention generally may be characterized as providing a process for reducing the generation of NOx gas in a burner by injecting fuel gas into a primary combustion zone associated with a burner tile, injecting a first portion of combustion air into the primary combustion zone such that the first portion of combustion air and the fuel gas react to generate a flame within the primary combustion zone, and injecting a second portion of combustion air into the primary combustion zone, the second portion of combustion air being injected into the primary combustion zone downstream of the first portion of combustion air. The second portion of combustion air may be injected via a bypass conduit. The second portion of combustion air may be injected via a plurality of bypass conduits each having an outlet configured to inject the second portion of combustion air into the primary combustion zone. The bypass conduits from the plurality of bypass conduits may be concentric. The bypass conduits from the plurality of bypass conduits may each have a different length with respect to the distance from the burner tile to the outlet of each bypass conduit. The process may include sending a NOx reducing medium into the combustion zone. The NOx reducing medium may be recirculated flue gas from the primary combustion zone. The NOx reducing medium may be flue gas from an FCC unit.

[0019] In a further aspect, the present invention is broadly characterized as providing a process for reducing the generation of NOx gas in a burner by injecting fuel gas into a primary combustion zone associated with a burner tile, injecting a first portion of combustion air into the primary combustion zone such that the first portion of combustion air reacts with the fuel gas to produce a flame within the primary combustion zone, injecting a second portion of combustion air into the primary combustion zone via a bypass conduit, wherein the second portion of combustion air is injected into the primary combustion zone downstream of the first portion of combustion air, and injecting a NOx reduction medium into the bypass conduit. The process may include monitoring at least one NOx value of the flame and adjusting the flow rate of the NOx reduction medium based on the at least one NOx value. The NOx reduction medium may be recirculated flue gas from the primary combustion zone. The NOx reduction medium may be flue gas from an FCC unit.

[0020] Furthermore, in some aspects, the present invention relates to injecting fuel gas into a primary combustion zone associated with a burner tile, injecting a first portion of combustion air into the primary combustion zone, wherein the first portion of combustion air reacts with the fuel gas to produce a flame and flue gas within the primary combustion zone, injecting a second portion of combustion air into the primary combustion zone, wherein the second portion of combustion air is injected into the primary combustion zone downstream of the first portion of combustion air, recovering a portion of the recirculated flue gas generated in the primary combustion zone, and recycling a portion of the flue gas back to the primary combustion zone, thereby generally providing a process for reducing the production of NOx gas in a burner. The process may include recovering and cooling heat from a portion of the recovered flue gas before the flue gas is recycled back to the primary combustion zone. The process may include mixing a portion of the recovered flue gas with combustion air. The process may include mixing a portion of the recovered flue gas with the first portion of combustion air. The process may include mixing a portion of the recovered flue gas with the second portion of combustion air. The process may include mixing a portion of the recovered flue gas with fuel gas. The process may include injecting a portion of the recovered flue gas and fuel gas into a premixer.

[0021] According to some aspects, the present invention relates to injecting fuel gas into a primary combustion zone associated with a burner tile, and injecting combustion air into the primary combustion zone, wherein the combustion air and the fuel gas react to generate a flame and flue gas in the combustion zone, and injecting a NOx reduction medium into the primary combustion zone to reduce NOx generation in the flame, wherein the NOx reduction medium includes flue gas from an FCC unit. In general, it can be characterized as providing a process for reducing the generation of NOx gas in a burner. The burner tile may be associated with a burner within an FCC unit. The process may include mixing the NOx reduction medium with the combustion air before the combustion air is injected into the primary combustion zone. The process may include mixing the NOx reduction medium with the fuel gas before the fuel gas is injected into the primary combustion zone. The process may include mixing the NOx reduction medium with the fuel gas before the fuel gas is injected into the primary combustion zone.

[0022] Further aspects, embodiments, and details of the present invention, all of which may be combinable in any manner, are described in the following detailed description of the present invention.

Brief Description of the Drawings

[0023] One or more exemplary embodiments of the present invention will be described below in conjunction with each of the following drawings.

FIG. 1A

FIG. 1B

FIG. 1C

FIG. 2A

FIG. 2B

FIG. 3

FIG. 4

FIG. 5

FIG. 6

FIG. 7

DETAILED DESCRIPTION OF THE INVENTION

[0024] As described above, the present invention provides, among other things, a novel burner. This novel burner utilizes one or more bypass ducts to transfer a portion of the combustion air from the plenum to the primary combustion zone at a location different from another portion of the combustion air. This facilitates the primary combustion zone to operate in a substantially stoichiometric manner, thereby significantly reducing the partial pressure of oxygen available for NOx formation in the primary combustion zone, typically delivering oxygen to a fuel-rich staged combustion zone with insufficient air. In addition, ducts can be used to inject a NOx reduction medium or fluid, particularly into the combustion air stream, the fuel gas, or even the bypass duct. Although only the bypass duct is thought to reduce the NOx formation of the flame, it is thought that combining the bypass duct with a NOx reduction medium provides the greatest reduction in NOx formation.

[0025] With these general principles in mind, the following description will be provided with the understanding that it is not intended to be limiting with respect to one or more embodiments of the present invention.

[0026] As shown in the figures and as starting with FIG. 1A, a burner 10 according to various embodiments of the present invention includes a plenum or windbox 12 and a tile 14 disposed on top of the plenum 12. The use of the phrase "on top" is with respect to the drawings, as the burner 10 can be installed in different configurations / orientations.

[0027] Referring to FIG. 1B, the windbox 12 includes a body 16 that forms a cavity 18 having at least one opening 20 such that air, also referred to as combustion air, naturally flows into the cavity 18. The flow of combustion air is indicated by arrow 100. Instead of a natural draft burner, there may be a fan or blower for pushing the combustion air 100 into the windbox 12 to create a forced air burner. The combustion air 100 entering the cavity 18 passes through the tile 14 and is used to generate a flame above the tile 14 in a primary combustion zone 22 in a combustion chamber that may be a chimney or a furnace.

[0028] In addition to the combustion air, the primary combustion zone receives fuel gas (indicated by arrow 200) for generating a flame. Thus, fuel lines or conduits 24a, 24b pass through the body 16 of the windbox 12 and the burner tile 14. Some of the fuel lines 24a have outlets for injecting a fuel stream, along with the fuel gas 200, into the primary combustion zone. As will be described in more detail below, the fuel stream may include the combustion air 100 and / or non-combustion gas or NOx reduction medium. The illustrated burner 10 also includes some fuel lines 24b configured to supply the fuel gas 200 to a secondary combustion zone outside the primary combustion zone. The intended source and / or composition of the fuel gas includes fuel gas from an essential oil plant, synthetic fuel gas, process off-gas, natural gas, propane, butane, LPG, hydrogen containing up to 100 volume %, and any combination of the above. The pressure of the fuel gas can vary from 0.07 to 2.07 Barg (1 to 30 psig).

[0029] As discussed above and as will be understood by those skilled in the art, the fuel gas 200 in the fuel stream and the oxygen in the combustion gas 100 can be mixed and used to generate a flame. This burner 10 attempts to reduce the amount of NOx gas generated as a result of this combustion by separating the combustion air 100 sent to the primary combustion zone into different portions. This is in contrast to prior designs where different portions of the combustion air are injected into the primary combustion zone and the secondary combustion zone.

[0030] Thus, as best shown in FIG. 1B, the burner tile 14 has a throat 26 and a bypass conduit or passage 28 that allows a portion of the combustion air 100 to pass from the plenum 12 to the primary combustion zone. More specifically, a conduit or passage 30 having an annular profile is formed between the surface of the throat 26 and the outer surface of the bypass conduit 28.

[0031] A first portion 100a of the combustion air 100 from the plenum 12 flows through the conduit 30 of the burner tile 14 to the primary combustion zone. A second portion 100b of the combustion air flows through the bypass conduit 28 and is injected into the primary combustion zone via the outlet 32. Thus, relative to the first portion 100a of the combustion air, the second portion 100b of the combustion air is injected downstream within the primary combustion zone.

[0032] Looking at FIG. 1C, another embodiment of the burner 10 according to the present invention is shown, where the same reference numerals are used for the same features.

[0033] The burner 10 of FIG. 1C is used to produce a "flat" flame. Thus, the conduit or passage 30 for the first portion 100a of the combustion air formed between the surface of the throat 26 and the outer surface of the bypass conduit 28 has a rectangular profile rather than an annular one. Similarly, the bypass conduit 28 for the second portion 100b of the combustion air also has a rectangular profile.

[0034] In either configuration, by separating the combustion air 100 into multiple portions 100a, 100b, the amount of oxygen that is first mixed with the fuel gas 200 in the primary combustion zone is less. The second portion 100b of the combustion air is further injected into the primary combustion zone, but the flame has a lower temperature, thereby producing less NOx compared to a burner that mixes all of the combustion air in the primary combustion zone simultaneously.

[0035] In addition, unlike a burner that premixes a portion of the combustion air and the fuel upstream of the burner tile 14, the present invention mixes the combustion air in both parts 100a, 100b with the fuel gas downstream of the burner tile 14. Thus, the amounts of fuel gas 200 in the first part 100a and the second part 100b of the combustion air should be approximately the same and minimal if any.

[0036] Referring to FIGS. 2A, 2B and 3, the burner 10 is contemplated to include a plurality of bypass conduits 28.

[0037] For example, in FIGS. 2A and 2B, a plurality of concentric bypass conduits 28 are shown. Each of the bypass conduits 28 has an outlet 32 that is more downstream compared to the outlet 32 surrounded by the bypass conduit 28.

[0038] Alternatively, as shown in FIG. 3, a plurality of non-concentric bypass conduits 28 may be utilized. In the burner 10 of FIG. 3, the bypass conduits 28 have different lengths, meaning that each outlet 32 is located at a different distance from the tile 14 and the outlets 32 can be sequentially downstream of each other within the primary combustion zone. Instead, although not shown as such, it is further contemplated that the non-concentric bypass conduits 28 have the same length. In either configuration, the non-concentric bypass conduits 28 are substantially parallel and the passage 30 for the second part 100b of the combustion air is formed by the open space between the various bypass conduits 28.

[0039] The plurality of bypass conduits 28 allows for fine control of the precise injection points of the second portion 100b of the combustion air injected into the combustion zone. The plurality of injection points extends the advantage that a portion of the combustion air bypasses the initial mixing in the primary combustion zone and allows for delicate application. For example, computational modeling or physical modeling can find that a particular physical location is where significant NOx formation occurs when bypass air is absent. Bypassing these locations within the burner 10 with a portion of the combustion air 100 changes the stoichiometric ratio at that particular location. Further modeling can reveal that a single bypass conduit 28 moves the location where more significant but reduced NOx formation occurs while reducing NOx formation. Additional bypasses of the combustion air around these new but fewer NOx formation locations, i.e., hot spots, further change the stoichiometric ratio at these new locations and further reduce NOx formation.

[0040] In addition, as should be understood, FIGS. 1A, 1B, 1C, 2A, and 2B illustrate a diffusion mixing burner in which all of the fuel gas 200 is injected into the combustion zone 22 (i.e., the furnace) and then mixed with the combustion air. In FIG. 3, a partially premixed burner is illustrated in which all of the fuel gas 200 is mixed with some of the combustion air 100 before being injected into the combustion zone 22. The remaining combustion air 100 that is not mixed with the fuel gas 200 is injected into the combustion zone 22 where it is mixed with the fuel gas 200.

[0041] Generally, each bypass conduit 28 also includes an inlet 34 on the opposite side of the outlet 32. The inlet 34 of the bypass conduit 28 can take many configurations for increasing, decreasing, regulating, and / or otherwise prescribing or actively controlling the combustion air entering the bypass conduit.

[0042] Thus, as shown in FIGS. 1B, 1C, and 2B, for example, in some configurations, the bypass conduit 28, and thus each inlet 34, may have a substantially constant dimension, such as the diameter of the bypass conduit 28 or the length or width along the longitudinal axis (extending from the inlet 34 to the outlet 32). Alternatively, in some configurations, as shown in FIG. 4, the inlet 34 may have an increasing dimension (also in this case, such as the diameter or length or width) compared to other portions of the bypass conduit 28 so as to provide a flared end or bell shape to the inlet. Similarly, in some configurations, as shown in FIG. 5, the inlet 34 may have a decreasing dimension (also in this case, such as the diameter or length or width) compared to other portions of the bypass conduit 28 so as to provide an inverted conical or pyramidal shape to the inlet 34. Finally, generally, the inlet 34 may also have a fixed or adjustable opening. In particular, it is contemplated that louvers, registers, or dampers (not shown) may be provided to facilitate variable control of the inlet 34. The inlet 34 may also be through a duct from an external fluid source to assist various fluid or air sources.

[0043] In addition, the outlet 32 of the bypass conduit 28 may also be configured or designed to achieve specific fluid flow characteristics. For example, in FIGS. 3 - 5, a mixing device 36 is disposed at the outlet 32 of the bypass conduit 28. The mixing device 36 enables rapid mixing with low pressure loss between a portion of the combustion air flowing through the bypass conduit 28 and the ambient partially combusted products within the primary combustion zone. Various mixing devices 36, such as static mixers, perforated bluff bodies, spin diffusers, and nozzles, may be applied at or near (upstream or downstream) the outlet 32 of the bypass conduit 28, and the illustrated mixing device 36 is not intended to be limiting.

[0044] By utilizing the flow control devices / configurations at the inlet 34 and outlet 32 of the bypass conduit 28, the partial pressure of oxygen, the oxygen available for combustion, the amounts of oxygen and other transport gases, and the mixing rate of oxygen and other gases can be adjusted and optimized in a fixed static design or as part of an actively managed and continuously optimized system.

[0045] To further lower the temperature of the flame within the primary combustion zone, fins 38 can be provided on the inner surface of the bypass conduit 28, as can be seen in FIGS. 1A and 1B. The fins 38 are for heat transfer so that heat can be radiated or conducted from the burner flame to the bypass conduit 28. The relatively low-temperature combustion air or other medium passing through the bypass conduit 28 conducts heat from the fins 38, thereby cooling the bypass conduit 28, reducing the influence or deterioration of the high temperature of the bypass conduit 28, and cooling the flame, thereby reducing NOx formation in the burner flame.

[0046] As described above, in some configurations of the burner 10 shown in FIGS. 3-7, all of the fuel gas 200 can be premixed with a portion of the combustion gas 100 before injection into the combustion zone 22. Thus, referring to FIG. 5, the burner 10 can include a premixer 40 having an inlet 42 configured to receive fuel gas 200 and a portion of the combustion air 100 from the plenum 12. This premixed combination passes through the premixer 40 and then moves to the fuel line 24a for the primary combustion zone and the fuel line 24b for the secondary combustion zone. The combustion air 100 premixed with the fuel gas 200 via the premixer 40 is not considered to be the first portion 100a and the second portion 100b of the combustion air 100 discussed above.

[0047] In summary, the burner 10 of the present invention is considered to produce a flame with less NOx generation by separating the combustion air into a plurality of portions and then staging the mixing with the fuel gas downstream of the burner tile 14 in the primary combustion zone.

[0048] As described above, it has been found that further control of NOx generation can be achieved by providing the NOx reduction medium 300. These NOx reduction media can include, but are not limited to, fluids such as flue gas from the combustion zone 22, flue gas from the exhaust of a heater, a boiler of a furnace, steam (water vapor), nitrogen, carbon dioxide, or fuel gas such as methane. Inert gases such as steam, nitrogen, and carbon dioxide injected into the fuel gas or air stream of a burner can help reduce NOx emissions by reducing the partial pressure of the reactants (both fuel and air), cooling, and transferring heat from the combustion section of the combustion zone. Further, steam, and flue gas containing steam, catalyze the combustion reaction and facilitate the solvated WGSR mechanism. Thus, in some of the various configurations of the present invention, some or all of the NOx reduction medium 300 is passed through the bypass conduit 28 to facilitate the selective and planned distribution of the NOx reduction medium at an optimal location within the flame zone.

[0049] As shown in FIGS. 1C, 2A, 2B, 3, 4, 5, 6, and 7, the NOx reduction medium 300 is injected into the burner 10 at any one or combination of locations via one or more conduits 44a, 44b, 44c, 44d. For example, in FIGS. 1C, 2A, 2B, 6, and 7, the conduit 44a injects the NOx reduction medium 300 into the passage 30 of the tile 14 and mixes it with the first portion 1 hundred a of the combustion air.

[0050] In addition, as shown in FIGS. 3, 4, 5, and 6, the conduit 44b injects the NOx reduction medium 300 into the plenum 12. Within the plenum 12, the NOx reduction medium 300 mixes with the combustion air 100. The mixture of the combustion air 100 and the NOx reduction medium 300 is sent to the primary combustion zone through both the bypass conduit 28 and the passage 30 of the tile 14 as described above with respect to the first portion 1 hundred a and the second portion 1 hundred b of the combustion air.

[0051] Furthermore, as shown in FIGS. 3, 4, 6, and 7, the conduit 44c injects the NOx reduction medium 300 into the conduit 46 that supplies the fuel gas 200 to the burner 10. The mixture of the fuel gas and the NOx reduction medium is injected into the premixer 40, and some combustion air 100 is also drawn into the premixer 40.

[0052] Furthermore, as shown in FIGS. 6 and 7, it is further contemplated that the conduit 44d injects the NOx reduction medium 300 (almost) directly into the bypass conduit 28. Additional conduits for the NOx reduction medium 300 can be utilized at various additional locations within the burner 10, and the burner 10 can receive different NOx reduction media (i.e., flows having different compositions or different sources).

[0053] There can be many different sources for the NOx reduction medium, but one preferred source is the flue gas from the combustion zone 22 itself. External flue gas recirculation is well known and practiced in the art and typically involves the movement of flue gas from an exhaust stack or chimney to the inlet of the burner by means of an electric fan. External flue gas recirculation is costly from both a capital and an operating cost perspective. The convection section of the heater, boiler, or furnace needs to be made larger to accommodate the additional recirculated flue gas in the system, there is a need to purchase and install ducts and fans, and there is a need to supply power to and operate the fans. Furthermore, when the flue gas is mixed with the combustion air, a relatively large amount of external flue gas (about 30% of the flue gas volume) needs to be recirculated to achieve significant NOx reduction.

[0054] In contrast to the current design, in all or part of the configuration of the present invention, as shown in FIG. 7, the flue gas can be drawn directly from the combustion zone 22 through the conduit 48, for example, by the power fan 50. If necessary, a heat exchanger 52 may be provided to manage the temperature of the flue gas. Thus, the flue gas from the combustion zone 22 can flow on one side of the heat exchanger 52, and the combustion air can pass through the other side of the heat exchanger 52 (and be sent to the plenum 12). This heat exchanger 52 not only reduces the temperature of the flue gas to enable easier compression and injection, but also conserves the heat from the flue gas and reintroduces it to the burner 10 via the combustion air.

[0055] The injection rate of the NOx reduction medium may be independent of the pressure, flow rate, and composition of the fuel gas. Generally, the flue gas drawn from the combustion zone 22 can be injected at any one or any combination of the injection points discussed above. For example, the flue gas may be injected into the premixer 40 by being mixed with the fuel gas from the conduit 46 through the conduit 44c, and although not shown as such, it may also be injected directly into the premixer 40.

[0056] Generally, the more recirculation and injection of the flue gas to the burner 10, the less NOx formation is formed as a result by both the thermal NOx mechanism and the prompt NOx mechanism. Furthermore, such high levels of flue gas recirculation can reduce or reform the oxidation of fuel-bound NOx to nitrogen molecules N2 or free nitrogen radicals produced from combustion. Thus, the burner of the present invention also reduces the NOx formed via the fuel NOx mechanism.

[0057] It has also been found that flue gas from a fluidized catalytic cracking (FCC) unit is another source of NOx reduction media that can be used to reduce NOx formation from burner flames. Exemplary FCC units are described in U.S. Patent Application Publication Nos. 2021 / 0009904 and 2020 / 0325087, both of which are incorporated herein by reference. The use of FCC flue gas alone is thought to reduce NOx formation, but when used in a burner having a bypass conduit 28, the formation of NOx gas is further reduced. However, it is contemplated that FCC flue gas can be used with any burner.

[0058] The composition of FCC flue gas varies somewhat such that the flue gas of a heater often contains some carbon monoxide and other unburned or incompletely burned hydrocarbons or other combustible gases. Thus, FCC flue gas can also act as part of the fuel gas providing the hydrocarbon for combustion. Further, FCC flue gas has a relatively high pressure (0.5 - 4.0 Barg (7.25 - 58 psig) at the burner). Such high-pressure flue gas allows for distribution to a number of different heaters, boilers, and furnaces, as well as their respective burners, across a refinery / petrochemical complex. In terms of pressure, such FCC flue gas may not require a heat exchanger 52 and a fan 50 as shown in FIG. 7.

[0059] It is considered particularly advantageous when FCC flue gas is used within the FCC unit. Specifically, the FCC unit utilizes steam for various purposes, such as as an NOx reduction medium in burners within the FCC unit. FCC flue gas can replace some or all of the steam typically used in the FCC unit, thereby reducing operating costs while producing a stable flame with low NOx formation. Again, in this case, although not necessary, burners within the FCC unit may include the bypass conduit 28 described above.

[0060] By designing and actively controlling the injection rate, location, local stoichiometric ratio, and NOx reduction medium introduced into the combustion process, the flame and NOx generation can be reduced to extremely low values of less than 10 ppmvd with a relatively small amount of NOx reduction medium such as flue gas. Increasing the flue gas recirculation rate can lead to burner instability and / or flame loss while further reducing NOx. By designing and actively controlling the injection rate, location, local stoichiometric ratio, and NOx reduction medium introduced into the combustion process, flame and NOx formation can be reduced while maintaining good burner and flame stability and continuous operation.

[0061] The lowest NOx emissions can be produced when burner 10 receives the highest rate of NOx reduction medium, but this can also be the initial point of burner instability. This initial instability can be detected by a high-speed pressure transmitter and associated instability detection software similar to that described in U.S. Patent No. 7,950,919. However, unlike U.S. Patent No. 7,950,919 where the oxygen in the combustion chamber is mainly controlled and adjusted to react to the instability, in the present invention, the ratio and location of the NOx reduction medium can be controlled.

[0062] Generally, the NOx emissions from the heater can be monitored along with the oxygen in the stack and the pressure or draft in the combustion chamber. The rate, amount, or both of the NOx reduction medium delivered can be increased at the desired location within the flame zone until the required NOx reduction is achieved. Once the desired NOx level is achieved, no additional NOx reduction medium can be introduced. If the burner becomes unstable, the rate and / or location of the NOx reduction medium can be controlled as suggested in U.S. Patent No. 7,950,919, or the excess air and oxygen level can be adjusted until burner stability is achieved.

[0063] It is further contemplated that an artificial intelligence (AI), such as that described in U.S. Patent Application Publication No. 2020 / 0386404, which is incorporated herein by reference, may be used with a vision camera or an infrared camera to monitor flame stability and quality aspects. If an instability or other anomaly in the flame image is detected by the AI, the amount and location of the NOx reduction medium and / or other control aspects of the heater control system, such as excess oxygen, can be adjusted and controlled to deliver the lowest level (or at least the required level) of NOx while maintaining good burner flame stability.

[0064] In the event of any loss of the NOx reduction medium at any time or instant, the burner 10 of the present invention operates safely as a conventional low NOx burner. The NOx emissions may increase, but the burner 10 remains otherwise stable and continues to reliably deliver heat to the process in the heater, boiler, or furnace. Further, the burner 10 operates in exactly the same manner as a conventional burner without any special operating problems from the perspective of the burner operator.

[0065] The introduction of the NOx reduction medium can be done by a fixed static control device or by automatic computer control. Thus, the burner operates in a conventional manner with respect to ventilation and oxygen management, as defined in "API Recommended Practice 535", Third Edition, May 2014, Burners for Fired Heaters in General Refinery Service, from the perspective of the operator. That is, ventilation and oxygen are controlled by the control setpoints of the stack damper and the burner air inlet register and / or the induced draft fan and the forced draft fan.

[0066] Although the drawings do not show various other components such as valves, pumps, fans, filters, coolers, etc., those skilled in the art should recognize and understand that these details are within the knowledge of those skilled in the art and that these explanations are not necessary to practice or understand the embodiments of the present invention.

[0067] Any of the above lines, conduits, units, devices, containers, ambient environments, zones, or the like may be equipped with one or more monitoring components including sensors, measurement devices, data capture devices, or data transmission devices. Signals, processes, or state measurements from the monitoring components, as well as data, can be used to monitor the situation within, around, and above the process equipment. The signals, measurements, and / or data generated or recorded by the monitoring components may be collected, processed, and / or transmitted via one or more networks or connections that may be private or public, general or specific, direct or indirect, wired or wireless, encrypted or unencrypted, and / or combinations thereof. This specification is not intended to be limiting in this regard.

[0068] The signals, measurements, and / or data generated or recorded by the monitoring components may be transmitted to one or more computing devices or systems. The computing device or system may include at least one processor and a memory storing computer-readable instructions that, when executed by the at least one processor, cause the one or more computing devices to perform a process that may include one or more steps. For example, the one or more computing devices may be configured to receive data from one or more monitoring components related to at least some parts of the equipment associated with the process. The one or more computing devices or systems may be configured to analyze the data. Based on the analysis of the data, the one or more computing devices or systems may be configured to determine one or more recommended adjustments to one or more parameters of one or more of the processes described herein. The one or more computing devices or systems may be configured to transmit encrypted or unencrypted data including one or more recommended adjustments to one or more parameters of one or more of the processes described herein.

[0069] The computing device of the system unit may comprise, for example, any type of general-purpose microprocessor or microcontroller, digital signal processing (DSP) processor, central processing unit (CPU), integrated circuit, field programmable gate array (FPGA), reconfigurable processor, other suitably programmed or programmable logic circuitry, or any combination thereof.

[0070] The memory may be any suitable known or other machine-readable storage medium. The memory may comprise, for example, but is not limited to, a non-transitory computer-readable storage medium such as an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. The memory may include, for example, a suitable combination of any type of computer memory, whether located internally or externally to the device, such as random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), ferroelectric RAM (FRAM), etc. The memory may include any storage means (e.g., device) suitable for removably storing computer-executable instructions executable by the controller or computing device.

[0071] The methods and steps described herein may be implemented in a high-level procedural language, an object-oriented programming language, a scripting language, or a combination thereof, to communicate with or assist in the operation of a controller or computing device. Alternatively, the methods and systems described herein may be implemented in assembly language or machine language. The language may be a compiler-type language or an interpreter-type language. Program code for implementing the methods and systems for controlling the gas flow to the burner described herein may be stored on a storage medium or device, such as a ROM, magnetic disk, optical disk, flash drive, or any other suitable storage medium or device. The program code may be readable by a general-purpose or special-purpose programmable computer to configure and operate the computer when the storage medium or device is read by the computer to perform the procedures described herein.

[0072] Computer-executable instructions may be in many forms and may include program modules executed by one or more computers or other devices. In general, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically, the functions of program modules may be combined or distributed as desired in various embodiments.

[0073] Particular embodiments The following is described in conjunction with particular embodiments, but it will be understood that this specification is illustrative of the scope of the foregoing description and the appended claims and is not intended to be limiting.

[0074] A first embodiment of the present invention is a burner, comprising a plenum, a burner tile, the burner tile being arranged such that a first portion of combustion air from the plenum flows through the burner tile to a primary combustion zone, at least one conduit having an outlet configured to inject a fuel stream containing fuel gas into the primary combustion zone, and a bypass conduit having an outlet configured to inject a second portion of combustion air from the plenum into the primary combustion zone, wherein the second portion of combustion air is injected downstream of the first portion of combustion air. An embodiment of the present invention further comprises a plurality of bypass conduits, each having an outlet configured to inject a part of the second portion of combustion air from the plenum into the primary combustion zone, and is one, part, or all of the first embodiment to the preceding embodiments of this paragraph. An embodiment of the present invention is one, part, or all of the first embodiment to the preceding embodiments of this paragraph, wherein the bypass conduits from the plurality of bypass conduits are concentric. An embodiment of the present invention is one, part, or all of the first embodiment to the preceding embodiments of this paragraph, wherein the bypass conduits from the plurality of bypass conduits each have a different length with respect to the distance from the burner tile to the outlet of each bypass conduit. An embodiment of the present invention is one, part, or all of the first embodiment to the preceding embodiments of this paragraph, wherein the bypass conduits from the plurality of bypass conduits are arranged in parallel. An embodiment of the present invention further comprises a premixer configured to mix fuel gas and a part of combustion air upstream of the combustion zone such that the fuel stream further contains combustion air, and is one, part, or all of the first embodiment to the preceding embodiments of this paragraph. An embodiment of the present invention is one, part, or all of the first embodiment to the preceding embodiments of this paragraph, wherein the bypass conduit has an inlet, and the inlet has either an increasing inner dimension for increasing the proportion of combustion air entering the bypass conduit from the plenum, or a decreasing inner dimension for decreasing the proportion of combustion air entering the bypass conduit from the plenum.An embodiment of the present invention is one, some, or all of the first embodiment of this paragraph to the preceding embodiment of this paragraph, further comprising at least one conduit configured to send a NOx reduction medium to a combustion zone.

[0075] A second embodiment of the present invention is a burner, comprising a plenum, a burner tile, at least one conduit having an outlet configured to inject a fuel stream containing fuel gas into a primary combustion zone, a bypass conduit having an outlet configured to inject a second portion of combustion air from the plenum into the primary combustion zone, wherein the second portion of combustion air is injected downstream of the first portion of combustion air, and at least one conduit configured to send a NOx reduction medium into the bypass conduit, the passage in the burner tile, or both. One embodiment of the present invention is that the NOx reduction medium is one, part, or all of the embodiments from the second embodiment to the preceding embodiment of this paragraph, including the recirculation flue gas generated in the primary combustion zone. One embodiment of the present invention further comprises a fan configured to draw flue gas from the primary combustion zone into a recirculation conduit, and is one, part, or all of the embodiments from the second embodiment to the preceding embodiment of this paragraph. One embodiment of the present invention further comprises a heat exchanger configured to recover heat from the recirculation flue gas and cool the recirculation flue gas before the recirculation flue gas is returned to the primary combustion zone, and is one, part, or all of the embodiments from the second embodiment to the preceding embodiment of this paragraph. One embodiment of the present invention further comprises a premixer configured to mix fuel gas and a portion of combustion air upstream of the combustion zone such that the fuel stream further contains combustion air, and the NOx reduction medium is injected into the premixer, and is one, part, or all of the embodiments from the second embodiment to the preceding embodiment of this paragraph. One embodiment of the present invention is that the NOx reduction medium is mixed with the fuel gas before the fuel gas is injected into the premixer, and is one, part, or all of the embodiments from the second embodiment to the preceding embodiment of this paragraph. One embodiment of the present invention is that the NOx reduction medium is mixed with the combustion air in the plenum, and is one, part, or all of the embodiments from the second embodiment to the preceding embodiment of this paragraph.

[0076] The third embodiment of the present invention is a process for reducing the generation of NOx gas in a burner, the process comprising injecting fuel gas into a primary combustion zone associated with a burner tile, injecting a first portion of combustion air into the primary combustion zone, wherein the first portion of combustion air reacts with the fuel gas to generate a flame within the primary combustion zone, and injecting a second portion of combustion air into the primary combustion zone, wherein the second portion of combustion air is injected downstream of the first portion of combustion air into the primary combustion zone. One, some, or all of the preceding embodiments of this paragraph to the third embodiment of this paragraph, in one embodiment of the present invention, the second portion of combustion air is injected via a bypass conduit. One, some, or all of the preceding embodiments of this paragraph to the third embodiment of this paragraph, in one embodiment of the present invention, the second portion of combustion air is injected via a plurality of bypass conduits, each having an outlet configured to inject the second portion of combustion air into the primary combustion zone. One, some, or all of the preceding embodiments of this paragraph to the third embodiment of this paragraph, in one embodiment of the present invention, the bypass conduits from the plurality of bypass conduits are concentric. One, some, or all of the preceding embodiments of this paragraph to the third embodiment of this paragraph, in one embodiment of the present invention, the bypass conduits from the plurality of bypass conduits each have a different length with respect to the distance from the burner tile to the outlet of each bypass conduit. One, some, or all of the preceding embodiments of this paragraph to the third embodiment of this paragraph, in one embodiment of the present invention, further comprises sending a NOx reduction medium to the combustion zone. One, some, or all of the preceding embodiments of this paragraph to the third embodiment of this paragraph, in one embodiment of the present invention, the NOx reduction medium comprises recirculated flue gas from the primary combustion zone. One, some, or all of the preceding embodiments of this paragraph to the third embodiment of this paragraph, in one embodiment of the present invention, the NOx reduction medium comprises flue gas from an FCC unit.

[0077] The fourth embodiment of the present invention is a process for reducing the generation of NOx gas in a burner, the process comprising injecting fuel gas into a primary combustion zone associated with a burner tile, injecting a first portion of combustion air into the primary combustion zone, wherein the first portion of combustion air reacts with the fuel gas to generate a flame within the primary combustion zone, injecting a second portion of combustion air into the primary combustion zone via a bypass conduit, wherein the second portion of combustion air is injected into the primary combustion zone downstream of the first portion of combustion air, and injecting a NOx reduction medium into the bypass conduit, thereby widely characterizing a process for reducing the generation of NOx gas in a burner. One, some, or all of the embodiments from the fourth embodiment to the preceding embodiments of this paragraph further include monitoring at least one NOx value of the flame and adjusting the flow rate of the NOx reduction medium based on the at least one NOx value. One, some, or all of the embodiments from the fourth embodiment to the preceding embodiments of this paragraph are such that the NOx reduction medium includes recirculated flue gas from the primary combustion zone. One, some, or all of the embodiments from the fourth embodiment to the preceding embodiments of this paragraph are such that the NOx reduction medium includes flue gas from an FCC unit.

[0078] The fifth embodiment of the present invention is a process for reducing the generation of NOx gas in a burner. The process includes injecting fuel gas into a primary combustion zone associated with a burner tile, injecting a first portion of combustion air into the primary combustion zone, where the first portion of combustion air reacts with the fuel gas to generate a flame and flue gas within the primary combustion zone, injecting a second portion of combustion air into the primary combustion zone, where the second portion of combustion air is injected downstream of the first portion of combustion air into the primary combustion zone, recovering a portion of the recirculation flue gas generated in the primary combustion zone, and recycling a portion of the flue gas back to the primary combustion zone. One, some, or all of the embodiments from the fifth embodiment to the preceding embodiments of this paragraph of the present invention further include recovering and cooling heat from a portion of the recovered flue gas before the flue gas is recycled back to the primary combustion zone. One, some, or all of the embodiments from the fifth embodiment to the preceding embodiments of this paragraph of the present invention further include mixing a portion of the recovered flue gas with combustion air. One, some, or all of the embodiments from the fifth embodiment to the preceding embodiments of this paragraph of the present invention further include mixing a portion of the recovered flue gas with the first portion of combustion air. One, some, or all of the embodiments from the fifth embodiment to the preceding embodiments of this paragraph of the present invention further include mixing a portion of the recovered flue gas with the second portion of combustion air. One, some, or all of the embodiments from the fifth embodiment to the preceding embodiments of this paragraph of the present invention further include mixing a portion of the recovered flue gas with fuel gas. One, some, or all of the embodiments from the fifth embodiment to the preceding embodiments of this paragraph of the present invention further include injecting a portion of the recovered flue gas and fuel gas into a premixer.

[0079] The sixth embodiment of the present invention is a process for reducing the generation of NOx gas in a burner, the process comprising injecting fuel gas into a primary combustion zone associated with a burner tile, injecting combustion air into the primary combustion zone, wherein the combustion air and the fuel gas react to generate a flame and flue gas in the combustion zone, injecting a NOx reduction medium into the primary combustion zone to reduce NOx generation in the flame, the NOx reduction medium comprising flue gas from an FCC unit, and generally characterized as providing a process for reducing the generation of NOx gas in a burner. One embodiment of the present invention is that the burner tile is one, some, or all of the sixth embodiment to the preceding embodiments of this paragraph, associated with a burner within an FCC unit. One embodiment of the present invention further comprises mixing the NOx reduction medium with the combustion air before the combustion air is injected into the primary combustion zone, which is one, some, or all of the sixth embodiment to the preceding embodiments of this paragraph. One embodiment of the present invention further comprises mixing the NOx reduction medium with the fuel gas before the fuel gas is injected into the primary combustion zone, which is one, some, or all of the sixth embodiment to the preceding embodiments of this paragraph. One embodiment of the present invention further comprises mixing the NOx reduction medium with the fuel gas before the fuel gas is injected into the primary combustion zone, which is one, some, or all of the sixth embodiment to the preceding embodiments of this paragraph.

[0080] Without further elaboration, using the foregoing description, those skilled in the art should be able to utilize the present invention to its fullest extent without departing from the spirit and scope of the present invention and can easily identify the essential characteristics of the present invention, make various changes and modifications to the present invention, and adapt it to various uses and conditions. Therefore, the preceding preferred specific embodiments should be construed as merely illustrative and not limiting the remainder of the present disclosure in any way, and are intended to cover various modifications and equivalent configurations within the scope of the appended claims.

[0081] In the above, all temperatures are described in degrees Celsius, and all parts and percentages are by weight unless otherwise noted.

[0082] In the foregoing detailed description of the present invention, at least one exemplary embodiment has been presented, but it should be understood that there are a vast number of variations. The exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description is provided to give those skilled in the art a convenient guide for implementing the exemplary embodiments of the invention, and it should be understood that various changes can be made to the arrangement of the functions and elements described in the exemplary embodiments without departing from the scope of the invention as set forth in the appended claims and their legal equivalents. <Supplementary Note> [Embodiment 1] A burner (10) comprising: a plenum (12); a burner tile (14) configured such that a first portion (100a) of combustion air from the plenum flows from the plenum through a passage (30) within the burner tile to a primary combustion zone; at least one conduit (24a, 24b) having an outlet configured to inject a fuel stream comprising fuel gas (200) into the primary combustion zone; a bypass conduit (28) having an outlet configured to inject a second portion (100b) of the combustion air from the plenum into the primary combustion zone, wherein the second portion (100b) of the combustion air is injected downstream of the first portion (100a) of the combustion air; and at least one conduit (44a, 44b, 44c, 44d) configured to send a NOx reduction medium (300) into the bypass conduit (28), the passage (30) within the burner tile, or both. [Embodiment 2] The burner (10) according to Embodiment 1, wherein the NOx reduction medium (300) comprises recirculated flue gas generated in the primary combustion zone. [Embodiment 3] The burner (10) according to Embodiment 2, further comprising a fan (50) configured to draw flue gas from the primary combustion zone into a recirculation conduit (48). [Embodiment 4] The burner (10) according to Embodiment 2, further comprising a heat exchanger (52) configured to recover heat from the recirculated flue gas and cool the recirculated flue gas before the recirculated flue gas is returned to the primary combustion zone. [Embodiment 5] The burner (10) further comprising a premixer (40) configured to mix the fuel gas (200) with a portion of the combustion air upstream (100) of the combustion zone such that the fuel stream further comprises the combustion air, wherein the NOx reduction medium (300) is injected into the premixer (40), the burner (10) according to any one of Embodiments 1 to 4. [Embodiment 6] The burner (10) according to Embodiment 5, wherein the NOx reduction medium (300) is mixed with the fuel gas (200) before the fuel gas is injected into the premixer (40). [Embodiment 7] The burner (10) according to any one of Forms 1 to 4, wherein the NOx reduction medium (300) is mixed with the combustion air in the plenum. [Form 8] A process for reducing the generation of NOx gas in a burner (10), the process comprising: Injecting fuel gas (200) into a primary combustion zone associated with a burner tile (14); Injecting a first portion (100a) of combustion air into the primary combustion zone through sending (30) the burner tile (14), wherein the first portion (100a) of the combustion air reacts with the fuel gas (200) to generate a flame in the primary combustion zone; Injecting a second portion (100b) of the combustion air into the primary combustion zone via a bypass conduit (28), wherein the second portion (100b) of the combustion air is injected into the primary combustion zone downstream of the first portion (100a) of the combustion air; Sending an NOx reduction medium (300) into the bypass conduit, the passageway (30) within the burner tile (14), or both. [Form 9] Monitoring at least one NOx value of the flame; Further comprising adjusting the flow rate of the NOx reduction medium (300) based on the at least one NOx value, the process according to Form 8. [Form 10] The process according to Form 8 or 9, wherein the NOx reduction medium (300) comprises recirculated flue gas from the primary combustion zone.

Claims

1. A burner (10), comprising: a plenum (12); a burner tile (14), wherein a first portion (100a) of combustion air from the plenum is arranged to flow from the plenum, through a passage (30) in the burner tile, into a primary combustion zone; at least one conduit (24a, 24b) having an outlet configured to inject a fuel stream comprising fuel gas (200) into the primary combustion zone; a bypass conduit (28) having an outlet configured to inject a second portion (100b) of the combustion air from the plenum into the primary combustion zone, wherein the second portion (100b) of the combustion air is injected downstream of the first portion (100a) of the combustion air; at least one conduit (44a, 44b, 44c, 44d) configured to pass NOx reduction medium (300) through the bypass conduit (28), the passage (30) in the burner tile (14), or both; and fins (38) provided on an inner surface of the bypass conduit (28) and configured to transfer heat from a burner flame to the bypass conduit (28).

2. The burner (10) according to claim 1, wherein the NOx reduction medium (300) comprises recirculated flue gas generated in the primary combustion zone.

3. A process for reducing the generation of NOx gas in a burner (10), the process comprising: injecting fuel gas (200) into a primary combustion zone associated with a burner tile (14); injecting a first portion (100a) of combustion air into the primary combustion zone through the passage (30) through the burner tile (14), wherein the first portion (100a) of the combustion air reacts with the fuel gas (200) to generate a flame in the primary combustion zone; injecting a second portion (100b) of the combustion air into the primary combustion zone via a bypass conduit (28), wherein the second portion (100b) of the combustion air is injected into the primary combustion zone downstream of the first portion (100a) of the combustion air; and passing NOx reduction medium (300) through the bypass conduit, the passage (30) in the burner tile (14), or both. A process including transmitting heat from a burner flame to the bypass conduit (28), the heat being transmitted through fins (38) provided on an inner surface of the bypass conduit (28).

Images