Burner and combustion furnace

Abstract

To enable stable combustion and suppression of NOx emissions in a burner for burning ammonia.SOLUTION: A burner includes: a first nozzle having a cylindrical shape using a burner axis as a center and including a main fuel outlet for ejecting a fluid mixture comprising main fuel and primary air; a flame holding plate having a truncated conical shape of which diameter is expanded toward a downstream side, disposed at a peripheral edge of the main fuel outlet at a tip of the first nozzle and generating flame holding swirl on the downstream side; a second nozzle having a secondary air outlet surrounding the main fuel outlet and blowing out secondary air from the secondary air outlet; and an auxiliary fuel nozzle disposed in a second flow passage in which the secondary air flows between the first nozzle and the second nozzle and having an auxiliary fuel outlet for ejecting gaseous fuel containing an N constituent along an outer surface of the flame holding plate or an outer surface of the first nozzle. The flame holding plate is disposed downstream of the auxiliary fuel outlet and has a projection continuing in the circumferential direction on the outer surface of the flame holding plate.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a burner that burns a gas fuel that contains a large amount of N, such as ammonia, and a combustion furnace that includes the burner. [Background technology]

[0002] In light of the trend toward reducing carbon dioxide (CO2) emissions, ammonia (NH3) has been attracting attention as a fuel that does not emit carbon dioxide when burned. Issues with using ammonia as fuel include its slow burning speed and low flame temperature compared to methane, the main component of city gas, making it difficult to burn and burn stably, and its high N content that tends to increase NOx emissions. Therefore, as disclosed in Patent Document 1, technology is being developed to suppress NOx emissions in burners that use ammonia as fuel.

[0003] The burner of Patent Document 1 includes a fuel supply nozzle that ejects a mixed fluid of a solid fuel such as pulverized coal and a carrier gas for the solid fuel, an air nozzle that is disposed outside the fuel supply nozzle and ejects combustion air from the mixed fluid toward the outer periphery, and an ammonia supply nozzle that ejects ammonia gas from the downstream side of the outlet of the fuel supply nozzle. The ammonia supply nozzle is passed through the air nozzle, and an ammonia outlet is disposed at the air outlet of the air nozzle. The ammonia supply nozzle supplies ammonia gas toward a high-temperature reduction region immediately downstream of the outlet of the fuel supply nozzle, where oxygen is consumed by the combustion of the fuel and the oxygen concentration is reduced. By burning ammonia in the high-temperature reduction region, NOx generated by the combustion is converted into nitrogen by a reduction reaction, thereby suppressing NOx emissions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-203631 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the burner of Patent Document 1, a flame-holding vortex is generated downstream of the flame-holding plate at a position sandwiched between the flow of the mixed fluid and the flow of the combustion air. In ammonia combustion, where it is difficult to stabilize the flame, protection of the flame-holding vortex is important for flame stabilization. In the burner of Patent Document 1, the flow of ammonia gas coming out of the ammonia supply nozzle passes through the flame-holding vortex and the flow of the mixed fluid toward the high-temperature reduction region. Therefore, if the flow rate of ammonia gas is low, there is a concern that the ammonia gas will be blocked by the flame-holding vortex or the flow of the mixed fluid and will not be able to reach the mixed reduction region. In addition, if the flow rate of ammonia gas is high, there is a concern that the flame-holding vortex and the circulating flow will be disturbed, making it impossible to stabilize the flame and causing unstable combustion.

[0006] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a technology that achieves both stable combustion and suppression of NOx emissions in a burner that burns a gas fuel containing N, such as ammonia. [Means for solving the problem]

[0007] In order to solve the above problems, a burner according to one aspect of the present disclosure includes: A first nozzle having a cylindrical shape centered on the burner axis and having a main fuel outlet for ejecting a mixed fluid of a main fuel and primary air; a flame-stabilizing plate having a truncated cone shape expanding toward a downstream side, the flame-stabilizing plate being disposed on a periphery of the main fuel outlet at a tip of the first nozzle and generating a flame-stabilizing vortex downstream; a second nozzle having a secondary air outlet surrounding the main fuel outlet and blowing out secondary air from the secondary air outlet; an auxiliary fuel nozzle disposed in a second flow passage through which the secondary air flows between the first nozzle and the second nozzle, the auxiliary fuel nozzle having an auxiliary fuel outlet for ejecting gas fuel containing an N component along an outer surface of the flame stabilizer or an outer surface of the first nozzle; The flame stabilizing plate is disposed downstream of the auxiliary fuel outlet and has a projection that is continuous in the circumferential direction on the outer surface of the flame stabilizing plate. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a technology that achieves both stable combustion and suppression of NOx emissions in a burner that burns a gas fuel that contains N, such as ammonia. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a boiler equipped with a burner according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram of a cross section including the burner axis of a burner according to the present disclosure. [Diagram 3] FIG. 3 is an enlarged view of a cross section including the burner axis of the outlet of the burner shown in FIG. [Figure 4] FIG. 4 is an enlarged view of a cross section including the burner axis of the flame stabilizer. [Diagram 5] FIG. 5 is an enlarged view of a cross section including the burner axis of the flame stabilizer. [Figure 6] FIG. 6 is an enlarged view of a cross section including the burner axis of the flame stabilizer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. First, a schematic configuration of a boiler 10 including a burner 5 according to an embodiment of the present disclosure will be described.

[0011] <<General configuration of boiler 10>> Fig. 1 is a diagram showing a schematic configuration of a boiler 10 including a burner 5 according to an embodiment of the present disclosure. The boiler 10 shown in Fig. 1 includes a combustion furnace 2 that burns fuel, and a boiler body 40 that generates steam by utilizing the combustion heat of the combustion furnace 2. The boiler 10 is a pulverized coal-fired thermal boiler that uses powdered or granular fossil fuel (i.e., solid fuel) as its main fuel. However, the boiler to which the burner 5 according to the present disclosure is applied is not limited to a pulverized coal-fired boiler, and may be a mixed combustion boiler using pulverized coal and biomass as its main fuel, a petroleum residue-fired boiler using petroleum residue as its main fuel, or the like.

[0012] The combustion furnace 2 has a vertical combustion chamber 20 therein. The combustion furnace 2 according to this embodiment is an inverted vertical furnace, in which a high-temperature reduction zone 21 is formed in the upper part of the combustion chamber 20, a low-temperature oxidation zone 22 is formed in the lower part of the combustion chamber 20, and a constricted section 23 is provided between the high-temperature reduction zone 21 and the low-temperature oxidation zone 22. However, the combustion furnace 2 may also be a vertical furnace in which the high-temperature reduction zone 21 is formed in the lower part of the combustion chamber 20, and the low-temperature oxidation zone 22 is formed in the upper part of the combustion chamber 20.

[0013] The portion of the inner wall of the combustion furnace 2 that forms the high-temperature reduction zone 21 is covered with a refractory material 25. At least one burner stage is provided in the furnace wall of the high-temperature reduction zone 21 of the combustion furnace 2 in the vertical direction, and each burner stage is formed of a plurality of burners 5 arranged in the horizontal direction. Each burner 5 blows fuel and air for first-stage combustion into the high-temperature reduction zone 21 to generate a flame. The outlet of the high-temperature reduction zone 21 is connected to the inlet of the low-temperature oxidation zone 22 via a throttle section 23.

[0014] A plurality of air nozzles 26 are provided on the furnace wall of the low-temperature oxidation zone 22 of the combustion furnace 2. Air for second-stage combustion is blown from each air nozzle 26 into the low-temperature oxidation zone 22. The cooling section 24 is located above and below the throttle section 23 and the plurality of air nozzles 26 in the low-temperature oxidation zone 22, and the furnace wall of the cooling section 24 is a water-cooled wall in which water pipes of the boiler body 40 are laid out. The outlet 11 of the low-temperature oxidation zone 22 is connected to the inlet of the flue 28. The flue 28 is provided with a heat transfer tube 43 of the boiler body 40. The outlet of the flue 28 is connected to the exhaust gas treatment system 30.

[0015] In the boiler 10 having the above-mentioned configuration, the air ratio between the fuel supplied to the high-temperature reduction zone 21 and the air for the first-stage combustion is maintained at less than 1 (for example, about 0.7). Moreover, the temperature inside the high-temperature reduction zone 21 covered with the refractory material 25 is less likely to drop than in other parts of the furnace. As a result, the high-temperature reduction zone 21 is in a high-temperature reducing atmosphere with an average temperature of about 1500°C (i.e., an atmosphere with an air shortage in which the amount of air is lower than the theoretical air amount), and gasification of the fuel is promoted in the high-temperature reduction zone 21.

[0016] In the high-temperature reduction zone 21, gasified fuel is generated by thermal decomposition of fuel. The gasified fuel flows into the low-temperature oxidation zone 22 through the constriction 23. The air ratio of the low-temperature oxidation zone 22 is maintained at 1 or more (for example, about 1.1) by air for second-stage combustion supplied to the low-temperature oxidation zone 22 from the air nozzle 26. This creates an oxidizing atmosphere in the low-temperature oxidation zone 22, promoting the combustion of the gasified fuel in the low-temperature oxidation zone 22.

[0017] In the low-temperature oxidation zone 22, the combustion of the fuel is completed. The combustion exhaust gas from the low-temperature oxidation zone 22 flows out to the exhaust gas treatment system 30 through the flue 28. The heat of the combustion exhaust gas is recovered by the heat transfer tubes 43 installed in the flue 28 and the furnace wall, and steam is generated in the boiler body 40. The generated steam is used, for example, in a steam turbine of a power generation facility.

[0018] << Configuration of Burner 5 >> Here, the configuration of the burner 5 provided in the boiler 10 having the above configuration will be described. The burner 5 is a multi-fuel burner that uses a solid fuel as a main fuel and a gas fuel 90 containing a large amount of N, such as ammonia, as an auxiliary fuel. The solid fuel according to this embodiment is a powdered or granular fossil fuel, such as pulverized coal. However, the main fuel of the burner 5 is not limited to fossil fuel, and may be biomass or petroleum residue. In addition, the gas fuel 90 according to this embodiment is a combustible gas containing 50% or more by volume of ammonia. However, the gas fuel 90 is not limited to ammonia gas as long as it is a gas containing N. The gas fuel 90 may be a gas containing 50% or more by volume of a combustible nitrogen compound (for example, hydrogen cyanide, methylamine, hydrazine, etc.). The gas fuel 90 may be a mixed gas of a combustible gas, such as methane or propane, and a gas containing N, such as nitrogen or a nitrogen compound.

[0019] Fig. 2 is a schematic cross-sectional view of a burner 5 according to the present disclosure, and Fig. 3 is an enlarged view of the vicinity of the outlet of the burner 5 in Fig. 2. As shown in Fig. 2 and Fig. 3, the burner 5 is equipped with a multiple nozzle consisting of a first nozzle 71, a second nozzle 72, and a third nozzle 73, which are arranged coaxially around a burner axis 70. The extension direction of the burner axis 70 is referred to as the "burner axis direction X".

[0020] The first nozzle 71 has a first passage 71f extending in the burner axial direction X therein, and a main fuel outlet 71a, which is the downstream end of the first passage 71f, at its tip. A flame stabilizing plate 77 is provided around the main fuel outlet 71a. The flame stabilizing plate 77 has a truncated cone shape that expands in diameter downstream. A swirl suppression plate 711 is provided in the first passage 71f. In addition, a dispersion vane 713 is provided upstream of the swirl suppression plate 711 in the first passage 71f.

[0021] A heavy oil burner 79 is inserted into the axial center of the first nozzle 71, overlapping with the burner axis 70. The outlet of the heavy oil burner 79 is disposed substantially in the center of the main fuel outlet 71a. The heavy oil burner 79 is mainly used for ignition.

[0022] The solid fuel and primary air are supplied to the first flow passage 71f. The primary air is the air for burning the fuel and also the gas for carrying the solid fuel. The mixed fluid 51 consisting of the solid fuel and the primary air is swirled by the action of the dispersion vane 713, and the swirling force is weakened by the action of the swirling suppression plate 711, and is ejected from the main fuel outlet 71a in the burner axial direction X.

[0023] A second nozzle 72 is provided on the outer periphery of the first nozzle 71. A second flow passage 72f having an annular flow passage cross section is formed between the first nozzle 71 and the second nozzle 72. A secondary air outlet 72a, which is the downstream end of the second flow passage 72f, surrounds the outer periphery of the main fuel outlet 71a. An air cone 72b, which expands in diameter toward the downstream, is provided on the periphery of the secondary air outlet 72a. Secondary air 52 is supplied from the wind box to the second flow passage 72f. The secondary air 52 is blown out from the secondary air outlet 72a toward the outer periphery of the flow of the mixed fluid 51. The secondary air 52 blown out from the secondary air outlet 72a is guided by the flame stabilizer 77 and the air cone 72b so as to move away from the mixed fluid 51 blown out from the first nozzle 71 to the outside.

[0024] A third nozzle 73 is provided on the outer periphery of the second nozzle 72. A third flow passage 73f having an annular flow passage cross section is formed between the third nozzle 73 and the second nozzle 72. A tertiary air outlet 73a, which is the downstream end of the third flow passage 73f, surrounds the outer periphery of the secondary air outlet 72a. An air cone 73b, which expands in diameter toward the downstream, is provided on the periphery of the tertiary air outlet 73a. A swirl vane 731 is arranged in the third flow passage 73f. The tertiary air 53 is supplied from the wind box to the third flow passage 73f. The tertiary air 53 is blown out from the tertiary air outlet 73a toward the outer periphery of the secondary air 52 while swirling due to the action of the swirl vane 731. The tertiary air 53 blown out from the third nozzle 73 is guided outwardly away from the secondary air 52 blown out from the second nozzle 72 by the air cone 72b and the air cone 73b.

[0025] The burner 5 is equipped with an auxiliary fuel nozzle 91 that ejects gaseous fuel 90 as auxiliary fuel. The multiple auxiliary fuel nozzles 91 are arranged in a line in the circumferential direction on the outer surface of the first nozzle 71. The auxiliary fuel nozzle 91 has an auxiliary fuel flow passage 91f therein, and has an auxiliary fuel outlet 91a, which is the downstream end of the auxiliary fuel flow passage 91f, at its tip. Gaseous fuel 90 is supplied from a gaseous fuel source to the auxiliary fuel flow passage 91f of the auxiliary fuel nozzle 91, and the gaseous fuel 90 is ejected from the auxiliary fuel outlet 91a.

[0026] The multiple auxiliary fuel outlets 91a are arranged in the secondary air outlet 72a and are aligned in the circumferential direction along the outer surface of the first nozzle 71 or the flame stabilizing plate 77. The surface of the flame stabilizing plate 77 facing the first flow passage 71f is referred to as the inner surface, and the surface of the flame stabilizing plate 77 facing the second flow passage 72f is referred to as the outer surface. The outer surface of the flame stabilizing plate 77 is provided with a projection 75 that continues in the circumferential direction. The projection 75 may be formed integrally with the flame stabilizing plate 77 or may be fixed to the flame stabilizing plate 77. The multiple auxiliary fuel outlets 91a are arranged upstream of the projection 75, and the projection 75 becomes an obstacle to the jet of gas fuel 90 discharged from the auxiliary fuel outlet 91a.

[0027] Burner 5 Combustion Method Next, a combustion method of the burner 5 having the above configuration will be described. As shown in Figs. 2 and 3, in the burner 5, the mixed fluid 51 of solid fuel and primary air supplied to the first nozzle 71 swirls due to the action of the dispersion vane 713, and the swirl force is weakened by the action of the swirl suppression plate 711, and the mixed fluid 51 is ejected as a swirling flow from the main fuel outlet 71a. In addition, on the outer periphery side of the main fuel outlet 71a, the secondary air 52 is ejected from the secondary air outlet 72a, and the tertiary air 53 is ejected from the tertiary air outlet 73a. The secondary air 52 is guided by the flame stabilizing plate 77 and the air cone 72b, and is ejected so as to spread toward the outer periphery side around the burner axis 70. Similarly, the tertiary air 53 is guided by the air cone 72b and the air cone 73b, and is ejected so as to spread toward the outer periphery side while swirling.

[0028] The solid fuel in the mixed fluid 51 ejected from the main fuel outlet 71a is pyrolyzed and gasified, and this gasified fuel is burned by the primary air. Immediately downstream of the main fuel outlet 71a, a circulation region 49 is created in which oxygen is consumed by combustion and a high-temperature reducing atmosphere is created. Immediately downstream of the flame-stabilizing plate 77, a flame-stabilizing vortex 55 is created by the action of the flame-stabilizing plate 77. The fluid that forms the flame-stabilizing vortex 55 contains burnt gas at a relatively high temperature produced by combustion.

[0029] In the circulation region 49 on the inner periphery side of the flame holding vortex 55, a circulating flow 50 is generated by the swirling flow of the tertiary air 53, which returns the fluid that flows downstream along the inner edge of the flame holding vortex 55 to the main fuel outlet 71a along the burner axis 70. The circulating flow 50 includes a forward flow section in which the fluid flows along the inner edge of the flame holding vortex 55 in a direction away from the main fuel outlet 71a, and a reverse flow section in which the fluid flows along the burner axis 70 in a direction toward the main fuel outlet 71a. The fluid that forms the circulating flow 50 includes burned gas at a relatively high temperature. The flame holding vortex 55 and the circulating flow 50 constantly exchange heat between the mixture of gasification fuel and primary air, and between unburned gas and high-temperature burned gas, promoting combustion and stabilizing the flame. Furthermore, the combustion air and fuel are mixed in stages in the order of the secondary air 52 and the tertiary air 53, and combustion occurs.

[0030] The gas fuel 90 ejected from the auxiliary fuel nozzle 91 flows out along the outer surface of the first nozzle 71 from the auxiliary fuel outlet 91a arranged in the second flow passage 72f. A part of the flow of the gas fuel 90, particularly a part including a boundary layer flowing along the outer surface of the first nozzle 71, comes into contact with the protrusion 75. As a result, the flow of the gas fuel 90 separates from the outer surface of the first nozzle 71, and a separation vortex 92 is generated behind the protrusion 75. The region in which the separation vortex 92 is generated extends from the upstream of the tip of the flame holding plate 77 to the downstream of the secondary air outlet 72a in the burner axial direction X. In the separation vortex 92, a fluid flow is generated that is drawn inward by the action of the gas fuel 90 and the secondary air 52 flowing on the outside. On the other hand, in the flame holding vortex 55 generated downstream of the flame holding plate 77, a fluid flow is generated that is drawn outward by the action of the flow of the mixed fluid 51. The flow of the separation vortex 92 and the flow of the flame holding vortex 55 form a vortex region, and the flame holding vortex 55 is substantially expanded toward the outer periphery.

[0031] The flow of the gas fuel 90 and the secondary air 52 passing outside the separation vortex 92 expands outward along the outer edge of the separation vortex 92 to bypass the separation vortex 92, but when it passes through the area of ​​the separation vortex 92, it is forced to change direction inward due to the pressure distribution of the separation vortex 92 and heads toward the flame holding vortex 55. The flow of the gas fuel 90 is caught in the flame holding vortex 55, and the gas fuel 90 burns in an environment with a low oxygen concentration. As a result, the emission of NOx after combustion is suppressed. In addition, the flame of the flame holding vortex 55 is stabilized by the combustion of the gas fuel 90 caught in the flame holding vortex 55, which contributes to stable combustion. Furthermore, by the flow of the gas fuel 90 avoiding the separation vortex 92 and heading inward, the flow of the gas fuel 90 passing by the side of the flame holding vortex 55 and colliding with the tertiary air 53 can be suppressed. This makes it possible to avoid the emission of a large amount of NOx due to the gas fuel 90 being rapidly mixed with the tertiary air 53 and burning in an environment with excessive oxygen.

[0032] A preferred embodiment of the projection 75 provided on the flame stabilizing plate 77 will be described below. As shown in FIG. 4, a coordinate axis in the burner axial direction X parallel to the burner axis 70 is defined, and the coordinate of the base end of the flame stabilizing plate 77 on the coordinate axis in the burner axial direction X is defined as [-L], and the coordinate of the tip of the flame stabilizing plate 77 on the coordinate axis in the burner axial direction X is defined as [0]. The value of this coordinate axis in the burner axial direction X increases toward the downstream of the flow of the mixed fluid 51 containing the main fuel. On the coordinate axis in the burner axial direction X, the coordinate P of the projection 75 is preferably equal to or larger than [-L / 2] and smaller than 0. In other words, the projection 75 is preferably disposed between the tip of the flame stabilizing plate 77 and 1 / 2 of the length L of the flame stabilizing plate 77 in the burner axial direction X. In this case, the coordinate of the auxiliary fuel outlet 91a is smaller than [-L / 2]. On the coordinate axis of the burner axial direction X, the coordinate of the auxiliary fuel outlet 91a may be equal to or larger than [-L] and smaller than [-L / 2], and the auxiliary fuel outlet 91a may be provided along the outer surface of the flame stabilizing plate 77, or the coordinate of the auxiliary fuel outlet 91a may be smaller than [-L] and the auxiliary fuel outlet 91a may be disposed upstream of the flame stabilizing plate 77. With the projections 75 disposed in this manner, the region in which the separation vortex 92 occurs when the flow of the gas fuel 90 separates reaches the rear end of the air cone 72b, that is, downstream of the secondary air outlet 72a. This allows the flame stabilizing vortex 55 generated by the flame stabilizing plate 77 to reliably interfere with the separation vortex 92.

[0033] The surface of the protrusion 75 against which the flow of gaseous fuel 90 collides is defined as the front surface, and the opposite surface is defined as the rear surface. As shown in Fig. 5, in a cross section including the burner axis 70, the angle θ between the front surface of the protrusion 75 and the outer surface of the flame stabilizing plate 77 is preferably 90 degrees or more and 135 degrees or less. By setting the angle θ in this manner, the flow of gaseous fuel 90 that collides with the protrusion 75 expands more radially outward, and the separation vortex 92 is expanded in reaction, thereby enhancing the interference between the separation vortex 92 and the flame stabilizing vortex 55.

[0034] 6, in a cross section including the burner axis 70, the angle α formed by a straight line connecting the protruding end of the front of the projection 75 and the tip of the flame stabilizing plate 77 and the outer surface of the flame stabilizing plate 77 is preferably 5 degrees or more and 20 degrees or less. However, the protruding height of the projection 75 from the outer surface of the flame stabilizing plate 77 is designed so that a part of the flow of the gas fuel 90 ejected from the auxiliary fuel outlet 91a collides with the projection 75 and the remaining part flows downstream without colliding with the projection 75. If the angle α is less than 5 degrees under the condition that the secondary air flow velocity is 20 m / s or more and 40 m / s or less on the flow path average and the auxiliary fuel gas flow velocity is 50 m / s or more and 100 m / s or less, the separation vortex 92 does not reach the downstream end of the flame stabilizing plate 77, and interference between the separation vortex 92 and the flame stabilizing vortex 55 is unlikely to occur. Moreover, under the same conditions, when the angle α exceeds 20 degrees, the separation vortex 92 is excessively expanded radially outward, compressing the secondary air flow passage 72f. When the secondary air flow passage 72f is excessively compressed, the secondary air flow velocity becomes excessive, and the balance between the tertiary air flow velocity and the secondary air flow velocity is lost.

[0035] [Summary] The burner 5 according to the first aspect of the present disclosure comprises: A first nozzle 71 having a cylindrical shape centered on a burner axis 70 and having a main fuel outlet 71a for ejecting a mixed fluid 51 of a main fuel and primary air; a flame-stabilizing plate (77) having a truncated cone shape expanding in diameter downstream and disposed on the periphery of the main fuel outlet (71a) at the tip of the first nozzle (71), and generating a flame-stabilizing vortex (55) downstream; a second nozzle 72 having a secondary air outlet 72a surrounding the main fuel outlet 71a and blowing out the secondary air 52 from the secondary air outlet 72a; an auxiliary fuel nozzle 91 that is disposed in a second flow passage 72f through which secondary air 52 flows between the first nozzle 71 and the second nozzle 72, and has an auxiliary fuel outlet 91a that ejects gas fuel 90 containing an N component along an outer surface of a flame stabilizing plate 77 or an outer surface of the first nozzle 71; The flame stabilizing plate 77 is disposed downstream of the auxiliary fuel outlet 91a, and has a projection 75 that is continuous in the circumferential direction on the outer surface of the flame stabilizing plate 77.

[0036] In the burner 5 having the above configuration, when combustion starts, a flame holding vortex 55 is generated downstream of the flame holding plate 77. In addition, a part of the ejection flow of the gas fuel 90 flowing along the outer surface of the flame holding plate 77 collides with the protrusion 75 and separates from the outer surface of the flame holding plate 77, generating a separation vortex 92 downstream of the protrusion 75. The flow of the separation vortex 92 is caught up in the flow of the flame holding vortex 55, generating a vortex region in which the flame holding vortex 55 is expanded outward. When the flow of the gas fuel 90 and the secondary air 52 flowing along the outer edge of the separation vortex 92 passes through the region of the separation vortex 92, the flow is forced to change direction inward due to the pressure distribution of the separation vortex 92, and heads toward the flame holding vortex 55. In this way, the flow of the gas fuel 90 is caught up in the flame holding vortex 55, and the gas fuel 90 burns in an environment with a low oxygen concentration. As a result, the emission of NOx after combustion is suppressed, and the flame is stabilized by the combustion of the gas fuel 90 in the flame holding vortex 55. In addition, by the flow of gas fuel 90 avoiding the separation vortex 92 and then turning inward, the flow of gas fuel 90 that passes directly by the flame holding vortex 55 and collides with the tertiary air 53 is suppressed, thereby suppressing the emission of NOx after combustion.

[0037] The burner 5 according to the second item is the burner 5 according to the first item, When a coordinate axis parallel to the burner axis 70 is defined, and the coordinate of the base end of the flame stabilizing plate 77 on that coordinate axis is defined as -L and the coordinate of the tip of the flame stabilizing plate 77 is defined as 0, the coordinate of the protrusion 75 is greater than or equal to -L / 2 and less than 0.

[0038] In the burner 5 having the above configuration, by arranging the protrusions 75 as described above, the region of the separation vortex 92 generated downstream of the protrusions 75 reaches the region of the flame-holding vortex 55 downstream of the secondary air outlet 72a of the second nozzle 72, and the separation vortex 92 can be drawn into the flame-holding vortex 55.

[0039] The burner 5 according to the third item is the burner 5 according to the first or second item, In a cross section including the burner axis 70, the angle θ between the front surface of the projection 75 and the outer surface of the flame stabilizing plate 77 is 90 degrees or more and 135 degrees or less.

[0040] As a result, the ejection flow of gas fuel 90 from the auxiliary fuel outlet 91a collides with the protrusion 75 and expands radially outward, causing the separation vortex 92 to expand in reaction, thereby strengthening the interference between the separation vortex 92 and the flame-holding vortex 55.

[0041] The burner 5 according to the fourth item is the burner 5 according to any one of the first to third items, In a cross section including the burner axis 70, the angle α between the straight line connecting the front protruding end of the projection 75 and the tip of the flame stabilizing plate 77 and the outer surface of the flame stabilizing plate 77 is greater than or equal to 5 degrees and less than or equal to 20 degrees.

[0042] This allows the separation vortex 92 to interfere with the flame-holding vortex 55 while maintaining a balance between the secondary air flow velocity and the tertiary air flow velocity.

[0043] A combustion furnace 2 according to a fifth aspect of the present disclosure includes a combustion chamber 20 and a burner 5 according to any one of the first to fourth aspects arranged on a wall of the combustion chamber 20.

[0044] The burner 5 having the above configuration is suitable as the burner 5 to be provided in the combustion furnace 2.

[0045] The above discussion of the present disclosure has been presented for purposes of illustration and description, and is not intended to limit the present disclosure to the form disclosed herein. For example, in the above detailed description, various features of the present disclosure are grouped together in one embodiment for the purpose of streamlining the present disclosure, but some of the features may be combined. In addition, the features included in the present disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above. [Explanation of symbols]

[0046] 2: Combustion furnace 5: Burner 20: Combustion chamber 51:Mixed fluid 52: Secondary air 55: Flame-holding vortex 70: Burner axis 71: No. 1 nozzle 71a: Main fuel outlet 72: Second nozzle 72a: Secondary air outlet 72f: Second flow path 75: Protrusion 77: Flame holding plate 90: Gas fuel 91: Auxiliary fuel nozzle 91a: Auxiliary fuel outlet 92: Separation vortex

Claims

1. A first nozzle having a cylindrical shape centered on a burner axis and having a main fuel outlet for ejecting a mixed fluid of a main fuel and primary air; a flame-stabilizing plate having a truncated cone shape expanding in a downstream direction, the flame-stabilizing plate being disposed on a periphery of the main fuel outlet at a tip of the first nozzle and generating a flame-stabilizing vortex downstream; a second nozzle having a secondary air outlet surrounding the main fuel outlet and blowing out secondary air from the secondary air outlet; an auxiliary fuel nozzle disposed in a second flow passage through which the secondary air flows between the first nozzle and the second nozzle, the auxiliary fuel nozzle having an auxiliary fuel outlet for ejecting gas fuel containing an N component along an outer surface of the flame stabilizer or an outer surface of the first nozzle; the flame holder is disposed downstream of the auxiliary fuel outlet and has a circumferentially continuous protrusion on an outer surface of the flame holder; Burner.

2. When a coordinate axis parallel to the burner axis is defined, and the coordinate of the base end of the flame stabilizing plate on the coordinate axis is defined as -L and the coordinate of the tip of the flame stabilizing plate on the coordinate axis is defined as 0, the coordinate of the protrusion is -L / 2 or more and less than 0; 2. A burner according to claim 1.

3. In a cross section including the burner axis, the angle between the front surface of the protrusion and the outer surface of the flame stabilizer is 90 degrees or more and 135 degrees or less.

2. A burner according to claim 1.

4. In a cross section including the burner axis, the angle between a straight line connecting the protruding end of the front surface of the protrusion and the tip of the flame stabilizing plate and the outer surface of the flame stabilizing plate is 5 degrees or more and 20 degrees or less.

3. A burner according to claim 2.

5. A combustion chamber; A burner according to any one of claims 1 to 4, arranged on a wall of the combustion chamber. Combustion furnace.

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