Burner, boiler equipped with same, and method for operating burner

Abstract

To provide a burner using liquid ammonia fuel that is capable of achieving stable combustion even when a load of the burner is adjusted. This burner comprises: an outer cylinder nozzle extending along the center axis and supplying ammonia fuel and air into the furnace; a flame holder holding flame formed by the outer cylinder nozzle; a liquid ammonia nozzle supplying the liquid ammonia fuel to the inside of the furnace from a position on the outer peripheral side of the flame holder; and a control unit adjusting the load by adjusting the supply amount of the liquid ammonia supplied from the liquid ammonia nozzle after making the supply amount of the ammonia fuel supplied to the outer cylinder nozzle constant.

Description

Burner, boiler equipped with same, and burner operating method

[0001] The present disclosure relates to a burner that burns, for example, ammonia fuel, a boiler including the burner, and a method for operating the burner.

[0002] Large boilers, such as power generation boilers, have a hollow furnace installed vertically, with multiple burners disposed on the furnace wall. Large boilers also have a flue connected vertically above the furnace, with a heat exchanger disposed in the flue for generating steam. The burner injects a mixture of fuel and air (oxidizing gas) into the furnace, forming a flame, generating combustion gas that flows down the flue. The heat exchanger is installed in the area where the combustion gas flows, and water or steam flowing through heat transfer tubes constituting the heat exchanger is heated to generate superheated steam.

[0003] For burners used in boilers, studies have been conducted to perform mixed combustion of pulverized coal and ammonia fuel, or to perform single combustion of pulverized coal and single combustion of ammonia fuel (for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2020-41748

[0005] When modifying a coal-fired boiler to enable mixed combustion with ammonia fuel, a method of supplying ammonia fuel in a liquid state and performing spray combustion is advantageous in order to reduce the size of the fuel piping, etc. However, Patent Document 1 assumes that ammonia fuel will be supplied as a gas, and does not consider using ammonia fuel as a liquid.

[0006] Ammonia is a gas at room temperature, and to supply it as a liquid, it must be pressurized to about 2 MPa. Furthermore, ammonia has a combustion speed about one-fifth that of common hydrocarbon fuels such as methane, making it difficult to ignite and burn. Furthermore, when directly burning ammonia as a liquid, the high heat of vaporization can make it difficult to ignite in a burner.

[0007] Furthermore, when reducing the burner load, the fuel supply is reduced, but this causes ignition to become unstable, making it impossible to reduce the burner load.Similarly, when increasing the burner load, ignition stability is also required.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a burner that can achieve stable combustion even when adjusting the load of a burner that uses liquid ammonia fuel, a boiler equipped with the same, and a method for operating the burner.

[0009] A burner according to one aspect of the present disclosure includes a first nozzle extending along a central axis and supplying ammonia fuel and air into the interior of a furnace, a flame stabilizer that stabilizes the flame formed by the first nozzle, a liquid ammonia nozzle that supplies liquid ammonia fuel into the interior of the furnace from a position more outer than the flame stabilizer, and a control unit that adjusts the load by adjusting the amount of liquid ammonia supplied from the liquid ammonia nozzle while keeping the amount of ammonia fuel supplied to the first nozzle constant.

[0010] A boiler according to one aspect of the present disclosure includes the burner described above.

[0011] A method for operating a burner according to one aspect of the present disclosure is a method for operating a burner that includes a first nozzle extending along a central axis and supplying ammonia fuel and air into the interior of a furnace, a flame stabilizer that stabilizes the flame, and a liquid ammonia nozzle that supplies liquid ammonia fuel into the interior of the furnace from a position more outer than the flame stabilizer, wherein the amount of ammonia fuel supplied to the first nozzle is kept constant, and the load is adjusted by adjusting the amount of liquid ammonia supplied from the liquid ammonia nozzle.

[0012] Stable combustion can be achieved even when adjusting the load of a burner that uses liquid ammonia fuel.

[0013] Fig. 4 is a schematic configuration diagram showing a boiler according to a first embodiment of the present disclosure. Fig. 5 is a longitudinal sectional view showing the burner of Fig. 1. Fig. 6 is a front view showing each position of the liquid ammonia nozzle of Fig. 2. Fig. 7 is a graph showing an ammonia flow rate when adjusting the burner load. Fig. 8 is a graph showing a modified example of Fig. 4. Fig. 9 is a longitudinal sectional view of a burner showing a modified example of Fig. 2.

[0014] An embodiment of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to this embodiment, and when there are multiple embodiments, it also includes configurations that combine the embodiments. In the following description, "up" and "upper" refer to the upper side in the vertical direction, and "lower" and "lower" refer to the lower side in the vertical direction, and the vertical direction is not precise and may include errors.

[0015] [First embodiment] FIG. 1 shows a pulverized fuel and / or ammonia (NH ３ The boiler 10 shown in this embodiment is a boiler that uses pulverized solid fuel and liquid ammonia fuel as its main fuel. The boiler 10 of this embodiment is a boiler that can generate superheated steam by burning pulverized solid fuel and liquid ammonia fuel using a burner and exchanging the heat generated by the combustion with feedwater or steam. Biomass fuel, coal, etc. are used as the solid fuel.

[0016] The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 has a hollow rectangular cylindrical shape and is installed vertically. The furnace wall 101 that forms the inner wall surface of the furnace 11 is composed of a plurality of heat transfer tubes and fins that connect the heat transfer tubes together. The heat generated by the combustion of pulverized fuel is recovered by heat exchange with water and steam circulating inside the heat transfer tubes, and the temperature rise of the furnace wall 101 is suppressed.

[0017] The combustion device 20 is installed in the lower region of the furnace 11. In this embodiment, the combustion device 20 has a plurality of burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter, when these burners are not distinguished, they will be simply referred to as "burners 21") attached to the furnace wall 101. The burners 21 are arranged at equal intervals in the furnace width direction along the furnace wall 101 (for example, they are arranged in the furnace width direction so as to face the opposing furnace walls 101, so as to perform opposed combustion), and are arranged in multiple rows along the vertical direction. The shape of the furnace, the number of burner rows, the number of burners per row, the arrangement of the burners, etc. are not limited to this embodiment.

[0018] The burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to a plurality of mills (pulverizers) 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter, when the pulverized fuel supply pipes are not distinguished, they will be simply referred to as "pulverized fuel supply pipes 22") via a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F, respectively (hereinafter, when the pulverized fuel supply pipes are not distinguished, they will be simply referred to as "mills 31"). The mill 31 is, for example, a vertical roller mill having a rotatable pulverizing table (not shown) supported therein and a plurality of pulverizing rollers (not shown) supported above the pulverizing table so as to be rotatable in conjunction with the rotation of the pulverizing table. The solid fuel pulverized by the cooperation of the pulverizing rollers and the pulverizing table is transported to a classifier (not shown) provided in the mill 31 by primary air (carrier gas, oxidizing gas) supplied to the mill 31. The classifier separates the pulverized fuel into pulverized fuel having a particle size smaller than that suitable for combustion in the burner 21 and coarse pulverized fuel having a particle size larger than that. The pulverized fuel passes through the classifier and is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. The coarse pulverized fuel that does not pass through the classifier falls onto the grinding table inside the mill 31 under its own weight and is re-ground.

[0019] At least some of the burners 21A, 21B, 21C, 21D, 21E, and 21F are ammonia-fired burners to which ammonia fuel is supplied. In this case, the other burners 21A, 21B, 21C, 21D, 21E, and 21F are pulverized coal-fired burners. The ammonia-fired burners are not supplied with pulverized coal fuel from the mill 31, but are supplied with ammonia fuel from the liquid ammonia supply source 50.

[0020] An air register 23 is provided outside the furnace 11 at the installation position of the burner 21, and one end of an air duct 24 is connected to the air register 23. The other end of the air duct 24 is connected to a forced draft fan (FDF) 32. Air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 and supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas) and introduced into the furnace 11.

[0021] The combustion gas passage 12 is connected to the vertical upper part of the furnace 11. The combustion gas passage 12 is provided with superheaters 102A, 102B, and 102C (hereinafter, when there is no need to distinguish between these superheaters, they will simply be referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter, when there is no need to distinguish between these reheaters, they will simply be referred to as "reheater 103"), and an economizer 104 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and feedwater or steam circulating inside each heat exchanger. Note that the arrangement and shape of each heat exchanger are not limited to those shown in FIG. 1.

[0022] A flue 13 is connected downstream of the combustion gas passage 12, and discharges the combustion gas whose heat has been recovered by the heat exchanger. An air preheater (air heater) 42 is provided between the flue 13 and the air duct 24, and heat is exchanged between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13, thereby heating the primary air supplied to the mill 31 and the secondary air supplied to the burner 21, thereby recovering further heat from the combustion gas after heat exchange with water and steam.

[0023] A denitration device 43 may be provided in the flue 13 upstream of the air preheater 42. The denitration device 43 supplies a reducing agent, such as ammonia or urea water, that has the ability to reduce nitrogen oxides to the combustion gas flowing through the flue 13. The denitration device 43 promotes a reaction between the nitrogen oxides (NOx) in the combustion gas and the reducing agent through the catalytic action of a denitration catalyst provided in the denitration device 43, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is provided with environmental devices, such as a dust collector 44, such as an electrostatic precipitator, that removes ash and the like from the combustion gas, and a desulfurization device 46 that removes sulfur oxides, as well as an induced draft fan (IDF) 45 that guides the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to a chimney 47, through which the combustion gas treated in the environmental device is discharged to the outside of the system as exhaust gas.

[0024] When the boiler 10 is performing mono-combustion of pulverized fuel (or co-combustion with ammonia fuel), the multiple mills 31 are driven, and pulverized and classified pulverized fuel is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. Secondary air heated by the air preheater 42 is supplied to the burner 21 from the air duct 24 via the wind box 23. The burner 21 blows a pulverized fuel mixture, which is a mixture of pulverized fuel and primary air, into the furnace 11, and also blows secondary air into the furnace 11. The pulverized fuel mixture blown into the furnace 11 ignites and reacts with the secondary air to form a flame. A flame is formed in the lower region of the furnace 11, and high-temperature combustion gas rises within the furnace 11 and flows into the combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air, secondary air), but the oxidizing gas may have a higher or lower oxygen content than air, and stable combustion can be achieved in the furnace 11 by adjusting the ratio of the amount of oxygen to the amount of fuel supplied within an appropriate range.

[0025] Additionally, above the mounting position of the burners 21 in the furnace 11, a plurality of additional air ports (AA ports) 25 are provided for supplying additional air for combustion (AA) into the furnace 11. The additional air ports 25 are connected to the ends of additional air ducts (AA ducts) 26 branching off from the air duct 24, and a portion of the air supplied from the forced draft fan 32 can be supplied to the additional air ports 25 via the additional air ducts 26 as additional air for combustion.

[0026] In region A (corresponding to the height of the wind box 23) inside the furnace 11 shown in FIG. 1 , a flame is formed by combustion of a mixture of primary air and pulverized fuel with secondary air. Here, the air ratio in region A is set to be 1 or less. Specifically, the amount of air (the total amount of primary air and secondary air) supplied to the burner 21 is set to be less than the theoretical air amount relative to the amount of fuel supplied to the burner 21. This creates a reducing atmosphere in regions A and B (regions between the top of the burner 21 and the bottom of the additional air port 25) inside the furnace 11, and nitrogen oxides (NOx) generated by combustion are reduced inside the furnace 11. Subsequently, in region C (region above the bottom of the additional air port 25), additional combustion air is supplied from the additional air port 25 to the combustion gas from which NOx has been reduced, completing the combustion. However, the amount of NOx generated is reduced by the reduction effect in regions A and B.

[0027] The combustion gas that has flowed into the combustion gas passage 12 exchanges heat with water and steam in a superheater 102, a reheater 103, and an economizer 104 arranged inside the combustion gas passage 12, and is then discharged into the flue 13, where nitrogen oxides are removed in a denitration device 43, and the combustion gas exchanges heat with primary air and secondary air in an air preheater 42, and is then discharged into the gas duct 41, where ash and the like are removed in a dust collector 44, and sulfur oxides are removed in a desulfurization device 46, and the combustion gas is then discharged to the outside of the system through a chimney 47. The arrangement of the heat exchangers in the combustion gas passage 12 and the arrangement of the devices from the flue 13 to the gas duct 41 with respect to the combustion gas flow do not necessarily have to be in the order described above.

[0028] The boiler 10 includes a liquid ammonia supply source 50. Ammonia is stored in liquid form as an ammonia fuel in the liquid ammonia supply source 50. The liquid ammonia is supplied from the liquid ammonia supply source 50 to each burner 21.

[0029] The control unit is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium, for example, in the form of a program. The CPU reads this program into RAM and executes information processing and arithmetic operations to realize various functions. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0030] 2 shows a burner 21 capable of exclusively burning ammonia fuel. The burner 21 includes an inner cylindrical nozzle (second nozzle) 61 extending along a central axis CL, and an outer cylindrical nozzle (first nozzle) 62 provided to cover the inner cylindrical nozzle 61. A core air nozzle (air nozzle) 63 is provided on the outer circumferential side of the inner cylindrical nozzle 61 and on the inner circumferential side of the outer cylindrical nozzle 62. Each of the nozzles 61, 62, and 63 has a common central axis CL, has a circular cross section, for example, and is made of metal.

[0031] The inner cylinder nozzle 61 is supplied with oil fuel (start-up fuel) and injects the oil fuel into the furnace 11. An injection tip (not shown) is provided at the tip of the inner cylinder nozzle 61 so that the oil fuel is sprayed. The oil fuel is supplied from an oil fuel supply source (not shown) and is used when starting up the burner 21.

[0032] When used as a pulverized coal burner, pulverized fuel and primary air are supplied into the outer cylindrical nozzle 62, and when used as an ammonia-fired burner, the supply of pulverized fuel and primary air is stopped.

[0033] The core air nozzle 63 is shorter than the inner cylinder nozzle 61, and its tip is located closer to the base end (left side in FIG. 2 ) than the tip of the inner cylinder nozzle 61. Core air (center air) as primary air and ammonia fuel are flowed through the core air nozzle 63. The ammonia fuel supplied to the core air nozzle 63 may be sprayed into the core air nozzle 63 or may be sprayed upstream of the core air nozzle 63. High-temperature air heated by, for example, the air preheater 42 is introduced from the air box 23 to the core air nozzle 63.

[0034] A first swirl vane 76 and a second swirl vane 77 are provided on the outer wall of the inner cylindrical nozzle 61. A plurality of these swirl vanes 76, 77 are provided in the circumferential direction around the central axis CL. The first swirl vane 76 and the second swirl vane 77 are provided between the tip of the core air nozzle 63 and the tip of the inner cylindrical nozzle 61.

[0035] The first swirl vane 76 imparts a swirl about the central axis line CL to the ammonia fuel and primary air flowing out of the core air nozzle 63. The second swirl vane 77 is located downstream of the first swirl vane 76 in the flow direction of the primary air, and imparts a swirl in the opposite direction to that of the first swirl vane 76.

[0036] A flame stabilizer 71, which is, for example, a baffle, is provided at the tip and outer periphery of the outer cylindrical nozzle 62. The flame stabilizer 71 has a ring shape when the outer cylindrical nozzle 62 is viewed from the front. The flame stabilizer 71 partially blocks the flow of secondary air flowing through the secondary air flow passage 73, forming a flame stabilization region downstream thereof. This stabilizes the flame FL of the premixed air-ammonia fuel and air supplied from the outer cylindrical nozzle 62 via the core air nozzle 63.

[0037] A secondary air nozzle 72 is provided on the outer circumferential side of the outer cylindrical nozzle 62. A secondary air flow path 73 is formed by the secondary air nozzle 72. The secondary air flow path 73 is provided so as to cover the outer cylindrical nozzle 62. An enlarged guide sleeve 72a is provided at the tip of the secondary air nozzle 72.

[0038] A tertiary air flow path 74 is provided on the outer periphery of the secondary air flow path 73 so as to cover the secondary air flow path 73. A swirler 74a is provided in the tertiary air flow path 74 to impart a swirl to the tertiary air.

[0039] A plurality of liquid ammonia nozzles 80 are provided penetrating through guide sleeve 72a from within tertiary air flow path 74. Each liquid ammonia nozzle 80 is tubular, and is provided on the outer circumferential side of outer cylindrical nozzle 62 at a position corresponding to tertiary air flow path 74. An injection tip (not shown) is provided at the tip of liquid ammonia nozzle 80 so that liquid ammonia fuel is sprayed.

[0040] As shown in FIG. 3 , a plurality of liquid ammonia nozzles 80 are provided on a concentric circle C1 centered on the central axis CL, and inject liquid ammonia fuel supplied from the liquid ammonia supply source 50 (see FIG. 1 ) into the furnace 11. The liquid ammonia nozzles 80 are arranged spaced apart from one another on the concentric circle C1. More specifically, as shown in FIG. 3 , for example, eight liquid ammonia nozzles 80 are provided at equal angular intervals of 45°. The number of liquid ammonia nozzles 80 is not particularly limited and may be four, six, or nine or more. The intervals are also not limited to equal intervals and may be any intervals. As an example, the injection direction of the liquid ammonia fuel is a direction inward (toward the central axis CL) at an angle of 35° or more from the direction of the tangent L1 on the concentric circle C1.

[0041] With the burner 21 configured as described above, ammonia combustion is performed as follows. Only at startup, oil fuel and primary air are supplied into the inner cylindrical nozzle 61 to form a startup flame. After that, once ammonia combustion is established, the supply of oil fuel and primary air into the inner cylindrical nozzle 61 is stopped.

[0042] 2, when pulverized fuel and ammonia fuel are mixed and burned, pulverized fuel and primary air are supplied between the outer cylindrical nozzle 62 and the inner cylindrical nozzle 61, and ammonia fuel and primary air are supplied from the core air nozzle 63, thereby forming a flame in the furnace 11. The flame is stabilized by a flame stabilizer 71.

[0043] 2, during ammonia combustion, ammonia fuel and primary air are supplied from the core air nozzle 63, and a flame is formed in the furnace 11. The flame is stabilized by the flame stabilizer 71.

[0044] Liquid ammonia fuel is sprayed toward the central axis line CL from the liquid ammonia nozzle 80. When the liquid ammonia fuel is sprayed, the ammonia fuel is vaporized and diffusion combustion occurs.

[0045] The load of the burner 21 is adjusted by the control unit as follows. As shown in Fig. 4, when the burner load is reduced, the amount of liquid ammonia fuel supplied from the liquid ammonia nozzle 80 is reduced while the amount of ammonia fuel supplied to the core air nozzle 63 is kept constant. In other words, the premixing ratio (solid line) is kept constant, while the diffusion ratio (dashed line) is reduced. This reduces the overall load of the burner 21.

[0046] When increasing the burner load, the procedure is reversed from the above, and the amount of ammonia fuel supplied to the core air nozzle 63 is kept constant, and the amount of liquid ammonia fuel supplied from the liquid ammonia nozzle 80 is increased. In other words, the premixing ratio (solid line) is kept constant, and the diffusion ratio (dashed line) is increased. This increases the overall load of the burner 21.

[0047] The effects of the present embodiment described above are as follows. The flame of the ammonia fuel supplied from the core air nozzle 63 is stabilized by the flame stabilizer 71. Liquid ammonia is supplied from the liquid ammonia nozzle 80 to this stabilized flame, thereby performing diffusion combustion. When adjusting the load, the amount of ammonia fuel supplied from the core air nozzle 63 is kept constant to maintain the stability of the premixed flame. Then, the amount of liquid ammonia fuel supplied from the liquid ammonia nozzle 80 is adjusted. This makes it possible to stabilize the ignition of the flame even when the load on the burner 21 changes.

[0048] <Modification 1> As shown in FIG. 5, when adjusting the burner load, the number of jets from the liquid ammonia nozzles 80 may be changed.

[0049] That is, when the burner load is reduced, the ammonia fuel supplied to the core air nozzle 63 is kept constant, and the number of injections from the liquid ammonia nozzle 80 is reduced. That is, the premix ratio (solid line) is kept constant, and the number of diffusion nozzles (dotted line) is reduced. This reduces the overall load on the burner 21.

[0050] To increase the burner load, the procedure is reversed, and the ammonia fuel supplied to the core air nozzle 63 is kept constant, and the number of injections from the liquid ammonia nozzle 80 is increased. In other words, the premixing ratio (solid line) is kept constant, and the number of diffusion nozzles (dotted line) is increased. This increases the overall load on the burner 21.

[0051] <Modification 2> As shown in Fig. 6, only high-temperature air may be supplied from the core air nozzle 63 (see Fig. 2) without supplying ammonia fuel, and ammonia fuel may be supplied to the inside of the inner cylinder nozzle 61. The high-temperature air to be flowed into the core air nozzle 63 is introduced from the air box 23 (see Fig. 1) to which air heated by the air preheater 42 is supplied, for example. Then, combustion air is supplied to the inner circumferential side of the outer cylinder nozzle 62 and the outer circumferential side of the inner cylinder nozzle 61. In this way, a diffusion flame of ammonia fuel may be formed at the outlet of the outer cylinder nozzle 62.

[0052] The burner, the boiler including the burner, and the method of operating the burner described in each of the above-described embodiments can be understood, for example, as follows.

[0053] A burner (21) according to a first aspect of the present disclosure includes a first nozzle (62) extending along a central axis (CL) and supplying ammonia fuel and air into the interior of a furnace, a flame stabilizer (71) that stabilizes the flame formed by the first nozzle, a liquid ammonia nozzle (80) that supplies liquid ammonia fuel into the furnace from a position on the outer periphery of the flame stabilizer, and a control unit that adjusts the load by adjusting the amount of liquid ammonia supplied from the liquid ammonia nozzle while keeping the amount of ammonia fuel supplied to the first nozzle constant.

[0054] The flame of the ammonia fuel supplied from the first nozzle is stabilized by a flame stabilizer. Liquid ammonia is supplied to this stabilized flame from the liquid ammonia nozzle, thereby performing diffusion combustion. When adjusting the load, the amount of ammonia fuel supplied from the first nozzle is kept constant to maintain flame stability. Then, the amount of liquid ammonia fuel supplied from the liquid ammonia nozzle is adjusted. This makes it possible to stabilize ignition of the flame even when the burner load changes. When the load is reduced, the amount of liquid ammonia fuel supplied from the liquid ammonia nozzle is reduced, and when the load is increased, the amount of liquid ammonia fuel supplied from the liquid ammonia nozzle is increased.

[0055] A burner according to a second aspect of the present disclosure is the burner of the first aspect, wherein the liquid ammonia nozzle is provided in a plurality of nozzles, and the control unit adjusts the load by changing the number of nozzles that inject liquid ammonia fuel from the liquid ammonia nozzles.

[0056] The load was adjusted by controlling the number of liquid ammonia fuel injections from the liquid ammonia nozzles.To lower the load, the number of liquid ammonia fuel injections was reduced, and to increase the load, the number of liquid ammonia fuel injections was increased.

[0057] The burner according to a third aspect of the present disclosure is the burner of the first or second aspect, which comprises a second nozzle (61) extending along the central axis on the inner periphery of the first nozzle and opening toward the inside of the furnace, and an air nozzle (63) located on the inner periphery of the first nozzle and on the outer periphery of the second nozzle, and arranged to cover the second nozzle, for supplying combustion air, and supplies ammonia fuel to the air nozzle.

[0058] A premixed gas of combustion air and ammonia fuel is formed in the air nozzle, and a premixed flame is formed at the outlet of the first nozzle. This makes it possible to form a premixed flame that is more stable than a diffusion flame, thereby further stabilizing flame ignition.

[0059] The burner according to a fourth aspect of the present disclosure is the burner of the third aspect, wherein swirl vanes (76, 77) are provided on the outer periphery of the second nozzle (61) between the tip of the second nozzle and the tip of the air nozzle.

[0060] By providing swirl vanes on the outer periphery of the second nozzle between the tip of the second nozzle and the tip of the air nozzle, it is possible to form a good premixture and to configure the burner compactly.

[0061] The burner according to the fifth aspect of the present disclosure is the first aspect described above, and is provided with a second nozzle (61) extending along the central axis on the inner periphery side of the first nozzle, opening toward the interior of the furnace, and into which ammonia fuel is supplied, and supplies combustion air to the inner periphery side of the first nozzle and the outer periphery side of the second nozzle.

[0062] Ammonia fuel may be supplied to the inside of the second nozzle, and combustion air may be supplied between the first and second nozzles to form a diffusion flame at the outlet of the first nozzle.

[0063] A boiler according to a first aspect of the present disclosure includes the burner according to any one of the above aspects.

[0064] A method for operating a burner according to a first aspect of the present disclosure is a method for operating a burner that includes a first nozzle extending along a central axis and supplying ammonia fuel and air into the interior of a furnace, a flame stabilizer that stabilizes the flame, and a liquid ammonia nozzle that supplies liquid ammonia fuel into the interior of the furnace from a position more outer than the flame stabilizer, wherein the amount of ammonia fuel supplied to the first nozzle is kept constant, and the load is adjusted by adjusting the amount of liquid ammonia supplied from the liquid ammonia nozzle.

[0065] 10: Boiler 11: Furnace 12: Combustion gas passage 13: Flue 20: Combustion device 21: Burner 22: Pulverized fuel supply pipe 23: Wind box 24: Wind duct 25: Additional air port 26: Additional air duct 31: Mill 32: Forced draft fan 41: Gas duct 42: Air preheater 43: Denitrification device 44: Device 46: Desulfurization device 47: Chimney 50: Liquid ammonia supply source 61: Inner cylindrical nozzle (second nozzle) 62: Outer cylindrical nozzle (first nozzle) 63: Core air nozzle 71: Flame holder 73: Secondary air flow path 74: Tertiary air flow path 74a: Swirler 76: First swirl vane 77 : Second swirl vane 80: Liquid ammonia nozzle 101: Furnace wall 102: Superheater 103: Reheater 104: Economizer C1: Concentric circle CL: Central axis L1: Tangent line

Claims

1. A burner comprising: a first nozzle extending along a central axis and supplying ammonia fuel and air into the interior of a furnace; a flame stabilizer for maintaining a flame formed by said first nozzle; a liquid ammonia nozzle for supplying liquid ammonia fuel into the interior of said furnace from a position on the outer periphery of said flame stabilizer; and a control unit for adjusting the load by adjusting the amount of liquid ammonia supplied from said liquid ammonia nozzle while keeping the amount of ammonia fuel supplied to said first nozzle constant.

2. The burner according to claim 1, wherein the liquid ammonia nozzle is provided in a plurality of nozzles, and the control unit adjusts the load by changing the number of the liquid ammonia nozzles that inject liquid ammonia fuel.

3. A burner as described in claim 1, comprising: a second nozzle extending along the central axis on the inner periphery of the first nozzle and opening toward the inside of the furnace; and an air nozzle located on the inner periphery of the first nozzle and on the outer periphery of the second nozzle, covering the second nozzle and supplying combustion air, wherein ammonia fuel is supplied to the air nozzle.

4. A burner as claimed in claim 3, wherein a swirl vane is provided on the outer periphery of said second nozzle between the tip of said second nozzle and the tip of said air nozzle.

5. A burner as described in claim 1, further comprising a second nozzle extending along the central axis on the inner periphery of the first nozzle, opening toward the inside of the furnace, and into which ammonia fuel is supplied, and further comprising a supply of combustion air to the inner periphery of the first nozzle and the outer periphery of the second nozzle.

6. A boiler equipped with the burner according to claim 1.

7. A method for operating a burner comprising: a first nozzle extending along a central axis and supplying ammonia fuel and air into the interior of a furnace; a flame stabilizer for maintaining a flame; and a liquid ammonia nozzle for supplying liquid ammonia fuel into the interior of the furnace from a position on the outer periphery of the flame stabilizer, wherein the amount of ammonia fuel supplied to the first nozzle is kept constant, and the load is adjusted by adjusting the amount of liquid ammonia supplied from the liquid ammonia nozzle.

Images