Ammonia combustion burners and boilers

Abstract

To stabilize an ignition position and suppress NOx generation in an ammonia combustion burner and a boiler.SOLUTION: An ammonia combustion burner related to at least one embodiment of this disclosure is an ammonia combustion burner for burning ammonia fuel by using a boiler, and includes: an ammonia injection nozzle for injecting ammonia fuel; a combustion air nozzle for ejecting combustion air from the outer side of the ammonia injection nozzle; and a flow speed distribution provision part for providing the combustion air ejected from the combustion air nozzle with flow speed distribution.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an ammonia combustion burner and a boiler.

Background Art

[0002] A boiler in which ammonia is supplied into a furnace as fuel is known. For example, in the boiler disclosed in Patent Document 1, ammonia co-firing is performed in which ammonia burns in a furnace together with coal.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When ammonia is burned in an ammonia-only combustion burner, the ignition position and the amount of NOx generated are relatively easily affected by the flow rate and flow velocity of combustion air. Therefore, it is required to supply combustion air so as to stabilize the ignition position and suppress the generation of NOx.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to stabilize the ignition position and suppress the generation of NOx in an ammonia combustion burner and a boiler.

Means for Solving the Problems

[0007] (2) A boiler according to at least one embodiment of the present disclosure is A furnace including the furnace wall, An ammonia combustion burner having the configuration described in (1) above is provided in the furnace wall, It is equipped with.

[0008] (3) A boiler according to at least one embodiment of the present disclosure is A furnace including the furnace wall, An ammonia combustion burner having the configuration described in (1) above is provided in the furnace wall, A non-fuel burner is provided in a position on the furnace wall different from the ammonia combustion burner, and burns fuels other than ammonia. It is equipped with. [Effects of the Invention]

[0009] According to at least one embodiment of this disclosure, the ignition position can be stabilized and NOx generation can be suppressed in an ammonia combustion burner and boiler. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing a boiler system comprising a boiler that primarily uses ammonia fuel and other fuels besides ammonia as its main fuel. [Figure 2] This is a schematic diagram illustrating the relationship between the flow rate of combustion air, the ignition point, and the amount of NOx generated in an ammonia-fired burner. [Figure 3] This is a schematic diagram of the first ammonia burner. [Figure 4] Figure 3 is a schematic diagram showing an example of a structure for driving the velocity distribution unit in the first ammonia burner. [Figure 5A] Figure 3 is a schematic diagram illustrating the operation of the velocity distribution unit in the first ammonia burner. [Figure 5B] It is a schematic diagram for explaining the action of the flow velocity distribution imparting part in the first ammonia burner shown in FIG. 3. [Figure 5C] It is a schematic diagram for explaining the action of the flow velocity distribution imparting part in the first ammonia burner shown in FIG. 3. [Figure 6A] It is a schematic diagram of the second ammonia burner. [Figure 6B] It is a schematic diagram of the second ammonia burner. [Figure 6C] It is a schematic diagram of the second ammonia burner. [Figure 7A] It is a schematic diagram of the third ammonia burner. [Figure 7B] It is a schematic diagram of the third ammonia burner. [Figure 7C] It is a schematic diagram of the third ammonia burner. [Figure 8A] It is a schematic diagram of the fourth ammonia burner. [Figure 8B] It is a schematic diagram of the fourth ammonia burner. [Figure 8C] It is a schematic diagram of the fourth ammonia burner. [Figure 9] It is a schematic diagram of the fifth ammonia burner. [Figure 10] It is a schematic diagram of the sixth ammonia burner. [Figure 11] It is a schematic diagram of the seventh ammonia burner. [Figure 12] It is a schematic diagram of the eighth ammonia burner.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples. For example, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" should not only strictly describe such arrangements, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. For example, expressions describing shapes such as squares or cylinders shall not only represent geometrically precise shapes such as squares or cylinders, but also shapes that include protrusions, chamfers, etc., to the extent that the same effect can be achieved. On the other hand, expressions such as "to possess," "to be equipped with," "to have," "to include," or "to have" a single component are not exclusive expressions that exclude the existence of other components.

[0012] <1. Overall configuration of boiler system 1> Figure 1 is a schematic diagram showing a boiler system 1 in this embodiment, which includes a boiler that primarily uses ammonia fuel and other fuels besides ammonia fuel.

[0013] The boiler 10 in the boiler system 1 of this embodiment is a boiler capable of burning ammonia fuel and other fuels other than ammonia fuel using a burner, and generating superheated steam by exchanging the heat generated by this combustion with feedwater or steam. As other fuels, solid fuels such as biomass fuel and coal are used. The solid fuel is, for example, pulverized coal fuel obtained by finely grinding coal. The ammonia fuel is a liquid or gas containing ammonia.

[0014] The boiler 10 has a furnace 11, combustion devices 20 and 50, and a combustion gas passage 12. The furnace 11 has a hollow rectangular shape and is installed along the vertical direction. The furnace wall 101 that makes up 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 to each other, and recovers the heat generated by the combustion of fuel by heat exchange with water or steam circulating inside the heat transfer tubes, while also suppressing the temperature rise of the furnace wall 101.

[0015] The combustion devices 20 and 50 are installed in the lower region of the furnace 11. In this embodiment, the combustion device 20 is configured to inject pulverized coal fuel into the furnace 11. The combustion device 50 is configured to inject ammonia fuel into the furnace 11.

[0016] The combustion device 20 has a plurality of burners 21 mounted on the furnace wall 101, and the combustion device 50 has a plurality of ammonia burners (ammonia combustion burners) 51. Each burner 21 is provided with an injection nozzle (not shown) configured to inject pulverized coal fuel into the furnace 11. Each ammonia burner 51 is also provided with an ammonia injection nozzle 52 (see, for example, Figure 3) at its tip. When a liquid ammonia injection system is adopted in which liquid ammonia fuel is injected into the furnace 11, the ammonia injection nozzle may be a two-fluid injection nozzle configured to atomize and inject liquid ammonia using an atomizing fluid such as steam, or it may be a one-fluid injection nozzle configured to inject only liquid ammonia fuel. When an ammonia gas injection system is adopted in which gaseous ammonia fuel is injected into the furnace 11, the ammonia injection nozzle may be a gas injection nozzle. In some embodiments of this disclosure, the ammonia burner 51 is an ammonia-only burner. As a result, as will be described later, it is possible to stabilize the ignition position and suppress the generation of NOx in ammonia-fired burners.

[0017] The burners 21 and ammonia burners 51 are arranged in multiple vertical rows, with each set consisting of four burners (for example, four burners installed at each corner of a rectangular furnace 11) arranged at equal intervals along the circumferential direction of the furnace 11. In the example shown in Figure 1, there are two rows of burner sets 21 and four rows of ammonia burners 51. Note that in Figure 1, for illustrative purposes, only two burners from each set are shown, and each set is labeled with reference numerals 21 and 51. The shape of the furnace, the number of burner rows, the number of burners in each row, and the arrangement of the burners are not limited to this embodiment. Furthermore, the combustion method in the furnace 11 of this embodiment is a swirling combustion method in which burners are installed at each corner and a flame that swirls spirally within the furnace 11 is formed, but other combustion methods may also be used. Depending on the combustion method adopted, the shape of the furnace 11 and the arrangement of the multiple burners 21 and multiple ammonia burners 51 may both be changed as appropriate. Another combustion method is, for example, a counter-combustion method in which burners are installed on both sides of a pair of opposing furnace walls of the furnace 11.

[0018] Each burner 21 of the combustion device 20 is connected to a plurality of mills 31A and 31B (hereinafter sometimes collectively referred to as "mills 31") via a plurality of pulverized coal fuel supply pipes 22A and 22B (hereinafter sometimes collectively referred to as "pulverized coal fuel supply pipes 22"). Mills 31 are, for example, vertical roller mills in which a grinding table (not shown) is supported inside so as to be rotatable, and a plurality of grinding rollers (not shown) are supported above the grinding table so as to be rotatable in conjunction with the rotation of the grinding table. The solid fuel, which is ground by the cooperation of the grinding rollers and the grinding table, is conveyed to a classifier (not shown) provided in mills 31 by primary air (conveyor gas, oxidizing gas) supplied to mills 31. In the classifier, the fuel is classified into pulverized coal fuel with a particle size of a particle size or smaller suitable for combustion in burners 21 and coarse pulverized coal fuel with a particle size larger than that. The pulverized coal fuel passes through the classifier and is supplied to the burner 21 via the pulverized coal fuel supply pipe 22 along with primary air. The coarse pulverized coal fuel that does not pass through the classifier falls onto the grinding table inside the mill 31 due to its own weight and is re-ground.

[0019] The primary air (conveyor gas, oxidizing gas) supplied to the mill 31 is sent to the mill 31 via the air pipe 30 from a primary air fan 33 (PAF) that takes in outside air. The air pipe 30 includes a hot air guide pipe 30A through which hot air heated by an air preheater 42 flows from the air sent from the primary air fan 33, a cold air guide pipe 30B through which cold air at near room temperature flows without passing through the air preheater 42 from the air sent from the primary air fan 33, and a conveyor gas passage 30C through which the hot air and cold air flow together.

[0020] The ammonia burner 51 of the combustion device 50 is connected to the ammonia fuel supply unit 90. The ammonia fuel supply unit 90 in this embodiment includes an ammonia tank 91 and an ammonia fuel supply pipe 92 for supplying ammonia fuel (e.g., liquid ammonia) stored in the ammonia tank 91 to the combustion device 50 of the boiler 10. If an ammonia gas injection method is adopted, a vaporizer (not shown) for vaporizing liquid ammonia may be provided in the ammonia fuel supply unit 90. Furthermore, if a liquid ammonia injection method is adopted, the ammonia fuel supply unit 90 may further include an atomizing fluid supply pipe (not shown) for supplying an atomizing fluid to atomize liquid ammonia to the combustion device 50.

[0021] An air register (air box) 23 is provided on the outside of the furnace 11 at the mounting positions of the burner 21 and the ammonia burner 51, and one end of an air duct 24 is connected to this air register 23. A forced draft fan (FDF) 32 is connected to the other end of the air duct 24. Air supplied from the forced draft fan 32 is heated in an air preheater 42 installed in the air duct 24, and is supplied to the burner 21 as secondary air (combustion air, oxidizing gas) and to the ammonia burner 51 as combustion air (oxidizing gas), and is introduced into the furnace 11.

[0022] The combustion gas passage 12 is connected to the upper vertical part of the furnace 11. The combustion gas passage 12 is equipped with superheaters 102A, 102B, 102C (hereinafter sometimes collectively referred to as "superheater 102"), reheaters 103A, 103B (hereinafter sometimes collectively referred to as "reheater 103"), and an economizer 104 as heat exchangers for recovering heat from the combustion gas. Heat exchange takes place between the combustion gas generated in the furnace 11 and the feedwater or steam circulating inside each heat exchanger. Note that the arrangement and shape of each heat exchanger are not limited to the configuration shown in Figure 1.

[0023] Downstream of the combustion gas passage 12 is a flue 13 through which the combustion gas, for which heat has been recovered by the heat exchanger, is discharged. An air preheater (air heater) 42 is installed between the flue 13 and the air duct 24, and heat exchange takes place between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13. By heating the primary air supplied to the mill 31 and the combustion air supplied to the burner 21 and the ammonia burner 51, heat is further recovered from the combustion gas after heat exchange with water and steam.

[0024] Furthermore, a denitrification device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitrification device 43 supplies a reducing agent, such as ammonia or urea solution, which has the effect of reducing nitrogen oxides, to the combustion gas flowing through the flue 13. The reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied and the reducing agent is promoted by the catalytic action of a denitrification catalyst installed in the denitrification device 43, thereby removing and reducing nitrogen oxides in the combustion gas. A gas duct 41 is connected downstream of the air preheater 42 in the flue 13. The gas duct 41 is equipped with dust collection devices 44, such as an electrostatic precipitator, to remove ash and other particles from the combustion gas, and environmental devices such as a desulfurization device 46 to remove sulfur oxides, as well as an induced draft fan (IDF) 45 to guide the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to the chimney 47, and the combustion gas treated by the environmental devices is discharged outside the system as exhaust gas.

[0025] In the boiler 10, when multiple mills 31 are driven, the crushed and classified pulverized coal fuel is supplied to the burner 21 via the pulverized coal fuel supply pipe 22 along with primary air. In addition, ammonia fuel is supplied to the ammonia burner 51 from the ammonia fuel supply unit 90. Furthermore, secondary air heated by the air preheater 42 is supplied to the burner 21 and the ammonia burner 51 via the air duct 24 and the air register 23. Burner 21 injects a pulverized coal fuel mixture, which is a mixture of pulverized coal fuel and primary air, into the furnace 11, along with secondary air. The pulverized coal fuel mixture injected into the furnace 11 ignites and reacts with the secondary air to form a flame. Ammonia burner 51 injects ammonia fuel along with combustion air into the furnace 11. The ammonia fuel injected into the furnace 11 reacts with the combustion air and burns. The high-temperature combustion gases generated by the combustion of pulverized coal fuel and ammonia fuel rise inside the furnace 11 and flow into the combustion gas passage 12. Furthermore, the timing of injecting ammonia fuel into the furnace 11 may be after the temperature inside the furnace 11 has risen to a certain temperature due to the combustion of pulverized coal fuel. For example, after the boiler 10 is started up and pulverized coal fuel is exclusively burned, ammonia fuel may be injected into the furnace 11, and ammonia co-firing of ammonia fuel and pulverized coal fuel may occur. After that, the injection of pulverized coal fuel may be stopped and ammonia exclusive burning may be performed. Furthermore, in this embodiment, air is used as the oxidizing gas (primary air, secondary air, combustion air), but it may also be a gas with a higher or lower oxygen content than air, and stable combustion can be achieved in the furnace 11 by adjusting the ratio of oxygen to the supplied fuel amount to an appropriate range.

[0026] The combustion gas flowing into the combustion gas passage 12 undergoes heat exchange with water and steam in the superheater 102, reheater 103, and economizer 104 located inside the combustion gas passage 12, before being discharged into the flue 13. There, nitrogen oxides are removed in the denitrification device 43, and after heat exchange with primary air, secondary air, and combustion air in the air preheater 42, it is further discharged into the gas duct 41. Ash and other contaminants are removed in the dust collector 44, and sulfur oxides are removed in the desulfurization device 46 before being discharged out of the system through the chimney 47. Note that the arrangement of each heat exchanger in the combustion gas passage 12 and each device from the flue 13 to the gas duct 41 does not necessarily have to be in the order described above with respect to the flow of combustion gas.

[0027] The boiler described herein is not limited to the embodiments described above. As the solid fuel used in the boiler, biomass fuel, petroleum coke (PC), petroleum residue, etc., may be used instead of or in conjunction with coal. Furthermore, the fuel used in boilers combined with ammonia fuel is not limited to solid fuels; liquid fuels such as heavy oil, light oil, heavy crude oil, and industrial wastewater can also be used. Gaseous fuels such as natural gas, various petroleum gases, and by-product gases generated in steelmaking processes can also be used. Furthermore, this can also be applied to co-fired boilers that use a combination of these various fuels. In the following explanation, ammonia fuel will also be simply referred to as ammonia.

[0028] As described above, a boiler 10 according to at least one embodiment of the present disclosure comprises a furnace 11 including a furnace wall 101, an ammonia burner 51 provided on the furnace wall 101 as will be described in detail later, and a burner 21 provided on the furnace wall 101 at a different location from the ammonia burner 51 as a pulverized coal burner for burning pulverized coal. This makes it possible to stabilize the ignition position and suppress the generation of NOx in the ammonia burner 51 of the boiler 10 according to at least one embodiment of the present disclosure. Burner 21 may be a multi-fuel burner that burns fuels other than ammonia. A pulverized coal burner is included in the category of multi-fuel burners.

[0029] A boiler 10 according to at least one embodiment of the present disclosure may be a swirling combustion boiler in which swirling combustion is performed in the furnace 11 by an ammonia burner 51 and a burner 21 as a pulverized coal burner. This makes it possible to stabilize the ignition position and suppress NOx generation in the ammonia burner 51 of the swirling combustion boiler. Burner 21 may also be a multi-fuel burner that burns fuels other than ammonia. Furthermore, the boiler 10 according to at least one embodiment of this disclosure may be a co-firing boiler that burns ammonia fuel and other fuels, or it may be an ammonia-only boiler that burns only ammonia fuel.

[0030] (Regarding the effect of combustion air velocity) When burning ammonia in an ammonia-only burner, the ignition point and the amount of NOx generated are relatively susceptible to the effects of the flow rate and velocity of the combustion air. Figure 2 is a schematic diagram illustrating the relationship between the flow velocity of combustion air in an ammonia-fired burner, the ignition point, and the amount of NOx generated. It uses an ammonia burner 51X, which has a single flow path for combustion air, as an example. In the ammonia burner 51X shown in Figure 2, the upper side of the diagram represents the case where the flow velocity of combustion air ejected from the combustion air nozzle 54 is relatively slow, while the lower side represents the case where the flow velocity of combustion air ejected from the combustion air nozzle 54 is relatively fast. The ammonia burner 51X shown in Figure 2 is a diffusion combustion type burner and is equipped with an ammonia injection nozzle 52 for injecting ammonia, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, and a flame holder 56. In the ammonia burner 51X shown in Figure 2, the flame holder 56 is, for example, a diffuser-type flame holder 56A with a hollow frustoconical shape. Furthermore, "outside the ammonia injection nozzle 52" refers to the region outside the ammonia injection nozzle 52 in the radial direction with respect to the central axis Ax of the ammonia injection nozzle 52. The same applies in the following explanation.

[0031] In Figure 2, the flame holding region (circulation flow generation region formed downstream of the flame holder) 81 is enclosed by a dashed line. In Figure 2, the ammonia injection range 82 injected from the ammonia injection nozzle 52 is schematically represented by a dashed line. In Figure 2, the mixing position 83 between the combustion air injected from the combustion air nozzle 54 and the ammonia injected from the ammonia injection nozzle 52 is enclosed by a solid line and represented by hatching.

[0032] When the flow velocity of the combustion air is relatively slow, the flame-holding region 81 becomes relatively small, and ignition tends to decrease. When the flow velocity of the combustion air is relatively slow, the inertia of the combustion air is relatively small, so the combustion air tends to concentrate near the ignition point. As a result, a region with a relatively high air-to-air ratio (high oxygen concentration region) is formed locally, and the amount of NOx generated tends to be relatively high.

[0033] When the flow velocity of the combustion air is relatively high, the flame-holding region 81 becomes relatively large, and ignition tends to improve. When the flow velocity of the combustion air is relatively high, the inertia of the combustion air becomes relatively large, so the mixing position 83 of the combustion air injected from the combustion air nozzle 54 and the ammonia injected from the ammonia injection nozzle 52 tends to be dispersed downstream. As a result, the formation of localized regions with a high air-to-air ratio is mitigated, and the amount of NOx generated tends to be relatively low.

[0034] As shown in Figure 2, with the ammonia burner 51X, when the combustion air flow path is a single path, the flow rate and velocity of the combustion air change simultaneously, making it relatively difficult to adjust the ignition point of the ammonia. Furthermore, during turndown, when reducing the burner's combustion rate, it is desirable to maintain the flow velocity of combustion air to ensure ignition. However, maintaining the flow velocity in a single flow path results in a constant flow rate of combustion air. On the other hand, during turndown, the amount of fuel injected decreases, so the air-to-air ratio increases, and NOx tends to increase. In particular, ammonia is more susceptible to the influence of the air-to-air ratio on NOx generation compared to other fuels, making air-to-air ratio control crucial. Therefore, it is necessary to supply combustion air in a way that stabilizes the ignition position and suppresses NOx generation, including during turndown.

[0035] Therefore, in the boiler 10 according to this embodiment, the ammonia burner 51 is configured as follows, so that the flow rate of combustion air is maintained during rated operation and turndown, while achieving an air ratio suitable for combustion that takes into account the generation of NOx. Several embodiments of the ammonia burner 51 will be described below.

[0036] (Regarding each embodiment of the ammonia burner 51) Figure 3 shows a schematic side cross-sectional view of the structure of a first ammonia burner 51A, one embodiment of an ammonia burner 51 according to several embodiments, and a schematic front view of this first ammonia burner 51A viewed from the downstream side in the direction of combustion air flow along the central axis Ax. Figure 4 is a schematic diagram showing an example of the structure for driving the flow velocity distribution unit 60, which will be described later, in the first ammonia burner 51A shown in Figure 3. Figures 5A, 5B, and 5C are schematic diagrams illustrating the operation of the flow velocity distribution unit 60 in the first ammonia burner 51A shown in Figure 3. Note that the structure for driving the flow velocity distribution unit 60 is omitted in Figures 3, 5A, 5B, and 5C. Figures 6A, 6B, and 6C are schematic diagrams illustrating the structure of a second ammonia burner 51B, which is another embodiment of the ammonia burner 51 according to several embodiments, and the operation of the flow velocity distribution unit 60. Figures 7A, 7B, and 7C are schematic diagrams illustrating the structure of a third ammonia burner 51C, which is yet another embodiment among several embodiments of the ammonia burner 51, and the operation of the flow velocity distribution unit 60. Figures 8A, 8B, and 8C are schematic side cross-sectional views illustrating the structure of a fourth ammonia burner 51D, which is yet another embodiment among several embodiments of the ammonia burner 51, and the operation of the flow velocity distribution unit 60, and a schematic front view of this fourth ammonia burner 51D viewed from the downstream side in the direction of combustion air flow along the central axis Ax. Figure 9 is a schematic side cross-sectional view illustrating the structure of a fifth ammonia burner 51E, which is yet another embodiment among several embodiments of the ammonia burner 51, and the operation of the flow velocity distribution unit 60, and a schematic front view of the fifth ammonia burner 51E viewed from the downstream side in the direction of combustion air flow along the central axis Ax. Figure 10 is a schematic side cross-sectional view illustrating the structure of a sixth ammonia burner 51F, which is yet another embodiment among several embodiments of the ammonia burner 51, and the operation of the flow velocity distribution unit 60, and a schematic front view of the sixth ammonia burner 51F viewed from the downstream side in the direction of combustion air flow along the central axis Ax. Figure 11 is a schematic side cross-sectional view illustrating the structure of a seventh ammonia burner 51G, which is yet another embodiment among several embodiments of the ammonia burner 51, and the operation of the flow velocity distribution unit 60, and a schematic front view of the seventh ammonia burner 51G viewed from the downstream side in the direction of combustion air flow along the central axis Ax. Figure 12 is a schematic side cross-sectional view illustrating the structure of the eighth ammonia burner 51H, which is yet another embodiment among several embodiments of the ammonia burner 51, and the operation of the flow velocity distribution unit 60, and a schematic front view of the eighth ammonia burner 51H viewed from the downstream side in the direction of combustion air flow along the central axis Ax.

[0037] In the following explanation, when referring to a general term for each ammonia burner 51A, 51B, 51C, 51D, 51E, 51F, 51G, and 51H, or when it is not necessary to distinguish between each ammonia burner 51A, 51B, 51C, 51D, 51E, 51F, 51G, and 51H, the alphabetical designation will be omitted, and it will simply be referred to as ammonia burner 51. Also, in the following explanation, within the direction of extension of the central axis Ax of the ammonia burner 51, the downstream side in the direction of combustion air flow will be simply referred to as the downstream side, and the upstream side in the direction of combustion air flow will be simply referred to as the upstream side.

[0038] (Regarding the first ammonia burner 51A) The first ammonia burner 51A shown in Figure 3 is a diffusion-type burner and includes an ammonia injection nozzle 52 for injecting ammonia, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, a flame holder 56, and a flow velocity distribution unit 60. In the first ammonia burner 51A shown in Figure 3, the flame holder 56 is, for example, a diffuser-type flame holder 56A with a hollow frustoconical shape.

[0039] In the first ammonia burner 51A shown in Figure 3, the combustion air nozzle 54 is a duct with a rectangular cross-section, exhibiting a rectangular shape when viewed along the central axis Ax. Near the downstream end, it is formed such that the flow path cross-sectional area decreases as it moves downstream while maintaining the rectangular cross-sectional shape. By forming a constricted section in this way, it is possible to suppress the effect of the decrease in flow velocity at the periphery of the cross-section due to the duct wall surface on the flow velocity distribution at the opening 54a at the downstream end of the combustion air nozzle 54.

[0040] In the first ammonia burner 51A shown in Figure 3, the ammonia injection nozzle 52 is arranged coaxially with the combustion air nozzle 54 and is configured to inject ammonia into the furnace 11 from multiple injection holes 52h. In the first ammonia burner 51A shown in Figure 3, in order to avoid interference with the flow velocity distribution unit 60, it is preferable that the nozzle tube on the upstream side of the ammonia injection nozzle 52 extends in the depth direction and the vertical direction of the paper in Figure 3.

[0041] In the first ammonia burner 51A shown in Figure 3, the combustion air supplied to the combustion air nozzle 54 is injected into the furnace 11 through the gap between the opening 54a at the outlet of the combustion air nozzle 54 and the outer edge of the diffuser-type flame holder 56A.

[0042] In the first ammonia burner 51A shown in Figure 3, the velocity distribution unit 60 is configured to impart a velocity distribution to the combustion air ejected from the combustion air nozzle 54. More specifically, in the first ammonia burner 51A shown in Figure 3, the velocity distribution unit 60 is a first velocity distribution unit 61 located inside the combustion air nozzle 54, which imparts a velocity distribution to the combustion air flowing inside the combustion air nozzle 54. In the first ammonia burner 51A shown in Figure 3, the first velocity distribution unit 61 includes a flow path restricting member 611 that extends outward from the center of the combustion air nozzle 54 when viewed along the central axis Ax of the combustion air nozzle 54. The flow path restricting member 611 forms a gap between itself and the inner circumferential surface 54i of the combustion air nozzle 54 through which combustion air can flow.

[0043] In the first ammonia burner 51A shown in Figure 3, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 changes depending on the position of the first velocity distribution unit 61 (flow path limiting member 611) along the central axis Ax. In Figures 5A, 5B, and 5C, the arrows shown downstream of the outlet of the combustion air nozzle 54 represent the trend of the velocity distribution of the combustion air ejected from the opening 54a at the downstream end of the combustion air nozzle 54, that is, the relationship between the distance from the central axis Ax and the velocity of the combustion air.

[0044] (When the flow path restricting member 611 is located relatively far from the opening 54a) Figure 5A shows the case where the flow path restricting member 611 is located relatively far from the opening 54a, that is, the case where the flow path restricting member 611 is located relatively upstream. The combustion air is guided into the gap by the flow path restricting member 611 away from the central axis Ax, as shown by arrow a in Figure 5A. A portion of the combustion air guided into the gap flows downstream of the downstream end 611d of the flow path restricting member 611, towards the central axis Ax due to the inertial force of the fluid, as shown by arrow b in Figure 5A. Therefore, as it approaches the opening 54a at the outlet of the combustion air nozzle 54, the flow velocity approaches a uniform state within the cross-section of the combustion air nozzle 54 perpendicular to the central axis Ax. As shown in Figure 5A, when the flow path limiting member 611 is located relatively upstream, the flow velocity within the cross-section of the combustion air nozzle 54 perpendicular to the central axis Ax approaches a uniform state. In other words, when the flow path limiting member 611 is located relatively upstream, the influence of the flow path limiting member 611 on the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 is almost eliminated. Therefore, as shown in Figure 5A, when the flow path limiting member 611 is located relatively upstream, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 will be such that the velocity is relatively equal regardless of the position of the central axis Ax.

[0045] (When the flow path restricting member 611 is located relatively close to the opening 54a) Figure 5C shows the case where the flow path restricting member 611 is located relatively close to the opening 54a, that is, the case where the flow path restricting member 611 is located relatively downstream. The combustion air is guided into the gap by the flow path restricting member 611 so as to move away from the central axis Ax, as shown by arrow d in Figure 5C. When the flow path restricting member 611 is located relatively downstream as shown in Figure 5C, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is such that the velocity is faster at positions farther from the central axis Ax than at positions closer to the central axis Ax, due to the influence of the combustion air flow as shown by arrow d. In this type of flow velocity distribution, combustion air is more easily supplied to a location relatively far from the ignition point, making it less likely for regions with a relatively high air-to-air ratio to form locally, and thus it is expected that the amount of NOx generated will be suppressed.

[0046] (When the flow path restricting member 611 approaches the opening 54a to a certain extent) Figure 5B shows a case where the flow path restricting member 611 is positioned between the position of the flow path restricting member 611 shown in Figure 5A and the position of the flow path restricting member 611 shown in Figure 5C, for example, when the flow path restricting member 611 is relatively close to the opening 54a. The combustion air is guided into the gap by the flow path restricting member 611 so as to move away from the central axis Ax, as shown by arrow c in Figure 5B. A portion of the combustion air guided into the gap flows downstream of the downstream end 611d of the flow path restricting member 611, approaching the central axis Ax. However, in the case shown in Figure 5B, the distance between the downstream end 611d of the flow path restricting member 611 and the opening 54a is shorter than in the case shown in Figure 5A, so the flow velocity in the region relatively close to the central axis Ax does not recover sufficiently. Therefore, as shown in Figure 5B, when the flow path limiting member 611 approaches the opening 54a to some extent, the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 becomes such that the flow velocity is faster at positions closer to the central axis Ax than at positions further from the central axis Ax. When such a flow velocity distribution occurs, the flow velocity of the combustion air around the flame holder 56 increases, which is expected to form a sufficient flame-holding region (circulation region) and improve ignition performance.

[0047] In the first ammonia burner 51A shown in Figure 3, it is preferable that the position of the first velocity distribution unit 61 (flow path limiting member 611) along the central axis Ax can be changed even while the boiler 10 is in operation. For example, in the first ammonia burner 51A shown in Figure 3, as shown in Figure 4, the velocity distribution unit 60 may include a moving device 613 configured to move the flow path limiting member 611 along the central axis Ax. For example, the moving device 613 may include a drive source 615 for moving the flow path restricting member 611 along the central axis Ax. The drive source 615 may be, for example, a hydraulic cylinder or an electric cylinder. The drive source 615 and the flow path restricting member 611 may be connected by, for example, a rod 616, and the flow path restricting member 611 may be moved along the central axis Ax via the rod 616. Furthermore, as shown in Figure 4, the flow path limiting member 611 may be configured to be guided along the central axis Ax by, for example, a guide rail 617 located inside the combustion air nozzle 54.

[0048] In the first ammonia burner 51A shown in Figure 3, by imparting a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54, the ignition position can be stabilized and NOx generation can be suppressed.

[0049] In the first ammonia burner 51A shown in Figure 3, a velocity distribution can be relatively easily imparted to the combustion air ejected from the combustion air nozzle 54 by the first velocity distribution imparting unit 61 (flow path limiting member 611) located inside the combustion air nozzle 54.

[0050] In the first ammonia burner 51A shown in Figure 3, by guiding the combustion air into the gap, the flow velocity of the combustion air can be made different in the central region and the outer region of the combustion air nozzle 54 when viewed along the central axis Ax of the combustion air nozzle 54. This makes it possible to impart a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0051] In the first ammonia burner 51A shown in Figure 3, the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 is affected by the position of the flow path limiting member 611 in the direction of extension of the central axis Ax. Therefore, the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 can be changed by changing the position of the flow path limiting member 611 in the direction of extension of the central axis Ax using the moving device 613. As a result, even if the flow rate of combustion air changes during turndown, for example, the ignition position can be stabilized and NOx generation can be suppressed by changing the position of the flow path limiting member 611 in the direction of extension of the central axis Ax.

[0052] In addition, in the first ammonia burner 51A shown in Figure 3, the position of the first velocity distribution unit 61 (flow path limiting member 611) along the central axis Ax may be fixed at a predetermined position and configured so that its position cannot be changed during operation of the boiler 10.

[0053] (Regarding the second ammonia burner 51B) The second ammonia burner 51B shown in Figures 6A, 6B, and 6C is a diffusion-type burner, similar to the first ammonia burner 51A shown in Figure 3, and includes an ammonia injection nozzle 52 for injecting ammonia, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, a flame holder 56, and a flow velocity distribution unit 60. In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the flame holder 56 is, for example, a diffuser-type flame holder 56A, similar to the first ammonia burner 51A shown in Figure 3.

[0054] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the combustion air nozzle 54 has the same structure as the first ammonia burner 51A shown in Figure 3.

[0055] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, similar to the first ammonia burner 51A shown in Figure 3, the ammonia injection nozzle 52 is arranged coaxially with the combustion air nozzle 54 and is configured to inject ammonia into the furnace 11 from multiple injection holes 52h. In addition, in the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, similar to the first ammonia burner 51A shown in Figure 3, the nozzle tube upstream of the ammonia injection nozzle 52 may or may not extend in the depth direction and the vertical direction of the paper in Figures 6A, 6B, and 6C.

[0056] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, similar to the first ammonia burner 51A shown in Figure 3, the combustion air supplied to the combustion air nozzle 54 is injected into the furnace 11 through the gap between the opening 54a at the outlet of the combustion air nozzle 54 and the outer edge of the diffuser-type flame holder 56A.

[0057] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the velocity distribution unit 60 is configured to impart a velocity distribution to the combustion air ejected from the combustion air nozzle 54, similar to the first ammonia burner 51A shown in Figure 3. More specifically, in the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the velocity distribution unit 60 is located inside the combustion air nozzle 54 and is a first velocity distribution unit 61 that imparts a velocity distribution to the combustion air flowing inside the combustion air nozzle 54, similar to the first ammonia burner 51A shown in Figure 3. In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the first velocity distribution unit 61 includes a guide vane 612 having a guide surface 612a inclined at a specified inclination angle θ with respect to the direction of extension of the central axis Ax.

[0058] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the guide vanes 612 may be arranged, for example, along each side of the combustion air nozzle 54 having a rectangular cross-section, with at least one guide vane per side. For example, in the examples shown in Figures 6A, 6B, and 6C, one guide vane 612 is arranged on each of the two sides of the combustion air nozzle 54 having a rectangular cross-section that are spaced apart in the vertical direction shown, and one guide vane 612 is arranged on each of the two sides (not shown) that are spaced apart in the depth direction shown. Furthermore, as shown in Figures 7A, 7B, and 7C later, for example, the third ammonia burner 51C may have multiple guide vanes 612 arranged in a direction perpendicular to the central axis Ax along each side of the combustion air nozzle 54 having a rectangular cross-section. Alternatively, multiple guide vanes 612 may be arranged along each side of the combustion air nozzle 54 having a rectangular cross-section, in the direction of extension of the side. Alternatively, multiple guide vanes 612 may be arranged in the direction of extension of the central axis Ax. Furthermore, guide vanes 612 may be arranged on each of two sides that are spaced apart in the vertical direction shown, but not on each of the two unshown sides that are spaced apart in the depth direction shown. Alternatively, guide vanes 612 may not be arranged on each of the two sides that are spaced apart in the vertical direction shown, but may be arranged on each of the two unshown sides that are spaced apart in the depth direction shown.

[0059] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 changes depending on the inclination angle θ of the guide surface 612a. In Figures 6A, 6B, and 6C, the arrows shown downstream of the outlet of the combustion air nozzle 54 represent the trend of the velocity distribution of the combustion air ejected from the opening 54a at the downstream end of the combustion air nozzle 54, that is, the relationship between the distance from the central axis Ax and the velocity of the combustion air.

[0060] (When the inclination angle θ is 0 degrees) Figure 6A shows the case where the inclination angle θ of the guide surface 612a of the guide vane 612 is 0 degrees. In the case shown in Figure 6A, the guide surface 612a of the guide vane 612 does not guide the combustion air flowing through the combustion air nozzle 54 toward the central axis Ax, nor does it guide it toward the central axis Ax. Therefore, in the case shown in Figure 6A, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 will be such that the velocity is relatively equal regardless of the position of the central axis Ax.

[0061] (When the guide surface 612a approaches the central axis Ax as it moves downstream) Figure 6B shows the case where the angle θ is set so that the guide surface 612a approaches the central axis Ax as it moves downstream. In the case shown in Figure 6B, the combustion air is guided by the guide surface 612a to approach the central axis Ax. Therefore, in the case shown in Figure 6B, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is such that the velocity is higher at positions closer to the central axis Ax than at positions further from the central axis Ax.

[0062] (When the guide surface 612a moves away from the central axis Ax as it moves downstream) Figure 6C shows the case where the angle θ is set such that the guide surface 612a moves away from the central axis Ax as it moves downstream. In the case shown in Figure 6C, the combustion air is guided away from the central axis Ax by the guide surface 612a. Therefore, in the case shown in Figure 6C, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is such that the velocity is higher at positions farther from the central axis Ax than at positions closer to the central axis Ax.

[0063] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, it is preferable that the inclination angle θ of the guide surface 612a can be changed even while the boiler 10 is in operation. For example, in the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the velocity distribution unit 60 may include a guide vane drive device 614 configured to change the inclination angle θ of the guide surface 612a. The guide vane drive device 614 may include a drive source (not shown) for changing the inclination angle θ of the guide surface 612a, and a transmission device (not shown) configured to transmit the driving force of the drive source to change the inclination angle θ of the guide surface 612a.

[0064] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the ignition position can be stabilized and NOx generation suppressed by providing a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0065] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, a velocity distribution can be relatively easily imparted to the combustion air ejected from the combustion air nozzle 54 by the first velocity distribution imparting unit 61 (guide vane 612) located inside the combustion air nozzle 54.

[0066] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the combustion air is guided by the guide vane 612, which makes it possible to make the flow velocity of the combustion air different in the central region and the outer region of the combustion air nozzle 54 when viewed along the central axis Ax of the combustion air nozzle 54. This makes it possible to impart a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0067] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is affected by the inclination angle θ. Therefore, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 can be changed by changing the inclination angle θ using the guide vane drive device 614. This allows for stabilization of the ignition position and suppression of NOx generation, for example, even if the flow rate of combustion air changes during turndown, by changing the inclination angle θ.

[0068] In the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the guide surface 612a may be fixed at a predetermined inclination angle θ, and the configuration may be such that the inclination angle θ cannot be changed while the boiler 10 is in operation.

[0069] (Regarding the 3rd ammonia burner 51C) The third ammonia burner 51C shown in Figures 7A, 7B, and 7C is a diffusion-type burner, similar to the first ammonia burner 51A shown in Figure 3, and includes an ammonia injection nozzle 52 for injecting ammonia, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, a flame holder 56, and a flow velocity distribution unit 60. In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the flame holder 56 is, for example, a diffuser-type flame holder 56A, similar to the first ammonia burner 51A shown in Figure 3.

[0070] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the combustion air nozzle 54 has the same structure as the first ammonia burner 51A shown in Figure 3.

[0071] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, similar to the first ammonia burner 51A shown in Figure 3, the ammonia injection nozzle 52 is arranged coaxially with the combustion air nozzle 54 and is configured to inject ammonia into the furnace 11 from a plurality of injection holes 52h. In addition, in the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, similar to the first ammonia burner 51A shown in Figure 3, the nozzle tube upstream of the ammonia injection nozzle 52 may extend in the depth direction and the vertical direction of the paper in Figures 7A, 7B, and 7C.

[0072] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, similar to the first ammonia burner 51A shown in Figure 3, the combustion air supplied to the combustion air nozzle 54 is injected into the furnace 11 through the gap between the opening 54a at the outlet of the combustion air nozzle 54 and the outer edge of the diffuser-type flame holder 56A.

[0073] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, similar to the first ammonia burner 51A shown in Figure 3, the velocity distribution unit 60 is configured to impart a velocity distribution to the combustion air ejected from the opening 54a at the downstream end of the combustion air nozzle 54. More specifically, in the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, similar to the first ammonia burner 51A shown in Figure 3, the velocity distribution unit 60 is located inside the combustion air nozzle 54 and is a first velocity distribution unit 61 that imparts a velocity distribution to the combustion air flowing inside the combustion air nozzle 54. In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the first velocity distribution unit 61 includes a guide vane 612 having a guide surface 612a inclined at a specified inclination angle θ with respect to the direction of extension of the central axis Ax. In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the first velocity distribution unit 61 includes a damper 618 located inside the combustion air nozzle 54 in a region inward from the guide vane 612. The damper 618 can adjust the flow rate of combustion air passing through this region (i.e., the damper 618).

[0074] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the guide vanes 612 may be arranged in multiple stages along each side of the combustion air nozzle 54 having a rectangular cross-section, in a direction perpendicular to the central axis Ax for each side. In the example shown in Figures 7A, 7B, and 7C, the guide vanes 612 are arranged in two stages along each side, in a direction perpendicular to the central axis Ax. In addition, in the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the number of stages of the guide vanes 612 may be one stage, similar to the second ammonia burner 51B shown in Figures 6A, 6B, and 6C. Furthermore, the guide vanes 612 may be arranged in multiple stages along each side of the combustion air nozzle 54 having a rectangular cross-section, in the direction of extension of the side. The guide vanes 612 may also be arranged in multiple stages in the direction of extension of the central axis Ax. Furthermore, the guide vanes 612 may be placed on each of the two sides that are spaced apart in the vertical direction as shown, but not on each of the two unshown sides that are spaced apart in the depth direction as shown. Alternatively, the guide vanes 612 may not be placed on each of the two sides that are spaced apart in the vertical direction as shown, but may be placed on each of the two unshown sides that are spaced apart in the depth direction as shown.

[0075] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 changes depending on the inclination angle θ of the guide surface 612a. Furthermore, in the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the flow rate of combustion air passing on the outer circumference of the damper 618 can be increased by restricting the flow rate of combustion air passing through the damper 618. Therefore, in the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 can be changed by adjusting the inclination angle θ of the guide surface 612a and the opening degree of the damper 618. In Figures 7A, 7B, and 7C, the arrows indicated downstream of the outlet of the combustion air nozzle 54 represent the trend of the flow velocity distribution of the combustion air ejected from the opening 54a at the downstream end of the combustion air nozzle 54, that is, the relationship between the distance from the central axis Ax and the flow velocity of the combustion air.

[0076] (When the tilt angle θ is 0 degrees and the damper 618 is not used to restrict the angle) Figure 7A shows the case where the inclination angle θ of the guide surface 612a of each guide vane 612 is 0 degrees, and the flow rate of combustion air passing through the damper 618 is not restricted. In the case shown in Figure 7A, the guide surface 612a of the guide vane 612 does not guide the combustion air flowing through the combustion air nozzle 54 toward the central axis Ax, nor does it guide it toward the central axis Ax. Also, since the flow rate of combustion air passing through the damper 618 is not restricted, the flow rate of combustion air passing on the outer circumference of the damper 618 does not increase. Therefore, in the case shown in Figure 7A, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 will be such that the velocity is relatively equal regardless of the position of the central axis Ax.

[0077] (When the guide surface 612a approaches the central axis Ax as it moves downstream) Figure 7B shows a case where the angle θ of the outer-circumferential guide vane 612 is set so that the guide surface 612a approaches the central axis Ax as it moves downstream, among the two stages of guide vanes 612 arranged on the outer and inner circumferential sides around the central axis Ax. In the case shown in Figure 7B, the combustion air is guided by the guide surface 612a of the outer peripheral guide vane 612 to approach the central axis Ax. In the case shown in Figure 7B, tilting the outer guide vane 612 increases the pressure loss, so the flow rate of combustion air passing through the damper 618 may be restricted to prevent a decrease in the flow rate of combustion air flowing around the outer circumference of the combustion air nozzle 54. However, if the flow rate of combustion air flowing around the outer circumference of the combustion air nozzle 54 does not decrease, it is not necessary to restrict the flow rate of combustion air passing through the damper 618. Therefore, in the case shown in Figure 7B, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is such that the velocity is higher at positions closer to the central axis Ax than at positions further from the central axis Ax.

[0078] (When the guide surface 612a moves away from the central axis Ax as it moves downstream) Figure 7C shows a case where the angle θ of the inner guide vane 612 is set so that the guide surface 612a moves away from the central axis Ax as it moves downstream, among the two stages of guide vanes 612 arranged on the outer and inner sides around the central axis Ax. In the case shown in Figure 7C, the combustion air is guided away from the central axis Ax by the guide surface 612a. In the case shown in Figure 7C, tilting the inner guide vane 612 increases the pressure loss, so the flow rate of combustion air passing through the damper 618 may be restricted to prevent a decrease in the flow rate of combustion air flowing on the outer circumference of the combustion air nozzle 54. However, if the flow rate of combustion air flowing on the outer circumference of the combustion air nozzle 54 does not decrease, it is not necessary to restrict the flow rate of combustion air passing through the damper 618. Therefore, in the case shown in Figure 7C, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is such that the velocity is higher at positions farther from the central axis Ax than at positions closer to the central axis Ax.

[0079] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, it is preferable that the inclination angle θ of the guide surface 612a be changed even while the boiler 10 is in operation. For example, in the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, similar to the second ammonia burner 51B shown in Figures 6A, 6B, and 6C, the velocity distribution unit 60 may include a guide vane drive device 614 configured to change the inclination angle θ of the guide surface 612a. The guide vane drive device 614 may include a drive source (not shown) for changing the inclination angle θ of the guide surface 612a, and a transmission device (not shown) configured to transmit the driving force of the drive source to change the inclination angle θ of the guide surface 612a.

[0080] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, it is preferable that the opening degree of the damper 618 can be changed even while the boiler 10 is in operation. For example, in the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the flow velocity distribution unit 60 may include a damper drive device 619 configured to change the opening degree of the damper 618. The damper drive device 619 may include a drive source (not shown) for changing the opening degree of the damper 618, and a transmission device (not shown) configured to transmit the driving force of the drive source to change the opening degree of the damper 618.

[0081] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the ignition position can be stabilized and NOx generation suppressed by providing a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0082] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, a velocity distribution can be relatively easily imparted to the combustion air ejected from the combustion air nozzle 54 by the first velocity distribution imparting unit 61 (guide vanes 612 and damper 618) located inside the combustion air nozzle 54.

[0083] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the combustion air is guided by the guide vane 612, and the flow rate of combustion air passing through the damper 618 is suppressed, thereby making the flow velocity of the combustion air different in the central region and the outer region of the combustion air nozzle 54 when viewed along the central axis Ax of the combustion air nozzle 54. This makes it possible to impart a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0084] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 is affected by the inclination angle θ and the opening degree of the damper 618. Therefore, the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 can be changed by changing the inclination angle θ with the guide vane drive device 614 and changing the opening degree of the damper 618 with the damper drive device 619. This makes it possible to stabilize the ignition position and suppress NOx generation by changing the inclination angle θ, even if the flow rate of the combustion air changes.

[0085] In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the guide surface 612a may be fixed at a predetermined inclination angle θ, and the configuration may be such that the inclination angle θ cannot be changed while the boiler 10 is in operation. In the third ammonia burner 51C shown in Figures 7A, 7B, and 7C, the damper 618 may be fixed at a preset opening, and the damper 618 may be configured so that its opening cannot be changed while the boiler 10 is in operation.

[0086] (Regarding the 4th ammonia burner 51D) The fourth ammonia burner 51D shown in Figures 8A, 8B, and 8C is a diffusion-type burner, similar to the first ammonia burner 51A shown in Figure 3, and includes an ammonia injection nozzle 52 for injecting ammonia, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, a flame holder 56, and a flow velocity distribution unit 60. In the fourth ammonia burner 51D shown in Figures 8A, 8B, and 8C, the flame holder 56 is, for example, a diffuser-type flame holder 56A, similar to the first ammonia burner 51A shown in Figure 3.

[0087] In the fourth ammonia burner 51D shown in Figures 8A, 8B, and 8C, the combustion air nozzle 54 has the same structure as the first ammonia burner 51A shown in Figure 3.

[0088] In the fourth ammonia burner 51D shown in Figures 8A, 8B, and 8C, similar to the first ammonia burner 51A shown in Figure 3, the ammonia injection nozzle 52 is arranged coaxially with the combustion air nozzle 54 and is configured to inject ammonia into the furnace 11 from multiple injection holes 52h. In addition, in the fourth ammonia burner 51D shown in Figures 8A, 8B, and 8C, similar to the first ammonia burner 51A shown in Figure 3, the nozzle tube upstream of the ammonia injection nozzle 52 may or may not extend in the depth direction and the vertical direction of the paper in Figures 8A, 8B, and 8C.

[0089] In the fourth ammonia burner 51D shown in Figures 8A, 8B, and 8C, similar to the first ammonia burner 51A shown in Figure 3, the combustion air supplied to the combustion air nozzle 54 is injected into the furnace 11 through the gap between the opening 54a at the outlet of the combustion air nozzle 54 and the outer edge of the diffuser-type flame holder 56A.

[0090] In the fourth ammonia burner 51D shown in Figures 8B and 8C, the velocity distribution unit 60 is configured to impart a velocity distribution to the combustion air ejected from the combustion air nozzle 54, similar to the first ammonia burner 51A shown in Figure 3. More specifically, in the fourth ammonia burner 51D shown in Figures 8B and 8C, the velocity distribution unit 60 is located inside the combustion air nozzle 54 and is a first velocity distribution unit 61 that imparts a velocity distribution to the combustion air flowing inside the combustion air nozzle 54, similar to the first ammonia burner 51A shown in Figure 3. In the fourth ammonia burner 51D shown in Figures 8B and 8C, the first velocity distribution unit 61 includes a guide vane 612 having a guide surface 612a inclined at a specified inclination angle θ with respect to the direction of extension of the central axis Ax.

[0091] In the fourth ammonia burner 51D shown in Figures 8B and 8C, the guide vane 612 is positioned, for example, near the opening 54a of the combustion air nozzle 54. In the fourth ammonia burner 51D shown in Figures 8B and 8C, the guide vane 612 is positioned so as to overlap in the direction of extension of the central axis Ax with at least a portion of the region near the outlet of the combustion air nozzle 54, where the flow path cross-sectional area decreases as it moves downstream while maintaining a rectangular cross-sectional shape. In addition, in the fourth ammonia burner 51D shown in Figures 8B and 8C, the guide vane 612 may be positioned in a region upstream of this region.

[0092] In the fourth ammonia burner 51D shown in Figures 8B and 8C, the guide vane 612 does not include a movable part for changing the inclination angle θ, and is fixed to, for example, the combustion air nozzle 54 at a preset inclination angle θ.

[0093] In the fourth ammonia burner 51D shown in Figures 8B and 8C, the guide vanes 612 may be arranged, for example, along each side of the combustion air nozzle 54 having a rectangular cross-section, with at least one guide vane per side. For example, in the example shown in Figures 8B and 8C, one guide vane 612 is arranged on each of the two sides of the combustion air nozzle 54 having a rectangular cross-section that are spaced apart in the vertical direction shown, and one guide vane 612 is arranged on each of the two sides (not shown) that are spaced apart in the depth direction shown. Furthermore, as shown in Figures 7A, 7B, and 7C, the guide vanes 612 may be arranged in multiple stages along each side of the combustion air nozzle 54 having a rectangular cross-section, in a direction perpendicular to the central axis Ax for each side. Also, the guide vanes 612 may be arranged on each of two sides that are spaced apart in the vertical direction shown, but not on each of the two sides that are spaced apart in the depth direction shown (not shown). Alternatively, the guide vanes 612 may not be arranged on each of the two sides that are spaced apart in the vertical direction shown, but may be arranged on each of the two sides that are spaced apart in the depth direction shown (not shown).

[0094] In the fourth ammonia burner 51D shown in Figures 8B and 8C, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 changes depending on the inclination angle θ of the guide surface 612a. In Figures 8A, 8B, and 8C, the arrows shown downstream of the outlet of the combustion air nozzle 54 represent the trend of the velocity distribution of the combustion air ejected from the combustion air nozzle 54, that is, the relationship between the distance from the central axis Ax and the velocity of the combustion air.

[0095] (If guide vane 612 is not installed) Figure 8A shows the case where the guide vane 612 is not present in the fourth ammonia burner 51D. In the case shown in Figure 8A, since the guide vane 612 is not present, the combustion air flowing through the combustion air nozzle 54 is neither guided towards the central axis Ax nor towards the central axis Ax. Therefore, in the case shown in Figure 8A, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is such that the velocity is relatively equal regardless of the position of the central axis Ax.

[0096] (When the guide surface 612a approaches the central axis Ax as it moves downstream) Figure 8B shows the case where the angle θ is set so that the guide surface 612a approaches the central axis Ax as it moves downstream. In the case shown in Figure 8B, the combustion air is guided by the guide surface 612a to approach the central axis Ax. Therefore, in the case shown in Figure 8B, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is such that the velocity is higher at positions closer to the central axis Ax than at positions further from the central axis Ax.

[0097] (When the guide surface 612a moves away from the central axis Ax as it moves downstream) Figure 8C shows the case where the angle θ is set such that the guide surface 612a moves away from the central axis Ax as it moves downstream. In the case shown in Figure 8C, the combustion air is guided away from the central axis Ax by the guide surface 612a. Therefore, in the case shown in Figure 8C, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is such that the velocity is higher at positions farther from the central axis Ax than at positions closer to the central axis Ax.

[0098] In the fourth ammonia burner 51D shown in Figures 8A, 8B, and 8C, the ignition position can be stabilized and NOx generation suppressed by providing a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0099] In the fourth ammonia burner 51D shown in Figures 8B and 8C, a velocity distribution can be relatively easily imparted to the combustion air ejected from the combustion air nozzle 54 by the first velocity distribution imparting unit 61 (guide vane 612) located inside the combustion air nozzle 54.

[0100] In the fourth ammonia burner 51D shown in Figures 8B and 8C, the combustion air is guided by the guide vane 612, which makes it possible to make the flow velocity of the combustion air different in the central region and the outer region of the combustion air nozzle 54 when viewed along the central axis Ax of the combustion air nozzle 54. This makes it possible to impart a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0101] The fourth ammonia burner 51D shown in Figures 8B and 8C does not include a movable part for changing the inclination angle θ, and therefore has a simple configuration.

[0102] (Regarding the 5th ammonia burner 51E) The fifth ammonia burner 51E shown in Figure 9 is a diffusion-type burner, similar to the first ammonia burner 51A shown in Figure 3, and includes an ammonia injection nozzle 52 for injecting ammonia, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, a flame holder 56, and a flow velocity distribution unit 60. In the fifth ammonia burner 51E shown in Figure 9, similar to the first ammonia burner 51A shown in Figure 3, the flame holder 56 is, for example, a diffuser-type flame holder 56A.

[0103] In the fifth ammonia burner 51E shown in Figure 9, the combustion air nozzle 54 is a duct with a rectangular cross-section, similar to the first ammonia burner 51A shown in Figure 3, and is formed such that the flow path cross-sectional area decreases as it moves downstream while maintaining the rectangular cross-sectional shape near the downstream end.

[0104] In the fifth ammonia burner 51E shown in Figure 9, similar to the first ammonia burner 51A shown in Figure 3, the ammonia injection nozzle 52 is arranged coaxially with the combustion air nozzle 54 and is configured to inject ammonia into the furnace 11 from multiple injection holes 52h. In addition, in the fifth ammonia burner 51E shown in Figure 9, similar to the first ammonia burner 51A shown in Figure 3, the nozzle tube on the upstream side of the ammonia injection nozzle 52 may or may not extend in the depth direction of the paper in Figure 9 or in the vertical direction of the paper.

[0105] In the fifth ammonia burner 51E shown in Figure 9, as will be described later, the combustion air supplied to the combustion air nozzle 54 is injected into the furnace 11 from between the opening 54a of the outlet of the combustion air nozzle 54 and the outer edge of the diffuser-type flame holder 56A.

[0106] In the fifth ammonia burner 51E shown in Figure 9, the velocity distribution unit 60 is configured to impart a velocity distribution to the combustion air ejected from the combustion air nozzle 54. Specifically, in the fifth ammonia burner 51E shown in Figure 9, the velocity distribution unit 60 is the second velocity distribution unit 62. The second velocity distribution unit 62 has a partition wall 625 that separates a first flow path 541 through which combustion air can flow inside the combustion air nozzle 54, and a second flow path 542 through which combustion air can flow outside the first flow path 541. In other words, in the fifth ammonia burner 51E shown in Figure 9, the combustion air nozzle 54 has a double structure, consisting of a first flow path 541 and a second flow path 542 formed to surround the outside of the first flow path 541, when viewed along the central axis Ax. In Figure 9, the first channel 541 and the second channel 542 are formed to surround the ammonia injection nozzle 52 radially outward in the circumferential direction, but they may also be formed in layers in the vertical direction as shown, or in layers in the depth direction as shown.

[0107] In the fifth ammonia burner 51E shown in Figure 9, the second velocity distribution unit 62 has a first flow rate adjustment device 621 that adjusts the flow rate of combustion air supplied to the first flow path 541. The second velocity distribution unit 62 also has a second flow rate adjustment device 622 that adjusts the flow rate of combustion air supplied to the second flow path 542. The first flow rate control device 621 is, for example, a flow rate control means (e.g., a damper) provided at the connection between the air duct 24 and the first flow path 541. However, if it is not necessary to change the flow rate of combustion air supplied to the first flow path 541 during the operation of the boiler 10, the first flow rate control device 621 may be, for example, a flow rate limiting means (e.g., an orifice) provided at the connection between the air duct 24 and the first flow path 541. Similarly, the second flow rate control device 622 is, for example, a flow rate control means (e.g., a damper) provided at the connection between the air duct 24 and the second flow path 542. However, if it is not necessary to change the flow rate of combustion air supplied to the second flow path 542 during the operation of the boiler 10, the second flow rate control device 622 may be, for example, a flow rate limiting means (e.g., an orifice) provided at the connection between the air duct 24 and the second flow path 542.

[0108] In the following explanation, the flow rate of combustion air flowing through the first flow path 541 will also be referred to as the first flow rate Q1, and the flow rate of combustion air flowing through the second flow path 542 will also be referred to as the second flow rate Q2. In the fifth ammonia burner 51E shown in Figure 9, the flow rate of combustion air supplied to the first flow path 541 (first flow rate Q1) is adjusted by the first flow rate control device 621, and the flow rate of combustion air supplied to the second flow path 542 (second flow rate Q2) is adjusted by the second flow rate control device 622, thereby relatively easily imparting a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54. In other words, in the fifth ammonia burner 51E shown in Figure 9, the flow velocity distribution of combustion air ejected from the opening 54a at the downstream end of the combustion air nozzle 54 can be changed by appropriately adjusting the first flow rate Q1, the second flow rate Q2, and the ratio of the first flow rate Q1 to the second flow rate Q2.

[0109] In other words, in the fifth ammonia burner 51E shown in Figure 9, increasing the number of combustion air passages in the combustion air nozzle 54 makes it easier to change the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54. Furthermore, by adjusting the flow rate of the combustion air flowing through each passage (first passage 541 and second passage 542), it is possible to make fine adjustments to the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54. This makes it easier to control the ignition point and the amount of NOx generated.

[0110] In the fifth ammonia burner 51E shown in Figure 9, for example, when the same amount of combustion air is injected equally into the furnace 11 from the first flow path 541 and the second flow path 542, compared to when it is injected into the furnace 11 from either the first flow path 541 or the second flow path 542, the flow velocity of the fuel air injected into the furnace 11 is faster in the latter case than in the former case. Therefore, the mixing position of the combustion air and ammonia is further away from the fifth ammonia burner 51E in the latter case than in the former case.

[0111] Furthermore, in the fifth ammonia burner 51E shown in Figure 9, for example, when the same amount of combustion air is injected into the furnace 11 only from the first flow path 541 compared to when it is injected only from the second flow path 542, the latter results in less entrainment of combustion air by the flame holder 56A (generation of circulating flow) than the former. Therefore, it is thought that the velocity component in the straight direction of the combustion air injected into the furnace 11 is larger in the latter case than in the former case, and the mixing position of the combustion air and ammonia is further away from the fifth ammonia burner 51E in the latter case than in the former case.

[0112] In the fifth ammonia burner 51E shown in Figure 9, the ignition position can be stabilized and NOx generation suppressed by imparting a velocity distribution to the combustion air ejected from the combustion air nozzle 54. Specifically, for example, as follows: Ra1 is the ratio of the first flow rate Q1 to the second flow rate Q2 when the velocity distribution of the combustion air ejected from the combustion air nozzle 54 is such that the velocity is relatively equal regardless of the position on the central axis Ax. For example, if the ratio of the first flow rate Q1 is increased to this ratio Ra1, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 will be such that the velocity is faster at positions closer to the central axis Ax than at positions farther from the central axis Ax. When such a flow velocity distribution occurs, the flow velocity of the combustion air around the flame holder 56 increases, which is expected to form a sufficient flame-holding region (circulation region) and improve ignition performance. Furthermore, if, for example, the ratio of the second flow rate Q2 is increased compared to the above ratio Ra1, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 will be such that the velocity is higher at positions farther from the central axis Ax than at positions closer to the central axis Ax. In this type of flow velocity distribution, combustion air is more easily supplied to a location relatively far from the ignition point, making it less likely for regions with a relatively high air-to-air ratio to form locally, and thus it is expected that the amount of NOx generated will be suppressed.

[0113] (Regarding the 6th ammonia burner 51F) The sixth ammonia burner 51F shown in Figure 10 has the same structure as the fifth ammonia burner 51E shown in Figure 9, except for the structure of the flame holder 56. In other words, the sixth ammonia burner 51F shown in Figure 10 is a diffusion-type burner, similar to the first ammonia burner 51A shown in Figure 3, and is equipped with an ammonia injection nozzle 52 for injecting ammonia, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, a flame holder 56, and a flow velocity distribution unit 60. In the sixth ammonia burner 51F shown in Figure 10, unlike the first ammonia burner 51A shown in Figure 3, the flame holder 56 is, for example, a swirling-type flame holder 56B.

[0114] In the sixth ammonia burner 51F shown in Figure 10, the combustion air nozzle 54 is a duct with a rectangular cross-section, similar to the first ammonia burner 51A shown in Figure 3, and is formed such that the flow path cross-sectional area decreases as it moves downstream while maintaining the rectangular cross-sectional shape near the downstream end.

[0115] In the sixth ammonia burner 51F shown in Figure 10, similar to the first ammonia burner 51A shown in Figure 3, the ammonia injection nozzle 52 is arranged coaxially with the combustion air nozzle 54 and is configured to inject ammonia into the furnace 11 from multiple injection holes 52h. In addition, in the sixth ammonia burner 51F shown in Figure 10, similar to the first ammonia burner 51A shown in Figure 3, the nozzle tube on the upstream side of the ammonia injection nozzle 52 may or may not extend in the depth direction of the paper and the vertical direction of the paper in Figure 9.

[0116] In the sixth ammonia burner 51F shown in Figure 10, the combustion air supplied to the combustion air nozzle 54 is injected between the opening 54a of the outlet of the combustion air nozzle 54 and the outer edge of the swirling flame holder 56B, and from the swirling flame holder 56B into the furnace 11.

[0117] In the sixth ammonia burner 51F shown in Figure 10, the velocity distribution unit 60 is configured to impart a velocity distribution to the combustion air ejected from the combustion air nozzle 54. More specifically, in the sixth ammonia burner 51F shown in Figure 10, the velocity distribution unit 60 is a second velocity distribution unit 62. The second velocity distribution unit 62 has a partition wall 625 that separates a first flow path 541 through which combustion air can flow inside the combustion air nozzle 54, and a second flow path 542 through which combustion air can flow outside the first flow path 541. That is, in the sixth ammonia burner 51F shown in Figure 10, the combustion air nozzle 54 has a double structure, consisting of a first flow path 541 and a second flow path 542 formed to surround the outside of the first flow path 541, when viewed along the central axis Ax. In Figure 10, the first channel 541 and the second channel 542 are formed to surround the ammonia injection nozzle 52 radially outward in the circumferential direction, but they may also be formed in layers in the vertical direction as shown, or in layers in the depth direction as shown.

[0118] In the sixth ammonia burner 51F shown in Figure 10, the second velocity distribution unit 62 has a first flow rate adjustment device 621 that adjusts the flow rate of combustion air supplied to the first flow path 541. The second velocity distribution unit 62 also has a second flow rate adjustment device 622 that adjusts the flow rate of combustion air supplied to the second flow path 542. In the sixth ammonia burner 51F shown in Figure 10, the first flow rate regulator 621 and the second flow rate regulator 622 are the same as those in the fifth ammonia burner 51E shown in Figure 9.

[0119] In the sixth ammonia burner 51F shown in Figure 10, the flow rate of combustion air supplied to the first flow path 541 (first flow rate Q1) is adjusted by the first flow rate control device 621, and the flow rate of combustion air supplied to the second flow path 542 (second flow rate Q2) is adjusted by the second flow rate control device 622, thereby relatively easily imparting a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54. In other words, in the sixth ammonia burner 51F shown in Figure 10, the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 can be changed by appropriately adjusting the first flow rate Q1, the second flow rate Q2, and the ratio of the first flow rate Q1 to the second flow rate Q2.

[0120] In the sixth ammonia burner 51F shown in Figure 10, increasing the number of combustion air passages in the combustion air nozzle 54 makes it easier to change the velocity distribution of the combustion air ejected from the combustion air nozzle 54. Furthermore, by adjusting the flow rate of the combustion air flowing through each passage (first passage 541 and second passage 542), it is possible to make fine adjustments to the velocity distribution of the combustion air ejected from the combustion air nozzle 54. In addition, in the sixth ammonia burner 51F shown in Figure 10, by adjusting the flow rate of the combustion air flowing through each passage (first passage 541 and second passage 542), it is possible to make fine adjustments to the swirling force of the combustion air generated by the swirling flame holder 56B. This makes it easier to control the ignition point and the amount of NOx emissions.

[0121] In the sixth ammonia burner 51F shown in Figure 10, for example, when the same amount of combustion air is injected equally into the furnace 11 from the first flow path 541 and the second flow path 542, compared to when it is injected into the furnace 11 from either the first flow path 541 or the second flow path 542, the flow velocity of the fuel air injected into the furnace 11 is faster in the latter case than in the former case. Therefore, the mixing position of the combustion air and ammonia is further away from the sixth ammonia burner 51F in the latter case than in the former case. By moving the mixing position of combustion air and ammonia away from the sixth ammonia burner 51F in this way, it becomes less likely for regions with a relatively high air-to-ammonia ratio to form locally, and thus it is expected that the amount of NOx generated will be suppressed.

[0122] Furthermore, in the sixth ammonia burner 51F shown in Figure 10, for example, when the same amount of combustion air is injected into the furnace 11 only from the first flow path 541 compared to when it is injected only from the second flow path 542, the latter results in less entrainment of the combustion air by the flame holder 56B (generation of swirling flow) than the former. Therefore, the straight-line velocity component of the combustion air injected into the furnace 11 is larger in the latter case than in the former case, and the mixing position of the combustion air and ammonia is further away from the sixth ammonia burner 51F in the latter case than in the former case. By moving the mixing position of combustion air and ammonia away from the sixth ammonia burner 51F in this way, it becomes less likely for regions with a relatively high air-to-ammonia ratio to form locally, and thus it is expected that the amount of NOx generated will be suppressed.

[0123] (Regarding the 7th ammonia burner 51G) The seventh ammonia burner 51G shown in Figure 11 is not a diffusion-type burner like the fifth ammonia burner 51E shown in Figure 9 and the sixth ammonia burner 51F shown in Figure 10, but rather a partially premixed spud (spatula-shaped) type burner. The seventh ammonia burner 51G shown in Figure 11 includes an ammonia injection nozzle 52 for injecting ammonia, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, and a flow velocity distribution unit 60. In the seventh ammonia burner 51G shown in Figure 11, the ammonia injection nozzle 52 is a partially premixed spud nozzle 52A.

[0124] In the seventh ammonia burner 51G shown in Figure 11, the combustion air nozzle 54 is a duct with a rectangular cross-section, similar to the first ammonia burner 51A shown in Figure 3, and is formed such that the flow path cross-sectional area decreases as it moves downstream while maintaining the rectangular cross-sectional shape near the downstream end.

[0125] In the seventh ammonia burner 51G shown in Figure 11, the spud nozzle 52A has multiple injection holes 52h for injecting ammonia. In the spud nozzle 52A, the multiple injection holes 52h are arranged, for example, spaced apart in one direction. In the seventh ammonia burner 51G shown in Figure 11, a cylindrical portion 58 is positioned downstream of the spud nozzle 52A, surrounding the spud nozzle 52A from the outside at a distance.

[0126] In the seventh ammonia burner 51G shown in Figure 11, as will be described later, the combustion air supplied to the combustion air nozzle 54 is injected into the furnace 11 from the opening 54a at the outlet of the combustion air nozzle 54.

[0127] In the seventh ammonia burner 51G shown in Figure 11, ammonia is injected into the cylindrical section 58 from multiple injection holes 52h of the spud nozzle 52A, and is premixed with combustion air that flows in through the gap between the spud nozzle 52A and the cylindrical section 58 before being injected into the furnace 11. In the seventh ammonia burner 51G shown in Figure 11, the combustion air flowing into the cylindrical section 58 through the gap between the spud nozzle 52A and the cylindrical section 58 is part of the combustion air flowing through the first flow path 541, which will be described later. In other words, partial premixed combustion is performed in the seventh ammonia burner 51G.

[0128] In the seventh ammonia burner 51G shown in Figure 11, the velocity distribution unit 60 is configured to impart a velocity distribution to the combustion air ejected from the combustion air nozzle 54. More specifically, in the seventh ammonia burner 51G shown in Figure 11, the velocity distribution unit 60 is a second velocity distribution unit 62. The second velocity distribution unit 62 has a partition wall 625 that separates a first flow path 541 through which combustion air can flow inside the combustion air nozzle 54, and a second flow path 542 through which combustion air can flow outside the first flow path 541. That is, in the seventh ammonia burner 51G shown in Figure 11, the combustion air nozzle 54 has a double structure, when viewed along the central axis Ax, consisting of a first flow path 541 and a second flow path 542 formed to surround the outside of the first flow path 541. In Figure 11, the first channel 541 and the second channel 542 are formed to surround the ammonia injection nozzle 52 radially outward and in the circumferential direction, but they may also be formed in layers in the vertical direction as shown, or in layers in the depth direction as shown.

[0129] In the seventh ammonia burner 51G shown in Figure 11, the second velocity distribution unit 62 has a first flow rate adjustment device 621 that adjusts the flow rate of combustion air supplied to the first flow path 541. The second velocity distribution unit 62 also has a second flow rate adjustment device 622 that adjusts the flow rate of combustion air supplied to the second flow path 542. In the seventh ammonia burner 51G shown in Figure 11, the first flow rate regulator 621 and the second flow rate regulator 622 are the same as those in the fifth ammonia burner 51E shown in Figure 9.

[0130] In the seventh ammonia burner 51G shown in Figure 11, the flow rate of combustion air supplied to the first flow path 541 (first flow rate Q1) is adjusted by the first flow rate control device 621, and the flow rate of combustion air supplied to the second flow path 542 (second flow rate Q2) is adjusted by the second flow rate control device 622, thereby relatively easily imparting a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54. In other words, in the seventh ammonia burner 51G shown in Figure 11, the flow velocity distribution of combustion air ejected from the combustion air nozzle 54 can be changed by appropriately adjusting the first flow rate Q1, the second flow rate Q2, and the ratio of the first flow rate Q1 to the second flow rate Q2.

[0131] In the seventh ammonia burner 51G shown in Figure 11, increasing the number of combustion air passages in the combustion air nozzle 54 makes it easier to change the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54. Furthermore, by adjusting the flow rate of the combustion air flowing through each passage (first passage 541 and second passage 542), it is possible to make fine adjustments to the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54.

[0132] In the seventh ammonia burner 51G shown in Figure 11, the flow rate of combustion air flowing through the first channel 541 can be adjusted, which is useful for adjusting the flow rate of combustion air that is partially premixed with ammonia inside the cylindrical section 58.

[0133] (Regarding the 8th ammonia burner 51H) The eighth ammonia burner 51H shown in Figure 12 corresponds to an embodiment in which the number of combustion air passages in the combustion air nozzle 54 of the fifth ammonia burner 51E shown in Figure 9 is further increased. In other words, the eighth ammonia burner 51H shown in Figure 12 is a diffusion-type burner, similar to the first ammonia burner 51A shown in Figure 3, and is equipped with an ammonia injection nozzle 52 for injecting ammonia, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, a flame holder 56, and a flow velocity distribution unit 60. In the eighth ammonia burner 51H shown in Figure 12, similar to the first ammonia burner 51A shown in Figure 3, the flame holder 56 is, for example, a diffuser-type flame holder 56A.

[0134] In the eighth ammonia burner 51H shown in Figure 12, the combustion air nozzle 54 is a duct with a rectangular cross-section, similar to the first ammonia burner 51A shown in Figure 3, and is formed such that the flow path cross-sectional area decreases as it moves downstream while maintaining the rectangular cross-sectional shape near the downstream end.

[0135] In the eighth ammonia burner 51H shown in Figure 12, similar to the first ammonia burner 51A shown in Figure 3, the ammonia injection nozzle 52 is arranged coaxially with the combustion air nozzle 54 and is configured to inject ammonia into the furnace 11 from multiple injection holes 52h. In addition, in the eighth ammonia burner 51H shown in Figure 12, similar to the first ammonia burner 51A shown in Figure 3, the nozzle tube upstream of the ammonia injection nozzle 52 may or may not extend in the depth direction or the vertical direction of the paper in Figure 12.

[0136] In the eighth ammonia burner 51H shown in Figure 12, as will be described later, the combustion air supplied to the combustion air nozzle 54 is injected into the furnace 11 from between the opening 54a of the outlet of the combustion air nozzle 54 and the outer edge of the diffuser-type flame holder 56A.

[0137] In the eighth ammonia burner 51H shown in Figure 12, the velocity distribution unit 60 is configured to impart a velocity distribution to the combustion air ejected from the combustion air nozzle 54. More specifically, in the eighth ammonia burner 51H shown in Figure 12, the velocity distribution unit 60 is a second velocity distribution unit 62. The second velocity distribution unit 62 has a partition wall 625 that separates a first flow path 541 through which combustion air can flow inside the combustion air nozzle 54 from a second flow path 542 through which combustion air can flow outside the first flow path 541, and a partition wall 626 that separates a third flow path 543 through which combustion air can flow outside the second flow path 542. In other words, in the eighth ammonia burner 51H shown in Figure 12, the combustion air nozzle 54 has a triple structure when viewed along the central axis Ax, consisting of a first flow path 541, a second flow path 542 formed to surround the outside of the first flow path 541, and a third flow path 543 formed to surround the outside of the second flow path 542. In Figure 12, the first flow path 541, the second flow path 542, and the third flow path 543 are formed to surround the ammonia injection nozzle 52 radially outward in the circumferential direction, but they may also be formed in layers in the vertical direction as shown, or in layers in the depth direction as shown.

[0138] In the eighth ammonia burner 51H shown in Figure 12, the second velocity distribution unit 62 has a first flow rate adjustment device 621 that adjusts the flow rate of combustion air supplied to the first flow path 541. The second velocity distribution unit 62 has a second flow rate adjustment device 622 that adjusts the flow rate of combustion air supplied to the second flow path 542. The second velocity distribution unit 62 has a third flow rate adjustment device 623 that adjusts the flow rate of combustion air supplied to the third flow path 543. In the eighth ammonia burner 51H shown in Figure 12, the first flow rate regulator 621 and the second flow rate regulator 622 are the same as those in the fifth ammonia burner 51E shown in Figure 9. In the eighth ammonia burner 51H shown in Figure 12, the third flow rate control device 623 is, for example, a flow rate regulator (e.g., a damper) provided at the connection between the air duct 24 and the third flow path 543. However, if it is not necessary to change the flow rate of combustion air supplied to the third flow path 543 during the operation of the boiler 10, the third flow rate control device 623 may be, for example, a flow rate limiting means (e.g., an orifice) provided at the connection between the air duct 24 and the third flow path 543.

[0139] In the following explanation, the flow rate of combustion air flowing through the third flow path 543 will also be referred to as the third flow rate Q3. In the eighth ammonia burner 51H shown in Figure 12, the first flow rate Q1 is adjusted by the first flow rate control device 621, the second flow rate Q2 is adjusted by the second flow rate control device 622, and the third flow rate Q3 is adjusted by the third flow rate control device 623, thereby relatively easily imparting a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54. In other words, in the eighth ammonia burner 51H shown in Figure 12, the flow velocity distribution of combustion air ejected from the opening 54a at the downstream end of the combustion air nozzle 54 can be changed by appropriately adjusting the first flow rate Q1, the second flow rate Q2, the third flow rate Q3, and the ratio of the first flow rate Q1 to the second flow rate Q2 to the third flow rate Q3.

[0140] In other words, in the eighth ammonia burner 51H shown in Figure 12, the number of combustion air passages in the combustion air nozzle 54 has been further increased, making it easier to change the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54. Furthermore, by adjusting the flow rate of the combustion air flowing through each passage (first passage 541, second passage 542, and third passage 543), it is possible to make fine adjustments to the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54. This makes it easier to control the ignition point and the amount of NOx generated.

[0141] In the eighth ammonia burner 51H shown in Figure 12, the combustion air nozzle 54 has a multi-layered structure of four or more layers, by further providing a flow path that surrounds the outside of the third flow path 543 when viewed along the central axis Ax, and the flow rate of combustion air flowing through each flow path may be adjustable.

[0142] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate. For example, the first ammonia burner 51A, the second ammonia burner 51B, the third ammonia burner 51C, the fourth ammonia burner 51D, the fifth ammonia burner 51E, and the eighth ammonia burner 51H described above are diffusion-type burners equipped with a diffuser-type flame holder 56A, but they may also be diffusion-type burners equipped with a swirler-type flame holder 56B, such as the sixth ammonia burner 51F, or partially premixed spud-type burners, such as the seventh ammonia burner 51G. In other words, in some of the embodiments described above, the ammonia combustion burner 51 may be a partially premixed spud type, a diffusion type swara type with a different flame holder structure, or a diffuser type burner. This makes it relatively easy to impart a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54 in each of the above-mentioned burner types of ammonia combustion burners 51.

[0143] For example, in the sixth ammonia burner 51F shown in Figure 10 and the seventh ammonia burner 51G shown in Figure 11, the combustion air nozzle 54 has a double structure consisting of a first flow path 541 and a second flow path 542 formed to surround the outside of the first flow path 541 when viewed along the central axis Ax. However, in the sixth ammonia burner 51F shown in Figure 10 and the seventh ammonia burner 51G shown in Figure 11, the combustion air nozzle 54 may have a triple or more multi-layer structure, similar to the eighth ammonia burner 51H shown in Figure 12, and may be configured to allow adjustment of the flow rate of combustion air flowing through each flow path.

[0144] The contents described in each of the above embodiments can be understood, for example, as follows: (1) An ammonia combustion burner 51 according to at least one embodiment of the present disclosure is an ammonia combustion burner 51 for burning ammonia fuel in a boiler 10. The ammonia combustion burner 51 according to at least one embodiment of the present disclosure comprises an ammonia injection nozzle 52 for injecting ammonia fuel, a combustion air nozzle 54 for ejecting combustion air from outside the ammonia injection nozzle 52, and a velocity distribution unit 60 for imparting a velocity distribution to the combustion air ejected from the combustion air nozzle.

[0145] The ignition point and NOx generation are affected by the velocity distribution of the combustion air ejected from the combustion air nozzle 54. Therefore, according to the configuration of (1) above, by imparting a velocity distribution to the combustion air ejected from the combustion air nozzle 54, it is possible to stabilize the ignition point and suppress the generation of NOx.

[0146] (2) In some embodiments, in the configuration of (1) above, the velocity distribution unit 60 may be located inside the combustion air nozzle 54 and may include a first velocity distribution unit 61 that imparts a velocity distribution to the combustion air flowing inside the combustion air nozzle 54.

[0147] According to the configuration described in (2) above, the first velocity distribution unit 61, which is located inside the combustion air nozzle 54, can relatively easily impart a velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0148] (3) In some embodiments, in the configuration of (2) above, the first flow velocity distribution unit 61 may include a flow path restricting member 611 that extends outward from the center of the combustion air nozzle 54 when viewed along the central axis Ax of the combustion air nozzle 54. The flow path restricting member 611 is preferably formed between itself and the inner circumferential surface 54i of the combustion air nozzle 54, allowing combustion air to flow through it.

[0149] According to the configuration described in (3) above, by guiding the combustion air into the gap, the flow velocity of the combustion air can be made different in the central region and the outer region of the combustion air nozzle 54 when viewed along the central axis Ax of the combustion air nozzle 54. This makes it possible to impart a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0150] (4) In some embodiments, in the configuration of (3) above, the flow velocity distribution unit 60 may include a moving device 613 configured to move the flow path limiting member 611 along the central axis Ax.

[0151] The flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 is affected by the position of the flow path limiting member 611 in the direction of extension of the central axis Ax. Therefore, according to the configuration of (4) above, the flow velocity distribution of the combustion air ejected from the combustion air nozzle 54 can be changed by changing the position of the flow path limiting member 611 in the direction of extension of the central axis Ax. As a result, even if the flow rate of the combustion air changes, for example, the ignition position can be stabilized and NOx generation can be suppressed by changing the position of the flow path limiting member 611 in the direction of extension of the central axis Ax.

[0152] (5) In some embodiments, in the configuration of (2) above, the first velocity distribution unit 61 may include a guide vane 612 having a guide surface 612a inclined at a predetermined inclination angle θ with respect to the direction of extension of the central axis Ax.

[0153] According to the configuration described in (5) above, by guiding the combustion air with the guide vane 612, the flow velocity of the combustion air can be made different in the central region and the outer region of the combustion air nozzle 54 when viewed along the central axis Ax of the combustion air nozzle 54. This makes it possible to impart a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0154] (6) In some embodiments, the velocity distribution unit 60 in the configuration of (5) above may include a guide vane drive device 614 configured to change the inclination angle θ.

[0155] The velocity distribution of the combustion air ejected from the combustion air nozzle 54 is affected by the inclination angle θ. Therefore, according to the configuration of (6) above, the velocity distribution of the combustion air ejected from the combustion air nozzle 54 can be changed by changing the inclination angle θ. As a result, even if the flow rate of the combustion air changes, for example, the ignition position can be stabilized and NOx generation can be suppressed by changing the inclination angle θ.

[0156] (7) In some embodiments, in the configuration of (5) or (6) above, the first velocity distribution unit 61 may include a damper 618 located inside the combustion air nozzle 54 in a region inside the guide vane 612, which adjusts the flow rate of combustion air passing through that region.

[0157] According to the configuration described in (7) above, by guiding the combustion air with the guide vane 612 and suppressing the flow rate of the combustion air passing through the damper 618, the flow velocity of the combustion air can be made different in the central region and the outer region of the combustion air nozzle 54 when viewed along the central axis Ax of the combustion air nozzle 54. This makes it possible to impart a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0158] (8) In some embodiments, the velocity distribution unit 60 in the configuration of (1) above may include a second velocity distribution unit 62. The second velocity distribution unit 62 may have a partition wall 625 that separates a first flow path 541 through which combustion air can flow inside the combustion air nozzle 54 from a second flow path 542 through which combustion air can flow outside the first flow path 541. The second velocity distribution unit 62 may have a first flow rate adjustment device 621 that adjusts the flow rate of combustion air supplied to the first flow path 541. The second velocity distribution unit 62 may have a second flow rate adjustment device 622 that adjusts the flow rate of combustion air supplied to the second flow path 542.

[0159] According to the configuration described in (8) above, the flow rate of combustion air supplied to the first flow path 541 (first flow rate Q1) is adjusted by the first flow rate adjustment device 621, and the flow rate of combustion air supplied to the second flow path 542 (second flow rate Q2) is adjusted by the second flow rate adjustment device 622, thereby relatively easily imparting a flow velocity distribution to the combustion air ejected from the combustion air nozzle 54.

[0160] (9) In some embodiments, in the configuration of (8) above, the ammonia combustion burner 51 may be a spud type, a swara type, or a diffuser type burner.

[0161] According to the configuration described in (9) above, in each of the above burner types of ammonia combustion burners 51, a flow velocity distribution can be relatively easily imparted to the combustion air ejected from the combustion air nozzle 54.

[0162] (10) In some embodiments, in any of the configurations (1) to (9) above, the ammonia combustion burner may be an ammonia-only burner.

[0163] According to the configuration described in (10) above, the ignition position can be stabilized and NOx generation can be suppressed in an ammonia-only burner.

[0164] (11) A boiler 10 according to at least one embodiment of the present disclosure comprises a furnace 11 including a furnace wall 101 and an ammonia combustion burner 51 provided on the furnace wall 101 having any of the configurations (1) to (10) above.

[0165] According to the configuration described in (11) above, the ignition position of the ammonia combustion burner 51 of the boiler 10 can be stabilized and the generation of NOx can be suppressed.

[0166] (12) A boiler 10 according to at least one embodiment of the present disclosure comprises a furnace 11 including a furnace wall 101, an ammonia combustion burner 51 provided on the furnace wall 101 having any of the configurations of (1) to (10) above, and a non-fuel burner (burner 21) provided on the furnace wall 101 at a different position from the ammonia combustion burner 51 for burning fuels other than ammonia.

[0167] According to the configuration described in (12) above, the ignition position can be stabilized and NOx generation can be suppressed in the ammonia combustion burner 51 of the boiler 10.

[0168] (13) In some embodiments, in the configuration of (12) above, the boiler 10 may be a swirling combustion boiler in which swirling combustion is performed in the furnace 11 by an ammonia combustion burner 51 and an other fuel burner (burner 21).

[0169] According to the configuration described in (13) above, the ignition position can be stabilized and NOx generation can be suppressed in the ammonia combustion burner 51 of the swirling combustion boiler. [Explanation of Symbols]

[0170] 1. Boiler System 10 Boilers 11 Furnace 20, 50 Combustion device 21 Burner 51. Ammonia burner (ammonia combustion burner) 51A First Ammonia Burner 51B Second Ammonia Burner 51C Third Ammonia Burner 51D No. 4 Ammonia Burner 51E Fifth Ammonia Burner 51F No. 6 Ammonia Burner 51G No. 7 Ammonia Burner 51H No. 8 Ammonia Burner 52 Ammonia spray nozzle 52A Spud Nozzle 54 Combustion air nozzle 54i Inner surface 56, 56A, 56B flame holder 60 Flow velocity distribution unit 61 First flow velocity distribution unit 62 Second velocity distribution unit 101 Furnace wall 541 First channel 542 Second channel 611 Flow path limiting member 612 Guide vanes 612a Guide surface 613 Mobile device 614 Guide vane drive mechanism 618 Damper 619 Damper drive unit 621 1st flow control device 622 2nd flow control device 625 Partition wall

Claims

1. An ammonia combustion burner for exclusively burning ammonia fuel in a boiler, an ammonia injection nozzle for injecting the ammonia fuel, A combustion air nozzle for ejecting combustion air from the outside of the ammonia injection nozzle, A velocity distribution unit that imparts a velocity distribution to the combustion air ejected from the combustion air nozzle, Equipped with, The velocity distribution unit is located inside the combustion air nozzle and includes a first velocity distribution unit that imparts a velocity distribution to the combustion air flowing inside the combustion air nozzle. The first velocity distribution unit includes a flow path limiting member that extends outward from the center of the combustion air nozzle when viewed along the central axis of the combustion air nozzle, The flow path limiting member is positioned inside the combustion air nozzle and forms a gap inside the combustion air nozzle between itself and the inner circumferential surface of the combustion air nozzle, allowing the combustion air to flow through. Ammonia combustion burner.

2. The flow velocity distribution unit is a moving device configured to move the flow path limiting member along the central axis. including The ammonia combustion burner according to claim 1.

3. An ammonia combustion burner for exclusively burning ammonia fuel in a boiler, an ammonia injection nozzle for injecting the ammonia fuel, A combustion air nozzle for ejecting combustion air from the outside of the ammonia injection nozzle, A velocity distribution unit that imparts a velocity distribution to the combustion air ejected from the combustion air nozzle, Equipped with, The velocity distribution unit is located inside the combustion air nozzle and includes a first velocity distribution unit that imparts a velocity distribution to the combustion air flowing inside the combustion air nozzle. The first velocity distribution unit has a guide vane having a guide surface inclined at a specified inclination angle with respect to the direction of extension of the central axis so as to be oriented in a direction different from the direction of extension of a virtual plane perpendicular to the direction of extension of the central axis of the combustion air nozzle. Includes, The flow velocity distribution unit includes a guide vane drive device configured to change the inclination angle. including Ammonia combustion burner.

4. The first velocity distribution unit is located inside the combustion air nozzle in a region inside the guide vane and includes a damper that adjusts the flow rate of the combustion air passing through that region. including The ammonia combustion burner according to claim 3.

5. A furnace including the furnace wall, An ammonia combustion burner according to any one of claims 1 to 4 is provided in the furnace wall, Equipped with Boiler.

6. A furnace including the furnace wall, An ammonia combustion burner according to any one of claims 1 to 4 is provided in the furnace wall, A non-fuel burner is provided in a position on the furnace wall different from the ammonia combustion burner, and burns fuels other than ammonia. Equipped with Boiler.

7. The boiler is a swirling combustion boiler in which swirling combustion is performed in the furnace by the ammonia combustion burner and the other fuel burner. The boiler according to claim 6.

8. The flame holder is further provided at the tip of the ammonia injection nozzle so as to be located inside the combustion air nozzle, The combustion air is ejected from the gap between the opening at the downstream end of the combustion air nozzle and the flame holder. An ammonia combustion burner according to any one of claims 1 to 4.

9. The flow velocity distribution unit is positioned upstream of the flame holder in the direction of the combustion air flow. The ammonia combustion burner according to claim 8.

10. The flame holder is configured to ignite and maintain the flame of the ammonia fuel injected from the ammonia injection nozzle. The ammonia combustion burner according to claim 8.

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