Multi-stage differentially resolved swirl burner for ammonia blended fuel based on carbon-nitrogen separation and low NOx control method

Abstract

This invention discloses a multi-stage, micro-swirl burner for ammonia-mixed fuel and a low-NOx control method. The burner includes a natural gas center tube, a primary air duct, and a burner shell, which are fitted from inside to outside to form a spaced-apart primary air passage and an overfire air duct. Natural gas is injected from the natural gas center tube, and swirl vanes are positioned within the primary air passage to swirl the primary air and mix it with the central natural gas. A diffusion flame is then formed under the action of an ignition device, forming a sustainably combustible pilot flame at the center of the burner's injection end. The ammonia-mixed fuel, formed by premixing ammonia gas and natural gas, generates negative pressure when ejected at high speed through a micro-swirl nozzle. The surrounding overfire air is constantly sucked in, while the ammonia is injected into the high-temperature combustion zone of the pilot flame at the center of the burner. This allows the ammonia to rapidly decompose, producing a large amount of hydrogen and improving combustion stability. This invention's novel and rational structural layout improves combustion stability and reduces NOx emissions.

Description

[Technical Field]

[0001] The present invention belongs to the field of combustion devices and relates to burners for burning gaseous fuels, in particular Based on carbon-nitrogen separation The present invention relates to a multi-stage differentially resolved swirl burner for ammonia-blended fuel and a low NOx control method. [Background technology]

[0002] In a premixed swirl burner, the mixing ratio and mixing uniformity of the ammonia mixed fuel and oxidizer during combustion directly determine the burner's NOx (nitrogen oxides) emission effect. In conventional swirl burners, the ammonia mixed fuel and oxidizer are not mixed sufficiently, resulting in an insufficient flame effect and high nitrogen oxide emissions, making it impossible to meet the safety and environmental protection requirements of current burners. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention aims to provide a multi-stage microdecomposition swirl burner for ammonia mixed fuel with high combustion stability and low NOx emissions, and a low NOx control method, in order to solve the problems of conventional burners, which have insufficient mixing of ammonia mixed fuel and oxidizer, resulting in less than ideal flame effects and high nitrogen oxide emissions. [Means for solving the problem]

[0004] To achieve the above objectives, the present invention provides the following technical solutions:

[0005] The present invention provides a multi-stage, differentially resolved swirl burner for ammonia-blended fuel, The apparatus includes a natural gas central pipe, a primary air duct, and a burner shell, which are fitted from the inside to the outside in this order, a primary air passage is formed between an outer wall of the natural gas central pipe and an inner wall of the primary air duct, and an overfire air duct is formed between the outer wall of the primary air duct and an inner wall of the burner shell, an ignition device and a swirl vane are provided within the primary air duct, the swirl vane is attached to the outer periphery of the outlet end of the natural gas central pipe, and the swirl vane is arranged to make the primary air in the primary air duct a swirling state and mix it with the natural gas injected from the outlet end of the natural gas central pipe, and the ignition device ignites and burns the mixed primary air and natural gas to form a pilot flame that can be sustained at the outlet end of the natural gas central pipe; A fuel distribution nozzle is provided in the overfire air duct, and the fuel distribution nozzle is disposed near the outlet end of the natural gas central pipe. A plurality of fine combustion holes are provided at the outlet end of the fuel distribution nozzle, which injects ammonia mixed fuel at high speed. The ammonia in the ammonia mixed fuel is burned under the action of the pilot flame. When the ammonia mixed fuel is injected at high speed, a negative pressure is formed at the end of the overfire air duct, and overfire air generated by the combustion of the ammonia mixed fuel is sucked in.

[0006] In addition, a primary air distribution pipe communicating with the primary air passage is further provided on the outer wall of the primary air duct, the primary air distribution pipe is located within the overfire air duct, the outlet end of the primary air distribution pipe is located on the outer periphery of the outlet end of the primary air duct, and the outlet end of the primary air distribution pipe is longer than the outlet end of the natural gas central pipe and the primary air duct.

[0007] In an optional modification, a distribution pipe nozzle is provided at the outlet end of the primary air distribution pipe, and the angle formed by the distribution pipe nozzle and the axial direction of the primary air distribution pipe is adjustable.

[0008] In an optional modification, a plurality of the primary air distribution pipes are arranged on the outer wall of the primary air duct at equal intervals along the circumferential direction of the outer wall of the primary air duct.

[0009] In an optional variation, a plurality of fuel distribution nozzles are provided in the overfire air duct, all of the fuel distribution nozzles are evenly arranged along the circumferential direction of the primary air duct, and the fine resolution holes in each of the fuel distribution nozzles are evenly arranged.

[0010] In an optional variation, the ignition device is an ignition gun.

[0011] In an optional modification, the swirl vane includes a plurality of rotary vanes evenly arranged along the circumferential direction, and the angle formed by any of the rotary vanes and the axial direction of the primary air duct is 30° to 45°.

[0012] In an optional variation, the diameter of any of said micro-holes is between 3 mm and 7 mm.

[0013] The present invention further provides a low NOx control method, which comprises the steps of carrying out the low NOx control method using the multi-stage differentially resolved swirl burner for ammonia-mixed fuel described in any one of the above, and forming the pilot flame by injecting a portion of natural gas corresponding to a volume ratio of 20% from an outlet end of the natural gas center tube and mixing and burning it with primary wind under the action of the ignition device, and premixing the remaining portion of natural gas corresponding to a volume ratio of 80% with ammonia gas to obtain an ammonia-mixed fuel at a predetermined equivalence ratio, and then injecting the ammonia-mixed fuel from the fuel distribution nozzle into a flame region by the pilot flame, and burning and decomposing the ammonia in the ammonia-mixed fuel under the action of the pilot flame.

[0014] In an optional modification, in the combustion process of the ammonia mixed fuel, an overall equivalence ratio between the ammonia mixed fuel and the multi-stage differentially resolved swirl burner for the ammonia mixed fuel is controlled to a lean combustion state, and a local equivalence ratio between overfire air and the ammonia mixed fuel is controlled to a rich combustion state.

[0015] In an optional variation, in the combustion process of the ammonia mixed fuel, an overall equivalence ratio between the ammonia mixed fuel and the multi-stage differentially resolved swirl burner for the ammonia mixed fuel is controlled to 0.7 to 0.8, and a local equivalence ratio between overfire air and the ammonia mixed fuel is controlled to 1.0 to 1.3. [Effects of the Invention]

[0016] Compared with the prior art, the present invention achieves the following technical advantages:

[0017] The multi-stage, slightly swirl-flow burner for ammonia-mixed fuel proposed in this invention has a natural gas central tube, a primary air duct, and a burner shell fitted together from the inside to the outside to form a spaced-apart primary air duct and an overfire air duct. Natural gas is injected from the natural gas central tube. Swirl vanes are arranged in the primary air duct and around the natural gas central tube, causing the primary air to mix with the central natural gas in a swirling state, and then forming a diffusion flame under the action of an ignition device. In this way, a sustained-burning pilot flame is formed at the center of the injection end of the multi-stage, slightly swirl-flow burner for ammonia-mixed fuel. The ammonia-mixed fuel obtained by premixing ammonia gas and natural gas is injected at high speed from the fine-composition hole, creating negative pressure that constantly draws in the surrounding overfire air. At the same time, the ammonia-mixed fuel is injected and enters the high-temperature combustion region of the pilot flame at the center of the burner. This allows the ammonia to rapidly decompose, producing a large amount of hydrogen, which helps improve combustion stability. This multi-stage differentially resolved swirl burner for ammonia mixed fuel has a novel and rational structural layout, which can improve combustion stability and reduce NOx emissions.

[0018] In some of the technical solutions disclosed in the present invention, a primary air distribution pipe with an adjustable nozzle angle is arranged outside the primary air duct, and the outlet end of the primary air distribution pipe is longer than the outlet ends of the natural gas central pipe and the primary air duct, which delays the flow of some of the primary air into the combustion area, ensures complete combustion of the fuel, and further improves combustion stability. [Brief explanation of the drawings]

[0019] In order to more clearly explain the embodiments of the present invention or the technical solutions of the prior art, the drawings necessary for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only a part of the embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without expending creative efforts. [Figure 1] 1 is a structural schematic diagram of a multi-stage differentially resolved swirl burner for ammonia mixed fuel disclosed in an embodiment of the present invention; FIG. [Figure 2] FIG. 1 is a front view of a multi-stage, differentially resolved swirl burner for ammonia-mixed fuel disclosed in an embodiment of the present invention. [Figure 3] 1 is a side view of a multi-stage, differentially resolved swirl burner for ammonia-blended fuel disclosed in an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the drawings according to the embodiments of the present invention, but it is obvious that the described embodiments are only some of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments described in the present invention, all other embodiments that can be obtained by those skilled in the art without any creative efforts are also included in the protection scope of the present invention.

[0021] One of the objectives of the present invention is to provide a multi-stage differentially resolved swirl burner for ammonia mixed fuel with high combustion stability and low NOx emissions in order to solve the problems of conventional burners, such as insufficient mixing of ammonia mixed fuel and oxidizer, resulting in less than ideal flame effect and high nitrogen oxide emissions.

[0022] Another object of the present invention is to provide a low NOx control method implemented using a multi-stage differentially resolved swirl burner for ammonia mixed fuel, which has high combustion stability and low NOx emissions, in order to solve the problem of insufficient mixing of ammonia mixed fuel and oxidizer, resulting in less than ideal flame effect and high nitrogen oxide emissions in conventional burners.

[0023] In order to make the above objects, features and advantages of the present invention more clearly and easily understandable, the present invention will be described in more detail with reference to the drawings and specific embodiments.

[0024] Example 1

[0025] As shown in FIGS. 1 to 3, this embodiment provides a multi-stage, fractionally resolved swirl burner 100 for ammonia-blended fuel, which includes a natural gas central tube 1, a primary air duct 2, and a burner shell 3, which are fitted from the inside to the outside in this order. A primary air passage 4 is formed between the outer wall of the natural gas central tube 1 and the inner wall of the primary air duct 2, and an overfire air duct 5 is formed between the outer wall of the primary air duct 2 and the inner wall of the burner shell 3. An ignition device 6 and a swirl vane 7 are provided in the primary air passage 4. The swirl vane 7 is attached to the outer periphery of the outlet end of the natural gas central tube 1. The swirl vane 7 is arranged to make the primary air in the primary air passage 4 swirl and mix it with the natural gas injected from the outlet end of the natural gas central tube 1. The ignition device 6 ignites and burns the mixed primary air and natural gas, forming a pilot flame that can be sustained at the outlet end of the natural gas central tube 1. A fuel distribution nozzle 8 is provided in the overfire air duct 5, and the fuel distribution nozzle 8 is arranged near the outlet end of the natural gas central pipe 1. A plurality of fine combustion holes 81 are provided at the outlet end of the fuel distribution nozzle 8, which injects the ammonia mixed fuel at high speed, so that the ammonia in the ammonia mixed fuel burns under the action of the pilot flame. When the ammonia mixed fuel is injected at high speed, a negative pressure is formed at the end of the overfire air duct 5, and the overfire air generated by the combustion of the ammonia mixed fuel is sucked in.

[0026] In this embodiment, a primary air distribution pipe 10 communicating with the primary air duct 4 is further provided on the outer wall of the primary air duct 2, and is located within the overfire air duct 5. The outlet end of the primary air distribution pipe 10 is located on the outer periphery of the outlet end of the primary air duct 2, and is longer than the outlet ends of the natural gas central pipe 1 and the primary air duct 2, so that the primary air injected from the primary air distribution pipe 10 enters the combustion area later than the primary air injected from the primary air duct 2, ensuring complete combustion of the fuel. The inlet end of the primary air distribution pipe 10 is usually connected near the tail end of the primary air duct 2, so that when the primary air is passed through the primary air duct 2, it immediately flows into the primary air distribution pipe 10.

[0027] In this embodiment, a distribution pipe nozzle is provided at the outlet end of the primary air distribution pipe 10, and the angle between the distribution pipe nozzle and the axial direction of the primary air duct 2 is adjustable, typically between -45° and 45°. The angle of the distribution pipe nozzle can be adjusted by directly using a nozzle with an angle adjustment function, such as an omnidirectional nozzle or the spherical angle-adjustable nozzle disclosed in Patent Document CN95106474.6. Alternatively, the nozzle can be attached using an existing spray angle adjustment structure, and the spray angle adjustment structure can be used to adjust the angle between the distribution pipe nozzle and the axial direction of the primary air duct 2. Examples of the spray angle adjustment structure include an omnidirectional valve, an omnidirectional adjuster, and the structure disclosed in Patent Document CN101121157A.

[0028] In this embodiment, the ratio of the air flow rate flowing through any one of the primary air distribution pipes 10 to the total amount of primary air is the ratio of the cross-sectional area of ​​the primary air distribution pipe 10 to the cross-sectional area of ​​the primary air duct 2.

[0029] In this embodiment, a plurality of primary air distribution pipes 10 are arranged on the outer wall of the primary air duct 2 at equal intervals along the circumferential direction of the outer wall of the primary air duct.

[0030] In this embodiment, multiple fuel distribution nozzles 8 are provided in the overfire air duct 5, and all of the fuel distribution nozzles 8 are arranged at equal intervals along the circumferential direction of the primary air duct 2. The fine-distribution holes 81 in each fuel distribution nozzle 8 are uniformly arranged to uniformize the burner outlet flow field. In a more preferred technical solution, the fuel distribution nozzles 8 are arranged around multiple primary air distribution pipes 10, as shown in Figures 1 and 2, and the outlet ends of the primary air distribution pipes 10 are longer than the outlet ends of the fuel distribution nozzles 8.

[0031] In this embodiment, each fuel distribution nozzle 8 is connected to a fuel supply pipe 9. The fuel supply pipes 9 connected to all fuel distribution nozzles 8 preferably have the same diameter, are parallel to each other, and are arranged at equal intervals. The load of the multi-stage differentially resolved swirl burner 100 for ammonia mixed fuel can be adjusted by changing the number of fuel supply pipes 9 that are opened or closed.

[0032] In this embodiment, the ignition device 6 is preferably an ignition gun, which can also be used as a gas inlet channel for other fuels after ignition.

[0033] In this embodiment, the swirl blade 7 includes a plurality of rotary vanes that are evenly arranged along the circumferential direction, and the angle formed between any of the rotary vanes and the axial direction of the primary air duct is 30° to 45°.

[0034] In this embodiment, the diameter of each of the micro-resolution holes 81 is 3 mm to 7 mm. More specifically, the diameter of each of the micro-resolution holes 81 may be 3 mm, 5 mm, or 7 mm.

[0035] In this embodiment, as shown in Figures 1 to 3, the natural gas central pipe 1 has a curved pipe structure, with one end thereof located within the primary air duct 2 and coaxially arranged therewith, and the other end thereof penetrating the side wall of the primary air duct 2 and extending outward from the primary air duct 2. This structural arrangement facilitates simultaneous ventilation of the natural gas central pipe 1 and the primary air duct 2 and prevents interference between them due to simultaneous ventilation. The inner wall of the outlet end of the natural gas central pipe 1 is provided with a blunt body 11 shaped to match the aerodynamic characteristics of a blunt body. The arrangement of the blunt body 11 is a conventional technical means in the field of burners and will not be described in detail here.

[0036] The multi-stage, finely divided swirl burner 100 for ammonia mixed fuel is configured by fitting a natural gas central tube 1, a primary air duct 2, and a burner shell 3 in order from the inside to the outside, thereby forming a primary air duct 4 and an overfire air duct 5 that are spaced apart from each other. Natural gas is injected from the natural gas central tube 1, and the volume of the natural gas in this portion accounts for approximately 20%. Swirl vanes 7 are disposed within the primary air duct 4 and positioned around the natural gas central tube 1 to mix the primary air with the central natural gas in a swirling state, and then form a diffusion flame under the action of an ignition device 6. In this way, a single pilot flame capable of sustained combustion is formed at the center of the injection end of the multi-stage, finely divided swirl burner 100 for ammonia mixed fuel. A primary air distribution pipe 10 with an adjustable nozzle angle is located outside the primary air duct 2, and the outlet end of the primary air distribution pipe 10 is longer than the outlet ends of the natural gas central pipe 1 and primary air duct 2, delaying the entry of a portion of the primary air into the combustion zone and ensuring complete combustion of the fuel. A fuel distribution nozzle 8 consisting of multiple fine decomposition holes 81 is located on the outer periphery of the primary air distribution pipe 10. 100% ammonia and the remaining 80% natural gas are premixed to form an ammonia-mixed fuel. The ammonia-mixed fuel is rectified by a fuel supply pipe 9 connected to the fuel distribution nozzle 8 and injected at high speed from the fine decomposition holes 81, creating negative pressure and continuously drawing in the surrounding overfire air. At the same time, the ammonia-mixed fuel is injected and enters the high-temperature combustion zone of the pilot flame at the center of the burner. The ammonia is rapidly decomposed, and the large amount of hydrogen produced helps improve combustion stability. In the combustion process of ammonia mixed fuel, generally, the overall equivalence ratio between the ammonia mixed fuel and the multi-stage differentially resolved swirl burner 100 for ammonia mixed fuel is controlled to a lean combustion state, for example, the overall equivalence ratio between the ammonia mixed fuel and the multi-stage differentially resolved swirl burner 100 for ammonia mixed fuel is controlled to 0.7 to 0.8, and at the same time, the local equivalence ratio between the overfire air and the ammonia mixed fuel is controlled to a rich combustion state, for example, the local equivalence ratio between the overfire air and the ammonia mixed fuel is controlled to 1.0 to 1.3. As a more preferred technical solution, in the combustion process of ammonia mixed fuel, generally, the local equivalence ratio between the overfire air and the ammonia mixed fuel is controlled to about 1.2.

[0037] From the above, in the multi-stage differentially resolved swirl burner 100 for ammonia blended fuel proposed by this technical solution, during operation the natural gas and swirling air in the center first form a stable high-temperature pilot flame by the ignition device 6, and the remaining natural gas is premixed with ammonia and then injected at a certain equivalence ratio through the differentially resolved holes 81 into the high-temperature area formed by the high-temperature pilot flame combustion, and by combining this with the setting of the primary air distribution pipe, complete combustion of the fuel is achieved, combustion stability is improved, and NOx emissions can be reduced. Compared to the prior art, this technical solution mainly has the following beneficial technical effects:

[0038] (1) A multi-stage differential swirl burner for ammonia-mixed fuel that allows precise control of NOx, which can solve the problem of high NOx emissions from current ammonia-mixed fuel.

[0039] (2) During combustion, a flame region consisting of different inner and outer passages is formed, and the flame field generated by the central pilot flame provides a stable, high-temperature environment for the decomposition of ammonia fuel, resulting in high combustion stability and low NOx emissions.

[0040] (3) By adjusting the number of times the fuel supply pipe 9 is opened and closed, the combustion output of the burner can be freely controlled.

[0041] (4) The micro-dissolution hole design increases the fuel flow rate, effectively preventing flashback during combustion.

[0042] (5) The primary air duct 4, the overfire air duct 5 and the primary air distribution pipe 10 are partitioned and tightly connected, so that the fuel and the oxidizer at each stage can reach a uniform mixed state when they reach the horizontal position of the burner outlet. This prevents premixing of the fuel and the oxidizer, and at the same time, the ratio of the fuel and the oxidizer can be accurately controlled according to the required working conditions, so that the ammonia mixed fuel can be rapidly decomposed and low NOx combustion technology can be achieved.

[0043] The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention. [Explanation of symbols]

[0044] 100 Multi-stage differentially resolved swirl burner for ammonia-mixed fuel 1 Natural gas central pipe 2 Primary wind pipe 3 Burner Shell 4 Primary air path 5. Overfire air duct 6 Ignition device 7 Swirl blade 8 fuel distribution nozzle 81 Differential resolution hole 9 Fuel supply pipe 10 Primary air distribution piping 11 Blunt body

Claims

1. A multi-stage, differentially resolved swirl burner for ammonia-mixed fuel, comprising a natural gas central tube (1), a primary air duct (2), and a burner shell (3), which are fitted together from the inside to the outside in this order, A primary air passage (4) is formed between an outer wall of the natural gas central pipe (1) and an inner wall of the primary air duct (2), and an overfire air duct (5) is formed between the outer wall of the primary air duct (2) and an inner wall of the burner shell (3). An ignition device (6) and a swirl vane (7) are provided in the primary air duct (4), The swirl vanes (7) are attached to the outer periphery of the outlet end of the natural gas central pipe (1), The swirl vanes (7) are arranged to make the primary air in the primary air passage (4) swirl and mix it with the natural gas injected from the outlet end of the natural gas central pipe (1), The ignition device (6) ignites and burns the mixed primary wind and natural gas to form a sustainably combustible pilot flame at the outlet end of the natural gas central tube (1); A fuel distribution nozzle (8) is provided in the overfire air duct (5), the fuel distribution nozzle (8) is located near the outlet end of the natural gas center tube (1); The outlet end of the fuel distribution nozzle (8) is provided with a plurality of fine resolution holes (81), A multi-stage differentially resolved swirl burner for ammonia mixed fuel, characterized in that ammonia mixed fuel is injected at high speed, and the ammonia in the ammonia mixed fuel is burned under the action of a pilot flame, and when the ammonia mixed fuel is injected at high speed, negative pressure is formed at the end opening of the overfire air duct (5), and overfire air generated by the combustion of the ammonia mixed fuel is sucked in.

2. A primary air distribution pipe (10) communicating with the primary air passage (4) is further provided on the outer wall of the primary air duct (2), The primary air distribution pipe (10) is located in the overfire air duct (5), 2. The multi-stage differentially resolved swirl burner for ammonia mixed fuel according to claim 1, wherein the outlet end of the primary air distribution pipe (10) is located on the outer periphery of the outlet end of the primary air duct (2), and the outlet end of the primary air distribution pipe (10) is longer than the outlet ends of the natural gas central pipe (1) and the primary air duct (2).

3. A distribution pipe nozzle is provided at the outlet end of the primary air distribution pipe (10); and 3. The multi-stage differential swirl burner for ammonia-mixed fuel according to claim 2, wherein the angle between the distribution pipe nozzle and the axial direction of the primary air duct (2) is adjustable.

4. 4. The multi-stage differentially resolved swirl burner for ammonia mixed fuel according to claim 2 or 3, characterized in that a plurality of the primary air distribution pipes (10) are uniformly arranged on an outer wall of the primary air duct (2) along a circumferential direction of the outer wall of the primary air duct (2).

5. A plurality of the fuel distribution nozzles (8) are provided in the overfire air duct (5), All the fuel distribution nozzles (8) are uniformly arranged along the circumferential direction of the primary air duct (2), 4. The multi-stage differential swirl burner for ammonia-mixed fuel according to claim 1, wherein the differential holes (81) in each of the fuel distribution nozzles (8) are uniformly arranged.

6. 4. The multi-stage, differentially resolved swirl burner for ammonia-mixed fuel according to claim 1, wherein the ignition device (6) is an ignition gun.

7. The swirl vane (7) includes a plurality of rotary vanes evenly arranged along the circumferential direction, The multi-stage differentially resolved swirl burner for ammonia mixed fuel according to any one of claims 1 to 3, characterized in that the angle formed between any of the rotary vanes and the axial direction of the primary air duct (2) is 30° to 45°.

8. 4. The multi-stage differentially decomposing swirl burner for ammonia-mixed fuel according to claim 1, wherein the diameter of each of the differentially decomposing holes (81) is 3 mm to 7 mm.

9. 1. A low NOx control method comprising: a step of injecting a portion of the natural gas corresponding to 20% by volume from the outlet end of the natural gas central pipe (1) and mixing and burning the natural gas with the primary wind under the action of the ignition device (6) to form the pilot flame; and a step of premixing the remaining portion of the natural gas, which corresponds to a volume ratio of 80%, with ammonia gas to obtain an ammonia-mixed fuel at a predetermined equivalence ratio, and then injecting the ammonia-mixed fuel from the fuel distribution nozzle (8) into a flame region formed by the pilot flame, and burning and decomposing the ammonia in the ammonia-mixed fuel under the action of the pilot flame.

10. In the combustion process of the ammonia mixed fuel, 10. The low NOx control method according to claim 9, wherein an overall equivalence ratio between the ammonia mixed fuel and the multi-stage differentially resolved swirl burner for the ammonia mixed fuel is controlled to a lean combustion state, and a local equivalence ratio between overfire air and the ammonia mixed fuel is controlled to a rich combustion state.

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