Direct current ammonia coal mixed combustion burner

Abstract

The application relates to a direct-current ammonia-coal mixed combustion burner and belongs to the technical field of coal-fired boilers. The application solves the problems that the existing ammonia fuel combustion technology is not mature, ammonia and coal cannot be efficiently and stably mixed and combusted, and NOx emission cannot be effectively controlled. The tail end of a main fuel pipe is fixed to a primary air inlet of a boiler, the head end of a standby structure extends from the main combustion structure, the tail end of the standby structure is coaxially arranged outside the main fuel pipe from inside to outside, an ammonia fuel ring pipe is located inside a secondary air pipe and forms a ring-shaped secondary air channel between the ammonia fuel ring pipe and the secondary air pipe, the secondary air pipe is located inside a primary air pipe and forms a ring-shaped primary air channel between the secondary air pipe and the primary air pipe, an outer swirling vane group is circumferentially distributed between a diffuser and the secondary air pipe, an inner swirling vane group is circumferentially distributed between the secondary air pipe and the ammonia fuel ring pipe, and the outer swirling vane group and the inner swirling vane group are opposite in rotation direction. The application is used for ammonia-coal mixed combustion.

Description

Technical Field

[0001] This invention relates to a direct-current ammonia-coal co-fired burner, belonging to the field of coal-fired boiler technology. Background Technology

[0002] Coal is one of my country's most important energy sources, accounting for approximately 56% of the country's total energy consumption. However, the use of coal generates a large amount of pollutants and greenhouse gases, especially carbon dioxide (CO2). As of 2022, carbon emissions from China's power generation industry accounted for 48% of the country's total emissions, and coal, as the main energy source for thermal power generation, is a major contributor to CO2 emissions. Therefore, to address this issue, the introduction of zero-carbon or low-carbon fuels to replace a certain proportion of coal combustion will fundamentally reduce carbon emissions. Among these, ammonia, as a zero-carbon fuel, has attracted widespread attention due to its high volumetric energy density, easy liquefaction, high safety, and low unit storage and transportation costs. Incorporating ammonia into coal-fired boilers for combustion to achieve low-carbon transformation from the fuel end is a carbon reduction pathway with great potential. However, current clean and efficient combustion technologies for ammonia fuel are not yet mature enough. This is because ammonia fuel has a high ignition temperature (651℃), a slow flame propagation speed, a narrow combustible limit range, and poor combustion reactivity. This results in problems such as difficulty in ignition, poor combustion stability, and incomplete combustion during the combustion process. Furthermore, because ammonia contains a large amount of nitrogen, co-firing it with coal increases the risk of high NOx emissions, and the NOx generated during combustion is extremely sensitive to the combustion environment. Therefore, a suitable ammonia-coal co-fired burner is urgently needed to overcome the combustion defects of ammonia fuel, achieve efficient and stable co-firing of ammonia and coal, effectively control NOx emissions, and promote the low-carbon transformation of coal-fired boilers. Summary of the Invention

[0003] The present invention aims to solve the above-mentioned technical problems and thereby provide a DC ammonia-coal co-fired burner.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: A direct-flow ammonia-coal co-fired burner includes a shift structure and a main combustion structure. The main combustion structure comprises a primary air inlet pipe, a bend, a square-round joint, and a main fuel pipe connected sequentially from end to end. The end of the main fuel pipe is fixed to the primary air inlet of the boiler. The first end of the shift structure extends out of the main combustion structure, and the end of the shift structure is coaxially arranged with the end of the main fuel pipe from the inside out, and the end of the shift structure is flush with the end of the main fuel pipe. The operating structure includes an ammonia fuel loop, a secondary air pipe, a primary air pipe, a diffuser, an inner swirling blade assembly, an outer swirling blade assembly, and an igniter. The ammonia fuel loop is located inside the secondary air pipe and forms an annular secondary air channel with it. The secondary air pipe is located inside the primary air pipe and forms an annular primary air channel with it. The small-diameter end of the diffuser is coaxially fixed to the end of the primary air pipe. Both the secondary air pipe and the ammonia fuel loop extend into the diffuser. The outer swirling blade assembly is circumferentially distributed between the diffuser and the secondary air pipe, and the inner swirling blade assembly is circumferentially distributed between the secondary air pipe and the ammonia fuel loop. The outer and inner swirling blade assemblies rotate in opposite directions. The working end of the igniter is located in the secondary air channel of the inner swirling blade assembly near the boiler primary air inlet. The end of the ammonia fuel ring pipe is a closed end, and several spray holes are opened circumferentially on the outer pipe of the ammonia fuel ring pipe. The outer swirl blade assembly has a duty room and a pre-combustion chamber on its two axial sides, respectively. The pre-combustion chamber is located on the side closer to the boiler primary air inlet, and several nozzles are located on the side of the inner swirl blade assembly away from the boiler primary air inlet.

[0005] Furthermore, a first partition plate is provided inside the bend, and two second partition plates are provided inside the main fuel pipe. The first partition plate is arranged inside the bend along the curvature of the bend, and the two second partition plates are symmetrically arranged between the main fuel pipe and the diffuser about the central axis of the diffuser. The main combustion path inside the main combustion structure is divided into a rich side and a lean side by the first partition plate and the two second partition plates, with the rich side located above and the lean side located below.

[0006] Furthermore, a perimeter ventilation duct is fitted around the end of the main fuel pipe, forming a perimeter ventilation channel between the perimeter ventilation duct and the main fuel pipe.

[0007] Furthermore, the diffuser includes an inlet straight section, an intermediate inclined section, and an outlet straight section, wherein the inlet straight section is connected to the end of the primary air pipe, and the outlet straight section is connected to the primary air inlet of the boiler.

[0008] Furthermore, the outer swirling blade assembly is located between the end of the intermediate inclined section and the secondary air tube.

[0009] Furthermore, the tilt angle of the blades in the internal swirling blade assembly is 30° to 60°.

[0010] Furthermore, a number of nozzles are arranged in three rows along the axial direction of the ammonia fuel ring pipe, totaling 24 nozzles. Each row of nozzles is evenly distributed along the circumference of the outer pipe of the ammonia fuel ring pipe.

[0011] Furthermore, the nozzles in each adjacent row are staggered at a circumferential angle of 22.5°.

[0012] Furthermore, the inner diameter of the nozzle is 10mm.

[0013] Furthermore, the axial length of the pre-combustion chamber is 100mm-200mm.

[0014] Compared with the prior art, the present invention has the following advantages: The burner is divided into a duty circuit and a main combustion circuit, which are formed within the burner through a duty circuit and a main combustion circuit, respectively. The duty circuit is mainly used for the combustion and introduction of ammonia. The main combustion circuit is used for the introduction of pulverized coal and air.

[0015] The outer swirling blade assembly and the inner swirling blade assembly constitute a double swirling diffuser, which divides the diffuser into a control chamber and a pre-combustion chamber. The pre-combustion chamber is located downstream of the control chamber, that is, at the outlet of the control structure, and is used to enhance the control flame. It is a cylindrical space that fits into the outlet.

[0016] Sufficient swirl intensity is generated by setting the outer swirl blade group and the inner swirl blade group in opposite directions.

[0017] The dual cyclone separator, diffuser, and downstream pre-combustion chamber work together to form a stable and enhanced flame for the duty circuit.

[0018] The duty path forms a stable high-temperature recirculation zone in the central recirculation zone through the double cyclone separator. The main combustion path envelops and dilutes this recirculation zone with a large amount of direct current air, forming a combustion process that gradually extends from the center to the surrounding area, ensuring that the flame develops fully. Furthermore, since it enters from the boiler primary air inlet, it has less interference with the overall tangential flow field of the boiler.

[0019] An igniter is installed within the control structure. The core function of the control path is to separately burn ammonia and provide sufficient heat for the combustion of pulverized coal. Pure ammonia has high ignition energy but a slow combustion rate, making direct ignition difficult. The control structure, through a swirling effect, creates a reflux zone that effectively anchors the control flame, providing a continuous high-temperature environment and active free radicals to support the subsequent ignition and stable combustion of pulverized coal. However, the control flame has limited energy; directly igniting a large amount of pulverized coal would easily cause it to extinguish. Therefore, a pre-combustion chamber is installed downstream of it, allowing the control flame to fully combust and release energy within a confined space before encountering the main combustion pulverized coal, ensuring that the main combustion path can be ignited and burn stably. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the first three-dimensional structure of the present invention; Figure 2 This is a schematic diagram of the second three-dimensional structure of the present invention; Figure 3 This is a first three-dimensional sectional view of the present invention; Figure 4 This is a second three-dimensional sectional view of the present invention; Figure 5 This is a schematic front sectional view of the present invention; Figure 6 This is a right-side schematic diagram of the present invention (the primary air inlet pipe, bend, and square / round joint are not shown). Figure 7 This is a schematic diagram of the three-dimensional structure of the final section of the duty roster; Figure 8 This is a partial three-dimensional sectional view of the duty structure; Figure 9 This is a three-dimensional sectional view of the diffuser.

[0021] In the picture: 1. Primary air inlet pipe; 2. Bend; 3. Square-round joint; 4. Main fuel pipe; 5. First partition plate; 6. Second partition plate; 7. Ammonia fuel ring pipe; 7-1. Nozzle; 8. Secondary air pipe; 9. Primary air pipe; 10. Diffuser; 10-1. Inlet straight section; 10-2. Intermediate inclined section; 10-3. Outlet straight section; 11. Inner swirl blade assembly; 12. Outer swirl blade assembly; 13. Ignition device; 14. Duty room; 15. Pre-combustion chamber; 16. Perimeter air duct; 20. Secondary air passage; 21. Primary air passage; 22. Ammonia passage. Detailed Implementation

[0022] Specific implementation method one: Combining Figures 1-9 This description of the embodiments provides a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] A direct-flow ammonia-coal co-fired burner includes a shift structure and a main combustion structure. The main combustion structure includes a primary air inlet pipe 1, a bend 2, a square-round joint 3, and a main fuel pipe 4 connected sequentially from end to end. The end of the main fuel pipe 4 is fixed to the primary air inlet of the boiler. The first end of the shift structure extends out of the main combustion structure, and the end of the shift structure is coaxially arranged with the end of the main fuel pipe 4 from the inside to the outside, and the end of the shift structure is flush with the end of the main fuel pipe 4. The operating structure includes an ammonia fuel loop pipe 7, a secondary air pipe 8, a primary air pipe 9, a diffuser 10, an inner swirling blade assembly 11, an outer swirling blade assembly 12, and an igniter 13. The ammonia fuel loop pipe 7 is located inside the secondary air pipe 8 and forms an annular secondary air channel 20 with it. The secondary air pipe 8 is located inside the primary air pipe 9 and forms an annular primary air channel 21 with it. The small-diameter end of the diffuser 10 is coaxially fixed to the end of the primary air pipe 9. Both the secondary air pipe 8 and the ammonia fuel loop pipe 7 extend into the diffuser 10. The outer swirling blade assembly 12 is circumferentially distributed between the diffuser 10 and the secondary air pipe 8. The inner swirling blade assembly 11 is circumferentially distributed between the secondary air pipe 8 and the ammonia fuel loop pipe 7. The outer swirling blade assembly 12 and the inner swirling blade assembly 11 rotate in opposite directions. The working end of the igniter 13 is located in the secondary air channel 20 of the inner swirling blade assembly 11 near the boiler primary air inlet. The end of the ammonia fuel ring pipe 7 is a closed end, and several nozzles 7-1 are circumferentially opened on the outer pipe of the ammonia fuel ring pipe 7. The outer swirl blade assembly 12 has a duty room 14 and a pre-combustion chamber 15 on its two axial sides. The pre-combustion chamber 15 is located on the side closer to the primary air inlet of the boiler, and several nozzles 7-1 are located on the side of the inner swirl blade assembly 11 away from the primary air inlet of the boiler.

[0024] The DC ammonia-coal co-fired burner of this invention is arranged in an internal and external hierarchical manner, and is integrally positioned at the primary air inlet of a tangentially circular boiler, replacing the simple pulverized coal inlet structure in the prior art. The main combustion structure is installed at the primary air inlet of the tangentially circular boiler via flanges, while the duty unit is located at the center of the main combustion structure.

[0025] The burner is divided into a duty circuit and a main combustion circuit, which are formed within the burner through a duty circuit and a main combustion circuit, respectively. The duty circuit is mainly used for the combustion and introduction of ammonia. The main combustion circuit is used for the introduction of pulverized coal and air.

[0026] An ammonia gas passage 22 is formed inside the ammonia fuel ring pipe 7.

[0027] The diffuser and its internal structure form the final section of the duty structure.

[0028] The primary air inlet pipe 1 is a straight circular pipe structure, the bend pipe 2 is a bent circular pipe structure, and the main fuel pipe 4 is a square pipe structure. The bend pipe 2 and the main fuel pipe 4 are connected by a square-circle joint 3.

[0029] The outer swirling blade assembly 12 and the inner swirling blade assembly 11 constitute a double swirling device, which divides the diffuser 10 into a duty chamber 14 and a pre-combustion chamber 15. The pre-combustion chamber 15 is located downstream of the duty chamber 14, that is, at the outlet position of the duty structure, and is used to enhance the duty flame. It is a cylindrical space that fits into the outlet.

[0030] Sufficient swirl intensity is generated by setting the outer swirl blade group 12 and the inner swirl blade group 11 in opposite directions.

[0031] The dual cyclone separator, diffuser 10, and downstream pre-combustion chamber 15 work together to form a stable and enhanced flame for the duty circuit.

[0032] The duty path forms a stable high-temperature recirculation zone in the central recirculation zone through the double cyclone separator. The main combustion path envelops and dilutes this recirculation zone with a large amount of direct current air, forming a combustion process that gradually extends from the center to the surrounding area, ensuring that the flame develops fully. Furthermore, since it enters from the boiler primary air inlet, it has less interference with the overall tangential flow field of the boiler.

[0033] An igniter 13 is installed within the control structure. The core function of the control path is to separately burn ammonia and provide sufficient heat for the combustion of pulverized coal. Pure ammonia has high ignition energy but a slow combustion rate, making direct ignition difficult. The control structure, through the swirling effect, forms a reflux zone that effectively anchors the control flame, providing a continuous high-temperature environment and active free radicals to support the subsequent ignition and stable combustion of pulverized coal. However, the control flame has limited energy, and directly igniting a large amount of pulverized coal would easily cause it to extinguish. Therefore, a pre-combustion chamber 15 is installed downstream of it, allowing the control flame to fully combust and release energy in a confined space before encountering the main combustion pulverized coal, ensuring that the main combustion path can be ignited and burn stably.

[0034] The control structure is equipped with an inner swirl blade group 11 and an outer swirl blade group 12 at the outlet. Utilizing the strong shearing effect and velocity difference between the inner and outer swirl fields, efficient instantaneous mixing of fuel and air is achieved. Simultaneously, through the counter-rotation of the inner and outer swirls, a stable high-temperature flue gas recirculation zone is formed in the central recirculation area. This not only effectively enhances ignition energy and flame stability, and broadens the range of stable combustion conditions, but also shortens the flame path to reduce the area of ​​local high-temperature zones, significantly suppressing thermal NOx. x Generation. The standby gas is ejected from the nozzle 7-1 through the ammonia fuel ring pipe 7, increasing the gas velocity and forming a vertical jet with the secondary standby air in the secondary air channel 20, achieving large-scale and rapid convective mixing. At the same time, due to the presence of the external swirling structure, the ammonia and air undergo secondary mixing, greatly improving the degree of mixing.

[0035] The nozzle 7-1 consists of multiple rows of circumferential holes, with a certain angle between adjacent rows of circumferential holes, ensuring a more uniform distribution of ammonia gas in the space.

[0036] The primary standby air in the primary air passage 21 passes through the diffuser 10, where its velocity decreases to match the low turbulence velocity of the pure ammonia flame. The standby combustion gas mixes with air in the secondary air passage 20 and then passes through the inner swirl vane assembly 11, where it is ignited by the igniter 13 located. It then flows into the pre-combustion chamber 15 and mixes with the reduced-velocity primary standby air for combustion. This configuration improves the combustion efficiency of ammonia.

[0037] A first partition plate 5 is installed inside the bend 2, and two second partition plates 6 are installed inside the main fuel pipe 4. The first partition plate 5 is arranged along the curvature of the bend 2 inside the bend 2, and the two second partition plates 6 are symmetrically arranged about the central axis of the diffuser 10 between the main fuel pipe 4 and the diffuser 10. The first partition plate 5 and the two second partition plates 6 divide the main combustion path inside the main combustion structure into a rich side and a lean side, with the rich side located above and the lean side located below. With this design, the main combustion path mainly uses the bend 2, the first partition plate 5, and the second partition plates 6 to classify the primary air containing pulverized coal introduced into the primary air input pipe 1 into rich and lean sides. The ignition of the pulverized coal on the rich side drives the combustion of the pulverized coal on the lean side. The flow velocity of the pulverized coal can be further increased through the square-round joint 3 to prevent the accumulation of pulverized coal on the rich side after classification, improve the ignition capacity, and at the same time, increase the outlet flow velocity to help maintain the swirling flow field inside the boiler.

[0038] The outer end of the main fuel pipe 4 is fitted with a perimeter ventilation duct 16, forming a perimeter ventilation channel between the perimeter ventilation duct 16 and the main fuel pipe 4. This design can form a perimeter ventilation film on the outside of the main fuel pipe 4, effectively isolating the main fuel pipe 4 from the heat radiation of high-temperature flue gas, preventing the fuel pipe from overheating and deforming, and improving structural durability.

[0039] The diffuser 10 includes an inlet straight section 10-1, an intermediate inclined section 10-2, and an outlet straight section 10-3. The inlet straight section 10-1 connects to the end of the primary air pipe 9, and the outlet straight section 10-3 connects to the primary air inlet of the boiler. This design allows the inlet straight section 10-1 to smoothly connect with the primary air pipe 9, reducing resistance loss and turbulence disturbance when the airflow enters the diffuser 10, and improving airflow stability. The intermediate inclined section 10-2 achieves smooth airflow diffusion, avoids airflow separation, and improves pressure recovery efficiency.

[0040] The outer swirl blade assembly 12 is located between the end of the intermediate inclined section 10-2 and the secondary air pipe 8. This design, with the outer swirl blade assembly 12 positioned between the end of the intermediate inclined section 10-2 and the secondary air pipe 8, allows for pre-swirl of the airflow during the later stages of diffusion, resulting in a more uniform airflow field entering the combustion zone. This provides a stable foundation for the coupling of the inner and outer swirl flows, while also optimizing the burner outlet velocity distribution and enhancing flame stability.

[0041] The blades in the inner swirl blade assembly 11 have an inclination angle of 30° to 60°. This design ensures sufficient swirl intensity to form a stable recirculation zone while avoiding premature airflow diffusion and insufficient jet rigidity caused by excessive swirl. The inclination angle of 30° to 60° effectively balances the size of the recirculation zone and the flame length, ensuring stable adhesion at the flame root while preventing the flame from excessively long enough to scour the furnace wall. It also optimizes the mixing path of fuel and air, improving combustion completeness.

[0042] A number of nozzles 7-1 are arranged in three rows along the axial direction of the ammonia fuel ring pipe 7, totaling 24 nozzles. The nozzles 7-1 in each row are evenly distributed along the circumference of the outer pipe of the ammonia fuel ring pipe 7. In this design, it is preferable that the number of nozzles 7-1 in the three rows is the same.

[0043] The nozzles 7-1 are staggered at 22.5° circumferentially between each pair of adjacent rows. This design allows for a more uniform injection distribution of ammonia fuel in both the circumferential and axial directions, avoiding localized fuel enrichment or depletion. The 22.5° staggered angle allows the fuel jets from different nozzles 7-1 to interweave and overlap spatially, improving the uniformity of fuel-air mixing, eliminating localized high-temperature zones, suppressing nitrogen oxide formation, and simultaneously enhancing the coverage of the fuel jet, ensuring stable and complete combustion.

[0044] The inner diameter of nozzle 7-1 is 10mm. This design ensures that the ammonia fuel has a suitable injection velocity and atomized particle size, avoiding problems such as nozzle 7-1 clogging and excessive pressure drop caused by excessively small nozzle diameter, and preventing insufficient fuel jet penetration and uneven mixing caused by excessively large nozzle diameter. The 10mm inner diameter, combined with the multi-row staggered arrangement, can achieve precise matching of fuel flow rate and injection momentum, optimizing the burner's load adjustment range and combustion performance.

[0045] The axial length of the pre-combustion chamber 15 is 100mm-200mm. This design allows the airflow, after exiting the dual swirl vane, to flow smoothly into the pre-combustion chamber 15 and achieve sufficient and stable combustion within it. After exiting the dual swirl vane assembly, the airflow can complete sufficient initial mixing and stable flame formation within the pre-combustion chamber 15. This length range avoids both insufficient mixing and flame instability due to excessive length, and excessive heat load and structural bulkiness of the pre-combustion chamber 15 due to excessive length. The axial length of 100mm-200mm effectively matches the development pattern of the dual swirl airflow, resulting in a more uniform temperature and component distribution of the pre-combustion chamber 15 outlet airflow, providing ideal conditions for efficient and low-NOx combustion in the subsequent main combustion zone.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A DC ammonia-coal co-fired burner, characterized in that: It includes a duty structure and a main combustion structure. The main combustion structure includes a primary air inlet pipe (1), a bend pipe (2), a square-round joint (3), and a main fuel pipe (4) connected end to end. The end of the main fuel pipe (4) is fixed to the primary air inlet of the boiler. The first end of the duty structure extends out of the main combustion structure. The end of the duty structure and the main fuel pipe (4) are arranged coaxially from the inside to the outside, and the end of the duty structure is flush with the end of the main fuel pipe (4). The operating structure includes an ammonia fuel loop (7), a secondary air pipe (8), a primary air pipe (9), a diffuser (10), an inner swirling blade assembly (11), an outer swirling blade assembly (12), and an igniter (13). The ammonia fuel loop (7) is located inside the secondary air pipe (8) and forms an annular secondary air passage (20) with the secondary air pipe (8). The secondary air pipe (8) is located inside the primary air pipe (9) and forms an annular primary air passage (21) with the primary air pipe (9). The small-diameter end of the diffuser (10) is coaxially fixed. At the end of the primary air pipe (9), the secondary air pipe (8) and the ammonia fuel ring pipe (7) both extend into the diffuser (10). The outer swirl blade group (12) is distributed circumferentially between the diffuser (10) and the secondary air pipe (8), and the inner swirl blade group (11) is distributed circumferentially between the secondary air pipe (8) and the ammonia fuel ring pipe (7). The outer swirl blade group (12) and the inner swirl blade group (11) rotate in opposite directions. The working end of the igniter (13) is located in the secondary air passage (20) on the side of the inner swirl blade group (11) near the boiler primary air inlet. The end of the ammonia fuel ring pipe (7) is a closed end, and several nozzles (7-1) are opened circumferentially on the outer pipe of the ammonia fuel ring pipe (7). The outer swirl blade assembly (12) has a duty room (14) and a pre-combustion chamber (15) on its two axial sides. The pre-combustion chamber (15) is located on the side close to the primary air inlet of the boiler, and several nozzles (7-1) are located on the side of the inner swirl blade assembly (11) away from the primary air inlet of the boiler.

2. The DC ammonia-coal co-fired burner according to claim 1, characterized in that: A first partition plate (5) is provided inside the bend (2), and two second partition plates (6) are provided inside the main fuel pipe (4). The first partition plate (5) is arranged inside the bend (2) along the arc of the bend (2), and the two second partition plates (6) are arranged symmetrically about the central axis of the diffuser (10) between the main fuel pipe (4) and the diffuser (10). The main combustion path inside the main combustion structure is divided into a rich side and a lean side by the first partition plate (5) and the two second partition plates (6). The rich side is located above and the lean side is located below.

3. The DC ammonia-coal co-fired burner according to claim 1, characterized in that: The outer end of the main fuel pipe (4) is fitted with a perimeter ventilation duct (16), and a perimeter ventilation channel is formed between the perimeter ventilation duct (16) and the main fuel pipe (4).

4. The DC ammonia-coal co-fired burner according to claim 1, characterized in that: The diffuser (10) includes an inlet straight section (10-1), an intermediate inclined section (10-2) and an outlet straight section (10-3), wherein the inlet straight section (10-1) is connected to the end of the primary air pipe (9) and the outlet straight section (10-3) is connected to the primary air inlet of the boiler.

5. A DC ammonia-coal co-fired burner according to claim 4, characterized in that: The outer swirling blade assembly (12) is located between the end of the middle inclined section (10-2) and the secondary air tube (8).

6. The DC ammonia-coal co-fired burner according to claim 1, characterized in that: The blades in the internal swirling blade group (11) have an inclination angle of 30° to 60°.

7. A DC ammonia-coal co-fired burner according to claim 1, characterized in that: Several nozzles (7-1) are arranged in three rows along the axial direction of the ammonia fuel ring pipe (7), with a total of 24 nozzles. The nozzles (7-1) in each row are evenly distributed along the circumference of the outer pipe of the ammonia fuel ring pipe (7).

8. A DC ammonia-coal co-fired burner according to claim 1, characterized in that: The two adjacent rows of nozzles (7-1) are staggered at 22.5° along the circumference.

9. A DC ammonia-coal co-fired burner according to claim 1, characterized in that: The inner diameter of the nozzle (7-1) is 10 mm.

10. A DC ammonia-coal co-fired burner according to claim 1, characterized in that: The axial length of the pre-combustion chamber (15) is 100mm-200mm.

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