A natural gas hydrogen-doped low-nitrogen burner for a boiler

Abstract

The utility model discloses a kind of natural gas hydrogen-doped low-nitrogen combustor for boiler, belong to combustor technical field, it is proposed to the defect that too much pollution emission of existing combustor in use process, it includes main combustion nozzle, sleeve and micro-mixing value class nozzle, sleeve and micro-mixing value class nozzle are for the structure of being set, and combustion channel is formed between the two, multiple main combustion nozzle is distributed along the circumference of sleeve, first premixing cavity for mixing and mixing fuel gas and flue gas is set in main combustion nozzle, sleeve respectively imports air into combustion channel and micro-mixing value class nozzle, gas cavity and air cavity second premixing cavity are set in micro-mixing value class nozzle, air outlet and second premixing cavity communicated with air cavity are machined on its barrel body end face, unit micro-mixing nozzle upstream is located in air cavity, downstream is located in second premixing cavity, and is communicated with gas cavity. The utility model reduces flame peak temperature and speed by enhancing mixing effectively, and then inhibit the generation of NOx.

Description

Technical Field

[0001] This utility model belongs to the field of industrial boiler burner technology, specifically relating to a natural gas hydrogen-blended low-NOx burner for boilers. Background Technology

[0002] Natural gas is a primary energy source that my country is vigorously developing during its energy transition. As of 2022, natural gas production reached 2200 × 10⁻⁶. 8 m 3 It ranks fourth in the world, with a consumption of 3663 × 10 8 m 3 Ranking third in the world, natural gas, as a clean energy source developed after fossil fuels such as coal, now faces the constraints of global climate change. With the advancement of the "dual-carbon" policy, the use of low-carbon fuels has become a trend. Hydrogen energy, with its advantages of being renewable, highly energy efficient, and clean and environmentally friendly, has received attention from many countries as a zero-carbon energy carrier. In 2020, the "Energy Law of the People's Republic of China (Draft for Solicitation of Comments)" included hydrogen energy in the energy category for the first time, marking the first time my country legally recognized hydrogen energy as an energy source.

[0003] Hydrogen has a wide flammability limit in air (4-75 vol%), low ignition energy (0.019 mJ), and low density (0.0899 kg / m³). 3 Hydrogen fuels have high adiabatic flame temperatures (2380 K) and laminar flame propagation speeds approximately seven times that of methane. This makes it highly likely that the flame propagation speed will exceed the fuel injection speed during combustion, significantly increasing the risk of flashback. Industrial burners typically prefer non-premixed combustion methods because they reduce the risk of flashback and explosion by injecting fuel and oxidizer separately. However, in this combustion method, the fuel and oxidizer can easily reach a stoichiometric ratio in local mixing zones, causing the local flame temperature to approach the adiabatic temperature, resulting in the generation of large amounts of thermal NOx. This is currently a major challenge facing hydrogen fuel applications.

[0004] In the field of industrial combustion, such as in boilers, the blending of hydrogen into combustion fuel has become an important trend in response to the "dual carbon" problem. The main technical challenge in designing hydrogen-blended burners is increasing the hydrogen content in the fuel and reducing NOx emissions under safe operating conditions. Therefore, there is an urgent need for a technological concept to retrofit existing natural gas boiler burners to meet the requirements of hydrogen-blended combustion. Summary of the Invention

[0005] This invention provides a natural gas-blended low-NOx burner for boilers to overcome the shortcomings of existing burners that emit excessive pollutants during use.

[0006] The technical solution adopted by this utility model is as follows: a natural gas hydrogen-blended low-NOx burner for a boiler, comprising a main combustion nozzle, a sleeve, and a micro-mixing duty nozzle arranged coaxially from the outside to the inside. The sleeve and the micro-mixing duty nozzle are a set structure that is respectively connected to air and gas source pipelines, and the two form a combustion-supporting channel through a radial clearance fit. Multiple main combustion nozzles are evenly distributed along the circumference of the sleeve. The gas source is connected to each main combustion nozzle. A first premixing chamber is provided in the main combustion nozzle. The first premixing chamber is used to mix the gas flowing out of the main combustion nozzle with the flue gas drawn in from the outside of the main combustion nozzle before spraying it out. The air source is introduced into the combustion-supporting channel and the micro-mixing duty nozzle through the sleeve. The micro-mixing duty nozzle is cylindrical, and its inner cavity is divided into upstream and downstream cavities by a flow divider. An annular gas chamber is provided in the upstream cavity, along the axial length direction of the outer wall of the inner ring of the gas chamber. An air guide channel is formed connecting the upstream and downstream cavities. The longitudinal section of the air guide channel is tapered funnel-shaped, and its outlet side is located in the downstream cavity. In the downstream cavity, the diversion baffle, the shell sidewall, and the end wall together form an air cavity. An air outlet coaxial with the air guide channel and a second premixing cavity connected to the air cavity are respectively machined on the cylindrical end face of the micro-mixing nozzle. The second premixing cavity consists of multiple circumferentially arrayed through holes around the outer periphery of the air outlet. A unit micro-mixing nozzle is installed in each second premixing cavity. Air enters the air cavity through the air guide channel and is distributed to the air outlet and the second premixing cavity. The fuel gas is distributed to each unit micro-mixing nozzle through the fuel gas cavity. The fuel gas flowing in the unit micro-mixing nozzle is ejected from the side wall of the unit micro-mixing nozzle at the second premixing cavity and mixed with the air before being ejected from the second premixing cavity.

[0007] Preferably, the micro-mixing duty nozzle includes a cylindrical housing, with an array of injection holes for accommodating the unit micro-mixing nozzle machined on the downstream end face of the housing, and the injection holes are opened on the outer periphery of the air outlet, and the second premixing chamber is the axial space from one end face of the injection hole to the other end face.

[0008] Preferably, the axial spatial lengths of the fuel chamber, air chamber, and second premixing chamber are the same.

[0009] Preferably, the unit micro-mixing nozzle is a straight pipe of equal diameter, with small holes for outward spraying spaced circumferentially at the downstream end face of the pipe body.

[0010] Preferably, swirl vanes are provided circumferentially on the outer wall of the unit micro-mixing nozzle, and the swirl vanes are fixed on the side away from the orifice and close to the upstream side of the pipe body.

[0011] Preferably, the main combustion nozzle is composed of a main combustion pipe and a sleeve. The intake side of the main combustion pipe is connected to the gas source. The sleeve is composed of an intake equal diameter section, a constricted section, and an outlet equal diameter section. The first premixing chamber is a cavity formed by the intake equal diameter section and the constricted section. The outlet side of the main combustion pipe is fitted inside the first premixing chamber. An opening is provided on the outer wall of the first premixing chamber to connect the inside of the sleeve with the outside.

[0012] Preferably, the constricted section has a gradually narrowing-expanding composite variable diameter structure, and the nozzle of the main combustion pipe is located at the throat section of the composite variable diameter structure.

[0013] Preferably, the throat section is the minimum flow section of the sleeve, and the axial length of the converging section is less than that of the expanding section.

[0014] Preferably, the main combustion pipe nozzle diameter is a constricted shape with a lobe structure, and the number of lobes in the lobe structure is greater than three.

[0015] Preferably, the opening is a circle with a uniform diameter.

[0016] The beneficial effects of this utility model are:

[0017] 1. Traditional swirling diffusion flames in standby burners exhibit high saturation ratios and large-scale combustion within the swirling shear layer, resulting in large localized high-temperature zones and high NOx emissions. Under low-load hydrogen-doped conditions, the stability of the swirling flame further deteriorates, posing a significant risk of backfire (nozzle erosion) or flameout. To overcome these shortcomings, this invention abandons the traditional swirling structure and innovatively adopts a micro-mixing nozzle array design. This design, through the synergistic effect of multiple discretely distributed micro-mixing nozzle units, deconstructs the single large-scale turbulent diffusion flame into numerous small, compact, and relatively independent turbulent diffusion flame units.

[0018] 2. This utility model uses the designed independent unit micro-mixing nozzle as the standby nozzle of the industrial burner. The unit micro-mixing nozzle passes through. This design significantly reduces the local high temperature peak of the standby diffusion flame, effectively suppressing the generation of thermal NOx; at the same time, it greatly improves the flame stability under low load and high hydrogen doping ratio conditions, and significantly reduces the risk of backfire.

[0019] 3. The main combustion nozzle in this invention adopts a composite structure design of a corrugated main combustion tube and a contraction sleeve. The corrugated structure disturbs the working fluid flow field at its lip, inducing enhanced vortex structures (such as horseshoe vortices), which significantly promotes the mixing of combustion gas and flue gas. This not only enhances fuel-air mixing during the ejection process and improves the uniformity of combustion gas distribution at the sleeve nozzle, but also effectively reduces the peak flame temperature and velocity by enhancing mixing, thereby suppressing NOx formation.

[0020] 4. This utility model adopts a modular integrated design, integrating the swirl micro-mixing nozzle and the main combustion nozzle into an independently detachable unit. During maintenance or replacement, the independent module can be easily disassembled and replaced, which greatly reduces the workload, modification cost and technical risk of engineering implementation, and significantly improves the convenience of maintenance. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of this utility model;

[0022] Figure 2 for Figure 1 A sectional view;

[0023] Figure 3 for Figure 2 Cross-sectional view of the main combustion nozzle;

[0024] Figure 4 for Figure 3 Exploded view:

[0025] Figure 5 for Figure 3 A sectional view;

[0026] Figure 6 for Figure 1 Cross-sectional view of the micro-mixing nozzle;

[0027] Figure 7 for Figure 6 Schematic diagram of the structure of the medium-unit micro-mixing nozzle;

[0028] Figure 8 for Figure 7 A sectional view;

[0029] Among them: 1. Air, 2. Gas, 3. Flue gas, 4. Gas pipeline, 5. First premixing chamber, 6. Main combustion nozzle, 7. Sleeve, 8. Micro-mixing duty nozzle, 9. Main combustion pipe, 10. Sleeve, 11. Lobe structure, 12. Circular hole, 13. Fuel chamber, 14. Air chamber, 15. Second premixing chamber, 16. Air inlet, 17. Unit micro-mixing nozzle, 18. Air outlet, 19. Unit nozzle annular slit, 20. Swirl blade, 21. Small hole. Detailed Implementation

[0030] Example 1

[0031] A natural gas-hydrogen-blended low-NOx burner for boilers is disclosed. The burner employs a radially graded arrangement, with its head fixed to the furnace wall via a flange and supplied with the required gas by a gas supply pipeline. The gas supply pipeline includes an air pipeline and a main gas pipeline, wherein the gas in the main gas pipeline is a mixture of natural gas and hydrogen, which is then split into multiple gas pipelines 4. The burner includes a main combustion nozzle 6, a sleeve 7, and a micro-mixing auxiliary nozzle 8. The sleeve 7 and the micro-mixing auxiliary nozzle 8 are coaxially mounted on the air pipeline and the gas pipeline 4, respectively. The radial gap between the sleeve 7 and the micro-mixing auxiliary nozzle 8 forms an air channel (i.e., a combustion-supporting channel) to supply the combustion air required for the main combustion nozzle 6. The main combustion nozzle 6 passes through a flange and is arranged on the outer periphery of the sleeve 7.

[0032] The main combustion nozzles 6 are multiple nozzles evenly arranged in a ring around the outer periphery of the sleeve 7. Preferably, six main combustion nozzles 6 have the same structure and are arranged in a hexagonal pattern. Since the micro-mixing duty nozzle 8 is located at the center of the six main combustion nozzles 6 and is separated by the sleeve 7, it can play a role in stabilizing the flame.

[0033] The main combustion nozzle 6 is mainly composed of a main combustion pipe 9 and a sleeve 10. The intake side of each main combustion pipe 9 is fixed to a flange and connected to the gas pipeline 4. The nozzle orifice on the outlet side of the main combustion pipe 9 is constricted and has a lobed structure. The number of lobes is three or more, preferably four, and the lip thickness is thinner than the wall thickness of the main combustion pipe 9. For example, the wall thickness of the main combustion pipe 9 is 4 mm and the lip thickness is 2 mm. Specifically, according to the airflow direction, the main combustion pipe 9 is composed of a constant diameter section, a constricted section, and a nozzle section in sequence.

[0034] The sleeve 10 contains a variable cross-section channel. Following the airflow direction, the sleeve 10 consists of an inlet equal-diameter section, a constriction section, and an outlet equal-diameter section. The cavity formed by the inlet equal-diameter section and the constriction section is designated as the first premixing chamber 5. The outlet side of the main combustion pipe 9 is fitted within the first premixing chamber 5. The constriction section employs a gradually narrowing-expanding composite variable-diameter structure. The area between the constriction and expansion sections forms the throat section, which is the minimum flow cross-section of the sleeve 10, and the axial length of the constriction section is less than that of the expansion section. This structure, based on the Bernoulli effect, creates a high-speed, low-pressure zone at the throat section. Simultaneously, the expansion section extends the axial flow path, allowing the gas to undergo a "contraction acceleration-expansion deceleration" process within the variable cross-section channel, effectively extending the residence time. During installation, the lobed structure of the nozzle of the main combustion pipe 9 is fixed to the throat section of the constriction section using fasteners. Multiple circular openings 12 of equal diameter are uniformly opened on the outer wall of the equal diameter section and the gradually expanding section of the first premixing chamber 5. Preferably, eight openings 12 are arranged circumferentially along its length, each with a radius of 8 mm. For example, the throat section of the sleeve 10 and the inner diameter of the nozzle of the main combustion pipe 9 are 23.63 mm and 10.26 mm, respectively.

[0035] When the combustion gas flows through the nozzle of the main combustion tube 9, it is disturbed by the lobe structure, inducing enhanced vortex structures (such as horseshoe vortices) at the lip edge. These vortices significantly enhance the mixing of combustion gas and flue gas in the shear layer, improving the uniformity of combustion gas distribution at the main combustion nozzle. Simultaneously, the constricted section of the outer constriction sleeve 10 creates an ejector effect, drawing furnace flue gas from the circumferential opening 12 into the sleeve. The introduced flue gas further mixes with the combustion gas, diluting the local equivalence ratio, thereby effectively suppressing local high-temperature peaks in the main combustion tube 9 region.

[0036] According to the direction of airflow, the upstream of the micro-mixing duty nozzle 8 is connected to the air supply pipeline, and its downstream end face is always flush with the end face of the sleeve 7.

[0037] The micro-mixing duty nozzle 8 includes a housing and a unit micro-mixing nozzle 17. The housing is provided with a flow divider, which divides the housing into upstream and downstream chambers according to the direction of airflow.

[0038] Within the upstream cavity, a ring-shaped fuel chamber 13 is machined on the diversion baffle. The cross-section of the fuel chamber gradually widens according to the airflow direction, and an air guide channel (i.e., a funnel-shaped trapping structure with a reduced-width horn-like longitudinal section) is formed in the middle of the fuel chamber 13, communicating with the downstream cavity. The air guide channel is coaxially arranged with the housing, and its inlet side communicates with the diverted air, while its outlet side is located downstream. The air guide channel is cylindrical, with an air inlet 16 on its outlet sidewall. The air inlet 16 consists of multiple densely packed, uniformly sized small holes arranged circumferentially. By creating dense and small air inlets 16, the uniformity of the outflowing air can be improved, and it also facilitates a more uniform passive distribution of subsequent air.

[0039] Within the downstream cavity, the diversion baffle, the side wall of the housing, and the inner end wall together form an air cavity 14, and the air inlet 16 is located within the air cavity 14. An air outlet 18, coaxial with the air guide channel, is provided on the end face of the housing. The air outlet 18 is a cylindrical channel, and an igniter is installed within it. An array of injection holes communicating with the air cavity 14 is arranged on the end face of the housing. The injection holes are located on the outer periphery of the air outlet 18, and both the air outlet 18 and the injection holes communicate with the air cavity 14. The axial space from one end face of the injection hole to the other end face is designated as a second premixing cavity 15.

[0040] The air inlet of the unit micro-mixing nozzle 17 is inserted through the injection hole and passes sequentially through the second premixing chamber 15, the air chamber 14, and the flow divider before communicating with the gas chamber 13. The air outlet of the unit micro-mixing nozzle 17 is located inside the second premixing chamber 15, and its end is flush with the end face of the housing. The radial distance between the unit micro-mixing nozzle 17 and the wall of the second premixing chamber 15 forms the unit nozzle annular slit 19.

[0041] The unit micro-mixing nozzle 17 is a straight pipe of equal diameter, for example, the outer diameter of the unit micro-mixing nozzle 17 is 12mm and the inner diameter is 10mm. The size of the second premixing chamber 15 is related to the full development of the air after it enters and the influence of the unit micro-mixing nozzle 17 on the mixing effect. Therefore, the axial spatial length of the air chamber 14 and the second premixing chamber 15 is the same, for example, the axial spatial length of both is 100mm. Preferably, the axial spatial length of the fuel chamber 13 is also the same as that of the air chamber 14. The specific length can be adjusted up or down according to the size of the space.

[0042] In accordance with the direction of airflow, the unit micro-mixing nozzle 17 is provided with swirl blades 20 and orifices 21 sequentially on its outer wall within the second premixing chamber 15. Multiple swirl blades 20 are circumferentially spaced on the outer wall of the unit micro-mixing nozzle 17, spaced apart from the orifices 21, preferably with a spacing of 20 mm. The radial length of each swirl blade 20 is the same as the size of the unit nozzle annular slot 19, both being 4 mm. There are six swirl blades 20, and the blade inclination angle of each swirl blade 20 is 45 degrees. By adjusting the inclination angle of the swirl blades 20, the swirl intensity can be precisely controlled, which is beneficial for achieving the desired combustion structure and thus achieving stable flame combustion. The orifices 21 are multiple circles of equal diameter, circumferentially evenly spaced 10 mm from the downstream end face of the nozzle body; preferably, there are eight orifices 21 with a radius of 1 mm. The location of the orifices 21 and their distance from the downstream end face determine the premixing length and mixing level of the fuel gas and air.

[0043] The distance between two unit micro-mixing nozzles 17 can be adjusted according to the size of the duty space located at the radial center of the burner. The specific dimensions of the unit micro-mixing nozzle 17, the size of the unit nozzle circumferential slit 19, the opening size of the orifice 21, and the axial position can all be determined according to the gas composition.

[0044] Combustion enters the combustion chamber 13 via combustion pipeline 4 and is distributed to each unit micro-mixing nozzle 17, finally exiting through orifice 21. Simultaneously, upstream staged air, after being captured by a funnel structure, enters the air chamber 14 through orifice 16. Within the air chamber 14, the air undergoes secondary distribution: part flows out through outlet 18 as cooling air, providing protective cooling to the igniter; the other part enters the second premixing chamber 15, where the airflow, after passing through swirl vanes 20, forms a rotating flow field, generating turbulent vortex structures. The air, after passing through swirl vanes 20, mixes with the combustion gas ejected through orifice 21 to form a partially premixed gas. Swirl vanes 20 significantly increase the mixing rate between the air and the combustion gas ejected through orifice 21. This premixed gas is ignited at the annular slot 19 of the unit nozzle downstream of the second premixing chamber 15. Through the coordinated operation of multiple unit micro-mixing nozzles 17 arranged in an array, the traditional single large-scale diffusion combustion mode is transformed into a spatially uniform small-scale partially premixed combustion mode. By utilizing the partial premixing characteristics to avoid the risks of backfire and burner end erosion, and by reducing the local equivalence ratio and flame temperature through small-scale uniform combustion, NOx formation can be effectively suppressed.

[0045] Example 2

[0046] This embodiment is based on Embodiment 1, but only the unit micro-mixing nozzle 17 is optimized. The other structures are the same as in Embodiment 1.

[0047] Even without the swirl vane 20 treatment on the outlet side of the unit micro-mixing nozzle 17, a sluggish recirculation zone can still be formed at the downstream end of the unit micro-mixing nozzle 17, which also has the same stable combustion effect.

[0048] The above description is merely a preferred embodiment of this utility model. These specific embodiments are different implementations based on the overall concept of this utility model, and the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A natural gas-blended low-NOx burner for boilers, characterized in that: The system includes a main combustion nozzle (6), a sleeve (7), and a micro-mixing duty nozzle (8) arranged coaxially from the outside to the inside. The sleeve (7) and the micro-mixing duty nozzle (8) are a set structure that is connected to the air and gas source pipelines respectively, and the two form a combustion-supporting channel through a radial clearance fit. Multiple main combustion nozzles (6) are evenly distributed around the sleeve (7). The gas source is connected to each main combustion nozzle (6). A first premixing chamber (5) is provided inside the main combustion nozzle (6). The first premixing chamber (5) is used to mix the main combustion gas... The gas (2) flowing out of the nozzle (6) is mixed with the flue gas (3) drawn in from the outside of the main combustion nozzle (6) and then sprayed out; the air source is introduced into the combustion channel and the micro-mixing duty nozzle (8) through the sleeve (7). The micro-mixing duty nozzle (8) is cylindrical, and its inner cavity is divided into upstream and downstream cavities by a flow divider. An annular gas chamber (13) is provided in the upstream cavity. An air guide channel connecting the upstream cavity and the downstream cavity is formed along the axial length of the outer wall of the inner ring of the gas chamber (13). The air guide channel... The longitudinal section of the channel is tapered funnel-shaped, and its outlet side is located in the downstream cavity. In the downstream cavity, the diversion baffle, the shell sidewall, and the end wall together form an air cavity (14). An air outlet (18) coaxial with the air guide channel and a second premixing cavity (15) communicating with the air cavity (14) are respectively machined on the cylindrical end face of the micro-mixing nozzle (8). The second premixing cavity (15) consists of multiple circumferentially arrayed through holes on the outer periphery of the air outlet (18). In each second premixing cavity (15) A unit micro-mixing nozzle (17) is provided; air (1) enters the air chamber (14) through the air guide channel, and the air (1) after entering is distributed to the air outlet (18) and the second premixing chamber (15); the gas (2) is distributed to each unit micro-mixing nozzle (17) through the gas chamber (13), and the gas (2) flowing in the unit micro-mixing nozzle (17) is sprayed out from the side wall of the unit micro-mixing nozzle (17) at the second premixing chamber (15) and mixed with the air (1) before being sprayed out from the second premixing chamber (15).

2. A natural gas hydrogen-blended low-NOx burner for boilers as described in claim 1, characterized in that: The micro-mixing duty nozzle (8) includes a cylindrical housing, and an array of injection holes for accommodating the unit micro-mixing nozzle (17) are machined on the downstream end face of the housing. The injection holes are opened on the outer periphery of the air outlet (18), and the second premixing chamber (15) is the axial space from one end face of the injection hole to the other end face.

3. A natural gas hydrogen-blended low-NOx burner for boilers as described in claim 1, characterized in that: The axial spatial lengths of the fuel chamber (13), air chamber (14), and second premix chamber (15) are the same.

4. A natural gas hydrogen-blended low-NOx burner for boilers as described in any one of claims 1-3, characterized in that: The unit micro-mixing nozzle (17) is a straight pipe of equal diameter, with small holes (21) for outward spraying spaced outward at circumferential intervals at the downstream end face of the pipe body.

5. A natural gas hydrogen-blended low-NOx burner for a boiler as described in claim 4, characterized in that: Swirl blades (20) are provided circumferentially on the outer wall of the unit micro-mixing nozzle (17). The swirl blades (20) are fixed on the side away from the small hole (21) and close to the upstream side of the pipe body.

6. A natural gas hydrogen-blended low-NOx burner for a boiler as described in claim 1, characterized in that: The main combustion nozzle (6) is composed of a main combustion pipe (9) and a sleeve (10). The intake side of the main combustion pipe (9) is connected to the gas source. The sleeve (10) is composed of an intake equal diameter section, a constricted section and an outlet equal diameter section. The first premixing chamber (5) is a cavity formed by the intake equal diameter section and the constricted section. The outlet side of the main combustion pipe (9) is fitted inside the first premixing chamber (5). An opening (12) is provided on the outer wall of the first premixing chamber (5) to connect the inside of the sleeve (10) with the outside.

7. A natural gas hydrogen-blended low-NOx burner for a boiler as described in claim 6, characterized in that: The constricted section has a gradually narrowing-expanding composite variable diameter structure, and the nozzle of the main combustion pipe (9) is located at the throat section of the composite variable diameter structure.

8. A natural gas hydrogen-blended low-NOx burner for a boiler as described in claim 7, characterized in that: The throat section is the minimum flow section of the sleeve (10), and the axial length of the converging section is less than that of the expanding section.

9. A natural gas hydrogen-blended low-NOx burner for a boiler as described in any one of claims 6-8, characterized in that: The main combustion pipe (9) nozzle diameter is a constricted shape with a lobe structure, and the number of lobes in the lobe structure is greater than three.

10. A natural gas hydrogen-blended low-NOx burner for a boiler as described in claim 6, characterized in that: The opening (12) is a circle with a uniform diameter.

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