Natural gas and hydrogen mixing device with bending structure and gas-fired boiler system

Abstract

The invention relates to the technical field of boilers, and provides a natural gas and hydrogen mixing device with a bent structure and a gas-fired boiler system.The natural gas and hydrogen mixing device comprises a natural gas pipeline and a hydrogen pipeline which are perpendicular to each other; the hydrogen pipeline is of a regular triangle structure, a first angle of the regular triangle structure is arranged at the center of the upstream of the natural gas pipeline, a first surface opposite to the first angle is arranged at the downstream of the natural gas pipeline, and a plurality of hydrogen output holes for outputting hydrogen are formed in the first surface; the hydrogen pipeline is of a bent structure bent towards the upstream of natural gas in the natural gas pipeline, the bent structure is divided into two parts along the central axis of the natural gas pipeline, and the first part extends to the central axis from an inlet of the hydrogen pipeline to the upstream of the natural gas; the second part extends from the central axis to the inner wall face of the natural gas pipeline in the natural gas downstream direction. The hydrogen and the natural gas are uniformly distributed in a short distance, and the phenomenon of non-uniform mixing is obviously reduced.

Description

Technical Field

[0001] This invention relates to the field of boiler technology, and in particular to a natural gas-hydrogen blending device with a bent structure and a gas-fired boiler system. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] A boiler is an energy conversion device. The energy input to a boiler can be in the form of chemical energy from fuel, electrical energy, or thermal energy from high-temperature flue gas. After conversion, the boiler outputs steam, high-temperature water, or organic heat carriers with a certain amount of thermal energy. With the completion of projects such as the West-East Gas Pipeline and the continuous development of gaseous energy sources such as biogas, gas-fired boilers that use natural gas, coal gas, coal gas, biogas, and other gases as fuels are becoming increasingly widely used.

[0004] Currently, there are approximately four types of fuels used in residential and industrial boilers: coal, fuel oil, natural gas, and machine-made organic firewood. However, these are all non-renewable energy sources that will gradually be depleted as people consume them and time passes. For a long time, making water a reusable alternative energy source has been a cherished aspiration: water molecules are composed of hydrogen and oxygen (H2O). By actual weight, each kilogram of water contains approximately 11% hydrogen and 89% oxygen. Hydrogen can burn, and oxygen supports combustion. The calorific value of hydrogen combustion is more than three times that of gasoline, and the product of hydrogen combustion is water, which does not pollute the environment, making it a very clean and reusable fuel.

[0005] Using hydrogen and natural gas together as fuels shows great promise. However, blending hydrogen and natural gas is necessary before they can be used together. Hydrogen's extremely low density, significantly different from natural gas, makes uniform mixing difficult. Traditional methods require long pipeline distances and considerable installation space. Incomplete mixing and prolonged contact of large amounts of hydrogen with metals can lead to hydrogen embrittlement, a safety concern. If blending occurs before gas equipment, it must be done as quickly and evenly as possible to ensure safe use. Therefore, whether transporting hydrogen through natural gas pipelines or using a mixture of both, it is essential to employ technical means to achieve uniform blending of hydrogen and natural gas within the shortest possible pipeline distance. Furthermore, insufficient mixing of hydrogen and natural gas can result in low combustion efficiency, incomplete combustion, and the potential for localized deflagration due to excessive hydrogen. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a natural gas-hydrogen blending device and a gas boiler system with a bent structure. The bent structure guides natural gas to form a more complex vortex flow field in the downstream region of the hydrogen pipeline. These periodic perturbation vortices further expand the blending range of hydrogen and natural gas, enabling hydrogen to be evenly distributed with natural gas over a short distance and significantly reducing the phenomenon of uneven blending.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a natural gas-hydrogen blending device with a bent structure, comprising a natural gas pipeline and a hydrogen pipeline arranged perpendicularly to each other; The hydrogen pipeline has an equilateral triangle structure. The first angle of the equilateral triangle structure is located at the center of the upstream of the natural gas pipeline, and the first face opposite to the first angle is located downstream of the natural gas pipeline. Multiple hydrogen output holes for hydrogen output are provided on the first face. The hydrogen pipeline is a bent structure within the natural gas pipeline, curving upstream towards the natural gas source. The bent structure is divided into two parts along the central axis of the natural gas pipeline. The first part extends upstream from the hydrogen pipeline inlet to the central axis, and the second part extends downstream from the central axis to the inner wall of the natural gas pipeline.

[0008] Furthermore, the bent structure is a straight structure, and the acute angle formed by the first part and the central axis is smaller than the acute angle formed by the second part and the central axis.

[0009] Furthermore, the bending structure is a curved structure, and along the direction of hydrogen flow, the acute angle formed by the first part of the curved tangent and the central axis gradually increases, while the acute angle formed by the second part of the curved tangent and the central axis gradually decreases.

[0010] Furthermore, along the direction of hydrogen flow, the acute angle formed by the first part of the curve tangent and the central axis gradually increases, while the acute angle formed by the second part of the curve tangent and the central axis gradually decreases.

[0011] Furthermore, the hydrogen pipeline is inserted vertically into the natural gas pipeline, and the flow area of ​​the hydrogen outlet hole increases from top to bottom in the vertical direction.

[0012] Furthermore, in the vertical direction from top to bottom, the flow area of ​​the hydrogen output orifice increases progressively.

[0013] Furthermore, the hydrogen pipeline is inserted vertically into the natural gas pipeline from below.

[0014] Furthermore, the hydrogen outlet is provided with a flow guiding device, which causes the hydrogen outlet to tilt upward at a certain angle.

[0015] Furthermore, along the vertical direction from bottom to top, the flow guiding device causes the hydrogen outlet port to tilt upward at an increasingly larger angle.

[0016] A second aspect of the present invention provides a gas-fired boiler system as described in the first aspect, comprising a boiler and a natural gas-hydrogen blending device having a bent structure as described in the first aspect.

[0017] Compared with the prior art, the beneficial effects of the present invention are: The present invention discloses a natural gas-hydrogen blending device with a bent structure, which arranges the hydrogen pipeline in a zigzag pattern in the middle section of the natural gas pipeline, with the zigzag pointing towards the natural gas inlet. This zigzag structure guides the natural gas to form a more complex vortex flow field in the downstream region of the hydrogen pipeline. These periodic perturbation vortices further expand the blending range of hydrogen and natural gas, enabling uniform distribution of hydrogen and natural gas over a short distance and significantly reducing blending unevenness.

[0018] The present invention discloses a natural gas-hydrogen blending device with a bent structure. The bent structure not only increases the effective contact area between the turbulence structure and the natural gas, but also utilizes the kinetic energy in the direction of natural gas inlet to reduce the formation of local stagnant zones, thus overcoming the disadvantage of low blending efficiency in traditional vertical conveying pipelines.

[0019] The present invention discloses a natural gas-hydrogen blending device with a bent structure. Because the triangular hydrogen pipe acts as a turbulent flow relative to the natural gas flow, vortex turbulence occurs when the natural gas passes through this structure, thereby enhancing the blending with hydrogen. Furthermore, as the natural gas turbulence passes through this structure, a negative pressure is generated on the surface directly opposite the natural gas flow (the surface where the flute-shaped orifice is located), allowing hydrogen to be introduced at a pressure lower than the natural gas pressure. Compared to traditional circular pipes as hydrogen inlet pipes, the triangular design generates higher frequency vortices and stronger turbulence at its rear, resulting in a highly efficient blending effect. This also shortens the uniform blending distance, saving pipeline and installation space. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 A side view of the natural gas-hydrogen blending device with a bent structure provided by the present invention; Figure 2 A front view of the natural gas-hydrogen blending device with a bent structure provided by the present invention; Figure 3 A front view of the first or second part provided by the present invention; Figure 4 A top view of the natural gas-hydrogen blending device with a bent structure provided by the present invention; Figure 5 This is a cross-sectional structural diagram of the gas-fired boiler system provided by the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any component or element in this invention. They should not be construed as limiting the invention.

[0026] In this invention, terms such as "fixed connection," "connected," and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0027] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0028] Example 1 This embodiment 1 provides a natural gas-hydrogen blending device with a bent structure, such as... Figure 1 As shown, it includes natural gas pipeline 1 and hydrogen pipeline 2.

[0029] Natural gas pipeline 1 is circular, with a natural gas inlet at one end and a boiler at the other.

[0030] Hydrogen pipeline 2 is inserted into natural gas pipeline 1, and then the hydrogen is mixed into a fuel mixture in natural gas pipeline 1 before being delivered to the burner of the boiler.

[0031] Hydrogen pipeline 2 is equipped with a flow regulating valve, which can automatically adjust according to boiler load and hydrogen blending ratio. The blending ratio is automatically stabilized based on the co-firing effect and pressure fluctuations of the two gases.

[0032] The hydrogen pipeline 2 is a bent structure in the natural gas pipeline 1 that bends upstream towards the natural gas. The bent structure is divided into two parts along the central axis of the natural gas pipeline 1. The first part 2-1 extends from the inlet of the hydrogen pipeline 2 upstream towards the central axis, and the second part 2-2 extends from the central axis downstream towards the inner wall of the natural gas pipeline 1. A hydrogen outlet hole 2-3 is provided on the hydrogen pipeline 2 located inside the natural gas pipeline 1.

[0033] This invention, by setting a bent structure facing the direction of natural gas flow, causes the natural gas to flow in both vertical and horizontal directions, resulting in more uniform dispersion of the natural gas. Moreover, the natural gas flow extends along the flow direction to the bent structure of the first part 2-1 and the second part 2-2. As the natural gas climbs up the slope of the first part 2-1 and the second part 2-2, the flow can be slowed down, and during the climbing process, it can be fully mixed with hydrogen, thereby improving the mixing effect.

[0034] The present invention arranges the hydrogen pipeline 2 in a zigzag pattern in the middle part of the natural gas pipeline 1, with the zigzag pointing towards the natural gas inlet. This structural design not only increases the effective contact area between the turbulence structure and the natural gas, but also uses the kinetic energy in the direction of the natural gas inlet to reduce the formation of local stagnant zones, thus overcoming the disadvantage of low mixing efficiency in traditional vertical transmission pipelines.

[0035] The broken-line structure of this invention guides natural gas to form a more complex vortex flow field in the downstream region of the hydrogen pipeline. These periodic perturbation vortices further expand the mixing range of hydrogen and natural gas, enabling hydrogen to be evenly distributed with natural gas over a short distance and significantly reducing the phenomenon of uneven mixing.

[0036] In this embodiment, the bending structure is either a straight bending structure or a curved bending structure.

[0037] As one implementation method, such as Figure 1 As shown, the bent structure is a straight structure, and the acute angle formed by the first part 2-1 and the central axis is smaller than the acute angle formed by the second part 2-2 and the central axis. This arrangement makes the first part 2-1 longer than the second part 2-2. Because the hydrogen flow rate in the first part 2-1 is large, thorough mixing is necessary. By increasing the length, the flow direction is extended, the natural gas flow rate is reduced, and thorough mixing is achieved.

[0038] As another implementation, the bending structure is a curved structure. Along the direction of hydrogen flow, the acute angle formed by the tangent of the first part 2-1 curve and the central axis gradually increases, and then the acute angle formed by the tangent of the second part 2-2 curve and the central axis gradually decreases. By setting the above angle change, the flow path of hydrogen in the direction of flow can be further extended, while the flow velocity of natural gas can be further reduced, allowing for thorough mixing; at the same time, the above setting can reduce the flow pressure.

[0039] Preferably, along the direction of hydrogen flow, the acute angle formed by the tangent of the first part 2-1 curve and the central axis gradually increases, while the acute angle formed by the tangent of the second part 2-2 curve and the central axis gradually decreases. This arrangement further ensures thorough mixing of natural gas and hydrogen.

[0040] like Figure 2 and Figure 3 As shown, the cross-section of hydrogen pipeline 2 is an equilateral triangle, thus making hydrogen pipeline 2 an equilateral triangle structure; the equilateral triangle structure is symmetrically distributed along the axis of natural gas pipeline 1, and the first angle 2-4 of the equilateral triangle structure is located at the center of the upstream of natural gas pipeline 1, as shown. Figure 4 As shown; the first face 2-5, which is opposite to the first corner 2-4, is located downstream of the natural gas pipeline 1, and a hydrogen output hole 2-3 for supplying hydrogen is provided on the first face 2-5.

[0041] Hydrogen pipe 2 is a triangular flute-shaped pipe with a triangular cross-section. Hydrogen pipe 2 is placed perpendicular to natural gas pipe 1, with the acute angle facing the direction of natural gas flow. The plane facing away from the direction of natural gas flow is machined with flute-shaped holes, i.e. hydrogen outlet holes 2-3. Hydrogen is introduced from both ends or one end of the flute-shaped pipe and discharged from the flute-shaped holes.

[0042] The equivalent diameter, length, and bending angle of the two bends can be adjusted according to the diameter of the natural gas header and the hydrogen flow rate. The number, spacing, and diameter of the outflow orifices can be adjusted according to the hydrogen flow rate.

[0043] The cross-sectional dimensions of hydrogen pipeline 2 and natural gas pipeline 1 can be changed according to the flow rates of natural gas and hydrogen.

[0044] In this embodiment, the hydraulic diameter D1 of the natural gas pipeline 1 is 3-7 times, preferably 5-6 times, the hydraulic diameter D2 of the hydrogen pipeline 2. The hydrogen flow velocity V1 is 1.1-1.7 times the natural gas flow velocity V2. The above-mentioned velocities and pipe diameters are optimized through simulation and experiments. This experiment uses a qualitative analysis method to conduct experiments on hydrogen pipelines with different hydraulic diameters, and it is found that as the ratio of the hydraulic diameter of the natural gas pipeline to that of the hydrogen pipeline increases or decreases, the mixing effect deteriorates.

[0045] Among them, D1 / D2 = a * V1 / V2, where 1.8 < a < 7, preferably 3 < a < 5. The above speed and pipe diameter ratio is a structure optimized through simulation and experiment. The ratio of pipe diameter to speed cannot be too large or too small. Being too large or too small will result in poor mixing. When the ratio of pipe diameter to speed reaches the optimal ratio, the mixing ratio of hydrogen and natural gas is the best.

[0046] In this embodiment, the size parameters of the hydrogen pipeline 2 and the natural gas pipeline 1, the hydrogen flow rate and the natural gas flow rate are set as follows: the diameter of the natural gas pipeline: 250 - 350 mm, the natural gas flow rate 6 - 8 m / s; preferably the length is 2200 - 2800 mm; the hydraulic diameter of the hydrogen pipeline is 55 - 75 mm, and the hydrogen flow rate is 8 - 11 m / s. The above sizes are the results of optimization through a large number of numerical simulations and experiments. Through the sizes selected above, the best mixing effect can be achieved.

[0047] As an implementation method, the hydrogen pipeline 2 is inserted into the natural gas pipeline 1 along the vertical direction (perpendicular to the natural gas flow direction). From top to bottom in the vertical direction, the flow area of the hydrogen output hole 2 - 3 becomes larger and larger. Because the density of hydrogen is relatively small, much smaller than that of natural gas, hydrogen naturally flows upward. By setting the change in the through-hole area size in the up and down direction, more air can enter the lower space, so that the hydrogen is evenly distributed in the overall space, avoiding uneven mixing caused by uneven hydrogen distribution, resulting in low combustion efficiency and different combustion points due to local uneven distribution, and avoiding accidents such as deflagration.

[0048] Preferably, from top to bottom in the vertical direction, the amplitude of the increasing flow area of the hydrogen output hole 2 - 3 continuously increases. Through the above settings, the hydrogen can be further evenly distributed and the combustion efficiency can be improved.

[0049] As another implementation method, the hydrogen pipeline 2 is inserted into the natural gas pipeline 1 from below along the vertical direction. By inserting from below, as much hydrogen as possible is distributed in the lower part, reducing the uneven distribution caused by the small density of hydrogen.

[0050] Preferably, a flow guiding device is provided for the hydrogen output hole 2 - 3, and the flow guiding device makes the hydrogen output hole 2 - 3 tilt upward at a certain angle. From bottom to top along the vertical direction, the flow guiding device makes the hydrogen output hole 2 - 3 tilt more and more upward. By setting it like this, the problem of small hydrogen density can be avoided, so that the inlet hydrogen at the bottom can flow downward as much as possible, thereby overcoming the density problem and greatly improving the overall mixing uniformity with natural gas.

[0051] Such as Figure 1As shown, when natural gas enters from the left inlet and bypasses hydrogen pipeline 2, a low-pressure zone and periodic vortices (Karman vortex streets) are formed behind hydrogen pipeline 2 due to flow separation. These vortices are continuously generated and detached behind hydrogen pipeline 2, providing strong dynamic support for the mixing of hydrogen and natural gas. In the separation region behind hydrogen pipeline 2, vortex motion generates significant shear and turbulence effects. Through these effects, the contact area between natural gas and hydrogen is significantly increased, thereby improving the mixing efficiency of the two gases. Hydrogen directly enters the surrounding separation region and, under the attraction of the low-pressure zone, rapidly mixes with natural gas. This arrangement design fully utilizes the vortex characteristics within the separation region, effectively enhancing the mixing process. The high-speed shear layer behind hydrogen pipeline 2 further enhances the gas mixing effect. The strong coupling between hydrogen and the shear layer significantly weakens the separation effect of the gas interface. By utilizing the mechanism of surrounding separation and vortex-enhanced mixing, rapid and uniform mixing is achieved.

[0052] This invention, specifically for low-density hydrogen gas, also offers the following technical advantages: Enhanced airflow disturbance and turbulent mixing. The triangular cylindrical structure of hydrogen pipe 2 has a unique flow disturbance effect, especially the vortices (Kármán vortex street) formed behind the cylinders, which enhance the turbulence of the airflow. For low-density hydrogen, it is more likely to stratify or become unevenly distributed in the flow field. The triangular turbulence cylinders accelerate the contact and mixing of hydrogen and natural gas by generating and maintaining strong vortices. Low-density hydrogen is rapidly drawn into these turbulent regions, and the collisions between gas molecules are enhanced by the vortices, thereby improving mixing efficiency.

[0053] Low-pressure zone and hydrogen diffusion. The low-pressure zone behind the triangular prism of hydrogen pipeline 2, combined with the low density of hydrogen, provides favorable conditions for hydrogen diffusion. Due to its lower density, hydrogen diffuses more quickly in low-pressure zones than natural gas. This design utilizes the attraction of the low-pressure zone to encourage hydrogen to rapidly enter the vortex region and achieve uniform mixing with natural gas in a short time, avoiding the uneven flow problems that may arise due to hydrogen's lower density.

[0054] The shear layer effect enhances mixing. The high-speed shear layer formed behind the triangular turbulence column of hydrogen pipeline 2, coupled with the strong coupling of hydrogen, further improves mixing efficiency. The shear layer, by providing a strong velocity gradient, forcefully pushes hydrogen and natural gas towards each other, increasing the contact area between the two gases. This is particularly important for hydrogen, as its lower density makes it prone to stratification at lower flow rates; the high-speed movement of the shear layer effectively breaks up this stratification, achieving rapid and uniform mixing.

[0055] The turbulence design enhances hydrogen stability. Due to its low density and high diffusivity, hydrogen is prone to uneven distribution in the airflow, potentially leading to localized hydrogen enrichment or depletion, which affects the stability of the combustion process. The triangular turbulence column in hydrogen pipe 2 enhances the turbulence effect of the airflow by altering the flow field structure, reducing the uneven distribution of hydrogen. Under the influence of the column, hydrogen avoids excessive stratification through the action of vortices and shear layers, ensuring the stability of the mixture.

[0056] Example 2 Embodiment 2 of the present invention provides a gas-fired boiler system.

[0057] This embodiment provides a gas-fired boiler system that improves combustion efficiency and reduces carbon monoxide emissions by fully mixing hydrogen and natural gas, while also preventing potential hazards.

[0058] This embodiment provides a gas-fired boiler system, such as Figure 5 As shown, the system includes a boiler and a natural gas-hydrogen blending device with a bent structure as described in Example 1. The natural gas-hydrogen blending device with a bent structure is connected to the boiler's burner nozzles, delivering fuel to the burner's fuel passage. The boiler's burners are located below the boiler, and external air is introduced into the furnace via natural draft. This air enters the boiler through an air inlet, mixes thoroughly with the natural gas-hydrogen blended fuel gas ejected from the burner nozzles, and then burns within the furnace.

[0059] The boiler comprises a shell composed of side plates and central plates distributed within the shell. The gaps between the central plates form flue gas passages, and the furnace is located between the central plates and the burners. Heat transfer aids are provided on the surfaces of both the central and side plates.

[0060] During combustion, the mixture of natural gas and hydrogen reacts fully with air in the furnace, releasing heat. The resulting flue gas rises through the boiler's distributed, structured intermediate boiler sections, which are filled with water, allowing for heat exchange between the flue gas and the water. In this way, the boiler effectively transfers the heat generated by combustion to the boiler water, thereby improving thermal efficiency. This boiler employs a no-return design, meaning the flue gas does not pass through a return path but is directly discharged from the boiler. Furthermore, the boiler utilizes natural draft, reducing reliance on external power supply and further enhancing energy utilization.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A natural gas-hydrogen blending device with a bent structure, characterized in that: This includes natural gas pipelines and hydrogen pipelines that are perpendicular to each other; The hydrogen pipeline has an equilateral triangle structure. The first angle of the equilateral triangle structure is located at the center of the upstream of the natural gas pipeline, and the first face opposite to the first angle is located downstream of the natural gas pipeline. Multiple hydrogen output holes for hydrogen output are provided on the first face. The hydrogen pipeline is a bent structure within the natural gas pipeline, curving upstream towards the natural gas source. The bent structure is divided into two parts along the central axis of the natural gas pipeline. The first part extends upstream from the hydrogen pipeline inlet to the central axis, and the second part extends downstream from the central axis to the inner wall of the natural gas pipeline.

2. The natural gas-hydrogen blending device with a bent structure as described in claim 1, characterized in that: The bent structure is a straight structure, and the acute angle formed by the first part and the central axis is smaller than the acute angle formed by the second part and the central axis.

3. The natural gas-hydrogen blending device with a bent structure as described in claim 1, characterized in that: The bending structure is a curved structure. Along the direction of hydrogen flow, the acute angle formed by the first part of the curved tangent and the central axis gradually increases, while the acute angle formed by the second part of the curved tangent and the central axis gradually decreases.

4. A natural gas-hydrogen blending device with a bent structure as described in claim 3, characterized in that: Along the direction of hydrogen flow, the acute angle formed by the first part of the curve tangent and the central axis gradually increases, while the acute angle formed by the second part of the curve tangent and the central axis gradually decreases.

5. A natural gas-hydrogen blending device with a bent structure as described in claim 1, characterized in that: The hydrogen pipeline is inserted vertically into the natural gas pipeline, and the flow area of ​​the hydrogen outlet increases from top to bottom in the vertical direction.

6. A natural gas-hydrogen blending device with a bent structure as described in claim 5, characterized in that: In the vertical direction from top to bottom, the flow area of ​​the hydrogen outlet hole increases continuously.

7. A natural gas-hydrogen blending device with a bent structure as described in claim 1, characterized in that: The hydrogen pipeline is inserted vertically into the natural gas pipeline from below.

8. A natural gas-hydrogen blending device with a bent structure as described in claim 1, characterized in that: The hydrogen outlet is equipped with a flow guiding device, which causes the hydrogen outlet to tilt upward at a certain angle.

9. A natural gas-hydrogen blending device with a bent structure as described in claim 8, characterized in that: Along the vertical direction from bottom to top, the flow guiding device causes the hydrogen outlet to tilt upward at an increasingly larger angle.

10. A gas-fired boiler system, characterized in that: It includes a boiler and a natural gas-hydrogen blending device with a bent structure as described in any one of claims 1-9.

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