A hydrogen-ammonia mixed low-nitrogen burner

Abstract

This invention proposes a hydrogen-ammonia mixed low-NOx burner, belonging to the field of burner technology. It solves the current combustion technology problems of using hydrogen and ammonia together as gaseous fuels, such as poor ammonia combustion reactivity, rapid hydrogen combustion leading to backfire and nozzle damage, and high NOx emission concentrations. It includes a hydrogen inlet pipe, an ammonia inlet pipe, a mixer, an annular header, ammonia branch pipes, and ammonia nozzles. The hydrogen inlet pipe includes a central hydrogen pipe and a combustion-supporting hydrogen pipe. The outlet end of the central hydrogen pipe passes through the annular header and is located at the center of the burner. The inlet end of the combustion-supporting hydrogen pipe is connected to the central hydrogen pipe, and its outlet end is connected to the mixer. The outlet end of the ammonia inlet pipe is connected to the mixer, and the outlet end of the mixer is connected to the annular header. The annular header connects to multiple ammonia branch pipes arranged in a ring, and each ammonia branch pipe has an ammonia nozzle at its outlet end. It is mainly used for hydrogen-ammonia mixed combustion.

Description

Technical Field

[0001] This invention belongs to the field of burner technology, and in particular relates to a hydrogen-ammonia mixed low-NOx burner. Background Technology

[0002] The widespread use of traditional fossil fuels and their non-renewable nature have led to increasingly serious environmental pollution, the greenhouse effect, and energy crises. Energy depletion and climate change have become two major challenges facing humanity in the 21st century. To fundamentally address the resource constraints and environmental problems facing society as a whole, applying carbon-free fuels to replace traditional fossil fuels in the combustion field is an important technological approach.

[0003] Hydrogen energy is considered one of the most ideal clean energy sources. Hydrogen fuel has advantages such as good combustibility, low ignition energy, and fast combustion reaction speed; water is the only byproduct of complete hydrogen combustion. However, hydrogen combustion also has many drawbacks, such as low volumetric energy density and the production of thermal nitrogen oxides (NOx) due to the high combustion temperature. x Pollutants and the rapid combustion rate of hydrogen can lead to problems such as pre-ignition and backfire, which limit the widespread use of pure hydrogen fuel. Ammonia is a low-cost chemical raw material. Under complete combustion conditions, the only products are nitrogen and water. Ammonia has a high volumetric energy density, does not produce CO2 during combustion, is easy to compress, liquefy, store, and transport, and has low storage and transportation costs. However, using ammonia as a fuel also has some significant drawbacks. Pure ammonia fuel has a low laminar combustion flame propagation speed, a relatively high auto-ignition temperature, and requires high ignition energy. Ammonia has a narrow flammability limit, with a flammable volume fraction of 15.5%-27% in air, making complete combustion of pure ammonia difficult. Furthermore, because ammonia itself contains nitrogen, the combustion products of ammonia contain the potential nitrogen oxides (NOx). x The emissions are relatively high.

[0004] Both ammonia and hydrogen fuels have certain shortcomings and drawbacks when used alone. However, combining these two fuels without introducing carbon-containing fuels is a better technical approach, integrating the advantages and disadvantages of both ammonia and hydrogen to achieve efficient and clean combustion with zero carbon emissions. Currently, there are relatively few known types of ammonia-hydrogen gas burners, and the solutions for efficient fuel combustion and reducing nitrogen oxides (NOx) have not been fully realized. x Regarding the coordination of emissions, and specifically the issue of poor combustion reactivity of ammonia, a common technical approach is to blend ammonia with more reactive combustible gases, such as natural gas or hydrogen. However, current burner designs tend to focus on organizing combustion rather than combining multiple combustion technologies, thus failing to effectively control nitrogen oxides (NOx). x Emissions values. Summary of the Invention

[0005] In view of this, the present invention aims to propose a hydrogen-ammonia mixed low-NOx burner to solve a series of technical problems in the current combustion of hydrogen and ammonia as gaseous fuels, such as: poor combustion reactivity of ammonia, fast combustion reaction rate of hydrogen leading to backfire and burnout of nozzles, and high NOx emission concentration.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A hydrogen-ammonia mixed low-NOx burner includes a hydrogen inlet pipe, an ammonia inlet pipe, a mixer, an annular header, ammonia branch pipes, and ammonia nozzles. The hydrogen inlet pipe includes a central hydrogen pipe and a combustion-supporting hydrogen pipe. The outlet end of the central hydrogen pipe passes through the annular header and is located at the center of the burner. The inlet end of the combustion-supporting hydrogen pipe is connected to the central hydrogen pipe, and its outlet end is connected to the mixer. The outlet end of the ammonia inlet pipe is connected to the mixer, and the outlet end of the mixer is connected to the annular header. The annular header is connected to multiple ammonia branch pipes arranged in a ring. An ammonia nozzle is provided at the outlet end of each ammonia branch pipe. A primary air annular cavity and a secondary air annular cavity are sequentially arranged outside the ammonia branch pipes of the burner. The primary air annular cavity is connected to a primary air inlet, and the secondary air annular cavity is connected to a secondary air inlet.

[0008] Furthermore, a central hydrogen regulating valve is installed on the central hydrogen pipe, and a combustion-supporting hydrogen regulating valve is installed on the combustion-supporting hydrogen pipe.

[0009] Furthermore, the outlet end of the central hydrogen pipe is connected to multiple central hydrogen branch pipes, and the central hydrogen branch pipes are connected to the central hydrogen nozzle.

[0010] Furthermore, the ends of the central hydrogen nozzle and the ammonia nozzle are provided with panels.

[0011] Furthermore, a flame stabilizer is provided on the outside of the panel, and the radial expansion angle of the flame stabilizer is 15°-25°.

[0012] Furthermore, an ammonia regulating valve is installed on the ammonia inlet pipe.

[0013] Furthermore, a primary air swirl blade is installed inside the primary air annular cavity, and the blade of the primary air swirl blade is deflected 30°-60° axially.

[0014] Furthermore, the secondary air annular cavity is provided with secondary air swirl blades, the blades of which are deflected 30°-60° axially, and the secondary air swirl blades are connected to a swirl blade adjustment mechanism.

[0015] Furthermore, the front end of the secondary air ring cavity is provided with a flange, the corresponding radial expansion angle is 15°-25°, and the side end of the secondary air ring cavity is provided with an arch.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. The combustion organization method of this invention promotes the combustion of ammonia. Adding an appropriate amount of hydrogen to ammonia can increase the combustion reaction rate of ammonia fuel. The outer layer of the jet is a mixture of ammonia and hydrogen gas. The combustibility of the mixed gas fuel is higher than that of pure ammonia fuel. The combustion organization forms a recirculation zone outside the burner nozzle. The recirculation zone can entrain high-temperature flue gas and return it to the root of the ammonia-hydrogen mixed gas jet, heating the ammonia-hydrogen mixed gas. The high temperature conditions can promote the ignition and combustion of the ammonia-hydrogen mixed gas fuel. Ultimately, the ammonia burnout rate is high and there is no ammonia escape phenomenon.

[0018] 2. This invention effectively reduces the fuel-type NO emissions from ammonia combustion. x Pollutant generation: Ammonia burns in a low-oxygen environment, and the high-temperature flame environment accelerates the pyrolysis reaction rate of ammonia, leading to rapid consumption of ammonia. The fuel-type nitrogen oxides (NOx) produced by the combustion of ammonia in a low-oxygen environment are... x The formation of NOx is suppressed. Ammonia can also act as a reducing agent for NOx, reducing the already formed nitrogen oxides (NOx). x The ammonia gas is reduced to nitrogen, thus solving the problem of high concentrations of fuel-type NO during combustion. x Technical challenges related to emission potential.

[0019] 3. The present invention has a simple structural design, and the combustion process is adjustable and controllable. The valve group can be used to adjust the ammonia-hydrogen mixing ratio of the outer gas fuel, and the swirl vane adjustment mechanism of the secondary air can adjust the swirl intensity of the secondary air, thereby changing the flow field morphology.

[0020] 4. This invention controls the hydrogen combustion process, preventing burner burnout. Since excessively rapid hydrogen combustion can lead to problems such as pre-ignition and backfire, this invention employs a diffusion combustion method, placing hydrogen in the inner layer of the gaseous fuel jet, delaying hydrogen distribution, and controlling the distance between the hydrogen combustion zone and the burner.

[0021] 5. This invention combines ammonia and hydrogen fuels without introducing carbon-containing fuels, making full use of the advantages and disadvantages of both ammonia and hydrogen fuels to achieve efficient and clean combustion with zero carbon emissions. Attached Figure Description

[0022] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 This is a schematic diagram of the structure of a hydrogen-ammonia mixed low-NOx burner according to the present invention;

[0024] Figure 2 This is a schematic diagram of the burner flow field and combustion organization.

[0025] 1-Hydrogen inlet pipe, 2-Central hydrogen pipe, 3-Central hydrogen regulating valve, 4-Combustion-supporting hydrogen pipe, 5-Combustion-supporting hydrogen regulating valve, 6-Central hydrogen branch pipe, 7-Central hydrogen nozzle, 8-Panel, 9-Flame stabilizer, 10-Ammonia inlet pipe, 11-Ammonia regulating valve, 12-Mixer, 13-Annular header, 14-Ammonia branch pipe, 15-Ammonia nozzle, 16-Primary air inlet, 17-Primary air annular cavity, 18-Primary air swirl vane, 19-Flange, 20-Secondary air inlet, 21-Secondary air annular cavity, 22-Secondary air swirl vane, 23-Swirl vane adjustment mechanism, 24-Arch. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0027] See Figure 1-2 This embodiment describes a hydrogen-ammonia mixed low-NOx burner, characterized by: a hydrogen inlet pipe 1, an ammonia inlet pipe 10, a mixer 12, an annular header 13, an ammonia branch pipe 14, and an ammonia nozzle 15. The hydrogen inlet pipe 1 includes a central hydrogen pipe 2 and a combustion-supporting hydrogen pipe 4. The outlet end of the central hydrogen pipe 2 is located at the center of the burner. The input end of the combustion-supporting hydrogen pipe 4 is connected to the central hydrogen pipe 2, and the output end is connected to the mixer 12. The output end of the ammonia inlet pipe 10 is connected to the mixer 12. The output end of the mixer 12 is connected to the annular header 13, which is connected to multiple ammonia branch pipes 14 arranged in a ring. The outlet end of the ammonia branch pipe 14 is equipped with an ammonia nozzle 15. A central hydrogen regulating valve 3 is installed on the central hydrogen pipe 2, a combustion hydrogen regulating valve 5 is installed on the combustion hydrogen pipe 4, and an ammonia regulating valve 11 is installed on the ammonia inlet pipe 10. A primary air annular cavity 17 and a secondary air annular cavity 21 are sequentially provided outside the ammonia branch pipes 14 of the burner. The primary air annular cavity 17 is connected to the primary air inlet 16, and the secondary air annular cavity 21 is connected to the secondary air inlet 20.

[0028] Hydrogen inlet pipe 1 introduces hydrogen to the burner, and ammonia inlet pipe 10 introduces ammonia to the burner. Hydrogen inlet pipe 1 is divided into a central hydrogen pipe 2 and a combustion-supporting hydrogen pipe 4. The flow rate in the central hydrogen pipe 2 is regulated by a central hydrogen regulating valve 3, and the flow rate in the combustion-supporting hydrogen pipe 4 is regulated by a combustion-supporting hydrogen regulating valve 5. The ammonia regulating valve 11 regulates the ammonia flow rate in the ammonia inlet pipe 10. The hydrogen in the combustion-supporting hydrogen pipe 4 and the ammonia in the ammonia inlet pipe 10, after their flow rates are regulated, enter the mixer 12 together, achieving thorough mixing of hydrogen and ammonia. The mixed ammonia-hydrogen gas enters the annular header 13, which is connected to multiple ammonia branch pipes 14 arranged in a ring. The front end of the ammonia branch pipes 14 is equipped with an ammonia nozzle 15, which injects the ammonia-hydrogen gas mixture into the furnace for combustion.

[0029] Combustion of hydrogen and ammonia as fuels in a burner controls the chemical reaction rate of the gaseous fuels and suppresses the combustion product, nitrogen oxides (NOx). x The combustion concentration is high, the burner structure is simple and stable without burning the nozzle, and high-efficiency combustion of gaseous fuels is ensured. Adding hydrogen to ammonia is an effective technical method to improve the combustion reaction rate of ammonia fuel. The outer layer of the jet is a mixture of ammonia and hydrogen gas. The combustibility of the mixed gas fuel is higher than that of pure ammonia fuel. The combustion organization forms a recirculation zone outside the burner. The recirculation zone can draw high-temperature flue gas back to the root of the ammonia-hydrogen mixture jet, heating the ammonia-hydrogen mixture. The high temperature conditions can promote the ignition and combustion of the ammonia-hydrogen mixture. Ultimately, the ammonia has a high burnout rate and no ammonia escape, effectively reducing the NO content of the fuel type of ammonia combustion. x Pollutant generation: Ammonia burns in a low-oxygen environment, and the high-temperature flame environment accelerates the pyrolysis reaction rate of ammonia, leading to rapid consumption of ammonia. The fuel-type nitrogen oxides (NOx) produced by the combustion of ammonia in a low-oxygen environment are... x The formation of ammonia is suppressed, and ammonia can also act as a form of NO. x The reducing agent will react with the generated nitrogen oxides NO. x By reducing it to nitrogen, the technical challenge of high NOx emission potential from fuels during ammonia combustion is solved. The hydrogen combustion process is controlled, preventing burner burnout. Excessive hydrogen combustion can lead to pre-ignition and backfire; therefore, a diffusion combustion method is used, placing hydrogen in the inner layer of the gaseous fuel jet, delaying hydrogen distribution, and maintaining an appropriate distance between the hydrogen combustion zone and the burner.

[0030] Furthermore, the outlet end of the central hydrogen pipe 2 is connected to multiple central hydrogen branch pipes 6, and the central hydrogen branch pipes 6 are connected to central hydrogen nozzles 7. The central hydrogen pipe 2 has multiple central hydrogen branch pipes 6 connected to its front end, and the front end of each central hydrogen branch pipe 6 is equipped with a central hydrogen nozzle 7 to inject pure hydrogen into the furnace for combustion. The gaseous fuel jet forms a gaseous fuel distribution pattern of central pure hydrogen and an outer ring of ammonia-hydrogen mixture.

[0031] Furthermore, the ends of the central hydrogen nozzle 7 and the ammonia nozzle 15 are provided with a panel 8. The panel 8 is connected to the ends of the ammonia nozzle 15 and the central hydrogen nozzle 7. The panel 8 is used for positioning and fixing the central hydrogen nozzle 7 and the ammonia nozzle 15. At the same time, it can protect the ammonia branch pipe 14 and the central hydrogen branch pipe 6 from the high temperature radiation of the furnace flame.

[0032] Furthermore, a flame stabilizer 9 is provided on the exterior of the panel 8, and the radial expansion angle of the flame stabilizer 9 is 15°-25°. The flame stabilizer 9 is located on the exterior of the panel 8 and is made of heat-resistant cast steel, so it will not burn out in high-temperature operating environments. The radial expansion angle of the flame stabilizer 9 is 15°-25°, which can guide the primary airflow and organize the flow field to help form a recirculation zone for the combustion flame.

[0033] Furthermore, a primary air swirl blade 18 is installed inside the primary air annular cavity 17. The blade of the primary air swirl blade 18 is deflected 30°-60° from the axial direction. After the primary air passes through, it forms a swirl and organizes the flow field morphology after entering the furnace.

[0034] Furthermore, the secondary air annular cavity 21 is provided with secondary air swirl blades 22, the blades of which are deflected 30°-60° axially. The secondary air swirl blades 22 are connected to a swirl blade adjustment mechanism 23. The front end of the secondary air annular cavity 21 is provided with a flange 19, corresponding to a radial expansion angle of 15°-25°. An arch 24 is provided on the side end of the secondary air annular cavity 21. Secondary air is introduced into the secondary air annular cavity 21 through the secondary air inlet 20. The secondary air annular cavity 20 is equipped with secondary air swirl blades 22, the blades of which are deflected 30°-60° axially. The secondary air swirl blades 22 are movable, and the swirl blade adjustment mechanism 23 can adjust the swirl intensity of the secondary air. The flange 19 at the front end of the secondary air annular cavity 20, with a corresponding radial expansion angle of 15°-25°, can guide the secondary air flow and organize the flow field, which helps to form a recirculation zone for the combustion flame.

[0035] Specific examples Figure 2As shown, the gaseous fuel ejected from the central hydrogen nozzle 7 and ammonia nozzle 15 forms a jet in the furnace outside the burner. The outer layer of the jet is an ammonia-hydrogen mixture, while the central gas is pure hydrogen. Primary and secondary air are supplied to the furnace from the front of the burner in a rotating jet manner, and after being guided by the flame stabilizer 9 and the flange 19, a recirculation zone is formed in the flow field outside the burner. The recirculation zone can draw high-temperature flue gas back to the root of the ammonia-hydrogen mixture jet, heating the ammonia-hydrogen mixture. The high temperature conditions can promote the ignition and combustion of the ammonia-hydrogen mixture. Adding hydrogen to ammonia is an effective technical method to improve the combustion reaction rate of ammonia fuel. The outer layer of the jet is an ammonia-hydrogen mixture, and the combustibility of the mixed gas fuel is higher than that of pure ammonia fuel. The design of the recirculation zone and the combination of hydrogen mixed into ammonia for combustion can effectively create suitable conditions for ammonia combustion. The oxygen concentration is low in the recirculation zone. Primary and secondary air are mixed and supplied in stages for gaseous fuel combustion, providing oxygen for the combustion process. Ammonia burns in this low-oxygen environment, and the high-temperature flame environment accelerates the pyrolysis reaction rate of ammonia, leading to its rapid consumption. The formation of fuel-type nitrogen oxides (NOx) from ammonia combustion is suppressed in this low-oxygen environment. Ammonia can also act as a NOx reducing agent, reducing the generated NOx to nitrogen. This combustion design effectively reduces the formation of fuel-type NOx pollutants from ammonia combustion. As the outer ammonia-hydrogen mixed fuel is consumed, the secondary air gradually comes into contact with the pure hydrogen at the center of the gaseous fuel jet. The rapid combustion rate of hydrogen creates a hydrogen combustion zone.

[0036] The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A hydrogen-ammonia mixed low-NOx burner, characterized in that: The system includes a hydrogen inlet pipe (1), an ammonia inlet pipe (10), a mixer (12), an annular header (13), an ammonia branch pipe (14), and an ammonia nozzle (15). The hydrogen inlet pipe (1) includes a central hydrogen pipe (2) and a combustion-supporting hydrogen pipe (4). The outlet end of the central hydrogen pipe (2) passes through the annular header (13) and is located at the center of the burner. The inlet end of the combustion-supporting hydrogen pipe (4) is connected to the central hydrogen pipe (2), and the outlet end is connected to the mixer (12). The outlet end of the ammonia inlet pipe (10) is connected to the mixer (12). The output end of the mixer (12) is connected to the annular header (13), which is connected to multiple ammonia branch pipes (14). The multiple ammonia branch pipes (14) are arranged in annular shape. The outlet end of the ammonia branch pipe (14) is provided with an ammonia nozzle (15). The ammonia branch pipe (14) of the burner is provided with a primary air annular cavity (17) and a secondary air annular cavity (21) in sequence. The primary air annular cavity (17) is connected to the primary air inlet (16), and the secondary air annular cavity (21) is connected to the secondary air inlet (20).

2. The hydrogen-ammonia mixed low-NOx burner according to claim 1, characterized in that: A central hydrogen regulating valve (3) is installed on the central hydrogen pipe (2), and a combustion-supporting hydrogen regulating valve (5) is installed on the combustion-supporting hydrogen pipe (4).

3. The hydrogen-ammonia mixed low-NOx burner according to claim 2, characterized in that: The outlet end of the central hydrogen pipe (2) is connected to multiple central hydrogen branch pipes (6), and the central hydrogen branch pipes (6) are connected to the central hydrogen nozzle (7).

4. A hydrogen-ammonia mixed low-NOx burner according to claim 3, characterized in that: The central hydrogen nozzle (7) and the ammonia nozzle (15) are provided with panels (8) at their ends.

5. A hydrogen-ammonia mixed low-NOx burner according to claim 4, characterized in that: The panel (8) is provided with a flame stabilizer (9) on its exterior, and the radial expansion angle of the flame stabilizer (9) is 15°-25°.

6. The hydrogen-ammonia mixed low-NOx burner according to claim 1, characterized in that: An ammonia regulating valve (11) is installed on the ammonia inlet pipe (10).

7. A hydrogen-ammonia mixed low-NOx burner according to claim 1, characterized in that: The primary air annular cavity (17) is equipped with a primary air swirl blade (18), and the blade of the primary air swirl blade (18) is deflected 30°-60° from the axial direction.

8. A hydrogen-ammonia mixed low-NOx burner according to claim 1, characterized in that: The secondary air annular cavity (21) is provided with a secondary air swirl blade (22), the blade of the secondary air swirl blade (22) is deflected 30°-60° from the axis, and the secondary air swirl blade (22) is connected to the swirl blade adjustment mechanism (23).

9. A hydrogen-ammonia mixed low-NOx burner according to claim 1, characterized in that: The front end of the secondary air ring cavity (21) is provided with a flange (19), and the corresponding radial expansion angle is 15°-25°. The side end of the secondary air ring cavity (21) is provided with an arch (24).

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