NH3 regenerative pre-decomposition stable-combustion low-nitrogen combustor and method

Abstract

The invention provides an NH3 regenerative pre-decomposition stable-combustion low-nitrogen combustor and method. The combustor comprises an outer barrel and an inner barrel which is nested in an inner cavity of the outer barrel in a matched mode. An inner cavity of the inner cylinder is a pre-combustion chamber, and a gas preheating area is formed between the inner cylinder and the outer cylinder; an axial distance is kept between the top end of the inner barrel and the top end of the outer barrel to form an annular opening; the annular opening is connected with an inner cavity of the inner barrel and the gas preheating area; the bottom of the inner cylinder is open and is an air outlet; an ammonia gas inlet and an air inlet which are tangentially communicated with the gas preheating area are formed in the side wall of the lower end of the outer barrel, a strong swirling flow field is formed in the gas preheating area in a tangential gas inlet mode, and ammonia gas-air mixing and heat exchange between mixed gas flow and the wall surface of the inner barrel are enhanced. High-efficiency and uniform heat exchange between high-temperature flue gas and ammonia gas can be realized, so that the pre-decomposition efficiency of the ammonia gas is ensured, a large amount of NOX pollutants are prevented from being generated, and meanwhile, rapid regulation and control and self-response of the system to the ammonia decomposition efficiency and load change are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia pre-decomposition combustion, and particularly to an NH3 regenerative pre-decomposition stable combustion low-nitrogen burner. Background Art

[0002] With the advancement of the "dual carbon" goal, the demand for zero-carbon fuels has surged. Ammonia (NH3) has become a research hotspot for alternative fuels in various fields at present because it contains no carbon, is convenient for storage and transportation (liquefies at -33°C), has a high energy density (18.6 MJ / kg), and has mature synthesis and storage and transportation technologies. However, when ammonia is directly used as a fuel, there are problems such as slow combustion speed, difficult ignition, and the generation of nitrogen oxides (NO X ) and so on. For this reason, the development of ammonia pre-decomposition combustion technology has been promoted. The core of this technology is to decompose ammonia into hydrogen and nitrogen (2NH3 → 3H2 + N2) at high temperature through an ammonia pre-decomposition burner, use the high reactivity of hydrogen to improve the combustion performance in the burner, and at the same time avoid the large generation of NO X pollutants, so as to achieve efficient and clean energy conversion. Currently, the mainstream ammonia pre-decomposition combustion technology uses a "high-temperature air entrainment combustion chamber" as the basic framework. Its typical implementation scheme is: an ammonia fuel injection device is arranged at the head of the combustion chamber, and the outside high-temperature flue gas is entrained through a swirler to mix with the newly entered ammonia in the combustion chamber. The waste heat of the high-temperature flue gas is used to cause the ammonia to undergo a decomposition reaction to generate hydrogen and nitrogen. The pre-decomposed mixed gas further burns with air in the main combustion area, but there are the following problems:

[0003] (1) Low entrainment and mixing efficiency

[0004] Entrainment and mixing rely on the flue gas flow rate and pressure difference to drive the mixing of ammonia and high-temperature flue gas. However, due to reasons such as uneven velocity distribution, low turbulence intensity, and gas diffusion rate differences, it is easy to cause poor gas mixing, insufficient temperature in some areas, resulting in incomplete ammonia decomposition. At the same time, uneven mixing causes local overheating, leading to the large generation of NO X pollutants.

[0005] (2) Insufficient stability of the high-temperature flue gas heat source

[0006] Efficient ammonia decomposition requires a stable high temperature (>800°C), but the temperature of industrial flue gas is easily affected by operating conditions fluctuations, resulting in unstable decomposition efficiency.

[0007] (3) Poor adaptability to load changes

[0008] When the system load changes, it is necessary to adjust the high-temperature flue gas inhalation amount in a timely manner, but this control process is cumbersome, making it difficult for the existing technology to adapt to frequent start-stop or rapid peak shaving requirements. Summary of the Invention

[0009] In view of the technical problems existing in the prior ammonia pre-decomposition burner in terms of mixing effect, heat source stability, adaptability to load changes, etc. in the above-mentioned background art, the present invention proposes an NH3 regenerative pre-decomposition stable combustion low-nitrogen burner and method, which can achieve efficient and uniform heat exchange between high-temperature flue gas and ammonia to ensure the ammonia pre-decomposition efficiency and avoid the large generation of NO X pollutants, and at the same time realize the rapid regulation and self-response of the system to ammonia decomposition efficiency and load changes.

[0010] To solve the above technical problems, an NH3 regenerative pre-decomposition stable combustion low-nitrogen burner provided by the present invention includes an outer cylinder and an inner cylinder nested in the inner cavity of the outer cylinder; the inner cavity of the inner cylinder is a pre-combustion chamber, and a gas pre-heating area is formed between the inner cylinder and the outer cylinder; there is an axial distance between the top end of the inner cylinder and the top end of the outer cylinder to form an annular opening, and the annular opening connects the inner cavity of the inner cylinder and the gas pre-heating area; the bottom of the inner cylinder is open and is an air outlet; the lower side wall of the outer cylinder is provided with an ammonia inlet and an air inlet that communicate with the gas pre-heating area in a tangential manner, and the tangential air intake method forms a strong swirling flow field in the gas pre-heating area, enhancing the mixing of ammonia-air and the heat exchange between the mixed gas flow and the inner cylinder wall.

[0011] For the NH3 regenerative pre-decomposition stable combustion low-nitrogen burner, wherein: a secondary air channel is provided at the top end of the inner cavity of the inner cylinder; the secondary air channel is used to introduce secondary air into the inner cavity of the inner cylinder and is internally equipped with a igniter.

[0012] For the NH3 regenerative pre-decomposition stable combustion low-nitrogen burner, wherein: the secondary air channel is coaxial with the outer cylinder and the inner cylinder.

[0013] For the NH3 regenerative pre-decomposition stable combustion low-nitrogen burner, wherein: the outer cylinder is an outer heat-insulating cylinder, and the inner cylinder is a ceramic heat-conducting cylinder; the inner cylinder and the outer cylinder are coaxially nested so that an annular space is formed between the inner cylinder and the outer cylinder, and the annular space is the gas pre-heating area.

[0014] For the NH3 regenerative pre-decomposition stable combustion low-nitrogen burner, wherein: the lower side wall of the outer cylinder is circumferentially and uniformly provided with a first tangential air intake, a second tangential air intake, a third tangential air intake and a fourth tangential air intake; the first tangential air intake, the second tangential air intake, the third tangential air intake and the fourth tangential air intake are connected to the annular space in a tangential manner; the first tangential air intake is the ammonia inlet, and the second tangential air intake, the third tangential air intake and the fourth tangential air intake are all air inlets.

[0015] For the NH3 regenerative pre-decomposition stable combustion low-nitrogen burner, wherein: the bottom of the inner cylinder is in the same plane as the bottom of the outer cylinder.

[0016] An NH3 regenerative pre - decomposition stable - combustion and low - nitrogen combustion method, based on the above - mentioned NH3 regenerative pre - decomposition stable - combustion low - nitrogen burner, wherein: ammonia and air respectively enter the gas pre - heating zone from the ammonia inlet and the air inlet at the bottom end of the outer cylinder and then rotate and rise. The swirling flow enhances the mixing of ammonia and air. At the same time, during the flow of the mixed gas stream, heat from the pre - combustion chamber is absorbed through the wall surface of the inner cylinder to pre - heat the mixed gas. The strong swirling flow enhances the heat - transfer efficiency between the gas stream and the wall surface of the inner cylinder, realizing the rapid temperature rise of the ammonia - air mixed gas;

[0017] The ammonia - air mixed gas stream flows to the annular opening and enters the inner - cylinder internal chamber. By then, the ammonia - air mixed gas has been heated to a temperature sufficient for ammonia decomposition. Subsequently, ammonia decomposes to produce hydrogen, which burns with air, releasing heat and maintaining the high temperature in the inner - cylinder internal chamber. When the high - temperature gas flows in the inner - cylinder internal chamber, heat is transferred back to the gas pre - heating zone through the wall surface of the inner cylinder, heating the ammonia - air mixed gas stream newly entering the annular space between the inner cylinder and the outer cylinder, forming an internal heat cycle of the system. The high - temperature gas also flows in a swirling manner in the inner - cylinder internal chamber, enhancing its heat transfer with the wall surface of the inner cylinder;

[0018] The high - temperature gas flows out from the air outlet at the bottom of the inner cylinder after flowing through the inner - cylinder internal chamber and is used in subsequent supporting equipment;

[0019] The igniter is arranged in the inner - cylinder internal chamber through the secondary - air channel. After being triggered for a single ignition, the igniter can achieve continuous operation relying on the heat feedback within the annular space between the inner cylinder and the outer cylinder itself.

[0020] In the NH3 regenerative pre - decomposition stable - combustion and low - nitrogen combustion method, wherein: the secondary - air channel also injects secondary air into the inner - cylinder internal chamber to regulate the equivalence ratio and temperature inside the inner - cylinder internal chamber, realizing the control of ammonia decomposition efficiency.

[0021] Adopting the above - mentioned technical solution, the present invention has the following beneficial effects:

[0022] The NH3 regenerative pre - decomposition stable - combustion low - nitrogen burner and method of the present invention are reasonably conceived, can achieve efficient and uniform heat transfer between high - temperature flue gas and ammonia, thus ensuring the ammonia pre - decomposition efficiency, avoiding the large generation of NO X pollutants, and at the same time realizing the rapid regulation and self - response of the system to ammonia decomposition efficiency and load changes.

[0023] The present invention abandons the dependence on external heat sources. Through the coupling of the high temperature (≥1977K) in the pre - combustion chamber and the directional heat transfer on the wall surface of the inner cylinder, the problem of insufficient stability of the high - temperature flue - gas heat source in the prior art is avoided; the double - swirling flow inside and outside the inner cylinder improves the heat - transfer performance, and the heat - flux density on the wall surface of the inner cylinder is stable at 42422 - 76539W / m2 Interval, avoiding the problem of local over - low / over - high temperature caused by uneven mixing in the prior art; a dynamic thermal cycle regulation can be realized in the annular space 2 between the inner cylinder 3 and the outer cylinder 1, and heat self - regulation can be achieved under load - fluctuation conditions; the inner cylinder separates the pre - combustion chamber from the gas pre - heating area, and there will be no local high - temperature and high - oxygen areas during the ammonia pre - decomposition process, realizing efficient ammonia decomposition and low NO X generation; adopting the regenerative cooling principle commonly used in liquid rocket engines to achieve rapid mixing and temperature rise of ammonia and air, while reducing the temperature of the inner cylinder to prevent wall ablation; the secondary air adjusts the equivalence ratio and temperature inside the pre - combustion chamber, and can realize the regulation of the ammonia decomposition degree; adding an inner cylinder to decouple the temperature rise, decomposition and combustion of the ammonia - air mixed gas flow, and the system can achieve self - regulation under load - change conditions. Brief Description of the Drawings

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following - described drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 is the overall structural schematic diagram of the NH3 regenerative pre - decomposition stable - combustion low - nitrogen burner of the present invention;

[0026] Figure 2 is the partial sectional view of the NH3 regenerative pre - decomposition stable - combustion low - nitrogen burner of the present invention;

[0027] Figure 3 is the top view of the NH3 regenerative pre - decomposition stable - combustion low - nitrogen burner of the present invention;

[0028] Figure 4 is the contour map of the temperature and heat - flux density distribution of the numerical simulation results;

[0029] Figure 5 is the contour map of the ammonia and hydrogen distribution of the numerical simulation results;

[0030] Figure 6 is NO X pollutant water - vapor distribution contour map.

[0031] 1 - outer cylinder; 2 - annular space; 3 - inner cylinder; 4 - inner - cylinder internal chamber; 5 - annular opening; 6 - air inlet; 7 - air inlet; 8 - air inlet; 9 - air inlet; 10 - air outlet; 11 - secondary - air channel. Detailed Embodiments

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] The present invention will be further explained below in conjunction with specific embodiments.

[0034] As Figure 1 shown, an NH3 regenerative pre-decomposition stable combustion low-nitrogen burner provided in this embodiment adopts a coaxial nested inner and outer double-cylinder structure and specifically includes an outer cylinder 1 and an inner cylinder 3.

[0035] The outer cylinder 1 is an outer heat-insulating cylinder, and the inner cylinder 3 is a ceramic heat-conducting cylinder and is nested in the inner cavity of the outer cylinder 1; the inner cavity 4 inside the inner cylinder 3 is a pre-combustion chamber, and an annular space 2 is formed between the inner cylinder 3 and the outer cylinder 1, and the annular space 2 is a gas pre-heating area; the top of the inner cylinder 3 is kept at an axial distance from the top of the outer cylinder 1 to form an annular opening 5 connecting the inner cavity 4 of the inner cylinder and the annular space 2; the bottom of the inner cylinder 3 is open and is an air outlet 10.

[0036] The lower side wall of the outer cylinder 1 is evenly distributed with a first tangential air inlet 6, a second tangential air inlet 7, a third tangential air inlet 8, and a fourth tangential air inlet 9 in the circumferential direction; the first tangential air inlet 6, the second tangential air inlet 7, the third tangential air inlet 8, and the fourth tangential air inlet 9 are communicated with the annular space 2 in a tangential manner, wherein the first tangential air inlet 6 is an ammonia inlet, and the second tangential air inlet 7, the third tangential air inlet 8, and the fourth tangential air inlet 9 are all air inlets. The tangential air inlet method forms a strong swirling flow field in the annular space 2, enhancing the mixing of ammonia-air and the heat exchange between the mixed air flow and the wall surface of the inner cylinder 3.

[0037] A secondary air channel 11 is provided at the top of the inner cavity 4 of the inner cylinder; the secondary air channel 11 is used to introduce secondary air into the inner cavity 4 of the inner cylinder and is internally provided with an igniter; wherein, the secondary air channel 11 is coaxially designed with the outer cylinder 1 and the inner cylinder 3, which can realize the rapid ignition and the rapid mixing of the secondary air and the combustible gas entering the inner cylinder 3 from the annular space 2 during normal operation: during operation, the secondary air channel 11 serves as an igniter channel, directly igniting the combustible gas in the inner cylinder 3 and heating and raising the temperature of the wall surface of the inner cylinder 3, preheating the combustible gas in the annular space 2 between the inner cylinder 3 and the outer cylinder 1, so that the combustible gas enters the inner cylinder 3 quickly to reach the ignition condition; during normal operation, the air entering the secondary air channel 11 is directly and strongly mixed with the preheated combustible gas in the annular space 2 in a timely manner and enters the inner cylinder 3, and the combustion temperature and the degree of ammonia pre-decomposition reaction in the inner cylinder 3 are intensively regulated by adjusting the amount of secondary air.

[0038] The NH3 regenerative pre - decomposition stable - combustion and low - nitrogen combustion method of the present invention is based on the above - mentioned NH3 regenerative pre - decomposition stable - combustion low - nitrogen burner, and specifically is as follows:

[0039] Ammonia and air respectively enter the annular space 2 from the ammonia inlet and the air inlet at the bottom end of the outer cylinder 1 and then rotate and rise. The swirling flow enhances the mixing of ammonia and air. At the same time, during the flow of the mixed gas stream, heat from the pre - combustion chamber is absorbed through the wall surface of the inner cylinder 3 to achieve pre - heating of the mixed gas. The strong swirling flow enhances the heat - transfer efficiency between the gas stream and the wall surface of the inner cylinder 3, realizing the rapid temperature rise of the ammonia - air mixed gas;

[0040] The ammonia - air mixed gas stream flows to the annular opening 5 and enters the inner - cylinder internal chamber 4. By then, the mixed gas has been heated to the temperature (800 °C) that satisfies the decomposition of ammonia. Subsequently, ammonia decomposes to produce hydrogen and burns with air, releasing heat and maintaining the high temperature of the inner - cylinder internal chamber 4, that is, the pre - combustion chamber. When the high - temperature gas flows in the inner - cylinder internal chamber 4, heat is transferred back to the annular space 2 through the wall surface of the inner cylinder 3, heating the ammonia - air mixed gas stream newly entering the annular space 2 between the inner cylinder 3 and the outer cylinder 1, forming an internal heat cycle of the system. The high - temperature gas also flows in a swirling manner in the inner - cylinder internal chamber 4, enhancing its heat transfer with the wall surface of the inner cylinder 3;

[0041] The high - temperature gas flows out from the air outlet 10 at the bottom of the inner cylinder after flowing through the inner - cylinder internal chamber 4 and is used in subsequent supporting equipment such as gas turbines, hydrogen - fuel engines, and high - temperature furnaces;

[0042] The igniter is arranged in the inner - cylinder internal chamber 4 through the secondary - air channel 11. According to the characteristics of the NH3 regenerative pre - decomposition stable - combustion low - nitrogen burner of the present invention having an internal heat cycle of the system, after a single ignition trigger, the igniter can achieve continuous operation by relying on the heat feedback within the annular space 2 between the inner cylinder 3 and the outer cylinder 1. In addition, another function of the secondary - air channel 11 is to inject secondary air into the inner - cylinder internal chamber 4 to regulate the equivalence ratio and temperature inside the pre - combustion chamber, realizing the control of ammonia decomposition efficiency.

[0043] The following details an embodiment of the present invention in conjunction with the accompanying drawings.

[0044] An NH3 regenerative pre - decomposition stable - combustion low - nitrogen burner of this embodiment includes an outer cylinder 1, an inner cylinder 3, a first tangential air inlet 6, a second tangential air inlet 7, a third tangential air inlet 8, a fourth tangential air inlet 9, and an air outlet 10. The height of the outer cylinder 1 is 4.75D, where D is the diameter of the outer cylinder 1. In the example, D = 40 mm. The first tangential air inlet 6, the second tangential air inlet 7, the third tangential air inlet 8, and the fourth tangential air inlet 9 are all circular air inlets with a diameter of 0.125D. They are evenly distributed at the lower end of the outer cylinder 1 and are tangentially connected to the outer cylinder, 0.5D away from the bottom of the outer cylinder.

[0045] The central axis of the inner cylinder 3 coincides with that of the outer cylinder 1, and the bottom of the inner cylinder 3 is in the same plane as the bottom of the outer cylinder 1. At this time, the large temperature difference between the high temperature on the outer wall surface at the lower end of the inner cylinder 3 and the low temperature of the combustible gas just entering from the annular space 2 between the inner cylinder 3 and the outer cylinder 1 can be used to enhance heat transfer, while avoiding ablation due to the excessive height of the lower wall surface of the inner cylinder 3. The height of the inner cylinder 3 is 4.25D, the inner diameter of the inner cylinder 3 is 0.625D, and the outer diameter of the inner cylinder 3 is 0.65D.

[0046] The secondary air passage is coaxial with the outer cylinder 1 and the inner cylinder 3, and has a diameter of 0.15D.

[0047] The main mechanism dimensions of the embodiment are shown in Table 1.

[0048] Numerical simulation is carried out on the example of the present invention, and the simulation conditions are that the total flow rate of ammonia and air is 16 Nm 3 / h, and the excess air coefficient is 0.66.

[0049] As Figures 4-6 shown by the simulation results, the strong swirling flow field structure enhances the heat transfer performance on both sides of the inner cylinder. Most areas of the inner cylinder wall surface maintain a uniform heat flux of 42422 - 76539 W / m 2 . This enhanced heat transfer mechanism uniformly heats the preheating zone of the ammonia-air mixed gas flow to above 1857 K (see Figure 4 ). After entering the pre-combustion chamber inside the inner cylinder, the ammonia mole fraction decreases to below 0.1, and the mole fraction of hydrogen rises to 0.062 (see Figure 5 ), indicating that a large amount of ammonia has decomposed into hydrogen. The hydrogen generated by the decomposition of ammonia burns with air to produce high temperature, raising the temperature inside the inner cylinder to above 1977 K (see Figure 4 ), providing heat for the mixed gas flow newly entering the burner in the preheating zone. Finally, the hydrogen mole fraction at the burner outlet reaches 0.09 (see Figure 5 ), and the NH3 and NO emissions at the device outlet are nearly zero (see Figure 5 and Figure 6 ), achieving efficient combustion and decomposition of NH3 with low NO x emissions.

[0050] The present invention can achieve efficient and uniform heat transfer between high-temperature flue gas and ammonia, thereby ensuring the pre-decomposition efficiency of ammonia, avoiding the large generation of NO X pollutants, and at the same time realizing the rapid regulation and self-response of the system to the ammonia decomposition efficiency and load changes.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A NH3 regenerative pre-decomposition stable combustion low-nitrogen burner, characterized in that: The ammonia decomposition device includes an outer cylinder (1) and an inner cylinder (2) that is nested in the inner cavity of the outer cylinder (1) in a matching manner; The inner cavity (4) of the inner cylinder (3) is a pre-combustion chamber, and a gas preheating zone is formed between the inner cylinder (3) and the outer cylinder (1); The top end of the inner cylinder (3) is axially spaced from the top end of the outer cylinder (1) to form an annular opening (5), and the annular opening (5) connects the inner cavity (4) of the inner cylinder to the gas preheating zone; The bottom of the inner cylinder (3) is open and is an air outlet (10); an ammonia inlet and an air inlet that are tangentially communicated with the gas preheating zone are provided on the lower side wall of the outer cylinder (1). The tangential air inlet mode forms a strong swirling flow field in the gas preheating zone, enhancing the mixing of ammonia and air and the heat exchange between the mixed gas flow and the wall surface of the inner cylinder (3).

2. The NH3 regenerative pre-decomposition stable combustion low-nitrogen burner according to claim 1, characterized in that: A secondary air channel (11) is provided at the top end of the inner cavity (4) of the inner cylinder; the secondary air channel (11) is used to introduce secondary air into the inner cavity (4) of the inner cylinder and is internally provided with a igniter in a matching manner.

3. The NH3 regenerative pre-decomposition stable combustion low-nitrogen burner according to claim 1, characterized in that: The secondary air channel (11) is coaxial with the outer cylinder (1) and the inner cylinder (3).

4. The NH3 regenerative pre-decomposition stable combustion low-nitrogen burner according to claim 1, characterized in that: The outer cylinder (1) is an outer heat-insulating cylinder, and the inner cylinder (3) is a ceramic heat-conducting cylinder; The inner cylinder (3) and the outer cylinder (1) are coaxially nested so that an annular space (2) is formed between the inner cylinder (3) and the outer cylinder (1), and the annular space (2) is the gas preheating zone.

5. The NH3 regenerative pre-decomposition stable combustion low-nitrogen burner according to claim 4, characterized in that: The lower side wall of the outer cylinder (1) is circumferentially provided with a first tangential air inlet (6), a second tangential air inlet (7), a third tangential air inlet (8) and a fourth tangential air inlet (9) in a circumferential distribution; the first tangential air inlet (6), the second tangential air inlet (7), the third tangential air inlet (8) and the fourth tangential air inlet (9) are tangentially communicated with the annular space (2); the first tangential air inlet (6) is an ammonia inlet, and the second tangential air inlet (7), the third tangential air inlet (8) and the fourth tangential air inlet (9) are all air inlets.

6. The NH3 regenerative pre-decomposition stable combustion low-nitrogen burner according to claim 1, characterized in that: The bottom of the inner cylinder (3) is in the same plane as the bottom of the outer cylinder (1).

7. An NH3 regenerative pre-decomposition stable combustion and low-nitrogen combustion method, based on the NH3 regenerative pre-decomposition stable combustion and low-nitrogen burner according to any one of the above claims 1 to 6, characterized in that: Ammonia and air respectively enter the gas preheating zone from the ammonia inlet and the air inlet at the bottom end of the outer cylinder (1) and then rotate and rise. The swirling flow enhances the mixing of ammonia and air. At the same time, the mixed gas flow absorbs heat from the pre-combustion chamber through the wall surface of the inner cylinder (3) to realize the preheating of the mixed gas. The strong swirling flow enhances the heat exchange efficiency between the gas flow and the wall surface of the inner cylinder (3), realizing the rapid temperature rise of the ammonia-air mixed gas; The ammonia-air mixed gas flow moves to the annular opening (5) and enters the internal chamber (4) of the inner cylinder. By this time, the ammonia-air mixed gas has been heated to a temperature sufficient for ammonia decomposition. Subsequently, ammonia decomposes to produce hydrogen, which burns with air, releasing heat and maintaining the high temperature in the internal chamber (4) of the inner cylinder. When the high-temperature combustion gas flows in the internal chamber (4) of the inner cylinder, heat is transferred through the wall surface of the inner cylinder (3) to the gas preheating zone, heating the ammonia-air mixed gas flow newly entering the annular space (2) between the inner cylinder (3) and the outer cylinder (1), forming an internal heat cycle of the system. The high-temperature combustion gas also flows in a swirling manner in the internal chamber (4) of the inner cylinder, enhancing its heat exchange with the wall surface of the inner cylinder (3). The high-temperature combustion gas flows through the internal chamber (4) of the inner cylinder and is discharged from the air outlet (10) at the bottom of the inner cylinder (3) for subsequent supporting equipment. The igniter is arranged in the internal chamber (4) of the inner cylinder through the secondary air passage (11). After being triggered for a single ignition, the igniter can achieve continuous operation relying on the heat feedback within the annular space (2) between the inner cylinder (3) and the outer cylinder (1).

8. The NH3 regenerative pre-decomposition stable combustion low-nitrogen combustion method according to claim 5, characterized in that: The secondary air passage (11) also injects secondary air into the internal chamber (4) of the inner cylinder, regulating the equivalence ratio and temperature inside the internal chamber (4) of the inner cylinder to achieve control of the ammonia decomposition efficiency.

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