Catalytic auxiliary cracking plasma pure ammonia burner and operation method thereof

Abstract

The invention relates to the technical field of pure ammonia combustors, in particular to a catalytic auxiliary cracking plasma pure ammonia combustor and an operation method thereof. According to the technical scheme, the device comprises catalytic cracking areas, a purification area, a pre-combustion area, a main combustion area, an ammonia supply area and a waste heat system, the catalytic cracking areas are arranged on the two sides of a combustor and comprise an ammonia gas inlet channel and a catalytic reaction area internally provided with a porous medium, and a catalyst fixedly grows on the surface of the porous medium; the purification area is located outside the combustor and connected with an outlet of the catalytic cracking area through a pipeline, and selective separation membranes are arranged at the outlet end and the exhaust end of the purification area respectively; the pre-combustion areas are distributed on the two sides of the main combustion area, comprise air inlet channels and plasma igniters and communicate with an outlet of the purification area. According to the invention, the problems of ignition, stable combustion and low NOx emission of the ammonia fuel are solved, the unification of efficient energy utilization and industrial applicability is realized, and a key technical support is provided for large-scale application of the ammonia alternative fuel in an industrial kiln.

Description

Technical Field

[0001] The present invention relates to the technical field of pure ammonia burners, and in particular to a catalytically assisted cracking plasma pure ammonia burner and an operating method thereof. Background Art

[0002] As a "zero-carbon" fuel with high hydrogen content, clean combustion products, and easy storage and transportation, ammonia has become a key candidate to replace traditional fossil fuels in high-temperature thermal equipment such as industrial furnaces, as the global energy structure shifts toward a low-carbon economy. The use of ammonia fuel in industrial furnaces can reduce carbon emissions at the source, which is of great significance for promoting carbon reduction and emission reduction in the high-temperature manufacturing industry.

[0003] However, the inherent properties of ammonia fuel make it face many technical challenges in practical application:

[0004] Difficulty in ignition and stable combustion: Ammonia has a high ignition energy (about 10 times that of methane) and a slow flame propagation speed (only about 1 / 5 of that of methane), which makes it difficult to ignite at room temperature. In addition, the flame stability is poor during the combustion process and flameout is prone to occur, especially under low-load conditions.

[0005] NOx emission problem: During the combustion of ammonia, nitrogen is easily converted into NOx (nitrogen oxides). If the combustion is not organized properly, it will cause serious environmental pollution and will not meet the current strict environmental emission standards.

[0006] Inadequate coupling between ammonia cracking and combustion systems: While existing technologies use high-temperature or catalytic cracking of ammonia to produce hydrogen to improve combustion performance, the coupling design between the ammonia cracker and the combustor presents challenges such as complex structure and low energy efficiency. For example, in some solutions, the resulting mixed gas is not purified, resulting in unstable hydrogen concentration and affecting flame stability. Alternatively, imperfect waste heat recovery mechanisms lead to high system energy consumption, limiting the large-scale deployment of ammonia fuel.

[0007] To solve the above problems, a series of studies have been carried out in related fields:

[0008] The invention patent "An ammonia-hydrogen co-combustion chamber and ammonia-hydrogen co-combustion combustion method" (patent number CN202211374834.X) uses the high-temperature heat in the combustion chamber to pyrolyze ammonia to produce hydrogen, thereby improving combustion performance, but does not involve cold ignition optimization, and the energy coupling efficiency of cracking and combustion needs to be improved.

[0009] The invention patent application "An ammonia burner based on plasma cracking, thermal cracking and plasma combustion-assisted and its operation method" (CN202310260532.8) realizes the formation of high-temperature flame by cracking ammonia and assisting combustion through plasma discharge. However, the cracked gas in the system directly participates in combustion and the hydrogen purity is not regulated, which may affect the pre-combustion stability.

[0010] The invention patent application "An ammonia burner based on thermal catalytic cracking, multi-stage partitioned combustion and plasma-assisted combustion and its operation method" (CN202411114741.2) uses a multi-stage flame design and heat-conducting ribs to heat the catalyst, which increases the flame propagation speed. However, there is no special waste heat recovery system in the structure, and there is room for improvement in energy utilization efficiency.

[0011] In view of the problems of unreasonable coupling design of ammonia cracking and combustion systems, high energy consumption, and insufficient coordinated control of ignition, stable combustion and low NOx emissions in existing technologies, it is urgent to develop a burner system with optimized structure, efficient energy utilization, and the ability to achieve ammonia cold ignition, stable combustion and low pollution emissions, so as to promote the practical application of ammonia fuel in industrial kilns.

[0012] In summary, the present application proposes a catalytically assisted cracking plasma pure ammonia burner and an operating method thereof. Summary of the Invention

[0013] The purpose of the present invention is to address the problems in the background technology such as unreasonable coupling design of ammonia cracking and combustion systems, high energy consumption, insufficient coordinated control of ignition, stable combustion and low NOx emissions, and to propose a catalytically assisted cracking plasma pure ammonia burner and its operation method.

[0014] In a first aspect, the present application provides a catalytically assisted cracking plasma pure ammonia burner, comprising:

[0015] The catalytic cracking zone is arranged on both sides of the burner and includes an ammonia inlet channel and a catalytic reaction zone with a built-in porous medium, on the surface of which a catalyst is fixedly grown;

[0016] The purification zone is located outside the burner and is connected to the outlet of the catalytic cracking zone through a pipeline. The outlet and exhaust ends of the zone are respectively provided with selective separation membranes;

[0017] The pre-combustion zone is located on both sides of the main combustion zone and includes an air inlet and a plasma igniter, and is connected to the outlet of the purification zone;

[0018] The main combustion zone includes the main fuel inlet, air inlet, swirler and central combustion zone;

[0019] Ammonia supply area, connected to the ammonia inlet duct;

[0020] Waste heat system, which recovers combustion heat and transports it to the ammonia supply area for liquid ammonia vaporization;

[0021] Among them, ammonia is cracked into a hydrogen-nitrogen mixture in the catalytic cracking zone, and nitrogen is separated in the purification zone. The hydrogen is then injected into the pre-combustion zone and mixed with air, and ignited cold by the plasma igniter to form a pre-combustion flame; the main fuel mixture in the main combustion zone is ignited by the pre-combustion flame to form a main combustion flame, and the main combustion flame nozzle lags behind the pre-combustion flame nozzle.

[0022] Optionally, the plasma igniter adopts a sliding arc discharge structure, including a high-voltage electrode, a ground electrode, a ceramic cyclone ring and a nozzle; a coaxial cyclone is provided in the pre-combustion zone, so that the ammonia-air mixture forms a cyclone and is ignited by the plasma.

[0023] Optionally, the pre-combustion flame continuously radiates heat to the wall surface of the catalytic cracking zone, and the outer walls of the catalytic cracking zone and the pre-combustion zone are coated with refractory materials.

[0024] Optionally, the combustion-supporting zone is an independent micro-pipe structure with a blunt body at its outlet end. After ignition, a duty flame is formed in the center of the main combustion flame, and a recirculation zone is formed downstream of the blunt body to promote stable combustion.

[0025] Optionally, the pipeline in the catalytic cracking zone is of a stacked structure to extend the residence time of the gas; and micropores with a pore size of ≤2 mm are provided on the wall of the pipeline in the catalytic reaction zone (except for the wall close to the pre-combustion zone).

[0026] Optionally, the main flow direction of the gas in the porous medium is consistent with the flow direction of the pipeline, and the material is porous metal or porous ceramic.

[0027] Optionally, the selective separation membrane in the purification zone intercepts nitrogen at the outlet end and passes hydrogen into the pre-combustion zone, and the separation membrane at the exhaust end discharges the intercepted nitrogen.

[0028] In a second aspect, the present application provides a method for operating the burner according to the first aspect, comprising the following steps:

[0029] Pre-combustion stage: Excess air and a small amount of ammonia are introduced into the pre-combustion zone, the flow rate is gradually increased through the valve, and the plasma igniter is used for cold ignition to form a lean pre-combustion flame;

[0030] Main combustion stage: Excess fuel and a small amount of air are introduced into the main combustion zone to form a fuel-rich mixture;

[0031] The pre-combustion flame heats the catalytic cracking zone to produce hydrogen, which is then purified and injected into the pre-combustion zone to increase the flame temperature; the main combustion mixture is ignited by the pre-combustion flame to form a main combustion flame with little / no oxygen in the center and rich oxygen in the outer layer, and the excess air in the pre-combustion zone is merged into the main combustion zone as secondary air.

[0032] Compared with the prior art, this application has at least one of the following beneficial technical effects:

[0033] The present invention realizes cold ignition of ammonia through the synergistic effect of plasma combustion-assisted and catalytic-assisted cracking; the heat of the pre-combustion flame activates the catalyst to produce hydrogen, thereby increasing the flame temperature, and cooperates with the main combustion zone duty flame and the blunt body reflux structure to ensure stable combustion.

[0034] The staged combustion and staggered arrangement technology is further adopted, with lean combustion in the pre-combustion zone and rich combustion in the main combustion zone. The excess air in the pre-combustion zone is used as secondary air to supply the outer layer of the main combustion zone, avoiding high temperature concentration of the flame and reducing NOx generation from a mechanistic perspective.

[0035] Furthermore, by building a closed-loop system, waste heat is recycled to vaporize liquid ammonia; the structure of the catalytic cracking zone is optimized to improve heat exchange and cracking efficiency, and the purification zone provides high-purity hydrogen, reducing ineffective energy consumption and achieving cascaded energy utilization.

[0036] In summary, the burner of the present invention has a compact structure and clear partitions, and is suitable for installation and operation in industrial kilns; the catalyst is fixed to the porous medium, and the outer wall is coated with refractory material, which extends the life of the equipment and facilitates the promotion of ammonia fuel.

[0037] While solving the problems of ammonia fuel ignition, stable combustion and low NOx emissions, the present invention achieves the unity of efficient energy utilization and industrial applicability, providing key technical support for the large-scale application of ammonia alternative fuel in industrial kilns. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the structure of a catalytically assisted cracking plasma pure ammonia burner Figure 1 ;

[0039] Figure 2 Schematic diagram of the structure of a catalytically assisted cracking plasma pure ammonia burner Figure 2 .

[0040] Figure numerals: 1, catalytic cracking zone; 2, pre-combustion zone; 3, main combustion zone; 4, purification zone; 5, ammonia supply zone; 6, waste heat system; 101, pre-combustion flame, 102, duty flame; 103, main combustion flame; 104, catalytic reaction zone; 105, plasma igniter; 106, cyclone; 107, combustion-supporting zone; 108, blunt body; 1-1, air inlet duct; 2-1, main fuel inlet duct; 2-2, ammonia inlet duct. DETAILED DESCRIPTION

[0041] The technical solutions of the present disclosure will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0042] The components of the embodiments of the present disclosure generally described and shown in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present disclosure provided in the drawings is not intended to limit the scope of the claimed disclosure, but merely represents selected embodiments of the present disclosure.

[0043] Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present disclosure.

[0044] In the description of this disclosure, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this disclosure and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this disclosure. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] In the description of this disclosure, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this disclosure based on the specific circumstances.

[0046] Example

[0047] like Figure 1 As shown, the present invention proposes a catalytically assisted cracking plasma pure ammonia burner and an operating method thereof, including: Figure 1 As shown, a catalytic cracking plasma pure ammonia burner system for industrial furnaces includes a catalytic cracking zone 1, a pre-combustion zone 2, a main combustion zone 3, a purification zone 4, an ammonia supply zone 5 and a waste heat system 6. Each area is described in detail below.

[0048] like Figure 2As shown, in this embodiment, the catalytic cracking zone 1 is located on both sides of the burner, including an ammonia inlet duct 2-2 and a catalytic reaction zone 104. The catalytic reaction zone 104 is filled with a porous medium, and the catalyst is uniformly fixed and grown in the porous medium. The catalytic cracking zone 1 is connected to the purification zone 4 outside the burner. The catalytic cracking zone 1 is connected to the purification zone 4 through a pipeline. The purification zone 4 is located outside the burner, and a selective separation membrane is provided at its outlet and exhaust port respectively. The cracked gas mixture passes through the selective separation membrane at the outlet, intercepting nitrogen, and the remaining gas enters the pre-combustion zone 3, and the intercepted nitrogen is discharged through the selective separation membrane at the exhaust port.

[0049] In this embodiment, the outlet of purification zone 4 communicates with precombustion zone 2. The pipeline design of catalytic cracking zone 1 is stacked to increase the gas residence time in the pipeline, providing ample time for the ammonia and catalyst to react. Micropores are arranged on the pipeline walls of catalytic reaction zone 104 to improve heat exchange efficiency. The micropores have a diameter of no more than 2 mm. Micropores are not provided on the pipeline walls adjacent to precombustion zone 2.

[0050] like Figure 2 As shown, the pre-combustion zone 2 is located on both sides of the main combustion zone 3. The pre-combustion zone 2 includes an air inlet 1-1 and a plasma igniter 105. The igniter in the pre-combustion zone 2 is a plasma igniter 105. Plasma igniter 105 utilizes a sliding arc discharge structure and includes a high-voltage electrode, a ground electrode, a ceramic swirl ring, and a nozzle. The main fuel mixture passes through the ceramic swirl ring to form a swirl, and plasma is formed between the high-voltage electrode and the ground electrode. Plasma igniter 105 is equipped with a coaxial swirler. The ammonia and air mixture is ejected through the swirler and ignited by the plasma igniter 105, forming a pre-combustion flame 101.

[0051] The main flow direction of the porous medium filled in the pipeline of catalytic cracking zone 1 is consistent with the pipeline gas flow direction. The porous medium material can be porous metal or porous ceramic. The outer walls of catalytic cracking zone 1 and pre-combustion zone 2 are coated with refractory material to prevent long-term ablation damage.

[0052] In addition, the main combustion zone 3 includes a main fuel inlet duct 2-1, an air inlet duct 1-1, a swirler 106 and a combustion-supporting zone 107 with independent micro-ducts arranged at the center of the main combustion zone 3. It is ignited by an igniter to form a duty flame 102 at the center of the main combustion flame 103, further igniting the main fuel mixture and promoting the self-sustaining stable combustion of the main combustion flame 103.

[0053] like Figure 2As shown, it should be noted that a bluff body 108 is provided at the outlet of the combustion-supporting zone 107. The main fuel mixture is ejected through the swirler 106, forming a recirculation zone downstream of the bluff body 108, and is ignited by the plasma-generated service flame 102. The pre-combustion flame 101 is located within the burner, continuously transmitting heat radiation to the wall of the catalytic cracking zone 1. The nozzle of the main combustion flame 103 lags behind the nozzle of the pre-combustion flame 101 and is located downstream of the pre-combustion flame 101.

[0054] During operation, ammonia enters the ammonia inlet 2-2 from the ammonia supply zone 5, passes through the catalytic cracking zone 1 and the purification zone 4, and enters the pre-combustion zone 2, where it mixes with air. The plasma igniter 105 in the pre-combustion zone 2 generates plasma through discharge between electrodes, achieving cold ignition and forming a pre-combustion flame 101, which increases the chamber temperature. Heat is transferred to the catalytic cracking zone 1 through the wall surface, where the porous medium attached to the catalyst stores heat. The catalyst used for ammonia cracking begins to react, and the ammonia is gradually cracked into hydrogen and nitrogen. The cracked gas mixture is passed through a pipeline to the purification zone 4 for purification to remove nitrogen. The addition of purified hydrogen further increases the temperature of the pre-combustion flame 101. The main fuel enters from the main fuel inlet 2-1 and mixes with air to form a main fuel mixture. It is ejected from the swirler 106 and ignited by the high-temperature pre-combustion flame 101, eventually forming a main combustion flame 103 in the main combustion zone 3 downstream of the pre-combustion flame 101. The high temperature generated by the flame flows back into the ammonia supply zone 5 through the waste heat system 6 to be used for vaporization of liquid ammonia in the ammonia tank.

[0055] In this embodiment, based on the above-mentioned catalytically assisted cracking plasma pure ammonia burner, a low NOx emission operation method is provided as follows:

[0056] Excess air is introduced into the pre-combustion zone 2 through the air inlet duct 1-1. A small amount of ammonia, which has passed through the catalytic cracking zone 1, mixes with the excess air. A valve is installed in the pipeline of the pre-combustion zone 2 to gradually increase the flow rate. The plasma igniter 105 achieves cold ignition of ammonia, forming a lean pre-combustion flame 101. Excess fuel and a small amount of air are introduced into the main fuel inlet duct 2-1 of the main combustion zone 3, resulting in low or no oxygen in the center of the main combustion flame 103, forming a rich combustion zone. The main combustion flame 103 lags behind the pre-combustion flame 101. Excess gas from the pre-combustion zone 2 flows into the main combustion zone 3 to form secondary air, ultimately forming a main combustion flame 103 with low oxygen in the center and high oxygen in the outer layer, achieving low NOx emissions.

[0057] It is worth noting that the present invention realizes the cold ignition and stable combustion of ammonia based on the synergistic effect of plasma combustion-assisted and catalytic-assisted cracking. When the cold furnace is started, a plasma igniter is used to directly ignite a small flow of ammonia in the pre-combustion zone without the need for additional preheating; the heat generated by the pre-combustion flame activates the catalyst in the catalytic cracking zone through wall thermal radiation, causing the ammonia to crack into hydrogen. The purified hydrogen is added to the pre-combustion zone to further increase the flame temperature, providing a stable high-temperature heat source for the subsequent ignition of the main combustion zone. At the same time, the duty flame and blunt body reflux structure set in the center of the main combustion zone can effectively maintain the continuous stability of the main combustion flame, completely solving the problem of stable combustion caused by the high ignition energy and slow flame propagation speed of ammonia fuel.

[0058] Among them, staged combustion and staggered layout technology are used to achieve low-nitrogen combustion. Excess air and a small amount of ammonia are introduced into the pre-combustion zone to form a pre-combustion flame under lean-burn conditions, reducing the generation of NOx caused by local high temperatures; excess fuel and a small amount of air are introduced into the main combustion zone to form a central rich combustion zone (low-oxygen or oxygen-free environment) to inhibit nitrogen oxidation; excess air in the pre-combustion zone flows into the outer layer of the main combustion zone as secondary air to achieve complete combustion of the fuel. The staggered arrangement of the pre-combustion flame and the main combustion flame (the main combustion flame is located downstream of the pre-combustion flame) further avoids the formation of a concentrated high-temperature zone of the flame, reduces NOx emissions from a mechanistic perspective, and meets strict environmental protection requirements.

[0059] Furthermore, by constructing a closed-loop system of "ammonia supply-cracking-combustion-waste heat recovery," a cascaded energy utilization system is achieved. The high temperature generated by combustion flows back to the ammonia supply zone through the waste heat system and is directly used to vaporize liquid ammonia, reducing the additional energy consumption required for liquid ammonia vaporization. The catalytic cracking zone utilizes a stacked pipeline design, combined with micropores in the tube wall and a porous media structure, significantly improving heat exchange efficiency and ammonia residence time, thereby increasing the catalytic cracking rate. The purification zone removes nitrogen from the cracked gas through a selective separation membrane, providing high-purity hydrogen to the pre-combustion zone, ensuring combustion efficiency while reducing ineffective energy consumption, significantly optimizing the overall system energy utilization efficiency.

[0060] Furthermore, the system boasts a compact structure and clearly defined functional zones. The catalytic cracking zone is located on either side of the burner, while the pre-combustion zone is located on either side of the main combustion zone. These zones are efficiently connected by pipelines, adapting to the installation and operating space requirements of industrial furnaces. The catalyst in the catalytic reaction zone is fixedly grown in a porous medium, enhancing its stability and service life. The outer walls of the catalytic cracking zone and pre-combustion zone are coated with refractory materials to resist long-term high-temperature ablation and extend the equipment's operating cycle. This system can directly replace traditional burners in industrial furnaces without requiring large-scale modifications to the furnace's main structure, facilitating the rapid promotion and application of ammonia fuel in the industrial sector.

[0061] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant inspirations of the above embodiments, those skilled in the art may make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A catalytically assisted cracking plasma pure ammonia burner, characterized in that: include: The catalytic cracking zone (1) is arranged on both sides of the burner and includes an ammonia inlet channel (2-2) and a catalytic reaction zone (104) with a built-in porous medium, wherein a catalyst is fixedly grown on the surface of the porous medium; The purification zone (4) is located outside the burner and is connected to the outlet of the catalytic cracking zone (1) through a pipeline, and the outlet end and the exhaust end thereof are respectively provided with selective separation membranes; The pre-combustion zone (2) is distributed on both sides of the main combustion zone (3), includes an air inlet channel (1-1) and a plasma igniter (105), and is connected to the outlet of the purification zone (4); A main combustion zone (3) comprising a main fuel inlet duct (2-1), an air inlet duct (1-1), a swirler (106) and a central combustion-supporting zone (107); an ammonia supply area (5), connected to the ammonia inlet duct (2-2); The waste heat system (6) recovers the combustion heat and transports it to the ammonia supply area (5) for vaporization of liquid ammonia; The ammonia is cracked into a hydrogen-nitrogen mixed gas in a catalytic cracking zone (1) and the nitrogen is separated in a purification zone (4). The hydrogen is then injected into a pre-combustion zone (2) and mixed with air. The mixture is then cold-ignited by a plasma igniter (105) to form a pre-combustion flame (101). The main fuel mixed gas in the main combustion zone (3) is ignited by the pre-combustion flame (101) to form a main combustion flame (103), and the nozzle of the main combustion flame (103) lags behind the nozzle of the pre-combustion flame (101).

2. The catalytically assisted cracking plasma pure ammonia burner according to claim 1, characterized in that: The plasma igniter (105) adopts a sliding arc discharge structure, comprising a high-voltage electrode, a ground electrode, a ceramic cyclone ring and a nozzle; the pre-combustion zone (2) is provided with a coaxial cyclone, so that the ammonia-air mixture forms a cyclone and is ignited by the plasma.

3. The catalytically assisted cracking plasma pure ammonia burner according to claim 1, characterized in that: The pre-combustion flame (101) continuously radiates heat to the wall surface of the catalytic cracking zone (1), and the outer walls of the catalytic cracking zone (1) and the pre-combustion zone (2) are coated with refractory materials.

4. The catalytically assisted cracking plasma pure ammonia burner according to claim 1, characterized in that: The combustion-supporting zone (107) is an independent micro-duct structure, and a blunt body (108) is provided at its outlet end. After ignition, a duty flame (102) is formed in the center of the main combustion flame (103), and a recirculation zone is formed downstream of the blunt body (108) to promote stable combustion.

5. The catalytically assisted cracking plasma pure ammonia burner according to claim 1, characterized in that: The pipeline of the catalytic cracking zone (1) is a stacked structure to extend the gas residence time; the wall surface of the pipeline of the catalytic reaction zone (104) is provided with micropores with a pore size of ≤2 mm.

6. The catalytically assisted cracking plasma pure ammonia burner according to claim 1, characterized in that: The main flow direction of the gas in the porous medium is consistent with the flow direction of the pipeline, and the material is porous metal or porous ceramic.

7. The catalytically assisted cracking plasma pure ammonia burner according to claim 1, characterized in that: The selective separation membrane of the purification zone (4) intercepts nitrogen at the outlet end and passes hydrogen into the pre-combustion zone (2), and the separation membrane at the exhaust end discharges the intercepted nitrogen.

8. A burner operation method according to any one of claims 1 to 7, characterized in that: The following steps are involved: Pre-combustion stage: excess air and a small amount of ammonia are introduced into the pre-combustion zone (2), the flow rate is gradually increased through a valve, and a plasma igniter (105) is used for cold ignition to form a lean pre-combustion flame (101); Main combustion stage: excess fuel and a small amount of air are introduced into the main combustion zone (3) to form a fuel-rich mixture; the pre-combustion flame (101) heats the catalytic cracking zone (1) to produce hydrogen, which is then injected into the pre-combustion zone (2) after purification to increase the flame temperature; the main combustion mixture is ignited by the pre-combustion flame (101) to form a main combustion flame (103) with little or no oxygen in the center and rich oxygen in the outer layer, and the excess air in the pre-combustion zone (2) is introduced into the main combustion zone (3) as secondary air.

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