Combustor system and method suitable for iron powder

Abstract

The invention discloses a burner system and method suitable for iron powder. The burner system sequentially comprises a premixing cavity, a pre-burning area, a main burning area, a burnout area and a flue gas distribution system in the flue gas flowing direction. According to the invention, tangential air on the side wall of the premixing cavity forms a homodromous swirling flow field, so that premixing of iron powder and air is enhanced; the pre-combustion area is provided with a high-energy igniter and a reverse jet nozzle, high-temperature flue gas is introduced to form a backflow area, iron powder ignition is assisted, and flames are stabilized; weak rotational flow air and adherent air are alternately arranged in the main combustion area, and a micro-bulge structure is matched, so that adherent slagging of iron powder is prevented, and sufficient combustion is promoted. The burnout area adopts a divergent conical structure and is supplemented with burnout air to ensure that iron powder particles are completely burnt out; the flue gas distribution system adopts a'main path + circulation path 'double-flow-direction design, the distribution proportion is regulated and controlled through an electromagnetic flow valve, flue gas in the main path enters a boiler hearth for heat exchange, flue gas in the circulation path is subjected to cyclone separation and then flows back to a pre-combustion area, and energy gradient utilization and stable combustion are achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of combustion equipment, and particularly relates to a burner system and method suitable for iron powder. BACKGROUND

[0002] Iron powder, as a potential zero-carbon energy carrier, has advantages of high volumetric energy density, low production and use cost, and abundant reserves. Its combustion products can be reduced by green energy such as hydrogen, realizing the cyclic storage and utilization of energy, and having broad application prospects. However, the physical and chemical properties of iron powder are significantly different from those of traditional fossil fuels (such as coal powder and fuel gas): first, the density of iron powder is much higher than that of coal powder, which is easy to settle and agglomerate in the gas flow, resulting in difficult transportation and uneven gas-solid mixing; second, the ignition temperature of iron powder is high, and it is difficult to ignite by conventional ignition methods, and the flame stability is poor; third, high-density and high-hardness iron powder particles are easy to cause erosion and wear of the burner wall under high-speed flow, and molten iron oxide is easy to adhere to the wall and form slag, affecting the safe and stable operation of the system. The existing coal powder burner or fuel gas burner cannot adapt to the above characteristics of iron powder, and direct application will cause problems such as difficult ignition, low combustion efficiency, serious slagging, and rapid equipment wear. Therefore, it is urgent to develop a burner system and method suitable for iron powder fuel to solve the technical problems of ignition, stable combustion, complete combustion, and safe operation, and to promote the large-scale application of iron powder clean energy. SUMMARY

[0003] In view of the deficiencies in the prior art, the purpose of the present application is to provide a burner system and method suitable for iron powder, which realizes uniform mixing of iron powder and air, stable ignition and efficient combustion of iron powder, prevents slagging and erosion and wear of the burner wall, and balances low nitrogen emission and energy efficient utilization, thereby providing technical support for the industrial application of iron powder as a zero-carbon energy carrier.

[0004] To achieve the above-mentioned purpose, the present application provides a burner system suitable for iron powder, which comprises a premixing chamber, a pre-combustion zone, a main combustion zone, a burnout zone and a burner outlet connected in sequence along the flue gas flow direction: The upstream end of the premixing chamber is provided with an iron powder-air inlet for introducing an iron powder-air mixture, and the side wall is provided with a tangential wind inlet for injecting tangential wind into the premixing chamber along the tangential direction of the chamber wall, and the downstream end is sealingly connected to the upstream end of the pre-combustion zone; The downstream end of the pre-combustion zone is sealingly connected to the upstream end of the main combustion zone; a local bulge structure is arranged on the cavity wall, and a high-energy igniter and a reverse jet nozzle are arranged; The downstream end of the main combustion zone is sealingly connected to the upstream end of the burnout zone; the side wall is alternately provided with a weak swirl wind inlet and a wall-attached wind inlet along the horizontal direction, and the cavity wall region corresponding to each weak swirl wind inlet and wall-attached wind inlet is provided with a micro-bulge structure; The downstream end of the burnout zone is sealed and connected to the upstream end of the burner outlet; and the burnout zone adopts a gradually expanding conical cavity structure with burnout air inlets evenly distributed on the side wall. The reverse jet nozzle is connected to the flue gas diversion circuit at the burner outlet through a pipeline, and is used to reversely inject part of the high-temperature flue gas at the burner outlet into the pre-combustion zone.

[0005] Downstream of the burner outlet, a flue gas diversion structure is provided to divide the high-temperature flue gas discharged from the burner outlet into main path flue gas and circulating path flue gas. The main path flue gas enters the boiler furnace along the main flue and participates in the heat exchange process. The circulating path flue gas is introduced into a cyclone separator along the diversion pipeline. The gas outlet of the cyclone separator is connected to a check valve and a flow control device in sequence through a return pipeline. The end of the return pipeline is connected to the reverse jet nozzle of the pre-combustion zone.

[0006] The flow control device includes a variable frequency booster fan that provides power for the flue gas recirculation along the flue gas flow direction of the recirculation pipeline, and an electromagnetic flow valve for precisely controlling the flow rate and pressure parameters of the flue gas recirculated to the pre-combustion zone.

[0007] The bottom of the cyclone separator is connected to a solid product collection device that collects the solid particles separated by the cyclone separator via a solid product outlet.

[0008] An iron powder supply system is provided upstream of the premixing chamber. The iron powder supply system includes an iron powder storage bin, a rotary feeder, and a blower. The outlet of the iron powder storage bin is connected to the inlet of the rotary feeder, and the outlet of the rotary feeder is connected to the outlet pipe of the blower through a pipeline.

[0009] The high-energy igniters are respectively embedded on the two side cavity walls of the pre-combustion zone entrance area, and the ignition ends of the two high-energy igniters extend into the pre-combustion zone to reliably ignite the iron powder-air mixture entering the pre-combustion zone.

[0010] The inner surface of the cavity wall of the main combustion zone is coated with a high-temperature and wear-resistant composite coating to resist the erosion and wear of iron powder particles under high temperature conditions.

[0011] A combustion method for iron powder based on the above system includes the following steps: S1: Iron powder is discharged from the iron powder storage silo and enters the rotary feeder, which quantitatively conveys it to the outlet pipeline of the blower; the blower sends air into the pipeline, which mixes with the quantitative iron powder to form an iron powder-air mixture; the iron powder-air mixture enters the premixing chamber through the iron powder-air inlet, while tangential air is sent in along the tangential direction of the premixing chamber wall through the tangential air inlet, forming an enhanced co-current swirling field in the premixing chamber, realizing uniform gas-solid premixing of iron powder and air; S2: The premixed iron powder-air mixture enters the pre-combustion zone, and the high-energy igniter is started and releases ignition energy to the mixture to ignite part of the iron powder particles; at the same time, the high-temperature flue gas at the outlet of the burner enters the reverse jet nozzle through the circulation path to inject high-temperature gas flow into the pre-combustion zone; the high-temperature flue gas forms a stable recirculation zone in the local bulging structure area of the pre-combustion zone, continuously providing preheating and ignition conditions for unburned iron powder particles, and the local bulging structure prolongs the residence time of the iron powder in the pre-combustion zone, ensuring stable ignition; S3: The stably ignited iron powder particles enter the main combustion zone, and the weak swirl wind is injected into the main combustion zone through the weak swirl wind inlet to provide rotational power for the combustion process and strengthen the turbulent mixing of iron powder and oxygen; the wall-attached wind is sent into the main combustion zone along the tangent direction of the inner wall to form a uniform anti-wall-attached gas film, which isolates the direct contact between high-temperature iron powder particles and the wall; the micro-bulging structure in the main combustion zone controls the local flue gas velocity to avoid the sedimentation of iron powder particles, realizing efficient and stable combustion of iron powder particles in a high-temperature environment; S4: The unburned iron powder particles enter the burnout zone with the flue gas, and the burnout wind is sent into the burnout zone through the burnout wind inlet to supplement the oxygen required for combustion; the gradually expanding cone structure of the burnout zone reduces the flue gas velocity and prolongs the residence time of the iron powder particles in the burnout zone, ensuring that the unburned iron powder particles are fully burned out; S5: The high-temperature flue gas after burning is discharged through the outlet of the burner, and most of the flue gas directly enters the boiler furnace to participate in heat exchange; a small part of the flue gas enters the cyclone separator through the shunt pipeline, and the gas-solid separation is realized through the cyclone separator to separate the solid products and collect them; the separated high-temperature gas is adjusted by the check valve, variable frequency booster fan and electromagnetic flow valve, and then flows back to the reverse jet nozzle of the pre-combustion zone to continue to provide stable combustion heat source for the pre-combustion zone.

[0012] In the step S5, the opening of the electromagnetic flow valve is adjusted to control the distribution ratio of the main path flue gas and the circulating path flue gas; while ensuring the heat exchange demand of the boiler furnace, the high-temperature characteristics of the circulating path flue gas are used to realize stable combustion in the pre-combustion zone, and the overall energy utilization rate of the burner system is improved.

[0013] The present application solves the technical problems of high density, easy agglomeration, high ignition temperature, easy slagging and wear, and difficult burning of iron powder as fuel by constructing a staged combustion process of "premixing cavity swirl premixing, high-temperature ignition in pre-combustion zone, mixed combustion in main combustion zone, and air supply and burning in burnout zone", and coupling a high-temperature flue gas internal circulation system. The high-temperature flue gas at the outlet of the system is divided into two parts, one part enters the boiler for heat exchange to realize energy output, and the other part enters the pre-combustion zone as a high-temperature gas source to assist ignition after being separated by a cyclone separator, realizing the cascade and recycling of energy within the system, and significantly improving the overall energy utilization efficiency.

[0014] The present application realizes the accurate control of the flow field, temperature field and reaction process in the iron powder combustion process by independently regulating the wind system parameters of the tangential wind, weak rotational flow wind, wall-attached wind and burnout wind in each functional area, ensuring the stable, efficient and safe operation of the combustion process. In addition, through the precise regulation of the temperature of the main combustion zone, the generation of thermal nitrogen oxides is effectively inhibited, achieving ultra-low emission of pollutants and having significant environmental advantages.

[0015] The present application has at least the following beneficial technical effects: (1) The iron powder combustion process does not produce greenhouse gases such as carbon dioxide, solving the carbon emission problem caused by traditional fossil fuels and providing a reliable technical path for achieving carbon neutralization in industrial heating scenarios.

[0016] (2) The solid product generated by combustion is mainly iron oxide, which can be efficiently collected through a cyclone separator. The collected iron oxide can be used as a raw material in the metallurgical and chemical industries, or can be regenerated into iron powder through hydrogen and other green energy sources, building a resource closed-loop utilization system and fitting the concept of circular economy development.

[0017] (3) The tangential wind rotational flow design of the premixing cavity and the iron powder supply system form a synergistic effect, which can effectively disperse iron powder agglomerate particles and specifically solve the technical pain point of high-density iron powder settlement, significantly improving the uniformity of gas-solid mixing and laying a foundation for subsequent stable combustion.

[0018] (4) The high-energy igniter and reverse jet nozzle are set in the precombustion zone to reduce the iron powder ignition energy consumption using high-temperature flue gas waste heat, adapt to the combustion characteristics of iron powder with high ignition temperature characteristics, and ensure the ignition success rate and stability.

[0019] (5) The integrated design of "weak rotational flow wind + wall-attached wind + micro-bulging" in the main combustion zone, on the one hand, strengthens the gas-solid mixing effect through weak rotational flow wind, and on the other hand, forms a uniform protective gas film through wall-attached wind, effectively avoiding direct contact of iron powder particles with the wall and melting oxide wall slag, significantly reducing the risk of equipment erosion and wear, and prolonging the service life of the burner.

[0020] (6) The gradual expansion type structure design is adopted in the burnout zone, which can prolong the residence time of iron powder particles in the combustion system, cooperate with the precise air supply design to provide sufficient oxygen for iron powder particles, ensure the full oxidation reaction of iron powder particles, and significantly improve the combustion efficiency.

[0021] (7) Through the flue gas shunting structure at the outlet of the burner, part of the high-temperature flue gas is backflowed to the precombustion zone as an auxiliary ignition and stable combustion heat source, without the need for additional auxiliary fuel, realizing the cascade utilization and recycling of energy within the system, significantly improving the overall energy utilization efficiency and reducing the equipment operation cost.

[0022] (8) The system adopts a hierarchical combustion mode to accurately control the reaction temperature of the main combustion zone, effectively inhibits the generation path of thermal nitrogen oxides, realizes low-nitrogen emission of the combustion process, meets the environmental protection emission requirements, and has outstanding environmental protection advantages.

[0023] (9) The application provides a key combustion technology equipment suitable for the large-scale industrial application of iron powder, breaks the technical bottleneck of the industrial scene application of iron powder as a zero-carbon energy carrier, enriches the utilization path of clean energy, and provides strong technical support for the energy structure transformation in the industrial field. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a structural schematic diagram of the iron powder burner system suitable for the application, and The numeral 1 is an iron powder storage bin, 2 is a rotary feeder, 3 is a blower, 4 is an iron powder-air inlet, 5 is a premixing chamber, 6 is a tangential air inlet, 7 is a high-energy igniter, 8 is a reverse jet nozzle, 9 is a precombustion zone, 10 is a main combustion zone, 11 is a weak swirl air inlet, 12 is a wall-attached air inlet, 13 is a burnout zone, 14 is a burnout air inlet, 15 is a burner outlet, 16 is a cyclone separator, 17 is a solid product, 18 is a check valve, 19 is a variable-frequency booster blower, and 20 is an electromagnetic flow valve. DETAILED DESCRIPTION

[0025] The application will be further described in detail below in combination with specific examples, which are an explanation rather than a limitation of the application.

[0026] As shown in Figure 1 The application provides an iron powder burner system suitable for the application, which is composed of an iron powder supply unit, a combustion core unit and a flue gas circulation unit, and the specific structure, connection relationship and function of each unit are as follows: (1) The iron powder supply unit includes an iron powder storage bin 1, a rotary feeder 2 and a blower 3; wherein the discharge port of the iron powder storage bin 1 is connected to the feeding end of the rotary feeder 2 through a pipeline, and the discharge end of the rotary feeder 2 is combined with the air outlet of the blower 3, and then they are jointly connected to the iron powder-air inlet 4 of the premixing chamber 5, so as to realize the quantitative mixing and conveying of iron powder and combustion air.

[0027] (2) The combustion core unit: the premixing chamber 5, the precombustion zone 9, the main combustion zone 10 and the burnout zone 13 are connected in series along the flue gas flow direction; The premixing chamber 5: tangential air inlets 6 are symmetrically opened on the two side walls in the circumferential direction, which are used to connect the tangential air; after the tangential air is connected through the inlet, a uniform co-swirl flow field is formed in the premixing chamber 5, and the swirl disturbance is used to strengthen the gas-solid mixing uniformity of the iron powder-air mixture; Precombustion zone 9: its upstream end is sealed with the downstream end of premixing cavity 5, the high-energy igniter 7 is symmetrically embedded in the wall on both sides of the inlet end, the ignition end of the high-energy igniter 7 extends into the precombustion zone 9, which is used to provide initial ignition energy; at the same time, 2 interfaces are symmetrically opened along the axis of the precombustion zone 9, and each interface is sealed and connected with a reverse jet nozzle 8, so that the backflow high-temperature flue gas can be uniformly injected into the precombustion zone 9, and a stable high-temperature ignition environment is formed with the high-energy igniter 7; Main combustion zone 10: its upstream end is sealed with the downstream end of the precombustion zone 9, and the weak swirl air inlets 11 and the wall-attached air inlets 12 are alternately and symmetrically opened in the flue gas flow direction on the two side walls; the micro-bulge structure is fixedly arranged on the cavity wall area corresponding to each weak swirl air inlet 11 and wall-attached air inlet 12, the weak swirl air is used for strengthening mixing, the wall-attached air is used for forming a wall gas film, and the micro-bulge structure is used for controlling the flow field, so that the iron powder is efficiently combusted and the wall is protected; Burnout zone 13: its upstream end is sealed with the downstream end of the main combustion zone 10, and the burnout air inlets 14 are symmetrically opened in the circumferential direction on the two side walls, which are used for supplementing oxygen required in the later stage of combustion; its downstream outlet end is sealed and communicated with the burner outlet 15, which is used for leading out the high-temperature flue gas after combustion.

[0028] (3) Flue gas circulation unit: the high-temperature flue gas discharged from the burner outlet 15 is divided into two paths: one path is used as the main path flue gas, which directly enters the boiler furnace through the flow guide channel to participate in heat exchange in the furnace and realize energy output; the other path is used as the circulation path flue gas, which is connected with the inlet of the cyclone separator 16, the check valve 18, the variable frequency booster fan 19 and the electromagnetic flow valve 20 in sequence through the shunt pipeline, and finally connected with the reverse jet nozzle 8 of the precombustion zone 9 through the pipeline to form a complete flue gas circulation loop.

[0029] The application provides a combustion method suitable for iron powder, which comprises the following steps: S1: the iron powder is discharged from the iron powder storage bin 1 into the rotary feeder 2, and then quantitatively fed to the outlet pipeline of the air feeder 3 by the rotary feeder 2; the air feeder 3 sends air into the pipeline to mix with the quantitative iron powder to form an iron powder-air mixture; the iron powder-air mixture enters the premixing cavity 5 through the iron powder-air inlet 4 of the premixing cavity 5, and the tangential wind is sent into the premixing cavity 5 along the tangent direction of the cavity wall to form a strengthened co-rotating swirl field in the premixing cavity 5, so as to realize uniform gas-solid premixing of the iron powder and air; S2: The premixed iron powder-air mixture enters the pre-combustion zone 9. The high-energy igniter 7 is activated and releases ignition energy into the mixture, igniting some of the iron powder particles. At the same time, the high-temperature flue gas from the burner outlet 15 enters the reverse jet nozzle 8 through the circulation path and injects high-temperature airflow into the pre-combustion zone 9. The high-temperature flue gas forms a stable reflux zone in the local bulging structure area of ​​the pre-combustion zone 9, continuously providing preheating and ignition conditions for the unburned iron powder particles. The local bulging structure also prolongs the residence time of the iron powder in the pre-combustion zone 9, ensuring ignition stability. S3: After stable ignition, the iron powder particles enter the main combustion zone 10. The weak swirling air is injected into the main combustion zone 10 through the weak swirling air inlet 11 to provide rotational power for the combustion process and enhance the turbulent mixing of iron powder and oxygen. The wall-adhering air is sent into the main combustion zone 10 along the tangential direction of the inner wall through the wall-adhering air inlet 12 to form a uniform anti-wall-adhering gas film, which isolates the high-temperature iron powder particles from direct contact with the vessel wall. The micro-bulge structure in the main combustion zone 10 regulates the local flue gas velocity to prevent iron powder particles from settling, thereby achieving efficient and stable combustion of iron powder particles in a high-temperature environment. S4: Incompletely burned iron powder particles enter the burnout zone 13 with the flue gas. Burnout air is sent into the burnout zone 13 through the burnout air inlet 14 to supplement the oxygen required for combustion. The gradually expanding conical structure of the burnout zone 13 reduces the flue gas velocity and prolongs the residence time of iron powder particles in the burnout zone 13, ensuring that the unburned iron powder particles are fully burned. S5: The high-temperature flue gas after combustion is discharged through the burner outlet 15. Most of the flue gas directly enters the boiler furnace to participate in heat exchange. A small part of the flue gas enters the cyclone separator 16 through the diversion pipeline. The cyclone separator 16 achieves gas-solid separation, separating out the solid products 17 (mainly iron oxide) and collecting them. After the separated high-temperature gas passes through the check valve 18, the variable frequency booster fan 19 and the electromagnetic flow valve 20 to adjust the parameters, it flows back to the reverse jet nozzle 8 of the pre-combustion zone 9 to continue to provide a stable combustion heat source for the pre-combustion zone 9.

Claims

1. A burner system suitable for iron powder, characterized in that, Along the flue gas flow direction, it includes a premixing chamber (5), a pre-combustion zone (9), a main combustion zone (10), a burnout zone (13), and a burner outlet (15) connected in sequence: The upstream end of the premixing chamber (5) is provided with an iron powder-air inlet (4) for introducing a mixture of iron powder and air, and the side wall is provided with a tangential air inlet (6) for injecting tangential air into the premixing chamber (5) along the tangential direction of the chamber wall. The downstream end is sealed and connected to the upstream end of the pre-combustion zone (9). The downstream end of the pre-combustion zone (9) is sealed and connected to the upstream end of the main combustion zone (10); its cavity wall is provided with a local bulge structure and is equipped with a high-energy igniter (7) and a reverse jet nozzle (8). The downstream end of the main combustion zone (10) is sealed and connected to the upstream end of the burnout zone (13); Its sidewalls are alternately distributed with weak swirling air inlets (11) and wall-mounted air inlets (12) in the horizontal direction, and each cavity wall area corresponding to a weak swirling air inlet (11) and a wall-mounted air inlet (12) is provided with a micro-bulge structure; The downstream end of the burnout zone (13) is sealed and connected to the upstream end of the burner outlet (15); and the burnout zone (13) adopts a gradually expanding conical cavity structure with burnout air inlets (14) evenly distributed on the side wall. The reverse jet nozzle (8) is connected to the flue gas diversion circuit of the burner outlet (15) through a pipeline, and is used to reversely inject part of the high-temperature flue gas from the burner outlet (15) into the pre-combustion zone (9).

2. The burner system for iron powder according to claim 1, characterized in that, Downstream of the burner outlet (15), there is a flue gas diversion structure that divides the high-temperature flue gas discharged from the burner outlet (15) into main path flue gas and circulating path flue gas; the main path flue gas enters the boiler furnace along the main flue and participates in the heat exchange process; the circulating path flue gas is introduced into the cyclone separator (16) along the diversion pipeline, and the gas outlet of the cyclone separator (16) is connected to the check valve (18) and the flow control device in sequence through the return pipeline, and the end of the return pipeline is connected to the reverse jet nozzle (8) of the pre-combustion zone (9).

3. The burner system for iron powder according to claim 2, characterized in that, The flow control device includes a variable frequency booster fan (19) that provides power for the flue gas recirculation along the flue gas flow direction of the recirculation pipeline, and an electromagnetic flow valve (20) for precisely controlling the flue gas flow and pressure parameters recirculated to the pre-combustion zone (9).

4. The burner system for iron powder according to claim 2, characterized in that, The bottom of the cyclone separator (16) is connected to a solid product collection device (17) that collects the solid particles separated by the cyclone separator (16) via a solid product outlet.

5. The burner system for iron powder according to claim 1, characterized in that, An iron powder supply system is provided upstream of the premixing chamber (5). The iron powder supply system includes an iron powder storage silo (1), a rotary feeder (2), and a blower (3). The outlet of the iron powder storage silo (1) is connected to the inlet of the rotary feeder (2), and the outlet of the rotary feeder (2) is connected to the outlet pipe of the blower (3) through a pipeline.

6. The burner system for iron powder according to claim 1, characterized in that, The high-energy igniters (7) are respectively embedded on the two side walls of the inlet area of ​​the pre-combustion zone (9), and the ignition ends of the two high-energy igniters (7) extend into the interior of the pre-combustion zone (9) to reliably ignite the iron powder-air mixture entering the pre-combustion zone (9).

7. The burner system for iron powder according to claim 1, characterized in that, The inner surface of the cavity wall of the main combustion zone (10) is coated with a high-temperature wear-resistant composite coating to resist the erosion and wear of iron powder particles under high temperature conditions.

8. A combustion method for iron powder based on the system according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Iron powder is discharged from the iron powder storage silo (1) and enters the rotary feeder (2), which quantitatively conveys it to the outlet pipeline of the blower (3); the blower (3) sends air into the pipeline and mixes it with the quantitative iron powder to form an iron powder-air mixture; the iron powder-air mixture enters the premixing chamber (5) through the iron powder-air inlet (4), and at the same time, tangential air is sent into the premixing chamber (5) along the tangential direction of the premixing chamber (5) wall through the tangential air inlet (6), forming a strengthened unidirectional swirling flow field in the premixing chamber (5) to achieve uniform gas-solid premixing of iron powder and air; S2: The premixed iron powder-air mixture enters the pre-combustion zone (9), the high-energy igniter (7) starts and releases ignition energy to the mixture, igniting some iron powder particles; at the same time, the high-temperature flue gas from the burner outlet (15) enters the reverse jet nozzle (8) through the circulation path and sprays high-temperature airflow into the pre-combustion zone (9); the high-temperature flue gas forms a stable reflux zone in the local bulging structure area of ​​the pre-combustion zone (9), continuously providing preheating and ignition conditions for unburned iron powder particles, and the local bulging structure prolongs the residence time of iron powder in the pre-combustion zone (9), ensuring ignition stability; S3: After stable ignition, the iron powder particles enter the main combustion zone (10). The weak swirling air is injected into the main combustion zone (10) through the weak swirling air inlet (11) to provide rotational power for the combustion process and enhance the turbulent mixing of iron powder and oxygen. The wall-adhering air is sent into the main combustion zone (10) along the tangential direction of the inner wall of the main combustion zone (10) through the wall-adhering air inlet (12) to form a uniform anti-wall-adhering gas film, which isolates the high-temperature iron powder particles from direct contact with the vessel wall. The micro-bulge structure in the main combustion zone (10) regulates the local flue gas velocity, avoids the settling of iron powder particles, and realizes efficient and stable combustion of iron powder particles in a high-temperature environment. S4: Incompletely burned iron powder particles enter the burnout zone (13) with the flue gas. Burnout air is sent into the burnout zone (13) through the burnout air inlet (14) to supplement the oxygen required for combustion. The gradually expanding conical structure of the burnout zone (13) reduces the flue gas flow rate and prolongs the residence time of iron powder particles in the burnout zone (13), ensuring that the unburned iron powder particles are fully burned. S5: The high-temperature flue gas after combustion is discharged through the burner outlet (15), and most of the flue gas directly enters the boiler furnace to participate in heat exchange; a small part of the flue gas enters the cyclone separator (16) through the diversion pipeline, and gas-solid separation is achieved through the cyclone separator (16), separating out the solid products (17) and collecting them; the separated high-temperature gas is returned to the reverse jet nozzle (8) of the pre-combustion zone (9) after the parameters are adjusted by the check valve (18), the variable frequency booster fan (19) and the electromagnetic flow valve (20), and continues to provide a stable combustion heat source for the pre-combustion zone (9).

9. The combustion method for iron powder according to claim 8, characterized in that, In step S5, the distribution ratio of main path flue gas and circulating path flue gas is controlled by adjusting the opening of electromagnetic flow valve (20); while ensuring the heat exchange requirements of boiler furnace, the high temperature characteristics of circulating path flue gas are used to achieve stable combustion in pre-combustion zone (9) and improve the overall energy utilization rate of burner system.

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