Iron powder fluidization combustion boiler

Abstract

The invention discloses an iron powder fluidization combustion boiler which comprises a boiler body, a feeding assembly, an ignition air supply device, an iron powder fluidization uniform air injection device and a balance separation return feeder assembly. High-pressure hot air passes through an iron powder fluidization uniform air injection device at the bottom of the combustion chamber to fluidize bed materials, iron powder in the combustion chamber of the boiler is subjected to fluidization combustion, and the combustion reaction formula is 3Fe + 2O2 = Fe3O4; and meanwhile, a large amount of heat is released, the iron powder is subjected to circulating fluidization combustion between the combustion chamber and the balance separation return feeder assembly, and Fe3O4 generated by the burnt-out iron powder is collected through a discharge port and used as an industrial production raw material. Iron powder is adopted as boiler fuel, the climate problem caused by CO2 emission and the environmental pollution problem caused by nitrogen and sulfur oxide emission can be effectively solved, and the dual-carbon target that carbon reaches the peak and is neutralized is achieved. In addition, a fluidization injection device and a balance separation return feeder are optimized, so that the fluidization air volume and air pressure are more stable, inertial separation of unburned iron powder particles is more facilitated, and the combustion efficiency and the operation stability of the boiler are improved.

Description

Technical Field

[0001] This invention belongs to the field of boiler equipment technology, specifically an iron powder fluidized combustion boiler. Background Technology

[0002] Most existing boilers use coal, oil, and natural gas as fuel. The main byproduct of fossil fuel combustion is carbon dioxide, the leading greenhouse gas causing global warming and sea-level rise. Nitrogen oxides and sulfur oxides produced by fossil fuel combustion are also major sources of air pollutants. Furthermore, the prices of oil and natural gas fluctuate wildly due to factors such as international politics, market supply and demand, and geopolitical conflicts. Users bear price risks, and in the long run, their prices are generally on an upward trend as fossil fuel resources gradually deplete and extraction costs increase.

[0003] Under the national "dual carbon" goal, the carbon-free alternatives to fossil fuels have become crucial. Currently, the mainstream carbon-free fuels are hydrogen and ammonia. However, hydrogen has a wide explosion limit range, poor safety, and high storage and transportation costs, making large-scale promotion difficult. Ammonia, on the other hand, suffers from difficulty in ignition and poor combustion stability, while its high nitrogen oxide emissions also pose environmental challenges. Therefore, seeking a new generation of high-energy-density, low-cost, easily stored and transported, and safe carbon-free fuels as renewable energy carriers is key to achieving carbon-free fuel alternatives.

[0004] Metallic fuels are a new type of carbon-free fuel, and one of the most promising. Firstly, their zero-carbon nature aligns with the urgent need for decarbonization. Metallic fuels outperform fossil fuels, hydrogen, and ammonia in energy density, and offer advantages in storage and long-distance transportation. Metallic additives are common in solid rocket propellants and explosives because they can increase energy density. Micron-sized iron powder is considered the most promising metallic fuel. Iron is abundant in the Earth's crust, and mining and smelting infrastructure is well-developed, making it widely available and inexpensive. Furthermore, unlike traditional hydrocarbon fuels, iron powder combustion is a typical heterogeneous combustion process, where iron particles melt first and then burn with oxygen on their surface. The adiabatic flame temperature of iron powder combustion is comparable to that of methane, and even smaller nanoscale oxides are generated during combustion. Therefore, micron-sized iron powder is considered the most promising metallic fuel. However, iron powder combustion is currently still in the laboratory research stage, and there is a lack of end-use equipment that can efficiently release the high energy density of iron powder. Summary of the Invention

[0005] This invention proposes a fluidized bed boiler for iron powder, which aims to solve the greenhouse gas and nitrogen oxide emissions problems of existing fossil fuel boilers and fill the market gap for end-use equipment that can efficiently release the high energy density of iron powder.

[0006] The purpose of this invention is to achieve efficient and stable combustion of iron powder in a boiler, providing a feasible solution for carbon-free energy substitution. The specific solution is as follows: A fluidized bed combustion boiler for iron powder includes a furnace body, a feeding assembly, an ignition and air supply device, an iron powder fluidized uniform air injection device, and a balanced separation and return material assembly. The furnace body has a vertical structure with water-cooled walls on its side walls. The furnace body has an air chamber and a combustion chamber arranged from bottom to top. The iron powder fluidizing uniform air injection device is located between the combustion chamber and the air chamber inside the furnace body. The discharge port of the feeding assembly is connected to the combustion chamber and is used to transport iron powder into the combustion chamber; The ignition and air supply device is connected to the air chamber, and the side wall of the ignition and air supply device is connected to an air inlet. An ignition component is installed inside the ignition and air supply device. The balanced separation return feeder assembly is connected to the flue gas exhaust port at the top of the furnace body via a connecting flue, and is used to separate unburned iron powder in the flue gas. The lower end of the balanced separation return feeder assembly is connected to the combustion chamber via a return pipe.

[0007] In this process, iron powder undergoes fluidized combustion within the boiler combustion chamber, with the combustion reaction 3Fe + 2O₂ = Fe₃O₄. This process releases a significant amount of heat. The iron powder circulates and undergoes fluidized combustion between the combustion chamber and the equilibrium separation and return feeder assembly, achieving a burnout rate of over 99%. The heat generated during combustion is exchanged with water through the boiler's water-cooled walls, providing hot water or steam for production and daily life.

[0008] In this invention, the boiler combustion chamber is vertically arranged with a bed material layer at the bottom. High-pressure hot air fluidizes the bed material through an iron powder fluidization and equalization air injection device at the bottom of the combustion chamber, with a fluidization height between 400 and 1000 mm. When the temperature reaches approximately 600 degrees Celsius, iron powder (Φ60~100 μm) is transported into the combustion chamber, where it undergoes intense spark-like combustion. Some unburned iron powder particles carried away by the hot air flow are separated by a balance separation return feeder assembly and return to the combustion chamber to participate in combustion. The burned iron powder generates Fe3O4, which is collected through the discharge port for use as raw material in industrial production.

[0009] Preferably, the iron powder fluidizing uniform air injection device includes a conical perforated plate and an air cap fixing perforated plate disposed in the furnace body. The air cap fixing perforated plate is located above the conical perforated plate. Multiple conical holes are evenly distributed on the conical perforated plate, and the inner diameter of the conical holes gradually decreases from bottom to top. The wind cap fixing plate has multiple small-hole wind caps connected by threads.

[0010] The distance between the conical perforated plate and the wind cap fixing perforated plate is 350~450mm, preferably 400mm.

[0011] Existing fluidization devices typically consist of a single air distribution plate, connecting pipes, and air caps. Due to the influence of the air chamber structure, the air volume and pressure distribution are not very uniform, thus affecting the fluidization effect of iron powder fuel. The conical perforated plate structure of this invention involves opening a certain number of conical holes of a certain diameter on a heat-resistant steel plate. The fluidizing air first passes through this plate for the first step of air volume and pressure balancing, then enters the stable volume and pressure space, and then enters the fixed air cap perforated plate and is ejected from the small-hole air cap, resulting in more stable and uniform air volume and pressure.

[0012] Specifically, after the fluidizing air enters the air chamber, it first passes through a conical orifice plate to balance the air volume and pressure in different parts of the air chamber space, with the air velocity controlled at around 10 m / s. After entering a stable volume and pressure space with a height of about 400 mm, the air volume and pressure distribution in different parts becomes more uniform. Then, it is injected into the iron powder fluidization space through a small-hole air cap. The small-hole air cap is threadedly fastened to the fixed air cap orifice plate. Each small-hole air cap has 6 Φ3 small holes that are evenly distributed around its perimeter and tilted downwards at 15 degrees. The air velocity injected through the small holes is controlled between 50 and 70 m / s to ensure stable and uniform fluidization and combustion of the iron powder.

[0013] Preferably, a slag discharge pipe is connected to the air cap fixing plate, and the slag discharge pipe passes downward through the conical plate and extends out of the lower part of the furnace body.

[0014] Preferably, the inner diameter of the top of the conical hole is 3~39mm, the diameter of the bottom is 4~40mm, and the air velocity at the top of the conical hole is 8~10m / s.

[0015] Preferably, the balanced separation return feeder assembly includes a flue gas inlet pipe and a cylindrical cylinder. The flue gas inlet pipe is connected between the connecting flue and the cylindrical cylinder, and the flue gas inlet pipe is arranged along the tangential direction of the cylindrical cylinder. The top of the cylindrical cylinder is connected to a flue gas outlet, and the lower end of the cylindrical cylinder is connected to a conical cylinder that gradually narrows radially downward. The bottom of the conical cylinder is connected to the combustion chamber through a return feed pipe.

[0016] Preferably, the flue gas inlet pipe is a tapered pipe, with an inlet flow velocity of 6 m / s and an outlet flow velocity of 20 m / s.

[0017] Preferably, the return pipe is provided with a first regulating valve.

[0018] Specifically, the flue gas inlet pipe of the balanced separation return feeder assembly is tangentially arranged with the circular cylinder. The flue gas enters the circular cylinder through a gradually narrowing inlet channel, its velocity gradually accelerating from an initial 6 m / s to approximately 20 m / s, facilitating the inertial separation of unburned iron powder particles. Upon entering the circular cylinder, the velocity decreases to approximately 2 m / s, forming a vortex airflow. Heavier iron powder particles collide and rub against the inner wall of the circular cylinder under centrifugal force, eventually settling into the conical cylinder. The flow rate is controlled by a first regulating valve between the conical cylinder and the return feed pipe, and the gas flows back to the boiler combustion chamber for re-combustion through the return feed pipe. Finally, the flue gas exits from the top of the circular cylinder at a velocity of approximately 6 m / s.

[0019] Preferably, the feeding assembly includes a feeder, the feed end of which is connected to a hopper, and the discharge end of which is connected to the combustion chamber via a feed pipe. A second regulating valve is provided on the feed pipe. The feeder may be a screw feeder or a rotor feeder.

[0020] Preferably, it also includes a flue gas heat exchange chamber, the top of which is connected to the flue gas outlet of the balanced separation return material assembly via a flue gas exhaust pipe, and the lower part of which is connected to a flue gas outlet; the cold end inlet of the flue gas heat exchange chamber is connected to a return water pipe, and the cold end outlet of the flue gas heat exchange chamber is connected to a water-cooled wall via a pipe; the high-temperature gas generated after combustion exchanges heat with the boiler return water through the flue gas heat exchange chamber, preheating the water entering the boiler water-cooled wall.

[0021] The bottom of the flue gas heat exchange chamber is connected to a slag outlet, which is equipped with a weight valve. The burned iron powder generates Fe3O4, which is collected through the discharge port and used as raw material for industrial production.

[0022] Beneficial effects Compared with the prior art, the present invention can achieve at least the following technical effects; This invention uses iron powder as boiler fuel. Iron powder combustion does not produce CO2, and because iron powder itself does not contain sulfur or nitrogen, the combustion process does not generate SOx or NOx, eliminating major pollutants at the source. Compared to hydrogen and ammonia fuels, iron powder is safer and easier to store, significantly reducing carbon taxes and environmental compliance costs, aligning with global energy transition trends.

[0023] Iron powder is abundant, boasts high energy density, low cost, and ease of storage and transportation. Iron is the fourth most abundant element in the Earth's crust, with a global annual production exceeding 2 billion tons, and its price is far lower than that of fossil fuels. Iron powder has an energy density as high as 11-12 kWh / L, more than 10 times that of lithium-ion batteries, and can be safely transported using conventional means of transport without the need for high-pressure or cryogenic equipment, thus reducing infrastructure investment. Therefore, this invention's use of iron powder as boiler fuel offers good economic and safety advantages.

[0024] This invention improves the fluidizing jet device for boilers. The fluidizing air first passes through a conical perforated plate for initial air volume and pressure balancing, then enters a stable air volume and pressure space, and is then ejected from the small-hole air cap through a fixed air cap perforated plate. The air volume and pressure are more stable and uniform, which is conducive to the full and stable combustion of iron powder, and helps to improve the combustion efficiency and operational stability of the boiler.

[0025] This invention optimizes the structure of the balanced separator return feeder, eliminating the return bed and high-pressure fluidizing air. It consists of a circular cylinder, a conical cylinder, a central cylinder, a return pipe, and a regulating valve. The regulating valve on the return pipe controls the material flow rate, simplifying the structure, reducing the likelihood of failure, and facilitating the inertial separation of unburned iron powder particles. Compared to traditional return feeders that rely on high-pressure air, which are energy-intensive and prone to clogging, this invention employs centrifugal separation. Flue gas enters the circular cylinder tangentially, forming a vortex, and iron powder particles settle under centrifugal force, achieving a separation efficiency of over 98%. The regulating valve precisely controls the return material volume, preventing overload or under-return, resulting in high system reliability and reducing maintenance costs by over 30%. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0027] Figure 2 This is a schematic diagram of the iron powder fluidization uniform air injection device of the present invention.

[0028] Figure 3 This is a schematic diagram of the balanced separation return material assembly of the present invention.

[0029] In the diagram: 1. Furnace body; 2. Hopper; 3. Feeder; 4. Feed pipe; 5. Combustion chamber; 6. Water-cooled wall; 7. Ignition assembly; 8. Air inlet; 9. Ignition and air supply device; 10. Air chamber; 11. Conical perforated plate; 1101. Conical hole; 12. Air cap fixing perforated plate; 13. Small-hole air cap; 14. Fluidized bed; 15. Return pipe; 16. First regulating valve; 17. Balanced separation return feeder assembly; 1701. Flue gas inlet pipe; 1702. Flue gas outlet; 1704. Circular cylinder; 1705. Conical cylinder; 18. Exhaust pipe; 19. Flue gas heat exchange chamber; 20. Return water pipe; 21. Exhaust port; 22. Self-weight valve; 23. Slag outlet; 24. Connecting flue; 25. Explosion-proof door; 26. Boiler outlet; 27. Connecting pipe; 28. Sewage outlet; 29. ​​Slag discharge pipe; 30. Second regulating valve. Detailed Implementation

[0030] The invention will be further explained below with reference to specific implementation examples.

[0031] Please see Figure 1-3This invention proposes a novel iron powder fluidized bed combustion boiler system. The boiler system mainly consists of core components such as a furnace body 1, a feeding assembly, an ignition and air supply device 9, an iron powder fluidized uniform air injection device, and a balanced separation and return feeder assembly 17. The furnace body 1 adopts a vertical structure design, with high-efficiency water-cooled walls 6 on its four side walls for heat exchange. The internal space of the furnace body 1 is divided into two functional areas from bottom to top: an air chamber 10 and a combustion chamber 5. The iron powder fluidized uniform air injection device is arranged at the junction between the combustion chamber 5 and the air chamber 10, which enables a more uniform distribution of fluidized air volume and pressure, improves the fluidization effect of the fuel, and ensures thorough mixing of fuel and air.

[0032] The feeding assembly is directly connected to the combustion chamber through its outlet. This feeding system can continuously and stably deliver precisely metered iron powder fuel into the combustion chamber, ensuring the continuity of the combustion process. The ignition air supply device 9 is connected to the air chamber 10 through a pipeline, and has an air inlet 8 on its side wall for introducing combustion air. The device integrates an ignition assembly 7, which can realize the safe and reliable start-up of the boiler system. The ignition assembly 7 can be an electric arc ignition device or an oil ignition device. The air supplied by the ignition air supply device 9 is heated to the ignition point of the iron powder.

[0033] High-pressure hot air is uniformly injected through the iron powder fluidization and uniform air injection device at the bottom of the combustion chamber, fully fluidizing the bed material to form a stable fluidized bed 14. The fluidized bed combustion principle is based on gas-solid two-phase dynamics. When the airflow velocity exceeds the minimum fluidization velocity of the iron powder particles, the particle layer becomes fluidized, forming the fluidized bed 14. This state enhances the gas-solid contact area, promotes mass and heat transfer, and makes the combustion reaction more complete. Iron powder combustion is a heterogeneous combustion reaction. The principle is that iron particles melt at high temperature and react with oxygen on the surface. The height of the fluidized bed 14 can be controlled within the range of 400~1000mm according to requirements. When the temperature in the combustion chamber reaches the suitable reaction temperature of about 600 degrees Celsius, the iron powder raw material is continuously and stably transported into the combustion chamber through the feeding assembly. In a high-temperature and oxygen-rich environment, the iron powder undergoes a violent spark combustion reaction. The main combustion chemical reaction equation is 3Fe + 2O2 = Fe3O4. This reaction process releases a large amount of heat energy. The high-temperature heat generated by combustion exchanges heat fully with the water medium through the efficient heat exchange surface of the boiler's water-cooled wall, heating the water into hot water or steam to provide a stable supply of hot water or steam for production and daily life. During combustion, some incompletely burned iron powder particles rise with the airflow and undergo gas-solid separation through the balance separation return feeder assembly 17. The separated iron powder particles return to the combustion chamber to continue participating in the combustion reaction. The balance separation return feeder assembly 17 is tightly connected to the exhaust port at the top of the furnace body 1 via the connecting flue 24, forming a complete flue gas treatment loop. Its main function is to use centrifugal force to separate and treat the high-temperature flue gas, iron oxide powder, and unburned iron powder generated during combustion. It can effectively recover the incompletely burned iron powder particles mixed in the flue gas, thereby achieving the recycling of fuel resources, significantly improving combustion efficiency, and reducing raw material consumption. The bottom of the component is connected to the combustion chamber 5 via a return pipe 15 at a certain angle, forming a closed material return channel. This allows the separated and recovered iron powder particles to automatically slide down under gravity and smoothly return to the combustion zone to participate in the high-temperature combustion reaction process, ensuring full utilization of the fuel. This circulating fluidized combustion method enables the iron powder to undergo multiple cycles of combustion between the combustion chamber and the balanced separation return device component, thereby achieving a high burnout rate of over 99%. The completely combusted iron powder is converted into Fe3O4 products. This process completely avoids the climate problems caused by CO2 emissions and the environmental pollution problems caused by nitrogen and sulfur oxide emissions from traditional fossil fuel combustion. These high-quality Fe3O4 products are collected centrally through the emission outlet and can be used as important industrial production raw materials. The entire system achieves efficient and clean utilization and resource recycling of iron powder fuel.

[0034] The particle size of the iron powder raw material is controlled within Φ60~100μm. Experiments show that within the range of iron powder particle size less than 10μm, the ignition temperature increases as the particle size decreases. Within the range of 10μm–50μm, the particle size has little effect on the ignition temperature. As the particle size increases, the ignition delay time increases. Therefore, the particle size range of Φ60~100μm can ensure a reasonable ignition delay and avoid incomplete combustion or deflagration.

[0035] To prevent a violent deflagration of iron powder inside the combustion chamber 5 that could lead to an explosion, an explosion-proof door 25 is specially designed and installed on the top of the furnace body 1. When deflagration or secondary combustion occurs in the tail flue of the combustion chamber 5, the door automatically opens to release pressure and prevent damage to the furnace walls, thus avoiding an escalation of the accident. When abnormal combustion of iron powder inside the combustion chamber causes the pressure to exceed the safety threshold, the explosion-proof door 25 automatically opens to release the excessive pressure in a timely manner, thereby eliminating the potential for explosion and ensuring the safe and reliable operation of the equipment.

[0036] For ease of maintenance, the furnace body 1 can be designed as a split upper and lower section, that is, the part containing the combustion chamber 5 and the part containing the air chamber 10 can be separated or assembled by bolts or other connecting parts, which facilitates maintenance of the furnace body. Correspondingly, the water-cooled walls 6 located on the upper and lower side walls of the furnace body 1 are also designed as a split section, with the upper water-cooled wall 6 and the lower water-cooled wall 6 connected by pipes and maintenance valves.

[0037] This embodiment further specifies that the iron powder fluidization uniform air injection device includes a conical perforated plate 11 and an air cap fixing perforated plate 12 disposed inside the furnace body 1. The air cap fixing perforated plate 12 is fixedly installed at a certain interval directly above the conical perforated plate 11, and the two work together to form a complete fluidization uniform air system. Multiple conical holes 1101 are evenly distributed on the conical perforated plate 11 according to a specific pattern. The inner diameter of these conical holes 1101 exhibits a gradually decreasing design from bottom to top, which can effectively improve the airflow distribution and ensure the uniformity and stability of the iron powder fluidization process. Through this precise structural design, the entire device achieves accurate control of the iron powder fluidization process and significantly improves the injection effect.

[0038] The inner diameter of the top of the conical hole 1101 is 3~39mm, the diameter of the bottom is 4~40mm, the contraction angle of the conical hole is controlled within the range of 15-25 degrees, and the air outlet velocity at the top of the conical hole is 8~10m / s.

[0039] The distance between the conical perforated plate 11 and the fixed perforated plate 12 is 350~450mm, preferably 400mm. This forms a stable volume and pressure space. After the fluidizing air enters the air chamber, it first passes through the conical perforated plate to balance the air volume and pressure in different parts of the air chamber space. The air velocity is controlled at about 10m / s. After entering the stable volume and pressure space, the air volume and pressure distribution in different parts is more uniform. Then, it is injected into the iron powder fluidization space through the small-hole air cap. The small-hole air cap 13 is threadedly fastened to the fixed perforated plate 12. Each small-hole air cap 13 has 6 Φ3mm small holes evenly distributed around its perimeter, tilted downwards at 15 degrees. The injection velocity of the small holes is controlled between 50 and 70m / s, ensuring stable and uniform fluidization and combustion of the iron powder.

[0040] When the airflow passes through the conical orifice 1101, the cross-section of the flow channel contracts. According to Bernoulli's principle, the fluid velocity increases while the static pressure decreases. This gradual change effectively "sorts out" the potentially unevenly distributed airflow within the front air chamber 10, making the airflow flow and pressure through each conical orifice 1101 more consistent. After being rectified by the conical orifice plate 11, the airflow enters the upper stable flow and pressure space. This space acts like an "air container," further absorbing and balancing minor pressure and flow fluctuations, ensuring a very stable airflow state transmitted to the second-stage device. The airflow is then ejected through the small-hole vent cap at a very high velocity of 50-70 m / s. This velocity is far higher than the minimum fluidization velocity of the iron powder, sufficient to suspend the iron powder particles, forming a fluid-like "fluidized state." The iron powder churns and mixes violently within the fluidized space, demonstrating full contact with the air. This also helps to break up any potential particle bridging, ensuring smooth fluidization startup and sustained stability.

[0041] In this embodiment, a slag discharge pipe 29 is connected to the air cap fixing orifice plate 12. The slag discharge pipe 29 penetrates downward through the conical orifice plate 11 and extends out of the lower part of the furnace body 1. By setting the slag discharge pipe 29, the molten oxidized liquid iron slag melted on the air cap fixing orifice plate 12 can be discharged periodically.

[0042] In this embodiment, the balanced separation return feeder assembly 17 includes a flue gas inlet pipe 1701 and a cylindrical cylinder 1704. The flue gas inlet pipe 1701 is connected between the connecting flue duct 24 and the cylindrical cylinder 1704, and is arranged along the tangential direction of the cylindrical cylinder 1704. A flue gas outlet 1702 is connected to the top of the cylindrical cylinder 1704, and a tapered cylinder 1705 that gradually narrows radially downwards is connected to the lower end of the cylindrical cylinder. The bottom of the tapered cylinder 1705 is connected to the combustion chamber 5 through a return feed pipe 15. A first regulating valve 16 is provided on the return feed pipe 15.

[0043] This invention optimizes the structure of the balanced separation return feeder assembly 17. Its flue gas inlet pipe 1701 is arranged tangentially to the circular cylinder 1704, which promotes a swirling flow of flue gas upon entering the separator. The flue gas inlet pipe 1701 employs a tapered design, effectively accelerating the flue gas. When the flue gas enters the flue gas inlet pipe 1701 with an initial velocity of approximately 6 m / s, the velocity is significantly increased to approximately 20 m / s due to the tapering section. This high-speed flow facilitates the separation of unburned iron powder particles from the airflow by inertia. Subsequently, as the high-speed flue gas enters the circular cylinder 1704, the velocity rapidly decreases to approximately 2 m / s due to the sudden expansion of the space, simultaneously creating a strong vortex airflow. Under centrifugal force, larger iron powder particles continuously collide and rub against the inner wall of the circular cylinder 1704, eventually settling downwards under gravity and converging into the lower conical cylinder 1705. The return flow rate of iron powder particles can be precisely controlled by adjusting the first regulating valve 16 located between the conical cylinder 1705 and the return pipe 15. These separated iron powder particles are ultimately returned to the boiler combustion chamber 5 through the return pipe 15 for secondary combustion, achieving fuel recycling. The separated flue gas maintains a velocity of approximately 6 m / s and exits the system from the top outlet of the circular cylinder 1704. The less dense iron oxide powder is discharged along with the flue gas for further separation. The entire separation and return process combines multiple separation mechanisms, including inertial separation, centrifugal separation, and gravity settling, ensuring efficient iron powder particle recovery and flue gas purification.

[0044] In this embodiment, the feeding assembly includes a feeder 3 for continuously and stably conveying materials. The feeder 3's feed end is connected to a conical hopper 2 via a flange connection to receive and temporarily store raw materials to be processed. The feeder 3's discharge end is connected to the side wall of the combustion chamber 5 via a feed pipe 4 with a heat-insulating jacket. The feed pipe 4 is made of high-temperature resistant stainless steel and has a high-precision second regulating valve 30 installed on it. This regulating valve is controlled by an electric actuator and can accurately adjust the feed flow rate and speed according to process requirements, ensuring the stability and controllability of material conveying. The entire feeding system is reasonably designed, and the connections of each component are reliable, meeting the requirements for continuous and stable feeding under different working conditions. The feeder 3 is selected as a screw feeder or rotor feeder with airtight function.

[0045] This embodiment is further configured to include a flue gas heat exchange chamber 19, the top of which is connected to the flue gas outlet of the balanced separation return material assembly 17 via a flue gas exhaust pipe 18, and the lower part of which is connected to a flue gas exhaust port 21; the cold end inlet of the flue gas heat exchange chamber 19 is connected to a return water pipe 20, and the cold end outlet of the flue gas heat exchange chamber 19 is connected to a water-cooled wall 6 via a pipe; The bottom of the flue gas heat exchange chamber 19 is connected to a slag outlet 23, and a weight valve 22 is installed on the slag outlet 23.

[0046] The flue gas heat exchange chamber 19 employs a shell-and-tube heat exchanger, with flue gas flowing through the shell side and water flowing through the tube side. The heat exchange area is 50-100 m², reducing the flue gas temperature from 600°C to below 150°C and recovering waste heat. The return water pipe 20 connects to the boiler feedwater system, preheating the water and improving thermal efficiency by 10-15%. The ash outlet 23 periodically discharges fine ash, and the weighted valve 22 is electrically controlled for automation. The heat exchange chamber is made of carbon steel with a coating, ensuring corrosion resistance. The exhaust outlet 21 connects to the chimney and meets emission standards.

[0047] The ignition and operation process of this invention is as follows: Step 1: First, start the blower system. The blower's power will stably deliver air into the furnace body 1 through the air inlet 8 of the ignition air supply device 9. After ensuring that the air supply speed reaches the preset value and remains stable, start the ignition assembly 9. The ignition assembly 9 can use flame jet or electric arc discharge to heat the flowing air, creating suitable temperature conditions for the subsequent combustion process. The blower can be a centrifugal fan, with airflow controlled by a frequency converter. A soft start is used during startup to avoid shock. A system self-check is performed before ignition, including pressure, temperature, and valve status, to ensure reliable ignition. Preheating time before ignition is approximately 5-10 minutes to ensure even heating of the furnace body.

[0048] Step Two: When the temperature monitoring system in combustion chamber 5 detects that the temperature has risen to 600℃, the feeder 3 is immediately activated. This feeder continuously delivers pre-prepared iron powder raw materials with a particle size range of Φ60~100μm into the combustion chamber. During the initial ignition stage, the flow rate of the iron powder is limited by adjusting the opening of the second regulating valve 30 to maintain a low feed rate and ensure the stability of the ignition process. After the combustion state stabilizes, the operation of the ignition assembly 9 is first shut off, and then the input flow rate of the iron powder is gradually increased according to the preset program to achieve a smooth increase in combustion intensity.

[0049] The initial feed rate is 20-30% of the normal value, then increases by 10% every 5 minutes until the design value is reached. Combustion stability is verified by both ultraviolet and pressure sensors. After ignition assembly 9 is turned off, the system switches to self-sustaining combustion mode.

[0050] Step 3: Throughout the operation, monitor and adjust the blower's operating parameters in real time, including key indicators such as air velocity and gas flow rate. Ensure that the iron powder remains within the ideal height range of 400~1000mm in the fluidized bed 14, thereby maintaining optimal combustion efficiency and material fluidization.

[0051] Step 4: Based on the real-time heat load demand of the boiler system, dynamically adjust the iron powder feed flow rate of the feeder 3 through the second regulating valve 30, and simultaneously adjust the air supply volume of the blower accordingly. During these adjustments, simultaneously operate the first regulating valve 16 to coordinate and control the return flow rate of unburned iron powder to the balanced separation return feeder assembly 17. When the amount of unburned iron powder separated by the separation return feeder assembly 17 exceeds the normal range, promptly increase the air supply volume of the ignition air supply device 9 by increasing the output power of the blower to ensure that the unburned material undergoes sufficient secondary combustion.

[0052] Step 5: Periodically open the weight valve 22 located at the slag outlet 23 according to the preset time interval or as needed for production. This will allow the iron tetroxide powder generated during combustion to be discharged from the system in an orderly manner, achieving effective product recovery and subsequent processing. After each operation, check the sealing performance of the weight valve to ensure the continuous and stable operation of the system.

[0053] In summary, this invention fundamentally solves the CO2 emission problem of traditional fossil fuel boilers and avoids pollution from sulfur oxides and nitrogen oxides. The combustion product, iron(III) oxide (Fe3O4), is a valuable industrial raw material, enabling resource recycling. Iron powder itself is abundant, low-cost, and safe to store and transport, giving this technology significant advantages in terms of economy and sustainability, perfectly aligning with the "dual-carbon" strategic goal. This invention optimizes the layout of the iron powder fluidized air injection device based on the combustion characteristics of iron powder, ensuring highly uniform and stable fluidized air distribution. This creates an ideal fluidized combustion environment for the iron powder, characterized by vigorous turbulence and full oxygen contact, significantly improving combustion efficiency and stability. Simultaneously, the optimized balanced separation and return feeder assembly cleverly combines inertial separation, centrifugal separation, and gravity settling principles. By accelerating the flue gas through a gradually narrowing pipe and tangentially entering to form a vortex, unburned iron powder is efficiently separated from the flue gas and automatically returned to the combustion chamber for secondary combustion. This closed-loop design greatly extends the residence time of iron powder in the furnace, achieving a burnout rate of over 99%, while simplifying the structure and improving operational reliability.

[0054] In the description of this invention, the term "a plurality of" refers to two or more. Unless otherwise explicitly defined, the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] In the description of this invention, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fluidized combustion boiler of iron powder, characterized in that, The application relates to a vertical iron powder smelting furnace, which comprises a furnace body (1), a feeding assembly, an ignition air feeding device (9), an iron powder fluidization and uniform air injection device and a balance separation and return feeder assembly (17). The furnace body (1) is vertically arranged, the side wall of the furnace body (1) is provided with a water cooling wall (6), the inside of the furnace body (1) is sequentially provided with an air chamber (10) and a combustion chamber (5) from bottom to top, and the iron powder fluidization and uniform air injection device is arranged between the combustion chamber (5) and the air chamber (10) in the furnace body (1). The discharge port of the feeding assembly is communicated with the combustion chamber and used for conveying iron powder into the combustion chamber. The ignition air feeding device (9) is communicated with the air chamber (10), the side wall of the ignition air feeding device (9) is connected with an air inlet (8), and the inside of the ignition air feeding device (9) is provided with an ignition assembly (7). The balance separation and return feeder assembly (17) is connected with the top smoke outlet of the furnace body (1) through a connecting flue (24) and used for separating unburned iron powder in flue gas, and the lower end of the balance separation and return feeder assembly (17) is communicated with the combustion chamber (5) through a return pipe (15).

2. A fluidized combustion iron powder boiler according to claim 1, characterized in that The iron powder fluidization and uniform air injection device comprises a conical hole plate (11) and a cap fixing hole plate (12) arranged in the furnace body (1), the cap fixing hole plate (12) is located above the conical hole plate (11), a plurality of conical holes (1101) are uniformly distributed on the conical hole plate (11), and the inner diameter of the conical hole (1101) gradually decreases from bottom to top. A plurality of small hole caps (13) are threadedly connected to the cap fixing hole plate (12).

3. A fluidized combustion iron powder boiler according to claim 2, characterized in that The distance between the conical hole plate (11) and the cap fixing hole plate (12) is 350-450 mm.

4. A fluidized combustion iron powder boiler according to claim 2, characterized in that The cap fixing hole plate (12) is connected with a slag discharge pipe (29), the slag discharge pipe (29) penetrates through the conical hole plate (11) downward and extends out of the lower part of the furnace body (1).

5. A fluidized combustion iron powder burner according to claim 2, wherein The inner diameter of the top of the conical hole (1101) is 3-39 mm, the diameter of the bottom is 4-40 mm, and the air outlet speed of the top of the conical hole is 8-10 m / s.

6. A fluidized combustion iron powder burner according to claim 1, wherein The balance separation and return feeder assembly (17) comprises a flue gas inlet pipeline (1701) and a circular cylinder (1704), the flue gas inlet pipeline (1701) is connected between the connecting flue (24) and the circular cylinder (1704), the flue gas inlet pipeline (1701) is arranged along the tangent direction of the circular cylinder (1704), the top of the circular cylinder (1704) is connected with a flue gas outlet (1702), the lower end of the circular cylinder is connected with a conical cylinder (1705) with a gradually decreasing inner diameter, and the bottom of the conical cylinder (1705) is communicated with the combustion chamber (5) through the return pipe (15).

7. A fluidized combustion iron powder boiler according to claim 6, characterized in that The flue gas inlet pipeline (1701) is a gradually tapered pipeline, the inlet flow speed of the flue gas inlet pipeline (1701) is 6 m / s, and the outlet flow speed is 20 m / s.

8. A fluidized combustion iron powder boiler according to claim 6, characterized in that The return pipe (15) is provided with a first adjusting valve (16).

9. A fluidized combustion iron powder burner according to claim 1, wherein The feeding assembly comprises a feeder (3), the feeding end of the feeder (3) is connected with a hopper (2), the discharge end of the feeder (3) is communicated with the combustion chamber (5) through a feeding pipe (4), and the feeding pipe (4) is provided with a second adjusting valve (30).

10. A fluidized combustion iron powder burner according to claim 1, wherein Further comprising a flue gas heat exchange chamber (19), a top of the flue gas heat exchange chamber (19) is connected with a flue gas outlet of the balanced separation return feeder assembly (17) through a flue gas exhaust pipe (18), a lower part of the flue gas heat exchange chamber (19) is connected with a flue gas exhaust port (21); a cold end inlet of the flue gas heat exchange chamber (19) is connected with a return water pipe (20), a cold end outlet of the flue gas heat exchange chamber (19) is connected with the water-cooled wall (6) through a pipe; A bottom of the flue gas heat exchange chamber (19) is connected with a slag outlet (23), a self-weight valve (22) is arranged on the slag outlet (23).

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