Rotary kiln system and method for reducing iron oxide using hydrogen

Abstract

The present invention provides a rotary kiln system and method for reducing iron oxide with hydrogen. The feed end and discharge end of the rotary kiln body are connected to the feed system and the discharge system, respectively. A waste heat recovery flue gas purification system and a preheating system are also provided between the discharge system and the feed system for heat recovery. The rotary kiln body is also connected to a hydrogen supply system and an electric heating system. The present invention adds equidistantly distributed air vents to the kiln body and adopts electric heating to inject hydrogen into the kiln body. The hydrogen injection causes the material to form a suspension, allowing a full chemical reaction between hydrogen and iron oxide. The temperature and hydrogen flow rate of the preheating zone and the metallizing zone are controlled in the direction of the rotary kiln body to realize the production process of reducing iron oxide with hydrogen. In the preheating zone, most of the iron oxide is reduced to ferrous oxide, and in the metallizing zone, the ferrous oxide is finally reduced to metallic iron. This achieves efficient reduction of iron and effectively improves the metallization rate of direct reduced iron.

Description

Technical Field

[0001] The invention provides a rotary kiln system and method for reducing iron oxide by using hydrogen, belonging to the technical field of smelting. Technical Background

[0002] The mining process of iron ore produces a large amount of by-product—iron ore fines. Currently, magnetic separation is used to reduce the iron content of the fines to over 65%. Sintering is then used to produce sintered ore, or concentrates are processed into pellets, which serve as raw material for blast furnaces to produce pig iron for steelmaking. Due to increasing international environmental protection requirements, particularly those regarding carbon emissions, the steel industry is a major source of environmental pollution during its production process. Dust, slag, and smoke are among the pollutants, particularly during the pig iron smelting process, where coal is used as a reducing agent, resulting in significant carbon monoxide production. Consequently, the metallurgical industry, both domestically and internationally, is considering how to improve its technological equipment and reduce carbon monoxide production.

[0003] As a completely green and pollution-free new energy source, hydrogen has great application prospects in the field of steel metallurgy. At present, a certain amount of hydrogen is added during the process of smelting iron in a blast furnace to reduce the production of carbon monoxide and achieve the purpose of reducing carbon emissions; there is also a method of producing pure iron by direct reduction, that is, using hydrogen as a reducing agent to produce pure iron under a certain temperature and pressure. However, due to the complexity of the equipment, the difficulty of production, the small output and the high production cost, steel companies are unable to use their products as raw materials for steelmaking. In particular, for the application of low-grade, high-gangue iron ore, there is still a lack of process equipment with practical applications. In response to the above-mentioned problems, the present invention makes a simple modification to the mature rotary kiln device to achieve the purpose of completely replacing the carbon reducing agent with hydrogen as the reducing agent. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the prior art of using hydrogen as a reducing agent to produce iron, such as high technical difficulty, low output and high production cost, and to provide a rotary kiln system and method for reducing iron oxide using hydrogen.

[0005] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] A rotary kiln system for reducing iron oxide with hydrogen includes a rotary kiln body, wherein the feed end and the discharge end of the rotary kiln body are connected to a feed system and a discharge system respectively; a waste heat recovery flue gas purification system and a preheating system are also provided between the discharge system and the feed system for heat recovery;

[0007] The rotary kiln body is also connected to the hydrogen supply system and the electric heating system, which respectively provide hydrogen and heat to the rotary kiln body; the electric heating system is also connected to the preheating system for heat supply, and the hydrogen supply system is also connected to the preheating system.

[0008] The rotary kiln body is fixed on an inclined support, with the feed end high and the discharge end low; the feed end is equipped with an induced draft fan, and the discharge end is equipped with a blower;

[0009] A cooler is provided below the discharge end, and the clinker enters the cooler from the discharge end;

[0010] The rotary kiln body is equipped with heating coils and tuyere;

[0011] The rotary kiln body is driven by the kiln drive motor.

[0012] Unlike traditional rotary kiln production processes, this invention does not require heat generated by solid fuel combustion to heat the charge or reaction gases. Instead, it electrically heats the charge and reduces hydrogen, controlling the temperature and hydrogen flow in two main zones (the preheating zone and the metallizing zone) along the rotary kiln body, thereby controlling the hydrogen reduction process for iron oxide.

[0013] The mixed material loaded into the rotary kiln is composed of iron oxide lumps of varying grades, ore powder / sand, limestone, dolomite, etc. In the preheating zone, moisture is first removed by electric heating. Simultaneously, preheated hydrogen is gradually introduced based on the temperature rise of the mixed material. In the preheating zone, most of the iron oxide is reduced to ferrous oxide by hydrogen according to equation (1):

[0014] Fe2O3+H2=2FeO+H2O (1)

[0015] Finally, it is reduced to metallic iron in the metallization zone. According to reaction equation (2), the final reduction is the reaction of H2 with FeO to generate H2O and metallic iron.

[0016] FeO+H2=Fe+H2O (2)

[0017] The gas discharged from the rotary kiln is composed of unreduced hydrogen, a large amount of high-temperature water vapor, and a small amount of furnace dust, with a temperature of 900-1000°C. These gases can be directly introduced into the preheating chamber at the feed end to heat the furnace charge and simultaneously achieve the sedimentation of coarse dust particles. They then enter the secondary burner to burn the unreduced hydrogen. After cooling and purification, they are discharged through the chimney.

[0018] The above-mentioned rotary kiln system for reducing iron oxide with hydrogen is used to independently control the temperature and hydrogen flow rate of the preheating zone and the metallizing zone along the rotary kiln body, thereby implementing a production process for reducing iron oxide with hydrogen. In the preheating zone, the majority of the iron oxide is reduced to ferrous oxide, while in the metallizing zone, the ferrous oxide is ultimately reduced to metallic iron.

[0019] At the start of production, the rotary kiln is heated electrically through the heating coils and preheating system on the kiln body to bring the charged charge to the reaction temperature. After completing the above operations, the material of different weights is weighed at the feed end according to the actual situation, and the material is continuously fed through the feed port to achieve a stable state. The specific steps are as follows:

[0020] S1. Pre-production test run of the rotary kiln and preparation work before ignition;

[0021] S2. Batching: According to the production plan, weigh a certain amount of iron ore with a TFe content of 45%-65% and slag-making agent.

[0022] S3. The weighed materials are transported from the mixing silo to the preheating chamber via a belt conveyor. The materials are preheated to 350-380°C by burning the waste gas and supplemented by heating coils.

[0023] S4. The preheated materials are sent to the feed end of the rotary kiln at a uniform speed through a vibrating feeder.

[0024] S5. Kiln temperature control. The kiln temperature is dynamically measured by heating coils placed at different locations within the kiln body. The temperature control system adjusts the power of the heating coils to ensure that the preheating zone temperature is between 900-1100°C and the metallizing zone temperature is between 1050-1200°C.

[0025] S6. Tuyere hydrogen flow regulation. Control the hydrogen flow at the kiln body tuyere and make dynamic adjustments based on the hydrogen supply system and process sampling and analysis results.

[0026] S7. Ensure the hydrogen flow rate and pressure of the blower at the discharge end of the rotary kiln, adjust the hydrogen pressure at each tuyere of the kiln body, and ensure that the pressure difference between the upper and lower layers of the rotary kiln material is no more than 2.3kPa.

[0027] S8. Process sampling and analysis: During continuous production, samples are taken twice every 8 hours at different locations in the kiln body. The hydrogen supply is adjusted according to the metallization rate.

[0028] S9. Iron tapping. The discharge material from the rotary kiln is 1000℃ solid reduced iron or 1200℃ molten reduced iron. Depending on actual needs, it is directly sent to the next process or enters a cooling drum through a sealed chute and cooled by air to obtain the desired product.

[0029] To enhance hydrogen reduction, this invention optimizes the rotary kiln's structure. Using an electric heating system, it completely replaces traditional solid carbon fuels and reducing agents, effectively reducing carbon dioxide emissions and preventing environmental pollution. Equally spaced tuyere openings at different locations within the kiln ensure material suspension within the kiln, ensuring good air permeability.

[0030] The raw materials of the present invention are in various forms, and can be traditional pellets, sintered ore, and lump ore, as well as fine iron ore and high-iron waste. By mixing the ingredients at the feed end, controlling the alkalinity to 0.85-1.05, and preheating with the heat from the combustion of waste flue gas, efficient reduction of iron oxide can be achieved.

[0031] The raw ore of the present invention can be of high or low grade. By controlling the electric heating temperature, furnace speed, hydrogen introduction amount and temperature, the grade and product form (solid lump ore, liquid cooling and sorting) of the clinker product can be effectively controlled.

[0032] This invention utilizes a waste heat recovery and flue gas purification system to nearly fully utilize the heat generated during the rotary kiln production process. An induced draft fan (IDF) at the feed end of the rotary kiln directs the reduced exhaust gas (partial hydrogen and water vapor) and flue gas discharged with the clinker through a settling chamber where coarse dust particles are removed. The exhaust gas is then introduced into a reburner, where the combustible gases in the exhaust gas are burned, generating heat that is used to preheat the raw meal.

[0033] The beneficial effects of the present invention are as follows: the present invention optimizes and transforms the structure of the rotary kiln, mainly by adding tuyere with equal spacing to the kiln body, and adopts electric heating, and injecting hydrogen into the kiln body by injection. The hydrogen injection makes the material into a suspended state, so that the hydrogen and iron oxides fully react chemically, thereby achieving efficient reduction of iron. About 1.8 tons of concentrate powder can produce 1 ton of direct reduced iron with a metallization rate of 80-98%, and the hydrogen consumption is only 450-580m3. 3 It can effectively improve the metallization rate of direct reduced iron, and the raw materials are in various forms, the raw material grade is not limited, the discharge forms are diverse, there is no carbon dioxide emission, the production process is simple, and the production cost is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of a rotary kiln system for reducing iron oxide with hydrogen according to the present invention;

[0035] Figure 2 It is a schematic diagram of the rotary kiln structure of the present invention. DETAILED DESCRIPTION

[0036] The specific technical solutions of the present invention are described with reference to the accompanying drawings.

[0037] The rotary kiln system for reducing iron oxide with hydrogen is composed of Figure 1 As shown, the rotary kiln body includes a rotary kiln body. The feed end and the discharge end of the rotary kiln body are connected to the feed system and the discharge system respectively; a waste heat recovery flue gas purification system and a preheating system are also provided between the discharge system and the feed system for heat recovery;

[0038] The rotary kiln body is connected to the hydrogen supply system and the electric heating system, which respectively provide hydrogen and heat to the rotary kiln body; the electric heating system is connected to the preheating system for heat supply, and the hydrogen supply system is also connected to the preheating system.

[0039] This invention optimizes the traditional rotary kiln structure based on the unique characteristics of the hydrogen reduction iron oxide production process. By replacing the traditional solid carbon fuel with electric heating, it effectively reduces carbon dioxide emissions and avoids environmental pollution. A series of innovative tuyere vents are arranged along the length and diameter of the rotary kiln. A blower at the discharge end introduces preheated reducing hydrogen, suspending the material in the kiln and ensuring good air permeability.

[0040] like Figure 2 As shown, the rotary kiln body is fixed on an inclined support, with the feed end high and the discharge end 4 low; the feed end is provided with an induced draft fan, and the discharge end 4 is provided with a blower;

[0041] A cooler 6 is provided below the discharge end 4, and the clinker 5 enters the cooler 6 from the discharge end 4;

[0042] The rotary kiln body is provided with a heating coil 2 and an air vent 1;

[0043] The rotary kiln body is driven by the kiln drive motor 3.

[0044] The preferred parameters of this embodiment are:

[0045] The rotary kiln is 74 meters long and 4.7 meters in diameter. It is mounted on a base that slopes 2.5% downward from the feed to the discharge end and rotates at a speed of 0.35-0.8 revolutions per minute. Eight fans supply hydrogen to the kiln through tuyere 1 evenly distributed throughout the kiln body.

[0046] The cooler 6 on this device is 13.5 meters long and 2.6 meters in diameter. A spiral guide mechanism conveys the clinker through the cooler 6, using air cooling as the cooling medium. The clinker 5 is cooled to approximately 150°C in the cooler 6, and the various components can be separated as needed.

[0047] The rotary kiln is mounted on an inclined support with a higher feed end and a lower discharge end. The kiln's inclination and rotational speed control the rate of charge transport within the kiln. Inlet and outlet cones are located at each end of the kiln, each cooled and heated by its own fan. Small sampling holes are located in the kiln shell. A series of heat-resistant steel hydrogen ducts, equidistantly spaced along the length and diameter of the kiln, serve as tuyere 1 to control the reduction process. The reduction temperature is controlled by preheating the incoming hydrogen at varying temperatures. The external ducts are replaceable during production.

[0048] At the rotary kiln's discharge end (4), a central blower with two speeds supplies hydrogen, electrically heated to control the temperature of the blown hydrogen. At the kiln's feed end, an induced draft fan directs the reduced exhaust gas (partial hydrogen plus water vapor) and flue gas discharged with the clinker through a settling chamber to remove coarse dust particles. The exhaust gas is then introduced into a reburner, where the combustible gases in the exhaust gas are burned, generating heat that is used to preheat the raw meal.

[0049] The rotary kiln's feed end is equipped with a series of high-level silos. Depending on the grade and particle size of the incoming iron ore fines, they are loaded into different silos via belt conveyors. Separate silos for slagging agents and desulfurizers are also located. During actual production, the ingredients are calculated and weighed according to the clinker requirements. After mixing in the intermediate silo, the materials are then fed into the preheating chamber for preheating.

[0050] At the discharge end 4 of the rotary kiln, there is a closed chute that transfers solid direct reduced iron with a temperature of about 1000°C or liquid direct reduced iron with a temperature of about 1200°C to the cooler 6.

[0051] In this invention, apart from the heat recovered from waste flue gas combustion and clinker cooling, all other kiln heating and hydrogen preheating are electrically heated. A series of heating coils (2) are arranged along the length of the kiln, with heating coils located at different locations within the kiln to monitor temperature. The control system automatically controls the coils' operating status.

[0052] By controlling the blower pressure at the discharge end, the induced draft fan pressure at the feed end, and the air inlet pressure along the length of the kiln body, the material can be kept in a suspended state in the kiln, ensuring the overall air permeability of the material layer.

[0053] Operational Procedure: At the start of production, the rotary kiln is electrically heated through the kiln body heating coils and preheating system to bring the charged charge to the reaction temperature. After completing the above operations, the charge is weighed at the feed end according to the actual situation and continuously fed through the feed end to achieve a stable state. The details are as follows.

[0054] 1. Preparation before ignition.

[0055] 1) Before starting the equipment, conduct a comprehensive inspection of the equipment and pipelines to remove any debris that may have fallen into the equipment or pipelines during installation or maintenance to prevent the equipment from getting stuck, being damaged, or wearing out during operation, or causing other accidents. After the internal inspection of the equipment is complete, all manholes and inspection doors must be strictly sealed to prevent air and material leakage during production.

[0056] 2) Check the tightness of the equipment

[0057] Check whether all fasteners meet the quality requirements, especially the anchor bolts and bearing connecting bolts of high-speed running equipment, which must be confirmed one by one.

[0058] 3) Confirm that the water supply and drainage should fully meet the water volume requirements and the holes of the system filter should not be blocked.

[0059] 4) Confirm whether each equipment is safe, and check that the indicated opening of each valve, the central control indicated opening and the mechanical devices are accurate to ensure flexible operation.

[0060] 5) Check the condition of the refractory castables and confirm that they are qualified.

[0061] 6) Confirm that the raw materials, fuel, lubricating oil and other auxiliary materials should be in sufficient quantity for long-term operation and whether they can meet the production needs of the kiln and downstream workshops.

[0062] 2. The order of heating operation and kiln opening

[0063] 1) After the pyrotechnician confirms that the equipment has been tested normally and is on standby, the pyrotechnician starts the electric heating system under the supervision of the corresponding team leader.

[0064] Start recording operation data at this time

[0065] 2) Use heating coils to heat the kiln body and preheat the reducing gas, turn on the high-speed fan at the discharge end to the minimum air volume; turn on the low-speed fan air volume and gradually increase the low-speed fan air volume.

[0066] 3) When the temperature inside the rotary kiln reaches 600 degrees, you can start to increase the kiln heating coil power and hydrogen preheating temperature. As the temperature gradually rises, the bright area at the end of the black fire head expands. At this time, the air volume should be appropriately increased.

[0067] 4) When the flame is formed, the air volume of the high-speed fan can be appropriately increased.

[0068] 5) When there is a clear boundary between the white flame and the black flame in the kiln, rotate the kiln at the lowest kiln speed, and appropriately increase the speed of the high-speed fan and dust removal fan at the kiln tail, increase the exhaust volume, maintain the flame length, and gradually increase the tail temperature.

[0069] 6) When the kiln tail temperature reaches 120-150°C, start feeding (50% of the normal amount, kiln speed 1.0-1.25 rpm). As the kiln tail temperature rises, gradually increase the amount of feeding to achieve continuous production.

[0070] Kiln opening sequence: start high-speed fan → rotary kiln heating coil heating → start main motor and start secondary air → start unloading belt → start tertiary fan.

[0071] Kiln stopping sequence: stop feeding → turn off rotary kiln heating coil → turn off secondary air → stop main motor → stop tertiary fan → stop high-speed fan.

[0072] Strictly control the slight negative pressure at the kiln head and prevent the outlet temperature at the kiln tail from being too high.

[0073] The principle of slow kiln rotation during the heating process. Temperature requirements table 1:

[0074] Table 1 Slow kiln temperature during heating process

[0075]

[0076] 3. Stop the kiln and inspect

[0077] During production, the kiln may need to be stopped for a short period of time for inspection or repair work. The number of kiln stops should be minimized. If a kiln stop is necessary, whether it is a long-term or short-term stop, appropriate preparations should be made before the stop.

[0078] 1) Short-term kiln shutdown

[0079] When the kiln is just stopped, it is in a high-temperature state. If the kiln body is not rotated frequently, the kiln centerline is prone to bending, and the temperature drops too quickly, causing the kiln lining to crack. Therefore, the temperature drop should be ≤ 100℃ / h, and the kiln rotation should be carried out according to the following system.

[0080] During the first hour after stopping the kiln, turn the kiln 1 / 5 every 5-10 minutes.

[0081] During the second hour after stopping the kiln, turn the kiln needle 2 / 5 every 15-20 minutes.

[0082] During the first 3-8 hours after the kiln is stopped, the kiln should be rotated 2 / 5 every 30 minutes.

[0083] 2) Long-term kiln shutdown and inspection

[0084] After shutting down the kiln, rotate it according to the prescribed cycle until it is completely cool and safe for entry. After shutting down the kiln, remove the tuyere and, depending on the maintenance task, remove some or all of the material from the kiln. Check the condition of all wear surfaces, the clearances between the shaft and bearings, and the clearances between the large and small gears. Also, check all connecting bolts for looseness or damage, especially the connecting bolts of the large ring gear, and the welds between the cylinder and the backing plate for cracks. Check to see if the lubricating oil in each lubrication point needs to be replaced, cleaned, or refilled. If replacement is necessary, drain any remaining oil. Clean thoroughly and refill with new oil.

[0085] 4. Rotary kiln trial operation.

[0086] 1) Before the trial run, check whether the foundation elevation has changed, check whether the bolts are tightened, whether the lubrication points are sufficiently lubricated, and use a sliding bearing to install the roller to rotate the kiln. Pour a layer of oil on the roller journal with an oiler before using it. Check whether there is anything stuck in the rotating parts and whether the cooling water pipes are unobstructed. The trial run can be carried out only after all the checks are correct.

[0087] 2) Before the entire kiln is tested, a single unit must be run cold. The motor must idle for 2 hours, and the reducer must idle for 8 hours (driven by the main motor for 4 hours). Record the current, increase the temperature, and listen for any abnormal sounds.

[0088] 3) The kiln shell shall be put into trial operation before pouring the kiln lining, and the time shall be no less than 1 day (continuous time).

[0089] Due to the increase in kiln weight, it is necessary to check that the temperature rise of each oil tank does not exceed 35°C, the temperature rise of the bearings does not exceed 30°C, and the motor load should not exceed 25% of the rated power. In particular, check whether the rollers are adjusted correctly, such as whether the rollers are in uniform contact with the tyre surface.

[0090] Example 1

[0091] The method of direct reduction of iron with hydrogen in a rotary kiln has the following specific steps:

[0092] S1. The preparatory work for the trial operation of the rotary kiln before production and the ignition is as described above.

[0093] S2. Ingredients.

[0094] This case uses iron ore with a grade of 65%, a particle size greater than 12mm accounting for 85%, acidic oxides SiO2 and Al2O3 contents in the gangue of 9%-12%, and a controlled basicity of 1.05. A certain amount of iron ore and slag-making agent are weighed separately.

[0095] S3. The weighed materials are transported from the mixing silo to the preheating chamber via a belt conveyor. They are preheated to 350°C by burning the exhaust gas and supplemented by heating coils.

[0096] S4. The preheated materials are sent to the feed end of the rotary kiln at a uniform speed through a vibrating feeder.

[0097] S5. Kiln temperature control. The kiln temperature is dynamically measured by heating coils placed at different locations within the kiln body. The temperature control system adjusts the power of the heating coils to ensure that the preheating zone temperature is between 900-1000°C and the metallizing zone temperature is between 1010-1060°C.

[0098] S6. Adjust the hydrogen flow rate at the tuyere. Control the hydrogen flow rate at the tuyere of the kiln body to be 28-38m 3 / min, and dynamically adjusted through the hydrogen supply system and process sampling analysis results.

[0099] S7. Ensure that the hydrogen flow rate of the blower at the discharge end of the rotary kiln is 48m 3 / min, pressure 200kPa, the power of the induced draft fan at the feeding end is 75% of the maximum power, and the hydrogen pressure of each tuyere of the kiln body is adjusted to ensure that the pressure difference between the upper and lower layers of the rotary kiln material is no more than 2kPa.

[0100] S8. Process sampling and analysis: During continuous production, samples are taken twice every 8 hours at different locations in the kiln body. The hydrogen supply is adjusted according to the metallization rate.

[0101] S9. Iron tapping. The solid reduced iron discharged from the rotary kiln passes through a sealed chute into the cooler and is cooled to 100°C by air cooling to obtain the required direct reduced iron, or is directly sent to the next production process at high temperature.

[0102] Example 2

[0103] The method of direct reduction of iron with hydrogen in a rotary kiln has the following specific steps:

[0104] S1. The preparatory work for the trial operation of the rotary kiln before production and the ignition is as described above.

[0105] S2. Ingredients.

[0106] This case uses iron ore with a grade of 52%, a particle size greater than 10 mm accounting for 90%, acidic oxides SiO2 and Al2O3 contents in the gangue of 15%-18%, and a controlled basicity of 1.01. A certain amount of iron ore and slag-making agent are weighed separately.

[0107] S3. The weighed materials are transported from the mixing silo to the preheating chamber via a belt conveyor. They are preheated to 360°C by burning the exhaust gas and supplemented by heating coils.

[0108] S4. The preheated materials are sent to the feed end of the rotary kiln at a uniform speed through a vibrating feeder.

[0109] S5. Kiln temperature control. The kiln temperature is dynamically measured by heating coils placed at different locations within the kiln body. The temperature control system adjusts the power of the heating coils to ensure that the preheating zone temperature is between 920-1070°C and the metallizing zone temperature is between 1030-1100°C.

[0110] S6. Adjust the hydrogen flow rate at the tuyere. Control the hydrogen flow rate at the kiln body tuyere to be 30-40m 3 / min, and dynamically adjusted through the hydrogen supply system and process sampling analysis results.

[0111] S7. Ensure that the hydrogen flow rate of the blower at the discharge end of the rotary kiln is 50m 3 / min, pressure 200kPa, the power of the induced draft fan at the feeding end is 75% of the maximum power, and the hydrogen pressure of each tuyere of the kiln body is adjusted to ensure that the pressure difference between the upper and lower layers of the rotary kiln material is no more than 2kPa.

[0112] S8. Process sampling and analysis: During continuous production, samples are taken twice every 8 hours at different locations in the kiln body. The hydrogen supply is adjusted according to the metallization rate.

[0113] S9. Iron tapping. The solid reduced iron discharged from the rotary kiln passes through a sealed chute into the cooler and is cooled to 100°C by air cooling to obtain the required direct reduced iron, or is directly sent to the next production process at high temperature.

[0114] Example 3

[0115] The specific steps for direct reduction of iron with hydrogen in a rotary kiln are as follows:

[0116] S1. The preparatory work for the trial operation of the rotary kiln before production and the ignition is as described above.

[0117] S2. Ingredients. This case uses iron ore with a grade of 45%, 85% of which is less than 10mm. The gangue contains acidic oxides SiO2 and Al2O3 at a content of 23%-30%, and the basicity is controlled at 0.93. A certain amount of iron ore and slag-making agent are weighed separately.

[0118] S3. The weighed materials are transported from the mixing silo to the preheating chamber via a belt conveyor. They are preheated to 380°C by burning the exhaust gas and supplemented by heating coils.

[0119] S4. The preheated materials are sent to the feed end of the rotary kiln at a uniform speed through a vibrating feeder.

[0120] S5. Kiln temperature control. The kiln temperature is dynamically measured by heating coils placed at different locations within the kiln body. The temperature control system adjusts the power of the heating coils to ensure that the preheating zone temperature is between 950-1100°C and the metallizing zone temperature is between 1100-1200°C.

[0121] S6. Adjust the hydrogen flow rate at the tuyere. Control the hydrogen flow rate at the kiln body tuyere to be 32-45m 3 / min, and dynamically adjusted through the hydrogen supply system and process sampling analysis results.

[0122] S7. Ensure that the hydrogen flow rate of the blower at the discharge end of the rotary kiln is 58m 3 / min, pressure 240kPa, the power of the induced draft fan at the feeding end is 80% of the maximum power, and the hydrogen pressure of each tuyere of the kiln body is adjusted to ensure that the pressure difference between the upper and lower layers of the rotary kiln material is no more than 2.3kPa.

[0123] S8. Process sampling and analysis: During continuous production, samples are taken twice every 8 hours at different locations in the kiln body. The hydrogen supply is adjusted according to the metallization rate.

[0124] S9. Iron tapping. The discharge material of the rotary kiln is molten reduced iron. It passes through a sealed chute and enters the cooling drum. It is cooled to 150℃ by air cooling. The various components of the discharge material are then screened and separated, or directly sent to the next production process at high temperature.

Claims

1. A rotary kiln system for reducing iron oxide with hydrogen, characterized in that: It includes a rotary kiln body, the feeding end and the discharging end of the rotary kiln body are connected to the feeding system and the discharging system respectively; a waste heat recovery flue gas purification system and a preheating system are also set between the discharging system and the feeding system for heat recovery; The rotary kiln body is connected to the hydrogen supply system and the electric heating system, which respectively provide hydrogen and heat to the rotary kiln body; the electric heating system is connected to the preheating system for heat supply, and the hydrogen supply system is also connected to the preheating system; By electrically heating the charge and reducing hydrogen, the temperature and hydrogen flow rate of the two main zones, namely the preheating zone and the metallizing zone, are controlled in the direction of the rotary kiln body, thereby controlling the production process of hydrogen reduction of iron oxide. The temperature of the preheating zone in the kiln is 900-1100℃, and the temperature of the metallizing zone is 1050-1200℃; In the preheating zone, moisture is first removed by electric heating, and preheated hydrogen is gradually introduced according to the temperature rise of the mixture; in the preheating zone, most of the iron oxide is reduced to ferrous oxide; in the metallization zone, the ferrous oxide is finally reduced to metallic iron; The gas discharged from the rotary kiln is directly introduced into the preheating chamber at the feed end for heating the charge and settling the coarse dust particles. It then enters the secondary burner to burn the unreduced hydrogen. After cooling and purification, it is discharged through the chimney.

2. The rotary kiln system for reducing iron oxide with hydrogen according to claim 1, characterized in that: The rotary kiln body is fixed on an inclined support, with the feed end higher and the discharge end lower; an induced draft fan is provided at the feed end and a blower is provided at the discharge end; A cooler is provided below the discharge end, and the clinker enters the cooler from the discharge end; The rotary kiln body is equipped with heating coils and tuyere; The rotary kiln body is driven by the kiln drive motor.

3. A method for reducing iron oxide with hydrogen, characterized in that: The rotary kiln system for reducing iron oxide with hydrogen according to claim 1 or 2 is adopted, and the temperature and hydrogen flow rate of the preheating zone and the metallizing zone are respectively controlled in the direction of the rotary kiln body to realize the production process of reducing iron oxide with hydrogen; in the preheating zone, most of the iron oxide is reduced to ferrous oxide, and in the metallizing zone, the ferrous oxide is finally reduced to metallic iron.

4. The method for reducing iron oxide with hydrogen according to claim 3, wherein: At the start of production, the rotary kiln needs to be heated electrically through the heating coils and preheating system on the kiln body to heat the loaded furnace charge to the reaction temperature. After completing the above operations, different weights of materials are weighed at the feeding end according to actual conditions, and continuous feeding is achieved through the feeding port to achieve a stable state. The specific steps are as follows: S1. Pre-production test run of the rotary kiln and preparations before ignition; S2. Ingredients: According to the production plan, weigh a certain amount of iron ore with a TFe content of 45%-65% and a slag-making agent; S3. The weighed material is transported from the mixing silo to the preheating chamber via a belt conveyor; the waste gas is burned and heated by a heating coil to preheat it to 350-380°C; S4. The preheated material is sent to the feed end of the rotary kiln at a uniform speed through a vibrating feeder; S5. Kiln temperature control: Heating coils placed at different locations within the kiln are used to dynamically measure the kiln temperature. The temperature control system adjusts the power of the heating coils to maintain a preheating zone temperature of 900-1100°C and a metallizing zone temperature of 1050-1200°C. S6. Tuyere hydrogen flow regulation: Control the hydrogen flow at the kiln body tuyere and dynamically adjust it through the hydrogen supply system and process sampling and analysis results; S7. Ensure the hydrogen flow and pressure of the blower at the discharge end of the rotary kiln, adjust the hydrogen pressure of each tuyere in the kiln body, and ensure that the pressure difference between the upper and lower layers of the rotary kiln material is no more than 2.3kPa; S8. Process sampling and analysis: During continuous production, samples are taken twice every 8 hours at different locations in the kiln body. The hydrogen supply is adjusted according to the metallization rate. S9. Iron tapping: The discharge material from the rotary kiln is solid reduced iron at 950-1050℃ or molten reduced iron at 1150-1250℃. Depending on actual needs, it is directly sent to the next process or enters a cooling drum through a sealed chute and cooled by air to obtain the desired product.

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