Process system and method for recovering iron from red mud

Abstract

The application provides a treatment system and method for recovering iron from red mud. The treatment system comprises a pretreatment unit, an oxidizing roasting device and a reduction reaction device. The pretreatment unit comprises sequentially connected drying device, crushing device and screening device, which are used for drying treatment, crushing treatment and screening treatment of the red mud to obtain red mud particles. The oxidizing roasting device is connected with the pretreatment unit, which is used for oxidizing roasting of the red mud particles in an oxidizing atmosphere to obtain a roasting product. The reduction reaction device is connected with the oxidizing roasting device, which is used for reduction reaction of the roasting product in a reducing gas to obtain a reduction product comprising iron single substance. The above treatment system can effectively improve the consistency and reaction efficiency of the reduction reaction, improve the metallization rate and the content of iron single substance in the reduction product, and reduce the reaction energy consumption and production cost.

Description

Technical Field

[0001] This application relates to the field of red mud resource utilization technology, and more specifically, to a processing system and method for recovering iron from red mud. Background Technology

[0002] Currently, the main technologies for recovering iron from red mud include hydrometallurgy and pyrometallurgical reduction. Hydrometallurgy separates iron components by dissolving them through acid leaching and alkali leaching, but it suffers from high reagent consumption, high wastewater treatment costs, and low iron recovery rates, making large-scale industrial application difficult. Pyrometallurgical reduction, with its advantages of high throughput and thorough metal recovery, has become the mainstream research direction. Among these, low-temperature hydrogen reduction using hydrogen as a reducing agent is considered one of the most promising technological pathways due to its clean and harmless process, the fact that the only byproduct is water, and the near absence of carbon emissions. However, iron oxides in red mud are mostly tightly bound to gangue phases such as alumina, and are embedded in extremely fine particles and encapsulated by the gangue phase. This results in extremely poor reduction activity of iron components under low-temperature conditions, making it difficult for reducing gas to contact the iron oxide phase, and causing high internal diffusion resistance in the reduction reaction. This technological bottleneck leads to low metallization rates (below 80%), low reaction efficiency (reduction time exceeding 4 hours), and excessively high energy and time costs in existing low-temperature hydrogen reduction processes, severely hindering the industrialization of this technology.

[0003] Professor Gao Minrui's team at the University of Science and Technology of China has proposed a plasma-enhanced low-temperature hydrogen reduction technology. Its core innovation lies in generating high-energy hydrogen plasma using a plasma-enhanced chemical vapor deposition (PECVD) device. This high-energy hydrogen plasma replaces conventional hydrogen as a reducing agent, utilizing the high energy activity of the plasma to lower the reduction energy barrier of iron oxides. This reduces the traditional high-temperature reduction temperature (above 1200℃) to 900℃. At this temperature, the reduction reaction of red mud iron can be completed in just a few minutes, with an iron content of 71% in the product and a green iron recovery rate of 88.1%. Furthermore, the pH value of the residue after the reaction is close to neutral, eliminating the need for additional neutralization treatment (Wen-Long Liang et al. Hydrogen-Based Reduction Boosts Sustainable Iron Production from Red Mud, JACS, 2025.09.29).

[0004] Matic Jovi evi In their article "Green steel from red mud through climate-neutral hydrogen plasma reduction" published in Nature, Klug et al. disclosed a method for directly treating red mud in an electric furnace using a hydrogen plasma arc (Ar-10% H2 plasma). No pretreatment is required, and the metallization rate reaches 70% and the iron purity reaches 95% after 10 minutes of reduction reaction. The content of harmful elements is extremely low, and the pH of the red mud can be reduced from 10.5 to 7.5 after the reaction, making it suitable for direct use as a building material.

[0005] However, both of the above methods rely on dedicated plasma generating equipment, and the cost of such equipment with a processing capacity of 1 ton is 5 to 8 times that of conventional equipment (such as rotary kilns and fluidized beds). Furthermore, the high-energy active region of the plasma is difficult to control precisely, and the reaction conditions (such as plasma intensity and hydrogen flow mode control) are difficult to regulate. When carrying out large-scale scale-up production, local incomplete reduction is likely to occur, resulting in a low metallization rate of the reduction reaction.

[0006] In summary, the research and development of a treatment system and method for recovering iron from red mud is of great significance for improving the metallization rate of the red mud iron reduction process and the resource utilization rate of red mud. Summary of the Invention

[0007] The main objective of this application is to provide a processing system and method for recovering iron from red mud, in order to solve the problems of low efficiency, low metallization rate and high production cost of red mud iron reduction process in the prior art.

[0008] To achieve the above objectives, this application provides a processing system for recovering iron from red mud. The system includes a pretreatment unit, an oxidative roasting device, and a reduction reaction device. The pretreatment unit sequentially performs drying, crushing, and screening on the red mud to obtain red mud particles. The pretreatment unit includes a drying device, a crushing device, and a screening device connected in sequence. The drying device has a red mud inlet; the screening device has a red mud particle outlet. The oxidative roasting device oxidizes and roasts the red mud particles in an oxidizing gas to obtain a roasting product. The oxidative roasting device has a red mud particle inlet, an oxidizing gas inlet, and a first roasting product outlet. The red mud particle inlet and the red mud particle outlet are connected. The reduction reaction device reduces the roasting product in a reducing gas to obtain a reduction product, which includes elemental iron. The reduction reaction device has a first roasting product inlet, a first reducing gas inlet, and a reduction product outlet. The first roasting product inlet and the first roasting product outlet are connected.

[0009] Furthermore, the inner cavity of the screening device is provided with a first screen and a second screen, with the first screen located above the second screen. The aperture of the first screen is 0.3 mm, and the aperture of the second screen is 0.15 mm. The screening device is used to perform screening processing to obtain red mud particles, first particles, and second particles. The particle size of the red mud particles is 0.15–0.3 mm, the particle size of the first particles is >0.3 mm, and the particle size of the second particles is <0.15 mm. The screening device is also provided with a first particle outlet and a second particle outlet. Preferably, the inner cavity of the screening device is provided with a vibrating component.

[0010] Furthermore, the crushing device is also provided with a first particle inlet, which is connected to a first particle outlet, so that the first particle is returned to the crushing device for repeated crushing until red mud particles are obtained.

[0011] Furthermore, the pretreatment unit is also equipped with a granulation device for granulating the second particles to obtain red mud particles; the granulation device is equipped with a second particle inlet, a binder inlet and a discharge outlet; the second particle inlet is connected to the second particle outlet, and the discharge outlet is connected to the red mud particle inlet; preferably, the granulation device is selected from a shear granulator or a disc granulator.

[0012] Furthermore, the inner cavity of the oxidation roasting device is provided with a heating component; and / or, the outer surface of the oxidation roasting device is provided with a heat insulation layer; preferably, the thickness of the heat insulation layer is 120-180 mm; preferably, the material of the heat insulation layer is selected from aluminum silicate fiber, alumina-based refractory material or magnesium oxide-based refractory material; preferably, the oxidation roasting device is selected from a rotary kiln, a pusher kiln or a tunnel kiln.

[0013] Furthermore, the processing system also includes a heat exchange device for exchanging heat between the calcined product and the reducing gas; the heat exchange device is provided with a second calcined product inlet, a second reducing gas inlet, a second calcined product outlet, and a reducing gas outlet; the second calcined product inlet is connected to the first calcined product outlet, and the second calcined product outlet is connected to the first calcined product inlet; preferably, the processing system also includes a preheating device for preheating the reducing gas; the inlet of the preheating device is connected to the reducing gas outlet, and the outlet of the preheating device is connected to the first reducing gas inlet.

[0014] Furthermore, a gas distribution plate is provided at the bottom of the inner cavity of the reduction reaction device, and the gas distribution plate has through holes; preferably, the total area of ​​the through holes accounts for 12-18% of the total area of ​​the gas distribution plate; preferably, a heating component is provided in the inner cavity of the reduction reaction device; preferably, a temperature sensing component and / or a pressure sensing component is provided in the inner cavity of the reduction reaction device for monitoring the temperature and / or pressure in the reduction reaction device; preferably, the reduction reaction device is also provided with a gas outlet for discharging the gaseous products obtained from the reduction reaction.

[0015] Furthermore, the processing system also includes a solid-gas separation device and a reducing gas recovery device connected in sequence; the inlet of the solid-gas separation device is connected to the gas outlet; the outlet of the reducing gas recovery device is connected to the first reducing gas inlet and / or the second reducing gas inlet.

[0016] To achieve the above objectives, another aspect of this application provides a method for recovering iron from red mud, which employs the aforementioned system for recovering iron from red mud provided in this application. The method includes: Step S1, feeding red mud into a pretreatment unit, and sequentially performing drying, crushing, and screening processes in a drying device, a crushing device, and a screening device to obtain red mud particles; Step S2, feeding the red mud particles into an oxidizing roasting device, whereby the red mud particles undergo oxidizing roasting in an oxidizing gas to obtain a roasting product; Step S3, feeding the roasting product into a reduction reaction device, whereby the roasting product undergoes a reduction reaction in a reducing gas to obtain a reduction product, which includes elemental iron.

[0017] Furthermore, in step S1, the drying temperature is 105–130°C, and the time is 1–3 hours.

[0018] Furthermore, a screening device equipped with a vibrating component is used for screening, with a vibration frequency of 15-20 Hz and an amplitude of 5-8 mm. Preferably, the particle size of the red mud particles is 0.15-0.3 mm. Preferably, the screening process also yields a first particle and a second particle, with the first particle having a particle size > 0.3 mm and the second particle having a particle size < 0.15 mm.

[0019] Furthermore, step S1 also includes returning the first particle to the crushing device for repeated crushing until red mud particles are obtained.

[0020] Further, step S1 also includes passing the second particles and the binder into a granulation device for granulation to obtain red mud particles; preferably, the weight ratio of the second particles to the binder is 100:(2-5); preferably, the binder is selected from water and / or bentonite; preferably, a shear granulator is used for granulation, the rotor speed of the shear granulator is 300-500 r / min, and the granulation time is 10-15 min.

[0021] Further, in step S2, the oxidative roasting temperature is 1100–1250℃, and the material residence time is 30–70 min; preferably, the feed rate of the red mud particles is 0.5–5 kg / h; preferably, the flow rate of the oxidizing gas is 0.2–2 m³ / h. 3 / h; preferably, the volume percentage of oxygen in the oxidizing gas is ≥18 vol%; preferably, a rotary kiln is used for oxidation roasting, and the rotation speed of the rotary kiln is 0.8 to 1.2 r / min.

[0022] Further, in step S3, the reduction reaction temperature is 600–700℃, and the material residence time is 0.5–2 h; preferably, the feed rate of the calcined product is 0.4–5 kg / h; preferably, the flow rate of the reducing gas is 0.1–5 m³ / h. 3 / h; preferably, the reducing gas is hydrogen.

[0023] Furthermore, between steps S2 and S3, the processing method further includes exchanging heat between the calcined product and the reducing gas in a heat exchange device, passing the heat-exchanged reducing gas into a preheating device for preheating, and then passing the preheated reducing gas into a reduction reaction device; preferably, the temperature of the preheated reducing gas is 600-700°C.

[0024] Furthermore, in step S3, the reduction reaction also yields gaseous products; step S3 further includes passing the gaseous products into a solid-gas separation device and a reducing gas recovery device connected in sequence for solid-gas separation and reducing gas recovery to obtain recovered reducing gas; preferably, at least a portion of the recovered reducing gas is returned to the reduction reaction device and / or heat exchange device for recycling.

[0025] Compared to traditional red mud reduction processes that only involve reduction reactions, the technical solution of this application provides a processing system for recovering iron from red mud, including a pretreatment unit, an oxidative roasting device, and a reduction reaction device. The pretreatment unit is used to sequentially dry, crush, and screen the red mud to obtain uniformly sized red mud particles, inhibiting their agglomeration in subsequent processing steps. This improves the efficiency of subsequent oxidative roasting and reduction reactions, enhancing reaction consistency. The oxidative roasting device is used to oxidize and roast the red mud particles, promoting the microscopic dissociation of the gangue phase (including alumina, silica, titanium dioxide, and calcium oxide phases) and the iron oxide phase within the red mud particles, yielding roasted products. This increases the exposure of the iron oxide phase, enhancing its reactivity in subsequent reduction reactions, thereby increasing the metallization rate of the reduction reaction. Simultaneously, it also improves the morphological defects of the red mud particles, inhibiting their agglomeration in subsequent reduction reactions, thus improving the reaction efficiency of the reduction reaction. The reduction reaction device is set up to enable the roasting products to undergo a reduction reaction in a reducing gas, thereby reducing the iron oxide phase in the red mud to elemental iron, thus realizing the resource utilization of iron recovered from the red mud.

[0026] Compared to the use of plasma generators for reduction reactions in existing technologies, the process equipment in the above-mentioned processing system provided in this application can all be general equipment in the field, eliminating the need for customized high-cost plasma generators. This effectively reduces equipment investment and maintenance costs, making it more suitable for large-scale production.

[0027] In summary, the above-mentioned processing system provided in this application for recovering iron from red mud can not only effectively improve the consistency and efficiency of the reduction reaction, increase its metallization rate and the content of elemental iron in the reduction products, but also reduce reaction energy consumption and production costs, providing strong technical support for promoting the industrialization process of red mud resource utilization. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0029] Figure 1 This invention provides a schematic diagram of a processing system for recovering iron from red mud according to one embodiment of the present application.

[0030] Figure 2 A schematic diagram of a processing system for recovering iron from red mud is shown in another embodiment of this application.

[0031] The above figures include the following reference numerals:

[0032] 100. Pretreatment unit; 110. Drying device; 111. Red mud inlet; 120. Crushing device; 121. First particle inlet; 130. Screening device; 131. Red mud particle outlet; 132. First particle outlet; 133. Second particle outlet; 140. Granulation device; 141. Second particle inlet; 142. Binder inlet; 143. Discharge port; 200. Oxidation roasting device; 201. Red mud particle inlet; 202. Oxidizing gas inlet ; 203, First roasted product outlet; 300, Reduction reaction device; 301, First roasted product inlet; 302, First reducing gas inlet; 303, Reduction product outlet; 304, Gas outlet; 400, Heat exchange device; 401, Second roasted product inlet; 402, Second reducing gas inlet; 403, Second roasted product outlet; 404, Reducing gas outlet; 500, Preheating device; 600, Solid-gas separation device; 700, Reducing gas recovery device. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0034] As described in the background section, existing red mud reduction processes suffer from low reduction reaction efficiency, low metallization rate, and high production costs. To address these technical problems, the first aspect of this application provides a processing system for recovering iron from red mud, such as... Figure 1As shown, the processing system includes a pretreatment unit 100, an oxidation roasting device 200, and a reduction reaction device 300. The pretreatment unit 100 is used to sequentially dry, crush, and screen the red mud to obtain red mud particles. The pretreatment unit 100 includes a drying device 110, a crushing device 120, and a screening device 130 connected in sequence. The drying device 110 is provided with a red mud inlet 111. The screening device 130 is provided with a red mud particle outlet 131. The oxidative roasting device 200 is used to oxidize and roast the red mud particles in an oxidizing gas to obtain roasting products. The oxidative roasting device 200 is provided with a red mud particle inlet 201, an oxidizing gas inlet 202, and a first roasting product outlet 203. The red mud particle inlet 201 is connected to the red mud particle outlet 131. The reduction reaction device 300 is used to reduce the roasting products in a reducing gas to obtain a reduction product, which includes elemental iron. The reduction reaction device 300 is provided with a first roasting product inlet 301, a first reducing gas inlet 302, and a reduction product outlet 303. The first roasting product inlet 301 is connected to the first roasting product outlet 203.

[0035] It should be noted that the metallization rate (MD) in this application refers to the proportion of iron oxide phase in red mud converted into metallic iron after the reduction reaction, which is calculated according to formula (I). (I), where MD is the metallization rate, w MFe To determine the iron content in the reduction product, w TFe This represents the total iron content in red mud (i.e., the total content of all forms of iron). The metallization rate reflects the efficiency of reducing the iron oxide phase in red mud to elemental iron, and also reflects the recovery rate of metallic iron in red mud.

[0036] The total iron content (w) in red mud was determined according to the method described in the national standard GB / T 6730.65-2009 "Determination of Total Iron Content in Iron Ore - Titration Method of Titanium Trichloride Reduction with Potassium Dichromate". TFe The content of elemental iron in the reduction product was determined by referring to the method described in the national standard GB / T 38812.2-2020 "Determination of iron content in direct reduced iron metal by titration of potassium dichromate by decomposition of ferric chloride".

[0037] Compared to traditional red mud reduction processes that only involve reduction reactions, this application provides a processing system for recovering iron from red mud, including a pretreatment unit 100, an oxidation roasting device 200, and a reduction reaction device 300. The pretreatment unit 100 is used to sequentially dry, crush, and screen the red mud to obtain uniformly sized red mud particles, inhibiting agglomeration in subsequent processing steps. This improves the efficiency of subsequent oxidation roasting and reduction reactions and enhances reaction consistency. The oxidation roasting device 200 is used to oxidize and roast the red mud particles, promoting the microscopic dissociation of the gangue phase (including alumina, silica, titanium dioxide, and calcium oxide phases) and the iron oxide phase in the red mud particles, obtaining roasted products. This increases the exposure of the iron oxide phase, enhancing its reactivity in subsequent reduction reactions, thereby increasing the metallization rate of the reduction reaction. Simultaneously, it also improves the morphological defects of the red mud particles, inhibiting agglomeration in subsequent reduction reactions, thus improving the reaction efficiency of the reduction reaction. The reduction reaction device 300 is set up to enable the roasting product to undergo a reduction reaction in the reducing gas, thereby reducing the iron oxide phase in the red mud to elemental iron, thus realizing the resource utilization of iron recovered from the red mud.

[0038] Compared to the use of plasma generators for reduction reactions in existing technologies, the process equipment in the above-mentioned processing system provided in this application can all be general equipment in the field, eliminating the need for customized high-cost plasma generators. This effectively reduces equipment investment and maintenance costs, making it more suitable for large-scale production.

[0039] In summary, the above-mentioned processing system provided in this application for recovering iron from red mud can not only effectively improve the consistency and efficiency of the reduction reaction, increase its metallization rate and the content of elemental iron in the reduction products, but also reduce reaction energy consumption and production costs, providing strong technical support for promoting the industrialization process of red mud resource utilization.

[0040] In a preferred embodiment, the inner cavity of the screening device 130 is provided with a first screen and a second screen, with the first screen located above the second screen. The first screen has an aperture of 0.3 mm, and the second screen has an aperture of 0.15 mm. The screening device 130 is used for screening to obtain red mud particles, first particles, and second particles. The particle size of the red mud particles is 0.15–0.3 mm, with the first particles having a particle size > 0.3 mm and the second particles having a particle size < 0.15 mm. The screening device 130 is also provided with a first particle outlet 132 and a second particle outlet 133. The screening device 130 is used to screen the crushed red mud to obtain red mud particles with a more suitable and uniform particle size, thereby helping to inhibit the agglomeration of red mud particles, improving the efficiency of subsequent oxidation roasting and reduction reactions, and increasing the metallization rate of the reduction reaction and the content of elemental iron in the reduction products. The arrangement of the first particle outlet 132 and the second particle outlet 133 facilitates the discharge of the first and second particles obtained from the screening process for subsequent processing, thereby improving the utilization rate of raw materials.

[0041] To further improve the efficiency and effectiveness of screening, in a preferred embodiment, the inner cavity of the screening device 130 is provided with a vibrating component.

[0042] like Figure 2 As shown, in a preferred embodiment, the crushing device 120 is further provided with a first particle inlet 121, which is connected to a first particle outlet 132, for returning the first particles to the crushing device 120 for repeated crushing until red mud particles are obtained. Discharging the first particles obtained from the screening process and returning them to the crushing device 120 through the first particle inlet 121 for further crushing improves the utilization rate of red mud raw materials, reduces resource waste, and also improves the particle size uniformity of the red mud particles.

[0043] like Figure 2 As shown, in a preferred embodiment, the pretreatment unit 100 is further provided with a granulation device 140 for granulating the second particles to obtain red mud particles. The granulation device 140 is provided with a second particle inlet 141, a binder inlet 142, and a discharge outlet 143. The second particle inlet 141 is connected to the second particle outlet 133, and the discharge outlet 143 is connected to the red mud particle inlet 201. The granulation device 140 facilitates the granulation of the second particles under the action of the binder, ensuring that the granulated particles meet the particle size requirements of red mud particles. This improves the particle size uniformity of the red mud particles and also increases the utilization rate of the red mud raw material, reducing resource waste.

[0044] To further improve the efficiency of the granulation process and better control the particle size distribution of the granulated particles, the granulation device 140 preferably includes, but is not limited to, a shear granulator or a disc granulator.

[0045] In a preferred embodiment, the inner cavity of the oxidative roasting apparatus 200 is provided with a heating element. The heating element facilitates better temperature control within the oxidative roasting apparatus 200, thereby improving the efficiency of oxidative roasting, promoting the microscopic dissociation of the gangue phase and iron oxide phase in the red mud particles, improving the morphological defects of the red mud particles, and further enhancing the reaction efficiency and metallization rate of subsequent reduction reactions.

[0046] In a preferred embodiment, the oxidative roasting apparatus 200 is provided with an external heat insulation layer. The heat insulation layer helps to reduce heat loss of the oxidative roasting apparatus 200, reduce energy consumption, and at the same time, helps to maintain temperature stability during the oxidative roasting process, better promote the microscopic dissociation of gangue phase and iron oxide phase in red mud particles, and increase the exposure degree of iron oxide phase.

[0047] In order to further reduce the heat loss of the oxidative roasting device 200 and better maintain the temperature stability during the oxidative roasting process, the thickness of the insulation layer is preferably 120-180 mm.

[0048] In order to further reduce the heat loss of the oxidation roasting device 200 and better maintain the temperature stability during the oxidation roasting process, preferably, the material of the insulation layer includes, but is not limited to, aluminum silicate fiber, alumina-based refractory material or magnesium oxide-based refractory material.

[0049] In a preferred embodiment, the oxidation roasting apparatus 200 includes, but is not limited to, a rotary kiln, a pusher kiln, or a tunnel kiln. Compared to other types, using the above-mentioned types of oxidation roasting apparatus 200 is beneficial to improving the efficiency of oxidation roasting, better promoting the microscopic dissociation of gangue phase and iron oxide phase in red mud particles, and also beneficial to reducing energy consumption.

[0050] The rotary kiln's ability to rotate ensures more uniform heat treatment of the red mud particles during the oxidative roasting process, helping to prevent localized overheating or uneven heating. To further improve the efficiency and effectiveness of the oxidative roasting and reduce energy consumption, the oxidative roasting device 200 is preferably a rotary kiln.

[0051] To further improve the efficiency and effect of oxidative roasting and further reduce energy consumption, more preferably, the kiln body length of the rotary kiln is 1 to 10 m, the inner diameter of the kiln body is 0.1 to 1.5 m, and the inclination angle of the kiln body is 2° to 5°.

[0052] like Figure 2As shown, in a preferred embodiment, the processing system further includes a heat exchanger 400 for exchanging heat between the roasted product and the reducing gas. The heat exchanger 400 is provided with a second roasted product inlet 401, a second reducing gas inlet 402, a second roasted product outlet 403, and a reducing gas outlet 404. The second roasted product inlet 401 is connected to the first roasted product outlet 203, and the second roasted product outlet 403 is connected to the first roasted product inlet 301. The heat exchanger 400 is used to exchange heat between the roasted product and the reducing gas, thereby fully utilizing the waste heat of the roasted product to preheat the reducing gas, which helps to reduce the energy consumption required for subsequent preheating of the reducing gas and improve resource utilization.

[0053] like Figure 2 As shown, in a preferred embodiment, the processing system further includes a preheating device 500 for preheating the reducing gas; the inlet of the preheating device 500 is connected to the reducing gas outlet 404, and the outlet of the preheating device 500 is connected to the first reducing gas inlet 302. The preheating device 500 is configured to heat the reducing gas to a preset temperature before the reduction reaction, thereby improving the reaction efficiency and metallization rate of the subsequent reduction reaction.

[0054] In order to improve the uniformity of the distribution of reducing gas in the reduction reaction apparatus 300, thereby enhancing the contact efficiency and reaction uniformity between the reducing gas and the calcination product, and further improving the reaction efficiency and metallization rate of the reduction reaction, in a preferred embodiment, a gas distribution plate is provided at the bottom of the inner cavity of the reduction reaction apparatus 300, and the gas distribution plate has through holes.

[0055] In order to further improve the uniformity of the distribution of reducing gas in the reduction reaction device 300, thereby further enhancing the contact efficiency and reaction uniformity between the reducing gas and the calcination product, and further improving the reaction efficiency and metallization rate of the reduction reaction, preferably, the total area of ​​the through holes accounts for 12-18% of the total area of ​​the gas distribution plate.

[0056] In a preferred embodiment, the inner cavity of the reduction reaction apparatus 300 is provided with a heating element. The heating element facilitates better temperature control within the reduction reaction apparatus 300, thereby improving the reaction efficiency of the reduction reaction, promoting the reduction of the iron oxide phase in the red mud to elemental iron, and further improving the metallization rate.

[0057] In order to better control the temperature and pressure in the reduction reaction apparatus 300 and improve the reaction efficiency and safety of the reduction reaction, in a preferred embodiment, the inner cavity of the reduction reaction apparatus 300 is provided with a temperature sensing component and / or a pressure sensing component for monitoring the temperature and / or pressure in the reduction reaction apparatus 300.

[0058] Fluidized bed reactors utilize reducing gas to suspend the calcined products, creating a boiling-like liquid state, thereby effectively improving the contact efficiency between the calcined products and the reducing gas, and thus enhancing the reduction reaction efficiency. Gas-based vertical shaft furnaces are vertical reactors specifically designed for metal reduction. The calcined products are continuously added from the top of the furnace, while reducing gas is introduced from the bottom. As the reducing gas rises, it contacts the descending calcined products, effectively improving the contact efficiency and enhancing the reduction reaction efficiency. To better control the reaction conditions and further improve the reduction reaction efficiency and metallization rate, while also reducing production costs, in a preferred embodiment, the reduction reaction apparatus 300 includes, but is not limited to, a fluidized bed reactor or a gas-based vertical shaft furnace.

[0059] In a preferred embodiment, the reduction reaction apparatus 300 is further provided with a gas outlet 304 for discharging the gaseous products obtained from the reduction reaction. The gas outlet 304 is provided to discharge the gaseous products obtained from the reduction reaction (including byproduct water vapor, unreacted reducing gas, and unreacted red mud powder), thereby improving the utilization rate of raw materials.

[0060] like Figure 2 As shown, in a preferred embodiment, the processing system further includes a solid-gas separation device 600 and a reducing gas recovery device 700 connected in sequence; the inlet of the solid-gas separation device 600 is connected to the gas outlet 304; the outlet of the reducing gas recovery device 700 is connected to the first reducing gas inlet 302 and / or the second reducing gas inlet 402. The solid-gas separation device 600 is used to separate fine solid particles (such as unreacted red mud powder) entrained in the gaseous products obtained from the reduction reaction, and the reducing gas recovery device 700 is used to separate and recover the reducing gas in the gaseous products, thereby improving the utilization rate of reducing gas, reducing resource waste, and thus helping to reduce production costs.

[0061] To further improve the reaction efficiency and metallization rate of the reduction reaction, in a preferred embodiment, the reducing gas is hydrogen.

[0062] In order to separate and purify hydrogen from the gaseous products and improve the purity of the recovered hydrogen, preferably, the inner cavity of the reducing gas recovery device 700 is provided with a metal hydrogen separation membrane for separating and obtaining recovered hydrogen.

[0063] To further improve the purity of the recovered hydrogen, preferably, the thickness of the metal hydrogen separation membrane is 2-30 μm, and preferably, the material of the metal hydrogen separation membrane is palladium.

[0064] The second aspect of this application also provides a method for recovering iron from red mud. This method uses the aforementioned iron recovery system from red mud provided in this application. The method includes: step S1, feeding red mud into a pretreatment unit 100, and sequentially performing drying, crushing, and screening treatments in a drying device 110, a crushing device 120, and a screening device 130 to obtain red mud particles; step S2, feeding the red mud particles into an oxidizing roasting device 200, and oxidizing and roasting the red mud particles in an oxidizing gas to obtain a roasting product; step S3, feeding the roasting product into a reduction reaction device 300, and reducing the roasting product in a reducing gas to obtain a reduction product, which includes elemental iron.

[0065] The above-mentioned processing method provided in this application is carried out using the processing system provided in this application. In step S1, the red mud is sequentially dried, crushed, and sieved to obtain red mud particles with uniform particle size, inhibiting their agglomeration in subsequent processing steps, thereby improving the efficiency of subsequent oxidation roasting and reduction reactions and enhancing the consistency of the reaction. In step S2, the oxidation roasting of the red mud particles promotes the microscopic dissociation of the gangue phase (including alumina phase, silica phase, titanium dioxide phase, and calcium oxide phase) and the iron oxide phase in the red mud particles, obtaining roasting products. This increases the exposure degree of the iron oxide phase, improves its reactivity in subsequent reduction reactions, and thus increases the metallization rate of the reduction reaction. At the same time, it can also improve the morphological defects of the red mud particles and inhibit their agglomeration in subsequent reduction reactions, thereby improving the reaction efficiency of the reduction reaction. In step S3, the roasting products undergo a reduction reaction in a reducing gas, promoting the reduction of the iron oxide phase in the red mud to metallic iron.

[0066] Compared with other methods, the above-mentioned treatment method provided in this application can effectively increase the exposure degree of iron oxide phase in red mud and significantly improve its reactivity. This not only reduces the reaction temperature of the reduction reaction and reduces energy consumption, but also improves the reaction efficiency and metallization rate of the reduction reaction, thereby significantly improving the resource utilization rate of red mud.

[0067] In a preferred embodiment, in step S1, the drying temperature is 105–130°C, and the time is 1–3 hours. The drying temperature and time include, but are not limited to, the above ranges. Limiting them to these ranges is beneficial for improving the removal efficiency of moisture from the red mud raw material, inhibiting its agglomeration during subsequent crushing and screening processes, and improving the efficiency of subsequent processing steps.

[0068] In order to further suppress the agglomeration of red mud raw materials during subsequent crushing and screening processes and to further improve the efficiency of subsequent processing steps, preferably, the water content in the dried red mud is ≤1 wt%.

[0069] In a preferred embodiment, a screening device 130 equipped with a vibrating component is used for screening. The vibration frequency of the screening process is 15-20 Hz, and the amplitude is 5-8 mm. Compared with other types and ranges, using the screening device 130 and limiting the vibration frequency and amplitude of the screening process within the above range is beneficial to improving the efficiency and effect of the screening process, and obtaining red mud particles with more suitable particle size.

[0070] In a preferred embodiment, the red mud particles have a particle size of 0.15–0.3 mm. Compared to other ranges, limiting the particle size of the red mud particles to the above range is beneficial to improving the uniformity of the red mud particles, inhibiting their agglomeration, and using red mud particles within the above particle size range for subsequent oxidative roasting is beneficial to better promote the microscopic dissociation between the gangue phase and the iron oxide phase, thereby increasing the exposure degree of the iron oxide phase, improving its reactivity, and thus improving the reaction efficiency of the subsequent reduction reaction, reducing the temperature of the reduction reaction and shortening the reaction time, while also improving the metallization rate of the reduction reaction.

[0071] Screening is beneficial for obtaining red mud particles with a more suitable particle size. It can also separate larger first particles and smaller second particles. Preferably, the screening process also yields first and second particles, with the first particle having a particle size > 0.3 mm and the second particle having a particle size < 0.15 mm.

[0072] In a preferred embodiment, step S1 further includes returning the first particle to the crushing device 120 for repeated crushing until red mud particles are obtained. Compared with other methods, the above method is beneficial to improve the utilization rate of red mud raw materials, reduce resource waste, and also improve the particle size uniformity of red mud particles.

[0073] In a preferred embodiment, step S1 further includes feeding the second particles and binder into the granulation device 140 for granulation to obtain red mud particles. Compared with other methods, the above method is beneficial to improve the utilization rate of red mud raw materials, reduce resource waste, and also improve the particle size uniformity of red mud particles.

[0074] In a preferred embodiment, the weight ratio of the second particle to the binder is 100:(2-5). The weight ratio of the second particle to the binder includes, but is not limited to, the above range. Limiting it to the above range is beneficial for obtaining red mud particles with more uniform particle size, and also for improving the utilization rate of raw materials.

[0075] To further improve the efficiency of the granulation process, preferably, the binder includes, but is not limited to, water and / or bentonite.

[0076] To further improve the efficiency of the granulation process and obtain red mud particles with more uniform particle size, it is preferable to use a shear granulator for granulation, with a rotor speed of 300-500 r / min and a granulation time of 10-15 min.

[0077] In a preferred embodiment, in step S2, the oxidative roasting temperature is 1100–1250°C, and the material residence time is 30–70 min. The oxidative roasting temperature and material residence time include, but are not limited to, the above ranges. Limiting them to these ranges is beneficial for improving the efficiency of oxidative roasting, for improving the morphological defects of red mud particles, and for promoting the microscopic dissociation of the gangue phase and iron oxide phase in the red mud particles, increasing the exposure degree of the iron oxide phase. This, in turn, is beneficial for improving the reactivity of the roasted product, thereby not only improving the reaction efficiency of the subsequent reduction reaction, reducing the reaction temperature and shortening the reaction time, but also for improving the metallization rate of the reduction reaction.

[0078] In a preferred embodiment, the feed rate of the red mud particles is 0.5–5 kg / h. The feed rate of the red mud particles includes, but is not limited to, the above range. Limiting it to the above range is beneficial to improving the uniformity of the distribution of red mud particles in the oxidative roasting device 200, thereby improving the efficiency and effect of oxidative roasting and better promoting the microscopic dissociation of gangue phase and iron oxide phase in the red mud particles.

[0079] To maintain the stability of the oxidizing atmosphere in the oxidizing roasting device 200 and suppress the reduction reaction of red mud particles during the oxidizing roasting process, which would affect the efficiency of subsequent reactions, in a preferred embodiment, the flow rate of the oxidizing gas is 0.2–2 m³ / h. 3 / h.

[0080] In order to better maintain the stability of the oxidizing atmosphere in the oxidizing roasting device 200, further suppress the reduction reaction of red mud particles during the oxidizing roasting process, and further improve the efficiency of oxidizing roasting, preferably, the volume percentage of oxygen in the oxidizing gas is ≥18 vol.

[0081] The rotary kiln's ability to rotate ensures more uniform heat treatment of the red mud particles during the oxidative roasting process, helping to suppress localized overheating or uneven heating. In a preferred embodiment, a rotary kiln is used for oxidative roasting, with a rotational speed of 0.8–1.2 r / min. Compared to other ranges, limiting the rotary kiln's rotational speed within this range helps suppress localized overheating, thereby improving the efficiency and uniformity of the oxidative roasting.

[0082] In a preferred embodiment, in step S3, the reduction reaction temperature is 600–700°C, and the material residence time is 0.5–2 hours. The reduction reaction temperature and material residence time include, but are not limited to, the above ranges. Limiting them to these ranges is beneficial for improving the contact efficiency between the reducing gas and the roasting product, improving the reaction efficiency of the reduction reaction, promoting the reduction of the iron oxide phase in the red mud into metallic iron, and also reducing the formation of by-products, thereby improving the metallization rate of the reduction reaction.

[0083] Oxidative roasting is beneficial for promoting the microscopic dissociation of gangue phase and iron oxide phase in red mud particles, increasing the exposure degree of iron oxide phase, and improving the reactivity of roasted products. This not only helps to improve the metallization rate of the reduction reaction, but also helps to further shorten the reaction time of the reduction reaction, further improve the reaction efficiency of the reduction reaction, and reduce the reaction energy consumption. Preferably, the material residence time of the reduction reaction is 0.5 to 1 hour.

[0084] In a preferred embodiment, the feed rate of the calcined product is 0.4–5 kg / h. The feed rate of the calcined product includes, but is not limited to, the above range. Limiting it to the above range is beneficial to improve the uniformity of the distribution of the calcined product in the reduction reaction apparatus 300, thereby improving the contact efficiency between the reducing gas and the calcined product, improving the reaction efficiency of the reduction reaction, and further improving the metallization rate of the reduction reaction.

[0085] To improve the contact efficiency between the reducing gas and the calcined product, thereby further improving the reaction efficiency of the reduction reaction, in a preferred embodiment, the flow rate of the reducing gas is 0.1–5 m³ / h. 3 / h.

[0086] To further improve the reaction efficiency and metallization rate of the reduction reaction, in a preferred embodiment, the reducing gas is hydrogen.

[0087] In order to make fuller use of the waste heat of the roasting product and improve energy efficiency, in a preferred embodiment, between step S2 and step S3, the processing method further includes exchanging heat between the roasting product and the reducing gas in the heat exchange device 400, passing the heat-exchanged reducing gas into the preheating device 500 for preheating, and passing the preheated reducing gas into the reduction reaction device 300 for reduction reaction.

[0088] To further improve the reaction efficiency and metallization rate of the reduction reaction, preferably, the temperature of the preheated reducing gas is 600–700°C.

[0089] In a preferred embodiment, in step S3, the reduction reaction further yields a gaseous product; step S3 also includes passing the gaseous product into a solid-gas separation device 600 and a reducing gas recovery device 700 connected in sequence for solid-gas separation and reducing gas recovery, to obtain recovered reducing gas. Compared with other methods, the above method is advantageous for recovering and utilizing the reducing gas in the gaseous product, which helps to improve the utilization rate of reducing gas and reduce costs.

[0090] To further improve the recovery and utilization rate of reducing gas, preferably, at least a portion of the recovered reducing gas is returned to the reduction reaction device 300 and / or heat exchange device 400 for recycling.

[0091] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0092] It should be noted that an XRF spectrometer (X-ray fluorescence spectrometer, Panalytical Axios, Netherlands) was used to detect the raw materials red mud A, red mud B, and red mud C used in all the following embodiments and comparative examples of this application. The composition and content of red mud A, red mud B, and red mud C are shown in Table 1.

[0093] Table 1

[0094]

[0095] Example 1

[0096] A method for recovering iron from red mud, employing, as follows: Figure 1 The process for recovering iron from red mud, as shown, includes the following steps:

[0097] (1) 2 kg of red mud A was fed into the pretreatment unit 100 and dried using a box dryer. The drying temperature was 120℃ and the time was 1 hour. During the drying process, the material was turned over every 30 minutes to prevent the red mud from forming hard lumps due to uneven heating. The moisture content of the dried red mud was <1 wt%. The dried red mud was crushed using a jaw crusher (the feed opening size was set to 300 mm × 200 mm, and the discharge opening gap was controlled between 5 and 10 mm). Then it was transferred to a vibrating screen (the aperture of the upper screen was 0.3 mm and the aperture of the lower screen was 0.15 mm) for screening. The vibration frequency was set to 15 Hz and the amplitude was 6 mm to obtain red mud particles with a particle size in the range of 0.15 to 0.3 mm.

[0098] (2) The red mud particles obtained in step (1) are fed into a rotary kiln (the length of the kiln body is 3m, the inner diameter is 0.1m, and the inclination angle is 2°) at a feed rate of 0.5kg / h. At the same time, air is continuously introduced into the rotary kiln at a flow rate of 0.5m³ / h, and oxidative roasting is carried out at 1200℃ to obtain roasted products. The material residence time is 30min, and the rotation speed of the rotary kiln is 1r / min.

[0099] (3) Nitrogen gas was used to replace the air in the bubbling fluidized bed, and this process was repeated three times. Then, the calcined product obtained in step (2) and hydrogen gas were introduced into the bubbling fluidized bed for a reduction reaction. The feed rate of the calcined product was 0.5 kg / h, and the flow rate of hydrogen gas was 0.12 m³ / h. 3 / h; the reduction reaction temperature was 600℃, the material residence time was 1h, and 1.7kg of reduction product was obtained; the iron content in the reduction product was determined to be 44.1wt% according to the method described in the national standard GB / T 38812.2-2020.

[0100] Example 2

[0101] The difference from Example 1 is that in step (1), raw material red mud B of equal weight is used to replace raw material red mud A in Example 1; the remaining steps are the same as in Example 1.

[0102] Example 3

[0103] The difference from Example 1 is that in step (1), an equal weight of raw material red mud C is used to replace the raw material red mud A in Example 1, and the remaining steps are the same as in Example 1.

[0104] Example 4

[0105] The difference from Example 1 is that the oxidation roasting temperature in step (2) is 1250℃ and the material residence time is 40min; the remaining steps are the same as in Example 1.

[0106] Example 5

[0107] The difference from Example 1 is that the oxidation roasting temperature in step (2) is 1100℃ and the material residence time is 70min; the remaining steps are the same as in Example 1.

[0108] Example 6

[0109] The difference from Example 1 is that the oxidation roasting temperature in step (2) is 1000℃ and the material residence time is 30min; the remaining steps are the same as in Example 1.

[0110] Example 7

[0111] The difference from Example 1 is that the temperature of the reduction reaction in step (3) is 700°C and the material residence time is 0.5h; the rest of the steps are the same as in Example 1.

[0112] Example 8

[0113] The difference from Example 1 is that the temperature of the reduction reaction in step (3) is 550°C and the material residence time is 1h; the rest of the steps are the same as in Example 1.

[0114] Example 9

[0115] The difference from Example 1 is that in step (1), a vibrating screen (the aperture of the upper screen is 0.45 mm and the aperture of the lower screen is 0.35 mm) is used for screening to obtain red mud particles with a particle size in the range of 0.35 to 0.45 mm; the remaining steps are the same as in Example 1.

[0116] Example 10

[0117] The difference from Example 1 is that in step (1), a vibrating screen (the aperture of the upper screen is 0.12 mm and the aperture of the lower screen is 0.05 mm) is used for screening to obtain red mud particles with a particle size in the range of 0.05 to 0.12 mm; the remaining steps are the same as in Example 1.

[0118] Example 11

[0119] A method for recovering iron from red mud, employing, as follows: Figure 2 The process for recovering iron from red mud, as shown, includes the following steps:

[0120] (1) 2 kg of red mud A was fed into the pretreatment unit 100 and dried using a box dryer. The drying temperature was 120℃ and the time was 1 hour. During the drying process, the material was turned over every 30 minutes to prevent the red mud from forming hard lumps due to uneven heating. The moisture content of the dried red mud was <1 wt%. The dried red mud was crushed using a jaw crusher (the feed opening size was set to 300 mm × 200 mm, and the discharge opening gap was controlled between 5 and 10 mm). Then it was transferred to a vibrating screen (the aperture of the upper screen was 0.3 mm and the aperture of the lower screen was 0.15 mm) for screening. The vibration frequency was set to 15 Hz and the amplitude was 6 mm to obtain red mud particles with a particle size in the range of 0.15 to 0.3 mm, the first particle with a particle size >0.3 mm, and the second particle with a particle size <0.15 mm.

[0121] The first particle is returned to the jaw crusher for further crushing until red mud particles with a particle size in the range of 0.15 to 0.3 mm are obtained.

[0122] The second particle is transferred to a shear granulator, and water is used as a binder for granulation. The weight ratio of the second particle to the binder is 100:2. The rotor speed of the shear granulator is 300 r / min, and the granulation time is 10 min, so that the particle size of the granulated particles is in the range of 0.15 to 0.3 mm.

[0123] (2) The red mud particles obtained in step (1) and the granulated particles are fed into a rotary kiln (3m long, 0.1m inner diameter, and 2° tilt angle) at a feed rate of 0.5kg / h. At the same time, air is continuously introduced into the rotary kiln at a flow rate of 0.5m³ / h, and oxidative roasting is carried out at 1200℃ to obtain roasted products. The material residence time is 30min, and the rotation speed of the rotary kiln is 1r / min.

[0124] (3) The calcined product and hydrogen obtained in step (2) are passed into a tubular heat exchanger for heat exchange, so that the temperature of the calcined product is reduced to below 200°C and the hydrogen is heated to 180±10°C to realize heat recovery and utilization; then the hydrogen is passed into the heater to preheat to 600°C.

[0125] (4) Nitrogen gas was used to replace the air in the bubbling fluidized bed, and this process was repeated three times. Subsequently, the calcined product after heat exchange and preheated hydrogen were introduced into the bubbling fluidized bed for a reduction reaction. The feed rate of the calcined product was 0.5 kg / h, and the flow rate of hydrogen was 0.12 m³ / h. 3 The reduction reaction was carried out at a temperature of 600℃ for 1 hour, yielding 1.7 kg of reduction product and gaseous product. The iron content in the reduction product was determined to be 45.9 wt% according to the method described in national standard GB / T 38812.2-2020.

[0126] (5) The gaseous product obtained in step (4) is passed into a cyclone separator to remove the solid fine powder entrained in the gaseous product. Then the gas is passed into a hydrogen recovery device equipped with a palladium membrane (15 μm thick) to separate and purify the hydrogen and obtain recovered hydrogen. The recovered hydrogen can be returned to the bubbling fluidized bed and tubular heat exchanger for recycling.

[0127] In Example 11, by crushing the first particle with a larger particle size and granulating the second particle with a smaller particle size in step (1), red mud particles with suitable particle size are obtained, which effectively improves the utilization rate of red mud raw materials and further increases the content of metallic iron in the reduction product. At the same time, through the heat exchange between the roasting product and hydrogen in step (3), heat is recovered and utilized, which can effectively reduce energy consumption. In addition, Example 11 effectively realizes the recovery and utilization of hydrogen by performing solid-gas separation and hydrogen purification on the gaseous products generated by the reduction reaction in step (5), which can significantly reduce production costs.

[0128] Comparative Example 1

[0129] The difference from Example 1 is that step (2) is omitted, the red mud particles obtained in step (1) are not oxidized and roasted, and are directly subjected to reduction reaction to obtain a reduction product containing metallic iron; the remaining steps are the same as in Example 1.

[0130] Comparative Example 2

[0131] The difference from Example 2 is that step (2) is omitted, the red mud particles obtained in step (1) are not oxidized and roasted, and are directly subjected to reduction reaction to obtain a reduction product containing metallic iron; the remaining steps are the same as in Example 1.

[0132] Comparative Example 3

[0133] The difference from Example 3 is that step (2) is omitted, the red mud particles obtained in step (1) are not oxidized and roasted, and are directly subjected to reduction reaction to obtain a reduction product containing metallic iron; the remaining steps are the same as in Example 1.

[0134] The metallization rate (MD) of the reduction reaction in all the above-described embodiments and comparative examples of this application is calculated according to formula (I). (I), where MD is the metallization rate, w MFe To determine the iron content in the reduction product, w TFe This refers to the total iron content in red mud (i.e., the total content of all forms of iron). It should be noted that the total iron content w in red mud was measured according to the method described in national standard GB / T6730.65-2009. TFe The content of elemental iron in the reduction product was determined according to the method described in national standard GB / T 38812.2-2020. MFe The calculation results are shown in Table 2.

[0135] Table 2

[0136]

[0137] Comparing Examples 1 to 3 and Comparative Examples 1 to 3, and referring to Table 2, it can be seen that oxidative roasting of red mud particles before the reduction reaction can promote the microscopic dissociation of gangue phase and iron oxide phase in red mud particles, increase the exposure degree of iron oxide phase, thereby significantly improving its reactivity in the subsequent reduction reaction, and thus effectively improving the metallization rate of the reduction reaction.

[0138] Comparing Examples 1, 4 to 6, and referring to Table 2, it can be seen that, compared to other ranges, limiting the oxidative roasting temperature and material residence time within the above ranges is beneficial to improving the morphological defects of red mud particles, promoting the microscopic dissociation of gangue phase and iron oxide phase in red mud particles, increasing the exposure degree of iron oxide phase, thereby improving the reactivity of roasted products. This not only helps to improve the reaction efficiency of subsequent reduction reactions, reduce reaction temperature and shorten reaction time, but also helps to improve the metallization rate of reduction reactions.

[0139] Comparing Examples 1, 7, and 8, and referring to Table 2, it can be seen that, compared to other ranges, limiting the temperature and material residence time of the reduction reaction within the above range is beneficial to improving the contact efficiency between the reducing gas and the roasted product, which is beneficial to improving the reaction efficiency of the reduction reaction, promoting the reduction of the iron oxide phase in the red mud into metallic iron, and also beneficial to reducing the generation of by-products, thereby improving the metallization rate of the reduction reaction and increasing the iron content in the reduction product.

[0140] Comparing Examples 1, 9, and 10, and referring to Table 2, it can be seen that, compared to other ranges, limiting the particle size of the red mud particles to the above range is beneficial to better promote the microscopic dissociation between the gangue phase and the iron oxide phase in the subsequent oxidative roasting, increasing the exposure degree of the iron oxide phase and improving its reactivity. Thus, in the subsequent reduction reaction process, it is not only beneficial to improve its reaction efficiency, reduce the reaction temperature and shorten the reaction time, but also beneficial to improve the metallization rate of the reduction reaction.

[0141] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0142] Compared to the traditional red mud hydrogen reduction process that only involves reduction reactions, this application provides a processing system for recovering iron from red mud, including a pretreatment unit 100, an oxidation roasting device 200, and a reduction reaction device 300. The pretreatment unit 100 is used to sequentially dry, crush, and screen the red mud to obtain red mud particles with uniform particle size, inhibiting agglomeration in subsequent processing steps, thereby improving the efficiency of subsequent oxidation roasting and reduction reactions and enhancing reaction consistency. The oxidation roasting device 200 is used to oxidize and roast the red mud particles, promoting the microscopic dissociation of the gangue phase (including alumina, silica, titanium dioxide, and calcium oxide phases) and the iron oxide phase in the red mud particles, obtaining roasted products. This increases the exposure of the iron oxide phase, enhancing its reactivity in subsequent reduction reactions, thereby increasing the metallization rate of the reduction reaction. Simultaneously, it can also improve the morphological defects of the red mud particles, inhibiting agglomeration in subsequent reduction reactions, thus improving the reaction efficiency of the reduction reaction. The reduction reaction device 300 is set up to enable the roasted products to undergo a reduction reaction in hydrogen gas, thereby reducing the iron oxide phase in the red mud to elemental iron, thus realizing the resource utilization of iron recovered from the red mud.

[0143] Compared to the use of plasma generators for reduction reactions in existing technologies, the process equipment in the above-mentioned processing system provided in this application can all be general equipment in the field, eliminating the need for customized high-cost plasma generators. This effectively reduces equipment investment and maintenance costs, making it more suitable for large-scale production.

[0144] In summary, the processing system provided in this application can not only effectively improve the consistency and efficiency of the reduction reaction, increase its metallization rate and the content of elemental iron in the reduction products, but also reduce reaction energy consumption and production costs, providing strong technical support for promoting the industrialization of red mud resource utilization.

[0145] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0146] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for recovering iron from red mud, characterized in that, The processing method employs a system for recovering iron from red mud, the system comprising: A pretreatment unit (100) is used to sequentially dry, crush, and screen the red mud to obtain red mud particles; the pretreatment unit (100) includes a drying device (110), a crushing device (120), and a screening device (130) connected in sequence; the drying device (110) is provided with a red mud inlet (111); the screening device (130) is provided with a red mud particle outlet (131); An oxidative roasting apparatus (200) is used to oxidize and roast the red mud particles in an oxidizing gas, thereby causing the gangue phase and iron oxide phase in the red mud particles to dissociate at the microscopic level and obtain roasting products. The oxidative roasting apparatus (200) is provided with a red mud particle inlet (201), an oxidizing gas inlet (202), and a first roasting product outlet (203). The red mud particle inlet (201) is connected to the red mud particle outlet (131). A reduction reaction apparatus (300) is used to reduce the calcined product in a reducing gas to obtain a reduction product, the reduction product including elemental iron; the reduction reaction apparatus (300) is provided with a first calcined product inlet (301), a first reducing gas inlet (302) and a reduction product outlet (303); the first calcined product inlet (301) is connected to the first calcined product outlet (203); The processing method includes: Step S1: The red mud is fed into the pretreatment unit (100), and the drying, crushing and screening processes are carried out sequentially in the drying device (110), the crushing device (120) and the screening device (130) to obtain the red mud particles; the particle size of the red mud particles is 0.15-0.3 mm. Step S2: The red mud particles are fed into the oxidative roasting device (200) to undergo oxidative roasting in the oxidizing gas, thereby obtaining the roasted product. The oxidative roasting temperature is 1100–1250°C, and the material residence time is 30–70 min. The feed rate of the red mud particles is 0.5–5 kg / h, and the flow rate of the oxidizing gas is 0.2–2 m³ / h. 3 / h; the volume percentage of oxygen in the oxidizing gas is ≥18 vol% Step S3: The calcined product is passed into the reduction reaction apparatus (300), whereby the calcined product undergoes the reduction reaction in the reducing gas to obtain the reduced product, which includes the elemental iron; the temperature of the reduction reaction is 600–700°C, the material residence time is 0.5–2 h, the feed rate of the calcined product is 0.4–5 kg / h, and the flow rate of the reducing gas is 0.1–5 m³ / h. 3 / h; the reducing gas is hydrogen.

2. The method for recovering iron from red mud according to claim 1, characterized in that, The screening device (130) has a first screen and a second screen inside its cavity. The first screen is located above the second screen. The aperture of the first screen is 0.3 mm, and the aperture of the second screen is 0.15 mm. The screening device (130) is used to perform the screening process to obtain the red mud particles, the first particles, and the second particles. The particle size of the first particles is >0.3 mm, and the particle size of the second particles is <0.15 mm. The screening device (130) is also provided with a first particle outlet (132) and a second particle outlet (133). And / or, The screening device (130) is equipped with a vibrating component in its inner cavity.

3. The method for recovering iron from red mud according to claim 2, characterized in that, The crushing device (120) is further provided with a first particle inlet (121), which is connected to a first particle outlet (132) for returning the first particles to the crushing device (120) for repeated crushing until the red mud particles are obtained; and / or, The pretreatment unit (100) is further provided with a granulation device (140) for granulating the second particles to obtain the red mud particles; the granulation device (140) is provided with a second particle inlet (141), a binder inlet (142) and a discharge outlet (143); the second particle inlet (141) is connected to the second particle outlet (133), and the discharge outlet (143) is connected to the red mud particle inlet (201).

4. The method for recovering iron from red mud according to claim 3, characterized in that, The granulation device (140) is selected from a shear granulator or a disc granulator.

5. The method for recovering iron from red mud according to claim 1, characterized in that, The inner cavity of the oxidation roasting apparatus (200) is provided with a heating element; and / or, The oxidation roasting device (200) is provided with an insulation layer on the outside; the thickness of the insulation layer is 120-180mm; the material of the insulation layer is selected from aluminum silicate fiber, alumina-based refractory material or magnesium oxide-based refractory material.

6. The method for recovering iron from red mud according to claim 5, characterized in that, The oxidation roasting device (200) is selected from a rotary kiln, a pusher kiln or a tunnel kiln.

7. The method for recovering iron from red mud according to claim 1, characterized in that, A gas distribution plate is provided at the bottom of the inner cavity of the reduction reaction device (300), and the gas distribution plate has through holes; the total area of ​​the through holes accounts for 12-18% of the total area of ​​the gas distribution plate; and / or, The inner cavity of the reduction reaction device (300) is provided with a heating element; and / or, The inner cavity of the reduction reaction device (300) is provided with a temperature sensing component and / or a pressure sensing component for monitoring the temperature and / or pressure within the reduction reaction device (300); and / or, The reduction reaction apparatus (300) is also provided with a gas outlet (304) for discharging the gaseous products obtained from the reduction reaction.

8. The method for recovering iron from red mud according to claim 7, characterized in that, The processing system further includes a heat exchange device (400) for exchanging heat between the calcined product and the reducing gas; the heat exchange device (400) is provided with a second calcined product inlet (401), a second reducing gas inlet (402), a second calcined product outlet (403) and a reducing gas outlet (404); the second calcined product inlet (401) is connected to the first calcined product outlet (203), and the second calcined product outlet (403) is connected to the first calcined product inlet (301); The processing system further includes a preheating device (500) for preheating the reducing gas; the inlet of the preheating device (500) is connected to the reducing gas outlet (404), and the outlet of the preheating device (500) is connected to the first reducing gas inlet (302).

9. The method for recovering iron from red mud according to claim 8, characterized in that, The processing system further includes a solid-gas separation device (600) and a reducing gas recovery device (700) connected in sequence; the inlet of the solid-gas separation device (600) is connected to the gas outlet (304); the outlet of the reducing gas recovery device (700) is connected to the first reducing gas inlet (302) and / or the second reducing gas inlet (402).

10. The method for recovering iron from red mud according to claim 1, characterized in that, In step S1, the drying process is carried out at a temperature of 105–130°C for 1–3 hours; and / or, The screening process is performed using a screening device (130) equipped with a vibrating component, wherein the vibration frequency of the screening process is 15–20 Hz and the amplitude is 5–8 mm; and / or, The sieving process also yields a first particle and a second particle, wherein the particle size of the first particle is >0.3 mm and the particle size of the second particle is <0.15 mm.

11. The method for recovering iron from red mud according to claim 10, characterized in that, Step S1 further includes returning the first particle to the crushing device (120) to repeat the crushing process until the red mud particles are obtained; and / or, Step S1 further includes passing the second particles and binder into a granulation device (140) for granulation to obtain the red mud particles.

12. The method for recovering iron from red mud according to claim 11, characterized in that, The weight ratio of the second particle to the adhesive is 100:(2-5); and / or, The binder is selected from water and / or bentonite; and / or, The granulation is carried out using a shear granulator, wherein the rotor speed of the shear granulator is 300-500 r / min, and the granulation time is 10-15 min.

13. The method for recovering iron from red mud according to claim 1, characterized in that, In step S2, the oxidation roasting is carried out using a rotary kiln with a rotation speed of 0.8 to 1.2 r / min.

14. The method for recovering iron from red mud according to claim 13, characterized in that, Between step S2 and step S3, the processing method further includes exchanging heat between the calcined product and the reducing gas in a heat exchanger (400), preheating the reduced gas after heat exchange in a preheating device (500), and then introducing the preheated reduced gas into the reduction reaction device (300); the temperature of the preheated reduced gas is 600–700°C; and / or, In step S3, the reduction reaction also yields a gaseous product; step S3 further includes passing the gaseous product into a solid-gas separation device (600) and a reducing gas recovery device (700) connected in sequence for solid-gas separation and reducing gas recovery to obtain recovered reducing gas; at least a portion of the recovered reducing gas is returned to the reduction reaction device (300) and / or the heat exchange device (400) for recycling.

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