Process for extracting iron and aluminum from high-iron red mud

Abstract

The application provides a process for extracting iron and aluminum from high-iron red mud, comprising the following steps: firstly, mixing high-iron red mud, a reducing agent and a composite agent to prepare a mixture; then, sequentially extracting iron and aluminum from the mixture to obtain waste residue; finally, processing the waste residue into building material to obtain a composite admixture for building material. The mass ratio of the high-iron red mud, the reducing agent and the composite agent is 100: (16-40): (25-60), the composite agent comprises lime, industrial soda and fluorite, and the mass ratio of the three is (5-20): (20-60): (0-5); the process not only effectively improves the recovery rate of iron and aluminum in the high-iron red mud, realizes the recycling of resources, reduces the influence on the environment, but also can improve the added value of the product, prepare a composite admixture for building material with good physical and chemical properties, realize the comprehensive resource utilization and recycling of the high-iron red mud, and finally achieve the purpose of 100% resource utilization of the red mud.

Description

Technical Field

[0001] This invention relates to the field of mineral processing and metal smelting technology, and more specifically, to a process for extracting iron and aluminum using high-iron red mud. Background Technology

[0002] Red mud is a solid, powdery waste product generated after extracting alumina from bauxite, primarily produced through three processes: the Bayer process, the sintering process, and a combined process. The main chemical components of red mud are SiO2, Al2O3, CaO, Fe2O3, Na2O, and TiO2. It is highly alkaline (pH ≥ 12), and long-term accumulation will alkalize the soil and pollute groundwater. Furthermore, the heavy metal toxicity and radioactivity in red mud severely restrict its comprehensive utilization in many fields. To address the serious environmental pollution caused by red mud, its harmless treatment, reduction, resource recovery, and industrialization are crucial solutions, satisfying both ecological civilization construction and ensuring a secure resource supply.

[0003] Currently, there are four technological directions for the comprehensive utilization of red mud: first, extracting valuable metals (iron, aluminum, and rare metals, etc.); second, preparing building materials (cement, bricks, roadbed materials, rock wool, etc.); third, applying it in the environmental protection field (purifiers and adsorbents for waste gas and wastewater treatment, etc.); and fourth, using it as a soil conditioner. Among these, extracting valuable metals from red mud while simultaneously preparing building materials is the best route to simultaneously achieve large-scale consumption and fully exploit its economic value.

[0004] Depending on the type of bauxite used, the resulting red mud is mainly divided into two categories: high-iron red mud (usually Fe2O3 greater than 30%) and low-iron red mud (usually Fe2O3 less than 30%). High-iron red mud is rich in iron resources and also contains high levels of aluminum, sodium, and other elements, making it a potential iron-aluminum composite mineral resource. If the iron resources are extracted, the content of remaining aluminum, sodium, and other components in the red mud will also increase, allowing for further extraction to fully exploit the valuable components and potential value of the red mud.

[0005] Currently, the main approach to iron recovery from red mud in high-speed railways is to directly perform magnetic separation on the undisturbed red mud to obtain iron concentrate. However, due to the characteristics of red mud particles being small and having low magnetic content, direct magnetic separation can lead to problems such as low iron recovery rate, low iron grade, low iron concentrate yield, large tailings discharge, and low utilization rate.

[0006] In existing eddy current mixing reduction technologies, large-scale eddy current mixing and heating equipment is expensive, requiring significant investment. Furthermore, the eddy currents are often generated using electromagnetic induction, resulting in high power consumption, high production and operating costs, and difficult equipment maintenance. Directly adjusting the composition of the molten slag to meet cement clinker requirements, while achieving the desired overall chemical composition, exceeds the optimal firing temperature for traditional clinker. This leads to coarse clinker mineral crystals, inhibiting the clinker hydration reaction process, affecting cement quality, and is also energy-intensive and economically unsound.

[0007] Furthermore, there are reports of using cupola furnaces to process red mud for molten iron smelting, adding raw materials such as aluminum ash and desulfurization gypsum to the red mud. However, this results in high sulfur content in the molten iron, affecting its quality. Additionally, the high aluminum content in the slag causes it to become sticky, which is detrimental to normal cupola smelting. Moreover, using cupola furnaces consumes large quantities of expensive coke, and since cupola furnaces are classified as phased out by the state, they have poor environmental performance. Therefore, there are still shortcomings in terms of technology, economics, and policy.

[0008] In view of the above, this application is hereby submitted. Summary of the Invention

[0009] The main objective of this invention is to provide a process for extracting iron and aluminum from high-speed iron red mud, in order to solve the problems of low iron recovery rate, low iron grade, low aluminum recovery rate, high alkali content in tailings which is not conducive to building material production and application, inability to achieve 100% resource utilization of red mud, and high production cost in the existing high-speed iron red mud recycling process.

[0010] To achieve the above objectives, according to one aspect of the present invention, a process for extracting iron and aluminum from high-iron red mud is provided, comprising the following steps: S1, mixing high-iron red mud, a reducing agent, and a compounding agent to form a mixture; wherein the mass ratio of high-iron red mud, reducing agent, and compounding agent is 100:(16~40):(25~60); the compounding agent includes lime, industrial soda ash, and fluorite, and the mass ratio of the three is (5~20):(20~60):(0~5); S2, sequentially extracting iron and aluminum from the mixture to obtain waste residue; S3, processing the waste residue into building materials to obtain a composite admixture for building materials.

[0011] Further, the process for extracting iron and aluminum using high-speed iron red mud includes the following steps: Step S1a, mixing high-speed iron red mud, reducing agent, and composite agent to form a mixture; wherein, in the mixture, the mass ratio of high-speed iron red mud, reducing agent, and composite agent is 100:(25~40):(25~55), and in the composite agent, the mass ratio of lime, industrial soda ash, and fluorite is (5~15):(25~60):(1~5). Step S2a, melting and reducing the mixture to obtain molten iron and slag; Step S2b, using a pretreatment agent to remove impurities and perform casting treatment on the molten iron to obtain pig iron and pretreatment slag, and cooling the slag through a water quenching process to obtain water-quenched slag; Step S2c, mixing the water-quenched slag with a first leaching agent and performing a first wet grinding to obtain a first aluminum-containing leaching solution and a first waste residue; Step S3a, mixing the first waste residue with the pretreatment slag and then drying and grinding to obtain a first composite admixture for building materials.

[0012] Furthermore, in step S2a, the melting reduction temperature is 1500~1650℃.

[0013] Furthermore, in step S2b, the pretreatment agent includes at least one of high-iron red mud, lime, CaC2, industrial soda ash, calcined white clay, and fluorite;

[0014] Furthermore, in step S2b, the mass ratio of the pretreatment agent to the molten iron is (0.05~3):100.

[0015] Further, in step S2c, the first leaching agent includes at least one of industrial caustic soda flakes, industrial soda ash, and sodium aluminate.

[0016] Furthermore, in step S2c, the mass ratio of the first leaching agent to the water-quenched slag is (2~15):100.

[0017] Furthermore, in step S2c, the liquid-to-solid ratio during the first wet milling process is (0.2~0.4):1.

[0018] Furthermore, in step S3a, the mass ratio of the first waste residue to the pretreated residue is 10:(1~3).

[0019] Furthermore, step S2c also includes extracting alumina from the first aluminum-containing leachate using an alumina extraction process.

[0020] Further, the process for extracting iron and aluminum using high-speed iron red mud includes the following steps: Step S1A, mixing high-speed iron red mud, reducing agent and compounding agent to form a mixture; wherein, in the mixture, the mass ratio of high-speed iron red mud, reducing agent and compounding agent is 100:(16~24):(30~60), and the compounding agent includes lime and industrial soda ash, and the mass ratio of the two is (12~20):(20~60); Step S2A, roasting and reducing the mixture first, and then performing a first magnetic separation to obtain magnetically separated iron particles and magnetically separated tailings; Step S2B, mixing the magnetically separated tailings with a second leaching agent, performing a second wet milling, and then performing a second magnetic separation to obtain magnetically separated iron concentrate and magnetically separated tailings slurry; Step S2C, performing solid-liquid separation on the magnetically separated tailings slurry to obtain a second aluminum-containing leaching solution and a second waste residue; Step S3A, mixing the second waste residue with a conditioning agent and then drying and grinding to obtain a second composite admixture for building materials.

[0021] Furthermore, in step S2A, the calcination and reduction temperature is 800~1200℃, and the calcination and reduction time is 0.5~2h.

[0022] Furthermore, in step S2A, the magnetic field strength of the first magnetic separation is 0.03~0.1T.

[0023] Furthermore, in step S2B, the second leaching agent includes at least one of industrial caustic soda flakes, industrial soda ash, and sodium aluminate.

[0024] Furthermore, in step S2B, the mass ratio of the second leaching agent to the magnetic separation tailings is (1~3):10.

[0025] Furthermore, in step S2B, the liquid-to-solid ratio during the second wet milling process is (0.2~0.5):1.

[0026] Furthermore, in step S2B, the magnetic field strength of the second magnetic separation is 0.08~0.2T.

[0027] Furthermore, in step S3A, the mass ratio of the modifier to the second waste residue is (0.5~1):1.

[0028] Furthermore, the modifier includes at least one of the following: fly ash, blast furnace slag powder, bottom slag powder, lithium slag, industrial by-product gypsum, quicklime, and cement.

[0029] Furthermore, step S2C also includes extracting alumina from the second aluminum-containing leachate using an alumina extraction process.

[0030] Furthermore, the reducing agent includes at least one of semi-coke, anthracite, lignite, coke, carbonaceous fly ash, and waste graphite electrodes.

[0031] Furthermore, the average particle size of the reducing agent is 1~10 mm.

[0032] Furthermore, the average particle size of the composite agent is 1~6mm.

[0033] Furthermore, step S1 also includes aging the mixture.

[0034] Furthermore, the aging process takes 6 to 24 hours.

[0035] Furthermore, the water content of the high-speed iron red mud is 10~30wt%, and the average particle size is ≤3mm.

[0036] Furthermore, the mixture is a spherical mixture with a particle size of 10~30mm.

[0037] Furthermore, by mass percentage, the high-iron red mud includes 54-68% Fe2O3, 2-10% SiO2, 0.2-5% CaO, 3-19% Al2O3, 1.2-8% TiO2, and 0.6-5% Na2O.

[0038] By applying the technical solution of this invention, a reducing agent and a composite agent are mixed with high-iron red mud in a specific mass ratio. The reducing agent ensures that Fe2O3 in the high-iron red mud is fully reduced to metallic iron, thereby promoting iron slag separation and improving iron recovery rate. This ensures sufficient reducing capacity while avoiding excessive use that would increase costs. The lime, industrial soda ash, and optional fluorite in the composite agent are combined in specific proportions: lime reacts with non-ferrous components in the red mud, releasing iron oxides and improving its reducing properties; soda ash promotes the conversion of aluminum into soluble sodium aluminate, and residual sodium in the red mud can also react with Al2O3 to form sodium aluminate for utilization; fluorite, as a flux, can lower the smelting temperature and improve reaction efficiency when added in small amounts. The synergistic use of the additives in the composite agent promotes a coupling effect. Excessive addition increases costs and deteriorates the chemical reaction process, while insufficient addition fails to achieve the desired reaction effect and wastes resources. This process achieves efficient aluminum recovery while significantly reducing the content of alkaline oxides in the waste residue. This not only reduces potential harm to the ecological environment but also significantly improves the performance of the waste residue as a composite admixture for building materials.

[0039] The process provided by this invention not only effectively improves the recovery rate of iron and aluminum in high-speed ferrous red mud, realizing resource recycling and reducing environmental impact, but also enhances product added value, producing composite admixtures for building materials with excellent physical and chemical properties. This achieves comprehensive resource utilization and recycling of high-speed ferrous red mud, ultimately reaching 100% resource utilization. Furthermore, by recovering waste heat from the process steps, the energy efficiency of the production process is greatly improved, production costs are reduced, and strong technical support is provided for sustainable resource management. Attached Figure Description

[0040] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0041] Figure 1 A schematic diagram of a process for extracting iron and aluminum from high-iron red mud according to some embodiments of the present invention is shown.

[0042] Figure 2 A schematic diagram of a process for extracting iron and aluminum from high-iron red mud according to other embodiments of the present invention is shown. Detailed Implementation

[0043] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0044] As analyzed in the background section of this application, existing processes for iron extraction and recovery from high-speed iron red mud suffer from problems such as low iron recovery rate, low iron grade, low aluminum recovery rate, high alkali content in tailings which is unfavorable for building material production, inability to achieve 100% resource utilization of red mud, and high production costs. To address these issues, this application provides a process for extracting iron and aluminum from high-speed iron red mud.

[0045] In a typical embodiment of this application, a process for extracting iron and aluminum using high-iron red mud is provided, comprising the following steps: S1, preparing a mixture of high-iron red mud, reducing agent, and composite agent; wherein the mass ratio of high-iron red mud, reducing agent, and composite agent is 100:(16~40):(25~60); the composite agent includes lime, industrial soda ash, and fluorite, and the mass ratio of the three is (5~20):(20~60):(0~5); S2, sequentially extracting iron and aluminum from the mixture to obtain waste residue; S3, processing the waste residue into building materials to obtain a composite admixture for building materials.

[0046] By applying the technical solution of this invention, a reducing agent and a composite agent are mixed with high-iron red mud in a specific mass ratio. The reducing agent ensures that Fe2O3 in the high-iron red mud is fully reduced to metallic iron, thereby promoting iron slag separation and improving iron recovery rate. This ensures sufficient reducing capacity while avoiding excessive use that would increase costs. The lime, industrial soda ash, and optional fluorite in the composite agent are combined in specific proportions: lime reacts with non-ferrous components in the red mud, releasing iron oxides and improving its reducing properties; soda ash promotes the conversion of aluminum into soluble sodium aluminate, and residual sodium in the red mud can also react with Al2O3 to form sodium aluminate for utilization; fluorite, as a flux, can lower the smelting temperature and improve reaction efficiency when added in small amounts. The synergistic use of the additives in the composite agent promotes a coupling effect. Excessive addition increases costs and deteriorates the reaction process, while insufficient addition fails to achieve the desired reaction effect and wastes resources. This process achieves efficient aluminum recovery while significantly reducing the content of alkaline oxides in the waste residue. This not only reduces potential harm to the ecological environment but also significantly improves the performance of the waste residue as a composite admixture for building materials.

[0047] The process method provided in this application not only effectively improves the recovery rate of iron and aluminum in high-speed iron red mud, realizing resource recycling and reducing environmental impact, but also enhances the added value of products, producing composite admixtures for building materials with excellent performance. This achieves comprehensive resource utilization and recycling of high-speed iron red mud, ultimately reaching the goal of 100% resource utilization. Furthermore, by recovering waste heat from the process steps, the energy efficiency of the production process is greatly improved, production costs are reduced, and strong technical support is provided for sustainable resource management.

[0048] In some embodiments, such as Figure 1 As shown, the extraction of iron and aluminum from high-speed iron red mud and the preparation of the first composite admixture for building materials can be achieved through the following steps: Step S1a, mixing high-speed iron red mud, reducing agent and composite agent to form a mixture; in the mixture, the mass ratio of high-speed iron red mud, reducing agent and composite agent is 100:(25~40):(25~55), and in the composite agent, the mass ratio of lime, industrial soda ash and fluorite is (5~15):(25~60):(1~5); Step S2a, melting and reducing the mixture to obtain molten iron and slag; Step S2b, using a pretreatment agent to remove impurities from the molten iron and casting treatment to obtain pig iron and pretreated slag; cooling the slag through a water quenching process to obtain water-quenched slag; Step S2c, mixing the water-quenched slag with a first leaching agent and performing a first wet grinding to obtain a first aluminum-containing leaching solution and a first waste residue; Step S3a, mixing the first waste residue with the pretreated slag and then drying and grinding to obtain the first composite admixture for building materials.

[0049] By directly immersing the mixture in the molten pool of the smelting furnace for high-temperature melting, the aforementioned proportion range ensures that the iron element in the high-iron red mud can be further and fully reduced, while avoiding increased energy consumption and costs caused by excessive addition of reducing agents. After processes such as heating, decomposition, sintering, solid-phase pre-reduction, semi-solid-phase reduction, and liquid-phase deep reduction, the mixture melts into a molten state, forming molten iron and slag. Due to its density, the molten iron settles and accumulates at the bottom of the furnace, while oxides of elements such as Si and Al float on the surface of the molten iron as slag, forming a slag layer. The aforementioned composite agent includes lime, industrial soda ash, and fluorite. Lime provides CaO as a flux, and fluorite (CaF2) acts as a fluxing agent. The combined use of these two agents results in a more efficient coupling effect, effectively reducing the smelting temperature of red mud reduction and the slag melting temperature, promoting phase transformation and enhancing the reducibility of the metal during the molten reduction process. Industrial soda ash (Na2CO3) helps react with Al2O3 in the red mud to form sodium aluminate. Fluorite (CaF2) helps reduce the viscosity of the molten slag, improving the separation of slag and molten iron, thereby promoting the separation of molten iron and increasing iron recovery. When the ratio of the three is controlled at (5~15):(25~60):(1~5), the fluidity of the molten slag is optimized, while promoting the separation of the molten slag from the molten iron, thus increasing the iron recovery rate. High-temperature smelting further promotes the reaction of sodium with Al2O3 to form sodium aluminate.

[0050] Subsequently, a pretreatment agent is added to the molten iron to remove some harmful elements such as Si, S, and P, bringing the molten iron to the required composition for steelmaking pig iron, foundry pig iron, or weighting pig iron. The quenched slag obtained by water quenching is mixed with the first leaching agent and subjected to a first wet milling process to further promote the leaching of soluble sodium aluminate, thereby increasing the aluminum recovery rate and the removal rate of residual sodium from the red mud. Sodium aluminate is leached into an aqueous solution to form the first aluminum-containing leachate, with the remaining material existing in the solid phase as the first waste residue. The content of alkaline oxides in the first waste residue is reduced. This waste residue is then mixed with the pretreated slag and placed in a drying mill, where it is dried and ground under the waste heat of flue gas, ultimately yielding the first composite admixture. The specific surface area of ​​this first composite admixture is not less than 400 m². 2 / kg, with an activity of not less than 80% after 28 days.

[0051] The above method enables the recovery of iron from high-speed iron red mud in the form of molten iron and aluminum in the form of sodium aluminate, thereby improving the recovery rates of iron and aluminum and the removal rate of sodium. Furthermore, the first waste residue and pretreated slag are combined to prepare the first composite admixture for building materials, achieving comprehensive resource utilization and recycling of high-speed iron red mud, and reaching the goal of 100% resource utilization of high-speed iron red mud.

[0052] To further promote iron reduction, the preferred temperature for molten reduction in step S2a is 1500~1650℃. The heating method during molten reduction is not limited; various heating methods such as pulverized coal heating, electric heating, and natural gas heating can be used. To further ensure sufficient iron reduction, the atmosphere on the surface of the molten pool is controlled to be a reducing atmosphere, preferably CO, with a CO concentration of not less than 20%, to ensure that the mixture is protected from oxidation and has sufficient reducing gas when it is added to the surface of the molten pool.

[0053] In order to further promote the adsorption and removal of harmful impurity elements such as Si, S, and P in molten iron, and thus further improve the quality of iron, the pretreatment agent in step S2b preferably includes any one or more of high-iron red mud, lime, CaC2, industrial soda ash, calcined white metal and fluorite.

[0054] In some embodiments, in step S2b, the mass ratio of the pretreatment agent to the molten iron is (0.05~3):100; the control of the amount of pretreatment agent added ensures that the reaction proceeds appropriately, effectively removing impurities while avoiding excessive consumption of the pretreatment agent and heat loss to the molten iron.

[0055] To further improve the leaching rate of sodium aluminate and thus further improve the aluminum recovery rate, in preferred step S2c, the first leaching agent includes any one or more of industrial caustic soda flakes, industrial soda ash, and sodium aluminate.

[0056] In some embodiments, in step S2c, the mass ratio of the first leaching agent to the water-quenched slag is (2~15):100; adding an appropriate leaching agent can ensure the effective leaching of sodium aluminate and improve the recovery rate. When the amount of the first leaching agent is too low, it cannot sufficiently promote the leaching of sodium aluminate, resulting in incomplete aluminum recovery; while when the amount of the first leaching agent is too high, it will increase the cost.

[0057] In some embodiments, in step S2c, the liquid-to-solid ratio during the first wet milling process is (0.2~0.4):1. An appropriate liquid-to-solid ratio ensures good dispersion of solid particles in the liquid, reducing particle adhesion and agglomeration, thereby improving wet milling efficiency. At the above liquid-to-solid ratio, the liquid can fully surround the solid particles, facilitating effective crushing and refining of the water-quenched slag, thereby increasing the contact area between the water-quenched slag and the leaching agent, further promoting the leaching of sodium aluminate and improving the aluminum recovery rate. Preferably, the water-quenched slag is thoroughly wet-milled to below 200 mesh (0.074 μm) to further improve the leaching rate of sodium aluminate.

[0058] In some embodiments, step S2c further includes using an alumina extraction process to extract alumina from the first aluminum-containing leachate, so as to convert aluminum into high-purity alumina (Al2O3), thereby realizing the recovery of valuable resources from waste and improving the comprehensive utilization rate of resources.

[0059] In some embodiments, in step S3a, the mass ratio of the first waste residue to the pretreated residue is 10:(1-3). By controlling the mass ratio of the two, not only can the various components in the first building material composite admixture be balanced and the building material performance improved, but also resource waste can be avoided and the maximum utilization of resources can be achieved.

[0060] To further improve energy efficiency, achieve energy conservation and emission reduction, and further reduce heating energy consumption and enhance overall economic benefits, the hot flue gas generated during high-temperature smelting is preferentially used for waste heat power generation, producing electricity and steam. The electricity is used within the plant, while the steam can be sent to the alumina extraction process. The flue gas temperature after power generation is 300~350℃, which can be used for equipment in processes such as drying and crushing, drying and grinding, air preheating, and steam curing.

[0061] In other embodiments, such as Figure 2 As shown, the extraction of iron and aluminum from high-speed iron red mud and the preparation of a second composite admixture for building materials can be achieved through the following steps: Step S1A, mixing high-speed iron red mud, reducing agent and composite agent to form a mixture; in the mixture, the mass ratio of high-speed iron red mud, reducing agent and composite agent is 100:(16~24):(30~60), the composite agent includes lime and industrial soda ash, and the mass ratio of the two is (12~20):(20~60); Step S2A, roasting and reducing the mixture first, and then performing a first magnetic separation to obtain magnetically separated iron particles and magnetic separation tailings; Step S2B, mixing the magnetic separation tailings with a second leaching agent, performing a second wet milling, and then performing a second magnetic separation to obtain magnetically separated iron concentrate and magnetic separation tailings slurry; Step S2C, performing solid-liquid separation on the magnetic separation tailings slurry to obtain a second aluminum-containing leaching solution and a second waste residue; Step S3A, mixing the second waste residue with a conditioning agent and then drying and grinding to obtain the second composite admixture for building materials.

[0062] In another process for extracting iron and aluminum from high-iron red mud provided in this application, the amounts of each component of the mixture and each component of the composite agent in step S1A are limited to the above-mentioned ranges. This is to better facilitate the reduction of iron oxides and the phase transformation of aluminum during the roasting and reduction process of the mixture in step S2A, forming magnetically recoverable metallic iron or magnetic iron, and soluble sodium aluminate phase, thereby achieving the simultaneous recovery of iron and aluminum elements. In the composite agent, lime and industrial soda ash are used in combination. Lime adjusts the alkalinity of the reaction system, promoting the reduction and magnetization process of iron elements. Simultaneously, lime and soda ash synergistically form a composite alkali effect, reducing the amount of expensive soda ash used and lowering costs. During roasting, industrial soda ash reacts with Al2O3 in the high-iron red mud to generate soluble sodium aluminate. Through the synergistic effect of the specific mass ratio of lime and industrial soda ash, the recovery rate of iron and aluminum elements is improved. At the same time, it avoids the adverse effects of excessive alkalinity on the subsequent application of waste residue in building materials.

[0063] The amount of reducing agent is related to the reduction performance. Too little reducing agent will lead to incomplete reduction of iron oxides, while too much will result in unnecessary energy consumption and raw material waste. At the above-mentioned ratio of high-iron red mud to reducing agent, the reducing agent can more effectively reduce iron oxides (such as Fe2O3) in the high-iron red mud to metallic iron or magnetic iron, which is more conducive to improving the reduction efficiency and avoiding side reactions caused by excessive reducing agent. Subsequently, the high-grade magnetic iron particles are effectively separated by the first magnetic separation to obtain magnetically separated granular iron, and the remaining material is retained in the magnetic separation tailings.

[0064] Correspondingly, the iron content in the magnetic separation tailings decreases, leading to aluminum enrichment. The tailings also contain soluble sodium aluminate. In step S2B, the magnetic separation tailings are mixed with a second leaching agent and subjected to a second wet milling to further promote the leaching of sodium aluminate into the aqueous solution. A second magnetic separation is then performed to further separate the magnetically charged iron particles, further improving the iron recovery rate and obtaining magnetically separated iron concentrate. In step S2C, the magnetic separation tailings slurry undergoes solid-liquid separation to obtain a second aluminum-containing leaching solution containing sodium aluminate. SiO2 and CaO mainly remain in the second waste residue. The second waste residue also contains small amounts of residual Al2O3, Fe2O3, Na2O, and glassy phases with potential hydration activity. The second waste residue is weakly alkaline. In step S3A, after mixing the second waste residue with the modifier, the release of the active ingredients of the second waste residue and the modifier can be promoted, thereby achieving the activation effect and producing an active second building material composite admixture. The strength and performance of the building material products made from it are further increased, which can effectively reduce the cost of building materials.

[0065] The above method involves mixing high-iron red mud, a reducing agent, and a composite agent in a specific ratio. Through calcination and reduction, the iron oxides in the high-iron red mud are reduced, and the aluminum phase transforms, forming magnetically recoverable metallic iron or magnetic iron, as well as soluble sodium aluminate. This achieves simultaneous recovery of iron and aluminum elements, and subsequent steps further improve the recovery rates of both. The activation effect of the second waste residue and the modifier further enhances the strength and performance of the composite admixture used in the second building material, realizing the comprehensive resource utilization and recycling of high-iron red mud, achieving 100% resource utilization.

[0066] In some embodiments, the calcination reduction temperature is 800~1200℃, and the calcination reduction time is 0.5~2h. Limiting the calcination reduction temperature and time within the above range further improves the reduction efficiency of iron oxides. If the calcination reduction temperature is too high or the time is too long, it will significantly increase energy consumption, raise production costs, or lead to excessive reaction and the generation of byproducts; if the calcination reduction temperature is too low or the time is too short, it will be detrimental to the formation and separation of magnetic iron-containing particles and the formation of sodium aluminate phase by aluminum elements, thereby reducing the recovery rate of iron and aluminum.

[0067] To more effectively separate magnetically separated iron particles, the magnetic field strength of the first magnetic separation is preferably 0.03~0.1T.

[0068] In some embodiments, in step S2B, the second leaching agent includes any one or more of industrial caustic soda flakes, industrial soda ash, and sodium aluminate; and / or, in step S2B, the mass ratio of the second leaching agent to the magnetic separation tailings is (1~3):10. The composition and dosage of the second leaching agent are limited to better improve the leaching rate of sodium aluminate, thereby further improving the aluminum recovery rate, while avoiding waste caused by excessive use of the leaching agent.

[0069] In order to more effectively separate and recover the remaining magnetic iron-containing particles and further improve the total amount and grade of iron concentrate, the magnetic field strength of the second magnetic separation in step S2B is preferably 0.08~0.2T.

[0070] To improve the wet grinding efficiency of magnetic separation tailings and ensure more thorough contact between the tailings and the second leaching agent, thereby increasing the leaching rate of sodium aluminate and further improving aluminum recovery, a liquid-to-solid ratio of 0.2–0.5:1 is preferred during the second wet grinding process. To further enhance the leaching rate of sodium aluminate, the slurry obtained after the second wet grinding is preferably stirred and heated, with a preferred heating temperature of 60–90°C and a heating time of 1–2 hours, allowing for further leaching of sodium aluminate under stirring and heating conditions. This is followed by a second magnetic separation to improve the grade of the iron concentrate.

[0071] In some embodiments, step S2C further includes extracting alumina from the second aluminum-containing leachate using an alumina extraction process to convert aluminum into high-purity alumina (Al2O3), thereby recovering valuable resources from waste and improving the overall utilization rate of resources. To avoid resource waste, it is preferable that the alkaline solution or alkaline material produced in the alumina extraction process can be reused in this process as an alkaline leaching agent or related additive.

[0072] In some embodiments, in step S3A, the mass ratio of the modifier to the second waste residue is (0.5~1):1; and / or, the modifier includes any one or more of the following: fly ash, blast furnace slag powder, bottom slag powder, lithium slag, industrial by-product gypsum (including desulfurization gypsum, phosphogypsum, fluorogypsum, titanium gypsum, etc., whose main component is calcium sulfate dihydrate), quicklime, and cement. By limiting the composition and dosage of the modifier, it is more beneficial to improve the hydration and cementitious properties of the composite admixture, thereby further increasing the strength and performance of the building materials.

[0073] In some embodiments, the hot flue gas generated during the roasting process and the hot air generated during the cooling of hot materials are returned to the process for reuse, thereby more effectively improving thermal efficiency and reducing overall energy consumption. Simultaneously, the alkaline filtrate and sodium alkali produced during the aluminum extraction process can also be returned to this high-iron red mud treatment process for continued use, achieving maximum recycling of alkaline substances.

[0074] To further promote the reduction of iron, the preferred reducing agents include any one or more of semi-coke, anthracite, lignite, coke, carbonaceous fly ash, and waste graphite electrodes.

[0075] To further promote the uniform mixing of the reducing agent and the high-iron red mud, and thus further improve the iron reduction effect and recovery rate, the average particle size of the reducing agent is preferably 1~10mm.

[0076] To further promote the uniform mixing of the composite agent and the high-iron red mud, and thus further improve the recovery rate of iron and aluminum, the average particle size of the composite agent is preferably 1~6mm.

[0077] To further improve the strength of the mixture, facilitate material transportation and in-furnace feeding, and reduce the breakage rate during transfer and the dust rate during feeding, step S1 preferably includes aging the mixture for 6 to 24 hours.

[0078] In some embodiments, the water content of the high-iron red mud is 10~30wt%, and the average particle size is ≤3mm. Controlling the water content between 10~30wt% can reduce the energy consumption of subsequent red mud smelting and ensure that the red mud has a certain degree of plasticity, which is convenient for subsequent mixing and briquetting. The average particle size of ≤3mm can further increase the dispersibility of the high-iron red mud and improve the uniformity of subsequent mixing.

[0079] To facilitate transportation and storage, and to ensure the stability of the mixture in the molten pool, the mixture is preferably spherical, with a particle size of 10~30mm.

[0080] In some embodiments, the high-iron red mud, by mass percentage, comprises 54-68% Fe2O3, 2-10% SiO2, 0.2-5% CaO, 3-19% Al2O3, 1.2-8% TiO2, 0.6-5% Na2O, and other components.

[0081] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0082] Example 1

[0083] This embodiment provides a process for extracting iron and aluminum from high-iron red mud, including the following steps:

[0084] By mass percentage, high-iron red mud comprises 60% Fe2O3, 3% Na2O, 5% SiO2, 19% Al2O3, 1% CaO, 6% TiO2, and other components. After drying and crushing to reduce the moisture content to 10% and the particle size to no more than 5mm, 35wt% anthracite (particle size 2-8mm) and 40wt% composite agent (lime: industrial soda ash: fluorite = 8:50:3, particle size 2-5mm) are mixed and stirred evenly, then pressed into 20mm pellets. After aging for 8 hours, the pellets are fed into a smelting furnace at 1550℃. After smelting and reduction, molten iron and slag are produced. Molten iron is poured into a ladle containing a pretreatment agent (1% of the molten iron weight, in a mass ratio of dry red mud: lime: calcined white clay = 30:50:20). Under the action of the pretreatment agent, impurities are removed, resulting in pretreated molten iron and pretreated slag. The pretreated molten iron is then cast into qualified pig iron. The slag is rapidly cooled by water spraying and then directly fed into a wet mill for wet grinding. The liquid-to-solid ratio in the wet mill is 0.3, and a first leaching agent (in a mass ratio of industrial caustic soda: industrial soda ash = 3:2) is added. The mass ratio of the first leaching agent to the water-quenched slag is 5:100. After approximately 30 minutes of wet grinding, the wet grinding slurry is discharged for washing and filtration, yielding a first aluminum-containing leaching solution and a first waste residue, to fully recover the aqueous solution and soluble sodium aluminate components. The first waste residue and the pretreated slag are mixed and ground at a mass ratio of 10:2, and then dried and ground under residual heat flue gas to a specific surface area of ​​approximately 400 m². 2 The first composite admixture product for building materials can be obtained after processing / kg.

[0085] Example 2

[0086] The difference from Example 1 is that in Example 2, the mass ratio of high-iron red mud, reducing agent and compound agent is 100:25:55.

[0087] Example 3

[0088] The difference from Example 1 is that the mass ratio of high-iron red mud, reducing agent and compound agent in Example 3 is 100:40:25.

[0089] Example 4

[0090] The difference from Example 1 is that the mass ratio of lime, industrial soda ash and fluorite in the composite agent of Example 4 is 5:60:1.

[0091] Example 5

[0092] The difference from Example 1 is that the mass ratio of lime, industrial soda ash and fluorite in the composite agent of Example 5 is 15:25:5.

[0093] Example 6

[0094] The difference from Example 1 is that the melting reduction temperature in Example 6 is 1500°C.

[0095] Example 7

[0096] The difference from Example 1 is that the melting reduction temperature in Example 7 is 1650°C.

[0097] Example 8

[0098] The difference from Example 1 is that in Example 8, the mass ratio of the pretreatment agent to the molten iron is 0.05:100.

[0099] Example 9

[0100] The difference from Example 1 is that in Example 9, the mass ratio of the pretreatment agent to the molten iron is 3:100.

[0101] Example 10

[0102] The difference from Example 1 is that in Example 10, the mass ratio of the first leaching agent to the water-quenched slag is 2:100.

[0103] Example 11

[0104] The difference from Example 1 is that in Example 11, the mass ratio of the first leaching agent to the water-quenched slag is 15:100.

[0105] Example 12

[0106] The difference from Example 1 is that in Example 12, the mass ratio of the first waste residue to the pretreated residue is 10:1.

[0107] Example 13

[0108] The difference from Example 1 is that in Example 13, the mass ratio of the first waste residue to the pretreated residue is 10:3.

[0109] Example 14

[0110] The difference from Example 1 is that the melting reduction temperature in Example 14 is 1400°C.

[0111] Example 15

[0112] The difference from Example 1 is that in Example 15, the mass ratio of the first leaching agent to the water-quenched slag is 0.5:100.

[0113] Example 16

[0114] The difference from Example 1 is that in Example 16, the mass ratio of the first waste residue to the pretreated residue is 10:0.5.

[0115] Example 17

[0116] The difference from Example 1 is that in Example 17, the mass ratio of the first waste residue to the pretreated residue is 10:4.

[0117] Comparative Example 1

[0118] The difference from Example 1 is that the mass ratio of high-iron red mud, reducing agent and compound agent in Comparative Example 1 is 100:10:70.

[0119] Comparative Example 2

[0120] The difference from Example 1 is that the mass ratio of lime, industrial soda ash and fluorite in the composite agent of Comparative Example 2 is 1:70:10.

[0121] Comparative Example 3

[0122] The difference from Example 1 is that the mass ratio of lime, industrial soda ash and fluorite in the composite agent of Comparative Example 3 is 20: 10: 3.

[0123] Test Example 1

[0124] The Fe recovery rate, Fe mass content in the pretreated molten iron, Al recovery rate, Na removal rate, and 28-day activity of the first building material composite admixture in Examples 1-17 and Comparative Examples 1-3 were tested. The results are shown in Table 1.

[0125] Wherein, Fe recovery rate = (Iron content in pig iron / Iron content in high-iron red mud) × 100%;

[0126] Al recovery rate = (1 - aluminum content in waste residue / aluminum content in high-iron red mud) × 100%;

[0127] Sodium removal rate = (1 - sodium content in waste residue / sodium content in ferrous red mud) × 100%;

[0128] Activity index test: The test was conducted in accordance with "JG / T 486-2015 Composite admixtures for concrete".

[0129] Table 1

[0130]

[0131] Example 18

[0132] This embodiment provides another process for extracting iron and aluminum from high-iron red mud, including the following steps:

[0133] The high-iron red mud, by mass percentage, comprises 60% Fe2O3, 3% Na2O, 5% SiO2, 19% Al2O3, 1% CaO, 6% TiO2, and other components. This high-iron red mud is weighed and mixed evenly with anthracite (3-6 mm particle size) and a composite agent (2-5 mm particle size) at a mass ratio of 100:20:45. The mixture is then pressed into 10 mm pellets. The composite agent includes lime and industrial soda ash at a mass ratio of 18:35. After 16 hours of aging, the mixture is sent to a roasting furnace, slowly heated to 1100℃, held at that temperature for about 1 hour, and then directly discharged into a cooler for rapid cooling to approximately 50℃ upon contact with cold air. The resulting roasted clinker is crushed and sieved, and then magnetically separated under a magnetic field strength of approximately 0.08T to remove impurities of metallic iron particles. The magnetic separation tailings are then fed into a wet mill with a liquid-to-solid ratio of 4:10. A second leaching agent (in the second leaching agent, the mass ratio of industrial caustic soda to soda ash is 2:3) is added at a mass ratio of 1.5:10 to the magnetic separation tailings before wet milling. After wet milling, the slurry is fed into a mixer and heated to 80°C with hot steam for approximately 1 hour of hot leaching. After hot leaching, the slurry is fed into a wet magnetic separator with a magnetic separation intensity of 0.1T to obtain magnetically separated iron concentrate. The magnetic separation tailings slurry is then filtered to obtain a second waste residue and a second alumina-containing leachate. The second alumina-containing leachate is sent to an alumina extraction process to recover alumina. A modifier (composed of blast furnace slag powder, fly ash, and cement) is mixed with the second waste residue at a mass ratio of 0.7:1, then dried and ground to obtain a second composite admixture for building materials.

[0134] Example 19

[0135] The difference from Example 18 is that in Example 19, the mass ratio of high-iron red mud, reducing agent and compound agent is 100:16:60.

[0136] Example 20

[0137] The difference from Example 18 is that in Example 20, the mass ratio of high-iron red mud, reducing agent and composite agent is 100:24:30.

[0138] Example 21

[0139] The difference from Example 18 is that in Example 21, the mass ratio of lime to industrial soda ash in the composite agent is 12:60.

[0140] Example 22

[0141] The difference from Example 18 is that in Example 22, the mass ratio of lime to industrial soda ash in the composite agent is 20:20.

[0142] Example 23

[0143] The difference from Example 18 is that the calcination and reduction temperature in Example 23 is 800°C and the calcination and reduction time is 2 hours.

[0144] Example 24

[0145] The difference from Example 18 is that the calcination and reduction temperature in Example 24 is 1200°C and the calcination and reduction time is 0.5h.

[0146] Example 25

[0147] The difference from Example 18 is that in Example 25, the mass ratio of the second leaching agent to the magnetic separation tailings is 1:10.

[0148] Example 26

[0149] The difference from Example 18 is that in Example 26, the mass ratio of the second leaching agent to the magnetic separation tailings is 3:10.

[0150] Example 27

[0151] The difference from Example 18 is that the magnetic field strength of the first magnetic separation in Example 27 is 0.03T, and the magnetic field strength of the second magnetic separation is 0.08T.

[0152] Example 28

[0153] The difference from Example 18 is that the magnetic field strength of the first magnetic separation in Example 28 is 0.1T, and the magnetic field strength of the second magnetic separation is 0.2T.

[0154] Example 29

[0155] The difference from Example 18 is that in Example 29, the mass ratio of the modifier to the second waste residue is 0.5:1.

[0156] Example 30

[0157] The difference from Example 18 is that in Example 30, the mass ratio of the modifier to the second waste residue is 1:1.

[0158] Example 31

[0159] The difference from Example 18 is that the calcination and reduction temperature in Example 31 is 600°C.

[0160] Example 32

[0161] The difference from Example 18 is that in Example 32, the mass ratio of the second leaching agent to the magnetic separation tailings is 0.5:10.

[0162] Example 33

[0163] The difference from Example 18 is that the magnetic field strength of the second magnetic separation in Example 33 is 0.04T.

[0164] Example 34

[0165] The difference from Example 18 is that the magnetic field strength of the second magnetic separation in Example 34 is 0.4T.

[0166] Example 35

[0167] The difference from Example 18 is that in Example 35, the mass ratio of the modifier to the second waste residue is 0.2:1.

[0168] Comparative Example 4

[0169] The difference from Example 18 is that the mass ratio of high-iron red mud, reducing agent and composite agent in Comparative Example 4 is 100:12:65.

[0170] Comparative Example 5

[0171] The difference from Example 18 is that the mass ratio of high-iron red mud, reducing agent and compound agent in Comparative Example 5 is 100:35:25.

[0172] Comparative Example 6

[0173] The difference from Example 18 is that the mass ratio of lime to industrial soda ash in the composite agent of Comparative Example 6 is 25:10.

[0174] Comparative Example 7

[0175] The difference from Example 18 is that the mass ratio of lime to industrial soda ash in the composite agent of Comparative Example 7 is 10:70.

[0176] Comparative Example 8

[0177] The difference from Example 18 is that the composite agent in Comparative Example 8 contains only lime.

[0178] Test Example 2

[0179] The results of testing Examples 18-35, Comparative Examples 4-8, and the Fe recovery rate, iron concentrate quality, Al recovery rate, Na removal rate, and 28-day activity index of the second building material composite admixture in high-iron red mud are shown in Table 2.

[0180] Wherein, Fe recovery rate = (iron content in (granular iron + iron concentrate) / iron content in high-iron red mud) × 100%;

[0181] Al recovery rate = (1 - aluminum content in waste residue / aluminum content in high-iron red mud) × 100%;

[0182] Sodium removal rate = (1 - sodium content in waste residue / sodium content in ferrous red mud) × 100%;

[0183] Iron concentrate grade = mass percentage of Fe in iron concentrate;

[0184] Activity index test: The test was conducted in accordance with "JG / T 486-2015 Composite admixtures for concrete".

[0185] Table 2

[0186]

[0187] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0188] The process method provided in this application not only effectively improves the recovery rate of iron and aluminum in high-speed iron ore red mud, realizing resource recycling and reducing environmental impact, but also enhances product added value, producing composite admixtures for building materials with excellent physical and chemical properties. This achieves comprehensive resource utilization and recycling of high-speed iron ore red mud, ultimately reaching the goal of 100% resource utilization. Furthermore, by recovering waste heat from the process steps, the energy efficiency of the production process is greatly improved, production costs are reduced, and strong technical support is provided for sustainable resource management.

[0189] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for extracting iron and aluminum from high-iron red mud, characterized in that, The process for extracting iron and aluminum using high-iron red mud includes the following steps: Step S1a: High-iron red mud, reducing agent, and composite agent are mixed to form a mixture; wherein, in the mixture, the mass ratio of the high-iron red mud, the reducing agent, and the composite agent is 100:(25~40):(25~55), the composite agent includes lime, industrial soda ash, and fluorite, and the mass ratio of the three is (5~15):(25~60):(1~5); the reducing agent includes at least one of semi-coke, anthracite, lignite, coke, carbonaceous fly ash, and waste graphite electrodes; Step S2a: The mixture is melted and reduced to obtain molten iron and slag; Step S2b: The molten iron is treated with a pretreatment agent to remove impurities and undergo casting treatment to obtain pig iron and pretreated slag; The slag is cooled by a water quenching process to obtain water-quenched slag; Step S2c: The water-quenched slag is mixed with a first leaching agent and subjected to a first wet grinding to obtain a first aluminum-containing leaching solution and a first waste residue; In step S2b, the mass ratio of the pretreatment agent to the molten iron is (0.05~3):100, and the pretreatment agent includes at least one of high-iron red mud, lime, CaC2, industrial soda ash, calcined white metal and fluorite; in step S2c, the first leaching agent includes at least one of industrial caustic soda flakes, industrial soda ash and sodium aluminate. Step S3a: After mixing the first waste residue with the pretreated residue, dry and grind them to obtain the first composite admixture for building materials; wherein the mass ratio of the first waste residue to the pretreated residue is 10:(1~3).

2. The process for extracting iron and aluminum from high-iron red mud according to claim 1, characterized in that, In step S2a, the melting and reduction temperature is 1500~1650℃; And / or, in step S2c, the mass ratio of the first leaching agent to the water-quenched slag is (2~15):100; And / or, in step S2c, the liquid-to-solid ratio during the first wet milling process is (0.2~0.4):

1.

3. The process for extracting iron and aluminum from high-iron red mud according to claim 1, characterized in that, Step S2c further includes extracting alumina from the first aluminum-containing leachate using an alumina extraction process.

4. The process for extracting iron and aluminum from high-iron red mud according to any one of claims 1 to 3, characterized in that, The average particle size of the reducing agent is 1~10 mm; And / or, the average particle size of the composite agent is 1~6 mm.

5. The process for extracting iron and aluminum from high-iron red mud according to any one of claims 1 to 3, characterized in that, Step S1 further includes aging the mixture for 6 to 24 hours.

6. The process for extracting iron and aluminum from high-iron red mud according to any one of claims 1 to 3, characterized in that, The high-speed iron red mud has a water content of 10~30wt% and an average particle size of ≤3mm; And / or, the mixture is a spherical mixture, and the particle size of the spherical mixture is 10~30mm; And / or, by mass percentage, the high-iron red mud comprises 54-68% Fe2O3, 2-10% SiO2, 0.2-5% CaO, 3-19% Al2O3, 1.2-8% TiO2, and 0.6-5% Na2O.

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