Method for preparing low-grade concentrate from Bayer process red mud

Abstract

The invention belongs to the technical field of Bayer process red mud treatment, and discloses a method for preparing low-grade iron ore concentrate from Bayer process red mud, which comprises the following steps: mixing the Bayer process red mud with a dissolution accelerator to obtain a first mixed material, and controlling the mixing ratio of the Bayer process red mud to the dissolution accelerator to be 100: (0.1-20); adding an alkaline excitation liquid into the first mixed material for reaction, and performing solid-liquid separation to obtain an aluminum-containing solution and an iron-rich solid phase; carrying out calcification treatment on the aluminum-containing solution, carrying out solid-liquid separation treatment to obtain aluminum-containing solid slag and purified liquid, returning the aluminum-containing solid slag to a Bayer process to produce aluminum oxide, and circularly returning the purified liquid to an alkaline excitation liquid blending process as supplement; and drying the iron-rich solid phase to obtain the low-grade iron ore concentrate. By adopting the method disclosed by the invention, the aluminum and iron elements in the red mud can be extracted and utilized in a gradient manner, and the total utilization of the iron resource and the deep extraction of the aluminum resource in the red mud are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of Bayer process red mud treatment, and particularly relates to a method for preparing low-grade concentrate from Bayer process red mud. Background Art

[0002] my country is a major steel industry country, with steel production accounting for more than 50% of the world's total. However, in the entire industrial chain, iron ore raw materials are extremely dependent on overseas imports. In 2023, my country imported more than 1.1 billion tons of iron ore and its concentrate, and resource security is insufficient. At the same time, my country is also a major aluminum industry country, and the raw material for producing alumina is bauxite. In 2023, my country imported nearly 100 million tons of Guinean bauxite. The Al2O3 content in Guinean bauxite is usually more than 45%, the Fe2O3 content is about 20-30%, and the SiO2 content is about 1-2.5%. At present, in the process of using the low-temperature Bayer process to treat Guinean bauxite to produce alumina, Al2O3 is partially extracted as a valuable resource (the alumina extraction rate is about 80%), and the unextracted Al2O3 and a large amount of Fe2O3 are abandoned in red mud and cannot be effectively utilized, which not only pollutes the environment and occupies land, but also is a great waste of precious aluminum and iron resources. If the aluminum- and iron-containing substances in Guinea's bauxite can be efficiently utilized, it will not only reduce the harm caused by the storage of red mud in my country's alumina industry, but also greatly reduce the import costs of iron ore and its concentrates for China's steel industry, and ensure the security of my country's strategic mineral resources. The patent (CN117144078A) provides a system and method for extracting iron from red mud by pyrolysis of biomass. The method uses biomass pyrolysis gas as a reducing agent to reduce the iron oxide in the red mud, and then magnetic separation is used to obtain ferromagnetic materials. This method essentially uses carbon thermal reduction to reduce and extract iron from red mud, which is a disposal of the discharged red mud, which adds an additional disposal process, and the process produces a large amount of carbon dioxide. Patent (CN112827644A) provides a comprehensive utilization method for red mud to extract iron and reduce aluminum. The method is to separate the mud and sand to obtain strong magnetic concentrate and strong magnetic tailings after the red mud is subjected to strong magnetic separation treatment. The strong magnetic concentrate is roasted, cooled and quenched in a weak reducing atmosphere using a multi-stage dynamic magnetization roasting furnace, and then demagnetized and sorted to obtain weak magnetic concentrate and weak magnetic tailings. The weak magnetic concentrate is concentrated and filtered, and bentonite is added as a binder to form balls, thereby realizing the reduced utilization of red mud. However, this method has the following disadvantages: ① Most of the iron-containing substances in the red mud are hematite, which is difficult to be pre-separated by strong magnetic separation treatment; ② The process is long after multiple magnetic separation, demagnetization, roasting, quenching and filter pressing steps; ③ The weak magnetic powder produced still contains a large amount of iron-containing substances, resulting in a waste of iron resources. Patent (CN109250737B) provides a method for extracting aluminum from red mud by the Bayer process. This method is to mix Bayer red mud with alkali solution and limestone for dissolution reaction, and then dilute the red mud dissolution slurry and separate it by sedimentation to obtain dealuminated red mud and sodium aluminate dissolution solution. This method utilizes the alumina in Bayer red mud and reduces the discharge of red mud. However, this method does not recycle a large amount of iron in the red mud. The red mud is still treated by stockpiling. At the same time, the red mud is treated with alkali solution, which further increases the alkali content in the red mud, making subsequent resource utilization more difficult. Summary of the invention

[0003] (I) Purpose of the invention

[0004] The purpose of the present invention is to provide a method for preparing low-grade concentrate from Bayer red mud. The method introduces a dissolution promoter to induce the Bayer red mud to transform into a new phase structure, and finally dissociates and dissolves to obtain an aluminum-containing solution and an iron-rich solid phase, thereby solving the problems of additional processing procedures and carbon dioxide emissions in the current carbon thermal reduction of red mud to extract iron, and realizes the full utilization of iron resources in red mud and the deep extraction of aluminum resources.

[0005] (II) Technical solution

[0006] To solve the above problems, the present invention provides a method for preparing low-grade iron ore concentrate from Bayer red mud, comprising the following steps:

[0007] S1, mixing the Bayer process red mud with the dissolution promoter to obtain a first mixed material, wherein the mixing mass ratio of the Bayer process red mud to the dissolution promoter is 100:(0.1-20);

[0008] S2, adding an alkaline stimulating liquid to the first mixed material for reaction, and obtaining an aluminum-containing solution and an iron-rich solid phase after solid-liquid separation;

[0009] S3, calcifying and solid-liquid separation treatment is performed on the aluminum-containing solution to obtain aluminum-containing solid slag and purified liquid for recycling; and low-grade iron concentrate is obtained by drying the iron-rich solid phase.

[0010] Furthermore, the liquid-to-solid ratio of the alkaline stimulating liquid to the first mixed material is (1.5-10):1.

[0011] Furthermore, the dissolution promoter is a composite compound containing aluminum, calcium and iron elements.

[0012] Furthermore, the mass ratio of aluminum, calcium and iron in the dissolution accelerator, calculated as oxides, is (1-10): (15-40): (30-75).

[0013] Furthermore, the alkaline stimulating solution includes aluminum oxide and sodium oxide.

[0014] Furthermore, the concentration ratio of the aluminum oxide to the sodium oxide is (0.1-130):(200-550), and the concentration unit is g / L.

[0015] Furthermore, in the step S2, the reaction temperature is controlled to be 220-280° C., and the reaction time is 5-60 min.

[0016] Furthermore, the components in the Bayer process red mud include, by mass percentage, 12%-25% Al2O3, 3%-8% SiO2, 40%-58% Fe2O3 and 4%-7% TiO2, and the remaining substances are 1-4% sodium oxide, 5-15% crystal water, and trace amounts of other metal oxides.

[0017] Furthermore, the calcification treatment of the aluminum-containing solution in the step S3 includes: adding at least one of lime, carbide slag and calcined dolomite to the separated aluminum-containing solution, and the added amount is 5-50% of the mass of the aluminum-containing solution in terms of CaO content.

[0018] Furthermore, after the solid-liquid separation treatment in step S3, aluminum-containing solid slag and purified liquid are obtained for recycling, including: the aluminum-containing solid slag is returned to the Bayer process as part of the raw material for producing alumina to continue cyclic extraction, and the purified liquid is returned to the alkaline stimulating liquid preparation process as a circulation supplement.

[0019] (III) Beneficial effects

[0020] The above technical scheme of the present invention has the following beneficial technical effects: The present invention provides a method for preparing low-grade concentrate from Bayer red mud. The method innovatively introduces a dissolution promoter (dissolution reaction promoter) to induce the Bayer red mud to transform into a new phase structure. The new phase refers to a silicon-iron-calcium composite mineral phase, which is different from the traditional sodium-silicon slag phase. The phase transition principle is that the dissolution reaction promoter (iron-aluminum-calcium multi-composite compound) can promote the combination reaction of sodium-silicon slag, boehmite, and goethite in the red mud, respectively, and the iron element in the promoter can form a placeholder to convert the sodium-silicon slag into a silicon-iron-calcium composite mineral phase, thereby releasing and recovering aluminum and sodium elements from the lattice to achieve the phase transition process. The specific process is to first mix the Bayer red mud and the dissolution promoter in a mass ratio of (100:0.1) to 20, and then use the prepared alkaline stimulating solution to dissociate and dissolve the alumina released during the red mud phase transition process to obtain an aluminum-containing solution and an iron-rich solid phase, that is, by adding an alkaline stimulating solution to the first mixed material for reaction, and obtaining an aluminum-containing solution and an iron-rich solid phase after solid-liquid separation, which solves the current problem of additional processes and carbon dioxide emissions in carbon thermal reduction of red mud for iron extraction. Finally, the aluminum-containing solution is calcified and solid-liquid separated to obtain aluminum-containing solid slag and purified liquid for recycling. After the aluminum-containing solution is purified by calcification, the alkaline stimulating solution is obtained for recycling, that is, the purified liquid is returned to the alkaline stimulating solution preparation process as a circulation supplement. The calcified product is returned to the Bayer process to produce alumina, realizing the deep extraction of aluminum resources in red mud; the iron-rich solid phase is dried to obtain low-grade iron concentrate, and the iron-rich solid phase after separating the aluminum resources contains a large amount of iron oxide resources, which can be used as a low-grade iron concentrate product for the steel industry as a partial raw material replacement, realizing the full utilization of iron resources in red mud. The method of the present invention can be used to extract and utilize aluminum and iron elements in red mud in a stepwise manner, realizing the full utilization of iron resources in red mud and the deep extraction of aluminum resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic flow chart of a method for preparing low-grade iron concentrate from Bayer red mud according to the present invention;

[0022] Figure numerals: 1. Bayer low-temperature red mud storage bin; 2. Dissolution reaction accelerator storage bin; 3. Mixer; 4. Alkaline excitation solution storage tank; 5. High-temperature reactor; 6. First solid-liquid separation unit; 7. Low-grade iron concentrate storage bin; 8. Aluminum-containing solution storage tank; 9. Calcium additive storage bin; 10. Second solid-liquid separation unit; 11. Aluminum-calcium rich solid slag storage bin. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0024] At present, most of the processes for recovering iron and aluminum from red mud have complex process flows, high carbon emissions or secondary pollution problems. Traditional methods for recovering aluminum and iron from red mud have the following disadvantages: ① The carbon thermal reduction method is used to treat red mud, which adds an additional disposal process to the discharged red mud, and the process produces a large amount of carbon dioxide; ② Direct high-intensity magnetic separation treatment makes it difficult to effectively separate a large amount of non-magnetic hematite in the red mud; ③ The use of alkaline solution to treat red mud further increases the alkali content in the red mud, making subsequent resource utilization more difficult. Therefore, the present invention provides a method for preparing low-grade iron concentrate from Bayer red mud, comprising the following steps:

[0025] S1, mixing the Bayer process red mud with a dissolution promoter to obtain a first mixed material. The present invention uses a dissolution reaction promoter as a main reaction aid. In the process of producing alumina by the Bayer process, according to the characteristics of the Bayer process low-temperature red mud components, it is mixed with a dissolution reaction promoter (dissolution promoter). The mixing mass ratio of the Bayer process red mud and the dissolution promoter is 100: (0.1-20), and the preferred range is 100: (0.5-15). The components of the Bayer process low-temperature red mud include (in mass percentage): Al2O3 content 12-25%, SiO2 content 3-8%, Fe2O3 content 40-58%, TiO2 content 4-7%. The dissolution promoter is a composite compound containing aluminum, calcium, and iron elements. The mass ratio of aluminum, calcium, and iron in the dissolution promoter is (1-10): (15-40): (30-75) in terms of oxides.

[0026] S2, add alkaline stimulating liquid to the first mixed material for reaction, and obtain aluminum-containing solution and iron-rich solid phase after solid-liquid separation. The material obtained after low-temperature red mud and dissolution reaction promoter are evenly mixed, and an alkaline stimulating solution is used for selective reaction. The reaction temperature is 220-280°C and the reaction time is 5-60min. The alkaline stimulating liquid is a mixed solution composed of aluminum oxide and sodium oxide. The concentration ratio of aluminum oxide and sodium oxide is (0.1-130):(200-550), in g / L. The liquid-solid ratio of the alkaline stimulating liquid to the first mixed material is (1.5-10):1.

[0027] S3, after calcification and solid-liquid separation of the aluminum-containing solution, aluminum-containing solid slag and purified liquid are obtained for recycling; the iron-rich solid phase is dried to obtain low-grade iron concentrate. The calcification process uses calcium additives to purify the aluminum-containing solution, and the product is recycled back to the production process and the process of replenishing the alkaline stimulating solution. Specifically comprising: adding at least one of lime, carbide slag and calcined dolomite to the separated aluminum-containing solution, and the amount added is 5-50% of the mass of the aluminum-containing solution in terms of CaO content. After the calcification reaction is completed, solid-liquid separation is performed again to obtain aluminum-calcium-rich solid slag (aluminum-containing solid slag) and purified liquid. The aluminum-containing solid slag is returned to the Bayer process as part of the raw material for producing alumina for continued cyclic extraction, and the aluminum-calcium-rich solid slag can be returned to the Bayer process for circulation as part of the raw material for producing alumina, and the purified liquid is returned to the alkaline stimulating liquid preparation process as a cyclic supplement. The present invention is a method for directly shortening the Bayer process of producing alumina to produce low-grade iron ore, and at the same time, the aluminum lost in the secondary reaction of red mud can be recovered and extracted in the Bayer process. The specific process of this method is as follows Figure 1 As shown:

[0028] The Bayer low-temperature red mud in the Bayer low-temperature red mud storage bin 1 and the dissolution reaction accelerator in the dissolution reaction accelerator storage bin 2 are fully mixed in the mixer 3, and an alkaline stimulating solution is added during the mixing process (the alkaline stimulating solution is stored in the alkaline stimulating solution storage tank 4), and the mixed slurry enters the high-temperature reactor 5 for dissolution reaction. After the reaction, the slurry enters the first solid-liquid separation unit 6 for solid-liquid separation. The separated solid is an iron-rich solid phase, which enters the low-grade iron concentrate storage bin 7 after drying. The separated liquid is an aluminum-containing solution, which enters the aluminum-containing solution storage tank 8. A calcium additive (the calcium additive is stored in the calcium additive storage bin 9) is added to the aluminum-containing solution for calcification reaction. After the calcification reaction, the slurry enters the second solid-liquid separation unit 10 for solid-liquid separation. The solid obtained in the second solid-liquid separation unit is aluminum-calcium-rich solid slag, which enters the aluminum-calcium-rich solid slag storage bin 11 and returns to the Bayer process cycle for use as part of the raw material for producing alumina. The separated solution is a purified solution, which is returned to the alkaline stimulating solution storage tank 4 for preparation as a circulating supplement.

[0029] Embodiment 1:

[0030] The Bayer low temperature red mud and the dissolution reaction accelerator are mixed in a mass ratio of 100:5. The composition of the Bayer low temperature red mud used (by mass percentage) is: Al2O3 content 12.83%, SiO2 content 5.21%, Fe2O3 content 56.69%, TiO2 content 5.66%. The dissolution accelerator is a composite compound containing aluminum, calcium and iron elements. The dissolution accelerator is a multi-component compound containing aluminum, iron and calcium, which is combined in the form of a composite oxide. The molecular formula of the dissolution reaction agent can be written as xCaO·yAl2O3·zFe2O3, and the values ​​of x, y, and z are the values ​​of the mass ratio of the ratio converted into the molar ratio. The aluminum: calcium: iron in the composition of the dissolution reaction accelerator are all calculated as oxides, and the mass ratio = 3:22:75, that is, x:y:z = 3:22:75, and the same applies to Examples 2-4. The first mixed material reacts with the alkaline stimulating solution at a temperature of 250°C for 20 minutes, and the liquid-solid ratio is controlled to be 3:1 (the liquid-solid ratio of the alkaline stimulating solution to the first mixed material is 3:1), and the concentration ratio of aluminum oxide to sodium oxide in the alkaline stimulating solution is 110:240, in g / L. After the reaction, the iron-rich solid phase obtained by solid-liquid separation has an iron oxide content of 70.23%, and the iron-rich solid phase is dried to obtain a low-grade iron concentrate. Lime and carbide slag are added to the separated aluminum-containing solution, and the addition ratio is calculated based on the CaO content, and the addition amount is 10% of the mass of the aluminum-containing solution. After the calcification reaction is completed, solid-liquid separation is performed again to obtain aluminum-calcium-rich solid slag (aluminum-containing solid slag) and purified liquid. The aluminum-calcium-rich solid slag is returned to the Bayer process cycle for use as part of the raw material for producing alumina, and the purified liquid is returned to the alkaline stimulating solution preparation process as a circulation supplement.

[0031] Embodiment 2:

[0032] The Bayer low-temperature red mud and the dissolution reaction promoter are mixed in a mass ratio of 100:10. The composition of the Bayer low-temperature red mud used (by mass percentage) is: Al2O3 content 17.21%, SiO2 content 6.32%, Fe2O3 content 53.35%, TiO2 content 5.71%. The composition of the dissolution reaction promoter is aluminum: calcium: iron, all calculated as oxides, with a mass ratio of 3:27:70. The first mixed material reacts with the alkaline excitation solution at a temperature of 260°C for 30 minutes, and the liquid-solid ratio is controlled to be 5:1. The concentration ratio of aluminum oxide to sodium oxide in the alkaline excitation solution is 80:220, in g / L. After the reaction is completed, the iron-rich solid phase obtained by solid-liquid separation has an iron oxide content of 68.75%, and the iron-rich solid phase is dried to obtain a low-grade iron concentrate. Lime and carbide slag are added to the separated aluminum-containing solution, and the addition ratio is calculated based on the CaO content, and the addition amount is 15% of the mass of the aluminum-containing solution. After the calcification reaction is completed, solid-liquid separation is performed again to obtain aluminum-calcium-rich solid slag and purified liquid. The treatment process of aluminum-calcium-rich solid slag and purified liquid is the same as in Example 1.

[0033] Embodiment 3:

[0034] The Bayer low-temperature red mud and the dissolution reaction promoter are mixed in a mass ratio of 100:15. The composition of the Bayer low-temperature red mud used (by mass percentage) is: Al2O3 content 19.11%, SiO2 content 6.67%, Fe2O3 content 54.35%, TiO2 content 5.04%. The aluminum: calcium: iron in the dissolution reaction promoter are all calculated as oxides, and the mass ratio is 2:32:66. The mixed material reacts with the alkaline excitation solution at 270°C for 40 minutes, and the liquid-solid ratio is controlled to be 5.5:1. The concentration ratio of aluminum oxide to sodium oxide in the alkaline excitation solution is 70:260. After the reaction is completed, the iron-rich solid phase obtained by solid-liquid separation has an iron oxide content of 71.87%, and the iron-rich solid phase is dried to obtain a low-grade iron concentrate. Lime, carbide slag and calcined dolomite are added to the separated aluminum-containing solution, and the addition ratio is calculated based on the CaO content, and the addition amount is 18% of the mass of the aluminum-containing solution. After the calcification reaction is completed, solid-liquid separation is performed again to obtain aluminum-calcium-rich solid slag and purified liquid. The treatment process of aluminum-calcium-rich solid slag and purified liquid is the same as in Example 1.

[0035] Embodiment 4:

[0036] The Bayer low-temperature red mud and the dissolution reaction promoter are mixed in a mass ratio of 100:20. The composition of the Bayer low-temperature red mud used (by mass percentage) is: Al2O3 content 22.09%, SiO2 content 7.24%, Fe2O3 content 51.21%, TiO2 content 5.37%. The mass ratio of aluminum: calcium: iron in the dissolution reaction promoter is 1:40:59 (by oxide). The mixed material reacts with the alkaline excitation solution at 280°C for 60 minutes, and the liquid-solid ratio is controlled to be 8:1. The concentration ratio of aluminum oxide to sodium oxide in the alkaline excitation solution is 50:250. After the reaction is completed, the iron-rich solid phase obtained by solid-liquid separation has an iron oxide content of 70.22%. The iron-rich solid phase is dried to obtain a low-grade iron concentrate. Lime, carbide slag and calcined dolomite are added to the separated aluminum-containing solution, and the addition ratio is calculated based on the CaO content, and the addition amount is 20% of the mass of the aluminum-containing solution. After the calcification reaction is completed, solid-liquid separation is performed again to obtain aluminum-calcium-rich solid slag and purified liquid. The treatment process of aluminum-calcium-rich solid slag and purified liquid is the same as in Example 1.

[0037] Comparative Example 1

[0038] The Bayer low temperature red mud and the dissolution reaction accelerator were mixed in a mass ratio of 100:5. The composition of the Bayer low temperature red mud used was: Al2O3 content 12.83%, SiO2 content 5.21%, Fe2O3 content 56.69%, TiO2 content 5.66%. The composition of the dissolution reaction accelerator was aluminum: calcium: iron = 12:12:76 (calculated as oxides), and the other conditions were the same as in Example 1. After the reaction was completed, the iron-rich solid phase iron oxide content obtained by solid-liquid separation was only 60.62%, and the iron content was relatively low.

[0039] Comparative Example 2

[0040] The Bayer low temperature red mud and the dissolution reaction accelerator were mixed in a mass ratio of 100:35. The composition of the Bayer low temperature red mud used was: Al2O3 content 17.21%, SiO2 content 6.32%, Fe2O3 content 53.35%, TiO2 content 5.71%. The composition of the dissolution reaction accelerator was aluminum: calcium: iron = 3:27:70 (calculated as oxides), and the other conditions were the same as those in Example 2. After the reaction was completed, the iron-rich solid phase iron oxide content obtained by solid-liquid separation was only 61.88%, and the iron content was relatively low.

[0041] Comparative Example 3

[0042] The Bayer low temperature red mud and the dissolution reaction accelerator are mixed in a mass ratio of 100:15. The composition of the Bayer low temperature red mud used is: Al2O3 content 19.11%, SiO2 content 6.67%, Fe2O3 content 54.35%, TiO2 content 5.04%. The composition of the dissolution reaction accelerator is aluminum: calcium: iron = 2:32:66 (calculated as oxides). The mixed material is reacted with the alkaline excitation solution at a temperature of 200°C for 120 minutes. The other conditions are the same as those in Example 3. After the reaction is completed, the iron-rich solid phase iron oxide content obtained by solid-liquid separation is only 59.04%, and the iron content is relatively low.

[0043] Comparative Example 4

[0044] The Bayer low temperature red mud and the dissolution reaction accelerator are mixed in a mass ratio of 100:20. The composition of the Bayer low temperature red mud used is: Al2O3 content 22.09%, SiO2 content 7.24%, Fe2O3 content 51.21%, TiO2 content 5.37%. The composition of the dissolution reaction accelerator is aluminum: calcium: iron = 1: 40: 59 (calculated as oxides). The mixed material reacts with the alkaline excitation solution at a temperature of 280°C for 60 minutes, and the liquid-solid ratio is controlled to be 8. The alkaline excitation solution composition contains aluminum oxide: sodium oxide = 180g / L: 150g / L. The remaining conditions are the same as those in Example 4. After the reaction is completed, the iron-rich solid phase iron oxide content obtained by solid-liquid separation is only 58.65%, and the iron content is relatively low.

[0045] The present invention provides a method for preparing low-grade iron concentrate from Bayer red mud. The method is used to directly generate low-grade iron concentrate in a short process during the Bayer process for producing alumina, and can also deeply extract aluminum resources from the red mud. The present invention innovatively introduces a dissolution reaction promoter to induce the Bayer red mud to transform into a new phase structure, and uses a formulated alkaline stimulating solution to dissociate and dissolve the alumina released during the red mud phase transition process to obtain an aluminum-containing solution and an iron-rich solid phase, thereby solving the current problem of additional processes and carbon dioxide emissions in the carbon thermal reduction of red mud for iron extraction. Finally, the aluminum-containing solution is subjected to calcification treatment and solid-liquid separation treatment to obtain aluminum-containing solid slag and purified liquid for recycling, and a calcium additive is used to purify the aluminum-containing solution, which is recycled back to the production process and the method of replenishing the alkaline stimulating solution. After the aluminum-containing solution is calcified and purified, the alkaline stimulating solution is recovered for recycling. The calcified product is returned to the Bayer process to produce alumina, realizing the deep extraction of aluminum resources in red mud; the iron-rich solid phase is dried to obtain low-grade iron concentrate, and the iron-rich solid phase after separating the aluminum resources contains a large amount of iron oxide resources, which can be used as a low-grade iron concentrate product for the steel industry as a partial raw material replacement, realizing the full utilization of iron resources in red mud. The invention has the following advantages:

[0046] (1) The invention does not introduce harmful impurities into the system for a second time, and efficiently extracts the residual aluminum resources in the ore;

[0047] (2) The source modification of red mud can be achieved, and there is no need for additional magnetic separation of red mud, and iron concentrate powder can be directly prepared. Through the process method designed in the present invention, the aluminum and iron in the solid waste red mud of the alumina industry can be extracted and utilized in a cascade manner, with significant economic and environmental benefits and broad prospects for promotion and application.

[0048] Obviously, the described embodiments are part of the embodiments of the present invention, but not all of them. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms "first", "second" and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. It should be understood that the above-mentioned specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation on the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the scope of protection of the present invention. In addition, the claims attached to the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the attached claims, or the equivalent forms of such scope and boundaries. The present invention is described above with reference to the embodiments of the present invention. However, these embodiments are for illustrative purposes only, not for limiting the scope of the present invention. The scope of the present invention is defined by the attached claims and their equivalents. Without departing from the scope of the present invention, a variety of substitutions and modifications can be made by those skilled in the art, and these substitutions and modifications should fall within the scope of the present invention. Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and modifications may be made to the embodiments of the present invention without departing from the spirit and scope of the present invention. Obviously, the above embodiments are merely examples for clear description and are not limitations on the embodiments. For those of ordinary skill in the art, other different forms of changes or modifications may be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived therefrom are still within the scope of protection created by the present invention.

Claims

1. A method for preparing low-grade iron ore concentrate from Bayer red mud, characterized in that: include: S1, mixing the Bayer process red mud with the dissolution promoter to obtain a first mixed material, wherein the mixing mass ratio of the Bayer process red mud to the dissolution promoter is 100:(0.1-20); S2, adding an alkaline stimulating liquid to the first mixed material for reaction, and obtaining an aluminum-containing solution and an iron-rich solid phase after solid-liquid separation; S3, subjecting the aluminum-containing solution to calcification and solid-liquid separation treatment to obtain aluminum-containing solid slag and purified liquid; and drying the iron-rich solid phase to obtain low-grade iron concentrate.

2. The method for preparing low-grade concentrate from Bayer red mud according to claim 1, characterized in that: The liquid-to-solid ratio of the alkaline stimulating liquid to the first mixed material is (1.5-10):

1.

3. The method for preparing low-grade concentrate from Bayer red mud according to claim 1, characterized in that: The dissolution accelerator is a composite compound containing aluminum, calcium and iron elements.

4. The method for preparing low-grade iron ore concentrate from Bayer red mud according to claim 3, characterized in that: The mass ratio of aluminum, calcium and iron in the dissolution accelerator, calculated as oxides, is (1-10):(15-40):(30-75).

5. The method for preparing low-grade iron ore concentrate from Bayer red mud according to claim 1, characterized in that: The alkaline stimulating solution is a mixed solution consisting of aluminum oxide and sodium oxide.

6. The method for preparing low-grade iron ore concentrate from Bayer red mud according to claim 5, characterized in that: The concentration ratio of the aluminum oxide to the sodium oxide is (0.1-130):(200-550).

7. The method for preparing low-grade iron ore concentrate from Bayer red mud according to claim 1, characterized in that: In the step S2, the reaction temperature is controlled to be 220-280° C., and the reaction time is 5-60 min.

8. The method for preparing low-grade iron ore concentrate from Bayer red mud according to claim 1, characterized in that: The components in the Bayer process red mud include, by mass percentage, 12%-25% of Al2O3, 3%-8% of SiO2, 40%-58% of Fe2O3 and 4%-7% of TiO2.

9. The method for preparing low-grade iron ore concentrate from Bayer red mud according to claim 1, characterized in that: The calcification treatment of the aluminum-containing solution in step S3 includes: adding at least one of lime, carbide slag and calcined dolomite to the separated aluminum-containing solution, and the added amount is 5-50% of the mass of the aluminum-containing solution in terms of CaO content.

10. The method for preparing low-grade iron ore concentrate from Bayer red mud according to claim 1, characterized in that: After the solid-liquid separation treatment in step S3, aluminum-containing solid slag and purified liquid are obtained for recycling, including: the aluminum-containing solid slag is returned to the Bayer process as part of the raw material for producing alumina to continue cyclic extraction, and the purified liquid is returned to the alkaline stimulating liquid preparation process as a circulation supplement.

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