Method for extracting iron from Bayer process red mud

Abstract

The invention relates to a method for extracting iron from Bayer process red mud. The method belongs to the field of industrial waste reutilization. The method comprises the following steps: crushing a reducing agent, blending with tap water, red mud and a dispersing agent to obtain ore pulp B, ball-milling to obtain ore pulp C, diluting, roughing to obtain primary concentrate and primary tailing pulp, finely selecting to obtain secondary concentrate and secondary tailing pulp, scavenging to obtain tertiary concentrate and tertiary tailing pulp, aerating the tertiary tailing pulp to obtain ore pulp, carrying out filter pressing to obtain filter residues and filtrate, and refluxing the filtrate. Heating and pressurizing are not needed, the process and equipment are simpler and more reliable, and more energy is saved. Nitrite is not added, so that the risk of secondary pollution is avoided; and water is saved through filtrate backflow, the cost is reduced, and secondary pollution of alkali is prevented. According to the method, iron can be used as a reducing agent, a cheaper reducing agent pyrite can also be adopted, and magnetization transformation of the hematite can be achieved without using an expensive nitrite reagent; meanwhile, wet red mud or red mud slurry can be directly used as a raw material for batching.

Description

Technical Field

[0001] The present invention belongs to the field of industrial waste recycling; specifically, it relates to a method for extracting iron from Bayer red mud. Background Art

[0002] Red mud is an alkaline waste residue produced in the alumina production industry. It is named red mud because it contains iron oxide and is in a red mud-like state. For every 1 ton of alumina produced, 1.5 - 2 tons of red mud are generated. According to the current alumina production, the stockpile of red mud in the country increases by nearly 100 million tons every year. The large stockpile of red mud not only wastes land and increases the cost of enterprises, but also poses a great ecological safety hazard. There have been several ecological disasters caused by red mud in the world, so it is urgent to treat red mud. Currently, there are various technologies for treating red mud, but very few have achieved industrialization. The main reason is that the economic feasibility is not good. Red mud mainly contains Fe, Al, Si, O, a small amount of Ca, Na, Ti, Mg, and generally also contains trace amounts of rare earth elements. It can be seen that the main components have low economic value. How to convert these main elements into products with higher economic value at low cost has become the key to solving the problem.

[0003] Bayer red mud contains about 30% - 60% iron oxide. Due to its very fine particles and lack of magnetism, it is difficult to recover by an economically efficient method. Currently, the methods for recovering iron from red mud are mainly high-temperature thermal reduction or high-temperature and high-pressure hydrothermal reduction, and the reduction products are iron or magnetite. There are also methods of room-temperature wet reduction, but the use of substances such as nitrites may cause secondary pollution and increase the treatment cost.

[0004] Methods for recovering iron from Bayer red mud: (1) Pyrometallurgical reduction, that is, using reducing agents such as carbon and pyrite to reduce the hematite in red mud to iron or magnetite, and then recovering iron by magnetic separation; (2) Wet reduction, that is, adding a reducing agent (such as hydrogen, iron powder, pyrite, organic matter, etc.) to a wet system to reduce the hematite in red mud to magnetite, and then recovering iron by magnetic separation. Since red mud is a solid waste produced in the wet production of alumina and has a high water content, pyrometallurgy generally requires heating to above 600°C, which has high energy consumption and is prone to secondary pollution, making it difficult to generate economic benefits. Wet reduction can be further divided into two categories: wet reduction under heating and pressure and wet reduction at room temperature and normal pressure.

[0005] In the patent "A Method for Treating High-Iron Red Mud by Debasing with Calcium Sucrate and Synchronously Reducing and Extracting Iron" with the application number 202411059171.1, it is mentioned that: First, put sucrose and calcium oxide into a beaker, add deionized water and mix evenly. Then, keep it warm and heat it in a water bath at 70°C and 420 r / min for 1.5 h to make sucrose complex with Ca(OH)₂ to form calcium sucrate. Then, configure the calcium sucrate solution and the quantitatively measured red mud into a reaction solution and put them into an alkaline high-pressure reactor together. React at 240°C and 420 r / min for 60 min, and then conduct magnetic separation to extract iron from the generated tailings. The iron recovery rate reaches over 40%.

[0006] In the patent "A Method for Efficiently Recovering Iron Concentrate from Iron-Containing Wastes" with the application number 202411873095.8, it is mentioned that: Mix the iron-containing wastes, concentrated alkali solution and additives evenly and then conduct hydrothermal reaction. Then, magnetically separate and recover iron from the solid reaction product.

[0007] In the patent "A Method for Producing Iron Concentrate by Using Bayer Red Mud Sand" with the application number 201010196397.8, it is mentioned that: Dry, crush and grind and classify the red mud sand so that the particle size of the red mud sand after grinding and classification is controlled within 10 μm to 90 μm. Then, mix the red mud sand after grinding and classification with caustic soda solution at a mass ratio of 1:8 to 1:2, and conduct a digestion reaction at 110°C to 180°C and 0.1 MPa to 0.6 MPa for 0.2 h to 2 h. Then, conduct wet magnetic separation on the solid reaction product to obtain iron concentrate.

[0008] The common disadvantages in the above three patent applications are as follows: The method of heating and pressurizing is adopted, which not only has more stringent requirements for the reaction equipment, but also has higher energy consumption compared with normal temperature and pressure.

[0009] In the patent "A Method for Recovering Fine-Grained Iron Oxide Minerals" with the application number 202310972695.9, it is mentioned that: Mix the raw material to be treated containing fine-grained iron oxide minerals with an iron reducing agent and nitrite, conduct wet grinding, and then conduct magnetic separation to extract iron twice to obtain iron concentrate. The disadvantage of this patent application is that this technology requires a carcinogen such as nitrite as a raw material for mixing reactions, which not only increases the cost, but also easily causes secondary pollution. Only iron is used as the reducing agent, and the cost of the reducing agent is relatively high. Summary of the Invention

[0010] The purpose of the present invention is to solve the problems existing in the above background technology, and provide a method for extracting iron from Bayer red mud.

[0011] A method for extracting iron from Bayer red mud is realized according to the following steps:

[0012] 1. Break large chunks of reducing agent into particles A with a particle size less than 2 mm, then mix with tap water, red mud and dispersant to obtain pulp B, and after ball milling, obtain pulp C;

[0013] 2. Dilute the above-mentioned pulp C with tap water to a solid content of 20% - 35% and introduce it into a permanent magnet drum magnetic separator for rough selection to obtain primary concentrate D and primary tailing pulp E. Then introduce the primary tailing pulp E into a high-gradient magnetic separator for fine selection to obtain secondary concentrate F and secondary tailing pulp G. Then introduce the secondary tailing pulp G into a wet high-intensity magnetic filter for scavenging to obtain tertiary concentrate H and tertiary tailing pulp I;

[0014] 3. Introduce the above-mentioned tertiary tailing pulp I into an aeration tank for aeration to obtain pulp J, then perform pressure filtration to obtain filter cake K and filtrate L. Then return 37.5% - 59.5% of the filtrate L to step 2 to replace tap water, and return the remaining filtrate L to step 1 to replace tap water, thus completing the iron extraction method.

[0015] Further, the reducing agent in step 1 is pyrite and / or iron filings.

[0016] Further, the dispersant in step 1 is sodium polyacrylate.

[0017] Further, the mass-volume ratio of particles A, red mud, tap water and dispersant in step 1 is (1.5 - 8) kg: 100 kg: (67 - 432) L: (0.1 - 1.08) kg.

[0018] Further, the ball milling in step 1: Use stainless steel balls with a diameter of 8 mm, the filling rate of the steel balls is 30% - 45%, the ball milling speed is 15 - 800 r / min, and the ball milling time is 6 - 8 h.

[0019] Further, the pulp B and the steel balls are charged according to a total filling rate of 60% - 75% in step 1.

[0020] Further, the magnetic field intensity for rough selection in step 2 is 0.2 - 0.5 T.

[0021] Further, the solid content for fine selection in step 2 is 15% - 35%, the magnetic field intensity is 1.0 - 1.5 T, and the flow rate is 0.1 - 0.5 m / s.

[0022] Further, the solid content for scavenging in step 2 is 10% - 25%, the magnetic field intensity is 1.5 - 2.4 T, and the flow rate is 0.1 - 0.5 m / s.

[0023] Further, the aeration in step 3: The DO concentration in the aeration tank is 1.5 - 2.5 mg / L, the pH value is 7 - 9, and the hydraulic retention time is 2 - 3 h.

[0024] Reaction principle of the present invention:

[0025] Due to the high-speed ball milling environment, the instantaneous temperature generated by the collision of stainless steel balls can reach 200 - 500 °C, and the temperature at which cavitation explodes instantaneously can even reach over 1000 °C. Although the time is extremely short and the range is extremely small, it also creates reaction conditions within multiple point ranges for equations (1) and (2).

[0026] FeS2 + 16Fe2O3 = 11Fe3O4 + 2SO2↑ (1)

[0027] Fe + 4Fe2O3 = 3Fe3O4 (2)

[0028] Since a major hazard of Bayer red mud is its strong alkalinity, the SO2 generated by equation (1) is an anhydride of medium-strength acid and can easily undergo complete neutralization reactions (3) and (4) with the remaining strong alkaline sodium hydroxide or calcium hydroxide in the red mud.

[0029] SO2 + 2NaOH = Na2SO3 + H2O (3)

[0030] SO2 + Ca(OH)2 = CaSO3 + H2O (4)

[0031] The generated sulfites react in the aeration tank during aeration to produce stable sulfates through reactions (5) and (6).

[0032] 2Na2SO3 + O2 = 2Na2SO4 (5)

[0033] 2CaSO3 + O2 = 2CaSO4 (6)

[0034] The present invention uses pyrite and / or iron filings as reducing agents, performs batching according to a certain batching method, performs ball milling according to certain ball milling parameters, and performs magnetic separation according to a certain magnetic separation scheme, ultimately realizing the extraction of iron concentrate from Bayer red mud at normal temperature and pressure.

[0035] Advantages of the present invention:

[0036] A method for extracting iron from Bayer red mud in the present invention is a new process that can be carried out at normal temperature and pressure and can realize the magnetization transformation and iron extraction of hematite in red mud without adding harmful substances such as nitrites. The present invention adopts an atmospheric and normal temperature wet magnetization technology, which does not require heating or pressurization, and the process and equipment are simpler and more reliable, and more energy-saving. The present invention can generate acidic substances to partially neutralize the alkalinity of red mud and reduce the harm of red mud; at the same time, the present invention does not add nitrites and has no risk of secondary pollution. The present invention adopts a filtrate reflux process, which not only saves water and reduces costs, but also prevents the secondary pollution of alkali.

[0037] In addition to using iron as a reducing agent, the present invention can also use pyrite, a cheaper reducing agent, and achieve the magnetization transformation of hematite without using relatively expensive nitrite reagents. At the same time, the present invention can directly use wet red mud or red mud slurry as raw materials for batching.

[0038] The method in the present invention is applicable to extracting iron from Bayer red mud. Specific embodiments

[0039] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination between the specific embodiments.

[0040] Specific embodiment one: A method for extracting iron from Bayer red mud in this embodiment is realized according to the following steps:

[0041] 1. Crush large pieces of the reducing agent into particles A with a particle size less than 2 mm, and then mix them with tap water, red mud, and a dispersant to obtain pulp B. After ball milling, obtain pulp C;

[0042] 2. Dilute the above pulp C with tap water to a solid content of 20% - 30% and introduce it into a permanent magnetic drum separator for rough selection to obtain primary concentrate D and primary tailing pulp E. Then introduce the primary tailing pulp E into a high-gradient magnetic separator for fine selection to obtain secondary concentrate F and secondary tailing pulp G. Then introduce the secondary tailing pulp G into a wet high-intensity magnetic filter for scavenging to obtain tertiary concentrate H and tertiary tailing pulp I;

[0043] 3. Introduce the above tertiary tailing pulp I into an aeration tank for aeration to obtain pulp J, then perform pressure filtration to obtain filter residue K and filtrate L. Then return 37.5% - 59.5% of the filtrate L to step 2 to replace tap water, and return the remaining filtrate L to step 1 to replace tap water, thus completing the iron extraction method.

[0044] The purpose of aeration in step 3 of this embodiment is to convert sulfite into sulfate.

[0045] Specific embodiment two: The difference between this embodiment and specific embodiment one is that the reducing agent in step 1 is pyrite and / or iron filings. Other steps and parameters are the same as those in specific embodiment one.

[0046] Specific embodiment three: The difference between this embodiment and specific embodiment one is that the dispersant in step 1 is sodium polyacrylate. Other steps and parameters are the same as those in specific embodiment one.

[0047] Embodiment 4: The difference between this embodiment and Embodiment 1 is that in Step 1, the mass-volume ratio of granule A, red mud, tap water and dispersant is (1.5 - 8) kg: 100 kg: (67 - 432) L: (0.1 - 1.08) kg. Other steps and parameters are the same as those in Embodiment 1.

[0048] Embodiment 5: The difference between this embodiment and Embodiment 1 is that in Step 1, for the ball milling: stainless steel balls with a diameter of 8 mm are used, the filling rate of the steel balls is 30% - 45%, the ball milling speed is 15 - 800 r / min, and the ball milling time is 6 - 8 h. Other steps and parameters are the same as those in Embodiment 1.

[0049] Embodiment 6: The difference between this embodiment and Embodiment 1 is that in Step 1, the slurry B and the steel balls are charged according to a total filling rate of 60% - 75%. Other steps and parameters are the same as those in Embodiment 1.

[0050] Embodiment 7: The difference between this embodiment and Embodiment 1 is that in Step 2, the magnetic field intensity for rough selection is 0.2 - 0.5 T. Other steps and parameters are the same as those in Embodiment 1.

[0051] Embodiment 8: The difference between this embodiment and Embodiment 1 is that in Step 2, the solid content for fine selection is 15% - 35%, the magnetic field intensity is 1.0 - 1.5 T, and the flow rate is 0.1 - 0.5 m / s. Other steps and parameters are the same as those in Embodiment 1.

[0052] Embodiment 9: The difference between this embodiment and Embodiment 1 is that in Step 2, the solid content for scavenging is 10% - 25%, the magnetic field intensity is 1.5 - 2.4 T, and the flow rate is 0.1 - 0.5 m / s. Other steps and parameters are the same as those in Embodiment 1.

[0053] Embodiment 10: The difference between this embodiment and Embodiment 1 is that in Step 3, for the aeration: the DO concentration in the aeration tank is 1.5 - 2.5 mg / L, the pH value is 7 - 9, and the hydraulic retention time is 2 - 3 h. Other steps and parameters are the same as those in Embodiment 1.

[0054] The beneficial effects of the present invention are verified through the following examples:

[0055] Example 1:

[0056] A method for extracting iron from Bayer red mud is realized according to the following steps:

[0057] I. Break the large-sized reducing agent into granules A with a particle size less than 2 mm, then carry out batching with tap water, red mud and dispersant to obtain slurry B, and obtain slurry C through ball milling;

[0058] II. Dilute the above-mentioned pulp C with tap water to a solid content of 25%, and introduce it into a permanent magnet drum magnetic separator for rough selection to obtain a primary concentrate D and a primary tailing pulp E. Then introduce the primary tailing pulp E into a high-gradient magnetic separator for cleaning to obtain a secondary concentrate F and a secondary tailing pulp G. Then introduce the secondary tailing pulp G into a wet high-intensity magnetic filter for scavenging to obtain a tertiary concentrate H and a tertiary tailing pulp I;

[0059] III. Introduce the above-mentioned tertiary tailing pulp I into an aeration tank for aeration to obtain a pulp J, then perform pressure filtration to obtain a filter residue K and a filtrate L. Then return 40% of the filtrate L to step II to replace tap water, and return the remaining filtrate L to step I to replace tap water, thus completing the method for iron extraction.

[0060] In step I of this embodiment, the reducing agent is pyrite, and the FeS2 content is 95.05%.

[0061] In step I of this embodiment, the dispersant is sodium polyacrylate.

[0062] In step I of this embodiment, the dosage of particle A is 3.47 kg (30% in excess);

[0063] The dosage of red mud is 100 kg, and the Fe2O3 content is 54.18%;

[0064] The dosage of tap water is 103.47 L; the dosage of the dispersant is 1.03 kg.

[0065] In step I of this embodiment, for the ball milling: stainless steel balls with a diameter of 8 mm are used, the filling rate of the steel balls is 30%, the ball milling speed is 500 r / min, and the ball milling time is 8 h.

[0066] In step I of this embodiment, the pulp B and the steel balls are charged according to a total filling rate of 70%.

[0067] In step II of this embodiment, the magnetic field intensity for the rough selection is 0.35 T.

[0068] In step II of this embodiment, the solid content for the cleaning is 20%, the magnetic field intensity is 1.5 T, and the flow rate is 0.3 m / s.

[0069] In step II of this embodiment, the solid content for the scavenging is 15%, the magnetic field intensity is 2.0 T, and the flow rate is 0.3 m / s.

[0070] In step III of this embodiment, for the aeration: the DO concentration in the aeration tank is 2 mg / L, the pH value is 8, and the hydraulic retention time is 2 h.

[0071] In this embodiment, the amount of the primary concentrate D obtained in step II is 4.88 kg (56.64% TFe ); The amount of the secondary concentrate F obtained is 25.27 kg (60.45% T Fe ); The amount of the tertiary concentrate H obtained is 10.09 kg (50.89% T Fe ).

[0072] In Step 1 of this example, the pH value of the pulp B is 12; in Step 3, the pH value of the filtrate L is 11.

[0073] Calculation of the iron recovery rate in this example: a% = (iron content in the primary concentrate D + iron content in the secondary concentrate F + iron content in the tertiary concentrate H) / (iron content in the red mud + iron content in the pyrite) × 100% = (4.88 × 56.64% + 25.27 × 60.45% + 10.09 × 50.89%) / (100 × 54.18% × 0.70 + 3.47 × 95.05% × 0.47) × 100% = 58.70%.

[0074] Example 2:

[0075] A method for extracting iron from Bayer red mud is realized according to the following steps:

[0076] I. Crush large-sized reducing agents into particles A with a particle size less than 2 mm, and then mix them with tap water, red mud, and a dispersant to obtain pulp B, and obtain pulp C after ball milling;

[0077] II. Dilute the above pulp C with tap water to a solid content of 25% and introduce it into a permanent magnet drum magnetic separator for rough selection to obtain a primary concentrate D and a primary tailing pulp E. Then introduce the primary tailing pulp E into a high-gradient magnetic separator for fine selection to obtain a secondary concentrate F and a secondary tailing pulp G. Then introduce the secondary tailing pulp G into a wet high-intensity magnetic filter for scavenging to obtain a tertiary concentrate H and a tertiary tailing pulp I;

[0078] III. Introduce the above tertiary tailing pulp I into an aeration tank for aeration to obtain pulp J, then perform pressure filtration to obtain a filter residue K and a filtrate L. Then return 50% of the filtrate L to Step II to replace tap water, and return the remaining filtrate L to Step I to replace tap water, thus completing the iron extraction method.

[0079] In Step 1 of this example, the reducing agent is iron filings, and the FeS2 content is 91.36%.

[0080] In Step 1 of this example, the dispersant is sodium polyacrylate.

[0081] In Step 1 of this example, the dosage of the particles A is 7.78 kg (50% in excess);

[0082] The dosage of the red mud is 100 kg, and the Fe2O3 content is 54.18%;

[0083] The water consumption of tap water is 161.67 L; the dosage of the dispersant is 1.08 kg.

[0084] In the ball milling described in step 1 of this embodiment: stainless steel balls with a diameter of 8 mm are used, the filling rate of the steel balls is 30%, the ball milling speed is 550 r / min, and the ball milling time is 6 h.

[0085] In step 1 of this embodiment, the pulp B and the steel balls are charged according to a total filling rate of 70%.

[0086] In step 2 of this embodiment, the magnetic field intensity for rough selection is 0.35 T.

[0087] In step 2 of this embodiment, the solid content for fine selection is 20%, the magnetic field intensity is 1.5 T, and the flow rate is 0.3 m / s.

[0088] In step 2 of this embodiment, the solid content for scavenging is 15%, the magnetic field intensity is 2.2 T, and the flow rate is 0.3 m / s.

[0089] In the aeration described in step 3 of this embodiment: the DO concentration in the aeration tank is 1.5 mg / L, the pH value is 8, and the hydraulic retention time is 3 h.

[0090] In this embodiment, the amount of the primary concentrate D obtained in step 2 is 6.02 kg (57.87% T Fe ); the amount of the secondary concentrate F obtained is 37.16 kg (65.34% T Fe ); the amount of the tertiary concentrate H obtained is 11.67 kg (49.55% T Fe ).

[0091] In step 1 of this embodiment, the pH value of the pulp B is 12; in step 3, the pH value of the filtrate L is 11.

[0092] In this embodiment, the iron recovery rate is calculated as follows: a% = (iron content in primary concentrate D + iron content in secondary concentrate F + iron content in tertiary concentrate H) / (iron content in red mud + iron content in pyrite) × 100% = (6.02 × 57.87% + 37.16 × 65.34% + 11.67 × 49.55%) / (100 × 54.18% × 0.70 + 7.78 × 91.36%) × 100% = 74.50%.

[0093] Example 3:

[0094] A method for extracting iron from Bayer red mud is realized according to the following steps:

[0095] 1. Crush the large reducing agent into particles A with a particle size less than 2 mm, then mix it with tap water, red mud and a dispersant to obtain pulp B, and obtain pulp C after ball milling;

[0096] II. Dilute the above-mentioned pulp C with tap water to a solid content of 25%, and introduce it into a permanent magnetic drum separator for rough selection to obtain a primary concentrate D and a primary tailing pulp E. Then introduce the primary tailing pulp E into a high-gradient magnetic separator for cleaning to obtain a secondary concentrate F and a secondary tailing pulp G. Next, introduce the secondary tailing pulp G into a wet high-intensity magnetic filter for scavenging to obtain a tertiary concentrate H and a tertiary tailing pulp I;

[0097] III. Introduce the above-mentioned tertiary tailing pulp I into an aeration tank for aeration to obtain a pulp J, then perform pressure filtration to obtain a filter cake K and a filtrate L. Then, 55% of the filtrate L is refluxed to step II to replace tap water, and the remaining filtrate L is refluxed to step I to replace tap water, thus completing the iron extraction method.

[0098] In step I of this embodiment, the reducing agent is pyrite (FeS2 content is 95.05%) and iron filings (FeS2 content is 91.36%).

[0099] In step I of this embodiment, the dispersant is sodium polyacrylate.

[0100] In step I of this embodiment, the dosage of pyrite in particle A is 1.90 kg, and the dosage of iron filings is 3.56 kg (i.e., the total reducing agent is in excess by 50%);

[0101] The dosage of red mud is 100 kg, and the Fe2O3 content is 54.18%;

[0102] The dosage of tap water is 158.19 L; the dosage of the dispersant is 1.05 kg.

[0103] In step I of this embodiment, for ball milling: stainless steel balls with a diameter of 8 mm are used, the filling rate of the steel balls is 30%, the ball milling speed is 450 r / min, and the ball milling time is 8 h.

[0104] In step I of this embodiment, the pulp B and the steel balls are charged according to a total filling rate of 70%.

[0105] In step II of this embodiment, the magnetic field intensity for rough selection is 0.35 T.

[0106] In step II of this embodiment, the solid content for cleaning is 20%, the magnetic field intensity is 1.5 T, and the flow rate is 0.3 m / s.

[0107] In step II of this embodiment, the solid content for scavenging is 15%, the magnetic field intensity is 2.0 T, and the flow rate is 0.3 m / s.

[0108] In step III of this embodiment, for aeration: the DO concentration in the aeration tank is 2 mg / L, the pH value is 8, and the hydraulic retention time is 2.5 h.

[0109] In step two of this embodiment, the amount of the primary concentrate D obtained is 6.33 kg (58.31% T Fe ); the amount of the secondary concentrate F obtained is 36.17 kg (66.00% T Fe ); the amount of the tertiary concentrate H obtained is 9.23 kg (50.83% T Fe ).

[0110] In step one of this embodiment, the pH value of the pulp B is 12; in step three, the pH value of the filtrate L is 11.

[0111] Calculation of the iron recovery rate in this embodiment: a% = (iron content in the primary concentrate D + iron content in the secondary concentrate F + iron content in the tertiary concentrate H) / (iron content in the red mud + iron content in the pyrite) × 100% = (6.33 × 58.31% + 36.17 × 66.00% + 9.23 × 50.83%) / (100 × 54.18% × 0.70 + 1.90 × 95.05% × 0.47 + 3.56 × 91.36%) × 100% = 76.74%.

[0112] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for extracting iron from Bayer red mud, characterized in that It is carried out according to the following steps:

1. Break large pieces of reducing agent into particles A with a particle size less than 2 mm, then mix with tap water, red mud and dispersant to obtain pulp B, and after ball milling, obtain pulp C; 2. Dilute the above pulp C with tap water to a solid content of 20% - 35% and introduce it into a permanent magnet drum magnetic separator for rough selection to obtain primary concentrate D and primary tailing pulp E. Then introduce the primary tailing pulp E into a high-gradient magnetic separator for fine selection to obtain secondary concentrate F and secondary tailing pulp G. Then introduce the secondary tailing pulp G into a wet high-intensity magnetic filter for scavenging to obtain tertiary concentrate H and tertiary tailing pulp I; 3. Introduce the above tertiary tailing pulp I into an aeration tank for aeration to obtain pulp J, then carry out pressure filtration to obtain filter cake K and filtrate L. Then reflux 37.5% - 59.5% of the filtrate L to step 2 to replace tap water, and reflux the remaining filtrate L to step 1 to replace tap water, thus completing the iron extraction method.

2. The method for extracting iron from Bayer red mud according to claim 1, characterized in that The reducing agent described in step 1 is pyrite and / or iron filings.

3. The method for extracting iron from Bayer red mud according to claim 1, wherein The dispersant described in step 1 is sodium polyacrylate.

4. The method for extracting iron from Bayer red mud according to claim 1, characterized in that The mass-volume ratio of particles A, red mud, tap water and dispersant in step 1 is (1.5 - 8) kg: 100 kg: (67 - 432) L: (0.1 - 1.08) kg.

5. The method for extracting iron from Bayer red mud according to claim 1, wherein The ball milling in step 1: Use stainless steel balls with a diameter of 8 mm, the filling rate of the steel balls is 30% - 45%, the ball milling speed is 15 - 800 r / min, and the ball milling time is 6 - 8 h.

6. The method for extracting iron from Bayer red mud according to claim 1, characterized in that The pulp B and the steel balls in step 1 are charged according to a total filling rate of 60% - 75%.

7. The method for extracting iron from Bayer red mud according to claim 1, characterized in that The magnetic field intensity of the rough selection described in step 2 is 0.2 - 0.5 T.

8. The method for extracting iron from Bayer red mud according to claim 1, wherein The solid content of the fine selection described in step 2 is 15% - 35%, the magnetic field intensity is 1.0 - 1.5 T, and the flow rate is 0.1 - 0.5 m / s.

9. The method for extracting iron from Bayer red mud according to claim 1, characterized in that The solid content of the scavenging described in step 2 is 10% - 25%, the magnetic field intensity is 1.5 - 2.4 T, and the flow rate is 0.1 - 0.5 m / s.

10. The method for extracting iron from Bayer red mud according to claim 1, characterized in that The aeration in step 3: The DO concentration in the aeration tank is 1.5 - 2.5 mg / L, the pH value is 7 - 9, and the hydraulic retention time is 2 - 3 h.