Method for recovering laterite-nickel ore tailings

Abstract

The invention provides a method for recovering laterite-nickel ore tailings, which comprises the following steps: (1) slurrying laterite-nickel ore tailings, and carrying out acid leaching treatment to obtain leached residues; (2) mixing the leaching residues with a reducing agent, and carrying out reduction desulfurization treatment to obtain reducing residues; (3) carrying out superfine grinding treatment on the reducing slag, and carrying out first magnetic separation treatment to obtain a first magnetic separation material; (4) the first magnetic separation material and a dispersing agent are mixed for second magnetic separation treatment, and a second magnetic separation material is obtained; and (5) carrying out alkali washing purification treatment on the second magnetic separation material, and drying to obtain sponge iron. According to the method, the problems of excessive accumulation, paid landfill and difficulty in recycling of the laterite-nickel ore tailings are solved, the laterite-nickel ore hydrometallurgy tailings are prepared into the sponge iron, and the magnetic separation tailings obtained in the recovery process can be used for producing building materials, cement and other additional products.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology and relates to a method for recycling tailings from laterite nickel ore. Background Technology

[0002] Nickel is a crucial industrial metal, playing a wide and critical role in modern industry and technology. It is used in the production of stainless steel, high-performance alloys, electroplating, casting, and catalysts. Nickel is an important component in the cathode materials of lithium-ion batteries, especially in high-energy-density batteries. Nickel extraction processes can be broadly categorized into pyrometallurgical and hydrometallurgical processes. Pyrometallurgical nickel-iron processes require high-grade nickel ore. With the continuous depletion of nickel resources, high-pressure acid leaching is becoming increasingly widespread. High-pressure acid leaching has lower requirements for nickel ore grade, but it generates a large amount of waste slag throughout the smelting process; for every ton of nickel metal produced, 100-200 tons of tailings are generated.

[0003] With the continuous increase in nickel metal production capacity, the large accumulation of tailings has become a significant environmental problem. Excessive tailings accumulation can easily lead to mudslides during heavy rainfall and poses a risk of dam collapse. Currently, the main disposal solution for tailings is paid landfill, but due to the massive volume of tailings, landfilling is not economically viable. The iron content in tailings is typically 30%-50%. If the iron metal can be extracted from the tailings, it can be used for iron and steel production, thus possessing certain potential development and utilization value.

[0004] CN117587226A discloses a method and system for the resource utilization of laterite nickel ore leaching tailings. The method includes: mixing laterite nickel ore leaching tailings with a flux to obtain a mixture; subjecting the mixture to melting and slag formation for desulfurization to obtain slag and SO2-containing flue gas; and mixing the slag with a reducing agent for reduction and iron extraction to obtain molten iron, iron extraction slag, and coal gas.

[0005] CN117403057A discloses a method for treating acid leaching slag from laterite nickel ore and an active material. The method includes the following steps: Step S1, mixing and pressing laterite nickel ore acid leaching slag, conditioning material, fluxing material and reducing agent to obtain a pre-product; Step S2, calcining the pre-product to obtain hot-burned slag and hot flue gas, the hot flue gas being used for acid production; Step S3, magnetically separating the hot-burned slag to obtain refined iron and tailings; Step S4, mixing and grinding the tailings, active material and activating material to obtain the active material.

[0006] The above-mentioned recycling methods have problems such as high energy consumption or low purity of iron, and produce a lot of by-products during the recycling process, resulting in poor practical application effects. Summary of the Invention

[0007] The purpose of this invention is to provide a method for recycling tailings from laterite nickel ore. This invention solves the problems of excessive accumulation of tailings from laterite nickel ore, paid landfilling, and difficulty in resource utilization. It prepares sponge iron from the tailings of laterite nickel ore hydrometallurgical process, resulting in low energy consumption and high-grade sponge iron. The magnetic separation tailings obtained during the recycling process can be used to produce building materials and cement and other by-products.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] This invention provides a method for recovering tailings from laterite nickel ore, the method comprising the following steps:

[0010] (1) After the tailings of laterite nickel ore are slurried, they are acid leached to obtain leaching residue;

[0011] (2) The leaching residue is mixed with a reducing agent for reduction desulfurization treatment to obtain reduced residue;

[0012] (3) After the reduction slag is subjected to ultrafine grinding, it is subjected to first magnetic separation to obtain the first magnetic separation material;

[0013] (4) The first magnetic separator is mixed with a dispersant and subjected to a second magnetic separation process to obtain the second magnetic separator;

[0014] (5) The second magnetic separator is subjected to alkaline washing and purification treatment and dried to obtain sponge iron.

[0015] The first and second magnetic separation processes of this invention are both liquid systems that require the addition of water to form a slurry.

[0016] This invention recycles tailings from laterite nickel ore. First, acid leaching removes some Al, S, and Ca from the tailings. Then, the acid-leached tailings undergo direct reduction desulfurization treatment, achieving direct iron reduction and sulfur removal without the need for additional high-temperature roasting desulfurization. The flue gas from the roasting section can be used to produce sulfuric acid, feeding back into the high-pressure acid leaching process, thus achieving the recycling of sulfur in the entire wet high-pressure acid leaching process. The resulting reduction tailings are ground into ultrafine powder and then subjected to a first magnetic separation to remove excess carbon. A second magnetic separation further improves iron recovery and the removal rate of non-magnetic substances. The tailings from the second magnetic separation are returned to the first magnetic separation treatment. Finally, alkaline washing further removes SiO2 from the concentrate, improving the grade of sponge iron and yielding high-purity sponge iron. The byproduct of the recycling process, the magnetic separation tailings, can be used to produce building materials and cement, among other byproducts, without environmental pollution.

[0017] Preferably, the tailings of laterite nickel ore in step (1) includes any one or a combination of at least two of the following: leaching residue from high-pressure acid leaching of laterite nickel ore, neutralization residue after neutralization of laterite nickel ore, or iron-aluminum slag obtained from the iron-aluminum section of laterite nickel ore.

[0018] Preferably, the solid-liquid mass ratio of the slurry is 1:(3~5), for example: 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Preferably, the acid leaching solution in step (1) includes hydrochloric acid.

[0020] This invention uses hydrochloric acid as the leaching agent for acid leaching. Industrial hydrochloric acid is cheaper than industrial sulfuric acid, and sulfuric acid, when used as a leaching agent, introduces sulfur (S). Sulfuric acid also cannot remove Al (aluminum and vanadium) present in the slag, nor can it remove Ca (Ca) present in the form of CaSO4. Hydrochloric acid, however, can react with and remove the vast majority of CaSO4. Using hydrochloric acid as the leaching agent solves the problem of CaSO4 encapsulation, facilitating subsequent direct reduction desulfurization and achieving total recovery of tailings from laterite nickel ore hydrometallurgical processes. Leaching slag, neutralization slag, and iron-aluminum slag can all be recovered.

[0021] Preferably, the pH of the acid leaching treatment in step (1) is 0.1~0.5, for example: 0.1, 0.2, 0.3, 0.4 or 0.5, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] Preferably, the acid leaching temperature in step (1) is 70℃~80℃, for example: 70℃, 72℃, 75℃, 78℃ or 80℃, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0023] Preferably, the acid leaching time in step (1) is 2h to 6h, for example: 2h, 3h, 4h, 5h or 6h, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0024] Preferably, after the acid leaching treatment in step (1), the leaching residue is washed with water and then dried.

[0025] Preferably, the solid-liquid mass ratio of the water washing treatment is 1:(2~4), for example: 1:2, 1:2.5, 1:3, 1:3.5 or 1:4, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Preferably, the number of water washing treatments is 2 to 5 times, for example: 2 times, 3 times, 4 times or 5 times.

[0027] Preferably, the reducing agent in step (2) includes any one or a combination of at least two of coke, anthracite, lignite, semi-coke or activated carbon. Typical but non-limiting combinations include a combination of coke and anthracite, a combination of lignite and semi-coke, or a combination of semi-coke and activated carbon.

[0028] Preferably, the mass ratio of the leaching residue to the reducing agent is 1:(0.2~0.4), for example: 1:0.2, 1:0.25, 1:0.3, 1:0.35 or 1:0.4, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the temperature of the reduction desulfurization treatment in step (2) is 1100℃~1300℃, for example: 1100℃, 1150℃, 1200℃, 1250℃ or 1300℃, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0030] This invention achieves desulfurization of leaching residue during high-temperature reduction without the need for additional oxidation roasting desulfurization processes. Metallic iron can be obtained at low temperatures (<1200℃), saving energy, reducing consumption, and lowering costs.

[0031] Preferably, the reduction desulfurization treatment time in step (2) is 3h to 5h, for example: 3h, 3.5h, 4h, 4.5h or 5h, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0032] Preferably, the reduction slag is subjected to water quenching after the reduction desulfurization treatment in step (2).

[0033] Preferably, the grinding concentration of the ultrafine grinding process in step (3) is 15% to 35%, for example: 15%, 18%, 20%, 25%, 30% or 35%, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] The ultrafine grinding process described in this invention is a wet grinding process, which requires the addition of water. The slurry concentration is calculated as: solid mass / (solid mass + water mass).

[0035] The Fe, Al, Si, and S components in laterite nickel ore tailings are extremely fine in size and exhibit encapsulation and intergrowth relationships. This invention can improve the subsequent magnetic separation effect through ultrafine grinding technology.

[0036] Preferably, the material obtained by the ultrafine grinding process in step (3) has a D50 < 10 μm.

[0037] Preferably, in step (3), the slurry concentration of the first magnetic separation process is 10% to 30%, for example: 10%, 15%, 20%, 25% or 30%, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0038] Preferably, the magnetic field strength of the first magnetic separation process in step (3) is 200mT~350mT, for example: 200mT, 220mT, 250mT, 300mT or 350mT, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the dispersant in step (4) comprises sodium hexametaphosphate.

[0040] Preferably, based on the mass of the first magnetic separator as 100%, the mass ratio of the dispersant is 0.05% to 0.1%, for example: 0.05%, 0.06%, 0.08%, 0.09% or 0.1%, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0041] Preferably, the slurry concentration of the second magnetic separation process in step (4) is 10% to 50%, for example: 10%, 20%, 30%, 40% or 50%, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the magnetic field strength of the second magnetic separation process in step (4) is 120mT~180mT, for example: 120mT, 140mT, 150mT, 160mT or 180mT, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0043] Preferably, the alkaline solution used in the alkaline washing and purification process in step (5) includes a sodium hydroxide solution.

[0044] Preferably, the molar concentration of the sodium hydroxide solution is 0.1 mol / L to 4 mol / L, for example: 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L or 4 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the alkaline washing and purification treatment in step (5) is followed by water washing.

[0046] Preferably, the drying method in step (5) includes vacuum drying.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present invention recovers sponge iron from the tailings of laterite nickel ore. The flue gas generated during the recovery process can be used to prepare sulfuric acid and then feed back into the high-pressure acid leaching process of laterite nickel ore. The by-product magnetic separation tailings can be used to produce building materials and cement and other by-products.

[0049] (2) The method for recovering laterite nickel ore tailings described in this invention yields sponge iron with a grade of over 88% and an iron recovery rate of over 88%, while the sulfur impurity content is below 0.03%. This invention uses hydrochloric acid as a leaching agent, which solves the problem of calcium sulfate encapsulation. Desulfurization and reduction can be completed simultaneously without reaching the melting temperature, saving energy, reducing consumption, and lowering costs. Ultimately, sponge iron with a TFe content of 90% and a sulfur content below 0.03 wt.% can be obtained. Attached Figure Description

[0050] Figure 1 This is a process flow diagram of the method for recovering tailings from laterite nickel ore provided in an embodiment of the present invention. Detailed Implementation

[0051] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0052] The mass composition of each metal element in the laterite nickel ore tailings used in the embodiments and comparative examples of this invention is shown in Table 1 below:

[0053] Table 1

[0054]

[0055] Example 1

[0056] This embodiment provides a method for recovering tailings from laterite nickel ore, the method comprising the following steps:

[0057] (1) Take 1 kg of lateritic nickel ore raw material, add water at a solid-liquid mass ratio of 1:4 to form a slurry, add hydrochloric acid to adjust the pH to 0.25, and acid leaching at 75℃ for 4 h. After the reaction is completed, wash the filter residue three times with water at a solid-liquid ratio of 1:3. After washing, dry to obtain leaching residue;

[0058] (2) The leaching residue and anthracite were mixed at a mass ratio of 1:0.2 and placed in a reduction furnace for direct reduction desulfurization treatment. The temperature of the reduction desulfurization treatment was 1200℃ and the reduction time was 3h. After the reduction reaction was completed, the roasted residue was placed in prepared cold water for water quenching. After cooling to room temperature, the reduced residue was obtained.

[0059] (3) The reduction slag was subjected to ultrafine grinding using a vertical stirred mill with circulation. The grinding concentration was 25%. The slag was ball-milled until D90 < 10 μm. After ball milling, the slag was subjected to a first magnetic separation process to obtain the first magnetic material. The magnetic field strength of the first magnetic separation process was 250 mT, and the slurry concentration of the first magnetic separation process was 20%.

[0060] (4) Sodium hexametaphosphate is mixed with the first magnetic separation material according to the mass ratio of the first magnetic separation material: sodium hexametaphosphate = 100: 0.08 and then subjected to a second magnetic separation process. The magnetic field strength of the second magnetic separation process is 180 mT and the slurry concentration of the second magnetic separation process is 25%. After the magnetic separation is completed, the second magnetic separation material and tailings are obtained. The tailings are returned to the first magnetic separation process.

[0061] (5) The second magnetic separator was purified by alkaline washing with 1 mol / L sodium hydroxide solution at 25°C for 3 hours. Finally, it was washed three times with water, filtered, and dried in a vacuum oven to obtain sponge iron.

[0062] Example 2

[0063] This embodiment provides a method for recovering tailings from laterite nickel ore, the method comprising the following steps:

[0064] (1) Take 1 kg of lateritic nickel ore raw material, add water to make a slurry at a solid-liquid mass ratio of 1:3, add hydrochloric acid to adjust the pH to 0.1, and acid leaching at 70℃ for 6 h. After the reaction is completed, wash the filter residue with water four times at a solid-liquid ratio of 1:4. After washing, dry to obtain leaching residue;

[0065] (2) The leaching residue and coke were mixed at a mass ratio of 1:0.3 and placed in a reduction furnace for direct reduction desulfurization treatment. The temperature of the reduction desulfurization treatment was 1100℃ and the reduction time was 5h. After the reduction reaction was completed, the roasted residue was placed in prepared cold water for water quenching. After cooling to room temperature, the reduced residue was obtained.

[0066] (3) The reduction slag was subjected to ultrafine grinding using a vertical stirred mill with circulation. The grinding concentration was 15%. The slag was ball-milled until D90 < 10 μm. After ball milling, the slag was subjected to a first magnetic separation process to obtain the first magnetic material. The magnetic field strength of the first magnetic separation process was 200 mT, and the slurry concentration of the first magnetic separation process was 10%.

[0067] (4) Sodium hexametaphosphate is mixed with the first magnetic separation material according to the mass ratio of the first magnetic separation material: sodium hexametaphosphate = 100: 0.05 and then subjected to a second magnetic separation process. The magnetic field strength of the second magnetic separation process is 150 mT and the slurry concentration of the second magnetic separation process is 10%. After the magnetic separation is completed, the second magnetic separation material and tailings are obtained. The tailings are returned to the first magnetic separation process.

[0068] (5) The second magnetic separator was purified by alkaline washing with 0.1 mol / L sodium hydroxide solution at 25°C for 4 hours. Finally, it was washed three times with water, filtered, and dried in a vacuum oven to obtain sponge iron.

[0069] Example 3

[0070] This embodiment provides a method for recovering tailings from laterite nickel ore, the method comprising the following steps:

[0071] (1) Take 1 kg of lateritic nickel ore raw material, add water at a solid-liquid mass ratio of 1:5 to form a slurry, add hydrochloric acid to adjust the pH to 0.5, and acid leaching at 80℃ for 2 h. After the reaction is completed, wash the filter residue with water four times at a solid-liquid ratio of 1:2. After washing, dry to obtain leaching residue;

[0072] (2) The leaching residue and lignite were mixed at a mass ratio of 1:0.4 and placed in a reduction furnace for direct reduction desulfurization treatment. The temperature of the reduction desulfurization treatment was 1300℃ and the reduction time was 3h. After the reduction reaction was completed, the roasted residue was placed in prepared cold water for water quenching. After cooling to room temperature, the reduced residue was obtained.

[0073] (3) The reduction slag was subjected to ultrafine grinding using a vertical stirred mill with circulation. The grinding concentration was 35%. The slag was ball-milled until D90 < 10 μm. After ball milling, the slag was subjected to a first magnetic separation process to obtain the first magnetic material. The magnetic field strength of the first magnetic separation process was 350 mT, and the slurry concentration of the first magnetic separation process was 30%.

[0074] (4) Sodium hexametaphosphate is mixed with the first magnetic separation material according to the mass ratio of the first magnetic separation material: sodium hexametaphosphate = 100: 0.1 and then subjected to a second magnetic separation process. The magnetic field strength of the second magnetic separation process is 120 mT and the slurry concentration of the second magnetic separation process is 50%. After the magnetic separation is completed, the second magnetic separation material and tailings are obtained. The tailings are returned to the first magnetic separation process.

[0075] (5) The second magnetic separator was purified by alkaline washing with 4 mol / L sodium hydroxide solution at 25°C for 4 hours. Finally, it was washed three times with water, filtered, and dried in a vacuum oven to obtain sponge iron.

[0076] Example 4

[0077] The only difference between this embodiment and Example 1 is that the pH in step (1) is 1, while the other conditions and parameters are exactly the same as in Example 1.

[0078] Example 5

[0079] The only difference between this embodiment and embodiment 1 is that the leaching residue in step (2) is mixed with anthracite at a mass ratio of 1:0.1, while the other conditions and parameters are exactly the same as in embodiment 1.

[0080] Example 6

[0081] The only difference between this embodiment and embodiment 1 is that the leaching residue in step (2) is mixed with anthracite at a mass ratio of 1:0.5, while the other conditions and parameters are exactly the same as in embodiment 1.

[0082] Example 7

[0083] The only difference between this embodiment and embodiment 1 is that the temperature of the reduction desulfurization treatment in step (2) is 1000℃, while the other conditions and parameters are exactly the same as in embodiment 1.

[0084] Example 8

[0085] The only difference between this embodiment and embodiment 1 is that the temperature of the reduction desulfurization treatment in step (2) is 1500℃, while the other conditions and parameters are exactly the same as in embodiment 1.

[0086] Example 9

[0087] The only difference between this embodiment and embodiment 1 is that the D90 of the material obtained after the ultrafine grinding process in step (3) is 20 μm. Other conditions and parameters are exactly the same as in embodiment 1.

[0088] Example 10

[0089] The only difference between this embodiment and embodiment 1 is that the magnetic field strength of the first magnetic separation in step (3) is 100mT, while the other conditions and parameters are exactly the same as in embodiment 1.

[0090] Example 11

[0091] The only difference between this embodiment and embodiment 1 is that the magnetic field strength of the first magnetic separation in step (3) is 400mT, while the other conditions and parameters are exactly the same as in embodiment 1.

[0092] Example 12

[0093] The only difference between this embodiment and embodiment 1 is that the magnetic field strength of the second magnetic separation in step (4) is 200mT, while the other conditions and parameters are exactly the same as in embodiment 1.

[0094] Comparative Example 1

[0095] The only difference between this comparative example and Example 1 is that the ultrafine grinding process is not performed; all other conditions and parameters are exactly the same as in Example 1.

[0096] Comparative Example 2

[0097] The only difference between this comparative example and Example 1 is that the second magnetic separation process is not performed; all other conditions and parameters are exactly the same as in Example 1.

[0098] Performance testing:

[0099] The sponge iron prepared in the examples and comparative examples was tested, and the test results are shown in Table 2:

[0100] Table 2

[0101]

[0102] As can be seen from Table 2, as obtained from Examples 1-3, the sponge iron obtained by the recovery method of laterite nickel ore tailings described in this invention can reach a grade of over 88%, an iron recovery rate of over 88%, and an S impurity content of less than 0.03 wt.%.

[0103] A comparison of Examples 1 and 4 shows that during the recovery process of laterite nickel ore tailings described in this invention, the pH of the acid leaching treatment affects the recovery effect. Controlling the pH of the acid leaching treatment at 0.1~0.5 results in a better recovery effect. If the pH of the acid leaching treatment is too high, impurities such as calcium in the laterite nickel ore tailings cannot be leached out, affecting the subsequent reduction and magnetic separation effects.

[0104] A comparison of Examples 1 and 5-6 shows that the amount of reducing agent added during the recovery process of laterite nickel ore tailings described in this invention affects the recovery effect. Controlling the mass ratio of leaching residue to reducing agent at 1:(0.2~0.4) results in a better recovery effect. If the amount of reducing agent added is too high, the reduction effect will not be further improved, which not only wastes the reducing agent but also introduces excessive carbon impurities, affecting the purity of subsequent magnetic separation and the obtained sponge iron. If the amount of reducing agent added is too low, the reduction of iron oxides will be incomplete, which is not conducive to subsequent magnetic separation and affects the quality of sponge iron.

[0105] A comparison of Examples 1 and 7-8 shows that, in the recovery process of laterite nickel ore tailings described in this invention, the temperature of the reduction desulfurization treatment affects the recovery effect. Controlling the reduction desulfurization treatment temperature between 1100℃ and 1300℃ yields better recovery results. If the temperature is too high, energy consumption increases without a significant improvement in efficiency; conversely, if the temperature is too low, the desulfurization rate will be low.

[0106] Fe2O3 cannot be completely reduced to elemental Fe, which means that Fe cannot be completely separated from impurities such as Al, Si, and Cr. As a result, Fe is often entrained, intergrowth, or embedded in other substances, affecting the grade and recovery rate of magnetic concentrate.

[0107] A comparison of Examples 1 and 9 shows that, in the recovery process of the laterite nickel ore tailings described in this invention, the particle size of the material obtained by ultrafine grinding affects the recovery effect. Controlling the D90 of the material obtained by ultrafine grinding to within 10 μm results in a better recovery effect. If the particle size of the material obtained by ultrafine grinding is too high, the magnetic minerals and non-magnetic minerals will not be fully dissociated, reducing the separation effect. Impurities such as silicates may be wrapped in iron particles, making them difficult to separate by magnetic separation. In addition, large particles have a small specific surface area, resulting in incomplete alkaline washing reaction and affecting purification.

[0108] A comparison of Examples 1 and 10-11 shows that during the recovery process of laterite nickel ore tailings described in this invention, the magnetic field strength of the first magnetic separator affects the recovery effect. Controlling the magnetic field strength of the first magnetic separator between 200mT and 350mT results in a better recovery effect. If the magnetic field strength of the first magnetic separator is too high, it will lead to excessive inclusion of weak magnetic impurities such as fir olivine, reducing the purity of the first magnetic separator material. If the magnetic field strength of the first magnetic separator is too low, the recovery rate of the target magnetic minerals will decrease, resulting in iron loss.

[0109] A comparison of Examples 1 and 12 shows that during the recovery process of laterite nickel ore tailings described in this invention, the magnetic field strength of the second magnetic separator affects the recovery effect. Controlling the magnetic field strength of the second magnetic separator at 120mT~180mT results in a better recovery effect. If the magnetic field strength of the second magnetic separator is too high, a small amount of weakly magnetic impurities, such as iron-containing silicates, will be adsorbed during the magnetic separation process, affecting the final purity of the sponge iron.

[0110] As can be seen from the comparison between Example 1 and Comparative Example 1, the present invention can significantly improve the effect of subsequent magnetic separation through ultrafine grinding, avoid impurities being wrapped in iron particles, and improve the impurity removal effect.

[0111] As can be seen from the comparison between Example 1 and Comparative Example 2, the present invention employs a two-stage magnetic separation. The first magnetic separation uses a higher magnetic field strength to recover as many magnetic minerals as possible, minimize iron loss, and ensure a high recovery rate. The second magnetic separation uses a lower magnetic field strength to selectively separate weakly magnetic impurities, thereby improving the iron grade of the final product. This approach balances high recovery rate and high purity, making it more suitable for the efficient recovery of laterite nickel ore tailings than single-stage magnetic separation.

[0112] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for recovering tailings from laterite nickel ore, characterized in that, The recycling method includes the following steps: (1) After the tailings of laterite nickel ore are slurried, they are acid leached to obtain leaching residue; (2) The leaching residue is mixed with a reducing agent for reduction desulfurization treatment to obtain reduced residue; (3) After the reduction slag is subjected to ultrafine grinding, it is subjected to first magnetic separation to obtain the first magnetic separation material; (4) The first magnetic separator is mixed with a dispersant and subjected to a second magnetic separation process to obtain the second magnetic separator; (5) The second magnetic separator is subjected to alkaline washing and purification treatment and dried to obtain sponge iron.

2. The recycling method as described in claim 1, characterized in that, The tailings of laterite nickel ore in step (1) include any one or a combination of at least two of the following: leaching residue from high-pressure acid leaching of laterite nickel ore, neutralization residue after neutralization of laterite nickel ore, or iron-aluminum residue obtained from the iron-aluminum section of laterite nickel ore. Preferably, the solid-liquid mass ratio of the slurry is 1:(3~5).

3. The recycling method as described in claim 1 or 2, characterized in that, The acid leaching solution used in step (1) includes hydrochloric acid; Preferably, the pH of the acid leaching treatment in step (1) is 0.1~0.5; Preferably, the acid leaching temperature in step (1) is 70℃~80℃; Preferably, the acid leaching treatment in step (1) takes 2 to 6 hours.

4. The recycling method according to any one of claims 1-3, characterized in that, After the acid leaching treatment in step (1), the leaching residue is washed with water and then dried. Preferably, the solid-liquid mass ratio of the water washing treatment is 1:(2~4); Preferably, the water washing process is performed 2 to 5 times.

5. The recycling method according to any one of claims 1-4, characterized in that, The reducing agent in step (2) includes any one or a combination of at least two of the following: coke, anthracite, lignite, semi-coke, or activated carbon; Preferably, the mass ratio of the leaching residue to the reducing agent is 1:(0.2~0.4).

6. The recycling method according to any one of claims 1-5, characterized in that, The temperature of the reduction desulfurization treatment in step (2) is 1100℃~1300℃; Preferably, the reduction desulfurization treatment in step (2) takes 3 to 5 hours. Preferably, the reduction slag is subjected to water quenching after the reduction desulfurization treatment in step (2).

7. The recycling method according to any one of claims 1-6, characterized in that, The grinding concentration of the ultrafine grinding process in step (3) is 15%~35%; Preferably, the material obtained by the ultrafine grinding process in step (3) has a D50 < 10 μm.

8. The recycling method according to any one of claims 1-7, characterized in that, Step (3) The slurry concentration of the first magnetic separation treatment is 10%~30%; Preferably, the magnetic field strength of the first magnetic separation process in step (3) is 200mT~350mT.

9. The recycling method according to any one of claims 1-8, characterized in that, The dispersant in step (4) includes sodium hexametaphosphate; Preferably, based on the mass of the first magnetically separated material being 100%, the mass ratio of the dispersant is 0.05% to 0.1%; Preferably, in step (4), the slurry concentration of the second magnetic separation process is 10%~50%; Preferably, the magnetic field strength of the second magnetic separation process in step (4) is 120mT~180mT.

10. The recycling method according to any one of claims 1-9, characterized in that, The alkaline solution used in the alkaline washing and purification process in step (5) includes sodium hydroxide solution; Preferably, the molar concentration of the sodium hydroxide solution is 0.1 mol / L to 4 mol / L; Preferably, the alkaline washing and purification treatment in step (5) is followed by water washing; Preferably, the drying method in step (5) includes vacuum drying.

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