A method for recovering iron concentrate from laterite nickel ore

Abstract

This invention provides a method for recovering iron concentrate from laterite nickel ore. The method includes: pretreating the laterite nickel ore with alkaline leaching to obtain iron-rich pretreated material; mixing a biomass reducing agent and the iron-rich pretreated material evenly, and then performing reduction roasting to obtain roasted material; and grinding and magnetically separating the roasted material to obtain iron concentrate. This invention, through a combined processing technology of alkaline leaching pretreatment, reduction roasting, and magnetic separation of laterite nickel ore, can obtain iron concentrate products that meet national standards. Simultaneously, the non-magnetic tailings material generated after magnetic separation, due to its stable physical properties, can be used as building material, thus realizing the cascade utilization and full-process value-added of laterite nickel ore resources.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to a method for recovering iron concentrate from laterite nickel ore. Background Technology

[0002] Research on iron concentrate recovery from laterite nickel ore mainly focuses on its resource characteristics and the limitations of existing processes. With the increasing depletion of high-grade sulfide nickel ore, laterite nickel ore, accounting for approximately 70% of global nickel resources, has become an important source for extracting valuable metals such as nickel, cobalt, and iron. Among them, limonite-type laterite ore, characterized by low nickel and high iron content (typically 25%–50%), represents a potential high-quality iron resource. However, this type of ore has a complex mineral composition (often containing limonite, serpentine, etc.), fine-grained iron minerals, and is closely associated with impurities such as aluminum, silicon, sulfur, and phosphorus, making it difficult to directly obtain qualified iron concentrate using traditional beneficiation methods. To achieve efficient iron resource recovery, various technical routes have been developed both domestically and internationally, including the following:

[0003] Pyrometallurgical processes: As a traditional method, nickel and iron are converted into metals or magnetic minerals through high-temperature reduction, followed by magnetic separation. The main technical directions include: Reduction roasting-magnetic separation process: Ore or metallurgical slag is mixed with a reducing agent (such as coal, coke, biochar, etc.) and additives, and then reduced and roasted at high temperatures. This converts weakly magnetic hematite or goethite into strongly magnetic magnetite or metallic iron, which is then separated by magnetic separation to obtain iron concentrate. When using coal as a reducing agent, by controlling the roasting conditions, iron concentrate with a grade >55% and a recovery rate of approximately 65%~80% can be obtained from raw materials containing 25%~40% iron. After optimization, the grade can reach over 60%. However, this process has high energy consumption, the reducing agent may introduce impurities or cause environmental impact, and impurities such as sulfur in the raw materials directly affect the quality of the concentrate.

[0004] Solid-state metallization reduction-magnetic separation: A more thorough reduction method designed to reduce nickel and iron to nickel-iron alloy particles, which are then separated by magnetic separation to obtain nickel-iron concentrate. This process typically requires higher temperatures (>1200℃) and longer reduction times to obtain high-grade nickel-iron products, but it also consumes more energy.

[0005] Hydrometallurgical processes: Primarily used for extracting nickel and cobalt, but the resulting leaching residue is rich in iron, making it an important research subject for iron concentrate recovery. Representative technologies include: Reduction roasting-ammonia leaching-magnetic separation: This process has been industrialized. It first selectively reduces and roasts laterite nickel ore, then extracts nickel and cobalt through ammonia leaching, and finally recovers iron concentrate from the ammonia leaching residue through magnetic separation. Industrial practice shows that processing ore containing approximately 25% iron can yield iron concentrate with an iron grade >55%~60% and a recovery rate >65%, achieving comprehensive utilization of nickel and iron, but the process flow is relatively long.

[0006] Iron recovery process from acid leaching residue: After nickel and cobalt are extracted from laterite nickel ore by high-pressure or atmospheric-pressure acid leaching, a large amount of acid leaching residue containing iron (35%~55%) and silica is produced. However, it often contains harmful elements such as sulfur. Directly stockpiling it is both wasteful of resources and pollutes the environment.

[0007] The recovery of iron concentrate from acid leaching residue has become a research hotspot. In recent years, researchers have proposed the "mineral phase transformation-magnetic separation" technology, such as reducing roasting at 700℃ and a 30% CO atmosphere to transform hematite into magnetite, followed by grinding and magnetic separation to obtain iron concentrate with an iron grade of 52.00% and a recovery rate of 80.11%. Using hydrogen-assisted mineral phase transformation technology to treat high-sulfuric acid leaching residue not only increases the iron grade to 61.00% and the recovery rate to over 90%, but also achieves deep desulfurization. However, the economical and efficient removal of impurities such as sulfur and silicon from acid leaching residue remains a technical challenge.

[0008] Currently, the recovery of iron concentrate from laterite nickel ore faces the following challenges: impurities such as aluminum, silicon, sulfur, and phosphorus in the ore not only affect the formation and growth of magnetic minerals during reduction roasting but also directly reduce the grade and quality of the iron concentrate after magnetic separation, making it difficult to meet smelting standards. Traditional pyrometallurgical processes and some enhanced reduction processes have high energy consumption. Although hydrometallurgical processes can comprehensively recover multiple metals, they are lengthy, consume large amounts of reagents, and generate a large amount of waste residue (such as acid leaching residue), resulting in high treatment costs. Many processes focus on recovering nickel and cobalt while neglecting iron recovery, or the recovered iron concentrate is of poor quality, leading to a large amount of iron resources entering the tailings and causing waste. The waste gas, wastewater, and waste residue (such as sulfur-containing tailings and acid leaching residue) generated by traditional processes pose a threat to the environment, necessitating the development of cleaner and lower-carbon recovery technologies.

[0009] Therefore, in order to meet the increasingly stringent impurity limits of iron concentrate for steelmaking and to achieve efficient removal of impurities such as aluminum, silicon, sulfur, and phosphorus, it is urgent to develop a new method for recovering iron concentrate from laterite nickel ore with higher separation efficiency and product quality. A new short-process technology that achieves efficient recovery of iron resources with lower energy consumption and cost and is environmentally friendly is a technical problem that urgently needs to be solved. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a method for recovering iron concentrate from laterite nickel ore. This invention utilizes a combined processing technique involving alkaline leaching pretreatment, reduction roasting, and magnetic separation of the laterite nickel ore to obtain iron concentrate products that meet national standards. Simultaneously, the non-magnetic tailings produced after magnetic separation, due to their stable physical properties, can be used as building materials, thus achieving the cascade utilization and value-added processing of laterite nickel ore resources. The method provided by this invention not only significantly improves the comprehensive utilization rate of laterite nickel ore resources but also effectively reduces solid waste emissions, creating considerable economic and environmental benefits and providing strong technical support for the green, low-carbon, and sustainable development of related industries.

[0011] To achieve this objective, the present invention adopts the following technical solution:

[0012] In a first aspect, the present invention provides a method for recovering iron concentrate from laterite nickel ore, the method comprising the following steps:

[0013] S1. Alkali leaching pretreatment is performed on laterite nickel ore to obtain iron-rich pretreated material;

[0014] S2. Mix the biomass reducing agent and the iron-rich pretreated material described in step S1 evenly, and then perform reduction roasting to obtain roasted material;

[0015] S3. The roasted material described in step S2 is subjected to magnetic separation to obtain iron concentrate.

[0016] This invention significantly improves the iron resource recovery rate and simultaneously reduces the content of impurities such as aluminum, silicon, sulfur, and phosphorus in iron concentrate products by combining alkaline leaching pretreatment, reduction roasting, and magnetic separation of laterite nickel ore (especially limonite-type laterite nickel ore). The synergistic effect of each process enhances the quality of iron concentrate and the overall recovery index. Specifically: First, an alkaline leaching pretreatment is performed to selectively dissolve acidic oxides such as SiO2 and Al2O3, as well as sulfur- and phosphorus-containing phases, in lateritic nickel ore, thereby achieving selective enrichment of iron and minimizing impurities entering the roasting stage, providing high-grade "clean" raw materials for subsequent processes. Then, reduction roasting is carried out, and by controlling the solid-solid reduction reaction process, the iron-containing phases such as hematite and goethite are directionally, efficiently, and to the maximum extent, transformed into strongly magnetic magnetite phases, creating optimal phase conditions for magnetic separation. Then, magnetic separation is carried out to obtain high-quality iron-rich magnetic concentrate, thereby improving the total iron recovery rate of limonite-type lateritic nickel ore and improving the quality of iron concentrate. Non-magnetic gangue is discharged as tailings and can be reused.

[0017] The close integration of the three processes described above in this invention not only achieves efficient recovery and quality improvement of low-grade iron resources in laterite nickel ore, but also provides a referable technical path for the comprehensive utilization of similar complex mineral resources. In addition, the process route is short, low-cost, and has a high metal recovery rate, and is both environmentally friendly and has industrialization promotion value, providing key technical support for the green development of laterite nickel ore resources.

[0018] The method provided by this invention overcomes the technical bottlenecks of existing processes, such as severe impurity entrainment and limited conversion efficiency of target minerals. It optimizes the mineral phase regulation and separation path from the source, thereby achieving selective enrichment and deep purification of iron components. By constructing a clean and efficient processing system, it not only provides technical support for the high-value utilization of iron resources in laterite nickel ore, but also helps to promote the upgrading of comprehensive utilization technology of mining resources and the sustainable development of related industrial chains.

[0019] As a preferred technical solution of the present invention, the laterite nickel ore in step S1 is laterite nickel ore that has undergone pretreatment.

[0020] Preferably, the pretreatment includes drying, crushing, grinding and sieving.

[0021] This invention pre-processes laterite nickel ore to obtain laterite nickel ore with uniform particle size and stable reactivity. Subsequent processes can significantly improve reduction roasting efficiency and iron metal recovery rate, reduce energy and reagent consumption, enhance process stability and product consistency, and reduce the risk of operational loss of control due to raw material fluctuations, laying a solid foundation for large-scale continuous production.

[0022] Preferably, the median grain size D50 of the laterite nickel ore in step S1 is 50μm-100μm, such as 50μm, 60μm, 70μm, 80μm, 90μm or 100μm.

[0023] Preferably, based on the total mass of the laterite nickel ore as 100wt%, the laterite nickel ore in step S1 includes 40wt%-45wt% iron, for example 40wt%, 41wt%, 42wt%, 43wt%, 44wt% or 45wt%, etc.; 2wt%-4.5wt% aluminum, for example 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt% or 4.5wt%, etc.; 2wt%-5wt% silicon, for example 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, etc.; 0wt%-2wt% sulfur, for example 0wt%, 0.5wt%, 1wt%, 1.5wt% or 2wt%, etc.; and 0wt%-1wt% phosphorus, for example 0wt%, 0.5wt% or 1wt%, etc.

[0024] As a preferred technical solution of the present invention, the alkaline solution used in the alkaline leaching pretreatment in step S1 includes sodium hydroxide solution and / or sodium carbonate solution.

[0025] Preferably, the concentration of the alkaline solution used in the alkaline leaching pretreatment in step S1 is 0.5 mol / L-2 mol / L, such as 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, or 2 mol / L.

[0026] In this invention, the concentration of the alkali solution used in the alkaline leaching pretreatment is controlled at 0.5 mol / L-2 mol / L. This allows for the selective dissolution of acidic oxides such as SiO2 and Al2O3, effectively disrupting the encapsulation structure of nickel-bearing minerals, exposing iron active sites, and simultaneously avoiding excessive dissolution that would result in the loss of valuable metals. This creates ideal mineralogical conditions for subsequent reduction roasting. If the concentration of the alkali solution is too high, it will lead to excessive dissolution of SiO2, forming soluble silicates, causing a sharp increase in slurry viscosity, making filtration difficult, resulting in significant iron leaching loss, increased alkali consumption costs, and high concentrations of OH... － Easy and Fe 3＋ / Al 3＋ Colloidal precipitates form and encapsulate particles, hindering the penetration of reducing agents and worsening roasting kinetics. If the concentration of the alkali solution is too low, it will lead to insufficient dissolution of SiO2 and Al2O3, and the encapsulation of iron by gangue minerals will not be effectively broken. The reduction roasting reaction activity will be insufficient, the iron recovery rate will be significantly reduced, and the reaction rate will be slow at low concentrations, the pretreatment time will be prolonged, the equipment capacity will be reduced, and the economic efficiency will deteriorate.

[0027] Preferably, the solid-liquid ratio of the laterite nickel ore and the alkaline solution in step S1 is 1g:(3-6)mL, for example, 1g:3mL, 1g:3.5mL, 1g:4mL, 1g:4.5mL, 1g:5mL, 1g:5.5mL or 1g:6mL, etc.

[0028] As a preferred technical solution of the present invention, the temperature of the alkaline leaching pretreatment in step S1 is 60°C-90°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C.

[0029] Preferably, the stirring speed of the alkaline leaching pretreatment in step S1 is 300rpm-600rpm, such as 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm or 600rpm.

[0030] Preferably, the time for the alkaline leaching pretreatment in step S1 is 1h-4h, for example 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h.

[0031] The temperature, stirring speed, and time of the alkaline leaching pretreatment in step S1 of this invention are coordinated to achieve efficient separation of impurities (elements) from iron.

[0032] Preferably, after the alkaline leaching pretreatment described in step S1, the process further includes solid-liquid separation, washing, and drying steps to obtain an iron-rich pretreated material.

[0033] The present invention obtains a leachate rich in impurities and an iron-rich solid residue after solid-liquid separation. The iron-rich solid residue is thoroughly washed to remove the residual solution and dissolved substances, and after drying, it can form a stable iron-rich pretreated material.

[0034] It should be noted that the present invention does not impose specific requirements or special limitations on the solid-liquid separation, washing and drying after alkaline leaching pretreatment. Commonly used solid-liquid separation, washing and drying methods in the art are applicable to the present invention. For example, it can be filtration, vacuum filtration or centrifugation. Deionized water can be used for washing, and as long as a completely dry iron-rich pretreated material can be obtained, it is acceptable. Those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0035] As a preferred technical solution of the present invention, in step S2, the amount of biomass reducing agent added is 2.5wt%-23.1wt% of the mass of the iron-rich pretreated material in step S1, such as 2.5wt%, 5wt%, 7.5wt%, 10wt%, 12.5wt%, 15wt%, 17.5wt%, 20wt%, 22.5wt%, or 23.1wt%.

[0036] This invention regulates the addition amount of biomass reducing agent to 2.5wt%-23.1wt% of the mass of the iron-rich pretreated material described in step S1. This enables efficient and selective conversion of iron oxides to the magnetite phase (Fe3O4), ensuring a high recovery rate of the magnetic iron phase while suppressing over-reduction and sintering, thus optimizing the balance between reducing agent utilization efficiency and production costs. Insufficient addition of biomass reducing agent leads to incomplete reduction, low Fe2O3→Fe3O4 conversion rate, large residual amount of non-magnetic iron oxides, and a significant decrease in iron recovery rate after magnetic separation. Reduction kinetics are limited, requiring extended roasting time for compensation, increasing energy consumption and reducing production capacity. Excessive addition of biomass reducing agent leads to over-reduction to generate metallic iron (Fe), severe particle sintering and agglomeration, deterioration of magnetic separation efficiency, and a decrease in iron concentrate grade. Furthermore, the surface of metallic iron is easily oxidized to regenerate Fe2O3 / FeO(OH), resulting in poor product stability. In addition, incomplete biomass combustion produces carbon deposits, polluting the iron concentrate and increasing ash content; reducing agent is wasted, flue gas treatment load increases, and production costs rise.

[0037] As a preferred technical solution of the present invention, the gas used in the reduction roasting in step S2 includes an inert gas.

[0038] Preferably, the inert gas includes nitrogen and / or argon.

[0039] Preferably, the holding temperature for reduction calcination in step S2 is 650°C-950°C, such as 650°C, 680°C, 700°C, 720°C, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, or 950°C.

[0040] As a preferred technical solution of the present invention, the heat preservation time of the reduction calcination in step S2 is 1h-4h, for example 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h.

[0041] This invention optimizes the following parameters: the amount of biomass reducing agent added is 2.5wt%-23.1wt% of the mass of the iron-rich pretreated material in step S1; the holding temperature of reduction roasting is 650°C-950°C; and the holding time of reduction roasting is 1h-4h. These parameters synergistically promote the directional transformation of iron oxides into strongly magnetic magnetite, maximize the magnetic conversion rate of the iron phase, create the best phase conditions for magnetic separation, and thus obtain higher quality iron concentrate (iron-rich magnetic concentrate).

[0042] As a preferred technical solution of the present invention, the preparation method of the biomass reducing agent in step S2 includes: carbonizing the biomass material under an inert atmosphere, and then activating it under a carbon dioxide atmosphere.

[0043] Preferably, the biomass material includes at least one of coconut shells, wheat straw, corn stalks, bamboo, rice straw, peanut shells, or tree branches.

[0044] Preferably, the inert atmosphere includes a nitrogen atmosphere and / or an argon atmosphere.

[0045] Preferably, the carbonization holding temperature is 350°C-600°C, such as 350°C, 400°C, 450°C, 500°C, 550°C or 600°C.

[0046] Preferably, the carbonization holding time is 80min-160min, such as 80min, 100min, 120min, 140min or 160min.

[0047] Preferably, the activation holding temperature is 350°C-600°C, such as 350°C, 400°C, 450°C, 500°C, 550°C or 600°C.

[0048] Preferably, the activation holding time is 40-70 minutes, such as 40 minutes, 50 minutes, 60 minutes or 70 minutes.

[0049] As a preferred technical solution of the present invention, before the magnetic separation in step S3, the roasting material in step S2 is further ground.

[0050] This invention improves the degree of dissociation between magnetic iron minerals and non-magnetic gangue by grinding the roasted material, laying the foundation for subsequent magnetic separation processes.

[0051] Preferably, the grinding includes ball milling.

[0052] Preferably, the ball milling time is 5 min to 15 min, such as 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min.

[0053] Preferably, the ball milling temperature is 20°C-30°C, such as 20°C, 22°C, 25°C, 28°C or 30°C.

[0054] Preferably, the rotational speed of the ball mill is 200rpm-500rpm, such as 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm or 500rpm.

[0055] As a preferred technical solution of the present invention, the magnetic separation in step S3 includes: mixing deionized water and the powder obtained after grinding evenly to obtain a magnetic separation slurry, and performing magnetic separation on the magnetic separation slurry.

[0056] Preferably, the magnetic field strength for magnetic separation in step S3 is 600Gs-2000Gs, such as 600Gs, 700Gs, 800Gs, 900Gs, 1000Gs, 1100Gs, 1200Gs, 1300Gs, 1400Gs, 1500Gs, 1600Gs, 1700Gs, 1800Gs, 1900Gs, or 2000Gs.

[0057] This invention regulates the magnetic field strength of magnetic separation to 600Gs-2000Gs, achieving an optimal balance between iron concentrate grade and iron recovery rate. If the magnetic field strength is too low, the magnetic force on the magnetic iron minerals will be insufficient to effectively overcome fluid resistance and gravity, resulting in a large loss of magnetic particles in the tailings, significantly reducing iron recovery rate and causing serious resource waste. Conversely, if the magnetic field strength is too high, non-magnetic or weakly magnetic impurities (such as intergrowths, inclusions, and residual silicates) will be mechanically entrained or magnetically captured, leading to a decrease in iron concentrate grade, an increase in aluminum and silicon impurity content, and increased energy consumption and maintenance costs for high-field-strength equipment.

[0058] Preferably, the mass ratio of the deionized water to the powder obtained after grinding is (20-60):1, such as 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1 or 60:1.

[0059] It should be noted that the present invention does not impose specific requirements or special limitations on the mixing of deionized water and the powder obtained after grinding. As long as the powder obtained after grinding can be uniformly dispersed, those skilled in the art can make adaptive selections and adjustments according to actual conditions. For example, it can be stirred for 10 minutes at 30°C and 400 rpm.

[0060] Preferably, after the magnetic separation described in step S3, the obtained magnetic material is further subjected to solid-liquid separation and drying to obtain iron concentrate.

[0061] It should be noted that the present invention does not impose specific requirements or special limitations on the solid-liquid separation and drying of magnetic materials. Commonly used solid-liquid separation and drying methods in the art are applicable to the present invention, such as filtration, vacuum filtration or centrifugation, as long as the powder can be completely dried. Those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0062] Compared with the prior art, the present invention has at least the following beneficial effects:

[0063] 1) This invention obtains iron concentrate products that meet national standards by sequentially performing alkaline leaching pretreatment, reduction roasting and magnetic separation on laterite nickel ore; at the same time, the non-magnetic tailings material generated after magnetic separation can be used as building material due to its stable physical properties, thus realizing the cascade utilization and full-process value-added of laterite nickel ore resources.

[0064] 2) The close integration of the above-mentioned alkaline leaching pretreatment, reduction roasting and magnetic separation processes in this invention not only achieves efficient recovery and quality improvement of low-grade iron resources in laterite nickel ore, but also provides a reference technical path for the comprehensive utilization of similar complex mineral resources. In addition, the process route is short, low-cost and high-metal recovery rate, and has both environmental friendliness and industrialization promotion value, providing key technical support for the green development of laterite nickel ore resources. Attached Figure Description

[0065] Figure 1 This is a flowchart of the method for recovering iron concentrate from laterite nickel ore provided by the present invention. Detailed Implementation

[0066] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0067] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0068] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0069] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0070] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0071] Figure 1 A flowchart of a method for recovering iron concentrate from laterite nickel ore provided by the present invention is shown. The method includes the following steps:

[0072] S1. Alkali leaching pretreatment is performed on laterite nickel ore to obtain iron-rich pretreated material;

[0073] S2. Mix the biomass reducing agent and the iron-rich pretreated material described in step S1 evenly, and then perform reduction roasting to obtain roasted material;

[0074] S3. The roasted material described in step S2 is subjected to magnetic separation to obtain iron concentrate.

[0075] The laterite nickel ore used in the specific embodiments of this invention has a water content of 33 wt%, and XRD analysis determined that its main phase is Ni3Si4O. 10 (OH)2 and FeO(OH) were detected by inductively coupled plasma optical emission spectrometry (ICP-OES), and the main elements and their contents are shown in Table 1.

[0076] Table 1

[0077]

[0078] Example 1

[0079] This embodiment provides a method for recovering iron concentrate from laterite nickel ore, the method comprising the following steps:

[0080] S1. The lateritic nickel ore was dried at 105℃ for 1440 min, then ground and crushed, and placed in a multi-size vibrating screen. After the above pretreatment, lateritic nickel ore with a median particle size D50 of 75 μm was obtained. Then it was placed in a 1 mol / L NaOH solution with a solid-liquid ratio of 1 g: 4 mL, heated to 60°C under stirring at 400 rpm and alkali leached for 2 h. After filtration, washing and drying at 105℃, iron-rich pretreated material was obtained.

[0081] S2. Mix the iron-rich pretreated material and biomass reducing agent evenly. The amount of biomass reducing agent added is 16.7 wt% of the mass of the iron-rich pretreated material. Carry out reduction roasting in a tube furnace under nitrogen atmosphere. Control the reduction roasting temperature at 900℃ and the reduction time at 2h to obtain roasted material.

[0082] The biomass reducing agent was prepared by the following method: coconut shells were crushed, rinsed with deionized water to remove surface impurities, dried at 100°C for 480 min, then carbonized at 500°C for 120 min under a nitrogen atmosphere, and naturally cooled to room temperature; the resulting product was activated at 500°C for 60 min under a carbon dioxide atmosphere, and naturally cooled to room temperature; the resulting material was crushed and ground in an agate mortar, passed through a 150-mesh sieve, and rinsed four times with deionized water to remove impurities, and then dried at 100°C for 680 min to obtain the above-mentioned biomass reducing agent;

[0083] S3. The roasted material is ball-milled at 400 rpm for 5 minutes, and then deionized water is added for slurry preparation. The mass ratio of deionized water to the powder obtained after grinding is 50:1. After stirring at 30℃ and 400 rpm for 10 minutes, a magnetic separation slurry is obtained. Then, the magnetic separation slurry is subjected to magnetic separation under a magnetic field strength of 600 Gs. The magnetic part is collected, filtered, and dried to obtain iron concentrate.

[0084] The non-magnetic components are collected, filtered, and dried before reuse.

[0085] Example 2

[0086] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S3, the magnetic separation slurry is magnetically separated under a magnetic field strength of 1000 Gs. The remaining preparation methods and parameters are consistent with those in Embodiment 1.

[0087] Example 3

[0088] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S1, the concentration of the NaOH solution is 2 mol / L, while the rest of the preparation methods and parameters remain the same as in Embodiment 1.

[0089] Example 4

[0090] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S2, the reduction roasting temperature is controlled at 750°C, while the remaining preparation methods and parameters are consistent with those in Embodiment 1.

[0091] Example 5

[0092] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S1, the solid-liquid ratio is 1g:5mL, while the remaining preparation methods and parameters are consistent with those in Embodiment 1.

[0093] Example 6

[0094] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S1, the ore is heated to 80°C for alkaline leaching, while the remaining preparation methods and parameters are consistent with those in Embodiment 1.

[0095] Example 7

[0096] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S1, the amount of biomass reducing agent added is 9.1 wt% of the mass of the iron-rich pretreated material, while the remaining preparation methods and parameters are consistent with Embodiment 1.

[0097] Example 8

[0098] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S2, the reduction time is 1 hour, while the remaining preparation methods and parameters are consistent with those in Embodiment 1.

[0099] Example 9

[0100] This embodiment provides a method for recovering iron concentrate from laterite nickel ore, the method comprising the following steps:

[0101] S1. The lateritic nickel ore was dried at 105℃ for 1440 min, then ground and crushed, and placed in a multi-size vibrating screen. After the above pretreatment, lateritic nickel ore with a median particle size D50 of 50 μm was obtained. Then it was placed in a 0.5 mol / L NaOH solution with a solid-liquid ratio of 1 g: 6 mL, heated to 90°C and alkali leached for 1 h under stirring at 300 rpm. After filtration, washing and drying at 105℃, iron-rich pretreated material was obtained.

[0102] S2. Mix the iron-rich pretreated material and biomass reducing agent evenly. The amount of biomass reducing agent added is 2.5 wt% of the mass of the iron-rich pretreated material. Carry out reduction roasting in a tube furnace under nitrogen atmosphere. Control the reduction roasting temperature at 650℃ and the reduction time at 4h to obtain roasted material.

[0103] The biomass reducing agent was prepared by the following method: peanut shells were crushed, rinsed with deionized water to remove surface impurities, dried at 100℃ for 480 min, carbonized at 350℃ for 160 min under nitrogen atmosphere, and then naturally cooled to room temperature; the obtained product was activated at 600℃ for 40 min under carbon dioxide atmosphere, and then naturally cooled to room temperature; the obtained material was crushed and ground in an agate mortar, passed through a 150-mesh sieve, and rinsed 4 times with deionized water to remove impurities, and then dried at 100℃ for 680 min to obtain the above-mentioned biomass reducing agent;

[0104] S3. The roasted material is ball-milled at 200 rpm for 15 minutes, and then deionized water is added for slurry preparation. The mass ratio of deionized water to the powder obtained after grinding is 20:1. After stirring at 30℃ and 400 rpm for 10 minutes, a magnetic separation slurry is obtained. Then, the magnetic separation slurry is subjected to magnetic separation under a magnetic field strength of 2000 Gs. The magnetic part is collected, filtered, and dried to obtain iron concentrate.

[0105] The non-magnetic components are collected, filtered, and dried before reuse.

[0106] Example 10

[0107] This embodiment provides a method for recovering iron concentrate from laterite nickel ore, the method comprising the following steps:

[0108] S1. The lateritic nickel ore was dried at 105℃ for 1440 min, then ground and crushed, and placed in a multi-size vibrating screen. After the above pretreatment, lateritic nickel ore with a median particle size D50 of 100 μm was obtained. Then it was placed in a 2 mol / L NaOH solution with a solid-liquid ratio of 1 g: 3 mL, heated to 60°C and alkali leached for 4 h under stirring at 600 rpm. After filtration, washing and drying at 105℃, iron-rich pretreated material was obtained.

[0109] S2. Mix the iron-rich pretreated material and the biomass reducing agent evenly. The amount of biomass reducing agent added is 23.1 wt% of the mass of the iron-rich pretreated material. Carry out reduction roasting in a tube furnace under nitrogen atmosphere, control the reduction roasting temperature at 950℃ and the reduction time at 1 h to obtain roasted material.

[0110] The biomass reducing agent was prepared by the following method: wheat straw was crushed, rinsed with deionized water to remove surface impurities, dried at 100℃ for 480 min, then carbonized at 600℃ for 80 min under nitrogen atmosphere, and naturally cooled to room temperature; the obtained product was activated at 350℃ for 70 min under carbon dioxide atmosphere, and naturally cooled to room temperature; the obtained material was crushed and ground in an agate mortar, passed through a 150-mesh sieve, and rinsed 4 times with deionized water to remove impurities, and then dried at 100℃ for 680 min to obtain the above-mentioned biomass reducing agent;

[0111] S3. The roasted material was ball-milled at 500 rpm for 10 minutes, and then deionized water was added for slurry preparation. The mass ratio of deionized water to the powder obtained after grinding was 60:1. After stirring at 30℃ and 400 rpm for 10 minutes, a magnetic separation slurry was obtained. Then, the magnetic separation slurry was subjected to magnetic separation under a magnetic field strength of 1400 Gs. The magnetic part was collected, filtered, and dried to obtain iron concentrate.

[0112] The non-magnetic components are collected, filtered, and dried before reuse.

[0113] Example 11

[0114] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S1, the concentration of the NaOH solution is 0.25 mol / L, while the rest of the preparation methods and parameters remain the same as in Embodiment 1.

[0115] Example 12

[0116] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S1, the concentration of the NaOH solution is 2.25 mol / L, while the rest of the preparation methods and parameters remain the same as in Embodiment 1.

[0117] Example 13

[0118] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S1, the amount of biomass reducing agent added is 2 wt% of the mass of the iron-rich pretreated material, while the remaining preparation methods and parameters are consistent with Embodiment 1.

[0119] Example 14

[0120] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S1, the amount of biomass reducing agent added is 23.8 wt% of the mass of the iron-rich pretreated material, while the remaining preparation methods and parameters are consistent with Embodiment 1.

[0121] Example 15

[0122] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S2, the reduction roasting temperature is controlled at 600℃, while the remaining preparation methods and parameters are consistent with those in Embodiment 1.

[0123] Example 16

[0124] This embodiment provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Embodiment 1 is that in step S2, the reduction roasting temperature is controlled at 1000℃, while the remaining preparation methods and parameters are consistent with those in Embodiment 1.

[0125] In this embodiment, due to the excessively high reduction roasting temperature, the iron element in the resulting roasted material exists in the form of elemental iron and ferric silicate, and is not the target iron concentrate (magnetite phase Fe3O4) product.

[0126] Comparative Example 1

[0127] This comparative example provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Example 1 is that step S1, alkaline leaching pretreatment, is omitted. That is, the laterite nickel ore is directly mixed with biomass reducing agent and then subjected to reduction roasting. The remaining preparation methods and parameters are consistent with those of Example 1.

[0128] Comparative Example 2

[0129] This comparative example provides a method for recovering iron concentrate from laterite nickel ore. The difference between this method and Example 1 is that steps S1 and S2 are interchanged. That is, laterite nickel ore and biomass reducing agent are first mixed evenly and then subjected to reduction roasting. The resulting roasted material is then subjected to alkaline leaching pretreatment. The remaining preparation methods and parameters are consistent with those of Example 1.

[0130] The purity of the iron concentrate recovered in Examples 1-15 and Comparative Examples 1-2 was tested, and the specific results are shown in Table 2.

[0131] Table 2

[0132]

[0133] The test results show that:

[0134] (1) As can be seen from Examples 1-10, the present invention can obtain iron concentrate products that meet national standards by sequentially performing alkaline leaching pretreatment, reduction roasting, and magnetic separation on laterite nickel ore. Specifically, the purity of the iron concentrate can reach 61.25%-64.48%.

[0135] (2) As can be seen from Examples 1 and 11-12, the concentration of the alkaline solution used in the alkaline leaching pretreatment of the present invention is 0.5mol / L-2mol / L, which can achieve selective dissolution of acidic oxides such as SiO2 and Al2O3, effectively destroy the encapsulation structure of nickel-containing minerals, expose iron active sites, and avoid excessive dissolution causing loss of valuable metals, thus creating ideal mineralogical conditions for subsequent reduction roasting.

[0136] (3) As can be seen from Examples 1 and 13-14, the amount of biomass reducing agent added in this invention is 2.5wt%-23.1wt% of the mass of the iron-rich pretreated material in step S1. This can achieve efficient and selective conversion of iron oxides to magnetite phase (Fe3O4), while ensuring a high recovery rate of magnetic iron phase, suppressing excessive reduction and sintering, and optimizing the balance between reducing agent utilization efficiency and production cost.

[0137] (4) As can be seen from Examples 1 and 15-16, the present invention controls the holding temperature of reduction roasting to 650°C-950°C, which can make iron oxides directionally transform into a strongly magnetic magnetite phase (target phase). If the temperature is lower than 650°C or higher than 950°C, there will be problems of under-reduction or over-reduction, resulting in a reduction of the target phase or even failure to form the target phase.

[0138] (5) As can be seen from Example 1 and Comparative Example 1, if the alkaline leaching pretreatment is omitted in this invention, impurities enter the iron concentrate, resulting in a significant reduction in the purity of the iron concentrate. As can be seen from Example 1 and Comparative Example 2, if the present invention first performs reduction roasting and then alkaline leaching pretreatment, once high-temperature roasting occurs, iron and silicon have already reacted to form stable ferrosilicon. Subsequent alkaline leaching cannot effectively destroy or dissolve the already formed ferrosilicon crystal structure, and ferrosilicon will remain as an impurity in the product (coexisting with the iron concentrate), resulting in a significant reduction in the purity of the iron concentrate.

[0139] In summary, this invention, through a combined processing method of alkaline leaching pretreatment, reduction roasting, and magnetic separation of laterite nickel ore, yields iron concentrate products that meet national standards. Simultaneously, the non-magnetic tailings produced after magnetic separation, due to their stable physical properties, can be utilized as building materials, thus achieving the tiered utilization and value-added throughout the entire process of laterite nickel ore resources. The method provided by this invention not only significantly improves the comprehensive utilization rate of laterite nickel ore resources but also effectively reduces solid waste emissions, creating considerable economic and environmental benefits and providing strong technical support for the green, low-carbon, and sustainable development of related industries.

[0140] 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 iron concentrate from laterite nickel ore, characterized in that, The method includes the following steps: S1. Alkali leaching pretreatment is performed on laterite nickel ore to obtain iron-rich pretreated material; S2. Mix the biomass reducing agent and the iron-rich pretreated material described in step S1 evenly, and then perform reduction roasting to obtain roasted material; S3. The roasted material described in step S2 is subjected to magnetic separation to obtain iron concentrate.

2. The method according to claim 1, characterized in that, The median grain size D50 of the laterite nickel ore described in step S1 is 50μm-100μm; Preferably, based on the total mass of the laterite nickel ore being 100wt%, the laterite nickel ore in step S1 comprises 40wt%-45wt% iron, 2wt%-4.5wt% aluminum, 2wt%-5wt% silicon, 0wt%-2wt% sulfur and 0wt%-1wt% phosphorus.

3. The method according to claim 1 or 2, characterized in that, The alkaline solution used in the alkaline leaching pretreatment in step S1 includes sodium hydroxide solution and / or sodium carbonate solution; Preferably, the concentration of the alkaline solution used in the alkaline leaching pretreatment in step S1 is 0.5 mol / L-2 mol / L; Preferably, the solid-liquid ratio of the laterite nickel ore and the alkaline solution in step S1 is 1g:(3-6)mL.

4. The method according to any one of claims 1-3, characterized in that, The temperature of the alkaline leaching pretreatment in step S1 is 60°C-90°C; Preferably, the stirring speed for the alkaline leaching pretreatment in step S1 is 300 rpm to 600 rpm; Preferably, the alkaline leaching pretreatment time in step S1 is 1-4 hours; Preferably, after the alkaline leaching pretreatment described in step S1, the process further includes solid-liquid separation, washing, and drying steps to obtain an iron-rich pretreated material.

5. The method according to any one of claims 1-4, characterized in that, In step S2, the amount of biomass reducing agent added is 2.5wt%-23.1wt% of the mass of the iron-rich pretreated material in step S1.

6. The method according to any one of claims 1-5, characterized in that, The holding temperature for the reduction roasting in step S2 is 650°C-950°C.

7. The method according to any one of claims 1-6, characterized in that, The holding time for reduction roasting in step S2 is 1h-4h.

8. The method according to any one of claims 1-7, characterized in that, The preparation method of the biomass reducing agent in step S2 includes: carbonizing the biomass material under an inert atmosphere, followed by activation under a carbon dioxide atmosphere.

9. The method according to any one of claims 1-8, characterized in that, Before the magnetic separation in step S3, the roasted material in step S2 is further ground. Preferably, the grinding includes ball milling; Preferably, the ball milling time is 5-15 minutes; Preferably, the temperature of the ball mill is 20°C-30°C; Preferably, the rotational speed of the ball mill is 200 rpm to 500 rpm.

10. The method according to claim 9, characterized in that, Step S3, the magnetic separation includes: mixing deionized water and the powder obtained after grinding evenly to obtain a magnetic separation slurry, and performing magnetic separation on the magnetic separation slurry; Preferably, the magnetic field strength for magnetic separation in step S3 is 600Gs-2000Gs.

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