Method for recovering fine-grained iron oxide minerals

Abstract

The present invention provides a method for recovering fine-grained iron oxide minerals. The recovery method comprises: mixing a raw material to be processed containing fine-grained iron oxide minerals with an iron reducing agent and a nitrite for wet grinding to obtain a first ore; and subjecting the first ore to magnetic separation in a first magnetic field and selection in a second magnetic field in sequence to recover the fine-grained iron oxide minerals in the raw material to be processed. The present application constructs a coupled redox system with iron-nitrite-iron oxide and coordinates mechanical activation during wet grinding, so that the surface of the weakly magnetic fine-grained iron oxide minerals in the raw material to be processed can form a stable and uniform strong magnetic Fe3O4 oxide, thereby causing the fine-grained iron oxide minerals to relatively selectively agglomerate due to enhanced surface magnetism, thereby increasing the apparent particle size of the mineral separation, and providing a mineral physicochemical property basis for subsequent separation and sorting, thereby greatly improving the recovery efficiency of the fine-grained iron oxide mineral material.

Description

Technical Field

[0001] The present invention relates to the technical field of iron mineral separation, and in particular to a method for recovering fine-grained iron oxide minerals. Background Art

[0002] The selective separation of fine-grained iron oxide minerals is a long-standing challenge in the mineral processing industry. These minerals primarily originate from natural fine-grained iron oxide ores (such as hematite / limonite, oolitic hematite), as well as various iron-containing slags produced during metallurgy (e.g., red mud from aluminum smelting and iron-removing slag from acid leaching). These fine-grained iron oxide minerals are weakly magnetic, with particle sizes ranging from 0.1 to 50 μm. Due to their small particle size, low specific magnetic susceptibility, large surface area, and strong hydrophilicity, these minerals are difficult to effectively disperse, flocculate, and adsorb using conventional mineral processing equipment and processes. This results in low iron metal resource utilization, difficulty in recovery and enrichment, and significant disposal challenges for hazardous iron-containing solid waste within the metallurgical industry. Therefore, the effective processing and utilization of weakly magnetic fine-grained and ultrafine-grained iron oxide minerals has become a key priority for the mineral processing industry.

[0003] At present, many types of sorting, smelting and other processing technologies have been reported for processing fine / ultrafine iron oxide mineral materials, such as: 1) magnetic roasting-reseparation (including carbon thermal reduction and its derived magnetic roasting technology), but the problems with this type of process are low heat exchange and mass transfer efficiency during the processing, large carbon consumption and carbon emissions for materials with low iron content, and high production costs; 2) wet leaching purification and separation system, but the problem with this type of process is that it is often affected by the complex composition of the raw minerals, resulting in high consumption of acid / alkali reagents, and in order to accelerate the reaction process, temperature treatment is often required, which is also prone to produce secondary materials to be processed; 3) mineral processing and sorting, but the problem with this type of process is that, due to the particle size characteristics of the mineral particles, conventional sorting processes are difficult to achieve high sorting efficiency.

[0004] Currently, mineral separation is mostly used in this field. The mineral separation technology with relatively comparative advantages that has been reported is fine particle flocculation and agglomeration separation, which includes polymer flocculation and separation, hydrophobic flocculation and separation, magnetic agglomeration and magnetic seed agglomeration separation process, composite agglomeration separation process, etc.

[0005] Among them, flocculation agglomeration flotation separation, under the action of selective reagents, causes fine mineral particles to agglomerate, significantly increasing the apparent size of the target mineral to meet the particle size requirements of subsequent sorting operations. For example, reported reagents such as sodium fluoride, sodium hexametaphosphate, polyacrylamide, guar gum, starch, sodium oleate, and kerosene have achieved relatively good performance within a certain range for natural fine-grained iron oxide ore materials. However, the selective capture and modification of target iron minerals by these reagents is still restricted by factors such as mineral particle size, surface characteristics, and mineral composition. In particular, they have poor adaptability to extremely fine-grained iron oxide minerals and are generally unsuitable for fine-grained, cryptocrystalline, or amorphous, highly hydrophilic iron-containing oxide materials produced during metallurgical processes. Therefore, in terms of adaptability to impurity components or degree of crystallinity in the material, magnetic agglomeration separation is relatively advantageous.

[0006] At present, there are methods for magnetic agglomeration and separation of materials by adding fine-grained strong magnetic magnetic seeds, such as magnetite, ferrosilicon, artificial ferrite, magnetic fluid, etc., such as the patent "A strong magnetic-magnetic seed magnetization combined separation process for refractory ore powder (CN110787906A)", which proposes the use of artificial magnetic seeds to improve the utilization rate of iron. This type of separation method that promotes magnetic agglomeration by adding fine-grained magnetic seeds has a poor effect on effectively agglomerating the target minerals due to the huge difference in magnetic expression between the magnetic seeds and the minerals to be processed; the magnetic properties of weakly magnetic iron oxide minerals are enhanced by reduction methods to facilitate subsequent separation, such as the patent "A method for improving the magnetic properties of weakly magnetic iron minerals". The patent "A method for the resource utilization of red mud (CN201710582083.3)" proposes to add strong reducing hydrazine or hydrazine and alcohol ethers, ammonia substances, ferrous salts, etc. in a hydrothermal environment to reduce the iron oxide in the red mud to strongly magnetic ferroferric oxide. This process is similar to the solvothermal method for reducing Fe 2+ The principle of ion synthesis of Fe3O4 crystals (paper "Synthesis and Characterization of Fe3O4 Octahedral Microcrystals by Solvothermal Method", Journal of Xinjiang University (Natural Science Edition), 2011, 20(1): 71-76). These existing technologies all utilize the mechanism of magnetic modification or reshaping of iron materials, and verify the relative technical advantages of magnetic modification for fine-grained iron minerals. However, they have not overcome technical difficulties such as high processing costs, poor adaptability to extremely fine particle size powders, and poor surface magnetic modification effects.

[0007] In summary, due to the complex mineral composition, weak magnetic properties of mineral particles, strong hydrophilicity, and the difficulty in effective selective dispersion or agglomeration of the sorting system, the existing processing and recovery technology of fine / ultrafine (0.1-50 μm) iron oxide (Fe2O3 / FeOOH and other weakly magnetic iron) materials has the following main shortcomings:

[0008] 1) It has poor adaptability to fine / ultrafine (below 20μm) iron oxide mineral particles, poor selective sorting and processing effect, low metal utilization rate, and low product quality. It is especially unsuitable for strongly hydrophilic iron-containing materials that have been smelted, such as red mud, iron slag, etc.

[0009] 2) Existing magnetization modification or reshaping technologies have high processing costs for the magnetization process; when magnetization is processed by calcination, the calcination energy consumption is high and the gas emissions are large; when magnetization is processed by hydrothermal method with the addition of strong reducing agents, the agent cost is high, the magnetization rate is slow, and heating is often required to accelerate the reaction process.

[0010] 3) When adding strong magnetic fine-particle magnetic seeds to promote magnetic agglomeration and separation, the magnetic agglomeration effect of the magnetic seeds on the fine-particle materials is poor due to the large difference in magnetic properties between the magnetic seeds and the materials to be processed.

[0011] Therefore, developing an efficient method for magnetic modification of fine / ultrafine particles, enhancing the magnetic agglomeration properties of fine / ultrafine particles, improving the selectivity of magnetic agglomeration, and improving the hydrophilicity of the surface of iron-containing minerals are of great significance for the processing and utilization of difficult-to-process fine / ultrafine iron-containing materials. Summary of the Invention

[0012] The main purpose of the present invention is to provide a method for recovering fine-grained iron oxide minerals to solve the problems of complex operation, high cost, low recovery efficiency, etc. in the existing technology for separating and recovering fine-grained iron oxide minerals.

[0013] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for recovering fine-grained iron oxide minerals is provided, which comprises: mixing a raw material to be processed containing fine-grained iron oxide minerals with an iron reducing agent and a nitrite and performing wet grinding to obtain a first ore; subjecting the first ore to magnetic separation in a first magnetic field and selection in a second magnetic field in sequence to recover the fine-grained iron oxide minerals in the raw material to be processed; wherein the first magnetic field is a rotating magnetic field or an alternating magnetic field, and the second magnetic field is a constant magnetic field; and the magnetic field strength of the first magnetic field is greater than the magnetic field strength of the second magnetic field.

[0014] Furthermore, based on the weight of dry ore, the weight ratio of the iron reducing agent, nitrite and raw material to be treated is 0.1-1:0.2-2.0:100; preferably, the weight ratio of the iron reducing agent to the nitrite is 1:2.0-20.0, and more preferably 1:4.0-10.0; preferably, the iron reducing agent is reduced iron powder.

[0015] Furthermore, wet grinding is performed in an iron medium mill; preferably, during the wet grinding process, the solid content of the slurry is 45 to 65 wt%; preferably, the processing time of the wet grinding is 10 to 60 minutes; preferably, the iron medium used in the wet grinding is spherical with a diameter of 2 to 20 mm.

[0016] Furthermore, the first magnetic field is a rotating magnetic field, and a vertical ring high gradient magnetic separator is used for the first magnetic field sorting; preferably, the magnetic field strength of the first magnetic field is 0.3 to 2.0 T; preferably, the solid content of the first mineral material is adjusted to 10 to 40 wt% before the first magnetic field sorting is performed.

[0017] Furthermore, the magnetic field strength of the second magnetic field is 0.1 to 0.5 T. Preferably, a permanent magnet drum magnetic separator or a wet countercurrent magnetic separator is used for the second magnetic field separation, preferably a wet countercurrent magnetic separator.

[0018] Furthermore, the particle size of the fine iron oxide mineral is 0.1 to 50 μm, more preferably 0.1 to 20 μm.

[0019] Furthermore, the raw material to be processed is natural fine-grained iron oxide ore material and / or iron-containing slag produced in the metal smelting process; preferably, the natural fine-grained iron oxide ore material is selected from one or more of hematite, limonite or goethite; preferably, the iron-containing slag produced in the metal smelting process is selected from red mud and / or iron precipitate slag.

[0020] Furthermore, the fine-grained iron oxide mineral is one or more of phaneritic, cryptocrystalline or amorphous Fe2O3, FeOOH or Fe2O3·H2O.

[0021] Furthermore, the particle size of the reduced iron powder is ≤100 μm, and more preferably 20 to 80 μm.

[0022] Furthermore, the nitrite is selected from alkali metal nitrite; preferably, the alkali metal nitrite is selected from one or more of sodium nitrite, potassium nitrite or calcium nitrite.

[0023] The present application constructs a coupled redox system with iron-nitrite-iron oxide and cooperates with mechanical activation in the wet grinding process, so that the surface of weakly magnetic fine-grained iron oxide minerals (such as Fe2O3) in the raw materials to be processed can form stable and uniform strong magnetic Fe3O4 oxides, thereby making the fine-grained iron oxide minerals relatively selectively agglomerated due to the enhanced surface magnetism, increasing the apparent particle size of the mineral sorting, providing the mineral physicochemical property basis for subsequent sorting and separation, thereby greatly improving the recovery efficiency of the fine-grained iron oxide mineral materials. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0025] As described in the background technology section of this application, the existing technology for separating and recovering fine-grained iron oxide minerals has problems such as complex operation, high cost, and low recovery efficiency. To solve this problem, this application provides a method for recovering fine-grained iron oxide minerals.

[0026] The recovery method includes: mixing a raw material to be processed containing fine-grained iron oxide minerals with an iron reducing agent and a nitrite and performing wet grinding to obtain a first ore; subjecting the first ore to magnetic separation in a first magnetic field and selection in a second magnetic field in sequence to recover the fine-grained iron oxide minerals in the raw material to be processed; wherein the first magnetic field is a rotating magnetic field or an alternating magnetic field, and the second magnetic field is a constant magnetic field; and the magnetic field strength of the first magnetic field is greater than the magnetic field strength of the second magnetic field.

[0027] The present application constructs a coupled redox system with iron-nitrite-iron oxide and cooperates with mechanical activation in the wet grinding process, so that the surface of weakly magnetic fine-grained iron oxide minerals (such as Fe2O3) in the raw materials to be processed can form stable and uniform strong magnetic Fe3O4 oxides, thereby making the fine-grained iron oxide minerals relatively selectively agglomerated due to the enhanced surface magnetism, increasing the apparent particle size of the mineral sorting, providing the mineral physicochemical property basis for subsequent sorting and separation, thereby greatly improving the recovery efficiency of the fine-grained iron oxide mineral materials.

[0028] In the above system, Fe, Fe 2+ 、Fe 3+ One or more of the - Directed oxidation and reduction to strong magnetic Fe3O4. The redox reaction is a dynamic equilibrium process; in which the iron minerals in the system are mainly in a trivalent state and have good oxidation activity, while Fe and Fe 2+ Relatively reducing, it tends to be oxidized to Fe in the above environment 3+ The tendency of Fe 3+ Fe3O4 can be roughly regarded as a FeO·Fe2O3 compound, where FeO can come from Fe oxidation and / or Fe 3+ Reduction to form FeO·Fe2O3.

[0029] Specifically, the main reactions involved are as follows:

[0030] NO3 - +NO+e→2NO2 - E 0 =-0.58V

[0031] NO2 - +H2O+e→NO+2OH - E 0 =-0.46V

[0032] 2NO2 - +3H2O+4e→N2O+6OH - E 0 =0.15V

[0033] N2O+5H2O+4e→2NH2OH+4OH - E 0 =-1.05V

[0034] NH2OH+2H2O+2e→NH3·H2O+2OH - E 0 =0.42V

[0035] Fe 2+ +2e→Fe E 0 =-0.45V

[0036] Fe 3+ +3e→Fe E 0 =-0.036V

[0037] Fe 3+ +e→Fe 2+ E 0 =0.77V

[0038] Fe(OH)3+e→Fe(OH)2+OH - E 0 =-0.56V

[0039] 9Fe+4NO2 - +12H2O→3Fe3O4+OH - +4NH3·H2O

[0040] 9Fe 2+ +4NO2 - +12H2O+18e→4NH3·H2O+3Fe3O4+4OH -

[0041] 9Fe 3+ +4NO2 - +12H2O+27e→4NH3·H2O+3Fe3O4+4OH -

[0042] The surface reactivity of fine iron oxide minerals (such as Fe2O3) in the raw materials to be processed and the Fe 3+Due to its high density, its surface is easily reduced to FeO, which deposits Fe3O4 or adsorbs on the surface. This highly magnetic Fe3O4 selectively adsorbs on the surface of fine-grained iron oxide minerals (such as Fe2O3), causing the Fe2O3 surface to be magnetized and modified to Fe3O4. This enhances the magnetic properties of the fine-grained iron oxide minerals in the processed raw material, allowing the fine-grained iron oxide minerals to agglomerate due to magnetic convergence, increasing the apparent particle size and facilitating subsequent separation. At the same time, the formation of Fe3O4 minerals with more complete crystal forms and smoother surfaces can effectively reduce the exposure of iron cations, weaken the impact of hydration, and strengthen the magnetic agglomeration process, further enhancing the subsequent separation and sorting process.

[0043] After wet grinding, the ore is sequentially subjected to magnetic separation in the first magnetic field and then concentration in the second magnetic field. The first magnetic field is a rotating or alternating magnetic field, which further promotes the selective magnetic agglomeration of magnetically modified fine iron minerals, enhances the dispersion of fine particles, and reduces the inclusion of non-magnetic species by varying the magnetic field, thereby achieving the goal of pre-enriching the ferromagnetic agglomerated materials. The second magnetic field is a constant magnetic field, and the magnetic field intensity of the second magnetic field is reduced. The constant magnetic field is used to separate the magnetically agglomerated iron minerals, thereby obtaining an iron ore concentrate product.

[0044] In summary, based on this, the present invention has the following beneficial effects:

[0045] 1) The present invention is based on the construction and regulation of the redox reaction of iron-containing materials within the system, utilizing the directional aggregation tendency of Fe species and relying on the Fe and its oxide-nitrite introduced during the mechanical activation process to construct a new redox iron species magnetization system, achieving a low-temperature composite catalytic magnetization modification reaction of weakly magnetic magnetite minerals. The modification process has a fast reaction rate, is stable and controllable, and has outstanding advantages in selective directional enrichment. 2) By enhancing the inherent magnetic properties of weakly magnetic iron minerals in the material, the minerals are encouraged to undergo magnetic agglomeration due to magnetic response, thereby increasing the apparent particle size of fine-grained minerals due to agglomeration. The agglomeration selectivity of the magnetic material is strong, effectively reducing the influence of fine / ultrafine particle size on the sorting process, achieving relative selectivity of magnetic agglomeration of fine-grained iron minerals, reducing the adverse effects of mineral composition, and having strong technical adaptability. 3) The scope of application is wide. Through redox modification, it is highly adaptable to fine / ultrafine-grained cryptocrystalline and amorphous iron oxide mineral materials, suitable for the sorting and recovery of iron from fine-grained iron oxide materials, such as red mud and iron slag. 4) The mechanical strengthening-directional magnetization modification and variable magnetic field re-strengthening technology are used to promote the formation of advantageous iron mineral magnetic agglomerates, which is convenient for improving the efficiency of separation and sorting of fine-grained iron oxide minerals, and can obtain high-quality and high-recovery iron concentrates.

[0046] It is further explained that the above-mentioned fine-grained iron oxide minerals include one or more of phaneritic, cryptocrystalline or amorphous Fe2O3, FeOOH or Fe2O3·H2O, and their particle size is 0.1 to 50 μm, for example, it can be 0.1 μm, 0.5 μm, 1 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, and more preferably 0.1 to 20 μm.

[0047] To further improve the efficiency of separation and sorting of fine-grained iron oxide minerals, the weight ratio of the iron reducing agent, nitrite, and raw material to be processed is 0.1-1:0.2-2.0:100, based on the weight of the dry ore. Preferably, the weight ratio of the iron reducing agent to the nitrite is 1:2.0-20.0, more preferably 1:4.0-10.0, and the iron reducing agent is reduced iron powder.

[0048] In a preferred embodiment, wet grinding is performed in an iron medium ball mill. The grinding medium is cast iron / ordinary iron. The milling medium interface collision provides active sites with similar components for the redox conversion between Fe element / Fe ions / Fe oxide species, thereby enhancing the agglomeration effect of iron species. In addition, the iron medium corrodes and dissolves Fe. 2+ Later, under the action of nitrite, it can be converted into strongly magnetic Fe₃O₄. Preferably, the iron medium used in the wet milling process is spherical, with a diameter of 2-20 mm. This increases the probability of collision between the medium balls, provides mechanical activation energy transfer, and accelerates the reaction between the modifying agent and the iron oxide material in the active areas between the medium balls, thereby enhancing the modification behavior of the directional conversion of ferromagnetic species during the process. Preferably, during the wet milling process, the solids content of the slurry is 45-65 wt%. Preferably, the wet milling process lasts for 10-60 minutes.

[0049] To further enhance the magnetic agglomeration of the fine-grained iron oxide minerals, the first magnetic field is preferably a rotating magnetic field, and a vertical ring high-gradient magnetic separator is used for first magnetic field separation. Preferably, the magnetic field strength of the first magnetic field is 0.3 to 2.0 T. Preferably, the solids content of the first ore is adjusted to 10 to 40 wt% before first magnetic field separation.

[0050] In order to further improve the separation efficiency, the magnetic field strength of the second magnetic field is preferably 0.1 to 0.5 T. Preferably, a permanent magnetic drum magnetic separator or a wet countercurrent magnetic separator is used for the second magnetic field separation, preferably a wet countercurrent magnetic separator.

[0051] In a preferred embodiment, the raw material to be processed is natural fine-grained iron oxide ore and / or iron-containing slag produced during metal smelting. The natural fine-grained iron oxide ore is selected from one or more of hematite, limonite, or goethite. Preferably, the iron-containing slag produced during metal smelting is selected from red mud and / or iron-precipitated slag.

[0052] To increase the activity of the modification reaction, the particle size of the reduced iron powder is preferably less than 100 μm, more preferably 20 to 80 μm. The nitrite is selected from alkali metal nitrites, such as one or more of sodium nitrite, potassium nitrite or calcium nitrite.

[0053] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0054] Example 1

[0055] The red mud produced by a Bayer aluminum smelting process contains T Fe The grade is 35.3%, with Fe primarily present in the highly hydrophilic Fe2O3\FeOOH mineral phase. By weight, the red mud composition is: 50.42% iron (measured as Fe2O3), 9.78% Al2O3, 1.82% CaO, 7.58% TiO2, 4.10% Na2O, 4.35% SiO2, 2.15% MgO, 0.42% S, 0.21% Zr, 0.16% Cr, 0.009% Cu, 0.033% Zn, 0.013% Nb, with the remainder being water and unavoidable impurities. Over 55% of this material is composed of material below 0.01mm in diameter, making it difficult to effectively recover Fe from this fine-grained material using conventional mineral processing methods.

[0056] The red mud is treated by the method of the present invention:

[0057] Step 1) Preparation of a mixed material for treatment: The red mud is classified into materials to be treated with a diameter of 0.038 mm or larger and materials to be treated with a diameter of less than 0.038 mm, and the materials to be treated with a diameter of greater than or equal to 0.038 mm are recovered by high gradient magnetic separation. The red mud materials to be treated with a diameter less than 0.038 mm are mixed in a weight ratio of reduced iron powder: nitrite: red mud materials to be treated of 0.2:1.0:100 to obtain a mixed material, wherein the average particle size of the reduced iron powder is 0.053 mm, and sodium nitrite is selected as the nitrite.

[0058] 2) Ball milling-magnetization modification operation: The mixed material obtained in step 1) was introduced into a cast iron ball mill with a grinding medium of 6 mm, and the solid content of the slurry was adjusted to 55 wt% for wet grinding (the solvent was an aqueous solution containing sodium nitrite, and the mass content of sodium nitrite was 80 mg / mL). The grinding time was 20 min to obtain magnetically modified slurry B.

[0059] 3) Magnetic agglomeration operation of the magnetic modified slurry in a rotating magnetic field. The magnetic modified slurry B obtained in step 2) is adjusted to a solid content of 20 wt%, and then added to a vertical ring high gradient magnetic separator for sorting using a 1.0 T magnetic field to enhance the formation of magnetic flocs of the magnetic mineral particles, thereby obtaining enhanced magnetic agglomerate slurry C and non-magnetic tailings D. The non-magnetic tailings are used to prepare other materials.

[0060] 4) Magnetic agglomerate slurry selection and separation operation: the magnetic agglomerate slurry C obtained in step 3) is added to a wet countercurrent magnetic separator with a 0.3T magnetic field to upgrade and select the magnetic agglomerates to obtain separated and recovered Fe concentrate E and weak magnetic tailings F.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that the red mud material to be processed with a size smaller than 0.038 mm is directly magnetically separated under a magnetic field of 2.0 T.

[0063] Comparative Example 2

[0064] The difference from Example 1 is that the red mud material to be treated, which is smaller than 0.038 mm, is subjected to reduction roasting in an atmosphere of nitrogen as a protective gas and CO as a reducing gas, with a CO content of 30% by volume in the atmosphere, a reduction roasting temperature of 650°C, and a roasting time of 30 minutes. After reduction roasting, the material is first subjected to a 1.0 T magnetic roughing separation and then to a 0.3 T magnetic separation.

[0065] Comparative Example 3

[0066] The difference from Example 1 is that the red mud material to be treated with a particle size less than 0.038 mm and hydrazine hydrate are mixed in a weight ratio of 1:0.2 and reacted at 180° C. for 4 h, and then ethanol is added to the system and hydrothermal magnetization is continued at 150° C. for 2 h; after hydrothermal magnetization, the material is first subjected to 1.0 T magnetic roughing and then magnetic fine separation at a magnetic separation intensity of 0.3 T.

[0067] Comparative Example 4

[0068] The difference from Example 1 is that a one-roughing, one-fining, one-scavenging process is adopted. Red mud material with particles smaller than 0.038 mm is first subjected to roughing to obtain a roughing concentrate and roughing tailings. The roughing tailings are then subjected to a first-stage scavenging to obtain a first-stage scavenging concentrate and a first-stage scavenging tailings. The first-stage scavenging concentrate and the roughing concentrate are then mixed and subjected to concentrating. After concentrating, the material is subjected to reverse flotation using polyacrylamide (CAS No. 9003-05-8) as a flocculant.

[0069] The results of the experiments comparing the method of the present invention (Example 1) with conventional iron separation technology (Comparative Examples 1 to 4) are shown in Table 1.

[0070] Table 1

[0071] <![CDATA[T Fe Grade, %]]> Fe recovery rate, % Example 1 65.2 87.2 Comparative Example 1 53.3 15.2 Comparative Example 2 63.3 44.2 Comparative Example 3 65.3 78.3 Comparative Example 4 53.2 32.2

[0072] Example 2

[0073] The iron removal slag produced by the high-pressure sulfuric acid leaching process of a laterite nickel ore contains T Fe The grade is 29.3%. The Fe species in the slag are essentially devoid of mineral crystals, primarily existing in the solid phase of Fe2O3\FeOOH. By weight, the slag composition, excluding iron, is: 41.86% iron (measured as Fe2O3), 17.22% CaO, 10.8% S, 3.83% MgO, 9.21% SiO2, and unavoidable impurities. Material below 0.01mm in diameter accounts for over 90% by weight, making it difficult to effectively recover Fe from this fine-grained material using conventional mineral processing methods.

[0074] The method of the present invention is used to treat the iron removal slag:

[0075] Step 1) Preparation of a mixture of materials to be processed: Mixing reduced iron powder: nitrite: iron removal slag to be processed at a weight ratio of 0.1:1.3:100, wherein the average particle size of the reduced iron powder is 0.030 mm, and potassium nitrite is selected as the nitrite.

[0076] 2) Ball milling-magnetization modification operation: The mixed material obtained in step 1) is introduced into a cast iron ball mill with a grinding medium of 20 mm, and the solid content of the slurry is adjusted to 45 wt% for wet grinding (the solvent is an aqueous solution containing potassium nitrite) for 30 min to obtain magnetically modified slurry B.

[0077] 3) Magnetic agglomeration operation of the magnetic modified slurry in a rotating magnetic field. The magnetic modified slurry B obtained in step 2) is adjusted to a solid content of 30 wt%, and then added to a vertical ring high gradient magnetic separator for sorting using a 1.5 T magnetic field to enhance the formation of magnetic flocs of magnetic mineral particles, thereby obtaining enhanced magnetic agglomerate slurry C and non-magnetic tailings D. The non-magnetic tailings are used to prepare other materials.

[0078] 4) Magnetic agglomerate slurry selection and separation operation: the magnetic agglomerate slurry C obtained in step 3) is added to a wet countercurrent magnetic separator with a 0.2T magnetic field to upgrade and select the magnetic agglomerates to obtain separated and recovered Fe concentrate E and weak magnetic tailings F.

[0079] Comparative Example 5

[0080] The difference from Example 2 is that the iron-removing slag to be treated is directly magnetically separated under a 2.0T magnetic field.

[0081] Comparative Example 6

[0082] The difference from Example 2 is that the treated iron removal slag is reduction roasted in an atmosphere of nitrogen as a protective gas and CO as a reducing gas, with a CO volume content of 30% in the atmosphere, a reduction roasting temperature of 650°C, and a roasting time of 30 minutes. After reduction roasting, the material is first subjected to 1.0T magnetic roughing and then to 0.3T magnetic separation.

[0083] Comparative Example 7

[0084] The difference from Example 2 is that the iron removal slag to be treated and hydrazine hydrate are mixed in a weight ratio of 1:0.15 and reacted at 180°C for 6 hours, and then ethanol is added to the system and hydrothermal magnetization is continued at 150°C for 2 hours; after hydrothermal magnetization, the material is first subjected to 1.0T magnetic roughing and then magnetic fine separation at a magnetic separation intensity of 0.3T.

[0085] Comparative Example 8

[0086] The difference from Example 2 is that a one-roughing, one-fining, one-scavenging process is adopted. The iron-removing slag to be processed is first subjected to roughing to obtain a roughing concentrate and roughing tailings. The roughing tailings are then subjected to a first-stage scavenging to obtain a first-stage scavenging concentrate and a first-stage scavenging tailings. The first-stage scavenging concentrate and the roughing concentrate are then mixed and subjected to concentrating. After concentrating, the material is subjected to reverse flotation using polyacrylamide (CAS No. 9003-05-8) as a flocculant.

[0087] The results of the experiments comparing the method of the present invention (Example 2) with conventional iron separation technologies (Comparative Examples 5 to 8) are shown in Table 2.

[0088] Table 2

[0089] Sorting process TFe grade, % Fe recovery rate, % Example 2 63.2 77.2 Comparative Example 5 45.3 10.2 Comparative Example 6 63.6 12.8 Comparative Example 7 63.7 70.5 Comparative Example 8 37.2 11.2

[0090] Example 3

[0091] Oolitic hematite, T Fe The grade is 44.5%, and the iron in the minerals appears in various forms, including nodules, kidneys, blocks, stars, and disseminated forms, such as pseudo-hematite, magnetite, and hematite, resulting in a complex mineral composition. By weight, the iron content, measured as Fe2O3, is 63.57%, SiO2 23.40%, Al2O3 5.44%, CaO 3.53%, MgO 1.89%, Mn 0.12%, K2O 1.10%, and P 0.45%. Over 95% of this material is composed of particles smaller than 0.038 mm in diameter. Conventional mineral processing methods make it difficult to effectively recover Fe from this fine-grained material.

[0092] The oolitic hematite is treated by the method of the present invention:

[0093] Step 1) Preparation of a mixed material for treatment: The oolitic hematite is mixed at a weight ratio of 0.2:1.0:100 of reduced iron powder: nitrite: oolitic hematite to be treated to obtain a mixed material, wherein the average particle size of the reduced iron powder is 0.053 mm, and the nitrite is calcium nitrite.

[0094] 2) Ball milling-magnetization modification operation: The mixed material obtained in step 1) was introduced into a cast iron ball mill with a grinding medium of 6 mm, and the solid content of the slurry was adjusted to 55 wt% for wet grinding (the solvent was an aqueous solution containing calcium nitrite). The grinding time was 20 min to obtain magnetically modified slurry B.

[0095] 3) Magnetic agglomeration operation of the magnetic modified slurry in a rotating magnetic field. After the magnetic modified slurry B obtained in step 2) is adjusted to a solid content of 20 wt%, it is added to a 0.7 T alternating magnetic field for sorting to strengthen the formation of magnetic flocs of magnetic mineral particles, thereby obtaining strengthened magnetic agglomerate slurry C and non-magnetic tailings D. The non-magnetic tailings are used to prepare other materials.

[0096] 4) Magnetic Agglomerate Slurry Concentration and Sorting: The magnetic agglomerate slurry C obtained in step 3) was added to a wet countercurrent magnetic separator with a 0.15T magnetic field for magnetic agglomeration and concentrating, thereby obtaining separated and recovered Fe concentrate E and weakly magnetic tailings F. The resulting iron concentrate had an iron concentrate grade of 66.4% and an iron recovery rate of 85.7%.

[0097] Comparative Example 9

[0098] The hematite ore was recovered and processed using a system-optimized stage grinding process of one-stage grinding, magnetic roughing, coarse concentrate regrinding, and three-stage magnetic concentration. The first-stage grinding process was to a fineness of -0.074 mm, accounting for 60%, which was then subjected to magnetic roughing with a magnetic field strength of 2.0 T. The magnetic coarse concentrate was regrinded to a fineness of -0.038 mm, accounting for 98%, and then subjected to three-stage concentration with a magnetic field strength of 0.7 T. The iron concentrate product had an Fe content of 60.3% and an iron recovery rate of 55.8%. Continuing grinding could not produce an iron concentrate of higher grade.

[0099] Example 4

[0100] The only difference from Example 1 is that the weight ratio of reduced iron powder, nitrite and raw material to be processed is 0.1:2:100.

[0101] Example 5

[0102] The only difference from Example 1 is that the weight ratio of reduced iron powder, nitrite and raw material to be processed is 1:0.2:100.

[0103] Example 6

[0104] The only difference from Example 1 is that the weight ratio of reduced iron powder, nitrite and raw material to be processed is 0.05:1:100.

[0105] Example 7

[0106] The only difference from Example 1 is that the weight ratio of reduced iron powder, nitrite and raw material to be processed is 0.2:3:100.

[0107] Example 8

[0108] The only difference from Example 1 is that the weight ratio of reduced iron powder to nitrite is 1:4.0.

[0109] Example 9

[0110] The only difference from Example 1 is that the weight ratio of reduced iron powder to nitrite is 1:10.0.

[0111] Example 10

[0112] The only difference from Example 1 is that the weight ratio of reduced iron powder to nitrite is 1:20.0.

[0113] Example 11

[0114] The only difference from Example 1 is that the wet grinding treatment time is 10 min.

[0115] Example 12

[0116] The only difference from Example 1 is that the wet grinding time is 60 min.

[0117] Example 13

[0118] The only difference from Example 1 is that the wet grinding treatment time is 80 min.

[0119] Example 14

[0120] The only difference from Example 1 is that the magnetic field strength of the first magnetic field is 0.3T, and the strength of the second magnetic field is 0.1T.

[0121] Example 15

[0122] The only difference from Example 1 is that the magnetic field strength of the first magnetic field is 2.0T, and the strength of the second magnetic field is 0.5T.

[0123] Example 16

[0124] The only difference from Example 1 is that the magnetic field strength of the first magnetic field is 0.1 T, and the strength of the second magnetic field is 1 T.

[0125] The performance parameters are shown in Table 3.

[0126] Table 3

[0127] TFe grade, % Fe recovery rate, % Example 1 65.2 87.2 Example 2 63.2 77.2 Example 3 66.4 85.7 Example 4 65.7 87.1 Example 5 63.2 84.5 Example 6 62.2 83.1 Example 7 65.8 87.3 Example 8 65.3 86.1 Example 9 65.4 87.1 Example 10 65.5 87.4 Example 11 64.7 83.2 Example 12 63.1 85.2 Example 13 62.3 83.7 Example 14 66.7 81.2 Example 15 64.3 87.8 Example 16 66.8 78.8

[0128] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for recovering fine-grained iron oxide minerals, characterized in that: The recovery method comprises: The raw material to be processed containing fine iron oxide minerals is mixed with an iron reducing agent and a nitrite and wet-grinded to obtain a first ore material; The first ore is subjected to magnetic separation in a first magnetic field and concentration in a second magnetic field in sequence to recover fine iron oxide minerals in the raw material to be processed; The first magnetic field is a rotating magnetic field or an alternating magnetic field, and the second magnetic field is a constant magnetic field; and the magnetic field strength of the first magnetic field is greater than the magnetic field strength of the second magnetic field.

2. The method for recovering fine-grained iron oxide minerals according to claim 1, characterized in that: Based on the weight of dry ore, the weight ratio of the iron reducing agent, the nitrite and the raw material to be processed is 0.1~1:0.2~2.0:

100.

3. The method for recovering fine-grained iron oxide minerals according to claim 2, characterized in that: Measured by dry ore weight, The weight ratio of the iron reducing agent to the nitrite is 1:2.0~20.0, The iron reducing agent is reduced iron powder.

4. The method for recovering fine-grained iron oxide minerals according to claim 3, characterized in that: Measured by dry ore weight, The weight ratio of the iron reducing agent to the nitrite is 1:4.0~10.

0.

5. The method for recovering fine-grained iron oxide mineral according to claim 1 or 2, characterized in that: The wet grinding was carried out in an iron media mill.

6. The method for recovering fine-grained iron oxide minerals according to claim 5, characterized in that: During the wet grinding process, the solid content of the slurry is 45-65 wt%; The wet grinding process time is 10 to 60 minutes; The iron medium used in the wet grinding is spherical and has a diameter of 2 to 20 mm.

7. The method for recovering fine-grained iron oxide minerals according to claim 1 or 2, characterized in that: The first magnetic field is the rotating magnetic field, and a vertical ring high gradient magnetic separator is used to perform the first magnetic field separation.

8. The method for recovering fine-grained iron oxide minerals according to claim 7, characterized in that: The magnetic field strength of the first magnetic field is 0.3~2.0T; The solid content of the first mineral material is adjusted to 10-40 wt% before the first magnetic field separation is performed.

9. The method for recovering fine-grained iron oxide minerals according to claim 1 or 2, characterized in that: The magnetic field strength of the second magnetic field is 0.1-0.5T.

10. The method for recovering fine-grained iron oxide minerals according to claim 9, characterized in that: The second magnetic field concentration is carried out by using a permanent magnetic drum magnetic separator or a wet countercurrent magnetic separator.

11. The method for recovering fine-grained iron oxide minerals according to claim 10, characterized in that: The second magnetic field concentration is performed using the wet countercurrent magnetic separator.

12. The method for recovering fine-grained iron oxide minerals according to claim 1 or 2, characterized in that: The particle size of the fine iron oxide mineral is 0.1-50 μm.

13. The method for recovering fine-grained iron oxide minerals according to claim 12, characterized in that: The particle size of the fine iron oxide mineral is 0.1-20 μm.

14. The method for recovering fine-grained iron oxide minerals according to claim 1 or 2, characterized in that: The raw materials to be processed are natural fine-grained iron oxide ore materials and / or iron-containing slag produced during metal smelting.

15. The method for recovering fine-grained iron oxide minerals according to claim 14, characterized in that: The natural fine-grained iron oxide ore material is selected from one or more of hematite, limonite or goethite; The iron-containing slag produced in the metal smelting process is selected from red mud and / or iron-precipitated slag.

16. The method for recovering fine-grained iron oxide minerals according to claim 1 or 2, characterized in that: The fine-grained iron oxide mineral is one or more of phaneritic, cryptocrystalline or amorphous Fe2O3, FeOOH or Fe2O3·H2O.

17. The method for recovering fine-grained iron oxide minerals according to claim 3, characterized in that: The particle size of the reduced iron powder is ≤100 μm.

18. The method for recovering fine-grained iron oxide minerals according to claim 3, characterized in that: The particle size of the reduced iron powder is 20-80 μm.

19. The method for recovering fine-grained iron oxide minerals according to claim 1 or 2, characterized in that: The nitrite is selected from alkali metal nitrites.

20. The method for recovering fine-grained iron oxide minerals according to claim 19, wherein: The alkali metal nitrite is selected from one or more of sodium nitrite, potassium nitrite or calcium nitrite.