A method for recovering iron lepidolite ore

Abstract

The application discloses a recovery method of iron lepidolite ore, which comprises the following steps: crushing and double-layer screening of iron lepidolite ore raw materials to obtain upper unscreened powder, middle unscreened powder and screened powder; magnetic separation preselection of the obtained middle unscreened powder to obtain preselected concentrate; mixing of the upper unscreened powder and the preselected concentrate for grinding; mixing of the obtained powder and the screened powder for two-stage classification; high-gradient magnetic separation of the obtained two-stage classification sand and two-stage classification overflow to obtain lithium concentrate and tailings. The recovery method has the advantages of simple process, convenient operation, low recovery cost, small loss of fine metal particles, low grinding amount, high separation efficiency, cleanness and non-toxicity, and can recover lithium concentrate with high Li2O grade and high Li2O recovery rate. The recovery method is a new beneficiation process with good separation effect, economic environmental protection and high efficiency in recovery of lithium resources from low-grade iron lepidolite ore, has high use value and good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology and relates to a method for recovering lithium iron ore, specifically a method for recovering lithium iron ore using a full magnetic separation method. Background Technology

[0002] Lithium is a crucial raw material for the new energy industry, and lepidolite is one of the main mineral sources for lithium extraction. Lepidolite (KLiFeAl[AlSi3O)) 10Lithium iron phosphate (Fe, OH)₂ ore is flaky, light brown or dark grayish-green, with a pearly luster. It is mainly found in greisen, but also in pegmatite and high-temperature hydrothermal veins. It is characterized by low lithium content, high impurity content, and difficulty in screening. In particular, the flaky nature of the lithium iron phosphate mica makes it difficult to grind finely, or easily leads to very serious mud formation, resulting in a low lithium oxide recovery rate, generally 65-70%. To address the aforementioned issues, researchers have proposed improved solutions, primarily based on flotation. This involves crushing and grinding the raw ore to form a slurry, then adding flotation reagents to separate the slurry through flotation to obtain lithium iron ore concentrate. However, these screening methods still have the following drawbacks: (a) They are difficult to effectively overcome the mud formation phenomenon in the slurry, which is not conducive to obtaining high-grade lithium iron ore concentrate with high recovery rates through flotation separation. For example, in the prior art with patent application number 201710322482.6, after crushing, ball milling, and flotation separation, only lithium iron ore concentrate with a Li2O content of 3.17% and a recovery rate of 66.38% can be obtained. (b) To overcome the mud formation phenomenon in the slurry, a large amount of flotation reagents is required. However, the extensive use of flotation reagents not only significantly increases screening costs but also easily leads to new environmental pollution. The treatment of these environmental pollutants will inevitably increase costs. For example, the prior art with patent application numbers 201310163993.X and 201510788440.2 uses a large amount of flotation reagents. (c) All the crushed raw ore is fed into a ball mill for grinding, without reducing the actual grinding volume. This is not only detrimental to simplifying the screening process but also easily reduces screening efficiency and increases recovery costs. For example, in the prior art with patent application number 202210094343.3, low-grade lithium iron phosphate mica is directly fed into the ball mill for grinding, which does not reduce the actual grinding volume. At the same time, this prior art also includes a reagent flotation step, which is still detrimental to reducing recovery costs and easily leads to new environmental pollution. Furthermore, existing recovery processes that do not involve flotation mainly include the following steps: lithium iron ore is fed into a ball mill for grinding; the milled material undergoes a first screening; the sieved powder obtained from the first screening is subjected to weak magnetic separation to separate non-magnetic and magnetic substances; the magnetic substances undergo a second screening; and the sieved powder obtained from the second screening is subjected to strong magnetic separation to separate non-magnetic and magnetic substances, with the magnetic substance being lithium iron ore concentrate. However, the above recovery process still has the following drawbacks: all the raw ore enters the ball mill for grinding, without reducing the actual grinding volume, resulting in low screening efficiency and high recovery costs; single-layer screening cannot separate fine-particle products, easily leading to a sharp increase in the loss of fine-particle metals; and the tailings contain a large amount of valuable components, easily causing resource waste.Therefore, obtaining a simple, easy-to-operate, low-cost, low-fine-particle-metal-loss, low-grinding-rate, high-recovery-rate, and high-grade iron-lithium mica ore recovery method is of great significance for the widespread acquisition of lithium resources and the promotion of the development of the new energy industry. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for recovering lithium mica ore that is simple in process, convenient in operation, low in recovery cost, low in fine metal loss, low in grinding amount, high in recovery rate and high in grade.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0005] A method for recovering lithium mica ore includes the following steps:

[0006] S1. Crushing the lithium mica ore raw material;

[0007] S2. The crushed lithium mica ore raw material is screened using a double-layer screen with different apertures to obtain three types of powder with particle sizes from large to small: the upper unscreened powder, the middle unscreened powder, and the underscreen powder.

[0008] S3. The unscreened powder in the middle is subjected to magnetic pre-selection to obtain pre-selected concentrate and coarse sand;

[0009] S4. Mix the unscreened powder from the upper layer with the pre-selected concentrate and then grind it.

[0010] S5. The powder obtained after grinding is mixed with the undersize powder for the first stage of classification, resulting in a stage of classified underflow and a stage of classified overflow.

[0011] S6. Perform a second stage of classification on the first stage of the overflow to obtain a second stage of classified sedimentation and a second stage of classified overflow.

[0012] S7. High-gradient magnetic separation is performed on the two-stage graded sediment and the two-stage graded overflow to obtain lithium concentrate and tailings.

[0013] The above-mentioned method for recovering lithium iron ore is further improved by using a high-gradient magnetic separator to pre-select the intermediate unscreened powder, including the following steps:

[0014] S3-1. Mix the unsieved powder with water to obtain a mixture;

[0015] S3-2. Feed the mixture into a high-gradient magnetic separator for high-gradient magnetic pre-selection to obtain pre-selected concentrate and non-magnetic coarse sand;

[0016] In a further improvement to the above-mentioned method for recovering lithium mica ore, in step S3-1, the mass concentration of the intermediate unscreened powder in the mixture is 30%.

[0017] In a further improvement to the above-mentioned method for recovering lithium mica ore, in step S3-2, the diameter of the magnetic medium in the high-gradient magnetic separator is matched with the particle size of the unscreened powder in the middle; during the high-gradient magnetic pre-selection process, the magnetic field strength is 1.75T, the magnetic medium is a rod medium with a diameter of 3mm, and the pulsation frequency is 100rpm.

[0018] The above-mentioned method for recovering lithium mica ore is further improved by using a high-gradient magnetic separator to perform high-gradient magnetic separation on the two-stage graded sand, including the following steps:

[0019] (1) Mix the two-stage graded sediment with water to obtain a mixture;

[0020] (2) The mixture is fed into a high-gradient magnetic separator for the first high-gradient magnetic separation to obtain the first rough concentrate and tailings;

[0021] (3) The first rough concentrate is fed into a high gradient magnetic separator for a second high gradient magnetic separation to obtain lithium concentrate and the first non-magnetic material.

[0022] The above-mentioned method for recovering lithium mica ore is further improved in step (1) by having the mass concentration of the two-stage graded sediment in the mixed liquid be 30%.

[0023] The above-mentioned method for recovering lithium mica ore is further improved in step (2), where the magnetic field strength is 1.75T, the magnetic medium is a rod medium with a diameter of 2mm, and the pulsation frequency is 100rpm.

[0024] The above-mentioned method for recovering lithium mica ore is further improved in step (3). In the second high-gradient magnetic separation process, the magnetic field strength is 1.75T, the magnetic medium is a rod medium with a diameter of 2mm, and the pulsation frequency is 100rpm. The first non-magnetic material is returned to step (2) and mixed with the second-stage graded sediment before continuing high-gradient magnetic separation.

[0025] The above-mentioned method for recovering lithium iron ore is further improved by using a high-gradient magnetic separator to perform high-gradient magnetic separation on the two-stage classification overflow, including the following steps:

[0026] (a) The two-stage graded overflow is fed into a high-gradient magnetic separator for the first high-gradient magnetic separation to obtain the second rough concentrate and tailings;

[0027] (b) The second rough concentrate is fed into a high-gradient magnetic separator for a second high-gradient magnetic separation to obtain lithium concentrate and a second non-magnetic substance.

[0028] The above-mentioned method for recovering lithium mica ore is further improved in step (a) by using a magnetic field strength of 1.75T, a coarse mesh medium, and a pulse frequency of 100rpm during the first high-gradient magnetic separation process.

[0029] In a further improvement to the above-mentioned method for recovering lithium mica ore, in step (b), during the second high-gradient magnetic separation process, the magnetic field strength is 1.75T, the magnetic medium is a coarse mesh medium, and the pulsation frequency is 100rpm; the second non-magnetic material is returned to step (a) and mixed with the two-stage graded overflow before continuing high-gradient magnetic separation.

[0030] The above-mentioned method for recovering lithium iron ore is further improved in that, in step S1, the particle size of the crushed lithium iron ore raw material is ≤5mm; and the mass percentage of Li2O in the lithium iron ore raw material is ≥0.3%.

[0031] In a further improvement to the above-mentioned method for recovering lithium iron ore, in step S2, when screening the crushed lithium iron ore raw material using a double-layer screen with different aperture sizes, the double-layer screen with different aperture sizes includes an upper screen and a lower screen arranged from top to bottom; the mesh size of the upper screen is 2mm to 2.5mm; the mesh size of the middle screen is 0.3mm to 0.8mm; the particle size of the unscreened powder in the upper layer is ≥2mm; the particle size of the unscreened powder in the middle layer is 0.3mm to 2mm; and the particle size of the undersize powder is ≤0.3mm.

[0032] The above-mentioned method for recovering lithium mica ore is further improved by step S3, in which a ball mill is used to grind the mixture of the upper unscreened powder and the middle unscreened powder; the grinding concentration is controlled at 75% during the grinding process.

[0033] The above-mentioned method for recovering lithium iron ore is further improved in step S4 by using a hydrocyclone to perform a first-stage classification on the mixture of powder obtained after grinding and undersize powder; the classification concentration is controlled at 55% during the first-stage classification process; 60% of the fineness of the first-stage classification overflow is -0.074mm; the first-stage classification sediment is returned to step S3 for grinding.

[0034] The above-mentioned method for recovering lithium mica ore is further improved by using a hydrocyclone in step S5 to perform a second stage of classification on the first stage of classification overflow; the classification concentration is controlled at 55% during the second stage of classification; and 95% of the fineness of the second stage of classification overflow is -0.045mm.

[0035] Compared with the prior art, the advantages of the present invention are as follows:

[0036] To address the shortcomings of existing methods for recovering lithium iron ore, such as complex processes, high operational difficulty, high recovery costs, significant loss of fine metal particles, and large grinding volumes, this invention creatively proposes a new method for recovering lithium iron ore. First, the crushed lithium iron ore raw material undergoes double-layer screening to obtain powder of suitable particle size. On the one hand, screening the large particles (the upper and middle unscreened particles) helps prevent magnetic media blockage during subsequent magnetic separation. On the other hand, pre-selecting the middle unscreened particles (intermediate particle size product) with magnetic separation improves the feed grade and reduces grinding volume. Furthermore, the undersize powder (fine particle size product) directly enters the subsequent classification process. This method also helps reduce the over-grinding of useful metals, thereby reducing the loss of fine-grained metals and improving the recovery index of the target mineral. Furthermore, the powder obtained after grinding is mixed with undersize powder of even smaller particle size for two-stage classification. This reduces the over-grinding loss of fine-grained powder while separating materials with particle sizes matching the magnetic medium. Finally, high-gradient magnetic separation is used for roughing and cleaning of the underflow and overflow from the two-stage classification, respectively. During this process, different beneficiation parameters are used for classification and magnetic separation based on the magnetic separation characteristics of different particle sizes of minerals, effectively reducing the loss rate of fine-grained particles in the ore and effectively improving the magnetic separation recovery rate of fine-grained lithium iron phosphate mica. This results in high-grade, high-recovery lithium concentrate. In addition, the recovery method of this invention does not use chemical reagents, which not only helps reduce recovery costs and simplify the recovery process but also reduces environmental pollution. The present invention provides a method for recovering lithium iron ore from lithium mica, which has the advantages of simple process, convenient operation, low recovery cost, small loss of fine metal particles, low grinding amount, high separation efficiency, and clean and non-toxic properties. It can also recover lithium concentrate with high Li2O grade and high Li2O recovery rate. It is a new mineral processing technology with good separation effect, economy and environmental protection, and can efficiently recover lithium resources from low-grade lithium iron ore. It has high use value and good application prospects. Attached Figure Description

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0038] Figure 1 This is a schematic diagram of the recovery process of lithium iron ore mica in Embodiment 1 of the present invention. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0040] In this embodiment of the invention, the lepidolite ore raw material used comes from the Xiangyuan Lithium Polymetallic Mine in Daoxian County, Hunan Province. The valuable minerals in this mining area are mainly lepidolite, followed by ferromanganese ore, cassiterite, etc., while the gangue ores are mainly quartz, feldspar, topaz, etc. The mass percentage of Li2O in the raw ore is about 0.35% (0.3% to 0.4%), mainly lepidolite and altered lepidolite. Both contain iron and are weakly magnetic. They together account for about 25% of the total mineral content. The two are closely intergrown. Alteration starts from the edge of the lepidolite and extends inward or along its cleavage fractures, spreading irregularly to the surrounding area, often forming a complex intergrown relationship between the two. In the following embodiments, experiments were conducted on different ore samples from this mining area, such as recovering lithium concentrate from raw ores with a Li2O mass percentage of 0.37% and 0.40%.

[0041] Example 1

[0042] A method for recovering lithium mica ore, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps:

[0043] S1. Crushing the lithium iron ore raw material, specifically: crushing lithium iron ore with a Li2O mass percentage of 0.37% to a particle size ≤5mm.

[0044] S2. The crushed lithium iron ore raw material is screened using two layers of screens with different apertures. Specifically, the crushed lithium iron ore raw material obtained in step S1 is fed into a double-layer vibrating screen. The mesh size (mesh aperture) of the upper screen is 2mm, and the mesh size (mesh aperture) of the lower screen is 0.5mm. Three types of powder with particle sizes from large to small are obtained: unscreened powder in the upper layer, unscreened powder in the middle layer, and underscreen powder. The particle size of the unscreened powder in the upper layer (coarse particle product) is 2mm to 5mm, the particle size of the unscreened powder in the middle layer (medium particle size product) is 0.5mm to 2mm, and the particle size of the underscreen powder (fine particle product) is ≤0.5mm.

[0045] S3. The unscreened powder is pre-selected by magnetic separation. Specifically, the unscreened powder is mixed with water to prepare a suspension of unscreened powder. The mass percentage of unscreened powder in the suspension is 30%. The suspension is fed into a vertical ring high gradient magnetic separator for pre-selection of the unscreened powder. The diameter of the magnetic medium used in the pre-selection process is matched with the particle size of the unscreened powder. Specifically, the magnetic field strength is 1.75T, the magnetic medium is a rod medium with a diameter of 3mm, and the pulse frequency is 100rpm. Pre-selected concentrate (magnetic product) and coarse sand (non-magnetic product) are obtained. The pre-selected concentrate is mixed with the upper unscreened powder and then ground. The coarse sand product can be sold directly as a by-product.

[0046] S4. The unscreened powder from the upper layer and the pre-selected concentrate are mixed and ground. Specifically, the unscreened powder from the upper layer obtained in step S2 and the pre-selected concentrate obtained in step S3 are combined and fed into a ball mill for grinding, wherein the grinding concentration is 75%, and the ground powder is obtained.

[0047] S5. The powder obtained after grinding is mixed with the undersize powder for the first stage of classification. Specifically, the grinding powder obtained in step S4 is combined with the undersize powder obtained in step S2 and fed into a hydrocyclone for classification. During the classification process, the classification concentration is controlled at 55%, resulting in a first stage of classified underflow and a first stage of classified overflow. The first stage of classified underflow is returned to the ball mill in step S3 for grinding to improve the recovery effect, and 60% of the first stage of classified overflow has a fineness of -0.074mm.

[0048] S6. Perform a second stage of classification on the first stage of the graded overflow. Specifically, the first stage of the graded overflow obtained in step S5 is fed into a hydrocyclone for classification. During the classification process, the classification concentration is controlled at 55%, resulting in a second stage of graded sedimentation and a second stage of graded overflow. In the resulting second stage of graded overflow, 95% of the sediments have a fineness of -0.045mm.

[0049] S7. High-gradient magnetic separation is performed on the two-stage graded sediment and the two-stage graded overflow, specifically as follows:

[0050] The high-gradient magnetic separation of the two-stage graded sand using a vertical ring high-gradient magnetic separator includes the following steps:

[0051] (1) Mix the two-stage graded grit with water to obtain a mixture, the mass concentration of the two-stage graded grit in the mixture is 30%.

[0052] (2) The mixture obtained in step (1) is fed into a vertical ring high gradient magnetic separator for the first high gradient magnetic separation. During the first high gradient magnetic separation, the magnetic field strength is 1.75T, the magnetic medium is a rod medium with a diameter of 2mm, and the pulsation frequency is 100rpm to obtain the first rough concentrate and tailings.

[0053] (3) The first rough concentrate obtained in step (2) is fed into a vertical ring high-gradient magnetic separator for a second high-gradient magnetic separation. During the second high-gradient magnetic separation, the magnetic field strength is 1.75T, the magnetic medium is a rod medium with a diameter of 2mm, and the pulsation frequency is 100rpm, resulting in lithium concentrate and a first non-magnetic substance. The first non-magnetic substance is returned to the vertical ring high-gradient magnetic separator in step (2), mixed with the second-stage classifying sand, and then subjected to high-gradient magnetic separation.

[0054] The high-gradient magnetic separation of the two-stage stage overflow using a vertical ring high-gradient magnetic separator includes the following steps:

[0055] (a) The two-stage graded overflow is fed into a vertical ring high gradient magnetic separator for the first high gradient magnetic separation. During the first high gradient magnetic separation, the magnetic field strength is 1.75T, the magnetic medium is a coarse mesh medium, and the pulse frequency is 100rpm, to obtain the second rough concentrate and tailings.

[0056] (b) The second rough concentrate is fed into a vertical ring high-gradient magnetic separator for a second high-gradient magnetic separation. During the second high-gradient magnetic separation, the magnetic field strength is 1.75T, the magnetic medium is a coarse mesh, and the pulse frequency is 100rpm, yielding lithium concentrate and a second non-magnetic substance. This second non-magnetic substance is returned to the vertical ring high-gradient magnetic separator from step (a), mixed with the two-stage classification overflow, and then subjected to further high-gradient magnetic separation.

[0057] Following the above process, lithium iron ore raw materials were recovered multiple times, and the average recovery results are shown in Table 1.

[0058] Example 2

[0059] A method for recovering lithium iron ore is basically the same as the recovery method in Example 1, except that the average mass percentage of Li2O in the lithium iron ore raw material used is 0.40%.

[0060] Following the above process, lithium iron ore raw materials were recovered multiple times, and the average recovery results are shown in Table 1.

[0061] Table 1 Comparison of average recovery indices of different raw ores in Examples 1 and 2 of the present invention.

[0062]

[0063] As shown in Table 1, in Example 1 of this invention, the lithium concentrate yield is 15.98%, the Li₂O content is 1.84%, and the Li₂O recovery rate is 80.05%. Simultaneously, 30.3% coarse sand can be screened from the raw ore, which can be sold as a by-product. Similarly, in Example 2 of this invention, the lithium concentrate yield is 17.24%, the Li₂O content is 1.87%, and the Li₂O recovery rate is 81.26%. Simultaneously, 30.3% coarse sand can be screened from the raw ore, which can be sold as a by-product.

[0064] Furthermore, tests revealed that in the recovery method used in Example 1 of this invention, the grinding amount was reduced by 30.3%, and the loss of fine metal particles was reduced by 42%. In the recovery method used in Example 2 of this invention, the grinding amount was reduced by 30.3%, and the loss of fine metal particles was reduced by 44%. In contrast, conventional recovery methods failed to reduce the grinding amount, and the loss of fine metal particles was as high as 70%.

[0065] Furthermore, omitting the magnetic pre-selection step in Example 1 would not reduce the grinding volume and would not effectively utilize the coarse sand, making it difficult to maximize the economic benefits of the raw ore. Simultaneously, omitting the two-stage classification steps in Example 1 and directly subjecting the ground powder to high-gradient magnetic separation would result in several adverse effects: a low lithium concentrate yield of only 14.07% and a very low Li2O recovery rate of only 71.79%. This indicates that without graded magnetic separation, it is difficult to improve the lithium concentrate yield and Li2O recovery rate, ultimately making it difficult to efficiently recover high-quality lithium resources from low-grade lithium iron ore. Therefore, the graded magnetic separation step in the recovery method of this invention allows for the use of different magnetic media for different graded products (such as +45μm and -45μm products from grinding), enhancing the recovery of fine-grained minerals and improving the overall recovery index of the target mineral.

[0066] For the lithium iron ore raw material used in Example 2 (with an average mass percentage of Li2O of 0.40%), after crushing, it was screened and separated using multi-layer screens with different pore sizes to investigate the distribution of Li2O in powder products of different sizes, as shown in Table 2.

[0067] As shown in Table 2, the Li2O content is higher in the raw material powder with smaller particle size. This indicates that the rational use of raw material powder with smaller particle size is more conducive to improving the grade of lithium concentrate. Therefore, reducing the loss of fine-particle metal in this invention is of great significance for improving the added value of lithium iron ore.

[0068] Table 2 Metal Distribution (%) of Full-Grain-Size Pre-Selected Tailings

[0069] Particle size Yield (%) <![CDATA[Li2O grade (%)]]> <![CDATA[Distribution rate of Li2O(%)]]> +1.18mm 8.25 0.090 5.84 -1.18 +0.15mm 56.19 0.101 44.60 -0.15 +0.0385mm 23.81 0.112 20.95 -0.0385mm 11.75 0.310 28.61 Tailings 100.00 0.127 100.00

[0070] The results above demonstrate that the method of this invention, through the coordinated steps of pre-screening followed by grinding, narrow-level pre-selection and waste removal, fine-particle pre-classification, classification screening, and classification magnetic separation, achieves narrow-level waste removal from the raw ore, reducing production costs and minimizing metal loss from waste removal. Furthermore, by employing different beneficiation parameters tailored to the magnetic separation characteristics of different particle sizes, it ultimately solves the problems of high loss rates and low recovery rates of fine-particle ore. In addition, the recovery method of this invention does not use chemical reagents, which not only helps reduce recovery costs and simplify the recovery process but also reduces environmental pollution. The present invention provides a method for recovering lithium iron ore from lithium mica, which has the advantages of simple process, convenient operation, low recovery cost, small loss of fine metal particles, low grinding amount, high separation efficiency, and clean and non-toxic properties. It can recover lithium concentrate with high Li2O grade (Li2O>1.8%) and high Li2O recovery rate (lithium recovery rate>80%) from low-grade lithium iron ore (Li2O is 0.3%~0.4%). It is a new mineral processing technology with good separation effect, economy and environmental protection, and can efficiently recover lithium resources from low-grade lithium iron ore. It has high use value and good application prospects.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for recovering iron lepidolite ore, characterized by, The method comprises the following steps: S1, crushing the iron-lithium mica ore, the particle size of the crushed iron-lithium mica ore is less than or equal to 5 mm; S2, screening the crushed iron-lithium mica ore by using a double-layer screen with different mesh sizes, to obtain three kinds of powder with different particle sizes from large to small, i.e., upper un-screened powder, middle un-screened powder and screened powder; the double-layer screen with different mesh sizes comprises an upper screen and a lower screen arranged from top to bottom; the mesh size of the upper screen is 2 mm-2.5 mm; the mesh size of the lower screen is 0.3 mm-0.8 mm; S3, performing magnetic pre-selection on the middle un-screened powder by using a high-gradient magnetic separator, comprising the following steps: S3-1, mixing the middle un-screened powder with water to obtain a mixed solution; S3-2, feeding the mixed solution into the high-gradient magnetic separator to perform high-gradient magnetic pre-selection, to obtain pre-selected concentrate and coarse sand; the diameter of the magnetic medium in the high-gradient magnetic separator matches the particle size of the middle un-screened powder; in the high-gradient magnetic pre-selection process, the magnetic field strength is 1.75 T, the magnetic medium is a rod medium with a diameter of 3 mm, and the pulsating frequency is 100 rpm; S4, mixing the upper un-screened powder and the pre-selected concentrate for grinding; S5, performing first-stage classification on the mixed powder obtained after grinding and the screened powder by using a hydrocyclone, to obtain first-stage classified sand and first-stage classification overflow; in the first-stage classification process, the classification concentration is controlled to be 55%; the fineness of -0.074 mm accounts for 60% in the first-stage classification overflow; the first-stage classified sand is returned to step S4 for grinding; S6, performing second-stage classification on the first-stage classification overflow by using a hydrocyclone, to obtain second-stage classified sand and second-stage classification overflow; in the second-stage classification process, the classification concentration is controlled to be 55%; the fineness of -0.045 mm accounts for 95% in the second-stage classification overflow; S7, performing high-gradient magnetic selection on the second-stage classified sand by using a high-gradient magnetic separator, comprising the following steps: (1) mixing the second-stage classified sand with water to obtain a mixed solution; (2) feeding the mixed solution into the high-gradient magnetic separator to perform first high-gradient magnetic selection, to obtain first coarse concentrate and tailings; in the first high-gradient magnetic selection process, the magnetic field strength is 1.75 T, the magnetic medium is a rod medium with a diameter of 2 mm, and the pulsating frequency is 100 rpm; (3) feeding the first coarse concentrate into the high-gradient magnetic separator to perform second high-gradient magnetic selection, to obtain lithium concentrate and first non-magnetic substance; in the second high-gradient magnetic selection process, the magnetic field strength is 1.75 T, the magnetic medium is a rod medium with a diameter of 2 mm, and the pulsating frequency is 100 rpm; the first non-magnetic substance is returned to step (2) to be mixed with the second-stage classified sand for further high-gradient magnetic selection; S8, performing high-gradient magnetic selection on the second-stage classification overflow by using a high-gradient magnetic separator, comprising the following steps: (a) feeding the second-stage classification overflow into the high-gradient magnetic separator to perform first high-gradient magnetic selection, to obtain second coarse concentrate and tailings; in the first high-gradient magnetic selection process, the magnetic field strength is 1.75 T, the magnetic medium is a coarse mesh medium, and the pulsating frequency is 100 rpm; (b) feeding the second rough concentrate into a high gradient magnetic separator for second high gradient magnetic separation to obtain a lithium concentrate and second non-magnetic substance; in the second high gradient magnetic separation, the magnetic field strength is 1.75T, the magnetic medium is a coarse mesh medium, and the pulsating pulse frequency is 100rpm; the second non-magnetic substance is returned to step (a) and mixed with the two-stage classification overflow to continue high gradient magnetic separation.

2. The method for recovering iron lepidolite ore according to claim 1, characterized by, In step S3-1, the mass concentration of the intermediate unscreened powder in the mixed solution is 30%.

3. The method of recovering triphylite according to claim 1, wherein, In step (1), the mass concentration of the two-stage classification sand in the mixed solution is 30%.

4. The recovery method of iron lepidolite ore according to any one of claims 1 to 3, characterized in that, In step S1, the mass percentage of Li2O in the spodumene ore raw material is ≥0.3%.

5. The recovery method of iron lepidolite ore according to any one of claims 1 to 3, characterized in that, In step S2, the particle size of the upper unscreened powder is ≥2 mm; the particle size of the intermediate unscreened powder is 0.3mm-2 mm; and the particle size of the underscreened powder is ≤0.3mm.

6. The recovery method of iron lepidolite ore according to any one of claims 1 to 3, characterized in that, In step S4, a ball mill is used to grind the mixture of the upper unscreened powder and the preselected concentrate; and the grinding concentration is controlled to be 75% during the grinding process.

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