Method for sorting and enriching low-quality lithium ore

Abstract

This invention relates to the field of mineral processing, providing a method for the separation and enrichment of low-quality lithium ore, comprising the following steps: crushing lithium ore to obtain particles with an average particle size of 1-5 mm; weighing the crushed lithium ore particles and mixing them with solid sodium hydroxide, then ball milling for 1-5 hours; adding water to the ball-milled product and ball milling for 5-20 hours until the average particle size of the solid particles is 1-50 μm; subjecting the ball-milled slurry to strong magnetic separation to obtain magnetic minerals; filtering the non-magnetic slurry, drying it, and obtaining filter residue; adding water to the filter residue to obtain a slurry with a mass concentration of 20%-40%, adding sodium hexametaphosphate to it, adjusting its pH to 7-9, stirring for 3-7 minutes, then adding disaccharidated dimethyl ammonium chloride, stirring for 5-8 minutes, and flotation for 5-10 minutes to obtain lithium concentrate. This method employs a combined approach of alkaline grinding and dissociation, strong magnetic separation, and selective flotation, overcoming the technical bottleneck of efficient enrichment of low-quality lithium ore, and eliminating the need for complex flotation reagents.

Description

Technical Field

[0001] This application relates to the field of mineral processing, and in particular to a method for separating and enriching low-quality lithium ore. Background Technology

[0002] Lithium and its compounds are indispensable materials in electric vehicles and renewable energy. With the continuous development of technologies such as computers, digital cameras, mobile phones, and electric vehicles, the role of lithium is becoming increasingly apparent. Furthermore, lithium holds a very important position in the industrial and scientific fields, leading to an increasingly urgent demand for it. Lithium is mainly extracted from lithium-bearing minerals. Global lithium resources are abundant, but unevenly distributed. To date, scientists have discovered more than 150 lithium-bearing minerals, but currently, only four are suitable for development: phosphogypsum (Li₂O content 7%–9%), spodumene (Li₂O content 6%–7%), lithium-bearing sanshosite (Li₂O content 3.5%–4.5%), and lepidolite (Li₂O content 3%–4%). Currently, lithium is mainly extracted from lithium ore and is the cornerstone of the new energy vehicle industry.

[0003] Besides lithium-bearing materials, the main minerals in lithium ore samples are gangue minerals such as feldspar, quartz, and mica, primarily composed of SiO2 and Al2O3. Furthermore, most lithium ore is fine-grained, embedded within the gangue minerals. Therefore, grinding is commonly used to liberate the lithium ore. However, over-grinding inevitably occurs during grinding, resulting in lithium loss in the fine mud. Additionally, ultrafine mineral flotation suffers from high reagent consumption and low flotation grades, leading to further lithium resource loss. Currently, 200 mesh is commonly used as the grinding particle size for lithium liberation. However, even at this size, some lithium remains incompletely liberated from the nested ore, resulting in significant lithium loss in the tailings.

[0004] Current research on this topic mainly focuses on developing new flotation reagents or adjusting processes. For example, CN115999774A discloses a beneficiation method for low-grade spodumene, including the following steps: wet grinding the raw ore to be beneficiated to obtain a first slurry; then adding water to the first slurry and stirring to obtain a slurry of a preset concentration; adding a first preset reagent to the obtained slurry for reverse flotation of slime to obtain slime and desliming tailings; adding a second preset reagent to the desliming tailings for direct flotation of the desliming tailings to obtain lithium concentrate and tailings; the second preset reagent includes a modifier, a composite depressant, and a composite collector; the composite depressant is prepared by compounding tannic acid, hydroxycitric acid, lactic acid, and sodium lignosulfonate; the composite collector is prepared by compounding oleic acid, talc oil, naphthenic acid, and white oil. Through the reverse flotation desliming-direct flotation process for recovering spodumene, a large amount of gangue minerals are separated; and under the combined action of the composite depressant and composite collector, the effective recovery of low-grade spodumene is achieved. CN116103514A discloses a method for extracting lithium, aluminum, sulfur, and silicon from low-grade clay-type lithium ore, including steps such as flotation desulfurization and decarbonization pre-enrichment, roasting, primary leaching, purification and impurity removal, and secondary leaching. The method addresses the issue that the clay-type lithium ore is mainly composed of clay minerals, with lithium oxide content not exceeding 1 wt%, and lithium mainly present in the form of lithium chlorite. By employing a combined beneficiation and metallurgical process and graded extraction, products such as sulfur concentrate, lithium carbonate, alumina, and high-silicon slag are obtained, achieving comprehensive utilization of low-grade clay-type lithium ore. CN115999762A discloses a gravity-flotation combined beneficiation method for low-grade spodumene ore. The raw ore is fed into a crushing-screening operation, and the undersize product is fed into a high-frequency vibrating screen for wet screening. The undersize product is fine mud, and the oversize product is fed into a three-product heavy medium hydrocyclone for separation, obtaining gravity spodumene concentrate, gravity tailings, and gravity medium. The fine mud and gravity medium are combined and fed into a grinding-classifying operation. The overflow from the classification is used as flotation feed for spodumene recovery. The spodumene flotation operation adopts a process flow of one roughing, two cleaning, one scavenging, and sequential return of medium. Finally, flotation spodumene concentrate with a Li2O grade ≥ 5.7% and flotation spodumene tailings with a Li2O grade ≤ 0.35% are obtained. CN115870086A discloses a method for recovering lithium concentrate from lithium-bearing ore. The method employs an SABC (Small Aperture Bracelet) grinding system to grind the lithium-bearing ore, obtaining ore particles with a diameter no greater than 0.25 mm. The material undergoes a first magnetic separation treatment to obtain a first magnetic mineral and a first non-magnetic mineral. The first non-magnetic mineral is then subjected to gravity separation to obtain gravity-separated non-lithium concentrate and gravity-separated tailings. The gravity separation treatment includes sequential processes of spreading sluice and shaking table treatment. The gravity-separated tailings are deslimed and classified to obtain ore sand and ore slime. The ore sand is then subjected to flotation to obtain lithium concentrate. This method has low production costs and is beneficial for improving the recovery rate and grade of lithium-bearing ore, especially ultra-low-grade lithium-bearing ore.CN113046548A discloses a method for beneficiating low-grade spodumene ore, comprising the following steps: S1, crushing the low-grade spodumene ore into blocks with a diameter of less than 5 cm; S2, preheating, preheating the crushed block ore in S1 to a temperature of 200-500℃; S3, sintering, transferring the preheated block ore in step S2 to a sintering furnace, heating it to 1000-1100℃, and sintering for 0.5-1 h; S4, lithium concentrate powder screening, allowing the powder from the sintering in step S3 to cool naturally to room temperature, and then screening it using a 100-200 mesh sieve. The fine powder that passes through the sieve is the beneficiated lithium concentrate powder; the coarse powder that passes through the sieve is coarse sand containing some lithium concentrate. CN109701735A discloses a composite collector comprising amino acids, fatty acids, and diesel oil, wherein the weight ratio of the amino acids, fatty acids, and diesel oil is (80-90):(5-10):(5-10). This composite collector can improve the lithium grade in spodumene concentrate without wasting lithium resources, while also reducing the content of iron impurities. However, the aforementioned methods all suffer from problems such as significant lithium loss, complex and costly flotation reagents, and cumbersome procedures.

[0005] Therefore, how to effectively sort low-grade lithium ore through simple processes, improve its economic value, and make full use of low-grade lithium ore is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] To address the problems of low lithium recovery rate from low-grade lithium ore, complex and costly flotation reagents, and cumbersome processes, a method for the separation and enrichment of low-grade lithium ore is provided, comprising the following steps: crushing the lithium ore; mixing the crushed lithium ore particles with solid sodium hydroxide and then ball milling; adding water to the ball milling product and continuing ball milling until the average particle size of the solid particles is 1-50 μm; obtaining magnetic minerals through strong magnetic separation; filtering the non-magnetic slurry; drying to obtain filter residue; adding sodium hexametaphosphate and disecyldimethylammonium chloride to the filter residue and stirring for flotation for 5-10 minutes to obtain lithium concentrate. This method employs a combined approach of alkaline milling dissociation, strong magnetic separation, and selective flotation, overcoming the technical bottleneck of efficient enrichment of low-grade lithium ore (Li₂O < 1.2%), and eliminating the need for complex flotation reagents. It offers significant advantages in grade improvement, recovery rate, cost control, and environmental friendliness.

[0007] Specifically, this invention proposes a method for separating and enriching low-quality lithium ore, comprising the following steps:

[0008] S1. Crush the lithium ore to obtain particles with an average particle size of 1~5mm;

[0009] S2. Weigh the crushed lithium ore particles and solid sodium hydroxide at a mass ratio of 1:1-1.5, mix them, and then ball mill for 1-5 hours. During the ball milling process, solid NaOH reacts chemically with lithium ore. NaOH penetrates into the mineral lattice, breaks the Si-O-Al bond, and promotes the dissociation of minerals such as spodumene and lepidolite.

[0010] S3. Add water to the ball-milled product from step S2 at a mass concentration of 1%-20% of lithium ore particles, and continue ball milling for 5-20 hours until the average particle size of the solid particles is 1-50 μm. Perform strong magnetic separation on the ball-milled slurry with a magnetic field strength of 1.2T-1.5T to obtain magnetic minerals. Filter the non-magnetic slurry, dry it, and obtain filter residue. Through two-step ball milling, the average particle size of the solid particles is finally reduced to 1-50 μm, which significantly improves the separation efficiency between the target mineral and gangue minerals. In addition, the strong alkaline environment further promotes the dissolution and separation of quartz and alumina, further improving the separation between the target mineral and gangue minerals.

[0011] S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20%~40%. Add sodium hexametaphosphate to it and adjust its pH to 7~9. Stir for 3-7 minutes, then add didecyl dimethyl ammonium chloride and stir for 5-8 minutes. Float for 5-10 minutes to obtain lithium concentrate.

[0012] Preferably, the low-quality lithium ore includes at least one of spodumene, lepidolite, and petalite, and the Li2O grade in the lithium ore is less than 1.2%.

[0013] Preferably, the crushing in step S1 is a multi-stage crushing process using a combination of a jaw crusher and a cone crusher, and the particle size D90 is controlled to be 1-5 mm after crushing and sieving. Using a combination of jaw crusher and cone crusher for multi-stage crushing helps to more effectively liberate valuable minerals from gangue minerals during subsequent ball milling, thereby improving the degree of liberation of individual minerals.

[0014] Preferably, in step S2, the purity of the solid sodium hydroxide is ≥95%, the ball mill is one of drum ball mill, planetary ball mill, or sand mill, the ball milling media is one of steel balls or zirconia balls, the ball-to-material mass ratio during ball milling is (5-10):1, and the ball mill speed is 300-500 rpm, thus achieving efficient crushing and mixing.

[0015] Preferably, in step S2, nitrogen gas is introduced for protection during ball milling to control the temperature inside the milling jar to ≤60℃. This prevents the ore from oxidizing at high temperatures, maintains mineral activity, and at the same time, controls the temperature to avoid changes in mineral structure caused by overheating.

[0016] Preferably, in step S3, the high-intensity magnetic separation uses a pulsating high-gradient magnetic separator with a pulsation frequency of 200-300 times / min and a slurry flow rate of 0.5-1.5 L / min. This treatment can effectively remove magnetic minerals such as iron-containing minerals, obtaining non-magnetic lithium ore slurry, reducing the impact of these impurities on the subsequent flotation process, thereby improving the concentrate grade.

[0017] Preferably, in step S4, the amount of sodium hexametaphosphate added is 0.5-2 kg / t of filter residue, and the amount of diecryldimethylammonium chloride added is 0.3-1 kg / t of filter residue.

[0018] Preferably, in step S4, the pH is adjusted using at least one of sodium carbonate, sodium hydroxide, hydrochloric acid, and sulfuric acid, the stirring speed is 1000-1500 rpm, and a mechanically stirred flotation machine is used for flotation. By adjusting the pH, selecting specific inhibitors and collectors, the slime can be effectively dispersed, preventing the slime from encapsulating the target mineral, further creating a suitable flotation environment with good selectivity and collection ability.

[0019] Preferably, after step S4, the lithium concentrate is further subjected to a washing step: washing with deionized water 3-5 times, filtering and drying after washing to obtain lithium concentrate with Li2O grade ≥8%.

[0020] Preferably, in step S4, the flotation froth product undergoes secondary purification, during which 0.2-0.5 kg / t of sodium hexametaphosphate and 0.1-0.4 kg / t of disecyldimethylammonium chloride are added. Through secondary purification, the concentrate is further purified, yielding high-quality lithium concentrate with a higher Li₂O grade. The secondary purification involves stirring for 2-5 minutes and flotation for 1-3 minutes.

[0021] The beneficial effects of this invention include:

[0022] 1. This invention can effectively improve the grade and recovery rate of lithium concentrate. Through multi-stage crushing, alkaline grinding and dissociation, high-concentration alkaline ball milling and selective flotation, the Li2O grade in the raw ore can be enriched from ≤1.2% to ≥8%, reaching the industrial grade lithium concentrate standard.

[0023] 2. By employing magnetic separation, secondary cleaning, and flotation with disecuryldimethylammonium chloride + sodium hexametaphosphate, the Li2O recovery rate can reach ≥95%, which is significantly higher than that of traditional processes.

[0024] 3. Specific processing techniques can effectively enhance the liberation of lithium ore. In the first ball milling, solid NaOH and ore undergo mechanochemical interaction during the milling process. NaOH penetrates into the mineral lattice, destroys Si-O-Al bonds, and promotes the liberation of minerals such as spodumene and lepidolite. The second ball milling under a strong alkaline environment allows for the full liberation of lithium minerals, while avoiding over-milling that leads to fine mud formation, reducing reagent consumption and flotation foam entrainment. In addition, it can further promote the destruction of Si-O-Al bonds and accelerate the liberation of lithium ore from gangue components such as quartz.

[0025] 4. The method of the present invention is simple and easy to operate, requires no complicated flotation reagents, has low cost, significantly improves the separation efficiency of lithium ore and concentrate grade, greatly enhances resource utilization and economic benefits, and provides reliable technical support for the effective development and utilization of low-grade lithium resources. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein. The reagents used herein may be commercially available related products, and performance testing standards refer to industry or national standards.

[0028] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0029] The features and performance of this application are further described in detail below with reference to the embodiments: The lithium ore is selected from the low-grade spodumene, lepidolite, and phosphine aluminum ore composite lithium ore of Jiajika Lithium Mine in Sichuan. The main valuable element in the raw ore is lithium, containing 1.05wt% Li2O, 68.4wt% SiO2 and 14.5wt% Al2O3, respectively. Lithium is mainly found in spodumene and lepidolite, and a small amount is found in phosphine aluminum ore. It belongs to the ultra-low grade spodumene, lepidolite and phosphine aluminum ore composite lithium ore.

[0030] Example 1

[0031] A method for separating and enriching low-quality lithium ore includes the following steps:

[0032] S1. A combination of jaw crusher and cone crusher is used for multi-stage crushing. After crushing, the particle size D90 is controlled to be 1-5mm by sieving.

[0033] S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity ≥95% according to a mass ratio of 1:1, mix them, and then ball mill for 5 hours. The ball mill is a drum ball mill, the ball milling medium is steel balls, the ball-to-material mass ratio during ball milling is 5:1, and the ball mill speed is 300 rpm. Nitrogen gas is introduced for protection during the ball milling process, and the temperature inside the ball mill jar is controlled to be ≤60℃.

[0034] S3. Add water to the ball-milled product from step S2 at a mass concentration of 1% of lithium ore particles, and continue ball milling for 20 hours until the average particle size of the solid particles is 10-50 μm. Perform strong magnetic separation on the ball-milled slurry using a pulsed high-gradient magnetic separator with a magnetic field strength of 1.2T, a pulse frequency of 300 times / min, and a slurry flow rate of 1.5L / min to obtain magnetic minerals. Filter the non-magnetic slurry, dry it, and obtain filter residue.

[0035] S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20%. Add 2 kg / t of sodium hexametaphosphate to the slurry and adjust its pH to 7. Stir at 1500 rpm for 7 min. Then add 1 kg / t of disaccharidodimethylammonium chloride to the slurry and stir for 5 min. Float in a mechanically stirred flotation machine for 10 min. Wash with deionized water 3-5 times. After washing, filter and dry to obtain lithium concentrate with a Li2O grade of 8.3%. The calculated Li2O recovery rate is 95.2%.

[0036] Example 2

[0037] A method for separating and enriching low-quality lithium ore includes the following steps:

[0038] S1. A combination of jaw crusher and cone crusher is used for multi-stage crushing. After crushing, the particle size D90 is controlled to be 1-5mm by sieving.

[0039] S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity ≥95% according to a mass ratio of 1:1.5, mix them, and then ball mill for 1 hour. The ball mill is a sand mill, the ball milling medium is zirconia balls, the ball-to-material mass ratio during ball milling is 10:1, and the ball mill speed is 500 rpm. Nitrogen gas is introduced for protection during the ball milling process, and the temperature inside the ball mill jar is controlled to be ≤55℃.

[0040] S3. Add water to the ball-milled product from step S2 at a mass concentration of 20% of lithium ore particles, and continue ball milling for 5 hours until the average particle size of the solid particles is 1-30 μm. Perform strong magnetic separation on the ball-milled slurry using a pulsed high-gradient magnetic separator with a magnetic field strength of 1.5T, a pulse frequency of 200 times / min, and a slurry flow rate of 0.5L / min to obtain magnetic minerals. Filter the non-magnetic slurry, dry it, and obtain filter residue.

[0041] S4. Add water to the filter residue to obtain a slurry with a mass concentration of 40%. Add 0.5 kg / t of sodium hexametaphosphate to the slurry and adjust the pH to 9. Stir at 1000 rpm for 3 minutes. Then add 0.8 kg / t of diecryldimethylammonium chloride and stir for 8 minutes. Float using a mechanically stirred flotation machine for 5 minutes. Wash 3-5 times with deionized water. After washing, filter and dry. Perform a second cleaning process on the product. During the second cleaning, add 0.2 kg / t of flotation foam sodium hexametaphosphate and 0.4 kg / t of flotation foam diecryldimethylammonium chloride. Stir for 5 minutes and float for 3 minutes. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 8.9%. The calculated Li2O recovery rate is 96.3%.

[0042] Example 3

[0043] A method for separating and enriching low-quality lithium ore includes the following steps:

[0044] S1. A combination of jaw crusher and cone crusher is used for multi-stage crushing. After crushing, the particle size D90 is controlled to be 2-3mm by sieving.

[0045] S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity ≥95% according to a mass ratio of 1:1.3, mix them, and then ball mill for 3 hours. The ball mill is a planetary ball mill, the ball milling media is zirconia balls, the ball-to-material mass ratio during ball milling is 7:1, and the ball mill speed is 400 rpm. Nitrogen gas is introduced for protection during the ball milling process, and the temperature inside the ball mill jar is controlled to be ≤50℃.

[0046] S3. Add water to the ball-milled product from step S2 at a mass concentration of 10% of lithium ore particles, and continue ball milling for 15 hours until the average particle size of the solid particles is 10-40 μm. Perform strong magnetic separation on the ball-milled slurry using a pulsed high-gradient magnetic separator with a magnetic field strength of 1.3T, a pulse frequency of 250 times / min, and a slurry flow rate of 1L / min to obtain magnetic minerals. Filter the non-magnetic slurry, dry it, and obtain filter residue.

[0047] S4. Add water to the filter residue to obtain a slurry with a mass concentration of 30%. Add 0.6 kg / t of sodium hexametaphosphate to the slurry and adjust the pH to 8. Stir at 1200 rpm for 5 min. Then add 0.3 kg / t of diecryldimethylammonium chloride and stir for 6 min. Float using a mechanically stirred flotation machine for 8 min. Wash 3-5 times with deionized water. After washing, filter and dry. Perform a second cleaning process on the product. During the second cleaning, add 0.5 kg / t of flotation foam sodium hexametaphosphate and 0.1 kg / t of flotation foam diecryldimethylammonium chloride. Stir for 3 min and float for 1 min. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 9.1%. The calculated Li2O recovery rate is 95.1%.

[0048] Comparative Example 1

[0049] A method for separating and enriching low-quality lithium ore includes the following steps:

[0050] S1. A jaw crusher is used to crush the lithium ore, and the particle size D90 is controlled to be 10-20mm after crushing and sieving.

[0051] S2. Weigh the crushed lithium ore particles and ball mill for 5 hours; the ball mill is a drum ball mill, the ball milling medium is steel balls, the ball-to-material mass ratio during ball milling is 5:1, and the ball mill speed is 300 rpm; nitrogen gas is introduced for protection during the ball milling process, and the temperature inside the ball mill jar is controlled to be ≤60℃.

[0052] S3. Add water to the ball-milled product from step S2 at a mass concentration of 1% of lithium ore particles, and continue ball milling for 20 hours until the average particle size of the solid particles is 74 μm. Perform strong magnetic separation on the ball-milled slurry using a pulsed high-gradient magnetic separator with a magnetic field strength of 1.2T, a pulse frequency of 300 times / min, and a slurry flow rate of 1.5L / min to obtain magnetic minerals. Filter the non-magnetic slurry, dry it, and obtain filter residue.

[0053] S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20%. Add 2 kg / t of sodium hexametaphosphate to the slurry and adjust its pH to 7. Stir at 1500 rpm for 7 min. Then add 1 kg / t of disaccharidodimethylammonium chloride to the slurry and stir for 5 min. Float in a mechanically stirred flotation machine for 10 min. Wash with deionized water 3-5 times. After washing, filter and dry to obtain lithium concentrate with a Li2O grade of 3.2%. The calculated Li2O recovery rate is 25.7%.

[0054] Comparative Example 2

[0055] A method for separating and enriching low-quality lithium ore includes the following steps:

[0056] S1. A combination of jaw crusher and cone crusher is used for multi-stage crushing. After crushing, the particle size D90 is controlled to be 1-5mm by sieving.

[0057] S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity ≥95% according to a mass ratio of 5:1, mix them, and then ball mill for 3 hours. The ball mill is a drum ball mill, the ball milling medium is steel balls, the ball-to-material mass ratio during ball milling is 5:1, and the ball mill speed is 300 rpm. Nitrogen gas is introduced for protection during the ball milling process, and the temperature inside the ball mill jar is controlled to be ≤60℃.

[0058] S3. Add water to the ball-milled product of step S2 at a mass concentration of 25% of lithium ore particles, and continue ball milling for 20 hours until the average particle size of the solid particles is 30-80 μm. Perform strong magnetic separation on the ball-milled slurry using a pulsed high-gradient magnetic separator with a magnetic field strength of 1.2T, a pulse frequency of 300 times / min, and a slurry flow rate of 2L / min to obtain magnetic minerals. Filter the non-magnetic slurry, dry it, and obtain filter residue.

[0059] S4. Add water to the filter residue to obtain a slurry with a mass concentration of 15%. Add 0.4 kg / t of sodium hexametaphosphate to the slurry and stir at 1500 rpm for 7 min. Then add 1.2 kg / t of disaccharide dimethyl ammonium chloride to the slurry and stir for 5 min. Float in a mechanically stirred flotation machine for 10 min. Wash with deionized water 3-5 times. After washing, filter and dry to obtain lithium concentrate with a Li2O grade of 5.4%. The calculated Li2O recovery rate is 52.8%.

[0060] Comparative Example 3

[0061] A method for separating and enriching low-quality lithium ore includes the following steps:

[0062] S1. A combination of jaw crusher and cone crusher is used for multi-stage crushing. After crushing, the particle size D90 is controlled to be 1-5mm by sieving.

[0063] S2. Weigh the crushed lithium ore particles at a mass ratio of 1:1.5 and mix them with sodium carbonate with a purity of ≥95%, then ball mill for 1 hour. The ball mill is a sand mill, the ball milling medium is zirconia balls, the ball-to-material mass ratio during ball milling is 10:1, and the ball mill speed is 500 rpm. Nitrogen gas is introduced for protection during the ball milling process, and the temperature inside the ball mill jar is controlled to be ≤55℃.

[0064] S3. Add water to the ball-milled product from step S2 at a mass concentration of 20% of lithium ore particles, and continue ball milling for 5 hours until the average particle size of the solid particles is 10-30 μm. Perform strong magnetic separation on the ball-milled slurry using a pulsed high-gradient magnetic separator with a magnetic field strength of 1.5T, a pulse frequency of 200 times / min, and a slurry flow rate of 0.5L / min to obtain magnetic minerals. Filter the non-magnetic slurry, dry it, and obtain filter residue.

[0065] S4. Add water to the filter residue to obtain a slurry with a mass concentration of 40%. Add 0.5 kg / t of sodium hexametaphosphate to the slurry and adjust the pH to 9. Stir at 1000 rpm for 3 minutes. Then add 0.8 kg / t of diecryldimethylammonium chloride and stir for 8 minutes. Float using a mechanically stirred flotation machine for 5 minutes. Wash 3-5 times with deionized water. After washing, filter and dry. Perform a second cleaning process on the product. During the second cleaning, add 0.2 kg / t of flotation foam sodium hexametaphosphate and 0.4 kg / t of flotation foam diecryldimethylammonium chloride, stir for 5 minutes, and float for 3 minutes. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 5.7%. The calculated Li2O recovery rate is 41.6%.

[0066] Comparative Example 4

[0067] A method for separating and enriching low-quality lithium ore includes the following steps:

[0068] S1. A combination of jaw crusher and cone crusher is used for multi-stage crushing. After crushing, the particle size D90 is controlled to be 1-5mm by sieving.

[0069] S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity ≥95% at a mass ratio of 1:1.5. Add water to the lithium ore particles at a mass concentration of 20% of the lithium ore particles. After stirring and dispersing evenly, add solid sodium hydroxide and ball mill for 5 hours until the average particle size of the solid particles is 40-100μm. The ball milling media is zirconia balls, the ball-to-material mass ratio is 10:1, and the ball mill speed is 500rpm. Nitrogen gas is introduced for protection during ball milling, and the temperature inside the ball mill is controlled to be ≤55℃. The ball-milled slurry is subjected to strong magnetic separation using a pulsed high-gradient magnetic separator with a magnetic field strength of 1.5T, a pulse frequency of 200 times / min, and a slurry flow rate of 0.5L / min to obtain magnetic minerals. Filter the non-magnetic slurry, dry it, and obtain filter residue.

[0070] S3. Add water to the filter residue to obtain a slurry with a mass concentration of 40%. Add 0.5 kg / t of sodium hexametaphosphate to the slurry and adjust the pH to 9. Stir at 1000 rpm for 3 minutes. Then add 0.8 kg / t of diecryldimethylammonium chloride and stir for 8 minutes. Float using a mechanically stirred flotation machine for 5 minutes. Wash 3-5 times with deionized water. After washing, filter and dry. Perform a second cleaning process on the product. During the second cleaning, add 0.2 kg / t of flotation foam sodium hexametaphosphate and 0.4 kg / t of flotation foam diecryldimethylammonium chloride. Stir for 5 minutes and float for 3 minutes. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 6.1%. The calculated Li2O recovery rate is 44.7%.

[0071] Comparative Example 5

[0072] A method for separating and enriching low-quality lithium ore includes the following steps:

[0073] S1. A combination of jaw crusher and cone crusher is used for multi-stage crushing. After crushing, the particle size D90 is controlled to be 1-5mm by sieving.

[0074] S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity ≥95% according to a mass ratio of 200:1, mix them, and then ball mill for 1 hour; the ball mill is a sand mill, the ball milling medium is zirconia balls, the ball-to-material mass ratio during ball milling is 10:1, and the ball mill speed is 500 rpm;

[0075] S3. Add 1M sodium hydroxide solution to the ball-milled product from step S2 at a mass concentration of 20% of lithium ore particles, and continue ball milling for 5 hours until the average particle size of the solid particles is 10-30 μm. Perform strong magnetic separation on the ball-milled slurry using a pulsed high-gradient magnetic separator with a magnetic field strength of 1.5T, a pulse frequency of 200 times / min, and a slurry flow rate of 0.5L / min to obtain magnetic minerals. Filter the non-magnetic slurry, dry it, and obtain filter residue.

[0076] S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20%. Add 0.5 kg / t of sodium hexametaphosphate to the slurry and adjust the pH to 8. Stir at 1000 rpm for 3 minutes. Then add 0.8 kg / t of diecryldimethylammonium chloride and stir for 8 minutes. Float using a mechanically stirred flotation machine for 5 minutes. Wash 3-5 times with deionized water. After washing, filter and dry. Perform a second cleaning process on the product. During the second cleaning, add 0.2 kg / t of flotation foam sodium hexametaphosphate and 0.4 kg / t of flotation foam diecryldimethylammonium chloride, stir for 5 minutes, and float for 3 minutes. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 6.7%. The calculated Li2O recovery rate is 56.8%.

[0077] The above provides a detailed description of a method for separating and enriching low-grade lithium ore. As can be seen from the examples and comparative examples, the specific method of the present invention can obtain high-grade lithium concentrate with a purity higher than 8%, and the Li2O recovery rate is also high, reaching 95%, which is significantly higher than that of traditional processes. The method of the present invention does not require complex flotation reagents and has a low cost, providing reliable technical support for the effective development and utilization of low-grade lithium resources.

[0078] The preferred embodiments of the present invention have been described in detail above, and are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for separating and enriching low-quality lithium ore, characterized in that, It consists of the following steps: S1. The lithium ore is crushed in multiple stages using a combination of jaw crusher and cone crusher, and then screened to obtain particles with an average particle size of 1~5mm. S2. Weigh the crushed lithium ore particles and solid sodium hydroxide at a mass ratio of 1:1-1.5, mix them, and then ball mill for 1-5 hours. The ball mill is one of the following: drum ball mill, planetary ball mill, and sand mill. The mass ratio of ball to material during ball milling is (5-10):

1. The ball mill speed is 300-500 rpm. Nitrogen gas is introduced for protection during the ball milling process, and the temperature inside the ball mill jar is controlled to be ≤60℃. S3. Add water to the ball milling product of step S2 at a mass concentration of 1%-20% of lithium ore particles, and continue ball milling for 5-20 hours until the average particle size of the solid particles is 1-50 μm; subject the ball-milled slurry to strong magnetic separation with a magnetic field strength of 1.2T-1.5T to obtain magnetic minerals; filter the non-magnetic slurry, dry it, and obtain filter residue. S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20%~40%. Add sodium hexametaphosphate to it and adjust its pH to 7~9. Stir for 3-7 minutes, then add didecyl dimethyl ammonium chloride and stir for 5-8 minutes. Float for 5-10 minutes to obtain lithium concentrate.

2. The method for separating and enriching low-quality lithium ore according to claim 1, characterized in that, The low-quality lithium ore includes at least one of spodumene, lepidolite, and petalite, and the Li2O grade in the lithium ore is less than 1.2%.

3. The method for separating and enriching low-quality lithium ore according to claim 1, characterized in that, In step S2, the purity of the solid sodium hydroxide is ≥95%, and the milling media is one of steel balls or zirconia balls.

4. The method for separating and enriching low-quality lithium ore according to claim 1, characterized in that, In step S3, the strong magnetic separation adopts a pulsating high gradient magnetic separator with a pulsation frequency of 200-300 times / min and a slurry flow rate of 0.5-1.5L / min.

5. The method for separating and enriching low-quality lithium ore according to claim 1, characterized in that, In step S4, the amount of sodium hexametaphosphate added is 0.5-2 kg / t of filter residue, and the amount of diecryldimethylammonium chloride added is 0.3-1 kg / t of filter residue.

6. The method for separating and enriching low-quality lithium ore according to claim 1, characterized in that, In step S4, the pH is adjusted using at least one of sodium carbonate and sodium hydroxide, the stirring speed is 1000-1500 rpm, and the flotation is performed using a mechanically stirred flotation machine.

7. The method for separating and enriching low-quality lithium ore according to claim 1, characterized in that, After step S4, the lithium concentrate is further washed with deionized water 3-5 times, filtered and dried to obtain lithium concentrate with a Li2O grade ≥8%.