Spodumene beneficiation for lithium recovery.

Abstract

A method for recovering a lithium concentrate from a spodumene-containing ore is provided. The ore is crushed to obtain a fine fraction and a coarse fraction. The coarse fraction is calcined at a temperature of about 950°C to about 1100°C to obtain a calcined coarse fraction containing spodumene particles having a β crystalline structure. The calcined coarse fraction is selectively screened to separate the spodumene particles and produce screened spodumene particles. The screened spodumene particles are subjected to magnetic separation to beneficiate the spodumene particles, separate non-magnetic contaminants, and recover a lithium concentrate.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from U.S. Provisional Patent Application No. 63 / 479,045, filed January 9, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates generally to the field of lithium recovery from spodumene ore. [Background technology]

[0003] As global demand for lithium continues to grow, there is also increasing pressure to extract lithium from ores such as spodumene. In recovering lithium from spodumene, the spodumene is typically beneficiated by flotation or a combination of flotation and heavy media separation. After the beneficiation step, the spodumene concentrate is typically calcined to allow for the extraction of lithium using conventional hydrometallurgical processes such as sulfuric acid leaching.

[0004] The flotation process requires many steps to achieve satisfactory metallurgical results: crushing, ore separation, fine grinding, fines removal, conditioning, mica removal (if necessary), spodumene flotation (in multiple steps), magnetic separation, filtration, and calcination. Given the complexity and the large number of steps required, lithium recovery rates from this process are generally less than 80%. Furthermore, the use of chemical reagents makes residue disposal difficult. Dense medium separation is another spodumene beneficiation method, but it is not applicable to all spodumene deposits, and recovery rates from this method are typically less than 50%.

[0005] Recently, calcination and selective screening of β-spodumene has been found to significantly improve lithium yields while limiting or eliminating the need for flotation and associated processes (WO 2022 / 204787).

[0006] However, further improvements in recovery rates are desired. Summary of the Invention

[0007] In one aspect, there is provided a method for recovering a lithium concentrate from a spodumene-containing ore, the method comprising crushing the ore to obtain a fine fraction and a coarse fraction; calcining the coarse fraction, preferably at a temperature of from about 950°C to about 1100°C, to obtain a calcined coarse fraction comprising spodumene particles having a β crystalline structure; selectively screening the calcined coarse fraction to separate the spodumene particles to produce screened spodumene particles; and / or subjecting the screened spodumene particles to magnetic separation to beneficiate the spodumene particles and separate non-magnetic contaminants and obtain a lithium concentrate.

[0008] In some embodiments, the lithium concentrate comprises at least about 3% Li2O. In some embodiments, selective screening includes vibratory screening, air classification, cyclone sizing, or any other particle size separation means.

[0009] In some embodiments, the crushing comprises mechanical grinding and / or milling. In some embodiments, the coarse fraction comprises particles having a particle size of 850 μm or greater. In some embodiments, the coarse fraction comprises particles having a particle size of 500 μm or greater.

[0010] In some embodiments, the particles of the coarse fraction have a particle size of up to 15 mm. In some embodiments, the spodumene particles have a particle size of at least about 300 μm.

[0011] In some embodiments, the method further comprises obtaining a lithium salt from the lithium concentrate. In some embodiments, the lithium salt is LiOH, Li2O, and / or Li2CO3.

[0012] In some embodiments, magnetic separation is performed using magnetized rolls or drums. In some embodiments, a rare earth roll magnetic separator is used for magnetic separation.

[0013] In some embodiments, a multi-pass magnetic separator is used for magnetic separation. In some embodiments, the multi-pass magnetic separator is a three-pass magnetic separator. In another embodiment, the methods described herein further comprise the step of determining the degree of fragilization of the spodumene particles in the calcined coarse fraction.

[0014] In one embodiment, the degree of embrittlement is determined by microscopic examination, visual inspection with the naked eye, or particle size distribution analysis. In a further embodiment, the methods described herein further include grinding and / or milling the spodumene particles if the embrittlement of the spodumene particles is below a predetermined threshold.

[0015] In one embodiment, the threshold is that the spodumene particles have a particle size that is about 4 times smaller than the mineral particles, about 4.25 times, 4.5 times, or preferably 5 times smaller than the mineral particles.

[0016] In a further embodiment, the methods described herein further comprise the step of autoclaving the lithium concentrate to produce a slurry. In one embodiment, the additive salt and / or aqueous phase is added during autoclaving.

[0017] In a further embodiment, the methods described herein further comprise biocarbonation of the slurry to produce a LiHCO3-containing solution. In one embodiment, biocarbonation removes impurities.

[0018] In another embodiment, the methods described herein produce a lithium concentrate containing less than 0.5% impurities. In one embodiment, the coarse fraction is calcined to change the crystal structure of the spodumene particles from an α- to a β-crystalline structure. Calcination of the coarse fraction can be carried out using natural gas, propane, heavy oil, biomass, and / or electricity, for example, using a directly heated rotary kiln, an indirectly heated rotary kiln, and / or a fluidized bed.

[0019] In one embodiment, a lithium ion battery is provided that includes a lithium salt produced by the method of the present disclosure. Many additional features and combinations thereof that improve the present invention will be apparent to those skilled in the art upon reading this disclosure. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a flow diagram illustrating a method according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0021] The disclosed method seeks to improve the yield of lithium recovered from ores, concentrates, or waste products by adding a post-calcination magnetic separation step (i.e., magnetic separation of β-spodumene). Magnetic separation is typically performed upstream of calcination to remove iron-containing gangue impurities (minerals) associated with the spodumene (when the spodumene is α-spodumene). For example, high-intensity magnetic separators may be used to remove iron-containing impurities. However, it has surprisingly been discovered herein that β-spodumene can be further purified as a magnetic species to remove contaminants such as quartz and other non-magnetic gangue minerals. This process is therefore the opposite of conventional magnetic separation performed upstream on α-spodumene, where α-spodumene is a non-magnetic mineral species and iron-rich, magnetically strong contaminants are removed.

[0022] Referring to FIG. 1 , a method 100 for producing a lithium concentrate is provided. First, ore obtained from a mine is crushed into a fine fraction and a coarse fraction (102). Alternatively, lithium-containing concentrate or waste may be provided. Crushing of the waste may be performed as needed. Thus, after completion of step 102, a crushed product can be obtained. Generally, the ore contains spodumene (and possibly other minerals). The ore may be a spodumene-containing crude ore (ROM) or a spodumene concentrate. Spodumene comprises the majority of the lithium present in the ore. In some examples, at least 95% of the lithium in the ore is contained in spodumene. The ore may be crushed to have a particle size of less than about 15 mm. Crushing the ROM can dissociate spodumene grains, which may be associated with other minerals. Thus, in some embodiments, the method includes crushing the ROM ore to obtain crushed ore particles having a particle size of less than 15 mm, and in some embodiments, less than 6 mm. The crushed ore is divided into a fine fraction and a coarse fraction. The spodumene ore fed to the process may have any LiO grade and may be crude, pre-concentrated, or beneficiated ore from any process. Examples of pre-concentration / beneficiation processes may include ore separation, heavy fluid separation, flotation, magnetic separation, etc. As described herein, in some embodiments, when performed on calcined ore (as opposed to calcined ore), flotation and heavy fluid separation are excluded from the process of the present invention. In that case, flotation and heavy fluid separation are not necessary, and therefore they only increase cost and complexity without significantly affecting the lithium yield that can be obtained. However, heavy fluid separation may be used prior to calcination of the coarse fraction, but only if desired, solely to reduce the mass to be calcined / reducing the energy required for calcination. In some embodiments, flotation may be applied to the fine fraction, if desired. In some embodiments, pressure separation is applied to the coarse fraction and flotation is applied to the fine fraction. In embodiments where the starting material is a concentrate, pressure separation and flotation may be performed. Another embodiment includes that the fine fraction may also be calcined.The lithium contained in the calcined product can be recovered through sieving and magnetic separators.

[0023] In a further embodiment, the method includes separating the shredded product to obtain a fine fraction and a coarse fraction. This can be achieved by particle size separation techniques (e.g., screening using an appropriately sized mesh or air classification). In one embodiment, the term "fine fraction," as used herein, refers to a fraction containing particles having a particle size of less than about 850 μm, less than about 700 μm, less than about 600 μm, less than about 500 μm, less than about 400 μm, or less than about 300 μm. The minimum particle size of the fine fraction can be, for example, 45 μm. The term "coarse fraction," as used herein, refers to a fraction containing particles having a particle size larger than that of the fine fraction. For example, the coarse fraction contains particles having a particle size of at least about 300 μm, at least about 400 μm, at least about 500 μm, at least about 600 μm, at least about 700 μm, or at least about 850 μm or larger.

[0024] Separation of the fine and coarse particles into fine and coarse fractions, respectively, prior to calcination can increase the gangue / spodumene separation efficiency of the coarse particles, which can result in higher spodumene concentrations (higher concentrate grades).

[0025] The coarse fraction derived from the crushed ore is then subjected to calcination step 104. In some embodiments, the coarse fraction is provided "as crushed," and no other separation steps are performed on the coarse fraction. For example, between crushing and calcination, the coarse fraction is not subjected to flotation or heavy fluid separation. Meanwhile, the fine fraction may be subjected to flotation and / or other suitable separation processes to extract lithium therefrom. This disclosure focuses on the coarse fraction. One objective of the present method is to reduce (e.g., by up to 90%) the amount of material subjected to flotation and / or heavy fluid separation by not including the coarse fraction, which is instead subjected to the separation methods described herein. Thus, significant cost savings can be realized, as flotation and heavy fluid separation require multiple steps and equipment.

[0026] Calcination 104 may be performed to modify the crystal structure of the spodumene particles to enable subsequent selective screening 106. Spodumene naturally exists in its α-crystal structure (i.e., α-spodumene), which is relatively stable (and in some embodiments, resistant to chemical degradation). To enable selective screening of the lithium-containing particles (spodumene) from the calcined ore, calcination 104 converts the spodumene crystal structure from the α-phase to the β-phase, resulting in β-spodumene.

[0027] According to DRX analysis, the alpha to beta conversion rate is over 90%, with a 100% conversion rate also possible. Calcination 104 of the spodumene ore may be carried out using any energy source, including, but not limited to, natural gas, propane, heavy oil, biomass, and / or electricity. Calcination 104 may be carried out by direct or indirect heating using any calcination equipment, including, but not limited to, a direct heated rotary kiln, an indirect heated rotary kiln, a fluidized bed, and / or any other similar equipment. Electric calciners may be heated by electrical resistance, an electric arc plasma torch, microwave, or any other similar device.

[0028] In some embodiments, calcination 104 modifies the crystal structure of at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more of the calcined spodumene particles (from alpha to beta). In one particular embodiment, all (i.e., 100%) of the crystal structure of the calcined spodumene particles is the β phase. More specifically, in some embodiments, the crystal structure of the spodumene expands and becomes embrittled during calcination 104. The term "embrittled" as used herein is defined as the spodumene particles transitioning from an α crystal structure to a β crystal structure. The term "embrittled" may also be defined as the loss of structural integrity in the spodumene particles (e.g., having one or more cracks).

[0029] Selective screening 106 of the calcined coarse fraction to separate spodumene particles to produce screened spodumene particles is possible because other minerals present in the coarse and fine ore particles being subjected to calcination 104 do not substantially change their crystal structure. Other (non-spodumene) minerals maintain substantially the same crystal structure and are therefore not significantly embrittled by calcination 104.

[0030] In one embodiment, calcination 104 is carried out at a temperature of about 950 to about 1100°C, about 975 to about 1080°C, about 1000 to about 1070°C, about 1030 to about 1060°C, about 950 to about 1060°C, about 950 to about 1050°C, or about 1050°C. It is understood that calcination at temperatures below about 950°C will not induce changes in the crystal structure of spodumene, and that calcination above about 1100°C may soften and melt (liquefy) some other minerals in the ore. Thus, in one embodiment, the calcination temperature is up to about 1100°C. In some embodiments, calcination is carried out at a temperature of about 1050°C. In some embodiments, calcination 104 is carried out at atmospheric pressure. In further embodiments, calcination is carried out for a time period of about 5 minutes to about 60 minutes, about 10 minutes to about 50 minutes, about 15 minutes to about 45 minutes, about 20 minutes to about 40 minutes, about 25 minutes to about 40 minutes, or about 30 minutes to about 35 minutes. Calcination 104 produces a calcined ore containing calcined spodumene and other minerals, such as quartz and / or other gangue minerals.

[0031] After calcination 104, the calcined spodumene may be characterized for embrittlement, if desired. The term "embrittlement," as used herein, may refer to a measure of the likelihood that a particle will at least partially lose its structural integrity (i.e., fracture). The embrittlement level may also be an indicator of the particle's suitability for selective screening 106. The embrittlement level may be determined at predetermined time intervals during operation for process control / regulation. If the particle is not suitable for selective screening based on its embrittlement level, further grinding (selective spodumene grinding) and / or milling may be required to increase the embrittlement level. The embrittlement level may be determined from the particle's crystalline structure based on direct or indirect analysis. For example, direct analysis may be performed by observing the crystalline structure under a microscope. In another example, indirect analysis may be performed by visual inspection with the naked eye or particle size distribution analysis to determine the embrittlement level. If the embrittlement level of the calcined spodumene is below a predetermined threshold, grinding and / or milling is performed to bring the embrittlement level above the predetermined threshold. In one example, the threshold may be that the spodumene particles have a particle size that is approximately 4 times smaller than the other (non-spodumene) mineral particles. In further embodiments, the threshold may be that the spodumene particles have a particle size that is approximately 4.25 times smaller, 4.5 times smaller, 5 times smaller, or even smaller than the particle size of the other (non-spodumene) mineral particles. If the embrittlement level is higher than the predetermined threshold, the calcined spodumene may be subjected to selective screening step 106. If the embrittlement level of the calcined spodumene is determined to be higher than the predetermined threshold of embrittlement, the calcined ore may be provided directly to selective screening 106. Thus, in some embodiments, the embrittlement level may be additionally determined after grinding and / or milling to assess whether the grinding and / or milling was sufficient. If appropriate, grinding and / or milling may be performed prior to or simultaneously with selective screening 106.Examples of grinding include, but are not limited to, adding steel / ceramic balls onto the screening deck to embrittle the spodumene particles, attrition milling before screening, soft ball milling before screening, and combinations thereof. Thus, in some embodiments, the method further includes determining the degree of embrittlement of the calcined spodumene particles. In further embodiments, the method further includes grinding and / or milling the calcined ore prior to or during selective screening 106.

[0032] The method of the present disclosure provides selective screening 106 for separating calcined spodumene particles from other minerals in the calcined coarse fraction that may be present in the ore, thereby obtaining screened spodumene particles. Selective screening can be performed to obtain screened spodumene particles having a particle size of less than about 300 μm. Selective screening can be performed using a suitable screen (or mesh), for example, having an aperture size of about 25 μm or more to about 300 μm or less, and in some specific embodiments, about 45 to about 300 μm. In some embodiments, the selectively screened spodumene particles have a particle size of less than 300 μm, less than 290 μm, less than 280 μm, less than 270 μm, less than 260 μm, or less than 250 μm. In one embodiment, selective screening 106 includes the use of a vibrating screen, an air classifier, an air classifier, a cyclone classifier, and / or any other particle size separation means. Vibration and other similar means may be used to facilitate and / or accelerate screening.

[0033] It has been discovered in the present invention that the screened spodumene particles can be further processed using magnetic separation 108 after calcination 104 and selective screening step 106 to recover β-spodumene particles from other non-magnetic particles, such as quartz and other gangue minerals. During the magnetic separation process, iron oxide minerals / particles and screened spodumene particles with a high amount of iron in the β crystal structure are concentrated in the magnetic product, while quartz and other gangue minerals are concentrated in the non-magnetic product. This is because the iron content in the spodumene crystals increases the magnetic susceptibility of β-spodumene particles during their alpha-to-beta transformation. Therefore, magnetic separation further improves the quality of the lithium concentrate. This magnetic separation should not be confused with magnetic separation traditionally used upstream in the industry to separate iron oxides from α-spodumene. In contrast, magnetic separation step 108 is used to separate magnetic iron-containing β-spodumene from other minerals / particles. One advantage of the magnetic separation process 108 is that it can be a dry process that does not involve wetting, filtering, and drying the product at all, thereby reducing the number of steps performed and the overall cost of the process.

[0034] Generally, iron is supplied from two different sources: iron-bearing minerals (usually separated from α-spodumene by magnetic separation) and iron contained in spodumene crystals (alpha and beta). The incorporation of iron into the spodumene crystal structure occurs during spodumene's geological formation. The iron content in α- and β-spodumene is generally considered to be comparable. However, α-spodumene is nonmagnetic. Roasting α-spodumene oxidizes the iron contained in its crystal structure, increasing its magnetic susceptibility. Therefore, β-spodumene is weakly magnetic and can be efficiently separated from nonmagnetic gangue minerals. The iron level in spodumene crystals can vary depending on the spodumene deposit, which will affect its magnetic behavior after calcination.

[0035] In some embodiments, magnetic separation is performed using a rare earth roll magnetic separator. The magnetic field generated by the magnets carries the more magnetic particles with the movement of the magnetic roll. This results in the magnetically separated mineral, in this case, β-spodumene particles. Preferably, prior to the calcination step, magnetic separation removes (magnetic) iron-containing minerals from the non-magnetic α-spodumene. This can be done, for example, using a wet high-intensity magnetic separator in the wet process or a rare earth roll magnetic separator in the dry process. However, this is done prior to the process of the present invention (i.e., before step 102). After calcination step 104, a rare earth roll magnetic separator (high-intensity magnetic field) is used to separate the weakly magnetic β-spodumene from the non-magnetic gangue minerals. Preferably, a multi-pass magnetic separator, such as a three-pass (three-roll) magnetic separator, is used to obtain a better quality product.

[0036] The lithium concentrate can be used to obtain lithium salts (110). The lithium salts can be obtained from the lithium concentrate (110) by any suitable method. The lithium salts can be commercially desirable salts, such as LiOH, LiO, and / or LiCO. Thus, in some embodiments, methods include obtaining lithium salts from the lithium concentrate. In some embodiments, these methods can produce battery-grade lithium carbonate with impurity content of less than 0.5%.

[0037] In one example, a hydrometallurgical process is performed to obtain LiOH from a lithium concentrate. The lithium concentrate is first autoclaved to obtain a slurry. Autoclaving can be performed, for example, by adding an additive salt (e.g., a sodium salt) and an aqueous phase (e.g., water). Autoclaving can be performed, for example, at a temperature of about 200 to 240°C and a pressure of about 320 to about 360 psi (i.e., 2.2 to 2.48 MPa). Autoclaving can be performed under stirring. Autoclaving can be performed for at least 60 minutes. The slurry obtained from the autoclave can then be converted into a suspension, i.e., a mixture of LiOH and CaO (e.g., a slurry), by adding water and CaO to make the lithium in a soluble form. The mixture of LiOH and CaO can then be filtered to obtain a LiOH filtrate containing LiOH. The LiOH is then precipitated by crystallization to obtain LiOH crystals suspended in the solution. In one embodiment, precipitation is performed by varying pressure (e.g., vacuum) and / or temperature to evaporate the liquid component of the filtrate. The LiOH crystals can then be separated from the solution by centrifugation or other similar solid / liquid separation means. If desired, by dissolving the LiOH crystals (e.g., in a dissolver), the LiOH crystals can be subjected to further precipitation (crystallization) and separation steps to recover more lithium and reduce the impurity content. The precipitated LiOH crystals are then dried to obtain dried LiOH crystals, which can then be packaged as desired. In one example, drying can be performed at a temperature of 50-90°C, or until all free water is removed and the lithium hydroxide is in the form of a monohydrate. Packaging can be, for example, in a sealed bag.

[0038] In another example, the lithium concentrate is autoclaved to obtain a slurry. The autoclaving can be performed under the same conditions as for LiOH. For example, the autoclaving can be performed by adding an additive salt (e.g., sodium salt) and an aqueous phase (e.g., water). The autoclaving can be performed, for example, at a temperature of about 200-240°C and a pressure of about 320-360 psi (i.e., 2.2-2.48 MPa). The autoclaving can be performed under stirring. The autoclaving can be performed for at least 60 minutes. After digestion by autoclaving, the slurry can be sent to a bicarbonation tank for bicarbonation to obtain a LiHCO3-containing solution. The bicarbonation step can be operated, for example, using CO2 injection at 140-160 psi (i.e., 0.965-1.1 MPa) at room temperature (e.g., 150 psi / 1.03 MPa and 20°C). Bicarbonation converts the moderately soluble lithium carbonate into more soluble lithium bicarbonate in solution (e.g., a solubilized slurry). The solution is then filtered to remove residual aluminosilicate. The filtrate is heated to 95°C to remove CO2, which can be recycled to the bicarbonation step. Heat-driven CO2 removal further converts the lithium bicarbonate into less soluble, precipitated lithium carbonate. The precipitated lithium carbonate can then be separated from the liquid phase using any suitable means, such as centrifugation. Depending on the quality of the initial feedstock, a second bicarbonation step can be optionally performed to remove impurities. Impurity removal can therefore include a second precipitation and centrifugation using the same conditions as above. Furthermore, impurity removal can optionally include ion exchange, such as ion exchange chromatography, to further improve purity. Finally, the crystals can be dried and packaged.

[0039] In some embodiments, the lithium concentrate comprises at least about 3% LiO. In some embodiments, other mineral particles of the calcined ore (those not retained by selective screening) comprise less than 2% LiO. Because the lithium concentrate is obtained by physical separation (i.e., selective screening 106 and magnetic separation 108) rather than the use of chemical additives (e.g., flotation), in one embodiment, the method for producing a lithium concentrate according to the present disclosure does not include chemical reagents or contaminants (e.g., flotation reagents). The absence of chemical contaminants reduces the environmental footprint of the disclosed method compared to prior art methods involving flotation. Indeed, the residual waste generated by the method of the present invention can be readily disposed of, as it can be free of harmful reagents, in contrast to residues generated by prior art methods.

[0040] The disclosed methods advantageously achieve a lithium recovery in the lithium concentrate of at least 80%, at least 85%, at least 87%, at least 88%, at least 89%, or at least 90%, where lithium recovery represents the amount of lithium contained in the concentrate divided by the amount of lithium contained in the ROM ore.

[0041] The manufacture of lithium ion batteries is contemplated as being within the scope of the present disclosure. Lithium salts (e.g., LiOH or Li2CO3) can be obtained by the methods of the present disclosure and included in the battery. For example, lithium can be included in the electrodes of the battery. Methods for manufacturing batteries are known to those skilled in the art. [Example]

[0042] The lithium concentrate was produced as follows. First, the crude ore (ROM) ore was crushed until a suitable degree of freedom of spodumene was reached, specifically to a maximum particle size of 6 to 15 mm, thereby obtaining crushed ore particles. The crushed ore particles were screened to separate the coarse ore particles (0.9 tonnes) from the fine ore particles (0.1 tonnes). Fine ore particles with a total weight of 0.1 tonnes having a particle size of less than 850 μm were separated by screening.

[0043] The coarse ore particles were calcined by heating at 1050°C under atmospheric pressure. The crystalline structure expanded, embrittling the spodumene grains, thereby obtaining calcined ore. The other minerals were not significantly embrittled and maintained essentially the same crystalline structure. Due to the embrittlement of spodumene that occurred during the calcination process, the spodumene grains broke or could be easily broken into smaller grains. The spodumene grains were separated from other coarser mineral grains by screening to obtain screened spodumene particles. The following procedure was carried out for two ores labeled Ore 1 (Table 1) and Ore 2 (Table 2). 1 - Crush the ore to 6.7 mm. 2 - Fine fractions (less than 850 μm) are removed by sieving using a low-tap sieve shaker. 3 - The coarse fraction (>850 μm) is subjected to magnetic separation to remove iron-containing minerals (using a rare earth roll magnetic separator, 1 pass, roll speed 50 rpm, 0.13 mm Kevlar belt, 3:1 magnet configuration, magnetic separator model: Outokumpu Technology high-force laboratory separator L / P 10-30). 4 - Calcining the non-magnetic coarse fraction in a muffle furnace at 1050 ° C for 30 minutes. 5 - Screen the calcined ore at 212 microns and 75 microns using a low tap sieve shaker. 6 - Magnetic separation is performed on the 75-212 μm fraction to separate magnetic β-spodumene from non-magnetic gangue minerals (same magnetic separator / parameters as used in step 3).

[0044] To obtain lithium salts, the lithium concentrate was subjected to a hydrometallurgical process. More specifically, the lithium concentrate was mixed with Na2CO3 and water in an agitated autoclave for 60 minutes or more at 340 psi (equivalent to 2.34 MPa) and 180-220°C. Lithium in the spodumene structure was replaced with aqueous sodium ions during the reaction. As a result, the lithium concentrate formed lithium carbonate with moderate solubility. The lithium carbonate existed primarily as a precipitate.

[0045] For the production of lithium hydroxide, the slurry discharged from the autoclave was subjected to conversion with CaO to convert Li2CO3 to the highly soluble LiOH. The residue of the filtration was the retentate (reject) containing aluminosilicate and CaCO3 (from the reaction of CaO with Li2CO3). The filtrate, containing LiOH, was sent to a first crystallizer, where water was evaporated under vacuum to precipitate LiOH. The LiOH crystals were separated from the remaining solution using centrifugation. Depending on the quality of the initial feedstock, a dissolution step was optionally performed, followed by a second crystallization and centrifugation to reduce the impurity level. Finally, the product was dried (LiOH(HO)).

[0046] Results are shown for two different ores, Ore 1 (Table 1) and Ore 2 (Table 2). For Ore 1, a head sample of 1.05% LiO was modified by 212 μm screening to achieve a 62.7% Li recovery with a 5.1% LiO grade (Table 3), whereas without magnetic separation only a 3.6% grade was obtained. For Ore 2, a head sample of 1.11% LiO was modified by 212 μm screening to achieve a 93.1% Li recovery with a 5.8% LiO grade (Table 4), whereas without magnetic separation only a 4.9% grade was obtained.

[0047] [Table 1]

[0048] [Table 2]

[0049] [Table 3]

[0050] [Table 4]

[0051] While the present disclosure has been described in relation to specific embodiments thereof, it will be understood that the disclosure is capable of further modifications, and that this application is intended to cover any changes, uses, or adaptations, including departures from the present disclosure, as within known or customary practice in the art and as may be applied to the essential features described hereinabove and as set forth in the following appended claims. Features that are described in the context of separate aspects and embodiments of the invention may be used together and / or interchangeable. Similarly, features that are described in the context of a single embodiment may be provided separately or in any suitable subcombination.

Claims

1. 1. A method for recovering lithium concentrate from spodumene-containing ore, comprising: crushing the ore to obtain a fine fraction and a coarse fraction; calcining said coarse fraction, preferably at a temperature of about 950°C to about 1100°C, to obtain a calcined coarse fraction comprising spodumene particles having a β crystalline structure; selectively screening the calcined crude fraction to separate the spodumene particles to produce screened spodumene particles; and / or performing magnetic separation on the screened spodumene particles to concentrate the spodumene particles and separate non-magnetic contaminants to obtain the lithium concentrate; A method comprising:

2. The lithium concentrate contains at least about 3% Li ２ The method of claim 1 , comprising:

3. 3. The method of claim 1 or 2, wherein selective screening comprises vibratory screening, air classification, cyclone sizing, and / or any other particle size separation means.

4. The method of any one of claims 1 to 3, wherein the crushing comprises mechanical grinding and / or milling.

5. 5. The method of claim 1, wherein the coarse fraction comprises particles having a particle size of 850 μm or greater.

6. The method of any one of claims 1 to 5, wherein the coarse fraction comprises particles having a particle size of 500 μm or greater.

7. 7. The method of claim 5 or 6, wherein the particles of the coarse fraction have a particle size of up to 15 mm.

8. The method of any one of claims 1 to 7, wherein the spodumene particles have a particle size of at least about 300 μm.

9. The method of any one of claims 1 to 8, further comprising obtaining a lithium salt from the lithium concentrate.

10. The lithium salt is LiOH, Li ２ O and / or Li ２ CO ３ The method of claim 9, wherein

11. The method according to any one of claims 1 to 10, wherein the magnetic separation is carried out using magnetized rolls or drums.

12. The method according to any one of claims 1 to 11, wherein a rare earth roll magnetic separator is used for the magnetic separation.

13. The method according to any one of claims 1 to 12, wherein a multi-pass magnetic separator is used for said magnetic separation.

14. 14. The method of claim 13, wherein the multi-pass magnetic separator is a three-pass magnetic separator.

15. 15. The method of any one of claims 1 to 14, further comprising determining the embrittlement level of spodumene particles in the calcined coarse fraction.

16. 16. The method of claim 15, wherein the embrittlement is determined by microscopic examination, visual inspection with the naked eye, or particle size distribution analysis.

17. 17. The method of claim 15 or 16, wherein further grinding and / or milling of the spodumene particles is performed if the embrittlement of the spodumene particles is below a predetermined threshold.

18. 18. The method of claim 17, wherein the threshold value is that the spodumene particles have a particle size that is about 4 times smaller than the mineral particles, about 4.25 times, 4.5 times, or preferably 5 times smaller than the mineral particles.

19. 19. The method of any one of claims 1 to 18, further comprising autoclaving the lithium concentrate to produce a slurry.

20. 20. The method of claim 19, wherein an additive salt and / or an aqueous phase is added during the autoclaving.

21. LiHCO ３ 21. The method of any one of claims 18 to 20, further comprising biocarbonation of the slurry to produce a containing solution.

22. 22. The method of claim 21, wherein biocarbonation removes impurities.

23. 23. The method of any one of claims 1 to 22, producing a lithium concentrate having an impurity content of less than 0.5%.

24. 24. The method of any one of claims 1 to 23, wherein calcining the coarse fraction changes the crystal structure of the spodumene particles from an α crystal structure to a β crystal structure.

25. 24. The method of any one of claims 1 to 23, wherein calcining the coarse fraction is carried out using natural gas, propane, heavy oil, biomass, and / or electricity.

26. 26. The method of any one of claims 1 to 25, wherein calcining the coarse fraction is carried out using a direct heated rotary kiln, an indirect heated rotary kiln, and / or a fluidized bed.

27. A lithium ion battery comprising a lithium salt produced by the method of claim 9 or 10.

28. 16. The lithium-ion battery of claim 15, comprising a grade of lithium carbonate containing less than 0.5% impurities.

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