Method for extracting lithium sulfate from spodumene concentrate
By introducing lithium-containing tailings and sulfate/carbonate additives into spodumene concentrate, and performing ball milling and spray drying pretreatment, the roasting temperature is reduced, solving the problem of high energy consumption in high-temperature roasting, and achieving efficient lithium recovery and cost reduction.
Patent Information
- Application Number
- CN202511336745.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-18
- Publication Date
- 2026-01-09
AI Technical Summary
Existing technologies for extracting lithium from spodumene concentrate involve high-temperature roasting, resulting in high energy consumption, large carbon emissions, and the need for support plates, which increases operational steps and costs.
Lithium concentrate is mixed with lithium-containing tailings, sulfates and/or carbonates as auxiliary materials. The pretreatment is carried out by wet ball milling and spray drying to reduce the roasting temperature. Roasting is carried out without pad support. Combined with ball milling and leaching purification steps, lithium is extracted efficiently.
Lowering the roasting temperature simplifies the process steps, improves lithium recovery rate, reduces energy consumption and cost, and eliminates the need for a backing plate, thus achieving a high lithium conversion rate.
Smart Images
Figure BDA0005602650740000071
Abstract
Description
Technical Field
[0001] This invention relates to the field of mineral processing technology, and in particular to a method for extracting lithium sulfate from spodumene concentrate. Background Technology
[0002] The main mineral raw materials for lithium production include spodumene, lepidolite, petalite, and phosphogypsum. Among these, spodumene concentrate is the most common hard-rock lithium ore. Lithium is typically extracted by high-temperature roasting and activation of the spodumene concentrate. To ensure complete spodumene conversion, the roasting temperature is usually above 1100℃, which not only results in high energy consumption and carbon emissions, but also requires pads to support the spodumene powder brick blanks to prevent deformation and sticking to the rollers at high temperatures. These pads are costly. Furthermore, the padding and recycling processes add to the operation, increase energy consumption, and reduce output. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide a method for extracting lithium sulfate from spodumene concentrate, which can achieve direct roasting without a backing plate, thereby improving the lithium recovery rate and reducing costs.
[0004] To address the aforementioned problems, this invention discloses a method for extracting lithium sulfate from spodumene concentrate, comprising the following steps:
[0005] Lithium spodumene concentrate and auxiliary materials are mixed and processed to obtain powder; the auxiliary materials include a first auxiliary material and a second auxiliary material, wherein the first auxiliary material is lithium-containing tailings and the second auxiliary material is sulfate and / or carbonate.
[0006] The powder is pressed into bricks to obtain powder brick blanks, which are then dried and fired at a temperature of 900℃~1050℃.
[0007] The calcined powder brick blanks are cooled and crushed to obtain calcined granular materials.
[0008] The roasted granular material is ball-milled with water and then leached to obtain leachate and leaching residue.
[0009] The leachate is purified and concentrated to obtain lithium sulfate.
[0010] As an improvement to the above technical solution, the process of mixing spodumene concentrate and auxiliary materials to obtain powder includes: mixing spodumene concentrate and auxiliary materials, and preparing a slurry by wet ball milling, wherein the residue on a 180-220 mesh sieve of the slurry is 5%-15%.
[0011] The slurry is spray-dried into powder, and the moisture content of the powder is 3% to 8%.
[0012] As an improvement to the above technical solution, the mass of the first auxiliary material is 15% to 40% of the mass of the spodumene concentrate.
[0013] As an improvement to the above technical solution, the mass of the second auxiliary material is 20% to 60% of the mass of the spodumene concentrate;
[0014] The sulfate is one or more of sodium sulfate, potassium sulfate, calcium sulfate, ammonium sulfate, ferric sulfate, and aluminum sulfate, and the carbonate is one or more of sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, and sodium bicarbonate.
[0015] As an improvement to the above technical solution, the sulfate is sodium sulfate and calcium sulfate, and the carbonate is calcium carbonate;
[0016] The mass ratio of spodumene concentrate, sodium sulfate, calcium sulfate and calcium carbonate is 1:(0.1~0.25):(0.1~0.25):(0.005~0.1).
[0017] As an improvement to the above technical solution, the calcination temperature is 960℃~1020℃, and the calcination holding time is 40min~60min.
[0018] As an improvement to the above technical solution, the powder is pressed into bricks, and the formed powder brick blanks are directly put into a drying kiln to dry the moisture. After exiting the drying kiln, they are put into a roller kiln for firing.
[0019] As an improvement to the above technical solution, the residue on a 60-100 mesh sieve of the roasted granular material is 5%-15%.
[0020] As an improvement to the above technical solution, the roasted granular material is ball-milled with water and leached to obtain leachate and leachate residue. The leaching temperature is 40℃~70℃, the leaching time is 30min~120min, and the liquid-solid ratio is 1:(1~10).
[0021] As an improvement to the above technical solution, one or more of the following methods—chemical precipitation, ion exchange, and adsorption—are used to purify the leachate.
[0022] Implementing this invention has the following beneficial effects:
[0023] This invention introduces lithium-containing tailings as a reinforcing agent, which works synergistically with spodumene concentrate to promote ion replacement reactions and reduce calcination temperature under the action of sulfates and / or carbonates. Due to the reduced calcination temperature, powder brick blanks can be calcined without support plates, eliminating the need for support plate filling and / or recycling. This allows for continuous processing of powder brick forming, drying, and calcination, simplifying the process. Combined with subsequent leaching, purification, and concentration, the lithium conversion rate reaches over 90%. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.
[0025] This invention provides a method for extracting lithium sulfate from spodumene concentrate, comprising the following steps:
[0026] S1. Mix spodumene concentrate and auxiliary materials to obtain powder.
[0027] The auxiliary materials include a first auxiliary material and a second auxiliary material. The first auxiliary material is lithium-containing tailings, and the second auxiliary material is sulfate and / or carbonate. This invention introduces lithium-containing tailings as a reinforcing agent, which works synergistically with spodumene concentrate. Under the action of sulfate and / or carbonate, it promotes ion replacement reaction and lowers the roasting temperature.
[0028] In one implementation, it specifically includes:
[0029] S11. Mix spodumene concentrate and auxiliary materials, and prepare a slurry by wet ball milling.
[0030] S12. The slurry is spray-dried into powder.
[0031] Pretreatment of spodumene concentrate before roasting, including ball milling for slurry preparation and spray drying for powder preparation, can significantly optimize the subsequent roasting effect. Ball milling ensures molecular-level contact between spodumene and auxiliary materials, avoiding insufficient localized reactions. The porous microspheres after spray drying facilitate heat and mass transfer during the roasting stage, increasing the crystal transformation rate from α-spodumene to β-spodumene. Strict control of slurry fineness and powder moisture content provides a foundation for efficient spodumene roasting. Specifically, the slurry residue on a 180-220 mesh sieve should be 5%-15%. If the slurry mesh size is too high, the viscosity will be high, leading to increased energy consumption in subsequent spray drying. Furthermore, excessively fine particles are prone to sintering and agglomeration, reducing roasting efficiency. If the slurry mesh size is too low, coarser particles will result in incomplete roasting, reducing lithium recovery. Preferably, the slurry residue on a 200 mesh sieve should be 5%-15%. Specifically, the moisture content of the powder should be 3% to 8%. If the moisture content is too low, the powder will have poor flowability and generate dust during transportation; if the moisture content is too high, the powder will splash due to moisture vaporization during roasting.
[0032] Spodumene powder is shaped by air jet milling to reduce sharp edges, decrease internal friction, and improve flexural strength. In a preferred embodiment, the powder obtained by spray drying has a particle size of 1μm to 150μm. The powder includes a first powder and a second powder. The first powder has a particle size of 80μm to 150μm, and the second powder has a particle size of 1μm to 10μm. The mass ratio of the first powder to the second powder is 1:(0.2 to 0.3). The first powder and the second powder form a close packing, increasing the green body density and improving the drying strength of the green body, which is ≥1.8MPa.
[0033] The first auxiliary material is lithium-containing tailings. In one embodiment, the lithium-containing tailings mainly include the following components: Li₂O 0.2%–0.4%, SiO₂ 64%–70%, Al₂O₃ 16%–18%, K₂O 3%–6%, Na₂O 2.5%–5%, and LOI 3%–8%. The unleached lithium in the lithium-containing tailings can improve the overall lithium yield after recycling. Furthermore, the sulfates in the tailings can lower the roasting temperature and promote the phase transformation from α-spodumene to β-spodumene. The Al₂O₃-SiO₂ eutectic in the tailings can reduce energy consumption in the high-temperature section. The introduction of lithium-containing tailings can also achieve environmental protection and solid waste reduction. In one embodiment, the mass of the first auxiliary material is 15%–40% of the mass of the spodumene concentrate, exemplarily 20%, 25%, 30%, 32%, or 35%, but not limited thereto. If the mass proportion of the first auxiliary material is too low, its fluxing and lithium replenishment effects will be weak; if the mass proportion of the first auxiliary material is too high, impurities will accumulate, increasing the difficulty of purifying the leachate and causing a decrease in lithium purity.
[0034] The second auxiliary material includes sulfates and / or carbonates. The cations in the sulfates undergo a displacement reaction with the lithium ions in the spodumene, generating lithium as lithium sulfate. The carbonates neutralize the acidic environment, reducing equipment corrosion. The oxides obtained from the high-temperature decomposition of the carbonates can also react with impurities such as Fe2O3 and Al2O3, reducing dissolution during leaching and lowering the difficulty of subsequent purification. In one embodiment, the mass of the second auxiliary material is 20% to 60% of the mass of the spodumene concentrate, exemplarily 25%, 30%, 40%, 45%, or 50%, but not limited to these. If the mass percentage of the second auxiliary material is too low, it is insufficient to completely convert α-spodumene to β-spodumene, resulting in a low lithium conversion rate. If the mass percentage of the second auxiliary material is too high, excessive sulfates may react with aluminum, iron, etc., to form soluble sulfates, increasing the impurity concentration in the leachate and increasing the difficulty of purification.
[0035] Specifically, the sulfate is one or more of sodium sulfate, potassium sulfate, calcium sulfate, ammonium sulfate, ferric sulfate, and aluminum sulfate, and the carbonate is one or more of sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, and sodium bicarbonate.
[0036] In a preferred embodiment, the sulfate is sodium sulfate and calcium sulfate, and the carbonate is calcium carbonate. Specifically, the mass ratio of the spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:(0.1-0.25):(0.1-0.25):(0.005-0.1), exemplarily 1:0.1:0.25:0.005, 1:0.25:0.1:0.005, 1:0.1:0.1:0.01, 1:0.2:0.2:0.01, or 1:0.2:0.2:0.05, but not limited to these. If sodium sulfate is in excess, too much low-melting-point liquid phase will be generated, leading to particle sintering and agglomeration, and the Na in the leachate will also increase. + Excessive sodium sulfate concentration increases the difficulty of subsequent lithium salt purification; insufficient sodium sulfate reduces the lithium leaching rate. Excessive calcium sulfate forms excessive calcium-iron oxides, which coat unreacted spodumene, leading to a decrease in lithium leaching rate; insufficient calcium sulfate results in a decrease in Fe content in the leachate. 3+ Excessive concentration can lead to problems. If calcium carbonate is excessive, too much CaO is generated, which reacts with SiO2, causing premature sintering of the green body, hindering lithium diffusion, and the violent release of CO2 may increase the risk of cracking. If calcium carbonate is insufficient, acidic gases are not adequately neutralized, and Fe2O3 is not effectively fixed, resulting in increased slag. Controlling the mass ratio of spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate within the above-mentioned range can balance reaction efficiency and impurity control, while also improving the sintering performance of the subsequently produced powder brick green bodies.
[0037] S2. Press the powder into bricks to obtain powder brick blanks, dry the powder brick blanks and fire them at a temperature of 900℃~1050℃.
[0038] Specifically, the powder is pressed into bricks, and the formed powder brick blanks are directly put into a drying kiln to dry the moisture. After exiting the drying kiln, they are put into a roller kiln for firing.
[0039] In one embodiment, the pressing specification is 600mm×600mm×(15~35)mm. The powder is pressed into bricks. Pressing into brick blanks can increase the density of the material, ensure sufficient contact between spodumene concentrate and auxiliary materials, reduce the diffusion resistance of heat and gas during subsequent roasting, and ensure uniform heating and more uniform and thorough reaction.
[0040] Specifically, the drying temperature is 80℃~200℃, and the drying time is 2h~5h, which can be adjusted according to the thickness of the powder brick blank during actual production. The firing temperature is 900℃~1050℃. Compared with conventional high-temperature firing (firing temperature ≥1100℃), the energy consumption is low, and the powder brick blank has good forming performance. It will not deform or stick to the rollers at the firing temperature, and there is no need to use a pad to support the powder brick blank. In a preferred embodiment, the firing temperature is 960℃~1020℃, and the firing holding time is 40min~60min. Due to the reduction in firing temperature, the powder brick blank can be fired without the support of a pad, eliminating the pad filling and / or recycling process, realizing continuous processing of powder brick pressing, drying and firing, simplifying the process steps and optimizing the sintering path.
[0041] More preferably, the calcination heating process is as follows: Heat to 200℃~500℃ at a rate of 2℃ / min~5℃ / min, hold for 10min~20min to avoid steam pressure causing cracking of the powder brick blank; heat to 500℃~800℃ at a rate of 5℃ / min~8℃ / min, hold for 10min~20min to achieve the initial transformation to the β phase, quickly passing through the unstable range of α-spodumene (700℃~750℃) to prevent lattice stress cracking; heat to 800℃~950℃ at a rate of 3℃ / min~5℃ / min, hold for 10min~20min to complete the phase transformation and generate β-spodumene; heat to 950℃~1050℃ at a rate of 2℃ / min~5℃ / min, hold for 40min~60min to promote particle bonding, reduce porosity, and increase density. By segmented temperature control and precise heat preservation, energy consumption and product performance are optimized while ensuring complete phase change.
[0042] S3. Cool and crush the calcined powder brick blank to obtain calcined granular material.
[0043] The powdered brick blanks emerge from the kiln intact after firing and can be cooled by natural cooling or water cooling. In one embodiment, the temperature is lowered to room temperature at a rate of 4°C / min to 8°C / min to suppress β-phase reversal and prevent cooling cracks. The cooled material is relatively loose, and the lithium has been largely converted into soluble lithium sulfate. It is then crushed into particles of a certain size using a crushing device for subsequent leaching operations. In one embodiment, the residue on a 60-100 mesh sieve of the calcined granular material is 5% to 15%, and the coarser particles reduce the filtration pressure of the leaching residue. Preferably, the residue on a 100 mesh sieve of the calcined granular material is 5% to 15%.
[0044] S4. The roasted granular material is ball-milled with water and leached to obtain leachate and leachate residue.
[0045] During the leaching process, lithium sulfate dissolves into the solution, while other insoluble substances form leaching residue. In one embodiment, the leaching temperature is 40°C to 70°C, the leaching time is 30 min to 120 min, and the liquid-to-solid ratio is 1:(1 to 10).
[0046] S5. The leachate is purified and concentrated to obtain lithium sulfate.
[0047] After leaching, the leachate and leaching residue are separated using filtration equipment. The leachate contains soluble substances such as lithium sulfate, while the leaching residue mainly consists of insoluble silicates, aluminates, and other impurities. After separation, the leachate can be purified using one or more of the following methods: chemical precipitation, ion exchange, and adsorption, to remove impurity ions such as iron, aluminum, calcium, and magnesium. The purified leachate contains a certain concentration of lithium sulfate. To obtain a high-purity lithium sulfate solution, the solution is concentrated by evaporation to remove water and increase the lithium sulfate concentration.
[0048] The present invention will be further described below with reference to specific embodiments:
[0049] Example 1
[0050] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate, including the following steps:
[0051] S1. Mix spodumene concentrate and auxiliary materials to obtain powder.
[0052] The auxiliary materials include lithium-containing tailings, sodium sulfate, calcium sulfate and calcium carbonate, with the mass ratio of spodumene concentrate, lithium-containing tailings, sodium sulfate, calcium sulfate and calcium carbonate being 1:0.4:0.2:0.2:0.05.
[0053] S2. Press the powder into bricks to obtain powder brick blanks. Dry the powder brick blanks and fire them at 980℃ for 60 minutes.
[0054] S3. Crush the calcined powder brick blanks to obtain calcined granular material.
[0055] S4. Add water to the roasted granular material, ball mill it, and leach it to obtain leachate and leach residue.
[0056] S5. The leachate is purified and concentrated to obtain lithium sulfate.
[0057] Example 2
[0058] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, lithium-containing tailings, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.35:0.2:0.2:0.05. All other aspects are the same as in Example 1.
[0059] Example 3
[0060] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, lithium-containing tailings, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.3:0.2:0.2:0.05. All other aspects are the same as in Example 1.
[0061] Example 4
[0062] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, lithium-containing tailings, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.25:0.2:0.2:0.05, and the roasting temperature is 960℃. All other aspects are the same as in Example 1.
[0063] Example 5
[0064] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, lithium-containing tailings, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.2:0.2:0.2:0.05, and the roasting temperature is 1020℃. All other aspects are the same as in Example 1.
[0065] Example 6
[0066] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, lithium-containing tailings, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.15:0.2:0.2:0.05. All other aspects are the same as in Example 1.
[0067] The properties of the powder brick blanks obtained in Examples 1 to 6 were tested, and the lithium conversion rate was calculated. The specific results are as follows:
[0068]
[0069] The above description is a preferred embodiment of the invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered to be within the scope of protection of the invention.
Claims
1. A method for extracting lithium sulfate from spodumene concentrate, characterized in that, Includes the following steps: Lithium spodumene concentrate and auxiliary materials are mixed and processed to obtain powder; the auxiliary materials include a first auxiliary material and a second auxiliary material, wherein the first auxiliary material is lithium-containing tailings and the second auxiliary material is sulfate and / or carbonate. The powder is pressed into bricks to obtain powder brick blanks, which are then dried and fired at a temperature of 900℃~1050℃. The calcined powder brick blanks are cooled and crushed to obtain calcined granular materials. The roasted granular material is ball-milled with water and then leached to obtain leachate and leaching residue. The leachate is purified and concentrated to obtain lithium sulfate.
2. The method for extracting lithium sulfate from spodumene concentrate as described in claim 1, characterized in that, The process of mixing spodumene concentrate and auxiliary materials to obtain powder includes: The spodumene concentrate and auxiliary materials are mixed and then slurried by wet ball milling. The residue of the slurry on a 180-220 mesh sieve is 5%-15%. The slurry is spray-dried into powder, and the moisture content of the powder is 3% to 8%.
3. The method for extracting lithium sulfate from spodumene concentrate as described in claim 1, characterized in that, The mass of the first auxiliary material is 15% to 40% of the mass of the spodumene concentrate.
4. The method for extracting lithium sulfate from spodumene concentrate as described in claim 1, characterized in that, The mass of the second auxiliary material is 20% to 60% of the mass of the spodumene concentrate; The sulfate is one or more of sodium sulfate, potassium sulfate, calcium sulfate, ammonium sulfate, ferric sulfate, and aluminum sulfate, and the carbonate is one or more of sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, and sodium bicarbonate.
5. The method for extracting lithium sulfate from spodumene concentrate as described in claim 4, characterized in that, The sulfate is sodium sulfate and calcium sulfate, and the carbonate is calcium carbonate; The mass ratio of spodumene concentrate, sodium sulfate, calcium sulfate and calcium carbonate is 1:(0.1~0.25):(0.1~0.25):(0.005~0.1).
6. The method for extracting lithium sulfate from spodumene concentrate as described in claim 1, characterized in that, The calcination temperature is 960℃~1020℃, and the calcination holding time is 40min~60min.
7. The method for extracting lithium sulfate from spodumene concentrate as described in claim 1, characterized in that, The powder is pressed into bricks, and the shaped powder brick blanks are directly put into a drying kiln to dry the moisture. After exiting the drying kiln, they are put into a roller kiln for firing.
8. The method for extracting lithium sulfate from spodumene concentrate as described in claim 1, characterized in that, The residue on a 60-100 mesh sieve of the roasted granular material is 5%-15%.
9. The method for extracting lithium sulfate from spodumene concentrate as described in claim 1, characterized in that, The roasted granular material is ball-milled with water and leached to obtain leachate and leaching residue. The leaching temperature is 40℃~70℃, the leaching time is 30min~120min, and the liquid-solid ratio is 1:(1~10).
10. The method for extracting lithium sulfate from spodumene concentrate as described in claim 1, characterized in that, The leachate is purified by one or more of the following methods: chemical precipitation, ion exchange, and adsorption.