Method for improving leaching rate of clinker lithium
By using dilute sulfuric acid to dissolve insoluble lithium complex salts and disrupt the physical encapsulation structure during the leaching stage, the problem of low lithium leaching rate in traditional water leaching processes is solved, achieving efficient extraction of lithium resources and cost reduction.
Patent Information
- Application Number
- CN202511438897.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-10
- Publication Date
- 2026-01-09
AI Technical Summary
Traditional water leaching processes result in low lithium leaching rates and high lithium content in the tailings, leading to lithium resource waste and increased production costs. This is mainly because some lithium is converted into water-insoluble compounds or physically encapsulated during the roasting process, making it impossible to effectively dissolve in water.
During the leaching stage, dilute sulfuric acid solution is used for acid washing to destroy the physical encapsulation structure, corrode and dissolve the insoluble lithium-containing complex salt, and improve the reaction kinetic rate through a slightly acidic environment, thereby promoting the dissolution of lithium.
It significantly improved the lithium leaching rate and reduced the lithium loss rate from 20% to 12-15%, thereby reducing processing costs.
Abstract
Description
Technical Field
[0001] This invention relates to the field of metallurgical technology, and in particular to a method for improving the lithium leaching rate of clinker. Background Technology
[0002] The lepidolite sulfate roasting method is a crucial technological pillar for lithium extraction from solid mineral sources in my country. Its standard process involves roasting a mixture of lepidolite and sulfate to produce clinker, followed by water leaching to extract soluble lithium sulfate, thus separating lithium from the insoluble residue. Within this traditional framework, the lithium leaching rate of the clinker is the lifeblood determining the economic viability of the entire process.
[0003] However, industrial production practice shows that even under optimized roasting conditions, the lithium leaching rate of traditional water leaching processes often falls short of ideal levels, generally exhibiting large fluctuations in leaching rate and high lithium content in the tailings. This results in the waste of valuable lithium resources and increased production costs. At its root, the problem does not lie entirely in the roasting stage, but largely stems from the inherent limitations of the water leaching process itself.
[0004] II. Bottlenecks and Mechanisms of Traditional Water Immersion Technology
[0005] Traditional water leaching methods are based on an ideal assumption: that almost all lithium in the roasted clinker exists in the form of water-soluble lithium sulfate (Li₂SO₄). However, the actual situation is far more complex:
[0006] 1. Incomplete conversion and generation of byproducts: During the roasting process, in addition to generating the target product Li2SO4, some lithium will form compounds that are difficult to dissolve in water, such as potassium lithium sulfate and other complex salts, due to incomplete reaction or combination with impurity components.
[0007] 2. The "encapsulation" effect that water immersion cannot break: Clinker particles are not homogeneous. At high roasting temperatures, some of the newly formed lithium sulfate is physically encapsulated by the molten aluminosilicate matrix or by slightly soluble substances such as the generated calcium sulfate (CaSO4). Neutral water cannot dissolve these encapsulation layers, thus preventing the internal lithium sulfate from contacting the solvent and dissolving it, which is eventually discharged with the tailings.
[0008] III. The Proposal and Advantages of Acid Leaching (Pickling) Technology
[0009] To address the aforementioned drawbacks of water leaching, this study proposes using dilute sulfuric acid solution (or other inorganic acids) instead of process water to leach the roasted clinker during the leaching stage, i.e., an "acid washing" process. The dilute acid effectively dissolves certain acid-soluble lithium-containing complex salts that cannot be treated by water leaching, releasing the "bound" lithium. Simultaneously, it disrupts the physical encapsulation structure, corroding and dissolving the aluminosilicate glass phase or substances such as CaSO4 encapsulating the lithium sulfate surface, breaking down the physical barrier and allowing the encapsulated lithium sulfate to be released, significantly reducing "encapsulation loss." Furthermore, the slightly acidic environment can improve reaction kinetics and promote ion exchange, thereby accelerating the lithium dissolution process and shortening the leaching time.
[0010] Therefore, this invention aims to explore in depth the technical feasibility and economic efficiency of acid leaching as an alternative to water leaching, and to provide key theoretical support and practical solutions for solving common technical problems in the industry and promoting the technological progress of lithium extraction processes. Summary of the Invention
[0011] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a method for improving the lithium leaching rate of clinker. This method employs water washing in the leaching stage and acid washing in the rinsing stage. While ensuring that most of the lithium sulfate in the clinker can be leached out by water, acid rinsing further dissolves the water-insoluble potassium lithium sulfate complex salt in the clinker, thereby increasing the lithium leaching rate. The amount of acid used can be determined according to an experimental formula: total molar amount of sulfuric acid = 0.2 × molar amount of lithium in clinker + 0.2 × molar amount of potassium in clinker + 0.03 molar amount of sodium in clinker. A 10% dilute sulfuric acid solution is prepared as the rinsing acid based on the total molar amount of sulfuric acid. Experiments have confirmed that using 10% acid as the washing solution has no significant impact on the filtration performance of the filter cake, ensuring a good washing effect. Separating the leaching solution from the washing solution and purifying them separately reduces processing costs and lithium loss in the solution.
[0012] This invention provides a method for improving the lithium leaching rate of clinker, comprising the following steps:
[0013] S1. Place the lepidolite concentrate in an oven and dry it to obtain lepidolite powder;
[0014] S2. Add calcium sulfate, calcium carbonate and sodium sulfate to the lithium mica ore obtained by drying in S1 and mix evenly to obtain raw material. The raw material is then roasted to obtain clinker.
[0015] S3. Take the clinker prepared in S2 and mix it with water, add it to a ball mill for washing, and obtain the washing product.
[0016] S4. Filter the leaching product prepared in S3 to obtain an aqueous leaching solution and a filter cake. Rinse the filter cake with acid to obtain an acid washing solution.
[0017] S5. Collect the water extract and the acid washing solution separately, and perform alkali adjustment and impurity removal treatments to obtain a lithium sulfate solution.
[0018] According to the method for improving lithium leaching rate of calcined materials provided by the present invention, the drying temperature of the oven in S1 is 100°C and the drying time of the oven is 2 hours.
[0019] According to the method for improving lithium leaching rate of clinker provided by the present invention, the mass ratio of lepidolite, calcium sulfate, calcium carbonate and sodium sulfate in S2 is 1:(0.2-0.35):(0.15-0.25):(0.1-0.2), and the potassium-sodium ratio in sodium sulfate is 2:5.
[0020] According to the method for improving lithium leaching rate of calcined material provided by the present invention, the calcination temperature in S2 is 900-1050°C, the calcination heating rate is 10°C / min, and the calcination time is 0.5-2 h.
[0021] According to the method for improving lithium leaching rate of clinker provided by the present invention, the mass-to-volume ratio of clinker and water in S3 is 1:1, the ball loading rate of the ball mill is 40%, the power of the ball mill is 740 W, and the working time of the ball mill is 3 min.
[0022] According to the method for improving lithium leaching rate of clinker provided by the present invention, the mass ratio of filter cake to acid in S4 is 2:1, the mass fraction of acid is 5-15%, the acid is sulfuric acid, and the total molar amount of sulfuric acid is 0.2 × molar amount of lithium in clinker + 0.2 × molar amount of potassium in clinker + 0.03 × molar amount of sodium in clinker.
[0023] According to the method for improving lithium leaching rate of clinker provided by the present invention, the lithium content in the lithium sulfate solution in step S5 is 3 to 3.5 g / L.
[0024] Compared with the prior art, the present invention has the following advantages:
[0025] This invention provides a method for improving the lithium leaching rate of clinker. The method employs water washing in the leaching stage and acid washing in the rinsing stage. While ensuring that most of the lithium that can be leached from the clinker by water is dissolved, the acid rinsing further improves the lithium leaching rate. The 10% dilute sulfuric acid used as washing water has no significant impact on the filtration performance of the filter cake and can ensure a good washing effect. Separating the leaching solution and washing solution and purifying them separately can reduce processing costs and the loss of lithium in the solution. Detailed Implementation
[0026] Example 1
[0027] This embodiment provides a method for improving the lithium leaching rate of clinker, including the following steps:
[0028] S1. The lepidolite was selected from Fengxin and had a lithium grade of 1.5%. The lepidolite concentrate was dried in an oven at 100°C for 2 hours to obtain lepidolite powder.
[0029] S2. Lithium mica concentrate, calcium sulfate, calcium carbonate and sodium sulfate are mixed evenly in a mass ratio of 1:0.2:0.2:0.2 to obtain raw material. The raw material is then placed in a crucible and placed in a muffle furnace for high-temperature roasting at a heating rate of 10℃ / min. The roasting is carried out at 930℃ for 1.5h, and the material is allowed to cool naturally to obtain clinker.
[0030] The potassium-to-sodium ratio in sodium sulfate is 2:5;
[0031] S3. Take the clinker prepared in S2 and water and mix them in a mass ratio of 1:1. Add the mixture to a ball mill and wash it by ball milling. The ball mill has a ball loading rate of 40%, a power of 740w, and a ball milling time of 3min.
[0032] S4. After ball milling, the mixture is filtered to obtain an aqueous extract and a filter cake. The total amount of acid required is calculated based on the molar amounts of lithium, potassium, and sodium in the clinker. In this embodiment, the clinker contains 0.21 mol of lithium, 0.67 mol of sodium, and 0.6 mol of potassium. The required amount of sulfuric acid is weighed and prepared into a 10% dilute sulfuric acid solution as an acid rinsing solution. The acid rinsing solution is then obtained.
[0033] Total molar amount of sulfuric acid = 0.2 × molar amount of lithium in clinker + 0.2 × molar amount of potassium in clinker + 0.03 molar amount of sodium in clinker;
[0034] Therefore, the total amount of sulfuric acid required is 0.21×0.2+0.6×0.2+0.67×0.03=0.1821mol;
[0035] S5. Collect the aqueous extract and the acid washing solution separately. Use sodium hydroxide to adjust the alkali once to adjust the pH of the solution to about 8. After filtration, mix the two to obtain the lithium-containing solution, i.e., lithium sulfate solution, for lithium precipitation.
[0036] The lithium content in the lithium sulfate solution prepared in this embodiment is 3.5 g / L.
[0037] This embodiment can reduce processing costs and lithium loss in the solution, with a lithium loss rate of 15%.
[0038] The immersion stage uses water washing, and the rinsing stage uses acid washing. This ensures that most of the lithium that can be extracted from the clinker by water immersion is dissolved, and then acid rinsing further improves the lithium leaching rate. In existing technologies using water washing and rinsing, the lithium loss rate is 20%. The method described in this example can reduce the lithium loss rate to 15%.
[0039] Example 2
[0040] This embodiment provides a method for improving the lithium leaching rate of clinker, including the following steps:
[0041] S1. The lepidolite was selected from Fengxin and had a lithium grade of 1.5%. The lepidolite concentrate was dried in an oven at 100°C for 2 hours to obtain lepidolite powder.
[0042] S2. Lithium mica concentrate, calcium sulfate, calcium carbonate and sodium sulfate are mixed evenly in a mass ratio of 1:0.2:0.2:0.2 to obtain raw material. The raw material is then placed in a crucible and placed in a muffle furnace for high-temperature roasting at a heating rate of 10℃ / min. The material is roasted at 920℃ for 1.2 h and then allowed to cool naturally to obtain clinker.
[0043] The potassium-to-sodium ratio in sodium sulfate is 2:5;
[0044] S3. Take the clinker prepared in S2 and water and mix them in a mass ratio of 1:1. Add the mixture to a ball mill and wash it by ball milling. The ball mill has a ball loading rate of 40%, a power of 740w, and a ball milling time of 3min.
[0045] S4. After ball milling, the mixture is filtered to obtain an aqueous extract and a filter cake. In this embodiment, the clinker contains 0.16 mol of lithium, 0.65 mol of sodium, and 0.6 mol of potassium. The required sulfuric acid is weighed and prepared into a 10% dilute sulfuric acid solution as an acid rinsing solution. The acid rinsing solution is obtained by rinsing.
[0046] Total molar amount of sulfuric acid = 0.2 × molar amount of lithium in clinker + 0.2 × molar amount of potassium in clinker + 0.03 molar amount of sodium in clinker;
[0047] The total amount of sulfuric acid required is 0.16×0.2+0.6×0.2+0.67×0.03=0.1715mol;
[0048] S5. Collect the water leaching solution and the acid washing solution separately, adjust the alkali once, adjust the pH value of the solution to about 8, and filter to obtain the lithium-containing solution, i.e., lithium sulfate solution, for lithium precipitation.
[0049] The lithium content in the lithium sulfate solution prepared in this embodiment is 3.4 g / L.
[0050] This embodiment can reduce processing costs and lithium loss in the solution, with a lithium loss rate of 17%.
[0051] Example 3
[0052] This embodiment provides a method for improving the lithium leaching rate of clinker, including the following steps:
[0053] S1. The lepidolite was selected from Fengxin and had a lithium grade of 1.5%. The lepidolite concentrate was dried in an oven at 100°C for 2 hours to obtain lepidolite powder.
[0054] S2. Lithium mica concentrate, calcium sulfate, calcium carbonate and sodium sulfate are mixed evenly in a mass ratio of 1:0.34:0.25:0.1 to obtain raw material. The raw material is then placed in a crucible and placed in a muffle furnace for high-temperature roasting at a heating rate of 10℃ / min. The roasting is carried out at 1050℃ for 0.5h, and the material is allowed to cool naturally to obtain clinker.
[0055] The potassium-to-sodium ratio in sodium sulfate is 2:5;
[0056] S3. Take the clinker prepared in S2 and water and mix them in a mass ratio of 1:1. Add the mixture to a ball mill and wash it by ball milling. The ball mill has a ball loading rate of 40%, a power of 740w, and a ball milling time of 3min.
[0057] S4. After ball milling, the mixture is filtered to obtain an aqueous extract and a filter cake. In this embodiment, the clinker contains 0.23 mol of lithium, 0.45 mol of sodium, and 0.46 mol of potassium. The required sulfuric acid is weighed and prepared into a 10% dilute sulfuric acid solution as an acid rinsing solution. The acid rinsing solution is obtained by rinsing.
[0058] Total molar amount of sulfuric acid = 0.2 × molar amount of lithium in clinker + 0.2 × molar amount of potassium in clinker + 0.03 molar amount of sodium in clinker;
[0059] The total amount of sulfuric acid required is 0.23×0.2+0.46×0.2+0.45×0.03=0.1515mol;
[0060] S5. Collect the water leaching solution and the acid washing solution separately, adjust the alkali once, adjust the pH value of the solution to about 8, and filter to obtain the lithium-containing solution, i.e., lithium sulfate solution, for lithium precipitation.
[0061] The lithium content in the lithium sulfate solution prepared in this embodiment is 3 g / L.
[0062] This embodiment can reduce processing costs and lithium loss in the solution, with a lithium loss rate of 12%.
[0063] The immersion stage uses water washing, and the rinsing stage uses acid washing. This ensures that most of the lithium that can be leached from the clinker by water dissolves, and then acid rinsing further improves the lithium leaching rate. In existing technologies using water washing and rinsing, the lithium loss rate is 20%. The method described in this example reduces the lithium loss rate to 12%.
[0064] Example 4
[0065] This embodiment provides a method for improving the lithium leaching rate of clinker, including the following steps:
[0066] S1. The lepidolite was selected from Fengxin and had a lithium grade of 1.5%. The lepidolite concentrate was dried in an oven at 100°C for 2 hours to obtain lepidolite powder.
[0067] S2. Lithium mica concentrate, calcium sulfate, calcium carbonate and sodium sulfate are mixed evenly in a mass ratio of 1:0.34:0.16:0.1 to obtain raw material. The raw material is then placed in a crucible and placed in a muffle furnace for high-temperature roasting at a heating rate of 10℃ / min. The material is roasted at 950℃ for 2 hours and then allowed to cool naturally to obtain clinker.
[0068] The potassium-to-sodium ratio in sodium sulfate is 2:5;
[0069] S3. Take the clinker prepared in S2 and water and mix them in a mass ratio of 1:1. Add the mixture to a ball mill and wash it by ball milling. The ball mill has a ball loading rate of 40%, a power of 740w, and a ball milling time of 3min.
[0070] S4. After ball milling, the mixture is filtered to obtain an aqueous extract and a filter cake. In this embodiment, the clinker contains 0.21 mol of lithium, 0.43 mol of sodium, and 0.46 mol of potassium. The required sulfuric acid is weighed and prepared into a 10% dilute sulfuric acid solution as an acid rinsing solution. The acid rinsing solution is obtained by rinsing.
[0071] Total molar amount of sulfuric acid = 0.2 × molar amount of lithium in clinker + 0.2 × molar amount of potassium in clinker + 0.03 molar amount of sodium in clinker;
[0072] The total amount of sulfuric acid required is 0.21×0.2 + 0.46×0.2 + 0.43×0.03 = 0.1469 mol;
[0073] S5. Collect the water leaching solution and the acid washing solution separately, adjust the alkali once, adjust the pH value of the solution to about 8, and filter to obtain the lithium-containing solution, i.e., lithium sulfate solution, for lithium precipitation.
[0074] The lithium content in the lithium sulfate solution prepared in this embodiment is 3.2 g / L.
[0075] This embodiment can reduce processing costs and lithium loss in the solution, with a lithium loss rate of 18%.
[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.
Claims
1. A method for improving the lithium leaching rate of clinker, characterized in that, Includes the following steps: S1. Place the lepidolite concentrate in an oven and dry it to obtain lepidolite powder; S2. Add calcium sulfate, calcium carbonate and sodium sulfate to the lithium mica ore obtained by drying in S1 and mix evenly to obtain raw material. The raw material is then roasted to obtain clinker. S3. Take the clinker prepared in S2 and mix it with water, add it to a ball mill for washing, and obtain the washing product. S4. Filter the leaching product prepared in S3 to obtain an aqueous leaching solution and a filter cake. Rinse the filter cake with acid to obtain an acid washing solution. S5. Collect the water extract and the acid washing solution separately, and perform alkali adjustment and impurity removal treatments to obtain a lithium sulfate solution.
2. The method for improving lithium leaching rate from clinker according to claim 1, characterized in that, The drying temperature of the oven in S1 is 100 ℃, and the drying time of the oven is 2 h.
3. The method for improving lithium leaching rate from clinker according to claim 1, characterized in that, The mass ratio of lepidolite, calcium sulfate, calcium carbonate and sodium sulfate in S2 is 1:(0.2-0.35):(0.15-0.25):(0.1-0.2), and the potassium-sodium ratio in sodium sulfate is 2:
5.
4. The method for improving lithium leaching rate from clinker according to claim 1, characterized in that, The calcination temperature in S2 is 920–1050 °C, the calcination heating rate is 10 °C / min, and the calcination time is 0.5–2 h.
5. The method for improving lithium leaching rate from clinker according to claim 1, characterized in that, The mass-to-volume ratio of clinker and water in S3 is 1:1, the ball loading rate of the ball mill is 40%, the power of the ball mill is 740 W, and the working time of the ball mill is 3 min.
6. The method for improving lithium leaching rate from clinker according to claim 1, characterized in that, The mass ratio of filter cake to acid in S4 is 2:1, the mass fraction of acid is 5-15%, the acid is sulfuric acid, and the total molar amount of sulfuric acid is 0.2 × molar amount of lithium in clinker + 0.2 × molar amount of potassium in clinker + 0.03 × molar amount of sodium in clinker.
7. The method for improving lithium leaching rate from clinker according to claim 1, characterized in that, The lithium content in the lithium sulfate solution described in S5 is 3–3.5 g / L.