Method for preparing battery-grade lithium carbonate from recyclable calcium carbonate

Abstract

The present application relates to the field of lithium ore lithium extraction, and discloses a battery-grade lithium carbonate preparation method with recyclable calcium carbonate, comprising the following steps: grinding roasted lithium concentrate; mixing roasted clinker with concentrated sulfuric acid for acidification reaction; after fine grinding of the acid clinker, mixing with deionized water to form a slurry, and then performing solid-liquid separation to obtain an acid leaching solution; adding heavy calcium into the acid leaching solution to adjust the pH, and then performing suction filtration to remove impurities and obtain a purified solution; collecting the calcium carbonate generated during the removal of impurities and adding it to the acid leaching process in subsequent experiments to replace part of the heavy calcium; evaporating and concentrating the purified solution to obtain a finished solution; adding the finished solution into heated soda solution, stirring, and performing suction filtration and leaching to obtain crude lithium carbonate; and purifying the crude lithium carbonate to obtain battery-grade lithium carbonate. The present application recycles calcium carbonate and directly uses it in the acid leaching process in the previous stage to adjust the pH of the leaching system, realizes the reuse of resources and environmental-friendly protection, and has important comprehensive resource utilization value.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction from lithium ore, and specifically to a method for preparing battery-grade lithium carbonate that can reuse calcium carbonate. Background Technology

[0002] Lithium is an important rare metal raw material, playing a crucial role in the new energy industry. With the rapid development of new energy technologies and the increasing demand for lithium resources, the development and utilization of lithium mines has become a global focus. Traditional lithium extraction processes from lithium ore mainly involve high-temperature calcination or roasting followed by wet processing, such as pressure leaching. However, these methods suffer from high energy consumption, long process flows, significant equipment corrosion, and environmental pollution, making them unsuitable for industrial production. Currently, the extraction rate and purity of lithium from lithium ore still need improvement. In the traditional sulfate process, the leaching solution contains high levels of impurities, resulting in a heavy subsequent purification load. Furthermore, existing methods generate a large amount of byproducts during leaching, and suitable solutions for their treatment have yet to be found. To address these issues, a novel method for preparing battery-grade lithium carbonate using recyclable calcium carbonate has been invented to improve the recovery and utilization of byproducts during leaching and enhance product purity and quality, achieving green and environmentally friendly comprehensive resource utilization.

[0003] The relevant reference CN107915240A discloses a method for producing battery-grade lithium carbonate using the sulfuric acid process, including conversion roasting, acid roasting, leaching, purification, lithium precipitation, washing, drying, and pulverization. Leaching employs a cyclic leaching method: A) Leaching: The acidified material is added to a reactor containing a slurry, and the pH of the slurry is adjusted while stirring. After a period of reaction, the slurry is filtered to obtain leachate and leach residue; B) Leach residue washing: The leach residue is washed twice with water, and the washing water obtained from the previous washing is used for the initial washing of the next leaching residue, alternating between high-concentration and low-concentration lithium-containing washing water; C) Circulating leaching: The leachate obtained in step A is used as the slurry, and steps A and B are repeated until the lithium oxide concentration in the leachate reaches above 50 g / L. The final leachate is then used in the next process to increase the lithium concentration in the leachate, but this process generates relatively more solid waste. Summary of the Invention

[0004] This invention discloses a method for preparing battery-grade lithium carbonate using reusable calcium carbonate. It utilizes the calcium carbonate generated during the impurity removal process in lithium concentrate production to adjust the pH of the acidic leachate. First, sodium carbonate is added during the impurity removal process to remove calcium ions from the system, simultaneously producing calcium carbonate precipitate. This precipitate is collected through filtration and other steps and reused in the leaching process to adjust the pH of the reaction. This process eliminates the need for complex additional steps, optimizes the lithium concentrate extraction process, achieves efficient lithium resource extraction, and improves product purity. Furthermore, by recycling the calcium carbonate precipitate, it achieves resource reuse and environmental friendliness, demonstrating significant value in comprehensive resource utilization.

[0005] To address the above technical problems, this invention provides a method for preparing battery-grade lithium carbonate with recyclable calcium carbonate, comprising the following steps: (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to undergo crystal transformation roasting at 900-1100℃ to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:3-6, and then acidification reaction is carried out for 1-3 hours to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:1-10 and stir evenly to form a slurry; stir the slurry at 60-90℃ for 20-60 minutes and then filter it to separate the solid and liquid to obtain an acidic leachate. (4) Add heavy calcium carbonate to the acidic leachate to adjust its pH to 4-6, filter and remove impurities; during the impurity removal process, first add calcium oxide at 60-80℃ and react for 10 minutes to adjust its pH to 9-11 to remove magnesium ions in the solution. After impurity removal, the concentration of magnesium ions is less than 0.01 g / L; then add sodium carbonate and react for 10 minutes to remove the remaining calcium ions in the solution. The molar ratio of the added sodium carbonate to the calcium ions in the solution is 1:1-1.25. After impurity removal, the concentration of calcium ions is less than 0.05 g / L, and calcium carbonate is generated to obtain the purified solution; collect the calcium carbonate and use it to replace part of the heavy calcium carbonate in subsequent experiments; (5) The purified liquid is evaporated and concentrated at 60-90℃ to obtain the finished liquid; (6) Heat the soda ash solution to 75-95℃, and then add the finished solution to it according to the excess coefficient of 1.05-1.2. The feeding time is 60-120 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate. (7) The crude lithium carbonate is purified to obtain battery-grade lithium carbonate.

[0006] Preferably, in step (1), the lithium oxide content in the lithium concentrate is between 1.0% and 5.5%.

[0007] Preferably, in step (2), the acidification temperature is 100-300℃.

[0008] Preferably, in step (7), during the purification process, the mass ratio of crude lithium carbonate to high-purity water is 1:1-3.

[0009] Preferably, in step (7), the number of washing cycles is 3.

[0010] Preferably, in step (7), the washing temperature is 80-95℃.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes the collected calcium carbonate to adjust the pH of the acidic leachate to 4-6 during the neutralization process. The process is simple and can be successfully implemented for industrial production. At the same time, the battery-grade lithium carbonate produced has high purity, and the reuse of calcium carbonate does not affect the product quality, thus achieving green utilization of resources.

[0012] 2. Unlike traditional processes that treat calcium carbonate as solid waste, this invention recycles it and directly reuses it in the upstream acidic leaching process to adjust the pH of the leaching system. This reuse model requires no additional processing steps or equipment; by simply optimizing the existing process flow, it achieves on-site resource utilization of the byproduct. This not only effectively reduces the need for purchased neutralizing agents and lowers production costs but also significantly reduces solid waste generation. More importantly, this recycling process reduces the difficulty of subsequent impurity removal, improves the overall lithium extraction efficiency and the purity of the final product, thereby more stably producing battery-grade lithium carbonate that meets standards.

[0013] 3. In this invention, sodium carbonate is added to the system for calcium removal treatment. The molar ratio of sodium carbonate to calcium ions is 1:1.05 to 1:1.25. Sodium carbonate reacts with calcium ions to form calcium carbonate precipitate, which effectively removes calcium impurities and ensures the purity of subsequent products. Attached Figure Description

[0014] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0015] To further illustrate the substantive content of the present invention, specific embodiments are described below. It should be noted that the present invention is not limited to the embodiments disclosed below, but can be implemented in different ways. The following embodiments are described to enable those skilled in the art to practice this application.

[0016] This invention provides a method for preparing battery-grade lithium carbonate with reusable calcium carbonate, comprising the following steps: (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace for crystal transformation roasting at a roasting temperature of 900-1100℃ and a roasting time of 1-3 hours to convert the α-lithium concentrate in the ore into β-lithium concentrate to obtain roasted clinker; preferably, the lithium oxide content in the lithium concentrate is between 1.0-5.5%.

[0017] (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:3-6. Then, an acidification reaction is carried out for 1-3 hours at an acidification temperature of 100-300℃ to convert lithium elements into soluble lithium elements and obtain acidified clinker.

[0018] (3) Grind the acidic material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:1-10 and stir evenly to form a slurry. Stir the slurry at 60-90℃ for 20-60 minutes and then filter it to separate the solid and liquid to obtain an acidic leachate.

[0019] (4) Add heavy calcium carbonate to the acidic leachate to adjust its pH to 4-6, and then filter it to remove impurities. During the impurity removal process, add calcium oxide at 60-80℃ and react for 10 minutes to adjust the pH of the solution to 9-11 to remove magnesium ions from the solution. The magnesium ion concentration after the reaction should not exceed 0.01 g / L. Then add sodium carbonate at 60℃-80℃ and react for 10 minutes. The molar ratio of the added sodium carbonate to the calcium ions in the solution is 1:1-1.25 to remove the remaining calcium ions in the solution. The calcium ion concentration after the reaction should not exceed 0.05 g / L. At the same time, calcium carbonate is generated to obtain the purified solution.

[0020] Calcium carbonate is collected and added to this step in subsequent experiments to replace part of the heavy calcium carbonate, adjusting the pH of the reaction and controlling the pH of the leachate at 4-6. Maintaining the pH of the leachate at 4-6 removes excess sulfate ions from the solution.

[0021] (5) The purified liquid is evaporated and concentrated at 60-90℃ to obtain the finished liquid; (6) Heat the soda ash solution to 75-95℃, and then add the finished solution to it according to the excess coefficient of 1.05-1.2. The feeding time is 60-120 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate. (7) The crude lithium carbonate is purified to obtain battery-grade lithium carbonate. The mass ratio of crude lithium carbonate to high-purity water is 1:1-3, and the washing is performed 3 times to remove excess impurities from the crude lithium carbonate. The washing temperature is 80-95℃ to reduce the solubility of lithium carbonate.

[0022] The lithium concentrate used in the comparative examples and embodiments of the present invention contains 5.5% lithium oxide.

[0023] Comparison Example (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to be roasted at 1100℃ for 2 hours to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:3, and then acidification reaction is carried out for 2 hours at an acidification temperature of 200℃ to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:5 and stir evenly to form a slurry; stir the slurry at 80°C for 30 minutes and then filter it to separate the solid and liquid to obtain an acidic leachate; (4) Add heavy calcium carbonate to the acidic leachate to adjust its pH to 6, filter and remove impurities; during the impurity removal process, add calcium oxide at 60℃ and react for 10 minutes to adjust the pH of the solution to 9 to remove magnesium ions in the solution. After impurity removal, the concentration of magnesium ions in the solution is less than 0.01 g / L; then add sodium carbonate at 60℃ and react for 10 minutes. The molar ratio of sodium carbonate added to calcium ions in the solution is 1:1.05 to remove the remaining calcium ions in the solution. After the reaction, the concentration of calcium ions is less than 0.05 g / L. At the same time, calcium carbonate is generated and collected to obtain the purified solution. (5) The purified liquid is evaporated and concentrated at 90°C to obtain the finished liquid; (6) Heat the soda ash solution to 90°C, and then add the finished solution to it at an excess coefficient of 1.05. The feeding time is 60 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate with a purity of 96.66%. (7) The crude lithium carbonate was washed three times with high-purity water at 95°C at a mass ratio of 1:2, filtered and dried to obtain battery-grade lithium carbonate with a purity of 99.61%. Example 1

[0024] (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to be roasted at 900°C for 2 hours to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:3, and then acidification reaction is carried out for 1 hour at an acidification temperature of 100℃ to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:1 and stir evenly to form a slurry; after stirring the slurry at 80°C for 20 minutes, perform solid-liquid separation by pressure filtration to obtain an acidic leachate; (4) Add the acidic leachate to the calcium carbonate recovered in the control example to replace part of the heavy calcium carbonate, and add an appropriate amount of heavy calcium carbonate to adjust the pH to 4. After filtration, remove impurities. During the impurity removal process, add calcium oxide at 80°C and react for 10 minutes to adjust the pH of the solution to 11 and remove magnesium ions from the solution. After impurity removal, the concentration of magnesium ions in the solution is less than 0.01 g / L. Then add sodium carbonate at 80°C and react for 10 minutes. The molar ratio of sodium carbonate added to calcium ions in the solution is 1:1.05 to remove the remaining calcium ions in the solution. After the reaction, the concentration of calcium ions is less than 0.05 g / L. At the same time, calcium carbonate is generated and collected to obtain the purified solution. (5) The purified liquid is evaporated and concentrated at 90°C to obtain the finished liquid; (6) Heat the soda ash solution to 95°C, and then add the finished solution to it with an excess coefficient of 1.05. The feeding time is 60 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate with a purity of 95.43%. (7) The crude lithium carbonate was washed three times with high-purity water at 95°C at a mass ratio of 1:2, filtered and dried to obtain battery-grade lithium carbonate with a purity of 99.5%. Example 2

[0025] (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to be roasted at 1000℃ for 2 hours to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:3, and then acidification reaction is carried out for 2 hours at an acidification temperature of 200℃ to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:5 and stir evenly to form a slurry; stir the slurry at 80°C for 30 minutes and then filter it to separate the solid and liquid to obtain an acidic leachate; (4) Add the acidic leachate to the calcium carbonate recovered in the control example to replace part of the heavy calcium carbonate, and add an appropriate amount of heavy calcium carbonate to adjust the pH to 4. After filtration, remove impurities. During the impurity removal process, add calcium oxide at 80°C and react for 10 minutes to adjust the pH of the solution to 9 and remove magnesium ions from the solution. After impurity removal, the concentration of magnesium ions in the solution is less than 0.01 g / L. Then add sodium carbonate at 80°C and react for 10 minutes. The molar ratio of sodium carbonate added to calcium ions in the solution is 1:1.05 to remove the remaining calcium ions in the solution. After the reaction, the concentration of calcium ions is less than 0.05 g / L. At the same time, calcium carbonate is generated and collected to obtain the purified solution. (5) The purified liquid is evaporated and concentrated at 90°C to obtain the finished liquid; (6) Heat the soda ash solution to 90°C, and then add the finished solution to it at an excess coefficient of 1.05. The feeding time is 60 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate with a purity of 95.79%. (7) The crude lithium carbonate was washed three times with high-purity water at 95°C at a mass ratio of 1:2, filtered and dried to obtain battery-grade lithium carbonate with a purity of 99.53%. Example 3

[0026] (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to be roasted at 1100℃ for 2 hours to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:3, and then acidification reaction is carried out for 2 hours at an acidification temperature of 200℃ to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:5 and stir evenly to form a slurry; stir the slurry at 80°C for 30 minutes and then filter it to separate the solid and liquid to obtain an acidic leachate; (4) Add the acidic leachate to the calcium carbonate recovered in the control example to replace part of the heavy calcium carbonate, and add an appropriate amount of heavy calcium carbonate to adjust the pH to 4. After filtration, remove impurities. During the impurity removal process, add calcium oxide at 80°C and react for 10 minutes to adjust the pH of the solution to 9 and remove magnesium ions from the solution. After impurity removal, the concentration of magnesium ions in the solution is less than 0.01 g / L. Then add sodium carbonate at 80°C and react for 10 minutes. The molar ratio of sodium carbonate added to calcium ions in the solution is 1:1.05 to remove the remaining calcium ions in the solution. After the reaction, the concentration of calcium ions is less than 0.05 g / L. At the same time, calcium carbonate is generated and collected to obtain the purified solution. (5) The purified liquid is evaporated and concentrated at 90°C to obtain the finished liquid; (6) Heat the soda ash solution to 90°C, and then add the finished solution to it at an excess coefficient of 1.05. The feeding time is 60 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate with a purity of 96.28%. (7) The crude lithium carbonate was washed three times with high-purity water at 95°C at a mass ratio of 1:2, filtered and dried to obtain battery-grade lithium carbonate with a purity of 99.59%. Example 4

[0027] (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to be roasted at 1100℃ for 2 hours to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:3, and then acidification reaction is carried out for 2 hours at an acidification temperature of 200℃ to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:5 and stir evenly to form a slurry; stir the slurry at 80°C for 30 minutes and then filter it to separate the solid and liquid to obtain an acidic leachate; (4) Add the acidic leachate to the calcium carbonate recovered in the control example to replace part of the heavy calcium carbonate, and add an appropriate amount of heavy calcium carbonate to adjust the pH to 5. After filtration, remove impurities. During the impurity removal process, add calcium oxide at 80°C and react for 10 minutes to adjust the pH of the solution to 9 and remove magnesium ions from the solution. After impurity removal, the concentration of magnesium ions in the solution is less than 0.01 g / L. Then add sodium carbonate at 80°C and react for 10 minutes. The molar ratio of sodium carbonate added to calcium ions in the solution is 1:1.05 to remove the remaining calcium ions in the solution. After the reaction, the concentration of calcium ions is less than 0.05 g / L. At the same time, calcium carbonate is generated and collected to obtain the purified solution. (5) The purified liquid is evaporated and concentrated at 90°C to obtain the finished liquid; (6) Heat the soda ash solution to 90°C, and then add the finished solution to it at an excess coefficient of 1.05. The feeding time is 60 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate with a purity of 96.41%. (7) The crude lithium carbonate was washed three times with high-purity water at 95°C at a mass ratio of 1:2, filtered and dried to obtain battery-grade lithium carbonate with a purity of 99.62%. Example 5

[0028] (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to undergo crystal transformation roasting at 1100℃ for 3 hours to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:6, and then acidification reaction is carried out for 3 hours at an acidification temperature of 300℃ to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:10 and stir evenly to form a slurry; after stirring the slurry at 90°C for 60 minutes, perform solid-liquid separation by pressure filtration to obtain an acidic leachate; (4) Add the acidic leachate to the calcium carbonate recovered in the control example to replace part of the heavy calcium carbonate, and add an appropriate amount of heavy calcium carbonate to adjust the pH to 6. After filtration, remove impurities. During the impurity removal process, add calcium oxide at 60°C and react for 10 minutes to adjust the pH of the solution to 9 and remove magnesium ions from the solution. After impurity removal, the concentration of magnesium ions in the solution is less than 0.01 g / L. Then add sodium carbonate at 60°C and react for 10 minutes. The molar ratio of sodium carbonate added to calcium ions in the solution is 1:1.25 to remove the remaining calcium ions in the solution. After the reaction, the concentration of calcium ions is less than 0.05 g / L. At the same time, calcium carbonate is generated and collected to obtain the purified solution. (5) The purified liquid is evaporated and concentrated at 60°C to obtain the finished liquid; (6) Heat the soda ash solution to 75°C, and then add the finished solution according to an excess coefficient of 1.2. The feeding time is 120 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate with a purity of 96.76%. (7) The crude lithium carbonate was washed three times with high-purity water at 80°C at a mass ratio of 1:3, filtered and dried to obtain battery-grade lithium carbonate with a purity of 99.65%. Example 6

[0029] (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to undergo crystal transformation roasting at 1100℃ for 3 hours to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:2, and then acidification reaction is carried out for 2 hours at an acidification temperature of 200℃ to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:5 and stir evenly to form a slurry; after stirring the slurry at 60°C for 30 minutes, filter the solid and liquid mixture to obtain an acidic leachate. (4) Add the acidic leachate to the calcium carbonate recovered in the control example to replace part of the heavy calcium carbonate, and add an appropriate amount of heavy calcium carbonate to adjust the pH to 5. After filtration, remove impurities. During the impurity removal process, add calcium oxide at 70°C and react for 10 minutes to adjust the pH of the solution to 10 and remove magnesium ions from the solution. After impurity removal, the concentration of magnesium ions in the solution is less than 0.01 g / L. Then add sodium carbonate at 70°C and react for 10 minutes. The molar ratio of sodium carbonate added to calcium ions in the solution is 1:1 to remove the remaining calcium ions in the solution. After the reaction, the concentration of calcium ions is less than 0.05 g / L. At the same time, calcium carbonate is generated and collected to obtain the purified solution. (5) The purified liquid is evaporated and concentrated at 80°C to obtain the finished liquid; (6) Heat the soda ash solution to 90°C, and then add the finished solution to it according to the excess coefficient of 1.1. The feeding time is 90 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate with a purity of 96.74%. (7) The crude lithium carbonate was washed three times with high-purity water at 90°C at a mass ratio of 1:1, filtered and dried to obtain battery-grade lithium carbonate with a purity of 99.72%. Example 7

[0030] (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to undergo crystal transformation roasting at 1100℃ for 3 hours to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:3, and then acidification reaction is carried out for 2 hours at an acidification temperature of 200℃ to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:5 and stir evenly to form a slurry; stir the slurry at 80°C for 30 minutes and then filter it to separate the solid and liquid to obtain an acidic leachate; (4) Add the acidic leachate to the calcium carbonate recovered in the control example to replace part of the heavy calcium carbonate, and add an appropriate amount of heavy calcium carbonate to adjust the pH to 6. After filtration, remove impurities. During the impurity removal process, add calcium oxide at 80°C and react for 10 minutes to adjust the pH of the solution to 11 and remove magnesium ions from the solution. After impurity removal, the concentration of magnesium ions in the solution is less than 0.01 g / L. Then add sodium carbonate at 80°C and react for 10 minutes. The molar ratio of sodium carbonate added to calcium ions in the solution is 1:1.05 to remove the remaining calcium ions in the solution. After the reaction, the concentration of calcium ions is less than 0.05 g / L. At the same time, calcium carbonate is generated and collected to obtain the purified solution. (5) The purified liquid is evaporated and concentrated at 90°C to obtain the finished liquid; (6) Heat the soda ash solution to 90°C, and then add the finished solution to it according to the excess coefficient of 1.1. The feeding time is 60 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate with a purity of 96.85%. (7) The crude lithium carbonate was washed three times with high-purity water at 95°C at a mass ratio of 1:2, filtered and dried to obtain battery-grade lithium carbonate with a purity of 99.79%.

[0031] This invention discloses a method for preparing battery-grade lithium carbonate by reusing calcium carbonate, achieving efficient recycling and process optimization of byproducts in lithium concentrate extraction. The calcium carbonate precipitate generated during the impurity removal process is reused for pH adjustment in the acidic leaching stage, thereby realizing internal resource recycling and green manufacturing.

[0032] This invention, in the lithium extraction process from lithium concentrate, first obtains a lithium-containing acidic leachate through a leaching process. To address the high concentration of calcium ion impurities in the leachate, sodium carbonate is added to the system for calcium removal. Sodium carbonate reacts with calcium ions to form calcium carbonate precipitate, effectively removing calcium impurities and ensuring the purity of subsequent products. After this impurity removal process, the generated calcium carbonate precipitate is efficiently collected using conventional solid-liquid separation methods such as filtration. Unlike traditional processes that treat calcium carbonate as solid waste, this invention recycles it and directly reuses it in the upstream acidic leaching process to adjust the pH of the leaching system. This reuse strategy requires no additional processing steps or equipment; only reasonable optimization of the existing process flow is needed to achieve on-site resource utilization of byproducts. Through this method, this invention not only effectively reduces the need for purchased neutralizing agents and lowers production costs but also significantly reduces the generation of solid waste. More importantly, this recycling process reduces the difficulty of subsequent impurity removal, improves the overall lithium extraction efficiency and the purity of the final product, thereby more stably producing battery-grade lithium carbonate that meets standards.

[0033] In summary, this invention achieves efficient extraction and purification of lithium resources while promoting the resource-based reuse of calcium carbonate byproducts, demonstrating the dual advantages of resource conservation and environmental friendliness, and possessing significant industrial application value and promising prospects for promotion.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing battery-grade lithium carbonate with recyclable calcium carbonate, characterized in that, Includes the following steps: (1) Grind the lithium concentrate to below 200 mesh, and then send the ground lithium concentrate into a muffle furnace to undergo crystal transformation roasting at 900-1100℃ to obtain roasted clinker; (2) After the roasting temperature drops to room temperature, the roasted clinker and concentrated sulfuric acid are mixed and stirred evenly at a mass ratio of 1:3-6, and then acidification reaction is carried out for 1-3 hours to obtain acidified clinker; (3) Grind the acidified material into a fine powder of less than 200 mesh using a ball mill, then mix it with deionized water at a mass ratio of 1:1-10 and stir evenly to form a slurry; stir the slurry at 60-90℃ for 20-60 minutes and then filter it to separate the solid and liquid to obtain an acidic leachate. (4) Add heavy calcium carbonate to the acidic leachate to adjust its pH to 4-6, filter and remove impurities; during the impurity removal process, first add calcium oxide at 60-80℃ and react for 10 minutes to adjust its pH to 9-11 to remove magnesium ions in the solution. After impurity removal, the concentration of magnesium ions is less than 0.01 g / L; then add sodium carbonate and react for 10 minutes to remove the remaining calcium ions in the solution. The molar ratio of the added sodium carbonate to the calcium ions in the solution is 1:1-1.

25. After impurity removal, the concentration of calcium ions is less than 0.05 g / L, and calcium carbonate is generated to obtain the purified solution; collect the calcium carbonate and use it to replace part of the heavy calcium carbonate in subsequent experiments; (5) The purified liquid is evaporated and concentrated at 60-90℃ to obtain the finished liquid; (6) Heat the soda ash solution to 75-95℃, and then add the finished solution to it according to the excess coefficient of 1.05-1.

2. The feeding time is 60-120 minutes. After feeding, stir for 5 minutes, and then filter and wash to obtain crude lithium carbonate. (7) The crude lithium carbonate is purified to obtain battery-grade lithium carbonate.

2. A method for preparing battery-grade lithium carbonate with recyclable calcium carbonate according to claim 1, characterized in that: In step (1), the lithium oxide content in the lithium concentrate is between 1.0% and 5.5%.

3. A method for preparing battery-grade lithium carbonate with recyclable calcium carbonate according to claim 1, characterized in that: In step (2), the acidification temperature is 100-300℃.

4. A method for preparing battery-grade lithium carbonate with recyclable calcium carbonate according to claim 1, characterized in that: In step (7), during purification, the mass ratio of crude lithium carbonate to high-purity water is 1:1-3.

5. A method for preparing battery-grade lithium carbonate with recyclable calcium carbonate according to claim 1, characterized in that: In step (7), the washing is performed 3 times.

6. A method for preparing battery-grade lithium carbonate with recyclable calcium carbonate according to claim 7, characterized in that: In step (7), the washing temperature is 80-95℃.

Images