Process for producing battery-grade lithium carbonate and lithium hydroxide by extracting lithium from spodumene

Abstract

The invention discloses a process for producing battery-grade lithium carbonate and lithium hydroxide by extracting lithium from lithium ores, which is characterized in that the lithium ores are treated by a pyrogenic process section and a wet process section in sequence, two high-added-value products, namely the battery-grade lithium carbonate and the battery-grade lithium hydroxide, are synchronously produced, meanwhile, anhydrous sodium sulphate is produced as a byproduct, waste discharge is avoided, and the value of raw materials is excavated to the maximum extent; a multi-stage purification and impurity removal system is formed by adopting leaching neutralization preliminary impurity removal, alkali liquor precipitation purification, ion resin deep impurity removal and hydrogenation impurity removal, impurities such as Fe, Al, Ca and Mg are removed, the product purity is guaranteed, and efficient recovery of the lithium element and maximum utilization of the raw material value are achieved.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction from ore, specifically a process for extracting lithium from spodumene to produce battery-grade lithium carbonate and lithium hydroxide. Background Technology

[0002] In recent years, with the rapid development of the new energy industry, the demand for basic lithium salt products such as lithium carbonate and lithium hydroxide has been strong. Currently, lithium extraction from ore is the main method for lithium salt production, including processes such as the sulfuric acid process, the sulfate process, and the limestone roasting process. Patent ZL201010279730.1 discloses a method for extracting lithium salts from spodumene, which involves sequentially processing spodumene concentrate through roasting and transformation, cooling and grinding, slurry preparation, pressure leaching, cooling and depressurization carbonation, separation, washing and impurity removal, heating and decomposition, centrifugal separation and rinsing, and drying to obtain qualified lithium carbonate products. Patent application CN113428882A discloses a method for preparing battery-grade lithium carbonate from spodumene, which involves mixing, roasting, neutral leaching, purification and impurity removal, and lithium precipitation processes to obtain battery-grade lithium carbonate.

[0003] The above technical solutions have optimized the production process, but they still have problems such as low process yield, waste of lithium resources, failure to fully utilize other elements in the ore to maximize the value of lithium ore, and insufficient process flexibility. They all aim at a single lithium salt product and cannot flexibly switch product types according to market demand, thus limiting the economic efficiency of production.

[0004] Therefore, developing a process that can improve lithium element yield, maximize the value of lithium ore raw materials, and simultaneously produce multiple lithium salt products to overcome the shortcomings of existing methods is of great significance for improving the efficiency of lithium resource utilization and meeting the development needs of the new energy industry. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a rapid method for determining the conversion rate of spodumene. The specific technical solution is as follows: In order to solve the problems of the existing lithium extraction process from ore mentioned in the background art, the present invention provides a process for producing battery-grade lithium carbonate and lithium hydroxide from spodumene. Spodumene is processed sequentially through a pyrometallurgical section and a hydrometallurgical section to obtain finished lithium hydroxide, lithium carbonate and by-product sodium sulfate, thereby achieving efficient recovery of lithium elements and maximizing the utilization of raw material value.

[0006] This process includes a pyrometallurgical section and a hydrometallurgical section. The pyrometallurgical section includes roasting and transformation, grinding, and acid roasting. The hydrometallurgical section includes leaching and neutralization, purification and impurity removal, lithium precipitation, hydrogenation, preparation of battery-grade lithium carbonate, causticizing, cryogenic sodium precipitation, preparation of sodium sulfate, and preparation of battery-grade lithium hydroxide. The specific scheme is as follows:

[0007] Step 1. Calcination Transformation Spodumene concentrate is preheated, transformed, roasted, and cooled through a multi-stage cyclone preheater system, rotary kiln, and fourth-generation grate cooler, thereby transforming α-spodumene into β-spodumene. After transformation, it is transported to the roasted material storage silo.

[0008] The material is fed into the vertical mill for grinding using transport equipment. The ground fine roasted material is then transported through ducts to a cyclone separator and a large dust collector. The collected fine roasted material is then conveyed into the fine roasted material silo using transport equipment.

[0009] Step 3. Acidification and roasting After the fine roasted material is metered, it is mixed with concentrated sulfuric acid in a certain proportion in a mixing machine. The mixed acid material is then calcined in an acidification kiln to produce acid-cooked material, which is then cooled by a cooling device and sent to the leaching workshop.

[0010] Step 4. Leaching and neutralization The acidified raw materials are leached into a slurry according to a specific ratio. Then, the sulfuric acid in the solution is neutralized using a calcium carbonate and calcium hydroxide solution, bringing the solution to neutral. Through the leaching and neutralization process, insoluble impurities in the material can be removed, while cations such as Fe and Al in the solution are also removed, thus performing preliminary purification of the lithium sulfate solution.

[0011] Step 5. Purification and impurity removal The pH of the lithium sulfate solution is adjusted using an alkaline solution, causing Ca, Mg, Al, and Fe ions to be removed by precipitation, thus purifying the lithium sulfate solution. Further deep purification is the core technical step, using Ca... 2+ Mg 2+ Ion-type ion exchange resins selectively adsorb Ca from solution through resin adsorption. 2+ Mg 2+ This achieves deep purification. Through these two purification methods, a high-purity lithium sulfate solution can be obtained for subsequent production.

[0012] Step 6. Lithium precipitation and hydrogenation Purified lithium sulfate solution and hot sodium carbonate solution are added to a lithium precipitation reactor at a certain stoichiometric ratio. A metathesis reaction generates lithium carbonate precipitate with low solubility. Industrial-grade lithium carbonate is then obtained through centrifugation, washing, and drying. The lithium carbonate is further prepared into a slurry at a certain liquid-to-solid ratio, and carbon dioxide is introduced. A soluble lithium bicarbonate solution is generated in a carbonation tower, and its soluble nature is used to separate insoluble impurities.

[0013] Step 7. Preparation of battery-grade lithium carbonate A portion of the lithium bicarbonate solution obtained from the lithium precipitation and hydrogenation processes is passed into a pyrolysis tower and heated to decompose it into lithium carbonate, thereby regenerating higher purity battery-grade lithium carbonate. After drying and packaging, the finished battery-grade lithium carbonate is obtained.

[0014] Step 8. Causticization A portion of the lithium bicarbonate solution obtained from the lithium precipitation and hydrogenation processes is added to a causticizing tank along with calcium hydroxide in a certain stoichiometric ratio. The mixture undergoes a metathesis reaction with stirring to generate a lithium hydroxide causticizing solution.

[0015] Step 9. Sodium precipitation by freezing The lithium hydroxide causticizing solution is fed into a cryogenic crystallization system via a conveying device. After two low-temperature freezing processes, sodium sulfate (sodium sulfate) precipitates out, removing Na+ from the causticized solution. + SO4 2- Impurities were removed, and the lithium hydroxide solution was initially purified.

[0016] Step 10. Preparation of Glauber's salt Glauber's salt is converted into sodium sulfate solution by hot melting, and then the finished product, sodium sulfate, is obtained by evaporation, crystallization, drying, and packaging.

[0017] Step 11. Preparation of battery-grade lithium hydroxide The lithium hydroxide solution after freezing and sodium precipitation is concentrated twice by evaporation crystallizer, so that lithium hydroxide crystallizes out in the form of monohydrate. At the same time, the lithium hydroxide is purified to meet the standard of battery-grade lithium hydroxide products. After drying and packaging, the finished battery-grade lithium hydroxide is obtained.

[0018] Furthermore, the roasting transformation process controls the material inlet temperature to be 250~300℃, the roasting temperature in the kiln to be 1050~1100℃, the material residence time in the kiln to be 90min, and the grate cooler outlet temperature to be 60℃ + ambient temperature.

[0019] Furthermore, the roasting conversion process is equipped with a desulfurization and denitrification system. The exhaust gas from the preheater is treated by the desulfurization and denitrification system to meet the standards before being discharged.

[0020] Furthermore, the acid roasting process employs a multi-burner jacketed indirect heating rotary kiln and an internal tubular water-cooled cooling kiln for acid roasting and cooling; the acid roasting temperature is 250~300℃, and the target acid cooling temperature is ≤65℃.

[0021] Furthermore, the equipment used in the leaching and neutralization process includes a stirring tank and a plate and frame filter press / vacuum belt filter.

[0022] Furthermore, the alkaline solution used in the purification and impurity removal process can be selected from Ca(OH)2, NaOH, or Na2CO3.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The lithium extraction process for producing battery-grade lithium carbonate and lithium hydroxide from spodumene disclosed in this invention reduces energy consumption and shrinks the rotary kiln equipment size by adding a preheater to the pyrometallurgical roasting conversion process; the hot air from the high-temperature section at the front end of the grate cooler enters the rotary kiln as secondary air, and the waste heat from the exhaust gas at the rear end can be used to dry lithium slag / lithium concentrate / to a steam boiler, realizing waste heat utilization and reducing energy consumption; the acidification roasting process uses a multi-burner jacketed heating system in the acidification kiln, which provides precise temperature control, uniform heating, and a smaller footprint; the cooling kiln is in the form of an inner tube, which increases the heat exchange area and further reduces the footprint.

[0024] 2. The lithium extraction process for producing battery-grade lithium carbonate and lithium hydroxide from spodumene disclosed in this invention uses acid-clinked raw materials as the core raw material in the wet process stage, simultaneously producing two high-value-added products: battery-grade lithium carbonate and battery-grade lithium hydroxide. It also produces sodium sulfate as a byproduct, eliminating wasteful emissions and maximizing the value of the raw materials. The process employs a multi-stage purification system consisting of "leaching neutralization for initial impurity removal + alkaline precipitation purification + ion exchange resin for deep impurity removal + hydrogenation impurity removal" to remove impurities such as Fe, Al, Ca, and Mg, ensuring product purity. It utilizes mature metallurgical equipment such as stirred tanks, plate and frame filter presses, ion exchange columns, freeze crystallization systems, and evaporator crystallizers, ensuring high operational reliability. Attached image description: Figure 1 This is a process flow diagram of the lithium extraction process from spodumene to produce battery-grade lithium carbonate and lithium hydroxide according to an embodiment of the present invention. Figure 2 This is a material flow diagram of the process for producing battery-grade lithium carbonate and lithium hydroxide from spodumene according to an embodiment of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, providing a basic understanding of the invention, but is not intended to identify the key or decisive elements of the invention or to limit the scope of protection sought.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the implementation of the present invention is not limited thereto.

[0028] Example 1: This embodiment provides a process for extracting lithium from lithium ore to produce battery-grade lithium carbonate and lithium hydroxide. The lithium ore is processed sequentially through a pyrometallurgical section and a hydrometallurgical section to obtain finished products lithium hydroxide and lithium carbonate, as well as the byproduct sodium sulfate. The specific steps are as follows: Step 1. Calcination Transformation Spodumene concentrate is preheated, transformed, roasted, and cooled through a multi-stage cyclone preheater system, rotary kiln, and fourth-generation grate cooler, thereby transforming α-spodumene into β-spodumene. After transformation, it is transported to the roasted material storage silo.

[0029] Step 2. Grinding The material is fed into the vertical mill for grinding using transport equipment. The ground fine roasted material is then transported through ducts to a cyclone separator and a large dust collector. The collected fine roasted material is then conveyed into the fine roasted material silo using transport equipment.

[0030] Step 3. Acidification and roasting After being metered, the fine roasted material is mixed with concentrated sulfuric acid in a certain proportion and then fed into a mixing machine for stirring. The resulting mixed acid is then... The acidification kiln is used for calcination, and the resulting acid clinker is cooled by cooling equipment and then sent to the leaching workshop.

[0031] Step 4. Leaching and neutralization The acidified raw materials are leached into a slurry according to a specific ratio. Then, the sulfuric acid in the solution is neutralized using a calcium carbonate and calcium hydroxide solution, bringing the solution to neutral. Through the leaching and neutralization process, insoluble impurities in the material can be removed, while cations such as Fe and Al in the solution are also removed, thus performing preliminary purification of the lithium sulfate solution.

[0032] Step 5. Purification and impurity removal The pH of the lithium sulfate solution is adjusted using an alkaline solution, causing Ca, Mg, Al, and Fe ions in the solution to be removed by precipitation, thereby purifying the lithium sulfate solution. Further purification involves using Ca... 2+ Mg 2+ Ion-type ion exchange resins selectively adsorb Ca from solution through resin adsorption. 2+ Mg 2+ This achieves deep purification. Through these two purification methods, a high-purity lithium sulfate solution can be obtained for subsequent production.

[0033] Step 6. Lithium precipitation and hydrogenation Purified lithium sulfate solution and hot sodium carbonate solution are added to a lithium precipitation reactor at a certain stoichiometric ratio. A metathesis reaction generates lithium carbonate precipitate with low solubility. Industrial-grade lithium carbonate is then obtained through centrifugation, washing, and drying. The lithium carbonate is further prepared into a slurry at a certain liquid-to-solid ratio, and carbon dioxide is introduced. A soluble lithium bicarbonate solution is generated in a carbonation tower, and its soluble nature is used to separate insoluble impurities.

[0034] Step 7. Preparation of battery-grade lithium carbonate A portion of the lithium bicarbonate solution obtained from the lithium precipitation and hydrogenation processes is passed into a pyrolysis tower and heated to decompose it into lithium carbonate. Higher purity battery-grade lithium carbonate is regenerated, and after drying and packaging, the finished battery-grade lithium carbonate is obtained.

[0035] Step 8. Causticization A portion of the lithium bicarbonate solution obtained from the lithium precipitation and hydrogenation processes is added to a causticizing tank along with calcium hydroxide in a certain stoichiometric ratio. The mixture undergoes a metathesis reaction with stirring to generate a lithium hydroxide causticizing solution.

[0036] Step 9. Sodium precipitation by freezing The lithium hydroxide causticizing solution is fed into a cryogenic crystallization system via a conveying device, and sodium sulfate precipitates after two low-temperature freezing processes. Nitrate, to remove Na from the solution after causticization + SO4 2- Impurities were removed, and the lithium hydroxide solution was initially purified.

[0037] Step 10. Preparation of Glauber's salt Glauber's salt is converted into sodium sulfate solution by hot melting, and then the finished product, sodium sulfate, is obtained by evaporation, crystallization, drying, and packaging.

[0038] Step 11. Preparation of battery-grade lithium hydroxide The lithium hydroxide solution after freezing and sodium precipitation is concentrated twice by evaporation crystallizer, so that lithium hydroxide crystallizes out in the form of monohydrate. At the same time, the lithium hydroxide is purified to meet the standard of battery-grade lithium hydroxide products. After drying and packaging, the finished battery-grade lithium hydroxide is obtained.

[0039] Example 2: This embodiment further describes the equipment used in the roasting conversion process based on Embodiment 1. The multi-stage cyclone preheater system used in the roasting conversion process is a 2-4 stage cyclone preheater, equipped with a desulfurization and denitrification system. The exhaust gas from the multi-stage cyclone preheater system is treated by the desulfurization and denitrification system to meet the standards before being discharged.

[0040] The other parts of this embodiment are the same as those in Embodiment 1, so they will not be described again.

[0041] Example 3: This embodiment, based on Embodiment 1 or 2, further explains the temperature requirements and operation time control for the roasting transformation process. The roasting transformation process controls the material inlet temperature to be 250~300℃, the roasting temperature in the kiln to be 1050~1100℃, the material residence time in the kiln to be 90 minutes, and the grate cooler outlet temperature to be 60℃ + ambient temperature.

[0042] The other parts of this embodiment are the same as those in Embodiment 1 or 2, so they will not be described again.

[0043] Example 4: This embodiment, based on Embodiment 1, 2, or 3, further explains the equipment selection and temperature requirements for the acid roasting process. The acid roasting process uses an indirect heating rotary kiln and an internal tubular water-cooled cooling kiln for acid roasting and cooling; the acid roasting temperature is 250~300℃, and the target acid cooling temperature is ≤65℃.

[0044] The other parts of this embodiment are the same as those in Embodiment 1, 2 or 3, so they will not be described again.

[0045] Example 5: This embodiment, based on Embodiment 1 or 2, further describes the equipment used in the leaching and neutralization process. The equipment used in the leaching and neutralization process includes a stirring tank and a plate and frame filter press / vacuum belt filter.

[0046] The other parts of this embodiment are the same as those in Embodiment 1 or 2, so they will not be described again.

[0047] Example 6: This embodiment, based on Embodiment 5, further explains the type of alkaline solution used in the purification and impurity removal process. The alkaline solution used in the purification and impurity removal process can be selected from Ca(OH)2, NaOH, or Na2CO3.

[0048] The other parts of this embodiment are the same as those in embodiment 5, so they will not be described again.

[0049] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for extracting lithium from lithium ore to produce battery-grade lithium carbonate and lithium hydroxide, characterized in that: Lithium ore is processed sequentially through a pyrometallurgical section and a hydrometallurgical section to obtain finished lithium hydroxide, lithium carbonate, and the byproduct sodium sulfate, including the following steps: Step 1. Calcination and transformation: Spodumene concentrate is preheated, transformed, roasted, and cooled through a multi-stage cyclone preheater system, rotary kiln, and fourth-generation grate cooler, thereby transforming α-type spodumene into β-type spodumene. After transformation, it is transported to the roasted material storage silo. Step 2. Grinding: The calcined material is fed into the vertical mill for grinding using a transport device; the ground fine calcined material is then transported through a duct to a cyclone separator and a large dust collector, and the collected fine calcined material is then sent to the fine calcined material silo via a conveying device. Step 3. Acidification and calcination: After the fine roasted material is metered, it is mixed with concentrated sulfuric acid in a mixing machine. The mixed acid material is then calcined in an acidification kiln to produce acid-cooked material, which is then cooled by a cooling device and sent to the leaching workshop. Step 4. Leaching and neutralization: The acid-cooked material is leached into a slurry, and then the sulfuric acid in the solution is neutralized with calcium carbonate and calcium hydroxide solution to adjust the solution to neutral, remove insoluble impurities from the material, and remove cations such as Fe and Al from the solution, thus performing preliminary purification of the lithium sulfate solution. Step 5. Purification and Impurity Removal: Adjust the pH of the solution using an alkaline solution to remove Ca, Mg, Al, Fe, and other ions from the lithium sulfate solution by forming a precipitate; further use Ca... 2+ Mg 2+ Ion-type ion exchange resins selectively adsorb Ca from solution through resin adsorption. 2+ Mg 2+ The solution is then subjected to deep purification to obtain a lithium sulfate solution with high purity. Step 6. Lithium precipitation and hydrogenation: The purified lithium sulfate solution and hot sodium carbonate solution are added to the lithium precipitation reactor. The lithium carbonate precipitate with low solubility is generated through metathesis reaction. Then, industrial-grade lithium carbonate is obtained through centrifugation, washing and drying. The lithium carbonate is further prepared into a slurry and carbon dioxide is introduced to generate a soluble lithium bicarbonate solution in the carbonation tower. The soluble lithium bicarbonate solution is used to separate the insoluble impurities. Step 7. Preparation of battery-grade lithium carbonate: The lithium bicarbonate solution obtained from the lithium precipitation and hydrogenation processes is passed into a pyrolysis tower and heated to decompose it into lithium carbonate, regenerating battery-grade lithium carbonate with higher purity. After drying and packaging, the finished battery-grade lithium carbonate is obtained. Step 8. Causticization: The lithium bicarbonate solution obtained from the lithium precipitation and hydrogenation processes is added to the causticization tank along with calcium hydroxide. The mixture undergoes a metathesis reaction with stirring to generate a lithium hydroxide causticization solution. Step 9. Sodium precipitation by freezing: The lithium hydroxide causticizing solution is fed into the cryogenic crystallization system via a conveying device. After two low-temperature freezing processes, sodium sulfate (sodium sulfate) precipitates out, removing Na from the causticized solution. + SO4 2- Impurities were initially removed from the lithium hydroxide solution for purification. Step 10. Preparation of sodium sulfate: Glauber's salt is converted into sodium sulfate solution by hot melting, and then the solution is obtained by evaporation, crystallization, drying and packaging. Step 11. Preparation of battery-grade lithium hydroxide: The lithium hydroxide solution after freezing and sodium precipitation is concentrated twice by evaporation crystallizer so that lithium hydroxide crystallizes out in the form of monohydrate. At the same time, the lithium hydroxide is purified to meet the standard of battery-grade lithium hydroxide product. After drying and packaging, the finished battery-grade lithium hydroxide is obtained.

2. The process for producing battery-grade lithium carbonate and lithium hydroxide from lithium ore according to claim 1, characterized in that: The multi-stage cyclone preheater system used in the roasting transformation process is a 2-4 stage cyclone preheater, equipped with a desulfurization and denitrification system. The exhaust gas from the multi-stage cyclone preheater system is treated by the desulfurization and denitrification system to meet the standards before being discharged.

3. The process for producing battery-grade lithium carbonate and lithium hydroxide from lithium ore according to claim 1 or 2, characterized in that: The roasting transformation process controls the material inlet temperature to be 250~300℃, the roasting temperature in the kiln to be 1050~1100℃, the material residence time in the kiln to be 90min, and the outlet temperature of the grate cooler to be 60℃ + ambient temperature.

4. The process for producing battery-grade lithium carbonate and lithium hydroxide from lithium ore according to any one of claims 1-3, characterized in that: The acidification and roasting process uses an indirect heating rotary kiln and an internal tubular water-cooled cooling kiln for acidification, roasting and cooling; the acidification and roasting temperature is 250~300℃, and the target acidification and cooling temperature is ≤65℃.

5. The process for producing battery-grade lithium carbonate and lithium hydroxide from lithium ore according to claim 1 or 2, characterized in that: The equipment used in the leaching and neutralization process includes a stirring tank and a plate and frame filter press / vacuum belt filter.

6. The process for producing battery-grade lithium carbonate and lithium hydroxide from lithium ore according to claim 5, characterized in that: The alkaline solution used in the purification and impurity removal process can be Ca(OH)2, NaOH, or Na2CO3.

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