A system and method for continuously producing high-purity lithium carbonate

Abstract

This invention discloses a system for the continuous production of high-purity lithium carbonate, comprising a first slurry storage tank, an extraction device, a purification device, a second slurry storage tank, a reaction vessel, and a filtration and collection device connected in sequence. The extraction device is equipped with a temperature control device. The second slurry storage tank is equipped with a concentration detection device and a concentration adjustment system. The reaction vessel includes a primary stirring vessel and an advanced stirring vessel, which are connected in sequence between the second slurry storage tank and the reaction vessel. This invention belongs to the field of lithium carbonate production and solves the problems of low production efficiency, low product purity, and high energy consumption in current batch production processes of ultrapure lithium carbonate.

Description

Technical Field

[0001] This invention relates to the field of lithium carbonate production technology, and in particular to a system and method for the continuous production of high-purity lithium carbonate. Background Technology

[0002] Lithium, the lightest known alkali metal with the smallest atomic nucleus radius, is a silvery-white metal. Lithium and its compounds possess many unique and excellent properties, making them widely used in glass, ceramics, lubrication, electronics, metallurgy, medicine, refrigeration, aerospace, and other fields. Lithium carbonate is an important lithium salt with a wide range of applications and strong market value. With the rapid development of mobile communication devices and electric vehicles, the demand for lithium batteries is increasing. Lithium cobalt oxide, lithium manganese oxide, and lithium nickel oxide are the preferred cathode materials for lithium-ion batteries due to their excellent thermal stability, cycle performance, safety, and environmental friendliness. As a key raw material for the production of lithium cobalt oxide, lithium manganese oxide, and lithium nickel oxide, the demand for lithium carbonate is also growing. However, traditional lithium carbonate preparation processes have many shortcomings, such as low production efficiency, low product purity, and high energy consumption. Especially in the extraction and purification process of lithium, the traditional intermittent operation method generally involves adding lithium sulfate solution to a sodium carbonate solution, followed by solid-liquid separation to obtain wet lithium carbonate, then stirring and washing, followed by another solid-liquid separation to obtain battery-grade lithium carbonate, which is finally dried and packaged. This method suffers from low production efficiency and struggles to meet the continuity and stability requirements of industrial-scale production. Furthermore, process control directly impacts the crystal morphology and purity of lithium carbonate, thus directly affecting the quality of the final product. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a novel system and method for the continuous production of high-purity lithium carbonate, which improves both production efficiency and product quality.

[0004] The present invention proposes a system for the continuous production of pure lithium carbonate, comprising a first slurry storage tank, an extraction device, a purification device, a second slurry storage tank, a reaction vessel, and a filtration and collection device connected in sequence. The extraction device is characterized by being equipped with a temperature control device; the second slurry storage tank is equipped with a concentration detection device and a concentration adjustment system; and the reaction vessel comprises a primary stirring vessel and an advanced stirring vessel, which are connected in sequence between the second slurry storage tank and the reaction vessel.

[0005] The first slurry storage tank includes a raw lithium solution storage tank, an organic phase solution storage tank, and a carbonic acid source storage tank, and the second slurry includes a refined lithium solution storage tank.

[0006] Preferably, the lithium solution stored in the raw material lithium solution storage tank is derived from lithium ore, salt lake brine, or recycled lithium battery materials. After pretreatment such as crushing, screening, filtration, and leaching, the solution enters the raw material lithium solution storage tank, awaiting further processing.

[0007] The organic solvent in the organic phase solution storage tank is selected from any one or more of dibutylphosphonic acid, diphosphonic acid (2-ethylhexyl), n-octanoic acid, 2-ethylhexanol, and nonane.

[0008] The carbonate source in the carbonate source storage tank is selected from sodium carbonate, sodium bicarbonate, or carbon dioxide gas.

[0009] The inventors discovered that the extraction efficiency of the same lithium source varies at different heating rates. Specifically, the optimal heating rate for lithium extraction can be determined by analyzing the TGA curves of the lithium source at different heating rates. When the curve shows a peak or a steep change region, it may indicate the rapid release of lithium components or the decomposition of other substances. After determining the optimal heating rate for lithium extraction based on the TGA curve, the heating rate and temperature range can be controlled in the extraction device by a temperature control device. Preferably, the temperature control device is a PID controller or a temperature sensor to ensure precise control of the upper and lower temperature limits and the heating rate.

[0010] To further improve the lithium recovery rate, the extraction process includes a multi-stage extraction and back-extraction process. Preferably, the number of extraction devices is set to 2-4, and more preferably, the number of extraction devices is set to 4.

[0011] After extraction and purification, the lithium solution enters the second slurry storage tank. This tank is equipped with a concentration detection device and a concentration adjustment system to monitor the lithium solution concentration in real time. The concentration range is controlled to be 0.05-0.5 mol / L. Within this range, the lithium ion concentration is suitable for the subsequent carbonation reaction, resulting in a high yield and good crystallinity. If the initial concentration of the lithium solution is below 0.05 mol / L, it needs to be concentrated to a suitable reaction concentration. If the initial concentration exceeds 0.5 mol / L, an appropriate amount of solvent needs to be added for dilution to adjust it to the aforementioned concentration range.

[0012] Preferably, the second slurry storage tank further includes a stirrer to ensure that the lithium solution remains uniformly mixed throughout the conditioning process.

[0013] Preferably, the concentration detection device is a densitometer or a refractometer, and the concentration adjustment system is a heating concentration device or a solvent replenishment device.

[0014] Preferably, the purification device is an adsorbent column or an ion exchange resin column.

[0015] The adjusted lithium solution reacts with a carbonic acid source to produce lithium carbonate. During this process, the carbonic acid source is added slowly and continuously to the lithium solution to control the reaction rate and the quality of lithium carbonate produced. The reaction process is monitored in real time, including pH, temperature, and stirring speed, to ensure the reaction proceeds under optimal conditions. Generally, the pH is controlled at 8-10, the temperature at approximately 60-80℃, and a two-stage stirring system is used, consisting of a primary stirring tank and an advanced stirring tank. The stirring intensity and time of the two tanks can be controlled independently. The primary stirring tank is responsible for the formation of lithium carbonate crystal nuclei, using a lower stirring speed and short stirring time to generate crystal nuclei. The lithium carbonate slurry containing crystal nuclei is then transferred to the advanced stirring tank, which is equipped with more powerful stirring equipment and has a variable speed. The advanced stirring tank uses a higher stirring speed during the growth phase to ensure uniform solution distribution. Later, a lower stirring speed is used to promote crystal growth. Online monitoring of crystal size and process parameters is implemented throughout the stirring tanks. Ultimately, the two-stage stirring process forms uniformly sized and highly intact lithium carbonate crystals, improving product quality and yield. After the lithium carbonate crystals reach the ideal size, they are collected by methods such as filtration or centrifugation.

[0016] Finally, the collected crystals are cleaned to remove surface impurities and then dried to obtain the final lithium carbonate product. The final product is then subjected to purity and quality tests to ensure that it meets the requirements.

[0017] The working steps of the system for continuous production of high-purity lithium carbonate proposed in this invention are as follows:

[0018] S1: The raw lithium solution is pumped from the storage tank into the extraction device, and the organic solvent in another storage tank is pumped from the other end of the extraction device into the extraction device to perform countercurrent contact extraction with the lithium solution. The temperature control device controls the temperature at 20-80℃ and the heating rate at 1-10℃ / min.

[0019] S2: The organic phase of lithium extraction obtained in step S1 is purified and output to the storage tank. The concentration detection device and concentration adjustment system dynamically adjust the concentration of the lithium solution to 0.05-0.5 mol / L according to the initial concentration of the lithium solution.

[0020] S3: Mix the lithium solution obtained in step S2 with the carbonic acid source. First, control the stirring speed at 10-100 rpm in the primary stirred tank to generate crystal nuclei. Then, transfer the lithium carbonate slurry containing crystal nuclei to the advanced stirred tank and control the stirring speed at 300-400 rpm until the lithium carbonate crystals reach the ideal size.

[0021] S4: The crystal nuclei obtained in step S3 are filtered, cleaned, and dried to finally obtain the lithium carbonate product.

[0022] Preferably, the extraction in step S1 is a multi-stage extraction and back-extraction process, including the following steps:

[0023] a. First-stage extraction: Lithium ions in the feed solution are extracted into the organic phase using an extractant;

[0024] b. First-stage back-extraction: Lithium ions are back-extracted from the organic phase to the aqueous phase using an alkaline back-extraction agent;

[0025] c. Second-stage extraction: The lithium ions in the aqueous phase after back-extraction are extracted again into the organic phase using the extractant;

[0026] d. Second-stage back-extraction: Lithium ions are back-extracted from the organic phase to the aqueous phase again using an alkaline back-extractant.

[0027] More preferably, the alkaline back-extraction agent in step b is a sodium carbonate solution. Compared with the prior art, the beneficial effects of the present invention are:

[0028] The process of this invention is a continuous reaction with a high degree of automation. Compared with traditional batch reactions, it improves production efficiency, ensures the stability of slurry properties, and facilitates the continuous and stable operation of the entire plant, while reducing the labor intensity of production. The system and method for producing high-purity lithium carbonate provided by this invention improves the extraction efficiency of lithium ions by precisely controlling the heating rate and temperature of the solvent extraction process. By dynamically adjusting the concentration and pH value of the lithium solution and precisely controlling the staged stirring process, the growth conditions of lithium carbonate crystals are optimized, significantly improving the purity and yield of the product. This not only improves product quality but also has significant economic and environmental benefits. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the system for the continuous production of high-purity lithium carbonate proposed in this invention.

[0030] In the diagram: 1-First slurry storage tank, 101-Raw lithium solution storage tank, 102-Organic phase solution storage tank, 103-Extraction agent storage tank, 104-Carbon dioxide source storage tank, 2-Extraction device, 3-Purification device, 4-Second slurry storage tank, 5-Primary stirred tank, 6-Advanced stirred tank, 201-Temperature control device, 401-Concentration detection device, 402-Heating device, 403-Solvent replenishment device, 601-Temperature and pH control device, 7-Filtration and collection device Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the embodiments and examples. It should be understood that these embodiments and examples are for illustrative purposes only and are not intended to limit the scope of the invention. The purpose of providing these embodiments and examples is to make the disclosure of the present invention more thorough and complete. It should also be understood that the present invention can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present invention, and the equivalent forms obtained also fall within the protection scope of this application. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of the present invention. It should be understood that the present invention can be implemented without one or more of these details.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for descriptive purposes only and is not intended to be limiting of the invention.

[0033] the term

[0034] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0035] In this document, terms such as "preferred," "better," "more suitable," and "ideal" are merely descriptions of more effective implementation methods or embodiments and should be understood not to limit the scope of protection of this invention. If multiple "preferred" terms appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "preferred" term shall be independent.

[0036] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features. It should be understood that when the chemical composition of a substance is described in a limiting manner, the substance may contain impurities present in normal amounts, including but not limited to impurities inevitably introduced due to the preparation process.

[0037] In this invention, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0038] Example 1

[0039] refer to Figure 1 The present invention proposes a system for the continuous production of high-purity lithium carbonate, comprising a first slurry storage tank 1, an extraction device 2, a purification device 3, a second slurry storage tank 4, a reaction vessel, and a filtration and collection device 7 connected in sequence. The extraction device is equipped with a temperature control device 201; the second slurry storage tank is equipped with a concentration detection device and a concentration adjustment system 401; the reaction vessel includes a primary stirring vessel 5 and an advanced stirring vessel 6, which are connected in sequence between the second slurry storage tank 4 and the reaction vessel. The first slurry storage tank includes a raw lithium solution storage tank 101, an organic phase solution storage tank 102, a back-extraction agent storage tank 103, and a carbonate source storage tank 104; the second slurry includes a refined lithium solution storage tank 4. The number of extraction devices is set to four. The temperature control device 201 is a temperature sensor, the concentration detection device 401 is a densitometer, and the concentration adjustment system is a heating concentration device 402 or a solvent replenishment device 403. The second slurry storage tank also includes a stirrer to ensure that the lithium solution remains uniformly mixed throughout the adjustment process. The purification device 3 is an adsorbent filling device. The primary stirred tank 5 is responsible for the generation of lithium carbonate crystal nuclei. The advanced stirred tank 6 uses a higher stirring speed to be responsible for crystal growth. The temperature and pH control device 601 detects the temperature and pH value of the reaction. After the lithium carbonate crystals reach the ideal size, they are filtered and collected by the filtration and collection device 7.

[0040] The working steps of the system for continuous production of high-purity lithium carbonate proposed in this invention are as follows:

[0041] S1: The raw lithium solution is pumped from the storage tank into the extraction device, and the organic solvent in another storage tank is pumped from the other end of the extraction device into the extraction device to perform countercurrent contact extraction with the lithium solution. The temperature control device controls the temperature at 20°C and the heating rate at 1°C / min.

[0042] S2: The dibutyl phosphate organic phase obtained from the lithium extraction in step S1 is purified and output to the storage tank. The concentration detection device and concentration adjustment system dynamically adjust the concentration of the lithium solution to 0.05 mol / L according to the initial concentration of the lithium solution.

[0043] S3: Mix the lithium solution obtained in step S2 with sodium carbonate. First, in a primary stirred tank, control the stirring speed at 100 rpm to generate crystal nuclei for 30 minutes. Then, transfer the lithium carbonate slurry containing crystal nuclei to an advanced stirred tank, control the stirring speed at 300 rpm for 2 hours, and then reduce the stirring speed to 100 rpm and continue stirring for 1 hour until the lithium carbonate crystals reach the ideal size.

[0044] S4: The crystal nuclei obtained in step S3 are filtered, cleaned, and dried to finally obtain the lithium carbonate product.

[0045] The extraction in step S1 is a multi-stage extraction and back-extraction process, including the following steps:

[0046] a. First-stage extraction: Lithium ions in the feed solution are extracted into the organic phase using dibutylphosphoric acid as the extractant;

[0047] b. First-stage back-extraction: Lithium ions are back-extracted from the organic phase to the aqueous phase using sodium carbonate back-extraction agent;

[0048] c. Second stage extraction: The lithium ions in the aqueous phase after back-extraction are extracted into the organic phase again using the extractant dibutylphosphoric acid;

[0049] d. Second-stage back-extraction: Lithium ions are back-extracted from the organic phase to the aqueous phase again using sodium carbonate back-extraction agent.

[0050] The lithium carbonate prepared in Example 1 had a yield of 56%, a purity of 99.5%, an average crystal size of 150 micrometers, and a uniform, regular cubic crystal morphology.

[0051] Example 2

[0052] In step S1 of Example 2, the temperature control device controls the temperature at 20°C and the heating rate at 5°C / min. The other steps are the same as in Example 1. The lithium carbonate yield is 57%, the purity is 99.7%, the average crystal size is 150 micrometers, and the crystal morphology is uniform and regular cubic.

[0053] Example 3

[0054] In step S1 of Example 3, the temperature control device controls the temperature at 20°C and the heating rate at 10°C / min. Other steps are the same as in Example 1. The lithium carbonate yield is 55%, the purity is 99.4%, the average crystal size is 150 micrometers, and the crystal morphology is uniform and regular cubic.

[0055] Comparative Example 1

[0056] In Comparative Example 1, the stirring speed in step S3 was a constant 200 rpm for 3 hours. Other steps were the same as in Example 1. The yield of the obtained lithium carbonate was 44%, the purity was 97%, the average crystal size was 100 micrometers, the crystal morphology was non-uniform, and some crystals exhibited irregular shapes.

Claims

1. A system for continuous production of high-purity lithium carbonate, comprising a first slurry storage tank, an extraction device, a purification device, a second slurry storage tank, a reaction vessel, and a filtration and collection device connected in sequence, characterized in that, The extraction device is equipped with a temperature control device; the second slurry storage tank is equipped with a concentration detection device and a concentration adjustment system; the reaction vessel includes a primary stirring vessel and an advanced stirring vessel, which are sequentially connected between the second slurry storage tank and the filtration and collection device; the primary stirring vessel is used to generate lithium carbonate crystal nuclei, and the advanced stirring vessel is used to grow lithium carbonate crystals to the ideal size; the primary stirring vessel uses a lower stirring speed, and the advanced stirring vessel uses a higher stirring speed; The first slurry storage tank includes a raw lithium solution storage tank, an organic phase solution storage tank, a stripping agent storage tank, and a carbonic acid source storage tank, and the second slurry storage tank includes a refined lithium solution storage tank.

2. The system for continuous production of high-purity lithium carbonate according to claim 1, characterized in that, The number of extraction devices is set to 2-4, and the temperature control device is a PID controller or a temperature sensor.

3. The system for continuous production of high-purity lithium carbonate according to claim 1, characterized in that, The concentration detection device is a densitometer or a refractometer, and the concentration adjustment system is a heating concentration device or a solvent replenishment device.

4. The system for continuous production of high-purity lithium carbonate according to claim 1, characterized in that, The purification device is an adsorbent filling device or an ion exchange resin filling device.

5. A method for operating a system for the continuous production of high-purity lithium carbonate as described in claim 1, characterized in that: Includes the following steps: S1: The raw lithium solution is pumped from the raw lithium solution storage tank into the extraction device, and the organic solvent in the organic phase solution storage tank is pumped from the other end of the extraction device into the extraction device to perform countercurrent contact extraction with the lithium solution. The temperature control device controls the temperature at 20-80°C and the heating rate at 1-10°C / min. S2: The organic phase of lithium extraction obtained in step S1 is purified and output to the storage tank. The concentration detection device and concentration adjustment system dynamically adjust the concentration of the lithium solution to 0.05-0.5 mol / L according to the initial concentration of the lithium solution. S3: Mix the lithium solution obtained in step S2 with the carbonic acid source. First, control the stirring speed at 10-100 rpm in the primary stirred tank to generate crystal nuclei. Then, transfer the lithium carbonate slurry containing crystal nuclei to the advanced stirred tank and control the stirring speed at 300-400 rpm until the lithium carbonate crystals reach the ideal size. S4: Filter, wash and dry the lithium carbonate crystals obtained in step S3 to finally obtain the finished lithium carbonate product.

6. The working method according to claim 5, characterized in that, The organic solvent in step S1 is selected from any one or more of dibutylphosphonic acid, diphosphonic acid (2-ethylhexyl), n-octanoic acid, 2-ethylhexanol, and nonane.

7. The working method according to claim 5, characterized in that, The carbonic acid source in step S3 is selected from sodium carbonate, sodium bicarbonate, or carbon dioxide gas.

8. The working method according to claim 5, characterized in that, The extraction in step S1 is a multi-stage extraction and back-extraction process, including the following steps: a. First-stage extraction: Lithium ions in the feed solution are extracted into the organic phase using an extractant; b. First-stage back-extraction: Lithium ions are back-extracted from the organic phase to the aqueous phase using an alkaline back-extraction agent; c. Second-stage extraction: The lithium ions in the aqueous phase after back-extraction are extracted again into the organic phase using the extractant; d. Second-stage back-extraction: Lithium ions are back-extracted from the organic phase to the aqueous phase again using an alkaline back-extractant.

9. The working method according to claim 8, characterized in that, The alkaline back-extraction agent in step b is a sodium carbonate solution.

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