Method for improving solubility of lithium in carbonate and / or bicarbonate system

Abstract

The invention relates to the field of processing and preparation of lithium salt products, in particular to a method for improving the solubility of lithium in a carbonate and / or bicarbonate system, which comprises the following steps: S1, mixing a lithium carbonate-containing raw material and a dissolving solution for reaction; s2, introducing a carbon dioxide-containing gas into the mixed system in the S1, and carrying out a carbonization reaction; and S3, stopping introducing the carbon dioxide-containing gas into the system in the S2, continuously adding the lithium carbonate-containing raw material, and reacting to obtain the carbonate and / or bicarbonate system with higher lithium concentration. According to the present invention, the lithium solubility in the lithium carbonate and / or bicarbonate system is improved through the secondary material feeding in the traditional carbonization process, such that the problems of low lithium ion solubility, low lithium carbonate yield, slow reaction and the like in the traditional carbonization process are solved, and the lithium solubility is significantly improved compared with the traditional carbonization process by using the scheme of the present invention.

Description

Technical Field

[0001] The present invention relates to the field of processing and preparation of lithium salt products, and in particular to a method for improving the solubility of lithium in a carbonate and / or bicarbonate system. Background Art

[0002] Lithium is one of the important raw materials for the new energy industry. With the growing global demand for lithium resources and lithium salt product development, further optimizing the efficient acquisition of high-purity lithium salt products from lithium-containing resources, especially the refining and processing technology of high-purity lithium carbonate for batteries, has become the current focus and difficulty. Currently, high-purity lithium carbonate for batteries is the most important and most in-demand raw material for the preparation of lithium-ion battery materials. Due to the strict requirements for the control of impurity types and impurity content, it is difficult to prepare it by direct extraction from ores or brine. Generally, industrial lithium carbonate products are obtained by further purification. One of the main preparation methods at this stage is the carbon dioxide carbonization-pyrolysis refining process, which mainly uses crude lithium carbonate raw materials with high impurities through the following processing steps: 1. Crude lithium carbonate is slurried and dissolved in water; 2. Carbon dioxide gas is introduced to carbonize the dissolved lithium carbonate to convert it into a lithium bicarbonate solution; 3. Insoluble impurities are removed by filtration; 4. The lithium bicarbonate solution is heated to thermally decompose it into high-purity refined lithium carbonate.

[0003] Compared with other lithium carbonate refining processes such as causticization and electrolysis, the above-mentioned carbonization-pyrolysis process has the advantages of low reagent consumption, simple equipment investment, simple process and easy operation. However, the carbonization process is limited by the low solubility of lithium carbonate in the lithium carbonate and lithium bicarbonate solution system (100g of water at 20°C can only dissolve about 1.33g of lithium carbonate). In industry, the preparation of battery-grade lithium carbonate by carbonization-pyrolysis requires a large amount of slurry water, which results in a large volume of reaction solution, large floor space for plant equipment, large subsequent filtration volume, long production cycle, low single product yield, difficulty in filtering wastewater treatment, high carbon dioxide consumption, and impurity accumulation caused by filtrate reuse affecting product quality, among other adverse effects.

[0004] To address this issue, existing technologies have proposed some solutions for the carbonization-pyrolysis refining process, such as: Patent CN109942009B discloses a method for preparing battery-grade lithium carbonate. The method addresses the low conversion efficiency caused by the slow reaction of the carbonization process by introducing a new packing tower device, adding a sulfate complexing agent to reduce the lithium bicarbonate content in the product, increasing the number of returns of the lithium extraction mother liquor, and other methods to improve the preparation efficiency of battery-grade lithium carbonate. However, this method only addresses the conversion efficiency issue and does not focus on improving solubility. It is also heavily dependent on a specially structured packing tower device and a special complexing agent. In addition, multiple alkaline and water washes are required, which not only increases the equipment and reagent investment and the difficulty of operation, but also the use of sulfate complexing agents and sodium hydroxide introduces additional impurity elements, significantly increasing the process cost and difficulty of operation, and does not have industrial advantages.

[0005] Patent CN112678849A discloses a method for preparing high-purity lithium carbonate using lithium hydroxide. This process focuses on the milder decomposition conditions of lithium bicarbonate. High-purity lithium carbonate is generated by adding lithium hydroxide to a lithium bicarbonate solution. The lithium carbonate filtrate can be recycled and reused. This provides a short process, mild operating conditions, and low-cost method for synthesizing high-purity lithium carbonate. However, it only focuses on the decomposition optimization process after the lithium carbonate is dissolved, and does not pay attention to or optimize the slurry dissolution process before decomposition.

[0006] Patent CN116789153A discloses a method for preparing high-purity lithium carbonate from crude lithium carbonate. This method primarily focuses on removing impurities from the crude lithium carbonate solution. A mixture of industrial lithium carbonate and water is pretreated with nitrilotriacetic acid to remove impurity elements through complexation, resulting in pretreated lithium carbonate. The pretreated lithium carbonate is then carbonized and mixed with ammonium phosphate for simultaneous impurity removal. This process focuses solely on the coordinated removal of impurities through multiple operations, without addressing or optimizing the carbonization process.

[0007] Patent CN109809441B discloses a method for improving the efficiency of lithium carbonate hydrogenation. To address the defects of slow dissolution and diffusion of lithium carbonate and slow mass transfer and absorption efficiency of carbon dioxide in the hydrogenation reaction, ultrasonic treatment is used to effectively increase the conversion rate of lithium carbonate into lithium bicarbonate. However, this process is heavily dependent on the use of ultrasonic equipment. In actual large-scale production, large-scale ultrasonic equipment is required, which significantly increases equipment investment and maintenance costs. Once the ultrasonic equipment fails, production will be directly hindered. Secondly, long-term intermittent high-power, high-frequency ultrasonic conditions and environment can easily lead to cavitation when the reaction liquid contacts the container, seriously reducing the service life of the equipment. In addition, long-term production in an ultrasonic environment will also cause significant health problems for workers.

[0008] Patent CN110467204A discloses a lithium hydroxide preparation system and process. To address the defect that lithium carbonate powder cannot effectively react with water, a mixture of distilled water and carbon dioxide gas is sprayed to form a water curtain. The mixture of lithium carbonate powder and carbon dioxide gas entering the first reaction chamber first contacts the water curtain to undergo a causticization reaction, generating a lithium bicarbonate solution. The mixture then undergoes a complexation reaction with EDTA in the first reaction chamber to remove magnesium and calcium ions from the solution, thereby increasing the concentration of lithium bicarbonate. This solves the technical problem that when lithium carbonate powder directly reacts with distilled water containing EDTA, the solid impurities formed are coated on the outside of the unreacted lithium carbonate powder, resulting in the inability of the reacted lithium carbonate powder to react to generate lithium bicarbonate. However, this solution requires the use of a specially structured preparation system and EDTA organic reagent, resulting in high equipment investment and maintenance costs and complex operation, which is not conducive to low-cost industrial implementation. Summary of the Invention

[0009] It can be seen that although the existing process technology has focused on the optimization of the carbonization-pyrolysis refining process, very little attention has been paid to the simple and efficient optimization of the process of converting lithium carbonate carbonization into lithium bicarbonate solution. In view of the shortcomings of the existing technology, the present invention provides a method for improving the solubility of lithium in carbonate and / or bicarbonate systems, which optimizes the carbonization process of crude lithium carbonate in a simple, efficient and low-cost manner, achieves a significant improvement in production efficiency, and does not rely on additional expensive and complex equipment and reagent investment, thereby reducing costs while improving the stable and smooth operation rate of the process.

[0010] In order to solve the above technical problems, the technical solutions of the present invention are as follows: A method for optimizing lithium solubility in a carbonate and / or bicarbonate system comprises the following steps: S1: mixing the raw material containing lithium carbonate and the dissolving solution for reaction; Li2CO3(s)→Li2CO3(aq) (slightly soluble) S2: introducing carbon dioxide-containing gas into the mixed system of S1 to carry out carbonization reaction; Li2CO3(s)+CO2(g)+H2O→LiHCO3(aq) S3: Stop introducing the carbon dioxide-containing gas into the system of S2, and continue adding the lithium carbonate-containing raw material to obtain a carbonate and / or bicarbonate system with a higher lithium concentration after the reaction; Li2CO3(s)+CO3 2- / CO2(aq)(excess)+H2O→LiHCO3(aq) Li2CO3(s)+H2O→LiOH(aq)+LiHCO3(aq) (a small amount) Preferably, the purity of lithium carbonate in the lithium carbonate raw material in S1 is 80% or more; further 90% or more; further 95% or more; further 99% or more.

[0011] Preferably, the lithium carbonate raw material in S1 is a powder; further a powder that has passed through a 50-500 mesh sieve; further a powder that has passed through an 80-300 mesh sieve; and further a powder that has passed through a 100-200 mesh sieve.

[0012] Preferably, the dissolving liquid in S1 is pure water, tap water, industrial water, production return water, lithium carbonate wash water, lithium carbonate precipitation mother liquor, lithium bicarbonate solution, lithium carbonate solution or any combination thereof.

[0013] Preferably, the weight ratio of the mixed solid to liquid in S1 is 1:5-1:40; further 1:10-1:35; further 1:15-1:30; further 1:20-1:25.

[0014] Preferably, stirring is applied during the S1 mixing reaction.

[0015] Preferably, the reaction temperature of S2 is 0-50°C; further 5-40°C; further 10-35°C; further 15-30°C.

[0016] Preferably, the ventilation flow rate of the carbon dioxide-containing gas in S2 is determined according to the reaction scale.

[0017] Preferably, the carbon dioxide content in the carbon dioxide-containing gas in S2 is 70% or more; further 85% or more; further 95% or more; further 99% or more.

[0018] Preferably, the flow rate of the carbon dioxide-containing gas introduced into each liter of solution in S2 is 0.01-10 L / min in terms of carbon dioxide; further 0.05-6 L / min, further 0.1-3 L / min, further 0.2-1 L / min.

[0019] Preferably, the reaction time in S2 is 0.5-12 h; further 1-10 h; further 1.5-6 h, further 2-4 h.

[0020] Preferably, the pressure during the reaction in S2 is 0.01-5 MPa; further 0.05-2 MPa; further 0.1-1 MPa; further 0.2-0.5 MPa.

[0021] Preferably, stirring is applied during the S2 reaction.

[0022] Preferably, the amount of lithium carbonate raw material added in S3 is 1%-200% of the initial amount added in S1; further 10-150%; further 20-100%; further 30%-80%; further 40-60%.

[0023] Preferably, the reaction time in S3 is 0.5-12 h; further 1-10 h; further 1.5-6 h; further 2-4 h; further 2.5-3 h.

[0024] Preferably, stirring is applied during the S3 reaction.

[0025] Preferably, stirring is applied during the reaction process of any step S1, S2 and S3, and the stirring speed is 5-500 rpm; further 20-300 rpm; further 50-200 rpm; further 60-100 rpm.

[0026] Preferably, after adding the crude lithium carbonate powder in S3, the reaction system is sealed and then the subsequent reaction is carried out.

[0027] Preferably, the process further comprises performing solid-liquid separation after the reaction of S4: S3 is completed, and obtaining a filtrate which is the carbonized liquid with improved lithium solubility.

[0028] Beneficial effects The inventors have found that by adding lithium carbonate material to the carbonized system for a second time, the lithium concentration in the solution can be significantly increased. Compared with the prior art, the present invention has the following beneficial effects: (1) The effective improvement of lithium solubility in lithium carbonate and / or bicarbonate solution system significantly reduces the amount of slurry water required in carbonization reaction, thereby solving a series of adverse effects such as large volume of slurry water, large plant equipment footprint, large subsequent filtration volume, long production cycle, low single product yield, difficulty in filtering wastewater treatment, high carbon dioxide consumption, and impurity accumulation caused by filtrate reuse affecting product quality.

[0029] (2) The operation is simple and does not require special equipment or external reinforcement means, which has practical optimization significance for industrial implementation.

[0030] (3) No other reagents or impurity elements are introduced into the process, which reduces costs while not adding extra impurity removal operations or increasing the difficulty of impurity removal in the subsequent process implementation. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to the embodiments. It should be noted that, unless otherwise specified, the embodiments and features of the embodiments of the present invention may be combined with each other. Unless otherwise specified, the relevant percentages are percentages by mass.

[0032] The examples of the present application use industrial-grade lithium carbonate as raw material, and the content of the main component lithium carbonate is 99.40%, of which the lithium content is 18.67%.

[0033] Example 1 S1. Take 150g of industrial-grade lithium carbonate and put it into 3L of water at room temperature and stir to obtain a mixed slurry; S2. Carbon dioxide gas was introduced into the mixed slurry obtained in S1 at a flow rate of 0.5 L / min. During the reaction, the system pressure was maintained at 0.2 MPa. The reaction was stirred continuously for 3 h. It was observed that the reaction solution gradually changed from a milky white suspension to a translucent pale white solution. During this period, the supernatant filtrate was taken at different reaction time periods for detection. The measured lithium concentrations in the solution were as follows: S3. Stop the introduction of carbon dioxide gas, add 50 g of industrial-grade lithium carbonate to the solution in S2, and then continue the reaction in a sealed container for 2 hours. During this period, samples are taken from the sampling hole and filtered for detection. The lithium concentration in the filtrate is as follows: An excess of lithium carbonate was added to the saturated carbonization system a second time to promote further dissolution of the lithium carbonate and obtain a lithium carbonate solution with a higher concentration. In this embodiment, the lithium concentration in the solution was increased from 8.12 g / L to 10.90 g / L, and the lithium concentration was increased by 34.24%.

[0034] Example 2 In this embodiment S2, the flow rate of carbon dioxide gas is 0.8 L / min, and the raw materials, S1 and S2 and other operations are the same as in Example 1. The lithium concentrations of the solution measured during the reaction of S2 are as follows: S3. Stop the introduction of carbon dioxide gas, add 30 g of industrial lithium carbonate to the solution obtained in S2, and continue the reaction in a sealed container for 3 hours. After the reaction, take a sample from the sampling hole and measure the lithium concentration in the supernatant filtrate of the solution as follows: In this embodiment, lithium carbonate was added twice to react for 2 hours to increase the lithium solution concentration in the system from 7.94 g / L to 9.63 g / L, and the lithium solution concentration increased by 21.28%. After 3 hours of reaction, the lithium concentration dropped back to 9.33 g / L.

[0035] Example 3 The raw materials, S1 and S2 of this embodiment are the same as those of Example 1. The lithium concentrations of the system measured during the reaction of S2 are as follows: Note: Due to different implementation times, ambient temperature differences and other factors, the lithium solubility of Example S1 is slightly different from that of Example 1.

[0036] S3. Add 80 g of crude lithium carbonate powder to the solution obtained in S2. Other operations are the same as in Example 1. The lithium concentration in the supernatant filtrate of the solution is measured as follows: In this embodiment, the concentration of the lithium solution in the system is increased from 8.03 g / L to 12.72 g / L, and the lithium concentration is increased by 58.41%.

[0037] Example 4 S1. Take 100g of industrial lithium carbonate and put it into 2L of water at room temperature, stir and mix thoroughly to obtain a mixed solution; S2. Carbon dioxide gas was introduced into the mixed solution obtained in S1 at a flow rate of 1 L / min. During the reaction, the system pressure was maintained at 0.4 MPa. The reaction was stirred continuously for 3 h. The reaction solution was observed to gradually change from a milky white suspension to a translucent pale white solution. During this period, the supernatant filtrate was taken at different reaction time periods for detection. The measured lithium concentrations of the solution were as follows: S3. Stop the introduction of carbon dioxide gas, add 30 g of industrial lithium carbonate to the system obtained in S2, and then continue the reaction in a sealed container for 2 hours. After the reaction, take a sample from the sampling hole and measure the lithium concentration in the clear liquid filtrate as follows: In this embodiment, the lithium concentration in the solution is increased from 8.27 g / L to 9.02 g / L, and the lithium concentration is increased by 9.07%.

[0038] Example 5 In this embodiment S2, the flow rate of carbon dioxide gas is 1 L / min, and the raw materials, S1 and S2 and other operations are the same as in Example 1. The lithium concentrations of the solution measured during the reaction of S2 are as follows: S3. Stop the introduction of carbon dioxide gas, add 50 g of industrial lithium carbonate to the solution obtained in S2, and then react for 3 hours under non-sealed conditions. After the reaction, take a sample from the sampling hole and measure the lithium concentration in the supernatant filtrate of the solution as shown below: In this example, the lithium solution concentration in the system was increased from 8.23 ​​g / L to 9.73 g / L, with the lithium solution concentration increased by 18.22%. After 3 hours of reaction, the lithium concentration dropped back to 9.36 g / L.

[0039] The contents illustrated in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent modifications of the present invention by those skilled in the art shall fall within the scope defined by the claims attached to this application.

Claims

1. A method for optimizing lithium solubility in carbonate and / or bicarbonate systems, characterized in that: The steps include: S1: mixing the raw material containing lithium carbonate and the dissolving solution for reaction; S2: introducing carbon dioxide-containing gas into the mixed system of S1 to carry out carbonization reaction; S3: Stop introducing the carbon dioxide-containing gas into the system of S2 and continue adding the raw material containing lithium carbonate to obtain a carbonate and / or bicarbonate system with a higher lithium concentration after the reaction.

2. The method according to claim 1, characterized in that The lithium carbonate content of the lithium carbonate-containing raw material in S1 is 80% or more; further 90% or more; further 95% or more; further 99% or more; Preferably, the lithium carbonate raw material in S1 is a powder; further a powder that has passed through a 50-500 mesh sieve; further a powder that has passed through an 80-300 mesh sieve; and further a powder that has passed through a 100-200 mesh sieve.

3. The method according to claim 1, characterized in that The dissolving liquid in S1 is pure water, domestic water, industrial water, production return water, lithium carbonate washing water, lithium carbonate precipitation mother liquor, lithium bicarbonate solution, lithium carbonate solution or any combination thereof; Preferably, the weight ratio of the mixed solid to liquid in S1 is 1:5-1:40; further 1:10-1:35; further 1:15-1:30; further 1:20-1:

25.

4. The method according to claim 1, wherein S1 Stirring is applied during the mixing reaction; Preferably, the reaction temperature of S2 is 0-50°C; further 5-40°C; further 10-35°C; further 15-30°C.

5. The method according to claim 1, wherein The ventilation flow rate of the carbon dioxide-containing gas in S2 is determined according to the reaction scale; Preferably, the carbon dioxide content in the carbon dioxide-containing gas in S2 is 70% or more; further 85% or more; further 95% or more; further 99% or more; Preferably, the flow rate of the carbon dioxide-containing gas introduced into each liter of solution in S2 is 0.01-10 L / min in terms of carbon dioxide; further 0.05-6 L / min, further 0.1-3 L / min, further 0.2-1 L / min.

6. The method according to claim 1, characterized in that The reaction time in S2 is 0.5-12 h; further 1-10 h; further 1.5-6 h, further 2-4 h; Preferably, the pressure during the reaction in S2 is 0.01-5 MPa; further 0.05-2 MPa; further 0.1-1 MPa; further 0.2-0.5 MPa; Preferably, stirring is applied during the S2 reaction.

7. The method according to claim 1, characterized in that The amount of lithium carbonate raw material added to S3 is 1%-200% of the initial amount of S1; further 10-150%; further 20-100%; further 30%-80%; further 40-60%; Preferably, the reaction time in S3 is 0.5-12 h; further 1-10 h; further 1.5-6 h; further 2-4 h; further 2.5-3 h. Preferably, stirring is applied during the S3 reaction.

8. The method according to claim 1, characterized in that Stirring is applied during the reaction process of any step S1, S2 and S3, with a stirring speed of 5-500 rpm; further 20-300 rpm; further 50-200 rpm; further 60-100 rpm.

9. The method according to claim 1, characterized in that After adding crude lithium carbonate powder in S3, the reaction system is sealed and the subsequent reaction is carried out.

10. The method according to claim 1, characterized in that The method also includes performing solid-liquid separation after the S4: S3 reaction is completed, and obtaining a filtrate, which is a carbonized liquid with a higher lithium concentration.

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