A method for preparing industrial-grade lithium carbonate from lithium-containing brine

Abstract

The present invention provides a method for preparing industrial-grade lithium carbonate using lithium-containing brine, comprising the following steps: 1) adding lithium carbonate seeds to a sodium carbonate solution, stirring and heating to 80-90 °C to obtain a first mixed solution; 2) at 25-50 °C, adding a first lithium-containing brine to the first mixed solution at a rate of 1-10 mL / min to obtain a first intermediate system; 3) at 50-80 °C, adding a second brine to the first intermediate system at a rate of 10-25 mL / min to obtain a second intermediate system; 4) at 80-99 °C, adding the remaining brine to the second intermediate system at a rate of 25-45 mL / min to obtain lithium carbonate; the molar ratio of sodium carbonate in the first mixed solution to lithium element in the lithium-containing brine is (0.5-0.65):1, and the volume ratio of the first brine, the second brine to the remaining brine is (1-8):(2-1):(7-1). The lithium carbonate prepared by the present invention has high purity and has the advantages of simple process and low cost.

Description

Technical Field

[0001] The present invention relates to a method for preparing industrial-grade lithium carbonate, and particularly to a method for preparing industrial-grade lithium carbonate from lithium-containing brine. Background Art

[0002] Lithium-ion batteries are widely used in various fields such as electric vehicles, smart home products, computers, mobile power supplies, and portable electronic products due to their advantages of high energy density, no memory effect, low pollution, and small size.

[0003] As one of the important raw materials for lithium-ion batteries, lithium carbonate can be used in electrolytes or cathode materials, so its demand is increasing with the development of lithium-ion batteries. At present, the raw materials for preparing lithium carbonate are mainly lithium ores. However, the resource reserves of lithium ores are limited and it is difficult to meet the growing market demand. The salt lake brine contains rich lithium resources and has great exploitation value. Therefore, the popularity of extracting lithium from lithium-containing brine is increasing.

[0004] At present, the methods for extracting lithium from brine mainly include extraction method, chemical precipitation method, and adsorption method. However, in the extraction method, it is difficult to select the extractant and the operation is complex. The lithium carbonate prepared by the chemical precipitation method is easy to wrap impurities, resulting in low purity of lithium carbonate. The production cost of the adsorption method is high, which is not conducive to expanding production.

[0005] Based on the above deficiencies, it is urgent to develop a method for preparing industrial-grade lithium carbonate from lithium-containing brine with simple process and high product purity. Summary of the Invention

[0006] The present invention provides a method for preparing industrial-grade lithium carbonate from lithium-containing brine. The lithium carbonate prepared by this method has high purity and has advantages such as simple process and low cost.

[0007] The present invention provides a method for preparing industrial-grade lithium carbonate from lithium-containing brine, comprising the following steps:

[0008] 1) Adding lithium carbonate seeds to a sodium carbonate solution, stirring and heating to 90 °C to obtain a first mixed solution;

[0009] 2) At 25 - 50 °C, adding the first part of lithium-containing brine to the first mixed solution at a feeding rate of 1 - 10 mL / min to obtain a first intermediate system;

[0010] 3) At 50 - 80 °C, adding the second part of lithium-containing brine to the first intermediate system at a feeding rate of 10 - 25 mL / min to obtain a second intermediate system;

[0011] 4) At 80 - 99 °C, the remaining lithium-containing brine is added to the second intermediate system at a feeding rate of 25 - 45 mL / min to obtain a second mixed solution, and the second mixed solution is subjected to solid-liquid separation to obtain lithium carbonate;

[0012] Among them, the molar ratio of sodium carbonate to lithium element in the lithium-containing brine in the first mixed solution is (0.5 - 0.65):1, and the volume ratio of the first part of the lithium-containing brine, the second part of the lithium-containing brine to the remaining lithium-containing brine is (1 - 8):(2 - 1):(7 - 1).

[0013] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein the molar ratio of sodium carbonate to lithium ions in the first intermediate system is (0.8 - 9.0):1.

[0014] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein the molar ratio of sodium carbonate to lithium ions in the second intermediate system is (0.7 - 7.7):1.

[0015] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein in the second mixed solution, the mass percentage content of lithium ions is not higher than 0.25%.

[0016] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein the purity of the lithium carbonate crystal seeds is 99.2 - 99.5%, the particle size is 5 - 30 μm, the mass percentage content of sodium element in the lithium carbonate crystal seeds is not higher than 800 ppm, and the mass percentage content of potassium element in the lithium carbonate crystal seeds is not higher than 400 ppm.

[0017] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein the addition amount of the lithium carbonate crystal seeds is 0 - 10 wt% of the lithium carbonate.

[0018] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein the mass concentration of the sodium carbonate solution is 10 - 32%.

[0019] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein in steps 2) - 4), the feeding process further includes a stirring treatment;

[0020] Among them, in step 2), the stirring speed is 200 - 250 r / min; in step 3), the stirring speed is 250 - 300 r / min; in step 4), the stirring speed is 300 - 400 r / min.

[0021] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein step 4) further includes a cleaning treatment of the lithium carbonate;

[0022] The mass ratio of the cleaning solution to the lithium carbonate is (2 - 8):1, the cleaning temperature is 60 - 90 °C, and the cleaning time is 10 - 60 min.

[0023] The method for preparing industrial-grade lithium carbonate from lithium-containing brine as described above, wherein the lithium-containing brine by mass concentration includes: 5 - 25 g / L of lithium ions, 100 - 120 g / L of sodium ions, 35 - 80 g / L of potassium ions, and other impurities not higher than 20 ppm.

[0024] By adding lithium carbonate seeds and adopting a segmented feeding method, and simultaneously controlling the molar ratio of sodium carbonate to lithium element in the lithium-containing brine and the volume ratio of the lithium-containing brine added at different temperatures, after the lithium ions in the lithium-containing brine fully react with the carbonate ions in the sodium carbonate solution, they attach to the surface of the lithium carbonate seeds to form larger lithium carbonate, and the probability of sodium ions and potassium ions in the lithium-containing brine being entrained and growing into the lithium carbonate can be reduced, thereby improving the purity of the lithium carbonate product. In addition, the process flow of this method is simple, the types of raw materials used are few, and the cost is low. Detailed Embodiments

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative efforts based on the embodiments of the present invention fall within the protection scope of the present invention.

[0026] The present invention provides a method for preparing industrial-grade lithium carbonate from lithium-containing brine, comprising the following steps:

[0027] 1) Add lithium carbonate seeds to a sodium carbonate solution, stir and heat to 90 °C to obtain a first mixed solution;

[0028] 2) At 25 - 50 °C, add the first part of the lithium-containing brine to the first mixed solution at a feeding rate of 1 - 10 mL / min to obtain a first intermediate system;

[0029] 3) At 50 - 80 °C, add the second part of the lithium-containing brine to the first intermediate system at a feeding rate of 10 - 25 mL / min to obtain a second intermediate system;

[0030] 4) At 80 - 99 °C, add the remaining lithium-containing brine to the second intermediate system at a feeding rate of 25 - 45 mL / min to obtain a second mixed solution, and perform solid-liquid separation on the second mixed solution to obtain lithium carbonate;

[0031] Among them, the molar ratio of lithium element in sodium carbonate and lithium-containing brine in the first mixed solution is (0.5-0.65):1, and the volume ratio of the first part of lithium-containing brine, the second part of lithium-containing brine and the remaining lithium-containing brine is (1-8):(2-1):(7-1).

[0032] Specifically, in step 1), after preparing the sodium carbonate solution, lithium carbonate seed crystals are added to the sodium carbonate solution, and the solution is heated while being stirred until the temperature reaches 90° C. to obtain a first mixed solution.

[0033] The mass concentration of the sodium carbonate solution is not particularly limited in the present invention and can be selected according to actual needs.

[0034] The present invention does not impose any special restrictions on the purity and particle size of the lithium carbonate seed crystals, which can be selected according to actual needs.

[0035] The present invention does not limit the stirring method and stirring rate, as long as the lithium carbonate seeds can be evenly dispersed in the sodium carbonate solution, for example, mechanical stirring can be used, and the stirring speed can be 200r / min.

[0036] The present invention does not limit the heating method, for example, direct heating, oil bath heating or water bath heating can be used.

[0037] In step 2), the first portion of lithium-containing brine is added to the first mixed solution at a temperature of 25-50° C. under stirring at a feed rate of 1-10 mL / min to obtain a first intermediate system.

[0038] The lithium-containing brine of the present invention refers to brine containing lithium ions, which also contains sodium ions, potassium ions and other impurity ions.

[0039] During the process of adding the first part of lithium-containing brine into the first mixed solution, the lithium ions in the lithium-containing brine fully react with the carbonate ions in the first mixed solution to generate lithium carbonate, and the lithium carbonate is attached to the surface of the lithium carbonate seed crystals in the first mixed solution, so that the particle size of the lithium carbonate seed crystals gradually increases, and a first intermediate system including the lithium carbonate seed crystals and a mixed solution is obtained, wherein the mixed solution includes lithium ions, sodium ions, potassium ions, carbonate ions and other impurity ions.

[0040] The present invention does not limit the content of lithium ions in the lithium-containing brine, and does not limit the type and content of impurity ions in the lithium-containing brine. For example, the lithium-containing brine also includes impurity ions such as sodium ions and potassium ions.

[0041] The present invention does not limit the method of adding the lithium-containing brine. For example, a spraying device may be used to spray the lithium-containing brine into the reaction device containing the first mixed solution.

[0042] The stirring method and stirring rate in step 2) are the same as those defined above and will not be described again here.

[0043] The heating method in step 2) is the same as the aforementioned limitation and will not be elaborated here.

[0044] In step 3), at a temperature of 50 - 80 °C, under stirring conditions, the second part of the lithium-containing brine is added to the first intermediate system at a feeding rate of 10 - 25 mL / min to obtain a second intermediate system.

[0045] Similar to the reaction in step 2), the lithium ions in the lithium-containing brine react fully with the carbonate ions in the first intermediate system to form lithium carbonate, which attaches to the surface of the lithium carbonate crystal seeds in the first intermediate system, causing the particle size of the lithium carbonate crystal seeds to further gradually increase, resulting in a second intermediate system including lithium carbonate crystal seeds and a mixed solution, where the mixed solution includes lithium ions, sodium ions, potassium ions, carbonate ions, and other impurity ions.

[0046] The adding method of the lithium-containing brine in step 3) is the same as the aforementioned limitation and will not be elaborated here.

[0047] The stirring method and stirring rate in step 3) are the same as the aforementioned limitation and will not be elaborated here.

[0048] The heating method in step 3) is the same as the aforementioned limitation and will not be elaborated here.

[0049] In step 4), at a temperature of 80 - 99 °C, under stirring conditions, the remaining lithium-containing brine is added to the second intermediate system at a feeding rate of 25 - 45 mL / min to obtain a second mixed solution, and then the second mixed solution is subjected to solid-liquid separation treatment, and the precipitate obtained from the solid-liquid separation is washed to obtain lithium carbonate.

[0050] Similar to the reactions in steps 2) and 3), the lithium ions in the lithium-containing brine react fully with the carbonate ions in the second intermediate system to form lithium carbonate, which attaches to the surface of the lithium carbonate crystal seeds in the second intermediate system, causing the particle size of the lithium carbonate crystal seeds to further increase, resulting in a second mixed solution including lithium carbonate and a mixed solution, where the mixed solution includes lithium ions, sodium ions, potassium ions, carbonate ions, and other impurity ions. Subsequently, the second mixed solution is subjected to solid-liquid separation to obtain a precipitate, and then the precipitate is washed with a washing solution to remove the ions on the surface of the precipitate to obtain lithium carbonate.

[0051] The adding method of the lithium-containing brine in step 4) is the same as the aforementioned limitation and will not be elaborated here.

[0052] The stirring method and stirring rate in step 4) are the same as the aforementioned limitation and will not be elaborated here.

[0053] The heating method in step 4) is the same as the aforementioned limitation and will not be elaborated here.

[0054] The method of solid-liquid separation in the present invention is not limited. For example, precipitation method, filtration method, centrifugation method and other methods can be adopted.

[0055] The method of washing treatment in the present invention is not limited and can be selected according to actual situations.

[0056] The molar ratio of sodium carbonate to lithium ions in the lithium-containing brine in the first mixed solution of the present invention is (0.5 - 0.65):1, and the volume ratio of the lithium-containing brine added in steps 2)-4) is (1 - 8):(2 - 1):(7 - 1).

[0057] The method for preparing industrial-grade lithium carbonate from lithium-containing brine in the present invention is to add lithium carbonate seeds to a sodium carbonate solution, add different volumes of lithium-containing brine at different temperatures, and at the same time control the molar ratio of sodium carbonate to lithium element in the lithium-containing brine and the volume ratio of the lithium-containing brine added at different temperatures. The purity of the prepared lithium carbonate product is high. The inventor analyzed this principle and believed that the reasons may be as follows: on the one hand, after the addition of seeds, lithium ions and carbonate ions fully react to obtain lithium carbonate and then attach to the surface of the lithium carbonate seeds to form lithium carbonate with a larger particle size, ensuring that during the growth process of lithium carbonate crystals, the problem of heterogeneous nucleation does not occur due to the presence of sodium ions and potassium ions, thereby improving the purity of the lithium carbonate product; on the other hand, the segmented feeding method is adopted. First, the reaction is carried out at a relatively low temperature, which can avoid the saturation in the mixed solution being too high, resulting in the rapid growth of lithium carbonate crystals and the growth of impurities being entrained into the lithium carbonate, reducing the purity of the lithium carbonate product. Finally, the reaction is carried out at a higher temperature, which is helpful for the full precipitation of lithium carbonate and avoids the dissolution of lithium carbonate in the solution, thereby increasing the yield of lithium carbonate; in addition, by controlling the molar ratio of sodium carbonate to lithium element in the lithium-containing brine and the volume ratio of the lithium-containing brine added at different temperatures, lithium ions can fully react with carbonate ions, and the growth rate of the seeds can be controlled to avoid the entrainment growth of sodium ions and potassium ions in the seeds, thereby improving the purity of the lithium carbonate product. Moreover, this method has a simple process and uses few types of raw materials, so the method has a low cost and can be scaled up for production.

[0058] In a specific embodiment, the molar ratio of sodium carbonate to lithium ions in the first intermediate system is (0.8 - 9.0):1. When the molar ratio of sodium carbonate to lithium ions in the first intermediate system is within the above range, the reaction between the first mixed solution and the first part of the lithium-containing brine stops. At this time, the particle size of the lithium carbonate seeds reaches a suitable range, and it can reduce the risk of sodium ions and potassium ions being entrained into the lithium carbonate due to the decrease in the lithium ion concentration in the mixed solution during the subsequent reaction, thereby improving the purity of the lithium carbonate.

[0059] The present invention does not limit the method of controlling the molar ratio of sodium carbonate to lithium ions in the first intermediate system. For example, by controlling the reaction time of the first part of the lithium-containing brine with the first mixed solution, the molar ratio of sodium carbonate to lithium ions in the first intermediate system is within the above range.

[0060] Specifically, the molar ratio of sodium carbonate to lithium ions in the first intermediate system can be obtained by ion testing through ICP.

[0061] In a specific embodiment, the molar ratio of sodium carbonate to lithium ions in the second intermediate system is (0.7 - 7.7):1. When the molar ratio of sodium carbonate to lithium ions in the second intermediate system is within the above range, the reaction between the first intermediate system and the second part of the lithium-containing brine stops. At this time, the particle size of the lithium carbonate seed crystal increases to an appropriate range, and the probability of entrainment growth of sodium ions and potassium ions during continuous reaction is reduced to a greater extent, thereby further improving the purity of lithium carbonate.

[0062] The present invention does not limit the method of controlling the molar ratio of sodium carbonate to lithium ions in the second intermediate system. For example, by controlling the reaction time of the second part of the lithium-containing brine with the first intermediate system, the molar ratio of sodium carbonate to lithium ions in the second intermediate system is within the above range.

[0063] Specifically, the molar ratio of sodium carbonate to lithium ions in the second intermediate system can be obtained by ion testing through ICP.

[0064] In a specific embodiment, the mass percentage content of lithium ions in the second mixed solution is not higher than 0.25%. When the mass percentage content of lithium ions in the second mixed solution is not higher than 0.25%, the reaction between the remaining part of the lithium-containing brine and the second intermediate system stops, further avoiding the entrainment growth of sodium ions and potassium ions in lithium carbonate, and improving the purity of lithium carbonate to a greater extent.

[0065] The present invention does not limit the method of controlling the mass percentage content of lithium ions in the second mixed solution. For example, by controlling the reaction time of the remaining part of the lithium-containing brine with the second intermediate system, the mass percentage content of lithium ions in the second mixed solution is within the above range.

[0066] Specifically, the mass percentage content of lithium ions in the second mixed solution can be obtained by ion testing through ICP.

[0067] In a specific embodiment, the purity of the lithium carbonate seed crystal is 99.2 - 99.5%, the particle size is 5 - 30 μm, the mass percentage content of sodium element in the lithium carbonate seed crystal is not higher than 800 ppm, and the mass percentage content of potassium element in the lithium carbonate seed crystal is not higher than 400 ppm. When the purity and particle size parameters of the lithium carbonate seed crystal are within the above ranges, the lithium carbonate generated by the reaction of lithium ions and carbonate ions is more likely to adhere to the surface of the lithium carbonate seed crystal, so that the particle size of the lithium carbonate gradually increases, making the crystallization of the lithium carbonate more perfect, reducing the probability of entrainment growth of sodium ions and potassium ions, and thus further improving the purity of the lithium carbonate product.

[0068] Specifically, the purity of the lithium carbonate seed crystal is obtained by acid-base neutralization titration for purity testing, the particle size of the lithium carbonate seed crystal is obtained by a laser particle size distribution analyzer for particle size testing, and the mass percentage content of impurity elements in the lithium carbonate seed crystal is obtained by ICP for ion testing.

[0069] In a specific embodiment, the addition amount of the lithium carbonate seed crystal is 0 - 10 wt% of the lithium carbonate. The mass of the lithium carbonate here refers to the mass of the lithium carbonate that can be prepared by theoretical calculation based on the molar ratio of lithium element in the lithium-containing brine. When the mass ratio of the addition amount of the lithium carbonate seed crystal to the mass of the lithium carbonate is within the above range, the addition amount of the lithium carbonate seed crystal is more appropriate, which can make the lithium carbonate generated by the reaction of lithium ions and carbonate ions fully adhere to the surface of the lithium carbonate seed crystal, prepare the lithium carbonate product more efficiently, and avoid waste of the lithium carbonate seed crystal and save the preparation cost.

[0070] In a specific embodiment, the mass concentration of the sodium carbonate solution is 10% - 32%. When the mass concentration of the sodium carbonate solution is within the above range, it can make the lithium ions and carbonate ions fully react to form lithium carbonate and fully and evenly adhere to the surface of the lithium carbonate seed crystal, so that the lithium carbonate seed crystal further grows, and can make the reaction rate of lithium ions and carbonate ions appropriate, making the crystallization of lithium carbonate more perfect, reducing the entrainment growth of sodium ions and potassium ions in lithium carbonate to a greater extent, and thus improving the purity of lithium carbonate.

[0071] In a specific embodiment, during the feeding process in steps 2)-4), stirring treatment is further included; wherein, in step 2), the stirring speed is 200-250 r / min; in step 3), the stirring speed is 250-300 r / min; in step 4), the stirring speed is 300-400 r / min. When the stirring speeds in steps 2)-4) are respectively within the above ranges, the lithium carbonate seeds are more uniformly dispersed in the mixed solution, the lithium ions and carbonate ions can react more fully, and can be more uniformly attached to the surface of the lithium carbonate seeds, so that the crystallization of lithium carbonate is more perfect, and the entrainment growth of sodium ions and potassium ions in lithium carbonate is reduced to a greater extent, thereby improving the purity of lithium carbonate.

[0072] In a specific embodiment, step 4) further includes a cleaning treatment of lithium carbonate; the mass ratio of the cleaning solution to lithium carbonate is (2-8):1, the cleaning temperature is 60-90 °C, and the cleaning time is 10-60 min. When the parameters of the cleaning treatment are within the above ranges, the lithium ions, sodium ions, potassium ions and other impurity ions on the surface of lithium carbonate can be cleaned, the purity of lithium carbonate is improved, and at the same time, lithium carbonate will not be dissolved in the cleaning solution, avoiding the reduction of the lithium carbonate yield.

[0073] Specifically, the present invention does not limit the selection of the cleaning solution, which can be selected according to actual needs, and water is preferred.

[0074] In a specific embodiment, the lithium-containing brine by mass concentration includes: lithium ions 5-25 g / L, sodium ions 100-120 g / L, potassium ions 35-80 g / L, and other impurities not higher than 20 ppm. When the mass concentrations of the components of the lithium-containing brine are within the above ranges, the crystallization of lithium carbonate seeds is more perfect, the entrainment growth of sodium ions and potassium ions is less, and the purity of the prepared lithium carbonate is higher.

[0075] Hereinafter, the present invention will be further described in detail through specific examples.

[0076] Example 1

[0077] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example includes the following steps:

[0078] 1. Add lithium carbonate seeds to the sodium carbonate solution, stir and heat to 90 °C to obtain a first mixed solution; wherein, the mass concentration of the sodium carbonate solution is 32%.

[0079] 2. At 30 °C, the first part of lithium-containing brine was added to the first mixed solution at a feeding rate of 5 mL / min, and stirring treatment was carried out at a stirring speed of 200 r / min to obtain the first intermediate system; wherein, the molar ratio of sodium carbonate to lithium element in the lithium-containing brine in the first mixed solution was 0.6:1, the dosage of lithium carbonate seed crystals was 5 wt% of the theoretically produced lithium carbonate, and the molar ratio of sodium carbonate to lithium ions in the first intermediate system was 2:1.

[0080] 3. At 60 °C, the second part of lithium-containing brine was added to the first intermediate system at a feeding rate of 15 mL / min, and stirring treatment was carried out at a stirring speed of 250 r / min to obtain the second intermediate system; wherein, the molar ratio of sodium carbonate to lithium ions in the second intermediate system was 3:2.

[0081] 4. At 90 °C, the remaining lithium-containing brine was added to the second intermediate system at a feeding rate of 45 mL / min, and stirring treatment was carried out at a stirring speed of 300 r / min to obtain the second mixed solution, and the second mixed solution was subjected to solid-liquid separation treatment and cleaning treatment to obtain lithium carbonate; wherein, the mass percentage content of lithium ions in the second mixed solution was 0.25%; the cleaning solution was water, the mass ratio of water to lithium carbonate was 5:1, the cleaning temperature was 90 °C, and the cleaning time was 15 min.

[0082] Among them, the volume ratio of the first part of lithium-containing brine, the second part of lithium-containing brine to the remaining lithium-containing brine was 7:2:1.

[0083] The purity of the lithium carbonate seed crystals was 99.2%, the particle size was 16.354 μm, the mass percentage content of sodium element in the lithium carbonate seed crystals was 800 ppm, and the mass percentage content of potassium element in the lithium carbonate seed crystals was 400 ppm.

[0084] The lithium-containing brine by mass concentration included: 15 g / L of lithium ions, 110 g / L of sodium ions, 40 g / L of potassium ions, and other impurities were 20 ppm.

[0085] Example 2

[0086] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example was basically the same as that in Example 1, except that the molar ratio of sodium carbonate to lithium ions in the first intermediate system was 0.7:1, the purity of the lithium carbonate seed crystals was 99.28%, and the particle size was 21.548 μm.

[0087] Example 3

[0088] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example was basically the same as that in Example 1, except that the molar ratio of sodium carbonate to lithium ions in the second intermediate system was 0.6:1, the purity of the lithium carbonate seed crystals was 99.23%, and the particle size was 23.236 μm.

[0089] Example 4

[0090] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example is basically the same as that in Example 1, except that the mass percentage content of lithium ions in the second mixed solution is 0.3%, the purity of the lithium carbonate crystal seeds is 99.23%, and the particle size is 29.641 μm.

[0091] Example 5

[0092] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example is basically the same as that in Example 1, except that the purity of the lithium carbonate crystal seeds is 99.00% and the particle size is 32.480 μm.

[0093] Example 6

[0094] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example is basically the same as that in Example 1, except that the lithium carbonate crystal seeds are 20 wt% of the theoretically produced lithium carbonate, the purity of the lithium carbonate crystal seeds is 99.34%, and the particle size is 25.125 μm.

[0095] Example 7

[0096] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example is basically the same as that in Example 1, except that the mass concentration of the sodium carbonate solution is 5%, the purity of the lithium carbonate crystal seeds is 99.23%, and the particle size is 29.657 μm.

[0097] Example 8

[0098] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example is basically the same as that in Example 1, except that in Step 2, the stirring speed is 100 r / min, in Step 3, the stirring speed is 200 r / min, in Step 4, the stirring speed is 250 r / min, the purity of the lithium carbonate crystal seeds is 99.20%, and the particle size is 28.465 μm.

[0099] Example 9

[0100] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example is basically the same as that in Example 1, except that the purity of the lithium carbonate crystal seeds is 99.28%, the particle size is 25.461 μm, and the lithium-containing brine includes, by mass concentration: 4 g / L of lithium ions, 90 g / L of sodium ions, 30 g / L of potassium ions, and other impurities not higher than 30 ppm.

[0101] Example 10

[0102] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this example is basically the same as that in Example 1, except that the purity of the lithium carbonate seed crystal is 99.26%, the particle size is 12.451 μm, in the cleaning treatment, the mass ratio of water to lithium carbonate is 1:1, the cleaning temperature is 20 °C, and the cleaning time is 5 min.

[0103] Comparative Example 1

[0104] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this comparative example includes the following steps:

[0105] 1. Add the lithium carbonate seed crystal into the sodium carbonate solution, stir and heat to 90 °C to obtain the first mixed solution; among them, the mass concentration of the sodium carbonate solution is 32%.

[0106] 2. At 90 °C, add the lithium-containing brine to the first mixed solution at a feeding rate of 45 mL / min, stir and process, the stirring speed is 300 r / min, to obtain the second mixed solution, and perform solid-liquid separation treatment and cleaning treatment on the second mixed solution to obtain lithium carbonate; among them, the molar ratio of sodium carbonate in the first mixed solution to lithium element in the lithium-containing brine is 0.6:1, the lithium carbonate seed crystal is 5 wt% of the theoretically produced lithium carbonate mass fraction, and the mass percentage of lithium ions in the second mixed solution is 0.25%; the cleaning solution is water, the mass ratio of water to lithium carbonate is 5:1, the cleaning temperature is 90 °C, and the cleaning time is 15 min.

[0107] The purity of the lithium carbonate seed crystal is 99.2%, the particle size D50 is 13.506 μm, the mass percentage of sodium element in the lithium carbonate seed crystal is 800 ppm, and the mass percentage of potassium element in the lithium carbonate seed crystal is 400 ppm.

[0108] The lithium-containing brine includes by mass concentration: 15 g / L of lithium ions, 110 g / L of sodium ions, 30 g / L of potassium ions, and other impurities are 20 ppm.

[0109] Comparative Example 2

[0110] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this comparative example is basically the same as that in Example 1, except that the temperature in step 2 is 70 °C, the temperature in step 3 is 85 °C, the temperature in step 4 is 70 °C, and the purity of the lithium carbonate seed crystal is 99.21%, and the particle size is 22.615 μm.

[0111] Comparative Example 3

[0112] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this comparative example is basically the same as that in Example 1, except that in Step 2, the feeding rate is 20 mL / min, in Step 3, the feeding rate is 40 mL / min, in Step 4, the feeding rate is 60 mL / min, the purity of the lithium carbonate seed crystal is 99.25%, and the particle size is 24.213 μm.

[0113] Comparative Example 4

[0114] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this comparative example is basically the same as that in Example 1, except that the molar ratio of sodium carbonate to lithium element in the lithium-containing brine in the first mixed solution is 7:10, the purity of the lithium carbonate seed crystal is 99.26%, and the particle size is 19.654 μm.

[0115] Comparative Example 5

[0116] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this comparative example is basically the same as that in Example 1, except that the volume ratio of the first part of lithium-containing brine, the second part of lithium-containing brine to the remaining lithium-containing brine is 2:3:5, the purity of the lithium carbonate seed crystal is 99.24%, and the particle size is 23.681 μm.

[0117] Test Example

[0118] The lithium-containing brine was subjected to ICP ion testing to obtain the molar concentration of lithium ions in the lithium-containing brine.

[0119] The first mixed solution was subjected to ICP ion and acid-base neutralization titration testing to obtain the molar concentrations of sodium carbonate, lithium ions, and sodium ions in the first mixed solution.

[0120] The first intermediate system was subjected to ICP ion testing to obtain the molar concentrations of sodium carbonate and lithium ions in the first intermediate system.

[0121] The second intermediate system was subjected to ICP ion testing to obtain the molar concentrations of sodium carbonate and lithium ions in the second intermediate system.

[0122] The second mixed solution was subjected to ICP ion testing to obtain the mass percentage of lithium ions in the second mixed solution.

[0123] The purity of the lithium carbonate seed crystal was tested by acid-base neutralization titration to obtain the purity of the lithium carbonate seed crystal. The particle size of the lithium carbonate seed crystal was tested by a laser particle size distribution analyzer to obtain the particle size of the lithium carbonate seed crystal. The lithium carbonate seed crystal was subjected to ICP ion testing to obtain the mass percentage of impurity elements in the lithium carbonate seed crystal.

[0124] The purity of lithium carbonate seeds was obtained by testing the purity of lithium carbonate through acid-base neutralization titration. The particle size of lithium carbonate seeds was obtained by testing the particle size of lithium carbonate through a laser particle size distribution analyzer. The mass percentage of impurity elements in lithium carbonate seeds was obtained by testing the ions of lithium carbonate through ICP.

[0125] Table 1 Parameters of the method for preparing industrial-grade lithium carbonate using lithium-containing brine

[0126]

[0127]

[0128] Table 2 Parameters of the method for preparing industrial-grade lithium carbonate using lithium-containing brine

[0129]

[0130]

[0131]

[0132] As can be seen from Table 2, by comparing Examples 1-10 and Comparative Examples 1-5, it can be known that the method for preparing industrial-grade lithium carbonate using lithium-containing brine provided by the present invention can prepare lithium carbonate with high purity; from Examples 1, 2, and 3, it can be seen that when the molar ratios of sodium carbonate to lithium ions in the first intermediate system and the second intermediate system exceed the ranges of (0.8-9.0):1 and (0.7-7.7):1 respectively, the purity of the product lithium carbonate decreases significantly. This is because the concentrations of sodium ions and potassium ions are too high during the reaction, resulting in an increased probability of entrainment growth; by comparing Examples 1, 5, and 6, it can be known that a decrease in the purity of the seeds, inappropriate particle size, and a decrease in the addition amount of the seeds will all lead to a decrease in the purity of the product lithium carbonate. This is because the addition of seeds will reduce heterogeneous nucleation, while the low quality of the seeds and the decrease in the addition amount of the seeds will cause heterogeneous nucleation of the product lithium carbonate; by comparing Examples 1 and 7, it can be known that the amount of sodium carbonate also affects the product lithium carbonate. Too high an amount of sodium carbonate will increase the probability of entrainment of impurities in the product, while too low an amount of sodium carbonate will affect the yield of the product lithium carbonate and increase the cost; in addition, from the comparison of Examples 1 and 8, it can be seen that the stirring speed affects the dispersion of the lithium-containing brine and the dissolution of lithium carbonate during the reaction. Appropriate stirring can make the reaction more uniform, avoid local supersaturation, and reduce the probability of entrainment of impurities; from the comparison of Examples 1 and 9, it can be known that a lithium-containing brine with appropriate components can improve the purity of the prepared lithium carbonate and reduce the probability of entrainment of impurities in the product; from the comparison of Examples 1 and 10, it can be known that washing the lithium carbonate can improve the purity of the lithium carbonate and reduce the attachment of impurities. In summary, the method for preparing industrial-grade lithium carbonate using lithium-containing brine provided by the present invention can prepare lithium carbonate with high purity and has advantages such as simple process and low cost.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing industrial-grade lithium carbonate from lithium-containing brine, characterized in that, It includes the following steps: 1) Add lithium carbonate seeds to a sodium carbonate solution, stir and heat to 90 °C to obtain a first mixed solution; 2) At 25 - 50 °C, add a first portion of lithium-containing brine to the first mixed solution at a feeding rate of 1 - 10 mL / min to obtain a first intermediate system; 3) At 50 - 80 °C, add a second portion of lithium-containing brine to the first intermediate system at a feeding rate of 10 - 25 mL / min to obtain a second intermediate system; 4) At 80 - 99 °C, add the remaining lithium-containing brine to the second intermediate system at a feeding rate of 25 - 45 mL / min to obtain a second mixed solution, and perform solid-liquid separation on the second mixed solution to obtain lithium carbonate; Wherein, the molar ratio of sodium carbonate to lithium element in the first mixed solution is (0.5 - 0.65):1, and the volume ratio of the first portion of lithium-containing brine, the second portion of lithium-containing brine to the remaining lithium-containing brine is (1 - 8):(2 - 1):(7 - 1).

2. The method for preparing industrial-grade lithium carbonate from lithium-containing brine according to claim 1, characterized in that, The molar ratio of sodium carbonate to lithium ions in the first intermediate system is (0.8 - 9.0):

1.

3. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to claim 1 or 2, characterized in that, The molar ratio of sodium carbonate to lithium ions in the second intermediate system is (0.7 - 7.7):

1.

4. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1-3, characterized in that In the second mixed solution, the mass percentage content of lithium ions is not higher than 0.25%.

5. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1-4, characterized in that, The purity of the lithium carbonate seeds is 99.2 - 99.5%, the particle size is 5 - 30 μm, the mass percentage content of sodium element in the lithium carbonate seeds is not higher than 800 ppm, and the mass percentage content of potassium element in the lithium carbonate seeds is not higher than 400 ppm.

6. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1-5, characterized in that, The mass ratio of the addition amount of the lithium carbonate seeds to the mass of the lithium carbonate is greater than 0 and less than or equal to 10%.

7. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1-6, characterized in that, The mass concentration of the sodium carbonate solution is 10% - 32%.

8. The method for preparing industrial-grade lithium carbonate from lithium-containing brine according to any one of claims 1-7, characterized in that, In steps 2) - 4), stirring treatment is also included during the feeding process; Among them, in step 2), the stirring speed is 200 - 250 r / min; in step 3), the stirring speed is 250 - 300 r / min; in step 4), the stirring speed is 300 - 400 r / min.

9. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1-8, characterized in that, Step 4) also includes a cleaning treatment for the lithium carbonate; The mass ratio of the cleaning solution to the lithium carbonate is (2 - 8):1, the cleaning temperature is 60 - 90 °C, and the cleaning time is 10 - 60 min.

10. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1-9, characterized in that, The lithium-containing brine includes by mass concentration: 5 - 25 g / L of lithium ions, 100 - 120 g / L of sodium ions, 35 - 80 g / L of potassium ions, and other impurities not higher than 20 ppm.

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