Method for preparing industrial-grade lithium carbonate from lithium-containing brine

Abstract

A method for preparing industrial-grade lithium carbonate from a lithium-containing brine, comprising the following steps: 1) adding a lithium carbonate seed crystal to a sodium carbonate solution, stirring and heating same to 90℃ to obtain a first mixed solution; 2) adding a first portion of a lithium-containing brine to the first mixed solution at a feeding speed of 1-10 mL / min and at 25-50℃, so as to obtain a first intermediate system; 3) adding a second portion of the lithium-containing brine to the first intermediate system at a feeding speed of 10-25 mL / min and at 50-80℃, so as to obtain a second intermediate system; and 4) adding the rest of the lithium-containing brine to the second intermediate system at a feeding speed of 25-45 mL / min and at 80-99℃, so as obtain lithium carbonate, the molar ratio of carbonate ions in the first mixed solution to the lithium element in the lithium-containing brine being (0.5-0.65):1, and the volume ratio of the first portion of the lithium-containing brine, the second portion of the lithium-containing brine and the rest of the lithium-containing brine being (1-8):(2-1):(7-1). Lithium carbonate prepared by the present method has high purity and the method has the advantages of simple process and low cost.

Description

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

[0001] This application requests the priority of the Chinese patent application filed with the China Patent Office on December 4, 2023, with application number 202311647502.9, and invention name “A method for preparing industrial-grade lithium carbonate using lithium-containing brine”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of lithium carbonate preparation, and in particular to a method for preparing industrial-grade lithium carbonate using lithium-containing brine. Background Art

[0003] 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 such as high energy density, no memory effect, low pollution and compact size.

[0004] Lithium carbonate, a key raw material for lithium-ion batteries, can be used in electrolytes or cathode materials. Therefore, its demand is growing with the development of lithium-ion batteries. Salt lake brines are rich in lithium resources and have great mining value, so the use of lithium-containing brines to extract lithium is becoming increasingly popular.

[0005] Currently, the main methods for extracting lithium from brine are extraction, chemical precipitation, and adsorption. However, the selection of extractants in the extraction method is difficult and the operation is complicated. The lithium carbonate produced by the chemical precipitation method is easily encapsulated with impurities, resulting in low purity of the lithium carbonate. The adsorption method has high production costs, which is not conducive to expanding production.

[0006] Based on the above-mentioned deficiencies, it is urgent to develop a method for preparing industrial-grade lithium carbonate using lithium-containing brine with simple process and high product purity. Summary of the Invention

[0007] This application provides a method for preparing industrial-grade lithium carbonate using lithium-containing brine. The lithium carbonate prepared by this method has high purity, simple process, and low cost. The specific technical solution is as follows:

[0008] The present application provides a method for preparing industrial-grade lithium carbonate using lithium-containing brine, comprising the following steps:

[0009] 1) adding lithium carbonate seed crystals to a sodium carbonate solution, stirring and heating to 90° C. to obtain a first mixed solution;

[0010] 2) adding a first portion of lithium-containing brine to the first mixed solution at a feed rate of 1-10 mL / min at 25-50° C. to obtain a first intermediate system;

[0011] 3) adding a second portion of lithium-containing brine to the first intermediate system at a temperature of 50-80° C. at a feed rate of 10-25 mL / min to obtain a second intermediate system;

[0012] 4) adding the remaining lithium-containing brine to the second intermediate system at a feed rate of 25-45 mL / min at 80-99° C. to obtain a second mixed solution, and subjecting the second mixed solution to solid-liquid separation to obtain lithium carbonate;

[0013] The molar ratio of carbonate ions to lithium elements 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 lithium-containing brine, the second part of lithium-containing brine and the remaining lithium-containing brine is (1-8):(2-1):(7-1).

[0014] In the above-mentioned method for preparing industrial-grade lithium carbonate using lithium-containing brine, the mass percentage of lithium ions in the second mixed solution is not higher than 0.25%.

[0015] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein the purity of the lithium carbonate seed crystals is 99.2-99.5%, the particle size is 5-30 μm, the mass percentage of the sodium element in the lithium carbonate seed crystals is not higher than 800 ppm, and the mass percentage of the potassium element in the lithium carbonate seed crystals is not higher than 400 ppm.

[0016] In the above-mentioned method for preparing industrial-grade lithium carbonate using lithium-containing brine, the amount of the lithium carbonate seed crystals added is 0-10 wt % of the lithium carbonate.

[0017] In the above-mentioned method for preparing industrial-grade lithium carbonate using lithium-containing brine, the mass concentration of the sodium carbonate solution is 10-32%.

[0018] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein, in steps 2)-4), the feeding process also includes stirring treatment; 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.

[0019] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein step 4) also includes cleaning 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 10-60min.

[0020] The method for preparing industrial-grade lithium carbonate using lithium-containing brine as described above, wherein 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 exceeding 20 ppm.

[0021] The present application adds lithium carbonate seeds and performs a staged feeding method, while controlling the molar ratio of carbonate ions in the first mixed solution to the lithium element in the lithium-containing brine and the volume ratio of the lithium-containing brine added at different temperatures. This allows the lithium ions in the lithium-containing brine to fully react with the carbonate ions in the sodium carbonate solution, attaching to the surface of the lithium carbonate seeds to form larger lithium carbonate. This also reduces the probability of sodium ions and potassium ions in the lithium-containing brine being entrained and grown into the lithium carbonate, thereby improving the purity of the lithium carbonate product. In addition, the method has a simple process flow, uses fewer types of raw materials, and is low in cost. DETAILED DESCRIPTION

[0022] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0023] The present application provides a method for preparing industrial-grade lithium carbonate using lithium-containing brine, comprising the following steps:

[0024] 1) adding lithium carbonate seed crystals to a sodium carbonate solution, stirring and heating to 90° C. to obtain a first mixed solution;

[0025] 2) adding a first portion of lithium-containing brine to the first mixed solution at a feed rate of 1-10 mL / min at 25-50° C. to obtain a first intermediate system;

[0026] 3) adding a second portion of lithium-containing brine to the first intermediate system at a temperature of 50-80° C. at a feed rate of 10-25 mL / min to obtain a second intermediate system;

[0027] 4) adding the remaining lithium-containing brine to the second intermediate system at a feed rate of 25-45 mL / min at 80-99° C. to obtain a second mixed solution, and subjecting the second mixed solution to solid-liquid separation to obtain lithium carbonate;

[0028] The molar ratio of carbonate ions in the first mixed solution to lithium elements in the lithium-containing brine 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).

[0029] 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.

[0030] The present application does not impose any particular limitation on the mass concentration of the sodium carbonate solution, which can be selected according to actual needs.

[0031] The present application 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.

[0032] The present application 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 200 r / min.

[0033] The present application does not limit the heating method, for example, direct heating, oil bath heating or water bath heating can be used.

[0034] In step 2), the first portion of lithium-containing brine is added to the first mixed solution at a temperature of 25-50° C. with stirring at a feeding rate of 1-10 mL / min to obtain a first intermediate system.

[0035] The lithium-containing brine in this application refers to brine containing lithium ions. The cations in the lithium-containing brine also include sodium ions, potassium ions, and other impurity ions. This application does not limit the anions in the lithium-containing brine, as long as they can meet the purposes of this application. For example, the anions in the lithium-containing brine can include sulfate ions and / or chloride ions.

[0036] During the process of adding the first part of lithium-containing brine to the first mixed solution, the lithium ions in the first part of lithium-containing brine fully react with the carbonate ions in the first mixed solution to generate lithium carbonate, which adheres to the surface of the lithium carbonate seed crystals in the first mixed solution, causing the particle size of the lithium carbonate seed crystals to gradually increase, thereby obtaining a first intermediate system including the lithium carbonate seed crystals and a mixed solution, wherein the mixed solution includes lithium ions, sodium ions, potassium ions, carbonate ions and other impurity ions.

[0037] The present application does not limit the content of lithium ions in the lithium-containing brine, and does not limit the types and contents 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.

[0038] The present application does not limit the method of adding the lithium-containing brine. For example, a spraying device can be used to spray the lithium-containing brine into the reaction device containing the first mixed liquid.

[0039] The stirring method and stirring rate in step 2) are the same as those defined above and will not be repeated here.

[0040] The heating method in step 2) is the same as defined above and will not be repeated here.

[0041] In step 3), the second portion of lithium-containing brine is added to the first intermediate system at a temperature of 50-80° C. with stirring at a feeding rate of 10-25 mL / min to obtain a second intermediate system.

[0042] As in the reaction in step 2), the lithium ions in the second portion of the lithium-containing brine fully react with the carbonate ions in the first intermediate system to generate lithium carbonate, which is attached to the surface of the lithium carbonate seed crystals in the first intermediate system, so that the particle size of the lithium carbonate seed crystals is further gradually increased, and a second intermediate system including the lithium carbonate seed crystals and the mixed solution is obtained.

[0043] The method of adding the lithium-containing brine in step 3) is the same as defined above and will not be repeated here.

[0044] The stirring method and stirring rate in step 3) are the same as those defined above and will not be described again here.

[0045] The heating method in step 3) is the same as defined above and will not be repeated here.

[0046] In step 4), the remaining lithium-containing brine is added to the second intermediate system under stirring at a temperature of 80-99° C. at a feed rate of 25-45 mL / min to obtain a second mixed solution, and the second mixed solution is then subjected to solid-liquid separation. The precipitate obtained by the solid-liquid separation is washed to obtain lithium carbonate.

[0047] As in the reactions of steps 2) and 3), the lithium ions in the remaining lithium-containing brine fully react with the carbonate ions in the second intermediate system to produce lithium carbonate, which then adheres to the surface of the lithium carbonate seed crystals in the second intermediate system, further increasing the particle size of the lithium carbonate seed crystals to obtain a second mixed solution comprising lithium carbonate and a mixed solution. The second mixed solution is then subjected to solid-liquid separation to obtain a precipitate, which is then washed with a washing solution to remove ions on the surface of the precipitate to obtain lithium carbonate.

[0048] The method of adding the lithium-containing brine in step 4) is the same as defined above and will not be repeated here.

[0049] The stirring method and stirring rate in step 4) are the same as those defined above and will not be described again here.

[0050] The heating method in step 4) is the same as defined above and will not be described again here.

[0051] The present application does not limit the method of solid-liquid separation, and for example, precipitation, filtration, centrifugation, etc. can be used.

[0052] This application does not limit the washing method, which can be selected according to actual conditions.

[0053] The molar ratio of carbonate ions in the first mixed solution of the present application to lithium ions in the lithium-containing brine is (0.5-0.65):1, and the volume ratio of the lithium-containing brine added in steps 2) to 4) is (1-8):(2-1):(7-1). In the present application, the "molar ratio of carbonate ions in the first mixed solution to lithium ions in the lithium-containing brine" refers to the molar ratio of carbonate ions in the first mixed solution to lithium ions in the entire lithium-containing brine.

[0054] The present application utilizes lithium-containing brine to prepare industrial-grade lithium carbonate. The method comprises adding lithium carbonate seeds to a sodium carbonate solution, adding different volumes of lithium-containing brine at different temperatures, and controlling the molar ratio of carbonate ions in the first mixed solution to the lithium element in the lithium-containing brine, as well as the volume ratio of the lithium-containing brine added at different temperatures. The obtained lithium carbonate product has high purity. The inventors analyzed this principle. On the one hand, the addition of seed crystals allows lithium ions to fully react with carbonate ions to obtain lithium carbonate, which then adheres to the surface of the lithium carbonate seed crystals to form lithium carbonate with a larger particle size. This ensures that during the growth of lithium carbonate crystals, heterogeneous nucleation problems will 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, a staged feeding method is adopted, in which the reaction is first carried out at a relatively low temperature, which can avoid excessive saturation in the mixed solution, resulting in rapid growth of lithium carbonate crystals, which causes impurities to be entrained and grown into the lithium carbonate, thereby reducing the purity of the lithium carbonate product. Finally, the reaction is carried out at a higher temperature, which helps to fully precipitate the lithium carbonate and prevent the lithium carbonate from dissolving in the solution, thereby improving the yield of lithium carbonate. In addition, by controlling the molar ratio of carbonate ions to lithium in the lithium-containing brine in the first mixed solution and the volume ratio of the lithium-containing brine added at different temperatures, the lithium ions can fully react with the carbonate ions, and the growth rate of the seed crystals can be controlled, thereby avoiding the entrainment and growth of sodium ions and potassium ions in the seed crystals, thereby improving the purity of the lithium carbonate product. Moreover, this method has a simple process and uses fewer types of raw materials, so the method is low in cost and can be expanded for production.

[0055] In one embodiment, the mass percentage of lithium ions in the second mixed solution is no more than 0.25%. When the mass percentage of lithium ions in the second mixed solution is no more than 0.25%, the reaction between the remaining lithium-containing brine and the second intermediate system stops, further preventing the entrainment and growth of sodium ions and potassium ions in the lithium carbonate, thereby greatly improving the purity of the lithium carbonate.

[0056] Specifically, the mass percentage of lithium ions in the second mixed solution can be obtained by performing ion testing using ICP.

[0057] In a specific embodiment, the purity of the lithium carbonate seed crystals is 99.2-99.5%, the particle size is 5-30 μm, the mass percentage of the sodium element in the lithium carbonate seed crystals is not higher than 800 ppm, and the mass percentage of the potassium element in the lithium carbonate seed crystals is not higher than 400 ppm. When the purity and particle size parameters of the lithium carbonate seed crystals are within the above ranges, the lithium carbonate generated by the reaction of lithium ions and carbonate ions is more easily attached to the surface of the lithium carbonate seed crystals, thereby gradually increasing the particle size of the lithium carbonate, making the lithium carbonate crystals more complete, reducing the probability of entrained growth of sodium ions and potassium ions, and further improving the purity of the lithium carbonate product.

[0058] Specifically, the purity of the lithium carbonate seeds is tested by acid-base neutralization titration to obtain the purity of the lithium carbonate seeds, the particle size of the lithium carbonate seeds is tested by a laser particle size distribution analyzer to obtain the particle size of the lithium carbonate seeds, and the lithium carbonate seeds are tested by ICP to obtain the mass percentage of impurity elements in the lithium carbonate seeds.

[0059] In a specific embodiment, the addition amount of lithium carbonate seed is 0-10wt% of lithium carbonate. The mass of lithium carbonate herein refers to the mass of lithium carbonate that can be prepared calculated by theoretical calculation based on the molar ratio of lithium element in lithium-containing brine. When the addition amount of lithium carbonate seed and the mass ratio of lithium carbonate are within the above range, the addition amount of lithium carbonate seed is more appropriate, and the lithium carbonate generated by the reaction of lithium ions and carbonate ions can be fully attached to the surface of lithium carbonate seed, thereby preparing lithium carbonate product more efficiently, avoiding waste of lithium carbonate seed, and saving preparation cost.

[0060] 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, lithium ions and carbonate ions can fully react to form lithium carbonate, which is fully and evenly attached to the surface of the lithium carbonate seed crystals, thereby allowing the lithium carbonate seed crystals to grow further. The reaction rate of lithium ions and carbonate ions can also be appropriate, resulting in more complete crystallization of lithium carbonate, and significantly reducing the entrainment and growth of sodium ions and potassium ions in the lithium carbonate, thereby improving the purity of the lithium carbonate.

[0061] In a specific embodiment, in steps 2)-4), the feeding process further includes stirring; wherein, in step 2), the stirring speed is 200-250r / min; in step 3), the stirring speed is 250-300r / min; in step 4), the stirring speed is 300-400r / min. When the stirring speeds in steps 2)-4) are respectively within the above ranges, the lithium carbonate seeds are more evenly dispersed in the mixed solution, the lithium ions and carbonate ions can react more fully, and can be more evenly attached to the surface of the lithium carbonate seeds, thereby making the crystallization of lithium carbonate more complete, and greatly reducing the entrained growth of sodium ions and potassium ions in lithium carbonate, thereby improving the purity of lithium carbonate.

[0062] In a specific embodiment, step 4) further includes a cleaning treatment of 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 10-60min. When the various parameters of the cleaning treatment are within the above ranges, the lithium ions, sodium ions, potassium ions on the surface of the lithium carbonate, the anions introduced into the lithium-containing brine, and other impurity ions can be cleaned, thereby improving the purity of the lithium carbonate. At the same time, the lithium carbonate will not dissolve in the cleaning solution, thereby improving the recovery rate of the lithium carbonate.

[0063] Specifically, the present application does not limit the choice of cleaning solution, which can be selected according to actual needs. For example, the cleaning solution can be water.

[0064] In one specific embodiment, the lithium-containing brine comprises, by mass concentration, the following: lithium ions 5-25 g / L, sodium ions 100-120 g / L, potassium ions 35-80 g / L, and other impurities not exceeding 20 ppm. When the mass concentrations of the components of the lithium-containing brine are within the above ranges, the crystallization of the lithium carbonate seed crystals is more complete, the entrained growth of sodium and potassium ions is reduced, and the resulting lithium carbonate has a higher purity. Lithium-containing brines have a wide range of sources, and this application does not specifically limit the source of the lithium-containing brine, as long as it meets the objectives of this application. For example, the lithium-containing brine can be salt lake brine, ore lithium extraction brine, battery lithium extraction solution, etc. The content of each element in the lithium-containing brine may fluctuate depending on the batch of incoming materials. This application does not limit the preparation method of the lithium-containing brine, as long as it meets the objectives of this application. For example, ore lithium extraction solution can be prepared by extracting lithium from spodumene or lepidolite as lithium sulfate into a solution, then adding lime or sodium hydroxide to remove impurities, and finally removing calcium with sodium carbonate to obtain the lithium-containing brine used.

[0065] Example

[0066] The following is a further detailed description of the embodiments of the present application through specific examples and comparative examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0067] Example 1

[0068] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this embodiment comprises the following steps:

[0069] 1. Divide 10L of lithium-containing brine into a first portion of lithium-containing brine, a second portion of lithium-containing brine, and the remaining lithium-containing brine. The volume ratio of the first portion of lithium-containing brine, the second portion of lithium-containing brine, and the remaining lithium-containing brine is 7:2:1. The lithium-containing brine is lithium brine extracted from spodumene ore. The lithium-containing brine includes the following mass concentrations: lithium ion 15g / L, sodium ion 110g / L, potassium ion 40g / L, and other impurities 20ppm.

[0070] Lithium carbonate seed crystals are added to a sodium carbonate solution, stirred and heated to 90° C. to obtain a first mixed solution; wherein the molar ratio of carbonate ions to lithium elements in all lithium-containing brine in the first mixed solution is 0.6:1, the amount of lithium carbonate seed crystals used is 5wt% of the theoretical output of lithium carbonate, and the mass concentration of the sodium carbonate solution is 32%.

[0071] 2. At 30° C., add the first portion of lithium-containing brine to the first mixed solution at a feed rate of 5 mL / min, and stir at a stirring rate of 200 r / min to obtain a first intermediate system.

[0072] 3. At 60° C., add the second portion of lithium-containing brine to the first intermediate system at a feed rate of 15 mL / min, and stir at a stirring rate of 250 r / min to obtain a second intermediate system.

[0073] 4. At 90°C, add the remaining lithium-containing brine to the second intermediate system at a feed rate of 45 mL / min, stir at a stirring speed of 300 r / min to obtain a second mixed solution, and filter and wash the second mixed solution to obtain lithium carbonate; wherein the mass percentage of lithium ions in the second mixed solution is 0.25%; the washing solution is water, the mass ratio of water to lithium carbonate is 5:1, the washing temperature is 90°C, and the washing time is 15 min.

[0074] The purity of the lithium carbonate seed crystals is 99.2%, the particle size is 16.354 μm, the mass percentage content of the sodium element in the lithium carbonate seed crystals is 800 ppm, and the mass percentage content of the potassium element in the lithium carbonate seed crystals is 400 ppm.

[0075] Example 2

[0076] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this embodiment is basically the same as that in Example 1, except that the purity of the lithium carbonate seed crystals is 99.00% and the particle size is 32.480 μm.

[0077] Example 3

[0078] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this embodiment is basically the same as that in Example 1, except that the lithium carbonate seed crystals are 20wt% of the theoretical output of lithium carbonate, the purity of the lithium carbonate seed crystals is 99.34%, and the particle size is 25.125μm.

[0079] Example 4

[0080] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this embodiment 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 seed crystals is 99.23%, and the particle size is 29.657 μm.

[0081] Example 5

[0082] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this embodiment 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, and in step 4, the stirring speed is 250 r / min. The purity of the lithium carbonate seed crystal is 99.20% and the particle size is 28.465 μm.

[0083] Example 6

[0084] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this embodiment is basically the same as that in Example 1, except that the purity of the lithium carbonate seed crystals is 99.28% and the particle size is 25.461 μm; the lithium-containing brine is lithium brine extracted from spodumene ore, 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 are not higher than 30 ppm.

[0085] Example 7

[0086] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this embodiment is basically the same as that in Example 1, except that the purity of the lithium carbonate seed crystals is 99.26%, the particle size is 12.451 μm, and during the cleaning process, the mass ratio of water to lithium carbonate is 1:1, the cleaning temperature is 20°C, and the cleaning time is 5 minutes.

[0087] Example 8 to Example 11

[0088] Except for adjusting the reaction temperature and feed rate in steps 2 to 4 according to Table 1 and Table 2, and adjusting the purity and particle size of the lithium carbonate seed crystals, the rest is the same as Example 1.

[0089] Example 12 to Example 15

[0090] Except for adjusting the volume ratio of the first part of lithium-containing brine, the second part of lithium-containing brine and the remaining lithium-containing brine according to Table 1 and Table 2, and adjusting the purity and particle size of the lithium carbonate seed crystals, the rest is the same as Example 1.

[0091] Example 16 to Example 17

[0092] The process is the same as in Example 1 except that the molar ratio of carbonate ions in the first mixed solution to lithium elements in all lithium-containing brine is adjusted according to Table 1, and the purity and particle size of lithium carbonate seed crystals are adjusted.

[0093] Example 18

[0094] Except for adjusting the mass concentration of the sodium carbonate solution according to Table 1 and adjusting the purity and particle size of the lithium carbonate seed crystals, the rest is the same as Example 1.

[0095] Example 19 to Example 20

[0096] Except for adjusting the addition amount of lithium carbonate seed crystals according to Table 1 and adjusting the purity and particle size of the lithium carbonate seed crystals, the rest is the same as Example 1.

[0097] Comparative Example 1

[0098] The method for preparing industrial-grade lithium carbonate using lithium-containing brine in this comparative example comprises the following steps:

[0099] 1. Take 10L of lithium-containing brine. The lithium-containing brine is obtained by extracting lithium from spodumene ore. The mass concentration of lithium-containing brine includes: lithium ion 15g / L, sodium ion 110g / L, potassium ion 40g / L, and other impurities 20ppm.

[0100] Lithium carbonate seed crystals are added to a sodium carbonate solution, stirred and heated to 90° C. to obtain a first mixed solution; wherein the molar ratio of carbonate ions to lithium elements in all lithium-containing brine in the first mixed solution is 0.6:1, the lithium carbonate seed crystals have a theoretical output of 5wt% lithium carbonate by mass, and the mass concentration of the sodium carbonate solution is 32%.

[0101] 2. At 90°C, add the lithium-containing brine to the first mixed solution at a feed rate of 45 mL / min, stir at a stirring rate of 300 r / min to obtain a second mixed solution, and filter and wash the second mixed solution to obtain lithium carbonate; wherein the mass percentage of lithium ions in the second mixed solution is 0.25%; the washing solution is water, the mass ratio of water to lithium carbonate is 5:1, the washing temperature is 90°C, and the washing time is 15 min.

[0102] The purity of the lithium carbonate seed crystals is 99.2%, the particle size D50 is 13.506 μm, the mass percentage content of the sodium element in the lithium carbonate seed crystals is 800 ppm, and the mass percentage content of the potassium element in the lithium carbonate seed crystals is 400 ppm.

[0103] Comparative Example 2

[0104] 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, the purity of the lithium carbonate seed crystals is 99.21%, and the particle size is 22.615 μm.

[0105] Comparative Example 3

[0106] 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 feed rate in step 2 is 20 mL / min, the feed rate in step 3 is 40 mL / min, and the feed rate in step 4 is 60 mL / min. The purity of the lithium carbonate seed crystals is 99.25%, and the particle size is 24.213 μm.

[0107] Comparative Example 4

[0108] 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 0.7:1, the purity of the lithium carbonate seed crystals is 99.26%, and the particle size is 19.654 μm.

[0109] Comparative Example 5 to Comparative Example 6

[0110] Except for adjusting the volume ratio of the first part of lithium-containing brine, the second part of lithium-containing brine and the remaining lithium-containing brine according to Table 1 and Table 2, and adjusting the purity and particle size of the lithium carbonate seed crystals, the rest is the same as Example 1.

[0111] Test methods and equipment

[0112] The lithium-containing brine is subjected to ICP ion testing to obtain the concentrations of lithium ions, sodium ions, potassium ions and other impurities in the lithium-containing brine.

[0113] An acid-base neutralization titration test is performed on the first mixed solution to obtain the molar concentration of carbonate ions in the first mixed solution.

[0114] An ICP ion test is performed on the second mixed solution to obtain the mass percentage of lithium ions in the second mixed solution.

[0115] The particle size of lithium carbonate seed crystals was measured using a laser particle size distribution analyzer. D50 represents the median particle size of the lithium carbonate seed crystals, which indicates that 50% of the total number of particles have a particle size smaller than this value. The purity of the lithium carbonate seed crystals was calculated by ICP testing to determine the mass percentage of impurity elements in the lithium carbonate seed crystals.

[0116] The mass percentage of impurity elements in the lithium carbonate product is obtained by ICP testing, and the purity of the lithium carbonate product is calculated.

[0117] As can be seen from Table 1 and Table 2, by comparing Examples 1-20 with Comparative Examples 1-6, the method for preparing industrial-grade lithium carbonate using lithium-containing brine provided by the present invention can prepare lithium carbonate with high purity;

[0118] It can be seen from Example 1, Examples 8 to 11, Comparative Example 2 and Comparative Example 3 that when the reaction temperature and feed rate in steps 2 to 4 are within the range of this application, the purity of the prepared lithium carbonate is relatively high; it can be seen from Example 1, Examples 12 to 15, Comparative Examples 5 to 6 that by controlling the volume ratio of the first part of the lithium-containing brine, the second part of the lithium-containing brine and the remaining lithium-containing brine within the range of this application, the lithium ions and carbonate ions can be fully reacted, and the growth rate of the lithium carbonate seeds can be controlled to avoid the entrainment and growth of sodium ions and potassium ions, so that the purity of the prepared lithium carbonate is relatively high; it can be seen from Example 1, Example 16, Example 17 and Comparative Example 4 that by controlling the molar ratio of the carbonate ions in the first mixed solution to the lithium element in all the lithium-containing brines within the range of this application, the purity of the prepared lithium carbonate is relatively high.

[0119] From the comparison of Examples 1, 2, 19 and 20, it can be seen that the purity, particle size and amount of seed crystals added beyond the scope of this application will lead to a decrease in the purity of the lithium carbonate product. This is because the addition of seed crystals will reduce heterogeneous nucleation, and low-quality seed crystals will cause heterogeneous nucleation of the lithium carbonate product; from the comparison of Examples 1, 4 and 18, it can be seen that the mass concentration of the sodium carbonate solution will also affect the purity of the lithium carbonate product. Too low a concentration of the sodium carbonate solution will affect the yield of the lithium carbonate product and increase the cost; in addition, from the comparison of Examples 1 and 5, 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 process. Appropriate stirring can make the reaction more uniform, avoid local oversaturation, and reduce the probability of entrained impurities; from the comparison of Examples 1 and 6, it can be seen that lithium-containing brine with suitable components can improve the purity of the prepared lithium carbonate and reduce the probability of entrained impurities in the product; from the comparison of Examples 1 and 7, it can be seen that cleaning the lithium carbonate can improve the purity of the lithium carbonate and reduce the adhesion of impurities. In summary, the method for preparing industrial-grade lithium carbonate using lithium-containing brine provided by the present invention can prepare high-purity lithium carbonate, and has the advantages of simple process and low cost.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, 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 embodiments of the present invention.

Claims

1. A method for preparing industrial-grade lithium carbonate using lithium-containing brine, characterized in that: The following steps are involved: 1) adding lithium carbonate seed crystals into a sodium carbonate solution, stirring and heating to 90° C. to obtain a first mixed solution; 2) adding a first portion of lithium-containing brine to the first mixed solution at a temperature of 25-50° C. at a feed rate of 1-10 mL / min to obtain a first intermediate system; 3) adding a second portion of lithium-containing brine to the first intermediate system at a temperature of 50-80° C. at a feed rate of 10-25 mL / min to obtain a second intermediate system; 4) adding the remaining lithium-containing brine to the second intermediate system at 80-99° C. at a feed rate of 25-45 mL / min to obtain a second mixed solution, and subjecting the second mixed solution to solid-liquid separation to obtain lithium carbonate; Among them, the molar ratio of carbonate ions in the first mixed solution and lithium elements in the lithium-containing brine 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).

2. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to claim 1, characterized in that: In the second mixed solution, the mass percentage of lithium ions is not higher than 0.25%.

3. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1-2, characterized in that: The purity of the lithium carbonate seed crystals is 99.2-99.5%, the particle size is 5-30 μm, the mass percentage content of the sodium element in the lithium carbonate seed crystals is not higher than 800 ppm, and the mass percentage content of the potassium element in the lithium carbonate seed crystals is not higher than 400 ppm.

4. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1 to 3, characterized in that: The amount of the lithium carbonate seed crystals added is 0-10 wt % of the lithium carbonate.

5. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1 to 4, characterized in that: The mass concentration of the sodium carbonate solution is 10%-32%.

6. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1 to 5, characterized in that: In steps 2)-4), the feeding process also includes stirring; 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.

7. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1 to 6, characterized in that: Step 4) also includes cleaning 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.

8. The method for preparing industrial-grade lithium carbonate using lithium-containing brine according to any one of claims 1 to 7, characterized in that: The lithium-containing brine includes, by mass concentration, 5-25 g / L lithium ions, 100-120 g / L sodium ions, 35-80 g / L potassium ions, and other impurities not exceeding 20 ppm.

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