Process and device for preparing battery-grade lithium carbonate based on mother liquor water concentrate

Abstract

The application discloses a process and device for preparing battery-grade lithium carbonate based on mother liquor water concentrate, and belongs to the technical field of lithium carbonate preparation. In the process, the mother liquor water is filtered, decarburized and concentrated, and then a low-valence metal cation is oxidized into a high-valence state by adding an oxidizing agent, so that the low-valence metal cation is more easily precipitated in subsequent steps; then, the pH is adjusted in sections to remove metal cation impurities, and then the purified liquid is obtained through ion exchange; the crystal seed is subjected to inert gas heat treatment to repair surface defects of the crystal seed, and then the crystal seed liquid is prepared; the lithium precipitation process is adjusted in sections to spray, so that the lithium precipitation efficiency is improved, and the loss of raw materials is reduced; finally, the battery-grade lithium carbonate is prepared through centrifugal washing, drying and crushing. The lithium precipitation device comprises a lithium precipitation kettle and a ring-shaped distributor, and can realize efficient reaction. The application can directly prepare high-purity battery-grade lithium carbonate from the mother liquor water, has a short process, low energy consumption, complete impurity removal and excellent product performance.

Description

Technical Field

[0001] This application relates to the field of lithium carbonate preparation technology, and in particular to a process and apparatus for preparing battery-grade lithium carbonate based on mother liquor concentrate. Background Technology

[0002] In recent years, with the vigorous development of the new energy industry, the demand for lithium-ion batteries has increased significantly. Battery-grade lithium carbonate, as a core raw material for lithium-ion batteries, directly affects the performance and application effects of these batteries due to its purity. In existing technologies, the process of preparing battery-grade lithium carbonate using lithium sulfate and sodium carbonate involves a primary lithium precipitation step that generates a large amount of mother liquor containing a significant amount of lithium ions, as well as high concentrations of impurity ions such as sodium, potassium, sulfate, and calcium. To recover lithium from this mother liquor, existing technologies typically involve decarbonization, evaporation and concentration, followed by a secondary lithium precipitation process.

[0003] However, due to the complex composition and high content of impurities in the mother liquor, the purity of the lithium carbonate product obtained from secondary lithium precipitation can only meet industrial-grade standards. To meet battery-grade requirements, multiple purification processes such as dissolution, impurity removal, and recrystallization are required. This type of process suffers from problems such as lengthy procedures, large equipment investment, high energy consumption, and large reagent consumption, which not only increases production costs but also leads to low production efficiency, making it difficult to meet the demands of large-scale, low-cost battery-grade lithium carbonate production. Furthermore, in traditional secondary lithium precipitation processes, the removal of impurity ions is incomplete, and the lithium precipitation reaction conditions are poorly controlled, easily resulting in insufficient purity and uneven particle size distribution of the generated lithium carbonate crystals, further increasing the difficulty of subsequent purification. Chinese invention patent CN112142080A provides a method for preparing battery-grade lithium carbonate by freezing and recycling the concentrated mother liquor from lithium precipitation. This method adds the remaining mother liquor from lithium carbonate preparation to the leachate from lithium carbonate preparation for recycling, improving lithium ion utilization and reducing costs.

[0004] However, existing technologies for preparing battery-grade lithium carbonate from recycled mother liquor suffer from problems such as low lithium-ion utilization, high impurity content in the produced battery-grade lithium carbonate, and poor practical application performance. Therefore, developing a simplified process for directly preparing battery-grade lithium carbonate from concentrated mother liquor in one step, achieving short-process, low-energy consumption, and high-purity production, has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a process and apparatus for preparing battery-grade lithium carbonate based on concentrated mother liquor. The process effectively removes metal cation impurities from the mother liquor by using an oxidant and a staged pH adjustment method to settle impurities. Then, the seed crystals are heat-treated to enhance their affinity for Li. +The adsorption properties are then utilized; the seed solution, saturated sodium carbonate solution, and purification solution are added to the lithium precipitation reactor for reaction. The purification solution adopts a segmented spraying process to save reaction raw materials. Finally, high-purity battery-grade lithium carbonate can be obtained by centrifugation, washing, drying, and pulverizing.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] In a first aspect, this application provides a process for preparing battery-grade lithium carbonate based on a concentrated mother liquor, comprising the following steps:

[0008] S1. The mother liquor is subjected to filtration, decarbonization, concentration, oxidation and impurity removal steps to obtain purified liquid;

[0009] S2. The seed crystals are heat-treated in an inert gas / CO2 mixed gas atmosphere and held at the temperature for 4-5 hours to obtain pretreated seed crystals. The pretreated seed crystals are then prepared into a seed crystal solution.

[0010] It should be noted that this step can effectively repair defects on the seed crystal surface, form a stable crystal structure, and improve the resistance to Li. + Adsorption effect.

[0011] S3. Add seed solution and saturated sodium carbonate solution to lithium precipitation tank, add chelating agent while stirring, heat to 85~95℃, spray purification liquid into the tank, after lithium precipitation is completed, keep warm and stir, then let stand, after complete sedimentation, drain the supernatant.

[0012] It should be noted that adding a chelating agent in this step can form a chelate with the impurity metal ions, thus preventing the impurities from precipitating and mixing with lithium carbonate.

[0013] S4. Repeat the above lithium precipitation steps until the settled solids in the lithium precipitation tank reach the upper limit of the effective volume of the lithium precipitation tank, then stop discharging the supernatant and terminate the lithium precipitation steps.

[0014] It should be noted that in the multiple lithium precipitation operations, each time lithium precipitation occurs, saturated sodium carbonate solution and purification liquid are added in proportion according to the remaining effective volume of the lithium precipitation vessel. Before spraying the purification liquid, chelating agent and saturated sodium carbonate solution need to be added to the lithium precipitation vessel. The induction period step is not required in the multiple lithium precipitation operations, and the rest is the same as the lithium precipitation steps.

[0015] S5. Centrifuge all materials in the lithium precipitation vessel. After the first centrifugation, wash the lithium carbonate with centrifugal water. After the washing, centrifuge again. After the second centrifugation, wash the lithium carbonate with deionized water again. After the second washing, start the third centrifugation. After centrifugation, the initial lithium carbonate and the centrifugal water are obtained.

[0016] S6. Dry the lithium carbonate raw material, and after drying, crush it to obtain battery-grade lithium carbonate.

[0017] Furthermore, the lithium content in the concentrated mother liquor water in S1 is 7~9 g / L; the oxidant used in the oxidation step includes any one of hydrogen peroxide, ozone water and chlorine dioxide.

[0018] It should be noted that the oxidant oxidizes low-valence metal cation impurities to high-valence states, making the metal cation impurities easier to precipitate and remove.

[0019] Further, the oxidation step described in S1 is as follows: add (0.01~0.1) parts by mass of oxidant to 100 parts by mass of mother liquor water, and control the pH value of the mother liquor water to 2~3, the temperature to 25~50℃, and react for 0.5~2h after stirring evenly;

[0020] The impurity removal steps include: adding (0.15~0.45) parts by mass of sodium hydroxide to 100 parts by mass of mother liquor, stirring evenly, controlling the pH value to 3.5~4, the temperature to 30~40℃, and reacting for 1~2 hours; adding (0.09~0.3) parts by mass of sodium hydroxide to the mother liquor, stirring evenly, controlling the pH value to 5~6, and heating to 45~50℃, reacting for 1.5~2 hours, and then filtering to obtain mother liquor after one impurity removal; adding (0.05~0.2) parts by mass of sodium carbonate to the mother liquor after one impurity removal, stirring evenly, and heating to 60℃, reacting for 2~3 hours, and then filtering out solid impurities, using ion exchange resin to remove the remaining impurity ions to obtain purified liquid.

[0021] It should be noted that by adjusting the pH value in stages, a sudden and significant increase in pH value is avoided, which would cause a large amount of Fe(OH)3 to precipitate and form a colloid, thus encapsulating Li in the solution. + This results in raw material loss; adding soda ash can effectively remove calcium and magnesium ions from the mother liquor, while ion exchange resin is used to remove sodium and potassium ions.

[0022] Furthermore, the ion exchange resin includes any one of lithium-repellent cation exchange resins containing sulfonic acid groups or carboxylic acid groups.

[0023] Furthermore, the seed crystals mentioned in S2 are battery-grade lithium carbonate micropowder with a particle size distribution of median particle size D. 50 The particle size D is 3~8μm, and has a 90% cumulative distribution. 90The particle size is not greater than 15 μm; the inert gas includes any one of nitrogen, argon and helium; the proportion of CO2 in the mixed gas is 0.5~1%; the heat treatment temperature range is controlled at 650~700℃; the seed solution is prepared by pumping 10 parts by mass of saturated sodium carbonate solution into the seed dispersion tank, then adding (0.5~1) parts by mass of pretreated seed crystals into the dispersion tank, turning on the disperser, and dispersing at high speed of 2000~5000 rpm for 2~5 min to obtain the seed solution.

[0024] Further, the chelating agent described in S3 includes any one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetrapropionic acid, hydroxyethylidene diphosphonic acid, and aminotrimethylenephosphonic acid; the mass ratio of the saturated sodium carbonate solution, seed solution, and chelating agent is 500:(3~5):(0.1~0.2).

[0025] Furthermore, the process for the spray purification liquid described in S3 is segmented spraying, including:

[0026] A1: Set the spray flow rate to 3~4m 3 / h, stirring speed is 100~150r / min, spraying time is 50~60min;

[0027] A2: Set the spray flow rate to 7~8m 3 / h, stirring speed is 300~400r / min, spraying time is 2~3h;

[0028] A3: Set the spray flow rate to 2~3m 3 The stirring speed is 80~100r / min / h. During this period, the mother liquor in the reactor is sampled and the carbonate concentration is tested. When the carbonate concentration drops to 14~17g / L, the lithium precipitation is stopped.

[0029] It should be noted that in stage A1, the above-mentioned spraying process helps the purification solution to fully contact the seed crystals and sodium carbonate in the reactor, improves the reaction efficiency, and promotes the adsorption and activation of lithium ions on the seed crystal surface. At the same time, the low-flow spraying and slow stirring prevent the seed crystals from moving too violently, which is not conducive to the formation of active sites. In stage A2, the spraying flow rate and stirring speed are increased to accelerate crystal growth and improve efficiency. In stage A3, the carbonate concentration in the reactor decreases and the crystal growth rate decreases. Therefore, the spraying flow rate and stirring speed are reduced to avoid adding too much purification solution.

[0030] Secondly, this application provides an apparatus for preparing battery-grade lithium carbonate based on mother liquor concentrate, comprising: a lithium precipitation tank, a feeder with a ring-shaped structure at the top of the lithium precipitation tank for spraying purification liquid into the lithium precipitation tank; a purification liquid valve penetrating the top side of the lithium precipitation tank, the feeder and the purification liquid valve being connected inside the lithium precipitation tank; a stirrer motor being installed at the top of the outer side of the lithium precipitation tank, and a stirrer being installed inside, the upper end of the stirrer passing through the center of the ring-shaped structure of the feeder, penetrating the top of the lithium precipitation tank and being connected to the stirrer motor; a feeding port and a steam valve being installed on the top side of the lithium precipitation tank, the feeding port being used to add seed crystal solution and saturated sodium carbonate solution; an electric valve being installed in the lower half of the lithium precipitation tank, and a bottom valve being installed at the bottom.

[0031] Furthermore, the fabric feeder is provided with spray holes.

[0032] Furthermore, the annular structure of the fabric feeder is a closed circular ring structure or a closed regular hexagonal structure.

[0033] The beneficial effects of this application are:

[0034] This application involves high-temperature pretreatment of lithium carbonate seed crystals in an inert gas and trace CO2 atmosphere. This pretreatment induces atomic migration on the seed crystal surface, promoting surface defect rearrangement, reducing irregular and rough defect sites, and forming a more regular, highly symmetric crystal structure. The trace CO2 inhibits minor decomposition reactions on the seed crystal surface, preventing the formation of CO32- on the seed crystal surface. 2- Vacancies lead to uneven surface charge in the seed crystals; highly symmetric crystal planes have low surface energy, uniform charge distribution, and regular atomic arrangement, therefore, during ion adsorption, they tend to adsorb ions that can maintain the lowest energy state. Clearly, Li... + It has a lower charge density for Li + The adsorption of Li is more conducive to maintaining a stable crystal structure; at the same time, the lattice sites in the high-symmetry crystal plane are more compatible with Li. + The radius is a better fit, therefore, the high symmetry crystal face of Li + The adsorption is significantly higher than that of Ca. 2+ Mg 2+ Furthermore, due to the uniform charge distribution on the highly symmetric crystal planes, the seed crystal surface exhibits a uniformly distributed negative charge, which is beneficial to SO42-. 2- It has a repulsive effect; ultimately, during crystal growth, the pretreated seed crystals will reduce the adsorption of impurities and increase the main content of lithium carbonate.

[0035] In the lithium deposition process, a ring-shaped feeder is used to more evenly disperse the purification solution in the lithium deposition vessel, improving the lithium deposition reaction efficiency. In the segmented lithium deposition process, the induction phase helps the purification solution to fully contact the seed crystals and sodium carbonate in the vessel, promoting the adsorption and activation of lithium ions on the seed crystal surface, while avoiding excessive seed crystal activity, which is not conducive to the formation of active sites. In the rapid growth phase, the spray flow rate and stirring speed are increased to accelerate crystal growth and reduce the lithium deposition time. In the slow growth phase, the carbonate concentration in the vessel is reduced, the crystal growth rate is slowed down, the spray flow rate and stirring speed are reduced, saving raw materials and reducing costs. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0037] Figure 1 This application provides a schematic diagram of an apparatus for preparing battery-grade lithium carbonate based on a concentrated mother liquor.

[0038] Figure 2 This is a schematic diagram of the closed ring structure of the feeder provided in this application.

[0039] Figure 3 A schematic diagram of the closed regular hexagonal structure of the feeder provided in this application.

[0040] Figure 4 This application provides a process flow diagram for preparing battery-grade lithium carbonate based on mother liquor concentrate.

[0041] Explanation of reference numerals in the attached diagram: 1. Lithium precipitation vessel; 2. Feeder; 3. Purified liquid valve; 4. Agitator; 5. Agitator motor; 6. Feed port; 7. Electric valve; 8. Steam valve; 9. Downward expansion valve; 201. Spray hole. Detailed Implementation

[0042] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0043] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0044] The following specific embodiments further illustrate this point:

[0045] Example 1

[0046] like Figures 1-3 As shown, an apparatus for preparing battery-grade lithium carbonate based on mother liquor concentrate includes: a lithium precipitation tank 1, a feeder 2 with a ring structure at the top of the lithium precipitation tank 1, a purification liquid valve 3 with a ring structure passing through the top side of the lithium precipitation tank 1, the feeder 2 and the purification liquid valve 3 being connected inside the lithium precipitation tank 1, a stirrer motor 5 with a stirrer 4 with a stirrer 4 with its upper end passing through the center of the ring structure of the feeder 2, passing through the top of the lithium precipitation tank 1 and being connected to the stirrer motor 5, a feed port 6 and a steam valve 8 with a top side of the lithium precipitation tank 1, an electric valve 7 with a lower half section, and a bottom expansion valve 9 with a bottom section.

[0047] The fabric feeder 2 is provided with spray holes 201.

[0048] The annular structure of the fabric feeder 2 is a closed circular ring structure or a closed regular hexagonal structure.

[0049] Example 2

[0050] like Figure 4 As shown, a process for preparing battery-grade lithium carbonate based on mother liquor concentrate includes the following steps:

[0051] S1. Take 100 parts by weight of the mother liquor, filter, decarbonize, and concentrate it to make the lithium content in the mother liquor 8 g / L. Then add 0.01 parts by weight of hydrogen peroxide to the mother liquor, control the pH of the mother liquor to 2, and the temperature to 40℃. After stirring, react for 1 hour. Then add 0.2 parts by weight of the first part of sodium hydroxide to the mother liquor, stir, control the pH to 3.5, and react at 40℃ for 1 hour. Then add 0.09 parts by weight of the second part of sodium hydroxide to the mother liquor, stir, control the pH to 5, and heat to 45℃ for 1.5 hours. Then filter to obtain the mother liquor after one purification. Add 0.1 parts by weight of sodium carbonate to the mother liquor after one purification, stir evenly, heat to 60℃, and react for 2 hours. Then filter out solid impurities. Then continue to use a lithium-repellent cation exchange resin containing sulfonic acid groups to remove the remaining impurity ions to obtain the purified solution.

[0052] S2. Under a nitrogen / CO2 mixed gas atmosphere, the particle size distribution is set to the median particle size D. 50 The particle size is 8 μm, and the 90% cumulative distribution particle size D 90Battery-grade lithium carbonate micropowder with a particle size of 12 μm was heated at 700 °C for 4 h in a tube furnace to obtain pretreated seed crystals, wherein the proportion of CO2 in the nitrogen / CO2 mixed gas was 0.5 vol.%; 10 parts by mass of saturated sodium carbonate solution were pumped into the seed crystal dispersion tank, and then 0.5 parts of the pretreated seed crystals were added to the dispersion tank. The disperser was turned on and dispersed at high speed of 2000 rpm for 3 min to obtain seed crystal solution;

[0053] S3. Add 3 parts by mass of seed solution and 500 parts by mass of saturated sodium carbonate solution sequentially into lithium precipitation tank 1 through feed port 6. Turn on stirrer 4, then add 0.1 parts by mass of ethylenediaminetetraacetic acid into lithium precipitation tank 1. Open steam valve 8 on lithium precipitation tank 1 to start heating. When the temperature inside lithium precipitation tank 1 reaches 90℃, open the closed hexagonal structure feeder 2 to spray purification liquid into lithium precipitation tank 1. A1: Set the spray flow rate to 3m³ / h. 3 / h, stirrer 4 speed is 100r / min, spray for 60min, A2: set spray flow rate is 8m 3 / h, stirrer 4 speed is 300r / min, continuous for 2h, A3: set spray flow rate to 2m 3 / h, stirrer 4 rotates at 80r / min. During this period, the mother liquor in the reactor is sampled and the carbonate concentration is tested. When the carbonate concentration drops to 17g / L, the feeder 2 is turned off, stirring is continued and the temperature is maintained for 20min. Then stirrer 4 is turned off. After the lithium precipitation reactor 1 has settled completely, the electric valve 7 is opened to discharge the supernatant in the lithium precipitation reactor 1.

[0054] S4. Repeat the above lithium precipitation steps to perform multiple lithium precipitation operations. After the settled solids in lithium precipitation tank 1 reach the upper limit of the effective volume of the lithium precipitation tank, stop discharging the supernatant and terminate the lithium precipitation step.

[0055] S5. Open the lower valve 9 on the lithium precipitation tank 1, transfer all the material in the lithium precipitation tank 1 to the centrifuge, start the first centrifugation, after the first centrifugation is completed, transfer the lithium carbonate to the washing tank, add centrifugation water three times, after the washing is completed, perform the second centrifugation, after the second centrifugation is completed, add condensed water to the washing tank for the second washing, after the second washing is completed, start the third centrifugation, after the centrifugation is completed, the initial lithium carbonate material and centrifugation water are obtained;

[0056] S6. Dry the lithium carbonate raw material, and after drying, pulverize it to obtain the battery-grade lithium carbonate described in Example 2.

[0057] Example 3

[0058] like Figure 4 As shown, a process for preparing battery-grade lithium carbonate based on mother liquor concentrate includes the following steps:

[0059] S1. Take 100 parts by weight of mother liquor water, filter, decarbonize and concentrate it to make the lithium content in the mother liquor water 7 g / L. Then add 0.04 parts by weight of ozone water to the mother liquor water, control the pH value of the mother liquor water to 2.5, the temperature to 25℃, stir and react for 0.5 h. Then add 0.45 parts by weight of the first part of sodium hydroxide to the mother liquor water, stir and control the pH value to 4, and react at 30℃ for 1.5 h. Then add 0.3 parts by weight of the second part of sodium hydroxide to the mother liquor water, stir and control the pH value to 5.5, and raise the temperature to 45℃ and react for 2 h. Then filter to obtain mother liquor water with one purification. Add 0.05 parts by weight of sodium carbonate to the mother liquor water with one purification, stir evenly and raise the temperature to 60℃ and react for 2 hours. Then filter out solid impurities. Then continue to use lithium repulsion cation exchange resin containing sulfonic acid groups to remove the remaining impurity ions to obtain purified liquid.

[0060] S2. Under an argon / CO2 mixed gas atmosphere, the particle size distribution is set to the median particle size D. 50 The particle size is 8 μm, and the 90% cumulative distribution particle size D 90 Battery-grade lithium carbonate micropowder with a particle size of 12 μm was heated at 680 °C for 5 h in a tube furnace to obtain pretreated seed crystals, wherein the proportion of CO2 in the argon / CO2 mixed gas was 0.7 vol.%; 10 parts by mass of saturated sodium carbonate solution were pumped into the seed crystal dispersion tank, and then 1 part of the pretreated seed crystals were added to the dispersion tank. The disperser was turned on and dispersed at high speed of 5000 rpm for 2 min to obtain seed crystal solution;

[0061] S3. Add 4 parts by mass of seed solution and 500 parts by mass of saturated sodium carbonate solution sequentially into lithium precipitation tank 1 through feed port 6. Turn on stirrer 4, then add 0.15 parts by mass of ethylenediaminetetraacetic acid into lithium precipitation tank 1. Open steam valve 8 on lithium precipitation tank 1 to start heating. When the temperature inside lithium precipitation tank 1 reaches 85℃, open the closed hexagonal structure feeder 2 to spray purification liquid into lithium precipitation tank 1. A1: Set the spray flow rate to 3.5m³ / h. 3 / h, stirrer 4 speed is 120r / min, after spraying for 50min, A2: set the spray flow rate to 7m 3 / h, stirrer 4 speed is 350r / min, continuous for 2.5h, A3: set spray flow rate to 2.5m 3 / h, stirrer 4 rotates at 90r / min. During this period, the mother liquor in the reactor is sampled and the carbonate concentration is tested. When the carbonate concentration drops to 14g / L, the feeder 2 is turned off, stirring is continued and the temperature is maintained for 10min. Then stirrer 4 is turned off. After the lithium precipitation reactor 1 has settled completely, the electric valve 7 is opened to discharge the supernatant in the lithium precipitation reactor 1.

[0062] S4. Repeat the above lithium precipitation steps to perform multiple lithium precipitation operations. After the settled solids in lithium precipitation tank 1 reach the upper limit of the effective volume of the lithium precipitation tank, stop discharging the supernatant and terminate the lithium precipitation step.

[0063] S5. Open the lower valve 9 on the lithium precipitation tank 1, transfer all the material in the lithium precipitation tank 1 to the centrifuge, start the first centrifugation, after the first centrifugation is completed, transfer the lithium carbonate to the washing tank, add centrifugal water, after the washing is completed, perform the second centrifugation, after the second centrifugation is completed, add deionized water to the washing tank for the second washing, after the second washing is completed, start the third centrifugation, after the centrifugation is completed, the initial lithium carbonate material and centrifugal water are obtained.

[0064] S6. Dry the lithium carbonate raw material, and after drying, pulverize it to obtain the battery-grade lithium carbonate described in Example 3.

[0065] Example 4

[0066] like Figure 4 As shown, a process for preparing battery-grade lithium carbonate based on mother liquor concentrate includes the following steps:

[0067] S1. Take 100 parts by weight of mother liquor water, filter, decarbonize and concentrate it to make the lithium content in the mother liquor water 9 g / L. Then add 0.1 parts by weight of chlorine dioxide to the mother liquor water, control the pH value of the mother liquor water to 3, the temperature to 50℃, stir and react for 2 hours. Then add 0.15 parts by weight of the first part of sodium hydroxide to the mother liquor water, stir and control the pH value to 3.5, and react at 35℃ for 2 hours. Then add 0.15 parts by weight of the second part of sodium hydroxide to the mother liquor water, stir and control the pH value to 6, and heat to 50℃ and react for 1.5 hours. Then filter to obtain mother liquor water with one purification. Add 0.2 parts by weight of sodium carbonate to the mother liquor water with one purification, stir evenly and heat to 60℃, react for 3 hours. Then filter out solid impurities. Then continue to use lithium repulsion cation exchange resin containing sulfonic acid groups to remove the remaining impurity ions to obtain purified liquid.

[0068] S2. Under a helium / CO2 mixed gas atmosphere, the particle size distribution is set to the median particle size D. 50 The particle size is 8 μm, and the 90% cumulative distribution particle size D 90 Battery-grade lithium carbonate micropowder with a particle size of 12 μm was heated at 650 °C for 4.5 h in a tube furnace to obtain pretreated seed crystals, wherein the proportion of CO2 in the helium / CO2 mixed gas was 1 vol.%; 10 parts by mass of saturated sodium carbonate solution was pumped into the seed crystal dispersion tank, and then 0.8 parts of the pretreated seed crystals were added to the dispersion tank. The disperser was turned on and dispersed at high speed of 3000 rpm for 5 min to obtain seed crystal solution;

[0069] S3. Add 5 parts by mass of seed solution and 500 parts by mass of saturated sodium carbonate solution sequentially into lithium precipitation tank 1 through feed port 6. Turn on stirrer 4, then add 0.2 parts by mass of ethylenediaminetetraacetic acid into lithium precipitation tank 1. Open steam valve 8 on lithium precipitation tank 1 to start heating. When the temperature inside lithium precipitation tank 1 reaches 95℃, open the closed hexagonal structure feeder 2 to spray purification liquid into lithium precipitation tank 1. A1: Set the spray flow rate to 4m³ / h. 3 / h, stirrer 4 speed is 150r / min, after spraying for 56min, A2: set the spray flow rate to 7.5m 3 / h, stirrer 4 speed is 400r / min, continuous for 3h, A3: set spray flow rate to 3m 3 / h, stirrer 4 rotates at 100r / min, during which the mother liquor in the reactor is sampled and the carbonate concentration is detected. When the carbonate concentration drops to 15g / L, the feeder 2 is turned off, stirring is continued and the temperature is maintained for 15min, then the stirrer 4 is turned off. After the lithium precipitation reactor 1 has settled completely, the electric valve 7 is opened to discharge the supernatant in the lithium precipitation reactor 1.

[0070] S4. Repeat the above lithium precipitation steps to perform multiple lithium precipitation operations. After the settled solids in lithium precipitation tank 1 reach the upper limit of the effective volume of the lithium precipitation tank, stop discharging the supernatant and terminate the lithium precipitation step.

[0071] S5. Open the lower valve 9 on the lithium precipitation tank 1, transfer all the material in the lithium precipitation tank 1 to the centrifuge, start the first centrifugation, after the first centrifugation is completed, transfer the lithium carbonate to the washing tank, add centrifugation water three times, after the washing is completed, perform the second centrifugation, after the second centrifugation is completed, add condensed water to the washing tank for the second washing, after the second washing is completed, start the third centrifugation, after the centrifugation is completed, the initial lithium carbonate material and centrifugation water are obtained;

[0072] S6. Dry the lithium carbonate raw material, and after drying, pulverize it to obtain the battery-grade lithium carbonate described in Example 4.

[0073] Example 5

[0074] like Figure 4 As shown, a process for preparing battery-grade lithium carbonate based on mother liquor concentrate includes the following steps:

[0075] S1. Take 100 parts by weight of mother liquor water, filter, decarbonize and concentrate it to make the lithium content in the mother liquor water 8 g / L. Then add 0.08 parts by weight of chlorine dioxide to the mother liquor water, control the pH value of the mother liquor water to 3, the temperature to 45℃, stir and react for 1.5 h. Then add 0.3 parts by weight of the first part of sodium hydroxide to the mother liquor water, stir and control the pH value to 3.5, and react at 40℃ for 1 h. Then add 0.1 parts by weight of the second part of sodium hydroxide to the mother liquor water, stir and control the pH value to 5.5, and raise the temperature to 48℃ and react for 1.8 h. Then filter to obtain mother liquor water with one purification. Add 0.1 parts by weight of sodium carbonate to the mother liquor water with one purification, stir evenly and raise the temperature to 60℃ and react for 2.5 h. Then filter out solid impurities. Then continue to use lithium repulsion cation exchange resin containing sulfonic acid groups to remove the remaining impurity ions to obtain purified liquid.

[0076] S2. Under a nitrogen / CO2 mixed gas atmosphere, the particle size distribution is set to the median particle size D. 50 The particle size is 8 μm, and the 90% cumulative distribution particle size D 90 Battery-grade lithium carbonate micropowder with a particle size of 12 μm was heated at 700 °C for 4 h in a tube furnace to obtain pretreated seed crystals, wherein the proportion of CO2 in the nitrogen / CO2 mixed gas was 0.5 vol.%; 10 parts by mass of saturated sodium carbonate solution were pumped into the seed crystal dispersion tank, and then 0.5 parts of the pretreated seed crystals were added to the dispersion tank. The disperser was turned on and dispersed at high speed of 3500 rpm for 3 min to obtain seed crystal solution;

[0077] S3. Add 3 parts by mass of seed solution and 500 parts by mass of saturated sodium carbonate solution sequentially into lithium precipitation tank 1 through feed port 6. Turn on stirrer 4, then add 0.15 parts by mass of diethylenetriaminepentaacetic acid into lithium precipitation tank 1. Open steam valve 8 on lithium precipitation tank 1 to start heating. When the temperature inside lithium precipitation tank 1 reaches 90℃, open the closed annular structure distributor 2 to spray purification liquid into lithium precipitation tank 1. A1: Set the spray flow rate to 3.5m³ / h. 3 / h, stirrer 4 speed is 120r / min, after spraying for 50min, A2: set the spray flow rate to 7.5m 3 / h, stirrer 4 speed is 350r / min, continuous for 3h, A3: set spray flow rate to 2.5m 3 / h, stirrer 4 rotates at 100r / min, during which the mother liquor in the reactor is sampled and the carbonate concentration is detected. When the carbonate concentration drops to 15g / L, the feeder 2 is turned off, stirring is continued and the temperature is maintained for 20min. Then stirrer 4 is turned off. After the lithium precipitation reactor 1 has settled completely, the electric valve 7 is opened to discharge the supernatant in the lithium precipitation reactor 1.

[0078] S4. Repeat the above lithium precipitation steps to perform multiple lithium precipitation operations. After the settled solids in lithium precipitation tank 1 reach the upper limit of the effective volume of the lithium precipitation tank, stop discharging the supernatant and terminate the lithium precipitation step.

[0079] S5. Open the lower valve 9 on the lithium precipitation tank 1, transfer all the material in the lithium precipitation tank 1 to the centrifuge, start the first centrifugation, after the first centrifugation is completed, transfer the lithium carbonate to the washing tank, add centrifugation water three times, after the washing is completed, perform the second centrifugation, after the second centrifugation is completed, add condensed water to the washing tank for the second washing, after the second washing is completed, start the third centrifugation, after the centrifugation is completed, the initial lithium carbonate material and centrifugation water are obtained;

[0080] S6. Dry the lithium carbonate raw material, and after drying, pulverize it to obtain the battery-grade lithium carbonate described in Example 5.

[0081] Example 6

[0082] like Figure 4 As shown, a process for preparing battery-grade lithium carbonate based on mother liquor concentrate includes the following steps:

[0083] S1. Take 100 parts by weight of mother liquor water, filter, decarbonize and concentrate it to make the lithium content in the mother liquor water 9 g / L. Then add 0.1 parts by weight of chlorine dioxide to the mother liquor water, control the pH value of the mother liquor water to 3, the temperature to 50℃, stir and react for 2 hours. Then add 0.15 parts by weight of the first part of sodium hydroxide to the mother liquor water, stir and control the pH value to 3.5, and react at 35℃ for 2 hours. Then add 0.15 parts by weight of the second part of sodium hydroxide to the mother liquor water, stir and control the pH value to 6, and heat to 50℃ and react for 1.5 hours. Then filter to obtain mother liquor water with one purification. Add 0.2 parts by weight of sodium carbonate to the mother liquor water with one purification, stir evenly and heat to 60℃, react for 3 hours. Then filter out solid impurities. Then continue to use lithium repulsion cation exchange resin containing sulfonic acid groups to remove the remaining impurity ions to obtain purified liquid.

[0084] S2. Under a helium / CO2 mixed gas atmosphere, the particle size distribution is set to the median particle size D. 50 The particle size is 8 μm, and the 90% cumulative distribution particle size D 90 Battery-grade lithium carbonate micropowder with a particle size of 12 μm was heated at 650 °C for 4.5 h in a tube furnace to obtain pretreated seed crystals, wherein the proportion of CO2 in the helium / CO2 mixed gas was 1 vol.%; 10 parts by mass of saturated sodium carbonate solution was pumped into the seed crystal dispersion tank, and then 0.8 parts of the pretreated seed crystals were added to the dispersion tank. The disperser was turned on and dispersed at high speed of 3000 rpm for 5 min to obtain seed crystal solution;

[0085] S3. Add 5 parts by mass of seed solution and 500 parts by mass of saturated sodium carbonate solution sequentially into lithium precipitation tank 1 through feed port 6. Turn on stirrer 4, then add 0.2 parts by mass of ethylenediaminetetrapropionic acid into lithium precipitation tank 1. Open steam valve 8 on lithium precipitation tank 1 to start heating. When the temperature inside lithium precipitation tank 1 reaches 95℃, open the closed annular structure feeder 2 to spray purification liquid into lithium precipitation tank 1. A1: Set the spray flow rate to 4m³ / h. 3 / h, stirrer 4 speed is 150r / min, after spraying for 56min, A2: set the spray flow rate to 7.5m 3 / h, stirrer 4 speed is 400r / min, continuous for 3h, A3: spray flow rate is 3m 3 / h, stirrer 4 rotates at 100r / min, during which the mother liquor in the reactor is sampled and the carbonate concentration is detected. When the carbonate concentration drops to 15g / L, the feeder 2 is turned off, stirring is continued and the temperature is maintained for 15min, then the stirrer 4 is turned off. After the lithium precipitation reactor 1 has settled completely, the electric valve 7 is opened to discharge the supernatant in the lithium precipitation reactor 1.

[0086] S4. Repeat the above lithium precipitation steps to perform multiple lithium precipitation operations. After the settled solids in lithium precipitation tank 1 reach the upper limit of the effective volume of the lithium precipitation tank, stop discharging the supernatant and terminate the lithium precipitation step.

[0087] S5. Open the lower valve 9 on the lithium precipitation tank 1, transfer all the material in the lithium precipitation tank 1 to the centrifuge, start the first centrifugation, after the first centrifugation is completed, transfer the lithium carbonate to the washing tank, add centrifugation water three times, after the washing is completed, perform the second centrifugation, after the second centrifugation is completed, add condensed water to the washing tank for the second washing, after the second washing is completed, start the third centrifugation, after the centrifugation is completed, the initial lithium carbonate material and centrifugation water are obtained;

[0088] S6. Dry the lithium carbonate raw material, and after drying, pulverize it to obtain the battery-grade lithium carbonate described in Example 6.

[0089] Comparative Example 1

[0090] The difference between Comparative Example 1 and Example 2 is that hydrogen peroxide was not used to oxidize the mother liquor. All other steps are the same as in Example 2 and will not be repeated here.

[0091] Comparative Example 2

[0092] The difference between Comparative Example 2 and Example 2 is that the pH value was not adjusted in stages to precipitate impurities in the mother liquor water. All other steps are the same as in Example 2 and will not be repeated here.

[0093] Comparative Example 3

[0094] The difference between Comparative Example 3 and Example 2 is that the lithium carbonate seed crystals were not subjected to heat treatment under an inert atmosphere. All other steps were the same as in Example 2 and will not be repeated here.

[0095] The lithium carbonate content and impurity content in the battery-grade lithium carbonate prepared in Examples 2 to 6 and Comparative Examples 1 to 3 were determined by chemical analysis.

[0096] The test results are shown in Table 1.

[0097] Table 1. Test results of battery-grade lithium carbonate content obtained in Examples 2-6 and Comparative Examples 1-3

[0098]

[0099] As shown in Table 1, the purity of battery-grade lithium carbonate prepared in Examples 2-6 is significantly higher than that in Comparative Examples 1-3. This is mainly because Comparative Example 1, compared to Examples 2-6, lacks the step of oxidizing metal cations with an oxidant. This step allows more metal cation impurities in the mother liquor to precipitate during the subsequent precipitation process, greatly reducing the content of metal cation impurities. Compared to Examples 2-6, Comparative Example 2 lacks the steps of adding an oxidant and adjusting the pH in stages for precipitation. Directly adjusting the pH value to a wide range easily forms colloids that adsorb lithium ions, which is also not conducive to the effective removal of metal cation impurities. Compared to Examples 2-6, Comparative Example 3 did not perform high-temperature heat treatment on the seed crystals, resulting in more defect sites on the seed crystal surface. During the lithium precipitation process, impurities such as calcium and magnesium are easily adsorbed, thus causing a decrease in the purity of lithium carbonate.

[0100] The above test results are sufficient to demonstrate that this application can effectively utilize mother liquor water to produce high-purity battery-grade lithium carbonate, solving the problems existing in the prior art.

[0101] It should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications and substitutions should be covered within the scope of the claims of this application.

Claims

1. A process for preparing battery-grade lithium carbonate based on mother liquor concentrate, characterized in that, Includes the following steps: S1. The mother liquor is subjected to filtration, decarbonization, concentration, oxidation, and impurity removal steps to obtain a purified liquid; in the impurity removal step, the pH value of the mother liquor is controlled in stages. First, a first part of sodium hydroxide is added to the mother liquor, stirred evenly, and the pH value is controlled at 3.5~4, the temperature is 30~40℃, and the reaction is carried out for 1~2 hours; then a second part of sodium hydroxide is added to the mother liquor, stirred evenly, the pH value is controlled at 5~6, and the temperature is raised to 45~50℃, and the reaction is carried out for 1.5~2 hours. Then, the mother liquor is filtered to obtain the mother liquor after one impurity removal. S2. The seed crystals are heat-treated in an inert gas / CO2 mixed gas atmosphere and held at the temperature for 4-5 hours to obtain pretreated seed crystals. The pretreated seed crystals are then prepared into a seed crystal solution. The heat treatment temperature is 650-700℃. S3. Add the seed solution to the lithium precipitation tank and carry out the lithium precipitation step; the lithium precipitation step is as follows: add saturated sodium carbonate solution to the lithium precipitation tank, add chelating agent while stirring, heat to 85~95℃, spray purification liquid into the tank, after the lithium precipitation is completed, keep warm and stir, then let stand, and after the sedimentation is complete, discharge the supernatant. S4. Repeat the above lithium precipitation steps until the settled solids in the lithium precipitation tank reach the upper limit of the effective volume of the lithium precipitation tank, then stop discharging the supernatant and terminate the lithium precipitation steps. S5. Centrifuge all materials in the lithium precipitation vessel. After the first centrifugation, wash the lithium carbonate with centrifugal water. After the washing, centrifuge again. After the second centrifugation, wash the lithium carbonate with deionized water again. After the second washing, start the third centrifugation. After centrifugation, the initial lithium carbonate and the centrifugal water are obtained. S6. Dry the lithium carbonate raw material, and after drying, crush it to obtain battery-grade lithium carbonate.

2. The process for preparing battery-grade lithium carbonate based on mother liquor concentrate according to claim 1, characterized in that, The lithium content in the concentrated mother liquor water described in S1 is 7~9 g / L; the oxidant used in the oxidation step includes any one of hydrogen peroxide, ozone water and chlorine dioxide.

3. The process for preparing battery-grade lithium carbonate based on mother liquor concentrate according to claim 1, characterized in that, The oxidation step described in S1 is as follows: add (0.01~0.1) parts by mass of oxidant to 100 parts by mass of mother liquor water, and control the pH value of the mother liquor water to 2~3, the temperature to 25~50℃, and react for 0.5~2 hours after stirring evenly; The impurity removal step further includes: adding sodium carbonate to the mother liquor water after the first impurity removal, stirring evenly and heating to 60°C, reacting for 2-3 hours, then filtering out solid impurities, and using ion exchange resin to remove the remaining impurity ions to obtain purified liquid; the mass ratio of mother liquor water, first part sodium hydroxide, second part sodium hydroxide and sodium carbonate in the impurity removal step is 100: (0.15~0.45): (0.09~0.3): (0.05~0.2).

4. The process for preparing battery-grade lithium carbonate based on mother liquor concentrate according to claim 3, characterized in that, The ion exchange resin includes any one of lithium-repellent cation exchange resins containing sulfonic acid groups or carboxylic acid groups.

5. The process for preparing battery-grade lithium carbonate based on mother liquor concentrate according to claim 1, characterized in that, The seed crystals mentioned in S2 are battery-grade lithium carbonate micropowder, with a particle size distribution of median particle size D. 50 The particle size D is 3~8μm, and has a 90% cumulative distribution. 90 The particle size is not greater than 15 μm; the inert gas includes any one of nitrogen, argon and helium; the proportion of CO2 in the mixed gas is 0.5~1 vol.%; the seed solution is prepared by pumping 10 parts by mass of saturated sodium carbonate solution into the seed dispersion tank, then adding (0.5~1) parts by mass of pretreated seed crystals into the dispersion tank, turning on the disperser, and dispersing at a speed of 2000~5000 rpm for 2~5 min to obtain the seed solution.

6. The process for preparing battery-grade lithium carbonate based on mother liquor concentrate according to claim 1, characterized in that, The chelating agent described in S3 includes any one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetrapropionic acid, hydroxyethylidene diphosphonic acid, and aminotrimethylenephosphonic acid; the mass ratio of the saturated sodium carbonate solution, seed solution, and chelating agent is 500:(3~5):(0.1~0.2).

7. The process for preparing battery-grade lithium carbonate based on mother liquor concentrate according to claim 1, characterized in that, The process for the spray purification liquid described in S3 is segmented spraying, including: A1: Set the spray flow rate to 3~4m 3 / h, stirring speed is 100~150r / min, spraying time is 50~60min; A2: Set the spray flow rate to 7~8m 3 / h, stirring speed is 300~400r / min, spraying time is 2~3h; A3: Set the spray flow rate to 2~3m 3 The stirring speed is 80~100r / min / h. During this period, the mother liquor in the reactor is sampled and the carbonate concentration is tested. When the carbonate concentration drops to 14~17g / L, the lithium precipitation is stopped.

Images