Process for the preparation of battery-grade lithium carbonate from spodumene by a short process

Abstract

This invention relates to the field of lithium extraction technology from ores, specifically a short-process method for preparing battery-grade lithium carbonate from spodumene, comprising the following steps: reacting β-lithium concentrate with soda ash under heating and pressure, followed by the introduction of carbon dioxide to obtain a mixed slurry of lithium bicarbonate solution and leaching residue; removing impurities; pyrolyzing under ultrasonic vibration and negative pressure to obtain wet lithium carbonate; and directly obtaining battery-grade lithium carbonate after filtration and drying. The advantages of this invention are a short process, high yield, no wall agglomeration, and low pyrolysis temperature.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from ores, specifically a short-process method for preparing battery-grade lithium carbonate from spodumene. Background Technology

[0002] Lithium, as a crucial rare element for promoting modernization and the development of related industries such as science and technology, is one of the most promising new energy sources and strategic resources. It is widely used in high-energy lithium batteries, the rubber industry, aerospace, ceramics, lasers, medicine, welding, explosives, cement, metallurgy, and new energy, earning it the title of "the energy metal of the 21st century." Many countries, considering both economic development needs and national security, have designated lithium resources as strategic reserves and are conducting extensive research into its application technologies.

[0003] Existing lithium extraction processes from ores mainly include the sulfuric acid process, lime process, and sulfate process, among which the sulfuric acid process is currently the mainstream process.

[0004] Patent CN103950956A discloses a process for producing lithium carbonate from spodumene concentrate using the sulfuric acid method. However, the lithium leaching solution obtained by this method has a high impurity content and a long process flow.

[0005] Patents CN109133118A, CN 103011207 A, and CN 101948124 B disclose a process for preparing lithium carbonate by pressure boiling of spodumene and soda ash. The specific steps include roasting, leaching, carbonation, and impurity removal, with the final pyrolysis yielding lithium carbonate. The separate steps of leaching and carbonation make the process lengthy, and the generated lithium carbonate is prone to forming scale rings on the inner wall of the reactor, requiring additional cleaning and descaling steps, making industrialization difficult. At the same time, the use of ordinary pyrolysis methods has the problem of lithium carbonate easily forming on the reactor wall, resulting in significant lithium loss.

[0006] Meanwhile, lithium carbonate obtained by traditional methods has a large particle size and requires further crushing.

[0007] Therefore, there is an urgent need to provide a lithium extraction process that is short, simple, has a high recovery rate, high product purity, and is green and efficient. Summary of the Invention

[0008] This invention provides a short-process method for preparing battery-grade lithium carbonate from spodumene, which solves the problems existing in the prior art.

[0009] One of the objectives of this invention is to directly introduce carbon dioxide after leaching and cooling to convert slightly soluble lithium carbonate into soluble lithium bicarbonate, thereby solving the problem of lithium loss and reduced equipment heat transfer efficiency caused by the agglomeration of lithium carbonate and the entrainment of sodium aluminum silicate leaching residue, which forms a large amount of scale. This enables a short-process lithium extraction from spodumene.

[0010] The second objective of this invention is to solve the problems of lithium carbonate agglomeration, large lithium loss, and low direct recovery rate in the pyrolysis process of purified lithium bicarbonate solution by using negative pressure ultrasound, so as to improve the recovery rate of battery-grade lithium carbonate.

[0011] This invention discloses a short-process method for preparing battery-grade lithium carbonate from spodumene, comprising the following steps:

[0012] S1, β-lithium concentrate and soda ash react under heating and pressure, and after cooling, carbon dioxide is directly introduced into the reactor to reach positive pressure, so as to obtain a mixed slurry of lithium bicarbonate solution and leaching residue in one step.

[0013] S2. After solid-liquid separation and impurity removal, the mixed slurry yields a lithium bicarbonate solution.

[0014] S3. Lithium bicarbonate solution is subjected to negative pressure ultrasonic pyrolysis to obtain lithium carbonate mixture;

[0015] S4. The mixture obtained in step S3 is directly used to obtain battery-grade lithium carbonate after solid-liquid separation and drying.

[0016] Preferably, the temperature in step S1 is 205-235°C, and more preferably, the temperature is 225°C.

[0017] Preferably, the pressure in step S1 is 2.4 to 3.4 MPa, more preferably, the pressure is 3.0 MPa.

[0018] Furthermore, the pressure at which carbon dioxide is introduced in step S1 does not exceed 0.6 MPa.

[0019] Furthermore, step S2 also includes a purification step, wherein the purification step employs at least one of resin purification and reagent purification.

[0020] Preferably, the ultrasonic frequency in step S3 is 24 kHz.

[0021] Preferably, the negative pressure in step S3 is -0.08 MPa.

[0022] Preferably, the pyrolysis temperature in step S3 is 79°C.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. After leaching lithium carbonate with alkaline solution, there is no need for filtration and separation. Carbon dioxide can be directly introduced to prepare lithium bicarbonate. The process is short, the loss is small, and there is no need to descale the equipment.

[0025] 2. The pyrolysis step utilizes a combination of ultrasonic waves and negative pressure to achieve the production of battery-grade lithium carbonate under relatively low temperature conditions, resulting in low energy consumption and high yield.

[0026] 3. The pyrolysis step utilizes a combination of ultrasonic waves and negative pressure, which simultaneously prevents the equipment from forming walls, simplifying subsequent processing.

[0027] 4. The obtained lithium carbonate product has a small particle size, eliminating the need for a crushing step. Attached Figure Description

[0028] Figure 1 Schematic diagram of the reaction vessel after step S1 (a is the diagram of Example 1, b is the diagram of Comparison 1)

[0029] Figure 2 Example 1: Experimental Results (a is the experimental diagram, b is the result diagram);

[0030] Figure 3 Comparative Example 2: Experimental Results (a is the experimental diagram, b is the result diagram);

[0031] Figure 4 Comparative Example 3: Experimental Results (a is the experimental diagram, b is the result diagram);

[0032] Figure 5 Comparative Example 4: Experimental results (a is the experimental diagram, b is the result diagram);

[0033] Figure 6 Comparative Example 5: Experimental Results (a is the experimental diagram, b is the result diagram);

[0034] Figure 7 Example 1: SEM image of lithium carbonate product;

[0035] Figure 8 Comparative Example 5: SEM image of lithium carbonate product;

[0036] Figure 9 This application process flowchart. Detailed Implementation

[0037] The specific embodiments of the present invention will be further described below with reference to the examples. The following examples are only used to illustrate the technical embodiments of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0038] Example 1

[0039] A method for preparing battery-grade lithium carbonate from spodumene using a short process includes the following steps:

[0040] S1, β-lithium concentrate and soda ash were reacted at 225℃ and 3.0MPa for 1.5h, and then carbon dioxide was directly introduced to obtain a mixed slurry of lithium bicarbonate solution and leaching residue in one step.

[0041] S2. Filtration and impurity removal to obtain a purified lithium bicarbonate solution;

[0042] S3. Under ultrasonic oscillation and a negative pressure of -0.08 MPa, wet lithium carbonate is obtained by pyrolysis at 79°C.

[0043] S4. After filtration and drying, battery-grade lithium carbonate is obtained directly.

[0044] The setting of step S1 significantly shortens the reaction process, and its effectiveness can be demonstrated under the premise of comparable recovery rate.

[0045] To further illustrate the beneficial effects of the short process S1 of the present invention, comparative example 1 is provided:

[0046] Comparative Example 1

[0047] Comparative Example 1 was subjected to the following conventional leaching procedure: (the procedure disclosed in CN109133118A)

[0048] β-lithium concentrate and soda ash were reacted at 225℃ and 3.0MPa for 1.5 h.

[0049] The mixture is diluted with water and kept at a constant temperature, and then carbon dioxide is introduced to obtain a mixed slurry of lithium bicarbonate solution and leaching residue.

[0050] The difference between Comparative Example 1 and Step S1 of Example 1 lies in whether carbon dioxide is directly introduced under high pressure. Observations show that, compared to Comparative Example 1, the scaling phenomenon in the container of Example 1 is significantly reduced after the reaction (as shown in the attached figure). Figure 1 (As shown). It can be seen that the process of directly introducing carbon dioxide in this application has achieved unexpected results.

[0051] To further illustrate the beneficial effects of the present invention, comparative examples 2 to 5 are provided regarding the beneficial effects of step S3:

[0052] Comparative Examples 2-5

[0053] In Comparative Examples 2-5, only the operation method of step S3 differs from that of Example 1; the other steps are the same. The specific differences are as follows:

[0054] Table 1 Comparison of operating parameters between comparative examples and embodiments

[0055] Group Heating method Stirring method Pressure (MPa) Temperature (°C) Insulation time (h) Example 1 decompression ultrasound none -0.08 79 2 Comparative Example 2 Atmospheric pressure ultrasound none 0 79 4 Comparative Example 3 Pressure-reducing oil bath none -0.08 95 1 Comparative Example 4 Atmospheric pressure electric heating Magnetic stir bar 0 95 1 Comparative Example 5 Atmospheric oil bath stirring paddle 0 95 1

[0056] The effects of Example 1 and Comparative Examples 2-5 are as follows:

[0057] Table 2 Comparison of the effects of the embodiments and comparative examples

[0058] Group Heating method Direct collection rate (%) Phenomenon Experimental results diagram Example 1 decompression ultrasound 82.39 No cell wall formation, higher yield Appendix Figure 2 Comparative Example 2 Normal pressure ultrasound 58.93 No cell wall formation, low yield Appendix Figure 3 Comparative Example 3 Pressure-reducing oil bath 55.62 Excessive cell wall formation, resulting in low yield. Appendix Figure 4 Comparative Example 4 Atmospheric pressure electric heating 65.50 It is prone to cell wall adhesion and has a low yield. Appendix Figure 5 Comparative Example 5 Atmospheric oil bath 75.93 Less cell wall formation, lower yield, requires stirring. Appendix Figure 6

[0059] The analysis mechanism is as follows:

[0060] 1. The maximum solubility of lithium carbonate at room temperature and pressure is approximately 1.4 g / L, and that of lithium bicarbonate is approximately 8.5 g / L. By using β-lithium concentrate and soda ash for pressurized leaching, followed by direct pressurized reaction with carbon dioxide, the solubility of lithium bicarbonate is further improved. This facilitates the one-step production of a lithium bicarbonate solution and slag mixture, solving the problem of amorphous growth and agglomeration on the solid surface during lithium carbonate crystallization, along with the formation of large amounts of scale from sodium aluminum silicate leaching residue. Compared to existing technologies, this reduces the need for filtration and re-hydrogenation of the leaching residue, while avoiding subsequent descaling steps, shortening the process flow and reducing production costs.

[0061] 2. In the process of preparing lithium carbonate from lithium bicarbonate solution by pyrolysis, a strong mechanical wave and negative pressure coupling effect are introduced. The strong mechanical wave can effectively prevent lithium carbonate from crystallizing on the inner wall of the reactor, assisting lithium carbonate to form smaller and more uniform crystals in the solution, and improving heat transfer efficiency and eliminating the need for a stirring device. The negative pressure can greatly reduce the pyrolysis temperature and promote the evaporation of the solvent, thereby reducing the solubility of lithium carbonate and achieving the goal of increasing the direct recovery rate of lithium carbonate.

[0062] This invention not only shortens the lithium extraction process and avoids the problem of scale formation inside the reactor, but also cleverly uses strong mechanical waves and negative pressure coupling to solve the problems of rapid nucleation and easy formation of lithium carbonate on the reactor walls. It can effectively improve the lithium recovery rate, produce small product particles, eliminate the need for crushing steps, reduce production costs, increase profits, and is suitable for practical applications in lithium carbonate production.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 short-process preparation of battery-grade lithium carbonate from spodumene, characterized in that, Includes the following steps: S1, β-lithium concentrate and soda ash react under heating and pressure, and after cooling, carbon dioxide is directly introduced into the reactor to reach positive pressure, so as to obtain a mixed slurry of lithium bicarbonate solution and leaching residue in one step. S2. After solid-liquid separation and impurity removal, the mixed slurry yields a lithium bicarbonate solution. S3. Lithium bicarbonate solution is subjected to negative pressure ultrasonic pyrolysis to obtain lithium carbonate mixture; S4. The mixture obtained in step S3 is directly used to obtain battery-grade lithium carbonate after solid-liquid separation and drying.

2. The method for preparing battery-grade lithium carbonate using spodumene in a short process according to claim 1, characterized in that, The heating temperature mentioned in step S1 is 205-235℃.

3. The method for preparing battery-grade lithium carbonate using spodumene in a short process according to claim 1, characterized in that, The pressurization pressure mentioned in step S1 is 2.4 to 3.4 MPa.

4. The method for preparing battery-grade lithium carbonate using spodumene in a short process according to claim 1, characterized in that, In step S1, the pressure of carbon dioxide introduced should not exceed 0.6 MPa.

5. The method for preparing battery-grade lithium carbonate using spodumene in a short process according to claim 1, characterized in that, Step S2 also includes a purification step, wherein the purification step employs at least one of resin purification and reagent purification.

6. The method for preparing battery-grade lithium carbonate using spodumene in a short process according to claim 1, characterized in that, The negative pressure in step S3 is -0.08 MPa.

7. The method for preparing battery-grade lithium carbonate using spodumene in a short process according to claim 1, characterized in that, The ultrasonic frequency in step S3 is 24 kHz.

8. The method for preparing battery-grade lithium carbonate using spodumene in a short process according to claim 1, characterized in that, The pyrolysis temperature in step S3 is 79℃.

9. The method for preparing battery-grade lithium carbonate using spodumene in a short process according to claim 1, characterized in that, The filtrate from step S4 can be recycled.

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