Method for recycling lithium-rich electrolyte lithium extraction waste residue
Through the treatment of acidic aluminum chloride solution and aluminum hydroxide particles and hydrofluoric acid, the problem of poor lithium extraction waste slag treatment in the electrolytic aluminum industry is solved, and the production of high-purity aluminum fluoride and the effective utilization of resources is achieved, avoiding the Environmental pollution and waste of resources.
Patent Information
- Application Number
- CN202411272278.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-11
- Publication Date
- 2024-12-13
AI Technical Summary
The lithium-rich electrolyte-extracting waste slag in the electrolytic aluminum industry is poorly treated, resulting in waste of resources and environmental pollution. It is difficult for the existing technology to effectively utilize the resources such as fluorine, aluminum, sodium and calcium in the remaining lithium-extracting waste slag.
Acid aluminum chloride solution reacts with lithium-rich electrolyte lithium-extracting waste residue, add aluminum hydroxide particles and hydrofluoric acid, and after stirring, filtration, washing and drying, high-purity aluminum fluoride products are obtained, avoiding the acid solution reaction and Difficulty in filtration improves product purity and resource utilization.
It realizes effective treatment of lithium-enhancing waste slag, avoids environmental pollution, improves resource utilization, and ensures high purity of aluminum fluoride products and the convenience of industrial production.
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Figure CN119118174A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of comprehensive utilization of electrolytic aluminum smelting slag, and in particular to a method for recycling lithium-rich electrolyte lithium-extracting waste slag. Background Art
[0002] Aluminum electrolyte waste slag containing lithium is produced when aluminum is produced industrially through cryolite-alumina molten salt electrolysis. The sources of these lithium can be divided into two parts, one part comes from the raw material bauxite, and the other part is to improve the properties of the electrolyte, a small amount of lithium fluoride is added. With the long-term operation of the system, the lithium salt content in the electrolyte system gradually increases, which will reduce the solubility of alumina, increase the superheat of the electrolyte, increase the precipitation at the bottom of the electrolytic cell, and shorten the service life of the electrolytic cell, affecting the economic benefits of aluminum electrolysis. Therefore, when the lithium content in the electrolyte is too high, it is necessary to discharge part of the electrolyte to control the balance of the system, and aluminum electrolyte waste slag containing lithium is produced.
[0003] According to statistics, the electrolytic aluminum industry produces millions of tons of aluminum electrolyte lithium-containing waste slag every year. In order to recycle solid waste resources and alleviate my country's current demand for lithium salts, people currently use a series of methods to extract and recycle lithium from lithium-containing waste slag, but there is no good way to dispose of the remaining lithium extraction waste slag. The remaining lithium extraction waste slag still contains about 45% fluorine, about 20% aluminum, about 15% sodium and about 5% calcium. If it is not used reasonably, it is undoubtedly a waste of resources.
[0004] Therefore, the present invention proposes a method for recycling lithium-rich electrolyte waste residue, which can achieve the treatment of lithium-extraction waste residue and avoid environmental pollution on the one hand, and also achieve resource utilization of lithium-extraction waste residue on the other hand, which is of great significance to environmental protection and resource conservation. Summary of the invention
[0005] The purpose of the present invention is to provide a method for recycling lithium-rich electrolyte waste residues, so as to solve the problem that the aluminum electrolytic industry currently extracts lithium from lithium-rich electrolytes, but has no good disposal method for the remaining lithium-extraction waste residues, resulting in waste of resources.
[0006] To achieve the above object, the present invention adopts the following technical scheme: a method for recycling lithium-rich electrolyte waste residue, comprising the following steps:
[0007] S1, taking lithium-rich electrolyte lithium extraction waste residue and preparing it into slurry;
[0008] S2, add acidic aluminum chloride solution to S1 slurry, add aluminum hydroxide particles to the reaction system after sufficient reaction, and stir evenly;
[0009] S3, filtering and washing the liquid after S2 is stirred evenly to obtain a solid component;
[0010] S4. Add hydrofluoric acid to the solid component obtained in S3, filter, wash and dry after sufficient reaction to obtain the aluminum fluoride product.
[0011] Furthermore, in the above S1, the lithium-rich electrolyte lithium extraction waste residue is the waste residue remaining after the lithium-rich electrolyte reacts with aluminum chloride acidic solution to dissolve lithium, and the main component of the waste residue is cryolite.
[0012] Furthermore, in the S2, the concentration of the acidic aluminum chloride solution is 0.5-1.5 mol / L, and the pH is controlled at 2-4; the ratio of the molar amount of aluminum chloride to the molar amount of cryolite in the aluminum chloride solution is 1-1.2:1.
[0013] Furthermore, in the S2, the reaction temperature is 70-90° C., the reaction time is 2-4 h, and the stirring intensity is 200-400 r / min.
[0014] Furthermore, in the S2, the particle size of the aluminum hydroxide particles is 40 to 60 meshes.
[0015] Furthermore, the amount of aluminum hydroxide particles added is 10-20% of the mass of the lithium extraction waste residue.
[0016] Furthermore, in the S3, the filtration is performed using a plate and frame filter press or a vacuum disc filter. When a plate and frame filter press is used, the filtration pressure is 3 to 4 MPa; when a vacuum disc filter is used, the filtration pressure is 1 to 2 MPa; after the filtration is completed, the filtration is washed with water 2 to 3 times.
[0017] Furthermore, in the S4, the mass fraction of hydrofluoric acid is 25-30%, and the liquid-to-solid ratio of hydrofluoric acid to solid components is 5-10:1.
[0018] Furthermore, in the S4, the reaction temperature is 70-90°C, the reaction time is 2-4h, and the stirring intensity is 200-300r / min; the filtration is performed using a plate and frame filter press or a vacuum disc filter, and the filtration is washed 2-3 times with water after completion; after washing, the mixture is dried at 500-600°C for 1-2h.
[0019] Furthermore, the purity of the aluminum fluoride product is above 99%.
[0020] Beneficial effects of the present invention:
[0021] 1. Directly using aluminum chloride solution to treat lithium extraction waste residue avoids the use of acid solution reaction, thereby effectively avoiding the generation of waste acid during the reaction process and contributing to environmental protection;
[0022] 2. Aluminum hydroxide particles are added to the reaction system after the reaction is completed. During the process, the pH of the reaction solution can be neutralized and the particles can also act as a filtering aid. Since aluminum chloride will inevitably hydrolyze to generate aluminum hydroxide during the reaction (the dissolution of calcium will consume acidity), the generated aluminum hydroxide is in a paste state and mixed with the generated aluminum fluoride, which makes it difficult to filter. The method of the present invention avoids the problem of filtering difficulties caused by the hydrolysis of aluminum chloride, which brings convenience to actual production applications.
[0023] 3. By adding aluminum hydroxide particles to react with hydrofluoric acid in the subsequent treatment process, the amount of the product can be increased and the purity can be guaranteed. There is no need to worry about the loss of resources, which is convenient for use in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a schematic diagram of the process flow of the method of the present invention. DETAILED DESCRIPTION
[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.
[0026] Example 1
[0027] 500 L of water was added to the reactor and 100 kg (absolutely dry) of lithium-rich electrolyte lithium extraction waste residue was slowly added to the reactor under stirring conditions.
[0028] After stirring evenly, add acidic aluminum chloride solution to the reactor, wherein the pH value of the acidic aluminum chloride solution is 3, the concentration is 1 mol / L, and the addition amount is 460 L; after the addition of the acidic aluminum chloride solution, react at 80°C, 300 r / min for 3 hours, and after the reaction is completed, add 15 kg of 60-mesh aluminum hydroxide particles to the reaction system. After the addition of aluminum hydroxide, continue to stir evenly and then filter.
[0029] In this embodiment, a plate and frame filter press is used for filtration, and the filtration pressure is 3.5 MPa. After the filtration is completed, the solid components are washed three times with water, and the obtained solid components are loose in shape and not compacted.
[0030] Add 800L of hydrofluoric acid solution (liquid-to-solid ratio is 8:1, which is the ratio of volume to mass, the same below) to the reactor, the mass fraction of the hydrofluoric acid solution is 26%, and then add the filtered solid components to the reactor, react at 80°C and 250r / min stirring intensity for 3h, and discharge the material after the reaction.
[0031] The discharged material is filtered through a plate and frame filter press, washed with water after filtration, and dried at 550° C. for 1.5 h to obtain the aluminum fluoride product of the present invention. After testing, the purity of the aluminum fluoride product of this embodiment is 99.37%.
[0032] Comparative Example 1
[0033] In this comparative example, the step of adding aluminum hydroxide particles was omitted, and the rest was the same as in Example 1.
[0034] Finally, the equipment pressure continued to increase during filtration, and in order to ensure production safety, the filtration was terminated.
[0035] After investigation, it was found that during the reaction of aluminum chloride solution and lithium extraction waste residue, hydrolysis of aluminum chloride solution occurred. The aluminum chloride solution was hydrolyzed to produce paste-like aluminum hydroxide. The paste-like aluminum hydroxide and the produced aluminum fluoride were mixed together, making the material very viscous, which seriously affected the subsequent filtration process.
[0036] Comparative Example 2
[0037] In this comparative example, the particle size of the added aluminum hydroxide is 100 mesh, and the rest is the same as in Example 1.
[0038] Finally, the equipment pressure continued to increase during filtration, and in order to ensure production safety, the filtration was terminated.
[0039] The reason for this comparative example is the same as that of comparative example 1, which indicates that the aluminum hydroxide particle size is too small and cannot play a filtering aid role.
[0040] Comparative Example 3
[0041] In this comparative example, the particle size of the added aluminum hydroxide particles is 20 mesh, and the rest is the same as in Example 1.
[0042] After adding aluminum hydroxide particles, the solution filtering effect is good, and the obtained aluminum fluoride is tested, and the purity of the aluminum fluoride is 96.31%.
[0043] This is probably because the particle size of aluminum hydroxide is too large, resulting in incomplete reaction during the subsequent reaction.
[0044] Comparative Example 4
[0045] In this comparative example, no aluminum hydroxide particles were added. In order to control the hydrolysis of aluminum chloride, hydrochloric acid solution was continuously added during the reaction to maintain the pH stability of the reaction solution. Other conditions were the same as in Example 1.
[0046] After the reaction between aluminum chloride and lithium extraction waste residue is completed, the reaction liquid is filtered. During the process, the filtration pressure continues to rise and the filtration is finally completed at about 8MPa. The resulting filter cake is very sticky and sticks to each other into lumps, making it difficult to separate.
[0047] After separation, the solid component is washed with water, and hydrofluoric acid is added to the solid component to continue the reaction. The reaction conditions are the same as those in Example 1 to obtain an aluminum fluoride product.
[0048] The aluminum fluoride product was tested and found to have a purity of 98.13%.
[0049] It can be seen that the purity of the obtained product is significantly lower than that of Example 1. It is found during the production process that even if hydrochloric acid is added in time, although the hydrolysis of aluminum chloride can be inhibited, it is difficult to completely avoid the hydrolysis of aluminum chloride under high temperature conditions; in actual operation, partial hydrolysis will still occur and affect the subsequent filtration and separation.
[0050] In addition, even if hydrofluoric acid is added to continue the reaction, it is found in practice that the material in the reactor will clump. This is closely related to the high-pressure pressing during the filtration process. It is difficult to mix evenly and fully react in subsequent reactions, which is also an important factor leading to low product purity.
[0051] Although it can be expected that the final result may be close to the effect of Example 1 by continuously increasing the amount of hydrochloric acid in the reaction stage of aluminum chloride and lithium extraction waste slag, and continuously increasing the stirring intensity in the subsequent hydrofluoric acid reaction stage, the raw material consumption and energy consumption in the process will increase geometrically, which is completely unfavorable for use in actual production.
[0052] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.
Claims
1. A method for recycling lithium-rich electrolyte waste residue, characterized in that: The following steps are involved: S1, taking lithium-rich electrolyte lithium extraction waste residue and preparing it into slurry; S2, add acidic aluminum chloride solution to S1 slurry, add aluminum hydroxide particles to the reaction system after sufficient reaction, and stir evenly; S3, filtering and washing the liquid after S2 is stirred evenly to obtain a solid component; S4. Add hydrofluoric acid to the solid component obtained in S3, filter, wash and dry after sufficient reaction to obtain the aluminum fluoride product.
2. The method for recycling lithium-rich electrolyte waste residue according to claim 1, characterized in that: In the above S1, the lithium-rich electrolyte lithium extraction waste residue is the waste residue remaining after the lithium-rich electrolyte reacts with aluminum chloride acid solution to dissolve lithium, and the main component of the waste residue is cryolite.
3. The method for recycling lithium-rich electrolyte waste residue according to claim 2, characterized in that: In the S2, the concentration of the acidic aluminum chloride solution is 0.5-1.5 mol / L, and the pH is controlled at 2-4; the ratio of the molar amount of aluminum chloride to the molar amount of cryolite in the aluminum chloride solution is 1-1.2:
1.
4. The method for recycling lithium-rich electrolyte waste residue according to claim 3, characterized in that: In the S2, the reaction temperature is 70-90°C, the reaction time is 2-4h, and the stirring intensity is 200-400r / min.
5. The method for recycling lithium-rich electrolyte waste residue according to claim 1, characterized in that: In the S2, the particle size of the aluminum hydroxide particles is 40 to 60 meshes.
6. The method for recycling lithium-rich electrolyte waste residue according to claim 5, characterized in that: The amount of aluminum hydroxide particles added is 10-20% of the mass of the lithium extraction waste residue.
7. The method for recycling lithium-rich electrolyte waste residue according to claim 1, characterized in that: In the S3, the filtration is carried out by a plate and frame filter press or a vacuum disc filter. When the plate and frame filter press is used, the filtration pressure is 3 to 4 MPa; when the vacuum disc filter is used, the filtration pressure is 1 to 2 MPa; after the filtration is completed, the filtration is washed with water 2 to 3 times.
8. The method for recycling lithium-rich electrolyte waste residue according to claim 1, characterized in that: In the S4, the mass fraction of hydrofluoric acid is 25-30%, and the liquid-to-solid ratio of hydrofluoric acid to lithium-rich electrolyte lithium extraction waste residue is 5-10:
1.
9. The method for recycling lithium-rich electrolyte waste residue according to claim 8, characterized in that: In the S4, the reaction temperature is 70-90°C, the reaction time is 2-4h, and the stirring intensity is 200-300r / min; the filtration is performed using a plate and frame filter press or a vacuum disc filter, and the filtration is washed 2-3 times with water after completion; after washing, the mixture is dried at 500-600°C for 1-2h.
10. The method for recycling lithium-rich electrolyte waste residue according to claim 1, characterized in that: The purity of the aluminum fluoride product is above 99%.