Lithium chloride mother liquor refining system for extracting lithium from salt lake

Abstract

The utility model discloses a lithium chloride mother liquor refining system for extracting lithium from a salt lake, which comprises a sodium sulfate dissolving kettle, a primary crystallization reaction kettle, a primary plate-and-frame filter press, a secondary crystallization reaction kettle, a secondary plate-and-frame filter press, a microporous filter element filter, nano-filtration equipment, a resin adsorption filter, a filter residue stirring kettle and a precipitation residue filter press, the sodium sulfate dissolving kettle is communicated with the interior of the primary crystallization reaction kettle through a sodium sulfate solution pipeline, the filter residue stirring kettle is communicated with slag outlets of the primary plate-and-frame filter press and the secondary plate-and-frame filter press, and the filter residue stirring kettle is communicated with the interior of the sodium sulfate dissolving kettle through a precipitation slag filter press. Compared with the prior art, the lithium chloride mother liquor is used as a raw material, insoluble impurities, soluble ions and organic matters in the raw material are removed through deep crystallization and impurity removal, solid-liquid separation of precipitates is easy, and meanwhile, entrainment of lithium ions in the precipitates is reduced, so that lithium chloride refined liquor is obtained, and 99.9% battery-grade lithium carbonate can be directly prepared in a lithium precipitation process.

Description

Technical Field

[0001] The utility model relates to the field of chemical industry, in particular to a lithium chloride mother liquor refining system for extracting lithium from a salt lake. Background Art

[0002] At present, lithium resources are mainly distributed in ores (spodumene, lepidolite, etc.), seawater and brine. The method of roasting and leaching is used to extract lithium from ores. The steps are cumbersome. A large amount of chemicals are used in the production process, which produces acidic wastewater and solid waste, causing water pollution, soil pollution, and air pollution. The total mass of lithium in seawater is abundant, but the concentration of lithium in seawater is very low, and it is challenging to selectively extract lithium from seawater. Brine includes salt lake brine, oilfield brine and geothermal brine, among which salt lake brine accounts for the largest proportion. More than 70% of the world's recoverable lithium exists in brine. Lithium extraction from brine is more effective, simpler and more economical.

[0003] The difficulty of mining lithium resources in salt lakes is not only determined by the concentration of lithium ions in the brine of the salt lake, but is also affected by other cations in the brine, especially the content of calcium and magnesium ions in the brine.

[0004] In recent years, with the strong support of the state for new energy vehicle companies, the sales of new energy vehicles have increased, the demand for power lithium batteries has increased, and the demand for lithium carbonate and lithium hydroxide as raw materials for synthesizing various lithium-ion battery materials has continued to rise, and the price has continued to rise. With the rapid development of lithium-ion batteries, the quality, output and price of lithium carbonate and lithium hydroxide have received widespread attention. The quality of lithium carbonate and lithium hydroxide is affected by the impurities in the lithium chloride mother liquor after lithium extraction from brine, so the refining process of lithium chloride mother liquor has become increasingly important.

[0005] The composition of salt lake brine is complex and diverse. Brine is a mixed solution of multiple salts with high mineralization, and the salt content is greater than 50g / L. According to statistics, salt lake brine contains more than 60 chemical components, among which Na + , K + , Ca 2+ Mg 2+ , Cl - 、SO4 2- 、HCO3 - and CO3 2- It is the main chemical component, and the remaining 52 chemical components include heavy metal elements, heavy radioactive elements, rare elements and alkali metal elements and other minor components.

[0006] At present, the technology for extracting lithium resources from salt lakes mainly adopts precipitation method. The precipitation method is to use lithium precipitation method to separate impurity ions such as magnesium, calcium, boron and so on in brine from lithium, and add precipitant or salting-out agent when the lithium concentration is appropriate to make it precipitate in the form of precipitation. The existing lithium chloride impurity removal process first uses oxalic acid to precipitate calcium oxalate, and after squeezing by a press, the filtrate is passed through a resin boron removal system to remove boron, and sodium carbonate and sodium hydroxide are added to precipitate calcium carbonate and magnesium hydroxide. After squeezing by a press, hydrochloric acid is added for neutralization and filtration, and the filtrate is directly sent to a multi-effect concentration system. After concentration, it is cooled by three stages to precipitate sodium, and the clear liquid is purified to complete the lithium precipitation process.

[0007] The existing impurity removal technology not only precipitates calcium and magnesium, but also takes away a large amount of lithium. The recovery rate of lithium resources is low. At the same time, there are still a large number of organic impurities in the mother liquor that have not been removed. The calcium and magnesium precipitates easily form colloids, which are difficult to filter and take a long time to filter. As a result, the product quality of the back-end lithium precipitation process does not meet the standards of battery-grade lithium carbonate. Utility Model Content

[0008] The purpose of the utility model is to provide a lithium chloride mother liquor refining system for extracting lithium from salt lakes which solves the above-mentioned problem.

[0009] In order to achieve the above-mentioned purpose, the technical scheme adopted by the utility model is: a lithium chloride mother liquor refining system for lithium extraction from salt lakes, comprising a sodium sulfate dissolving kettle, a primary crystallization reactor, a primary plate and frame filter press, a secondary crystallization reactor, a secondary plate and frame filter press, a microporous filter element filter, a nanofiltration device, a resin adsorption filter, a filter residue stirring kettle and a precipitated residue filter press, wherein the primary crystallization reactor, the primary plate and frame filter press, the secondary crystallization reactor, the secondary plate and frame filter press, the microporous filter element filter, the nanofiltration device and the resin adsorption filter are sequentially connected through a lithium chloride delivery pipeline, the sodium sulfate dissolving kettle is connected to the interior of the primary crystallization reactor through a sodium sulfate solution pipeline, the filter residue stirring kettle is respectively connected to the slag outlets of the primary plate and frame filter press and the secondary plate and frame filter press through a filter residue pipeline, a condensate inlet pipe and a condensate outlet pipe are connected to the filter residue stirring kettle, the filter residue stirring kettle is connected to the precipitated residue filter press through the condensate outlet pipe, and the filtrate outlet of the precipitated residue filter press is connected to the interior of the sodium sulfate dissolving kettle through a filtrate pipeline.

[0010] Preferably, it further comprises a primary seed configuration box and a secondary seed configuration box, wherein the concentrate water outlet of the nanofiltration device is connected to the interior of the primary seed configuration box and the secondary seed configuration box respectively through a concentrate water delivery pipeline, the primary seed configuration box is connected to the interior of the primary crystallization reactor through a seed output pipeline, and the secondary seed configuration box is connected to the interior of the secondary crystallization reactor through a seed output pipeline.

[0011] Preferably, the filter residue pipeline at the residue outlet of the primary plate and frame filter press is divided into two routes, one route is connected to the filter residue stirring kettle, and the other route is connected to the primary crystal seed configuration box; the filter residue pipeline at the residue outlet of the secondary plate and frame filter press is divided into two routes, one route is connected to the filter residue stirring kettle, and one route is connected to the secondary crystal seed configuration box.

[0012] Preferably, the primary crystallization reactor is connected to a lithium chloride mother liquor feed pipeline and a sodium hypochlorite feed pipeline.

[0013] Preferably, the secondary crystallization reactor is connected to a sodium hydroxide feed pipeline and an oxalic acid feed pipeline.

[0014] Preferably, the primary crystallization reaction kettle and the secondary crystallization reaction kettle are both crystallization reactors.

[0015] Preferably, the microporous filter element adopts an ultrafiltration membrane filter element, and the pore size of the ultrafiltration membrane is 0.01-0.1 μm.

[0016] Preferably, a transfer tank is provided on the lithium chloride delivery pipeline between the microporous filter element filter and the nanofiltration device.

[0017] Compared with the prior art, the utility model has the following advantages: the utility model uses lithium chloride mother liquor as raw material, removes insoluble impurities, soluble ions and organic matter in the raw material through deep crystallization and impurity removal, and the precipitate is easy to separate solid and liquid, while reducing the entrainment of lithium ions in the precipitate to obtain lithium chloride refined liquid, which can enable the lithium precipitation process to directly produce 99.9% battery-grade lithium carbonate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the system principle diagram of the utility model;

[0019] Figure 2 This is a process flow chart of the utility model.

[0020] In the figure, 1. sodium sulfate dissolving kettle; 2. primary crystallization reactor; 3. primary plate and frame filter press; 4. secondary crystallization reactor; 5. secondary plate and frame filter press; 6. microporous filter element filter; 7. nanofiltration equipment; 8. resin adsorption filter; 9. filter residue stirring kettle; 10. sedimentation residue filter press; 11. primary seed configuration box; 12. secondary seed configuration box; 13. transfer tank; 14. lithium chloride conveying pipeline; 15. sodium sulfate solution pipeline; 16. lithium chloride mother liquor feed pipeline; 17. sodium hypochlorite feed pipeline; 18. sodium hydroxide feed pipeline; 19. oxalic acid feed pipeline; 20. concentrated water conveying pipeline; 21. seed output pipeline; 22. filter residue pipeline; 23. condensate inlet pipe; 24. condensate outlet pipe; 25. filtrate pipeline. DETAILED DESCRIPTION

[0021] The utility model will be further described below.

[0022] A lithium chloride mother liquor refining system for lithium extraction from salt lakes, see Figure 1 , comprising a sodium sulfate dissolving kettle 1, a primary crystallization reactor 2, a primary plate-frame filter press 3, a secondary crystallization reactor 4, a secondary plate-frame filter press 5, a microporous filter element filter 6, a nanofiltration device 7, a resin adsorption filter 8, a filter residue stirring kettle 9 and a precipitated residue filter press 10, wherein the primary crystallization reactor 2, the primary plate-frame filter press 3, the secondary crystallization reactor 4, the secondary plate-frame filter press 5, the microporous filter element filter 6, the nanofiltration device 7 and the resin adsorption filter 8 are connected in sequence through a lithium chloride delivery pipeline 14, and the The sodium sulfate dissolving kettle 1 is connected to the interior of the primary crystallization reaction kettle 2 through the sodium sulfate solution pipeline 15, the filter residue stirring kettle 9 is connected to the slag outlets of the primary plate-frame filter press 3 and the secondary plate-frame filter press 5 through the filter residue pipeline 22, the filter residue stirring kettle 9 is connected to a condensed water inlet pipe 23 and a condensed water outlet pipe 24, the filter residue stirring kettle 9 is connected to the precipitated residue filter press 10 through the condensed water outlet pipe 24, and the filtrate outlet of the precipitated residue filter press 10 is connected to the interior of the sodium sulfate dissolving kettle 1 through the filtrate pipeline 25. The utility model uses lithium chloride mother liquor as raw material, removes insoluble impurities, soluble ions, and organic matter in the raw material through deep crystallization and impurity removal, and the precipitate is easy to separate solid and liquid, while reducing the entrainment of lithium ions in the precipitate, to obtain lithium chloride refined liquid, which can directly produce 99.9% battery-grade lithium carbonate in the lithium precipitation process.

[0023] For detailed process flow, see Figure 2 ,as follows:

[0024] (1) Dissolve sodium sulfate in water, raise the temperature to 60°C, and obtain a sulfate ion concentration of 57-58.5 g / l;

[0025] (2) using calcium sulfate as a seed crystal, and pre-preparing a calcium sulfate suspension having a solid content of 2.5 to 4% in a primary crystallization reactor;

[0026] (3) adding lithium chloride mother liquor (lithium content 40-60 g / l) into a primary crystallization reactor, heating to 60° C., sequentially adding sodium hypochlorite and sodium sulfate solution for reaction, the reaction time is 90 min, chemical impurity removal is performed, and the sulfate ion concentration at the reaction end point is 2-3 g / l;

[0027] (4) subjecting the reaction liquid after chemical impurity removal to plate-and-frame filter pressing to obtain a primary impurity-removed filtrate and calcium sulfate slag, and part of the calcium sulfate slag is returned for crystal seed configuration;

[0028] (5) using calcium oxalate and magnesium hydroxide as seed crystals, and pre-preparing a calcium oxalate and magnesium hydroxide suspension having a solid content of 2.5 to 4% in a secondary crystallization reactor;

[0029] (6) adding the crude impurity-removed filtrate to a secondary crystallization reactor, heating it to 80° C., adding oxalic acid and sodium hydroxide solution in turn to react, controlling the solution pH to 11 to 12.5, reacting for 60 min, and performing chemical impurity removal. At the reaction end point, the oxalate ion concentration is 1.5 to 2 g / l, and the hydroxide ion concentration is 0.5 to 1 g / l;

[0030] (7) subjecting the reaction liquid after the secondary chemical impurity removal to plate-and-frame filter pressing to obtain the secondary impurity removal filtrate and calcium oxalate and magnesium hydroxide slag, and part of the calcium sulfate slag is returned for crystal seed configuration;

[0031] (8) ultrafiltration of the secondary impurity removal filtrate, wherein the pore size of the ultrafiltration membrane is 0.01 to 0.1 μm;

[0032] (9) subjecting the ultrafiltration filtrate to nanofiltration, wherein the sulfate ion concentration of the nanofiltration filtrate is less than 1 g / l, and the total calcium and magnesium ion concentration is less than 4 ppm, and the nanofiltration concentrated water is returned for crystal seed preparation;

[0033] (10) treating the nanofiltration filtrate with an ion exchange resin to obtain a refined lithium chloride solution, wherein the concentrations of calcium, magnesium, sulfate, and boron ions in the refined solution are less than 5 ppb;

[0034] In order to realize the recycling of lithium ions in the filter residue, the utility model recycles the calcium sulfate residue generated by the primary plate-frame filter press 3 and the calcium oxalate and magnesium hydroxide residue generated by the secondary plate-frame filter press 5 through the filter residue stirring kettle 9, and stirs by introducing the evaporation condensation water of the waste salt after lithium precipitation from the condensation water inlet pipe 23, and introduces the evaporation condensation water of the waste salt after lithium precipitation generated by the back-end program, so as to realize the reuse of waste water, and then filter through the sediment filter press 10 after stirring and washing, and the filtrate after the filtration is returned for the preparation of sodium sulfate solution, and the filter residue is discharged. Not only the reuse of the plate-frame slag washing water is realized, but also the lithium ions in the sediment residue can be recovered, and the lithium resource recovery rate is improved, so that the lithium resource recovery rate is ≥95%.

[0035] The utility model also includes a primary seed configuration box 11 and a secondary seed configuration box 12. The concentrated water outlet of the nanofiltration device 7 is connected to the interior of the primary seed configuration box 11 and the secondary seed configuration box 12 through a concentrated water delivery pipeline 20. The primary seed configuration box 11 is connected to the interior of the primary crystallization reactor 2 through a seed output pipeline 21. The secondary seed configuration box 12 is connected to the interior of the secondary crystallization reactor 4 through a seed output pipeline 21. The filter residue pipeline 22 of the slag outlet of the primary plate-frame filter press 3 is divided into two paths, one of which is connected to the filter residue stirring kettle 9 and the other is connected to the primary seed configuration box 11. The filter residue pipeline 22 of the slag outlet of the secondary plate-frame filter press 5 is divided into two paths, one of which is connected to the filter residue stirring kettle 9 and the other is connected to the secondary seed configuration box 12. The concentrated water delivery pipeline 20 is used to realize the recycling of the nanofiltration concentrated water of the nanofiltration device 7, and the configuration and delivery of the seeds are carried out through the seed output pipeline 21 and the filter residue pipeline 22.

[0036] The primary crystallization reactor 2 is connected to a lithium chloride mother liquor feed pipe 16 and a sodium hypochlorite feed pipe 17, and sodium hypochlorite is used to remove organic matter to prevent cross-linking and accumulation of precipitate crystals and gelling. The secondary crystallization reactor 4 is connected to a sodium hydroxide feed pipe 18 and an oxalic acid feed pipe 19, and oxalic acid and sodium hydroxide solutions are used for chemical impurity removal.

[0037] The utility model performs chemical impurity removal through a primary crystallization reactor 2 and a secondary crystallization reactor 4. Both the primary crystallization reactor 2 and the secondary crystallization reactor 4 adopt crystallization reactors. The generated precipitate has no colloid and is easy to filter. The precipitation filtering speed of crystallization impurity removal can be increased by 10 times compared with the existing process.

[0038] The microporous filter element filter 6 adopts an ultrafiltration membrane filter element, and the pore size of the ultrafiltration membrane is 0.01-0.1 μm, and the microporous filter element filter 6 is further used for physical impurity removal and filtration.

[0039] The nanofiltration device 7 uses a nano-scale nano-membrane that can intercept organic matter and multivalent ions, allowing small molecular organic matter and monovalent ions to pass through, and can effectively filter out ultra-low concentration SO4 2- It has a good removal effect. This link can intercept divalent SO4 2- ,CO3 2- .

[0040] Combined with resin ion adsorption technology, the resin adsorption filter 8 is used as a means of deep impurity removal. The resin adsorption filter 8 uses a resin that can adsorb Ca 2+ Mg 2+ Ions and SO4 2- , BO3 3- The resin adsorption filter 8 has three levels, which adsorb calcium and magnesium ions, sulfate and borate respectively. This link can further remove Ca in the solution. 2+ Mg 2+ 、SO4 2- , BO3 3- ion.

[0041] A transfer tank 13 is provided on the lithium chloride delivery pipeline 14 between the microporous filter element filter 6 and the nanofiltration device 7 , and the lithium chloride is cached by the transfer tank 13 so as to facilitate the nanofiltration device 7 and the resin adsorption filter 8 .

[0042] The utility model can directly prepare lithium chloride refined liquid with qualified impurity content in one step, wherein the concentrations of calcium, magnesium, sulfate and boron ions in the refined liquid are less than 5 ppb, and a 99.9% battery-grade lithium carbonate product can be directly prepared after lithium precipitation, and the lithium carbonate does not need to be refined again.

[0043] The above is a detailed introduction to a lithium chloride mother liquor refining system for lithium extraction from salt lakes provided by the utility model. Specific examples are used in this article to illustrate the principle and implementation method of the utility model. The description of the above embodiments is only used to help understand the method and core idea of ​​the utility model; at the same time, for those skilled in the art, according to the idea of ​​the utility model, there will be changes in the specific implementation method and application scope, and changes and improvements to the utility model will be possible without exceeding the concept and scope specified in the attached claims. In summary, the content of this specification should not be understood as a limitation on the utility model.

Claims

1. A lithium chloride mother liquor refining system for lithium extraction from salt lakes, characterized in that: The invention comprises a sodium sulfate dissolving kettle, a primary crystallization reaction kettle, a primary plate-frame filter press, a secondary crystallization reaction kettle, a secondary plate-frame filter press, a microporous filter element filter, a nanofiltration device, a resin adsorption filter, a filter residue stirring kettle and a sediment residue filter press. The primary crystallization reaction kettle, the primary plate-frame filter press, the secondary crystallization reaction kettle, the secondary plate-frame filter press, the microporous filter element filter, the nanofiltration device and the resin adsorption filter are sequentially connected through a lithium chloride delivery pipeline. The sodium sulfate dissolving kettle is connected to the interior of the primary crystallization reaction kettle through a sodium sulfate solution pipeline. The filter residue stirring kettle is respectively connected to the residue outlets of the primary plate-frame filter press and the secondary plate-frame filter press through a filter residue pipeline. A condensate inlet pipe and a condensate outlet pipe are connected to the filter residue stirring kettle. The filter residue stirring kettle is connected to the sediment residue filter press through the condensate outlet pipe. The filtrate outlet of the sediment residue filter press is connected to the interior of the sodium sulfate dissolving kettle through a filtrate pipeline.

2. A lithium chloride mother liquor refining system for extracting lithium from a salt lake according to claim 1, characterized in that: It also includes a primary seed configuration box and a secondary seed configuration box. The concentrated water outlet of the nanofiltration device is connected to the interior of the primary seed configuration box and the secondary seed configuration box respectively through a concentrated water delivery pipeline. The primary seed configuration box is connected to the interior of the primary crystallization reactor through a seed output pipeline, and the secondary seed configuration box is connected to the interior of the secondary crystallization reactor through a seed output pipeline.

3. A lithium chloride mother liquor refining system for extracting lithium from a salt lake according to claim 2, characterized in that: The filter residue pipeline at the residue outlet of the primary plate and frame filter press is divided into two routes, one route is connected to the filter residue stirring kettle, and the other route is connected to the primary seed configuration box. The filter residue pipeline at the residue outlet of the secondary plate and frame filter press is divided into two routes, the other route is connected to the filter residue stirring kettle, and the other route is connected to the secondary seed configuration box.

4. A lithium chloride mother liquor refining system for extracting lithium from a salt lake according to claim 1, characterized in that: The primary crystallization reactor is connected with a lithium chloride mother liquor feeding pipeline and a sodium hypochlorite feeding pipeline.

5. A lithium chloride mother liquor refining system for extracting lithium from a salt lake according to claim 1, characterized in that: The secondary crystallization reactor is connected with a sodium hydroxide feed pipeline and an oxalic acid feed pipeline.

6. A lithium chloride mother liquor refining system for extracting lithium from a salt lake according to claim 1, characterized in that: The primary crystallization reaction kettle and the secondary crystallization reaction kettle both adopt crystallization reactors.

7. A lithium chloride mother liquor refining system for extracting lithium from a salt lake according to claim 1, characterized in that: The microporous filter element adopts an ultrafiltration membrane filter element, and the pore size of the ultrafiltration membrane is 0.01-0.1 μm.

8. A lithium chloride mother liquor refining system for extracting lithium from a salt lake according to claim 1, characterized in that: A transfer tank is provided on the lithium chloride delivery pipeline between the microporous filter element filter and the nanofiltration device.

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