Preparation system equipment of high-quality lithium hydroxide

Abstract

The utility model discloses high-quality lithium hydroxide preparation system equipment which comprises a reaction kettle, a cooling crystallization system, a first-stage evaporative crystallization system, a dissolving kettle and a second-stage evaporative crystallization system, and an impurity removal system is arranged between the first-stage evaporative crystallization system and the second-stage evaporative crystallization system. The impurity removal system is sequentially composed of an impurity removal kettle, a plate-and-frame filter press, a microporous filter element filter, nano-filtration equipment and a resin adsorption filter, and a dosing tank is arranged on the impurity removal kettle. Compared with the prior art, according to the process route of chemical impurity removal, physical impurity removal, membrane system impurity removal and resin adsorption, a set of preparation system equipment with higher filtering and impurity removal effects is designed, the purity of finished lithium hydroxide is greatly improved, the lithium hydroxide product reaches the battery-grade lithium hydroxide standard, and the production cost is reduced. The mother liquor replacement rate of the secondary recrystallization link is reduced by 70%, and the lithium hydroxide yield of the secondary recrystallization link is improved by 10%.

Description

Technical Field

[0001] The utility model relates to the field of lithium hydroxide preparation, in particular to a system equipment for preparing fine lithium hydroxide. Background Art

[0002] At present, the preparation of fine lithium hydroxide mainly adopts the reaction of lithium sulfate and sodium hydroxide in a reactor to generate lithium hydroxide and sodium sulfate. The huge difference in solubility of lithium hydroxide and sodium sulfate under temperature change is used to cool the material to 5°C for freezing, so as to separate sodium sulfate by freezing. The remaining lithium hydroxide solution is evaporated and crystallized by MVR evaporator, and crude lithium hydroxide is separated by centrifugation. The separated crude lithium hydroxide has more impurities, and the lithium hydroxide solid needs to be redissolved, filtered through a plate and frame filter, and evaporated and crystallized twice by MVR, and fine lithium hydroxide is separated by centrifugation.

[0003] The process system has the following problems: the raw materials lithium sulfate and sodium hydroxide used need to be removed to a certain extent at the front end, but the removal accuracy is limited. As the reaction solution is continuously concentrated in the MVR system, the impurity components (impurities are ultrafine particles, insoluble matter, potassium, sodium, iron, calcium, boron, zinc, sulfate, chloride ions, etc.) are also concentrated and enriched, and the quality of lithium hydroxide products is reduced. The solidification process needs to adopt the method of secondary dissolution and recrystallization to improve product quality. However, the secondary re-dissolution and recrystallization essentially just leaves the impurities in the mother liquor and does not remove them. After several concentrations, the impurities gather again, and the mother liquor must be discharged and the lithium hydroxide is dissolved and concentrated with fresh water. This results in a low yield of secondary re-dissolution and recrystallization of lithium hydroxide, high system energy consumption; the product quality is good at the beginning, but it decreases in the later stage. Utility Model Content

[0004] The purpose of the utility model is to provide a system equipment for preparing high-quality lithium hydroxide that solves the above-mentioned problems. Some specific impurity removal methods are added between the secondary evaporation and crystallization processes of lithium hydroxide, and the process flow line is adjusted in combination to reduce system energy consumption and effectively improve product quality.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the utility model is: a system equipment for preparing fine lithium hydroxide, including a reaction kettle, a cooling crystallization system, a primary evaporation crystallization system, a dissolving kettle and a secondary evaporation crystallization system, a de-impurity system is arranged between the primary evaporation crystallization system and the secondary evaporation crystallization system, the de-impurity system is composed of a de-impurity kettle, a plate and frame filter press, a microporous filter element filter, a nanofiltration device and a resin adsorption filter in sequence, the cooling crystallization system, the primary evaporation crystallization system, the dissolving kettle, the de-impurity kettle, the plate and frame filter press, the microporous filter element filter, the nanofiltration device, the resin adsorption filter and the secondary evaporation crystallization system are connected in sequence through a lithium hydroxide delivery pipeline, and a drug adding box is arranged on the de-impurity kettle.

[0006] Preferably, transfer tanks are provided on the lithium hydroxide delivery pipelines between the plate and frame filter press and the microporous filter element filter, between the microporous filter element filter and the nanofiltration device, and between the resin adsorption filter and the secondary evaporation crystallization system.

[0007] Preferably, the cooling crystallization system consists of a cooling crystallizer and a sodium sulfate centrifuge, the reactor is connected to the feed port of the cooling crystallizer through a lithium hydroxide delivery pipeline, the discharge port of the cooling crystallizer is connected to the primary evaporation crystallization system through the sodium sulfate centrifuge, a circulation pipe is provided at the bottom of the cooling crystallizer, a circulation pump and a cooler are provided on the circulation pipe, the circulation pipe is connected to the feed port of the cooling crystallizer, and a transfer tank is provided on the lithium hydroxide delivery pipeline between the sodium sulfate centrifuge and the primary evaporation crystallization system.

[0008] Preferably, the primary evaporation crystallization system consists of a primary evaporation crystallizer and a primary centrifuge, the cooling crystallization system is connected to the feed port of the primary evaporation crystallizer through a lithium hydroxide delivery pipeline, the discharge port of the primary evaporation crystallizer is connected to the dissolution kettle through a primary centrifuge, a circulation pipe is provided at the bottom of the primary evaporation crystallizer, a circulation pump and a heater are provided on the circulation pipe, and the circulation pipe is connected to the feed port of the primary evaporation crystallizer.

[0009] Preferably, the secondary evaporation crystallization system consists of a secondary evaporation crystallizer and a secondary centrifuge, the impurity removal system is connected to the feed port of the secondary evaporation crystallizer through a lithium hydroxide delivery pipeline, the discharge port of the secondary evaporation crystallizer is connected to the secondary centrifuge through a lithium hydroxide delivery pipeline, a circulation pipe is provided at the bottom of the secondary evaporation crystallizer, a circulation pipe is provided on the circulation pipe, and the circulation pipe is connected to the feed port of the secondary evaporation crystallizer.

[0010] Preferably, a delivery pump is provided on the lithium hydroxide delivery pipeline.

[0011] Preferably, the dosing box stores an impurity remover, which is a specific organic compound such as oxalate.

[0012] Preferably, the filtration accuracy of the microporous filter element is 0.3 μm.

[0013] Preferably, the nanofiltration device uses a nano-scale nano-membrane with a molecular weight cut-off in the range of 80-1000.

[0014] Preferably, the resin adsorption filter is a resin adsorbable Ca 2+ Mg 2+ Resin adsorption filter for ions.

[0015] Compared with the prior art, the advantages of the utility model are: the utility model is aimed at the purification and preparation system of fine lithium hydroxide, and according to the process route of chemical impurity removal → physical impurity removal → membrane system impurity removal → resin adsorption, a set of preparation system equipment with higher filtration and impurity removal effect is designed, which greatly improves the purity of the finished lithium hydroxide, reduces the mother liquor replacement rate in the secondary recrystallization link by 70%, and increases the lithium hydroxide yield in the secondary recrystallization link by 10%. The lithium hydroxide product meets the "Battery Grade Lithium Hydroxide GB / T26008-2020" standard, and the quality is improved from grade 3 to grade 1. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a system schematic diagram of the utility model.

[0017] In the figure, 1. reactor; 2. cooling crystallization system; 21. cooling crystallizer; 22. sodium sulfate centrifuge; 23. cooler; 3. primary evaporation crystallization system; 31. primary evaporation crystallizer; 32. primary centrifuge; 4. dissolving kettle; 5. secondary evaporation crystallization system; 51. secondary evaporation crystallizer; 52. secondary centrifuge; 6. dosing box; 7. impurity removal kettle; 8. plate and frame filter press; 9. microporous filter element filter; 10. nanofiltration equipment; 11. resin adsorption filter; 12. transfer tank; 13. circulation pump; 14. heater. DETAILED DESCRIPTION

[0018] The product indicators given in "Battery Grade Lithium Hydroxide GB / T26008-2020" show the items of impurity content that should be controlled in this project. Many key indicators have reached the PPM (parts per million) level, and impurity control is quite demanding. Therefore, various control indicators for lithium hydroxide solution impurity removal should be formulated based on a combination of theoretical calculations and experiments.

[0019]

[0020] Through analysis and determination, the impurities contained are mainly divided into three aspects:

[0021] ①Soluble ions. The main cations are Na + , K + , Fe 3+ , Ca 2+ , Cu 2+ Mg 2+ , Mn 2+ 、Si 4+ ;

[0022] The main anions are Cl - 、SO 4 2- wait;

[0023] ② Insoluble impurities. These impurities are mainly dust introduced from the environment;

[0024] ③Organic matter.

[0025] The impurity removal methods adopted at home and abroad have their own advantages. Targeted impurity removal or a combination of multiple impurity removal methods is required according to the impurity composition of the raw materials and the product indicators. However, for the requirement of battery-grade lithium hydroxide of ≤50PPM, ordinary filtration methods can no longer meet this filtration accuracy. It is necessary to select appropriate filtration processes and special equipment. Therefore, it is urgent to design a set of high-quality lithium hydroxide preparation system equipment with higher filtration and impurity removal effects. The utility model will be further explained below.

[0026] A system equipment for preparing high-quality lithium hydroxide, see Figure 1 , comprising a reaction kettle 1, a cooling crystallization system 2, a primary evaporation crystallization system 3, a dissolving kettle 4 and a secondary evaporation crystallization system 5, wherein an impurity removal system is arranged between the primary evaporation crystallization system 3 and the secondary evaporation crystallization system 5, and the impurity removal system is sequentially composed of an impurity removal kettle 7, a plate and frame filter press 8, a microporous filter element filter 9, a nanofiltration device 10 and a resin adsorption filter 11, the cooling crystallization system 2, the primary evaporation crystallization system 3, the dissolving kettle 4, the impurity removal kettle 7, the plate and frame filter press 8, the microporous filter element filter 9, the nanofiltration device 10, the resin adsorption filter 11 and the secondary evaporation crystallization system 5 are sequentially connected through a lithium hydroxide conveying pipeline, a dosing box 6 is arranged on the impurity removal kettle 7, and a conveying pump is arranged on the lithium hydroxide conveying pipeline, and material is conveyed by the conveying pump.

[0027] Transfer tanks 12 are respectively provided on the lithium hydroxide delivery pipelines between the plate and frame filter press 8 and the microporous filter element filter 9, between the microporous filter element filter 9 and the nanofiltration device 10, and between the resin adsorption filter 11 and the secondary evaporation crystallization system 5. The filtered lithium hydroxide solution is transferred and cached through the transfer tanks 12 to control the filtration time and the filtration effect.

[0028] The reason why the utility model designs an impurity removal system between lithium hydroxide re-dissolution and secondary evaporation crystallization is that at the beginning of the scheme design, it is also considered to remove organic impurities from raw materials of lithium sulfate and sodium hydroxide by Fenton oxidation process equipment before the raw materials enter the reactor 1, but the use of Fenton oxidation will increase iron ions, which is not worth the loss. Moreover, sodium and potassium ions are elements of the same group as lithium in the chemical periodic table, and it is very difficult to remove them at low concentrations, or the cost is too high. The anions in CL - 、SO 4 2-The concentration is very low. In this case, the utility model designs the impurity removal link to be carried out between the lithium hydroxide re-dissolution and the secondary evaporation crystallization, and the previous stage does not need to be pre-treated, that is, the impurities are left in the mother liquor by recrystallization through the cooling crystallization system 2, and then removed through the impurity removal link of the utility model.

[0029] From the indicators, it can be seen that the most stringent control is Fe 3+ , Cu 2+ Mg 2+ , Mn 2+ Ions, the utility model adds a specific impurity removal step between the primary concentration and separation of the re-dissolved lithium hydroxide solution and the secondary evaporation crystallization to remove impurities. The impurity removal in this step can achieve the purpose of economical impurity removal, and the purpose is to remove solid insoluble matter and heavy metal ions.

[0030] Research on the process of heavy metal removal: For Fe 3+ , Ca 2+ , Cu 2+ Mg 2+ , Mn 2+ 、Si 4+ Removal of cations. For example, sodium carbonate is often used to remove Ca in water treatment. 2+ Mg 2+ ions, but in fact calcium carbonate and magnesium carbonate still need 10 -4 Solubility level, in the next step of evaporation and crystallization, it will be precipitated after concentration, and the consolidation step must adopt a removal method with lower solubility. Therefore, the utility model adds a dosing box 6 on the dissolving kettle 4, and the dosing box 6 is connected to the inside of the dissolving kettle 4 through a dosing pipeline. The dosing box 6 stores impurity removers. By screening suitable impurity removers, the impurity removers are specific organic compounds such as oxalate, which can be used for Fe 3+ , Ca 2+ , Cu 2+ Mg 2+ , Mn 2+ 、Si 4+ Cations have a deep impurity removal effect. By adding impurity removers, high-valent ions can be precipitated to 10 -5 Solubility level to achieve chemical removal of impurities.

[0031] The impurity removal equipment serves as a guarantee for removing insoluble impurities, and is composed of a plate and frame filter press 8, a microporous filter element filter 9, a nanofiltration device 10 and a resin adsorption filter 11 in sequence. The plate and frame filter press 8, the microporous filter element filter 9, the nanofiltration device 10 and the resin adsorption filter 11 are connected in sequence through a lithium hydroxide delivery pipeline.

[0032] The plate-and-frame filter press 8 and the microporous filter element filter 9 are used as two-stage physical filtration equipment to perform secondary physical filtration on the lithium hydroxide solution after chemical impurity removal. The first stage uses the plate-and-frame filter press 8 to mainly filter the original insoluble matter and the high-valent metal compounds precipitated by the previous reaction. The second stage uses the microporous filter element filter 9 with a filtration accuracy of 0.3 μm to further perform physical impurity removal filtration.

[0033] After physical impurity removal, the lithium hydroxide solution enters the nano-membrane filtration system for further impurity removal. The nano-device uses a nano-scale nano-membrane. Nanofiltration (NF) is a membrane separation technology between ultrafiltration and reverse osmosis. Its molecular weight cutoff is in the range of 80-1000, and its pore size is a few nanometers, so it is called nanofiltration. It can intercept organic matter and multivalent ions, and allow small molecular organic matter and monovalent ions to pass through. It is very effective for ultra-low concentration SO 4 2- It has a good removal effect. This step can intercept divalent SO 4 2- ,CO 2- .

[0034] Combined with resin ion adsorption technology, the resin adsorption filter 11 is used as a means of deep impurity removal. The resin adsorption filter 11 uses a resin that can adsorb Ca 2- Mg 2- Ion resin adsorption filter 11, this link can further remove Ca in lithium hydroxide solution 2- Mg 2- ion.

[0035] Through the above-mentioned impurity removal technology, the mother liquor replacement rate in the secondary recrystallization stage was reduced by 70%, and the lithium hydroxide yield in the secondary recrystallization stage was increased by 10%. Its lithium hydroxide products met the "Battery Grade Lithium Hydroxide GB / T26008-2020" standard, and the quality was improved from grade 3 to grade 1.

[0036] The cooling crystallization system 2 consists of a cooling crystallizer 21, a circulation pump 13, a cooler 23 and a sodium sulfate centrifuge 22. The reactor 1 is connected to the feed port of the cooling crystallizer 21 through a lithium hydroxide delivery pipeline. The discharge port of the cooling crystallizer 21 is connected to the primary evaporation crystallization system 3 through the sodium sulfate centrifuge 22. Sodium sulfate is frozen and separated by the cooling crystallization system 2. A circulation pipe is provided at the bottom of the cooling crystallizer 21. A circulation pump 13 and a cooler 23 are provided on the circulation pipe. The circulation pipe is connected to the feed port of the cooling crystallizer 21. Self-circulation in the cooling crystallizer 21 is performed through the circulation pipe and the cooler 23. A transfer tank 12 is provided on the lithium hydroxide delivery pipeline between the sodium sulfate centrifuge 22 and the primary evaporation crystallization system 3. The transfer tank 12 transfers and caches the lithium hydroxide solution separated by centrifugation.

[0037] The primary evaporation crystallization system 3 is composed of a primary evaporation crystallizer 31, a circulation pump 13, a heater 14 and a primary centrifuge 32. The cooling crystallization system 2 is connected to the feed port of the primary evaporation crystallizer 31 through a lithium hydroxide delivery pipeline. The discharge port of the primary evaporation crystallizer 31 is connected to the dissolution kettle 4 through the primary centrifuge 32. The primary evaporation crystallizer 31, i.e., the MVR evaporator, is used for evaporation and crystallization, and crude lithium hydroxide is separated by centrifugation. A circulation pipe is provided at the bottom of the primary evaporation crystallizer 31, and a circulation pump 13 and a heater 14 are provided on the circulation pipe. The circulation pipe is connected to the feed port of the primary evaporation crystallizer 31. The self-circulation in the primary evaporation crystallizer 31 is realized through the circulation pipe, thereby improving the evaporation and crystallization efficiency.

[0038] The secondary evaporation crystallization system 5 is composed of a secondary evaporation crystallizer 51, a circulation pump 13, a heater 14 and a secondary centrifuge 52. The impurity removal system is connected to the feed port of the secondary evaporation crystallizer 51 through a lithium hydroxide delivery pipeline. The discharge port of the secondary evaporation crystallizer 51 is connected to the secondary centrifuge 52 through a lithium hydroxide delivery pipeline. The secondary evaporation crystallizer 51 is used to extract fine lithium hydroxide. A circulation pipe is provided at the bottom of the secondary evaporation crystallizer 51. The circulation pipe is provided with a circulation pump 13 and a heater 14. The circulation pipe is connected to the feed port of the secondary evaporation crystallizer 51. The self-circulation in the secondary evaporation crystallizer 51 is realized through the circulation pipe, thereby improving the evaporation crystallization efficiency.

[0039] The above is a detailed introduction to the preparation system equipment and process of a fine lithium hydroxide 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 of the utility model and its core idea; 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. 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 system for preparing fine lithium hydroxide, characterized by: The invention comprises a reaction kettle, a cooling crystallization system, a primary evaporation crystallization system, a dissolving kettle and a secondary evaporation crystallization system; an impurity removal system is arranged between the primary evaporation crystallization system and the secondary evaporation crystallization system; the impurity removal system is composed of an impurity removal kettle, a plate and frame filter press, a microporous filter element filter, a nanofiltration device and a resin adsorption filter in sequence; the cooling crystallization system, the primary evaporation crystallization system, the dissolving kettle, the impurity removal kettle, the plate and frame filter press, the microporous filter element filter, the nanofiltration device, the resin adsorption filter and the secondary evaporation crystallization system are connected in sequence through a lithium hydroxide conveying pipeline; and a drug adding box is arranged on the impurity removal kettle.

2. A system for preparing a fine lithium hydroxide according to claim 1, characterized in that: Transfer tanks are respectively arranged on the lithium hydroxide delivery pipelines between the plate and frame filter press and the microporous filter element filter, between the microporous filter element filter and the nanofiltration device, and between the resin adsorption filter and the secondary evaporation crystallization system.

3. A system for preparing a fine lithium hydroxide according to claim 1, characterized in that: The cooling crystallization system consists of a cooling crystallizer and a sodium sulfate centrifuge. The reactor is connected to the feed port of the cooling crystallizer through a lithium hydroxide delivery pipeline. The discharge port of the cooling crystallizer is connected to the primary evaporation crystallization system through the sodium sulfate centrifuge. A circulation pipe is provided at the bottom of the cooling crystallizer. A circulation pump and a cooler are provided on the circulation pipe. The circulation pipe is connected to the feed port of the cooling crystallizer.

4. A system for preparing a fine lithium hydroxide according to claim 1, characterized in that: The primary evaporation crystallization system consists of a primary evaporation crystallizer and a primary centrifuge. The cooling crystallization system is connected to the feed port of the primary evaporation crystallizer through a lithium hydroxide delivery pipeline. The discharge port of the primary evaporation crystallizer is connected to the dissolution kettle through the primary centrifuge. A circulation pipe is provided at the bottom of the primary evaporation crystallizer. A circulation pump and a heater are provided on the circulation pipe. The circulation pipe is connected to the feed port of the primary evaporation crystallizer.

5. The system equipment for preparing a fine lithium hydroxide according to claim 1, characterized in that: The secondary evaporation crystallization system consists of a secondary evaporation crystallizer and a secondary centrifuge. The impurity removal system is connected to the feed port of the secondary evaporation crystallizer through a lithium hydroxide delivery pipeline. The discharge port of the secondary evaporation crystallizer is connected to the secondary centrifuge through a lithium hydroxide delivery pipeline. A circulation pipe is provided at the bottom of the secondary evaporation crystallizer. A circulation pump and a heater are provided on the circulation pipe. The circulation pipe is connected to the feed port of the secondary evaporation crystallizer.

6. A system for preparing a fine lithium hydroxide according to claim 1, characterized in that: A delivery pump is provided on the lithium hydroxide delivery pipeline.

7. The system equipment for preparing a fine lithium hydroxide according to claim 1, characterized in that: The impurity remover is stored in the medicine adding box.

8. The system equipment for preparing a fine lithium hydroxide according to claim 1, characterized in that: The filtration accuracy of the microporous filter element is 0.3 μm.

9. The system equipment for preparing a fine lithium hydroxide according to claim 1, characterized in that: The nanofiltration device adopts a nano-scale nano-membrane with a molecular weight cut-off in the range of 80-1000.

10. The system equipment for preparing fine lithium hydroxide according to claim 1, characterized in that: The resin adsorption filter adopts a resin adsorption filter capable of adsorbing Ca 2+ Mg 2+ Resin adsorption filter for ions.

Images