CN115215357B - Method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate - Google Patents
Method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate Download PDFInfo
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- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 title claims abstract description 55
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 238000000034 method Methods 0.000 title claims abstract description 35
- PQVSTLUFSYVLTO-UHFFFAOYSA-N ethyl n-ethoxycarbonylcarbamate Chemical compound CCOC(=O)NC(=O)OCC PQVSTLUFSYVLTO-UHFFFAOYSA-N 0.000 title claims abstract description 25
- GLXDVVHUTZTUQK-UHFFFAOYSA-M lithium hydroxide monohydrate Substances [Li+].O.[OH-] GLXDVVHUTZTUQK-UHFFFAOYSA-M 0.000 title claims abstract description 25
- 229940040692 lithium hydroxide monohydrate Drugs 0.000 title claims abstract description 25
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims abstract description 118
- 238000001704 evaporation Methods 0.000 claims abstract description 39
- 230000008020 evaporation Effects 0.000 claims abstract description 37
- 238000007710 freezing Methods 0.000 claims abstract description 34
- 230000008014 freezing Effects 0.000 claims abstract description 34
- 239000003513 alkali Substances 0.000 claims abstract description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000001291 vacuum drying Methods 0.000 claims abstract description 12
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 239000002002 slurry Substances 0.000 claims abstract description 10
- 239000013078 crystal Substances 0.000 claims abstract description 9
- 238000009993 causticizing Methods 0.000 claims abstract description 6
- 238000009461 vacuum packaging Methods 0.000 claims abstract description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 57
- 239000000243 solution Substances 0.000 claims description 50
- 239000000047 product Substances 0.000 claims description 27
- 238000002425 crystallisation Methods 0.000 claims description 23
- 230000008025 crystallization Effects 0.000 claims description 23
- 238000001035 drying Methods 0.000 claims description 21
- 239000007787 solid Substances 0.000 claims description 20
- 238000000926 separation method Methods 0.000 claims description 18
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 14
- RSIJVJUOQBWMIM-UHFFFAOYSA-L sodium sulfate decahydrate Chemical compound O.O.O.O.O.O.O.O.O.O.[Na+].[Na+].[O-]S([O-])(=O)=O RSIJVJUOQBWMIM-UHFFFAOYSA-L 0.000 claims description 14
- 238000003756 stirring Methods 0.000 claims description 14
- 230000008569 process Effects 0.000 claims description 13
- 238000005406 washing Methods 0.000 claims description 13
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 claims description 11
- 229910001947 lithium oxide Inorganic materials 0.000 claims description 11
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 10
- 239000011575 calcium Substances 0.000 claims description 10
- 239000000706 filtrate Substances 0.000 claims description 10
- 238000001914 filtration Methods 0.000 claims description 10
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 claims description 9
- 229910001424 calcium ion Inorganic materials 0.000 claims description 9
- 229910001425 magnesium ion Inorganic materials 0.000 claims description 9
- 238000002360 preparation method Methods 0.000 claims description 8
- 230000001105 regulatory effect Effects 0.000 claims description 7
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 7
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 239000003456 ion exchange resin Substances 0.000 claims description 6
- 229920003303 ion-exchange polymer Polymers 0.000 claims description 6
- 239000011259 mixed solution Substances 0.000 claims description 6
- 238000004806 packaging method and process Methods 0.000 claims description 5
- 239000007769 metal material Substances 0.000 claims description 3
- 239000002244 precipitate Substances 0.000 claims description 3
- 238000000746 purification Methods 0.000 claims 1
- 239000007788 liquid Substances 0.000 abstract description 18
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 6
- 238000009826 distribution Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 238000010902 jet-milling Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052755 nonmetal Inorganic materials 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 229910052938 sodium sulfate Inorganic materials 0.000 description 2
- 235000011152 sodium sulphate Nutrition 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000012043 crude product Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/02—Oxides; Hydroxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/06—Preparation of sulfates by double decomposition
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
- C01P2006/82—Compositional purity water content
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The invention discloses a method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate, which comprises the following specific steps: dissolving and purifying crude lithium sulfate to remove impurities; causticizing by mixing alkali; freezing and crystallizing; primary evaporation and concentration; secondary evaporation concentration and crystal slurry crushing; and (5) vacuum drying and packaging. The invention adopts an MVR forced circulation evaporator to carry out primary evaporation concentration on the secondary centrifugal freezing liquid; and then the obtained crude lithium hydroxide is dissolved by pure water, and secondary evaporation concentration is carried out, so that the operation is relatively simple and the working efficiency is relatively high.
Description
Technical Field
The invention belongs to the technical field of lithium hydroxide production, and particularly relates to a method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate.
Background
In recent years, along with the transformation of energy structures, related industries of new energy automobiles have been rapidly developed, wherein the lithium battery electric automobile is rapidly focused on the market by virtue of the advantages of long endurance mileage, high safety coefficient, mature technology and the like. In contrast to fuel vehicles, the core of electric vehicles is no longer the engine, but the power battery and battery management system. The ternary battery produced by taking the battery-grade lithium hydroxide as one of the raw materials has high energy density, is safe and portable, and takes the dominant role in the field of vehicle-mounted power batteries.
Currently, the industry mainly adopts MVR technology, takes lithium sulfate as raw material, and produces battery grade lithium hydroxide monohydrate through processes of alkali mixing causticization, freezing crystallization, evaporation concentration and the like. MVR is an acronym for vapor mechanical recompression technique (mechanical vapor recompression). MVR is an energy saving technology that reuses the energy of the secondary steam that it generates, thereby reducing the need for external energy. The conventional MVR technology for preparing lithium hydroxide monohydrate often has the following disadvantages: 1) The micro powder content of the product after jet milling is high; 2) The byproduct sodium sulfate decahydrate can take away a part of lithium oxide, so that the yield of the lithium oxide is reduced; 3) Fluidized bed or tray drying can increase the content of magnetic foreign matter and carbon dioxide in the finished product. These deficiencies seriously affect the quality and utilization of battery grade lithium hydroxide monohydrate.
The preparation method of the battery-grade lithium hydroxide monohydrate disclosed in CN100455512C comprises the following steps: (1) Adding sodium hydroxide into the lithium sulfate purifying liquid, completely dissolving, and cooling to obtain Na 2 SO 4 ·10H 2 O solids and LiOH liquids; (2) filtering and separating to obtain LiOH liquid; (3) Evaporating and concentrating LiOH liquid, cooling and crystallizing, filtering, separating and leaching to obtain LiOH H 2 Crude O is obtained once; (4) In LiOH.H 2 Adding deionized water into the O primary crude product, stirring to dissolve completely to obtain LiOH H 2 O primary crude heavy solution, (5) LiOH.H 2 Adding a refining agent into the O primary crude heavy solution, and filtering and separating the O primary crude heavy solution after the reaction is finished, wherein filtrate is LiOH refined solution; (6) Evaporating, concentrating, cooling and crystallizing LiOH refined solution, filtering and separating the LiOH refined solution to obtain solid which is battery-grade LiOH H 2 Wet O product; (7) Battery grade LiOH H 2 Taking out the O wet product after drying to obtain battery grade LiOH H 2 And (3) a product O. The invention has simple production process, easy operation and good product quality. But it is also required to be concentrated in LiOH H after one evaporation 2 According to Na in O primary crude heavy solution + The concentration of the mixed solution is added with the refined agent to carry out stirring reaction, the steps are relatively complicated, and the working efficiency is relatively low.
Disclosure of Invention
The invention aims to provide a method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate, which is relatively simple to operate and can improve the yield of lithium oxide.
In order to solve the technical problems, the invention provides a method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate, which is characterized by comprising the following specific steps:
s1, dissolving and purifying crude lithium sulfate, and removing impurities: dissolving crude lithium sulfate with pure water to obtain a solution, regulating the pH of the solution to 10-12 with sodium hydroxide, adding sodium carbonate, stirring, heating to 78-85 ℃ for reaction to primarily precipitate calcium and magnesium ions, often dissolving high-valence metal ions such as calcium and magnesium in the solution, regulating the pH to 10-12, and adding sodium carbonate to precipitate the solution in the form of carbonate. Filtering the reacted mixed solution by a filter to obtain filtrate, and further removing calcium and magnesium ions from the filtrate by ion exchange resin to obtain the lithium sulfate purifying solution.
S2, causticizing by mixed alkali: and (3) delivering the lithium sulfate purifying solution obtained in the step (S1) into a mixing alkali preparation tank, and adding solid sodium hydroxide to carry out mixing and stirring to obtain mixed alkali liquor.
S3, freezing and crystallizing: and (3) carrying out twice freezing crystallization and centrifugal separation on the mixed alkali liquor obtained in the step (S2) to obtain twice centrifugal frozen liquor and sodium sulfate decahydrate solid.
S4, primary evaporation concentration: and (3) performing primary evaporation concentration on the secondary centrifugal frozen solution obtained in the step (S3) by adopting an MVR forced circulation evaporator, and performing centrifugal separation on the obtained concentrated solution to obtain crude lithium hydroxide.
S5, secondary evaporation concentration: dissolving crude lithium hydroxide with pure water, introducing the obtained solution into a secondary evaporation crystallizer for crystallization, crushing the precipitated crystal slurry by crushing equipment in the forced circulation process, and then performing centrifugal separation to obtain wet lithium hydroxide.
S6, vacuum drying and packaging: and (3) delivering the wet product lithium hydroxide obtained in the step (S5) into a belt type vacuum dryer for vacuum drying, grading the dried product by a vibration sieve, crushing by air flow, and packaging and storing.
Further, in step S2, the molar ratio of the added sodium hydroxide to the total lithium oxide in the lithium sulfate purifying solution is 2:1-2.5:1, so as to ensure the maximum separation of lithium ions and sulfate ions after freezing crystallization, and avoid unnecessary consumption of sodium hydroxide.
In the step S3, the sodium sulfate decahydrate solid is washed by pure water at the temperature of 3-10 ℃, the washed washing liquid is used for dissolving the crude lithium sulfate in the step S1, the content of sodium sulfate in the washing liquid can be greatly reduced compared with the washing liquid by pure water at normal temperature in low temperature, and the washing liquid is used for dissolving the crude lithium hydroxide, so that lithium resources in the washing liquid can be directly recovered, and the yield of lithium oxide is improved.
Further, in the step S3, the temperature of freezing crystallization is controlled to be 5 ℃ to 0 ℃, and the solubility of sodium sulfate is small within the temperature range, so that the content of sulfate ions in the centrifugal freezing solution is low, and the quality control of lithium hydroxide products is facilitated.
In step S3, the freezing crystallization machine is a forced circulation freezing crystallizer, so as to improve the heat transfer efficiency in the freezing crystallization process and realize the purpose of high-efficiency continuous freezing.
Further, in step S5, the crushing device is a crushing pump connected in parallel with the secondary evaporation crystallizer, and the introduction of the crushing device can effectively control the particle size distribution of wet lithium hydroxide, inhibit the generation of agglomeration effect and the production of large grains, thereby strengthening the subsequent drying effect.
Further, in the step S6, the temperature of vacuum drying is controlled at 50-70 ℃ and the drying time is 40-60 min, so that the main content and the moisture content of the dried finished product are ensured to meet the requirements of battery-grade lithium hydroxide, and the introduction of carbon dioxide is avoided.
Further, in step S6, the conveying crawler in the belt type vacuum dryer is made of a non-metal material, the direct contact area between the conveying crawler and the material is large, and the conveying crawler made of the non-metal material can effectively reduce the introduction of magnetic foreign matters such as iron and nickel in the drying process, so that the stability of the product quality is ensured.
Compared with the prior art, the invention has the following beneficial effects:
1. firstly, dissolving crude lithium sulfate, regulating the pH value of the obtained solution to be 10-12 by using sodium hydroxide, adding sodium carbonate, stirring and heating to 78-85 ℃ for reaction to initially precipitate calcium and magnesium ions, filtering to obtain filtrate, and removing the calcium and magnesium ions from the filtrate by using ion exchange resin to obtain lithium sulfate purifying solution; mixing and stirring the lithium sulfate purifying solution and solid sodium hydroxide to obtain mixed alkali liquor; performing twice freezing crystallization and centrifugal separation on the mixed alkali liquor to obtain twice centrifugal frozen liquid and sodium sulfate decahydrate solid; then, performing primary evaporation concentration on the secondary centrifugal frozen solution by adopting an MVR forced circulation evaporator, and performing centrifugal separation on the obtained concentrated solution to obtain crude lithium hydroxide; and then the crude lithium hydroxide is dissolved by pure water, and the secondary evaporation concentration is carried out, so that the operation is relatively simple and the working efficiency is relatively high.
2. According to the method, on the basis of MVR technology, the grain size distribution of lithium hydroxide wet products can be effectively controlled by introducing a crystal slurry crushing process after a crystallization system in a secondary evaporation concentration section, so that the grain size distribution is uniform, the overall crushing efficiency is improved, the impurity embedding probability is reduced, and continuous production can be realized.
3. According to the invention, the byproduct sodium sulfate decahydrate in the freezing and crystallizing section is washed by the low-temperature pure water at the temperature of 3-10 ℃, the washing liquid is used for dissolving crude lithium sulfate, and lithium oxide mixed in the sodium sulfate decahydrate solid is returned to the production flow, so that the yield of lithium oxide can be effectively improved.
4. The vacuum drying method is adopted in the drying working section, so that the introduction of carbon dioxide and magnetic substances in the drying process can be effectively avoided, the stability of the product quality is ensured, and the product quality is improved.
Drawings
FIG. 1 is a process flow diagram of a method of the present invention for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate.
Detailed Description
The above-described features of the invention and those specifically described in the following (example embodiments) may be combined with each other to constitute new or preferred embodiments, but the invention is not limited to these embodiments, nor is they limited to them in any way.
The experimental methods in the following examples are conventional methods unless otherwise specified. The preparations according to the examples below are commercially available and are commercially available unless otherwise specified.
The process flow chart of the method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate is shown in figure 1.
Example 1
A method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate, comprising the following specific steps:
s1, dissolving and purifying crude lithium sulfate, and removing impurities: dissolving crude lithium sulfate with pure water, regulating the pH value of the solution to 10 with sodium hydroxide, adding sodium carbonate, stirring, heating to about 77 ℃ for reaction, filtering the reacted mixed solution by a membrane filter press or a plate-and-frame filter press, and further removing calcium and magnesium ions from the filtrate by ion exchange resin to obtain lithium sulfate purified solution;
s2, causticizing by mixed alkali: delivering the lithium sulfate purifying solution obtained in the step S1 into a mixed alkali preparation tank, adding solid sodium hydroxide, mixing and stirring to obtain mixed alkali liquor; wherein, the mol ratio of the added sodium hydroxide to the total lithium oxide in the lithium sulfate purifying liquid is controlled to be 2:1;
s3, freezing and crystallizing: performing twice freezing crystallization and centrifugal separation on the mixed alkali liquor obtained in the step S2, wherein the freezing crystallizer is a forced circulation freezing crystallizer, and the freezing crystallization temperature is controlled at 5 ℃ below zero to obtain twice centrifugal freezing liquor and sodium sulfate decahydrate solid; washing the sodium sulfate decahydrate solid with low-temperature pure water, wherein the washing liquid is used for dissolving crude lithium sulfate in the step S1;
s4, primary evaporation concentration: performing primary evaporation concentration on the secondary centrifugal frozen solution obtained in the step S3 by adopting an MVR forced circulation evaporator, and performing centrifugal separation on the concentrated solution to obtain crude lithium hydroxide;
s5, secondary evaporation concentration: dissolving crude lithium hydroxide with pure water, introducing the solution into a secondary evaporation crystallization system, crushing the precipitated crystal slurry by a crushing pump connected with a secondary evaporation crystallizer in parallel in the forced circulation process, and performing centrifugal separation to obtain wet lithium hydroxide;
s6, vacuum drying and packaging: and (3) conveying the wet product lithium hydroxide obtained in the step (S5) into a belt type vacuum dryer for drying, controlling the drying temperature at 50 ℃ and the drying time at 40 minutes, and packaging and storing the dried product after vibration screen classification and jet milling.
Example 2
A method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate, comprising the following specific steps:
s1, dissolving and purifying crude lithium sulfate, and removing impurities: dissolving crude lithium sulfate with pure water, regulating the pH value of the solution to 11 with sodium hydroxide, adding sodium carbonate, stirring, heating to about 80 ℃ for reaction, filtering the reacted mixed solution by a membrane filter press or a plate-and-frame filter press, and further removing calcium and magnesium ions from the filtrate by ion exchange resin to obtain lithium sulfate purified solution;
s2, causticizing by mixed alkali: delivering the lithium sulfate purifying solution obtained in the step S1 into a mixed alkali preparation tank, adding solid sodium hydroxide, mixing and stirring to obtain mixed alkali liquor; wherein, the mol ratio of the added sodium hydroxide to the total lithium oxide in the lithium sulfate purifying liquid is controlled to be 2.2:1;
s3, freezing and crystallizing: performing twice freezing crystallization and centrifugal separation on the mixed alkali liquor obtained in the step S2, wherein the freezing crystallizer is a forced circulation freezing crystallizer, and the freezing crystallization temperature is controlled at 3 ℃ below zero to obtain twice centrifugal freezing liquor and sodium sulfate decahydrate solid; washing the sodium sulfate decahydrate solid with low-temperature pure water, wherein the washing liquid is used for dissolving crude lithium sulfate in the step S1;
s4, primary evaporation concentration: performing primary evaporation concentration on the secondary centrifugal frozen solution obtained in the step S3 by adopting an MVR forced circulation evaporator, and performing centrifugal separation on the concentrated solution to obtain crude lithium hydroxide;
s5, secondary evaporation concentration: dissolving crude lithium hydroxide with pure water, introducing the solution into a secondary evaporation crystallization system, crushing the precipitated crystal slurry by a crushing pump connected with a secondary evaporation crystallizer in parallel in the forced circulation process, and performing centrifugal separation to obtain wet lithium hydroxide;
s6, vacuum drying and packaging: and (3) conveying the wet product lithium hydroxide obtained in the step (S5) into a belt type vacuum dryer for drying, controlling the drying temperature at 60 ℃ and the drying time at 45min, and packaging and storing the dried product after vibration screen classification and jet milling.
Example 3
A method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate, comprising the following specific steps:
s1, dissolving and purifying crude lithium sulfate, and removing impurities: dissolving crude lithium sulfate with pure water, regulating the pH value of the solution to 12 with sodium hydroxide, adding sodium carbonate, stirring, heating to about 84 ℃ for reaction, filtering the reacted mixed solution by a membrane filter press or a plate-and-frame filter press, and further removing calcium and magnesium ions from the filtrate by ion exchange resin to obtain lithium sulfate purified solution;
s2, causticizing by mixed alkali: delivering the lithium sulfate purifying solution obtained in the step S1 into a mixed alkali preparation tank, adding solid sodium hydroxide, mixing and stirring to obtain mixed alkali liquor; wherein, the mol ratio of the added sodium hydroxide to the total lithium oxide in the lithium sulfate purifying liquid is controlled to be 2.5:1;
s3, freezing and crystallizing: performing twice freezing crystallization and centrifugal separation on the mixed alkali liquor obtained in the step S2, wherein the freezing crystallizer is a forced circulation freezing crystallizer, and the freezing crystallization temperature is controlled at 0 ℃ to obtain twice centrifugal freezing liquor and sodium sulfate decahydrate solid; washing the sodium sulfate decahydrate solid with low-temperature pure water, wherein the washing liquid is used for dissolving crude lithium sulfate in the step S1;
s4, primary evaporation concentration: performing primary evaporation concentration on the secondary centrifugal frozen solution obtained in the step S3 by adopting an MVR forced circulation evaporator, and performing centrifugal separation on the concentrated solution to obtain crude lithium hydroxide;
s5, secondary evaporation concentration: dissolving crude lithium hydroxide with pure water, introducing the solution into a secondary evaporation crystallization system, crushing the precipitated crystal slurry by a crushing pump connected with a secondary evaporation crystallizer in parallel in the forced circulation process, and performing centrifugal separation to obtain wet lithium hydroxide;
s6, vacuum drying and packaging: and (3) conveying the wet product lithium hydroxide obtained in the step (S5) into a belt type vacuum dryer for drying, controlling the drying temperature at 70 ℃ and the drying time at 60 minutes, and packaging and storing the dried product after vibration screen classification and jet milling.
Comparative example 1
The difference from example 2 is that the fluidized bed drying method was used as the drying method, and all the other are the same.
Comparative example 2
The difference from example 2 is that the secondary evaporation concentration section did not introduce a slurry crushing process, all other things being equal.
The content of the battery grade lithium hydroxide monohydrate products prepared in example 2 and comparative examples 1 to 2 was analyzed, and the results are shown in table 1.
From the results in Table 1, it can be seen that the battery grade lithium hydroxide monohydrate product obtained by the preparation method in example 2 of the invention has high main content, low content of other impurities, uniform particle size distribution and good quality; in contrast, in comparative example 1, the fluidized bed drying method is adopted for drying, the carbonate and magnetic substance content in the product is obviously increased, and in particular, the magnetic substance content is increased by more than 4 times compared with that in example 2; in comparative example 2, the crystal slurry crushing process is not introduced in the secondary evaporation concentration section, the particle size distribution is wide, and part of impurities are slightly higher than those in example 2; the invention is illustrated that the impurity content in the product can be effectively reduced by introducing the crystal slurry crushing process after the crystallization system of the secondary evaporation concentration section and simultaneously using the vacuum drying method, the particle size distribution is more uniform, and the quality of the battery grade lithium hydroxide monohydrate product is improved.
Finally, it should be emphasized that the foregoing description is merely illustrative of the preferred embodiments of the invention, and that various changes and modifications can be made by those skilled in the art without departing from the spirit and principles of the invention, and any such modifications, equivalents, improvements, etc. are intended to be included within the scope of the invention.
Claims (7)
1. A method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate, which is characterized by comprising the following specific steps:
s1, dissolving and purifying crude lithium sulfate, and removing impurities: dissolving crude lithium sulfate with pure water to obtain a solution, regulating the pH of the solution to 10-12 with sodium hydroxide, adding sodium carbonate, stirring, heating to 77-84 ℃ for reaction to primarily precipitate calcium and magnesium ions, filtering the reacted mixed solution with a filter to obtain a filtrate, and further removing the calcium and magnesium ions from the filtrate with ion exchange resin to obtain a lithium sulfate purifying solution;
s2, causticizing by mixed alkali: delivering the lithium sulfate purifying solution obtained in the step S1 into a mixing alkali preparation tank, and adding solid sodium hydroxide to carry out mixing stirring to obtain mixed alkali liquor;
s3, freezing and crystallizing: performing twice freezing crystallization and centrifugal separation on the mixed alkali liquor obtained in the step S2 to obtain twice centrifugal frozen liquor and sodium sulfate decahydrate solid;
s4, primary evaporation concentration: performing primary evaporation concentration on the secondary centrifugal frozen solution obtained in the step S3 by adopting an MVR forced circulation evaporator, and performing centrifugal separation on the obtained concentrated solution to obtain crude lithium hydroxide;
s5, secondary evaporation concentration: dissolving crude lithium hydroxide with pure water, introducing the obtained solution into a secondary evaporation crystallizer for crystallization, crushing the precipitated crystal slurry by crushing equipment in the forced circulation process, and then performing centrifugal separation to obtain wet lithium hydroxide; the crushing equipment is a crushing pump connected with the secondary evaporation crystallizer in parallel;
s6, vacuum drying and packaging: and (3) delivering the wet product lithium hydroxide obtained in the step (S5) into a belt type vacuum dryer for vacuum drying, grading the dried product by a vibration sieve, crushing by air flow, and packaging and storing.
2. The method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate according to claim 1, wherein in step S2, the molar ratio of the added sodium hydroxide to the total lithium oxide in the lithium sulfate purification solution is 2:1-2.5:1.
3. The method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate according to claim 1, wherein in step S3, the sodium sulfate decahydrate solid is washed with pure water at 3-10 ℃, and the washed washing solution is used for dissolving crude lithium sulfate in step S1.
4. The method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate according to claim 1, wherein the temperature of the freeze crystallization is controlled between-5 ℃ and 0 ℃ in step S3.
5. The method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate according to claim 1, wherein in step S3 the machine for freeze crystallization is a forced circulation freeze crystallizer.
6. The method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate according to claim 1, wherein in step S6, the temperature of the vacuum drying is controlled between 50 ℃ and 70 ℃ and the drying time is 40 to 60 minutes.
7. The method for preparing battery grade lithium hydroxide monohydrate from crude lithium sulfate of claim 1, wherein in step S6, the conveyor belt in the belt vacuum dryer is a non-metallic material.
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