Preparation method of low-silicon battery grade lithium hydroxide monohydrate

Abstract

The invention relates to the technical field of lithium salt production, in particular to a preparation method of low-silicon battery grade lithium hydroxide monohydrate, which comprises the following steps: after lithium concentrate is transformed, acidified and roasted, acidified ore is added for pulping to obtain a leaching solution, then the leaching solution is subjected to multi-stage filtration to control the solid content of a lithium sulfate solution, and filtering, adding a silicon removal agent for leaching, callback and deep impurity removal, and performing evaporation concentration causticization, freezing, crystallizing and drying on the impurity-removed solution in a subsequent process. In the leaching and callback process, the silicon in the feed liquid is further removed by controlling the pH of the feed liquid, adding chemicals, controlling the adding proportion of sodium metaaluminate, controlling the reaction time and controlling the reaction temperature, the treatment operation is simple, the silicon removal effect is stable and good, the silicon content in the obtained finished product reaches 3 ppm, various customer requirements are met, and the market competitiveness is high.

Description

Technical Field

[0001] The invention relates to the technical field of lithium salt production, and in particular to a method for preparing low-silicon battery-grade lithium hydroxide monohydrate. Background Art

[0003] In the process of leaching spodumene sulfuric acid smelting process to prepare battery-grade lithium hydroxide monohydrate, the main component of spodumene, LiAlSi2O6, in which silicon is partially dissolved to form soluble silicates. The existing production process has a low removal rate and is brought into the finished product through the crystallization process during the production process, seriously affecting the purity of the lithium hydroxide monohydrate product. In the downstream battery material production process, the high content of silicon impurities can directly lead to limited battery charging and discharging functions.

[0004] Patent CN201210126529.9 discloses a method for preparing high-purity lithium hydroxide monohydrate, comprising the following steps: adding Ca(OH)2 to the lithium sulfate leachate to adjust the pH, filtering to obtain a sulfuric acid primary purification liquid, adding sodium hydroxide, then filtering and removing impurities, and crystallizing to obtain Na2S04·10H20 solid and Li0H frozen liquid; after the Li0H frozen liquid is precisely filtered, it is evaporated and separated to obtain a Li0H primary crude product, which is dissolved in water, and a refining agent is added to remove sodium, and then evaporated and concentrated, separated, and eluted to obtain a Li0H·H20 secondary crude product; water is added to the secondary crude product, evaporated and concentrated, cooled, crystallized, and dried to obtain high-purity lithium hydroxide monohydrate. Although this method successfully uses lithium sulfate solution to obtain a lithium hydroxide monohydrate product through purification and impurity removal, causticization and freezing, evaporation and crystallization, etc., the silicon impurities in the lithium sulfate primary purification liquid exist in the form of silicates, and the Si content is ≤10g / l. Its Si impurity content is relatively high, and the risk of product indicators exceeding the limit in the subsequent deep processing process is relatively high.

[0005] According to the requirements for impurity indicators in the GB / T 26008-2020 "Battery-grade lithium hydroxide monohydrate" standard, the national standard for battery-grade lithium hydroxide monohydrate requires that the Si content of each brand of product be less than 50ppm. The silicon impurity content of commercially available lithium hydroxide products is mostly in the range of 15 to 30ppm.

[0006] At present, there are some methods for preparing battery-grade lithium hydroxide monohydrate by controlling the impurity silicon, but the effect is not ideal, and there are problems such as low removal rate, unstable indicators, high cost, and complicated operation. Therefore, it is of great practical significance to develop a simple, stable, efficient, and low-cost method for preparing low-silicon battery-grade lithium hydroxide monohydrate. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing low-silicon battery-grade lithium hydroxide monohydrate, so as to solve the technical problems that the method for preparing battery-grade lithium hydroxide monohydrate for controlling impurity silicon in the prior art has unsatisfactory effect, low removal rate, unstable indicators, high cost, complicated operation and the like.

[0008] The present invention discloses a method for preparing low-silicon battery-grade lithium hydroxide monohydrate, comprising the following steps:

[0009] After the lithium concentrate is transformed and acidified and roasted, the acidified ore is added to make pulp to obtain the leaching solution, and then the leaching solution is filtered at multiple stages to control the solid content of the lithium sulfate solution. After filtration, a silicon remover is added to perform leaching callback and deep impurity removal. The impurity-removed solution enters the subsequent process for evaporation, concentration, causticization, freezing, crystallization and drying.

[0010] Furthermore, a pH adjustment agent is added during the acidified ore pulping process to reduce silicon leaching.

[0011] Furthermore, the pH adjustment agent is at least one of alkali metal, alkaline earth metal oxide, hydroxide and carbonate.

[0012] Furthermore, the PH adjustment agent is PH adjustment agent 1 and PH adjustment agent 2.

[0013] Furthermore, the pH adjustment agent 1 is double fly powder, and the pH adjustment agent 2 is lime powder, sodium hydroxide or lithium hydroxide.

[0014] Furthermore, the pH adjustment agent is a solid or a solution.

[0015] Furthermore, the reaction time of the acidified ore pulping process is 5 to 60 minutes, the reaction pH is 5 to 9, and the temperature is controlled at 30° C. to 80° C.

[0016] Furthermore, the solid content of lithium slag in the lithium sulfate solution is controlled to be 25% to 40%.

[0017] Furthermore, in the leaching adjustment, the pH value of the liquid is 5-12, the reaction temperature is 40-60° C., and the reaction time is 15-90 minutes.

[0018] Furthermore, the multi-stage filtering stages are 2-4.

[0019] Furthermore, the multi-stage filtration includes at least one of plate and frame filtration desiliconization, bag filtration desiliconization, precision filtration desiliconization or membrane filtration desiliconization.

[0020] Furthermore, the mesh number of the filter cloth used in the multi-stage filtration is 200-2000 meshes; or the specification of the filter element used is 4-75 microns; or the specification of the filter membrane used is 1-10 microns.

[0021] Furthermore, after filtering, the impurity removal pH is adjusted to 11-12 and then a silicon removal agent is added.

[0022] Furthermore, the silicon removal agent is sodium aluminate.

[0023] Furthermore, the molar ratio of silicon to the silicon removing agent is 1:3 to 1:10.

[0024] Furthermore, the impurity removal temperature is 40-50° C., and the stirring time is 20-30 min.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. In the acidification ore pulping process, by adding appropriate reagents, controlling the reaction time, controlling the reaction pH, and controlling the solid content, the leaching of silicon is reduced, and the difficulty of subsequent silicon removal is reduced;

[0027] 2. In the multi-stage filtration process of the leaching solution, the dissolution of silicon impurities is reduced by controlling the filtration stage, filtration accuracy and other conditions;

[0028] 3. In the leaching callback process, the pH of the feed solution is controlled, the proportion of sodium aluminate added is controlled, the reaction time is controlled, and the reaction temperature is controlled to further remove the silicon in the feed solution. The processing operation is simple, the silicon removal effect is stable and good, and the silicon content in the finished product reaches 3ppm, which meets the needs of various customers and has strong market competitiveness. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0030] In the following examples, the amount of wash water added to the pulping tank each time is 18 ml. 3 , 25m3 of liquid is added each time 3 .

[0031] Example 1

[0032] The method for preparing low-silicon battery-grade lithium hydroxide monohydrate using the above-mentioned device in this embodiment comprises the following steps:

[0033] Add 18.0m3 of wash water into the pulping tank 3, add 1000.8kg of double fly powder, stir evenly, then add 9.12t of acid ore, add 58.4kg of lime powder, the pH of the liquid is 7.5, the reaction temperature is 55℃, the reaction time is 45min, and the solid content of the slurry is 32.9%. The silicon concentration in the filtrate is 0.0195g / L. After using the first-level plate-frame filtration with a filtration accuracy of 70 microns and the first-level fine bag filtration with a filtration accuracy of 15 microns, the silicon concentration in the filtrate is 0.0105g / L. Adjust the impurity removal pH to 12 and add 3 times the molar number of silicon sodium aluminate reagent. Stir for 30 minutes under the condition of impurity removal temperature of 45℃ for leaching and callback, and then filter. The composition and impurity element content in the filtrate and the silicon content in the obtained product are shown in Table 1.

[0034] Example 2

[0035] In this embodiment, as a preferred embodiment of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate comprises the following steps:

[0036] Add 18.0m3 of wash water into the pulping tank 3 , add 1150.5kg of double fly powder, stir evenly, then add 10.31t of acid ore, add 80.6kg of sodium hydroxide, the feed liquid pH = 7.0, the reaction temperature is 50℃, the reaction time is 45min, and the slurry solid content is 37.2%. The silicon concentration in the filtrate is 0.0197g / L. After using the first-level plate and frame filtration with a filtration accuracy of 70 microns and the second-level plate and frame filtration with a filtration accuracy of 15 microns, the silicon concentration in the filtrate is 0.0090g / L. Adjust the impurity removal pH = 12 and add 10 times the silicon molar number of sodium aluminate reagent. Stir for 30 minutes under the condition of impurity removal temperature of 45℃ for leaching and callback, and then filter. The composition and impurity element content in the filtrate and the silicon content in the obtained product are shown in Table 1.

[0037] Example 3

[0038] In this embodiment, as a preferred embodiment of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate comprises the following steps:

[0039] Add 18.0m3 of wash water into the pulping tank 3, add 1155.3kg of double fly powder, stir evenly, then add 10.81t of acid ore, add 20.6kg of sodium hydroxide, the feed liquid pH = 5.5, the reaction temperature is 45℃, the reaction time is 30min, and the slurry solid content is 35.2%. The silicon concentration in the filtrate is 0.0186g / L. After the first-level plate and frame filtration with a filtration accuracy of 70 microns and the second-level plate and frame filtration with a filtration accuracy of 15 microns, the silicon concentration in the filtrate is 0.0078g / L. Adjust the impurity removal pH = 12 and add 5 times the silicon molar number of sodium aluminate reagent. Stir for 30 minutes under the condition of impurity removal temperature of 45℃ for leaching and callback, and then filter. The composition and impurity element content in the filtrate and the silicon content in the obtained product are shown in Table 1.

[0040] Comparative Example 1

[0041] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are that 1123.3 kg of double fly ash, 30.5 kg of lime powder, 9.89 t of acidified ore are added, the pH value of the slurry is 4, the solid content of the slurry is 33%, the components and impurity element contents in the filtrate, and the silicon content in the obtained product are as shown in Table 1.

[0042] Comparative Example 2

[0043] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are that 1110.3 kg of double fly ash, 481.5 kg of lithium hydroxide, 9.3 t of acidified ore are added, the pH value of the slurry is 10, the solid content of the slurry is 33%, the components and impurity element contents in the filtrate, and the silicon content in the obtained product are as shown in Table 1.

[0044] Comparative Example 3

[0045] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are the addition of 1050.7 kg of double fly ash, 435.2 kg of lithium hydroxide, 9.34 t of acidified ore, reaction temperature of 85°C, slurry solid content of 32.7%, components and impurity element contents in the filtrate, and silicon content in the obtained product, as shown in Table 1.

[0046] Comparative Example 4

[0047] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are the addition of 1010.3 kg of double fly ash, 450.6 kg of lithium hydroxide, 9.28 t of acidified ore, 70 min of reaction time, 33.3% of slurry solid content, components and impurity element contents in the filtrate, and silicon content in the obtained product, as shown in Table 1.

[0048] Comparative Example 5

[0049] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are the addition of 1180.6 kg of double fly ash, 88.5 kg of sodium hydroxide, 12.55 t of acidified ore, 43.2% solid content of slurry, components and impurity element contents in the filtrate, and silicon content in the obtained product, as shown in Table 1.

[0050] Comparative Example 6

[0051] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are that 1090.8 kg of double fly ash, 55.1 kg of lime powder, 9.59 t of acid ore, and a slurry solid content of 33.4% are added. A first-level plate and frame filtration with a filtration accuracy of 70 microns is used. The composition and impurity element content in the filtrate, and the silicon content in the obtained product are as shown in Table 1.

[0052] Comparative Example 7

[0053] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are that 1120.4 kg of double fly ash, 77.2 kg of sodium hydroxide, 10.01 t of acidified ore are added, the slurry solid content is 35.7%, and filtration is performed using a first-level plate frame with a filtration accuracy of 70 microns and a second-level plate frame with a filtration accuracy of 30 microns. The components and impurity element contents in the filtrate, and the silicon content in the obtained product are as shown in Table 1.

[0054] Comparative Example 8

[0055] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are that 1050.5 kg of double fly ash, 75.6 kg of sodium hydroxide, 9.76 t of acidified ore are added, the pH value of the slurry is 7, the reaction temperature is 50°C, the solid content of the slurry is 33.9%, sodium aluminate with 2 times the molar number of silicon is used, and the components and impurity element contents in the filtrate and the silicon content in the obtained product are as shown in Table 1.

[0056] Comparative Example 9

[0057] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are that 1130.2 kg of double fly ash, 85.5 kg of sodium hydroxide, 9.95 t of acidified ore, 32.9% solid content of slurry, and 5 times the molar number of silicon in magnesium oxide are used as a silicon removal agent. The components and impurity element contents in the filtrate and the silicon content in the obtained product are as shown in Table 1.

[0058] Comparative Example 10

[0059] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are the addition of 1095.1 kg of double fly ash, 56.3 kg of lime powder, 9.79 t of acidified ore, 30°C impurity removal temperature, 32.9% solid content of slurry, components and impurity element content in the filtrate, and silicon content in the obtained product, as shown in Table 1.

[0060] Comparative Example 11

[0061] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are the addition of 1125.2 kg of double fly ash, 82.5 kg of sodium hydroxide, 9.56 t of acidified ore, 80°C impurity removal temperature, 32.1% solid content of slurry, components and impurity element content in the filtrate, and silicon content in the obtained product, as shown in Table 1.

[0062] Comparative Example 12

[0063] In this embodiment, as a comparative example of the present invention, a method for preparing low-silicon battery-grade lithium hydroxide monohydrate is disclosed. The only changes on the basis of Example 1 are that 1026.1 kg of double fly ash, 430.4 kg of lithium hydroxide, 10.12 t of acidified ore, 7, impurity removal stirring time of 10 min, slurry solid content of 33.4%, components and impurity element contents in the filtrate, and silicon content in the obtained product are as shown in Table 1.

[0064] Table 1

[0065]

[0066]

[0067] As can be seen from Table 1, by controlling the ore leaching process conditions, suppressing the leaching concentration of impurity silicon, and by increasing high-precision filtration and deep silicon removal, controlling the content of silicon impurities in the leachate, the impurity content in the lithium hydroxide monohydrate product can be reduced, and finally the preparation of a low-silicon lithium hydroxide product with a Si content of 3PPM can be achieved.

[0068] The above are the implementation methods listed in this embodiment, but this embodiment is not limited to the above optional implementation methods. Those skilled in the art can arbitrarily combine the above methods to obtain other various implementation methods. Anyone can derive other various forms of implementation methods under the inspiration of this embodiment. The above specific implementation methods should not be understood as limiting the scope of protection of this embodiment. The scope of protection of this embodiment shall be based on the definition in the claims, and the description can be used to interpret the claims.

Claims

1. A method for preparing low-silicon battery-grade lithium hydroxide monohydrate, characterized in that: The following steps are involved: After the lithium concentrate is transformed and acidified and roasted, the acidified ore is added to make pulp to obtain the leaching solution, and then the leaching solution is filtered at multiple stages to control the solid content of the lithium sulfate solution. After filtration, a silicon remover is added to perform leaching callback and deep impurity removal. The impurity-removed solution enters the subsequent process for evaporation, concentration, causticization, freezing, crystallization and drying.

2. The method for preparing low-silicon battery-grade lithium hydroxide monohydrate according to claim 1, characterized in that: The pH adjustment agent is added during the acidification ore pulping process to reduce the leaching of silicon.

3. The method for preparing low-silicon battery-grade lithium hydroxide monohydrate according to claim 2, characterized in that: The pH adjustment agent is at least one of alkali metal, alkaline earth metal oxide, hydroxide and carbonate.

4. The method for preparing low-silicon battery-grade lithium hydroxide monohydrate according to claim 3, characterized in that: The pH adjustment agent is double fly ash + lime powder, double fly ash + sodium hydroxide or double fly ash + lithium hydroxide.

5. The method for preparing low-silicon battery-grade lithium hydroxide monohydrate according to claim 1, characterized in that: The reaction time of the acidified ore pulping process is 5 to 60 minutes, the reaction pH is 5 to 9, and the temperature is controlled at 30° C. to 80° C.

6. The method for preparing low-silicon battery-grade lithium hydroxide monohydrate according to claim 1, characterized in that: The multi-stage filtering stages are 2-4.

7. The method for preparing low-silicon battery-grade lithium hydroxide monohydrate according to claim 1, characterized in that: The solid content of lithium slag in the lithium sulfate solution is controlled to be 25% to 40%.

8. The method for preparing low-silicon battery-grade lithium hydroxide monohydrate according to claim 1, characterized in that: In the leaching process, the pH value of the liquid is 5-12, the reaction temperature is 40-60° C., and the reaction time is 15-90 minutes.

9. The method for preparing low-silicon battery-grade lithium hydroxide monohydrate according to claim 1, characterized in that: The silicon removal agent is sodium aluminate.

10. The method for preparing low-silicon battery-grade lithium hydroxide monohydrate according to claim 1, characterized in that: The molar ratio of silicon to silicon remover is 1:3 to 1:10.

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