阅读说明：本技术 一种回收空气净化用氢氧化锂制备高纯碳酸锂的方法 (Method for preparing high-purity lithium carbonate by recycling lithium hydroxide for air purification ) 是由 刘杰 闫月明 刘彤 闫亚辉 李栋梁 于 2021-08-27 设计创作，主要内容包括：本发明涉及一种回收空气净化用氢氧化锂制备高纯碳酸锂的方法,属于化工生产技术领域。所述方法首先将回收的空气净化用氢氧化锂物料进行烘干,然后与工业级二氧化碳进行反应,得到碳酸锂粗品,精制后与氢氧化钙进行苛化反应,得到氢氧化锂溶液,之后再经碳化、固液分离、搅洗、烘干后得到高纯碳酸锂。所述方法在苛化反应前对物料进行预处理一方面可以除去物料中的部分杂质,降低杂质离子含量；另一方面可以提高锂的转化率,通过初步碳化可以将锂尽可能地转化为碳酸锂,物料组成均匀一致。所述方法工序简单、成本较低、易于工业化生产；且所述方法中引入的化学试剂较少,降低了产品中杂质离子的含量,有效提高了产品的纯度。(The invention relates to a method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification, belonging to the technical field of chemical production. The method comprises the steps of firstly drying a recovered lithium hydroxide material for air purification, then reacting with industrial-grade carbon dioxide to obtain a lithium carbonate crude product, carrying out causticization reaction on the refined lithium carbonate crude product and calcium hydroxide to obtain a lithium hydroxide solution, and then carrying out carbonization, solid-liquid separation, stirring and washing and drying to obtain the high-purity lithium carbonate. The method can remove part of impurities in the material and reduce the content of impurity ions on the one hand by pretreating the material before the causticization reaction; on the other hand, the conversion rate of lithium can be improved, lithium can be converted into lithium carbonate as much as possible through primary carbonization, and the material composition is uniform and consistent. The method has simple process, low cost and easy industrial production; and the method introduces less chemical reagents, reduces the content of impurity ions in the product and effectively improves the purity of the product.)

1. A method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification is characterized by comprising the following steps: the method comprises the following steps:

(1) drying materials: drying the recovered lithium hydroxide material for air purification to obtain a dried material;

(2) preparing a lithium carbonate crude product: placing the dried material in a closed container, introducing industrial-grade carbon dioxide gas for reaction, and converting lithium hydroxide into lithium carbonate to obtain a crude lithium carbonate product;

(3) and (3) refining lithium carbonate: crushing the crude lithium carbonate product, stirring and washing with pure water, drying, and crushing to obtain refined lithium carbonate powder;

(4) carrying out causticization reaction: adding calcium hydroxide into pure water while stirring, fully and uniformly mixing, adding the lithium carbonate powder for causticization reaction, after the reaction is finished, roughly filtering, collecting filtrate, and finely filtering to obtain a lithium hydroxide solution;

(5) carbonizing: adding the lithium hydroxide solution into a reaction kettle, introducing industrial-grade carbon dioxide gas while stirring, reacting at normal pressure, stopping introducing gas when the pH value of the reaction solution is reduced to 10, continuously stirring, heating to 80-98 ℃, preserving heat for 10-30 min, and finishing the reaction to obtain a suspension;

(6) collecting high-purity lithium carbonate: and after centrifugally separating the suspension, stirring and washing the obtained solid with pure water, and drying to obtain the high-purity lithium carbonate.

2. The method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification as claimed in claim 1, wherein the method comprises the following steps: the moisture content in the material dried in the step (1) is less than or equal to 0.5 wt%.

3. The method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification as claimed in claim 1, wherein the method comprises the following steps: and (3) placing the dried material in a closed container in the step (2), wherein a gas inlet is formed above the closed container, a gas outlet is formed below the closed container, industrial-grade carbon dioxide gas is introduced into the closed container from the gas inlet to react, and when the flow of the industrial-grade carbon dioxide gas at the gas outlet is constant, the reaction is finished to obtain a crude lithium carbonate product with the purity of more than or equal to 98.5%.

4. The method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification as claimed in claim 1, wherein the method comprises the following steps: in the step (3), the particle size of the crushed particles is more than or equal to 30 meshes.

5. The method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification as claimed in claim 1, wherein the method comprises the following steps: and (3) during stirring and washing, the mass ratio of the crude lithium carbonate to the pure water is 0.3: 1-0.5: 1, the stirring and washing temperature is greater than or equal to 80 ℃ and less than 100 ℃, and the stirring and washing time is 30-60 min.

6. The method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification as claimed in claim 1, wherein the method comprises the following steps: the purity of the lithium carbonate powder in the step (3) is greater than or equal to 99%.

7. The method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification as claimed in claim 1, wherein the method comprises the following steps: the mass ratio of the calcium hydroxide to the pure water in the step (4) is 0.03: 1-0.05: 1.

8. The method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification as claimed in claim 1, wherein the method comprises the following steps: in the step (4), the filtration precision is less than or equal to 0.1 mu m during fine filtration; when the content of metal impurity ions in the filtrate is more than 10ppm, adding a complexing agent into the filtrate to remove the impurity ions, and then performing fine filtration.

9. The method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification as claimed in claim 1, wherein the method comprises the following steps: in the step (6): stirring and washing, wherein the solid-liquid ratio is 0.3: 1-0.5: 1; the purity of the high-purity lithium carbonate is more than 4N grade.

10. The method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification as claimed in claim 1, wherein the method comprises the following steps: the moisture content in the dried material in the step (1) is less than or equal to 0.5 wt%;

placing the dried material in a closed container in the step (2), wherein a gas inlet is formed above the closed container, a gas outlet is formed below the closed container, industrial-grade carbon dioxide gas is introduced into the closed container from the gas inlet to react, and when the flow of the industrial-grade carbon dioxide gas at the gas outlet is constant, the reaction is finished to obtain a crude lithium carbonate product with the purity of more than or equal to 98.5%;

in the step (3): the crushed grain size is more than or equal to 30 meshes; when stirring and washing are carried out, the mass ratio of the lithium carbonate crude product to pure water is 0.3: 1-0.5: 1, the stirring and washing temperature is more than or equal to 80 ℃ and less than 100 ℃, and the stirring and washing time is 30-60 min; the purity of the lithium carbonate powder is greater than or equal to 99%;

in the step (4): the mass ratio of the calcium hydroxide to the pure water is 0.03: 1-0.05: 1; the filtration precision is less than or equal to 0.1 mu m during fine filtration; when the content of metal impurity ions in the filtrate is more than 10ppm, adding a complexing agent into the filtrate to remove the impurity ions, and then performing fine filtration;

in the step (6): stirring and washing, wherein the solid-liquid ratio is 0.3: 1-0.5: 1; the purity of the high-purity lithium carbonate is more than 4N grade.

Technical Field

The invention relates to a method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification, belonging to the technical field of chemical production.

Background

Currently, lithium carbonate is widely applied to the fields of ceramics, glass, atomic energy, aerospace, lithium batteries, lithium alloys, medicines and the like. Lithium carbonate is also a raw material for preparing various lithium compounds. With the maturity of various lithium extraction technologies, the development cost of industrial-grade lithium carbonate is reduced, the price is greatly reduced, the demand gradually tends to be saturated, the market space is gradually reduced, and the competition is increasingly intense. Meanwhile, with the expansion of market demand of new energy and new materials for high-purity lithium salt and the continuous progress of technological research, the demand of high-purity lithium carbonate is increasing at home and abroad, so that the development of high-purity lithium carbonate with high added value is imperative.

The existing preparation method of high-purity lithium carbonate mainly comprises the following steps: recrystallization, causticization and carbonization, causticization and urea precipitation, causticization and ammonium carbonate precipitation, hydrogenation, lithium hydroxide carbonization, etc. The raw materials generally have higher requirements, and are industrial-grade lithium carbonate, battery-grade lithium carbonate or industrial-grade lithium hydroxide and battery-grade lithium hydroxide, and the raw material cost is high. And certain production process conditions are harsh, and large-scale production is difficult.

Lithium hydroxide is a high-efficiency carbon dioxide absorbent, and is often used in closed spaces (such as submarines, underground tunnels and safety cabins) to absorb carbon dioxide to purify air, so that normal life and production activities of personnel in the spaces are guaranteed. During the use process, the lithium hydroxide absorbs the carbon dioxide and converts the carbon dioxide into lithium carbonate, and other acid gases are absorbed at the same time. Because lithium hydroxide has different use environments and conditions and different reaction degrees, moisture and impurity contents, the lithium hydroxide cannot be directly used as a raw material for other production activities. At present, no report related to the recovery of lithium hydroxide for air purification and the reuse of lithium hydroxide for preparing high-purity lithium carbonate exists.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for preparing high purity lithium carbonate by recovering lithium hydroxide for air purification.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a method for preparing high-purity lithium carbonate by recovering lithium hydroxide for air purification comprises the following steps:

(1) drying materials: drying the recovered lithium hydroxide material for air purification to obtain a dried material;

(2) preparing a lithium carbonate crude product: placing the dried material in a closed container, introducing industrial-grade carbon dioxide gas for reaction, and converting lithium hydroxide into lithium carbonate to obtain a crude lithium carbonate product;

(3) and (3) refining lithium carbonate: crushing the crude lithium carbonate product, stirring and washing with pure water, drying, and crushing to obtain refined lithium carbonate powder;

(4) carrying out causticization reaction: adding calcium hydroxide into pure water while stirring, fully and uniformly mixing, adding the lithium carbonate powder for causticization reaction, after the reaction is finished, roughly filtering, collecting filtrate, and finely filtering to obtain a lithium hydroxide solution;

(5) carbonizing: adding the lithium hydroxide solution into a reaction kettle, introducing industrial-grade carbon dioxide gas while stirring, reacting at normal pressure, stopping introducing gas when the pH value of the reaction solution is reduced to 10, continuously stirring, heating to 80-98 ℃, preserving heat for 10-30 min, and finishing the reaction to obtain a suspension;

(6) collecting high-purity lithium carbonate: and after centrifugally separating the suspension, stirring and washing the obtained solid with pure water, and drying to obtain the high-purity lithium carbonate.

In the step (1): preferably, the moisture content in the dried material is less than or equal to 0.5 wt%.

In the step (2): preferably, the dried material is placed in a closed container, a gas inlet is formed above the closed container, a gas outlet is formed below the closed container, industrial carbon dioxide gas is introduced into the closed container from the gas inlet to react, and when the flow of the industrial carbon dioxide gas at the gas outlet is constant, the reaction is finished, so that the crude lithium carbonate product with the purity of more than or equal to 98.5% is obtained.

In the step (3):

preferably, the pulverized particle size is 30 mesh or larger.

Preferably, during stirring and washing, the mass ratio of the lithium carbonate crude product to pure water is 0.3: 1-0.5: 1, the stirring and washing temperature is greater than or equal to 80 ℃ and less than 100 ℃, and the stirring and washing time is 30-60 min.

Preferably, the purity of the lithium carbonate powder is 99% or more.

In the step (4):

preferably, the mass ratio of the calcium hydroxide to the pure water is 0.03: 1-0.05: 1.

Preferably, the filtration precision during fine filtration is less than or equal to 0.1 μm; when the content of metal impurity ions in the filtrate is more than 10ppm, adding a complexing agent into the filtrate to remove the impurity ions, and then performing fine filtration.

In the step (6):

preferably, the solid-liquid ratio is 0.3:1 to 0.5:1 during stirring and washing.

Preferably, the purity of the high-purity lithium carbonate is more than 4N grade.

Advantageous effects

In the method, the materials are pretreated before the causticization reaction, so that on one hand, partial impurities in the materials can be removed, and the content of impurity ions is reduced; on the other hand, the conversion rate of lithium can be improved (more than 80%), lithium can be converted into lithium carbonate as far as possible through primary carbonization, the material composition is uniform and consistent, and the lithium carbonate can be conveniently subjected to batch production in subsequent production links. Specifically, the method comprises the following steps: during pretreatment, firstly, drying the recovered lithium hydroxide material for air purification to evaporate water in the material, and forming a certain porosity on the surface and inside of the material, so as to facilitate full contact reaction with carbon dioxide in the subsequent ventilation process; if the drying is not carried out, the water molecules can prevent carbon dioxide from entering the material, so that the conversion rate of lithium hydroxide is reduced, and the material is high in non-uniform degree; then, the dried material is reacted with industrial grade carbon dioxide with low impurity content, so that the lithium carbonate obtained by the reaction has high purity; then crushing the lithium carbonate to reduce the particle size of the lithium carbonate, further fully contacting with pure water in the stirring and washing process, effectively removing soluble components in the material, reducing the particle size by crushing again after stirring and washing, increasing the material contact area in the subsequent causticization reaction, and improving the reaction rate.

In the method, when the recovered lithium hydroxide material for air purification is dried, the moisture content in the dried material is controlled to be less than or equal to 0.5 wt%, so that the conversion rate of lithium hydroxide can be effectively improved.

In the method, the mass ratio of the solid to the pure water is controlled in the stirring and washing process of the crude lithium carbonate product, so that the solid material can be fully washed, and the pure water can be fully utilized; the agitation washing process is performed at a high temperature, which contributes to a reduction in the amount of lithium carbonate dissolved, thereby improving the yield.

The method has simple process, low cost and easy industrial production; and the method introduces less chemical reagents, reduces the content of impurity ions in the product and effectively improves the purity of the product.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

Example 1:

(1) drying materials: 6Kg of the recovered LiOH material for air purification was taken, wherein the water content was 9.41 wt%, the lithium hydroxide content was 11.00 wt%, and the lithium carbonate content was 78.50 wt%. Drying for 5h at 150 ℃ to obtain a dried material, wherein the moisture content is detected to be 0.3 wt%.

(2) Preparing a lithium carbonate crude product: and (3) putting the dried material into a closed container, wherein a gas inlet is formed above the closed container, a gas outlet is formed below the closed container, industrial-grade carbon dioxide is introduced into the closed container, industrial-grade carbon dioxide gas is introduced into the closed container from the gas inlet to react, and when the flow of the industrial-grade carbon dioxide gas at the gas outlet is constant, the reaction is finished to obtain a crude lithium carbonate product with the purity of 98.5%.

(3) And (3) refining lithium carbonate: and crushing the crude lithium carbonate product by using a crusher, sieving the crushed lithium carbonate product by using a 30-mesh sieve, weighing 300g of undersize material, adding the undersize material into a stainless steel beaker, adding 1Kg of primary pure water into the stainless steel beaker, stirring the mixture for 30min at 95 ℃, filtering the mixture by using a 400-mesh sieve, drying the obtained solid for 5h at 150 ℃, cooling the dried solid, crushing the cooled solid, and sieving the sieved solid by using a 30-mesh sieve, wherein the undersize material is refined lithium carbonate powder with the purity of 99.10 percent.

(4) Carrying out causticization reaction: adding 1Kg of primary pure water into a stainless steel cup, slowly adding 46g of calcium hydroxide powder while stirring at 95 ℃, slowly adding 40g of lithium carbonate powder into the solution after the solution is uniformly stirred, heating and stirring for reacting for 40min, stopping the reaction, roughly filtering (the filtering precision is 5 mu m), and finely filtering the obtained filtrate (the filtering precision is 0.020 mu m) to obtain a lithium hydroxide solution.

(5) Carbonizing: transferring the lithium hydroxide solution into a reaction kettle, introducing industrial-grade carbon dioxide gas into the refined lithium hydroxide solution, wherein the gas flow rate is 10L/min, reacting while stirring at 25 ℃, stopping introducing gas when the pH value of the solution is reduced to 10, heating to 95 ℃, continuously and slowly stirring for 20min, and obtaining a suspension after the reaction is finished.

(6) Collecting high-purity lithium carbonate: and introducing the suspension into a centrifugal machine, and performing centrifugal separation to obtain a solid which is a lithium carbonate wet material. And taking out the lithium carbonate wet material, putting the lithium carbonate wet material into a stirring and washing device, stirring and washing the lithium carbonate wet material twice at 95 ℃, adding 130mL of primary pure water each time, stirring and washing the lithium carbonate wet material for 10min, and then filtering and drying the lithium carbonate wet material to obtain high-purity lithium carbonate, wherein the detection results are shown in Table 1.

Example 2:

(1) drying materials: 18Kg of the recovered LiOH material for air purification was taken, wherein the water content was 3.50% by weight, the lithium hydroxide content was 3.08% by weight, and the lithium carbonate content was 91.50% by weight. Drying for 5h at 150 ℃ to obtain a dried material, and detecting the water content to be 0.

(2) Preparing a lithium carbonate crude product: and (3) putting the dried material into a closed container, wherein a gas inlet is formed above the closed container, a gas outlet is formed below the closed container, industrial-grade carbon dioxide is introduced into the closed container, industrial-grade carbon dioxide gas is introduced into the closed container from the gas inlet to react, and when the flow of the industrial-grade carbon dioxide gas at the gas outlet is constant, the reaction is finished to obtain a crude lithium carbonate product with the purity of 98.7%.

(3) And (3) refining lithium carbonate: and crushing the crude lithium carbonate product by using a crusher, sieving the crushed lithium carbonate product by using a 30-mesh sieve, weighing 17Kg of undersize material, adding the undersize material into a stainless steel beaker, adding 50Kg of primary pure water into the stainless steel beaker, stirring the mixture for 30min at 95 ℃, filtering the mixture by using a 400-mesh sieve, drying the obtained solid for 5h at 150 ℃, cooling the dried solid, crushing the cooled solid, and sieving the cooled solid by using a 30-mesh sieve, wherein the undersize material is refined lithium carbonate powder with the purity of 99.28 percent.

(4) Carrying out causticization reaction: adding 50Kg of first-grade pure water into a stainless steel cup, slowly adding 4.95Kg of calcium hydroxide powder at 95 ℃ while stirring, slowly adding 3.30Kg of the lithium carbonate powder into the solution after uniformly stirring the solution, heating and stirring the solution for reaction for 65min, stopping the reaction, roughly filtering the solution (the filtering precision is 5 mu m), adding 30g of Ethylene Diamine Tetraacetic Acid (EDTA) into the filtrate, stirring the solution for 20min, and finely filtering the solution (the filtering precision is 0.050 mu m) to obtain the lithium hydroxide solution.

(5) Carbonizing: transferring the lithium hydroxide solution into a reaction kettle, introducing industrial-grade carbon dioxide gas into the refined lithium hydroxide solution, wherein the gas flow rate is 100L/min, reacting while stirring at 25 ℃, stopping introducing gas when the pH value of the solution is reduced to 10, heating to 95 ℃, continuously and slowly stirring for 30min, and obtaining a suspension after the reaction is finished.

(6) Collecting high-purity lithium carbonate: and introducing the suspension into a centrifugal machine, and performing centrifugal separation to obtain a solid which is a lithium carbonate wet material. Taking out the lithium carbonate wet material, putting the lithium carbonate wet material into a stirring and washing device, stirring and washing the lithium carbonate wet material twice at 95 ℃, adding 60L of primary pure water each time, stirring and washing the lithium carbonate wet material for 20min, and then filtering and drying the lithium carbonate wet material to obtain high-purity lithium carbonate, wherein the detection results are shown in Table 1.

TABLE 1

Comparative example 1:

6Kg of the recovered LiOH material for air purification was taken to have a composition identical to that in example 1, wherein the water content was 9.41% by weight, the lithium hydroxide content was 11.00% by weight, and the lithium carbonate content was 78.50% by weight. Directly putting the materials into a closed container with an upper air inlet and a lower air outlet without drying, introducing industrial-grade carbon dioxide into the closed container, and stopping introducing the air after the reaction is finished. Detecting the material composition: the moisture content was 8.30 wt%, the lithium hydroxide content was 9.52 wt%, and the lithium carbonate content was 81.08 wt%. The subsequent operation steps were the same as in example 1, and the recovery rate of lithium was reduced by 10% and the yield of high-purity lithium carbonate was also reduced by 10% as compared with comparative document 1. The reason is that if the recycled LiOH material for air purification is not dried, but carbon dioxide is directly introduced, the reaction is not sufficient, and how much lithium hydroxide remains in the LiOH material means that the yield of high-purity lithium carbonate is reduced, and after treatment, the composition uniformity of the LiOH material is still poor, and the subsequent batch treatment is difficult.

In summary, the invention includes but is not limited to the above embodiments, and any equivalent replacement or local modification made under the spirit and principle of the invention should be considered as being within the protection scope of the invention.