CN-122010147-A - Method for preparing battery grade lithium hydroxide monohydrate by utilizing lithium carbonate causticization

CN122010147ACN 122010147 ACN122010147 ACN 122010147ACN-122010147-A

Abstract

The invention belongs to the technical field of lithium salt preparation, and provides a method for preparing battery grade lithium hydroxide monohydrate by utilizing lithium carbonate causticization. The method performs synergistic effect by washing raw materials, purifying by ion exchange and combining multi-stage crystallization impurity removal processes comprising evaporation concentration, cyclone classification and elutriation, effectively controls the impurity content of the product and actively removes the lithium carbonate component causing scaling, thereby remarkably relieving the scaling problem of evaporation crystallization equipment while improving the purity of the product, and realizing stable and continuous production of lithium hydroxide monohydrate meeting the quality requirement of a battery grade by taking industrial-grade lithium carbonate as the raw material.

Inventors

SANG YUAN
ZHENG YAQI
DU GUOSHAN
DUAN LIQIANG
YANG YONGLIANG

Assignees

中国恩菲工程技术有限公司
中国有色工程有限公司

Dates

Publication Date: 20260512
Application Date: 20260129

Claims (10)

1. A method for preparing battery grade lithium hydroxide monohydrate by utilizing lithium carbonate causticization, which is characterized by comprising the following steps: (1) The pretreatment of the lithium source comprises the steps of washing a lithium source raw material containing lithium carbonate and carrying out solid-liquid separation to obtain a pretreated material and a washing liquid; (2) The causticizing reaction is carried out by mixing the pretreatment material with alkaline calcium-containing substances to carry out the causticizing reaction to obtain a solid-liquid mixture containing lithium hydroxide; (3) Ion exchange purification treatment, namely performing ion exchange treatment on the lithium hydroxide solution to obtain a purification liquid; (4) Evaporating and concentrating and impurity grading, namely evaporating and concentrating the purified liquid to obtain concentrated liquid, and performing cyclone grading treatment on the concentrated liquid to obtain first lithium carbonate impurities and concentrated overflow liquid, wherein the concentration of lithium hydroxide in the concentrated liquid is 100 g/L-120 g/L; (5) Performing primary evaporation crystallization and elutriation separation, namely performing primary evaporation crystallization and solid-liquid separation on the concentrated overflow liquid to obtain first lithium hydroxide monohydrate crystal slurry, performing primary elutriation on the first lithium hydroxide monohydrate crystal slurry to separate out second lithium carbonate impurities; (6) Refining, redissolving and secondarily evaporating and crystallizing, namely dissolving crude lithium hydroxide monohydrate with water, refining and filtering to obtain redissolved refined solution, secondarily evaporating and crystallizing the redissolved refined solution to obtain second lithium hydroxide monohydrate crystal slurry, performing second-stage elutriation on the second lithium hydroxide monohydrate crystal slurry to separate out third lithium carbonate impurities, and performing solid-liquid separation on the slurry after the second-stage elutriation to obtain wet refined lithium hydroxide monohydrate and secondary crystallization mother liquor; (7) And drying, namely drying the wet refined lithium hydroxide monohydrate to obtain the battery grade lithium hydroxide monohydrate.
2. The method of claim 1, further comprising a step of recycling lithium carbonate, wherein the first lithium carbonate impurity, the second lithium carbonate impurity and the third lithium carbonate impurity are mixed with at least part of primary crystallization mother liquor, carbon dioxide is introduced for carbonation reaction, and solid-liquid separation is carried out after the reaction to obtain a wet lithium carbonate product and a mother liquor for recycling lithium carbonate, wherein the wet lithium carbonate product is returned to the step (2) and is used together with pretreatment materials for subsequent causticization reaction; And/or, the method further comprises a lithium chloride preparation step, namely carrying out a reaction for generating lithium chloride by sequentially carrying out a neutralization reaction with hydrochloric acid and a neutralization reaction with sodium hydroxide on the washing liquid and/or the lithium carbonate recovery mother liquid obtained in the step (1) and the material circulation step, and then carrying out concentration treatment to obtain a lithium chloride product solution.
3. The method according to claim 1 or 2, further comprising returning at least a part of the secondary crystallization mother liquor obtained in step (6) to step (5), mixing with the concentrated overflow liquor, and performing primary evaporation crystallization; and/or the method further comprises the step of recycling the steam condensate water generated in the evaporation concentration of the step (4) and/or the primary evaporation crystallization of the step (5) to the water use step of the method.
4. A method according to claim 1 or 2, wherein in step (1), the washing agent used for the washing comprises water; and/or the washing temperature is 85-100 ℃, and the washing time is 15-60 min; And/or in the step (1), in the process of washing the lithium source raw material containing lithium carbonate, the mass ratio of the lithium source raw material containing lithium carbonate to the detergent is 1 (2-4).
5. The method according to claim 1 or 2, wherein in the step (2), the temperature of the causticizing reaction is 85 ℃ to 98 ℃ and the reaction time is 1h to 5h; And/or the molar ratio of the lithium carbonate in the pretreatment material to the alkali calcium-containing substance calculated by Ca element is (0.5-1.5).
6. The method according to claim 1 or 2, wherein in step (2), the basic calcium-containing substance comprises at least one of calcium hydroxide, calcium oxide; and/or the step (2) further comprises the steps of washing and calcining the causticized slag; And/or in the step (3), the process of the ion exchange treatment comprises the step of sequentially passing the lithium hydroxide solution through a cation exchange resin and an anion chelating resin.
7. The method of claim 6, wherein the washing mode is countercurrent washing, the washing times are more than or equal to 2 times, the mass ratio of causticized slag to water in each washing process is 1 (2-4), and the time of each washing is 15-20 min; and/or the temperature of the calcination treatment is 1000-1200 ℃, and the time of the calcination treatment is more than or equal to 30min; And/or the flow rate through the cation exchange resin and the anion chelating resin is 1.5 m/s-2 m/s each independently.
8. The method according to claim 1 or 2, wherein in the step (4), the evaporation concentration is performed under the conditions of 60 ℃ to 80 ℃ and 20 kPa to 50 kPa; And/or the primary evaporation crystallization is carried out under the conditions of 50-80 ℃ and 20-50 kPa.
9. The method according to claim 1 or 2, wherein the step (5) further comprises a back flushing device arranged at a discharge hole of the crystallizer for primary evaporation crystallization, back flushing is carried out on the discharged material, and the solid phase material separated by the back flushing is returned to the step (2) and is used together with the pretreatment material for subsequent causticizing reaction.
10. The method according to claim 1 or 2, wherein in the step (6), the concentration of lithium hydroxide in the redissolved refined solution is 80 g/L to 120 g/L; And/or the secondary evaporation crystallization is carried out under the conditions of 50-80 ℃ and 20-50 kPa; and/or in the step (7), the drying temperature is 75-90 ℃.

Description

Method for preparing battery grade lithium hydroxide monohydrate by utilizing lithium carbonate causticization Technical Field The invention relates to the technical field of lithium salt preparation, in particular to a method for preparing battery grade lithium hydroxide monohydrate by utilizing lithium carbonate causticization. Background The lithium carbonate causticization method is an important process for converting industrial grade lithium carbonate into lithium hydroxide monohydrate, and is widely paid attention to because of a simple route and environmental friendliness. The method is particularly suitable for treating the inferior grade industrial grade lithium carbonate with lower main content and higher impurity content due to raw material or process fluctuation, and is an effective path for realizing the conversion from low-added value lithium salt resources to high-added value products. In recent years, with the rapid increase of the demand of new energy automobile industry for battery grade lithium salt, the use of this route to produce battery grade lithium hydroxide monohydrate meeting the stringent impurity control requirements has become an urgent industry demand. However, conventional lithium carbonate causticizing processes face a number of challenges in pursuing high purity of the product. In the prior art, after the lithium hydroxide solution is obtained through a causticizing reaction, part of impurities can be removed through a conventional impurity removal means, but in the subsequent key evaporation crystallization process, trace impurity ions such as lithium carbonate and the like remained in the solution are easy to separate out in the thermal concentration process. The precipitated impurities not only directly affect the chemical purity of the final product, so that the final product is difficult to reach the battery level standard, but also is more easy to form intractable scaling on the heat transfer surfaces of core equipment such as evaporators, heat exchangers and the like. Even if the content of most metal impurities in the solution is reduced by adopting a deep purification technology, even products with the main content reaching the standard can be produced, but the problem of equipment scaling in the production process cannot be avoided. The root cause is that two processes of lithium hydroxide crystallization and lithium carbonate precipitation exist in the evaporation crystallization process at the same time, and the crystallization operation condition for improving the purity of the product often aggravates the deposition of lithium carbonate on the surface of the heat exchanger. The scaling phenomenon can obviously reduce the heat transfer efficiency and the production capacity of equipment, increase energy consumption, frequently cause production interruption to carry out cleaning maintenance, severely restrict the continuous, stable and efficient operation of a production line, and lead the large-scale and economical production of battery-grade lithium hydroxide monohydrate to face a great obstacle through the path. Therefore, there is a need for an improved process for causticizing lithium hydroxide monohydrate at a battery level to effectively solve the problems of purity and scaling as described above. Disclosure of Invention The invention provides a method for preparing battery grade lithium hydroxide monohydrate by utilizing lithium carbonate causticization, which aims to solve the problems that the purity of a lithium hydroxide monohydrate product prepared by a lithium carbonate causticization method in the prior art is low, and evaporation and crystallization equipment is easy to scale in the production process, so that the battery grade lithium hydroxide monohydrate cannot be efficiently and continuously produced. In a first aspect, the present invention provides a method for preparing battery grade lithium hydroxide monohydrate by utilizing lithium carbonate causticization, comprising the following steps: (1) The pretreatment of the lithium source comprises the steps of washing a lithium source raw material containing lithium carbonate and carrying out solid-liquid separation to obtain a pretreated material and a washing liquid; (2) The causticizing reaction is carried out by mixing the pretreatment material with alkaline calcium-containing substances to carry out the causticizing reaction to obtain a solid-liquid mixture containing lithium hydroxide; (3) Ion exchange purification treatment, namely performing ion exchange treatment on the lithium hydroxide solution to obtain a purification liquid; (4) Evaporating and concentrating and impurity grading, namely evaporating and concentrating the purified liquid to obtain concentrated liquid, and performing cyclone grading treatment on the concentrated liquid to obtain first lithium carbonate impurities and concentrated overflow liquid, wherein the concentration of lithium hydroxide in the concentrated liqui