WO2023169432A1

WO2023169432A1 - Method and system for preparing battery-grade lithium hydroxide and lithium carbonate

Info

Publication number: WO2023169432A1
Application number: PCT/CN2023/080142
Authority: WO
Inventors: 石苏洋; 雍晨阳; 顾志强; 顾宇
Original assignee: 宁夏中化锂电池材料有限公司; 宁夏瑞泰科技股份有限公司
Priority date: 2022-03-08
Filing date: 2023-03-07
Publication date: 2023-09-14
Also published as: CN114956128A

Abstract

Provided in the present invention are a method and a system for preparing lithium hydroxide and lithium carbonate. The method comprises: (1) synthesis of lithium hydroxide: carrying out at least two stages of causticization reactions on lithium chloride and alkali, and carrying out separation after the reactions to obtain causticization slag of each stage and a last-stage causticization mother liquor, the causticization slag of each stage being a lithium hydroxide crude product; (2) impurity removal for lithium hydroxide: continuously carrying out washing and separation twice or more times on the lithium hydroxide crude product to obtain the last lithium hydroxide washing slag, preparing a solution of the last lithium hydroxide washing slag, and carrying out evaporative crystallization, separation and post-treatment to obtain a lithium hydroxide product; (3) synthesis of lithium carbonate: carrying out evaporative concentration and separation on the last-stage causticization mother liquor to obtain causticization liquid concentrated slag, preparing a solution of the causticization liquid concentrated slag, carrying out a lithium precipitation reaction, and carrying out separation after the reaction to obtain a lithium carbonate crude product; and (4) impurity removal for lithium carbonate: removing impurities from the lithium carbonate crude product to obtain a lithium carbonate product.

Description

A method and system for preparing battery-grade lithium hydroxide and lithium carbonate

Technical field

The invention belongs to the field of lithium-ion battery materials and relates to a method and system for preparing battery-grade lithium hydroxide from salt lake lithium chloride to co-produce battery-grade lithium carbonate.

Background technique

76% of global lithium resources are concentrated in salt lakes, and 24% come from ores.

At present, the mainstream production process of battery-grade lithium hydroxide is the lithium sulfate causticization method using ore as raw material: the lithium concentrate is transformed at high temperature and then acidified to prepare lithium sulfate. After two steps of impurity removal, a pure lithium sulfate solution is obtained, and sodium hydroxide is added to prepare it. Lithium hydroxide and sodium sulfate are produced as a by-product. The causticization reaction is as follows:

2NaOH+Li ₂ SO ₄ =Na ₂ SO ₄ +2LiOH·H ₂ O

Sodium sulfate is precipitated through low-temperature freezing, and the by-product Yuanming powder is obtained after concentration and drying. The frozen mother liquor is concentrated, recrystallized and dried to obtain battery grade lithium hydroxide.

Due to resource constraints, the production capacity of this method is subject to certain constraints.

At present, lithium chloride produced in salt lakes is mainly used to prepare lithium carbonate. Lithium carbonate is obtained through lithium precipitation with sodium carbonate. Due to limitations of the lithium extraction method, the quality of lithium carbonate can generally only reach industrial grade.

The mainstream process for preparing lithium hydroxide from lithium chloride in salt lakes is the lithium carbonate causticization method. The electrolysis method is in the research stage. In addition, there is the lithium chloride causticization method:

(1) Lithium carbonate causticization method

Mix refined lime milk and lithium carbonate in a ratio of 1.08:1, adjust a certain concentration of causticizing liquid, heat to boiling and stir vigorously, the causticizing reaction is as follows

Ca(OH) ₂ +Li ₂ CO ₃ =CaCO ₃ +2LiOH·H ₂ O

The reaction can obtain a lithium hydroxide solution with a concentration of about 3.5%. Insoluble residues (mainly CaCO ₃ ) are removed. After separation, the mother liquor is concentrated under reduced pressure and crystallized to obtain lithium hydroxide monohydrate. After drying, the lithium hydroxide product is obtained.

This process is currently the mainstream process for preparing lithium hydroxide from salt lake lithium chloride. The raw materials are lithium carbonate and calcium hydroxide. Since the solubility of the two raw materials is very small, the reaction concentration is low and the reaction time is long, the energy consumption is high, and the single-pass conversion rate is low. The product lithium hydroxide after the causticization reaction is in the solution and filtered. The residual amount of lithium in the cake is large, the yield of lithium hydroxide is low, and the cost is high. The product lithium hydroxide cannot reach battery grade and can only be used in the lubricant industry.

(2) Lithium chloride electrolysis method

Concentrate the brine to remove sodium chloride and potassium chloride, and remove boron ions and sulfate ions through a certain method. ion, so that the concentration of anions (excluding chloride ions) does not exceed 5%, adjust the pH value to 10.5-11.5, remove calcium and magnesium ions, and further concentrate to obtain refined brine (the main component is LiCl), and the concentration of lithium ions reaches 5-7 % (equivalent to the concentration of lithium chloride 30-42%), and then the refined brine is used as the electrolyte in a special electrolytic tank for electrolysis. The anolyte is refined brine, and the catholyte is water or LiOH solution; in the anolyte There is a cation selective permeability membrane between the catholyte and the catholyte. The cations can pass through, but the anions are blocked and cannot pass through. During electrolysis, Li ⁺ can migrate through the membrane to the cathode and be converted into lithium hydroxide. Finally, a lithium hydroxide solution with a concentration of about 14% can be obtained at the cathode. After concentration, crystallization, recrystallization, washing, and drying, lithium hydroxide is finally obtained. product. This process is technically complex and requires a dedicated ion membrane. It consumes a lot of electricity and steam and requires a lot of investment. It is still in the research stage.

(3) Lithium chloride causticization method

Patent document CN106006675A discloses a method for preparing lithium hydroxide monohydrate using lithium chloride solution as raw material, which uses a certain concentration of lithium chloride solution and a certain concentration of alkali to react under a certain temperature and pressure. The reaction solution Concentrate to obtain lithium hydroxide monohydrate precipitate, and filter, wash, and dry the precipitate to obtain lithium hydroxide monohydrate product. This process does not involve how to utilize the remaining lithium in the causticizing liquid, and the unreasonable impurity removal process results in unstable product quality.

"Experimental research on obtaining a series of lithium products from crude lithium sulfate ores in salt fields" (Wang Chun, "China's Excellent Master's Thesis Full-text Database", Issue 3, pp. 35-44, March 15, 2016) published a A method for preparing lithium hydroxide monohydrate using a lithium chloride enriched solution, and specifically discloses: continue evaporating the first-level concentrated liquid to concentrate Li ⁺ to about 49g/L, so that most of the sulfate radicals are converted into lithium sulfate monohydrate Precipitate in the form, and after solid-liquid separation, a secondary concentrated solution (that is, a highly enriched solution of lithium chloride) is obtained. According to the stoichiometric ratio, 5 mol/L NaOH solution is added to the secondary concentrated solution to obtain a lithium hydroxide solution. The solution is evaporated and concentrated, evaporating about 60% of the water, crystallizing and precipitating lithium hydroxide, adding sodium hydroxide to convert lithium chloride into lithium hydroxide and generating sodium chloride at the same time. The composition of the obtained lithium hydroxide precipitate is mainly 36.3% Lithium hydroxide monohydrate and 62.34% sodium chloride. The lithium hydroxide product obtained by this method contains a large amount of sodium chloride product. The purity of lithium hydroxide is extremely low. Battery-grade lithium hydroxide cannot be obtained, and the purification of lithium hydroxide has not been studied.

Patent document CN109516479A describes a method for producing lithium hydroxide by lithium chloride causticization. This process obtains lithium hydroxide-containing slag and lithium precipitation mother liquor by reacting lithium chloride with sodium hydroxide/potassium hydroxide. The synthetic slag is then Purification is performed to obtain battery-grade lithium hydroxide, and the lithium precipitation mother liquor is neutralized and recovered with hydrochloric acid. In this process, a large amount of lithium exists in the synthesis mother liquor and is neutralized by hydrochloric acid into lithium chloride, which cannot achieve a higher conversion rate in a single time. The synthesis mother liquor also contains a large amount of alkali that cannot be fully utilized, so the hydrochloric acid neutralization method is used. This makes the amount of hydrochloric acid used larger; overall raw material consumption and lithium utilization are at a disadvantage.

It can be seen that the existing method of producing lithium hydroxide from lithium chloride has the problems of low product purity, low yield and high cost:

(1) Low purity: Add sodium hydroxide to the lithium chloride solution to obtain a solution of lithium hydroxide and sodium chloride. Since the solubility of lithium hydroxide and sodium chloride is not large, and the solubility changes little with temperature, post-processing is required. Process Lithium Hydroxide Monohydrate It precipitates together with sodium chloride, resulting in excessive chloride ions and sodium ions in lithium hydroxide, making it difficult to obtain battery-grade lithium hydroxide;

(2) Low yield: Since lithium hydroxide monohydrate has a certain solubility in water, the yield of the single-pass reaction product is low. In addition, the dissolution loss of the post-processing lithium hydroxide filter cake washing results in a higher yield of the final product lithium hydroxide. Low;

(3) High cost: Due to the low single-pass yield, the amount of recycled materials is large, the excess alkali in multiple causticizations is not effectively utilized, and the alkali consumption is high. Compared with the ore method, the cost is not competitive. In addition, the electrolysis method requires large investment and It consumes high energy and is not economical for industrialization.

Therefore, there is a need in this field for a method and system for preparing high-purity lithium hydroxide from lithium chloride with high yield and low cost.

Contents of the invention

In view of the problems existing in the prior art, the present invention provides a method and system for preparing battery-grade lithium hydroxide monohydrate and capable of co-producing battery-grade lithium carbonate. The method and system of the present invention have a high one-way utilization rate of lithium resources, both lithium hydroxide and lithium carbonate can reach battery level, have competitive costs and are industrially feasible.

A first aspect of the invention provides a method for preparing lithium hydroxide and lithium carbonate, the method comprising the following steps:

(1) Lithium hydroxide synthesis: carry out a first-level causticization reaction between lithium chloride and the first alkali in a solvent. After the reaction, the first-level causticizing slag and the first-level causticizing mother liquor are separated, and the first-level causticizing mother liquor and the first-level causticizing mother liquor are separated. The two alkali performs a secondary causticizing reaction. After the reaction, the secondary causticizing slag and the secondary causticizing mother liquor are separated. The N-level causticizing mother liquor and the N+1th alkali are optionally subjected to an N+1-level causticizing reaction. The reaction Afterwards, N+1 level causticizing slag and N+1 level causticizing mother liquor are obtained, where N≥2, and the obtained causticizing slag of each level is crude lithium hydroxide; for example, N can be 2, 3 or 4;

(2) Lithium hydroxide impurity removal: Wash and separate the crude lithium hydroxide twice or more continuously to obtain each lithium hydroxide washing liquid and the last lithium hydroxide washing residue, and wash the last lithium hydroxide The slag is prepared into a solution, and after evaporation, crystallization and separation, lithium hydroxide crystallization mother liquor and lithium hydroxide crystallization slag are obtained. The lithium hydroxide crystallization slag is post-processed to obtain lithium hydroxide products;

(3) Synthesis of lithium carbonate: The last-stage causticization mother liquor obtained in step 1 is evaporated, concentrated and separated to obtain the causticizing liquid concentrate and the causticizing liquid concentrated residue, and the causticizing liquid concentrate is used as the second step in step 1. As an alkali source for the first-level or higher causticization reaction, the concentrated residue of the caustic liquid is configured into a solution, and carbon dioxide is introduced to carry out the lithium precipitation reaction. After the reaction, the crude lithium carbonate product is separated;

(4) Lithium carbonate impurity removal: Configure crude lithium carbonate into a solution, perform evaporation, crystallization and separation to obtain lithium carbonate crystallization mother liquor and lithium carbonate crystallization slag. Wash and separate the lithium carbonate crystallization slag to obtain lithium carbonate washing slag. The lithium carbonate washing residue is post-processed to obtain lithium carbonate product.

In one or more embodiments, a two-stage causticization reaction is performed in step 1.

In one or more embodiments, the separation in step 1 is performed by filtration, preferably filter press.

In one or more embodiments, in step 1, the moisture content of the causticizing slag at each stage is no higher than 8 wt%.

In one or more embodiments, in step 1, the lithium chloride is in the form of solid lithium chloride or a solution containing lithium chloride. Provided in the form; preferably, the lithium chloride-containing solution is selected from brine containing lithium chloride, the primary lithium hydroxide washing solution obtained in step 2, or a combination thereof.

In one or more embodiments, in step 1, the base is selected from sodium hydroxide, potassium hydroxide, ammonia or a combination thereof, preferably sodium hydroxide.

In one or more embodiments, in step 1, the base is provided in the form of a solid base or a base solution; the base solution is preferably an aqueous base solution.

In one or more embodiments, in step 1, the solvent is water.

In one or more embodiments, in step 1, the molar ratio of alkali to lithium chloride in the primary causticization reaction is (0.8-2):1, preferably (0.8-1.3):1.

In one or more embodiments, in step 1, the concentration of lithium ions in the primary causticization reaction system before reaction is 20-35g/L.

In one or more embodiments, in step 1, the causticization reaction temperature of each stage and the separation temperature of each stage are independently 10-80°C.

In one or more embodiments, in step 1, the primary causticization reaction time is 0.5-1 h.

In one or more embodiments, in step 1, the N-stage causticization reaction times are each independently 1-2 h, where N≥2.

In one or more embodiments, in step 1, the causticization reaction temperature of each stage is the same as the separation temperature of the same stage.

In one or more embodiments, in step 1, the molar ratio of the alkali in the N-stage causticization reaction to the alkali in the N-1-stage causticization reaction is 1: (0.7-0.85), where N≥2.

In one or more embodiments, in step 2, the causticization residues of all levels obtained in step 1 are combined and then washed.

In one or more embodiments, in step 2, filtration, preferably filtration, is used for separation.

In one or more embodiments, in step 2, the moisture content of the lithium hydroxide washing residue after each washing and separation is not higher than 8 wt%.

In one or more embodiments, in step 2, the crude lithium hydroxide is washed and separated twice.

In one or more embodiments, in step 2, the crude lithium hydroxide product is washed using a lithium hydroxide solution, each lithium hydroxide washing liquid, a lithium hydroxide crystallization mother liquor, or a mixture thereof, which can be used for the Nth washing The lithium hydroxide washing liquid is the Mth lithium hydroxide washing liquid, wherein M>N; Preferably, in step 2, use lithium hydroxide solution, the N+1th lithium hydroxide washing liquid or a mixture thereof for hydroxide The crude lithium product is washed for the Nth time, where N ≤ the total number of washes -1, and the crude lithium hydroxide product is washed for the last time using lithium hydroxide solution, lithium hydroxide crystallization mother liquor or a mixture thereof; the lithium hydroxide solution is preferably saturated Lithium hydroxide solution.

In one or more embodiments, in step 2, the primary lithium hydroxide washing liquid is used as the raw material for the primary causticization reaction in step 1.

In one or more embodiments, in step 2, the quality of the liquid used in each washing is the same as that of crude lithium hydroxide. The quantity ratios are independently 1.5-2.2:1.

In one or more embodiments, in step 2, each washing time is independently 1 h to 3 h.

In one or more embodiments, in step 2, the temperature of each washing and the separation temperature after each washing are independently 10-80°C.

In one or more embodiments, in step 2, the temperature of each wash is the same as the separation temperature after the same wash.

In one or more embodiments, in step 2, the last lithium hydroxide washing residue is configured into an aqueous solution.

In one or more embodiments, in step 2, the evaporation pressure is -0.04MPa to -0.085MPa.

In one or more embodiments, in step 2, the final evaporation temperature and the separation temperature after evaporation and crystallization are not higher than 80°C.

In one or more embodiments, in step 2, the final evaporation temperature is the same as the separation temperature after evaporation and crystallization.

In one or more embodiments, a forced circulation evaporator is used for evaporative crystallization in step 2.

In one or more embodiments, in step 2, post-treatment of the lithium hydroxide crystallization slag includes drying and optional demagnetization.

In one or more embodiments, in step 3, the evaporation pressure is -0.02MPa to -0.085MPa.

In one or more embodiments, in step 3, the final temperature of evaporation and the separation temperature after evaporation and concentration are not higher than 90°C.

In one or more embodiments, in step 3, the final evaporation temperature is the same as the separation temperature after evaporation and concentration.

In one or more embodiments, in step 3, filtration, preferably filtration, is used for separation.

In one or more embodiments, in step 3, the moisture content of the caustic liquid concentrated residue and crude lithium carbonate is no higher than 8 wt%.

In one or more embodiments, in step 3, the caustic liquid concentrated residue is configured into an aqueous solution.

In one or more embodiments, in step 3, the feeding mass ratio of carbon dioxide and caustic liquid concentrated residue is 1: (3.8-4.5).

In one or more embodiments, in step 3, the lithium precipitation reaction temperature is 10-90°C.

In one or more embodiments, in step 4, crude lithium carbonate is prepared into an aqueous solution.

In one or more embodiments, a forced circulation evaporator is used for evaporative crystallization in step 4.

In one or more embodiments, in step 4, filtration, preferably filtration, is used for separation.

In one or more embodiments, water is used to wash the lithium carbonate crystallization residue in step 4.

In one or more embodiments, in step 4, the mass ratio of the liquid used for washing to the lithium carbonate crystallization residue is (5-10):1.

In one or more embodiments, in step 4, the washing time is 1 h to 3 h.

In one or more embodiments, in step 4, the washing temperature and the separation temperature after washing are each independently 10-90°C.

In one or more embodiments, in step 4, the washing temperature is the same as the separation temperature after washing.

In one or more embodiments, in step 4, the post-processing of the lithium carbonate washing residue includes drying.

In one or more embodiments, in step 4, the lithium carbonate crystallization mother liquor and/or the lithium carbonate washing liquid obtained by washing the lithium carbonate crystallization residue is merged into the last causticization mother liquor obtained in step 1 for use in step 3. Lithium carbonate synthesis.

In one or more embodiments, the method includes performing the operations of steps 1 to 4 in two or more batches by using materials;

Among them, the lithium chloride used in step 1 in the second and subsequent batches comes from the primary lithium hydroxide washing liquid obtained in step 2 in the previous batch and selected from solid lithium chloride and lithium chloride-containing brine. one or both;

The alkali used in the secondary and higher-level causticization reactions in step 1 of the second and subsequent batches comes from the caustic liquid concentrate obtained in step 3 of the previous batch;

In the second and subsequent batches, in step 3, combine the final causticization mother liquor obtained in step 1 in the same batch with the lithium carbonate crystallization mother liquor obtained in step 4 in the previous batch and the obtained product from washing the lithium carbonate crystallization residue. The lithium carbonate washing liquid is combined and used to synthesize lithium carbonate.

Another aspect of the present invention provides a method for preparing lithium hydroxide, the method comprising step 1 and step 2 described in any embodiment herein.

Another aspect of the present invention provides a system for preparing lithium hydroxide and lithium carbonate, the system comprising:

The lithium hydroxide synthesis unit includes a lithium chloride primary causticizing unit, a primary separation unit, a lithium chloride secondary causticizing unit, a secondary separation unit, a causticizing mother liquor storage tank and optional lithium chloride tertiary or Three or more levels of causticizing devices and corresponding levels of separation devices, in which each level of lithium chloride causticizing devices is connected to the material input end of the same-level separation device, and the liquid output end of each level of separation device is connected to the next-level lithium chloride causticizing device. The devices are connected, and the liquid output end of the last stage separation device is connected to the causticization mother liquor storage tank;

Lithium hydroxide impurity removal unit, including at least two-stage lithium hydroxide washing devices, separation devices corresponding to each level of lithium hydroxide washing devices, lithium hydroxide washing residue solution configuration device, and lithium hydroxide washing residue solution evaporation and crystallization device , a separation device corresponding to the lithium hydroxide washing residue solution evaporation and crystallization device and a lithium hydroxide post-processing device, in which the solid output ends of the separation devices at each level of the lithium hydroxide synthesis unit are connected to the first-level lithium hydroxide washing device, and each level The lithium hydroxide washing device is connected to the material input end of the corresponding separation device, and the material output end of the separation device corresponding to the upper level lithium hydroxide washing device is connected to the next level lithium hydroxide washing device, which corresponds to the last level hydrogen The solid output end of the separation device of the lithium oxide washing device is connected to the lithium hydroxide washing residue solution configuration device, and the lithium hydroxide washing residue solution evaporation and crystallization device is connected to the material input end of the corresponding separation device, corresponding to the lithium hydroxide washing residue solution The solid output end of the separation device of the evaporation crystallization device is connected to the lithium hydroxide post-treatment device;

The lithium carbonate synthesis unit includes a causticization mother liquor concentration device, a first separation device of the lithium carbonate synthesis unit, a lithium carbonate synthesis device and a second separation device of the lithium carbonate synthesis unit, in which the causticization mother liquor storage tank of the lithium hydroxide synthesis unit and the causticization The mother liquor concentration device is connected, the causticization mother liquor concentration device is connected to the material input end of the first separation device of the lithium carbonate synthesis unit, the solid output end of the first separation device of the lithium carbonate synthesis unit is connected to the lithium carbonate synthesis device, and the lithium carbonate synthesis unit The device is connected to the material input end of the second separation device of the lithium carbonate synthesis unit;

The lithium carbonate impurity removal unit includes a lithium carbonate lithium precipitation slag solution preparation device, a lithium carbonate lithium precipitation slag solution evaporation and crystallization device, a first separation device of the lithium carbonate impurity removal unit, a lithium carbonate washing device, and a second separation device of the lithium carbonate impurity removal unit. , a lithium carbonate post-processing device, wherein the solid output end of the second separation device of the lithium carbonate synthesis unit is connected to a lithium carbonate precipitation slag solution configuration device, and the lithium carbonate lithium precipitation solution configuration device is connected to a lithium carbonate precipitation lithium slag solution evaporation and crystallization device, The evaporation and crystallization device of the lithium carbonate precipitation slag solution is connected to the material input end of the first separation device of the lithium carbonate impurity removal unit. The solid output end of the first separation device of the lithium carbonate impurity removal unit is connected to the lithium carbonate washing device. The lithium carbonate washing device is connected to the material input end of the first separation device of the lithium carbonate impurity removal unit. The material input end of the second separation device of the lithium carbonate impurity removal unit is connected, and the solid output end of the second separation device of the lithium carbonate impurity removal unit is connected to the lithium carbonate post-processing device.

In one or more embodiments, the separation device in the system is a filtration device, preferably a filter press device.

In one or more embodiments, the lithium hydroxide impurity removal unit further includes a primary washing liquid intermediate tank, and the material input end of the primary washing liquid intermediate tank is connected to the lithium hydroxide impurity removal unit. The liquid output end of the separation device corresponding to the first-level lithium hydroxide washing device is connected, and the material output end of the first-level washing liquid intermediate tank is connected to the first-level lithium chloride causticizing device of the lithium hydroxide synthesis unit.

In one or more embodiments, the lithium hydroxide impurity removal unit also includes an N-stage washing liquid intermediate tank, where N≥2, and the material input end of the N-stage washing liquid intermediate tank is connected with the lithium hydroxide impurity removal unit. The liquid output end of the separation device corresponding to the N-level lithium hydroxide washing device in the hybrid unit is connected, and the material output end of the N-level washing liquid intermediate tank is connected to the M-level lithium hydroxide washing device, where M < N, preferably M=N-1.

In one or more embodiments, the lithium hydroxide impurity removal unit also includes a lithium hydroxide crystallization mother liquor intermediate tank, and the material input end of the lithium hydroxide crystallization mother liquor intermediate tank is connected to the lithium hydroxide impurity removal unit. The liquid output end of the separation device corresponding to the lithium hydroxide washing residue solution evaporation crystallization device is connected, and the material output end of the lithium hydroxide crystallization mother liquor intermediate tank is connected to the lithium hydroxide washing device, preferably to the last stage of lithium hydroxide The washing unit is connected.

In one or more embodiments, the lithium hydroxide washing residue solution evaporation and crystallization device is a forced circulation evaporator.

In one or more embodiments, the lithium hydroxide post-treatment device includes a drying device and an optional demagnetization device.

In one or more embodiments, the lithium hydroxide synthesis unit further includes an alkali liquid storage tank, and the material input end of the alkali liquid storage tank is connected to the liquid output end of the first separation device of the lithium carbonate synthesis unit, The material output end of the alkali liquid storage tank is connected to the secondary or higher secondary lithium chloride causticizing device in the lithium hydroxide synthesis unit.

In one or more embodiments, the evaporation and crystallization device of lithium carbonate precipitation slag solution is a forced circulation evaporator.

In one or more embodiments, the lithium carbonate impurity removal unit also includes a lithium carbonate crystallization mother liquor intermediate tank, and the material input end of the lithium carbonate crystallization mother liquor intermediate tank is connected to the first separation device of the lithium carbonate impurity removal unit and /or the liquid output end of the second separation device of the lithium carbonate impurity removal unit is connected to the material output end of the lithium carbonate crystallization mother liquor intermediate tank Connected to the causticization mother liquor concentration device in the lithium carbonate synthesis unit.

In one or more embodiments, the lithium hydroxide synthesis unit includes a lithium chloride primary causticizing device, a primary separation device, a lithium chloride secondary causticizing device, a secondary separation device, and a causticizing mother liquor storage tank and lye storage tanks. The lithium chloride causticizing devices at all levels are connected to the material input ends of the separation devices at the same level. The liquid output end of the primary separation device is connected to the secondary causticizing device of lithium chloride. The liquid output end of the secondary separation device is connected to the causticizing mother liquor storage tank. The material output end of the alkali storage tank is connected to the lithium chloride secondary causticizing device.

The lithium hydroxide impurity removal unit includes a primary lithium hydroxide washing device, a first separation device of the lithium hydroxide impurity removal unit, a primary washing liquid intermediate tank, a secondary lithium hydroxide washing device, and a third lithium hydroxide impurity removal unit. Second separation device, secondary washing liquid intermediate tank, lithium hydroxide washing residue solution preparation device, lithium hydroxide washing residue solution evaporation and crystallization device, lithium hydroxide impurity removal unit third separation device, lithium hydroxide crystallization mother liquor intermediate tank, hydrogen Lithium oxide post-treatment device. The primary lithium hydroxide washing device is connected to the material input end of the first separation device of the lithium hydroxide impurity removal unit. The solid output end of the first separation device of the lithium hydroxide impurity removal unit is connected to the secondary lithium hydroxide washing device. The secondary lithium hydroxide washing device is connected to the material input end of the second separation device of the lithium hydroxide impurity removal unit. The solid output end of the second separation device of the lithium hydroxide impurity removal unit is connected to the lithium hydroxide washing residue solution configuration device. The lithium hydroxide washing residue solution preparation device is connected to the lithium hydroxide washing residue solution evaporation and crystallization device. The lithium hydroxide washing residue solution evaporation and crystallization device is connected to the material input end of the third separation device of the lithium hydroxide impurity removal unit. The solid output end of the third separation device of the lithium hydroxide impurity removal unit is connected to the lithium hydroxide post-treatment device. The material input end of the primary washing liquid intermediate tank is connected to the liquid output end of the first separation device of the lithium hydroxide impurity removal unit. The material output end of the primary washing liquid intermediate tank is connected to the primary lithium chloride causticizing device. The material input end of the secondary washing liquid intermediate tank is connected to the liquid output end of the second separation device of the lithium hydroxide impurity removal unit. The material output end of the secondary washing liquid intermediate tank is connected to the primary lithium hydroxide washing device. The material input end of the lithium hydroxide crystallization mother liquor intermediate tank is connected to the liquid output end of the third separation device of the lithium hydroxide impurity removal unit. The material output end of the lithium hydroxide crystallization mother liquor intermediate tank is connected to the secondary lithium hydroxide washing device.

The lithium carbonate synthesis unit includes a causticization mother liquor concentration device, a first separation device of the lithium carbonate synthesis unit, a lithium carbonate synthesis device and a second separation device of the lithium carbonate synthesis unit. The causticization mother liquor storage tank of the lithium hydroxide synthesis unit is connected to the causticization mother liquor concentration device. The causticizing mother liquor concentration device is connected to the material input end of the first separation device of the lithium carbonate synthesis unit. The solid output end of the first separation device of the lithium carbonate synthesis unit is connected to the lithium carbonate synthesis device. The lithium carbonate synthesis device is connected to the material input end of the second separation device of the lithium carbonate synthesis unit. The liquid output end of the first separation device of the lithium carbonate synthesis unit is connected to the material input end of the alkali liquid storage tank of the lithium hydroxide synthesis unit.

In one or more embodiments, the lithium carbonate impurity removal unit includes a lithium carbonate lithium precipitation slag solution preparation device, a lithium carbonate lithium precipitation slag solution evaporation and crystallization device, a first separation device of the lithium carbonate impurity removal unit, and a lithium carbonate washing device. , the second separation device of the lithium carbonate impurity removal unit, the lithium carbonate post-treatment device and the lithium carbonate crystallization mother liquor intermediate tank. The solid output end of the second separation device of the lithium carbonate synthesis unit is connected to the lithium carbonate precipitation slag solution configuration device. The lithium carbonate precipitation solution configuration device is connected to the lithium carbonate precipitation slag solution evaporation and crystallization device, the lithium carbonate precipitation lithium slag solution evaporation and crystallization device is connected to the material input end of the first separation device of the lithium carbonate impurity removal unit, and the lithium carbonate impurity removal unit is connected to the material input end of the first separation device. A separation device for solids The output end is connected to the lithium carbonate washing device. The lithium carbonate washing device is connected to the material input end of the second separation device of the lithium carbonate impurity removal unit. The solid output end of the second separation device of the lithium carbonate impurity removal unit is connected to the lithium carbonate post-treatment device. The material input end of the lithium carbonate crystallization mother liquor intermediate tank is connected to the liquid output end of the first separation device of the lithium carbonate impurity removal unit and the second separation device of the lithium carbonate impurity removal unit. The material output end of the lithium carbonate crystallization mother liquor intermediate tank is synthesized with lithium carbonate. The causticizing mother liquor concentration device of the unit is connected.

Another aspect of the present invention provides a method for preparing lithium hydroxide and lithium carbonate, the method comprising preparing lithium hydroxide and lithium carbonate using a system for preparing lithium hydroxide and lithium carbonate according to any embodiment herein; preferably Preferably, the method includes step 1 to step 4 described in any embodiment herein.

Another aspect of the present invention provides a system for preparing lithium hydroxide, which system includes the lithium hydroxide synthesis unit and the lithium hydroxide impurity removal unit described in any embodiment herein.

Another aspect of the present invention provides a method for preparing lithium hydroxide, the method comprising preparing lithium hydroxide using a system for preparing lithium hydroxide according to any embodiment of this document; preferably, the method comprises any of the embodiments herein. Step 1 and step 2 of one embodiment.

Description of the drawings

Figure 1 is an overall schematic diagram of the lithium hydroxide and lithium carbonate preparation system of the present invention. In Figure 1, part A is the lithium hydroxide synthesis unit, including lithium chloride primary caustic kettle 1, filtration mechanism 2, lithium chloride secondary caustic kettle 3, filtration mechanism 4, concentrated alkali storage tank 5, causticization Mother liquor storage tank 6; Part B is the lithium hydroxide impurity removal unit, including primary washing kettle 7, filtering mechanism 8, primary washing liquid intermediate tank 9, secondary washing kettle 10, filtering mechanism 11, secondary washing liquid intermediate tank 12, Secondary washing residue solution configuration kettle 13, forced circulation evaporator 14, filtration mechanism 15, lithium hydroxide crystallization mother liquor intermediate tank 16, drying mechanism 17, demagnetization mechanism 18; Part C is the lithium carbonate synthesis unit, including causticization mother liquor Concentration kettle 19, filtering mechanism 20, lithium carbonate synthesis kettle 21, filtering mechanism 22; Part D is the lithium carbonate impurity removal unit, including lithium precipitation slag solution configuration kettle 23, forced circulation evaporator 24, filtering mechanism 25, and lithium carbonate crystallization mother liquor Intermediate tank 26, lithium carbonate washing kettle 27, filtering mechanism 28, drying mechanism 29; m is brine containing lithium chloride, n is sodium hydroxide solution, r is carbon dioxide, o is lithium precipitation mother liquor, p is battery-grade hydroxide Lithium, q is battery grade lithium carbonate.

Detailed ways

In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the terms and expressions mentioned in the description and claims are generally described and defined below. Unless otherwise specified, all technical and scientific terms used in the text have their usual meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

In this article, all characteristics such as numerical values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, a description of a numerical range or percentage range shall be deemed to cover and specifically disclose all possible subranges and individual values within the range (including integers and fractions). In this article, unless otherwise stated, percentage refers to mass percentage, and ratio refers to mass ratio.

When embodiments or examples are described herein, it is to be understood that they are not intended to limit the invention to these embodiments. Embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described in the invention are intended to be within the scope of the appended claims. Herein, in order to keep the description concise, not all possible combinations of each technical feature in each embodiment or example are described. Therefore, as long as there is no contradiction in the combination of these technical features, each technical feature in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

In this article, unless otherwise specified, the meanings of “connection”, “connection” and similar terms include direct connection and indirect connection, where indirect connection may be through one or more middlewares. For example, when "device A and device B are connected" are disclosed herein, "device A and device B are directly connected" and "device A and device B are connected through middleware" should be deemed to have been disclosed herein.

The invention provides a method and system for preparing lithium hydroxide through the causticization reaction of lithium chloride and alkali and the purification methods of solid-liquid washing and evaporation crystallization. In this article, the causticization reaction (referred to as causticization) refers to the reaction in which lithium chloride reacts with alkali to produce lithium hydroxide. In the present invention, the causticization reaction is carried out in a solution system. Lithium chloride can be provided in the form of a brine containing lithium chloride. In the present invention, brine refers to an aqueous solution whose solute is mainly lithium chloride. In the present invention, the lithium chloride-containing brine used as the raw material is preferably relatively pure brine. The mass of lithium chloride usually accounts for more than 98% of the total mass of solutes contained in the brine, preferably more than 99% and more than 99.5%. The cations contained in brine are mainly lithium ions. Common metal cations in brine also include sodium ions. There is no special requirement for the concentration of sodium ions in the brine, and the mass content of sodium ions is preferably no more than 0.5%. Trace cations in brine include potassium ions, calcium ions, magnesium ions, boron ions, etc., and the mass concentration is preferably <50 ppm. In the present invention, the source of lithium chloride can be salt lake lithium chloride, and the brine prepared from salt lake lithium chloride can meet the aforementioned requirements. The lithium hydroxide prepared by the invention can meet the requirements of battery-grade lithium hydroxide. In some embodiments, the present invention can co-produce battery-grade lithium carbonate while preparing lithium hydroxide. In the present invention, the battery-grade lithium hydroxide index is based on the national standard GB/T 26008-2020, and the battery-grade lithium carbonate index is based on the industry standard YST 582-2013.

The method for preparing lithium hydroxide of the present invention includes the following steps: (1) lithium hydroxide synthesis; and (2) lithium hydroxide impurity removal.

In the synthesis of lithium hydroxide in step 1, lithium chloride and alkali are subjected to causticization reaction in a multi-stage reactor and then separated to obtain crude lithium hydroxide and causticization mother liquor. In the present invention, the raw material alkali for the causticization reaction may be sodium hydroxide, potassium hydroxide, ammonia or a combination thereof, preferably sodium hydroxide. The base can be provided in the form of a solid base or a base solution. The alkaline solution is usually an aqueous alkaline solution. The causticization reaction takes place in water. The temperature of the causticizing reaction may be 10-80°C, such as 20°C, 30°C, 40°C, 50°C, or 60°C. In some embodiments, when performing the synthesis of the first batch of lithium hydroxide, a lower temperature is used for the primary causticization reaction, such as 20-40°C, 25-35°C, to achieve the precipitation of more lithium hydroxide. The causticization reaction uses higher temperatures, such as 40-60°C, 45-55°C, to reduce the precipitation of impurities, thereby ensuring the stable output of high-purity lithium hydroxide. In the embodiment of recycling materials, when producing the second batch and subsequent batches, it is preferable to use higher temperatures for each level of causticization reaction, such as 40-60°C, 45-55°C, to reduce the precipitation of impurities. This ensures the temperature output of high-purity lithium hydroxide. The causticizing reaction can be carried out under heating and stirring conditions. In the present invention, filtration, preferably filter press, can be used for separation. In the present invention, the moisture content of the solid matter after solid-liquid separation is preferably not high. At 8wt%, more preferably no higher than 4wt%, such as 3wt%, 2wt%, 1wt%, in order to remove impurities in the solid matter as much as possible and ensure the stable output of high-purity products. In this article, moisture content refers to the percentage of free water mass in solid matter to the total mass of solid matter. The temperature for solid-liquid separation of materials after the causticization reaction can be 10-80°C, such as 20°C, 30°C, 40°C, 50°C, or 60°C. Preferably, the causticization reaction at all levels and the separation temperature after the corresponding reaction are the same. Considering that the solubility of products and impurities is greatly different at different temperatures, the same treatment temperature is conducive to the consistency of the system composition and the stability of product quality.

In step 1, at least two stages of causticization reaction are carried out. In some embodiments, only two stages of causticization are performed. In step 1, the lithium chloride source for the primary causticization reaction may be brine containing lithium chloride. When preparing lithium hydroxide by recycling materials, the primary lithium hydroxide washing liquid can be used to completely or partially replace the brine containing lithium chloride as the lithium chloride source for the primary causticization reaction. When recycling materials, it is preferred not to use the caustic liquid concentrate but to use an alkali solution with less impurity content as the alkali source for the primary causticization reaction, which is beneficial to improving the purity of the lithium hydroxide product. In the primary causticization reaction, the molar equivalent of alkali to lithium chloride is preferably 0.8-2, more preferably 0.8-1.3, such as 0.9, 1, 1.1, 1.2. The concentration of lithium ions before the reaction in the primary causticization reaction system is preferably 20-35g/L, such as 25g/L or 30g/L. Controlling the input molar equivalents and lithium ion concentration of the primary causticization reaction within the aforementioned range is beneficial to the stable production of battery-grade lithium hydroxide. The time of the primary causticization reaction is preferably 0.5-1h, such as 0.75h. The secondary and secondary causticization reactions are preferably carried out for a longer time, such as 1-2h, 1.5h, to ensure the stability of product quality. The feeding molar ratio of the alkali in the second-level and above-level causticization reactions and the corresponding alkali in the previous-level causticization reaction is preferably 1: (0.7-0.85), such as 1:0.73, 1:0.75, 1:0.8, which It is conducive to the stable production of battery-grade lithium hydroxide.

In the present invention, third-level and higher-level causticization reactions are optionally carried out, that is, the lithium hydroxide synthesis step optionally includes N-level causticization mother liquor and N+1th alkali for N+1-level causticization reaction. Afterwards, N+1 level causticizing slag and N+1 level causticizing mother liquor are obtained, where N≥2, for example, N can be 2, 3, or 4. For example, the secondary causticizing mother liquor and the third alkali can be optionally subjected to a third-level causticization reaction to obtain the third-level causticizing slag and the third-level causticizing mother liquor, and then the third-level causticizing mother liquor can be optionally reacted with the fourth alkali. Carry out the fourth-level causticization reaction to obtain the fourth-level causticizing slag and the fourth-level causticizing mother liquor, and then optionally carry out the fifth-level causticizing reaction between the fourth-level causticizing mother liquor and the fifth alkali to obtain the fifth-level causticizing slag and the fifth-level causticizing mother liquor. Causticizing mother liquor.

In step 2 of lithium hydroxide impurity removal, the crude lithium hydroxide is washed twice or more with solid and liquid, and then the crude lithium hydroxide is configured into a solution and then undergoes evaporation, crystallization, separation, and post-processing to obtain battery-grade lithium hydroxide. product. Crude lithium hydroxide comes from various levels of causticizing slag in the lithium hydroxide synthesis step. Crude lithium hydroxide can be washed using a lithium hydroxide solution, preferably a saturated lithium hydroxide solution. After each washing, solid-liquid separation can be performed to obtain the corresponding number of washing residues and washing liquid. The washing liquid obtained from the last washing and separation can be used as the liquid for this washing. For example, the second washing liquid (that is, the liquid obtained by washing and separating the crude lithium hydroxide for the second time) can be used to wash the crude lithium hydroxide. First wash. The washing method may be to thoroughly mix the solid to be washed and the liquid used for washing by stirring or other means. The lithium hydroxide primary washing solution is a lithium-containing mixed solution with many impurities. It can be used as a reaction raw material in the first-level causticization system to reduce the unit consumption of sodium hydroxide and lithium chloride. The lithium hydroxide primary washing residue is washed again and separated to obtain the secondary washing residue and the secondary washing liquid. The lithium hydroxide secondary washing solution is a saturated lithium hydroxide solution containing a small amount of impurities. The liquid has a difference in impurity concentration from the causticizing slag and can be used for the first washing of crude lithium hydroxide. In some embodiments, the crude lithium hydroxide is washed only twice. In the present invention, the mass ratio of the liquid used for each washing to the crude lithium hydroxide is independently (1.5-2.2):1, such as 1.6:1, 1.8:1, 2:1. The time for each washing of crude lithium hydroxide can be 1h-3h, such as 1.5h, 2h, 2.5h. Each washing temperature and the separation temperature after each washing are independently 10-80°C, such as 30°C, 40°C, 50°C, 60°C, and 70°C. Preferably, each washing temperature is the same as the corresponding separation temperature after washing, which is beneficial to the consistency of the system composition and the stability of product quality.

In step 2, add enough water to completely dissolve the last washing residue, then evaporate and crystallize it, remove a certain amount of water and then separate to obtain lithium hydroxide crystal residue and crystallization mother liquor. In the present invention, when the separated solid is configured into an aqueous solution, the amount of water used is not particularly limited, as long as all the solid is dissolved. Preferably, when the last washing residue is configured into a solution in step 2, the mass ratio of water to solid is ≥ 25:3. Evaporative crystallization can be performed once or more than once. In some embodiments, only one evaporative crystallization is performed in step 2. A forced circulation evaporator can be used for evaporative crystallization. The solution crystallizes during the evaporation process, and the viscosity of the material in the later stage is relatively large. A forced circulation evaporator is used to resist salt precipitation. The evaporation pressure may be -0.04MPa to -0.085MPa, such as -0.05MPa, -0.06MPa, -0.07MPa. The final evaporation temperature and the separation temperature after evaporation and crystallization are preferably no higher than 80°C, such as 60°C, 65°C, or 70°C. The final evaporation temperature is preferably the same as the separation temperature after evaporation and crystallization, which is beneficial to the consistency of the system composition and the stability of product quality. Post-treatment of the lithium hydroxide crystal slag may be drying and optional demagnetization. Drying can be done by drying to remove free water and retain crystal water. The crystallization mother liquor is a saturated lithium hydroxide solution containing trace impurities. There is a concentration difference with the primary washing residue. It can be used as a raw material to replace the lithium hydroxide solution for the second washing, reducing the consumption of the raw material lithium hydroxide solution.

The present invention also provides a method for producing lithium carbonate by-product while preparing lithium hydroxide. The method further includes the following steps based on steps 1 and 2 of the aforementioned method for preparing lithium hydroxide: (3) lithium carbonate synthesis, and (4) Lithium carbonate removes impurities.

In the synthesis of lithium carbonate in step 3, the causticization mother liquor is concentrated, crystallized, and separated. The obtained crystalline solid is dissolved in water and then carbon dioxide gas is introduced to precipitate lithium to obtain crude lithium carbonate. Concentration and crystallization can be carried out by evaporation and concentration. The evaporation pressure may be -0.02MPa to -0.085MPa, such as -0.03MPa, -0.04MPa, -0.05MPa, -0.06MPa, -0.07MPa. The final evaporation temperature and the separation temperature after evaporation and concentration are preferably no higher than 90°C, such as 60°C, 65°C, 70°C, or 80°C. Preferably, the final evaporation temperature is the same as the separation temperature after evaporation and concentration, which is beneficial to the consistency of the system composition and the stability of product quality. The concentrated liquid obtained by concentrating, crystallizing and separating the causticization mother liquor is a high-concentration alkali that basically does not contain chlorine radicals. It can be recycled into the second-level or higher-level causticization reaction and used as a reaction raw material to replace alkali, thereby reducing the unit consumption of raw material alkali. After the obtained concentrated residue is completely dissolved in water, carbon dioxide gas is introduced to precipitate lithium, and after the lithium precipitation is completed, it is filtered to obtain the lithium precipitation mother liquor and lithium precipitation residue (crude lithium carbonate). Crude lithium carbonate is lithium carbonate containing impurities chloride ions and sodium ions. The present invention uses carbon dioxide to precipitate lithium, and the impurities precipitated are less than those of sodium carbonate. The subsequent purification steps are simpler and the product quality is better. The amount of carbon dioxide used is preferably 1/4.5-1/3.8 of the mass of the caustic liquid concentrated residue, such as 1/4.3, 1/4.2, 1/4.1, 1/4, 1/3.9. The temperature of the lithium precipitation reaction can be 10-90°C, such as 60°C, 70°C, or 80°C. The lithium precipitation mother liquor is a mixed solution containing a trace amount of lithium and a large amount of sodium chloride and sodium carbonate. It cannot be reused in the process and can be returned to halogen. The lithium in the lithium precipitation mother liquor accounts for about 5wt% of the total lithium input.

In step 4 of lithium carbonate impurity removal, crude lithium carbonate is prepared into a solution, crystallized by evaporation, separated, washed and separated from solid and liquid, and battery-grade lithium carbonate is obtained through post-processing. First, after all the crude lithium carbonate is dissolved in water, lithium carbonate crystallization slag and crystallization mother liquor are obtained through evaporation crystallization and solid-liquid separation. It is preferred to use a forced circulation evaporator for evaporative crystallization. The lithium carbonate crystallization residue is washed with water to remove remaining trace impurities. After solid-liquid separation, lithium carbonate washing liquid and lithium carbonate washing residue are obtained. The amount of water used can be 5-10 times the mass of crystallized slag, such as 6 times, 7 times, 8 times, or 9 times. The washing time can be 1h-3h, such as 1.5h, 2h, 2.5h. The washing temperature and the separation temperature after washing are each independently 10-90°C, such as 60°C, 70°C, or 80°C. Preferably, the washing temperature is the same as the separation temperature after washing, which is beneficial to the consistency of the system composition and the stability of product quality. After drying the washing residue, it becomes a battery-grade lithium carbonate product. Lithium carbonate crystallization mother liquor and lithium carbonate washing liquid contain a small amount of lithium ions, carbonate ions, trace sodium ions, and chloride ions, and can be used in a causticization mother liquor concentration device to concentrate together with the causticization mother liquor. The reason why the lithium carbonate crystallization mother liquor and the lithium carbonate washing liquid can be used in the causticization mother liquor concentration device and concentrated together with the causticization mother liquor is: 1) The composition and absolute amount of impurities in the lithium carbonate crystallization mother liquor and the lithium carbonate washing liquid are much less than The causticizing mother liquor will not affect subsequent results due to the introduction of a large number of impurities; 2) The crystallization mother liquor and lithium carbonate washing liquid still contain some lithium ions, which have application value; 3) The carbonate ions introduced by the crystallization mother liquor and lithium carbonate washing liquid have been The carbonate precipitated after concentration does not affect the subsequent introduction of carbon dioxide to precipitate lithium. The highly concentrated alkali obtained after concentration contains a negligible amount of carbonate and does not affect the synthesis of lithium hydroxide.

The present invention also provides a method for preparing lithium hydroxide and optional lithium carbonate in multiple batches by recycling materials, wherein each batch can include the aforementioned steps 1, 2 and optional steps 3 and 3. 4. In the first batch, the lithium chloride source can be brine containing lithium chloride, the alkali used for each level of causticization reaction can come from pre-configured alkali solution, and the pre-configured saturated lithium hydroxide solution can be used for each batch. Wash with crude lithium hydroxide. In the second and subsequent batches, the lithium chloride source can be brine containing lithium chloride and the lithium hydroxide primary washing liquid obtained in the previous batch (such as the previous batch), and the alkali used for the primary causticization reaction It can come from the pre-configured alkali solution. The alkali used for the second-level and higher-level causticization reactions can come from the causticization mother liquor concentrate obtained in the previous batch (such as the previous batch), and the previous batch (such as the previous batch) can be used. For example, the crude lithium hydroxide can be washed with the lithium hydroxide secondary washing liquid obtained in the previous batch). For example, the crude lithium hydroxide can be washed once with the lithium hydroxide secondary washing liquid obtained in the previous batch. For washing, you can use the lithium hydroxide crystallization mother liquor obtained in the previous batch (such as the previous batch) for the last crude lithium hydroxide washing. When concentrating the causticization mother liquor, you can add the previous batch (such as the previous batch) Lithium carbonate crystallization mother liquor and lithium carbonate washing liquid obtained from The operating conditions for each batch can be as described in any of the embodiments herein. In some embodiments, the method for preparing lithium hydroxide and optional lithium carbonate of the present invention includes preparing two batches of lithium hydroxide and optional lithium carbonate by recycling materials.

The lithium hydroxide and optional lithium carbonate production system of the present invention includes a lithium hydroxide synthesis unit and a lithium hydroxide impurity removal unit, and optionally also includes a lithium carbonate synthesis unit and a lithium carbonate impurity removal unit. An exemplary lithium hydroxide and lithium carbonate production system is shown in Figure 1.

The lithium hydroxide synthesis unit includes at least two-stage causticizing devices (such as lithium chloride primary causticizing kettle 1, lithium chloride secondary causticizing kettle 3) and various levels of separation devices corresponding to each level of causticizing devices (such as filtration Mechanism 2, filtering mechanism 4). The causticizing device is used to react lithium chloride and alkali to produce lithium hydroxide, and may be a reactor known to be used for causticizing reactions, such as a causticizing kettle. In the present invention, each separation device is a solid-liquid separation device, such as a filtering mechanism, which is used to separate the causticization reaction system into the solid component causticized slag and the liquid component causticized mother liquor. In some embodiments, the filtration mechanism is a filter press device. The lithium hydroxide synthesis unit also includes a causticization mother liquor storage tank (for example, a causticization mother liquor storage tank 6) for storing the causticization mother liquor. In the present invention, the storage tank refers to a device for storing liquid, and its structure is not particularly limited. It can be a container with a liquid input end and a liquid output end. The lithium hydroxide synthesis unit may also include an alkali liquid storage tank (such as a concentrated alkali storage tank 5) for storing alkali liquid, such as alkali liquid obtained after concentration and filtration of causticization mother liquor. The material output end of the alkali storage tank (such as the concentrated alkali storage tank 5) can be connected to one or more lithium chloride causticizing devices (such as the first-level lithium chloride causticizing kettle 1, the second-level lithium chloride causticizing kettle 3) Connected, preferably connected to a lithium chloride secondary or higher causticizing device (for example, a lithium chloride secondary causticizing kettle 3).

The lithium hydroxide impurity removal unit includes at least two-stage lithium hydroxide washing devices (such as primary washing kettle 7, secondary washing kettle 10) and various levels of separation devices (such as filtering mechanism 8, filtering mechanism 11) corresponding to the washing devices at each level. . In the present invention, the washing device may be a known device that uses liquid to clean and remove impurities from solids, such as a washing kettle. The washing device can be a container with a stirring device, which can fully stir the solid and liquid to reduce the impurity concentration of the solid. The solid output ends of the separation devices at each level are connected to the washing device at the next level, thereby achieving continuous washing and separation of solids multiple times. The solid output end of the last stage separation device is connected to the lithium hydroxide washing residue solution dispensing device (for example, the secondary washing residue solution dispensing kettle 13). In the present invention, the solution preparation device may be a known device capable of dissolving a solid in a solvent and preparing a solution, such as a solution preparation kettle. The cleaned lithium hydroxide is configured into a lithium hydroxide washing residue solution in the lithium hydroxide washing residue solution preparation device, and then enters the lithium hydroxide washing residue solution evaporation and crystallization device (such as the forced circulation evaporator 14) for evaporation and crystallization. In the present invention, the evaporation crystallization device may be a device known to be used for evaporation and crystallization of solutions, such as a forced circulation evaporator. After the solid-liquid mixture produced by the lithium hydroxide washing residue solution evaporation and crystallization device is separated by the separation device (such as the filtering mechanism 15), the solid lithium hydroxide passes through the post-processing device (such as the drying mechanism 17 and the demagnetization mechanism 18) to obtain hydrogen. Lithium oxide products. The solid output ends of the separation devices at each stage of the lithium hydroxide synthesis unit can be connected to the primary lithium hydroxide washing device. For example, the solid output ends of the filtering mechanism 2 and the filtering mechanism 4 can be connected to the primary washing kettle 7 . The lithium hydroxide washing devices at each level can be connected to the material input end of the corresponding separation device. For example, the first-level lithium hydroxide washing device (such as the primary washing kettle 7) can be connected to the first separation device (such as the filtering mechanism) of the lithium hydroxide impurity removal unit. 8) is connected to the material input end, and the secondary lithium hydroxide washing device (for example, the secondary washing kettle 10) can be connected to the material input end of the second separation device (for example, the filtering mechanism 11) of the lithium hydroxide impurity removal unit. The material output end of the separation device corresponding to the upper-level lithium hydroxide washing device is connected to the next-level lithium hydroxide washing device, for example, corresponding to the lithium hydroxide removal device of the first-level lithium hydroxide washing device (such as the primary washing kettle 7). The material output end of the first separation device (for example, the filtering mechanism 8) of the miscellaneous unit can be connected to the secondary lithium hydroxide washing device (for example, the secondary washing kettle 10). The solid output end of the separation device corresponding to the last stage of lithium hydroxide washing device can be connected to the lithium hydroxide washing residue solution preparation device, for example, in the embodiment of performing two-stage crude lithium hydroxide washing, corresponding to the secondary hydroxide Lithium hydroxide removal in lithium washing device (such as secondary washing kettle 10) The solid output end of the second separation device of the miscellaneous unit (for example, the filtering mechanism 11) can be connected to the lithium hydroxide washing residue solution dispensing device (for example, the secondary washing residue solution dispensing kettle 13). The lithium hydroxide washing residue solution preparation device (for example, the secondary washing residue solution preparation kettle 13) can be connected to the lithium hydroxide washing residue solution evaporation and crystallization device (for example, the forced circulation evaporator 14). The lithium hydroxide washing residue solution evaporation and crystallization device (such as the forced circulation evaporator 14) can be connected to the material input end of the corresponding separation device (such as the filter mechanism 15). The solid output end of the separation device (such as the filtering mechanism 15) corresponding to the lithium hydroxide washing residue solution evaporation and crystallization device is connected to the lithium hydroxide post-treatment device (such as the drying mechanism 17 and the demagnetization mechanism 18). The liquid output ends of the separation devices at each level corresponding to the lithium hydroxide washing devices at each level can be connected to the washing liquid intermediate tanks at each level, and the lithium hydroxide washing liquid at each level is stored in the washing liquid intermediate tanks at each level for use. For example, a separation device (eg, filtering mechanism 8) corresponding to the primary lithium hydroxide washing device (eg, primary washing tank 7) can be connected to the primary washing liquid intermediate tank (eg, primary washing liquid intermediate tank 9). The material output end of the primary washing liquid intermediate tank (for example, the primary washing liquid intermediate tank 9) can be connected to the lithium chloride primary causticizing device (for example, the lithium chloride primary causticizing kettle 1). The liquid output end of the separation device corresponding to the N-level lithium hydroxide washing device in the lithium hydroxide impurity removal unit can be connected to the material input end of the N-level washing liquid intermediate tank of the lithium hydroxide impurity removal unit, and the N-level washing liquid intermediate tank The material output end of the tank can be connected to an M-level lithium hydroxide washing device, where N≥2, such as 2, 3, 4, M<N, preferably M=N-1. For example, a separation device (eg, filtering mechanism 11) corresponding to the secondary lithium hydroxide washing device (eg, secondary washing tank 10) can be connected to the secondary washing liquid intermediate tank (eg, secondary washing liquid intermediate tank 12). The material output end of the secondary washing liquid intermediate tank (for example, the secondary washing liquid intermediate tank 12) can be connected to the primary lithium hydroxide washing device (for example, the primary washing kettle 7). In the embodiment of performing two-stage crude lithium hydroxide washing, the material input end of the lithium hydroxide crystal mother liquor intermediate tank (for example, the lithium hydroxide crystal mother liquor intermediate tank 16) can be connected to the third separation device of the lithium hydroxide impurity removal unit (for example, The liquid output end of the filter mechanism 15) is connected. The liquid output end of the separation device (such as the filtering mechanism 15) corresponding to the lithium hydroxide washing residue solution evaporation and crystallization device (such as the forced circulation evaporator 14) can be connected to the lithium hydroxide crystallization mother liquor intermediate tank (such as the lithium hydroxide crystallization mother liquor intermediate tank). 16) is connected to the material input end. The material output end of the lithium hydroxide crystallization mother liquor intermediate tank (such as the lithium hydroxide crystallization mother liquor intermediate tank 16) can be connected to one or more lithium hydroxide washing devices (such as the primary washing kettle 7, the secondary washing kettle), preferably with the secondary The lithium hydroxide washing device (for example, the secondary washing tank 10) is connected.

The lithium carbonate synthesis unit includes a causticization mother liquor concentration device (such as a causticization mother liquor concentration kettle 19), a first separation device (such as a filtration mechanism 20) of the lithium carbonate synthesis unit, and a lithium carbonate synthesis device (such as a lithium carbonate synthesis kettle 21) that are connected in sequence. and the second separation device (for example, filtering mechanism 22) of the lithium carbonate synthesis unit. The causticization mother liquor concentration device may be a known device that can be used to concentrate solutions, such as a concentration kettle. The lithium carbonate synthesis device may be a known device that can be used to react lithium chloride and carbon dioxide to perform a lithium precipitation reaction to generate lithium carbonate, such as a synthesis kettle. The causticization mother liquor storage tank (for example, the causticization mother liquor storage tank 6) of the lithium hydroxide synthesis unit is connected to the causticization mother liquor concentration device (for example, the causticization mother liquor concentration tank 19). The liquid output end of the first separation device (for example, the filtering mechanism 20) of the lithium carbonate synthesis unit can be connected to the alkali liquid storage tank (for example, the concentrated alkali storage tank 5) of the lithium hydroxide synthesis unit.

The lithium carbonate impurity removal unit includes sequentially connected lithium carbonate precipitation slag solution preparation devices (such as lithium precipitation slag solution preparation Kettle 23), lithium carbonate sedimentation slag solution evaporation and crystallization device (such as forced circulation evaporator 24), lithium carbonate impurity removal unit first separation device (such as filter mechanism 25), lithium carbonate washing device (such as lithium carbonate washing kettle 27 ), the second separation device of the lithium carbonate impurity removal unit (such as the filtering mechanism 28) and the lithium carbonate post-processing device (such as the drying mechanism 29). The lithium carbonate post-treatment device can be a drying device. The lithium carbonate impurity removal unit may also include an intermediate tank of lithium carbonate crystallization mother liquor (for example, the lithium carbonate crystallization mother liquor intermediate tank 26). The liquid output ends of the first separation device (such as the filter structure 25) of the lithium carbonate impurity removal unit and the second separation device (such as the filter mechanism 28) of the lithium carbonate impurity removal unit can pass through the lithium carbonate crystallization mother liquor intermediate tank (such as the lithium carbonate crystallization mother liquor intermediate tank). Tank 26) provides the separated liquid to the causticization mother liquor concentration device of the lithium carbonate synthesis unit (for example, the causticization mother liquor concentration kettle 19). The material output end of the lithium carbonate crystallization mother liquor intermediate tank (for example, the lithium carbonate crystallization mother liquor intermediate tank 26) can be connected to the causticization mother liquor concentration device (for example, the causticization mother liquor concentration kettle 19) of the lithium carbonate synthesis unit.

In some embodiments, the lithium hydroxide preparation system of the present invention is shown in Figure 1. In the lithium hydroxide synthesis unit A, the lithium chloride primary causticizing kettle 1 (lithium chloride primary causticizing device) and the filtering mechanism 2 (primary separation device) is connected, the liquid output end of the filtering mechanism 2 is connected to the lithium chloride secondary causticizing kettle 3 (lithium chloride secondary causticizing device), the lithium chloride secondary causticizing kettle 3 is connected to the filtering mechanism 4 (secondary separation device), the liquid output end of the filtering mechanism 4 is connected to the causticization mother liquor storage tank 6, and the concentrated alkali storage tank 5 (alkali liquid storage tank) is connected to the lithium chloride secondary causticization kettle 3. The solid output end of the filtering mechanism 4 is connected to the primary washing kettle 7 (a first-level lithium hydroxide washing device) in the lithium hydroxide impurity removal unit B. The primary washing kettle 7 is connected to the filtering mechanism 8 (corresponding to the first-level lithium hydroxide washing device). separation device) connected. The liquid output end of the filtering mechanism 8 is connected to the primary washing liquid intermediate tank 9 (the primary washing liquid intermediate tank). The solid output end of the filtering mechanism 8 is connected to the secondary washing kettle 10 (secondary lithium hydroxide washing device). The secondary washing kettle 10 is connected to the filtering mechanism 11 (a separation device corresponding to the secondary lithium hydroxide washing device). The liquid output end of the filtering mechanism 11 is connected to the secondary washing liquid intermediate tank 12 (secondary washing liquid intermediate tank). The solid output end of the filtering mechanism 11 is connected to the secondary washing residue solution dispensing kettle 13 (lithium hydroxide washing residue solution dispensing device). The configured solution enters the forced circulation evaporator 14 (lithium hydroxide washing residue solution evaporation and crystallization device). The outlet end of the forced circulation evaporator 14 and the filtering mechanism 15 (the separation device corresponding to the lithium hydroxide washing residue solution evaporation and crystallization device) connect. The liquid output end of the filtering mechanism 15 is connected to the lithium hydroxide crystallization mother liquor intermediate tank 16, and the solids directly enter the drying mechanism 17 and the demagnetization mechanism 18 (lithium hydroxide post-treatment device) in sequence. The causticization mother liquor storage tank 6 is connected to the causticization mother liquor concentration kettle 19 (causticization mother liquor concentration device) in the lithium carbonate synthesis unit C. The causticization mother liquor concentration kettle 19 is connected to the filtering mechanism 20 (the first separation device of the lithium carbonate synthesis unit). The liquid output end of the filtering mechanism 20 is connected to the concentrated alkali storage tank 5, and the solid output end is connected to the lithium carbonate synthesis kettle 21 (lithium carbonate synthesis device). The outlet of the lithium carbonate synthesis kettle 21 is connected to the filtering mechanism 22 (the second separation device of the lithium carbonate synthesis unit). The solid output end of the filtering mechanism 22 is connected to the lithium precipitation slag solution dispensing kettle 23 (lithium carbonate lithium slag solution dispensing device) in the lithium carbonate impurity removal unit D, and the lithium slag solution dispensing kettle 23 is connected to the forced circulation evaporator 24 (lithium carbonate). Lithium precipitation slag solution evaporation and crystallization device), the outlet of the forced circulation evaporator 24 is connected to the filtering mechanism 25 (the first separation device of the lithium carbonate impurity removal unit). The liquid output end of the filtering mechanism 25 is connected to the lithium carbonate crystallization mother liquor intermediate tank 26, and the solid output end is connected to the lithium carbonate washing kettle 27 (lithium carbonate washing device). The output of lithium carbonate washing kettle 27 The port is connected to the filtering mechanism 28 (the second separation device of the lithium carbonate impurity removal unit). The liquid output end of the filtering mechanism 28 is connected to the lithium carbonate crystallization mother liquor intermediate tank 26, and the solid output enters the drying mechanism 29 (lithium carbonate post-processing device) .

The lithium hydroxide preparation method of the present invention can be implemented by using the lithium hydroxide preparation system of the present invention. Therefore, the present invention also includes a method of preparing lithium hydroxide, which includes using the lithium hydroxide preparation system of the present invention to prepare lithium hydroxide.

The present invention has the following advantages: (1) The present invention has high lithium utilization rate, low consumption of lithium chloride, and low raw material consumption. Reasonable utilization and treatment of materials in each process can achieve efficient utilization of sodium hydroxide and lithium. The specific implementation methods include: by concentrating the causticization mother liquor, the high-concentration alkali that does not participate in the reaction is used as the raw material for lithium chloride causticization. It can greatly reduce the consumption of sodium hydroxide; by using the lithium hydroxide primary washing liquid as the raw material for the lithium chloride causticization reaction, the lithium utilization rate can be improved and the alkali consumption can be reduced; the lithium carbonate washing liquid and the lithium carbonate crystallization mother liquor are combined with lithium chloride The causticizing mother liquors are combined and concentrated to effectively recover the lithium contained therein. The comprehensive utilization rate of lithium reaches more than 90%. (2) The process conditions of the present invention are mild, the energy consumption is low, and there is basically no production of three wastes. The process synthesis and purification technology provided by the invention has mild control points, low requirements on equipment materials, relatively low energy consumption, and basically no three wastes, and is green and environmentally friendly. (3) The quality of the product of the present invention can stably reach the indicators of battery-grade lithium hydroxide and battery-grade lithium carbonate, and the system stability is excellent.

The present invention will be explained below by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the invention. Unless otherwise stated, the methods, reagents and materials used in the examples are conventional methods, reagents and materials in the art. The raw material compounds in the examples can all be purchased through commercial channels.

Embodiment 1

This embodiment uses the lithium hydroxide and lithium carbonate preparation system shown in Figure 1 to prepare lithium hydroxide and lithium carbonate:

Lithium hydroxide synthesis: Put 478.75kg of brine containing 30.1wt% lithium chloride and 679.4kg of 20% mass fraction sodium hydroxide solution into the lithium chloride primary causticizer 1, stir and keep at 30°C for 0.5h , use filter mechanism 2 to carry out pressure filtration at 30°C to obtain first-level causticizing slag (moisture content 3wt%) and first-level causticizing liquid; transfer the first-level causticizing liquid to the lithium chloride second-level causticizing kettle 3, add 185.5kg sodium hydroxide, stir and keep at 50°C for 1.5h, use filter mechanism 4 to perform press filtration at 50°C to obtain secondary causticizing slag (moisture content 3wt%) and secondary causticizing liquid ; Pour the secondary causticizing liquid into the causticizing mother liquor storage tank 6 for treatment.

Lithium hydroxide impurity removal: Combine the two-stage causticizing slag (total 174.8kg) and 280.3kg saturated lithium hydroxide solution, mix and wash in primary washing kettle 7, stir and keep at 50°C for 1.5h, use filter mechanism 8 to filter the materials Perform press filtration at 50°C to obtain 150.53kg of lithium hydroxide primary washing residue (moisture content: 3wt%) and 304.57kg of lithium hydroxide primary washing liquid; the lithium hydroxide primary washing liquid is poured into the primary washing liquid intermediate tank 9 for waiting. For treatment, the primary washing slag and 278.8kg saturated lithium hydroxide solution are mixed and washed in the secondary washing kettle 10, stirred and kept at 50°C for 1.5 hours. Most of the impurities sodium chloride and sodium hydroxide in the causticizing slag are removed through two washings. Transfer the mass to the washing liquid, use the filtering mechanism 11 to filter the material at 50°C, and obtain 143.96kg lithium hydroxide secondary washing residue (moisture content 3wt%) and 285.37kg lithium hydroxide secondary washing liquid; hydrogen The lithium oxide secondary washing liquid is poured into the secondary washing liquid intermediate tank 12 for treatment. Deionized water is added to the secondary washing slag solution configuration kettle 13 to dissolve all the lithium hydroxide secondary washing slag. After forced circulation The evaporator 14 performs evaporation and crystallization at -0.06Mpa and 70°C. After the crystallization is completed, the filtering mechanism 15 is used for pressure filtration to obtain 280.3kg of lithium hydroxide crystallization mother liquor and put into the lithium hydroxide crystallization mother liquor intermediate tank 16 for later use. The lithium hydroxide crystallizes After the slag (moisture content 3wt%) is dried by the drying mechanism 17 and demagnetized by the demagnetization mechanism 18, 83.9kg of battery-grade lithium hydroxide product (lithium hydroxide monohydrate) is obtained.

Lithium carbonate synthesis: 1158.85kg of the secondary causticization liquid in the causticization mother liquor storage tank 6 is evaporated and concentrated through the causticization mother liquor concentrator 19 at -0.04Mpa and 80°C. After concentration, the filtering mechanism 20 is used to pressurize at 80°C. Filter to obtain 233kg concentrated liquid and 198kg concentrated residue (moisture content 3wt%). The obtained concentrated liquid is a high-concentration alkali, which is poured into the concentrated alkali storage tank 5 for later use. The obtained concentrated residue is stored in the lithium carbonate synthesis kettle 21 After all the water is dissolved, the temperature is raised to 80° C. and 48.29 kg of carbon dioxide gas is introduced to precipitate lithium. The filtering mechanism 22 is used to filter to obtain crude lithium carbonate slag (lithium precipitation slag, moisture content is 3wt%).

Lithium carbonate impurity removal: add water to dissolve the obtained crude lithium carbonate slag in the lithium precipitation slag solution configuration kettle 23, then add it to the forced circulation evaporator 24 for evaporation and crystallization. After crystallization, use the filtering mechanism 25 to press filter, and the obtained lithium carbonate crystallization mother liquor is poured into The lithium carbonate crystallization mother liquor intermediate tank 26 is ready for use. The lithium carbonate crystallization slag (moisture content 3wt%) is added to 6 times the mass of deionized water, mixed in the lithium carbonate washing kettle 27, stirred and washed at 80°C for 1.5 hours, and filtered after washing. The mechanism 28 performs pressure filtration at 80°C, and the obtained lithium carbonate washing liquid is poured into the lithium carbonate crystallization mother liquor intermediate tank 26 for later use. The obtained lithium carbonate washing residue (moisture content 3wt%) is dried by the drying mechanism 29 You can obtain 62.3kg of battery-grade lithium carbonate product.

Embodiment 2

This embodiment uses the lithium hydroxide and lithium carbonate preparation system shown in Figure 1 to prepare lithium hydroxide and lithium carbonate by recycling the materials of each process in Example 1:

Lithium hydroxide synthesis: 298.2kg of brine containing 30.1wt% lithium chloride was stored in the primary washing liquid intermediate tank 9 of the previous batch (Example 1) of the lithium hydroxide primary washing liquid 304.57kg and 555.38kg with a mass fraction of 20 % sodium hydroxide solution was put into the first-level causticizing kettle 1 of lithium chloride, stirred and kept at 50°C for 0.5h, and filtered using the filtering mechanism 2 at 50°C to obtain the first-level causticizing slag (moisture content: 3wt%) and the primary causticizing liquid, transfer the primary causticizing liquid into the lithium chloride secondary causticizing kettle 3, and transfer the previous batch (embodiment one) of the secondary causticizing liquid from the concentrated alkali storage tank 5 Add 233kg of the concentrated liquid into the lithium chloride secondary causticizing kettle 3, start stirring and keep it at 50°C for 2.0 hours, use the filter mechanism 4 to perform pressure filtration at 50°C to obtain the secondary causticizing slag (moisture content 3wt% ) and secondary causticizing liquid, drive the secondary causticizing liquid into the causticizing mother liquor storage tank 6 for treatment.

Lithium hydroxide impurity removal: Combine the two-stage causticizing slag (183.8kg in total) with the previous batch (Example 1) lithium hydroxide secondary washing liquid 285.37kg from the secondary washing liquid intermediate tank 12 in the primary washing kettle 7 Mix and wash in medium, stir and keep at 50°C for 1.5h, use filter mechanism 8 to press filter the material at 50°C, and obtain 153.88kg of lithium hydroxide primary washing residue (moisture content 3wt%) and lithium hydroxide primary washing liquid 315.29kg, the lithium hydroxide primary washing liquid is poured into the primary washing liquid intermediate tank 9 for treatment. Combine the lithium hydroxide primary washing residue with 280.3 kg of the previous batch (Example 1) lithium hydroxide crystal mother liquor from the lithium hydroxide crystal mother liquor intermediate tank 16, mix and wash in the secondary washing tank 10, stir and keep warm at 50°C 1.5h, through two washings, most of the impurities sodium chloride and sodium hydroxide in the causticization residue are transferred to In the washing liquid, use the filter mechanism 11 to filter the material at 50°C to obtain 145.02kg lithium hydroxide secondary washing residue (moisture content 3wt%) and 289.16kg lithium hydroxide secondary washing liquid; lithium hydroxide secondary washing liquid The primary washing liquid is pumped into the secondary washing liquid intermediate tank 12 for treatment, and deionized water is added to the secondary washing residue solution dispensing kettle 13 to dissolve all the lithium hydroxide secondary washing residue, and then passes through the forced circulation evaporator 14 at -0.06 MPa and 70°C for evaporation and crystallization. After the crystallization is completed, use the filtering mechanism 15 to press filter to obtain 281.2kg of lithium hydroxide crystallization mother liquor and put it into the lithium hydroxide crystallization mother liquor intermediate tank 16 for later use. The lithium hydroxide crystallization slag (moisture content: 3wt%), 81.2kg of battery-grade lithium hydroxide product (lithium hydroxide monohydrate) was obtained after drying and demagnetization.

Synthesis of lithium carbonate: 1150.35kg of secondary causticization liquid in the causticization mother liquor storage tank 6 is evaporated and concentrated through the causticization mother liquor concentrator 19 at -0.04Mpa and 80°C. After concentration, the filtering mechanism 20 is used to pressurize at 80°C. Filter to obtain 223kg concentrated liquid and 202kg concentrated residue (moisture content 3wt%). The obtained concentrated liquid is a high-concentration alkali, which is poured into the concentrated alkali storage tank 5 for later use. The obtained concentrated residue is stored in the lithium carbonate synthesis kettle 21 After all the water is dissolved, the temperature is raised to 80° C. and 49.27 kg of carbon dioxide gas is introduced to precipitate lithium. The filtering mechanism 22 is used to filter to obtain crude lithium carbonate slag (lithium precipitation slag, moisture content is 3wt%).

Lithium carbonate impurity removal: add water to dissolve the obtained crude lithium carbonate slag in the lithium precipitation slag solution configuration kettle 23, then add it to the forced circulation evaporator 24 for evaporation and crystallization. After crystallization, use the filtering mechanism 25 to press filter, and the obtained lithium carbonate crystallization mother liquor is poured into The lithium carbonate crystallization mother liquor intermediate tank 26 is ready for use. The lithium carbonate crystallization slag (moisture content 3wt%) is added with 6 times the mass of deionized water, mixed in the lithium carbonate washing kettle 27, stirred and washed at 80°C for 1.5 hours, and used after washing. The filtering mechanism 28 performs pressure filtration at 80° C., and the obtained lithium carbonate washing liquid is poured into the lithium carbonate crystallization mother liquor intermediate tank 26 for later use. The obtained lithium carbonate washing residue (moisture content 3wt%) is dried by the drying mechanism 29 After that, 63.58kg of battery-grade lithium carbonate product can be obtained.

The lithium hydroxide products prepared in Examples 1 and 2 were tested according to the national standard GB/T 11064 method, and the test results are shown in Table 1. In Table 1, “nd” indicates that the content is lower than the detection limit. It can be seen that the lithium hydroxide product produced by the present invention meets the battery-grade lithium hydroxide index.

Table 1: Chemical composition of lithium hydroxide products prepared in Example 1 and Example 2

The lithium carbonate products prepared in Examples 1 and 2 were tested according to the national standard GB/T 11064 method, and the test results are shown in Table 2. In Table 2, “nd” indicates that the content is lower than the detection limit. It can be seen that the by-product lithium carbonate product produced by the present invention meets the battery-grade lithium carbonate index.

Table 2: Chemical composition of lithium carbonate products prepared in Example 1 and Example 2

The materials of the lithium purification system during the two-batch circulation process of Implementation 1 and 2 are lithium hydroxide product p, lithium carbonate product q, and lithium carbonate lithium precipitation mother liquor o, in which lithium carbonate lithium precipitation mother liquor accounts for 6 to 8% of the total lithium input. The one-way lithium yield is about 74%, and the total lithium utilization rate is about 92%.

Lithium hydroxide and lithium carbonate were prepared in multiple batches according to the methods of Example 1 and Example 2. The raw material consumption per unit is as shown in Table 3. In Table 3, the unit consumption is the unit consumption of multi-batch cycles. Taking lithium hydroxide as the main product, the raw material consumption in Table 3 is the amount of raw materials consumed per ton of battery-grade lithium hydroxide. The by-product output in Table 3 is the by-product per ton of battery-grade lithium hydroxide. Amount of battery grade lithium carbonate.

Table 3: Raw material unit consumption and by-product lithium carbonate output of the present invention

The lithium carbonate crystallization mother liquor obtained by filtering through the filtering mechanism 25 and the lithium carbonate washing liquid obtained by filtering through the filtering mechanism 28 are combined and poured into the lithium carbonate crystallization mother liquor intermediate tank 26 to obtain the mixed material (abbreviated as J), which can be applied to the causticized mother liquor. In the concentration kettle 19, it is combined with the causticization mother liquor (K for short) and concentrated. The inventor noticed that 1) the composition and absolute amount of impurities in material J are much smaller than material K, and the subsequent results will not be affected by the introduction of a large amount of impurities; 2) material J still contains some lithium ions, which has application value; 3) the introduction of material J The carbonate ions precipitated after concentration will not affect the subsequent introduction of carbon dioxide to precipitate lithium. The highly concentrated alkali obtained after concentration will have a negligible amount of carbonate and will not affect the synthesis of lithium hydroxide. Therefore, the materials in the intermediate tank 26 of the lithium carbonate crystallization mother liquor can be reused. The compositions of material J obtained in Example 1 and material K obtained in Example 2 are shown in Table 4.

Table 4: Main element composition of material J and material K (unit: g/L)

Comparative Example 1

This comparative example uses the following method to prepare lithium hydroxide:

Take 455.07kg of brine containing 27wt% lithium chloride, add 443kg of sodium hydroxide solution (alkali solution) with a mass concentration of approximately 25.8%, and react at room temperature for 60 minutes to form a solid-liquid mixture containing lithium hydroxide precipitate. The resulting material is processed Filter to obtain causticizing residue (crude lithium hydroxide) and causticizing liquid (lithium precipitation mother liquor). Use saturated lithium hydroxide solution to wash the filter cake (crude lithium hydroxide) to obtain the first lithium hydroxide filter cake; under heating conditions, use 300kg to remove After the first lithium hydroxide filter cake is completely dissolved in the ionized water, a lithium hydroxide solution is obtained, and 2/3 of the water is evaporated by heating, followed by cooling and crystallization, controlling the crystallization temperature at 60°C, and filtering to obtain the second lithium hydroxide filter cake; use The second lithium hydroxide filter cake is washed again with the saturated lithium hydroxide solution; the washed second lithium hydroxide filter cake is vacuum dried at 50°C for 5 hours to remove free water in the filter cake, and finally obtain hydrogen monohydrate Lithium oxide products. Add hydrochloric acid to the lithium precipitation mother liquor for neutralization to obtain a solution containing sodium chloride. The solution is evaporated, crystallized, filtered, washed, and dried to obtain industrial grade sodium chloride; the solution containing sodium chloride is obtained by evaporation, crystallization, and filtration. The filtrate is returned to the system and combined with brine as the lithium precipitation reaction solution for recycling; the washing liquid after the second washing of the crude lithium hydroxide is combined with the filtrate obtained by cooling and filtering during the evaporation and crystallization of the lithium hydroxide solution, and then returned to the hydrogen hydroxide solution together. During the first washing process of crude lithium oxide; during the first washing process of crude lithium hydroxide, the washing liquid is obtained for evaporation and crystallization, cooling, and filtering, and the obtained filtrate is returned to prepare alkali solution and participates in the reaction to precipitate lithium as part of the alkali solution. process, and combine the obtained filter residue with crude lithium hydroxide for the first washing process; the sodium chloride washing liquid is returned to neutralize the obtained solution containing sodium chloride for the evaporation and crystallization step.

Two batches of continuous processing were carried out according to the scheme of Comparative Example 1, and the components of the obtained lithium hydroxide product were tested according to the national standard GB/T 11064 method. The results are shown in Table 5. It can be seen that the first batch of lithium hydroxide reached battery-grade standards, but due to improper treatment of the first washing liquid, subsequent materials were enriched with impurities, resulting in unqualified product quality and low lithium utilization. After calculation, the single-pass yield of lithium is 24.7%.

Table 5: Chemical composition of lithium hydroxide products prepared in Comparative Example 1 and Comparative Example 2

The raw material unit consumption for preparing lithium hydroxide using the method of Comparative Example 1 is shown in Table 6, where the raw material unit consumption is the amount of raw material consumed per ton of battery-grade lithium hydroxide. It can be seen that since this method only performs one-stage causticization reaction, dissolution and evaporation crystallization are performed between two lithium hydroxide washings, and the first washing liquid is evaporated and crystallized, and returned to the processing method for preparing alkali solution. It is not good. The filtrate after neutralizing and crystallizing the lithium precipitation mother liquor is used as brine for the lithium precipitation reaction. This method has high raw material consumption and low lithium chloride utilization rate.

Table 6: Comparative Example 1 Raw Material Consumption

Comparative Example 2

This comparative example uses the following method to prepare lithium hydroxide and lithium carbonate:

Take 455.07kg of brine containing 27wt% lithium chloride, add 443kg of sodium hydroxide solution with a mass concentration of approximately 25.8%, and react at room temperature for 60 minutes to form a solid-liquid mixture containing lithium hydroxide precipitate. The resulting material is filtered to obtain caustic acid. Slag (crude lithium hydroxide) and causticizing liquid (lithium precipitation mother liquor). Use saturated lithium hydroxide solution to wash the filter cake (crude lithium hydroxide) to obtain the first lithium hydroxide filter cake; under heating conditions, use 300kg of deionized water to completely dissolve the first lithium hydroxide filter cake, and then heat and evaporate it. 2/3 water, carry out cooling crystallization, control the crystallization temperature at 60°C, filter to obtain the second lithium hydroxide filter cake; use a saturated lithium hydroxide solution to wash the second lithium hydroxide filter cake again; The lithium hydroxide filter cake is vacuum dried at 50°C for 5 hours to remove free water in the filter cake to obtain lithium hydroxide monohydrate product. Add sodium carbonate to the lithium precipitation mother liquor for reaction, and filter to obtain the filter residue and filtrate. The filter residue is washed and dried to obtain the lithium carbonate product. The washing liquid after the second washing of the crude lithium hydroxide is combined with the filtrate obtained by cooling and filtering during the evaporation and crystallization of the lithium hydroxide solution, and then returned together to the first washing process of the crude lithium hydroxide; the first washing of the crude lithium hydroxide During the first washing process, the washing liquid is obtained, evaporated, crystallized, cooled, and filtered. The obtained filtrate is returned to prepare alkali solution and participates in the reaction lithium precipitation process as part of the alkali solution. The obtained filter residue is combined with crude lithium hydroxide for the first step. Second washing process; the lithium carbonate washing liquid is returned to the lithium precipitation mother liquor to continue preparing lithium carbonate.

Two batches of continuous processing were carried out according to the scheme of Comparative Example 2, and the problem of unstable product quality occurred. After calculation, the single-pass yield of lithium is 44.06%.

The raw material consumption for preparing lithium hydroxide using the method of Comparative Example 2 is as shown in Table 7. With lithium hydroxide as the main product, the raw material consumption in Table 7 is the amount of raw materials consumed per ton of battery-grade lithium hydroxide; the by-product output in Table 7 is the by-product per ton of battery-grade lithium hydroxide produced. Amount of battery grade lithium carbonate. It can be seen that since this method only performs one-stage causticization reaction, dissolution and evaporation crystallization are performed between two lithium hydroxide washings, and the first washing liquid is evaporated and crystallized, and returned to the processing method for preparing alkali solution. The method of directly adding sodium carbonate to the lithium precipitation mother liquor for lithium precipitation reaction is not good. This method has high raw material consumption and low lithium chloride utilization rate.

Table 7: Comparative Example 2 Raw material consumption and by-product lithium carbonate production

Claims

A method for preparing lithium hydroxide and lithium carbonate, characterized in that the method includes the following steps:

(1) Lithium hydroxide synthesis: carry out a first-level causticization reaction between lithium chloride and the first alkali in a solvent. After the reaction, the first-level causticizing slag and the first-level causticizing mother liquor are separated, and the first-level causticizing mother liquor and the first-level causticizing mother liquor are separated. The two alkali performs a secondary causticizing reaction. After the reaction, the secondary causticizing slag and the secondary causticizing mother liquor are separated. The N-level causticizing mother liquor and the N+1th alkali are optionally subjected to an N+1-level causticizing reaction. The reaction Afterwards, N+1 level causticizing slag and N+1 level causticizing mother liquor are obtained, where N≥2, and the obtained causticizing slag of all levels is crude lithium hydroxide;

(2) Lithium hydroxide impurity removal: Wash and separate the crude lithium hydroxide twice or more continuously to obtain each lithium hydroxide washing liquid and the last lithium hydroxide washing residue, and wash the last lithium hydroxide The slag is prepared into a solution, and after evaporation, crystallization and separation, lithium hydroxide crystallization mother liquor and lithium hydroxide crystallization slag are obtained. The lithium hydroxide crystallization slag is post-processed to obtain lithium hydroxide products;

(3) Synthesis of lithium carbonate: The last-stage causticization mother liquor obtained in step 1 is evaporated, concentrated and separated to obtain the causticizing liquid concentrate and the causticizing liquid concentrated residue, and the causticizing liquid concentrate is used as the second step in step 1. As an alkali source for the first-level or higher causticization reaction, the concentrated residue of the caustic liquid is configured into a solution, and carbon dioxide is introduced to carry out the lithium precipitation reaction. After the reaction, the crude lithium carbonate product is separated;

(4) Lithium carbonate impurity removal: Configure crude lithium carbonate into a solution, perform evaporation, crystallization and separation to obtain lithium carbonate crystallization mother liquor and lithium carbonate crystallization slag. Wash and separate the lithium carbonate crystallization slag to obtain lithium carbonate washing slag. The lithium carbonate washing residue is post-processed to obtain lithium carbonate product.
The method of claim 1, wherein the method has one or more of the following characteristics:

Perform a two-stage causticization reaction in step 1;

In step 1, separation is carried out by filtration, preferably filter press;

In step 1, the moisture content of causticizing slag at all levels is not higher than 8wt%;

In step 1, lithium chloride is provided in the form of solid lithium chloride or a solution containing lithium chloride; preferably, the solution containing lithium chloride is selected from brine containing lithium chloride, primary hydrogen obtained in step 2 Lithium oxide cleaning solution or combination thereof;

In step 1, the base is selected from sodium hydroxide, potassium hydroxide, ammonia or a combination thereof, preferably sodium hydroxide;

In step 1, the alkali is provided in the form of solid alkali or alkali solution; the alkali solution is preferably an aqueous alkali solution;

In step 1, the molar ratio of alkali to lithium chloride in the primary causticization reaction is (0.8-2):1, preferably (0.8-1.3):1;

In step 1, the concentration of lithium ions in the first-level causticization reaction system before the reaction is 20-35g/L;

In step 1, the causticization reaction temperature at each level and the separation temperature at each level are independently 10-80°C;

In step 1, the first-level causticization reaction time is 0.5-1h;

In step 1, the N-level causticizing reaction times are each independently 1-2h, where N≥2;

In step 1, the causticization reaction temperature at each stage is the same as the separation temperature at the same stage;

In step 1, the molar ratio of the alkali in the N-level causticization reaction and the alkali in the N-1-level causticization reaction is 1: (0.7-0.85), where N≥2.
The method of claim 1, wherein the method has one or more of the following characteristics:

In step 2, the causticizing residues of all levels obtained in step 1 are combined and washed;

In step 2, separation is carried out by filtration, preferably filter press;

In step 2, the moisture content of the lithium hydroxide washing residue after each washing and separation is not higher than 8wt%;

In step 2, wash and separate the crude lithium hydroxide product twice;

In step 2, use lithium hydroxide solution, each lithium hydroxide washing liquid, lithium hydroxide crystallization mother liquor or a mixture thereof to wash the crude lithium hydroxide, wherein the lithium hydroxide washing liquid that can be used for the Nth washing is the Mth Lithium subhydroxide washing liquid, wherein M>N; preferably, in step 2, use lithium hydroxide solution, N+1th lithium hydroxide washing liquid or a mixture thereof to wash the crude lithium hydroxide for the Nth time, wherein N≤total number of washings-1, use lithium hydroxide solution, lithium hydroxide crystallization mother liquor or a mixture thereof to wash the crude lithium hydroxide for the last time; the lithium hydroxide solution is preferably a saturated lithium hydroxide solution;

In step 2, the primary lithium hydroxide washing liquid is used as the raw material for the primary causticization reaction in step 1;

In step 2, the mass ratio of the liquid used for each washing to the crude lithium hydroxide is independently 1.5-2.2:1;

In step 2, each washing time is independently 1h-3h;

In step 2, the temperature of each washing and the separation temperature after each washing are independently 10-80°C;

In step 2, the temperature of each washing is the same as the separation temperature after the same washing;

In step 2, the last lithium hydroxide washing residue is prepared into an aqueous solution;

In step 2, the evaporation pressure is -0.04MPa to -0.085MPa;

In step 2, the final evaporation temperature and the separation temperature after evaporation and crystallization are not higher than 80°C;

In step 2, the final evaporation temperature is the same as the separation temperature after evaporation and crystallization;

In step 2, use a forced circulation evaporator for evaporation and crystallization;

In step 2, the post-processing of the lithium hydroxide crystallization slag includes drying and optional demagnetization.
The method of claim 1, wherein the method has one or more of the following characteristics:

In step 3, the evaporation pressure is -0.02MPa to -0.085MPa;

In step 3, the final evaporation temperature and the separation temperature after evaporation and concentration are not higher than 90°C;

In step 3, the final evaporation temperature is the same as the separation temperature after evaporation and concentration;

In step 3, separation is carried out by filtration, preferably filter press;

In step 3, the moisture content of the causticizing liquid concentrated residue and crude lithium carbonate is not higher than 8wt%;

In step 3, the caustic liquid concentrated residue is prepared into an aqueous solution;

In step 3, the feeding mass ratio of carbon dioxide and caustic liquid concentrated residue is 1: (3.8-4.5);

In step 3, the lithium precipitation reaction temperature is 10-90°C.
The method of claim 1, wherein the method has one or more of the following characteristics:

In step 4, prepare the crude lithium carbonate into an aqueous solution;

In step 4, use a forced circulation evaporator for evaporation and crystallization;

In step 4, separation is carried out by filtration, preferably filter press;

In step 4, use water to wash the lithium carbonate crystallization residue;

In step 4, the mass ratio of the liquid used for washing to the lithium carbonate crystal slag is (5-10):1;

In step 4, the washing time is 1h-3h;

In step 4, the washing temperature and the separation temperature after washing are independently 10-90°C;

In step 4, the washing temperature is the same as the separation temperature after washing;

In step 4, the post-processing of the lithium carbonate washing residue includes drying;

In step 4, the lithium carbonate crystallization mother liquor and/or the lithium carbonate washing liquid obtained by washing the lithium carbonate crystallization residue is incorporated into the final causticization mother liquor obtained in step 1 for the synthesis of lithium carbonate in step 3.
The method according to claim 1, characterized in that the method includes performing the operations of steps 1 to 4 in two or more batches by applying materials;

Among them, the lithium chloride used in step 1 in the second and subsequent batches comes from the primary lithium hydroxide washing liquid obtained in step 2 in the previous batch and selected from solid lithium chloride and lithium chloride-containing brine. one or both;

The alkali used in the secondary and higher-level causticization reactions in step 1 of the second and subsequent batches comes from the caustic liquid concentrate obtained in step 3 of the previous batch;

In the second and subsequent batches, in step 3, combine the final causticization mother liquor obtained in step 1 in the same batch with the lithium carbonate crystallization mother liquor obtained in step 4 in the previous batch and the obtained product from washing the lithium carbonate crystallization residue. The lithium carbonate washing liquid is combined and used to synthesize lithium carbonate.
A method for preparing lithium hydroxide, characterized in that the method includes step 1 to step 2 described in any one of claims 1-6.
A system for preparing lithium hydroxide and lithium carbonate, characterized in that the system includes:

The lithium hydroxide synthesis unit includes a lithium chloride primary causticizing unit, a primary separation unit, a lithium chloride secondary causticizing unit, a secondary separation unit, a causticizing mother liquor storage tank and optional lithium chloride tertiary or Three or more levels of causticizing devices and corresponding levels of separation devices, in which each level of lithium chloride causticizing devices is connected to the material input end of the same-level separation device, and the liquid output end of each level of separation device is connected to the next-level lithium chloride causticizing device. The devices are connected, and the liquid output end of the last stage separation device is connected to the causticization mother liquor storage tank;

Lithium hydroxide impurity removal unit, including at least two-stage lithium hydroxide washing devices, separation devices corresponding to each level of lithium hydroxide washing devices, lithium hydroxide washing residue solution configuration device, and lithium hydroxide washing residue solution evaporation and crystallization device , a separation device corresponding to the lithium hydroxide washing residue solution evaporation and crystallization device and a lithium hydroxide post-processing device, in which the solid output ends of the separation devices at each level of the lithium hydroxide synthesis unit are connected to the first-level lithium hydroxide washing device, and each level The lithium hydroxide washing device is connected to the material input end of the corresponding separation device, and the material output end of the separation device corresponding to the upper level lithium hydroxide washing device is connected to the next level lithium hydroxide washing device, which corresponds to the last level hydrogen Lithium Oxide Wash The solid output end of the separation device of the device is connected to the lithium hydroxide washing slag solution configuration device, and the lithium hydroxide washing slag solution evaporation and crystallization device is connected to the material input end of the corresponding separation device, which corresponds to the lithium hydroxide washing slag solution evaporation and crystallization device. The solid output end of the separation device is connected to the lithium hydroxide post-treatment device;

The lithium carbonate synthesis unit includes a causticization mother liquor concentration device, a first separation device of the lithium carbonate synthesis unit, a lithium carbonate synthesis device and a second separation device of the lithium carbonate synthesis unit, in which the causticization mother liquor storage tank of the lithium hydroxide synthesis unit and the causticization The mother liquor concentration device is connected, the causticization mother liquor concentration device is connected to the material input end of the first separation device of the lithium carbonate synthesis unit, the solid output end of the first separation device of the lithium carbonate synthesis unit is connected to the lithium carbonate synthesis device, and the lithium carbonate synthesis device is connected to the carbonic acid synthesis unit. The material input end of the second separation device of the lithium synthesis unit is connected;

The lithium carbonate impurity removal unit includes a lithium carbonate lithium precipitation slag solution preparation device, a lithium carbonate lithium precipitation slag solution evaporation and crystallization device, a first separation device of the lithium carbonate impurity removal unit, a lithium carbonate washing device, and a second separation device of the lithium carbonate impurity removal unit. , a lithium carbonate post-processing device, wherein the solid output end of the second separation device of the lithium carbonate synthesis unit is connected to a lithium carbonate precipitation slag solution configuration device, and the lithium carbonate lithium precipitation solution configuration device is connected to a lithium carbonate precipitation lithium slag solution evaporation and crystallization device, The evaporation and crystallization device of the lithium carbonate precipitation slag solution is connected to the material input end of the first separation device of the lithium carbonate impurity removal unit. The solid output end of the first separation device of the lithium carbonate impurity removal unit is connected to the lithium carbonate washing device. The lithium carbonate washing device is connected to the material input end of the first separation device of the lithium carbonate impurity removal unit. The material input end of the second separation device of the lithium carbonate impurity removal unit is connected, and the solid output end of the second separation device of the lithium carbonate impurity removal unit is connected to the lithium carbonate post-processing device.
The system according to claim 8, characterized in that the system has one or more of the following characteristics:

The separation device in the system is a filter device, preferably a filter press device;

The lithium hydroxide impurity removal unit also includes a first-level washing liquid intermediate tank, and the material input end of the first-level washing liquid intermediate tank corresponds to the first-level lithium hydroxide washing device in the lithium hydroxide impurity removal unit. The liquid output end of the separation device is connected, and the material output end of the first-level washing liquid intermediate tank is connected to the first-level lithium chloride causticizing device of the lithium hydroxide synthesis unit;

The lithium hydroxide impurity removal unit also includes an N-level washing liquid intermediate tank, where N ≥ 2, and the material input end of the N-level washing liquid intermediate tank is in contact with the N-level hydroxide in the lithium hydroxide impurity removal unit. The liquid output end of the separation device corresponding to the lithium washing device is connected, and the material output end of the N-level washing liquid intermediate tank is connected to the M-level lithium hydroxide washing device, where M<N, preferably M=N-1;

The lithium hydroxide impurity removal unit also includes a lithium hydroxide crystallization mother liquor intermediate tank. The material input end of the lithium hydroxide crystallization mother liquor intermediate tank is evaporated with the lithium hydroxide washing residue solution in the lithium hydroxide impurity removal unit. The liquid output end of the separation device corresponding to the crystallization device is connected, and the material output end of the lithium hydroxide crystal mother liquor intermediate tank is connected to the lithium hydroxide washing device, preferably to the last stage lithium hydroxide washing device;

The evaporation and crystallization device of the lithium hydroxide washing residue solution is a forced circulation evaporator;

The lithium hydroxide post-treatment device includes a drying device and an optional demagnetization device;

The lithium hydroxide synthesis unit also includes an alkali liquid storage tank. The material input end of the alkali liquid storage tank is connected to the liquid output end of the first separation device of the lithium carbonate synthesis unit. The material output of the alkali liquid storage tank end with the hydroxide The lithium chloride causticizing device in the lithium synthesis unit is connected, preferably connected to a secondary or higher lithium chloride causticizing device;

The evaporation and crystallization device of the lithium carbonate precipitation slag solution is a forced circulation evaporator;

The lithium carbonate impurity removal unit also includes a lithium carbonate crystallization mother liquor intermediate tank. The material input end of the lithium carbonate crystallization mother liquor intermediate tank is connected to the first separation device of the lithium carbonate impurity removal unit and/or the second lithium carbonate impurity removal unit. The liquid output end of the separation device is connected, and the material output end of the lithium carbonate crystallization mother liquor intermediate tank is connected to the causticization mother liquor concentration device in the lithium carbonate synthesis unit.
The system of claim 8, wherein:

The lithium hydroxide synthesis unit includes a lithium chloride primary causticizing device, a primary separation device, a lithium chloride secondary causticizing device, a secondary separation device, a causticizing mother liquor storage tank and an alkali liquid storage tank, wherein the chlorination The various levels of lithium causticizing devices are connected to the material input end of the same-level separation device, the liquid output end of the first-level separation device is connected to the secondary lithium chloride causticization device, and the liquid output end of the second-level separation device is connected to the causticization mother liquor storage tank. Connected, the material output end of the alkali storage tank is connected to the lithium chloride secondary causticizing device;

The lithium hydroxide impurity removal unit includes a primary lithium hydroxide washing device, a first separation device of the lithium hydroxide impurity removal unit, a primary washing liquid intermediate tank, a secondary lithium hydroxide washing device, and a third lithium hydroxide impurity removal unit. Second separation device, secondary washing liquid intermediate tank, lithium hydroxide washing residue solution preparation device, lithium hydroxide washing residue solution evaporation and crystallization device, lithium hydroxide impurity removal unit third separation device, lithium hydroxide crystallization mother liquor intermediate tank, hydrogen Lithium oxide post-processing device, in which the primary lithium hydroxide washing device is connected to the material input end of the first separation device of the lithium hydroxide impurity removal unit, and the solid output end of the first separation device of the lithium hydroxide impurity removal unit is connected to the secondary hydroxide The lithium washing device is connected, the secondary lithium hydroxide washing device is connected to the material input end of the second separation device of the lithium hydroxide impurity removal unit, and the solid output end of the second separation device of the lithium hydroxide impurity removal unit is connected to the lithium hydroxide washing residue solution The configuration device is connected, the lithium hydroxide washing residue solution configuration device is connected to the lithium hydroxide washing residue solution evaporation and crystallization device, the lithium hydroxide washing residue solution evaporation and crystallization device is connected to the material input end of the third separation device of the lithium hydroxide impurity removal unit, The solid output end of the third separation device of the lithium hydroxide impurity removal unit is connected to the lithium hydroxide post-processing device, and the material input end of the primary washing liquid intermediate tank is connected to the liquid output end of the first separation device of the lithium hydroxide impurity removal unit. The material output end of the primary washing liquid intermediate tank is connected to the lithium chloride primary causticizing device. The material input end of the secondary washing liquid intermediate tank is connected to the liquid output end of the second separation device of the lithium hydroxide impurity removal unit. The material output end of the washing liquid intermediate tank is connected to the first-level lithium hydroxide washing device. The material input end of the lithium hydroxide crystallization mother liquor intermediate tank is connected to the liquid output end of the third separation device of the lithium hydroxide impurity removal unit. The lithium hydroxide crystallization The material output end of the mother liquor intermediate tank is connected to the secondary lithium hydroxide washing device;

The lithium carbonate synthesis unit includes a causticization mother liquor concentration device, a first separation device of the lithium carbonate synthesis unit, a lithium carbonate synthesis device and a second separation device of the lithium carbonate synthesis unit, in which the causticization mother liquor storage tank of the lithium hydroxide synthesis unit is connected to the causticization mother liquor storage tank. The causticization mother liquor concentration device is connected to the material input end of the first separation device of the lithium carbonate synthesis unit, the solid output end of the first separation device of the lithium carbonate synthesis unit is connected to the lithium carbonate synthesis device, and the lithium carbonate synthesis device is connected to The material input end of the second separation device of the lithium carbonate synthesis unit is connected, and the liquid output end of the first separation device of the lithium carbonate synthesis unit is connected to the material input end of the alkali liquid storage tank of the lithium hydroxide synthesis unit;

Preferably, the lithium carbonate impurity removal unit includes a lithium carbonate lithium slag solution configuration device, a lithium carbonate lithium slag solution evaporation and crystallization device, a first separation device of the lithium carbonate impurity removal unit, a lithium carbonate washing device, and a lithium carbonate impurity removal unit. The second separation device, the lithium carbonate post-treatment device and the lithium carbonate crystallization mother liquor intermediate tank, wherein the solid output end of the second separation device of the lithium carbonate synthesis unit is connected to the lithium carbonate precipitation lithium slag solution configuration device, the lithium carbonate precipitation lithium solution configuration device is connected to The lithium carbonate precipitated slag solution evaporation and crystallization device is connected, the lithium carbonate precipitated slag solution evaporation and crystallization device is connected to the material input end of the first separation device of the lithium carbonate impurity removal unit, and the solid output end of the first separation device of the lithium carbonate impurity removal unit is connected to The lithium carbonate washing device is connected to the material input end of the second separation device of the lithium carbonate impurity removal unit. The solid output end of the second separation device of the lithium carbonate impurity removal unit is connected to the lithium carbonate post-processing device. The lithium carbonate crystallizes The material input end of the mother liquor intermediate tank is connected to the liquid output end of the first separation device of the lithium carbonate impurity removal unit and the second separation device of the lithium carbonate impurity removal unit, and the material output end of the lithium carbonate crystallization mother liquor intermediate tank is connected to the caustic acid of the lithium carbonate synthesis unit. The mother liquor concentration device is connected.
A method for preparing lithium hydroxide and lithium carbonate, characterized in that the method includes preparing lithium hydroxide and lithium carbonate using the system for preparing lithium hydroxide and lithium carbonate according to any one of claims 8-10;

Preferably, the method includes step 1 to step 4 described in any one of claims 1-6.
A system for preparing lithium hydroxide, characterized in that the system includes the lithium hydroxide synthesis unit and the lithium hydroxide impurity removal unit described in any one of claims 8-10.
A method for preparing lithium hydroxide, characterized in that the method includes preparing lithium hydroxide using the system for preparing lithium hydroxide according to claim 12;

Preferably, the method includes step 1 to step 2 described in any one of claims 1-6.