阅读说明：本技术 一种碳酸锂的制备方法 (Preparation method of lithium carbonate ) 是由 马珍 李生廷 张正风 莫延香 谢建明 董昌吉 张晓龙 文生才 李鹏业 李国栋 张 于 2021-04-19 设计创作，主要内容包括：本发明公开一种碳酸锂的制备方法,反应釜中预先设置底留液,底留液至少包含2％-15％的碳酸锂晶种,碳酸锂晶种的粒径大于等于设定值,将氯化锂精制液和碳酸钠溶液加入到反应釜中,进行反应,生成碳酸锂浆料；过滤碳酸锂浆料得到含有氯化钠和碳酸锂的滤饼；滤饼用水洗涤；干燥洗涤后的所述滤饼,得到碳酸锂产品。本发明提供的碳酸锂的制备方法中,反应釜中提前设置含有较大粒径的碳酸锂晶种的底留液,再加入碳酸钠和氯化锂进行反应时,生成的碳酸锂在碳酸锂晶核的基础上结晶长大,实现碳酸锂的控速结晶,制得的碳酸锂结晶粒度大；而且在高氯体系下,氯化钠和碳酸锂分别结晶,氯化钠再通过水洗涤,氯含量能控制在0PPM-500PPM。(The invention discloses a preparation method of lithium carbonate, wherein a bottom liquid is preset in a reaction kettle, the bottom liquid at least comprises 2-15% of lithium carbonate seed crystal, the particle size of the lithium carbonate seed crystal is more than or equal to a set value, and lithium chloride refined liquid and a sodium carbonate solution are added into the reaction kettle to react to generate lithium carbonate slurry; filtering the lithium carbonate slurry to obtain a filter cake containing sodium chloride and lithium carbonate; washing the filter cake with water; and drying the washed filter cake to obtain a lithium carbonate product. In the preparation method of the lithium carbonate, provided by the invention, the bottom solution containing the lithium carbonate crystal seed with larger particle size is arranged in advance in the reaction kettle, and then sodium carbonate and lithium chloride are added for reaction, the generated lithium carbonate is crystallized and grown on the basis of the lithium carbonate crystal nucleus, so that the speed-controlled crystallization of the lithium carbonate is realized, and the prepared lithium carbonate has large crystal size; in a high-chlorine system, sodium chloride and lithium carbonate are respectively crystallized, and the sodium chloride is washed by water, so that the chlorine content can be controlled to be 0-500 PPM.)

1. A preparation method of lithium carbonate comprises the following steps:

step S1, presetting a bottom liquid in a reaction kettle, wherein the bottom liquid at least comprises 2-15% of lithium carbonate seed crystal in mass fraction, the particle size of the lithium carbonate seed crystal is larger than or equal to a set value, adding a lithium chloride refined liquid and a sodium carbonate solution into the reaction kettle for reaction to generate lithium carbonate slurry, the lithium chloride refined liquid at least comprises 5-25% of lithium chloride in mass fraction and 0-30% of sodium chloride in mass fraction, the mass fraction of the sodium carbonate solution is 10-30%, and the temperature of the reaction kettle is 40-100 ℃;

step S2, filtering the lithium carbonate slurry to obtain a filter cake containing sodium chloride and lithium carbonate;

step S3, washing the filter cake with water to remove sodium chloride in the filter cake;

and step S4, drying the washed filter cake to obtain a lithium carbonate product.

2. The method for preparing lithium carbonate according to claim 1, wherein in step S1, the lithium chloride refined liquid is heated to 40 to 100 ℃ before being added to the reaction kettle.

3. The method for preparing lithium carbonate according to claim 1, wherein in the step S1, the sodium carbonate solution is heated to 40 to 100 ℃ before being added to the reaction kettle.

4. The method for preparing lithium carbonate according to claim 1, wherein in step S1, the lithium chloride refined solution and the sodium carbonate solution are added to the reaction kettle, and a reaction is performed in the reaction kettle to generate lithium carbonate slurry.

5. The method for preparing lithium carbonate according to claim 1, wherein in step S1, the lithium chloride refined solution and the sodium carbonate solution are fed from the top of the reaction kettle, and are transported from the bottom of the reaction kettle to the secondary reaction kettle, and the warming reaction is continued in the secondary reaction kettle, so as to generate the lithium carbonate slurry.

6. The method for preparing lithium carbonate according to claim 1, wherein in step S1, the sodium carbonate solution is added in excess in an amount of 5% to 15% of the theoretical reaction amount of sodium carbonate.

7. The method for preparing lithium carbonate according to claim 1, wherein the set value is 200 to 400 micrometers.

8. The method for preparing lithium carbonate as claimed in claim 1, wherein in step S1, the reaction kettle is stirred at a speed of 100-1000 rpm.

9. The method for preparing lithium carbonate according to claim 1, wherein in step S1, the bottom liquid further contains 0% to 30% by mass of sodium chloride.

10. The method for preparing lithium carbonate according to claim 1, wherein in the step S3, the water is deionized water and the solid-to-liquid ratio is 1:3 to 1: 6.

Technical Field

The invention relates to the technical field of lithium carbonate production, and particularly relates to a preparation method of crystalline lithium carbonate with low chloride impurity and large particle size in a high-chloride water salt system.

Background

Lithium is used as an energy metal in the 21 st century, the demand of lithium carbonate is rapidly increased along with the development of new energy automobiles, and the lithium carbonate is widely used for preparing various lithium compounds, metallic lithium and isotopes thereof, lithium ion batteries, analytical reagents and the like and is the most basic lithium salt product.

The lithium resources in China are mainly distributed in Qinghai-Tibet plateau, Xinjiang, inner Mongolia and Sichuan and account for 25.6 percent of the basic reserve of the lithium resources in salt lakes in the world, and the lithium resources in salt lake brine are the main existing forms of the lithium resources in China and account for about 85 percent of the total reserve of the lithium which has been proved in China.

Currently, according to the relevant national standards for lithium carbonate products, the higher the specification, the higher the lithium carbonate content, the less impurities should be contained. Generally, when lithium carbonate is synthesized by sodium carbonate and lithium chloride, the main content of the lithium carbonate is generally 98% -99.2%, the microscopic agglomerated particle size is small and is about 0-200 microns, and sodium chloride impurities exist in the lithium carbonate all the time, even if lithium and sodium are separated, two moles of sodium chloride are generated every time one mole of lithium carbonate is generated through reaction, chlorine impurities are easily wrapped in a molecular group and exist all the time, only impurities such as surface chlorine and the like can be washed away even through washing, the chlorine impurities wrapped in the molecular group and the like cannot be washed away by a common method, the chlorine content is often high and often affects the purity and quality of the lithium carbonate at 500 plus 3000 PPM. When the salt lake brine is used as a raw material to prepare the lithium chloride, the lithium chloride often carries part of sodium chloride impurities, and the prepared lithium carbonate has higher chlorine content in a high-chlorine water salt system.

Disclosure of Invention

The invention aims to provide a preparation method of lithium carbonate, which is used for solving the problems that the lithium carbonate is small in particle size and high in chlorine content and affects the quality of the lithium carbonate when the lithium carbonate is produced by the conventional method.

In order to achieve the above purpose, the invention provides the following technical scheme: a preparation method of lithium carbonate comprises the following steps:

step S1, presetting a bottom liquid in a reaction kettle, wherein the bottom liquid at least comprises 2-15% of lithium carbonate seed crystal in mass fraction, the particle size of the lithium carbonate seed crystal is larger than or equal to a set value, adding a lithium chloride refined liquid and a sodium carbonate solution into the reaction kettle for reaction to generate lithium carbonate slurry, the lithium chloride refined liquid at least comprises 5-25% of lithium chloride in mass fraction and 0-30% of sodium chloride in mass fraction, the mass fraction of the sodium carbonate solution is 10-30%, and the temperature of the reaction kettle is 40-100 ℃;

step S2, filtering the lithium carbonate slurry to obtain a filter cake containing sodium chloride and lithium carbonate;

step S3, washing the filter cake with water to remove sodium chloride in the filter cake;

and step S4, drying the washed filter cake to obtain a lithium carbonate product.

According to an embodiment of the present invention, in the step S1, before the lithium chloride refined liquid is added to the reaction kettle, the lithium chloride refined liquid is heated to 40 to 100 ℃.

According to one embodiment of the present invention, in the step S1, the sodium carbonate solution is heated to 40 to 100 ℃ before being added to the reaction kettle.

According to an embodiment of the present invention, in step S1, the lithium chloride refined solution and the sodium carbonate solution are added to the reaction kettle, and a reaction is performed in the reaction kettle to generate a lithium carbonate slurry.

According to an embodiment of the present invention, in step S1, the lithium chloride refined solution and the sodium carbonate solution are fed from the top of the reaction kettle, and are transported from the bottom of the reaction kettle to the secondary reaction kettle, and the warming reaction is continued in the secondary reaction kettle, so as to generate the lithium carbonate slurry.

According to one embodiment of the present invention, in the step S1, the sodium carbonate solution is added in excess, which is 5% to 15% excess of the theoretical reaction amount of sodium carbonate.

According to an embodiment of the present invention, the set value is 200 to 400 micrometers.

According to an embodiment of the present invention, in the step S1, the reaction kettle is stirred at a stirring speed of 100 and 1000 rpm.

According to an embodiment of the present invention, in the step S1, the bottom liquid further includes sodium chloride with a mass fraction of 0% to 30%.

According to an embodiment of the present invention, in the step S3, the solid-to-liquid ratio is 1:3 to 1:6 during washing.

Compared with the prior art, the preparation method of the lithium carbonate provided by the invention has the following advantages:

in the preparation method of the lithium carbonate, the bottom solution containing the lithium carbonate crystal seed with larger particle size is arranged in advance in the reaction kettle, and then sodium carbonate and lithium chloride are added for reaction, the generated lithium carbonate is crystallized and grown on the basis of the lithium carbonate crystal nucleus, so that the speed-controlled crystallization of the lithium carbonate is realized, the impurity entrainment is reduced, the prepared lithium carbonate has large crystal particle size which is between 200 microns and 400 microns, and the main content of the lithium carbonate in the obtained lithium carbonate product can reach 99.5%; and the lithium chloride solution contains sodium chloride, the sodium chloride and the lithium carbonate are respectively crystallized in the high-chlorine system, the sodium chloride is washed by water, the chlorine content can be controlled to be 0PPM-500PPM, and the lithium carbonate with low chlorine impurity content is prepared.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. In the drawings:

FIG. 1 is a flow chart showing the steps of a method for preparing lithium carbonate according to a preferred embodiment of the present invention;

fig. 2 is an SEM photograph (magnified 10000 times) of lithium carbonate crystals before being washed, which was prepared based on the method for preparing lithium carbonate shown in fig. 1;

fig. 3 is an SEM photograph (magnification 5000 times) of lithium carbonate crystals before being washed, which were prepared based on the method for preparing lithium carbonate shown in fig. 1;

fig. 4 is an SEM photograph (magnification 1000 times) of lithium carbonate crystals before being washed, which were prepared based on the method for preparing lithium carbonate shown in fig. 1;

fig. 5 is an SEM photograph (magnified 400 times) of lithium carbonate crystals before being washed, prepared based on the method for preparing lithium carbonate shown in fig. 1;

fig. 6 is an SEM photograph (magnification 100 times) of lithium carbonate crystals before being washed, which were prepared based on the method for preparing lithium carbonate shown in fig. 1.

Detailed Description

The present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific examples described in the following embodiments of the present invention are merely illustrative of specific embodiments of the present invention and do not limit the scope of the invention.

The invention is further described with reference to the following figures and detailed description of embodiments.

Fig. 1 is a flowchart illustrating steps of a method for preparing lithium carbonate according to a preferred embodiment of the present invention, in which fig. 1 is a flowchart.

This embodiment is a method for preparing lithium carbonate, where the method for preparing lithium carbonate includes:

step S1, presetting a bottom liquid in a reaction kettle, wherein the bottom liquid at least comprises 2-15% of lithium carbonate seed crystal in mass fraction, the particle size of the lithium carbonate seed crystal is larger than or equal to a set value, adding a lithium chloride refined liquid and a sodium carbonate solution into the reaction kettle for reaction to generate lithium carbonate slurry, the lithium chloride refined liquid at least comprises 5-25% of lithium chloride in mass fraction and 0-30% of sodium chloride in mass fraction, the mass fraction of the sodium carbonate solution is 10-30%, and the temperature of the reaction kettle is 40-100 ℃;

step S2, filtering the lithium carbonate slurry to obtain a filter cake containing sodium chloride and lithium carbonate;

step S3, washing the filter cake with water to remove sodium chloride in the filter cake;

and step S4, drying the washed filter cake to obtain a lithium carbonate product.

In the preparation method of the lithium carbonate, the bottom solution containing the lithium carbonate crystal seed with larger particle size is arranged in advance in the reaction kettle, and then sodium carbonate and lithium chloride are added for reaction, the generated lithium carbonate grows up in a crystal form on the basis of the lithium carbonate crystal nucleus, and the crystal form is in a sugar-like agglomeration state, so that the speed-controlled crystallization of the lithium carbonate is realized, the impurity entrainment is reduced, the prepared lithium carbonate has large crystal grain size which is 200-400 microns, and the main content of the lithium carbonate in the obtained lithium carbonate product can reach 99.5%; and the lithium chloride solution contains sodium chloride, the sodium chloride and the lithium carbonate are respectively crystallized in the high-chlorine system, mixed crystal sodium chloride possibly exists in a crystallization group, the mixed crystal sodium chloride is washed by water, the chlorine content can be controlled to be 0-500 PPM, and the lithium carbonate with low chlorine impurity content close to the battery level is prepared.

Of course, the impurities are not limited to sodium chloride, but other chloride salts are also possible.

The steps are explained in detail below.

In the step S1, in the above step,

the bottom liquid can only contain 2-15% of lithium carbonate seed crystal by mass fraction, can also contain 0-30% of sodium chloride by mass fraction, and can also contain other trace potassium, magnesium, boron, sulfate radicals and the like, the sodium chloride with the mass fraction of 0-30% and other trace potassium, magnesium, boron, sulfate radicals can also exist in the lithium chloride refined liquid, and even if the impurities exist, the lithium carbonate product with low chlorine impurity content and large particle size can be prepared by the method of the application.

The particle size of the lithium carbonate seed crystal is large, and the set value is 200-400 microns. The specific set value can be set according to the actual production condition, the generated lithium carbonate continues to crystallize and grow on the lithium carbonate seed crystal, the particle size of the lithium carbonate product is convenient to control, and the dissolution of the lithium carbonate is reduced as far as possible when the sodium chloride is removed by water dissolution in the later period.

The lithium chloride refined solution is prepared by extracting lithium from salt lake brine, and the magnesium and lithium are separated.

And respectively heating the lithium chloride refined solution and the sodium carbonate solution to 40-100 ℃ before adding the lithium chloride refined solution and the sodium carbonate solution into the reaction kettle. The temperature of the reactants in the reaction kettle is consistent with the reaction temperature by heating in advance, the reaction speed is higher, and the preparation time is saved.

Wherein the sodium carbonate solution is a preparation solution of industrial-grade sodium carbonate, and is added according to the theoretical reaction amount of 5-15% of sodium carbonate. The sodium carbonate is in an excessive state, so that the reaction is carried out in a direction favorable for generating lithium carbonate, and the yield of the lithium carbonate is improved.

Feeding lithium chloride refined solution and sodium carbonate solution from the top of the reaction kettle, conveying the lithium chloride refined solution and the sodium carbonate solution from the bottom of the reaction kettle to a secondary reaction kettle, and continuously carrying out heating reaction in the secondary reaction kettle to generate lithium carbonate slurry. In the reaction kettle, lithium chloride and sodium carbonate react instantaneously, the feeding and discharging in the reaction kettle are basically maintained in an equilibrium state or liquid level, the temperature is continuously increased in the secondary reaction kettle, the temperature of the secondary reaction kettle is increased to reach the boiling point of slurry, in the embodiment, the temperature is 86-100 ℃, the heating and boiling are realized to realize the maximum precipitation of lithium carbonate, and the yield of precipitated lithium is improved. Naturally, the lithium chloride refined solution and the sodium carbonate solution are added into the reaction kettle, or the reaction can be carried out in the reaction kettle to generate lithium carbonate slurry; the lithium chloride refined solution and the sodium carbonate solution can be added simultaneously or sequentially.

Stirring is carried out in the reaction kettle and the secondary reaction kettle, and the stirring speed is 1000 revolutions per minute at 100.

In the step S2, the solid content in the filter cake is 70% -80%, and the water content is 30% -20%.

In the step S3, during washing, water is deionized water, and the solid-to-liquid ratio is 1:3 to 1: 6. The washing times and the washing amount are determined according to the content of the lithium carbonate, so that the yield of the lithium carbonate is ensured, and the sodium chloride is washed and removed as much as possible. Compared with the existing washing method which only can wash away chlorine on the surface of lithium carbonate, in the application, lithium carbonate and sodium chloride are respectively crystallized, and the washing method removes more sodium chloride crystals and has lower chlorine content. Under the method of battery-grade lithium carbonate specified by the national standard, chloride ions are not detected, and the chloride ions are close to 0 or in a trace level.

As shown in fig. 2 to 6, SEM photographs of lithium carbonate crystals prepared based on the method for preparing lithium carbonate shown in fig. 1 before washing were enlarged from 10000 times, 5000 times, 1000 times, 400 times to 100 times.

As can be seen from the figure, the lithium carbonate crystals have a larger particle size before being washed, the microstructure part of the particles is columnar, and part of the lithium carbonate crystals continue to grow into a larger cubic sugar-shaped aggregate from the columnar shape, which indicates that the lithium carbonate particles grow into a larger aggregate state through rate-controlled crystallization under the method provided by the present application.

Detailed description of the preferred embodiment 1

Presetting a bottom liquid in a reaction kettle, wherein the bottom liquid comprises 5% by mass of lithium carbonate seed crystals and 18% by mass of sodium chloride, the particle size of the lithium carbonate seed crystals is more than or equal to 200 micrometers, heating lithium chloride refined liquid and a sodium carbonate solution to 60 ℃, adding the lithium chloride refined liquid and the sodium carbonate solution into the reaction kettle at 60 ℃, feeding the lithium chloride refined liquid from the top of the reaction kettle, conveying the lithium chloride refined liquid and the sodium carbonate solution into a secondary reaction kettle from the bottom of the reaction kettle, continuing heating reaction in the secondary reaction kettle, and generating lithium carbonate slurry at 86 ℃ for 10min, wherein the lithium chloride refined liquid comprises 12% by mass of lithium chloride and 18% by mass of sodium chloride, the sodium carbonate solution is 25% by mass, the sodium carbonate is added in an excess amount of 5% according to the theoretical reaction amount of the sodium carbonate, and the stirring speed in the reaction kettle is 200 revolutions per minute; filtering the lithium carbonate slurry to obtain a filter cake containing sodium chloride and lithium carbonate, wherein the solid content in the filter cake is 72% and the water content is 28%; washing the filter cake with deionized water twice to remove sodium chloride in the filter cake, wherein the solid-to-liquid ratio is controlled to be 1:3 each time; and drying the washed filter cake to obtain a lithium carbonate product.

In the obtained lithium carbonate product, according to the detection method of national standard battery lithium carbonate, the main content of lithium carbonate is 99.55 percent, the chlorine content is not detected and is basically close to zero or a trace level, the sodium content is 1000PPM, and the sulfate radical is 11 PPM. Except sodium, calcium and magnesium, other indexes are close to the battery grade standard of lithium carbonate.

Specific example 2

Presetting a bottom liquid in a reaction kettle, wherein the bottom liquid comprises 5% by mass of lithium carbonate seed crystals and 18% by mass of sodium chloride, the particle size of the lithium carbonate seed crystals is more than or equal to 200 micrometers, heating lithium chloride refined liquid and a sodium carbonate solution to 80 ℃, adding the lithium chloride refined liquid and the sodium carbonate solution into the reaction kettle at 80 ℃, feeding the lithium chloride refined liquid from the top of the reaction kettle, conveying the lithium chloride refined liquid and the sodium carbonate solution into a secondary reaction kettle from the bottom of the reaction kettle, continuing heating reaction in the secondary reaction kettle, and generating lithium carbonate slurry at 100 ℃ and 10min, wherein the lithium chloride refined liquid comprises 12% by mass of lithium chloride and 8% by mass of sodium chloride, the sodium carbonate solution is 15% by mass, the sodium carbonate is added in an excess of 8% according to the theoretical reaction amount of the sodium carbonate, and the stirring speed in the reaction kettle is 300 revolutions per minute; filtering the lithium carbonate slurry to obtain a filter cake containing sodium chloride and lithium carbonate, wherein the solid content in the filter cake is 70%, and the water content is 30%; washing the filter cake with deionized water twice to remove sodium chloride in the filter cake, wherein the solid-to-liquid ratio is controlled to be 1:5 each time; and drying the washed filter cake to obtain a lithium carbonate product.

In the obtained lithium carbonate product, according to the detection method of national standard battery lithium carbonate, the main content of lithium carbonate is 99.56 percent, the chlorine content is not detected and is basically close to zero or a trace level, the sodium content is 530PPM, and the sulfate radical is 0 PPM. Except sodium, calcium and magnesium, other indexes are close to the battery grade standard of lithium carbonate.

Specific example 3

Presetting a bottom liquid in a reaction kettle, wherein the bottom liquid comprises lithium carbonate seed crystals with the mass fraction of 10% and sodium chloride with the mass fraction of 25%, the particle size of the lithium carbonate seed crystals is more than or equal to 200 micrometers, heating lithium chloride refined liquid and a sodium carbonate solution to 75 ℃, adding the lithium chloride refined liquid and the sodium carbonate solution into the reaction kettle with the mass fraction of 25%, feeding the lithium chloride refined liquid from the top of the reaction kettle, conveying the lithium chloride refined liquid and the sodium carbonate solution into a secondary reaction kettle from the bottom of the reaction kettle, continuing heating reaction in the secondary reaction kettle, and generating lithium carbonate slurry at 95 ℃ for 10min, wherein the lithium chloride refined liquid comprises lithium chloride with the mass fraction of 12% and sodium chloride with the mass fraction of 25%, the sodium carbonate solution with the mass fraction of 15%, the sodium carbonate is added in excess of 15% according to the theoretical reaction amount of the sodium carbonate, and the stirring speed in the reaction kettle is; filtering the lithium carbonate slurry to obtain a filter cake containing sodium chloride and lithium carbonate, wherein the solid content in the filter cake is 68%, and the water content is 20%; washing the filter cake with deionized water twice to remove sodium chloride in the filter cake, wherein the solid-to-liquid ratio is controlled to be 1:6 each time; and drying the washed filter cake to obtain a lithium carbonate product.

In the obtained lithium carbonate product, according to the detection method of national standard battery lithium carbonate, the main content of lithium carbonate is 99.53 percent, the chlorine content is not detected and is basically close to zero or a trace level, the sodium content is 400PPM, and the sulfate radical is 10 PPM. Except sodium, calcium and magnesium, other indexes are close to the battery grade standard of lithium carbonate.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim.