Method for preparing lithium carbonate

Abstract

Provided is a method for preparing lithium carbonate, comprising a step of heating a lithium bicarbonate solution to precipitate lithium carbonate, wherein a lithium carbonate seed is added to the lithium bicarbonate solution, and then is heated. The method for preparing lithium carbonate can increase the yield of lithium carbonate by suppressing scale generation in a reactor.

Description

Method for manufacturing lithium carbonate

[0001] The present invention relates to a method for manufacturing lithium carbonate.

[0002] Lithium carbonate produced from brine is obtained by removing impurities to increase the purity of the lithium carbonate. To obtain high-purity lithium carbonate of battery grade, a lithium bicarbonate (LiHCO3) solution is first obtained from the extracted low-purity lithium carbonate, and then divalent impurities (Ca, Mg) can be further removed using an ion exchange method, and then the lithium carbonate is reprecipitated by raising the temperature to produce high-purity lithium carbonate of battery grade.

[0003] The objective of the present invention is to provide a method for producing lithium carbonate that can increase the yield of lithium carbonate by suppressing scale formation in the reactor.

[0004] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0005] In one embodiment of the present invention, a method for producing lithium carbonate is provided, comprising the step of heating a lithium bicarbonate solution to precipitate lithium carbonate, and adding a lithium carbonate seed to the lithium bicarbonate solution and then heating.

[0006] The average particle size (D50) of the above lithium carbonate seeds may be 40㎛ or less.

[0007] At least a portion of the lithium carbonate obtained by the above precipitation can be used as the lithium carbonate seed.

[0008] 10 to 30 wt% of the lithium carbonate obtained by the above precipitation can be reintroduced as the lithium carbonate seed.

[0009] The amount of reintroduction can be adjusted so that the average particle size of the lithium carbonate seeds reintroduced above is inversely proportional to the amount of reintroduction.

[0010] The particle size distribution of the lithium carbonate obtained by the above precipitation may have a unimodal distribution.

[0011] The method for manufacturing the lithium carbonate described above may further include a step of washing the reactor in which the step of precipitating lithium carbonate by heating the lithium bicarbonate solution is performed after recovering the lithium carbonate.

[0012] The method for producing the lithium carbonate described above may involve repeatedly performing the step of heating the lithium bicarbonate solution to precipitate lithium carbonate at least twice, and performing the step of washing the reactor between each of the repeated steps.

[0013] The average particle size (D50) of the lithium carbonate obtained by the above precipitation may be 50㎛ to 150㎛.

[0014] The method for manufacturing the lithium carbonate described above may further include the step of grinding the lithium carbonate obtained by precipitation.

[0015] The purity of the lithium carbonate obtained by the above precipitation may be 99 wt% or higher.

[0016] The average particle size (D50) of the lithium carbonate reintroduced above may be 1㎛ to 40㎛.

[0017] When obtaining lithium carbonate using the above method for manufacturing lithium carbonate, the yield of lithium carbonate can be increased by suppressing the formation of scale in the reactor in which the step of precipitating lithium carbonate by heating the lithium bicarbonate solution is performed.

[0018] In addition to the effects described above, the specific effects of the present invention are described together with the specific details for implementing the invention below.

[0019] FIG. 1 is a graph showing the particle size distribution of a powder obtained by drying high-purity lithium carbonate obtained by a method for manufacturing lithium carbonate according to one embodiment of the present invention.

[0020] FIG. 2 is a graph showing the particle size distribution of a powder obtained by drying high-purity lithium carbonate obtained by a method for manufacturing lithium carbonate according to one embodiment of the present invention.

[0021] FIG. 3 is a graph showing the particle size distribution of a powder obtained by drying high-purity lithium carbonate obtained by a method for manufacturing lithium carbonate according to one embodiment of the present invention.

[0022] FIG. 4 is a graph showing the particle size distribution of a powder obtained by drying high-purity lithium carbonate obtained by a method for manufacturing lithium carbonate according to one embodiment of the present invention.

[0023] Figure 5 is a graph showing the particle size distribution of a powder obtained by drying high-purity lithium carbonate obtained by a method for comparison with the present invention.

[0024] Figure 6 is a graph showing the particle size distribution of a powder obtained by drying high-purity lithium carbonate obtained by a method for comparison with the present invention.

[0025] The aforementioned objectives, features, and advantages are described in detail below with reference to the attached drawings, thereby enabling those skilled in the art to easily implement the technical concept of the present invention. In describing the present invention, detailed descriptions of known technologies related to the present invention are omitted if it is determined that such descriptions would unnecessarily obscure the essence of the invention. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0026] In the following, the statement that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0027] In addition, where it is stated that one component is "connected," "combined," or "connected" to another component, it should be understood that while the components may be directly connected or connected to each other, another component may be "interposed" between each component, or each component may be "connected," "combined," or "connected" through another component.

[0028] In this specification, lithium, sulfur, magnesium, calcium, sodium, potassium, etc., may be in a form that exists in raw materials, extracts, or precipitates, and are collectively referred to as types of elements without being limited to a specific form, such as metal atoms, atoms, ions, or salts, and when distinction is necessary, they may be understood as being in a state that exists according to the laws of nature.

[0029] In one embodiment of the present invention, a method for producing lithium carbonate is provided, comprising the step of heating a lithium bicarbonate solution to precipitate lithium carbonate, and adding a lithium carbonate seed to the lithium bicarbonate solution and then heating.

[0030] Lithium carbonate that can be used as a secondary battery material is produced by extracting lithium from brine or ore. The lithium carbonate obtained in this way has low purity, so in order to be used for battery grades, it must be obtained as high-purity lithium carbonate. To obtain high-purity lithium carbonate of battery grade, the extracted low-purity lithium carbonate is first slurried, then converted into a lithium bicarbonate (LiHCO3) solution using CO2 gas, and then the lithium bicarbonate solution is heated to reprecipitate the lithium carbonate to produce high-purity lithium carbonate of battery grade.

[0031] The lithium bicarbonate solution in the above method for manufacturing lithium carbonate may be the lithium bicarbonate solution as described above, obtained as an intermediate product during the process for manufacturing high-purity lithium carbonate.

[0032] When obtaining lithium carbonate using the above method for manufacturing lithium carbonate, the yield of lithium carbonate can be increased by suppressing the formation of scale in the reactor in which the step of precipitating lithium carbonate by heating the lithium bicarbonate solution is performed.

[0033] In the above method for producing lithium carbonate, when the lithium bicarbonate solution is heated, lithium carbonate may be precipitated as the lithium bicarbonate decomposes according to the following reaction scheme 1.

[0034] <Reaction Equation 1>

[0035]

[0036]

[0037] In the above method for producing lithium carbonate, the condition for heating the lithium bicarbonate solution can be carried out under the condition known in the process of precipitating lithium carbonate from lithium bicarbonate according to the above reaction equation 1.

[0038] For example, the temperature at which the lithium bicarbonate solution is heated may be 80 to 95°C for 30 to 60 minutes, but is not limited thereto.

[0039] When lithium carbonate is produced by the above reaction, some of it grows on the reactor walls, forming and adhering to the reactor as scale. Since the lithium carbonate attached to this scale cannot be recovered, it can reduce the lithium carbonate yield.

[0040] The above method for producing lithium carbonate can suppress scale formation on the reactor wall by introducing a seed, thereby inducing lithium carbonate to grow on the seed instead of on the reactor wall.

[0041] The above method for producing lithium carbonate is a case where lithium carbonate is generated within the lithium bicarbonate solution and some of the lithium carbonate adheres to the reactor wall and grows stably, and, for example, can effectively suppress scale formation on the reactor wall even when the reactor surface is relatively smooth.

[0042] Since the above seed must be produced from lithium carbonate, a lithium carbonate seed with lithium carbonate as the main component is used.

[0043] In one embodiment, the average particle size (D50) of the lithium carbonate seed may be 40 μm or less, specifically 40 μm or less, specifically 1 μm to 40 μm.

[0044] In this specification, the average particle size (D50) refers to the volume cumulative 50% particle size D50.

[0045] By controlling the average particle size of the lithium carbonate seeds as described above, the particle size distribution of the lithium carbonate obtained can be formed unimodally, which is advantageous for suppressing the formation of scale on the reactor wall.

[0046] If the above method for manufacturing lithium carbonate is intended to obtain high-purity lithium carbonate, then the lithium carbonate seed will also require high purity. Since the lithium carbonate obtained by the above precipitation is of high purity, it can be used as a high-purity lithium carbonate seed.

[0047] In one embodiment, at least a portion of the lithium carbonate obtained by precipitation is used as the lithium carbonate seed. In this way, using the lithium carbonate obtained by precipitation as the lithium carbonate seed has the advantage of being able to obtain the seed within the process.

[0048] In one embodiment, 10 to 30 wt% of the lithium carbonate obtained by precipitation can be reintroduced as the lithium carbonate seed.

[0049] In one embodiment, 20 to 30 wt% of the lithium carbonate obtained by precipitation can be reintroduced as the lithium carbonate seed.

[0050] By adding the lithium carbonate seed in an amount within the above numerical range, the particle size distribution of lithium carbonate can be formed as unimodal, which is advantageous for suppressing scale formation on the reactor wall. If the lithium carbonate seed is added in an amount less than the above numerical range, the resulting lithium carbonate particle size distribution may exhibit bimodal characteristics. The meaning of the resulting lithium carbonate particle size distribution exhibiting bimodal characteristics is that a group of particle distributions formed by newly nucleated particles without lithium carbonate growing from the lithium carbonate seed, and another group of particle distributions formed by the growth of lithium carbonate from the lithium carbonate seed, are formed together in a bimodal manner. While the growth of lithium carbonate from the lithium carbonate seed can suppress nucleation on the reactor wall, newly nucleated particles cannot suppress nucleation on the reactor wall during their formation; therefore, it is desirable to weaken the formation of bimodal characteristics. The fact that a bimodal distribution is exhibited due to an increase in newly nucleated particles instead of growing seeds means that the scale formation inhibition effect of the reactor is reduced.

[0051] Meanwhile, if an excess amount of lithium carbonate seeds is added in an amount exceeding the above numerical range, it may exceed the loading amount that can be processed in the subsequent process, so the amount of lithium carbonate seeds added can be determined to a limit that can be processed in the process.

[0052] As described above, within the numerical range of the average particle size of the lithium carbonate seed and the amount of reintroduced additive, the particle size distribution of the obtained lithium carbonate may not be bimodal and may be unimodal.

[0053] In one embodiment, the amount of reintroduction can be adjusted so that the average particle size of the lithium carbonate seed being reintroduced and the amount of reintroduction are inversely proportional.

[0054] If the average particle size of the lithium carbonate seed increases, the total surface area of ​​the lithium carbonate seed decreases, which may reduce the effect of inducing growth in the seed; conversely, if the average particle size of the lithium carbonate seed decreases, the total surface area of ​​the lithium carbonate seed increases, which may increase the effect of inducing growth in the seed. Since the amount of addition can be adjusted by considering these factors together, if the average particle size of the lithium carbonate seed increases, the amount of addition can be increased to compensate for the effect of inducing growth in the seed, and if the average particle size of the lithium carbonate seed decreases, the amount of addition can be relatively reduced. Conversely, if the amount of lithium carbonate added is small, the average particle size can be reduced to compensate for the effect of growth in the seed, and if the amount of lithium carbonate added is sufficient, there may be no need to grind the average particle size further to make it smaller. In other words, by adjusting the relationship between the average particle size and the amount of reintroduction so that the average particle size of the lithium carbonate seed being reintroduced is inversely proportional to the amount of reintroduction, it is possible to control the process so that scale is not formed in the reactor at a constant rate.

[0055] In this way, by the method of manufacturing the lithium carbonate above, the particle size distribution of the lithium carbonate obtained by precipitation can have a unimodal distribution.

[0056] The method for manufacturing the lithium carbonate described above may further include the step of washing the reactor in which the above step was performed after recovering the lithium carbonate.

[0057] The step of heating the lithium bicarbonate solution to precipitate and obtain lithium carbonate can be performed repeatedly, and the step of washing the reactor can be performed between each step performed repeatedly. That is, the step of heating the lithium bicarbonate solution to precipitate and obtain lithium carbonate and the step of washing the reactor can be performed alternately.

[0058] The average particle size of the lithium carbonate obtained by the above precipitation can be ground in a subsequent step to suit the intended use. Although the average particle size of the final lithium carbonate obtained by precipitation may increase due to the addition of the lithium carbonate seed, this is not a problem since a grinding process follows. This is because, even without the addition of a seed, lithium carbonate obtained by the thermal decomposition of lithium bicarbonate typically requires a grinding process.

[0059] In one embodiment, the average particle size (D50) of the lithium carbonate obtained by precipitation may be 80 μm to 130 μm.

[0060] As described above, since at least a portion of the lithium carbonate obtained by precipitation can be reintroduced as a lithium carbonate seed, the average particle size (D50) of the lithium carbonate reintroduced can be 50 μm to 150 μm.

[0061] In one embodiment, the step of grinding the lithium carbonate obtained by precipitation may be further included.

[0062] As described above, the method for producing the lithium carbonate is a method that can be obtained in high purity by bicarbonating low-purity lithium carbonate and then reprecipitating it.

[0063] In one embodiment, the purity of the lithium carbonate obtained by precipitation may be 99 wt% or higher.

[0064] Examples and comparative examples of the present invention are described below. The following examples are merely embodiments of the present invention, and the present invention is not limited to the following examples.

[0065]

[0066] (Example)

[0067] Example 1

[0068] 400g of low-purity lithium carbonate and 5L of deionized water were mixed in a 5L beaker, and CO2 was introduced at 25℃ and 1.5 barg (2.5 bar) and bubbling was performed for 4 hours to obtain a lithium bicarbonate solution, and the results of the analysis of its components are listed in Table 1.

[0069] LiNaCaBaKAlPSMgFeNi Concentration (g / L) 8.2 10.36 90.00 200.00 200.00 10.13 4000

[0070] 400 ml of the above lithium bicarbonate solution was introduced into a 500 ml SS304 reactor and reacted at 90°C for 60 minutes to obtain approximately 30 g of high-purity lithium carbonate. The obtained high-purity lithium carbonate was dried and ground to obtain a D50 powder of 6.8 μm.

[0071] 400 ml of the above lithium bicarbonate solution was added to a 500 ml SS304 reactor, and 1 g of the obtained powder was added as a lithium carbonate seed and reacted at 90°C for 60 minutes to obtain approximately 30 g of high-purity lithium carbonate (1st test).

[0072] The high-purity lithium carbonate obtained from the above first test was dried and ground to obtain a D50 6.8㎛ powder.

[0073] 400 ml of the above lithium bicarbonate solution was added to an unwashed reactor, and 1 g of the powder obtained from the first test was added as a lithium carbonate seed and reacted at 90°C for 60 minutes to obtain approximately 30 g of high-purity lithium carbonate (second test).

[0074] The same method was repeated up to the 7th test.

[0075]

[0076] Example 2

[0077] Tests up to the 7th were performed using the same method as in Example 1, except that 3g of lithium carbonate seed was added instead of 1g.

[0078]

[0079] Comparative Example 1

[0080] Tests up to the 7th were performed in the same manner as in Example 1, except that lithium carbonate seeds were not added.

[0081]

[0082] Experimental Example 1

[0083] In Examples 1-2 and Comparative Example 1, the amount of scale generated in the reactor after the 7th test was measured and listed in Table 2 below.

[0084] Example 1 Example 2 Comparative Example 1 Reactor weight 109.3g 109.2g 108.2g Weight after scale formation 126.6g 143.6g 161.3g Amount of scale formed 17.3g 34.4g 53.1g

[0085] From the results of Table 2 above, it was confirmed that the amount of scale generated in the reactor in Examples 1-2, in which lithium carbonate seeds were added, was less than in Comparative Example 1, in which lithium carbonate seeds were not added. Specifically, Examples 1 and 2 showed results of reduction of 35% and 67%, respectively, compared to Comparative Example 1.

[0086] When examining the reactor of Comparative Example 1, it was confirmed that the scale inside the reactor grew on the entire surface in contact with the lithium bicarbonate solution, and when examining the reactors of Example 1 and Example 2, the lithium bicarbonate solution showed a tendency to grow downwards from the interface portion in contact with the upper gas phase.

[0087] Meanwhile, although the reactor was not cleaned in Examples 1-2 and Comparative Example 1, it is expected that the scale prevention effect in Examples 1-2 would be superior if the reactor had been cleaned between each test.

[0088]

[0089] Experimental Example 2

[0090] The particle size distribution was measured for the powder obtained by drying the high-purity lithium carbonate obtained from the 1st and 7th tests in Examples 1-2 and Comparative Example 1 (wet particle size analyzer, HORIBA (LA-950V2)).

[0091] Figures 1 and 2 are graphs showing the particle size distribution of powder obtained by drying high-purity lithium carbonate obtained from the first and seventh tests of Example 1, respectively.

[0092] Figures 3 and 4 are graphs showing the particle size distribution of powder obtained by drying high-purity lithium carbonate obtained from the first and seventh tests of Example 2, respectively.

[0093] Figures 5 and 6 are graphs showing the particle size distribution of powder obtained by drying high-purity lithium carbonate obtained from the first and seventh tests of Comparative Example 1, respectively.

[0094]

[0095] Figures 3 and 4, which are the results of Example 2, clearly show a unimodal distribution, and Figures 1 and 2, which are the results of Example 1, show a slightly bimodal distribution, but it can be confirmed that this is a much weaker form than the bimodal distribution shown in Figures 5 and 6, which are the results of Comparative Example 1, in which no lithium carbonate seed was used.

[0096]

[0097] Although the present invention has been described above with reference to embodiments, the present invention is not limited by the embodiments disclosed in this specification, and it is obvious that various modifications can be made by a person skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention were not explicitly described while describing the embodiments of the present invention above, it is natural to acknowledge that the effects predictable by said configuration should also be recognized.

Claims

1. A method for producing lithium carbonate comprising the step of precipitating lithium carbonate by heating a lithium bicarbonate solution, and adding a lithium carbonate seed to the lithium bicarbonate solution and then heating.

2. In Paragraph 1, The average particle size (D50) of the above lithium carbonate seed is 40㎛ or less Method for manufacturing lithium carbonate.

3. In Paragraph 1, At least a portion of the lithium carbonate obtained by the above precipitation is used as the lithium carbonate seed. Method for manufacturing lithium carbonate.

4. In Paragraph 1, 10 to 30 wt% of the lithium carbonate obtained by precipitation above is reintroduced as the lithium carbonate seed. Method for manufacturing lithium carbonate.

5. In Paragraph 4, Adjusting the amount of reintroduction so that the average particle size of the lithium carbonate seeds reintroduced above is inversely proportional to the amount of reintroduction. Method for manufacturing lithium carbonate.

6. In Paragraph 1, The particle size distribution of the lithium carbonate obtained by the above precipitation has a unimodal distribution. Method for manufacturing lithium carbonate.

7. In Paragraph 1, The method further includes a step of washing the reactor that performed the step of precipitating lithium carbonate by heating the lithium bicarbonate solution after recovering the lithium carbonate. Method for manufacturing lithium carbonate.

8. In Paragraph 7, The step of heating the lithium bicarbonate solution to precipitate lithium carbonate is performed repeatedly at least twice, and the step of washing the reactor is performed between each step performed repeatedly. Method for manufacturing lithium carbonate.

9. In Paragraph 1, The average particle size (D50) of the lithium carbonate obtained by the above precipitation is 50㎛ to 150㎛. Method for manufacturing lithium carbonate.

10. In Paragraph 1, A method further comprising the step of grinding the lithium carbonate obtained by precipitation as described above. Method for manufacturing lithium carbonate.

11. In Paragraph 1, lithium carbonate obtained by the above precipitation has a purity of 99 wt% or higher Method for manufacturing lithium carbonate.

12. In Paragraph 4, The average particle size (D50) of the lithium carbonate reintroduced above is 1㎛ to 40㎛. Method for manufacturing lithium carbonate.

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