KR101238890B1 - Production method of lithium carbonate from brines - Google Patents

Abstract

Disclosed is a method for producing lithium carbonate using brine. Lithium carbonate manufacturing method using the brine according to the present invention is the first chemical purification step of removing and depositing precipitates of magnesium, sulfate ions and boron by adding lime to the brine, by adding caustic soda to the brine from which the precipitate is removed A second chemical purification step of removing the step, concentrating the calcium removed brine using vacuum evaporation, lithium carbonate step of forming lithium carbonate using sodium carbonate or carbon dioxide in the concentrated brine, and the lithium carbonate Cleaning process for improving purity.

Description

Production method of lithium carbonate using brine {PRODUCTION METHOD OF LITHIUM CARBONATE FROM BRINES}

The present invention relates to a method for producing lithium carbonate, and more specifically, to produce a high concentration of lithium chloride-containing saline through a chemical purification process and a vacuum evaporation concentration process to remove impurities such as magnesium, calcium, boron, sulfate from natural brine Here, the present invention relates to a method for producing high purity lithium carbonate through a lithium carbonation reaction and a high purity process.

From a commercial point of view, in order to produce lithium carbonate having a purity of a certain concentration or more, it must be concentrated in a high concentration to remove specific cations and anions coexisting in the brine and to recover lithium.

A general process for removing impurities of such an ionic component below a specific concentration is known and it is necessary to apply respective processes to remove each component. Brown and Boryta, in US Pat. No. 5219550, developed a technique for removing and concentrating many components by evaporation using solar heat in the process of producing lithium carbonate from natural brine.

In solar brine concentrations, unwanted precipitates, such as salt, occur. Substances such as boron that are concentrated at the same time as lithium are removed by subsequent subsequent purification. In the case of the remaining magnesium, alkali is added to precipitate in the form of magnesium carbonate or magnesium hydroxide.

Finally, sodium carbonate is added to the purified brine through this process to precipitate lithium carbonate. Patents for each of these processes are disclosed in US Pat. Nos. 4036718, 4243392.

Other techniques for producing high purity lithium salts include the use of cooling in lithium chloride solutions to reduce sodium (German Patent DE 19541558).

US Patent 4980136 discloses a process for producing lithium chloride crystals of high purity (battery grade, 20 ppm or less of sodium, 5 ppm or less of magnesium) from brine having a high magnesium / lithium concentration ratio in nature. In the subsequent process, sodium chloride (salt) other than lithium chloride is removed in a dissolved state by an extraction method using alcohol. The alcohol containing lithium chloride is then filtered and evaporated to produce high purity lithium chloride crystals.

The above techniques occur in high altitude salt lakes of 3,700 m above sea level, and the evaporation rate is only half of the existing commercial salt lakes, and the magnesium content of impurities compared to the dissolved lithium concentration is much higher than that of conventional salt lakes. It is difficult to apply effectively to very expensive brine.

The present invention is designed to solve the above problems, the first chemical purification and the second chemical purification step for removing impurities in the brine in order to produce a high purity lithium carbonate from natural brine, lithium in the brine removed impurities Brine consisting of the first concentration, the second concentration and the third concentration process to concentrate the concentration step by step, the lithium carbonate process to crystallize the concentrated lithium to lithium carbonate and the high purity cleaning process to increase the purity of the lithium carbonate crystal It is an object to provide a method for producing lithium carbonate.

Lithium carbonate manufacturing method using a brine according to a preferred embodiment of the present invention for achieving the above object is a first chemical purification step of removing the precipitate by adding calcium hydroxide to brine to form a precipitate of magnesium, sulfate ions and boron, the precipitate is Second chemical purification step of removing the calcium by adding caustic soda to the removed brine, concentrating the calcium-free brine by vacuum evaporation, to form lithium carbonate using sodium carbonate or carbon dioxide in the concentrated brine Lithium carbonate step, and a washing step to improve the purity of the lithium carbonate.

In the first chemical purification step, the lime is added by the number of moles corresponding to 70% to 90% of the magnesium content in the brine to adjust the pH to about 9.5 to 10.5, and the precipitate produced therein (magnesium hydroxide (Mg (OH) ₂ )). , Calcium sulfate (CaSO ₄ ), boron (B) is filtered and the final pH is adjusted to about 10.7 ~ 11.3 by re-injecting the molar lime corresponding to the number of moles of 10% to 40% of the magnesium content in the brine. The resulting precipitate (magnesium hydroxide) is transferred to the final filtered brine to the second chemical purification step, the precipitate is characterized in that the washing solution is washed with condensate generated in the concentration process and then re-injected the washing solution into the brine raw water.

In addition, in the lithium carbonate manufacturing method using the brine according to the present invention by adjusting the pH to 11.5 ~ 12.5 by adding caustic soda (NaOH) by the number of moles corresponding to 100% to 110% of the calcium content in the brine that the precipitate was finally filtered. After precipitate and precipitate the calcium hydroxide (Ca (OH) ₂ ) precipitate, the calcium hydroxide precipitate is characterized in that it is re-injected to the first chemical purification step and the filtrate is transferred to the concentration step of the next step.

In addition, the step of concentrating using the vacuum evaporation, is made in three steps to increase the lithium concentration in the brine, 1.5 times to 3.0 times in the first concentration step, 5.0 times to 7.0 times in the second concentration step, In the third concentration step, the concentration of the lithium salt in the brine is at least 5 g / L or more by concentrating 10 times or more, wherein the precipitation salts produced in the first and second concentration steps are reused as by-products and are produced in the third concentration step. The precipitate is characterized in that it is re-injected into the filtrate after the first concentration step.

In the lithium carbonate step, sodium carbonate (Na ₂ CO ₃ ) or carbon dioxide (CO ₂ ) is added to the brine concentrated using the vacuum evaporation to produce lithium carbonate, wherein the amount of sodium carbonate is at least 10 g / L lithium concentration. When the molar amount of 1.0 times ~ 1.5 times compared to the lithium content, and adjusted to pH 10 ~ 11 at room temperature, the amount of carbon dioxide is injected into the molar number of 1.0 times ~ 2.0 times compared to the lithium content when the concentration of lithium 5g / L or more and 20 ℃ The pH is adjusted to 10.5 ~ 11.5 below and after the preparation of the lithium carbonate is characterized in that the filtrate is re-injected to the secondary concentrated filtrate.

In addition, the method for producing lithium carbonate using brine according to the present invention washes the prepared lithium carbonate with methanol and water, and when washed with methanol, uses methanol 10 times or more (volume / weight) than the crystallized lithium carbonate. After washing, the filtered lithium carbonate was dried at 100 ° C. for at least 2 hours to completely remove the methanol component, and methanol, a washing filtrate, was recycled by distillation and reused. When washing with water, 10 times or more of the lithium carbonate (volume / The lithium carbonate filtered using 90 ° C. water and washed after washing is dried at 100 ° C. for at least 3 hours to completely remove water, and the washing filtrate is re-injected into the secondary concentrated filtrate.

As described above, the method for preparing lithium carbonate using the brine according to the present invention is configured to facilitate the commercialization of impurities removal and concentration in the brine, and to increase the lithium recovery rate to offset the energy costs additionally added to the concentration process In addition, it is possible to minimize the production cost of lithium carbonate through the high value added of by-products generated during the process.

1 is a view showing a lithium carbonate manufacturing process using brine according to the present invention.
2 to 4 are graphs showing lithium carbonate crystal phases when the carbon dioxide / lithium molar ratio is 1.0, 2.0, and 4.0 in a carbonation process using carbon dioxide when producing lithium carbonate using brine according to the present invention, respectively.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, a method of manufacturing lithium carbonate using saline according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

1 is a process chart showing a method for producing lithium carbonate using brine according to the present invention.

Lithium carbonate manufacturing method using a brine according to an embodiment of the present invention is the first chemical purification step of removing the precipitate by adding calcium hydroxide to brine to form a precipitate of magnesium, sulfate ions and boron, caustic to the brine removed the precipitate A secondary chemical purification step of removing calcium by adding soda, concentrating the calcium-free brine by vacuum evaporation, forming a lithium carbonate using sodium carbonate or carbon dioxide in the concentrated brine, And a cleaning process for improving the purity of the lithium carbonate.

First, in order to remove impurities present in a large amount such as magnesium, boron and sulfate ions while minimizing the loss of lithium present in the brine, lime (Ca (OH) ₂ ) is added to the brine to selectively precipitate them. At this time, the reaction mechanism is the same as in Scheme 1 below.

<Reaction Scheme 1>

Mg + Ca (OH) ₂ → Mg (OH) ₂ ↓ + Ca

Ca + SO ₄ → CaSO ₄ ↓

B is ₃ BO ^{3 -} in the form Mg (OH) ₂ to remove adsorbed

This primary chemical purification process can remove 99.99% magnesium, 99% sulfate ions, 87% boron. At this time, precipitates (Mg (OH) ₂ , CaSO ₄ , B) removed by sedimentation are recovered through the process of recovering lithium present in the sediment through washing with condensate generated in the vacuum evaporation concentration process at the next stage, and the filtrate is washed again. It is added to the original brine and recycled to undergo the first chemical purification process. The lithium recovery rate is 97.4%.

On the other hand, if the magnesium hydroxide is separated from the precipitate remaining after washing and undergoing a calcination process, low-grade MgO can be produced.

The filtrate after the process is subjected to a secondary chemical purification process, where the calcium ions increased due to the calcination circuit introduced in the primary chemical purification process is added to the caustic soda to selectively precipitate and remove. At this time, calcium is removed 99.4% through Ca + 2NaOH → Ca (OH) ₂ ↓ + 2Na reaction, the calcium hydroxide removed by precipitation is recycled as a substitute for slaked lime in the first chemical purification process. Lithium recovery up to secondary chemical purification is 97.3%.

Through the above process, a three-stage vacuum evaporation concentration process is performed to concentrate lithium concentration on brine from which major impurities such as magnesium, sulfate ions, boron, and calcium are removed. In this process, the lithium concentration in the brine is minimized to the lithium concentration suitable for the carbonation reaction. The multi-step evaporation reactor is used to control the concentration drainage step by step to reduce the input energy and induce the selective precipitation of dissolved impurities in the brine. The precipitation principle is to selectively precipitate and remove using the difference in solubility of dissolved impurities such as sodium and potassium.

After the three-stage enrichment process, to maintain the lithium concentration above 11 g / L, first 1.5 to 3 times in the first enrichment process, 5 to 7 times in the secondary enrichment process, and 10 times in the final tertiary enrichment process Concentration is carried out above to increase the lithium concentration to 5 g / L or more suitable for the carbonation reaction.

By-products from this concentration process are sodium chloride (NaCl) in the first concentration, sodium chloride and potassium chloride mixed precipitates (NaCl, KCl) in the second concentration, and mixed precipitates of sodium chloride, potassium chloride and lithium compounds in the final third concentration (NaCl, KCl, Li compounds), sodium chloride and potassium chloride generated in the first and second concentration processes are recycled as a raw material for the production of salt and high purity potassium chloride.

The mixed precipitate of sodium chloride, potassium chloride and lithium compound of the final tertiary concentration process is re-injected into the filtrate of the primary concentration process to recover the high concentration of lithium in the precipitate. The lithium recovery from the original brine to the concentration process is 87.9%.

Sodium carbonate (Na ₂ CO ₃ ) or carbon dioxide (CO ₂ gas) is used to induce a carbonation reaction to produce lithium carbonate crystals from the tertiary concentrated filtrate. The reaction mechanism at this time is as shown in Scheme 2 below.

<Reaction Scheme 2>

2LiCl + Na ₂ CO ₃ → Li ₂ CO ₃ ↓ + 2NaCl ↓

2LiCl + CO ₂ + H ₂ O → Li ₂ CO ₃ ↓ + 2HCl

In order to purify the lithium carbonate crystal obtained through this reaction with a purity of 99% or more, impurities such as sodium and chlorine ions contained in the crystal are dissolved and washed with methanol or water.

Methanol in the washing liquid is recycled by distillation, and after the reaction generated in the carbonation process and the high purity process through water washing, the total amount of the secondary filtrate is reintroduced into the filtrate to recover lithium.

When manufacturing high purity lithium carbonate from natural salt water 1m ³ through all the above processes, the weight change of the components dissolved in the salt water for each step is shown in Table 1 below.

As described above, magnesium, boron and sulfate ions are removed through primary chemical refining process for natural saline containing about 800 ppm of lithium, and calcium is removed after secondary chemical refining, followed by concentration and carbonation and high purity. It can be seen that a high purity lithium carbonate of 99.6% can be produced through the process. In addition, the lithium recovery of the entire process is 86.9%.

Bolivia brine 1m ³ Material Balance of the respective components during processing (unit: kg) division Saline Primary chemical
refine Secondary chemical
refine concentration
(1st, 2nd, 3rd) Carbonation High purity Low Grade Lithium Carbonate
(Purity,%) High Quality Lithium Carbonate
(Purity,%) Li 0.769 0.749 0.748 0.676 0.674
(93.3%) 0.668
(99.6%) Na 95.6 74.3 91.1 2.38 2.28 0.1284 K 17.5 12.9 12.6 2.15 1.26 0.0485 Mg 16.2 0.002 0.00 0.00 0.000 0.0015 Ca 0.371 14.2 0.092 0.082 0.0026 0.0375 Sr 0.007 0.006 0.006 0.0 0.0052 0.0191 B 0.699 0.091 0.09 0.039 0.3485 0.0917 SO ₄ 21.1 0.366 0.340 0.193 0.5575 0.019

Hereinafter, a method for producing lithium carbonate using saline according to the present invention will be described in detail with reference to Examples. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

<Examples>

Referring to the high purity lithium carbonate manufacturing process from the natural saline devised in the present invention is the process diagram of FIG. The method devised in the present invention removes the main impurities through the first and second chemical purification processes for the target brine having a high impurity content other than lithium, and then vacuum evaporates to a lithium concentration suitable for the lithium carbonate process and then subjects the same. Lithium carbonate is crystallized through a carbonation reaction, and the crystallized lithium carbonate is made of high purity through a washing process to produce a high quality lithium carbonate of 99% or more.

The composition of the brine to prepare a high purity lithium carbonate through the present invention is shown in Table 2 below. As can be seen from Table 2, the magnesium / lithium concentration ratio is 21.1, which is more than three times higher than the general magnesium / lithium concentration ratio of 6-7, which is used in the existing commercialized lithium carbonate manufacturing process. You can expect to.

In addition, it can be seen that the contents of boron and sulfate ions which are likely to be contained as impurities in the production of lithium carbonate are very high, and therefore, it is necessary to remove them first.

 Brine composition Li (g / L) Na (g / L) K (g / L) Mg (g / L) Ca (g / L) B (g / L) Sr (mg / L) Si (mg / L) Cl (g / L) SO ₄ (g / L) 0.769 95.641 17.492 16.213 0.371 0.699 6.1 2.40 192.64 21.13

As a process for removing magnesium from the target brine first, hydrated lime (Ca (OH) ₂ ) is added in the same manner as the number of moles of magnesium in the brine and stirred at room temperature. When the lime is added to reach pH 11, the reaction is terminated and the final filtration is performed. At this time, hydrated lime is added by the number of moles corresponding to 70 to 90% of the magnesium content in the brine to adjust the pH to about 9.5 to 10.5, and the precipitates (magnesium hydroxide (Ca (OH) ₂ ) and calcium sulfate (CaSO ₄₎ ) And boron (B)) were filtered primarily.

Thereafter, as much molar lime as 10-40% of the magnesium content in the raw water was added again, and the final pH was adjusted to about 10.7 to 11.3 to remove magnesium, boron, and sulfate ions in the brine.

Table 3 below shows the composition of the filtrate after the first chemical purification.

 Composition of Components in Filtrate After Primary Chemical Purification Li (g / L) Na (g / L) K (g / L) Mg (g / L) Ca (g / L) B (g / L) Sr (mg / L) Si (mg / L) Cl (g / L) SO ₄ (g / L) 0.779 94.277 16.395 0.002 18.023 0.116 19.8 0.12 195.56 0.465

After the addition of hydrated lime again, the filtrate obtained by filtering the precipitate (magnesium hydroxide) produced at this time was increased in calcium as shown in Table 3 above, and was transferred to a secondary chemical refining process to remove it. After washing with condensed water (pure water), the washing solution was added again to brine raw water.

In order to remove the calcium in the brine increased by the slaked lime added in the previous process, caustic soda (NaOH) in the same amount as the calcium contained in the filtrate is added and stirred at room temperature, at which time 100-110% of the calcium content in the filtrate When sodium hydroxide (NaOH) was added as much as the corresponding mole number, the pH was adjusted to 11.5-12.5, and calcium hydroxide precipitate (Ca (OH) ₂ ) was precipitated to remove calcium.

After the filtrate was again filtered, the precipitate was put back into the first chemical purification process and the filtrate was transferred to the next step of concentration.

Looking at the chemical composition in the final filtrate at this time, it can be seen that magnesium, calcium, boron, sulfate ions are removed as shown in Table 4 below.

Composition of Components in Filtrate After Secondary Chemical Purification Li (g / L) Na (g / L) K (g / L) Mg (g / L) Ca (g / L) B (g / L) Sr (mg / L) Si (mg / L) Cl (g / L) SO ₄ (g / L) 0.737 121.495 16.740 0.0002 0.123 0.120 17.7 0.06 195.41 0.453

Concentration was carried out in three steps using vacuum evaporation to increase the lithium concentration in the brine to a level suitable for the carbonation reaction for producing lithium carbonate in the saline to remove impurities.

At this time, vacuum evaporation utilizes a three-effect evaporation concentrator, and in the first concentration, the precipitates are separated after concentration and concentrated to 1.5 ~ 3.0 times based on the volume of the remaining filtrate. Volume) / (volume of filtrate after enriched stone filtration plus precipitate water volume).

Concentrate the filtrate after primary concentration from 5.0 times to 7.0 times in the second concentration, and then concentrate more than 10 times in the third concentration with respect to the secondary concentrated filtrate, through which the final lithium concentration is at least 5 g / L. It concentrated above.

As shown in Table 5 below, 0.737 g / L of lithium in brine that has undergone the second chemical purification process may be concentrated to 11.04 g / L level after the three-stage concentration process.

Precipitation salts produced during the first and second concentrations are mainly composed of sodium chloride (NaCl) and potassium chloride (KCl), and these by-products are reused as raw materials for salt production, and high concentrations of lithium compounds are precipitated together with sodium chloride and potassium chloride. The precipitate of the third concentration process is re-injected into the filtrate after the first concentration process to recover the lithium.

Composition of components in filtrate after 1, 2 and 3 concentration Li (g / L) Na (g / L) K (g / L) Mg (g / L) Ca (g / L) B (g / L) Sr (mg / L) Si (mg / L) Cl (g / L) SO ₄ (g / L) 11.04 66.224 59.615 0.000 2.270 1.095 182.4 0.43 224.62 5.35

Sodium carbonate (Na ₂ CO ₃ ) is added or carbon dioxide (CO ₂ gas) is added to produce lithium carbonate through the carbonation reaction of the filtrate after the third concentration. In the case of sodium carbonate, the lithium concentration in the filtrate is 10 g / L. If more than 30% solution is used as a molar number of 1.0 ~ 1.5 times compared to the lithium content to adjust the pH to 10 ~ 11 at room temperature, in the case of carbon dioxide when the concentration of lithium is 5g / L or more than 1.0 ~ 2.0 times molar number of lithium It is added and reacted under the condition of pH 10.5 ~ 11.5 at 20 ℃ or lower.

When comparing the recovery rate and purity of lithium according to carbon dioxide / lithium molar ratio during carbonation reaction using carbon dioxide, as shown in Table 6 below, the lithium recovery rate increases as the molar ratio increases, but the lithium carbonate purity tends to decrease. 4, when the molar ratio is 4.0, impurities such as sodium chloride (NaCl) and sodium carbonate (Na ₂ CO ₃ ) are increased by the carbonation reaction, so the appropriate molar ratio of carbon dioxide / lithium introduced in the carbonation reaction using carbon dioxide is increased. Was set to 1.0 to 2.0.

 Lithium recovery and lithium carbonate purity according to carbon dioxide / lithium molar ratio CO2 / lithium molar ratio Lithium recovery Lithium carbonate purity 1.0 92.9% 94.9% 2.0 95.7% 93.7% 4.0 95.9% 92.0%

In addition, as shown in Table 7 below, as a result of the carbonation reaction on the third concentrated filtrate having a lithium concentration of 10 g / L or less and 5 g / L or more, the reaction using carbon dioxide rather than carbonation using sodium carbonate was performed in terms of lithium recovery rate and lithium carbonate purity. Found to be excellent.

Comparison of Recovery and Purity of Salted Carbonation Reaction of 6.6g / L Lithium Sodium carbonate carbonation Carbon dioxide carbonation Lithium recovery 61.8% 77.9% Lithium carbonate purity 87.9% 90.6%

The filtrate after the carbonation reaction was re-injected into the secondary concentrated filtrate in order to recover the unreacted lithium, and the filtered precipitate was dried and introduced into the next high purity cleaning process.

In order to increase the purity of the lithium carbonate crystal prepared from the carbonation process, impurities such as sodium chloride and potassium chloride contained in the crystal should be removed. The present invention devises a method for filtration and washing of dried lithium carbonate crystals with methanol or water after the carbonation reaction. It was.

In the case of methanol washing, 10 times more (volume / weight) of methanol than crystallized lithium carbonate is used. The dried lithium carbonate crystal powder is placed in a methanol solution and stirred for 30 minutes to induce impurities to dissolve into the methanol solution.

After washing, the filtered lithium carbonate was dried at 100 ° C. for at least 2 hours to completely remove the methanol component, and methanol, which was a washing filtrate, was regenerated and reused by distillation. The purity of the lithium carbonate thus produced is 98.9% and the impurity content is shown in Table 8 below.

 Impurity content of high quality lithium carbonate obtained by washing lithium carbonate (%) Na K Mg Ca B Sr Cl SO ₄ 0.229 0.305 0.00039 0.0577 0.0520 0.0067 0.0289 0.4575

When washing with water, 10 times more (volume / weight) of water than lithium carbonate powder is used. At this time, water is used by heating the condensed water generated in the above-mentioned concentration process to 90 ° C., and the filtered lithium carbonate is After drying at 100 ° C. for 3 hours or more, the water was completely removed, and the washing filtrate was reinserted into the secondary concentrated filtrate.

The present invention is a method for producing high purity lithium carbonate from natural brine, the primary chemical purification and secondary chemical purification step for removing impurities in the brine, through which the concentration of lithium in the brine to remove impurities 1 It is composed of a secondary concentration, a secondary concentration and a tertiary concentration process, a lithium carbonate process for crystallizing the concentrated lithium with lithium carbonate, and a high purity cleaning process for increasing the purity of the lithium carbonate crystal.

In order to produce more than 99.6% of high purity lithium carbonate from brine containing about 0.8 g / L lithium, magnesium, sodium, potassium, calcium, boron, sulfuric acid, chlorine in large quantities besides lithium can be minimized while minimizing the loss of lithium in the brine. Impurities such as ions should be preferentially separated and removed, and then the concentration of lithium should be concentrated to an appropriate level so that the carbonation reaction of lithium in brine for crystallization of lithium carbonate can be more effectively performed.

The method for producing lithium carbonate according to the present invention is particularly generated in the high-altitude salt lake of 3,700 m above sea level, and the amount of evaporation is only half of the existing commercial salt lake. It can be effectively applied to brine with very high chemical cost to remove.

The brine may be difficult to apply the salt-based solar evaporation method of the salt-type, which is mostly employed as a method of concentrating the lithium-containing brine in the conventional commercial process.

Therefore, the present invention is configured to facilitate the commercialization of the above-mentioned impurities removal and concentration process from the brine, wherein the lithium recovery rate is increased to offset the energy cost additionally added to the concentration process, and the high value-added by-products generated during the process Through this, it is possible to provide methods for minimizing the manufacturing cost of lithium carbonate.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. .

Claims (6)

First chemical purification step of adding slaked lime to brine to form and remove precipitates of magnesium, sulfate ions and boron;
A second chemical purification step of removing calcium by adding caustic soda to the brine from which the precipitate is removed;
Concentrating the calcium removed saline using vacuum evaporation;
A lithium carbonate step of forming lithium carbonate using sodium carbonate or carbon dioxide in the concentrated brine; And
Including a cleaning process for improving the purity of the lithium carbonate,
The first chemical purification step,
By adjusting the number of molar lime corresponding to 70 to 90% of the magnesium content in the brine to adjust the pH to 9.5 ~ 10.5, the precipitates (magnesium hydroxide (Mg (OH) ₂ ), calcium sulfate (CaSO ₄ ), boron (B) is filtered), and the final pH is adjusted to about 10.7 to 11.3 by re-injecting the molar lime corresponding to 10 to 40% of the magnesium content in the brine to the brine, and the resulting precipitate (magnesium hydroxide). After the final filtered brine is transferred to the second chemical purification step, the precipitate is washed with condensate generated in the concentration process, and then the washing solution is re-injected into the brine raw water,
Caustic soda (NaOH) was added as much as the number of moles corresponding to 100 to 110% of the calcium content in the final filtered brine to adjust the pH to 11.5 to 12.5 to precipitate calcium hydroxide (Ca (OH) ₂ ) precipitate and filtered. After that, the calcium hydroxide precipitate is introduced into the first chemical purification step as it is, and the filtrate is characterized in that the transfer to the concentration step of the next step
Method for producing lithium carbonate using brine. delete delete The method of claim 1,
Concentrating using the vacuum evaporation,
In order to increase the lithium concentration in the brine is made over three steps, 1.5 ~ 3.0 times in the first concentration step, 5 times to 7.0 times the first concentration step, the second concentration step 2 The lithium concentration in the brine by concentrating at least 10 times of the secondary concentration step is at least 5g / L, wherein the precipitate salt produced in the first and second concentration step is reused as a by-product, the precipitate produced in the third concentration step The lithium carbonate manufacturing method using a brine, characterized in that the first re-injection into the filtrate after the concentration step. The method of claim 4, wherein
The lithium carbonation step,
Lithium carbonate is prepared by injecting sodium carbonate (Na ₂ CO ₃ ) or carbon dioxide (CO ₂ ) into the brine concentrated using the vacuum evaporation, wherein the amount of sodium carbonate is 1.0 to the lithium content at a lithium concentration of 10 g / L or more. The amount of mole is 1.5 times and adjusted to pH 10 ~ 11 at room temperature.The amount of carbon dioxide is 1.0 ~ 2.0 times mole compared to the lithium content when the lithium concentration is 5g / L or more, and the pH is adjusted to pH 10.5 ~ 11.5 at 20 ℃ or less. And after the preparation of the lithium carbonate, the filtrate is re-injected into the secondary concentrated filtrate. The method of claim 5, wherein
The prepared lithium carbonate was washed with methanol and water, and when washed with methanol, 10 times or more (volume / weight) of methanol than the crystallized lithium carbonate was used, and the filtered lithium carbonate was washed at 100 ° C. for 2 hours or more. After drying, the methanol component is completely removed and methanol, the washing filtrate, is recycled by distillation and reused.In the case of washing with water, at least 10 times (volume / weight) of lithium carbonate water is used, and after washing, filtered carbonic acid Lithium is dried at 100 ℃ for 3 hours or more to completely remove the water, the washing filtrate is a lithium carbonate production method using a brine, characterized in that the re-input in the secondary concentrated filtrate.

Images