RU2283283C1 - Process of producing h-purity lithium carbonate from lithium-bearing chloride brines - Google Patents

Abstract

FIELD: industrial organic synthesis.

SUBSTANCE: process comprises: preparation of chloride lithium concentrate, purification of chloride lithium concentrate to remove major part of calcium, magnesium, and sulfate ion impurities, and reagent-mediated precipitation of lithium carbonate from purified chloride lithium concentrate. Precipitation of lithium carbonate is performed by means of water slurry of ammonium bicarbonate at 20-40°C. Carbon dioxide thereby formed is withdrawn from reaction space and, after removing ammonia impurity therefrom, is used as carbonation agent to convert precipitated and separated from liquid phase lithium carbonate into saturated lithium bicarbonate solution. From the latter, pure impurities-free lithium carbonate is precipitated on heating. Mother liquor obtained from lithium carbonate precipitation operation is evaporated to give solid phase of ammonium chloride and liquid phase containing 300-350 g/L lithium chloride. Liquid phase is separated from solids and returned to lithium carbonate precipitation operation and solid phase of ammonium chloride is washed out with saturated ammonium chloride solution to remove remains of lithium chloride and then dried.

EFFECT: avoided use of sodium ions in lithium carbonate precipitation process, utilized recycled carbon dioxide, and eliminated waste solutions.

2 cl, 4 dwg, 1 tbl, 2 ex

Description

Technical field

The invention relates to the field of chemical technology for the production of inorganic compounds, specifically to methods for producing lithium carbonate from natural brines and technological salt chloride solutions containing lithium.

State of the art

A known method of deposition of lithium carbonate from lithium sulfate solutions formed during the processing of lithium ores with sulfuric acid [1]. Ammonium carbonate is used for precipitation, which is obtained by thermal dissociation of a solution of ammonium bicarbonate or by reacting a solution of ammonium bicarbonate with ammonia water. The deposition rate of lithium carbonate at one time is approximately 80%.

The disadvantages of the method are: a) the need for the stage of conversion of ammonium bicarbonate to its carbonate, in which there is an inevitable loss of ammonium bicarbonate, as a result of which the consumption of NH ₄ HCO ₃ increases by 30-40% of the stoichiometric amount required for the deposition of lithium carbonate; b) the use for the process of ammonia water related to the category of toxic substances.

A known method of producing lithium carbonate from a lithium-containing brine, according to which lithium carbonate is precipitated with a soda solution [2], as is customary in world practice for the production of lithium carbonate from galurgic raw materials. For this, the brine is concentrated to a lithium content of ~ 4-6.5 wt.%, Purified from impurities of boron, magnesium and alkaline earth metals using known chemical methods, and then a saturated solution of Na ₂ CO ₃ is introduced into the purified, heated concentrated LiCl solution at elevated temperature (about 90 ° C).

The disadvantage of this method is the use of a soda solution, which, as a result of interaction with lithium chloride, is converted to a sodium chloride solution, which requires a large flow of water to remove from the precipitated target product. The resulting product nevertheless still contains a certain amount of sodium and, as a result, the quality of the manufactured product is limited to the “technical” grade.

A known method of producing high purity lithium carbonate with a low sodium content [3]. According to this method, natural brine is concentrated by solar evaporation to a lithium content of about 6 wt.%. and then cleaned of impurities of boron, calcium, magnesium and sulfate ions. Boron is removed by extraction with alcohol, as described in the patent [2]. Magnesium is removed in two stages. In the first, 97% of magnesium is removed by mixing concentrated brine with the mother liquor from the lithium carbonate precipitation stage. In the second stage, a mixture of lime and soda is added to the concentrated lithium chloride solution, and Mg (OH) ₂ and CaCO ₃ are precipitated. The presence of the latter improves the filterability of the precipitate of magnesium hydroxide. Sulfate ions are precipitated with barium chloride. The concentrated LiCl solution, purified from impurity components, is further treated with a soda solution to precipitate lithium carbonate by reaction

and the mother liquor is recycled to the first stage of magnesium deposition. The process is carried out at a temperature of about 90 ° C. Filtered, washed with water and dried lithium carbonate has a technical grade and, as a typical technical carbonate, contains about 0.04 wt.% Sodium.

To obtain Li ₂ CO ₃ with a lower sodium content, it is converted into a bicarbonate solution by carbonizing the pulp of industrial carbonate with water (3-5% solid) with carbon dioxide at a temperature of 10-40 ° C. The resulting solution of LiHCO ₃ (7-8 wt.% Lithium bicarbonate) is sent to a decarbonizer, in which the temperature is maintained at 70-95 ° C. Upon decomposition solution LiHCO ₃ deposited pure Li ₂ CO _3, and eye-catching in this carbon dioxide is recycled to the slurry carbonization step Technical lithium carbonate. The precipitate is continuously removed, filtered while hot and washed with deionized water, without sodium. The mother liquor from the LiHCO ₃ decarbonization step containing soluble lithium is circulated in circulation to minimize lithium loss. The number of turns of the mother liquor is determined by the content of sodium ion impurities accumulated in it.

Obtained by this method, lithium carbonate, purified from sodium, contains 99.4 wt.% Of the basic substance and the following impurities (wt.%): Na - 0.0002, Mg - 0.0005, K - 0.00015, Ca - 0.012 , SO ₄ ^2- - 0.003. To obtain ultra-high-purity lithium carbonate containing 99.995 wt.% Of the basic substance, the LiHCO ₃ solution after the bicarbonization stage of Li ₂ CO ₃ pulp is passed through an ion exchange column with Amberlite IRC-718 resin in order to reduce the total impurities in the solution to less than 0.001 wt.% .

According to the technical nature and the achieved result, this method is the closest to the claimed one and is selected as a prototype.

The disadvantages of the prototype method are the use of soda as a precipitant Li ₂ CO ₃ , which introduces a macro amount of sodium ions, as well as the formation of a large amount of waste solution of sodium chloride (2 mol per 1 mol of lithium carbonate), which cannot be recycled.

SUMMARY OF THE INVENTION

The technical result of the claimed invention is the exclusion of the participation of sodium ions in the deposition of lithium carbonate, the use of recycled carbon dioxide and the elimination of waste solutions.

The technical result is achieved in that the deposition of lithium carbonate from purified lithium chloride concentrate obtained by helioconcentration of the original natural brine, followed by purification from calcium, magnesium and sulfate ions, is carried out with an aqueous pulp of ammonium bicarbonate at 20-40 ° C, removing from the reaction generated carbon dioxide, which is used as a carbonizing agent to transfer precipitated, separated from the liquid phase and washed lithium carbonate into a saturated bicarbonate solution lithium, which is then subjected to decarbonization to obtain high purity lithium carbonate.

The technical result is also achieved by the fact that the mother liquor of the lithium carbonate precipitation operation is first freed from the residual amount of unreacted ammonium bicarbonate by thermal decomposition into ammonia and carbon dioxide, which are removed from the mother liquor during its countercurrent contact with the carrier gas stream containing ammonia and carbon dioxide the gas is purified from ammonia by countercurrent washing with water while cooling to obtain a solution of ammonium bicarbonate, directed to the operation water pulp of ammonium bicarbonate.

The technical result is also achieved by the fact that the mother liquor, freed from ammonium bicarbonate, is evaporated, obtaining a solid phase of ammonium chloride and a liquid phase with a concentration of lithium chloride of 300-350 g / l; the liquid phase is separated from the solid and returned to the deposition of lithium carbonate from lithium chloride concentrate, and the solid phase of ammonium chloride is washed with a saturated solution of the remaining lithium chloride and dried. It is a simultaneously obtained commodity product.

The carbon dioxide released at the stage of decarbonization of the lithium bicarbonate solution is mixed with the residual amount of carbon dioxide coming from the stage of lithium carbonate carbonization when the latter is transferred to the lithium bicarbonate solution, and an excess of carbon dioxide is used to produce marketable carbon dioxide by any of the known methods. This technique allows you to make the technology waste-free, reduce the cost of high-purity lithium carbonate and eliminate gas exhaust into the atmosphere.

The interaction of a concentrated solution of lithium chloride with ammonium bicarbonate proceeds according to the reaction:

The dependence of the degree of deposition of lithium on temperature is presented in figure 1. From the obtained data it can be seen that the interaction proceeds even at temperatures below 20 ° C, but increasing the temperature to 30-40 ° C accelerates the reaction. A further increase in the interaction temperature above 40 ° C leads to a decrease in the degree of lithium deposition in the form of lithium carbonate, since in this temperature range ammonium bicarbonate decomposes with loss of ammonia and, as a result, the stoichiometric ratio of the reacting components is violated. The time required to complete the interaction is 60-120 minutes, preferably 90 minutes. The degree of deposition of lithium carbonate is 70-78%. The residual concentration of lithium in the mother liquor is 9-10 g / l. After lithium carbonate was separated by filtration, the remaining mother liquor after removal of unreacted ammonium bicarbonate was evaporated approximately 60 times to a lithium chloride concentration of 300-350 g / l and returned to the lithium carbonate precipitation stage. Thus, despite the not very high degree of deposition of lithium carbonate in one go, with the return of unreacted lithium chloride to the cycle, it increases and the lithium chloride solution is almost completely processed.

A waste-free scheme for producing high-purity lithium carbonate from lithium chloride concentrate is shown in FIG. 2. The initial concentrated solution of lithium chloride can be obtained from lithium-containing chloride sodium brine by means of helioconcentration, during which salts of macrocomponents (NaCl, KCl, CaSO ₄ , MgCl · H ₂ O) precipitate and the concentration of lithium chloride increases. After removal of the precipitated salts, the concentrated solution has the following composition (g / l): LiCl - 250-300; NaCl - 2; KCl - 0.4; MgCl ₂ - 65.3; CaCl ₂ - 0.91; SO ₄ ^2- - 0.2. Such a solution is cleaned of impurities in the same way as described in the patent [3], that is, 90-97% of magnesium and calcium impurities are removed using lithium carbonate, and their purification is carried out using a mixture of calcium hydroxide and soda. From the sulfate ions, the concentrated solution is purified using barium chloride. After cleaning, the solution contains (g / l): LiCl - 300; NaCl - 0.08; KCl - 0.02; MgCl ₂ - 0.008; CaCl ₂ - 0.005; SO ₄ ^2- - 0.005.

If due to the chemical composition of the brine (very high initial content of calcium and magnesium chlorides) it is impossible to helioconcentrate it, then lithium chloride is extracted from the brine using a selective sorbent [4, 5], and then the resulting eluate in the form of a solution of lithium chloride is concentrated and purified in the same way as described above.

Such a purified lithium chloride concentrate is reacted with a pulp of ammonium bicarbonate. After the reaction (2) is carried out, the precipitate of lithium carbonate is filtered off, washed with washing water from the washing stage of high-purity commodity lithium carbonate, squeezed on the filter, then pulp is recycled with the mother liquor from the filtration stage of high-purity lithium carbonate and sent to the stage of carbonization of lithium carbonate with carbon dioxide to transfer its in lithium bicarbonate solution. Carbon dioxide, emitted by reaction (2), and passed through the stage of purification of the mother liquor from the stage of deposition of lithium carbonate from unreacted ammonium bicarbonate, is also supplied here.

After separation of the precipitate of lithium carbonate in the mother liquor, the concentration of ammonium chloride is ~ 200 g / l and it contains ~ 25% of unreacted ammonium bicarbonate. To eliminate the loss of ammonium bicarbonate, the mother liquor, together with the washing water attached to it, from the washing stage of lithium carbonate, is subjected to thermal decomposition at a temperature of about 60 ° C, as a result of which ammonium bicarbonate decomposes into ammonia and carbon dioxide, which are removed from the mother liquor during its contact with gas -carrier, which is carbon dioxide formed by reaction (2). Ammonia released is absorbed by water and in the presence of carbon dioxide in accordance with the reaction

a solution of ammonium bicarbonate is formed, which is used to prepare pulp of ammonium bicarbonate at the stage of the reaction (2).

The separation of ammonia from bicarbonate-ammonium solutions by air desorption was carried out at a temperature of 50-60 ° C. The degree of desorption of ammonia from the solution is 85-90%. This is clearly seen from the data of figure 3. Excess carbon dioxide from the ammonia absorption stage, purified from ammonia impurities, is sent to the stage of carbonization of lithium carbonate.

After decomposition of unreacted ammonium bicarbonate and its distillation in the form of ammonia and carbon dioxide, the mother liquor containing ammonium chloride and unreacted lithium chloride is evaporated by heating or in natural conditions, for example, in a pool. When the concentration of lithium chloride in the solution reaches about 100 g / l, saturation of ammonium chloride is achieved and solid ammonium chloride begins to precipitate. With further concentration, the concentration of lithium chloride increases, and the concentration of ammonium chloride begins to decrease. This is clearly shown in figure 4. Upon reaching a concentration of lithium chloride equal to 300 g / l, the concentration of ammonium chloride in the stripped off solution is 82 g / l; at a concentration of 363 g / l, it decreases to 55 g / l. The filtered solid ammonium chloride is washed with a saturated solution to avoid dissolution and dried at a temperature of 50-60 ° C. The concentrated lithium chloride solution after evaporation and separation of the precipitated ammonium chloride is returned to the head of the process.

At the stage of carbonization from lithium carbonate from the precipitation stage and the mother liquor from the filtration stage of high-purity lithium carbonate, a pulp is prepared with a solids content of 3-5% and carbon dioxide is passed through it at a temperature of 10-40 ° C for 2-4 hours. The following occurs reaction:

The resulting lithium bicarbonate solution containing 7-8 wt.% Lithium bicarbonate, then filtered off from insoluble particles and sent to the stage of decarbonization. At a temperature of 70-95 ° C, the reverse process occurs and a saturated solution of lithium bicarbonate decomposes with the release of pure lithium carbonate, and all soluble impurities remain in the solution. The precipitate of pure lithium carbonate is filtered off, washed with deionized water and dried at a temperature of 120 ° C. It contains (wt.%): Basic substance 99.9; Na 0.0002; K - 0.00015; Mg - 0.0005; Ca - 0.002; NH ₄ ⁺ is absent.

The washing water is sent to the washing stage of lithium carbonate, and the mother liquor from the decarbonization stage is returned to the pulping of lithium carbonate before the stage of its carbonization. As impurities accumulate in it, the mother liquor is withdrawn from the turnover partially or completely, replacing it with deionized water. The mother liquor contaminated with impurities for disposal of lithium contained therein is sent to the preliminary purification stage of the initial concentrated lithium chloride solution.

The pure carbon dioxide emitted in this process, which is practically free of impurities, is sent to obtain a simultaneously generated marketable product - carbon dioxide according to any of the known methods (compressed or in the form of dry ice).

Thus, the main distinguishing features of the claimed invention are:

1) the use of ammonium bicarbonate to obtain lithium carbonate of high purity from lithium chloride brines;

2) non-waste method due to the implementation of simultaneously formed marketable products - NH ₄ Cl and carbon dioxide.

3) lack of waste solutions;

4) increasing the efficiency of the initial solution of lithium chloride due to its return to the head of the process after evaporation of the mother liquor;

5) increasing the efficiency of ammonium bicarbonate due to the capture of ammonia during thermal decomposition of the mother liquor and returning it in the form of a solution of ammonium bicarbonate to the head of the process at the stage of preparing the pulp of ammonium bicarbonate;

6) reduction in the cost of lithium carbonate of high purity due to the use of cheaper than soda ammonium bicarbonate and the sale of the resulting commodity ammonium chloride, as well as high-purity carbon dioxide.

These features in combination allow to obtain lithium carbonate of high purity and create a waste-free technological process for producing lithium carbonate from lithium-bearing natural and technogenic chloride solutions.

The claimed invention has novelty, since for the first time a direct interaction of a solution of lithium chloride with ammonium bicarbonate is proposed to obtain high-purity lithium carbonate, about which information is not available in available sources of information.

List of drawings and tables

Figure 1. Dependence of the degree of lithium deposition in the form of Li ₂ CO ₃ (α,%) on temperature.

Figure 2. Waste-free technological scheme for producing lithium carbonate of high purity.

Figure 3. Dependence of the degree of desorption of ammonia from the mother liquor on the ratio of the volume of the passed gas to the volume of the solution.

Figure 4. Dependence of the content of NH ₄ Cl (g / l) in the mother liquor on the concentration of LiCl (g / l) upon evaporation of the mother liquor obtained by reaction (2).

The table presents data on the conditions of the experiments and the degree of deposition of Li ₂ CO ₃ during the interaction of a concentrated solution of lithium chloride with ammonium bicarbonate.

Information confirming the possibility of carrying out the invention is set forth in the examples.

Example 1

20 l of natural chloride brine composition (g / l): LiCl - 9; NaCl - 182; KCl - 35.3; MgCl ₂ 54.2; CaCl ₂ - 3.19; SO ₄ ^2- - 2.8 (total mineralization ~ 286 g / l) was concentrated under the influence of an incandescent lamp. Upon reaching the saturation limit of the solution by components, precipitation of the NaCl, KCl, CaSO _4, and MgCl ₂ · 6H ₂ O salts occurred, and the LiCl concentration increased. After removal of the precipitated salts, the concentrated solution has the following composition (g / l): LiCl - 250; NaCl - 2; KCl - 0.4; MgCl ₂ - 65.3; CaCl ₂ - 0.91; SO ₄ ^2- - 0.2. This concentrated solution was purified from Ca ²⁺ , Mg ²⁺ and SO ₄ ^{2+ ions} . The primary purification from Ca ²⁺ , Mg ^{2+ was} carried out using Li ₂ CO ₃ .

In 600 ml of a concentrated solution, heated to 80 ° C, 27.5 g of Li ₂ CO _{3 was} added and stirred for 1 h. The precipitate of MgCO ₃ and CaCO _{3 was} filtered. The concentration of LiCl in solution increased to 300 g / L. The residual concentration of MgCl ₂ was 6.5 g / l, CaCl ₃ - 0.10 g / l. For a deeper purification of the concentrated LiCl solution from Ca ²⁺ , Mg ²⁺ , a mixture of 3 g of Ca (OH) ₂ and 4.3 g of Na ₂ CO ₃ was introduced into it based on the precipitation of Mg (OH) ₂ and CaCO ₃ . The solution was separated from the precipitated precipitate, and then the SO ₄ ^2– ions were purified. 0.26 g of BaCl ₂ was introduced into the solution acidified to pH 2 and heated to 80 ° C with stirring until the SO ₄ ^2– ions completely precipitated as insoluble BaSO ₄ . Leave the solution with the precipitate for 6-8 hours to enlarge the particles of the precipitate and filtered. Thus, a purified concentrated LiCl solution was obtained.

500 ml of a concentrated solution of lithium chloride containing (g / l): LiCl - 300; Mg - 0.008; Ca - 0.005, Na - 0.08, K - 0.02, SO ₄ ^2- - 0.005 is added to a pulp containing 200 ml of H ₂ O and 279.7 g of solid ammonium bicarbonate. Stir the resulting pulp for 1.5 hours at a temperature of 20 ° C. The precipitate obtained is filtered on a Buchner funnel. The degree of deposition of primary lithium carbonate from solution is 70.1%.

The mass of wet sediment is 142 g with a moisture content of about 30%. It is washed by pulping the precipitate in 300 ml of distilled water (W: T = 3). Wash water containing (g / l): Li - 1.5; HCO ₃ - 6; NH ₄ ⁺ - 8; Cl - 17, attached to the mother liquor.

The mother liquor contains (g / l): Li - 10.3, HCO ₃ ^- - 64.4, NH ₄ ⁺ - 83.5, Cl - 171 (which in the percentage of salts in solution is: LiCl ~ 18%, NH ₄ HCO ₃ ~ 25% and NH ₄ Cl - 57%). The mother liquor, together with the wash water attached to it, is used further at the stage of desorption of unreacted ammonium bicarbonate from it.

The desorption of ammonia from the mother liquor was carried out on a column with a diameter of 8 cm at a gas flow rate of 1.2 m ³ / h and a gas volume to solution volume ratio of 2500. Over 1.5 hours, the degree of ammonia desorption was ~ 90%. Sorption of desorbed ammonia with water at a temperature of about 40 ° C was carried out on the same column as desorption. The ratio of gas volume to solution volume was 9000. The degree of absorption of ammonia reached 98%. (Captured ammonia and carbon dioxide in the form of a solution of ammonium bicarbonate with a concentration of 310 g / l and in a volume of 200 ml was used to implement example 2.)

The mother liquor together with the wash water after the operation of desorption of ammonia was further subjected to evaporation under natural conditions at an air temperature of 22-25 ° C and a relative humidity of 25-30%. 1 liter of the resulting solution was evaporated over 80 hours to a concentration of lithium chloride of approximately 300 g / L. The precipitated crystals of ammonium chloride crystals (185.7 g) were separated on a Buchner funnel and washed from the mother liquor, treating it with 400 ml of a saturated solution of NH ₄ Cl (~ 300 g / l) to avoid loss of soluble ammonium chloride during washing. The washing solution contains 4.9 g / l of lithium. After drying the crystals of NH ₄ Cl at a temperature of about 60 ° C for 14 hours, a product was obtained with a lithium content of 0.09 wt.% And a residual moisture content of 0.6 wt.%, Corresponding to the requirements of GOST. The yield of NH ₄ Cl was 1.3 kg per 1 kg of lithium carbonate. One stripped off concentrated solution of lithium chloride (mother liquor after separation of NH ₄ Cl), containing (g / l): Li - 50; NSO ₃ ^- - 0.03; NH ₄ ⁺ - 27.5; Cl - 264 was used in subsequent experiments at the deposition stage of primary lithium carbonate (see example 2).

The wet washed precipitate of primary Li ₂ CO _{3 was} further carbonated. Pulp was prepared from 142 g of wet sediment and 2000 ml of distilled water with a solid phase concentration of 3.6% in a stirred reactor equipped with a porous ceramic nozzle for dispersing carbon dioxide supplied from a cylinder. At 20 ° C, the carbonization process was carried out for 2 hours. The resulting lithium bicarbonate solution was filtered and heated to 95 ° C. Decarbonization at this temperature was carried out for 1 hour. The precipitate of pure lithium carbonate was separated from the mother liquor by filtration on a Buchner funnel and washed by pulping with 300 ml of hot deionized water in a stirred reactor. The washed lithium carbonate was separated by filtration and dried at 120 ° C. Dry dried product had the following composition (wt.%): Basic substance - 99.9; Na 0.0002; K - 0.00015; Mg - 0.0005; Ca - 0.002; SO ₄ ^2- - 0.003; NH ₄ ⁺ is absent.

Data on the conditions for the interaction of a concentrated solution of lithium chloride with ammonium bicarbonate and the degree of deposition of primary lithium carbonate are presented in the table.

Example 2

The same as in example 1, but at the deposition stage of primary lithium carbonate, 380 ml of the initial concentrated LiCl solution are taken (instead of 500 ml), 120 ml of the mother liquor of LiCl obtained in example 1 at the stage of evaporation and charging of NH ₄ Cl are added to it ( containing 303 g / l LiCl and 82 g / l NH ₄ Cl), and poured into a pulp containing 217 grams of solid NH ₄ HCO ₃ and 200 ml of a solution of ammonium bicarbonate obtained in example 1 at the stage of absorption of ammonia and CO ₂ and containing 310 g / l ammonium bicarbonate. The composition of the resulting mother liquor is almost identical to example 1. The degree of deposition of primary lithium carbonate was 74%. In this case, the saving of spent solid NH ₄ HCO ₃ was about 22% due to the use of a secondary solution of ammonium bicarbonate, obtained in accordance with the scheme shown in figure 2.

Industrial applicability.

The proposed method in comparison with the prototype method allows you to:

- replace soda with a cheaper reagent - ammonium bicarbonate, the cost of which is ~ 1.5 times lower than the cost of soda;

- make the process environmentally friendly by eliminating the discharge of the mother liquor containing a NaCl solution with a concentration of ~ 150-200 g / l;

- to process the mother liquor with the release of a marketable product - ammonium chloride, used in the national economy as fertilizer and flux;

- reduce the cost of the obtained lithium carbonate of high purity due to the sale of by-products of the market - ammonium chloride and carbon dioxide;

- implement the creation of a closed, waste-free technology for producing lithium carbonate of high purity.

Table
The experimental conditions and the degree of deposition of lithium in the interaction of a concentrated solution of lithium chloride with ammonium bicarbonate Experience Number Test conditions The content in the mother liquor, g / l The degree of deposition of Li ₂ CO ₃ ,% The concentration of the LiCl solution, g / l Temperature ° C Interaction time, min Li ⁺ NH ₄ ⁺ NSO ₃ ^- one 300 twenty thirty 11.5 82.0 82.1 64.1 2 300 twenty 60 10.1 83.0 76,2 69.3 3 300 twenty 90 10.3 82.0 71.7 70.0 four 300 twenty 120 10.3 85.5 60,4 70.1 5 350 twenty 90 10.1 85.0 59.2 73.1 6 350 thirty 90 9.74 97.5 43.9 78.0 7 350 40 90 9.40 94.4 47.0 77.3 8 300 60 thirty 9.5 69.3 no 68.7

Information sources

1. Pat. CN No. 1059702, declared 09/10/90, publ. 03/25/92 / Wang Guiying, Shi Ying.

2. Pat. US No. 5219550, C 01 D 015/08, decl. 12/06/90, publ. 06/15/1993 / Brown P.M., Boryta D.A.

3. Pat. US No. 6207126, C 22 V 26/12; C 01 F 5/2/2; C 01 D 15/04, claimed 06/14/1999, publ. 03/27/2001 / Boryta D.A., Kullberg T.F., Thurston A.M. (prototype).

4. Pat. RF №2223142, С 01 D 15/00, decl. 11/22/2001, publ. 02.10.2004 / Menzherez L.T., Ryabtsev A.D., Mamylova E.V., Kotsupalo N.P.

5. Pat. RF №2234367, 01 J 20/00, C 01 D 15/00, decl. 12/15/2002, publ. 08/20/2004 / Menzherez L.T., Ryabtsev A.D., Mamylova E.V., Kotsupalo N.P.

Claims (2)

1. A method of producing lithium carbonate of high purity from lithium chloride brines, including the production of lithium chloride concentrate, purification of lithium chloride concentrate from the main amount of calcium, magnesium, sulfate ions, reagent deposition of lithium carbonate from purified lithium chloride concentrate, washing of lithium carbonate, the conversion of the washed lithium carbonate into a saturated solution of lithium bicarbonate with carbon dioxide, decarbonization of a saturated solution of lithium bicarbonate with heating, separated the solution of high purity solid lithium carbonate freed from residual impurities from the solution and its drying, characterized in that the precipitation of lithium carbonate from the purified lithium chloride concentrate is carried out with an aqueous pulp of ammonium bicarbonate at 20-40 ° C, removing carbon dioxide from the reaction volume, which after it purification of ammonia impurities is used as a carbonizing agent for the conversion of lithium carbonate precipitated and separated from the liquid phase into a saturated solution of lithium bicarbonate, and the mother liquor is opera and the deposition of lithium carbonate is first freed from the residual mixture of bicarbonate and ammonium carbonate by thermal decomposition into ammonia and carbon dioxide, which are removed by the carrier gas stream containing ammonia and carbon dioxide formed during the deposition of lithium carbonate, while the carrier gas stream is cleaned of ammonia by countercurrent washing it with water while cooling to obtain a solution of ammonium bicarbonate, directed to the operation of preparing an aqueous pulp of ammonium bicarbonate, and then evaporated, Obtain solid phase of ammonium chloride and a liquid phase with lithium chloride concentration of 300-350 g / l, the liquid phase is recycled to the precipitation step of the primary lithium carbonate from lithium chloride concentrate and the solid phase was washed with ammonium chloride, a saturated solution of lithium chloride and the residue was dried. 2. The method according to claim 1, characterized in that the carbon dioxide released at the stage of decarbonization of the lithium bicarbonate solution, together with the residual amount of carbon dioxide supplied from the stage of carbonization of lithium carbonate, is used to produce marketable carbon dioxide.

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