EA040900B1 - METHOD FOR OBTAINING GRANULATED SORBENT FOR EXTRACTION OF LITHIUM FROM LITHIUM-CONTAINING BRINES UNDER CONDITIONS OF MANUFACTURING COMMERCIAL LITHIUM PRODUCTS - Google Patents

Description

In the proposed method, a lithium-containing solution of aluminum chloride is used to obtain a sorbent in the form of G1SG2A1(OH) ₃ -tH2O (DGAL-C1) powder. To obtain it, aluminum chloride hexahydrate is dissolved in aqueous solutions containing commercial lithium compounds: LiCl, LiOIIIGO. Ei ₂ CO ₃ , and solutions containing them coming from various stages of lithium production. The synthesis of DHAL-C1 is carried out at an atomic ratio of Al:Li in the reaction mixture equal to 2.0:2.3. At the same time, a solution of sodium hydroxide is introduced into the reaction mixture to pH 7. The resulting DHAL-C1 is separated by centrifugation, pulped in water, removing excess LiCl, and subjected to two-stage drying, first in a fluidized bed mode at t=10-15°C, then vacuum drying at t=60-65°C. A paste is prepared from the dried and crushed powder by mixing DHAL-C1 with a pre-prepared solution of polyvinyl chloride in an organochlorine solvent. As a solvent, both methylene chloride and trichlorethylene or tetrachlorethylene or mixtures thereof are used. The resulting paste is extruded through dies with a diameter of 5 mm with countercurrent supply of heated air, freeing the extrudate from the organic solvent evaporating into the air stream. After the air degassing stage, the extrudate enters the vacuum degassing stage. Next, the extrudate is subjected to crushing and classification with the return of the fine fraction to the preparation of the paste. Granules with a size of 1-2 mm enter the drum rolling, giving them a rounded shape, screenings are sent to the preparation of pasta. The air cooled after degassing of the extrudate, saturated with vapors of an organochlorine solvent and water, is sent for compression at a pressure of 6 atm, while cooling the air flow to -3°C. The liquid phase of vapors of organochlorine solvents or mixtures thereof and water formed during condensation is separated. The gas stream, freed from the condensed phase, is subjected to deep cooling to -15°C for deep condensation of vapors of an organochlorine solvent or a mixture of solvents and water vapor. The solid phase of ice is separated, and the liquid phase of the organochlorine solvent or solvent mixture is decompressed by heating to 0°C. With deeper deposition down to -70°C, the process of condensation of liquid phases from the air stream can be carried out in one stage. The liquid phase from the decompression and deep cooling operation is used in the pasta preparation operation. The cleaned and dried air flow is heated to 120-140°C and used in the extrudate degassing operation.

Technical field

The invention relates to chemical materials science, in particular to methods for producing inorganic sorbents based on aluminum hydroxide, which selectively extract lithium from natural brines and technogenic chloride salt solutions containing lithium.

State of the art

In world practice, for the selective extraction of lithium, an inorganic sorbent based on a hydrated composite material of the composition LiCl/Al(OH) ₃ is proposed, which is capable of selectively extracting lithium from brines [1]. The preparation of such a sorbent is carried out by the interaction of commercial crystalline Al (OH) ₃ (crystal size not less than +140 μm) in the form of gibbsite, bayerite or nordstrandite with lithium hydroxide in the presence of water at W: T = 0.69, thus producing a LiOH / Al composite (OH) ₃ . The resulting composite is further treated with a 20% hydrochloric acid solution to convert it into the sorption form LiCl/Al(OH) ₃ . After separating the solid phase of the sorbent from the mother liquor, it is brought into contact with water to remove the required amount of LiCl from the structure.

Upon subsequent contact of such a sorbent with a lithium-containing chloride brine, the removed amount of LiCl is restored in its structure. Next, the lithium adsorbed from the brine is desorbed with water. When this sorption and desorption of lithium is carried out at a temperature of 80°C. The disadvantages of this method are the two-stage and duration of the process of synthesis of the sorbent, the need to use a strong solution of hydrochloric acid and high operating temperature (80°C) processes of sorption and desorption of lithium chloride. However, the biggest drawback of this sorbent is the mechanical destruction of its crystals during operation, which makes its practical application impossible.

A known method for the synthesis of microcrystalline hydrated selective sorbent, corresponding to the formula LiCl-2Al(OH) ₃ , suspended directly in the macropores of the anion-exchange resin [2]. The method includes:

a) introducing freshly precipitated Al(OH)3 into the pores of the resin, for which the resin is soaked in a saturated solution of AlCl ₃ followed by treatment with an aqueous solution of ammonia;

b) washing the resin to remove excess reagents;

c) treating the resin containing Al(OH)3 with a solution of LiOH to obtain an intermediate LiOH-2Al(OH) ₃ ;

d) treating the resin with the intermediate with a solution of hydrochloric acid or a solution of lithium chloride to convert the intermediate to LiCl-2Al(OH) ₃ .

The disadvantages of this method are, firstly, the complexity and multi-stage synthesis process, and secondly, the rapid leaching of the LiCl-2Al (OH) ₃ compound (within 7-10 days from the start of the sorbent operation) from the resin macropores during sorption - desorption cycles .

A known method for producing a granular selective sorbent for the extraction of lithium from brines by electrochemical dissolution of metallic aluminum in a concentrated solution of lithium chloride with the formation of a compound of the composition LiCl-2Al(OH) ₃ -mH2O, separating the sorbent phase from the solution phase, drying and granulating the dry powder of the sorbent with a binder (fluoroplast powder) dissolved in acetone [3]. The disadvantages of this method of synthesis of the sorbent are: the high energy intensity of the process of electrochemical synthesis of powder LiCb2Al(OH) ₃ -mH ₂ O at the same time low productivity and high explosion and fire hazard of the granulation process, due to the use of acetone as a solvent.

A method for obtaining a granular sorbent for the extraction of lithium from brines and a plant for its implementation [4] have been developed, including the preparation of LiCl-2Al(OH) ₃ -nH2O powder by mixing aluminum hydroxide with lithium chloride in a high-speed mixer for bulk materials with a stirrer in the presence of a calculated amount water, followed by processing the resulting mixture in a centrifugal mill - activator to obtain a powder corresponding to the formula LiCl-2Al (OH) ₃ -nH2O with a particle size of not more than 0.16 mm.

Granulation of the produced powder is carried out by extruding a paste obtained by mixing the sorbent powder with a polyvinyl chloride resin (binder) dissolved in methylene chloride. The extrudate after distillation of methylene chloride vapor is crushed and classified to obtain a product with a granule size of 1.0-1.5 mm. Vapors of methylene chloride released during granulation are absorbed by a stream of freon oil (type KhF-22s-16) from a carrier gas stream (air), obtaining a 20% solution of methylene chloride in oil, which is directed to thermal desorption of methylene chloride, followed by condensation of its vapors and return of the condensed phase of methylene chloride in the production of sorbents. The disadvantage of this method is the high energy consumption of the technological operation of the synthesis of the powder compound LiCl-2Al(OH) ₃ -nH2O, the low stability of the chemical composition of the resulting compound and the lack of reliable mechanical activation equipment. These disadvantages do not allow to implement the method on an industrial scale.

A method for obtaining a sorbent for the extraction of lithium from brines [5] was proposed, which eliminates the disadvantages of the previous method [4]. The technical result is achieved by the fact that the production of LiCl-2Al(OH) ₃ -mH2O is carried out by direct interaction of a mixture of crystalline chloride

- 1 040900 aluminum and lithium hydroxide in the presence of a small amount of water or their concentrated solutions. In this case, the interaction proceeds according to the reaction:

2A1C13 + 6LiOH + nH ₂ O LiCl 2A1(OH)3 nH ₂ O + 5LiCl (1).

Despite the high quality of the resulting product and high stability and reproducibility, a significant disadvantage of this method is the high consumption of the most expensive commercial lithium product - lithium hydroxide. For 1 mole of the resulting compound, 6 moles of LiOH are required. In addition, the method is characterized by the presence of a large amount of lithium-containing waste in the form of a solution of LiCl, which requires additional costs for the disposal of lithium.

Later, the same authors proposed a method for obtaining a sorbent for extracting lithium from brines, which is based on the replacement of LiCl-2Al(OH) ₃ -nH2O LiOH with cheaper and less scarce Li ₂ CO ₃ in the synthesis of LiCl-2Al(OH) 3 -nH2O [6]. The formation of the solid phase of the product is carried out according to the reaction:

2A1C13 + 3CHCO3 + (3 + n)H ₂ O LiCl 2A1(OH)3 nH ₂ O + 5LiCl + 3CO ₂ (2)

In this case, the resulting synthesis waste is easily converted into lithium carbonate by precipitation from a solution with soda according to the reaction:

2LiCl + Na ₂ CO ₃ -+ Li ₂ CO ₃ ; + 2NaCl (3)

Recycled lithium carbonate is returned to the production of the sorbent. Thus, in order to obtain 1 mol of the LiCl-2Al(OH) ₃ -nH2O compound, 0.5 mol of Li ₂ CO ₃ is ultimately consumed. However, despite the obvious advantages, this method also has significant drawbacks. The disadvantages of this method include the low rate of interaction according to reaction (2) and the associated duration of the synthesis of the sorbent by this method, which takes several hours. In addition, during the synthesis, a gel-like phase LiCl-2Al(OH) ₃ -nH2O is often formed, which makes it difficult to separate it from the mother liquor. The method also does not provide for granulation of the sorbent powder.

The developed method for obtaining a granular sorbent for the extraction of lithium from lithium-containing solutions [7] significantly eliminates the disadvantages of the above method. The method includes obtaining a chlorine-containing variety of aluminum and lithium double hydroxide (LiCl-2Al(OH) ₃ -nH2O) from an aluminum chloride solution preliminarily mixed with lithium hydroxide or carbonate at an Al:Li atomic ratio of 2.0-2.3 when adding in a mixed NaOH solution to a pH of 6-7. The resulting precipitate LiCl-2Al(OH) ₃ -nH2O is separated from the solution, dried, crushed to particle size and granulated with the addition of polyvinyl chloride and methylene chloride as a solvent with the recovery of methylene chloride evaporating during the granulation process and return to production.

In terms of its technical essence and the achieved result, this method is the closest to the claimed one and was chosen by us as a prototype. However, along with the undoubted advantages, this method has disadvantages. The disadvantages of the method are:

the use of filtration to separate the synthesized DHAL-Cl from the mother liquor leads to the formation of a very dense cake, which must be crushed before moving on to the next technological operation;

excessive content of lithium chloride in the finished product, leading to unreasonable increased consumption of expensive lithium reagents in the production of the DGAL-Cl sorbent;

unreasonably long duration of the one-stage drying process of the DHAL-Cl powder;

high residual content of organic solvent in the extrudate, which leads to increased consumption of the solvent, on the one hand, and the deterioration of sanitary and hygienic conditions in the workplace, on the other hand;

unreasonably low index of mechanical strength of the initial granules of DHAL-Cl, obtained by crushing degassed extrudate, due to their irregular shape;

methylene chloride recovery system based on oil absorption - desorption of its vapors with subsequent condensation into the liquid phase is not only cumbersome and difficult to operate, but also fire hazardous due to the simultaneous use of a large volume of combustible material in the form of vacuum oil;

high vapor pressure of methylene chloride due to its low boiling point (40°C), leading to large losses of this organochlorine solvent during extrusion;

the use of only expensive commercial lithium products in the form of Li ₂ CO ₃ and LiOH-H2O to obtain an aqueous solution of AlCl ₃ containing lithium, while in the conditions of the existing lithium production there are a number of lithium-containing intermediate products and production waste that can be successfully used for preparation of aluminum-lithium solution.

The proposed method for obtaining a granular sorbent for the extraction of lithium from lithium-containing brines in the production of commercial lithium products retains all the advantages of the prototype and eliminates the above disadvantages.

The essence of the invention

The technical result, which ensures the elimination of these shortcomings, is achieved using the following methods and operations.

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The dispersed phase (powder) of aluminum and lithium double hydroxide (DHAL-Cl) is obtained from an aluminum chloride solution with a concentration level of AlCl ₃ 45-220 kg / m ³ containing lithium, with the addition of sodium hydroxide until a pH of 6.5 to 7 is reached, while the atomic ratio of Al:Li in a solution of aluminum chloride containing lithium is from 2.0 to 2.3. An aluminum chloride solution containing lithium is prepared by dissolving crystalline aluminum chloride hexahydrate in aqueous solutions containing the calculated amount of lithium, both in the form of individual (commercial) lithium compounds LiCl, Li ₂ CO ₃ , LiOH-H ₂ O, and in the form of mixtures of these compounds and / or in the form of lithium-containing solutions and mixtures of lithium-containing solutions or in the form of mixtures of lithium-containing solutions with individual lithium compounds coming from the corresponding stages of production of commercial lithium products LiCl, Li ₂ CO ₃ , LiOH-H ₂ O obtained from natural lithium-containing brines. The separation of the dispersed phase of DHAL-Cl from the mother liquor (aqueous solution of NaCl) is carried out by centrifugation with further use of centrifuge for the production of a disinfecting solution of sodium hypochlorite. The dispersed phase of DHAL-Cl after separation from the centrate is pulped in the calculated volume of water, removing excess LiCl from DHAL-Cl by desorption into the liquid phase with stirring of the pulp for 20-30 min. The pulp is centrifuged by directing the centrifuge (an aqueous solution of LiCl) to the operation of preparing a solution of aluminum chloride containing lithium, and the dispersed phase of DHAL-Cl is sent to a two-stage drying, carried out at the first stage with heated air in a fluidized bed mode with maintaining a temperature in the drying zone of 70-75 °C to a residual moisture content of DGAL-Cl 9.0-9.5 wt.%, at the second stage in the vacuum drying mode with agitation and maintaining a temperature in the drying zone of 60-65°C to a residual moisture content of DGAL-Cl 1.5-2 .0 wt.%.

A paste is prepared from the dried and crushed DGAL-Cl powder by mixing it with a pre-prepared solution of chlorinated polyvinyl chloride (CPVC resin) with an organochlorine solvent, which, along with methylene chloride, uses trichlorethylene or tetrachlorethylene or mixtures thereof. The prepared paste is extruded through dies with a diameter of 5 mm. The extrudate is brought into countercurrent contact with an air stream heated to 120-130°C, releasing the extrudate from the chlorine-containing solvent evaporating into the air stream. The extrudate that has passed the stage of air degassing is sent to the stage of vacuum degassing under a vacuum of 0.4-0.6 at. The extrudate after degassing is subjected to crushing and classification with the return of the retur (fine fraction of granulated DHAL-Cl) to the paste preparation operation. Granules of DGAL-Cl with a size of not less than 1.0 mm and not more than 2.0 mm are subjected to pelletizing, giving the granular sorbent a rounded shape of the granules, thereby increasing their mechanical strength and returning screenings to the paste preparation operation.

The air stream cooled during degassing of the extrudate, saturated with vapors of an organochlorine solvent or a mixture of their vapors, is directed to compression under a pressure of 6 atm, while cooling the vapor-air stream to -3°C with condensation of vapors of an organochlorine solvent or a mixture of vapors of organochlorine solvents and water into the liquid phase. The separation of the condensed phase from the gaseous phase is carried out by fogging with settling and separation of the phases of the organochlorine solvent or mixture of organochlorine solvents from water.

Deep cooling of the compressed vapor-air flow released from the condensed phase is carried out to -15°C with deep condensation of vapors of an organochlorine solvent or a mixture of their vapors into a liquid phase and water vapor into ice crystals, followed by separation of the condensed phases from the air stream and separation of the condensed phases into solid (ice ) and liquid (organochlorine solvent or mixture of organochlorine solvents). The decompression of the air flow released from the condensed phases is carried out by heating to 0°C. After that, the purified and dried air flow is heated up to 120-130°C with return to the extrudate degassing operation.

After combining the liquid condensed phases of an organochlorine solvent or a mixture of organochlorine solvents isolated in the operations of compression and deep cooling of the vapor-air flow, the liquid solvent is returned to the operation of dissolving chlorinated polyvinyl chloride. The combined phase of ice crystals with the liquid condensed phase of the operation of compressing the steam-air flow is fed to the operation of preparing an AlCl3 solution containing lithium.

As a result of the method according to the present invention, a granular sorbent based on the LiCl-2Al(OH) ₃ -nH ₂ O compound is obtained, having a mechanical strength of 98.9±0.2% to 99.2±0.2% and a static exchange capacity for LiCl, mg Li/g sorbent, from 5.9±0.1 mg to 6.2±0.1 mg.

The advantages of the proposed solutions compared to the prototype are:

1) in reducing the cost of production of granular lithium-selective sorbent DGAL-Cl by reducing the consumption of lithium-containing reagent in the synthesis of the dispersed phase of DGAL-Cl, replacing expensive commercial lithium products with lithium-containing intermediates and waste products from the production of commercial lithium products, for example, from lithium-bearing natural brines, extraction and return to production of the excess LiCl contained in the synthesized DHAL-Cl, simplification of the system

- 3 040900 recovery of organochlorine solvent;

2) in increasing the mechanical strength of the granular sorbent DGAL-Cl;

3) in reducing the fire hazard of production;

4) in reducing the emission of organochlorine solvent vapors into the air of the working area and the environment.

The reality of achieving the technical result is confirmed by the description of the technological scheme of the production process of the granular sorbent DGAL-Cl.

List of drawings and tables

Fig. 1. Technological scheme for obtaining a granular sorbent for the extraction of lithium from lithium-containing brines in the conditions of production of commercial lithium products.

Fig. 2. Table of indicators of the properties of organic solvents used in the granulation of DHAL-Cl powder.

Fig. 3. Graphs of the dependence of the vapor pressure of trichlorethylene (TCE) on temperature.

Fig. 4. Table of test results for samples of granular sorbent DGAL-Cl produced using mixed lithium-aluminum-containing aqueous solutions obtained from various lithium-containing sources.

Fig. Fig. 5. Comparative chemical compositions of samples of granular sorbent DHAL-Cl with and without preliminary removal of free lithium chloride from the synthesized dispersed phase of DHAL-Cl.

Fig. Fig. 6. Results of testing a sample of the granular sorbent DGAL-Cl that underwent the operation of removing free (excess) lithium chloride before drying the dispersed phase of DHAL-Cl, grinding and granulating in comparison with the sample that underwent the stage of removing free lithium chloride after granulating and cooling.

In accordance with the technological scheme (Fig. 1), the main technological stages in the industrial production of lithium products, for example, in the production of lithium products from lithium-bearing hydro-mineral raw materials, are: sorption enrichment of brine for lithium chloride, followed by removal of the remaining brine and obtaining a primary lithium concentrate containing as a rule, not more than 10 kg/m ³ LiCl, concentration of the primary lithium concentrate to a productive one containing LiCl from 60 to 480 kg/m ³ depending on the need to obtain one or another lithium product, obtaining commercial lithium products from the productive lithium concentrate in the form technical lithium carbonate, battery grade lithium carbonate, lithium hydroxide monohydrate grades LGO-3, LGO-2. LGO-1, technical lithium chloride. Each of the manufactured commercial products can be used as a starting reagent for the preparation of an aqueous lithium aluminum chloride solution used in the synthesis of the dispersed phase of the chlorine-containing variety of aluminum and lithium double hydroxide (LiCl 2Al(OH) ₂ nH ₂ O).

The process of obtaining an aqueous lithium aluminum chloride solution from commercial lithium products is described by the following equations of chemical reactions:

H ₂ O + A1C1z + P ₂ COz A1C1 (OH) ₂ + 2LiCl + CO ₂ $ (1)

H ₂ O + A1C1z + LiCl A1C1 ₂ (OH) + LiCl + HC1 (2)

LiOH H ₂ O + A1C13 AlCh(OH) + LiCl + H ₂ O(3)

Since there are no strict requirements for the content of impurities in a mixed lithium-aluminum chloride solution, not only commercial lithium products, but also technogenic lithium-containing materials and production waste in the form and mixtures of solutions can be used for its preparation. So, for the preparation of a mixed lithium-aluminum aqueous solution, primary lithium concentrate (LiCl solution 10 kg / m ³ with NaCl and KCl admixture), productive lithium concentrate (concentrated LiCl solution with NaCl and KCl admixture), which are taken from the corresponding technological stages in the calculated quantities. In addition, an effective reagent for obtaining a mixed lithium aluminum chloride solution can be a solution of lithium bicarbonate, which is a technogenic intermediate in the production of lithium carbonate of battery quality. In this case, the chemical description of the process is as follows:

L1HCO3 + A1C13 A1C1 ₂ (OH) + LiCl + CO ₂ $ (4)

The starting reagents for obtaining a mixed lithium-aluminum aqueous chloride solution can be: waste from the production of battery lithium carbonate - lithium carbonate-alkaline solution containing NaCl and KCl as the main impurity; waste production of LiOH-H ₂ O - LiOH solution containing NaOH and KOH as impurities.

The optimal range of aluminum concentrations in a mixed lithium-aluminum containing aqueous chloride solution is 45-220 g/dm ³ in terms of AlCl3, since when the AlCl3 content is below 45 g/dm ³ , the resulting DHAL-Cl precipitate begins to intensively water and is poorly separated from the mother liquor, and when the content of AlCl3 is higher than 220 g/ ^dm3 , the mother liquor becomes supersaturated with NaCl and the DHAL-Cl precipitate is charged with common salt crystals.

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The mixed lithium-aluminum aqueous chloride solution is brought into contact with stirring with a 1.0-2.5N NaOH solution added in portions until the pH of the resulting pulp is set to 6.5-7.0. The resulting pulp is centrifuged, separating the liquid phase (aqueous solution of NaCl) from the solid phase of the synthesized compound LiCl-2Al(OH) ₃ -nH2O. The liquid phase (fugate) is used either as a productive solution to obtain crystalline common salt by evaporation and drying, or as a make-up solution to obtain a disinfecting sodium hypochlorite solution produced from NaOH and Cl ₂ obtained by membrane electrolysis of an aqueous solution of NaCl.

The synthesized solid phase of the compound LiCl-2Al(OH) ₃ -nH2O (DHAL-Cl) is mechanically unloaded from the centrifuge by a screw (grinding of the solid phase is not required) and pulped in a given volume of fresh water and stirred for 20-30 min to remove excess LiCl from the DHAL-Cl phase to the liquid phase. The resulting aqueous solution of LiCl is separated from DHAL-Cl by pulp centrifugation. An aqueous solution of LiCl (centrate) is used to prepare a mixed lithium aluminum chloride aqueous solution.

The stripped DHAL-Cl is dried. Since the drying of DHAL-Cl should proceed at a temperature in the drying zone, which excludes the production of highly crystalline material, to achieve maximum productivity, DHAL-Cl is dried in two stages: at the first stage at a temperature of 70-75 ° C in a fluidized bed created by an air flow, to a residual moisture content 9.0-9.5 wt.%; in the second stage at 60-65°C in vacuum drying mode with agitation to a residual moisture content of 1.5-2.0 wt.%. The dry powder of DHAL-Cl is ground to a particle size of <0.1 mm.

The crushed powder is mixed until a homogeneous paste is formed with chlorinated polyvinyl chloride powder (CPVC - plasticizer) and an organic solvent (P), which is either methylene chloride, or trichlorethylene, or tetrachlorethylene (perchlorethylene), or mixtures thereof. The paste is extruded through dies with a diameter of 5 mm. The size of the die diameter of 5 mm is optimal, since it provides the highest yield of the product of a given size with a sufficiently high degree of degassing of the extrudate. The extrudate is degassed in a countercurrent flow of air. As follows from the contents of the table and the graphic dependences of the vapor pressure of solvents on temperature, presented in Fig. 2 the use of tetrachlorethylene is preferable due to the minimization of its losses during the production of paste and extrusion due to the significantly lower elasticity of its vapors, the minimum solubility of water in it, the minimum heat of evaporation, which ultimately ensures its minimum losses during recovery and maximum return to production with a high quality of the returned reagent .

For a more complete removal of the solvent, the extrudate that has passed the stage of air degassing is subjected to vacuum degassing under a vacuum of 0.4-0.6 at. The degassed extrudate is crushed and classified. The fine fraction is sent to the mixing operation (obtaining a paste), and the DHALCl granules with sizes in the range > 1.0 mm and < 2.0 mm are rolled to give the granules a rounded shape, the fine fraction is screened out and also sent to the mixing operation. Commodity granulated DGAL-Cl is packed into drums.

The air stream saturated with solvent vapors (P) is directed to compression (pressure 6 at., temperature -3°C), partially condensing solvent vapors and water vapors into the liquid phase and separating them from the vapor-air mixture by fogging. The condensate is settled by separating the water phase from the solvent phase. The compressed vapor-air mixture that has passed the misting stage is cooled to a temperature of -15°C, condensing the solvent vapor into a liquid phase, and the water vapor into crystals and separating it from the air flow also by misting. The condensed liquid phase of the solvent is separated from the ice crystals, mixed with the solvent condensed in the compression operation and sent to the mixing paste production operation. The ice crystals are mixed with the liquid phase of water condensed in the compression step and used in the mixed lithium aluminum chloride aqueous solution step. This technological process allows to bring the degree of recovery: in the case of using low-boiling solvents up to 97-99%.

The cleaned and dried air flow is heated to a temperature of 120-130°C and sent to the operation of air degassing of the extrudate.

It is possible to implement the solvent recovery process in one stage by freezing. In this case, to ensure the degree of recovery of methylene chloride 94-95%, it is necessary to cool the steam stream to -70°C. In the case of using trichlorethylene or tetrachlorethylene as solvents, in order to achieve a degree of recovery of 97% or more, it is sufficient to cool the steam-air flow to -15°C. The choice of one or another variant of solvent recovery is carried out on the basis of the results of technical and economic calculations performed at the stage of investment justification for the practical implementation of the development.

Example 1. Comparative testing of the sorption-desorption properties of batches of granular DGAL-Cl sorbent produced from various lithium-containing materials was carried out in laboratory conditions in accordance with the technological scheme shown in Fig. 1.

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Sample No. 1 was produced using a mixed lithium-aluminum-containing aqueous chloride solution obtained by dissolving 385.1 g of AlCl ₃ -6H2O in 3.03 l of an alkaline carbonate aqueous solution of composition (g / dm ³ ): lithium in terms of Li2CO ₃ - 10, 9000; SO ₄ - 0.0531; Ni - 0.0016; Pb 0.0075; Cu - 0.0060; Na - 0.5056; Ca - 0.0209; Mg - 0.0138; Fe - 0.0006; B - 0.0938; Cl - 0.7502; pH 9.7, which is a real waste from the production of battery-grade lithium carbonate from technical grade lithium carbonate.

Sample No. 2 was produced using a mixed lithium-aluminum-containing aqueous chloride solution obtained by diluting with water to bring the total volume to 1 l of a mixture of 403.5 g AlCl ₃ -6H ₂ O with 0.17 l of spent catholyte composition (g / dm ³ ): LiOH - 120; NaOH - 3.5, which is a waste product of LiOH-H2O production from lithium carbonate or lithium chloride.

Sample No. 3 was produced using a mixed lithium-aluminum-containing aqueous chloride solution obtained by dissolving 403.4 g of AlCl ₃ -6H ₂ O in 1.0 L of lithium bicarbonate solution (LiHCO ₃ content - 63.5 g/dm ³ ).

Sample No. 4 was produced using a mixed lithium-aluminum-containing aqueous chloride solution obtained by dissolving 403.2 g of AlCl ₃ -6H ₂ O in 3.82 l of primary lithium chloride concentrate of the composition (g/dm ³ ): LiCl - 10.40; NaCl - 0.20; KCl - 0.1; MgCl ₂ - 0.02; CaCl ₂ - 0.04; At 0.005; SO ₄ - 0.03, which is a semi-product of the production of technical lithium carbonate from natural lithium-bearing brine.

Sample No. 5 was produced using a mixed lithium-aluminum-containing aqueous chloride solution obtained by mixing 0.39 L of an aqueous solution of lithium bicarbonate, 1.50 L of primary lithium concentrate, 1.25 L of a lithium-containing carbonate-alkaline solution, and 403.2 g of AlCl3-6H2O.

Sample No. 6 was produced using a mixed lithium-aluminum-containing aqueous chloride solution obtained by mixing 403.1 g of AlCl ₃ with 0.097 l of a productive lithium concentrate of the composition (g/dm ³ ): LiCl - 481, KCl + LiCl < 4.0 g/dm ³ s subsequent addition of water in order to bring the total volume of the solution to 1 liter.

Sample No. 7 was produced using a mixed lithium-aluminum-containing aqueous chloride solution obtained by mixing 403.3 g of AlCl ₃ -6H ₂ O with 40.7 g of technical Li ₂ CO ₃ produced from a lithium-bearing natural brine, with the addition of water to adjust the total volume solution up to 1 liter.

A 1.0 N NaOH solution was used as an alkaline reagent in the preparation of all samples. Trichlorethylene was used as a solvent for granulation. The obtained samples of granular DGAL-Cl sorbents were tested for indicators: static exchange capacity for LiCl, mechanical strength, bulk density, swelling according to the methods specified in TU2133-23599583-2002 Sorbent for selective extraction of lithium. For testing, lithium-bearing natural brine of the Znamensky deposit of the Irkutsk region was used with the composition (g/dm ³ ): LiCl - 2.2; NaCl - 6.1; KCl - 8.2; MgCl ₂ - 115; CaCl ₂ - 330; Br - 8.3; SO ₄ - 0.6; B - 0.3; SrCl ₂ - 3.6 pH - 5.1 and distilled water. As follows from the results obtained, presented in the table in Fig. 3, all seven samples have almost identical characteristics in terms of exchange capacity and mechanical strength, which confirms the possibility of using a wide range of lithium-containing starting reagents for the synthesis of granular sorbent containing lithium in the form of chloride, carbonate, hydroxide, including waste products from the production of commercial lithium products.

At the same time, impurities contained in lithium-bearing waste do not adversely affect the characteristics of the synthesized granular sorbent.

Example 2. Using as initial reagents AlCl ₃ -6H ₂ O, Li ₂ CO ₃ technical, distilled water, PVC resin, methylene chloride as an organic solvent, two samples of the granular sorbent DGAL-Cl were obtained.

Sample No. 8 was manufactured strictly according to the technological schedule provided for by the scheme in Fig. 1. Sample no. 9 differed from sample no. 8 in that the procedure for removing excess LiCl from the synthesized dispersed phase of DHAL-Cl was excluded from the technological schedule. Samples of 0.2 kg were taken from each of the samples, which were tested according to the methods presented in example 1. Before testing, the sorbent samples were analyzed to determine their initial quantitative material composition. In this case, sample No. 9 before testing was brought into contact with 0.5 dm ³ of distilled water to remove excess lithium chloride and dried to constant weight in a vacuum dryer. The results of the chemical analysis of the quantitative material composition of the initial samples are presented in the table in Fig. 5. Test results in the table in FIG. 6. It follows from the obtained results that the test parameters of the compared samples are identical. However, the removal of excess lithium at the stage of synthesis of the dispersed phase of DHAL-Cl makes it possible, firstly, to return 22.5% of the expensive lithium chloride from its used amount to the production of the sorbent at the stage of synthesis, and secondly, to eliminate the need for the operation of preparing a granular sorbent for use in direct purpose.

- 6 040900

Example 3. Using AlCl ₃ -6H2O, Li2CO ₃ technical, distilled water, PVC resin and various organic solvents (methylene chloride, trichlorethylene and tetrachlorethylene) as initial reagents, three samples of granular sorbent were obtained according to the technological schedule corresponding to the technological scheme (Fig. 1). Sample No. 10 - solvent methylene chloride, sample No. 11 - solvent trichlorethylene, sample No. 12 - solvent - tetrachlorethylene. The obtained samples were tested for mechanical strength. The mechanical strength indicators of the tested samples were as follows (%): sample No. 10 - 99.1 ± 0.1; sample No. 11 - 99.0±0.1; sample No. 12 99.1±0.1. The difference in the mechanical strength of the tested samples of granular DHAL-Cl obtained using various solvents is within the error of determination.

Example 4. From the reagents described in examples 2 and 3, a sample of the dispersed phase of DHAL-Cl was obtained, which, after removing free LiCl, was divided into two equal portions. Portions were dried each separately to a residual moisture content of 2 wt.%. Sample #13 was dried in one stage on a vacuum dryer. Sample No. 14 was dried in two stages: in the fluidized bed mode at the first stage to a residual moisture content of 9 wt.%; in the vacuum mode (vacuum 0.6 atm) during tedding. Sample no. 13 took 12 hours and 40 minutes to dry. The total drying time for sample no. 14 was 3 hours 37 minutes. The transfer of the technological process to two-stage drying makes it possible to reduce the drying time by almost three times.

Example 5. A batch of granular sorbent DGAL-Cl was obtained according to the technology presented in Fig. 1. After the completion of the technological stage of crushing and classifying the degassed extrudate, the resulting batch of DHAL-Cl of a given granule size was divided into two equal parts. One sample (sample no. 15) was tested for mechanical strength without rounding. The second sample (sample no. 16) was rolled in a rotating drum for 75 min, and after screening out the fine fraction, it was also tested for mechanical strength. Sample No. 15 showed a mechanical strength of 97.7±0.2%. Sample No. 16 showed mechanical strength at the level of 99.0±0.2%. Tests have shown that pelletizing particles of crushed DHAL-Cl by more than 1% increases its mechanical strength.

Example 6. According to the technological regulations (Fig. 1) produced two samples of granular sorbent DGAL-Cl. One sample (sample No. 17) using commercial tetrachlorethylene as the organic solvent. Another sample (sample no. 18) using recovered tetrachlorethylene, which was obtained by freeze-drying (-15°C) from a vapor-saturated circulating air stream in the preparation of a bulk batch of granular DHAL-Cl. Sample No. 17 showed a mechanical strength of 99.1%, sample No. 18 - 99.0%. The difference turned out to be within the error, which confirms the suitability of the recovered organic solvent for granulating the DHAL-Cl powder.

Information sources used

1. Patent US 6280693, CO1D 15/00 / William C. Bauman John L. Burba, Composition for the recovery of lithium values from brine and process of making/using said composition. Appl. 09/20/1996, publ. 08/28/2001.

2. Patent US 4347327, CO8D 5/20, B0i 20/00 / J.M. Lee, W.C. Bauman, Recovery of lithium from brines. dec. 11/19/79, publ. 08/31/82.

3. Patent RF 2028385, V0i 20/00, S25V 1/00 / N.P. Kotsupalo, L.L. Sitnikova, L.T. Mengeres, App. 05/25/1992, publ. 02/09/1995. Bull. No. 4.

4. PCT/DE 2001/004062, Method for producing granulated sorbents and installation for carrying out the method. Appl. October 25, 2001, publ. 12/29/2004.

5. RF patent 2223142, VOL 20/02, CO1D 15/00 / L.T. Menzheres, A.D. Ryabtsev, E.V. Mamylova et al. Method for obtaining a sorbent for extracting lithium from brine. Published 02/10/2004. Bull. No. 23.

6. RF patent 2234367, B01J 20/02, C01D 15/00 / L.T. Menzheres, A.D. Ryabtsev, E.V. Mamylova, N.P. Kotsupalo. Method for obtaining a sorbent for the extraction of lithium from brines. Appl. 12/15/2002, publ. 08/20/2004. Bull. No. 23.

7. RF patent 2455063, Method for obtaining a granular sorbent for extracting lithium from brine / A.D. Ryabtsev, V.I. Titarenko, N.P. Kotsupalo et al. Appl. 10/13/2010, publ. 07/10/2012. Bull. No. 19 (prototype).

Claims (11)

1. A method for obtaining a granular sorbent based on LiCl-2Al(OH) ₃ -nH2O for the extraction of lithium from lithium-containing brines and a granular sorbent under the conditions for the production of commercial lithium products, including obtaining a precipitate of LiCl-2Al(OH) ₃ -nH2O (DHAL-Cl) from a solution of aluminum chloride containing lithium, with the addition of an alkaline reagent; separating the DHAL-Cl precipitate from the resulting solution by centrifugation, followed by removal of excess LiCl; two-stage drying of the DGAL-Cl precipitate, carried out at the first stage with heated air in the fluidized bed mode while maintaining the temperature in the drying zone 70-75°C to a residual moisture content of DHAL-Cl 9.0-9.5 wt.%, at the second stage in the mode vacuum drying with tedding and holding - 7 040900 temperature in the drying zone 60-65°C to a residual moisture content of DGAL-Cl 1.5-2.0 wt.%; preparing a paste by mixing the powder obtained from the dried DHAL-Cl precipitate with a solution of chlorinated polyvinyl chloride and an organochlorine solvent selected from the group consisting of methylene chloride, trichlorethylene, tetrachlorethylene, or mixtures thereof; extruding the resulting paste through a die with a diameter of 5 mm, followed by bringing the extrudate into countercurrent contact with a heated air stream, thus separating the extrudate from the organochlorine solvent, directing the extrudate to the vacuum degassing stage, followed by crushing and classifying the resulting granules; pelleting of DHAL-Cl granules with a size of not less than 1.0 mm and not more than 2.0 mm; to obtain a granular sorbent based on LiCl-2Al(OH) ₃ -nH2O, where an aluminum chloride solution is obtained by dissolving crystalline aluminum chloride hexahydrate in an aqueous solution containing lithium in the form of LiCl, Li ₂ CO ₃ or LiOH-H ₂ O, or mixtures thereof ; and the concentration of aluminum chloride in the solution is from 45 to 220 kg/m ³ . 2. The method according to claim 1, characterized in that the alkaline reagent is sodium hydroxide and sodium hydroxide is added until a pH of 6.5 to 7 is reached. 3. The method according to claim 1, characterized in that the removal of excess LiCl is carried out by forming a pulp of DHAL-Cl powder in water with additional centrifugation and separation of the DHALCl precipitate. 4. The method according to claim 1, characterized in that the excess LiCl, separated from the DHAL-Cl precipitate, is sent to the stage of obtaining an aluminum chloride solution containing lithium. 5. The method according to claim 1, characterized in that the Al:Li atomic ratio in the aluminum chloride solution containing lithium is from 2.0 to 2.3. 6. The method of claim 1 further comprising grinding the dried DHAL-Cl precipitate prior to making a paste. 7. The method according to claim 6, characterized in that the grinding is carried out to a particle size of <0.10 mm. 8. The method according to claim 1, characterized in that the air stream saturated with vapors of an organochlorine solvent or a mixture of vapors of an organochlorine solvent is sent to the compression stage with the release of an organochlorine solvent or a mixture of organochlorine solvents, which are returned to the paste preparation stage. 9. The method according to claim 8, characterized in that the stage of compression includes the condensation of an air stream saturated with vapors of an organochlorine solvent or a mixture of vapors of an organochlorine solvent, under a pressure of 6 atm with cooling to -3°C to obtain a liquid phase of a vapor of an organochlorine solvent or a mixture of vapors organochlorine solvents and water, followed by separation of the condensed phase from the gas phase by misting with sedimentation and phase separation of the organochlorine solvent or mixture of organochlorine solvents from water; cooling down to -15°C a compressed steam-air flow with condensation of vapors of an organochlorine solvent or a mixture of their vapors into a liquid phase and water vapor into ice crystals, followed by separation of the condensed phases from the air stream and separation of the condensed phases into a solid phase of ice and a liquid phase in the form of an organochlorine solvent, decompression of the air stream released from condensed phases with heating up to 0°C; heating the air flow to 120-130°C with a return to the operation of processing the extrudate with a heated air flow; isolation of liquid condensed phases of an organochlorine solvent or a mixture of organochlorine solvents. 10. The method according to claim 9, characterized in that after combining the ice crystals with the liquid condensed phase of water, the aqueous phase is fed to the stage of obtaining a solution of aluminum chloride containing lithium. 11. Granular sorbent based on the compound LiCl-2Al(OH) ₃ -nH ₂ O, obtained by the method according to any one of claims 1-10, having a mechanical strength of 98.9±0.2% to 99.2±0.2 % and static exchange capacity for LiCl, mg Li/g sorbent, from 5.9±0.1 mg to 6.2±0.1 mg.