EA042618B1 - METHOD FOR PRODUCING LITHIUM CONCENTRATE FROM LITHIEN-BEARING NATURAL BRINES AND ITS PROCESSING INTO LITHIUM CHLORIDE OR LITHIUM CARBONATE - Google Patents

Description

Technical field

The present invention relates to lithium hydrometallurgy and can be used to obtain lithium concentrates by enriching natural lithium brines and producing commercial lithium products from these concentrates.

State of the art

In world practice, lithium products are obtained from both solid mineral (spodumene, lepidolite, petalite) and hydromineral lithium-bearing raw materials (lake brines, salar brines, deep underground brines, mineralized waters).

At the same time, if in the last century, manufacturers of lithium products used mainly solid-mineral raw materials, then in the 21st century. preference is given to lithium-bearing hydromineral raw materials, since the use of raw materials of this type allows not only to build lithium enterprises with higher economic and environmental performance, but also to create production complexes for the deep processing of raw materials of this type, due to its multicomponent nature and the availability of other valuable components (Ostroushko Yu. I., Degtyareva T.V. Hydromineral raw materials - an inexhaustible source of lithium Analytical review TsNIIATOMINFORM, 1999, 64 pp.) [1].

All modern technologies for obtaining lithium salts from lithium-bearing hydromineral raw materials are based on its enrichment in lithium. The lithium enrichment of traditional lithium-bearing hydromineral raw materials (natural sodium chloride-type brines with a low content of magnesium and calcium), as a rule, is carried out by successive salting out of macrocomponents during evaporation (NaCl, KCl, KCl-MgCl ₂ -6H ₂ O, MgCl ₂ -6H ₂ O ) and simultaneous concentration of the initial lithium brine to the content allowing to produce lithium chloride and (or) carbonate of 98-99% purity from the obtained lithium concentrates (U.S. Pat. 4243392, U.S. Pat. 274834) [2, 3]. Purification of impurities (SO ₄ ^2- , Ca ²⁺ , Mg ²⁺ ) of lithium concentrates produced in this way is carried out with the transfer of impurities into sparingly soluble salts CaSO ₄ , CaCO ₃ , Mg(OH) ₂ using CaCl ₂ , CaO, Na ₂ CO ₃ (US Pat. US 4271131) [4]. After reagent purification before obtaining lithium products from lithium concentrates, as a rule, boron is extracted in the form of boric acid by extraction with high molecular weight alcohols (US patent 5219550) [5].

To obtain lithium products of higher qualification, lithium salts LiCl and Li ₂ CO ₃ produced from lithium concentrates are processed into more pure salts either using isopropyl alcohol, in which, unlike insoluble NaCl, KCl, CaCl ₂ , MgCl _2, lithium chloride is highly soluble ( US patent 4271131) [4], or by carbonizing lithium carbonate until it is completely converted into soluble and free from major impurities lithium bicarbonate, followed by decarbonization and precipitation of purer lithium carbonate (US patent 6207126) [6].

Thus, when receiving a lithium concentrate from traditional lithium-bearing hydromineral raw materials, its deep purification from impurities is not provided, since it is very difficult. The increase in the purity of lithium products produced from such a concentrate is carried out by repurifying the obtained products.

From non-traditional lithium-bearing hydromineral raw materials (natural brines of magnesium chloride, calcium chloride and mixed types) it is impossible to obtain lithium concentrates with a high concentration of lithium by traditional gallurgical methods, since the formation and salting out of double salts of the type LiCl-MgCl ₂ -6H ₂ O and LiCl-CaCl ₂ -5H ₂ O together with salted-out crystalline hydrates CaCl ₂ -6H ₂ O and MgCl ₂ -6H ₂ O. Therefore, obtaining lithium concentrates from non-traditional lithium-bearing hydro-mineral raw materials is possible only by selective extraction of lithium with subsequent concentration to a lithium content that makes it possible to produce lithium carbonate or chloride. US patents have appeared describing the use of sorbents for the selective isolation of lithium from lithium-bearing brines, which are microcrystalline lithium aluminates synthesized in the pores of an ion-exchange resin (US patents 4159311, 4221767, 4347327, 4477367, 5389349) [7–11]. However, under real operating conditions of such sorbents, it turned out that, firstly, the resin macropores are clogged with mechanical impurities contained in brines, hindering the access of lithium to the selective sorbent crystals, and secondly, the selective sorbent crystals are very quickly washed out of the carrier.

Later, a method was proposed for extracting lithium from lithium-bearing brines using a sorbent based on a coarse-grained variety of the LiX / Al (OH) ₃ compound, where X-OH-, Cl ^- , NO3 ^- , SO4 ^2- , capable of introducing lithium without breaking the structure (US patent 5599516) [12].

However, the main disadvantages of this method were large losses of the sorbent due to the destruction (cracking) of its crystals due to the inevitable local overvoltages in the synthesized crystals and the need to heat the desorbing liquid to 90°C when extracting lithium from a saturated sorbent.

A process has been developed for obtaining lithium concentrate by enrichment of natural lithium-bearing brines on a granular sorbent, the basis of which is a composite-amorphous ^variety of the compound LiCl-2Al(OH) ₃ -mH2O ¹ ) with a deficiency of LiCl, where m=3-5, with a defect in its structure, which allows, with appropriate preparation of the sorbent (water treatment), to create a deficiency of lithium in its composition and carry out a reversible process of intercalation of lithium chloride in a brine medium and its deintercalation in a fresh water medium water (Chemistry and technology for obtaining lithium compounds from lithium-bearing hydromineral raw materials) [13].

The method of obtaining a granular sorbent selective to lithium is described in the following sources: application PCT/DE. 01.04062, Germany [14], RF patents 2223142, 2455063 [15, 16]. Based on this sorbent, a method was developed for the selective extraction of lithium chloride from lithium-bearing natural brines with the release of a primary lithium concentrate capable of further concentration for lithium by any of the known methods, including evaporation. The use of a granular sorbent based on an amorphous variety of the LiCl-2Al(OH) ₃ -mH ₂ O compound instead of crystalline granules from a hydrated LiCl/Al(OH)3 compound makes it possible to carry out all technological operations of the enrichment process at room temperature, while obtaining a primary lithium concentrate, containing, depending on the concentration of lithium in the brine, 4.0 -6.0 g / l of lithium chloride with a residual content of the brine macrobase of not more than 6.0 g / l. To minimize the mass of a single load of granular sorbent in this development, a sorption-desorption enrichment module with a moving sorbent bed was used. Based on the use of a granular selective sorbent, a method for producing lithium chloride from lithium-bearing brines and an installation for its implementation are described (application PCT/DE 01/04061, Germany) [17].

However, along with the undoubted advantages described above, this method has disadvantages, one of which is a high degree of sorbent attrition (above 37% per year) during its movement in the equipment. Lithium chloride obtained by this method has a purity of not more than 98%. Obtaining the most popular lithium compound - lithium carbonate - this method does not provide. In addition, the implementation of the method in the variant of the moving bed of the sorbent requires the development of complex non-standardized equipment, which increases the cost of the practical implementation of this method.

In order to eliminate the shortcomings of this technological process, a method was proposed for obtaining lithium concentrate from natural brines and processing it into lithium products (RF patent 2516538) [18].

Elimination of the above disadvantages is achieved by the fact that in the proposed method for producing lithium concentrate from lithium-bearing brines, the process of enrichment of the brine for lithium is carried out in a sorption-desorption module consisting of two columns filled with a granular selective sorbent. One of the columns is constantly in the lithium saturation (intercalation) mode, while the other column is in the brine removal and lithium extraction (deintercalation) mode from the saturated granular sorbent. The mode of movement of the brine through the column at the stage of saturation can be either flow-through or portioned (portions of brine of a given volume with different content of LiCl, increasing in the order of use of the portions). In the batch mode of movement of the brine, the first portion of the brine that has passed the operation of contact with the granular sorbent is considered to be spent according to the lithium content. Removal of brine from a saturated granular sorbent is carried out by stepwise displacement of portions of sodium chloride solution or portions of lithium concentrate. The desorption of lithium chloride from the granular sorbent freed from brine is also carried out stepwise by portions of water with different LiCl content until the intercalated lithium chloride is completely removed from the granular sorbent. The resulting primary lithium concentrate-aqueous solution of LiCl with a concentration of 5.0-5.5 kg/m ³ containing CaCl ₂ , MgCl ₂ , NaCl, KCl, sulfation in the form of impurities, purified from calcium and magnesium by ion exchange on the KU-2 cation exchanger in Li form or by transferring into insoluble compounds CaCO ₃ and Mg(OH) ₂ -3MgCO ₃ -3H ₂ O by contacting the primary lithium concentrate with a solid phase of lithium carbonate at a temperature of 60-90°C. Next, the primary lithium concentrate is subjected to concentration in evaporation pools to a LiCl content of 220-350 kg / m ³ or by reverse osmosis, followed by evaporation to a LiCl content of 350-400 kg / m ³ , while salting out NaCl and KCl, diluted with demineralized water to a content of 190- 210 kg/m ³ , subjected to reagent purification from calcium and magnesium and used as a productive lithium concentrate to obtain lithium compounds: lithium carbonate, lithium hydroxide monohydrate, lithium chloride, etc. The proposed method allows to reduce the degree of sorbent attrition to 7-10% and to bring the purity of lithium carbonate produced by this method to 99.5%.

In terms of its technical essence and the achieved result, this method of obtaining lithium concentrate from lithium-bearing natural brines and its processing in terms of technical essence and the achieved result is the closest to the claimed method and was chosen by us as a prototype. Along with the advantages described above, the prototype method has the following disadvantages.

One of the disadvantages is the impossibility of achieving a high degree of lithium extraction from brines under conditions of achieving a high degree of saturation of the granular sorbent. To bring

- 2 042618 dynamic capacity for lithium chloride to a value close to the predicted value under conditions that provide the maximum driving force for the lithium intercalation process, that is, when filtering the initial brine through a layer of sorbent to the flow, the degree of extraction of lithium chloride from the brine is 50-55% . With a stepwise mode of contact of the brine with the sorbent, the degree of extraction of lithium chloride can be increased to 75-80%, but the total volume of the brine filtered through the sorbent for the same period of time increases several times. This has a particularly negative effect when processing brine with a low content of LiCl (below 1 kg/m ³ ), the total volumetric flow rate of the brine filtered through the sorbent is beyond the real throughput of the equipment.

The second significant disadvantage of this method is the organization of the process of displacing brine from the sorbent layer of the displacing liquid in the top-down direction and using a sodium chloride solution or primary lithium concentrate as a displacing liquid. The movement of the displacing fluid in the top-down direction leads to a significant compaction of the sorbent layer and an increase in hydraulic resistance. Due to the high content of CaCl ₂ and MgCl ₂ in the brine, during the contact of the brine with the sodium chloride solution, during displacement, sodium chloride is salted out from the solution and its solid phase is deposited in the sorbent layer. The use of primary lithium concentrate as a salting out liquid leads to a decrease in the yield of commercial primary lithium concentrate.

In addition, the purification of the primary lithium concentrate in the prototype method is associated either with high capital costs in the case of using the ion-exchange purification option on the KU-2 cation exchanger in Li-form, or with the low productivity of the purification process in the case of the option of removing calcium and magnesium in the form of sparingly soluble compounds when contact of the heated primary lithium concentrate with the solid phase of lithium carbonate, which is a significant disadvantage of this method. The disadvantages of the prototype method should also include: the lack of technological solutions for the purification of natural lithium-bearing brine from mechanical impurities, the lack of measures for the disposal of solid production waste in the form of sodium chloride when evaporating the mother liquor of the soda precipitation of lithium carbonate; the impossibility of obtaining battery-quality lithium carbonate (qualification 99.9%) due to the increased content of impurities in the form of alkali metals, calcium and magnesium. Among other things, the method does not provide for the production of anhydrous lithium chloride from a secondary lithium concentrate, which, along with lithium carbonate, is a popular commercial lithium product.

The proposed method for producing lithium concentrate from lithium-bearing natural brines and processing it into lithium chloride and (or) lithium carbonate retains all the advantages of the prototype and eliminates its main disadvantages.

The essence of the invention

The technical result, which makes it possible to eliminate these disadvantages, is achieved by the fact that in the proposed method, the natural brine is previously freed from suspended particles by sedimentation centrifugation of the brine with the removal of the resulting precipitate and subsequent filtering of the centrate on fine filters, if the content of suspended particles in the original natural lithium-bearing brine is 1 .0 kg/m ³ and above, or by filtering the original natural lithium-bearing brine on fine filters, if the content of suspended particles in the original natural brine is below 1.0 kg/m ³ ;

the regeneration of spent fine filters is carried out by backwashing with a filtered brine stream, followed by the flow of the spent regenerating brine to the precipitation centrifugation operation together with the original lithium-bearing natural brine.

The technical result is achieved by the fact that the primary lithium concentrate is obtained by its sorption enrichment for lithium using a granular sorbent based on the compound: LiCL2Al(OH) ₃ -mH ₂ O with a deficiency of LiCl, where m=3-5; primary lithium concentrate is produced in sorption-desorption modules, consisting of four columns filled with granular sorbent each, two of which are in the stage of sorption of lithium chloride from brine, one of the columns is in the stage of washing the sorbent saturated with lithium chloride from brine and one column is in the stage desorption of lithium chloride from a sorbent washed from brine, the flow of brine purified from suspended particles is always passed first through a column with a sorbent partially saturated with lithium chloride (the first stage of sorption), then through a column with a sorbent that has passed the stage of desorption of lithium chloride from the sorbent (the second stage of sorption ), while after complete saturation of the sorbent with lithium chloride in the first column along the brine flow, it is transferred to the stage of washing the sorbent from the brine, the column, which was in the stage of washing the sorbent from the brine, is transferred to the stage of desorption of lithium chloride from the saturated sorbent, the column that was in stages of desorption of lithium chloride from a saturated sorbent are transferred to the stage of sorption as a column of the second stage, using as the first stage of sorption a column with a partially saturated sorbent, which was used as a column of the second stage at the previous stage of sorption, then the cycle is repeated according to an experimentally substantiated cyclogram; linear velocity of liquid phases in columns at all

- 3 042618 stages of production of primary lithium concentrate are maintained at a level of 5-7 m/h, while washing the sorbent from the brine is carried out by preliminary draining the brine from the column, then stepwise washing of the sorbent sequentially with five portions of the washing liquid in the direction from bottom to top with a volume of 1/3 of the volume of the sorbent in the column each, four out of five portions are washing liquids with different contents of brine components in order of decreasing their content in the washing steps, and the fifth portion is the volume of fresh water, with the first portion of the washing liquid filling the column and displacing it from the column the second portion of the washing liquid, directing the displaced volume for mixing with the natural lithium-bearing brine purified from suspended particles, the second portion of the washing liquid is displaced from the column by the third portion of the washing liquid and used in the next washing cycle as the first portion of the washing liquid, the third portion of the washing liquid is displaced from the column of the fourth portion of the washing liquid and used in the next cycle as the second portion of the washing liquid, the fourth portion of the washing liquid is displaced by the fifth portion of the washing liquid (fresh water) and used in the next cycle as the third portion of the washing liquid, the fifth portion of the washing liquid is forced out of the column by the corresponding portion of the stripping liquid and is used in the next cycle as the fourth portion of the washing liquid, a fresh portion of fresh water is used as the fifth portion of the washing liquid in the next cycle, the desorption of lithium chloride from the sorbent washed from the brine is carried out by successive stepwise filtration of the given volumes of desorbing liquid, which is a dilute aqueous solution of lithium chloride with an admixture of the remainder of the brine components (desorbing liquid of the first stage), after contact with the sorbent, is removed from the process as a primary lithium concentrate, the second volume of the desorbing liquid, which is fresh water (desorbing liquid of the second stage), after contact with the sorbent, it is used as the stripping liquid of the first stage of the desorption stage in the next cycle, together with the volume of stripping liquid displaced from the column by the corresponding volume of lithium-bearing brine in the sorption stage of the next cycle;

The technical result is achieved by the fact that the primary lithium concentrate obtained from the lithium-bearing natural brine is converted into a secondary lithium concentrate by one of the options:

According to the first option, the primary lithium concentrate is subjected to helioconcentration with respect to lithium chloride in the evaporation pool with simultaneous purification from calcium and magnesium by preliminary division of the primary lithium concentrate into two streams, in one of which a given weight amount of lithium carbonate is pulped, the pulp is carbonized with carbon dioxide or a gas mixture, containing CO2, in the slurry circulation mode until lithium carbonate is completely dissolved, then this stream is mixed with another stream of primary lithium concentrate, the mixed solution is sent to the evaporation pool for concentrating the liquid phase in terms of LiCl up to 220 kg / m ³ , decarbonization and gradual transfer of soluble calcium chlorides and magnesium into sparingly soluble compounds CaCO ₃ and Mg (OH) ₂ -3Mg (OH) ₂ -3H ₂ O, which are separated from the concentrated solution of lithium chloride containing NaCl and KCl as the main impurities, bringing the resulting secondary lithium concentrate to the content of LiCl 190- 200 kg/m ³ used later to produce lithium chloride or lithium carbonate;

according to the second option, a given weight amount of Li ₂ CO ₃ is pulped in a stream of primary lithium concentrate produced by reverse osmosis concentration-desalination, the pulp is carbonized with carbon dioxide or a gas mixture containing CO ₂ in the pulp circulation mode until lithium carbonate is completely dissolved, the solution is heated to a temperature of 80- 85°C with a vacuum to 0.5 atm, decarbonize, directing the released carbon dioxide to the carbonization operation of the pulp prepared from lithium carbonate and reverse osmosis lithium concentrate, and simultaneously converting CaCl ₂ and MgCl ₂ into insoluble precipitates CaCO ₃ and Mg(OH) ₂ -3MgCO3-3H ₂ O, which are separated from the liquid phase, the liquid phase, which is an aqueous solution of LiCl with an admixture of NaCl and KCl, is concentrated by lithium chloride by electrodialysis or thermal means, or a combination of them, after which the LiCl solution is adjusted to a concentration of 190-200 kg / m ³ (secondary lithium concentrate), used later to produce lithium chloride or lithium carbonate.

The technical result is achieved by the fact that the production of lithium chloride from a secondary lithium concentrate is carried out by dividing it into two streams, one of which is first subjected to reagent purification from magnesium, calcium, sulfate and borate ions using hydroxide or barium oxide and carbon dioxide as reagents, then deep ion-exchange purification on polyampholyte Lewatit 208-TP in Li-form or its analogues, concentration by evaporation to the content of LiCl 485-490 kg / m ³ (lithium chloride brine), while salting out NaCl and KCl crystals, the resulting lithium chloride brine is cooled to room temperature, the precipitated NaCl and KCl crystals with an admixture of LiCl-H ₂ O crystals are separated from the liquid phase, the crystals are washed stepwise in the repulping and squeezing mode with three portions of the washing chloride brine with a volume equal to two portion volumes of the washed crystals each, two portions of which are mixed chloride

- 4 042618 solutions of NaCl + KCl + LiCl in order of decreasing content of LiCl in them, and the third portion is a mixed solution of alkali metal chlorides that do not contain LiCl, the first portion of the washing chloride solution after contact with the crystals (waste washing liquid) is sent to the evaporation operation , pre-mixing with a secondary lithium concentrate purified from impurities, two other portions of the washing chloride solution are used for successive stepwise washing of the next portion of the crystals, a fresh (third) portion of the chloride washing solution is prepared by dissolving sodium chloride or sodium chloride with an admixture of potassium chloride in demineralized water, with At the same time, the lithium chloride brine cooled and freed from crystals of precipitated salts with a residual NaCl + KCl content of not more than 2 kg / m ³ is evaporated until LiCl passes into the solid phase of lithium chloride monohydrate, the remainder of the mother liquor of the operation of evaporation of the lithium chloride brine and crystallization of LiCl-H ₂ O separated from the crystals of lithium chloride monohydrate and mixed with the purified secondary lithium concentrate supplied for evaporation, the crystals of lithium chloride monohydrate are washed from the remainder of the mother liquor with a washing liquid of the composition (wt.%): LiCl - (98.5-99.0), LiOH - ( 1.0-1.5), the waste liquid is acidified with hydrochloric acid to pH 6-7 and mixed with the purified secondary lithium concentrate supplied for evaporation, the washed LiCl-H ₂ O crystals are freed from residual alkalinity by contact with the calculated amount of hydrochloric acid and dried to obtaining anhydrous lithium chloride by two-stage drying in an air stream, maintaining the temperature in the drying zone at the first stage 85-90°C, at the second stage 108-110°C with a moisture content of the air stream at the exit from the drying zones of 75-80%, another secondary stream lithium concentrate is used to precipitate lithium carbonate from it upon contact with a solution of sodium carbonate or a solution of sodium carbonate containing potassium carbonate, the precipitated lithium carbonate is separated from the mother liquor of the Li ₂ CO ₃ precipitation operation by centrifugation and sent for pulping with a part of the flow of the primary lithium concentrate or with flow of reverse osmosis lithium concentrate for subsequent carbonization, the mother liquor of the lithium carbonate precipitation operation is acidified with hydrochloric acid to pH 6.0-6.5, evaporated until the LiCl concentration in the liquid phase reaches 485-490 kg/m ³ , the liquid phase is separated from the salted-out NaCl crystals with an admixture of KCl crystals and mixed with a stream of secondary lithium concentrate used to produce lithium chloride, NaCl crystals with an admixture of KCl crystals are washed from the remainder of the mother liquor, mixed with washed NaCl and KCl crystals salted out during the evaporation process of a stream of secondary lithium concentrate in the production of LiCl, dissolved in the calculated volume of demineralized water, obtaining an alkali metal chloride solution with a NaCl concentration of 250-260 kg/m ³ , the resulting solution is subjected to membrane electrolysis, producing a NaOH solution and hydrogen at the cathode and chlorine at the anode, the hydrogen produced is mixed with a natural gas stream, the mixture gases are burned using thermal energy to produce heating water vapor, which, in turn, is used as a heat carrier during the evaporation of lithium concentrates and the mother chloride solution of the Li2CO3 precipitation operation, the CO2-containing flue gas carbonizes the NaOH solution, turning it into a Na2CO3 solution (carbonate solution ) and using as a precipitating agent in the lithium carbonate precipitation operation, anodic chlorine is ejected with a stream of an aqueous solution of urea, thus producing a solution of hydrochloric acid used to acidify carbonate-containing solutions before their evaporation and to regenerate spent polyampholyte Lewatit 208-TP;

The technical result is achieved by the fact that the production of technical lithium carbonate from a secondary lithium concentrate that has undergone reagent purification from calcium, magnesium, sulfate and borate ions is carried out by precipitation of lithium carbonate from the entire stream of secondary lithium concentrate by contact with stirring and at a temperature of 90-95 ° C with a solution of sodium carbonate containing potassium carbonate, while after separation from the mother liquor, one part of lithium carbonate is used to obtain a solution of lithium bicarbonate and then to purify the primary lithium concentrate or reverse osmosis lithium concentrate from calcium and magnesium, the other (productive) part of lithium carbonate is washed stepwise in the mode of pulping and centrifugation with three portions of the wash solution with a volume equal to three volumes of a portion of the washed lithium carbonate at a temperature of 90-95 ° C, first with two portions of a saturated solution of lithium carbonate in order of decreasing sodium and chloride ion content in them and then with a portion of demineralized water , while the first portion of the washing solution after contact with lithium carbonate is sent to the operation of obtaining a pulp of Li ₂ CO ₃ used for carbonization, transferring the solid phase of Li ₂ CO ₃ to a solution of LiHCO ₃ and using for purification of primary lithium concentrate or reverse osmosis lithium concentrate from calcium and magnesium, two other portions of the washing solution are used for successive stepwise washing of the next portion of lithium carbonate, the washed lithium carbonate crystals are subjected to microwave drying to a residual moisture content of 0.4 wt.%

The technical result is achieved by the fact that the production of battery-quality lithium carbonate from a secondary lithium concentrate that has undergone reagent purification from calcium, magnesium, sulfate and borate ions and deep ion-exchange purification from calcium and magnesium on Lewatit 208-TP polyampholyte in Liform is carried out by precipitation with saturated water ammonium carbonate solution at room temperature

- 5 042618 temperature, the lithium carbonate precipitate is separated from the mother solution of ammonium chloride, one part of the lithium carbonate precipitate is used to obtain a lithium bicarbonate solution, further used to purify the primary lithium concentrate or reverse osmosis lithium concentrate from calcium and magnesium, the other (productive) part of the carbonate precipitate lithium is washed stepwise in the mode of repulpation and centrifugation with three portions of the washing solution with a volume equal to three portions of a portion of the washed lithium carbonate each, at a temperature of 90-95 ° C, and first with two portions of a saturated solution of lithium carbonate in order of decreasing the content of ammonium and chloride ions in them and then with a portion of demineralized water, the first portion of the washing solution after contact with lithium carbonate is sent to the operation of obtaining a pulp of Li ₂ CO ₃ used for carbonization, transferring the solid phase of Li ₂ CO ₃ to a solution of LiHCO ₃ and using for purification of primary lithium concentrate or reverse osmosis lithium concentrate from calcium and magnesium, two other portions of the washing solution are used for sequential washing of the next portion of lithium carbonate, the washed crystals of lithium carbonate are subjected to microwave drying to a residual moisture content of 0.2 wt.%, ammonium chloride is salted out from the mother liquor of the lithium carbonate precipitation operation by evaporation, after separation from the mother liquor of evaporation, it is washed from the remainder of the mother liquor, the spent washing solution is sent for evaporation, mixing with the mother liquor of the lithium carbonate precipitation operation, in turn, the mother liquor of the operation of evaporation and salting out of ammonium chloride crystals, which is a solution of LiCl 480-490 kg / m ³ with an admixture of NH ₄ Cl, mixed with a secondary lithium concentrate before its ion-exchange purification on Lewatit 208-TP polyampholyte in Li-form, ammonium chloride washed from the mother liquor is decomposed by treating with an aqueous pulp containing CaO or CaO with an admixture in the form of a solid phase MgO, SiO ₂ and Fe ₂ O ₃ , removing the released ammonia, mixing it with carbon dioxide in a ratio of 2:1 and absorbing the mixture of gases with water while cooling in a stepwise countercurrent mode of contact of the liquid and gas phases with the withdrawal of the spent absorbent in the form of a saturated solution of ammonium carbonate , used to precipitate lithium carbonate, the pulp formed after removal of ammonia is separated by filtration or centrifugation, the liquid phase, which is a solution of calcium chloride with an admixture of NaCl and KCl, is removed from the process and used in public utilities as a reagent for strengthening dirt roads (summer period) and as an anti-icing reagent (winter period), the solid phase, which is MgO with an admixture of SiO ₂ and Fe ₂ O ₃ , is used to produce magnesium products, calcium oxide and carbon dioxide, necessary for the decomposition of ammonium chloride and the production of a solution (NH ₄ ) ₂ CO ₃ is obtained by thermal decomposition of the precipitate of CaCO ₃ and Mg(OH) ₂ -3MgCO ₃ -H ₂ O salts, formed during the purification of the primary lithium concentrate from calcium and magnesium, mixed with crushed natural limestone or dolomite.

The advantages of the proposed solutions in comparison with the prototype method consist of the following.

1. In expanding the range of lithium-bearing hydro-mineral raw materials suitable for the production of lithium compounds through the use of lithium-bearing natural brines containing suspended particles in their composition.

2. In increasing the degree of selective extraction of lithium chloride during the sorption enrichment of lithium-bearing natural brines for lithium chloride on a granular sorbent DGAL-Cl to obtain a primary lithium concentrate.

3. In reducing the losses of lithium chloride and reducing energy costs in the production of lithium concentrate by developing a rational scheme for removing brine from the columns of sorption-desorption modules before the desorption operation.

4. In a more economical way to purify primary lithium concentrate or reverse osmosis lithium concentrate from calcium and magnesium.

5. In the production of anhydrous lithium chloride with a qualification corresponding to TU 95.1926-89 and suitable for the production of battery-quality lithium metal.

6. In the exclusion of the use of imported soda in the production of technical Li2CO3 by replacing it with a soda solution produced from the mother liquor of the Li2CO3 precipitation operation and the exhaust flue gas.

7. In the possibility of production from primary lithium concentrate of lithium carbonate of battery quality with the replacement of imported expensive soda reagent with cheaper local limestone or dolomite.

Information confirming the possibility of implementing the proposed invention is presented in Fig. 1-4 and in the examples.

List of drawings

Fig. 1 (sheets 1.1, 1.2, 1.3, 1.4) - a technological scheme for obtaining primary lithium concentrate from lithium-bearing natural brines and processing it into anhydrous lithium chloride

Fig. 2 - scheme of operation of the sorption-desorption module of four columns with granular selective sorbent DGAL-Cl.

Fig. 3 (sheets 3.1, 3.2, 3.3) - technological scheme for obtaining primary lithium concentrate

- 6 042618 from lithium-bearing natural brines and processing it into technical lithium carbonate according to the soda scheme.

Fig. 4 (sheets 4.1, 4.2, 4.3) - a technological scheme for obtaining primary lithium concentrate from lithium-bearing natural brines and processing it into lithium carbonate of battery quality according to a lime scheme.

Note: in schemes 1, 3, 4 abbreviations are accepted: DHAL-Cl-granular sorbent based on a chlorine-containing variety of double aluminum hydroxide, lithium; PZh-flushing fluid.

The following is a description of the implementation of the proposed method.

In accordance with the technological scheme (Fig. 1) obtaining primary lithium concentrate from lithium-bearing natural brine and its processing into anhydrous lithium chloride is carried out as follows. The original natural brine goes through the stage of purification from mechanical impurities. When the content of mechanical impurities is 1.0 kg/m ³ and above, the brine is subjected first to precipitation centrifugation, then fine filtration. Regeneration of spent filter elements is carried out by a flow of filtered brine supplied countercurrently to the direction of the brine during filtration cleaning. The spent brine from the operation of regeneration of the filter elements is mixed with the original natural brine supplied for centrifugation.

The brine purified from mechanical impurities is first sent to recuperative heating with a stream of lithium-used brine that has passed the sorption enrichment stage, then to heating by utilizing the process heat generated during evaporation and cooling operations, where natural brine is used as a refrigerant.

The heated brine enters the sorption-desorption complex for the selective two-stage sorption of lithium chloride by the granular sorbent DGAL-Cl. At the first stage of sorption, the brine flow contacts with a partially saturated sorbent, thereby ensuring the complete saturation of the latter during the time period allotted for the sorption operation. At the same time, at the second stage of sorption, the brine flow, freed from lithium chloride by 45–55%, contacts the initial (fresh) sorbent, where it is freed from lithium chloride by another 45–55%, partially saturating the sorbent. The brine that has passed the sorption stage (mother brine) is subjected to filtration in order to capture the fine fraction of the sorbent carried out of the columns. The sorbent of the first stage, saturated with lithium chloride, is first released from the brine by draining it from the column and returning the drained volume to sorption, then by stepwise successive washing with five volumes of washing liquid, four of which contain washing liquid with different contents of brine components in order of decreasing content with increasing washing steps, and the fifth portion is fresh water. The column freed from brine is filled with the first portion of the washing liquid (PJ-1) and it is displaced from the column with the second portion of the washing liquid (PJ-2). Directing the displaced volume for mixing with the suspended solids-free and heated natural lithium-bearing brine, the second portion of the washing liquid is displaced from the column by the third portion of the washing liquid (PZh-3) and used in the next cycle as PZh-1, the third portion of the washing liquid is displaced from the column of the fourth washing liquid (PZh-4) and used in the next cycle as PZh-2, the fourth portion of the washing liquid is displaced by the fifth portion of the washing liquid (fresh water) and used in the next cycle as PZh-3, the fifth portion of the washing liquid is displaced from the column by the corresponding portion of the desorbing liquid (aqueous solution of LiCl) and used in the next cycle as PJ-4. As the fifth portion of the washing liquid in the next cycle, a fresh portion of fresh water is used; this organization of brine removal from the column is optimal, since it provides a sufficiently deep degree of brine removal (above 98%) with a minimum number of washing steps equal to five. A predetermined amount of lithium chloride is desorbed from the sorbent washed from the brine and saturated with lithium chloride by filtration through the sorbent layer of portions of predetermined volumes of desorbing liquids, based on the fact that the first portion of the desorbing liquid, which is a dilute aqueous solution of lithium chloride with an admixture of the remainder of the brine components, after contact with sorbent is removed from the process as a primary lithium concentrate. The second portion of the stripping liquid, which is fresh water, after contact with the sorbent, is used as the stripping liquid of the first stage in the next cycle, together with the volume of the stripping liquid displaced from the sorbent by the corresponding volume of lithium-bearing brine at the sorption stage of the next cycle. A more detailed diagram of the cycle of operation of the sorption-desorption module of four columns is shown in Fig. 2. The resulting primary lithium concentrate is filtered to capture the fine fraction of the sorbent removed from the sorption-desorption columns during the desorption process.

After filtration, the primary lithium concentrate is subjected to reverse osmosis concentration-desalination, producing reverse osmosis lithium concentrate with a total mineralization of up to 60 kg/m ³ , on the one hand, and permeate (demineralized water with a total mineralization of not more than 30 g/ ^m flushing, displacing and desorbing fluids, thus reducing fresh water consumption. In turn, in the reverse osmosis lithium concentrate, pre-mixed with the spent regenerate of the ion-exchange purification of the secondary lithium concentrate and the washing carbonate solution of the lithium carbonate precipitation operation,

- 7 042618 the calculated amount of lithium carbonate is pulped, the pulp is carbonized with carbon dioxide until the lithium carbonate is completely dissolved and it passes into the lithium bicarbonate solution according to the reaction:

L12CO3 + CO ₂ + H ₂ O 2L1HCO3 (1).

The resulting bicarbonate-chloride lithium-containing solution is concentrated to a LiCl content of 190-200 kg/m ³ by evaporation with simultaneous purification from calcium and magnesium, producing a secondary lithium concentrate. At the same time, in the case of using a natural helioconcentration solution in pools for evaporation, the process of natural evaporation is accompanied by a gradual decomposition of lithium bicarbonate and the transfer of calcium and magnesium ions into insoluble compounds by CO3 ^2- and OH ^- anions formed during the decomposition of LiHCO3.

The process can be described by the following chemical reactions:

2LiHCO ₃ Li ₂ CO ₃ + H ₂ O + CO2T (2),

Li ₂ CO ₃ + H ₂ O L1HCO3 + LiOH (3),

Ca ²⁺ + CO3 ² ' CaCO3T (4),

4Mg ²⁺ + 3CO3 ² ' + 2OH- + 3H ₂ O Mg(OH) ₂ 3MgCO ₃ 3H ₂ O|(5).

In the absence of the possibility of using natural helioconcentration, the lithium-containing chloride-bicarbonate solution is first heated with vigorous stirring and a rarefaction of 0.5 atm to a temperature of 85 ° C, decarbonizing and precipitating calcium and magnesium into insoluble compounds CaCO ₃ and Mg (OH) ₂ -3MgCO ₃ -3H ₂ O. The process of complete decarbonization takes 45-60 minutes. After completion of the decarbonization process and sedimentation of impurities, the solution after acidification is evaporated to obtain a secondary lithium concentrate and juice vapor condensate.

The resulting secondary lithium concentrate after mixing with a concentrated solution of LiCl obtained during the processing of the mother liquor of the lithium carbonate precipitation operation is sent for reagent purification from calcium, magnesium and sulfate ions due to an increase in the content of impurities as a result of evaporation of the secondary lithium concentrate. Reagent purification is carried out on the basis of two possible options. According to the first option, BaCl ₂ is used as a reagent for barium precipitation, and the calculated amount of Na ₂ CO ₃ is used as a reagent for removing calcium and magnesium.

The purification process can be described by the following equations of chemical reactions:

Wa ²⁺ + SO?' _BaSO4 |(6),

CaCh + Na ₂ CO ₃ CaCO3 | + 2NaCl(7),

Na ₂ CO ₃ + H ₂ O -► NaOH + NaHCO ₃ (8),

4MgCl ₂ + 3Na ₂ CO ₃ + 2NaOH + 3H ₂ O Mg(OH) ₂ 3MgCO ₃ 3H ₂ O + 8NaCl (9).

According to the second option, Ba(OH) ₂ is used as a reagent for purification of secondary lithium concentrate from sulfate ions, and LiHCO ₃ solution obtained by carbonization of pulp prepared from calculated amounts of lithium carbonate and washing carbonate solution. The purification process according to this option can be described by the following chemical reactions:

Ba(OH) ₂ Ba ²⁺ + 2OH'(10),

Ba ²⁺ + SO4 ² ^BaSO4|(11),

HCO ³ ' + OH' Aoc + H ₂ O (12),

Ca ²⁺ + CO3 ² '^CaCO3! (13),

4Mg ²⁺ + 3CO3 ² ' + 2OH- + 3H ₂ O Mg(OH) ₂ 3MgCO ₃ 3H ₂ O^(14).

The feasibility of using one or another treatment option is determined at the production design stage.

After filtration and separation from the solid phase of precipitation, the reagent-purified secondary lithium concentrate, which is a solution of lithium chloride, is divided into two given streams, one of which is directed to the precipitation of Li ₂ CO ₃ by contact with a saturated solution of Na ₂ CO ₃ . The resulting Li ₂ CO ₃ is used to purify the primary lithium concentrate or purify the reverse osmosis lithium concentrate from calcium and magnesium. Another stream of lithium chloride solution is directed to deep ion-exchange purification from the residual amount of calcium and magnesium on Lewatit 208TP ampholyte in Li-form or its analogues.

The process of ion-exchange purification is described by the following equations.

1) Sorption and

Ca ²⁺ + [L] - |L|=Ca + 2Li' (15),

Li

Li

Mg ²⁺ + [L] ' [L]=Mg + 2Li ⁺ (16).

Li

2) Regeneration

- 8 042618 / ⁿ [L]=Ca + [L]=Mg + 4HC1 ^2[L] + CaCl ₂ + MgCl ₂ (17).

\H

3) Transfer to Li-form

HLi

2[L] + 4LiOH^2[L] + 4H ₂ O(18).

HLi

The transfer of the resin to the Li-form can also be carried out with a LiHCO ₃ solution used instead of a LiOH solution according to the reaction:

H

[L] _h + 2L1HCO3 ^ [L] _χ + 2Н ₂ 0+2С0 ₂ (19).

HLi

The spent regeneration solution is sent for mixing with reverse osmosis lithium concentrate to prepare Li ₂ CO ₃ slurry by carbonization and use for purification of reverse osmosis lithium concentrate or primary lithium concentrate from calcium and magnesium.

The stream of secondary lithium concentrate, which has undergone deep purification from calcium and magnesium, is evaporated to a LiCl content of 485-490 kg/m ³ , cooled to room temperature, salting out NaCl and KCl from the solution to their residual total concentration not exceeding 4 kg/m ³ .

After separating the crystals of NaCl and KCl from the LiCl solution, the latter is evaporated, crystallizing lithium chloride monohydrate (LiCl-H ₂ O), the resulting crystals are separated from the remainder of the liquid phase by centrifugation. The centrate is returned to evaporation, the LiCl-H ₂ O crystals are washed from the remainder of the mother liquor with an alkaline chloride solution (1.0-1.5 wt.% LiOH in a saturated LiCl solution). The addition of LiOH to the LICl solution ensures that the residual sodium and potassium impurities contained in the solid phase of the LiCl-H ₂ O crystalline hydrate are transferred to the wash solution. The spent washing solution containing sodium and potassium after acidification is sent for mixing with secondary lithium concentrate deeply purified from calcium and magnesium and evaporation. The LiCl-H ₂ O crystals washed from the mother liquor are sent to a two-stage drying process. Drying is carried out in a stream of air. In the first stage, the crystals of lithium chloride monohydrate are dried to a residual moisture content of 10-12 wt.% at a temperature in the drying zone of 90°C. In the second stage, the temperature in the drying zone is raised to 110°C, obtaining anhydrous LiCl with a residual moisture content of <4 wt.%, corresponding to the requirements of THE 95.1926-89. To avoid condensation of water vapor, the relative humidity of the air at the outlet of the drying zones in both stages is maintained within 75-80%. The crystals of NaCl and KCl, which contain crystals of LiCl-H2O as an impurity, which have been dried out during the evaporation process of the secondary lithium concentrate purified from impurities, are washed with a saturated chloride solution prepared from a mixture of NaCl and KCl crystals. The washed crystals of NaCl and KCl are used as raw materials to obtain an alkaline solution (NaOH and KOH), which in turn is used to obtain a carbonate solution (Na ₂ CO ₃ and K ₂ CO ₃ ). Lithium-containing waste washing solution, formed as a result of washing the NaCl and KCl crystals, is sent for mixing with a purified secondary lithium concentrate and evaporation. In turn, the mother liquor of the lithium carbonate precipitation operation, which is a NaCl solution with a concentration of 220-230 kg / m ³ with an admixture of KCl (content 2 kg / m ³ ) and Li ₂ CO ₃ (content 11-12 kg / m ³ ), acidified, decarbonized and evaporated, salting out crystals of NaCl and KCl, until the concentration of LiCl in stripped off solution of 485-490 kg/m ³ .

After separating the lithium-containing liquid phase from the NaCl and KCl crystals, it is sent for mixing with the secondary lithium concentrate supplied to the reagent purification from impurities. NaCl and KCl crystals are washed from the mother liquor with juice vapor condensate, mixed with NaCl and KCl crystals separated as a result of evaporation of the flow, secondary lithium concentrate deeply purified from calcium and magnesium, sent to obtain commercial lithium chloride, the mixture of crystals is dissolved in juice vapor condensate, producing an aqueous solution of NaCl with an admixture of KCl with a total salt content of 260-270 kg/m ³ . The solution is deeply purified from impurities of calcium and magnesium by ion-exchange on Lewatit 208-TP resin in the Na form and sent to membrane electrolysis to obtain a NaOH solution (catholyte) and anode chlorine gas. The catholyte is carbonized with flue gas, producing a saturated solution of Na ₂ CO ₃ according to the reaction:

CO ₂ + 2NaOH Na ₂ CO ₃ + H ₂ O (20).

Soda solution is used as a precipitation agent to obtain a given amount of Li ₂ CO ₃ . Flue gas is a waste product of the process of production of heating steam in a waste heat boiler by burning a gas mixture consisting of natural gas and hydrogen. The gas mixture is obtained by ejection of cathode hydrogen from the gas separator of the catholytic circuit of the membrane electrolysis unit with the flow of the initial natural gas. Anode chlorine is converted into a 3.0N-3.5N hydrochloric acid solution by ejection of anode chlorine with a stream of an aqueous solution of carbamide from the gas separator of the anolyte circuit of the membrane electrolysis unit, followed by absorption, accompanied by the following chemical reaction:

3Cl ₂ + (NH ₂ ) ₂ CO + H ₂ O 6HC1 + N4 + SOD (21).

- 9 042618

Hydrochloric acid solution is used for regeneration of ion exchange resin, acidification and decarbonization of solutions before evaporation and for other production purposes.

The technology for obtaining primary lithium concentrate and its processing into technical lithium carbonate (Fig. 3) differs from the technology for obtaining primary lithium concentrate and its processing into anhydrous lithium chloride only in that the entire flow of secondary lithium concentrate produced and purified from impurities of calcium and magnesium is processed into Li ₂ CO ₃ in the same way.

The technology for obtaining primary lithium concentrate and its processing into battery-quality lithium carbonate is shown in Fig. 4. The main differences between this technology and the technology for producing technical lithium carbonate (Fig. 3) is that the flow of reagent-purified secondary lithium concentrate from impurities of calcium and magnesium is subjected to deep ion-exchange purification on Lewatit 208-TP ampholyte in Li-form or its analogues, and the precipitation of lithium carbonate from a secondary lithium concentrate deeply purified from impurities is carried out with ammonium carbonate according to the reaction:

2LiCl + (NH ₄ ) ₂ CO ₃ -+ Li ₂ CO ₃ + 2NH ₄ C1 (22).

At the same time, the mother liquor of the precipitation operation, which is an aqueous solution of NH ₄ Cl with a small admixture of NaCl and KCl after acidification, is evaporated by salting out NH ₄ Cl, to a LiCl content of 485-490 kg/m ³ . The liquid phase after the separation of the crystals is sent for mixing with a secondary lithium concentrate before its ion-exchange purification, and the NH ₄ Cl crystals with impurities are brought into interaction with the CaO or CaO slurry with an admixture of MgO, produced by decomposition of the CaCO ₃ precipitate with an admixture of 3MgCO ₃ -Mg (OH ) ₂ -3H ₂ O or limestone and dolomite according to the reaction:

t=850°C

CaCO3 CaO + CO ₂ ((23), t=850°C

CaCO3 + MgCO ₃ CaO + MgO + 2CO ₂ ?(24).

The interaction of NH ₄ Cl with CaO in the presence of water proceeds with the release of heat (Q) and is accompanied by intensive distillation of ammonia in accordance with the exothermic reaction:

2NH ₄ C1 + CaO 2NH D + CaC1 ₂ + H ₂ O + Q(25).

In turn, the gaseous mixture of ammonia with carbon dioxide formed during the production of CaO is absorbed by water while cooling in countercurrent mode, obtaining a concentrated solution of (NH ₄ ) ₂ CO ₃ according to the reaction:

2NH3 + CO ₂ + H ₂ O (NH ₄ ) ₂ CO3 (26).

The (NH ₄ ) ₂ CO ₃ solution produced in this way is used to precipitate Li ₂ CO ₃ from the highly purified secondary lithium concentrate (reaction 22).

The mother slurry formed at the operation of lime decomposition of NH ₄ Cl and distillation of NH ₃ is centrifuged, separating the solid phase of MgO with an admixture of SiO ₂ and Fe ₂ O ₃ from the liquid phase. The liquid phase, which is a solution of CaCl ₂ 250-270 kg / m ³ with a small admixture of NaCl and KCl 2-4 kg / m ³ , is used either in public utilities as an anti-dust and anti-icing agent, or as a reagent to reduce the content of sulfate ions in the original natural brine, if the brine is characterized by a high content of sulfate ions.

Since the content of sodium and potassium chlorides in the secondary lithium concentrate deeply purified from calcium and magnesium is in the range of 2-4 kg / m ³ , after washing the precipitated lithium carbonate from the mother liquor, the total concentration of sodium and potassium in the finished product is less than 0.002 wt.% The main impurity in the washed Li ₂ CO ₃ is NH ₄ Cl. However, during the drying process of wet lithium carbonate, NH ₄ Cl is hydrolyzed, eventually forming volatile products NH ₃ and HCl in accordance with the chemical reaction equation:

t=80-90°C

NH ₄ C1 + H ₂ O NH ₄ OH + NSC (27).

t<20°C

NH ₄ OH - + N ND + H ₂ O (28).

Thus, the proposed technological process (Fig. 4) makes it possible, in the presence of a limestone or dolomite deposit, to produce lithium carbonate of battery quality from polycomponent lithium-bearing natural brines, while reducing the cost of production by replacing expensive soda with cheaper reagents limestone or dolomite.

In the following, the invention is illustrated by specific examples.

Example 1

Natural drainage lithium-bearing brine with a density of 1215 g / dm ³ , pH 6.2, material composition (g / dm ³ ): LiCl - 1.16; NaCl - 53.5; KCl - 21.3; CaCl ₂ - 182.3; MgCl ₂ - 47.2; Br-- 4.0; Fe _total - 0.01; suspended particles - 4.3; the total salt content of 305.4 g/DM ³ was subjected to centrifugation on a precipitation laboratory centrifuge, the centrifuge was separated from the precipitate of the solid phase. The centrifuge was analyzed for the residual content of suspended particles and filtered on a fine fabric filter. The filtrate was analyzed for the content of suspended particles. The suspended particles caught on the filter were washed off with a countercurrent flow of a mixture of the filtrate with air (regenerate). The spent regenerate was analyzed for

- 10 042618 content of suspended particles. The results obtained are presented in table. 1.

From the contents of the table it follows that the combined purification of natural brine from suspended particles (centrifugation + filtration) provides a degree of purification at the level of 99.9%. At the same time, the regeneration of the filter requires no more than 5% of the volume of the filtered brine, providing the concentration of suspended particles in the flow of the spent regenerate, close to the content of suspended particles in the original brine.

Table 1

The content of suspended particles in the original brine, g / dm ³ The volume of the original centrifuged brine, dm ³ Residual content of suspended particles in centrate, g/dm ³ Residual content of suspended particles in centrifuge filtrate, g/dm ³ Volume of filtrate used for filter regeneration, dm ³ Concentration of suspended particles in spent regenerate, g/dm ³ 4.36 2.17 0.24 Less than 0.005 0.13 3.95

Example 2

On a laboratory bench representing sorption-desorption modules of two columns (prototype) and four columns (proposed module, Fig. 4), comparative tests were carried out using natural formation lithium-bearing brine of the Znamenskoye deposit, Irkutsk region, purified from suspended particles and iron. The composition of the brine (g/DM ³ ): LiCl - 2.5; NaCl - 6.1; KCl - 8.2; CaCl ₂ - 330; MgCl ₂ - 115; Br ^- - 10.1; total salt content 472 g/dm ³ , pH 4.2. 28.2 dm ³ of the initial brine were passed through each of the modules: in the prototype, through one column with a sorbent that passed the regeneration stage, in the proposed module, through two columns in series (the first column along the brine flow with a partially saturated sorbent, the second column with a sorbent passed through the regeneration stage). The results of comparative tests are presented in table. 2.

From the contents of Table 2 it clearly follows that the degree of extraction in the proposed sorption-desorption module is more than 1.6 higher than in the prototype module. In addition, the degree of saturation of lithium chloride sorbent in the frontal column (column, passing in the stage of removal of brine and regeneration) in the proposed module is 10% higher than in the prototype.

table 2

Design of the sorption-desorption module The volume of the missed brine, dm ³ The volume of the sorbent in the column, DM ³ The degree of extraction of LiCl from brine, % The average content of LiCl in the sorbent of the frontal column, g / dm ³ Prototype 28.2 3.7 56.1 1.76 Proposed 28.2 3.7 93.0 1.95

Example 3

On a pilot plant, consisting of two identical sorption-desorption columns prepared for the stage of brine removal with loading of 3.7 dm ³ granular sorbent DGAL-Cl each, comparative tests were carried out according to the following procedure.

In column No. 1, a displacing fluid (an aqueous solution of LiCl with a concentration of 6 g/dm ³ ) with a volume of 10 dm ³ was pumped in the direction of the flow of the displacing fluid through the section of the column from top to bottom. In column No. 2, the displacing liquid was supplied with the same volume by a similar pump in the direction from bottom to top. The initial displacement fluid flow through both columns was set at 0.2 dm ³ /min. By the end of the experiment, the liquid flow through column No. 1 decreased to 0.08 dm ³ /min, while the flow through column No. 2 was unchanged throughout the experiment. At the same time, 10 dm ³ of the displacing liquid was passed through column No. 1 for 77 minutes, while the same volume of displacing liquid was passed through column No. 2 for 50 minutes. The results obtained unambiguously show that the displacement of brine from the sorbent bed in the downward direction leads to compaction of the granular layer and a significant increase in its resistance to the displacement flow, which ultimately leads to an increase in pressure in the column while maintaining a constant flow rate of the washing liquid. Further, comparative tests were continued in the direction of establishing the influence of the direction of movement of the displacing fluid on the depth of washing from the brine. For this purpose, LiCl was desorbed from the sorbent freed from brine in columns No. 1 and No. 2. As a result of desorption, the following primary lithium concentrates were obtained. Concentrate from column No. 1 (composition, g/dm ³ ): LiCl - 5.3; residual brine - 6.4. Concentrate from column No. 2 (composition, g/dm ³ ): LiCl - 5.1; residual brine - 6.2. The experiment showed that the depth of washing the sorbent from the brine practically does not depend on the direction of movement of the displacing liquid through the sorbent layer. Thus, by the combination of two factors, the displacement of the brine in the direction

- 11 042618 from bottom to top is preferred.

Example 4

On a pilot stand, including a sorption-desorption module of four columns, we studied the effect of the number of stages of washing the sorbent from brine in the column that passed the sorption stage on the residual brine content in the resulting primary lithium concentrate. The study was carried out in a steady state, strictly following the sequence of technological operations presented in Fig. 1. As a lithium-bearing brine, the natural brine of the Znamensky deposit of the Irkutsk region was used (composition in example 2). The loading volume of the granulated sorbent in the columns of the sorption-desorption module was 3.7 DM ³ . The volume of washing liquid at each of the washing steps was 1.1 DM ³ . The results obtained are presented in table. 3.

Studies have shown that the optimal number of steps in the stepwise countercurrent washing of the sorbent from brine is five washing steps, since a further increase in the number of washings does not lead to a significant increase in the purity of the resulting primary lithium concentrate, while operating costs associated with an increase in the number of washings increase. essential. At the same time, a reduction in the number of washing stages leads to an increase in the content of brine components in the primary lithium concentrate by more than three times.

Table 3

Number of wash steps Volume for- loads of sorbent Wash liquid volume The composition of the original brine, g / dm ³ Composition of produced primary lithium concentrate columns SDK, dm ³ at each step, DM ³ LiCl the remaining components of the brine in total LiCl the remaining components of the brine in total 3 3.7 1.1 2.5 469.5 6.0 77.2 4 3.7 1.1 2.5 469.5 5.9 23.7 5 3.7 1.1 2.5 469.5 6.1 6.9 6 3.7 1.1 2.5 469.5 6.0 6.4

Example 5

On the experimental stand was processed 200 dm ³ natural lithium-bearing brine Znamenskoye deposits of the Irkutsk region (composition in example 2). Processing was carried out according to the technological schemes shown in Fig. 1 and 2, producing anhydrous lithium chloride. In this case, a variant of reverse osmosis preconcentration of the primary lithium concentrate was used with purification of the reverse osmosis lithium concentrate from calcium and magnesium by thermal decomposition of lithium bicarbonate produced as part of the reverse osmosis lithium concentrate by carbonization of the solid phase of lithium carbonate with carbon dioxide, previously introduced into the composition of the reverse osmosis lithium concentrate. To obtain lithium carbonate, necessary for the purification of reverse osmosis lithium concentrate, in this experiment, a soda solution with a concentration of 300 g/dm ³ obtained by dissolving commercial Na ₂ CO ₃ in demineralized water was used. As a result, 464.8 g of anhydrous lithium chloride were obtained, the chemical composition of which is presented in table. 4.

Table 4

Substance (element, ion) Content, % May. LiCl 99.52 (Na + K) 0.03 Sa Less than 0.005

- 12 042618

In addition, in the process of obtaining LiCl from the primary lithium concentrate, the following products were produced as by-products: NaCl - 644.9 g (641.1 g from the mother liquor of the lithium carbonate precipitation operation, 3.8 g from the secondary lithium concentrate); KCl 10.6 g, containing LiCl as an impurity in the amount of 0.02 wt.%, i.e. 0.13 g.

Example 6

NaCl + KCl crystals with an admixture of LiCl were dissolved in demineralized water, bringing the total salt content in the solution to 262 g/dm ³ (solution volume 11 dm ³ ). The solution was subjected to membrane electrolysis on a laboratory electrolysis unit (membrane CTIEM-1, current density 2 kA/m ² ) in the circulation-selective mode of the catholyte and the circulation-feed mode of the anolyte (alkali metal chloride solution). As a result of processing, 2.73 dm ³ of an alkaline solution was obtained containing (g/dm ³ ): NaOH - 160.57; KOH - 2.92; LiOH - 0.03. The solution was brought into contact with the exhaust flue gases of a gas burner in which a propane-butane mixture was burned. The carbonization was stopped by the transition of the alkaline indicator of the carbonized solution to pH 10. After carbonization, the volume of the solution decreased to 1.98 DM ³ . The content of alkali metal carbonates was as follows (g/dm ³ ): Na2CO3 - 293.23; K2CO3 - 4.93; Li2CO3 - 0.05. The resulting solution, having a temperature of 75.4°C, was brought into contact with a LiCl solution with a concentration of 196 g/DM ³ and a volume of 2.41 DM ³ . The output of Li2CO ₃ in the solid phase was 365.3 g with the content of Li ₂ CO ₃ in the mother liquor 11.2 g/DM ³ . It clearly follows from the obtained results that the chloride crystals isolated from the mother chloride solution formed after the precipitation of Li ₂ CO ₃ from the secondary lithium concentrate can be processed into a Na2CO3 carbonate solution containing K2CO3 and Li2CO3, which is also an effective precipitator of Li ₂ CO ₃ from LiCl solution.

Example 7

700 dm ³ of natural lithium-bearing brine of magnesium chloride type of Qinghai province (Germu, China) were processed on the experimental stand, composition, g/dm ³ : LiCl - 2.75; NaCl - 23.1; KCl - 19.1; MgCl ₂ - 349.2; B ₄ O ₇ - 1.2; SO ₄ - 2.3; Fe - 0.003; density - 1280 g/dm ³ , pH 6; the total salt content is 401 g/dm ³ strictly according to the technological scheme shown in Fig. 3.

The brine was processed in portions of 50 dm ³ each. The average degree of lithium extraction from brine was 90%. 14 samples of lithium carbonate were obtained in a total amount of 1507.9 g. The chemical analysis of the samples showed the stability of the composition of the resulting product. The results of the analysis are presented in table. 6.

Table 6

Analyzed Ingredient Ingredient content, % wt. typical product best product L12CO3 99.6 99.7 Na 0.0250 0.0230 Cl 0.0080 0.0040 Sa 0.0290 0.0040 mg 0.0040 0.0024 SO4 0.0100 0.007 TO 0.0030 0.0021 PPP (200°C) 0.0960 0.0622 But. (HC1) 0.1550 0.0950 Fe 0.0004 0.0003

- 13 042618

It follows from the obtained results that the purity of lithium carbonate obtained from natural lithium-bearing brine according to the proposed technology (scheme in Fig. 3) is significantly higher than 99%, and the manufactured product meets the requirements of the world market for Li ₂ CO ₃ technical qualification.

Example 8

On the experimental stand, 600 dm ³ of natural lithium-bearing brine of the Znamenskoye deposit in the Irkutsk region were processed (composition in example 2) according to the flow diagram shown in Fig. 4. The brine was processed in portions of 50 dm ³ each. The average recovery of LiCl from brine was 93%. To decompose the NH4Cl salt, we used slaked lime produced by PJSC Krasnoyarsk Chemical and Metallurgical Plant. Bottled carbon dioxide was used to obtain an absorbable mixture of NH ₃ :Cl ₂ = 2:1. The average return rate of the ammonium salt was 99.2%. The decomposition of limestone was not carried out due to the fact that the practical implementation of this process is obvious. 12 samples of lithium carbonate were obtained. A quarter of the mass was taken from each sample and thoroughly mixed. Representative samples were taken from the resulting mixture and analyzed for the content of the main substance and impurities, the content of which is limited by the requirements for lithium carbonate of battery quality. The results obtained are presented in table. 7.

Table 7

Soder- The content of impurities, % May. janis S ₂ COz, % May. Na mg Sa TO Fe Zn Xi Pb Si A1 MP Ni SO 2- ci- more me me me me me- me- me- me me- me me 0.00 me 0.0 99.8 her her her her her her her her her her her 05 her 01 0.0 0.0 0.0 0.0 0.00 0.00 0.00 0.0 0.00 0.0 0.0 0.0 01 02 02 01 05 03 03 01 03 01 01 1

It follows from the contents of the table that the purity of lithium carbonate obtained from natural lithium-bearing brine according to the proposed technology (scheme in Fig. 4) is above 99.8%, and the manufactured product meets the requirements of the world market for Li ₂ CO ₃ battery quality.

Sources of information used.

1. Yu.I. Ostroushko, T.V. Degtyareva Hydromineral raw materials are an inexhaustible source of lithium. Analytical review. Moscow Ed. TsNIIATOMINFORM, 1999, 64 p.

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18. Pat. No. 2516538RU Method for producing lithium concentrate from lithium-bearing natural brines and its processing (prototype).

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Claims (6)

CLAIM 1. Method for producing primary lithium concentrate from lithium-bearing brine, including: a) purification of the used natural lithium-bearing brine from suspended particles by sedimentation centrifugation of the brine to obtain a sediment of suspended particles and centrifuge, which is filtered on fine filters to obtain a sediment of suspended particles and lithium-bearing brine, purified from suspended particles, if the content of suspended particles in the initial brine is 1.0 kg/m ³ and above, or by filtering the original natural brine on fine filters, if the content of suspended particles in the original brine is below 1.0 kg/m ³ ; regeneration of spent fine filters is carried out by backwashing with a stream of filtered brine, followed by supplying a stream of spent regenerating brine to the precipitation centrifugation operation together with the original lithium-bearing natural brine; b) sorption of lithium chloride from a lithium-bearing brine purified from suspended particles using a sorption-desorption module filled with a granular sorbent based on the compound LiCl-2Al(OH) ₃ -mH2O with a deficiency of LiCl and m = 3-5, by filtering the brine through a layer of granular sorbent in the direction from bottom to top at a linear filtration rate of 5-7 m/h with saturation of the sorbent with lithium chloride; c) washing the granular sorbent saturated with lithium chloride from the brine, carried out by preliminary draining the brine from the column, then stepwise countercurrent washing of the sorbent sequentially with five portions of the washing liquid in the upward direction at a linear velocity of the liquid of 5-7 m/h in volume, each of the portions is 1 /3 of the volume of granulated sorbent in a single column of the sorption-desorption module, with four portions of five being washing liquids with different contents of brine components in order of decreasing their content by washing steps, and the fifth portion is the volume of fresh water, while the first portion washing liquid fill the column and displace it from the column with the second portion of the washing liquid, directing the displaced volume for mixing with the lithium-bearing brine cleaned of suspended particles, the second portion of the washing liquid is displaced from the column with the third portion of the washing liquid and used in the next washing cycle as the first portion of the washing liquid, the third portion of the washing liquid is displaced from the column by the fourth portion of the washing liquid and is used in the next cycle as the second portion of the washing liquid, the fourth portion of the washing liquid is displaced by the fifth portion and used in the next cycle as the third portion of the washing liquid, the fifth portion of the washing liquid is displaced by the corresponding portion of the stripping liquid and used in the next cycle as the fourth portion of the washing liquid, fresh portion of fresh water is used as the fifth portion of the washing liquid; d) desorption of lithium chloride from a granular sorbent saturated with lithium chloride and washed from brine is carried out by successive stepwise filtration through a layer of granular sorbent in a column, which is part of the sorption-desorption module at the desorption stage, with a given volume of desorbing liquids in the direction from bottom to top with a linear speed of 5- 7 m/h, based on the fact that the first volume of the desorbing liquid, which is a dilute aqueous solution of lithium chloride with an admixture of residual brine components, is removed from the process as a primary lithium concentrate, and after contact with the sorbent, the second volume of the desorbing liquid, which is fresh water, it is used as a desorbing liquid at the first stage of desorption in the next cycle of the process, together with the volume of the desorbing liquid displaced from the column with the sorbent by the corresponding volume of lithium-bearing brine at the sorption stage of the next cycle, while the sorption-desorption module consists of four columns filled with granular sorbent , where two columns are in the stage of sorption of lithium chloride from brine, one of the columns is in the stage of washing the sorbent saturated with lithium chloride from the brine, and one column is in the stage of desorption of lithium chloride from the sorbent washed from the brine, while the brine flow is always passed first through a column with a sorbent partially saturated with lithium chloride - the first stage of sorption, then the brine flow is passed through a column with a sorbent that has passed the stage of desorption of lithium chloride from the sorbent - the second stage of sorption, while after the sorbent is completely saturated with lithium chloride in the first column along the brine flow, it is transferred to the stage of washing the sorbent from the brine, the column that was at the stage of washing the sorbent from the brine is transferred to the stage of desorption of lithium chloride from the saturated sorbent, the column that was at the stage of desorption of lithium chloride from the saturated sorbent is transferred to the stage of sorption as a column of the second stage and the column , which was at the stage of sorption as a column of the second stage, is transferred to the stage of sorption as a column of the first stage, then the cycle is repeated. 2. A method for producing a secondary lithium concentrate by helioconcentration in an evaporation pool, including obtaining a primary lithium concentrate according to claim 1, helioconcentration of one stream of primary lithium concentrate by lithium chloride in an evaporation pool with simultaneous purification from calcium and magnesium by pulping lithium carbonate with carbonization of the pulp with carbon dioxide or a gas mixture containing CO ₂ in the pulp circulation mode until lithium carbonate is completely dissolved, mixing this stream with another stream of primary lithium concentrate, sending the mixed solution to the evaporation pool for concentrating the liquid phase in LiCl, decarbonization and gradual transfer of soluble calcium and magnesium chlorides into sparingly soluble compounds CaCO ₃ and Mg(OH) ₂ -3MgCO ₃ -3H ₂ O, which are separated from a concentrated solution of LiCl containing NaCl and KCl as the main impurities, to obtain a secondary lithium concentrate used to obtain lithium chloride or lithium carbonate. 3. A method for obtaining a secondary lithium concentrate, including obtaining a primary lithium concentrate according to claim 1, pulping Li ₂ CO ₃ in the flow of primary lithium concentrate produced by reverse osmosis concentration and desalination, carbonizing the pulp with carbon dioxide or a gas mixture containing CO ₂ in the pulp circulation mode to complete dissolution of lithium carbonate, heating the solution to a temperature of 80-85°C while evacuating to 0.5 atm., decarbonization, directing the released carbon dioxide to the carbonization operation of the pulp prepared from lithium carbonate and reverse osmosis lithium concentrate, and simultaneously converting CaCl2 and MgCl2 into insoluble precipitates of CaCO ₃ and Mg(OH) ₂ -3MgCO ₃ -3H ₂ O, which are separated from the liquid phase, the concentration of the liquid phase, which is an aqueous solution of LiCl with an admixture of NaCl and KCl, in lithium chloride by electrodialysis or thermal means, or their combination to obtaining a LiCl solution with a concentration of 190-200 kg/m ³ to obtain a secondary lithium concentrate used to obtain lithium chloride or lithium carbonate. 4. A method for producing lithium chloride, including obtaining a secondary lithium concentrate by the method according to claim 2 or 3, separating the obtained secondary lithium concentrate into two streams, while one stream of the secondary lithium concentrate is first subjected to reagent purification from magnesium, calcium, sulfate and borate ions with using barium hydroxide or oxide and carbon dioxide as reagents, then deep ion-exchange purification from calcium and magnesium on Lewatit 208-TP polyampholyte in Li-form, concentration by evaporation to a LiCl content of 485-490 kg / m ³ , the resulting lithium chloride brine is cooled to room temperature, the precipitated NaCl and KCl crystals with an admixture of LiCl-H ₂ O crystals are separated from the liquid phase, the crystals are washed stepwise in the repulping and squeezing mode with three portions of the washing chloride solution with a volume equal to two portion volumes of the washed crystals each, two portions of which are mixed chloride solutions NaCl + KCl + LiCl in order of decreasing content of LiCl in them, and the third portion is a mixed solution of alkali metal chlorides that does not contain LiCl, the first portion of the washing chloride solution after contact with the crystals is sent to the evaporation operation, pre-mixing with purified from impurities with a secondary lithium concentrate, two other portions of the washing chloride solution are used for successive stepwise washing of the next portion of the crystals, a fresh third portion of the chloride washing solution is prepared by dissolving sodium chloride or sodium chloride with an admixture of potassium chloride in demineralized water, chilled and freed from crystals lithium chloride brine with with a residual content of NaCl + KCl not more than 2 kg / m ³ is evaporated until LiCl passes into the solid phase of lithium chloride monohydrate crystal hydrate, the remainder of the mother liquor of the operation of evaporation of lithium chloride brine and crystallization of LiCl-H ₂ O is separated from LiCl-H ₂ O crystal hydrate and mixed with the purified secondary lithium concentrate entering the evaporation, the hydrated lithium chloride monohydrate is washed from the remainder of the mother liquor with a washing liquid of the composition: LiCl solution - 98.5-99.0 wt.%; LiOH - 1.0-1.5 wt.%, the spent washing liquid is acidified with hydrochloric acid to pH 6-7 and mixed with the purified secondary lithium concentrate supplied for evaporation, the washed crystals are freed from residual alkalinity by contact with the calculated amount of hydrochloric acid and dried to obtaining anhydrous lithium chloride by two-stage drying in an air stream, maintaining the temperature in the drying zone at the first stage 85-90°C, at the second stage 108-110°C with a moisture content in the air stream at the exit from the drying zone of 75-80%, and the other flow - 16 042618 secondary lithium concentrate is used to precipitate lithium carbonate from it upon contact with a solution of sodium carbonate or a solution of sodium carbonate containing potassium carbonate, the precipitated lithium carbonate is separated from the mother liquor by centrifugation and sent for pulping with a part of the flow of the primary lithium concentrate or with a reverse osmosis flow lithium concentrate for subsequent carbonization, the mother liquor of the lithium carbonate precipitation operation is acidified to pH 6.0-6.5, evaporated until the concentration of lithium chloride in the liquid phase is 485-490 kg/m ³ , the liquid phase is separated from salted-out NaCl crystals with an admixture of crystals KCl and mixed with the stream of secondary lithium concentrate used to produce lithium chloride, NaCl crystals with an admixture of KCl crystals are washed from the mother liquor, mixed with washed NaCl and KCl crystals salted out during evaporation of the stream of secondary lithium concentrate in the production of LiCl, dissolved in demineralized water , obtaining a chloride solution of alkali metals with a NaCl concentration of 250-260 kg / m ³ , the solution is subjected to membrane electrolysis, producing a NaOH solution and hydrogen at the cathode and chlorine at the anode, the hydrogen produced is mixed with a natural gas stream, the mixture of gases is burned using thermal energy for heating water vapor, which, in turn, is used as a heat carrier _{in the} evaporation of lithium concentrates and the mother _chloride solution _; precipitant in the lithium carbonate precipitation operation, anodic chlorine is ejected and absorbed by a stream of aqueous urea solution, thus producing a hydrochloric acid solution used to acidify carbonate-containing solutions before their evaporation and to regenerate spent Lewatit 208-TP polyampholyte. 5. A method for producing technical lithium carbonate, including obtaining a secondary lithium concentrate by the method according to claim 2 or 3, precipitating lithium carbonate from the entire stream of the obtained secondary lithium-bearing concentrate by contacting it with stirring with a solution of sodium carbonate containing potassium carbonate at a temperature of 90-95 °C, separating the precipitated and freed from the mother liquor of lithium carbonate into two parts, while one part of the lithium carbonate is used to obtain a solution of lithium bicarbonate, which is further used to purify the reverse osmosis lithium concentrate or primary lithium concentrate from calcium and magnesium, and the other, the productive part lithium carbonate is washed stepwise in the mode of repulpation and centrifugation with three portions of the washing solution, equal to three portion volumes of the washed lithium carbonate, each at a temperature of 90-95 ° C, and first with two portions of a saturated solution of lithium carbonate in order of decreasing sodium and chloride ion content and then with a portion of demineralized water, the first portion of the washing solution after contact with lithium carbonate is sent to the operation of obtaining a pulp of lithium carbonate used to purify the primary lithium concentrate or reverse osmosis lithium concentrate from calcium and magnesium, the other two portions of the washing solution are used for successive stepwise washing of the next portion lithium carbonate, the washed crystals of lithium carbonate are subjected to microwave drying to a residual amount of moisture of 0.4 wt.%. 6. A method for producing battery-quality lithium carbonate, including obtaining a secondary lithium concentrate by the method according to claim 2 or 3, ion-exchange purification of calcium and magnesium from the resulting secondary lithium concentrate on Lewatit 208-TP polyampholyte in Li-form, precipitation of lithium carbonate from purified secondary lithium concentrate with a saturated aqueous solution of ammonium carbonate at room temperature, the precipitate of the resulting lithium carbonate is separated from the mother liquor of ammonium chloride, one part of the precipitate of lithium carbonate is used to obtain a solution of lithium bicarbonate, further used to purify the reverse osmosis lithium concentrate from calcium and magnesium, the other part of the lithium carbonate is washed stepwise in the mode of repulpation and centrifugation with three portions of the washing solution with a volume equal to three volumes of a portion of the washed lithium carbonate each, at a temperature of 9095 ° C, and first with two portions of a saturated solution of lithium carbonate in order of decreasing the content of ammonium and chloride ion in them and then with a portion of demineralized water, the first portion of the washing solution after contact with lithium carbonate is sent to the operation of obtaining a pulp of Li ₂ CO ₃ and used to purify the primary lithium concentrate or reverse osmosis lithium concentrate from calcium and magnesium, two other portions of the washing solution are used to sequentially wash the next portion of lithium carbonate, the washed crystals of lithium carbonate are subjected to microwave drying to a residual moisture content of 0.2 wt.%, ammonium chloride is salted out from the mother liquor of the lithium carbonate precipitation operation by evaporation, after separation from the mother liquor of evaporation, ammonium chloride is washed from the remainder of the mother liquor, the spent washing solution is sent for evaporation , mixing with the uterine