Method and system for preparing lithium fluoride

Abstract

The invention belongs to the field of new energy, and discloses a method for preparing lithium fluoride, which comprises the following steps: step 1, taking lithium-containing brine and soluble bicarbonate as raw materials, and combining cations in the lithium-containing brine with bicarbonate anions in the soluble bicarbonate by adopting electrodialysis equipment to prepare a first solution containing lithium bicarbonate; 2, removing non-+ 1 valence metal cations in the first solution to obtain a second solution containing lithium bicarbonate; 3, reacting the second solution with fluoride to prepare lithium fluoride; the fluoride is ammonium fluoride or hydrogen fluoride. According to the method, high-purity lithium salt does not need to be prepared before lithium fluoride is prepared, electrodialysis equipment is adopted, lithium-containing brine and soluble bicarbonate are used as raw materials, the production process can be simplified, the process difficulty is effectively reduced, and battery-grade lithium fluoride can be prepared through the method.

Description

Technical Field

[0001] The present invention relates to the field of new energy, and in particular to a method and system for preparing lithium fluoride. Background Art

[0002] As countries are becoming more and more popular with new energy, the research on new energy materials is becoming more and more in-depth. As lithium-ion batteries are the main research object of new energy and their widespread use, we have also put forward higher requirements on the cost of lithium-ion batteries. As one of the raw materials of lithium-ion batteries, the demand for lithium fluoride electrolyte is increasing. At present, most lithium source materials for preparing lithium fluoride are concentrated on high-purity lithium carbonate, which is used to prepare high-purity lithium bicarbonate, and then lithium fluoride is prepared by reacting high-purity lithium bicarbonate with hydrogen fluoride (such as CN116395716A, the subject is a preparation method of high-purity lithium fluoride; CN117800369A, the subject is a method for continuous production of lithium fluoride). The above methods have particularly high requirements on the purity of the raw materials; high-purity lithium carbonate or high-purity lithium salts are mostly refined from lithium-containing brine; lithium-containing brine contains various anions and cations, and the existing refining methods are generally divided into precipitation method and resin exchange method; precipitation method requires the use of different precipitants to precipitate metal ions of different properties in batches, and the production process is complicated and the production cost is high; the resin exchange method requires the removal of cations and anions, and the operation is particularly complicated.

[0003] In the actual production process, no matter which process is used, it is necessary to ensure that the lithium source has a high purity.

[0004] In the art, there are few solutions for directly preparing lithium fluoride using lithium-containing brine, especially lithium sulfate brine. In the process of preparing lithium fluoride using a small amount of lithium-containing brine, it is difficult to ensure that the impurities of lithium fluoride are very low. For example, the subject of the publication No. CN117361590A is a method for treating lithium-containing industrial brine, which directly uses brine and fluoride to react and separate precipitation. The precipitate inevitably contains other fluoride salts, anions, and trace amounts of other metal ions that are difficult to elute.

[0005] The technical problem to be solved by this scheme is: how to prepare battery-grade lithium fluoride using lithium-containing brine with relatively high impurity content. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing lithium fluoride. The method adopts an electrodialysis process, uses lithium-containing brine and soluble bicarbonate as raw materials to produce a lithium bicarbonate-containing solution, and subsequently removes impure metal cations, which can simplify the production process and eliminate the need to prepare high-purity lithium salts before preparing lithium fluoride, effectively reducing the process difficulty. Battery-grade lithium fluoride can be prepared by the method of the present invention; in addition, the present invention is the first solution in the art to use lithium-containing brine as a raw material to achieve truly continuous production.

[0007] Meanwhile, the present invention also provides a system for implementing the above method.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing lithium fluoride comprises the following steps:

[0010] Step 1: using lithium-containing brine and soluble bicarbonate as raw materials, using electrodialysis equipment to combine cations in the lithium-containing brine and bicarbonate anions in the soluble bicarbonate to prepare a first solution containing lithium bicarbonate;

[0011] Step 2: removing non-+1 valence metal cations in the first solution to obtain a second solution containing lithium bicarbonate;

[0012] Step 3: reacting the second solution with fluoride to prepare lithium fluoride;

[0013] The fluoride is ammonium fluoride or hydrogen fluoride.

[0014] The basic principle of the present invention that lithium-containing brine can be used as a raw material to prepare battery-grade lithium fluoride is:

[0015] 1. Directly using lithium-containing brine as a raw material, removing anion impurities in the brine through an electrodialysis process, so that most of the anions in the first solution containing lithium bicarbonate obtained in step 1 are bicarbonate;

[0016] 2. In step 2, non-+1-valent metal cations are removed to obtain a second solution containing lithium bicarbonate (containing sodium ions and / or potassium ions). The solution obtained by step 2 contains almost no +2-valent or +3-valent metal ions and sulfate ions. After entering step 3, the obtained lithium fluoride can be eluted to remove Na + , K + Remove to obtain battery-grade lithium fluoride;

[0017] It should be noted that the fluoride of the present invention should be ammonium fluoride or hydrogen fluoride. If other fluoride salts are selected, it will be difficult for lithium fluoride to completely elute metal ions. If sodium fluoride is used as a raw material, a very high concentration of sodium ions will exist in the product, resulting in the difficulty in maintaining a low sodium ion concentration after lithium fluoride has been washed many times.

[0018] Compared with the prior art, the innovation of this case lies in:

[0019] First, the electrodialysis technology, the impurity removal step after electrodialysis and the precipitation reaction of fluoride are innovatively combined to prepare lithium bicarbonate by electrodialysis, and the metal cation impurity removal is carried out after electrodialysis to remove the impurity metal ions in the raw lithium-containing brine and soluble bicarbonate. This makes it possible to realize a continuous production process for preparing high-purity lithium fluoride using lithium-containing brine as raw material, effectively overcoming the problem that the brine needs to undergo a long process of refining before lithium fluoride can be prepared in the traditional method.

[0020] In the above-mentioned method for preparing lithium fluoride, the soluble bicarbonate is one or more combinations of ammonium bicarbonate, sodium bicarbonate, and potassium bicarbonate; and the fluoride is ammonium fluoride.

[0021] Preferably, the step 3 specifically comprises: reacting the second solution with ammonium fluoride, wherein the solid product after the reaction is lithium fluoride, and the liquid product after the reaction is ammonium bicarbonate solution; and the ammonium bicarbonate solution is used as the raw material of step 1.

[0022] The present invention adopts ammonium fluoride as a raw material, and can effectively utilize the waste liquid of step 3. Specifically, in step 3, ammonium fluoride and lithium bicarbonate are reacted to obtain lithium fluoride precipitation and ammonium bicarbonate solution (containing potassium ions and / or sodium ions); the ammonium bicarbonate solution can be used as a raw material for step 1. Of course, in step 1, the filtrate of step 3 cannot be used as the only raw material, and additional ammonium bicarbonate needs to be added to the filtrate of step 3 to increase the concentration of the filtrate; or, the filtrate of step 3 is added as a supplementary liquid to the pre-prepared ammonium bicarbonate solution, and used as a raw material for step 1. Although the ammonium bicarbonate solution recovered by step 3 contains potassium ions and / or sodium ions, when the solution enters the electrodialysis equipment for electrodialysis, the potassium ions and / or sodium ions can be separated from the bicarbonate anions, so that even if these +1-valent impurity ions exist, it will not affect the production.

[0023] Preferably, in step 2, an ion exchange resin is used to remove the non-+1-valent metal cations. More preferably, an ion exchange resin column for adsorbing sulfate is also used; the non-+1-valent metal cations include but are not limited to calcium ions, magnesium ions, etc.; in practical applications, the ion exchange resin for removing the non-+1-valent metal cations is an LSC-500 series resin column, more preferably an LSC-500B resin column; the ion exchange resin column for adsorbing sulfate is more commonly KP-305 resin, and in actual production, it is also feasible to select other types of resin columns that can achieve the same function.

[0024] Preferably, the lithium-containing brine is one or more combinations of ore lithium extraction liquid, electrode lithium extraction liquid, and lithium sulfate solution after impurities are removed.

[0025] For example, the cation composition of lithium ore extraction solution is roughly: Li≧10g / L, Na≦1g / L, K≦500ppm, Ca≦30ppm, Mg≦30ppm, other impurities≦5ppm;

[0026] The cation composition of the electrode lithium extraction solution is roughly: Li≧10g / L, K≦1g / L, Ca≦30ppm, Mg≦30ppm, other impurities≦5ppm;

[0027] The preferred cation composition of the lithium-containing brine of the present invention is: the cation composition of the lithium-containing brine is: Li≧10g / L, Na≦1g / L, K≦100ppm, Ca≦30ppm, Mg≦30ppm, other impurities≦1ppm; more preferably, Li≧10g / L, Na≦1g / L, K≦100ppm, Ca≦5ppm, Mg≦5ppm, other impurities≦1ppm.

[0028] In the above-mentioned method for preparing lithium fluoride, the electrodialysis equipment includes a multilayer cation exchange membrane, anion exchange membrane and an outermost positive electrode plate and negative electrode plate; the cation exchange membrane and the anion exchange membrane are alternately arranged to form a plurality of liquid channels; the positive electrode plate and the negative electrode plate and the corresponding adjacent cation exchange membranes respectively form a first electrode liquid channel and a second electrode liquid channel; the plurality of liquid channels are sequentially: a first liquid channel, a second liquid channel, a third liquid channel, and a fourth liquid channel; the first electrode liquid channel and the second electrode liquid channel form a circulation and the circulating liquid is the electrode liquid;

[0029] The second liquid channel is used to introduce the raw material soluble bicarbonate solution, provide bicarbonate to the first liquid channel, and provide cations to the third liquid channel;

[0030] The fourth liquid channel is used to introduce raw lithium-containing brine, provide anions in the lithium-containing brine to the third liquid channel, and provide cations in the lithium-containing brine to the second electrode liquid channel to supplement the cations in the electrode liquid;

[0031] The first electrode liquid channel is used to provide cations in the electrode liquid to the first liquid channel;

[0032] A first liquid channel: used to generate the first solution using cations provided by the first electrode liquid channel and bicarbonate ions provided by the second liquid channel;

[0033] The third liquid channel is used to recover the cations of the raw material passed into the second liquid channel and the anions of the raw material passed into the fourth liquid channel;

[0034] The lithium ion concentration in the electrode solution is preferably 10 g / L to 25 g / L;

[0035] In the above-mentioned method for preparing lithium fluoride, the soluble bicarbonate is ammonium bicarbonate; the fluoride is ammonium fluoride; in the step 3, the solid product after the reaction is lithium fluoride, and the liquid product after the reaction is an ammonium bicarbonate solution; the second liquid channel to which the ammonium bicarbonate solution is transported;

[0036] The cations of the solute in the electrode solution are lithium ions, and the anions of the solute in the electrode solution are one or more combinations of nitrate, sulfate, chloride, hydroxide, and perchlorate.

[0037] In the above-mentioned method for preparing lithium fluoride, the soluble bicarbonate exists in the form of a soluble bicarbonate solution; the concentration of bicarbonate in the soluble bicarbonate solution is 20-35wt%; preferably, the concentration of bicarbonate in the soluble bicarbonate solution is 20wt%, 25wt%, 30wt%, 35wt%;

[0038] The fluoride is in the form of a fluoride solution, and the concentration of the fluoride solution is 30-35wt%; preferably, the concentration of the fluoride solution is 30wt%, 32wt%, 33wt%, 34wt%, 35wt%;

[0039] The lithium ion concentration in the lithium-containing brine is 10 g / L to 25 g / L;

[0040] Preferably, the lithium ion concentration in the lithium-containing brine is 10 g / L, 15 g / L, 20 g / L or 25 g / L;

[0041] In step 3, the molar ratio of the fluoride ions to the lithium ions in the lithium bicarbonate is 1:1;

[0042] In the step 3, the second solution is added to the fluoride solution by spraying; after the reaction in step 3 is completed, filtering is performed, and the filter residue is lithium fluoride; the filter residue is washed to obtain battery-grade lithium fluoride;

[0043] The reaction temperature of step 3 is 20-35° C., and the reaction time is 1-4 hours.

[0044] In the above-mentioned method for preparing lithium fluoride, the lithium-containing brine in step 1 is pre-cleaned to remove impurity metal ions; the impurity metal ions are metal ions that form a precipitate after combining with bicarbonate or that form a precipitate after the formed bicarbonate is hydrolyzed. Impurity metal ions such as iron ions, aluminum ions, etc., are easy to form hydroxide precipitates after combining with bicarbonate, which seriously affects the life of the electrodialysis equipment, so they should be removed in advance, and the impurity removal method is to add a small amount of sodium bicarbonate to the solution.

[0045] At the same time, the present invention also provides a system for implementing the above method, the system comprising an electrodialysis device, an impurity removal device, a reactor, and a filter connected in sequence;

[0046] The electrodialysis equipment comprises a multilayer cation exchange membrane, anion exchange membrane and an outermost positive electrode plate and negative electrode plate; the cation exchange membrane and the anion exchange membrane are alternately arranged to form a plurality of liquid channels; the positive electrode plate and the negative electrode plate and the corresponding adjacent cation exchange membranes respectively form a first electrode liquid channel and a second electrode liquid channel; the plurality of liquid channels are sequentially: a first liquid channel, a second liquid channel, a third liquid channel and a fourth liquid channel; the first electrode liquid channel and the second electrode liquid channel form a circulation and the circulating liquid is the electrode liquid;

[0047] The second liquid channel is used to introduce the raw material soluble bicarbonate solution, provide bicarbonate to the first liquid channel, and provide cations to the third liquid channel;

[0048] The fourth liquid channel is used to introduce raw lithium-containing brine, provide anions in the lithium-containing brine to the third liquid channel, and provide cations in the lithium-containing brine to the second electrode liquid channel to supplement the cations in the electrode liquid;

[0049] The first electrode liquid channel is used to provide cations in the electrode liquid to the first liquid channel;

[0050] A first liquid channel: used to generate the first solution using cations provided by the first electrode liquid channel and bicarbonate ions provided by the second liquid channel;

[0051] The third liquid channel is used to recover the cations of the raw material passed into the second liquid channel and the anions of the raw material passed into the fourth liquid channel;

[0052] The impurity removal equipment is used to process the first solution to obtain the second solution;

[0053] More specifically, the impurity removal device includes a first resin adsorption column for removing non-+1 valent metal ions;

[0054] The reaction kettle is used to react the second solution with the fluoride;

[0055] The filter is used to filter the reaction product of the reactor, and the collected filter residue is lithium fluoride.

[0056] In the above system, the soluble bicarbonate is ammonium bicarbonate; the fluoride is ammonium fluoride;

[0057] The filtrate outputted from the filter is transported to the inlet of the second liquid channel through a pipeline.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention innovatively combines the electrodialysis technology, the impurity removal step after electrodialysis and the precipitation reaction of fluoride, prepares lithium bicarbonate by electrodialysis, and removes metal cation impurities after electrodialysis to remove impurity metal ions in the raw material lithium-containing brine and soluble bicarbonate, so that the preparation of high-purity lithium fluoride using lithium-containing brine as raw material can be realized, effectively overcoming the difficulty that the brine needs to be refined in a long process before lithium fluoride can be prepared in the traditional method.

[0060] In a preferred embodiment of the present invention, ammonium fluoride is used as a raw material, and the waste liquid of step 3 can be effectively utilized to realize the reuse of the product ammonium bicarbonate, which is environmentally friendly. Although the ammonium bicarbonate solution recovered by step 3 contains potassium ions and / or sodium ions, when the solution enters the electrodialysis equipment for electrodialysis, the potassium ions and / or sodium ions can be separated from the bicarbonate anion, so even if these +1 valence impurity ions exist, it will not affect the production. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a structural schematic diagram of an electrodialysis device;

[0062] Figure 2 It is a structural schematic diagram of lithium fluoride preparation system 1;

[0063] Figure 3 This is a schematic diagram of the structure of lithium fluoride preparation system 2. DETAILED DESCRIPTION

[0064] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] Part 1 Equipment and Systems

[0066] Electrodialysis equipment 100

[0067] Electrodialysis Equipment 100 Reference Figure 1, which has 3 layers of cation exchange membranes, 2 layers of anion exchange membranes, a positive plate 6 and a negative plate 7; the exchange membrane, i.e., the electrodialysis membrane, is a thin film made of a polymer material that is selective for ions; the cation exchange membrane, because the fixed groups inside the membrane carry negative charges, anions are repelled in the solution and cannot pass through, and only cations are allowed to pass through; the anion exchange membrane, because the fixed groups inside the membrane carry positive charges, positive ions are repelled in the solution and cannot pass through, and only anions are allowed to pass through. It should be noted that the cation exchange membrane and the anion exchange membrane of the present invention are not absolutely able to repel opposite ions. In actual production, a small amount of opposite ions will still enter the adjacent channels.

[0068] Both cation exchange membranes and anion exchange membranes are commercially available products and can be purchased through commercial channels.

[0069] The three layers of cation exchange membranes and the two layers of anion exchange membranes are named first cation exchange membrane 1, first anion exchange membrane 2, second cation exchange membrane 3, second anion exchange membrane 4, and third cation exchange membrane 5, respectively;

[0070] The structure of the electrodialysis device 100 is as follows: a positive electrode plate 6, a first cation exchange membrane 1, a first anion exchange membrane 2, a second cation exchange membrane 3, a second anion exchange membrane 4, a third cation exchange membrane 5, and a negative electrode plate 7;

[0071] A first electrode liquid channel 8 is provided between the positive electrode plate 6 and the first cation exchange membrane 1;

[0072] A first liquid channel 9 is provided between the first cation exchange membrane 1 and the first anion exchange membrane 2;

[0073] A second liquid channel 10 is provided between the first anion exchange membrane 2 and the second cation exchange membrane 3;

[0074] A third liquid channel 11 is provided between the second cation exchange membrane 3 and the second anion exchange membrane 4;

[0075] A fourth liquid channel 12 is provided between the second anion exchange membrane 4 and the third cation exchange membrane 5;

[0076] A second electrode liquid channel 13 is provided between the third cation exchange membrane 5 and the negative electrode plate 7;

[0077] The first liquid channel 9 is used to generate a first solution using cations provided by the first electrode liquid channel and bicarbonate ions provided by the second liquid channel; the first solution contains lithium bicarbonate and other metal cations in the lithium-containing brine, such as Na + , K + , Ca 2+ Mg 2+ wait;

[0078] In the initial stage, deionized water is introduced into the first liquid channel 9. As the reaction time increases, the concentration of lithium bicarbonate contained therein becomes higher and higher. At this time, part of the liquid in the first liquid channel 9 is discharged and supplemented with deionized water, or all the liquid is replaced with deionized water.

[0079] The second liquid channel 10 is used to pass the soluble bicarbonate solution, provide bicarbonate anions to the first liquid channel 9, and provide cations of the soluble bicarbonate solution to the third liquid channel 11;

[0080] As the reaction proceeds, the bicarbonate concentration in the second liquid channel 10 becomes lower and lower. When it is low to a certain extent, a bicarbonate solution with a higher concentration should be added, or the solution therein should be replaced with a bicarbonate solution with a higher concentration.

[0081] The third liquid channel 11 is used to generate salt. The anions of the salt are derived from the fourth liquid channel 12, and the cations of the salt are derived from the second liquid channel 10. The most abundant component in the lithium-containing brine is sulfate, so the main component of the salt is sulfate;

[0082] In the initial stage, deionized water is introduced into the third liquid channel 11, and the liquid in the third liquid channel 11 can be continuously discharged and replenished with deionized water, or, after the salt concentration therein reaches a certain level, the liquid inside is completely or partially replaced by deionized water;

[0083] The fourth liquid channel 12 is used for introducing lithium-containing brine, providing anions in the lithium-containing brine to the third liquid channel 11, and providing cations in the lithium-containing brine to the second electrode liquid channel 13 to supplement the cations in the electrode liquid;

[0084] As the reaction proceeds, the concentration of the lithium-containing brine in the fourth liquid channel 12 becomes lower and lower. When the concentration of the lithium-containing brine is as low as a certain level, fresh lithium-containing brine with a higher concentration is used to partially or completely replace the liquid inside the fourth liquid channel 12.

[0085] The first electrode liquid channel 8 and the second electrode liquid channel 13 form a circulation and the circulating liquid is the electrode liquid;

[0086] It can be seen from the above records that the first electrode liquid channel 8 and the second electrode liquid channel 13 only need to be filled with electrode liquid in the initial stage, and then they obtain cations from the fourth liquid channel 12 and transfer to the first liquid channel 9, playing the role of cation carrier.

[0087] Preferably, the first liquid channel 9, the second liquid channel 10, the third liquid channel 11, and the fourth liquid channel 12 all circulate with their respective inlets and outlets as circulation connection points, that is, the liquids inside the first liquid channel 9, the second liquid channel 10, the third liquid channel 11, and the fourth liquid channel 12 all circulate inside their respective channels.

[0088] More specifically, from the perspective of liquid flow, there are two modes:

[0089] Mode 1: Cycle Mode

[0090] The inlet and outlet of the first liquid channel 9 are circulated, and when the concentration of lithium bicarbonate inside reaches the standard, a part of the solution is output and water is added to the first liquid channel 9; the inlet and outlet of the second liquid channel 10 are circulated, and when the concentration of soluble bicarbonate is lower than the standard, soluble bicarbonate or soluble bicarbonate solution is added to the second liquid channel 10; the inlet and outlet of the third liquid channel 11 are circulated, and when the concentration of the salt inside reaches a certain standard, it is discharged and water is added; the inlet and outlet of the fourth liquid channel 12 are circulated, and when the concentration of lithium-containing brine is lower than a certain standard, lithium-containing brine is added to the fourth liquid channel 12; the liquid in the second electrode liquid channel 13 is circulated to the first electrode liquid channel 8;

[0091] Mode 2: Non-loop mode

[0092] The liquid in the second electrode liquid channel 13 circulates to the first electrode liquid channel 8; the inlet of the first liquid channel 9 inputs water and the outlet outputs lithium bicarbonate solution; the inlet of the second liquid channel 10 inputs bicarbonate solution and the outlet discharges the solution; the inlet of the third liquid channel 11 inputs water and the outlet discharges the salt solution; the inlet of the fourth liquid channel 12 inputs lithium brine and the outlet discharges the solution;

[0093] In industrial production, mode 2 has high losses and is not environmentally friendly, so mode 1 is generally adopted.

[0094] Lithium fluoride preparation system 1

[0095] refer to Figure 2 , using the electrodialysis device 100 as described above, as well as the first resin adsorption column 200, the second resin adsorption column 300, the reactor 400, the filter 500, and the washing device 600;

[0096] The outlet of the first liquid channel 9 of the electrodialysis device 100 is connected to the inlet of the first resin adsorption column 200, the outlet of the first resin adsorption column 200 is connected to the inlet of the second resin adsorption column 300, the outlet of the second resin adsorption column 300 is connected to the inlet of the reactor 400, the reaction product of the reactor 400 is discharged to the filter 500, the filter 500 is filtered to obtain a filter residue, and the filter residue is washed to obtain battery-grade lithium fluoride;

[0097] The reactor 400 is provided with a spray module 410 for spraying the lithium bicarbonate solution into the reactor 400 with the fluoride solution added therein for stirring reaction.

[0098] The first resin adsorption column 200 and the second resin adsorption column 300 are used to adsorb part of the cations and part of the anions, respectively, to improve the purity of lithium bicarbonate; specifically, the first resin adsorption column 200 is LSC-500B resin, which is used to adsorb metal ions such as calcium and magnesium, and the second resin adsorption column 300 is KP-305 resin, which is used to remove trace sulfate in the solution.

[0099] Lithium fluoride preparation system 2

[0100] refer to Figure 3 , which is substantially the same as the first lithium fluoride preparation system, except that the filtrate outlet of the filter 500 is connected to the inlet of the second liquid channel 10 through a pipeline to provide ammonium bicarbonate to the second liquid channel 10. The filtrate discharged from the filter 500 inevitably contains Na ions and / or potassium ions, but when the filtrate enters the electrodialysis device, the potassium ions and / or sodium ions can be separated from the bicarbonate anions and do not enter the first liquid channel 9.

[0101] The second lithium fluoride preparation system has certain particularities in terms of raw material selection. Specifically, the liquid in the second liquid channel 10 must be ammonium bicarbonate; and the fluoride solution in the reaction kettle 400 must be ammonium fluoride solution.

[0102] Part II Preparation of lithium fluoride

[0103] Example 1

[0104] This embodiment 1 adopts lithium fluoride preparation system 1 for production, and adopts mode 1 circulation mode for production;

[0105] The production materials are as follows:

[0106] Lithium brine: The main components are lithium sulfate, Li + :10g / L、Na + ≦1g / L, K + ≦100ppm, Ca 2+ ≦30ppm, Mg 2+ ≦30ppm, other impurities ≦1ppm;

[0107] It should be noted that if lithium-containing brine contains Al and Fe, they can be removed by adjusting the pH value or by adding bicarbonate.

[0108] Soluble bicarbonate: sodium bicarbonate solution, concentration 25wt%;

[0109] water;

[0110] Electrode solution: lithium sulfate solution, lithium ion concentration is 10g / L;

[0111] Ammonium fluoride: concentration 33wt%;

[0112] The concentration standard of the lithium bicarbonate solution discharged from the first liquid channel 9 is 6 to 10 g / L of lithium ions; the sodium bicarbonate concentration in the second liquid channel 10 is maintained at 15 to 25 wt%; the concentration standard of the sodium sulfate solution discharged from the third liquid channel 11 is 20 to 33 g / L of sodium ions; the fourth liquid channel 12 maintains the lithium ion concentration in the lithium sulfate solution at 5 to 10 g / L;

[0113] The lithium bicarbonate solution discharged from the first liquid channel 9 flows through the first resin adsorption column 200 at a flow rate of 1BV / h at room temperature to remove calcium and magnesium ions in the solution, and flows through the second resin adsorption column 300 at a flow rate of 1BV / h to remove trace sulfate in the solution; the indicators of the obtained lithium bicarbonate solution are: Li: 6~10g / L, Na: + ≦1g / L, K + ≦100ppm, Ca 2 + ≦1ppm, Mg 2+ ≦1ppm, other impurities ≦1ppm.

[0114] The solution treated by the second resin adsorption column 300 is sprayed into the reactor; the reactor 400 contains an ammonium fluoride solution configured in a molar ratio of 1:1 with lithium ions; the feeding rate of the lithium bicarbonate solution is 25 ml / min, the feeding time is controlled at 2h, the feeding temperature is 30°C, and the stirring speed is 250r / min; after the feeding is completed, it is kept warm at 30°C for 40min, and the stirring speed is 250r / min;

[0115] After the reaction is completed, the reaction product is discharged to the filter 500, the filter residue is lithium fluoride, and the filtrate is ammonium bicarbonate;

[0116] The filter residue is washed for 5 to 30 minutes with washing water of 400% of the mass of the output, and the washing method is two stirring washings at a stirring temperature of 90°C. Finally, battery-grade lithium fluoride is obtained, and the test results are: purity ≧99.95%, particle size 5-20μm, Na + ≦10ppm, K+ ≦1ppm, other impurities ≦1ppm.

[0117] Example 2

[0118] This embodiment 2 adopts lithium fluoride preparation system 1 for production, and adopts mode 1 circulation mode for production;

[0119] The production materials are as follows:

[0120] Lithium-containing brine: The main components are lithium sulfate, Li: 20g / L, Na + ≦1g / L, K + ≦100ppm, Ca 2+ ≦30ppm, Mg 2 + ≦30ppm, other impurities ≦1ppm;

[0121] Soluble bicarbonate: potassium bicarbonate solution, concentration 30wt%;

[0122] water;

[0123] Electrode solution: lithium sulfate solution, lithium ion concentration is 20g / L;

[0124] Hydrogen fluoride: concentration 35wt%;

[0125] The concentration standard of the lithium bicarbonate solution discharged from the first liquid channel 9 is 6 to 10 g / L of lithium ions; the potassium bicarbonate concentration in the second liquid channel 10 is maintained at 15 to 30 wt%; the concentration standard of the potassium sulfate solution discharged from the third liquid channel 11 is 33 to 56 g / L of potassium ions; the lithium ion concentration in the lithium sulfate solution is maintained at 10 to 20 g / L by the fourth liquid channel 12;

[0126] The lithium bicarbonate solution discharged from the first liquid channel 9 flows through the first resin adsorption column 200 at a flow rate of 1BV / h at room temperature to remove calcium and magnesium ions in the solution, and flows through the second resin adsorption column 300 at a flow rate of 1BV / h to remove trace sulfate in the solution; the indicators of the obtained lithium bicarbonate solution are: Li: 6~10g / L, Na: + ≦500ppm, K + ≦50ppm, Ca 2+ ≦1ppm, Mg 2+ ≦1ppm, other impurities ≦1ppm.

[0127] The solution treated by the second resin adsorption column 300 is sprayed into the reactor; the reactor 400 contains a hydrogen fluoride solution configured in a molar ratio of 1:1 with lithium ions; the feeding rate of the lithium bicarbonate solution is 10 ml / min, the feeding time is controlled at 3 hours, the feeding temperature is 25°C, and the stirring speed is 200 r / min; after the feeding is completed, it is kept warm at 25°C for 30 minutes, and the stirring speed is 300 r / min;

[0128] After the reaction is completed, the reaction product is discharged to the filter 500, the filter residue is lithium fluoride, and the filtrate is a carbonic acid solution;

[0129] The filter residue is washed for 5 to 30 minutes with washing water of 200% of the mass of the output, and the washing method is two stirring washings at a stirring temperature of 90°C. Finally, battery-grade lithium fluoride is obtained, and the test results are: purity ≧99.95%, particle size 5-20μm, Na + ≦10ppm, K + ≦1ppm, other impurities ≦1ppm.

[0130] Example 3

[0131] This embodiment 3 adopts lithium fluoride preparation system 1 for production, and adopts mode 1 circulation mode for production;

[0132] The production materials are as follows:

[0133] Lithium-containing brine: The main components are lithium sulfate, Li: 25g / L, Na + ≦1g / L, K + ≦100ppm, Ca 2+ ≦30ppm, Mg 2 + ≦30ppm, other impurities ≦1ppm;

[0134] Soluble bicarbonate: ammonium bicarbonate solution, concentration 30wt%;

[0135] water;

[0136] Electrode solution: lithium sulfate solution, lithium ion concentration is 25g / L;

[0137] Ammonium fluoride: concentration 30wt%;

[0138] The concentration standard of the lithium bicarbonate solution discharged from the first liquid channel 9 is 6 to 10 g / L of lithium ions; the concentration of ammonium bicarbonate in the second liquid channel 10 is maintained at 15 to 30 wt%; the concentration standard of the ammonium sulfate solution discharged from the third liquid channel 11 is 15 to 26 g / L of ammonium ions; the lithium ion concentration in the lithium sulfate solution is maintained at 15 to 25 g / L in the fourth liquid channel 12;

[0139] The lithium bicarbonate solution discharged from the first liquid channel 9 flows through the first resin adsorption column 200 at a flow rate of 1BV / h at room temperature to remove calcium and magnesium ions in the solution, and flows through the second resin adsorption column 300 at a flow rate of 1BV / h to remove trace sulfate in the solution; the indicators of the obtained lithium bicarbonate solution are: Li: 6~10g / L, Na: + ≦400ppm, K + ≦40ppm, Ca 2+ ≦1ppm, Mg 2+ ≦1ppm, other impurities ≦1ppm.

[0140] The solution treated by the second resin adsorption column 300 is sprayed into the reactor; the reactor 400 contains an ammonium fluoride solution configured in a molar ratio of 1:1 with lithium ions; the feeding rate of the lithium bicarbonate solution is 30 ml / min, the feeding time is controlled at 2h, the feeding temperature is 25°C, and the stirring speed is 200r / min; after the feeding is completed, it is kept warm at 25°C for 30min, and the stirring speed is 200r / min;

[0141] After the reaction is completed, the reaction product is discharged to the filter 500, the filter residue is lithium fluoride, and the filtrate is ammonium bicarbonate;

[0142] The filter residue is washed for 5 to 30 minutes with washing water of 500% of the mass of the output, and the washing method is two stirring washings at a stirring temperature of 90°C. Finally, battery-grade lithium fluoride is obtained, and the test results are: purity ≧99.95%, particle size 5-20μm, Na + ≦10ppm, K + ≦1ppm, other impurities ≦1ppm.

[0143] Example 4

[0144] This embodiment 4 adopts lithium fluoride preparation system 2 for production, and adopts mode 1 circulation mode for production;

[0145] The production materials are as follows:

[0146] Lithium-containing brine: The main component is lithium sulfate, Li: 25g / L, K + ≦1g / L, other impurities ≦5ppm;

[0147] Soluble bicarbonate: ammonium bicarbonate solution, concentration 30wt%;

[0148] water;

[0149] Electrode solution: lithium sulfate solution, lithium ion concentration is 25g / L;

[0150] Ammonium fluoride: concentration 35wt%;

[0151] The concentration standard of the lithium bicarbonate solution discharged from the first liquid channel 9 is 6 to 10 g / L of lithium ions; the concentration of ammonium bicarbonate in the second liquid channel 10 is maintained at 15 to 30 wt%; the concentration standard of the ammonium sulfate solution discharged from the third liquid channel 11 is 15 to 26 g / L of ammonium ions; the lithium ion concentration in the lithium sulfate solution is maintained at 15 to 25 g / L in the fourth liquid channel 12;

[0152] The lithium bicarbonate solution discharged from the first liquid channel 9 flows through the first resin adsorption column 200 at a flow rate of 1BV / h at room temperature to remove calcium and magnesium ions in the solution, and flows through the second resin adsorption column 300 at a flow rate of 1BV / h to remove trace sulfate in the solution; the indicators of the obtained lithium bicarbonate solution are: Li: 6-10g / L, K + ≦60ppm, Ca≦1ppm, other impurities≦5ppm, SO4 2- ≦5ppm.

[0153] The solution treated by the second resin adsorption column 300 is sprayed into the reactor; the reactor 400 contains an ammonium fluoride solution configured in a molar ratio of 1:1 with lithium ions; the feeding rate of the lithium bicarbonate solution is 30 ml / min, the feeding time is controlled at 2h, the feeding temperature is 25°C, and the stirring speed is 200r / min; after the feeding is completed, it is kept warm at 25°C for 30min, and the stirring speed is 200r / min;

[0154] After the reaction is completed, the reaction product is discharged to the filter 500, the filter residue is lithium fluoride, the filtrate is ammonium bicarbonate, and the ammonium ion concentration is 4.5-7 g / L; the concentration of ammonium bicarbonate is 23.7 g / L-36.9 g / L, which can be directly reused in the electrodialysis equipment or adjusted to 30 wt% before reuse in the electrodialysis equipment.

[0155] The filter residue is washed for 5 to 30 minutes with washing water of 300% of the mass of the output, and the washing method is two stirring washings at a stirring washing temperature of 90°C. Finally, battery-grade lithium fluoride is obtained, and the test results are: purity ≧99.95%, particle size 5 to 20 μm, K + ≦10ppm, other impurities ≦1ppm.

[0156] Result analysis:

[0157] 1. It can be seen from Examples 1 to 3 that by using an electrodialysis device, lithium-containing brine and soluble bicarbonate as raw materials, it is not necessary to purify the lithium-containing brine to a high purity. After electrodialysis, cation adsorption can be performed to prepare lithium fluoride. The process is simple and there is no need to purify the raw materials to a high purity.

[0158] The process and system of the present invention are the first continuous production process and flow for preparing battery-grade lithium fluoride from brine in the industry.

[0159] 2. It can be seen from Example 4 that by using ammonium bicarbonate as the raw material for electrodialysis and ammonium fluoride as the raw material for preparing lithium fluoride, the generated filtrate can provide bicarbonate for the first liquid channel after entering the electrodialysis device, thereby achieving complete reuse of the filtrate.

[0160] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing lithium fluoride, characterized in that: The steps include: Step 1: using lithium-containing brine and soluble bicarbonate as raw materials, using electrodialysis equipment to combine cations in the lithium-containing brine and bicarbonate anions in the soluble bicarbonate to prepare a first solution containing lithium bicarbonate; Step 2: removing non-+1 valence metal cations in the first solution to obtain a second solution containing lithium bicarbonate; Step 3: reacting the second solution with fluoride to prepare lithium fluoride; The fluoride is ammonium fluoride or hydrogen fluoride.

2. The method for preparing lithium fluoride according to claim 1, characterized in that: The soluble bicarbonate is one or more combinations of ammonium bicarbonate, sodium bicarbonate and potassium bicarbonate; and the fluoride is ammonium fluoride.

3. The method for preparing lithium fluoride according to claim 2, characterized in that: The step 3 specifically comprises: reacting the second solution with ammonium fluoride, wherein the solid product after the reaction is lithium fluoride, and the liquid product after the reaction is ammonium bicarbonate solution; and the ammonium bicarbonate solution is used as the raw material of step 1.

4. The method for preparing lithium fluoride according to claim 1, characterized in that: In step 2, ion exchange resin is used to remove the non-+1 valence metal cations.

5. The method for preparing lithium fluoride according to claim 1, characterized in that: The lithium-containing brine is one or more combinations of ore lithium extraction liquid, electrode lithium extraction liquid, and lithium sulfate solution after impurities are removed; The cation composition of the lithium-containing brine is: Li≧10g / L, Na≦1g / L, K≦100ppm, Ca≦30ppm, Mg≦30ppm, and other impurities≦1ppm.

6. The method for preparing lithium fluoride according to claim 1, characterized in that: The cations of the solute of the electrode solution used in the electrodialysis equipment are lithium ions, and the anions of the solute of the electrode solution are one or more combinations of nitrate, sulfate, chloride, hydroxide, and perchlorate.

7. The method for preparing lithium fluoride according to claim 1, characterized in that: The soluble bicarbonate exists in the form of a soluble bicarbonate solution; the concentration of bicarbonate in the soluble bicarbonate solution is 20 to 35 wt%; The fluoride exists in the form of a fluoride solution, and the concentration of the fluoride solution is 30-35wt%; The lithium ion concentration in the lithium-containing brine is 10 g / L to 25 g / L; In step 3, the molar ratio of the fluoride ions to the lithium ions in the lithium bicarbonate is 1:1; In the step 3, the second solution is added to the fluoride solution by spraying; after the reaction in step 3 is completed, filtering is performed, and the filter residue is lithium fluoride; the filter residue is washed to obtain battery-grade lithium fluoride; The reaction temperature of step 3 is 20-35° C., and the reaction time is 1-4 hours.

8. The method for preparing lithium fluoride according to claim 1, characterized in that: The lithium-containing brine in step 1 is pre-cleaned to remove impurity metal ions; the impurity metal ions are metal ions that form precipitates after combining with bicarbonate or that form precipitates after the formed bicarbonate is hydrolyzed.

9. A system for implementing the methods of claims 1 to 8, characterized in that: It includes an electrodialysis device, an impurity removal device, a reactor, and a filter connected in sequence; The electrodialysis equipment comprises a multilayer cation exchange membrane, anion exchange membrane and an outermost positive electrode plate and negative electrode plate; the cation exchange membrane and the anion exchange membrane are alternately arranged to form a plurality of liquid channels; the positive electrode plate and the negative electrode plate and the corresponding adjacent cation exchange membranes respectively form a first electrode liquid channel and a second electrode liquid channel; the plurality of liquid channels are sequentially: a first liquid channel, a second liquid channel, a third liquid channel and a fourth liquid channel; the first electrode liquid channel and the second electrode liquid channel form a circulation and the circulating liquid is the electrode liquid; The second liquid channel is used to introduce the raw material soluble bicarbonate solution, provide bicarbonate to the first liquid channel, and provide cations to the third liquid channel; The fourth liquid channel is used to introduce raw lithium-containing brine, provide anions in the lithium-containing brine to the third liquid channel, and provide cations in the lithium-containing brine to the second electrode liquid channel to supplement the cations in the electrode liquid; The first electrode liquid channel is used to provide cations in the electrode liquid to the first liquid channel; A first liquid channel: used to generate the first solution using cations provided by the first electrode liquid channel and bicarbonate ions provided by the second liquid channel; The third liquid channel is used to recover the cations of the raw material passed into the second liquid channel and the anions of the raw material passed into the fourth liquid channel; The impurity removal equipment is used to process the first solution to obtain the second solution; The reaction kettle is used to react the second solution with the fluoride; The filter is used to filter the reaction product of the reactor, and the collected filter residue is lithium fluoride.

10. The system according to claim 9, characterized in that The soluble bicarbonate is ammonium bicarbonate; the fluoride is ammonium fluoride; The filtrate outputted from the filter is transported to the inlet of the second liquid channel through a pipeline.

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