Manufacturing method for lithium hydroxide

Abstract

The present invention relates to a manufacturing method for lithium hydroxide and, particularly, to a manufacturing method for high-purity lithium hydroxide. More particularly, the present invention relates to a manufacturing method for lithium hydroxide, comprising: a step in which a lithium salt aqueous solution is injected into a salt compartment between adjacent anion dialysis and cation dialysis membranes of a bipolar electrodialysis device, an acid-compartment reaction solution is injected into an acid compartment between a bipolar membrane and the anion dialysis membrane, and a base-compartment reaction solution is injected into a base compartment between a bipolar membrane and the cation dialysis membrane; a step in which a desalted solution formed in the salt compartment is supplied to a salt tank, an acid solution formed in the acid compartment is supplied to an acid tank, and a lithium hydroxide solution formed in the base compartment is supplied to a base tank; and a step in which the desalted solution in the salt tank is circulated and supplied to the salt compartment, the acid solution in the acid tank is circulated and supplied to the acid compartment, and the lithium hydroxide solution in the base tank is circulated and supplied to the base compartment, wherein the gauge pressure of the salt compartment is higher than the gauge pressure of the acid compartment.

Description

Method for producing lithium hydroxide

[0001] The present invention relates to a method for producing lithium hydroxide, and more specifically, to a method for producing high-purity lithium hydroxide using an electrodialysis method capable of controlling impurities.

[0002]

[0003] With the recent rapid growth of the IT and electric vehicle markets, demand for lithium, a key raw material for secondary batteries, is expected to increase significantly. The lithium market for secondary batteries is heavily concentrated in Korea, China, and Japan. However, Korea relies entirely on imports, necessitating a stable supply and demand mechanism. Therefore, lithium extraction technologies from ore and brine are being developed, and a demonstration plant for producing lithium carbonate and lithium hydroxide from ore is in operation in Korea. Several companies in South America and China are producing large quantities of lithium, and research into lithium production is also underway in Korea.

[0004] The lithium production process currently underway in Korea extracts lithium from ore in the form of a lithium sulfate solution and then uses electrodialysis to produce lithium hydroxide. This lithium hydroxide solution is then crystallized to produce lithium hydroxide (LiOH-H2O). The crystallization rate of the crystallizer is determined by the concentration of impurities in the lithium hydroxide solution produced during the electrodialysis process, and the availability and production volume of battery-grade lithium depend on this crystallization rate. Ultimately, controlling impurities during the electrodialysis process is a critical factor in lithium production.

[0005] Therefore, there is a need to develop a method for manufacturing lithium hydroxide that can reduce impurities.

[0006]

[0007] One object of the present invention is to provide a method for efficiently producing lithium hydroxide while reducing the generation of impurities, and more specifically, to provide a method for producing lithium hydroxide capable of reducing impurities in a lithium hydroxide solution produced by controlling the pressure of a base chamber, an acid chamber, etc., depending on the state of a membrane in an electrodialysis process.

[0008]

[0009] A method for producing high-purity lithium hydroxide according to one embodiment of the present invention comprises the steps of: introducing a lithium salt aqueous solution into a salt chamber between adjacent anion dialysis membranes and cation dialysis membranes of a bipolar electrodialysis device, introducing an acid chamber reaction solution into an acid chamber between the bipolar membranes and the anion dialysis membrane, and introducing a base chamber reaction solution into a base chamber between the bipolar membranes and the cation dialysis membrane; supplying a demineralized solution formed in the salt chamber to a salt tank, supplying an acid solution formed in the acid chamber to an acid tank, and supplying a lithium hydroxide solution formed in the base chamber to a base tank; And it may include a step of circulating and supplying the demineralized solution of the salt tank to the salt room, circulating and supplying the acid solution of the acid tank to the acid room, and circulating and supplying the lithium hydroxide solution of the base tank to the base room. The gauge pressure of the salt room may be higher than the gauge pressure of the acid room.

[0010] The gauge pressure difference between the salt chamber and the acid chamber may be 0.001 to 0.5 bar, and specifically, 0.005 to 0.05 bar.

[0011] The gauge pressure inside the salt chamber, acid chamber, and base chamber may be 0.1 to 2 bar, and specifically, 0.1 to 0.5 bar.

[0012] The pressure difference between the salt chamber and the acid chamber and the pressure difference between the salt chamber and the base chamber may be 0 to 1 bar.

[0013] The linear velocity of the internal solution flow in the acid and base chambers may be 1 to 30 cm / s.

[0014] By controlling the flow rate of the demineralized solution circulated from the salt tank to the salt room, the flow rate of the acid solution circulated from the acid tank to the acid room, and the flow rate of the lithium hydroxide solution circulated from the base tank to the base room, the internal pressures of the salt room, the acid room, and the base room can be controlled.

[0015] The method includes a step of supplying a lithium hydroxide solution formed in the base chamber to a base tank, and then supplying a portion of the lithium hydroxide solution supplied to the base tank to a subsequent crystallization device to form lithium hydroxide monohydrate (LiOH·H2O) crystals, wherein the crystallization rate of the lithium hydroxide monohydrate (LiOH·H2O) may be 90% or more.

[0016]

[0017] According to one embodiment of the present invention, impurities in lithium hydroxide produced by controlling the pressure of a base chamber, an acid chamber, etc., depending on the state of the membrane in the electrodialysis process can be reduced.

[0018] In addition, the production of battery-grade lithium hydroxide can be increased by minimizing the content of impurities in the lithium hydroxide solution produced in the electrodialysis process and thereby increasing the crystallization rate of the subsequent lithium hydroxide crystallization process.

[0019]

[0020] Figure 1 schematically illustrates an electrodialysis device according to one embodiment of the present invention.

[0021] Figure 2 schematically illustrates an electrodialysis system according to one embodiment of the present invention.

[0022] Figure 3 shows the gauge pressures of the base chamber and acid chamber of the electrodialysis device in a continuous experiment of a demo plant.

[0023] Figure 4 shows the concentration of sulfur (S) components in the lithium hydroxide aqueous solution formed in the base chamber of the electrodialysis device in a continuous experiment of a demo plant.

[0024]

[0025] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0027] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0028] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0029] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0030] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0031] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0032]

[0033] Figure 1 schematically illustrates an electrodialysis device according to one embodiment of the present invention.

[0034] Referring to FIG. 1, a bipolar electrodialysis device according to one embodiment of the present invention may include unit pairs that are repeatedly stacked and positioned between an anode cell and a cathode cell. The unit pair may have a configuration in which a bipolar membrane, an anion dialysis membrane, and a cation dialysis membrane are sequentially positioned. Specifically, the configuration may have a bipolar membrane, a spacer gasket, an anion dialysis membrane, a spacer gasket, a cation dialysis membrane, and a spacer gasket sequentially positioned. The unit pairs of the configuration may be sequentially positioned adjacent to each other. Among two adjacent unit pairs, the spacer gasket positioned at the rear end of the cation dialysis membrane of the unit pair positioned at the front may be positioned adjacent to the biopolar membrane of the unit pair positioned adjacent to the rear end.

[0035] Referring to Figure 1, the first bipolar membrane and the anion dialysis membrane may form an acid chamber, and the anion dialysis membrane and the cation dialysis membrane may form a salt chamber. In addition, the cation dialysis membrane and the second bipolar membrane may form a base chamber.

[0036] Hereinafter, a method for producing lithium hydroxide according to one embodiment of the present invention will be described.

[0037] First, a lithium salt solution is injected into the salt chamber of the unit pair, an acid chamber reaction solution is injected into the acid chamber, and a base chamber reaction solution is injected into the base chamber to perform bipolar electrodialysis.

[0038] At this time, when voltage is applied to the bipolar electrodialysis device to cause current to flow, an acid solution is formed in the acid chamber, a lithium hydroxide aqueous solution is formed in the base chamber, and a deionized water containing the remaining lithium salt that did not react in the introduced lithium salt aqueous solution is formed in the salt chamber.

[0039] Specifically, the formation process of the acid solution and lithium hydroxide aqueous solution is as follows.

[0040] First, the acid reaction solution introduced into the acid chamber is hydrolyzed on the surface of the first bipolar membrane of the acid chamber and decomposed into hydrogen ions and hydroxide ions. At this time, the decomposed hydroxide ions move to the positive electrode cell, and the decomposed hydrogen ions move between the first bipolar membrane and the anion dialysis membrane. Meanwhile, the anions of the lithium salt aqueous solution introduced between the anion dialysis membrane and the cation dialysis membrane pass through the anion dialysis membrane and move between the first bipolar membrane and the anion dialysis membrane. Then, the hydrogen ions and the anions are concentrated between the first bipolar membrane and the anion dialysis membrane to form an acid solution.

[0041] Next, the process by which lithium hydroxide solution is formed is as follows. The base reaction solution introduced into the base chamber is hydrolyzed on the surface of the second bipolar membrane and decomposed into hydrogen ions and hydroxide ions. At this time, the decomposed hydrogen ions move to the cathode cell, and the decomposed hydroxide ions move between the cation dialysis membrane and the second bipolar membrane. Meanwhile, the lithium ions of the lithium salt solution introduced between the anion dialysis membrane and the cation dialysis membrane pass through the cation dialysis membrane and move to the base chamber into which they are introduced. In addition, the hydroxide ions and the lithium ions are concentrated in the base chamber to form a lithium hydroxide solution.

[0042] More specifically, the acid group meets the hydrogen hydrolyzed in the bipolar membrane on the positive cell side and is converted into an acid, and the lithium ions moving to the negative electrode through the cation dialysis membrane are converted into hydroxyl groups (OH) generated in the bipolar membrane. - ) reacts with lithium and converts to lithium hydroxide (LiOH).

[0043] As an example, the overall reaction equation may be as follows.

[0044] Li2SO4(aq) ⇔ 2Li+ (base chamber) + SO4 2- (acid chamber)

[0045] H2O ⇔ H + (acid chamber) + OH - (base chamber)

[0046] Li2SO4(aq)+ 2H2O ⇔ 2LiOH(aq, base chamber) + H2SO4(aq, acid chamber)

[0047] At this time, the high-concentration lithium salt solution injected into the salt chamber is decomposed into lithium ions and acid groups and escapes, and a low-concentration lithium salt solution with some remaining is generated and can be discharged outside the electrodialysis device.

[0048] In one embodiment of the present invention, the lithium salt may be specifically sulfate (Li2SO4), and the acid may be sulfuric acid (H2SO4). Meanwhile, the acid reaction solution may be a low-concentration acid or water (deionized water), and the base reaction solution may be a low-concentration lithium hydroxide aqueous solution or water (deionized water).

[0049] In addition, the lithium salt solution formed in the above salt room can be injected into a unit pair located adjacent to the rear end to perform the same electrodialysis as the previous unit pair.

[0050] At this time, the direction of cation or anion movement may vary depending on the state of the membranes. For example, if a pinhole is formed in the membrane, a physical flow of solution occurs through the pinhole. In this case, the pressure in each chamber can be adjusted to minimize the flow of solution, thereby controlling the flow of solution through the pinhole and minimizing the inflow of impurities.

[0051] Figure 2 schematically illustrates an electrodialysis system according to one embodiment of the present invention.

[0052] Referring to FIG. 2, an electrodialysis system for producing lithium hydroxide according to one embodiment of the present invention may mainly include the electrodialysis device and circulation unit of FIG. 1.

[0053] The above circulation section may mainly include a base tank, an acid tank, and a salt tank.

[0054] Specifically, a lithium hydroxide-containing solution formed and discharged in the base chamber of the electrodialysis device flows into the base tank of the circulation unit, a high-concentration acid-containing solution formed and discharged in the acid chamber of the electrodialysis device flows into the acid tank of the circulation unit, and a demineralized solution formed and discharged in the salt chamber of the electrodialysis device flows into the salt tank of the circulation unit.

[0055] A partition is installed in the base tank, acid tank, and salt tank so that a portion of the solutions flowing into each tank can be discharged to the outside, and the remainder can be mixed with water (deionized water) or salt solution that is additionally introduced separately and circulated to the electrodialysis device. The circulating solutions in each tank of the circulation section can be circulated to the electrodialysis device through a circulation pump or the like.

[0056] In one embodiment of the present invention, the gauge pressure of the acid chamber, base chamber, and salt chamber may be 0.1 to 2 bar, specifically 0.1 to 1 bar, more specifically 0.1 to 0.5 bar, and even more specifically 0.2 to 0.45 bar.

[0057] Meanwhile, the pressure difference (△P) between adjacent rooms in the above electrodialysis device may be 1 bar or less, specifically 0.001 to 0.5 bar, more specifically 0.001 to 0.1 bar, and even more specifically 0.001 to 0.05 bar.

[0058] When the pressure inside each chamber of the electrodialysis device and the pressure difference (△P) between adjacent chambers satisfy the above range, the device can be operated stably by preventing damage to each membrane located between each chamber.

[0059] In one embodiment of the present invention, the base chamber pressure of the electrodialysis device may be higher than the acid chamber pressure. Specifically, the pressure difference between the base chamber pressure and the acid chamber pressure may be 1 bar or less, specifically 0.001 to 0.5 bar, more specifically 0.001 to 0.1 bar, and even more specifically 0.005 to 0.05 bar.

[0060] When the above base pressure, acid pressure, and the pressure difference between the base pressure and the acid pressure satisfy the above conditions, not only can lithium hydroxide be stably manufactured, but also the base pressure is relatively high, so impurities in the manufactured lithium hydroxide solution can be reduced.

[0061] In one embodiment of the present invention, a portion of the solutions introduced into the base tank, acid tank, and salt tank may be discharged to the outside, and the remaining solutions may be mixed with additionally introduced water (deionized water) or salt solution to adjust the concentration, and then circulated and supplied to the electrodialysis device.

[0062] A partition may be installed within the above-described base tank, acid tank, and salt tank to form a space capable of separating and containing solutions. The concentrations of the solutions described below can be controlled within the space formed. As long as the lithium hydroxide desired in the present invention can be stably and efficiently produced, there are no particular limitations on the materials, shapes, etc. of the base tank, acid tank, salt tank, and partition.

[0063]

[0064] Specifically, a portion of the lithium hydroxide solution introduced into the base tank is supplied to the subsequent crystallization process. The Li concentration of the lithium hydroxide solution may be 10 g / L to 30 g / L, specifically 15 g / L to 25 g / L, and more specifically 18 g / L to 22 g / L. If the Li concentration in the lithium hydroxide solution is too low, the amount of water that must be evaporated in the subsequent crystallization process increases, which increases energy costs. If the Li concentration is too high, the current efficiency of the electrodialysis device itself decreases. If the current efficiency decreases, there is a problem that the electricity cost required to produce Li increases. The remaining lithium hydroxide solution may be mixed with water (deionized water) introduced separately and circulated back to the base chamber of the electrodialysis device. At this time, the lithium hydroxide solution mixed with the water (deionized water) can be circulated and supplied to the base chamber of the electrodialysis device through a circulation pump, and the circulated supply flow rate can be adjusted according to the target pressure of the base chamber of the electrodialysis device. In other words, the pressure inside the base chamber can be controlled by adjusting the supply flow rate of the lithium hydroxide solution circulated and supplied to the base chamber of the electrodialysis device.

[0065] A portion of the high-concentration acid solution introduced into the acid tank is discharged to the outside. The discharged acid is a sulfuric acid solution, and the mass concentration may be 5% to 20%, specifically 8% to 12%. The concentration of sulfuric acid should be controlled within a range that maintains the pH of the salt room, and in this facility, the pH of the salt is maintained between 1.5 and 2.5. OH diffuses from the base room and passes to the acid room. - H passing from acid to salt room than the amount of ions + When the amount of ions is large, the pH of the salt decreases. Therefore, depending on the concentration of the base, the H that diffuses + The pH of the salt is maintained by adjusting the amount of Li in the base. + For concentration, the above acid concentration is appropriate. The remaining acid can be mixed with additionally introduced water (deionized water) and circulated back into the acid chamber of the electrodialysis device. The acid solution can be circulated into the acid chamber of the electrodialysis device through a circulation pump, and the circulating supply flow rate can be controlled according to the target pressure of the acid chamber of the electrodialysis device. In other words, the pressure inside the acid chamber can be controlled by controlling the supply flow rate of the acid solution circulated into the acid chamber of the electrodialysis device.

[0066] A portion of the desalinated solution introduced into the salt tank is discharged to the outside, and the remaining salt is mixed with a separately introduced salt solution and then circulated back into the salt chamber of the electrodialysis device. The desalinated solution can be circulated into the salt chamber of the electrodialysis device through a circulation pump, and the circulating supply flow rate can be adjusted according to the target pressure of the salt chamber of the electrodialysis device.

[0067] Meanwhile, the linear velocity of the solution flow in each of the acid, base, and salt chambers may be 1 to 30 cm / s, specifically 1 to 15 cm / s, more specifically 1 to 7.5 cm / s, and even more specifically 3 to 7 cm / s.

[0068] When the linear velocity of the solution flow in each of the acid, base, and salt chambers is within the above range, lithium hydroxide can be stably produced while reducing impurities in the produced lithium hydroxide solution.

[0069] A portion of the lithium hydroxide solution introduced into the base tank may be supplied to a subsequent crystallization process to form lithium hydroxide monohydrate (LiOH·H2O) crystals. When producing lithium hydroxide monohydrate (LiOH·H2O) by crystallizing the lithium hydroxide aqueous solution, the crystallization rate of the lithium hydroxide monohydrate (LiOH·H2O) may be 90% or more, and specifically, 92% to 96%. The crystallization rate may decrease. This is because the crystallization rate must decrease as the impurities increase in order to produce battery-grade lithium hydroxide monohydrate.

[0070] The crystallization rate of lithium hydroxide monohydrate (LiOH·H2O) is affected by impurities contained in the lithium hydroxide aqueous solution supplied to the crystallization device. The impurity that directly affects the crystallization rate is SO4. 2- In particular, since the selectivity of the cation dialysis membrane, anion dialysis membrane, and bipolar (BP) membrane applied to the electrodialysis device that manufactures lithium hydroxide (LiOH) from lithium sulfate (Li2SO4) cannot be 100%, it can be seen that it is impossible to manufacture a pure product with no impurities at all. Therefore, it is necessary to reduce as much as possible the impurities generated in the electrodialysis process, such as impurities in the lithium hydroxide solution formed in the base room.

[0071] In one embodiment of the present invention, the concentration of sulfur (S) in the lithium hydroxide-containing solution formed and discharged from the base chamber of the electrodialysis device may be less than 1 g / L, and specifically may be 0.9 g / L or less.

[0072]

[0073] (Lithium hydroxide production experiment)

[0074] A lithium hydroxide production experiment was conducted in a demo plant including an electrodialysis system of the configuration shown in Fig. 2.

[0075] A method for producing lithium hydroxide, comprising a step of obtaining a lithium hydroxide aqueous solution from the above lithium salt aqueous solution, wherein a lithium sulfate (Li2SO4) aqueous solution is introduced into a salt chamber, and a deionized solution containing residual lithium sulfate (Li2SO4) is discharged from the salt chamber and supplied to a separately provided salt tank. A sulfuric acid (H2SO4) aqueous solution is formed by introducing water (deionized water) into an acid chamber, and is discharged from the acid chamber and supplied to an acid tank. Water (deionized water) is introduced into a base chamber, and a lithium hydroxide aqueous solution formed in the base chamber is discharged from the base chamber and supplied to a base tank.

[0076] A portion of the demineralized solution supplied to the above salt tank is discharged outside the salt tank. The remaining demineralized solution is mixed with lithium sulfate (Li2SO4) additionally supplied from outside, and the lithium sulfate (Li2SO4) concentration is adjusted, and then circulated to the salt chamber of the electrodialysis device. At this time, the circulating supply flow rate is 8 to 15 m 3 / hr.

[0077] A portion of the sulfuric acid (H2SO4) aqueous solution supplied to the acid tank is discharged outside the acid tank, and the sulfuric acid (H2SO4) aqueous solution remaining in the acid tank is mixed with additionally supplied water (deionized water) and then circulated to the acid chamber of the electrodialysis device. At this time, the circulating supply flow rate is 8 to 15 m 3 / hr. The gauge pressure of the acid chamber of the above electrodialysis device is shown in Table 1 below.

[0078] A portion of the lithium hydroxide (LiOH) aqueous solution supplied to the above base tank can be supplied to a crystallization device to form lithium hydroxide monohydrate (LiOH H2O) crystals. The lithium hydroxide (LiOH) aqueous solution remaining in the base tank is circulated to the base chamber of the electrodialysis device after its concentration is adjusted by additionally supplied water (deionized water). At this time, the circulating supply flow rate is 8 to 15 m 3 / hr.

[0079] Meanwhile, the effective area of ​​the cation dialysis membrane, anion dialysis membrane, and bipolar membrane placed in the electrodialysis device is 0.5 m 2 , and 720 sheets of film were applied per press. At this time, the linear velocity of the fluid inside the acid room, base room, and salt room is approximately 6 cm / s.

[0080] The sulfur (S) concentration in the lithium hydroxide aqueous solution and the crystallization rate of lithium hydroxide monohydrate (LiOH·H2O) formed in the crystallization device according to comparative examples and examples in which the gauge pressure difference between the base chamber and the acid chamber of the electrodialysis device was changed are shown in Table 1 below. These are the test results when producing battery grade lithium hydroxide monohydrate in an actual process.

[0081] Gauge pressure (bar) Base discharge S concentration in LiOH aqueous solution (g / L) Crystallization rate (%) Base discharge Acid discharge △P(P base -P acid) Comparative Example 10.2310.236-0.0051.00~1.0388~90 Exemplary Example 10.2290.2160.0120.80~0.8592~95 Exemplary Example 20.2320.2180.0130.80~0.8592~95 Exemplary Example 30.4110.3790.0310.60~0.6494~96

[0082] Referring to Table 1 above, in the cases of Examples 1 to 3 in which the gauge pressure of the base chamber was higher than that of the acid chamber, the sulfur (S) concentration in the lithium hydroxide (LiOH) aqueous solution formed and discharged from the base chamber of the electrodialysis device was found to be 0.60 to 0.85 g / L. On the other hand, in the case of Comparative Example 1 in which the gauge pressure of the base chamber was lower than that of the acid chamber, the sulfur (S) concentration in the manufactured lithium hydroxide (LiOH) aqueous solution was found to be high, at 1.00 to 1.03 g / L.

[0083] In addition, in the case of Examples 1 to 3, the crystallization rate of lithium hydroxide monohydrate (LiOH·H2O) formed in the crystallization device was higher than 90%, whereas in the case of Comparative Example 1, the crystallization rate of lithium hydroxide monohydrate (LiOH·H2O) was found to be 90% or less.

[0084]

[0085] A continuous experiment was conducted for 24 hours in a demo plant. Figure 3 shows the gauge pressures of the base chamber and acid chamber of the electrodialysis device in a continuous experiment in the demo plant, and Figure 4 shows the concentration of sulfur (S) components in the lithium hydroxide aqueous solution formed in the base chamber of the electrodialysis device in a continuous experiment in the demo plant.

[0086] Referring to FIGS. 3 and 4, when the gauge pressure of the base chamber is higher than the gauge pressure of the acid chamber in the first reaction section, it can be confirmed that the sulfur (S) concentration in the lithium hydroxide aqueous solution formed and discharged from the base chamber of the electrodialysis device is 1 g / L or more. When the gauge pressure of the base chamber is lower than the gauge pressure of the acid chamber in the second reaction section, it can be confirmed that the sulfur (S) concentration in the lithium hydroxide aqueous solution formed and discharged from the base chamber of the electrodialysis device is less than 0.95 g / L.

[0087]

[0088] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A step of injecting a lithium salt solution into a salt chamber between adjacent anion dialysis membranes and cation dialysis membranes of a bipolar electrodialysis device, injecting an acid chamber reaction solution into an acid chamber between the bipolar membranes and anion dialysis membrane, and injecting a base chamber reaction solution into a base chamber between the bipolar membranes and cation dialysis membrane; A step of supplying the demineralized solution formed in the salt room to a salt tank, supplying the acid solution formed in the acid room to an acid tank, and supplying the lithium hydroxide solution formed in the base room to a base tank; and A step of circulating and supplying the demineralized solution of the salt tank to the salt room, circulating and supplying the acid solution of the acid tank to the acid room, and circulating and supplying the lithium hydroxide solution of the base tank to the base room; The gauge pressure of the above salt chamber is higher than the gauge pressure of the above acid chamber. Method for producing lithium hydroxide.

2. In paragraph 1, The gauge pressure difference between the salt chamber and the acid chamber is 0.001 to 0.5 bar. Method for producing lithium hydroxide.

3. In paragraph 2, The gauge pressure difference between the salt chamber and the acid chamber is 0.005 to 0.05 bar. Method for producing lithium hydroxide.

4. In paragraph 1, The gauge pressure inside the salt room, acid room and base room is 0.1 to 2 bar. Method for producing lithium hydroxide.

5. In paragraph 4, The gauge pressure inside the salt room, acid room and base room is 0.1 to 0.5 bar. Method for producing lithium hydroxide.

6. In paragraph 1, The pressure difference between the salt chamber and the acid chamber and the pressure difference between the salt chamber and the base chamber are 0 to 1 bar. Method for producing lithium hydroxide.

7. In paragraph 1, The linear velocity of the internal solution flow in the acid and base chambers is 1 to 30 cm / s. Method for producing lithium hydroxide.

8. In paragraph 1, By controlling the flow rate of the demineralized solution circulated from the salt tank to the salt room, the flow rate of the acid solution circulated from the acid tank to the acid room, and the flow rate of the lithium hydroxide solution circulated from the base tank to the base room, the internal pressure of the salt room, the acid room, and the base room is controlled. Method for producing lithium hydroxide.

9. In paragraph 1, The lithium hydroxide solution formed in the above base room is then supplied to the base tank, A step of supplying a portion of the lithium hydroxide solution supplied to the base tank to a subsequent crystallization device to form lithium hydroxide monohydrate (LiOH·H2O) crystals is included. The crystallization rate of the lithium hydroxide monohydrate (LiOH·H2O) is 90% or more. Method for producing lithium hydroxide.

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