Spacer for electrodialysis system and electrodialysis system comprising same

Abstract

The spacer for electrodialysis according to the present invention comprises: a first outer peripheral portion; a second outer peripheral portion; and a central portion located between the first and second outer peripheral portions. At least one of the first and second outer peripheral portions has a different flow resistance from the central portion.

Description

Spacer for an electrodialysis system and an electrodialysis system comprising the same

[0001] The present invention relates to a spacer for an electrodialysis system and an electrodialysis system including the same.

[0002] With the advent of the electric vehicle era, the lithium-ion battery industry is growing rapidly, and as a result, the demand for lithium as a battery material is continuously increasing.

[0003] Lithium is commercially produced largely through extraction from ore and production from brine. Most lithium produced from ore is produced using the sulfuric acid process from spodumene concentrate. Lithium produced from brine is primarily produced from underground brine in South America, using natural drying, byproduct removal, and additional processing. In the future, with the proliferation of electric vehicles, the proportion of recycled lithium, which is re-extracted from spent batteries and used in lithium-ion battery production, is expected to increase.

[0004] Meanwhile, lithium intermediates used in the production of battery materials were mainly in the form of lithium carbonate in the past, but as extending the driving range of electric vehicles has emerged as a major technological issue, demand for high-power-density batteries is increasing, and the demand for lithium hydroxide, a raw material for high-power-density battery materials, is rapidly increasing.

[0005] Lithium hydroxide is mainly produced by the lime process, which involves reacting lithium carbonate and calcium hydroxide. However, recently, a process for producing lithium hydroxide directly from intermediate substances such as lithium sulfate, lithium chloride, and lithium phosphate without going through lithium carbonate has been attracting attention.

[0006] Representative processes for producing lithium hydroxide directly from ore include the causticization process, which reacts a lithium sulfate solution with sodium hydroxide to produce lithium hydroxide, generating sodium sulfate as a byproduct, and the bipolar electrodialysis (BPED) process, which separates a lithium hydroxide solution into lithium hydroxide and sulfuric acid through electrodialysis. The bipolar electrodialysis process is both economical and environmentally friendly because it uses no auxiliary materials like sodium hydroxide and reuses sulfuric acid in the spodumene concentrate treatment, producing no byproducts.

[0007] A bipolar electrodialysis system includes an anion exchange membrane and a cation exchange membrane, and a spacer is placed between the anion exchange membrane and the cation exchange membrane to secure a flow path, reduce a pressure difference, and prevent contact between the ion exchange membranes to secure space to increase the electrochemical potential.

[0008] In an electrodialysis system, when stagnation occurs between ion-exchange membranes due to impurities or other factors, the influx of ions within the stagnant region decreases, and the CP (viscosity) modulus changes. A localized decrease in ion concentration can reduce the effective membrane area of ​​ion-exchange membranes, spacers, and other membranes, resulting in decreased ion transport efficiency. Furthermore, some damage to ion-exchange membranes, spacers, and other membranes due to electrical resistance heat generation can occur.

[0009] Therefore, there is a need for the development of an electrodialysis system that can improve ion exchange performance.

[0010] The present invention aims to provide a spacer for an electrodialysis system capable of improving ion exchange performance by suppressing stagnation phenomenon at the outer portion of the spacer.

[0011] In addition, the present invention seeks to provide an electrodialysis system having excellent ion transfer efficiency and suppressing the generation of electrical resistance heat.

[0012] The present invention provides a spacer for an electrodialysis system, comprising: a first outer portion; a second outer portion; and a central portion positioned between the first outer portion and the second outer portion; wherein at least one of the first outer portion and the second outer portion has a different flow resistance from the central portion.

[0013] In addition, the present invention provides an electrodialysis system including: an anode; a cathode positioned facing the anode; a cation exchange membrane and an anion exchange membrane alternately installed between the anode and the cathode; and the above-described spacer interposed between the cation exchange membrane and the anion exchange membrane.

[0014] The spacer for the electric dialysis system according to the present invention has the advantage of minimizing the occurrence of a flow stagnation area because the flow resistance of the outer portion and the center portion are different.

[0015] FIG. 1 is a diagram illustrating a spacer for an electrodialysis system according to some embodiments of the present invention.

[0016] FIG. 2 is a diagram showing the shape of a grid within the first outer portion, the second outer portion, and the central portion of a spacer for an electric dialysis system according to an embodiment.

[0017] Figures 3 and 4 are diagrams showing flow analysis according to the shape of the grid of a spacer for an electric dialysis system.

[0018] Figures 5 and 6 are diagrams showing the size of the flow rate of the spacer for electric dialysis according to the examples and comparative examples, respectively.

[0019] Figures 7 and 8 are diagrams showing the standard deviation of the flow rate at positions from 10% to 90% of the total height in the width direction of the spacer for the electric dialysis system according to the embodiment and comparative example, respectively.

[0020] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention. The present invention is defined solely by the scope of the claims set forth below.

[0021] In the present invention, when it is said that a member is located “on” another member, this includes not only cases where a member is in direct contact with another member, but also cases where another member is interposed between the two members.

[0022] When a part of the present invention is said to "include" a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated.

[0023]

[0024] <Spacer for Electrodialysis System>

[0025] One aspect of the present invention relates to a spacer for an electrodialysis system, comprising: a first outer portion (10); a second outer portion (20); and a central portion (30) positioned between the first outer portion (10) and the second outer portion (20); wherein at least one of the first outer portion (10) and the second outer portion (20) has a different flow resistance from the central portion (30).

[0026] Electrodialysis systems can be used to extract lithium. For example, a unit process is used to produce lithium hydroxide solution by passing a lithium sulfate solution through an electrodialysis membrane. In this process, the formation of a uniform flow field within the wide, thin dialysis membrane is crucial. Uneven flow fields can cause operational or equipment problems.

[0027] For example, when the flow rate is low, impurities may be concentrated due to problems such as stagnant areas, which may damage the membrane, and when the flow rate is high, it may cause deformation of the membrane.

[0028] In the present invention, damage to the membrane can be suppressed by placing a part with different flow resistance, specifically a part with lower flow resistance than the center (30), in the outer part where stagnant areas mainly occur.

[0029]

[0030] In the present invention, the “outer portion” may refer to an area within 30% of the width of the spacer for the electrodialysis system from both ends of the spacer for the electrodialysis system, specifically, an area within 20%.

[0031] In the present invention, “center (30)” may refer to an area excluding the outer portion of the spacer for the electric dialysis system.

[0032]

[0033] In one embodiment of the present invention, the first outer portion (10) and the second outer portion (20) may have different flow resistances from the central portion (30).

[0034] When both the first outer portion (10) and the second outer portion (20) have different flow resistances from the central portion (30), a more uniform flow field can be formed, which is preferable. Specifically, since the inlet and outlet provided in the spacer for the electrodialysis system are not symmetrical left and right, it may be advantageous to appropriately adjust the flow resistance according to the positions of the inlet and outlet. More specifically, since there is a high probability that a stagnant region will occur in the first outer portion (10) and the second outer portion (20) corresponding to both ends of the spacer for the electrodialysis system, it is preferable that both the first outer portion (10) and the second outer portion (20) have different flow resistances from the central portion (30).

[0035]

[0036] The first outer portion (10) and the second outer portion (20) may have the same or different flow resistance.

[0037]

[0038] In another embodiment of the present invention, the first outer portion (10) and the second outer portion (20) may have the same flow resistance.

[0039] If the flow resistance of the first outer portion (10) and the second outer portion (20) is the same, it may be advantageous in terms of commercialization, such as ease of manufacturing and assembly.

[0040]

[0041] In another embodiment of the present invention, at least one of the first outer portion (10) and the second outer portion (20) may have a lower flow resistance than the central portion (30).

[0042] When at least one of the first outer portion (10) and the second outer portion (20) has a lower flow resistance than the central portion (30), as the flow velocity in the outer portion, that is, in the vicinity of the first outer portion (10) and the second outer portion (20), increases, the occurrence of a stagnant region can be minimized, thereby suppressing damage to the spacer, and there is an advantage in that it is advantageous for ion exchange by having a uniform ion concentration.

[0043]

[0044] In another embodiment of the present invention, the first outer portion (10) and the second outer portion (20) may have lower flow resistance than the central portion (30).

[0045] When both the first outer portion (10) and the second outer portion (20) have lower flow resistance than the central portion (30), the desired effect is further improved, which is preferable.

[0046]

[0047] In another embodiment of the present invention, the angle of the lattice structure disposed within the central portion (30) may be greater than the angle of the lattice structure disposed within the first outer portion (10) or the second outer portion (20).

[0048] In the present invention, the “angle of the lattice structure” is θ in Fig. 1. f , θ f’ , θ f” It means.

[0049] Specifically, the first outer portion (10), the second outer portion (20), and the central portion (30) may include a lattice structure having a diamond or parallelogram shape with respect to the flow direction (see Fig. 1).

[0050] More specifically, a lattice structure having a diamond shape may be included within the first outer portion (10), the second outer portion (20), and the central portion (30).

[0051] In the present invention, by varying the angles of the lattice structures arranged in the first outer portion (10), the second outer portion (20), and the central portion (30), the flow resistance of the first outer portion (10), the second outer portion (20), and the central portion (30) can be controlled.

[0052]

[0053] In another embodiment of the present invention, the angle of the lattice structure disposed within the central portion (30) may be greater than the angle of the lattice structure disposed within the first outer portion (10) and the second outer portion (20).

[0054] When the angle of the lattice structure arranged within the central portion (30) is greater than the angle of the lattice structure arranged within the first outer portion (10) and the second outer portion (20), it is preferable that a large change in flow velocity is caused to induce the flow to the outer portion, thereby suppressing the phenomenon of a stagnant region occurring in the outer portion.

[0055]

[0056] In another embodiment of the present invention, the angle (θ) of the lattice structure arranged within the first outer portion (10) f’ ) may be 30 to 80°, preferably 40 to 80°, and more preferably 50 to 60°.

[0057] In another embodiment of the present invention, the angle (θ) of the lattice structure arranged within the second outer portion (20) f”) may be 30 to 80°, preferably 40 to 80°, and more preferably 50 to 60°.

[0058] In another embodiment of the present invention, the angle (θ) of the lattice structure arranged within the central portion (30) f ) may be 90 to 150°, preferably 100 to 130°, and more preferably 110 to 120°.

[0059] When the angles of the lattice structures arranged within the first outer portion (10), second outer portion (20) and central portion (30) each satisfy the above range, it is preferable to maximize the effect of suppressing the phenomenon of a stagnant region occurring in the outer portion by causing a large change in flow velocity.

[0060]

[0061] In another embodiment of the present invention, the length of one side of the lattice structure arranged within the first outer portion (10) may be 0.5 to 10 mm, preferably 1 to 8 mm, and more preferably 2 to 5 mm.

[0062] In another embodiment of the present invention, the length of one side of the lattice structure arranged within the second outer portion (20) may be 0.5 to 10 mm, preferably 1 to 8 mm, and more preferably 2 to 5 mm.

[0063] In another embodiment of the present invention, the length of one side of the lattice structure arranged within the central portion (30) may be 0.5 to 10 mm, preferably 1 to 8 mm, and more preferably 2 to 5 mm.

[0064] In short, when the lattice structure arranged within the first outer portion (10) is in the shape of a diamond, the lengths of the four sides of the diamond can satisfy the above range.

[0065] When the lattice structure arranged within the first outer portion (10) is in the shape of a parallelogram, the lengths of the long and short sides of the parallelogram can each satisfy the above range.

[0066] When the length of one side of the lattice structure arranged in the first outer portion (10), second outer portion (20), and center portion (30) satisfies the above range, it is preferable because the desired ion exchange performance is excellent while the problem of damage to the spacer for the electrodialysis system due to the flow rate, differential pressure, etc. of the treated water can be suppressed.

[0067]

[0068] The diameter of the strand forming the above lattice structure may be, but is not limited to, 0.1 to 1.0 mm, preferably 0.2 to 0.8 mm, and more preferably 0.35 to 0.5 mm.

[0069] However, when the diameter of the strand satisfies the above range, it is preferable because the durability of the spacer (100) for electric dialysis according to the present invention becomes excellent.

[0070]

[0071] The above-mentioned spacer for electrodialysis (100) may have a width of 10 mm to 1,500 mm, preferably 300 mm to 1,500 mm, and more preferably 400 mm to 1,200 mm. When the width of the spacer for electrodialysis (100) satisfies the above range, it is advantageous in that it is located within the manufacturing range of a commercial membrane, making system configuration easy.

[0072]

[0073] The spacer (100) for electric dialysis according to the present invention may have a thickness of 0.3 to 2.0 mm, preferably 0.3 to 1.2 mm, and more preferably 0.6 to 1.0 mm, but is not limited thereto.

[0074] However, when the thickness of the above-mentioned spacer for electrodialysis (100) satisfies the above range, it is preferable that the thickness of the above-mentioned spacer for electrodialysis (100) be minimized while deformation of the above-mentioned spacer for electrodialysis (100) can be suppressed and the flow rate between the membranes can be appropriately maintained.

[0075]

[0076] The electric dialysis spacer (100) according to the present invention may have a height of 500 to 1,500, preferably 700 to 1,500, more preferably 1,220 to 1,500, but is not limited thereto.

[0077] When the height of the above-mentioned electric dialysis spacer (100) satisfies the above range, a gradient of ion concentration is formed in the direction of the entire length (height), which is advantageous in that the ion exchange performance is improved.

[0078]

[0079] The above-mentioned electric dialysis spacer (100) may further include, but is not limited to, an outlet for treated water, an inlet, etc.

[0080]

[0081] The present invention does not limit the manufacturing method of the above-mentioned spacer (100) for electrodialysis. For example, the spacer (100) for electrodialysis can be manufactured using a method of weaving by injection molding or drawing a polymer material into a thread shape. In the case of weaving, two or more spacers having different flow resistances, specifically, different angles within a lattice structure, can be manufactured and then joined together, but the present invention is not limited thereto.

[0082] The above-mentioned spacer (100) for electric dialysis can be manufactured using a non-conductive polymer material such as Teflon, but is not limited thereto.

[0083]

[0084] The spacer (100) for electrodialysis according to the present invention can improve ion exchange performance by controlling the physical shape without being limited by material.

[0085] Since the spacer for the electrodialysis system according to the present invention includes an outer portion and a center portion (30) having different flow resistances, it generates a relatively stronger flow velocity in the outer portion compared to a conventional spacer, thereby suppressing the phenomenon of stagnation in the flow between the ion exchange membranes of the cation exchange membrane and the anion exchange membrane, and thus has the advantage of increasing the efficiency of ion movement.

[0086]

[0087] The spacer (100) for electrodialysis according to the present invention can be usefully applied to a reverse osmosis (RO) system, a bipolar electrodialysis (BPED) system, etc.

[0088]

[0089] <Electrodialysis system>

[0090] Another aspect of the present invention relates to an electrodialysis system comprising: an anode; a cathode positioned opposite the anode; a cation exchange membrane and an anion exchange membrane alternately installed between the anode and the cathode; and the above-described spacer interposed between the cation exchange membrane and the anion exchange membrane.

[0091] The electrodialysis system according to the present invention has the advantage of excellent ion exchange performance.

[0092]

[0093] The anode may include a substrate comprising titanium (Ti), tantalum (Ta), nickel (Ni) or a similar metal.

[0094] The surface of the above substrate may be coated with, but is not limited to, a non-deactivatable, electrocatalytic film.

[0095] For example, the surface of the substrate may be coated with a conductive (discharge) material that is an oxide of platinum (Pt), iridium (Ir), rhodium (Rh), ruthenium (Ru), zirconium (Zr), titanium (Ti) or similar metals, or includes at least one of the aforementioned metal oxides.

[0096] For example, the film may be formed by coating an organic compound containing at least one of the aforementioned metals (e.g., iridium alcoholate, ruthenium alcoholate, tantalum alcoholate, or titanium alcoholate, wherein the alcohol used may be methanol, ethanol, propanol, butanol, isopropanol, isobutanol, or the like) on the surface of a metallic substrate, followed by, but not limited to, a sintering process to remove the organic components.

[0097] The cathode may include, but is not limited to, nickel, iron, stainless steel, nickel-plated titanium, graphite, carbon steel, or combinations thereof.

[0098] The above positive electrode may be included in a positive electrode cell, and the above negative electrode may be included in a negative electrode cell.

[0099] An acid solution tank may be further arranged outside the positive electrode cell, and an alkaline solution tank may be further arranged outside the negative electrode cell.

[0100]

[0101] The above cation exchange membrane has an anionic group inside, so it selectively allows only cations to pass through.

[0102] Specifically, the cation exchange membrane is composed of ion groups with a negative (-) charge, such as Na.+ , K + , Ca 2+ , Mg 2+ , Fe2 2+ It allows the cations such as Cl to pass through. - , Br - , NO3 - , SO4 2- , HCO3 - The membrane may be such that negative ions do not pass through due to repulsion of like charges.

[0103] The above cation exchange membrane may have a thickness of 70 to 170 μm, preferably 75 to 150 μm, and more preferably 80 to 120 μm, but is not limited thereto.

[0104] The above cation exchange membrane may include a plurality of inlets, and the diameter of the inlets, etc. is not limited in the present invention.

[0105]

[0106] The above anion exchange membrane has a cationic group inside, so it selectively allows only anions to pass through.

[0107] Specifically, the anion exchange membrane is composed of ion groups with a positive (+) charge, Cl - , Br - , NO3 - , SO4 2- , HCO3 - Negative ions such as Na are allowed to pass through. + , K + , Ca 2+ , Mg 2+ , Fe2 2+ The membrane can prevent positive ions from passing through due to repulsion of like charges.

[0108] The above anion exchange membrane may have a thickness of 70 to 170 μm, preferably 75 to 150 μm, and more preferably 80 to 120 μm, but is not limited thereto.

[0109] The above anion exchange membrane may include a plurality of inlets, and the diameter of the inlets, etc. is not limited in the present invention.

[0110]

[0111] The above cation exchange membrane and the above anion exchange membrane may be included in multiple numbers, and the electrodialysis spacer (100) may be interposed between the multiple cation exchange membranes and the anion exchange membranes.

[0112]

[0113] The electrodialysis system according to the present invention may further include, but is not limited to, a bipolar membrane, a gasket, etc.

[0114]

[0115] Specifically, the electrodialysis system according to the present invention may be a reverse osmosis (RO) system or a bipolar electrodialysis (BPED) system, but is not limited thereto.

[0116]

[0117] Hereinafter, preferred embodiments and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0118]

[0119] Example

[0120] A spacer having a grid having a diamond shape with respect to the flow direction was applied, and spacers having a diamond shape angle of 60° with respect to the flow direction were placed on both outer sides as the first outer side and the second outer side, and a spacer having a diamond shape angle of 120° was placed in the center as the center, and then combined to model an electric dialysis spacer (using the COMSOL program).

[0121] At this time, the width of the first outer part and the second outer part was modeled as 84 mm, the width of the center was modeled as 252 mm, the thickness of the spacer for electric dialysis was modeled as 0.8 mm, the height of the spacer was modeled as 1,220 mm, the length of the four sides of the grid within the spacer was modeled as 2 mm, and the strand diameter of the grid was modeled as 0.35 mm.

[0122] The left image of Fig. 2 shows the shape of the grid within the first outer part and the second outer part, and the right image of Fig. 3 shows the shape of the grid within the central part.

[0123] Specifically, θ in Fig. 2 t is θ f It means the angle facing θ a is θ t Wow θ f It means the angle between.

[0124]

[0125] Comparative example

[0126] A spacer having a diamond-shaped grid shape and an angle of 60° was manufactured. The width and length of the spacer were the same as those of the electrodialysis spacer manufactured according to the embodiment, and the shape of the grid within the spacer was the same as the shape of the grid within the first outer portion and the second outer portion according to the embodiment.

[0127]

[0128] Experimental example

[0129] In order to observe the flow analysis of the spacers manufactured according to the examples and comparative examples, flow analysis was performed according to the angle of the spacer (using the COMSOL program), and the results are shown in Figures 3 and 4, respectively.

[0130] Specifically, the flow analysis was performed using a 3D flow analysis program.

[0131] Figure 3 is an image showing the results of a flow analysis for a spacer with a 60° grid structure within the spacer, and Figure 4 is an image showing the results of a flow analysis for a spacer with a 120° grid structure within the spacer.

[0132] Referring to FIGS. 3 and 4, it can be seen that the flow analysis results change as the angle of the lattice structure within the spacer changes.

[0133] Figures 5 and 6 are diagrams showing flow analysis showing the velocity and vector of a solution passing through a spacer modeled according to an embodiment and a comparative example.

[0134] Specifically, the standard deviation of the velocity of the solution in the width direction at the outlet of the treated water of the spacer modeled according to the examples and comparative examples was predicted (using the COMSOL program), and the results are shown in Figures 5 and 6, respectively.

[0135] In addition, the standard deviation of the flow rate at a specific height (10-90%) in the width direction of the spacer for the electrodialysis system according to the examples and comparative examples are shown in FIGS. 7 and 8, respectively.

[0136] Referring to FIGS. 7 and 8, it can be seen that the deviations in the width direction of the flow velocity of the spacer according to the comparative example are 0.0069 m / s and 0.00642 m / s, while the deviation in the flow velocity of the electrodialysis spacer manufactured according to the embodiment is 0.028 m / s, showing a much larger change in the flow velocity. In particular, it can be seen that the flow velocity is uneven overall in the direction of flow, and thus the occurrence of stagnant areas in the outer portion can be minimized.

[0137]

[0138] 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.

[0139]

[0140] [Explanation of symbols]

[0141] 10: 1st Outer Zone

[0142] 20: Second Outer Zone

[0143] 30: Center

[0144] 100: Spacer for electrodialysis system

Claims

1. A first outer portion; a second outer portion (20); and a center portion located between the first outer portion and the second outer portion; Including, At least one of the first outer portion and the second outer portion has a different flow resistance from the central portion. Spacer for electrodialysis system.

2. In paragraph 1, A spacer for an electrodialysis system, wherein the first outer portion and the second outer portion have different flow resistances from the central portion.

3. In paragraph 2, A spacer for an electrodialysis system, wherein the first outer portion and the second outer portion have the same flow resistance.

4. In paragraph 1, A spacer for an electrodialysis system, wherein at least one of the first outer portion and the second outer portion has lower flow resistance than the central portion.

5. In paragraph 4, A spacer for an electrodialysis system, wherein the first outer portion and the second outer portion have lower flow resistance than the central portion.

6. In paragraph 1, The angle of the lattice structure arranged within the above center is, A spacer for an electrodialysis system having an angle greater than that of a grid structure disposed within the first outer portion or the second outer portion.

7. In paragraph 6, The angle of the lattice structure arranged within the above center is, A spacer for an electrodialysis system having an angle greater than that of the lattice structures disposed within the first outer portion and the second outer portion.

8. In paragraph 6, A spacer for an electrodialysis system, wherein the angle of the grid structure arranged within the first outer portion is 30 to 80°.

9. In paragraph 6, A spacer for an electrodialysis system, wherein the angle of the grid structure arranged within the second outer portion is 30 to 80°.

10. In paragraph 6, A spacer for an electrodialysis system, wherein the angle of the lattice structure arranged within the center is 90 to 150°.

11. In paragraph 6, A spacer for an electrodialysis system, wherein a side length of a lattice structure disposed within the first outer portion is 0.5 to 10 mm.

12. In paragraph 6, A spacer for an electrodialysis system, wherein a side length of a lattice structure disposed within the second outer portion is 0.5 to 10 mm.

13. In paragraph 6, A spacer for an electrodialysis system, wherein the length of one side of a lattice structure arranged within the center is 0.5 to 10 mm.

14. Bipolar; A cathode positioned opposite the anode; Cation exchange membranes and anion exchange membranes alternately installed between the anode and the cathode; and A spacer for an electrodialysis system according to any one of claims 1 to 13, interposed between the cation exchange membrane and the anion exchange membrane; An electrodialysis system comprising:

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