Spacer for electrodialysis system and electrodialysis system comprising same

Abstract

A spacer for an electrodialysis system, according to the present invention, includes: a first end portion; a second end portion which is located to face the first end; and a central portion disposed between the first end portion and the second end portion, wherein the spacer is in a trapezoidal shape in which the second end portion is wider than the first end 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, through 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 seeks to provide a spacer for an electrodialysis system capable of generating a strong flow rate to improve ion exchange performance.

[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 end; a second end positioned opposite the first end; and a central portion positioned between the first end and the second end; wherein the second end is wider than the first end and has a trapezoidal shape.

[0013] In addition, the present invention provides an electrodialysis system including: 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 a spacer for the electrodialysis system described above interposed between the cation exchange membrane and the anion exchange membrane.

[0014] The spacer for the electrodialysis system according to the present invention has the advantage of generating a strong flow rate, thereby improving ion exchange performance.

[0015] In addition, the spacer for the electrodialysis system according to the present invention has the advantage of excellent ion movement efficiency and suppressing the generation of electrical resistance heat.

[0016] FIG. 1 is a diagram illustrating a spacer for an electrodialysis system according to some embodiments of the present invention.

[0017] FIG. 2 is a diagram illustrating a case where a plurality of spacers for an electrodialysis system according to some embodiments of the present invention are stacked.

[0018] FIG. 3 is a diagram predicting a flow analysis when a plurality of spacers for an electrodialysis system according to some embodiments of the present invention are stacked.

[0019] FIG. 4 is a diagram showing the flow analysis of a spacer for an electrodialysis system according to some embodiments of the present invention and the velocity distribution along the width direction of the solution according to position.

[0020] Figure 5 is a diagram showing the flow analysis of a spacer for an electric dialysis system according to a comparative example and the widthwise velocity distribution of the solution according to position.

[0021] Figures 6 and 7 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025]

[0026] <Spacer for Electrodialysis System>

[0027] One aspect of the present invention relates to a spacer (100) for an electrodialysis system, comprising: a first end (10); a second end (20) positioned facing the first end (10); and a central portion positioned between the first end (10) and the second end (20); wherein the second end (20) is wider than the first end (10) and has a trapezoidal shape.

[0028] The spacer (100) for the electrodialysis system according to the present invention has a trapezoidal shape, so it can generate a strong flow velocity compared to a conventional rectangular 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.

[0029]

[0030] A spacer (100) for an electric dialysis system according to the present invention includes a first end (10) and a second end (20) positioned facing the first end (10).

[0031] At this time, the second end (20) is longer than the first end (10).

[0032] The fact that the first end (10) and the second end (20) are positioned facing each other means that the first end (10) and the second end (20) face each other.

[0033] Specifically, the first end (10) and the second end (20) may be referred to as the base and the lower side, respectively, of a trapezoid.

[0034]

[0035] In another embodiment of the present invention, the spacer (100) for the electrodialysis system may include an outlet (11) for the treated water, which will be described later.

[0036] In general, the outlet (11) of the above-mentioned treated water may have somewhat lower ion exchange performance than the center.

[0037] Conventional rectangular spacers have a uniform flow rate in the width direction, and the flow rate deviation in the width direction is also formed symmetrically left and right. This causes a decline in the overall ion exchange performance at the outlet (11) of treated water with relatively low ion exchange performance.

[0038] On the other hand, since the spacer (100) for the electrodialysis system according to the present invention has a trapezoidal shape, it can generate a strong flow rate at the outlet (11) of the treated water compared to the same flow rate. Therefore, ion exchange is actively performed, and a large difference in ion concentration is also generated across the spacer (100) for the electrodialysis system, which has the advantage of improving the performance of the entire system.

[0039] In addition, in the process of ions moving through the membrane by electrical application, the temperature of the upper part of the spacer, that is, the first end (10), may rise relatively higher than that of the lower part of the spacer, that is, the second end (20). Therefore, by forming the first end narrower than the second end (20), a uniform flow can be formed.

[0040]

[0041] In another embodiment of the present invention, the size of the base angle (A, A') of the second end (20) may be 70 to 86°.

[0042] In another embodiment of the present invention, the size of the base angle (A, A') of the second end (20) may be 80 to 86°.

[0043] When the size of the base angle (A, A') of the second end (20) satisfies the above range, a flow resistance is formed corresponding to the increasing flow velocity toward the first end (10), so that a uniform flow field can be formed up to the edge of the spacer (100) for the electrodialysis system, which is preferable.

[0044]

[0045] In another embodiment of the present invention, the sizes of the two base angles (A, A') of the second end (20) may be different.

[0046] In another embodiment of the present invention, the sizes of the two base angles (A, A') of the second end (20) may be the same.

[0047] Specifically, the spacer (100) for the electric dialysis system according to the present invention may be a symmetrical trapezoid or an asymmetrical trapezoid.

[0048] In short, the two base angles (A, A') of the second end (20) may have different angles or may have the same angle.

[0049]

[0050] Preferably, the spacer (100) for the above-mentioned electric dialysis system may have angles where both base angles (A, A') are equal to each other.

[0051] When the two base angles (A, A') of the spacer (100) for the above-mentioned electric dialysis system have the same angle, it is preferable because it is easy to assemble and manage the system.

[0052]

[0053] In another embodiment of the present invention, the length of the first end (10) may be 30 to 90% of the length of the second end (20).

[0054]

[0055] In another embodiment of the present invention, the length of the first end (10) may be 40 to 60% of the length of the second end (20).

[0056] When the length of the first end (10) satisfies the above range with respect to the length of the second end (20), it is preferable that the desired ion exchange performance is excellent while the problem of damage to the spacer (100) for the electrodialysis system due to the flow rate, differential pressure, etc. of the treated water be suppressed.

[0057]

[0058] The above second end (20) may have a length of 300 to 1,500 mm, but is not limited thereto.

[0059] The length of the first end (10) can be selected to satisfy the above ratio to the length of the second end (20).

[0060]

[0061] The spacer for electrodialysis 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.

[0062] However, when the thickness of the electrodialysis spacer satisfies the above range, it is preferable that the thickness of the electrodialysis spacer be minimized while suppressing deformation of the electrodialysis spacer. In addition, it is preferable that an ion concentration gradient is formed across the entire thickness, thereby increasing ion exchange performance.

[0063]

[0064] The spacer for electrodialysis 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.

[0065] When the height of the above-mentioned spacer for electric dialysis 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.

[0066]

[0067] The outlet (11) of the above-mentioned treatment water can be formed on the side of the first end (10).

[0068] In addition, the spacer for electric dialysis according to the present invention may include an inlet (21) for the treated water formed on the side of the second end (20).

[0069] Since the effective cross-sectional area of ​​the electrodialysis spacer in the longitudinal direction becomes smaller as it moves toward the outlet (11) of the treated water, a uniform flow can be formed.

[0070] The outlets (11) of the treated water may be arranged to be offset from each other in the vertical direction of the length of the electrodialysis spacer, that is, in the width direction. For example, the outlet (11) of the treated water may be provided on the right side of the first end (10), and the inlet (21) of the treated water may be provided on the left side of the second end (20). Referring to Fig. 1, 11 represents an outlet, and 21 represents an inlet.

[0071]

[0072] The above central portion can serve to provide a compartment in which movement of ions in a solution occurs by the positive (+) electrode and the negative (-) electrode.

[0073] The above central portion may include a mesh area, a non-woven fabric having openings, etc.

[0074] In another embodiment of the present invention, the central portion may include a mesh region.

[0075] The shape of the above mesh area is not particularly limited in the present invention.

[0076] In another embodiment of the present invention, the mesh region may include one or more patterns selected from the group consisting of a circle, an ellipse, a square, a parallelogram, a diamond shape, and a mesh shape.

[0077] Specifically, the mesh region may include a uniform lattice structure in a diamond shape.

[0078]

[0079] The present invention does not limit the method for manufacturing the electrodialysis spacer. For example, the electrodialysis spacer can be manufactured using a method of injection molding or weaving a polymer material into a thread shape.

[0080] The above-mentioned spacer for electric dialysis can be manufactured using a non-conductive polymer material such as Teflon, but is not limited thereto.

[0081]

[0082] The spacer for electrodialysis according to the present invention can improve ion exchange performance by controlling the physical shape without being limited by material.

[0083] Since the spacer for electrodialysis according to the present invention has a trapezoidal shape in which the second end (20) is wider than the first end (10), it can forcibly form a high flow rate at the outlet (11) of the treated water, which has relatively low ion exchange performance. Therefore, it is possible to suppress the phenomenon of stagnation in the flow due to pinholes caused by impurities, etc., and has the advantage of improving ion exchange performance.

[0084]

[0085] The electrodialysis spacer according to the present invention can be usefully applied to a reverse osmosis (RO) system, a bipolar electrodialysis (BPED) system, etc.

[0086]

[0087] <Electrodialysis system>

[0088] 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 a spacer (100) for the electrodialysis system described above interposed between the cation exchange membrane and the anion exchange membrane.

[0089] The electrodialysis system according to the present invention has the advantage of excellent ion exchange performance.

[0090]

[0091] The anode may include a substrate comprising titanium (Ti), tantalum (Ta), nickel (Ni) or a similar metal.

[0092] The surface of the above substrate may be coated with, but is not limited to, a non-deactivatable, electrocatalytic film.

[0093] 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.

[0094] 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.

[0095] The cathode may include, but is not limited to, nickel, iron, stainless steel, nickel-plated titanium, graphite, carbon steel, or combinations thereof.

[0096] 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.

[0097] 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.

[0098]

[0099] The above cation exchange membrane has an anionic group inside, so it selectively allows only cations to pass through.

[0100] 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.

[0101] 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.

[0102] 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.

[0103]

[0104] The above anion exchange membrane has a cationic group inside, so it selectively allows only anions to pass through.

[0105] 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.

[0106] 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.

[0107] 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.

[0108]

[0109] The above cation exchange membrane and the above anion exchange membrane may be included in multiple numbers, and the above electrodialysis spacer may be interposed between the multiple cation exchange membranes and the above anion exchange membranes.

[0110] In another embodiment of the present invention, when the plurality of spacers for electrodialysis are included, the plurality of spacers for electrodialysis may be arranged so that the outlets (11) of the treated water are misaligned with each other.

[0111] In another embodiment of the present invention, the plurality of electrodialysis spacers may be arranged so that the outlets (11) of the treated water are horizontally offset from each other.

[0112] Specifically, the spacers for the electric dialysis, which are arranged most closely together, are arranged in a form that is flipped 180° horizontally, so that the outlets (11) of the treated water can be arranged to be misaligned with each other.

[0113] It is preferable that the outlets (11) of the treated water of the plurality of electric dialysis spacers are arranged horizontally so that they are offset from each other, so that the parts having high flow rates can be alternately arranged and stacked, thereby further improving the ion exchange performance.

[0114] Preferably, all of the plurality of electrodialysis spacers may be arranged to be offset from each other.

[0115]

[0116] The electrodialysis system according to the present invention may further include, but is not limited to, a bipolar membrane, a gasket, etc.

[0117]

[0118] Specifically, the electrodialysis system according to the present invention may be, but is not limited to, a reverse osmosis (RO) system or a bipolar electrodialysis (BPED) system.

[0119]

[0120] 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.

[0121]

[0122] Example

[0123] A trapezoidal spacer with a first end length of 250 mm, a second end length of 420 mm, a height of 1,220 mm, and a base angle of 86° was modeled and computerized (using the COMSOL program). The center was formed with a mesh having a diamond-shaped pattern, and the analysis was conducted under three-dimensional steady-state conditions.

[0124]

[0125] Comparative example

[0126] A rectangular spacer measuring 420 mm in width and 1,220 mm in length was modeled using the same program as in the example and subjected to computational analysis. At this time, the same mesh as in the example was applied to the central region.

[0127]

[0128] Experimental example

[0129] Flow analysis of the spacers manufactured according to the examples and comparative examples was performed (using the COMSOL program), and the results are shown in Figures 4 and 5, respectively.

[0130] The left images of Figures 4 and 5 are diagrams showing flow analysis showing the velocity and vector of the solution passing through the spacer, and the right image is a diagram showing the velocity distribution of the solution along the width direction of the spacer.

[0131] 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 4 and 5, respectively.

[0132] More specifically, the standard deviation of the solution velocity was calculated by taking the standard deviation of the velocity at 83 equally spaced points in the width direction of the spacer (based on the second end in the example). This calculation was performed starting from the second end with respect to the height of the spacer, and designating seven flow direction heights indicated by dotted lines as 10%, 15%, 20%, 50%, 80%, and 90%, and calculating the velocity deviation in the width direction at those positions. It can be seen that the standard deviation of the velocity is the largest when approaching the outlet, which is 90% of the total height.

[0133] Figures 6 and 7 show the standard deviation of the flow rate at a specific height (10 to 90%) in the width direction of the spacer for the electrodialysis system according to the examples and comparative examples, respectively.

[0134] Referring to Figures 5 and 7, it can be seen that the spacer for the electrodialysis system according to the comparative example has a uniform flow rate in the width direction, and the flow rate deviation in the width direction is also formed symmetrically on both sides. This results in a decrease in the overall ion exchange capacity at the outlet where the ion exchange performance is poor. In addition, when the spacer for the electrodialysis system according to the comparative example was used, the flow rate had a maximum of approximately 0.1 m / s, and the velocity deviation was 0.013 m / s.

[0135] On the other hand, referring to FIGS. 4 and 6, it can be seen that when a spacer manufactured according to the embodiment is used, the flow rate is at most 0.155 m / s, which is a local increase in flow rate of more than 50%, and the velocity deviation is 0.023 m / s, which is an improvement of about 77%.

[0136]

[0137] 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.

[0138] [Explanation of symbols]

[0139] 10: Part 1

[0140] 11: Outlet

[0141] 20: Part 2

[0142] 21: Inlet

[0143] 100: Spacer for electrodialysis system

Claims

1. Section 1; a second end positioned opposite the first end; and Including a central portion disposed between the first end and the second end; A spacer for an electrodialysis system having a trapezoidal shape in which the second end is wider than the first end.

2. In paragraph 1, A spacer for an electrodialysis system, wherein the base angle of the second end is 70 to 86°.

3. In paragraph 2, A spacer for an electrodialysis system, wherein the base angle of the second end is 80 to 86°.

4. In paragraph 1, A spacer for an electrodialysis system, wherein the sizes of the two base angles of the second end are different.

5. In paragraph 1, A spacer for an electrodialysis system, wherein the sizes of the two base angles of the second end are the same.

6. In paragraph 1, A spacer for an electrodialysis system, wherein the length of the first end is 30 to 90% of the length of the second end.

7. In paragraph 6, A spacer for an electrodialysis system, wherein the length of the first end is 40 to 60% of the length of the second end.

8. In paragraph 1, A spacer for an electric dialysis system having a height of 500 mm to 1500 mm.

9. In paragraph 1, A spacer for an electrodialysis system, wherein the central portion includes a mesh region.

10. In paragraph 9, A spacer for an electrodialysis system, wherein the mesh region comprises at least one pattern selected from the group consisting of a circle, an ellipse, a square, a parallelogram, a diamond shape and a mesh shape.

11. In paragraph 1, A spacer for an electrodialysis system comprising an outlet for treated water.

12. 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 11, interposed between the cation exchange membrane and the anion exchange membrane; An electrodialysis system comprising:

13. In paragraph 12, An electrodialysis system in which, when the above-mentioned spacers for electrodialysis are included in a plurality, the outlets of the treated water of the plurality of spacers are arranged so as to be offset from each other.

14. In paragraph 13, An electrodialysis system in which the plurality of spacers are arranged so that the outlets of the treated water are horizontally misaligned from each other.

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