Membrane for electrodialysis system and electrodialysis system comprising same

Abstract

A separator for electrodialysis according to the present application is characterized in that the separator includes: a first peripheral portion; a second peripheral portion; and a central portion between the first peripheral portion and the second peripheral portion, at least one of the first peripheral portion and the second peripheral portion being different in flow resistance from the central portion.

Description

Technical Field

[0001] This invention relates to a partition for an electrodialysis system and an electrodialysis system including the partition. Background Technology

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

[0003] Commercial lithium production primarily involves extraction from ores and production from brine. Lithium produced from ores is mostly generated from spodumene concentrate via the sulfuric acid process. Lithium production from brine mainly utilizes underground brine from South America, undergoing natural drying followed by the removal of byproducts and additional processing. It is anticipated that with the increasing prevalence of electric vehicles, the proportion of recycled lithium extracted from spent batteries and used in lithium-ion battery production will gradually increase.

[0004] On the other hand, lithium intermediates used in the past to manufacture battery materials were mainly in the form of lithium carbonate. However, as the expansion of the driving range of electric vehicles has become a major technical issue, the demand for high power density batteries is increasing, and the demand for lithium hydroxide, as a raw material for high power density batteries, is also increasing dramatically.

[0005] Lithium hydroxide is mainly produced by the lime process, which involves reacting lithium carbonate with calcium hydroxide. However, recently, there has been much interest in processes that produce lithium hydroxide directly from intermediates such as lithium sulfate, lithium chloride, and lithium phosphate without using lithium carbonate.

[0006] There are two main representative processes for directly producing lithium hydroxide from ore: one is the causticization process, which produces lithium hydroxide by reacting lithium sulfate solution with sodium hydroxide, generating sodium sulfate as a byproduct; the other is the bipolar electrodialysis (BPED) process, which treats the lithium hydroxide solution through electrodialysis to separate it into lithium hydroxide and sulfuric acid. The bipolar electrodialysis process does not use auxiliary raw materials such as sodium hydroxide and can recover sulfuric acid for use in the processing of spodumene concentrate, thus producing no byproducts. Therefore, it is an economical and environmentally friendly process.

[0007] The bipolar membrane electrodialysis system includes anion exchange membranes and cation exchange membranes, and a partition is arranged between the anion exchange membranes and the cation exchange membranes. The partition serves to ensure flow channels, reduce pressure differentials, and ensure space to increase electrochemical potential by preventing contact between the ion exchange membranes.

[0008] In an electrodialysis system, if impurities or other factors cause stagnation in the flow field between ion exchange membranes, the ion inflow within the stagnant region will decrease, and the concentration polarization (CP) modulus will change. When the ion concentration is locally reduced, the effective membrane area, including the ion exchange membrane and separators, may decrease, potentially leading to reduced ion migration efficiency and damage to these membranes due to resistance heating.

[0009] Therefore, there is a need to develop electrodialysis systems that can improve ion exchange performance. Summary of the Invention

[0010] (a) Technical problems to be solved The present invention aims to provide a separator for an electrodialysis system, which can improve ion exchange performance by suppressing stagnation at the periphery of the separator.

[0011] Furthermore, the present invention aims to provide an electrodialysis system with excellent ion migration efficiency and suppression of resistive heating.

[0012] (II) Technical Solution The present invention provides a partition for an electrodialysis system, comprising: a first peripheral portion; a second peripheral portion; and a central portion located between the first peripheral portion and the second peripheral portion, wherein at least one of the first peripheral portion and the second peripheral portion has a different flow resistance than the central portion.

[0013] Furthermore, the present invention provides an electrodialysis system comprising: an anode; a cathode disposed opposite to the anode; a cation exchange membrane and an anion exchange membrane alternately disposed between the anode and the cathode; and the aforementioned partition sandwiched between the cation exchange membrane and the anion exchange membrane.

[0014] (III) Beneficial Effects The dialysis system dialysis plate according to the present invention has the following advantages: due to the difference in flow resistance between the outer and central parts, the generation of flow stagnation areas can be minimized. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a partition for an electrodialysis system according to several embodiments of the present invention.

[0016] Figure 2 This is a schematic diagram showing the shape of the first outer perimeter, the second outer perimeter, and the inner grid of the central portion of the partition plate for the electrodialysis system according to an embodiment.

[0017] Figure 3 and Figure 4 This is a schematic diagram of flow analysis based on the shape of the grid used in an electrodialysis system.

[0018] Figure 5 and Figure 6 These are schematic diagrams showing the flow rate of the separator for electrodialysis according to the embodiments and comparative examples, respectively.

[0019] Figure 7 and Figure 8 These are schematic diagrams showing the standard deviation of flow velocity at 10% to 90% of the overall height relative to the width direction for the partitions of the electrodialysis system according to the embodiments and comparative examples. Detailed Implementation

[0020] Embodiments of the present invention will be described in detail below. However, these are presented by way of example only, and the invention is not limited thereto; rather, it is defined solely by the scope of the claims.

[0021] In this invention, when it is said that a component is "on" another component, this includes not only the case where the component is in direct contact with the other component, but also the case where another component is interposed between the two components.

[0022] In this invention, when a part is referred to as "including" a certain constituent element, unless otherwise specifically stated to the contrary, it means that other constituent elements may also be included, and does not exclude other constituent elements.

[0023] <Baffles for electrodialysis systems> One aspect of the present invention relates to a partition for an electrodialysis system, comprising: a first peripheral portion 10; a second peripheral portion 20; and a central portion 30 located between the first peripheral portion 10 and the second peripheral portion 20, wherein at least one of the first peripheral portion 10 and the second peripheral portion 20 has a different flow resistance than the central portion 30.

[0024] For lithium extraction, an electrodialysis system can be used. For example, a unit process can be used to produce a lithium hydroxide solution by passing a lithium sulfate solution through an electrodialysis membrane. In this case, it is crucial to create a uniform flow field within the wide and thin dialysis membrane; a non-uniform flow field can lead to operational or equipment problems.

[0025] For example, if the flow rate is low, impurities may concentrate due to problems such as stagnant areas, which may lead to membrane damage; if the flow rate is high, it may cause membrane deformation.

[0026] In this invention, by arranging portions with different flow resistances on the periphery of the main stagnant region, specifically arranging portions with flow resistance lower than that of the central portion by 30, damage to the membrane can be suppressed.

[0027] In this invention, "peripheral portion" can refer to the area within 30% of the width direction of the partition of the electrodialysis system, starting from both ends of the partition of the electrodialysis system, specifically the area within 20%.

[0028] In this invention, "central part 30" can refer to the area in the partition of the electrodialysis system other than the outer part.

[0029] In one embodiment of the present invention, the flow resistance of the first peripheral portion 10 and the second peripheral portion 20 may be different from that of the central portion 30.

[0030] When the flow resistance of both the first peripheral portion 10 and the second peripheral portion 20 differs from that of the central portion 30, a more uniform flow field can be formed, which is therefore preferable. Specifically, since the inlet and outlet of the partition plate for the electrodialysis system are not symmetrical, it may be more advantageous to appropriately adjust the flow resistance according to the positions of the inlet and outlet. More specifically, since the probability of stagnation regions being generated in the first peripheral portion 10 and the second peripheral portion 20 corresponding to both ends of the partition plate for the electrodialysis system is relatively high, it is preferable that the flow resistance of both the first peripheral portion 10 and the second peripheral portion 20 differs from that of the central portion 30.

[0031] The flow resistance of the first peripheral portion 10 and the second peripheral portion 20 may be the same or different.

[0032] In another embodiment of the present invention, the flow resistance of the first peripheral portion 10 and the second peripheral portion 20 may be the same.

[0033] If the flow resistance of the first peripheral portion 10 and the second peripheral portion 20 is the same, it may be more advantageous in terms of commercialization, such as ease of manufacturing and assemblability.

[0034] In another embodiment of the invention, at least one of the first peripheral portion 10 and the second peripheral portion 20 may have a lower flow resistance than the central portion 30.

[0035] When at least one of the first peripheral portion 10 and the second peripheral portion 20 has a lower flow resistance than the central portion 30, as the flow velocity near the peripheral portion, namely the first peripheral portion 10 and the second peripheral portion 20, increases, the generation of stagnant areas can be minimized, thereby suppressing damage to the partition and having a uniform ion concentration, thus providing an advantage for ion exchange.

[0036] In another embodiment of the invention, the first peripheral portion 10 and the second peripheral portion 20 may have a lower flow resistance than the central portion 30.

[0037] When both the first peripheral portion 10 and the second peripheral portion 20 have lower flow resistance than the central portion 30, the expected effect will be better, and therefore it is preferred.

[0038] In another embodiment of the present invention, the angle of the grid structure arranged in the central portion 30 may be greater than the angle of the grid structure arranged in the first peripheral portion 10 or the second peripheral portion 20.

[0039] In this invention, "the angle of the grid structure" refers to Figure 1 θ f θ f’ θ f” .

[0040] Specifically, the first peripheral portion 10, the second peripheral portion 20, and the central portion 30 may include a grid structure having a rhomboid or parallelogram shape relative to the flow direction (see reference). Figure 1 ).

[0041] More specifically, the first peripheral portion 10, the second peripheral portion 20, and the central portion 30 may include a grid structure with a diamond shape.

[0042] In this invention, the flow resistance of the first peripheral portion 10, the second peripheral portion 20, and the central portion 30 can be controlled by changing the angle of the grid structure arranged in the first peripheral portion 10, the second peripheral portion 20, and the central portion 30.

[0043] In another embodiment of the present invention, the angle of the grid structure arranged in the central portion 30 may be greater than the angle of the grid structure arranged in the first peripheral portion 10 and the second peripheral portion 20.

[0044] When the angle of the grid structure arranged in the central part 30 is greater than the angle of the grid structure arranged in the first peripheral part 10 and the second peripheral part 20, it can cause a large change in flow velocity, guide the flow to the peripheral part, and thus suppress the phenomenon of stagnation in the peripheral part, which is preferred.

[0045] In another embodiment of the invention, the angle (θ) of the grid structure arranged within the first peripheral portion 10 is... f’ The angle can be 30 to 80°, preferably 40 to 80°, and more preferably 50 to 60°.

[0046] In yet another embodiment of the invention, the angle (θ) of the grid structure arranged within the second peripheral portion 20 is... f” The angle can be 30 to 80°, preferably 40 to 80°, and more preferably 50 to 60°.

[0047] In yet another embodiment of the invention, the angle (θ) of the grid structure arranged within the central portion 30 is... fThe angle can be 90 to 150°, preferably 100 to 130°, and more preferably 110 to 120°.

[0048] When the angles of the grid structures arranged in the first peripheral portion 10, the second peripheral portion 20 and the central portion 30 respectively meet the range, a large change in flow velocity can be caused, thereby maximizing the effect of suppressing the phenomenon of stagnation in the peripheral portion, which is therefore preferred.

[0049] In another embodiment of the present invention, the length of one side of the grid structure arranged in the first peripheral portion 10 can be 0.5 to 10 mm, preferably 1 to 8 mm, and more preferably 2 to 5 mm.

[0050] In another embodiment of the present invention, the length of one side of the grid structure arranged in the second peripheral portion 20 can be 0.5 to 10 mm, preferably 1 to 8 mm, and more preferably 2 to 5 mm.

[0051] In another embodiment of the invention, the length of one side of the grid structure arranged in the central portion 30 can be 0.5 to 10 mm, preferably 1 to 8 mm, and more preferably 2 to 5 mm.

[0052] In other words, when the grid structure arranged in the first peripheral portion 10 is rhomboid in shape, the lengths of the four sides of the rhombus can satisfy the range.

[0053] When the grid structure arranged within the first peripheral portion 10 is a parallelogram shape, the lengths of the long side and the short side of the parallelogram can respectively satisfy the range.

[0054] When the length of one side of the grid structure arranged in the first peripheral portion 10, the second peripheral portion 20 and the central portion 30 respectively meets the range, it can obtain excellent target ion exchange performance and suppress the problem of damage to the partition of the electrodialysis system caused by the flow rate and pressure difference of the treated water, so it is preferred.

[0055] The diameter of the strands constituting the grid structure can be 0.1 to 1.0 mm, preferably 0.2 to 0.8 mm, more preferably 0.35 to 0.5 mm, but is not limited thereto.

[0056] However, when the diameter of the strands meets the specified range, the durability of the electrodialysis separator 100 according to the present invention is improved, and therefore preferred.

[0057] The width of the electrodialysis separator 100 can be from 10 mm to 1500 mm, preferably from 300 mm to 1500 mm, and more preferably from 400 mm to 1200 mm. When the width of the electrodialysis separator 100 meets the above range, it is preferred because it falls within the manufacturing range of commercial membranes and has the advantage of easy system configuration.

[0058] The electrodialysis separator 100 according to the present invention may have a thickness of 0.3 to 2.0 mm, preferably 0.3 to 1.2 mm, more preferably 0.6 to 1.0 mm, but is not limited thereto.

[0059] However, when the thickness of the electrodialysis separator 100 meets the specified range, the thickness of the electrodialysis separator 100 can be minimized to the maximum extent, while the deformation of the electrodialysis separator 100 can be suppressed, and the flow rate between the membranes can be maintained appropriately, which is therefore preferred.

[0060] The separator 100 for electrodialysis according to the present invention may have a height of 500 to 1500 mm, preferably 700 to 1500 mm, more preferably 1220 to 1500 mm, but is not limited thereto.

[0061] When the height of the electrodialysis partition 100 meets the specified range, an ion concentration gradient is formed relative to the entire length (height) direction, which has the advantage of increased ion exchange performance, and is therefore preferred.

[0062] The electrodialysis partition 100 may further include a water outlet, an inlet, etc., but is not limited thereto.

[0063] In this invention, the manufacturing method of the electrodialysis separator 100 is not limited. For example, the electrodialysis separator 100 can be manufactured by injection molding or by drawing polymer materials into filaments and weaving them. When using the weaving method, two or more separators with different flow resistances (specifically, different angles within the grid structure) can be made first and then joined together for manufacturing, but this is not a limitation.

[0064] The electrodialysis separator 100 can be made of non-conductive polymer materials such as polytetrafluoroethylene, but is not limited to this.

[0065] The electrodialysis separator 100 according to the present invention is not limited by material, and its ion exchange performance can be improved by adjusting its physical shape.

[0066] The separator for an electrodialysis system according to the present invention, having a peripheral portion and a central portion 30 with different flow resistances, generates a relatively stronger flow rate in the peripheral portion compared to conventional separators, which can suppress the phenomenon of stagnation in the flow field between the cation exchange membrane and the anion exchange membrane, and thus has the advantage of increasing ion migration efficiency.

[0067] The electrodialysis separator 100 according to the present invention can be effectively applied to reverse electrodialysis systems (RO), bipolar electrodialysis systems (BPED), etc.

[0068] <Electrodialysis System> Another aspect of the present invention relates to an electrodialysis system comprising: an anode; a cathode disposed opposite to the anode; a cation exchange membrane and an anion exchange membrane alternately disposed between the anode and the cathode; and the aforementioned partition sandwiched between the cation exchange membrane and the anion exchange membrane.

[0069] The electrodialysis system according to the present invention has the advantage of excellent ion exchange performance.

[0070] The anode may include a substrate containing titanium (Ti), tantalum (Ta), nickel (Ni), or a similar metal.

[0071] The surface of the substrate may be coated with a non-deactivatable electrocatalytic film, but is not limited thereto.

[0072] For example, the surface of the substrate may be coated with a conductive (discharge) material, which is an oxide of platinum (Pt), iridium (Ir), rhodium (Rh), ruthenium (Ru), zirconium (Zr), titanium (Ti) or similar metals, or contains at least one of the aforementioned metal oxides.

[0073] For example, the thin film can be formed by coating an organic compound containing at least one of the aforementioned metals (e.g., iridium alkoxide, ruthenium alkoxide, tantalum alkoxide, or titanium alkoxide, wherein the alcohol used can be methanol, ethanol, propanol, butanol, isopropanol, isobutanol, etc.) onto the surface of a metal substrate, followed by a sintering process for removing the organic components, but not limited thereto.

[0074] The cathode may include, but is not limited to, nickel, iron, stainless steel, nickel-plated titanium, graphite, carbon steel, or combinations thereof.

[0075] The anode can be located in the anode chamber, and the cathode can be located in the cathode chamber.

[0076] An acidic solution tank may be further arranged outside the anode chamber, and an alkaline solution tank may be further arranged outside the cathode chamber.

[0077] The cation exchange membrane has anionic groups inside, thus allowing only cations to selectively pass through.

[0078] Specifically, the cation exchange membrane can be composed of negatively (-) charged ionic groups, such that Na... + K + Ca 2 + Mg 2+ Fe2 2+ Cations pass through, while Cl... - ,Br - NO3 - SO4 2- HCO3 - Anions cannot pass through due to the repulsion of like charges.

[0079] The thickness of the cation exchange membrane can be 70 to 170 μm, preferably 75 to 150 μm, more preferably 80 to 120 μm, but is not limited thereto.

[0080] The cation exchange membrane may include multiple inlets, and the present invention does not limit the diameter of the inlets, etc.

[0081] The anion exchange membrane contains cationic groups, thus allowing only anions to selectively pass through.

[0082] Specifically, the anion exchange membrane can be composed of positively (+) charged ionic groups, such that Cl... - ,Br - NO3 - SO4 2- HCO3 - Anions pass through, while Na... + K + Ca 2+ Mg 2+ Fe2 2+ Cations cannot pass through due to the repulsion of like charges.

[0083] The thickness of the anion exchange membrane can be 70 to 170 μm, preferably 75 to 150 μm, more preferably 80 to 120 μm, but is not limited thereto.

[0084] The anion exchange membrane may include multiple inlets, and the present invention does not limit the diameter of the inlets, etc.

[0085] Multiple cation exchange membranes and multiple anion exchange membranes can be provided, and the electrodialysis separator 100 can be provided between multiple cation exchange membranes and multiple anion exchange membranes.

[0086] The electrodialysis system according to the present invention may further include bipolar membranes, gaskets, etc., but is not limited thereto.

[0087] Specifically, the electrodialysis system according to the present invention can be a reverse electrodialysis system (RO; Reverse Osmosis) or a bipolar membrane electrodialysis system (BPED; Bipolar Electrodialysis), but is not limited thereto.

[0088] Preferred embodiments and comparative examples of the present invention are described below. However, the following embodiments are merely one of the preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

[0089] Example A baffle with a rhomboid grid relative to the flow direction was applied. Baffles with a rhomboid shape at an angle of 60° relative to the flow direction were arranged on both sides as the first and second outer perimeters, and a baffle with an angle of 120° was arranged in the middle as the center. The baffle for electrodialysis was then modeled by combination (using the COMSOL program).

[0090] At this point, the modeling parameters are set as follows: the width of the first and second outer perimeters is 84mm, the width of the center is 252mm, the thickness of the electrodialysis partition is 0.8mm, the height of the partition is 1220mm, the length of the four sides of the grid inside the partition is 2mm, and the diameter of the grid strands is 0.35mm.

[0091] Figure 2 The image on the left shows the grid shapes within the first and second outer perimeters. Figure 3 The image on the right shows the shape of the grille in the center.

[0092] Specifically, in Figure 2 In, θ t It refers to θ f The relative angle, θ a It refers to θ t With θ f The angle between them.

[0093] Comparative example A partition with a rhomboid inner grid shape and an angle of 60° was manufactured. The width and length of the partition are the same as those of the electrodialysis partition manufactured according to the embodiment, and the shape of the inner grid of the partition is the same as the grid shape in the first and second peripheral portions according to the embodiment.

[0094] Experimental Example To observe the flow analysis of the baffles manufactured according to the embodiments and comparative examples, flow analysis based on the baffle angle was performed (using the COMSOL program), and the results are shown below. Figure 3 and Figure 4 middle.

[0095] Specifically, flow analysis was performed using a three-dimensional flow analysis program.

[0096] Figure 3 This is an image showing the flow analysis results for a diaphragm with a 60° internal grid structure. Figure 4 This is an image showing the flow analysis results of a 120° grid structure.

[0097] Reference Figure 3 and Figure 4 It can be seen that the flow analysis results will change as the angle of the grid structure inside the partition changes.

[0098] Figure 5 and Figure 6 This is a graph showing the flow analysis of the velocity and vector of the solution passing through the modeled partition, based on the examples and comparative examples.

[0099] Specifically, for the baffles modeled according to the embodiments and comparative examples, the standard deviation of the solution flow rate along the width direction at the outlet of the treated water was predicted (using the COMSOL program), and the results are shown in the figures below. Figure 5 and Figure 6 middle.

[0100] also, Figure 7 and Figure 8 The standard deviation of the flow rate at a specific height (10-90%) relative to the width direction is shown for the dialysis system dialysis ...

[0101] Reference Figure 7 and Figure 8 It can be seen that the flow velocity deviation in the width direction of the baffle according to the comparative example is 0.0069 m / s and 0.00642 m / s, while the flow velocity deviation of the electrodialysis baffle manufactured according to the embodiment is 0.028 m / s, which has a much larger flow velocity variation. In particular, it can be found that the non-uniformity of flow velocity occurs generally in the flow direction, thus minimizing the generation of stagnant areas at the periphery.

[0102] This invention is not limited to the embodiments described above, and can be prepared in various different ways. Those skilled in the art should understand that this invention can be implemented in other specific ways without changing the technical concept or essential features of the invention. Therefore, it should be understood that the above embodiments are exemplary in all respects and not restrictive.

[0103] [Explanation of reference numerals in the attached figures] 10: First outer perimeter 20: Second outer perimeter 30: Central Department 100: Partition for electrodialysis systems

Claims

1. A partition for an electrodialysis system, wherein, The partition includes: a first peripheral portion; a second peripheral portion (20); and a central portion located between the first peripheral portion and the second peripheral portion. At least one of the first peripheral portion and the second peripheral portion has a different flow resistance than the central portion.

2. The partition for the electrodialysis system according to claim 1, wherein, The flow resistance of the first peripheral portion and the second peripheral portion is different from that of the central portion.

3. The partition for the electrodialysis system according to claim 2, wherein, The flow resistance of the first peripheral portion and the second peripheral portion is the same.

4. The partition for the electrodialysis system according to claim 1, wherein, At least one of the first peripheral portion and the second peripheral portion has a lower flow resistance than the central portion.

5. The partition for the electrodialysis system according to claim 4, wherein, The first peripheral portion and the second peripheral portion have lower flow resistance than the central portion.

6. The partition for the electrodialysis system according to claim 1, wherein, The angle of the grid structure arranged in the central part is greater than the angle of the grid structure arranged in the first peripheral part or the second peripheral part.

7. The partition for an electrodialysis system according to claim 6, wherein, The angle of the grid structure arranged in the central part is greater than the angle of the grid structure arranged in the first peripheral part and the second peripheral part.

8. The partition for an electrodialysis system according to claim 6, wherein, The angle of the grid structure arranged in the first peripheral part is 30 to 80°.

9. The partition for an electrodialysis system according to claim 6, wherein, The angle of the grid structure arranged in the second peripheral part is 30 to 80°.

10. The partition for an electrodialysis system according to claim 6, wherein, The angle of the grid structure arranged in the central part is 90 to 150°.

11. The partition for an electrodialysis system according to claim 6, wherein, The length of one side of the grid structure arranged in the first peripheral area is 0.5 to 10 mm.

12. The partition for an electrodialysis system according to claim 6, wherein, The length of one side of the grid structure arranged in the second outer perimeter is 0.5 to 10 mm.

13. The partition for an electrodialysis system according to claim 6, wherein, The length of one side of the grid structure arranged in the central part is 0.5 to 10 mm.

14. An electrodialysis system comprising: anode; A cathode is disposed opposite to the anode; A cation exchange membrane and an anion exchange membrane are alternately disposed between the anode and the cathode; as well as A separator for an electrodialysis system according to any one of claims 1 to 13 sandwiched between the cation exchange membrane and the anion exchange membrane.

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