Membrane for electrodialysis system and electrodialysis system comprising same

Abstract

A diaphragm for an electrodialysis system according to the present application includes a first end portion, a second end portion disposed opposite the first end portion, and a central portion disposed between the first end portion and the second end portion, the diaphragm being trapezoidal in shape with the second end portion being wider than the first end 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 that can generate a high flow rate to improve ion exchange performance.

[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 end; a second end disposed opposite to the first end; and a central portion disposed between the first end and the second end, wherein the partition for the electrodialysis system is a trapezoidal shape in which the second end is wider than the first end.

[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 a separator for the aforementioned electrodialysis system sandwiched between the cation exchange membrane and the anion exchange membrane.

[0014] (III) Beneficial Effects The separator for the electrodialysis system according to the present invention has the advantage of generating a strong flow rate to improve ion exchange performance.

[0015] Furthermore, the separator for the electrodialysis system according to the present invention has the advantages of excellent ion migration efficiency and suppression of resistive heating. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a partition for an electrodialysis system according to several embodiments of the present invention.

[0017] Figure 2 This is a schematic diagram of multiple layers of partitions stacked in an electrodialysis system according to several embodiments of the present invention.

[0018] Figure 3 This is a flow analysis prediction diagram of a multilayer stacked partition plate in an electrodialysis system according to several embodiments of the present invention.

[0019] Figure 4 This is a schematic diagram of the flow analysis of a dialysis system dialysis plate according to several embodiments of the present invention, and the velocity distribution of the solution along the width direction as a function of position.

[0020] Figure 5 This is a schematic diagram of the flow analysis of the diaphragm in the electrodialysis system of the comparative example and the change of the velocity distribution of the solution along the width direction with position.

[0021] Figure 6 and Figure 7 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

[0022] 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.

[0023] 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.

[0024] 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.

[0025] <Baffles for electrodialysis systems> One aspect of the present invention relates to a partition 100 for an electrodialysis system, comprising: a first end 10; a second end 20 disposed opposite to the first end 10; and a central portion disposed between the first end 10 and the second end 20, wherein the partition 100 for the electrodialysis system is a trapezoidal shape in which the second end 20 is wider than the first end 10.

[0026] Because the separator 100 used in the electrodialysis system is trapezoidal in shape, it can generate a stronger flow rate compared to the traditional rectangular separator. This can suppress the stagnation of the flow field between the cation exchange membrane and the anion exchange membrane, thus improving the ion migration efficiency.

[0027] The separator 100 for an electrodialysis system according to the present invention includes a first end 10 and a second end 20 disposed opposite to the first end 10.

[0028] At this time, the length of the second end 20 is greater than that of the first end 10.

[0029] The first end 10 and the second end 20 are arranged opposite each other.

[0030] Specifically, the first end 10 and the second end 20 can refer to the base and lower base of the trapezoid, respectively.

[0031] In another embodiment of the invention, the partition 100 of the electrodialysis system may include the treated water outlet 11 described later.

[0032] Typically, the ion exchange performance of the treated water outlet 11 can be slightly lower than that of the center.

[0033] Traditional rectangular baffles exhibit a uniform flow velocity along their width, and the velocity deviation along this width is also symmetrical. This leads to a decrease in overall ion exchange performance at the outlet 11 of the treated water, where ion exchange performance is relatively low.

[0034] In contrast, the partition 100 for the electrodialysis system according to the present invention, being trapezoidal in shape, can generate a stronger flow rate at the outlet 11 of the treated water relative to the same flow rate. Therefore, ion exchange can proceed efficiently, and the ion concentration gradient across the partition 100 also increases, thus offering the advantage of improved overall system performance.

[0035] Furthermore, during the migration of ions through the membrane under the influence of electricity, the temperature at the upper end of the separator, i.e., the first end 10, may rise relative to the lower end of the separator, i.e., the second end 20. Therefore, by forming the first end narrower than the second end 20, a uniform flow can be achieved.

[0036] In another embodiment of the present invention, the size of the bottom angle (A, A') of the second end 20 can be 70 to 86°.

[0037] In another embodiment of the present invention, the size of the bottom angle (A, A') of the second end 20 can be 80 to 86°.

[0038] When the size of the bottom angle (A, A') of the second end 20 meets the range, as it approaches the first end 10, a flow resistance will be formed corresponding to the rising flow velocity, thereby forming a uniform flow field at the edge of the partition 100 of the electrodialysis system, which is therefore preferred.

[0039] In another embodiment of the invention, the two bottom corners (A, A') of the second end 20 may be of different sizes.

[0040] In another embodiment of the invention, the two bottom corners (A, A') of the second end 20 may be the same size.

[0041] Specifically, the partition 100 of the electrodialysis system according to the present invention can be a symmetrical trapezoid or an asymmetrical trapezoid.

[0042] In other words, the two bottom angles (A, A') of the second end 20 can have different angles or the same angle.

[0043] Preferably, the two bottom corners (A, A') of the partition 100 in the electrodialysis system can have the same angle.

[0044] When the two bottom corners (A, A') of the partition 100 of the electrodialysis system have the same angle, it has the advantage of convenient operation in terms of system assembly and management, and is therefore preferred.

[0045] In another embodiment of the present invention, the length of the first end 10 can be 30 to 90% of the length of the second end 20.

[0046] In another embodiment of the present invention, the length of the first end 10 can be 40 to 60% of the length of the second end 20.

[0047] When the length of the first end 10 is within the range relative to the length of the second end 20, excellent target ion exchange performance can be obtained, and the problem of damage to the partition 100 of the electrodialysis system caused by the flow rate and pressure difference of the treated water can be suppressed. Therefore, it is preferred.

[0048] The length of the second end 20 can be from 300 to 1500 mm, but is not limited thereto.

[0049] The length of the first end 10 can be selected to satisfy a ratio relative to the length of the second end 20.

[0050] The separator 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, more preferably 0.6 to 1.0 mm, but is not limited thereto.

[0051] However, when the thickness of the electrodialysis separator meets the specified range, the thickness of the electrodialysis separator can be minimized, and deformation of the electrodialysis separator can be suppressed, which is therefore preferred. Furthermore, since an ion concentration gradient is formed throughout the entire thickness, it has the advantage of increased ion exchange performance, which is also preferred.

[0052] The separator 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.

[0053] When the height of the separator for electrodialysis 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.

[0054] The outlet 11 of the treated water can be formed on the side of the first end 10.

[0055] Furthermore, the electrodialysis baffle according to the present invention may include an inlet 21 for the treated water formed on the second end 20 side.

[0056] The closer to the outlet 11 of the treated water, the smaller the effective cross-sectional area of ​​the electrodialysis baffle along its length, thus enabling a uniform flow.

[0057] The outlets 11 of the treated water can be staggered in the direction perpendicular to the length of the electrodialysis partition, i.e., in the width direction. For example, the outlets 11 of the treated water can be located on the right side of the first end 10, and the inlet 21 of the treated water can be located on the left side of the second end 20. (Refer to...) Figure 1 11 represents an exit, and 21 represents an entrance.

[0058] The central portion can serve as a compartment in which ions in the solution migrate under the influence of the anode (+) electrode and the cathode (-) electrode.

[0059] The central portion may include a grid area, a nonwoven fabric with openings, etc.

[0060] In another embodiment of the invention, the central portion may include a mesh area.

[0061] There are no particular limitations on the shape of the grid region in this invention.

[0062] In another embodiment of the present invention, the grid area may include one or more patterns selected from the group consisting of circles, ellipses, quadrilaterals, parallelograms, rhombuses and mesh shapes.

[0063] Specifically, the grid area may include a uniform grid structure in the shape of a rhombus.

[0064] In this invention, the manufacturing method of the electrodialysis separator is not limited. For example, the electrodialysis separator can be manufactured by injection molding or by drawing polymer materials into filaments and weaving them.

[0065] The separator used for electrodialysis can be made of non-conductive polymer materials such as polytetrafluoroethylene (Teflon), but is not limited to this.

[0066] The electrodialysis separator according to the present invention is not limited by material, and its ion exchange performance can be improved by adjusting its physical shape.

[0067] The electrodialysis baffle according to the present invention has a trapezoidal shape in which the second end 20 is wider than the first end 10, thereby forcing a faster flow rate at the outlet 11 of the treated water where the ion exchange performance is relatively low. Therefore, flow field stagnation caused by pinholes due to impurities can be suppressed, and it has the advantage of improving ion exchange performance.

[0068] The electrodialysis separator according to the present invention can be effectively applied to reverse electrodialysis systems (RO), bipolar electrodialysis systems (BPED), etc.

[0069] <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 a partition 100 for the aforementioned electrodialysis system sandwiched between the cation exchange membrane and the anion exchange membrane.

[0070] The electrodialysis system according to the present invention has the advantage of excellent ion exchange performance.

[0071] The anode may include a substrate containing titanium (Ti), tantalum (Ta), nickel (Ni), or a similar metal.

[0072] The surface of the substrate may be coated with a non-deactivatable electrocatalytic film, but is not limited thereto.

[0073] 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.

[0074] 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.

[0075] The cathode may include, but is not limited to, nickel, iron, stainless steel, nickel-plated titanium, graphite, carbon steel, or combinations thereof.

[0076] The anode can be located in the anode chamber, and the cathode can be located in the cathode chamber.

[0077] 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.

[0078] The cation exchange membrane has anionic groups inside, thus allowing only cations to selectively pass through.

[0079] 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.

[0080] 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.

[0081] The cation exchange membrane may include multiple inlets, and the present invention does not limit the diameter of the inlets, etc.

[0082] The anion exchange membrane contains cationic groups, thus allowing only anions to selectively pass through.

[0083] 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.

[0084] 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.

[0085] The anion exchange membrane may include multiple inlets, and the present invention does not limit the diameter of the inlets, etc.

[0086] Multiple cation exchange membranes and multiple anion exchange membranes can be provided, and the separator for electrodialysis can be provided between multiple cation exchange membranes and multiple anion exchange membranes.

[0087] In another embodiment of the present invention, when multiple electrodialysis baffles are provided, the treated water outlets 11 of the multiple electrodialysis baffles can be arranged alternately.

[0088] In another embodiment of the present invention, the treated water outlets 11 of the plurality of electrodialysis baffles can be arranged alternately in the horizontal direction.

[0089] Specifically, the adjacent electrodialysis baffles are arranged in a horizontal manner by rotating 180°, so that the outlets 11 of the treated water are staggered.

[0090] By arranging the treated water outlets 11 of the plurality of electrodialysis baffles in a staggered manner in the horizontal direction, the high-flow-rate sections can be alternately arranged and stacked, thereby further improving the ion exchange performance, which is therefore preferred.

[0091] Preferably, the plurality of electrodialysis partitions can be arranged in an alternating pattern.

[0092] The electrodialysis system according to the present invention may further include bipolar membranes, gaskets, etc., but is not limited thereto.

[0093] 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.

[0094] 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.

[0095] Example A trapezoidal partition with a first end length of 250 mm, a second end length of 420 mm, a height of 1220 mm, and two base angles of 86° was modeled and computational analysis was performed (using the COMSOL program). The central portion consisted of a mesh with a rhomboid pattern, and simulation analysis was conducted according to three-dimensional steady-state conditions.

[0096] Comparative example Using the same procedure as in the embodiment, a rectangular partition with a width of 420 mm and a length of 1220 mm was modeled and computational analysis was performed. In this case, the same mesh as in the embodiment was used in the center.

[0097] Experimental Example Flow analysis (using COMSOL program) was performed on the baffles manufactured according to the embodiments and comparative examples, and the results are shown below. Figure 4 and Figure 5 middle.

[0098] Figure 4 and Figure 5 The left image is a flow analysis diagram showing the velocity and vector of the solution passing through the partition, and the right image is a diagram showing the velocity distribution of the solution along the width of the partition.

[0099] Specifically, the standard deviation of the solution velocity along the width direction at the outlet of the treated water was predicted using the COMSOL program for the baffle modeled according to the embodiments and comparative examples, and the results are shown in the figures below. Figure 4 and Figure 5 middle.

[0100] More specifically, the standard deviation of the solution velocity was obtained by calculating the standard deviation of the flow velocity at 83 equally spaced points along the width of the baffle (based on the second end in this embodiment). For this calculation, with respect to the height of the baffle, the heights in seven flow directions, indicated by dashed lines, were designated as 10%, 15%, 20%, 50%, 80%, and 90%, starting from the second end, and the velocity deviation in the width direction was calculated at these locations. It can be observed that the standard deviation of the velocity is largest near the outlet, which is close to 90% of the total height.

[0101] Figure 6 and Figure 7 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 ...

[0102] Reference Figure 5 and Figure 7It can be observed that the dialysis system dialysis plate according to the comparative example has a uniform flow velocity in the width direction, and the deviation of the flow velocity in the width direction is also symmetrically distributed from left to right. This leads to a decrease in the overall ion exchange capacity at the outlet where the ion exchange performance is low. Furthermore, when using the dialysis system dialysis plate according to the comparative example, the maximum flow velocity is approximately 0.1 m / s, and the velocity deviation is 0.013 m / s.

[0103] In comparison, refer to Figure 4 and Figure 6 It can be observed that when the baffle manufactured according to the embodiment is used, the maximum flow rate is 0.155 m / s, which means that more than 50% of the local flow rate is increased, and the velocity deviation is 0.023 m / s, resulting in a performance improvement of about 77%.

[0104] 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.

[0105] [Explanation of reference numerals in the attached figures] 10: First end 11: Exports 20: Second end 21: Entrance 100: Partition for electrodialysis systems

Claims

1. A partition for an electrodialysis system, comprising: First end; A second end is disposed opposite to the first end; as well as Arranged at the center between the first end and the second end. The partition in the electrodialysis system is trapezoidal in shape, with the second end being wider than the first end.

2. The partition for the electrodialysis system according to claim 1, wherein, The bottom angle of the second end is 70 to 86°.

3. The partition for the electrodialysis system according to claim 2, wherein, The bottom angle of the second end is 80 to 86°.

4. The partition for the electrodialysis system according to claim 1, wherein, The two bottom corners at the second end are different in size.

5. The partition for the electrodialysis system according to claim 1, wherein, The two bottom corners at the second end are the same size.

6. The partition for the electrodialysis system according to claim 1, wherein, The length of the first end is 30% to 90% of the length of the second end.

7. The partition for an electrodialysis system according to claim 6, wherein, The length of the first end is 40% to 60% of the length of the second end.

8. The partition for the electrodialysis system according to claim 1, wherein, The height of the partition is 500mm to 1500mm.

9. The partition for an electrodialysis system according to claim 1, wherein, The central part includes a grid area.

10. The partition for an electrodialysis system according to claim 9, wherein, The grid area includes at least one pattern selected from the group consisting of circles, ellipses, squares, parallelograms, rhombuses, and mesh shapes.

11. The partition for an electrodialysis system according to claim 1, wherein, The baffle includes an outlet for treated water.

12. 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 11 sandwiched between the cation exchange membrane and the anion exchange membrane.

13. The electrodialysis system according to claim 12, wherein, When multiple partitions are provided for electrodialysis, the treated water outlets of the multiple partitions are arranged in an alternating manner.

14. The electrodialysis system according to claim 13, wherein, The treated water outlets of the multiple baffles are arranged in a staggered manner in the horizontal direction.

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