Gasket system for electrodialysis

Abstract

The present invention relates to a system capable of increasing a production rate of a target fluid relative to applied electrical energy by providing an optimized gasket configuration for supplying a working fluid to an electrodialysis system and converting the working fluid into the target fluid. Specifically, the present invention provides a system capable of enhancing electrodialysis efficiency and electrical energy efficiency by modifying the inlet and outlet structure of a gasket having an interposed spacer for use in an electrodialysis apparatus.

Description

Gasket system for electrodialysis

[0001] The present invention relates to a system capable of increasing the production rate of a target fluid relative to the applied electrical energy by presenting an optimal shape of a gasket that supplies a working fluid to an electrodialysis system and changes it into a target fluid.

[0002]

[0003] The global electric vehicle market is projected to grow from 2.3 million units in 2019 to 21.9 million units in 2030.

[0004] Accordingly, battery performance is also continuously improving through increased capacity and longer lifespan.

[0005] The share of high-energy-density High-Ni batteries as cathode active materials for secondary batteries is also predicted to rise to 76% by 2030.

[0006] Therefore, the demand for lithium hydroxide, a lithium raw material for high-Ni cathode active materials, is also expected to increase.

[0007] Lithium, which serves as a raw material for lithium-ion batteries, was conventionally extracted from salt lakes in the form of lithium carbonate and reacted with lime to obtain lithium hydroxide; however, this method had the problem of generating excessive carbon dioxide during fixation. Consequently, a process for manufacturing lithium hydroxide using an electrodialysis method with a bipolar membrane is currently being applied.

[0008] However, a problem has recently been raised that in a lithium hydroxide extraction process using the above-mentioned bipolar membrane, the solution flowing along the spacer (40) inserted into the gasket (10) causes uneven flow uniformity across the entire effective membrane of the spacer (40), which becomes a factor in generating excessive electrical resistance.

[0009] The electrodialysis process using the aforementioned bipolar membrane is seeking to scale up for the mass production of lithium hydroxide; however, since this increase in electrical resistance can result in unnecessary consumption of electrical energy, it is urgent to devise a solution for this.

[0010]

[0011] The present invention has been devised to solve the aforementioned problems and provides a method for increasing flow uniformity by changing the shape of a gasket through which the working fluid and the target fluid are supplied or discharged in an electrodialysis system.

[0012] In addition, a method is provided to increase the efficiency of electrical energy applied to the electrodialysis system by changing the inlet and outlet shapes of the gasket.

[0013] In addition, a range of possible design changes to the gasket can be presented to increase the production volume of the target fluid.

[0014]

[0015] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0016]

[0017] To solve the above-mentioned problem, the present invention comprises a unit pair formed by sequentially arranging a bipolar membrane (61), a gasket (11) with a spacer (40) inserted therein, an anion exchange membrane (62), a gasket (12) with a spacer (40) inserted therein, a cation exchange membrane (63), and a gasket (13) with a spacer (40) inserted therein; wherein a working fluid supplied to a plurality of inlets (20) formed in the gasket (10) by an externally applied electrode is obtained through a plurality of outlets (30) formed in the gasket, wherein the inlets (20) and outlets (30) of the gaskets (11, 12, 13) with the spacer (40) inserted therein are formed in an isosceles trapezoid shape that protrudes outward and has a reduced width, and the ratio of the minimum width (CW) and maximum width (CW) of the inlets (20) and outlets (300) is 0.8 It can be characterized as being up to 0.95.

[0018] In one embodiment of the present invention, the length (MH) of the effective film exposed to the spacer (40) inserted into the gasket (10) may be characterized as being 1 m to 2.5 m.

[0019] In one embodiment of the present invention, the area (MW) of the effective film exposed to the spacer (40) inserted into the gasket (11, 12, 13) may be characterized as being 0.29 m to 2.5 m.

[0020] In one embodiment of the present invention, the value (GFR) obtained by dividing the value obtained by multiplying the average value of the width (CW) of the first inlet (21) and the second inlet (22) by the number (CN) of the inlet (20) or outlet (30) by the width (MW) of the effective film may be 0.3 to 0.5.

[0021] In one embodiment of the present invention, the ratio of the average width (CW) of the inlet (20) or outlet (30) installed in the gasket (11, 12, 13) to the number (CN) of the inlet (20) or outlet (30) may be 0.43 to 1.54.

[0022] In one embodiment of the present invention, the speed of the working fluid supplied to the inlet (20) of the gasket (11, 12, 13) may be characterized as being 5 cm / sec to 11 cm / sec.

[0023] In one embodiment of the present invention, the working fluid may be characterized as being at least one of water or a lithium aqueous solution.

[0024] In one embodiment of the present invention, the target fluid may be characterized as being at least one of an aqueous lithium hydroxide solution or an acidic aqueous solution.

[0025] In one embodiment of the present invention, the ratio of the width (CW) of the first outlet (31) of the outlet (30) to the width (CW) of the second outlet (32) may be 0.8 to 0.95.

[0026]

[0027] According to various embodiments of the present invention, the production volume of the target fluid can be increased by changing the shape of the gasket used in the electrodialysis system to improve the flow uniformity of the working fluid and the target fluid flowing through the spacer inserted into the gasket.

[0028] According to various embodiments of the present invention, the electrical energy efficiency required for electrodialysis can be improved by changing the shape of a gasket used in an electrodialysis system to improve the flow uniformity of the working fluid and the target fluid flowing through the spacer inserted into the gasket.

[0029] According to various embodiments of the present invention, by setting limits on design changes for the gasket of an electrodialysis system, guidelines can be provided to the user to quickly design an electrodialysis system process suitable for the usage environment and purpose.

[0030]

[0031] Figure 1 is a conceptual diagram of the unit configuration of the electrodialysis device of the present invention.

[0032] FIG. 2 is a front view illustrating an example of a gasket with a spacer inserted therein, used in the electrodialysis device of the present invention.

[0033] FIG. 3 is a schematic diagram illustrating a method for finding optimal improvement by adjusting the shape and number of gasket inlets and outlets of the present invention.

[0034] Figure 4 is a numerical analysis result showing the hydraulic pressure change at one end and the other end of the inlet while the GFR coefficient of the present invention is fixed.

[0035]

[0036] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0037] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may also be the second component.

[0038] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0039] In the following, the statement that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0040] In addition, where it is stated that one component is "connected," "combined," or "connected" to another component, it should be understood that while the components may be directly connected or connected to each other, another component may be "interposed" between each component, or each component may be "connected," "combined," or "connected" through another component.

[0041] Singular expressions used in this specification include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "composed of" or "comprising" should not be interpreted as necessarily including all of the various components or steps described in the specification, and should be interpreted as meaning that some of the components or steps may be omitted or additional components or steps may be included.

[0042] Throughout the specification, "A and / or B" means A, B, or A and B unless specifically stated otherwise, and "C to D" means C or more and D or less unless specifically stated otherwise.

[0043]

[0044] Hereinafter, a gasket system used for electrodialysis according to various embodiments will be described with reference to the attached drawings.

[0045]

[0046] [Basic Structure]

[0047] FIG. 1 illustrates an example of an electrodialysis system formed by sequentially arranging a bipolar membrane (61), a gasket (11) with a spacer (40) inserted therein, an anion exchange membrane (62), a gasket (12) with a spacer (40) inserted therein, a cation exchange membrane (63), and a gasket (13) with a spacer (40) inserted therein.

[0048] Since the above system is briefly illustrated with only one unit pair, it is obvious that in the actual system, multiple pairs are arranged and the ion exchange process is carried out by the electrical energy applied by the electrodes (51, 52) located at both ends thereof.

[0049] FIG. 2 shows a front view of an embodiment of a gasket (10) with a spacer (40) inserted therein, used in the electrodialysis system of the present invention.

[0050] The above gasket (10) creates a flow path and space in the spacer (40) through which the solution can flow, and the spacer (40) performs the function of making the introduced solutions into turbulence so that the solutions can be mixed evenly.

[0051] In the present invention, the space in the gasket (10) where the spacer is exposed to the solution is defined as the effective film area.

[0052] The inlet (20) of the gasket (10) performs the function of supplying working fluid to the spacer (40), and the working fluid supplied to the spacer (40) undergoes ion exchange with the cation exchange membrane (62) and anion exchange membrane (63) arranged front and back as shown in FIG. 1 by the applied electrical energy, and can be converted into a target fluid to be produced in the process and discharged through the outlet (30).

[0053] In the lithium production process, the working fluid may be water or an aqueous lithium solution, but this may be changed depending on the process method or purpose.

[0054] In addition, the target fluid may be a receptacle containing lithium, and may be an aqueous solution of lithium hydroxide, an acidic aqueous solution, or an alkaline aqueous solution from which lithium ions have been removed from the lithium aqueous solution.

[0055] It is obvious that the aforementioned target fluid, like the working fluid, can also be changed depending on the process method or purpose.

[0056] As will be explained later, the inlet (20) and outlet (30) installed at one end and the other end of the gasket (10) based on the fluid flow direction may be installed in multiple (CN) places, and preferably, the number of inlets (20) and outlets (30) may be the same.

[0057] Additionally, the effective film exposed to the spacer (40) inserted into the gasket (10) can be defined in shape with a height (MH) in the same direction as the fluid flow direction and a width (MW) in the direction perpendicular thereto.

[0058] Figure 3 shows the above effective film separated.

[0059] The above inlet (20) can be divided into a first inlet (21) that initially supplies the working fluid and a second inlet (22) that supplies the working fluid to the effective membrane.

[0060] Likewise, the above outlet (30) can also be divided into a first outlet (31) where the target fluid is initially discharged and a second outlet (32) that discharges the target fluid to the outside.

[0061] The above inlet (20) and outlet (30) can be defined by a channel height (CH) and a channel width (CW) perpendicular to it, in the same direction as the fluid flow direction.

[0062] Here, the channel width (CW) may be defined as the channel width (CW) measured at an intermediate position of the channel height (CH) of the inlet (20) and outlet (30), or the average width (CW) of the inlet (20) and outlet (30).

[0063] In the prior art, the inlet (20) and outlet (30) are basically configured as rectangles so that the first inlet (21), second inlet (22) and first outlet (31), second outlet (32) have the same width, or even if the inlet (20) and outlet (30) are not rectangles, there was no recognition that the performance of the electrodialysis system could be improved by changing their shapes.

[0064]

[0065] [First Example]

[0066] It is evident that ion exchange can proceed smoothly if the fluid flowing through the above effective membrane has a constant flow velocity.

[0067] This is because the same electrical energy is applied to the ion exchange membranes placed before and after the effective membrane, so if local flow delay or flow acceleration occurs in the effective membrane, the mass of the fluid flowing per unit area changes, making it difficult to perform smooth ion exchange.

[0068] In the present invention, the flow uniformity of fluids flowing through the effective film can be defined by the following mathematical formula 1.

[0069]

[0070] [Mathematical Formula 1]

[0071]

[0072]

[0073] Here, λ is the fluid flow uniformity, n is the number of cells in which the effective film is divided along the length, A i is the area of ​​the segmented cell, A is the total effective film area, w i is the fluid velocity in each cell, and W is the average fluid velocity in the effective membrane.

[0074] In other words, the closer λ is to 1, the more uniformly the fluid flows, and the higher the ion exchange performance can be set.

[0075] In this embodiment, the working fluid is supplied to the inlet (20) at a speed of 5 cm / sec to 11 cm / sec, and the effective film height (MH) and effective film width (MW) are tested by changing them to 1 m to 2.5 m and 0.29 m to 2.5 m, respectively.

[0076] When the above range is exceeded, the flow uniformity is rapidly reduced under any experimental conditions, and this can be seen as being due to the hydraulic pressure of the solution supplied to the gasket (10) being converted into the target fluid and discharged when it deviates from the shape range of the effective film within the above-set working fluid supply speed range, which is excessive or insufficient.

[0077] In addition, the Gasket Flow Ratio (GFR), which represents the area occupied by the inlet (20) or outlet (30) relative to the effective membrane width (MW), can be defined by the following mathematical formula 2.

[0078]

[0079] [Mathematical Formula 2]

[0080]

[0081]

[0082] That is, the closer GFR is to 1, the larger the area of ​​the inlet installed on the cross-section of the gasket (10) is. Through experiments, it was confirmed that in the range other than 0.3 to 0.5, the result obtained was that the minimum design value of the fluid flow uniformity defined by the above mathematical formula 1 was lowered to 0.93 or lower.

[0083] In this embodiment, the inlet (20) and outlet (30) are formed as isosceles trapezoids that protrude outward and have reduced widths, and the ratio of the width of the first inlet (21) to the width of the second inlet (22) and the ratio of the width of the first outlet (31) to the width of the second outlet (32) are simultaneously changed to check the change in the flow uniformity.

[0084] Table 1 below shows the results of an experiment conducted with the GFR fixed at 0.3 as one of the examples, and also describes the result obtained through numerical analysis of the hydraulic pressure difference between the first inlet (21) and the second inlet (22) as another performance coefficient to determine the optimal value.

[0085]

[0086] Classification GFR = 0.3 1st Inlet / 2nd Inlet 100% 95% 90% 85% 80% 75% Uniformity 0.99 30.99 40.99 50.99 50.99 50.99 5 Hydraulic Difference 100% 101% 103% 107% 119% 123%

[0087]

[0088] Looking at Table 1 above, it can be seen that the highest level of flow uniformity is maintained when the ratio of the width of the first inlet (21) to the width of the second inlet (22) is 0.8 to 0.95.

[0089] Of course, even if the ratio of the width of the first inlet (21) to the width of the second inlet (22) is 0.75 or less, the flow uniformity is high, but since the pressure difference at the inlet (20) exceeds 120% and the pump supplying the working fluid to the gasket (10) inlet (20) may be strained, the ratio of the width of the first inlet (21) to the width of the second inlet (22) can be set to be 0.8 to 0.95 as the optimal range for commercial use.

[0090] FIG. 4 illustrates some of the results of numerical analysis of hydraulic changes at the inlet (20).

[0091]

[0092] [2nd Example]

[0093] In this embodiment, a method for calculating the optimal density range of the inlet (20) and outlet (30) installed at each end of the effective membrane of the gasket (10) is presented.

[0094] The Channel Flow Ratio (CFR) defined in Equation 3 below can be used as the performance coefficient of this embodiment.

[0095] The above CFR has a physical meaning representing the number of distributions of the inlet (20) and outlet (30) in a state where the aspect ratio of the gasket (10) and the area occupied by the inlet and outlet are determined, i.e., a certain GFR coefficient.

[0096]

[0097] [Mathematical Formula 3]

[0098]

[0099]

[0100] Table 2 below shows the results of an experiment conducted with GFR set to 0.3 and the ratio of the width (CW) of the first inlet (21) and the second inlet (22) set to 0.8. In addition, the result obtained through numerical analysis of the hydraulic pressure difference between the first inlet (21) and the second inlet (22) is also listed as another performance coefficient to determine the optimal value.

[0101] Table 2 above shows one example of the gasket (10) and operating conditions as experimental results.

[0102]

[0103] Classification GFR = 0.3, 1st Inlet Width / 2nd Inlet Width = 0.8 CFR 3.7 8 1.5 4 1.1 2 0.6 4 0.4 3 0.3 Uniformity 0.9 4 0.9 4 0.9 6 0.9 7 0.9 7 0.9 8 Hydraulic Difference 107% 100% 95.8% 95.1% 97.2% 108%

[0104]

[0105] Looking at Table 2 above, it can be seen that the lower the CFR coefficient, that is, the smaller the number of inlets (20) or outlets (30) when assuming the same area, the higher the fluid flow uniformity.

[0106] On the other hand, it can be seen that the pressure difference between the first inlet (21) and the second inlet (22) increases when the CFR coefficient goes out of the range of 0.43 to 1.54.

[0107] This means that if the inlet (20) or outlet (30) is too dense, the area through which each fluid can flow becomes smaller, and a large pressure difference may occur.

[0108] In addition, if the density of the inlet (20) or outlet (30) decreases, it means that the area of ​​the second inlet (22) in contact with the effective membrane increases compared to the hydraulic pressure applied to the first inlet (21), so the pressure drops rapidly at an instant, which may mean that a large pressure difference is applied.

[0109] Although the reasons for hydraulic pressure difference in the two cases above are different, they are consistent in that unnecessary pump driving force must be consumed, so it is desirable to set the appropriate CFR coefficient to 0.43 to 1.54.

[0110]

[0111] Although the present invention has been described above with reference to the illustrated drawings, the present invention is not limited by the embodiments and drawings disclosed in this specification, and it is obvious that various modifications can be made by a person skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention were not explicitly described while describing the embodiments of the present invention above, it is natural to acknowledge that the effects predictable by said configuration should also be recognized.

Claims

1. An electrodialysis device comprising a unit pair formed by sequentially arranging a bipolar membrane (61), a gasket (11) with a spacer (40) inserted therein, an anion exchange membrane (62), a gasket (12) with a spacer (40) inserted therein, a cation exchange membrane (63), and a gasket (13) with a spacer (40) inserted therein, wherein a working fluid supplied to a plurality of inlets (20) formed in the gaskets (11, 12, 13) by an externally applied electrode is used to obtain a target fluid through a plurality of outlets (30) formed in the gaskets. The inlet (20) and outlet (30) of the gasket (10) into which the spacer (40) is inserted are formed as isosceles trapezoids that protrude outward and have reduced width, and the ratio of the width (CW) of the first inlet (21) of the inlet (20) to the width (CW) of the second inlet (22) is 0.8 to 0.95, characterized in that it is an electrodialysis gasket system.

2. In Claim 1, An electrodialysis gasket system characterized in that the length (MH) of the effective membrane exposed to the spacer (40) inserted into the gasket (10) is 1m to 2.5m.

3. In Claim 2, An electrodialysis gasket system characterized in that the width (MW) of the effective membrane exposed to the spacer (40) inserted into the gaskets (11, 12, 13) is 0.29 m to 2.5 m.

4. In Claim 3, An electrodialysis gasket system characterized in that the value (GFR) obtained by dividing the value obtained by multiplying the average value of the widths (CW) of the first inlet (21) and the second inlet (22) by the number (CN) of the inlet (20) or outlet (30) by the width (MW) of the effective membrane is 0.3 to 0.

5.

5. In Claim 4, An electrodialysis gasket system characterized in that the ratio (CFR) of the average width (CW) of the inlet (20) or outlet (30) installed in the gasket (11, 12, 13) and the number (CN) of the inlet (20) or outlet (30) is 0.43 to 1.

54.

6. In any one of claims 1 to 5, An electrodialysis gasket system characterized in that the velocity of the working fluid supplied to the inlet (20) of the gasket (11, 12, 13) is 5 cm / sec to 11 cm / sec.

7. In Claim 6, An electrodialysis gasket system characterized in that the above working fluid is at least one of water or a lithium aqueous solution.

8. In Claim 7, An electrodialysis gasket system characterized in that the above-mentioned target fluid is at least one of an aqueous lithium hydroxide solution or an acidic aqueous solution.

9. In Claim 8, An electrodialysis gasket system characterized in that the ratio of the width (CW) of the first outlet (31) of the above outlet (30) to the width (CW) of the second outlet (32) is 0.8 to 0.95.

Images