Spacer system for electrodialysis

Abstract

The present invention provides a method in which, by changing the shape of a spacer used in an electrodialysis device, flow uniformity in a feed solution and a product stream which flow on the spacer is improved, thus increasing the production of the product stream, and minimizing the amount of electrical energy required for electrodialysis.

Description

Electrodialysis spacer system

[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 spacer inserted into 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 improving flow uniformity in an electrodialysis system by changing the shape of a spacer through which the working fluid and the target fluid flow.

[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 spacer (40) is formed of a plurality of meshes (M) having square pores inclined at a predetermined angle with respect to the inlets (20) and outlets (30), and the ratio of the row spacing (FG) of the mesh (M) to the thickness (FT) of the spacer (40) is 2.59 to 3.64.

[0018] In one embodiment of the present invention, the predetermined angle may be characterized as being 45 degrees.

[0019] In one embodiment of the present invention, the speed of the working fluid supplied to the inlet (20) of the gasket (10) may be characterized as being 7 cm / sec to 11 cm / sec.

[0020] In one embodiment of the present invention, the thickness (FT) of the spacer (40) may be characterized as being 0.76 mm to 0.33 mm.

[0021] In one embodiment of the present invention, the mesh (M) row spacing (FG) of the spacer (40) may be characterized as being 2.2 mm to 1.2 mm.

[0022] In one embodiment of the present invention, the porosity (FP) of the spacer (40) may be characterized as being 0.73 to 0.79.

[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 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.

[0026] In one embodiment of the present invention, the width (MW) of the effective film exposed to the spacer (40) inserted into the gasket (10) may be characterized as being 0.29 m to 2.5 m.

[0027]

[0028] According to various embodiments of the present invention, the production volume of the target fluid can be increased by changing the shape of the spacer used in the electrodialysis system to improve the flow uniformity of the working fluid and the target fluid flowing over the spacer.

[0029] According to various embodiments of the present invention, the electrical energy efficiency required for electrodialysis can be improved by changing the shape of a spacer used in an electrodialysis system to improve the flow uniformity of the working fluid and the target fluid flowing over the spacer.

[0030] According to various embodiments of the present invention, by setting limits on design changes for spacers of an electrodialysis system, guidelines can be provided to users to quickly design an electrodialysis system process suitable for the usage environment and purpose.

[0031]

[0032] Figure 1 is a conceptual diagram of the unit configuration of the electrodialysis device of the present invention.

[0033] Figure 2 is a conceptual diagram illustrating the occurrence of concentration density due to fluid stagnation on the surface of an ion exchange membrane.

[0034] FIG. 3 is a schematic diagram illustrating the mesh structure of the gasket of the present invention and the spacer inserted therein.

[0035] FIG. 4 is a schematic diagram illustrating the row spacing and thickness of the spacer of the present invention.

[0036]

[0037] 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.

[0038] 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.

[0039] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044]

[0045] Hereinafter, a gasket system used for electrodialysis according to various embodiments will be described with reference to the attached drawings.

[0046]

[0047] [Basic Structure]

[0048] 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.

[0049] 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.

[0050] FIG. 2 illustrates a stagnation phenomenon in which ions are concentrated on the surface due to non-uniform fluid flow in the ion exchange membrane.

[0051] If the above ions become stagnant in the ion exchange membrane, the quality of the target fluid may deteriorate, and since greater electrical energy must be applied to obtain the desired target fluid, it may act as a factor in increasing production costs.

[0052] In addition, the lifespan of the ion exchange membrane may also be shortened due to excessive electrical energy being applied to the anode plate (51) and cathode plate (52).

[0053] The ion stagnation phenomenon occurring on the surface of the ion exchange membrane may occur because the solvent flowing on the spacer (40) adheres to the surface of the ion exchange membrane and undergoes laminar flow.

[0054] If the above solvent flows laminarly on the surface of the ion exchange membrane, the fluid flow becomes stagnant and the frictional force with the surface decreases, increasing the likelihood that the solvent will flow locally through the entire spacer (40), which can reduce the electrodialysis efficiency.

[0055] In addition, since the velocity of the aforementioned solvent decreases at the surface of the ion exchange membrane, the scale of production of the working fluid into the target fluid is also inevitably reduced.

[0056] The ion stagnation phenomenon caused by the laminar flow of such a solvent can be resolved by adjusting the flow rate of the solvent supplied to the inlet (20) along with the shape of the spacer (40).

[0057] In addition, the above ion stagnation phenomenon may also occur when the solvent flowing through the spacer (40) accumulates on one side.

[0058] This phenomenon of solvent accumulation on one side can have an adverse effect on the production volume and quality of the target fluid because only a portion of the ion exchange membrane facing the spacer (40) is used.

[0059] Therefore, it is necessary to change the shape of the spacer (40) to create a uniform distribution of the flowing solvent across the entire effective film.

[0060] The present invention proposes a method to change the shape of the spacer (40) so that the ratio of the average ion concentration (Cb) of the solvent flowing on the spacer (40) to the ion concentration (Cm) on the surface of the ion exchange membrane is close to 1.

[0061] FIG. 3 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.

[0062] 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.

[0063] 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.

[0064] 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).

[0065] 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.

[0066] 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.

[0067] It is obvious that the aforementioned target fluid, like the working fluid, can also be changed depending on the process method or purpose.

[0068] The above spacer (40) can form a plurality of meshes (M) by connecting or fixing a plurality of lines horizontally or vertically.

[0069] The line forming the spacer (40) can be made of various synthetic resin materials such as PE (polyethylene), PP (polypropylene), PF (phenol-formaldehyde resin), PPE (phenylene ether), and PC (polycarbonate).

[0070] In the present invention, the mesh (M) can be formed into a square.

[0071] For example, the mesh (M) may be formed at a predetermined angle of inclination opposite to the inlet (20) and outlet (30).

[0072] The above predetermined angle may be 45 degrees.

[0073] The 45-degree inclination angle between the mesh (M) and the inlet (20) and outlet (30) is a result obtained through repeated experiments, but the details are not explained in the present invention.

[0074] If the inclination angle of the above mesh (M) is different from 45 degrees, the trend described in the following examples is the same, but the overall electrical energy efficiency may be reduced.

[0075] In the present invention, the inlet (20) and outlet (30) for supplying and discharging solvent to the spacer (40) may be installed in multiple (CN) portions at one end and the other end of the gasket (10) based on the flow direction, and preferably, the number of the inlet (20) and outlet (30) may be the same.

[0076] 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.

[0077] FIG. 4 shows a perspective view of the above spacer (40).

[0078] The above spacer (40) is formed in a three-dimensional shape having a certain thickness (FT), and since the mesh (M) is formed in a square shape as described above, the mesh (M) can be expressed as a line spacing (FG).

[0079] In the prior art, details regarding the material of the strings constituting the mesh (M) of the spacer (40) are disclosed, but the size of the mesh (M) and the relationship between the size of the spacer (40) and the mesh (M) are not described. Furthermore, there was no awareness of the problem of improving the electrical energy usage efficiency of the electrodialysis system by utilizing the relationship between the thickness of the spacer (40), the flow rate of the solvent, and the shape of the mesh (M).

[0080]

[0081] [Example]

[0082] In this embodiment, the shape of the spacer (40) is changed, and the optimal shape range of the spacer (40) is determined from the change in the efficiency (CE) of the electrical energy applied to the electrodialysis system.

[0083] Ultimately, it is important to find a range in which the spacer (40) causes the solvent flow to become turbulent so that the supply rate of the solvent supplied to the inlet (20) does not change until it is discharged to the outlet (30), and the solvent can flow at a constant rate across the entire effective membrane of the spacer (40).

[0084] Accordingly, the most important design change factors of the spacer (40) may be the thickness (FT), effective film area, mesh (M) line spacing (FG), etc. of the spacer (40).

[0085] Generally, the thinner the thickness (FT) of the spacer (40), the larger the effective film area, and the smaller the area occupied by the mesh (M) in the spacer (40), the higher the electrical energy efficiency tends to be.

[0086] However, if the thickness (FT) of the spacer (40) is reduced to a level below a certain level, the fixing force that maintains the shape of the spacer (40) is reduced, and a phenomenon may occur in which a part of the effective film is deformed depending on the speed or flow amount of the flowing fluid.

[0087] Such local deformation is caused by the spacer (40) losing its ability to maintain its shape, and when this phenomenon occurs, the solvent, i.e., the working fluid or the target fluid, may accumulate on one side of the spacer (40), resulting in a decrease in flow uniformity.

[0088] In addition, making the thickness (FT) of the spacer (40) thinner than a certain level may result in a deterioration of maintainability.

[0089] This means that in order to make the thickness (FT) of the above spacer (40) thin, the thickness of the line forming the mesh (M) must also be reduced.

[0090] Since the above working fluid or target fluid may be an acidic or alkaline solvent, if a thin wire is used, the problem may arise that the spacer (40) is easily damaged by continuous corrosion.

[0091] In addition, when the effective membrane area of ​​the spacer (40) is increased, the pump device must also gradually increase in size to supply the solvent to the inlet (20) of the spacer (40) at a constant hydraulic pressure and flow rate, so it may not be possible to expand the area beyond a certain limit.

[0092] In addition, if the effective film area is increased, the strength required for the spacer (40) to maintain its shape is inversely proportional, and as described above, the possibility of a phenomenon in which a part of the effective film is deformed increases.

[0093] In this embodiment, considering the problems described above, 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 varying between 1 m to 2.5 m and 0.29 m to 2.5 m, respectively.

[0094] The performance index used in this embodiment is as follows.

[0095] First, the porosity of the above mesh (M) can be defined by the following mathematical formula 1.

[0096]

[0097] [Mathematical Formula 1]

[0098]

[0099]

[0100] The porosity (FP) of the spacer (40) above refers to the ratio of the remaining area excluding the area occupied by the rows of the mesh (M) relative to the effective membrane area, that is, the ratio of the space where ions contained in the solvent can come into contact with the ion exchange membrane and perform ion exchange.

[0101] In addition, the electrical energy efficiency (CE) applied to the electrodialysis system can be defined by the following mathematical formula 2.

[0102] The above electrical energy efficiency (CE) refers to the amount of lithium ions produced relative to the input electrical energy.

[0103]

[0104] [Mathematical Formula 2]

[0105]

[0106]

[0107] Here, Li(mol) is the lithium production amount, FC(A / m²) 2 ) is the current density, A(m 2 ) represents the effective film area of ​​the spacer (40), and T represents the time during which electrical energy is applied.

[0108] In addition, the flow uniformity of fluids flowing through the effective membrane of the spacer (40) in the present invention can be defined by the following mathematical formula 3.

[0109]

[0110] [Mathematical Formula 3]

[0111]

[0112]

[0113] 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 effective film area, w i is the fluid velocity in each cell, and W is the average fluid velocity in the effective membrane.

[0114] That is, the closer the flow uniformity (λ) is to 1, the more the fluid flows at a uniform speed, and the higher the ion exchange performance can be set.

[0115] A high porosity (FP) may mean that the spacer (40) does not have the strength to maintain its shape as described above.

[0116] Therefore, if the porosity is below a certain range, the flow uniformity (λ) is lowered, and the electrical energy efficiency (CE) is lowered; thus, in this embodiment, the porosity (FP) of the spacer (40) is fixed to about 0.7 to 0.8.

[0117] For the reasons mentioned above, in this embodiment, the thickness of the spacer (40) was gradually changed from 0.73 mm to 0.23 mm to determine the optimal value.

[0118] In addition, for the reasons mentioned above, in this embodiment, the experiment was conducted by changing the line spacing (FG) of the square mesh (M) to 0.8 mm to 2.8 mm.

[0119] Of course, at this time, the thickness (FT) of the spacer (40) could be adjusted along with the above-mentioned row spacing (FG) to match the above-mentioned porosity (FP).

[0120] 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 varying between 1 m to 2.5 m and 0.29 m to 2.5 m, respectively.

[0121] As a result of the experiment, when the working fluid velocity exceeds the effective surface range of the spacer (40), the flow uniformity was found to decrease rapidly under any experimental condition.

[0122] 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 membrane within the above-set operating fluid supply speed range, resulting in an excessive or insufficient amount.

[0123] The above experimental results can be summarized as shown in Table 1.

[0124]

[0125] FT(mm) FG(mm) FR FPCE Example 10.76 2.8 3.68 0.79 100.0% Example 20.76 2.2 2.89 0.73 101.3% Example 30.56 1.45 2.59 0.72 102.5% Example 40.56 1.6 2.86 0.73 106.3% Example 50.56 23.57 0.78 105.3% Example 60.43 1.6 3.72 0.79 105.9% Example 70.33 1.2 3.64 0.78 7101.8% Example 80.23 0.8 3.48 0.77 96.2%

[0126]

[0127]

[0128] Looking at the results above, it can be seen that while the porosity (FP) is maintained at a constant, the electrical energy efficiency (CE) tends to improve as the thickness (FT) of the spacer (40) decreases, but if it becomes thinner from 0.33 mm, the electrical energy efficiency (CE) actually decreases.

[0129] Under the above operating conditions, if the thickness of the spacer (FT) is 0.76 mm or more, ion exchange is limited as described above, so the electrical energy efficiency (CE) is reduced, and since this is obvious, it is not listed in Table 1 above.

[0130] In Table 1 above, the electrical energy efficiency (CE) is evaluated relatively based on Example 1.

[0131] The above phenomenon may be determined to occur as the strength of the spacer (40) is weakened as described above, causing the flow of the solvent to become unstable.

[0132] Therefore, under the pre-set porosity (FP) condition, it may be reasonable to set the thickness (FT) of the spacer (40) to 0.33 mm to 0.76 mm in commercial situations.

[0133] If the electrical energy efficiency (CE) is to be improved more actively, it may be desirable to set the thickness (FT) of the spacer (40) to 0.43 mm to 0.56 mm.

[0134] It can be seen that the electrical energy efficiency (CE) can be improved by setting the row spacing (FG) of the mesh (M) to within 1.2 mm to 2.2 mm along with the thickness (FT) and conditions of the spacer (40).

[0135] In addition, it can be seen that the ratio (FR) of the line spacing (FG) of the mesh (M) and the thickness (FT) of the spacer (40) must be set within the range of 2.59 to 3.72 to improve the electrical energy efficiency (CE).

[0136] The present invention provides a method to improve the efficiency of electrical energy applied to an electrodialysis system by changing the shape of a spacer (40) used in a general electrodialysis system.

[0137] The present invention provides an appropriate ratio range for the thickness (FT) of a spacer (40) that fits the housing of the electrodialysis system and the row spacing (FG) of the mesh (M) when expanding or redesigning the electrodialysis system.

[0138]

[0139] 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 above spacer (40) is formed of a plurality of meshes (M) having square gaps inclined at a predetermined angle with respect to the inlet (20) and outlet (30), and An electrodialysis spacer system characterized in that the ratio (FR) of the row spacing (FG) of the mesh (M) and the thickness (FT) of the spacer (40) is 2.59 to 3.

72.

2. In Claim 1, An electrodialysis spacer system characterized in that the above-mentioned predetermined angle is 45 degrees 3. In Claim 2, An electrodialysis gasket system characterized in that the velocity of the working fluid supplied to the inlet (20) of the gasket (10) is 7 cm / sec to 11 cm / sec.

4. In Claim 3, An electrodialysis spacer system characterized in that the thickness (FT) of the spacer (40) is 0.33 mm to 0.76 mm.

5. In Claim 4, An electrodialysis spacer system characterized in that the mesh (M) row spacing (FG) of the spacer (40) is 1.2 mm to 2.2 mm.

6. In Claim 1, An electrodialysis spacer system characterized in that the porosity (FP) of the spacer (40) is 0.73 to 0.

79.

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

10. In Claim 9, An electrodialysis gasket system characterized in that the width (MW) of the effective membrane exposed to the spacer (40) inserted into the gasket (10) is 0.29 m to 2.5 m.

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