Electrodeionizer

Abstract

In this electrodeionizer, a plurality of cation exchange membranes 3 and a plurality of anion exchange membranes 4 are arranged between an anode 1 and a cathode 2 to form concentration chambers 6, 8, 10, and 12, desalination chambers 7 and 11, and a buffer chamber 9. The concentration chambers 6 and 8 are separated by the buffer chamber 9. The buffer chamber 9 and the concentration chamber 8 are separated by an anion exchange membrane 4, the buffer chamber 9 and the concentration chamber 10 are separated by a cation exchange membrane 3, and the buffer chamber 9 is filled with an ion exchanger.

Description

Electrodeionization Equipment

[0001] The present invention relates to an electrodeionization apparatus, and more particularly to an electrodeionization apparatus capable of preventing scale problems in a concentration compartment and a deionization compartment.

[0002] When tap water that has been treated with clarification, dechlorination, and softening treatment at a water purification plant, such as river water or groundwater, is directly used as treated water for an electrodeionization device, or when the treated water has a high calcium concentration, scale formation in the concentration chamber and CO ２ Conventionally, such water has not been passed directly through an electrodeionization apparatus as treatment water, because the increased load would cause a deterioration in the conductivity of the treated water.

[0003] Among these problems, CO ２ The increased load can be solved by using a relatively inexpensive decarbonation device as a pretreatment device for the electrodeionization device. To prevent scale buildup in the concentration compartment, a softening device or other device can be installed upstream of the electrodeionization device to completely remove hardness components from the water being treated. However, using a softening device requires regeneration, which eliminates the advantage of using an electrodeionization device that does not require regeneration.

[0004] To solve this problem, a reverse osmosis membrane device (RO membrane device) is installed before the electrodeionization device to remove hardness components and CO ２ In some cases, the concentration of hardness components in the water to be treated is reduced, and when the concentration of hardness components in the water to be treated is high, two RO membrane devices may be installed in series. However, in this case, the installation costs of the RO membrane devices and the costs of cleaning the membranes are incurable.

[0005] An electrodeionization device has a structure in which a deionization compartment and a concentration compartment are installed between an anode and a cathode. In an electrodeionization device, cations and anions in the water being treated move from the deionization compartment to the concentration compartment and are removed. The removed cations and anions combine in the concentration compartment, causing scale to form. This scale formation causes an increase in operating voltage and differential pressure, making the device unstable.

[0006] To solve this problem, it is known to place a bipolar membrane in the concentrating compartment of an electrodeionization device to prevent the association of calcium ions and carbonate ions, which become scale components, in the concentrating compartment (Patent Documents 1 and 2).However, when a bipolar membrane is used, uneven current flow occurs, which makes blisters more likely to occur and shortens the life of the device.

[0007] JP 2001-198577 A JP 2008-30004 A

[0008] An object of the present invention is to provide an electrodeionization device that can suppress the generation of scale in the concentration compartments without using a bipolar membrane.

[0009] The electrodeionization apparatus of the present invention has the following configuration.

[0010] [1] An electrodeionization device comprising a plurality of cation exchange membranes and anion exchange membranes alternately arranged between an anode and a cathode to form alternating concentration compartments and deionization compartments, wherein the concentration compartments arranged between the deionization compartments are divided by a buffer compartment into an anode-side concentration compartment and a cathode-side concentration compartment, the buffer compartment and the anode-side concentration compartment are separated by an anion exchange membrane, and the buffer compartment and the cathode-side concentration compartment are separated by a cation exchange membrane, and the buffer compartment is filled with an ion exchanger.

[0011] [2] The electrodeionization device according to [1], wherein an anode chamber, a first concentrating chamber, a first deionization chamber, a second concentrating chamber, a buffer chamber, a third concentrating chamber, a second deionization chamber, a fourth concentrating chamber, and a cathode chamber are arranged in this order from the anode to the cathode.

[0012] [3] The electrodeionization apparatus according to [1], wherein the buffer chamber is filled with a mixture of anion exchange resin and cation exchange resin.

[0013] [4] The electrodeionization apparatus according to any one of [1] to [3], further comprising a water-passing means for passing a portion of the pure water that has passed through the deionization compartment into the buffer compartment.

[0014] [5] The electrodeionization apparatus according to [4], further comprising a circulation means for circulating the buffer chamber wastewater that has passed through the buffer chamber to the concentration chamber, the anode chamber, and the cathode chamber.

[0015] In the electrodeionization apparatus of the present invention, the concentrating compartment disposed between the deionization compartments is divided into an anode-side concentrating compartment and a cathode-side concentrating compartment by a buffer compartment. This allows calcium ions (Ca ２＋ ) and carbonate ions (CO ３ ２－ This prevents the association of the RO membrane device, which was previously required as a pretreatment device for the electrodeionization device, and reduces the equipment and treatment costs.

[0016] The electrodeionization device of the present invention does not use a bipolar membrane, and therefore has the advantage of being less prone to blisters due to less distribution of current flow, resulting in a longer device life.

[0017] Fig. 1 is a configuration diagram of an electrodeionization apparatus according to an embodiment; Fig. 2 is an explanatory diagram of the operation of an electrodeionization apparatus according to an embodiment; Fig. 3 is an explanatory diagram of another water flow path to an electrodeionization apparatus according to an embodiment; Fig. 4 is an explanatory diagram of another water flow path to an electrodeionization apparatus according to an embodiment; Fig. 5 is a configuration diagram of an electrodeionization apparatus according to another embodiment.

[0018] Hereinafter, an embodiment will be described with reference to the drawings.

[0019] 1 shows the configuration of an electrodeionization apparatus according to an embodiment of the present invention. A plurality of cation exchange membranes (C membranes) 3 and anion exchange membranes (A membranes) 4 are alternately arranged between an anode 1 and a cathode 2, forming, in order from the anode 1 side to the cathode 2 side, an anode chamber 5, a first concentrating chamber 6, a first deionizing chamber 7, a second concentrating chamber 8, a buffer chamber 9, a third concentrating chamber 10, a second deionizing chamber 11, a fourth concentrating chamber 12, and a cathode chamber 13.

[0020] Anion exchangers and cation exchangers, such as ion exchange resins, ion exchange fibers, or graft exchangers, are packed in a mixture or in a multi-layered form in the deionization compartments 7, 11 and buffer compartment 9. Preferably, a mixture of anion exchange resins and cation exchange resins is packed in the deionization compartments 7, 11 and buffer compartment 9. In addition, the concentration compartments 6, 8, 10, and 12, the anode compartment 5, and the cathode compartment 13 are also packed with ion exchangers, activated carbon, or electrical conductors such as metals.

[0021] In conventional electrodeionization apparatuses, the buffer chamber 9 is not provided, and the second concentrating chamber 8 and the third concentrating chamber 10 are provided as a single concentrating chamber. In contrast, in the electrodeionization apparatus of this embodiment, the buffer chamber 9 is provided midway between the deionization chambers 7 and 11 in the direction from the anode 1 to the cathode 2, dividing the concentrating chamber into the second concentrating chamber 8 on the anode 1 side and the third concentrating chamber 10 on the cathode 2 side.

[0022] To form the buffer chamber 9, an anion exchange membrane 4 is placed on the second concentration chamber 8 side of the buffer chamber 9, and a cation exchange membrane 3 is placed on the third concentration chamber 10 side of the buffer chamber 9, with an ion exchanger filled between them.

[0023] In this embodiment, as shown in Figure 2, water to be treated (raw water) is passed through each deionization compartment 7, 11. Raw water is passed through concentration compartments 6, 8, 10, 12 in the opposite direction to that of the deionization compartments 7, 11. Pure water (in this embodiment, a portion of the effluent water from the deionization compartments 7, 11) is passed through buffer compartment 9 in the same direction as that of the concentration compartments 6, 8, 10, 12. Raw water is passed through anode compartment 5 and cathode compartment 13. The direction of water flow through anode compartment 5 and cathode compartment 13 is arbitrary, but it is preferable to pass water in the same direction as that of the concentration compartments 6, 8, 10, 12.

[0024] The reason for passing pure water through the buffer chamber 9 is to prevent scale formation if the passing water contains scale components.

[0025] The water flow direction may be a parallel flow type instead of the counter flow type.

[0026] Furthermore, a portion of the pure water flowing out from the deionization compartments 7 and 11 may be passed as pure water not only through the buffer compartment 9 but also through the concentration compartments 6, 8, 10, and 12, the anode compartment 5, and the cathode compartment 13. Figure 3 shows one example. In Figure 3, the water to be treated (raw water) is passed through each of the deionization compartments 7 and 11. A portion of the pure water flowing out from the deionization compartments 7 and 11 is passed through the concentration compartments 6, 8, 10, and 12 in a counterflow manner. A portion of the water flowing out from the deionization compartments 7 and 11 is also passed through the anode compartment 5 and the cathode compartment 13 in the same direction as the water flow through the concentration compartments 6, 8, 10, and 12.

[0027] As shown in FIG. 4, a portion of the outflow water from the deionization compartments 7 and 11 may be passed only to the buffer compartment 9, and the outflow water from the buffer compartment 9 may be passed to the concentration compartments 6, 8, 10, and 12, the anode compartment 5, and the cathode compartment 13.

[0028] In the electrodeionization device configured as described above, calcium carbonate (CaCO ３ ) Ca ２＋ As shown in FIG. 2, HCO moves from the dilution compartment 7 to the concentration compartment 8, and from the dilution compartment 11 to the concentration compartment 12. ３ － moves from dilution compartment 7 to concentration compartment 6, and from dilution compartment 11 to concentration compartment 10.

[0029] Ca moved to concentration chamber 8 ２＋ Since the anion exchange membrane 4 is present between the concentration compartment 8 and the buffer compartment 9, OH does not move further toward the cathode 2 side. － Only calcium carbonate (CaCO ３ ) No scale is produced.

[0030] As described above, HCO 2 is supplied to the concentration compartment 10 from the deionization compartment 11. ３ － However, since the cation exchange membrane 3 exists between the concentration compartment 10 and the buffer compartment 9, it does not move further toward the anode 1. H ＋ Only the calcium carbonate is transferred to the water, and no calcium carbonate scale is formed.

[0031] In the above embodiment, buffer chamber 9 is disposed in the concentrating compartment located between dilution compartment 7 and dilution compartment 11 to divide the concentrating compartment into concentrating compartments 8 and 10. Only one buffer chamber 9 is provided in the entire electrodeionization apparatus, and only one combination of "demineralizing compartment / concentrating compartment / buffer chamber / concentrating compartment / demineralizing compartment" is provided. However, in the present invention, two or more of these combinations may be provided.

[0032] An example of an electrodeionization apparatus having two buffer compartments, which is achieved by providing two of the above combinations, is shown in Figure 5. In Figure 5, the following are arranged, from anode 1 to cathode 2: anode compartment 5, first concentrating compartment 6, first deionizing compartment 7, second concentrating compartment 8, buffer compartment 9, third concentrating compartment 10, second deionizing compartment 11, concentrating compartment 18, buffer compartment 19, concentrating compartment 20, deionizing compartment 21, fourth concentrating compartment 12, and cathode compartment 13.

[0033] An electrodeionization apparatus having three buffer compartments is configured as shown in Figure 5, with a combination of concentrating compartment 18, buffer compartment 19, concentrating compartment 20, and deionizing compartment 21 arranged between deionizing compartment 21 and fourth concentrating compartment 12. In the case of four or more compartments, the number of such combinations arranged is increased.

[0034] The above-described embodiment is an example of the present invention, and the present invention may have other configurations.

[0035] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the present invention. This application is based on Japanese Patent Application No. 2024-032304, filed on March 4, 2024, and is incorporated by reference in its entirety.

[0036] 1 anode 2 cathode 3 cation exchange membrane 4 anion exchange membrane 5 anode chamber 6, 8, 10, 12, 18, 20 concentration chamber 7, 11, 21 deionization chamber 9, 19 buffer chamber

Claims

1. An electrodeionization device comprising a plurality of cation exchange membranes and anion exchange membranes arranged alternately between an anode and a cathode to form alternating concentration compartments and deionization compartments, wherein the concentration compartments arranged between the deionization compartments are divided by a buffer compartment into an anode-side concentration compartment and a cathode-side concentration compartment, the buffer compartment and the anode-side concentration compartment are separated by an anion exchange membrane, and the buffer compartment and the cathode-side concentration compartment are separated by a cation exchange membrane, and the buffer compartment is filled with an ion exchanger.

2. The electrodeionization apparatus of claim 1, wherein the anode chamber, the first concentrating chamber, the first deionizing chamber, the second concentrating chamber, the buffer chamber, the third concentrating chamber, the second deionizing chamber, the fourth concentrating chamber, and the cathode chamber are arranged in this order from the anode to the cathode.

3. The electrodeionization apparatus of claim 1, wherein the buffer chamber is filled with a mixture of anion exchange resin and cation exchange resin.

4. An electrodeionization apparatus according to any one of claims 1 to 3, further comprising a water passing means for passing a portion of the pure water that has passed through the deionization compartment into the buffer compartment.

5. An electrodeionization apparatus according to claim 4, further comprising a circulation means for circulating the wastewater from the buffer chamber, which has passed through the buffer chamber, to the concentration chamber, the anode chamber and the cathode chamber.

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