Electrical deionization apparatus

Abstract

To provide an electrical deionization apparatus capable of suppressing scale formation in a concentration chamber without using a bipolar membrane.SOLUTION: An electrical deionization apparatus includes a series of cation exchange membranes 3 and anion exchange membranes 4 arranged between an anode 1 and a cathode 2 to form concentration chambers 6, 8, 10, 12, desalination chambers 7, 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 the anion exchange membrane 4, while the buffer chamber 9 and the concentration chamber 10 are separated by the cation exchange membrane 3. An ion exchange resin is packed within the buffer chamber 9.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[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. [Background technology]

[0002] When tap water, such as river water or groundwater, is directly treated at a water purification plant to remove turbidity, dechlorinate, and soften it, or when the treated water has a high calcium concentration, it can cause scale formation in the concentration chamber and a deterioration in the electrical conductivity of the treated water due to an increased CO2 load. For these reasons, such water has not previously been passed directly through an electrodeionization device.

[0003] Among these problems, the increase in CO2 load can be resolved by using a relatively inexpensive decarbonation device as a pretreatment device for the electrodeionization device. To prevent scale formation 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 these problems, a reverse osmosis membrane device (RO membrane device) is sometimes installed before the electrodeionization device to reduce the concentration of hard components and CO2. If the concentration of hard components in the water to be treated is high, two RO membrane devices may be installed in series. However, this method incurs costs for installing the RO membrane devices and cleaning the membranes.

[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 these problems, it has been described that a bipolar membrane is placed in the concentration compartment of an electrodeionization device to prevent the association of calcium ions and carbonate ions, which become scale components, in the concentration compartment (Patent Documents 1 and 2).However, when using a bipolar membrane, there is a disadvantage that blisters are more likely to occur due to uneven current flow, which shortens the life of the device. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-198577 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-30004 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

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

[0010] [1] An electrodeionization device having a plurality of cation exchange membranes and anion exchange membranes alternately arranged between an anode and a cathode to form concentration compartments and deionization compartments alternately, The concentration compartment disposed between the deionization compartments is divided into an anode-side concentration compartment and a cathode-side concentration compartment by a buffer compartment; the buffer chamber and the anode-side concentrating chamber are separated by an anion exchange membrane, and the buffer chamber and the cathode-side concentrating chamber are separated by a cation exchange membrane; An electrodeionization apparatus characterized in that the buffer chamber is filled with an ion exchanger.

[0011] [2] The electrodeionization apparatus of [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. [Effects of the Invention]

[0015] In the electrodeionization apparatus of the present invention, the concentrating compartments arranged between the deionization compartments are 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 (CO3 2- This prevents the association of the RO membrane device, which was previously required as a pretreatment device for electrodeionization equipment, and reduces 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. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating the configuration of an electrodeionization apparatus according to an embodiment. [Figure 2] 4A to 4C are explanatory diagrams illustrating the operation of the electrodeionization apparatus according to the embodiment. [Figure 3]FIG. 10 is an explanatory diagram of another water flow path to the electrodeionization apparatus according to the embodiment. [Figure 4] FIG. 10 is an explanatory diagram of another water flow path to the electrodeionization apparatus according to the embodiment. [Figure 5] FIG. 10 is a diagram illustrating the configuration of an electrodeionization apparatus according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0019] Figure 1 shows the configuration of an electrodeionization apparatus according to an embodiment. A plurality of cation exchange membranes 3 and anion exchange 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 multiple layers 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, metals, or other electrical conductors.

[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 in the direction from the anode 1 to the cathode 2 within the concentrating chamber interposed between the deionization chambers 7 and 11, 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 chamber 7, 11. Raw water is passed through concentration chambers 6, 8, 10, 12 in the opposite direction to that of the deionization chambers 7, 11. Pure water (in this embodiment, a portion of the effluent water from the deionization chambers 7, 11) is passed through buffer chamber 9 in the same direction as that of the concentration chambers 6, 8, 10, 12. Raw water is passed through anode chamber 5 and cathode chamber 13. The direction of water flow through anode chamber 5 and cathode chamber 13 is arbitrary, but it is preferable to pass water in the same direction as that of the concentration chambers 6, 8, 10, 12.

[0024] The reason why pure water is passed 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 an example of this. 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 flowing through the concentration compartments 6, 8, 10, and 12.

[0027] 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, the calcium carbonate (CaCO3) that is a scale component is2+ As shown in Figure 2, HCO3 moves from the dilution compartment 7 to the concentration compartment 8, and from the dilution compartment 11 to the concentration compartment 12. - 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, the OH does not move further toward the cathode 2 side. - Only the calcium carbonate (CaCO3) scale is transferred to the water, and no calcium carbonate (CaCO3) scale is formed.

[0030] As mentioned above, HCO3 - 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, a buffer chamber 9 is placed in the concentration chamber between the deionization chamber 7 and the deionization chamber 11 to divide the concentration chamber into concentration chambers 8 and 10. Only one buffer chamber 9 is installed in the entire electrodeionization device. However, in an electrodeionization device having two or more concentration chambers between the deionization chambers, a buffer chamber is installed in each of the concentration chambers.

[0032] An example of an electrodeionization apparatus equipped with two buffer compartments is shown in Figure 5. In Figure 5, the following are arranged from the anode 1 to the 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] In the configuration of an electrodeionization apparatus with three buffer compartments, the combination of concentration compartment 18, buffer compartment 19, concentration compartment 20, and deionization compartment 21 is arranged between deionization compartment 21 and fourth concentration compartment 12 in Figure 5. 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. [Explanation of symbols]

[0035] 1 Anode 2 cathode 3. Cation exchange membrane 4 Anion exchange membrane 5 Anode chamber 6, 8, 10, 12, 18, 20 Concentration room 7, 11, 21 Desalination room 9, 19 Buffer room

Claims

1. An electrodeionization device having a plurality of cation exchange membranes and anion exchange membranes alternately arranged between an anode and a cathode to form concentration compartments and deionization compartments alternately, The concentration compartment disposed between the deionization compartments is divided into an anode-side concentration compartment and a cathode-side concentration compartment by a buffer compartment; the buffer chamber and the anode-side concentrating chamber are separated by an anion exchange membrane, and the buffer chamber and the cathode-side concentrating chamber are separated by a cation exchange membrane; An electrodeionization apparatus characterized in that the buffer chamber is filled with an ion exchanger.

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

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

4. 4. The electrodeionization apparatus according to claim 1, further comprising a water-passing means for passing a portion of the pure water that has passed through said deionization compartment into said buffer compartment.

5. 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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