Electrodeionization Equipment

Abstract

Provided is an electrodeionization device capable of suppressing scale generation in a concentration compartment without using a bipolar membrane. [Solution] An electrodeionization device in which a plurality of cation exchange membranes 3 and anion exchange membranes 4 are arranged between an anode 1 and a cathode 2 to form concentration chambers 6, 8, 10, 12, deionization chambers 7, 11, and a buffer chamber 9. The concentration chambers 6, 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, and the buffer chamber 9 and the concentration chamber 10 are separated by the cation exchange membrane 3, and the buffer chamber 9 is filled with an ion exchanger.

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, which has been treated at water purification plants, etc. to remove turbidity, dechlorination, and soften river water or groundwater, is directly used as the treated water for an electrodeionization device, or when the treated water has a high calcium concentration, scale formation occurs in the concentration chamber and the treated water's electrical conductivity deteriorates due to an increase in CO2 load. For these reasons, in the past, such water was not directly used as the treated water for an electrodeionization device.

[0003] Among these problems, the increase in the CO2 load can be solved by using a relatively inexpensive decarbonation device as a pretreatment device for the electrodeionization device. In addition, in order to prevent the formation of scale in the concentration chamber, a method is available in which a softening device or the like is installed in front of the electrodeionization device to completely remove the hardness components in the water to be treated, but when a softening device is used, it must be regenerated, 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 hardness components and CO2, and when the concentration of hardness components in the water to be treated is high, two RO membrane devices are sometimes installed in series. However, in this case, the installation cost of the RO membrane device and the cost of cleaning the membrane are incurable.

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

[0006] To solve these problems, it has been described that a bipolar membrane is placed in the concentration chamber of an electric deionization device to prevent calcium ions and carbonate ions, which become scale components, from associating with each other in the concentration chamber (Patent Documents 1 and 2). However, when a bipolar membrane is used, there is a disadvantage that blisters are easily formed due to unevenness in the ease of current flow, shortening the life of the device. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2001-198577 A [Patent Document 2] JP 2008-30004 A 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 arranged alternately between an anode and a cathode to form concentration compartments and deionization compartments alternately, A concentration chamber disposed between the deionization chambers is divided into an anode-side concentration chamber and a cathode-side concentration chamber by a buffer chamber; 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; 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 part of the pure water that has passed through the deionization compartment into the buffer compartment.

[0014] [5] An 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. Effect of the Invention

[0015] In the electrodeionization apparatus of the present invention, the concentrating chamber disposed between the deionization chambers is divided into an anode-side concentrating chamber and a cathode-side concentrating chamber by the buffer chamber. 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 the electrodeionization device, and reduces the equipment and treatment costs.

[0016] The electrodeionization device of the present invention has the advantage that it does not use a bipolar membrane, and therefore there is less distribution in the ease with which current flows, making blisters less likely to occur, and therefore the device has a long life. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a configuration diagram of an electrodeionization apparatus according to an embodiment. [Diagram 2] 5 is an explanatory diagram of the operation of the electrodeionization device according to the embodiment. FIG. [Diagram 3]FIG. 13 is an explanatory diagram of another water passage system to the electrodeionization apparatus according to the embodiment. [Figure 4] FIG. 13 is an explanatory diagram of another water passage system to the electrodeionization apparatus according to the embodiment. [Diagram 5] FIG. 11 is a diagram showing the configuration of an electrodeionization apparatus according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0019] Fig. 1 shows the configuration of an electrodeionization device 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 to form, in this 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 made of ion exchange resins, ion exchange fibers, graft exchangers, etc. are packed in a mixture or in a multi-layered form in the deionization compartments 7, 11 and the buffer compartment 9. Preferably, anion exchange resins and cation exchange resins are mixed and packed in the deionization compartments 7, 11 and the buffer compartment 9. In addition, the concentration compartments 6, 8, 10, 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 a concentrating chamber interposed between deionization chambers 7 and 11, and the concentrating chamber is divided 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 disposed on the second concentration chamber 8 side of the buffer chamber 9, and a cation exchange membrane 3 is disposed 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 the 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 outflow water from the deionization chambers 7, 11) is passed through the buffer chamber 9 in the same direction as that of the concentration chambers 6, 8, 10, 12. Raw water is passed through the anode chamber 5 and the cathode chamber 13. The direction of water flow through the anode chamber 5 and the cathode chamber 13 is arbitrary, but it is preferable to pass the 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 the formation of scale 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 chambers 7 and 11 may be passed as pure water not only to the buffer chamber 9 but also to the concentration chambers 6, 8, 10, and 12, the anode chamber 5, and the cathode chamber 13. Figure 3 shows one example. In Figure 3, the water to be treated (raw water) is passed through each of the deionization chambers 7 and 11. A portion of the pure water flowing out from the deionization chambers 7 and 11 is passed in a countercurrent manner through the concentration chambers 6, 8, 10, and 12. A portion of the water flowing out from the deionization chambers 7 and 11 is also passed through the anode chamber 5 and the cathode chamber 13 in the same direction as the water flowing through the concentration chambers 6, 8, 10, and 12.

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

[0028] In the electrodeionization device configured in this way, the Ca2+ As shown in FIG. 2, HCO3 moves from the dilution chamber 7 to the concentration chamber 8, and from the dilution chamber 11 to the concentration chamber 12. - moves from dilution compartment 7 to concentration compartment 6, and from dilution compartment 11 to concentration compartment 10.

[0029] Ca transferred to concentration chamber 8 2+ Since the anion exchange membrane 4 is present between the concentration chamber 8 and the buffer chamber 9, the OH does not move any further toward the cathode 2. - Only the calcium carbonate (CaCO3) scale is generated.

[0030] As mentioned above, HCO3 - However, because the cation exchange membrane 3 is present between the concentration chamber 10 and the buffer chamber 9, it does not move any 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 disposed 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, and only one buffer chamber 9 is provided in the entire electrodeionization apparatus. However, in an electrodeionization apparatus having two or more concentration chambers between the deionization chambers, a buffer chamber is provided 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, from the anode 1 to the cathode 2, an anode compartment 5, a first concentrating compartment 6, a first deionizing compartment 7, a second concentrating compartment 8, a buffer compartment 9, a third concentrating compartment 10, a second deionizing compartment 11, a concentrating compartment 18, a buffer compartment 19, a concentrating compartment 20, a deionizing compartment 21, a fourth concentrating compartment 12, and a cathode compartment 13 are arranged.

[0033] In the configuration of an electrodeionization apparatus having three buffer chambers, in FIG. 5, a combination of concentrating chamber 18, buffer chamber 19, concentrating chamber 20, and deionization chamber 21 is arranged between deionization chamber 21 and fourth concentrating chamber 12. In the case of four or more chambers, the number of such combinations is increased.

[0034] The above-described embodiment is merely an example of the present invention, and the present invention may have configurations other than those described above. [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 apparatus having a plurality of cation exchange membranes and anion exchange membranes arranged alternately between an anode and a cathode to form concentration compartments and deionization compartments alternately, A concentration chamber disposed between the deionization chambers is divided into an anode-side concentration chamber and a cathode-side concentration chamber by a buffer chamber; 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; The buffer chamber is filled with an ion exchanger, The electrodeionization apparatus further comprises a water passing means for passing a part of the pure water that has passed through the deionization compartment into the buffer compartment.

2. 2. The electrodeionization apparatus of claim 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.

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 circulation means for circulating the buffer chamber wastewater having passed through said buffer chamber to said concentration chamber, said anode chamber and said cathode chamber.

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