Electrical deionization device and method of operating the same

Abstract

To provide an electrical deionization device capable of individually controlling a current density on a water supply inflow side and a deionized water outflow side, and a method for operating this electrical deionization device.SOLUTION: The water to be treated is introduced from the inlet side of the deionization chamber 6, and deionized water is extracted from the outlet side of the deionization chamber 6. A part of this deionized water is passed through the concentration chamber 5 in a counter-current flow direction opposite to the flow direction of the deionization chamber 6, and the effluent from the concentration chamber 5 is discharged to the outside of the system. Anodes 11 to 13 and cathodes 21 to 23 are each divided into three sections in the direction of the treated water flow.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrodeionization apparatus for removing ionic components from water to be treated, and a method for operating the electrodeionization apparatus. [Background technology]

[0002] A typical electrodeionization device has multiple cation exchange membranes and anion exchange membranes alternately arranged between a cathode and an anode to form alternating concentration compartments and deionization compartments, and the deionization compartments are filled with ion exchange resin. Furthermore, some devices also have concentration compartments filled with ion exchange resin.

[0003] When the water supply load temporarily exceeds the treatment capacity of an electrodeionization device, the device's performance deteriorates. When performance deteriorates, electrical resistance increases, making it difficult for current to flow.

[0004] Therefore, the electrical conductivity or resistivity of the water to be treated (feedwater) flowing into the electrodeionization device may be measured, and if the electrical conductivity or resistivity exceeds a set value, the current value may be increased.Also, the electrical conductivity or resistivity, or the boron concentration or silica concentration of the deionized water from the electrodeionization device may be measured, and if the measured value exceeds a predetermined value, the current value may be increased. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-176968 [Patent Document 2] Japanese Patent Application Publication No. 2019-177327 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional electrodeionization devices, the anode and cathode are integrated as a whole (for example, in the form of a single plate), and it is not possible to individually control the applied voltage or current density on the feedwater inlet side and the deionized water outlet side of the electrodeionization device.

[0007] Therefore, the current density increases in areas with lower electrical resistance within the electrodeionization device, which can cause unevenness in the current density and reduce the overall efficiency of the electrodeionization process.

[0008] An object of the present invention is to provide an electrodeionization apparatus capable of separately controlling the current density on the inlet side of the feed water and the outlet side of the deionized water, and a method for operating the electrodeionization apparatus. [Means for solving the problem]

[0009] The gist of the present invention is as follows.

[0010] [1] A concentration compartment and a deionization compartment are separated by an ion exchange membrane between an anode and a cathode, In an electrodeionization apparatus, concentrated water is passed through the concentration compartment, and water to be treated is passed through the deionization compartment, and the water is taken out as deionized water. At least one of the anode and cathode electrodes is divided into a plurality of electrodes in the direction of flow of the water to be treated.

[0011] [2] A third electrode is disposed between the first electrode and the second electrode; the first electrode and the second electrode are anodes and the third electrode is cathode, or the first electrode and the second electrode are cathodes and the third electrode is anode; a concentration compartment and a deionization compartment are formed between the first electrode and the third electrode, and between the third electrode and the second electrode by an ion exchange membrane, respectively; In an electrodeionization apparatus, concentrated water is passed through the concentration compartment, and water to be treated is passed through the deionization compartment, and the water is taken out as deionized water. 1. An electrodeionization apparatus, wherein at least one of the third electrode and the first and second electrodes is divided into a plurality of parts in the direction in which the water to be treated flows.

[0012] [3] The electrodeionization device according to [1] or [2], characterized in that an electrical insulator is disposed between the divided electrodes.

[0013] [4] A method for operating an electrodeionization apparatus according to [1] to produce deionized water having a water quality index value within a specified range, comprising: A method for operating an electrodeionization apparatus, characterized in that when the water quality index value of the water to be treated or the water quality index value of the deionized water falls outside a specified range, the current density between the divided electrode on the inlet side of the water to be treated and the opposing electrode is increased. [Effects of the Invention]

[0014] According to the present invention, it is possible to control the current density separately on the inlet side of the feed water and the outlet side of the deionized water, and it is also possible to ease the water supply conditions, improve the treatment performance, and reduce power consumption. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view of an electrodeionization device according to an embodiment. [Figure 2] 1 is a schematic cross-sectional view of an electrodeionization device according to an embodiment. [Figure 3] 1 is a schematic cross-sectional view of an electrodeionization device according to an embodiment. [Figure 4] 1 is a schematic cross-sectional view of an electrodeionization device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Figure 1 is a schematic cross-sectional view of an electrodeionization apparatus according to an embodiment of the present invention. This electrodeionization apparatus has a plurality of anion exchange membranes (A membranes) 3 and cation exchange membranes (C membranes) 4 alternately arranged between electrodes (anodes 11-13, cathodes 21-23) to form alternating concentration compartments 5 and deionization compartments 6. Additionally, an anode compartment 7 is formed along the anodes 11-13, and a cathode compartment 8 is formed along the cathodes 21-23. The deionization compartments 6 are filled with ion exchange resin, preferably with an average particle size of 0.1-0.4 mm, especially 0.2-0.3 mm.

[0017] The concentration compartment 5, the anode compartment 7, and the cathode compartment 8 are also filled with an ion exchanger, activated carbon, or an electrical conductor such as a metal. The number of deionization compartments is preferably about 10 to 100, and more preferably about 40 to 60.

[0018] A mixed resin of anion exchange resin and cation exchange resin is usually filled as the ion exchange resin in the deionization chamber 6. The mixing ratio of the mixed resins of anion exchange resin and cation exchange resin is preferably in the range of anion exchange resin:cation exchange resin = 60 to 90:40 to 10, particularly 60 to 80:40 to 20 (dry weight ratio).

[0019] It is preferable to also fill the concentration compartment 5 with an ion exchange resin, and particularly to fill it with a mixed resin of anion exchange resin:cation exchange resin=40-70:60-30, preferably 50-70:50-30 (dry weight ratio).

[0020] In this embodiment, the anodes and cathodes are each divided into three in the direction of flow of the water to be treated. That is, the first anode 11 and first cathode 21 are located at the top of the drawing, the third anode 13 and third cathode 23 are located at the bottom of the drawing, and the second anode 12 and second cathode 22 are located between them. Each of the anodes (small anodes) 11-13 and cathodes (small cathodes) 21-23 is in the form of a single plate.

[0021] An electrical insulator 15 is interposed between the first anode 11 and the second anode 12, and between the second anode 12 and the third anode 13. An electrical insulator 25 is interposed between the first cathode 21 and the second cathode 22, and between the second cathode 22 and the third cathode 23. As the electrical insulator, a spacer made of rubber, synthetic resin, or the like is suitable.

[0022] The proportions of d1, d2, d3 to the total d1+d2+d3 of the dimensions (lengths) d1, d2, d3 in the water flow direction of the first anode 11, the second anode 12, and the third anode 13 are preferably d1: 10 to 25%, d2: 10 to 25%, and d3: 80 to 50%.

[0023] The first anode 11 and the first cathode 21 are equal in size. The second anode 12 and the second cathode 22 are equal in size. The third anode 13 and the third cathode 23 are equal in size.

[0024] In an electrodeionization apparatus configured as described above, raw water (water to be treated) is introduced into the inlet of the deionization chamber 6, and deionized water is taken out from the outlet of the deionization chamber 6. A portion of this deionized water is passed through the concentration chamber 5 in a countercurrent manner in the opposite direction to the flow direction of the deionization chamber 6, and the effluent from the concentration chamber 5 is discharged outside the system. A portion of the deionized water is fed to the inlet of the anode chamber 7, the effluent from the anode chamber 7 is fed to the inlet of the cathode chamber 8, and the effluent from the cathode chamber 8 is discharged outside the system as wastewater.

[0025] In this electrodeionization apparatus, by passing deionized water through the concentration compartment 5 in a countercurrent manner to the deionization compartment 6, the concentration of the concentrated water in the concentration compartment 5 becomes lower as the deionized water is taken out, reducing the effect of concentration diffusion on the deionization compartment 6 and increasing the removal rate of ions such as boron. However, water may also be passed through the concentration compartment 5 and the deionization compartment 6 in a parallel flow. The water to be treated may be passed through the concentration chamber 5 and the deionization chamber 6 in a countercurrent or parallel flow.

[0026] The water flow LV of the deionization compartment 6 is preferably about 100 to 200 m / hr, and the water flow LV of the concentration compartment 5 is preferably about 10 to 50 m / hr. The water recovery rate is preferably about 80 to 95%.

[0027] The current density of the electrodeionization device when the treated water is passed through is 1000mA / dm 2 or more, for example, 1000 to 2000mA / dm 2 It is preferable to set the following.

[0028] In one aspect of this method of operating an electrodeionization apparatus, when the electrical conductivity of the water to be treated increases above a predetermined value (or when the resistivity decreases below a predetermined value; the same applies below), the current density between the first anode 11 and the first cathode 21 is increased. This allows the quality (e.g., electrical conductivity) of the deionized water to fall within a target range.

[0029] In addition, in conventional operating methods of electrodeionization devices, when the conductivity of the water to be treated increases above a predetermined value, the current density is increased throughout the entire area between the anode and cathode. In contrast, in this embodiment, the current density between the first anode 11 and the first cathode 21 is increased only to address the increase in the conductivity of the water to be treated, thereby suppressing an increase in power consumption.

[0030] In the above explanation, when the conductivity of the water to be treated increases above a predetermined value, only the current density between the first anode 11 and the first cathode 21 is increased, but the current density between the second anode and the second cathode may also be increased. In this case, the increase in the current density between the second anode and the second cathode is smaller than the increase in the current density between the first anode and the first cathode.

[0031] In another aspect of this method of operating an electrodeionization apparatus, when the conductivity of the deionized water exceeds a specified value, the current density between the third anode 13 and the third cathode 23 is increased. This allows the quality (e.g., conductivity) of the deionized water to fall within a target range. This method reduces the increase in power consumption compared to increasing the current density across the entire area between the anode and cathode.

[0032] In this embodiment, when the conductivity of the water to be treated increases above a predetermined value, the current density between the second anode and the second cathode may also be increased, in addition to the current density between the third anode 13 and the third cathode 23. In this case, the increase in the current density between the second anode and the second cathode is smaller than the increase in the current density between the third anode and the third cathode.

[0033] In this way, according to the method for operating the electrodeionization apparatus, by dividing the electrodes, it is possible to ease the water supply conditions, improve the treatment performance, and reduce the power consumption.

[0034] In the above explanation, the conductivity is used as the water quality index value, but the resistivity may also be used, or the boron concentration or silica concentration may also be used as the index value.

[0035] In the electrodeionization device 1 of FIG. 1, both the anode and the cathode are divided, but only one of the anode and the cathode may be divided.

[0036] An example is shown in Figure 2. In the electrodeionization apparatus 1A shown in Figure 2, only the cathode is divided into three parts, as in Figure 1, and the anode 10 is an integrated unit (a single plate-like element) as a whole. The other components in Figure 2 are the same as those in Figure 1, and the same reference numerals denote the same parts.

[0037] Although only one pair of anode and cathode is provided in Fig. 1, anodes may be arranged on both sides of a cathode (a cathode may be arranged between the anode and the anode), or cathodes may be arranged on both sides of an anode (an anode may be arranged between the cathode and the cathode). Fig. 3 shows one such example, in which anodes 10L and 10R are arranged on both sides of first to third cathodes 21, 22, and 23 that are arranged in three sections.

[0038] In the electrodeionization device 1B shown in Figure 3, multiple cation exchange membranes (C membrane) 4 and anion exchange membranes (A membrane) 3 are alternately arranged between the left anode 10L and cathodes 21-23 to form alternate concentration chambers 5L and deionization chambers 6L, an anode chamber 7L is formed along the anode 10L, and a cathode chamber 8L is formed along the left side of the cathodes 21-23. Additionally, multiple anion exchange membranes (A membrane) 3 and cation exchange membranes (C membrane) 4 are alternately arranged between the cathodes 21-23 and the right anode 10R to form alternate concentration chambers 5R and deionization chambers 6R, an anode chamber 7R is formed along the anode 10R, and a cathode chamber 8R is formed along the right side of the cathodes 21-23.

[0039] The water to be treated may be passed through the left and right portions of the cathodes 21 to 23 separately, or deionized water obtained by passing through one portion may be passed through the other portion for further deionization.

[0040] The electrodeionization apparatus 1B of FIG. 3 can reduce the number of cathodes and the installation space for the electrodeionization apparatus compared to when two separate electrodeionization apparatuses are installed.

[0041] In FIG. 3, the anodes 10L and 10R are arranged on both sides of the cathodes 21 to 23, but the cathodes may be arranged on both sides of the anodes 11 to 13.

[0042] Alternatively, a configuration may be adopted in which anodes 11 to 13 are disposed on both sides of one cathode 20, or in which cathodes 21 to 23 are disposed on both sides of one anode 10, respectively.

[0043] 1 to 3, the electrodes are divided into three, but they may also be divided into two. An example is shown in Fig. 4. In the electrodeionization apparatus 1C of Fig. 4, two separate anodes and cathodes, i.e., anodes 11 and 12 and cathodes 21 and 22, are installed. The ratio of the dimensions (lengths) d1 and d2 of the first anode 11 and the second anode 12 in the water flow direction to the sum d1 + d2 is preferably 20 to 40%.

[0044] The first anode 11 and the first cathode 21 are equal in size, and the second anode 12 and the second cathode 22 are equal in size. The other configuration in Figure 4 is the same as in Figure 2, and the same reference numerals indicate the same parts.

[0045] In addition, in FIG. 4 as well, only one of the anode and cathode may be divided into two, and the other may not be divided.

[0046] The above-described embodiments are merely examples of the present invention, and the present invention may have configurations other than those described above. [Explanation of symbols]

[0047] 1, 1A, 1B, 1C Electrodeionization Device 10,11~13 Anode 20,21~23 Cathode 3 Anion exchange membrane 4. Cation exchange membrane 5 Concentration chamber 6 Deionization Chamber 7,7L,7R Anode chamber 8,8L,8R Cathode chamber 15,25 Electrical insulators

Claims

1. A concentration compartment and a deionization compartment are partitioned by an ion exchange membrane between the anode and the cathode, In an electrodeionization apparatus, concentrated water is passed through the concentration compartment, and water to be treated is passed through the deionization compartment, and the water is taken out as deionized water. At least one of the anode and cathode electrodes is divided into a plurality of electrodes in the direction of flow of the water to be treated.

2. a third electrode disposed between the first electrode and the second electrode; the first electrode and the second electrode are anodes and the third electrode is cathode, or the first electrode and the second electrode are cathodes and the third electrode is anode; a concentration compartment and a deionization compartment are defined between the first electrode and the third electrode, and between the third electrode and the second electrode by an ion exchange membrane, respectively; In an electrodeionization apparatus, concentrated water is passed through the concentration compartment, and water to be treated is passed through the deionization compartment, and the water is taken out as deionized water.

1. An electrodeionization apparatus, wherein at least one of the third electrode and the first and second electrodes is divided into a plurality of parts in the direction of flow of water to be treated.

3. 3. The electrodeionization apparatus according to claim 1, wherein an electrical insulator is disposed between the divided electrodes.

4. 2. A method for operating an electrodeionization apparatus according to claim 1 to produce deionized water having a water quality index value within a specified range, comprising: A method for operating an electrodeionization apparatus, characterized in that when the water quality index value of the water to be treated or the water quality index value of the deionized water falls outside a specified range, the current density between the divided electrode on the inlet side of the water to be treated and the opposing electrode is increased.

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