JP2008259961A - Electrodeionizing apparatus and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrodeionizing apparatus capable of preventing the occurrence of scales even if water in which inorganic carbonic acid or a hardness component remains is supplied to a concentration chamber and capable of being stably operated over a long period of time. <P>SOLUTION: A flow channel R1 of water W1 to be treated is connected to the desalting chamber 2 of the electrodeionizing apparatus 1 and the outlet side of the desalting chamber 2 is formed as a flow channel R2 of water W2 to be treated. A branch flow channel R3 is provided to the flow channel R2 and connected to the concentration chamber 3 to make it possible to introduce a part of the water W2 to be treated in the desalting chamber 2 into the concentration chamber 3. A water quality sensor 4 being a sensing means is provided to the flow channel R2 while a storage tank 5 of an acid or a scale inhibitor is allowed to communicate with the branch flow channel R3 through a liquid feed pump 6 being a supply means. The water quality sensor 4 and the liquid feed pump 6 are connected to a control means 7 such as a microcomputer or the like and the liquid feed pump 6 can be controlled corresponding to the output of the water quality sensor 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrodeionization apparatus in which a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a cathode and an anode to alternately form a concentration chamber and a desalting chamber, and an operating method thereof. In particular, the present invention relates to an electrodeionization apparatus capable of preventing the formation of calcium carbonate scale in the concentration chamber and an operating method thereof when treating water to be treated having a high scale component concentration.

  Conventionally, for the production of deionized water used in various industries such as semiconductor manufacturing factory, liquid crystal manufacturing factory, pharmaceutical industry, food industry, electric power industry, etc. A plurality of anion exchange membranes and cation exchange membranes are alternately arranged to alternately form a concentration chamber and a desalting chamber, and the anion exchanger comprising an ion exchange resin, an ion exchange fiber, or a graft exchanger in the desalting chamber In addition, an electrodeionization apparatus in which the cation exchanger and the cation exchanger are mixed or packed in multiple layers is often used (see Patent Documents 1 to 3).

The electrodeionization device generates H ⁺ ions and OH ⁻ ions by water dissociation and continuously regenerates the ion exchanger filled in the desalting chamber, enabling efficient desalting treatment. Thus, it does not require a regeneration treatment using chemicals such as the ion exchange resin apparatus that has been widely used so far, and complete continuous water sampling is possible, and an excellent effect that high-purity water is obtained is exhibited.

However, when river water, groundwater, tap water, etc. are treated water of the electrodeionization device, the treated water conductivity decreases due to the generation of scale in the concentration chamber and increased CO ₂ load. Water is not directly passed as the water to be treated in the electrodeionization apparatus.

The increase in CO ₂ load among the above problems can be solved by using a relatively inexpensive decarboxylation device as a pretreatment device for an electrodeionization device. On the other hand, in order to prevent scale, there is a method to completely remove the hardness component in water by installing a softening device etc. in front of the electrodeionization device. However, if a softening device is used, regeneration is necessary. Thus, the advantages of using a regeneration-free electrodeionization apparatus are lost.

In order to solve such problems, a method of installing a reverse osmosis membrane device (RO membrane device) has been used as a pretreatment device for an electrodeionization device in order to reduce hardness components and CO ₂ concentration. It has been. And when the hardness component density | concentration in to-be-processed water is high, the method of installing RO membrane apparatus in two steps in series is used.

  However, since the RO membrane device is operated at a high pressure of 0.5 to 2 MPa, expensive equipment is required and the operating cost increases. In addition, even when an RO membrane device is used as a pretreatment device for an electrodeionization device, calcium carbonate scale is generated in the concentration chamber of the electrodeionization device due to slight leakage of calcium from the RO membrane. There was also a problem that stable operation could not be performed. Thus, two stages of RO membrane devices are arranged in series to further remove calcium and the like, but this is not practical in terms of costs. For this reason, if treatment can be performed with a single-stage RO membrane device under normal water supply conditions, a pure water production system must be designed with a single-stage RO membrane device. In addition, there is a concern that scale cannot be generated in the concentration chamber because it cannot cope with a decrease in water supply conditions such as an increase in the concentration of carbon dioxide or a breakthrough of the RO membrane device.

In Patent Document 4 and Patent Document 5, the concentration chamber of the electrodeionization device is partitioned by a bipolar membrane to prevent association of calcium ions and carbonate ions, which are scale components, and There has been proposed a method capable of omitting the RO membrane device that has been required as a pretreatment device and reducing the equipment cost and the treatment cost.
Japanese Patent No. 1782943 Japanese Patent No. 2751090 Japanese Patent No. 2699256 JP 2001-198577 A JP 2002-186773 A

The scale of the concentrating chamber is suppressed by the electrodeionization apparatus described in Patent Document 4, but inorganic carbonic acid (H ₂ CO ₃ , HCO ₃ ⁻ , CO ₃ ⁻ ) and hardness components (calcium, magnesium) are contained in the concentrating chamber. When water containing) is supplied, since the pH in the concentration chamber is partially increased, carbonate scale (CaCO ₃ , MgCO ₃ ) may be precipitated in the concentration chamber. This is because even when the treatment water of the demineralization chamber is supplied to the concentration chamber, the treatment with the electrodeionization apparatus is insufficient and the inorganic carbonic acid (H ₂ CO ₃ , HCO ₃ ⁻ , This may be a problem when CO ₃ ⁻ ) and hardness components (calcium and magnesium) are not completely removed and remain. And if the scale is made in the concentrating chamber, the electric resistance of the electrodeionization device is increased and it becomes difficult for the current to flow. As a result, the quality of the treated water is lowered or the concentrating chamber is blocked. In particular, the anode-side concentrating chamber has a high cation concentration and a high pH, so scale is likely to occur, and special attention is required for the inflow of inorganic carbonic acid into the anode-side concentrating chamber.

  However, the water supply conditions (allowable concentration) of the electrodeionization device are due to poor control of the pretreatment process such as an increase in water supply load to the concentrating chamber, deterioration of the RO membrane, and insufficient decarboxylation due to pH adjustment problems. ), When the amount of inorganic carbonic acid and hardness component exceeding is supplied, components that cannot be removed may remain in the treated water and be introduced into the concentration chamber.

  The present invention solves the above-mentioned conventional problems and can prevent the generation of scale even if inorganic carbonic acid or water with a hardness component remaining is supplied to the concentrating chamber. It is an object of the present invention to provide an electrodeionization apparatus that can be operated well and an operation method thereof.

  In order to solve the above problems, first, the present invention alternately forms a concentration chamber and a desalting chamber by alternately arranging a plurality of anion exchange membranes and cation exchange membranes between a cathode and an anode. In the electrodeionization apparatus, the detection means for measuring the quality of the treated water in the demineralization chamber, the addition means for adding an acid or a scale inhibitor to the feed water of the concentration chamber, and the output value of the detection means And a control means for controlling the addition means based on the above. (Claim 1)

  According to the above invention (invention 1), the quality of the treated water in the desalination chamber is monitored by the detection means, and if it is detected that the water quality has been lowered by the output value of the detection means, the concentration of inorganic carbonic acid and the hardness component is present in the concentration chamber. It is judged that the possibility of being supplied has occurred, and by adding acid to the supply water of the concentration chamber by adding means, the pH is lowered to prevent precipitation of carbonate scale, or a scale inhibitor is introduced into the concentration chamber. Precipitation of carbonate scale can be prevented.

  Second, the present invention relates to an electrodeionization apparatus in which a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a cathode and an anode to alternately form a concentration chamber and a desalting chamber. Detecting means for measuring an electrical resistance between the cathode and the anode; an adding means for adding an acid or a scale inhibitor to the feed water of the concentration chamber; and the adding means based on an output value of the detecting means. An electrodeionization apparatus comprising a control means for controlling is provided (claim 2).

  According to the above invention (invention 2), the electrical resistance between the cathode and the anode is monitored by the detection means, and it is determined that a scale has started to occur when an increase in electrical resistance is detected by the output value of the detection means, The carbonate scale can be dissolved by adding acid to the feed water of the concentration chamber to lower the pH by adding means, or precipitation of carbonate scale can be prevented by introducing a scale inhibitor into the concentration chamber.

  In the said invention (invention 1,2), it is preferable to provide the flow path which supplies a part of effluent of the said desalination chamber to the inflow side of the said concentration chamber (invention 3). According to this invention (invention 3), even when water having a high calcium concentration such as tap water is treated, a part of deionized water is introduced into the concentrating chamber, so that the circulating water in the concentrating chamber can be obtained. Can be diluted with deionized water to reduce the calcium concentration, thereby further preventing the generation of scale. Moreover, the scaling tendency can be determined more accurately by the detecting means.

  In the said invention (Invention 1-3), it is preferable to provide the said concentration chamber by providing a bipolar membrane in the said concentration chamber (Invention 4). Particularly in such an invention (invention 4), the bipolar membrane is provided in the concentration chamber such that the anion exchange layer surface of the bipolar membrane is located on the anode side and the cation exchange layer surface is located on the cathode side. (Claim 5).

According to the above inventions (Inventions 4 and 5), by preventing association of calcium ions (Ca ²⁺ ) and inorganic carbonate ions (CO ₃ ²⁻ etc.) which are scale components in the concentration chamber of the electrodeionization apparatus. In this case, since the pH of the anode-side concentrating chamber is likely to increase due to an increase in pH, acid is added to the water supplied to the concentrating chamber by an adding means, or the scale is added to the concentrating chamber. By introducing an inhibitor, precipitation of carbonate scale can be prevented.

  Thirdly, the present invention relates to an electrodeionization apparatus in which a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a cathode and an anode to alternately form a concentration chamber and a desalting chamber. In the operation method, the quality of the treated water in the desalination chamber is measured, and when the quality of the treated water is lower than a predetermined quality, an acid or a scale inhibitor is added to the supply water in the concentration chamber. An operation method of the electrodeionization apparatus is provided (claim 6).

  According to the above invention (invention 6), the quality of the treated water in the desalination chamber is monitored by the detection means, and when it is detected by the output value of the detection means that the water quality has decreased, the concentration chamber contains inorganic carbonic acid and a hardness component. It is judged that the possibility of being supplied has occurred, and by adding acid to the supply water of the concentration chamber by adding means, the pH is lowered to prevent precipitation of carbonate scale, or a scale inhibitor is introduced into the concentration chamber. Precipitation of carbonate scale can be prevented.

  Fourthly, the present invention provides an electrodeionization apparatus in which a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a cathode and an anode to alternately form a concentration chamber and a desalting chamber. In the operation method, an electrical resistance between the cathode and the anode is measured, and when the electrical resistance becomes smaller than a predetermined resistance, an acid or a scale inhibitor is added to the supply water of the concentration chamber. An operation method of the electrodeionization apparatus is provided (claim 7).

  According to the above invention (invention 7), the electrical resistance between the cathode and the anode is monitored by the detection means, and it is determined that a scale has started to occur when an increase in electrical resistance is detected by the output value of the detection means, The carbonate scale can be dissolved by adding acid to the feed water of the concentration chamber to lower the pH by adding means, or precipitation of carbonate scale can be prevented by introducing a scale inhibitor into the concentration chamber.

  Fifthly, the present invention provides a pure water production system comprising the electrodeionization apparatus according to the above invention (Inventions 1 to 5) (Invention 8).

  According to the electrodeionization apparatus of the present invention, the detection unit detects the tendency of the concentration chamber to scale, and when the scale is likely to be generated, the addition unit adds acid to the supply water of the concentration chamber to lower the pH. Thus, precipitation of carbonate scale can be prevented, or precipitation of carbonate scale can be prevented by introducing a scale inhibitor into the concentration chamber.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flowchart showing the system configuration of an electrodeionization apparatus according to the first embodiment of the present invention, and FIG. 2 shows the flow of water to the demineralization chamber and the concentration chamber of the electrodeionization apparatus. FIG. 3 is a schematic view, FIG. 3 is an enlarged view showing a desalting chamber and a concentration chamber, and FIG. 4 is a cross-sectional view showing the flow of ions in the desalting chamber and the concentration chamber.

  In the present embodiment, the electrodeionization apparatus 1 includes a demineralization chamber 2 and a concentration chamber 3, and the demineralization chamber 2 is connected to the flow path R <b> 1 of the treated water W <b> 1, while the outlet of the demineralization chamber 2. The side is a flow path R2 of the treated water W2. This flow path R2 is branched, and this branch flow path R3 is connected to the concentration chamber 3, so that a part of deionized water (treated water) W2 in the demineralization chamber 2 can be introduced into the concentration chamber 2. ing. And after diluting the circulating water of the concentration chamber 2 with deionized water to reduce the calcium concentration, the concentrated water W3 is discharged from the flow path R4.

  In such a system configuration, the flow path R2 is provided with a water quality sensor 4 serving as detection means, while the branch flow path R3 is provided with an acid or scale inhibitor storage tank 5 via a liquid feed pump 6 serving as supply means. It is communicated. The water quality sensor 4 and the liquid feed pump 6 are connected to a control means 7 such as a microcomputer so that the liquid feed pump 6 can be controlled according to the output of the water quality sensor 4. As the water quality sensor 4, a specific resistance meter (conductivity meter), an IC meter, a hardness system, or the like can be used.

  The electrodeionization apparatus 1 provided with the system as described above specifically has a configuration as shown in FIG. That is, the electrodeionization apparatus 1 includes a plurality of anion exchange membranes (A membranes) 13 and cation exchange membranes (C membranes) 14 arranged alternately between the electrodes (anode 11 and cathode 12) and desorbed from the concentration chamber 3. The salt chambers 2 are alternately formed, and the desalting chamber 2 is filled with an ion exchange resin 19. In FIG. 3, 17 is an anode chamber and 18 is a cathode chamber.

  In the present embodiment, the bipolar membrane 20 is provided in the concentrating chamber 3 to partition the concentrating chamber 3, thereby forming the cathode-side compartment 15 A and the anode-side compartment 15 B. The bipolar membrane 20 is installed in the concentration chamber 3 so that the anion exchange layer surface 20B side of the bipolar membrane 20 is located on the anode 11 side and the cation exchange layer surface 20A side of the bipolar membrane 20 is located on the cathode 12 side.

  The bipolar membrane 20 used in the present invention is not particularly limited as long as it has an anion exchange layer and a cation exchange layer and has high water electrolysis efficiency. Moreover, depending on the case, it may include using an anion exchange membrane and a cation exchange membrane in an overlapping manner.

  In such an electrodeionization apparatus 1, it is preferable that the cathode side compartment 15A and the anode side compartment 15B are filled with an ion exchanger, in particular, a mixed resin 21 of an anion exchange resin and a cation exchange resin. The ratio of the anion exchange resin to the cation exchange resin in the mixed resin 21 is not particularly limited, but the anion exchange resin / cation exchange resin is 10/90 to 90/10, particularly 30/70 to 70/30. Is preferred. Thereby, in the cathode side compartment 15A, the movement of hydrogen ions generated by water dissociation at the interface of the bipolar film 20 is promoted, while in the anode side compartment 15B, hydroxylation generated by water dissociation at the interface of the bipolar film 20 is promoted. The movement of object ions is promoted. As a result, current can easily flow and voltage rise can be suppressed.

Next, the operation of the above-described electrodeionization apparatus 1 will be described.
As shown in FIG. 1, first, the water to be treated W1 is supplied from the flow path R1 to the demineralization chamber 2 of the electrodeionization apparatus 1. In this electrodeionization apparatus 1, treated water (deionized water) W2 from which ionic impurities such as calcium, magnesium and hydrogen carbonate ions have been removed from the treated water W1 in the desalting chamber 2 is sub-flowed from the flow path R2. Supplied to the system etc. A part of the treated water W2 is supplied from the flow path R2 to the concentration chamber 3 of the electrodeionization apparatus 1 via the branch flow path R3.

FIG. 4 schematically shows the flow of ions in the electrodeionization apparatus 1. That is, in the concentration chamber 3 of the electrodeionization apparatus 1, anions such as hydrogen carbonate ions (HCO ₃ ⁻ ) permeate from the anion exchange membrane 13 side of the desalting chamber 2 and calcium ions (from the cation exchange membrane 14 side). Cations such as Ca ²⁺ ) permeate.

At this time, in this embodiment, since the concentration chamber 3 is partitioned by the bipolar membrane 20, anions such as hydrogen carbonate ions (HCO ₃ ⁻ ) that have permeated the anion exchange membrane 13 cannot permeate the bipolar membrane 20. On the other hand, cations such as calcium ions (Ca ²⁺ ) that have permeated the cation exchange membrane 14 cannot permeate. For this reason, generation | occurrence | production of the calcium carbonate scale in the concentration chamber 3 is prevented. For convenience of explanation, the mixed resin 21 is omitted in FIG.

  At this time, in the bipolar membrane 20, water dissociation occurs by applying a voltage equal to or higher than the theoretical water electrolysis voltage (0.83 V), so that a current flows. For this reason, installing the bipolar membrane 20 in the concentration chamber 3 does not impair the deionization performance of the electrodeionization apparatus 1.

By such an action, the inside of the anode side compartment 15B becomes alkalic (high pH) by supplying hydroxide ions (OH ⁻ ) generated by water dissociation at the interface of the bipolar membrane 20. . There are also calcium ions (Ca ²⁺ ) and sodium ions (Na ⁺ ) that have permeated through the cation exchange membrane 14. Therefore, if inorganic carbonic acid (H ₂ CO ₃ , HCO ₃ ⁻ , CO ₃ ⁻ ) remains in the deionized water (treated water W2) that has passed through the desalting chamber 2, a scale is formed in the anode compartment 15B. Is likely to occur.

Therefore, in the present embodiment, the water quality sensor 4 is provided in the flow path R2 of the treated water W2, and the treated water W2 of inorganic carbonic acid (H ₂ CO ₃ , HCO ₃ ⁻ , CO ₃ ⁻ ) or a hardness component (calcium, magnesium). Residue inside is monitored by specific resistance value, inorganic carbonate concentration, calcium ion concentration, etc. These items can be continuously monitored by an on-line analyzer by providing a sensor for a desired detection object as the water quality sensor 4.

  In the water quality sensor 4, for example, when the specific resistance value is less than 1 MΩ · cm, the control means 7 determines that the water quality has decreased, and drives the liquid feed pump 6 to drive the acid or scale inhibitor from the storage tank 5. Is supplied to the branch flow path R3.

  At this time, when the acid is added, the pH of the water supplied to the concentration chamber 3 flowing through the branch flow path R3 is adjusted to be pH = 3.0 to 5.0 at the inlet of the concentration chamber 3. Is preferred. Thereby, precipitation of carbonate scale in the concentration chamber 3, particularly the anode-side compartment 15B can be prevented, or when scale is deposited, it can be dissolved and removed. Moreover, when adding a scale inhibitor, precipitation of carbonate scale can be prevented.

  In addition, hydrochloric acid, sulfuric acid, nitric acid, etc. can be used as the acid to be added. However, hydrochloric acid, nitric acid, etc. may generate harmful gases in the electrode reaction, and halogen acids such as hydrochloric acid may cause oxidative degradation of the filled resin. Sulfuric acid is preferred because of the risk of promoting Moreover, as a scale inhibitor, commercially available scale inhibitors such as phosphoric acid type and polymer type can be used.

  For example, when the specific resistance value is 1 MΩ · cm or more, control is performed to stop the liquid feed pump 6. By controlling in this way, it is possible to operate without stopping the continuous water collection of the electrodeionization apparatus 1. Further, when adding acid, the same effect as that of chemical cleaning is obtained regularly, so that it is not necessary to perform maintenance after stopping the electrodeionization apparatus 1 or the frequency of maintenance is reduced. There is also an effect that it can be remarkably reduced.

  The electrodeionization apparatus according to the first embodiment as described above can be applied as a primary pure water production system as shown in FIG. 5, for example.

  In FIG. 5, the primary pure water production system includes an activated carbon device 31 to which city water is supplied, a reverse osmosis membrane (RO membrane) device 32 that processes the permeated water of the activated carbon device 31, and the RO membrane device 32. A deaeration membrane 33 for treating the RO-treated water, and an electrodeionization apparatus 34 for treating the deaeration water obtained by the deaeration membrane 33 in the demineralization chamber 35 to produce treated water (deionized water) W2. Is provided. The electrodeionization device 34 basically has a configuration as described in the first embodiment.

  The demineralization chamber 35 of the electrodeionization device 34 communicates with a subsystem or the like via a flow path r2. A branch channel r3 branched from the channel r2 communicates with an anode chamber and a cathode chamber (not shown) and also communicates with the concentration chamber 36.

  In such a system configuration, a specific resistance meter 37 as a water quality sensor is provided in the flow path r2, and a sulfuric acid storage tank 38 communicates with the branch flow path r3 via a liquid feed pump 39 as supply means. Has been. The specific resistance meter 37 is connected to a control means 40 such as a microcomputer, and when the specific resistance value measured by the specific resistance meter 37 is less than 1 MΩ · cm, it is determined that the water quality has deteriorated. Then, the liquid feed pump 39 is driven and stopped when the specific resistance value becomes 1 MΩ · cm or more. In FIG. 5, reference numeral 41 denotes a vacuum pump for the deaeration membrane 33.

Next, the operation of the primary pure water production system having such a configuration will be described.
First, city water is supplied to the activated carbon device 31 from the starting end of the flow path r1 to adsorb and remove fine particles, residual chlorine, etc., and the treated water of the activated carbon device 31 is supplied to the RO membrane device 32 to be treated water. Remove calcium, silica, etc. contained. Although not shown, the concentrated water discharged from the RO membrane device 32 may be supplied to another RO membrane device provided separately, and the treated water may be merged with the supply water of the RO membrane device 32. .

  Then, the RO-treated water treated by the RO membrane device 32 is supplied to the deaeration membrane 33, and after removing carbonate ions and the like contained in the RO-treated water as carbon dioxide, the obtained deaerated water is subjected to electrodeposition. It is supplied to the desalting chamber 35 of the ion device 34. Although not shown, deaeration may be performed after adding sulfuric acid, hydrochloric acid or the like to the RO-treated water to lower the pH in order to facilitate removal of carbonate ions.

  In this electric deionization apparatus 34, the water to be treated (degassed water) W1 is treated water (deionized water) from which ionic impurities such as calcium ions, magnesium ions, and bicarbonate ions have been removed in the desalting chamber 35. W2 is supplied to the subsystem or the like from the flow path r2 or used as it is.

  A part of the treated water W2 is supplied from the branch channel r3 to the concentration chamber 36 of the electrodeionization device 34, and the concentrated water W3 from the concentration chamber 36 is circulated to the front stage of the activated carbon device 31.

And in the electrodeionization apparatus 34, as mentioned above, the flow of ion as shown in FIG. 4 is produced. Here, by providing a specific resistance meter 37 in the flow path r2 of the treated water W2, inorganic carbonic acid (H ₂ CO ₃ , HCO ₃ ⁻ , CO ₃ ⁻ ) or a hardness component (calcium, magnesium) or the like is contained in the treated water W2. When the specific resistance value becomes less than 1 MΩ · cm, it is determined that the water quality has decreased, and the liquid feeding pump 39 is driven to supply sulfuric acid. At this time, it is preferable to add sulfuric acid so that the pH of the water supplied to the concentration chamber 36 flowing through the branch flow path r3 is pH = 3.0 to 5.0 at the inlet of the concentration chamber 36. Thereby, precipitation of carbonate scale can be prevented, or when scale is deposited, it can be dissolved and removed. Then, when the specific resistance value is 1 MΩ · cm or more, the liquid feed pump 39 may be stopped to stop the supply of sulfuric acid.

  Thereby, even if the water quality of the treated water W2 of the electrodeionization apparatus 34 is deteriorated, generation of calcium carbonate or the like in the concentration chamber 36, particularly the anode side compartment 15B, can be suppressed.

  Next, a second embodiment of the present invention will be described with reference to FIG. In addition, since the electrodeionization apparatus of this embodiment has the same structure as the said 1st Embodiment fundamentally, the same code | symbol is attached | subjected to the same structure and the detailed description is abbreviate | omitted.

  In this embodiment, instead of providing the water quality sensor 4 in the flow path R2, an electric resistance detector 8 for measuring the electric resistance between the cathode and the anode of the electrodeionization apparatus 1 is provided. The detector 8 and the liquid feed pump 6 are connected to a control means 7 such as a microcomputer, and the liquid feed pump 6 can be controlled according to the output of the electric resistance detector 8.

Next, the operation of the above-described electrodeionization apparatus will be described.
First, the water to be treated W1 is supplied from the flow path R1 to the demineralization chamber 2 of the electrodeionization apparatus 1. In this electric deionization apparatus 1, the water to be treated W1 is treated as a treated water (deionized water) W2 from which ionic impurities such as calcium, magnesium, hydrogen carbonate ions have been removed in the demineralization chamber 2 from the flow path R2. Etc. A part of the treated water W2 is supplied to the concentrating chamber 3 of the electrodeionization apparatus 1 via a branch channel R3 branched from the channel R2.

At this time, in the electrodeionization apparatus 1, an ion flow as shown in FIG. 4 is generated as in the first embodiment described above. For this reason, the inside of the anode-side compartment 15B is alkalic (high pH) by being supplied with hydroxide ions (OH ⁻ ) generated by water dissociation at the interface of the bipolar membrane 20. There are also calcium ions (Ca ²⁺ ) and sodium ions (Na ⁺ ) that have permeated through the cation exchange membrane 14. Thus, if inorganic carbonic acid (H ₂ CO ₃ , HCO ₃ ⁻ , CO ₃ ⁻ ) remains in the deionized water (treated water) W2 that has passed through the desalting chamber 2, the inside of the anode-side compartment 15B It becomes easy to generate scale.

  And when a scale precipitates, the movement of the ion of a precipitation location is inhibited, As a result, the flow of an electric current stagnates. Therefore, when a constant current operation is performed, a voltage increase occurs, and when a constant voltage operation is performed, a current decrease occurs. Therefore, scale deposition can be detected by increasing the electrical resistance of the electrodeionization apparatus 1.

Therefore, in the present embodiment, an electric resistance detector 8 for measuring the electric resistance between the cathode and the anode of the electrodeionization apparatus 1 is provided, and inorganic carbonic acid (H ₂ CO ₃ , HCO ₃ ⁻ , CO ₃ ⁻ ) is provided. Alternatively, when the scale component is deposited in the concentration chamber 3 due to an increase in the hardness component (calcium, magnesium) and the electrical resistance increases irreversibly (for example, when the increase in electrical resistance continues for one day or more), the control means 7 It is determined that scale has occurred, and the liquid feed pump 6 is driven to supply acid or scale inhibitor from the storage tank 5 to the branch flow path R3. When adding acid at this time, the pH of the water supplied to the concentrating chamber 3 flowing through the branch flow path R3 is adjusted so that pH = 3.0 to 5.0 at the inlet of the concentrating chamber 3. preferable. Thereby, precipitation of carbonate scale can be prevented, or when scale is deposited, it can be dissolved and removed. Moreover, when adding a scale inhibitor, precipitation of carbonate scale can be prevented. As the acid and the scale inhibitor, the same ones as in the first embodiment described above can be used. For example, when the electric resistance becomes 1Ω or less, control is performed to stop the liquid feed pump 6.

  By controlling in this way, it is possible to operate without stopping the continuous water collection of the electrodeionization apparatus 1. Furthermore, when adding an acid, since chemical cleaning is performed periodically, it is not necessary to perform maintenance after stopping the electrodeionization apparatus 1 or the frequency of maintenance can be significantly reduced. Also has the effect of.

  As mentioned above, although the electrodeionization apparatus of this invention has been demonstrated with reference to an accompanying drawing, this invention is not restricted to the said 1st and 2nd embodiment, A various deformation | transformation implementation is possible.

  For example, in the above embodiment, control is performed based on an increase in electrical resistance. However, if the scale grows until the flow path inside the concentrating chamber 3 is blocked, the water flow differential pressure increases, so the water flow differential pressure increases. Then, it may be considered that the water quality has deteriorated, and the addition of the acid or the scale inhibitor may be controlled. The electrodeionization apparatus of the second embodiment can also be applied to a system as shown in FIG.

  Furthermore, the electrodeionization apparatus 1 can be applied without being limited to the one in which the bipolar membrane 20 is disposed in the concentration chamber 3.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, this invention is not limited to the following Example at all.

In addition, as a test apparatus used in the following Examples and Comparative Examples, an electrodeionization apparatus (manufactured by Kurita Kogyo Co., Ltd., product name: Critenon SH type, treated water amount 420 L / hr) was used.
Moreover, the following water quality | type which processed the city water with the reverse osmosis membrane apparatus (The product made from Nitto Denko Corporation, product name: ES-20) was prepared as to-be-processed water for a test.
Water to be treated: Feed water Ca concentration 1.03ppm (CaCO ₃ conversion)
Feed water Mg concentration 0.21ppm (CaCO ₃ conversion)
Feed water CO ₂ concentration 4.07 ppm (CaCO ₃ conversion)

[Example 1]
The following is used as an ion exchange membrane and an ion exchange resin filled in a demineralization chamber of an electrodeionization device, and an electrodeionization device in which a bipolar membrane 20 is arranged in the concentration chamber 3 as shown in FIG. Water was passed under the conditions shown in Table 1 below with the apparatus having the system configuration as shown in FIG. At this time, for the purpose of increasing the load of the electrodeionization device 34, an aqueous sodium hypochlorite solution is added to the front stage of the RO membrane device 32 so that the chlorine concentration becomes 0.1 ppm, and the RO membrane device 32 is deteriorated, Operation was performed at a constant current setting (3.8 A).

Anion exchange membrane: Aciplex A501SB (Asahi Kasei Kogyo Co., Ltd.)
Cation exchange membrane: Aciplex K501SB (Asahi Kasei Kogyo Co., Ltd.)
Bipolar membrane: Neoceptor BP-1 (manufactured by Astom)
Ion exchanger: Anion exchange resin (Mitsubishi Chemical Corporation, SA10A) and cation exchange resin (Mitsubishi Chemical Corporation, SK1B) mixed at a volume mixing ratio of 6: 4

  In the above operation, the treated water W2 of the desalting chamber 35 is supplied to the concentrating chamber 36 and the electrode chamber (not shown), the specific resistance value of the treated water W2 is continuously measured by the specific resistance meter 37, and the treated water is measured. When the specific resistance was less than 1 MΩ · cm, the amount of sulfuric acid (62.5% concentration) injected into the concentrating chamber 36 was controlled so that the concentration at the inlet of the concentrating chamber was 0.5 to 1.0%.

  The applied voltage, concentration chamber inlet conductivity, inlet total hardness component concentration, and treated water specific resistance value were measured after operating this primary pure water production system for one week in January and March. The results are shown in Table 1 together with the desalination chamber flow rate and the concentration chamber flow rate.

[Comparative Example 1]
In the system configuration as shown in FIG. 5, the constant current of the electrodeionization device 34 is the same as in the first embodiment except that the specific resistance meter 37, the sulfuric acid storage tank 38 and the liquid feed pump 39 are not provided and sulfuric acid is not injected. Operation was performed with the setting (3.8 A).
The results are shown in Table 2.

As apparent from Tables 1 and 2, the electrodeionization apparatus 34 of Example 1 was able to operate stably for three months, while the electrodeionization apparatus 34 of Comparative Example 1 was operated. One week after the start, the voltage increased and eventually became inoperable. This is because, in the electrodeionization apparatus 34 of Comparative Example 1, the quality of the feed water of the electrodeionization apparatus 34 is lowered with the decrease in the performance of the RO membrane apparatus 32, and the treated water W <b> 2 of the demineralization chamber 35, i. This is probably because the concentration of inorganic carbonic acid (H ₂ CO ₃ , HCO ₃ ⁻ , CO ₃ ⁻ ) and hardness components (calcium, magnesium) in the feed water increased and scale was generated in the anode compartment 15B. .

1 is a system diagram showing an electrodeionization apparatus according to a first embodiment of the present invention. It is the schematic which shows the flow of the water of the electrodeionization apparatus of the said embodiment. It is sectional drawing which shows the demineralization chamber and the concentration chamber of the electrodeionization apparatus of the said embodiment. It is sectional drawing which shows the flow of the demineralization chamber and the concentration chamber ion of the electrodeionization apparatus of the said embodiment. It is a flowchart which shows the primary pure water manufacturing system using the electrodeionization apparatus of the said embodiment. It is a system diagram which shows the electrodeionization apparatus by the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrodeionization apparatus 2 ... Desalination chamber 3 ... Concentration chamber 4 ... Water quality sensor (detection means)
5 ... Acid or scale storage tank 7 ... Control means 11 ... Anode 12 ... Cathode 13 ... Anion exchange membrane (A membrane)
14 ... Cation exchange membrane (C membrane)
15A ... Cathode side compartment 15B ... Anode side compartment 20 ... Bipolar membrane 20A ... Cation exchange layer surface 20B ... Anion exchange layer surface 37 ... Specific resistance meter (water quality sensor)
38 ... Sulfuric acid tank (acid or scale inhibitor tank)
W2 ... treated water R3 ... branch channel (channel)

Claims (8)

In the electrodeionization apparatus in which a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between the cathode and the anode to alternately form a concentration chamber and a desalting chamber,
Detection means for measuring the quality of treated water in the desalination chamber;
An adding means for adding an acid or a scale inhibitor to the feed water of the concentrating chamber;
An electrodeionization apparatus comprising: control means for controlling the addition means based on an output value of the detection means. In the electrodeionization apparatus in which a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between the cathode and the anode to alternately form a concentration chamber and a desalting chamber,
Sensing means for measuring the electrical resistance between the cathode and anode;
An adding means for adding an acid or a scale inhibitor to the feed water of the concentrating chamber;
An electrodeionization apparatus comprising: control means for controlling the addition means based on an output value of the detection means.   The electrodeionization apparatus according to claim 1 or 2, further comprising a flow path for supplying a part of the effluent water of the demineralization chamber to the inflow side of the concentration chamber.   The electrodeionization apparatus according to any one of claims 1 to 3, wherein the concentration chamber is partitioned by providing a bipolar membrane in the concentration chamber.   5. The bipolar membrane according to claim 4, wherein the bipolar membrane is provided in the concentration chamber such that the anion exchange layer surface of the bipolar membrane is located on the anode side and the cation exchange layer surface is located on the cathode side. Electrodeionizer. An operation method of an electrodeionization apparatus, wherein a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a cathode and an anode to alternately form a concentration chamber and a desalting chamber,
The quality of the treated water in the desalination chamber is measured, and if the quality of the treated water is lower than a preset water quality, an acid or a scale inhibitor is added to the supply water in the concentration chamber. Operation method of the electrodeionization apparatus. An operation method of an electrodeionization apparatus, wherein a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a cathode and an anode to alternately form a concentration chamber and a desalting chamber,
The electrical resistance between the cathode and the anode is measured, and when the electrical resistance becomes smaller than a predetermined resistance, an acid or a scale inhibitor is added to the supply water of the concentration chamber. Operation method of the electrodeionization apparatus.   A pure water production system comprising the electrodeionization apparatus according to claim 1.

Images