JP2009279525A - Electrodialyser and method for operating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrodialyser and a method for operating the same using no expensive electrode and capable of preventing the corrosion of an electrode throughout the duration of actual servicing. <P>SOLUTION: The electrodialysis tank is partitioned off into a plurality of chambers arranged between electrodes with ion exchange membranes in between, and the chambers are supplied with each prescribed liquid in order to electrodialyze raw water. At least one chamber is washed with a liquid supplied as cleaning water and having a lower concentration of the raw water component than those of the liquids for the electrodialysis of the raw water. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrodialysis apparatus that treats, for example, wastewater containing fluorine (fluorine-containing wastewater) and an operation method thereof.

  Electrodialyzers are widely used for recovering valuable materials in liquids or for deionization / desalination.

A problem related to resources in recent years is that the price of fluorine is rising because high-quality fluorite, which is a raw material for fluorine, is unevenly distributed in China and other countries. In the fluorine handling industry, such as the semiconductor manufacturing industry and the electronic component manufacturing industry, a large amount of fluorine-containing wastewater is discharged due to the large amount of hydrofluoric acid (HF), buffered hydrofluoric acid (NH ₄ F + HF) or PFCs gas handled. Has been. For dilute wastewater with a fluorine concentration of about 10 to 1000 mg / L, technology to recover fluorine as a concentrated solution by separation and concentration technology such as electrodialysis, and technology to recycle fluorine in the collected concentrated solution is required. ing.

  FIG. 1 shows electrodialysis of an electrodialysis apparatus in which fluorine-containing wastewater having a low fluorine concentration is used as raw water and electrodialyzed to obtain fluorine-concentrated water in which fluorine is concentrated and treated water in which fluorine concentration is reduced. An example of the tank is schematically shown, and FIG. 2 schematically shows an example of the entire configuration of the electrodialysis apparatus including the electrodialysis tank shown in FIG.

  As shown in FIG. 1, an anode 12 and a cathode 14 are disposed on both sides of the electrodialysis tank 10, and an anode chamber 16a, a buffer chamber 16b, The fluorine concentration chamber 16c, the desalting chamber 16d, the fluorine concentration chamber 16e, the desalting chamber 16f, the fluorine concentration chamber 16g, and the cathode chamber 16h are partitioned and arranged by ion exchange membranes 18a to 18g. Among these ion exchange membranes 18a to 18g, an ion exchange membrane 18a disposed between the anode chamber 16a and the buffer chamber 16b, an ion exchange membrane 18b disposed between the buffer chamber 16b and the fluorine concentration chamber 16c, The ion exchange membrane 18d disposed between the desalting chamber 16d and the fluorine concentrating chamber 16e and the ion exchange membrane 18f disposed between the desalting chamber 16f and the fluorine concentrating chamber 16g are cation exchange membranes. The ion exchange membranes 18c, 18e, and 18g are anion exchange membranes.

  Then, while applying a predetermined voltage between the anode 12 and the cathode 14, fluorine-containing waste water (raw water) is supplied to the desalting chambers 16d and 16f, and at the same time, as shown in FIG. Anode water in the chamber 16a, cathode water from the cathode water tank (not shown) to the cathode chamber 16h, buffer water from the buffer water tank 22 to the buffer chamber 16b, and further from the fluorine concentrated water tank 24 to the fluorine concentrated chambers 16c, 16e, 16g. Fluorine-concentrated water is circulated through each water.

As a result, fluorine in the fluorine-containing waste water (raw water) supplied to the desalting chambers 16d and 16f is separated as fluorine ions F ⁻ , and the separated fluorine ions F ⁻ are passed through the fluorine concentration chambers 16c and 16e. The fluorine concentration is removed from the raw water, and at the same time the fluorine concentration of the fluorine concentration water is increased. As a result, fluorine-concentrated water in which fluorine is concentrated and treated water in which the fluorine concentration is reduced can be obtained.

  In addition, as shown in FIG. 3, the electrodialysis tank 10a is omitted by omitting the buffer chamber 16b and the ion exchange membrane 18b disposed between the buffer chamber 16b and the fluorine concentration chamber 16c from the electrodialysis tank 10 shown in FIG. It may be configured.

FIG. 4 schematically shows another example of the electrodialysis tank, and FIG. 5 shows an example of the configuration of the electrodialysis apparatus including the electrodialysis tank shown in FIG. This is an example in which raw water contains Ca ²⁺ , Mg ^{2+ that} cause scale generation, and NH ₄ ⁺ that inhibits recycling, and is a configuration in which these substances and fluorine are separately concentrated.

  As shown in FIG. 4, the anode 12 and the cathode 14 are disposed on both sides of the electrodialysis tank 10b, and the anode chamber 26a, the buffer chamber 26b, Fluorine concentration chamber 26c, desalting chamber 26d, alkali concentration chamber 26e, acid supply chamber 26f, bipolar electrode 26g, buffer chamber 26h, fluorine concentration chamber 26i, desalting chamber 26j, alkali concentration chamber 26k, acid supply chamber 26l and cathode The chambers 26m are partitioned and arranged by ion exchange membranes 28a to 28l. Of these ion exchange membranes 28a to 28l, an ion exchange membrane 28a disposed between the anode chamber 26a and the buffer chamber 26b, an ion exchange membrane 28b disposed between the buffer chamber 26b and the fluorine concentration chamber 26c, An ion exchange membrane 28d disposed between the salt chamber 26d and the alkali concentrating chamber 26e, an ion exchange membrane 28g disposed between the bipolar chamber 26g and the buffer chamber 26h, and the buffer chamber 26h and the fluorine concentrating chamber 26i. The ion exchange membrane 28h disposed between them, and the ion exchange membrane 28j disposed between the desalting chamber 26j and the alkali concentration chamber 26k are cation exchange membranes, and other ion exchange membranes 28c, 28e, 28f, 28i, 28k and 28l are anion exchange membranes.

  In this example, while applying a predetermined voltage between the anode 12 and the cathode 14, fluorine-containing waste water (raw water) is supplied to the desalting chambers 26d and 26j, and at the same time, as shown in FIG. Anode water from the anode water tank 20 to the anode chamber 26a and the bipolar chamber 26g, cathode water from the cathode water tank (not shown) to the cathode chamber 26m, buffer water from the buffer water tank 22 to the buffer chambers 26b and 26h, and a fluorine concentrated water tank Fluorine concentrated water is circulated through the fluorine concentration chambers 26c and 26i from 24 respectively. Further, an acid such as HCl is supplied from the acid supply tank 30 to the acid supply chambers 26f and 26l, and alkali concentrated water is supplied from the alkali concentrated water tank 32 to the alkali concentration chambers 26e and 26k and circulated.

Thus, fluorine in the fluorine-containing waste water (raw water) supplied to the desalting chambers 26d and 26j is separated as fluorine ions F ⁻ , and the separated fluorine ions F ⁻ are supplied to the fluorine concentration chambers 26c and 26i. Move to the circulating fluorine concentrated water side to increase the fluorine concentration of the fluorine concentrated water. At the same time, it is separated from fluoride ions as cations M ⁺ such as Ca ²⁺ , Mg ²⁺ and NH ₄ ⁺ contained in fluoride in fluorine-containing waste water (raw water), and the separated cations M ⁺ are separated into alkali concentration chambers. 26e and 26k are moved to the side of the alkali concentrated water to be circulated to increase the alkali concentration of the alkali concentrated water. As a result, fluorine-concentrated water, alkali-concentrated water, and treated water with a reduced fluorine concentration can be obtained.

  As shown in FIG. 6, from the electrodialysis tank 10b shown in FIG. 4, the buffer chambers 26b and 26h, the ion exchange membrane 28b disposed between the buffer chamber 26b and the fluorine concentrating chamber 26c, and the buffer chamber 26h and the fluorine The electrodialysis tank 10c may be configured by omitting the ion exchange membrane 28h disposed between the concentrating chamber 26i.

  Further, as shown in FIG. 7, the acid supply chambers 26f and 26l are omitted from the electrodialysis tank 10b shown in FIG. 4, so that the electrodialysis tank 10d is configured. Further, as shown in FIG. The electrodialysis tank 10e may be configured by omitting the buffer chambers 26b and 26h from the illustrated electrodialysis tank 10d.

  Fluorine is highly corrosive. For this reason, as shown in FIGS. 1 and 2, for example, when an electrodialysis apparatus is applied to the treatment of fluorine-containing waste water, the electrodes 12 and 14 are corroded. For the anode 12 of the electrodialysis tank 10, an electrode (platinum plating electrode) obtained by platinum-plating a titanium material is generally used. When the fluorine concentration in the anode water circulated through the anode chamber where the anode is installed is less than 1 mg-F / L, the platinum plating electrode is not corroded by hydrofluoric acid, and the electrodialysis apparatus continues to operate stably. However, when the fluorine concentration in the anode water exceeds 1 mg-F / L, corrosion of the platinum plating electrode is observed in a very short time, and the platinum plating electrode is gradually consumed, so that the titanium of the base material is dissolved. Advances, and at the same time, the operating voltage of the electrodialysis tank increases. Therefore, there is a demand for an electrode that can withstand fluorine. However, there is no electrode that can be stably used for a long period of time, and when electrodialysis is used for treatment of fluorine-containing wastewater, the electrode can be used in a short time. It was essential to replace the electrode.

  It is known that gold and platinum are the only metals that resist hydrofluoric acid. Gold is a very stable metal with excellent corrosion resistance and low electrical resistance, but is expensive. In order to reduce the amount of gold used as an electrode, there are many pinholes in a thin gold-plated film when trying to use a gold-plated electrode (gold-plated electrode) on a conductive base material. There is a problem that the base material is corroded from there. When the plating film thickness is increased, the number of pinholes decreases, but it does not become zero, and the problem of corrosion of the base material cannot be solved. Moreover, since the amount of gold used increases, it becomes expensive. Further, pure gold plating is too soft and inferior in wear resistance, and has a drawback that it is weak in adhesion to the base material and easily peels off. Furthermore, when the gold plating electrode is used as an anode of an electrodialysis tank, a phenomenon that the electrode surface is consumed by oxygen generated when water is electrolyzed is also observed. For this reason, until now, the gold plating electrode has not been used as an anode of an electrodialysis tank.

  Electroplating base material, especially platinum-plated electrode plated with platinum on titanium metal, (1) very good electrical conductivity, (2) not only neutral electrolytes, but also acidic and alkaline electrolytes It has excellent corrosion resistance, (3) can withstand nascent oxygen, (4) processing by electroplating is the simplest process, and plating with a thickness of 1 to 10 μm is achieved by improving plating technology It has excellent characteristics as an electrode such that the film can be freely plated, and (5) platinum can be peeled off from titanium and can be easily reprocessed. For this reason, although platinum is expensive, platinum-plated electrodes are widely used as universal electrodes.

  However, the platinum plating film has a problem that dendrites are likely to grow and defects in the plating film are likely to occur due to problems such as pinholes with large irregularities and hydrogen storage. When a defect occurs in the plating film, the defect portion is in a state where titanium is exposed. Therefore, when used as an electrode in a highly corrosive hydrofluoric acid environment, corrosion of titanium itself is likely to occur.

  The corrosion of titanium proceeds in the plane direction under the platinum plating film (undercutting corrosion), causing the platinum plating film to fall off by losing the bonding force between the platinum plating film and titanium. Since this undercutting corrosion proceeds at an accelerated rate, the electrode life is shortened in a short time when the electrode starts to deteriorate. For this reason, when a pure platinum plate is used as an anode in a hydrofluoric acid environment, the elution and wear of platinum is very small. There was a problem of not being.

  For this reason, attempts have been made to develop a technology for forming a dense and defect-free plating film for the purpose of extending the life of the electrode in a hydrofluoric acid environment. Not. In addition, there are reports of electrodes having a longer life compared to conventional platinum-plated electrodes. In this case, (1) the electrode manufacturing method is complicated and expensive, and (2) the size and shape of the electrode that can be manufactured. (3) There is a problem that it is far from the life equivalent to that of pure platinum, and the electrodes that are practically used industrially and that are stably used for a long time in a hydrofluoric acid environment are The current situation is that it has not been developed yet.

  Regarding the electrodialysis apparatus for fluorine-containing wastewater, an electrode in which a CVD diamond thin film doped with boron is formed on the surface of a conductive substrate (see Patent Document 1), an electrode chamber, A buffer chamber is provided between the concentration chamber and the concentration chamber in which the hydrofluoric acid is concentrated, so that the concentration of hydrofluoric acid present in the concentration chamber at the electrode chamber is suppressed (see Patent Documents 2 and 3), etc. Has been proposed.

JP 2003-126863 A JP 2003-305475 A JP 2004-174439 A

  However, if the electrode itself is a diamond electrode having high corrosion resistance, the electrode itself is considerably expensive. In addition, even if a buffer chamber is provided between the electrode chamber and the concentration chamber in which hydrofluoric acid is concentrated, the behavior of fluorine in the concentration chamber during the rest or stop of the electrodialyzer becomes a problem, and practical problems are It has not been solved. Hereinafter, the behavior of fluorine in the concentration chamber when the electrodialysis apparatus is stopped or stopped will be described.

For example, as shown in FIGS. 1 and 2, the electrodialysis tank 10 has an anode chamber 16 a in which the anode 12 is installed and a cathode chamber 16 h in which the cathode 14 is installed, and a voltage is applied between the anode 12 and the cathode 14. By applying it, the fluorine in the fluorine-containing waste water (raw water) is moved to the fluorine concentrated water side. During operation, the fluorine ions in the fluorine-enriched water can be stably operated without leaking to the anode chamber 16a and the cathode chamber 16h. However, after the operation is stopped, if the fluorine concentration chambers 16c, 16e, and 16g through which the fluorine-concentrated water is circulated are left in a state where the fluorine concentration is high and left for a long time, the concentration is diffused as shown in FIGS. As described above, the fluorine ions F ⁻ in the fluorine concentration chambers 16 c and 16 e leak into the anode chamber 16 a and corrode the anode 12. The same applies to the cathode side.

Similarly, even in the electrodialysis tank 10b shown in FIG. 4, after the operation is stopped, the fluorine concentration chambers 26c and 26i in which the fluorine concentrated water is circulated and circulated are left for a long time in a state where the fluorine concentration is high. 5, fluorine ions F ⁻ leak to the anode side and corrode the anode 12 as shown in FIG.

  Therefore, at present, an electrode that is inexpensive and can be used stably over a long period of time in a hydrofluoric acid environment has not yet been developed. It is conceivable that the electrodialyzer is operated stably for a long period of time by washing with washing water and reducing the fluorine concentration in each chamber to prevent corrosion of the electrode due to the leakage of fluorine ions.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrodialysis apparatus and an operation method thereof that do not cause corrosion of the electrode throughout an actual operation period without using an expensive electrode. .

  The invention according to claim 1 is an electrodialysis tank in which a plurality of chambers partitioned by an ion exchange membrane are arranged between electrodes and a predetermined liquid is supplied to each chamber to perform electrodialysis of raw water. A liquid supply system for supplying a liquid and at least one of the plurality of chambers is supplied with a fluid having a lower raw water component concentration than the liquid supplied at the time of electrodialysis as washing water to wash the chamber. The electrodialysis apparatus further includes a control unit for controlling the liquid supply system.

  According to a second aspect of the present invention, at least one chamber of an electrodialysis tank that performs electrodialysis of raw water by arranging a plurality of chambers partitioned by an ion exchange membrane between electrodes and supplying a predetermined liquid to each chamber. An operation method of an electrodialysis apparatus, characterized in that a liquid having a lower raw water component concentration than that supplied during electrodialysis is supplied as cleaning water to clean the chamber.

  Thus, by washing at least one chamber of the plurality of chambers constituting the electrodialysis tank with a liquid (washing water) having a raw water component concentration lower than the liquid supplied to the chamber at the time of electrodialysis, The raw water component concentration in the chamber, for example, the fluorine concentration can be lowered to prevent leakage of fluorine ions and the like when the operation is stopped.

The invention according to claim 3 is characterized in that the liquid having a low concentration of raw water components supplied to the chamber as the wash water is a liquid supplied to another chamber during electrodialysis or treated water. The operation method of the electrodialysis apparatus according to claim 2.
Thereby, the liquid used for an electrodialysis apparatus, or treated water can be used effectively, and simplification as an apparatus can be achieved.

The invention according to claim 4 is the operation method of the electrodialyzer according to claim 2 or 3, wherein the cleaning of the chamber with the wash water is performed before or after the operation of the electrodialyzer is stopped. .
Here, before or after stopping the operation of the electrodialyzer, before or after stopping the application of voltage between the anode and the cathode of the electrodialysis tank, or raw water treated by the electrodialyzer Before or after stopping the supply.

The invention according to claim 5 is the method of operating an electrodialysis apparatus according to any one of claims 2 to 4, wherein the raw water is waste water containing fluorine.
Accordingly, wastewater containing fluorine having strong corrosive properties can be treated without using an expensive electrode and without causing electrode corrosion throughout the actual operation period.

  As a result, when fluorine-containing wastewater is treated with an electrodialyzer, the fluorine concentration in the fluorine concentration chamber where the fluorine concentration is the highest is reduced, for example, corrosion of the electrode due to fluorine ion leakage at the time of shutdown or shutdown. Can be prevented.

  According to the present invention, at least one of the plurality of chambers constituting the electrodialysis tank is washed with a liquid (washing water) having a lower raw water component concentration than the liquid supplied to the chamber during electrodialysis. Therefore, the raw water component concentration in the chamber, for example, the fluorine concentration is lowered to prevent corrosion of the electrode due to, for example, leakage of fluorine ions at the time of operation stop or operation stop, and without using an expensive electrode, Operation can be performed stably for a period of time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following examples, raw water is fluorine-containing wastewater having a low fluorine concentration.

In the operation method of the electrodialysis apparatus of the present invention, as shown in FIG. 9, before or after stopping the operation of the electrodialysis apparatus in the middle of the operation of the electrodialysis apparatus from the operating state to the operation standby state, The chamber is washed to reduce the fluorine concentration in the chamber, thereby preventing the electrode from being corroded by the leakage of fluorine ions F ⁻ when the electrodialyzer is in a standby state.

  FIG. 10 shows a simplified configuration of the electrodialysis tank in the electrodialysis apparatus according to the embodiment of the present invention. As shown in FIG. 10, the A chamber 40 partitioned and arranged in the electrodialysis tank by an ion exchange membrane and washed with washing water is connected to the A tank 46 by a supply pipe 42 and a return pipe 44. An inlet side three-way valve 48 is interposed in the supply pipe 42, and an outlet side three-way valve 50 is interposed in the return pipe 44. Here, a configuration having the same function as the three-way valve may be formed by a plurality of two-way valves. The A tank 46 is a tank that stores a liquid 52 that is circulated through the A chamber 40 during electrodialysis. One end of a liquid extraction pipe 54 a is connected to the bottom of the A tank 46, and the other end of the liquid extraction pipe 54 a is connected to the B tank 56.

  In addition, when this A tank 46 is a fluorine concentrated water tank, the internal liquid (fluorine concentrated water) 52 is drawn into the A tank (fluorine concentrated water tank) 46 and led to a fluorine recycling apparatus, or industrial waste treatment. A liquid extraction tube 54b is connected.

  The A tank 46 is connected with a cleaning water supply pipe 58a for supplying cleaning water directly into the tank A. Further, a cleaning water supply pipe 58 b is connected to one inlet port of the inlet side three-way valve 48, and a cleaning water discharge pipe 60 is connected to one outlet port of the outlet side three-way valve 50. The end is connected to the B tank 56. A liquid supply system to the A chamber 40 is configured by these pipes, and this liquid supply system is controlled by a control unit.

  Here, specifically, in the electrodialysis tank 10 shown in FIGS. 1 and 2, the A chamber 40 is any of the anode chamber 16a, the buffer chamber 16b, the fluorine concentration chambers 16c and 16d, and the cathode chamber 16h. In the electrodialysis tank 10b shown in FIGS. 4 and 5, the anode chamber 26a, the buffer chambers 26b and 26h, the fluorine concentration chambers 26c and 26i, the alkali concentration chambers 26e and 26k, the bipolar chamber 26g and one of the acid supply chambers 26f and 26l.

  Specifically, the A tank 46 in the electrodialysis tank 10 shown in FIGS. 1 and 2 is any one of the anode water tank 20, the buffer water tank 22, the fluorine concentrated water tank 24, and the cathode water tank (not shown). In the electrodialysis tank 10b shown in FIGS. 4 and 5, any one of the anode water tank 20, the buffer water tank 22, the fluorine concentrated water tank 24, the cathode water tank, the acid supply tank 30, and the alkali concentrated water tank 32 is provided. There are two tanks. The B tank 56 is a circulation tank or a raw water tank other than the A tank 46 installed in the electrodialysis apparatus.

  The washing water is stored in the A tank 46 and has a lower fluorine concentration than the liquid 52 circulated through the A chamber 40 during electrodialysis. For example, when the A tank 46 is a fluorine concentration tank, washing is performed. As liquid that corresponds to water, the concentration of fluorine is lower than that of concentrated fluorine water, buffer water, anode water, cathode water, alkali concentrated water, acid supply water, treated water, ion-exchanged water (pure water), city water, industrial Water, etc. are mentioned.

  Next, a first cleaning method for the A chamber 40 will be described with reference to FIGS. 11 to 18. In FIG. 11 and FIG. 18, the bold line indicates the flow of the liquid. The same applies to the following examples.

  11 supplies a predetermined liquid to the chambers 16a to 16h of the electrodialysis tank 10 while applying a predetermined voltage between the anode 12 and the cathode 14 of the electrodialysis tank 10 shown in FIGS. 1 and 2, for example. The operation state of the electrodialysis apparatus that separates and concentrates fluorine in fluorine-containing wastewater (raw water) as fluorine ions is shown. At this time, as the circulation pump (not shown) is driven, a liquid (for example, fluorine concentrated water) 52 is passed from the A tank (for example, fluorine concentrated water tank) 46 to the A chamber (for example, fluorine concentrated chamber) 40. Circulate.

  When stopping the operation of the electrodialysis apparatus, for example, the application of voltage between the anode 12 and the cathode 14 of the electrodialysis tank 10 shown in FIGS. The supply of a predetermined liquid to 16a to 16h is stopped. Thereby, as shown in FIG. 12, the flow of the liquid 52 from the A tank 46 to the A chamber 40 is stopped.

  Next, as shown in FIG. 13, for example, when the tank A 46 is a fluorine concentrated water tank, the liquid (fluorine concentrated water) 52 in the tank A (fluorine concentrated water tank) 46 is drained through the liquid extraction pipe 54b. To lead to fluorine recycling equipment or to dispose of industrial waste. When the A tank 46 is a tank other than the fluorine-concentrated water tank, the liquid 52 in the A tank 46 is drained through the liquid extraction pipe 54 a and led to the B tank 56.

  When the inside of the A tank 46 becomes empty, as shown in FIG. 14, the cleaning water 62 is supplied into the A tank 46 from the cleaning water supply pipe 58a. The washing water 62 is a liquid having a lower fluorine concentration than the liquid 52 supplied from the A tank 46 to the A chamber 40 at the time of electrodialysis. For example, when the A tank 46 is a fluorine concentration tank, the washing water 62 includes buffer water, Anode water, cathode water, acid supply water, treated water, ion exchange water (pure water) or the like is used.

  Then, after the supply of the cleaning water is stopped, as shown in FIG. 15, a circulation pump (not shown) is driven to pass the cleaning water 62 in the A tank 46 through the A chamber 40 for circulation. Thereby, the inside of the A chamber 40 is washed with the washing water 62 having a fluorine concentration lower than that of the liquid 52 supplied from the A tank 46 to the A chamber 40 during electrodialysis, and the fluorine concentration in the A chamber 40 is reduced.

After the inside of the A chamber 40 is cleaned with the cleaning liquid 62 for a predetermined time, as shown in FIG. 16, the cleaning liquid 62 in the A tank 46 is extracted through the liquid extraction pipe 54a and drained into the B tank 56.
The steps shown in FIGS. 14 to 16 may be repeated as necessary (repeated cleaning), thereby gradually reducing the fluorine concentration in the A chamber 40 using new cleaning water. Can do.

  Then, as shown in FIG. 17, the cleaning water 62 is supplied again into the A tank 46 through the cleaning water supply pipe 56 a, and the A tank 46 is filled with the cleaning liquid 62. Then, as shown in FIG. 18, in this state, the apparatus waits until the next start of operation of the electrodialyzer, and the A chamber 40 is cleaned with the cleaning liquid 62 as described above, and the fluorine concentration in the A chamber 40 is increased. Therefore, it is possible to prevent the fluorine ions in the A chamber 40 from leaking to other adjacent chambers due to diffusion during this standby time.

Next, a second cleaning method for the A chamber 40 will be described with reference to FIGS.
FIG. 19 is similar to FIG. 11, for example, while applying a predetermined voltage between the anode 12 and the cathode 14 of the electrodialysis tank 10 shown in FIGS. An operation state of an electrodialysis apparatus is shown in which a predetermined liquid is supplied to 16h to separate and concentrate fluorine in fluorine-containing wastewater (raw water) as fluorine ions. At this time, as the circulation pump (not shown) is driven, a liquid (for example, fluorine concentrated water) 52 is passed from the A tank (for example, fluorine concentrated water tank) 46 to the A chamber (for example, fluorine concentrated chamber) 40. Circulate.

  When stopping the operation of the electrodialysis apparatus, for example, the application of voltage between the anode 12 and the cathode 14 of the electrodialysis tank 10 shown in FIGS. The supply of a predetermined liquid to 16a to 16h is stopped. Thereby, as shown in FIG. 20, water flow of the liquid 52 from the A tank 46 to the A chamber 40 is stopped.

  Next, as shown in FIG. 21, the A tank 46 side port of the inlet side three-way valve 48 installed in the supply pipe 42 and the outlet side three-way valve 50 interposed in the return pipe 44 is closed to close the A chamber 40 and the A tank 46. And the cleaning water supply pipe 58b side port of the inlet side three-way valve 48 and the cleaning water discharge pipe 60 side port of the outlet side three way valve 50 are opened.

  In this state, as shown in FIG. 22, the cleaning water is continuously supplied into the A chamber 40 through the cleaning water supply pipe 58b, and the cleaning water that has passed through the A chamber 40 passes through the cleaning water discharge pipe 60 to the tank B. To 56. This washing water is a liquid having a lower fluorine concentration than the liquid 52 stored in the A tank 46 and circulated through the A chamber 40 during electrodialysis as described above. Thus, the inside of the A chamber 40 is washed with washing water having a lower fluorine concentration than the liquid 52 circulated from the A tank 46 to the A chamber 40 during electrodialysis, and the fluorine concentration in the A chamber 40 is reduced.

  After the inside of the A chamber 40 is washed with washing water for a predetermined time, as shown in FIG. 23, the supply of the washing water from the washing water supply pipe 58b is stopped, and then, as shown in FIG. Then, the A tank 46 side port of the inlet side three-way valve 48 and the outlet side three way valve 50 is opened, and the cleaning water supply pipe 58 b side port of the inlet side three way valve 48 and the cleaning water discharge pipe 60 side port of the outlet side three way valve 50 are closed. . Then, as shown in FIG. 25, in this state, the apparatus waits until the next operation start of the electrodialysis apparatus.

  Next, with reference to FIGS. 26 to 37, a cleaning example of the fluorine concentration chamber and the buffer chamber constituting the electrodialysis tank of the electrodialysis apparatus will be described. As shown in FIGS. 26 to 37, the electrodialysis apparatus includes a raw water tank 70 for storing fluorine-containing waste water (raw water) to be treated, an electrodialysis tank 72 for performing electrodialysis of raw water, and a circulation tank. An anode water tank 74, a buffer water tank 76, a fluorine concentrated water tank 78 and a cathode water tank 80, a treated water tank 82 for storing treated water after treatment, and a concentrated water tank 84 for storing fluorine concentrated water having a higher fluorine concentration are provided. The electrodialysis tank 72 includes an anode chamber 86a, a buffer chamber 86b, a fluorine concentration chamber 86c, a desalting chamber 86d, and a cathode chamber 86e, which are partitioned by an ion exchange membrane (not shown). Is provided with an anode, and a cathode is provided in the cathode chamber 86e.

  During operation of the electrodialyzer, the raw water in the raw water tank 70 is applied as shown in FIG. 26 while applying a predetermined voltage between the anode installed in the anode chamber 86a and the cathode installed in the cathode chamber 86e. (Fluorine-containing wastewater) is supplied to the desalting chamber 86d. At the same time, the anode water in the anode water tank 74 is supplied to the anode chamber 86a, the buffer water in the buffer water tank 76 is supplied to the buffer chamber 86b, and the fluorine in the fluorine concentrated water tank 78 is supplied. The concentrated water is circulated through the fluorine concentration chamber 86c. As a result, the fluorine in the fluorine-containing waste water (raw water) supplied to the desalting chamber 86d is separated as fluorine ions, and the separated fluorine ions are circulated through the fluorine concentration chamber 86c for circulation. To remove fluorine from the raw water and at the same time increase the fluorine concentration of the fluorine-enriched water.

  While supplying pure water into the anode water tank 74, a part of the anode water in the anode water tank 74 is transferred to the buffer water tank 76 and a part of the buffer water in the buffer water tank 76 is transferred to the fluorine concentrated water tank 78. Then, a part of the fluorine-concentrated water in the fluorine-concentrated water tank 78 in which the fluorine concentration has been increased is drawn out to the concentrated water tank 84 and used as a resource for recycling in the fluorine-recycling apparatus, or disposed of. In the cathode water tank 80, a part of the cathode water in the cathode water tank 80 is transferred to the raw water tank 70 while supplying pure water to the cathode water tank 80. On the other hand, the treated water that has exited the desalting chamber 86d and has a reduced fluorine concentration is stored in the treated water tank 82 and sent to, for example, a pure water production apparatus, used as scrubber circulating water, or neutralized. It is sent to the treatment tank.

  The fluorine concentration of raw water in the raw water tank 70 is, for example, about 10 to 100 ppm, and the fluorine concentration of treated water in the treated water tank 82 is, for example, several ppm or less. The fluorine concentration of the concentrated fluorine water in the concentrated water tank 84 is, for example, about 10,000 ppm.

  When the operation of the electrodialysis apparatus is stopped, the voltage application between the anode in the anode chamber 86a and the cathode 14 in the cathode chamber 86e is released, and as shown in FIG. Water supply (supply) of a predetermined liquid to each of the chambers 86a to 86e is stopped. Then, immediately after the operation of the electrodialyzer is stopped, washing of the buffer chamber 86b and the fluorine concentration chamber 86c is started.

  First, as shown in FIG. 28, the fluorine concentrated water in the fluorine concentrated water tank 78 is drawn out and discharged to the concentrated water tank 84. The fluorine concentrated water stored in the concentrated water tank 84 is transferred to a fluorine recycling apparatus or discarded. 29, the buffer water in the buffer water tank 76 is transferred into the fluorine-concentrated water tank 78, and further, the anode water in the anode water tank 74 is transferred into the buffer water tank 76 as shown in FIG. . Thereby, the fluorine concentrated water tank 78 is filled with buffer water having a lower fluorine concentration than the fluorine concentrated water circulated through the fluorine concentration chamber 86c when performing electrodialysis, and the buffer water tank 76 is buffered when performing electrodialysis. It is filled with anode water having a lower fluorine concentration than the buffer water circulated through the chamber 86b. In this example, the fluorine concentrating chamber 86c is cleaned using buffer water as cleaning water, and the buffer chamber 86b is cleaned using anode water as cleaning water.

  That is, in the state where the inside of the fluorine-concentrated water tank 78 is filled with buffer water and the inside of the buffer water tank 76 is filled with anode water, as shown in FIG. 31, the buffer water as washing water is supplied to the fluorine concentration chamber 86c as washing water. The anode water is circulated through the buffer chamber 86b. As a result, the inside of the fluorine concentrating chamber 86c is washed with buffer water, and the inside of the buffer chamber 86b is washed with anode water, so that the fluorine concentrations in the fluorine concentrating chamber 86c and the buffer chamber 86b are reduced.

  After finishing the cleaning of the fluorine concentration chamber 86c and the buffer chamber 86b, as shown in FIG. 32, the buffer water used as the cleaning water remaining in the fluorine concentration water tank 78 is transferred to the raw water tank 70, and thereafter, as shown in FIG. As shown, the anode water used as the cleaning water remaining in the buffer water tank 76 is transferred to the fluorine concentrated water tank 78. In this state, as shown in FIG. 34, anodic water as cleaning water is passed through the fluorine concentration chamber 86c and circulated. As a result, the inside of the fluorine concentration chamber 86c is washed again with the anode water, and the fluorine concentration in the fluorine concentration chamber 86c is further reduced.

  Next, as shown in FIG. 35, the anode water used as the cleaning water remaining in the fluorine concentrated water tank 78 is transferred to the raw water tank 70, and the cathode water in the cathode water tank 80 is also transferred to the raw water tank 70. Thereafter, as shown in FIG. 36, the treated water having a fluorine concentration of, for example, several ppm or less in the treated water tank 82 is transferred to the anode water tank 74, the buffer water tank 76, the fluorine concentrated water tank 78, and the cathode water tank 80, respectively. Then, as shown in FIG. 37, in this state, the apparatus waits until the next operation start of the electrodialysis apparatus.

  According to this example, in the fluorine concentration chamber 86c through which the fluorine concentration water having the highest fluorine concentration is circulated during electrodialysis, immediately after the operation is stopped, the buffer water having a fluorine concentration lower than that of the fluorine concentration water, Immediately after the operation is stopped, the inside of the buffer chamber 86b, in which the buffer water is circulated and passed through the electrodialysis, is washed by anodic water having a fluorine concentration lower than that of the buffer water to lower the fluorine concentration in the fluorine concentration chamber 86c. The fluorine concentration in the buffer chamber 86b can be lowered by washing with anode water having a fluorine concentration lower than that of the buffer water. Accordingly, for example, when the operation is stopped or stopped, the electrode is prevented from being corroded by the leakage of fluorine ions, and the operation can be stably performed for a long time without using an expensive electrode.

It is a figure which shows typically the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows typically the electrodialysis apparatus which has an electrodialysis tank shown in FIG. It is a figure which shows typically the other example of an electrodialysis tank. It is a figure which shows typically the other example of an electrodialysis tank. It is a figure which shows typically the electrodialysis apparatus which has an electrodialysis tank shown in FIG. It is a figure which shows typically the other example of an electrodialysis tank. It is a figure which shows typically the other example of an electrodialysis tank. It is a figure which shows typically the other example of an electrodialysis tank. It is a block diagram which shows the operation method of the electrodialysis apparatus of this invention. It is a figure which simplifies and shows the structure in the electrodialysis tank in the electrodialysis apparatus of embodiment of this invention. It is a figure which shows the driving | running state when implementing the 1st washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the operation stop state when implementing the 1st washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the liquid discharge process when implementing the 1st washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the washing | cleaning liquid inflow process when implementing the 1st washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the circulation washing | cleaning process by the washing | cleaning liquid at the time of implementing the 1st washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the washing water discharge process when implementing the 1st washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the washing | cleaning water inflow process when implementing the 1st washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the operation standby state when implementing the 1st washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the driving | running state when implementing the 2nd washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the operation stop state when implementing the 2nd washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the state after valve switching at the time of implementing the 2nd washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the water flow washing | cleaning process at the time of implementing the 2nd washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the state at the time of a water flow stop at the time of implementing the 2nd washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the state after valve switching at the time of implementing the 2nd washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the operation standby state when implementing the 2nd washing | cleaning method of a chamber using the electrodialyzer shown in FIG. It is a figure which shows the driving | running state of the electrodialysis apparatus in the washing | cleaning example of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the operation stop state of the electrodialysis apparatus in the example of washing | cleaning of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the fluorine concentrated water discharge process in the example of washing | cleaning of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the transfer process to the fluorine concentration water tank of the buffer water in the washing | cleaning example of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the transfer process to the buffer water tank of the anode water in the washing | cleaning example of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the washing | cleaning process of the fluorine concentration chamber and the buffer chamber in the example of washing | cleaning of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the fluorine concentration chamber washing water discharge process in the example of washing | cleaning of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the transfer process to the fluorine concentration chamber of the buffer water (anode water) in the example of washing | cleaning of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the washing | cleaning process of the fluorine concentration chamber in the example of washing | cleaning of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the discharge process of the fluorine concentration chamber washing | cleaning water and cathode water in the washing | cleaning example of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the transfer process to each tank of the process water in the washing | cleaning example of the electrodialysis tank of an electrodialysis apparatus. It is a figure which shows the operation standby state in the example of washing | cleaning of the electrodialysis tank of an electrodialysis apparatus.

Explanation of symbols

10 Electrodialysis tank 12 Anode 14 Cathode 40 A chamber 42 Supply pipe 44 Return pipe 46 A tank 48, 50 Three-way valve 52 Liquid 54a, 54b Liquid extraction pipe 56 B tank 58a, 58b Wash water supply pipe 60 Wash water discharge pipe 62 Wash Water 70 Raw water tank 72 Electrodialysis tank 74 Anode water tank 76 Buffer water tank 78 Fluorine concentrated water tank 80 Cathode water tank 82 Treated water tank 84 Concentrated water tank 86a Anode chamber 86b Buffer chamber 86c Fluorine concentration chamber 86d Desalination chamber 86e Cathode chamber

Claims (5)

An electrodialysis tank that arranges a plurality of chambers partitioned by an ion exchange membrane between electrodes and supplies a predetermined liquid to each chamber to perform electrodialysis of raw water,
A liquid supply system for supplying a liquid to each chamber;
Control for controlling the liquid supply system so that at least one of the plurality of chambers supplies a fluid having a raw water component concentration lower than that of the liquid supplied during electrodialysis as washing water to wash the chamber. An electrodialysis apparatus having a section.   A plurality of chambers partitioned by ion exchange membranes are arranged between the electrodes, and a predetermined liquid is supplied to each chamber to supply at least one chamber of an electrodialysis tank for performing electrodialysis of raw water during electrodialysis. An operation method of an electrodialysis apparatus, comprising supplying a liquid having a lower raw water component concentration than the liquid as cleaning water to clean the chamber.   The electrodialysis apparatus according to claim 2, wherein the liquid having a low concentration of raw water components supplied to the chamber as the wash water is a liquid supplied to another chamber during electrodialysis or treated water. Operation method.   4. The method of operating an electrodialysis apparatus according to claim 2, wherein the chamber is washed with water before or after the operation of the electrodialysis apparatus is stopped.   The method of operating an electrodialysis apparatus according to any one of claims 2 to 4, wherein the raw water is wastewater containing fluorine.

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