JP2001058186A - Method and apparatus for making pure water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain highly pure water easily at a low cost by simple equipment by holding stable purity over a long period of time. SOLUTION: In a pure water making apparatus, a cathode chamber 4 having a cathode 3 and an anode chamber 6 having an anode 5 are formed in opposed relationship. Desalting chambers 9 and concn. chambers 10 are successively formed by cation exchange membranes 7 and anion exchange membranes 8 alternately arranged between the cathode chamber 4 and the anode chamber 5. While voltage is applied across the cathode 3 and the anode 5, water to be treated is allowed to flow to the desalting chambers 9 and water to be treated is allowed to flow to the concn. chambers 10 as conc. water. Water to be treated is allowed to flow to the anode chamber 6 as electrode water and the electrode water passed through the anode chamber 6 to become acidic is allowed to flow to the cathode chamber 4. Ions in water to be treated passed through the desalting chambers 9 move to the concn. chambers 10 to make deionized pure water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for producing pure water by electro-regeneration using electrodialysis.

[0002]

2. Description of the Related Art As a conventional method for producing pure water, there is an ion exchange method using an ion exchange resin in which water to be treated is passed through a packed tower filled with an ion exchange resin and the water to be treated is converted into pure water. Are known.

In this ion exchange method, the exchange capacity of the ion exchange resin is saturated with the generation of pure water to be treated, and the exchange capacity of the ion exchange resin having the saturated exchange capacity is regenerated with an acidic or alkaline regenerant. , Ion-exchange resin is used repeatedly. The operation of regenerating the ion exchange resin is complicated, a large amount of acidic and alkaline regenerating waste liquid is discharged, and there is a problem that careful storage and handling of the acidic regenerating agent and the alkaline regenerating agent are required.

In recent years, an electric regeneration type pure water production method has been developed, and a pure water production apparatus 2 used in this electric regeneration type pure water production method has a cathode 3 having a cathode 3 as shown in FIG. A chamber 4, an anode chamber 6 having an anode 5, and a desalination chamber 9 formed by a cation exchange membrane 7 and an anion exchange membrane 8 alternately arranged between the cathode chamber 4 and the anode chamber 6. And a concentrating chamber 10, and the water to be treated is supplied to the cathode chamber 4, the anode chamber 6, and the desalination chamber 9.
And it supplies it to the concentration room 10.

[0005] The desalting chamber 9 is filled with an ion exchanger 11, and the electrolyte contained in the water to be treated is passed through the ion exchanger 11 by applying a voltage between the anode 5 and the cathode 3. The water moves in the direction of the potential, passes through the ion exchange membranes 7 and 8, is concentrated in the concentration chamber 10, and the water to be treated flowing in the desalting chamber 9 is deionized to generate pure water.

As the water to be treated in the pure water producing apparatus 2, permeated water passing through the reverse osmosis membrane of the reverse osmosis membrane apparatus 1 or primary pure water treated by another primary pure water producing apparatus is used. Most of the electrolytes and organic components contained in the water to be treated supplied to the pure water production apparatus 2 are removed in advance, and the load on the pure water production apparatus 2 is reduced to produce high-purity pure water. Like that.

In this method of producing pure water of the electric regeneration type, the ions in the desalting chamber 9 move inside the ion exchanger 11 and the ion exchange capacity is not saturated, so that the regeneration operation of the ion exchanger 11 is unnecessary. There is an advantage that an acidic or alkaline regenerating agent for regenerating the ion exchanger 11 is not required.

[0008]

However, due to the deterioration of the quality of the water to be treated and the deterioration of the pretreatment primary pure water producing apparatus, as shown in FIG. In some cases decreased in purity.

As a result of the study by the inventors, when the water to be treated contains a large amount of hardness components such as calcium, the hardness component is not sufficiently removed only by the treatment of the reverse osmosis membrane device 1 or the primary pure water production device. Due to the deterioration and clogging of the reverse osmosis membrane, the deterioration of the primary pure water production device, etc., the hardness component may remain in the treated water of the pure water production device, or the hardness component may leak to the cathode chamber 4 and the anode chamber 6. .

When the hardness component leaks into the cathode chamber 4, the hardness component tends to be concentrated in the cathode chamber 4, and a part of the electrode water in the cathode chamber 4 becomes alkaline because electrons are supplied from the cathode 3. , The formation and precipitation of calcium carbonate and calcium hydroxide are liable to occur, and they become scales and adhere to the electrode portion of the cathode 3, making it difficult to supply electricity to the cathode 3 and reducing the purity of the treated water. There was found.

Further, the scale adhering to the cathode 3 changes the water flow area in the cathode chamber 4, thereby disrupting the water flow balance between the anode chamber 6 and the cathode chamber 4, and reducing the water flow to the cathode chamber 4. Then, the concentration in the cathode chamber 4 further proceeds, and the generation of scale is amplified. Therefore, a method of removing a hardness component by installing a water softener using a cation exchange resin before or after the reverse osmosis membrane device 1 has been proposed, or Japanese Patent Application Laid-Open No. H10-128338 has been proposed in order to prevent precipitation of scale. As described in the publication, a method has been proposed in which an electrolytic device is installed in a stage preceding the pure water production device 2 to supply acidic water to the pure water production device.

However, the method of removing the hardness component in advance and the method of supplying the acidic water require regeneration of the water softening device and the electrolysis device, which makes the operation complicated, and the soft water device uses salt. The running cost increases, and the pure water producing apparatus 2 cannot be operated during regeneration of the water softening device and the electrolytic device. Therefore, it is necessary to install a plurality of water softening devices and the electrolytic devices and operate them alternately. The cost is high, which is a problem in terms of installation space.

In view of the above problems, the present invention concentrates anions in the electrode water in the anode compartment and concentrates cations in the electrode water in the cathode compartment. Electrode water flowing in the anode compartment is electrolyzed to the anode. It becomes acidic to supply electrons, and part of the electrode water in the cathode chamber becomes alkaline because electrons are supplied from the cathode,
By mixing the electrode water flowing out of the cathode chamber and the anode chamber, the water quality near neutrality was focused on, and the raw water deteriorated easily and at low cost with simple equipment. Another object of the present invention is to provide a pure water production method and a pure water production apparatus capable of maintaining stable purity for a long period of time even if the pretreatment deteriorates.

[0014]

According to a first aspect of the present invention, there is provided a method for producing pure water, comprising a cation exchange membrane and a cathode alternately disposed between a cathode chamber having a cathode and an anode chamber having an anode. A desalting chamber and a concentrating chamber are sequentially formed with the ion-exchange membrane, and while applying a voltage between the cathode and the anode, the water to be treated flows through the desalting chamber and is concentrated in the concentrating chamber. Flowing water, further flowing electrode water into the anode chamber, flowing the electrode water that has become acidic after passing through the anode chamber to the cathode chamber, and ionizing the water to be treated flowing through the desalting chamber. The deionized water is moved to the concentration chamber to produce pure water.

[0015] Then, while applying a voltage between the cathode and the anode, the water to be treated flows into the desalting chamber, whereby ions in the water to be treated are moved to the concentration chamber, and the water to be treated is deionized. Purified water is produced. At this time, even if the electrode water in the cathode chamber becomes alkaline, the electrode water that has become acidic in the anode chamber is supplied to the cathode chamber and neutralized as it passes through the cathode chamber, and the electrode water flows out of the cathode chamber. Is almost neutral, and the cathode compartment can prevent the scale components from being precipitated as calcium hydroxide scale,
The scale can be prevented from adhering to the cathode, and the operation can be continuously performed without reducing the purity of the treated water.

The pure water producing apparatus according to the second aspect of the present invention comprises:
A desalination chamber and a concentrator formed sequentially with a cathode chamber having a cathode, an anode chamber having an anode, and a cation exchange membrane and an anion exchange membrane alternately arranged between the cathode chamber and the anode chamber. Chamber, a water supply system for flowing the water to be treated into the desalting chamber, the concentrated water to the concentrating chamber, and the electrode water to the anode chamber, and the electrode water passing through the anode chamber and becoming acidic. And a water distribution system for flowing deionized water into the cathode chamber, and moving ions in the water to be treated flowing through the demineralization chamber to the concentration chamber to produce deionized pure water.

Then, by flowing the water to be treated into the desalting chamber while applying a voltage between the cathode and the anode, ions in the water to be treated are moved to the concentration chamber, and the water to be treated is subjected to deionization treatment. Purified water is produced. At this time, even if the electrode water in the cathode chamber becomes alkaline, the water in the anode chamber becomes acidic due to the water distribution system that allows the electrode water that has passed through the anode chamber to flow into the cathode chamber. Supplied,
The electrode water is neutralized as it passes through the cathode chamber, and the electrode water flowing out of the cathode chamber is almost neutral, and the cathode chamber can prevent the scale component from being precipitated as calcium hydroxide scale, The scale can be prevented from adhering to the cathode, and the operation can be continuously performed without reducing the purity of the treated water.

The desalting chamber of each of the above-mentioned inventions is filled with an ion exchanger in an appropriate form such as resin or fiber as required.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for producing pure water and an apparatus for producing pure water according to the present invention will be described with reference to FIG.
The same components as those shown in FIG.

The pure water producing apparatus 2 has a cathode chamber 4 having a cathode 3 and flowing electrode water, and an anode chamber 6 having an anode 5 and flowing electrode water. A cation exchange membrane (cation exchange membrane) 7 and an anion exchange membrane (anion exchange membrane) 8 are alternately arranged between the cathode chamber 4 and the anode chamber 6, and the cation exchange membrane is arranged from the cathode chamber 4 side. A desalination chamber 9 filled with an ion exchanger 11 is formed between the anion exchange membrane 7 and the anion exchange membrane 8, and between the anion exchange membrane 8 and the cation exchange membrane 7 adjacent to the desalination chamber 9. A concentration chamber 10 is formed. Further, a desalting chamber 9 and a concentration chamber 10 separated by a cation exchange membrane 7 and an anion exchange membrane 8 are sequentially formed, and an anion exchange membrane 8 and a cation exchange membrane 7 are arranged adjacent to the anode chamber 6. To form a desalting chamber 9.

Each of the desalting chambers 9 is filled with an ion exchanger 11 of an appropriate form such as resin or fiber.

A reverse osmosis membrane device 1 having a reverse osmosis membrane 12 is provided in front of the pure water production device 2, and the permeated water permeating the reverse osmosis membrane device 1 is passed through the respective desalination chambers 9. And a water supply system 13 for supplying each of the desalting chambers 9 to the inlet side and flowing the water to be treated which has passed through the reverse osmosis membrane device 1 to the inlet side of each of the concentrating chambers 10 as concentrated water. A water supply system 14 for flowing each of the concentrating chambers 10 and a water supply system for supplying water to be treated that has passed through the reverse osmosis membrane device 1 to the introduction side of the anode chamber 6 as electrode water to flow the anode chamber 6 15 are provided.

Further, a water distribution system 16 is provided for supplying the electrode water, which has become acidic after passing through the anode chamber 6, to the introduction side of the cathode chamber 4 and flowing the same to the cathode chamber 4.

Further, an outlet of each of the desalting chambers 9 is connected to a water distribution system 17 for treated water generated in pure water, and an outlet of each of the enrichment chambers 10 is connected to a concentrated drainage system 18. Further, an electrode drainage system 19 is connected to the outlet side of the cathode chamber 4.

Next, the operation of this embodiment will be described.

While applying a voltage between the cathode 3 and the anode 5, the permeated water permeated through the reverse osmosis membrane device 1 is supplied to each desalting chamber 9 by the water supply system 13 on the introduction side. Each of the desalting chambers 9 is made to flow, and the water to be treated that has passed through the reverse osmosis membrane device 1 is supplied as concentrated water to the introduction side of each of the concentrating chambers 10 by the water supply system 14 so that each of the concentrating chambers 10 is made to flow. Further, the water to be treated that has passed through the reverse osmosis membrane device 1 is supplied by the water supply system 15 to the introduction side of the anode chamber 6 as electrode water, and the anode chamber 6 is caused to flow.

Further, a water distribution system 16 is provided for supplying the electrode water, which has become acidic after passing through the anode chamber 6, to the introduction side of the cathode chamber 4 and flowing the same to the cathode chamber 4.

Ions in the water to be treated flowing through the desalting chamber 9 filled with the ion exchanger 11 move in the direction of the electric potential in the ion exchanger 11 to become the cation exchange membrane 7 or the anion exchange membrane 8. The water to be treated passes through the condensing chamber 10 and is concentrated. The water to be treated that has passed through the desalting chamber 9 is deionized to be purified water, and is supplied to a water distribution system 17 connected to the outlet of each desalting chamber 9. Treated water generated in pure water is distributed.

Further, anions move through the anion exchange membrane 8 into the anode chamber 6, and cations move through the cation exchange membrane 7 into the cathode chamber 4. The ion reaction in the reaction becomes H ₂ O → 2H ⁺⁺ ／ O ₂ ↑ + 2e ⁻ , the ion reaction in the cathode chamber 4 becomes H ₂ O + e ⁻ → H ₂ ↑ + OH ⁻ , and the anode chamber 6 becomes acidic, The cathode chamber 4 becomes alkaline.

As described above, when the inside of the cathode chamber 4 becomes alkaline, a small amount of scale components such as calcium contained in the permeated water of the reverse osmosis membrane device 1 is precipitated as scale components of calcium hydroxide.

Calcium hydroxide is precipitated in a basic condition of pH 9 or more. The electrode water which has passed through the anode chamber 6 by the water distribution system 16 and is made acidic is supplied to the introduction side of the cathode chamber 4. On the inlet side of the chamber 4, the electrode water is acidic, and is neutralized as it flows through the cathode chamber 4, so that the cathode water 4
Is almost neutral on the outlet side, and calcium hydroxide is not precipitated in the vicinity of neutrality. Therefore, the electrode water is not alkaline in the cathode chamber 4, and the scale component does not precipitate calcium hydroxide in the cathode chamber 4. 3 does not cause scale adhesion.

Therefore, when the scale 3 is attached to the electrode portion of the cathode 3, it is difficult to conduct electricity to the cathode 3, and the quality of the treated water is deteriorated. The water flow area changes, and the water flow balance between the anode chamber 6 and the cathode chamber 4 is lost.
The amount of water flowing to the cathode chamber 4 is reduced, the concentration in the cathode chamber 4 is advanced, and the generation of scale is amplified, so that the purity of the treated water led out from the desalting chamber 9 is not reduced.

The concentrated water discharged from the concentrating chamber 10 and the electrode water discharged from the cathode chamber 4 are supplied to the concentrated drainage system 18 on the outlet side of each of the concentrating chambers 10 and the electrode drainage system 19 on the outlet side of the cathode chamber 4.
Drained from

In the above embodiment, the pure water producing apparatus 2
The cation exchange membrane 7 and the anion exchange membrane 8 are alternately arranged between the cathode chamber 4 and the anode chamber 6 which are arranged to face each other, and the desalting chamber 9 and the concentration chamber 10 are formed alternately. Although described as a configuration, the anode chamber 6, the desalination chamber 9, the concentration chamber 10 and the cathode chamber 4 are formed concentrically, or the anode chamber 6, the desalination chamber 9, the concentration chamber
10 and the cathode chamber 4 can be formed in a spiral shape.

Further, in the above embodiment, the concentrated water discharged from the concentration chamber 10 and the electrode water discharged from the cathode chamber 4 are supplied to the concentrated drainage system 18 and the cathode chamber 4 on the discharge side of each concentration chamber 10.
Although the configuration in which the drain water is drained from the electrode drainage system 19 on the outlet side of the above in a temporary manner has been described, in order to increase the power supply efficiency, the concentrated water extracted from the concentration chamber 10 and the concentrated water extracted from the cathode chamber 4 are extracted. Forming circulation systems 20 and 21 for circulating the electrode water to the water supply systems 14 and 15, supplying part of the liquid to be treated as concentrated water and electrode water from the water supply systems 14 and 15, It is also possible to mix the water and the electrode water derived from the cathode chamber 4 and also to discharge a part of the concentrated water and the electrode water from the concentrated drainage system 18 and the electrode drainage system 19.

Further, in the above embodiment, a reverse osmosis membrane device 1 having a reverse osmosis membrane 12 is provided in front of the pure water production device 2, and the water to be treated that has passed through the reverse osmosis membrane device 1 is subjected to pure water production. Although it is configured to be supplied to the apparatus 2, the primary pure water to be treated that has passed through the primary pure water producing apparatus such as another electrolytic apparatus or an ion exchange apparatus of an ion exchange resin in place of the reverse osmosis membrane apparatus 1 is purified water. It can also be supplied to the manufacturing apparatus 2.

Further, the water to be treated is directly supplied to the pure water producing apparatus 2 without installing a reverse osmosis membrane apparatus 1 or another primary pure water producing apparatus such as an electrolytic apparatus or an ion exchange apparatus. You can also.

[0038]

Next, the present invention will be described in detail with reference to examples and comparative examples.

Experimental Example 1 FIG. 1 (the present invention, in which the outlet side of the anode chamber 6 is connected to the introduction side of the cathode chamber 6) and FIG. 2 (conventional example, the cathode), using city water in Sakai-machi, Ibaraki as raw water for the liquid to be treated. (The introduction sides of the chamber 4 and the anode chamber 6 are connected in parallel.) The deionized pure water was produced by the electric regeneration type pure water producing apparatus 2 shown in FIG.

The reverse osmosis membrane device 1 is AG4040 manufactured by Desaru.
FF type (synthetic polymer composite membrane, NaCl desalting rate 99%) was used. The amount of permeated water of this reverse osmosis membrane device 1 (the amount of water supplied to the pure water production device 2) is 1.13 m ³ / h. In addition, the electric regeneration type pure water production apparatus 2 is an EP made by Electropure.
M-32 type was used.

The pure water produced by the experiment is as shown in Table 1.

[0042]

[Table 1] From this experiment, it was found that in the conventional method (comparative example), the electrode water exhibited alkalinity on the outlet side of the cathode chamber 4,
In the method of the present invention, it was clearly recognized that the electrode water was almost neutral on the outlet side of the cathode chamber 4.

EXPERIMENTAL EXAMPLE 2 FIG. 1 (the present invention: the outlet side of the anode chamber 6 is connected to the inlet side of the cathode chamber 6) and FIG. 2 (conventional example: cathode) (The introduction sides of the chamber 4 and the anode chamber 6 are connected in parallel.) The deionized pure water was produced by the electric regeneration type pure water producing apparatus 2 shown in FIG. Raw water contained trace amounts of calcium and magnesium ions (each 1 mg / L or less).

As the reverse osmosis membrane device 1, a reverse osmosis membrane device having a synthetic polymer composite membrane and a NaCl desalting rate of 99% was used for both the device of the present invention and the comparative example. The amount of permeated water of this reverse osmosis membrane device 1 (the amount of water supplied to the pure water production device 2) is 1.13 m ³ / h or more.
1.2 m ³ / h. In addition, a commercially available apparatus was used for the electric regeneration type pure water production apparatus 2 used in the apparatus of the present invention and the comparative example.

The transition of the purity of the pure water produced by this experiment is as shown in FIG.

From this experiment, it is clear that the purity was lowered with the passage of water passage time in the comparative example. When the apparatus was disassembled and the inside was confirmed, the cathode 3 in the cathode chamber 4 was confirmed.
It was observed that the scale adhered to the electrode surface of. Further, in the apparatus of the present invention, stable operation could be performed without lowering the purity.

[0047]

According to the present invention, even if the quality of the raw water is deteriorated or the pretreatment device is deteriorated, the purity of the purified water is not reduced and the pure water having a stable high purity is not reduced. Can be manufactured continuously and for a long period of time, operation management can be simplified and simplified, operation costs can be reduced, and it is extremely advantageous for production of industrial pure water.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a pure water production apparatus showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional pure water production apparatus.

FIG. 3 is a graph showing a change in purity of pure water produced by the apparatus of the present invention and a conventional apparatus.

[Explanation of symbols]

 3 Cathode 4 Cathode compartment 5 Anode 6 Anode compartment 7 Cation exchange membrane 8 Anion exchange membrane 9 Desalination compartment 10 Concentration compartment 13,14,15 Water supply system 16 Water distribution system

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ito Mamoru 2-22-6 Senzoku, Meguro-ku, Tokyo Aquas Co., Ltd. (72) Inventor Ryugo Umehara 2-22-6 Senzoku, Meguro-ku, Tokyo Aquas Incorporated (72) Inventor Naoki Azuma 3-3 Akasaka, Minato-ku, Tokyo APM Ionics Inc. F-term (reference) 4D006 GA03 GA17 HA41 KA31 KA52 KA57 KB01 KC27 MA03 MA06 MA13 MA14 PA02 PB06 PB27 PC04 4D061 DA03 DB13 EA09 EB01 EB13 EB17 EB20 EB22 FA09

Claims (2)

[Claims] 1. A desalting chamber and a concentrating chamber are sequentially formed by a cation exchange membrane and an anion exchange membrane alternately arranged between a cathode chamber having a cathode and an anode chamber having an anode. While applying a voltage between the cathode and the anode, flowing the water to be treated into the desalting chamber and flowing the concentrated water into the concentrating chamber, further flowing electrode water into the anode chamber, Making the electrode water that has become acidic after passing through the chamber flow into the cathode chamber, and moving ions in the water to be treated flowing through the desalting chamber to the concentration chamber to produce deionized pure water. The method for producing pure water characterized by the following. 2. A cathode chamber having a cathode, an anode chamber having an anode, and a cation exchange membrane and an anion exchange membrane which are alternately arranged between the cathode chamber and the anode chamber. A desalting chamber and a concentrating chamber; a water supply system for flowing the water to be treated into the desalting chamber and flowing the concentrated water to the concentrating chamber; and further allowing the electrode water to flow to the anode chamber. And a water distribution system that causes the electrode water to flow to the cathode chamber, wherein ions in the water to be treated flowing in the desalting chamber are moved to the concentration chamber to produce deionized pure water. Characteristic pure water production equipment.