KR20210044187A - Pure water production system and pure water production method - Google Patents

Abstract

The present invention provides a pure water production system and a pure water production method capable of stably producing high-quality pure water for a long period of time, wherein a reverse osmosis membrane device, an ultraviolet oxidation device, an electric deionization device, and these devices are connected in that order. A pure water production system having a treated water pipe, wherein the electric deionization device comprises alternately arranged cation exchange membranes and anion exchange membranes, concentration chambers and desalination chambers alternately formed between the cation exchange membranes and anion exchange membranes, and the And a pair of electrode chambers disposed outside the cation exchange membrane and the anion exchange membrane, and the treated water pipe is the electric type so as to supply the treated water treated by the ultraviolet oxidation device to at least the desalination chamber of the electric deionization device. In addition to being connected to the deionization device, the pure water production system includes a first bypass pipe for supplying the permeated water of the reverse osmosis membrane device to the electrode chamber of the electric deionization device without passing through the ultraviolet oxidation device. It relates to a pure water production system characterized by.

Description

Pure water production system and pure water production method

The present invention relates to a pure water production system and a pure water production method.

Conventionally, in the production of pure water applied to washing water or medical water used in the manufacturing process of semiconductors or liquid crystal displays, an electric deionization apparatus (EDI) is used. The electric deionization apparatus performs deionization treatment of raw water while electrically regenerating an ion exchanger in the apparatus. For this reason, the electric deionization apparatus does not require regeneration by a chemical like an ion exchange resin tower, and continuous water collection is possible.

The electric deionization device constitutes a desalination chamber by filling an ion exchanger between a cation exchange membrane that permeates only cation (cation) and an anion exchange membrane that only transmits anion (anion). It is a configuration in which a concentration chamber is arranged on the outside. In addition, as viewed from the desalination chamber, an anode is disposed on the side of the anion exchange membrane through an electrode chamber (anode chamber), and a cathode is disposed on the side of the cation exchange membrane through an electrode chamber (cathode chamber). When the water to be treated is passed through the desalination chamber while a direct current voltage is applied between the anode and the cathode, ionic components in the water to be treated are captured by the ion exchanger in the desalination chamber, and hydrogen ions (H ⁺⁾ and hydroxide ions (OH ^- regeneration of the ion exchangers by a) is carried out.

In this way, in the electric deionization apparatus, the water to be treated is deionized and purified by passing through the desalination chamber. On the other hand, water to be treated is also passed through the concentration chamber and the electrode chamber, for example. In the water to be treated passing through the concentration chamber and the electrode chamber, ionic components that have moved from the desalination chamber are concentrated and discharged to the outside of the electric deionizer as concentrated water.

As an ultrapure water production system using this electric deionization device, deionized water is obtained from a reverse osmosis membrane device (RO), an ultraviolet oxidation device (TOC-UV) decomposes the organic matter in the deionized water, and then generated by the ultraviolet oxidation device. There is a system that treats ionic components such as low molecular weight organic acids in an electric deionization device. As a system equipped with such an electric deionization device, a system in which an electric deionization device is installed in two stages, and a part of the treated water in the desalination chamber is passed through the concentration chamber (for example, see Patent Document 1), or an ultraviolet oxidation device In order to prevent the deterioration of the ion exchanger due to the oxidizing component generated in the system, a system in which an ultraviolet sterilization device that irradiates ultraviolet rays of longer wavelengths than the ultraviolet oxidizing device is also proposed between the ultraviolet oxidizing device and the electric deionization device. (See, for example, Patent Document 2).

In recent years, with the ultra-high integration of large-scale integrated circuits (LSIs), there is an increasing demand for additional high quality of ultrapure water for semiconductor manufacturing. In particular, ultrapure water in which trace impurities such as silica and boron in water are significantly reduced in concentration is required. However, in order to improve the removal rate of trace impurities, a conventional method of installing an electric deionization apparatus in two stages has a problem that the water recovery rate and current efficiency in the electric deionization apparatus are lowered. In a device in which the ultraviolet lamp is installed in two stages, there is a problem that the system becomes complicated or the cost increases as the number of devices to be used increases. For this reason, there has been a demand for a method capable of producing high-quality pure water with high efficiency over a long period of time.

Japanese Patent Application Publication No. 2006-51423 Japanese Unexamined Patent Publication No. 2011-45824

The present invention has been made to solve the above problems, and an object of the present invention is to provide a pure water production system and a pure water production method capable of stably producing high-quality pure water for a long period of time.

The pure water production system of the present invention is a pure water production system comprising a reverse osmosis membrane device, an ultraviolet oxidation device, an electric deionization device, and a treated water pipe connecting these devices in that order from an upstream side. Is a cation exchange membrane and anion exchange membrane alternately disposed, a concentration chamber and a desalination chamber alternately formed between the cation exchange membrane and the anion exchange membrane, and a pair of electrodes disposed outside the cation exchange membrane and the anion exchange membrane A chamber is provided, and the treated water pipe is connected to the electric deionization device to supply the treated water treated by the ultraviolet oxidizing device to at least the desalination chamber of the electric deionization device, and the pure water production system includes the reverse osmosis membrane. And a first bypass tube for supplying the permeated water of the device to the electrode chamber of the electric deionization device without passing through the ultraviolet oxidizing device.

It is preferable that the pure water production system of the present invention further includes a second bypass pipe for supplying the permeated water from the reverse osmosis membrane device to the concentration chamber of the electric deionization device without passing through the ultraviolet oxidation device.

In the pure water production system of the present invention, the electric deionization apparatus has a common inlet nozzle leading to the concentration chamber and the electrode chamber of the electric deionization apparatus, and the first bypass pipe and the second bypass pipe are all the It is preferably connected to a common inlet nozzle.

In the pure water production system of the present invention, the electric deionization apparatus has a concentration chamber inlet nozzle leading to the concentration chamber and an electrode chamber inlet nozzle leading to the electrode chamber of the electric deionization apparatus, and the first bypass pipe is the electrode chamber. It is preferable that it is connected to an inlet nozzle, and the second bypass pipe is connected to an inlet nozzle of the concentration chamber.

In the pure water production system of the present invention, it is preferable to have an ion exchanger in the concentration chamber and the electrode chamber.

In the pure water production system of the present invention, it is preferable that the hydrogen peroxide concentration in the treated water treated by the ultraviolet oxidation device is 100 µg/L or less.

The pure water production method of the present invention is a pure water production method in which raw water is sequentially treated in a reverse osmosis membrane device, an ultraviolet oxidation device, and an electric deionization device, wherein the electric deionization device comprises an alternating cation exchange membrane and an anion. An exchange membrane, a concentration chamber and a desalination chamber alternately formed between the cation exchange membrane and the anion exchange membrane, and a pair of electrode chambers disposed outside the cation exchange membrane and the anion exchange membrane. The treated water is supplied to at least a desalination chamber of the electric deionization apparatus, and the permeated water of the reverse osmosis membrane apparatus is supplied to the electrode chamber of the electric deionization apparatus without passing through the ultraviolet oxidizing apparatus. .

In the pure water production method of the present invention, it is preferable to supply the permeated water from the reverse osmosis membrane device to the concentration chamber of the electric deionization device without passing through the ultraviolet oxidation device.

In the pure water production method of the present invention, it is preferable that the hydrogen peroxide concentration in the treated water treated by the ultraviolet oxidizing apparatus is 100 µg/L or less.

According to the pure water production system and pure water production method of the present invention, high-quality pure water can be stably produced for a long period of time.

1 is a block diagram schematically showing an example of a pure water production system according to an embodiment.
FIG. 2A is a diagram schematically showing an example of an electric deionization apparatus used in the pure water production system shown in FIG. 1.
FIG. 2B is a diagram schematically showing another example of an electric deionization apparatus used in the pure water production system shown in FIG. 1.
3 is a block diagram schematically showing another example of the pure water production system of the embodiment.
4 is a block diagram schematically showing another example of the pure water production system of the embodiment.
5 is a block diagram schematically showing a pure water production system used in Examples.

Hereinafter, embodiments will be described in detail with reference to the drawings. In addition, the present invention is not limited to these embodiments, and these embodiments can be changed or modified without departing from the spirit and scope of the present invention. In addition, in the following plurality of drawings, the same components are denoted by the same reference numerals, and description of overlapping operations is omitted.

The pure water production system 1 of the embodiment shown in FIG. 1 includes a reverse osmosis membrane device 10, an ultraviolet oxidation device (TOC-UV) 11, an electric deionization device (EDI) 12, and these devices. It is provided with a treated water pipe 133 which connects in that order from the upstream side. The pure water production system 1 is a system that processes water to be treated supplied from the treatment water supply unit 20 to produce pure water, and supplies the obtained pure water to a use point (POU) 14.

In the pure water production system 1, the treated water pipe 133 includes a first treated water pipe 133a for supplying water to be treated from the treatment water supply unit 20 to the reverse osmosis membrane device 10, and a reverse osmosis membrane device. A second treatment water pipe 133b for supplying the permeated water of (10) to the ultraviolet oxidizing device 11, and a third treatment for supplying the treated water treated in the ultraviolet oxidizing device 11 to the electric deionization device 12 It comprises a water pipe 133c and a fourth treated water pipe 133d for supplying the permeated water from the electric deionization device 12 to the youth point 14, which is a place where pure water is used.

The pure water production system 1 diverges from the second treated water pipe 133b supplying the permeated water from the reverse osmosis membrane device 10 to the ultraviolet oxidation device 11, and converts the permeated water from the reverse osmosis membrane device 10 into an electrical system. It has a first bypass pipe 131 supplied to the deionization device 12. A discharge pipe 135 for discharging concentrated water is connected to the reverse osmosis membrane device 10.

As exemplified below, the electric deionization apparatus 12 has a cation exchange membrane and an anion exchange membrane alternately arranged, and a concentration chamber and a desalination chamber alternately formed between these cation exchange membranes and anion exchange membranes. Further, the electric deionization device 12 includes a cation exchange membrane and a pair of electrode chambers disposed outside the anion exchange membrane.

In the pure water production system 1, a third treated water pipe 133c and a first bypass pipe 131 are connected to the electric deionization device 12 as a water supply pipe. The treated water treated by the ultraviolet oxidizing device 11 supplied to the electric deionization device 12 through the third treated water pipe 133c from the ultraviolet oxidizing device 11 is transferred to at least the desalination chamber of the electric deionizing device 12. Is supplied. In addition, in the pure water production system 1, the permeated water of the reverse osmosis membrane device 10 supplied from the reverse osmosis membrane device 10 to the electric deionization device 12 through the first bypass pipe 131 is It is supplied to the electrode chamber of the electric deionization apparatus 12. Further, a fourth treated water pipe 133d for discharging permeated water, which is deionized water, and a concentrated water discharge pipe 136 for discharging concentrated water are connected to the electric deionizer 12 as a drain pipe.

2A and 2B schematically show an example and another example of the electric deionization apparatus 12 used in the pure water production system 1, respectively. 2A shows an example of the electric deionization device 12 in the case where the treated water treated by the ultraviolet oxidation device 11 is supplied to the desalination chamber and the concentration chamber, and the permeated water from the reverse osmosis membrane device 10 is supplied to the electrode chamber. Show. 2B shows an example of the electric deionization device 12 in the case where the treated water treated by the ultraviolet oxidation device 11 is supplied to the desalination chamber and the permeated water from the reverse osmosis membrane device 10 is supplied to the electrode chamber and the concentration chamber. . In addition, in the electric deionization apparatus 12, the direction of water passage of the desalination chamber, the concentration chamber, and the electrode chamber is not limited to the directions of Figs. 2A and 2B. For example, the water passing direction of the desalination chamber and the water passing direction of the concentration chamber and the electrode chamber may be reversed.

The electric deionization apparatus 12 shown in FIG. 2A has a cation exchange membrane 21 and an anion exchange membrane 22 arranged alternately, and is concentrated between the cation exchange membrane 21 and the anion exchange membrane 22. The chamber 23 and the desalination chamber 24 are formed alternately. Further, a pair of electrode chambers comprising an anode chamber 25a and a cathode chamber 25b are disposed outside the cation exchange membrane 21 and the anion exchange membrane 22. In addition, the electric deionization apparatus 12 includes an anode 26a adjacent to the anode chamber 25a and a cathode 26b adjacent to the cathode chamber 25b, and the anode 26a and the cathode 26b (hereinafter , Also referred to as "electrodes 26a, 26b") are connected to a power supply 27 for applying a DC voltage.

The electric deionization device 12 shown in FIG. 2A is a concentration that supplies treated water treated by the ultraviolet oxidation device 11 supplied from the third treated water pipe 133c to the concentration chamber 23 and the desalination chamber 24, respectively. It has a seal water supply pipe 123 and a desalination chamber water supply pipe 124. In addition, the permeated water of the reverse osmosis membrane device 10 supplied from the first bypass pipe 131 is referred to as the anode chamber 25a and the cathode chamber 25b (hereinafter also referred to as ``electrode chambers 25a, 25b''). ) Has an electrode chamber water supply pipe (125).

The electric deionization apparatus 12 shown in FIG. 2A has a desalination chamber drain pipe 224 for transferring deionized water (permeated water) deionized in the desalination chamber 24 to the fourth treated water pipe 133d. In addition, it has a concentration chamber drain pipe 223 and an electrode chamber drain pipe 225 for transferring the concentrated water in which the ionic component is discharged from the concentration chamber 23 and the electrode chambers 25a and 25b to the concentrated water discharge pipe 136. .

The electric deionization apparatus 12 shown in FIG. 2B is of the same configuration as the electric deionization apparatus 12 shown in FIG. 2A except that the connection portion on the upstream side of the concentration chamber water supply pipe 123 is the first bypass pipe 131. to be.

As described above, in the pure water production system 1, after the permeated water of the reverse osmosis membrane device 10 is treated in the ultraviolet oxidizing device 11, the electric deionization device 12 is passed through the third treated water pipe 133c. In addition to supplying at least to the desalination chamber 24, the permeated water of the reverse osmosis membrane device 10 is bypassed by the ultraviolet oxidation device 11, and the electric deionization device 12 is passed through the first bypass pipe 131. Is supplied to at least the electrode chambers 25a and 25b. The treated water treated by the ultraviolet oxidizing device 11 may be supplied to the concentration chamber 23 or the permeated water of the reverse osmosis membrane device 10 may be supplied. However, when the concentration chamber 23 is filled with an ion exchanger, it is preferable that the permeated water from the reverse osmosis membrane device 10 is supplied.

With the configuration described above, in the pure water production system of the embodiment, compared with the conventional pure water production system, the following effects are obtained, for example.

In the ultraviolet oxidizing apparatus, when excessive ultraviolet irradiation is performed, OH radicals that do not contribute to the oxidation decomposition of organic substances react with each other to generate hydrogen peroxide. The generated hydrogen peroxide may deteriorate an electrode or an ion exchanger of a downstream electric deionization device. For example, in a conventional pure water production system in which the treated water from an ultraviolet oxidation device is supplied to the desalination chamber, the electrode chamber, and the concentration chamber of the electric deionizer, ultraviolet oxidation is performed in the electrode chamber while a voltage is applied to the electric deionizer. Hydrogen peroxide-containing water is supplied as treatment water for the device. As a result, the corrosion of the electrode due to hydrogen peroxide is promoted by the energy of the voltage, and it is easy to cause deterioration of the water quality of the permeated water of the electric deionization apparatus discharged from the desalination chamber.

In addition, when the concentration chamber is filled with an ion exchanger, deterioration of the ion exchanger is also promoted, and the water quality of the permeated water of the electric deionization apparatus is liable to deteriorate. In order to improve the removal rate of trace impurities such as silica and boron in the electric deionization device, a voltage near the permissible upper limit may be applied, but in this case, in particular, penetration due to the progress of corrosion of the electrode or ion exchanger. It is thought that the deterioration of the water quality of the water is more likely to proceed.

In contrast, in the pure water production system 1 of the embodiment, the electrode chambers 25a and 25b, while supplying the treated water treated by the ultraviolet oxidation device 11 to at least the desalination chamber 24 of the electric deionization device 12, Alternatively, the permeated water from the reverse osmosis membrane device 10 that has not passed through the ultraviolet oxidation device 11 is introduced into the electrode chambers 25a and 25b and the concentration chamber 23. According to this, for example, the pipe in a conventional pure water production system that has supplied the permeated water from the reverse osmosis membrane device 10 to the desalination chamber, electrode chamber, and concentration chamber of the electric deionization device via an ultraviolet oxidation device. And only by changing the connection point, it is possible to suppress adverse effects on the electric deionization apparatus by hydrogen peroxide generated in the ultraviolet oxidizing apparatus without increasing the number of treatment apparatuses.

In addition, in the conventional method, in order to prevent the progress of corrosion of the electrode or ion exchanger described above, water was sometimes supplied to the electric deionization apparatus in a secondary pure water system disposed immediately before the use point. In the pure water production system 1, this is also not necessary. In addition, in the pure water production system 1, the permeated water of the reverse osmosis membrane device 10 is formed in the electrode chambers 25a and 25b of the electric deionization device 12, or the electrode chambers 25a and 25b and the concentration chamber 23. Since they are supplied to both, the hardness scale in the electrode chambers 25a and 25b, or the electrode chambers 25a and 25b and the concentration chamber 23 is less likely to occur, and boron or boron in the treated water of the electric deionizer 12 The deterioration of the silica water quality is also alleviated.

The pure water production system of the embodiment may have a reverse osmosis membrane device, an ultraviolet oxidation device, and an electric deionization device, as well as other water treatment devices other than these, if necessary. Examples of such other water treatment devices include a degassing membrane device, a vacuum degassing device, an ion exchange resin tower, a hardness removal device (softener), an activated carbon packed tower, a coagulation and precipitation tank, a filtration device, and the like. It is preferably used. When the pure water production system of the embodiment has other water treatment devices, the placement point may be the front end of the reverse osmosis membrane device, between the essential water treatment devices, or the rear end of the electric deionization device.

The pure water production system 1A of the embodiment shown in FIG. 3 is an example in which a degassing membrane device is provided at the rear end of the electric deionization device as other water treatment devices. The pure water production system 1A shown in FIG. 3 comprises a reverse osmosis membrane device 10, an ultraviolet oxidation device 11, an electric deionization device 12A, a degassing membrane device (MGD) 13, and these devices. A treated water pipe 133 connected in that order from the upstream side is provided. Specifically, the reverse osmosis membrane device 10, the ultraviolet oxidation device 11, the electric deionization device 12A, and the degassing membrane device 13 are formed by the second treated water pipes 133b to the fourth treated water pipes 133d. It is connected. The water to be treated is supplied to the reverse osmosis membrane device 10 through the first treated water pipe 133a. The permeated water from the degassing membrane device 13 is delivered to a youth point (POU) 14 that is a place where pure water is used by the fifth treated water pipe 133e.

The pure water production system 1A includes a first bypass pipe 131 and a second bypass pipe 132 branching from the second treated water pipe 133b and extending to the electric deionization apparatus 12A.

The electric deionization apparatus 12A can be, for example, an electric deionization apparatus having the same configuration as shown in Fig. 2B except for the connection point of the condensation chamber water supply pipe 123. The electric deionization apparatus 12A includes a concentration chamber inlet nozzle 23c leading to the concentration chamber 23 inside the electric deionization apparatus, a desalination chamber inlet nozzle 24c leading to the desalination chamber 24, and an electrode chamber 25a. , And an electrode chamber inlet nozzle 25c that leads to 25b).

In the pure water production system 1A shown in FIG. 3, the third treated water pipe 133c is connected to the desalination chamber inlet nozzle 24c of the electric deionization device 12A, and the reverse osmosis membrane device 10, The treated water sequentially treated by the ultraviolet oxidation device 11 is supplied to the desalination chamber 24 of the electric deionization device 12A.

The first bypass pipe 131 provided branching from the second treated water pipe 133b is connected to the electrode chamber inlet nozzle 25c of the electric deionization apparatus 12A. Further, the second bypass pipe 132 provided branching from the second treated water pipe 133b is connected to the concentration chamber inlet nozzle 23c of the electric deionization apparatus 12A. The first bypass pipe 131 supplies the permeated water of the reverse osmosis membrane device 10 to the electrode chambers 25a and 25b of the electric deionization device 12A without passing through the ultraviolet oxidation device 11. The second bypass pipe 132 supplies the permeated water of the reverse osmosis membrane device 10 to the concentration chamber 23 of the electric deionization device 12A without passing through the ultraviolet oxidation device 11.

In addition, in the pure water production system 1A shown in Fig. 3, instead of branching the second bypass pipe 132 from the second treated water pipe 133b, it is also possible to branch from the third treated water pipe 133c. Do. In this case, the treated water treated by the ultraviolet oxidation device 11 is supplied to the concentration chamber 23 of the electric deionization device 12A.

In the pure water production system 1A shown in Fig. 3, an example in which the electric deionization apparatus 12A having an electrode chamber inlet nozzle 25c and a concentration chamber inlet nozzle 23c independently of each other is used has been described. In the pure water production system of the embodiment, for example, an electric deionization apparatus having a common inlet nozzle serving as an electrode chamber inlet nozzle and a concentration chamber inlet nozzle may be used.

The pure water production system 1B shown in Fig. 4 is a pure water production system having the same configuration as the pure water production system 1A shown in Fig. 3 except that the electric deionization device 12A is replaced with the electric deionization device 12B. The electric deionization apparatus 12B is the same as the electric deionization apparatus 12A except that the electrode chamber inlet nozzle 25c and the concentration chamber inlet nozzle 23c are replaced by a common inlet nozzle 31c serving as these two nozzles. Have a composition. In the pure water production system 1B, both the first bypass pipe 131 and the second bypass pipe 132 are connected to the common inlet nozzle 31c of the electric deionization apparatus 12B.

In the electric deionization device 12B, the treated water treated by the ultraviolet oxidizing device 11 is supplied to the desalination chamber 24, and the permeated water of the reverse osmosis membrane device 10 is applied to the electrode chambers 25a, 25b and the concentration chamber 23. ).

In addition, in the pure water production system 1B shown in FIG. 4, the second bypass pipe 132 may not be disposed, and the first bypass pipe 131 may also serve as a second bypass pipe.

Next, the pure water production method of the embodiment will be described by taking the pure water production method using the pure water production system 1A shown in FIG. 3 as an example. In addition, a reverse osmosis membrane device, an ultraviolet oxidation device, and an electric deionization device used in the pure water production system of the embodiment will be described in detail.

The water to be treated to be treated in the pure water production system 1A is, for example, raw water or raw water pretreated by a pretreatment unit. Raw water is pretreated by a pretreatment unit as necessary and supplied to the reverse osmosis membrane device 10. As raw water, tap water, well water, ground water, industrial water, and semiconductor manufacturing plants are used, and water (recovered water) that has been recovered and pretreated is used. The pretreatment unit removes suspended substances in raw water to generate pretreatment water. The pretreatment unit is configured by appropriately selecting, for example, a sand filtration device for removing suspended substances in raw water, a fine filtration device, and the like, and further includes a heat exchanger or the like for controlling the temperature of the pretreated water as necessary. In addition, depending on the quality of the raw water, the pretreatment unit may be omitted.

In the reverse osmosis membrane device 10, the water to be treated is filtered through the reverse osmosis membrane to remove salts, ionic organic substances, colloidal organic substances, and the like in the water to be treated. The reverse osmosis membrane of the reverse osmosis membrane device 10 includes, for example, a cellulose triacetate-based asymmetric membrane, a polyamide-based, polyvinyl alcohol-based, or polysulfone-based composite membrane. The membrane shape is a sheet flat membrane, a spiral membrane, a tubular membrane, a hollow fiber membrane, or the like, but is not limited thereto. Especially, it is preferable that it is a polyamide-based composite film, and it is more preferable that it is a crosslinked wholly aromatic polyamide-based composite film from the viewpoint of a high blocking rate. It is preferable that the film shape is a spiral film.

It is preferable that the reverse osmosis membrane device 10 has a desalination rate of 96 to 99.8%. Desalination rate is 25°C, pH=7, water supply with a NaCl concentration of 0.2% by mass has a water recovery rate of 15%, and the water supply pressure is at standard pressure (e.g., 1.5 MPa for a low pressure reverse osmosis membrane device, and 0.75 for an ultra low pressure reverse osmosis membrane device) MPa) can be measured as the removal rate of sodium ions when water is passed through the reverse osmosis membrane. The recovery rate of the reverse osmosis membrane device 10 is preferably 60 to 98%, and more preferably 80 to 95%, from the viewpoint of efficiently removing salts and ionic organic substances.

The reverse osmosis membrane device 10 may be any of an ultra-low pressure type, a low pressure type, and a high pressure type reverse osmosis membrane device, and from the viewpoint of the production efficiency of ultrapure water, it is preferable that it is an ultra low pressure type or a low pressure type reverse osmosis membrane device. In addition, it is preferable that a feed water pump is provided at the front end of the reverse osmosis membrane device 10 to supply the reverse osmosis membrane device 10 by pressurizing the water to be treated at a predetermined pressure. In addition, a scale inhibitor, a disinfectant, a pH adjuster, or the like may be added to the water supply of the reverse osmosis membrane device 10 as necessary.

Here, the ultra-low pressure reverse osmosis membrane has an operating pressure of 0.4 MPa to 0.8 MPa, preferably 0.6 MPa to 0.7 MPa. The low-pressure reverse osmosis membrane has an operating pressure of more than 0.8 MPa and less than 2.5 MPa, preferably 1 MPa to 1.6 MPa. The high-pressure reverse osmosis membrane has an operating pressure of more than 2 MPa and not more than 8 MPa, preferably more than 5 MPa and not more than 6 MPa. In addition, the ultra-low pressure type, low pressure type, and high pressure type are classified by the design pressure (standard pressure) at the time of manufacture of each reverse osmosis membrane, but in reality, the operation may be operated at a pressure outside the above range.

The reverse osmosis membrane device 10 may be constituted by a two-stage reverse osmosis membrane device in which two reverse osmosis membrane devices are connected in series. In this case, from the viewpoint of efficiently removing salts and ionic organic substances, the water recovery rate is preferably 60 to 98%, and more preferably 80 to 95% in the first stage reverse osmosis membrane device. In the second stage reverse osmosis membrane device, 80 to 95% is preferable, and 85 to 95% is more preferable.

Commercially available products of the reverse osmosis membrane device 10 include TM820K-400, TM720-400, TM720D-400, SUL-G20 manufactured by Toray, BW30-400, BW30-400FR manufactured by DOW, CPA5 manufactured by Nitto Denko, CPA5-LD or the like can be used.

The permeated water of the reverse osmosis membrane device 10 is then introduced into the ultraviolet oxidizing device 11. The ultraviolet oxidation device 11 irradiates ultraviolet rays to the permeated water of the reverse osmosis membrane device 10 to decompose and remove organic substances (TOC) in water. The ultraviolet oxidizing device 11 is, for example, a device that has an ultraviolet lamp and generates ultraviolet rays with a wavelength of around 185 nm. The ultraviolet oxidizing device 11 may further generate ultraviolet rays in the vicinity of a wavelength of 254 nm. When ultraviolet rays are irradiated to water in the ultraviolet oxidation device 11, the ultraviolet rays decompose water to generate OH radicals, and these OH radicals oxidize and decompose organic substances in water.

In the ultraviolet oxidation device 11, when excessive ultraviolet irradiation is performed, OH radicals that do not contribute to the oxidation decomposition of organic substances react with each other to generate hydrogen peroxide. The generated hydrogen peroxide may deteriorate the electrodes 26a and 26b and the ion exchanger of the downstream electric deionization device 12A. In order to reduce hydrogen peroxide flowing out of the ultraviolet oxidation device 11 and to suppress deterioration of the electrodes 26a and 26b and the ion exchanger of the downstream electric deionization device 12A, the ultraviolet oxidation device 11 It is preferable that the ultraviolet irradiation amount is 0.02 to 0.5 kWh/m 3. The concentration of hydrogen peroxide in the treated water treated by the ultraviolet oxidation device 11 is preferably 100 µg/L or less, and more preferably about 10 µg/L to 40 µg/L.

The treated water of the ultraviolet oxidizing apparatus 11 is supplied into the desalination chamber 24 from the desalination chamber inlet nozzle 24c of the electric deionization apparatus 12A through the third treated water pipe 133c. In the concentration chamber 23 and the electrode chambers 25a and 25b of the electric deionization apparatus 12A, the reverse osmosis membrane apparatus 10 is formed through the second bypass pipe 132 and the first bypass pipe 131, respectively. Permeate water is supplied.

In addition, in the pure water production system 1A shown in Fig. 3 using the electric deionization device 12A, instead of branching the second bypass pipe 132 from the second treated water pipe 133b, the third treatment By branching from the water pipe 133c, the treated water of the ultraviolet oxidation device 11 is transferred to the desalination chamber 24 and the concentration chamber 23 of the electric deionization device 12A, and the permeated water from the reverse osmosis membrane device 10 is transferred. It may be supplied to the electrode chambers 25a and 25b. As described above, in the pure water production method of the embodiment, the treated water of the ultraviolet oxidation device is supplied to at least the desalination chamber of the electric deionization device, and the permeated water of the reverse osmosis membrane device is supplied to at least the electrode chamber of the electric deionization device. will be.

The configuration of the electric deionization device 12A is as described above. In the electric deionization apparatus 12A, the desalination chamber 24 is filled with an ion exchanger. The inside of the concentration chamber 23 and the electrode chambers 25a and 25b may be hollow, or may be filled with an ion exchanger, activated carbon, or an electric conductor made of metal.

At this time, the amount of water supplied into the desalination chamber 24 of the electric deionization apparatus 12A and the total amount of water supplied into the concentration chamber 23 of the electric deionization apparatus 12A and the electrode chambers 25a and 25b are The ratio is a value of the ratio represented by (water supplied to the desalination chamber 24)/(the sum of the water supplied into the condensation chamber 23 and the electrode chambers 25a and 25b), and is preferably 6 to 20. Thereby, it becomes easy to improve the effect of suppressing the deterioration of the electric deionization apparatus 12A and the effect of improving the quality of treated water.

In the electric deionization apparatus 12A, the ion exchange membrane disposed on the anode 26a side in contact with the desalination chamber 24 is an anion exchange membrane 22, and is disposed on the cathode 26b side in contact with the desalination chamber 24 The ion exchange membrane to be used is a cation exchange membrane (21). Further, the electric deionization device 12A may be configured such that a plurality of cells are arranged in parallel by having a plurality of desalination chambers 24 and concentration chambers 23 alternately between the anode 26a and the cathode 26b. .

As the cation exchange membrane 21 and the anion exchange membrane 22, there are a heterogeneous membrane, a semi-homogeneous membrane, and a homogeneous membrane in the structure of the membrane. The homogeneous membrane is the aspect of removal efficiency of ionic components and resistance in electric deionization equipment It is preferable from the viewpoint of suppressing the increase.

As the ion exchanger to be filled in the desalination chamber 24, an ion exchanger obtained by mixing a cation exchange resin and an anion exchange resin may be used. The mixing ratio of the cation-exchange resin and the anion-exchange resin is a volume ratio of 20 to 80% of the anion-exchange resin in terms of removal efficiency of ionic components, and in addition, suppression of increase in resistance in the electric deionization device 12A. It is preferable in terms of. As the ion exchanger, it is also possible to use an ion exchanger in which a cation exchange resin and an anion exchange resin are stacked in the flow path direction. The electrodes (anode 26a and cathode 26b) are made of, for example, a metal material coated with a platinum group element or a platinum group element, and the cathode is made of stainless steel.

In the electric deionization apparatus 12A, it is preferable that the concentration chamber 23 or the electrode chambers 25a and 25b are filled with an ion exchange resin as an ion exchanger. When the concentration chamber 23 or the electrode chambers 25a, 25b are filled with an ion exchange resin, if the method of the present invention is used, the ion exchange resin in the concentration chamber 23 or the electrode chambers 25a, 25b is deteriorated. Because is suppressed, deterioration of the electric deionization apparatus 12A is suppressed, and high-quality treated water can be continuously obtained. In addition, if the ion exchange resin is filled in either the concentration chamber 23 or the electrode chambers 25a, 25b, the effect of the present invention is remarkably obtained, and both the concentration chamber 23 and the electrode chambers 25a, 25b If it is filled in, the effect of the present invention is more remarkably obtained.

In addition, as in the electric deionization device 12 shown in Fig. 2A, when the permeated water of the reverse osmosis membrane device 10 is supplied only to the electrode chambers 25a, 25b, ion exchange resin is supplied to the electrode chambers 25a, 25b. When filled, the effect of the present invention is remarkable.

In the electric deionization apparatus 12A, water to be treated is supplied from one end of the desalination chamber 24 and flows out from the tartan of the desalination chamber 24. In this process, ionic components in the water to be treated are adsorbed to the ion exchanger in the desalination chamber 24. Further, at this time, a rectified direct current is supplied between the anode 26a and the cathode 26b. The current flows in a direction orthogonal to the flow of the water to be treated in the desalination chamber 24. Water is dissociated into hydrogen ions and hydroxide ions by this electric current, and the dissociated hydrogen ions and hydroxide ions are exchanged with ionic components adsorbed on the ion exchanger, respectively. The exchanged ionic component moves to the concentration chamber 23, the anode chamber 25a, and the cathode chamber 25b, and flows out through the concentrated water discharge pipe 136 from the electric deionization device 12A through these.

Be recovery ratio of the electrical deionization apparatus (12A) is 90-96% is desirable, and the current density in the electrical deionization apparatus (12A) is a 300~3000mA / dm ^2, and preferably, 1500~2500mA / dm ² of It is more preferable. If the current density is 300 mA/dm ² or more, corrosion of the electrode due to hydrogen peroxide is likely to occur in general, but in the pure water production system of the embodiment, at least the electrode chamber of the electric deionization device, preferably the electrode chamber and the concentration chamber, and an ultraviolet oxidation device are provided. This is because it supplies water that has not passed through, so it can be suppressed. Moreover, by making the current density into a more preferable range, the removal rate of weak electrolytes, such as boron, can be stabilized for a long period of time.

As the electric deionization apparatus 12A, a commercially available electric deionization apparatus can be used. As commercial items of the electric deionization device 12A, for example, VNX50, VNX55, VNX-55EX (above, manufactured by Evoqua), EDI-50 (manufactured by IONICS) and the like can be used.

The power source 27 is, for example, an AC-DC converter that converts an alternating current (AC) current supplied from an alternating current power source into a direct current (DC) current. The power supply 27 is preferably an AC-DC converter using a switching method or an AC-DC converter using a full-wave rectification method from the viewpoint of low voltage ripple and easy to obtain high-quality treated water at an early stage.

The water quality of the permeated water that has passed through the electric deionization device 12A may be used in a single stage, the boron concentration is, for example, 1 μg/L (as B, hereinafter the same) or less, and the specific resistance is 17.5 MΩ·cm You can get the ideal. One electric deionization device 12A may be used in a single stage, or two or more units may be connected in series to be used in a plurality of stages. The permeated water passed through the electric deionization apparatus 12A is then supplied to the degassing membrane apparatus 13.

The degassing device 13 mainly removes carbon dioxide gas generated by decomposing organic substances in the ultraviolet oxidizing device 11. The degassing membrane device 13 is a device that transfers and removes only the dissolved gas in the water to be treated to the secondary side by decompressing the secondary side of the membrane as necessary while passing water to be treated through the primary side of the gas-permeable membrane (degassing membrane). . An inert gas source such as nitrogen may be connected to the decompression side (secondary side) of this membrane to improve the degassing performance. The degassing membrane may be a membrane that passes gases such as oxygen, nitrogen, and steam, but does not permeate water. For example, there are membranes such as silicone rubber, polytetrafluoroethylene, polyolefin, and polyurethane.

According to the pure water production system of the embodiment described above, since deterioration of electrodes and ion exchangers in the electric deionization apparatus can be suppressed, high-quality pure water can be obtained over a long period of time. In addition, since the permeated water of the reverse osmosis membrane device is introduced into at least the electrode chamber, preferably the electrode chamber and the concentration chamber, silica scale can be suppressed, and the removal rate of trace impurities such as silica and boron is improved or the removal rate is decreased. It is also easy to obtain the inhibitory effect of.

Example

Next, examples will be described. The present invention is not limited to the following examples.

(Example 1 and Comparative Example 1)

5 is a diagram showing the configuration of a pure water production system 50 used in Example 1 and Comparative Example 1. FIG. In the pure water production system 50, the electric deionization apparatus 53 is used in Example 1, and the electric deionization apparatus 54 is used in Comparative Example 1. Other than that, the apparatus of the pure water production system 50 is commonly used in Example 1 and Comparative Example 1.

The pure water production system 50 includes a reverse osmosis membrane device 51 (Toray Co., Ltd., TM820K-400) and an ultraviolet oxidation device 52 (Nihon Photoscience Co., Ltd., AUV-8000TOC, UV irradiation dose 0.3kWh/㎥) ) In order, and the concentration chamber and the electrode chamber at the rear end of the ultraviolet oxidation device 52 are filled with ion exchange resins (53, 54) (EVOQUA, VNX-55EX, treated water 10㎥) /h, recovery rate 95%) are arranged in parallel.

The pure water production system 50 includes a replenishing water line 55a for supplying water to be treated to the reverse osmosis membrane device 51, and a replenishing water line 55b connecting the reverse osmosis membrane device 51 and the ultraviolet oxidizing device 52. ), treatment of discharging the replenishing water line 55c connecting the inlet of each desalination chamber of the ultraviolet oxidation device 52 and the electric deionization devices 53 and 54, and the permeated water of the electric deionization devices 53 and 54, respectively. Male lines 55d are provided. In the above, the permeated water of the reverse osmosis membrane device 51 flows through the replenishing water line 55b. The concentrated water of the reverse osmosis membrane device 51 is discharged through the drain pipe 57. The concentrated water of the electric deionization devices 53 and 54 is discharged by the drain pipe 56.

In addition, to the electric deionization device 53 used in Example 1, the permeated water from the reverse osmosis membrane device 51 is supplied to the electrode chamber and the entrance of the concentration chamber of the electric deionization device without passing through the ultraviolet oxidizing device 52. The bypass replenishing water line 53a is connected. Further, to the electric deionization device 54 used in Comparative Example 1, a replenishing water line 54a for supplying the treated water of the ultraviolet oxidation device 52 to the electrode chamber and the concentration chamber is connected.

In Example 1 and Comparative Example 1, water to be treated from which chlorine was removed by passing tap water through activated carbon was supplied from the replenishing water line 55a to the pure water production system 50, and continuous operation was performed for 24 hours to produce pure water. At this time, in the electric deionization apparatuses 53 and 54, since it becomes easy to evaluate the performance degradation due to deterioration of the electric deionization apparatus, a direct current was applied in a constant voltage mode of 180 V. The current density was 1810 mA/dm ² at the initial stage of passing water.

Immediately after the start of operation (initial water passing) and 300 days after the start of operation, each point (near the point of connection with the reverse osmosis membrane device 51 of the reverse osmosis membrane device 51 (the permeate outlet of the reverse osmosis membrane device 51) ), the treated water outlet of the ultraviolet oxidizing device 52 (near the connection point of the supply water line 55c with the ultraviolet oxidizing device 52), and the permeated water outlet of the electric deionization devices 53 and 54 (each treated water line ( The water quality (conductivity [μS/cm]) in 55d) was measured in the vicinity of the connection point with the electric deionization apparatus 53 and 54). Table 1 shows the results.

In the pure water production system of Example 1 in Table 1, the conductivity of the treated water discharged from the permeate outlet of the electric deionization device 53 does not change from the initial value of water passing through 300 days after the start of operation. It was found that the water quality of the treated water was improved even when compared with the conductivity of the treated water discharged from the permeate outlet of the electric deionization device 54 in the pure water production system of Comparative Example 1.

(Example 2 and Comparative Example 2)

In the system of Fig. 5, the electric deionization devices 53 and 54 in which the concentration chamber and the electrode chamber are not filled with ion exchange resin (IONICS, EDI-50, treated water amount 10㎥/h, concentrated water circulating water amount 15㎥ /h, 95% recovery rate), the same test as in Example 1 and Comparative Example 1 was conducted. In addition, EDI-50 usually requires circulation of concentrated water and injection of sodium chloride into the concentrated water, and was also carried out in Example 2 and Comparative Example 2, but is omitted in the drawings. Further, at this time, in the electric deionization devices 53 and 54, a direct current was applied in a constant voltage mode of 580V. The current density was 314 mA/dm ² at the initial stage of passing water. Table 2 shows the results.

In Table 2, the method of supplying the permeated water from the permeable membrane device to the concentration chamber and the electrode chamber of the electric deionization device without passing through the ultraviolet oxidizing device is, as in the pure water production system of Example 2, the ion exchange resin is added to the concentration chamber and the electrode chamber. It can be seen that there is an effect even when an electric deionization device that is not charged is used. However, the difference in the water quality of the treated water after 300 days between the pure water production system of Example 2 and the pure water production system of Comparative Example 2 is an electric type in which an ion exchange resin is filled in the concentration chamber and the electrode chamber as in Example 1 and Comparative Example 1. It is smaller than the difference in water quality of treated water when a deionization device is used. This is considered to be due to the fact that the concentration chamber and the electrode chamber are not filled with an ion exchange resin, so that there are few parts affected by hydrogen peroxide.

As described above, in the pure water production systems of Examples 1 and 2 in which the permeated water of the reverse osmosis membrane device 51 is used as replenishment water to the inlet of the electrode chamber of the electric deionization device 53, the ultraviolet oxidation device 52 Compared to the pure water production systems of Comparative Examples 1 and 2 in which the water at the outlet is used as supply water to the inlet of the desalination chamber and the inlet of the electrode chamber of the electric deionization device 54, it is possible to supply treated water having a low conductivity over a long period of time. Confirmed.

As described above, according to the pure water production system according to the present invention, the permeated water of the reverse osmosis membrane device which does not contain hydrogen peroxide, which is a by-product of the ultraviolet oxidation device, as replenishment water to the electrode chamber entrance of the electric deionization device. By using, it is possible to provide high-purity treated water over a long period of time without corrosion of the electrode.

1, 1A, 1B... Pure water manufacturing system, 10… Reverse osmosis membrane device, 11... Ultraviolet Oxidizer (TOC-UV), 12, 12a, 12b... Electric deionization device (EDI), 13... Degassing Membrane Device (MDG), 14... Youth Point (POU), 23c... Concentration chamber inlet nozzle, 24c... Desalting chamber inlet nozzle, 25c... Electrode chamber inlet nozzle, 31c... Common inlet nozzle, 131... 1st bypass pipe, 132... 2nd bypass pipe, 133... Treatment water pipe, 21... Cation Exchange Membrane, 22... Anion Exchange Membrane, 23... Concentration chamber, 24… Desalting room, 25a... Anode chamber, 25b... Cathode chamber, 26a... Anode, 26b... Cathode, 27... power.

Claims (9)

A pure water production system comprising a reverse osmosis membrane device, an ultraviolet oxidation device, an electric deionization device, and a treated water pipe connecting these devices in that order from an upstream side,
The electric deionization device includes alternately disposed cation exchange membranes and anion exchange membranes,
A concentration chamber and a desalination chamber alternately formed between the cation exchange membrane and the anion exchange membrane,
And a pair of electrode chambers disposed outside the cation exchange membrane and the anion exchange membrane,
The treated water pipe is connected to the electric deionization device so as to supply the treated water treated by the ultraviolet oxidation device to at least the desalination chamber of the electric deionization device,
The pure water production system includes a first bypass pipe for supplying the permeated water of the reverse osmosis membrane device to the electrode chamber of the electric deionization device without passing through the ultraviolet oxidation device. The method of claim 1,
The pure water production system further comprising a second bypass pipe for supplying the permeated water of the reverse osmosis membrane device to the concentration chamber of the electric deionization device without passing through the ultraviolet oxidation device. The method of claim 2,
The electric deionization apparatus has a common inlet nozzle leading to the concentration chamber and the electrode chamber of the electric deionization apparatus,
The pure water production system, wherein the first bypass pipe and the second bypass pipe are all connected to the common inlet nozzle. The method of claim 2,
The electric deionization apparatus has a concentration chamber inlet nozzle leading to the concentration chamber and an electrode chamber inlet nozzle leading to the electrode chamber of the electric deionization apparatus,
The first bypass pipe is connected to the electrode chamber inlet nozzle,
The second bypass pipe is connected to the concentration chamber inlet nozzle, pure water production system. The method according to any one of claims 1 to 4,
A pure water production system having an ion exchanger in the electrode chamber and in the concentration chamber. The method according to any one of claims 1 to 5,
The pure water production system, wherein the concentration of hydrogen peroxide in the treated water treated by the ultraviolet oxidation device is 100 μg/L or less. As a pure water production method in which raw water is sequentially treated in a reverse osmosis membrane device, an ultraviolet oxidation device, and an electric deionization device,
The electric deionization device includes alternately disposed cation exchange membranes and anion exchange membranes,
A concentration chamber and a desalination chamber alternately formed between the cation exchange membrane and the anion exchange membrane,
And a pair of electrode chambers disposed outside the cation exchange membrane and the anion exchange membrane,
Supplying the treated water treated in the ultraviolet oxidation device to at least a desalination chamber of the electric deionization device,
A pure water production method wherein the permeated water of the reverse osmosis membrane device is supplied to an electrode chamber of the electric deionization device without passing through the ultraviolet oxidation device. The method of claim 7,
Supplying the permeated water from the reverse osmosis membrane device to the concentration chamber of the electric deionization device without passing through the ultraviolet oxidizing device. Pure manufacturing method. The method according to claim 7 or 8,
A method for producing pure water, wherein the concentration of hydrogen peroxide in the treated water treated by the ultraviolet oxidation device is 100 μg/L or less.

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