JP2003266097A - Ultrapure water making apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrapure water making apparatus capable of highly removing weak electrolytes such as silica and, boron in a primary pure water system suitable for a field of a semiconductor, or the like, requiring high water quality. <P>SOLUTION: This ultrapure water making apparatus has a pretreatment system 1, a primary pure water system 2 and a sub-system 3. The primary pure water system 2 is constituted by successively connecting a reverse osmosis membrane separator 22, a degassing device 21, an electrodeionizing device 23, an ultraviolet oxidation device 24 and a non-regeneration type ion exchanger 25 in this order or by connecting the degassing device 21, the reverse osmosis membrane separator 22, the electrodeionizing device 23, the ultraviolet oxidation device 24 and the non-regeneration type ion exchanger 25 in this order. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrapure water production system for producing ultrapure water used in various industries such as semiconductors, liquid crystals, pharmaceuticals, foods, electric power, and for consumer or research facilities. In particular, it relates to improvement of a primary pure water system for an ultrapure water producing apparatus that requires high water quality in weak electrolytic substances such as silica, boron and TOC.

[0002]

2. Description of the Related Art Conventionally, ultrapure water used in the field of semiconductors is an ultrapure water consisting of a pretreatment system, a primary pure water system for treating the pretreated water, and a subsystem for treating the primary pure water. It is produced by treating raw water (industrial water, city water, well water, etc.) with a water production device.

Coagulation, pressure floating (precipitation), filtration (membrane filtration)
A pretreatment system consisting of equipment removes suspended substances and colloidal substances in raw water. Further, in this process, it is also possible to remove high molecular weight organic substances, hydrophobic organic substances and the like.

Reverse osmosis (RO) membrane separation device, degassing device and regenerative ion exchange device (mixed bed type or 4 bed 5 tower type, etc.)
In the primary pure water system equipped with, the ions and organic components in the raw water are removed. In addition, in the RO membrane separator, not only salts but also ionic and colloidal TOC are removed. In the ion exchange device, TOC that removes salts and is adsorbed or ion exchanged by the ion exchange resin
Remove components. In the degasser, inorganic carbon (I
C), dissolved oxygen is removed.

Non-regeneration type ion exchange device, low-pressure ultraviolet ray (U
V) A subsystem equipped with an oxidizer and an ultrafiltration (UF) membrane separator further enhances the water purity to ultrapure water. In the low-pressure UV oxidizer, TOC was converted into organic acid by ultraviolet rays of 185 nm emitted from a low-pressure ultraviolet lamp.
Furthermore, it decomposes to CO ₂ . The organic matter and CO ₂ generated by the decomposition are removed by the ion exchange resin in the subsequent stage. U
In the F membrane separation device, fine particles are removed, and outflow particles of the ion exchange resin are also removed.

In recent years, an electric deionization device has been widely used instead of a regenerative ion exchange device as a deionization device, which is a central step of the primary pure water system of such an ultrapure water production device. Came.

As shown in FIG. 2, the electric deionization apparatus has a concentrating chamber 1 in which a plurality of anion exchange membranes 13 and a plurality of cation exchange membranes 14 are alternately arranged between electrodes (anode 11 and cathode 12).
5 and the desalting chambers 16 are alternately formed, and the desalting chambers 16 are mixed or filled in a multi-layered manner with an anion exchanger and a cation exchanger made of an ion exchange resin, an ion exchange fiber, a graft exchange or the like. (Patent No. 1782943)
Japanese Patent, Japanese Patent No. 2751090, Japanese Patent No. 2699
256, EP1038837A2). Note that FIG.
In the figure, 17 is an anode chamber and 18 is a cathode chamber.

The electric deionization apparatus uses H ⁺ by water dissociation.
Efficient desalting treatment is possible by generating ions and OH ⁻ ions and continuously regenerating the ion exchanger filled in the desalting chamber. The electric deionization device does not require a regeneration treatment using a chemical such as an ion exchange resin device which has been widely used for desalination treatment, and
It has an excellent feature that it enables complete continuous water sampling and obtains highly pure water.

Further, in the electric deionization apparatus, the weak electrolytic substances such as silica and boron can be removed to some extent by causing the following ionization reaction in the desalting chamber to generate ions. SiO ₂ + OH ⁻ → HSiO ₃ ⁻ (pKa = 9.86) H ₃ BO ₃ + OH ⁻ → B (OH) ₄ ⁻ (pKa = 9.24)

However, a general electric deionization apparatus has a removal rate of silica and boron of 30 to 99%, though it varies depending on the apparatus, and is a multi-bed type (3 beds 4 towers, 4 beds 5 beds).
It is not possible to expect complete and stable removal up to the lower limit of analysis as in the case of (column type) ion exchanger.

By the way, the required water quality of ultrapure water differs depending on the field in which it is used. Therefore, the ultrapure water production apparatus, especially the primary pure water system, has an ultrapure water satisfying the required water quality for each field. It is built to be obtained. Table 1 shows the required water quality of ultrapure water in typical fields.

[0012]

[Table 1]

In the fields of liquid crystals and medicinal water, since the required water quality of silica and boron is not present or is loose, an electric deionization device has come to be used in the desalting section of the purified water production system and the primary pure water system. In addition, the desalting section is composed of the RO membrane separation device and the electric deionization device.

On the other hand, the required water quality of ultrapure water used in the semiconductor field is the most severe, and silica, boron, and TOC are required to be below the lower limit of the current level of analysis. The removal of silica and boron to an ultratrace amount cannot be achieved by an electric deionization device, and is possible by using a multibed ion exchange device. However, silica, an ion exchange resin,
The exchange capacity (removal amount) of boron and the like is extremely low, and according to our knowledge, it is 0.05 to 0.1 meq per anion exchange resin.
/ ML, which is 1 / mL compared to the exchange capacity for Cl ions, etc.
It is 10 to 1/20.

From the above, when guaranteeing silica and boron in ultrapure water, it is important to completely remove these substances with the primary pure water system. That is, when silica and boron are brought into the subsystem, the non-regenerative ion exchange device in the subsystem immediately breaks through, and stable water quality cannot be guaranteed.

When the desalting section of the primary pure water system is composed of a regenerative ion exchange device as in the prior art, it is relatively easy to deal with advanced removal of silica and boron by increasing the frequency of regeneration. Was achieved. However, frequent regeneration leads to the discharge of a large amount of recycled wastewater, which is not preferable from the viewpoint of global environment and resource protection. Therefore, even in the primary pure water system of the ultrapure water production system in the semiconductor field, it is strongly desired to adopt an environmentally friendly electric deionization system as a desalination means while maintaining high purity water quality. However, since the removal rate of silica and boron in an electrodeionization device is lower than that of other ions, when the treated water contains 1 ppm or more of silica or boron, the RO membrane separation device and In combination with a deionization device, these could not be reduced to the required water quality level in the semiconductor field.

In order to reduce the silica load on the electrodeionization device, a method of using two or more RO membrane separators in the preceding stage can be considered. With this method, silica concentration <0.
In order to achieve 1 ppb, an RO membrane separation device with three or more stages is required, which complicates the device and increases the capacity of the high-pressure pump, which is not economical. In addition, a method of removing silica and boron leaked from the electric deionization device by a non-regeneration type ion exchange device installed in the primary deionized water system by using one or two RO membrane separators is also conceivable. Since the exchange capacity of the ion exchange resin is extremely low, the frequency of resin exchange is once every 20 days to 3 months.
The replacement frequency is extremely high as compared with the usual replacement frequency of once every one to three years, and the replacement cost increases, which is not economical.

For this reason, the introduction of the electric deionization device is delayed compared to other fields in fields such as the semiconductor field where ultrapure water silica and boron concentrations are required to be in extremely small amounts. The current situation.

[0019]

DISCLOSURE OF THE INVENTION The present invention is capable of highly removing weak electrolytic substances such as silica and boron in a primary pure water system suitable for the field of semiconductors and the like which require high water quality. It is an object of the present invention to provide an ultrapure water production apparatus that can be used.

[0020]

An ultrapure water producing system of the present invention comprises a pretreatment system, a primary pure water system for treating the pretreated water treated by the pretreatment system to obtain primary pure water, The present invention relates to an ultrapure water production system having a subsystem for treating primary pure water. In the ultrapure water production system according to claim 1, the primary pure water system is arranged in the order of a reverse osmosis membrane separation device, a degassing device, an electric deionization device, an ultraviolet oxidation device, and a non-regenerative ion exchange device. There is.

In the ultrapure water producing system of claim 2, the primary pure water system comprises a degasser, a reverse osmosis membrane separator, an electric deionizer, an ultraviolet oxidizer, and a non-regenerative ion exchanger in this order. It is arranged.

In this way, the R
By providing the O membrane separation device and the degassing device, the removal rate of silica and boron in the electrodeionization device can be increased. Further, by further treating with a UV oxidation device and a non-regeneration type ion exchange device, the required water quality can be sufficiently satisfied.

According to the present invention, in the field where the required water quality of silica and boron concentration is strict, the regenerative ion exchange device or the multi-stage RO membrane separation device, which is indispensable for the primary pure water system, is unnecessary, and the degassing device is eliminated. , RO membrane separation device, electric deionization device, UV oxidation device and non-regeneration type ion exchange device can be used to produce high purity water.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an ultrapure water producing system of the present invention will be described in detail below with reference to the drawings.

The ultrapure water production system shown in FIGS. 1 (a) and 1 (b) comprises a pretreatment system 1, a primary pure water system 2 and a subsystem 3. The primary deionized water system 2 of the ultrapure water production system shown in FIG. 1A includes a degasser 21, an RO membrane separator 22, an electric deionizer 23, a UV oxidizer 24, and a non-regenerative ion exchanger 25. It is configured to be connected in order. The primary pure water system 2 of the ultrapure water production system of FIG. 1 (b) includes an RO membrane separation device 22, a degassing device 21, an electric deionization device 23, a UV oxidation device 24 and a non-regenerative ion exchange device 25. It is configured to be connected in order.

Next, the function of each device of the primary pure water system according to the present invention will be described.

The degassing device 21 is installed to remove dissolved oxygen (DO) and carbon dioxide (CO ₂ ) in the water to be treated. When DO flows into the electrodeionization device 23, the ion exchange member deteriorates. Also, if CO ₂ is present,
The deionization efficiency in the electric deionization device 23 decreases. Therefore, the degassing device 21 is used to
O and CO ₂ are removed beforehand. Electrodeionization device 2
In order to prevent the deterioration of the ion exchange member in 3 and improve the deionization efficiency, it is preferable to remove the treated water in the degassing device 21 so that the DO concentration is less than 1 ppm and the CO ₂ concentration is less than 1.0 ppm. . As a degasser,
A membrane deaerator, a vacuum deaerator, a nitrogen deaerator, etc. can be used.

The RO membrane separation device 22 is installed for separating and removing salts, silica, boron, TOC, fine particles and the like in the water to be treated. There is a limit to the removal rate of these impurities by the RO membrane separation device 22, and when general city water or industrial water is treated as raw water, the specific resistance value of the treated water of the RO membrane separation device 22 is about 0.5 MΩ.・ Cm, silica concentration is about 50
Since 0 ppb, boron concentration is about 10 ppb, and TOC concentration is about 100 ppb, in order to satisfy the required water quality,
An electric deionization device 23 or the like is further required in the subsequent stage.

The RO membrane of the RO membrane separator 22 is N
The film is not particularly limited as long as the film has an aCl removal rate of 98% or more, but a polyamide film is preferable.

As described above, when the RO membrane separators are provided in multiple stages in series, the load of the electric deionization device at the latter stage is reduced, but the structure of the device is complicated and the high-pressure pump capacity is increased. Then, the RO membrane separation device is composed of one stage.

The RO membrane separation device 22 and the degassing device 21
There is no limitation on the connection order of the RO membrane separation device, as shown in FIG. 1A, the degassing device 21 may be the first stage and the RO membrane separation device 22 may be the second stage. Further, as shown in FIG. 22 may be the first stage and the degassing device 21 may be the latter stage, but in order to reduce the initial equipment cost, for example, to suppress the number of membranes of the membrane degassing device as the degassing device 21, as shown in FIG. , The RO membrane separation device 22 is followed by a degassing device 21.
Is preferably provided.

The electrodeionization device 23 is preferably an electrodeionization device having a silica removal rate of 99% or more. This is because in the present invention, the RO membrane separation device is a one-stage process. That is, when the silica concentration of the treated water of the RO membrane separation device 22 is 1 ppm, the silica concentration of the treated water of the RO membrane separation device 22 is about 100 ppb, and this water is treated by the electric deionization device 23 to obtain the silica concentration. In order to make it less than 1 ppb, a silica removal rate of 99% or more is required.

There is no particular limitation as to the electric deionization apparatus having a silica removal rate of 99% or more, but there is no limitation.
281, the treated water having a pH of 8.5 or less (feed water of the electric deionization device) is treated without adding an alkaline chemical and has a pH of 1.0 than the treated water.
As described above, it is preferable to use the one configured so as to obtain the treated water (deionized water) which is preferably 1.3 to 3.0 higher.

In this electric deionization apparatus, the weak electrolytic substance such as silica and boron and the hardness component are efficiently removed by raising the pH of water in the electric deionization apparatus.

Such an electrodeionization device having a high silica removal rate preferably employs the following configurations i) and ii). i) The thickness of the desalination chamber is preferably 7 mm or more, and the thickness of the desalination chamber is 8 to 30 in order to efficiently raise the pH of the treated water.
mm is more preferable. The thickness of the deionization chamber refers to the thickness of the deionization chamber 16 between the anode 11 and the cathode 12, as indicated by W in FIG. ii) The ion exchanger in the desalting chamber is best composed of a mixed layer of anion exchanger and cation exchanger. When the applied voltage is high, it may be a single layer of anion exchanger. Some desalting chambers may be filled with the mixed layer and other desalting chambers may be filled with the anion exchanger layer.

In the present invention, the electric deionization apparatus of the above i) or ii) and a conventional ordinary electric deionization apparatus may be connected in series and used. For example, the above electric deionization apparatus of i) may be used. As a pre-stage electric deionization device, as the post-stage electric deionization device, an electric deionization device having a deionization chamber having a thinner thickness than the deionization chamber of the pre-stage electric deionization device, for example,
An electric deionization device having a deionization chamber having a thickness of about 2.0 to 6.0 mm may be provided.

The thickness of the deionization chamber of the former-stage electric deionization device is 7
mm or more, particularly 8 to 30 mm, and the thickness of the deionization chamber of the latter-stage electric deionization device is 2.0 to 6.0 mm, the weak electrolytic substance and hardness component such as silica and boron in the first-stage electric deionization device. Are removed, and silica and boron are further removed in the latter stage electrodeionization device.

By using such an electric deionization apparatus, as the treated water of the electric deionization apparatus, the primary pure water produced by the primary pure water system or the primary pure water is further processed by the subsystem to obtain the treated water. It is possible to obtain water having a water quality equal to or lower than the silica concentration and the boron concentration required for the ultrapure water.

In the present invention, since the RO membrane separation device is provided in a single stage, in order to remove TOC to a higher degree, a UV oxidizer 24 as an organic substance decomposer, an organic acid produced by decomposition in the UV oxidizer 24, etc. A non-regeneration type ion exchange device 25 for removing the ionic substances is provided. The UV oxidizer 24 is preferably a low pressure UV oxidizer, but is not limited thereto. An oxidation accelerator such as ozone or hydrogen peroxide may be added to the water to be treated in the UV oxidation device 24. In the non-regeneration type ion exchange device 25 at the rear stage of the UV oxidation device 24, silica is highly removed by the RO membrane separation device 22 and the electric deionization device 23 at the front stage, and there is almost no silica load. It is enough once a year.

The primary pure water obtained by such a primary pure water system is further processed by the subsystem to produce ultrapure water. The subsystem is not particularly limited, and for example, a general one configured by connecting a non-regeneration type ion exchange device, a low pressure UV oxidation device and a UF membrane separation device in this order can be used.

In the ultrapure water production system of the present invention, since silica and boron can be removed to an extremely low concentration in the primary pure water system, the ion load of the non-regeneration type ion exchange system of the subsystem is low, The exchange frequency of the non-regeneration type ion exchange device can be sufficiently reduced.

[0042]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

The specifications of each device used in the following examples and comparative examples are as follows. Activated carbon device: Kurita Water Industries Co., Ltd. "Curicol KW10-30" Water SV; 20 / hr RO Membrane separation device: Kurita Water Industries Co., Ltd. "Membrane Ace KN200" Degassing device: Degassing membrane module; Dainippon Ink Chemical Industry Co., Ltd. Electrodeionization equipment: Kurita Water Industries Co., Ltd. throughput: 100 L / hr Low-pressure UV oxidation equipment: Nippon Photoscience Co., Ltd. UL-UVox lamp “AZ26” 1 non-regenerative ion exchange Device: Kurita Water Industries Co., Ltd. "DZ-50"

The water quality of the treated raw water was as shown in Table 2.

[0045]

[Table 2]

Example 1 Raw water was treated in the order of activated carbon device → RO membrane separation device → degassing device → electric deionization device → low pressure UV oxidation device → non-regenerative ion exchange device to obtain primary pure water. The water quality of the obtained primary pure water is shown in Table 5.

However, the following is used as the ion exchange membrane in the electric deionization apparatus, and the following anion exchange resin and cation exchange resin are used as the ion exchange resin to be filled in the desalting chamber. : Cation exchange resin = 6: 4 (volume ratio) is used, the desalting chamber has three cells, and the desalting chamber has a thickness of 10 mm. The water passage conditions shown in Table 3 were established by providing two cells in series with a second-stage electric deionization device having a desalting chamber thickness of 2.5 mm and having 12 cells. Anion Exchange Membrane: “Neoceptor AH” manufactured by Tokuyama Corporation
A "cation exchange membrane:" Neoceptor CM "manufactured by Tokuyama Corporation
B "Anion exchange resin:" SA10A "manufactured by Mitsubishi Chemical Co., Ltd. Cation exchange resin:" SK1B "manufactured by Mitsubishi Chemical Co., Ltd.

[0048]

[Table 3]

Example 2 In Example 1, the RO membrane separation device and the degassing device were replaced with each other, and raw water was replaced with activated carbon device → degassing device → RO membrane separating device → electric deionization device → low pressure UV oxidation device → non-regeneration. Table 5 shows the water quality of the primary pure water obtained by performing the same treatment except that the treatment was performed in the order of the type ion exchange apparatus.

Comparative Example 1 In Example 1, the RO membrane separation device was omitted, and raw water was treated in the order of activated carbon device → degassing device → electric deionization device → low pressure UV oxidation device → non-regeneration type ion exchange device. Other than that, the same treatment was performed, and the quality of the primary pure water obtained is shown in Table 5.

Comparative Example 2 In Example 1, the degassing device was omitted, and the raw water was treated in the order of activated carbon device → RO membrane separation device → electric deionization device → low pressure UV oxidation device → non-regeneration type ion exchange device. Other than that, the same treatment was performed, and the quality of the primary pure water obtained is shown in Table 5.

Comparative Example 3 In Example 1, an RO membrane separator was used instead of the degasser, and the electric deionizer and UV oxidizer were omitted.
Raw water is activated carbon device → RO membrane separation device → RO membrane separation device →
Table 5 shows the water quality of the primary pure water obtained by performing the same treatment except that the treatment was performed in the order of the non-regeneration type ion exchange device.

Comparative Example 4 In Comparative Example 3, an electric deionization device was used instead of the non-regeneration type ion exchange device, and raw water was treated in the order of activated carbon device → RO membrane separation device → RO membrane separation device → electric deionization device. Table 5 shows the water quality of the primary pure water obtained by the same treatment except the above.

As the electrodeionization device, only the one used as the latter stage electrodeionization device in Example 1 was used in one stage, and water was passed under the conditions shown in Table 4 below.

[0055]

[Table 4]

[0056]

[Table 5]

From Table 5, according to the present invention, silica, boron, and TOC can be removed to an extremely low concentration in the primary pure water system, and highly pure ultrapure water can be stably produced over a long period of time. I understand.

[0058]

As described above in detail, according to the ultrapure water production system of the present invention, the degassing system, the RO membrane separation system, the electric deionization system, the UV oxidation system and the non-regenerative ion exchange system are constructed. In the primary pure water system, the weak electrolytic substances such as silica and boron can be highly removed, and the load on the subsystem in the subsequent stage can be reduced.

According to the present invention, the regenerative ion exchange device or the multi-stage RO membrane separation device, which is indispensable for the primary pure water system, is not required in the field where the required water quality of silica and boron concentration is high, such as semiconductors, Silica and boron can be removed to an extremely low concentration by combining a one-stage RO membrane separation device and an electric deionization device, and thus a regeneration process of an ion exchange device unlike the conventional device is not required. The replacement frequency of the non-regenerative ion exchange device can also be significantly reduced. Since the ion exchange device does not need to be regenerated and the frequency of replacement is low, continuous operation is possible for a long period of time. Since the multi-stage RO membrane separation device is not used, the operation is easy and the electricity bill can be greatly reduced. Based on such an excellent effect, highly pure ultrapure water can be produced stably and efficiently over a long period of time.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of an ultrapure water production system of the present invention.

FIG. 2 is a schematic cross-sectional view showing the configuration of a general electric deionization apparatus.

[Explanation of symbols]

1 Pretreatment system 2 Primary pure water system 3 subsystems 10 Ion exchanger 11 Anode 12 cathode 13 Anion exchange membrane 14 Cation exchange membrane 15 Concentration room 16 Desalination chamber 17 Anode chamber 18 Cathode chamber 21 Degassing device 22 RO membrane separator 23 Electrodeionization device 24 UV oxidizer 25 Non-regenerative ion exchanger

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C02F 9/00 C02F 9/00 502Z 4D061 504 504 504B 504D B01D 19/00 B01D 19/00 H 61/48 61/48 C02F 1 / 20 C02F 1/20 A 1/32 1/32 1/42 1/42 A 1/44 1/44 J 1/469 1/72 101 1/72 101 1/46 103 F term (reference) 4D006 GA03 GA17 GA32 JA30Z KA01 KA31 KA72 KB04 KB11 KB17 MA12 MC54 PA01 PB02 PB23 PB70 PC02 4D011 AA14 AA16 AA17 AD03 4D025 AA04 AB17 AB33 BB07 DA01 DA04 DA05 DA06 CA08 CA1 CA08 CA1 CA08 CA10 CA02 CA01 CA05 CA04 CA11 CA15 4D011 A1814 DA02 DB18 DC18 DC19 EA09 EB01 EB04 EB13 EB37 GA20 GA21

Claims (4)

[Claims] 1. Ultra pure water having a pretreatment system, a primary pure water system for treating the pretreated water treated by the pretreatment system to obtain primary pure water, and a subsystem for treating the primary pure water. In the manufacturing apparatus, the primary pure water system is configured such that a reverse osmosis membrane separation device, a degassing device, an electric deionization device, an ultraviolet oxidation device, and a non-regenerative ion exchange device are connected in this order. Characteristic ultrapure water production equipment. 2. Ultra pure water having a pretreatment system, a primary pure water system for treating the treated water treated by the pretreatment system to obtain primary pure water, and a subsystem for treating the primary pure water. In the manufacturing apparatus, the primary pure water system is configured such that a degassing device, a reverse osmosis membrane separation device, an electric deionization device, an ultraviolet oxidation device, and a non-regenerative ion exchange device are connected in this order. Characteristic ultrapure water production equipment. 3. The silica concentration and the boron concentration of the treated water of the electric deionization apparatus according to claim 1 or 2, wherein the pure water obtained in the primary pure water system or the ultrapure water obtained in the subsystem is A device for producing ultrapure water, which is equal to or lower than the required silica concentration and boron concentration. 4. The silica concentration according to any one of claims 1 to 3, wherein the pretreated water has a silica concentration of 1 ppm as SiO 2.
_{2. The} ultrapure water production system, wherein the treated water of the electric deionization system has a silica concentration of ₂ or more and less than 1 ppba as SiO ₂ .