JPH1094785A - Ultrapure water producing method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the increase of dissolved oxygen and organic material concentration in the final step of an ultrapure water production process by using a CO3 type anion exchange resin to capture hydroxyl radical (.OH) and decreasing the dissolved oxygen in the ultrapure water production process. SOLUTION: After a pretreated pure water is introduced into a dehydrating device to remove the dissolved oxygen and other gases in the treated water and passed through a primary system to exidation-decompose the organic mateiral coexisting in the water by an ultraviolet oxidation device 2 and the treated water is passed through the anion exchange resin device 3. In the device 3, CO2 <-2> and HCO<-3> in the treated water are increased to captur the hydroxyl radical (.OH) causing the increase of the dissolved oxygen. Next, the water to be treated in an acidic atmosphere is controlled to pH8-14 by adding CO2 , passed through the a secondary system to oxidation-decompose the organic material by the ultraviolet oxidation device 4 and the decomposed organic material is removed by a mixed bed ion exchanging device 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor manufacturing plant,
The present invention relates to a method and an apparatus for producing ultrapure water widely used in a pharmaceutical manufacturing plant and the like, and more particularly to a method and an apparatus for producing ultrapure water that efficiently remove oxygen dissolved in treated water.

[0002]

2. Description of the Related Art In recent years, with the improvement in the degree of integration of semiconductor devices (LSI), the influence of contamination by ultra-trace substances in ultrapure water on the surface of a substrate such as a silicon substrate has become a problem. There is a demand for ultrapure water having a very small amount of impurities such as substances, fine particles, organic substances, metals, and dissolved gases.

[0003] The requirements for the purity of ultrapure water are becoming more and more severe, and in particular, the TOC concentration (TOC:
Reduction of total organic carbon (DO) and dissolved oxygen (DO) has become a major issue.

[0004] Generally, the production of ultrapure water involves a pretreatment system for removing turbid components in raw water, ionic substances, fine particles,
A primary system that removes organic matter, dissolved gas, viable bacteria, etc. using a reverse osmosis membrane device or a degassing device, and further removes impurities by ultraviolet oxidation, ion exchange, filtration, etc. of primary pure water obtained in the primary system This is done in combination with a secondary system for the purpose of doing so.

[0005] In the secondary system, as a treatment method for reducing the concentration of organic substances in ultrapure water, primary pure water is irradiated with ultraviolet rays to oxidatively decompose organic substances, and then the organic acids and the like generated by this decomposition are removed. A method of removing by a mixed bed type ion exchange apparatus filled with a mixed resin of cation and anion is generally used.

[0006] The reaction mechanism in the secondary system will be described in more detail. In the ultraviolet oxidation apparatus, the water to be treated, from which salts, organic substances, fine particles and viable bacteria have been removed by the primary reverse osmosis membrane apparatus, is irradiated with ultraviolet rays. Organic substances in the water to be treated are almost completely oxidatively decomposed and decomposed into organic acids or carbon dioxide.

[0007] The reaction in the ultraviolet oxidation apparatus is represented by the following reaction formula, as shown in the following reaction formula.
By OH), organic substances in the water to be treated are oxidatively decomposed to a stage of an organic acid such as carboxylic acid, and a part is oxidatively decomposed to carbon dioxide.

(1) H ₂ O + hν → OH (2) RC + OH → RCOOH (3) RCOOH → CO ₂ + H ₂ O The water to be treated is introduced into a mixed bed type ion exchange apparatus and treated. Trace ionic components and the like in the water are removed and supplied to the point of use.

[0009] However, when the primary pure water whose TOC concentration is reduced to an extremely low concentration in the primary system is treated in the secondary system, the TOC concentration and the dissolved oxygen concentration are higher than those after the treatment in the primary system. There is a problem that the phenomenon occurs.

The rise of dissolved oxygen in the water to be treated at the end of the treatment process is a serious problem. For example, in cleaning a silicon substrate in a semiconductor factory, an unintended oxide film is formed, which affects the device. Become. Further, if the treated water is supplied to the boiler as it is, it causes corrosion of the steel plate of the boiler and causes inconvenience.

[0011] The increase in dissolved oxygen is also caused by oxygen originally dissolved in the water to be treated, but the dissolved oxygen concentration and the organic matter concentration are increased by the following reaction in an ultraviolet oxidizer and a mixed bed ion exchanger. It is supposed to be.

(1) UV irradiation causes UV decomposition of water to generate hydroxyl radical (.OH).

(2) The generated hydroxy radical (.O
H) cannot react with a trace amount of organic matter in the primary purified water, and the hydroxy radicals combine with each other to generate hydrogen peroxide (H ₂ O ₂ ).

(3) The leaked hydrogen peroxide oxidizes and degrades the ion exchange resin installed in the subsequent stage, and at this time, a part of the hydrogen peroxide is decomposed into oxygen and water, and the hydrogen peroxide passes through the ion exchange device. The dissolved oxygen concentration in the treated water increases compared to the primary pure water before the treatment in the secondary process.

(4) Regarding the increase in the concentration of the organic substance, the leaked hydrogen peroxide causes the ion exchange resin to oxidize and deteriorate, so that fine resin fragments and organic substances are generated from the ion exchange resin and pass through the ion exchange apparatus. The concentration of organic substances in the water to be treated increases.

The reactions of (1) to (3) are represented by the following reaction formulas.

(1) H ₂ O + 185 nm → OH + H (2) OH + OH → H ₂ O ₂ (3) 4H ₂ O ₂ + resin (contact) → O ₂
+ For 2H ₂ O These problems, several solutions have been studied. Organic matter by utilizing the property of consuming the hydroxyl radical (· OH), and a method of adding the organic material prior to the ultraviolet irradiation treatment in order to consume the hydroxyl radical (· OH) generated by the ultraviolet irradiation treatment, H ₂
A method of reducing O ₂ by adding a compound has been proposed. However, a method that still leads to the fundamental problem solving, that is, a method of removing dissolved oxygen and organic matter,
Had not been found.

[0018]

As described above, in the conventional ultrapure water production method, the above-mentioned reaction occurs in the final stage of the production process, so that a large amount of dissolved oxygen is generated in the treated water. When pure water is supplied, this dissolved oxygen generates an unintended oxide film when cleaning a silicon substrate in a semiconductor factory or the like. In addition, there is a problem that equipment such as a boiler is corroded.

Although some solutions have been considered, in this ultrapure water production aimed at producing water that removes dissolved substances as much as possible, adding additives to the water to be treated should be avoided. It should be, and thus no clear solution has been invented yet.

Accordingly, the present invention has been made in order to solve such a drawback of the conventional production apparatus, and the use of a CO ₃ type anion exchange resin in the production process of ultrapure water makes it possible to obtain a hydroxyl radical (. OH) to reduce dissolved oxygen and further include a step of installing a deaerator after the pretreatment to reduce the amount of dissolved oxygen in the water to be treated in order to further ensure this treatment. Pure water production equipment.

It is an object of the present invention to prevent an increase in the concentration of dissolved gas, particularly oxygen, and organic substances in the final stage of the ultrapure water production process.

[0022]

SUMMARY OF THE INVENTION The present invention relates to an ultrapure device having an ultraviolet oxidizing device for decomposing organic substances and a mixed-bed ion exchange device filled with a cation / anion mixed resin for adsorbing and removing decomposition products caused by ultraviolet irradiation. In water production equipment,
An anion exchange device filled with a CO ₃ type anion exchange resin is arranged at the preceding stage of the ultraviolet oxidation device, and the above-mentioned object is achieved by this device and the method. It is possible to efficiently reduce the dissolved oxygen in pure water without adding any additives. In the present invention, more reliable effects can be expected by further providing a deaerator in the manufacturing process. As deaerators, there are a normal pressure deaerator, a membrane deaerator, a vacuum deaerator, etc.
It is preferable to use a high-efficiency vacuum deaerator with good performance.

The ultraviolet oxidizer is installed in each of the primary system and the secondary system.
An ultraviolet oxidizer equipped with a low-pressure ultraviolet lamp for irradiating ultraviolet light having a wavelength peak at -190 nm, particularly 184.9 nm.

The irradiation amount of the low-pressure ultraviolet lamp is 0.1
22 kW · h / m ³ , preferably 0.2-1 kW · h /
m is ^3. When the output of the low-pressure ultraviolet light exceeds 2 kWh / m ³ , the decomposition of organic substances is promoted, but the power consumption increases and the ratio of decomposition into carbon dioxide increases, and the mixed-bed ion exchange device It is not preferable because the capacity load is increased. At 0.1 kW · h / m ³ or less, the irradiation amount is small and organic matter is not decomposed.

The anion exchange device used in the present invention is C
An O ₃ type anion exchange resin is used. The CO ₃ type anion exchange resin is obtained by passing OH type anion exchange resin through Na ₂ CO ₃ or the like.

The mechanism by which the dissolved oxygen is reduced by using the CO ₃ type anion exchange resin can be explained as follows.

(1) Exchange ions in pure water with CO ₃ .

(2) CO ₃ ^2- and HCO ₃ ^- are produced.

[0029] (3) the resulting CO ₃ ^2- and HCO ₃ ^- is the scavenger hydroxyl radical (· OH).

(4) H ₂ O ₂ generated by recombination between OHs
Is reduced.

(5) As a result of (4), the resin of the mixed bed type ion exchange apparatus is not oxidized and degraded, and the increase in the dissolved oxygen concentration and the increase in the TOC concentration are suppressed.

The mixed bed type ion exchange apparatus 5 is a regeneration type or non-regeneration type packed with a strong basic anion exchange resin and a cation exchange resin for removing organic acids, trace amounts of carbon dioxide or other ionic components in the water to be treated. A regenerative mixed-bed ion exchange device can be preferably used. As the ion exchange resin to be used for this, a new product without crushing and a resin having high ion exchange performance and no elution are preferable.

The present invention is not limited to the automatic regeneration type apparatus, and in the case of a small-scale apparatus, a non-regeneration type column type apparatus may be used.

[0034]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of a pure water producing apparatus according to the present invention.

The apparatus for producing ultrapure water according to the present invention comprises a deaerator 1, a primary system comprising a first ultraviolet oxidizer 2 and a CO ₃ type anion exchanger 3, and a second ultraviolet oxidizer 4 and a mixed bed type. It is composed of a secondary system consisting of an ion exchange device 5,
They are arranged along the flow path in this order.

The anion exchange device 3 is used CO ₃ type anion exchange resin, Na ₂ the OH type anion exchange resin
CO _{3 and the} like were used to form a CO ₃ type by passing water. CO
_The method for producing the type ₃ anion exchange resin is as follows.

Regeneration was performed at 200 g / l-Resin. Na ₂ CO ₃ per 7 l of OH type anion exchange resin
(Kanto Chemical Co., Ltd., Deer Grade 1) dissolved in pure water 5.3
wt%. Then, 26.4 l is converted to SV = 4 / h (28 l / h
In # 7 l), water was passed through the resin for regeneration. Next, 14 l of pure water was passed through the extrusion at SV = 4 / h, and then 1 l of pure water at 70 l / h.
Washing was carried out by passing water for a time to produce a CO ₃ type anion exchange resin.

The mixed bed type ion exchange apparatus 5 is a strong basic anion exchange resin Duolite A- as an anion exchange resin.
33plus (plus Rohm & Haas), strong acid cation exchange resin Duolite C- as cation exchange resin
23 (20 Lohm & Haas Co.) was used, regenerated and converted into OH type and H type before mixing and filling. The ion exchange capacity of this mixed bed ion exchanger is
0.9 equivalent / l-Resin.

Next, the operation of this embodiment will be described.

The pure water after the pretreatment is led to the deaerator 1,
Dissolved oxygen and other gases in the water to be treated are removed. Thereafter, water is passed through the primary system. In the primary system, organic substances present in water are oxidatively decomposed by the ultraviolet oxidizing device 2 and passed through the anion exchange device 3. When the treatment is performed in the anion exchange device 3, CO ₃ ²⁻ and HCO ₃ ⁻ increase in the treated water. These ions have a role of capturing a hydroxyl radical (.OH), which is a cause of increasing dissolved oxygen.

Thereafter, CO ₃ ^2- and HCO were further added to the solution.
CO ₂ is added as needed to further increase ₃ ⁻ . At this time, the water to be treated in the acidic atmosphere is adjusted to pH 8
After adjusting to ~ 14, water is passed through the secondary system. Carbon dioxide is p
Different forms of dissolving the H, CO ₃ ^2- and HCO ₃ in which pH is in the 5 following was ionized ^- most of CO ₂
This causes the efficiency to worsen.

In the secondary system, organic substances are further oxidatively decomposed in the ultraviolet oxidizing apparatus 4, and the decomposed organic substances are removed by the mixed-bed type ion exchange apparatus 5.

[0044]

EXAMPLE 1 The concentration of dissolved oxygen in the water to be treated and the TOC concentration at each point were compared using the apparatus of the present invention and a conventional apparatus.

The apparatus used for comparison was provided with an OH type anion exchange resin instead of the CO ₃ type anion exchange resin.
Using this as Comparative Example 1, a comparative experiment was performed between the conventional apparatus and the apparatus of the present invention.

The results of the comparative experiment are shown in Table 1 for the dissolved oxygen concentration and Table 2 for the TOC concentration.

A: Vacuum deaerator outlet B: Primary system (ultraviolet oxidizer + anion exchanger) outlet C: Secondary system (ultraviolet oxidizer + mixed bed ion exchanger)
The outlet was used, and the value at each point was measured for each concentration (dissolved oxygen concentration, TOC concentration).

The TOC concentration and the dissolved oxygen concentration were measured using an online TOC meter (A-1000, A-1000).
S-20) and a highly sensitive dissolved oxygen meter (Orbis Fair Laboratories, model 2713) were used.

[0049]

[Table 1]

[Table 2] As is clear from Table 1, Comparative Example 1 was obtained at the primary system outlet (B).
Is the dissolved oxygen removal rate of 20 to 33%, but in Example 1,
It has risen significantly from 80 to 83%. Secondary system outlet (C)
In Comparative Example 1, the dissolved oxygen concentration increased by 2 to 3.5 ppb from the vacuum deaerator outlet (A), but in Example 1, there was no increase.

Further, Table 2 shows the results relating to the TOC concentration. According to the apparatus of the present invention, the primary system outlet (B) has about 8% of the conventional system outlet, and the secondary system outlet (C) has the conventional system. As a result, the TOC removal rate is improved by about 10%. As can be seen from this example, according to the present invention, it can be said that ultrapure water can be efficiently produced without increasing dissolved oxygen concentration and TOC concentration in the final stage of ultrapure water production.

[0051]

According to the present invention, when water is passed through an anion exchange device filled with a CO ₃ type anion exchange resin, CO ₃ ²⁻ and HCO ₃ ⁻ are increased in the water to be treated, whereby dissolved oxygen is increased. The hydroxyl radical (.OH), which is a cause of the generation, is efficiently removed without adding any additives to the water to be treated. This makes it possible to provide an ultrapure water producing apparatus that produces ultrapure water containing extremely little dissolved oxygen and organic substances.

[Brief description of the drawings]

FIG. 1 is a flowchart of an ultrapure water production apparatus according to the present invention.

[Explanation of symbols]

1 ... degassing device 2 ... 1st ultraviolet oxidation device 3
... anion exchange device 4 ... second ultraviolet oxidation device, 5
…… Mixed bed ion exchanger

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C02F 1/32 C02F 1/32 9/00 502 9/00 502J 502N 502R 503 503B 504 504B 504E

Claims (5)

[Claims] 1. A first step in which water is passed through an ultraviolet oxidizer, followed by treatment with an anion exchanger filled with a CO ₃ type anion exchange resin, and subsequently, a cation / anion is passed through the ultraviolet oxidizer. And a second step of treating with a mixed resin of the above. 2. A first step in which water is sequentially passed through a deaerator for removing dissolved gases and an ultraviolet oxidizer, and then treated with an anion exchanger filled with a CO ₃ type anion exchange resin. And a second step of treating with a mixed resin of cation and anion after passing the water through the apparatus. 3. An aqueous solution which has been passed through an anion exchange device filled with a CO ₃ type anion exchange resin is adjusted to a pH of 8 to 14 by adding an alkaline solution and then supplied to a subsequent stage. 4. The method for producing ultrapure water according to 2 or 3. 4. The ultrapure water according to claim 2, wherein carbon dioxide gas is supplied to the treated water that has passed through the anion exchange device filled with the CO ₃ type anion exchange resin and supplied to the latter stage. Water production method. 5. An ultrapure water producing apparatus comprising: an ultraviolet oxidizing device for decomposing organic substances; and a mixed-bed ion exchange device filled with a mixed resin of cation and anion for adsorbing and removing decomposition products by ultraviolet irradiation. An ultrapure water production apparatus, wherein an anion exchange apparatus filled with a CO ₃ type anion exchange resin is arranged at a stage preceding the oxidation apparatus.