JPH05285477A - Method for making ultrapure water - Google Patents

Abstract

PURPOSE:To continuously and easily obtain ultrapure water of high quality extremely low in silica concn. by setting the mixing ratio of the strong acidic cation exchange resin and strong basic anion exchange resin received in a polisher apparatus and the height of the packed resin bed to predetermined values and passing water to be treated through the resin bed at a predetermined water passing speed. CONSTITUTION:In an ultrapure water making method having a pretreatment means of water to be treated, a primary pure water making means and a secondary pure water making means 3 equipped with the nonregeneration type polisher device 3b'', the mixing ratio of the strong acidic cation exchange resin and strong basic anion exchange resin received in the polisher device 3b'' is set to 1/5 and the height of the packed resin bed is set to at least 0.4m and water to be treated is passed through the resin bed at a water passing speed satisfying formula 2m10<-2= height (m) of packed resin bed/linear velocity m/h of water to be treated <=8X10<-2> at the time of 0.4m<= height of packed resin bed < 0.8m and formula 1.5X10<-2= height (m) of packed resin bed/linear velocity m/h of water to be treated <=1X10<-1> at the time of 0.8<= height of packed resin bed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrapure water purification method, and more particularly to an ultrapure water purification method capable of continuously producing high-purity water having a significantly reduced silica concentration.

[0002]

2. Description of the Related Art Ultrahigh-purity pure water is widely used in fields such as semiconductor manufacturing and pharmaceutical manufacturing.
Then, such ultra-high-purity pure water is usually manufactured by ultra-high-purified water through a pretreatment means, a primary-purification means, and a secondary-purification means in this order. That is,
A pretreatment means such as a coagulating sedimentation tank or a sand filter for removing colloids in raw water, and an ion exchange device that contributes to the removal of most of the ions, organic substances, bacteria and fine particles in the pretreated water to be treated, For depurification means (DG), vacuum degassing equipment (VDG), reverse osmosis equipment (RO), etc., and for removing residual organic substances etc. in the water to be treated which has been subjected to this primary deionization treatment. Contribution UV organic matter decomposition device
(TOC-UV), ion-exchange resin-filled polisher, ultrafiltration membrane (UF) (or reverse osmosis (RO)), etc. Ultra high pure water is obtained.

FIG. 3 shows an example of a flow chart of such an ultrapure water purification method. Reference numeral 1 denotes a pretreatment means comprising a flocculation-precipitation apparatus 1a, a gravity type filtration apparatus 1b and a pretreated water tank 1c. Further, 2 is a two-bed three-tower type ion exchange device 2a, a reverse osmosis device (RO) 2b, a vacuum degassing device 2c, a mixed bed type ion exchange device 2d,
It is a primary pure water purification means consisting of the primary pure water tank 2e.
Is a secondary water purifying means composed of an ultraviolet organic substance decomposing device (TOC-UV) 3a, a non-regeneration type polisher device 3b filled with an ion exchange resin, and an ultrafiltration membrane (UF) 3c. The water quality of primary pure water in such a treatment process generally has a resistivity of ≧ 10 M.
Ω · cm, total organic carbon (TOC) ≦ 30 ppb, and the quality of secondary pure water (ultra-high-purity water) is as high as specific resistance ≧ 18 MΩ · cm, total organic carbon (TOC) ≦ 5 ppb. Then, it is sent to the youth point 4 for practical use.

[0004]

By the way, in the above ultrapure water purification method, most of the cations are Na ⁺ in the trace ions in the primary pure water supplied to the secondary pure water means 3, and the anions are Is silica (SiO ₂ ), carbon dioxide (C
O ₂ ), bicarbonate ion (HCO ^- ₃ ) account for the majority. That is, the selectivity of the ion exchange resin is generally as follows, and monovalent ions are worse than divalent ions, and silica (SiO ₂ ) is the worst anion.

[0005] Selection of the cation exchange resin _{^{Na + <NH + 4 <K}} + <Mg 2+ <Ca 2+ anion exchange resin selective ^{_{SiO 2 <F - <HCO -}} 3 <Cl - <NO - 3 <SO ²⁺ ₄ Further, in the reverse osmosis device (RO) 2b, the removal rate of monovalent ions is lower than that of divalent ions, and it can be said that the removal rate of CO ₂ which is a dissolved gas is 0.

As described above, trace impurities in the primary pure water are removed in the secondary pure water purification means 3, but first, when the ultraviolet organic substance decomposing device (TOC-UV) 3a is irradiated with ultraviolet rays of 185 nm. Organic matter is decomposed into organic acids and CO ₂ , and in addition to these organic acids and CO ₂ , a trace amount of N contained in primary pure water
Ions mainly composed of a ⁺ , SiO ₂ , CO ₂ , and HCO ^- ₃ are
After completely removing with a non-regeneration type polisher device 3b filled with an ion exchange resin, fine particles and bacteria are removed with an ultrafiltration membrane (UF) 3c.

From this point of view, as shown in the flow chart of FIG. 3, in the secondary deionizing means 3, the non-regeneration type polisher device 3b has, for example, an inner diameter of 254 mm and a length of 12
A structure in which a mixture of a highly acidic cation exchange resin and a strong basic anion exchange resin (almost equal ratio in ion exchange capacity) with a height of 1 m) is packed in an ion exchange tower of about 00 mm. 4, or as shown in FIG. 4, a non-regeneration type polisher device 3b ′ of the same structure, in which the mixing ratio of the strongly acidic cation exchange resin and the strongly basic anion exchange resin is increased and filled, Installation has also been attempted in front of the mold polisher device 3b.

In the structure of the secondary deionizing means 3, by using the non-regeneration type polisher device 3b having the above structure, high-purity (very high water quality) water can be obtained. The problem is recognized. That is, in continuous deionization operation, a slight amount of silica leaks from the outlet of the non-regeneration type polisher device 3b with the lapse of operating time, resulting in deterioration of water quality at the use point 4. This silica leak level is 1 ppb or less, which can be confirmed (discovered) by the improvement of the lower limit of quantification in the analysis of a trace amount of silica.

The present invention has been made in view of such circumstances, and an object thereof is to provide an ultrapure water purification method capable of ultrapure water purification in which the silica concentration is further reduced.

[0010]

The ultrapure water purification method according to the present invention comprises pretreatment means for treating water to be treated, primary purification means for purifying the pretreated water to be primary purification water, and Secondary purification means provided with a polisher device filled with a strongly acidic cation exchange resin-strongly basic anion exchange resin mixed system for secondary purification of the primary purified water to be treated. In the ultrapure water purification method, the mixing ratio of the strongly acidic cation exchange resin and the strongly basic anion exchange resin filled in the polisher device is 1/1 to 5/1, and the height of the filled resin layer is at least 0.4 m. When set and the following formula 0.4m ≤ height of filled resin layer <0.8m 2 x 10 ^-2 ≤ height of filled resin layer (m) / linear velocity of treated water (m / h) ≤ 8 x 10 ^-2 0.8 m ≤ height of filled resin layer 1.5 x 10 ^-2 ≤ height of filled resin layer (m) / linear velocity of treated water (m / h) ≤ 1 x 10 ^-1 Water speed (m / h) The feature is that the treated water is passed through.

The present invention is based on the following circumstances. That is, although the cause of the trace amount of silica leak is not clearly understood,
The ion exchange rate of the cation exchange resin for ⁺ is slower than the ion exchange rate of the anion exchange resin for the anion. In other words, the ion exchange rate of Na ^{+ in} the liquid to be treated flowing into the polisher device is the slowest, while in the ion exchange of anions, due to the difference in selectivity with respect to the ion exchange resin, CO ₂ and HCO ^- ₃ and organic acids are faster. Exchanged and slows down SiO ₂ . In this ion exchange process, started to CO ₂ and HCO ^- _3, the organic acid is adsorbed on the ion exchange resin OH ^- generates, generates a wake no small amount of NaOH in the presence of this time Na ^+, SiO _{When 2} is difficult to be adsorbed or the adsorbed SiO ₂ is easily desorbed, a small amount of silica leak will occur.
Alternatively, the lower the strongly acidic cation exchange resin / strongly basic anion exchange resin ratio in the polisher device, the more prominent the tendency of the trace silica leak to occur.

In order to solve such a tendency or problem, a mixture of a strongly acidic cation exchange resin and a strongly basic anion exchange resin filled in a non-regenerating type polisher device which constitutes a part of the secondary deionizing means as described above. When the ratio, the height of the ion exchange resin layer, and the height of the ion exchange resin layer and the water flow rate of the primary pure water are set within a predetermined range, it is possible to effectively avoid the problem of a slight amount of silica leak. It was confirmed that the present invention has been achieved.

[0013]

According to the ultrapure water purification method of the present invention, as described above, the mixing ratio of the strongly acidic cation exchange resin and the strongly basic anion exchange resin filled in the non-regeneration type polisher device and the high ion exchange resin layer are high. By setting the height of the ion-exchange resin layer and considering the height of the ion-exchange resin layer and selecting the water flow rate of the primary pure water to a relatively low range, Na ⁺ contained in the primary pure water can be completely adsorbed and removed. Since the generation and generation of NaOH in the non-regeneration type polisher can be eliminated, the generation of silica leak can be completely avoided, and high-quality ultrapure water can be easily and constantly obtained.

[0014]

Embodiments of the present invention will now be described with reference to FIGS.

FIG. 1 is a flow chart showing a secondary water purification means used in the ultrapure water purification method according to the present invention.
The secondary deionizing means 3'is an ultraviolet organic substance decomposing device (TOC-UV)
3a, non-regeneration type polisher device filled with ion exchange resin 3
b ″, composed of an ultrafiltration membrane (UF) 3c. where:
The non-regeneration type polisher device 3b ″ is configured as described below, but it is a UV organic substance decomposing device (TOC-U
V) 3a and ultrafiltration membrane (UF) 3c are common commercial products.
That is, the non-regenerative polishing device 3b ″ has an inner diameter
In a cylindrical column of 254 mm and 1200 mm in length, 30 l of strongly acidic cation exchange resin SK1B (trade name, manufactured by Mitsubishi Kasei Co., Ltd.) having a regeneration rate of 99% and a strongly basic anion exchange having a regeneration rate of 95% are used. Resin SA10A (trade name, manufactured by Mitsubishi Kasei Co., Ltd.), 20 liters of which are mixed and prepared almost uniformly, has a composition in which the packed bed has a thickness (height) of about 1 m. ..

A secondary water purifying means 3'having such a structure.
As a system in which the secondary deionizing means 3 in the flowchart of FIG. 3 is replaced, the primary deionized water (specific resistance ≧ 15Ω
・ Cm, SiO ₂ concentration ≤ 10 ppb, organic matter concentration ≤ 30 ppb)
Water is continuously passed through the secondary deionizing means 3'at a water flow rate of 2.0 m ³ / h (linear velocity = 40), and is subjected to a secondary deionization process through a non-regeneration type polisher device 3b "and the like. Next pure water (ultra pure water) was obtained, and the water quality of this ultra pure water was sampled and evaluated during the process of continuous secondary pure water treatment.
As shown in FIG. 2, the SiO ₂ concentration was below the detection limit (0.1 μg / l), the organic substance concentration was ≦ 2 ppb, and the silica concentration was extremely low.

Comparative Example 1 In the structure of the secondary deionizing means 3'of the above-mentioned example, a strong acid cation exchange resin SK1B (trade name, Mitsubishi) having a regeneration rate of 99% filled in the non-regenerating type polisher apparatus 3b "was used. Strongly basic anion exchange resin SA10A (trade name, manufactured by Mitsubishi Kasei) with 17 l and 95% regeneration rate 3
Under the same conditions as above, except that 3 l of mixed ion exchange resin was used, secondary pure water treatment was continuously performed, and the quality of ultrapure water was appropriately sampled and evaluated. Although it was 18 Ω · cm, the SiO ₂ concentration was above the detection limit (0.1 μg / l) as shown in FIG.

Comparative Example 2 In the structure of the secondary deionizing means 3'of the above-mentioned embodiment, the water passing speed of the primary deionized water continuously passing through the secondary deionizing means 3'was 3.
Under the same conditions as in the example, except that 0 m ³ / h (linear velocity = 59), secondary pure water treatment was continuously performed, and the quality of ultrapure water was sampled and evaluated. As a result, the specific resistance was ≧ 18 Ω · cm, but the SiO ₂ concentration was above the detection limit (0.1 μg / l) as shown in FIG.

Comparative Example 3 In Comparative Example 1, the water flow rate of primary pure water was 3.0 m ³ / h.
(Linear velocity = 59) Under the same conditions except that the secondary pure water treatment was continuously performed, the quality of the ultrapure water was sampled and evaluated. However, the SiO ₂ concentration was lower than the detection limit (0.1 μg /
l) or more.

Although a specific example is shown above, the mixing ratio of the strongly acidic cation exchange resin and the strongly basic anion exchange resin packed in the non-regeneration type polisher device is 1/1 to 5
/ 1, set the height of the filling resin layer to at least 0.4m, 0.4m
≤2 x 10 ^-2 when the height of the filled resin layer <0.8 m ≤Height of the filled resin layer (m) / linear velocity of treated water (m / h) ≤ 8 x 10 ^-2 ,
Also, when 0.8 m ≤ height of filled resin layer, 1.5 x 10 ^-2
≤Height of filled resin layer (m) / linear velocity of treated water (m / h) ≤ 1
Select × 10 ^-1 and the water flow rate (m / h) of the water to be treated.
When set, high-quality ultrapure water with an extremely low silica concentration can be obtained in any case.

[0021]

As is apparent from the above description and the examples, according to the ultrapure water purification method of the present invention, the specific resistance is ≧ 18 Ω · cm without requiring any particularly complicated means or operation. , Organic matter concentration ≤ 2 ppb, and SiO ₂ concentration is the detection limit (0.1 μg /
l) It is possible to continuously and easily obtain high-quality ultrapure water with extremely low silica concentration, which is used in semiconductor device manufacturing, pharmaceutical manufacturing, etc. It can be said that it will greatly contribute to the provision of.

[Brief description of drawings]

FIG. 1 is a flowchart showing a main part of an ultrapure water purification method according to the present invention.

FIG. 2 is a curve diagram showing a tube system of silica concentration in secondary pure water obtained by continuous operation by the ultrapure water purification method according to the present invention and continuous operation time in comparison with a case outside the present invention.

FIG. 3 is a flowchart of an ultrapure water purification method including pretreatment means, primary pure water treatment means, and secondary pure water treatment means.

FIG. 4 is a flowchart showing a secondary pure water treatment means in a conventional ultrapure water purification method.

[Explanation of symbols]

1 ... Pretreatment means 1a ... Precipitation apparatus 1b ... Self-powered filtration apparatus 1c ... Pretreated water tank 2 ... Primary pure water treatment means
2a ... 2 beds, 3 towers type ion exchange device 2b ... Reverse osmosis device
2c ... Vacuum deaeration device 2d ... Mixed bed type ion exchange device
2e ... Primary pure water treated water tank 3, 3 '... Secondary pure water treatment means 3a ... UV organic substance decomposing device 3b, 3b', 3b "... Non-regenerative polishing device 3c ... Ultrafiltration membrane 4 ... Use point

Claims (1)

[Claims] 1. A pretreatment means for treating water to be treated, a primary pure water purification means for converting the pretreated water to be primary purified water, and a purified water to be treated to be secondary purified water. In the ultrapure water purification method, which comprises a secondary pure water purification means provided with a polisher device filled with a strongly acidic cation exchange resin-strongly basic anion exchange resin mixed system, a strong acid filled in the polisher device is provided. The mixing ratio of the basic cation exchange resin and the strongly basic anion exchange resin from 1/1 to 5
/ 1, the height of the filling resin layer is set to at least 0.4m, and the following formula 0.4m ≤ height of the filling resin layer <0.8m 2 x 10 ^-2 ≤ height of the filling resin layer (m) / Linear velocity of treated water (m / h) ≤ 8 × 10 ^-2 0.8 m ≤ height of filled resin layer 1.5 × 10 ^-2 ≤ height of filled resin layer (m) / linear velocity of treated water An ultrapure water purification method characterized in that treated water is passed through at a water flow rate (m / h) satisfying (m / h) ≤ 1 × 10 ^-1 .