JP2003251362A - Sterilization method for ultrapure water feed pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an effective method for sterilizing bacteria propagating in the ultrapure water feed piping of an ultrapure water manufacturing apparatus. <P>SOLUTION: The ultrapure water feed piping 7 of a secondary pure water system is provided with an ozone/carbon-dioxide gas injection device 10 for injecting carbon dioxide gas and ozone, and bypass piping 9a, 9b connecting the inlet side piping 7 of an ion exchange device 5 and the outlet side piping 7 of an ultrafiltration device 6. Carbon dioxide gas and ozone are injected from the ozone/carbon-dioxide gas injection device 10 into the ultrapure water feed piping 7 and made to flow into the ultrapure water feed piping 7 while bypassing the ion exchange device 5 and the ultrafiltration device 6. After completing the sterilization operation, the treated water is introduced in an ultraviolet irradiation device 4 to decompose ozone, and then discharged. <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 secondary pure water used for wet cleaning in industries handling electronic materials such as silicon substrates for semiconductors and glass substrates for liquid crystals. The present invention relates to a method for sterilizing a water supply pipe, and particularly to a method for sterilizing an ultrapure water supply pipe in a secondary pure water production line.

[0002]

2. Description of the Related Art Conventionally, ultrapure water has been widely used for cleaning silicon substrates for semiconductors, glass substrates for liquid crystals and the like.

Generally, an ultrapure water production system comprises a primary pure water system consisting of a filtration device, a reverse osmosis membrane device, a degassing device, an ion exchange device, etc., and a primary pure water produced from the primary pure water system to a secondary pure water system. It is composed of an ultraviolet irradiation device, an ion exchange membrane device, an ultrafiltration device (UF device), and a secondary pure water system including points of use for producing water.

In such an ultrapure water production system, the primary pure water once stored in the water storage tank is treated with an ultraviolet irradiation device, an ion exchange membrane device, a UF device, etc. through a main pipe to form secondary pure water. Will be supplied to the point of use. Secondary pure water that was not consumed at the point of use is returned to the water tank through the main pipe that connects the point of use and the water tank, and is sent to the point of use while being purified again by each water treatment device in the same flow path. .

By the way, when the ultrapure water production system is stopped for maintenance or the like, the longer the stop time, the more the trace amount of microorganisms (bacteria) propagate in the ultrapure water supply pipe.
Microorganisms in ultrapure water must be removed because they cause defects in electronic materials.

[0006] As a method of killing the propagated microorganisms,
A method of sterilizing microorganisms by injecting ozone water into the ultrapure water supply pipe is also being investigated, but dissolved ozone in ozone water is unstable and easily decomposes into water and oxygen gas There was a problem that it was difficult to sterilize.

Further, ozone is dissolved in the treated water obtained by sterilizing the ultrapure water supply pipe with ozone water, and it is necessary to decompose and remove ozone when discharging it. The decomposition method using activated carbon has a problem that the equipment cost increases because the equipment increases.

[0008]

As described above, in the conventional ultrapure water production system, when microorganisms are generated, propagated and aggregated on the downstream side of the final stage UF device, they are released from the use point. There is a problem that it adheres to the object to be cleaned.

As a method for preventing the growth of microorganisms, a method of sterilizing microorganisms by injecting ozone water into an ultrapure water supply pipe has been studied. However, dissolved ozone in ozone water is unstable and decomposes into oxygen gas. There is a problem that it is difficult to sterilize the entire length of the long-distance pipe because it tends to occur.

Further, in the conventional decomposition method using activated carbon for decomposing and removing ozone from the treated water sterilized with ozone water in the ultrapure water supply pipe, there is a problem that the equipment cost increases because the equipment increases.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object thereof is to provide a method for effectively sterilizing the inside of an ultrapure water supply pipe by using ozone water to which carbon dioxide gas is added. To do.

Further, the present invention is an ultrapure water supply pipe in which treated water containing ozone after sterilizing the inside of the ultrapure water supply pipe is decomposed into ozone and drained without using activated carbon. It aims at providing the sterilization method of.

[0013]

A method of sterilizing an ultrapure water supply pipe according to the present invention comprises a water storage tank for storing primary pure water produced in a primary pure water production line, and a downstream side of the water storage tank. An ultraviolet irradiation device, a plurality of water treatment devices including an ion exchange device and an ultrafiltration device disposed on the downstream side of the ultraviolet irradiation device, and a use for supplying the ultrapure water treated by each of the water treatment devices. Points and the water storage tank,
Ultrapure water production including a main pipe connecting each water treatment device and the use point and further connecting the use point and the water storage tank to form a circulation path, and a water supply pump provided in the main pipe In the method of sterilizing ultrapure water supply pipe in an apparatus, an ozone / carbon dioxide injection device for injecting carbon dioxide and ozone is provided in the main pipe, and the main pipe on the inlet side of the ion exchange device and the ultrafiltration device are provided. A bypass pipe that bypasses the outlet side main pipe is provided, carbon dioxide gas and ozone are injected into the main pipe from the ozone / carbon dioxide injection device, and ultrapure water in which the carbon dioxide gas and ozone are dissolved is It is characterized in that the ion exchange device and the ultrafiltration device are bypassed to flow in the main pipe.

In the present invention, the primary pure water produced by the primary pure water producing apparatus has, for example, a specific resistance value of 18.2 MΩcm or more, a TOC concentration of 1 ppb or less, and a metal impurity of 10 pp.
t or less, silica: 0.1 ppb or less, fine particles 0.05 μ
It has a high purity of about 1 to 2 pieces / ml in m size.

In the present invention, as an ozone / carbon dioxide dissolving device for dissolving ozone and carbon dioxide in pure water flowing through the main pipe and the bypass pipe of the sterilizer for the ultrapure water supply pipe, for example, PTFE (trade name: Teflon <registered A trademark>) hollow fiber membrane device can be used. In the present invention, even a simple gas dissolving means such as an ejector can finally obtain a sufficient melting effect.

The ozone and carbon dioxide gas used in the present invention may be generated by injecting carbon dioxide gas into ultrapure water and electrolyzing it to generate ultrapure water in which ozone and carbon dioxide gas are dissolved. . The electrolytic ozone water producing apparatus can generate ozone and oxygen at the anode by the following reaction to generate ozone water having an ozone concentration of 14 to 20% by weight.

The ozone concentration in the main pipe is 0.05
˜2 ppm, preferably 0.1 to 0.5 ppm, more preferably about 0.2 ppm is suitable. The concentration of carbon dioxide gas injected with ozone in the main pipe is preferably in the range of 4 to 6 in pH.

The ozone / carbon dioxide injection device is preferably connected to the main pipe downstream of the bypass pipe bypassing the UF device.

Further, it is possible to circulate in the main pipe by bypassing the ion exchange device and the UF device injected into the main pipe.

A plurality of ultraviolet irradiators are arranged in parallel, and at least one of them is separated from the main pipe by using a sluice valve and a bypass pipe if necessary, and flows through the main pipe. It is also possible to treat pure water that dissolves ozone with this independent ultraviolet irradiation device and discharge it to the outside of the system. Further, by providing a heat exchanger for controlling the temperature of the ultrapure water in the main pipe in the ultrapure water producing device and controlling the water temperature in the main pipe within the range of 5 to 15 ° C., the duration of ozone It is also possible to extend.

As the ion exchange apparatus, a cation exchange resin tower or an anion exchange resin tower may be used alone or in combination, or an electric ion exchange apparatus tower may be used.

It is preferable to use a fluorine-based resin which is less likely to be deteriorated by ozone as a material forming a portion which comes into contact with ozone water, such as each of the water treatment devices and pipes. Specifically, PVDF is suitable for the piping, and PTFE is suitable for packing.

Further, in addition to the above water treatment device, a degassing device and other water treatment devices can be added to the ultrapure water producing device of the present invention, if necessary.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments embodying the present invention will be described below.

(Embodiment) As shown in FIG. 1, the sterilizer for an ultrapure water supply pipe of this embodiment has a water storage tank 1 for storing the primary pure water produced in the primary pure water production line, and a water storage tank 1. A water supply pump 2, a heat exchanger 3, an ultraviolet irradiation device 4, an ion exchange resin tower (mixed bed of cation exchange resin and anion exchange resin) 5, and a UF device 6 which are sequentially arranged on the downstream side. These water treatment devices are sequentially connected by the main pipe 7, and the secondary pure water treated by each water treatment device is
It is sent to the use point 8 by the main pipe 7 extending further from the F device 6. . The secondary pure water not used at the use point 8 is returned to the water storage tank 1 through the main pipe 7. Incidentally, these water treatment devices and pipes are the standard configuration of the ultrapure water production device.

By-pass pipes 9a and 9b are connected to the inlet pipe and the outlet pipe of the ion-exchange resin tower 5 and the UF device 6 through sluice valves V3, V6, V7 and V10. Pure water containing carbon dioxide and ozone flowing therein is bypassed between the ion exchange resin tower 5 and the UF device 6 via bypass pipes 9a and 9b.

Further, the main pipe 7 is provided with a bypass pipe 10 connecting between just before the water storage tank 1 and just before the ultraviolet irradiation device 4 and a drain pipe 11 immediately after the ultraviolet irradiation device 4.
The pure water returned from the point of use 8 can be discharged as drain through the ultraviolet irradiation device 4 without returning to the water storage tank 1.

As shown in FIG.
Pure water is connected in parallel to the main pipe 7 and always flows in parallel through both of the ultraviolet irradiation devices 4a and 4b. However, by operating the sluice valves V11 to V14, one of the 4a is independent of the main pipe 7. Then, it can be used for decomposing the remaining ozone.

Immediately after the connecting portion of the bypass pipe 9b bypassing the UF device 6 to the main pipe 7, an ozone / carbon dioxide dissolving device 12 for injecting carbon dioxide and ozone into pure water flowing in the main pipe 7. Are connected. As the ozone / carbon dioxide dissolving device 12, a known ozone dissolving pump, ozone dissolving module, ejector or the like can be used. The injection amount of carbon dioxide and ozone is the pH not shown.
By feedback control using a sensor that monitors the ozone concentration, the concentrations of carbon dioxide and ozone when dissolved in pure water are adjusted to pH 4 to 6 and 0.05 to 2 ppm, respectively.

In the apparatus of this embodiment, the sluice valves V2, V3, V6, V7, V10, V11, V13 are closed and the sluice valves V1, V4, V5, V8, V8, V12 are used during the normal production of secondary pure water. , V14 is opened, the bypass pipes 9a, 9b, 10 and the drain pipe 11 are closed, and the main pipe 7 is opened, and the same operation as that of the conventional ultrapure water production system is performed.

That is, the primary pure water supplied from the primary pure water producing device is temporarily stored in the water storage tank 1 and is sent by the water supply pump 2 to the ultraviolet irradiation device 4 via the heat exchanger 3 where a slight amount of it exists. The organic impurities are decomposed into organic acids and sent to the ion exchange resin tower 5 to remove the ionic components. Next, the secondary pure water sent to the use point 7 through the UF membrane device 6 and not used at the use point 7 is returned to the water storage tank 1.

In the present invention, as the sterilization of the ultrapure water supply pipe, either a circulation system or a one-pass system can be adopted as required.

[Circulation method] In this method, after water containing carbon dioxide and ozone is circulated in the ultrapure water supply pipe for a required time, ozone is decomposed by an ultraviolet irradiation device and waste water is discharged to the outside of the system. It is then discarded or reused as raw water for primary pure water.

In this system, after the inflow of primary pure water into the water storage tank 1 is stopped, the gate valves V2, V4, V5, V8, V9 and V1 are shut off.
Close 1, V13, gate valves V1, V3, V6, V7, V10, V11,
V13 is opened to operate the water supply pump 1, and ozone water containing carbon dioxide is injected into the main pipe 7 from the ozone / carbon dioxide injection device 12. At this time, the temperature of the ultrapure water in the main pipe 7 is controlled by the heat exchanger 5 so as to be in the range of 5 to 15 ° C.

The concentrations of carbon dioxide and ozone in the main pipe 7 are
The pH and carbon dioxide concentration in the main pipe 1 are monitored by a pH meter and an ozone concentration measuring device (both not shown) arranged downstream of the ozone / carbon dioxide injecting device 12 (both are not shown), and the ozone concentration is 4 to 6 It should be in the range of 0.05 to 2 ppm.

After the circulation operation is finished, the gate valves V1, V12, V
14 is closed, the sluice valves V2, V11 and V13 are opened, and the ultraviolet irradiation device 4a is operated to decompose the dissolved ozone by the ultraviolet irradiation device 4a, and all the pure water in the water storage tank 1 is discharged to the outside of the system.

By this treatment, the number of microorganisms which was 500 cells / ml before the treatment was reduced to 0-1 cells / 100 ml. The number of bacteria is based on a method of culturing bacteria (mainly Pseudomonas sp.) Filtered through a membrane filter and measuring the number of bacteria.

[One-pass method] In this method, water containing carbon dioxide and ozone is passed through the ultrapure water supply pipe only once, and then ozone is decomposed to discharge the wastewater to the outside of the system or discard it. Alternatively, it is a method of reusing it as raw water of primary pure water.

In this system, after shutting off the inflow of the primary pure water into the water storage tank 1, the gate valves V1, V12, V4, V5, V8, V
9, V12, V14 are closed and gate valves V2, V3, V6, V7, V10, V
11, V13 is opened and the water supply pump 1 is operated,
Ozone water containing carbon dioxide gas is injected into the main pipe 7 from the ozone / carbon dioxide injection device 12. At this time, the temperature of the ultrapure water in the main pipe 7 is controlled by the heat exchanger 5 so as to be in the range of 5 to 15 ° C.

The concentrations of carbon dioxide and ozone in the main pipe 7 are
The carbon dioxide concentration in the main pipe 1 is in the range of 4 to 6 and the ozone concentration is in the range of 0.05 to 2 ppm monitored by a pH meter and an ozone concentration measuring device arranged downstream of the ozone / carbon dioxide injection device 12 and by feedback control. So that

By this treatment, the number of microorganisms which was 500 cells / ml before the treatment was reduced to 0 to 3 cells / 100 ml.

[0042]

As apparent from the above examples, in the sterilizing method of the ultrapure water supply pipe of the present invention, the ozone water in which the carbon dioxide gas is dissolved and stabilized is used, and therefore, the dissolved ozone in the ozone water is used. Is stabilized, and it becomes possible to sterilize over the entire length of the long distance pipe. Also, ozone water is
There is no risk of ozone degrading the ion exchange resin or UF membrane that flows around the ion exchange device and the UF device.
Further, by treating the treated water obtained by sterilizing the ultrapure water supply pipe with the ultraviolet irradiation device, the dissolved ozone in the wastewater can be easily decomposed and removed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a main part of a configuration of an embodiment of the present invention.

[Explanation of symbols]

1 ... water tank 2 ... Water pump 3 ... Heat exchanger 4 ... Ultraviolet irradiation device 5: Mixed bed type ion exchange resin tower 6 ... UF device 7 ... Main piping 8 ... Use point 9a, 9b ... Bypass piping 10 ... Ozone / carbon dioxide dissolver 11 ... Drain piping 12 ... Ozone / carbon dioxide dissolver V1 to V14 ... Gate valve

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) A61L 2/20 A61L 2/20 J C02F 1/32 C02F 1/32 1/78 1/78 (72) Invention Naoichi Yonekawa 2-9-8 Okada, Atsugi-shi, Kanagawa Nomura Micro Science Co., Ltd. (72) Inventor Arihiro Nomura 2-9-8 Okada, Atsugi-shi, Kanagawa F-term (Nomura Micro Science Co., Ltd.) Reference) 4C058 AA20 BB06 BB07 BB09 CC04 CC07 DD04 DD11 JJ07 JJ14 JJ16 JJ28 KK02 KK46 4D037 AA03 AB03 BA18 BB01 BB02 CA02 CA12 CA14 CA15 4D050 AA05 AB06 BB02 BD06 BD08 CA07 CA13 CA20

Claims (6)

[Claims] 1. A water storage tank for storing primary pure water produced in a primary pure water production line, an ultraviolet irradiation device arranged on the downstream side of the water storage tank, and an ultraviolet irradiation device arranged on the downstream side of the ultraviolet irradiation device. A plurality of water treatment devices including an ion exchange device and an ultrafiltration device, a use point for supplying ultrapure water treated by each of the water treatment devices, and the water storage tank,
Ultrapure water production including a main pipe connecting each water treatment device and the use point and further connecting the use point and the water storage tank to form a circulation path, and a water supply pump provided in the main pipe A method for sterilizing ultrapure water supply pipe in an apparatus, wherein the main pipe is provided with an ozone / carbon dioxide injection device for injecting carbon dioxide and ozone, and the main pipe on the inlet side of the ion exchange device and the ultrafiltration device are provided. A bypass pipe that bypasses the outlet side main pipe is provided, and carbon dioxide gas and ozone are injected into the main pipe from the ozone / carbon dioxide injection device to obtain ultrapure water in which the carbon dioxide gas and ozone are dissolved.
A method for sterilizing an ultrapure water supply pipe, characterized in that the ion exchange device and the ultrafiltration device are bypassed to flow into the main pipe. 2. Ultra-pure water in which carbon dioxide gas and ozone are dissolved is circulated in the circulation path.
A method for sterilizing the ultrapure water supply pipe described. 3. The ultrapure water supply pipe according to claim 1, wherein the ozone / carbon dioxide injection device is connected to a main pipe downstream of a bypass pipe that bypasses the ultrafiltration device. Sterilization method. 4. The method for sterilizing the ultrapure water supply pipe according to claim 1, wherein a plurality of the ultraviolet irradiation devices are arranged in parallel. 5. At least one of the ultraviolet irradiation devices arranged in parallel is separated from the main pipe by a sluice valve, and ozone that flows in the main pipe and is discharged to the outside of the system is dissolved. 5. The sterilizing method of the ultrapure water supply pipe according to claim 4, wherein the water to be treated is treated by the independent ultraviolet irradiation device and discharged to the outside of the system. 6. The ultrapure water producing apparatus comprises a heat exchanger for controlling the temperature of the ultrapure water flowing in the main pipe within a range of 5 to 15 ° C. Or 1
The method for sterilizing the ultrapure water supply pipe according to the item.