JPH0716581A - Method for sterilizing ultrapure water with ozone and device therefor - Google Patents

Abstract

PURPOSE:To reduce the number of bacteria to the lowest level by injecting ozone- containing gas and hydrogen-containing gas successively into used pure water in a system of circulating and using the ultrapure water prepared in an ultrapure water preparation device for washing or the like, and then flowing the same back and circulating. CONSTITUTION:Primary pure water prepared by a pure water preparation device 11 by means of distillation or ion exchange is stored in a primary pure water tank 12, and supplied to an ultrapure water preparation device 16 by a circulating pump 13 through a hydrogen dispersion device 15. Inorganic substances in the pure water are removed by a polisher 17 and also removed together with organic particles and the like by a filter device 18 to prepare ultrapure water. The ultrapure water thus prepared is supplied to use points 21... and used for washing electronic parts and the like. The used pure water is returned to the primary pure water tank 12 through a return line 22, and at that time, ozone-containing gas prepared by an ozonizer 23 is injected and sterilization is carried out, and the ozone-containing water is reacted with hydrogen dispersed from a hydrogen dispersion device 15 to remove ozone and oxygen from the pure water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for maintaining a highly sterile state of a system for producing and supplying a large amount of ultrapure water required in the technical fields such as electronic industry and pharmaceutical manufacturing.

[0002]

2. Description of the Related Art When producing ultrapure water required in the technical fields of electronic parts washing and pharmaceutical manufacturing, pure water produced by primary purification such as distillation or ion exchange is passed through a polisher or the like. It is supplied to an ultrapure water producing apparatus containing the same to further remove impurities such as particles and improve the purity. The ultrapure water produced in this way is supplied to the point of use through the supply line and used for cleaning, etc., and then unused or used ultrapure water or pure water is circulated to the primary purification step for reuse. I am trying to do it.

That is, as shown in FIG. 2, a pure water producing apparatus 1
The pure water produced in step 1 and stored in the primary pure water tank 2 is sent to the ultrapure water producing apparatus 4 using the pump 3. The ultrapure water producing device 4 comprises at least a polisher 5 for removing inorganic substances in pure water and a microfilter 6 for removing fine particles and high molecular weight organic substances, and a microfilter 6 such as an ultrafiltration membrane. The purity of the inside is improved and the resulting impurities are removed by filtration. The ultrapure water production system 4 may include an ultraviolet germicidal lamp for sterilizing live bacteria. In the illustrated example, the ultrapure water produced by the ultrapure water producing apparatus 4 is supplied to two use points 8 in the illustrated example, and at the use points 8, an operation such as cleaning of electronic parts is performed and an object to be treated is processed. Process. Used pure water or unused ultrapure water which has been used in this treatment operation or supplied excessively and which has not been used is collected and circulated through the return line 9 to the primary pure water tank 2 to produce ultrapure water again. Water is sent to the device 4 and used for cleaning and the like.

As described above, in the treatment system using the ultrapure water circulation shown in the figure, the ultrapure water is effectively used and the object to be treated can be efficiently treated. However, even when the ultraviolet sterilizing lamp is used, the sterilization is performed. Even if the circulation pump 3 is constantly operated so that the sterilizing power of the lamp is weak and the water flow does not become stagnant so that the circulation flow is not interrupted, the generation of bacteria is observed. This bacterium deteriorates the water quality of the ultrapure water, and the ultrapure water with the deteriorated water quality causes a deterioration in the quality of the product obtained by treating the object at the point of use and a decrease in the yield and productivity. . As the number of bacteria increases, the number of particles in the ultrapure water in the system and the TOC
Also tends to increase.

Conventionally, in order to keep the number of bacteria inevitably generated in the ultrapure water circulation system at a low level as much as possible, the operation is periodically stopped to remove sodium hypochlorite, hydrogen peroxide, ozone, etc. It has been common to sterilize and clean the system by holding a bactericide and hot water in the system. According to this method, although the growth of bacteria can be suppressed, the operation of the ultrapure water circulation system must be stopped for several hours to 1 day, and therefore, the production of ultrapure water and the production activities using the ultrapure water are also required. During this time, the operation must be stopped or slowed down, and it is not desirable to adopt the above method which causes a decrease in productivity, especially in the electronic industry aiming at continuous operation for a year.

Further, in the above-mentioned bactericidal agent addition method, a secondary problem occurs accordingly. For example, thorough post-cleaning of the system with ultrapure water is necessary so that the sterilizing agent does not remain in the system after the sterilizing agent is used, and there is a problem of treatment of cleaning waste water. Further, even when hot water is used, there are problems such as heat energy consumption required for raising and lowering temperature, heat resistance of apparatus piping for organic materials and the like, and these are unsolved.

[0007]

It is an object of the present invention to solve the above-mentioned problems of the prior art by continuously operating the ultrapure water production and supply system without substantially stopping the operation of the ultrapure water production and supply system. It is an object of the present invention to provide an ultrapure water ozone sterilization method and apparatus capable of treating an object to be treated with high-purity ultrapure water while keeping the number of bacteria at the minimum level.

[0008]

According to the present invention, primary pure water in a primary pure water tank is supplied to an ultrapure water producing apparatus containing at least a polisher to form ultrapure water, and the ultrapure water is supplied to a supply line. Ultrapure water ozone that is supplied to the point of use through which water is sent to the point of use to treat the object using the ultrapure water and the used pure water is circulated to the primary pure water tank via a return line. In the sterilization method, ozone is injected into the used pure water between the point of use and the primary pure water tank, and a hydrogen-containing gas is supplied between the primary pure water tank and the ultrapure water producing apparatus to remain. It is an ultrapure water ozone sterilization method characterized by performing ozone removal and deoxidation, and an apparatus used for the method.

The present invention will be described in detail below. Ozone has a stronger oxidizing power than chlorine, has an effect on sterilization, deodorization, decolorization, and the like, and since it does not cause the problem of secondary pollution by decomposing into oxygen after the oxidation action, the range of use of ozone is being expanded in recent years, Ozone is used in various fields such as water treatment for semiconductor cleaning water, medical treatment, and food.

Also in the present invention, the sterilizing power of ozone is utilized to sterilize the ultrapure water production and supply system. Ultrapure water or pure water that circulates between the use point and the primary pure water tank in the proper place of the ultrapure water circulation system of the present invention (the ultrapure water and pure water may be simply referred to as pure water)
Ozone-containing gas is continuously or intermittently injected therein. As a result, the ultrapure water or pure water contains ozone. Therefore, the inside of the system downstream from the injection point is kept substantially sterile, and the generation and propagation of bacteria and the like is suppressed.
However, the system of the present invention includes an ultrapure water production apparatus having poor resistance to ozone, and if the ultrapure water containing ozone or pure water is supplied as it is, the purity of the ultrapure water produced by the apparatus decreases. The quality of the object to be processed by the ultrapure water is also reduced. Therefore, in the present invention, hydrogen-containing gas is supplied to the line between the primary pure water tank and the ultrapure water producing device to remove residual ozone, and pure water containing substantially no ozone is produced in the ultrapure water producing device. Supply to.

The residual ozone can be removed by using a hydrogen diffuser or the like. When pure water containing ozone or oxygen is supplied in a spray state to a hydrogen diffuser filled with a catalyst for a reaction that produces water by the reaction of ozone or oxygen with a hydrogen-containing gas, the ozone or oxygen in the pure water becomes hydrogen. It reacts with the gas and becomes water and is removed. Unlike the activated carbon treatment, impurities are unlikely to be mixed in when removing residual ozone using hydrogen gas. Since ozone does not exist between these devices and the ultrapure water producing device and the generation of bacteria cannot be suppressed, the device is installed immediately before the ultrapure water producing device to make the ozone-free line as short as possible. Is desirable.

The ozone used in the present invention must be high-purity ozone containing almost no impurities. The ozone can be produced by a silent discharge method in which a high voltage is applied to oxygen gas to convert a part of oxygen into ozone, but the ozone produced by the method has a considerable amount of particles and metals mixed therein, Not desirable for cleaning in the electronics industry. In the present invention, it is desirable to use an oxygen-mixed ozone gas by an electrolysis method that can obtain ozone of higher purity than the ozone obtained by the silent discharge method. To electrolyze pure water to obtain the oxygen-ozone mixed gas,
A substrate having ozone resistance as an anode on one side of the solid electrolyte, for example, a material in which lead oxide or tin oxide is coated on a titanium substrate, and on the other side a platinum group metal such as platinum using stainless steel or carbon as a substrate as a cathode. It is sufficient to supply pure water to the anode continuously or intermittently and apply a DC voltage between the anode and the cathode by using each of the materials coated with. Further, in order to effectively sterilize with ozone, it is desirable to inject the ozone-containing gas so that the ozone concentration in ultrapure water or pure water will be about 10 × 10 ^{−3 to} 500 × 10 ⁻³ mg / liter.

Although hydrogen gas in a cylinder may be used as the hydrogen-containing gas and supplied, the hydrogen gas is supplied to the hydrogen diffuser or the like because a high concentration hydrogen gas is obtained at the cathode by the electrolysis. Is desirable. Further, it is desirable to maintain the ratio of the hydrogen gas supplied to the hydrogen diffuser to the ozone gas injected into the line in the range of 2: 1 to 5: 1.

Next, an example of the ultrapure water ozone sterilization method according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a flow sheet showing an example of the ultrapure water ozone sterilization method according to the method of the present invention. Pure water production equipment by distillation or ion exchange 11
The primary pure water produced in step 1 is first stored in the primary pure water tank 12. This primary pure water is then passed through a hydrogen diffuser 15 by a circulation pump 13 connected to the tank 12 and an ultrapure water producing device.
Supplied to 16.

The ultrapure water producing device 16 comprises a polisher 17 and a microfiltration device 18. The inorganic substance in the pure water is removed by the polisher 17 and removed by the filtration device 18 together with already existing organic particles. To produce ultrapure water. The ultrapure water is supplied to the two use points 21 in parallel in the illustrated example through the supply line 19, and at the use points 21, operations such as cleaning of electronic parts are performed to process the object. Spent pure water or unused ultrapure water used or excessively supplied in this treatment operation is collected and circulated to the primary pure water tank 12 through a return line 22. The ozone-containing gas produced by the ozonizer 23 is injected into the used pure water or unused ultrapure water in 22.

The pure water circulated in the primary pure water tank 12 is similarly supplied to the hydrogen diffuser 15 by the circulation pump 13. The hydrogen diffuser 15 is filled with a decomposition catalyst for ozone and oxygen, and the ozone and oxygen supplied to the hydrogen diffuser 15 react with hydrogen to generate water, so that the ozone and oxygen are in pure water. And is supplied to the ultrapure water production system 16.

With such an operation, each use point 21
The object is treated with ultrapure water at the supply line
Since ozone-containing gas is injected into the ultrapure water by the ozonizer 23 in the return line 22 and the return line 22, the pure water or ultrapure water circulating in the system contains ozone up to the hydrogen diffuser 15 and therefore the propagation of bacteria. Each point of use is suppressed by ultrapure water that is substantially free of bacteria.
It makes it possible to process the object at 21.

[0018]

EXAMPLES Next, examples of ultrapure water ozone sterilization according to the present invention will be described, but the examples do not limit the present invention.

[0019]

Example 1 Ultrapure water ozone sterilization was performed according to the flow chart shown in FIG. Raw water having a specific resistance of 10 ⁴ Ωcm was brought into contact with anion and cation exchange resins in a pure water production apparatus to remove impurities and stored in a primary pure water tank.
Use this pure water with polisher and micron filter (pore size 0.1
micrometer) to produce ultrapure water, which is then supplied to the semiconductor substrate cleaning step to obtain specific resistance before cleaning, TOC, number of bacteria, ozone concentration and dissolved oxygen. The quantity was measured. The results are shown in Table 1. After cleaning with pure water, the electrolyzed ozone-oxygen mixed gas was injected at 1 mg / min in the return line after cleaning, and then circulated in the primary pure water tank. At this time, the specific resistance, TOC, number of bacteria, ozone concentration and dissolved oxygen amount were measured, and the results are shown in Table 1. This pure water was sprayed at a rate of 20 ml / min into a hydrogen diffuser filled with a catalyst in which a carrier polypropylene resin was loaded with a catalytic metal Pd at a rate of 10 mg / cm ² . The ozone concentration in pure water taken out from the hydrogen diffuser was 0.

[0020]

[Comparative Example 1] Ultrapure water ozone sterilization was performed using the same apparatus as in Example 1 except that ozone was not injected and a hydrogen diffuser was not installed, and the ultrapure water ozone was sterilized in the primary pure water tank and at the point of use. The specific resistance, TOC, number of bacteria, ozone concentration, and dissolved oxygen amount of ultrapure water or pure water were measured. The results are shown in Table 1. From Table 1, TO at the point of use
It can be seen that C, dissolved oxygen and the number of bacteria are greatly reduced in Example 1.

[0021]

[Table 1]

[0022]

According to the present invention, the primary pure water in the primary pure water tank is supplied to an ultrapure water producing apparatus containing at least a polisher to obtain ultrapure water, and the ultrapure water is passed through a supply line to a use point. In the ultrapure water ozone sterilization method in which the ultrapure water is used to treat the object to be treated at the point of use and the used pure water is circulated to the primary pure water tank through a return line, Injecting ozone-containing gas into the used pure water between the point of use and the primary pure water tank,
Further, there is provided an ultrapure water ozone sterilization method characterized in that a hydrogen-containing gas is supplied between the primary pure water tank and the ultrapure water production apparatus to perform residual ozone removal and deoxidation, and an apparatus usable for the method. .

Therefore, in the present invention, ozone is present in ultrapure water or pure water located up to the hydrogen diffuser on the downstream side of the ozone injecting section to prevent the generation and propagation of bacteria and the like,
The bacteria concentration in ultrapure water is made substantially zero without stopping the operation. Therefore, the quality of the object to be treated by the ultrapure water is improved and the treatment capacity of the ultrapure water is maximized. Moreover, since a hydrogen-containing gas is supplied to the upstream side of the ultrapure water production system, which has poor resistance to ozone, to convert residual ozone into water and remove it, the ultrapure water production capability of the ultrapure water production system. Is not damaged.

[Brief description of drawings]

FIG. 1 is a flow sheet illustrating the procedure of ultrapure water ozone sterilization according to the present invention.

FIG. 2 is a flow sheet illustrating the procedure of ultrapure water ozone sterilization according to a conventional technique.

[Explanation of symbols]

11 ・ ・ ・ Pure water production system 12 ・ ・ ・ Primary pure water tank 13 ・
・ ・ Circulation pump 15 ・ ・ ・ Hydrogen aeration device 16 ・ ・ ・ Ultrapure water production device 17 ・ ・ ・ Pollisher 18 ・ ・ ・ Microfiltration device 19 ・ ・ ・ Supply line 21 ・ ・ ・ Use point 22
... Return line 23 ... Ozonizer

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C02F 1/50 550 H 9045-4D

Claims (3)

[Claims] 1. The primary pure water in the primary pure water tank is supplied to an ultrapure water producing apparatus containing at least a polisher to obtain ultrapure water, and the ultrapure water is sent to a point of use via a supply line. In the ultrapure water ozone sterilization method of treating an object to be treated with the ultrapure water at a use point and circulating the used pure water to the primary pure water tank through a return line, the use point and the An ozone-containing gas is injected into the used pure water between primary pure water tanks, and a hydrogen-containing gas is supplied between the primary pure water tank and the ultrapure water producing apparatus to remove residual ozone and deoxidize. An ultrapure water ozone sterilization method characterized by the above. 2. The method according to claim 1, wherein the ozone-containing gas is an anode gas produced by water electrolysis and the hydrogen-containing gas is a cathode gas produced by water electrolysis. 3. An ultrapure water production apparatus including a primary pure water tank for storing primary pure water, a polisher located downstream of the primary pure water tank for converting the primary pure water into ultrapure water, and the ultrapure water. It includes one or more use points for treating the object with the ultrapure water supplied from the manufacturing apparatus through the supply line, and a return line for circulating the used pure water at the use points to the primary pure water tank. In the ultrapure water ozone sterilizer, the ozone injection unit for injecting an ozone-containing gas into the used pure water between the point of use and the primary pure water tank, the primary pure water tank, and the ultrapure water producing apparatus. An ultrapure water ozone sterilizer having a hydrogen diffusing device for supplying oxygen between the primary pure water to remove ozone contained in the primary pure water and deoxidize the ozone.