JPH06126271A - Ultrapure water production system and method - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an ultrapure water production apparatus and method capable of constantly producing highly pure ultrapure water. [Structure] In a primary pure water production process of an ultrapure water production system comprising a primary pure water production process and an ultrapure water production process, conventional activated carbon 101 and a fine pore having a pore diameter of 20 to 1000 Å are provided on the inlet side of tap water 1. High-performance activated carbon 102 having 5 to 10% or more of all pores, and silica-alumina-based adsorbent 10
A multi-layer adsorption device 105 composed of three layers of 3 and 3, a reverse osmosis device 110 and an ion exchange device 120 are installed on the outlet side of the pure water 2. [Effect] Since organic substances that have been difficult to remove can be efficiently removed, stable high-purity ultrapure water can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing ultrapure water and a method therefor, and more particularly to an apparatus for producing ultrapure water used in the electronic industry, medical fields and the like, and a water quality control method therefor.

[0002]

2. Description of the Related Art In recent years, the development and mass production of LSIs and VLSIs have become popular, and pure water and ultrapure water are used in many cleaning processes. However, as the degree of integration of LSIs increases, the quality of ultrapure water used must be even higher.
Development of water production technology that is very close to theoretical pure water with almost no impurities contained is being carried out.

An example of the prior art relating to ultrapure water production will be described with reference to the drawings. FIG. 3 is a block diagram of the entire conventional ultrapure water production system.

As shown in FIG. 3, the pure water 2 is usually composed of an activated carbon adsorption device 100, a reverse osmosis device 110, an ion exchange device 120 and the like after pretreatment of tap water 1 and ground water etc. for coagulation and filtration. Manufactured in the primary pure water manufacturing process,
It is stored in the pure water tank 130.

Next, the pure water 2 is sent to the ultrapure water manufacturing process, where it passes through the ultraviolet oxidation device 140 and the anion exchange device 150 to be sterilized and removed of a small amount of organic substances, and further, anion and cation exchange resin are exchanged. After the tracer inorganic substance is removed by the polisher device 160 composed of a mixed bed, the ultrafine water is removed by the ultrafiltration device 170 to obtain high purity ultrapure water 3.

This ultrapure water 3 is sent to each cleaning step which becomes a use point 180, and the remaining ultrapure water is the pure water tank 1.
Returned to 30.

Impurities in ultrapure water include granular substances and dissolved substances, the former include fine particles and bacteria (particularly live bacteria), and the latter include organic substances and inorganic substances. Conventionally, as the evaluation index of the water quality of ultrapure water, the TOC value representing the number of fine particles, the number of viable bacteria, and the amount of organic matter (TOC value is the value of the amount of organic matter in the total amount of organic carbon. Of the total amount of organic substances contained in water, it is a value of the amount of organic substances that can be inspected by a TOC meter described later, not the total amount of organic substances contained in ultrapure water.), And a ratio representative of the amount of inorganic substances. The resistance (reciprocal of electrical conductivity) value was mainly used.

Before the ultrapure water 3 is sent to the use point 180, each of these indexes is a particle counter-200 for the number of particles, a TOC value 210 for the TOC value, and a specific resistance value 220 for the specific resistance value. Then, each is measured online, and the number of viable bacteria is measured in batches by sampling ultrapure water 3 in the liquid sampling chamber 230.

However, the pure water 2 obtained by the above process
Since bacteria and trace amounts of organic substances remain in the water, the water quality of the washing water in the finishing process of semiconductor manufacturing is insufficient.

Therefore, in order to remove those impurities remaining in the pure water, the bacteria are sterilized by irradiation with ultraviolet rays having a wavelength of 170 to 400 nm, a trace amount of organic substances are oxidatively decomposed and ionized, and then the ionized organic substances are anionic. A method of removing the resin through an exchange resin is disclosed in, for example, Japanese Patent Publication No. 54-192.
No. 27, or Japanese Patent Laid-Open No. 1-164488.

Further, it is said that the impurities in the ultrapure water are mainly organic substances, and various studies have been made to improve the performance of ultraviolet oxidation which is the only organic substance removing means in the ultrapure water production process. For example, the combined use of ultraviolet oxidation and a photocatalyst is disclosed in JP-A-62-62.
Japanese Patent Publication No. 193696/1993, and Japanese Patent Publication No. 56-18191 discloses the combined use of ultraviolet oxidation and hydrogen peroxide.

[0012]

However, with the progress of VLSI, the quality of water required for ultrapure water has become higher, and it has become necessary to improve the performance of manufacturing equipment commensurate with it.

For example, there is a limit to the reduction of impurities in ultrapure water only by the improvement means disclosed in the above publication, and it is becoming difficult to obtain ultrapure water that meets the required water quality.

The present invention aims to provide an ultrapure water production apparatus and method capable of stably supplying high-purity ultrapure water by investigating the root cause of such problems and solving the problems. To aim.

[0015]

The above object can be achieved as follows.

(1) In an ultrapure water production system comprising an adsorption device and at least one treatment device of a reverse osmosis device, an ion exchange device, an ultraviolet oxidation device, an anion exchange device, a polisher device or an ultrafiltration device, Filling the adsorption device with an adsorbent capable of selectively removing organic substances having a molecular weight of 50 to 1000.

(2) In (1), as the adsorbent, at least one of a plurality of activated carbons having different pore diameters or a silica-alumina adsorbent is used.

(3) In (2), the adsorbent is activated carbon having a pore size of 20 to 1000Å.

(4) In (2), the silica-alumina-based adsorbent is at least one of silica gel, alumina gel, activated alumina or activated clay.

(5) Adsorption treatment, reverse osmosis treatment, ion exchange treatment, ultraviolet oxidation treatment, anion ion exchange treatment,
In the method for producing ultrapure water, which is carried out by at least one treatment of polisher treatment or ultrafiltration treatment,
The adsorption treatment is carried out using a plurality of activated carbons having different pore sizes or a silica-alumina-based adsorbent for adsorption removal means, and the removal capacity of the adsorption removal means is controlled according to the quality of the ultrapure water produced.

(6) In (5), the removal capacity is controlled by adjusting the amount of water flowing into the adsorption removal means.

[0022]

In the present invention, in order to achieve the above object, the behavior of impurities in the entire ultrapure water production process was first examined by various experiments, and the following was clarified.

That is, most of the impurities remaining in the ultrapure water produced are organic substances, and the means for removing organic substances is
In the ultrapure water manufacturing process, there is only an ultraviolet oxidizer, and since the water has a high purity, water itself becomes a solvent, and the amount of organic substances and silica eluted from the synthetic resin and glass, which are constituent materials of the ultraviolet oxidizer, increases. , It was found that the total organic matter removal capacity is limited.

Therefore, focusing on the fact that it is a good idea to remove the organic matter as much as possible in the primary pure water production process in which the purity of water is not high and elution is not a problem, the organic matter in the following primary pure water production process is considered. It was clarified that the behavior of the organic acid was clarified, and appropriate treatment measures were taken based on it, and it was examined to increase the organic substance removing ability.

However, at present, it is impossible to measure the absolute amount of the organic matter, and it is possible to measure the TOC value in the organic matter, and it is considered that the increase or decrease in the absolute amount of the organic matter is proportional to that of the TOC value. Here, the behavior of TOC was clarified, and appropriate treatment means was taken based on the behavior to increase the organic substance removal capacity.

FIG. 4 is an explanatory diagram of the behavior of the TOC in the process of the primary pure water production process, which is the basis of the present invention. FIG. 4 (a) shows the primary pure water production process, and FIG. Shows the change in TOC value in each processing step of the process. FIG. 4B is obtained from the examination result as shown in FIG.

That is, conventionally, TOC removal is small in the activated carbon adsorption device 100, and most of the TOC removal is performed in the reverse osmosis device 110, and the ion exchange device 12 removes ions.
Since it is scarcely removed by 0, the activated carbon adsorption device 10
At 0, it was considered that the organic substance removing effect was small.

However, the inventors were able to discover the importance of organic matter removal by the activated carbon adsorption device 100 by investigating which component of TOC was removed and by how much. This will be described with reference to the drawings.

FIG. 5 is an explanatory diagram of a removal model showing the relationship between the removal capacity of each removal means and the molecular weight of organic substances, which is the basis of the present invention, and was prepared based on many experimental data.

As shown in FIG. 5, TOC is 3 in terms of molecular weight.
A, with 0, 50, 200 and 1000 as boundary values,
The TOC removal rate for each component was modeled for each removal means of the reverse osmosis device, the activated carbon adsorption device, and the ultraviolet oxidation device.

As a result, in the reverse osmosis device, the higher the molecular weight of the TOC, the easier it is to remove (E>D> C), and in the UV oxidizer, the low molecular weight TOC which is easily decomposed into carbon dioxide gas by oxidation is removed (A> B). It was also found that TOC (C and D) having a molecular weight intermediate between the two was easily removed by the activated carbon adsorption device.

Further, the behavior of each component region (A, B, C, D and E) of TOC in each processing step of the primary pure water production process was examined based on the model of FIG.

As a result, the result shown in FIG. 4B was obtained. FIG. 4 (b) shows the components (A, B, C, D and E) remaining after the respective removal means and after each removal means.
Are relatively compared.

From this figure, it was found that the root cause that cannot improve the purity of ultrapure water is the residual of each component of C and D. That is, most of the TOC remaining in the produced pure water is the C and D components that are adsorbed only on the activated carbon, and the TOC remaining in the pure water is used in the ultrapure water production process.
Of these, a small amount of each component of A and B can be sufficiently removed by the ultraviolet oxidizer 140 because of its small molecular weight, but a large amount of each component of C and D that is not removed is the ultrapure water finally obtained. Will remain inside.

From the above component behavior analysis results, how to remove the components C and D by adsorbing activated carbon in the primary pure water production process is the key to improving the quality of ultrapure water. I understood it.

Therefore, as a result of further study by the inventors, each of the remaining C and D components has an unsaturated bond of carbon (-C≡C- or> C = C <) which is difficult to be oxidized by ultraviolet rays. It was found that TOC and TOC with a large polarity having a hydrophilic group (OH) were many, and it was found that silica-alumina-based adsorbents such as silica gel, alumina gel, activated alumina or activated clay are effective for removing them.

Further, in order to adsorb the D component having a relatively large molecular weight by the activated carbon, there are many pores having a pore diameter of 20 to 1000Å (effective when the volume of the pores is 5% or more of the total pore volume). However, 10% or more is preferable), so-called high performance activated carbon was found to be suitable.

As a specific means for producing this high-performance activated carbon, there is a method of lengthening the holding time during activation or a method of slowing the temperature rising rate. Furthermore, activation of zinc chloride is more advantageous than activation of steam because pores can be made larger.

In the present invention, based on the above-mentioned examination results,
In an ultrapure water production system, an adsorber used in the primary pure water production process has a silica-alumina-based adsorbent for removing C and D components that are difficult to remove by UV oxidation, and a C component that is difficult to adsorb with conventional activated carbon. The pore diameter for removing
At least one of high-performance activated carbon having 000 Å pores having 5 to 10% or more of the total pore volume was used. As a result, the water quality of ultrapure water could be significantly improved.

That is, in the activated carbon adsorption step of the primary pure water production process, the silica-alumina-based adsorbent is used to remove the components C and D, which are difficult to remove by ultraviolet oxidation, among the organic substances contained therein. Pore size 20-1
It is possible to remove D component, which is difficult to be adsorbed and removed by conventional activated carbon, by using high-performance activated carbon having pores of 000Å of 5 to 10% or more.

Therefore, since the TOC remaining in the ultrapure water obtained in the next ultrapure water production process can be greatly reduced, it can be considered that the total amount of organic substances can also be significantly reduced.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view of an embodiment in the primary pure water production process of the ultrapure water production system of the present invention, of which
FIG. 1A is a block diagram of the primary pure water production process,
FIG. 1B is a column diagram showing the water quality behavior in the process, and shows the change in the TOC value in each treatment step of the process. The reference numerals A, B, C, D and E are the same as those described in FIG.

The difference between the embodiment of FIG. 1 (a) and FIG. 3 of the conventional example is that instead of the activated carbon adsorbing device 100 (see FIG. 3), the conventional activated carbon 101 and 5 pores having a pore diameter of 20 to 1000Å are used. ~
This is because a multi-layer adsorption device 105 including three layers of high-performance activated carbon 102 having 10% or more and silica-alumina-based adsorbent 103 was used.

In the present invention, by using the high-performance activated carbon 102 and the silica-alumina type adsorbent 103, the removal rate of the C component is increased by the former and the removal rate of the D component is significantly increased by the latter, as shown in FIG. Can be increased.

Therefore, as shown in FIG. 1B, it is difficult to remove the organic matter in the water by the reverse osmosis device 110 or the ultraviolet oxidation device 140 (see FIG. 3) in the ultrapure water production process. Since each component of C and D having a molecular weight of 1 can be selectively removed, each component of C and D contained in the obtained pure water 2 is significantly reduced and the concentration of TOC is halved.

This effect greatly contributes to the improvement of the quality of ultrapure water. That is, in this embodiment, since the C and D components that are difficult to remove by the ultraviolet oxidizer in the ultrapure water manufacturing process can be selectively removed, the TOC of ultrapure water is 1 /
It can be significantly reduced to 3 or less.

In this embodiment, a multilayer adsorption device is used. Conventional activated carbon 101 and high performance activated carbon 102 are used.
The same effect can be obtained even when a so-called mixed layer adsorption device in which the silica gel and the alumina-based adsorbent 103 are mixed is used.

As described above, according to this example, the TOC of ultrapure water can be greatly reduced, and therefore, the amount of all organic substances contained in the ultrapure water can be significantly reduced.

Next, a second embodiment will be described with reference to the drawings. FIG. 2 is a block diagram of the entire ultrapure water production system including the control of the second embodiment of the present invention.

In the second embodiment, the conventional activated carbon 101, the high-performance activated carbon 102 and the silica-alumina adsorbent 103 used in the first embodiment are housed, and in the second embodiment, the activated carbon adsorbing device 100 and the high performance activated carbon are housed. Performance activated carbon adsorption device 1
This is the case where the 06 and silica-alumina adsorbing device 107 is replaced with these devices, and the following effects are obtained.

That is, since the high-performance activated carbon 102 and the silica-alumina adsorbent 103 have strong selectivity, overadsorption occurs in which components that can be removed by the reverse osmosis device 110 or the ultraviolet oxidation device 140 in the next step are adsorbed, Adsorption may be saturated in a short time.

Therefore, by-pass control valve A 261, control valve B 262 and control valve C 263 are installed in these adsorption devices.
Is installed and the adsorption flow rate of each adsorption device is controlled by adjusting the processing flow rate, so that the state in which over-adsorption is always minimized can be maintained.

That is, the water quality of the ultrapure water 3 is monitored, and the control valve opening is maximized as much as possible while monitoring the water quality so that each of the above adsorption devices can operate at the lowest flow rate at which the water quality does not deteriorate. The flow rate in each adsorption device is minimized to minimize the adsorption load. This allows
High-purity ultrapure water 3 can be stably obtained while preventing the adsorption life of each adsorption device from decreasing.

Specifically, the water quality of the ultrapure water 3 is detected by the TOC meter 210 for the organic matter concentration or the TS meter 240 for measuring the amount of residue (TS) after evaporation of all the impurities, and the water quality signal 280 thereof is detected. To the control unit 250, from which control valve A 261, control valve B 262 and control valve C 263
To the control signal A 291, the control signal B 292, and the control signal C 293, respectively.

These control signals are usually signals for opening the control valve, that is, signals for reducing the flow rate to each adsorbing device as much as possible to minimize the adsorbing load. When the water quality starts to deteriorate, the control signals are reversed. Replace with a signal that closes the valve, that is, a signal that increases the flow rate of the adsorption device and increases the adsorption load,
The maximum control valve opening is always controlled with the highest water quality, that is, the lowest adsorption load is controlled.

[0056]

As described above, according to the ultrapure water production system of the present invention, the ability to remove organic substances in the primary pure water production process can be significantly improved, and high-purity ultrapure water containing few organic substances can be stabilized. Can be manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a primary pure water production process of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an entire ultrapure water production system according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an entire conventional ultrapure water production apparatus.

FIG. 4 is an explanatory diagram of a primary pure water production process step which is the basis of the present invention.

FIG. 5 is an explanatory diagram of an organic matter removal model that is the basis of the present invention.

[Explanation of symbols]

1 ... Tap water, 2 ... Pure water, 3 ... Ultra pure water, 100 ... Activated carbon adsorption device, 101 ... Conventional activated carbon, 102 ... High performance activated carbon,
103 ... Silica-Alumina-based adsorbent, 105 ... Multi-layered adsorption device, 106 ... High-performance activated carbon adsorption device, 107 ... Silica-alumina-based adsorption device, 110 ... Reverse osmosis device, 120 ... Ion exchange device, 130 ... Pure water tank, 140 ... UV oxidation device, 150 ... Anion exchange device, 160 ... Polisher device, 170 ... Ultrafiltration device, 180 ... Use point, 200 ... Fine particle counter, 210 ... TOC meter, 2
20 ... Resistivity meter, 230 ... Liquid sampling chamber, 240 ...
TS meter, 250 ... Control unit, 261, ... Control valve A, 2
62 ... Control valve B, 263 ... Control valve C, 280 ... Water quality signal, 291 ... Control signal A, 292 ... Control signal B, 293
... control signal C.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B01J 20/20 A 7202-4G C02F 1/32 1/42 A B 1/44 J 8014-4D 9 / 00 Z 7446-4D (72) Inventor Nobuko Hashimoto 1-1-14, Uchikanda, Chiyoda-ku, Tokyo Within Hitachi Plant Construction Co., Ltd. (72) Inventor Satoshi 1-1-14, Uchikanda, Chiyoda-ku, Tokyo No. Hiratsugi Plant Construction Co., Ltd. (72) Inventor Kazuhiko Takino 1-1-14 Kanda Uchi, Chiyoda-ku, Tokyo

Claims (6)

[Claims] 1. An ultrapure water production system comprising an adsorption device and at least one treatment device of a reverse osmosis device, an ion exchange device, an ultraviolet oxidation device, an anion exchange device, a polisher device or an ultrafiltration device, An ultrapure water production system comprising an adsorbent filled with an adsorbent capable of selectively removing organic substances having a molecular weight of 50 to 1000. 2. The ultrapure water production system according to claim 1, wherein at least one of a plurality of activated carbons having different pore sizes or a silica-alumina-based adsorbent is used as the adsorbent. 3. The adsorbent has a pore size of 20 to 10
The ultrapure water production system according to claim 2, wherein the activated carbon is 00Å. 4. The apparatus for producing ultrapure water according to claim 2, wherein the silica-alumina-based adsorbent is at least one of silica gel, alumina gel, activated alumina, and activated clay. 5. A method for producing ultrapure water, which is carried out by at least one of adsorption treatment, reverse osmosis treatment, ion exchange treatment, ultraviolet oxidation treatment, anion ion exchange treatment, polisher treatment or ultrafiltration treatment. , The adsorption treatment is performed using a plurality of activated carbons having different pore diameters or an adsorption removal means using a silica-alumina-based adsorbent, and the removal capacity of the adsorption removal means is changed according to the water quality of the ultrapure water produced. A method for producing ultrapure water characterized by controlling. 6. The method for producing ultrapure water according to claim 5, wherein the removal capacity is controlled by adjusting the amount of water flowing into the adsorption removal means.