JP6400918B2 - Hydrogen dissolved water production apparatus and pure water production system - Google Patents

Description

  The present invention relates to an apparatus for producing hydrogen-dissolved water by dissolving hydrogen in pure water or ultrapure water, and by feeding and passing such hydrogen-dissolved water to a catalyst layer, The present invention relates to a pure water production system that removes oxidizing substances.

  In the manufacture of semiconductor devices, liquid crystal display devices, pharmaceuticals, and the like, pure water such as ultrapure water from which impurities are highly removed is used. Ultrapure water is generally prepared by pre-treating raw water such as industrial water, well water, tap water, etc., and then treating the raw water with a primary pure water production device composed of a reverse osmosis membrane separation device and an ion exchange device. It is produced by producing pure water and further treating the primary pure water by a secondary pure water system (subsystem) composed of an ultraviolet (UV) oxidizer, an ion exchanger, an ultrafiltration membrane separator, and the like. The

  Ultrapure water has such a purity that it is difficult to quantify impurities, but it is not without impurities at all. It is also known that a process using ultrapure water may be greatly affected by a very small amount of specific impurities.

  For example, when ultrapure water is used in a semiconductor device manufacturing process, a natural oxide film is formed on the surface of a silicon (Si) wafer by dissolved oxygen contained in the ultrapure water. The natural oxide film formed on the wafer surface hinders the growth of epitaxial Si thin films at low temperatures, hinders precise control of the gate oxide film thickness and film quality, and increases the contact resistance in contact holes. It becomes. Therefore, the formation of a natural oxide film on the wafer surface needs to be suppressed as much as possible. For this purpose, it is necessary to suppress the amount of dissolved oxygen in the ultrapure water. Conventionally, various methods for suppressing the amount of dissolved oxygen in ultrapure water have been proposed. For example, in Patent Document 1, in a sub-system (secondary pure water system), ultrapure water with a reduced amount of dissolved oxygen is supplied to a use point by disposing a membrane-type deaerator after the ion exchange device. It is disclosed. Further, in the [Prior Art] column of Patent Document 1, it is also described that a degassing device is provided in the primary pure water system to reduce dissolved oxygen.

  In order to suppress the formation of a natural oxide film, when a device for manufacturing ultrapure water for manufacturing semiconductor devices is provided with a degassing device in the primary pure water system to reduce dissolved oxygen, this degassing device The dissolved oxygen concentration in the water to be treated (that is, primary pure water) at the system inlet is usually reduced to 100 μg / L or less. Furthermore, it may be managed so that the dissolved oxygen concentration in the primary pure water is 10 μg / L or less.

A sub-system is generally installed at the subsequent stage of the primary pure water system, but an ultraviolet oxidizer is provided in the sub-system in order to decompose organic matter (TOC (total organic carbon) component) in pure water. The ultraviolet oxidizer decomposes the TOC component with hydroxy radicals (.OH) generated when ultraviolet light is irradiated to pure water. When excessively generated hydroxy radicals are combined with each other, hydrogen peroxide (H ₂ O ₂ ) is generated, so that hydrogen peroxide is contained in the outlet water of the ultraviolet oxidation apparatus.

  Hydrogen peroxide is an oxidizing substance like dissolved oxygen, and is desirably removed from ultrapure water. Hydrogen peroxide can be easily removed by a catalyst or activated carbon supporting a noble metal. However, there is a problem that oxygen is generated by the decomposition reaction of hydrogen peroxide as shown in the following formula, and the dissolved oxygen concentration increases.

2H ₂ O ₂ → 2H ₂ O + O ₂
By the way, dissolved oxygen contained in the primary pure water or generated in the subsystem is added to the system and hydrogen is reacted with hydrogen on the catalyst as shown in the following formula to form water. Can be removed.

2H ₂ + O ₂ → 2H ₂ O
As a catalyst suitable for allowing the above reaction to proceed at a high speed, Patent Document 2 proposes a monolithic organic porous anion (anion) exchanger carrying a platinum group metal.

  By the way, as a supply source of hydrogen added to ultrapure water in order to reduce dissolved oxygen, a hydrogen cylinder filled with gaseous hydrogen under pressure, or a hydrogen production apparatus using an electrolysis method (see, for example, Patent Document 3) )and so on. However, in recent years, from the viewpoint of safety management, hydrogen cylinders may not be installed depending on the location, or the use of hydrogen gas may be prohibited. In particular, in a closed space such as a clean room or a basement, the introduction of hydrogen cylinders tends to be prohibited. As a method of supplying hydrogen to places where hydrogen cylinders cannot be installed, it is also possible to install hydrogen supply places such as hydrogen cylinders separately and supply hydrogen from the hydrogen supply place to the place where hydrogen is used via hydrogen piping. However, the hydrogen piping tends to be long, and there is a possibility that the possibility of hydrogen gas leakage due to damage to the piping is increased.

  As an alternative means when a hydrogen cylinder or the like cannot be installed, it is conceivable that hydrogen is generated using an electrolysis method, and this hydrogen is dissolved in water to obtain hydrogen-dissolved water. However, in order to obtain hydrogen-dissolved water, it is necessary to provide a hydrogen gas-dissolving part that performs gas-liquid mixing using a gas-dissolving membrane such as a hollow fiber membrane. In this case, in order to increase the hydrogen concentration, a method of increasing the hydrogen pressure in the gas phase part in accordance with Henry's law is used. However, for the same reason as in the case of the hydrogen cylinder described above, high-pressure hydrogen gas dissolution is performed. The presence of the part may make it impossible to install the electrolysis apparatus for generating hydrogen itself.

JP-A-9-29251 JP 2010-240642 A JP 2003-245669 A

  As described above, the addition of hydrogen is effective for removing oxidizing substances in pure water or ultrapure water. However, even if hydrogen is added directly to pure water or ultrapure water, It was necessary to use hydrogen in the gaseous state at any stage even when adding. Since hydrogen in a gaseous state has a risk of explosion and there are strong restrictions on the place of handling, hydrogen may not be added to pure water or ultrapure water as a result.

  An object of the present invention is to provide a hydrogen-dissolved water production apparatus capable of producing hydrogen-dissolved water without generating any gaseous hydrogen that has a risk of explosion.

  Another object of the present invention is to generate hydrogen-dissolved water from the water to be treated without generating any gaseous hydrogen that has a risk of explosion, and react with hydrogen in the hydrogen-dissolved water in the presence of a catalyst. An object of the present invention is to provide a pure water production system that removes oxidizing substances such as hydrogen oxide and dissolved oxygen.

  The apparatus for producing hydrogen-dissolved water of the present invention comprises an anode chamber provided with an anode and through which pure water or ultrapure water is passed, a cathode chamber provided with a cathode, and a cation exchange membrane provided between the anode chamber and the cathode chamber And a voltage applying means for applying a DC voltage between the anode and the cathode, generating hydrogen ions in the anode chamber by the DC voltage, and supplying hydrogen to the cathode chamber through the cation exchange membrane. A hydrogen-dissolved water production apparatus for obtaining hydrogen-dissolved water by introducing ions and recombining with electrons to generate hydrogen molecules, and dissolving hydrogen molecules in pure water or ultrapure water passed through the cathode chamber, Hydrogen dissolving means for generating hydrogen-dissolved water so that hydrogen gas bubbles do not substantially remain is provided.

  The pure water production system of the present invention comprises an ultraviolet irradiation means for irradiating the water to be treated with ultraviolet light, a hydrogen-dissolved water production apparatus of the present invention in which water treated by the ultraviolet irradiation means is supplied to the cathode chamber, And dissolved oxygen removing means for removing water from the cathode chamber of the dissolved water production apparatus and contacting the platinum group metal-supported catalyst to remove oxidizing substances in the water. In this pure water production system, one of the water branched into two treated with the ultraviolet irradiation means is supplied to the cathode chamber of the hydrogen-dissolved water production apparatus, and the water flowing out from the cathode chamber of the hydrogen-dissolved water production apparatus The other water branched into two may be mixed in the dissolved oxygen removing means, and the oxidizing substance in the mixed water may be removed.

  The saturation solubility of hydrogen in ultrapure water is 1.6 mg / L at 20 ° C. under atmospheric pressure. Oxidizing substances contained in trace amounts in pure water or ultrapure water, not in applications requiring hydrogen-dissolved water such as so-called functional water containing high-concentration hydrogen used for cleaning semiconductor substrates For example, if hydrogen-dissolved water having a slight excess of hydrogen than the stoichiometric amount necessary to produce water relative to the amount of dissolved oxygen in ultrapure water is obtained, Good. The amount of dissolved oxygen of general pure water and ultrapure water circulating in the subsystem (including oxygen caused by hydrogen peroxide generated by ultraviolet oxidation treatment) is about 100 μg / L. If the oxygen concentration is 100 μg / L, the stoichiometrically corresponding dissolved hydrogen amount is 12.5 μg / L, which is a percentage of the saturation solubility of hydrogen at 20 ° C. under atmospheric pressure. 1 or less.

  The present invention generates such hydrogen-dissolved water containing low-concentration hydrogen, generates hydrogen molecules using an electrolytic cell, and dissolves hydrogen so that hydrogen gas bubbles do not substantially remain. Use hydrogen dissolving means to produce water. Accordingly, in the present invention, it is not necessary to provide a hydrogen gas dissolving part having a gas dissolving film, so that the apparatus can be made compact and there is no fear that hydrogen gas is generated inside the apparatus. In the hydrogen-dissolved water producing apparatus of the present invention, oxygen is generated in the anode chamber of the electrolysis cell, but this oxygen is generated in a very small amount and can be discharged to the outside dissolved in water. Therefore, in this hydrogen-dissolved water producing apparatus, there is no fear that hydrogen and oxygen are mixed and explode.

  As described above, according to the present invention, hydrogen-dissolved water can be generated without generating hydrogen gas and without handling hydrogen gas. Therefore, hydrogen in a clean room or the like can be formed without setting a long external hydrogen pipe. Hydrogen-dissolved water can be obtained even in places where gas handling is restricted. Further, by generating hydrogen-dissolved water in this way, it is possible to easily obtain pure water or ultrapure water having a very low concentration of oxidizing substances such as dissolved oxygen and hydrogen peroxide.

It is a figure which shows the conceptual structure of the SPE (solid polymer electrolyte) electrolysis cell used for a hydrogen dissolution apparatus. It is a figure which shows an example of a structure of the hydrogen dissolved water manufacturing apparatus of one Embodiment of this invention. It is a figure which shows another example of a structure of a hydrogen dissolved water manufacturing apparatus. It is a figure which shows another example of a structure of a hydrogen dissolved water manufacturing apparatus. (A) is a figure which shows the structure of the pure water manufacturing system of one Embodiment of this invention, (b) is a figure which shows the structure of the pure water manufacturing system of another embodiment. It is a figure which shows the apparatus structure in Example 1. FIG. 3 is a graph showing the relationship between the hydrogen concentration of hydrogen-dissolved water and the number of detected fine particles in Example 1. It is a figure which shows the apparatus structure in the comparative example 1. FIG. (A), (b) is the relationship between the hydrogen concentration of the hydrogen-dissolved water in Comparative Example 1 and the number of detected fine particles when the microfiltration (MF) membrane module is provided and when not provided, respectively. It is a graph which shows.

  Next, a preferred embodiment of the present invention will be described with reference to the drawings.

  An electrolytic method is sometimes used as a method for generating hydrogen when a hydrogen cylinder cannot be installed. Since general electrolysis is based on electrolysis of water, water with an electrolyte added to lower the electrical resistivity is used, but an electrolysis method for efficiently electrolyzing pure or ultrapure water with high electrical resistance. There is a water electrolysis method (SPE electrolysis method) using a solid polymer electrolyte (Solid Polymer Electrolyte). The SPE electrolysis method is capable of electrolyzing water at a low voltage of about several volts, and is used as a simple hydrogen gas generation method. Therefore, in the hydrogen-dissolved water producing apparatus according to one embodiment of the present invention, hydrogen is generated using the SPE electrolysis method.

  FIG. 1 shows a configuration of an SPE electrolysis cell 10 that is an electrolysis cell used in the hydrogen-dissolved water production apparatus of the present embodiment. The SPE electrolysis cell 10 includes an anode chamber 12 having an anode 11, a cathode chamber 14 having a cathode 13, and a cation exchange membrane that is a solid polymer electrolyte membrane provided between the anode chamber 12 and the cathode chamber 14. 15. As the cation exchange membrane 15, for example, “Nafion” manufactured by DuPont is used. In order to reduce the electrolysis voltage and improve the electrolysis efficiency, a catalyst electrode made of platinum (Pt) or the like is bonded to both surfaces of the cation exchange membrane 15, and one is an anode 11 and the other is a cathode 13. The anode 11 and the cathode 13 have, for example, a net shape so that pure water can reach the interface with the cation exchange membrane 15. Furthermore, the hydrogen dissolved water production apparatus of this embodiment is provided with a DC power supply 16, and the anode 11 and the cathode 13 are electrically connected to the positive output terminal and the negative output terminal of the DC power supply 16, respectively. ing. Both the anode chamber 12 and the cathode chamber 14 are supplied with pure water from the outside.

In the SPE electrolysis cell 10 shown in FIG. 1, when pure water (H ₂ O) is passed through the anode chamber 12 while applying a DC voltage between the anode 11 and the cathode 13 by the DC power source 16, The reaction shown in FIG.

2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻
The produced oxygen (O ₂ ) is discharged out of the anode chamber 12 together with unreacted pure water. Further, the hydrogen ions (H ⁺ ) generated here move through the cation exchange membrane 15 toward the cathode 13, receive electrons at the cathode 13 as shown in the following formula, and generate hydrogen molecules.

4H ^{+ +} 4e ^- → 2H ₂
In the present embodiment, hydrogen generated on the surface of the cathode 13 of the SPE electrolysis cell 10 is instantaneously dissolved with a large amount of water before the bubbles are formed, so that hydrogen gas is not generated without generating gaseous hydrogen. It is intended to obtain hydrogen-dissolved water very safely in the absence of bubbles. Considering the electrode reaction at the anode 11 and the cathode 13, the hydrogen generated at the cathode 13 is not derived from the electrolysis of pure water supplied to the cathode chamber 14, but is derived from pure water supplied to the anode chamber 12. Is. Accordingly, a DC voltage is applied between the anode 11 and the cathode 13 while supplying a small amount of pure water to the anode chamber 12, and further pure water or ultrapure water is supplied to the cathode chamber 14, whereby the cathode chamber 14 Hydrogen is dissolved in pure water or ultrapure water supplied to the cathode chamber 14, and hydrogen-dissolved water is discharged from the cathode chamber 14.

  As described above, the saturation solubility of hydrogen in pure water is 1.6 mg / L at 20 ° C. under atmospheric pressure, but this value is the solubility in an equilibrium state, and the solution equilibrium is reached when hydrogen-dissolved water is generated. In the time to reach, hydrogen gas bubbles may exist even if the amount of hydrogen is less than the saturation solubility. Therefore, in this embodiment, as will be described later, hydrogen dissolving means for generating hydrogen dissolved water is provided so that hydrogen gas bubbles do not substantially remain in the hydrogen dissolved water.

The pure water supplied to the anode chamber 12 in the SPE electrolysis cell 10 preferably has a specific resistance of 5 MΩ / cm or more, particularly preferably 10 MΩ / cm or more. Extremely high-purity water such as ultrapure water is superior in ability to dissolve substances compared to low-purity water, and hydrogen is considered to be easily dissolved. In addition, since a small amount of water travels from the anode 11 to the cathode 13 when hydrogen ions (H ⁺ ) move through the cation exchange membrane 15, a decrease in the purity of the hydrogen-dissolved water produced in the cathode chamber 14 is suppressed. It is preferable that not only the water supplied to 14 but also the water supplied to the anode chamber 12 is pure water having a higher specific resistance.

  In order to adjust the dissolved hydrogen concentration in the hydrogen-dissolved water obtained from the cathode chamber 14, the amount of water and the current or voltage supplied from the DC power source 15 may be adjusted, but the flow rate of pure water or ultrapure water is not changed. The method of adjusting the current or voltage is preferable because it can avoid the influence of the pressure fluctuation associated with the flow rate adjustment. In addition, since the current or voltage can be precisely controlled in a shorter time than the flow rate, it is preferable to adjust the current in order to control the dissolved hydrogen concentration stably. When adjusting the current or voltage, for example, if the current value is too large, hydrogen is supersaturated on the surface of the cathode 13 and bubbles are likely to be generated. Moreover, since an excessive current causes generation of excess hydrogen and causes an increase in cost as well as a decrease in water quality, it is preferable to control the amount of hydrogen generation by appropriately controlling the current. Thus, the adjustment of the hydrogen generation amount for achieving a predetermined dissolved hydrogen concentration in the hydrogen-dissolved water can be performed by adjusting and controlling the voltage or current applied to the SPE electrolysis cell 10. The current or voltage control method at that time is not particularly limited, but the dissolved hydrogen concentration is determined by the relationship between the flow rate to the cathode chamber 14 and the hydrogen generation amount, and the hydrogen generation amount is determined by Faraday's law. Since it is determined by the amount, it is possible to perform a feedback control by installing a dissolved hydrogen meter at the outlet of the cathode chamber 14 to measure the dissolved hydrogen concentration.

  When hydrogen-dissolved water is generated for the purpose of reducing the amount of dissolved oxygen contained in pure water or ultrapure water, it is dissolved by reacting dissolved oxygen in the hydrogen-dissolved water with dissolved oxygen to form water. A dissolved oxygen meter can be installed at the outlet of the catalyst layer for removing oxygen, and the amount of hydrogen generation can be adjusted while monitoring the value of dissolved oxygen.

  In the hydrogen-dissolved water production apparatus of this embodiment, in order to generate hydrogen-dissolved water so that hydrogen gas bubbles do not substantially remain, it is preferable that the dissolved hydrogen concentration in the generated hydrogen-dissolved water is low. The range of the dissolved hydrogen concentration is, for example, 1 ppb or more and 500 ppb or less.

  In the present invention, the fact that hydrogen gas bubbles do not substantially remain means that the number of hydrogen gas bubbles contained in hydrogen-dissolved water is equal to that of polystyrene latex (PSL) particles having a diameter of 0.1 μm or more in pure water. It means that it is 100 / mL or less in terms of conversion. The number of bubbles can be detected optically using a particle counter. Here, since the detection target of bubbles is water, it is common to use a water particle counter. The particle counter for water uses PSL particles as a calibration substance, and the threshold value is determined by the size of PSL particles in water. The particle (signal) exceeding the threshold value is counted and a numerical value is output. In the case of the present invention, if the number of bubbles is 100 / mL or less in terms of PSL particles having a diameter of 0.1 μm or more in pure water, it can be said that there are substantially no problematic bubbles.

  When the hydrogen-dissolved water producing apparatus of this embodiment is used as a hydrogen source of a dissolved oxygen removing apparatus that removes dissolved oxygen in treated water by reacting hydrogen and oxygen using a catalyst, it is stoichiometrically necessary. A hydrogen-dissolved water having a dissolved hydrogen concentration may be produced. In particular, when the water to be treated is pure water or ultrapure water having a relatively low dissolved oxygen concentration, the dissolved hydrogen concentration may be adjusted to, for example, 100 ppb, 50 ppb, or 10 ppb according to the water to be treated. In this way, when the amount of dissolved hydrogen is particularly low, the supply line for water (pure water or ultrapure water, etc.) used as a raw material for generating hydrogen-dissolved water is branched into two to adjust the concentration. On the other hand, a hydrogen-dissolved water production apparatus is arranged, and water from two branched lines can be merged and mixed for use. In this case, since the pressure drop occurs in the line where the hydrogen-dissolved water production apparatus is provided, a booster pump can be provided to compensate for this pressure drop.

  A higher water pressure is preferred in order to increase the dissolution efficiency of hydrogen while substantially eliminating bubbles. The solubility of hydrogen gas can be increased by providing a booster pump as a hydrogen dissolving means on the inlet side or the outlet side of the SPE electrolysis cell 10 and increasing the pressure. It is desirable that the pressure of hydrogen-dissolved water is 0.1 MPa or more. However, if the water pressure is too high, it may cause water leakage from the SPE electrolysis cell or cell destruction, so the water pressure is preferably 0.7 MPa or less.

  Moreover, when performing the process which uses hydrogen dissolved water as a hydrogen source in a dissolved oxygen removal apparatus or an ultrapure water manufacturing system, the process is performed in a pressure state. At this time, the pressure of hydrogen-dissolved water is preferably 0.1 MPa or more. The upper limit of the pressure depends on the pressure resistance of the dissolved oxygen removing device and the ultrapure water production system, but when the hydrogen dissolved water production device of this embodiment is applied to a general ultrapure water production system, the pressure of the hydrogen dissolved water is Is, for example, 0.7 MPa or less, 0.5 MPa or less, or 0.3 MPa or less.

  In addition to increasing the water pressure, hydrogen dissolution water can be passed through a microfiltration membrane (MF) to increase hydrogen dissolution efficiency and remove hydrogen gas bubbles. FIG. 2 shows a hydrogen-dissolved water producing apparatus provided with a microfiltration membrane module 21 as a hydrogen dissolving means. The SPE electrolysis cell 10 in this hydrogen-dissolved water production apparatus is the same as that shown in FIG. 1, but FIG. 2 does not show the DC power supply 16 or the like for the sake of simplicity. The microfiltration membrane module 21 including the microfiltration membrane is connected to the outlet of the cathode chamber 14 of the SPE electrolysis cell 10, and hydrogen-dissolved water is supplied to the outside as supply water from the secondary side outlet of the microfiltration membrane module 21. Can be supplied.

  By passing water through the microfiltration membrane, even when hydrogen gas bubbles exist in the hydrogen-dissolved water, the contact efficiency between the bubbles and water is improved when passing through the micropores of the microfiltration membrane (that is, Gas-liquid mixing is performed efficiently), and hydrogen gas bubbles are substantially absent on a secondary side of the microfiltration membrane under a wide range of conditions. In addition, due to the particle removal effect inherent to microfiltration membranes, it is possible to reduce contamination and reduce particles in processes such as hydrogen-dissolved water generation, removal of dissolved oxygen removal, and ultrapure water production. it can.

  When a microfiltration membrane is used, water containing hydrogen gas bubbles (drain water) is discharged from a discharge port (drain) provided on the primary side (inlet side) of the microfiltration membrane in the microfiltration membrane module. In some cases, this drain water is returned to the SPE electrolysis cell or the microfiltration membrane module which is a hydrogen dissolving means, and hydrogen can be dissolved again. At this time, the pressure reduced by the differential pressure generated in the microfiltration membrane itself can be supplemented by a booster pump. The drain water containing hydrogen gas bubbles may be returned to either the inlet side or the outlet side of the cathode chamber 14 of the SPE electrolysis cell 10, but is preferably returned to a position on the primary side of the booster pump.

  FIG. 3 shows an example of the configuration of the hydrogen-dissolved water production apparatus configured to return the drain water. This hydrogen-dissolved water production apparatus is provided with a booster pump 22 connected to the inlet of the cathode chamber 14 of the SPE electrolysis cell 10 in the hydrogen-dissolved water production apparatus shown in FIG. A pipe 23 for returning the drain water to the primary side of the booster pump 22 is provided. Moreover, FIG. 4 has shown another example of the structure of the hydrogen-dissolved water manufacturing apparatus comprised so that drain water might be returned. The apparatus shown in FIG. 4 is different from the apparatus shown in FIG. 3 in that a booster pump 24 is provided at the outlet of the cathode chamber 14 instead of providing a booster pump at the inlet of the cathode chamber 14. A pipe 25 that branches from the pipe 23 that returns the drain water to the inlet of the cathode chamber 14 and connects to the primary side of the booster pump 24 is also provided.

  The hydrogen-dissolved water producing apparatus of the present embodiment described above can be used when pure water such as ultrapure water is produced by removing dissolved oxygen and hydrogen peroxide in the water to be treated. The water to be treated (water containing dissolved oxygen) to be dissolved oxygen is not particularly limited. For example, the production of ultrapure water used for cleaning the surface of a semiconductor device or cleaning a semiconductor device manufacturing apparatus. Water generated in various steps in Specifically, the water to be treated for removing dissolved oxygen includes water generated in a primary pure water production apparatus or a secondary pure water system (subsystem). Further, hydrogen peroxide to be removed is generated, for example, in an ultraviolet oxidation apparatus provided in the subsystem.

  The water to be treated is passed through the cathode chamber 14 of the SPE electrolysis cell 10 of the hydrogen-dissolved water production apparatus to dissolve hydrogen in the water to be treated, and then the water to be treated is dissolved in dissolved oxygen or peroxidized. By passing water through a removing device that removes hydrogen, pure water or ultrapure water from which dissolved oxygen and hydrogen peroxide have been removed can be obtained. As the removal device, for example, a catalyst device having a catalyst supporting a platinum group metal can be used, or a treatment tower filled with activated carbon can be used. However, from the viewpoint of reducing the footprint of the apparatus, a catalyst apparatus having a catalyst supporting a platinum group metal is preferable. When a hydrogen-dissolved water production apparatus is used to remove dissolved oxygen and hydrogen peroxide in the subsystem, the hydrogen-dissolved water is placed downstream of the ultraviolet oxidation apparatus along the flow of pure water in the subsystem. It is preferable to provide a production apparatus, and further to provide a catalyst apparatus immediately after the hydrogen-dissolved water production apparatus. In this case, the entire amount of pure water discharged from the ultraviolet oxidizer may be supplied to the cathode chamber of the hydrogen-dissolved water production apparatus, or only a part of the pure water discharged from the ultraviolet oxidizer is dissolved in hydrogen. The remaining pure water supplied to the cathode chamber of the water production device may be mixed with the pure water discharged from the cathode chamber and dissolved in hydrogen and processed in the catalyst device.

A catalyst device having a catalyst carrying a platinum group metal is filled with a monolithic organic porous ion exchange resin carrying a platinum group metal (hereinafter also referred to as a monolith), an ion exchange resin carrying a platinum group metal, or the like. It is desirable. The platinum group metal here refers to ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum belonging to 5 to 6 periods and 8 to 10 groups of the periodic table. Although it is a general term for (Pt), it is desirable that the platinum group metal supported on the monolith or ion exchange resin is platinum or palladium, and palladium is particularly preferable. Since the monolith has a large specific surface area, by using the palladium-supported monolith for the removal of hydrogen peroxide in the UV-oxidized water, high-speed treatment with an SV (space velocity) of about 2000 to 20000 h ⁻¹ becomes possible. Advantages such as reduction in scale occur. Although the footprint is increased and the cost is increased, it is possible to perform processing such that SV is 2000 h ⁻¹ or less. For the monolith carrying a platinum group metal, it is preferable to use a porous ion exchange resin having an anion exchange group excellent in the decomposition of hydrogen peroxide and having an ion form of OH. It is particularly preferable to use a strongly basic anion exchange resin.

  FIG. 5A shows an example of a configuration of a pure water production system that is configured as a subsystem that includes the ultraviolet oxidation device, the hydrogen-dissolved water production device, and the catalyst device described above and generates ultrapure water from one pure water. Show.

  This pure water production system includes a primary pure water tank 1 that stores primary pure water as supply water, and a pump (P) 2 that delivers pure water from the primary pure water tank 1. An ultraviolet oxidizer 3 that is an ultraviolet irradiating means for irradiating water (pure water) with ultraviolet rays, a hydrogen-dissolved water production apparatus 4, the above-described catalyst device 5 that is a dissolved oxygen removing means, and a non-regenerative mixed bed type An ion exchange device (CP: cartridge polisher) 6 and an ultrafiltration device (UF) 7 are connected in this order, and water from the ultrafiltration device 7 is supplied to the use point as ultrapure water. Yes. The ultrapure water that is discharged from the ultrafiltration device 7 but not supplied to the use point is returned to the primary pure water tank 1. As the hydrogen-dissolved water production apparatus 4, the hydrogen-dissolved water production apparatus described in the above-described embodiment is used, and the pure water discharged from the ultraviolet oxidation apparatus 3 is the cathode chamber 14 of the SPE electrolysis cell 10 of the hydrogen-dissolved water production apparatus. The pure water discharged from the cathode chamber 14 after dissolving hydrogen and being discharged from the cathode chamber 14 is sent to the catalyst device 5.

In such a system, the pure water stored in the primary pure water tank 1 is first sent to the ultraviolet oxidizer 3 by the pump 2 as treated water and irradiated with ultraviolet rays. As a result, the TOC component in the water to be treated is decomposed and hydrogen peroxide is also generated. Thereafter, the water to be treated is sent to the hydrogen-dissolved water production device 4 to which hydrogen is added, and then sent to the catalyst device 5. In the catalyst device 5, dissolved oxygen reacts with hydrogen in the presence of the catalyst to become water, whereby the dissolved oxygen is removed. Hydrogen peroxide is also decomposed in the presence of a catalyst such as Pd into oxygen (O ₂ ) and water, and this decomposition product, oxygen, reacts with hydrogen in the presence of the catalyst to become water. Hydrogen will also be removed. The water to be treated from which dissolved oxygen and hydrogen peroxide have been removed is sent to the non-regenerative mixed bed ion exchanger 6 and the organic acid and carbon dioxide (CO ₂ ) generated by the ultraviolet oxidizer 3 are non-regenerative. It is removed in the mixed bed type ion exchanger 6. Further, the water to be treated is sent to the ultrafiltration device 19 and becomes water from which impurities are highly removed, that is, ultrapure water, and is sent to the use point. Water that has not been used is circulated and returned to the primary pure water tank 1.

  In a conventional subsystem (secondary pure water system), a membrane deaerator (MD) is often used to remove dissolved oxygen, and this membrane deaerator is a non-regenerative mixed bed ion exchanger. Often installed immediately before or after. In contrast, in the pure water production system of this embodiment, a hydrogen-dissolved water production device and a catalyst device are provided between the ultraviolet oxidation device and the non-regenerative mixed bed ion exchange device to remove dissolved oxygen. It is preferable to provide it.

FIG.5 (b) has shown the pure water manufacturing system of another embodiment. The system shown in FIG. 5 (b) is different from the system shown in FIG. 5 (a) in that the pipe from the outlet of the ultraviolet oxidizer 3 is branched into two, and the water flowing through the branched pipe is dissolved in hydrogen. Supplied to the water production apparatus 4,
The water that flows out from the hydrogen-dissolved water production apparatus 4 and the water from the other pipe branched into two are mixed and processed by the catalyst apparatus 5. In this configuration, the dissolved hydrogen concentration can be accurately controlled to an extremely small value by controlling the amount of hydrogen generated in the hydrogen-dissolved water production apparatus 4 and the branching ratio in the bifurcated pipe.

  Next, the present invention will be described in more detail based on examples and comparative examples.

[Example 1]
The apparatus shown in FIG. 6 was assembled. In this apparatus, a cation exchange membrane (Nafion (registered trademark) N-117, film thickness 183 μm) manufactured by DuPont was used as the cation exchange membrane 15 in the SPE electrolytic cell 10. Each electrode had a substantially circular shape, and its area was 50 cm ² .
Ultra pure water having a specific resistance of 18 MΩ / cm can be supplied to the anode chamber 12 and the cathode chamber 14 of the SPE electrolysis cell 10. Piping from the outlet of the cathode chamber 14 is a main line 31, and a PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin) tube having an inner diameter of 10 mm is used for the main line 31. In this position, a sampling line 32 having a length of 3 m, which is a branch pipe for collecting sample water, was connected. For the sampling line 32, an FPA tube having an inner diameter of 4 mm was used.

  A dissolved hydrogen meter 34 (DH-35A manufactured by Toa DKK) was connected to a position on the main line 31 in the vicinity of the outlet of the cathode chamber 14. In the middle of the main line 31, a microfiltration membrane module (MF) 33 as a hydrogen dissolving means was installed. As the microfiltration membrane module 33, Micropore-010HE-P3SE manufactured by Organo Corporation for removing particles having a diameter of 0.1 μm or more was used. A particle counter 35 (UP 100 manufactured by Anatel) was connected to the end of the sampling line 32 in order to measure the number of hydrogen gas bubbles contained in the hydrogen-dissolved water flowing out from the cathode chamber 14.

  Using such an apparatus, a DC power supply is connected to the SPE electrolysis cell 10, ultrapure water is supplied to the anode chamber 12 and the cathode chamber 14 of the SPE electrolysis cell 10 to electrolyze the ultrapure water, and the cathode 13 The generated hydrogen was directly dissolved in ultrapure water that passed through the cathode chamber 14. At this time, ultrapure water was blown through the anode chamber 12 at 10 L / h. While confirming the dissolved hydrogen concentration in the water (hydrogen-dissolved water) flowing out from the cathode chamber 14 with the dissolved hydrogen meter 34, the supply flow rate of ultrapure water to the cathode chamber 14, the voltage between the anode 11 and the cathode 13, and The dissolved hydrogen concentration was controlled by adjusting the current. The outlet pressure of the SPE electrolysis cell 10 was controlled by the opening degree of a valve (not shown) provided at the outlet of the cathode chamber 14.

  When the outlet pressure of the SPE electrolysis cell 10 is 0.12 MPa and 0.17 MPa, the number of fine particles in the hydrogen-dissolved water (with a diameter of 0.1 μm or more when the dissolved hydrogen concentration is controlled to various values). Measured in terms of the number of PSL particles). This number of fine particles represents the number of bubbles of hydrogen gas in the hydrogen-dissolved water. The results are shown in FIG.

  As shown in FIG. 7, when the pressure was 0.12 MPa, no bubbles were observed until the dissolved hydrogen concentration reached 1.4 ppm at the maximum. Furthermore, by setting the pressure to 0.17 MPa, the dissolved hydrogen concentration could be increased to 2.5 ppm or more without generating bubbles. In addition, when the pressure is 0.12 MPa, the dissolved hydrogen concentration is 1.6 ppm or more, and the number of bubbles increases rapidly. This is because the hydrogen concentration reaches the saturation solubility of hydrogen or exceeds the saturation solubility. This is probably because

[Comparative Example 1]
Assembling the apparatus shown in FIG. 8 so that the microfiltration membrane module 33 can be installed on the sampling line 32 instead of installing the microfiltration membrane module on the main line 31, and the same experiment as in Example 1 was performed. went. The results are shown in FIG. At this time, the experiment was performed both when the microfiltration membrane module 33 was provided on the sampling line 32 (FIG. 9A) and when it was not provided (FIG. 9B).

  When the microfiltration membrane module 33 was provided, the number of bubbles was 100 / mL or less even when the pressure was 0.05 MPa, whereas when the microfiltration membrane module 33 was not provided, the water pressure was 0. When the pressure is 09 MPa, the number of bubbles is 100 / mL or more when the hydrogen concentration is 270 ppb, and when the water pressure is lowered to 0.04 MPa, the number of bubbles is 100 / mL or more even at a hydrogen concentration of 160 ppb. Air bubbles were generated in the area.

  This is because when hydrogen is generated at the cathode 13 of the SPE electrolysis cell 10 and all of the amount is dissolved in ultrapure water, it takes time to reach dissolution equilibrium. It is confirmed that hydrogen gas bubbles can be generated even when the pressure is sufficiently below, and hydrogen gas bubbles generated when the hydrogen concentration is lower than the saturation solubility can be removed by passing water through the microfiltration membrane module 33. Show.

[Example 2]
The hydrogen-dissolved water production apparatus shown in FIG. 2 was assembled to produce hydrogen-dissolved water, and pure water was produced by removing hydrogen peroxide and dissolved oxygen using this hydrogen-dissolved water. As the SPE electrolytic cell 10, the one used in Example 1 was used. The amount of dissolved oxygen in the water to be treated (pure water) at the hydrogen-dissolved water production apparatus inlet was 10 μg / L. The hydrogen peroxide concentration of the water to be treated was 16 μg / L as measured using the phenol phthaline method. For removal of hydrogen peroxide and dissolved oxygen, a catalyst device having an anion exchanger monolith carrying Pd was used. The ion form in the anion exchanger was OH form, and the supported amount of Pd was 30 mg per 1 g of dry weight of monolith. Ultrapure water in which hydrogen was dissolved was passed through a wet volume of 4 mL of the Pd-supporting anion exchanger monolith at a flow rate of 0.3 L / min. The SV was 5000h- ¹ . The pressure was 0.14 MPa and the dissolved hydrogen concentration was 50 ppb. The number of bubbles (converted to the number of PSL particles having a diameter of 0.1 μm or more) in ultrapure water in which hydrogen was dissolved was 30 / mL.

  At this time, the amount of hydrogen peroxide and dissolved oxygen at the outlet of the catalyst device was 1 μg / L or less.

DESCRIPTION OF SYMBOLS 1 Primary pure water tank 2 Pump 3 Ultraviolet oxidizer 4 Hydrogen dissolved water production apparatus 5 Catalyst apparatus 6 Non-regenerative mixed bed type ion exchange apparatus (CP)
7 Ultrafiltration equipment (UF)
DESCRIPTION OF SYMBOLS 10 SPE (solid polymer electrolyte) electrolysis cell 11 Anode 12 Anode chamber 13 Cathode 14 Cathode chamber 15 Cation (cation) exchange membrane 16 DC power supply 21, 33 Microfiltration (MF) membrane module 22, 24 Booster pump 23, 25 Piping 31 Main line 32 Sampling line 34 Dissolved hydrogen meter 35 Particle counter

Claims (4)

An electrolytic cell having an anode chamber with an anode chamber through which pure water or ultrapure water is passed, a cathode chamber with a cathode, and a cation exchange membrane provided between the anode chamber and the cathode chamber;
Voltage applying means for applying a DC voltage between the anode and the cathode;
Have
Hydrogen ions are generated in the anode chamber by the DC voltage, and the hydrogen ions are led to the cathode chamber through the cation exchange membrane and recombined with electrons to generate hydrogen molecules, which are passed through the cathode chamber. A hydrogen-dissolved water production apparatus for obtaining hydrogen-dissolved water by dissolving the hydrogen molecules in pure water or ultrapure water,
Hydrogen dissolving means for generating the hydrogen-dissolved water so that hydrogen gas bubbles do not substantially remain,
The hydrogen dissolving means is means for increasing the pressure of the pure water or ultrapure water passed through the cathode chamber to dissolve hydrogen in the pure water or ultrapure water passed through the cathode chamber. ,
Wherein the pressure of the pure water or ultrapure water is passed through the cathode chamber Ri der least 0.12 MPa,
The hydrogen dissolving means includes a filtration device provided at the outlet of the cathode chamber,
The filtration device Ru Ah in microfiltration membrane module, hydrogen-dissolved water generator. The precise further comprising a pipe for returning to said cathode chamber water flowing out from the discharge port provided at the inlet side of the microfiltration membrane in the filtration membrane module, hydrogen-dissolved water generator of claim 1. Ultraviolet irradiation means for irradiating the water to be treated with ultraviolet rays;
The hydrogen-dissolved water production apparatus according to claim 1 or 2 , wherein the water treated by the ultraviolet irradiation means is supplied to the cathode chamber,
Dissolved oxygen removing means for contacting the water flowing out from the cathode chamber of the hydrogen-dissolved water production apparatus with a platinum group metal-supported catalyst to remove oxidizing substances in the water;
Having a pure water production system. Ultraviolet irradiation means for irradiating the water to be treated with ultraviolet rays;
3. The hydrogen-dissolved water production apparatus according to claim 1, wherein one of the water branched by the ultraviolet irradiation means is supplied to the cathode chamber. ,
The water flowing out from the cathode chamber of the hydrogen-dissolved water production apparatus and the other branched water are mixed and brought into contact with the platinum group metal-supported catalyst, and the oxidizing substance in the mixed water is A means for removing dissolved oxygen to be removed;
Having a pure water production system.

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