JP7143595B2 - Particle control method for ultrapure water production system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fine particle control method for an ultrapure water production system, and more particularly to a fine particle control method for an ultrapure water production system capable of maintaining a reduced number of fine particles in ultrapure water.

Ultrapure water production equipment used in the electronics industry can be broadly divided into pretreatment equipment that removes turbidity from ordinary water such as industrial water and tap water, and A primary pure water system that produces pure water from which impurities are partially removed, and a secondary pure water system (subsystem) that produces ultrapure water by further purifying the primary pure water to remove impurities almost completely. consists of

Of these, the secondary pure water system (subsystem) is basically a low-pressure ultraviolet (UV) irradiation oxidizer that decomposes organic matter, and a non-regenerative mixed bed filled with ion exchange resin that adsorbs and removes ionic impurities. An ion exchange device and an ultrafiltration membrane (UF membrane) separation device for completely removing fine particles are provided as a basic configuration, and the purity of water is further increased to obtain ultrapure water. Here, in the low-pressure UV irradiation oxidation apparatus, TOC is decomposed into organic acids and further to CO ₂ by ultraviolet rays with a wavelength of 185 nm emitted from a low-pressure UV lamp. The decomposed organic acid and _CO2 are removed by the subsequent ion exchange resin. UF membrane separators remove fine particles such as ion exchange resin effluent particles. In this way, in the past, nanometer-sized particles were removed by installing a particle removal membrane such as a UF membrane at the end of the subsystem, but in recent years, semiconductor products have become more sophisticated and miniaturized. Accordingly, fine particle control is becoming more stringent. For example, in semiconductor factories, the control value is often set to 1 particle/mL or less for particles with a diameter of 50 nm or more. For this reason, the number of fine particles in the ultrapure water is measured and controlled at the outlet of the UF membrane separator of the subsystem.

A representative example of this subsystem is shown in FIG. 5, a sub-system 21 includes a sub-tank 22 for storing primary pure water W, a pump 24 provided at the base end of a supply line 23 for the primary pure water W stored in this tank 22, and this pump 24, a heat exchanger 25, a low-pressure UV irradiation oxidation device 26, a non-regenerative mixed-bed ion exchange device 27, and a UF membrane separation device 28. A particle counter (PC) 29 as an off-line monitor is provided on the exit side of the UF membrane separation device 28 .

During operation of the sub-system 21 as described above, the pump 24 is operated to transfer the primary pure water W in the sub-tank 22 to the heat exchanger 25, the low-pressure UV irradiation oxidizer 26, and the non-regenerative mixed-bed ion exchanger 27. and the UF membrane separator 28, and the obtained ultrapure water W1 is sent to the point of use POU. On the other hand, the ultrapure water W1 not used at the point of use POU is returned to the sub-tank 22 via the circulation line 23A and processed again.

In the conventional subsystem 21 as shown in FIG. 5, the number of fine particles in the ultrapure water W1 is controlled by the fine particle counter 29 on the outlet side of the UF membrane separation device 28, while the non-regenerative mixed bed ion exchange device 27 , the ion load on the outlet side is measured by a conductivity meter, a resistivity meter, etc., and if this exceeds a predetermined value, it is replaced periodically. However, even with such a management method, there is a problem that fine particles may leak into the ultrapure water W1, and the number of fine particles in the ultrapure water W1 may not be maintained in a reduced state.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a fine particle control method for an ultrapure water production system capable of maintaining a reduced number of fine particles in ultrapure water. do.

In view of the above object, the present invention provides fine particles for an ultrapure water production system in which primary pure water produced in a primary pure water system is treated by a subsystem comprising a non-regenerative mixed bed ion exchange device and a fine particle removal membrane device in this order. In the management method, the number of fine particles in the ultrapure water at the outlet of the fine particle removal membrane device is monitored by measuring the number of fine particles with a fine particle number measuring means, and the fine particles in the treated water of the non-regenerative mixed bed ion exchange device number is measured by a fine particle number measuring means, and when the number of fine particles in the treated water of the non-regenerative mixed bed ion exchange device exceeds a predetermined value, the non-regenerative mixed bed ion exchange device is replaced, ultra-pure A fine particle control method for a water production system is provided (Invention 1).

According to this invention (Invention 1), the number of fine particles in the treated water of the non-regenerative mixed-bed ion exchange device is measured and managed by the fine particle number measuring means, whereby the ultrapure water at the outlet of the fine particle removal membrane device It is possible to stably reduce the number of fine particles of It is presumed that this is due to the following reasons. In other words, when fine particles in ultrapure water are controlled only on the outlet side of the fine particle removal membrane device, it is possible to detect an increase in fine particles when they leak from the fine particle removal membrane device. It is not possible to prevent the supply of ultrapure water with an increased number of fine particles. Therefore, the inventors of the present invention investigated the relationship between the number of fine particles in the treated water of the non-regenerative mixed-bed ion exchange device and the number of fine particles in the ultrapure water obtained by treatment with the fine particle removal membrane device. It was found that when the number of fine particles in the treated water of the mixed-bed ion exchange device increases, fine particles tend to leak into the ultrapure water at the outlet of the fine particle removal membrane device. Therefore, by controlling the increase in fine particles in the treated water of the non-regenerative mixed bed ion exchange device and by checking the number of fine particles in the ultrapure water at the outlet of the fine particle removal membrane device, the ultrapure water obtained can be stably supplied in a state in which the number of fine particles is reduced.

In the above invention (invention 1), the subsystem includes a low-pressure ultraviolet (UV) irradiation oxidation device, a non-regenerative mixed-bed ion exchange device, and an ultrafiltration membrane (UF membrane) separation device as the fine particle removal membrane device. It is preferable to prepare in this order (Invention 2). Further, in the above invention (Invention 1), the subsystem includes a low-pressure ultraviolet (UV) irradiation oxidation device, a catalyst resin (hydrogen peroxide removal) device, a membrane deaerator, a non-regenerative mixed bed ion exchange device, and It is preferable to provide an ultrafiltration membrane (UF membrane) separation device as the fine particle removal membrane device in this order (Invention 3). Further, in the above invention (Invention 1), the subsystem includes a low-pressure ultraviolet (UV) irradiation oxidation device, a non-regenerative mixed-bed ion exchange device, a membrane degassing device, and an ultrafiltration device as the fine particle removal membrane device. It is preferable to provide the membrane (UF membrane) separation device in this order (Invention 4).

According to such inventions (inventions 2 to 4), the non-regenerative mixed-bed ion exchange device arranged in the preceding stage of the ultrafiltration membrane (UF membrane) separation device has colloidal silica compared to ions such as sodium and chlorine. Fine particles such as the When the number of fine particles in the treated water of the device is controlled and the number of fine particles exceeds a predetermined value, the non-regenerative mixed bed ion exchange device is replaced, and the number of fine particles in the ultrapure water at the outlet of the fine particle removal membrane device By confirming the above, supply of ultrapure water with an increased number of fine particles can be prevented.

In the above inventions (inventions 1 to 4), the particle number measuring means is a particle counter, and It is preferable to measure the number of fine particles inside by switching one fine particle counter (Invention 5).

According to this invention (invention 5), one particle counter measures the number of particles in the treated water of the non-regenerative mixed bed ion exchange device and the number of particles in the ultrapure water at the outlet of the particle removal membrane device. be able to.

In the above inventions (inventions 1 to 4), the means for measuring the number of particles is a particle counter, and the particle counters are provided on the outlet side of the non-regenerative mixed bed ion exchange device and on the outlet side of the particle removal membrane device, respectively. Then, it is preferable to measure the number of fine particles in the treated water of the non-regenerative mixed bed ion exchange device and the number of fine particles in the ultrapure water at the outlet of the fine particle removal membrane device (Invention 6).

According to this invention (invention 6), the number of fine particles in the treated water of the non-regenerative mixed bed ion exchange device and the number of fine particles in the ultrapure water at the outlet of the fine particle removal membrane device can be measured independently. .

In the present invention, the number of fine particles in the treated water of the non-regenerative mixed bed ion exchange device is measured, and when the number of fine particles exceeds a predetermined value, the non-regenerative mixed bed ion exchange device is replaced to remove fine particles. By checking the number of fine particles in the ultrapure water at the outlet of the membrane device, it is possible to prevent supply of ultrapure water with an increased number of fine particles.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an ultrapure water production system to which a fine particle control method for an ultrapure water production system according to a first embodiment of the present invention can be applied; FIG. 2 is a schematic diagram showing an ultrapure water production system to which the method for controlling fine particles in an ultrapure water production system according to a second embodiment of the present invention can be applied; FIG. 10 is a schematic diagram showing an ultrapure water production system to which a method for controlling fine particles for an ultrapure water production system according to a third embodiment of the present invention can be applied; FIG. 11 is a schematic diagram showing an ultrapure water production system to which the fine particle control method for an ultrapure water production system according to a fourth embodiment of the present invention can be applied; FIG. 2 is a schematic diagram showing an ultrapure water production system to which a conventional particle control method for ultrapure water production systems can be applied;

Hereinafter, a fine particle control method for an ultrapure water production system according to a first embodiment of the present invention will be described in detail with reference to FIG.

A subsystem to which the fine particle control method of the ultrapure water production system of this embodiment can be applied has basically the same configuration as that shown in FIG. That is, in FIG. 1, a sub-system 1 includes a sub-tank 2 for storing primary pure water W, a pump 4 provided at the proximal end of a supply line 3 for the primary pure water W stored in the sub-tank 2, and A heat exchanger 5 provided after the pump 4, a low-pressure UV irradiation oxidation device 6, a non-regenerative mixed bed ion exchange device 7, and an ultrafiltration membrane (UF membrane) separation device 8 as a fine particle removal membrane device. have. Particle counters (PC) 9, which are means for measuring the number of particles, are connected switchably to the outlet side of the UF membrane separation device 8 and the outlet side of the non-regenerative mixed bed ion exchange device 7, respectively. As the particle counter 9, "K-LAMIC" (trade name) manufactured by Kurita Water Industries Ltd., "UDI-50" (trade name) manufactured by PMS, etc. can be used.

During the operation of the sub-system 1 as described above, the pump 4 is operated to transfer the primary pure water W in the sub-tank 2 to the heat exchanger 5, the low-pressure UV irradiation oxidizer 6, and the non-regenerative mixed-bed ion exchanger 7 in sequence. The treated water W2 from the non-regenerative mixed-bed ion exchange device 7 is passed through the UF membrane separation device 8 to obtain ultrapure water W1. Then, the obtained ultrapure water W1 is supplied to the point of use POU. On the other hand, the ultrapure water W1 not used at the point of use POU is returned to the sub-tank 2 through the circulation line 3A and processed again.

In addition, as the ultrapure water W1 in this embodiment, resistivity: 18.1 MΩ cm or more, fine particles: 1000 / L or less with a particle size of 50 nm or more, viable bacteria: 1 / L or less, TOC (Total Organic Carbon ): 1 μg/L or less Total silicon: 0.1 μg/L or less Metals: 1 ng/L or less Ions: 10 ng/L or less Hydrogen peroxide: 30 μg/L or less Water temperature: 25±2°C is preferred.

Next, a fine particle control method for such an ultrapure water production system will be described.
[Normal operation]
In the process of producing ultrapure water as described above, by appropriately switching the particle counter 9 between the outlet side of the UF membrane separation device 8 and the outlet side of the non-regenerative mixed bed ion exchange device 7 at a predetermined timing, The number of fine particles in the ultrapure water W1 on the outlet side of the UF membrane separation device 8 and the number of fine particles in the treated water W2 of the non-regenerative mixed-bed ion exchange device 7 are measured. Then, if the number of fine particles in the ultrapure water W1 is 1/mL or less and the number of fine particles in the treated water W2 of the non-regenerative mixed bed ion exchange device 7 is 10/mL or less, the sub system 1 is operated. Ultrapure water W1 is continuously supplied to the point of use POU.

[Particle number control operation]
On the other hand, even if the number of fine particles in the ultrapure water W1 on the outlet side of the UF membrane separation device 8 measured by the fine particle counter 9, which is an offline monitor, is 1/mL or less, the non-regenerative mixed bed ion exchange device 7 When the number of fine particles in the treated water W2 exceeds 10/mL, the operation of the sub-system 1 is temporarily stopped and the non-regenerative mixed bed ion exchanger 7 is replaced. As a result, the number of fine particles in the ultrapure water W1 on the outlet side of the UF membrane separation device 8 can be kept at 1/mL or less, and the ultrapure water W1 with the number of fine particles exceeding the reference value is supplied to the point of use POU. can be prevented from occurring. If the number of fine particles in the ultrapure water W1 on the outlet side of the UF membrane separation device 8 exceeds 1/mL even after such management, it is determined that the UF membrane separation device 8 has broken. , the UF membrane separation device 8 may be replaced.

<Mechanism of action>
Such an effect is obtained by the following action mechanism. That is, it has been reported that soluble silica is generally very easy to remove in an ion exchange device, whereas colloidal silica is much harder to remove (easy to break through) than boron ("UPW Micro 2017, UPW IRDS and SEMI update, Slava Libman et al.). And this boron is much more difficult to remove than sodium ions (Na ⁺ ), chloride ions (Cl ⁻ ) or carbonate ions (HCO ₃ ⁻ ) contained in the primary pure water W (easy to break through). . That is, colloidal silica is much easier to break through than sodium ions (Na ⁺ ), chloride ions (Cl ⁻ ), and carbonate ions (HCO ₃ ⁻ ).

Therefore, as a result of investigation by the present inventors, it was found that the increase in the number of fine particles on the outlet side of the non-regenerative mixed bed ion exchange device 7, that is, on the inlet side of the UF membrane separation device 8, is mainly caused by colloidal silica particles. I found out. Conventionally, the non-regenerative mixed-bed ion exchange apparatus 7 measures the ion load by providing a means for measuring the ion load such as a conductivity meter or a resistivity meter on the outlet side, and measures the ion load when it exceeds a predetermined value. However, the colloidal silica microparticles would flow into the UF membrane separation device 8. On the other hand, by controlling the number of fine particles in the treated water of the non-regenerative mixed bed ion exchange device 7 as in the present embodiment, the fine particles are prevented from reaching the outlet of the UF membrane separation device 8 by Since the regenerative mixed-bed ion exchange device 7 can be replaced, the number of fine particles in the ultrapure water W1 at the outlet of the UF membrane separation device 8 can be stabilized. Then, it can be confirmed by measuring with the particle counter 9 that the number of particles in the ultrapure water W1 does not increase.

As described above, the first embodiment of the present invention has been described with reference to the attached drawings, but the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, as shown in FIG. 2, a first particle counter 9A is provided on the outlet side of the UF membrane separation device 8 and a second particle counter 9B is provided on the outlet side of the non-regenerative mixed bed ion exchange device 7, The number of fine particles in the treated water W2 of the non-regenerative mixed-bed ion exchange device 7 and the number of fine particles in the ultrapure water W1 at the outlet of the UF membrane separation device 8 may be measured independently. Further, the particle number measuring means may be an online monitor using a centrifugal filtration method instead of an offline monitor such as the particle counter 9 .

Also, the subsystem 1 is not limited to those of the first and second embodiments described above, and can be applied to various subsystems. For example, as shown in FIG. 3, a catalyst resin (hydrogen peroxide removal) device 10 and a membrane degassing device 11 are filled with an ion-exchange resin carrying platinum group metal or the like in the latter stage of a low-pressure ultraviolet (UV) irradiation oxidation device 6. is provided, followed by a non-regenerative mixed bed ion exchange device 7 and an ultrafiltration membrane (UF membrane) separation device 8 in this order. Furthermore, as the subsystem 1, for example, as shown in FIG. It is also suitably applicable to In this case, if the means for measuring the number of fine particles such as the fine particle counter 9 is on the exit side of the non-regenerative mixed bed ion exchange device 7 and before the UF membrane separation device 8, other elements such as the membrane deaerator 12 may intervene, in which case the number of fine particles may be measured on the exit side of another element, or may be measured immediately after the non-regenerative mixed bed ion exchange device 7 .

The following specific examples further illustrate the invention.

[Experimental example 1]
Ultrapure water was produced using city water as raw water by the ultrapure water production system shown in FIG. The low-pressure UV irradiation oxidation device 6 constituting the subsystem 1 is a product of Nippon Photo Science Co., Ltd., the non-regenerative mixed bed ion exchange device 7 is Kurita Water Industries Ltd.'s "KR-FM", and the UF membrane separation device. As 8, "KU-1510-HP-H" manufactured by Kurita Water Industries Ltd. was used, and as particle counter 9, "K-LAMIC" manufactured by Kurita Water Industries Ltd. was used.

In the ultrapure water production process in the ultrapure water production system, the number of fine particles in the treated water W2 of the non-regenerative mixed bed ion exchange device 7 and the ultrapure water W1 at the outlet of the UF membrane separation device 8 is monitored. , When the number of fine particles in the treated water W2 of the non-regenerative mixed-bed ion exchange device 7 exceeds 10 / mL, the operation of replacing the non-regenerative mixed-bed ion exchange device 7 is repeated. As a result, the UF membrane separation device The number of fine particles in the ultrapure water W1 at the outlet of 8 did not exceed 1/mL. It is considered that this is because the number of fine particles caused by colloidal silica or the like in the treated water W2 flowing into the UF membrane separation device 8 can be suppressed.

[Comparative Example 1]
In Example 1, without measuring the number of fine particles in the treated water W2 of the non-regenerative mixed bed ion exchange device 7, the specific resistance value was measured with a resistivity meter, and the ion load was determined from this specific resistance value, As a result of repeating the work of replacing the non-regenerative mixed-bed ion exchange device 7 when the ion load exceeds a predetermined value, the number of fine particles in the ultrapure water W1 at the outlet of the UF membrane separation device 8 decreased to 1 with the passage of time. /mL. It is considered that this is because the UF membrane separation device 8 was partially broken due to deterioration over time, and colloidal silica leaked.

1 Subsystem 2 Subtank 3 Supply line 3A Circulation line 4 Pump 5 Heat exchanger 6 Low-pressure ultraviolet (UV) irradiation oxidizer 7 Non-regenerative mixed-bed ion exchange device 8 Ultrafiltration membrane (UF membrane) separator (fine particle removal membrane Device)
9, 9A, 9B particle counter (fine particle number measuring means)
POU Point of use W Primary pure water W1 Ultrapure water W2 Treated water from non-regenerative mixed-bed ion exchange equipment

Claims (6)

A fine particle management method for an ultrapure water production system in which primary pure water produced in a primary pure water system is treated by a subsystem comprising a non-regenerative mixed bed ion exchange device and a fine particle removal membrane device in this order, comprising:
The number of particles in the ultrapure water W1 at the outlet of the particle removal membrane device and the number of particles in the treated water W2 of the non-regenerative mixed bed ion exchange device are measured by a particle number measuring means, and the ultrapure When the number of fine particles in the water W1 is 1/mL or less and the number of fine particles in the treated water W2 exceeds 10/mL, the operation of the subsystem is temporarily stopped, and the non-regenerative mixing replace the bed ion exchanger,
Particle control method for ultrapure water production system. 2. A system according to claim 1, wherein said subsystem comprises a low-pressure ultraviolet (UV) irradiation oxidizer, a non-regenerative mixed bed ion exchange device, and an ultrafiltration membrane (UF membrane) separation device as said particulate removal membrane device in this order. fine particle control method for ultrapure water production system. The subsystem includes a low-pressure ultraviolet (UV) irradiation oxidizer, a catalyst resin (hydrogen peroxide removal) device, a membrane deaerator, a non-regenerative mixed bed ion exchange device, and an ultrafiltration membrane as the fine particle removal membrane device. 2. The fine particle control method for an ultrapure water production system according to claim 1, wherein the (UF membrane) separation devices are provided in this order. The subsystem comprises a low-pressure ultraviolet (UV) irradiation oxidizer, a non-regenerative mixed-bed ion exchange device, a membrane deaerator, and an ultrafiltration membrane (UF membrane) separation device as the particulate removal membrane device in this order. , The fine particle control method for an ultrapure water production system according to claim 1. The means for measuring the number of fine particles is a fine particle counter, and the number of fine particles in the treated water W2 of the non-regenerative mixed bed ion exchange device and the number of fine particles in the ultrapure water W1 at the outlet of the fine particle removal membrane device are counted by one unit. 5. The method for managing fine particles in an ultrapure water production system according to any one of claims 1 to 4, wherein the measurement is performed by switching the fine particle meter of the. The means for counting the number of particles is a particle counter, and a particle counter is provided on each of the exit side of the non-regenerative mixed bed ion exchange device and the exit side of the particulate removal membrane device. The ultrapure water production system according to any one of claims 1 to 4, wherein the number of particles in the treated water W2 of the device and the number of particles in the ultrapure water W1 at the outlet of the particle removal membrane device are respectively measured. Particulate control method.

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