JP6897392B2 - Operation method of ultrapure water production equipment and ultrapure water production equipment - Google Patents

Description

The present invention relates to an operation method of an ultrapure water production apparatus for producing ultrapure water having a small amount of fine particles. The present invention also relates to an ultrapure water producing apparatus suitable for carrying out the operation method of the ultrapure water producing apparatus.

The ultrapure water production apparatus used in the semiconductor production process or the like is composed of, for example, a pretreatment system 22, a primary pure water system 23, and a subsystem (secondary pure water system) 24, as shown in FIG. Ultrapure water W3 is produced by treating raw water (industrial water, city water, well water, etc.) W with such an ultrapure water production apparatus 21. The roles of each system in FIG. 3 are as follows.

In the pretreatment system 22 including agglomeration, pressure levitation (precipitation), filtration (membrane filtration) equipment, etc., suspended substances and colloidal substances in the raw water W are removed. Further, in this process, it is possible to remove high molecular weight organic substances and hydrophobic organic substances. The primary pure water system 23 removes ions and organic components in the pretreated water W1. The subsystem 24 includes a low-pressure ultraviolet oxidizing device, a catalytic oxidative substance removing device, a degassing membrane device, an ion exchange device, and an ultrafiltration membrane separation device, and the subsystem 24 is obtained by the primary pure water system 23. The purity of the pure water (primary pure water) W2 is further increased to obtain ultrapure water W3, and this ultrapure water W3 is supplied to the use point (UP).

As described above, conventionally, nanometer-sized fine particles are removed by installing an ultrafiltration membrane (UF membrane) device at the end of the subsystem 24. In addition, a mini-subsystem is installed as a use point polisher just before the cleaning machine for cleaning semiconductors and electronic materials, and a UF membrane device for removing fine particles is installed at the last stage, and fine particles are installed just before the nozzle in the washing machine at the use point. It is also being considered to install a UF membrane for removal to highly remove fine particles of a smaller size.

In recent years, with the development of semiconductor manufacturing processes, the control of fine particles in water has become more and more strict. For example, according to the International Technology Roadmap for Semiconductors (ITRS), in 2019, the particle size> 11.9 nm. It is required that the guaranteed value <1,000 pieces / L (control value <100 pieces / L) of.

Therefore, as a technique for highly removing impurities such as fine particles in water to increase the purity in an ultrapure water production apparatus, Patent Document 1 describes viable bacteria and fine particles in a subsystem using an electric deionization apparatus. It is stated to be removed. Further, in Patent Document 2, a membrane separation means is provided in any of the pretreatment device, the primary pure water device, the secondary pure water device (subsystem) or the recovery device constituting the ultrapure water supply device, and a membrane separation means is provided in the subsequent stage. It is described that a reverse osmosis membrane that has been subjected to a treatment for reducing amine elution is arranged. Patent Document 3 also describes that a reverse osmosis membrane device is provided in front of the final stage UF membrane device in the subsystem. Patent Document 4 describes that a functional material having an anionic functional group or a reverse osmosis membrane is arranged after the UF membrane of the ultrapure water line. Further, Patent Document 5 describes that a pre-filter is built in a membrane module used in an ultrapure water production line to remove particles.

Japanese Patent No. 3429808 Japanese Patent No. 39066884 Japanese Unexamined Patent Publication No. 5-138167 Japanese Patent No. 4508469 Japanese Patent No. 3059238

However, when an electric deionizer is used for the subsystem as described in Patent Document 1, the electric deionizer removes the removed substance by passing it through an ion exchange membrane in the apparatus. However, since the fine particles cannot pass through the ion exchange membrane, there is a problem that the electric deionization device cannot have the function of removing fine particles.

Further, the ultrapure water supply device described in Patent Documents 2 and 3 removes fine particles by a reverse osmosis membrane, but in order to operate the reverse osmosis membrane, the pressure must be increased and the amount of permeated water is also increased. At a pressure of 0.75 MPa, it is as small as ^{1 m 3} / m ^{2 / day.} On the other hand, in the subsystem using the UF membrane, ^{the water volume is 7 m 3} / m ² / day, which is 50 times or more at a pressure of 0.1 MPa, and in order to cover the water volume comparable to that of the UF membrane with the reverse osmosis membrane. A huge membrane area is required. Further, there is a problem that driving the booster pump causes a risk of generating new fine particles and metals.

In Patent Document 4, a functional material or reverse osmosis membrane having an anionic functional group is arranged after the UF film, and the functional material or reverse osmosis membrane having an anionic functional group is intended to reduce amines. There is a problem that it is not suitable for removing fine particles having a particle diameter of 10 nm or less, which is the object of removal in the present invention. Further, it is not preferable to arrange the reverse osmosis membrane as in the cases of Patent Documents 2 and 3.

Further, as described in Patent Document 5, the method of removing particles by incorporating a pre-filter in a membrane module used in an ultrapure water production line aims to remove particles having a particle size of 0.01 mm or more. There is a problem that it is not suitable for removing fine particles having a particle size of 10 nm or less.

The present invention has been made in view of such a problem, and provides an operation method of an ultrapure water production apparatus capable of producing ultrapure water suitable for manufacturing an electronic device or the like in which it is desired to avoid mixing of ultrafine fine particles. The purpose. Another object of the present invention is to provide an ultrapure water production apparatus suitable as an apparatus for carrying out an operation method of this ultrapure water production apparatus.

In view of the above object, the present invention first has a primary pure water system and a subsystem for processing the primary pure water produced by this primary pure water system, and the subsystem uses ultrapure water as a point of use. It is an operation method of an ultrapure water production apparatus including a liquid feeding / pressurizing means for feeding and a membrane filtration device provided after the liquid feeding / boosting means, wherein the liquid feeding / boosting means is used. When stopping, the step of stopping the supply of ultrapure water to the use point, the step of stopping the liquid feeding to the membrane filtration device, and the step of stopping the liquid feeding / pressurizing means are carried out in this order. , Provide an operation method of an ultrapure water production apparatus (Invention 1).

According to the present invention (Invention 1), it is possible to produce ultrapure water by maximizing the performance of the membrane filtration device and avoiding the mixing of fine particles. This is presumed to be due to the following reasons. That is, as a result of the present inventors examining the cause of the increase in the number of fine particles in the ultrapure water, it is not only due to the inherent performance of the membrane filtration device at the end of the ultrapure water production device, but is stopped. Sudden flow fluctuations and pressure fluctuations at the time put stress on the membrane of the membrane filtration device, and repeated activation and stoppage causes minute damage to the membrane of the membrane filtration device, and fine particles are generated from this damaged part. Was found to be one of the causes. Therefore, when stopping the ultrapure water production device equipped with the membrane filtration device, first stop the supply of ultrapure water to the use point, then stop the liquid supply to the membrane filtration device, and finally send it. If the liquid / pressurizing means is stopped, the flow rate fluctuation and pressure fluctuation applied to the membrane of the membrane filtration device at the time of stop can be minimized, and the increase of fine particles due to the stop of the ultrapure water production device can be avoided. The performance of the membrane filtration device can be maximized.

In the above invention (Invention 1), when the liquid feeding / pressurizing means is stopped and then restarted, the liquid feeding to the membrane filtration device and the supply of ultrapure water to the use point are stopped. It is preferable to restart the liquid / pressurizing means, then restart the liquid feeding to the membrane filtration device, and then restart the supply of ultrapure water to the use point (Invention 2).

According to the invention (Invention 2), when restarting the ultrapure water production apparatus provided with the membrane filtration apparatus stopped in the above invention 1, the operation opposite to the case of stopping is performed again. Fluctuations in the flow rate and pressure applied to the membrane of the membrane filtration apparatus during operation can be minimized, damage to the membrane of the membrane filtration apparatus can be prevented, and contamination of fine particles can be avoided.

In the above inventions (Inventions 1 and 2), the ultrapure water production apparatus has a first bypass flow path that bypasses the use point and a second bypass flow path that bypasses the membrane filtration device. It is preferable (Invention 3).

According to the present invention (Invention 3), when the ultrapure water production apparatus is stopped, the supply of ultrapure water to the use point is stopped by using the first bypass flow path without stopping the membrane filtration apparatus. By using the second bypass flow path, the liquid feeding to the membrane filtration device can be stopped without stopping the liquid feeding / pressurizing means. In addition, by using the second bypass flow path to restart the ultrapure water production equipment, the liquid feeding / pressurizing means is restarted while the liquid feeding to the membrane filtration device is stopped, and the first bypass is performed. By using the flow path, the membrane filtration device can be restarted while stopped at the point of use.

The present invention secondly has a primary pure water system and a subsystem for processing the primary pure water produced by the primary pure water system, and the subsystem stores the primary pure water and an ultrapure water. An ultrapure water production device including a liquid feeding / pressurizing means for feeding water to a use point and a membrane filtration device provided after the liquid feeding / pressurizing means. A return pipe that communicates with the sub-tank is provided, and a first bypass flow path that bypasses the use point and communicates with the return pipe in front of the use point, and a first opening / closing that opens / closes the first bypass flow path. Provided is an ultrapure water production apparatus including a means, a second bypass flow path bypassing the membrane filtration device, and a second opening / closing means for opening / closing the second bypass flow path (Invention 4).

According to the present invention (Invention 4), when the ultrapure water production apparatus is stopped, the first opening / closing means is switched to open the first bypass flow path, so that the membrane filtration apparatus can be reached without stopping. By stopping the supply of pure water and switching the second opening / closing means to open the second bypass flow path, it is possible to stop the liquid feeding to the membrane filtration device without stopping the liquid feeding / boosting means. In addition, when restarting the ultrapure water production equipment, the second bypass flow path and the first bypass flow path are closed, so that the liquid transfer to the membrane filtration device is stopped and the pressure is increased. By restarting the means and switching the second opening / closing means to close the second bypass flow path, the membrane filtration device was restarted with the supply of ultrapure water to the point of use stopped. Then, by switching the first opening / closing means and closing the first bypass flow path, the liquid feeding to the use point can be restarted. Further, when restarting the ultrapure water production apparatus provided with the stopped membrane filtration apparatus, the operation opposite to the case of stopping may be executed. As a result, the ultrapure water production device can be stopped and restarted while the flow rate fluctuation and pressure fluctuation applied to the membrane of the membrane filtration device are suppressed to the minimum, and the membrane of the membrane filtration device can be prevented from being damaged. It is possible to avoid the contamination of fine particles.

In the above invention (Invention 4), it is preferable to include the first opening / closing means and the control means for controlling the second opening / closing means (Invention 5).

According to the invention (Invention 5), the operation of the ultrapure water production apparatus of the invention 4 can be automatically controlled by controlling the first opening / closing means and the second opening / closing means.

The present invention comprises a step of stopping the supply of ultrapure water to a use point when stopping an ultrapure water production apparatus provided with a liquid feeding / pressurizing means and a membrane filtration apparatus, and a liquid feeding to the membrane filtration apparatus. Since the step of stopping the process and the process of stopping the liquid feeding / pressurizing means are carried out in this order, ultrapure water that maximizes the performance of the membrane filtration device and avoids the mixing of fine particles is produced. be able to.

It is the schematic which shows the subsystem provided with the ultrapure water production apparatus of 1st Embodiment. It is the schematic which shows the subsystem provided in the ultrapure water production apparatus of the 2nd Embodiment. It is a flow chart which shows the ultrapure water production apparatus.

Hereinafter, the first embodiment of the ultrapure water production apparatus of the present invention will be described in detail with reference to the accompanying drawings.

The ultrapure water production apparatus of this embodiment has the configuration shown in FIG. 3, and the subsystem 24 in FIG. 3 has the configuration shown in FIG. In FIG. 1, the subsystem 1 supplies and boosts a sub tank 2 for storing a primary pure water W2 supplied from a primary pure water device (not shown) and a primary pure water W2 stored in the sub tank 2. A pump 3 as a means, a heat exchanger 4 provided after the pump 3, a low-pressure UV irradiation oxidizing device 5, a catalytic oxidizing substance decomposition device 6, an ultrafiltration membrane device 7, and a mixed-bed ion exchanging device 8. It also has a UF membrane separator 9 as a membrane filtration device. The UF membrane separation device 9 communicates with the use point (UP), and the excess water at the use point (UP) is recirculated from the return pipe 10 to the sub tank 2.

In such a subsystem 1, a first bypass flow path 11A is provided after the UF membrane separation device 9 and before the use point (UP). A first automatic valve as an opening / closing means (not shown) is attached to the base end portion of the first bypass flow path 11A, and it is possible to switch between the use point side and the first bypass flow path 11A side. ing. Further, a second bypass flow path 11B that bypasses the UF membrane separation device 9 is provided between the mixed bed type ion exchange device 8 and the UF membrane separation device 9. A second automatic valve as an opening / closing means (not shown) is attached to the base end of the second bypass flow path 11B, and switches between the UF membrane separation device 9 side and the second bypass flow path 11B side. It is possible. The first automatic valve and the second automatic valve can be automatically controlled by a control means (not shown) such as a PLC, and the flow path can be switched.

In the subsystem 1 having the above-described configuration, any method can be used as the UF membrane separation device 9, but the external pressure type hollow fiber membrane module produces ultrapure water having a small number of fine particles. It is preferable because it is suitable for. However, this external pressure type hollow fiber membrane module has a high risk of being damaged (broken) due to sudden flow fluctuations, and when it is broken, fine particles are generated (dusted) from the broken portion, so that the number of fine particles in ultrapure water increases. It is desirable to apply this embodiment because it will increase significantly.

Further, the pump 3 as a liquid feeding / boosting means is not particularly limited, and a can pump or a centrifugal pump generally used in an ultrapure water production apparatus can be used. These pumps can be equipped with an inverter to gently raise and lower the operating frequency to mitigate flow rate fluctuations due to start and stop, but large-scale ultrapure water production using multiple pumps in parallel. Since it is often the case that the device does not always have a sufficient effect of mitigating the flow rate fluctuation, it is desirable to use this embodiment in combination.

Next, the operation method at the time of starting and stopping of the ultrapure water production apparatus as described above will be described based on the operation of the subsystem 1.

First, during the production of ultrapure water, the primary pure water W2 treated by the pretreatment device and the primary pure water device is treated by the subsystem 1, and the ultrapure water W3 that has passed through the UF membrane separation device 9 is a point of use ( The surplus water sent to UP) and not used at this use point (UP) is returned from the return pipe 10 to the sub tank 2 for reuse.

Then, when the pump 3 which is the liquid feeding / pressurizing means is stopped in order to stop the ultrapure water production apparatus, if the pump 3 is stopped immediately, the flow rate fluctuation and the pressure fluctuation are caused by the membrane of the UF membrane separation device 9. Will put stress on you. Therefore, it is conceivable to stop (block) the liquid feeding to the UF membrane separation device 9, but the ultrapure water W3 that has been pumped and boosted by the pump 3 can be used without passing through the UF membrane separation device 9. If it is supplied to (UP), water from which fine particles have not been removed will be supplied to the use point (UP). Therefore, the first automatic valve is opened and closed by the control means to open the first bypass flow path 11A and close the flow path on the use point (UP) side. At this time, the second bypass flow path 11B is closed by the second automatic valve, and the flow path on the UF membrane separation device 9 side is open. As a result, the ultrapure water W3 that has passed through the UF membrane separation device 9 returns from the first bypass flow path 11A to the sub tank 2 via the return pipe 10 ((i) in FIG. 1).

Next, the second automatic valve is opened and closed by the control means to open the second bypass flow path 11B, and the flow path on the UF membrane separation device 9 side is closed. As a result, the ultrapure water W3 treated by the mixed-bed ion exchange device 8 does not flow to the UF membrane separation device 9, and the return pipe 10 is connected from the second bypass flow path 11B and the first bypass flow path 11A. It returns to the sub tank 2 via ((ii) in FIG. 1). After shutting off the water supply to the UF membrane separation device 9 side in this way, the pump 3 may be stopped. As a result, the ultrapure water production apparatus can be stopped by suppressing fluctuations in the flow rate and pressure of the liquid sent to the UF membrane separation apparatus 9.

Further, when restarting the ultrapure water production apparatus, the operation opposite to that at the time of stopping may be performed. That is, the flow path on the use point (UP) side is closed with the first bypass flow path 11A open, and the flow path on the UF membrane separation device 9 side is closed by opening the second bypass flow path 11B. , The pump 3 is restarted in a state where the ultrapure water W3 is not supplied to the liquid feeding device 9 and the use point (UP) ((ii) in FIG. 1). As a result, the ultrapure water W3 treated by the mixed bed type ion exchange device 8 does not flow to the UF membrane separation device 9 side and is not supplied to the use point (UP), and the second bypass flow path 11B, the second bypass flow path 11B, It returns from one bypass flow path 11A to the sub tank 2 via the return pipe 10.

Next, the second automatic valve is opened and closed by the control means to close the second bypass flow path 11B and open the flow path on the UF membrane separation device 9 side to restart the liquid feeding to the UF membrane separation device 9. To do. As a result, the ultrapure water W3 treated by the mixed-bed ion exchange device 8 passes through the UF membrane separation device 9 and the fine particles are removed from the first bypass flow path 11A via the return pipe 10. It returns to the sub tank 2 ((i) in FIG. 1).

Subsequently, the first automatic valve is opened and closed by the control means to close the first bypass flow path 11A and open the flow path on the use point (UP) side. As a result, the supply of ultrapure water W3 that has passed through the UF membrane separation device 9 to the use point (UP) is resumed, and the excess water at this use point (UP) is returned from the return pipe 10 to the sub tank 2 for reuse. Will be done. As a result, the ultrapure water production apparatus can be restarted by suppressing fluctuations in the flow rate and pressure to the UF membrane separation apparatus 9.

When switching the flow paths of the first bypass flow path 11A and the second bypass flow path 11B described above, the flow rate fluctuation and the pressure fluctuation may occur due to the operation of the automatic valve. Therefore, it is preferable to prevent the flow rate fluctuation and the pressure fluctuation by controlling the opening / closing speed of the first automatic valve and the second automatic valve to a slow speed.

Although one embodiment of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiment and various modifications can be made. For example, the subsystem 1 is not limited to the one shown in FIG. 1, and can be applied to various types of subsystems. For example, as shown in FIG. 2, a heat exchanger 4, a low-pressure UV irradiation oxidizing device 5, a mixed bed ion exchanging device 8, and an ultrafiltration membrane device 7 are placed after the pump 3 without using the catalytic oxidizing substance decomposition device 6. It is also applicable to a device in which a UF membrane separation device 9 as a membrane filtration device is arranged and a booster pump 12 as a liquid feeding / pressurizing means is arranged in front of the UF membrane separation device 9 (second embodiment). .. In such a second embodiment, the same operation may be performed for stopping / restarting the booster pump 12, and further, in the first and second embodiments described above, the membrane filtration device Although the case where the UF membrane separator 9 is used has been described above, the same applies even when a microfiltration membrane (MF membrane) separator is used instead of the UF membrane separator 9.

1 Subsystem 3 Pump (liquid feeding / boosting means)
9 UF membrane separation device (membrane filtration device)
10 Return pipe 11A First bypass flow path 11B Second bypass flow path 12 Booster pump (liquid feeding / boosting means)
21 Ultrapure water production equipment 23 Primary pure water system 24 Subsystem (secondary pure water system)
W Raw water W1 Pre-treated water W2 Primary pure water W3 Ultrapure water UP Use point

Claims (3)

It has a primary pure water system and a subsystem that processes the primary pure water produced by this primary pure water system, and the subsystem serves as a liquid feeding / boosting means for supplying ultrapure water to a use point. This is a method of operating an ultrapure water production device equipped with a membrane filtration device provided after the liquid feeding / pressurizing means.
When stopping the liquid feeding / boosting means,
The process of stopping the supply of ultrapure water to the use point and
The step of stopping the liquid feeding to the membrane filtration device and
A method of operating an ultrapure water production apparatus, wherein the steps of stopping the liquid feeding / boosting means are carried out in this order. When the liquid feeding / boosting means is stopped and then restarted, the liquid feeding / boosting means is restarted with the liquid feeding to the membrane filtration device and the supply of ultrapure water to the use point stopped.
Next, the liquid feeding to the membrane filtration device was restarted,
Subsequently, the supply of ultrapure water to the use point is resumed.
The operation method of the ultrapure water production apparatus according to claim 1. The ultrapure water according to claim 1 or 2, wherein the ultrapure water production apparatus has a first bypass flow path that bypasses the use point and a second bypass flow path that bypasses the membrane filtration device. How to operate the manufacturing equipment.

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