CN112203988A

CN112203988A - Ultrapure water production apparatus and ultrapure water production method

Info

Publication number: CN112203988A
Application number: CN201980033935.0A
Authority: CN
Inventors: 中村清一
Original assignee: Nomura Micro Science Co Ltd
Current assignee: Nomura Micro Science Co Ltd
Priority date: 2018-06-13
Filing date: 2019-05-24
Publication date: 2021-01-08
Also published as: JP2019214022A; KR20210018207A; WO2019239853A1

Abstract

An ultrapure water production apparatus capable of continuously producing ultrapure water having a desired water quality even when an ion exchange resin is replaced. An ultrapure water production apparatus of the present invention comprises a plurality of branch flow paths, a plurality of ion exchange units, a plurality of opening/closing valves, and an opening degree changing unit. The plurality of branch flow paths branch the flow paths of the water to be treated and join at the downstream side. The plurality of ion exchange devices are provided on the plurality of branch flow paths, respectively, and each have an ion exchange resin. The plurality of opening/closing valves are provided before and after the respective ion exchange devices in the respective branch flow paths. The opening degree changing unit changes the opening degree of the on-off valve according to the set time.

Description

Ultrapure water production apparatus and ultrapure water production method

Technical Field

The present invention relates to an ultrapure water production apparatus and an ultrapure water production method.

Background

Ultrapure water used in semiconductor manufacturing processes and the like has been conventionally manufactured using an ultrapure water manufacturing apparatus. The ultrapure water production apparatus mainly includes, for example, a pretreatment unit for producing pretreated water by removing suspended substances in raw water, a primary pure water production unit for producing primary pure water by removing total organic carbon components and ionic components in the pretreated water using a reverse osmosis membrane apparatus and an ion exchange apparatus, and a secondary pure water production unit for producing ultrapure water by removing very small amounts of impurities in the primary pure water (see, for example, patent document 1). As the raw water, used ultrapure water (recovered water) or the like recovered at a use point as a use place of ultrapure water is used in addition to tap water, well water, underground water, industrial water or the like.

Here, the secondary pure water production unit includes an ion exchange device (ion polisher) to which an ion exchange resin is attached, in addition to an ultraviolet oxidation device, an ultrafiltration membrane (ultrafiltration membrane) device, and the like. For example, 4 to 5 ion exchange units are arranged in parallel to a flow path of water to be treated. That is, the plurality of ion exchange devices are provided for each of the plurality of branch flow paths that once branch the flow path of the water to be treated and join at the downstream side.

However, the ion exchange resin needs to be replaced at a cycle of, for example, about 1 year, with deterioration of performance with the passage of time. When the ion exchange resin is replaced, the valves in front of and behind 1 ion exchange device provided in the branch flow path are closed, and then the ion exchange resin of the ion exchange device is replaced. In addition, in the process of replacing the ion exchange resins of 1 ion exchange apparatus, while operating a plurality of other ion exchange apparatuses which do not replace the ion exchange resins, the production of ultrapure water was continuously performed.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5135654

Disclosure of Invention

Problems to be solved by the invention

However, when the valve is closed during the replacement of the ion exchange resin, the pressure loss increases with an increase in the flow rate in the branch flow passage in which the ion exchange device is operating, and as a result, the pressure and the flow rate fluctuate greatly in the flow passage on the downstream side of the ion exchange device. Conventionally, this operation has been performed manually, and the above-described valves of the ion exchange resin apparatus have been manually operated to manually operate the discharge valves of the inlet-side pumps while observing fluctuations in pressure and flow rate in the flow paths on the downstream side of the ion exchange apparatus, thereby carefully maintaining the flow path pressure and flow rate on the downstream side of the ion exchange apparatus at a constant level. In recent years, the variable flow rate and pressure are controlled by the amount of water supplied from the pump or the like corresponding to the measured values of the flow rate meter and the pressure gauge, but in the conventional valve mechanism, the valve is rapidly closed in a short time such as 3 to 5 seconds, and therefore the above control cannot follow the rapid variation of the flow rate and pressure.

When the flow rate or pressure in the flow path of the water to be treated or the ultrapure water to be produced varies greatly, fine particles such as metal colloids are generated from, for example, a metallic water flow contact surface of an ultraviolet oxidation apparatus, a pump, or the like due to the influence of the variation. The generated fine particles such as metal colloids may be gradually ionized and dissolved in water. At this time, the amount of residual ions in the water increases due to the dissolved metal ions, which leads to a decrease in the quality of the produced ultrapure water.

Further, when the flow rate or pressure in the flow path of the water to be treated or the ultrapure water to be produced fluctuates largely, for example, a stable water flow accumulates in a reservoir in the structure of an ultraviolet oxidation device, a pump, or the like, or a reservoir in a pipe or a valve member, and thus, a substance that deteriorates water quality such as fine particles may flow out due to the influence of the fluctuation. In this case, the quality of the produced ultrapure water is lowered. Further, for example, the yield and the like may be affected by fluctuations in the flow rate of pure water in a semiconductor manufacturing facility or the like connected to a place of use (POU) due to fluctuations in the supply pressure of the produced ultrapure water.

The present invention has been made to solve the above-described problems, and an object thereof is to provide an ultrapure water production apparatus and an ultrapure water production method capable of continuously producing ultrapure water in which a desired water quality is ensured even at the time of replacement of an ion exchange resin provided in the ultrapure water production apparatus.

Means for solving the problems

An ultrapure water production apparatus of the present invention comprises a plurality of branch flow paths, a plurality of ion exchange units, a plurality of opening/closing valves, and an opening degree changing unit. The plurality of branch flow paths branch the flow paths of the water to be treated and join at the downstream side. The plurality of ion exchange devices are provided on the plurality of branch flow paths, respectively, and each have an ion exchange resin. The plurality of opening/closing valves are provided before and after the respective ion exchange devices in the respective branch flow paths. The opening degree changing unit changes the opening degree of the on-off valve according to the set time.

The ultrapure water production apparatus of the present invention includes a primary pure water production unit and a secondary pure water production unit. The primary pure water production unit removes organic components and ionic components in the pretreatment water after pretreatment of the raw water to produce primary pure water. On the other hand, the secondary pure water producing unit removes impurities from the primary pure water produced as described above to produce secondary pure water as ultrapure water. The plurality of branch flow paths, the plurality of ion exchangers, and the plurality of opening/closing valves are provided in the secondary pure water production unit.

Further, the opening degree changing unit of the ultrapure water production system of the present invention individually sets the time interval for changing the opening degree and the amount of change in the opening degree. The opening degree changing unit selectively changes the opening degree of any one of the plurality of opening/closing valves, i.e., 1 opening/closing valve.

Further, the ultrapure water production apparatus of the present invention comprises a pump, a meter and an inverter. The pump is provided in a flow path before branching on the upstream side of the plurality of branch flow paths. The measuring device is provided in a flow path that merges into a plurality of branch flow paths on the downstream side, and measures the flow rate or pressure in the merged flow path. The inverter controls the operation of the pump based on the measurement result obtained by the measurement device.

Further, an ultrapure water production method of the present invention is an ultrapure water production method using the ultrapure water production apparatus provided with the plurality of branch flow paths, the plurality of ion exchange units, the plurality of opening/closing valves, and the opening degree changing unit, and includes: completely closing, by the opening degree changing unit, opening and closing valves provided in front of and behind the ion exchange device in 1 of the plurality of branch flow paths through which the water to be treated flows; a step of replacing the ion exchange resin of the ion exchange device in which the front and rear opening/closing valves are completely closed; and a step of fully opening the front and rear opening/closing valves completely closed by the opening degree changing part after the ion exchange resin is replaced.

Effects of the invention

According to the present invention, it is possible to provide an ultrapure water production apparatus and an ultrapure water production method which can continuously produce ultrapure water in which a desired water quality is ensured even at the time of replacement of an ion exchange resin provided in the ultrapure water production apparatus.

Drawings

FIG. 1 is a block diagram schematically showing the configuration of an ultrapure water production apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a secondary pure water production unit provided in the ultrapure water production apparatus of FIG. 1.

FIG. 3 is a block diagram showing the configuration of a control system including an opening degree changing unit provided in the ultrapure water production apparatus of FIG. 1.

Fig. 4 is a diagram schematically showing valve opening gradient control with the elapse of time by the opening changing unit in fig. 3.

Fig. 5 is a diagram showing the pressure (or flow rate) and the variation of the inverter output in the flow path on the downstream side in the process of fully closing the valves of 1 ion polisher provided in the secondary pure water production unit of fig. 2.

FIG. 6 is a block diagram showing the configuration of a control system of a secondary pure water production unit provided in an ultrapure water production apparatus of a comparative example.

Fig. 7 is a diagram showing the pressure (or flow rate) and the variation of the inverter output in the flow path on the downstream side in the process of fully closing the valves of 1 ion polisher provided in the secondary pure water production unit of fig. 6.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in fig. 1, an ultrapure water production apparatus 10 according to the present embodiment includes a pretreatment unit 12, a primary pure water production unit 14, a tank 16, and a secondary pure water production unit 18. The pretreatment unit 12 introduces tap water, well water, industrial water, and the like as raw water. The pretreatment unit 12 is appropriately configured according to the quality of raw water and the like, and removes suspended substances from the raw water to generate pretreatment water. The pretreatment unit 12 includes, for example, a sand filter, a microfiltration device, and the like, and further includes a heat exchanger for adjusting the temperature of the water to be treated, as necessary.

The primary pure water production unit 14 removes organic components, ionic components, dissolved gases, and the like in the pretreatment water to produce primary pure water, and supplies the primary pure water to the tank 16. The primary pure water production unit 14 is configured by appropriately combining 1 or more of a reverse osmosis membrane device, an ion exchange device (a cation exchange device, an anion exchange device, a mixed bed ion exchange device, and the like), an ultraviolet oxidation device, and a degassing device (a vacuum degassing device, a degassing membrane device, and the like), for example. The primary pure water has a Total Organic Carbon (TOC) concentration of 5 [ mu ] gC/L or less and a resistivity of 17M [ omega ]. cm or more. The tank 16 stores primary pure water and supplies a required amount of the primary pure water to the secondary pure water production unit 18.

On the other hand, the secondary pure water production unit 18 removes impurities from the primary pure water produced by the primary pure water production unit 14 to produce secondary pure water as ultrapure water, and supplies the secondary pure water to the point Of use pou (point Of use) as a use location Of the ultrapure water. The remaining amount of ultrapure water after passing through the point of use POU is recovered by the tank 16.

More specifically, as shown in fig. 2, the secondary pure water producing unit 18 includes a circulation pump (treated water supply pump) 11, a heat exchanger 17, an ultraviolet oxidation device (TOC-UV) 19, a treated water Flow path 7, a plurality of

branch Flow paths

8a and 8b … 8n, a plurality of

inlet valves

3a and 3b … 3n and

outlet valves

4a and 4b … 4n as opening and closing valves, a plurality of ion polishers 1a and 1b … 1n as ion exchange devices, a degasifier 21, a pressure gauge (PI) 23 as a measuring device, and a Flow meter (FI) 24.

Further, as shown in fig. 2, the secondary pure water producing unit 18 includes a pressure switch 15 as a measuring device, a booster pump (treated water pressurizing pump) 20, a plurality of

branch flow paths

9a and 9b … 9n, a plurality of inlet valves 5a and 5b … 5n and outlet valves 6a and 6b … 6n as opening and closing valves, a plurality of ion polishing machines 2a and 2b … 2n as ion exchange devices, an ultrafiltration membrane device 22, a flow meter 26 as a measuring device, a pressure control valve (automatic pressure control valve: PCV)29, and a pressure gauge 27.

The circulation pump 11 is provided in the flow path 7 before branching on the upstream side of the plurality of

branch flow paths

8a and 8b … 8 n. The circulation pump 11 supplies primary pure water (water to be treated) contained in the tank 16 to the heat exchanger 17. The heat exchanger 17 adjusts the temperature of the primary pure water supplied from the circulation pump 11. At this time, it is preferable to adjust the temperature of the primary pure water passing through the heat exchanger 17 to, for example, 25 ± 3 ℃.

The ultraviolet oxidation apparatus 19 irradiates the primary pure water whose temperature has been adjusted by the heat exchanger 17 with ultraviolet rays to decompose and remove a trace amount of organic substances in the water. The ultraviolet oxidation apparatus (TOC-UV) 19 has, for example, an ultraviolet lamp and generates ultraviolet rays having a wavelength of about 185 nm. The ultraviolet oxidation device 19 may generate ultraviolet rays having a wavelength of about 254 nm. When the water to be treated is irradiated with ultraviolet rays in the ultraviolet oxidation device 19, the ultraviolet rays decompose the water to be treated to generate OH groups (hydroxyl groups) which oxidize and decompose organic substances in the water to be treated.

As shown in fig. 2, the ion polishers 1a and 1b … 1n are provided in a plurality of

branch passages

8a and 8b … 8n, respectively, which branch the passage 7 of the water to be treated and merge at the downstream side, and the ion polishers 2a and 2b … 2n are provided in a plurality of

branch passages

9a and 9b … 9n, respectively, which branch the passage 7 of the water to be treated and merge at the downstream side. The ion polishing machines 1a, 1b … 1n and 2a, 2b … 2n are non-regenerative mixed bed type ion exchange resin devices which have a mixed bed type ion exchange resin in which a cation exchange resin and an anion exchange resin are mixed and which adsorb and remove a small amount of cation components and anion components in water to be treated. Here, the number of the

branch flow paths

8a and 8b … 8n and the number of the

branch flow paths

9a and 9b … 9n are preferably 2 to 9(n is 2 to 9), more preferably 3 to 8, and still more preferably 3 to 4, respectively.

That is, in order to enable continuous operation of the ultrapure water production system 10 even at the time of replacement of the ion exchange resin, the number of the lower limit of the branch flow paths is at least 2, preferably 3. On the other hand, if the number of the branch flow paths exceeds 9, for example, the number of the devices such as the inlet valve, the outlet valve, and the ion polisher increases, and the management of these devices becomes troublesome, and the restriction of the installation space of the devices increases, and the practicability of the ultrapure water production system 10 is lowered.

Further, although the flow rate and pressure fluctuation in the downstream side flow path can be suppressed to be small when the inlet valve and the outlet valve are operated to open and close when the number of the branch flow paths is large, the flow rate per 1 branch flow path is, for example, less than 10m when the number of the branch flow paths is too large³In the case of/h, the size of the ion polisher (the capacity of the ion exchange resin) corresponding thereto becomes too small to be practical. On the other hand, the flow rate per 1 branch flow path exceeds 100m, for example³In the case of/h, the size of the ion polisher corresponding thereto becomes too large, and if the ion exchange resin replacement work or the like is taken into consideration, a problem occurs in terms of practicality.

Examples of the cation exchange resin included in the ion polishing machines 1a, 1b … 1n and 2a, 2b … 2n include strongly acidic cation exchange resins and weakly acidic cation exchange resins, and examples of the anion exchange resin include strongly basic anion exchange resins and weakly basic anion exchange resins. As a commercial product of the mixed bed type ion exchange resin, for example, N-Lite MBSP, MBGP or the like manufactured by Nomura Micro Science (Nomura Micro Science) can be used.

The

inlet valves

3a, 3b … 3n and the

outlet valves

4a, 4b … 4n are provided respectively before and after the ion polishers 1a, 1b … 1n (ion exchange devices) disposed in the

branch flow paths

8a, 8b … 8n, and the inlet valves 5a, 5b … 5n and the outlet valves 6a, 6b … 6n are provided respectively before and after the ion polishers 2a, 2b … 2n (ion exchange devices) disposed in the

branch flow paths

9a, 9b … 9 n. Here, as shown in fig. 2, the flow path 7 of the water to be treated constitutes a circulation flow path that returns the water from the tank 16 to the tank 16 via the circulation pump 11, the ultraviolet oxidation device 19, the

branch flow paths

8a and 8b … 8n, the ion polishers 1a and 1b … 1n, the booster pump 20, the

branch flow paths

9a and 9b … 9n, the ion polishers 2a and 2b … 2n, the ultrafiltration membrane device 22, the point of use POU, and the like.

The degasifier 21 is a device such as a degassing membrane device that depressurizes the secondary side of a gas permeable membrane and removes only dissolved gas in water flowing through the primary side by permeating the secondary side. For example, commercially available products such as X50 and X40 manufactured by 3M company and Separel manufactured by DIC company can be used for the deaerator 21. The degasifier 21 removes dissolved oxygen from the water to be treated, and produces, for example, treated water having a dissolved oxygen concentration of 1. mu.g/L or less.

The pressure gauge 23 and the flow meter 24 are provided on the flow path 7 that merges downstream of the degasifier 21, that is, downstream of the plurality of

branch flow paths

8a and 8b … 8n, and measure the pressure and the flow rate in the merged flow path 7. The booster pump 20 supplements the supply of water by the circulation pump 11. The pressure switch 15 monitors the shortage of the supply water pressure in the flow path in the vicinity of the booster pump 20.

The ultrafiltration membrane apparatus 2 removes fine particles having a particle diameter of, for example, 50nm or more, preferably 20nm or more, and more preferably 10nm or more, by treating the water to be treated obtained by the ion polisher 2a, 2b … 2n, thereby obtaining ultrapure water (secondary pure water). The ultrapure water has a water quality such that the number of microparticles having a particle diameter of 50nm or more is 50 pcs/L or less, the Total Organic Carbon (TOC) concentration is 1 [ mu ] gC/L or less, and the specific resistance is 18M Ω cm or more.

The flow meter 26 is provided between the ultrafiltration membrane 22 and the point of use POU, that is, on the flow path 7 merged on the downstream side of the plurality of

branch flow paths

9a and 9b … 9n, and measures the flow rate in the merged flow path 7. The pressure gauge 27 is provided in the flow path 7 between the point of use POU and the pressure control valve 29. The pressure control valve 29 automatically controls the valve opening degree of its main body so that the pressure measured by the pressure gauge 27 becomes a predetermined constant pressure (designed value pressure).

As shown in fig. 3, the ultrapure water production apparatus 10 of the present embodiment includes a control panel 31, and the secondary pure water production unit 18 includes a controller 32, a controller 33 functioning as an opening degree changing unit, and an inverter 34. The control panel 31 supplies electric power to each unit of the ultrapure water production apparatus main body including the

controllers

32, 33 and the inverter 34, and comprehensively controls these units.

The controller 32 obtains the measurement results of the pressure gauge 23 and the flow meter 24. The inverter 34 controls the operation of the circulation pump 11 (the rotation speed of the pump drive motor) based on the measurement result of the pressure gauge 23 or the flow meter 24 obtained from the controller 32 so that the measured pressure or flow rate becomes a predetermined constant pressure or flow rate. Further, although not shown, the controller 32 can also acquire the measurement result of the flowmeter 26. The inverter 34 also controls the operation of the booster pump 20 (the rotation speed of the pump drive motor) so that the flow rate measured by the flow meter 26 becomes a predetermined constant flow rate, based on the measurement result of the flow meter 26 obtained from the controller 32.

Here, the

inlet valves

3a, 3b … 3n and 5a, 5b … 5n and the

outlet valves

4a, 4b … 4n and 6a, 6b … 6n provided before and after the ion polishers 1a, 1b … 1n and 2a, 2b … 2n are on-off valves (opening adjusting valves) of a positioner type having the positioner (positioner)35 described above. The positioner 35 is an electronic opening degree controller that is controlled by a controller (opening degree changing unit) 33 and controls the opening degrees of the

inlet valves

3a and 3b … 3n and the

outlet valves

4a and 4b … 4n, and the inlet valves 5a and 5b … 5n and the outlet valves 6a and 6b … 6 n. Based on an instruction from the controller 33, the positioner 35 moves the position of an actuator that adjusts the opening degrees of the

inlet valves

3a, 3b … 3n and the

outlet valves

4a, 4b … 4n by using a driving force of air, for example.

The controller (opening degree changing unit) 33 can change the opening degrees of the

inlet valves

3a and 3b … 3n and the

outlet valves

4a and 4b … 4n, and the inlet valves 5a and 5b … 5n and the outlet valves 6a and 6b … 6n in accordance with the elapse of a set time. The controller (opening degree changing unit) 33 selectively changes the opening degrees of one set of the

inlet valves

3a, 3b … 3n and the

outlet valves

4a, 4b … 4n, and the inlet valves 5a, 5b … 5n and the outlet valves 6a, 6b … 6n, at the time of actual operation. The controller 33 sets the time interval for changing the opening degrees of 1 set of the inlet valve and the outlet valve and the change amount of the opening degrees.

That is, the controller 33 receives an input operation from a user via a predetermined interface, and sets the time interval and the change amount corresponding to the input value. As shown in fig. 4, the controller 33 can perform gradient control of the opening degree of the valve by setting, for example, amounts of 1%, 3%, 5%, 10% and the like as a change amount (increase/decrease amount) of the opening degree in an opening degree range from 0% of the fully closed opening degree of the valve to 100% of the fully open opening degree of the valve, and setting, for example, time intervals of 6 seconds, 60 seconds and the like as time intervals (increase/decrease periods) required for the change amount of the opening degree. Preferably, the opening degree of the opening/closing valve is changed at a constant rate from fully open to fully closed or from fully closed to fully open based on the setting.

As conceptually shown in fig. 4, when the open signal or the close signal of the valve is received from the control panel 31, the controller 33 forcibly changes the opening degree of the valve from the fully closed (0%) to the fully open (100%) or gradually changes the opening degree of the valve from the fully open to the fully closed (100%) for a relatively long time such as 10 minutes to 20 minutes (or a time exceeding 20 minutes) set in advance for the opening degree of one of 1 group of valves out of the plurality of

inlet valves

3a, 3b … 3n and

outlet valves

4a, 4b … 4 n. In fig. 4, the case where the opening degree is continuously changed is exemplified, but the change may be performed discontinuously in stages.

Incidentally, the ion exchange resins of the ion polishing machines 1a, 1b … 1n and 2a, 2b … 2n need to be replaced at a cycle of, for example, about 1 year due to deterioration of performance with time. When the ion exchange resin is replaced, the inlet and outlet valves of the ion polisher on the front and rear sides of 1 of the plurality of

branch flow paths

8a, 8b … 8n and 9a, 9b … 9n are completely closed by the controller 33, and then the ion exchange resin of the ion polisher is replaced. In addition, in the process of replacing the ion exchange resin in the ion polisher, the production of ultrapure water is continuously performed while operating a plurality of other ion polishers that do not replace the ion exchange resin.

Here, when the inlet valve and the like are closed during the replacement of the ion exchange resin, the pressure loss increases with an increase in the flow rate in the branch flow path in which the ion polisher is operating, and as a result, the pressure or flow rate fluctuates in the flow path 7 on the downstream side of the ion polisher. However, in the ultrapure water production apparatus 10 of the present embodiment, by using the aforementioned positioner type inlet and outlet valves and the controller (opening degree changing unit) 33 as an electronic opening degree controller, it is possible to change the opening degree of the inlet valve and the like from fully Open (Open) to fully closed (Close) in a relatively long period of time, for example, 10 to 20 minutes, as shown in fig. 5. The valve to be used is not limited to the positioner type, and any other mechanism may be used as long as it can adjust the opening degree with the time described above.

Therefore, as shown in fig. 5, since fluctuations (vibrations) a1, a2 in pressure or flow rate in the flow path 7 on the downstream side of the ion polisher and vibrations A3, a4 outputted from the inverter can be suppressed to be small, the drop in water quality of the ultrapure water produced by the secondary pure water production unit 18 is suppressed, and thus ultrapure water having a desired water quality can be continuously produced.

On the other hand, fig. 6 is a block diagram showing the configuration of a control system including a control panel 81 in the secondary pure water producing unit provided in the ultrapure water producing apparatus of the comparative example. As shown in fig. 6, the

inlet valves

83a and 83b … 83n and the outlet valves 84a and 84b … 84n provided before and after the ion polisher are conventional air-driven on-off valves. These conventional inlet and outlet valves do not have a function of adjusting the opening degree in accordance with the elapse of time, and when a close signal or an open signal is sent from the control panel 81, the valve is switched from fully open to fully closed in a short time such as 3 seconds to 5 seconds, for example, by the biasing force of a spring or the like. In conventional air-driven inlet and outlet valves, even if an orifice (small hole) is disposed in a ventilation path for driving air, the transition time from full opening to full closing is, for example, 10 seconds to 15 seconds.

In the ultrapure water production apparatus of the comparative example using the conventional inlet valves 83a and 83B … 83n and outlet valves 84a and 84B … 84n, for example, when the inlet valve 83a is fully closed during replacement of the ion exchange resin of the ion polisher 1a, the pressure loss increases with an increase in the flow rate in the branch flow path in which the ion exchange device is operated, and as a result, as shown in fig. 7, the pressure or flow rate fluctuates greatly in the flow path 7 on the downstream side of the ion polisher 1a (the vibrations B1 and B2 with large pressure or flow rate and the vibrations B3 and B4 with large output of the inverter).

Specifically, although the flow rate or pressure of the fluctuation is controlled by the inverter by the feed water amount of the circulation pump 11 via the inverter 34 or the like based on the measured values of the flow meter 23 and the pressure gauge 24, the inlet valve 83a is rapidly closed in a short time such as 3 seconds to 5 seconds in the mechanism such as the conventional inlet valve 83a, and therefore the inverter control cannot follow the rapid fluctuation of the flow rate or pressure.

When the flow rate or pressure in the flow path 7 of the water to be treated (secondary pure water) varies greatly, for example, fine particles such as metal colloids are generated from a metallic water flow contact surface of an ultraviolet oxidation device, a pump, or the like, and metal components of the fine particles are gradually ionized and dissolved in the water due to the influence of the variation. At this time, the amount of residual ions in the water is increased by the dissolved metal ions, and therefore, the water quality of the produced ultrapure water (secondary pure water) may be lowered.

In addition, when the flow rate or pressure in the flow path of the water to be treated or the ultrapure water to be produced fluctuates largely, substances that deteriorate the water quality, such as fine particles accumulated in the accumulation portion of the structure of the ultraviolet oxidation device, the pump, or the like, the piping, or the accumulation portion of the valve member due to the steady water flow, for example, may flow out due to the influence of the fluctuation. In this case, the quality of the produced ultrapure water is lowered.

In contrast, in the ultrapure water production apparatus 10 of the present embodiment, since the on-off valve before and after the ion polisher can be closed in a relatively long time, it is possible to produce ultrapure water while suppressing the decrease in water quality even at the time of exchanging the ion exchange resin. The time taken to close the on-off valve is preferably 5 to 30 minutes, and more preferably 10 to 20 minutes. If the time is shorter than 5 minutes, the flow rate or pressure cannot be suppressed. Further, if it exceeds 30 minutes, it takes too much time in the operation, so that the practicality is lowered. In addition, the optimal value of the time taken to open and close the valve is strictly different depending on the number of branches of the flow path, but even if this is considered, the above range can be approximately satisfied regardless of the number of branches.

Next, a method for producing ultrapure water using the ultrapure water production apparatus 10 will be schematically described.

First, ultrapure water is produced by a normal operation using the ultrapure water production apparatus 10 shown in FIG. 1. Since the performance of the ion exchange resin deteriorates with time as described above by continuing the production of ultrapure water, the ion exchange resin is replaced at an appropriate timing. In the replacement of the ion exchange resin, as shown in fig. 2 and 3, first, 1 ion polisher out of the plurality of

branch flow paths

8a, 8b … 8n, 9a, and 9b … 9n is determined as a replacement target. Here, a case where the ion polisher to be exchanged is, for example, the ion polisher 1a provided in the branch flow path 8a will be described as an example. Next, the inlet valve 3a and the outlet valve 4a, which are provided before and after the ion polisher 1a, through which the water to be treated flows, are fully opened by gradually changing the opening thereof by the controller (opening changing unit) 33 for a long time such as 20 minutes. Specifically, after the inlet valve 3a is completely closed, the outlet valve 4a is completely closed. By completely closing the outlet valve 4a, the reverse flow of the water to be treated to the ion polisher 1a can be prevented.

Next, the ion exchange resin of the ion polisher 1a, in which the front and rear inlet valves 3a and outlet valves 4a are completely closed, is replaced with a new ion exchange resin. After the ion exchange resin is replaced, it takes a long time such as 20 minutes to fully open the outlet valve 4a by the controller 33, and then it takes a long time to fully open the inlet valve 3 a. Thereby, the ion polisher 1a can perform the treatment of the water to be treated with a new ion exchange resin.

Similarly, the ion exchange resins in the other ion polishers 1b to 1n and 2a to 2n are replaced by 1 ion polisher in sequence. Thus, the ion exchange resin of the ion polisher can be smoothly replaced without stopping the ultrapure water production operation.

As described above, in the ultrapure water production apparatus 10 and the ultrapure water production method according to the present embodiment, when the ion exchange resin included in the ion polisher is replaced, the inlet and outlet valves before and after the ion polisher can be closed with time, and therefore, fluctuations in pressure and flow rate in the flow path on the downstream side of the ion polisher can be suppressed. Therefore, the reduction in the quality of the water to be treated by the secondary pure water production unit 18 is suppressed, and thereby ultrapure water having a desired quality can be continuously produced.

The ultrapure water production apparatus 10 of the present embodiment has a function of forcibly stopping the supply of ultrapure water at the point of use POU by the control panel 31 when the measured value of the pressure switch 15 on the upstream side of the booster pump 20 is lower than a predetermined minimum pressure, for example. However, in the ultrapure water production apparatus 10, even when the inlet valves and the outlet valves before and after the ion polishers 1a and 1b … 1n are closed as described above, the pressure fluctuation in the flow path 7 on the downstream side thereof can be suppressed, and therefore, the risk of supply stop of ultrapure water at the use point POU or the like due to the drop detection by the pressure switch 15 on the upstream side of the booster pump 20 or the like can be reduced.

The present invention has been described specifically by the embodiments, but the present invention is not limited to these embodiments as it is, and various modifications can be made in the implementation stage without departing from the gist thereof. For example, some of the components may be deleted from all the components shown in the embodiments, or a plurality of the components disclosed in the above embodiments may be appropriately combined.

Description of the reference symbols

1a to 1n, 2a to 2n … ion polishing machines (ion exchange devices); inlet valves (opening and closing valves) of 3a to 3n and 5a to 5n …; 4a to 4n, 6a to 6n … outlet valves (opening and closing valves); 10 … ultrapure water production system; 11 … circulating pump; 14 … primary pure water producing section; 18 … secondary pure water producing unit; 19 … ultraviolet oxidation unit (TOC-UV); 20 … booster pump; 23 … manometer (meter); 24. 26 … flow meter (counter); 31 … control panel; 32 … control machine; a 33 … controller (opening degree changing part); 34 … frequency converter; 35 … locator.

Claims

1. An apparatus for producing ultrapure water, comprising a water supply unit,

the disclosed device is provided with:

a plurality of branch flow paths for branching the flow paths of the water to be treated and joining the flow paths at the downstream side;

a plurality of ion exchange devices provided on the plurality of branch flow paths, respectively, and each having an ion exchange resin;

a plurality of opening/closing valves provided before and after the ion exchangers in the branch flow paths, respectively; and

and an opening degree changing unit for changing the opening degree of the on-off valve according to the set time.

2. The apparatus for producing ultrapure water according to claim 1,

the disclosed device is provided with:

a primary pure water production unit for producing primary pure water by removing organic components and ionic components from pretreated water obtained by pretreating raw water; and

a secondary pure water production unit for removing impurities from the primary pure water produced as described above to produce secondary pure water as ultrapure water;

the plurality of branch flow paths, the plurality of ion exchangers, and the plurality of opening/closing valves are provided in the secondary pure water production unit.

3. The apparatus for producing ultrapure water according to claim 1 or 2,

the opening degree changing unit individually sets a time interval for changing the opening degree and a change amount of the opening degree.

4. The ultrapure water production apparatus according to any one of claims 1 to 3,

the opening degree changing unit selectively changes the opening degree of any one of the plurality of opening/closing valves.

5. The ultrapure water production apparatus according to any one of claims 1 to 4,

the opening/closing valve is a detent type opening/closing valve.

6. The ultrapure water production apparatus according to any one of claims 1 to 5,

the disclosed device is provided with:

a pump provided in a flow path before branching on an upstream side of the plurality of branch flow paths;

a measuring device provided in a flow path merged at a downstream side of the plurality of branch flow paths, and measuring a flow rate or a pressure in the merged flow path; and

and an inverter for controlling the operation of the pump based on the measurement result obtained by the measurement device.

7. An ultrapure water production method using an ultrapure water production apparatus which comprises a plurality of branch flow paths for branching a flow path of water to be treated and joining the flow path on the downstream side, a plurality of ion exchange units provided on the branch flow paths and having ion exchange resins, respectively, a plurality of on-off valves provided in front of and behind the ion exchange units on the branch flow paths, respectively, and an opening degree changing unit for changing the opening degree of the on-off valves in accordance with elapse of a set time,

the method for producing ultrapure water comprises:

completely closing, by the opening degree changing unit, opening and closing valves provided in front of and behind the ion exchange device in 1 of the plurality of branch flow paths through which the water to be treated flows;

a step of replacing the ion exchange resin of the ion exchange device in which the front and rear opening/closing valves are completely closed; and

and a step of fully opening the opening/closing valves before and after the replacement of the ion exchange resin by the opening degree changing part.