JP7405066B2 - Ultrapure water production equipment and ultrapure water production method - Google Patents

Description

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

Ultrapure water, which is used in large quantities as cleaning water in the manufacturing process of electronic devices, especially semiconductors, is used in an ultrapure water production system consisting of a pretreatment system, a primary pure water system, and subsystems. It is manufactured by processing water (e.g., tap water, well water, used ultrapure water discharged from the electronic device manufacturing process, etc.).

Conventionally, the following systems have been proposed as such ultrapure water production systems.

Patent Document 1 discloses an ultrapure water production system comprising a primary pure water system and a subsystem for treating treated water of the primary pure water system, and in which at least the primary pure water system is provided with a reverse osmosis membrane separation device. An ultrapure water production device is proposed, wherein the reverse osmosis membrane separation device installed in the primary pure water system is a high-pressure reverse osmosis membrane separation device, and is installed in a single stage. ing.
Patent Document 2 describes an ultrapure system that includes a pretreatment system, a primary pure water system that processes the pretreated water treated by the pretreatment system to produce primary pure water, and a subsystem that processes the primary pure water. In the water production equipment, the primary pure water system has a configuration in which a reverse osmosis membrane separation device, a degassing device, an electrodeionization device, an ultraviolet oxidation device, and a non-regenerative ion exchange device are connected in this order. An ultrapure water production device featuring the following has been proposed.
Patent Document 3 describes an ultrapure water production device consisting of a primary pure water system and a secondary pure water system, in which the primary pure water system includes a two-bed three-column ion exchange device, a reverse osmosis membrane device, and a 180-190 nm A combination of an ultraviolet irradiation device equipped with a low-pressure ultraviolet lamp that irradiates ultraviolet rays containing wavelengths and a mixed bed type ion exchange device is provided along the flow path, and the secondary pure water system includes a wavelength containing wavelengths of 180 to 190 nm. An ultrapure water production apparatus has been proposed, comprising at least one combination of an ultraviolet irradiation device equipped with a low-pressure ultraviolet lamp that irradiates ultraviolet rays and a mixed bed ion exchange device along a flow path. There is.
Patent Document 4 describes an ultrapure water production apparatus consisting of a pretreatment system, a primary pure water system, and a secondary pure water system, in which a wavelength of 180 to 190 nm is applied to the primary pure water system and the secondary pure water system, respectively. An ultrapure water production apparatus has been proposed, which is characterized in that at least one combination of an ultraviolet irradiation device equipped with a low-pressure ultraviolet lamp that irradiates ultraviolet rays containing ultraviolet rays and a mixed bed ion exchange device is provided along a flow path. There is.

Japanese Patent Application Publication No. 2012-245439 Japanese Patent Application Publication No. 2003-266097 Japanese Patent Application Publication No. 2004-25184 Japanese Patent Application Publication No. 7-75780

BACKGROUND ART In recent years, as electronic devices such as semiconductors have become highly integrated and circuit patterns have become finer, there has been an increasing demand for improved water quality for ultrapure water used as cleaning water.
In an ultrapure water production device or ultrapure water production system, it is the primary pure water system that determines the achieved water quality and water quality stability at the point of use.
The device configuration of a primary pure water system is generally to have a reverse osmosis membrane separation device, a deaeration device, and an ion exchange device each installed in a single stage. There are problems that cannot be addressed by the equipment configuration of such a general primary pure water system.

For this reason, in recent years, in cutting-edge semiconductor factories, etc., the primary pure water system has been replaced with a reverse osmosis membrane separation device and/or an ion exchange device (including an "ion exchange column") as shown in (A) and (B) below. The system is designed to have multiple stages of ultrapure water (similar to the above) installed in order to increase the purity of the obtained ultrapure water.

(A) Multi-stage RO system incorporating a plurality of reverse osmosis membrane (RO membrane) separation devices Specifically, the following device configuration with seven constituent units can be mentioned.
Reverse osmosis membrane (RO membrane) separation equipment → mixed bed ion exchange equipment (MB) → ultraviolet sterilizer (UVst) → reverse osmosis membrane (RO membrane) separation equipment → ultraviolet oxidation equipment (UVox) → non-regenerative ion exchange equipment →Deaerator (MDG)
(B) Multi-stage electrically regenerative ion exchange deionization device (CDI) system incorporating a plurality of electrically regenerative deionizers Specifically, the following device configuration with six constituent units is exemplified.
Reverse osmosis membrane (RO membrane) separation equipment → Reverse osmosis membrane (RO membrane) separation equipment → Deaerator (MDG) → Ultraviolet oxidation equipment (UVox) → Multistage electrical regeneration type ion exchange pure water equipment (CDI) → Multistage electrical regeneration type ion exchange water purifier (CDI)

Here, the term "unit" in this specification refers to a device capable of performing one or more of the main purposes of treatment in a primary pure water system: "desalination," "deaeration," and "organic matter removal." The number of constituent units means the number of units included in a system, for example a primary pure water system.

For example, pre-treated water obtained by treating raw water (industrial water, tap water, well water, used ultrapure water discharged from electronic device manufacturing processes, etc.) with a pre-treatment system as described in (A), ( By treating with a primary pure water system such as B), specific resistance is 18 MΩcm or more, TOC (Total Organic Carbon) concentration is 2 μg/L or less, boron (B) concentration is 1 ng/L or less, and silica (SiO ₂ ) concentration is 0. Primary pure water (treated water of the primary pure water system, ie, outlet water of the primary pure water system) with a high purity of 1 μg/L or less can be obtained.

However, primary pure water systems like the above (A) and (B) have a large number of constituent units, so the installation area (footprint) of the equipment is large, and equipment costs (initial costs) and operating costs (running costs) are high. There is a problem with the increase in

In addition, the level of demand for ultrapure water quality is expected to continue to rise in the future, and the number of units in primary pure water systems will further increase. In order to maintain stable water quality regardless of the conditions, operation will be carried out under excessive operating conditions. Moreover, once the operating conditions are determined, pure water will continue to be supplied without any changes, including the amount of water supplied, so even if the required amount of ultrapure water decreases due to a decrease in the production volume of a semiconductor factory, etc., a fixed amount of water will be maintained. In order to continue supplying pure water, excess ultrapure water has to be drained or treated again to be recovered and reused, resulting in more costs than necessary.

The present invention has been made in view of the above circumstances, and provides highly pure ultrapure water that fully satisfies the required water quality, regardless of fluctuations in water quantity or water quality, at a low cost and with a reduced installation area. It is an object of the present invention to provide an ultrapure water production device and an ultrapure water production method that can produce ultrapure water stably and reliably.

The present inventors installed appropriate devices in an appropriate order in a primary pure water system installed in an ultrapure water production device, and then controlled the operating conditions of these devices according to fluctuations in water quality and/or water quantity. It has been found that by doing so, it is possible to inexpensively, stably and reliably produce high-purity ultrapure water that fully satisfies the required water quality while reducing the number of constituent units.
That is, in the present invention, the primary pure water system is a four-unit primary pure water system comprising a reverse osmosis membrane separation device, a deaeration device, an ultraviolet oxidation device, and an electric regeneration type ion exchange device in this order. , monitors are installed to monitor water quantity and/or water quality, and for example, in order to suppress fluctuations in water quality caused by changing the amount of water supplied according to the required production volume, each unit is operated based on the signals from the monitors. A control means will be provided to automatically change conditions and maintain stable water quality.

The present invention has been achieved based on such knowledge, and its gist is as follows.

[1] The primary pure water system comprises a pre-treatment system for treating raw water, a primary pure water system for treating the treated water of the pre-treatment system, and a subsystem for treating the treated water of the primary pure water system. However, the ultrapure water production equipment is equipped with at least a reverse osmosis membrane separation device, a deaeration device, an ultraviolet oxidation device, and an ion exchange device in this order as constituent devices, and the water quantity and/or water quality in the primary pure water system is controlled. An ultrapure water production apparatus comprising a monitor for monitoring, and a control means for controlling operating conditions of one or more of the constituent devices according to values detected by the monitor.

[2] The ultrapure water production device according to [1], wherein the ion exchange device is an electrical regeneration ion exchange device in which one or more stages of electrical regeneration deionization devices are connected in series.

[3] An ultrapure water production method for producing ultrapure water using the ultrapure water production apparatus according to [1] or [2].

[4] As the treated water of the ion exchange device, obtain treated water having a specific resistance value of 18 MΩcm or more, a TOC concentration of 2 μm/L or less, a boron concentration of 1 ng/L or less, and a silica concentration of 0.1 μg/L or less. The ultrapure water production method described.

According to the present invention, with a low-cost ultrapure water production device that has a small number of constituent units and therefore a small device installation area, each unit can be operated in an optimal state according to the water amount even if the required water amount is changed. By doing so, it is possible to stably, reliably, and inexpensively produce high-purity ultrapure water that fully satisfies the required water quality.
In addition, by operating each unit in the optimal condition in response to fluctuations in water quality, we can stably, reliably, and inexpensively produce high-purity, ultrapure water that fully satisfies the required water quality. can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows an example of embodiment of the primary pure water system of the ultrapure water production apparatus of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated. Note that the embodiment described below is an example of a typical embodiment of the present invention, and the scope of the present invention is not interpreted to be limited thereby.

The ultrapure water production device of the present invention includes a pretreatment system, a primary pure water system, and a subsystem, and the primary pure water system includes a reverse osmosis membrane separation device, a degassing device, an ultraviolet oxidation device, and an ion exchange device in this order.
According to the ultrapure water production device of the present invention and the ultrapure water production method of the present invention using the ultrapure water production device, it is possible to produce ultrapure water of high purity that fully satisfies the required water quality, even in the installation area of the device. It can be manufactured stably and reliably at low cost while suppressing equipment costs (initial costs) and operating costs (running costs).

In addition, although the primary pure water system characteristic of the ultrapure water production apparatus of the present invention will be mainly explained below, there are no particular limitations on the configuration of the pretreatment system and subsystems in the ultrapure water production apparatus of the present invention. do not have.
For example, as a pre-treatment system, raw water (industrial water, tap water, well water, used ultra-pure water discharged from the electronic device manufacturing process) is Examples include systems that remove suspended solids and colloidal substances in (water, etc.), as well as polymeric organic substances and hydrophobic organic substances.
In addition, the subsystem is equipped with a low-pressure ultraviolet oxidation device, an ion exchange water purification device, and an ultrafiltration membrane separation device, which further increases the purity of the pure water obtained in the primary water purification system and converts it into ultrapure water. can be mentioned. The low-pressure ultraviolet oxidation device in the subsystem decomposes TOC into organic acids and further into _CO2 using ultraviolet light with a wavelength of 185 nm emitted from a low-pressure ultraviolet lamp. Organic matter and CO ₂ produced by decomposition are removed by an ion exchange pure water device in the latter stage. The ultrafiltration membrane separator removes particulates and also removes particles effluent from the ion exchange water purifier.

[Equipment configuration of primary pure water system]
The primary pure water system of the ultrapure water production apparatus of the present invention is a system consisting of only 4 units, comprising a reverse osmosis membrane separation device, a deaeration device, an ultraviolet oxidation device, and an ion exchange device in this order. . The primary pure water system uses a pre-treatment system to process raw water (industrial water, tap water, well water, used ultra-pure water discharged from electronic device manufacturing processes, etc.) and ions in the treated water (pre-treated water). and remove organic components.
Despite the fact that the primary pure water system consists of only 4 units, the water quality of the ultrapure water produced by the ultrapure water production apparatus of the present invention is as follows. Water quality equivalent to or higher than that of ultrapure water produced by ultrapure water production equipment equipped with a primary pure water system that has multiple stages of reverse osmosis membrane separation equipment and/or ion exchange equipment, such as a pure water system. It can be assumed that the
Therefore, the ultrapure water produced by the ultrapure water production apparatus of the present invention is highly pure ultrapure water that fully satisfies the required water quality.

Each component of the primary pure water system according to the present invention will be explained below.

<Reverse osmosis membrane separation device>
The reverse osmosis membrane separation device according to the embodiment of the present invention removes salts and also removes organic substances. As the reverse osmosis membrane separation device, a reverse osmosis membrane separation device conventionally used for seawater desalination, such as a high-pressure reverse osmosis membrane separation device with an operating pressure of about 0.2 to 7.0 MPa, can be used. The shape of the reverse osmosis membrane may be any shape as long as it achieves the purpose of the present invention and exhibits its effects, but examples include a spiral shape, a hollow fiber shape, a flat membrane shape, etc. It will be done.

<Deaerator>
The deaerator according to the embodiment of the present invention removes IC (inorganic carbon) and dissolved oxygen.
The reason why a degassing device (degassing device) is provided after the reverse osmosis membrane separation device is as follows.
In other words, when a deaerator is installed before a reverse osmosis membrane separation device, the turbidity present in the raw water, Al, _SiO2 , etc. There is a risk that the filling material in the equipment etc. will be contaminated and the degassing efficiency will decrease. These turbid substances, Al, _SiO2 , etc. can be removed using a high-pressure reverse osmosis membrane separation device, so after being treated with a high-pressure reverse osmosis membrane separation device, the permeated water is passed through a deaeration device. , it is possible to prevent a decrease in deaeration efficiency.

Further, the reason why the deaerator is installed before the ion exchange device and the ultraviolet oxidation device is as follows.
That is, the IC (inorganic carbon) component that can be removed by the deaerator becomes a radical scavenger for the ultraviolet oxidation device and becomes an anion load for the ion exchange device. Similarly, if there is an excess of dissolved oxygen that can be removed by a degassing device, the dissolved oxygen will act as a radical scavenger for the ultraviolet oxidation device, similar to the above-mentioned IC (inorganic carbon) component. In addition, dissolved oxygen becomes a factor causing resin oxidation deterioration in an ion exchange device.
Therefore, the deaerator needs to be installed before the ultraviolet oxidation device and the ion exchange device.

The deaerator may be any deaerator as long as it achieves the purpose of the present invention and produces the effects of the present invention. For example, a decarbonator, a membrane deaerator, a vacuum deaerator, a nitrogen deaerator, etc. A deaerator, a catalytic resin deoxidizer, etc. can be used.

<Ultraviolet oxidation device>
The reason why the ultraviolet oxidation device is installed after the deaerator and before the ion exchange device is as follows.
That is, in the ultraviolet oxidation device, organic substances in water (water to be treated) are decomposed into CO ₂ and organic acids by the oxidizing power of OH radicals. CO ₂ or organic acid generated in the ultraviolet oxidation device can be removed by an ion exchange device in the subsequent stage.

The ultraviolet oxidation device according to the embodiment of the present invention emits light with a wavelength of 185 nm, and is not particularly limited as long as it achieves the object of the present invention and exhibits the effects of the present invention.
In the embodiment of the present invention, from the viewpoint of organic substance decomposition efficiency, it is preferable to use an ultraviolet oxidation apparatus in which both the lamp and the outer tube are made of synthetic quartz with extremely few impurities.

<Ion exchange device>
The ion exchange device according to the embodiment of the present invention removes salts from water and also removes charged organic substances.
The ion exchange device is not particularly limited as long as it achieves the purpose of the present invention and exhibits the effects of the present invention, but the ion exchange device according to the embodiment of the present invention may include a regenerative ion exchange device. is preferred.
Examples of regenerative ion exchange equipment include a two-bed two-column regenerative ion exchange equipment, a two-bed single-column regenerative ion exchange equipment, a mixed bed regenerative ion exchange equipment, and a single-stage electrical regenerative deionization equipment. Alternatively, an electric regeneration type ion exchange device in which multiple stages are connected in series can be mentioned. Among these, preferred is an electrical regenerative ion exchange device in which regeneration is performed continuously without using regeneration chemicals, specifically a regenerative ion exchange device in which one or more stages of electrical regenerative deionization devices are connected in series.

<Monitor/control means>
The primary pure water system according to the ultrapure water production apparatus of the present invention includes a monitor that monitors water quantity and/or water quality, and one or more component devices depending on the values detected by the monitor, namely, a reverse osmosis membrane separation device, It has a control means for controlling any one or more of the deaerator, the ultraviolet oxidizer, and the ion exchange device. The monitor for monitoring the amount of water is not particularly limited, and may be a flowmeter for measuring the amount of water to be treated provided at the outlet of each component device, or a flowmeter for measuring the amount of water to be supplied provided at the inlet. Further, examples of monitors for monitoring water quality include a pH meter, a resistivity meter, and the like for monitoring the quality of inlet water and outlet water of each component device.
The control means includes a calculation unit that performs calculations to achieve an optimal operating state according to measurement signals from the monitor, and automatically adjusts the operating conditions of each component device based on the calculation results.

There are no particular limitations on the configuration of the monitor and control means according to the present invention, but examples include the following.

The reverse osmosis membrane separation device is equipped with a flow meter, a flow control valve for adjusting the flow rate, and a pump for injecting the chemical solution into the water supply of the reverse osmosis membrane separation device. Configure so that the injection amount can be controlled.
A deaerator, for example a membrane deaerator, is equipped with a vacuum pressure gauge, a pressure control valve that can control the degree of vacuum, a flow meter for a sweep gas such as nitrogen gas, and a control device such as a valve that can control the gas flow rate. The configuration is such that each can be controlled by the signals of
The ultraviolet oxidation device is provided with an output control device that can control the output of ultraviolet rays, and is configured so that the output can be controlled by a signal from the calculation section.
For ion exchange equipment, for example, electrical regeneration type ion exchange equipment, a flow meter, a flow control valve for adjusting the flow rate, and a current control device that can control the current are installed, and the flow rate and electrical output can be controlled by signals from the calculation unit. Configure it as follows.

One or more of the above-mentioned monitors, calculation units, and control devices such as flowmeters, flow rate control valves, pressure control valves, chemical dosing pumps, and current control devices are provided, and there are no particular restrictions on the number. However, water quality and flow rate monitors, calculation units that process signals from the monitors, and flow control valves and pumps that control flow rates and chemical injection amounts based on signals from the calculation units are commonly used. , not particularly limited.

[Embodiment of primary pure water system]
An embodiment of a primary pure water system according to the present invention will be described below with reference to FIG.

In FIG. 1, 1 is a storage tank, into which pretreated water from a pretreatment system is introduced through a pipe 11. A slime control agent is injected into this pipe 11 through a pipe 12, and a scale preventive agent is injected through a pipe 13 by chemical injection pumps _P1 and _P2, respectively. The pretreated water in the storage tank 1 is introduced into the reverse osmosis membrane separation device 2 via a pipe 14 by a high-pressure pump _P3 , and is membrane-separated into permeated water and concentrated water, which are taken out from pipes 15 and 16, respectively. The water supply pipe 14 of the reverse osmosis membrane separation device 2 is provided with a pH adjuster injection pipe 17, into which the pH adjuster is injected by a chemical injection pump _P4 . This water supply pipe 14 is provided with a pH meter M ₁ as a water quality monitor, a water supply flow meter FI ₁ , and a water supply pressure gauge PI ₁ . The permeated water piping 15 is provided with a flow meter FI ₂ , a treated water flow rate control valve V ₁ , and a treated water pressure gauge PI ₂ , and the concentrated water piping 16 is provided with a flow meter FI ₃ and a concentrated water flow rate control valve V ₂ . It is being

Concentrated water from the reverse osmosis membrane separation device 2 is discharged to the outside of the system through piping 16, and permeated water is discharged from piping 15 to a degassing device (in this embodiment, a membrane degassing device in which a liquid chamber and a gas chamber are separated by a degassing membrane) The gas is sent to the air device) 3 for deaeration treatment. The degassed water is sent to the ultraviolet oxidation device 4 through the pipe 17.
In this deaerator 3, nitrogen gas for sweeping is introduced into the gas chamber through the piping 18, and is evacuated via the piping 19 by the vacuum pump _P4 , thereby degassing the water flowing through the liquid chamber. will be held. The piping 18 is provided with a nitrogen gas flow rate control valve _V3 and a nitrogen gas flow meter _FI4 . The vacuum piping 19 is provided with a pressure control valve _V4 and a vacuum pressure gauge _PI3 .

Reference numeral 6 denotes a current control device that controls the amount of current supplied to the ultraviolet oxidation device 4. The treated water from the ultraviolet oxidation device 4 is sent to the demineralization chamber of the electrically regenerative ion exchange device 5 through a pipe 20 and is treated therein. This piping 20 is provided with a demineralization chamber inlet flow meter FI ₅ of the electrically regenerative ion exchange device 5 . Reference numeral 7 denotes a current control device that controls the amount of current supplied to the electric regenerative ion exchange device 5. Further, the inflow piping 21 and the outflow piping 22 to the concentration chamber of the electric regenerative ion exchanger 5 are provided with a flow rate control valve V ₅ for concentration chamber inlet water and a flow rate control valve V ₆ for outlet water, respectively. is equipped with a concentration chamber outlet flow meter _FI6 .

Desalinated water (primary pure water) taken out from the desalination chamber of the electrically regenerative ion exchanger 5 is sent to the subsystem via piping 23 and further processed to produce ultrapure water.
This primary pure water piping 23 is provided with a desalination chamber outlet flow meter FI ₇ and a pressure gauge PI ₄ , as well as a resistivity meter M ₂ as a water quality monitor, a TOC meter M ₃ , a silica concentration meter M 4, and a pressure gauge PI ₄ . A boron concentration meter _M5 is provided.

In the primary pure water system of FIG. 1, the measured values of each monitor M ₁ , M ₂ , M ₃ , M ₄ , M ₅ and the flow meters FI ₁ , FI ₂ , FI ₃ , FI ₄ , FI ₅ , FI ₆ , The measured values of FI ₇ and pressure gauges PI ₁ , PI ₂ , PI ₃ , and PI ₄ are input to a calculation section of a control means (not shown), and this calculation section calculates operating conditions that match the optimal operating state of each device. Based on the calculation results, control signals for the chemical injection pump, flow rate control valve, and current control device are output.

Below, a control method for controlling the operating conditions of each component device in response to fluctuations in water quantity and water quality using an ultrapure water production apparatus incorporating the primary pure water system shown in FIG. 1 will be specifically described.

Control example I: When the amount of water used in the subsystem increases Increase the output of the high-pressure pump _P3 and increase the amount of water at the inlet of the reverse osmosis membrane separation device 2 (water supply amount). On the inlet side of the reverse osmosis membrane separation device 2, chemical injection control of the chemical injection pumps P ₁ and P ₂ is performed in accordance with the flow meter FI ₁ of the reverse osmosis membrane separation device, and the value of the pH meter M ₁ is kept constant. The chemical injection pump _P3 is controlled so that
In the reverse osmosis membrane separation device 2, the concentrated water flow rate control valve _V2 opens in accordance with the feed water flow meter _FI1 , and while maintaining the balance of the water amount in the reverse osmosis membrane separation device 2, the amount of processed water in the reverse osmosis membrane separation device 2 is controlled. (permeated water amount).

In the deaerator 3, in response to an increase in the measured value of the treated water outlet flow meter _FI2 of the reverse osmosis membrane separation device 2, the nitrogen gas flow rate control valve _V3 opens to increase the amount of nitrogen gas injected. Further, the pressure control valve _V4 is opened so that the vacuum pressure gauge _V4 reaches a predetermined degree of vacuum, the output of the vacuum pump _P4 is increased, and the degree of vacuum of the deaerator 3 is increased.

In the ultraviolet oxidation device 4, as the amount of water increases, the amount of organic matter to be decomposed in a predetermined time increases, so the current control device 6 of the ultraviolet oxidation device 4 increases the supplied current value to promote the decomposition of the organic matter.

The electric regenerative ion exchange device 5 increases the concentration chamber inlet water of the electric regenerative ion exchange device ₅ while monitoring the concentration chamber outlet flow meter FI ₆ according to an increase in the measured value of the demineralization chamber inlet flow meter FI 5. The flow rate control valve _V5 opens to increase the flow rate of concentrated water and adjust the water balance within the electrically regenerative ion exchange device 5. Furthermore, as the flow rate at the inlet of the demineralization chamber of the electrically regenerative ion exchanger 5 increases, the amount of ions to be processed increases. Increase the current value.

With the above operations, when the amount of water used in the subsystem increases, the amount of primary purified water produced as treated water in the primary purified water system can be increased according to the increased amount while maintaining water quality.

Control example II: When the amount of water used in the subsystem decreases The output of the high-pressure pump _P3 is lowered, and the amount of water at the inlet of the reverse osmosis membrane separation device 2 (water supply amount) is reduced. On the inlet side of the reverse osmosis membrane separation device 2, the chemical injection of the chemical injection pumps P ₁ and P ₂ is controlled in accordance with the flow meter FI ₁ of the reverse osmosis membrane separation device, and the value of the pH meter M ₁ is kept constant. The chemical injection pump _P3 is controlled so that
In the reverse osmosis membrane separation device 2, the concentrated water flow rate control valve _V2 is closed in accordance with the feed water flow meter _FI1 , and while maintaining the balance of the water amount in the reverse osmosis membrane separation device 2, the amount of water processed by the reverse osmosis membrane separation device 2 is controlled. (permeated water amount).

In the deaerator 3, the nitrogen gas flow rate control valve _V3 is closed in response to a decrease in the measured value of the treated water outlet flow meter _FI2 of the reverse osmosis membrane separation device 2, thereby reducing the amount of nitrogen gas injected. Further, the pressure control valve V ₄ is closed so that the vacuum pressure gauge V ₄ reaches a predetermined degree of vacuum, the output of the vacuum pump P ₄ is lowered, and the degree of vacuum of the deaerator 3 is lowered.

In the ultraviolet oxidation device 4, when the amount of water decreases, the amount of organic matter to be decomposed in a predetermined time decreases, so the current control device 6 of the ultraviolet oxidation device reduces the supplied current value to reduce excess electrical energy.

The electric regenerative ion exchange device 5 monitors the concentration chamber outlet flow meter FI ₆ in response to a decrease in the measured value of the demineralization chamber inlet flow meter FI ₅ , and increases the concentration chamber inlet water of the electric regenerative ion exchange device. The flow rate control valve _V5 is closed to reduce the flow rate of concentrated water and adjust the water balance within the electric regenerative ion exchange device 5. Furthermore, when the flow rate at the inlet of the demineralization chamber of the electric regenerative ion exchanger 5 decreases, the amount of ions to be processed decreases, so the current control device 7 of the electric regenerative ion exchanger 5 reduces the amount of ions supplied to the electric regenerative ion exchanger 5. Reduce excess electrical energy by reducing the current value.

If the amount of water used in the subsystem decreases as a result of the above operations, the water quality of the treated water in the primary pure water system can be maintained by using the minimum amount of chemical injection and electrical energy according to the amount of decrease. As a result, primary pure water production can be reduced.

Control example III: The amount of water used in the subsystem is constant, but if the quality of the primary pure water decreases,
Control examples I and II show control examples in which the amount of water used in the subsystem fluctuates; FI ₇ is constant), but when the quality of the primary pure water produced changes, for example, when the measured value of the water quality monitor deteriorates and the water quality decreases (for example, when the measured value of resistivity meter _M2 decreases) ) can perform the following controls.

When the measured value of the resistivity meter _M2 becomes low, the output of the high pressure pump _P3 is increased to increase the amount of water supplied to the reverse osmosis membrane separation device 2 in order to increase the resistivity. On the inlet side of the reverse osmosis membrane separation device 2, chemical injection control of chemical injection pumps P ₁ and P ₂ is performed in accordance with the feed water flow meter FI ₁ , and the chemical injection is controlled so that the value of the pH meter M ₁ is constant. Injection pump _P3 is controlled.
In accordance with the increased value of the water supply flowmeter FI ₁ , the flow rate control valve V ₂ opens in the reverse osmosis membrane separation device 2 to change the balance of water volume in the reverse osmosis membrane separation device 2, thereby increasing the recovery rate of treated water. Increase the amount of treated water (permeated water amount) while lowering the amount of water. By lowering the recovery rate of treated water, the quality of the treated water of the reverse osmosis membrane separation device 2 can be improved.

In the deaerator 3, in response to an increase in the measured value of the treated water outlet flow meter _FI2 of the reverse osmosis membrane separation device 2, the nitrogen gas flow rate control valve _V3 opens to increase the amount of nitrogen gas injected. Further, the pressure control valve _V4 is opened so that the vacuum pressure gauge _V4 reaches a predetermined degree of vacuum, the output of the vacuum pump _P4 is increased, and the degree of vacuum of the deaerator 3 is increased.

In the ultraviolet oxidation device 4, as the amount of water increases, the amount of organic matter to be decomposed in a predetermined time increases, so the current control device 6 of the ultraviolet oxidation device 4 increases the supplied current value to promote the decomposition of the organic matter.

The electric regenerative ion exchange device 5 monitors the concentration chamber outlet flow meter FI ₆ according to an increase in the measured value of the demineralization chamber inlet flow meter FI ₅ , and adjusts the concentration chamber inlet water of the electric regenerative ion exchange device. The flow rate control valve _V5 is opened to increase the flow rate of concentrated water and change the water balance within the electric regenerative ion exchange device 5 to increase ion exchange efficiency. Furthermore, since the amount of ions is increasing due to the deterioration of water quality, the current control device 7 of the electric regenerative ion exchange device 5 increases the value of current supplied to the electric regenerative ion exchange device 5 to increase desalination efficiency.

With the above operations, it is possible to restore the water quality in response to a decrease in the quality of the primary pure water, and then stably supply the primary pure water as treated water for the primary pure water system.

According to the present invention, the calculation unit analyzes data from signals from the flowmeter and water quality monitor in response to changes in water volume and water quality so that the water quality remains constant, and adjusts the opening of the flow rate control valve and the chemical dosing pump. By controlling the output of the UV oxidizer and the current value of the ultraviolet oxidation device and electric regenerative ion exchange device, it is possible to suppress electrical energy and stably supply primary pure water that maintains a constant water quality.

In the ultrapure water production method of the present invention, the ultrapure water production apparatus of the present invention is used to produce primary pure water, which is treated water in the primary pure water system, with a resistivity of 18 MΩcm or more and a TOC concentration of 2 μg/L. Hereinafter, treated water with a boron concentration of 1 ng/L or less and a silica concentration of 0.1 μg/L or less is obtained, and primary pure water of such water quality is further processed in a subsystem to achieve a resistivity value of 18.2 MΩcm or more and a TOC. It is preferable to produce ultrapure water with a concentration of 0.1 μg/L or less, a boron concentration of 1 ng/L or less, and a silica concentration of 0.1 μg/L or less.

1 Storage tank 2 Reverse osmosis membrane separation device 3 Deaerator 4 Ultraviolet oxidation device 5 Electric regenerative ion exchange device

Claims (2)

A pretreatment system for treating raw water, a primary pure water system for treating treated water of the pretreatment system, and a subsystem for treating treated water of the primary pure water system,
The primary pure water system is an ultrapure water production device comprising a reverse osmosis membrane separation device, a deaeration device, an ultraviolet oxidation device, and an ion exchange device as constituent devices in this order, and the amount of water in the primary pure water system and /or a monitor that monitors water quality; and a control means that controls the operating conditions of one or more of the component devices according to the value detected by the monitor;
The degassing device includes a degassing membrane, a liquid chamber and a gas chamber partitioned by the degassing membrane, a means for introducing nitrogen gas for sweeping into the gas chamber, and a vacuum pump for evacuating the gas chamber. It is a membrane deaerator with
The ion exchange device is an ultrapure water production method in which ultrapure water is produced using an ultrapure water production device that is an electrical regeneration ion exchange device in which one or more stages of electrical regeneration deionization devices are connected in series . ,
A method for producing ultrapure water, characterized in that when the specific resistance of the treated water of the primary pure water system falls below a predetermined value, the following controls a to c are performed.
a: Increase the amount of water supplied to the reverse osmosis membrane separation device, and lower the recovery rate of treated water from the reverse osmosis membrane separation device.
b: In the ultraviolet oxidation device, the value of current supplied to the ultraviolet oxidation device is increased to promote decomposition of organic matter.
c: In the electric regenerative ion exchange device, increase the flow rate of concentrated water and increase the current value supplied to the electric regenerative ion exchange device to increase desalination efficiency. 2. The method according to claim 1 , wherein treated water of the ion exchange device is obtained with a specific resistance value of 18 MΩcm or more, a TOC concentration of 2 μg /L or less, a boron concentration of 1 ng/L or less, and a silica concentration of 0.1 μg/L or less. Ultrapure water production method.

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