Method for operating a pure water production system

Abstract

The primary pure water production apparatus of the present invention includes a reverse osmosis membrane device, a degassing membrane device, an ultraviolet oxidation device, an electro-deionization device (9), and a water supply pump for supplying water to the electro-deionization device (9). In this primary pure water production apparatus, treated water (W4) treated by the ultraviolet oxidation device (7) is passed through the electro-deionization device (9) to remove ionic impurities caused by the decomposition of organic matter by UV oxidation, thereby producing demineralized water (W5). At this time, by separating and supplying demineralized water (electrode water) from the concentration chamber (26) and electrode chambers (anode chamber (27) and cathode chamber (28)) of the electro-deionization device (9), the hydrogen peroxide concentration of the supply water in the concentration chamber (26) and electrode chambers (anode chamber (27) and cathode chamber (28)) of the electro-deionization device (9) is lower than the hydrogen peroxide concentration of the treated water (W4) supplied to the desalination chamber (25). According to the present invention, a method for operating a pure water production system with a simple structure that can suppress the deterioration of the electrodes, concentration chamber, and ion exchanger within the electrode chamber of an electro-deionization device is provided.

Description

Technical Field

[0001] This invention relates to a method for operating a pure water manufacturing system, and particularly to a method for operating a pure water manufacturing system that constitutes an ultrapure water manufacturing apparatus used in the semiconductor, liquid crystal, and other electronic industries. Background Technology

[0002] Previously, ultrapure water used in the semiconductor and other electronics industries was produced by treating raw water using an ultrapure water manufacturing unit consisting of a pretreatment system, a primary pure water unit, and a subsystem for treating the primary pure water.

[0003] For example, such as Figure 1 As shown, the ultrapure water production apparatus 1 consists of three parts: a pretreatment unit 2, a primary pure water production unit (pure water production system) 3, and a subsystem 4. In the pretreatment unit 2 of this ultrapure water production apparatus 1, pretreatment of raw water W is carried out, including filtration, coagulation and sedimentation, and the use of microfiltration membranes, mainly to remove suspended solids.

[0004] The primary pure water production unit 3 includes a reverse osmosis membrane unit (RO) 5, a degassing membrane unit (MDG) 6, an ultraviolet oxidation unit (UV) 7, an electrodeionization unit (EDI) 9, and a water supply pump (P) 8 that supplies water to the electrodeionization unit 9. This primary pure water production unit 3 removes most of the electrolytes, particles, and live bacteria from the pretreated water W1 and decomposes organic matter.

[0005] Furthermore, subsystem 4 includes a secondary tank (STK) 10, a supply pump (P) 11, an ultraviolet oxidation device 12, a non-regenerative mixed-bed ion exchange device (DI) 13, and an ultrafiltration membrane (UF membrane) 14, configured such that water flows back from the ultrafiltration membrane (UF membrane) 14 to the secondary tank 10 via a point of use (POU) 15. In this subsystem 4, trace amounts of organic matter (TOC) contained in the primary pure water W2 produced by the primary pure water production device 3 are oxidized and decomposed to remove carbonate ions, organic acids, anionic substances, and even metal ions and cationic substances. Finally, ultrapure water W3 is formed by removing particulate matter using the ultrafiltration (UF) membrane 14, and is supplied to the point of use 15. Unused ultrapure water is returned to the front end of the subsystem.

[0006] In the primary pure water production unit 3 of the ultrapure water production device 1 described above, a reverse osmosis membrane device 5, an ultraviolet oxidation device 7, and an electro-deionization device 9 are arranged in sequence. When the treated water from the ultraviolet oxidation device 7 is introduced into the electro-deionization device 9, the hydrogen peroxide generated in the ultraviolet oxidation device sometimes causes the electrodes, concentration chamber, or ion exchanger in the electrode chamber of the electro-deionization device 9 to deteriorate.

[0007] As a countermeasure, Patent Document 1 proposes an operation method for a pure water production system that bypasses the ultraviolet oxidation device and introduces the treated water from the reverse osmosis membrane device into the concentration chamber and electrode chamber of the electro-deionization device.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent document 1: International Publication No. 2020 / 045061. Summary of the Invention

[0011] The problem the invention aims to solve

[0012] However, in the operation method of the pure water production system described in Patent Document 1, a bypass line is required to feed the treated water of the reverse osmosis membrane device into the electro-deionization device. In large-scale pure water production systems, there is a problem that the cost of the device increases due to the increase in long-distance piping.

[0013] The present invention was made in view of the above-mentioned problems, and its object is to provide a method for operating a pure water production system that can suppress the deterioration of the electrodes, concentration chamber, and ion exchanger in the electrode chamber of an electro-deionization device with a simple structure.

[0014] means for solving problems

[0015] In view of the above objectives, the present invention provides an operation method for a pure water production system, which is an operation method for a pure water production system having an ultraviolet oxidation device and an electro-deionization device, and water being sequentially supplied to these devices from the upstream side, such that the hydrogen peroxide concentration of the concentrated water in the concentration chamber and the electrode water in the electrode chamber of the electro-deionization device is less than the hydrogen peroxide concentration of the treated water passing through the desalination chamber of the electro-deionization device (Invention 1). In particular, in the above invention (Invention 1), it is preferable to set the hydrogen peroxide concentration of the concentrated water in the concentration chamber and the electrode water in the electrode chamber of the electro-deionization device to be less than 1 / 3 of the hydrogen peroxide concentration of the treated water passing through the desalination chamber of the electro-deionization device (Invention 2).

[0016] According to the aforementioned inventions (Inventions 1 and 2), the increased hydrogen peroxide concentration in the treated water after treatment by the ultraviolet oxidation device promotes the deterioration of the ion exchangers in the electrodes, concentration chamber, and electrode chamber of the electro-deionization device when this treated water flows into them. Therefore, by adjusting or setting the operating conditions of the electro-deionization device to keep the hydrogen peroxide concentration in the supply water to the concentration chamber and electrode chamber low, particularly to less than 1 / 3 of the hydrogen peroxide concentration in the treated water passing through the desalination chamber, the deterioration of the ion exchangers in the electrodes, concentration chamber, and electrode chamber of the electro-deionization device can be suppressed, thereby extending the service life of the electro-deionization device.

[0017] In the above-described inventions (Inventions 1 and 2), it is preferable that the treated water obtained by the ultraviolet oxidation device is supplied as the treated water to the desalination chamber of the electro-deionization device, and a portion of the permeate from the desalination chamber of the electro-deionization device is used as concentrated water and electrode water to flow into the concentration chamber and electrode chamber of the electro-deionization device (Invention 3). In particular, in the above-described invention (Invention 3), it is preferable that the water flow direction in the desalination chamber and the water flow direction in the concentration chamber of the electro-deionization device are set to a convection flow (Invention 4).

[0018] According to the inventions described above (Inventions 3 and 4), when the treated water from the ultraviolet oxidation device passes through the desalination chamber of the electro-deionization device, the hydrogen peroxide concentration decreases. Therefore, by introducing this portion of the permeate water into the concentration chamber and electrode chamber of the electro-deionization device, water with a lower hydrogen peroxide concentration than the treated water passing through the desalination chamber can be used as the permeate water for the concentration chamber and electrode chamber. In particular, by setting the water flow direction in the desalination chamber of the electro-deionization device to a convection pattern with the water flow direction in the concentration chamber, this can be achieved with a simple structure.

[0019] In the above inventions (Inventions 1 to 4), the pure water production system is preferably a primary pure water device (Invention 5) that has a primary pure water device and a secondary pure water device for ultrapure water production.

[0020] According to the invention described above (Invention 5), since the service life of the electro-deionization device can be extended as described above, by setting the pure water production system of the primary pure water device constituting the ultrapure water production device to the operation control as described above, the service life of the ultrapure water production device can also be extended, and the ultrapure water produced by the ultrapure water production device can be supplied stably for a long time.

[0021] The effects of the invention

[0022] According to the operating method of the pure water production system of the present invention, by keeping the hydrogen peroxide concentration of the supply water to the concentration chamber and electrode chamber low, particularly to less than one-third of the hydrogen peroxide concentration of the treated water passing through the desalination chamber, the deterioration of the ion exchangers in the electrodes, concentration chamber, and electrode chamber of the electro-deionization device can be suppressed, thereby extending the service life of the electro-deionization device. Thus, the extended service life of the electro-deionization device can be achieved with a pure water production system of simple structure. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating an ultrapure water manufacturing apparatus having a primary pure water unit, which is capable of operating a pure water manufacturing system according to an embodiment of the present invention.

[0024] Figure 2This is a schematic diagram illustrating an example of the structure of the electro-deionization device in the operation method of the pure water production system according to the described embodiment.

[0025] Figure 3 This is a schematic diagram illustrating the structure of the electro-deionization device in the operation method of the pure water production system of Example 1.

[0026] Figure 4 This is a schematic diagram showing the structure of the electro-deionization device in the operation method of the pure water production system of Comparative Example 1. Detailed Implementation

[0027] Hereinafter, the operation method of a pure water production system according to an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a flowchart illustrating the operation method of the pure water production system to which this embodiment can be applied. The basic structure of the pure water production system is the same as that of the aforementioned conventional example, therefore, its detailed description is omitted.

[0028] In the primary pure water production unit 3 of the pure water production system of the ultrapure water production device 1, treated water from the ultraviolet oxidation device 7 is introduced into the electrode deionization unit 9. In this embodiment, the electrode deionization unit 9 preferably has... Figure 2 The structure shown.

[0029] [Electrodeionization device]

[0030] exist Figure 2 In this device, the electro-deionization apparatus 9 is a device in which a plurality of anion exchange membranes 23 and cation exchange membranes 24 are alternately arranged between electrodes (anode 21, cathode 22) to alternately form desalination chambers 25 and concentration chambers 26, and anode chambers 27 and cathode chambers 28 are formed on both sides. In the desalination chamber 25, ion exchangers (anion exchangers and cation exchangers) composed of ion exchange resins, ion exchange fibers, or graft exchangers are mixed or filled in multiple layers. In addition, ion exchangers are also filled in the concentration chamber 26, anode chamber 27, and cathode chamber 28.

[0031] Furthermore, in this embodiment, the electro-deionization device 7 is configured with a concentration chamber water supply mechanism (not shown) that introduces treated water W4, which has been treated by the ultraviolet oxidation device 7, into the desalination chamber 25, removes demineralized water W5, separates the demineralized water W5, and supplies water to the concentration chamber 26. The demineralized water W5 from the desalination chamber 25 is introduced into the concentration chamber 26 from the side of the desalination chamber 25 near the outlet of the demineralized water W5, and flows out from the side of the desalination chamber 25 near the inlet of the raw water (treated water W4), that is, from the direction opposite to the flow direction of the treated water W4 in the desalination chamber 25, to spray out concentrated water W6. On the other hand, the structure separates the demineralized water W5 and allows it to circulate as electrode water in the anode chamber 27 and cathode chamber 28, respectively, and discharges it as anode discharge water W7 and cathode discharge water W8.

[0032] How a pure water production system operates.

[0033] The operation method of the primary pure water unit 3 having the above-described configuration will be described. First, pretreated water W1, which has been pretreated by the pretreatment unit 2, is supplied to the primary pure water unit 3. In addition to removing salts by the reverse osmosis (RO) membrane unit 5, ionic and colloidal TOCs are also removed. Then, dissolved gases are removed by the degassing membrane unit 6, and residual organic matter is decomposed in the ultraviolet oxidation unit 7. The treated water W4, which has been treated by the ultraviolet oxidation unit 7, is introduced into the electrodeionization unit 9 to remove ionic impurities caused by the decomposition of organic matter by UV oxidation, thereby producing primary pure water W2.

[0034] At this time, the hydrogen peroxide concentration of the water supplied to the concentration chamber 26 and electrode chambers (anode chamber 27, cathode chamber 28) of the electro-deionization device 9 is lower than the hydrogen peroxide concentration of the treated water W4 supplied to the desalination chamber 25. The increased hydrogen peroxide concentration in the treated water W4 treated by the ultraviolet oxidation device 7 promotes the deterioration of ion exchangers within the electrodes 21, 22, concentration chamber 26, anode chamber 27, or cathode chamber 28 of the electro-deionization device 9 as it flows through these chambers. Therefore, by reducing the hydrogen peroxide concentration of the water supplied to the concentration chamber 26, anode chamber 27, and cathode chamber 28, the deterioration of ion exchangers within the electrodes 21, 22, concentration chamber 26, anode chamber 27, or cathode chamber 28 of the electro-deionization device 9 can be suppressed, thus preventing an increase in the operating voltage of the electro-deionization device 9 and extending its service life. In particular, by setting the concentration of hydrogen peroxide in the treated water passing through the desalination chamber to less than 1 / 3, the above-mentioned effects can be appropriately achieved.

[0035] In this embodiment, demineralized water W5 is separated and supplied to the concentration chamber 26 and electrode chambers (anode chamber 27, cathode chamber 28) of the electro-deionization device 9. Generally, since the hydrogen peroxide concentration of the demineralized water W5 in the electro-deionization device 9 is lower than that of the treated water W4 treated by the ultraviolet oxidation device 7, a simple structure can be implemented. Furthermore, the hydrogen peroxide concentrations of the treated water W4 treated by the ultraviolet oxidation device 7 and the demineralized water W5 after passing through the desalination chamber 25 can be measured, and it can be confirmed in advance that the hydrogen peroxide concentration of the demineralized water W5 is lower than that of the treated water W4, preferably less than 1 / 3. Alternatively, the hydrogen peroxide concentrations of the treated water W4 treated by the ultraviolet oxidation device 7 and the demineralized water W5 after passing through the desalination chamber 25 can be continuously or intermittently measured using a hydrogen peroxide monitor, and the voltage applied to the electro-deionization device 9 can be controlled to ensure that the hydrogen peroxide concentration of the demineralized water W5 is less than 1 / 3 of that of the treated water W4.

[0036] Specifically, in this embodiment, as the electro-deionization device 9, a portion of the demineralized water W5 after passing through the desalination chamber 25 is passed into the concentration chamber 26 as concentrated water in a convection flow pattern in the opposite direction to the water flow direction of the desalination chamber 25. Concentrated water W6 is then discharged from the concentration chamber 26 to the outside of the system. Therefore, on the outlet side of the desalination chamber 25, the ion concentration in the concentrated water of the concentration chamber 26 is lower, and the effect of concentration diffusion on the desalination chamber 25 is smaller. Consequently, the removal rate of weak ions such as boron is improved. Furthermore, the hydrogen peroxide concentration of the demineralized water W5 is lower than that of the treated water W4 treated by the ultraviolet oxidation device 7, and in particular, it can be set to less than 1 / 3. Therefore, by adopting such a structure, concentrated water with a low hydrogen peroxide concentration can be easily supplied to the concentration chamber 26.

[0037] After primary pure water W2 is produced in this way, it is stored in auxiliary tank 10 and supplied to the primary pure water W2 for treatment via supply pump 11. In subsystem 4, the primary pure water W2 is treated by a UV oxidation unit 12, a non-regenerative mixed-bed ion exchange unit 13, and an ultrafiltration membrane 14. In the UV oxidation unit 12, TOC is decomposed to organic acid and even CO2 levels using ultraviolet light with a wavelength of 185nm emitted from a UV lamp. The decomposed organic acids and CO2 are removed by the subsequent non-regenerative mixed-bed ion exchange unit 13. In the ultrafiltration membrane 14, fine particles are removed, as well as effluent particles from the non-regenerative mixed-bed ion exchange unit 13, thus producing secondary pure water (ultrapure water) W3. Then, this ultrapure water W3 is supplied to the point of use 15, and the unused portion is returned to auxiliary tank 10, thereby enabling the ultrapure water production unit 1 to operate.

[0038] The present invention has been described above based on the embodiments described, but the present invention is not limited to the embodiments described, and various modifications can be made. For example, as an ultrapure water manufacturing apparatus 1 applicable to the present invention, as long as the primary pure water unit 3 is structured to treat the treated water from the ultraviolet oxidation unit 7 by means of an electro-deionization unit 9, various structures of apparatuses can be applied. In addition, the electro-deionization unit 9 may also be a type of apparatus having demineralized water and concentrated water in the same direction. Furthermore, in the above embodiment, demineralized water W5 may be supplied as concentrated water to the concentration chamber 26 of the electro-deionization unit 9, while water with a lower hydrogen peroxide concentration than the treated water W4 may be supplied separately.

[0039] Example

[0040] [Example 1]

[0041] Water containing added hydrogen peroxide (hydrogen peroxide concentration: 400 μg / L) was prepared as simulated water for the treatment of the ultraviolet oxidation device 7. This prepared water was used as the treated water W4 and subjected to the water flow conditions shown in Table 2. Figure 3 Water was passed through the electro-deionization device 9 with the structure shown in Table 1, and the results of the hydrogen peroxide concentrations at the inlet of the desalination chamber 25, measured by a dissolved hydrogen peroxide meter (hydrogen peroxide monitor manufactured by Kurita Kogyo Co., Ltd., Japan), and at the outlet of the desalination chamber 25 are shown in Table 3.

[0042] Furthermore, voltage changes were measured as an indicator to confirm the deterioration caused by hydrogen peroxide. Voltage is one of the factors determining the lifespan of the device, and voltage increases need to be suppressed for long-term use. Therefore, the rate of voltage rise was measured after the treated water W4 was continuously supplied for one week. The allowable voltage rise (voltage change until the lifespan is reached) in the electro-deionization device used in this experiment was from the initial voltage of the water supply to 5V. The device lifespan under each condition was calculated based on this value. In addition, 400 μg / L of hydrogen peroxide was added in this experiment. The actual hydrogen peroxide concentration in the treated water of the UV oxidation device 7 was about 100 μg / L. Therefore, the predicted device lifespan when the treated water of the UV oxidation device was supplied was calculated by converting the concentration. The calculated results of the assumed voltage rise rate, device lifespan, and device lifespan of the UV oxidation device (UV oxidation device) when the treated water was supplied are shown in Table 4.

[0043] [Comparative Example 1]

[0044] In Example 1, under the water flow conditions shown in Table 2, water was supplied to... Figure 4The electro-deionization device 9, with the same structure as shown in Table 1, was fed with the same treated water W4 as in Example 1. The hydrogen peroxide concentrations at the inlet of the desalination chamber 25 (treated water W4) and the outlet (desalinated water W5), measured by a dissolved hydrogen peroxide meter, are shown in Table 3. Furthermore, as in Example 1, the assumed voltage rise rate, device lifespan, and device lifespan when treating water with ultraviolet oxidation were calculated. The results are shown in Table 4.

[0045] Table 1

[0046] Composition of an electro-deionization device

[0047]

[0048] Table 2

[0049] Water supply conditions

[0050] Concentrator flow rate 100mL / min Electrode chamber flow 50mL / min Recovery rate 0.8 Current value 2A

[0051] Table 3

[0052]

[0053] Table 4

[0054]

[0055] As shown in Table 4, in Example 1 and Comparative Example 1, there was a difference of more than 700 days in the comparison of the device lifespan under the assumption that the treated water from the actual UV oxidation device was supplied to the desalination chamber. This can be presumed to be because, as shown in Table 3, in Example 1, the hydrogen peroxide concentrations of the concentrated water supplied to the concentration chamber and the electrode water supplied to the electrode chamber were lower than the hydrogen peroxide concentration of the untreated water supplied to the desalination chamber, particularly less than 1 / 3 and further less than 1 / 4, which was 100 μg / L.

[0056] Explanation of reference numerals in the attached figures

[0057] 1 Ultrapure water production unit

[0058] 2. Pre-treatment device

[0059] 3. Primary Pure Water Production Unit

[0060] 4 Subsystems

[0061] 5. Reverse osmosis membrane unit

[0062] 6. Degassing membrane device

[0063] 7. Ultraviolet Oxidation Device

[0064] 8 Water supply pumps

[0065] 9. Electrodeionization device

[0066] 21 Anode (Electrode)

[0067] 22 Cathode (Electrode)

[0068] 23 Anion exchange membrane

[0069] 24. Cation exchange membrane

[0070] 25 Desalination Chamber

[0071] 26 Concentration Chamber

[0072] 27. Anode Chamber (Electrode Chamber)

[0073] 28. Cathode Chamber (Electrode Chamber)

[0074] W raw water

[0075] W1 Pretreatment Water

[0076] W2 Pure Water

[0077] W3 Ultrapure Water

[0078] W4 treated water

[0079] W5 desalinated water (concentrated water, electrode water)

[0080] W6 Concentrated Water

[0081] W7 Anode Discharge Water

[0082] Water is discharged from the W8 cathode.

Claims

1. A method for operating a pure water production system, comprising a pure water production system having an ultraviolet oxidation device and an electro-deionization device, wherein water is sequentially supplied to these devices from the upstream side, wherein... The hydrogen peroxide concentration in the concentrated water in the concentration chamber and the electrode water in the electrode chamber of the electro-deionization device is lower than the hydrogen peroxide concentration in the treated water passing through the desalination chamber of the electro-deionization device. The treated water obtained by the ultraviolet oxidation device is supplied to the desalination chamber of the electro-deionization device as the treated water. A portion of the permeate from the desalination chamber of the electro-deionization device is used as concentrated water and electrode water to flow into the concentration chamber, anode chamber, and cathode chamber of the electro-deionization device. The water flow direction of the desalination chamber of the electro-deionization device is set to be convection-type with the water flow direction of the concentration chamber.

2. The method of operating the pure water production system as described in claim 1, wherein, The hydrogen peroxide concentration of the concentrated water in the concentration chamber and the electrode water in the electrode chamber of the electro-deionization device is set to be less than 1 / 3 of the hydrogen peroxide concentration of the treated water passing through the desalination chamber of the electro-deionization device.

3. The method of operating the pure water production system as described in claim 1 or 2, wherein, The pure water manufacturing system is a primary pure water unit of an ultrapure water manufacturing system that includes a primary pure water unit and a secondary pure water unit.

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