Electrodeionization system and method for cleaning an electrodeionization device

Abstract

To provide an electric regeneration type ion exchange system capable of shortening a washing operation time by early reducing the metal concentration of deionized water.SOLUTION: The electric regenerative ion-exchange system comprises a concentration chamber 15 and a desalting chamber 16 filled with ion-exchange resins, a pair of electrodes 11, 12, an electric regenerative ion-exchange device 1A for deionizing water to be treated, and an acidic liquid feeder for feeding an acidic liquid to at least the desalting chamber 16.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electrically regenerated ion exchange system and a method for cleaning an electrically regenerated ion exchange device. [Background technology]

[0002] In the electronics industry, where liquid crystal display panels, semiconductors, and other products are manufactured, pure water or ultrapure water is required for cleaning and other processes. Known production systems for producing pure water or ultrapure water generally include a pretreatment system, a primary pure water system, and a subsystem. Subsystems often include a non-regenerative ion exchange resin device to remove trace amounts of ions from the pure water.

[0003] Non-regenerative ion exchange resin devices are installed relatively close to the point of use. Therefore, if ions leak from a non-regenerative ion exchange resin device, there is a concern that production facilities for LCD panels, semiconductors, etc. may be shut down. As a countermeasure, for example, conventional methods involve replacing non-regenerative ion exchange resin devices early. However, early replacement can result in regular running costs.

[0004] Patent Document 1 describes a subsystem in which pure water supplied from a primary water purification system is further purified and supplied to a point of use, in which the treatment device constituting the subsystem consists solely of an electrically regenerated ion exchange device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3429808 Summary of the Invention [Problem to be solved by the invention]

[0006] When restarting an electrically regenerated ion exchange device after a shutdown for periodic inspection or other reasons, it is necessary to perform a so-called cleaning operation, in which impurities that have entered or remain in the system are discharged and pure water is continuously flowed until the pure water produced and supplied reaches the desired quality. However, with conventional electrically regenerated ion exchange devices, the cleaning operation must be carried out over a long period of time in order to sufficiently reduce the concentration of metal impurities, particularly the concentration of sodium, and it may take a longer time to return to normal operation than with non-regenerated ion exchange resin devices.

[0007] The present invention has been made in consideration of the above circumstances, and its objective is to provide an electrically regenerated ion exchange system and a cleaning method for an electrically regenerated ion exchange device that can quickly reduce the metal concentration in deionized water and shorten the cleaning operation time. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs the following configuration. [1] An electric regenerative ion exchange device that deionizes water to be treated, comprising a concentration compartment and a deionization compartment filled with ion exchange resin and a pair of electrodes; and an acidic liquid supply device that supplies an acidic liquid to at least the deionization compartment. [2] The electrically regenerated ion exchange system according to [1], wherein the acidic liquid supply device supplies the acidic liquid to both the concentration compartment and the deionization compartment. [3] The electrically regenerated ion exchange device further comprises: a water inlet channel for allowing the water to be treated to flow into the concentration compartment and the deionization compartment; a deionized water outlet path for discharging deionized water from the deionization compartment; The electrically regenerated ion exchange system according to [1], wherein the acidic liquid supply device supplies the acidic liquid from the deionized water outlet channel toward the deionization compartment. [4] The electrically regenerated ion exchange device further includes: a water inlet channel for allowing the water to be treated to flow into the concentration compartment and the deionization compartment; a deionized water outlet channel for discharging deionized water from the deionization compartment; a concentrated water outlet channel for discharging concentrated water from the concentration chamber; a concentrated water inlet channel for allowing a portion of the concentrated water to flow into the concentration chamber; The acidic liquid supply device supplies the acidic liquid from the deionized water outlet channel to the deionization compartment and from the concentrated water inlet channel to the concentration compartment. [5] The electrically regenerated ion exchange system according to any one of [1] to [4], which is provided in a subsystem of a pure water production system. [6] A cleaning method for an electric regenerative ion exchange device that deionizes water to be treated, comprising: The electrically regenerated ion exchange device includes a concentration compartment and a deionization compartment filled with an ion exchange resin, and a pair of electrodes; A method for cleaning an electrically regenerated ion exchange device, comprising supplying an acidic solution to the deionization compartment. [7] The cleaning method for an electrically regenerated ion exchange device according to [6], wherein the acidic solution is supplied to the concentration compartment and the deionization compartment. [8] The electrically regenerated ion exchange device further comprises: a water inlet channel for allowing the water to be treated to flow into the concentration compartment and the deionization compartment; a deionized water outlet path for discharging deionized water from the deionization compartment; The method for cleaning an electrically regenerated ion exchange device according to [6], wherein the acidic solution is supplied from the deionized water outlet channel toward the deionization compartment. [9] The electrically regenerated ion exchange device further comprises: a water inlet channel for allowing the water to be treated to flow into the concentration compartment and the deionization compartment; a deionized water outlet channel for discharging deionized water from the deionization compartment; a concentrated water outlet channel for discharging concentrated water from the concentration chamber; a concentrated water inlet channel for allowing a portion of the concentrated water to flow into the concentration chamber; The method for cleaning an electrically regenerated ion exchange device according to [7], wherein the acidic solution is supplied from the deionized water outlet channel toward the deionization compartment and from the concentrated water inlet channel toward the concentration compartment.

[10] The cleaning method for an electrical regeneration ion exchange device according to [6] or [8], wherein the acidic solution is supplied to the deionization compartment before starting operation of the electrical regeneration ion exchange device.

[11] The cleaning method for an electrically regenerated ion exchange device according to [7] or [9], wherein the acidic solution is supplied to the concentration compartments and the deionization compartments before starting operation of the electrically regenerated ion exchange device.

[12] The cleaning method for an electrically regenerated ion exchange device according to any one of [6] to [9], wherein the electrically regenerated ion exchange device is provided in a subsystem of a pure water production system. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an electrically regenerated ion exchange system and a cleaning method for an electrically regenerated ion exchange device that can reduce the metal concentration in treated water at an early stage and shorten the cleaning operation time. Furthermore, the electrically regenerated ion exchange system and the method for cleaning an electrically regenerated ion exchange device of the present invention can be suitably used in a subsystem that constitutes a pure water production system. Furthermore, the electrically regenerated ion exchange system and the method for cleaning an electrically regenerated ion exchange device of the present invention can be suitably used not only in subsystems but also in primary pure water systems that constitute pure water production systems and other pure water production systems. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an electrically regenerated ion exchange system according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional schematic diagram of a continuous electrodeionization device provided in an electrical regeneration ion exchange system according to an embodiment of the present invention. [Figure 3] 2 is a graph showing the change over time in sodium concentration of deionized water in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an electrically regenerated ion exchange system and a cleaning method for an electrically regenerated ion exchange device according to an embodiment of the present invention will be described with reference to the drawings.

[0012] Fig. 1 is a block diagram showing the configuration of an electrically regenerated ion exchange system according to this embodiment, and Fig. 2 is a cross-sectional schematic diagram showing an electrically regenerated ion exchange device provided in the electrically regenerated ion exchange system.

[0013] As shown in FIG. 1, the electrically regenerated ion exchange system 1 of this embodiment includes an electrically regenerated ion exchange device 1A and an acidic liquid supply device 20.

[0014] As shown in Figure 2, the electrically regenerated ion exchange device 1A is composed of an anode 11 (electrode), a cathode 12 (electrode), a plurality of anion exchange membranes 13 and cation exchange membranes 14 arranged alternately between the anode 11 and the cathode 12, a plurality of concentration compartments 15 and deionization compartments 16 partitioned by the anion exchange membranes 13 and cation exchange membranes 14, and cation exchange resins 10A and 10B.

[0015] In the electrically regenerated ion exchange device 1A, a plurality of concentrating compartments 15 and deionizing compartments 16 are alternately formed by arranging a plurality of anion exchange membranes 13 and cation exchange membranes 14. The concentrating compartments 15 and deionizing compartments 16 are filled with cation exchange resins 10A and anion exchange resins 10B, respectively. The forms of the cation exchange resins 10A and anion exchange resins 10B in the concentrating compartments 15 and deionizing compartments 16 are not particularly limited; for example, they may be mixed together, or the cation exchange resins 10A and anion exchange resins 10B may be in a layered state.

[0016] An anode chamber 17 (electrode chamber) is provided between the anode 11 and the cation exchange membrane 14 arranged closest to the anode 11. Similarly, a cathode chamber 18 (electrode chamber) is provided between the cathode 12 and the anion exchange membrane 13 arranged closest to the cathode 12.

[0017] As shown in Figures 1 and 2, the electrical regeneration ion exchange device 1A is also provided with a water inlet channel 31 for allowing water to be treated W1 to flow into the concentration chamber 15 and the deionization chamber 16, a deionized water outlet channel 41 for allowing deionized water W2 to flow out from the deionization chamber 16, and a concentrated water outlet channel 42 for allowing concentrated water W3 to flow out from the concentration chamber 15.

[0018] The electrically regenerated ion exchange device 1A is also provided with a concentrated water inlet channel 32.

[0019] Furthermore, the electrically regenerated ion exchange device 1A is provided with an electrode water inlet channel 33 for allowing electrode water W4 to flow into the anode chamber 17 and the cathode chamber 18 (electrode chamber), and an electrode water outlet channel 43 for allowing electrode water W4 to flow out of the anode chamber 17 and the cathode chamber 18 (electrode chamber).

[0020] These flow paths are indicated by arrows in Figures 1 and 2. The direction of the arrows indicates the flow direction of water flowing through each flow path during normal operation and during cleaning operation.

[0021] 1 includes an acidic solution tank 20A that stores an acidic solution, a first supply path 20B that connects the acidic solution tank 20A with the deionized water outlet path 41, a second supply path 20C that connects the acidic solution tank 20A with the concentrated water inlet path 32, and on-off valves (not shown) that are provided on each of the first supply path 20B and the second supply path 20C. The acidic solution supply device 20 may also include a control unit for controlling the opening and closing of the on-off valves. The acidic solution supply device 20 supplies the acidic solution to the deionized solution compartment 16, or to both the concentrating compartment 15 and the deionized solution compartment 16.

[0022] The acidic liquid is not particularly limited as long as it can regenerate the cation exchange resin, and may be, for example, an aqueous solution of hydrochloric acid with a concentration of about 1 to 10%, or an aqueous solution of sulfuric acid or nitric acid with a similar concentration.

[0023] Next, a method for cleaning the electrically regenerated ion exchange device of this embodiment will be described.

[0024] First, before describing the cleaning method, the deionization treatment of treated water using the electrical regeneration type ion exchange device 1A will be described.

[0025] The water to be treated W1 is supplied to the concentration compartment 15 and the deionization compartment 16 of the electrical regeneration ion exchange device 1A through the water to be treated inlet channel 31. The water to be treated W1 can be, for example, pure water produced in a primary pure water system.

[0026] A DC voltage is applied to the anode 11 and the cathode 12 of the electrically regenerated ion exchange device 1A.

[0027] The water to be treated W1 that flows into deionization chamber 16 comes into contact with ion exchange resins 10A and 10B filled in deionization chamber 16. At this time, trace amounts of Na ions (sodium ions) in the water to be treated W1 are adsorbed by cation exchange resin 10A and removed from the water to be treated W1, and trace amounts of Cl ions (chlorine ions) in the water to be treated W1 are adsorbed by anion exchange resin 10B and removed from the water to be treated W1. In this way, the water to be treated W1 is deionized to become deionized water W2, which flows out from deionized water outlet channel 41.

[0028] The Na ions and Cl ions adsorbed on the ion exchange resins 10A and 10B pass through the anion exchange membrane 13 and the cation exchange membrane 14 due to the potential difference of the DC voltage applied to the anode 11 and the cathode 12, and move to the concentration chamber 15, where they become concentrated water W3 and are discharged from the concentrated water outlet channel 42.

[0029] Furthermore, electrode water W4 flows into the anode chamber 17 and the cathode chamber 18 from an electrode water inlet channel 33. To ensure electrical conductivity, concentrated water W3, which is the outflow water from the concentration chamber 15 and has a high ion concentration, is used as the electrode water W4. Furthermore, a portion of the concentrated water W3 flowing out from the concentration chamber 15 is returned to the inlet side of the concentration chamber 15 from a concentrated water inlet channel 32 to improve the water recovery rate.

[0030] An electrically regenerative ion exchange device 1A that has been continuously operated for a certain period of time may be shut down for periodic inspections, etc. When restarting after a shutdown, a cleaning operation is required in which pure water (water to be treated W1) is continuously flowed until the deionized water W2 reaches the desired water quality. Conventionally, cleaning operations of such electrically regenerative ion exchange devices 1A have had to be performed continuously for a long period of time, especially until the sodium concentration reaches a predetermined level or less. One of the reasons why it takes a long time to reduce the sodium concentration is thought to be that Na ions adsorbed to the cation exchange resin 10A during normal operation are gradually released during the cleaning operation. In addition to sodium, impurities remaining in the system of the electrically regenerative ion exchange device 1A may be mixed into the pure water and released out of the system due to changes in the water flow when switching from a shutdown state to an operating state.

[0031] Therefore, in this embodiment, before starting normal operation of the electrical regeneration ion exchange device 1A, an acidic solution is supplied to at least the deionization compartments 16 to perform cleaning. Specifically, when the electrical regeneration ion exchange device 1A is in a dormant state, an acidic solution is supplied from the acidic solution supply device 20 to the deionization compartments 16. The acidic solution is sent from the acidic solution tank 20A to the deionized water outlet channel 41 via the first supply channel 20B, and then sent from the deionized water outlet channel 41 to the deionized compartments 16. This causes the acidic solution to flow in the opposite direction to the supply direction of the water to be treated W1 to the deionization compartments 16 during normal operation. The acidic solution is supplied from the acidic solution supply device 20 to the deionization compartments 16 by operating an on-off valve installed in the first supply channel 20B. The on-off valve may be operated manually by an operator or automatically by a control unit.

[0032] Furthermore, in this embodiment, the acidic liquid may be supplied not only to the deionization compartment 16, but also to both the concentration compartment 15 and the deionization compartment 16. When the acidic liquid is supplied to the concentration compartment 15, the acidic liquid is sent from the acidic liquid tank 20A via the second supply path 20C to the concentrated water inlet path 32, and then sent from the concentrated water inlet path 32 to the concentration compartment 15. This allows the acidic liquid to flow in the same direction as the supply of concentrated water W3 to the concentration compartment 15 during normal operation. The acidic liquid is supplied from the acidic liquid supply device 20 to the concentration compartment 15 by operating an on-off valve installed in the second supply path 20C. The on-off valve may be operated manually by an operator or automatically by a control unit.

[0033] When the acidic liquid is supplied to the deionization compartment 16, the Na ions adsorbed on the cation exchange resin 10A in the deionization compartment 16 are replaced with hydrogen ions, and the liberated Na ions are discharged from the deionization compartment 16 together with the acidic liquid. The acidic liquid also washes away other impurities remaining inside the deionization compartment 16.

[0034] Furthermore, when the acidic liquid is supplied to the concentration compartment 15, the Na ions adsorbed on the cation exchange resin 10A in the concentration compartment 15 are replaced with hydrogen ions, and the liberated Na ions are discharged from the concentration compartment 15 together with the acidic liquid. The acidic liquid also washes away other impurities remaining inside the concentration compartment 15.

[0035] In particular, by circulating the acidic liquid from the outlet side of the deionization chamber 16, the amount of residual Na ions in the cation exchange resins 10A in the deionization chamber 16 decreases as the resin approaches the outlet side of the deionization chamber 16 (the amount of residual Na ions is almost zero at the outlet side). As a result, even if the water to be treated flows from the inlet side of the deionization chamber 16 to the outlet side during normal operation, the amount of residual Na ions in the cation exchange resins 10A at the outlet side of the deionization chamber 16 is extremely small, reducing the risk of Na ions being mixed into the deionized water W2.

[0036] The time for washing with an acidic solution is not particularly limited, but may be, for example, 5 to 30 hours, 10 to 25 hours, or 12 to 20 hours.

[0037] In this manner, the electrical regeneration type ion exchange device 1A is washed with the acidic solution.

[0038] Once the cleaning is complete, the cleaning operation is performed. The cleaning operation is performed by supplying the water to be treated W1 to the electrical regeneration ion exchange device 1A, just like normal operation. The cleaning operation flushes out impurities remaining in the system. The cleaning operation continues until the impurity concentration in the deionized water W2 falls below the desired concentration.

[0039] As described above, according to this embodiment, by supplying an acidic liquid to at least the desalination chamber 16 of the electrically regenerated ion exchange device 1A before starting normal operation to perform cleaning, the time required for the subsequent cleaning operation can be significantly reduced compared to conventional methods.

[0040] The electrical regeneration ion exchange system 1 and the cleaning method for the electrical regeneration ion exchange device 1A of this embodiment can be suitably used in a subsystem that constitutes a pure water production system.

[0041] Furthermore, the cleaning method for the electrically regenerated ion exchange system 1 and electrically regenerated ion exchange device 1A of this embodiment can be suitably used not only in subsystems, but also in primary pure water systems that constitute pure water production systems and other pure water production systems. [Example]

[0042] Example 1 The electrically regenerated ion exchange device used was shown in Figures 1 and 2. The dimensions of the concentration compartment and deionization compartment were 90 mm wide x 5 mm deep x 485 mm high (inside the cell: 48.5 mm wide x 5 mm deep x 395 mm high), and the concentration compartment and deionization compartment were filled with a mixture of ion exchange resins, consisting of cation exchange resin and anion exchange resin, to form the electrically regenerated ion exchange device. There were three concentration compartments and two deionization compartments.

[0043] Ultrapure water was continuously supplied to the electrical regeneration ion exchange device as the water to be treated under condition 1 in Table 1 (the water flow time was counted), and deionization was carried out to continuously produce deionized water. It was confirmed that the resistivity of the deionized water reached 18.24 MΩ cm.

[0044] Thereafter, while continuing to count the water flow time, pickling solution was supplied to both the deionizing compartment and the concentrating compartment to clean them, as shown in condition 2 in Table 2. The pickling solution supplied to the deionizing compartment was supplied from the outlet side of the deionizing compartment. The pickling solution supplied to the concentrating compartment was supplied from the inlet side of the concentrated water.

[0045] After cleaning the deionization and concentration compartments, the water flow time was continued while the deionization process was again carried out by continuously supplying ultrapure water as the treated water under condition 1 in Table 1. After the resistivity of the deionized water reached 18.24 MΩ·cm, the sodium concentration of the deionized water was measured over time.

[0046] [Table 1]

[0047] [Table 2]

[0048] (Comparative Example 1) An electrically regenerated ion exchange device was constructed in the same manner as in Example 1. As in Example 1, the number of concentration compartments was three and the number of deionization compartments was two.

[0049] Ultrapure water was continuously supplied to the electrical regeneration ion exchange device as the water to be treated under condition 1 in Table 1 (the water flow time was counted), and deionization was carried out to continuously produce deionized water. It was confirmed that the resistivity of the deionized water reached 18.24 MΩ cm.

[0050] Thereafter, without performing cleaning with the pickling solution, the water flow time was continued to be counted, and the supply of ultrapure water was continued under Condition 1 in Table 1 to produce deionized water, while the sodium concentration in the deionized water was measured over time.

[0051] FIG. 3 shows the change over time in the sodium concentration of the deionized water produced by Example 1 and Comparative Example 1. The horizontal axis of FIG. 3 represents the number of days elapsed since the start of counting the water flow time. The vertical axis of FIG. 3 represents the sodium concentration of the deionized water. As shown in FIG. 3, in Comparative Example 1 (without washing), in which no washing operation was performed, it took 75 days for the sodium concentration of the deionized water to reach 0.01 μg / L. On the other hand, in Example 1 (with washing), in which washing was performed under Condition 2, the sodium concentration reached 0.01 μg / L or less on the 17th day after the start of water flow.

[0052] From the above results, it was confirmed that when using an electrically regenerated ion exchange device in a subsystem, cleaning the demineralization and concentration compartments with an acidic solution before starting use can reduce the metal concentration of the treated water more quickly than if cleaning was not done. [Explanation of symbols]

[0053] 1...electrically regenerated ion exchange system, 1A...electrically regenerated ion exchange device, 10A...cation exchange resin, 10B...anion exchange resin, 11...anode (electrode), 12...cathode (electrode), 13...anion exchange membrane, 14...cation exchange membrane, 15...concentration compartment, 16...demineralization compartment, 17...anode chamber (electrode chamber), 18...cathode chamber (electrode chamber), 20...acidic liquid supply device, 20A...acidic liquid tank, 20B...first supply channel, 20C...second supply channel, 31...treated water inlet channel, 32...concentrated water inlet channel, 33...electrode water inlet channel, 41...deionized water outlet channel, 42...concentrated water outlet channel, 43...electrode water outlet channel.

Claims

1. an electric regeneration ion exchange device that includes a concentration compartment and a deionization compartment filled with ion exchange resin and a pair of electrodes, and that deionizes the water to be treated; and an acidic liquid supply device that supplies an acidic liquid to at least the deionization compartment.

2. 2. The electrically regenerated ion exchange system according to claim 1, wherein the acidic liquid supply device supplies the acidic liquid to both the concentration compartment and the deionization compartment.

3. The electrically regenerated ion exchange device further comprises: a water inlet channel for allowing the water to be treated to flow into the concentration compartment and the deionization compartment; a deionized water outlet path for discharging deionized water from the deionization compartment; 2. The electrically regenerated ion exchange system according to claim 1, wherein the acidic solution supplying device supplies the acidic solution from the deionized water outlet channel toward the deionization compartment.

4. The electrically regenerated ion exchange device further comprises: a water inlet channel for allowing the water to be treated to flow into the concentration compartment and the deionization compartment; a deionized water outlet channel for discharging deionized water from the deionization compartment; a concentrated water outlet channel for discharging concentrated water from the concentration chamber; a concentrated water inlet channel for allowing a portion of the concentrated water to flow into the concentration chamber; 3. The electrically regenerated ion exchange system according to claim 2, wherein the acidic liquid supply device supplies the acidic liquid from the deionized water outlet channel toward the deionization compartment and from the concentrated water inlet channel toward the concentration compartment.

5. 5. The electrically regenerated ion exchange system according to claim 1, which is provided in a subsystem of a pure water production system.

6. A cleaning method for an electric regenerative ion exchange device that deionizes water to be treated, comprising: The electrically regenerated ion exchange device includes a concentration compartment and a deionization compartment filled with an ion exchange resin, and a pair of electrodes; A method for cleaning an electrically regenerated ion exchange device, comprising supplying an acidic solution to the deionization compartment.

7. The method for cleaning an electrically regenerated ion exchange device according to claim 6, wherein the acidic solution is supplied to the concentration compartment and the deionization compartment.

8. The electrically regenerated ion exchange device further comprises: a water inlet channel for allowing the water to be treated to flow into the concentration compartment and the deionization compartment; a deionized water outlet path for discharging deionized water from the deionization compartment; 7. The method for cleaning an electrically regenerated ion exchange device according to claim 6, wherein the acidic solution is supplied from the deionized water outlet toward the deionization compartment.

9. The electrically regenerated ion exchange device further comprises: a water inlet channel for allowing the water to be treated to flow into the concentration compartment and the deionization compartment; a deionized water outlet channel for discharging deionized water from the deionization compartment; a concentrated water outlet channel for discharging concentrated water from the concentration chamber; a concentrated water inlet channel for allowing a portion of the concentrated water to flow into the concentration chamber; 8. The method for cleaning an electrically regenerated ion exchange device according to claim 7, wherein the acidic solution is supplied from the deionized water outlet channel toward the deionization compartment and from the concentrated water inlet channel toward the concentration compartment.

10. 9. The method for cleaning an electrical regeneration ion exchange device according to claim 6, wherein the acidic solution is supplied to the deionization compartment before starting operation of the electrical regeneration ion exchange device.

11. 10. The method for cleaning an electrically regenerated ion exchange device according to claim 7 or 9, wherein the acidic solution is supplied to the concentrating compartments and the deionization compartments before starting operation of the electrically regenerated ion exchange device.

12. 10. The cleaning method for an electrically regenerated ion exchange device according to claim 6, wherein the electrically regenerated ion exchange device is provided in a subsystem of a pure water production system.

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