Ion exchange system and ultrapure water production device

Abstract

An ion exchange system is provided with: an ion exchange device; the pump is used for introducing treated water into the ion exchange device; a desorption water tank into which the deionized water from the ion exchange device is introduced; a flow rate adjustment valve for adjusting the amount of water flowing from the ion exchange device to the separation sub-water tank; the water level detection mechanism is used for detecting the water level in the separated sub water tank; a flow rate or pressure detection means for detecting the flow rate or pressure of the flow from the ion exchange device toward the separator water tank; the control mechanism controls the opening degree of the flow adjusting valve in the mode that the water level, detected by the water level detection mechanism, in the separated water sub-tank is within a specified range. The pump is controlled such that the flow rate or pressure detected by the flow rate or pressure detection means after the opening degree of the flow rate adjustment valve has been changed is within a prescribed range.

Description

Technical Field

[0001] This invention relates to an ion exchange system, and more particularly to an ion exchange system suitable for integration into a primary pure water system of an ultrapure water production apparatus. Additionally, this invention relates to an ultrapure water production apparatus including the aforementioned ion exchange system. Background Technology

[0002] Previously, ultrapure water used for semiconductor cleaning was produced by treating raw water (industrial water, tap water, well water, etc.) using an ultrapure water manufacturing device consisting of a pretreatment system, a primary pure water system, and subsystems (see, for example, Patent Document 1).

[0003] Figure 5 This diagram illustrates an example of an ultrapure water production apparatus. Suspended or colloidal substances in the raw water are removed in a pretreatment system 1, which consists of a coagulation unit, a pressurized flotation (sedimentation) unit, and a filtration unit. The water treated by the pretreatment system 1 is then passed through a pretreatment water tank 2 to a primary pure water system, which includes a heat exchanger 3, a reverse osmosis membrane separation unit (RO unit) 4, a low-pressure ultraviolet oxidation unit (UV unit) 5, an ion exchange unit 6, and a degassing unit 7. Ions and organic components in the pretreated water are removed, resulting in primary pure water. This primary pure water is then transported to a secondary tank 10 via piping 8. Furthermore, the remaining primary pure water is returned to the pretreatment water tank 2 via a return piping 9 branching off from piping 8.

[0004] The water in the auxiliary tank 10 is treated by a subsystem 11, which includes a heat exchanger, a low-pressure ultraviolet (UV) oxidation unit, a platinum group metal catalyst resin tower, a membrane degassing unit, an RO unit, a non-regenerative mixed-bed ion exchange unit, and an ultrafiltration (UF) membrane separation unit, to become ultrapure water. The ultrapure water is transported to the usage location 13 via piping 12, and unused ultrapure water is returned to the auxiliary tank 10 via return piping 14.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent document 1: Japanese Patent Application Publication No. 2018-94531. Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In conventional ultrapure water production systems, even if the ultrapure water usage at point 13 changes, the flow rate to the ion exchange unit 6 remains constant. Therefore, when ultrapure water usage at point 13 is low, excess primary pure water is produced. As a result, the pump's unit power consumption increases, or the ion exchange unit 6 is subjected to excessive load, leading to an increase in the regeneration frequency or exchange frequency of the ion exchange resin.

[0010] The objective of this invention is to solve the aforementioned problem and provide an ion exchange system capable of varying the amount of water treated by the ion exchange, as well as an ultrapure water manufacturing apparatus including the ion exchange system.

[0011] Methods for solving problems

[0012] The ion exchange system of the present invention comprises: an ion exchange device; a pump for introducing water to be treated into the ion exchange device; a deionized water tank into which deionized water from the ion exchange device is introduced; a flow regulating valve for adjusting the inflow rate of water from the ion exchange device to the deionized water tank; a water level detection mechanism for detecting the water level in the deionized water tank; a flow rate or pressure detection mechanism for detecting the flow rate or pressure of water flowing from the ion exchange device toward the deionized water tank; and a control mechanism for controlling the opening of the flow regulating valve such that the water level in the deionized water tank detected by the water level detection mechanism is within a predetermined range, and for controlling the pump such that the flow rate or pressure detected by the flow rate or pressure detection mechanism after the opening of the flow regulating valve is changed is within a predetermined range.

[0013] In one aspect of the present invention, the control frequency of the pump controlled by the control mechanism is less than 7 times / minute (min), and the variation range of the water volume of the pump accompanying the control of the pump is within ±20%.

[0014] In one aspect of the present invention, the ion exchange device is an ion exchange device having a cation exchange tower and an anion exchange tower, a regenerative ion exchange device mixed with cation exchange resin and anion exchange resin, or a non-regenerative ion exchange device having cation exchange resin and anion exchange resin.

[0015] The ultrapure water manufacturing apparatus of the present invention is an apparatus that includes the ion exchange system of the present invention in a primary pure water system. Preferably, the flow rate of water from the primary pure water system to the auxiliary tank is controlled based on the amount of ultrapure water returned from the location of use to the auxiliary tank.

[0016] The effects of the invention

[0017] According to the ion exchange system of the present invention, the flow rate to the ion exchange device can be controlled according to the required amount of water for ion exchange treatment. Therefore, the unit power consumption of the pump during operation of the ion exchange system is reduced, and the regeneration frequency or exchange frequency of the ion exchange resin can be decreased.

[0018] The ultrapure water manufacturing apparatus of the present invention includes the ion exchange system of the present invention, thereby reducing the manufacturing cost of ultrapure water. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the ion exchange system according to the implementation method.

[0020] Figure 2 This is a structural diagram of the ion exchange system according to the implementation method.

[0021] Figure 3 This is a structural diagram of an ion exchange device.

[0022] Figure 4 This is a structural diagram of an ion exchange device.

[0023] Figure 5 This is a structural diagram of a previous ultrapure water manufacturing device. Detailed Implementation

[0024] The embodiments will now be described with reference to the accompanying drawings.

[0025] Figure 1 This diagram illustrates an example of the ion exchange system of the present invention. The water to be deionized is supplied to the ion exchange unit 20 via piping 17, the first pump 18, and piping 19, where it comes into contact with the ion exchange resin to undergo deionization treatment, thus becoming deionized water. The deionized water is introduced into the deionized water tank 26 via piping 21, the second pump 22, piping 23, the flow regulating valve 24, and piping 25, and then transported to the next process via piping 27. A flow meter or pressure gauge 28 is installed on piping 23, and a level gauge 29 is installed on the deionized water tank 26; all detection signals are input to the controller 30.

[0026] The controller 30 adjusts the opening of the flow regulating valve 24 by means of proportional-integral-derivative (PID) control, etc., so that the water level detected by the water level gauge 29 is within a specified range.

[0027] In addition, the controller 30 performs inverter control on the water delivery volume (motor speed) of the first pump 18 or the second pump 22 in such a way that the flow rate or pressure detected by the flow meter or pressure gauge 28 after the opening of the flow regulating valve 24 is adjusted is within a specified range.

[0028] Furthermore, the control frequency of the first pump 18 or the second pump 22 controlled by the controller 30 is preferably less than 7 times / minute, and the variation range of the water volume of the pump controlled by the pump is preferably within ±20%.

[0029] The reasons for preferably setting the flow rate adjustment frequency to 7 times / minute or less are as follows.

[0030] Generally speaking, if the metal used in the pump is in the range of N=2×10 7 When friction occurs, wear and fatigue failure will occur. Assuming the pump is used for 5 years, this would result in 2 × 10⁻⁶ cycles. 7 The time interval is calculated as follows: times / 5 years / 365 days / 24 hours / 60 minutes = 7.62 times / minute. Therefore, the preferred flow adjustment frequency is 7 times / minute or less.

[0031] The control measures the amount of water to be treated so that the water level in the deionized water tank 26 remains within a specified range. Specifically, the flow rate to the ion exchange unit 20 is controlled based on the amount of water transported from the deionized water tank 26 to the next process via piping 27. This reduces the power consumption per pump unit during operation of the ion exchange system and decreases the regeneration frequency or exchange frequency of the ion exchange resin.

[0032] Figure 2 This is a diagram illustrating another example of the ion exchange system of the present invention.

[0033] In the ion exchange system, a flow meter or pressure gauge 28 is installed in the piping 25, and a pressure gauge 31 is installed in the piping 23. Various detection signals and the detection signal of the water level gauge 29 of the ion exchange tank 26 are input to the controller 30.

[0034] Figure 2 Other structures and Figure 1 Same; the same symbol indicates the same part.

[0035] In the Figure 2 In this process, the opening of the flow regulating valve 24 is controlled by the water level detected by the water level gauge 29 and the flow rate or pressure detected by the flow meter or pressure gauge 28, or both of which are within a specified range. Additionally, the rotational speed of one or both of the first pump 18 and the second pump 22 is controlled by an inverter so that the pressure detected by the pressure gauge 31 after the opening of the flow regulating valve 24 is adjusted is within a specified range.

[0036] Through the above Figure 2The ion exchange system also controls the flow rate to the ion exchange unit 20 based on the amount of water transported from the deionized water tank 26 to the next process via piping 27. As a result, the unit power consumption of the pump during operation of the ion exchange system is reduced, and the regeneration frequency or exchange frequency of the ion exchange resin is decreased.

[0037] Figure 1 or Figure 2 The ion exchange system is suitable for integration into the primary pure water system of an ultrapure water production unit. Figure 1 or Figure 2 Ion exchange system as Figure 5 In the case of ion exchange unit 6 of a primary pure water system assembly, the water supply piping from ultraviolet oxidation unit 5 to ion exchange unit 6 is equivalent to... Figure 1 or Figure 2 Piping 17, the water supply piping from ion exchange unit 6 to degassing unit 7, is equivalent to... Figure 1 or Figure 2 Piping 27.

[0038] Thus, Figure 1 or Figure 2 The ion exchange system, integrated into the ultrapure water production unit within the primary pure water system, controls the flow rate from piping 27 based on the ultrapure water usage at location 13. Specifically, the primary pure water production rate in the primary pure water system is controlled by a predetermined sum of the primary pure water flow rate from piping 8 to auxiliary tank 10 and the return ultrapure water flow rate from return piping 14 to auxiliary tank 10. Therefore, by controlling the flow rate to the ion exchange unit 20 based on the ultrapure water usage at location 13, excess water is prevented from being unnecessarily fed into the ion exchange unit 20, thereby reducing pump power costs and lowering the regeneration and exchange frequencies of the ion exchange resin.

[0039] In this invention, the structure of the ion exchange device 20 is not particularly limited. An example of a structure that can be used as the ion exchange device 20 is shown below. Figure 3 , Figure 4 middle.

[0040] exist Figure 3 In the ion exchange unit, the water to be treated from pipe 19 is introduced into cation exchange tower 40, flows downwards for cation exchange treatment, and then is transported through pipe 44 to decarbonation tower 50 for decarbonation treatment. The decarbonated water is introduced into anion exchange tower 60 through pump 53 and pipe 54, flows downwards for anion exchange treatment to become deionized water, and then flows out through pipe 21.

[0041] Furthermore, packed beds 41 and 42 containing strongly acidic cation exchange resin are provided in the cation exchange tower 40. Baffles (notation omitted) with water passage sections are horizontally arranged on the lower sides of the upper and lower sides of the packed beds 41 and 42, respectively. The water passage sections of the baffles are configured to allow water to pass through but not the cation exchange resin particles. A connecting pipe 43 is provided to allow cation exchange resin particles from the lower packed bed 42 to move to the upper side of the baffles when the cation exchange resin is backwashed with a large flow of upward-flowing water.

[0042] The regeneration of the cation exchange resin is carried out by flowing hydrochloric acid upwards.

[0043] The decarbonation tower 50 has a packing material layer 51. The pressure inside the decarbonation tower 50 is reduced by a vacuum pump (not shown). During the flow through the packing material layer 51, dissolved carbon dioxide in the water is degassed. Water falling into the groove 52 is pumped by a pump 53.

[0044] The anion exchange tower 60 has a packed bed 61 and a packed bed 63 with strong basic anion exchange resin, and a packed bed 62 with weak basic anion exchange resin between the two. A baffle plate (symbol omitted) with a water passage section is horizontally arranged on the underside of each of the packed beds 61 to 63.

[0045] A connecting pipe 64 is provided, which allows anion exchange resin particles in the lower packed bed 63 to move to the packed bed 61 when the anion exchange resin is backwashed with a large flow of backwash water.

[0046] Regeneration of the anion exchange resin is carried out by flowing an aqueous sodium hydroxide solution upwards.

[0047] Figure 4 The ion exchange unit also includes a cation exchange tower 40, a decarbonation tower 50, and an anion exchange tower 60. Figure 4 In this context, the anion exchange tower 60 only includes packed beds 61 and 63 of strongly basic anion exchange resin.

[0048] exist Figure 4 In the process, the treated water flows upward to the cation exchange tower 40. Additionally, the decarbonated water from the decarbonation tower 50 flows upward to the anion exchange tower 60.

[0049] During regeneration, hydrochloric acid flows downward to cation exchange tower 40, and sodium hydroxide aqueous solution flows downward to anion exchange tower 60.

[0050] Although the illustration is omitted, a mixed-bed ion exchange tower (mixed-bed polisher) filled with a mixture of strong acid cation exchange resin and strong base anion exchange resin can also be used as an ion exchange device.

[0051] Alternatively, non-regenerative ion exchange devices can also be used. In a non-regenerative ion exchange device, cation exchange resins and anion exchange resins can be packed as separate beds or as a mixed bed.

[0052] Although the present invention has been described in detail using specific methods, it will be apparent to those skilled in the art that various modifications can be made without departing from the intent and scope of the invention.

[0053] This application is based on Japanese Patent Application No. 2023-083228, filed on May 19, 2023, the entire contents of which are incorporated herein by reference.

[0054] Explanation of reference numerals in the attached figures

[0055] 1: Preprocessing system.

[0056] 6, 20: Ion exchange device.

[0057] 10: Secondary tank.

[0058] 11: Subsystem.

[0059] 13: Location of use.

[0060] 24: Flow regulating valve.

[0061] 26: Deionizer tank.

[0062] 28: Flow meter or pressure gauge.

[0063] 29: Water level gauge.

[0064] 30: Controller.

[0065] 31: Pressure gauge.

[0066] 40: Cation exchange tower.

[0067] 50: Decarbonation tower.

[0068] 60: Anion exchange tower.

Claims

1. An ion exchange system, wherein the ion exchange system has: an ion exchange device; a pump for passing treated water into the ion exchange device; a deionized water tank into which deionized water from the ion exchange device is introduced; a flow rate adjustment valve for adjusting the amount of inflow water from the ion exchange device to the deionized water tank; a water level detection mechanism for detecting the water level in the deionized water tank; a flow rate or pressure detection mechanism for detecting the flow rate or pressure of the flow from the ion exchange device toward the deionized water tank; and a control mechanism for controlling the opening degree of the flow rate adjustment valve in such a manner that the water level in the deionized water tank detected by the water level detection mechanism is within a prescribed range, and for controlling the pump in such a manner that the detected flow rate or pressure of the flow rate or pressure detection mechanism after the opening degree of the flow rate adjustment valve is changed is within a prescribed range.

2. The ion exchange system according to claim 1, wherein the control frequency of the pump controlled by the control mechanism is 7 times / minute or less, and the variation range of the water amount of the pump accompanying the control of the pump is within ±20%.

3. The ion exchange system according to claim 1, wherein the ion exchange device is an ion exchange device having a cation exchange tower and an anion exchange tower, a regenerative ion exchange device in which a cation exchange resin and an anion exchange resin are mixedly packed, or a non-regenerative ion exchange device having a cation exchange resin and an anion exchange resin.

4. An ultrapure water manufacturing device including a primary pure water system having an ion exchange system, a sub tank into which primary pure water from the primary pure water system and returned ultrapure water from a use site are introduced, and a subsystem to which water from the sub tank is supplied, characterized in that the ion exchange system is the ion exchange system according to any one of claims 1 to 3.

5. The ultrapure water manufacturing device according to claim 4, wherein the amount of water sent from the primary pure water system to the sub tank is controlled in accordance with the amount of returned ultrapure water from the use site to the sub tank. ​

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