Pure water production device and method

Abstract

To provide a pure water production apparatus and a pure water production method capable of grasping an internal state of an ion exchange resin and stably supplying high-quality pure water or ultrapure water.SOLUTION: A pure water production apparatus includes a resin conductivity meter 3 that is arranged so as to be in contact with an ion exchange resin contained in a mixed bed tower 17 for producing pure water or ultrapure water or polisher devices 24 and 25, and measures a conductivity of the ion exchange resin.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pure water production apparatus and a pure water production method, and more particularly to a pure water production apparatus and a pure water production method suitable for producing ultrapure water. [Background technology]

[0002] Ion exchange type pure water production systems are known for producing pure water or ultrapure water for use in the manufacture of pharmaceuticals, semiconductor manufacturing, power generation boiler water, food, etc. Ion exchange type pure water production systems are devices that produce pure water by contacting raw water with ion exchange resins or the like and removing anion and cation components contained in the raw water through an ion exchange reaction. Ion exchange resins can be reused by periodically regenerating them with acid and alkali.

[0003] In recent years, with the increasing integration of semiconductors, the purity of the pure water required for pure water production equipment has increased, and there is also a demand to reduce the amount of chemicals used for regeneration and to minimize running costs. However, if the frequency of regeneration and the amount of chemicals used for regeneration are not properly adjusted, the ion exchange resin will not regenerate properly, increasing the risk of a decrease in the quality of the pure water.

[0004] The most conventional method for determining the regeneration frequency is to consider the ion concentration of the raw water to be constant and to regenerate the ion exchange resin when the amount of raw water passing through exceeds a certain amount.

[0005] However, if the ion concentration of the raw water increases due to seasonal fluctuations, the regeneration frequency will be insufficient, and the quality of the treated water will deteriorate. If the amount of chemicals or the regeneration frequency is increased in anticipation of seasonal fluctuations, the chemicals will be wasted, resulting in increased running costs.

[0006] Since ion exchange resins deteriorate over time due to contamination by organic matter and other substances contained in the raw water, the ion exchange capacity of the water purifier decreases even without seasonal fluctuations, and the quality of the treated water deteriorates. If the amount of chemicals and the frequency of regeneration are set taking into account the deterioration of the ion exchange capacity of the water purifier, there is also the problem of further increases in running costs.

[0007] One of the means for solving these problems is a method described in, for example, JP-A-3-181384 (Patent Document 1), in which the conductivity of the raw water is measured, the ion load is calculated, and the regeneration frequency is determined by taking into account the ion load of the raw water.

[0008] Further examples of conventional techniques include a method of measuring the pH of the regenerated wastewater from an ion exchange resin tower and monitoring the amount of regenerant passed through based on the measured value, thereby reducing the amount of chemicals used for regeneration (JP Patent Publication No. 9-117679 (Patent Document 2)), and a method of measuring silica in the treated water using an analyzer.

[0009] Furthermore, JP 2014-188456 A (Patent Document 3) describes a method for operating an ion exchange resin device in which water to be treated is passed through an anion exchange resin layer to perform anion exchange treatment, the resistivity or electrical conductivity of the resulting treated water is measured, and the anion exchange resin is regenerated or replaced based on the measurement results. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 3-181384 [Patent Document 2] Japanese Patent Application Publication No. 9-117679 [Patent Document 3] JP 2014-188456 A [Patent Document 4] Patent No. 6315721 Summary of the Invention [Problem to be solved by the invention]

[0011] However, in all of the inventions described in Patent Documents 1 to 3, a measuring instrument is placed outside a tower filled with ion exchange resin to indirectly predict the internal state of the ion exchange tower, and the internal state of the ion exchange tower is not directly measured. Therefore, it may not be possible to appropriately grasp the internal state of the ion exchange resin tower.

[0012] The quality of ultrapure water required in general semiconductor manufacturing processes is said to have a resistivity of 18 MΩ·cm or higher. However, with the increasing integration and density of semiconductor elements in recent years, the required quality level of ultrapure water has also increased, and the impurity ion concentration in ultrapure water is moving from the ppb to the ppt level. When producing ultrapure water, in addition to the elution of impurity ions from ion exchange resins, the effects of elution of material components in the ultrapure water production equipment that comes into contact with the ultrapure water can no longer be ignored, and it can sometimes be difficult to constantly and stably supply the required high-quality ultrapure water.

[0013] For example, in a pure water production system for producing ultrapure water, when the amount of raw water passing through the system exceeds a certain amount, a measure is generally taken to periodically replace the entire polisher device. Usually, a mixture of cation exchange resin and anion exchange resin is charged into the polisher device. It is preferable that the anion exchange resin and the cation exchange resin are charged in a uniform mixed state at a predetermined ratio, but depending on the state at the time of charging or the state after regeneration, the respective resins may be unevenly distributed, making it difficult to detect the state inside the tower. In addition, for example, components such as boron and silica are weak electrolytes and have low adsorption power to ion exchange resins, and may be eluted into ultrapure water. Therefore, at present, the ion exchange capacity of the ion exchange resin in the polisher device is not fully used, and even though there is still exchange capacity, the polisher device is replaced for safety, and the ion exchange resin after replacement is regenerated.

[0014] In view of the above problems, the present invention provides a pure water producing apparatus and a pure water producing method capable of grasping the internal state of an ion exchange resin and stably supplying high-quality pure water or ultrapure water. [Means for solving the problem]

[0015] As a result of intensive research by the inventors to solve the above problems, it was found that it is effective to measure the conductivity of the ion exchange resin placed in a mixed bed tower or polisher apparatus, for example, to determine the state in which the anion exchange resin and the cation exchange resin are mixed inside the mixed bed tower or polisher apparatus, or to detect the exchange state of weak electrolytes such as boron and silica, depending on the conductivity value.

[0016] In one aspect, the pure water production system according to an embodiment of the present invention, which was completed based on the above findings, is a pure water production system equipped with a resin conductivity meter that is arranged in contact with an ion exchange resin contained in a mixed bed tower or polisher device for producing pure water or ultrapure water, and that measures the conductivity of the ion exchange resin.

[0017] In one embodiment of the pure water producing system according to the present invention, a calculator is provided for calculating the mixing ratio of the anion exchange resin and the cation exchange resin in accordance with the value of the resin conductivity meter.

[0018] In another embodiment of the pure water producing system according to the present invention, a calculator is provided for calculating the adsorption state of boron on the ion exchange resin in accordance with the value of the resin conductivity meter.

[0019] In yet another embodiment of the pure water producing system according to the present invention, a resin conductivity meter is disposed at at least one location at a height of at least 60 cm from the outlet of the mixed bed tower or polisher device.

[0020] In yet another embodiment of the pure water producing system according to the present invention, the polisher device is a polisher device in a subsystem that produces ultrapure water from primary pure water.

[0021] In another aspect, the present invention provides a method for producing pure water or ultrapure water, comprising arranging a resin conductivity meter in contact with an ion exchange resin contained in a mixed bed tower or a polisher apparatus for producing pure water or ultrapure water, and estimating the mixing ratio of the anion exchange resin and the cation exchange resin in the mixed bed tower or the polisher apparatus and / or the adsorption state of boron on the ion exchange resin based on a change in conductivity of the ion exchange resin. Effect of the Invention

[0022] According to the present invention, it is possible to provide a pure water producing apparatus and a pure water producing method that are capable of grasping the internal state of an ion exchange resin and stably supplying high-quality pure water or ultrapure water. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic diagram showing an example of a pure water producing apparatus according to an embodiment of the present invention. [Diagram 2] 1 is a graph showing examples of measurement results of resin conductivity under conditions in which the mixing ratio of anion exchange resin and cation exchange resin is changed. [Diagram 3] 1 is a graph showing an example of the results of measuring the change in electrical conductivity of an ion exchange resin when pure water is passed through the ion exchange resin in a new mixed bed tower. [Figure 4] 1 is a graph showing an example showing the relationship between the time of water flow and the boron ion concentration of treated water when boron-containing water is passed through an anion exchange resin. [Diagram 5] 1 is a graph showing the measurement results of the resin conductivity of a boron exchange resin (B type) and an anion exchange resin (OH type). [Figure 6] FIG. 1 is a schematic diagram showing an example of a pure water producing system according to a first modified example. [Figure 7] FIG. 11 is a schematic diagram showing an example of a pure water producing system according to a second modified example. [Figure 8] FIG. 11 is a schematic diagram showing an example of a pure water producing system according to a third modified example. [Figure 9]FIG. 13 is a schematic diagram showing an example of a pure water producing system according to a fourth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. The embodiments shown below are examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited to the structure, arrangement, etc. of the components described below.

[0025] (Pure water production equipment) 1, a pure water production apparatus according to an embodiment of the present invention includes a primary pure water system 1 for treating water to be treated, and a secondary pure water system (subsystem) 2. The primary pure water system 1 can include, for example, a sand filtration device 11, an activated carbon device 12, a cation exchange tower 13, an anion exchange tower 14, an ultraviolet irradiation (UV) device 15, a reverse osmosis (RO) device 16, and a degassing device 18 equipped with a mixed bed tower 17 and a degassing membrane.

[0026] The secondary pure water system 2 may include, for example, an ultrapure water tank 21 for storing the pure water obtained in the primary pure water system 1, a TOC-UV device 22, a degassing device 23, polisher devices 24 and 25, and an ultrafiltration membrane (UF) device 26.

[0027] Typically, but not limited to, pure water having a resistivity of about 10 MΩ·cm at 25° C., typically 0.01 to 15 MΩ·cm, and a conductivity of about 0.1 to 100 μS / cm is obtained by treatment in the primary pure water system 1. Ultrapure water having a conductivity of about 18 MΩ·cm, typically even 18.248 MΩ·cm, and a conductivity of 0.05482 μm / cm is obtained by treatment in the secondary pure water system 2. The ultrapure water obtained in the secondary pure water system 2 is circulated to an ultrapure water tank 21. For example, when ultrapure water is used in semiconductor manufacturing equipment or the like, a portion of the circulating water is drawn off and used.

[0028] In the pure water production system shown in Fig. 1, water to be treated is subjected to sand filtration, activated carbon treatment, ion exchange treatment, membrane treatment, and deaeration treatment to remove, for example, chloride ions, nitrate ions, sulfate ions, potassium ions, calcium ions, magnesium ions, boron ions, silica, and the like contained in the water to be treated. Meanwhile, boron ions and silica in particular are weak electrolytes, and are less likely to be adsorbed by ion exchange resins and more likely to be eluted than ions other than boron ions and silica. However, boron ions and silica are contained in trace amounts, and are difficult to detect simply by measuring the conductivity and pH of the effluent water flowing out of each device.

[0029] Therefore, in this embodiment, a conductivity meter 3 for measuring the conductivity of the ion exchange resin (hereinafter referred to as a "resin conductivity meter") is placed in the mixed bed tower 17 or polisher device 24, 25 installed in the primary pure water system 1 or secondary pure water system 2 for producing pure water or ultrapure water.

[0030] By directly measuring the conductivity of the ion exchange resin contained in the mixed bed tower 17 or the polisher devices 24, 25 using the resin conductivity meter 3, the internal state of the ion exchange resin contained in the mixed bed tower 17 or the polisher devices 24, 25 can be grasped in real time. From the internal state, the mixed state of the anion exchange resin and the cation exchange resin can be grasped, and the optimal time for regenerating the ion exchange resin can be estimated.

[0031] There are no particular limitations on the resin conductivity meter 3 as long as it is capable of measuring the conductivity of the ion exchange resin. In order to prevent components from leaking out of the members constituting the resin conductivity meter 3 into the pure water and ultrapure water, it is preferable to use a resin conductivity meter 3 in which the portion inserted into the mixed bed tower 17 or the polisher devices 24 and 25 is covered with a covering material.

[0032] The ion exchange resin includes an anion exchange resin and a cation exchange resin. The anion exchange resin and the cation exchange resin can be added in any ratio, but it is preferable to adjust the exchange capacity ratio to 1:1 and the volume capacity ratio to 1:2, for example. Alternatively, the ion exchange resin is preferably a boron exchange resin that adsorbs and removes boron from pure water or ultrapure water.

[0033] The resin conductivity meter 3 is preferably inserted in consideration of the length of the exchange zone of the boron ion of the ion exchange resin, and is preferably placed at a position at least 60 cm or more, and more preferably 70 cm or more higher than the height of the outlet (height of the lowest end of the resin-filled part) of the mixed bed tower 17 or the polisher device 24, 25. Furthermore, by placing the resin conductivity meter 3 at at least one point, preferably any multiple points, typically three points, along the height direction of the mixed bed tower 17 or the polisher device 24, 25, the mixing ratio of the anion exchange resin and the cation exchange resin at the cross section where the resin conductivity meter 3 is installed, that is, the weight ratio per unit area of ​​the anion exchange resin and the cation exchange resin near the position where the resin conductivity meter 3 is inserted and the leakage of boron ions can be grasped in more detail, and therefore the internal state of the ion exchange resin can be easily grasped from the outside.

[0034] Figure 2 shows examples of resin conductivity measurements under conditions where the mixing ratio of anion exchange resin and cation exchange resin is changed. The resin conductivity is lowest when the anion exchange resin ("OH type abundance ratio" in Figure 2) is 50-70%. In this case, the two are distributed almost equally. It is not clear why the resin conductivity is close to zero when anion exchange resin and cation exchange resin are mixed in almost equal amounts, but it is speculated that this is because the positive charge of the cation exchange resin and the negative charge of the anion exchange resin cancel each other out.

[0035] On the other hand, when the proportion of anion exchange resin is 30% (OH proportion, in this case the proportion of cation exchange resin is 70%) or when the proportion of anion exchange resin is 80% (OH proportion, in this case the proportion of cation exchange resin is 20%), it is found that the resin conductivity rises to about 0.5 mS / m. Therefore, by measuring the resin conductivity value, it is possible to estimate and visualize the mixture ratio of anion exchange resin and cation exchange resin. It is presumed that the resin conductivity rises when the balance between the two charges is lost.

[0036] By utilizing such characteristics, for example, a computer is provided that calculates the mixing ratio of anion exchange resin and cation exchange resin according to the value of a resin conductivity meter arranged so as to contact the ion exchange resin in the mixed bed tower 17 or the polisher devices 24, 25, although the invention is not limited thereto. This makes it possible to grasp the internal state of the ion exchange resin, in particular the mixed state of the anion exchange resin and the cation exchange resin and the adsorption state of boron.

[0037] The computing device may be a general-purpose computer well known to those skilled in the art, and the specific configuration is not particularly limited. If the computing device is configured so that the results of the computation can be output to an output device such as an operator's monitor, the operator can visually recognize the mixed state of the ion exchange resin in the mixed bed tower 17 or the polisher devices 24 and 25 via the output device. This allows the operator to visualize the mixed state of the ion exchange resin.

[0038] Of course, instead of using a calculator, an operator may manually evaluate the change in the measured resin conductivity value of the resin conductivity meter 3 using a graph or the like as shown in Fig. 2 to evaluate the internal state of the ion exchange resin. Also, by further providing a warning means or the like for warning the operator when the resin conductivity exceeds a predetermined threshold value, it becomes possible to stably supply high-quality pure water or ultrapure water.

[0039] Figure 3 shows an example of the results of measuring the change in conductivity of an ion exchange resin when pure water is passed through the ion exchange resin in a new mixed bed tower. "Resin section conductivity" in Figure 3 shows the conductivity value of the ion exchange resin, and "Pure water section conductivity" shows the conductivity value of the liquid phase (pure water) excluding the resin. "Run 1" in Figure 3 shows the resin conductivity in the initial state, indicating a state in which both ion exchange resins are well mixed. In this case, the resin conductivity value is extremely low, less than 0.5 mS / m. The pure water section conductivity value shows an even lower value.

[0040] On the other hand, "Run 2" in FIG. 3 shows the conductivity in a state where new cation exchange resin and anion exchange resin saturated with boron are mixed in the same ratio as Run 1. In this case, the resin conductivity rises to 2 mS / m. The value of the pure water part conductivity also rises slightly, but the rate of increase is very low. According to the example shown in FIG. 3, it can be seen that the resin conductivity rises as a result of boron being ion-exchanged into the OH site of the anion exchange resin. Therefore, according to this embodiment, by measuring the change in the conductivity of the resin conductivity, it is possible to grasp the amount of boron adsorbed to the ion exchange resin at the height cross section where the resin conductivity meter 3 is inserted, and it becomes possible to visualize the exchange capacity and calculate the leak timing.

[0041] Furthermore, by observing the change in the resin conductivity value using the resin conductivity meter 3 according to this embodiment, it is also possible to grasp the transition of boron ions from the inlet side to the outlet side of the ion exchange band.

[0042] Figure 4 shows an example showing the relationship between the time of water flow and the boron ion concentration of the treated water when boron-containing water was passed through an anion exchange resin. The boron concentration was about 7500 mg / L, and the water flow LV was 1.6 m / h. The results showed that boron leaked between 20 and 25 minutes of water flow. The boron concentration of the treated water became almost the same as that of the raw water after about 60 minutes of water flow.

[0043] The length of the exchange zone of an ion exchange resin is expressed by the following formula: Inflow concentration (eq / L) x LV (m / h) x ΔT (h) / (Ion exchange capacity in equilibrium with inlet concentration (eq / LR) + porosity x inflow concentration (eq / L))

[0044] In this case, the inflow concentration was 0.68 (eq / L), the ion exchange capacity to be in equilibrium with the inlet concentration was 0.88 (eq / LR), and the porosity was 0.74. At this time, the length of the exchange zone for boron ions was 52 cm.

[0045] The substances most likely to leak in pure water production systems are silica and boron. In particular, the adsorption amount of boron is said to be about 1 / 1000 of other ions, and it has lower selectivity than other ions, so the risk of leakage is high. Usually, anion exchange resin and cation exchange resin are mixed uniformly in the mixed bed tower 17 for treatment, but there are cases where the anion exchange resin and cation exchange resin are not mixed uniformly. When the anion exchange resin and cation exchange resin are unevenly distributed in the tower, there is a problem that boron suddenly leaks.

[0046] Figure 5 shows the measurement results of the resin conductivity of boron exchange resin (B type) and anion exchange resin (OH type). The measurement method was to put 150 mL of boron exchange resin and pure water into a 300 mL beaker and measure the conductivity of the resin part and the pure water part at 25 ° C. The conductivity is shown as the result of measurement with a benchtop conductivity meter. From Figure 5, it can be seen that the conductivity of the boron exchange resin (RB) is 2.42 mS / m, the resin conductivity of the anion exchange resin (R-OH) is 5.66 mS / m, and the resin conductivity is R-OH>RB. Furthermore, from the results of Figures 3 and 5, it can be seen that the resin part conductivity increased due to the adsorption of boron in the pure water, but the pure water part conductivity did not change significantly, so it can be seen that the boron exchange of the ion exchange resin can be detected by directly measuring the resin part conductivity.

[0047] (Modification) The pure water production system according to the embodiment of the present invention can include various apparatus configurations other than that shown in Fig. 1. For example, as shown in Fig. 6, the pure water production system according to a first modification is different from the pure water production system shown in Fig. 1 in that it includes an RO device 19 instead of the cation exchange tower 13 and the anion exchange tower 14 of the primary pure water system 1 in Fig. 1, and a degassing device 18 instead of the UV device 15. According to the pure water production system according to the first modification, while the ion load of the RO device 16 is high, the operation is simple and can contribute to the miniaturization of the system.

[0048] As shown in Fig. 7, the pure water production system according to the second modification is different from the pure water production system shown in Fig. 6 in that it includes a cation exchange tower 13 and an anion exchange tower 14 instead of the RO device 16 and mixed bed tower 17 of the primary pure water system 1 in Fig. 6. The pure water production system according to the second modification requires only ion exchange resin compared to the first modification, and can be operated more efficiently.

[0049] As shown in Fig. 8, the pure water production system according to the third modification may be configured such that the primary pure water system 1 is composed of a sand filtration unit 11 and an activated carbon unit 12, followed by a two-bed, three-tower system consisting of a cation exchange unit 13, a degassing unit 18, and an anion exchange unit 14, and then RO treatment is performed by an RO unit 16. The pure water production system according to the third modification is simpler to operate than that shown in Fig. 1 because no polisher is installed. However, the ion load on the ultrapure water tank 21 is also higher.

[0050] As shown in FIG. 9, the pure water manufacturing apparatus of the fourth modified example may be configured such that a primary pure water system 1 includes a sand filtration device 11 and an activated carbon device 12, followed by an RO device 19 and a degassing device 18, and then an electrically regenerated ion exchange process is performed using an electrically regenerated ion exchange device 111.

[0051] Thus, the present invention has been described by the above embodiment and modified examples, but the description and drawings forming a part of this disclosure should not be understood as limiting the present invention. Various alternative embodiments and operation techniques will become apparent to those skilled in the art from this disclosure. The present invention is expressed by the invention-specific matters in the appropriate claims from the above disclosure, and can be modified and embodied in the implementation stage without departing from the spirit of the invention. [Explanation of symbols]

[0052] 1...Primary pure water system 2…Secondary pure water system 3…Resin conductivity meter 11…Sand filter device 12...Activated carbon device 13…Cation exchange tower 14...Anion exchange tower 15...UV device 16...RO device 17…Mixed bed tower 18…Deaeration device 19…RO device 21…Ultra-pure water tank 22…TOC-UV device 23… Deaeration device 24, 25...Polisher device 26…UF device 111... Electrically regenerated ion exchange device

Claims

1. a mixed bed tower or polisher apparatus disposed in contact with the contained ion exchange resin to produce pure or ultrapure water; a resin conductivity meter for measuring the conductivity of the ion exchange resin; a calculator for calculating an adsorption state of boron on the ion exchange resin in response to a change in the electrical conductivity measured by the resin electrical conductivity meter; Equipped with the computing device calculates an amount of boron adsorbed to the ion exchange resin at a height cross section into which the resin conductivity meter is inserted by measuring the change in conductivity of the resin conductivity meter; A pure water producing apparatus, characterized in that the resin conductivity meter is disposed at at least one location at a height of 60 cm or more from the outlet of the mixed bed tower or the polisher device.

2. 2. The method for producing pure water according to claim 1, wherein the polisher device is a polisher device in a subsystem for refining ultrapure water from primary pure water.

3. A method for producing pure water or ultrapure water, comprising the steps of: mixing equivalent amounts of ion exchange resins including anion exchange resin and cation exchange resin in a mixed bed tower or polisher device for producing the pure water or the ultrapure water; A resin conductivity meter is disposed at least at one location at a height of 60 cm or more from an outlet of the mixed bed tower or the polisher device so as to come into contact with the ion exchange resin contained in the mixed bed tower or the polisher device; measuring the conductivity of the ion exchange resin with the resin conductivity meter by passing the pure water or ultrapure water through the ion exchange resin; Based on the change in the conductivity of the ion exchange resin, an amount of boron adsorbed to the ion exchange resin at the height cross section where the resin conductivity meter is inserted is estimated. A method for producing pure water comprising the steps of:

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