Pure water production apparatus

Abstract

This pure water production apparatus comprises a reverse osmosis membrane and an electrodeionization device 2. In the electrodeionization device 2, anion exchange membranes 11 and cation exchange membranes 12 are alternately arranged between an anode plate 15 and a cathode plate 16, and by constituting compartments with the anion exchange membranes 11 and the cation exchange membranes 12, a desalting chamber 13 and a concentration chamber 14 are formed, and an anode chamber and a cathode chamber are formed at respective ends. As feed water to the desalting chamber 13, permeated water W1 from a reverse osmosis membrane device 1 is supplied to the desalting chamber 13 to obtain treated water W2. Further, as feed water W3 to the concentration chamber 14, permeate from the reverse osmosis membrane device 1 is supplied, and concentrated water W4 is discharged. In the electrodeionization device 2, the desalting chamber 13 is filled with substantially 100% by weight of an anion exchange resin. According to this pure water production apparatus, the removal efficiency of weak acid ions such as boron and silica can be improved without using chemicals.

Description

Pure water production equipment

[0001] The present invention relates to a pure water production apparatus, such as a primary pure water production apparatus or an ultrapure water production apparatus, that uses an electrodeionizer capable of improving the removal efficiency of weak acid ions such as boron and silica.

[0002] Traditionally, ultrapure water used in the electronics industry, such as semiconductors, is produced by treating raw water in an ultrapure water production system that consists of a pretreatment system, a primary pure water production system (pure water production system), and a subsystem (secondary pure water production system) that processes the primary pure water.

[0003] In recent years, the required boron and silica concentrations in treated water have decreased in primary pure water systems, and simply using reverse osmosis membrane systems, regenerative ion exchange systems, or electrodeionization systems as desalination methods may not satisfy the water quality requirements. Therefore, as shown in Figure 4, a pure water production system is used in which a regenerative ion exchange system 42 is installed downstream of the reverse osmosis membrane system 41. In this pure water production system, the water to be treated W is passed through the reverse osmosis membrane system 41, and the permeate W1 is treated with the regenerative ion exchange system 42, thereby reducing the boron and silica concentrations in the treated water W2.

[0004] Furthermore, as shown in Figure 5, a pure water production system is also used in which an electrodeionization exchange system 52 is installed downstream of the reverse osmosis membrane system 51. In this pure water production system, the water to be treated W is passed through the reverse osmosis membrane system 51, and the permeate W1 is treated with the electrodeionization exchange system 52, thereby reducing the boron and silica concentrations in the treated water W2.

[0005] However, in the pure water production apparatus shown in Figure 4, the regenerative ion exchange device 42 alternates between deionization and regeneration with chemicals. In order to improve the removal rate of weak acid ions such as boron and silica in the regenerative ion exchange device 42, the frequency of regeneration with chemicals increases, which not only increases running costs but also increases the burden of processing used chemicals.

[0006] In the pure water production apparatus shown in Figure 5, the electrodeionization exchange device 52 is inefficient at removing weak acid ions, so a large current is required to obtain a sufficient removal rate, which results in high power consumption. Furthermore, it is said that the water dissociation phenomenon occurs most frequently at the junction between the anion exchange membrane and the cation resin exchange. In that case, the H generated by water dissociation ＋ and OH － Of these, OH － There is concern that the ions will permeate the anion exchange membrane and immediately enter the concentration chamber. Therefore, it is important to cause water dissociation at the contact point between the cation exchange membrane and the anion exchange resin. For this reason, OH is used to regenerate the anion resin in the desalination chamber. － It is possible that this is not being fully utilized. Furthermore, in the area that appears to be the best from the perspective of water dissociation, using the heterogeneous cation film and anion exchange resin and cation exchange resin, which are standard specifications, presents the problem of poor electrical conductivity.

[0007] Conventionally, removing weak acid ions such as boron and silica requires the consumption of large amounts of chemicals or electricity, and there is a need for pure water production equipment that can remove boron and silica more efficiently.

[0008] This invention has been made in view of the above problems, and aims to provide a pure water production apparatus that can improve the removal efficiency of weak acid ions such as boron and silica without using chemicals.

[0009] In view of the above objectives, the present invention provides a pure water production apparatus having an electrodeionizer downstream of a desalination means, wherein the electrodeionizer has a desalination chamber substantially filled with an anion exchanger (Invention 1). In the above invention (Invention 1), it is preferable that the anion exchanger is an anion exchange resin (Invention 2).

[0010] According to the inventions described above (Inventions 1 and 2), when desalted water is passed through the desalting chamber of an electrodeionizer in which the desalting chamber is substantially filled with an anion exchanger, only the anionic components in the feedwater are selectively removed, thereby improving the removal rate of weak acid ions such as boron and silica.

[0011] In the above invention (Invention 1), the desalination chamber and concentration chamber of the electrodeionizer are partitioned by a cation exchange membrane and an anion exchange membrane, and it is preferable that the cation exchange membrane is a homogeneous cation exchange membrane (Invention 3). In the above invention (Invention 3), it is preferable that the homogeneous cation exchange membrane has a film thickness of 500 μm or less (Invention 4). Furthermore, in the above invention (Invention 4), it is preferable that the maximum height (RY) of the homogeneous cation exchange membrane is 20 μm or more (Invention 5). The maximum height (RY) of the homogeneous cation exchange membrane is obtained by taking a reference length from the roughness curve in the direction of its average line, measuring the distance between the peak line and the trough line of this taken portion in the direction of the vertical magnification of the roughness curve, and expressing this value in micrometers (μm).

[0012] According to the above inventions (inventions 3 to 5), by forming a desalination chamber by partitioning it with a dense, thin, homogeneous cation exchange film, an electric current flows even when only an anion exchanger is filled into the desalination chamber, and OH is generated by water dissociation. － Because the regeneration efficiency of the anion exchange resin in the desalination chamber is increased, the removal rate of anionic components is improved compared to conventional electrodeionizers, and the removal rate of weak acid ions such as boron can be improved without the use of chemicals.

[0013] In the above inventions (inventions 1 to 5), it is preferable that the desalination means is a reverse osmosis membrane device, a regenerative ion exchange device, or an electrodeionization device (invention 6).

[0014] According to the above invention (Invention 6), when applied to a pure water production apparatus having various desalination means, weak acid ions such as boron and silica can be efficiently removed.

[0015] The pure water production apparatus of the present invention has an electrodeionizer downstream of the desalination means, and since the desalination chamber of this electrodeionizer is substantially filled with an anion exchanger, when desalination water is passed through the desalination chamber of this electrodeionizer, only the anionic components in the desalination water are selectively removed, so weak acid ions such as boron and silica can be efficiently removed.

[0016] This is a flow diagram showing the configuration of the desalination means and electrodeionizer in a pure water production apparatus according to one embodiment of the present invention. This is a schematic diagram showing the configuration of the electrodeionizer in the above embodiment. This is a schematic diagram showing the configuration of an electrodeionizer of a comparative example (conventional example). This is a flow diagram showing the configuration of a reverse osmosis membrane and a regenerative ion exchange apparatus. This is a flow diagram showing the configuration of a reverse osmosis membrane and an electrodeionizer.

[0017] The pure water production apparatus of the present invention will be described below with reference to the attached drawings.

[0018] [Pure Water Production Apparatus] The pure water production apparatus of this embodiment only needs to have an electrodeionizer after a desalination means such as a reverse osmosis membrane apparatus, an ion exchange apparatus, or an electrodeionizer, and can be suitably applied to the primary pure water production apparatus in an ultrapure water production apparatus.

[0019] In this embodiment, the pure water production apparatus has an electrodeionizer 2 downstream of the reverse osmosis membrane apparatus 1, as shown in Figure 1.

[0020] (Reverse Osmosis Membrane) There are no particular restrictions on the reverse osmosis membrane apparatus 1, but it is common to use an ultra-low pressure reverse osmosis membrane. An ultra-low pressure reverse osmosis membrane has a permeation flux of 0.4 to 0.9 m at an effective membrane pressure (water temperature 25°C, pure water (RO permeate)) of 0.4 to 0.9 MPa. ３ / (m ２ This reverse osmosis membrane has a performance of removing over 90% of NaCl and over 30% of boron. Furthermore, ultra-low pressure reverse osmosis membranes and extremely low pressure reverse osmosis membranes, which can operate at even lower pressures, can also be used.

[0021] (Electrodeionization Device) As schematically shown in FIG. 2, the electrodeionization device 2 alternately arranges anion exchange membranes 11 and cation exchange membranes 12 between an anode plate 15 and a cathode plate 16, and forms desalination chambers (D chambers) 13 and concentration chambers (C chambers) 14 by partitioning with these anion exchange membranes 11 and cation exchange membranes 12, and forms anode chambers and cathode chambers (not shown) at both ends. In this case, the number of desalination chambers is preferably 10 to 100, particularly preferably about 40 to 60. In the present embodiment, permeate water (feed water) W1 of the reverse osmosis membrane device 1 is supplied as feed water to the desalination chamber 13 to obtain treated water W2. Further, permeate of the reverse osmosis membrane device 1 is supplied as feed water (concentrate water to be concentrated) W3 to the concentration chamber 14, and concentrated water W4 is discharged.

[0022] The electrodeionization device 2 as described above is filled with an anion exchange resin (black circles in the figure), preferably a strong anion exchange resin, as an anion exchanger in the desalination chamber 13 substantially at 100% by weight (based on dry conditions). In this specification, substantially 100% by weight of the anion exchange resin means not only the case of only the anion exchange resin, but also the case where the anion exchange resin is 75% by weight or more, particularly 90% by weight or more, and further 95% by weight or more, and a small amount of cation exchange resin or the like may be mixed. In the concentration chamber 14, an anion exchange resin (black circles in the figure) as an anion exchanger and a cation exchange resin (white circles in the figure) as a cation exchanger are filled at a mixing ion exchange resin ratio of 30:70 to 70:30 (weight ratio), particularly 40:60 to 60:40 (weight ratio) based on dry conditions.

[0023] Further, the cation exchange membrane 12 is preferably a strong cation exchange membrane and preferably a homogeneous cation exchange membrane. When a homogeneous membrane is used as the cation exchange membrane 12, the resistance between the anode and the cathode becomes smaller than when a heterogeneous membrane is used, and when a voltage is applied between the two electrodes, current flows more easily. And H ＋ and OH － Among them, OH －The material moves across the desalination chamber 13 toward the anode, and during this time, the anion exchange material, such as the anion exchange resin, inside the desalination chamber 13 is sufficiently regenerated. As a result, productive water (desalination water) with sufficiently removed anionic components is obtained, and scale formation inside the desalination chamber is also suppressed.

[0024] The homogeneous cation exchange membrane 12 preferably has a film thickness of 500 μm or less, and more preferably 300 μm or less. The lower limit of the film thickness of the homogeneous cation exchange membrane 12 is about 100 μm. Furthermore, the maximum height (RY) of the homogeneous cation exchange membrane 12 is preferably 20 μm or more, and more preferably 25 μm or more. The upper limit of the maximum height (RY) is about 50 μm. By using such a homogeneous cation exchange membrane 12, water dissociation occurs well in the desalination chamber, and the removal rate of weak acid ions caused by boron, silica, etc. can be improved. As such a homogeneous membrane cation exchange membrane, commercially available products such as CMB (surface height (RY): 33 μm, film thickness: 215 μm) manufactured by ASTOM Corporation and TYPE10 (surface height (RY): 27 μm, film thickness: 128 μm) manufactured by Fujifilm Corporation can be used. It is preferable to use a homogeneous membrane as the anion exchange membrane 11.

[0025] In this type of electrodeionizer 2, OH is generated by water dissociation. － Because this improves the regeneration efficiency of the anion exchange resin in the desalination chamber, the removal rate of anionic components is improved compared to conventional electrodeionizers.

[0026] [Operation Method of the Pure Water Production System] The operation method of the pure water production system described above will be explained based on Figures 1 and 2.

[0027] First, a water supply pump (not shown) is driven to supply the water to be treated W to the reverse osmosis membrane device 1. This reverse osmosis membrane device 1 removes salts, as well as ionic components and TOC from the water to be treated W.

[0028] Next, the permeate (feedwater) W1 from the reverse osmosis membrane apparatus 1 is supplied to the electrodeionizer 2. As shown in Figure 2, the electrodeionizer 2 has a desalination chamber 13 that is substantially filled with 100% by weight of anion exchange resin. When the permeate (feedwater) W1 passes through the desalination chamber 13, only the anionic components in the permeate (feedwater) W1 are selectively removed. This makes it possible to obtain treated water W2 from which weak acid ions caused by boron and silica have been removed.

[0029] Furthermore, the treated water W2 of the electrodeionizer 2, which is substantially filled with 100% by weight of anion exchange resin, can be further treated with a general-purpose electrodeionizer or reverse osmosis membrane as needed to remove trace amounts of ionic impurities contained in the treated water W2, thereby producing pure water of higher purity.

[0030] The pure water production apparatus of the present invention has been described above with reference to the attached drawings, but the present invention only requires that an electrodeionizer 2, which is substantially filled with anion exchanger, be placed downstream of the desalination means, and various modifications can be made. For example, a regenerative ion exchanger or an electrodeionizer may be provided instead of the reverse osmosis membrane apparatus 1, or two reverse osmosis membrane apparatuses 1 may be provided in series. Furthermore, the pure water production apparatus can be composed of various general-purpose elements of a pure water production apparatus, as long as an electrodeionizer 2, which is substantially filled with anion exchanger, is placed downstream of the desalination means.

[0031] The present invention will be described in more detail below based on specific examples, but the present invention is not limited to the following examples.

[0032] [Test Electrodeionizer] <Example 1> An electrodeionizer with the configuration shown in Figure 2 was constructed with the following specifications: Size of anion exchange membrane, cation exchange membrane and electrode: 46 mm (length) x 48.5 mm (width) Cation exchange membrane: CMB manufactured by ASTOM Corporation (homogeneous membrane, surface height (RY): 33 μm, film thickness: 215 μm) Anion exchange membrane: AHA manufactured by ASTOM Corporation (homogeneous membrane, surface height (RY): 44 μm, film thickness: 219 μm) Resin in concentration chamber: Mixture and filling of 60% by weight of anion exchange resin and 40% by weight of cation exchange resin Cation exchange resin: KR-UC1 manufactured by Kurita Water Industries Ltd. Anion exchange resin: KR-UA1 manufactured by Kurita Water Industries Ltd.

[0033] <Example 2> The configuration was the same as in Example 1, except that Fujifilm Corporation's TYPE10 (surface height (RY): 27 μm, film thickness: 128 μm) was used as the cation exchange membrane.

[0034] <Comparative Examples 1 and 2> As general-purpose electrodeionizers for Comparative Examples 1 and 2, the apparatus shown in Figure 3 was prepared. In Figure 3, the electrodeionizer 21 alternately arranges anion exchange membranes 22 and cation exchange membranes 23 between an anode plate 26 and a cathode plate 27, and by forming compartments with these anion exchange membranes 22 and cation exchange membranes 23, a desalination chamber (D chamber) 24 and a concentration chamber (C chamber) 25 are formed, and an anode chamber and a cathode chamber (not shown) are formed at both ends. Permeate water (feed water) W1 from the reverse osmosis membrane apparatus 1 is supplied to the desalination chamber 13 as the feedwater for the desalination chamber 24 to obtain treated water W2. Permeate water from the reverse osmosis membrane apparatus 1 is supplied as the feedwater (water to be concentrated) W3 for the concentration chamber 25 to discharge concentrated water W4. The desalination chamber 24 and concentration chamber 25 of this electrodeionizer 21 were filled with anion exchange resin and cation exchange resin in a weight ratio of 60:40. The same anion exchange resin and cation exchange resin as in Example 1 were used. In addition, an Evoqua AS0069 (heterogeneous film, surface height (RY): 16.5 μm, film thickness: 715 μm) was used as the cation exchange membrane 23.

[0035] <Configuration of the Electro-deionization Device>The electro-deionization devices shown in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were each configured as shown in Table 1. In Table 1, the mixing means mixing and filling an anion exchange resin and a cation exchange resin at a weight ratio of 60:40 (based on dry weight).

[0036]

[0037] <Operating Conditions of the Electro-deionization Device>The electro-deionization devices of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were operated under the conditions shown in Table 2 below.

[0038]

[0039] <Water Quality Test>Water with the properties shown in Table 3 below was supplied to the desalination chamber and the concentration chamber of each electro-deionization device.

[0040]

[0041] The boron removal rate and the silica removal rate of the treated water W2 in these electro-deionization devices were measured. The results are shown in Table 4.

[0042]

[0043] As is clear from Table 4, when comparing Comparative Example 1 with Example 1 and Comparative Example 2 with Example 2, in both cases, the removal rates of boron and silica are higher in the examples. Comparative Examples 1 and 2 are ordinary electro-deionization devices filled with a mixed resin of an anion exchange resin and a cation exchange resin in the desalination chamber, while Examples 1 and 2 are filled with an anion exchange resin in the desalination chamber. Therefore, it can be seen that by using an electro-deionization device filled with an anion exchange resin in the desalination chamber, boron and silica can be removed with high efficiency.

[0044] 1 Reverse Osmosis Membrane Device (Desalination Means) 2 Electro-deionization Device 11 Anion Exchange Membrane 12 Cation Exchange Membrane 13 Desalination Chamber (D Chamber) 14 Concentration Chamber (C Chamber) 15 Anode Plate 16 Cathode Plate W Treated Water W1 Permeate Water (Feed Water) W2 Treated Water W3 Concentrated Water to be Treated W4 Concentrated Water

Claims

1. A pure water production apparatus having an electrodeionizer downstream of a desalination means, wherein the electrodeionizer has a desalination chamber substantially filled with an anion exchanger.

2. The pure water production apparatus according to claim 1, wherein the anion exchange body is an anion exchange resin.

3. The pure water production apparatus according to claim 1, wherein the desalination chamber and concentration chamber of the electrodeionizer are partitioned by a cation exchange membrane and an anion exchange membrane, and the cation exchange membrane is a homogeneous cation exchange membrane.

4. The pure water production apparatus according to claim 3, wherein the homogeneous cation exchange membrane has a film thickness of 500 μm or less.

5. The pure water production apparatus according to claim 4, wherein the maximum height (RY) of the homogeneous cation exchange membrane is 20 μm or more.

6. The pure water production apparatus according to any one of claims 1 to 5, wherein the desalination means is a reverse osmosis membrane apparatus, a regenerative ion exchange apparatus, or an electrodeionizer.

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