Electrodeionization water production apparatus and method for producing deionized water

Abstract

An electric deionization water manufacturing device (EDI device) that improves the removal performance of weak acid components such as boron has a desalination chamber divided by a pair of ion exchange membranes between an anode and a cathode. A particle size of 0.1 mm or more and 0.4 mm or less is set as a small particle size, and a particle size exceeding 0.4 mm is set as a large particle size. In the desalination chamber, a large particle size layer composed of ion exchange resin of the large particle size and a mixed particle size layer in which ion exchange resin of the large particle size and ion exchange resin of the small particle size are mixed are arranged in the flow direction of the water to be treated.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrodeionization water producing apparatus and a method for producing deionized water, which produce deionized water from treated water containing weak acid components such as boron. BACKGROUND

[0002] There is a demand for removing weak acid components in treated water. For example, in recent years, in ultra-pure water and the like used in the production of semiconductor devices, further reduction in the content of boron is required. Boron in water is a weak acid component that is difficult to remove by ion exchange treatment with a general ion exchange resin. As a means for removing boron, reverse osmosis membrane apparatuses, boron-selective ion exchange resins, electrodeionization water producing apparatuses (EDI apparatuses), and the like are known. Among these, an EDI apparatus is an apparatus that combines electrophoresis and electro-dialysis, and is filled with an ion exchange resin at least in a desalination chamber thereof to produce deionized water from treated water. The EDI apparatus is filled with an ion exchange resin at least in the desalination chamber thereof, and is also capable of removing ion components other than boron, and has the advantage that it does not require a process for regenerating the ion exchange resin with a chemical agent. However, in the EDI apparatus, only a general ion exchange resin is filled in the desalination chamber, and sufficient removal performance for weak acid components such as boron is not always obtained, and in such a case, a two-stage EDI apparatus is sometimes used in series connection.

[0003] A general ion exchange resin has a shape of beads or particles, and has a standard particle diameter of more than 0.4 mm and around 1 mm or less. In order to improve the removal performance for weak acid components such as boron in an EDI apparatus, it has been proposed to fill an ion exchange resin having a smaller particle diameter in the desalination chamber. For example, Patent Literature 1 discloses filling an ion exchange resin having an average particle diameter of 150 to 250 μm in a single bed in the desalination chamber of an EDI apparatus. Patent Literature 2 discloses filling an ion exchange resin having an average diameter of 0.2 to 0.3 mm in a single bed in the desalination chamber. Patent Literatures 3 and 4 disclose filling an ion exchange resin having an average particle diameter of 0.1 to 0.4 mm in a region that becomes the middle in the vertical direction in a desalination chamber in which treated water flows in the vertical direction, and filling an ion exchange resin having an average particle diameter of more than 0.4 mm in the upper and lower regions.

[0004] In order to reduce the electric resistance of the desalination chamber and improve the desalination efficiency at the time of operation of the EDI apparatus, it is important to control the filling rate of the ion exchange resin in the desalination chamber. Patent Literature 5 discloses mixing and filling a plurality of ion exchange resin particles having different particle diameters of uniform particle diameters in the desalination chamber in order to reduce the electric resistance of the desalination chamber.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Laid-Open (JP A) No. 2016-150304

[0008] Patent Literature 2: Japanese Patent Application Laid-Open (JP A) No. 2017-176968

[0009] Patent Literature 3: Japanese Patent Application Laid-Open (JP A) No. 2019-177327

[0010] Patent Literature 4: Japanese Patent Application Laid-Open (JP A) No. 2020-78772

[0011] Patent Literature 5: Japanese Patent Application Laid-Open (JP A) No. Hei 10-258289 SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] In a case where ion exchange resins of small particle diameter are filled in the desalination chamber of the EDI device in order to improve the removal performance of weak acid components such as boron, in order to reduce the voids between the particles of the ion exchange resins, the water passage pressure difference becomes large. Therefore, the water to be treated must be passed through the desalination chamber at a high pressure, and the airtightness of the EDI device needs to be improved. Furthermore, passing the water to be treated at a high pressure reduces the durability of the EDI device.

[0014] An object of the present application is to provide an electrodeionization water manufacturing device (EDI device) and a method of manufacturing such deionized water, which improve the removal performance of weak acid components typified by boron while suppressing the increase in the water passage pressure difference of the desalination chamber.

[0015] TECHNICAL SOLUTION FOR SOLVING THE PROBLEMS

[0016] According to one embodiment of the present application, an electrodeionization water manufacturing device has a desalination chamber divided by a pair of ion exchange membranes between an anode and a cathode, and ion exchange resins are filled in the desalination chamber. A particle diameter of 0.1 mm or more and less than 0.4 mm is set as a small particle diameter, and a particle diameter exceeding 0.4 mm is set as a large particle diameter. In the desalination chamber, a large particle diameter layer composed of ion exchange resins of the large particle diameter and a mixed particle diameter layer in which ion exchange resins of the large particle diameter and ion exchange resins of the small particle diameter are mixed are arranged in the flow direction of the water to be treated in the desalination chamber.

[0017] According to a further aspect of the present application, an electrodeionization water producing apparatus has a desalination chamber divided by a pair of ion exchange membranes between an anode and a cathode, and ion exchange resins are filled in the desalination chamber. A particle diameter of 0.1 mm or more and less than 0.4 mm is set as a small particle diameter, and a particle diameter exceeding 0.4 mm is set as a large particle diameter. An apparent volume of the ion exchange resins of the large particle diameter is set as L, and an apparent volume of the ion exchange resins of the small particle diameter is set as S. A mixed particle diameter layer in which the ion exchange resins of the large particle diameter and the ion exchange resins of the small particle diameter are mixed at a mixing ratio in a range of 1:1 to 20:1 of L:S is arranged in the desalination chamber. Boron-containing treated water is supplied to the desalination chamber to remove boron from the treated water.

[0018] According to a further aspect of the present application, an electrodeionization water producing apparatus has a desalination chamber divided by a pair of ion exchange membranes between an anode and a cathode, and ion exchange resins are filled in the desalination chamber. A particle diameter of 0.1 mm or more and less than 0.4 mm is set as a small particle diameter, and a particle diameter exceeding 0.4 mm is set as a large particle diameter. An apparent volume of the ion exchange resins of the large particle diameter is set as L, and an apparent volume of the ion exchange resins of the small particle diameter is set as S. A mixed particle diameter layer in which the ion exchange resins of the large particle diameter and the ion exchange resins of the small particle diameter are mixed at a mixing ratio in a range of 1:1 to 20:1 of L:S is arranged in the desalination chamber. Boron-containing treated water is supplied to the desalination chamber to remove boron from the treated water.

[0019] According to a further aspect of the present application, an electrodeionization water producing apparatus has a desalination chamber divided by a pair of ion exchange membranes between an anode and a cathode, and ion exchange resins are filled in the desalination chamber. A particle diameter of 0.1 mm or more and less than 0.4 mm is set as a small particle diameter, and a particle diameter exceeding 0.4 mm is set as a large particle diameter. An apparent volume of the ion exchange resins of the large particle diameter is set as L, and an apparent volume of the ion exchange resins of the small particle diameter is set as S. A mixed particle diameter layer in which the ion exchange resins of the large particle diameter and the ion exchange resins of the small particle diameter are mixed at a mixing ratio in a range of 1:1 to 20:1 of L:S is arranged in the desalination chamber. Boron-containing treated water is supplied to the desalination chamber to remove boron from the treated water.

[0020] Effects of the Invention

[0021] According to the present application, an electrodeionization water producing apparatus (EDI apparatus) in which removal performance of weak acid components represented by boron is improved while an increase in a water passage pressure difference of a desalination chamber is suppressed, and a method of producing such deionized water can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a view showing an EDI apparatus of a first embodiment of the present application.

[0023] Figures 2A to 2Eis a view showing a packed example of ion exchange resin in a desalting chamber.

[0024] Figure 3 is a view showing an EDI device of a second embodiment of the present application.

[0025] Figure 4 is a view showing another example of the EDI device of the second embodiment.

[0026] Figure 5 is a view showing another example of the EDI device of the second embodiment.

[0027] Figure 6 is a view showing another example of the EDI device of the second embodiment.

[0028] Figure 7 is a view showing an EDI device of a third embodiment of the present application.

[0029] Figure 8 is a flow chart showing the structure of a pure water manufacturing system.

[0030] Figure 9 is a view showing an EDI device of Comparative Example 1.

[0031] Figure 10 is a view showing an EDI device of Comparative Example 2.

[0032] Figure 11 is a chart showing the results of Example 3.

[0033] Figure 12 is a chart showing the results of Example 4. DETAILED DESCRIPTION

[0034] Next, a mode of carrying out the present application will be described with reference to the drawings. Generally, in an electrodeionization water producing apparatus (EDI apparatus), a desalination chamber divided by a pair of ion exchange membranes is provided between an anode and a cathode, and ion exchange resin is filled in the desalination chamber. Also, in the EDI apparatus, when treated water is supplied to the desalination chamber in a state where a direct current voltage is applied between the anode and the cathode, desalination (deionization) treatment of the treated water is performed, as a result of which water from which ionic components have been removed is discharged from the desalination chamber as treated water. The EDI apparatus according to the present application is provided with a mixed particle diameter layer in which ion exchange resin of a large particle diameter and ion exchange resin of a small particle diameter are mixed, in a desalination chamber, when a particle diameter of 0.1 mm or more and 0.4 mm or less is defined as a small particle diameter, and a particle diameter exceeding 0.4 mm is defined as a large particle diameter. By providing the mixed particle diameter layer in the desalination chamber of the EDI apparatus, the removal performance of weak acid components represented by boron is improved. In the desalination chamber, in addition to the mixed particle diameter layer, a large particle diameter layer composed of ion exchange resin of a large particle diameter can be provided. In the case where the large particle diameter layer is provided, the large particle diameter layer and the mixed particle diameter layer are provided in the flow direction of the treated water in the desalination chamber. The particle diameter of the ion exchange resin in a bead shape or a granular shape is generally 1 mm or less, and therefore, as ion exchange resin of a large particle diameter, ion exchange resin having a particle diameter exceeding 0.4 mm and 1 mm or less can also be used. In addition, the particle diameter of the ion exchange resin can be measured using a sieve (sieve), but the catalog value of the ion exchange resin manufacturer can also be used as the particle diameter in the present application. In the present application, a mixed particle diameter layer in which anion exchange resin of a large particle diameter and anion exchange resin of a small particle diameter are mixed can be used as the anion exchange resin, and a mixed particle diameter layer in which cation exchange resin of a large particle diameter and cation exchange resin of a small particle diameter are mixed can be used as the cation exchange resin.

[0035] In the present application, in the case where the weak acid component is mainly boron, the concentration of boron contained in the treated water is, for example, 1 ppb or more and 100 ppb or less. Of course, even in the case where the concentration of the weak acid component in the treated water is less than 1 ppb or exceeds 100 ppb, the weak acid component in the treated water can be removed based on the present application.

[0036] [First Embodiment]

[0037] Figure 1An EDI device 10 of a first embodiment of the present application is shown. In this EDI device 10, between an anode chamber 21 provided with an anode 11 and a cathode chamber 25 provided with a cathode 12, a concentration chamber 22, a desalination chamber 23, and a concentration chamber 24 are provided in this order from the anode chamber 21 side. The anode chamber 21 and the cathode chamber 25 are collectively referred to as electrode chambers. The anode chamber 21 and the concentration chamber 22 are adjacent to each other with a cation exchange membrane (CEM) 31 interposed therebetween, the concentration chamber 22 and the desalination chamber 23 are adjacent to each other with an anion exchange membrane (AEM) 32 interposed therebetween, the desalination chamber 23 and the concentration chamber 24 are adjacent to each other with a cation exchange membrane 33 interposed therebetween, and the concentration chamber 24 and the cathode chamber 25 are adjacent to each other with an anion exchange membrane 34 interposed therebetween. Thus, the desalination chamber 23 is divided by a pair of ion exchange membranes between the anode 11 and the cathode 12. In the example shown here, the desalination chamber 23 is divided by the anion exchange membrane 32 and the cation exchange membrane 33. In each drawing, as shown in the legend, Figure 1

[0038] Treated water is supplied to the desalination chamber 23, and treated water obtained by performing a desalination treatment on the treated water, i.e., deionized water, flows out from the desalination chamber 23. The interior of the desalination chamber 23 is filled with ion exchange resin, but in the example shown here, the desalination chamber 23 is filled with anion exchange resin (AER). Along the flow direction of the treated water in the desalination chamber 23, the interior of the desalination chamber 23 is divided into two regions, in the region on the inlet side of the treated water, a large-particle-size layer is formed by filling the interior with large-particle-size anion exchange resin, and in the region on the outlet side of the treated water, a mixed-particle-size layer is formed by mixing and filling the interior with large-particle-size ion exchange resin and small-particle-size ion exchange resin. In the drawing, the large-particle-size layer formed by the anion exchange resin is denoted as "L-AER", and the mixed-particle-size layer formed by the anion exchange resin is denoted as "L-S mixed AER". In the example shown in the drawing, the boundary between the large-particle-size layer and the mixed-particle-size layer is located approximately in the vicinity of the center of the desalination chamber 23 in the flow direction of the treated water.

[0039] ​In the EDI device 10, cation exchange resin (CER) is filled in the anode chamber 21, and anion exchange resin is filled in the concentration chambers 22, 24 and the cathode chamber 25. In addition, it is not necessarily required that ion exchange resin (i.e., anion exchange resin or cation exchange resin) is filled in the anode chamber 21, the concentration chambers 22, 24 and the cathode chamber 25, but in order to reduce the direct current voltage that should be applied between the anode 11 and the cathode 12 at the time of operation of the EDI device 1, it is preferable that ion exchange resin is also filled in the anode chamber 21, the concentration chambers 22, 24 and the cathode chamber 25. The concentration chambers 22, 24 are supplied with supply water for concentration chamber, and discharge concentrated water. Supply water for electrode chamber is supplied to the cathode chamber 25, and the supply water supplied to the cathode chamber 25 is supplied to the anode chamber 21 after passing through the cathode chamber 25, and thereafter, is discharged from the anode chamber 21 as electrode water. In addition, a structure in which the concentration chamber and the electrode chamber are combined can also be adopted.

[0040] If the concentration chamber is denoted as "C", the ion exchange membrane is denoted as "M", and the desalination chamber is denoted as "D", then in the EDI device, a plurality of basic structures of [C|M|D|M|C] can be provided in parallel with the anode and the cathode. At this time, two concentration chambers adjacent to each other with the ion exchange membrane interposed therebetween can be formed into a single concentration chamber by removing the ion exchange membrane interposed therebetween. In addition, the desalination chamber can be formed by combining the desalination chambers adjacent to each other with the ion exchange membrane interposed therebetween. Figure 1 In the EDI device 10 shown in the drawing, as a device in which one basic structure of the anion exchange membrane 32, the desalination chamber 23, the cation exchange membrane 33 and the concentration chamber 24 are formed, it is possible to arrange N of the basic structures between the concentration chamber 22 closest to the anode chamber 21 and the anion exchange membrane 34 connected to the cathode chamber 25, with N being an integer of 1 or more. A plurality of basic structures can be provided in parallel, which is indicated by the notation of "X N" in the drawing.

[0041] Next, the operation of the EDI device 10 will be described. Figure 1The production of the deionized water (i.e., treated water) by the EDI device 10 will be described. As in the case of the general EDI device, the feed water for the concentrating chamber is supplied to the concentrating chambers 22, 24, the electrode chamber feed water is supplied to the cathode chamber 25, and the electrode chamber feed water is supplied to the anode chamber 21, and the treated water is supplied to the desalting chamber 23, while a direct current voltage is applied between the anode 11 and the cathode 12. Thus, the deionization (desalination) of the ion components in the treated water by the ion exchange resins in the desalting chamber 23 is performed, and the deionized water flows out of the desalting chamber 23 as the treated water. The treated water first passes through the large-particle-size layer in the desalting chamber 23, and even the strong acid components, the weak acid components, and the components that are more easily adsorbed to the anion exchange resins are removed from the treated water. The components that are more difficult to remove, such as boron, contained in the treated water are then adsorbed to the anion exchange resins and removed from the treated water when the treated water passes through the mixed-particle-size layer containing the small-particle-size anion exchange resins. As a result, the treated water in which the weak acid components, such as boron, are sufficiently removed is discharged from the desalting chamber 23. The water resistance of the mixed-particle-size layer is greater than that of the large-particle-size layer, but the desalting chamber 23 as a whole is not the mixed-particle-size layer, and the large-particle-size layer is also present, so in the EDI device 10 of the present embodiment, the increase in the water pressure difference when the treated water is supplied to the desalting chamber 23 is also within an allowable range.

[0042] In the EDI device 10 of the present embodiment, the order of the arrangement of the large-particle-diameter layer and the mixed-particle-diameter layer in the direction of the flow of the treated water is arbitrary. The large-particle-diameter layer and the mixed-particle-diameter layer can each be provided as one layer, or at least one of the large-particle-diameter layer and the mixed-particle-diameter layer can be provided as two or more layers. However, it is preferable to provide a structure in which components that are relatively difficult to remove are removed after components that are relatively easy to remove in the treated water are removed, and thus it is preferable to arrange the mixed-particle-diameter layer at a position in the desalination chamber 23 that is close to the outlet of the treated water. In this case, the mixed-particle-diameter layer can be arranged so as to be in contact with the outlet of the treated water, or at least a portion of the mixed-particle-diameter layer can be contained in a range from the outlet of the treated water to 25% of the length of the desalination chamber 23 in the flow direction of the treated water. Both the mixed-particle-diameter layer and the large-particle-diameter layer are arranged in the desalination chamber 23, but the proportion of the mixed-particle-diameter layer among them is, for example, preferably such that the total of the packed heights of the ion exchange resins in the mixed-particle-diameter layer in the flow direction of the treated water in the mixed-particle-diameter layer is 20% or more and 80% or less of the length of the desalination chamber 23 in the flow direction of the treated water. In the case where the proportion of the mixed-particle-diameter layer is too small, the removal performance of weakly acidic components containing boron decreases, and in the case where the proportion of the mixed-particle-diameter layer is too large, the water pressure difference in the desalination chamber 23 becomes large. As described later, when the removal of weakly acidic components, particularly boron, is the object, a structure in which no large-particle-diameter layer is provided in the desalination chamber 23 can also be provided. In the present specification, the packed height of the ion exchange resin in the flow direction of the treated water in the large-particle-diameter layer, the mixed-particle-diameter layer, or the like is sometimes referred to as the packed height of the layer. The length of the desalination chamber 23 refers to the length of the desalination chamber 23 in the flow direction of the treated water, and refers to the length of the portion in which the ion exchange resin is provided in the desalination chamber 23.

[0043] The weakly acidic components in the treated water are adsorbed to the anion exchange resin that constitutes the mixed-particle-diameter layer by ion exchange, and move to the concentrated chamber 22 on the anode 11 side through the anion exchange membrane 32 as anions. The lower the concentration of anions in the concentrated chamber 22, the more easily the weakly acidic components move to the concentrated chamber 22, and thus it is preferable that the concentration of anions in the water flowing in the mixed-particle-diameter layer that is opposite to the desalination chamber 23 with the anion exchange membrane 32 interposed therebetween in the concentrated chamber 22 be low. Furthermore, as described above, in the desalination chamber 23, the mixed-particle-diameter layer is preferably provided at a position close to the outlet. Due to this, the flow of the outlet water in the desalination chamber 23 and the flow of the supply water supplied to the concentrated chamber 22 are preferably counterflow.

[0044] The mixing ratio of the large-particle-size ion exchange resin and the small-particle-size ion exchange resin in the mixed-particle-size layer is described. Even if the particle size is large, even if the particle size is small, since the ion exchange resins are in a bead shape or a granular shape, the apparent volume including the inter-particle voids can be measured. The apparent volume of the large-particle-size ion exchange resin before mixing is set to L, and the apparent volume of the small-particle-size ion exchange resin is set to S, and the mixing ratio L:S is preferably between 1:1 and 20:1, more preferably between 5:1 and 10:1. If the ratio of the large-particle-size ion exchange resin is too high, sufficient removal performance for weak acid components such as boron cannot be obtained, and if the ratio of the small-particle-size ion exchange resin is too high, the water passage pressure difference becomes large. In addition, even after the large-particle-size ion exchange resin and the small-particle-size ion exchange resin are mixed to form the mixed-particle-size layer, the mixing ratio of the large-particle-size ion exchange resin and the small-particle-size ion exchange resin can be calculated. For example, the mixed-particle-size layer is taken out from the desalination chamber 23, fractionated using a sieve, separated into ion exchange resins having a particle size of 0.1 mm or more and 0.4 mm or less and ion exchange resins having a particle size exceeding 0.4 mm, and the apparent volumes of each are measured, whereby the mixing ratio L:S can be calculated.

[0045] In Figure 1 the EDI device 10 shown in FIG. 1, the large-particle-size layer composed of anion exchange resins is disposed at the inlet side of the desalination chamber 23, and the mixed-particle-size layer composed of anion exchange resins is disposed at the outlet side of the desalination chamber 23. As described above, the disposition of the ion exchange resins in the desalination chamber 23 is not limited to the disposition shown in Figure 1 FIG. 1. Figures 2A to 2E Another example of the disposition of the ion exchange resins in the desalination chamber 23 is shown by extracting only the desalination chamber 23 and the ion exchange membranes on both sides thereof and drawing. In Figure 2A the example shown in FIG. 2, in the desalination chamber 23 in the EDI device 10 shown in FIG. 1, the large-particle-size layer is disposed at a smaller packing height in contact with the outlet side of the desalination chamber 23, and the mixed-particle-size layer is disposed sandwiched by the large-particle-size layer on the inlet side and the large-particle-size layer on the outlet side of the desalination chamber 23. In Figure 1 the example shown in FIG. 2, the packing height of the mixed-particle-size layer is about 36% of the length of the desalination chamber 23, and in addition, the packing height of the large-particle-size layer on the outlet side is about 14% of the length of the desalination chamber 23. Figure 2A

[0046] In order to remove ionic impurities as cations, not only the anion exchange resins but also the cation exchange resins (CER) can be packed in the desalination chamber 23. In Figure 2B ​In the example shown, in the desalination chamber 23, a large-particle-size layer composed of cation exchange resin, a large-particle-size layer composed of anion exchange resin, a large-particle-size layer composed of cation exchange resin, and a mixed-particle-size layer composed of anion exchange resin are arranged in this order from the inlet side thereof. In the figure, the large-particle-size layer composed of cation exchange resin is denoted as "L-CER". The filling heights of the respective layers are substantially the same. In the example shown, the desalination chamber 23 is configured to have a large-particle-size layer composed of cation exchange resin at the outlet side thereof. Figure 2B In the example shown, in order to promote the dissociation reaction of water on the cathode 12 side of the anion exchange resin, an anion exchange membrane 37 is arranged at the interface between the cation exchange membrane 33 and the anion exchange resin in the desalination chamber 23.

[0047] Figure 2C The desalination chamber 23 shown is configured to have a mixed-particle-size layer composed of cation exchange resin at the outlet side of the two large-particle-size layers composed of cation exchange resin. Figure 2B In the desalination chamber 23 shown, the large-particle-size layer composed of cation exchange resin at the outlet side of the two large-particle-size layers composed of cation exchange resin is replaced by a mixed-particle-size layer composed of cation exchange resin. The anion exchange membrane 37 arranged in contact with the cation exchange membrane 33 can also not be provided. In the figure, the mixed-particle-size layer composed of cation exchange resin is denoted as "L-S mixed CER". Figure 2D In the example shown, the desalination chamber 23 is configured to have a mixed-particle-size layer composed of anion exchange resin at the outlet side of the two large-particle-size layers composed of cation exchange resin. Figure 2E The structures shown are structures in which the anion exchange membrane 37 is removed from the structures shown. Figure 2B In the example shown, the desalination chamber 23 is configured to have a mixed-particle-size layer composed of anion exchange resin at the outlet side of the two large-particle-size layers composed of cation exchange resin. Figure 2C In the example shown, the desalination chamber 23 is configured to have a mixed-particle-size layer composed of anion exchange resin at the outlet side of the two large-particle-size layers composed of cation exchange resin.

[0048] [Second Embodiment]

[0049] In the EDI device based on the present application, it is possible to configure the desalination chamber itself to be divided into two small desalination chambers by an ion exchange membrane, to supply the water to be treated to one of the small desalination chambers, and to supply the water flowing out of one of the small desalination chambers to the other small desalination chamber. Deionized water is obtained from the other small desalination chamber as the treated water. Figure 3 The EDI device 10 of the second embodiment of the present application shown is configured to have a desalination chamber 23 in which a large-particle-size layer composed of cation exchange resin, a large-particle-size layer composed of anion exchange resin, a large-particle-size layer composed of cation exchange resin, and a mixed-particle-size layer composed of anion exchange resin are arranged in this order from the inlet side thereof. Figure 1The desalting chamber 23 in the EDI device 10 shown is divided into two small desalting chambers 26, 27 by the anion exchange membrane 36 as an intermediate ion exchange membrane, and the configuration of ion exchange resin within the desalting chamber is made different. The first small desalting chamber 26 is configured on the side closer to the anode 11 with the anion exchange membrane 36 interposed, and the second small desalting chamber 27 is configured on the side closer to the cathode 12. The water to be treated is supplied to the first small desalting chamber 26, and the outlet water from the first small desalting chamber 26 is supplied to the second small desalting chamber 27. The outlet water from the second small desalting chamber 27 is the treated water (i.e., the deionized water) from the EDI device 10. In the case where the desalting chamber is divided into the first small desalting chamber 26 on the inlet side and the second small desalting chamber 27 on the outlet side, the length of the desalting chamber refers to the sum of the length of the portion in which ion exchange resin is provided in the first small desalting chamber 26 and the length of the portion in which ion exchange resin is provided in the second small desalting chamber 27, along the flow direction of the water to be treated.

[0050] In Figure 3 In the EDI device 10 shown, the flow direction in the first small desalting chamber 26 and the flow direction in the second small desalting chamber 27 are opposite directions, i.e., countercurrent. In addition, the flow direction in the concentrating chamber 22 on the anode 11 side and the flow direction in the first small desalting chamber 26 adjacent thereto are the same, and the two are in parallel flow. The flow direction in the second small desalting chamber 27 on the outlet side of the desalting chamber and the flow direction in the concentrating chamber 24 adjacent thereto are in countercurrent. In the first small desalting chamber 26, an anion exchange resin is filled as a large-particle-size layer. In the second small desalting chamber 27, a cation exchange resin is filled on the inlet side thereof, and an anion exchange resin is filled on the outlet side thereof as a mixed-particle-size layer. The cation exchange resin is normally provided as a large-particle-size layer, but can also be provided as a mixed-particle-size layer. The position at which the mixed-particle-size layer of the anion exchange resin and the cation exchange resin in the second small desalting chamber 27 become boundaries is approximately half the length of the second small desalting chamber 27, in other words, a position of about 25% of the length of the desalting chamber measured from the outlet side of the desalting chamber. The interface at which the cation exchange membrane 33 and the anion exchange resin within the second small desalting chamber 27 meet is provided with an anion exchange membrane 37. The anion exchange membrane 37 can also not be provided, and the anion exchange resin within the second small desalting chamber 27 can be made to directly meet the cation exchange membrane 33. In Figure 3 In the EDI device 10 shown, the water to be treated also passes through the mixed-particle-size layer formed of anion exchange resin, and thus weak acid components such as boron can be efficiently removed. In addition, since there is at least a large-particle-size layer composed of anion exchange resin, the increase in the water passage pressure difference can be suppressed.

[0051] In the second embodiment in which the desalting chamber is divided into two small desalting chambers by an intermediate ion exchange membrane, the preferable mixing ratio of the ion exchange resin of large particle diameter and the ion exchange resin of small particle diameter in the mixed particle diameter layer, the preferable ratio of the sum of the filling heights of the mixed particle diameter layer with respect to the length of the desalting chamber are also the same as explained in the first embodiment. In the second embodiment, it is also preferable to arrange the mixed particle diameter layer at a position close to the outlet of the treated water of the entire desalting chamber, and it can be configured to include at least a part of the mixed particle diameter layer in a range from the outlet of the treated water to 25% of the length of the desalting chamber.

[0052] Figure 4 Another configuration example of the EDI device of the second embodiment is shown. Figure 4 The EDI device 10 shown is configured to include a desalting chamber 20, a treated water chamber 21, and a brine chamber 22. Figure 3 In the EDI device 10 shown, the anion exchange resin filled in the first small desalting chamber 26 is configured as a mixed particle diameter layer, and instead, the anion exchange resin filled in the second small desalting chamber 27 is configured as a large particle diameter layer.

[0053] Figure 5 Another configuration example of the EDI device of the second embodiment is shown. Figure 5 The EDI device 10 shown is configured to include a desalting chamber 20, a treated water chamber 21, and a brine chamber 22. Figure 3 In the EDI device 10 shown, the anion exchange resin filled in the first small desalting chamber 26 is configured as a mixed particle diameter layer. In the EDI device 10, the cation exchange resin filled in the second small desalting chamber 27 is configured as a large particle diameter layer.

[0054] Figure 6 Another configuration example of the EDI device of the second embodiment is shown. In the EDI device 10 shown, Figure 5 In the EDI device 10 shown, Figure 6The EDI device 10 shown uses resin in which a large-particle-size anion exchange resin and a small-particle-size and uniform-particle-size anion exchange resin are mixed as the anion exchange resin filled as a mixed-particle-size layer in the first small desalination chamber 26 and the second small desalination chamber 27. In the figure, the mixed-particle-size layer composed of anion exchange resin composed of an ion exchange resin using an ion of uniform particle size as a small-particle-size ion exchange resin is shown as "L-S (uniform) mixed AER". Uniform particle size means that the deviation in particle size among the particles of the ion exchange resin is small, for example, a uniformity coefficient of 1.2 or less. The uniformity coefficient is the ratio of the mesh corresponding to 40% to the effective diameter when the mesh corresponding to 90% is taken as the effective diameter, by measuring the size of the particles of the ion exchange resin by sieving and plotting the state of normal distribution as a straight line in a log probability graph. As the unit of the mesh, millimeters (mm) are used. The theoretical minimum value of the uniformity coefficient is 1, and the closer it is to 1, the more uniform the particle size. As will be understood from the examples described later, by using an ion exchange resin of uniform particle size as a small-particle-size anion exchange resin in the mixed-particle-size layer, the removal rate of weak acid components is improved.

[0055] [Third Embodiment]

[0056] Figure 7 The structure of the EDI device 10 of the third embodiment of the present application is shown. Figure 7 The EDI device 10 shown is suitable for use when removing boron from treated water containing boron. The concentration of boron in the treated water is, for example, 1 ppb or more and 100 ppb or less. Figure 7 The EDI device 10 shown is the same as the EDI device 10 shown in Figure 1 The EDI device 10 shown is the same as the EDI device 10 shown in Figure 1 Further, in the mixed-particle-size layer filled in the desalination chamber 23, the large-particle-size anion exchange resin and the small-particle-size anion exchange resin are mixed at a mixing ratio L:S in the range of 1:1 to 20:1.

[0057] Next, the EDI device 10 of the fourth embodiment of the present application is described. Figure 7The production of deionized water by the EDI device 10 will be described. As in the case of the EDI device 10 of the first and second embodiments, feed water is supplied to the concentrating chambers 22, 24, the cathode chamber 25, and the anode chamber 21, and treated water containing boron is supplied to the desalting chamber 23 under the condition that a direct current voltage is applied between the anode 11 and the cathode 12. Thus, deionization in which the ion components in the treated water are adsorbed by the ion exchange resin in the desalting chamber 23 is performed, and deionized water flows out of the desalting chamber 23 as treated water. At this time, boron contained in the treated water is also removed. In the case where only a large-particle-size anion exchange resin is used, it is difficult to efficiently perform the adsorption and removal of boron, but in the EDI device 10 of the present embodiment, the mixed-particle-size layer including the small-particle-size anion exchange resin is provided in the desalting chamber 23, and boron in the treated water is efficiently adsorbed by the small-particle-size anion exchange resin in the mixed-particle-size layer and removed from the treated water. As a result, treated water containing almost no boron flows out of the desalting chamber 23. Boron can also be removed when only a small-particle-size anion exchange resin is packed in the desalting chamber 23, but in this case, the water supply pressure difference in the desalting chamber 23 greatly increases, as will be understood from the examples described later. In the present embodiment, by packing the anion exchange resin in the desalting chamber 23 as a mixed-particle-size layer in which a large-particle-size anion exchange resin and a small-particle-size anion exchange resin are mixed, it is possible to increase the removal efficiency of boron while suppressing an increase in the water supply pressure difference in the desalting chamber 23.

[0058] The EDI device based on the present application has been described above, and the EDI device can be used, for example, when producing pure water or ultrapure water from raw water. Figure 8 is a flowchart showing the structure of a pure water production system using the EDI device 10 described above. In this figure, the electrodes and the ion exchange membranes are not depicted. Further, this figure depicts the EDI device 10 of the first or third embodiment as the EDI device 10, but the EDI device 10 of the second embodiment can also be used. A reverse osmosis (RO) membrane device 40 that supplies raw water is provided, and a reverse osmosis membrane 41 is provided inside the reverse osmosis membrane device 40. Water that does not pass through the reverse osmosis membrane 41 in the reverse osmosis membrane device 40, that is, RO concentrated water contains a large amount of impurities, and the RO concentrated water is blown to the outside. Water that passes through the reverse osmosis membrane 41 in the reverse osmosis membrane device 40, that is, RO permeated water is water that contains relatively few impurities, and is supplied to the desalting chamber (D) 23 of the EDI device 10 as treated water. A part of the RO permeated water is supplied to the concentrating chambers (C) 22, 24 and the cathode chamber (K) 25 as feed water for the concentrating chambers and feed water for the electrode chambers. Water discharged from the cathode chamber 25 is then supplied to the anode chamber (A) 21. Electrode water discharged from the anode chamber 21 is blown to the outside, and concentrated water discharged from the concentrating chambers 22, 24 is also blown to the outside.

[0059] The anode provided in the anode chamber 21Figure 8 (not shown in the figure) and the cathode (located in the cathode chamber 25) Figure 8 A DC voltage is applied between the RO permeate and the desalination chamber 23 (not shown in the diagram), and the RO permeate is supplied as the treated water. Desalination is then performed in the desalination chamber 23, and pure water, i.e., deionized water, flows out of the desalination chamber 23. Weak acidic components in the raw water, especially boron, easily permeate through the reverse osmosis membrane 41 and are contained in the RO permeate. In cases where an EDI device is installed downstream of the reverse osmosis membrane unit to remove boron, the boron removal performance in conventional EDI devices is insufficient. Therefore, sometimes two EDI devices are connected. However, by using the EDI device 10 of the above embodiments, only one EDI device 10 is needed downstream of the reverse osmosis membrane unit 40 to sufficiently remove boron from the treated water.

[0060] As explained above, according to the EDI device based on the present invention, by arranging a mixed particle size layer of ion exchange resin containing large and small particle sizes in the desalination chamber, the removal rate of weak acid components, represented by boron, can be improved, resulting in pure water and ultrapure water with higher water quality. The improved removal rate of weak acid components in the EDI device is related to the miniaturization of components such as reverse osmosis membrane devices installed upstream of the EDI device, and sometimes to the miniaturization of components such as ion exchange devices installed downstream of the EDI device.

[0061] Example

[0062] The present invention will now be described in more detail using examples and comparative examples. In the following description, the mixing ratio of large-particle-size ion exchange resin and small-particle-size ion exchange resin to form a mixed particle size layer is expressed as L:S. L is the apparent volume of the large-particle-size ion exchange resin before mixing, and S is the apparent volume of the small-particle-size ion exchange resin before mixing.

[0063] [Example 1]

[0064] As an example of the EDI device in Embodiment 1, it is assembled with Figure 7The EDI device 10 shown. In Example 1, it was confirmed that by providing the anion exchange resin arranged in the desalination chamber as a mixed particle size layer, the removal rate of boron as a weak acid component became higher compared to the case where the anion exchange resin as a large particle size layer was used. The anode chamber 21, the concentration chambers 22, 24, the desalination chamber 23, and the cathode chamber 25 each used a frame-shaped unit having an opening of 10 cm x 10 cm in size and a thickness of 1 cm. Ion exchange resin was filled in the units of each chamber, and these units were stacked in the thickness direction with an ion exchange membrane interposed therebetween, thereby constituting the EDI device. As the cation exchange resin (CER), AMBERJET (registered trademark) 1020 manufactured by DuPont was used and filled in the anode chamber 21. The particle size of this cation exchange resin was 0.60 to 0.70 mm, and the uniformity coefficient was 1.20 or less. As the large particle size anion exchange resin (AER), AMBERJET (registered trademark) 4002 manufactured by DuPont was used. The particle size of this large particle size anion exchange resin was 0.50 to 0.65 mm, and the uniformity coefficient was 1.20 or less. As the small particle size anion exchange resin, DOWEX (registered trademark) 1 x 4 50-100 mesh anion exchange resin manufactured by DuPont was used. The particle size of this small particle size anion exchange resin was 0.15 to 0.3 mm, and the uniformity coefficient was 1.3 or less. The large particle size anion exchange resin and the small particle size anion exchange resin were mixed at a mixed ratio L:S of 10:1 and filled in the desalination chamber 23 as a mixed particle size layer. In the concentration chambers 22, 24, and the cathode chamber 25, the above-described large particle size anion exchange resin was also filled.

[0065] As the treated water to be supplied to the desalination chamber 23, treated water in which boric acid was added so as to have a boron concentration of 50 ppb in permeated water obtained by causing raw water to permeate a two-stage reverse osmosis membrane device was used. The conductivity of this treated water was 0.3 to 0.4 μS / cm. The treated water was supplied to the desalination chamber 23 at a flow rate of 30 L / h, the permeated water obtained by causing raw water to permeate a two-stage reverse osmosis membrane device was supplied to each of the concentration chambers 22, 24 at a flow rate of 10 L / h, and the cathode chamber 25 was supplied at 5 L / h. A direct current voltage was applied at a current of 0.5 A between the anode 11 and the cathode 12, and the EDI device was operated. Furthermore, the boron concentration in the outlet water of the desalination chamber 23, that is, the treated water was measured, and the boron removal rate of the EDI device was calculated to be 96.2%.

[0066] [Comparative Example 1]

[0067] As the EDI device of Comparative Example 1, an EDI device 10 shown in FIG. 1 was assembled. Figure 9 The EDI device 10 shown. Figure 9The EDI device shown is an embodiment of the EDI device in Example 1, where the entire anion exchange resin filling the desalination chamber 23 is used as a large-particle layer. The units used, the cation exchange resin used, and the large-particle anion exchange resin are all the same as in Example 1. For the completed EDI device, water was passed through under the same conditions as in Example 1, a DC voltage was applied, and the boron concentration in the treated water was measured. Based on this measurement, the boron removal rate of the EDI device was determined to be 95%.

[0068] As can be seen from the results of Example 1 and Comparative Example 1, by setting the anion exchange resin filling the salt chamber 23 as a mixed particle size layer, the boron removal rate is improved.

[0069] [Example 2-1]

[0070] The above were assembled Figure 3 The EDI device 10 shown is constructed by stacking the frame-shaped units used in Example 1 in the anode chamber 21, concentration chambers 22 and 24, cathode chamber 25, first small desalination chamber 26, and second small desalination chamber 27, in the same manner as in Example 1. The same substances used in Example 1 are used as the cation exchange resin (CER), large-particle-size anion exchange resin (AER), and small-particle-size anion exchange resin. Large-particle-size anion exchange resin is also filled in the concentration chambers 22 and 24 and the cathode chamber 25, and cation exchange resin is also filled in the anode chamber 21. Large-particle-size anion exchange resin and small-particle-size anion exchange resin are mixed at a mixing ratio of 10:1 and filled as a mixed particle size layer on the outlet side of the second small desalination chamber 27.

[0071] The treated water supplied to the first small desalination chamber 26 is the treated water obtained by passing raw water through a two-stage reverse osmosis membrane system, after adding boric acid to the permeate at a boron concentration of 50 ppb. The conductivity of this treated water is 0.3–0.4 μS / cm. The treated water is passed into the desalination chamber 23 at a flow rate of 30 L / h. Furthermore, the permeate obtained by passing raw water through a two-stage reverse osmosis membrane system is used as supply water, flowing into each of the concentration chambers 22 and 24 at a flow rate of 10 L / h, and supplied to the cathode chamber 25 at a flow rate of 5 L / h. A DC voltage of 0.5 A is applied between the anode 11 and the cathode 12 to operate the EDI device. The boron concentration in the outlet water (treated water) of the second small desalination chamber 27 is measured. Furthermore, the pressure of the treated water at the inlet of the first small desalination chamber 26 and the pressure of the treated water at the outlet of the second small desalination chamber 27 are measured, and the difference is calculated to determine the pressure difference. The results are shown in Table 1.

[0072] [Example 2-2]

[0073] As the EDI device of Example 2-2, the EDI device 10 shown in FIG. 2 was assembled. Specifically, the same units as those of Example 2-1 were used, and the EDI device of Example 2-2 was assembled by filling the anion exchange resin as a mixed particle size layer in the first small desalination chamber 26. In this EDI device, the same substances as those used in Example 2-1 were used as the anion exchange resin and the cation exchange resin of large particle size and small particle size. The mixing ratio of the anion exchange resin of large particle size and the anion exchange resin of small particle size in the mixed particle size layer was also the same as that of Example 2-1. Also, the EDI device was operated in the same manner as Example 2-1, and the removal rate of boron and the water passage pressure difference were found. The results are shown in Table 1. Figure 4

[0074] [Example 2-3]

[0075] As the EDI device of Example 2-3, the EDI device 10 shown in FIG. 2 was assembled. Specifically, the same units as those of Example 2-1 were used, and the EDI device of Example 2-3 was assembled by filling the anion exchange resin as a mixed particle size layer in the first small desalination chamber 26. In this EDI device, the same substances as those used in Example 2-1 were used as the anion exchange resin and the cation exchange resin of large particle size and small particle size. The mixing ratio of the anion exchange resin of large particle size and the anion exchange resin of small particle size in the mixed particle size layer was also the same as that of Example 2-1. Also, the EDI device was operated in the same manner as Example 2-1, and the removal rate of boron and the water passage pressure difference were found. The results are shown in Table 1. Figure 5

[0076] [Example 2-4]

[0077] As the EDI device of Example 2-4, the EDI device 10 shown in FIG. 2 was assembled. Specifically, the same units as those of Example 2-1 were used, and the EDI device of Example 2-4 was assembled by filling the anion exchange resin as a mixed particle size layer in the first small desalination chamber 26. In this EDI device, the same substances as those used in Example 2-1 were used as the anion exchange resin and the cation exchange resin of large particle size and small particle size. The mixing ratio of the anion exchange resin of large particle size and the anion exchange resin of small particle size in the mixed particle size layer was also the same as that of Example 2-1. Also, the EDI device was operated in the same manner as Example 2-1, and the removal rate of boron and the water passage pressure difference were found. The results are shown in Table 1. Figure 6 ​​The EDI device 10 shown in Example 2-4 was the same as that of Example 2-3, but differed from that of Example 2-3 in that the EDI device of Example 2-4 used a resin having the same particle diameter as the small-particle-diameter anion exchange resin used in the mixed-particle-diameter layer composed of the anion exchange resin filled in the first and second small desalination chambers 26 and 27. Specifically, the DOWEX (registered trademark) 1 x 4 50-100 mesh anion exchange resin manufactured by DuPont Company having a particle diameter of 0.15 to 0.3 mm and a uniformity coefficient of 1.3 or less was separated by a sieve to thereby take out only the particles having a particle diameter of about 0.3 mm. Further, the taken-out particles were used as the small-particle-diameter and uniform-particle-diameter anion exchange resin constituting the mixed-particle-diameter layer. At this time, the uniformity coefficient of the small-particle-diameter anion exchange resin constituting the mixed-particle-diameter layer was 1.15. In addition, the mixing ratio L:S of the large-particle-diameter anion exchange resin and the small-particle-diameter anion exchange resin in the mixed-particle-diameter layer was set to 5:1. Further, the EDI device was operated in the same manner as in Example 2-1, and the removal rate of boron and the water passage pressure difference were calculated. The results are shown in Table 1.

[0078] [Comparative Example 2]

[0079] As the EDI device of Comparative Example 2, an EDI device was assembled in which Figure 10 The EDI device 10 shown in Example 2-4 was the same as that of Example 2-3, but differed from that of Example 2-3 in that the EDI device of Example 2-4 used a resin having the same particle diameter as the small-particle-diameter anion exchange resin used in the mixed-particle-diameter layer composed of the anion exchange resin filled in the first and second small desalination chambers 26 and 27. Specifically, the DOWEX (registered trademark) 1 x 4 50-100 mesh anion exchange resin manufactured by DuPont Company having a particle diameter of 0.15 to 0.3 mm and a uniformity coefficient of 1.3 or less was separated by a sieve to thereby take out only the particles having a particle diameter of about 0.3 mm. Further, the taken-out particles were used as the small-particle-diameter and uniform-particle-diameter anion exchange resin constituting the mixed-particle-diameter layer. At this time, the uniformity coefficient of the small-particle-diameter anion exchange resin constituting the mixed-particle-diameter layer was 1.15. In addition, the mixing ratio L:S of the large-particle-diameter anion exchange resin and the small-particle-diameter anion exchange resin in the mixed-particle-diameter layer was set to 5:1. Further, the EDI device was operated in the same manner as in Example 2-1, and the removal rate of boron and the water passage pressure difference were calculated. The results are shown in Table 1.

[0080] [Table 1]

[0081]

[0082] As shown in Table 1, by providing the mixed particle size layer in which the small particle size anion exchange resin is mixed in the large particle size anion exchange resin in the EDI device, the boron removal performance is improved. By using the uniform particle size anion exchange resin as the small particle size anion exchange resin contained in the mixed particle size layer, the boron removal rate is further improved. Further, by providing the mixed particle size layer at the outlet side in the flow of the treated water in the desalting chamber, in the example shown herein, by providing the mixed particle size layer in the second small desalting chamber, the boron removal performance is further improved. It is known that in the case where the small particle size ion exchange resin is mixed in the large particle size ion exchange resin, there is a concern that the water passage pressure difference rises, but when the ratio of the large particle size anion exchange resin is high in the mixed ratio L:S of the large particle size anion exchange resin and the small particle size anion exchange resin is 5:1 or more, the water passage pressure difference hardly changes compared to the case where only the large particle size anion exchange resin is used, and the increase in the water passage pressure difference can be suppressed. As shown in Table 1, by providing the mixed particle size layer of the anion exchange resin from the region of 25% of the length of the desalting chamber from the outlet side of the desalting chamber, it is possible to achieve the improvement in the boron removal performance while suppressing the increase in the water passage pressure difference.

[0083] [Example 3]

[0084] An increase in water permeation pressure difference caused by providing a mixed particle size layer mixing a large particle size ion exchange resin and a small particle size ion exchange resin was investigated. A cylindrical column having a diameter of 5 cm and a length of 5 cm was prepared, and for this column, permeated water obtained by permeating raw water through a two-stage reverse osmosis membrane device was flowed at each flow rate of 100, 140, 210, and 250 L / h. The pressure at the inlet and the pressure at the outlet of the column at this time were found, and the difference thereof was taken as the water permeation pressure difference when the column was in a blank state. Next, the same column was filled with a cation exchange resin, and the permeated water was permeated at the same flow rate as in the blank state, and similarly, the pressure at the inlet and the pressure at the outlet were found, and the water permeation pressure difference was found. At this time, a large particle size cation exchange resin and a small particle size cation exchange resin were prepared as the cation exchange resin, and they were filled into the column alone or mixed. As the large particle size cation exchange resin, AMBERJET (registered trademark) 4002 manufactured by DuPont was used. The particle size of this large particle size cation exchange resin was 0.5 to 0.65 mm, and the uniformity coefficient was 1.20 or less. In addition, as the small particle size cation exchange resin, DOWEX (registered trademark) 1 x 4 50-100 mesh cation exchange resin manufactured by DuPont was used. The particle size of this small particle size cation exchange resin was 0.15 to 0.3 mm, and the uniformity coefficient was 1.3 or less. The mixing ratio L:S of the large particle size cation exchange resin and the small particle size cation exchange resin in the cation exchange resin filled in the column was 0:1, 1:1, 5:1, 10:1, 20:1, and 1:0. L:S = 0:1 indicates that only the small particle size cation exchange resin was used, and L:S = 1:0 indicates that only the large particle size cation exchange resin was used.

[0085] From the water permeation pressure difference of the column filled with the cation exchange resin, the water permeation pressure difference in the blank state was subtracted, the water permeation pressure difference formed only by the cation exchange resin was calculated for each water permeation flow rate in the column and the mixing ratio in the cation exchange resin filled in the column, and a comparison was made. Furthermore, in order to simulate a desalination chamber of an EDI device composed of a cell having a thickness of 9 mm, a width of 160 mm, and a height of 280 mm, only the water permeation pressure difference of the cation exchange resin obtained by the column was converted by calculation to the water permeation pressure difference of only the cation exchange resin in the cell. The results are shown in Figure 11 In Figure 11 , the water permeation pressure difference is represented by a relative value, and 1 in the relative value is a reference value indicating a value of the water permeation pressure difference generally allowed in an EDI. In Figure 11 , the horizontal axis is the linear flow rate LV of the permeated water.

[0086] From Figure 11It is known that the more the anion exchange resin having a large particle diameter is contained, the smaller the water permeation pressure difference becomes. If the mixing ratio L:S is in the range from 1:0 to 5:1, even at the linear flow rate of 127 m / h, the increase in the water permeation pressure difference converges within a practical range. If the linear flow rate is 90 m / h, even when the mixing ratio L:S is 1:1, the increase in the water permeation pressure difference can be converged within a practical range.

[0087] [Example 4]

[0088] As in Example 3, the increase in the water permeation pressure difference caused by providing a mixed particle diameter layer in which the anion exchange resin having a large particle diameter and the anion exchange resin having a small particle diameter are mixed was investigated. However, in Example 4, as the anion exchange resin having a small particle diameter, an anion exchange resin having a uniform particle diameter was used. The same cylindrical column as that used in Example 3 was used, and as in Example 3, the water permeation pressure difference in the empty state and the water permeation pressure difference when the anion exchange resin was filled were found. As the anion exchange resin having a large particle diameter, the same substance as that used in Example 2 was used. Further, the DOWEX (registered trademark) 1 x 4 50-100 mesh anion exchange resin manufactured by DuPont Company having a particle diameter of 0.15 to 0.3 mm and a uniformity coefficient of 1.3 or less was separated by sieving, and thus only the particles having a particle diameter of about 0.3 mm were taken out. Further, the taken-out particles were used as the anion exchange resin having a small particle diameter and a uniform particle diameter constituting the mixed particle diameter layer. At this time, the uniformity coefficient of the anion exchange resin having a small particle diameter constituting the mixed particle diameter layer was 1.15. The mixing ratio L:S of the substance having a large particle diameter and the substance having a small particle diameter in the anion exchange resin filled in the column was 0:1, 1:1, 5:1, 10:1, 20:1, and 1:0.

[0089] From the water permeation pressure difference of the column filled with the anion exchange resin, the water permeation pressure difference in the empty state was subtracted, the water permeation pressure difference formed only by the anion exchange resin was calculated, and a comparison was made, for each water permeation flow rate in the column, and for the mixing ratio in the anion exchange resin filled in the column. Further, in order to simulate the desalination chamber of the EDI device constituted by a unit having a thickness of 9 mm, a width of 160 mm, and a height of 280 mm, only the water permeation pressure difference of the anion exchange resin formed by the column was converted into the water permeation pressure difference of only the anion exchange resin in the unit by calculation. The results are shown in Figure 12 In Figure 12 , the water permeation pressure difference is represented by a relative value, and 1 in the relative value is a reference value indicating a value of the water permeation pressure difference generally allowed in the EDI. In Figure 12 , the horizontal axis is the linear flow rate LV of the permeated water.

[0090] From Figure 12It is understood that further reduction of the water passage pressure difference can be achieved by using a substance having a uniform particle diameter as the small-particle-diameter ion exchange resin that constitutes the mixed particle diameter layer. In particular, it is understood that the uniformity coefficient of the small-particle-diameter ion exchange resin is preferably 1 or greater and 1.2 or less, and more preferably 1 or greater and 1.15 or less. If the linear flow rate is 100 m / h, the water passage pressure difference can be kept within a practical range even if the mixing ratio L:S is 1:1.

[0091] BRIEF DESCRIPTION OF DRAWINGS

[0092] 10 EDI device

[0093] 11 anode

[0094] 12 cathode

[0095] 21 anode chamber

[0096] 22, 24 concentration chamber

[0097] 23 desalination chamber

[0098] 25 cathode chamber

[0099] 26, 27 small desalination chamber

[0100] 31, 33 cation exchange membrane (CEM)

[0101] 32, 34, 36, 37 anion exchange membrane (AEM)

[0102] 40 reverse osmosis membrane device

[0103] 41 reverse osmosis membrane

Claims

1. An electro-deionized water manufacturing apparatus, comprising a desalination chamber separated by a pair of ion exchange membranes between an anode and a cathode, and said desalination chamber being filled with ion exchange resin, characterized in that... Particle sizes between 0.1 mm and 0.4 mm are defined as small particle sizes, and particle sizes exceeding 0.4 mm are defined as large particle sizes. In the desalination chamber, a large-particle-size layer composed of large-particle-size ion exchange resin and a mixed-particle-size layer composed of large-particle-size ion exchange resin and small-particle-size ion exchange resin are arranged along the flow direction of the water to be treated in the desalination chamber. The mixed particle size layer disposed in the desalination chamber comprises a mixed particle size layer of anion exchange resin composed of a mixture of large-particle-size anion exchange resin and small-particle-size anion exchange resin.

2. The electro-deionized water manufacturing apparatus according to claim 1, wherein, The large-particle-size layer disposed in the desalination chamber comprises a large-particle-size layer of anion exchange resin with large particle size.

3. The electro-deionized water manufacturing apparatus according to claim 1 or 2, wherein, The desalination chamber contains at least a portion of the mixed particle size layer within a range of 25% of the length of the desalination chamber from the outlet of the treated water to the direction of flow of the treated water.

4. The electro-deionized water manufacturing apparatus according to claim 1 or 2, wherein, At least one of the large particle size layers is disposed upstream of the mixed particle size layer along the flow direction of the water being treated.

5. The electro-deionized water manufacturing apparatus according to claim 1 or 2, wherein, The total filling height of the ion exchange resin along the flow direction of the treated water in the mixed particle size layer is more than 20% and less than 80% of the length of the desalination chamber along the flow direction of the treated water.

6. The electro-deionized water manufacturing apparatus according to claim 1 or 2, wherein, The apparent volume of the large-particle-size ion exchange resin is set as L, and the apparent volume of the small-particle-size ion exchange resin is set as S. In the mixed particle size layer, the large-particle-size ion exchange resin and the small-particle-size ion exchange resin are mixed in a mixing ratio of L:S in the range of 1:1 to 20:

1.

7. An electro-deionized water manufacturing apparatus, comprising a desalination chamber separated by a pair of ion exchange membranes between an anode and a cathode, and said desalination chamber being filled with ion exchange resin, characterized in that... Particle sizes between 0.1 mm and 0.4 mm are defined as small particle sizes, and particle sizes exceeding 0.4 mm are defined as large particle sizes. The apparent volume of the large-particle-size anion exchange resin is defined as L, and the apparent volume of the small-particle-size anion exchange resin is defined as S. A mixed particle size layer containing the large-particle-size anion exchange resin and the small-particle-size anion exchange resin is prepared in the desalination chamber at a mixing ratio of L:S ranging from 1:1 to 20:

1. Boron-containing treated water is supplied to the desalination chamber to remove boron from the treated water.

8. The electro-deionized water manufacturing apparatus according to claim 1 or 7, wherein, The desalination chamber has an intermediate ion exchange membrane located between the pair of ion exchange membranes and is divided into a first small desalination chamber and a second small desalination chamber by the intermediate ion exchange membrane. The first small desalination chamber is in communication with the second small desalination chamber so that the water to be treated is supplied to one of the first and second small desalination chambers and the water flowing out of the first small desalination chamber flows into the other small desalination chamber.

9. The electro-deionized water manufacturing apparatus according to claim 8, wherein, An anion exchange resin is filled in the small desalination chamber near the anode in the first and second small desalination chambers, and a portion of the small desalination chamber near the cathode in the first and second small desalination chambers is filled with a cation exchange resin.

10. A method for producing deionized water, comprising applying a direct current voltage between an anode and a cathode while passing water to be treated through a desalination chamber disposed between the anode and the cathode and divided by a pair of ion exchange membranes, thereby obtaining deionized water, characterized in that... Particle sizes between 0.1 mm and 0.4 mm are defined as small particle sizes, and particle sizes exceeding 0.4 mm are defined as large particle sizes. In the desalination chamber, the water to be treated is passed through both a large-particle layer composed of large-particle-size ion exchange resins and a mixed-particle-size layer composed of large-particle-size and small-particle-size ion exchange resins. The mixed particle size layer disposed in the desalination chamber comprises a mixed particle size layer of anion exchange resin composed of a mixture of large-particle-size anion exchange resin and small-particle-size anion exchange resin.

11. The method for producing deionized water according to claim 10, wherein, The treated water is passed through at least one of the large-particle-size layer composed of anion exchange resin and the mixed-particle-size layer composed of anion exchange resin.

12. A method for producing deionized water, comprising applying a direct current voltage between an anode and a cathode while passing boron-containing water to be treated through a desalination chamber disposed between the anode and the cathode and divided by a pair of ion exchange membranes, thereby obtaining deionized water, characterized in that... Particle sizes between 0.1 mm and 0.4 mm are defined as small particle sizes, and particle sizes exceeding 0.4 mm are defined as large particle sizes. In the desalination chamber, the apparent volume of the large-particle-size anion exchange resin is set as L, and the apparent volume of the small-particle-size anion exchange resin is set as S. The water to be treated is passed through a mixed particle size layer containing the large-particle-size anion exchange resin and the small-particle-size anion exchange resin in a mixing ratio of L:S ranging from 1:1 to 20:1, thereby removing boron from the water to be treated.

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