JP2009208046A - Apparatus for producing electrodeionization water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EDI which can produce deionized water with reduced electric power consumption and a stable voltage, and can provide high water quality stably. <P>SOLUTION: The EDI includes a desalting chamber 40 defined by a space which is partitioned by a cation exchange membrane 32 on one side and an anion exchange membrane 36 on the other side, and which is filled with an ion exchange material. The desalting chamber 40 includes small desalting chambers 42 and 44 which are formed by partitioning the desalting chamber 40 in the thickness direction into a plurality of stages with an intermediate ion exchange membrane 34 disposed between the cation exchange membrane 32 and the anion exchange membrane 36. A concentrating chamber 22 is installed on each side of the desalting chamber 40 via the cation exchange membrane 32 or the anion exchange membrane 36 disposed inbetween. The desalting chamber 40 and the concentrating chamber 22 are disposed between an anode chamber 18 equipped with an anode 16 and a cathode chamber 14 equipped with a cathode 12. The flow directions of to-be-treated water in the small desalting chambers 42 and 44, adjacent to each other with the intermediate ion exchange membrane 34 disposed inbetween, are opposite to each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric deionized water production apparatus.

As a method for producing deionized water, a method for deionizing by passing water to be treated through an ion exchange resin is conventionally known. However, in this method, when the ion exchange resin is saturated, it is necessary to regenerate with a drug. In recent years, in order to eliminate such disadvantages in processing operation, an electric deionization apparatus (hereinafter referred to as EDI) that does not require regeneration with a drug has been put into practical use.
EDI is a pure water production apparatus that combines electrophoresis and electrodialysis. EDI is an apparatus in which an ion exchanger is filled between an anion exchange membrane and a cation exchange membrane, and an anode electrode and a cathode electrode are arranged outside the ion exchange membrane. In the method of producing deionized water by EDI, by passing water to be treated through the ion exchanger layer with a DC voltage applied to the electrodes, ion components in the water to be treated are adsorbed by the ion exchanger, Ions are migrated to the membrane surface by electrophoresis and electrodialyzed through an ion exchange membrane to be removed into concentrated water.

Conventionally, various attempts have been made to reduce the electrical resistance of EDI in order to remove impurity ions in water to be treated with power saving using EDI. For example, a method of reducing an electrical resistance in a concentration chamber by adding an electrolyte to concentrated water is disclosed (for example, Patent Document 1). In addition, the method of reducing the electrical resistance of the concentrating chamber by promoting the increase of conductivity by circulating the concentrated water, and drastically improving the EDI structure, the number of concentrating chambers per desalting chamber A method for reducing the electrical resistance of EDI significantly by halving is disclosed (for example, Patent Document 2).
Furthermore, EDI which suppresses the production | generation of the scale in a concentration chamber by filling an ion exchanger in a concentration chamber is disclosed (for example, patent document 3), and the ionic component contained in the to-be-processed water supplied to EDI The allowable range of the concentration (ion load) tends to increase.
Japanese Patent No. 3644759 Japanese Patent No. 3385553 JP 2004-358440 A

However, as the ion load of the water to be treated increases, there is a problem that the operating voltage increases with time in constant current operation. A significant increase in operating voltage may exceed the capacity of the EDI power supply at an early stage, resulting in a decrease in current. In this case, constant current operation cannot be performed, resulting in an early decrease in water quality or early replacement of the deionization module. There was a problem that it was necessary. In addition, further improvement in water quality and stability have been demanded.
The present invention is directed to EDI capable of producing deionized water with low power consumption and stable voltage. Furthermore, it aims at EDI which can obtain high water quality stably.

The present inventors diligently studied the cause of the voltage increase in the conventional EDI. As a result, it was found that if the production of deionized water is continued, the current density becomes non-uniform due to the formation of an ion adsorption zone, which leads to an increase in the operating voltage of EDI. For this phenomenon, an intermediate ion exchange membrane is arranged between the anion exchange membrane and the cation exchange membrane, and a plurality of small desalting chambers are formed in the desalting chamber. ) Will be described below as an example.
FIG. 8 is a schematic diagram showing the direction of current flow in a conventional EDI deionization module 230. As shown in FIG. 8, the deionization module 230 has a cation exchange membrane 232 arranged on the cathode side, an anion exchange membrane 236 arranged on the anode side, and the cation exchange membrane 232 and the anion exchange membrane 236 formed facing each other. The space thus formed is filled with an ion exchanger, and a desalting chamber 240 is formed. An intermediate ion exchange membrane 234 is arranged between the cation exchange membrane 232 and the anion exchange membrane 236, the desalting chamber 240 is divided into two, and a small desalting chamber 242 and a small desalting chamber 244 are formed. Yes.
In the production of deionized water, the water to be treated is circulated to the small desalting chamber 244 in the flow direction a1, during which the anion component is mainly removed. Moreover, the to-be-processed water distribute | circulates the small desalination chamber 242 by the flow direction a2, and during this time, a cation component is mainly removed.

Here, the removal of ionic components in the water to be treated is mainly performed on the upstream side of the desalting chamber. Therefore, in the deionization module 230, the ion component is removed mainly on the upstream side of the small desalting chambers 242, 244. If the production of deionized water is continued, the ion exchangers in each small desalting chamber will not gradually exhibit the ion exchange function from the upstream side, and ion adsorption zones 243b and 245b, which are layers in which ion exchange is difficult to be performed, are formed. Is done. As time passes, the ion adsorption zones 243b and 245b expand from the upstream side toward the downstream side. In the conventional EDI, since the flow direction of the water to be treated in the small desalting chambers 242 and 244 is the same, as shown in FIG. 8, ion adsorption zones 243b and 245b are formed when viewed from the current flow direction. There will be an upstream region and downstream regions 243a, 245a where no ion adsorption zone is formed. Since the current flows in the flow directions e1 to e6 while avoiding the ion adsorption bands 243b and 245b having a large electric resistance, the current density is concentrated in the downstream region and becomes non-uniform, and the energization area is reduced. The reduction of the energization area causes a decrease in current efficiency with respect to ionic components in the water to be treated in the desalination chamber 240, which contributes to an increase in operating voltage.
The present invention has been made based on the above findings.

  That is, the EDI of the present invention is provided with a desalination chamber filled with an ion exchanger in a space defined by a cation exchange membrane on one side and an anion exchange membrane on the other side. The intermediate ion exchange membrane disposed between the cation exchange membrane and the anion exchange membrane forms small desalting chambers that are partitioned in multiple stages in the thickness direction of the desalting chamber, and the cation exchange membrane and the anion exchange membrane A concentration chamber is provided on both sides of the desalting chamber through a membrane, and the desalting chamber and the concentration chamber are disposed between an anode chamber having an anode and a cathode chamber having a cathode, The flow direction of the water to be treated in each of the small desalting chambers adjacent via the intermediate ion exchange membrane is countercurrent.

In the EDI of the present invention, the concentration chamber is preferably filled with an ion exchanger, and the concentration chamber has an anion exchanger layer filled with the anion exchanger in contact with the anion exchange membrane. Is preferred.
The EDI of the present invention is preferably controlled so that the water to be treated flows from an arbitrary small desalting chamber to another small desalting chamber.
In the EDI of the present invention, two or more desalting chambers are arranged between the anode chamber and the cathode chamber via the concentration chamber, and an anion exchange membrane and an intermediate ion exchange membrane in any desalting chamber And a small desalting chamber formed by partitioning with an anion exchange membrane and an intermediate ion exchange membrane in another desalting chamber adjacent via the concentration chamber. A small desalting chamber formed by partitioning a cation exchange membrane and an intermediate ion exchange membrane in an arbitrary desalting chamber, and a concentration chamber. The flow direction of the water to be treated may be countercurrent in the small desalting chamber formed by partitioning the cation exchange membrane and the intermediate ion exchange membrane in another desalting chamber adjacent to each other.
In the EDI of the present invention, the flow direction of the concentrated water in the concentrating chamber is a counter-current in the flow direction of the water to be treated in the small desalting chamber at a later stage in the small desalting chamber adjacent to the concentrating chamber. It is preferable.
In the EDI of the present invention, the ion exchanger filled in the small desalting chamber formed by partitioning the anion exchange membrane and the intermediate ion exchange membrane has an anion exchanger volume ratio of 50 to 100. %, And the ion exchanger filled in the small desalting chamber formed by partitioning the cation exchange membrane and the intermediate ion exchange membrane has a volume ratio of the cation exchanger of 50 to 50%. It may be 100%.

  According to the EDI of the present invention, deionized water can be produced with power saving and stable voltage. Furthermore, high water quality can be stably obtained.

The EDI of the present invention is a demineralization chamber multi-cell type EDI, and the flow direction of the water to be treated in each small desalination chamber adjacent through the intermediate ion exchange membrane is countercurrent.
The principle of equalizing the current density in the EDI of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing the direction of current flow in a deionization module 30 used in the EDI of the present invention. As shown in FIG. 1, the deionization module 30 includes a cation exchange membrane 32 disposed on the cathode side, an anion exchange membrane 36 disposed on the anode side, and the cation exchange membrane 32 and the anion exchange membrane 36 facing each other. The remaining space is filled with an ion exchanger, and a desalting chamber 40 is formed. An intermediate ion exchange membrane 34 is arranged between the cation exchange membrane 32 and the anion exchange membrane 36, the desalting chamber 40 is divided into two, and a small desalting chamber 42 and a small desalting chamber 44 are formed. Yes.

  In the production of deionized water, the water to be treated flows through the small desalting chamber 44 in the flow direction A1. During this time, the anion component is mainly removed from the water to be treated, and the removed anion component is attracted to the anode side, passes through the anion exchange membrane 36, and is removed from the small desalting chamber 44. On the other hand, the water to be treated flows through the small desalting chamber 42 in the flow direction A2. During this time, the cation component is mainly removed from the water to be treated, and the removed cation component is attracted to the cathode side, passes through the cation exchange membrane 32, and is removed from the small desalting chamber. Thus, the water to be treated is deionized water from which ionic components are removed.

If the production of deionized water as described above is continued, an ion adsorption zone 43 b is formed on the upstream side of the small demineralization chamber 42, and similarly, an ion adsorption zone 45 b is formed on the upstream side of the small demineralization chamber 44. The ion adsorption zones 43b and 45b expand in the downstream direction over time due to the production of deionized water. Here, the flow direction A1 of the water to be treated in the small desalination chamber 44 and the flow direction A2 of the water to be treated in the small desalination chamber 42 adjacent to the small desalination chamber 44 via the intermediate ion exchange membrane 34 are countercurrent. It has become. For this reason, since the ion adsorption zone 43b expands in the direction of the flow direction A2, and the ion adsorption zone 45b expands in the direction of the flow direction A1, in the deionization module 30, the positions of the ion adsorption zones 43b and 45b are as shown in FIG. Are distributed vertically. On the other hand, in the conventional EDI, as described above, an ion adsorption zone is formed on the same side in all the small desalting chambers, so that all the desalting chambers 240 in the thickness direction are seen from the current flow direction. Thus, there is a region where an ion adsorption band is formed (FIG. 8).
In the present invention, as shown in FIG. 1, the region where the ion adsorption bands 43b and 45b are formed overlaps with the region 43a and 45a where the ion adsorption bands are not formed as viewed from the direction of current flow. Therefore, the difference in the ease of current flow is reduced, current flows in the flow directions E1 to E6 during EDI operation, and a uniform current density can be maintained. As a result, deionized water can be produced at a low voltage and a stable voltage.

The EDI of the present invention will be described with an example, but is not limited to this embodiment.
(First embodiment)
A first embodiment of EDI of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view of the EDI 10 of the present embodiment.
As shown in FIG. 2, in the EDI 10, a plurality of deionization modules 30 are interposed between a concentration chamber 22 between a cathode chamber 14 and an anode chamber 18.
In the deionization module 30, a cation exchange membrane 32, a frame 33, an intermediate ion exchange membrane 34, a frame 35, and an anion exchange membrane 36 are arranged in this order from the cathode 12 side. The opening of the frame 33 is filled with an ion exchanger to form a small desalting chamber 42, and the opening of the frame 35 is filled with an ion exchanger to form a small desalting chamber 44. ing. The small desalting chamber 42 and the small desalting chamber 44 constitute a desalting chamber 40. Thus, the desalting chamber 40 is substantially bisected in the thickness direction by the intermediate ion exchange membrane 34.
The small desalting chamber 44 is connected with a to-be-treated water inflow line 52 and a pipe 53. The pipe 53 is connected to the small desalting chamber 42, and a deionized water outflow pipe 54 is connected to the small desalting chamber 42.
The cathode chamber 14 is formed by sandwiching a mesh between the cathode 12 and the partition film 20. The anode chamber 18 is formed by sandwiching a mesh between the anode 16 and the partition film 20. The cathode 12 and the anode 16 are connected to a power source (not shown). In addition, an electrode water inflow line 13 and an electrode water outflow line 15 are connected to the cathode chamber 14, and an electrode water inflow line 17 and an electrode water outflow line 19 are connected to the anode chamber 18. 15 and the electrode water inflow line 17 are connected by piping not shown.
The concentration chamber 22 is formed by disposing a frame body 24 on both sides of the deionization module 30 and filling an opening of the frame body 24 with an ion exchanger. A concentrated water inflow line 56 and a concentrated water outflow line 58 are connected to the concentration chamber 22.

  Roughly classified as ion exchange membranes, a homogenous membrane formed by impregnating a raw material monomer solution into a reinforcing body and then polymerized to form a homogeneous whole, and a non-homogeneous material obtained by grinding and pulverizing together with a polyolefin resin capable of dissolving and molding the ion exchange resin There are two types of membranes. The cation exchange membrane 32 and the anion exchange membrane 36 in this embodiment are not particularly limited, and should be selected according to the ease of production of EDI, the quality of water to be treated, the quality of water required for deionized water, the amount of treatment, and the like. Can do.

The intermediate ion exchange membrane 34 in the present embodiment is not particularly limited, and is preferably selected according to the quality of water to be treated and the quality of water required for deionized water. The intermediate ion exchange membrane 34 may be either an anion exchange membrane, a single membrane of a cation exchange membrane, or a composite membrane in which both an anion exchange membrane and a cation exchange membrane are arranged.
A composite membrane refers to a membrane in which the ion exchange membrane has regions with different polarities. For example, a mosaic film or a hyperpolar film can be used. The ratio of the anion exchange membrane to the cation exchange membrane in the composite membrane can be appropriately determined depending on the quality of the water to be treated, the purpose of treatment, and the like.

The ion exchanger filled in the small desalting chamber 44 is not particularly limited as long as it has an ion exchange function. For example, an ion exchange resin, an ion exchange fiber, a monolithic porous ion exchanger, etc. can be mentioned. Of these, ion exchange resins, which are the most versatile, are preferred. Examples of the ion exchange resin include an anion exchange resin and a cation exchange resin. Examples of the anion exchange resin include strongly basic anion exchange resins and weakly basic anion exchange resins. For example, commercially available products include Amberlite (trade name) manufactured by Rohm and Haas. Examples of the cation exchange resin include a strong acid cation exchange resin and a weak acid cation exchange resin, and examples thereof include amberlite (trade name) manufactured by Rohm & Haas. These may be used alone or in combination of two or more.
Moreover, the filling form of an ion exchanger is not specifically limited, It is preferable to select in consideration of the water quality of to-be-processed water and the water quality requested | required of deionized water. Therefore, the ion exchanger may be packed in any form such as anion exchanger single bed form, cation exchanger single bed form, mixed bed form of anion exchanger and cation exchanger, or multiple bed form. Can do. Among these, it is preferable to use an anion exchanger single bed form, a mixed bed form of an anion exchanger and a cation exchanger, or a double bed form. When the mixed bed form of the anion exchanger and the cation exchanger or the double bed form is used, the anion exchanger is preferably 50% by volume or more and less than 100% by volume. This is because the anion component is mainly removed in the small desalting chamber 44 on the anion exchange membrane 36 side.

The ion exchanger filled in the small desalting chamber 42 is not particularly limited, and the same ion exchanger filled in the small desalting chamber 44 described above can be used.
In addition, the filling mode of the ion exchanger in the small desalting chamber 42 is not particularly limited in the same manner as the filling mode of the small desalting chamber 44 described above. It is preferable to select them. Especially, it is preferable to set it as the cation exchanger single bed form, the mixed bed form of an anion exchanger and a cation exchanger, or a multiple bed form. In the case of a mixed bed form of an anion exchanger and a cation exchanger or a double bed form, the cation exchanger is preferably 50% by volume or more and less than 100% by volume. This is because the small desalting chamber 42 on the cation exchange membrane 32 side mainly removes the cation component.

The ion exchanger filled in the concentration chamber 22 is not particularly limited, and the same ion exchanger as that filled in the small desalting chamber 44 can be used.
In addition, the filling form of the ion exchanger in the concentration chamber 22 is not particularly limited and can be determined in consideration of the quality of the water to be treated, and the anion exchanger single bed form, the cation exchanger single bed form, or Any of a mixed bed form of an anion exchanger and a cation exchanger or a double bed form can be used. For example, from the viewpoint of preventing scale formation on the anion exchange membrane 36 surface of the concentration chamber 22, the anion exchanger may be filled in a single bed form. By having the anion exchanger layer in contact with the anion exchange membrane 36, the movement of the anion component from the small desalting chamber 44 to the concentration chamber 22 is promoted, and the anion component has a high concentration on the surface of the anion exchange membrane 36 on the concentration chamber 22 side. This is because it is possible to suppress the occurrence of concentration polarization.

The frames 33 and 35 are not particularly limited as long as they have insulating properties and do not leak treated water. For example, frames made of resin such as polyethylene, polypropylene, polyvinyl chloride, ABS, polycarbonate, noryl, etc. Can be mentioned.
The thickness of the frames 33 and 35 is not particularly limited, and can be set according to the desired thickness of the small desalting chamber 42 and the small desalting chamber 44.
Moreover, when the area of the opening part of the frame bodies 33 and 35 is large, you may provide a support body in the space which the frame bodies 33 and 35 were hollowed out. By providing the support, it is possible to prevent the cation exchange membrane 32, the intermediate ion exchange membrane 34, and the anion exchange membrane 36 from being curved and the amount of the ion exchanger in each desalting zone from becoming uneven. is there. The support is not particularly limited as long as it is a material that has insulating properties and does not hinder the flow of water to be treated. For example, polyethylene, polypropylene, polyvinyl chloride, ABS, polycarbonate, noryl, etc., provided with slits. The resin-made support body can be mentioned.

  The thickness of the desalting chamber 40 is not particularly limited, and an appropriate thickness can be determined depending on the type and filling form of the ion exchanger filled in the small desalting chamber 42 and the small desalting chamber 44. preferable. For example, the thickness of the desalting chamber 40 is preferably determined in the range of 10 to 100 mm, and is suitably determined in the range of 10 to 60 mm.

The thicknesses of the small desalting chamber 42 and the small desalting chamber 44 can be determined in consideration of the quality of water to be treated and deionized water, etc., and they may be the same thickness or different. good. When the thicknesses of the small desalting chamber 42 and the small desalting chamber 44 are different from each other, it is preferable to increase the thickness of the small desalting chamber 44. Normal raw water to be treated water contains many anion components such as carbonic acid and silica, which are weak acid components, as components that are difficult to remove, and it is highly effective to remove anion components in treated water efficiently. This is because it is effective in obtaining deionized water of water quality.
Although the thickness of the small desalting chambers 42 and 44 is not specifically limited, For example, it can determine in the range of 5-50 mm.

The frame body 24 is not particularly limited as long as it has insulating properties and does not leak concentrated water, and the same material as the frame body 33 can be used.
The thickness of the frame body 24 is not particularly limited, and can be set according to the desired thickness of the concentration chamber 22, and can be determined within a range of 3 to 10 mm, for example.

  The thickness of the concentration chamber 22 is not particularly limited, and can be determined in consideration of the quality of water to be treated and deionized water. For example, it can be determined within a range of 3 to 10 mm.

The cathode 12 is not particularly limited as long as it functions as a cathode, and examples thereof include plate-like stainless steel and mesh-like stainless steel.
The anode 16 is not particularly limited as long as it functions as an anode. However, when Cl ⁻ is present in the water to be treated, chlorine generation occurs in the anode, and therefore, an anode 16 having chlorine resistance is preferable. For example, a noble metal such as platinum, palladium, iridium, or a net-like or plate-like electrode obtained by coating the noble metal on titanium or the like can be given.

  The mesh used for forming the cathode chamber 14 is not particularly limited as long as electrode water can be circulated and the cathode chamber 14 having a desired width can be formed. Polyethylene, polypropylene, polyvinyl chloride, ABS, polycarbonate And a mesh made of resin such as Noryl, and a grid-like frame material having water permeability. The thickness of the mesh is not particularly limited and can be selected according to the desired space of the cathode chamber 14. For example, it is preferable to select in the range of 0.3 to 4 mm. The same mesh can be used for forming the anode chamber 18.

  The partition membrane 20 is not particularly limited, and can be selected in consideration of the quality of the water to be treated, the operating conditions of the EDI 10, and the like. For example, a cation exchange membrane or an anion exchange membrane can be selected.

The manufacturing method of the deionized water in this embodiment is demonstrated using FIG. In the description, the intermediate ion exchange membrane 34 is an anion exchange membrane, the small desalting chamber 42 is filled with a cation exchanger in a single bed form, and the small desalting chamber 44 is filled with an anion exchanger in a single bed form. Then, the concentration chamber 22 is filled with an anion exchanger in a single bed form as an example.
First, electrode water is caused to flow into the cathode chamber 14 from the electrode water inflow line 13, and a DC voltage is applied between the cathode 12 and the anode 16. Next, the concentrated water is passed downwardly from the concentrated water inflow line 56 to the concentration chamber 22. The concentrated water flows through the concentration chamber 22 in the flow direction B1. Next, the water to be treated is caused to flow into the small desalting chamber 44 from the water to be treated inflow line 52. The treated water that has flowed in flows through the anion exchanger in the small desalting chamber 44 in the flow direction A1 while diffusing. During this time, mainly anion components (Cl ⁻ , HCO ₃ ⁻ , CO ₃ ²⁻ , SiO ₂ (silica often takes a special form, so it is displayed differently from general ions), etc.) Adsorbed on the anion exchanger. The adsorbed anion component is attracted to the anode 16 side, passes through the anion exchange membrane 36, and moves to the concentration chamber 22. The treated water flows through the small desalting chamber 44 and then flows into the small desalting chamber 42 via the pipe 53.
The treated water that has flowed into the small desalting chamber 42 circulates in the flow direction A <b> 2 while diffusing through the cation exchanger in the small desalting chamber 42. During this time, mainly cation components (Na ⁺ , Ca ²⁺ , Mg ^2+, etc.) are adsorbed on the cation exchanger. The adsorbed cation component is attracted to the cathode 12 side, passes through the cation exchange membrane 32, and moves to the concentration chamber 22. On the other hand, the anion component in the for-treatment water that could not be removed in the small desalting chamber 44 is attracted to the anode 16 side, passes through the intermediate ion exchange membrane 34, and moves to the small desalting chamber 44. Thus, both the anion component and the cation component are removed from the water to be treated, and the deionized water flows out from the deionized water outflow line 54.

Concentrated water that has flowed into the concentrating chamber 22 from the concentrated water inflow line 56 flows in the concentrating chamber 22 in the flow direction B <b> 1, takes in ionic components that have moved from the desalting chamber 40, and discharges from the concentrated water outflow line 58. Is done.
The electrode water that has flowed into the cathode chamber 14 from the electrode water inflow line 13 circulates in the cathode chamber 14 in an upward flow and flows to the electrode water outflow line 15. Then, the electrode water that has flowed into the electrode water outflow line 15 flows into the anode chamber 18 from the electrode water inflow line 17 via a pipe (not shown), and circulates in the anode chamber 18 in an upward flow. It flows out from the outflow line 19. During this time, the electrode water takes in H _{2 and the} like generated from the cathode 12 and Cl ₂ and O _{2 and the} like generated from the anode 16 and discharges them outside the EDI 10.

Although the to-be-processed water is not specifically limited, The water etc. which processed the water which removed the turbid component of industrial water and well water with the turbidity membrane with the reverse osmosis (RO) membrane, etc. are mentioned.
The amount of water flow in the desalting chamber 40 of the water to be treated is not particularly limited, and can be determined in consideration of the ability of the EDI 10 and the quality of the water to be treated. Passing water is represented by space velocity (SV), the unit of the SV is a flow rate for circulating per hour to the unit volume of the ion-exchange resin (L-R) (L) L / L-R · h - ¹ (same in the following). In the present embodiment, SV = 30 to 300 L / LR · h ⁻¹ is preferable. If the SV is too high, the ion removal performance deteriorates, the differential pressure increases due to an increase in the water flow rate (LV) that occurs with the increase in SV, and the deionization module 30 may be damaged, causing operational difficulties. It is not preferable because it causes it. Here, LV is a flow rate per unit area, which is a linear velocity expressed in m / h.
On the other hand, if the SV is too low, the flow distribution to each deionization module is not performed properly, resulting in deionization modules with sufficient demineralization treatment and deionization modules with insufficient demineralization treatment. The flow between the salt chambers becomes non-uniform, which may adversely affect the performance of the EDI 10 as a whole.

  The flow rate of the concentrated water in the concentration chamber 22 is not particularly limited, and can be determined in consideration of the ability of the EDI 10, the quality of the water to be treated, and the amount to be treated. The concentrated water has the purpose of diffusing the ions that have moved to the concentration chamber 22 into the concentrated water and flowing them out of the EDI 10. Therefore, the flow rate of the concentrated water is preferably determined by the relationship between the flow rate of the water to be treated, the ion concentration of the water to be treated, and the recovery rate of the deionized water. It is preferable to determine the flow rate of the concentrated water so that the concentration ratio is 3 to 20. The concentration ratio according to the following equation (1) is defined on the assumption that the same raw water is used for the water to be treated and the concentrated water, and all the ions in the desalting chamber 40 are transferred to the concentration chamber 22.

If the flow rate of the concentrated water is too small, the concentration diffusion of ions transferred to the concentration chamber 22 becomes uneven, the concentration polarization layer on the surface of the ion exchange membrane becomes thick, and scale may be generated. On the other hand, if the flow rate of the concentrated water is too large, the recovery rate of deionized water decreases, which is not preferable.
The concentrated water is not particularly limited, and water from the same water source as the water to be treated may be used as the concentrated water, or deionized water or pure water may be used.

The current to be applied is not particularly limited and is preferably determined in consideration of the quality of the water to be treated, the scale of the EDI 10, and the like. In addition, when the cathode 12 and the anode 16 are divided into two or more, they may be applied with different current values for each of the divided electrode pairs. This is because the water quality can be improved by selecting an optimal current value according to the quality of the water to be treated.
The flow rate of the electrode water is not particularly limited, and is preferably determined according to the applied voltage or the like. If the flow rate of the electrode water is too small, it will be difficult to sufficiently discharge the generated H ₂ , O ₂ , and Cl ₂ gases, and if the flow rate of the electrode water is too large, the recovery rate is lowered, which is not preferable.

  In the EDI 10 of the present embodiment, the flow direction A1 of the water to be treated in the small desalting chamber 44 and the flow direction A2 of the water to be treated in the small desalting chamber 42 that are adjacent via the intermediate ion exchange membrane 34 are countercurrent. It has become. For this reason, the current density is made uniform as viewed from the direction of current flow, and the current efficiency is improved with respect to the ionic components in the water to be treated flowing through the desalting chamber 40, thereby reducing power consumption and stable voltage. It is possible to produce deionized water.

Furthermore, since the concentration chamber 22 is filled with an ion exchanger, scale generation can be effectively prevented. This effect will be described by taking as an example the case where the concentration chamber 22 is filled with an anion exchanger in the form of a single bed.
In concentrating compartment 22, ^Mg 2+ came moved from the desalting chamber 40, the hardness components ^{Ca 2+} or the like, remaining in the high pH portion of the anion exchange membrane 36 near, desalting compartment of deionized module 30 adjacent In some cases, it reacts with carbonate ions (CO ₃ ²⁻ ) that have moved from 40 to generate hardness scales (CaCO ₃ , MgCO ₃ ). However, when the anion exchanger is filled in the concentrating chamber 22 in a single-bed form, hardness components such as Mg ²⁺ and Ca ²⁺ move through the liquid phase through the gap between the filled anion exchangers. Therefore, it is difficult to reach the anion exchange membrane 36 on the counter electrode side having a high pH. On the other hand, CO ₃ ²⁻ that has moved to the concentration chamber 22 side moves in the counter electrode direction at a high speed on the ion exchange group of the anion exchanger. For this reason, CO ₃ ²⁻ is released to the liquid layer side in the vicinity of the neutrality where the pH is more inclined toward the acid side. Therefore, the amount of CO ₃ ²⁻ according to the change in pH is converted into hydrogen carbonate ions (HCO ₃ ⁻ ) by the ion equilibrium shown in the following formula (2).
CO ₃ ²⁻ + H ⁺ → HCO ₃ ⁻ (2)
Since the concentration in the liquid phase of CO ₃ ²⁻ which is a reaction product of the hardness scale can be lowered by the equilibrium reaction, the generation of the hardness scale can be effectively prevented.
Similarly, when the concentration chamber 22 has an anion exchanger layer along with the anion exchange membrane 36, the hardness component and CO ₃ ²⁻ do not come into contact with each other at a high concentration in the vicinity of the anion exchange membrane 36. Generation can be prevented.

(Second Embodiment)
A second embodiment of EDI of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view of the EDI 60 of this embodiment. Note that the electrode water inflow line and the electrode water outflow line have the same arrangement as that of the EDI 10 in FIG. 2, and are not shown in FIG. 3 for convenience of explanation.

As shown in FIG. 3, in the EDI 60, a plurality of deionization modules 30 and deionization modules 61 are sandwiched between the concentration chambers 22, and are alternately arranged between the cathode chambers 14 and the anode chambers 18. In the deionization module 61, a cation exchange membrane 32, a frame 33, an intermediate ion exchange membrane 34, a frame 35, and an anion exchange membrane 36 are arranged in this order from the cathode 12 side. The opening of the frame 33 of the deionization module 61 is filled with an ion exchanger to form a small demineralization chamber 67, and the opening of the frame 35 of the deionization module 61 is filled with an ion exchanger. Thus, a small desalting chamber 68 is formed. The small desalting chamber 67 and the small desalting chamber 68 constitute a desalting chamber 66. Thus, the desalting chamber 66 is substantially bisected in the thickness direction by the intermediate ion exchange membrane 34. A treated water inflow line 62 and a pipe 63 are connected to the small desalting chamber 68 of the deionization module 61. The pipe 63 is connected to a small desalting chamber 67, and a deionized water outflow line 64 is connected to the small desalting chamber 67.
In the desalting chamber 40, the water to be treated is circulated in the order of flow direction A1 → A2, and in the desalting chamber 66, the water to be treated is circulated in the order of flow direction A3 → A4. That is, in the desalting chamber 40, the small desalting chamber 44 partitioned by the anion exchange membrane 36 and the intermediate ion exchange membrane 34 and the anion exchange membrane 36 and the intermediate ion exchange membrane 34 in the desalting chamber 66 are partitioned. With the small desalting chamber 68, the flow direction of the water to be treated is countercurrent. In the desalting chamber 40, the small desalting chamber 42 is defined by the cation exchange membrane 32 and the intermediate ion exchange membrane 34, and the cation exchange membrane 32 and the intermediate ion exchange membrane 34 in the desalting chamber 66. In the small desalting chamber 67 formed by dividing the water to be treated, the flow direction of the water to be treated is countercurrent. Such a desalting chamber 40 and a desalting chamber 66 are disposed adjacent to each other via the concentration chamber 22.

  The kind and filling form of the ion exchanger filled in the small desalting chamber 67 are the same as those filled in the small desalting chamber 42. Further, the type and filling form of the ion exchanger filled in the small desalting chamber 68 are the same as those of the small desalting chamber 44.

  The thickness of the desalting chamber 61 is the same as that of the desalting chamber 40. Further, the thickness of the small desalting chamber 67 is the same as that of the small desalting chamber 42, and the thickness of the small desalting chamber 68 is the same as that of the small desalting chamber 44.

  The manufacturing method of deionized water by EDI60 is demonstrated. The treated water flows from the treated water inflow line 52 into the small demineralization chamber 44 of the deionization module 30, flows through the demineralization chamber 40, and then deionized water flows out from the deionized water outflow line 54. To do. On the other hand, to-be-treated water flows into the small desalting chamber 68 from the to-be-treated water inflow line 62. The treated water that has flowed in flows in the small desalting chamber 68 in the flow direction A3 and flows into the small desalting chamber 67 through the pipe 63. To-be-processed water which circulated in the small demineralization chamber 67 in the flow direction A4, both anion components and cation components are removed, and deionized water flows out from the deionized water outflow line 64.

  In the EDI 60 of the present embodiment, the flow direction of the water to be treated in the desalting chamber 40 and the desalting chamber 66 adjacent to each other via the concentration chamber 22 is reverse. Here, the small desalting chambers 44 and 68 are filled with an anion exchanger in a single bed form, the small desalting chambers 42 and 67 are filled with a cation exchanger in a single bed form, and the intermediate ion exchange membrane 34 is replaced with an anion exchange membrane. An example will be described. The small desalting chambers 44 and 68 mainly remove anionic components. For this reason, in the small desalting chambers 44 and 68, an ion adsorption zone in which mainly an anionic component is adsorbed is formed. The small desalting chambers 42 and 67 mainly remove cation components. For this reason, in the small desalting chambers 42 and 67, an ion adsorption zone in which mainly cation components are adsorbed is formed. As described above, in the small desalting chamber 44 and the small desalting chamber 68, and in the small desalting chamber 42 and the small desalting chamber 67, the flow direction of the water to be treated is countercurrent. Therefore, even if an ion adsorption zone is formed on the upstream side of each small desalting chamber, an ion adsorption zone mainly formed by adsorbing an anionic component and an ion adsorption zone mainly formed by adsorbing a cation component are formed. Are alternately present in the direction of current flow. As described above, since the overlap of the same kind of ion adsorption bands is reduced in a specific region as seen from the direction of current flow, the current density can be further uniformized. As a result, deionized water can be produced at a lower voltage and a stable voltage over a long period of time.

(Third embodiment)
A third embodiment of EDI of the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view of the EDI 70 of the present embodiment. Note that the electrode water inflow line and the electrode water outflow line have the same arrangement as that of the EDI 10 in FIG. 2, and are not shown in FIG. 4 for convenience of explanation.

As shown in FIG. 4, in the EDI 70, a plurality of deionization modules 71 and deionization modules 171 are sandwiched between the concentration chambers 22, and are alternately arranged between the cathode chambers 14 and the anode chambers 18. In the deionization module 71, a cation exchange membrane 32, a frame 33, an intermediate ion exchange membrane 34, a frame 35, and an anion exchange membrane 36 are arranged in this order from the cathode 12 side. The opening of the frame 33 of the deionization module 71 is filled with an ion exchanger to form a small demineralization chamber 77, and the opening of the frame 35 of the deionization module 71 is filled with an ion exchanger. Thus, a small desalting chamber 78 is formed. The small desalting chamber 77 and the small desalting chamber 78 constitute a desalting chamber 76. Thus, the desalting chamber 76 is substantially bisected in the thickness direction by the intermediate ion exchange membrane 34. In the deionization module 171, the cation exchange membrane 32, the frame 33, the intermediate ion exchange membrane 34, the frame 35, and the anion exchange membrane 36 are arranged in this order from the cathode 12 side. The opening of the frame 33 of the deionization module 171 is filled with an ion exchanger to form a small desalting chamber 177 of the deionization module 171, and the opening of the frame 35 is filled with an ion exchanger. Thus, a small desalting chamber 178 is formed. The small desalting chamber 177 and the small desalting chamber 178 constitute a desalting chamber 176. Thus, the desalting chamber 176 is substantially bisected in the thickness direction by the intermediate ion exchange membrane 34.
A treated water inflow line 73 and a pipe 74 are connected to a small desalting chamber 77 of the deionization module 71. The piping 74 is connected to a small desalting chamber 78, and the treated water outflow line 75 is connected to the small desalting chamber 78. On the other hand, to-be-treated water inflow line 173 and piping 174 are connected to small demineralization chamber 177 of deionization module 171. The pipe 174 is connected to a small desalting chamber 178, and a deionized water outflow line 175 is connected to the small desalting chamber 178. In addition, the treated water outflow line 75 and the treated water inflow line 173 are connected by a pipe (not shown).

  The kind and filling form of the ion exchanger filled in the small desalting chambers 77 and 177 are the same as the ion exchanger filled in the small desalting chamber 42. Further, the type and filling form of the ion exchanger filled in the small desalting chambers 78 and 178 are the same as those of the ion exchanger filled in the small desalting chamber 44.

  The thickness of the desalting chambers 71 and 171 is the same as that of the desalting chamber 40 in the first embodiment. The thicknesses of the small desalting chambers 77 and 177 are the same as those of the small desalting chamber 42 of the first embodiment, and the thicknesses of the small desalting chambers 78 and 178 are the same as those of the first embodiment. This is the same as the salt chamber 44.

The manufacturing method of deionized water by EDI70 is demonstrated. Generally, carbon dioxide gas is dissolved in raw water used for water to be treated and is a weak acid (pH 5.5 to 6.0). Therefore, the intermediate ion exchange membrane 34 is an anion exchange membrane, and a small desalting chamber 77 is used. A case where cation exchanger is filled in 177 with a single bed and anion exchanger is filled in small desalting chambers 78 and 178 in a single bed will be described as an example. The treated water flows from the treated water inflow line 73 into the small desalting chamber 77 and circulates in the small desalting chamber 77 in the flow direction A5. During this time, mainly cation components in the water to be treated are adsorbed on the cation exchanger. The adsorbed cation component is attracted toward the cathode 12, passes through the cation exchange membrane 32, and moves to the concentration chamber 22. Here, when the removal of the cation component in the water to be treated proceeds, the pH of the water to be treated shifts to the acidic side, and the H ⁺ concentration that is a competitive ion of the cation component increases. As a result, the current efficiency with respect to the cation component is lowered, and the cation component hardly reaches a certain concentration or less. Then, the water to be treated flows into the small desalting chamber 78 via the pipe 74 in a state where a certain amount of the cation component remains. The treated water that has flowed in flows in the small desalination chamber 78 in the flow direction A6. During this time, mainly the anion component is adsorbed on the anion exchanger. The adsorbed anion component is attracted to the anode 16 side, passes through the anion exchange membrane 36 and moves to the concentration chamber 22. Since the water to be treated flows into the small desalting chamber 78 in a state where the pH is shifted to the acidic side, the OH ⁻ concentration that is a competing ion of the anion component is low. For this reason, the current efficiency with respect to an anion component is high, and the anion component is removed favorably.

Subsequently, the treated water flows into the small desalting chamber 177 via the treated water outflow line 75 and the treated water inflow line 173. At this time, the pH of the water to be treated is in a neutral region. The treated water that has flowed in flows in the small desalination chamber 177 in the flow direction A7. During this time, the cation component is mainly removed. Here, even if the removal of the cation component in the water to be treated progresses, the H ⁺ concentration becomes lower than that in the small desalting chamber 77. For this reason, current efficiency becomes high and the removal of the cation component in to-be-processed water is performed favorably. At this stage, ionic components contained in the water to be treated are generally removed. However, among the anion components removed in the small desalting chamber 78, carbonate ions may gasify in the concentration chamber 22, pass through the cation exchange membrane 32, and move back to the small desalting chamber 177. is there. For this reason, the anion component is removed again in the small desalting chamber 178. The treated water that has flowed through the small desalting chamber 177 flows into the small desalting chamber 178 via the pipe 174 and flows in the flow direction A8. In this way, both ionic components of the cation component and the anion component are highly removed, and deionized water flows out from the deionized water outflow line 175.

  According to the EDI 70 of the present embodiment, since the treated water treated by the deionization module 71 is treated again by the deionization module 171 as described above, deionized water with higher water quality can be obtained.

(Fourth embodiment)
A fourth embodiment of EDI of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view of the EDI 80 of the present embodiment. Note that the electrode water inflow line and the electrode water outflow line are arranged in the same manner as the EDI 10 in FIG. 2 and are not shown in FIG. 5 for convenience of explanation.

As shown in FIG. 5, a plurality of deionization modules 81 are sandwiched between the concentration chambers 22 and disposed between the cathode chamber 14 and the anode chamber 18. In the deionization module 81, a cation exchange membrane 32, a frame 33, an intermediate ion exchange membrane 34, a frame 35, and an anion exchange membrane 36 are arranged in this order from the cathode 12 side. The opening of the frame 33 of the deionization module 81 is filled with an ion exchanger to form a small demineralization chamber 92, and the opening of the frame 35 of the deionization module 81 is filled with an ion exchanger. Thus, a small desalting chamber 94 is formed. The small desalting chamber 92 and the small desalting chamber 94 constitute a desalting chamber 90. Thus, the desalting chamber 90 is substantially bisected in the thickness direction by the intermediate ion exchange membrane 34.
The treated water supply line 82 has a plurality of treated water inflow lines 83. The treated water inflow line 83 is connected to the small desalting chamber 92. In addition, a plurality of treated water outflow lines 84 and piping 87 are connected to the piping 85. The treated water outflow line 84 is connected to the small desalting chamber 92. The pipe 87 is connected to the pipe 88. A plurality of to-be-treated water inflow lines 86 are connected to the pipe 88, and the to-be-treated water inflow lines 86 are connected to the small desalination chamber 94. A deionized water outflow line 89 is connected to the small desalting chamber 94.

  The type and form of ion exchanger charged in the small desalting chamber 92 are the same as those of the ion exchanger charged in the small desalting chamber 42. Further, the type and filling form of the ion exchanger filled in the small desalting chamber 94 are the same as those of the ion exchanger filled in the small desalting chamber 44.

  The thickness of the desalting chamber 90 is the same as that of the desalting chamber 40 in the first embodiment. Further, the thickness of the small desalting chamber 92 is the same as that of the small desalting chamber 42 of the first embodiment, and the thickness of the small desalting chamber 94 is the same as that of the small desalting chamber 44 of the first embodiment. It is the same.

The manufacturing method of deionized water by EDI80 is demonstrated.
The treated water flows from the treated water supply line 82 into the small desalting chamber 92 via the treated water inflow line 83. Then, in the flow direction A9, the cation component is mainly removed while flowing in the small desalting chamber 92, and then reaches the pipe 85 via the treated water outflow line 84. In the pipe 85, the water to be treated that has flowed out from the plurality of small desalting chambers 92 merges. And the to-be-processed water in the piping 85 is poured into the piping 88 via the piping 87, distribute | circulates the to-be-processed water inflow line 86 from the piping 88, and flows in into the small desalination chamber 94. The water to be treated flows in the small desalting chamber 94 in the flow direction A10 while mainly removing the anion component. Then, both ionic components of the cation component and the anion component are removed to form deionized water, which flows out from the deionized water outflow line 89.

  According to the EDI 80 of the present embodiment, the water to be treated that has circulated through the plurality of small desalting chambers 92 is collected by the pipe 85 and then distributed to the small desalting chamber 94. The load can be made uniform, and the deionized water can be homogenized and stabilized.

(Fifth embodiment)
A fifth embodiment of EDI of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view of the EDI 100 of this embodiment. Note that the electrode water inflow line and the electrode water outflow line are arranged in the same manner as the EDI 10 in FIG. 2, and are not shown in FIG. 6 for convenience of explanation.
As shown in FIG. 6, the EDI 100 is arranged between the cathode chamber 14 and the anode chamber 18 with a plurality of deionization modules 30 sandwiched between the concentration chambers 23. A concentrated water inflow line 102 and a concentrated water outflow line 104 are connected to the concentration chamber 23. In the EDI 100, the flow direction B1 (downflow) of the concentrated water of the EDI10 (FIG. 2) is changed to the flow direction B2 (upflow).

The kind and filling form of the ion exchanger filled in the concentration chamber 23 are the same as those of the concentration chamber 22 of the first embodiment.
The thickness of the concentration chamber 23 is the same as that of the concentration chamber 22 of the first embodiment.

A method for producing deionized water using EDI 100 will be described.
The concentrated water flows from the concentrated water inflow line 102 into the concentration chamber 23 and circulates in the flow direction B2. During this time, the concentrated water takes in the ionic components that have moved from the desalting chamber 40 to the concentration chamber 23. Then, the concentrated water flowing through the concentration chamber 23 is discharged from the concentrated water outflow line 104.

  The flow rate of the concentrated water is the same as that in the first embodiment.

According to the EDI 100, the concentrated water is set in the flow direction B2, and the treated water flow direction A2 in the small desalting chamber 42, which is the latter of the small desalting chamber 42 and the small desalting chamber 44 adjacent to the concentrating chamber 23. By using countercurrent, higher-quality deionized water can be stably obtained. This point will be described.
According to this embodiment, the flow direction B2 of the concentrated water is the flow direction and countercurrent in the small desalination chamber of the water to be treated whose ionic components have been removed, that is, the outlet side of the deionized water is upstream of the concentrated water. It has become. Here, in the concentration chamber 23, the anion component transferred from the small desalting chamber 44 exists at a high concentration on the downstream side of the cation exchange membrane 32 surface on the concentration chamber 23 side. As described above, the anion component present at a high concentration on the membrane surface may be further attracted to the anode 16 (counter electrode) side and may move back to the small desalting chamber 42. For this reason, deionized water with higher water quality can be stably produced by circulating concentrated water like EDI100.

(Other embodiments)
The EDI and the deionized water production method of the present invention are not limited to the above-described embodiment.
In the first, second, and fifth embodiments described above, the water to be treated is circulated to an arbitrary small desalting chamber and then circulated to another small desalting chamber. It is good also as deionized water by distribute | circulating only to one of the small desalination chambers. This will be specifically described with reference to EDI in FIG. For example, deionized water can be obtained by circulating the water to be treated only in the small desalting chamber 44 in the flow direction A1. Further, the treated water can be circulated only in the small desalting chamber 42 in the flow direction A2 to obtain deionized water.

In the first to fourth embodiments described above, the concentrated water is circulated in the downward flow, but the concentrated water may be circulated in the upward flow. Moreover, in the 1st-5th embodiment, although the flow direction of concentrated water is the same in all the concentration chambers, you may differ for every concentration chamber.
From the viewpoint of obtaining deionized water with higher water quality, the flow direction of the concentrated water is countercurrent to the flow direction of the water to be treated in the small demineralization chamber at the later stage among the small demineralization chambers adjacent to the concentration chamber. It is preferable.

  In the first to fifth embodiments described above, the concentration chambers 22 and 23 are filled with ion exchangers, but a mesh or the like may be arranged without filling the ion exchangers. However, in order to reduce the electrical resistance of the entire EDI, it is preferable to fill the concentration chambers 22 and 23 with an ion exchanger.

In the first, second, and fifth embodiments described above, the intermediate ion exchange membrane 34 and the cation exchange membrane 32 are separated from the small desalting chamber formed between the intermediate ion exchange membrane 34 and the anion exchange membrane 36. The treated water is circulated in order to the small desalting chambers formed in the middle, but the flow order may be reversed, or the dewatering chambers having different flow orders may be combined.
In the third and fourth embodiments, a small desalting chamber formed between the intermediate ion exchange membrane 34 and the cation exchange membrane 32 is formed between the intermediate ion exchange membrane 34 and the anion exchange membrane 36. The treated water is circulated through the small desalting chambers in order, but the distribution order may be reversed, or combinations of different distribution orders may be combined for each desalting chamber.

  In the first and fifth embodiments described above, a plurality of deionization modules are arranged, but the number of deionization modules may be one.

  In the first to fifth embodiments described above, the desalting chamber is divided into two to form small desalting chambers, but the number of small desalting chambers formed in the desalting chamber may be three or more. .

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, it is not limited to an Example.
(Conductivity / specific resistance)
For water quality evaluation, conductivity and specific resistance were used. In the case of water containing no impurities (theoretical pure water), the theoretical value of conductivity in water at 25 ° C. is 0.055 μS / cm, and the theoretical value of specific resistance is 18.2 MΩ · cm. As for the water quality of deionized water, the specific resistance approaches 18.2 MΩ · cm, and the higher, the higher the water quality. The quality of the water to be treated was evaluated with electrical conductivity, and the quality of the deionized water was evaluated with specific resistance.
The conductivity was measured using a conductivity meter (873CC, manufactured by FOXBORO). The specific resistance was measured using a specific resistance meter (873RS, manufactured by FOXBORO).

Example 1
An EDI-A having four deionization modules 30 arranged in the same manner as the EDI 10 (FIG. 2) according to the first embodiment was manufactured with the following specifications. In EDI-A, the flow direction B1 of the concentrated water and the flow direction A2 of the water to be treated in the small desalting chamber 42 adjacent to the concentration chamber 22 are the same direction. Using EDI-A thus obtained, EDI-A was continuously operated under the following conditions. The operating voltage and the specific resistance of deionized water after 1500 hours from the start of operation were measured, and the results are shown in Table 1. The hardness component concentration of the water to be treated is a value measured with an atomic absorption spectrophotometer (SpectrAA, manufactured by VARIAN), and the total carbonic acid concentration is measured with a wet ultraviolet oxidation TOC analyzer (model 900, manufactured by SIEVERS). Value. Further, SiO ₂ concentration, spectrophotometer (U-3010, manufactured by Hitachi High-Technologies Corporation) using a value measured by a molybdenum blue absorptiometry.

<EDI specifications>
(1) Cation exchange membrane 32: Astom Co., Ltd. (2) Intermediate ion exchange membrane 34: Astom Co., Ltd. anion exchange membrane (3) Anion exchange membrane 36: Astom Co., Ltd. (4) Small desalting chamber 42: Width 100mm, height 300mm, thickness 8mm
(5) Small desalination chamber 44: width 100 mm, height 300 mm, thickness 8 mm
(6) Filled ion exchanger in small desalting chamber 42: Mixed bed of cation exchange resin (Rohm and Haas) / anion exchange resin (Rohm and Haas) = 1/1 (volume ratio) Form (7) Filling ion exchanger in small desalination chamber 44: Single bed form of anion exchange resin (8) Concentration chamber 22: width 100 mm, height 300 mm, thickness 3 mm
(9) Filling ion exchanger in concentration chamber 22: Single bed form of anion exchange resin (10) Cathode chamber 14 and anode chamber 18: width 100 mm, height 300 mm, thickness 1 mm

<Operating conditions>
(1) Conductivity of water to be treated: 8 to 10 μS / cm
(2) Specific resistance of water to be treated: 0.1 to 0.125 MΩ · cm
(3) Hardness component concentration in water to be treated: 0.8 to 1.0 mg CaCO ₃ / L
(4) Total carbonic acid concentration in the treated water: 8-9 mg CO ₂ / L
(5) SiO ₂ concentrations of the water to be treated: 900～1000Ppb
(6) Flow rate of treated water: 150 L / h
(7) Concentrated water flow rate: 10 L / h
(8) Electrode water flow rate: 30 L / h
(9) Operating current value: 1.0A

(Example 2)
Similar to the EDI 60 (FIG. 3) according to the second embodiment, the desalting chamber 40 and the desalting chamber 66 adjacent to each other via the concentration chamber 22 are removed so that the flow direction of the water to be treated is reversed. Four ion modules 30 and four deionization modules 61 were alternately arranged to obtain EDI-B according to the following specifications. Continuous operation was performed in the same manner as in Example 1 using EDI-B. The operating voltage and the specific resistance of deionized water after 1500 hours from the start of operation were measured, and the results are shown in Table 1.

<EDI specifications>
(1) Cation exchange membrane 32: Astom Co., Ltd. (2) Intermediate ion exchange membrane 34: Astom Co., Ltd. anion exchange membrane (3) Anion exchange membrane 36: Astom Co., Ltd. (4) Small desalting chambers 42, 67 : 100mm width, 300mm height, 8mm thickness
(5) Small desalting chambers 44 and 68: width 100 mm, height 300 mm, thickness 8 mm
(6) Filled ion exchanger in small desalting chambers 42 and 67: cation exchange resin (Rohm and Haas) / anion exchange resin (Rohm and Haas) = 1/1 (volume ratio) Mixed bed form (7) Filling ion exchanger in small desalting chambers 44 and 68: Single bed form of anion exchange resin (8) Concentration chamber 22: width 100 mm, height 300 mm, thickness 3 mm
(9) Filling ion exchanger in concentration chamber 22: Single bed form of anion exchange resin (10) Cathode chamber 14 and anode chamber 18: width 100 mm, height 300 mm, thickness 1 mm

(Example 3)
Similar to the EDI 100 (FIG. 6) according to the fifth embodiment, the flow direction B2 of the concentrated water is counterflowed with the flow direction A2 of the water to be treated in the small desalting chamber 42 adjacent to the concentration chamber 23. Except that, EDI-C similar to EDI100 was obtained in the same manner as Example 1. The size of the concentrating chamber 23 and the type and form of the charged ion exchanger were the same as those of the concentrating chamber 22 of EDI-A. Using the obtained EDI-C, continuous operation was performed in the same manner as in Example 1. The operating voltage and the specific resistance of deionized water after 1500 hours from the start of operation were measured, and the results are shown in Table 1. Further, the operation voltage from the start of operation to 1500 hours after the start of operation was measured over time, and the result is shown as a legend (X) in FIG.

(Comparative Example 1)
The conventional EDI used in Comparative Example 1 will be described with reference to FIG.
FIG. 9 is a cross-sectional view of a conventional multi-cell type EDI 200 for a desalination chamber. In the EDI 200, four deionization modules 230 are sandwiched between the concentration chamber 222 between the cathode chamber 214 and the anode chamber 218.
In the deionization module 230, a cation exchange membrane 232, a frame 233, an intermediate ion exchange membrane 234, a frame 235, and an anion exchange membrane 236 are arranged in this order from the cathode 212 side. The opening of the frame 233 is filled with an ion exchanger to form a small desalting chamber 242, and the opening of the frame 235 is filled with an ion exchanger to form a small desalting chamber 244. ing. The small desalting chamber 244 and the small desalting chamber 242 constitute a desalting chamber 240. A treated water inflow line 252 and a treated water outflow line 253 are connected to the small desalting chamber 244. A treated water inflow line 254 and a deionized water outflow line 255 are connected to the small desalting chamber 242. And the to-be-processed water outflow line 253 and the to-be-processed water inflow line 254 are connected by piping which is not shown in figure.
The cathode chamber 214 is formed by sandwiching a mesh between the cathode 212 and the partition film 220. The anode chamber 218 is formed by sandwiching a mesh between the anode 216 and the partition film 220. In addition, an electrode water inflow line 213 and an electrode water outflow line 215 are connected to the cathode chamber 214, and an electrode water inflow line 217 and an electrode water outflow line 219 are connected to the anode chamber 218. 215 and the electrode water inflow line 217 are connected by a pipe (not shown). The cathode 212 and the anode 216 are connected to a power source (not shown).
The concentration chamber 222 is formed by disposing a frame body 224 on both sides of the deionization module 230 and filling an opening of the frame body 224 with an ion exchanger. A concentrated water inflow line 256 and a concentrated water outflow line 258 are connected to the concentration chamber 222.

As with the EDI 200, four de-in modules 230 are arranged and manufactured according to the following specifications to obtain EDI-D. Continuous operation was performed in the same manner as in Example 1 using EDI-D. In operation, treated water flows into the small desalination chamber 244 from the treated water inflow line 252 and flows through the small desalination chamber 244 in the flow direction a1, and then the treated water outflow line 253 and the treated water inflow line 254 are passed through. It was made to flow into the small desalting chamber 242 via. Next, the deionized water was obtained by flowing the water to be treated through the small desalting chamber 242 in the flow direction a2 and flowing out the deionized water from the deionized water outflow line 255.
The operating voltage and the specific resistance of deionized water after 1500 hours from the start of operation were measured, and the results are shown in Table 1. Further, the operation voltage from the start of operation to 1500 hours after the start of operation was measured over time, and the results are shown as a legend (Y) in FIG.

<EDI specifications>
(1) Cation exchange membrane 232: Astom Co., Ltd. (2) Intermediate ion exchange membrane 234: Astom Co., Ltd. anion exchange membrane (3) Anion exchange membrane 236: Astom Co., Ltd. (4) Small desalination chamber 242: Width 100mm, height 300mm, thickness 8mm
(5) Small desalination chamber 244: width 100 mm, height 300 mm, thickness 8 mm
(6) Packed ion exchanger in small desalting chamber 242: Mixed bed of cation exchange resin (Rohm and Haas) / anion exchange resin (Rohm and Haas) = 1/1 (volume ratio) Form (7) Filling ion exchanger in small desalination chamber 244: Single bed form of anion exchange resin (8) Concentration chamber 222: width 100 mm, height 300 mm, thickness 3 mm
(9) Filling ion exchanger in concentration chamber 222: Single bed form of anion exchange resin (10) Cathode chamber 214 and anode chamber 218: width 100 mm, height 300 mm, thickness 1 mm

From the results of Table 1, in Examples 1 to 3 in which the flow direction of the water to be treated in the adjacent small desalting chamber was countercurrent, the flow direction of the water to be treated in the adjacent small desalination chamber was compared in the same direction. Compared to Example 1, it was found that operation was possible at a lower voltage.
Furthermore, in Example 2 in which the flow direction of the water to be treated of the entire deionization module adjacent through the concentration chamber was reversed, the lowest operating voltage was obtained. Further, in Example 3 in which the flow direction of the concentrated water is countercurrent to the flow direction of the water to be treated in the subsequent small desalination chamber among the adjacent small desalination chambers, the highest water quality is obtained. The specific resistance was 17.9 MΩ · cm.
As described above, the specific resistance is a measure representing the purity of water, and the specific resistance of theoretical pure water is 18.2 MΩ · cm. Here, the specific resistance of water used by use is exemplified by a small boiler of about 4 MΩ · cm, a large power plant of about 10 MΩ · cm, and a nuclear power plant of about 15 MΩ · cm. Generally, water of 15 MΩ · cm or more is called “ultra pure water”, but in the electronics industry etc., water quality (18.2 MΩ · cm) closer to the theoretical pure water is required, and it is on the order of 0.1 MΩ · cm. Water quality improvement is required. Considering these things, when the specific resistance of 17.9 MΩ · cm of Example 3 and the specific resistance of 16.9 MΩ · cm of Comparative Example 1 are compared, EDI-C of Example 3 significantly improves the water quality. I found out that it was planned.

As shown in FIG. 7, in Example 3 (Legend (X)), the operating voltage rose to 48V at the start of operation 400 hours, and then remained stable without significant fluctuation until 1500 hours. The operating voltage 33V at the beginning of the EDI-C operation was suppressed to 1.6 times 52V after 1500 hours from the start of the operation.
In Comparative Example 1 (Legend (Y)), a significant increase in operating voltage was confirmed from 400 hours to 1500 hours after the start of operation. The operating voltage 36V at the beginning of EDI-D operation increased 2.4 times to 86V after 1500 hours of operation.
Comparing the transition of the operating voltage between Example 3 and Comparative Example 1, Example 3 in which the flow direction of the water to be treated in the adjacent small desalination chamber is countercurrent can be operated at a very stable voltage, It was found that deionized water with stable water quality can be produced.

It is a schematic diagram which shows the flow direction of the electric current in the deionization module of EDI of this invention. It is sectional drawing which shows EDI concerning the 1st Embodiment of this invention. It is sectional drawing which shows EDI concerning the 2nd Embodiment of this invention. It is sectional drawing which shows EDI concerning the 3rd Embodiment of this invention. It is sectional drawing which shows EDI concerning the 4th Embodiment of this invention. It is sectional drawing which shows EDI concerning the 5th Embodiment of this invention. 6 is a graph showing changes with time in operating voltage of Example 3 and Comparative Example 1. It is a schematic diagram which shows the flow direction of the electric current in the deionization module of the conventional EDI. It is sectional drawing which shows the conventional EDI.

Explanation of symbols

10, 60, 70, 80, 100, 200 Electric deionized water production apparatus 14, 214 Cathode chamber 18, 218 Anode chamber 22, 23, 222 Concentration chamber 32, 232 Cation exchange membrane 34, 234 Intermediate ion exchange membrane 36, 236 Anion exchange membrane 40, 66, 76, 90, 176, 240 Desalination chamber 42, 44, 67, 68, 77, 78, 92, 94, 177, 178, 242, 244 Small desalination chamber

Claims (8)

A space partitioned by the cation exchange membrane on one side and the anion exchange membrane on the other side is filled with an ion exchanger to provide a desalting chamber,
In the desalting chamber, a small desalting chamber that is partitioned in multiple stages in the thickness direction of the desalting chamber is formed by an intermediate ion exchange membrane disposed between the cation exchange membrane and the anion exchange membrane,
A concentration chamber is provided on both sides of the desalting chamber via the cation exchange membrane or the anion exchange membrane,
The desalting chamber and the concentration chamber are disposed between an anode chamber having an anode and a cathode chamber having a cathode;
An electric deionized water production apparatus in which the flow direction of water to be treated in each small demineralization chamber adjacent through the intermediate ion exchange membrane is countercurrent.   The electric deionized water production apparatus according to claim 1, wherein the concentrating chamber is filled with an ion exchanger.   The electric deionized water production apparatus according to claim 2, wherein the concentration chamber has an anion exchanger layer filled with an anion exchanger in contact with the anion exchange membrane.   It is controlled so that to-be-processed water distribute | circulates from the arbitrary said small desalting chambers to the other said small desalting chambers, The electric type of any one of Claims 1-3 characterized by the above-mentioned. Deionized water production equipment. Between the anode chamber and the cathode chamber, two or more desalting chambers are arranged via the concentration chamber,
Anion exchange membrane and intermediate ion in a small desalting chamber formed by partitioning an anion exchange membrane and an intermediate ion exchange membrane in any desalting chamber, and in another desalting chamber adjacent through the concentration chamber With the small desalination chamber formed by partitioning with the exchange membrane, the flow direction of the water to be treated is countercurrent,
And a small desalting chamber formed by partitioning a cation exchange membrane and an intermediate ion exchange membrane in an arbitrary desalting chamber, and a cation exchange membrane in another desalting chamber adjacent via the concentration chamber, The small water desalination chamber formed by partitioning with an intermediate ion exchange membrane has a countercurrent flow direction of water to be treated. Electric deionized water production equipment.   The flow direction of the concentrated water in the concentrating chamber is a countercurrent in the flow direction of the water to be treated in the small desalting chamber at a later stage in the small desalting chamber adjacent to the concentrating chamber, The electric deionized water production apparatus according to any one of claims 1 to 5.   The ion exchanger filled in the small desalting chamber formed by partitioning with the anion exchange membrane and the intermediate ion exchange membrane has a volume ratio of 50 to 100% of the anion exchanger. The electric deionized water production apparatus according to any one of claims 1 to 6, characterized in that it is characterized by the following.   The ion exchanger filled in the small desalting chamber formed by partitioning with the cation exchange membrane and the intermediate ion exchange membrane has a volume ratio of cation exchanger of 50 to 100%. The electric deionized water production apparatus according to any one of claims 1 to 7, characterized in that it is characterized by the following.

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