JP2009136824A - Electric deionized water production device and deionized water production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric deionized water production device and a deionized water production method which can suppress the generation of back diffusion of carbonic acid to obtain deionized water of high water quality. <P>SOLUTION: In the electric deionized water production device, desalting chambers each filled with an ion exchanger and partitioned by a cation exchange membrane on one side and an anion exchange membrane on the other side, and concentration chambers filled with an anion exchanger and provided on both sides of the desalting chamber through the cation exchange membrane and the anion exchange membrane are disposed between an anode and a cathode, so that a supply means is provided which supplies concentrated water to the concentration chamber. The concentrated water is a solution containing anions whose ion selectivity order by the anion exchanger is higher than a bicarbonate ion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for an electric deionized water production apparatus and a deionized water production method used in various industries such as semiconductors, liquid crystals, pharmaceuticals, and food industries, consumer use, and research facilities.

  As a method for producing deionized water, a method of performing deionization by passing water to be treated through an ion exchange resin has been known. However, in this method, when the ion exchange resin is saturated with ions, regeneration is usually performed with a drug. Such regeneration treatment is disadvantageous in processing operation, and in order to eliminate such a point, a deionized water production method by an electric deionization method that does not require regeneration by a chemical agent has been established and has been put into practical use. .

  In an electric deionized water production apparatus (EDI) that performs such desalting treatment, an ion exchanger is partitioned between an anode and a shade by a cation exchange membrane on one side and an anion exchange membrane on the other side. And a concentrating chamber on both sides of the desalting chamber via a cation exchange membrane and an anion exchange membrane. Usually, a plurality of sets of desalting chambers and concentrating chambers are arranged. When deionized water is produced by an electric deionized water production apparatus, water to be treated is placed in a demineralization chamber filled with an ion exchanger in a state where a direct current is passed between the anode and the cathode. By passing the concentrated water, ions in the water to be treated are moved into the concentrated water to obtain deionized water.

  Here, when the hardness of the water to be treated flowing into the desalination chamber is high, for example, when tap water or water obtained by subjecting tap water to RO membrane treatment is used as the water to be treated, a hardness scale is formed on the anion exchange membrane surface of the concentration chamber. Likely to happen. In other words, if the water to be treated contains a carbonate component and a hardness component, calcium ions and magnesium ions that have moved to the concentration chamber of the electric deionized water production apparatus are combined with carbonate ions etc. on the anion exchange membrane surface of the concentration chamber. However, it is easy to produce hardness scales such as calcium carbonate and magnesium carbonate.

  Patent Document 1 proposes an electric deionized water production apparatus in which an anion exchanger having a specific structure is disposed on the anion exchange membrane side of a concentration chamber. According to the apparatus of Patent Document 1, diffusion dilution of OH ions into a concentrated liquid is promoted from the surface of the porous anion exchanger, and the OH ion concentration on the surface of the porous anion exchanger can be quickly reduced. On the other hand, hardness component ions are less likely to enter the interior of the porous anion exchanger, and the opportunity for OH ions and hardness component ions to contact and react with each other is reduced, so that precipitation and accumulation of hardness components are suppressed.

However, when carbonic acid in the water to be treated (generic name for free carbonate, bicarbonate ion, carbonate ion) moves from the desalting chamber to the concentration chamber via the anion exchange membrane on the anode side (details will be described later), The anion exchanger is in the HCO ₃ form. Then, a current flows through the anion exchanger of HCO ₃ form, HCO ₃ ^- (and CO 3 ^_2-) but are attracted to the cation exchange membrane near by the electric field, can not be transmitted through the cation exchange membrane, a cation exchange It is concentrated near the membrane. Further, since hydrogen ions permeate the cation exchange membrane, the pH in the vicinity of the cation exchange membrane is lowered. Then, water and carbon dioxide (CO ₂ ) are generated, and a high-concentration carbon dioxide-containing aqueous solution layer is formed in the vicinity of the cation exchange membrane. Then, the carbon dioxide gas permeates through the cation exchange membrane 10 by diffusion and moves (back diffuses) to the desalting chamber. That is, carbon dioxide once removed from the water to be treated is dissolved again as carbon dioxide gas in the water to be treated, so-called reverse diffusion of carbonic acid occurs, and the treated water discharged from the desalting chamber is contaminated with carbonic acid components. .

In Patent Document 2, by providing a water permeable body having no strongly basic anion group between an anion exchange resin and a cation exchange membrane filled in a concentrating chamber, A deionized water production apparatus has been proposed. According to the apparatus of Patent Document 2, it is possible to prevent the reverse diffusion of carbonic acid by preventing HCO ₃ ^{− and the} like from being blocked by the water permeable material and diffusing to the vicinity of the cation exchange membrane.

  Patent Document 3 proposes an electric deionized water production apparatus that suppresses the occurrence of reverse diffusion of carbonic acid by filling an anion exchange resin and a cation exchange resin in a concentration chamber. According to the apparatus of Patent Document 3, both the cation and the anion can move in the concentration chamber, so that the reverse diffusion of carbon dioxide can be made relatively small and the generation of scale can be reduced.

Japanese Patent Laid-Open No. 2001-225078 JP 2004-358440 A JP 2004-34004 A

  An object of the present invention is to provide an electric deionized water production apparatus and a deionized water production method capable of suppressing the occurrence of reverse diffusion of carbonic acid by a method different from the above and obtaining high-quality deionized water. It is in.

  The present invention includes a desalting chamber partitioned between an anode and a cathode by a cation exchange membrane on one side and an anion exchange membrane on the other side and filled with an ion exchanger, the cation exchange membrane, and the anion exchange An electric deionized water production apparatus comprising a concentration chamber provided on both sides of the demineralization chamber through a membrane and filled with an anion exchanger, and having a supply means for supplying concentrated water to the concentration chamber. The concentrated water is a solution containing anions having higher ion selectivity than the bicarbonate ions.

  Moreover, in the electric deionized water production apparatus, it is preferable that the supply means supplies the concentrated water such that an ion concentration of the anion in the concentration chamber is equal to or higher than a carbonic acid concentration in the concentration chamber.

  In the electric deionized water production apparatus, the anion is preferably a chlorine ion.

  Further, the present invention provides a desalting chamber partitioned between an anode and a cathode by a cation exchange membrane on one side and an anion exchange membrane on the other side and filled with an ion exchanger, the cation exchange membrane, An electric deionized water production apparatus is provided on both sides of the demineralization chamber via an anion exchange membrane, and a concentration chamber filled with an anion exchanger and supplying concentrated water to the concentration chamber. In the method for producing deionized water, the concentrated water is a solution containing anions having higher ion selectivity than the bicarbonate ions in the anion exchanger.

  In the method for producing deionized water, the concentrated water is preferably supplied so that the ion concentration of the anion in the concentration chamber is equal to or higher than the carbonic acid concentration in the concentration chamber.

  In the method for producing deionized water, the anion is preferably a chlorine ion.

  The present invention includes a desalting chamber partitioned between an anode and a cathode by a cation exchange membrane on one side and an anion exchange membrane on the other side and filled with an ion exchanger, the cation exchange membrane, and the anion exchange In an electric deionized water production apparatus having a concentration chamber provided on both sides of the demineralization chamber through a membrane and provided with a concentration chamber filled with an anion exchanger, and having a supply means for supplying concentrated water to the concentration chamber, The concentrated water is a solution containing anions whose ion selectivity ranks higher than bicarbonate ions. Thereby, generation | occurrence | production of the reverse diffusion of a carbonic acid can be suppressed and high-quality deionized water can be obtained.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  In the electric deionized water production apparatus according to the present embodiment, a desalting solution is partitioned between an anode and a cathode by a cation exchange membrane on one side and an anion exchange membrane on the other side and filled with an ion exchanger. A chamber and a concentration chamber provided on both sides of the desalting chamber via the cation exchange membrane and the anion exchange membrane and filled with an anion exchanger are disposed. Here, as long as the demineralization chamber of the electric deionized water production apparatus according to the present embodiment has the above configuration, for example, the cation exchange membrane and the anion A desalination chamber partitioned into two small desalination chambers by an intermediate ion exchange membrane positioned between the exchange membranes and configured to allow water to be treated to flow sequentially through the two small desalination chambers. There may be. If the desalting chamber divided into these two small desalting chambers is used, it becomes possible to efficiently perform desalting treatment of the water to be treated.

  In the present embodiment described below, a desalting chamber divided into two small desalting chambers by an intermediate ion exchange membrane located between the cation exchange membrane and the anion exchange membrane is taken as an example.

  FIG. 1 is a schematic configuration diagram of an electric deionized water production apparatus according to this embodiment. In the electric deionized water production apparatus 1, the cation exchange membrane 10, the intermediate ion exchange membrane 12, and the anion exchange membrane 14 are alternately arranged apart from each other, and the intermediate ion exchange membrane 12, the anion exchange membrane 14, The first small desalting chambers d1, d3, d5 and the second small desalting chambers d2, d4, d6 partitioned by the cation exchange membrane 10 and the intermediate ion exchange membrane 12 are formed. The first small desalination chamber d1 and the second small desalination chamber d2 are the desalination chamber D1, the first small desalination chamber d3 and the second small desalination chamber d4 are the desalination chamber D2, and the first small desalination chamber d2. A desalting chamber D3 is defined by d5 and the second small desalting chamber d6. A portion formed by the anion exchange membrane 14 and the cation exchange membrane 10 located between the desalting chambers D1 and D2 and D2 and D3 is a concentration chamber 16 (16a, 16b) for flowing concentrated water. And By sequentially arranging these, a desalting chamber D1, a concentrating chamber 16a, a desalting chamber D2, a concentrating chamber 16b, and a desalting chamber D3 are formed from the left in FIG. In addition, the number of the desalting chambers and the concentration chambers in FIG. 1 is an example, and is not limited thereto. Further, the concentration chamber is also provided between the desalting chamber and an electrode chamber, which will be described later, as necessary.

  The first small desalting chambers d1, d3, and d5 shown in FIG. 1 are filled with an anion exchanger 20, and the second small desalting chambers d2, d4, and d6 are a mixture of an anion exchanger and a cation exchanger. 18 (hereinafter referred to as the mixture 18). However, the ion exchanger filled in the first small desalting chambers d1, d3, d5 and the second small desalting chambers d2, d4, d6 is not necessarily limited to the above, and for the purpose of desalting treatment. It may be appropriately selected depending on the case.

  The intermediate ion exchange membrane 12 of the present embodiment is an anion exchange membrane, but is not particularly limited.

  The concentration chambers 16a and 16b are filled with an anion exchanger 22. By filling the concentration chambers 16a and 16b with the anion exchanger 22, it is possible to prevent carbon dioxide from diffusing on the surface of the cation exchange membrane 10 of the concentration chambers 16a and 16b and generating a hardness scale on the surface of the cation exchange membrane 10, Further, the presence of the high conductivity anion exchanger 22 can reduce the applied voltage.

  In addition, the spaces between the outer sides of the desalting chambers D1 and D3 at both ends and the electrodes (cathode 24, anode 26) are set as electrode chambers 28 and 30, respectively, and electrode water (treated water in this embodiment) is used here. Is passed. The electrode chambers 28 and 30 may be filled with a cation exchanger, an anion exchanger, or the like as necessary. In the example of FIG. 1, the anion exchanger 32 is filled in the electrode chamber 28 and the cation exchanger 34 is filled in the electrode chamber 30, but this is not restrictive.

  In the electric deionized water production apparatus 1 of FIG. 1, first inflow lines 36 through which treated water flows are connected to the inlets of the first small demineralization chambers d1, d3, d5, respectively. A first outflow line 38 for flowing out the water to be treated from the outlets of the salt chambers d1, d3, d5 is a second for flowing the water to be treated into the inlets of the second small desalting chambers d2, d4, d6. It is connected to the inflow line 40. A second outflow line 42 through which the treated water flows out is connected to the outlets of the second small desalting chambers d2, d4, d6, respectively. With the above configuration, the water to be treated is first supplied to the first small desalting chambers d1, d3, and d5 and desalted. And the to-be-processed water which passed 1st small desalination chamber d1, d3, d5 is supplied to 2nd small desalination chamber d2, d4, d6, is further desalted, and is discharged | emitted as treated water. The flow path of the water to be treated is not limited to the above, and for example, the second anion exchanger 20 filled with the anion exchanger 20 from the second small desalting chambers d2, d4, d6 filled with the mixture 18 is used. The treated water may be passed through the small desalting chambers d1, d3, and d5.

  Moreover, the electric deionized water production apparatus 1 according to the present embodiment includes an anion having an ion selectivity higher than the bicarbonate ion as the concentrated water supply means for supplying the concentrated water to the concentration chamber. A tank 44 containing a solution (for example, a salt solution described later), a pump 46 for feeding the solution, a sub inflow line 47 serving as a flow path for the solution, an on-off valve 49 for opening / closing the sub inflow line 47, the solution And the concentrated water inflow line 48, which is a flow path of the mixed liquid (that is, concentrated water), and the concentrated water inflow line 48 and the first inflow line 36 are connected, and a part of the treated water is connected to the concentrated water inflow line. A bypass line 51 is provided to flow into 48. In the case where the solution stored in the tank 44 is allowed to flow naturally down to the concentrated water inflow line 48, the pump 46 is not necessary. The concentrated water inflow line 48 is connected to the bypass line 51 and the inlets of the concentration chambers 16a and 16b, respectively. The sub inflow line 47 is connected to the concentrated water inflow line 48 and the outlet of the tank 44 so that the solution is supplied to the concentration chambers 16a and 16b. The concentrated water outflow line 50 is connected to the outlets of the concentration chambers 16a and 16b, respectively. In the present embodiment, when the RO stock solution described later is used as a solution containing anions having an ion selectivity higher than that of bicarbonate ions in the anion exchanger 22, a sub for supplying the RO stock solution to the concentrated water inflow line 48. The tank 44 and the pump 46 are not necessarily required as long as the inflow line 47 and the opening / closing valve 49 are provided. The electrode water inflow line is the same line as the first inflow line 36 and is connected to the inlets of the electrode chambers 28 and 30, respectively. The electrode water outflow line 53 is connected to the outlets of the electrode chambers 28 and 30, respectively. Yes. In the present embodiment, the electrode water inflow line and the first inflow line 36 are the same line, but may be different lines. Moreover, although the solution made to flow in as treated water and electrode water is made to flow through as the same thing, it is not restricted to this, It is good also considering treated water and electrode water as different solutions.

  In this embodiment, the flow direction of the water to be treated flowing into the first small desalination chambers d1, d3, d5 and the flow direction of the water to be treated flowing into the second small desalination chambers d2, d4, d6 are both. Although it is a downward direction, the flow direction of concentrated water is the reverse upward direction, but is not limited thereto.

  An example of an operation method in the case of producing deionized water by the electric deionized water production apparatus 1 according to this embodiment will be described below. First, in a state where a direct current is passed between the cathode 24 and the anode 26, the water to be treated is caused to flow from the first inflow line 36, and the water to be treated is caused to flow into the concentrated water inflow line 48 via the bypass line 51. At the same time, the pump 46 is operated, the on-off valve 49 is opened, and a solution containing an anion having an ion selectivity higher than the bicarbonate ion from the tank 44 through the sub inflow line 47 (for example, described later). Salt solution or the like) is introduced into the concentrated water inflow line 48. The water to be treated that flows in from the first inflow line 36 flows through the first small desalting chambers d1, d3, and d5, and is carbonated (free carbonic acid, bicarbonate ions, carbonate ions when passing through the packed bed of the anion exchanger 20). ), Anions such as silica are removed. Furthermore, the water to be treated that has passed through the first outflow line 38 of the first small desalting chambers d1, d3, d5 flows through the second inflow line 40 of the second small desalting chambers d2, d4, d6, and the mixture 18. When passing through the packed bed, cations and anions are removed, and treated water (deionized water) is obtained from the second outflow line 42. In addition, the solution flowing from the tank 44 to the concentrated water inflow line 48 and the mixed solution of the water to be treated (flowing water according to the present embodiment) flowing from the bypass line 51 to the concentrated water inflow line 48 are supplied to the respective concentration chambers 16a, 16a, The ions that flow through 16b and move through the cation exchange membrane 10 and the anion exchange membrane 14 are received and flowed out from the concentrated water outflow line 50 as concentrated water obtained by concentrating the ions. Furthermore, the electrode water flowing in from the first inflow line 36 (electrode water inflow line) flows out from the electrode water outflow line 53. By the above operation, treated water (deionized water) from which ions in the water to be treated have been removed is obtained.

Carbonic acid (free carbonic acid, bicarbonate ion, carbonate ion) trapped by the anion exchanger 20 in the first small desalting chambers d1, d3, d5 flowing in first is captured by the hydroxide ion or the anion exchanger 20. It passes through the anion exchange membrane 14 on the anode side together with the other anion components thus formed, and moves to the concentration chambers 16a and 16b. Here, when the concentrated water supplied to the concentration chambers 16a and 16b is water treated with a conventional RO membrane or the like, or treated water treated with a conventional electric deionized water production apparatus, the concentration chamber The anion exchangers 22 of 16a and 16b become HCO _{3 type} anion exchangers by the carbon dioxide that has moved. When a current flows through the anion exchanger of HCO ₃ form, HCO ₃ ^- (and _CO ^{3 2-)} is attracted to the cation exchange membrane 10 near by the electric field, it can not be transmitted through the cation exchange membrane 10, a cation exchange It is concentrated near the membrane 10. Thus, at a cation exchange membrane 10, concentrating chambers 16a, 16b (thick side) and a second small depletion chamber d4, d6 HCO between (lean side) ₃ ^- (and _CO ^{3 2-)} steep Concentration gradient occurs. Further, since hydrogen ions permeate from the cation exchange membrane 10, the pH in the vicinity of the cation exchange membrane 10 in the concentration chambers 16a and 16b is lowered. Then, water and carbon dioxide (CO ₂ ) are generated, and a high-concentration carbon dioxide-containing aqueous solution layer is formed in the vicinity of the cation exchange membrane 10, and the carbon dioxide permeates through the cation exchange membrane 10 by diffusion and becomes the second small desalting. It moves (reverse diffusion) to the chambers d4 and d6. As a result, the final treated water discharged from the second small desalting chambers d4 and d6 is contaminated with carbonic acid.

On the other hand, in this embodiment, a solution containing an anion having an ion selectivity higher than that of bicarbonate ion (HCO ₃ ⁻ ) is used for the concentrated water flowing through the concentrated water inflow line 48. Examples of the anion having an ion selectivity higher than the bicarbonate ion of the anion exchanger 22 include Cl ⁻ , NO ₃ ⁻ , SO ₄ ^{2− and the} like. Examples of the solution containing anions such as Cl ⁻ , NO ₃ ⁻ and SO ₄ ²⁻ include a salt solution, a hydrochloric acid solution, a nitric acid solution, a sulfuric acid solution, and an RO stock solution. From the viewpoint of durability and ease of handling of the electric deionized water production apparatus 1, it is preferable to use a solution containing Cl ⁻ such as a salt solution as concentrated water.

When a solution containing Cl ⁻ such as the salt solution flows into the concentration chambers 16a and 16b, the anion exchanger 22 in the concentration chambers 16a and 16b is in an anion form having higher ion selectivity than bicarbonate ions, for example, a Cl form. , NO ₃ form, SO ₄ form, etc., the carbon dioxide moving from the first small desalting chambers d 1, d 3 through the anion exchange membrane 14 to the concentration chambers 16 a, 16 b is converted into the anion exchanger 22. Without being captured by the water, it is discharged together with the concentrated water to the concentrated water outflow line 50. As a result, it is possible to prevent the generation of a high-concentration carbon dioxide-containing aqueous solution layer in the vicinity of the cation exchange membrane 10 on the concentration chambers 16a and 16b side. That is, it is possible to suppress the carbon dioxide gas from moving to the second small desalting chambers d4 and d6 through the cation exchange membrane 10 and backdiffusing into the water to be treated. Further, when an electric current flows through an anion-type anion exchanger having higher selectivity than bicarbonate ions, the anions are attracted and concentrated near the cation-exchange membrane 10 by an electric field. However, in the vicinity of the cation exchange membrane 10, only a high-concentration liquid layer of hydrogen ions that permeate the cation exchange membrane 10 and the anion is formed, and the anion permeates the cation exchange membrane 10 to form the second small desalting. It does not move to the chambers d4 and d6.

  In this way, in the configuration in which the water to be treated is brought into contact in the order of the anion exchanger filled in the first small desalting chamber to the mixture (anion exchanger and cation exchanger) filled in the second small desalting chamber. When the reverse diffusion phenomenon of carbonic acid occurs, the carbonic acid moves to the second small desalting chamber of the final treatment, so that the treated water is easily contaminated with carbonic acid. However, since the reverse diffusion phenomenon of carbonic acid is suppressed by using the concentrated water, carbonic acid contamination of the final treated water can be prevented even with such a configuration. In addition, the mixture filled in the desalting chamber can remove both anions and cations, and high-quality deionized water can be obtained.

  Moreover, in this embodiment, the ion concentration of the anion higher than the bicarbonate ion in the ion selectivity rank of the anion exchanger 22 in the ion concentration of the concentrated water in the concentration chambers 16a and 16b is within the concentration chambers 16a and 16b. It is preferable to supply concentrated water to the concentration chambers 16a and 16b so as to be equal to or higher than the carbonic acid concentration. In order to achieve the above ion concentration state, for example, the amount of carbonic acid entering the desalting chamber and the concentration chamber or the amount of carbonic acid discharged from the concentration chamber is detected, and the anion concentration in the concentrated water becomes higher than the amount of carbonic acid. As described above, this is achieved by increasing the amount of the solution containing the anion supplied to the concentration chamber. An example is described below. Thereby, the anion exchanger 22 of the concentrating chambers 16a and 16b is likely to be an anion-type anion exchanger having higher selectivity than bicarbonate ions, and can efficiently suppress reverse diffusion of carbonic acid.

FIG. 2 is a schematic configuration diagram of an electric deionized water production apparatus according to another embodiment of the present invention. In the electric deionized water production apparatus 2 shown in FIG. 2, the same components as those in the electric deionized water production apparatus 1 shown in FIG. To do. The electric deionized water production apparatus 2 shown in FIG. 2 has an ion sensor 52 installed in the concentrated water outflow line 50. The ion sensor 52 is electrically connected to the pump 46 via a regulator (not shown) or the like. The ion sensor 52 can detect the concentration of anions such as carbonic acid and Cl 2 ^{− in the} concentrated water passing through the concentrated water outflow line 50.

Concentrating chamber 16a, the anion exchanger 22 in 16b is Cl ^- not in anion form, such as (i.e. has become HCO ₃ form) despreading the carbonate occurs. Therefore, in the present embodiment, when the ratio of the concentration of anions such as carbonic acid and Cl ⁻ detected by the ion sensor 52 deviates by a predetermined value or more, an instruction is sent from the ion sensor 52 to increase the flow rate of the pump 46. The amount of the solution containing anions such as Cl ⁻ supplied to the concentration chambers 16a and 16b is increased. Above by, concentrating chamber 16a, Cl supplied to 16b ^- while appropriately controlling the addition amount of a solution containing such anion concentration compartments 16a, the concentrated water in 16b Cl ^- anions concentration such as concentration compartments 16a, The carbonic acid concentration in 16b can be increased, and the reverse diffusion of carbonic acid can be efficiently suppressed.

  In these embodiments, the configuration in which the water to be treated is brought into contact with the anion exchanger 20 filled in the first small desalting chambers d1, d3, d5 is illustrated. In the present embodiment, the water flow order of the ion exchanger filled in the desalting chamber and the ion exchanger filled in the desalting chamber are not particularly limited, but are described below in the first small desalting chamber. An electric deionized water production apparatus will be described in which a cation exchanger is filled, an anion exchanger is filled in the second small desalting chamber, and the water to be treated is brought into contact in the order of the cation exchanger to the anion exchanger.

  FIG. 3 is a schematic configuration diagram of an electric deionized water production apparatus according to another embodiment of the present invention. The first small desalting chambers d1, d3, d5 shown in FIG. 3 are partitioned by the cation exchange membrane 10 and the intermediate ion exchange membrane 12, and the second small desalting chambers d2, d4, d6 are the intermediate ion exchange membrane 12. And an anion exchange membrane 14. The first small desalting chambers d1, d3, d5 are filled with a cation exchanger 54, and the second small desalting chambers d2, d4, d6 are filled with an anion exchanger 20. In the present embodiment, the intermediate ion exchange membrane 12 is an anion exchange membrane, but is not limited to an anion exchange membrane. Moreover, since the concentration chambers 16a and 16b and the electrode chambers 28 and 30 have the same configuration as the electric deionized water production apparatus 1 in FIG.

  In the electric deionized water production apparatus 3 of FIG. 3, the first inflow lines 36 through which the water to be treated flows are connected to the inlets of the first small demineralization chambers d1, d3, d5, respectively. A first outflow line 38 for flowing out the water to be treated from the outlets of the salt chambers d1, d3, d5 is a second for flowing the water to be treated into the inlets of the second small desalting chambers d2, d4, d6. It is connected to the inflow line 40. A second outflow line 42 through which the treated water flows out is connected to the outlets of the second small desalting chambers d2, d4, d6, respectively. With the above configuration, the water to be treated is first supplied to the first small desalting chambers d1, d3, and d5 and desalted. And the to-be-processed water which passed 1st small desalination chamber d1, d3, d5 is supplied to 2nd small desalination chamber d2, d4, d6, is further desalted, and is discharged | emitted as treated water. Moreover, the structure of the tank 44, the pump 46, the concentrated water inflow line 48, etc. as a supply means which supplies concentrated water to the concentration chamber 16a, 16b is the same structure as the electric deionized water production apparatus 1 of FIG. Therefore, explanation is omitted.

  An example of an operation method in the case of producing deionized water by the electric deionized water production apparatus 3 according to this embodiment will be described below. First, in a state where a direct current is passed between the cathode 24 and the anode 26, the water to be treated is caused to flow from the first inflow line 36, and the water to be treated is caused to flow into the concentrated water inflow line 48 via the bypass line 51. At the same time, the pump 46 is operated, the on-off valve 49 is opened, and a solution containing an anion having an ion selectivity higher than the bicarbonate ion from the tank 44 through the sub inflow line 47 (for example, described later). Salt solution or the like) is introduced into the concentrated water inflow line 48. The treated water that has flowed in from the first inflow line 36 flows through the first small desalting chambers d1, d3, and d5, and the cations are removed when passing through the packed bed of the cation exchanger 54. Furthermore, the treated water that has passed through the first outflow line 38 of the first small desalting chambers d1, d3, d5 passes through the second inflow line 40 of the second small desalting chambers d2, d4, d6, When flowing through the small desalting chambers d2, d4, d6 and passing through the packed bed of the anion exchanger 20, anions such as carbonic acid (free carbonic acid, bicarbonate ion, carbonate ion), silica and the like are removed, and treated water (deionized) Water) is obtained from the second outlet line 42. Further, the solution flowing from the tank 44 to the concentrated water inflow line 48 and the mixed solution of the water to be treated (flowing water according to the present embodiment) flowing from the bypass line 51 to the concentrated water inflow line 48 are supplied to the respective concentration chambers 16a, The ions that flow through 16b and move through the cation exchange membrane 10 and the anion exchange membrane 14 are received and flowed out from the concentrated water outflow line 50 as concentrated water obtained by concentrating the ions. Furthermore, the electrode water flowing in from the first inflow line 36 (electrode water inflow line) flows out from the electrode water outflow line 53.

  As explained above, carbonic acid (free carbonic acid, bicarbonate ion, carbonate ion) trapped by the anion exchanger 20 in the second small desalting chambers d2, d4, d6 is hydroxide ions or anion exchangers. The other anion component trapped by 20 passes through the anion exchange membrane 14 on the anode side and moves to the concentration chambers 16a and 16b. In the present embodiment, since a solution containing anions higher than bicarbonate ions in the order of ion selectivity of the anion exchanger 22 is supplied to the concentration chambers 16a and 16b, the carbon dioxide that has moved to the concentration chambers 16a and 16b It is not trapped by the anion exchanger in the anionic form, which has higher selectivity for carbonate ions, and is discharged together with the concentrated water to the concentrated water outlet line 50. Therefore, it is possible to suppress the carbon dioxide gas from moving to the first small desalting chambers d3 and d5 through the cation exchange membrane 10 and backdiffusing into the water to be treated.

  In the present embodiment, the thickness of the first small desalting chambers d1, d3, d5 or the second small desalting chambers d2, d4, d6 is not particularly limited, but the thickness of the first small desalting chambers d1, d3, d5. If the thickness is 0.8 to 600 mm, preferably 2 to 100 mm, and the thickness of the second small desalting chambers d2, d4, and d6 is 0.8 to 600 mm, preferably 6 to 100 mm, low electrical resistance and high current This is preferable in that efficiency can be obtained. If the thickness of the first small desalting chambers d1, d3, d5 is less than 0.8 mm, sufficient residence time cannot be secured, and the water quality tends to deteriorate. On the other hand, if it exceeds 600 mm, the electric resistance is too large, and the stable operation of the apparatus tends to be hindered. Similarly, if the thickness of the second small desalting chambers d2, d4, d6 is less than 0.8 mm, sufficient residence time cannot be secured, and the water quality tends to deteriorate. On the other hand, if it exceeds 600 mm, the increase in electrical resistance tends to be more significant than the increase in current efficiency.

  The ion exchanger used as the anion exchanger (20, 32) and cation exchanger (34, 54) may be any substance as long as it has an ion exchange function, such as an ion exchange resin and an ion exchange fiber. May be combined.

  Examples of the anion exchanger 22 filled in the concentration chambers 16a and 16b include a strongly basic anion exchanger. Examples of the anion exchanger include anion exchange resins, anion exchange fibers, and organic porous anion exchangers described in JP-A No. 2002-306976. The strong basic anion exchanger may partially contain a weak basic anion exchange group. The anion exchange resin has an advantage that the reaction is sufficiently performed even when the free carbonic acid concentration is low, and scale generation can be suppressed. Moreover, it is preferable that the particle size of the anion exchange resin is uniform in that the differential pressure in the concentration chamber is reduced.

  As thickness of the concentration chambers 16a and 16b, 0.5 mm-60 mm are preferable, and 1 mm-10 mm are especially preferable. If it is less than 0.5 mm, even if the anion exchanger 22 is filled, it becomes difficult to obtain an effect of suppressing the occurrence of scale, and the water flow differential pressure tends to increase. On the other hand, if it exceeds 60 mm, the electrical resistance increases and the power consumption tends to increase.

  In the electric deionized water production apparatus, the treatment amount (SV, LV), the energization amount, and other operating conditions can be appropriately set according to the properties of the water to be treated.

In the present embodiment, the water to be treated that is to be treated is not particularly limited, but even water to be treated that contains a large amount of carbonic acid components can prevent carbonation of the final treated water. Examples of water to be treated containing a large amount of carbonic acid component include tap water or water obtained by treating tap water with an RO membrane or the like. Domestic tap water usually contains a hardness component in addition to a carbonic acid component, but according to the present embodiment, the anion exchanger 22 is filled in the concentrating chambers 16a and 16b, so that they have moved to the concentrating chambers 16a and 16b. Ca ²⁺ ions and Mg ²⁺ ions are hardly combined with carbonate ions (CO ₃ ²⁻ ) on the surface of the anion exchange membrane 14 in the concentration chambers 16a and 16b to form a hardness scale, and the flow path is blocked in the concentration chambers 16a and 16b. There is almost no such thing.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

FIG. 4 is a schematic configuration diagram showing a test cell for measuring the amount of carbonic acid components moving from the concentration chamber to the desalting chamber. As shown in FIG. 4, an anion exchange membrane 64 and a first cation exchange membrane 66 are partitioned between a cathode chamber 58 filled with an anion exchange resin 56 and an anode chamber 62 filled with a cation exchange resin 60. A test cell 4 having a concentration chamber 68 filled with an anion exchange resin 56, a first cation exchange membrane 66 and a second cation exchange membrane 70, and a desalting chamber 72 filled with a cation exchange resin 60 is prepared. Then, the amount of carbonic acid component moving from the concentration chamber 68 to the desalting chamber 72 was measured under the following conditions. Ultrapure water is passed through the desalting chamber 72 and the electrode chambers (58, 62), and a NaCl + NaHCO ₃ solution (carbonate concentration 30 mg-CaCO ₃ / L, [Cl] 50%, [HCO ₃ ] 50%), and this was taken as an example.
<Ion exchanger used>
Cation exchange resin: Rohm and Haas, Amberlite IRA402BL
Anion exchange resin: Rohm and Haas, Amberlite IRA402BL
First cation exchange membrane, second cation exchange membrane: manufactured by Astom Co., Ltd., C66-10F
Anion exchange membrane: AHA made by Astom Co., Ltd.
<EDI size>
Test cell: 10cm long x 10cm wide x 8mm thick
<Flow conditions>
Ultrapure water, NaCl + NaHCO ₃ solution: 8000 ml / hr
<Current conditions>
Constant current: 0.5 A / dm ²

(Comparative example)
A comparative example was prepared under the same conditions as in Example except that carbonated water ([HCO ₃ ] 100%) was passed through the concentration chamber 68 instead of the NaCl + NaHCO ₃ solution.

The amount of carbonic acid in the treated water (ultra pure water) discharged from the desalting chambers of Examples and Comparative Examples was measured. Specifically, inorganic carbon (IC) in the treated water was measured with a TOC meter (A-1000) manufactured by Altena, and the amount of carbonic acid in the treated water was measured using this as carbonic acid. The treated water discharged from the desalting chamber of the comparative example contained 8400 μg-CaCO ₃ / hr of a carbonic acid component. On the other hand, the treated water discharged from the desalting chamber of the example contained 700 μg-CaCO ₃ / hr of a carbonic acid component, but the amount of the carbonic acid component was significantly suppressed as compared with the comparative example. That is, by supplying a solution containing an anion (in the embodiment, chlorine ion) having an ion selectivity higher than that of bicarbonate ion to the concentration chamber, the carbon component in the concentration chamber is passed through the cation exchange membrane. It was confirmed that movement to the desalting chamber can be suppressed.

It is a schematic block diagram of the electrical deionized water manufacturing apparatus which concerns on this embodiment. It is a schematic block diagram of the electrical deionized water manufacturing apparatus which concerns on other embodiment of this invention. It is a schematic block diagram of the electrical deionized water manufacturing apparatus which concerns on other embodiment of this invention. It is a schematic block diagram which shows the test cell for measuring the amount of carbonic acid components which moves to a desalination chamber from a concentration chamber.

Explanation of symbols

  1-3 Electric deionized water production apparatus, 4 test cells, 10, 66, 70 cation exchange membrane, 12 intermediate ion exchange membrane, 14, 64 anion exchange membrane, 16a, 16b, 68 concentration chamber, 18 mixture, 20 , 22, 32 Anion exchanger, 34, 54 Cation exchanger, 24 cathode, 26 anode, 28, 30, 58, 62 electrode chamber, 36 first inlet line, 38 first outlet line, 40 second inlet line, 42 Second Outflow Line, 44 Tank, 46 Pump, 47 Sub Inflow Line, 48 Concentrated Water Inflow Line, 49 Open / Close Valve, 50 Concentrated Water Outflow Line, 51 Bypass Line, 52 Ion Sensor, 53 Electrode Water Outflow Line, 56 Anion Exchange Resin , 60 cation exchange resin, 72, D1, D2, D3 desalting chamber, d1, d3, d5 first small desalting chamber, d2, d4 d6 Second small desalination chamber.

Claims (6)

Between the anode and the cathode, it is partitioned by a cation exchange membrane on one side and an anion exchange membrane on the other side, and a desalting chamber filled with an ion exchanger, through the cation exchange membrane and the anion exchange membrane An electric deionized water production apparatus having a supply unit provided on both sides of the demineralization chamber and having a concentration chamber filled with an anion exchanger, and supplying concentrated water to the concentration chamber;
The concentrated deionized water is a solution containing anions having an ion selectivity higher than that of bicarbonate ions in the anion exchanger.   2. The electric deionized water production apparatus according to claim 1, wherein the supply means supplies the concentrated water so that an ion concentration of the anion in the concentration chamber is equal to or higher than a carbonic acid concentration in the concentration chamber. An electrical deionized water production apparatus.   The electric deionized water production apparatus according to claim 1 or 2, wherein the anion is a chlorine ion. Between the anode and the cathode, it is partitioned by a cation exchange membrane on one side and an anion exchange membrane on the other side, and a desalting chamber filled with an ion exchanger, through the cation exchange membrane and the anion exchange membrane A deionized water is produced by using an electric deionized water production apparatus that is provided on both sides of the demineralization chamber and is provided with a concentration chamber filled with an anion exchanger and supplies the concentrated water to the concentration chamber. A method for producing deionized water comprising:
The method for producing deionized water, wherein the concentrated water is a solution containing anions having higher ion selectivity than the bicarbonate ions.   5. The method for producing deionized water according to claim 4, wherein the concentrated water is supplied so that an ion concentration of the anion in the concentration chamber is equal to or higher than a carbonic acid concentration in the concentration chamber. Manufacturing method.   6. The method for producing deionized water according to claim 4, wherein the anion is a chlorine ion.

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