JP2007268331A - Apparatus for manufacturing electrically deionized water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing electrically deionized water which can prevent a deterioration in the quality of water to be treated caused by reversed diffusion of weakly basic materials in concentrated water to a desalting chamber. <P>SOLUTION: In an apparatus for manufacturing deionized water installed with concentrating chambers on both sides of the desalting chambers, and with these desalting chambers and the concentrating chambers located between electrode chambers, impurity ions in the water to be treated are removed through making the water to be treated containing the weakly basic ions flow into the desalting chambers, the concentrated water into the concentrating chambers, and electrode water into the electrode chambers respectively, while applying voltage between an anode and a cathode. The apparatus for manufacturing the electrically deionized water is provided with a pH adjusting means adjusting the pH of circulating concentrated water flowing out of a concentrated water tank toward the concentrating chambers in a concentrated water circulation system including the concentrated water tank circulating the concentrated water flowing through the concentrating chambers so as to prevent non-dissociation molecules from reversed diffusion from the concentrating chambers side to the desalting chamber side. The pH of the concentrated water is adjusted and kept to the pH which keeps the weakly basic materials ionized so as to prevent a reversed diffusion toward the water to be treated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric deionized water production apparatus suitable for the production of so-called deionized water, which is used as boiler water, condensate of a power plant, water in a steam generator of a power plant, etc. The present invention relates to an electrical deionized water production apparatus suitable for producing deionized water by subjecting water to be treated containing ions, particularly ammonia, to demineralization treatment.

  As a method for producing deionized water (hereinafter sometimes referred to as demineralized water), a method of deionizing water through treated water through an ion exchange resin is conventionally known. In this method, an ion exchange resin is used. When it is saturated with ions, it is necessary to regenerate with a chemical. To eliminate such disadvantages in processing operation, there is a method for producing deionized water by an electrical deionization method that does not require any chemical regeneration. Established and put into practical use.

  In an electric deionized water production apparatus that performs such desalting treatment, for example, as shown in FIG. 3, basically, a chamber defined by a cation exchange membrane and an anion exchange membrane is filled with an ion exchanger. The demineralization chamber 101 is configured, and the concentration chambers 102 are provided on both sides of the desalination chamber 101. The demineralization chamber 101 and the concentration chamber 102 are both electrodes including an anode chamber having an anode and a cathode chamber having a cathode. A main body 104 is configured by being disposed between the chambers 103 and 103. The treated water 105 is passed through the ion exchanger layer filled in the desalting chamber 101, a voltage is applied between the anode and the cathode, and the treated water is passed through both the ion exchange membranes. By applying a direct current in a direction perpendicular to the flow, the impurity ions in the water to be treated are electrically excluded from the concentrated water flowing in the concentration chamber 102 disposed outside the both ion exchange membranes. Deionized water as water 106 is produced. In addition, this figure is a conceptual diagram, and is usually a device in which a plurality of concentration chambers and desalting chambers are alternately arranged.

  In order to suppress the generation of scale such as calcium carbonate and magnesium hydroxide in the concentration chamber 102 or to increase the water recovery rate, the concentrated water in such an electric deionized water production apparatus is usually a circulation pump (illustrated). And a concentrated water circulation system 108 having a concentrated water tank 107. In this concentrated water circulation system 108, ionic impurities and the like desalted from the desalting chamber through the ion exchange membrane are concentrated, so that water to be treated is appropriately replenished as makeup water from the makeup water supply pipe 109 for adjusting the concentration. Meanwhile, the concentrated water is partially discharged out of the system through the blow system 110. In addition, a part of the water to be treated is often supplied and used as electrode water from the electrode water supply pipe 111 to the electrode chambers 103 and 103. In the electrode chambers 103, 103, chlorine and oxygen are by-produced on the anode side and hydrogen etc. are by-produced on the anode side, so that the electrode water supplied to the electrode chambers 103, 103 is systemized by the electrode water outflow pipe 112. It is discharged outside. The discharged electrode water is processed by a gas-liquid separator (not shown), and hydrogen is exhausted.

  The installation of the gas-liquid separator that treats this electrode water is an indispensable facility for safely discharging in a dilute hydrogen concentration because there is a risk of explosion if the hydrogen concentration exceeds a predetermined concentration. . Further, a configuration in which exhaust means is attached to the concentrated water tank 107 in the concentrated water circulation system 108 is also known (for example, Patent Document 1).

In addition, in order to suppress the generation of scale in the concentration chamber 102, an acidic liquid is added to the concentrated water circulated in the concentration chamber so that the pH of the concentrated water is 2 or more and less than 4. Although a deionized water production apparatus is also known (Patent Document 2), the purpose and effect of this invention are limited to prevention of scale precipitation. Therefore, the technical idea is basically different from the present invention described below.
JP 2003-170169 A Japanese Patent No. 3511459

  However, when the water to be treated is an alkaline solution containing a large amount of weak electrolyte, when the concentrated water is circulated, the weak electrolytic substance concentrated in the concentrated water circulation system is not ionized. This causes the problem of despreading and reducing the resistivity of the treated water.

  The reason is as follows. Weakly basic substances (eg ammonia) are present as ammonia when the pH is high. The ammonia in the water to be treated flowing into the desalting chamber is firstly charged in the form of ammonium ions that are moved to the concentrating chamber by an electric current and discharged into the concentrating water for removal. However, the pH of the concentrated water in the concentration chamber gradually increases, and ammonium ions in the concentrated water exist as ammonia that does not dissociate. Such non-dissociated ammonia is not affected by the current. Therefore, ammonia concentrated in such a high concentration is reversely diffused into the desalting chamber through the ion exchange membrane and flows out into the treated water, thereby deteriorating the quality of the treated water. Specifically, for example, treated water having a resistivity of 16 MΩ-cm or more in the initial stage of water flow is reduced to a resistivity of about 2 MΩ-cm due to the back diffusion of ammonia.

  Therefore, the object of the present invention is to focus on the above-mentioned problems, and to prevent the weakly basic substance in the concentrated water from back-diffusing into the desalting chamber and reducing the quality of the treated water. It is to provide a manufacturing apparatus.

  In the above situation, as a result of intensive studies, the present inventors have installed a pH adjusting means in the concentrated water circulation system, and the pH of the concentrated water is adjusted not to the form of molecules in which the weakly basic substance is not dissociated. If the pH can be controlled and maintained so that the form can be maintained, the weakly basic substance will not permeate the ion-exchange membrane, so that it is possible to prevent deterioration of the quality of the treated water due to the reverse diffusion of the weakly basic substance. The headline and the present invention were completed.

  In other words, the electric deionized water production apparatus according to the present invention is a dewatering treatment in which water to be treated is desalted by filling an ion exchanger into a chamber defined by a cation exchange membrane on one side and an anion exchange membrane on the other side. A salt chamber is formed, and a concentration chamber is provided on both sides of the desalting chamber via the cation exchange membrane and the anion exchange membrane. The desalting chamber and the concentration chamber are divided into an anode chamber having an anode and a cathode chamber having a cathode. Disposed between both electrode chambers, and while applying a voltage between the anode and the cathode, water to be treated containing weakly basic ions in the desalting chamber, concentrated water in the concentration chamber, and the electrode A concentrated water circulation system including a concentrated water tank that circulates the concentrated water flowing through the concentration chamber, wherein the electrode water is introduced into the chamber to remove impurity ions in the water to be treated to produce deionized water. From the concentration chamber side to the desalting chamber side of molecules that have not been dissociated In order to prevent reverse diffusion, consisting of those which characterized in that a pH adjusting means concentrated water to adjust the pH of the circulating concentrated water flowing out toward the concentrating compartment from the concentrated water tank. That is, by adjusting the pH of the circulating concentrated water by the pH adjusting means of the concentrated water, the weakly basic substance contained in the concentrated water can be kept in the ionic form. This is an apparatus that prevents non-dissociated molecules from back-diffusing from the concentration chamber side to the desalting chamber side.

  In this electric deionized water production apparatus, the pH adjusting means preferably comprises means for adjusting the pH of the circulating concentrated water to 5 or less, preferably to pH 5-1. By adjusting and maintaining such pH, it is possible to prevent the weakly basic substance contained in the concentrated water from back-diffusing from the concentration chamber side to the desalting chamber side in the form of non-dissociated molecules. .

  Further, when the water to be treated contains ammonia, in particular, when the water to be treated comprises ammonia having a pH of 9 to 11 and an ammonia concentration of 500 μg / L to 100 mg / L, preferably 1 mg / L to 100 mg / L, the pH The adjusting means preferably comprises means for adjusting the pH of the circulating concentrated water to 3 or less, preferably to pH 3-1. By adjusting and maintaining such pH, it is possible to prevent the ammonia contained in the concentrated water from back-diffusing from the concentration chamber side to the desalting chamber side in the form of molecules that have not been dissociated.

  The structure of the electric deionized water production apparatus according to the present invention is such that the demineralization chamber is divided into two small demineralization chambers by an intermediate ion exchange membrane located between the cation exchange membrane and the anion exchange membrane. Therefore, the present invention can also be applied to a so-called power-saving electric deionized water production apparatus configured such that the water to be treated flows sequentially through two small desalting chambers. Thereby, the quality of treated water can be improved with efficient desalting.

  In this case, of the two small desalting chambers, one anion exchanger is filled in one small desalting chamber through which treated water is first passed, and the other small desalting chamber is filled with a cation exchanger. It is particularly preferred that the anion exchanger is packed in a mixed bed form. By adopting such a packed form of the ion exchanger, a desalting chamber on the outlet side of the treated water, that is, a cation exchanger and an anion exchanger, even when weak electrolyte (ammonia) is contained in the anode side concentrated water In order to reach the mixed bed demineralization chamber by reverse diffusion, the ion exchange membrane must be despread twice. Therefore, the mixed bed demineralization chamber entrance is along the flow path of the treated water rather than moving by reverse diffusion. Since it is treated as ammonium ions by the cation exchanger in the mixed bed demineralization chamber and discharged to the cathode-side concentration chamber, deionized water with further excellent water quality can be obtained.

  According to the electric deionized water production apparatus of the present invention, it is possible to keep weakly basic substances, particularly ammonia, in the concentrated water in an ionized state by appropriately adjusting the pH with the pH adjusting means of the concentrated water. In addition, the reverse diffusion of the weakly basic substance from the concentration chamber side to the desalting chamber side can be reliably prevented, and deterioration of the quality of treated water (for example, decrease in resistivity) due to the reverse diffusion can be prevented. For this reason, highly purified deionized water can be obtained.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a basic configuration of an electric deionized water production apparatus according to an embodiment of the present invention. In FIG. 1, a chamber partitioned by a cation exchange membrane on one side and an anion exchange membrane on the other side is filled with an ion exchanger (eg, ion exchange resin, monolithic organic porous ion exchanger, ion exchange fiber, etc.). Thus, a desalting chamber 1 for desalting the treated water 5 containing weakly basic ions is configured. Concentration chambers 2 are provided on both sides of the desalination chamber 1, and the desalination chamber 1 and the concentration chamber 2 are both electrode chambers 3, 3 (one of which is an anode chamber having an anode and a cathode chamber having a cathode). The main body 4 is configured by being arranged between the anode chamber and the other cathode chamber). Although FIG. 1 shows a form in which the concentration chambers 2 are provided on both sides of one desalting chamber 1, a plurality of sets of the desalting chamber 1 and the concentration chamber 2 can be arranged. The water to be treated 5 is passed through the ion exchanger layer filled in the desalting chamber 1, a predetermined voltage is applied between the anode and the cathode, and the water to be treated is passed through both the ion exchange membranes. By applying a direct current in a direction perpendicular to the water flow, impurity ions in the water to be treated are electrically removed from the concentrated water flowing in the concentration chamber 2 disposed outside the ion exchange membranes. Then, deionized water as the treated water 6 is produced.

  A concentration pump having a circulation pump (not shown) and a concentrated water tank 7 for circulating the concentrated water flowing through the concentration chamber 2 to the concentration chamber 2 of the main body 4 in the electric deionized water production apparatus. A water circulation system 8 is provided. In the concentrated water circulation system 8, ionic impurities and the like desalted from the desalting chamber through the ion exchange membrane are concentrated, so that the treated water 5 is appropriately replenished as makeup water from the makeup water supply pipe 9 for adjusting the concentration. Meanwhile, the concentrated water is partially discharged out of the system through the blow system 10. Further, a part of the water to be treated is supplied from the electrode water supply pipe 11 to the electrode chambers 3 and 3 as electrode water so that it can be used. In the electrode chambers 3 and 3, chlorine and oxygen are by-produced on the anode side and hydrogen and the like are by-produced on the anode side due to the electrolysis of water, so that the electrode water supplied to the electrode chambers 3 and 3 is systemized by the electrode water outflow pipe 12. It can be discharged to the outside. The discharged electrode water is preferably treated with a gas-liquid separator (not shown) to discharge hydrogen. Note that FIG. 1 is also a conceptual diagram, and normally, a concentration chamber and a desalting chamber are arranged alternately.

  The configuration so far is basically the same as that of the conventional apparatus shown in FIG. 3, but in the above-described embodiment according to the present invention, the pH adjusting agent is added to the concentrated water circulation system 8, particularly to the concentrated water tank 7. Back diffusion of non-dissociated molecules from the concentration chamber 2 side to the desalting chamber 1 side, which includes a stored pH adjustment drug tank 13 and a drug injection pump 14 for injecting the pH adjustment drug into the concentrated water tank 7 Concentrated water pH adjusting means 15 is attached to prevent this. Further, the concentrated water tank 7 may be provided with a pH detector (not shown), and its detection signal may be fed back to the drug infusion pump 14 so that it can be controlled within the target pH range. However, when there is no change in the quality of the water to be treated, the pH detector may not be provided. The pH adjustment of the concentrated water by the pH adjusting means 15 can basically keep the weakly basic substance in the concentrated water in an ionized state as described above, and dissociate from the concentration chamber side to the desalting chamber side. This is done to prevent back-diffusion of molecules of weakly basic substances.

  In the electric deionized water production apparatus according to this embodiment configured as described above, the pH is adjusted to a pH within a target range by the concentrated water tank 7 of the concentrated water circulation system 8 (for example, 5 or less). The concentrated water adjusted to the pH of the concentrated water is sent to the concentration chamber 2 and circulated through the concentrated water circulation system 8. By adjusting the pH, the weakly basic substance in the concentrated water flowing through the concentration chamber 2 is kept in an ionized state and is prevented from existing in the state of a weakly basic substance molecule that has not been dissociated. Back diffusion to the desalting chamber 1 side is avoided. In particular, weakly basic substances contained in concentrated water become ions by acidifying the pH, so that molecules that have not been dissociated do not reversely diffuse into the desalting chamber 1 via the ion exchange membrane. The water quality is not deteriorated. Therefore, in the desalting chamber 1, the impurity ions contained in the water to be treated 5 are electrically removed to the concentration chamber 2 through each ion exchange membrane, and the target desalting treatment is efficiently performed. Desired deionized water (for example, having a desired resistivity) is obtained as the treated water 6. Impurity ions include, for example, carbonate ion, ammonium ion, sodium ion, chloride ion, sulfate ion, etc., and these charged ions are brought into the concentration chamber 2 side by the current flowing between the anode and the cathode. It moves and is discharged into concentrated water.

  Note that the method of adding a drug for adjusting the pH by the pH adjusting unit 15 is not limited to the above embodiment, and the concentration of the additive may be determined as appropriate depending on the scale of the apparatus and the installation location.

  In addition, the form of the main body of the electric deionized water production apparatus according to the present invention is not particularly limited, and examples thereof include a spiral type, a concentric circular type, and a flat plate laminated type.

  Further, the water to be treated supplied to the electric deionized water production apparatus according to the present invention is not particularly limited. For example, boiler water, power plant condensate, steam generator blowdown water, sewage, industrial Permeated water that has been treated with reverse osmosis membranes, such as cleaning water from river water, semiconductor devices in semiconductor manufacturing plants, or recovered water from concentration chambers, and recovered water used at point of use at semiconductor manufacturing plants, etc. And water that has not been subjected to reverse osmosis membrane treatment. Moreover, these mixed water may be sufficient.

  In the electric deionized water production apparatus according to the present invention, the demineralization chamber is divided into two small demineralization chambers by an intermediate ion exchange membrane located between the cation exchange membrane and the anion exchange membrane, Two small desalting chambers can be configured to flow sequentially. This form makes it possible to perform a more efficient desalting treatment. This form is particularly effective when the water to be treated is water to be treated containing ammonia (for example, water to be treated containing ammonia having a pH of 9 to 11 and an ammonia concentration of 500 μg / L to 100 mg / L). When the water to be treated is treated water containing ammonia, anion exchanger is filled in a single-bed form in one of the two small desalting chambers where the treated water is first passed. The other small desalting chamber is preferably filled with a cation exchanger and an anion exchanger in a mixed bed form.

FIG. 2 illustrates an example of the power-saving electrodeionized water production apparatus 21 having the above configuration.
The desalting chamber 22 is divided into two small desalting chambers, a D1 chamber 23 and a D2 chamber 24, by a cation exchange membrane 30, an anion exchange membrane 32, and an intermediate ion exchange membrane 31 located between both membranes 30 and 32. First, the D1 chamber 23 into which the water to be treated flows is a single-bed desalination chamber of the anion exchanger, and then the D2 chamber 24 into which the outlet water of the D1 chamber 23 flows is mixed with the cation exchanger and the anion exchanger. A floor desalination chamber is provided, and a concentration chamber 25 is disposed on both sides of the desalination chamber 22 and an electrode chamber 26 is disposed outside the concentration chamber 25. An anion exchange membrane 29 is disposed between the cathode-side concentration chamber 25 and the electrode chamber 26, and a cation exchange membrane 33 is disposed between the anode-side concentration chamber 25 and the electrode chamber 26. Concentrated water adjusted to a target pH is circulated in the concentrating chamber 25 by a concentrated water circulation system 28 equipped with pH adjusting means 27. In addition, although this example illustrated an example of the power saving type deionized water manufacturing apparatus, it is not restricted to this example, The ion exchange membrane, ion exchanger, etc. to be used are selected suitably.

Thus, by making the desalination chamber into two small desalination chambers D1 chamber 23 and D2 chamber 24, as shown in FIG. 2, for example, the concentrated water in the concentration chamber 25 located on the anode side of the desalination chamber 22 In addition, when ammonia is present in the form of molecules (NH ₃ ), in order for ammonia to flow into the treated water, the deionization chamber side anion exchange membrane is back-diffused and moved into the D1 chamber 23, from there Further, the anion exchange membrane as the intermediate ion exchange membrane must be back-diffused and moved into the D2 chamber 24. On the other hand, ammonia flowing from the inlet of the D2 chamber 24 along the flow path of the water to be treated is treated by the cation exchanger in the D2 chamber 24 and discharged to the cathode side concentrating chamber, so that ammonia flows out into the treated water. Is suppressed.

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention. In the following examples, JIS-B8224 “Indophenol blue absorptiometry” was used as a method for quantifying ammonia.

Example 1
The treated water containing ammonia was desalted in a mixed bed desalting cell. Using the following equipment specifications, operating conditions and the electric deionized water production system with the flow shown in Fig. 1, ammonium ion 20mg / L, sodium ion 1mg / L, chloride ion 1mg / L, sulfate ion 1mg / L Deionized water was produced from the treated water. The evaluation method was the resistivity of treated water after 100 hours of continuous operation at an applied voltage of 100 V and an applied current of 1.2 A. As a result, the resistivity of the treated water was 15.8 MΩ-cm.

(Operating conditions)
Electric deionized water production apparatus; electric deionized water production apparatus shown in FIG. 1 (hereinafter, sometimes referred to as EDI)
・ Desalination chamber: width 75mm, height 330mm, thickness 4mm
-Ion exchange resin filled in the desalting chamber; mixed ion exchange resin of anion exchange resin (A) and cation exchange resin (K) (mixing ratio is A: K = 1: 1 by volume)
・ Concentration chamber: width 75mm, height 330mm, thickness 1mm
・ Flow rate of the entire device: 60 L / h
・ Circulating tank; Liquid phase capacity 20L
-Hydrochloric acid was added so that the pH of the concentrated water was 1.5.

Comparative Example 1
Compared to Example 1, the pH of the concentrated water was not adjusted and the pH was kept at 10.0. In this case, the resistivity of the treated water was 1.8 MΩ-cm.

Example 2
Compared to Example 1, the desalination chamber is partitioned into two small desalination chambers by an intermediate ion exchange membrane located between the cation exchange membrane and the anion exchange membrane, and the water to be treated is divided into two small desalination chambers. In a so-called power-saving electric deionized water production apparatus (hereinafter sometimes abbreviated as power-saving EDI). + Desalination treatment was performed in a mixed bed desalting cell, and water was passed in the order of cation single bed → mixed bed. It was carried out in the same manner as in Example 1 except that the main body of the electric deionized water production apparatus was an apparatus having the following specifications. As a result, the resistivity of the treated water was 16.6 MΩ-cm.

(Operating conditions)
・ Electric deionized water production equipment; power-saving EDI
・ Intermediate ion exchange membrane; anion exchange membrane ・ Small desalination chamber (D2); width 75mm, height 330mm, thickness 4mm
-Ion exchange resin filled in small desalting chamber (D2); mixed ion exchange resin of anion exchange resin (A) and cation exchange resin (K) (mixing ratio is A: K = 1: 1 by volume)
・ Small desalination chamber (D1); width 75mm, height 330mm, thickness 8mm
・ Small desalination chamber (D1) filled ion exchange resin; cation exchange resin ・ concentration chamber; width 75 mm, height 330 mm, thickness 1 mm
・ Flow rate of the entire device: 60 L / h
・ Circulating tank; capacity 20L
-Hydrochloric acid was added so that the pH of the concentrated water was 1.5 ± 0.5.

Comparative Example 2
Compared to Example 2, the pH of the concentrated water was not adjusted and the pH was kept at 10.0. In this case, the resistivity of the treated water was 6.2 MΩ-cm.

Example 3
Weakly basic water to be treated containing ammonia was desalted in an anion single bed + mixed bed desalting cell. The method was the same as in Example 2 except that the main body of the electric deionized water production apparatus was an apparatus having the following specifications. As a result, the resistivity of the treated water was 17.6 MΩ-cm.

(Operating conditions)
・ Electric deionized water production equipment; power-saving EDI
・ Intermediate ion exchange membrane; anion exchange membrane ・ Small desalination chamber (D2); width 75mm, height 330mm, thickness 4mm
-Ion exchange resin filled in small desalting chamber (D2); mixed ion exchange resin of anion exchange resin (A) and cation exchange resin (K) (mixing ratio is A: K = 1: 1 by volume)
・ Small desalination chamber (D1); width 75mm, height 330mm, thickness 8mm
・ Small desalination chamber (D1) filled ion exchange resin; anion exchange resin ・ concentration chamber; width 75 mm, height 330 mm, thickness 1 mm
・ Flow rate of the entire device: 60 L / h
・ Circulating tank; capacity 20L
-Hydrochloric acid was added so that the pH of the concentrated water was 1.5 ± 0.5.

Comparative Example 3
Compared to Example 3, the pH of the concentrated water was not adjusted and the pH was kept at 13.5. In this case, the resistivity of the treated water was 10.2 MΩ-cm.

  According to the said Examples 1-3, the resistivity of treated water was high compared with Comparative Examples 1-3, and the highly purified treated water was obtained.

  In particular, in the form of the anion exchanger single bed demineralization chamber + mixed bed demineralization chamber in Example 3, as shown in FIG. Some are captured and discharged by the cationic resin in the salt chamber. Further, in order to reach the mixed bed desalting chamber by back diffusion, it is necessary to back diffuse the anion exchange membrane twice. For this reason, a better result was obtained than the apparatus having only the mixed bed desalination chamber.

  In addition, when the pH is adjusted by the pH adjusting means as described above, the resistivity is higher. However, for the purpose of removing impurity ions, if it is practically 10 MΩ-cm, a high-concentration weak electrolytic substance is present. When contained in the water to be treated, the decrease in the resistivity is often caused by outflow to the treated water due to the back diffusion of ammonia molecules, and the impurity ions in the treated water are often sufficiently low. Even if it is not added (only an anion single bed + mixed bed apparatus), sufficient water quality may be obtained.

  The electric deionized water production apparatus according to the present invention can be applied to the production of deionized water in all fields when the water to be treated contains weak basic ions, and in particular, boiler water, condensate of power plants, power generation This is suitable for the production of deionized water used as the water in the steam generator of the plant.

It is a schematic equipment system diagram of the electric deionized water manufacturing apparatus concerning one embodiment of the present invention. It is a schematic apparatus system diagram of the electrical deionized water production apparatus according to another embodiment of the present invention. It is a schematic equipment system diagram of the conventional electric deionized water production apparatus.

Explanation of symbols

1 Desalination chamber 2 Concentration chamber 3 Electrode chamber (one is an anode chamber, the other is a cathode chamber)
4 Main Body 5 Water to be treated 6 Deionized water as treated water 7 Concentrated water tank 8 Concentrated water circulation system 9 Makeup water supply pipe 10 Blow system 11 Electrode water supply pipe 12 Electrode water outflow pipe 13 pH adjustment chemical tank 14 Chemical injection pump DESCRIPTION OF SYMBOLS 15 pH adjustment means 21 Electric deionized water production apparatus 22 Desalination chambers 23 and 24 Small demineralization chamber 25 Concentration chamber 26 Electrode chamber 27 pH adjustment means 28 Concentrated water circulation system 29 and 32 Anion exchange membranes 30 and 33 Cation exchange membrane 31 Intermediate ion exchange membrane

Claims (5)

  A demineralization chamber for demineralizing treated water by filling an ion exchanger in a chamber defined by a cation exchange membrane on one side and an anion exchange membrane on the other side is configured. Concentration chambers are provided on both sides of the desalting chamber, and the desalting chamber and the concentration chamber are disposed between both electrode chambers including an anode chamber having an anode and a cathode chamber having a cathode. Impurities in the water to be treated by flowing water to be treated containing weak basic ions into the desalting chamber, concentrated water into the concentration chamber, and electrode water into the electrode chamber while applying a voltage between An apparatus for removing deionized water to produce deionized water, wherein the deionized water from the concentration chamber side of undissociated molecules is introduced into a concentrated water circulation system including a concentrated water tank that circulates the concentrated water flowing through the concentration chamber. In order to prevent reverse diffusion to the salt chamber side, the concentrated water tank Electrodeionization water producing apparatus characterized in that a pH adjusting means concentrated water to adjust the pH of the circulating concentrated water flowing out toward the chamber.   The electric deionized water production apparatus according to claim 1, wherein the pH adjusting means comprises means for adjusting the pH of the circulating concentrated water to 5 or less.   The treated water is composed of treated water containing ammonia having a pH of 9 to 11 and an ammonia concentration of 500 μg / L to 100 mg / L, and the pH adjusting means is composed of means for adjusting the pH of the circulating concentrated water to 3 or less. The electric deionized water production apparatus according to claim 1 or 2.   The desalting chamber is partitioned into two small desalting chambers by an intermediate ion exchange membrane located between the cation exchange membrane and the anion exchange membrane, and the water to be treated sequentially passes through the two small desalting chambers. The electric deionized water production apparatus according to any one of claims 1 to 3, wherein the apparatus is configured to flow.   Of the two small desalting chambers, one small desalting chamber through which treated water is first passed is filled with an anion exchanger in a single bed form, and the other small desalting chamber is filled with a cation exchanger and an anion exchange. The electric deionized water production apparatus according to claim 4, wherein the body is filled in a mixed bed form.

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