JP2004261648A - Electrodeionization apparatus, and operating method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrodeionization apparatus which suppresses the concentration diffusion of carbonate ions from a concentrating chambers, so that production water having an extremely low carbonate ion concentration can be obtained, and to provide an operating method therefor. <P>SOLUTION: Raw water is introduced into a desalting chambers 16, and produced water is discharged from desalting chambers 16. Part of the produced water is passed to a concentrating chambers 15 in a direction reverse to the water passing direction in the desalting chambers 16 in a counter-current single pass system, and outflow water of the concentrating chambers 15 is discharged outside the system. The discharge side of the produced water in each desalting chamber 16 is provided with the inflow port of each concentrating chamber 15, and the inflow side of the raw water in each desalting chamber 16 is provided with the outflow port of each concentrating chamber 15. Anions of a part of the treated water are removed by using an anion removal means 9, and is passed to each concentrating chamber 15. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrodeionization apparatus for producing product water having a low anion concentration and a method of operating the same.
[0002]
[Prior art]
2. Description of the Related Art Electrodeionization devices are used in fields such as producing pure water and ultrapure water. The plate and frame type electrodeionization apparatus has a flat membrane shape in which an anode, a cathode, and a concentration chamber and a desalination chamber (dilution chamber) are alternately formed between the anode and the cathode. It has a cation exchange membrane and an anion exchange membrane. The desalting chamber is filled with an ion exchanger such as an ion exchange resin. Water to be subjected to a desalination treatment is circulated through the desalting chamber, and ions in the water pass through the ion exchange membrane and move from the desalting chamber to the concentration chamber.
[0003]
Japanese Patent Application Laid-Open No. 2002-205069 discloses that in order to produce product water having a low silica concentration and low boron concentration, water having a lower silica or boron concentration than raw water is used as concentrated water near a deionized water outlet of a desalination chamber. It is described that the condensate is introduced into the concentrating chamber from the side and is discharged from the side of the concentrating chamber that is closer to the raw water inlet of the desalting chamber, and at least a part of the condensed water flowing out of the concentrating chamber is discharged out of the system. ing.
[0004]
In the same publication, water having a lower silica or boron concentration than raw water is used as concentrated water, and water having such a good water quality is supplied from the deionized water (production water) extraction side of the desalination chamber to the raw water inflow side. By passing the water through the concentrating chamber in the direction toward it, it is possible to obtain high-quality water with reduced silica and boron concentrations to extremely low concentrations.
[0005]
[Patent Document 1]
JP-A-2002-205069
[Problems to be solved by the invention]
The present invention provides an operation method of an electrodeionization apparatus and an electrodeionization apparatus capable of sufficiently suppressing the concentration diffusion of anions such as carbonate ions from a concentration chamber and thereby obtaining product water having an extremely low carbonate concentration. The purpose is to do.
[0007]
[Means for Solving the Problems]
The operation method of the electrodeionization apparatus of the present invention is an operation method of the deionization apparatus, wherein the water to be treated flows through the desalting chamber and the concentrated water flows through the concentration chamber. The low-anion-concentration water treated by the anion removal treatment means flows into the concentrating chamber from the side near the outlet of the desalting chamber and flows through the concentrating chamber so as to flow out from the side near the inlet of the desalting chamber. It is characterized by the following.
[0008]
Also, in the electrodeionization apparatus of the present invention, the concentration chamber and the desalination chamber are partitioned by the ion exchange membrane between the anode and the cathode, and the water to be treated is circulated to the desalination chamber, and the concentrated water is concentrated. In the electrodeionization apparatus circulated through the chamber, the concentrated water introduction means and the outflow means are arranged so that the concentrated water flows into the concentration chamber from a side near the outlet of the desalination chamber and flows out from a side near the entrance of the desalination chamber. And a means for removing anions from the concentrated water flowing into the concentration chamber.
[0009]
In the present invention, in order to produce high-purity production water having an extremely low concentration of anions such as carbonic acid, the concentration of anions such as carbonic acid in the concentrated water supplied to the concentration chamber is reduced.
[0010]
Thereby, even in the vicinity of the outlet of the concentration chamber, the anion concentration gradient from the concentration chamber to the desalination chamber becomes relatively small, the diffusion of carbonic acid from the concentration chamber to the desalination chamber is suppressed, and the carbon dioxide concentration of the produced water is reduced. be able to.
[0011]
In the present invention, by setting the total inorganic carbonic acid concentration of the concentrated water flowing into the concentrating chamber to 50 ppb or less, diffusion of carbonate ions from the concentrating chamber to the desalting chamber due to the concentration gradient is suppressed, and the total inorganic carbonic acid concentration is extremely low. Production water can be produced.
[0012]
In the present invention, similarly, by setting the silica concentration of the concentrated water flowing into the concentration chamber to 100 ppb or less and the boron concentration to 10 ppb or less, the diffusion of these ions from the concentration chamber to the desalination chamber due to the concentration gradient is prevented. It is possible to significantly reduce the silica concentration and boron in the production water.
[0013]
In order to reduce the total inorganic carbonic acid concentration, the silica concentration or the boron concentration in the concentrated water flowing into the concentrated water, a part of the production water flowing out of the desalting chamber may be used as the concentrated water. Further, the water supplied to the concentration chamber may be treated by an ion exchange device or an electrodeionization device.
[0014]
In order to reduce the total inorganic carbonic acid concentration in the concentrated water flowing into the concentration chamber, a degassing means such as a degassing membrane device may be used.
[0015]
In the present invention, after the raw water has been subjected to the anion removal treatment, it may be supplied to the desalting chamber, whereby the anion concentration of the produced water can be further reduced. As the anion removing treatment, a reverse osmosis treatment and a deaeration treatment are preferable, and in particular, a multistage reverse osmosis treatment and a further deaeration treatment are preferable.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a schematic sectional view of an electrodeionization apparatus showing an embodiment of the present invention. In this electrodeionization apparatus 10, a plurality of anion exchange membranes (A membranes) 13 and a plurality of cation exchange membranes (C membranes) 14 are alternately arranged between electrodes (anode 11 and cathode 12) to form a concentration chamber 15 and desalination. The chamber 16 is formed alternately, and the desalting chamber 16 is filled with an anion exchanger and a cation exchanger composed of an ion exchange resin, an ion exchange fiber, a graft exchanger, or the like in a mixed or multilayered manner. .
[0018]
Further, the concentration chamber 15, the anode chamber 17 and the cathode chamber 18 may also be filled with an electric conductor such as an ion exchanger, activated carbon or metal.
[0019]
The water to be treated is introduced into the desalting chamber 16, from which product water is taken out. Part of the water to be treated is sent to the anion removing means 9 and subjected to anion removing treatment. The water from which anions have been removed by the anion removal treatment means 9 is passed through the concentrating chamber 15 in a countercurrent one-way manner in the direction opposite to the water flowing direction of the desalting chamber 16. It is discharged outside. In this electrodeionization apparatus, the concentration chambers 15 and the desalination chambers 16 are alternately arranged side by side, and the inlet of the concentration chamber 15 is provided on the product water take-out side of the desalination chamber 16. The outlet of the concentration chamber 15 is provided on the raw water inflow side. Thereby, the concentrated water flows into the concentration chamber 15 from the outlet side of the desalting chamber (lower side in FIG. 1) and flows out from the inlet side of the desalination chamber (upper side in FIG. 1).
[0020]
A part of the water flowing out of the anion removing means 9 is supplied to the inlet side of the anode chamber 17, and the water flowing out of the anode chamber 17 is supplied to the inlet side of the cathode chamber 18, The effluent is discharged out of the system as wastewater. In addition, the inlet water of the anode chamber 17 may be water to be treated which does not pass through the anion removing means.
[0021]
In this way, by passing the anion-removed treated water through the condensing chamber 15 and the desalting chamber 16 in a countercurrent, the concentration of the condensed water in the concentrating chamber 15 becomes lower toward the production water takeout side. The influence of the diffusion on the desalting chamber 16 is reduced, and the removal rate of not only strong anions but also weak anions such as carbonic acid, silica, and boron can be dramatically increased. According to this electrodeionization apparatus, it is possible to produce production water having a specific resistance of 18 MΩ · cm or more.
[0022]
When the conductivity of the anion-removed water passed through the concentrating chamber is low and the electric resistance of the electrodeionization apparatus is high, the concentrating chamber is filled with a conductor such as an ion exchanger. This eliminates the need to add an electrolyte such as salt to the concentrated water to lower the electric resistance. It is preferable that the electrode chambers 17 and 18 are also filled with an ion exchanger, activated carbon, or a metal that is an electric conductor in order to secure a current. This makes it possible to secure a necessary current even when high-quality water such as ultrapure water is passed.
[0023]
In the electrode chamber, an oxidizing agent such as chlorine and ozone is generated particularly in the anode chamber. Therefore, in the long term, it is preferable to use activated carbon as the filler rather than using an ion exchange resin or the like. In addition, supplying the production water to the electrode chamber as shown in FIG. 1 can prevent chlorine from being generated because the water supplied to the electrode chamber hardly contains Cl ^−. desirable.
[0024]
FIG. 2 is a simplified illustration of a water flow system to the desalination chamber and the concentration chamber of the electrodeionization apparatus of FIG. As shown in the figure, the water to be treated is passed through the desalination chamber 16 to become the product water. Part of the water to be treated is passed through the concentration chamber 15 after the anion removal treatment, and is discharged as concentrated wastewater. The flow direction of the water in the concentrating chamber is opposite (countercurrent) in the desalting chamber 16.
[0025]
By setting the total inorganic carbonic acid concentration to 50 ppb or less, preferably 30 ppb or less by the anion removing means 9, the total inorganic carbonic acid concentration in the production water is significantly reduced. Further, by setting the silica concentration to 100 ppb or less, preferably 80 ppb or less and the boron concentration to 10 ppb or less, preferably 8 ppb or less by the anion removing means 9, the silica concentration and the boron concentration in the production water can be remarkably reduced.
[0026]
Examples of the anion removing means 9 include a degassing device such as a degassing membrane device, a decarbonation column, and a vacuum degassing column, a reverse osmosis membrane separation device, an electrodialysis device, and an ion exchange resin column containing an anion exchanger. An ion exchange device or an electrodeionization device is exemplified.
[0027]
In order to remove carbonic acid, it is desirable to include deaeration means such as a deaeration film, a decarbonation tower, and a vacuum deaeration tower. In particular, a degassing membrane processing apparatus that performs a vacuum suction method (for example, 20 Torr or less), a sweep method using nitrogen or the like, or both, has excellent carbonic acid removal efficiency.
[0028]
FIG. 3 is a system diagram showing an example when the electrodeionization device 8 is employed as the anion removal means 9. The electrodeionization apparatus 8 has a deionization chamber 8D and concentration chambers 8A and 8B formed between an anode and a cathode by an anion membrane 8a and a cation membrane 8c. The water to be treated is circulated in the respective chambers 8A, 8B, 8D in a parallel flow, and the desalinated water from the desalting chamber 8D and the concentrated water from the concentrating chamber 8B are combined with the deionized water of the concentrated water 15 of the electrodeionization apparatus 10. It is supplied to the outlet side and flows out from the inlet side of the desalting chamber. The electrodeionization apparatus 8 includes a concentration chamber 8A on the anion membrane 8a side of the desalting chamber 8D and a concentration chamber 8B on the cation membrane 8c side. Only the anion component concentrated in the concentration chamber 8A is discharged, and the cations are concentrated. The concentrating chamber 8B is supplied to the concentrating chamber 15 of the electrodeionization apparatus 10 together with the desalinated water from the desalting chamber 8D. The electrodeionization device 8 removes and reduces only the anion component as described above.
[0029]
In the present invention, the water to be treated supplied to the desalting chamber may be the one subjected to the anion removal treatment. By doing so, the anion load in the desalting chamber is reduced. Further, it is possible to obtain a lower level of production water. As the anion removing treatment, a degassing treatment, a reverse osmosis treatment, or the like is preferable. It is also preferable to adsorb and remove organic components by activated carbon and ionize chlorine.
[0030]
In the case where carbonate ions are removed from the water supplied to the deionization chamber by anion removal treatment, it is particularly preferable to use deaeration means (particularly a membrane deaerator) as anion removal means. In addition, it is desirable to recirculate a part of the deaerated treatment water to the deaerator inlet to increase the carbon dioxide removal efficiency.
[0031]
In the deaeration treatment for removing carbonic acid, it is desirable to adjust the inflow water to acidic, preferably pH 4 to 6, and more preferably to pH 4 to 5 to increase the carbonic acid removal efficiency.
[0032]
When the gas side of the degassing film is sucked by a vacuum pump, the degree of vacuum is desirably 50 Torr or less, and more desirably 20 Torr or less, from the viewpoint of increasing the efficiency of removing carbon dioxide.
[0033]
When raw water is subjected to reverse osmosis treatment (hereinafter sometimes referred to as RO treatment), it is desirable to sufficiently reduce weak anion components such as carbonic acid, silica, and boron by performing treatment in multiple stages, for example, two stages.
[0034]
In this case, by making the RO inlet water of the first and / or second stage alkaline (pH 8 to 10), the efficiency of removing the weak anion component is improved.
[0035]
Further, as an alkali generating means for making the alkalinity, there is disclosed an electrodeposition device disclosed in JP-A-2001-113281, in which a desalination chamber has a thickness of 7 mm or more (preferably 15 mm) and is filled with a mixed anion / cation ion exchanger. An ion device may be used. With this, the weak anion component is reduced at the same time as the generation of alkali. Such an electrodeionization device is desirably arranged between the first and second stage RO devices.
[0036]
The pretreatment may include the above-described two-stage RO treatment and deaeration treatment, and may be performed using ultrapure ultrapure water, for example, having a specific resistance of 18.2 MΩ · cm or more, a silica concentration of 0.05 ppb or less, and a boron concentration of 0.005 ppb or less. It is particularly suitable for obtaining treated water.
[0037]
FIGS. 4 to 7 show configuration examples in which the above-described pretreatment device is arranged in a stage preceding the electrodeionization device 10.
[0038]
In FIG. 4, raw water is degassed by the degassing membrane device 1 and used as the water to be treated by the electrodeionization device 10. In addition, a part of the degassing treatment water of the degassing membrane device 1 is returned to the upstream side of the degassing membrane device 1 and is repeatedly treated.
[0039]
In FIG. 5, raw water is passed through the activated carbon adsorption tower 2 and the two-stage RO devices 3 to 3 to be treated water.
[0040]
In FIG. 6, raw water is treated by the activated carbon adsorption tower 2, the first RO device 3, the electrodeionization device 4, and the second RO device 3 to be treated water of the electrodeionization device 10. In addition, as the electrodeionization apparatus 4, for example, an electrodeionization apparatus described in JP-A-2001-113281 can be used, but the invention is not limited to this.
[0041]
In FIG. 7, the raw water is treated by the activated carbon adsorption tower 2, the two-stage RO apparatuses 3 and 3, and the degassing membrane apparatus 1, and used as the water to be treated by the electrodeionization apparatus 10.
[0042]
In the present invention, the means for removing anions from the concentrated water supplied to the concentration chamber may be the electrodeionization apparatus 10 itself. That is, as shown in FIG. 8, the entire amount of the water to be treated is circulated to the desalting chamber 16 of the electrodeionization apparatus 10, and a part of the produced water is transferred from the outlet of the desalting chamber to the inlet of the desalting chamber. May be distributed to the public.
[0043]
In the present invention, the electrodeionization apparatus 10 may be installed in multiple stages, and the raw water may be deionized in multiple stages.
[0044]
FIG. 9 is a water flow diagram of an electrodeionization system in which the electrodeionization devices 10 (10A, 10B) are installed in multiple stages as described above, and shows a first electrodeionization device 10A and a second electrodeionization device. 10B are connected in series.
[0045]
In the electrodeionization system of FIG. 9, the water to be treated is passed through the desalting chamber 16A of the first electrodeionization device 10A to become primary product water. This primary product water is circulated to the desalting chamber 16B of the second electrodeionization device. The flow direction of the concentrated water in the concentration chambers 15A and 15B is in the countercurrent direction to the desalination chambers 16A and 16B. Secondary production water (production water) is taken out from the desalting chamber 16B, and a part thereof is supplied to the concentration chamber 15B. The concentrated water flowing out of the concentration chamber 15B of the second electrodeionization apparatus 2 has a low anion concentration and is supplied to the concentration chamber 15A.
[0046]
The effluent from the concentration chamber 15A of the first electrodeionization device 1 is discharged as concentrated wastewater.
[0047]
In the present invention, the thickness of the desalting chamber is preferably 2 to 7 mm, and the flow rate is preferably LV = 60 to 120 m / h and SV = 100 to 200 / h. The thickness of the concentration chamber is preferably 2 to 7 mm, and the flow rate is preferably LV = 10 to 30 m / h and SV = 25 to 50 / h. Further, both the desalting chamber and the concentrating chamber are filled with an ion exchanger, particularly filled with a mixture of anion cations, and are preferably operated at a current density of 300 to 700 mA / dm ² . It is desirable that the water supplied to the concentration chamber be of a one-time type without being recirculated to the inlet of the concentration chamber by a circulation pump or the like.
[0048]
Further, when water is passed in series to a plurality of desalination chambers as shown in FIG.
[0049]
【The invention's effect】
As described above, according to the electrodeionization apparatus and the operation method thereof of the present invention, it is possible to surely produce product water having an anion concentration, particularly a total inorganic carbonate concentration, which is extremely low.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an electrodeionization apparatus according to an embodiment.
FIG. 2 is a water flow diagram of the electrodeionization apparatus of FIG. 1;
FIG. 3 is a water flow diagram of an electrodeionization system according to another embodiment.
FIG. 4 is a water flow diagram of an electrodeionization system according to still another embodiment.
FIG. 5 is a water flow diagram of an electrodeionization system according to another embodiment.
FIG. 6 is a water flow diagram of the electrodeionization system according to the embodiment.
FIG. 7 is a water flow diagram of the electrodeionization system according to the embodiment.
FIG. 8 is a water flow diagram of the electrodeionization system according to the embodiment.
FIG. 9 is a water flow diagram of the electrodeionization system according to the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Electrodeionization apparatus 11 Anode 12 Cathode 15, 15A, 15B Concentration chamber 16, 16A, 16B Deionization chamber

Claims (12)

An operation method of an electrodeionization apparatus in which a concentration chamber and a desalination chamber are partitioned by an ion exchange membrane between an anode and a cathode,
In the operating method of flowing the water to be treated through the desalting chamber and flowing the concentrated water through the concentrating chamber,
As the concentrated water, the low-anion-concentration water treated by the anion removal treatment means flows into the concentrating chamber from the side near the outlet of the desalting chamber and flows out from the side near the inlet of the desalting chamber. A method for operating an electrodeionization device, characterized in that the device is circulated through a vessel. 2. The method according to claim 1, wherein the total inorganic carbonic acid concentration of the low anion concentration water treated by the anion removal treatment means is 50 ppb or less. 3. The method for operating an electrodeionization apparatus according to claim 1, wherein the silica concentration of the low anion concentration water treated in the anion removal treatment is 100 ppb or less. The method of operating an electrodeionization apparatus according to any one of claims 1 to 3, wherein the boron concentration of the low anion concentration water treated in the anion removal treatment is 10 ppb or less. The method according to any one of claims 1 to 4, wherein a part of the production water flowing out of the desalting chamber is supplied to a concentration chamber. The method of operating an electrodeionization apparatus according to any one of claims 1 to 5, wherein the anion removal treatment means includes a deaeration means. The method for operating an electrodeionization apparatus according to any one of claims 1 to 5, wherein the anion removal treatment means includes an ion exchange device or an electrodeionization device. The method of operating an electrodeionization apparatus according to any one of claims 1 to 7, wherein raw water is subjected to anion removal treatment, and the treated water is supplied to the desalination chamber as treated water. The method according to claim 8, wherein the raw water is subjected to anion removal treatment by reverse osmosis treatment and degassing treatment. A concentration chamber and a desalination chamber are partitioned by an ion exchange membrane between the anode and the cathode,
The water to be treated is circulated to the desalting chamber, and the concentrated water is circulated to the concentrating chamber.
A concentrated water introduction means and an outflow means are provided so that the concentrated water flows into the concentration chamber from a side near the outlet of the desalination chamber and flows out from a side near the entrance of the desalination chamber,
The electrodeionization apparatus further includes means for removing anions from the concentrated water flowing into the concentration chamber. 11. The electrodeionization apparatus according to claim 10, wherein the means for removing the anion is configured to reduce the total inorganic carbonic acid concentration after the anion removal treatment to 50 ppb or less. The electrodeionization apparatus according to claim 10 or 11, further comprising means for removing anions from water supplied to the desalting chamber.

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