JP2000263059A - Electric desalting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric desalting apparatus preventing the precipitation of a hardness component and capable of performing desalting operation extremely reduced in the lowering of capacity with the elapse of time. SOLUTION: Water to be desalted flows in a desalting chamber 8 from an inflow port 6 to flow zigzag and flows out of a desalted water outflow part 7. During this process, anions and cations in water to be desalted permeate anion exchange membranes 4 or cation exchange membranes 5 to move into first and second concn. chambers 10, 20. Conc. water flows through the first and second concn. chambers 10, 20 and ions transferred to first and second cone. waters flow out of the conc. water outflow ports 12, 22 of the first and second concn. chambers 10, 20 on the rearmost side. The first conc. water and second conc. water flowing out of conc. water outflow ports 12, 22 are circulated to an inflow port 11 of first cone. water and an outflow port 12 of second conc. water without being mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric desalination apparatus, and more particularly to an electric desalination apparatus improved to prevent scale formation in a concentration chamber.

[0002]

2. Description of the Related Art An electric desalination apparatus is widely used in the field of producing pure water, ultrapure water and the like. In this electrodeionization apparatus, a flat membrane-like cation exchange membrane and an anion exchange membrane stretched on a frame are alternately arranged between a plate-like anode and a cathode, and a concentration chamber and a desalination chamber are arranged. (Dilution chamber) are alternately arranged, and the water to be desalinated is circulated through the desalination chamber, and the so-called plate and frame type is configured to move ions to the concentration chamber. ing. The desalting chamber is filled with an ion exchanger such as an ion exchange resin.

In Japanese Patent Publication No. 56-16688, rod-shaped electrodes (anode and cathode) are arranged in parallel in a cylindrical apparatus casing, and these electrodes are surrounded by a cylindrical ion-exchange membrane to perform ion exchange. An electric desalination apparatus is described in which a concentration chamber is provided between a membrane and an electrode, and deionized water flows outside each ion exchange membrane.

In the electric desalination apparatus of the same publication, the concentrated water from the concentrating chamber around the anode and the concentrated water from the concentrating chamber around the cathode are mixed and circulated to the respective concentrating chambers.

[0005]

In a conventional general plate-and-frame type electric desalination apparatus, the concentrating chamber is sandwiched between a cation exchange membrane and an anion exchange membrane, and calcium ions are separated from the cation exchange membrane. Bicarbonate ions are concentrated from the ion and anion exchange membranes. Also, since OH ^- ions are concentrated from the anion exchange membrane, even if the pH of the entire concentrated water side is not in the calcium carbonate precipitation region,
There has been a problem that the concentration of OH ^- ions locally increases in the boundary layer of the anion exchange membrane on the side of the concentration chamber, and precipitation of a hardness component occurs.

In the electric desalination apparatus disclosed in Japanese Patent Publication No. 56-16688, since the concentrated water from the anode-side concentrating chamber and the concentrated water from the cathode-side concentrating chamber are mixed, the hardness component tends to precipitate.

[0007] The present invention provides an electric desalination apparatus in which concentrated calcium ions and concentrated bicarbonate ions do not coexist in a concentration chamber, thereby preventing precipitation of hardness components such as calcium carbonate. The purpose is to provide.

[0008]

According to the present invention, there is provided an electric desalination apparatus comprising: a casing through which a liquid flows; an anode and a cathode disposed in the casing; and an anode and a cathode surrounding the anode. An anion exchange membrane forming a first concentration chamber, a cation exchange membrane surrounding the cathode and forming a second concentration chamber between the cathode and the anion exchange membrane in the casing. An electric desalination apparatus comprising: a deionized water injection part and an outflow part provided in the casing so as to flow demineralized water into a desalination chamber between the ion exchange membrane and the cation exchange membrane. The present invention is characterized in that concentrated water is separately circulated through a first concentration chamber and a second concentration chamber.

In this electric desalination apparatus, the concentrated water flows independently from the concentrated chambers on the anode side and the cathode side, so that the concentrated waters from the concentrated chambers on the anode side and the cathode side do not mix with each other, and the hardness component does not increase. Is prevented.

[0010] In one embodiment of the present invention, the anode and the cathode are each in the form of a flat plate, and are disposed substantially in parallel in the casing. Is configured to flow through the casing so as to go around the other end of the enrichment chamber. In this case, means for introducing the first concentrated water to one plate surface side of the anode in the first concentration chamber and flowing out the first concentrated water from the other side, and one of the cathodes in the second concentration chamber The second concentrated water is introduced into the plate surface and the second concentrated water is introduced from the other plate surface.
Means for causing the concentrated water to flow out.

In another embodiment of the present invention, the anode and the cathode are rod-shaped bodies, which are arranged substantially in parallel in a casing, and the anion exchange membrane and the cation exchange membrane are each cylindrical and have a rod-like shape. Is arranged coaxially with
Means for introducing the first concentrated water at one end in the longitudinal direction of the first concentrating chamber and flowing out the first concentrated water from the other end; Means for introducing the second concentrated water and flowing out the second concentrated water from the other side.

In any of the embodiments, the concentrated water on the anode side and the concentrated water on the cathode side do not mix,
Precipitation of the hardness component is prevented.

[0013]

FIG. 1 is a horizontal sectional view of an electric desalination apparatus according to a first embodiment. Plate-shaped anodes 2 and cathodes 3 are alternately arranged in parallel in an apparatus casing 1. In this embodiment, the anode 2 is supported on one side surface 1a of the casing 1, and its tip is separated from the other side surface 1b. The cathode 3 is supported on the other side surface 1b of the casing 1, and its tip is connected to one side surface 1a.
Away from

The anode 2 is surrounded by an anion exchange membrane 4, and a first between the anode 2 and the anion exchange membrane 4.
Is formed. The cathode 3 is surrounded by the cation exchange membrane 5, and a second concentration chamber 20 is formed between the cathode 3 and the cation exchange membrane 5.

The first concentrated water is introduced into one plate surface of the anode 2 in the first concentrating chamber 10 and the first concentrated water flows out from the other plate surface into the casing 1 so as to flow out the first concentrated water. Of the concentrated water are provided.

The second concentrated water is introduced into one plate side of the cathode 3 in the second concentrating chamber 20 and the second concentrated water flows out of the second plate into the casing 1 so as to flow out from the other plate side. An inlet 21 and an outlet 22 for the concentrated water are provided.

In this embodiment, a plurality of first concentrating chambers 10 and a plurality of second concentrating chambers 20 are provided.
Each first enrichment chamber 10 is connected in series so that the concentrated water flowing out from the first enrichment chamber 10 on the leftmost side of the drawing sequentially flows to the first enrichment chamber 10 on the right side. , Each first
The first concentrated water may be circulated in parallel to the concentrating chamber 10.

Similarly, in the embodiment shown in the figure, the second concentrated water is circulated in series with each second concentrating chamber 20, but the second concentrated water is flown in parallel to each second concentrating chamber 20. May be distributed.

An inlet 6 for desalinated water is provided at the left end of the casing 1 in the figure, and an outlet 7 for desalted water is provided at the right end. A portion of the casing 1 outside the anion exchange membrane 4 and the cation exchange membrane 5 constitutes a desalination chamber 8 which is a flow path of deionized water. The desalting chamber 8 may be filled with an ion exchanger such as an ion exchange resin.

In the thus constructed electric desalination apparatus, the desalinated water flows into the desalination chamber 8 from the inlet 6 and flows around the anion exchange membrane 4 on the tip side of the anode 2 to form an anion exchange membrane. It flows between the cation exchange membrane 4 and the cation exchange membrane 5 and then goes around the cation exchange membrane 5 on the tip side of the cathode 3. The desalinated water similarly flows in the form of a zigzag in the desalination chamber 8 and flows out of the desalinated water outlet 7.

During this time, anions and cations in the demineralized water pass through the anion exchange membrane 4 or the cation exchange membrane 5 and move into the first or second concentration chamber 10 or 20, respectively.
Concentrated water is circulated in each of the concentrating chambers 10 and 20, and the ions transferred to the first and second condensed waters are finally converted to the first and second concentrating chambers 10 and 20 at the rearmost stage. It flows out of the 20 concentrated water outlets 12 and 22.

In this embodiment, the first and second concentrated waters flowing out of the concentrated water outlets 12 and 22 are not mixed with each other without mixing the first and second concentrated waters. The concentrated water is circulated to the outlet 12 of the concentrated water. If necessary, a part of the concentrated water is collected from the circulating concentrated water and low-ion-concentration water is supplied.

Thus, the first concentration chamber 1 on the anode side
Since the concentrated water separately circulates in 0 and the second concentrated chamber 20 on the cathode side, the first concentrated water and the second concentrated water do not mix with each other, so that the precipitation of the hardness component is prevented.

For example, bicarbonate ions and OH ^- ions are concentrated in the first concentration chamber 10 and calcium ions are concentrated in the second concentration chamber 20.

In the embodiment shown in FIG. 1, the anode 2 and the cathode 3 are connected to one of the side surfaces 1a and 1b of the casing 1, but may be connected to the ceiling surface or the bottom surface of the casing 1.

FIG. 2 is a longitudinal sectional view of an electric desalination apparatus according to another embodiment of the present invention, FIG. 3 is a sectional view taken along the line III-III of FIG. 2, and FIG. It is a typical perspective view explaining.

The upper plate 31 of the cylindrical device casing 30
The bottom plate 32 is provided with an inlet 33 and an outlet 34 for the desalinated water.

A cylindrical anion exchange membrane 35 and a cation exchange membrane 36 are provided so as to straddle the top plate 31 and the bottom plate 32. A rod (solid rod or hollow rod) is formed at the axis of each anion exchange membrane 35 and cation exchange membrane 36.
Of the first concentration chamber 4 between the anode 37 and the anion exchange membrane 35.
0 is formed, and a second concentration chamber 50 is formed between the cathode 38 and the cation exchange membrane 36.

In order to allow the concentrated water to flow through the concentration chambers 40 and 50, inlets 41 and 51 for the concentrated water are provided in the upper plate 31 at the upper part of each of the chambers 40 and 50, and the concentrated water is supplied to the bottom plate 32. Outlets 42 and 52 are provided.

The anode 37 and the cathode 38 extend upward through the upper plate 31. The lower portions of the anode 37 and the cathode 38 are preferably supported by the bottom plate 32, respectively, but may be disposed in the respective chambers 40 and 50 in a hanging manner.

Inside the casing 30 and outside the anion exchange membrane 35 and the cation exchange membrane 36, there is a desalination chamber 39 through which desalinated water flows. The desalting chamber 39 may be filled with an ion exchanger such as an ion exchange resin.

In the thus constructed electric desalination apparatus, the desalinated water flows into the desalting chamber 39 from the inlet 33 and flows out from the outlet 34. During this time, ions pass through the anion exchange membrane 35 or the cation exchange membrane 36,
Into the concentrating chamber 40 or 50. Each first concentration chamber 40
Inside, the first concentrated water flows in parallel as shown in FIG.
The second concentrated water flows in each second concentrating chamber 50 in parallel.

The first concentrated water flowing out of the outlet 42 of the first concentration chamber 40 is circulated to the inlet 41 of the first concentration chamber 40 without being mixed with the second concentrated water. The concentrated water flowing out of the outlet 52 of the second concentrating chamber 50 is mixed with the inlet 51 of the second concentrating chamber 50 without being mixed with the first concentrated water.
Circulated to

As described above, the first concentrated water and the second concentrated water circulate without being mixed, thereby preventing the precipitation of the hardness component.

In this embodiment, a plurality of first concentrating chambers 40 may be connected in series, and a plurality of second concentrating chambers 50 may be connected in series.

[0036]

As described above, according to the present invention, the precipitation of the hardness component in the electric desalination apparatus is prevented, and the desalting operation with extremely little deterioration in performance over time can be performed. In addition, since the precipitation of the hardness component is prevented, it is possible to increase the value of the current flowing through the anode and the cathode, and to remove ions at a high level.

[Brief description of the drawings]

FIG. 1 is a horizontal sectional view of an electric desalination apparatus according to an embodiment.

FIG. 2 is a horizontal sectional view of an electric desalination apparatus according to another embodiment.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a perspective view illustrating a method of passing water through the electric desalination apparatus of FIGS.

[Explanation of symbols]

 1,30 Casing 2,37 Anode 3,38 Cathode 4,35 Anion exchange membrane 5,36 Cation exchange membrane 10,40 First concentration chamber 20,50 Second concentration chamber

Claims (4)

[Claims] 1. A casing in which a liquid flows, an anode and a cathode disposed in the casing, and an anion surrounding the anode and forming a first concentrating chamber between the anode and the anode. An exchange membrane, a cation exchange membrane surrounding the cathode and forming a second enrichment chamber between the cathode, and a deionizer between the anion exchange membrane and the cation exchange membrane in the casing. An electric desalination apparatus comprising a demineralized water injection part and an outflow part provided in the casing so as to flow demineralized water into the salt chamber, wherein the first and second concentrating chambers are concentrated. An electric desalination apparatus wherein water is separately circulated. 2. The method according to claim 1, wherein the anode and the cathode each have a flat plate shape, and are arranged substantially in parallel in the casing. An electric desalination apparatus characterized by being circulated in the casing so as to go around the other end of the concentration chamber of (2). 3. The means according to claim 2, wherein the first concentrated water is introduced into one plate surface side of the anode in the first concentration chamber and the first concentrated water flows out from the other side; Means for introducing the second concentrated water to one plate surface side of the cathode in the concentration chamber and flowing out the second concentrated water from the other plate surface side. 4. The rod-shaped body according to claim 1, wherein the anode and the cathode are rod-shaped bodies, and are disposed substantially in parallel in the casing. Means for introducing the first concentrated water at one end in the longitudinal direction of the first concentrating chamber and flowing out the first concentrated water from the other end; Means for introducing the second concentrated water from one side in the longitudinal direction of the chamber and flowing out the second concentrated water from the other side.