JP2008178847A - Electrodialysis apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrodialysis apparatus connected to a treating liquid tank causing no local heating in the tank and allowing measurement of weight variation of the treating liquid in the tank. <P>SOLUTION: An electrolyte cell is provided with at least a positive electrode, a positive electrode chamber, a negative electrode, a negative electrode chamber, and an ion exchange membrane. The treating liquid tank is connected to the electrolyte cell, and is provided with a balance capable of measuring the weight variation of the treating liquid in the tank, and a means heating the treating liquid. A product of an overall heat transfer coefficient and a heat transfer area of the means is 2-12 W/K per 1L of the volume of the treating liquid tank. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrodialysis apparatus.

The electrodialysis apparatus includes at least an anode (2), an anode chamber (3), a cathode (4), a cathode chamber (5) and an ion exchange membrane in an electrolytic cell, and the electrolytic cell contains an anion and a cation. Is filled. When concentrating salt water, as an ion exchange membrane, from an anode chamber (3), an anion exchange membrane (7-1), a cation exchange membrane (6-1), an anion exchange membrane (7-2), and a cation exchange membrane (6-2) in order, and a desalting chamber (8-1), a cation exchange membrane (6-1), and an anion between an anion exchange membrane (7-1) and a cation exchange membrane (6-1). A concentration chamber (9) is provided between the exchange membrane (7-2), and a desalting chamber (8-1) is provided between the anion exchange membrane (7-2) and the cation exchange membrane (6-2). The electrolytic cell (1) shown in FIG. 1 is used. The principle of the electrodialysis apparatus will be described in detail with reference to FIG. 1. When voltage is applied to the anode (2) and the cathode (4), cations in the desalting chamber (8-1) are converted into cation exchange membranes (6-1). The anion in the desalting chamber (8-2) permeates the anion exchange membrane (7-2) and moves to the concentration chamber (9). If the liquid to be treated (11) is circulated in the desalting chamber, the concentrated liquid (12) of the liquid to be treated is circulated in the concentration chamber (9). Specifically, when diluted salt water is used for the liquid to be treated and chlorine ions are used as anions and sodium ions are used as cations, concentrated salt water can be obtained from the concentration chamber (9).
Recently, from the viewpoint of securing the adsorption capacity of an ion exchange resin, preventing its deterioration, and reducing the amount of eluate from the ion exchange resin, it has been proposed to provide a temperature controller having a cooling function between successive electrodialysis apparatuses. It is described in.
Moreover, a small electrodialysis apparatus suitable for prior examination of an industrial scale electrodialysis apparatus is commercially available (for example, Non-Patent Document 1).

JP 11-128691 A (paragraph number 0013) http://www.astom-corp.jp/en/ja-main2.html (Small desktop electrodialysis machine)

When electrodialysis is performed by an electrodialysis apparatus, as described in [0008] to [0009] of Patent Document 1, a liquid to be treated at about room temperature usually has a higher temperature.
In order to examine whether or not to perform electrodialysis industrially at a high temperature, the present inventor used a small electrodialysis apparatus such as Non-Patent Document 1, and because of the large amount of heat release, It has become clear that the temperature does not rise only by carrying out, and it is difficult to raise the temperature to about 40 ° C. realized by an industrial electrodialysis apparatus.
Therefore, a case where a liquid tank to be treated is provided in a small electrodialysis apparatus, and the liquid to be treated in the liquid tank to be treated is heated to about 110 ° C. with a heater and circulated through the apparatus. It was not possible to raise the temperature to about 40 ° C. after 40 minutes because of staying. In addition, it is difficult to heat the heater any more because there is a possibility that the thermally unstable substance contained in the liquid to be treated is destroyed by local heating, and it is dangerous to boil near the heater. .
Furthermore, although it was examined that the liquid to be treated in the liquid tank to be treated is stirred to avoid local heating, the liquid tank to be treated vibrates when the stirrer is used, and the change in the weight of the liquid to be treated can be measured. It became difficult. The data on the change in the weight of the liquid to be treated connected to the small electrodialysis apparatus is indispensable for the examination of an industrial electrodialysis apparatus.
An object of the present invention is an electrodialysis apparatus to which a liquid tank to be treated is connected, and does not cause local heating in the liquid tank to be treated, and the weight change of the liquid to be treated in the liquid tank to be treated It is to provide a measurable electrodialyzer.

  That is, the present invention comprises at least an anode, an anode chamber, a cathode, a cathode chamber, and an ion exchange membrane in an electrolytic cell, and a liquid tank to be treated is connected to the electrolytic cell. A scale capable of measuring the weight change of the liquid to be treated in the liquid tank to be treated and a means for heating the liquid to be treated are provided, and the product of the overall heat transfer coefficient and the heat transfer area of the means is the This is an electrodialysis apparatus having a capacity of 2 to 12 W / K per liter of the treatment liquid tank.

  According to the present invention, even a small electrodialysis apparatus can be heated to a desired temperature, and the change in the weight of the liquid to be treated in the liquid tank to be treated without causing local heating in the liquid tank to be treated. As a result, it has become possible to examine whether it can be applied to an industrial electrodialysis apparatus with simple equipment.

Hereinafter, as an embodiment of the present invention, description will be made based on FIG. 2 in which the electrolytic bath of FIG. 1 is provided with a liquid bath (21), a concentration bath (22), and an electrolytic bath (20).
The liquid tank (21) to be treated is connected to the electrolytic cell (1) of the electrodialysis apparatus of the present invention. In the case of concentration of salt, the liquid to be treated is usually connected to a chamber corresponding to a salt desalting chamber (8-1 and 8-2). As shown in FIG. 2, two (several) demineralization chambers may be connected to one liquid tank (21) to be processed, or a plurality of chambers may be connected to different liquid tanks (21) to be processed. Good.
In the case of concentration of the salt, the salt solution is circulated from the liquid tank (21) to the desalting chamber (8-1 and 8-2) by a pump or the like (11).

The treatment liquid tank (21) is provided with a scale (23) capable of measuring a change in the weight of the treatment liquid in the treatment liquid tank and a means (13) for heating the treatment liquid.
The product of the overall heat transfer coefficient and the heat transfer area of the means is 2 to 12 W / K, preferably 4 to 7 W / K per 1 L of the volume of the liquid tank to be treated.
When the above product is 2 W / K or more, it is preferable because the heating temperature tends to be easily increased, and when it is 12 W / K or less, local heating tends to be suppressed.
In order to give the product of the overall heat transfer coefficient and the heat transfer area in the above range, the heat transfer area per volume may be set to be large, or the overall heat transfer coefficient may be increased. Specifically, a heat exchanger having a large heat transfer area per volume such as a coiled heat exchanger such as a coil heater or a plate heat exchanger is used, and the heat transfer portion of the heat exchanger is stainless steel, It is preferably made of a metal such as titanium steel, steel, and aluminum.

The overall heat transfer coefficient of the heating means is usually 45 to 300 W / (m ² · K), preferably 90 to 160 W / (m ² · K).

  A to-be-processed liquid tank is 20-20 degreeC normally, Preferably, it adjusts to about 30-60 degreeC. When the temperature of the heat medium such as a heat exchanger is set 5 to 25 ° C. higher than the desired temperature of the liquid to be treated, it is adjusted to the desired temperature of the liquid to be treated. According to the electrodialysis apparatus of the present invention, the temperature of the liquid tank to be treated can be set to a desired temperature even by heating at this temperature difference, and local heating does not occur without stirring.

  The scale (23) capable of measuring the change in the weight of the liquid to be treated usually includes an upper pan balance. If the balance (23) is a digital balance, it is preferable because the measured value can be immediately transferred to a computer or the like.

In the concentration chamber (9), salt water is usually circulated from the concentration tank (22) by a pump or the like (12). In FIG. 2, one concentration tank (22) is connected to one concentration chamber (9), but each concentration tank may be connected to a plurality of concentration chambers, or 1 to a plurality of concentration chambers. Two concentration tanks (22) may be connected.
Further, a plurality of ion-exchange membranes may be used in the electrolytic cell, and a plurality of desalting chambers and concentration chambers may exist.

  In the anode chamber (3) and the cathode chamber (4), an electrolytic solution such as salt water is usually circulated from the electrolytic solution tank (20) by a pump or the like (10). In FIG. 2, although connected by one electrolyte tank (20), the anode chamber (3) and the cathode chamber (4) may have each electrolyte tank (20).

  Each tank other than the liquid tank to be processed may be provided with a scale (23). In addition, each tank including the liquid tank to be processed may be equipped with devices such as a conductivity meter and a pH meter.

Examples of the anode of the electrodialyzer used in the present invention include platinum, titanium coated with platinum, carbon, nickel, titanium coated with ruthenium, and titanium coated with iridium. Examples of the cathode include iron, nickel, platinum, titanium coated with platinum, carbon, and stainless steel.
Examples of the structure of the electrode such as the anode and the cathode of the electrodialysis apparatus include a mesh shape, a lattice shape, a plate shape, and the like.

Examples of the anion exchange membrane used in the present invention include a polymer of an anion exchange group-containing monomer, a copolymer of an anion exchange group-containing monomer and a hydrocarbon monomer, and the like.
Here, examples of the anion exchange group-containing monomer include monomers containing a primary to tertiary amino group, a quaternary ammonium group, and the like.
Specifically, N-vinylimidazole, N-vinyl-2-methylimidazole, N-vinyl-2,4-dimethylimidazole, N-vinyl-2-ethylimidazole, N-vinyl-2-ethyl-4-methyl Examples thereof include vinyl imidazoles such as imidazole, 2-vinylimidazole and 1-methyl-2-vinylimidazole; and heterocyclic monomers such as vinylpyridines such as 4-vinylpyridine.
Further, the tertiary amino group-containing polymer may be converted to a quaternary ammonium salt with methyl chloride, methyl iodide, dibromohexane, dimethyl sulfate or the like.

Examples of the cation exchange membrane used in the present invention include a polymer of a cation exchange group-containing monomer, a copolymer of a cation exchange group-containing monomer and a hydrocarbon monomer, and a polymer of a hydrocarbon monomer as concentrated sulfuric acid or fuming. Examples thereof include a polymer obtained by sulfonation with sulfuric acid or the like.
Here, examples of the cation exchange group-containing monomer include monomers containing a sulfonic acid group (—SO ₃ ^— ), a carboxyl group (—CO ₂ ^— ), a phenolic hydroxyl group, and the like. Examples thereof include vinyl sulfonic acid, styrene sulfonic acid, acrylic acid, methacrylic acid, maleic acid, itaconic acid, and vinyl phenol.

  Examples of the hydrocarbon monomer include ethylene, propylene, butene, acrylonitrile, acrolein, methyl vinyl ketone, vinyl chloride, vinylidene chloride, styrene, acrylic ester, methacrylic ester, maleic ester, maleic anhydride, itacone. Examples include acid esters, itaconic anhydride, divinylbenzene, divinyltoluene, trivinylcyclohexane, divinylnaphthalene, chloromethylstyrene, and the like.

Examples of the anion exchange membrane and the cation exchange membrane include a polymerization type, a condensation type, a uniform type, and a heterogeneous type because of their production methods. These ion exchange membranes may have a reinforcing core. Further, it may be a composite film of a hydrocarbon type and a fluorine type.
The anion exchange membrane and cation exchange membrane used in the present invention usually have a thickness of about 0.1 to 0.6 mm and an electrical resistance of about 0.2 to 10 Ω · cm ² .
Examples of the ion exchange membrane used in the present invention include Neoceptor (trade name, manufactured by Astom Co., Ltd.), Selemion (trade name, manufactured by Asahi Glass Co., Ltd.), Flemion (trade name, manufactured by Asahi Glass Co., Ltd.), and Nafion. Commercially available ion exchange membranes such as (trade name, manufactured by DuPont) may be used.
Further, an ion exchange membrane in which an anion exchange membrane and a cation exchange membrane are bonded together, such as a bipolar membrane commercially available from Astom Co., Ltd., may be used.

The electrolytic cell used in the present invention comprises at least an anode (2), an anode chamber (3), a cathode (4), a cathode chamber (5), and an ion exchange membrane. Used for hydrogen production by electrolysis of water.
In addition, the arrangement sequence of the ion exchange membrane may be appropriately designed depending on the purpose. For example, as shown in FIG. 1 of JP-A-2006-306753, the cathode chamber, the anion exchange membrane, the desalting chamber, the cation exchange membrane, the concentration The chamber, the anion exchange membrane, and the anode chamber may be sequentially arranged.

In the present invention, a heating means is provided as an essential constituent in the liquid tank to be treated, but a heating means may be provided in the electrolytic cell (20) and the desalting tank (21).
If the liquid tank to be treated is a small electrodialysis apparatus of about 1 L, the desalting chamber can be quickly heated up if only the liquid tank to be treated is equipped with heating means.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

(Example 1)
A stainless steel coiled heat exchanger (13, overall heat transfer coefficient 83 m ² · K, heat transfer area 4.5 × 10 ⁻² m ² ) was added to a small desktop electrodialyzer having the configuration of FIG. , These products are 4.2 W / K), put the liquid to be processed into the liquid tank (21, 1L), the desalting chamber (8-1 and 8-2) and the liquid tank (21 ) And diluted saline.
Saline was put into a concentration tank (22) not equipped with a heating means and circulated through the concentration chamber (9) and the concentration tank (22) to concentrate the saline.
Diluted brine was added as an electrolytic solution to an electrolytic bath (20) that did not have a heating means, and was circulated through the electrolytic bath (20), the anode chamber (3), and the cathode chamber (4).
Subsequently, a voltage of 10 V was applied to both electrodes, and the temperature changes in the liquid tank (21) to be processed and the concentration tank (22) are shown in FIG.
If the temperature of the heat exchanger is set to 40 ° C. until 20 minutes have passed since the start of dialysis, the temperature in the non-treatment liquid tank exceeds 30 ° C. in about 20 minutes, and the temperature in the concentration tank is similarly 30 ° C. Exceeded. Subsequently, when the temperature of the heat exchanger is set to 45 ° C. after 20 minutes, the temperature in the liquid tank reaches 40 ° C. in 30 minutes and becomes almost constant, and the temperature in the concentration tank is also 30. It became constant at 40 ° C. in minutes (see FIG. 4).
As is clear from FIG. 4, immediately after setting the temperature of the heat exchanger, the temperatures in the liquid tank to be treated and in the concentration tank are substantially the same, so that the temperature can be raised quickly and locally It can be seen that no heating has occurred.

(Comparative Example 1)
As a heating means, a ceramic casting heater (bar-shaped, product of overall heat transfer coefficient and heat transfer area is 0.6 W / K) was used, and the same procedure as in Example was performed except that the heat exchanger temperature was set to 110 ° C. As a result, the temperature in the liquid tank to be treated did not rise even after 40 minutes.

Example of electrolytic cell (Principle of electrodialysis principle) Schematic diagram of the electrodialysis apparatus of the present invention Minimum form of electrolytic cell used in the present invention Temperature change in the liquid tank to be treated and the concentration tank in Example 1

  The electrodialysis apparatus of the present invention can be used for production of sodium chloride by concentration of seawater, desalting and purification of amino acid solution, recovery of metal salt from plating waste liquid, and the like.

Claims (2)

  The electrolytic bath includes at least an anode, an anode chamber, a cathode, a cathode chamber, and an ion exchange membrane, and a liquid tank to be treated is connected to the electrolytic tank. And a means for heating the liquid to be processed, and the product of the overall heat transfer coefficient and the heat transfer area of the means is a volume of 1 L of the liquid to be processed. An electrodialyzer that is 2-12 W / K.   The electrodialysis apparatus according to claim 1, wherein the means for heating the liquid to be treated is a serpentine heat exchanger.

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