JP2001179261A - Method for keeping electric desalting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for keeping an electric desalting apparatus so as to prevent the lowering of the capacity of an ion exchange membrane or the like caused by the surface contamination in the apparatus at a time when the apparatus is kept over a long period of time without supplying water and a current. SOLUTION: When the electric desalting apparatus is kept over a long period of time without supplying water and a current, the water content of an ion exchange membrane and an ion exchange resin is set to 30% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is used in pure water utilization facilities such as boilers and research facilities in addition to industrial fields such as salt production industry, waste liquid treatment industry, pharmaceutical production industry, semiconductor production industry, food industry and the like. The present invention relates to a method for storing an electric desalination apparatus.

[0002]

2. Description of the Related Art A cation exchange membrane and an anion exchange membrane are alternately arranged between an anode chamber having an anode and a cathode chamber having a cathode, and the anode side is partitioned by an anion exchange membrane and the cathode side is a cation exchange membrane. A partitioned deionization chamber, a concentration chamber is formed in which the anode side is partitioned by a cation exchange membrane and the cathode side is partitioned by an anion exchange membrane, and ions in the liquid to be treated supplied into the desalination chamber by applying a voltage are formed. 2. Description of the Related Art There is known an electric desalination apparatus that moves a liquid to be treated by moving the liquid into a liquid supplied into a concentration chamber. Usually, a desalination chamber of this electric desalination apparatus is filled with an ion exchange resin.

[0003] For long-term storage when the electric desalination apparatus is not used, a storage method is known in which the used solution is simply filled or a small amount of the solution is left even when the used solution is withdrawn. I have. For example, there is a storage method in which a 50% propylene glycol solution is filled in the apparatus. According to these methods, when storing for a long time without supplying electricity for more than one week, there is a concern that mold or the like may occur. For this reason, there is a possibility that the performance of the ion-exchange membrane or the like may be reduced, the voltage required for operating the apparatus may be increased, and further, in the pharmaceutical industry, the quality may be deteriorated due to TOC (organic carbon) or endotoxin.

[0004] In order to prevent mold contamination, a method of filling the inside of the apparatus with a liquid having a fungicidal effect can be considered. For example, in the case of an apparatus for producing ultrapure water or the like, the chemical liquid is contained in the treated water after reactivation. In order to obtain predetermined water quality, impurities may be required for re-starting for a long time.
Further, in the method of filling the inside of the apparatus with the solution, the weight of the apparatus is increased by the amount of the solution, so that movement and distribution are affected.
Further, in a cold region, there is a possibility that the ion exchange membrane, the ion exchange resin, or the device itself may be destroyed due to freezing of water inside the device in some cases.

On the other hand, in ion-exchange resin towers and the like, the performance may deteriorate during long-term storage for several months or more. The reason for this is that since the anion exchange resin and the cation exchange resin are mixed in the tower, the surface of the anion exchange resin may be contaminated by eluates such as organic substances from the cation exchange resin during the storage period. Have been. For this reason, as described in, for example, JP-A-7-116526, an attempt has been made to maintain the performance by separating the anion exchange resin and the cation exchange resin to reduce the contact portion between the two. However, when the ion exchange resin is filled in the desalination chamber of the electric desalination apparatus, the operation of separating the ion exchange resin is difficult due to a problem in the apparatus, and no actual application has been performed.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to prevent deterioration of the quality of an ion-exchange membrane or the like when stored for a long period of time without passing electricity through an electric desalination apparatus.

[0007]

According to the present invention, first, a cation exchange membrane and an anion exchange membrane are alternately arranged between an anode chamber having an anode and a cathode chamber having a cathode, and the anion side has an anion. An electric type configured by alternately forming a desalting chamber partitioned by an exchange membrane and a cathode side partitioned by a cation exchange membrane, and a concentration chamber partitioned by an anode side by a cation exchange membrane and a cathode side partitioned by an anion exchange membrane. In a desalination apparatus, when storing for a long time without supplying water, the liquid in the electric desalination apparatus is discharged, and the water content of the cation exchange membrane and the anion exchange membrane is 30% during operation. % Storage method of an electric desalination apparatus that is dried so as to be less than 0.1%.

[0008] Secondly, the present invention relates to the above-mentioned first method, wherein the ion-exchange resin is accommodated in the desalting chamber of the electric desalination apparatus and stored for a long time without supplying water. The present invention also provides a method of drying and storing the inside of the desalination apparatus such that the water content of the ion exchange resin is 30% or less during operation.

Further, the present invention thirdly provides the above-described first embodiment.
And the second method, wherein the difference between the membrane size in the dry state and the membrane size in the operation state is 1 to the membrane size in the operation state.
% Is provided.

Further, the present invention fourthly provides the first to third embodiments.
In the storage method of the electric desalination apparatus described above, a storage method is provided in which the cation exchange membrane and the anion exchange membrane are dried and then a dry gas is sealed in the electric dechlorination.

[0011]

FIG. 1 shows an example of an electric desalination apparatus used in the present invention. In the electric desalination apparatus 1 shown in FIG.
Between an anode chamber 3 having a cathode and a cathode chamber 8 having a cathode 9;
A cation exchange membrane 4 and an anion exchange membrane 5 are alternately arranged, a desalting chamber 6 in which the anode side is partitioned by an anion exchange membrane and the cathode side is partitioned by a cation exchange membrane, and the anode side is partitioned by a cation exchange membrane and the cathode side is anion exchange membrane. A concentration chamber 7 partitioned by a membrane is formed. Then, by applying a voltage, ions in the liquid to be treated supplied into the desalting chamber 6 are moved into the solution supplied to the concentration chamber 7, and the liquid to be treated is desalted.

More specifically, the cations in the liquid to be treated, which are supplied to the desalting chamber 6 through the desalting chamber supply duct 10, pass through the cation exchange membrane and move to the concentration chamber 7, where the next anion exchange is performed. The movement is blocked by the membrane and stays in the concentration chamber 7. On the other hand, the anions in the liquid to be treated, which are supplied to the desalting chamber through the desalting chamber supply duct 10, pass through the anion exchange membrane and move to the concentration chamber 7, where the movement is blocked by the next cation exchange membrane. And stays in the concentration room 7. The desalted solution is discharged through a desalting chamber discharge duct 15.
An electrolyte solution is supplied to the concentration chamber 7 from a concentration chamber supply duct 11. The liquid in the concentration chamber 7 in which the ions permeating from the adjacent desalting chamber are concentrated is discharged through the concentration chamber discharge duct 14.

The liquid in the anode chamber 3 of the electric desalination apparatus is discharged through an anode chamber discharge duct 12, and the liquid in the cathode chamber 8 is discharged through a cathode chamber discharge duct 13.

An anion exchange membrane or a cation exchange membrane (hereinafter collectively referred to as an ion exchange membrane) used in the electric desalination apparatus of the present invention is generally classified as long as the membrane strength at the time of drying is sufficient. Either a homogeneous film or a heterogeneous film may be used. In particular, a heterogeneous membrane prepared by mixing an ion-exchange resin and a binder is preferable in that the dimensional change of the membrane during swelling and re-drying is small. In order to prevent film breakage, it is preferable that the film has a strength that can withstand the tensile stress generated when water is removed to 30% or less of the water content during operation after being once swollen with water. In particular,
The tensile strength is desirably 20 N / cm or more.

In the present invention, it is necessary that the water content of the ion-exchange membrane is not more than 30% of the water content of the ion-exchange membrane during operation when the battery is stored for a long period of time without supplying electricity. . The water content is preferably 20% or less from the viewpoint of suppressing the generation of viable bacteria and the like.

The ion-exchange membrane used in the present invention is an ion-exchange membrane of a styrene-divinylbenzene copolymer system because of its advantages such as chemical resistance, heat resistance, ion exchange characteristics and easy control of permselectivity. Is preferred.

The ion exchange group in the ion exchange membrane is
As the cation exchange group, a sulfonic acid type which is a strong acid is preferable, and as an anion exchange group, a quaternary ammonium salt type or a pyridinium salt type which is a strong base is preferable in terms of ion exchange characteristics and chemical stability. The ion exchange capacity of the ion exchange membrane is preferably 0.5 to 7 meq / g dry resin. If the ion exchange capacity is lower than 0.5 meq / g dry resin,
It is not preferable because adsorption and desalting of ions in the desalting chamber are not sufficiently performed, and the purity of treated water may be reduced. When the ion exchange capacity is 1 to 5 meq / g dry resin, a high purity of treated water can be obtained, and the performance stability is also excellent.

The change in the dimensions of the ion exchange membrane is preferably such that the difference between the dimensions in the dry state and the dimensions in the operation state is 1% or less. Each of these methods
Measure without fixing the membrane. More preferably, the dimensional difference is 0.5% or less in order to avoid film breakage.

In the present invention, the desalting efficiency can be further improved by accommodating the ion exchange resin in the desalting chamber. In this case, at the time of drying, it is preferable that the ion exchange resin accommodated in the desalting chamber is also dried so that the water content thereof is 30% or less of the water content during operation.

The ion exchange resin used in the present invention may be a bead or fibrous material represented by an ion exchange resin filled in a desalting chamber of an electric desalination apparatus generally used as a pure water producing apparatus. , A sheet-like ion exchange resin is used, and the shape and composition are not particularly limited. Further, it is preferable to use an ion exchange resin porous body which can be obtained by mixing and molding these with components other than the ion exchange resin.

In the present invention, it is preferable that after the ion exchange membrane is dried, a dry gas is sealed in an electric desalination apparatus. The gas used in this case may be any gas having no oxidizing property such as nitrogen, dry air having a dew point of −10 ° C. or less, or any other gas that does not destroy the ion exchange group. It is more preferable if it is provided.
As a method for encapsulating these gases, a method for encapsulating a liquid or a solid that generates the gas by changing the temperature is preferable.

[0022]

[Example 1] With the configuration as shown in FIG.
A room electric desalination unit was used. Cation exchange resin (Mitsubishi Chemical Corporation, trade name SK-1B), anion exchange resin (Mitsubishi Chemical Corporation, trade name SA-10A) and binder (Dow Chemical Co., trade name SM-1300) in the desalting chamber
Was mixed and molded into an ion-exchange resin porous body. In addition, as the ion exchange membrane, an anion exchange membrane in which an anion exchange group is introduced into a styrene-divinylbenzene copolymer and a cation exchange membrane in which a cation exchange group is introduced into the same polymer (trade name: Selemion, manufactured by Asahi Glass Co., Ltd.) are used. did. The enrichment chamber was filled with a resin spacer for securing a flow path. As the liquid to be treated, ion-exchanged water treated with a reverse osmosis membrane apparatus was passed through, and reagent-grade sodium chloride was added to the concentration chamber, the cathode chamber and the anode chamber so that the conductivity became about 300 μS / cm. The aqueous solution was passed.

Next, after performing a predetermined regeneration operation, the flow rate of the water to be treated is 2800 L / h, the current is 1.0 A, and the voltage is 150 to 1.
Table 1 shows the results of confirming the performance under the operating conditions of 80 V and the electric conductivity of the water to be treated of 2.5 μS / cm. However, the voltage has some width due to the constant current operation.

Thereafter, the apparatus was stopped, the liquid in the desalting chamber, the concentrating chamber, the cathode chamber and the anode chamber was drained, and nitrogen gas was supplied to the desalting chamber, the concentrating chamber, the cathode chamber and the anode chamber in order to further promote the drying state. Was allowed to flow. At this time, the water contents of the ion exchange membrane and the ion exchange resin were 9% and 5%, respectively, and the dimensional change of the membrane was 0.5%. After storing for 3 months without supplying electricity in this state, the water to be treated was flown again into the desalting chamber, the concentrating chamber, the cathode chamber and the anode chamber to swell the ion exchange membrane and the ion exchange resin. At this time, ultrapure water treated by another electric desalination apparatus was used for water swelling treatment.

Thereafter, the liquid was collected from the lower duct of the apparatus, and the viable cells were measured by a predetermined method using a simple viable cell detection kit (manufactured by Millipore, trade name: Water Sampler MSPC00025). The results are shown in the column of viable cell count after storage in Table 1. When the same measurement was performed using ultrapure water obtained by this electric desalination apparatus, the viable cell count was 0.9.
Pcs / mL. Further, a desalination test was performed under the same operating conditions. Table 1 shows the measurement results. Furthermore, Shimadzu TO
Table 2 shows the TOC measurement results measured using C-500A. The unit is ppb in terms of CO ₂ .

Example 2 (Comparative Example) The same electric desalination apparatus as in Example 1 was stored for 3 months without drainage and without water flow. Three months later, the liquid was collected from the lower duct, and viable bacteria were measured. Table 1 shows the results. Similarly, a desalination test was performed, and the resistivity and the voltage of the treated water before and after storage are shown in Table 1, and the TOC measurement results are shown in Table 2.

[0027]

[Table 1]

[0028]

[Table 2]

In Example 1 stored by the method of the present invention, no increase in voltage and no decrease in resistivity before and after storage were observed, and the performance was equivalent to that of Example 2. In addition, in Example 1, since the water pool was not in the battery case, the number of viable bacteria was smaller from the beginning even after re-watering than in the comparative example stored in the liquid immersion state. Therefore, almost no flushing time is required for re-use. The same is true for TOC. At the time of the battery case disassembly inspection of Examples 1 and 2 after the test, neither of the ion exchange membranes nor the ion exchange resin had any defects affecting the performance. In addition, the weight of the battery case that has been dried and stored this time is reduced by about 15% when it is full, and it is expected that the moving cost can be reduced. Furthermore, even in a cold region, freezing inside the battery case can be avoided.

[0030]

According to the present invention, it is possible to prevent contamination of the anion exchange resin surface, deterioration of the ion exchange membrane or the like due to generation of fungi or viable bacteria during the stop period of the electric desalination apparatus, and to prevent the desalination. The contamination of the impurities in the treated water after the restart of the apparatus is prevented, and the problem of prolonging the time for obtaining the predetermined water quality is solved.

[Brief description of the drawings]

FIG. 1 is a view schematically showing the structure of an example of an electrodialysis apparatus used in the present invention.

[Explanation of symbols]

 1: Electric desalination device 2: Anode 3: Anode compartment 4: Cation exchange membrane 5: Anion exchange membrane 6: Desalination compartment 7: Concentration compartment 8: Cathode compartment 9: Cathode

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4D006 GA17 HA47 JA70Z KA26 KA82 KA84 KB01 LA01 MA08 MA13 MA14 MB07 MC24 MC74 MC78 PA05 PB02 PB27 PC01 PC11 PC31 PC41 4D025 AA01 BA09 BA14 BA27 DA05 DA06 DA10 4D061 DA01 DB13 EA09 EB09 FA

Claims (4)

[Claims] A cation exchange membrane and an anion exchange membrane are alternately arranged between an anode chamber having an anode and a cathode chamber having a cathode, and the anode side is defined by an anion exchange membrane and the cathode side is a cation exchange membrane. In an electric desalination apparatus configured by forming alternately a partitioned desalting chamber and a concentrating chamber in which the anode side is partitioned by a cation exchange membrane and the cathode side is partitioned by an anion exchange membrane, no water flow is conducted. During long-term storage, the liquid in the electric desalination apparatus is discharged, and the water content of the cation exchange membrane and the anion exchange membrane is 30% at the time of operation.
% Storage method of an electric desalination apparatus that is dried so as to be less than 10%. 2. An ion exchange resin is accommodated in the desalination chamber of the electric desalination apparatus, and when stored for a long time without supplying water, the water content of the ion exchange resin is reduced to 30% of that during operation. The method for storing an electric desalination apparatus according to claim 1, wherein the drying is performed as follows. 3. The cation exchange membrane or the anion exchange membrane, wherein a difference between a membrane size in a dry state and a membrane size in an operation state is 1% or less of a membrane size in an operation state. The method for storing an electric desalination apparatus according to claim 1 or 2. 4. The method according to claim 1, wherein after drying the cation exchange membrane and the anion exchange membrane, a dry gas is sealed in the electric desalination apparatus.