JP4826912B2 - Storage method of electrodeionization equipment - Google Patents

Description

  The present invention provides an electrodeionization apparatus for use in pure water utilization facilities such as boilers and research facilities in addition to industrial fields such as salt production industry, waste liquid treatment related industry, pharmaceutical production industry, semiconductor production industry, and food industry. The present invention relates to a method for stably storing a product while preventing a decrease in performance during the period when electricity flow is stopped.

  Desalination in which 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, the anode side being partitioned by an anion exchange membrane and the cathode side being partitioned by a cation exchange membrane And a concentration chamber 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 for-treatment water supplied into the desalting chamber by applying a voltage are placed in the concentration chamber. There is known an electrodeionization apparatus that moves into a supplied liquid and deionizes the water to be treated. Usually, the demineralization chamber of the electrodeionization apparatus is filled with an ion exchanger such as an ion exchange resin, and the concentration chamber may also be filled with an ion exchanger.

  Conventionally, when such an electrodeionization apparatus is stored for a long time when not in use, the apparatus is stored with the use solution as it is or filled with another storage solution. . For example, a 50% propylene glycol solution is used as the storage solution.

  However, when the electrodeionization device is turned off and stored for a long period of one week or longer, the performance of the ion exchange membrane or ion exchanger during the outage is deteriorated, which is necessary for the operation of the device at the restart. There was a problem that the voltage increased or the quality of the treated water decreased due to the outflow of TOC (organic carbon), and it took a long time to collect treated water after restarting.

  In order to prevent degradation of the device performance during the storage period, a method of filling the inside of the device with a chemical solution can be considered, but in this case, in an electrodeionization device that produces ultrapure water etc., after restarting There is a possibility that it takes a long time after restarting to obtain a predetermined water quality by mixing impurities such as chemicals in the treated water.

Japanese Patent Laid-Open No. 2001-179261 discloses that the liquid in the apparatus is discharged for the purpose of preventing the quality deterioration of the ion exchange membrane and the like when the energization of the electrodeionization apparatus is stopped and stored for a long time. In addition, a method is described in which the moisture content of the ion exchange membrane and the ion exchange resin is stored at 30% or less during operation.
JP 2001-179261 A

  However, the method described in JP-A-2001-179261 is not preferable because the ion exchange membrane may be broken by lowering the water content.

  The present invention solves the above-mentioned problems of the prior art, prevents the deterioration of the performance during the long-term water energization stop storage period of the electrodeionization device, stably stores it, and performs predetermined processing when restarting operation. It aims at providing the storage method of the electrodeionization apparatus which shortens the time required in order to obtain water quality.

As a result of intensive studies to solve the above problems, the present inventors have obtained the following knowledge.
Even in an ion exchange resin tower or the like, the performance may deteriorate during long-term storage for several months or more. The reason for this is that the anion exchange resin and cation exchange resin are mixed in the column, and the surface of the anion exchange resin may be contaminated by effluent such as TOC from the cation exchange resin during the storage period. It has been.

  On the other hand, most of the ion exchange resin filled in the demineralization chamber of the electrodeionization apparatus is regenerative (OH type, H type) due to electric regeneration when energized. In the regenerative type, the ion exchange resin swells and the volume increases. For example, the volume increases due to swelling of cation exchange resin by 108% and anion exchange resin by 120%. And if it becomes a reproduction | regeneration type, a network structure will become dense from sparse, and it will become easy to elute the TOC component confined inside the ion exchange resin. For this reason, when the stop period becomes longer, the amount of TOC eluted from the ion exchange resin increases. As a result, it takes time to discharge the TOC when the operation is resumed, and the time required for sampling the treated water becomes longer.

  Therefore, the present inventors can reduce the TOC elution amount from the resin during the storage period by suppressing the swelling by making the ion exchange resin not the regenerative type but the non-regenerative type, and the operation of the apparatus after long-term storage. The present inventors have found that the TOC discharge time at the time of resumption can be shortened and completed the present invention.

In the storage method of the electrodeionization apparatus of the present invention (Claim 1), an anion exchange membrane and a cation exchange membrane are alternately arranged between an anode and a cathode, and the anion exchange membrane and the cation exchange membrane are arranged between the anion exchange membrane and the cation exchange membrane. When an electrodeionization apparatus that forms a desalination chamber and a concentration chamber and is filled with an ion exchanger at least in the desalination chamber is stored for a long time without passing water, the ion exchanger is in a salt form. A method of storing an electrodeionization apparatus that converts to an ionizer and stores the ion exchanger, wherein the ion exchanger is a mixture of an anion exchange resin and a cation exchange resin, Passing a salt solution at least 1 equivalent to the ion exchange resin filled in the deionizer, 99% or more of the anion exchange resin is converted to Cl form, and 99% or more of the cation exchange resin is converted to Na form. wherein the store by converting each To.

Storage method of electrodeionization apparatus of claim 2, Oite to claim 1, wherein after converting the ion exchanger in salt form, the electric conductivity 1 mS / m or less pure water is sealed in electrical deionization apparatus It is characterized by being stored.

  According to the storage method of the electrodeionization apparatus of the present invention, an increase in the TOC elution amount due to swelling of the ion exchanger is effectively suppressed when the electrodeionization apparatus is turned off and stored for a long time. Thus, it is possible to shorten the TOC discharge time when resuming the operation and to collect the treated water at an early stage.

  The embodiment of the storage method of the electrodeionization apparatus of this invention is described in detail below.

  In the electrodeionization apparatus to which the storage method of the present invention is applied, 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 anion-exchanged. A desalination chamber partitioned by a membrane and a cathode side partitioned by a cation exchange membrane and a concentration chamber partitioned by a cation exchange membrane and an anode side partitioned by an anion exchange membrane are formed and desalted by applying voltage. This is a general electrodeionization apparatus that deionizes the water to be treated by moving ions in the water to be treated supplied into the liquid into the liquid supplied into the concentration chamber, and is not particularly limited.

  An ion exchanger such as an ion exchange resin obtained by mixing an anion exchange resin and a cation exchange resin is filled in the demineralization chamber of such an electrodeionization apparatus. The exchanger may be filled.

  In the present invention, the ion exchanger in the demineralization chamber is converted into a salt form and stored when the energization of such an electrodeionization apparatus is stopped and stored for a long period of time, for example, one month or more.

In the case of converting the mixed ion exchange resin of the anion exchange resin and the cation exchange resin in the desalting chamber into a salt form, saline is passed through the desalting chamber . The concentration of the salt solution to be used is 0.5 to 5% by weight, and the amount of salt solution to be passed is preferably 1 to 10 times the amount of the ion exchange resin in the desalting chamber as the amount of salt. If the concentration of the salt solution to be used is too low, the amount of salt solution required to convert the ion exchange resin to the salt form is large, which is not preferable because it requires a long water passage time. Conversely, it is meaningless if the concentration is too high. On the other hand, if the water flow rate is too small, the ion exchange resin in the desalting chamber cannot be converted into the salt form sufficiently, and if it is too much, there is no difference in effect, and the water flow time is undesirably long.

In addition, although there is no restriction | limiting in particular in a water flow rate, if it is too fast, a differential pressure will be added and an inlet pressure will become high, and it will result in exceeding an allowable pressure | voltage resistance, and if it is too slow, a liquid drift will arise. It is preferably about 50 hr ⁻¹ .

By passing the saline solution in this manner, 99% or more, preferably substantially 100% of the anion exchange resin in the desalting chamber is in the Cl form, and 99% or more, preferably substantially, of the cation exchange resin. as a state in which 100% is converted into Na form, the you store.

  In addition, after the ion exchange resin is converted into a salt form in this way, the saline solution in the apparatus is replaced with water having a conductivity of 1 mS / m or less, and all the desalting chamber, concentration chamber and electrode chamber are electrically conductive. It is preferable to enclose and store water with a rate of 1 mS / m or less.

  When restarting the operation after storage, it is only necessary to restart the energization as it is. However, according to the present invention, since the TOC elution from the ion exchange resin during storage is prevented, the processing at the time of restarting the operation is performed. The amount of TOC elution into water is small, and as a result, desired high-purity treated water can be adopted early.

  Hereinafter, the present invention will be described more specifically with reference to examples.

In the following examples and comparative examples, as a test electrodeionization apparatus, the demineralization chamber has 10 cells with a width of 320 mm, a length of 600 mm, and a thickness of 5.2 mm, and the concentration chamber has a width of 320 mm and a length of 600 mm. An electrodeionization apparatus having a treatment amount of 1 m ³ / hr composed of 11 cells having a thickness of 4 mm was used.

The following were used as the anion exchange resin and cation exchange resin filled in the ion exchange membrane and demineralization chamber of this electrodeionization apparatus. The concentration chamber was also filled with the same ion exchange resin as the desalting chamber.
Anion exchange membrane: "Neocepta AHA" manufactured by Astom Co., Ltd.
Cation exchange membrane: "Neocepta CMB" manufactured by Astom Co., Ltd.
Anion exchange resin: “SBR-PC” manufactured by Dow Chemical
Cation exchange resin: “650C” manufactured by Dow Chemical

  The filling rate of the ion exchange resin was anion exchange resin: cation exchange resin = 60: 40 in the desalting chamber, and anion exchange resin: cation exchange resin = 60: 40 in the concentration chamber (both volume ratio).

Example 1
First, the permeated water (RO treated water: conductivity 0.5 mS / m) obtained by treating tap water with a reverse osmosis membrane separator is passed as treated water of an electrodeionization apparatus, and has a current of 10 A and a voltage of 40 V. I drove in. The specific resistance of the treated water obtained was 18 MΩ · cm.
Thereafter, the water flow was stopped, and then 1 wt% saline was passed through the desalting chamber at 250 L / hr for 1 hour. This water passage condition is a condition in which water containing salt equivalent to five times the ion exchange resin filled in the desalting chamber is passed at SV = 25 hr ⁻¹ . Thereafter, the saline solution was replaced with RO treatment water (conductivity 0.5 mS / m), which was to be treated, and this RO treatment water was sealed in a desalting chamber, a concentration chamber, and an electrode chamber and stored for 6 months. The salt form ratio of the ion exchange resin in the desalting chamber during storage was as shown in Table 1.
After storage, water flow energization was resumed, and simultaneously with the resumption of water flow energization, the time-dependent change in the TOC elution amount was examined from the TOC concentration difference of the treated water and treated water of the electrodeionization apparatus, and the results are shown in FIG.

Comparative Example 1
In Example 1, the change in the TOC elution amount with time after restarting was examined in the same manner except that the saline solution was not passed and stored as it was after the water flow was stopped, and the results are shown in FIG. It was.
The salt form ratio of the ion exchange resin in the desalting chamber at the time of storage was as shown in Table 1.

The following can be seen from the results of Example 1 and Comparative Example 1.
If treated water is stopped after storing treated water having sufficiently low specific resistance as in Comparative Example 1, the amount of TOC elution increases when operation is resumed. As a result, it takes about 30 hours until TOC elution is almost eliminated and high purity water having a TOC elution amount of 1 ppb or less can be supplied. On the other hand, in Example 1, the amount of TOC elution at the time of resuming operation was small, and high-purity water having a TOC elution amount of 1 ppb or less could be supplied after about 16 hours of water flow.

In general, in the field of ultrapure water, there are many places where the TOC concentration is 1 ppb or less, and it is desired that such pure water can be supplied within 24 hours after resuming operation.
According to the present invention, the ion exchange resin in the electrodeionization apparatus is converted into a salt form and stored, thereby reducing the amount of TOC eluted during the storage period and required for starting up the electrodeionization apparatus. Time can be significantly reduced.

4 is a graph showing changes with time in the TOC elution amount in Example 1 and Comparative Example 1.

Claims (2)

An anion exchange membrane and a cation exchange membrane are alternately arranged between the anode and the cathode to form a desalination chamber and a concentration chamber between the anion exchange membrane and the cation exchange membrane, and at least ions in the desalination chamber An electrodeionization apparatus filled with an exchanger is a storage method of an electrodeionization apparatus for storing the ion exchanger by converting it into a salt form when storing for a long time without passing water ,
The ion exchanger is a mixture of an anion exchange resin and a cation exchange resin, and after the passage of water through the electrodeionization device is stopped, the ion exchange resin is charged at least 1 equivalent to the ion exchange resin. Storage of an electrodeionization apparatus characterized in that 99% or more of the anion exchange resin is converted to Cl form and 99% or more of the cation exchange resin is converted to Na form by passing a saline solution of Method. Oite to claim 1, said after converting the ion exchanger in salt form, electrodeionization apparatus, characterized in that the storage by sealing Conductivity 1 mS / m or less in pure water to the electric deionizer Storage method.

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