JP2003337194A - Waste liquid treatment method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste liquid treatment method capable of being employed for a nuclear power plant, wherein treated water having a high purity can be obtain economically by using a cation resin with a high degree of crosslinking, and provide a waste liquid treatment apparatus. <P>SOLUTION: In the waste liquid treatment method for cleaning waste liquid, the waste liquid is made to pass through a mixed bed consisting of a strong acid gel cation resin having a degree of crosslinking of 12-16% and a strong basic anion resin for cleaning, and one or both of the cation resin and the anion resin have a uniform particle size distribution. Preferably, the cation resin has a degree of crosslinking of 14%, and the waste liquid may be filtered before being made to pass through the mixed bed of the ion exchange resins. The waste liquid may be filtered by employing a hollow fiber membrane filter, a precoat filter device or a pleat filter. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to waste liquid treatment,
Particularly, the present invention relates to a waste liquid treatment method and device for purifying waste liquid generated in a nuclear power plant.

[0002]

2. Description of the Related Art In a nuclear power plant, in order to purify and reuse generated waste liquid, waste liquid desalination equipment using an ion exchange resin, filtration equipment such as a hollow fiber membrane filter, etc. Concentrators are usually installed. The waste liquid generated in the nuclear power plant may contain radionuclides, and all the waste liquid is collected in the tank for purification treatment. There are various types of waste liquid collected in the tank, such as equipment drain water such as reactor water and rotating equipment seal water, floor drain water such as floor cleaning waste liquid, and recycle waste liquid generated by backwashing ion exchange resin or passing a chemical. There is a waste liquid of the nature. The treatment method differs depending on the properties of these waste liquids.For waste liquids containing a large amount of suspending substances, filtration treatment is performed, and for waste liquids with high ion concentration, concentration treatment is performed, and finally treatment is performed with a waste liquid desalting device for recovery. , Reused.

The ion exchange resin used in the waste water desalting apparatus uses a strongly acidic gel type cation resin and a strongly basic gel type anion resin having a crosslinking degree of 8% to 10% in a mixed bed. In a recent waste liquid desalination apparatus for a nuclear power plant, organic impurities eluted from a strongly acidic cation resin have been a factor of reducing the reaction rate of anion resin. That is, the organic impurities eluted from the strongly acidic cation resin include a sulfone group as a functional group, which is negatively charged, and therefore is adsorbed by the anion resin. However, when the molecular weight of the organic impurities eluted from the cation resin is large, the adsorbed organic impurities remain on the surface of the anion resin, which lowers the reaction rate, lowers the water quality, and shortens the resin life. Has become.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, the present invention makes it possible to obtain economical and highly pure treated water by using a cationic resin having a high degree of crosslinking, and to use it in a nuclear power plant. It is an object of the present invention to provide a waste liquid treatment method and apparatus that can be used.

[0005]

In order to solve the above problems, in the present invention, in a method for treating a waste liquid for purifying the waste liquid, the waste liquid is a strong acidic gel type cation resin having a cross-linking degree of 12 to 16%. This is a waste liquid treatment method in which water is passed through a mixed bed of a strongly basic anion resin for purification treatment. In the waste liquid treatment method, it is preferable that the cation resin and the anion resin have a uniform particle size distribution of one or both of the ion exchange resins, and the cation resin has a cross-linking degree of 14%. Water flow to the ion exchange resin mixed bed,
The waste liquid can be filtered before passing water, and the filtering treatment can be performed by a hollow fiber membrane filter, a precoat type filter or a pleated filter. Also,
According to the present invention, in a waste liquid treatment apparatus for purifying waste liquid, a packing layer composed of a mixed bed of a strongly acidic gel type cation resin and a strong basic anion resin having a degree of crosslinking of 12 to 16% is provided in a processing channel of the waste liquid. The waste liquid treatment device is characterized by being provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an ion exchange resin having a higher degree of crosslinking than conventional ion exchange resins used for desalting treatment is used. A cationic resin having a high degree of cross-linking has high chemical stability and thus has high oxidation resistance, and elution of organic impurities is less than that of a resin having a low degree of cross-linking. Also, the molecular weight of the organic impurities to be eluted is small. Therefore, by using a cation exchange resin having a high degree of crosslinking, good treated water quality can be obtained, and the life of the resin can be extended, which is economical. Particularly in a nuclear power plant, the used ion-exchange resin becomes a radioactive solid waste, which makes it difficult to process and dispose of it, and it is necessary to reduce the amount generated, and the present invention is effective. In addition, there is a certain correlation between the degree of cross-linking and the exchange capacity of the ion-exchange resin, and the resin with higher degree of cross-linking has a larger exchange capacity, and the use of resin with higher degree of cross-linking reduces the frequency of drug regeneration. It becomes possible to do.

On the other hand, the ion-exchange resin having a high degree of cross-linking has a characteristic that the internal structure of the resin is dense, and thus the reaction rate is slightly inferior to the conventionally used ion-exchange resins. In order to make up for this drawback, there is a method of using a resin having a uniform particle size. That is, by making the particle size distribution uniform and reducing the average particle size, the surface area of the resin layer can be increased and the reaction rate can be increased. Further, it is known that the elution of organic impurities from the cationic resin proceeds due to the oxidation reaction of the resin matrix. Therefore, when the metal oxide such as iron contained in the waste liquid to be treated is captured by the ion exchange resin, it acts as a catalyst for the oxidation reaction. Therefore, the waste liquid to be treated with the ion exchange resin is treated in advance with a filtering device such as a hollow fiber membrane filter, a precoat type filter or a pleated filter to remove the metal oxide contained in the waste liquid, thereby removing the ion exchange resin. It is possible to reduce the load on the substrate and reduce the elution of organic impurities.

The present invention will be described in detail below. The waste liquid treatment method of the present invention uses a mixed bed in which a cation exchange resin and an anion exchange resin are mixed. The ion exchange resin used has a copolymer of styrene and divinylbenzene as a base material. The cation exchange resin has, for example, a strongly acidic sulfonic acid group as a functional group, and the anion exchange resin has, for example, a strongly basic quaternary ammonium group as a functional group. The cation exchange resin used in the present invention has a divinylbenzene content, that is, a degree of crosslinking of 12 to.
It is 16%, more preferably 14%. Crosslinking degree is 12%
If it is less than the above range, the elution of organic impurities becomes large, which is not preferable. If it exceeds 16%, not only is the reaction rate slow, but also the regeneration characteristics are low when conducting regenerant regeneration to restore the ion exchange capacity, which is not preferable. Conversely, the degree of crosslinking is 12
As long as it is in the range of ˜16%, the elution of organic impurities is small and the influence on the reaction rate of the anion resin is small, which is preferable.

The particle size distribution of the ion exchange resin used is 350 to 1200 μm, preferably 550.
It is preferable to use a substantially uniform so-called uniform particle size product having a particle size of up to 750 μm. It is advisable to pass treated water, which has been passed through a filtering device installed on the inlet side, to the ion exchange resin. As the filtration device, a hollow fiber membrane filter, a precoat type filter or a pleated filter may be used.

[0010]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 In this example, the relationship between the degree of crosslinking of the cationic resin and the elution rate of organic impurities (TOC) was investigated. Inner diameter 25 mm
Using the test apparatus shown in FIG. 1 having a glass column of No. 1, a cation resin and an anion resin were mixed at a volume ratio of 2/1 to fill 50 mL, and pure water at 40 ° C. was circulated to pass the water.
The OC elution rate was determined. The results are shown in Figure 2. As is clear from FIG. 2, the higher the degree of crosslinking, the less the elution.

Example 2 In Example 2, the molecular weight distribution of organic impurities (TOC) eluted from the cationic resin was examined. The cationic resin and pure water were dipped in a volume ratio of 1/2, treated at 60 ° C. for 2 weeks, and the molecular weight distribution of TOC eluted was measured with a gel permeation chromatograph analyzer. The results are shown in Fig. 3. As is clear from FIG. 3, TOC eluted with resin having a higher degree of cross-linking
It can be seen that the molecular weight distribution of is small.

Example 3 In Example 3, the influence of the organic matter on the molecular weight and anion resin reaction rate was examined. Polystyrene sulfonic acid was used as a substance simulating organic impurities eluted from the cation resin, and polystyrene sulfonic acid of known molecular weight was adsorbed on the anion resin, and the reaction rate of the anion resin was measured. The reaction rate was measured as a desalting rate by the shallow bed method. The results are shown in Fig. 4. As is clear from FIG. 4, the polystyrene sulfonic acid having a low molecular weight has almost no effect on the desalination rate of the anion resin, but the polystyrene sulfonic acid having a high molecular weight has a large effect on the anion resin desalination rate.

Example 4 20 mL of ion exchange resin was added to a glass column having an inner diameter of 25 mm.
Containing radionuclides such as Co, Mn, and Fe.
Waste liquid with a radioactivity concentration of 4 Bq / mL is SV (space velocity) = 2
Water was passed through at 5, and the removal rate of the radionuclide after 2 hours was measured. As an ion exchange resin, a strong acid gel type cation exchange resin having a cross-linking degree of 8%, which is a conventional technique, and a strong acid gel type cation resin having a cross-linking degree of 14%, which is the present invention, are firstly added in 0.5% hydrogen peroxide After treating at 60 ° C. for 6 hours, it was mixed with an anion resin in a volume ratio of 2/1 to carry out a water flow test. The results are shown in Table 1. As is clear from Table 1, the resin of the present invention has a higher removal rate than the ion exchange resins conventionally used.

[0014]

[Table 1]

[0015]

EFFECTS OF THE INVENTION According to the present invention, a method for treating waste liquid in a nuclear power plant is economically advantageous by using a mixed bed of a strongly acidic gel type cation resin and a strongly basic anion resin having a crosslinking degree of 12 to 16%. It is also possible to improve the quality of treated water.

[Brief description of drawings]

FIG. 1 is a flow process diagram of a test apparatus used in Example 1.

FIG. 2 is a graph showing the relationship between the degree of crosslinking of a cationic resin and the TOC elution rate.

FIG. 3 is a graph showing the relationship between the degree of crosslinking of a cation resin and the molecular weight distribution of eluted organic matter.

FIG. 4 is a graph showing the relationship between the molecular weight of organic substances and the anion resin desalination rate.

Claims (5)

[Claims] 1. A method of treating a waste liquid for purifying the waste liquid, wherein the waste liquid is passed through a mixed bed of a strongly acidic gel type cation resin and a strongly basic anion resin having a degree of crosslinking of 12 to 16% for purification treatment. A waste liquid treatment method characterized by the above. 2. The waste liquid treatment method according to claim 1, wherein the cation resin and the anion resin have a uniform particle size distribution of one or both of the ion exchange resins. 3. The waste liquid treatment method according to claim 1, wherein the cationic resin has a degree of crosslinking of 14%. 4. The waste liquid treatment method according to claim 1, wherein the waste liquid is passed through the ion-exchange resin mixed bed by filtering the waste liquid and then passing the water. 5. A waste liquid treatment apparatus for purifying waste liquid, wherein a packing layer comprising a mixed bed of a strongly acidic gel type cation resin and a strongly basic anion resin having a cross-linking degree of 12 to 16% in the waste liquid processing channel. A waste liquid treatment device provided with.