JP2947849B2 - Method for removing ionic components from electrolyte solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an electrolyte solution in which the electrolyte solution is corrosive, can be dialyzed even at high temperatures, and has a long life even after reprocessing. And a method for removing ionic components.

(Prior art) Various radioactive waste liquids generated in a nuclear power plant are treated with radioactive cladding (iron oxide, Fe ₃ O ₄ , α-Fe ₂ O _3, etc. constituting equipment installed in a nuclear power plant) (Including submicron to several μm particle size), Ca ²⁺ ,
Contains ionic components such as Mg ²⁺ and Cl ⁻ . That is, such radioactive waste liquid is a kind of electrolyte solution. When the radioactive waste liquid is reused, these cladding and ionic components are removed by the radioactive waste treatment system shown in FIG.

That is, the nuclear power plant 2 of the nuclear power plant 1 includes the reactor system 3 and the turbine system 4, and the reactor pressure vessel 6 housed in the reactor containment vessel 5 of the reactor system 3,
Steam 7 generated by heating the coolant is discharged. Steam 7
Is guided to the turbine 8 in the turbine system 4 and works on the turbine 8 to operate the adjacent generator 9. Steam 7
Then, the water is condensed by the main condenser 11 through the cooling water 10, sent out by the low-pressure condensate pump 12, passes through the condensate filtration device 13, and then passes through the condensate desalination device 14, and is filtered and desalinated. You. The condensed water that has been cleaned after filtering and desalting is returned to the reactor pressure vessel 6 via a high-pressure condensate pump 15 and then a feedwater pump 16.

Further, a recirculation pump 17 is installed in the reactor containment vessel 5, and the coolant flowing into the reactor pressure vessel 6 is once taken out and forcibly recirculated into the reactor pressure vessel 6 again. The coolant removed by the recirculation pump 17 is partially filtered and desalted via a reactor coolant purifier 18.

Further, the reactor system 2 is provided with a fuel pool 19 for temporarily storing spent fuel.
The stored water is sent to the fuel pool purification device 20 to be purified, and then returned to the fuel pool 19 again.

In such a reactor system 2, mainly a condensate desalination device
From 14, a chemical waste liquid 21 is taken out. The equipment drain 22 is collected from the installed various devices, and the floor drain 23 is collected from the floor of the nuclear power plant 1 building in which these devices are stored.
Further, from the condensate filtration device 13, the condensate desalination device 14, the reactor coolant purification device 18 and the fuel pool purification device 20, each of the used resins 24 used for purification such as filtration and desalination is supplied.
Is collected. The chemical waste liquid 21, the equipment drain 22, the floor drain 23, and the resins 24 are in contact with the coolant or the fuel assembly used in the reactor pressure vessel 5 and have radioactivity. Waste treatment facility
It is sent to 25 to be treated for waste liquid or reuse.

The radioactive waste treatment facility 25 includes a low-conductivity waste liquid system 26, a high-conductivity waste liquid system 27, a waste sludge system 28, a volume reduction solidification system 29, and other systems 30. The low-conductivity waste liquid system 26 is a system for purifying a waste liquid having a relatively high radioactivity concentration but a low electric conductivity. On the other hand, the high-conductivity waste liquid system 27 is a system for purifying a waste liquid having a relatively low radioactivity concentration but a high electric conductivity. The waste sludge system 28 is a system for separating the spent resin 24 into a liquid component and a solid component. In the waste sludge system 28, the resin 24 is separated from the sedimentation component 32 by the sedimentation separation tank 31.
And the supernatant liquid 33, and the supernatant liquid 33 is handled together with the device drain 22. In this case, the supernatant 33 mainly contains Na
₂ SO ₄ included.

Here, the equipment drain 22 has a relatively high radioactivity concentration,
Waste liquid with low conductivity. Therefore, this equipment drain 22 is a collection tank 34, a filter 35,
The water is purified by passing through a tank 36, a desalter 37, and a sample tank 38 in this order. The equipment drain 22 is a filter equipped with a hollow fiber membrane filter and a clad separator before passing through the desalter 37.
The clad is filtered and separated by 35 to prevent the desalination efficiency in the desalter 37 from decreasing.

On the other hand, the chemical waste liquid 21 and the floor drain 23 are waste liquids having relatively low radioactivity concentrations but high electrical conductivity. Therefore, these chemical waste liquid 21 and floor drain 23 are used in the high-conductivity waste liquid system 27,
First, through a collection tank 39 and an evaporator / concentrator 40, the residue is mainly separated into a residue containing a clad and a distillation. The residue is then sent to a concentrated waste liquid storage tank 41, while the distillate then passes through a condenser 42, a tank 43, a desalter 44 and a sample tank 45 in that order. Therefore, even if the distillate contains an ionic component, it is removed in the desalter 44.

The condensate collected in the sample tank 38 of the low-conductivity waste liquid system 26 and the sample tank 45 of the high-conductivity waste liquid system 27 is
The water is returned to the main condenser 11 via the condensate storage tank 46 and is reused.

On the other hand, the concentrated waste liquid collected in the concentrated waste liquid storage tank 41 of the high-conductivity waste liquid system 27, together with the settling component 32 deposited in the settling separation tank 31 of the waste sludge system 28, is sent to the volume reduction solidification system 29,
After being reduced in volume and solidified, it is stored in a drum storage 47 together with wastes from other systems 30.

By the way, the low-conductivity waste liquid system 26 described above and the high-conductivity waste liquid system
In 27, the ionic components of the waste liquid are removed by desalters 37 and 44. These desalters 37 and 44 include various organic materials such as ion exchange resins, ion exchange membranes, reverse osmosis membranes, An ion separating means made of a polymer is used.

(Problems to be Solved by the Invention) However, if the waste liquid is heated before being introduced into the desalter, the ion separation means using the above-described organic polymer significantly reduces the separation efficiency at, for example, 150 ° C. or more. . For this reason,
The waste liquid heated for concentration must be cooled to a temperature suitable for ion separation before being introduced into the desalter. Therefore, the time required for desalination is prolonged, and the wastewater that has been heated once is cooled, resulting in a processing process with low energy efficiency.

In addition, since the ion separation means using the organic polymer has poor resistance to microorganisms such as bacteria and chemicals,
It cannot be used in an environment exposed to these. Further, these ion separation means can be reused after the cleaning treatment, but have a short life. Although the ion separation means whose service life has expired is discarded, it is desirable that the amount of waste contaminated by such radioactive materials is as small as possible.
Therefore, from the viewpoint of reducing the volume of radioactive waste, there is a need for an ion separation means having a long service life.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for removing an ionic component of an electrolyte solution that is erodible, can be dialyzed even at a high temperature, and has a long life even after reprocessing. Aim.

[Configuration of the invention]

(Means for Solving the Problems) According to the method for removing an ionic component of an electrolyte solution according to the present invention, in order to solve the above-described problems, a filter made of a porous sintered body made of conductive ceramics is manufactured. This is a method in which a ceramic filter is used for both electrodes to electrodialyze an electrolyte solution to separate ionic components into cations and anions.

(Action) In the method for removing an ionic component of an electrolyte solution according to the present invention, the electrolyte solution is electrodialyzed with a conductive ceramic filter. In other words, ceramics used as filter materials are superior in heat resistance, chemical resistance, and bacterial resistance to organic polymers that have been used as filter materials in the past, and have a long service life even when washed and reused. Has features. For this reason, it is possible to perform dialysis and desalting without cooling even the once heated waste liquid, and labor and time related to desalting are saved. Since the method of this embodiment is electrodialysis, ions can be separated much faster than ordinary dialysis. In addition, dialysis and desalination can be performed even in an erosive environment, and the range of use is expanded. Furthermore, even when it becomes unusable and is treated as waste due to its long service life, the amount can be kept very small.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG. 1 and FIG.

FIG. 1 is a diagram schematically showing an apparatus used for carrying out the method of the present invention. That is, the container 51 is partitioned by two filters 52a and 52b made of conductive ceramics.
Then, an electrolyte solution 50 containing an ionic component is introduced into a portion partitioned by the two filters 52a and 52b. On the other hand, the filter 52a,
On the outside of 52b, a liquid 49 of the same type as the solvent of the electrolyte solution 50 is provided.
Fill. The filters 52a and 52b are porous because the material is ceramics. Also, filters 52a and 52b
Are connected to the poles of the DC power supply 53, respectively. Therefore, the filter 52a and the filter 52b are electrically charged. In the container 51, an electrode 54a is provided outside the filter 52a, and an electrode is provided outside the filter 52b.
Each 54b is immersed in the electrolyte 50. This device configuration is a normal device configuration for electrodialysis, except that the filters 52a and 52b are made of conductive ceramics.

In other words, the electrolyte 50 which has been electrolyzed into ions (cations: cations) and ions (anions: anions) in the interior partitioned by the filters 52a, 52b draws ions to the filter 52b and ions to the filter 52a by Coulomb force. Can be Then, ions and ions pass through the holes of the filters 52b and 52a, respectively, and
It escapes outside 52b and 52a, and the separation of the ionic components is achieved.

Thereafter, the ion components are attracted to the electrode 54b and the electrode 54a by the Coulomb force.
Therefore, according to this apparatus, it is possible to separate the ion component into ions and process the ions.

Here, the ceramic used as a material for the filter 52 is not particularly limited as long as it is conductive, and for example, alumina,
ZrB ₂ , SiC, Si ₃ N _{4 and the} like can be used. And
The diameter of the hole is preferably 40 to 2000 mm. Ceramic filters having such a pore size can be manufactured by a known technique. For example, for an alumina membrane, AICHE, Symp. Ser. 34
(261), 19-27, 1988; Membrane, 10 , 297, 1985; Ch.
em.Eng., Jan, 20, 18, 1986; Chemical Optics, 48, 682, 1984; J. Che.
m. Eng. Japan, 17 , 514, 1984 and the like.

When ZrB ₂ is used as a material, if ZrB ₂ is used alone, Si
Since the sintering temperature is higher than C, Si ₃ N ₄ etc., it takes time and effort to manufacture, and it is easily oxidized and decomposed in the air, so it should be a composite sintered body containing 10 to 20% by weight of SiC. Is preferred. Furthermore, when improving the thermal shock resistance of the ZrB ₂ is hexagonal BN
It is preferable to form a composite sintered body with (hBN). However, in this case, strength and hardness are slightly lost. Conversely, when improving the hardness and wear resistance, a composite sintered body may be formed with B ₄ C. In this case, Vickers hardness of 1300 for ZrB ₂ alone
~1600kg / mm ² is almost doubled.

FIG. 2 shows a filter manufactured using only the aforementioned ZrB _{2 and} a ZrB ₂ filter.
Is a graph showing the relationship between temperature and resistivity for the composite sintered body of B ₂ and B ₄ C. Both filters are 1800-2200 ℃
Manufactured under a temperature and pressure condition of 350 kg / cm ² . Membrane potential in each filter, the applied voltage can be changed by changing the content ratio of the film thickness and ZrB _2. According to this example, within the temperature range up to 1500 ° C., the specific resistance is about
It was possible to obtain an electrodialysis filter having a practical level of 4.0 × 10 ⁻³ or less. Therefore using a ZrB ₂ -B ₄ C filter composite sintered body (average pore diameter 1000 Å), was treated with 300 ° C. of radioactive liquid waste in the apparatus configuration shown in FIG. 1, in the ZrB ₂ -B ₄ C filter It was confirmed that ions such as Na ⁺ , Mg ²⁺ , SO ₄ ^{2- and the} like were promptly removed from the radioactive liquid waste in the partition. Needless to say, these filters are made of ceramics and have excellent chemical resistance and bacterial resistance, and have a long life even after repeated use.

〔The invention's effect〕

As described above, the in-component removal method of the electrolyte solution according to the present invention is to manufacture a filter made of a porous sintered body with conductive ceramics, and to use the conductive ceramics filter for both electrodes to form an electrolyte. Since the solution is electrodialyzed and the ionic component is separated into cations and anions, it has excellent heat resistance, chemical resistance, and bacterial resistance.
Even when washing and reusing, a filter made of conductive ceramics with a long service life can be used, and it can be applied directly to high-temperature waste liquid, saving labor and time related to waste liquid cooling,
Dialysis and desalination can be carried out even in an aggressive environment, and the filter can be used for a long time, so that even when it becomes unusable and is treated as waste, the amount can be kept very small.

Further, in the present invention, since the electrolyte solution is subjected to electrodialysis using a filter made of conductive ceramics for both electrodes, ion components can be separated much faster than ordinary dialysis, and dialysis and desorption can be performed even in an aggressive environment. It has effects such as being able to perform salt.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an electrodialysis apparatus for carrying out the method of the present invention, FIG. 2 is a graph showing the relationship between the temperature and the specific resistance of a conductive ceramic filter used in the method of the present invention, and FIG. The figure is a schematic diagram of a radioactive waste treatment system in a nuclear power plant. 31 ... sedimentation separation tank, 37, 44 ... desalinator, 40 ... evaporative concentrator.

Continuing from the front page (72) Inventor Toshihiko Kubogawa 4-7-1 Kajiwara, Kamakura-shi, Kanagawa Pref. Inside the Company Nomura Research Institute (72) Inventor Sakae Takagi 4-7-1 Kajiwara, Kamakura-shi, Kanagawa Pref. In the laboratory (72) Inventor Makoto Yokozawa 4-7-1 Kajiwara, Kamakura-shi, Kanagawa Prefecture Nomura Research Institute, Inc. (56) References JP-A-1-47403 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) B01D 61/46 500 G21F 9/06 511

Claims (1)

(57) [Claims] 1. A filter comprising a porous sintered body made of conductive ceramics is manufactured. Electrolyte solution is electrodialyzed by using the filter made of conductive ceramics for both electrodes, and an ionic component is converted into a cation and an anion. A method for removing an ionic component of an electrolyte solution, comprising: