JPH0153117B2 - - Google Patents

Description

[Detailed description of the invention]

Ions, colloidal substances, suspended solid substances, etc. in water are used in condensate systems and pure water systems in nuclear power plants, thermal power plants, etc., or in drainage systems with relatively low ion concentrations with conductivity of 50 μs/cm or less. There is a growing need to remove Conventionally, as a method for treating such an aqueous solution, there is a pre-coating method in which a particulate cation exchange resin and an anion exchange resin are mixed or each is used individually and pre-coated on a perelement. However, the conventional precoating method has the following drawbacks. First, if a mixture of finely divided cationic and anionic ion exchange resins is precoated on a permeable element and water is passed through it, there is a drawback that cracks often occur in the precoat layer during water passage. The formation of such cracks is generally considered to be caused by the shape or particle size distribution of the particles of the precoating agent. In other words, fine particulate ion exchange resin is generally produced by crushing particulate ion exchange resin with a particle size of about 0.2 mm to 0.6 mm, so it has a crushed appearance, which is why it is thought that cracks occur. . When such cracks occur, there is a defect that contaminates the over-element and deteriorates the quality of the treated water. Second, the membrane layer that is formed when a mixture of particulate cationic and anionic ion exchange resins is precoated on the membrane element is generally an extremely thin membrane layer of about 5 to 15 mm. It is necessary to remove trace amounts of ions, colloidal substances, suspended solid substances, etc., but the membrane layer is extremely dense and the excess properties are superficial.
Although the removal performance of colloidal substances and suspended solids is good,
The removal capacity is small, and therefore, when water is passed through, the membrane layer is blocked by the accumulation of suspended solids, and the pressure loss of the membrane layer increases in a relatively short period of time. The present invention provides a new technology for aqueous solution processing that eliminates the various drawbacks of the conventional methods. In treating an aqueous solution, the present invention involves a first step of mixing particulate ion exchange resin with a particle size of 2 to 250 μm in water, and a filtering process of the particulate ion exchange resin mixed with water obtained in the first step. A second step of precoating the support to form a membrane layer; and elongated cation exchange fibers having a thickness of 2 to 200 μm and a length of at least twice the thickness, and a particle size of 2 to 250 μm. A third step is to mix and entangle the fine particulate ion exchange resin in water, and a second step is to mix and entangle the ion exchange fibers and fine particulate ion exchange resin with the water obtained in the third step. A fourth step of further precoating on the membrane layer of the precoated particulate ion exchange resin to form a double membrane layer in which the particulate ion exchange resin layer and the ion exchange fiber layer are intertwined; A fifth step of passing an aqueous solution through the membrane layer to remove ions, colloidal substances, and suspended solids to obtain treated water, and backwashing the supersupported material using gas or water or gas and water. The present invention relates to a method for treating an aqueous solution using a particulate ion exchange resin and an ion exchange fiber, which is characterized by combining six steps including a sixth step of peeling off and removing a used membrane layer. Treatment of an aqueous solution using a double membrane layer in which a membrane layer of cation exchange fibers and a fine particulate ion exchange resin are intertwined and stacked on a membrane layer of the fine particulate cation and anion exchange resin of the present invention. This method is a new method for treating an aqueous solution that does not have any of the drawbacks or problems of the conventional treatment method using a precoat layer of only particulate ion exchange resin, and has many features and advantages as follows. There is. First, cracks do not occur in the membrane layer. In the method of the present invention, a double membrane layer is formed by intertwining and overlapping a membrane layer of ion exchange fibers on a membrane layer of fine particulate cation/anion exchange resin, so that the membrane layer formed is is covered with a strong net-like layer made of intertwined ion-exchange fibers, and this net-like layer is further intertwined with a membrane layer of particulate cation and anion exchange resin, creating an integrated and durable structure. have. Therefore, the structure of the precoat layer has no weak spots and no cracks occur. Therefore, during treatment, the aqueous solution to be treated may contaminate the over-element, the over-support may become clogged, and the quality of the treated water may deteriorate due to the aqueous solution passing through the cracks. There are no drawbacks or obstacles to the method. Second, it has a large removal capacity for colloidal substances and suspended solids. The method of the present invention exhibits a volumetric tendency on a dense membrane layer made of particulate cation/anion exchange resin, and has a large removal capacity.
In addition, unlike a pre-coated layer made of ion exchange fibers alone, the cation exchange fibers and fine particles have a certain degree of precise overcapacity, and are designed to reduce the burden on the underlying membrane layer of fine particulate cation/anion exchange resin. Since there is a membrane layer made of ion exchange resin, it has a membrane layer with good overall removal performance and a large removal capacity. This means that, for example, the method of the invention
When used to remove iron-based crud in the primary cooling water of a BWR nuclear power plant, the amount of used ion exchange resin discharged as secondary radioactive waste will decrease in inverse proportion to the removal capacity. 1.1 million
In the case of a KW class power plant, the amount of particulate ion exchange resin discharged as radioactive waste annually is estimated to be approximately 38,000 kg in dry weight, but if the removal capacity were doubled, it would be 19,000 kg, and if the removal capacity was tripled, it would be 19,000 kg. This is a significant decrease to 12,700Kg. This greatly reduces work in the condensate system and Radwest system, which in turn is highly effective in significantly reducing radiation exposure for nuclear power plant personnel. Thirdly, it is easy to form a uniform membrane layer by precoating the membrane support, and the used membrane layer can be completely and easily peeled off. In the present invention, as described above, elongated cation exchange fibers and particulate ion exchange resin are mixed and entangled in water, and the entangled body is further pre-coated on a membrane layer of particulate cation and anion exchange resin. Due to the double pre-coating method in which a membrane layer is formed using the cation-exchange fibers and the particulate ion-exchange resin, a strong network-like membrane is formed by physically or physically and electrostatically intertwining the cation exchange fibers and the particulate ion exchange resin. Since the layer covers the lower particulate ion exchange resin layer and integrally forms a double membrane layer on the supersupport, it is easy to form a uniform and strong membrane layer. In addition, when backwashing the supersupport with gas or water or gas and water to remove the used membrane layer and re-form a new membrane layer, the used membrane layer is completely integrated. Since the used membrane layer has a structured structure, all or most of the used membrane layer is peeled off as one, so that the used membrane layer can be completely and extremely easily peeled off. The formation and peeling-off state of the membrane layer in the method of the present invention is characterized by being extremely different from the conventional formation and removal of a pre-coat layer using only particulate ion-exchange resin. . Fourthly, ions, colloidal substances, and suspended solid substances in the aqueous solution to be treated can be removed stably and effectively, and extremely pure treated water can be obtained at a high flow rate for a long period of time. In the method of the present invention,
The treatment is carried out by passing the aqueous solution through a double membrane layer in which cation exchange fibers and particulate ion exchange resins are physically and electrostatically intertwined, so ions in the aqueous solution are removed by ion exchange reactions. The colloidal substances are dissolved or aggregated and removed by the cation exchange fibers and particulate ion exchange resin, and the suspended solid substances are removed by the removal ability of the upper layer of cation exchange fibers and particulate ion exchange resin. A large and precise membrane layer separates most of the material and makes the process more effective. Furthermore, as mentioned above, the membrane layer formed by the present invention is uniform and does not cause cracks, so long-term treatment can be carried out stably and effectively, and extremely pure treated water can be produced. can be obtained. In addition, as mentioned above, the membrane layer formed according to the present invention is extremely unlikely to block the membrane support and cause clogging, and has the feature of low pressure loss, allowing processing to be carried out at high flow rates and for long periods of time. It has the advantage of being stable. Examples of cation exchange fibers, particulate cation exchange resins, and anion exchange resins used in the present invention include styrene,
All materials similar to the base materials of normal ion exchange resins such as divinylbenzene and acrylic resins as well as reactive carbon fibers can be used, and the ion exchange groups include sulfonic acid groups, carboxyl groups, and trimethylammonium groups. 4th of
The same ion exchange resins as ammonium groups, primary to tertiary amine groups, etc. can be used, but in terms of treatment performance for aqueous solutions, cation exchange fibers or fine particulate cation exchange resins and anion exchange resins can be used. A quaternary ammonium group such as a strongly acidic sulfonic acid group or a strongly basic trimethylammonium group is preferred in terms of physical and electrostatic entanglement with the group. The types of ion exchange groups include H ⁺ type, NH ₄ ⁺ type, and
Select and use the OH ^- type as appropriate. The shapes of the ion exchange fibers used in the present invention include linear fibers, branched fibers, crimped fibers, and aggregates formed by intertwining these fibers, and the cross-sectional shape of the fibers is circular. , oval, bell-shaped, square, star-shaped, hollow, etc. shapes can be used. The size of the cation exchange fiber used in the present invention is 2 to 200 μm in thickness.
Thin ion-exchange fibers with a thickness of 30 μm or less are preferable because they have a high reaction rate during treatment and have good performance in removing colloidal substances and suspended solid substances. The length of the cation exchange fibers used in the present invention is at least twice the thickness, and long and thin ones with a length of about 5 to 50 times the thickness are used to entangle the cation exchange fibers, and Integration of the membrane layer by intertwining them with particulate ion exchange resin, uniformity and ease of membrane layer formation by pre-coating, prevention of cracks in the membrane layer, and peeling and removal of the used membrane layer. This is preferable in terms of ease. The particulate ion exchange resin used in the present invention is obtained by pulverizing large particles used in the normal packed bed ion exchange method, or by pulverizing the particles into fine particles when producing the base material of the ion exchange resin. The particles may be made by, for example, a suspension polymerization method, and the particle shape may be crushed, spherical, spheroidal, or dart-shaped. The size of the particulate ion exchange resin used is one with a particle size of 2 to 250 μm,
Fine particles with a particle size of 50 μm or less are preferable because they have a high reaction rate during treatment and have good removal performance for colloidal substances and suspended solid substances, and are also effective in integrating the membrane layer and preventing cracks in the membrane layer. It is also preferable in these respects. The present invention involves mixing particulate cation and anion exchange resins in water prior to precoating, and mixing cation exchange fibers and particulate ion exchange resins in water to physically or physically remove them. The electrostatic entanglement step is extremely important in order for the precoat to form a durable, uniform, and stable membrane layer. These steps are carried out by thorough stirring and mixing in water, and stirring and mixing in water is carried out, for example, at about 100 to 300 rpm. FIGS. 1 and 2 show an example of a partially enlarged explanatory view of the state of particles when fine particulate ion exchange resin is stirred and mixed in water in a conventional pre-coating method. FIG. 1 shows a case where the particulate cation exchange resin C is individually stirred and mixed, and the particulate cation exchange resin C is individually dispersed. In addition, the fine particulate cation exchange resin C has cracks B, and the ultrafine particles of the cation exchange resin
Contains C′. Even when the particulate anion exchange resin is stirred and mixed alone, the state of the particles is the same as that shown in FIG. 1. FIG. 2 shows a case where a particulate cation exchange resin and an anion exchange resin are stirred and mixed in water, and the particulate cation exchange resin C and the particulate anion exchange resin A weakly attract each other electrostatically. Each of the fine particulate ion exchange resins has cracks B, and also contains ultrafine particles C' of a cation exchange resin and ultrafine particles A' of an anion exchange resin. Therefore, when such a particulate ion exchange resin is precoated, the membrane layer becomes relatively dense, the membrane characteristics are superficial, and the removal capacity of suspended solids is relatively small. Figure 3A is a partially enlarged view showing the case where linear cation exchange fiber D, particulate cation exchange resin C, and particulate anion exchange resin A used in the present invention are stirred and mixed in water and entangled. It is an explanatory diagram, and FIG.
The cation exchange fiber D, which is an aggregate of branched, crimped, etc., intertwined, the particulate cation exchange resin C, and the particulate anion exchange resin A are stirred and mixed in water to further entangle them. This is a partially enlarged explanatory diagram of the case. In addition, FIG. 4 shows that fine particulate cation and anion exchange resins C and A are mixed and pre-coated on a supersupport 11, and then
This is a partially enlarged sectional view of the double membrane layer of the present invention, which is precoated by mixing cation exchange fiber D and particulate cation/anion exchange resins C and A. are intertwined with each other in a network structure, and incorporate fine particulate cation/anion exchange resins C and A into the network structure.
It is also electrostatically and physically intertwined with the fine particulate cation/anion exchange resins C and A in the lower layer. In addition, the ratio of the particulate ion exchange resin and the cation exchange fiber in the present invention depends on the purpose of the treatment, the ion exchange capacity of the cation exchange fiber and the particulate ion exchange resin, the ions to be removed, the colloidal substances, and the suspended solids. It is determined by considering various points such as the composition and concentration of the substance, and the strength and uniformity of entanglement of cation exchange fibers. The ratio of the amount of pre-coating agent between the cation exchange fiber and the particulate ion exchange resin is such that the former is about 10% or more of the total of the former and the latter on a dry weight basis, and in most cases it is 30 to 80%.
Approximately %. Typical examples of the proportions of these precoating agents are shown in Table 1. Table 1 Precoat agent amount ratios and component ratios are shown in dry weight ratios. Fc: Cation exchange fiber Rc: Particulate cation exchange resin Ra: Particulate anion exchange resin F: Ion exchange fiber R: Total particulate ion exchange resin c: Total cation exchanger a: Total anion exchanger

[Example 1]

The equipment and precoat agent used in the test are shown below. Overtube (transparent acrylic resin cylinder) Dimensions: Inner diameter 150mm, height 2000mm Oversupport type: Stainless steel wire mesh Dimensions: Outer diameter 50.8mm, height 1500mm Opening: 63μm Excess area 0.239m Including ² oversupports The over-element is installed upright in the over-cylinder. Pre-coat agent used (1) Conventional method fine particulate ion exchange resin polystyrene sulfonic acid type (H type) strongly acidic cation exchange resin (Rc) Average particle size: 51 μm Total ion exchange capacity: 4.5 meq/g dry resin polystyrene type Trimethylammonium type (OH type) strongly basic anion exchange resin (Ra) Average particle size: 39 μm Total ion exchange capacity: 4.1 meq/g dry resin (2) Particulate ion exchange resin of the present invention and cation exchange fiber polystyrene Sulfonic acid type (H type) strongly acidic cation exchange resin Use the same thing as Rc in (1) Polystyrene trimethylammonium type (OH type) strong basic anion exchange resin Use the same thing as Ra in (1) Polystyrene sulfonic acid type (H type) strongly acidic cation exchange fiber (Fc) used Average thickness: 20 μm Average length: 250 μm Total ion exchange capacity: 4.6 meq/g Dry fiber pre-coating conditions (water temperature 28°C) Pre-coating agent formulation Ratio (dry weight unit) Conventional method, Rc:Ra=2:1 Method of the present invention, Rc:Ra=2:1 0.4Kg/m ²
Overarea Fc:Rc:Ra=3:2:1 0.6Kg/m ²
Mixing and stirring conditions for over-area precoat agent: While putting the precoat agent into water, use a stirrer with a blade diameter of 70 mm to stir and mix at 300 rpm for 5 minutes. Slurry concentration, 5% by dry weight Precoat amount (dry weight), 1Kg/ ^m2 Over area Precoat flow rate, 5m/h Water flow conditions After precoating, 500ppb as Fe ₃ O ₄
An aqueous solution containing triiron tetroxide (more than 90% Fe ₃ O ₄ particles with a particle size of 3 μ or less) was passed through the water at an overflow rate of 10 m/h, and the pressure loss in the membrane layer was 1.75 Kg/cm. The end point was when it reached ² . Triiron Tetroxide Removal Capacity Figure 8 shows the relationship between the triiron tetroxide removal capacity and the pressure loss of the membrane layer. The vertical axis shows pressure loss (Kg/cm ² ), and the horizontal axis shows triiron tetroxide removal capacity (g (as Fe ₃ O ₄ )/Kg precoat dry weight), where ○ indicates conventional method, ☆ indicates The method of the present invention is illustrated. At a pressure loss of 1.75Kg/ ^cm2 ,
The removal capacity is 213 g (as Fe ₃ O ₄ )/Kg - dry weight in the conventional method, while it is 618 g (as Fe ₃ O ₄ )/Kg - dry weight in the method of the present invention, and The removal capacity is approximately 2.94 times larger. During the test, the concentration of triiron tetroxide in the treated water was 1 ppb or less in both the conventional method and the method of the present invention. In the case of the conventional method, cracks may occur in the membrane layer when the pressure loss in the membrane layer reaches about 0.3 kg/cm ² , and in that case, the concentration of triiron tetroxide in the treated water is 300 kg/cm2.
An increase of ~400ppb was observed. However, in the method of the present invention, no cracks occurred in the membrane layer, and the process could be carried out stably. In this way, compared to the conventional method, the method of the present invention has the following advantages:
The treated water quality is stable and good, and the removal capacity is approximately three times larger. Therefore, when the method of the present invention is used to remove iron-based crud from the primary cooling water of a BWR nuclear power plant, it is estimated that the removal capacity will be 1.5 to 3 times that of the conventional method. An increase in the removal capacity means that the amount of used super-aid that is discharged as secondary radioactive waste is inversely reduced. As mentioned above, in the case of a 1.1 million KW class power plant, the amount of particulate ion exchange resin discharged as radioactive waste annually is estimated to be approximately 38,000 kg in dry weight, but if the removal capacity increases by 1.5 times, the amount of particulate ion exchange resin discharged as radioactive waste per year is estimated to be approximately 38,000 kg. 25,000Kg, and if it triples, it will decrease significantly to about 12,700Kg. Furthermore, since the method of the present invention produces extremely high-quality treated water, it is expected that the amount of crud brought into the reactor will be greatly reduced, and the activation of crud due to neutron irradiation inside the reactor will be kept to an extremely low level. Ru. The above two points will greatly reduce the work in the condensate system and Radwest system, which will in turn be extremely effective in significantly reducing the amount of radiation exposure for nuclear power plant personnel.

[Brief explanation of drawings]

Figures 1 and 2 are partially enlarged explanatory diagrams showing an example of the state of particles when fine particulate ion exchange resin is stirred in water in the conventional precoating method;
Figure A shows the linear cation exchange fiber and particulate ion exchange resin used in the present invention when they are stirred and mixed in water and entwined, and Figure 3 B shows the linear, branched fiber used in the present invention. Partially enlarged explanatory diagram showing an example of the state when cation exchange fibers, which are aggregates of crimped fibers, etc., and particulate ion exchange resin are stirred and mixed in water and further entangled. Figure 4 is a partially enlarged explanatory diagram showing the state of the double membrane layer of the present invention, in which the upper layer is pre-coated with an intertwined body of cation exchange fibers and particulate ion exchange resin, and the lower layer is pre-coated with particulate ion exchange resin. 5 and 6 are flow explanatory diagrams illustrating the aqueous solution processing apparatus used in the present invention and embodiments of the present invention, and FIG. 7 is a longitudinal cross-sectional explanatory diagram illustrating an example of the structure of the over-element used in the present invention. , FIG. 8 is a graph showing the removal capacity of triiron tetroxide in an example of the present invention, where the vertical axis shows pressure loss (Kg/cm ² ),
Triiron tetroxide removal capacity (g (as Fe ₃ O ₄ )/Kg precoat dry weight is plotted on the horizontal axis, ○ indicates the conventional method, ☆ indicates the method of the present invention. Explanation of Figs. 1 to 7) The explanations of the symbols used are as follows: A...fine particulate anion exchange resin, A'...ultrafine particles of anion exchange resin, B...cracks, C
...Fine particulate cation exchange resin, C'...Ultrafine particles of cation exchange resin, D...Cation exchange fiber,
1... Tube sheet, 2... Tube sheet, 3...
Over-element receiver, 4...Over-element, 5...
...Inlet pipe, 6...Outlet pipe, 7...Precoat tank,
8...Pre-coat pump, 9...Batsuful (7th
Figure) Day distributor (Figure 8), 10...
Element core, 11... Oversupport, 12...
Membrane layer, 13...Air vent pipe, 14...Stirrer, _V1 to _V9 ...Valve.

Claims (1)

[Claims] 1 When processing aqueous solutions, particles with a particle size of 2~
The first step is to mix 250μm particulate ion exchange resin in water, and the second step is to pre-coat the supersupport with the particulate ion exchange resin mixed with water obtained in the first step to form a film layer. process, elongated cation exchange fibers with a thickness of 2 to 200 μm and a length of at least twice the thickness, and a particle size of 2 to 200 μm.
A third step in which 250 μm particulate ion exchange resin is mixed and entangled in water, and a second step in which the mixture of ion exchange fibers and particulate ion exchange resin mixed and entangled in water obtained in the third step is mixed. A fourth step of further precoating on the membrane layer of the particulate ion exchange resin pre-coated with to form a double membrane layer in which the particulate ion exchange resin layer and the ion exchange fiber layer are intertwined; A fifth step is to pass the aqueous solution through the membrane layer to remove ions, colloidal substances, and suspended solids to obtain treated water, and the membrane layer is inverted using gas or water or gas and water. A method for preparing an aqueous solution using a double membrane layer using a particulate ion exchange resin and an ion exchange fiber, which is characterized by a combination of six steps, including the sixth step of washing and peeling off the used membrane layer. Processing method.