JPH0212635B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an over-desalination device that pre-coats a super-aid agent, and in particular, a multi-tube over-desalination device used for purifying condensate, etc. in a nuclear power plant. Regarding.

[Prior art]

Figure 1 shows the water treatment systems of a nuclear power plant (BWR) condensate purification system and reactor water purification system. In the figure, steam (286°C, 70 kg/cm ² ) generated in reactor 1 passes through steam pipe 2 to rotate turbine 3 to generate electricity, and then flows into condenser 4 where it condenses into water. do. Water from the condenser 4 is transferred to the condensate purification system piping 15
and is sent to a super-demineralizer 6 by a pump 5. The super desalination device 6 removes crud generated in the condensate purification system (crud is a general term for fine suspended particles that are mainly corrosion products in the condensate purification system and do not normally pass through a 0.45 μm Silibor filter). The main component is
These include Fe ₂ O ₃ and Fe ₃ O ₄ . ) and nuclide ions are removed by excessive desalination using a resin layer pre-coated on the outer diameter surface to a thickness of several mm evenly with a resin mixture of powdered ion exchange resin of cations and anions in a specific ratio in a cylindrical filter element. Perform purification. The water purified by the super-demineralizer 6 is then sent to the demineralizer 7, where the water is purified in the super-demineralizer 6 by stacking anion and cation granular ion exchange resins inside the demineralizer. Residual cladding and nuclide ions that have not been removed are trapped and desalted.
The purified water that has passed through the demineralizer 7 is heated by a low-pressure feedwater heater 8, sent to a high-pressure feedwater heater 10 by a pump 9, heated again at high pressure, and returned to the reactor 1. In this way, the steam generated in the nuclear reactor drives the turbine and then is purified by condensation.
Since it is returned to the reactor, it is constantly circulated through the condensate purification system.

On the other hand, some of the reactor water is returned to the reactor by the pump 11 through the reactor water purification system piping 16, and the rest is sent to the cooler 12. The reactor water cooled by the cooler 12 is sent to a reactor water purifier 14 by a pump 13, and after being purified, is returned to the reactor. The structure of the reactor water purifier 14 is the same as that of the condensate demineralizer, and the reactor water is circulated to be demineralized and purified.

FIG. 2 is a vertical cross-sectional view showing an outline of the internal structure of a conventional over-desalination device. Inside the over demineralizer, the outer diameter
It is a multi-tube type filter in which over 200 cylindrical filtration elements 30 with a diameter of 50 mm and a total length of about 1.5 m are installed at intervals of about 80 mm. The upper end of the overflow element is attached to the ceiling plate 22 by a hanging fitting, and the lower end is installed with an overwater extraction pipe passing through the bottom plate 21.
Super-demineralized water 18 from each filter element enters chamber 25.
Gather at. Umbrella-shaped guide plates 23 and 24 are provided at the discharge part of the water supply pipe 15 into the super-demineralizer.
The introduced water is made to flow in an average amount between the element groups.

FIG. 3 shows an outline of the over-element structure and the state during over-desalination. The over-element is made by bundling and twisting ultra-fine fiber threads and wrapping it around a cylindrical support material 32 with holes to form an over-supporting layer 31 with a thickness of about 10 mm.
By itself, it is possible to remove excess particles with a particle size on the micron order. On the surface, the average particle size is several tens of μm.
An auxiliary agent overlayer 33 is formed by precoating powdered ion exchange resin. Introduced water 17 rises along the element, passes through the overlayer, is over-desalinated, and over-desalinated water 18 is extracted from the inside.

Pre-coating of the super-assistant onto the element is carried out by introducing it from the same water supply pipe as that used for water. Slurry (resin concentration 0.5 to 1 wt% in resin mixed water) is applied at linear velocity (L, V) relative to element surface area, usually 3 to
A method is used in which the auxiliary agent is introduced at a speed of 4 m/h and precoated, but the precoat forming layer of the auxiliary agent is not evenly distributed over the entire element, as shown in Figure 4.
At LV4m/h, it becomes extremely thin at positions 1000 and above. In addition, in the case of LV, 6.5, and 10 m/h, the precoat formation at the upper position is improved, but because the flow velocity near the 0 position is high, the formation of super-aid agent at the lower position is poor, and it is easy to peel off. . If over-desalination treatment is carried out when the thickness of the layer formed by the auxiliary agent is uneven, the over-desalination rate of the treated water will be low in areas where the layer thickness is thin, and the excessive volume of the over-water mechanism will increase. Because of this, when the precoat layer is uniformly formed, the differential pressure rises rapidly rather than gradually, which shortens the overlife. When the differential pressure reaches the set pressure or higher, the pre-coated auxiliary agent is peeled off and replaced with a new auxiliary agent. As a result, the number of replacements increases, and the amount of used waste resin, that is, the amount of radioactive waste increases.

[Summary of the invention]

The purpose of the present invention is to make the thickness of the auxiliary pre-coat layer formed on the over-element uniform throughout. FIG. 5 shows the results of precoating the auxiliary agent onto the element at LV4 m/h, collecting the precoating auxiliary agent from each position of the element, and measuring the sedimentation rate of the auxiliary agent in still water. Depending on the element position, the sedimentation rate of the adhesion aid decreases sharply from position 1000 and above. This means that a material with a light specific gravity is thinly pre-coated at the upper position, and it is thought that this is caused by the fact that a heavy material cannot reach the upper position. Therefore, FIG. 6 shows the rising speed of water flow between element groups for each LV. At LV4m/h, when the position exceeds 1000, the rising speed between the element groups becomes the resin settling speed of 36m/h.
Since the slurry water reaches the position below h, the slurry water reaches the position more slowly, and the amount of the resin reaching the position is small, so that the thickness of the precoat forming layer becomes thinner. It was also found that when the LV was increased to 6 or 10 m/h, the position of the element whose velocity was above the sedimentation velocity line also moved upward, but not completely. Therefore, in order to make the thickness of the precoat forming layer uniform throughout, it is necessary that the rising speed be higher than the resin settling speed over the entire element.
The present invention has been made in consideration of the above matters.

[Embodiments of the invention]

FIG. 7 is an elevational sectional view showing the internal structure of the over-desalination device of the present invention. The upper end of the over-element is attached to the ceiling plate 22 forming the over-demineralization chamber, and the lower end is provided with a filtered demineralized water outlet pipe passing through the bottom plate 21 to seal introduced water and over-demineralized water.
The water supply pipe 15 is provided with guide plates 23 and 24 corresponding to the elements to guide the water flow from the lower part of the element to between the element groups. 24 is provided for the nearby area. A pipe 26 reaching the upper part is provided on the guide plate 24 so that a part of the introduced water rises and flows out from the upper end.
7 and 28 are provided. The guide 27 is provided for a group of elements in a nearby area, and the guide plate 28 is provided for a group of elements in a far area. The structure is such that filtered demineralized water is extracted from the bottom end. Next, when precoating the element with a super-aid agent, a slurry of a predetermined concentration is introduced from the pipe 15 at a predetermined flow rate. A part of the introduced slurry is spread horizontally by the guide plates 23 and 24, the slurry from the guide plate 23 is spread far away, the slurry from the guide plate 24 is spread nearby,
Ascend between groups of elements.

On the other hand, a part of the slurry rises up the pipe 26, and at the upper part, it is spread horizontally by the guides 27 and 28, and is spread far from the guide plate 28 and near the guide plate 27. While the slurry is flowing between the element groups, by continuously drawing out superhydrant from inside the superelement, the surface of the superelement 30 is precoated with the auxiliary agent 29 to form a superaid agent layer. The thickness of the super-aid layer varies depending on the flow rate between the elements shown in FIG. 8, forming the super-aid layer shown in FIG. 9. The flow velocity from the bottom upward is v _b , and the flow velocity from the top downward is
If v _a , the figure shows LV4m/h for the element.
In the case of , is the value obtained by dividing the flow rate by the spatial area between elements, and the linear velocity per unit area LV
is at position a, v _a = 105.5 m/h, v _b = 12 m/h,
is the result of precoating the auxiliary agent under the conditions of v _a =9.5 m/h and v _b =108.5 m/h. Because the amount of auxiliary agent reaching the upper position is small, the precoat forming layer in that area is thin. In this case, the precoat layer is formed relatively uniformly, but the sedimentation speed of the resin is accelerated by the downward flow from the top, so when the upper LV is large, the precoat layer in the lower part becomes thicker. Also, there is a large amount of resin that settles out without being precoated on the element. is the result of precoating the auxiliary agent under the conditions of V _a =5.0 m/h and V _b =113 m/h. Although water flowing from the top and bottom directions accumulates at the center of the element, the precoat forming layer is formed uniformly over the entire element.

As described above, when precoating an auxiliary agent onto an element by introducing water to the outer periphery of the element from above and below, a uniform precoat layer can be formed if the sedimentation rate of the auxiliary agent used is taken into account. After completion of the auxiliary pre-coating, over-desalination treatment begins, but the LV for the element gradually increases, usually reaching 8.
It runs at ~10m/h.

〔Effect of the invention〕

In this method, water is introduced into the element from two directions, which prevents the element precoat layer near the inlet port from peeling off due to increased flow velocity, which would occur due to an increase in LV compared to the conventional method of introducing water from one direction. Since a uniform precoat layer is formed, the present invention is highly effective in improving over-desalination performance and over-life.

[Brief explanation of drawings]

Figure 1 is a water purification system diagram at a nuclear power plant (BWR), Figure 2 is a cross-sectional structural diagram of a conventional demineralizer, Figure 3 is an over-element model diagram, and Figure 4 is a pre-coat layer. Fig. 5 is a sedimentation velocity diagram of the resin, Fig. 6 is a flow velocity diagram, Fig. 7 is an elevation cross-sectional structural diagram of the super-demineralizer of the present invention, and Fig. 8 is a flow model outside the super-element. FIG. 9 is a state diagram of a precoat forming layer according to the present invention. 6... Super demineralizer, 21... Bottom plate, 22...
Ceiling board, 23, 24, 27, 28...information board, 2
6... Pipe, 29... Resin (auxiliary agent), 30... Perelement, 31... Perelement fiber layer, 3
2...Fiber layer support cylinder, 33...Superior agent precoat forming layer.

Claims (1)

[Claims] 1 The surface is pre-coated with a super-assistant, water is allowed to permeate through the super-aid layer and super-support layer, and super-water is removed from the inside of the super-element for super-desalination. There,
A water supply pipe is located approximately in the center of the vertically arranged group of superelements, and water flow guides are provided in the water supply pipes at positions corresponding to the lower and upper end positions of the superelements. Device.