JPS6132054B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ion exchange resin cleaning method, and more particularly to an ion exchange resin cleaning method that can effectively remove crud from an ion exchange resin contaminated by desalination of condensate and reduce the amount of waste liquid. In order to operate a nuclear power plant smoothly,
There are issues such as (1) reducing the amount of radiation exposure for drivers, (2) improving maintainability and reducing the amount of waste liquid, and in particular, developing effective means to reduce the radioactivity level in the primary system. This has become an urgent matter. Currently, (1) condensate desalination equipment and (2) reactor cleanup equipment are used to purify water in the primary system, but from the viewpoint of the amount of water to be treated, (1) condensate desalination equipment is currently used. The main method is using equipment. The main part of the condensate desalination equipment is a mixed bed desalination tower made of anion and cation exchange resins. ) is ion-exchanged and filtered through an ion-exchange resin layer to purify the condensate. The ionic components and cladding components trapped in the ion exchange resin layer are converted into ions by chemical regeneration of the ion exchange resin with acid and alkali and physical regeneration of the ion exchange resin through backwashing in the regeneration tower of the condensate desalination equipment. It separates from the exchange resin and is discharged outside the system. Therefore, if the regeneration operation, especially the backwashing operation, is incomplete, the crud content will accumulate in the system, increasing the radioactivity level and causing a major operational problem. In the conventional backwashing method for regeneration towers, contaminated ion exchange resin (hereinafter simply referred to as resin) suspended in water from multiple desalination units is transferred to the lower part of the regeneration tower, and the water level inside the regeneration tower is lowered to a freeboard drain pipe. After the crud content is removed from the resin by blowing air from the bottom and scrubbing, backwash water is supplied from the bottom of the regeneration tower, and backwash water is supplied from the overflow pipe at the top of the regeneration tower. The operations of backwashing and freeboard drain pipe extraction, which consist of discharging the crud content together with the washing water, and then discharging the upper water still containing the crud content from the freeboard drain pipe in the middle of the regeneration tower, are carried out in steps 2 to 2.
This was repeated three times, and then the ion exchange resin was separated and backwashed. However, in this method, backwash water containing crud content is discharged from the overflow pipe, so most of the crud content does not reach the overflow pipe and stagnates above the resin layer, resulting in poor backwashing efficiency. The drawback was that the amount of water increased and the amount of waste liquid increased. The present invention was made in view of the current situation, and its purpose is to effectively remove the crud content from ion exchange resins contaminated by desalination treatment of condensate, and to reduce the amount of waste liquid after treatment. An object of the present invention is to provide a method for cleaning an ion exchange resin that can be used. To summarize the present invention, the ion exchange resin cleaning method of the present invention involves (a) removing the contaminated ion exchange resin from a free board in the regeneration tower when regenerating the ion exchange resin contaminated by the desalination treatment of condensate; The first step is to open the vent valve of the regeneration tower and inject water and scrubbing air until the water level in the regeneration tower reaches the top of the freeboard drain pipe; (b) vent valve; The second step is to close the drain valve to stop the water supply, open the freeboard drain valve, continue to supply scrubbing air, and drain the water until the water level in the waste water regeneration tower containing crud reaches the level of the freeboard drain pipe. and (c) Close the freeboard drain valve to stop the supply of scrubbing air, open the vent valve, open the freeboard drain pipe backwash valve, and inject water or air into the freeboard drain pipe to clean the freeboard drain pipe. This method is characterized by including a plurality of washing steps combined with a third step. In the present invention, in the first step of the scrubbing operation, water is injected together with air, and the amount of water at the top of the freeboard drain pipe in the regeneration tower is approximately equal to the amount of water at the bottom of the freeboard drain pipe. It is injected so that Through this step, the cladding adhering to the resin surface is effectively separated into the water, and is pushed up into the water above the resin layer and above the freeboard drain pipe, accompanied by the introduced water and air. In the second process of scrubbing and freeboard draining, the freeboard drain valve is opened while the scrubbing air is being introduced, and the pressurized air valve is opened to introduce air from the top of the regeneration tower. The waste liquid containing most of the crud in the upper part of the drain pipe can be effectively discharged from the freeboard drain pipe.
Next, in the third step of backwashing of the freeboard drain pipe, the freeboard drain valve and vent valve are opened, and water or air is injected into the regeneration tower from the outside through the freeboard drain valve, thereby flushing the freeboard drain pipe. The ion exchange resin attached to the tank is removed by backwashing. This operation can be easily completed in a short time of about 10 to 30 seconds, thereby greatly improving the original cleaning efficiency. According to the present invention, the above three steps can be carried out multiple times (3 to 4 times).
By repeating the procedure (about 30 times) and then performing the normal backwashing (overflow) and settling operations, it is possible to remove the crud content more effectively in a shorter time than with conventional methods, and also to reduce the amount of waste liquid. Note that the amount of water injected in the first step can be determined as follows. The resin slurry suspended in water contains approximately 50% water by volume, and the resin flows through the bottom of the freeboard drain pipe of the regeneration tower.
If the height of the resin layer when injected to about 300 to 500 mm is a, the actual height of the amount of water in it is about a/2. Also, if the distance between the upper surface of the resin layer and the level of the freeboard drain pipe is b, then (a/
2+b)×(cross-sectional area of the regeneration tower) is calculated as the volume of water to be injected. This water capacity is not necessarily limited; the amount of water in the resin slurry,
It can be adjusted as appropriate depending on the type of resin slurry. Next, the present invention will be explained in order of each step with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the apparatus according to the present invention, in which 1 is a vent valve of the regeneration tower (hereinafter simply referred to as a vent valve), 2 is a pressurized air valve (not used in the present invention), and 3 is a water valve. , 4 is a scrubbing air valve, 5 is an overflow valve, 6 is a freeboard drain pipe backwash valve, 7 is a freeboard drain valve,
8 is a backwash water valve, 9 is a regeneration tower, 10 is an air and water supply pipe, 11 is a freeboard drain pipe, and 12 is an overflow pipe. First step (scrubbing) The resin slurry suspended in water is introduced into the regeneration tower 9, and about 300 to 500 m
Accommodates resin to a level of about mm. The water level at the time of accommodation is the level of the freeboard drain pipe 11.
Next, a vent valve 1 and a scrubbing air valve 4
Open the resin layer, inject air and water from the bottom of the resin layer, mix vigorously, and remove the crud adhering to the resin surface into the water. If this operation is continued, the water level will rise because the vent valve 1 is open. The amount of water to be injected is such that the amount of water in the upper part of the freeboard drain pipe 11 is equal to the amount of water in the lower part of the freeboard drain pipe 11. (Approximately 50% by volume of the resin amount) Second step (scrubbing and freeboard draining) Close the water valve 3, leave the vent valve 1 and the scrubbing air valve 4 open, and leave the freeboard drain valve 7 open.
The water containing the crud separated in the first step, i.e., the portion piled up on the freeboard drain pipe 11, is mixed vigorously with air and transferred to the freeboard drain pipe 1 by the air pressure inside the regeneration tower 9.
Discharge from 1. When the water level in the regeneration tower 9 reaches the position of the freeboard drain pipe, the process moves to the next step. Third step (backwashing of freeboard drain pipe) Vent valve 1 and freeboard drain pipe backwashing valve 6
is opened, all other valves are closed, and water or air is injected from the backwash valve 6 to backwash and remove the resin adhering to the freeboard drain pipe 11 to prevent its clogging. Continue this operation for 10-30 seconds. The above three steps are repeated multiple times (about 3 to 4 times), and the number of times can be increased or decreased as appropriate depending on the degree of contamination to perform optimal cleaning and reduce the amount of waste liquid. Next, only the overflow valve 5 and the backwash water valve 8 are opened to perform normal backwashing, and then the system is allowed to settle and the anion exchange resin and cation exchange resin in the regeneration tower 9 are separated based on the difference in specific gravity. . After separation, each resin is sent to an anion exchange resin tower and a cation exchange resin tower (not shown), and the resins are washed by repeating the first to third steps about three times in each tower. It can be done perfectly. In addition, if the freeboard drain pipe 11 in the regeneration tower 9 is completely buried under the surface of the resin layer due to the equipment, a normal backwash separation operation is performed and each resin is transferred to each regeneration tower. After sending, the operations of the first to third steps can be performed. A series of operations including three steps in the present invention are as follows:
Although manual operation is possible, complete automatic operation can be achieved by using a program timer, microcomputer, etc. Next, the present invention will be explained with reference to Examples, but the present invention is not limited thereto in any way. Example: The contaminated resin suspended in the water transferred from the demineralization tower was introduced into the regeneration tower, and after repeating the first to third steps of the present invention four times, a normal backwash separation operation was carried out. I did it. Table 1 shows the flow rate and amount of water and air used in each step, as well as the time required for each operation and the amount of waste liquid. The graph in FIG. 2 shows the change in the total iron concentration in the waste liquid with respect to the amount of waste liquid in each process. A, B, C and D in the figure are respectively the 1st to 4th
The second washing operation stage is shown, E is a backwashing stage, and F is a settling stage. Note that the amount of resin was 6.1 m ³ .

[Table] In addition, as a comparison, the three steps of scrubbing, backwashing, and freeboard drain removal using the conventional method were performed twice.
After circulating and further scrubbing, a normal backwash separation operation was performed. Table 2 shows the flow rate and amount of water and air used, their required time, and amount of waste liquid in each process. Further, the graph in FIG. 3 shows the change in the total iron concentration in the waste liquid with respect to the amount of waste liquid in each process. In addition, A ₁ and A ₂ in the figure indicate the first backwashing and freeboard draining stages, respectively, B ₁ and B ₂ indicate the second backwashing and freeboard draining stage, respectively, and C indicates the backwashing stage and D indicates the settling stage.

【table】

[Table] As is clear from Tables 1 and 2 and Figures 2 and 3, cleaning of the resin according to the present invention can be carried out in a relatively short time compared to cleaning using the conventional method, and the amount of cladding, which is a contaminant, can be removed. (mainly iron compounds) can be removed efficiently, and the amount of waste liquid is also small. The graph in Figure 4 shows the change in the cumulative iron concentration in the waste liquid with respect to the amount of waste liquid in this example and the comparative control (conventional method).
This supports the above evaluation. As described above, according to the present invention, it is possible to effectively remove the crud content from an ion exchange resin contaminated by desalination treatment and to reduce the amount of waste liquid after treatment.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of the apparatus according to the present invention, and FIGS. 2 and 3 are graphs showing changes in the amount of waste liquid and the total iron concentration in the waste liquid for each process in the present invention and the conventional method. FIG. 4 is a graph showing the change in cumulative iron concentration with respect to the amount of waste liquid in the present invention and the conventional method. 1... Regeneration tower vent valve, 2... Pressurized air valve,
3...Water valve, 4...Air valve for scrubbing, 5...
...Overflow valve, 6...Freeboard drain pipe backwash valve, 7...Freeboard drain valve, 8...
Backwash water valve, 9... Regeneration tower, 10... Air and water supply pipe, 11... Freeboard drain pipe, 12...
overflow tube.

Claims (1)

[Scope of Claims] 1. In regenerating ion exchange resin contaminated by desalination of condensate, (a) accommodating the contaminated ion exchange resin to a level below the freeboard drain pipe in the regeneration tower; The first step is to open the vent valve of the regeneration tower and inject water and scrubbing air until the water level in the regeneration tower reaches the top of the freeboard drain pipe; (b) close the vent valve to stop the water supply and remove the freeboard The second step is to open the drain valve and continue supplying scrubbing air until the water level in the contaminated water regeneration tower containing crud reaches the level of the freeboard drain pipe; and (c) close the freeboard drain valve and scrub. A multiple cleaning process that combines the third process of stopping the supply of air, opening the vent valve, opening the freeboard drain pipe backwash valve, and injecting water or air into the freeboard drain pipe to clean the freeboard drain pipe. An ion exchange resin cleaning method characterized by comprising: 2. The ion exchange resin cleaning method according to claim 1, wherein in the first step, water is injected so that the amount of water in the upper part of the freeboard drain pipe is equal to the amount of water in the lower part of the freeboard drain pipe.