JPS5827982B2 - How to clean ion exchange resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the regeneration of a mixed bed demineralization tower, and more particularly to cleaning after chemical passage in the regeneration of an ion exchange resin.

The regeneration treatment in the mixed-bed intracolumn regeneration type demineralization tower is carried out by mixing the ion exchange resin that has been passed through the reactor and washed with water.

Generally, the resin mixed bed is stratified into an anion exchange resin and a cation exchange resin, and before mixing the resin layers that have been passed through the resin and washed with water, the water held in the tower is drained to near the resin surface, and the resin is mixed when the resin is mixed. Prevent spills from vents.

For this reason, the water held in the tower is discharged to that level through a strainer installed slightly above the surface of the settled resin.

The waste liquid from the regeneration of the desalting tower before the resin is mixed contains a large amount of residual chemicals, ion-exchanged ions, etc., and therefore it is necessary to appropriately treat these waste liquids.

For example, desalination tower wastewater at a nuclear power plant contains radionuclides, and such wastewater is stored by evaporation and concentration, so treatment equipment and working environments must be designed to reduce the amount of wastewater in order to reduce radiation exposure, operating costs, etc. is a particularly important issue.

The present invention aims to reduce desalination tower wastewater in order to meet these demands.

According to the present invention, the amount of waste water accompanying these processes is reduced by combining water washing after chemical passage in the desalination tower regeneration and draining of water retained in the tower.

Regeneration of ion exchange resin in a mixed bed in-column regeneration type demineralization tower in which the treated fluid is desalted using a mixed bed of anion exchange resin and cation exchange resin, and then the resin is regenerated in the tower. Generally, resin separation, chemical passage, water washing, and mixing operations are performed.

FIG. 1 is a schematic diagram of a hot bed type intracolumn regeneration type demineralization tower.

Strainers 1 to 5 are installed in the tower.

The resin regeneration process is implied in FIGS. 2 to 12.

To explain the conventional regeneration process with reference to Figs. 2 to 12, air is first introduced from the top of the column, and the liquid retained in the column is discharged from the strainer 3 above the resin bed (Fig. 2, free Board drain-1).

Next, water and air are introduced from the bottom of the tower to separate the stuck solids from the resin (Fig. 3, scrubbing), and water is introduced from the bottom of the tower to flow out from the strainer 1 to wash the resin. Separate the negative and positive ion exchange resins (Figure 4, backwash separation).

Next, after the separated resin is allowed to settle down (Fig. 5), an alkaline chemical solution is introduced from the strainer 2, an acid is introduced from the bottom of the column, and the resin is flowed out from the strainer 4 in the direction of the resin layer separation (Fig. 6,
medicine).

Next, water is introduced into the strainer 2 and the bottom of the column to cause the chemical solution to flow out from the strainer 4 (Fig. 7, extrusion), and then the flow rate of the washing water is increased to perform washing (Fig. 8, rapid washing). Air is introduced from the upper part of the rear column and the water held in the column is strained.
3 (Figure 9, freeboard drain-2)
.

Next, air and water are introduced from the bottom of the tower to mix the resin layer to form a mixed bed (Fig. 10, mixing), and water is introduced from strainer 1 to fill the tower with water, as shown in Fig. 11. , filling with water) and further (FIG. 12, final washing) to complete the regeneration process.

Note that the strainer 5 is used for draining the liquid after the desalination treatment.

According to the present invention, in the regeneration step, the operation of draining water after rapid cleaning (freeboard train-2) is incorporated into the rapid cleaning operation, and the retained water to be drained is used for cleaning the upper anion exchange resin layer. Therefore, the amount of waste liquid is reduced (first
Figure 3, Figure 14).

The operation was carried out by appropriately shortening the normal rapid cleaning process (
After the first rapid cleaning step (Fig. 13), the supply of new cleaning water from the strainer 1 is stopped, and while air is introduced from the upper part of the tower, the retained water is not allowed to flow out from the strainer 3, and the upper resin layer is On the other hand, the washing water that has passed through the lower resin layer (cation exchange resin) from the bottom of the column is discharged from the strainer 4 located at the separation surface of both the horizontal fat layers (Fig. 14, second rapid washing step).

The retained water is therefore washed through the resin layer, unlike the conventional outflow path, so that the water required for a corresponding rapid washing is saved and the total amount of waste water is therefore reduced.

In this case, strainer 3 is used to prevent the level of retained water from falling below the resin layer and the resin from being exposed to the air.
The water level after cleaning is controlled to a desired level after the freeboard drain 2 by a level switch 6 (FIG. 1) provided at the level of the drain.

Thereafter, the resin is formed into a mixed bed by a conventional method, and the regeneration process is completed through water filling and final washing.

Since a separate freeboard drain-2 is incorporated into the cleaning process, regeneration time is reduced.

According to the present invention, the water retained in the tower that is discharged after washing is effectively used for washing the resin, so that the amount of 5-hour waste liquid associated with resin regeneration can be reduced, and the regeneration time can also be shortened.

Therefore, it is also effective in downsizing the processing equipment for recycled waste liquid, thereby reducing operating costs, and reducing radiation exposure measures.

Example 1 Cation exchange resin 7001 (bed height of about 6207
fi7M) Anion exchange resin 14001 (layer height approx. 124
0771 door) and desalination was performed.

The cation exchange resin is DIAION 5KIB, and the anion exchange resin is DIAION 5AIOB.
was used.

A comparison of the amount of waste liquid generated during regeneration between the conventional method and the method of the present invention in the above example is as shown in the table below.

From the above, it is clear that by implementing the regeneration method of the present invention, a reduction effect of 6.2% in the total amount of waste liquid can be obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a mixed-bed internal regeneration type demineralization tower equipped with a level switch according to the present invention, Figures 2 to 12 are explanatory diagrams of the conventional resin regeneration process, and Figures 13 and 14 are FIG. 3 is an explanatory diagram of a water washing process according to the present invention. 1 to 5...Strainer-6...Level switch.

Claims (1)

[Claims] 1. During the internal regeneration of a mixed-bed desalination tower, after the ion exchange resin is passed through the ion exchange resin and water washing is appropriately shortened, air is supplied to the upper space of the tower to remove the water held in the tower above the resin surface. Washing water is supplied from the bottom of the column through the upper anion exchange resin layer and passed through the lower cation exchange resin layer, and the water retained in the column and the washing water are passed through a strainer installed on the separation surface of the upper and lower resin layers. A method for cleaning after applying an ion exchange resin, which is characterized by simultaneously performing cleaning and draining water by discharging it.