JPS59136141A - Regenerating method of ion exchange resin for condensate desalting device - Google Patents

Abstract

PURPOSE:To maintain high desalting performance for a long time and to decrease the amt. of the waste liquid of regeneration to be produced from resin regeneration in a titled regenerating method in nuclear power generation by passing chemicals through anion and cation exchange resins respectively in upward current to regenerate said resins. CONSTITUTION:The ion exchange resins having the decreased desalting performance in a desalting column 5 are transferred into an ion exchange resin regenerating column 8, where the resins are separated to anion and cation exchange resins 9, 10 according to a difference in specific gravity by the water 15 and air 16 injected into said column. The resin 9 is transferred into an anion exchange resin regenerating column 11, where the resin is regenerated in upward current by caustic soda 13. The resin 10 is regenerated in upward current by a sulfuric acid 12 in the column 9. The regenerated resins are transferred to a resin mixing column 14 where the resins 9, 10 are mixed and thereafter the resin mixture is again packed in the column 5. Condensate 17 is treated and feed water 18 is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for regenerating an ion exchange resin for a condensate desalination device, and in particular to a method for regenerating an ion exchange resin used in condensate desalination in nuclear power generation. The present invention relates to a method for regenerating an ion exchange resin for a water desalination device.

[Prior art]

In nuclear reactors, especially boiling water reactors, corrosion products are generated due to corrosion of sub-system equipment and piping. The problem is that the fs quantity rate increases. Therefore, it is important to remove as much corrosion products as possible in the condensate purification system and reduce the amount of corrosion products brought into the furnace.

FIG. 1 shows an example of a system outline of a conventional boiling water reactor. Steam discharged from the reactor pressure vessel 1 passes through a high-pressure turbine 2 and a low-pressure turbine 3, and becomes condensed water in a condenser 4. Condenser 4. Corrosion products (ions and oxides of iron, cobalt, etc.) generated in the extraction system 7 that connects the turbine 3 and the feedwater heater 6 and the feedwater heater 6 become impurities in the condensate and are desalinated in the condensate demineralization tower 5. The water is then circulated through the feed water heater 6 and back to the reactor pressure vessel 1. Note that the condenser 4 is normally cooled by seawater or the like.

By the way, impurities that are not removed in the condensate demineralization tower 5 are carried into the nuclear reactor, where they are activated. Recently, it has become clear that the rate of increase in dose in the nuclear couplant can be reduced by reducing iron, which is one of the impurities brought into the reactor from the water supply system, and the target f: 1 ppb for iron brought into the feed water. I'm starting to moan like this. For this reason, there is a demand for higher performance of the condensate demineralization tower 5. On the other hand, the condensate demineralization tower 5 is filled with L (type cation A!, a mixture of Boku resin and OH type anion exchange resin) in case of an emergency such as a leak of cooling seawater in the condenser 4. Several units with a volume of several m3/tower have been installed.

By the way, conventional resin regeneration in a condensate demineralization tower in a boiling water atomic coupler plant involves removing resin from the condensate demineralization tower in order to avoid contamination of condensate and water supply lines (7. Out-of-column regeneration method in which resin is regenerated separately). are common, and an increase in the amount of waste such as recycled waste liquid accompanying the recycling of these resins has become a problem.

FIG. 2 shows the regeneration system of the mixed bed type condensate desalination apparatus using the conventional outside-column regeneration method. The ion exchange resin whose desalination performance has decreased in the desalination tower 5 is transferred to the ion exchange resin regeneration tower 8.
15. The ion exchange resin is separated here by the air 16 into a ion exchange resin 9 and a cation exchange resin 10 according to the difference in specific gravity. The separated anion exchange resin 9 is transferred to an anion exchange resin regeneration tower 11. Cation exchange resin 1 in ion exchange resin regeneration tower 8
0 is regenerated in a downward flow with sulfuric acid 12, and anion exchange resin 9 is regenerated in a downward flow with caustic soda 13 in an anion conversion resin regeneration tower 11. The regenerated resin is transferred to the resin mixing tower 14, where the cation exchange resin and anion exchange resin are mixed, and then packed into the condensate demineralization tower 5 again, where the condensate 17 is treated and feed water 18 is obtained.

In the conventional condensate desalination equipment as described above, resins with reduced desalination performance are separated into anion exchange resin 9 and cation exchange resin 10.
After separation, the cation exchange resin 10 is regenerated with sulfuric acid and the anion exchange resin 9 is regenerated with caustic soda.
It is reused as the opposite ion eOHm. here,
Impurities in condensate 17 include metal ions such as iron, copper, and cobalt and fine particles (crud) caused by corrosion of equipment piping, as well as sodium ions and chloride ions caused by seawater leaks in the condenser. The opposing ions of the resin with low desalting performance are iron, copper, and cobalt for the cation exchange resin 10, and chlorine for the anion exchange resin 9. Among these impurities, radioactive substances, especially heavy metals such as iron, have long half-lives and require high-level removal from condensate. I have to keep it.

For this reason, cationic and anionic exchange resins with reduced desalination performance are regenerated using Nagaya's regenerating agent in the regeneration tower.
There were problems such as insufficient regeneration efficiency and large amount of recycled waste liquid.

[Purpose of the invention]

An object of the present invention is to provide a method for regenerating an ion exchange resin for a condensate desalination apparatus, which maintains high desalination performance for a long period of time and reduces the amount of recycled waste liquid accompanying resin regeneration.

[Summary of the invention]

The present invention provides an effective way to regenerate ion exchange resins whose desalination performance has deteriorated due to condensate treatment, by taking into account the state of capture of impurities in condensate in the ion exchange resin packed bed in the condensate demineralization tower. In order to perform regeneration, the regenerant is passed in an upward flow while the resin layer remains fixed during regeneration by utilizing the difference in resin sedimentation speed in still water caused by the particle size distribution of the ion exchange resin. In particular, the above object is achieved by making it possible to effectively regenerate ion exchange resins whose desalination performance has deteriorated.

[Embodiments of the invention]

The present invention will be explained in detail below.

FIG. 3 shows the state of capture of impurities in the condensate in the ion exchange resin packed bed in the condensate demineralization tower immediately before starting the regeneration operation after the condensate has been treated. Normally, a condensate demineralizer processes a large amount of condensate at high speed, so the water is passed in a downward flow that keeps the resin layer in a stable state.Because the water is so fast as to keep the resin layer stable, ion exchange reactions actually occur within the resin layer. Ion exchange zone 20 where
The width is several tens (7). When trapped impurities leak from the bottom of the ion exchange resin bed (when the tip of the ion exchange zone reaches the bottom of the resin packed bed), regeneration operations are immediately initiated to minimize the amount of impurities carried into the reactor. For this reason, the resin that has entered the regenerated state contains some uncontaminated resin 21 (which has the ability to capture impurities).Ion exchange resin regeneration is carried out by backwashing and positive After separating into anion exchange resin, they are regenerated by passing with acid and alkali, respectively.

Here, too, downward flow regeneration is performed, which usually increases the regeneration speed.

As a result of detailed investigation into the condensate treatment and resin regeneration methods in such conventional condensate demineralizers, the following points were found. In other words, the particle size of the ion exchange resin filled in the condensate demineralizer has a distribution, and is usually about 300 to 1,200 μm, which causes a difference in sedimentation rate in still water, resulting in a difference in condensate demineralization. When packed in a salt chamber, large particle size resin with a fast settling rate is present at the bottom of the packed bed, and small particle size resin with a slow settling rate is present at the top of the packed bed. Therefore, as can be seen from FIG. 3, when the ion exchange resin regeneration operation is started, it is found that the large particle diameter resin at the bottom of the packed bed is not yet contaminated.

After the resin in this state is backwashed and separated into cationic and anionic exchange resins, it is transferred to each regeneration tower and filled, and then the chemical solution is passed through in a downward flow for regeneration. Large particle size resin with a fast settling rate is at the bottom of the resin layer, small particle size resin with a slow settling rate is at the top of the resin layer, highly contaminated resin is at the top layer, and uncontaminated resin is at the bottom. For this reason, when the drug is passed in a downward flow, the highly contaminated resin in the upper layer is sequentially regenerated, and the recycled waste liquid is directed to the bottom and the uncontaminated resin is sequentially contaminated, resulting in poor regeneration efficiency and a large amount of Requires regenerating agent.

FIG. 4 is an explanatory diagram showing an ion exchange resin regeneration system of a mixed bed type condensate desalination apparatus using an external regeneration method to which the method for regenerating a condensate desalination apparatus of the present invention is applied.

The ion exchange resin whose desalination performance has decreased in the desalination tower 5 is transferred to the ion exchange resin regeneration tower 8, where the ion exchange resin is converted into anions according to the difference in specific gravity. It is separated into an exchange resin 9 and a cation exchange resin 10. The separated anion exchange resin 9 is transferred to an anion exchange resin regeneration tower 11. In the ion exchange resin regeneration tower 8, the cation exchange resin 10 is regenerated in an upward flow with sulfuric acid 12,
In the anion exchange resin regeneration tower 11 , the anion exchange resin 9 is regenerated in an upward flow with caustic soda 13 . The regenerated resin is transferred to the resin mixing tower 14, where the cation exchange resin and anion exchange resin are mixed, and then charged into the condensate demineralization tower 5 again, where the condensate 17'f is treated and the feed water 18f is obtained. .

In the regeneration of resins whose desalination performance has deteriorated as described above,
By performing chemical regeneration in an upward flow, countercurrent regeneration can be performed without contaminating uncontaminated resin, making regeneration easier and lower-level regeneration (lower chemical usage) than in countercurrent regeneration. A high regeneration rate can be obtained, and a reduction in the amount of recycled waste liquid and deterioration of desalination performance can be prevented.In J countercurrent regeneration, if the resin layer floats up, effective regeneration cannot be performed. For this reason, the flow velocity of the upward flow must be such that the resin does not float and maintains a fixed bed state.The chemical passing velocity in conventional countercurrent regeneration is 1 m to ensure sufficient ion exchange regeneration reaction. /h, and at this flow rate, the resin will not float even with an upward flow, and the resin can be effectively regenerated in the same regeneration time as conventional methods.

〔Effect of the invention〕

As described above, according to the ion exchange resin regeneration method for a condensate desalination apparatus of the present invention, high salt performance can be maintained for a long time and the amount of regenerated waste liquid accompanying resin regeneration can be reduced.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a conventional boiling water nuclear power plant, Figure 2 is a configuration diagram showing the regeneration system of a mixed bed condensate desalination equipment using the conventional out-of-column regeneration method, and Figure 3 is A diagram showing the capture state of impurity ions in the ion exchange resin layer after condensate treatment,
FIG. 4 is a block diagram showing the method for regenerating the condensate desalination apparatus of the present invention. Death...Demineralization tower, 8...Ion exchange resin regeneration tower, 9...
・Anion exchange resin, 10...Cation exchange resin, 1
2... Sulfuric acid, 13... Caustic soda, 14... Resin mixing tower, 15... Water, 16... Air, 17...
Condensate, 18... Water supply.

Claims (1)

[Claims] ■, In chemical regeneration of ion exchange resins with degraded desalination performance in a mixed bed demineralizer filled with a mixture of cation exchange resins and anion exchange resins, after the mixed state of cation and anion exchange resins are expanded and separated. A method for regenerating an ion exchange resin for a condensate desalination apparatus, characterized in that the cation and anion exchange resins are regenerated in an upward flow under conditions where the resin layer remains in a fixed bed state.