JP3238619B2 - Regeneration method of desalination equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating a condensate desalination apparatus of a condensing system mainly in a nuclear power plant or the like, and more particularly to a method suitable for operation in a boiling water (BWR) type nuclear power plant. The present invention relates to a method for regenerating a water desalination apparatus.

[0002]

2. Description of the Related Art BW known as a direct method for guiding steam, in which cooling water (light water) is boiled in a nuclear reactor, to a turbine for power generation.
As is well known, water to which a corrosion inhibitor or a pH adjuster is added cannot be used as cooling water in an R-type nuclear power plant, and high-purity water (pure water) that is neutral deionized water A small amount of soluble inorganic substances, corrosion products, ions, etc. are extracted from the cooling water in the middle of the circulation path where the steam after driving the turbine is condensed by the condenser, returned to the water, and returned to the reactor. A condensate desalination device and the like for removal are provided.

[0003] The above condensate desalination apparatus comprises a cation exchange resin (usually a strongly acidic cation exchange resin (H type)) and an anion exchange resin (usually a strongly basic anion exchange resin (OH).
)) Is configured as a mixed bed type ion exchange resin tower, and a regenerating facility is attached to the condensate desalination unit in addition to the ion exchange resin tower. In general, this equipment is composed of a two-column system of a cation (cation) exchange resin regeneration column also serving as a separation / mixing column and an anion (anion) exchange resin regeneration column. And a three-tower type with a resin storage tank. Regeneration of ion-exchange resin, both when regenerating both resins and when regenerating only anion-exchange resin,
It is carried out by transferring the ion exchange resin from the desalting tower to the regeneration equipment, separating the anion exchange resin and the cation exchange resin by backwashing and standing, dividing the resin into another regeneration tower, and passing each of the regenerated chemicals. .

[0004] The ion exchange capacity of the cation exchange resin and the anion exchange resin forming the mixed bed ion exchange resin bed of such a condensate desalination apparatus is less than that of the conventional condensate desalination apparatus.
Because the WR type nuclear power plant is a so-called direct method,
It is set by anticipating the load of each ion so that there is no effect on the reactor even if there is a leak to the condensate system of the seawater often used as a cooling medium for the condenser. , 1 to 2 per year in consideration of the reduction of the holding capacity over time
It was premised that about two times of regeneration treatment was performed for both resins. For the cation exchange resin, since the load of metal ions is also taken into account, the ion exchange capacity is usually set to a range that is considerably more than the ion exchange capacity of the anion exchange resin.

The actual load of impurities on the ion-exchange resin is determined by the demand for reducing the volume of radioactive waste, the use of corrosion-resistant materials in turbine systems, and the use of titanium tubes in condenser cooling tubes. The cation exchange resin is regenerated because the cation exchange resin has a large ion exchange capacity to counter seawater leaks as described above, and the amount of heavy metal ions is very small. An operation method of regenerating only an anion exchange resin without performing the method has also been proposed (Japanese Patent Application Laid-Open No. 57-71689). In the regeneration of the ion exchange resin in the condensate desalination apparatus, if the cation exchange resin is mixed in the anion exchange resin, the cation exchange resin becomes R-Na by passing NaOH, which is a regenerating chemical, and this is converted into a desalination tower. It is known that there is a problem of causing a Na leak when returned to. For this reason, in the regeneration equipment, a separation method in which the cation exchange resin is not mixed in the anion exchange resin is required.
It has been conventionally pointed out that the backwash separation method by standing still does not always easily form a clear separation surface.

[0006] As one of the methods of operating the condensate desalination apparatus, as a result of research on the load ion species and load, the main substances removed by the condensate desalination apparatus are metal oxides, Heavy metal ions such as iron ions and copper ions, and anions mainly composed of carbon dioxide gas. Of these, metal oxides are physically filtered instead of ion-exchanged, and other ions are ions set in conventional equipment. Because it is very small compared to the exchange capacity,
In order to reduce the amount of radioactive waste generated at the time of regeneration, there has been proposed an apparatus of a non-regenerative operation type which operates for a long time without chemical regeneration.

[0007]

However, the present inventor has
According to the results of an examination of the factors that lower the ion exchange capacity of the anion exchange resin in the actual facility and a study to further reduce the volume of radioactive waste, compared to the non-regeneration operation method described above, It has been found that if the anion exchange resin can be appropriately regenerated, more desirable operation can often be performed by extending the life of the resin. That is, the anion-exchange resin has a problem that impurities such as a rust inhibitor attached to the construction material are attached to lower the ion-exchange ability, and the CO is released due to the effect that the condenser is opened to the atmosphere at the time of regular inspection. There is a problem of a temporary increase in ion load in which ₂ is loaded on the anion exchange resin and the ion exchange capacity is reduced.Therefore, in such a case, the capacity is reduced rather than simply applying the non-regenerative operation method. It is considered preferable that a method of appropriately regenerating the anion exchange resin, for example, a known operation method of regenerating only the anion exchange resin be performed in a timely manner.

[0008] However, in order to actually carry out the improved ion exchange resin regeneration treatment in consideration of the above various problems, the cation exchange resin is mixed into the anion exchange resin, and consequently the cation exchange resin is used. Unless the above-mentioned problem of returning to the desalination tower as R-Na and causing a sodium leak is not solved, the significance of the operation method is extremely small or almost zero, and it is difficult to adopt the method in industrial practice. There's a problem.

The inventor of the present invention has solved the above problem by regenerating an ion exchange resin in a condensate desalination apparatus while regenerating a larger amount of anion exchange resin in order to extend the resin life. The inventors of the present invention have thought that it is important to establish a technique for minimizing the possibility of the cation exchange resin being mixed into the anion exchange resin as much as possible, and have conducted intensive research to arrive at the present invention.

[0010] In addition, this problem is actually caused by BW
This involves problems specific to the condensate system equipment installed in the R-type nuclear power plant. For example, it is pointed out that a particular problem is that it is extremely difficult to modify existing equipment that is already in operation. In addition, it is pointed out that it is necessary to make the equipment as small as possible for new equipment.

[0011] Furthermore, regardless of the existing or newly installed regeneration equipment, recently, the anion and cation to be filled in the condensate desalination apparatus have been improved with the improvement of the ion exchange resin and the peripheral technology. It is not negligible that the ratio of both ion exchange resins may change, but it has been pointed out that there are no measures proposed to address this problem, and new proposals are needed to address this. .

More specifically, in order to realize the separation of the anion exchange resin while preventing the contamination of the cation exchange resin, theoretically, the separation upper layer side should be located as far as possible from the separation surface of both resins. It is conceivable to connect the resin transfer tube so that only the anion exchange resin side can be transferred.However, in the existing double ion exchange resin regeneration system equipment that often connects the resin transfer tube near the boundary of the separation surface, It is extremely difficult to reduce the degree of mixing of the cation exchange resin. To cope with this problem, the connection position of the resin transfer pipe may be changed, but it is not desirable to change the facilities of the nuclear power plant as described above.

[0013] On the other hand, in the newly installed regeneration equipment, although the connection position of the resin transfer pipe can be set in consideration of the above-mentioned points, the miniaturization of the equipment cannot be realized by this alone.

When the filling ratio of both ion-exchange resins changes, the level (height) of the back-separated and separated upper-layer ion-exchange resin changes. For this reason, it is difficult to reduce the degree of mixing of the cation exchange resin.

SUMMARY OF THE INVENTION The present invention has been made to improve the operation of the above-mentioned conventional condensate and desalination unit in a nuclear power plant, and one object of the present invention is to regenerate an anion exchange resin. In addition to extending the life of the ion exchange resin to reduce the volume of radioactive waste, the contamination of the cation exchange resin into the anion exchange resin during regeneration is made as small as possible to reduce the Na leakage after regeneration. The present invention provides a method for regenerating an ion-exchange resin of a condensate desalination apparatus capable of substantially eliminating the above.

Another object of the present invention is to provide a condensate desalination apparatus provided in an existing condensate system and an anion exchange resin free of Na leak by simply changing the treatment procedure while using the regenerating equipment as it is. The object of the present invention is to provide a reproduction method that enables appropriate reproduction of a video signal. Still another object of the present invention is to provide a method which can be provided in a smaller size than a conventional one when a new regeneration facility is provided.

Another object of the present invention is to provide a method for producing an anion-exchange resin in which the mechanical ratio of an anion exchange resin and a cation exchange resin is changed without changing the mechanical structure of the equipment. It is an object of the present invention to provide a method capable of regenerating an anion exchange resin while preventing a cation exchange resin from being mixed into an exchange resin as much as possible.

[0018]

SUMMARY OF THE INVENTION One of the features of the method for regenerating a condensate desalination apparatus according to the present invention that achieves the above objects is as follows.
A method for transferring both ion exchange resins from a desalting tower of a condensate desalination apparatus having a mixed bed of a cation exchange resin and an anion exchange resin to a regeneration facility for regeneration, wherein the transferred cation exchange resin and anion The exchange resin is backwashed and separated in the first column, and the ion exchange resin separated into the upper layer is transferred to the second column through a resin transfer pipe connected to a predetermined height position of the first column, and the remaining ion exchange resin is removed. After the first separation / transfer operation of transferring the ion-exchange resin to the third column, the ion-exchange resin transferred to the second column is returned to the first column, backwashed again, and separated into an upper layer through the resin transfer tube. The second separation / transfer operation of transferring the ion-exchange resin to the second column and transferring the remaining ion-exchange resin to the third column, if necessary, comprises an anion exchange resin and a cation exchange resin after backwash separation. Of the mixed resin layer The connecting position of the tube until downward,
Usually, it is performed once or a plurality of times, and thereafter, the anion exchange resin in the second column is subjected to a regeneration treatment. In the above, when transferring the resin from the first tower to the third tower, it is normal to transfer the entire amount of the resin,
It is not limited and may be a part.

The above-mentioned regenerating method of the present invention is typically applied to an existing condensate desalination apparatus provided with the above-mentioned two-column type regenerating equipment, that is, a regenerating equipment for regenerating an anionic resin. In a condensate demineralizer equipped with a column and a column for separation and regeneration of a cationic resin, the present invention can be carried out simply by changing the resin transfer procedure.

In the method of the present invention, in the last (in the case of only one time) second separation / transfer operation, that is, in the case of performing this operation a plurality of times, in the last second separation / transfer operation, In many cases, it is preferable to transfer the ion-exchange resin to the second column by expanding the ion-exchange resin by adjusting the ascending flow rate (expansion). This is because anion exchange resin not contained in the mixed resin layer located below the resin transfer pipe connection portion can be transferred to increase the amount of regeneration, and such a second separation / transfer operation and expansion can be performed. By combining the cations, it is possible to appropriately regenerate the anion exchange resin while preventing the cation exchange resin from being mixed, which has been conventionally difficult to solve.

The amount of the anion exchange resin regenerated by the method of the present invention is not limited, but is preferably as large as possible within the range of 25 to 95% of the total amount of the anion exchange resin. From the viewpoint of reducing the volume of radioactive waste as much as possible by extending the resin life by regeneration, it is preferable to increase the amount of regeneration as much as possible. On the other hand, to prevent Na leakage due to the incorporation of cation exchange resin, 95% It is preferred that: 25% regeneration
If less, the effect of extending the resin life by regeneration is small.

The regenerating procedure of the anion exchange resin used in the present invention, such as regenerating chemicals and passing-through washing, can be performed in the same manner as in the prior art, and NaOH is usually used as the regenerating chemical. Further, the present invention proposes a method for regenerating an anion exchange resin, but does not exclude regenerating a cation exchange resin as needed. For example, in an existing condensate desalination apparatus in which a two-column type regenerating facility of an anion resin regeneration tower and a cation resin regeneration tower is attached to the desalination tower of the above-described condensate desalination apparatus, When the ion exchange resin (cation exchange resin) is transferred to the desalting tower, the H ₂ SO ₄
The regenerating process can be performed by passing the liquid.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to the drawings.

FIG. 1 shows a relationship between a condensate desalination apparatus and a regenerating facility in a condensate system of a BWR type nuclear power plant. In this figure, reference numeral 1 denotes a desalination tower (D tower) of the condensate desalination apparatus. )
The condensate returned to the water by a condenser (not shown) is introduced from the condensate inlet at the top of the tower, and passes through the mixed bed 2 where the anion exchange resin and the cation exchange resin are mixed. After removing impurity ions and the like contained in the water by a treatment or the like, it is returned to the reactor side from the condensate outlet.

Reference numeral 3 denotes a cation resin regeneration tower (C tower) which also serves as a separation tower. The cation resin regeneration tower 3 is connected to the desalination tower 1 by a transfer pipe 4 so that the mixed resin is fed from the top of the tower, and from the bottom of the tower. It is connected so that the resin in the column can be returned and transferred to the desalination tower (D tower) 1 by the return transfer pipe 5.
In addition, the upper part of the tower is connected so that the resin in the upper part can be taken out from the middle part in the vertical direction and sent to the anion resin regeneration tower (A tower) 7 via the transfer pipe 6. Reference numeral 8 denotes a return transfer pipe connected so that the resin in the anion resin regeneration tower 7 can be returned from the bottom of the tower to the cation resin regeneration tower (C tower) 3. Reference numeral 301 denotes a regenerant passing means provided in the upper part of the cation resin regeneration tower 3. In addition, the cation resin regeneration tower 3 has a discharge pipe for the passed regenerant and a resin for backwashing and separation of the resin. , A pump for transfer and the like are provided, but are not shown. Similarly, reference numeral 701 denotes a regenerant passage means provided at the upper part of the anion resin regeneration tower 7, and a discharge pipe for the regenerant passed therethrough is not shown.

The regenerating facility having the above-described structure is a conventionally known two-column regenerating facility in which the cation regenerating column also serves as a separation / mixing column. The regenerating facility having such a configuration is operated as described with reference to FIG. In addition, the anion exchange resin can be regenerated with substantially no Na leak.

FIG. 2 is a schematic view of the apparatus of FIG. 1 showing the transfer of the resin and the state in each tower. The operations 1 to 13 shown in the figure are performed sequentially.

The first stage in the figure shows the state before the start of regeneration, and the mixed resin is present in the desalting tower (D). In the second stage, the resin in the resin tower (D) is transferred to the cationic resin regeneration tower (C) which also serves as a separation / mixing tower. In step 3, the resin in the cation resin regeneration tower (C) is backwashed, left standing, and backwashed and separated. The stage of FIG. 3 shows the state after this separation. The upper layer is an anion exchange resin layer having a lower specific gravity, the lower layer is a cation exchange resin layer having a higher specific gravity, and the middle portion is a mixed layer in which these resins are mixed. Has become.

In step 4, the anion exchange resin in the upper layer is transferred to the anion resin regeneration tower (A), and in step 5, the resin and cation exchange resin in the mixed layer are transferred to the desalination tower (D). When regenerating the cation exchange resin, this 4
The regeneration can be carried out by passing a cationic resin regenerant (sulfuric acid) in the cationic resin regenerating tower (C) between the steps (a) and (b).

Next, the anion exchange resin is returned from the anion resin regeneration tower to the cation resin regeneration tower (C) which has been emptied in the step 6, and is again subjected to backwashing and standing. As a result, the cation exchange resin slightly mixed in the anion exchange resin collects on the bottom side in the column due to the specific gravity.

Next, in step 7, a predetermined amount of the anion exchange resin on the upper side is transferred to the anion resin regenerating tower (A), and in step 8, an anion regenerating agent (NaOH) is passed through the anion resin regenerating tower (A). The regenerating process is performed by passing the solution. Steps 9 to 12 return the regenerated anion exchange resin and the cation exchange resin (including the mixed anion exchange resin) in the desalination tower (D) to the cation resin regeneration tower (C),
After mixing, it is a step of transferring to the desalting tower (D), and the regeneration treatment of the ion exchange resin according to the method of the present invention is completed by performing the above treatment (Step 13).

[0032]

【Example】

Example 1 Using the apparatus shown in FIG. 1 above, only the following anion resin was used according to the processing procedure shown in FIG.
The operation in the case where the reproduction processing is performed so as to be set to% or 53% will be described with reference to FIG.

That is, the volume ratio of both ion exchange resins is (cation exchange resin) / (anion exchange resin) = 1 /
The ion-exchange resin transferred from the desalination tower packed in the ratio of 2 to the C tower (cation regeneration tower) 3, which is the first tower of the regeneration equipment, is subjected to backwashing and standing, and the upper anion exchange resin layer,
It is backwashed and separated into a lower cation exchange resin layer A and an intermediate mixed resin M layer (see). In this example, the separation surface was formed at the position of about 33 vol% of the resin amount from the bottom, and the mixed layer was usually formed at about 5 to 20%.

Next, from the lower part of the first tower, LV1 (m /
In step h), water is supplied to fluidize the resin by the upward flow, and the resin is transferred by the resin transfer pipe 6 connected to the position of the mixed resin layer.
The upper ion-exchange resin A was mainly transferred to the second tower A (anion regeneration tower) 7 (the amount of transferred resin was about 67%), and the remaining resin was transferred to the desalting tower (see). Thus, the first separation / transfer operation has been completed.

Next, the resin transferred to the second tower (resin amount of about 6
7%) was returned to the empty first tower (see), and backwashing-standstill backwashing separation was performed again. Then, only the ion exchange resin A in the upper layer side was transferred to the resin transfer tube 6 in LV1 in the same manner as described above. Through to the second tower. As a result, about 33% of the resin was transferred to the second column (the transfer amount relative to the total amount of the anion exchange resin was about 50%) (see).

In this state, the second separation / transfer operation is completed, and the anion exchange resin can be regenerated in the second column. In this example, the anion exchange resin is further expanded from the above state by expansion. The amount of exchange resin A transferred to the second column was increased. That is, the anion exchange resin A was transported to the second column while developing the fluid from the above state with the ascending flow supplied from the lower portion of the first column being set to LV5 (m / h) while fluidizing the resin. ). As a result, the amount of the resin transferred to the second column was 53% (the transfer amount based on the total amount of the anion exchange resin was about 80%) (see).

As described above, in the regeneration equipment of the existing condensate desalination apparatus, it has become possible to appropriately regenerate the anion exchange resin while preventing the cation exchange resin from being mixed.

Example 2 In this example, the regeneration operation of the anion exchange resin in the case where the ratio of both ion exchange resins in Example 1 was changed to (cation exchange resin) / (anion exchange resin) = 1/1 was shown in FIG. The ion exchange resin transferred from the desalting tower to the first tower (C tower) 3 is subjected to backwashing and standing, and the upper anion exchange resin A layer and the lower cation exchange resin C layer In the present example, a separation surface is formed in the vicinity of a position where the resin amount is about 50 vol% from the bottom, while being separated by backwashing into an intermediate mixed resin M layer (see reference). Therefore, the connection position of the resin transfer pipe 4 is in the middle of the layer of the cation exchange resin C.

In this state, LV1 (m / m
In step h), water is supplied to fluidize the resin by the upward flow, and the anion exchange resin A containing the mixed resin M on the upper layer side is transferred to the second tower (A tower) 7 through the resin transfer pipe 6 (the amount of transferred resin). About 67%), the remaining resin was transferred to a desalination tower (see),
The first separation / transfer operation has been completed. Thus, about 17% of the cation exchange resin is contained in the resin transferred to the second column.

Next, the resin transferred to the second tower (resin amount of about 6
7%) was returned to the empty first tower (see), and backwashing-standstill backwashing separation was performed again. Then, only the ion exchange resin A in the upper layer side was transferred to the resin transfer tube 6 in LV1 in the same manner as described above. Through to the second tower. As a result, about 33% of the anion exchange resin (the transfer amount relative to the total amount of the anion exchange resin was about 66%) was transferred to the second column (see).

In this state, the second separation / transfer operation was completed and the anion exchange resin was regenerated in the second column, whereby about 66% of the anion exchange resin could be regenerated.

According to this example, even if the resin ratio is changed from the state shown in FIG. 3, it can be seen that the anion exchange resin can be properly regenerated while preventing the cation exchange resin from being mixed.

[0043]

According to the present invention, the contamination of the cation exchange resin into the anion exchange resin at the time of regeneration, which has been a problem in the regeneration treatment of a condensate desalination unit in a conventional nuclear power plant, can be minimized. An effect of realizing the regeneration of the anion exchange resin substantially eliminating the Na leak after the treatment and an effect of being effective in reducing the volume of radioactive waste by extending the life of the resin are also obtained.

Further, according to the method of the present invention, the condensate demineralizer installed in the existing condensate system and its regenerating equipment can be used without modification, and the Na leak can be reduced only by changing the treatment procedure. This has the effect of enabling regeneration of the anion exchange resin.

Further, according to the method of the present invention, when a new regenerating facility is provided, the facility can be downsized as compared with the conventional one.
Also, even if the filling ratio of the anion exchange resin and the cation exchange resin is changed, it is possible to mix the cation exchange resin into the anion exchange resin without changing the mechanical structure of the equipment. The effect is that the anion exchange resin can be regenerated while preventing the anion exchange resin.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the outline of the configuration of a two-tower type regenerating facility implemented by applying the method of the present invention.

FIG. 2 is a view for explaining an example of an operation in the case of a reproducing method in which the method of the present invention is applied to the apparatus of FIG. 1;

FIG. 3 is a view for explaining the relationship between the regeneration operation and the amount of anion exchange resin to be regenerated when the resin ratio of both ion exchange resins is (cation exchange resin) / (anion exchange resin) = 1/2.

FIG. 4 is a view for explaining the relationship between the regeneration operation and the amount of anion exchange resin to be regenerated when the resin ratio of both ion exchange resins is changed to (cation exchange resin) / (anion exchange resin) = 1/1.

[Explanation of symbols]

1 ... desalination tower (D tower), 2 ... mixed bed, 3 ...
・ Cation resin regeneration tower (C tower) (also used as separation / mixing tower),
4 ... transfer pipe, 5 ... return transfer pipe, 6 ... transfer pipe, 7 ... anion resin regeneration tower, 8 ... return transfer pipe.

Claims (3)

(57) [Claims] 1. A method for transferring both ion exchange resins from a desalting tower of a desalination apparatus having a mixed bed of a cation exchange resin and an anion exchange resin to a regenerating facility, wherein the transferred cation exchange resin is regenerated. First resin and anion exchange resin
The ion-exchange resin separated into an upper layer is transferred to the second column through a resin transfer pipe connected to a predetermined height position of the first column, and the remaining ion-exchange resin is transferred to the third column. After performing the first separation / transfer operation for transferring, the ion exchange resin transferred to the second column is returned to the first column, backwashed and separated again, and the ion exchange resin separated to the upper layer through the resin transfer tube is separated. The second separation / transfer operation for transferring to the second column and, if necessary, transferring the remaining ion exchange resin to the third column is performed by a mixed resin layer of the anion exchange resin and the cation exchange resin after the backwash separation. A method for regenerating a desalination apparatus, wherein the method is performed at least once until the position is below the connection position of the resin transfer pipe, and thereafter, the anion exchange resin in the second column is regenerated. 2. The method according to claim 1, wherein the transfer of the ion-exchange resin to the second column in the final second separation / transfer operation is performed by controlling the amount of resin transferred by adjusting the ascending flow rate in the first column. A method for regenerating a desalination apparatus, comprising adjusting. 3. The first column according to claim 1, wherein the first column has a function of backwashing and separating the cation exchange resin and the anion exchange resin, and a function of regenerating the cation resin. A method for regenerating a desalination apparatus, comprising using the above desalination tower.