JPH058058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for regenerating a mixed ion exchange resin in an out-of-column regeneration type mixed bed ion exchange desalination apparatus, particularly in a condensate desalination apparatus.

[Prior art]

In thermal power plants or nuclear power plants, large amounts of highly purified water are recycled and reused. The steam that has passed through the turbine is returned to water (hereinafter referred to as condensate) in a cooler called a condenser. Since this condensate contains impurities within the system, it is necessary to remove the impurities with a condensate desalination device in order to recycle and reuse the condensate. As a condensate desalination device, a so-called mixed bed ion exchange desalination device in which a cation exchange resin and an anion exchange resin are mixed is used. By passing condensate through this mixed ion exchange resin layer, sodium ions ( Na ⁺ ) can remove ions such as chlorine ions (Cl ^- ) as well as suspended solids (usually referred to as cladding) mainly composed of metal oxides such as iron oxide.

Although mixed-bed ion exchange desalination equipment has excellent performance as described above, since the water to be treated is treated by mixing cation exchange resin and anion exchange resin, both ion and ion exchangers have lost their desalination ability. In order to regenerate the exchange resin, the mixed ion exchange resin must be separated into a cation exchange resin and an anion exchange resin. This separation method is usually carried out by backwashing from the bottom of the mixed ion exchange resin and forming two layers of both ion exchange resins due to the difference in specific gravity.

A conventional mixed-bed ion exchange desalination apparatus of the external regeneration type basically consists of the following steps.

Transfer step The mixed ion exchange resin in the demineralization tower that has completed the desalination step is transferred to a cation exchange resin regeneration tower (hereinafter referred to as cation regeneration tower).

Backwash separation process The mixed ion exchange resin is backwashed in the cation regeneration tower, and separated into an upper layer of anion exchange resin and a lower layer of cation exchange resin due to the difference in specific gravity, and stratified the resin.

Transfer step: The anion exchange resin is transferred from the cation regeneration tower to the anion exchange resin regeneration tower (hereinafter referred to as an anion regeneration tower).

Regeneration process Mineral acid is passed through the cation regeneration tower, and alkali is passed through the anion regeneration tower to regenerate both ion exchange resins, followed by water washing.

Transfer process Both regenerated ion exchange resins are transferred from both regeneration towers to a resin mixing tower.

Mixing process Both ion exchange resins are usually mixed by introducing air from the bottom of the resin mixing column.

Transfer process If necessary, the resin is transferred from the resin mixing tower to the demineralization tower and filled.

Desalination and regeneration are repeated through the above series of steps.

By the way, taking the example of condensate water quality, in recent years there has been an increasingly strict requirement to improve water quality, especially in pressurized water reactors (PWRs) of nuclear power plants.
In the secondary system of a boiling water reactor (BWR) or the reactor water system of a boiling water reactor (BWR), the impurity ion concentration is 0.1μg/
(ppb) and below, it has become a major problem.
For this reason, a problem arises in that the quality of the water treated by the condensate desalination apparatus often becomes poor in purity, and it has been difficult to stably control the impurity ion concentration to 0.1 μg/or less.

[Problem that the invention seeks to solve]

The main reason for the poor purity is that the anion exchange resin and cation exchange resin cannot be sufficiently separated. In other words, the factors governing the water quality of the water at the outlet of the desalination tower are the resins that were not regenerated in the regeneration process, or more precisely, the salt-form ion exchange resins generated during the regeneration process, such as the sodium ion form (hereinafter referred to as Na ⁺ form). ) cation exchange resin and chloride ion form (hereinafter referred to as Cl ^- form) anion exchange resin.

The main reason why these Na ⁺ type cation exchange resins and Cl ^- type anion exchange resins are generated in the regeneration process is that the separation of both resins is insufficient during the backwash separation process and the transfer process, so the anion exchange resin is not present in the cation regeneration tower. The problem is that the exchange resin remains and the cation exchange resin is carried into the anion regeneration tower. Therefore, if hydrochloric acid is used as a regenerating agent in the cation regeneration tower, all of the remaining anion exchange resin will be in the Cl ^- form, and all the cation exchange resin brought into the anion regeneration tower will be in the Na ⁺ form by passing caustic soda. I end up. If the mixing rate of these salt-type ion exchange resins increases, the amount of impurity leakage into the treated water also increases proportionally. For example, 0.02 μ of Na ⁺ ions in condensate
g/(as Na), Cl ^- ion 0.05μg/
(as Cl) To do the following, see Figures 2 and 3.
The relationship between the mixing rate of Na ⁺ type cation exchange resin and the Na ion concentration in the demineralization tower outlet water, and the relationship between the mixing rate of Cl ^- type anion exchange resin and the Cl ion concentration in the demineralization tower outlet water shown in the figure. Therefore, it is necessary to keep the mixing rate of the Na ⁺ type cation exchange resin at about 0.65% or less and the mixing rate of the Cl ^- type anion exchange resin at about 9% or less.

However, in conventional methods, the cation regeneration tower also serves as a resin separation tower, so in order to maintain high purity water quality at the outlet of the demineralization tower, it is necessary to keep the amount of anion exchange resin remaining in the cation regeneration tower as small as possible. It is essential.

However, in order to almost completely separate the anion exchange resin and cation exchange resin, the following conditions are essential.

1. The separation interface between the anion exchange resin and the cation exchange resin in the cation regeneration tower is always constant.

2. The above separation interface is clear and kept horizontal.

3. The separation interface is always kept uniform and horizontal when the anion exchange resin is transferred from the cation regeneration tower to the anion regeneration tower.

However, in reality, as shown below, it is almost impossible to satisfy all of these conditions. That is, first, the number of demineralization towers is usually not one, but three to four, and it is not always possible to completely transfer the mixed ion exchange resin in the demineralization tower to the cation regeneration tower. Therefore, there is no guarantee that the amount of mixed ion exchange resin in each demineralization tower is the same. In fact, it has become clear from the results of many studies that when desalination and regeneration are repeated over a long period of time, the amount of resin in each desalination tower is different. Therefore, it is natural to think that the separation interface in a cation regeneration tower is not always at a constant height.

Next, FIGS. 8 and 9 show the fractional states of both resins when the mixed resin is backwashed in a conventional cation regeneration tower. In FIG. 8, reference numeral 3 indicates a conventional cation regeneration tower, and 3' indicates a separation interface between a cation exchange resin and an anion exchange resin. When a mixed resin is separated by backwashing, theoretically the two resins can be clearly separated as shown in Figure 8 based on the difference in their specific gravity, but in reality, the anion exchange shown in Figure 9. As can be seen from the diagram showing the abundance rate of resin and the abundance rate of cation exchange resin, looking at the resin composition near the separation interface, the anion exchange resin and cation exchange resin form a mixed layer where they are mixed with each other.
It is a well-known fact that there cannot be a clear separation interface. Furthermore, when transferring from the cation regeneration tower to the anion regeneration tower, the resin near the interface is in a fluid state, and even if a separation interface clearly exists, it is quite difficult to maintain the separation interface uniformly and horizontally.

As is clear from the above description, when an anion exchange resin and a cation exchange resin are separated using a conventional cation regeneration tower, it is not possible to almost completely separate both ion exchange resins. For this reason, the
It is difficult to reduce the contamination rate of Na ⁺ type cation exchange resin and Cl ^- type anion exchange resin, and the problem is that the water quality of the demineralization tower outlet water cannot always be maintained at a stable high purity. It was hot.

[Means for solving problems]

In order to solve the above problems, the present inventor investigated a method for regenerating a mixed ion exchange resin that is easy to manage and can stably supply high-purity treated water. It has been found that the objective can be easily achieved by eliminating as much as possible of the mutually mixed resin layers, rather than separating them into two. That is, the technical limitations of the conventional method are fundamentally due to problems with the column configuration in the regeneration system.

In the present invention, the cation regeneration tower does not also serve as a resin separation tower, but the cation regeneration tower and the resin separation tower are separate towers, and the resin separation tower is used solely for the purpose of separating mixed ion exchange resins, while the cation regeneration tower is used for cation exchange. By adding a new function of measuring the cation exchange resin in addition to the function of regenerating the resin, we have solved the above problems all at once, creating a mixed ion system with extremely low impurity ion leakage and very easy operation management. The purpose of this invention is to provide a method for recycling exchange resin.

The feature of the present invention is that, as described above, by making the resin separation tower independent, (a) the mixed ion exchange resin of the desalting tower that has completed the desalting process can be replaced with a mixed ion exchange resin prepared separately in advance; Step (b) Transferring the mixed ion exchange resin to the resin separation tower containing the mixed ion exchange resin is backwashed in the resin separation tower to separate and stratify the mixed ion exchange resin into upper and lower layers such that the lower layer is a cation exchange resin layer and the upper layer is an anion exchange resin layer. (c) Step (d) of extracting the anion exchange resin in the upper layer from the anion exchange resin extraction port located in the anion exchange resin layer in the resin separation tower and transferring it to the anion regeneration tower. ) Next, the cation exchange resin in the layer above the cation exchange resin extraction port is extracted from the cation exchange resin extraction port located in the cation exchange resin layer in the resin separation tower, and is transferred to the cation regeneration tower. Step (e) of stopping the transfer of the cation exchange resin before the cation exchange resin near the separation interface between the resin layer and the anion exchange resin layer starts to be drawn out; (e) After backwashing in the cation regeneration tower, the cation exchange resin Step (f) of transferring the cation exchange resin in the layer above the surface cation exchange resin extraction port to the resin separation tower from the surface cation exchange resin extraction port located at the top of the layer; (g) The cation exchange resin in the cation regeneration tower and the anion exchange resin in the anion regeneration tower are Step (h) of transferring the resin mixed in the resin mixing column to the mixing column and subsequently mixing the resin in the resin mixing column; Subsequently transferring the resin mixed in the resin mixing column to the desalting column. Through the above series of steps It is composed of

Further, in the step (c), after the anion exchange resin is transferred to the anion regeneration tower, backwashing is performed in the anion regeneration tower, and in the step (g),
When the anion exchange resin is transferred to the resin mixing tower, the anion exchange resin in the layer above the anion exchange resin drawing port is extracted from the anion exchange resin drawing port located in the anion exchange resin layer and is transferred to the resin mixing tower. By causing a predetermined amount of anion exchange resin to remain at the bottom of the anion regeneration tower without being transferred to the resin mixing tower, and after the transfer step is completed, by transferring the residual resin to the resin separation tower,
By further separating a small amount of cation exchange resin brought into the anion regeneration tower, it is possible to prevent the Na ⁺ type cation exchange resin from entering the demineralization tower as much as possible.

Furthermore, in step (f), before or after washing the anion regeneration tower with alkali, the surface anion exchange resin is pulled out from the surface anion exchange resin extraction port located above the anion exchange resin layer in the anion regeneration tower. By transferring the resin to the resin separation tower, the amount of anion exchange resin required in the demineralization tower can be measured, and the fine cation exchange resin that is slightly mixed in the surface layer of the anion exchange resin can be separated from the fine cation exchange resin in the demineralization tower. By transferring most of the fine anion exchange resin that causes pressure loss to the resin separation tower, the water quality of the demineralization tower outlet water can be controlled more strictly.

Here, to explain in more detail the control method when transferring the cation exchange resin from the resin separation tower to the cation regeneration tower, in step (d), the cation exchange resin is transferred by setting the transfer time of the cation exchange resin in advance. The amount of resin withdrawn can be easily controlled.

Further, in the step (d), there is provided a means for detecting the position of the separation interface, and the transfer is performed when the position of the separation interface, which descends as the cation exchange resin transfer process progresses, reaches a predetermined position. By ending the process, it is possible to more strictly prevent the anion exchange resin from being carried into the cation regeneration tower by controlling the amount of the cation exchange resin withdrawn.

[Effect]

FIGS. 1 and 4 show one embodiment of the present invention.
This will be explained based on the drawings and FIG.

In FIG. 1, reference numeral 1 is a resin separation tower, 2 is an anion regeneration tower, 3 is a cation regeneration tower, 4 is a mixed resin transfer pipe, 5 is an anion exchange resin extraction port, and 6
is an anion exchange resin transfer pipe, 7 is a cation exchange resin extraction port, 8 is a cation exchange resin transfer pipe, 9
1 is a surface cation exchange resin extraction port, 10 is a surface cation exchange resin transfer pipe, 11 is a resin mixing column, 1
2 indicates an anion exchange resin transfer tube, and 13 indicates a cation exchange resin transfer tube. In FIGS. 4 and 5, the same symbols as in FIG. 1 have the same meanings as explained in FIG. 14 indicates a detector.

In the figure, 〓 indicates a mixed ion exchange resin, 〓 indicates an anion exchange resin, and 〓 indicates a cation exchange resin.

Note that in each drawing, backwash water supply pipes, etc. are not shown.

As shown in FIG. 1a, a mixed ion exchange resin prepared separately in advance is charged to the bottom of the resin separation column 1 (FIG. 1a). Then, the mixed ion exchange resin is transferred from the desalting tower that has completed the desalting process to the resin separation tower 1 through the mixed resin transfer pipe 4 (FIG. 1b). Next, as shown in FIG. 1c, backwashing is performed in the resin separation column 1 to separate and stratify the resin into two layers: an upper layer is a cation exchange resin layer and a lower layer is a cation exchange resin layer. The resin composition near the separation interface between the anion exchange resin and the cation exchange resin is a mixed layer in which both ion exchange resins are mixed together, as shown in Figure 9, so the resin composition is located as high as possible above the mixed layer. Anion exchange resin extraction port 5 installed to
The anion exchange resin in the upper layer is extracted from the anion exchange resin and transferred to the anion regeneration tower 2 via the anion exchange resin transfer pipe 6 (FIG. 1d). Since the anion exchange resin is forced to remain in the resin separation column 1 in this way, it is not necessary to separate the anion exchange resin and cation exchange resin more strictly than before.

Next, the cation exchange resin is transferred from the resin separation tower 1 to the cation regeneration tower 3, and as shown in FIG. The extracted cations are transferred to the cation regeneration tower 3 via the resin transfer pipe 8. At this time, the transfer of the cation exchange resin is stopped before the cation exchange resin near the separation interface between the cation exchange resin layer and the anion exchange resin layer begins to be extracted. This reason is number 9
This is because, as shown in the figure, the resin layer near the separation interface is a mixed layer in which both ion exchange resins are mixed together. The amount of cation exchange resin withdrawn can be easily controlled by setting the transfer time of the cation exchange resin in advance using a timer or the like. If it is necessary to more precisely control the amount of cation exchange resin withdrawn, as shown in FIGS. 4 and 5, a detector 14 is used to detect the position of the separation interface, such as a conductivity detector, or an optical device that detects color tone or brightness. It is sufficient to use a target detector or the like and stop drawing out the cation exchange resin when the interface reaches the position of the detector (FIG. 5). These means are already known, and the purpose can be easily achieved by installing the detector above the cation exchange resin extraction port 7.

Furthermore, the reason why the cation exchange resin outlet port 7 is located in the cation exchange resin above the bottom of the resin separation column 1 is that even if the lower part of the cation exchange resin layer is backwashed, as shown in FIG. In the part where the anion exchange resin is not converted, that is, the peripheral part of the wall at the bottom of the tower, the contamination rate of anion exchange resin may reach 0.5 to 5%, so cation exchange resin with a high contamination rate of anion exchange resin should be avoided as much as possible to be brought into the cation regeneration tower 3. It's for a reason.

Next, after backwashing the cation exchange resin again in the cation regeneration tower 3, the cation exchange resin in the surface layer is pulled out from the surface cation exchange resin extraction port 9 located at the upper part of the cation exchange resin layer, and the cation exchange resin in the surface layer is extracted from the surface layer cation exchange resin transfer pipe 10. (FIG. 1f). As a result, even if a small amount of anion exchange resin is brought into the cation regeneration tower 3, the resin will be separated into the surface layer of the cation exchange resin by backwashing, so the resin in the surface layer will be separated. Cation regeneration tower 3 of anion exchange resin by transferring to tower 1
This has the advantage that the contamination rate can be further reduced. The second advantage is that when the cation exchange resin is transferred from the resin separation tower 1 to the cation regeneration tower 3, there is no need to strictly control the amount of the cation exchange resin to be transferred. During this transfer, care must be taken to transfer the cation exchange resin in the resin separation tower 1 to the cation regeneration tower 3 in a slightly excess amount than the amount of cation exchange resin required for regeneration, that is, from the surface cation exchange resin extraction port 9. The only thing to do is to ensure that the surface of the cation exchange resin layer is on the upper side, and to prevent the resin near the separation interface in the resin separation tower 1 from being carried into the cation regeneration tower 3. These precautions can be easily solved if there is enough cation exchange resin. Furthermore, the third advantage is that the amount of cation exchange resin required for regeneration can be made constant, and regeneration conditions can be uniformly controlled. More specifically, even if the balance of resin amounts in each demineralization tower collapses, by making resin separation tower 1 independent and adding a function to measure the resin amount to both regeneration towers, the amount of resin can be adjusted in the regeneration process. The balance can be redressed.

Next, both ion exchange resins regenerated in both regeneration towers are transferred to the resin mixing tower 11 via the anion resin transfer pipe 12 and the cation resin transfer pipe 13, respectively (FIG. 1f). Next, the resin in the resin mixing tower 11 can be uniformly mixed by generally introducing air. This mixed resin is transferred to a demineralization tower or stored in the resin mixing tower 11 as required.

By configuring the mixed ion exchange resin regeneration process through the series of steps described above, highly purified water can be easily obtained without using any special equipment or more advanced technology.

A method for further suppressing the Na ⁺ type cation exchange resin from being carried into the demineralization tower will be explained based on FIGS. 6 and 7.

In FIGS. 6 and 7, the same symbols as those shown in FIG. 1 have the same meanings as explained in connection with FIG. The tube, reference numeral 17 (see FIG. 7), indicates a port for drawing out the surface anion exchange resin.

To explain based on FIG. 6, anion regeneration tower 2
An anion exchange resin extraction port 15 is provided at the lower part of the anion exchange resin (Fig. 6a), and the anion exchange resin is transferred from the resin separation tower 1 to the anion regeneration tower 2 for regeneration and backwashing. A small amount of cation exchange resin brought into the regeneration tower 2 is separated. That is, after the backwash separation, the cation exchange resin naturally collects at the bottom of the anion regeneration tower 2, so when the anion exchange resin is transferred from the anion regeneration tower 2 to the resin mixing tower 11, the anion exchange resin located in the anion exchange resin layer is Only the upper layer anion exchange resin is extracted from the resin extraction port 15 and transferred to the resin mixing column 11 via the anion resin transfer pipe 12 (FIG. 6b). Therefore, a trace amount of Na ⁺ type cation exchange resin generated by regenerating the anion exchange resin is not carried into the resin mixing tower 11 together with the anion exchange resin remaining in a predetermined amount at the bottom of the anion regeneration tower 2. After the transfer step is completed, the residual resin is transferred from the anion regeneration tower 2 to the resin separation tower 1 via the mixed resin transfer pipe 16, thereby completing preparations in the resin separation tower 1 for the next regeneration step (Fig. 6c). .

Furthermore, as shown in FIG. 7a, the anion regeneration tower 2 is further provided with a surface anion exchange resin withdrawal port 17 to remove the fine anion exchange resin that causes pressure loss in the demineralization tower and the fine cation exchange resin that is slightly mixed in. The resin is also drawn out from the surface anion exchange resin drawing port 17 before or after being washed with alkali and transferred to the resin separation tower via the mixed resin transfer pipe 16 (FIG. 7b). Through this process, the resin mixing tower 1
The amount of the anion exchange resin transferred to the resin mixing column 1 can be kept constant, and the fine resin and the Na ⁺ type cation exchange resin can be sufficiently prevented from being brought into the resin mixing column 11. The regenerated anion exchange resin is then transferred from the anion regeneration tower 2 to the resin mixing tower 11 (FIG. 7c), as previously described.

As described above, the present invention enables separation of anion exchange resin and cation exchange resin, which was conventionally performed in a cation regeneration tower, by providing a separate resin separation tower.
carrying out the mixed ion exchange resin in the resin separation tower,
By leaving the mixed resin layer in which both ion exchange resins near the separation interface of both ion exchange resins are mixed together in the resin separation tower, the anion exchange resin brought into the cation regeneration tower and the cation exchange resin brought into the anion regeneration tower are removed. The amount of impurity ions can be controlled to an extremely small amount, and leakage of impurity ions from the demineralization tower can be almost completely suppressed.

Furthermore, the present invention provides the cation regeneration tower and the anion regeneration tower with a function of metering each ion exchange resin in the regeneration process even if an imbalance occurs in the resin amount of the mixed ion exchange resin in each demineralization tower. Therefore, the amount of ion exchange resin always remains constant at the end of regeneration, and the entire desalination and regeneration system is highly stabilized.

〔Effect of the invention〕

As is clear from the above, the present invention is more efficient than conventional methods by simply repeating the operation of transferring anion exchange resin and cation exchange resin between the resin separation tower and each regeneration tower. It enables sufficient separation of the ion exchange resin and dramatically improves the quality of water treated by the desalting tower.

[Brief explanation of drawings]

Figure 1 is a process diagram for explaining one embodiment of the method of the present invention, and Figure 2 is the relationship between the mixing rate of Na ⁺ type cation exchange resin in the demineralization tower and the Na ⁺ ion concentration of the water at the outlet of the demineralization tower. Figure 3 is a diagram showing the demineralization tower.
Cl ^- type anion exchange resin contamination rate and demineralization tower outlet water
Figures 4 and 5 are diagrams showing the relationship with Cl ^- ion concentration, Figures 4 and 5 are diagrams showing the state in which the detector is attached to the resin separation tower and the state in which the interface of the cationic resin is detected, and Figures 6 and 7 are , a process diagram for explaining an example different from the example shown in FIG. 1, FIG. 8 is a diagram showing a state in which an anion exchange resin and a cation exchange resin are separated in a conventional cation regeneration tower, and FIG.
The figure shows a state in which another resin is mixed into the separated resin, particularly a state in which both resins are mixed at the separation interface. 1...Resin separation tower, 2...Anion regeneration tower, 3
...Cation regeneration tower, 4...Mixed resin transfer pipe, 5
...Anion exchange resin extraction port, 6...Anion exchange resin transfer pipe, 7...Cation exchange resin extraction port, 8...Cation exchange resin transfer pipe, 9...
Surface layer cation exchange resin extraction port, 10... Surface layer cation exchange resin transfer pipe, 11... Resin mixing tower,
12... Anion exchange resin transfer tube, 13... Cation exchange resin transfer tube, 14... Detector, 15...
Anion exchange resin extraction port, 16... Mixed resin transfer pipe, 17... Surface anion exchange resin extraction port.

Claims (1)

[Scope of Claims] 1. In a method for regenerating a mixed ion exchange resin in an external regeneration type mixed bed ion exchange desalination apparatus, (a) the mixed ion exchange resin of a desalination tower that has completed a desalination process is A process in which a separately prepared mixed ion exchange resin is transferred to a resin separation column charged at the bottom. (b) A step of backwashing in the resin separation tower to separate and stratify the mixed ion exchange resin into two layers, an upper layer and an upper layer, such that the lower layer is a cation exchange resin layer and the upper layer is an anion exchange resin layer. (c) A step of extracting the anion exchange resin in the layer above the anion exchange resin extraction port from the anion exchange resin extraction port located in the anion exchange resin layer in the resin separation tower and transferring it to the anion exchange resin regeneration tower. (d) From the cation exchange resin extraction port located in the cation exchange resin layer in the resin separation tower, the cation exchange resin in the layer above the cation exchange resin extraction port is extracted and transferred to the cation exchange resin regeneration tower. A step of stopping the transfer of the cation exchange resin before the cation exchange resin near the separation interface between the cation exchange resin layer and the anion exchange resin layer begins to be extracted. (e) After backwashing in the cation exchange resin regeneration tower, the cation exchange resin in the layer above the surface cation exchange resin extraction port is removed from the surface cation exchange resin extraction port located above the cation exchange resin layer. Process of transferring to resin separation tower. (f) A step in which a mineral acid such as hydrochloric acid or sulfuric acid is passed through the cation exchange resin regeneration tower, and an alkaline solution such as sodium hydroxide is passed through the anion exchange resin regeneration tower, followed by washing. (g) A step of transferring the cation exchange resin in the cation exchange resin regeneration tower and the anion exchange resin in the anion exchange resin regeneration tower to a resin mixing tower, and then mixing the resins in the resin mixing tower. (h) A step of subsequently transferring the resin mixed in the resin mixing tower to the demineralization tower. A method for regenerating a mixed ion exchange resin, characterized by comprising the above series of steps. 2 In the step (c), after the anion exchange resin is transferred to the anion exchange resin regeneration tower, backwashing is performed in the anion exchange resin regeneration tower, and the step
In (g), when the anion exchange resin is transferred to the resin mixing tower, the anion exchange resin in the layer above the anion exchange resin extraction port is pulled out from the anion exchange resin extraction port located in the anion exchange resin layer, and the resin is mixed. A patent claim in which a predetermined amount of anion exchange resin is left at the bottom of the anion exchange resin regeneration tower without being transferred to the resin mixing tower, and the residual resin is transferred to the resin separation tower after the transfer step is completed. A method for regenerating a mixed ion exchange resin according to item 1. 3 In step (f), before or after washing the anion exchange resin regeneration tower with alkali, remove the surface anion exchange resin from the surface anion exchange resin extraction port located above the anion exchange resin layer in the anion exchange resin regeneration tower. The method for regenerating a mixed ion exchange resin according to claim 1 or 2, wherein the mixed ion exchange resin is extracted and transferred to the resin separation column. 4. According to any one of claims 1 to 3, in the step (d), the amount of cation exchange resin withdrawn is controlled by setting the transfer time of the cation exchange resin in advance. A method for regenerating mixed ion exchange resins. 5. In step (d), the means for detecting the position of the separation interface terminates the transfer when the position of the separation interface, which descends as the cation exchange resin transfer process progresses, reaches a predetermined position. Any one of claims 1 to 3, which controls the amount of cation exchange resin withdrawn by
A method for regenerating a mixed ion exchange resin as described in .