JPS6014942A - Regeneration method of ion exchange resin - Google Patents

Abstract

PURPOSE:To perform regeneration with high effeciency by extracting anion exchange resin from boundary layer where anion and cation exchange resins are mixed, replacing the anion exchange resin with SO4 ion type resin and treating it with alkali. CONSTITUTION:Ion exchange resin which has reached percolation point is extracted from a condensate desalting tower 1 and is charged to a separation and regeneration tower 2, where H2SO4 is injected to regenerate cation exchange resin. Then, washing water is fed from the bottom of the separation and regeneration tower 2 to separate cation exchange resin from anion exchange resin by the difference of specific gravity. The anion exchange resin alone is extracted from the boundary layer and is charged to a regenerating tower for anion exchange resin 3, and the anion exchange resin is regenerated by injecting NaOH from the top of the regenerating tower 3. Finally, the resin is washed sufficiently with water.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating an ion exchange resin used in a hot bed type ion exchange device (hereinafter referred to as a condensate desalination device) that desalinates condensate, and particularly In addition to making the regeneration efficiency of the resin extremely high, Na ions and C1,
The present invention relates to a method for regenerating ion exchange resins that does not cause ion leaks such as ions.

As one of the desalination treatments for condensate, condensate is passed through a condensate desalination device that contains a mixture of cation exchange resin and anion exchange resin, and the cations and anions in the condensate are converted to both of the above ions. There is a method of removing it by adsorbing it to exchange resin. For such condensate desalination, there are H-011 type operation and NH3-OH type operation that only passes ammonia in the condensate.The latter is economical because it requires fewer regenerations, and is suitable for power plants, etc. It is commonly used in By the way, even in the above-mentioned NH, -0f (type condensate desalination equipment), when the ion exchange capacity of the ion exchange resin decreases (reaches the flow-through point), the ion exchange resin must be regenerated. A similar method was adopted.

Figure 1 is a flow diagram explaining an example of a regeneration method (external regeneration method), and 1 is a condensate desalination device (hereinafter referred to as a condensate desalination tower).
, 2 is a separation and regeneration tower, 3 is an anion exchange resin regeneration tower, and 4 is a mixing storage tank. For regeneration, first, the ion exchange resin that has reached the flow-through point is transferred from the condensate demineralization tower 1 to the separation and regeneration tower 2, and then washing water is introduced from the lower part of the separation and regeneration tower 2 to remove cations. Exchange resin (specific gravity 1.2-1.3)
and anion exchange resin (specific gravity 1.05 to 1.1) are separated by specific gravity. Next, the upper layer of anion exchange resin is separated and regenerated tower 2
The resin is taken out and transferred to the anion exchange resin regeneration tower 3.

Then, in the separation and regeneration tower 2 where the cation exchange resin remains, H
2SO4, and Na1 in the anion exchange resin regeneration tower 3.
After introducing and regenerating each resin, the regenerated ion exchange resins are thoroughly washed with water, and then the regenerated ion exchange resins are transferred to the mixing storage tank 4, and after mixing both resins, the resins are returned to the condensate demineralization tower 1.

However, in the above separation and regeneration method, although efforts are made to achieve as complete a specific gravity separation of the cation exchange resin and the ion exchange resin in the separation and regeneration tower 2 as possible, there is a limit to the degree of separation. Under the present circumstances, it is unavoidable that ion exchange resins of different types are mixed together by about 1 to 8. As a result, the anion exchange resin remaining in the separation and regeneration tower 2 is H2
S.O.

At the same time, the anion exchange resin regeneration tower 3
The cation exchange resin mixed in is treated with Na OH to produce an S04 type anion exchange resin and an Na type cation exchange resin, respectively.

Moreover, among the anion exchange resins, the Cl type anion exchange resin produced by ion exchange in the condensate demineralization tower 1 has a poor regeneration rate to the OH type by NaOH, so some CI type anion exchange resins are There was a tendency for the resin to remain unregenerated.

As mentioned above, in the conventional method, in addition to H-type cation exchange resin and OH-type anion exchange resin, considerable amounts of Na-type cation exchange resin, S04-type anion exchange resin, and C1-type anion exchange resin are produced or While remaining, these non-regenerated ion exchange resins are returned to the condensate demineralization tower 1 through the mixing storage tank 4 together with the regenerated ion exchange resin. In this case, these non-regenerated ion exchange resins cause leakage of Na ions, Cl- ions, etc., resulting in a problem of lowering the purity of the treated water. Regarding the so4”-ion,
Since the anion exchange resin has a strong selective adsorption property for 804'-ions, the problem of ion leakage does not occur.

On the other hand, in the condensate demineralization tower 1, the ion exchange resin has an ion exchange function as well as iron oxide (iron oxide) in the form of suspended solids contained in the condensate.
It also has the function of filtering out clad iron (clad iron), etc., and as the desalting process progresses, clad iron adheres to the surface of the ion exchange resin. Therefore, the adhered clad iron is removed by backwashing and scrubbing techniques during the regeneration operation, but such physical removal alone is not sufficient to remove the clad iron, and the accumulation of clad iron progresses, eventually reaching the flow-through point. This leads to a decrease in the amount of water that can be treated. If such a situation occurs, it will be necessary to perform iron removal treatment using a special iron removal agent, but this iron removal treatment requires a longer time than the regeneration operation described above, so it is a bottleneck in equipment operation. It becomes.

The inventor of the present invention was concerned about this situation and conducted repeated research to find out the causes of each problem.

That is, the problems with the conventional method can be divided into the following three points.

(f) Leakage of Na ions (ii) Leakage of C1- ions 011) Decrease in the amount of treated water up to the flow-through point due to iron oxide (clad iron) Problem (1) is basically caused by the separation and regeneration tower. However, when observed in detail, when specific gravity separation is performed, the incomplete separation is only in a very narrow region of the boundary layer in the vertical direction of the column, and the upper layer of the column is separated from the boundary layer. The anion exchange resin in the boundary layer and the cation exchange resin in the lower layer are sufficiently separated.

Therefore, it is assumed that if only the anion exchange resin in the upper layer of the boundary layer is extracted, the contamination of the cation exchange resin into the anion exchange resin regeneration tower 3 can be almost completely prevented. On the other hand, a small amount of the anion exchange resin contained in the boundary layer remains in the separation and regeneration tower 2, and this becomes S04 type by H2SO4 treatment, but as mentioned above, 80% of the anion exchange resin
Since the selective adsorption of 4'- is strong, the problem of 804'-ion leakage often occurs.

Next, the cause of problem (11) is that, as described above, the regeneration rate to OH type anion exchange resin when C4 type anion exchange resin is treated with NaOH is low. However, SO
Since the regeneration rate from type 2 to OH type is much better than the above, the Cl type anion exchange resin is preheated with H2S.
It is thought that if treated with O, to form the S04 type, and then treated with NaOH, it is possible to efficiently regenerate the resin into an OH type ion exchange resin without leaving any C1 type ion exchange resin remaining.

Furthermore, the cause of problem (iii) is, of course, the accumulation of clad iron, but when looking at the accumulation situation, it is biased towards anion exchange resins. In other words, the iron oxide deposited on the cation exchange resin is eluted and removed in the regeneration process using If2So, whereas the iron oxide deposited on the anion exchange resin is partially converted to iron hydroxide during the regeneration process using NaOH. Since it is returned almost as is, the accumulation proceeds at a rate 3 to 4 times that of cation exchange resins. Therefore, it is expected that it is possible to reduce the accumulation of iron oxide even with respect to anion exchange fat by treating it with 12S04.

The present invention has been made based on the knowledge of the above-mentioned problems, and it is an object of the present invention to provide a method for regenerating ion exchange resins that can solve all of the problems at once.

Therefore, the method of the present invention is a method for regenerating an ion exchange resin used in a condensate demineralization tower, in which a cation exchange resin and an anion exchange resin are mixed among the ion exchange resins separated by specific gravity in the separation regeneration tower. After extracting only the anion exchange resin in the upper layer of the boundary layer to the anion exchange resin regeneration tower and replacing the anion exchange resin with the sulfate ion type, Na
The main point is that it is a combination of OH processing operations.

The specific configuration and effects of the present invention will be explained below along with the drawings.

That is, in FIG. 1, after the ion exchange resin that has reached the flow-through point is extracted from the condensate demineralization tower 1 and introduced into the separation and regeneration tower 2,
H2SO4 (2 to 10% by weight) is injected into the separation and regeneration tower 2 to regenerate the cation exchange resin and exchange the anion exchange resin to SO type. Next, washing water is injected from the bottom of the separation and regeneration tower, and the ion exchange resin in the tower is stirred to separate the cation exchange resin and the anion exchange resin by specific gravity. still)
Scrubbing may be performed before injecting 12SO. Then, only the anion exchange resin in the upper layer of the boundary layer where the cation exchange resin and anion exchange resin are mixed is extracted and put into the anion exchange resin regeneration tower 3, and then N a OH is injected from the upper part of the regeneration tower 3. to regenerate the anion exchange resin. In addition, sufficient water washing should be carried out during the regeneration operation.

Thereafter, the regenerated cation exchange resin and anion exchange resin are introduced into the mixing storage tank 4 and mixed sufficiently, and then returned to the condensate demineralization tower 1. This can prevent the pNa type cation exchange resin and C6 type anion exchange resin from remaining and the adhesion of clad iron, increasing the purity of the treated water and increasing the amount of treated water up to the flow-through point. Successful.

Incidentally, step (e) and ζ-formation of the method of the present invention is not limited to the above-mentioned method, and the following methods can also be used for regeneration.

That is, in FIG. 1, the ion exchange resin (that has reached the flow-through point) charged into the separation and regeneration tower 2 is first subjected to specific gravity separation, and then the anion exchange resin (\' (J fat) in the upper layer of the boundary layer and After injecting H, SO, (2 to 10 weight 9+5) into the separation and regeneration tower 2 to regenerate the cation exchange resin, the discharged liquid is poured into the separation and regeneration tower 2 as shown by the one-point chain line. Then, the anion exchange resin is injected into the anion exchange resin regeneration tower 3 to convert the anion exchange resin to SO6 type.Then, N a OI-I is injected into the anion exchange resin regeneration tower 3 to regenerate the anion exchange resin. It is also possible to adopt this method, and the same effect as described above can be obtained.

The present invention is roughly configured as described above, and can obtain the effects summarized below.

(1) The anion exchange resin is converted to the S04 type by H2SO, and then regenerated to the Of type by NaOH, so no C1 type anion exchange resin remains and there is no leakage of C1- ions. S04
Ion exchange from the mold to the OH type progresses efficiently, improving the regeneration level.

(2) During the separation operation of cation exchange resin and anion exchange resin, the boundary layer in which both are mixed is not fed into the anion exchange resin regeneration tower at all, so that the cation exchange resin is NaOH
No Na-type cation exchange resin is generated at all. Therefore, leakage of Na+ ions can be completely eliminated.

(3) For the anion exchange resin, temporarily add H and SO.

Since the metal oxides such as clad iron are almost completely eluted and removed in the regeneration process. Since metal oxides do not accumulate and the ion exchange resin is not encapsulated by clad iron or the like, the amount of water treated up to the flow-through point can be increased.

[Brief explanation of the drawing]

FIG. 1 is a flow chart for explaining the conventional ion exchange resin regeneration method and the present invention. 1... Condensate demineralization tower 2... Separation and regeneration tower 3... Anion exchange resin regeneration tower 4... Mixing storage tank

Claims (1)

[Claims] A method for regenerating ion exchange resin used in a mixed bed ion exchange device for desalting condensate, in which cation exchange resin and anion exchange resin are mixed among the ion exchange resins separated by specific gravity in a separation and regeneration tower. This is a combination of an operation in which only the anion exchange resin in the upper layer of the boundary layer is extracted to an anion exchange resin regeneration tower, and an operation in which the anion exchange resin is replaced with a sulfate ion type and then treated with NaOH. A method for regenerating an ion exchange resin, characterized by: