JPH11216373A - Regeneration method of condensate desalination ion exchange resin - Google Patents

Abstract

(57) [Problem] To regenerate an ion-exchange resin obtained by desalinating condensate, to prevent generation of an oxidizing substance and prevent elution from the ion-exchange resin. SOLUTION: When condensed water is desalted to regenerate an ion-exchange resin to which hydrazine is adsorbed, the temperature of water in contact with the ion-exchange resin is set to 15 ° C. or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for regenerating an ion-exchange resin adsorbed with hydrazine (hereinafter sometimes referred to as "condensate-deionized ion-exchange resin") by desalinating condensate. In particular, the present invention relates to a method for preventing the generation of an oxidizing substance in the regeneration of the condensed deionized ion exchange resin and performing an effective regeneration.

[0002]

2. Description of the Related Art A condensate treatment facility of a thermal power plant mainly comprises a condensate filter comprising an electromagnetic filter for removing suspended substances such as iron rust in the condensate and an impurity ion contained in the condensate. And a condensate desalination unit. The condensate desalination unit includes a strongly acidic cation exchange resin (H type) and a strong base anion exchange resin (OH type). (A mixed-bed ion-exchange resin bed tower, sometimes referred to as a "desalting tower").

In the regeneration of the ion exchange resin in the mixed bed tower, the ion exchange resin in the desalination tower is transferred to a regeneration-only tower in order to prevent a chemical such as a regenerant from entering the boiler or the like. Generally, the regenerating process is performed through the following steps.

First transfer step (transfer of ion exchange resin from desalting tower to separation / regeneration tower) → backwash separation step (backwashing of ion exchange resin and separation of anion exchange resin / cation exchange resin in separation / regeneration tower) → Second transfer step (transfer of anion exchange resin or cation exchange resin from separation regeneration tower to regeneration tower) →
Regeneration step (regeneration of each ion exchange resin in the regeneration tower and separation / regeneration tower) → water washing step (extrusion washing of the regenerant) → third transfer step (transfer of the ion exchange resin from the regeneration tower and the separation / regeneration tower to the storage tank) → Standby process The backwash separation process is to separate and separate cation exchange resin and anion exchange resin with a specific gravity difference to form a layer, while removing turbid components such as oxides trapped in the desalination treatment of condensate. This is a step of passing backwash water through the mixed bed type ion exchange resin layer in an upward flow (at this time, air may be supplied simultaneously to obtain a sufficient stirring action). This backwash separation
Although it may be carried out in a desalination tower, it is generally carried out in a separation and regeneration tower. When the backwash separation is performed in the separation / regeneration tower, the first transfer step is to transfer the ion exchange resin in the desalination tower to the separation / regeneration tower by using transfer water before the backwash separation. In this transfer, pressurized air may be used.

After the anion exchange resin and the cation exchange resin are separated and stratified in the separation / regeneration tower, one of the ion exchange resins is transferred to the regeneration tower in the second transfer step.

[0006] Thereafter, in the regeneration step, regeneration of the ion exchange resin remaining after the second transfer step is performed in the separation regeneration tower.
In the regeneration tower, regeneration of the ion exchange resin transferred in the second transfer step is performed by passing a regenerating agent through each tower.

[0007] After the regeneration of the ion exchange resin, in a water washing step, pure water is passed through each tower, and the regenerant is extruded and washed.

The ion exchange resin thus regenerated and washed in each column is transferred to an ion exchange resin storage tank (third transfer step) and stored until the next use (standby step).

[0009] In recent years, it has become clear that the ion exchange resin is oxidized during regeneration, and the oxidation during regeneration of the ion exchange resin in the condensate desalination unit of a PWR (Pressurized Water Reactor) is described as thermal nuclear power generation. Magazine Vol. 45N
o. 8 According to this research report, it is estimated that hydrazine-type or ammonia-type ion-exchange resins (cation-exchange resins) undergo oxidative decomposition when supplied with sufficient oxygen in the presence of oxides.

[0010]

When regenerating an ion-exchange resin in a condensate desalination apparatus, an oxidizing substance is generated under specific conditions, and the generated oxidizing substance oxidizes the ion-exchange resin. The eluate comes out of the exchange resin. If there is any eluate from the ion exchange resin, a large amount of washing water is required in the water washing step after the regeneration step, or this eluate flows out into the treated water in the condensate demineralization step, resulting in poor water quality. Occurs.

The present invention solves the above-mentioned conventional problems, and provides a condensed water-desalted ion-exchange resin for preventing the generation of eluate from the ion-exchange resin in the regeneration of the ion-exchange resin in which the condensate is desalted. It is intended to provide a reproduction method.

[0012]

A method for regenerating a condensed water-desalted ion exchange resin according to the present invention is a method for regenerating an ion-exchange resin adsorbing hydrazine by subjecting condensed water to a desalination treatment.
The temperature of water in contact with the ion exchange resin is set to 15 ° C. or less.

[0013] Oxidation degradation of the ion exchange resin and deterioration of the treated water during regeneration of the condensed deionized ion exchange resin occur according to the following principle.

In a condensate desalination tower of a thermal power plant or a PWR type nuclear power plant, ammonia or hydrazine injected as a condensate water quality control agent is adsorbed on a cation exchange resin. Deionized ion exchange resin, as described above,
The water is transferred from the desalting tower to the separation and regeneration tower and the regeneration tower. At this time, pressurized air or water is used to transfer the ion exchange resin. During this transfer operation, almost saturated oxygen exists in the transfer water, while ammonia and hydrazine are adsorbed on the ion exchange resin (cation exchange resin). It can be said that all the conditions under which the oxidation of the ion exchange resin occurs are satisfied.

When the cation exchange resin is oxidized, for example, the styrene chains and the cross-linking agent are oxidized and decomposed to lower the molecular weight, so that the distance between the styrene chains is increased, and the organic material having the reduced molecular weight is extended from the gap. Easily leaks to the outside. For this reason, the amount of organic eluate from the oxidized ion exchange resin increases.

The organic eluate from this cation exchange resin exhibits the same behavior as lignin sulfonic acid, and can be adsorbed on an anion exchange resin. As described above, the eluate from the cation exchange resin cannot be removed by adsorption. For this reason, when the eluate of the cation exchange resin further flows into the anion exchange resin having the reduced adsorption capacity, there is no longer any ability to remove and adsorb the cation exchange resin. I do.

The present inventors have conducted intensive studies on the reaction between a hydrazine-type / ammonia-type cation exchange resin and dissolved oxygen in water, and as a result, have confirmed that an oxidizing agent is generated during regeneration of the ion-exchange resin. A method for preventing the generation of the oxidizing agent was examined as follows.

First, as an environment of the ion exchange resin in the condensate desalination apparatus, ions such as hydrazine and ammonia, and iron oxide as a clad (metal oxide) often found in the ion exchange resin in the condensate desalination apparatus. The oxidation state of the cation exchange resin was tested using copper oxide and the presence or absence of oxygen as an oxidizing agent as a factor. As a result, the oxidation state of the cation exchange resin was confirmed as follows.

That is, for the cation exchange resin species, H
Oxidation hardly occurs when only the cation exchange resin is used, or when the H cation exchange resin and the ammonia cation exchange resin coexist, the most difficult when the H cation exchange resin and the hydrazine cation exchange resin coexist. Oxidation easily occurs. Further, regarding the presence of the metal oxide, when the metal oxide does not exist, the oxidation hardly occurs, and when the iron oxide or the copper oxide exists, the oxidation easily occurs.
Taken together, it has been found that oxidation occurs most easily when the H-type cation exchange resin and the hydrazine-type cation exchange resin coexist and iron oxide is present, especially when copper oxide is present.

The test results confirmed that the oxidation of the cation exchange resin occurred most severely in the presence of hydrazine, copper and oxygen. This oxidation was presumed to be due to the generation of OH radicals.

This was supported by measuring the concentration of hydrogen peroxide in the test solution by the method described in JP-B-56-54582.

That is, in a state where copper oxide or iron oxide is adsorbed on the ion exchange resin and hydrazine is adsorbed on the ion exchange resin, the dissolved oxygen in the water reacts with hydrazine to form hydrogen peroxide. It is considered that oxidizing substances such as are generated.

During this test, the reaction was affected by the temperature conditions, and formation of an oxidizing substance was observed under the condition of about 40 ° C. which is the temperature condition of a general condensate desalination apparatus. However, it was confirmed that the generation of oxidizing substances was extremely small at a temperature of 15 ° C. or lower, which is the temperature condition of general natural water in winter in Japan.

The present invention has been completed on the basis of these findings. In regenerating a condensed deionized ion exchange resin, the regeneration water having a water temperature of 15 ° C. or lower is used for transferring the ion exchange resin or backwashing. By using as water for separation, generation of oxidizing substance and deterioration of ion exchange resin due to it,
Prevent deterioration of ion exchange treatment water quality.

The effect of the present invention is also supported by the seasonal variation of Na ions and SO ₄ ions in the water in the steam generator where the treated water of the actual condensate desalination apparatus is concentrated about 20 to 50 times. Can be FIG. 1 is a graph showing a seasonal change in water ion concentration (SG water quality) in a steam generator of an actual PWR power plant. Here, Na ion is considered to indicate the ion exchange capacity of the cation exchange resin, and SO ₄ ion is a portion of the cation exchange resin that is oxidized and eluted, and a part of the eluted component that is not removed by the anion exchange resin. It is thought to indicate the concentration of This is because the anion exchange resin in the condensate desalination unit of the PWR nuclear power plant has been regenerated with hydrochloric acid, and the anion exchange resin cannot be in the sulfate ion form, and therefore, the sulfate ion does not leak from the anion exchange resin. Therefore, the sulfate ion is recognized as being generated by the decomposition of the sulfonate, which is the elution component of the cation exchange resin, by the high temperature in the steam generator.

According to this graph, in winter when the water temperature is low, the SO ₄ ion concentration is low, and the amount of eluted substances from the cation exchange resin is small.

[0027]

Embodiments of the present invention will be described below in detail.

In the present invention, in the regeneration of the condensed deionized ion exchange resin, the temperature of the water in contact with the condensed deionized ion exchange resin is set to 40 ° C., which is the most common temperature condition of the conventional regeneration conditions. It can be carried out according to a conventional method except that the temperature is 15 ° C. or lower, which is much lower than that.

As described above, the regeneration treatment of the condensed deionized ion exchange resin generally includes a first transfer step, a backwash separation step, and a second transfer step.
The transfer step, the regeneration step, the washing step, and the third transfer step are performed. In the present invention, it is particularly preferable that all of these steps are performed under the condition of a water temperature of 15 ° C. or lower, but a part of them may be performed. In this case, it is preferable that the temperature of the water used in at least the first transfer step, the backwash separation step, and the regeneration step be 15 ° C. or less. That is,
Since most of hydrazine is removed in the regeneration step, the amount of oxidizing substance generated in the subsequent steps is relatively small. Therefore, even at a water temperature exceeding 15 ° C., the oxidation of the ion exchange resin by the oxidizing substance is extremely small.

According to the present invention, by controlling the temperature of water used for regenerating the condensed deionized ion exchange resin to 15 ° C. or lower, the oxidizing agent formed by the reaction between dissolved oxygen in water and hydrazine can be used. The generation of substances can be suppressed, the oxidative decomposition of the cation exchange resin can be prevented, and the amount of resin effluent mainly composed of sulfonate can be significantly reduced. Also,
As a result, a decrease in the performance of the anion exchange resin, which is considered to be caused by the sulfonate eluted from the cation exchange resin, can be suppressed, and a significant cost reduction can be achieved.

In the present invention, when the temperature of the water used for regeneration is higher than 15 ° C., adjustment is made so that the temperature of the water for regeneration is 15 ° C. or lower. When the temperature of the water for regeneration is 15 ° C. or less, such adjustment is not sufficient. However, water for regeneration at 10 to 15 ° C is 10 ° C.
Such adjustment is made in the following cases.

As described above, in order to adjust the temperature of the water used for the regeneration of the condensed deionized ion exchange resin to 15 ° C. or less, the water used in the regeneration step (transfer water, backwashing separation water, regeneration water, etc.) May be adjusted to 15 ° C. or lower in the water storage tank, or may exchange heat with cold water at an arbitrary place in the water supply pipe.
Room temperature water and cold water may be used as a mixture, or each tower or pipe may be surrounded by a cooling jacket for cooling. As the cooling means, any cold water producing device can be used.

In the present invention, the temperature of the water used for regeneration is adjusted to 15 ° C. or less, and preferably 10 ° C. or less. By setting the temperature to 10 ° C. or lower, elution from the ion exchange resin can be more sufficiently suppressed.

In consideration of the cooling cost and the like, it is preferable that the temperature of the regeneration water is in the range of 10 to 15 ° C.

[0035]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1 and 2, Comparative Examples 1 and 2 N ₂ H _{5 type} resin amount: 10%, NH _{4 type} resin, which is the amount of hydrazine adsorbed during normal operation of the most common PWR condensate desalination apparatus A cation exchange resin having an amount of 60% and an H-type resin of 30% (the amount of metal adhering to the resin: 0.1 g of Fe ₃ O _4, 0.1 g of CuO.
02g) 1 L of water (dissolved oxygen-saturated state, water component: NH ₃ 1 ppm, N ₂ H ₄ 0.2 pp) at the temperature shown in Table 1
m), the concentration of hydrogen peroxide in the water after contact for 15 minutes was measured, and the results are shown in Table 1.

[0037]

[Table 1]

As shown in Table 1, according to the method of the present invention in which the temperature of the treated water is set to 15 ° C. or less, the generation of hydrogen peroxide during regeneration can be greatly reduced, and as a result, the oxidative decomposition of the ion exchange resin and the eluate resulting therefrom It can be seen that the occurrence of the occurrence can be effectively prevented.

[0039]

As described above in detail, according to the method for regenerating a condensate-desalted ion-exchange resin of the present invention, it is possible to prevent the generation of an oxidizing substance in the regeneration of an ion-exchange resin obtained by subjecting condensate to desalination. For effective playback. Therefore, according to the present invention, the oxidative decomposition of the cation exchange resin, the generation of sulfonic acid-based eluted substances eluted from the cation exchange resin in the oxidative decomposition, the deterioration of the performance of the anion exchange resin caused by the sulfonic acid salt and the like The water quality of the ion-exchange treated water can be effectively prevented from being lowered.

[Brief description of the drawings]

FIG. 1 is a graph showing seasonal variations in SG water quality of a PWR power plant.

Claims (1)

[Claims] 1. A method for regenerating an ion-exchange resin adsorbing hydrazine by desalinating condensate, wherein the temperature of water in contact with the ion-exchange resin is set to 15 ° C. or lower. A method for regenerating a desalted ion exchange resin.