JP3525623B2 - Condensate treatment method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a condensate treatment method,
In particular, PW containing 30-500 μg / L hydrazine
TECHNICAL FIELD The present invention relates to a method for reducing the ionic load of a desalination device and increasing the amount of water collected when treating condensate of an R-type (pressurized water reactor) nuclear power plant with the desalination device.

[0002]

2. Description of the Related Art Condensed water in a power plant is generally circulated and used after being passed through a condensate demineralizer comprising a mixed bed column of cation exchange resin and anion exchange resin for desalination.

By the way, in recent years, in a power plant, a high hydrazine operation has been performed in which the hydrazine concentration in the condensate is increased to prevent corrosion of the condensate system.

For this reason, the hydrazine concentration in the condensate of the thermal power plant is at most 2 μg / L, but in the condensate of the PWR type power plant whose steam temperature is lower than that of the thermal power plant, 30 to 500
There was a relatively high concentration of hydrazine at μg / L.

Regarding the treatment of hydrazine, JP-A-53-91094 discloses that hydrazine-containing liquid is mixed with air and brought into contact with a catalytic metal for oxidative decomposition.

[0006]

When condensate having a high hydrazine concentration during high hydrazine operation is passed through a condensate demineralizer, hydrazine becomes an ionic load on the cation exchange resin, and the amount of water collected by the condensate demineralizer is increased. Is reduced. The regeneration frequency of the ion exchange resin increases. As a result, the operating efficiency of the apparatus is reduced, the amount of regenerant used is increased, the amount of reclaimed waste water is increased, and the treatment cost is increased. Such a problem occurs. This problem is particularly noticeable in a PWR power plant where the concentration of hydrazine in condensed water is relatively high.

Japanese Unexamined Patent Publication (Kokai) No. 53-91094 describes a treatment method by catalytic oxidative decomposition of hydrazine.
Corrosion-preventing drainage of boiler containing high concentration of about 00 mg / L, hydrazine-containing liquid with hydrazine concentration of the order of μg / L, especially hydrazine treatment of condensate of PWR power plant used for condensate demineralizer Is not mentioned at all. Further, since it is a wastewater treatment, a large excess of oxygen-containing gas is blown in with respect to the amount of hydrazine contained.

The present invention solves the above-mentioned conventional problems, and when the condensate of a PWR type power plant with a hydrazine concentration of 30 to 500 μg / L is treated with a desalting apparatus, almost the theoretical amount of oxygen required for the decomposition of hydrazine is used. By blowing in the contained gas to efficiently remove hydrazine, the ion load of the desalting device and the load of the heating degassing device can be reduced, the regeneration frequency of the desalting device can be reduced, and the amount of water taken by the desalting device can be increased. The object is to provide a method that can be achieved.

[0009]

The condensate treatment method according to claim 1 is a method for treating condensate of PWR type nuclear power plant containing hydrazine in an amount of 30 to 500 μg / L by passing it through a desalination apparatus. After blowing a theoretical amount of oxygen-containing gas required for hydrazine decomposition into water to dissolve oxygen, Pd
It is characterized in that hydrazine is oxidatively decomposed by bringing it into contact with the held anion exchange resin, and then water is passed through a desalting apparatus.

According to the condensate treatment method of claim 2, hydrazine is added to
In a method of treating PWR-type nuclear power plant condensate containing 0 to 500 μg / L by passing it through a desalination apparatus, a substantially theoretical amount of oxygen-containing gas required for hydrazine decomposition is blown into the condensate to dissolve oxygen. It was followed, with Ani-exchange resin carrying Pd to oxidative decomposition of hydrazine was passed through the demineralizer filled, characterized by desalting.

In the condensate treatment method of the present invention, hydrazine in the condensate is mixed with anion exchanged with Pd as a catalyst.
In the presence of the exchange resin , oxygen is catalytically oxidized and decomposed into nitrogen and water by the following reaction.

N ₂ H ₄ + O ₂ → N ₂ ↑ + 2H ₂ O Therefore, it is possible to reduce the ion load of the desalting apparatus, reduce the regeneration frequency of the desalting apparatus, and increase the amount of water taken by the desalting apparatus. it can.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the condensate treatment method of the present invention will be described below with reference to the drawings.

1 and 2 are system diagrams showing a treatment apparatus suitable for carrying out the condensate treatment method of the present invention.

In the apparatus shown in FIG. 1, the condensate introduced from the pipe 10 (PW containing 30 to 500 μg / L of hydrazine is used).
After injecting air into the R-type nuclear power plant condensate) through the pipe 11, water is sequentially passed through the catalyst tower 1 and the desalting tower (desalination apparatus) 2. In injecting air into the condensate, the hydrazine monitor 3 measures the hydrazine concentration in the condensate of the pipe 10 (or the condensate in the raw water tank when a raw water tank is provided), and the arithmetic controller In step 4, calculate the amount of air that corresponds to the amount of oxygen necessary and sufficient to oxidize hydrazine in the condensate from the measured value of hydrazine concentration, and adjust the opening of valve 5 based on this calculation result. Control the amount of air injected.

In this way, the condensate, into which an amount of air necessary and sufficient for the oxidation of hydrazine is injected, comes into contact with the catalyst in the catalyst tower 1, whereby the contained hydrazine is oxidatively decomposed into nitrogen and water. To be done. Outflow water of the catalyst tower 1 is desalted from the pipe 12 and then in the desalting tower 3, and the treated water is the pipe 1
It is discharged from the system from 3. In this desalination process, since the hydrazine has been removed from the catalyst tower 1 in the inflow water of the desalination tower 2, the ion load of the desalination tower 2 is small, and high-quality treated water is continuously collected over a long period of time. can do.

The water flow rate through the catalyst tower 1 is SV = 10.
It is preferably 200 hr ⁻¹ , particularly 50 to 100 hr ^−1, and the pressure is 0.5 to 30 kg / cm ² , particularly 4 kg /
It is preferably at least cm ² . Further, the water flow rate of the desalting tower 2 is preferably SV = 60 to 120 hr ⁻¹ .

In the present invention, as the oxygen-containing gas,
In addition to air, oxygen or oxygen-enriched air can be used.

Oxidative decomposition of hydrazine requires an equimolar amount of oxygen to hydrazine. In the present invention, 1.0 to 1.1 moles of oxygen are contained in the condensate with respect to hydrazine in the condensate. It is preferable to inject an oxygen-containing gas such as air so as to dissolve.

As the hydrazine monitor 3, a commercially available product can be used, and also in the desalting tower 2, a cation exchange resin and an anion exchange resin of a conventional condensate demineralizer are mixed at a ratio of 3 to 1: 1. It is possible to use a desalting tower composed of a packed mixed bed type ion exchange resin tower.

The apparatus shown in FIG. 1 has a control function of adjusting the air injection amount based on the hydrazine concentration in the condensate. However, when there is no significant change in the hydrazine concentration of the condensate, or the hydrazine concentration is When the temperature is relatively low, these control means may be omitted and the device may be simplified by injecting a fixed amount of oxygen-containing gas such as air.

[0022] In the present invention, as a catalytic, palladium
An anion exchange resin supporting a metal ( Pd) is used. Pd
As the catalyst, metal Pd, palladium oxide can be used Pd compound such as palladium hydride, 0.1 to 10% by weight relative to the anion exchange resin in charge Jiryou typically comprise a carrier
It is a degree . By using the anion-exchange resin as a responsible body, it can exhibit an excellent effect with less palladium weight, is very suitable.

In order to support Pd on the anion exchange resin, the column may be filled with the anion exchange resin and then an acidic solution of palladium chloride may be passed through. If metal P
If it is carried as d, it may be reduced by further adding formalin or the like to the above.

[0024]

The catalyst may be used in any shape such as powder, granules or pellets. When using a powdery substance, a reaction tank is provided and an appropriate amount is added to this reaction tank. The granular or pellet-shaped one is advantageous when it is packed in a column or the like as in the catalyst tower of FIG. 1 and continuously treated with water. Needless to say, even a powdery material can be packed in a column and subjected to liquid flow treatment in a fluidized bed.

[0026] In the present invention, P to the anion exchange resin
For use those carrying the d catalysts, the use of this catalyst resin as at least a part of the anion exchange resin desalting, it is possible to omit the catalyst tower.

FIG. 2 shows such an embodiment. Condensate introduced from the pipe 10 is injected with an oxygen-containing gas such as air from the pipe 11 and then cation exchange resin and catalyst are carried. Water is passed through a desalting tower 2A in which a mixed bed with an anion exchange resin is formed. In the desalting tower 2A, hydrazine is oxidatively decomposed and desalination is carried out by ion exchange. Is discharged to the outside of the system.

In this apparatus, the water flow rate of the desalting tower 2A is SV = 60 to 120 hr ^-1 , and the pressure is 1.0 to 5.0 k.
It is preferably g / cm ² .

Needless to say, the apparatus of FIG. 2 may also be provided with the same air injection amount control means as in FIG.

According to the condensate treatment method of the present invention as described above,
Condensate ion load demineralizer is of a conventional N ₂ H ₄ and NH ₃
As a result, only NH ₃ is used, and the amount of water taken by the desalting device is significantly improved.

[0031]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below. In the following Examples and Comparative Examples, as raw water, ammonia and hydrazine were NH ₃ : 900 by simulating condensate water quality during high hydrazine operation.
μg / L, N ₂ H ₄ : Synthetic water dissolved in pure water so as to be 500 μg / L was used.

Example 1 As shown in FIG. 1, raw water was passed through an apparatus in which a catalyst tower and a desalting tower were arranged in series at 360 L / hr for treatment (SV of the catalyst tower was 180 hr ⁻¹ , pressure was 1.5 kg / cm ² , SV of the desalting tower is 80 hr ^-1 ).

The catalyst tower used was a catalyst resin "Lewatit OC 1045" (manufactured by Bayer Co., in which palladium was supported on an OH type anion exchange resin) packed in an acrylic column having a volume of 2 L. In addition, as a desalting tower, H-type cation exchange resin Diaion “PK22” manufactured by Mitsubishi Chemical Corporation
An acrylic column filled with 3 L of 8 "and 1.5 L of the same OH-type anion exchange resin Diaion" PA312 "was used.

At the inlet side of the catalyst tower, the air is adjusted to 0.7 L (0 ° C., 1 ° C.) so that the oxygen concentration of the raw water is 500 μg / L.
It was injected at (atm conversion) / hr.

As a result, the amount of water collected until the electric conductivity of the outflow water (treated water) from the desalting tower reaches 0.2 μS / cm is about 9
It was 6 m ³ .

Example 2 As shown in FIG. 2, 3 L of H-type cation exchange resin DIAION "PK228" manufactured by Mitsubishi Chemical Co., Ltd. and 1.5 L of catalyst resin "Lewatit OC 1045" manufactured by Bayer were packed in an acrylic column for desalting. Raw water was passed through the tower for treatment. The raw water flow rate and the air injection amount were the same as in Example 1.

As a result, the amount of water collected until the electric conductivity of the outflow water (treated water) of the desalting tower becomes 0.2 μS / cm is about 9
It was 4 m ³ .

Comparative Example 1 A treatment was carried out in the same manner as in Example 1 except that the catalyst tower was not provided, air was not injected, and raw water was directly passed through the desalination tower.

As a result, the amount of water collected until the electric conductivity of the outflow water (treated water) of the desalting tower becomes 0.2 μS / cm is about 7.
It was 3 m ³ .

As is clear from the results of Examples 1 and 2 and Comparative Example 1, in Examples 1 and 2, about 1.
According to the present invention, it is possible to increase the amount of water taken by the desalination apparatus and reduce the frequency of regeneration according to the present invention.

[0041]

As described above in detail, according to the condensate treatment method of the present invention, when condensing the condensate of a PWR type nuclear power plant containing hydrazine, it is possible to increase the amount of water taken by the desalination apparatus and to improve the regeneration frequency. It can be reduced. Therefore, the operation efficiency and treatment efficiency of the desalting device can be improved, the treatment cost for regenerating the regenerant and the like can be reduced, and the regeneration wastewater can be reduced, which is extremely advantageous industrially.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a treatment apparatus suitable for carrying out the condensate treatment method of the present invention.

FIG. 2 is a system diagram showing another embodiment of a treatment apparatus suitable for carrying out the condensate treatment method of the present invention.

[Explanation of symbols]

1 catalyst tower 2,2A desalination tower 3 Hydrazine monitor 4 arithmetic controller

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C02F 1/72 CDH C02F 1/72 CDHB G21F 9/12 512 G21F 9/12 512A (58) Fields investigated (Int.Cl. ⁷ , DB name) G21F 9/06 G21F 9/12 G21C 19/30

Claims (2)

(57) [Claims] 1. A method for treating PWR-type nuclear power plant condensate containing hydrazine in an amount of 30 to 500 μg / L by passing it through a desalting apparatus, and treating the condensate with an approximately theoretical amount of oxygen-containing gas required for hydrazine decomposition. Is blown in to dissolve oxygen, the hydrazine is brought into contact with an anion exchange resin carrying Pd to oxidize and decompose hydrazine, and then water is passed through a desalting apparatus. 2. A method of treating PWR-type nuclear power plant condensate containing hydrazine in an amount of 30 to 500 μg / L by passing it through a desalting apparatus, and treating the condensate with an approximately theoretical amount of oxygen-containing gas required for hydrazine decomposition. after blowing in dissolved oxygen, with Ani-exchange resin carrying Pd to oxidative decomposition of hydrazine was passed through the demineralizer packed, condensate treatment method characterized by desalting .