JP2007125453A - Operation method of condensate treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method of a condensate treatment apparatus which reduces elution of fluorine from a filter as much as possible, and enables use of a filter made of a fluorine-based material excellent in strength properties without causing a deterioration in thermal efficiency and corrosion problems of a heat-transfer pipe in a steam generator etc. <P>SOLUTION: In a power generating plant carrying out all volatile treatment, system water is treated by a condensate filtering device 1 using the filter made of the fluorine-based material and a condensate demineralizer 4 using ion exchange resins, and installed downstream of the filtering device, and the filter made of the fluorine-based material is immersed in purified water of a secondary system during stop of supplying water to the condensate filtering device 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for operating a condensate treatment apparatus, and more particularly to a method suitable for operation of a condensate treatment apparatus in a pressurized water nuclear power plant (PWR).

  In a pressurized water nuclear power plant (PWR), hydrazine is used to prevent the inflow of iron to the steam generator (hereinafter sometimes abbreviated as SG) to prevent corrosion of secondary equipment and piping. All volatile chemical treatment (AVT) is carried out by degassing the system water and controlling the pH to about 9.2 using ammonia and ethanolamine (ETA).

On the other hand, in recent years, condensate filtration devices have been applied for the purpose of condensate system water purification, but as a membrane material for the filters of condensate filtration devices, fluorine-based materials with excellent chemical and mechanical strength are used. Application is under consideration (for example, Patent Document 1). However, under the AVT operation, since the pH of the system water is high and the elution of fluorine from the fluorine-based material increases, it is difficult to put it into practical use.
JP 2002-346346 A

  In a power plant implementing AVT, when a filter using a fluorine-based material alone is applied to a condensate filtration device, fluorine is eluted from the filter due to the influence of pH, and the fluorine is concentrated in the SG. As a result, the thermal efficiency of the SG heat transfer tube is reduced and corrosion is caused.

  Accordingly, an object of the present invention is to elute fluorine from a filter as described above in a condensate treatment device of a power plant having a condensate filtration device using a filter made of a fluorine-based material having excellent chemical and mechanical strength. Condensate treatment device operation method that makes it possible to use a filter made of a fluorine-based material with excellent strength characteristics without reducing the heat efficiency of the heat transfer tube in a steam generator, etc., or causing corrosion problems Is to provide.

  In order to solve the above-described problems, a method for operating a condensate treatment apparatus according to the present invention is a condensate filtration method using a filter made of a fluorine-based material in a power plant that performs all volatile chemical treatment (AVT). The system water is treated with a condensate demineralizer using ion exchange resin installed in the apparatus and the subsequent stage, and the filter made of the fluorine-based material is treated with pure water while the water flow to the condensate filtration apparatus is stopped. It consists of the method characterized by immersing in.

  In this operation method, the filter made of the fluorine-based material is immersed in pure water while the flow of water to the condensate filtration device is stopped, during the power plant inspection, during the bypass operation of the condensate filtration device. It may be done at any time or at both times.

  In the operation method of the condensate treatment apparatus, the system water can be purified by a filter using a fluorine-based material and an ion exchange resin installed in the subsequent stage. And in order to reduce the elution of fluorine from the filter itself, the filter is immersed and stored in pure water other than when the condensate filtration device is used. In other words, normally, the condensate filtration device is filled with condensate only when the condensate filtration device is stopped, and in power plants that implement AVT, the filter is (Even if the condensate is removed from the condensate filtration device, the condensate remains on the secondary side. Will remain exposed to water). In such a state, as described above, elution of fluorine from the filter proceeds, and at least it takes a long time for the power plant to start up after regular inspection. By completely immersing the filter in neutral pure water, it is possible to prevent the elution of fluorine during the stoppage of water flow to at least the condensate filtration device. Elution will be reduced.

  According to the operation method of the condensate treatment apparatus according to the present invention, system water is treated by a condensate filtration apparatus using a filter made of a fluorine-based material and a condensate demineralizer using an ion exchange resin installed in the subsequent stage. System water can be appropriately purified by immersing the filter made of a fluorine-based material in pure water while the water flow to the condensate filtration device is stopped. Use a filter made of a fluorine-based material that can reduce the elution of fluorine and has excellent chemical and mechanical strength, without causing problems such as a decrease in thermal efficiency and corrosion of the heat transfer tube in a steam generator. It becomes possible.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the recovery of a power plant (especially a pressurized water nuclear power plant) that performs all volatile chemical treatment (AVT) used in the implementation of the operation method of the condensate treatment apparatus according to one embodiment of the present invention. The equipment system around the water filter is shown. In FIG. 1, reference numeral 1 denotes a condensate filtration device. In this condensate filtration device 1, a filter (for example, a hollow fiber filter) made of a fluorine-based material (for example, vinylidene difluoride (PVDF)) is used. ing. The condensate introduced from the condensate inlet 2 side is sent from the condensate outlet 3 side to a condensate demineralizer 4 using an ion exchange resin installed in the subsequent stage. However, there is also provided a line 5 that does not pass water to the condensate demineralizer 4 (that is, bypasses the condensate demineralizer 4) and directly sends it to a condenser (not shown). In addition, a bypass line 6 that bypasses the condensate filtration device 1 without passing through the condensate filtration device 1 is also provided.

  In such a condensate treatment apparatus, the filter made of a fluorine-based material can be immersed in pure water by the following steps. For example, when the apparatus is stopped at the start of regular inspection, as shown in FIG. 1, water flow to the condensate filtration apparatus 1 is stopped, and condensate (that is, alkaline water by AVT treatment) accumulates in the shaded area in FIG. ing.

  From the above state, as shown in FIG. 2, the compressed air from the air compressor 7 is introduced into the filtration tower of the condensate filtration device 1 through the air storage tank 8 and accumulated on the primary side of the condensate filtration device 1. For example, the condensate is drained into a backwash tank. For the air compressor 7 and the air storage tank 8, it is also possible to use a resin transfer device of the condensate demineralizer 4.

  Next, as shown in FIG. 3, the vent valve of the condensate filtration device 1 is opened, for example, the inside of the tower is opened to atmospheric pressure, and the condensate accumulated on the secondary side of the condensate filtration device 1 is dropped into the tower. At the same time, the drain valve is opened to drain the condensate accumulated in the secondary pipe to the outside of the system.

  And as shown in FIG. 4, compressed air is again introduce | transduced in a filtration tower, and the water in the tower | column of the condensate filtration apparatus 1 is drained to a backwash tank, for example.

  Next, as shown in FIG. 5, secondary pure water is introduced from the lower part of the filtration tower of the condensate filtration device 1, and the primary side of the condensate filtration device 1 is replaced with pure water.

  Furthermore, as shown in FIG. 6, the vent valve of the condensate filtration apparatus 1 is opened, and the secondary side of the condensate filtration apparatus 1 is replaced with pure water by pure water introduced from the lower part of the filtration tower.

  Through the above steps, the inside of the filtration tower is completely replaced with pure water, and the filter made of the fluorine-based material is completely immersed in pure water. In this state, it is stored for a predetermined period. If during regular inspection, at least during regular inspection, and during bypass operation of the condensate filtration device 1, it is immersed and stored in pure water for the entire period or part of the bypass operation.

  Compared to the condition of being immersed in high pH condensate in a power plant where AVT is implemented, the filter is immersed and stored in completely neutral pure water, preventing elution of fluorine from the filter. As a result, fluorine elution is reduced during the subsequent operation period, and further throughout the entire period including the regular inspection. Reduction of fluorine elution makes it possible to use filters made of fluorine-based materials with excellent chemical and mechanical strength without causing problems such as a decrease in thermal efficiency and corrosion of heat transfer tubes in steam generators. Become.

In order to confirm the effect of the method according to the present invention, the following test was performed.
A hollow fiber filter using a fluorine-based material made of vinylidene difluoride (PVDF) and a device filled with ion exchange resin in the subsequent stage to remove fluorine eluted from this hollow fiber membrane filter, and AVT treatment 5 ppm N ₂ H ₄ solution was passed through assuming condensate, and the elution concentration of fluorine (F) from the hollow fiber membrane filter was measured.

The initial water flow conditions are shown in Table 1, and the water flow test results are shown in Table 2. As the water used for the initial water flow, a 5 ppm N ₂ H ₄ solution was used assuming condensate in which AVT treatment is performed. From the results shown in Tables 1 and 2, it was confirmed that the fluorine eluted from the fluorine-based hollow fiber membrane filter can be removed by the ion exchange resin in the subsequent stage.

  Moreover, the comparison test in the case of immersing and storing in pure water and in the case of immersing and storing as it is in condensate water is performed. Table 3 shows the immersion test conditions, and Table 4 shows the results of the immersion test. From the results shown in Tables 3 and 4, it was confirmed that fluorine elution can be significantly reduced by immersing and storing the fluorine-based hollow fiber membrane filter in pure water.

  The operation method of the condensate treatment apparatus according to the present invention is a method suitable for application to the operation of the condensate treatment apparatus of a pressurized water nuclear power plant (PWR) in which all volatile chemical treatment (AVT) is performed. With the application of the present invention, it is possible to use a filter made of a fluorine-based material having excellent strength characteristics without causing problems such as a decrease in thermal efficiency and corrosion of the heat transfer tube in a steam generator or the like.

It is an equipment system diagram around a condensate filtration device of a power plant used for implementation of an operation method of a condensate treatment apparatus concerning one embodiment of the present invention, and is an equipment system diagram showing a state at the time of condensate water stoppage. . FIG. 2 is an equipment system diagram showing the next step of FIG. 1 for replacing the inside of the condensate filtration device of the apparatus of FIG. 1 with pure water. FIG. 3 is an equipment diagram showing the next step of FIG. 2 of the apparatus of FIG. 1. FIG. 4 is a device system diagram showing the next step of FIG. 3 of the apparatus of FIG. 1. FIG. 5 is an equipment diagram showing the next step of FIG. 4 of the apparatus of FIG. 1. FIG. 6 is an equipment diagram showing the next step of FIG. 5 of the apparatus of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Condensate filtration apparatus 2 Condensate inlet 3 Condensate outlet 4 Condensate demineralizer 5 Line to condenser 6 Bypass line 7 Air compressor 8 Air storage tank

Claims (2)

  In power plants that carry out all volatile chemical treatment, system water is treated with a condensate filtration device using a filter made of a fluorine-based material and a condensate demineralizer using an ion exchange resin installed in the subsequent stage. A method for operating the condensate treatment apparatus is characterized in that the filter made of the fluorine-based material is immersed in pure water while water flow to the condensate filtration apparatus is stopped.   The filter made of the fluorine-based material is immersed in pure water while water flow to the condensate filtration device is stopped during the regular inspection of the power plant and / or during the bypass operation of the condensate filtration device. The operation method of the condensate treatment apparatus of Claim 1.

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