JPS61181506A - Method and apparatus for washing filter in atomic power plant - Google Patents

Abstract

PURPOSE:To wash efficiently a filter, to reduce the exchange frequency of an element, and to reduce the secondary waste by placing a hollow yarn membrane element contaminated with clad iron in a washing vessel contg. an aq. org. acid soln., and sending a bubbling gas into the soln. CONSTITUTION:A suspended matter soln. contg. clad iron in atomic reactor water is supplied from a condensate inlet pipe 20, and the treated water filtered by a hollow yarn membrane element 23 is sent to a desalting tower from a condensate outlet pipe 21. When the clad is deposited on the element 23, compressed air in an air accumulator 25 is forced under pressure into a filter 22 to release and remove the suspended matter. The waste liq. is discharged into a tank 28. When the function is not restored by backwashing, the element 23 is incorporated into a washing vessel 29 at the outside of the system, an aq. org. acid soln. 37 is replenished, and the element is washed by using compressed air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for cleaning a hollow fiber membrane element installed in an FM child couplant and used in a filtration device.

[Background of the invention]

The increase in radioactivity concentration in reactor water and piping surface dose at nuclear power plants is due to corrosion products generated in plant components, piping, etc. brought into the reactor from the water supply system and activated by neutron irradiation on the fuel rod surfaces. After that, turn on the primary system equipment again,
This is thought to be caused by adhesion to piping. Corrosion products include Fe.

There are Go, Ni, etc. Among these, Fe exists as an insoluble substance, and eNx repeatedly adheres and peels off on the fuel rod surface.
and Go are adsorbed and desorbed by the Fe cladding, and are activated while circulating in the reactor. Therefore, F brought in from the water supply system
It is known that by suppressing the concentration of e-cladding to about 1 pPb or less, activation of Co and Ni and adhesion to the reactor-subsystem piping can be suppressed, and the radioactivity level of the plant can be reduced.

In recent nuclear power plants, this is used to remove crud from condensate systems as a crud reduction measure.

The condensate purification system is redundant with a condensate demineralizer that removes ions and a condensate operation device that is installed upstream to remove crud, improving crud removal efficiency. Also.

Materials with good corrosion resistance are used for the oil system and condenser.

It has become common practice to reduce the amount of crud generated and to form a stable oxide film on the material surface of water supply system piping 9 equipment by injecting oxygen into the water supply system to prevent corrosion. As a result, the system configuration is such that the iron cladding concentration in the water supply system can be reduced to 1 pPb or less.

In plants with dual condensate purification systems.

A large amount of used ion exchange resin was generated from the condensate extraction equipment, and there was room for improvement in its storage and operating costs. For this reason, a non-auxiliary filter that generates less secondary waste is desired as a pre-filter for a condensate demineralizer, and a filtration device using a hollow fiber membrane element was developed as a non-auxiliary filter. . As a method for cleaning particulates adhering to hollow fiber membrane elements, there is a method of introducing compressed air and vibrating the hollow fiber membrane to remove the adhering particulates (Japanese Unexamined Patent Application Publication No. 5-1111)
3-108882, Japanese Unexamined Patent Publication No. 183906/1983).

The hollow fiber membrane element is made of a polymer compound with a pore size of 0.1μ.
It is one or more filtration bundles made by bundling a large number of porous polymer membranes with a structure in which micropores of m or less are uniformly arranged in the cross section,
It is built into a filter and has a structure that allows it to remove suspended solids from the supplied water.

However, experiments using filtration devices using hollow fiber membrane elements have shown that when hollow fiber membrane elements are used for long periods of time, suspended matter flows into and adheres to the micropores, and even when compressed air is introduced and vibrated,
Adhering fine particles cause clogging.

As a result, the initial pressure difference across the hollow fiber membrane element increases.

Furthermore, according to recent operating results of nuclear power plants,
As shown in Table 1, it was shown that the iron clad particle size distribution from the feedwater differed between plants.

In other words, in a filtration device using a hollow fiber membrane element, suspended matter flows into and adheres to the micropores of the hollow fiber membrane, and even if the hollow fiber membrane element is vibrated with compressed air, the hollow fiber membrane element is not effectively cleaned. Reduce the operational life of the filtration device due to the increase in the initial differential pressure of the membrane element, deteriorate the life of the hollow fiber membrane element, and reduce the secondary waste (hollow fiber membrane element and deposits that have reached the end of its life) due to the reduction in the number of years of use of the hollow fiber membrane element. cause an increase in

Here, the system configuration of a nuclear power plant that takes measures to reduce crud will be explained using FIG. 6.

The steam generated in the reactor 1 is recovered as condensate in the turbine condenser 10, and then passed through the condensate filtration device 12 and the condensate demineralizer 1.
3, is heated in the feed water heater 14, and is heated in the reactor 1.
will be collected. Water retained in the reactor 1 is purified by a purification device of the reactor purification system 4.

In the water supply system, 200 ppb or less of oxygen is injected from an oxygen injection system consisting of an oxygen cylinder 15 and an oxygen injection pipe 16, and an oxide film is formed on the surface of the water supply system piping and equipment to prevent corrosion.
Suppresses the generation of Fe cladding in the water supply system.

As a pre-filter for the condensate demineralizer 13 of the condensate purification system, in addition to the powder resin pre-coat type filtration device, a hollow membrane element equipped with a hollow membrane element as described in the example of the present invention as a non-auxiliary material type filter can be used. A thread membrane filtration device will be installed.

FIG. 7 shows a system diagram of a hollow fiber membrane filtration device equipped with a conventional hollow membrane element.

The stock solution containing suspended matter such as clad iron is introduced into the condensate filter 12 from the condensate inlet pipe 20 . The introduced stock solution is filtered by the hollow fiber membrane element 23 to remove suspended substances such as clad iron contained in the stock solution. The purified treated water comes from the condensate outlet pipe 21.

The condensate is led to the downstream condensate desalination tower. When suspended matter such as clad iron accumulates on the hollow fiber membrane element 23 in the condensate filter 12 and the filtration capacity decreases, compressed air from the air storage tank 25 is supplied from the air pipe 24 to the inside of the condensate filter 22. The suspension containing clad iron adhering to the surface of the hollow fiber membrane element 23 is peeled off and removed. The separated waste liquid containing suspended matter is separated.

The backwash liquid is discharged from the backwash waste pipe 27 to the backwash receiving tank 28 . −
In the backwashing St:P operation, if the peeling and separation of the suspended matter containing clad iron attached to the surface of the hollow fiber membrane element 23 is insufficient, the washing water 26 is supplied to the condensate filter 12, The compressed air from the air storage tank 25 is again forced into the condensate filter 22 from the supply air pipe 24, and the hollow fiber membrane element 23
The suspended matter containing clad iron attached to the surface of <J1!
have it removed.

Such backwashing operation is repeated 3 to 5 times.

Figure 8 shows that the condensate shows the structure of the filter body, and when the stock solution containing suspended matter such as clad iron is filtered for a long period of time, the pore size is 0.1.
A suspension containing clad iron infiltrates into the micropores of a porous polymer membrane having a structure in which micropores of micrometers or less are arranged in a cross section. If only the backwashing operation is performed using compressed air, suspended solids containing clad iron will enter and accumulate in the micropores of the hollow fiber membrane element 23, causing clogging, and the initial differential pressure of the hollow fiber membrane element 23 will increase. The hollow fiber membrane element must be cleaned because it will not be able to fully demonstrate its performance.

FIG. 4 is an example showing changes in the initial differential pressure of a hollow fiber membrane element over a period of one year. If the hollow fiber membrane element is backwashed only with compressed air, suspended solids containing clad iron will enter the micropores of the hollow fiber membrane, causing clogging, and the initial differential pressure of the hollow fiber membrane element will decrease within a year. Approximately 0.5 kg/cgf
Shows an upward trend.

As is clear from the measured examples of the condensate system clad iron particle size distribution of each plant shown in Table 1, the condensate system clad iron particle size distribution in nuclear power plants differs depending on the nuclear power plant. It is presumed that clad iron penetrates and accumulates in the micropores of the hollow fiber membrane, increasing the cause of clogging. Simply backwashing the hollow fiber membrane element with compressed air is insufficient to clean the hollow fiber membrane element, and cleaning the hollow fiber membrane sufficiently with chemical cleaning increases the initial differential pressure of the hollow fiber membrane element. It is necessary to prevent this and ensure filtration performance.

The hollow fiber membrane element cost is 10 condensate filters,
300 hollow fiber membrane elements per unit.

If one hollow fiber membrane element costs 50,000 yen, it will cost 1a50,000,000 yen. Therefore, extending the lifespan is expected to lead to cost reduction.

[Purpose of the invention]

An object of the present invention is to provide a cleaning method and a cleaning device for efficiently cleaning a hollow fiber membrane element of a condensate filtration device installed in a condensate system of a nuclear power plant using an organic acid aqueous solution.

[Summary of the invention]

In the method of the present invention, an organic acid aqueous solution is used to clean a hollow fiber membrane element used in a filtration device installed in a condensate system of a nuclear power plant to remove suspended matter containing iron cladding. It is characterized by In addition, a cleaning tank that contains an organic acid aqueous solution for cleaning hollow fiber membrane elements to clean these elements, and a gas supply device that sends bubble gas to the cleaning tank to promote cleaning in the cleaning tank.
-Nobuwa-1 A cleaning device including an organic acid aqueous solution supply device to a cleaning tank is provided.

Furthermore, in order to wash the hollow fiber membrane element, the condensate filter is used as a cleaning tank, and a device is provided to supply an organic acid aqueous solution for cleaning the hollow fiber membrane element to the condensate filter, which also serves as a cleaning tank. A cleaning device is obtained.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIG.

The condensate passing column 22 is equipped with a hollow fiber membrane element 23,
It is connected as part of a condensate system by a condensate inlet pipe 20 and a condensate outlet pipe 21. For cleaning the hollow fiber membrane element 23, an air storage tank 25, a compressed air supply pipe 24, and a backwash waste liquid pipe 2 are provided.
7, a backwash receiving tank 28, a hollow fiber membrane elm 31 attached to the condensate flow tower 22, and a waste liquid pipe 3 for cleaning waste liquid after cleaning with an organic acid.
The hollow fiber membrane element 23 is washed outside the condensate flow tower 22 system/Af.
t i (i).

A suspension solution containing clad iron in the reactor water is supplied to a condensate filter 22 from a condensate inlet pipe 20 .

The supplied stock solution is filtered by a hollow fiber membrane element 23 attached to a condensate filter 22 to remove suspended substances such as clad iron contained in the stock solution. The purified treated water is led from the condensate outlet pipe 21 to the condensate desalination tower downstream. If suspended matter such as clad iron accumulates on the hollow fiber membrane element 23 in the filter 22 and the purification capacity of the condensate decreases, the air storage tank 25
Compressed air is forced into the condensate filter 22 from the supply air pipe 24 to peel off and remove suspended matter containing clad iron adhering to the surface of the hollow fiber membrane element 23, thereby cleaning the hollow fiber membrane element 23. The suspended matter waste liquid containing clad iron is discharged from the backwash waste liquid pipe 27 to the backwash receiving tank 28.

As shown in FIG. 4, the hollow fiber membrane element 23 installed in the filter 22 accumulates suspended substances such as clad iron, and the purification capacity decreases by about 0. 3kg/c
The number of days required for the differential pressure d to rise is about 20 to 40 days, and during this period, the hollow fiber membrane element 23 is vibrated with compressed air to remove and clean the suspended solids containing clad iron. However, suspended matter containing clad iron enters and accumulates in the micropores of the hollow fiber membrane, and even if the hollow fiber membrane element 23 is repeatedly cleaned with compressed air two to three times, the hollow fiber membrane element is completely washed away. As a result of experiments, it was found that the suspended matter in the condensate filtration device cannot be sufficiently cleaned with compressed air alone, leading to clogging and the initial pressure difference of the hollow fiber membrane element increasing by approximately 0.5 kg/ffl. shows.

In the present invention, the organic acid aqueous solution 37 and the hollow fiber membrane element 23 supplied from the organic acid supply piping 31 to the cleaning tank 29 installed outside the system are treated with an organic aqueous solution having a stronger cleaning power such as clad iron than air or water. The hollow fiber membrane element 2 is removed from the condensate filter 22 at the time of regular inspection once a year using the compressed supply air pipe 24 from the air storage tank 25.
By incorporating 3 into the cleaning tank 29 and finishing with an organic oxidizing solution and compressed air, it is possible to easily clean the infiltrated deposits of clad iron in the micropores of the hollow fiber membrane of the hollow fiber membrane element 23, and remove the deposits caused by the decrease in filtration capacity. It is possible to prevent an increase in secondary waste by shortening the number of operating days and reducing the use of hollow fiber membrane elements by half.

Moreover, in order to check and inspect the state of damage, the condensate drainer 22 is
Hollow fiber membrane element 23 taken out from.

It becomes possible to wash the water outside the condensate filter 22 system.

Another embodiment of the present invention will be described with reference to FIG.

A state in which the hollow fiber membrane element 23 is installed in the condensate filtration tower 22 and the suspended matter containing clad iron is clogged by the infiltration and accumulation of the clad iron into the fine pores of the hollow fiber membrane. 3 shows a configuration in which an organic acid aqueous solution 37 is circulated from an organic acid supply tank 32 through an organic acid circulation pipe 34 by an organic acid supply pump 33 for cleaning.

When suspended matter containing clad iron enters the fine pores of the hollow fiber membrane and causes clogging, and the differential pressure of the hollow fiber membrane element 23 increases during operation of the condensate filtration device, the condensate An organic acid aqueous solution 37 is introduced from an organic acid supply tank 32 into the hollow fiber membrane element 23 attached to the passage column 22 using an organic acid supply pump 33, and an inert gas is supplied from an inert gas supply device such as air or carbon dioxide. Press in and perform backwash cleaning.

At this time, the turbidity of the cleaning waste liquid is measured with a turbidity meter installed in the organic acid supply tank 32, and a differential pressure indicator 35 is installed between the immersion inlet pipe 20 and the condensate outlet pipe 21 of the condensate filter 22. The cleaning of the hollow fiber membrane element is monitored by the method, and it is confirmed that the initial pressure difference due to clogging of the hollow fiber membrane element 23 is reduced.

Condensate filter 22. Condensate inlet pipe 20. Condensate outlet pipe 21, organic acid supply tank 32. Organic acid feed injection pump 33. The organic acid cleaning liquid such as the organic acid circulation pipe 34 and the cleaning water 26
is supplied and circulated and cleaned using the organic acid supply injection pump 33. In addition, an inert gas such as air or carbon dioxide gas is pressurized from an inert gas supply device to perform backwash cleaning, and the organic acid solution used for the cleaning is transferred to a backwash liquid receiving tank 28 via a backwash waste liquid pipe 27. be discharged.

Even if clad iron, etc. infiltrates and accumulates on the surface and micropores of the hollow fiber membrane during operation of the condensate filtration system, the hollow fiber membrane element can be removed from the system without being taken out, and without exposing the operating staff to radiation. The hollow fiber membrane element 23 can be easily washed, and the operational performance of the condensate filtration device can be improved.

〔Effect of the invention〕

According to the invention, JJ! Hollow fiber membrane elements of filtration equipment installed in child power generation plants can be efficiently cleaned.
This has the effect of improving the operational performance of the condensate filtration device, reducing the frequency of replacing hollow fiber membrane elements, and reducing secondary waste.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a filtration device equipped with a cleaning device according to the present invention, Fig. 2 is a system diagram of a filtration device equipped with another cleaning device according to the present invention, and Fig. 3 shows the amount of iron dissolved in an aqueous citric acid solution. Figure 4 is a diagram showing changes in excess pressure over time, Figure 5 is a diagram showing changes in excess pressure over time.
[1 is a diagram showing an example of the system configuration of a nuclear power plant, FIG. 6 is a system diagram of a conventional filtration device, and FIG. 7 is a diagram showing the structure of a condensate filter. 1... Reactor pressure vessel, 2... Reactor recirculation system, 3
...Reactor recirculation pump, 4...Reactor coolant purification system. 5... Reactor coolant purification system heat exchanger, 6... Reactor coolant purification system is a reactor, 7... Main steam system, 8... Water supply system. 9... Feed and condensate water recirculation system, 10... Turbine condenser. 11...Low pressure condensate pump, 12...Condensate filtration device. 13... Condensate demineralizer, 14... Feed water heater, 15.
...Oxygen cylinder, 16...Oxygen injection pipe, 20...Condensate inlet pipe. 21... Condensate outlet pipe, 22... Condensate filter, 23...
... Hollow fiber membrane element, 24 ... Supply air pipe, 25
... Air storage tank, 26 ... Water for cleaning, 27 ... Backwash liquid pipe, 28 ... Backwash liquid receiving tank, 29 ... Cleaning tank, 30 ... Washing liquid pipe, 31 ...・Organic acid supply piping, 32...Organic acid supply tank, 33...Organic acid supply injection pump, 34...Organic acid circulation pipe, 35...Differential pressure indicator, 36...Turbidity Total, 37...Organic acid aqueous solution.

Claims (1)

[Claims] 1. A method for cleaning a filtration device installed in a condensate system of a nuclear power plant to remove suspended solids containing iron cladding, a hollow fiber membrane filtration method in which a hollow fiber-like porous polymer membrane is bundled. A method for cleaning a nuclear power plant filtration device, which comprises cleaning an element with an organic acid aqueous solution. 2. In a cleaning device for a filtration device that is installed in a condensate system of a nuclear power plant and has a built-in hollow fiber membrane element in which hollow fiber-shaped porous polymer membranes are bundled to remove suspended matter containing iron cladding. , a cleaning tank that contains an organic acid aqueous solution for cleaning hollow fiber membrane elements to clean these elements, a gas supply device that sends bubble gas to the cleaning tank to promote cleaning in the cleaning tank, and an organic acid aqueous solution to the cleaning tank. A cleaning device for a nuclear power plant filtration device, characterized in that it is equipped with an acid aqueous solution supply device. 3. A filtration device that is installed in the condensate system of a nuclear power plant and includes a condensate filter that incorporates a hollow fiber membrane element in which hollow fiber-shaped porous polymer membranes are bundled to remove suspended solids containing iron cladding. A device for supplying an organic acid aqueous solution for cleaning the hollow fiber membrane element to the condensate filter that also serves as a cleaning tank and the condensate filter that also serves as a cleaning tank in the cleaning device. A cleaning device for a nuclear power plant filtration device, characterized by comprising: 4. A cleaning device for a nuclear power plant filtration device according to claim 3, characterized in that the cleaning device includes a gas supply device that feeds bubble gas into the cleaning tank to promote cleaning inside the cleaning tank.