JPH08105995A - Condensate filter - Google Patents

Abstract

PURPOSE: To eliminate the need of removing a suspended substance contained in supernatant liquid in a tank to store a filtrated and separated suspended substance by adding an electrolytic substance to the tank. CONSTITUTION: Steam generated in a nuclear reactor 1 is condensed into condensate via a condenser 5 after driving a turbine 3 and a generator 4. The condensate, after fed from a condensate pump 7 to a condensate filter 11 and a condensate denitration device 14, is returned to the reactor 1 on the operation of a suction pump 16. When the suspended substance in the condensate arrested with the filter 11 amounts to the prescribed volume, a backwashing process begins. Liquid in the filter 11 containing the suspended substance due to the backwashing process is carried to a tank 25. Also, when the liquid held in the tank 25 reaches the preset volume, a valve 15 is opened and an electrolyte in an electrolyte tank 13 is added to the tank 25. As a result, the conductivity or pH value of the liquid can be increased. Thus, the coagulating sedimentation of the floating suspended substance can be improved, and the suspended substance can be properly precipitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter device, and more particularly to a condensate filter device suitable for filtering condensate of a nuclear power plant.

[0002]

2. Description of the Related Art For example, as a condensate purification treatment facility in a nuclear power plant, a condensate filtering device for removing impurities of a suspension mainly composed of iron rust component called clad in condensate, A condensate demineralizer is installed to remove ionic impurities such as cobalt ions and nickel ions. This is to prevent each impurity from being brought into the nuclear reactor and being activated by neutron irradiation in the nuclear reactor, and then adhering to the equipment, pipes, etc. around the nuclear reactor and increasing the radiation dose. is there.

FIG. 3 shows the system configuration of a nuclear power plant. The steam generated in the reactor 1 drives the turbine 3 and the generator 4 connected to the turbine 3, and then is condensed in the condenser 5 to be condensed water. This condensate is supplied from the condensate pump 7 to the condensate filter 11 and the condensate demineralizer 14, and then returned to the reactor 1 by the feed pump 16. As the condensate filter device 11, a precoat type filter device has been conventionally used in which a filter aid such as a powder ion exchange resin is precoated on an element and a suspension is separated and removed by a filter aid precoat layer. In recent plants, a hollow fiber membrane type filtration device that uses a hollow fiber membrane that does not use a filter aid as a filtration element is adopted.

FIG. 2 shows a schematic structure around a filter of a hollow fiber membrane type filtration device. Raw water that needs to be filtered is passed through the raw water inlet pipe 33 and the raw water inlet valve 34 to the filtration tower 2
The hollow fiber membrane is guided to the hollow fiber membrane 8 and is subjected to a filtration treatment with the hollow fiber membrane springed in the hollow fiber membrane filtration element 27, collected in the lid container 26, and sent to the downstream system through the treatment liquid outlet valve 29 and the treatment liquid outlet pipe 30. . When the amount of the suspension captured by the hollow fiber membrane reaches a specified amount, the hollow fiber membrane is backwashed. In backwashing the hollow fiber membrane, first, the bypass valve 31 is opened, the raw water inlet valve 34 and the treatment liquid outlet valve 29 are closed, and the condensate is bypassed from the condensate pump 7 to the condensate demineralizer 14. Next, the air inlet valve 40 is opened, and the hollow fiber membrane is vibrated by the low pressure air supplied from the lower air inlet pipe 32 to remove the suspended matter. The air used for this backwash is exhausted through the vent valve 37 and the vent pipe 38. Further, the retained liquid in the filtration tower 28 containing the suspension is transferred to the storage tank 25, and then the filtration tower 28 is put into operation in the reverse order of the isolation procedure described above. The suspension transferred to the storage tank 25 is stored in the storage tank 25.

[0005]

In the above-mentioned prior art, by repeating the operation of transferring the retained liquid to the storage tank 25 to the filtration tower 28 containing the suspension, the liquid containing the suspension accumulated in the storage tank 25 is repeated. When the amount exceeds the capacity of the storage tank 25, it is necessary to discard the supernatant of the storage tank 25 to another waste treatment system. However, the suspension contained in this supernatant is removed during the disposal process. It was necessary to do so, and equipment for that was also necessary.

[0006] An object of the present invention is to provide a condensate filtration device which eliminates the need to remove the suspension contained in the supernatant.

[0007]

In order to achieve the above object, the present invention uses a steam as a power source or a heat source, and then recovers a suspension of condensate condensed in a condenser by filtering the suspension. The water filter device is provided with a tank for storing the suspension separated by filtration, and an electrolyte substance is added to this tank.

[0008]

According to the present invention, by adding an electrolyte substance to a liquid containing a suspension component, the conductivity of the liquid or the p
Since H can be increased, it is possible to improve the flocculation / sedimentation property of the suspended suspension, and to reliably sediment the suspension. Therefore, it is possible to eliminate the process of removing the suspension contained in the supernatant.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the basic configuration of a nuclear power plant according to the present invention. The basic configuration including the reactor 1, the turbine 3, the condensate filter 11 and the condensate demineralizer 14 remains unchanged. That is, the steam generated in the reactor 1 drives the turbine 3 and the generator 4 connected to the turbine 3 and then is condensed in the condenser 5 to become condensed water, and this condensed water is condensed from the condensate pump 7. After being supplied to the water filtering device 11 and the condensate demineralizing device 14, the water is returned to the reactor 1 by the water supply pump 16. The configuration around the condensate filtering device 11 does not change as shown in FIG. Further, when the suspension in the condensate captured by the filtration tower 28 of the condensate filtration device 11 reaches a specified amount, the backwashing is performed and the method is not changed. Characteristically, the conductivity and pH are stored in the storage tank 25 that temporarily stores the backwash waste liquid.
In order to adjust the above, or to add an anionic polymer flocculant, equipment for adding an electrolyte substance is provided. That is, the electrolytic solution tank 13 for accumulating the electrolytic substance is connected to the storage tank 25 through the pipe and the valve 15.

Next, a method for precipitating a suspension in the backwash water in the backwash water receiving tank will be described. By backwashing the filtration tower 28, the retained liquid in the filtration tower 28 containing the suspension is
When transferred to the storage tank 25 and the amount of the retained liquid in the storage tank 25 reaches a certain amount, the valve 15 is opened and the electrolyte solution in the electrolyte solution tank 13 is added to the storage tank 25. As will be described later, this addition amount is adjusted by opening / closing the valve 15 so as to be an optimum amount. The suspended components in the storage tank 25 are mainly iron rust components generated by the corrosion of steel materials forming the equipment and piping of the condensate system of the power plant in contact with the condensate, and the chemical form thereof is Fe. Iron oxides of ₃ O ₄ and Fe ₂ O ₃ , and FeO
It is an iron hydroxide of OH. Condensate in a nuclear power plant has few impurities and its water quality is close to that of pure water. Therefore,
By backwashing the filtration tower 28, the liquid retained in the storage tank 25 transferred from the filtration tower 28 also has a quality close to that of pure water, its conductivity is low at about 1 μS / cm, and its pH value is around 6. . Under such conditions, FeOOH which is an iron hydroxide
Is dispersed in the liquid in a colloidal state, and sedimentation due to gravity is less likely to occur. This FeOOH is stored in the storage tank 25 as follows.
By controlling the water quality of the liquid inside, the colloid can be aggregated and settled.

First, a method for controlling the conductivity of the liquid in the storage tank 25 will be described. The electrolyte substance put in the electrolyte liquid tank 13 is not particularly limited as long as it is added to the liquid to improve the conductivity, but for example, an aqueous solution of sodium sulfate (Na ₂ SO ₄ ) is used. While appropriately checking the conductivity of the liquid in the storage tank 25, the valve 15 is opened, and the Na ₂ SO ₄ aqueous solution in the electrolyte solution tank 13 is added to the storage tank 25.
When the conductivity of the liquid in 5 reaches 30 μS / cm or more, the valve 15 is closed. In this case, for example, when the conductivity of the liquid in the storage tank 25 is set to about 50 μS / cm, Na ₂ SO _{4 of} about 30 ppm in concentration in the storage tank 25 may be added. FIG.
7 is a graph illustrating the effect of increasing the conductivity of the liquid in the storage tank 25. The horizontal axis of this figure represents the passage of time, and represents the elapsed time after the addition of the electrolyte substance at time 0. The vertical axis represents the iron concentration in the supernatant liquid in the storage tank 25. As a comparison, curve A in the graph shows the case where no electrolyte substance is added, and curves B, C, D and E show the conductivity of the liquid in the storage tank 25 of 5 μS / cm and 10 μS / cm, respectively. , 30μS / cm and 50μS /
The case is cm. If no electrolyte material is added,
Although the iron component FeOOH is floating in the supernatant, this precipitation is promoted by adding an electrolyte substance to increase the conductivity. The broken line in the figure shows the target iron concentration in the supernatant of 100 ppm or less, and the range within 3 days of elapsed time. As a result, it was confirmed that when the conductivity was set to 30 μS / cm or more, the iron component was efficiently precipitated in a short time, and it was found that the iron component was within the target range.

Next, a method for controlling the pH of the liquid in the storage tank 25 will be described. The electrolyte substance to be added to the electrolyte liquid tank 13 is one that is added to the liquid to raise the pH,
That is, there is no particular limitation as long as it is an alkaline electrolyte substance, but, for example, an aqueous solution of sodium hydroxide (NaOH) is used. The valve 15 is opened while appropriately checking the pH of the liquid in the storage tank 25, the NaOH aqueous solution in the electrolyte solution tank 13 is added to the storage tank 25, and the valve 15 is closed when the pH of the liquid in the storage tank 25 reaches 8 or more. . In this case, for example, when the pH of the liquid in the storage tank 25 is set to 8, the concentration in the storage tank 25 is 4 ppm.
It is sufficient to add about NaOH. FIG. 5 is a graph for explaining the effect of increasing the pH of the liquid in the storage tank 25. The horizontal axis of this figure represents the passage of time, and represents the elapsed time after the addition of the electrolyte substance at time 0. The vertical axis represents the iron concentration in the supernatant liquid in the storage tank 25.
As a comparison, a curve F is a case where the pH is about 6 when the electrolyte substance is not added, and a curve G is a case where the pH of the liquid in the storage tank 25 is 8 by adding the electrolyte substance.
The broken line in the figure is the target iron concentration in the supernatant, which is 100 ppm.
The following shows the range and the elapsed time within 3 days. As a result, the iron component FeOOH floats in the supernatant liquid when no electrolyte substance is added, but when the pH is adjusted to 8 by adding the electrolyte substance, the iron component can be efficiently precipitated in a short time. It was confirmed and found to be within the target range.

Further, a method of adding an anionic polymer flocculant as an electrolyte solution in the storage tank 25 will be described.
A solution of an anionic polymer coagulant is used as an electrolyte substance to be placed in the electrolyte solution tank 13. The valve 15 is opened, the anionic polymer flocculant in the electrolyte solution tank 13 is added, and the valve 15 is closed when the concentration in the storage tank 25 reaches several ppm. FIG. 6 is a graph illustrating the effect when an anionic polymer flocculant is added to the storage tank 25. The horizontal axis of this figure represents the passage of time, and represents the elapsed time after the addition of the anionic polymer flocculant at time 0. The vertical axis represents the iron concentration in the supernatant liquid in the storage tank 25. Curve J in the graph is the case where the electrolyte substance is not added, and curve H is the case where 1 ppm of the anionic polymer coagulant is added for comparison. The broken line in the figure shows the target iron concentration in the supernatant of 100 ppm or less, and the range within 3 days of elapsed time. As a result, when the anionic polymer flocculant was not added, the iron component FeOOH was suspended in the supernatant liquid, but when this was added, it was confirmed that the iron component sedimented efficiently in a short time, It was found to be within the target range.

[0015]

According to the present invention, the suspension components filtered and separated by the condensate filter can be reliably settled at the bottom of the storage tank. Therefore, when the supernatant water of the storage tank is discarded, the suspension components are treated. Is unnecessary. Therefore, since the equipment for this purpose can be deleted, the scale of the equipment can be reduced and the equipment cost can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a nuclear power plant system of the present invention.

FIG. 2 is a diagram showing an outline of a system around a condensate filtering device.

FIG. 3 is a diagram showing an outline of a conventional nuclear power plant system.

FIG. 4 is a graph showing the relationship between conductivity and the concentration of supernatant water suspended matter.

FIG. 5 is a graph showing the relationship between pH and the concentration of supernatant water suspended matter.

FIG. 6 is a diagram showing the relationship between the addition of an anionic polymer flocculant and the concentration of supernatant water suspended matter.

[Explanation of symbols]

1 ... Reactor, 3 ... Turbine, 4 ... Generator, 5 ... Condenser,
7 ... Condensate pump, 11 ... Condensate filter, 13 ... Electrolyte tank, 14 ... Condensate demineralizer, 15 ... Valve, 16 ... Water pump, 25 ... Storage tank, 26 ... Lid container, 27 ... Hollow fiber membrane Filtration element, 28 ... Filtration tower, 29 ... Treatment liquid outlet valve, 30
Treatment liquid outlet pipe, 31 ... Bypass valve, 32 ... Lower air inlet pipe, 33 ... Raw water inlet pipe, 34 ... Raw water inlet valve, 37 ... Vent valve, 38 ... Vent piping, 40 ... Air inlet valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Rinzo Yoshikawa 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (4)

[Claims] 1. After using steam as a power source or a heat source,
In a condensate filtering device for filtering a suspension in condensed water condensed in a condenser, a tank for storing the suspension separated by filtration is provided, and an electrolyte substance is added to the tank. Condensate filter device. 2. The condensate filter according to claim 1,
A condensate filtration device, characterized in that the conductivity of water in the tank is controlled to 30 μS / cm or more. 3. The condensate filter according to claim 1,
A condensate filtration device, wherein the pH of water in the tank is controlled to 8 or more. 4. The condensate filtration device according to claim 1,
A condensate filtration device, wherein an anionic polymer flocculant is added as the electrolyte substance.