JPH0811228B2 - How to operate the plant - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for operating a plant, and more particularly to a method for operating a hollow fiber membrane filter for purifying condensed water.

[Conventional technology]

In the conventional condensate purification equipment in a nuclear power plant, it is common to arrange a precoat type filter and a bed type desalinator in the condensate treatment system. An example of this is shown in FIG.

In FIG. 2, the steam 2 generated in the nuclear reactor 1 rotates the steam turbine 3 to generate electric power in the generator 4, then enters the condenser 5, and is cooled by the seawater 6 to become the condensed water 7. This condensate contains solid and ionic impurities (mainly iron oxide) due to corrosion of pipes, etc. These impurities should be added to improve the safety and reliability of the power plant. Need to be removed. Therefore, the precoat type filter 16 and the bed type demineralizer 10 are installed in the flow path from the condenser 5 to the reactor 1 via the condensate pump 8 to form a condensate treatment system. As shown in FIG. 3, the precoat filter 16 includes a large number of cylindrical filtration elements contained in the filtration tower 17.
18 is precoated with a powdery ion-exchange resin in a layered manner, and condensate is passed through this precoated layer for the purpose of filtering a solid product. The demineralizer 10 is a column filled with a granular ion-exchange resin, and its purpose is to remove ionic impurities, especially chlorine ions when seawater leaks from the condenser 5.

Condensate treatment facilities have contributed significantly to the reduction of radioactivity in nuclear power plants. However, the precoat filter 16 uses powdery ion exchange resin as the precoat material,
Since this is discarded, the increase in the amount of radioactive waste due to waste resin has become a problem.

Therefore, in recent years, attention has been paid to the application of a filter that does not use a precoat material, particularly to a hollow fiber membrane filter.
For example, there are known examples in JP-A-49-9767, JP-A-56-76208 and JP-A-59-4403, but as shown in FIG. 4, a hollow shape having an outer diameter of about 1 mm is used. The hollow fiber membrane module 22 in which thousands of the membranes 21 are packed is packed in about 100 filtration towers 17. The surface of the hollow fiber membranes 21 has many fine pores of about 0.1 μm. On this side, solid impurities in the condensate are removed.

 19 is a water inlet and 20 is a water outlet.

[Problems to be solved by the invention]

In this way, the hollow fiber membrane filter captures solids directly on the membrane surface, so unlike the precoat filter that captures solids via the precoat material, there is no problem that the precoat material is generated as waste. is there.

However, as shown in FIG. 5, depending on the type of solid matter, it may stick to the membrane surface and block the pores of the membrane because the solid matter is directly captured. In some cases, the film could not be peeled off or removed from the film surface. In FIG. 5, 23 is a hollow fiber membrane, 24 is a membrane pore, and 25 is a membrane clogging substance. If the washing operation is not carried out well, the initial differential pressure of the hollow fiber membrane filter rises, resulting in an increase in the frequency of membrane washing due to an increase in the filtration differential pressure increasing rate, which necessitates replacement of the membrane or washing of chemicals. There was a problem to do.

An object of the present invention is to provide a plant operating method capable of realizing a hollow fiber membrane filter with less membrane clogging without increasing the amount of waste from the hollow fiber membrane filter.

[Means for solving problems]

The above-mentioned object is a method of operating a plant for removing impurities in condensate using a hollow fiber membrane filter, and before the start-up operation of the plant, on the surface of the hollow fiber membrane filter, as a precoat material, iron oxide or iron hydroxide. It is achieved by pre-coating about 1 g / m ² for operation.

[Action]

A solid substance that adheres to the membrane of the hollow fiber membrane filter and easily clogs the pores of the membrane is an amorphous amorphous / adhesive substance, or a substance with a relatively small particle size close to the pore size of the membrane. It is known from the past filtration tests that there is a small amount of iron hydroxide,
Oil and organic matter are examples. In the condensate of a nuclear power plant, the presence of these substances in the condensate is almost limited to the time when the operation is resumed from the suspended state due to periodic inspections, etc. Very few promoters.

Therefore, as in the present invention, by pre-coating the surface of the hollow fiber membrane filter with a pre-coating material before the start-up operation of the plant, the pre-coating material is present at a time when many solid matters that are clogging promoting substances are present in the condensate. Since the solid matter can be captured and the solid matter can be prevented from reaching the membrane surface of the hollow fiber membrane filter, the membrane clogging of the hollow fiber membrane filter can be effectively suppressed. Further, by limiting the precoating operation at the time when the precoating is necessary, it is possible to suppress the increase in the amount of waste due to the precoating material as much as possible.

Furthermore, 1 g / m of iron oxide or iron hydroxide as a precoat material
By precoating about ² pieces, the solid matter can be efficiently trapped with a small amount of the precoat material by utilizing the excellent solid matter trapping ability of iron oxide or iron hydroxide. Details of this effect will be described later with reference to FIG.

Further, since iron oxide or iron hydroxide has a good releasability, it is possible to prevent the precoat material itself from clogging the hollow fiber membrane filter when cleaning the hollow fiber membrane filter.

〔Example〕

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

The steam 2 generated in the nuclear reactor 1 rotates the steam turbine 3 to generate electric power in the generator 4, then enters the condenser 4, and is cooled by the seawater 6 to become the condensed water 7. Condensate 7 is supplied by a condensate pump 8 to a hollow fiber membrane filter 9 and a demineralizer 10 that form a condensate purification system, and is purified and supplied to the reactor 1 as feed water 11.

A precoat material injection pipe is connected to the upstream side of the hollow fiber membrane filter 9, and an agitator is installed in the precoat material tank 12.
The precoat material 13 that has been stirred in 14 is precoated
Send in at 15.

The precoat material is injected into the condensate during the pre-startup purification operation of the plant and the stoppage of the plant immediately before the start-up operation or during the start-up operation. FIG. 6 shows a state in which a layer of the precoat material is formed on the outer surface of the hollow fiber membrane. Even if the membrane clogging substance is contained in the condensate during the pre-startup purification operation or the start-up operation, it is captured by the layer of the precoat material 13, so that the membrane clogging material can be prevented from reaching the membrane surface as much as possible. The film clogging can be reduced as much as possible. If the plant operation becomes steady, the film clogging substances in the condensate will also decrease, so the normal method, that is, the method of directly capturing the solids with the film, is sufficient, and the increase in the amount of waste due to the precoat material is almost a problem. I won't.

The particle size of the precoat material is larger than the pores of the film,
μm to 10 μm is desirable, and it is preferable that it has compression resistance and is crystalline. For example, crystalline iron oxides Fe ₂ O ₃ and Fe ₃ O ₄ can be cited.

If sludge (mainly iron oxide and iron hydroxide) generated by washing the hollow fiber membrane filter is used as the precoat material, the amount of waste is not increased at all.

FIG. 7 shows the result of an experiment conducted using the driving method according to the embodiment of the present invention. The hollow fiber membrane filter used for the test was a hollow fiber membrane with an outer diameter of 1.2φ, an inner diameter of 0.7φ, and a length of 2 m.
It was a module of 3 m ² , and the filtration flow rate was 0.2 m / h. The solid matter in the simulated condensate is assumed to be in the actual plant operation, and amorphous iron hydroxide Fe (OH) ₃ , 0.2 μm,
Crystalline iron oxide Fe ₂ O ₃ , 1 μm was used as a stationary state. As a result, the relationship between the amount of trapped solids and the increase in the filtration pressure difference and the recovery property of the filtration pressure difference after washing were evaluated. In the case of the conventional example, if the solid matter assumed at the time of start-up is captured, the increase in the filtration differential pressure is large, and the solid matter assumed at the time of steady state has a small filtration differential pressure. It was washed with air bubbling and water backwashing since reaching the washing setting pressure rise 0.3 kg / cm ^2, in the conventional example than at the start of operation 0.
An initial differential pressure increase of 15 kg / cm ² was observed, and it is speculated that the pores of the membrane were blocked by the assumed amorphous iron hydroxide at startup. Next, in the case of this example, crystalline iron oxide Fe ₂ O ₃ , 1 μm was pre-coated with 1 g Fe / m ² as a pre-coating material before the start of operation. Although it was the same, the recovery of the filtration differential pressure after washing was very good,
It was clarified that the precoating of Fe ₂ O ₃ had a remarkable effect in preventing the film clogging by the solid matter assumed at the time of startup.

A method of injecting a precoat material during operation, that is, a body feed method was also tried, but it was found that the same effect as that of the precoat method before operation was obtained, and that any method can be applied.

〔The invention's effect〕

According to the present invention, when a large amount of solid substances that are clogging-promoting substances are present in condensate, the solid substances are efficiently captured by a small amount of iron oxide or iron hydroxide (precoat material), Since it is possible to prevent the hollow fiber membrane filter from reaching the membrane surface, it is possible to effectively suppress the membrane clogging of the hollow fiber membrane filter.

Further, by limiting the precoating operation to the time when the precoating is necessary, it is possible to suppress the increase in the amount of waste due to the precoating material as much as possible.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, FIG. 2 is a system diagram of an example of condensate purification equipment of a nuclear power plant, FIG. 3 is a structural diagram of a precoat filter, and FIG. 4 is a hollow fiber membrane filter. FIG. 5, FIG. 5 is an explanatory view of the clogging of the membrane, FIG. 6 is an explanatory view of the clogging prevention effect of the membrane according to the present invention, and FIG. 7 is a diagram showing the effect of one embodiment of the present invention. . 1 ... Reactor, 3 ... Steam turbine, 4 ... Generator, 5
…… Condenser, 8 …… Condensate pump, 9 …… Hollow fiber membrane filter, 10 …… Salting machine.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Ohsumi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (56) References JP-A-52-103384 (JP, A) JP-A-60-225612 (JP, A) JP-A-61-181506 (JP, A)

Claims (7)

[Claims] 1. A method of operating a plant for removing impurities in condensate using a hollow fiber membrane filter, wherein iron oxide or hydroxide is used as a pre-coating material on the surface of the hollow fiber membrane filter before starting the plant. 1 g / m ^{2 of} iron
A method of operating a plant, which is characterized by pre-coating and operating. 2. The method of operating a plant according to claim 1, wherein the "before the start-up operation" is a time when the plant is stopped immediately before the start-up operation. 3. The method for operating a plant according to claim 1, wherein the "before start-up operation" is a pre-start-up cleaning operation. 4. The method of operating a plant according to claim 1, wherein "before the start-up operation" means a pre-start-up cleaning operation and a plant stop immediately before the start-up operation. 5. A method for operating a plant according to claim 1, further comprising the step of applying the precoat during the start-up operation. 6. The method for operating a plant according to claim 1, wherein the precoat material is a particulate material having a particle size in the range of 1 μm to 10 μm. 7. The method for operating a plant according to claim 1, wherein the precoat material is produced by an iron electrolysis method.