JP2000218110A - Operation of condensed water filter apparatus in power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the stable operation of a power plant performing the quality treatment of supplied water by an oxygen treatment method and performing the filtering treatment of condensed water by a condensed water filter apparatus using a filter membrane by enhancing the iron removing capacity of the condensed water filter apparatus and reducing the load of a condensed water desalting apparatus of a rear stage. SOLUTION: A mixture of fine particles formed from a material selected from iron oxide, iron hydroxide, activated carbon, a cation exchange resin and a polymeric porous material are preliminarily applied to the filtering surface of a condensed water filter apparatus 80 before condensed water is passed through the condensed water filter apparatus 80. For example, a condensed water inlet valve 14 is closed while a precoating agent inlet valve 68 is opened and the precoating agent 70 in a precoating agent tank 62 is passed through the condensed water filter apparatus through a condensed water inlet piping 10 to perform precoating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a condensate filtration device in a power plant, and more particularly, to water quality treatment of feed water by an oxygen treatment method.
The present invention relates to a method of operating a condensate filtration device suitably used in a power plant that performs a condensate filtration process using a condensate filtration device using a filtration membrane.

[0002]

2. Description of the Related Art FIG. 6 shows an outline of a steam-condensation system of a general thermal power plant. The water is heated by the boiler to become high-temperature and high-pressure steam. After the steam performs expansion work in the turbine, it is cooled and condensed by the condenser to be condensed. This condensed water is treated by a condensate treatment device including a condensate filtration device and a condensate desalination device, and then is sequentially heated by a low-pressure feedwater heater and a high-pressure feedwater heater, and sent to the boiler again. The water used in the brackish water circulation system of such a power plant should be maintained at an appropriate water quality according to the plant type, pressure, temperature, etc. in order to avoid water quality problems such as corrosion and scale formation. is necessary.

[0003] In a plant of a thermal power plant, a volatile substance treatment method (AVT: Al
l Volatile Treatment) is generally applied and many plants still use this treatment. Current AVT
In addition to adding ammonia to the feed water to make the pH alkaline (pH = 9.0 to 9.6) and adding a little hydrazine, the deaerator and the hydrazine deaeration condition (oxygen removal) ), A protective film of iron oxide (Fe ₃ O ₄ : magnetite) is formed on the surface of a steel material such as a pipe to prevent corrosion.

[0004] On the other hand, in recent years, an oxygen treatment method, particularly a combined water treatment method (CWT: Combined Water Treatment) has been applied as a water quality treatment method for feed water instead of AVT. The current CWT adds ammonia to the feed water to make its pH alkaline (pH = 8.0-9.0), and injects a trace amount of oxygen, so that trivalent trivalent is added to the surface of steel materials such as piping. A protective film of iron oxide (α-Fe ₂ O ₃ : hematite) is formed to prevent corrosion.
Hematite has a lower solubility and a finer particle size than magnetite, so that the protective coating of hematite is smooth and dense and has a high anticorrosion effect. CW
FIG. 6 shows an application example of T. In this example, oxygen is injected into the feedwater at the condensate desalination device outlet and the deaerator outlet, and ammonia is injected into the feedwater at the low-pressure feedwater heater inlet. In addition, in addition to the above-mentioned CWT, a neutral water treatment method (NWT: Neutral Water Treatment) for neutralizing the pH of feedwater is used in the oxygen treatment method.
The NWT protective film has the same characteristics as the CWT protective film.

[0005] In a thermal power plant, AVT is used.
In addition to the water quality treatment of the feed water by CWT or CWT, the condensate treatment device performs the treatment as the condensate treatment in the system. Among them, the condensate filtration device is intended to remove suspended matter contained in condensate water, mainly to remove iron oxides (iron removal). As such a condensate filtration device, a pleated filter or the like is used. A filter using a hollow fiber membrane filter is used. In order to increase the area of the filtration membrane per unit volume of the filtration element, a pleated filter is formed by folding a filtration membrane made of non-woven fabric into a pleated shape to form a cylindrical shape having a large number of pleats. This filter has a structure reinforced with a plate or the like.

[0006]

Generally, in a power plant to which the CWT is applied, when the plant is shut down for periodic inspection and then restarted, the quality of the water supplied by the AVT in the early stage of the startup is generally high. The treatment is performed to form a protective coating of magnetite, and then, after the plant starts power generation, the water treatment method is switched to CWT, thereby facilitating the transfer to the protective coating of hematite.

In this case, when water quality treatment is performed by AVT in the early stage of plant startup, relatively large iron oxide particles having a particle diameter of 3 μm or more are 70 to 80% by weight of the total iron oxide particles. Occupy a degree. On the other hand, after the plant started power generation, the water treatment method was changed to CWT.
The iron oxide particles in the condensed water are finer than in the AVT operation, and the ratio of iron oxide particles having a particle diameter of 3 μm or more is reduced to about 50 to 60% by weight of the total iron oxide particles. The proportion of iron particles increases.

On the other hand, in the above-described condensate treatment apparatus, when the condensate filtration is performed by a condensate filtration apparatus using a pleated filter or a hollow fiber membrane filter, the pleated filter or the hollow fiber membrane filter is relatively inexpensive. Iron oxide particles with a large particle size can be captured, but iron oxide particles with a small particle size cannot be captured, so the iron removal performance of the condensate filtration device is good at the time of AVT operation at the initial stage of plant startup, but switched to CWT operation. Then, as a result, a phenomenon occurs in which many fine iron oxide particles leak into the treated water of the condensate filtration device, and the iron oxide particles flow into the downstream condensate desalination device.

[0009] Therefore, in a power plant that applies CWT and performs condensate treatment by a condensate filtration device using a pleated filter or a hollow fiber membrane filter, C
During the WT operation, the load on the ion exchange resin of the condensate desalination apparatus increases, and the differential pressure of the apparatus tends to increase. As a result, complicated washing operations of the condensate desalination apparatus are often required, and There has been a problem that the stable operation of the plant is hindered. In addition, there has been a problem that the amount of the cleaning waste liquid increases, the processing cost increases, and the burden increases economically.

The present invention has been made in view of the above circumstances, and performs water quality treatment of feed water by an oxygen treatment method such as CWT and condensate filtration using a filtration membrane such as a pleated filter or a hollow fiber membrane filter. In a power plant plant that performs condensate filtration by using a device, the iron removal performance of the condensate filtration device during operation of the oxygen treatment method is improved, and the load on the subsequent condensate desalination device is reduced. It is an object of the present invention to provide an operation method of a condensate filtration device capable of realizing stable operation of a plant.

[0011]

As a result of various studies to achieve the above object, the present inventors have found that fine particles of iron oxide, iron hydroxide, When pre-coating fine particles of activated carbon, cation exchange resin, or polymer porous material and then passing water through a condensate filtration device,
Even when the iron oxide particles in the condensate have a small particle size as in the case of WT operation, the iron oxide fine particles in the condensate are well captured by the filtration membrane of the condensate filtration device, and the condensate filtration device is removed. It has been found that iron performance is improved.

The present invention has been made on the basis of the above findings. In a power plant, a feed water quality treatment is carried out by an oxygen treatment method, and a condensate filtration treatment is carried out by a condensate filtration device using a filtration membrane. When performing, before passing the condensate water to the condensate filtration device, particulate iron oxide, iron hydroxide,
A condensate filtration device in a power plant plant, characterized in that one or a mixture of two or more selected from activated carbon, a cation exchange resin and a polymer porous material is precoated on a filtration surface of a filtration membrane of a condensate filtration device. Provide driving method.

[0013] The reason why the present invention improves the iron removal performance of the condensate filtration device is that fine and non-magnetic trivalent iron oxide that is often contained in condensate during CWT operation is
It is presumed that by precoating the fine particles on the filtration surface of the filtration membrane, the fine particles are adsorbed on the filtration surface by an electric adsorption action.

Hereinafter, the present invention will be described in more detail. In the present invention, the oxygen treatment method refers to the CWT described above.
Or NWT. Further, the operation method of the condensate filtration device according to the present invention is suitably used for a condensate filtration device using a pleated filter or a hollow fiber membrane filter, but the condensate filtration device is not limited thereto, and the present invention is not limited thereto. As other filters of the condensate filtration device to which the filter can be applied, a disc type filter or the like can be mentioned from the aspect of the filter shape, and a polymer membrane filter, a ceramic filter, a metal filter, a sintered metal And a carbon filter.

In the present invention, one or two or more kinds of fine particles of iron oxide, iron hydroxide, activated carbon, cation exchange resin and polymer porous material are formed on the filtration surface of the filtration membrane of the condensing filtration device. Pre-coat the mixture. In this case, α-Fe ₂ O ₃ , γ-Fe ₂ O ₃ , Fe ₃ O ₄ ,
Α-FeOOH, γ-Fe
OOH, powdered activated carbon as fine-particle activated carbon, granular activated carbon, strong-acid powdered cation-exchange resin as fine-particle cation exchange resin, weakly-acidic powder cation exchange resin, polyether as fine-particle porous polymer It is particularly preferable to use ether ketone (PEEK) powder.

When iron oxide or iron hydroxide is used as the fine particles, artificially synthesized iron oxide or iron hydroxide may be used. It is also possible to use the collected iron oxide or iron hydroxide. In this case, iron oxide or iron hydroxide collected from the backwash water may be used in combination with artificially synthesized iron oxide or iron hydroxide, or other fine particles.

In the present invention, the size of the fine particles used in the precoating and the amount of the fine particles are not particularly limited. Usually, the particle diameter of the fine particles is 1 to 100 μm, and the precoat amount of the fine particles is the amount of the fine particles coated on the filtration surface. Two
It is preferably 50 g / m ² .

In the present invention, as a means for pre-coating the filtration surface of the filtration membrane with fine particles, before the condensate is treated by a condensate filtration device, the fine particle-containing liquid in which the fine particles are suspended is subjected to condensate filtration. Means for passing the liquid through the apparatus can be suitably employed, but is not limited thereto.

After the precoating, the condensate filtration device maintains good iron removal performance for a certain period of time. However, while the filtration process is continued, the condensate filtration device gradually removes iron. Performance tends to decrease. Therefore, when the iron removal rate decreases, it is possible to temporarily stop the operation of the condensate filtration device and restart water flow after restoring the iron removal performance by newly precoating the fine particles on the filtration surface of the filtration membrane. preferable.

[0020]

FIG. 1 shows an example of a condensate filtration apparatus to which the present invention is applied. In the condensate filtration device 80 of this example,
2 indicates a filtration container. The filtration container 2 is manufactured by connecting the lower portion 3 and the upper portion 4 with a partition plate 5 interposed therebetween, and thus the inside of the filtration container 2 is connected to the lower chamber 6 by the partition plate 5. The upper room 7 is partitioned. A condensate inlet pipe 10 and a drain pipe 11 are connected to the lower chamber 6 of the filtration container 2, and a treated water outlet pipe 12 is connected to the upper chamber 7. The condensate inlet pipe 10 is provided with a condensate pump 13 and a condensate inlet valve 14, the drain pipe 11 is provided with a drain valve 15, and the treated water outlet pipe 12 is provided with a treated water outlet valve 16. On the upstream side of the treated water outlet valve 16 of the treated water outlet pipe 12,
The air vent pipe 17 in which the air vent valve 18 is interposed is connected. Further, a baffle plate 20 is provided below the lower chamber 6 of the filtration container 2.

A large number of pleated filters 22 are provided inside the filtration container 2. This filter 22
As shown in FIGS. 2 and 3, a cylindrical water collecting core 30 formed of a metal perforated plate such as a stainless steel punching plate or a synthetic resin perforated plate such as polypropylene provided on the innermost side, and The support net 3 includes a cylindrical support net 32, a filtration membrane 34, and a microspun bond 36 which are sequentially arranged in a multilayer shape on the outside.
2. A filtration body 38 is constituted by the filtration membrane 34 and the microspun bond 36. Micro spun bond 3
6 is a function of ensuring uniform water flow to the filtration membrane 34 and a function of fixing and holding the cake layer formed on the surface of the filtration membrane 34;
The filtration membrane 34 has a function of capturing insoluble substances in condensed water, and the support net 32 has a function of securing a water passage for permeated water of the filtration membrane 34 and a function of reinforcing the structural strength of the filtration membrane 34. On the outermost side, a cylindrical protector 40 made of a net made of stainless steel or synthetic resin is provided to protect the whole. End plates 44 and 46 are attached to both ends of the protector 40, and both ends of the filter body 38 are joined to the end plates 44 and 46 by an adhesive seal 42 in a watertight manner. In the figure, reference numeral 48 denotes a reinforcing ring of the core 30.

The support net 32, the filtration membrane 34, and the microspun bond 36 are each formed into a pleated shape and have pleats extending in the longitudinal direction. Filtration membrane 34
For the microspun bond 36, a polypropylene nonwoven fabric, a polyamide nonwoven fabric, a polysulfone film, or the like is used, and for the support net 32, for example, a polyethylene molded product is used. The aperture of the filtration membrane 34 can be appropriately selected depending on the application. Usually, for example, the aperture is 0.5 to several μm.
And the filtration area is about ² to 7 m ² .

In the condensate filtration device 80 of this embodiment, the three pleated filters 22 are connected in series, and the upper part of the upper pleated filter 22 is fixed to the partition plate 5. However, the number of connected pleated filters 22 may be two, four or more, and one long pleated filter may be used.

When condensate filtration is performed by the condensate filtration device 80 of this embodiment, condensate is introduced at a predetermined pressure from the condensate inlet pipe 10 into the lower chamber 6 of the filter vessel 2. As a result, the condensate flows from outside the pleated filter 22 to the protector 40.
And a micro-spun bond 36 to reach the filtration membrane 34, where the insoluble matter (mainly iron oxide) in the condensate is captured. The treated water after filtration passes through the support net 32 and the core 30, flows out of the filtered water outlet 50 formed in the upper end plate 46 through a hole (not shown) of the partition plate 5, and flows out to the outside. It is discharged out of the filtration container 2 through the pipe 12.

The structure of the pleated filter is not limited to the above example. That is, the essential requirement of the pleated filter according to the present invention is to provide a filtration membrane having a large number of pleats folded in a pleated shape, and to filter condensed water by the filtration membrane, and other configurations are appropriately selected. be able to. As another example of the pleated filter, as shown in FIG. 4, for example, a filter in which the fold of the filtration membrane is perpendicular to the axis of the core is exemplified. Although the condensate filtration device of the above example is of the upward flow type, it may be of the downward flow type.

When the present invention is applied to the condensate filtration device 80, for example, the precoat means 60 shown in FIG. The precoating means 60 includes a precoating agent tank 62 for storing a particle-containing liquid (precoating agent) 70 in which the above-mentioned fine particles are suspended, an inflow end at the precoating agent tank 62, and an outflow end at the condensing inlet pipe 10.
And a precoating agent injection pipe 64 connected to the downstream side of the condensate inlet valve 14, and a precoating agent injection pump 66 and a precoating agent inlet valve 68 interposed in the precoating agent injection piping 64.

When the above-mentioned fine particles are precoated on the filtration surface of the filtration membrane 34 of the condensate filtration device 80 by the precoating means 60 before the condensate is passed through the condensate filtration device 80, the condensate inlet valve 14 is set. The precoating agent inlet valve 68 is opened and the precoating agent injection pump 66 is operated to pass the precoating agent 70 in the precoating agent tank 62 to the condensate filtration device 80 through the condensate inlet pipe 10.

[0028]

EXAMPLES Using the condensate filtration device 80 shown in FIG. 1, experiments shown in the following Examples and Comparative Examples were performed. In this case, as the pleated filter 22 of the condensate filtration device, a filtration membrane 34 is used.
Used had an opening of 1 μm. The condensate passing through the condensate filtration device was condensed water at the time of CWT operation.

(Comparative Example: Conventional Method) The water flow rate is 0.25 m / h without precoating the pleated filter.
For about 500 hours. 500 at the start of water flow
After an hour, the iron concentration in the outlet water of the condensate filtration device was measured.

(Example 1) Prior to water flow, fine particles of Fe ₃ were applied to a pleated filter by a precoating means 60.
O ₄ was pre-coated. The precoat amount was 10 gFe / m ² as the amount of iron per unit film surface. Thereafter, water was passed for about 1000 hours at a flow rate of 0.25 m / h. At the start of water flow and after 1000 hours, the iron concentration in the outlet water of the condensate filtration device was measured.

(Example 2) Prior to the passage of water, a fine γ-F
e ₂ O ₃ was pre-coated. The precoat amount was 10 gFe / m ² as the amount of iron per unit film surface. Thereafter, water was passed for about 1000 hours at a flow rate of 0.25 m / h. At the start of water flow and after 1000 hours, the iron concentration in the outlet water of the condensate filtration device was measured.

(Embodiment 3) Prior to water passage, fine particles of α-F
eOOH was pre-coated. The precoat amount was 10 gFe / m ² as the amount of iron per unit film surface. afterwards,
Water was passed at a flow rate of 0.25 m / h for about 1000 hours. At the start of water flow and after 1000 hours, the iron concentration in the outlet water of the condensate filtration device was measured.

(Example 4) Prior to water flow, a pleated filter was pre-coated with fine-particle activated carbon (Powder Activated Carbon Diasorb F, Mitsubishi Chemical Corporation) by a pre-coating means 60. The precoat amount was 0.5 liter / m ² per unit film surface. Thereafter, water was passed for about 1000 hours at a flow rate of 0.25 m / h. Start of water flow and 100
After 0 hour, the iron concentration in the outlet water of the condensate filtration device was measured.

(Example 5) Prior to the passage of water, a cation-exchange resin in the form of fine particles (powder cation-exchange resin PC manufactured by Graver Co.)
H) was precoated. The precoat amount was 0.5 liter / m ² per unit film surface. After that, the water flow velocity is set to 0.
Water was passed at 25 m / h for about 1000 hours. At the start of water flow and after 1000 hours, the iron concentration in the outlet water of the condensate filtration device was measured.

Example 6 Prior to water passage, a pleated filter was pre-coated with a particulate polymer porous material (PEEK powder) by a pre-coating means 60. The precoat amount was 100 g / m ² per unit film surface. afterwards,
Water was passed at a flow rate of 0.25 m / h for about 1000 hours. At the start of water flow and after 1000 hours, the iron concentration in the outlet water of the condensate filtration device was measured.

FIG. 5 shows the above results. As shown in FIG. 5, before the condensate is passed through the condensate filtration device, fine particles of iron oxide, iron hydroxide, activated carbon, a cation exchange resin or a polymer porous material are pre-coated on the filtration surface of the filtration membrane. , CWT
It was confirmed that the iron removal performance of the condensate filtration device was maintained in a good state even when the number of iron oxide particles having a small particle size in the condensate increased as in operation.

[0037]

According to the present invention, the iron removal performance of the condensate filtration device during CWT operation can be improved, thereby reducing the load on the downstream condensate desalination device and reducing the load on the power plant. Stable operation can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a condensate filtration device to which the present invention is applied.

FIG. 2 is a partially cutaway front view showing an example of a pleated filter.

FIG. 3 is a partially developed perspective view of the filter.

FIG. 4 is a partially developed perspective view showing another example of the pleated filter.

FIG. 5 is a graph showing a relationship between a water passage time and an iron oxide removal rate in Examples and Comparative Examples.

FIG. 6 is a flowchart showing an outline of a steam-condensation system of a general thermal power plant.

[Explanation of symbols]

 2 Filtration Vessel 10 Condensate Inlet Pipe 12 Treated Water Outlet Pipe 22 Pleated Filter 34 Filtration Membrane 60 Precoat Means 62 Precoat Agent Tank 64 Precoat Agent Injection Pipe 66 Precoat Agent Injection Pump 68 Precoat Agent Inlet Valve 70 Precoat Agent 80 Condensate Filter

Continued on the front page F term (reference) 4D017 AA01 BA13 CA03 CA05 CA17 CB01 DA01 EA03 4D066 BA01 BB06 BB16 BB20 CA01 CA05 CA12

Claims (3)

[Claims] In a power plant, when a feed water quality treatment is carried out by an oxygen treatment method and a condensate filtration treatment is carried out by a condensate filtration device using a filtration membrane, a return to the condensate filtration device is carried out. Before passing water, one or a mixture of two or more selected from fine particles of iron oxide, iron hydroxide, activated carbon, a cation exchange resin, and a polymer porous material is filtered on a filtration surface of a filtration membrane of a condensate filtration device. A method for operating a condensate filtration device in a power plant, characterized by pre-coating. 2. The iron oxide is α-Fe ₂ O ₃ , γ-Fe ₂ O ₃ or Fe ₃ O ₄ , and the iron hydroxide is α-FeOOH or γ-Fe
The method for operating a condensate filtration device in a power plant according to claim 1, wherein the device is FeOOH. 3. As fine-particle iron oxide or iron hydroxide,
The method for operating a condensate filtration device in a power plant according to claim 1 or 2, wherein iron oxide or iron hydroxide collected from the backwash water of the condensate filtration device is used.