JPH0295704A - Starting-up method for steam plant and condenser adopted therefor - Google Patents

Abstract

PURPOSE:To save power required for starting-up of a plant by providing an air rupture unit which is freely opened and closed in a condenser so as to device space thereof into upper and lower parts, and opening/closing the air rupture unit according to start and stoppage of the plant. CONSTITUTION:A condenser 10, to which steam is introduced after the work at a steam turbine 9 of a combined cycle generation plant and the operation of a generator E, condenses the steam by means of a cooling water in a cooling water pipe 11, and stores the condensed water in a condensed water reservoir 13. An air rupture unit 25 composed of an air rupture valve 22 and an air rupture plate 23 is arranged inside the condenser 10. The cooling water pipe 11 and a cooling capillary bundle 12 are arranged in an upper space A partitioned by the air rupture unit 25, while an adjust valve 21 is connected to a lower space B. At the stoppage of the plant, the air rupture valve 22 is entirely closed before vacuum is broken so that both spaces A and B are partitioned completely.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for starting up a steam power plant and a condensing device used in the method, and particularly relates to a method for degassing condensate at the time of starting up. This invention relates to a method for starting a steam turbine brand that can be shortened and a condenser used in the method.

(Prior Art) FIG. 4 shows a conventional combined cycle power plant. In the figure, air pressurized by a compressor 1 is introduced into a combustor 2, and the gas combusted here performs work in a gas turbine 3 before being introduced into a heat recovery boiler 4. A steam pipe 5 is disposed within the heat recovery boiler 4, into which water is introduced through a water supply pump 6 and a steam drum 7, and this water recovers the thermal energy of the exhaust gas and becomes steam. Note that the exhaust gas after heat recovery is released into the atmosphere through the duct 8.

The steam from which the thermal energy has been recovered is introduced into the steam turbine 9, where it does work and turns the generator E, and then introduced into the condenser 10. A cooling water pipe 11 and a cooling thin tube bundle 12 are arranged in the condenser 10, and the steam that has done work in the steam turbine 9 is condensed by the cooling water introduced into the cooling water pipe 11, and becomes water and condenses. The water is stored in the water reservoir 13. Note that the non-condensable gas in the steam in the condenser 10 is discharged to the atmosphere through the non-condensable gas extraction device 15.

Condensate from the condensate reservoir 13 is discharged by a condensate pump 16 and introduced into a steam turbine gland steam condenser 17, where the gland leak steam extracted through a gland steam pipe 18 is condensed. Further, the condensate that has passed through the steam turbine grand steam condenser 17 passes through the condensate pipe 19 and reaches the feed water pump 6, where it becomes high-pressure condensate and is sent to the heat recovery boiler 4 as described above. Further, a part of the condensate that has passed through the gland steam condenser 17 is sent to the condenser 10 via a regulating valve 21 installed in the middle of the recirculation system piping 20 and circulated within the circulation system again.

(Problems to be Solved by the Invention) However, in this type of boiler, there is a problem in that the inner surface of the steam pipe 5 in the heat recovery boiler 4 is corroded during operation.

In order to suppress this corrosion, conventionally, during normal operation, 71)
l) The oxygen concentration in the water supply is limited to 80 ppb or less at startup. Here, 7pp during normal operation
For the following items, the condensate from the condenser 10 is circulated through the recirculation system piping 20 and the regulating valve 21 and degassed within the condenser 10, or the non-condensable gas extractor 15 is used to degas the condensate. This is fully achieved by

However, it cannot be said that s o I) pbb or less at the time of start-up has been sufficiently achieved. Therefore, the oxygen concentration in the condensate is about 10,000 ppb.At the time of startup, this oxygen concentration is degassed in the condenser 10,
Alternatively, deaeration using the non-condensable gas extraction device 15 would take too long.

Furthermore, plant operations in recent years have been switching from base load operation to DSS operation, which involves repeated startup and shutdown every day.
Therefore, if degassing takes a long time, not only will it not be possible to meet the urgent demands of the power system, but also a large amount of power will be consumed for degassing, which is not preferable.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional techniques, shorten the deaeration time at startup, and reduce the power required for deaeration at the same time as starting a steam power plant. An object of the present invention is to provide a method and a condenser for use in the method.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object 1), the present invention provides a method for starting a steam power plant comprising a condenser that condenses steam produced by a steam turbine and converts it into condensation. In the above condenser, an air shutoff device is provided which can be opened and closed to partition the inside of the condenser into two spaces: an upper space that accommodates the cooling tube bundle and a lower space that communicates with the condensate reservoir, and when the plant is stopped, , This isolation device isolates the upper space and the lower space to maintain a vacuum in the lower space, and when starting up the plant, after the upper space is evacuated, the above isolation device shuts off the upper space and the lower space. Another invention is to connect a drain discharge pipe with an on-off valve in the middle to the space above the condenser, and when starting up the plant. , the above-mentioned opening/closing valve is opened to discharge the drain in the upper space and the upper space is evacuated, and then the upper space and the lower space are made to communicate with each other by the above-mentioned shutoff device, and others. In the invention, inside the condenser,
Another invention is characterized in that it is provided with an air blocking device that can be opened and closed to partition into two spaces: an upper space that accommodates a bundle of cooling thin tubes and a lower space that communicates with a condensate reservoir.
The present invention is characterized in that a drain discharge pipe having an on-off valve incorporated therein is connected to the space above the condenser.

(Function) According to the present invention, when the plant is stopped, the upper space and lower space within the condenser are partitioned off by the air blocking device. Then, even if the vacuum in the upper space is broken and air flows into the space, and the oxygen concentration in the condensate or drain that remains there increases, in the lower space the same level as before in plant operation will be maintained. A vacuum is maintained, so even if the plant is stopped, the increase in oxygen concentration in the condensate in the space below is suppressed. Therefore, when starting up the plant, after maintaining the vacuum in the upper space, if the upper space and the lower space in the condenser are communicated with each other by an air cutoff device, the oxygen concentration of the condensate in the lower space can be reduced. Since this is kept low, the oxygen concentration in the condensate at startup is kept low, and the time and power required to degas this oxygen can be saved.

According to another invention, when starting up the plant, the on-off valve is opened and the vacuum in the upper space is ensured while draining condensate or drain from the upper space through the drain discharge pipe. After this vacuum is maintained, if the upper space and lower space in the condenser are communicated with each other by an air blocking device, the condensate or condensate with a high oxygen concentration remaining in the upper space will be discharged to the outside. Since there is no leakage into the lower space at the same time as the rain space is connected, and the oxygen concentration of condensate in the lower space is kept low, the oxygen concentration of condensate at startup can be kept even lower. , the time and power for degassing this oxygen can be significantly reduced.

(Example) Hereinafter, an example of a method for starting up a steam power plant according to the present invention and a condenser used in the method will be described in FIGS. 1 to 3, in which the same parts as in FIG. This will be explained with reference to the figures. Note that the same constituent parts as those of the conventional example shown in FIG. 4 have already been explained, so their explanation will be omitted.

In FIG. 1, 10 indicates a condenser. Inside the condenser 10, an air cutoff device 25 consisting of an air cutoff valve 22 and an air cutoff plate 23 is provided. In the upper space A partitioned off by the air blocking device 25, the cooling water pipe 11 and the cooling thin tube bundle 12 are arranged as in the conventional case, and in the lower space B communicating with the condensate reservoir 13, a regulating valve 21 is arranged.
is connected.

Next, the operation of this embodiment will be explained.

When this plant shifts from shutdown to startup, the oxygen concentration in the condensate is required to be 80 ppb or less, as described above. However, conventionally, when the plant is stopped, the vacuum inside the condenser 10 is broken, so oxygen flows into the condenser 10, and the oxygen concentration in the condensate is about 100.
00 ppb.

Therefore, according to this embodiment, complete destruction of the vacuum inside the condenser 10 is prevented in order to suppress the increase in oxygen concentration.

That is, when the plant is stopped, the air cutoff valve 22 is fully closed before the vacuum is broken, and the cooling capillary tube bundle 1 is closed.
The upper space A that accommodates the condensate 2 and the lower space B that communicates with the condensate reservoir 13 are completely cut off. After that, the cooling capillary tube bundle 1
Only the upper space A side that accommodates the air conditioner 2 is broken to atmospheric pressure, and the inside of the lower space B partitioned off by the air cutoff device 25 is maintained at a vacuum. Therefore, the plant is stopped and the non-condensable gas extraction device 15, the circulating water pump (not shown),
Even if the condensate pump 16 is stopped, the oxygen concentration contained in the condensate in the condensate reservoir 13 and condenser 10 does not increase, and is maintained at the level 71) l) b during operation as described above. .

Furthermore, when starting up the plant, the non-condensable gas extraction device 15, circulating water pump (not shown), and condensate pump 16 are started to supply condensate to the steam turbine grand steam condenser 17, A turbine gland seal recovers the return steam of the steam to prevent air from flowing into the steam turbine 9,
The vacuum inside the condenser 10 is increased. After that, 0. 08
When a high vacuum on the order of ata is obtained and the air is sufficiently exhausted, the air cutoff valve 22 is fully opened to allow communication between the upper and lower spaces. At this time, the saturation state of 0.08 ata is approached and the oxygen concentration may become 71) ppb or less, but the oxygen concentration required at startup of 80 ppb or less is sufficiently secured. In addition, in actual operation, the plant operation starts immediately after opening the air cutoff valve 22, so 7pI)b
It is also possible to supply the following condensate water:

FIG. 2 shows another embodiment.

In this embodiment, a drain discharge pipe 26 is connected to an upper space A partitioned off by an air cutoff device 25, and an on-off valve 27 is connected in the middle of this drain discharge pipe 26. The other configurations are the same as shown in FIG.

According to this, when the plant is stopped, the air cutoff valve 22
is fully opened, and the upper space A accommodates the cooling capillary tube bundle 12.
Then, the lower space B communicating with the condensate reservoir 13 is completely blocked. After that, the upper space A that accommodates the cooling capillary tube bundle 12
Only the side is vacuum broken to atmospheric pressure, and the air cutoff device 25
The inside of the lower space B partitioned by is maintained in a vacuum. At this time, the steam that subsequently flows into the upper space A, which is at atmospheric pressure, condenses and remains as drain with a high oxygen concentration.

Also, when starting up a plant, first, before starting up,
The on-off valve 27 is opened, and then a vacuum pump (not shown) is started to create a high vacuum in the upper space A partitioned off by the air cutoff device 25. Once this high vacuum is maintained, the air cutoff valve 22 is fully opened, and the upper space A and the lower space B are communicated with each other. The rest is the same as in the embodiment described above.

When the air cutoff valve 22 is suddenly fully opened at the time of starting up this plant, the high oxygen concentration condensate remaining in the upper space A flows out through the air cutoff valve 22 to the condensate reservoir 13 side.
There is a risk that the oxygen concentration in the lower space B, which has been kept low, will increase.

According to this embodiment, after the high oxygen concentration drain remaining in the upper space A is completely discharged to the outside through the on-off valve 27, the air cutoff valve 22 is fully opened. Therefore, the fear that the oxygen concentration in the lower space B will increase due to the inflow of drain with a high oxygen concentration can be completely eliminated. Furthermore, at the time of startup, the condensate and condensed water flowing into the upper space of the condenser 10 after the on-off valve 27 is closed will flow in while the vacuum is rising, so the oxygen concentration will be It is about 1000ppb,
Even if this condensate merges with the condensate in the condensate reservoir 13, the oxygen concentration in the condensate after the merge is 80 ppb or less, and the conditions are fully satisfied.

FIG. 3 shows another embodiment.

In this embodiment, the condenser 10 and the condensate reservoir 13 are placed separately, and are connected by an air cutoff pipe 28, with an air cutoff valve 29 installed in the middle of the air cutoff pipe 28. Here, the inside of the condenser 10 corresponds to the lower space A, and the inside of the air cutoff pipe 28 corresponds to the lower space B. The other configurations are the same as shown in FIG. Even in this case, if the air cutoff valve 29 is closed in the same way as described above, the vacuum on the condensate reservoir 13 side can be maintained when the plant is stopped.

Also, if the on-off valve 27 is fully opened when starting up the plant,
The drain in the upper space A can be completely discharged.

Therefore, the oxygen concentration at the time of plant startup can be reduced in a short time.

An example of a combined cycle power generation plant has been described above, but according to the present invention, a boiler, a steam turbine driven by steam generated in the boiler, a condenser that condenses turbine exhaust gas, and a condensate water supply system are combined. Similar effects can be obtained with equipment that has the following. Furthermore, according to the present invention, the oxygen concentration limit in condensate water at startup can be satisfied, and the time required for conventional degassing, which is 1 to 2 hours, can be reduced to 0 minutes according to the present invention, and the time required for vacuum rise can be reduced to 0 minutes. The time can be reduced to about 15 minutes.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, an openable and closable air blocking device is provided in the condenser to partition the inside of the condenser into two spaces, an upper space and a lower space, and when the plant is stopped, air is The upper space and the lower space are shut off by a shutoff device to maintain a vacuum in the lower space, and when the plant is started, the upper space is evacuated and then the upper space and the lower space are communicated with each other by an air cutoff device. Therefore, when the plant is started up, the oxygen concentration in the condensate remaining in the space below is low, so the time required to degas this oxygen can be significantly shortened, and the power required for this process can be significantly reduced. Can be done.

According to another invention, a drain discharge pipe with a shutoff valve installed in the middle is connected to the space above the condenser, and when the plant is started up, the shutoff valve is opened to drain the drain remaining in the space above the condenser. The upper space is evacuated while the air is being discharged, and then the upper space and the lower space are communicated with each other by the air blocking device. The oxygen concentration of condensate in the space can be kept low, and therefore the oxygen concentration of condensate in the space below can be kept low.
The time required to degas this oxygen can be significantly shortened.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of a condenser used in the method for starting up a steam power plant according to the present invention, Fig. 2 is a system diagram showing another embodiment, and Fig. 3 is a system diagram showing another embodiment. FIG. 4 is a system diagram showing a conventional steam power plant startup method and a condenser used in the method. 4... Heat recovery boiler, 5... Steam pipe, 9... Steam turbine, 10... Condenser, 11... Cooling water pipe, 1
2... Cooling tube bundle, 13... Condensate reservoir, 22.29
...Air cutoff valve, 23...Air cutoff plate, 25...
Air blocking device, 26...Drain discharge pipe, 27...Opening/closing valve, 28...Air blocking piping, A...Upper space, B
...Downward space.

Claims (1)

[Claims] 1. A method for starting a steam power plant comprising a condenser that condenses steam produced by a steam turbine to condensate, in which a bundle of thin tubes for cooling the inside of the condenser is provided. An air shut-off device that can be opened and closed is installed to divide the plant into two spaces: an upper space that accommodates the condensate and a lower space that communicates with the condensate reservoir. A vacuum is maintained in the lower space, and when the plant is started up, the upper space is evacuated and then the above-mentioned shutoff device communicates the upper space with the lower space in which the vacuum is maintained. How to start up a steam power plant. 2. A drain discharge pipe with an on-off valve installed in the middle is connected to the space above the condenser, and when starting up the plant, the on-off valve is opened to discharge the drain in the above space while the drain is discharged. 2. The method for starting a steam power plant according to claim 1, wherein after the upper space is evacuated, the upper space is communicated with the lower space in which the vacuum is maintained by the shutoff device. 3. A condensing device characterized in that the condenser is provided with an air blocking device that can be opened and closed to partition the inside of the condenser into two spaces: an upper space that accommodates a bundle of cooling tubes and a lower space that communicates with a condensate reservoir. vessel. 4. The condenser according to claim 3, wherein a drain discharge pipe having an on-off valve installed in the middle is connected to the space above the condenser.