JPH04283394A - condenser - Google Patents

Abstract

PURPOSE:To immediately start the operation of a plant, by a method wherein on a connection pipe, at which an upper space and a lower space are connected, a separation valve is so located that the path on the upstream side of the separation valve is made a condensed water staying region, and the oxygen content dissolved in the condensed water in the lower space is kept low. CONSTITUTION:A steam condenser 10 is divided into an upper space A holding a tube bundle 11 and a lower space B holding a hot well, by a partition member 19. Both of the spaces A, B are connected with connecting pipes 20a, 20b having the separation valve 21a between them, and the separation valve 21a is located so as to sink under condensed water. When the operation of a plant is stopped, the separation valve 21a is completely closed in the state of sinking under the condensed water. For that reason, even if the upper space A is opened to the atmosphere, a vacuum in the lower space B is kept and the oxygen content dissolved in the condensed water stored in the lower space B is kept low. On the other hand, the condensed water exposed to the atmosphere on the upstream side of the separation valve 21a is discharged through a drain pipe 22a, and as the degree of vacuum is increased, the separation valve 21a is opened, and thus both of the spaces A, B are made to communicate with each other.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to steam turbine plants, and more particularly to a condensing system configured to reliably isolate a hot well region within a condenser from the atmospheric environment in the event of plant shutdown. .

0003

[Prior Art] In recent years, combined cycle power generation plants have gained an established reputation as a power generation method that can achieve both excellent load followability and high thermal efficiency. Continuous efforts are being made to improve the. In terms of plant operation methods, the range from base load operations to operations that assume daily startup and shutdown,
In other words, there is a movement toward DSS (daily start and stop) operation, and improvements to steam turbine equipment are also in line with this movement.

FIG. 6 shows a schematic diagram of 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, and then introduced into an exhaust heat recovery boiler 4. An evaporator 7 is disposed within this exhaust heat recovery boiler 4, and water supply pumps 5a, 5
The feed water pressurized in b and 5c is supplied to steam drums 6a, 6b, 6
This feed water is introduced through c and recovers the thermal energy of the exhaust gas to become steam.

[0005] The steam from which the thermal energy has been recovered is introduced into steam turbines 8a, 8b, and 8c, where it does work and turns a generator 9, and then is discharged to a condenser 10. A tube bundle 11 formed of a large number of cooling pipes is arranged in the condenser 10, and the steam that has done work in the steam turbines 8a, 8b, 8c is condensed by cooling water introduced into the cooling pipes, and is condensed. The water becomes water and falls into the hot well 12, where it is stored. Note that the non-condensable gas contained in the steam in the condenser is discharged to the atmosphere by the air extraction device 13.

The condensate in the hot well 12 is pumped by the condensate pump 1.
4 and introduced into the gland steam condenser 15, where the gland leak steam extracted through the gland steam pipe 16 is condensed. Further, the condensate that has passed through the grand steam condenser 15 is sent to the water supply pumps 5a, 5b, and 5c, where it becomes high-pressure water and is sent to the exhaust heat recovery boiler 4 as described above. A part of the condensate that has passed through the gland steam condenser 15 is sent to the condenser 10 via a stop valve 18 built in the middle of the condensate level ring system piping 17, and is again circulated within the condensate circulation system. be done.

By the way, in this type of plant,
There is a problem in that the inner surfaces of the evaporators 7a, 7b, and 7c in the exhaust heat recovery boiler 4 corrode during operation. To suppress this corrosion, the dissolved oxygen concentration in the feed water is limited to 80 ppb or less at startup. However, when the plant is started up, the vacuum inside the condenser 10 is broken and the atmosphere flows into the condenser 10, so the condensate and the atmosphere come into contact, and a large amount of oxygen dissolves in the condensate. Dissolved oxygen concentration is 7 ppb during normal operation.
The dissolved oxygen concentration reached a high value of approximately 10,000 ppb.
It will be necessary to lower it to.

[0008]

[Problems to be Solved by the Invention] In order to suppress such an increase in dissolved oxygen concentration in condensate, the inside of the condenser 10 is provided with an upper space for accommodating the tube bundle 11 and for receiving and storing condensed condensate. The lower space that accommodates the hot well 12 is airtightly partitioned using a partition member, and a communication pipe having an isolation valve that can be opened and closed is connected between both spaces to serve as a passage for condensed water condensed in the upper space. When the plant is shut down, the isolation valve is closed to shut off the upper space and lower space within the condenser shell, and even after the vacuum in the upper space is destroyed, the vacuum in the lower space is maintained. , the dissolved oxygen concentration in the condensate in the hot well is stored as it is during normal operation, and when the plant is started, the vacuum in the upper space is increased, the isolation valve is opened to communicate the two spaces, and then the lower space is A method is being considered to shorten the time required for deaeration to the limit value of 80 ppb by guiding condensate from space to the waste heat recovery boiler 4.

However, when this method is adopted, the problem is whether the sealing performance between the upper and lower spaces is good or not. In other words, if the seal between both spaces is not maintained, air will flow from the upper space to the lower space while the plant is stopped, and the dissolved oxygen concentration of the condensate stored in the lower space will increase. , cannot fulfill its original purpose. Among the members that isolate both spaces, the partition member is attached to the condenser body by welding, so its sealing performance is reliable, but the isolation valve requires opening and closing operations due to its function, and it does not last for a long time. It is difficult to maintain sealing performance over a long period of time. In other words, it is conceivable to apply a butterfly valve, which has traditionally been used in power generation plants, as this isolation valve, but this butterfly valve is generally used in water system pipes where pressure is applied. The usage conditions here are particularly high vacuum on one side, and it is difficult to say that it has a perfect sealing performance as a device that blocks the inflow of air.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to maintain good sealing performance of an isolation valve installed in a communication pipe connecting an upper space and a lower space to suppress an increase in dissolved oxygen concentration in condensate. The purpose of the present invention is to provide a condenser designed to do the following.

[Configuration of the invention]

0012

[Means for Solving the Problems] A condenser according to the present invention has an upper space having a tube bundle for cooling and condensing steam turbine exhaust gas in the condenser body, and a hot well for receiving and storing condensed water. In a condenser that is divided into a lower space that accommodates
The isolation valve is characterized in that the isolation valve is arranged so that the area upstream from the isolation valve in the communication pipe route is a condensate retention area.

[0013]

[Operation] In general, the viscosity of water is about 1 cp, which is higher than the viscosity of air (about 0.02 cp).
This study focuses on the fact that water has a harder time passing through microscopic spaces than air under the same conditions. In other words, in the present invention, when the isolation valve is closed, a condensate retention area is formed on the upstream side of the isolation valve, and the area around the seat of the isolation valve is filled with water. Good sealing performance is maintained. This makes it possible to use conventional butterfly valves as isolation valves without major modifications, and the sealing performance is better than when air is in contact with them, so when the plant is shut down, atmospheric air is removed from the lower space. It is possible to suppress an increase in the dissolved oxygen concentration of the condensate due to the inflow.

[0014]

[Example] An example of a condenser according to the present invention is shown below in Fig. 1.
This will be explained with reference to FIG. Note that the same components as those of the conventional example shown in FIG. 4 are designated by the same reference numerals, and the explanation thereof will be omitted.

In FIG. 1, the interior of the condenser 10 is airtightly divided into an upper space A that accommodates the tube bundle 11 and a lower space B that accommodates the hot well 12 by a partition member 19. Communication pipes 20a and 20 have isolation valves 21a that can be opened and closed between the upper and lower spaces A and B.
b is connected and serves as the only communication passage for condensate. Here, the isolation valve 21a is provided below the level of condensate in the hot well 12 and is submerged in the condensate. Also,
A drain pipe 22a is connected to the upstream side of the isolation valve 21a.

Furthermore, as shown in FIG.
A weir 23 surrounding the inlet of the communication pipe 20a is provided at the connection portion between the pipe a and the partition member 19.

Next, the operation of the present invention will be explained together with the method of operating the plant. As mentioned above, when the plant transitions from shutdown to startup, the dissolved oxygen concentration in the condensate is required to be 80 ppb or less. However, in the conventional technology, the vacuum inside the condenser 10 is broken when the plant is stopped, so the atmosphere flows into the condenser 10, and the dissolved oxygen concentration in the condensate rises to about 10,000 ppb. do.

According to this embodiment, when the plant is stopped, the isolation valve 21a is fully closed while submerged in water before the vacuum in the condenser 10 is broken, and the tube bundle 11
The upper space A and the lower space B, which accommodate the above, are completely cut off. After that, even if only the upper space A breaks the vacuum and is opened to the atmosphere, the vacuum in the lower space B partitioned by the isolation valve 21a and the partition member 19 remains maintained, and the vacuum is stored in the lower space B. The dissolved oxygen concentration in the condensate is kept low. On the other hand, since the upper space A of the condensate remaining upstream of the isolation valve 21a is open to the atmosphere, oxygen in the atmosphere is dissolved and the concentration of dissolved oxygen is high. At the next plant start-up, the condensate with a high dissolved oxygen concentration accumulated on the upstream side of the isolation valve 21a is discharged by the drain pipe 22a, and the vacuum in the upper space A is increased. When a certain value is reached, the isolation valve 21a
1a is opened to allow both spaces A and B to communicate with each other. That is, since the upper space A is open to the atmosphere while the plant is stopped, a large amount of oxygen is dissolved in the condensate in the condensate retention area provided upstream of the isolation valve 21a, resulting in a high oxygen concentration. However, the plant can be operated without bringing this high dissolved oxygen concentration condensate into the lower space B. After this, by supplying the condensate with a low dissolved oxygen concentration stored in the lower space B to the boiler, the time conventionally required for degassing the condensate can be significantly shortened. .

Further, according to this embodiment, foreign matter mixed in the condensate flows onto the seat portion of the isolation valve 21a, and the isolation valve 2
The weir 23 can prevent the sheet portion from being damaged and the sealing performance to be impaired due to foreign matter getting caught when closing 1a. That is, in a DSS operated plant that is the object of the present invention, the isolation valve 21a is used to start and stop the plant once a day or more.
Since the seat is opened and closed as many times as the seat is started and stopped, it is expected that there will be more opportunities for foreign objects to get caught.
It is possible to catch it and prevent it from flowing into the communication pipe 20a. This more reliably prevents the seat portion from being damaged and the sealing performance of the isolation valve 21a being impaired. Furthermore, FIG. 3 shows another embodiment of the invention. In this embodiment, the isolation valve 21a is the hot well 1
Although it is installed above the condensate level of isolation valve 2,
A supply pipe 24a that supplies water and a drain pipe 22a are connected to the upstream side of 1a, and when the isolation valve 21a is closed, water is supplied through the supply pipe 24a, and when the plant is restarted, the drain pipe 22a is connected. The structure is such that this water can be drained through. In addition, in this embodiment, the supply pipe 24a and the drain pipe 22a are separate systems, but these are integrated into one pipe and water is supplied by a pump or the like.
It is also possible to perform a discharge.

FIG. 4 shows another embodiment to which the present invention is applied. In this embodiment, the balance pipe 25 connecting the upper space A and the lower space B is provided with an isolation valve 21b, a supply pipe 24b, and a drain pipe 22b to improve the sealing performance of the balance pipe 25.

As for the weir, it is possible to construct a weir 26 by having the upper end of the communication pipe 20a protrude above the upper surface of the partition member 19, as shown in FIG.

[0022]

[Effects of the Invention] As explained above, in the present invention, the isolation valve is arranged so that the area upstream from the isolation valve in the communication pipe route is the condensate retention area, so that the sealing performance of the isolation valve is always maintained. The dissolved oxygen concentration in the condensate can be maintained within the limit value at plant start-up.

Therefore, according to the present invention, it is possible to shorten the time required for deaeration of condensate when starting up a plant, and it is possible to quickly respond to demands from the power demand side, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a condenser according to the present invention.

FIG. 2 is a sectional view showing a connecting pipe connection portion of the condenser shown in FIG. 1;

FIG. 3 is a configuration diagram showing another embodiment of the present invention.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

FIG. 5 is a sectional view showing a connecting pipe connection portion of a condenser according to the present invention.

FIG. 6 is a system configuration diagram showing an example of a conventional combined cycle power generation plant.

[Explanation of symbols]

10……Condenser 12……Hotwell 19……Partition member 20a...Connection pipe 21a, 21b...isolation valve 22a, 22b...Drain drain piping 23, 26...cough 24a, 24b...supply pipe 25……Balance tube

Claims (1)

[Claims] Claim 1: The inside of the condenser body is divided into an upper space having a tube bundle for cooling and condensing the exhaust gas of a steam turbine, and a lower space accommodating a hot well for receiving and storing condensed water. In a condenser configured to communicate these two spaces by a communication pipe having an isolation valve that can be opened and closed, an area upstream from the isolation valve in the route of the communication pipe is used as a condensate retention area. A condenser characterized in that the isolation valve is arranged.