JP2945532B2 - Standby method and apparatus for stopping steam turbine condenser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a standby method and apparatus for a steam turbine when a condenser is stopped. In particular, the present invention relates to a method for separating degassed water equivalent to that during normal operation by isolating a hot well when a plant is stopped. The present invention relates to a standby method for stopping a condenser for a steam turbine which is suitable for storing water and supplying water to a steam generator in a short time without requiring deaeration of condensed water at startup, and an apparatus for performing the method.

[0002]

2. Description of the Related Art As described in Japanese Patent Application Laid-Open No. 60-57191, a conventional condenser for a steam turbine always condenses the condensate stored in the hot well of the condenser when the plant is started. It is necessary to recirculate through the condenser recirculation pipe connected to the condenser outlet, and at the same time, heat the condensate with the heating steam injection pipe for degassing, and require heating steam for degassing at the time of startup. In addition, in this structure, the start-up time becomes longer due to the deaeration operation.

Further, as described in JP-A-59-52192, a partition is provided between a tube nest for condensing steam and a hot well for storing condensed condensate, and the partition is separated by a water seal. While condensing water to the hot well, a pressure equalizing pipe with an isolation valve is installed between the pipe nest and the hot well to prevent air from stagnating in the space below the partition wall. There is a method in which the condensate of the hot well is prevented from coming into direct contact with the atmosphere by a seal and an isolation valve in the pressure equalizing pipe, thereby reducing the dissolution of oxygen into the condensate. However, this method also requires
Since the pressure of the hot well becomes the atmospheric pressure, it is impossible to maintain the dissolved oxygen level which can be started as it is.

[0004] Since each of the above-mentioned prior arts has both advantages and disadvantages, these are combined, and further, instead of the water seal, a condensate downcomer provided with an isolation valve as in the case of the pressure equalizing pipe is provided. A scheme to further enhance the effect is planned.

[0005]

As described in the prior art, in a condenser for a steam turbine planned to combine a hot well isolation method and a deaeration structure for condensate, the condensate condensed in a tube nest is considered. A condensing downcomer and a pressure equalizing pipe, each of which is connected to a hot well, are provided with an isolation valve. By closing the isolation valve, the hot well is maintained in the same vacuum state as during operation and isolated. However, in this plan, the diameter of the isolation valve is considerably large, and the frequency of opening and closing of the valve is extremely high in normal times. Therefore, complete airtightness may occur due to deterioration of the valve over time or foreign matter getting into the valve body. There is a problem that it is difficult to secure the amount of air leaked, and effective means for reducing the amount of leaked air when the plant is stopped is desired.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, reduce the amount of air leaking into a hot well isolated from the atmosphere, and supply water degassed immediately at the start of a plant to a steam generator. It is an object of the present invention to provide a standby method for stopping a condenser for a steam turbine which can be sent to a steam turbine.

Another object of the present invention is to provide a steam turbine condenser condenser standby device which can accurately carry out the above method.

[0008]

An object of the present invention is to supply degassed condensed water to a hot well isolated when a plant is stopped, fill the hot well with condensed water to eliminate a gas phase portion, and This is achieved by setting the pressure in the well slightly above atmospheric pressure to prevent air from leaking into the hot well isolated from the atmosphere.

Another object of the present invention is to provide a make-up water supply device for supplying degassed condensed water to an isolated hot well, to keep the hot well full and quarantine when the plant is stopped, and to make up the make-up water. This is achieved by providing a configuration in which the water level of the supply device can be set above the top of the isolated hot well.

Further, another object of the present invention is to provide a nitrogen filling device for filling pressurized nitrogen in a space above a water level of the makeup water supply device so that the condensate in the hot well is completely separated from the atmosphere. This can be achieved even more favorably by the configuration that can be shut off.

[0011]

The concentration of dissolved oxygen in condensate greatly depends on the pressure when in contact with air, and the higher the pressure, the higher the concentration of dissolved oxygen. Thus, in the method of the present invention, the hot well isolated when the plant is stopped is filled with water to eliminate the gas phase,
The isolation in a state where it does not come into contact with air prevents an increase in dissolved oxygen concentration. Further, in the method of the present invention, the pressure in the hot well is set to be slightly higher than the atmospheric pressure without vacuum, thereby preventing air from leaking to the hot well isolated from the atmosphere. That is, since the internal pressure of the hot well is set to be higher than the atmospheric pressure only for the head pressure, even if the isolation valve deteriorates over time or foreign matter is caught,
Thus, intrusion of leaked air can be prevented, and an increase in dissolved oxygen concentration can be prevented. As a result, when the plant is stopped, the deaeration operation of the condensed water is not required, and the plant can be started in a short time.

Further, in the apparatus of the present invention, a makeup water supply device for supplying degassed condensed water to the isolated hot well is provided. Then, when the plant is stopped, the hot wells are stored in full isolation. Therefore, the gas phase portion of the hot well isolated when the plant is stopped can be eliminated. Moreover, in the apparatus of the present invention, the water level of the makeup water supply device is set above the top of the isolated hot well. As a result, the pressure in the isolated hot well can be made higher than the atmospheric pressure by the water head pressure, and leakage of air from the atmosphere side into the hot well can be prevented. As a result, the method of the present invention can be accurately performed. Furthermore, a change in volume due to a change in condensate temperature can be dealt with by a change in water level of the makeup water supply device.

Further, in the apparatus of the present invention, the condensed nitrogen in the hot well is completely exchanged with the atmosphere by filling the pressurized nitrogen into the space above the water level of the makeup water supply device through the nitrogen filling device. I try to shut it off. As a result, the concentration of dissolved oxygen due to contact with air can be more effectively prevented, and the method of the present invention can be carried out more favorably.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of an apparatus for carrying out the method of the present invention, and FIGS. 2 and 3 are flow charts of the operation of a condenser. In this embodiment, as shown in FIG. 1, a condenser section 4 having a tube nest 3 for condensing steam from a turbine 2 in a condenser body 1, a hot well 5 for storing condensed condensate, and a condenser A horizontal partition wall 6 for separating the water portion 4 and the hot well 5 is provided. The partition 6 is provided with a condensate downcomer 8 having an isolation valve 7 for allowing condensate to flow down to the hot well 5. The hot well 5 further includes a condensate recirculation device 9 disposed immediately below the partition 6, a zigzag baffle 10 for retaining condensate in the hot well 5, and a ceiling plate 1.
1, a condensing outlet 12, and a degassing heating device 13 that injects steam below the water surface in the hot well 5.
The water level during the operation of the condenser is indicated by the position N shown in the lower part of the ceiling plate 11.
The volume is set to WL, and the volume of the condensate in the hot well 5 and the volume of the remaining gas phase are larger in the gas phase.

A makeup water supply device 1 which is a main part of the present invention for supplying degassed makeup water to the hot well 5.
5 is formed in a vertically elongated shape as a whole.
An inlet provided at an upper part of the makeup water supply device 15 is connected to a makeup water tank 14 via a makeup water pump 16. Further, an outlet provided at a lower portion of the makeup water supply device 15 is connected to the hot well 5 via an outlet valve 17. Further, a system from the make-up water tank 14 toward the inlet of the make-up water supply device 15 includes a regular make-up water supply system 1.
The service water supply system 18 supplies makeup water to the condenser during operation of the plant. Also, on the upper side of the makeup water supply device 15,
An overflow valve 19 is provided. The overflow valve 19 is connected to the condensing section 4, and is configured such that the water level of the makeup water supply device 15 can be set to a dimension H slightly higher than the top of the isolated hot well 5 when the plant is stopped. I have.

The condensate outlet 12 of the hot well 5 is connected to a steam generator (not shown) via a condensate pump 20, a condensate pump front-rear valve 21 and a gland steam condenser 22. A condensate return system 23 for sending condensate water to the makeup water tank 14 is connected to the upstream side of the gland steam condenser 22, and the condensate recirculation device 9 is connected to the downstream side. In addition, above the isolation valve 7 of the hot well 5,
A condensate drain valve 24 is provided, and a communication valve 25 is provided between the condensate 4 and the hot well 5.

Next, an example of the method of the present invention will be described in relation to the operation of the above-mentioned apparatus.

First, referring to FIGS. 1 and 2, the procedure for stopping the condenser after stopping the turbine load during the normal operation of the plant will be described step by step.

When the load on the turbine is stopped, it is not necessary to supply water from the condenser to the steam generator, but a vacuum must be maintained to maintain the dissolved oxygen concentration in the condensate in the condenser. In order to continue the function of the ground steam condenser 22 necessary for maintaining the vacuum of the condenser, “condenser recirculation start” is performed in step (1). Thereby, the condenser can maintain the condenser 4 and the hot well 5 in the same vacuum state as in the normal operation.

Next, by opening the outlet valve 17 of the makeup water supply device 15, "hot well water supply" is performed in step (2). After confirming that the hot well 5 is full, the isolation valve 7 and the communication valve 25 are closed. Perform “hot well isolation” in (3). Then, "stop the condensing pump" in step (4), "stop the vacuum pump" in step (5), "stop the ground steam condenser" in step (6), step (7)
Perform “Circulating water pump stop” to release to the atmosphere. Further, by operating the overflow valve 19 of the make-up water supply device 15, the "setting of the make-up water supply device water level" is performed in step (8). And the stop operation is completed.

In the method of the present invention, the basic concept at the time of the operation of stopping the condenser after the turbine load is stopped is that the deaerated water is supplied from the makeup water tank 14 to the gas phase of the hot well 5 when the condenser is in a vacuum state. The vacuum is released after the water is filled, and the water level of the makeup water supply device 15 is set to the dimension H in FIG. 1, and only the pressure corresponding to the water head difference is applied to the hot well 5.
The pressure inside is to be higher than the atmospheric pressure. In the case of the conventional hot well isolation method, the pressure difference between the inside and outside of the hot well is close to 10 m water column which is almost completely vacuum, and the pressure difference in this case causes fluid leakage from the atmosphere side into the hot well 5, and The leaked fluid in this case is air that easily leaks. On the other hand, in the method of the present invention, the pressure when the plant is stopped is higher than the atmospheric pressure in the hot well 5, the pressure difference is at most 2 to 3 m water column, and the leaked fluid is hard to leak. Since it is (liquid), it has a great feature that the sealing function when the condenser is stopped can be further enhanced as compared with the conventional technology. As a result, in the method of the present invention, it is possible to prevent air leakage into the hot well 5 when the plant is stopped, and to absorb a change in volume due to a change in condensate temperature by a change in the water level of the makeup water supply device 15. Can be.

Next, referring to FIGS. 1 and 3, a procedure for starting the condenser after the above-mentioned plant stoppage will be described.

In preparation for the vacuum rise of the condenser, "circulation pump activation" is performed in step (10).
Perform “Condensate recirculation start” in 1). Next, since the concentration of the dissolved oxygen in the drain collected in the condensate when the plant is stopped is high, step (1) is performed by operating the condensate drain valve 24.
After “condensate drainage” is performed in 2), “grand steam condenser activation” is performed in step (13), and “vacuum pump activation” is performed in step (14) to increase the vacuum.
Further, in step (15), "the outlet valve of the makeup water supply device is closed", and the isolation valve 7 and the communication valve 25 are opened, so that in step (16), "isolation and opening of the hot well" is performed.
In order to return the water level of the hot well 5 to the normal operation water level, "returning the condensate water to the makeup water tank" is performed in step (17), and then "stop condensate recirculation" is performed in step (18). Then, in step (19), the operation of "start steam generator water supply" is performed.

In the method of the present invention, the basic idea at the time of the plant start-up operation is to raise the vacuum in a state where the hot wells 5 are isolated, and then perform the isolation and opening of the hot wells 5 after the vacuum increase, thereby condensing the condensate. A major feature is that it is possible to shift to startup without increasing the dissolved oxygen concentration. In the method of the present invention, the makeup water tank 14
The supply of degassed water in the make-up water tank 14 is carried out by the service water supply system 18 and the condensate return system 23 by the condenser during normal operation of the plant. This can be dealt with by a replacement operation of returning the dehydrated condensed water to the makeup water tank 14.

FIG. 4 is a system diagram showing another embodiment of the apparatus of the present invention. In the apparatus of the embodiment shown in FIG.
Nitrogen filling device 2 at makeup water inlet of makeup water supply device 15
6 are provided. From the nitrogen sealing device 26, nitrogen pressurized to a pressure corresponding to the dimension H in FIG. 1 is sealed above the water surface of the make-up water supply device 15 to completely shut off condensate and air. .

Thus, according to the apparatus of the embodiment shown in FIG. 4, the contact between the condensed water and the air can be completely eliminated, and the increase of the dissolved oxygen concentration can be prevented more reliably. Also in the case of this embodiment, the pressure in the hot well 5 when the plant is stopped is higher than the pressure on the atmosphere side, so that leakage of air into the hot well 5 can be prevented. In addition,
The operation procedure of the embodiment shown in FIG. 4 is basically the same as that of the embodiment shown in FIG.

[0028]

According to the method of the present invention described above, the degassed condensed water is supplied into the isolated hot well when the plant is stopped, and the hot water is filled with the condensed water to eliminate the gas phase. The pressure in the hot well is set slightly higher than the atmospheric pressure to prevent air from leaking to the hot well isolated from the atmosphere, and the air in the isolated hot well is shut down when the plant is stopped. Can be prevented, and even if the isolation valve deteriorates over time or foreign substances are caught, the intrusion of air from the atmosphere side can be prevented. When resuming operation later, degassing operation for condensate water is not required,
There is an effect that the plant can be started in a short time.

According to the apparatus of the present invention, a make-up water supply device for supplying degassed condensed water to the isolated hot well is installed. Since the apparatus is configured so that the water level of the apparatus can be set above the uppermost part of the isolated hot well, there is an effect that the method of the present invention can be carried out accurately.

Further, according to the apparatus of the present invention, a nitrogen enclosing device for enclosing pressurized nitrogen is provided in a space above the water level of the make-up water supply device, and the condensate in the hot well is completely separated from the atmosphere. It is configured to be shut off, and pressurized nitrogen is sealed in the upper part of the water surface in the make-up water supply device, so that the contact between the condensed water and the air can be completely eliminated, so that the method of the present invention can be further improved. There are effects that can be implemented.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of an apparatus for carrying out the method of the present invention.

FIG. 2 is a flowchart showing a procedure for stopping a steam turbine condenser of the apparatus shown in FIG. 1;

FIG. 3 is a flowchart showing a starting operation procedure of a steam turbine condenser of the apparatus shown in FIG. 1;

FIG. 4 is a system diagram showing another embodiment of an apparatus for carrying out the method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Condenser body, 2 ... Turbine, 3 ... Tube nest, 4 ... Condenser part, 5 ... Hot well, 7 ... Isolation valve, 8 ... Condenser downcomer,
14: makeup water tank, 15: makeup water supply device, 16: makeup water pump, 17: makeup water outlet valve, 19: overflow valve, H: dimension of makeup water set slightly higher than the top of the hot well , 20: condensate pump, 23: condensate return system, 26: nitrogen filling device.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshiya Iwata 3-1-1 Sachimachi, Hitachi City, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (56) References JP-A-3-275905 (JP, A) JP-A-60-200086 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F28B 1/00-11/00

Claims (3)

(57) [Claims] 1. A degassed condensate is supplied into a hot well isolated when a plant is stopped, and the condensate is filled in the hot well to eliminate a gaseous phase portion, and the pressure in the hot well is reduced from atmospheric pressure. A method for standby of a condenser for a steam turbine when the condenser is stopped, wherein the condenser is set slightly higher to prevent air from leaking to a hot well isolated from the atmosphere. 2. A condensing section having a tube nest for condensing steam flowing from a turbine and a hot well storing condensate from the condensing section, and a condensing section having an isolation valve in the partition. A condensate downcomer is provided for guiding condensate from the water section to the hot well, and in the steam turbine condenser for storing condensate in the isolated hot well, the condenser degassed by the isolated hot well. A make-up water supply device that supplies water is installed, and when the plant is stopped, hot wells are filled and stored, and the water level of the make-up water supply device can be set above the top of the isolated hot wells. Standby device when the steam turbine condenser is stopped. 3. A nitrogen filling device for filling pressurized nitrogen is provided in a space above a water level of the makeup water supply device,
3. The standby device for a steam turbine condenser according to claim 2, wherein the condensate in the hot well can be completely shut off from the atmosphere.