JPH08200010A - Combined generation plant and operating method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a combined power generation plant that employs an exhaust heat recovery boiler of a reheat triple pressure type system equipped with an optimal system for supplying seal steam to a steam turbine gland part, and an operating method thereof. To aim. [Structure] A first extraction pipe 22 branched from an exhaust pipe 19 for supplying exhaust gas of a high-pressure steam turbine 15 to a reheater 5 and a second extraction pipe 22.
Of the high pressure steam turbine 15 from the second extraction pipe 26 to the third extraction pipe 30.
Of the exhaust gas is supplied to the steam turbine gland portion 34. Further, the ground steam backup pipe 35 branched from the intermediate pressure steam bypass pipe 21 is connected to the third extraction pipe 30, and the intermediate pressure steam generated in the exhaust heat recovery boiler 1 is supplied to the steam turbine ground portion 34. It has become so.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an exhaust heat recovery boiler equipped with three types of steam pressure systems (high pressure system, medium pressure system, low pressure system) and a reheat system for reheating exhaust gas of a steam turbine. The present invention relates to a combined cycle power plant, and more particularly to a combined cycle power plant including a supply system suitable for supplying seal steam to a steam turbine gland section and a method for operating the combined cycle power plant.

[0002]

2. Description of the Related Art In recent years, thermal power plants have mainly been combined power plants having a gas turbine, an exhaust heat recovery boiler, and a steam turbine, but recently, there have been three types of steam pressure systems (high pressure systems). , Intermediate pressure system, low pressure system) and a reheat triple pressure type exhaust heat recovery boiler equipped with a reheat system have been adopted, and there is seen a combined power plant that seeks to further improve thermal efficiency. Incidentally, such a combined cycle power generation plant is introduced in "Hitachi Review, Vol. 74, No. 11, Issued November 1, 1992, pages 9 to 14, high-efficiency combined power generation plant".

However, the above publication does not describe a supply system for supplying the seal steam to the steam turbine gland portion.

[0004]

In this respect, a combined power generation plant described in Japanese Patent Laid-Open No. 62-237013 is known as a combined power generation plant having a system for supplying the steam turbine gland portion. This combined cycle power plant extracts the main steam generated in the exhaust heat recovery boiler and supplies it to the steam turbine gland part.The exhaust heat recovery boiler of the reheat triple pressure type system described above is adopted. Not.

The present invention provides a combined power generation plant having an optimum system for supplying seal steam to a steam turbine gland part in a combined power generation plant having an exhaust heat recovery boiler of a reheat triple pressure type system and an operating method thereof. The purpose is to provide.

[0006]

[MEANS FOR SOLVING THE PROBLEMS] In order to obtain a combined cycle power generation plant that achieves the above object, the present invention is provided by an exhaust heat recovery boiler that generates steam by using exhaust gas of a gas turbine as a heat source, and the exhaust heat recovery boiler. In a combined power plant having a steam turbine using steam as a drive source, and a reheat system that guides exhaust of the steam turbine to a reheater of the exhaust heat recovery boiler, the exhaust is extracted from the reheat system, and A pipe was provided to supply the gland of the steam turbine.

Further, in order to obtain a combined cycle power generation plant that achieves the above object, the present invention drives an exhaust heat recovery boiler that generates steam by using the exhaust gas of a gas turbine as a heat source, and the steam obtained by the exhaust heat recovery boiler. In a combined cycle power plant having a steam turbine as a source and a reheat system that guides exhaust of the steam turbine to a reheater of the exhaust heat recovery boiler, the exhaust is extracted from the reheat system and ground of the steam turbine. A first pipe for supplying the steam to the exhaust gas heat recovery boiler and a second pipe for supplying the steam generated in the medium pressure evaporator of the exhaust heat recovery boiler to the gland part of the steam turbine are provided.

Further, the second pipe may be connected to the first pipe.

In the exhaust heat recovery boiler, a high pressure system, a medium pressure evaporator (medium pressure drum), which heats high pressure steam generated in a high pressure evaporator (high pressure drum) by a high pressure superheater and supplies it to a high pressure steam turbine. The medium pressure system that supplies the medium pressure steam generated in the reheater to the reheater, the low pressure system that superheats the steam generated in the low pressure evaporator (low pressure drum) in the low pressure superheater and supplies it to the low pressure steam turbine,
The reheat triple pressure system is adopted, which includes a reheat system that superheats steam from the medium pressure system and exhaust of the high pressure steam turbine with a reheater and supplies the superheated steam to the medium pressure steam turbine.

The steam turbine comprises a high-pressure steam turbine driven by high-pressure steam, an intermediate-pressure steam turbine driven by reheat steam, and a low-pressure steam turbine driven by low-pressure steam. It is the exhaust of a high-pressure steam turbine.

In order to obtain a method of operating a combined cycle power plant that achieves the above object, the present invention supplies exhaust gas from a gas turbine to an exhaust heat recovery boiler to generate steam, and drives the steam turbine with the generated steam. In an operating method of a combined cycle power generation plant that supplies the steam after driving the steam turbine to a reheater of the exhaust heat recovery boiler, the steam after driving the steam turbine is extracted and supplied to the ground portion of the steam turbine. did.

Further, in order to obtain a method for operating a combined cycle power plant that achieves the above object, the present invention supplies exhaust gas from a gas turbine to an exhaust heat recovery boiler to generate steam, and drives the steam turbine with the generated steam. Then, in the operating method of the combined power generation plant that supplies the steam after driving the steam turbine to the reheater of the exhaust heat recovery boiler, during normal operation, the steam after driving the steam turbine is extracted to extract the ground of the steam turbine. The steam generated in the intermediate pressure evaporator of the exhaust heat recovery boiler is supplied to the gland part of the steam turbine during the independent operation in the plant.

[0013]

[Operation] While branching from the reheat system,
Specifically, by providing a pipe for supplying the exhaust of the high-pressure steam turbine to the gland of the steam turbine, the exhaust of the high-pressure steam turbine is supplied to the gland of the steam turbine as seal steam during normal operation.

Further, by providing a pipe for supplying the steam superheated by the medium-pressure superheater of the exhaust heat recovery boiler to the gland part of the steam turbine, the exhaust heat recovery is performed in the gland part of the steam turbine during the independent operation in the plant. Medium-pressure steam generated in the boiler is supplied as backup seal steam.

As described above, by providing the seal steam supply system during the normal operation and the single operation inside the plant, stable seal steam is generated without adversely affecting the plant operation and minimizing the decrease in thermal efficiency. It can be supplied to the gland part of the turbine.

[0016]

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

FIG. 1 is a system diagram showing a combined power generation plant which is an embodiment of the present invention, and shows a portion excluding a gas turbine system, a condensate and a water supply system. In the drawing,
The exhaust heat recovery boiler 1 for exchanging heat between exhaust gas from a gas turbine system (not shown) and feed water to generate driving steam for driving the steam turbine system includes a low pressure system, an intermediate pressure system, a high pressure system, and a reheat system. It is a reheat triple type system equipped with, and in order from the inflow side (the right side in the drawing) of the exhaust gas of the gas turbine, the high-pressure superheater 2, the high-pressure evaporator 3 (high-pressure drum 4), the reheater 5, and the medium-pressure superheater 6 , Medium pressure evaporator 7 (medium pressure drum 8),
A low pressure superheater 9 and a low pressure evaporator 10 (low pressure drum 11) are provided.

The steam turbine system driven by the steam generated in the exhaust heat recovery boiler 1 has a high pressure steam turbine 15 driven by the high pressure steam supplied through the high pressure steam pipe 12 and a reheat steam pipe 13 between them. Medium pressure steam turbine 16 driven by reheated steam supplied by the
The low-pressure steam turbine 17 driven by the low-pressure steam supplied via 4 is uniaxially directly connected. In addition, 18 is a generator directly connected to the steam turbine and driven by the steam turbine.

The exhaust pipe 19 for supplying the exhaust of the high-pressure steam turbine 15 to the reheater 5 has a first extraction pipe 2 for supplying a part of the exhaust of the high-pressure steam turbine 15 to the auxiliary steam header 23.
2 is connected to the first extraction pipe 22.
Pressure reducing valve 24 for reducing the pressure of the steam flowing through the extraction pipe 22 of
A desuperheater 25 that reduces the temperature of the steam decompressed by the decompression valve 24 is provided. A second bleeder pipe 26 for bleeding steam flowing through the first bleeder pipe 22 is connected to the downstream side of the temperature reducer 25 of the first bleeder pipe 22, and the second bleed pipe 26 is connected to the second bleed pipe 26. On the downstream side, the high pressure steam turbine warming pipe 27, the steam turbine cleaning pipe 28,
It branches to the condenser deaeration steam pipe 29.

A third extraction pipe 30 for supplying the steam flowing through the second extraction pipe 26 to the gland steam pipe 33 is connected in the middle of the second extraction pipe 26, and the third extraction pipe 30 is connected.
An electric valve 31 and a steam seal make-up valve 32 are provided in the. The intermediate pressure steam bypass pipe 21 is provided downstream of the steam seal make-up valve 32 of the third extraction pipe 30.
A gland steam backup pipe 35 that supplies the steam that flows to the gland steam pipe 33 is connected to the gland steam backup pipe 35. A steam seal make-up backup valve 36 is provided in the gland steam backup pipe 35. In addition, 3 in the figure
4 is a steam turbine gland part, 37 is a steam seal dump valve, 38 is a control valve, and 41, 42 and 43 are steam control valves.

The combined power generation plant of this embodiment having the above-mentioned structure is operated as follows. First, the normal operation will be described.

Not shown gas turbine system (air compressor, combustor for combusting compressed air compressed by the air compressor and fuel, gas turbine driven by combustion gas obtained by the combustor, gas turbine Gas turbine system consisting of a generator that is directly connected to and driven by a gas turbine)
Exhaust gas at about 600 ° C. discharged from the gas turbine is supplied to the exhaust heat recovery boiler 1.

In the exhaust heat recovery boiler 1, the exhaust gas and the feed water are heat-exchanged in each evaporator and superheater, and steam for driving the steam turbine is generated. The heat exchange causes the exhaust gas to become an exhaust gas at about 100 ° C.

The high-pressure steam generated in the high-pressure evaporator 3 (high-pressure drum 4) is superheated by the high-pressure superheater 2 and the high-pressure steam pipe 1
It is supplied to the high pressure steam turbine 15 via 2 and drives the high pressure steam turbine 15. The steam that has driven the high-pressure steam turbine 15 is supplied to the reheater 13 via the exhaust pipe 19 and superheated. Further, to the reheater 13, the intermediate pressure steam generated in the intermediate pressure evaporator 7 (intermediate pressure drum 8) and superheated by the intermediate pressure superheater 6 is supplied via the intermediate pressure steam pipe 20 to be superheated. The reheated steam superheated by the reheater 13 is reheated steam pipe 13
Is supplied to the intermediate-pressure steam turbine 16 via the to drive the intermediate-pressure steam turbine 16. Low-pressure evaporator 10 (low-pressure drum 1
The low-pressure steam generated in 1) is superheated by the low-pressure superheater 9, is supplied to the low-pressure steam turbine 17 via the low-pressure steam pipe 14, and drives the low-pressure steam turbine 17. Then, by driving these steam turbines, the generator 18 directly connected to the steam turbines is driven, and electric power is obtained.

The exhaust gas of the high-pressure steam turbine 15 supplied to the reheater 13 via the exhaust pipe 19 is extracted by the first extraction pipe 22 and the auxiliary steam via the pressure reducing valve 24 and the temperature reducer 25. It is supplied to the header 23. The steam whose pressure has been reduced and decreased by the pressure reducing valve 24 and the temperature reducer 25 is extracted by the second extraction pipe 26. The steam extracted by the second extraction pipe 26 is extracted by the third extraction pipe 30, and is supplied to the gland steam pipe 33 via the electric valve 31 and the steam seal makeup valve 32. The steam supplied to the gland steam pipe 33 is supplied to each steam turbine gland portion 34 and seals each steam turbine gland portion 34.

The exhaust of the high-pressure steam turbine 15 supplied to the reheater 13 via the exhaust pipe 19 is used as the seal steam source of the steam turbine gland portion 34 during the normal operation for the following reason. Is.

The seal steam source of the steam turbine gland portion 34 includes a high pressure system from the high pressure superheater 2 to the high pressure steam turbine 15, a reheat system from the high pressure steam turbine 15 to the reheater 5, and a medium pressure superheater 6. 4 of low pressure system from low pressure superheater 9 to low pressure steam turbine 17
The lineage is considered. Of these, when the high pressure system is used as the supply source, it is necessary to reduce the pressure and temperature of the steam supplied to the steam turbine gland section 34. In addition, the thermal efficiency is significantly reduced by reducing the pressure and decreasing the temperature. When the medium pressure system is used as the supply source, the amount of steam generated during the rated operation of the medium pressure system is about 3
While 0t / h, the amount of auxiliary steam required at the time of continuous startup is about 45t / h (high-pressure steam turbine warming steam + steam turbine cleaning steam + condenser deaeration steam), You cannot bleed. When a low pressure system is used as a supply source, if a large amount of steam is extracted from the low pressure system, the steam may enter the wet region, and the low pressure steam turbine may cause erosion.

On the other hand, when the reheat system is used as the supply source, the reheat system has a pressure and temperature of steam close to the requirement of the seal steam of the steam turbine gland portion 34, and can be dealt with by relatively small pressure reduction and temperature reduction. It is possible to minimize the decrease in thermal efficiency due to depressurization and temperature reduction. Further, since the amount of steam in the reheat system is abundant, the effect of steam extraction on the entire plant is small.

From the above, in the present embodiment, during normal operation, the reheat system from the high-pressure steam turbine 15 to the reheater 5 is used as the seal steam supply source to the steam turbine gland section 34, and the seal steam is extracted. are doing. As a result, during normal operation, it is possible to supply the seal steam to the steam turbine gland portion 34 without significantly reducing the thermal efficiency. Therefore, the thermal efficiency is improved and the reliability of the plant is improved.

Next, a description will be given of the operation when the station is independent. When the load is cut off due to a power transmission accident or the like, the power plant shifts to the island operation. In the in-house independent operation, the steam power control valve 3
9, 40, 41 are cut off. For this reason, since steam is not supplied to the steam turbine system, steam is not supplied to the exhaust of the high-pressure steam turbine 15, that is, the steam turbine gland portion 34 whose seal heat source is the reheat system.

FIG. 2 shows a graph in which the horizontal axis represents time and the vertical axis represents pressure. The upper graph in the figure shows the vapor pressure (reheat system) flowing through the exhaust pipe 19 during independent operation in the plant. Steam pressure) change, and the lower graph in the figure shows the change in steam pressure (medium pressure system steam pressure) flowing through the intermediate pressure steam bypass pipe 21 during the single operation in the plant. As is apparent from the graph in the upper part of FIG. 2, the pressure of the reheat system steam (steam flowing through the exhaust pipe 19) supplied to the steam turbine gland part 34 gradually decreases during the islanding single operation. You will understand.

By the way, the steam turbine is idling during the independent operation in the plant. Also, in order to promptly restart the condenser, it is necessary to maintain the degree of vacuum of the condenser. That is, the inside of the condenser is evacuated in order to keep the dissolved oxygen contained in the condensate at a predetermined value. If the vacuum inside the condenser is broken, the atmosphere penetrates into the condenser and the dissolved oxygen contained in the condensate exceeds a predetermined value. Therefore, at the time of restarting, the inside of the condenser must be evacuated and the dissolved oxygen contained in the condensate must be readjusted to a predetermined value, and it takes time to restart,
It is necessary to maintain the degree of vacuum of the condenser. For this reason,
The seal steam must be supplied to the steam turbine gland portion 34 even during the independent operation in the plant. However, as described above, the pressure of the steam flowing through the exhaust pipe 19, which is the seal steam supply source of the steam turbine gland portion 34, gradually decreases to less than the minimum necessary pressure of the gland seal during the in-house single operation, Steam cannot be supplied to the gland portion 34.

From the above, during the independent operation in the plant, the steam turbine gland part 34 is discharged from the system where steam is generated.
Must be supplied with steam. In addition, when supplying steam, it is necessary to prevent the operation of the plant from being adversely affected.

In this embodiment, a medium pressure system is used as a backup steam supply source to the steam turbine gland section 34 which is operating independently in the plant, in consideration of thermal efficiency, steam amount, arrangement and the like.
This is for the following reason. When the high-pressure system is used as a backup steam supply source, it is necessary to reduce the temperature and reduce the pressure to the necessary conditions for the sealing steam in the steam turbine gland section 34. Further, when the low-pressure system is used as a backup steam supply source, when the load is suddenly reduced, the generated steam is used for steam turbine cooling steam or the like, so that the steam amount becomes insufficient.

On the other hand, when the intermediate pressure system is used as the backup steam supply source, the steam pressure at the outlet pipe of the intermediate pressure drum 8 is as shown in FIG.
As is clear from the graph at the bottom, it is constant even during independent operation in the plant. Further, the amount of steam generated in the intermediate-pressure drum 8 is sufficient as compared with the amount of sealing steam required for the steam turbine gland portion 34, so that stable steam can be supplied to the steam turbine gland portion 34.

Therefore, in the present embodiment, during independent operation in the office,
Medium-pressure steam is bypassed by the medium-pressure steam turbine bypass pipe 21.
The air is extracted further and is supplied to the ground steam pipe 33 through the ground steam backup pipe 35. Ground steam pipe 3
The medium-pressure steam supplied to No. 3 is supplied to each steam turbine gland part 34 and seals each steam turbine gland part 34.

According to this embodiment operated in this way,
Steam turbine gland part 34 even when operated independently in the plant
The seal steam can be stably supplied to. This allows the condenser vacuum to be maintained and a quick restart. Therefore, the operation can be performed so as to adversely affect the operation of the plant and the reliability of the plant is improved. In addition, in the present embodiment, the description is given for the case of the independent operation in the office, but it is also effective when the load is cut off.

Next, the steam turbine gland portion 3 described above
The control required to supply the seal steam to No. 4 will be described with reference to the drawings. In order to stably supply the seal steam to the steam turbine gland portion 34 during the single operation in the plant, the steam seal make-up valve 32, the steam seal dump valve 37, and the steam seal make-up backup valve 36 are controlled to supply the seal steam. It is necessary to switch the source from reheat system to medium pressure system. At this time, it is not desirable to control two or more valves at the same time because of the convenience of control. For this reason, in the present embodiment, the system described below controls the system that supplies the seal steam to the steam turbine gland section 34.

FIG. 3 is a block diagram showing an example of the control device. The control device 50 is a subtractor for subtracting the detection signal detected by the detector 51 and the set value preset in the setter 54. 53 and the output value of the subtractor 53 to obtain the opening signal of the steam seal make-up backup valve 36. The steam seal make-up backup valve opening calculator 55 and the output value of the subtractor 53 are input to input the steam seal. Steam seal make-up valve opening calculator 56 for obtaining the opening signal of make-up valve 32, and steam seal dump valve opening calculator for obtaining the opening signal of steam seal dump valve 37 by inputting the output value of subtractor 53 57. In the figure, reference numeral 52 designates a local islanding operation signal (load cutoff signal) generator for generating a signal when the plant shifts to the local islanding operation, and 58 a fully closed signal for generating a fully closed signal of the steam seal make-up valve 32. The generator 61 is a signal switch.

First, when the auxiliary steam is not used on the auxiliary steam header 23 side, or when the steam having a pressure lower than or equal to the pressure of the steam for sealing the steam turbine gland is used, the steam for sealing the steam turbine gland 34 is sealed. A method of controlling the system for supplying the electricity will be described.

During normal operation, the pressure P _{34 of} the steam turbine gland 34 detected by the detector 51 and the setter 54
The set pressure value P _c set in advance at is input to the subtractor 53 and is calculated (P ₃₄ -P _c ). The differential pressure value ΔP obtained by this calculation is input to each valve opening calculator described above. When the differential pressure value ΔP input to each valve opening calculator is ΔP> 0, the steam seal make-up valve opening calculator 56 indicates that the steam seal makeup valve opening calculator 56 A fully closed signal is output to the seal make-up valve 32. Further, the steam seal dump valve opening calculator 57 outputs an open signal to the steam seal dump valve 37 in order to reduce the pressure of the steam turbine gland portion 34 to the set pressure value P _c . As a result, the surplus steam is discharged to the condenser or the like via the steam seal dump valve 37.

When the differential pressure value ΔP input to each valve opening calculator is ΔP <0, the pressure in the steam turbine gland portion 34 is too low, so the steam seal dump valve opening calculator 57 is used. Outputs a fully closed signal to the steam seal dump valve 37. Further, the steam seal make-up valve opening calculator 56 outputs an open signal to the steam seal make-up valve 32 in order to raise the pressure of the steam turbine gland portion 34 to the set pressure value P _c .

On the other hand, during the independent operation in the plant, the steam control valve 39,
Since 40 and 41 are cut off, the reheat system has no supply steam, and the pressure of the steam turbine gland part 34 decreases,
The differential pressure value ΔP output from the subtractor 53 is ΔP <0. When the differential pressure value ΔP becomes ΔP <0, the pressure in the steam turbine gland portion 34 is low, so the steam seal make-up valve opening calculator 56 holds the pressure in the steam turbine gland portion 34. An open signal is output to the steam seal makeup valve 32.

However, the steam seal make-up valve 32
Is opened and fully opened by the open signal of the steam seal make-up valve opening calculator 56, but since the steam pressure of the reheat system is lower than the minimum pressure required for the gland seal as described above with reference to FIG. 2,
The pressure of the steam turbine gland 34 cannot be maintained.
Therefore, the steam seal make-up backup valve opening degree calculator 55 uses the steam seal make-up backup valve 36.
Output an open signal to. As a result, the medium pressure steam is supplied to the steam turbine gland portion 34. At this time, the steam seal dump valve 37 is fully closed.

Next, a method of controlling the system for supplying the sealing steam to the steam turbine gland portion 34 when the steam having a pressure higher than the sealing steam pressure of the steam turbine gland portion on the auxiliary steam header 23 side is used will be described.
Note that, during normal normal operation, description is omitted because it is the same as the above case.

During independent operation in the plant, the steam control valves 39, 40,
Since 41 is cut off, the supply steam disappears in the reheat system, the pressure in the steam turbine gland portion 34 decreases, and the differential pressure value ΔP output from the subtractor 53 becomes ΔP <0. However, in this case, the pressure of the auxiliary steam supplied from the auxiliary steam header 23 to the ammonia vaporizer or the like must be maintained, and the steam seal make-up valve 32 is operated together with the in-house independent operation.
Need to shut off. Therefore, when the in-house isolated operation is performed due to load shedding, the in-house isolated operation signal is output from the in-house isolated operation signal generator 52 to the switch 61, and the switch 61 receiving the in-house isolated operation signal causes the steam seal make-up valve to open. The open signal of the frequency calculator 56 is switched to the fully closed signal of the fully closed signal generator 58. As a result, the steam seal make-up valve 32 is fully closed together with the in-house independent operation. The subtractor 5
The differential pressure value ΔP output from 3 is faster than that when no steam is used on the auxiliary steam header 23 side, and ΔP <0.

The differential pressure value ΔP output from the subtractor 53 is Δ
When P <0, since the pressure of the steam turbine gland portion 34 is low, the steam seal make-up backup valve opening degree calculator 55 keeps the pressure of the steam turbine gland portion 34 so that the steam seal make-up backup valve opens. An open signal is output to 36. As a result, the medium pressure steam is supplied to the steam turbine gland portion 34. still,
At this time, the steam seal dump valve 37 is fully closed.

Further, the control in the case of using the steam having a pressure higher than the steam pressure of the steam turbine gland seal on the auxiliary steam header 23 side can be realized also by the control device shown in FIG. In order to maintain the pressure of the auxiliary steam supplied from the steam header 23 to the ammonia vaporizer or the like, the electric valve 31 is shut off at the same time as the in-house independent operation. Therefore, the control device 5
0 is provided with a motor-operated valve opening / closing signal generator 60 that generates a signal for opening / closing the motor-operated valve 31 based on a signal from the on-site isolated operation signal generator 52 or the normal operation signal generator 59. .

During normal operation, the normal operation signal generator 59 outputs a normal operation signal to the electric valve opening / closing signal generator 60. The motor-operated valve opening / closing signal generator 60 outputs a fully open signal to the motor-operated valve 31 in response to the normal operation signal,
Fully open.

On the other hand, during the in-house independent operation, the in-house isolated operation signal generator 52 outputs a in-house isolated operation signal to the motor-operated valve opening / closing signal generator 60 as a normal operation signal. The motor-operated valve opening / closing signal generator 60 outputs a fully-closed signal to the motor-operated valve 31 in response to the in-house isolated operation signal to fully close the motor-driven valve 31. Further, since the differential pressure value ΔP output from the subtractor 53 becomes ΔP <0, and the pressure of the steam turbine gland portion 34 is low, the steam seal make-up backup valve opening degree calculator 55 indicates the steam turbine gland opening degree. Steam seal make-up backup valve 36 so as to maintain the pressure of section 34
Output an open signal to. As a result, the medium pressure steam is supplied to the steam turbine gland portion 34. At this time, the steam seal dump valve 37 is fully closed.

In this embodiment, various valves (steam seal make-up valve 3) provided in the system for supplying the seal steam to the steam turbine gland part 34 by the above-mentioned control device.
2, the steam seal make-up backup valve 36, the steam seal dump valve 37, and the motor-operated valve 31) are controlled, so that the steam turbine gland part can be used not only during normal operation but also during independent operation inside the plant (or during load shedding). It is possible to stably supply the sealing steam to 34. Therefore, the reliability of the plant is improved.

[0052]

As described above, according to the present invention, a combined power generation plant adopting an exhaust heat recovery boiler of a reheat triple pressure type system equipped with an optimum system for supplying seal steam to a steam turbine gland part and a method of operating the same. Can be provided.

[Brief description of drawings]

FIG. 1 is a system diagram showing a configuration of a combined cycle power plant that is an embodiment of the present invention.

FIG. 2 is a graph showing pressure changes in a reheat system and an intermediate pressure system during a single operation in a center, where the horizontal axis represents time and the vertical axis represents pressure.

FIG. 3 is a block diagram showing a control device that controls various valves provided in a steam turbine gland seal steam supply system.

FIG. 4 is a block diagram showing a control device that controls various valves provided in the steam turbine gland seal steam supply system.

[Explanation of symbols]

1 ... Exhaust heat recovery boiler, 2 ... High pressure superheater, 3 ... High pressure evaporator, 4 ... High pressure drum, 5 ... Reheater, 6 ... Medium pressure superheater, 7
... Medium-pressure evaporator, 8 ... Medium-pressure drum, 9 ... Low-pressure superheater, 10
... low pressure evaporator, 11 ... low pressure drum, 15 ... high pressure steam turbine, 16 ... medium pressure steam turbine, 17 ... low pressure steam turbine, 19 ... exhaust pipe, 22 ... first extraction pipe, 26 ... second extraction pipe, 30 ... 3rd extraction pipe, 31 ... Motorized valve, 32 ... Steam seal make-up valve, 34 ... Steam turbine gland part, 35 ... Grand steam backup pipe, 36 ... Steam seal make-up backup valve, 37 ... Steam seal dump valve .

Continuation of the front page (72) Inventor Hiroshi Hattori 3-2-1 Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Engineering Co., Ltd.

Claims (4)

[Claims] 1. An exhaust heat recovery boiler for generating steam by using exhaust gas of a gas turbine as a heat source, a steam turbine driven by steam obtained by the exhaust heat recovery boiler, and exhaust gas of the steam turbine for exhaust heat. In a combined cycle power plant having a reheat system that leads to a reheater of a recovery boiler, a combined cycle plant is provided, in which a pipe is provided to extract the exhaust gas from the reheat system and supply it to a gland portion of the steam turbine. . 2. An exhaust heat recovery boiler that generates steam by using exhaust gas of a gas turbine as a heat source, a steam turbine that uses the steam obtained by the exhaust heat recovery boiler as a drive source, and exhaust gas of the steam turbine that exhausts the exhaust heat. In a combined cycle power plant having a reheat system that leads to a reheater of a recovery boiler, a first pipe that extracts the exhaust gas from the reheat system and supplies the exhaust gas to a gland portion of the steam turbine, and the exhaust heat recovery boiler A combined power plant comprising: a second pipe for supplying the steam generated in the medium-pressure evaporator to the gland portion of the steam turbine. 3. Exhaust gas from a gas turbine is supplied to an exhaust heat recovery boiler to generate steam, the generated steam drives a steam turbine, and the steam after driving the steam turbine is reheated in the exhaust heat recovery boiler. In the method for operating a combined cycle power plant, the steam after driving the steam turbine is extracted and supplied to the ground portion of the steam turbine. 4. Exhaust gas of a gas turbine is supplied to an exhaust heat recovery boiler to generate steam, the steam turbine is driven by the generated steam, and the steam after driving the steam turbine is reheater of the exhaust heat recovery boiler. In the operation method of the combined power generation plant to be supplied to, in normal operation, the steam after driving the steam turbine is extracted and supplied to the gland portion of the steam turbine, and when operating independently in the plant, the intermediate pressure evaporation of the exhaust heat recovery boiler. A method of operating a combined cycle power plant, comprising supplying steam generated in a steam generator to a gland portion of the steam turbine.