JPH08319852A - Gas turbine plant and its cooling method - Google Patents

Abstract

PURPOSE: To eliminate risk of dew condensation even at the time of cold start of a gas turbine plant, preclude generation of unbalance or vibration in a rotor, and prevent oxidation or corrosion of metal components of gas turbine. CONSTITUTION: A gas turbine plant concerned uses vapor as a cooling medium when rotor blades 123 and the second stage stator blades 129 as components installed on a gas passage in a gas turbine are to be cooled, wherein the vapor is arranged so as to circulate through the cooling medium system. In this cooling method of gas turbine plant, air is used as a cooling medium for the components installed on the gas passage at starting of gas turbine and at the time of cold start, and vapor is used as cooling medium when the specified level is exceeded by the temp. of the flow path for cooling medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine plant and a gas turbine plant cooling method, and more particularly to a cooling medium closed cycle gas turbine plant.

[0002]

2. Description of the Related Art Gas turbines tend to have higher efficiency as the combustion temperature increases, and therefore, the combustion temperature is currently about to exceed 1400.degree. Therefore, gas turbine parts, such as moving blades and stationary blades, which are arranged in the hot gas flow passage (gas path passage) and are in direct contact with the hot gas, must be cooled due to their material strength, and generally must be cooled. Air is used as a medium for this cooling. The discharge air of the gas turbine compressor is used as this cooling air, and the air after cooling the moving blades and the stationary blades is made to flow to the gas path.

That is, an example of this type of gas turbine is shown in FIG. 11, which is a gas turbine air compressor 11
Part of the discharge air of 03 is guided to the gas turbine moving blade 1123 and the stationary blade 1122, and after cooling the inside of these blades,
Discharge to gas path and merge with hot gas. In this cooling system, the cooling medium cools the moving blades of the gas turbine and then merges with the high-temperature gas. Therefore, the temperature of the combustion gas, that is, the working gas is also lowered, and the thermal efficiency of the gas turbine is lowered.

As for the cooling efficiency in this type of cooling, as the temperature of the cooling medium is lower, the flow rate of the cooling medium can be decreased and the cooling efficiency is also increased. As described above, in the conventional cooling method of flowing the cooling medium to the high temperature gas path after cooling, since the working gas temperature is lowered by this cooling medium,
There is a drawback that hinders the improvement of the thermal efficiency of the gas turbine, and in order to compensate for this drawback, recently, there is an idea to circulate the cooling medium without releasing it to the closed cycle, that is, the gas path, by making the cooling medium high pressure and low temperature. Cooling medium closed cycle gas turbine plants are drawing attention.

That is, in the case of this high-pressure low-temperature cooling medium closed cycle, since the cooling medium that has cooled the gas turbine moving vanes is formed in a system that returns the cooling medium to the original without passing it to the hot path of the gas turbine, Unlike the scheme, the cooling medium does not reduce the temperature of the working gas. In this case, air or steam is generally used as the cooling medium.

FIG. 10 shows an example in which steam is used as the cooling medium.
Is shown in. In the case of the combined cycle, the steam is 10 to 15 out of the steam supplied to the steam turbine.
ata relatively moderate pressure steam is used. The steam after cooling the gas turbine moving blade 1023 and the stationary blade 1022 can be put into the low-pressure steam pipe of the steam turbine, but if it is disliked that even a small amount of air is mixed, it is put into the deaerator. . In the figure, 1011 and 1013
Reference numeral 1020 denotes a steam supply pipe, which includes 1015, 1017, 1
Reference numeral 021 is a steam discharge pipe. Also, 1012 and 1016
Is a three-way valve.

In the case of a cogeneration plant or the like without a steam turbine, the steam generation line of the boiler has 10 to 10
A steam pipe having a pressure of 15 ata is selected, or a pressure pipe having a pressure higher than that is taken out through a pressure reducing valve.

As for those related to these, for example, JP-A-3-264703 can be cited.

[0009]

As described above, when steam is used for cooling the moving blades of the gas turbine in the cooling medium closed-cycle gas turbine plant, the steam temperature is significantly lower than the compressor discharge air temperature used conventionally. From
Since the blade temperature can be sufficiently lowered and the flow rate of the cooling medium can be reduced, the thermal efficiency is good, and further, the cooling passage in the blade can be designed relatively easily, which is an effective cooling method.

However, water vapor may cause dew condensation when it comes into contact with an object having a temperature below its dew point, and during gas turbine operation, the gas turbine shaft, disk, moving vanes, etc. are all at room temperature, The temperature gradually rises after the gas turbine ignites, but it takes more than 2 hours to settle at a constant temperature after full load. In such a case, the water vapor passes through a region having a temperature equal to or lower than the dew point of the water vapor, which is a cooling medium, so that dew condensation occurs on an object in that region. Condensation is water, and when it is large, it causes imbalance of the rotating body and causes vibration, and water may cause oxidation or corrosion of the metal of the gas turbine parts together with oxygen and other corrosive gases. There is.

The present invention has been made in view of the above, and an object thereof is to prevent condensation even when a gas turbine plant is cold-started even in a gas turbine plant in which steam is used as a cooling medium. That is, it is an object of the present invention to provide a gas turbine plant of this kind and a cooling method for the gas turbine plant, which does not cause imbalance or vibration in the rotating body, or oxidize or corrode the metal of the gas turbine component.

[0012]

That is, according to the present invention, when cooling a component arranged in a gas path of a gas turbine, steam is used as a cooling medium and the steam is formed so as to circulate in the cooling medium system. In the method for cooling a gas turbine plant, when the gas turbine is started, and at the time of cold start, cooling air is used as a cooling medium for cooling the components arranged in the gas path, and the temperature of the cooling medium flow passage is When the temperature exceeds a predetermined temperature, steam is used as a cooling medium so that the intended purpose is achieved.

Further, at the time of starting the gas turbine and at the time of cold starting, cooling air is circulated as a cooling medium for cooling the components arranged in the gas path, so that the temperature of the cooling medium flow passage is not condensed when the steam flows. When the temperature becomes equal to or higher than the temperature, the circulation of cooling air is stopped and the cooling steam is caused to flow.

Further, a moving vane arranged in a gas path of the gas turbine and having a cooling medium cooling passage therein, and a cooling medium system for supplying a cooling medium to the cooling medium cooling passage of the moving vane to cool the moving vane. And a steam is used as the cooling medium of the cooling medium system, and in a gas turbine plant in which this steam is formed to circulate through the cooling medium system, the cooling medium system is provided with a flow passage of the cooling medium system. A temperature measuring device for measuring a temperature is provided, and a cooling medium system for cooling air is provided in the cooling medium system for the steam via a cooling medium switching device, and the temperature of the temperature measuring device is set to a predetermined value in the cooling medium switching device. A control device is provided to perform switching control so that cooling air flows through the cooling medium system when the temperature is lower than the temperature, and cooling steam flows when the temperature is higher than a predetermined temperature. It is intended.

Further, the cooling medium system is provided with a temperature measuring device for measuring the temperature of the flow passage of the cooling medium system, and the cooling medium system of the steam is provided with a cooling medium system of cooling air through a cooling medium switching device. Along with the cooling medium switching device, when the temperature of the temperature measuring device is a temperature at which condensation occurs during the flow of steam, cooling air flows through the cooling medium system, and at a temperature at which condensation occurs during the flow of steam. A control device is provided to perform switching control so that cooling steam flows.

Further, in this case, a temperature measuring device for measuring the temperature of the flow passage of the cooling medium system is provided in the cooling medium flow passage near the moving blade. Further, as the cooling air, the extracted air of the air compressor discharge air of the gas turbine is flowed to the cooling system of the gas turbine as it is, flowed to the cooling system of the blades of the gas turbine low pressure stage after recovery, and then to the high temperature gas path. Is formed.

[0017]

That is, in the gas turbine plant thus formed, cooling air is used as a cooling medium for cooling the components arranged in the gas path when the gas turbine is started and when the gas turbine is cold started. When the temperature of the flow passage becomes equal to or higher than the predetermined temperature, the cooling medium is formed so that the steam is used, so that the above-mentioned problem of dew condensation does not occur, and therefore, the cooling medium is not affected by the steam. Even in the gas turbine plant used, there is no risk of dew condensation occurring at cold start of the gas turbine plant, that is, the dew condensation water causes imbalance or vibration in the rotating body, or oxidizes the metal of gas turbine parts. There is no fear of corrosion or corrosion.

[0018]

The present invention will be described in detail below with reference to the illustrated embodiments. As an embodiment of the present invention, FIG. 1 shows an example in which steam and air discharged from the compressor are boosted by a booster to be used as a cooling medium, FIG. 2 shows an example in which no booster is used, and FIG. The improvement is shown in FIG. 3, and FIG. 5 shows a combined cycle system adopting the gas turbine plant of the present invention.

In FIG. 1, the gas turbine 101, the combustor 102, the compressor 103, and the generator 105 are almost the same type as the conventional one, but the gas turbine shaft 104 is significantly different from the conventional one. That is, when the conventional cooling medium is air, the passage for supplying the cooling medium to the moving blades enters the shaft hollow from the compressor discharge side and the turbine side surface (wheel space).
To the rotor blade fitting portion (dovetail), and then to the cooling holes prepared in the rotor blade to cool the rotor blade and discharge it into the gas path passage. A collection route is required.

That is, the gas turbine 101 and the generator 1
Between 05, a seat 126 for taking in and out the cooling medium is provided, and a seat 127 for the supplied cooling medium and a pool 128 for the recovered cooling medium are provided at the seat 126. The inlet and outlet of the supply hole and the recovery hole provided on the shaft 104 are assembled so as to correspond to the reservoirs 127 and 128, respectively.

A supply hole 124 and a recovery hole 125 of the shaft 104.
Are separately bored in the longitudinal direction of the shaft and separately communicate with two holes prepared in the turbine disc (turbine wheel) to communicate with the fitting portion of the moving blade 123. Cooling medium supply holes and recovery holes are prepared in the rotor blade fitting section.
The gap between the turbine disk fitting portion is minimized to minimize the leakage of the cooling medium to the outside of the blade.

The cooling medium to and from the seat 126 for putting in and taking out the cooling medium flows from the medium pressure steam pipe through the pipe 120 to the three-way valve 109.
Here, although it joins with the air compressor discharge air pipe 108, these two types of cooling media are selected by operating this three-way valve according to the temperature state of the cooling medium flow passage of the gas turbine.

That is, to start the gas turbine,
Cooling air is circulated as a cooling medium for cooling the components arranged in the gas path, and when the temperature of the cooling medium flow passage is equal to or higher than the temperature at which condensation does not occur during the flow of steam, the three-way valve is switched to turn the cooling air The flow is stopped and the cooling steam is allowed to flow.

That is, this cooling medium system is provided with a temperature measuring device 150 for measuring the temperature of the flow passage of the cooling medium system, and the three-way valve, that is, the cooling medium switching device, has a temperature measuring device of a predetermined temperature. A control device 151 is provided to perform switching control so that cooling air flows through the cooling medium system in the following cases, and cooling steam flows when the temperature is equal to or higher than a predetermined temperature.

With this configuration, when the gas turbine is started and stopped, air is extracted from the rear of the final stage of the air compressor, and the pipe 1
At 06, the booster 107 takes out a pressure ratio of about 1.
2 is compressed and is supplied to the three-way valve 109 through the pipe 108,
Here, the pipe 120 side from the medium pressure steam pipe is closed, and the pipe 1
The 08 side is opened, compressed air is supplied to the pipe 110, and the three-way valve 112 is used to connect the pipe 113 to the moving blade side and the pipe 1 to the stationary blade side.
The flow rate is distributed to 11. Although this three-way valve is automatically operated by remote control, an orifice may be inserted in the pipes 113 and 111 and the three-way valve 112 may be omitted and the three-way valve may be directly connected.

The cooling medium after cooling the moving vanes flows into the pipe 117 on the moving vane side and into the pipe 115 on the vane side and joins the three-way valve 116. The opening of the three-way valve on the side of the pipes 117 and 115 adjusts the pressure and flow rate in the pipes 117 and 115. After passing through the three-way valve 116 and reaching the three-way valve 119 through the pipe 118, in the case of compressed air, the pipe 114 side is opened, returned to the inside of the combustor casing, and merged with the combustion air. In this case, the amount of heat recovered by the cooling medium is also returned to the combustor.

When the temperature of each part rises as the gas turbine approaches the rated load from the partial load, and when the temperature of the temperature measuring device exceeds a predetermined temperature, the three-way valves 109 and 118 are operated by the control device 151 to cool them. The medium is switched from compressed air to steam. Since the time for the cooling medium to return to the three-way valve 118 through the three-way valve 109 is different on the moving blade side and the stationary blade side, it is necessary to adjust so that the compressed air does not flow through the pipe 121 to the deaerator. However, even if a small amount of air flows into the pipe 121, the air is removed by the deaerator.

The cooling medium for the second stage moving blades 130 is supplied through the passage 133 having the compressor discharge air as the shaft. Second
As the cooling medium for the stationary vanes 129, a three-way valve 131 is attached between the pipes 106 and 132, and compressed air from the pipe 106 is supplied through the pipe 134. Both of the cooling media for the second stage moving vanes are open cooling, and after cooling the vanes, they are discharged to the hot gas path. The reason why the booster 107 is installed and the pressure is increased 1.2 times is that the discharge air pressure and the pipe 114 in the final stage of the compressor are set.
The discharge air pressure at the position of returning to the inside of the combustor is 1%
This is because the compressed air is a cooling medium, and the pressure loss until it returns after cooling the moving and stationary blades is as much as several percent to ten and several percent.

Next, the embodiment shown in FIG. 2 will be described. In this figure, the booster 107 of FIG. 1 is excluded, and the return of compressed air is supplied to cool the low-pressure stage (second stage) vanes or is discharged to the exhaust chamber.

Three-way valve 21 which is the confluence of the cooling medium for recovery
If the compressed air from 9 passes through the pipe 214 and flows into the pipe 236 by the three-way valve 235, it is discharged to the exhaust chamber, and the three-way valve 235.
From the pipe 237 to the three-way valve 231 and the pipe 234.
If it flows to, the second stage stationary blade 229 is cooled. Whether this compressed air is discharged to the exhaust chamber or is used for cooling the second stage stationary blade depends on the pressure balance, and is decided by studying at the time of design.

As in FIG. 1, the second stage moving blades 230 are supplied with compressor discharge air through a passage 233 provided on the shaft. These compressed air flows into the hot gas path after cooling the second stage moving vanes. After the cooling medium is switched from air to water vapor, all of the cooling medium is returned to the deaerator. Therefore, the cooling medium for the second stage stationary vanes 229 uses the compressor discharge air from the pipe 206 to the three-way valve 20.
7 to the pipe 232 and further to the pipe 234 via the three-way valve 231.

Although the pressure loss when cooling the first-stage moving vane is large, it does not drop to the gas pressure at the gas path position behind the second-stage vane, and therefore flows as shown in the figure. When it does not flow, it is discharged to the exhaust chamber, and the compressor discharge air via the pipe 232 is supplied.

Next, the embodiment shown in FIG. 3 will be described. This drawing is an improvement of a part of the embodiment of FIG. 2, and the improvements are as follows. That is, the second stage stationary blade is always open-cooled, extracted from the compressor discharge air, used for cooling, and then discharged to the gas path. The second-stage rotor blade is closed-cooled, and a part of the cooling air supplied to the first-stage rotor blade is also supplied to the second-stage rotor blade.

The second stage blade cooling air supply pipe is shown as 233a and the discharge pipe is shown as 232a. 20
7a and 235a are stop valves. Other symbols are attached with a subscript a so as to correspond to the symbols in FIG.

As described above with reference to the embodiments, in the present invention, when the temperature of the cooling medium flow passage of the gas turbine is low, that is, at the time of starting, cooling air is circulated as a cooling medium for cooling the components arranged in the gas path. Then, when the temperature of the cooling medium flow passage becomes equal to or higher than the temperature at which no condensation occurs during the flow of steam, steam is used.

Since the cooling medium is supplied to the first-stage rotor blades through the gas turbine shaft as shown in the figure, the CVD is performed in the shaft inner hole to limit the heat transfer between this shaft and the cooling medium. It is preferable to construct the pipe or to install a pipe made of a material having a high heat shield rate.

FIG. 4 shows the relationship between the type of cooling medium used and the start / stop of the gas turbine. In this figure, the switching time point is near the rated load, but it goes without saying that this differs depending on the conditions of the cooling medium flow passage and the operating conditions.

FIG. 6 shows an example of the cooling system for the first stage vanes. In the figure, 601 indicates the supply of the cooling medium, and 602 indicates the return recovery. Reference numeral 603 denotes a cooling medium that is discharged to the hot gas path after cooling the trailing edge of the blade. Reference numeral 604 represents a situation in which the cooling medium returns within the vane. In the figure, this return is shown once, but since it is possible with the current precision casting technology to construct a structure with two or three returns, the working gas, cooling medium, blade temperature and cooling medium It is decided at the time of design after considering the pressure and consideration.

Since the trailing edge portion of the stationary blade is long and thin, it cannot be sufficiently cooled by the return flow of the cooling medium, so that it has to be cooled while being discharged to the hot gas path as shown in the figure.

7 to 9 are longitudinal sectional views of the first-stage rotor blade, showing an example of the cooling system. In the figure, 701, 801, 901
Indicates the supply of the cooling medium, and 702, 802 and 902 indicate the return recovery. Reference numerals 703, 803, and 903 denote escapes for preventing clogging of the places where the cooling medium returns 704, 804, and 904 due to dust, and the cooling medium exiting from these blades joins the gas path passage behind the moving blades.

705, 805 and 905 are blade profile portions, 706, 806 and 906 are shank portions, 707 and 8
Reference numerals 07 and 907 denote fitting portions, and reference numerals 708, 808, and 908 denote outer peripheral portions of the turbine disc (turbine wheel) portion. Since the trailing edge of the blade is shorter and thicker than that of the stationary blade, the cooling system as shown in the figure does not require the cooling medium to be discharged to the hot gas path while cooling the trailing edge like the stationary blade. The edge temperature can be lowered sufficiently.

The CVD shown in the figure is a chemical vapor.
It is an abbreviation for "cum Deposition", which is a type of heat shield applied to the internal hole of a component. As for the construction method, the discharge holes of 803 and 903 are closed, and the CVD gas is put into the blade from the hole on the side of 801 in the case of FIG. 8 and the hole of 902 in the case of FIG. Let In this way, the side into which the CVD gas is introduced is selected to control the degree to which the heat shielding material is deposited on the inner hole surface.

This CVD hinders the heat transfer between the cooling medium and the blade material, and a temperature difference of several tens of degrees can be obtained as compared with the case without CVD. In the case of FIG. 8 in which the CVD is performed from the 801 side, the fitting portion (dovetail) 807 and the shank portion 806 are heat shielded from being cooled unnecessarily by the cooling medium having a low temperature, and the temperature of the cooling medium itself does not rise. It flows into the inner hole of the leading edge where the temperature becomes the highest in the blade, and the leading edge can be cooled sufficiently. On the other hand, in the case of FIG. 9 constructed from the 902 side, the fitting portion 907 and the shank portion 906 are heat shielded so as not to be unnecessarily heated by the cooling medium whose temperature has risen after heat exchange. The effect of this CVD is described in detail in (Kiken) patent application reference number PNT94021.

As described above, in the gas turbine plant thus formed, when the temperature of the gas turbine component is low, the compressor discharge air is used as the cooling medium, and the temperature of the component becomes high. Since the method is switched to steam, there is no fear of the above-mentioned problem of dew condensation. The difference in the temperature of the cooling medium will be described in Table 1.

[0045]

[Table 1]

This table uses air and steam as the cooling medium,
These figures compare the unloaded and full-loaded states of a gas turbine, respectively. When steam is used as the cooling medium from the start of the gas turbine, the steam pressure is 11.3 at
a, When the temperature is 190 ° C., the dew condensation phenomenon appears on the inner surface when the metal temperature of the first stage moving / vanes is 190 ° C. or lower. If air is used as the cooling medium when the metal temperature is low, the air compressor discharge temperature 292 can be obtained without load on the gas turbine.
C., 320.degree. C. when boosted by a booster, and even if the metal temperature of the first stage moving and stationary blades is low, the blades are heated and no dew condensation occurs.

[0047]

As described above, according to the present invention, even in a gas turbine plant in which steam is used as a cooling medium, there is no risk of dew condensation even at the cold start of the gas turbine plant. It is possible to obtain this type of gas turbine plant that is free from imbalance and vibration, and from oxidizing or corroding the metal of the gas turbine component.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of a gas turbine plant of the present invention.

FIG. 2 is a vertical sectional side view showing another embodiment of the gas turbine plant of the present invention.

FIG. 3 is a vertical sectional side view showing another embodiment of the gas turbine plant of the present invention.

FIG. 4 is a diagram showing a relationship of starting and stopping a gas turbine.

FIG. 5 is a system diagram of a combined cycle gas turbine plant adopting the present invention.

FIG. 6 is a perspective view of a gas turbine first stage vane of the present invention.

FIG. 7 is a vertical cross-sectional view of a first-stage rotor blade adopted in the gas turbine plant of the present invention.

FIG. 8 is a vertical cross-sectional view of a first-stage rotor blade adopted in the gas turbine plant of the present invention.

FIG. 9 is a vertical cross-sectional view of a first-stage rotor blade adopted in the gas turbine plant of the present invention.

FIG. 10 is a vertical cross-sectional side view showing an example of a conventional gas turbine plant.

FIG. 11 is a vertical sectional side view showing an example of a conventional gas turbine plant.

[Explanation of symbols]

501 ... Compressor, 502 ... Gas turbine, 503 ... Combustor, 504 ... Exhaust heat boiler, 505 ... High pressure steam turbine, 506 ... Low pressure steam turbine, 507 ... Generator, 50
8 ... Condenser, 509 ... Condensate pump, 510 ... Deaerator, 5
11 ... Boiler feed pump, 1001 ... Gas turbine,
1002 ... Combustor, 1003 ... Compressor, 1004 ... Shaft,
Reference numeral 1005 ... Generator, 1011 ... First stage stationary blade supply steam piping, 1012 ... Supply steam split three-way valve, 1013 ... Gas turbine first stage moving blade supply steam piping, 1015 ... First stage stationary blade outlet recovery steam piping, 1016 ... First Stage moving vane outlet recovery steam three-way valve, 1017 ... First stage moving blade outlet recovery steam pipe, 1
020 ... Steam supply pipe from medium-pressure steam pipe, 1021 ... Recovery steam pipe to deaerator, 1022 ... Gas turbine first stage stationary blade, 1023 ... Gas turbine first stage moving blade, 1024 ... Steam supply shaft inner hole, 1025 ... Shaft inner hole for recovered steam, 102
6 ... Seat for loading / unloading steam body, 1027 ... Pool for supply steam, 1028 ... Pool for recovered steam, 1101 ... Gas turbine, 1102 ... Combustor, 1103 ... Compressor, 11
04 ... Shaft, 1105 ... Generator, 1122 ... Gas turbine first stage stationary blade, 1123 ... Gas turbine first stage moving blade, 11
24 ... A shaft inner hole for supplying compressor discharge air.

Claims (10)

[Claims] 1. A method for cooling a gas turbine plant, wherein steam is used as a cooling medium when cooling a component arranged in a gas path of a gas turbine, and the steam is formed so as to circulate through the cooling medium system. In, at the start of the gas turbine, and at the time of cold start, using cooling air as a cooling medium for cooling the components arranged in the gas path, when the temperature of the cooling medium flow passage is equal to or higher than a predetermined temperature, A method for cooling a gas turbine plant, characterized in that the steam is used as a cooling medium. 2. A method of cooling a gas turbine plant, wherein steam is used as a cooling medium when cooling a component arranged in a gas path of a gas turbine, and the steam is formed so as to circulate through the cooling medium system. At the start of the gas turbine, and at the time of cold start, cooling air is circulated as a cooling medium for cooling the components arranged in the gas path, and the temperature of the cooling medium flow passage is a temperature at which no condensation occurs during the flow of steam. A cooling method for a gas turbine plant, characterized in that when the above is reached, the circulation of the cooling air is stopped and the cooling steam is caused to flow. 3. A method for cooling a gas turbine plant, wherein steam is used as a cooling medium when cooling a component arranged in a gas path of a gas turbine, and the steam is formed so as to circulate through the cooling medium system. In, the temperature of the flow passage of the cooling medium system is measured from the time of starting the gas turbine, and at the time of cold start of the gas turbine, cooling air is circulated as a cooling medium for cooling the components arranged in the gas path. The cooling of the gas turbine plant is characterized in that the cooling medium is switched from cooling air to cooling steam when the temperature of the flow passage of the cooling medium system becomes equal to or higher than a temperature at which condensation does not occur when the steam flows. Method. 4. The cooling method for a gas turbine plant according to claim 3, wherein when measuring the temperature of the flow passage of the cooling medium system, the temperature of a portion of the cooling medium system where the temperature rises most slowly is measured. 5. A cooling passage provided in the component to be cooled is common to both cooling air and cooling steam, and cooling air is supplied by compressing and extracting bleed air of discharge air from a gas turbine air compressor. The method for cooling a gas turbine plant according to claim 1, 2, 3 or 4, wherein the latter is returned to the original discharge air side. 6. Arranged in the gas path of the gas turbine,
And a moving vane having a cooling medium cooling passage therein, and a cooling medium system for supplying a cooling medium to the cooling medium cooling passage of the moving vane to cool the moving vane, and steam is provided to the cooling medium of the cooling medium system. Used, in a gas turbine plant in which this steam is formed so as to circulate in a cooling medium system, the cooling medium system is provided with a temperature measuring device for measuring the temperature of the flow passage of the cooling medium system, and A cooling medium system for cooling air is provided in the cooling medium system via a cooling medium switching device, and when the temperature of the temperature measuring device is below a predetermined temperature, the cooling air flows through the cooling medium system in the cooling medium switching device. A gas turbine plant is provided with a control device that performs switching control so that cooling steam flows when the temperature is equal to or higher than a predetermined temperature. 7. Arranged in the gas path of the gas turbine,
And a moving vane having a cooling medium cooling passage therein, and a cooling medium system for supplying a cooling medium to the cooling medium cooling passage of the moving vane to cool the moving vane, and steam is provided to the cooling medium of the cooling medium system. Used, in a gas turbine plant in which this steam is formed so as to circulate in a cooling medium system, the cooling medium system is provided with a temperature measuring device for measuring the temperature of the flow passage of the cooling medium system, and A cooling medium system for cooling air is provided in the cooling medium system via a cooling medium switching device, and in the cooling medium switching device, when the temperature of the temperature measuring device is a temperature at which condensation occurs during the flow of steam, the cooling medium system is provided. A gas turbine characterized by being provided with a control device for performing switching control so that cooling air flows, and cooling steam flows when the temperature of dew condensation occurs when the steam flows. Plant. 8. The gas turbine plant according to claim 6, wherein the temperature measuring device for measuring the temperature of the flow passage of the cooling medium system is provided in the cooling medium flow passage near the moving blades. 9. The supply source of the cooling steam is a coal gasifier boiler or a cogeneration plant boiler,
The gas turbine plant according to 7 or 8. 10. The cooling air is the extracted bleed air of the air compressor discharge air of the gas turbine as it is, flows to the blade cooling system of the gas turbine, flows to the cooling system of the blade of the gas turbine low-pressure stage after recovery, and then becomes high temperature. The gas turbine plant according to claim 6, 7 or 8, which is formed so as to flow to a gas path.