JPH0693810A - Combined power generating system - Google Patents

Abstract

PURPOSE:To provide a combined power generating system which can easily control the flow rate, pressure and the temperature of steam at the inlet of a steam turbine without deteriorating the feature of a system which use a part of steam used in the steam turbine system so as to cool blades of a gas turbine. CONSTITUTION:Steam led from a high drum 143 incorporated in a gas turbine blade cooling system 34 is led through a cooling passage 150 formed in each of blades 149 in a gas turbine 11, and is then led through a passage 151 to a merging point 138 where it merges into steam led from a high pressure drum 134. The merging steam is led through a passage 139 into a high pressure heater 125 for heating the steam, and is then led through a passage 140 into a steam turbine 180.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined power generation system combining a gas turbine system and a steam turbine system.

[0002]

2. Description of the Related Art Recently, there has been a strong demand for higher efficiency of thermal power generation systems. In order to meet this demand, not only new thermal power plants but also existing thermal power plants are being integrated into a combined cycle by repowering.

FIG. 4 shows a system diagram of a typical combined power generation system. This combined power generation system is composed of a gas turbine system 1 and a steam turbine system 2 driven by exhaust heat energy of the gas turbine system 1.

The gas turbine system 1 includes a gas turbine 11
And a compressor 13 connected to the gas turbine 11 via a shaft 12, and the high-pressure air and fuel sent from the compressor 13 are introduced and burned, and the high-temperature high-pressure gas obtained by this combustion is used. It is composed of a combustor 14 that drives the gas turbine 11. That is, the compressor 13 compresses the room temperature air guided through the passage 15. Compressor 1
The high-pressure air sent out from No. 3 has a part of the gas turbine 1
It is used for cooling the blades in 1 and for sealing the rotating part, and the rest is guided to the combustor 14. The combustor 14 burns fuel supplied from a fuel supply system (not shown) using high-pressure air as a combustion-supporting gas. The hot gas obtained by combustion is supplied to the gas turbine 11 via the passage 16, expands to give a driving force to the gas turbine 11, and then flows to the passage 17.

On the other hand, the steam turbine system 2 generates steam by the steam turbine 18, a generator 20 connected to the steam turbine 18 via a shaft 19 and the exhaust heat of the gas turbine system 1 described above, and this steam is generated. And a steam cycle 21 that drives the steam turbine 18. In this figure, an example in which the rotor of the steam turbine 18 and the rotor of the gas turbine 11 are connected by a shaft 22 is shown.

The steam cycle 21 is provided with an exhaust heat recovery boiler 23 for recovering heat from the exhaust gas of the gas turbine 11 guided through the passage 17 and generating high temperature and high pressure steam necessary for driving the steam turbine 18. . Exhaust heat recovery boiler 23
The exhaust gas that has passed therethrough is discharged into the atmosphere via the flue 27.

A high-pressure heater 24, a high-pressure evaporator 25, and a high-pressure preheater 26 are provided in this order from the upstream side to the downstream side in the exhaust heat recovery boiler 23, and these and the steam turbine 18 have the following relationship. They are connected to form a steam cycle 21. That is, the steam discharged from the steam turbine 18 is guided to the condenser 29 through the passage 28, and is returned to the room temperature water by the condenser 29. The returned room temperature water is introduced into the high pressure preheater 26 through the circulation pump 30 and the passage 31 to be preheated, and then introduced into the high pressure drum 32 through the passage 32. Then, the high-pressure water in the high-pressure drum 32 is guided to the high-pressure evaporator 25 via the circulation pump 34 and the passage 35 to be evaporated, and the high-pressure high-temperature steam generated by this evaporation is passed through the passage 36 to the high-pressure drum 32. Return to the upper space. The returned steam is guided to the high pressure heater 24 through the passage 37,
After being reheated here, the steam turbine 1 is passed through the passage 38.
I am trying to supply to 8.

By the way, in such a combined cycle power generation system, it is desired to raise the inlet gas temperature of the gas turbine 11 in order to further improve the thermal efficiency. As the inlet gas temperature of the gas turbine 11 rises, it is necessary to form the combustor 14, the stationary blades and the moving blades of the gas turbine 11 with a material capable of withstanding high temperatures.

However, the critical temperature of the heat-resistant superalloy material that can be used as a member for turbines is currently 800-
It is 900 ° C. On the other hand, the turbine inlet temperature in a recent gas turbine reaches about 1300 ° C., which is far above the limit temperature of the heat-resistant superalloy material. Therefore, it is necessary to cool the blades of the turbine 11 to the limit temperature of the heat-resistant superalloy material by some means, and in a gas turbine with a turbine inlet temperature of 1300 ° C., the compressor 1 is usually used.
An air-cooling system is adopted in which the blades are cooled by part of the air discharged from the No. 3 air conditioner.

However, the air-cooling method using air as the cooling medium is inherently low in cooling characteristics. For this reason, if the gas turbine inlet temperature exceeds 1300 ° C., the flow rate of cooling air required for cooling the blades increases significantly. Moreover, sufficient cooling effect cannot be obtained only by convection cooling inside the blade, and there is no choice but to use a film cooling method in which cooling air is blown from the small holes formed on the blade surface of the blade effective portion to the outside of the blade. Absent. When this film cooling system is adopted, the temperature of the mainstream gas is lowered because the blown cooling air and the mainstream gas are mixed. Therefore, not only is it necessary to design to make the outlet temperature of the combustor 14 higher, but also the development of a new low NOx type combustor 14 is required even in a high temperature field, and consumption by the combustor 14 is required. Inevitably increases the amount of air and fuel used.

As described above, the method of air-cooling the blades of the turbine causes a decrease in the thermal efficiency of the gas turbine, which causes a problem of a decrease in the thermal efficiency of the entire combined cycle power generation system. Further, there is a problem that it cannot be applied to poor fuel containing impurities because it may cause clogging of the small holes formed on the blade surface.

Therefore, in order to solve such a problem, recently, Japanese Patent Publication No. 63-40244 and Japanese Unexamined Patent Publication (Kokai) No.
As shown in Japanese Patent No. 124414, it is considered to use a vapor having a specific heat which is about twice as large as that of air as a cooling medium. That is, part of the steam used in the steam turbine system is made to flow through the cooling passages provided in the blade of the gas turbine to cool the blade, and the steam used for cooling is supplied to the steam turbine together with the remaining steam. I am trying to do it.

In such a combined power generation system, a smaller amount of steam than air is used, and the blade can be cooled well without blowing this steam out of the blade, and the steam used for cooling the blade is recovered. Can be fed to a steam turbine. Therefore, when this method is adopted, the temperature of the mainstream gas is not lowered, and the increase of fuel and air in the combustor can be suppressed, so that the thermal efficiency can be improved, and poor fuel can also be dealt with.

However, in the conventional combined cycle power generation system in which the blades of the gas turbine are cooled with steam, a part of the steam used in the steam turbine system flows through the cooling passage provided in the blades of the gas turbine. The steam that has passed through the cooling passage and the remaining steam are combined at the inlet of the steam turbine, and the combined steam is supplied to the steam turbine. It was difficult to match the steam pressure and steam temperature to the target values, and the controllability was poor, which made it difficult to operate at maximum thermal efficiency.

[0015]

As described above, in the conventional combined cycle power generation system, in particular, the one that adopts the method of cooling the blades of the gas turbine with steam, it is possible to operate the steam turbine at maximum thermal efficiency. It was difficult and it was difficult to raise the total thermal efficiency to the target. Therefore, an object of the present invention is to provide a combined power generation system capable of improving the total thermal efficiency without impairing the features of the steam cooling system.

[0016]

In order to achieve the above object, the present invention drives a turbine with a gas turbine system and steam obtained by recovering exhaust heat of the gas turbine system with an exhaust heat recovery boiler. A steam turbine system having a steam cycle, and a gas turbine blade cooling system for returning a part of the steam obtained by the exhaust heat recovery boiler to the steam cycle via a cooling passage provided in the blade of the gas turbine. In the combined power generation system including the above, the gas turbine blade cooling system is configured to return substantially all of the steam that has passed through the cooling passage to the heating process region of the steam cycle.

[0017]

[Operation] Since the gas turbine blade cooling system is configured to return the steam after cooling the blades of the gas turbine to the heating process region of the steam cycle, the steam after cooling the blades of the gas turbine is In the heating process area, the steam merges with the remaining steam, and the combined steam is supplied to the steam turbine after being reheated in the heating process area. Therefore, it becomes easy to match the steam flow rate, the steam pressure, and the steam temperature at the inlet of the steam turbine to the target values, and eventually it becomes possible to operate at the maximum thermal efficiency.

[0018]

Embodiments will be described below with reference to the drawings.

FIG. 1 is a system diagram of a combined power generation system according to an embodiment of the present invention. This combined power generation system includes a gas turbine system 41 and a steam turbine system 42 driven by exhaust heat energy of the gas turbine system 41.
And a gas turbine blade cooling system 4 for cooling the blades of the gas turbine by using a part of the steam of the steam turbine system 42.
3 and 3.

The gas turbine system 41 includes the gas turbine 1
11, a compressor 113 connected to the gas turbine 111 via a shaft 112, and the high-pressure air and fuel sent from the compressor 113 are introduced and burned, and the high-temperature high-pressure gas obtained by this combustion is introduced. And a combustor 114 that drives the gas turbine 111.

The compressor 113 compresses the room temperature air introduced through the passage 115. The high pressure air sent from the compressor 113 is guided to the combustor 114. Combustor 114
Burns fuel supplied from a fuel supply system (not shown) using high-pressure air as a combustion-supporting gas. The hot gas obtained by combustion is supplied to the gas turbine 111 via the passage 116, expands to give a driving force to the gas turbine 111, and then flows to the passage 117.

The steam turbine system 42 includes the steam turbine 1
18, the generator 120 connected to the steam turbine 118 via the shaft 119, and the exhaust heat of the gas turbine system 41 described above to generate steam, and the steam is used to generate steam.
And a steam cycle 121 for driving In this figure, an example in which the rotor of the steam turbine 118 and the rotor of the gas turbine 111 are connected by a shaft 122 is shown.

The steam cycle 121 is provided with an exhaust heat recovery boiler 123 for recovering heat from the exhaust gas of the gas turbine 111 guided through the passage 117 and generating high temperature and high pressure steam necessary for driving the steam turbine 118. . The exhaust gas that has passed through the exhaust heat recovery boiler 123 is discharged into the atmosphere via the flue 124. In the exhaust heat recovery boiler 123, the high pressure heater 125, the second high pressure evaporator 126, the first high pressure evaporator 127, and the high pressure preheater 1 are sequentially arranged from the upstream side to the downstream side.
28 is provided, and these are connected to the steam turbine 118 in the following relationship to form a steam cycle 121.

That is, the steam discharged from the steam turbine 118 is supplied to the condenser 130 via the passage 129, and is returned to room temperature water by the condenser 130. The returned normal temperature water is introduced into the high-pressure preheater 128 through the circulation pump 131 and the passage 132 to be preheated, and then the first through the passage 133.
Of the high pressure drum 134. Then, the high-pressure water in the first high-pressure drum 134 is guided to the first high-pressure evaporator 127 via the circulation pump 135 to be evaporated, and the high-pressure high-temperature steam generated by this evaporation is passed through the passage 136 to the first high-pressure evaporator 127. 1. Return to the upper space of the high pressure drum 134. The returned steam is guided to the high-pressure heater 125 through the passage 137, the confluence 138, and the passage 139, and is reheated there, and then the passage 1
40 to the steam turbine 118.

On the other hand, the gas turbine blade cooling system 43 is constructed as follows. That is, part of the high-pressure water existing in the first high-pressure drum 134 is guided to the second high-pressure drum 143 via the pump 141 and the passage 142, and the high-pressure water in the second high-pressure drum 143 is circulated. 14
4, the gas is introduced into the second high-pressure evaporator 126 through the passage 145 to be evaporated, and the high-pressure and high-temperature vapor generated by this evaporation is returned to the upper space of the second high-pressure drum 143 through the passage 146. The returned steam is supplied to the cooling passage 150 formed in the blade 149 of the gas turbine via the passage 147 and the flow rate control valve 148. This cooling passage 150
Is completely separated from the mainstream gas passage. The steam that has passed through the cooling passage 150 is then passed through the passage 15
1 and the steam guided from the first high-pressure drum 134 side. In addition,
Reference numeral 152 in the drawing denotes a bypass valve.

With this structure, the steam guided through the passage 147 is cooled by the cooling passage 15 formed in the blade 149 of the gas turbine 111 through the flow rate adjusting valve 148.
0 to be used for cooling the blade 149. Cooling passage 15
0 is not released to the outside world. Therefore, the steam flowing through the cooling passage 150 does not mix with the mainstream gas and does not lower the temperature of the mainstream gas.
An increase in fuel and air in the combustor 114 can be suppressed, and thermal efficiency can be improved. Moreover, it can handle poor fuel.

In particular, in this example, the steam that has passed through the cooling passage 150 passes through the passage 151 and meets the confluence 13
8. That is, in the heating process region of the steam cycle 121, the steam guided from the first high-pressure drum 134 side is combined, and the combined steam is reheated by the high-pressure heater 125 and then supplied to the steam turbine 118. Therefore, the steam flow rate, the steam pressure, and the steam temperature at the inlet of the steam turbine 118 can be easily adjusted to the target values without being affected by the gas turbine blade cooling system 43, and eventually, the operation can be performed with the maximum thermal efficiency. Becomes

FIG. 3 shows the total efficiency of the combined power generation system according to the present invention and that of the conventional system. As can be seen from this figure, in the combined power generation system according to the present invention, the efficiency on the steam turbine side can be improved, so that the overall efficiency can be greatly improved especially in the region where the gas turbine inlet temperature is high.

FIG. 2 is a system diagram of a combined power generation system according to another embodiment of the present invention. In this figure, the same parts as those in FIG. 1 are designated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

The system according to this embodiment differs from that shown in FIG. 1 in the configuration of the gas turbine blade cooling system 43a. That is, this gas turbine blade cooling system 43a
Then, the passage located between the flow rate adjusting valve 148 and the cooling passage 150 can be connected to the outlet of the compressor 113 via the flow rate adjusting valve 153, and is located between the bypass valve 152 and the confluence point 138. Intervening the valve 154 in the passage,
Further, the passage located between the bypass valve 152 and the valve 154 can be connected to the passage 117 via the valve 155.

With such a structure, the same effect as that of the embodiment shown in FIG. 1 can be obtained, and the second high pressure can be obtained, for example, when the turbine is started / stopped or at the partial load operation. When it is extremely difficult to supply the steam for cooling the blades from the drum 143, instead of the steam, a part of the air discharged from the compressor 113 is caused to flow through the cooling passage 150, and the blades 14 are cooled.
9 can be air cooled. That is, when the flow rate control valve 148, the bypass valve 152, and the valve 154 are controlled to be “closed” and the flow rate control valve 153 and the valve 155 are controlled to be “open”, a part of the high pressure air discharged from the compressor 113 is controlled. Flow can be made to flow through the path of the flow rate control valve 153 to the cooling passage 150 to the valve 155 to the passage 117, and the steam passage can be completely separated to air-cool the blade 149.

Therefore, with the above-described structure, the blades 149 of the gas turbine 111 can be satisfactorily cooled under any operating conditions such as starting and stopping of the turbine, partial load operation, and steady operation. it can.

[0033]

As described above, according to the present invention,
The steam flow rate, pressure, and temperature at the inlet of the steam turbine can be easily controlled without impairing the characteristics of the method of cooling the blades of the gas turbine using part of the steam used in the steam turbine system. This can contribute to the improvement, and thus the total thermal efficiency can be further improved.

[Brief description of drawings]

FIG. 1 is a system diagram of a combined power generation system according to an embodiment of the present invention.

FIG. 2 is a system diagram of a combined power generation system according to another embodiment of the present invention.

FIG. 3 is a diagram showing the total thermal efficiency of the combined cycle power generation system according to the present invention and that of a conventional combined cycle power generation system.

FIG. 4 is a system diagram of a conventional combined cycle power generation system.

[Explanation of symbols]

41 ... Gas turbine system 42 ... Steam turbine system 43, 43a ... Gas turbine blade cooling system 111 ... Gas turbine 113 ... Compressor 114 ... Combustor 118 ... Steam turbine 120 ... Generator 121 ... Steam cycle 123 ... Exhaust heat recovery boiler 125 … High-pressure heater 126… Second
High pressure evaporator 127 ... first high pressure evaporator 128 ... high pressure preheater 130 ... condenser 134 ... first
High-pressure drum 138 ... Confluence 143 ... Second
High pressure drum 148, 153 ... Flow rate adjusting valve 152 ... Bypass valve 154, 155 ... Valve

Claims (2)

[Claims] 1. A gas turbine system, a steam turbine system having a steam cycle for driving a turbine with steam obtained by recovering exhaust heat of the gas turbine system with an exhaust heat recovery boiler, and the exhaust heat recovery boiler. In a combined power generation system with a gas turbine blade cooling system for returning a part of the obtained steam to the steam cycle via a cooling passage provided in the blade of the gas turbine, the gas turbine blade cooling system, A combined power generation system configured to return substantially all of the steam that has passed through the cooling passage to a heating process region of the steam cycle. 2. A switching means for disconnecting the cooling passage from the steam cycle in the gas turbine blade cooling system, and allowing a part of high pressure air generated in the gas turbine system to flow through the cooling passage in this state. The combined power generation system according to claim 1, further comprising: