CA2284491C - Combined cycle electric power plant - Google Patents

Combined cycle electric power plant Download PDF

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Publication number
CA2284491C
CA2284491C CA002284491A CA2284491A CA2284491C CA 2284491 C CA2284491 C CA 2284491C CA 002284491 A CA002284491 A CA 002284491A CA 2284491 A CA2284491 A CA 2284491A CA 2284491 C CA2284491 C CA 2284491C
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Canada
Prior art keywords
steam
combustor
air
power plant
turbine
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Expired - Fee Related
Application number
CA002284491A
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French (fr)
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CA2284491A1 (en
Inventor
Akimasa Muyama
Jun Yasuraoka
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Mitsubishi Power Ltd
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Mitsubishi Heavy Industries Ltd
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Priority claimed from PCT/JP1998/000260 external-priority patent/WO1999037900A1/en
Publication of CA2284491A1 publication Critical patent/CA2284491A1/en
Application granted granted Critical
Publication of CA2284491C publication Critical patent/CA2284491C/en
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00Combustion technologies with mitigation potential
    • Y02E20/16Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]

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  • Engine Equipment That Uses Special Cycles (AREA)

Abstract

A combined cycle electric power plant comprising a combination of a gas turbine plant and a steam turbine plant, and using a cooling steam for cooling a high temperature portion (5) being cooled, of a combustor (4) on a gas turbine (2). When a cooling steam is short at the time of startup or suspension, an air line (9) for permitting an outlet air of an air compressor (1) to pressurize a steam passage (7) of the high temperature portion (5) being cooled to make the same higher in pressure than the combustor (4), is connected to the steam passage (7) to air cool the same to protect the combustor (4) and accessory pipe lines from burning, thereby enabling operating the plant safely and stably over a long term.

Description

SPECIFICATION
COMBINED CYCLE POWER PLANT
TECHNICAL FIELD
The present invention relates to a combined cycle power plant including combined gas and steam turbine plants.
BACKGROUND ART
The combined cycle power plant is a power generation system which has combined gas and steam turbine plants. In this system, the gas turbine takes charge of a higher-temperature range of the thermal energy, while the steam turbine takes charge of the remaining lower-temperature range, thereby efficiently recovering and using the thermal energy. This is currently the most common power generation system.
In order to improve the efficiency, the development of the combined cycle power plant has been focused on how high the higher-temperature range of the gas turbine can be set.
To realize a higher-temperature range, a cooling system must be provided in consideration of the heat resistance of the turbine structure. Conventionally, air is used as a cooling medium in such a cooling system.
However, as long as air is used as the cooling medium, even if a desirable higher-temperature range can be achieved, the plant will inevitably suffer from (i) loss of power necessary for boosting the air (which was used for cooling) up to a specified pressure by using an internal air compressor, and (ii) lowering of the average gas temperature and thus the energy of the gas because the air used for cooling target portions is finally made flow through the passage (in the turbine) together with the high-temperature gas. As a result of the above effects (i) and (ii), it is very difficult to further improve the thermal efficiency.
In order to solve the above problem and to further improve the efficiency, another type of combined cycle power plant has been proposed, in which the steam is used as the cooling medium of the gas turbine instead of air as mentioned above.
Japanese Unexamined Patent Application, First Publication, No. Hei 5-163960 discloses an example thereof. Although this publication discloses the concept that steam is used as a cooling medium for gas turbine 13, it also has many problems.
For example, in this system, when the gas turbine is activated or stopped, cooling steam is not supplied to the high-temperature portion to be cooled because it is considered in this system that at these times (i.e., when starting or stopping), the thermal load is relatively low and the cooling operation is unnecessary.
On the other hand, the compressed air of the gas-turbine compressor is the only cooling medium used as a substitute for the cool steam in such a power plant.
Therefore, if the high-temperature portion of the gas turbine must be cooled when the gas turbine is activated or stopped, the compressed air of the gas-turbine compressor must be used.
In the above system disclosed in Hei 5-163960, when the compressed air of the gas-turbine compressor is used as a substitute, air in the gas turbine chamber is extracted to be introduced into the original steam cooling system. Therefore, this air passes through piping, valves, or the like, and thus a pressure loss inevitably occurs.
Here, the combustor is the highest-temperature part of all the high-temperature parts in the gas turbine, and the inner pressure thereof is only a little lower than the pressure of air in the gas turbine chamber. Therefore, if the above-described cooling with air is employed, the air pressure in the cooling path must be lower than the pressure in the combustion atmosphere of the combustor.
Accordingly, if a small hole such as a pinhole exists in the structure for cooling the combustor, high-pressure combustion gas will enter the cooling path via the hole, and the combustor and attached piping arrangement may be locally heated or burned.

It is an object of the present invention to solve the above problems in the conventional system and to maintain the safety of the system, and to provide a combined cycle power plant which can reliably operate for a long time.
This invention provides a combined cycle power plant having a gas turbine and a steam turbine combined together, in which the power plant comprises an exhaust-heat recovery boiler for generating steam for driving the steam turbine by using exhaust heat from the gas turbine; a combustor provided for the gas turbine which has a high-temperature compartment surrounding the combustor; and a steam cooling system for cooling the high-temperature compartment of the combustor by using the steam, wherein superheated steam from the steam cooling system is recovered and used in the steam turbine. The combined cycle power plant also .has an air duct connected to a steam path for supplying steam for cooling the high-temperature compartment of the combustor and provided for cooling the high-temperature compartment by extracting and supplying air from compressed air in a turbine chamber surrounding the combustor when the steam for cooling is insufficient; the air duct including a booster for boosting the air to a pressure higher than a pressure inside the combustor.
By another aspect of the invention a combined cycle power plant having a gas turbine and a steam turbine combined together comprises. a combustor for the gas turbine, the combustor having a high-temperature compaortment surrounding the combustor, an exhaust-heat recovery boiler positioned and configured to generate steam for driving the steam turbine by using exhaust heat from the gas turbine, a steam cooling path positioned and configured to supply the steam used in the steam turbine into the high-temperature compartment ofthe combustor for cooling, and an air duct communicating with the steam path and configured to extract and supply air from compressed air in a turbine chamber surrounding the combustor into the high-temperature compartment of the combustor. Means for boosting the pressure of the 3a air is provided wherein the air is compressed to a pressure higher than a pressure inside the combustor.
By another aspect a combined cycle power plant having a gas turbine and a steam turbine combined together can comprise a combustor for the gas turbine, the combustor having a high-temperature compartment surrounding it, an exhaust heat recovery boiler positioned and configured to generate steam for driving the steam turbine by using exhaust heat from the gas turbine; and a steam cooling path positioned and configured to supply the steam used in the steam turbine into the high-temperature compartment of the combustor for cooling. An air duct communicates with the steam path and is configured to extract and supply air from compressed air in a turbine chamber surrounding the combustor for cooling the high-temperature compartment, and a boost-up pressurizer disposed inside; the air duct is configured to compress the air from a turbine chamber to a higher pressure than a pressure inside the combustor.
Accordingly, if the supplied cool steam is insufficient (i) when the plant is activated or stopped or (ii) for another reason with respect to the operation of the plant, or if no cool steam is supplied because the cooling operation itself is unnecessary, then the pressure in the steam path can be maintained higher than that in the combustor, so that no gas enters from the combustor to the steam path. Therefore, the combustor and attached piping arrangement can be reliably protected.
In the above structure, a boost-up pressurizer may be inserted in the air duct.
In this case, the pressure in the air duct, that is, in the steam path can be increased by the boost-up pressurizer so that this pressure can be maintained higher than that in the combustor. Therefore, the combustor and attached piping arrangement can be reliably protected, as explained above.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic diagram for explaining the general structure of the gas turbine plant of the combined cycle power plant as an embodiment according to the present invention.
MODES FOR CARRYING OUT THE INVENTION
Hereinbelow, an embodiment of the present invention will be explained in detail with reference to Fig. 1.
In the figure, reference numeral 1 indicates an air compressor, reference numeral 2 indicates a gas turbine, and air compressor 1 and gas turbine 2 are joined with each other via common shaft 3. Reference numeral 4 indicates a combustor having trunk portion 4a and tail pipe portion 4b, around which there is a high-temperature portion 5 to be cooled.
Reference numeral 6 indicates a turbine chamber which surrounds a connected part of air compressor 1; gas turbine 2, and combustor 4. Reference numeral 7 indicates a steam path for introducing cool steam, which is supplied from a steam source (not shown) via closing/opening valve 8, into the high-temperature portion 5 to be cooled.
Reference numeral 9 indicates an air duct which joins the turbine chamber 6 and steam path 7. A boost-up pressurizer 10 and closing/opening valve 11 are inserted in the path of the air duct.
Fig. 1 shows only the relevant parts in the gas turbine plant of the combined cycle power plant. The whole arrangement of the combined cycle power plant including the whole structure of the gas turbine plant, the steam turbine plant, and the exhaust heat recovery boiler are not shown and explanations thereof are omitted.
In the structure of the present embodiment explained above, when the gas turbine is activated or stopped, the closing/opening valve 8 is closed so as to close the path for supplying cool steam, while the closing/opening valve 11 is opened so as to communicate the turbine chamber 6 with the steam path 7 via the air duct 9. In this way, the compressed air supplied from the air compressor 1 to turbine chamber 6 is supplied to the high-temperature portion 5 (to be cooled) of combustor 4.
During this process, the pressure of the compressed air is increased using the boost-up pressurizer 10 provided in the supply path of the compressed air;
thus, the compressed air supplied to the high-temperature portion 5 has a pressure higher than that measured when the compressed air was supplied from the air compressor 1 to turbine chamber 6.
Because of the pressure loss of air while passing through the relevant paths, the compressed air supplied from the air compressor 1 via turbine chamber 6 to combustor 4 has a pressure lower than that of compressed air which is directly supplied from the turbine chamber 6 to combustor 4. However, the pressure of the compressed air from the turbine chamber 6 is increased using the boost-up pressurizer so that the pressure of the compressed air supplied to the high-temperature portion 5 to be cooled of the combustor 4 is reliably maintained at a sufficiently high level.
Therefore, according to the present embodiment, it is possible to prevent the combustion gas from being introduced into the cooling path (including the high-temperature portion 5 or steam path 7) and to prevent the combustor 4 and attached piping arrangement from being locally heated or burned.
The present invention is not limited to the shown embodiment explained above, but each element in the embodiment can be variously modified within the scope of the claimed invention.
INDUSTRIAL APPLICABILITY
According to the present invention, if the cooling steam is in short supply when the gas turbine is activated, stopped, or the like, the combustor and appended piping arrangement can be prevented from burning. Therefore, a plant having long-term reliability and operability can be obtained, and thus the reliability of the plant can be remarkably improved.

Claims (10)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A combined cycle power plant having a gas turbine and a steam turbine combined together, the combined cycle power plant comprising:
an exhaust-heat recovery boiler for generating steam for driving the steam turbine by using exhaust heat from the gas turbine;
a combustor provided for the gas turbine, and having a high-temperature compartment surrounding the combustor; and a steam cooling system for cooling the high-temperature compartment of the combustor by using the steam, where superheated steam from the steam cooling system is recovered and used in the steam turbine;
wherein the combined cycle power plant has an air duct connected to a steam path for supplying steam for cooling the high-temperature compartment of the combustor and provided for cooling the high-temperature compartment by extracting and supplying air from compressed air in a turbine chamber surrounding the combustor when the steam for cooling is insufficient, the air duct including a booster for boosting the air to a pressure higher than a pressure inside said combustor.
2. A combined cycle power plant as claimed in claim 1, wherein the booster for boosting the air is a boost-up pressurizer.
3. A combined cycle power plant having a gas turbine and a steam turbine combined together, the combined cycle power plant comprising:
a combustor for the gas turbine, the combustor having a high-temperature compartment surrounding said combustor;
an exhaust-heat recovery boiler positioned and configured to generate steam for driving the steam turbine by using exhaust heat from the gas turbine:

a steam cooling path positioned and configured to supply the steam used in the steam turbine into said high-temperature compartment of said combustor for cooling;
an air duct communicating with the steam path and configured to extract and supply air from compressed air in a turbine chamber surrounding said combustor into the high-temperature compartment of said combustor; and means for boosting the pressure of the air;
wherein the air is compressed by said means for boosting to a pressure higher than a pressure inside said combustor.
4. A combined cycle power plant as claimed in claim 3, wherein:
said gas turbine comprises the turbine chamber connecting said combustor and said gas turbine; and said means for boosting the air pressure intakes air from inside said turbine chamber.
5. A combined cycle power plant as claimed in claim 3 or 4, further comprising:
a first valve disposed in said steam cooling path; and a second valve disposed in said air duct;
wherein said first valve is closed while said second valve is opened during a start-up stage of said combined cycle power plant, and the air is used to cool the high-temperature compartment during the start-up stage.
6. A combined cycle power plant as claimed in claim 5, wherein said first valve is closed while said second valve is opened during a shut-off stage of said combined cycle power plant, and the air is used to cool the high-temperature compartment during the shut-off stage.
7. A combined cycle power plant having a gas turbine and a steam turbine combined together, the combined cycle power plant comprising:

a combustor for the gas turbine, the combustor having a high-temperature compartment surrounding said combustor.
an exhaust heat recovery boiler positioned and configured to generate steam for driving the steam turbine by using exhaust heat from the gas turbine;
a steam cooling path positioned and configured to supply the steam used in the steam turbine into said high-temperature compartment of said combustor for cooling;
an air duct communicating with the steam path and configured to extract and supply air from compressed air in a turbine chamber surrounding said combustor for cooling the high-temperature compartment; and a boost-up pressurizer disposed inside said air duct and configured to compress the air from a turbine chamber to a higher pressure than a pressure inside said combustor.
8. A combined cycle power plant as claimed in claim 7, wherein:
said gas turbine comprises the turbine chamber connecting said combustor and said gas turbine; and said means for boosting the air pressure intakes air from inside said turbine chamber.
9. A combined cycle power plant as claimed in claim 7 or 8, further comprising:
a first valve disposed in said steam cooling path; and a second valve disposed in said air duct;
wherein said first valve is closed while said second valve is opened during a start-up stage of said combined cycle power plant, and the air is used to cool the high-temperature compartment during the start-up stage.
10. A combined cycle power plant as claimed in claim 9, wherein said first valve is closed while said second valve is opened during a shut-off stage of said combined cycle power plant, and the air is used to cool the high-temperature compartment during the shut-off stage.
CA002284491A 1998-01-23 1998-01-23 Combined cycle electric power plant Expired - Fee Related CA2284491C (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP1998/000260 WO1999037900A1 (en) 1996-07-24 1998-01-23 Combined cycle electric power plant

Publications (2)

Publication Number Publication Date
CA2284491A1 CA2284491A1 (en) 1999-07-29
CA2284491C true CA2284491C (en) 2002-08-27

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Family Applications (1)

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CA002284491A Expired - Fee Related CA2284491C (en) 1998-01-23 1998-01-23 Combined cycle electric power plant

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DE (1) DE19882185T1 (en)

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DE19882185T1 (en) 2000-03-16
CA2284491A1 (en) 1999-07-29

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