Power plants – Combustion products used as motive fluid – Multiple fluid-operated motors
Reexamination Certificate
2000-09-29
2001-10-09
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Multiple fluid-operated motors
C060S039550, C060S039780
Reexamination Certificate
active
06298656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a combustion turbine power plant and, more specifically, to a combustion turbine power plant having a compressed air steam generator which is coupled to a transition section between the combustor assembly and turbine assembly of the combustion turbine power plant.
2. Background Information
Combustion turbine power plants, generally, have three main assemblies: a compressor assembly, a combustor assembly, and a turbine assembly. A transition section is located between the combustor assembly and the turbine assembly. In operation, the compressor assembly compresses ambient air. The compressed air is channeled into the combustor assembly where it is mixed with a fuel. The fuel is ignited in the combustor assembly creating a heated working gas. The heated working gas passes through the transition section and into the turbine assembly. Within the transition section, the working gas is typically between 2500-2900° F. (1371-1593° C.). The transition section is heated by the working gas to temperatures near its structural limits. Components subjected to such extreme temperatures may degrade due to thermal stress. Therefore, it is advantageous to provide a cooling system to remove heat from the transition section.
A typical cooling apparatus comprises a heat recovery steam generator located in the exit path from the turbine. The heat recovery steam generator is coupled to a water supply. When the combustion turbine is in operation, heated exhaust gas exits the turbine assembly and passes through the heat recovery steam generator converting water into steam. The steam from the heat recovery steam generator is passed through cooling channels within the casing of the transition section. As the steam passes through the transition section it absorbs heat thereby cooling the transition section. This heated steam may be channeled back into the flow path of the combustion turbine to provide power augmentation or may be channeled to a separate steam turbine.
Because the heat recovery steam generator is located in the exhaust path of the combustion turbine, the heat recovery steam generator may not provide a sufficient amount of steam during the start up cycle to cool the transition section of the combustion turbine. Additionally, combustion turbines which rely on a single heat recovery steam generator have to be shut down to perform maintenance operations on the heat recovery steam generator.
There is, therefore, a need for a steam generator to provide steam to a combustion turbine during the start up cycle of the combustion turbine.
There is a further need for a steam generator which could be used in conjunction with a heat recovery steam generator to provide an alternative source of steam when the heat recovery steam generator is undergoing maintenance.
There is a further need for a steam generator which provides an output of both steam and cooled air which may be used to cool the transition section and the turbine section respectively.
SUMMARY OF THE INVENTION
These needs, and others, are satisfied by the invention which provides a compressed air steam generator which is coupled to the combustion turbine compressor and to a feed water source.
To create steam during the start-up cycle, a compressed air bleed line is coupled to the compressor assembly. The bleed line passes through a steam generator which is also coupled to a feed water source. After the bleed line passes through the steam generator, the bleed line is coupled by a cool air line to the turbine assembly. The steam generator also includes plenum connected to a feed water source and to a steam pipe which is coupled to a series of channels within the transition section. The transition section includes a steam outlet pipe. The steam outlet pipe may be connected to a separate steam turbine or coupled to the flow path of the combustion turbine.
The steam generator is, essentially, a heat exchanger. The compressed air bleed line passes through a quantity of water. The water is contained in a plenum around the compressed air bleed line. The water will absorb heat from the compressed air bleed line and be converted to steam. The plenum is coupled by a steam pipe to the channels within the turbine section. The compressed air circuit and the water/steam circuit are separate; the compressed air and water are not mixed.
In operation, the compressor assembly compresses ambient air, thereby raising the temperature of the compressed air to a temperature of 600° F. (315° C.) or more. The majority of the compressed air is channeled into the combustor assembly. A portion of the compressed air, however, is channeled through the bleed line through the inner plenum in the steam generator. Feed water from the feed water source is channeled into the inner plenum and passes over the compressed air bleed line. Heat from the compressed air is transferred through the bleed line to the feed water thereby converting the feed water to steam and cooling the compressor bleed air. The steam exits the steam generator through the steam pipe, which is coupled to the channels within the walls of the transition section. As the steam passes through the transition section, the transition section transfers heat to the steam thereby lowering the temperature of the walls of the transition section and raising the temperature of the steam. The heated steam exits the transition section further through the outlet pipe and may be directed to the working gas flow path of the combustion turbine or to a separate steam turbine.
The compressed air in the bleed line leaving the steam generator contains cooled compressor air. The cool compressed air travels through a cool air line to channels within the casing of the turbine assembly. The cooled air absorbs heat from the turbine assembly thereby cooling the turbine assembly. The reheated air exits the system through an exhaust and/or is mixed with the working gas in the turbine assembly.
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Donovan Jon Peter
McManus Michael Todd
Casaregola Louis J.
Siemens Westinghouse Power Corporation
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