Power plants – Combustion products used as motive fluid – Multiple fluid-operated motors
Utility Patent
1998-06-29
2001-01-02
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
Multiple fluid-operated motors
C060S039120, C060S736000
Utility Patent
active
06167692
ABSTRACT:
TECHNICAL FIELD
This invention relates to power generating plants generally, and more specifically, to the use of a fuel gas expander for reducing fuel gas pressure in a power generating plant.
BACKGROUND
Fuel gas used in power generating plants is available, in many situations, at much higher pressure than is needed for combustion in the power generating equipment. The source of high pressure fuel gas for power generation may be a natural gas pipeline, pressurized fuel conversion gasifier, a chemical process plant, or any other high pressure combustible gas generating equipment. Usually, the fuel gas pressure needs to be reduced and controlled to the level required for stable combustion in the power generating combustion equipment, such as the combustor in a gas turbine generator, or a fuel burner in a waste heat boiler and fully fired boiler turbine generator, etc. Typically, pressure reduction is achieved by throttling the fuel gas, but this is not particularly efficient since it does not make use of the fuel gas pressure differential.
DISCLOSURE OF THE INVENTION
In accordance with this invention, a fuel gas expander device is utilized in a power generation plant, and utilizes the difference between the fuel gas source pressure and the combustor/burner pressure in the power generating plant, resulting in improved power output and efficiency of the plant.
In one exemplary embodiment, one or more fuel gas expanders are used in a gas turbine, combined cycle power generating plant. Specifically, the fuel gas from a high pressure fuel gas source is introduced into a fuel gas expander prior to introduction into the combustor of the gas turbine. The excess pressure between the high pressure fuel gas and the lower pressure fuel gas exiting the fuel gas expander may be employed to drive a load such as a generator, compressor or other component. Optionally, the fuel gas can be cooled and/or conditioned if required prior to introduction into the fuel gas expander in order to remove any solid particles or harmful contaminants which may adversely effect the continued operation and/or reduce the blade life of the expander.
The fuel gas can then, also optionally, be heated in a heat exchanger to a temperature higher than the minimum required to avoid any undesirable fluid condensation or deposition in the expander equipment. The source of this heat can be thermal energy recovered either upstream (for example, from a gasifier with a high temperature cooler) or downstream (for example, from the exhaust gas heat recovered from the gas turbine exhaust in a waste heat boiler) of the expander.
The fuel gas may be expanded further in a second fuel gas expander if the fuel is to be used at two pressure levels, for example, where it is first expanded to an intermediate pressure level suitable for the gas turbine combustor, with a portion further expanded to an even lower pressure in a separate fuel gas expander prior to introduction as a supplemental fuel in the fuel burner of a waste heat or fully fired boiler.
It is further contemplated that a portion of the fuel gas may be bypassed around the first fuel gas expander via a throttling device to combine with the discharge stream from the expander to continue plant operation during start-up, shutdown, or during other events when the expander is not operating.
In another exemplary embodiment of the invention, a similar fuel gas expander setup is employed in connection with a fuel burner in a fully fired boiler turbo-expander (typically steam) power plant.
In its broader aspects therefore, the present invention provides, in a power generating plant which utilizes fuel gas for combustion at a predetermined pressure to drive a primary load, and where the fuel gas is supplied at a pressure higher than the predetermined pressure, an improvement including at least one fuel gas expander located downstream of a source of the fuel gas and upstream of a combustor, the fuel gas expander decreasing the pressure of the fuel gas below the higher pressure; and wherein excess energy resulting from a differential between the predetermined pressure and the higher pressure is used to drive a secondary load.
Other objects and advantages of the subject invention will become apparent from the detailed description which follows.
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patent: 5337554 (1994-08-01), Bertels
patent: 5517815 (1996-05-01), Fujioka et al.
patent: 5581128 (1996-12-01), Royle
patent: 5822974 (1998-10-01), McGowing et al.
patent: 5918466 (1999-07-01), Cloyd et al.
patent: 5955039 (1999-09-01), Dowdy
Anand Ashok Kumar
Smith Raub Warfield
General Electric Co.
Nixon & Vanderhye
Thorpe Timothy S.
Torrente David J.
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