Power plants – Combustion products used as motive fluid – For nominal other than power plant output feature
Reexamination Certificate
2002-04-10
2003-03-18
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
For nominal other than power plant output feature
C060S039520
Reexamination Certificate
active
06532745
ABSTRACT:
BACKGROUND OF THE INVENTION
When Brayton Simple Cycle gas turbines operate as mechanical power drive sources to electric generators and other mechanically driven devices, atmospheric air is compressed and mixed with hydrocarbon gases or atomized hydrocarbon liquids for the resulting mixture's ignition and combustion at constant pressure. To produce power, the hot combustion and working motive fluid gases are expanded to near atmospheric pressure across one or more power extraction turbine wheels, positioned in series.
The majority of Brayton simple open-cycle aeroderivative-style Low-NO.sub.x art gas turbines are predominantly presently limited in achieving shaft output horsepower rating with 34 to 36% thermal efficiencies, whereas most simple cycle industrial-style Low-NO.sub.x art gas turbines are predominantly presently limited in achieving shaft output horsepower rating with 37 to 40% thermal efficiencies. These higher efficiencies are achieved when the gas turbines operate with compressor ratios ranging from 18 to 26 and predominant power turbine inlet temperatures ranging from 180° to 2300° F.
Existing gas turbines employ combustion chamber air/fuel combustion chemical reactions, wherein the elements of time and high peak flame temperatures increase the presence of disassociation chemical reactions that produce the fugitive emissions of carbon monoxide (CO) and other chemical reactions that produce nitrogen oxides (NO.sub.x).
The best available applied turbine low-nitrogen oxide combustion technology for limiting gas turbine NO.sub.x emissions, using stiochiometric air/fuel primary combustion reaction chemistry means, still results in the production of over one million pounds a year of fugitive emissions, when a 100 megawatt gas turbine facility operates continuously. Such emissions of NO.sub.x and CO are no longer acceptable for new power facilities being built in numerous states and metropolitan environmental compliance jurisdictions, particularly for the more economically popular sizes of 400 MW to 1200 MW power generation plants.
With the conventional gas turbine's use of compressed atmospheric air as a source of oxygen (O.sub.2), which acts as a fuel combustion oxidizer reactant, nitrogen (N.sub.2) is the 78.1% predominant mass component within the cycle's working motive fluid. Due to its diatomic molecular structure, the nitrogen molecules are capable of absorbing combustion heat only through convective heat transfer means resulting from their collisions with higher temperature gas molecules or higher temperature interior walls of the combustion chamber.
Despite the very brief time it takes a conventional cycle to reach a molecular primary flame combustion zone gas equilibrium temperature of less than 2600° F. to 2900° F. within the combustion chamber, there are sufficiently excessive high flame temperatures and ample time for a portion of the highly predominate nitrogen gas to enter into chemical reactions that produce nitrogen oxides. The same combined elements of time and sufficiently excessive high flame temperature permit carbon dioxide to enter into dissociation chemical reactions that produce carbon monoxide gas.
To achieve a goal of greatly reducing a turbine cycle's fugitive emissions without sacrificing simple and cogeneration power thermal efficiencies, it is necessary to alter both the fuel combustion chemical reaction formula and the means by which acceptable combustion flame temperatures can be precisely maintained within the turbine combustor. Maintenance of an acceptably low fuel combustor gas temperature requires a change in the means by which the heat of combustion can be better controlled and more rapidly distributed uniformly throughout the gases contained within the fuel combustor.
It has been well known and practiced for decades that higher humidity air and injected water or steam in the presence of conventional air working motive fluid increases combustion flame speeds and fuel combustion thermal efficiencies within gas turbines and other apparatus using air/fuel combustion. It has also been well known and practiced that partially re-circulating, combustion flue gases containing carbon dioxide back into a combustion chamber results in a reduced level of nitrogen oxides within the fuel combustion exhaust gases. Due to the high temperatures and speed of completed fuel combustion, the scientific community has been unable to reach a consensus as to precisely what series of altered chemical reactions occur when water vapor and/or carbon dioxide is introduced into a turbine combustion chamber.
Conventional gas turbines must be de-rated from their standard ISO horsepower or kW ratings at ambient temperatures exceeding 59° F., or at operating site altitudes above sea level. Thus, during summer's peak power demand periods, when the temperature rises to 95° F., a 19 to 22% horsepower deration of a conventional gas turbine's ISO rating occurs. It is desirable that a gas turbine cycle not be susceptible to such temperature deration.
Present gas turbines' high combustor operating pressures require a gas-pipeline source of 280 to over 550-psi gage pressure. If a manufacturing facility, process facility, or utility power generating facility has access only to a lower pressure source of natural a gas, then one or more high horsepower fuel gas booster compressors must be employed to raise the fuel supply pressure. It is therefore desirable that gas turbines be able to operate on fuel gas supply pressures of less than 100 psi gage.
SUMMARY OF THE INVENTION
To achieve ultra-low fugitive turbine exhaust emissions, the AES power cycle of the present invention employs a continuous controllable mass flow rate of recycled superheated vapor-state mixture of carbon dioxide (CO.sub.2) and water vapor (H.sub.2 O), in identical mixture Mol percent proportions as each occurs as products of chemical combustion reactions from the gaseous or liquid hydrocarbon fuel employed.
Provided herein is a partially-open gas turbine cycle for use with modified gas turbines, preferably presently designed with a final stage of air compression that has radial means connected to one or more exterior-mounted turbine combustion chambers. The partially-open gas turbine cycle can also be used with alternative power cycle configurations that utilize existing mechanical equipment components which are not specifically designed for, nor applied to, the manufacture of current technology gas turbine systems.
The AES power cycle of the present invention provides a non-air working motive fluid means that reduces mass flow fugitive emissions by over 98% from that of conventional Low-NO.sub.2 designed gas turbines.
The AES power cycle of the present invention offers means of controlling a combustor's internal temperatures to avoid the creation of fugitive turbine exhaust emissions.
The AES power cycle of the present invention offers the equivalent or higher thermal efficiencies than open simple-cycle gas turbines operating alone or within cogeneration. power facilities. The AES simple-cycle is susceptible to 42.5% output shaft thermal efficiency and, which applied to a cogeneration system, the overall thermal efficiency may approach 100%.
The AES power cycle described herein has turbine compression ratios of 3.0 to 6.5 (3.0 to 6.5 bar operating pressure) with presented example cycle efficiencies at 60 psi absolute (3.12 bar).
The AES power cycle of the present invention offers high thermal efficiencies with turbine fuel gas supply pressures of less than 100 psi gage (7.9 bar).
The AES power cycle and power cycle equipment components described herein include the means by which its turbine power cycle and separately associated power plant auxiliaries are monitored and controlled for safe operation, as well as means of controlling working motive flows in response to changes in power demands. The combined turbine/recycle compressor and driven mechanical equipment safe operating and output functions are monitored and controlled by a turbine manufacturer's PLC bas
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