Power plants – Combustion products used as motive fluid
Reexamination Certificate
2000-09-05
2001-07-31
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S039182, C060S039463, C123S003000
Reexamination Certificate
active
06266953
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method of operating a gas and steam turbine plant, in which heat contained in an expanded working medium from a gas turbine, which is operated by a fuel, is used to generate steam for a steam turbine, and a reducing agent is introduced by a metering system, with a supply of an adjustable quantity of carrier air, into the working medium, for the catalytic cleaning of the working medium. The invention also relates to a plant operating in accordance with the method.
In a gas and steam turbine plant, the heat contained in the expanded working medium from the gas turbine is used for generating steam for the steam turbine. The heat transfer takes place in a waste-heat steam generator which is installed downstream of the gas turbine and in which heating surfaces are disposed in the form of tubes or tube bundles. The heating surfaces are in turn connected into a water/steam circuit of the steam turbine. The water/steam circuit usually includes a plurality of pressure stages, for example two. Each pressure stage usually has a preheater heating surface (economizer), an evaporator heating surface and a superheater heating surface.
The selective catalytic reduction method, the so-called SCR method, can be employed to decrease the amount of oxides of nitrogen in the exhaust gases of the gas turbine. In the SCR method, oxides of nitrogen (NO
x
) are reduced to nitrogen (N
2
) and water (H
2
O) with the aid of a reducing agent and a catalytic converter.
In a gas and steam turbine plant constructed for an SCR method, a catalytic converter is generally disposed in the waste-heat steam generator. The catalytic converter is used to initiate and/or maintain a reaction between the reducing agent introduced into the exhaust gas and the oxides of nitrogen.
As is known from U.S. Pat. No. 4,473,536, the reducing agent required for the method can be injected with air generated by an air compressor or fan, as a carrier flow, into the exhaust gas from the gas turbine, that is flowing through the waste-heat steam generator. It is possible to vary the quantity of reducing agent to be injected by controlling the quantity of air as a function of the exhaust gas mass flow from the gas turbine.
As a rule, however, the emission of oxides of nitrogen from the gas turbine is higher in the case of oil operation than in the case of gas operation. In order to keep within the legally specified limiting values, the quantity of reducing agent to be injected for the oil operation of the gas turbine is therefore greater than that for gas operation. However, because of an undesirable cooling of the exhaust gas caused by the injection of the air/reducing agent mixture, the efficiency of the gas and steam turbine plant in that configuration can be impaired to a different extent, depending on the operating condition.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method of operating a gas and steam turbine plant and such a plant, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type and in which a particularly high efficiency is ensured, under all operating conditions of the gas turbine, with a particularly low level of technical complexity and without a complicated control system.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of operating a gas and steam turbine plant, which comprises providing a gas turbine and a steam turbine; operating the gas turbine with a fuel to produce an expanded working medium; generating steam for the steam turbine from heat contained in the expanded working medium leaving the gas turbine; introducing a reducing agent and a supply of an adjustable quantity of carrier air into the working medium with a metering system, for catalytically cleaning the working medium; adjusting the quantity of carrier air as a function of a type of the fuel supplied to the gas turbine; controlling the quantity of carrier air only with a first air compressor for gas operation of the gas turbine; and controlling the quantity of carrier air additionally with a second air compressor, connected in parallel with the first air compressor, for oil operation of the gas turbine.
In this configuration, the invention is based on the consideration that a particularly high efficiency of the gas and steam turbine plant is provided if the heat made available, by the exhaust gas of the gas turbine, for the waste-heat steam generator, can be utilized almost completely for the steam process. Therefore, the quantity of carrier air should be kept particularly small in the SCR method. It should therefore be possible for the carrier air quantity to be adapted to suit the quantity of reducing agent to be introduced as a function of the type of fuel for the gas turbine. Particularly simple control of the carrier air quantity can be achieved if the output of the air compressors can be adjusted as a function of the type of fuel supplied to the gas turbine.
In this configuration, a first air compressor is advantageously connected in parallel with a second air compressor. In this embodiment, the first and second air compressors can be operated both simultaneously and alternately. One air compressor can then be operated in the case of gas operation and both air compressors can be operated in the case of oil operation of the gas turbine. However, a precondition for this is an appropriate configuration of the air compressors. In this way, the carrier air quantity that is necessary can be adjusted particularly simply.
Each air compressor advantageously has a drive with a speed controlled relative to the output of the air. In this configuration, the control of the air output is possible through the use of the number of drives as well as through the use of the respective speed-controlled drives. The carrier air quantity to be injected can therefore, in addition, be particularly well adapted to the various types of fuel supplied to the gas turbine.
With the objects of the invention in view, there is also provided, a gas and steam turbine plant, comprising a gas turbine to be selectively operated both with gas and with oil as a fuel for producing an expanded working medium; a waste-heat steam generator disposed downstream of the gas turbine; a catalytic converter disposed in the steam generator for catalytically cleaning the expanded working medium from the gas turbine; and a metering system having first and second air compressors for introducing a reducing agent into the working medium, the second air compressor connected in parallel with the first air compressor at least during oil operation of the gas turbine.
The advantages achieved through the use of the invention reside, in particular, in ensuring an air supply for the metering system, which can be adjusted, with a particularly low level of technical complexity through the use of the air compressors. Since the air supply can be adjusted as a function of the type of fuel supplied to the gas turbine, the cooling (caused by the SCR process) of the exhaust gas flowing through the waste-heat steam generator is particularly small under all operating conditions of the gas turbine. A particularly high efficiency of the gas and steam turbine plant is therefore ensured under all operating conditions of the gas turbine plant.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method of operating a gas and steam turbine plant and such a plant, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
REFERENCES:
patent: 4473536 (1984-09-01), Carberg et al.
patent: 5098680 (1992-03-01), Fellows et al.
patent: 5282355 (1994-02-01), Yamaguchi
patent:
Ramstetter Asbjoern
Sigling Ralf
Greenberg Laurence A.
Kim Ted
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
LandOfFree
Method of operating a gas and steam turbine plant does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of operating a gas and steam turbine plant, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of operating a gas and steam turbine plant will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2540183