Power plants – Combustion products used as motive fluid – Multiple fluid-operated motors
Reexamination Certificate
2002-08-16
2004-08-10
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Multiple fluid-operated motors
Reexamination Certificate
active
06772582
ABSTRACT:
This application claims priority on European Patent Application No. 01119852.0, filed Aug. 16, 2001, the entire contest of which are hereby incorporated herein by reference.
FIELD OF THE INVENTION
The invention generally relates to a power station installation and a method of operating a power station installation.
BACKGROUND OF THE INVENTION
Steam power installations are known in which a steam turbine is usually employed in a power station installation for driving a generator or, in an industrial installation, for driving a machine. For this purpose, hot and pressurized steam, which acts as the flow medium and which expands in the steam turbine so as to do work, is supplied to the steam turbine. After its expansion, the steam usually reaches a condenser connected downstream of the steam turbine and condenses there. The condensate is then supplied as feed water to a steam generator and, after its evaporation, again reaches the steam turbine so that there is, in general, a closed water/steam circuit. An installation having the components necessary for this purpose and therefore having, in particular, a steam turbine and a steam generator, is also designated as steam turbines or steam power installation.
Likewise known are power station concepts in which a gas turbine process is combined with a steam turbine process in a joint installation. In a gas turbine and steam turbine process of this type, a waste-heat steam generator is connected downstream of the exhaust gas end of the gas turbine, with the exhaust gas from the gas turbine being used to evaporate water in the waste-heat steam generator. The steam generated in the waste-heat steam generator, utilizing the waste heat from the exhaust gas of the gas turbine, is utilized in a steam turbine installation connected downstream of the waste-heat steam generator, which steam turbine installation generally has a plurality of steam turbines. Such a process has substantial advantages in comparison with the pure gas turbine process. The main advantages are the high efficiency and an increase in power. Efficiencies of up to between 56 and 58% are achieved in modern gas/steam installations.
Both a steam power installation and a gas/steam installation, however, require a substantial quantity of fresh water, or at least desalinated sea water, for the steam generation. For this reason, the operation of the steam power installation or a gas turbine and steam turbine installation presents a problem in countries with a small supply of fresh water, for example in the dry desert countries of Africa. Because of the fresh water requirement of the conventional power station concepts based on steam, therefore, only the pure gas turbine power stations are, as a rule, employed in such regions of the earth. The efficiency of a gas turbine power station is, however, distinctly less than the efficiency of a combined power station or a conventional steam power station.
SUMMARY OF THE INVENTION
An object of an embodiment of the invention is, therefore, to provide a power station installation which permits operation of a gas turbine with improved efficiency. A further object of an embodiment of the invention is to provide a method of operating a power station installation.
A power station installation is achieved, according to an embodiment of the invention, by a gas turbine and air turbine installation, having a gas turbine to which, downstream of its exhaust gas end, the primary side of a heat exchanger for heating air is connected, which heat exchanger has an air turbine connected downstream of its secondary side.
A completely new installation concept is used which—in contrast to the conventional combined power stations having a steam process associated with a gas turbine process for example—permits the utilization of the waste heat in the exhaust gas of the gas turbine, but without involving a steam process. In order to increase the efficiency of a gas turbine installation, the waste heat from the exhaust gas of the gas turbine is, in this case, utilized in a completely novel combined process, namely in a gas turbine and air turbine process. Because fresh water is dispensed with, the gas turbine and air turbine installation of the invention can be employed, particularly advantageously, in regions of the earth where fresh water is only available to a limited extent or can only be obtained at substantial cost.
A particular advantage of this arrangement is that existing gas turbine power stations can be retrofitted, to form a gas turbine and air turbine installation, at a cost which can be appraised. The efficiency advantage, as compared with a pure gas turbine installation, may very rapidly outweigh the investment costs of such a retrofit measure. From initial estimations, the efficiency of the gas turbine and air turbine installation is increased by some 9 to 10 percentage points. The power of such a combined installation, based on a gas and air process, is increased by up to 24% relative to a pure gas turbine process.
Compared with a conventional gas turbine and steam turbine installation, furthermore, there is a markedly reduced requirement with respect to production costs in the case of the gas turbine and air turbine installation according to an embodiment of the invention. This is because essentially lower-cost installation components, such as the heat exchanger and the air turbine, are employed. Compared with this, a steam generator, for example, with a water/steam circuit and the steam turbines downstream, is substantially more expensive in the case of a gas/steam installation and this is so precisely with respect to the material costs.
Depending on the gas turbine type selected, an efficiency of some 45 to 50% can be achieved in the case of the gas turbine and air turbine installation. This installation concept, based on a gas and air process, therefore appears to be particularly interesting in countries which are short of water. The waste heat from the exhaust gas of the gas turbine is used in the heat exchanger, which is connected downstream of the exhaust gas end of the gas turbine, in order to heat air which is supplied to the secondary side of the heat exchanger. The air heated in this way is supplied to the air turbine, which is connected downstream of the heat exchanger and which expands so as to do work.
In a preferred embodiment, an air compressor, which is connected upstream of the secondary side of the heat exchanger, is provided so that compressed air can be supplied to the heat exchanger for heating. In this arrangement, the air is compressed in the air compressor from 1 bar to some 5 to 6 bar. The air compressed in this way is supplied to the heat exchanger so that the compressed air is heated. The employment of an air compressor makes it possible to appropriately increase the pressure condition and temperature condition of the working medium to be supplied to the air turbine, i.e. the compressed and heated air. By this means, more energy is available to the air driving the air turbine, which energy is released to do work on the air turbine for the generation of electricity.
The primary side of a further heat exchanger for heating air is preferably connected downstream of the exhaust gas end of the heat exchanger. Multiple utilization of the waste heat of the exhaust gas flowing out of the gas turbine is possible in this way. A part of the waste heat is first used in the heat exchanger to heat the working medium for the air turbine, i.e. the air. In a second, downstream heat exchanger process, a further part of the waste heat is extracted from the exhaust gas in the further heat exchanger and transferred to air. In analogy with a waste-heat steam generator, it is possible to realize a “waste-heat air generator” by means of this multistage process, in which process—depending on the pressure and temperature condition of the air heated in a waste-heat/air heat exchanger stage—an air turbine can be employed which is specially adapted to the conditions. A multi-stage operation also provides the particular advantage that the output pow
Casaregola Louis J.
Harness & Dickey & Pierce P.L.C.
Siemens Aktiengesellschaft
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