Power plants – Combustion products used as motive fluid – With exhaust treatment
Reexamination Certificate
1998-06-29
2001-03-20
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
With exhaust treatment
C060S723000
Reexamination Certificate
active
06202402
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a gas-turbine construction having an air compressor, a heat exchanger connected downstream of the air compressor, a combustion chamber, and a turbine which can be driven by hot combustion gases and from which the combustion gases are fed to the heat exchanger for heating the compressed supply air coming from the air compressor.
2. Discussion of Background
Gas turbines, which are classified as heat engines, are operated with the combustion gases of liquid fuels. A typical gas-turbine construction, which is shown in
FIG. 1
a,
has an air compressor V, also called turbocompressor, which draws in fresh air L, which is typically compressed to a pressure of 4 to 6 bar and is forced into a heat exchanger W, in which it is preheated by still hot combustion gases VG flowing from the turbine T. Finally, the preheated and compressed supply air passes together with fuels BS into the combustion chamber, in the course of which hot or combustion gases of at least 600° C. are produced. These combustion gases flow with great velocity into the turbine T and drive the latter, which is normally connected to a generator G for the generation of electricity.
The efficiency of a gas turbine is all the greater, the higher is the temperature of the combustion gases entering the turbine blades and the lower is the temperature of the exhaust gases escaping into the open from the gas turbine. Therefore the still hot combustion gases issuing from the turbine blades are nearly always directed through the heat exchanger, where they can give off their waste heat largely to the fresh air delivered by the compressor before said fresh air enters the combustion chamber.
A further advantage of the heat exchangers which are also known as recuperators consists in the fact that their thermodynamic optimum can be achieved at relatively low pressure ratios, as a result of which the turbine construction only needs a few turbine stages, so that the overall construction of a gas-turbine arrangement can be of relatively simple design.
However, the operation of heat exchangers at full load is problematic, since very hot combustion gases are formed by the very high temperatures arising in the combustion chamber, and these combustion gases lead to very intense air preheating inside the heat exchanger, as a result of which, however, reliable operation with low-pollutant premix combustion processes becomes difficult.
It has been found that an important component for the optimization of gas-turbine arrangements is the heat exchanger or recuperator, which makes a substantial contribution to the efficiency of such a machine.
In contrast to the conventional type of construction of a so-called tubular heat exchanger, which, however, only has a low power density, modern, compact heat exchangers usually consist of a stack of suitably shaped plates, which are arranged in layers one above the other and in this way form through-flow ducts through which the precompressed supply air and, in the opposite direction to the direction of flow of the supply air, the hot combustion gases flow alternately.
Since the specific output of a heat exchanger of plate-shaped design primarily depends on the characteristic length of the heat-exchanger element, plate-type heat exchangers having very fine ducts with high transfer capacity are being produced nowadays.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to further optimize gas-turbine arrangements of the generic type in their power spectrum and in particular to simplify their construction. The operation of all the components and in particular the use of heat exchangers is also to be reliably ensured at high combustion-gas temperatures, in which case special attention is to be paid to compliance with corresponding exhaust-gas standards.
The achievement of the object of the invention is specified in claim
1
. A method according to the invention of operating the gas-turbine construction specified in claim
1
is the subject matter of claim
11
. Features advantageously developing the idea behind the invention are the subject matter of the subclaims.
According to the invention, a gas-turbine construction, having an air compressor, a heat exchanger connected downstream of the air compressor, a combustion chamber, and a turbine which can be driven by hot combustion gases and from which the combustion gases are directed in the heat exchanger for heating the compressed supply air coming from the air compressor, is developed in such a way that the heat exchanger and the combustion chamber are integrated in a common unit, and that fuel can be added to the supply air before entry into the unit, which fuel can be ignited catalytically in the form of an air/fuel mixture inside the unit, in which a catalyst is provided.
In contrast to conventional gas-turbine arrangements, in which, as described above, heat exchanger and combustion chamber form two separate units which are accordingly connected to one another via feed and discharge lines, the idea behind the invention is based on the combination of heat exchanger and combustion chamber. For this purpose, a plate-type heat exchanger known per se is preferably modified by the ducts which feed compressed air normally being surrounded or coated with a catalyst coating on the inside. Platinum is normally used as active material for the catalyst.
The plate-type heat exchanger modified in this way provides a multiplicity of through-ducts which are arranged one above the other in a stack and are composed alternately of ducts coated with catalyst material on the inside and of uncoated ducts enclosed by heat-exchanger walls.
For further simplification, the usually gaseous fuel is to be homogeneously admixed with the supply air upstream of the compressor unit, as a result of which the conventional gas compressor for compressing and injecting the fuel into the combustion chamber can be dispensed with.
The pressure ratios achievable in the compressor are to be set at such a low level that the temperatures achievable in the compressor rule out the possibility of self-ignition.
Of course, as an alternative to the admixing of the fuel with the supply air as described above, the injection, known per se, of the fuel into the compressed supply air downstream of the compressor is also possible.
According to the invention, the air/fuel mixture obtainable in this way is directed into the feeding ducts of the combination unit according to the invention, which ducts are lined with catalyst material and in which the air/fuel mixture is heated by thermal coupling to the hot combustion gases flowing through the unit in the opposite direction. The heating by the hot combustion gases, on account of their very high characteristic temperature, leads in the course of the duct to the ignition temperature of the air/fuel mixture being exceeded, as a result of which an ignited hot gas, which is passed directly into the turbine, is formed inside the duct.
According to the invention, it has been recognized that, for the combustion of the hot gases required for the operation of a turbine, the waste heat of the exhaust gases produced during the combustion is sufficient, with the use of a suitable catalyst, in order to ignite the air/fuel mixture.
As still to be explained below, the hot combustion gases, in addition to the heating effect over the range of the ignition temperature of the air/fuel mixture, can also help to cool the heat-exchanger/combustion-chamber combination according to the invention in order to thereby avoid uncontrolled heating of the unit.
REFERENCES:
patent: Re. 30629 (1981-06-01), Dawson
patent: 3563031 (1971-02-01), Topouzian
patent: 3797231 (1974-03-01), McLean
patent: 4062190 (1977-12-01), Dawson
patent: 4307568 (1981-12-01), Hiiller et al.
patent: 4754607 (1988-07-01), Mackay
patent: 4875436 (1989-10-01), Smith et al.
patent: 5453003 (1995-09-01), Pfefferle
patent: 5512250 (1996-04-01), Betta et al.
patent: 5518697 (1996-05-01), Betta et al.
patent: 5634784 (1997-06-01),
ABB Research Ltd.
Burns Doane Swecker & Mathis L.L.P.
Thorpe Timothy S.
Torrente David J.
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