Power plants – Combustion products used as motive fluid
Reexamination Certificate
1998-06-11
2001-02-20
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S723000
Reexamination Certificate
active
06189310
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thermal energy system comprising at least one gas turbine intended to generate mechanical and/or electrical energy by operating a gas-turbine cycle in which exhaust gases of the cycle having a certain amount of energy capable of beneficiation, in particular mechanical and/or thermal beneficiation, are produced.
TECHNOLOGICAL BACKGROUND
The use of conventional gas turbines for the proposed industrial applications is well known. Thus, when a cycle comprising one or more gas turbines is placed upstream of an existing steam cycle of a power station, the overall energy efficiency of a conventional power station may go from 0.4 to 0.45 at the cost of extensive modification of the steam cycle, in particular by the addition of economizer exchangers. However, this technique proves to be expensive and only justifiable if the cost of the fuel itself is high. What is more, this technique involves an appreciable reduction in the useful power of the steam cycle. This results in only a modest overall gain in power, which for economic reasons is often unsatisfactory.
Another technique involves heat/force cycles, in which the gas turbine delivers mechanical energy and the exhaust gases deliver heat which can be exploited in various forms. In the case of a conventional gas turbine, this technique may prove to be useful when the necessary thermal energy is at low temperature, generally below 600° C. On the other hand, this technique is not applicable when the thermal requirement is at a higher temperature level, in some cases even markedly higher, as is the case for instance in cement works, glassworks and steelworks or in certain furnaces. These plants, upstream of which the gas-turbine cycle may be applied, are all provided with heat regenerators for reheating the combustion air, this heat no longer being able to be recovered after the modification.
The conventional gas-turbine cycle involved in heat/force combined systems comprises an air compressor, a combustion chamber with a large excess of air and a turbine which generates the mechanical power. Downstream of the turbine, only the heat from the exhaust gases can be recovered.
Yet another technique involves combined cycles consisting of gas turbines and steam turbines of specific design. Their efficiency is currently between 0.5 and 0.53.
Even though conventional combined systems are operational, problems of implementation remain.
In so-called partial-oxidation systems, combustion is certainly complete, but staged. Firstly, partial oxidation is carried out, using air in substoichiometric quantity and steam, in a catalytic reactor which replaces the combustion chamber of the conventional gas-turbine cycle. Next, the combustion is completed downstream in the power turbine before the thermal energy of the exhaust gases is used.
The principles of a partial-oxidation gas turbine have already been presented earlier, but the arrival of nuclear power stations and other factors, such as the possibility of supplying with natural gas, have not encouraged its development. Moreover, it would also seem from the prior art that the technological elements essential for improving the application of these principles were not forthcoming.
STATE OF THE ART
The publications mentioned below should be considered: “Cycle de turbine à gaz comportant un réacteur d'oxydation partielle catalytique de gaz naturel, son application dans les systèmes énergie-chaleur” by J. Ribesse at the 8th World Energy Conference in Bucharest from Jun. 28 to Jul. 2, 1971 and in Gas Wärme International, Vol. 20-7/6 July and August 1971; “Cycle combiné avec réacteur à oxydation partielle du combustible” by J. Ribesse, A. Jaumotte and A. De Goeyse, Entropy, 1976 and “The Isotherm Partial-Oxidation Gas Turbine” by J. Ribesse, December 1990, in the European Journal, Vol. 36, No.1, pages 27 to 32. It follows from these publications that the principle of partial oxidation consists in carrying out a catalysed exothermic reaction on the fuel, such as natural gas, with compressed air under substoichiometric conditions and a limited amount of steam, so as to reach a predetermined reaction-gas temperature selected for the gas-turbine cycle.
This results in a reaction gas composed of CO, H
2
, CO
2
, H
2
O, CH
4
, N
2
and fuel. The reactions involved are:
CH
4
+2O
2
+8N
2
→CO
2
+2H
2
O+8N
2
(exothermic)
CH
4
+½O
2
+2N
2
→CO+2H
2
+2N
2
(exothermic)
CH
4
+H
2
O→CO+3H
2
(endothermic)
Belgian Patent No. 769,133 describes a machine using specific elements, namely two compression stages and a catalytic partial-oxidation reactor producing a combustible gas which is expanded in the power turbine with intermediate injection of water and steam. This exhaust gas can be consumed in a thermal application benefiting from its enthalpic content. The process used involves the use of machines of a specific construction, such as turbines and compressors, the specific elements of which are not, however, described.
Belgian Patent No. 1,003,760 describes a gas turbine system designed specifically for partial oxidation. For this purpose, it comprises a compressor adapted so as to have a higher pressure level, a catalytic reactor and a turbine providing isothermal expansion by the effect of gradual internal combustion by means of the air for cooling the turbine blades. This futuristic system will be able to be implemented only after the systems described in Belgian Application 09500879 and in the present patent application have been applied in more directly realizable assemblies.
In the aforementioned patent, the more specific means of the invention are not described either.
The systems briefly described in the aforementioned Patents BE-769,133 and BE-1,003,760 have a major drawback as they do not allow the available commercial gas turbines to be (re) converted. This consequently requires the use of machines which are not produced at the present time and which thus have to be specifically developed, thereby involving very considerable investments.
Belgian Patent No. 1,004,714 describes the structure of a partial-oxidation gas-turbine cycle. For this purpose, a catalytic oxidation reactor is provided. The reactor contains reforming catalyst, a booster-ejector and a system for ignition and for temperature maintenance at stoppage. Fitting it to existing turbines is presented in the case of the use of a pressure ranging from 50 to 60 bar and the use of the cooling air as oxidant in order to obtain expansion in the gas turbine at a constant temperature.
Moreover, the aforementioned Patent BE-1,004,714 deals briefly, and in a theoretical manner, with two of the three applications of partial oxidation which are described below, namely the conversion of conventional gas turbines and the constant-temperature expansion turbine, of specific design.
Thus, in general, problems of, for instance, implementing each of the aforementioned patents remain.
SUBJECT OF THE INVENTION
The object of the invention is to remedy the aforementioned drawbacks and to provide a solution appropriate to the problems resulting from the foregoing with regard to the state of the art.
The system according to the invention is intended to be applicable in all energy systems which comprise a cycle consisting of one or more gas turbines, whether this cycle is combined with a steam-turbine cycle or with thermal beneficiation of the effluent of the gas-turbine cycle.
Thus, the first subject of the present invention is the procedure for increasing the power of a thermal power station, which procedure is commonly called repowering. The present invention also relates to particular aspects of the use of this technology in the applications mentioned above, especially energy systems which involve a gas-turbine cycle combined with beneficiation of the thermal energy of the exhaust gases of this cycle. This beneficiation is achieved either by complementary generation of mechanical energy (cycles comprising one or more gas turbines and steam tur
Kalitventzeff Boris
Ribesse Jacques
Casaregola Louis J.
Meroni & Meroni P.C.
Meroni, Jr. Charles F.
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