Power plants – Combustion products used as motive fluid
Reexamination Certificate
1998-12-10
2001-01-30
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S039170, C060S039590
Reexamination Certificate
active
06178738
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of operating a gas-turbine group.
2. Discussion of Background
Premix burners of the newer generation, for example for the operation of a combustion chamber of a gas turbine, are able to ensure efficient and low-pollution combustion when using a gaseous fuel. The use of a liquid fuel results in shortcomings which are connected with the very high vaporization temperature of such fuels. Depending on the proportion of non-volatile fractions in these fuels, residues form during the vaporization of these fuels and may lead to coke in the limit case. There is also the fact that the very high pressure level required for the admission to gas-turbine burners increases the vaporization temperature even further. Even the vaporization of fuel oils under partial-pressure conditions does not bring about any lasting change in this situation, so that it may be assumed that the operation of a premix burner with superheated oil vapor cannot be taken into consideration.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention, as defined in the claims, in a method of the type mentioned at the beginning, is to propose novel measures which permit the operation of a premix burner with liquid fuels. In this case, according to the invention, a liquid fuel, preferably oil, is preheated to a maximum of 150-200° C. and directed into a flow of hot pressurized water as close to the saturation temperature as possible. This emulsion is then used for the operation of a premix burner, as disclosed by EP-0 321 809 B1 (corresponding to U.S. Pat. No. 4,932,861) or EP-0 780 629 A2 (corresponding to U.S. Pat. No. 5,735,687), the last-mentioned patents being an integral part of the present description.
A further method according to the invention provides for the spray of the liquid fuel, which is preheated to as high a degree as possible, to be directed into a flow of highly superheated steam. The latter functions as a carrier gas for the fuel mist, so that the mixture in the case of a premix burner can be directed via the nozzles provided for a gaseous fuel.
The essential advantages of the invention may be seen in the fact that the atomization of the very hot fuel/water emulsion guarantees the generation of the finest possible mist, which can be readily mixed with the hot combustion air. This enables the injection plane inside the premix burner to be shifted further downstream, so that the flame formation upstream in the interior of the burner, which flame formation is feared on account of the high ignition quality of the liquid fuel, is suppressed without inadequate combustion having to be tolerated.
Advantageous and expedient further developments of the achievement of the object according to the invention are defined in the further claims.
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Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Freay Charles G.
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