Power plants – Combustion products used as motive fluid
Patent
1998-06-29
2000-11-21
Thorpe, Timothy S.
Power plants
Combustion products used as motive fluid
60 39465, 60 39826, F02C 726
Patent
active
061486035
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of operating a gas turbine group with low calorific value fuel, whereby the gas turbine group essentially comprises a compressor, a combustion chamber, a turbine and a generator and whereby the low calorific value fuel is compressed by means of a fuel compressor.
2. Discussion of Background
Such methods are known. In contrast to gas turbines which are operated with conventional medium calorific value or high calorific value fuels, such as natural gas or oil with a calorific value of 40 MJ/kg or more, the stabilization of the combustion represents a problem in the case of gas turbines which use a low calorific value fuel with a calorific value of an order of value below 10 MJ/kg. In the particular case of calorific values below 3 MJ/kg (approximately 700 kcal/m.sub.n.sup.3), the flame becomes unstable.
U.S. Pat. No. 5,451,160 describes a burner for the combustion of gases with the most varied calorific values. The burner contains an inner part, which acts as the pilot burner, and an outer main burner which concentrically surrounds the pilot burner. When the pilot burner and the main burner are operated with low calorific gases, however, the stability of the flame represents a problem and the danger of flame extinction exists.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to provide a novel way of stabilizing the combustion of fuels of low calorific value in a method of operating a gas turbine group with low calorific value fuel.
This is achieved, in accordance with the invention, by means of the features of the first claim.
The core of the invention is therefore an arrangement wherein low calorific value fuel in excess of the stoichiometric quantity is mixed into part of the combustion air during the starting of the gas turbine group so that a stable flame appears, wherein after the attainment of the rated rotational speed and synchronization, at the latest, the quantity of low calorific value fuel is reduced to such an extent that a ratio is attained which is just over the stoichiometric ratio and wherein the rest of the low calorific value fuel is mixed into the rest of the combustion airflow in order to attain the desired load.
The advantages of the invention may, inter alia, be seen in the fact that the gas turbine group can essentially be operated exclusively with low calorific value fuel. By this means, the economy of gas turbines which are operated with low calorific value materials of the lowest calorific values is increased.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
FIG. 1 shows a diagrammatic representation of a gas turbine group;
FIG. 2 shows a partial cross section through a burner of the gas turbine group;
FIG. 3 shows a diagrammatic representation of the operating method of the gas turbine group;
FIG. 4 shows a combustion chamber, with burner, of the gas turbine group;
FIG. 5 shows a partial cross section through the burner of FIG. 4;
FIG. 6 shows a partial development of the burner of FIG. 4;
FIG. 7 shows a plan view from the combustion space onto the burner outlet.
Only the elements essential to understanding the invention are shown.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawing, wherein like reference numerals designate identical or corresponding parts throughout the several views, FIG. 1 shows, diagrammatically, a gas turbine group which comprises essentially of a compressor 40, a gas turbine 41 and a generator 46, which are connected together by means of a shaft 42, and a combustion chamber 43 is diagrammatically shown. A fuel compressor 48 for compressing low calorific value, gaseous fuel is additionally provided between the compressor 40 and the generator 46. The compression of the
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Asea Brown Boveri AG
Gartenberg Ehud
Thorpe Timothy S.
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