METHOD AND BURNER ARRANGEMENT FOR THE PRODUCTION OF HOT GAS, AND USE OF SAID METHOD
A method for producing hot gas for operating a turbomachine fired with at least one combustion chamber includes premixing a fuel with a plurality of operating gases by introducing fuel into the plurality of operating gases in a mixing chamber disposed upstream of the combustion chamber using a burner arrangement, wherein the fuel includes at least one of a combustible gas and a H2-rich fuel; and introducing the premixed fuel into the combustion chamber.
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This application is a divisional of U.S. patent application Ser. No. 12/876,508, filed Sep. 7, 2010, which is a continuation of International Patent Application No. PCT/EP2009/051764, filed Feb. 16, 2009, which claims priority to Swiss Patent Application No. CH 00350/08, filed Mar. 7, 2008. The entire disclosure of both applications is incorporated by reference herein.
FIELDThe present invention relates to the field of combustion technology. It refers to a method for combusting H2-rich fuels. It also refers to a burner arrangement for implementing the method and for its use.
BACKGROUNDFrom WO-A1-2006/069861, a premix burner with subsequent mixing section or mixer tube (a so-called AEV burner) has been known, in which in the premix burner, which is formed according to EP-A1-704 657, a first fuel can be centrally injected and between the air inlet slots or passages which are formed by the shells in the swirler (shown clearly especially in EP-A1 321 809) at least one second fuel can be introduced into the air which flows into the inner space there. In the subsequent mixer tube, provision is made for a further device for injecting a third fuel. All printed publications which are referred to here or later, and their further developments, form an integrating element of this application.
For combusting H2-rich fuels, as created for example in the form of syngas during coal gasification, it has already been proposed to inject at least some of the H2-rich fuel via the mixer tube of such a premix burner. Also, such a premix burner has already been tested with natural gas in lean premix operation, during which under high pressure H2-rich fuels with H2-to-N2 ratios of 70/30 and 60/40 have been injected in an axially staged manner in the premix burner and in the mixer tube.
During these tests, it has been shown that if a changeover is made from natural gas entirely to the H2-rich fuel, the flame migrates upstream into the mixer tube. Although the burner was able to be operated in this way without damage and with sufficiently low NOx emission, numerous disadvantages arose, however, specifically:
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- The pressure losses in the premix burner are increased by the factor of 3. This is undesirable in the case of gas turbines with regard to an associated gas turbine cycle.
- The available mixing length, i.e. the distance between the location of the injection of the fuel and the flame front, is reduced, which leads to increased NOx-emission.
- High-frequency pulsations gain in importance. In this context, it may be mentioned that the thermoacoustic vibrations represent a hazard for each type of combustion application. They lead to high-amplitude pressure vibrations, to limitation of the operating range, and they can increase pollutant emissions. This applies especially to combustion systems with low acoustic damping, as is the case for example in annular combustion chambers with reverberant walls. In order to ensure a high performance conversion over a wide operating range with regard to pulsations and pollutant emissions, provisions against these pulsations must be made.
In an aspect of the invention, a method for combusting H2-rich fuels is provided which reliably prevents migrating of the flame back into the burner and also pulsations, even during a changeover from natural gas to H2-rich fuels.
In an embodiment of the invention, in addition to the H2-rich fuel, a small amount of natural gas is introduced into the burner arrangement during premix operation and combusted together with the H2-rich fuel.
One development of the method according to the invention is characterized in that first of all an air/fuel mixture is created from the air and the natural gas, and in that the H2-rich fuel is then injected into the air/fuel mixture. In particular, a burner arrangement, which comprises a premix burner and a mixer tube which is connected to it, is used for this purpose, wherein the fuel/air mixture is created in the premix burner. The H2-rich fuel can be injected into the mixer tube and/or into the swirler. A swirler can be advantageously used as the head stage of the premix burner, as is described for example in EP-A1-321 809.
Another development of the method according to the invention is characterized in that first of all the natural gas and the H2-rich fuel are intermixed, and in that the resulting fuel mixture is mixed and combusted with air in the burner arrangement. As a result of this, the system of fuel feed and fuel distribution can especially be simplified. Also in this case, a burner arrangement can preferably be used which comprises a premix burner and a mixer tube which is connected to it, wherein in the premix burner the air/fuel mixture is created from the air and the fuel mixture.
A burner arrangement can also be used, however, as is disclosed for example in WO-A1-2007/113074, in which within the scope of a sequential combustion a fuel lance projects into a hot gas flow, and wherein the fuel mixture is injected via the fuel lance, if necessary with additional air, into the hot gas flow. The fuel lances which are shown in this printed publication (FIGS. 2-6) are designed for use in the low-pressure combustion chamber (Pos. 14). Also, this last-named printed publication forms an integrating element of this application. The operation of such a low-pressure combustion chamber with the use of a fuel lance which is described above in a sequentially fired gas turbine, results for example from EP 620 362 A1, which printed publication also represents an integrating element of this description.
The invention shall subsequently be explained in more detail based on exemplary embodiments in conjunction with the drawing. All elements which are not necessary for the direct understanding of the invention have been omitted. Like elements are provided with the same designations in the various figures. The flow direction of the media is indicated by arrows.
In the drawings:
Reproduced in
According to the exemplary embodiment which is shown in
-
- The pressure loss coefficient Zeta is reduced from 2.8 to 1.5, which corresponds to a sharp reduction of the pressure loss in the burner.
- The high-frequency pulsations (of 2 to 4 kHz) are practically eliminated.
- NOx-emissions are minimized, this based on the fact that the flame is maintained by a maximized premixed air/fuel mixture.
- The fuel feed lines 17 in the region of the swirler 11 are constantly purged for the natural gas so that changing over to natural gas operation is possible within an extremely short time.
- If the flame front actually migrates upstream into the burner, it is anchored relatively far downstream in the mixer tube and burns in a stable and reliable manner. If in a multi-burner arrangement, as is customary in gas turbines, a flashback occurs in a burner, this leads more easily to a stable state in the burner and not to an operation-relevant negative development in which the flame front migrates still further upstream until destruction of the burner commences, as is immanently the case in normal burners. If this state occurs, then the reason to be looked for is that the burner in question is blocked and the throughflow of air is reduced. This then also means that an individual burner can be temporarily shut down and reignited. The operation of the other burners in the gas turbine is consequently not affected.
- The reason that the flame front in this case cannot flash back to the premixed burner 11 which is used according to the invention, and destruction cannot correspondingly occur, is to be seen as that of the very same flame front assuming a fixed local anchoring inside the mixer tube 13 in such a way that it also cannot creep upstream either, the air flow hardly being impaired in the process.
Whereas in the exemplary embodiment of
Stabilizing the flame position and limiting NOx-emissions which is associated therewith, and avoiding pulsations by means of a small addition of natural gas, can also be applied in a gas turbine with sequential combustion, specifically in the second or subsequent combustion stage. In
The subject according to the invention can be used with particular advantage in a gas turbine with at least one combustion chamber stage, wherein the hot gas which is produced is expanded in the gas turbine, performing work.
LIST OF DESIGNATIONS
- 10 Burner arrangement
- 11 Swirler
- 12 Air/fuel mixture
- 13 Mixer tube
- 14 Combustion chamber
- 15 Axis
- 16 Injection device
- 17, 18 Fuel feed line
- 19 Valve
- 20 Fuel lance
- 21 Vertical outer tube of the fuel lance
- 21′ Horizontal outer tube of the fuel lance
- 22 Inner tube
- 23 Injection orifice
- 24 Fuel
- 25 Air
- 26 Hot gas flow
- 27 Low-pressure combustion chamber operated by means of self-ignition
- 28 Vortex generators
- 29 Fuel injection
- 30 Fuel injection
- F1 Fuel (natural gas)
- F2 Fuel (H2-rich, for example syngas)
- α Injection angle
- α′ Injection angle
Claims
1. A burner arrangement disposed upstream of a combustion chamber comprising:
- a mixing chamber configured to premix a fuel with a plurality of operating gases; and
- a swirler having at least two hollow partial conical shells nested one inside the other in a flow direction and complementing one another to form a body with an interior space, wherein a cross section of the interior space increases in the flow direction, wherein the at least two conical shells each have a wall and each have a longitudinal axis of symmetry, wherein the longitudinal axes of symmetry of the hollow shells run offset with respect to one another such that the walls of each shell are adjacent to each other and form a tangential air inlet slot extending longitudinally for an inflow of the air into the interior space.
2. The burner arrangement as recited in claim 1, further comprising a mixing tube and a transition region disposed between the swirler and the mixing tube, the transition region containing transition passages for a transfer of a flow formed in the swirler and into a throughflow cross section of the mixer tube connected downstream of the transfer passages.
3. The burner arrangement as recited in claim 2, wherein a number of the transfer passages corresponds to a number of the at least two shells.
4. A burner arrangement disposed upstream of a combustion chamber comprising:
- a mixing chamber configured to premix a fuel with a plurality of operating gases; and
- a swirler having at least two hollow partial shells nested one inside the other in a direction of flow and complementing one another to form a body with an interior space, wherein a cross section of the interior space is substantially cylindrical in a flow direction, and wherein the at least two hollow shells each have a wall and each have a longitudinal axis of symmetry, wherein the longitudinal axes of symmetry of the hollow shells run offset with respect to one another such that the walls of each shell are adjacent to each other and form a tangential air inlet slot extending longitudinally for an inflow of the air into the interior space, wherein the interior space includes an internal body having a decreasing cross section in the flow direction.
5. The burner arrangement as recited in claim 4, wherein a size of the inner body decreases conically in the direction of flow.
6. The burner arrangement as recited in claim 4, further comprising a mixing tube and a transition region disposed between the swirler and the mixing tube, the transition region containing transition passages for a transfer of a flow formed in the swirler and into a throughflow cross section of the mixer tube connected downstream of the transfer passages.
7. The burner arrangement as recited in claim 6, wherein a number of the transfer passages corresponds to a number of the at least two shells.
Type: Application
Filed: Apr 9, 2013
Publication Date: Aug 29, 2013
Applicant: ALSTOM Technology Ltd (Baden)
Inventor: Alstom Technology Ltd
Application Number: 13/859,002
International Classification: F23D 14/02 (20060101); F23D 14/62 (20060101);