GB2341641A

GB2341641A - Ring fuel conduits having switchable valves

Info

Publication number: GB2341641A
Application number: GB9911677A
Authority: GB
Inventors: Michael Witt; Gunnar Breitsprecher; Josef Just; Ung-Lap Ngo Beelmann; Udo Kowal; Klaus Langenbacher; Pierre Gerodez; Gerhard Mueller; Robin Mcmillan
Original assignee: ABB Patent GmbH
Current assignee: ABB Patent GmbH
Priority date: 1998-06-05
Filing date: 1999-05-19
Publication date: 2000-03-22
Also published as: JP2000002421A; GB9911677D0; DE19825335A1

Abstract

A gas turbine engine receives fuel from a main supply 20, which flows via ring conduits 12,14,16 to an annular combustion chamber having burners arranged in groups. Conduit 24 feeds pilot flames via conduit 12, while conduits 24,26 supply conduits 14,16. Switchable valves 25,27,29 are activated by a control circuit 30 via lines 32 to allow the delivery of a part quantity of fuel. Thus the pilot flames may be extinguished soon after start-up, and the number of burners set for a part-load state by switching burners on and off, so the burners can work in a low-pollutant range. Each burner group may have a different number of burners, but preferably between 10 and 60, the valves being arranged to switch individual burners, two, four or eight burners or whole groups. The valves may be solenoid, hydraulic or pneumatic or a combination of these. A relief valve 23 may be present. The emission of nitric oxides, carbon monoxide and unburnt hydrocarbons is reduced in the part-load state.

Description

2341641 Method for oiDeratinq a cras turbine

Description

The invention relates to a method for operating a gas turbine, the working medium of which is supplied by annularly arranged combustion chambers which are fed with fuel which flows in from a specific number of valves. The invention also relates to a gas turbine plant which is suitable for carrying out the method according to the invention.

Gas turbine plants and the operation of these have been known for a long time. In gas turbines with annular combustion chambers, the fuel has hitherto been supplied to the combustion chamber by means of a few regulatable inflow valves. In a known and tested gas turbine plant, for example, the 72 burners which are present in the annular combustion chamber are fed from three regulating valves.

This allocation proved to be a disadvantage, inasmuch as, on the one hand, there is some sensitivity in terms of combustion stability, particularly in the case of dynamic processes, and, on the other hand, in the partload mode, a high fraction of pollutants, such as, for example, nitric oxides (NOx), is emitted together with the exhaust gas.

It is known, furthermore, that, in order to protect the environment, the adverse emissions of pollutants or their harmful compounds, which occur in the exhaust gas due to the combustion of fuel in order to generate the working medium of the gas turbine, are to be reduced.

2 In particular, the aim is to achieve a reduction in the emissions of nitric oxides (NO,), of carbon monoxide (C0) and of unburnt hydrocarbons WHC) which occur to a particularly pronounced degree when the gas turbine plant 5 is operating in the part-load mode.

Proceeding from this state of the art, the object of the invention is to specify a method of the type mentioned in the introduction, which makes it possible, by the simplest possible means, to reduce the quantities of pollutants in the exhaust gas. Furthermore, an increase in combustion stability in the case of dynamic processes and, consequently, an increase in availability are to be achieved by means of this method. Moreover, a gas turbine plant suitable for carrying out this method is to be is provided.

Claims

This object is achieved, according to the invention, by means of the

characterizing features of Claims 1 and 5. Further advantageous embodiments and developments of the invention are characterized in the subclaims.

According to the invention, therefore, there is provision for delivering a part quantity of the fuel to the combustion chamber via switchable valves, and for the switchable valves to be activated in the part-load range and switched on or off, depending on the respective requirement.

Allocating the supply of fuel to the burners in this way according to the invention advantageously ensures that the number of burners harmonizes better with the loaddependant gas quantity and, even in the part-load range, the burners can be operated in their low-pollutant working range. It is thereby possible to guarantee the necessary operating licences for large gas turbines with annular combustion chambers.

According to an advantageous embodiment of the invention, 3 the actuation of the switchable valves is load-dependent, that is to say the burners fed by switchable valves are switched on or put out of operation depending on the load state of the gas turbine plant or depending on the 5 respective load requirement.

The switch-on sequence of the burners is symmetrical with respect to the annular combustion chamber, so that an imbalance in charging the gas turbine with working medium is avoided. At the same time, according to the invention, when the switchable valves are actuated the supply can be switched for at least 1 burner or for a plurality of burners, preferably at each switching point.

A gas turbine plant for carrying out the above-described method is equipped with a gas turbine having a compressor is and having at least one annular combustion chamber arranged annularly around the gas turbine and the individual burners of which are connected to a fuel supply via activatable valves. The fuel supply is implemented preferably with the aid of at least one ring conduit which, according to a preferred embodiment, is subdivided into individual sections which ensure the supply of the individual burners in groups or individually via the activatable valves, each valve influencing the inflow of fuel to the associated individual burners.

In a further advantageous embodiment of the invention, the switchable valves may be designed as solenoid valves or as pneumatic valves. According to a particular variant, the switchable valves may be designed as combinations of pneumatic and solenoid valves.

With a view to the abovementioned aim of reducing pollutant emissions, it proves advantageous to design the valves, at least partly, as switchable valves which are assigned in each case to specific burners, to which fuel flows or not, depending an the switching position of the switchable valves, whilst, according to a preferred embodiment of the invention, a switchable valve is assigned in each case to two burners. However, groups of four or eight burners may also additionally be combined.

The aim, in general, is to extinguish, as soon as poss ible after start-up, the ignition or pilot flame provided on virtually every individual burner for igniting the respective operating flame, since, due to the high flame temperature of the said ignition or pilot flame, combus tion takes place with an excessive proportion of pollu- tants and therefore adversely influences the pollutant balance obtained during combustion.

In order to achieve this aim, it proves advantageous, according to the invention, to have the possibility of setting the number of burners, depending on the respect- ive load state. This ensures that the pilot flame can be switched of f as early as when the gas turbine is operating at markedly less than 60% of its rated power, so that only the actual low-pollutant flame is burnt in the working range of the burner. This leads to a decisive reduction in pollutant emissions.

Particularly the possibility of setting the fuel supply to the individual burners, or the individual burner groups, arranged so as to be distributed over the circumference of the at least one annular combustion chamber, affords the possibility of setting as uniform a pollutant level as possible over the entire load spectrum, so that subsequent exhaust-gas purification may be virtually dispensed with or the exhaust-gas purification requirements are appreciably reduced and therefore simplified.

These and other advantageous embodiments and improvements of the invention are the subject-matter of the subclaims.

The invention and advantageous embodiments and improvements as well as particular advantages of the invention will be explained and described in more detail with reference to an exemplary embodiment illustrated in the diagrammatic drawing.

The single f igure shows a diagrammatic control concept for activating the switchable valves.

The single figure illustrates a diagrammatic control concept which explains how the fuel is supplied to the individual burners or to the burner groups.

By way of a main supply conduit 20, which can be shut off by means of a quick-action stop valve 22, the fuel gas flows via ring conduits 12, 14, 16 to an annular combus- tion chamber, not illustrated in any more detail, with individual burners which are assigned, in a differing arrangement and number, to individual burner groups. In the present example, the main conduit 20 is, in this case, first divided into three supply conduits 24, 26, 28, which are in each case provided with regulating valves 25, 27, 29, before the said conduits are connected to the respective ring conduits.

The first conduit 24 feeds the pilot flames of a first ring conduit 12, whilst, in the present case, the other two supply conduits 26, 28 in each case supply a further ring conduit with fuel gas. The number of individual burners assigned in each case to a burner group may be different and is preferably between 10 and 60. Further- more, there may be provision for connecting one supply conduit 28 to an additional group of further individual burners for the individual supply of these.

in addition, both the main conduit 20 and one supply conduit 26 may in each case be connected to a relief valve 23 via a relief conduit.

The switchable valves 25, 27, 29 are activated via a special control circuit 30 which is illustrated, here, by broken lines and, in particular, takes into account the 1 current values for the intake pressure, intake temperature and respective power. The switchable valves 25, 27, 29 are activated by corresponding control lines 32.

7 Patent Claims 1. Method for operating a gas turbine, the working medium of which is generated in at least one annularly arranged combustion chamber with individ ual burners which are supplied, via at least one ring conduit (12, 14, 16), with fuel, the inflow of which is controlled by a specific number of valves (25, 27, 29), characterized in that a part quantity of the fuel is delivered via switchable valves (25, 27, 29) to the ring conduits (12, 14, 16) serving f or the supply of individual burners, and in that the switchable valves (25, 27, 29) are activated and, in the part-load range, are switched on or off, depending on the respective requirement.

is
2. Method according to Claim 1, characterized in that the actuation of the switchable valves (25, 27, 29) is load-dependent.
3. Method according to Claim 1 or 2, characterized in that the switchable valves (25, 27, 29) are actuated individually or in groups.
4. Method according to one of the preceding claims, characterized in that, for the actuation of the switchable valves (25, 27, 29), the supply is switched for at least one individual burner or for a plurality of, preferably for two, individual burners, at each switching point.
5. Method according to one of Claims 1 to 3, characterized in that, for the actuation of the switchable valves (25, 27, 29), the supply is switched for at least four individual burners, preferably for eight individual burners, at each switching point.
6. Gas turbine plant for carrying out the method accor- 8 ding to one of the preceding claims, with a gas turbine having a compressor and having at least one annular combustion chamber (10) arranged annularly around the gas turbine, with individual burners which are connected to a fuel supply via a ring conduit provided with valves, characterized in that the valves are designed, at least partly, as switchable valves (25, 27, 29) which are assigned in each case to specific individual burners, and in that fuel flows in or not, depending on the switch ing position of the switchable valves (25, 27, 29).
7. Gas turbine plant according to Claim 6, character ized in that a switchable valve (25, 27, 29), which influences the inflow of fuel to the individual is burners, is assigned in each case to one or a plu rality of individual burners.
8. Gas turbine plant according to Claim 6, character ized in that a switchable valve (25, 27, 29), which influences the inflow of fuel to the individual burners, is assigned in each case to four individual burners.
9. Gas turbine plant according to one of Claims G to 8, characterized in that the switchable valves (25, 27, 29) are designed as solenoid valves or as pneumatically or hydraulically actuated valves.
10. Gas turbine plant according to one of Claims 6 to 8, characterized in that the switchable valves (25, 27, 29) are designed as combinations of pneumatically or hydraulically actuated valves and solenoid valves.