EP1963748B1 - Combustion chamber with burner and associated operating method - Google Patents

Description

Technical area

The present invention relates to a method for operating a combustion chamber of a gas turbine, in particular a power plant.

State of the art

From the US 6,358,040 For example, a catalytic burner is known which, when operating from a rich fuel / air mixture, can generate a syngas containing hydrogen gas and which can be used as a pilot burner for a normally lean burn burner of a gas turbine combustor. By injecting a synthesis gas containing hydrogen gas into the burner or into a combustion chamber of the combustion chamber, the homogeneous combustion reaction which takes place in the combustion chamber during operation of the combustion chamber can be stabilized. In particular, this can be used to lower the extinguishing temperature of the combustion reaction in lean burners. Overall, this allows the combustion temperatures in the combustion chamber of the combustion chamber can be reduced. This is of particular advantage because the formation of nitrogen oxides increases exponentially with the reaction temperature. Generic stabilized combustion process with Low emissions are also in the documents WO 2004/020901 and WO 2004/020905 described.

WO 2004/020901 discloses a hybrid burner and a method of operation thereof, wherein the hybrid burner includes in parallel within a housing a Volloxidationskatalysator and a partial oxidation catalyst, which are traversed by a first and a second fuel-oxidizer mixture. The two mixtures have a different fuel-to-oxidant ratio such that the former is a rich mixture and the second is a lean mixture and that the partial oxidation catalyst is designed to produce a hydrogen-containing off-gas. WO 2004/020905 discloses a method of combusting a fuel-oxidizer mixture and an apparatus for carrying it out, wherein a total oxidizer stream is split into a main and a side stream, the former lean-burned and burned with a main fuel stream in a premix burner and the second split again in a pilot oxidizer stream and a heat exchanger oxidizer stream downstream of preheating the pilot oxidizer stream, the pilot oxidizer stream is fat blended with fuel and partially oxidized in contact with a catalyst to form hydrogen and then co-currently with the second substream is introduced into a combustion zone of the main fuel oxidizer stream.

These methods achieve lower pollutant emissions due to the reduced combustion chamber temperatures. However, in order to operate the combustion chamber with a higher power, the combustion chamber must be operated so that it reaches a higher outlet temperature.

Presentation of the invention

This is where the present invention begins. The invention, as characterized in the claims, deals with the problem of pointing out a way for a combustion chamber of the type mentioned that allows for varying combustion chamber performance safe operation and low pollutant emissions.

This object is achieved by the subject of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The inventive method is based on the general idea of controlling the pilot burner as a function of the combustion chamber performance such that the synthesis gas produced therewith contains a comparatively high proportion of hydrogen gas at a low combustion chamber power, while it contains a relatively low proportion of hydrogen gas at a comparatively high combustion chamber power , The invention uses the knowledge that synthesis gas with a relatively low proportion of hydrogen gas at high flame temperatures reduces the formation of nitrogen relatively strongly. At the same time, lowering the extinguishing limit is not necessary at high flame temperatures. In contrast, a synthesis gas with a high hydrogen gas content at high flame temperatures would increase pollutant emissions, in particular nitrogen oxide emissions. Furthermore, the invention uses the knowledge that at lower flame temperatures, the injection of synthesis gas with a relatively high proportion of hydrogen gas significantly stabilizes the homogeneous combustion reaction by significantly lowering the extinction limit. At the same time, there is no increase in nitrogen oxide formation.

The operating method according to the invention thus leads to a stabilized operation of the combustion chamber with a comparatively small combustion chamber power, For example, at low load or partial load, while at the same time with greater combustion chamber performance, for example at full load, the pollutant emissions are reduced compared to a operation without pilot burner.

According to an advantageous embodiment, the synthesis gas production of the pilot burner can be controlled by the amount of fuel supplied to the pilot burner, while at the same time the amount of air supplied to the pilot burner is kept constant. The hydrogen gas content in the synthesis gas is thus controlled by the fuel / air ratio supplied to the catalytic pilot burner. With such a procedure, elaborate control and regulating devices for the air supply of the pilot burner can be saved.

In this way, a common air supply can be provided for the burner and the associated pilot burner, which is designed so that it distributes the supplied air with a constant distribution to the burner and the associated pilot burner. A burner designed in this way can be realized comparatively inexpensively, because said control and regulation devices for the air supply of the pilot burner can be dispensed with.

In another important embodiment, the burner is designed so that a larger proportion of the synthesis gas is introduced radially into the burner and / or into the combustion chamber with respect to a longitudinal axis of the respective burner, while a smaller proportion of the synthesis gas with respect to the longitudinal axis axially into the burner or . is introduced into the combustion chamber. It has been found that with a predominantly radial introduction of the synthesis gas, the best results with regard to pollutant emissions and combustion stabilization can be achieved.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

Brief description of the drawings

Fig. 1

einen stark vereinfachten, prinzipiellen Längsschnitt durch einen Brenner zur Durchführung des Verfahrens,

Fig. 2a

einen Längsschnitt wie in Fig. 1, jedoch bei einer anderen Ausführungsform,

Fig. 2b

einen Querschnitt durch den Brenner gemäß Fig. 2a,

Fig. 3

eine stark vereinfachte axiale Ansicht einer Ringbrennkammer.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components. Show, in each case schematically,

Fig. 1

a highly simplified, fundamental longitudinal section through a burner for carrying out the method,

Fig. 2a

a longitudinal section as in Fig. 1 but in another embodiment,

Fig. 2b

a cross section through the burner according to Fig. 2a .

Fig. 3

a greatly simplified axial view of an annular combustion chamber.

Ways to carry out the invention

According to the Fig. 1 and 2a comprises a burner 1 a combustion chamber 2 (see. Fig. 3 For carrying out the method according to the invention, a catalytically operating pilot burner 3. The burner 1 comprises a fuel supply 4, which is indicated here merely by an arrow and which supplies it with fuel during operation of the burner 1. Furthermore, it is an additional fuel supply 5 is provided, which is likewise symbolized by an arrow and which supplies the pilot burner 3 with fuel during operation of the burner 1. In addition, an air supply 6 is provided, which is provided jointly for the burner 1 and its pilot burner 3. This common air supply 6 is designed in a manner not further explained in such a way that it distributes the supplied air to the burner 1, see arrows 7, and the pilot burner 3, see arrow 8.

The burner 1 is used to generate a homogeneous combustion reaction in a combustion chamber 9 of the combustion chamber 2, which is arranged downstream of the burner 1 in the assembled state. The combustion chamber 2 in turn serves to generate hot gases for acting on a gas turbine, in particular a power plant.

The burner 1 also has a mixture forming space 10, which is open in the assembled state to the combustion chamber 9. The air supply 6 brings the burner 1 associated air quantity 7 in this mixture forming space 10 a. The introduction takes place here in a tangential flow over axially aligned gaps in the burner wall 11, which encloses the mixture forming space 10 circumferentially with respect to a longitudinal axis 12 of the burner 1. Also in the region of the axial gap for introducing the combustion air, the fuel supply 4 supplies the amount of fuel allocated to the burner 1 to the mixture-forming space 10, which is symbolized here by a plurality of arrows 13. The fuel supply 4 extends within the burner wall 11. Usually, such a burner 1 is operated lean to achieve the lowest possible combustion reaction in the combustion chamber 9.

The catalytically operating pilot burner 3 is a certain proportion of the total amount of air supplied to the burner 1 via the air supply 6 The auxiliary fuel supply 5 is now operated so that a rich fuel / air mixture is adjusted, which is supplied to the pilot burner 3. By selecting the respective fuel / air ratio and the associated operating parameters in the catalyst of the pilot burner 3 is a partial oxidation of the fuel, in which a synthesis gas containing hydrogen gas is produced as combustion exhaust gas. This synthesis gas is then introduced according to arrows 14 and 15 from the pilot burner 3 into the mixture-forming space 10 or into the combustion chamber 9. Corresponding to the arrows 14, a part of the synthesis gas with respect to the longitudinal axis 12 is introduced substantially radially into the mixture formation space 10. In contrast, according to the arrows 15, a different part of the synthesis gas with respect to the longitudinal axis 12 is injected substantially axially into the mixture formation space 10 and into the combustion chamber 9, respectively.

According to the invention, the radially introduced synthesis gas fraction 14 is now greater than the axially introduced synthesis gas fraction 15. This particular division of the synthesis gas introduction into the mixture formation space 10 or into the combustion chamber 9 is based on the finding that with the aid of this distribution of the synthesis gas injection, particularly favorable results for low nitrogen oxide production and a stabilizing effect for the homogeneous combustion reaction in the combustion chamber 9 can be achieved. According to a preferred embodiment, the pilot burner 3 can be configured, for example, such that at least 50% to 70% of the synthesis gas generated by the pilot burner 3 enters the mixture-forming space 10 radially. Accordingly, the proportion of the synthesis gas, which is introduced axially from the pilot burner 3 into the mixture formation space 10 or into the combustion space 9, is at most 30% to 50%.

In addition, it may be expedient to design the pilot burner 3 in addition such that the amount of synthesis gas 14 introduced radially at least partially also has a tangential with respect to the longitudinal axis 12 component.

According to the embodiment according to Fig. 1 For example, the pilot burner 3 may have a lance 16. The lance 16 extends coaxially with the longitudinal axis 12 of the burner 1. Furthermore, the lance 16 projects axially from a burner head 17 and protrudes into the mixture-forming space 10. In order to achieve the radial and axial injection of the synthesis gas into the mixture formation space 10 and / or into the combustion chamber 9, the lance 16 has corresponding, only partially indicated radial outlet openings 18 and at least one axial outlet opening 19th

Alternatively, according to the Fig. 2a and 2b the burner 1 in another embodiment, a pilot burner 3, which is integrated into the burner wall 11. For example, a catalytically active channel is integrated into the burner wall 11 for this purpose. It is also possible to arrange a catalyst further upstream and to integrate only the exhaust gas channels in the burner wall 11, which then transport the synthesis gas. In any case, the burner wall 11 includes a plurality of radial outlet openings 20 through which the larger radial synthesis gas portion 14 enters the mixture formation space 10. Furthermore, the burner wall 11 contains a plurality of axial outlet openings 21, through which then the smaller axial proportion of synthesis gas 15 can be injected into the combustion chamber 9.

With regard to the fuel supply 4 and the air supply 7 of the burner 1, the works in Fig. 2a shown burner 1 substantially identical to that in Fig. 1 shown burner 1, wherein the radial fuel injection 13 in Fig. 2a is rendered simplified.

Corresponding Fig. 3 comprises a combustion chamber 2, which is designed here as an annular combustion chamber, a plurality of burners 1 upstream of the in Fig. 3 not shown combustion chamber 9 are arranged distributed in a ring. Each of these burners 1 is equipped with a pilot burner 3, which operates catalytically and can generate the hydrogen gas-containing synthesis gas. Usually, a common air supply 22 is provided for all burners 1, which is symbolized here by an arrow. Furthermore, the burners 1 are usually divided into fuel supply groups. For example, two burner groups are provided to which each half of all burners 1 is assigned. Each burner group has its own fuel supply 23 or 23 '. The burners 1 of one group are expediently arranged alternately with the burners 1 of the other group. Correspondingly, the pilot burners 3 of one group can be supplied with fuel via a common auxiliary fuel supply 24, while the pilot burners 3 of the other burner group are supplied with fuel via a further common additional fuel supply 24 '. The air supply within the individual burners 1 takes place again together, with a constant distribution of the supplied air quantity to the respective burner 1 and the associated pilot burner 3.

• Wenn die Brennkammer 2 eine vergleichsweise niedrige Brennkammerleistung erzeugen soll, wird zum einen die Brennstoffversorgung 23 bzw. 23' der Brenner 1 entsprechend reduziert. Zum anderen werden die Pilot-Brenner 3 so angesteuert, dass sie jeweils ein Synthesegas erzeugen, das einen vergleichsweise hohen Anteil an Wasserstoffgas enthält. Dieses Synthesegas wird über die Pilot-Brenner 3 in die Gemischbildungsräume 10 der Brenner 1 bzw. in den Brennraum 9 der Brennkammer 2 eingebracht und bewirkt dort aufgrund seines hohen Wasserstoffgas-Anteils eine Absenkung der Löschgrenze. Im Experiment konnte die Löschgrenze um etwa 100 K abgesenkt werden. Auf diese Weise kann die Verbrennungsreaktion im Brennraum 9 stabil ablaufen, auch wenn die Temperatur im Brennraum 9 aufgrund der reduzierten Brennkammerleistung vergleichsweise niedrig ist. Beispielsweise charakterisiert sich eine niedrige Brennkammerleistung durch eine Austrittstemperatur der Verbrennungsabgase aus dem Brennraum 9 von maximal 1600 K. Die niedrigen Brennraumtemperaturen führen dabei trotz des relativ hohen Wasserstoffgasanteils nicht zu einer Zunahme der Stickoxidbildung.

According to the invention, the burners 1 in the combustion chamber 2 can be operated as follows:

• If the combustion chamber 2 is to generate a comparatively low combustion chamber power, the fuel supply 23 or 23 'of the burner 1 is correspondingly reduced on the one hand. On the other hand, the pilot burners 3 are controlled in such a way that they each generate a synthesis gas which contains a comparatively high proportion of hydrogen gas. This synthesis gas is introduced via the pilot burner 3 into the mixture-forming chambers 10 of the burner 1 or into the combustion chamber 9 of the combustion chamber 2, where it causes its action high hydrogen gas content, a reduction of the extinction limit. In the experiment, the extinction limit was lowered by about 100 K. In this way, the combustion reaction in the combustion chamber 9 can proceed stably, even if the temperature in the combustion chamber 9 is comparatively low due to the reduced combustion chamber power. For example, a low combustion chamber performance is characterized by an exit temperature of the combustion exhaust gases from the combustion chamber 9 of at most 1600 K. The low combustion chamber temperatures do not lead to an increase in nitrogen oxide formation despite the relatively high proportion of hydrogen gas.

In the event that the combustion chamber 2 is to deliver a comparatively high combustion chamber power, on the one hand the burners 1 are supplied with a correspondingly increased amount of fuel. On the other hand, the pilot burners 3 are controlled so that the synthesis gas generated by them contains a lower proportion of hydrogen gas. The increased fuel supply via the burner 1 leads to an increase in the temperature in the combustion chamber 9, whereby the combustion chamber power increases and the outlet temperature is at least 1800 K. The comparatively low proportion of hydrogen gas in the synthesis gas leads to a significant reduction in nitrogen oxide formation at high combustion chamber temperatures. Accordingly, pollutant emissions can be significantly reduced with the help of synthesis gas injection. In the experiment, the nitrogen oxide formation could be reduced by about 33%.

Preferably, the synthesis gas injected from the pilot burners 3 contains at the low burner chamber capacity a hydrogen gas content of at least 30% by volume. Preferably, the hydrogen gas content at the low combustor power is between 30% by volume and 50% by volume. In contrast, the hydrogen gas content in the synthesis gas at a high combustion chamber capacity is at most 30% by volume, in particular in a range from 5% by volume to 30% by volume.

The synthesis gas production or the hydrogen gas fraction in the synthesis gas can be changed particularly easily in the catalytically operating pilot burners 3 by varying the fuel / air ratio. This fuel / air ratio can be particularly easy to change by varying the amount of fuel supplied to the pilot burners 3, which is relatively easy to implement. In contrast, the amount of air supplied remains substantially constant, so that can be dispensed with complex control and regulation facilities here.

The inventive operation of the combustion chamber 2 and its burner 1 ensures that the combustion chamber 2 can be operated comparatively stable at low power, while at high combustion chamber performance, the production of nitrogen oxides can be greatly reduced.

Furthermore, the integration of pilot burners 3 in the burner 1 of the annular combustion chamber 2 has an additional valuable advantage. In annular combustion chambers 2, there are usually undesirable interactions of the individual burner 1 with each other. These interactions can lead to pulsations and thus to an undesirable vibration load of the components and to an undesirable noise pollution of the environment. Furthermore, the interactions can reduce the stability of the combustion reactions, locally increase the temperature and thus support the formation of nitrogen oxides.

One cause of these undesirable interactions is seen in the fact that the common air supply to the burner 1 of the same burner group does not supply the individual burners 1 exactly with the same amount of air, which is due, for example, to manufacturing tolerances. To this In principle, it is possible to control the air supply and / or the fuel supply for each burner 1 separately. However, this is associated with a huge effort. Here the equipment of the burner 1 with the pilot burners 3 remedy.

As mentioned, the amount of air supplied to the individual burners 1 can deviate from an ideal air quantity or set air quantity. Since, as explained above, the distribution of the quantity of air supplied to the individual burner 1 to the burner 1 and its pilot burner 3 is constant, the quantity of air supplied to the individual pilot burner 3 changes in the same proportion as the total quantity of air supplied to the individual burner 1 , If the total amount of air or actual air quantity actually supplied to the individual burner 1 deviates from the desired setpoint air quantity, the quantity of air supplied to the respective pilot burner 3 also changes as a result. Since in a stationary operation of the combustion chamber 2, the amount of fuel supplied to the pilot burner 3 remains constant, a change in the amount of air leads to a change in the fuel / air ratio. However, the fuel / air ratio correlates with the synthesis gas production or with the hydrogen gas content in the synthesis gas generated by the catalytic pilot burners 3.

In the event that the actual amount of air is greater than the target air quantity, the combustion air / fuel ratio increases. An increased combustion air / fuel ratio increases the hydrogen gas content in the synthesis gas and leads to an increased exhaust gas temperature of the respective pilot burner 3, ie to an increased synthesis gas temperature. As a result, the portion of the flame front associated with this burner 1 or this pilot burner 3 is moved upstream in the combustion chamber 9. This local change in position of the flame front increases the pressure drop at this burner 1, that is, its flow resistance, and leads to a sequence in the sequence Reduction of this burner 1 supplied amount of air. In this way, the actual air quantity decreases and approaches the set air quantity.

Otherwise, if the actual air amount is smaller than the target air amount, the combustion air / fuel ratio decreases. This causes the associated flame front section moves downstream, whereby the pressure loss through this burner 1 decreases accordingly. As a result, the air flow through this burner 1 can increase again and the actual amount of air increases.

As a result, it comes thus to each burner 1 to an individual, self-running control of the amount of air to a previously set in the design of the respective burner 1 value. Elaborate control strategies, facilities and the like are not required.

At the same time 3 acoustic interactions can be reduced by means of the pilot burner, that the synthesis gas is introduced into the combustion chamber 9. Because the supply of fuels of higher reactivity leads to a reduction of the acoustic interactions.

LIST OF REFERENCE NUMBERS

1

burner

2

combustion chamber

3

Pilot burner

4

fuel supply

5

Additional fuel supply

6

air supply

7

Air flow rate for 1

8th

Air flow rate for 3

9

combustion chamber

10

Mixture formation chamber

11

burner wall

12

Longitudinal axis of 1

13

amount of fuel

14

radial synthesis gas injection

15

axial synthesis gas injection

16

lance

17

burner head

18

radial outlet opening

19

axial outlet opening

20

radial outlet opening

21

axial outlet opening

22

air supply

23

fuel supply

24

Additional fuel supply

Claims (11)

1. Method for operating a combustion chamber (2) of a gas turbine, in particular of a power plant,

   - the combustion chamber (2) having at least one burner (1) which is provided with a catalytic pilot burner (3),

   - characterized in that the pilot burner (3) is actuated at low power of the combustion chamber (2) such that it generates as a reaction product a synthesis gas with a high proportion of hydrogen gas,

   - and in that the pilot burner (3) is actuated at high power of the combustion chamber (2) such that the synthesis gas generated has a low proportion of hydrogen gas.
2. Method according to Claim 1,
   characterized

   - in that at low combustion chamber power, the synthesis gas contains a proportion of at least 30% by volume of hydrogen gas.
3. Method according to Claim 2,
   characterized

   - in that at low combustion chamber power, the hydrogen gas proportion in the synthesis gas is between 30% by volume and 50% by volume.
4. Method according to Claim 1,
   characterized

   - in that the synthesis gas at high combustion chamber power contains a proportion of at most 30% by volume of hydrogen gas.
5. Method according to Claim 4,
   characterized

   - in that at high combustion chamber power, the hydrogen gas proportion in the synthesis gas is between 5% by volume and 30% by volume.
6. Method according to one of Claims 1 to 5,
   characterized

   - in that at low combustion chamber power, the combustion chamber (2) has an outlet temperature of a maximum of 1600 K, and/or

   - in that at high combustion chamber power, the combustion chamber (2) has an outlet temperature of at least 1800 K.
7. Method according to one of Claims 1 to 6,
   characterized

   - in that a relatively large proportion (14) of the synthesis gas is introduced into the burner (1) and/or into the combustion chamber (2) radially relative to a longitudinal axis (12) of the respective burner (1), and

   - in that a relatively small proportion (15) of the synthesis gas is introduced into the burner (1) and/or into the combustion chamber (2) axially relative to the longitudinal axis (12).
8. Method according to Claim 7,
   characterized

   - in that a proportion of the synthesis gas of at least 50% to 70% is introduced radially, and

   - in that a proportion of the synthesis gas of at most 30% to 50% is introduced axially.
9. Method according to Claim 7 or 8,
   characterized
   in that the radially introduced synthesis gas at least partially also has a tangential component relative to the longitudinal axis (12).
10. Method according to one of Claims 1 to 9,
    characterized
    in that the burner (1) and the associated pilot burner (3) are provided with a common air supply (6) with constant division of the air between the burner (1) and the pilot burner (3).
11. Method according to one of Claims 1 to 10,
    characterized
    in that the synthesis gas generation of the pilot burner (3) is controlled by means of the fuel quantity supplied to the pilot burner (3), while the air quantity supplied to the pilot burner (3) is kept constant.

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