EP4008955B1 - Device and method for supplying combustion air and exhaust gas recirculation for a burner - Google Patents

Description

The invention relates to a device and a method for combustion air supply and exhaust gas recirculation for a burner and to a burner with a device for combustion air supply and exhaust gas recirculation.

Hydrogen, particularly so-called green hydrogen, which is obtained by splitting water from renewable energies such as wind energy, solar energy or hydropower, or from biomass, is becoming increasingly important as an energy source, initially as an additive to natural gas and later as pure gas. Although hydrogen burns with almost no emissions, oxygen and nitrogen are components of the combustion air, so nitrogen oxides can also form when hydrogen is used. Thermal nitrogen oxide formation begins at high temperatures and then increases exponentially with temperature. Due to the high reaction rate of hydrogen, thermal nitrogen oxide formation increases sharply when using hydrogen compared to using pure natural gas. For example, burners without special measures produce around 50 ppm of nitrogen oxide in the exhaust gas with natural gas (CH4) and over 100 ppm with hydrogen.

Flue gas recirculation or exhaust gas recirculation is known as an effective measure against the thermal formation of nitrogen oxide in the exhaust gas of combustion plants, whereby the oxygen content is reduced by recirculating the exhaust gas and thus the flame temperature is lowered. In connection with the application, an exhaust gas recirculation ratio (EGR) is defined as the ratio of the mass flows of the recirculated or recirculated exhaust gas and the supplied combustion air (m _A /m _L ). The exhaust gases are also referred to as combustion exhaust gases or combustion gases.

A distinction is usually made between external and internal exhaust gas recirculation. With external exhaust gas recirculation, exhaust gas is led out of the combustion chamber and a partial exhaust gas flow is taken from the exhaust tract, for example in a chimney, and mixed with the combustion air or fuel before or as it flows into a combustion chamber. An EGR can be regulated to a desired ratio using suitable controls. A major disadvantage of external exhaust gas recirculation is an increase in the amount of exhaust gas, which is why areas for extracting the heat must be enlarged accordingly.

In internal exhaust gas recirculation, exhaust gas or combustion gas present in a combustion chamber is returned to the reaction zone with the impulse of the combustion air. If a temperature in the combustion chamber is above the ignition temperature of the fuel, the exhaust gas recirculation ratio can be increased as desired, since flame stability plays no role.

For example, EP 0 463 218 A1 a method and a device for burning fuel in a combustion chamber are known, wherein combustion air emerging from a nozzle device with a number of nozzles arranged in a ring can be mixed with sucked-back exhaust gases partially cooled in the combustion chamber to form a combustion air/exhaust gas mixture having at least the ignition temperature in an exhaust gas recirculation ratio AGR >=2.

If, however, the temperature in the combustion chamber is below the ignition temperature, the exhaust gas recirculation ratio must be limited to prevent the flame from extinguishing.

DE 199 17 662 A1 describes a burner for liquid and/or gaseous fuels, which consists of at least one fuel nozzle and a feed for liquid fuel and/or at least one further feed for gaseous fuel as well as a flame tube surrounding the fuel nozzle. This flame tube is connected to means for the supply of air or oxygen and to means for the supply of exhaust gas, wherein the means for the supply of air or oxygen consist of at least two nozzles which are arranged in front of the burner nozzle in the outflow direction.

DE 39 23 238 A1 describes a generic device for returning combustion products or exhaust gases in combustion plants for the combustion of flowable and gaseous fuel, with a burner nozzle arranged in a burner tube for the supply of fuel, with a device for the supply of combustion air into the combustion chamber and with a device for returning combustion products or exhaust gases into the combustion zone, wherein nozzles are located on the inside of the burner tube (for accelerating a part of the combustion air and for generating a low pressure behind these nozzles), and wherein openings are arranged in the wall of the burner tube in the area of the outlet openings of the nozzles for injecting combustion products into the low-pressure area and for further conveying them via an annular gap located between the burner tube and the outer edge of a baffle plate into the combustion zone.

EP 0 386 732 A2 describes a combustion device with an air supply channel which is closed off by a nozzle plate with first and second nozzles, a fuel supply device which is guided through the supply channel, a flame tube which is arranged at a distance in front of the nozzle plate so that a flue gas recirculation opening is formed, the cross-section of which is adjustable, and a tube which is arranged at a distance in front of the nozzle plate and encloses the second nozzles of the inner nozzle ring and the mouth area of the fuel supply device. Due to this arrangement, separate partial flows formed from recirculated flue gas and combustion air flow into the flame tube.

TASK AND SOLUTION

It is an object of the invention to provide a device and a method for combustion air supply and internal exhaust gas recirculation for a burner, in particular for low-temperature processes, with a defined exhaust gas recirculation ratio.

According to a first aspect, a device for supplying combustion air and recirculating exhaust gases for a burner with a combustion chamber is provided, the device comprising a plurality of drive nozzles arranged distributed around a central axis and fluidically connected to a combustion air supply, and a mixing chamber downstream of the drive nozzles, the drive nozzles and the mixing chamber forming a jet pump, combustion air emerging from the drive nozzles in the mixing chamber being mixable with exhaust gases flowing out of the combustion chamber and sucked back by means of the drive nozzles to form a combustion air/exhaust gas mixture, and the combustion air/exhaust gas mixture being feedable to a reaction zone downstream of the mixing chamber, a bypass channel being provided by means of which combustion air can be fed to the reaction zone while bypassing the drive nozzles, and an adjustable bypass valve being provided in the bypass channel.

A mixing chamber is a space with a defined cross-section that is separated from the environment and is provided between the propellant nozzles and the reaction zone of the combustion chamber. The cross-section of the mixing chamber can be selected by the expert depending on the application. In advantageous embodiments, the cross-section is constant in the direction of flow, with one embodiment providing a converging or diverging cross-section in an inlet and/or outlet area for improved inflow or outflow.

The distributed drive nozzles and the mixing chamber form a jet pump, whereby the exhaust gas recirculation ratio of the combustion air/exhaust gas mixture conveyed by the jet pump depends on a cross-sectional ratio of the mixing chamber and the drive nozzles as well as on operating parameters such as a temperature of the recirculated exhaust gas. The exhaust gas recirculation ratio can thus be set in advance by a specialist through a suitable design of the mixing chamber and the drive nozzles, for example up to a limit of flame stability, for certain operating parameters. In other words, the cross-section of the mixing chamber is matched to an outlet cross-section of the drive nozzles and a number of drive nozzles.

In one embodiment, an end of the mixing chamber facing the drive nozzles is at least partially spaced apart in the direction of flow from a wall on which the drive nozzles are arranged, so that a circumferential or interrupted gap is created which acts as an intake opening of the jet pump, through which exhaust gas can be sucked back and conveyed into the mixing chamber. In another embodiment, an intake chamber with an opening for sucking in exhaust gas is provided upstream of the mixing chamber. An end of the mixing chamber facing the combustion chamber is arranged in use upstream of an outlet opening of a fuel supply, with a distance being suitable and selectable by the person skilled in the art depending on the application.

Similar to an external exhaust gas recirculation, the combustion air and the exhaust gas are mixed with each other before being mixed with the fuel in a defined exhaust gas recirculation ratio that may depend on operating parameters, without the need to increase the amount of exhaust gas in an exhaust tract as is the case with an external exhaust gas recirculation.

The exhaust gas recirculation reduces the flame temperature. The rate of nitrogen oxide formation is around 10 ⁴ ppm/s at flame temperatures of conventional fuels of around 2000°C and drops to around 10 ppm/s at 1500°C. At low flame temperatures and residence times in the range of tenths of a second, single-digit nitrogen oxide values can be achieved in the exhaust gas.

The arrangement of the drive nozzles distributed around a central axis is also referred to as a ring-shaped arrangement in connection with the application. In one embodiment, the drive nozzles are arranged in parallel. In other embodiments, the axes of the drive nozzles are inclined relative to the central axis. By designing the jet pump with several drive nozzles distributed around a central axis and a drive nozzle A downstream mixing chamber creates a small jet pump that can be integrated into existing burners with standard dimensions. The device is therefore also suitable for retrofitting existing systems.

The device with a jet pump formed by the mixing chamber and the drive nozzles is suitable for burners in a power range of a few kW as well as for burners with a MW power range.

As mentioned above, an exhaust gas recirculation ratio (EGR) that is optimal for pollutant prevention also depends on operating parameters. For example, depending on the temperature of the recirculated exhaust gas, an exhaust gas recirculation ratio (EGR) of 1 to 1.5 with an oxygen content of the combustion air/exhaust gas mixture of between approx. 10% and approx. 12% is required to reduce the flame temperature to 1500°C.

The device therefore has a bypass channel, by means of which combustion air can be fed to the reaction zone, bypassing the drive nozzles. This makes it possible, for example, to reduce the EGR for flame stability by guiding part of the combustion air past the drive nozzles via the bypass channel. The bypass channel is designed in one embodiment as an annular gap channel, which is arranged around a fuel lance during use and runs in sections between the mixing chamber and the fuel lance.

In one embodiment, a mixing chamber with an annular cross-section is provided. An inner diameter of the mixing chamber is selected such that the mixing chamber can be arranged around a fuel lance provided coaxially to the central axis during use.

The number of drive nozzles can be determined by the specialist depending on the application and the size of the burner. In one embodiment, eight or more drive nozzles are provided, evenly distributed around the central axis. This creates a good suction effect, particularly for a mixing chamber with a supply opening in the form of an annular gap.

A cross-sectional ratio of the mixing chamber and the jet pump's motive nozzles is designed to achieve a specific exhaust gas recirculation ratio EGR, whereby the cross-sectional area of the motive nozzles is referred to as a resulting cross-sectional area of all motive nozzles. In a The cross-sectional ratio of the mixing chamber and the drive nozzles is less than or equal to 20.

In one embodiment, nozzle openings are provided at an outlet end of the bypass channel in order to achieve rapid and complete mixing of the combustion air supplied via the bypass channel with the combustion air/exhaust gas mixture of the jet pump.

In one embodiment, the bypass valve can only be adjusted between an open and a closed position. In other embodiments, a continuously or continuously adjustable bypass valve is provided. In embodiments, the bypass valve is adjusted by means of a controllable or adjustable actuating device, whereby, depending on the embodiment, the bypass valve is opened or closed or a passage is varied by means of regulating or control interventions. By means of the bypass valve, the oxygen content of the combustion air/exhaust gas mixture for combustion can be changed and, in particular, kept within a defined range for flame stability by means of a variable supply of additional combustion air.

In addition to a bypass channel, in one embodiment an adjustable valve is provided in an intake opening for the re-sucked exhaust gas, wherein the valve is preferably continuously or continuously adjustable. By means of the valve in the intake opening for the re-sucked exhaust gas, an oxygen content of the combustion air/exhaust gas mixture for combustion can be changed and, in particular, kept within a defined range for flame stability by a variable supply of exhaust gas.

In one embodiment, a probe is provided for oxygen measurement. The probe is preferably provided upstream of outlet openings of a fuel supply and thus upstream of a flame. The oxygen content of the mixture of the combustion air/exhaust gas mixture supplied by means of the jet pump and possibly the combustion air supplied via the bypass channel, determined using the probe, can be determined and varied by regulating or control interventions on the bypass valve and/or on the valve in the intake opening for the exhaust gas sucked back in.

Alternatively or additionally, in one embodiment, a sensor is provided for measuring the temperature of the recirculated exhaust gas. In this case, an exhaust gas recirculation ratio optimized for an exhaust gas temperature can be determined and adjusted by means of control interventions on the Bypass valve and/or the valve in the intake opening, preferably by measuring the oxygen content.

According to a second aspect, a burner is created, comprising a device for supplying combustion air and recirculating exhaust gases with a jet pump, the jet pump having a preferably annular gap-shaped mixing chamber and a plurality of drive nozzles arranged in a ring around a central axis, and a fuel lance arranged coaxially to the central axis with outlet openings. The outlet openings are arranged downstream of an outlet opening of the mixing chamber, a distance being suitably selected by the person skilled in the art. To improve flame stability, in one embodiment a baffle plate is provided upstream of the outlet openings of the fuel lance. The burner created in this way can be installed in a conventional chamber.

In one embodiment, a flame tube is provided which delimits a reaction zone transversely to the flow direction. The exhaust gas can flow in an annular gap between a wall of the chamber and the flame tube to the jet pump and/or to an exhaust gas outlet. In one embodiment, the flame tube is arranged immediately adjacent to the mixing chamber. The length of the flame tube can be selected by the person skilled in the art depending on the fuel. In one embodiment, for operation with fuels with a low reaction rate, such as natural gas, an extended flame tube is selected for an extended residence time in order to ensure burnout. However, since a residence time also influences the formation of nitrogen oxide, a short flame tube is provided in other embodiments.

In one embodiment, the fuel lance comprises an ignition device or a pilot burner. An outlet opening of the ignition device or the pilot burner is preferably offset with respect to the outlet openings of the fuel lance for normal operation.

According to a third aspect, a method for supplying combustion air and recirculating exhaust gases for a burner with a combustion chamber is created, wherein combustion air is supplied to a mixing chamber downstream of the drive nozzles by means of a plurality of drive nozzles arranged distributed around a central axis, while exhaust gases are sucked in from the combustion chamber, in the mixing chamber the combustion air emerging from the drive nozzles is mixed with exhaust gases flowing out of the combustion chamber and sucked back in by means of the drive nozzles to form a combustion air/exhaust gas mixture, and the combustion air/exhaust gas mixture is supplied to a reaction zone downstream of the mixing chamber, wherein optionally Combustion air is supplied to the reaction zone via a bypass channel, bypassing the drive nozzles, and wherein an oxygen content of a mixture of the combustion air selectively supplied via the bypass channel and the combustion air/exhaust gas mixture is monitored and an amount of the combustion air supplied via the bypass channel is adjusted to maintain a defined oxygen content and/or a temperature of the recirculated exhaust gas is detected and an amount of the combustion air supplied via the bypass channel is adjusted depending on the detected temperature.

The drive nozzles and the mixing chamber form a jet pump, by means of which, depending on certain operating parameters, a combustion air/exhaust gas mixture with a defined EGR can be fed to the reaction zone.

A portion of the combustion air supplied via the bypass channel is variable in order to make an adjustment depending on certain operating parameters.

For this purpose, in one embodiment, an oxygen content of a mixture of the combustion air supplied via the bypass channel and the combustion air/exhaust gas mixture is monitored and an amount of the combustion air supplied via the bypass channel is adjusted to maintain a defined oxygen content.

Alternatively or additionally, another embodiment provides that a temperature of the recirculated exhaust gas is detected and an amount of combustion air supplied via the bypass channel is adjusted depending on the detected temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1:

eine geschnittene Seitenansicht eines Brenners mit einer Vorrichtung zur Verbrennungsluftzufuhr und Abgasrezirkulation;

Fig. 2:

den Brenner gemäß Fig. 1 in einer geschnittenen Draufsicht gemäß einer Markierung II-II in Fig. 1;

Fig. 3:

eine geschnittene Seitenansicht eines Brenners ähnlich Fig. 1 mit einer Vorrichtung zur Verbrennungsluftzufuhr und Abgasrezirkulation;

Fig. 4:

den Brenner gemäß Fig. 3 in einer geschnittenen Draufsicht gemäß einer Markierung IV-IV in Fig. 3;

Fig. 5:

einen Brenner ähnlich Fig. 1 in einer geschnittenen Seitenansicht mit einer Kammer.

Further advantages and aspects of the invention emerge from the claims and from the description of embodiments of the invention, which are explained below with reference to the figures.

Fig.1:

a sectional side view of a burner with a device for combustion air supply and exhaust gas recirculation;

Fig. 2:

the burner according to Fig.1 in a sectional plan view according to a marking II-II in Fig.1 ;

Fig. 3:

a cutaway side view of a burner similar Fig.1 with a device for combustion air supply and exhaust gas recirculation;

Fig.4:

the burner according to Fig.3 in a sectional plan view according to a marking IV-IV in Fig.3 ;

Fig.5:

a burner similar Fig.1 in a sectioned side view with one chamber.

DETAILED DESCRIPTION OF THE EXAMPLES

Fig. 1 and 2 show a burner 1 with a combustion chamber 10 and with a device 2 for combustion air supply and exhaust gas recirculation in a sectional side view or in a sectional top view according to a marking II-II in Fig.1 .

The illustrated burner 1 has a fuel supply 3 with a supply nozzle 30, a fuel lance 31 running coaxially to a central axis A and outlet nozzles 32. Upstream of the outlet nozzles 31, a flame holder 4 is provided in the illustrated embodiment for stabilizing a flame front. The illustrated fuel supply 3 further comprises an internal pilot burner or ignition device 34. The ignition device 34 is arranged in a tube 35 which delimits a channel for the fuel supply in the fuel lance 31 of the fuel supply. The combustion chamber 10 is delimited transversely to the flow direction by a flame tube 12.

The device 2 comprises a combustion air supply with a supply nozzle 20, a plurality of, in the embodiment shown sixteen, drive nozzles 21 fluidically connected to the combustion air supply, arranged distributed around the central axis A and around the fuel lance 31, and a mixing chamber 22 downstream of the drive nozzles 21. The drive nozzles 21 and the mixing chamber 22 form a jet pump. The combustion air supplied by means of the drive nozzles 21 serves as a drive medium, which generates a pumping effect, so that exhaust gas flowing out of the combustion chamber 10 is sucked in via an intake opening 25 provided between the drive nozzles 21 and the mixing chamber 22. In the mixing chamber 22, the combustion air exiting from the drive nozzles 21 is mixed with the exhaust gases flowing out of the combustion chamber 10 and sucked back by means of the drive nozzles 21 to form a combustion air/exhaust gas mixture, and the combustion air/exhaust gas mixture is fed downstream of the mixing chamber 22 to a reaction zone in the combustion chamber 10.

The mixing chamber 22 of the device 2 shown has an annular cross-section and surrounds the fuel lance 31. The flame tube 12 is connected to the mixing chamber 22. In the exemplary embodiment shown, the flame tube 12 and the mixing chamber 22 are realized by a common component. In other embodiments, separate components are provided.

The Figures 1 and 2 The device 2 shown further has a bypass channel 23, by means of which combustion air can be fed to the reaction zone, bypassing the drive nozzles 21. In the exemplary embodiment shown, the bypass channel 23 is designed as an annular channel running coaxially to the central axis A between the fuel lance 31 and the mixing chamber 22. The bypass channel 23 ends downstream of the mixing chamber 22 and upstream of the flame holder 4. For rapid and complete mixing of the combustion air supplied via the bypass channel 23 with the combustion air/exhaust gas mixture coming from the mixing chamber 22, nozzle openings 230 are provided at an outlet end of the bypass channel 23 in the exemplary embodiment shown. In the exemplary embodiment shown, a continuously or continuously adjustable bypass valve 232 is provided in the bypass channel 23.

Downstream of the mixing chamber 22 and, in the illustrated embodiment, downstream of the outlet end of the bypass channel 23 and upstream of the flame holder 4 and the outlet nozzles 32 of the fuel supply 3, a probe 5 for oxygen measurement is provided.

Furthermore, a measuring sensor 6 is provided for measuring the temperature of the recirculated exhaust gas. In the embodiment shown, the measuring sensor 6 is arranged in the region of the intake opening 25 of the jet pump formed by the mixing chamber 22 and the drive nozzles 21.

An exhaust gas recirculation ratio of the combustion air/exhaust gas mixture conveyed by the jet pump depends on a cross-sectional ratio of the mixing chamber 22 and the drive nozzles 21 as well as on operating parameters such as a temperature of the recirculated exhaust gas.

In order to reduce a flame temperature to 1500°C, an exhaust gas recirculation ratio of 1 to 1.5 is required, depending on the temperature of the recirculated exhaust gas. A cross-sectional ratio of the mixing chamber 22 and the drive nozzles 21 is accordingly determined by the Experts will design it to be suitable for a temperature range of the recirculated exhaust gas. In the exemplary embodiment shown, the cross-sectional ratio is selected to be less than 20. The mixing chamber 22 shown has funnel-shaped inlet and outlet areas. A cross-section of the mixing chamber 22 is determined in an intermediate section with a constant cross-section.

If it is necessary to reduce an exhaust gas recirculation ratio during operation in order to maintain flame stability, for example due to deviations in the temperature of the recirculated exhaust gas, a portion of the combustion air can be supplied via the bypass channel 23 in the embodiment shown. An oxygen content can be detected by means of the probe 5 and regulated to a specific value using the bypass valve 232.

Fig. 3 and 4 show a burner 1 with a combustion chamber 10 and with a device 2 for combustion air supply and exhaust gas recirculation in a sectional side view or in a sectional top view according to a marking II-II in Fig.1 . Burner 1 according to the Fig. 3 and 4 is similar to burner 1 according to the Fig. 1 and 2 and uniform reference symbols are used for identical components. A detailed description of components that have already been described is omitted.

In contrast to the embodiment according to the Fig. 1 and 2 the device 2 according to the Fig. 3 and 4 no bypass channel 23. Instead, a continuously or continuously adjustable valve 27 is provided in the intake opening 25 for the exhaust gas that is sucked back in. If it is necessary to reduce an exhaust gas recirculation ratio during operation in order to maintain flame stability, in the embodiment according to the Fig. 3 and 4 a recirculation of exhaust gas by means of the valve 27. In this case, analogous to the embodiment according to the Fig. 1 and 2 by means of the probe 5, an oxygen content of the combustion air/exhaust gas mixture upstream of the outlet nozzles 32 of the fuel supply can be detected and - in contrast to the embodiment according to the Fig. 1 and 2 - can be regulated to a specific value using the valve 27. In the embodiment shown, an annular cavity remains between the fuel lance 31 of the fuel supply 3 and the mixing chamber 22, which can be used, for example, for a cable guide for the probe 5. In other embodiments, an inner diameter of the annular mixing chamber 22 is equal to an outer diameter of the channel 31, so that no cavity remains.

Fig.5 shows burner 1 according to Fig.1 and a heating chamber 7 delimited by a housing 70. In the embodiment shown, a double-walled housing 70 is provided. A coiled tube 71 is arranged in the double-walled housing 70, through which a medium to be heated is guided. The exhaust gas or combustion gas is guided through the double-walled housing 70 to an outlet 72 and in the process heats the medium guided in the coiled tube. In addition, to avoid thermal nitrogen oxide formation, part of the exhaust gas is sucked in by the jet pump formed by the drive nozzles 21 and the mixing chamber 22 and mixed with the combustion air.

In contrast to the design according to the Fig. 1 and 2 is in the design according to Fig.5 For operation with fuels having a low reaction rate, such as natural gas, an extended flame tube 112 is provided for an extended residence time to ensure burnout.

Claims (12)

1. A device for supplying combustion air and for recirculating exhaust gas for a burner (1) having a burner chamber (10), wherein the device (2) comprises a plurality of driving nozzles (21) which are distributed about a central axis (A) and are fluidically connected to a combustion air supply, wherein a mixing chamber (22) arranged downstream of the driving nozzles (21) is provided, the driving nozzles (21) and the mixing chamber (22) forming a jet pump, wherein in the mixing chamber (22), combustion air emerging from the driving nozzles (21) being mixable with exhaust gases, which flow out of the combustion chamber (10) and are sucked back by means of the driving nozzles (21), to form a combustion air/exhaust gas mixture, and the combustion air/exhaust gas mixture being suppliable to a reaction zone downstream of the mixing chamber (22), and wherein a bypass duct (23) is provided by means of which combustion air can be supplied to the reaction zone, bypassing the driving nozzles (21), characterized in that an adjustable bypass valve (231) is provided in the bypass duct (23).
2. The device as claimed in claim 1, characterized in that the mixing chamber (22) has an annular cross section.
3. The device as claimed in claim 1 or 2, characterized in that eight or more driving nozzles (21) which are distributed uniformly about the central axis (A) are provided.
4. The device as claimed in claim 1, 2 or 3, characterized in that a cross-sectional ratio of the mixing chamber (22) and the driving nozzles (21) is smaller than or equal to 20.
5. The device as claimed in one of claims 1 to 4, characterized in that nozzle openings (230) are provided at an outlet end of the bypass duct (23).
6. The device as claimed in one of claims 1 to 5, characterized in that the bypass valve (231) is adjustable continuously or infinitely variably.
7. The device as claimed in one of claims 1 to 6, characterized in that an adjustable valve (27) is provided in an intake opening (25) for the sucked-back exhaust gas, the valve (27) preferably being adjustable continuously or infinitely variably.
8. The device as claimed in one of claims 1 to 7, characterized in that a probe (5) is provided for measuring oxygen, preferably upstream of outlet openings of a fuel supply (3), and/or a measurement sensor (6) is provided for measuring the temperature of the recirculated exhaust gas.
9. A burner comprising a device as claimed in one of claims 1 to 8 and a fuel lance (31) which is arranged coaxially with respect to the central axis (A) and has outlet openings (32).
10. The burner as claimed in claim 9, characterized in that a flame tube (12, 112) is provided which delimits the combustion chamber (10) transversely with respect to the direction of flow.
11. The burner as claimed in claim 9 or 10, characterized in that the fuel supply (3) comprises an ignition means (34) or a pilot burner.
12. A method for supplying combustion air and for recirculating exhaust gas for a burner (1) having a combustion chamber (10), wherein combustion air is supplied by means of a plurality of driving nozzles (21), which are distributed about a central axis (A), to a mixing chamber (22) arranged downstream of the driving nozzles (21) with exhaust gases being sucked up from the combustion chamber (10), and, in the mixing chamber (22), the combustion air emerging from the driving nozzles (21) is mixed with exhaust gases, which flow out of the combustion chamber (10) and are sucked back by means of the driving nozzles (21), to form a combustion air/exhaust gas mixture, and the combustion air/exhaust gas mixture is supplied to a reaction zone downstream of the mixing chamber (22), wherein combustion air is selectively supplied via a bypass duct (23) to the reaction zone, bypassing the driving nozzles (21), characterized in that an oxygen content of a mixture of the combustion air supplied selectively via the bypass duct (23) and the combustion air/exhaust gas mixture is monitored and a quantity of the combustion air supplied via the bypass duct (23) is adjusted to maintain a defined oxygen content, and/or a temperature of the recirculated exhaust gas is detected and a quantity of the combustion air supplied via the bypass duct (23) is adjusted depending on the detected temperature.

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