EP3864345A1

EP3864345A1 - Burner for reducing nox emissions and method for operating the burner

Info

Publication number: EP3864345A1
Application number: EP19732650.7A
Authority: EP
Inventors: Bert DOMBROWSKI; Horst Graf Von Schweinitz
Original assignee: Econova GmbH
Current assignee: Econova GmbH
Priority date: 2019-06-21
Filing date: 2019-06-21
Publication date: 2021-08-18
Also published as: US20220034504A1; MX2021006327A; WO2020253970A1; JP2022536998A; CN113167467B; CN113167467A

Abstract

The invention relates to a burner (10; 11; 12) for heating a heating space (55; 55'), with reduction of NOx emissions. The burner (10; 11; 12) comprises a mixing and combustion chamber (54; 54'), a mixing and igniting device (51) which is arranged in the mixing and combustion chamber (54; 54'), and a fuel supply (50) which is connected to the mixing and igniting device (51) and is designed to supply fuel to the mixing and igniting device (51). Furthermore, an air supply (30, 30') is provided, which is designed to supply at least one partial air flow (L1) to the mixing and combustion chamber (54; 54'). A combustion chamber opening (53; 53') opens the mixing and combustion chamber (54; 54') toward a heating space (55; 55') to be heated. In addition, control means (60) are designed to control a fuel flow (B) via the fuel supply (50) and to control at least one partial air flow (L1) via the air supply (30; 30'), the burner (10; 11; 12) and the control means (60) being designed for operation of the burner (10; 11; 12) with a stable flame (56; 56') which extends from the mixing and igniting device (51) into the heating space (55; 55') through the combustion chamber opening (53; 53'). The cross-sectional area of the combustion chamber opening (53; 53'), which area is relative to the burner power, lies in the range between 1.5 mm²/kW and 10 mm²/kW.

Description

Burners to reduce NOx emissions and

Procedure for operating the burner

Description:

The invention relates to a burner for heating a boiler room with the reduction of NOx emissions, comprising a mixing and combustion chamber and a combustion chamber opening which opens the mixing and combustion chamber to a boiler room to be heated. A flame is generated in the mixing and combustion chamber, the heat of which is used to heat the boiler room. The invention also relates to a method for operating such a burner.

Such burners are used in particular for heating furnaces in industrial thermoprocessing systems, which can be, for example, chamber furnaces for heat treatment, shuttle furnaces for heating and forging, roller hearth furnaces or rotary hearth furnaces. However, these examples are only to be understood as examples, because the uses of such industrial burners are diverse. The burners are operated with a gaseous or liquid fuel together with air or oxygen. Pulse or high-performance burners are increasingly being used, in which fuel and air are mixed and ignited in a combustion chamber. The resulting hot combustion gases flow at high speed through a combustion chamber opening into the heating room to be heated. The boiler room can be a furnace room itself or a

Acting jet pipe, which protrudes gas-tight through a furnace wall into a furnace chamber.

The aim is to achieve the lowest possible NOx values during combustion, which, however, depends on various parameters that interact with one another. Operating an industrial burner in two operating modes has proven to be an advantageous measure, for example, the second operating mode including flameless oxidation, which enables low NOx values. For example, EP 0 685 683 B1 discloses an industrial burner which can be switched between a start-up mode with a flame inside a mixing and combustion chamber and a heating mode with flameless oxidation outside the mixing and combustion chamber. For this purpose, two different fuel nozzle devices are provided with which fuel can optionally be brought into the mixing and combustion chamber (start-up mode) and near a combustion chamber outlet opening (heating mode). The switch between start-up mode and heating mode takes place after a predetermined temperature has been reached in the boiler room, this temperature being above the ignition temperature of the fuel / air ~

Mixture is so that the mixture can burn for a flameless oxidation without additional ignition in the area of the combustion chamber outlet opening.

However, this type of industrial furnace requires two different fuel feeds and a shade in high-temperature operation. In addition, due to the flameless oxidation, it cannot achieve its low NOx values in areas of a boiler room that do not reach or have not yet reached the specified ignition temperature. Furthermore, the industrial furnace requires complex monitoring, since the flame in the mixing and combustion chamber goes out after switching to heating mode and the furnace can therefore no longer be monitored based on the presence of this flame.

The object of the invention is therefore to provide a burner and a method for operating the burner with which low NOx values can be achieved while avoiding in particular the disadvantages mentioned.

According to the invention, this object is achieved by a burner according to independent claim 1. Advantageous further developments of the burner emerge from the dependent claims 2-13. The invention is also achieved by a method for operating such a burner according to claim 14 and advantageous developments of the method according to claims 15 to 19

It should be pointed out that the features listed individually in the claims can be combined with one another in any technically meaningful way and show further embodiments of the invention. The description additionally characterizes and specifies the invention, in particular in connection with the figures.

A heating space can be heated with the burner according to the invention, the heating space being, for example, a furnace space or a radiant tube which protrudes into a furnace space to be heated. The burner can therefore be operated with an open furnace or a jet pipe. Various types of radiant tubes can be used as the jet pipe. For example, it is a radiant tube of the SER (Single Ended Radiant Tube) type. However, it is also possible, for example, to use P-type or DP-type radiant tubes. A furnace chamber is preferably equipped with several burners. It is an industrial burner that is used in particular for the direct heating of furnace rooms in industrial thermoprocessing systems. With the construction and the mode of operation of the burner according to the invention, the NOx emissions can be reduced, but the burner has further advantages

For this purpose, the burner according to the invention has a mixing and combustion chamber, inside which a mixing and ignition device is arranged. A fuel supply is connected to the mixing and ignition device and is designed to supply fuel to the mixing and ignition device. Furthermore, an air supply is provided which is designed to supply a first partial air flow to the mixing and combustion chamber. The burner is operated with air and a fuel that is liquid or preferably gaseous. For example, natural gas is used. The mixing and combustion chamber opens via a combustion chamber opening to the boiler room to be heated.

The burner also provides control devices which are designed to control a fuel flow B via the fuel supply and to control at least one partial air flow via the air supply. The burner and this control means are designed to operate the burner with a stable flame which extends from the mixing and ignition device through the combustion chamber opening into the Boiler room extends. Such an elongated flame has flame areas with different characteristics. At least one is concerned with a first flame area within the mixing and combustion chamber which can be detected, for example, by an ionization electrode. A second flame area is formed outside the combustion chamber opening, which is characterized by the high speed of the exiting streams.

According to the invention, the cross section of the combustion chamber opening related to the burner output is in the range between 1.5 mm ² / kW and 10 mm ² / kW. In one embodiment of the invention, the cross section of the combustion chamber opening related to the burner output is in the range between 1.5 mm ² / kW and 8 mm ² / kW, preferably between 1.5 mm ² / kW and 6 mm ² / kW, particularly preferably between 1.5 mm ² / kW and 5 mm ² / kW. With these values, very high exit velocities can be achieved in the area of the combustion chamber opening, which in turn means that exhaust gases from the boiler room are increasingly sucked into the flame in this area. The cross section of the combustion chamber opening is selected to be much smaller than is the case with known burners. For example, known air / fuel burners often result in cross-sections of the combustion chamber opening of over 10 mm ² / kW in relation to the burner output. A considerable reduction in this value is avoided, since experience has shown that the flame can then no longer be operated in a stable and reliable manner. However, the invention is based on the knowledge that, with a suitable construction and operation of a burner, values significantly below 10 mm ² / kW can also be achieved. In particular, this takes place together with the generation of a stable flame in the area of the ignition and mixing device. The control means and the mixing and ignition device are therefore designed to generate a stable flame in the mixing and combustion chamber. The invention results in higher exit velocities at the combustion chamber opening, which in turn increase the suction of exhaust gases from the boiler room, whereby the NOx emissions can be reduced. NOx values in the range from 5 to 100 mg / Nm ³ or with an SER jet tube can be achieved from 50 to 150 mg / Nm ³ based on 3% O ₂ can be achieved in the dry exhaust gas. In addition, in particular with a long SER radiant tube, the increased exit speeds improve the temperature profile in the boiler room. The invention also has the advantage that the stable flame in the area of the mixing and ignition device can be continuously detected and thus monitored . In one embodiment of the invention, therefore, flame monitoring means are provided in the mixing and combustion chamber, which are designed to detect a flame in the area of the mixing and ignition device. The flame monitoring means are, for example, an ionization rod that protrudes into an area of the flame. The flame monitoring means are used to monitor the presence of the flame in the mixing and combustion chamber, which is comparatively easy and reliable compared to solutions with high temperature switching is to be carried out.

The function of the burner can be monitored in a simple manner based on the presence of the flame in the combustion chamber. The invention therefore offers the possibility of not having to use flameless oxidation in particular to achieve low NOx values in the range from 5 to 100 mg / Nm ³ or 50 to 150 mg / Nm ³ based on 3% O ₂ in the dry exhaust gas Monitoring is expensive and comparatively insecure, since there is no monitorable flame

Furthermore, with the burner according to the invention, a NOx reduction is already possible from a boiler room temperature of around 300 to 500 ° C, while this is only possible at temperatures of around 800 ° C when using flameless oxidation. The burner according to the invention can thus be used advantageously in areas of a thermal process system in which high performance is required, but the temperature in an area to be heated is not or not yet above 800 ° C. For example, the burner according to the invention is fully effective in the powerful first zones of a continuous furnace.

A recuperator is preferably also provided which at least partially surrounds the air supply to the burner. However, the invention can also be used in burner designs can be used without a recuperator. Such recuperators can be designed in a variety of ways and essentially have means for receiving hot exhaust gases from a heating room into the recuperator. They also have means for supplying air for combustion to the recuperator and for heating this combustion air by means of the hot exhaust gases passed through the recuperator. The recuperator is designed accordingly in order to realize a suitable heat transfer between hot exhaust gases and the supplied combustion pleasure. A second air flow L2 can thus be fed to the mixing and combustion chamber or to the heating space outside the mixing and combustion chamber via the recuperator. Whether this second air flow L2 is fed from the recuperator to the mixing and combustion chamber or directly to the heating room to be heated depends on the design of the burner. The first partial air flow L1 can optionally also be preheated by the recuperator.

The cross-sections of the combustion chamber opening that can be achieved also depend essentially on the design of the burner with recuperator, since the combustion air preheated by the recuperator can be supplied to the combustion in various ways. within which the mixing and ignition device is arranged in such a way that the mixing and combustion chamber is formed. The air supply pipe forms the combustion chamber opening. With such a design, very small diameters for the combustion chamber opening can be realized, the cross section of the combustion chamber opening related to the burner output, for example, in the range between 1.5 mm ² / kW and 5 mm ² / kW, particularly preferably between 2, 5 mm ² / kW and 3.5 mm ² / kW.

In the case of a design with a recuperator, the second partial air flow L2 is passed from the recuperator into the boiler room, for example. There is then no supply of a second, preheated air flow L2 directly into the mixing and combustion chamber, but this second partial air flow L2 is supplied to the flame area outside the mixing and combustion chamber. In another design of the burner with recuperator, the air supply is also formed by an air supply pipe, within which the mixing and ignition device is arranged in such a way that the mixing and combustion chamber is formed. In this embodiment, however, the recuperator forms the combustion chamber opening, while the second, preheated partial air flow L2 from the recuperator is preferably also passed into the mixing and combustion chamber. The total air flow into the mixing and combustion chamber is thus higher than in the previously described embodiment, but very small diameters can still be implemented for the combustion chamber opening, the cross section of the combustion chamber opening related to the burner output in the range between 3 mm ² / kW and

10 mm ² / kW, particularly preferably between 3 mm ² / kW and 6 mm ² / kW.

In one embodiment of the invention, the control means are also designed to vary, in particular to increase, the ratio of fuel flow B to air flow after reaching a predetermined parameter value. In the case of designs with recuperator and thus several partial air flows, the ratio of fuel flow B to the sum of the first and second, preheated air flow is varied, in particular increased. In one embodiment of the invention, the control means are preferably designed to after reaching a predetermined parameter value to increase the fuel flow B with an approximately constant air flow (in particular the sum of the first and second, preheated air flow). The predetermined parameter value is a temperature value, in particular a reference temperature in a room to be heated or in a specific zone within the room to be heated (zone temperature).

However, the room does not have to be the heating room according to the invention, but rather a suitable reference point is determined for a temperature which can vary depending on the installation situation of the burner. The reference temperature is preferably selected or determined experimentally so that, for example, when using natural gas as fuel, the ratio of fuel flow B to air flow can be changed from 1:20 to 1:10 from this temperature. This temperature is between 200 ° C and 500 ° C, for example. With other gaseous fuels, other suitable mixing ratios may result. so that the specified change in the mixing ratio for natural gas is only used as an example to explain the invention

With this type of control means it is particularly possible to start up the burner in the cold state with a ratio of fuel flow B to air flow (in particular to the sum of the first and second, preheated partial air flow) of 1:20. This enables the formation of a stable flame that extends through the combustion chamber opening into the heating space. If the burner and the furnace heat up as the burner continues to operate, the ratio can, however, be reduced to 1:10 without destabilizing the flame. The burner is preferably operated with the full amount of air initially at half power, and can then be continued at full power when certain temperature conditions are reached that also allow adequate stabilization of the flame. In this way, a stable flame can be generated in the various heating stages of the burner despite the high exit speed in the area of the combustion chamber opening.

The burner optionally has means to switch the burner to operation with flameless oxidation. For this purpose, means are provided for deflecting the flow of the fuel flow and / or the first partial air flow, when activated by the control device, the flame is destabilized and extinguished . The burner is also designed in such a way that flameless oxidation of fuel and air takes place outside the combustion chamber opening, and these air escape at high speed from the combustion chamber opening. This presupposes that the temperature in this area has reached a value above the ignition temperature of the mixture, ie around 800 ° C. For this purpose, appropriate temperature monitoring means are provided which are connected to the control means. Even with this flameless oxidation, the increased exit velocities of fuel and air at the combustion chamber opening bring about an advantageous intake of exhaust gases to a greater extent, which in turn reduces the NOx values. Such a flow deflection for switching to flameless oxidation can be implemented, for example, by an extended fuel lance that protrudes into the area of the combustion chamber opening, as is proposed in EP 0 685 683 B1. It is also possible to control a modified exit of fuel from the ignition and mixing device

The invention also encompasses a method for operating a burner according to one embodiment of the invention, in which the control means control a fuel flow and at least one partial air flow in such a way that a stable flame is formed which extends from the mixing and ignition device through the Combustion chamber opening extends through into the boiler room.

In particular, for a warm-up phase, the method includes the optional measure that the control means increase the ratio of fuel flow to air flow after a predetermined parameter value has been reached. In particular, this takes place in that the control items, as already described, increase the fuel flow with an approximately constant air flow. For example, the control means change the ratio of fuel flow to air flow from 1:20 to 1:10. In designs with a recuperator, the aforementioned air flow is composed of a first and a second partial air flow. The method also provides that the predetermined parameter value is a temperature in a room to be heated and this temperature is between 200 ° C and 500 ° C lies. This procedure has the advantages mentioned above. For an optional switch to operation with flameless oxidation, the method provides in one embodiment that a temperature TH of the heating room is determined and, when a predetermined temperature TH above the ignition temperature of the fuel / air mixture is reached, the flow of the fuel stream and / or the fuel flow first partial air flow is deflected so that the flame is destabilized and extinguished, and then outside the combustion chamber opening a flameless oxidation of fuel and air takes place, which exit from the combustion chamber opening. This procedure has the advantages mentioned above. Further advantages, special features and expedient developments of the invention result from the subclaims and the following presentation of preferred exemplary embodiments on the basis of the figures.

From the pictures shows:

1 shows a schematic section through a first embodiment of a burner according to the invention;

2 shows an illustration of an embodiment of control means for controlling a burner in a flow diagram;

3 shows a schematic section through a second embodiment of a burner according to the invention; and

Fig. 4 is a schematic section through a third embodiment of a burner according to the invention.

1 shows schematically a first embodiment of a burner 10 according to the invention, on the basis of which the essential features of the invention are to be explained. However, the structure of the burner is not to be understood as limiting and FIG. 1 in particular only shows a schematic representation of the components and component dimensions. The same applies to FIGS. 3 and 4, which show further embodiments. Designs without a recuperator are also included.

The burner 10 is built into a furnace wall 20 and generates a flame 56 with which a heating space 55 is to be heated. In this embodiment, it is an open flame, which heats the heating space 55 directly. However, other embodiments with indirect heating are also possible in which a radiant tube is used. Such an embodiment is shown in FIG. 4. The burner 10 has a mixing and combustion chamber 54 which is formed by an air supply 30 in the form of an air supply pipe. Combustion air is introduced into this air supply 30 (not shown) and flows as the first partial air flow L1 into the mixing and supplying Combustion chamber 54. Within this air supply pipe 30, an ignition and mixing device 51 is attached, which is connected to a fuel supply 50 through which fuel is supplied to the ignition and mixing device 51. The fuel is, for example, natural gas.

The ignition and mixing device 51 is designed in a suitable manner such that the fuel emerges from it in such a way that a stable flame 56 can arise through ignition of the mixture of fuel flow B and first partial air flow 11. In the schematic representation of FIG. 1, several fuel flows emerge laterally at an angle from the ignition and mixing device 51, but this is not to be understood as limiting. Any other suitable ignition and mixing device 51 can also be used.

In this embodiment, the burner also has a recuperator 40, which surrounds the air supply pipe 30. From the heating space 55, hot exhaust gases A1 are drawn into the recuperator 40 and a second partial air flow L2 is heated in the opposite direction. Optionally, the first partial air flow L1 can also have been preheated in the recuperator 40. The second, preheated partial air flow L2 is fed to the heating space 55. This takes place in the area of an elongated flame 56, this flame 56 having different flame areas. A first flame area 56a is located inside the mixing and combustion chamber 54, the air supply pipe 30 forming a combustion chamber opening 53 through which the flame 56 extends from the ignition and mixing device 51. A second flame area 56b is formed in the heating space 55 in front of the combustion chamber opening 53. The second, preheated partial air flow L2 from the recuperator 40 is fed to this flame region 56b. At the same time, hot exhaust gases A2 are sucked from the heating space 55 into the flame area 56b With this burner construction, the cross section of the combustion chamber opening 53 related to the burner output is in the range between 1.5 mm ² / kW and 5 mm ² / kW, particularly preferably between 2.5 mm ² / kW and 3.5 mm ² / kW. This results in high exit velocities at the combustion chamber opening 53, which result in low NOx values in the flame region 56b. In sum with the NOx formation of the flame 56 within the mixing and combustion chamber, overall low NOx values in the range from 5 to 100 mg / Nm ³ based on 3% O ₂ in the dry exhaust gas can be achieved with open firing . Furthermore, the flame 56 can be monitored well, with an ionization rod 52 being provided in the mixing and combustion chamber 54 for this purpose, with which the presence of the flame 56 can be detected.

In order to bring the burner into the operating state of FIG. 1, a heating-up phase with a specific control of fuel flow B and the partial air flows L1, L2 is preferably carried out in order to be able to generate a stable flame 56 even when the burner 10 is cold. To this end, control means 60 are provided, the structure of which is shown in FIG. 2 can be found. A burner 10 is equipped with control means 60 which enable the burner 10 to be supplied with fuel and air. The fuel is referred to in the following simply as gas. An adjusting valve 61, a gas valve 63, a compensator 64 and a ball valve 65 for connection to a gas supply are provided in series for the flow of gas, starting from the burner 10 (not shown). An adjusting valve 66, an air valve 67, a compensator 68 and a slide 69 for connection to an air supply are provided in series for the flow of air, starting from the burner 10 (not shown). A constant pressure regulator 62 with a gas valve and a further gas valve 62a in the bypass are provided in parallel between the setting valve 61 and the gas valve 63. An impulse line 70 branches off between the setting valve 66 and the air valve 67 to the constant pressure regulator 62 with the gas valve.

With these control means, the burner can initially be started in the cold state with a ratio of fuel to air of about 1:20, which enables a stable flame 56 to be formed. The full amount of air is already made available while the fuel flow via valve 62a is initially reduced. Depending on the structure of the burner 10 and the surroundings Practice conditions in a furnace, the fuel flow can be increased from a predetermined temperature, since the flame 56 is now stabilized even with a higher fuel content. From this temperature, the fuel flow is switched from valve 62a to valve 62, the fuel flow is increased and, for example, a ratio of fuel to air of about 1:10 is set.

Fig. 3 shows an alternative embodiment of the burner 11 according to the invention, in which, however, the recuperator 40 forms the combustion chamber opening 53 '. Thus, the second partial air flow L2 'preheated in the recuperator 40' flows together with the first partial air flow L1 in the mixing and combustion chamber 54 '. The flame 56 with the two flame areas 56a and 56b is formed analogously, however, and the other components also correspond to the embodiment of FIG. 1. Only the cross section of the combustion chamber opening 53 'related to the burner output is in the range between 3 mm ² / kW and 10 mm ² / kW, particularly preferably between 3 mm ² / kW and 6 mm ² / kW.

4 shows a burner 12 according to the embodiment of FIG. 3, in which a heating space 55 'to be heated is arranged within a flame tube 42. The flame tube 42 is surrounded by a radiant tube 41, which is used for indirect heating from the furnace wall 20 into a furnace interior protrudes. The flame tube 42 within the radiant tube 41 allows the flow of hot exhaust gases A3 back to the burner 12, whereby they are either fed to the recuperator as exhaust gases A1 or sucked in as exhaust gases A2 from the flame region 56b. When using, for example, an SER jet pipe, the invention can achieve NOx values in the range from 50 to 150 mg / No. ³ based on 3% O ₂ in the dry exhaust gas. List of reference symbols:

10,11,12 burner

20 furnace wall

30.30 'air supply, air supply pipe

40,40 'recuperator

41 lance

42 flame tube

50 fuel supply

51 Mixing and ignition device

52 Flame monitoring equipment, ionization rod

53 Burner chamber opening

54.54 'mixing and combustion chamber

55.55 'boiler room

56 flame

56a, 56b flame area

60 tax means

61 Gas adjustment valve

62 Equal pressure regulator with gas valve V2

62a gas valve bypass

63 Gas valve V1

64 compensator

65 ball valve

66 Air adjustment valve

67 air valve

68 compensator

69 slider

70 Impulse line

L1 partial air flow

L2 partial air flow, preheated

B fuel flow A1 exhaust gas flow in recuperator

A2 flue gas flow in flame

A3 exhaust gas flow recirculation

Claims

Patent claims:

1. Burner (10; 11; 12) for heating a boiler room (55; 55 ‘) with reduction of NOx emissions, comprising:

a mixing and combustion chamber (54; 54 ‘);

a mixing and ignition device (51) in the mixing and combustion chamber

(54; 54 ‘) is arranged;

a fuel supply (50) which is connected to the mixing and ignition device (51) and is designed to supply fuel to the mixing and ignition device (51);

an air supply (30; 30 ‘) which is designed to supply at least one partial air flow (L1) to the mixing and combustion chamber (54; 54‘);

a combustion chamber opening (53; 53 ‘) which opens the mixing and combustion chamber (54; 54‘) to a heating space (55; 55 ‘) to be heated;

Control devices (60) which are designed to control a fuel flow (B) via the fuel supply (50) and to control at least one partial air flow (L1) via the air supply (30; 30 '), the burner (10; 11; 12) and the control means (60) for operating the burner <10; 11; 12) are formed with a stable flame (56; 56 ') which extends from the mixing and ignition device (51) through the combustion chamber opening (53; 53') into the heating space (55; 55 ') ;

and the cross section of the combustion chamber opening (53; 53 ') related to the burner output is in the range between 1.5 mm ² / kW and 10 mm ² / kW

2. Burner according to claim 1, wherein the cross-section of the combustion chamber opening (53; 53 ') based on the burner output is in the range between 1.5 mm ² / kW and 8 mm ² / kW, preferably between 1.5 mm ² / kW and 6 mm ² / kW, particularly preferably between 1.5 mm ² / kW and 5 mm ² / kW.

3. Burner according to claim 1 or 2, wherein the air supply is formed by an air supply pipe (30), within which the mixing and ignition device (51) is arranged so that the mixing and combustion chamber (54) is formed, and that the air supply pipe (30) forms the combustion chamber opening (53).

4. Burner according to claim 3, wherein the cross section of the combustion chamber opening (53) related to the burner output is in the range between 1.5 mm ² / kW and

5 mm ² / kW, particularly preferably between 2.5 mm ² / kW and 3.5 mm ² / kW.

5. Burner according to one of claims 1 to 4, wherein it has a recuperator (40; 40 ') at least partially surrounding the air supply (30; 30'), via which a second partial air flow (L2) of the mixing and combustion chamber (54; 54 ') or the heating space (55; 55') outside the mixing and combustion chamber (54) can be fed.

6. Burner according to claim 5, wherein the air supply is formed by an air supply pipe (30 '), within which the mixing and ignition device (51) is arranged so that the mixing and combustion chamber (54') is formed, and that the recuperator (40 ') forms the combustion chamber opening (53'), while the second partial air flow (L2) is passed from the recuperator (40) into the mixing and combustion chamber (54 ').

7. Burner according to claim 6, wherein the cross section of the combustion chamber opening (53 ') related to the burner output is in the range between 3 mm ² / kW and 10 mm ² / kW, particularly preferably between 3 mm ² / kW and 6 mm ² / kW lies.

8. Burner according to one of claims 1 to 7, wherein the control means (60) are designed to increase the fuel flow (B) after reaching a predetermined parameter value with approximately the same air flow.

9. Burner according to claim 8, wherein the control means (60) are designed to change the ratio of fuel flow (B) to air flow from 1:20 to 1:10.

10. Burner according to one of claims 8 and 9, wherein the predetermined parameter value is a temperature in a room to be heated.

11. Burner according to claim 10, wherein the temperature is between 200 ° C and 500 ° C.

12. Burner according to one of claims 1 to 11, wherein in the mixing and combustion chamber (54; 54 ') flame monitoring means (52) are provided which are used to detect a flame (56; 56') in the area of the mixing and Ignition device (51) are formed.

13. Burner according to one of claims 1 to 12, wherein means for deflecting the flow of the fuel flow (B) and / or the first partial air flow (L1) are provided, and when activated by the control means (60) the flame (56; 56 ') is destabilized and extinguished, and the burner (10; 11; 12) is designed in such a way that a flameless oxidation of fuel and air takes place outside the combustion chamber opening (53; 53'), which is released from the combustion chamber opening - exit (53; 53 ').

14. A method for operating a burner according to one or more of claims 1 to 13, in which the control means (60) control a fuel flow (B) and at least one partial air flow (L1) in such a way that a stable flame (56; 56 ') which extends from the mixing and ignition device (51) through the combustion chamber opening (53; 53') into the heating space (55; 55 ').

15. The method according to claim 14, wherein the control means (60) increase the fuel flow (B) with an approximately constant air flow once a predetermined parameter value has been reached.

16. The method according to claim 15, wherein the control means (60) change the ratio of fuel flow (B) to air flow from 1:20 to 1:10.

17. The method according to any one of claims 15 and 16, wherein the predetermined parameter value is a temperature in a room to be heated.

18. The method of claim 17, wherein the temperature is between 200 ° C and 500 ° C

19. The method according to any one of claims 14 to 18, wherein the temperature TH of the heating space (55; 55 ‘) is determined and when a predetermined temperature TH is reached above the ignition temperature of the fuel / air mixture

Flow of the fuel flow (B) and / or the first partial air flow (L1) is deflected so that the flame (56; 56 ') is destabilized and extinguished, and then outside the combustion chamber opening (53; 53') a flameless oxidation of fuel and Air takes place, which emerge from the combustion chamber opening (53; 53 ').