Burner with recuperator and reduced NOx emissions

Abstract

Burner (12) for heating a boiler room (55) with reduction of NOx emissions, comprising: a mixing and combustion chamber (54); a mixing and ignition device (51) arranged in the mixing and combustion chamber (54); 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 with an air supply pipe (30) delimiting the mixing and combustion chamber (54), which is designed to supply a first partial air flow (L1) to the mixing and combustion chamber (54); a recuperator (40) at least partially surrounding the air supply pipe (30), through which a second partial air flow (L2) is supplied to the mixing and combustion chamber (54) via the air supply; a combustion chamber opening (53) formed by the recuperator (40), which opens the mixing and combustion chamber (54) to a heating room (55) to be heated; Control means (60) designed to control a fuel flow (B) via the fuel supply (50) and to control at least the first partial air flow (L1) via the air supply, wherein the burner (12) and the control means (60) are designed to operate the burner (12) with a stable flame (56) extending from the mixing and ignition device (51) through the combustion chamber opening (53) into the heating chamber (55); wherein the air supply pipe (30) and the recuperator (40) each form an associated through-hole (33, 43) at their free end pointing in an axial direction (Z), which are arranged coaxially, wherein the through-hole (43) of the recuperator (40) forms the combustion chamber opening (53) and at least one air channel (39) through which the second partial air flow (L2) flows is formed between the recuperator (40) and the air supply pipe (30), which opens into the mixing and combustion chamber (54) between the through-hole (43) of the recuperator (40) and the through-hole (33) of the air supply pipe (30); characterized by the fact that the air supply pipe (30) forms a pipe extension (31) with an outer surface (32) tapering in the axial direction (z) towards the associated through hole (33) and the recuperator (40) forms a recuperator extension (41) with an inner surface (42) tapering in the axial direction (z) towards the associated through hole (43), wherein the pipe extension (31) and the recuperator extension (41) are arranged interlocking.

Description

[0001] The invention relates to a burner with recuperator for heating a boiler room with reduced NOx emissions, comprising a mixing and combustion chamber and a combustion chamber opening which opens the mixing and combustion chamber towards the boiler room to be heated. A flame is generated in the mixing and combustion chamber, the heat from which is used to heat the boiler room.

[0002] These types of burners are used particularly for heating furnace chambers in industrial thermal processing plants, such as chamber furnaces for heat treatment, bogie hearth furnaces for heating and forging, roller hearth furnaces, or rotary hearth furnaces. However, these examples are merely illustrative, as the applications of such industrial burners are manifold.

[0003] The burners are operated with a gaseous or liquid fuel, such as natural gas or hydrogen, together with air or oxygen as the initial airflow (no distinction will be made between air and oxygen in the following discussion). Increasingly, pulse or high-performance burners are 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 chamber. This heating chamber can be the furnace itself or a radiant tube that extends gas-tight through a furnace wall into the furnace chamber.

[0004] The aim is to minimize NO emissions during combustion. xto achieve certain values, which, however, depends on various interacting parameters. For example, operating an industrial burner in two modes has proven advantageous, with the second mode involving flameless oxidation, which results in low NOₓ emissions. x -values ​​are enabled, as known from EP 0 685 683 B1. Another measure is exhaust gas recirculation. This specifically influences thermal NOx formation by reducing the oxygen content per cubic meter of air. The aim is therefore to increase the airflow velocity, which shortens the residence time of the combustion gases in the hot reaction zone, increases the amount of recirculated exhaust gas, and simultaneously lowers the flame temperature.

[0005] To improve efficiency, a recuperator is also provided, which at least partially surrounds the burner's air supply. Such recuperators can be designed in various ways and essentially comprise means for receiving hot exhaust gases from the combustion chamber. Furthermore, they include means for supplying combustion air to the recuperator and for heating this air by means of the hot exhaust gases passing through the recuperator. The recuperator is designed to ensure adequate heat transfer between the hot exhaust gases and the supplied air. Thus, a second airflow is supplied to the mixing and combustion chamber or the boiler room via the recuperator, i.e., outside the mixing and combustion chamber.If this second airflow from the recuperator is fed directly into the boiler room to be heated instead of into the mixing and combustion chamber, it disrupts the mixing of the exhaust gases with the flame, or, in the case of flameless combustion, with the flameless oxidation zone in the boiler room. Depending on the design and arrangement of the corresponding outlet opening for the second airflow—for example, as an annular outlet surrounding the combustion chamber opening—it can even lead to the shielding of the flame or the flameless oxidation zone. To avoid this effect, feeding the second airflow directly into the mixing and combustion chamber is preferred. However, the location of the second airflow's inlet within the mixing and combustion chamber has proven problematic.Furthermore, the reproducible positioning of this feed in the mixing and combustion chamber was not guaranteed, which is due on the one hand to the extensive thermal stress profile but also to the comparatively enormous manufacturing tolerances of the thermally highly resilient components used, which, despite selection and pairing, did not lead to a satisfactory result.

[0006] The object of the invention is therefore to provide a burner with which improved low NO emissions can be achieved. x -values, especially reproducible ones, can be achieved.

[0007] According to the invention, this problem is solved by a burner according to independent claim 1. Advantageous embodiments of the burner are described in the dependent claims.

[0008] It should be noted that the features listed individually in the claims can be combined with one another in any technically meaningful way and demonstrate further embodiments of the invention. The description further characterizes and specifies the invention, particularly in conjunction with the figures.

[0009] The burner according to the invention can be used to heat a heating chamber, which may be, for example, a furnace chamber or a radiant tube projecting into a furnace chamber to be heated. The burner can therefore be operated with an open combustion system or a radiant tube. Various types of radiant tubes can be used. For example, a SER-type (Single Ended Radiant Tube) radiant tube can be used. However, P-type or DP-type radiant tubes can also be used. Preferably, a furnace chamber is equipped with several burners. This is an industrial burner, which is used in particular for the direct heating of furnace chambers in industrial thermal processing plants. The design and operation of the burner according to the invention reduce NOx emissions, and the burner also offers further advantages.

[0010] The burner according to the invention comprises a mixing and combustion chamber within 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. For example, this is a fuel lance projecting into the mixing and combustion chamber. 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 or hydrogen is used.

[0011] According to the invention, an air supply is provided with an air supply pipe that delimits the mixing and combustion chamber and is designed to supply a first partial air flow to the mixing and combustion chamber. For example, the first partial air flow is supplied to the interior of the air supply pipe via an end of the air supply pipe furthest from the mixing and combustion chamber.

[0012] According to the invention, a recuperator is further provided, at least partially surrounding the air supply pipe, through which a second partial air flow is supplied to the air supply of the mixing and combustion chamber. For example, the recuperator is essentially tubular in shape. Preferably, the second partial air flow is supplied via a cavity volume bounded by an outer surface of the air supply pipe and an inner surface of the recuperator.

[0013] The recuperator forms a combustion chamber opening that connects the mixing and combustion chamber to the boiler room to be heated. Such recuperators can be designed in various ways and essentially include means for drawing hot exhaust gases from the boiler room into the recuperator. Furthermore, air is supplied to the recuperator for combustion and for heating this combustion air by means of the hot exhaust gases passed through the recuperator. The recuperator is designed to ensure adequate heat transfer between the hot exhaust gases and the supplied combustion air. Optionally, the first air stream can also be preheated by the recuperator.

[0014] Preferably, the feed pipe and recuperator are made of the same material, in particular a ceramic material.

[0015] Furthermore, the burner includes control means designed to regulate the fuel flow via the fuel supply and to control at least the first air flow, and optionally also the second air flow, via the air supply. The burner and these control means are designed to operate the burner with a stable flame that extends from the mixing and ignition device through the combustion chamber opening into the boiler room. Such an elongated flame exhibits flame zones with different characteristics. At a minimum, there is a first flame zone within the mixing and combustion chamber, which can be detected, for example, by an ionization electrode. Outside the combustion chamber opening, a second flame zone is formed, characterized by the high velocity of the exiting air streams.

[0016] According to the invention, the air supply pipe and the recuperator each form a through-hole at their free, axially directed end, which are arranged coaxially, wherein the through-hole of the recuperator forms the combustion chamber opening and at least one air channel through which the second partial air flow flows is formed between the recuperator and the air supply pipe, which opens into the mixing and combustion chamber between the through-hole of the recuperator and the through-hole of the air supply pipe. For example, the opening through which the second air flow enters the mixing and combustion chamber is bounded on one side by the edge of the through-hole of the recuperator and on the other side by the edge of the through-hole of the air supply pipe.

[0017] According to the invention, the air supply pipe forms a pipe extension with an outer surface that tapers axially towards the associated through-hole, and the recuperator forms a recuperator extension with an inner surface that tapers axially. The pipe extension and recuperator extension are arranged in an interlocking manner. This interlocking arrangement, combined with the fact that the second air flow opens into the mixing and combustion chamber between the through-hole of the recuperator and the through-hole of the air supply pipe, ensures that the second air flow is introduced only in the immediate vicinity of the combustion chamber opening. This prevents the exhaust gas recirculation into the flame, which takes place outside the mixing and combustion chamber, from being obstructed by the second air flow. It has been shown that this approach is particularly advantageous for reducing NOx emissions.Furthermore, the proximity of the feed to the flame allows for particularly good reproducible adjustment of NOx emissions, since at this point both the recuperator and the feed pipe are exposed to a comparatively similar temperature and a comparatively similar temperature gradient, and in particular due to a predictable thermal expansion of both components, the combustion behavior of the burner can be adjusted more reproducibly without the need for a complex selection of the components during the manufacture of the burner.

[0018] Preferably, the outer surface of the pipe extension and the inner surface of the recuperator extension do not taper uniformly and continuously in the axial direction, but rather taper in steps.

[0019] In order to be able to reliably and permanently specify and adjust the size of the opening between the through-hole of the air supply pipe and the through-hole of the recuperator for the entry of the second partial air flow into the mixing and combustion chamber, particularly over an extended temperature range, the air supply pipe is elastically prestressed against the inner surface of the recuperator extension according to a preferred embodiment.

[0020] Preferably, the outer surface of the pipe extension and the inner surface of the recuperator extension each have a shoulder section extending axially to a maximum section with maximum diameter, with which they are arranged adjacent to each other, preferably exclusively.

[0021] According to a preferred embodiment of the burner according to the invention, the inner surface of the recuperator extension and the outer surface of the pipe extension define the air channel provided for the second air flow, and the inner surface of the recuperator extension and the outer surface of the pipe extension extend, at least section by section, parallel to each other and to the axial direction in a region designated as the parallel section. In this parallel section, the cross-section effective for the flow of the second air flow is comparatively insensitive to temperature-induced axial displacement between the recuperator and the feed pipe.

[0022] Preferably, an outer surface of the pipe extension has several recesses arranged circumferentially, each forming an air channel section for the second air flow, and preferably located in the shoulder section. This makes the cross-section effective for the flow of the second air flow less susceptible to relative axial misalignment between the recuperator and the supply pipe.

[0023] Preferably, the cross-section of the through-hole of the air supply pipe is smaller than the maximum cross-section of the air supply pipe and larger than the cross-section of the combustion chamber opening.

[0024] Preferably, the cross-section of the combustion chamber opening, relative to the burner output, is in the range of 3 mm. 2 / kW and 10 mm 2 / kW, especially preferred between 3 mm 2 / kW and 6 mm 2 / kW.

[0025] In one embodiment of the invention, the control means are further configured to vary the ratio of fuel flow to the total air flow consisting of a first air flow and a second air flow after a predetermined parameter value has been reached. In a preferred embodiment of the invention, the control means are preferably configured to increase the fuel flow while maintaining an approximately constant total air flow after a predetermined parameter value has been reached. The predetermined parameter value is a temperature value, which is in particular a reference temperature in the heating chamber to be heated or in a specific zone within the heating chamber to be heated (zone temperature). The reference temperature is preferably selected or experimentally determined such that, for example, when using natural gas as fuel, the ratio of fuel flow to total air flow can be changed from 1:20 to 1:10 from this temperature onwards.This temperature, for example, lies between 200°C and 500°C. Other suitable mixing ratios may result with other gaseous fuels, so the specified change in the mixing ratio for natural gas serves only as an example to illustrate the invention.

[0026] With this type of control mechanism, it is particularly possible to start the burner when cold with a fuel flow to total air flow ratio of 1:20. This allows for the formation of a stable flame that extends through the combustion chamber opening into the boiler room. As the burner and boiler room heat up during operation, the ratio can be increased to 1:10 without destabilizing the flame. The burner is preferably initially operated at half power with full air volume and can then be operated at full power once certain temperature conditions are reached that also ensure sufficient flame stabilization. In this way, a stable flame can be generated at the various heating stages of the burner, despite the high exhaust velocity in the combustion chamber opening.

[0027] Optionally, the burner includes means to switch it to flameless oxidation operation. For this purpose, means for diverting the fuel flow and / or the first air flow and / or the second air flow are preferably provided. When activated by the control means, these diverting means destabilize and extinguish the flame. The burner is further designed such that flameless oxidation of fuel and air then takes place outside the combustion chamber opening, with the mixture exiting the combustion chamber opening at high velocity. This requires that the temperature in this area has reached a value above the ignition temperature of the mixture, i.e., approximately 800°C. Appropriate temperature monitoring means, connected to the control means, are provided for this purpose.Even in this flameless oxidation process, the increased exit velocities of fuel and air at the combustion chamber opening result in a beneficial intake of exhaust gases to an increased degree, which in turn reduces NOx levels.

[0028] Such a flow deflection for switching to flameless oxidation can be achieved, for example, by an extended fuel lance that projects into the area of ​​the combustion chamber opening, as proposed in EP 0 685 683 B1. It is also possible to control a modified fuel outlet from the ignition and mixing device.

[0029] According to a preferred embodiment, 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.

[0030] Further advantages, special features and expedient further developments of the invention will become apparent from the dependent claims and the following presentation of preferred embodiments with reference to the illustrations.

[0031] The illustrations show: Fig. 1 a schematic section through a first embodiment of a burner according to the invention 12; Fig. 2 a detailed enlargement of the section of the burner 12 in a second embodiment; and Fig. 3 A representation of an embodiment of control means for controlling the burner in a flow diagram.

[0032] Fig. Figure 1 schematically shows a first embodiment of a burner 12 according to the invention, which is used to illustrate the essential features of the invention. However, the design of the burner 12 is not to be understood as limiting. Fig. Figure 1, in particular, only provides a schematic representation of the components and component dimensions. The same applies to the Fig. 2 and Fig. 3.

[0033] The burner 12 is installed in a furnace wall 20 and generates a flame 56, which is used to heat a heating chamber 55. A radiant tube 101 is used for indirect heating. The burner 12 has a mixing and combustion chamber 54, which is formed by an air supply in the form of an air supply pipe 30. Combustion air is introduced axially z into the opening of the air supply 30 and flows as the first partial air flow L1 into the mixing and combustion chamber 54. An ignition and mixing device 51 is located inside this air supply pipe 30 and 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 or hydrogen, or a mixture thereof.

[0034] The ignition and mixing device 51 is suitably designed so that the fuel exits it in such a way that a stable flame 56 can be produced by igniting the mixture of fuel stream B and first partial air stream L1. In the schematic representation of the Fig. 1 For this purpose, several fuel streams exit the ignition and mixing device 51 laterally at an angle, but this is not to be understood as a limitation. Any other suitable ignition and mixing device 51 can also be used.

[0035] The burner 12 also has a recuperator 40, which surrounds the air supply pipe 30. Hot exhaust gases A1 from the combustion chamber 55 are drawn into the recuperator 40, and a second air stream L2 is heated in counterflow. Optionally, the first air stream L1 can also be preheated in the recuperator 40. The second, preheated air stream L2 is supplied to the combustion chamber 55. This occurs in the area of ​​an elongated flame 56, which has different flame zones. A first flame zone 56a is located within the mixing and combustion chamber 54, with the recuperator 40 forming a combustion chamber opening 53 by means of a through-opening 43 provided at its free end pointing in the z-direction, through which the flame 56 extends from the ignition and mixing device 51. A second flame area 56b forms in the heating chamber 55 in front of the combustion chamber opening 53.While the second, preheated air flow L2 from the recuperator 40 is fed to the flame zone 56a of the flame 56 before exiting the combustion chamber opening 53, hot exhaust gases A2 from the boiler room 55 are drawn into the flame zone 56b. With this burner 12 configuration, the cross-sectional area of ​​the combustion chamber opening 53, relative to the burner output, is in the range of 3 mm. 2 / kW and 10 mm 2 / kW, especially preferred between 3 mm 2 / kW and 6 mm 2 / kW.

[0036] This results in high exhaust velocities at the combustion chamber opening 53, which in turn lead to low NOx values ​​in the flame area 56b. Combined with the NOx formation of the flame 56 within the mixing and combustion chamber, overall low NOx values ​​in the range of 5 to 100 mg / Nm³ can be achieved during open combustion. 3This is achieved with a reference to 3% O2 ​​in the dry exhaust gas. Furthermore, the flame 56 can be easily monitored, for which purpose an ionization rod 52 is provided in the mixing and combustion chamber 54, with which the presence of the flame 56 can be detected.

[0037] How the embodiments of Fig. 1 and Fig. As shown in Figure 2, the air supply pipe 30 and the recuperator 40 each form a through-hole 33 and 43, respectively, at their free ends pointing in the axial direction z. These through-holes are arranged coaxially, with the through-hole 43 of the recuperator 40 forming the combustion chamber opening 51, and at least one air channel 39, through which the second partial air flow L2 flows, being formed between the recuperator 40 and the air supply pipe 30. This air channel opens into the mixing and combustion chamber 54 between the through-hole 43 of the recuperator 40 and the through-hole 33 of the air supply pipe 30. The opening through which the second air flow L2 enters the mixing and combustion chamber 54 is bounded on one side by the edge of the through-hole 43 of the recuperator 40 and on the other side by the edge of the through-hole 33 of the air supply pipe 30.The cross-section of the through-hole 33 of the air supply pipe 30 is smaller than the maximum cross-section of the air supply pipe 30 but larger than the cross-section of the combustion chamber opening 53, or of the through-hole 43 of the recuperator 40.

[0038] The air supply pipe 30 further forms a pipe extension 31 with an outer surface 32 that tapers axially towards the associated through-hole 33, and the recuperator 40 forms a recuperator extension 41 with an inner surface 42 that tapers axially in the z direction. The pipe extension 31 and the recuperator extension 41 are arranged to interlock. Due to this interlocking and the fact that the second partial air flow L2 opens into the mixing and combustion chamber 54 between the through-hole 43 of the recuperator 40 and the through-hole 33 of the air supply pipe 30, the second partial air flow L2 is only introduced in the immediate vicinity of the combustion chamber opening 53, so that the exhaust gas recirculation into the flame 56, which takes place outside the mixing and combustion chamber 54, is not obstructed by the second partial air flow L2. It has been shown that such an approach has a particularly beneficial effect on reducing NOx emissions.Furthermore, the NOx emission can be adjusted particularly well and reproducibly by arranging the feed close to the flame, since at this point both recuperator 40 and feed pipe 30 are exposed to a comparatively similar temperature and a comparatively similar temperature gradient, and in particular due to a predictable thermal expansion of both components, the combustion behavior of the burner 12 can be adjusted more reproducibly without the need for a complex selection of the components in the manufacture of the burner 12.

[0039] How the embodiments of Fig. 1 and Fig. As shown in Figure 2, the inner surface 42 of the recuperator 40 and the outer surface 32 of the feed pipe 30 define the air duct 39 provided for the second partial air flow L2. The outer surface 32 of the pipe extension 31, which terminates in the z-direction, and the inner surface 42 of the recuperator extension 41, which terminates in the z-direction, do not taper uniformly and continuously in the axial z-direction, but rather, in the embodiment shown in Figure 2, Fig. 1 parallel curved with radius of curvature lying in the mixing and combustion chamber 54 or taper in stages, as in the second embodiment according to Fig. 2 is shown.

[0040] In order to be able to reliably and permanently specify and adjust the size of the outlet opening for the inlet of the second partial air flow L2 into the mixing and combustion chamber 54, arranged between the through-hole 33 of the air supply pipe 30 and the through-hole 43 of the recuperator 40, particularly over an extended temperature range, the air supply pipe 30 is designed via the outer surface 32 of the pipe extension 31 according to the Fig. In the second embodiment shown in Figure 2, the recuperator extension 41 is supported against the inner surface 42 by an elastic prestressing force. For this purpose, the outer surface 32 of the tube extension 31 and the inner surface 42 of the recuperator extension 41 each have a shoulder section 34 or 44 extending axially z to a maximum section with maximum diameter, with which they are preferably arranged adjacent to one another, forming an approximately annular, common contact area K. To ensure the passage of the second partial air flow L2, the outer surface 32 of the tube extension 31 has several recesses 35 arranged in a circumferential direction, each forming an air channel section for the second partial air flow L2, which are located in the shoulder section 34.

[0041] In the z-direction, a parallel section adjoins the shoulder section 34 of the pipe extension 31 and the recuperator extension 41, respectively, in which the inner surface 42 of the recuperator extension 41 and the outer surface 32 of the pipe extension 31 run parallel to each other and to the axial direction. In this parallel section, the cross-section effective for the flow of the second air partial flow L2 is comparatively insensitive to temperature-induced axial displacement between the recuperator 40 and the supply pipe 30.

[0042] To put burner 12 into operating mode Fig. To achieve this, a preheating phase is preferably carried out with a specific control of the fuel flow B and the air partial flows L1, L2, in order to generate a stable flame 56 even when the burner 10 is cold. Control means 60 are provided for this purpose, the design of which is exemplified in the Fig.As can be seen in Figure 3. A burner 12 is equipped with control devices 60 that enable the supply of fuel and air to the burner 12. The fuel is referred to as gas in the following for simplicity. For the gas flow, a control valve 61, a gas valve 63, a compensator 64, and a ball valve 65 for connection to a gas supply are provided in series from the burner 12 (not shown). For the air flow, a control valve 66, an air valve 67, a compensator 68, and a slide valve 69 for connection to an air supply are provided in series from the burner 12 (not shown). A constant pressure regulator 62 with a gas valve and another gas valve 62a in bypass are connected in parallel between the control valve 61 and the gas valve 63. A pulse line 70 branches off between the control valve 66 and the air valve 67 to the constant pressure regulator 62 with the gas valve.

[0043] With these control means 60, the burner 12 can initially be started up in its cold state with a fuel-to-air ratio of approximately 1:20, which enables the formation of a stable flame 56. The full air volume from the first air flow L1 and the second air flow L2 is already provided, while the fuel flow B is initially reduced via the valve 62a. Depending on the design of the burner 12 and the ambient conditions in a furnace, the fuel flow can be increased from a predetermined temperature, as the flame 56 now stabilizes even with a higher fuel proportion. From this temperature, the fuel flow B is switched from valve 62a to valve 62, thus increasing the fuel flow B and, for example, setting a fuel-to-air ratio of approximately 1:10. Reference symbol list: 12 burners 20 Oven wall 30 air supply pipe 31 Tube extension 32 Exterior surface 33 Through hole 34 Shoulder section 35 exceptions 39 Air duct 40 recuperator 41 Recuperator process 42 Interior surface 43 Through hole 50 Fuel supply 51 Mixing and ignition device 52 Flame monitoring devices, ionization rod 53 Combustion chamber opening 54 Mixing and combustion chamber 55 Boiler room 56 flames 56a, 56b Flame area 60 tax revenues 61 Gas control valve 62 Constant 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 sliders 70 Impulse line 101 Nozzle 102 Flame tube K Contact area L1 first airflow L2 second air flow, preheated B Fuel flow A1 Exhaust gas flow in recuperator A2 Exhaust gas flow in flame A3 Exhaust gas flow recirculation QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 0 685 683 B1

[0004]

Claims

[1] Burner (12) for heating a boiler room (55) with reduction of NOx emissions, comprising: a mixing and combustion chamber (54); a mixing and ignition device (51) arranged in the mixing and combustion chamber (54); 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 with an air supply pipe (30) delimiting the mixing and combustion chamber (54), which is designed to supply a first partial air flow (L1) to the mixing and combustion chamber (54); a recuperator (40) at least partially surrounding the air supply pipe (30), through which a second partial air flow (L2) is supplied to the mixing and combustion chamber (54) via the air supply; a combustion chamber opening (53) formed by the recuperator (40), which opens the mixing and combustion chamber (54) to a heating room (55) to be heated; Control means (60) designed to control a fuel flow (B) via the fuel supply (50) and to control at least the first partial air flow (L1) via the air supply, wherein the burner (12) and the control means (60) are designed to operate the burner (12) with a stable flame (56) extending from the mixing and ignition device (51) through the combustion chamber opening (53) into the heating chamber (55); wherein the air supply pipe (30) and the recuperator (40) each form an associated through-hole (33, 43) at their free end pointing in an axial direction (Z), which are arranged coaxially, wherein the through-hole (43) of the recuperator (40) forms the combustion chamber opening (53) and at least one air channel (39) through which the second partial air flow (L2) flows is formed between the recuperator (40) and the air supply pipe (30), which opens into the mixing and combustion chamber (54) between the through-hole (43) of the recuperator (40) and the through-hole (33) of the air supply pipe (30); characterized by , that the air supply pipe (30) forms a pipe extension (31) with an outer surface (32) tapering in the axial direction (z) towards the associated through hole (33) and the recuperator (40) forms a recuperator extension (41) with an inner surface (42) tapering in the axial direction (z) towards the associated through hole (43), wherein the pipe extension (31) and the recuperator extension (41) are arranged interlocking. [2] Burner (12) according to claim 1, characterized by , that the outer surface (32) of the pipe extension (31) and the inner surface (42) of the recuperator extension (41) do not taper uniformly and continuously in the axial direction, but preferably taper in steps. [3] Burner (12) according to any one of the preceding claims, characterized by , that the air supply pipe (30) is elastically prestressed and supported via the outer surface (32) of the pipe extension (31) against the inner surface (42) of the recuperator extension (41). [4] Burner (12) according to any one of the preceding claims, characterized by , that the outer surface (32) of the pipe extension (31) and the inner surface (42) of the recuperator extension (41) each have a shoulder section (34, 44) adjoining a maximum section with maximum diameter in an axial direction, with which they are arranged adjacent to each other, preferably exclusively. [5] Burner (12) according to the preceding claim, characterized by , that the inner surface (42) of the recuperator extension (41) and the outer surface (32) of the pipe extension (31) define the air channel (39) provided for the second partial air flow (L2) and extend at least sectionally parallel to each other and to the axial direction (z). [6] Burner (12) according to any one of the preceding claims, characterized by, that an outer surface (32) of the pipe extension (31) has several recesses (35) arranged in a circumferential direction, each forming an air duct section for the second partial air flow (L2) for the section-by-section formation of the air duct (39), which are preferably arranged in the shoulder section (34) of the pipe extension (31). [7] Burner (12) according to any one of the preceding claims, characterized by , that a cross-section of the through-hole (33) of the air supply pipe (30) is smaller than a maximum cross-section of the air supply pipe (30) and larger than a cross-section of the combustion chamber opening (53). [8] Burner (12) according to any one of the preceding claims, characterized by , that 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, especially preferred between 3 mm 2 / kW and 6 mm 2 / kW [9] Burner (12) according to any one of the preceding claims, characterized by , that the control means (60) are designed to increase the fuel flow (B) after reaching a predetermined parameter value, while maintaining an approximately constant total air flow from the first partial air flow (L1) and the second partial air flow (L2). [10] Burner (12) according to claim 9, characterized by , that the control means (60) are designed to change the ratio of fuel flow (B) to total air flow from first air flow (L1) and second air flow (L2) from 1:20 to 1:

10. [11] Burner (12) according to one of claims 9 or 10, characterized by that the predetermined parameter value is a temperature value in the heating room to be heated. [12] Burner (12) according to claim 11, characterized by that the temperature is between 200°C and 500°C. [13] Burner (12) according to any one of the preceding claims, characterized by, that flame monitoring means (52) are provided in the mixing and combustion chamber (54) which are designed to detect a flame (56) in the area of ​​the mixing and ignition device (51). [14] Burner (12) according to one of the preceding claims, wherein means for deflecting the fuel flow (B) and / or the first air flow (L1) and / or the second air flow (L2) are provided, the activation of which by the control means (60) destabilizes and extinguishes the flame (56), and the burner (12) is designed such that a flameless oxidation of fuel and air exiting the combustion chamber opening (53) then takes place outside the combustion chamber opening (53).

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