Brenner recuperator

Abstract

A recuperator burner (100) comprises a burner base (10) and a combustion chamber tube (30) with a burner nozzle (41), as well as an exhaust gas recirculation device with a combustion air-driven jet pump. The jet pump includes a jet nozzle with a cross-section that decreases in the flow direction and has an annular jet pump gap (26) for drawing in exhaust gases by means of an annular jet. The exhaust gas recirculation device is located upstream of the mixing plane of the combustion gases flowing into the combustion chamber tube (30; 230), between the burner base (10) and the combustion chamber tube (30; 230). It comprises at least one continuous exhaust gas intake opening (34; 234) and / or a circumferential, self-contained arrangement of several exhaust gas intake openings that lead into the interior of the combustion chamber tube (30). Upstream of the combustion chamber tube (30), a recuperator (20) with a heat transfer body (21) is arranged, which has flow channels (29.1, 29.2) designed to guide counter-flowing fluids. The fluids enter and exit the flow channels (29.1, 29.2) in the heat transfer body (21) via inlet and outlet openings (23, 24). One fluid consists of combustion air to be preheated, and the other of exhaust gas.

Description

[0001] The invention relates to a recuperative burner having the features of the preamble of claim 1.

[0002] DE 10 2014 224 086 A1 describes a burner with an exhaust gas recirculation device in which the exhaust gas is mixed with the combustion air within the burner, thus continuously circulating a portion of the exhaust gas within the burner. This increases the mass flow in the combustion chamber and simultaneously lowers the temperature; high peak temperatures in the combustion chamber are avoided. For this purpose, the air duct system is provided with a Venturi region with a reduced cross-section, forming a Venturi nozzle. The vacuum connection of the Venturi nozzle thus formed is connected to the exhaust gas duct system. This draws in a portion of the exhaust gas flowing out of the combustion chamber and mixed with the combustion air. The Venturi region is preferably located directly adjacent to the combustion chamber.However, such a burner provides for exhaust gas recirculation directly from the outlet area of ​​the combustion chamber and not from outside the burner, from the furnace chamber, so that it cannot be combined with an upstream heat exchanger that draws in from the environment.

[0003] US2018 / 0080647A1 discloses a method and combustion device for reducing nitrogen oxide formation. A Venturi nozzle positioned just upstream of the burner nozzle is used to draw in exhaust gas from outside the combustion chamber and direct it into the fuel gas mixture, thereby diluting it. Since the burner provides an open exhaust duct outside the combustion chamber tube and the exhaust gas is drawn in from the furnace chamber, a combination with an upstream recuperator is fundamentally possible. However, the exhaust gas intake capacity is already limited by the fact that only small openings in the wall can be provided in the area of ​​the constriction of the Venturi nozzle, so that the flow of the mixture of air and fuel gas inside is not excessively impeded. Nevertheless, the radial entry of the exhaust gas into the Venturi nozzle creates turbulence when it impacts the gas mixture flowing past at a right angle.A further disadvantage is that the mixture of fuel gas and combustion air must already be formed before entering the Venturi nozzle and therefore the flow velocities of air and fuel gas can no longer be regulated individually.

[0004] DE 3041177A1 shows a burner with an exhaust gas recirculation device. However, the mixture of exhaust gas from the furnace chamber and fresh air supplied from outside does not enter the burner tube, but rather along the outside of the burner tube to its end. Furthermore, no fresh air is supplied inside the burner tube. The mixing of all gases only occurs immediately upstream of the burner nozzle, which is positioned at the front edge of the burner tube. This creates turbulence in front of the burner tube, which complicates the optimization of the burner's efficiency and the reduction of nitrogen oxides.

[0005] WO2022117345A1 describes a burner with an exhaust gas recirculation device in which the exhaust gas is mixed with the combustion air within the burner. Several jet nozzles ensure the flow of the mixture within the burner tube into the area of ​​influence of the burner nozzle.

[0006] Recuperator burners are also known, in which efficiency is increased through heat exchange between the burner supply air and the burner's exhaust gas stream. The recuperator causes heat transfer between the two gas streams. The recuperator can be made of different materials, particularly metallic and ceramic materials. Metallic materials are particularly suitable for low and medium temperature zones, and ceramic materials for high-temperature zones. By combining materials, the individual sections of the recuperator can be optimized for good heat transfer.

[0007] The object of the invention is therefore to improve a recuperative burner of the type mentioned above so that larger amounts of nitrogen oxides can be eliminated. Furthermore, the volume flows of fuel gas and combustion air should be adjustable separately, in particular to enable the combustion of different fuel gases such as methane and hydrogen, or fuel gas mixtures thereof, with the same recuperative burner.

[0008] This object is achieved by a recuperator burner having the features of claim 1.

[0009] The recuperative burner according to the invention has an exhaust gas recirculation device with a jet pump driven by combustion air, which has a jet pump annular gap formed upstream of the mixing plane of the combustion gases flowing into the combustion chamber tube. This leaves the flow of the combustion gas itself completely unaffected. Instead, the combustion gas is directed directly to the burner nozzle, where the mixture of combustion air and the intake exhaust gas is added.

[0010] The jet pump annular gap is preferably annular, in particular circular, and converges in the flow direction.

[0011] "Annular" within the meaning of the invention also includes a meandering cross-section of the jet pump annular gap, especially when the jet pump is connected to an upstream heat transfer body with a linked arrangement of several outlet openings for the combustion air. A meandering shape adapts the jet pump annular gap to the shape of the outlet openings on the front side of the heat transfer body.

[0012] As a rule, the jet pump ring gap is designed to be endless, with at most a few support points being provided in the jet pump ring gap in order to keep an outer nozzle ring spaced from an inner pipe or the like.

[0013] Furthermore, it is possible to design the jet pump annular gap as an alternating sequence of closed and open cross-sectional areas along a circumferential line. Such a design of the jet pump annular gap is particularly feasible using an additive manufacturing process and serves the specific purpose of increasing the flow velocity of the combustion air by reducing the cross-section in the flow channel, thereby achieving a jet pump effect. In many cases, a converging shape of the jet pump annular gap is not required for this.

[0014] The jet pump, according to the invention, creates a recuperative burner for diluted combustion through exhaust gas intake. The recirculation of exhaust gas reduces nitrogen oxide formation, both with natural gas and with hydrogen or other fuels such as propane, butane, LPG, or ammonia. Because the invention provides a narrow annular gap at the jet pump nozzle, a thin, but large-diameter, propulsion jet is generated. The large outer surface of the annular air flow ensures effective intake of exhaust gas into the combustion chamber tube, with only the outer surface of the air flow providing the intake.

[0015] A flow-free interior space is formed within the annular air flow. Gas supply lines and other elements such as a mixing unit, an ignition device, a burner nozzle, etc., can be routed within the interior space and thus do not pose any flow obstructions.

[0016] Preferably, the aforementioned elements are combined to form a burner insert that can be removed as a whole from the combustion chamber tube. For such a burner design with a centrally feedable or removable burner insert, the exhaust gas recirculation device designed according to the invention thus represents neither a structural nor a functional flow obstruction.

[0017] In order to be able to operate the recuperator burner either with natural gas or hydrogen, two fuel gas lines are preferably provided, which are only brought together directly at the burner nozzle.

[0018] Preferably, an inner tube is provided adjoining the burner base, with an inner cavity having a continuous clear opening cross-section. The burner unit, in which the burner nozzle, fuel gas lines, etc. are connected to each other, can be inserted from the burner base through the cavity of the inner tube or pulled out backwards, toward the burner base.

[0019] The invention provides a recuperator arranged upstream of the combustion chamber tube with a heat transfer body which has at least two separate flow channels provided for guiding counterflowing fluids, wherein the at least two fluids enter and exit via inlet and outlet openings of the flow channels in the heat transfer body and of the fluids, one is formed by combustion air to be preheated and the other by the exhaust gas of the recuperator burner.

[0020] Alternatively, the flow-free interior can also be filled with a heat exchanger element, with the fuel gas lines integrated into the heat exchanger element. A heat exchanger element arranged within the annular jet of the jet pump can be provided as a supplement to the heat exchanger of a larger recuperator. This can provide additional heat exchange surface area. However, a rear-removable burner insert can no longer be provided.

[0021] In the preferred embodiment of a recuperative burner, the jet nozzle is formed on the outside of the inner tube of the heat transfer body. Outside the inner tube, one or more combustion air outlets are provided on the heat exchanger, where the combustion air flow channel of the heat exchanger ends.

[0022] If a conical outer nozzle ring is provided, it is designed and arranged to cover the combustion air outlets and direct the air flow to the outside of the inner tube, where it is compressed. A very narrow air ring gap is formed between the outer nozzle ring and the casing of the inner tube or another inner nozzle ring, thus achieving the function of a jet pump with an annular propulsion jet. At the same time, the outer nozzle ring leaves the exhaust gas inlets of the heat exchanger, located radially further outward, open for the exhaust gas flow channel, allowing exhaust gases to be drawn in from there.

[0023] The preferred design of the exhaust gas recirculation device further provides that the inner tube opens into or at an inlet opening of an eductor that is larger in diameter than the combustion chamber tube, to which the combustion chamber tube is connected. An annular exhaust gas intake opening is formed between the outer side of the inner tube and the edge of the inlet opening. At the exhaust gas intake opening, the recuperator burner thus opens toward the furnace chamber, into which the recuperator burner extends, so that exhaust gas can be drawn in directly from there.

[0024] In a further positive design, the annular jet gap can be tapered inward. This ensures a more homogeneous mixing of combustion air and exhaust gas before this mixture reaches the axial position where the fuel gas is added.

[0025] To minimize flow resistance, it is preferably provided that the burner base or heat transfer body on one side and the eductor on the other side are connected to each other via several spacer elements distributed around the circumference. The very slim spacer elements hardly pose any flow obstruction, so that the exhaust gas intake opening functionally extends over almost 360°.

[0026] The eductor, the spacer elements, and the heat transfer body or burner base can be formed as a single piece using an additive manufacturing process. Preferably, the conical nozzle ring for forming the jet pump annular gap is also formed as a single piece with the heat transfer body.

[0027] It is also possible for the heat transfer body and the combustion chamber tube to be manufactured separately and then subsequently connected to each other using welded spacer elements.

[0028] The heat transfer body can thus be manufactured separately from the combustion chamber tube, particularly in an additive manufacturing process.

[0029] The jet pump integrated into the recuperative burner designed according to the invention recirculates the exhaust gas into the combustion air. This changes the composition of the mixture of combustion air, fuel gas, and exhaust gas burning at the burner nozzle.

[0030] In combustion technology, the qualitative terms “rich” and “lean” are commonly used to describe the ratio between oxidizer and fuel.

[0031] This ratio remains unchanged during exhaust gas recirculation, as only another gas (exhaust gas) is added. To be able to describe a change in the properties of the gas mixture during different operating stages, for example, during start-up, a "lean" fuel gas-air mixture, within the meaning of the present invention, has a high exhaust gas content and a lower oxygen concentration. A "rich" fuel gas-air mixture, on the other hand, describes a condition in which little to no exhaust gas is recirculated, and the oxygen concentration is thus higher.

[0032] In this sense, a gas mixture of combustion air, fuel gas, and exhaust gas is considered "lean," so the ignitability of such a non-preheated mixture is reduced. Therefore, the recuperative burner extinguishes in a cold state as soon as exhaust gas is recirculated.

[0033] By delaying the air preheating of the recuperator, the ignitability of the air / exhaust gas / fuel mixture is gradually increased. To warm up the cold recuperator burner with the exhaust gas recirculation device, an additional control device for the exhaust gas recirculation device is preferably provided so that recirculation can be reduced for a few minutes during ignition until the system reaches operating temperature and warmed combustion air reaches the combustion chamber.

[0034] The control device is preferably formed by a bypass line inserted into the burner base. A portion of the air flow forming the jet pump's propulsion jet is guided via the bypass line through the supply port or another channel past the exhaust gas recirculation device. This temporarily eliminates the intake power of the jet pump or reduces it to such an extent that the proportion of exhaust gas in the gas mixture in the combustion chamber is significantly reduced.

[0035] The bypass line should preferably be closable via a valve to deactivate its function once the start-up process is complete. This can be achieved by manually switching the valve if start-up processes are only required occasionally.

[0036] An automatic valve adjustment allows the start-up process to be integrated into the burner control system so that it can be carried out without user intervention.

[0037] Using a stepwise or continuously adjustable valve, the opening cross-section in the bypass line can be adjusted depending on the increasing temperature of the combustion air in the heat exchanger before the bypass line is completely closed.

[0038] For further reduction of nitrogen oxides through even more intensive exhaust gas aftertreatment, it may be advantageous to connect the recuperative burner according to the invention in series with another exhaust gas recirculation unit, thus forming a cascaded exhaust gas aftertreatment system. In this case, the flame or the mixture of combustion air and fuel gas serves as the driving force for a jet pump, which then draws exhaust gas into the flame downstream of the mixing plane.

[0039] The additional exhaust gas recirculation device preferably comprises a Venturi nozzle module whose inlet opening is arranged behind the burner mouth cone. The efficiency of an exhaust gas recirculation device designed in this way depends significantly on the velocity of the propellant jet. In a conventional recuperative burner, this velocity results solely from the volume flow of the fuel gas and the volume flow of the supplied combustion air, with a slight increase in velocity resulting from the reaction that begins in the flame root. In conjunction with a recuperative burner designed according to the invention, with which so-called "diluted combustion" can be carried out, the velocity of the propellant jet for the downstream, second exhaust gas recirculation device increases significantly by the additional exhaust gas volume drawn in via the diluted combustion; a factor of 2 or more is conceivable in this case.In addition to the already reduced NOx load due to the first recirculation, the cascaded arrangement improves the effectiveness of the second recirculation device, as the velocity of the propellant jet is increased accordingly. As a result, the NOx emissions of the recuperative burner are significantly improved compared to a burner with only one exhaust gas recirculation device.

[0040] The invention, with further advantageous embodiments, is explained in more detail below with reference to the exemplary embodiments shown in the drawings. The figures show in detail: Fig. 1 a recuperator burner with exhaust gas recirculation device and recuperator in side view; Fig. 2 a recuperator burner according to Fig. 1 in a perspective sectional view in longitudinal section; Fig. 3 an enlarged section of Fig. 2; Fig. 4 parts of the exhaust gas recirculation device on the recuperator burner in a partially sectioned perspective view, seen from the front; Fig. 5 parts of the exhaust gas recirculation device on the recuperator burner in a partially sectioned perspective view, seen from the rear; Fig. 6 the recuperator burner with complete burner base in a perspective sectional view in longitudinal section; Fig. 7 the recuperator burner in a perspective sectional view in longitudinal section in a Fig. 6 cutting plane rotated by 90°; Fig. 8 shows a recuperator for a recuperator burner according to a further embodiment of the invention; Fig. 9 a sectional view along the line XX in Fig. 8 and Fig. 10 a recuperator burner with a second exhaust gas recirculation device in section.

[0041] In Fig. Figure 1 shows a side view of a recuperative burner 100 according to the invention, designed as a recuperative burner. A burner base 10 with a combustion chamber flange 11 is used for attachment to a furnace wall of a furnace chamber. The parts located in the wall passage of the furnace chamber and those outside the furnace chamber, which adjoin the combustion chamber flange 11 on the right side of a recuperative burner installed in a furnace, are not shown here.

[0042] Adjacent to the burner base 10 is a recuperator 20 with an internal heat exchanger, in which incoming combustion air and outgoing exhaust gases are guided in opposite directions in separate flow channels, so that the incoming combustion air is preheated by the outgoing exhaust gas. The recuperator burner 100 opens into a combustion chamber in a combustion chamber tube 30, which tapers at the end at a burner mouth cone 31.

[0043] In the Fig. In the embodiment of the invention shown in Figure 1, the recuperator 20 and the combustion chamber tube 30 do not merge directly into one another. Rather, the combustion chamber tube 30 has an expanded diameter at its end facing the recuperator 20, which is caused by an eductor 32 inserted between them. The combustion chamber tube 30 is held at a distance from the recuperator 20 by inserted spacer elements 36. At the same time, the inner diameter of the eductor 32 is larger than the outer diameter of a nozzle ring 25 at the downstream end of the recuperator 20. The nozzle ring 25 separates the flow paths of the combustion air flowing into the combustion chamber tube 30 and the exhaust gas drawn in via an exhaust gas inlet opening 24 at the recuperator 20. Due to the axial distance between the eductor 32 and the recuperator 20 and the diameter difference therebetween, an opening extending over the entire circumference is formed therebetween.This serves as the exhaust gas intake opening 34 for the combustion chamber tube 30.

[0044] At a short axial distance from the exhaust gas intake opening 34, a jet pump annular gap 26 is formed, from which combustion air emerges from the corresponding flow channel in the recuperator 20 at high speed and with a largely laminar flow. As a result, a jet pump is formed in the opening between the eductor 32 and the recuperator 20, which leads to the intake of portions of the exhaust gas flowing in the opposite direction into the exhaust gas inlet opening 24. This partial flow of exhaust gas is guided, together with the combustion air, into the burner chamber in the combustion chamber tube 30, so that the recirculation of the exhaust gas and a reduction in the oxygen partial pressure in the burner chamber bring about a reduction in nitrogen oxides. Furthermore, the dilution of the combustion air can reduce the temperature in the combustion chamber, particularly during the combustion of hydrogen.

[0045] In Fig. Figure 2 shows a perspective sectional view of the burner 100. To maximize the metallic surfaces of the flow channels usable for heat exchange, the heat transfer body 21 of the recuperator 20 has a very complex spatial geometry for the exhaust gas and combustion air and is shown here only in a simplified manner, with the dashed line indicating the internal separation of flow channels 29.1, 29.2. On the side of the heat transfer body facing the eductor 32, there is an annular combustion air outlet opening 23 on the inside and an annular exhaust gas inlet opening 24 on the outside, with the conical nozzle ring 25 in between.

[0046] The heat transfer body 21 has a continuous inner tube 22 at its center, which extends along its length and has a cavity 27 that allows a burner insert 40 to be inserted from the side of the burner base 10 until the burner nozzle 41 is positioned in the combustion chamber tube 30. The burner nozzle 41 divides the combustion chamber tube 30 into a burner chamber 33 and an intermediate chamber 35.

[0047] In the illustrated embodiment, the nozzle insert 40 comprises a fuel gas pipe 42 for the supply of methane and another fuel gas pipe 43 for the supply of hydrogen. An inspection pipe 49 is also part of the burner insert 40 to allow the flame at the burner nozzle 41 to be observed visually and / or by sensor. Not visible in the sectional view of the Fig. 2 is a bypass pipe through which additional combustion air can be passed into the intermediate chamber 35, as will be described in detail below.

[0048] In order to better illustrate the design of the jet pump provided according to the invention and the flow conditions in the area between the combustion chamber tube 30 and the recuperator 20, Fig. 3 an enlarged section of the sectional view in Fig. 2.

[0049] The hatched arrows indicate the exhaust gas flow. A major portion of the exhaust gas flow is drawn from the furnace chamber into the exhaust gas inlet opening 24 of the recuperator 20 by an external extraction device acting on an exhaust gas outlet opening at the base 10. A secondary flow is drawn laterally into the exhaust gas intake opening 34 by the jet pump formed at the transition between the combustion chamber tube 30 and the recuperator 20.

[0050] The unhatched arrows refer to the combustion air exiting the combustion air outlet openings 23 of the recuperator 20. The air flow is concentrated in a narrow jet pump annular gap 26 formed between the outer wall of the inner tube 22 and the inner wall of the conical, outer nozzle ring 25. The inner tube 22 extends axially further toward the combustion chamber tube 30 than the conical nozzle ring 25, in particular at least to the axial position where the eductor 32 begins. The air jet exiting the jet pump annular gap 26 is supported by the extended inner tube 22 and guided into the combustion chamber tube 30 with little or no turbulence.The annular air flow, thus supported on the inner circumference, is exposed on its outer side exactly at the transition between the nozzle ring 25 and the eductor 32, so that exhaust gas is entrained from there and the combustion air diluted by the exhaust gas flows into the combustion chamber tube 30. The combustion air diluted by the exhaust gas is symbolized by the dot-hatched arrows.

[0051] In Fig. Figure 4 shows the heat transfer body 21 with an eductor 32 cut in half. The combustion air outlet openings are covered by the conical nozzle ring 25 and are therefore not visible. An exhaust gas inlet opening 24 is formed by an annular arrangement of several individual exhaust gas inlet openings located radially outside the nozzle ring 25. In a recuperative burner installed in a furnace, the exhaust gas inlet opening 24 is open toward the furnace chamber.

[0052] It becomes clear in Fig. 4 also the very small radial width of the jet pump ring gap 26 and the axial offset between the nozzle ring 25 outside and the inner tube 22 inside.

[0053] Fig. Figure 5 is another perspective section, specifically a view obliquely from above and behind the transition between the heat transfer body 21 and the eductor 32. The radial width of the exhaust gas intake opening 34 is chosen to be large, so that from this perspective, a view into the interior of the combustion chamber tube 30 with a fuel gas tube 42 running therein is possible. The gap width is deliberately chosen to be large enough to minimize the flow resistance for the incoming exhaust gas, thus ensuring high efficiency of the jet pump.

[0054] In Fig. 6, the recuperator burner 100 according to the invention is shown in a perspective sectional view, in full length, i.e. also with the sections of the burner base 10 located beyond the combustion chamber flange 11. The sectional plane is in comparison to the Fig. 2 and Fig. 3 is rotated by 90° so that only one fuel gas pipe 42 is visible.

[0055] The normal path of the combustion air leads from an external fan via an air inlet nozzle 13 into a combustion air chamber 14 and from there into the radially inner flow path in the heat transfer body 21 of the recuperator 20. Exhaust gas enters the radially outer flow channels 29.1, 29.2 in the heat transfer body 21 at the exhaust gas inlet opening 24 and flows through them into an exhaust gas chamber 15, which surrounds the combustion air chamber 14. Extraction from the exhaust gas chamber 15 occurs via an external fan. Due to the jet pump annular gap 26 provided according to the invention, a portion of the exhaust gas is sucked directly from the furnace chamber back into the combustion chamber tube 30 at the exhaust gas intake opening 34.

[0056] The flow conditions described above correspond to the normal operation of the recuperative burner 100. However, for start-up operation, the fuel gas-air mixture in the combustion chamber 33, which is diluted by exhaust gas, is too lean, so that an ignited flame quickly extinguishes again.

[0057] Since the high temperature load in the recuperator burner 100 makes it impossible to temporarily close the jet pump annular gap 26 using mechanically adjustable flaps or the like, a control device for carrying out a start-up process is designed in the form of a closable bypass line. The bypass line comprises a bypass line pipe 46, which also forms part of the burner insert 40 that can be inserted through the cavity 27 in the inner pipe 22. The bypass line pipe 46, like the inspection pipe 49, extends to a rear end flange 19 of the burner base 10. There, it is connected to the combustion air chamber 14 via a bypass pipe bend 17, with the flow path between the bypass line pipe 46 and the combustion air chamber 14 being closable via a valve 18.

[0058] The fuel gas lines, the inspection pipe 49 and the bypass pipe 46 run through the combustion air chamber 14. However, to prevent the combustion air from passing into the cavity 27 of the inner pipe 22, the various lines of the burner insert 40 are bundled by a common bulkhead plate 47, which creates an airtight barrier in the inner pipe 22, which can be bypassed by the bypass pipe 46 passing through the bulkhead plate 47.

[0059] By opening valve 18, combustion air flows through the bypass pipe 46 into the intermediate chamber 35, and thus into the immediate vicinity of the burner nozzle 41. Since the flow resistance in the combustion air flow channel within the heat transfer body 21 is significantly higher than in the bypass line, the air flow through the heat transfer body 21 is significantly weakened, which also reduces the effectiveness of the jet ring pump and consequently only a small amount of exhaust gas is drawn in. A rich gas-air mixture with only a small amount of exhaust gas is thus combusted, resulting in a stable flame in the burner chamber 33.

[0060] The recuperative burner 100 heats up with increasing combustion time solely through heat conduction and radiation. Since the air paths through the heat transfer body 21 are not completely interrupted even during start-up operation with the bypass line open, and air preheating also occurs in the combustion air chamber 14 surrounded by the exhaust gas chamber 15, the combustion air supplied through the bypass pipe 46 also heats up increasingly.

[0061] The valve 18 can be completely closed when a certain minimum temperature is reached in the combustion chamber 33. It is also possible to gradually reduce the air flow through the bypass line using a motor-driven valve adjustable via a control device, whereby the flow velocity at the jet pump annular gap 26 increases progressively and the exhaust gas content in the combustion chamber 33 increases until the start-up process is completed and the bypass line can be completely closed.

[0062] Fig. 7 shows the recuperation burner 100 with the burner base 10 again in a Fig. 6 section plane rotated by 90°, whereby this view is shortened by the combustion chamber tube adjoining the eductor 32.

[0063] The section plane intersects the bypass pipe 46 along its entire length. Also visible is the branch of the bypass pipe bend 17 at the bottom of the combustion air chamber 14. In particular, the formation of an exhaust chamber 15 surrounding the combustion air chamber 14 can be seen, to which a large-diameter exhaust outlet flange 16 is laterally connected, through which effective extraction of the exhaust gas is achieved.

[0064] Fig. Figure 8 shows parts of another embodiment of a recuperator burner with an exhaust gas recirculation device in a perspective longitudinal section. In a recuperator 220, an inner tube 222 with an inner cavity 227 passes through a heat transfer body 221. A combustion chamber tube 230 having the same inner diameter is arranged in alignment with the inner tube 222.

[0065] The special feature of this embodiment of a recuperative burner according to the invention is that an exhaust gas recirculation device with a jet pump that draws in exhaust gas is formed at the transition between the inner tube 222 and the combustion chamber tube 230, wherein this transition is located within the area surrounded by the heat transfer body 221. The jet pump is thus directly integrated into the heat transfer body 221. A jet pump annular gap 226 is formed between an inner conical nozzle ring 228 and an outer, likewise conical nozzle ring 225.

[0066] Two flow channels 229.1, 229.2 are formed in the heat transfer body 221. Combustion air is supplied to the inner flow channel 229.1 and flows through the jet pump annular gap 226 into the combustion chamber tube 230. The exhaust gas enters the heat transfer body 221 at at least one exhaust gas inlet opening 224 and flows toward a burner base in the opposite flow direction to the combustion air in the outer flow channel 229.2. A portion of the exhaust gas flow is sucked in at an annular exhaust gas intake opening 234 by means of the propulsion jet formed from fresh air at the jet pump annular gap 226 and guided into the combustion chamber tube 230.

[0067] In order to return the flow from the expanded diameter area in the area of ​​the jet pump annular gap 226 to the cross section of the combustion chamber tube 230, a conical eductor 232 is integrated into the heat transfer body 221.

[0068] The complex shape of the heat transfer body 221, into which both the flow channels 229.1, 229.2 with maximized heat exchange surface as well as the exhaust gas recirculation device with the nozzle rings 225, 228 and the eductor 232 are integrated, possibly also the inner tube 222 and the combustion chamber tube 230 as further integral components, is realized using an additive manufacturing process.

[0069] Fig. Figure 9 shows a further perspective sectional view, wherein the cutting plane is transverse to the central axis, namely along the section line XX in Fig. 8. The view is directed into the jet pump ring gap 226. Only the inner nozzle ring 228 is visible. The outer nozzle ring is hidden in this viewing direction.

[0070] In Fig.10 shows a recuperative burner 100 supplemented by a second exhaust gas recirculation device 300. The combustion chamber tube 30 and the second exhaust gas recirculation device 300 are arranged in a common jet tube 301. The exhaust gas recirculation device 300 comprises a Venturi nozzle module 302, which is arranged upstream of the burner mouth cone 31 of the recuperative burner 100 in the flow direction and whose inlet opening is located behind the outlet opening of the burner mouth cone 31, with an annular gap remaining between them. Downstream of the Venturi nozzle module 302, several segmented flame tubes 303 are arranged in series one behind the other. The segmented flame tubes 303 are used to guide the hot flue gases in the jet tube 301.The exhaust gas recirculation device 300 is closed by a cross-shaped spacer 305, which ensures optimal dimensioning of a recirculation gap between the segmented flame tube 303 and the jet tube 301. Reference symbol: 100; 100' recuperator burner 10 burner base 11 Connection flange 12 Fuel gas supply connection 13 Air intake nozzle 14 Combustion air chamber 15 Exhaust chamber 16 Exhaust outlet flange 17 Bypass pipe bend 18 Valve 19 End flange 20; 220 recuperator 21; 221 heat transfer bodies 22; 222 inner tube 23 Combustion air outlet opening 24; 224 exhaust inlet opening 25; 225 outer nozzle ring 26; 226 jet pump annular gap 27; 227 inner cavity 228 inner nozzle ring 29.1, 29.2; 229.1, 229.2 Flow channels 30; 230 combustion chamber tube 31 Burner mouth cone 32; 232 eductor 33 Combustion chamber 34;234 exhaust intake opening 35 Intermediate chamber 36 spacer elements 40 burner insert 41 Burner nozzle 42, 43 Fuel gas lines 46 Bypass pipe 47 bulkhead plate 49 Inspection pipe QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2014 224 086 A1

[0002] US2018 / 0080647A1

[0003] DE 3041177A1

[0004] WO2022117345A1

[0005]

Claims

[1] Recuperator burner (100), comprising at least: - a burner base (10) and - a combustion chamber tube (30) in which at least one burner nozzle (41) is positioned, at which at least one fuel gas line (42, 43) opens, - an exhaust gas recirculation device with a jet pump operated with combustion air, which comprises a jet nozzle with a jet pump annular gap (26; 226) reducing in cross-section in the flow direction for sucking in exhaust gases from outside the combustion chamber tube (30; 230) by means of an annular propulsion jet, wherein the exhaust gas recirculation device is formed upstream of the mixing plane of the combustion gases flowing into the combustion chamber tube (30; 230), between the burner base (10) and the combustion chamber tube (30; 230), and wherein the exhaust gas recirculation device comprises at least one endless exhaust gas intake opening (34; 234) and / or a circumferential, self-contained arrangement of a plurality of exhaust gas intake openings, from which a flow path leads into the interior of the combustion chamber tube (30), characterized bya recuperator (20; 220) arranged upstream of the combustion chamber tube (30) with a heat transfer body (21; 221) which has at least two separate flow channels (29.1, 29.2; 229.1, 229.2) provided for guiding counterflowing fluids, wherein the at least two fluids enter / exit the heat transfer body (21; 221) via inlet and outlet openings (23, 24) of the flow channels (29.1, 29.2; 229.1, 229.2) and of the fluids, one is formed by combustion air to be preheated and the other is formed by the exhaust gas of the recuperator burner (100). [2] Recuperator burner (100) according to claim 1, characterized by that the jet nozzle is formed on a combustion air outlet opening (23) of the recuperator (20; 220). [3] Recuperator burner (100) according to claim 1 or 2, characterized by , - that an inner tube (22) with an inner cavity (27) is connected to the base (10), which is guided through the combustion chamber tube (30) and / or through the heat transfer body (21); - that the combustion air outlet opening (23) of the combustion air flow channel extends around the outside of the inner tube (22), - that the nozzle of the jet pump is formed on the inside by the inner tube (22) and on the outside by the conical nozzle ring (25), which is guided with its tapered end to the outside of the inner tube (22), wherein the jet pump ring gap (26) is formed between the inner tube (22) and the nozzle ring (25) and - that at least one exhaust gas inlet opening (24) for the exhaust gas flow channel of the combustion chamber tube (30) and / or the heat exchanger (21) is arranged outside the nozzle ring (25). [4] Recuperator burner (100) according to claim 3, characterized bythat the inner tube (22) opens into or at an inlet opening of an eductor (32) which is wider in diameter than the combustion chamber tube (30) and to which the combustion chamber tube (30) is connected, wherein the annular exhaust gas intake opening (34) is formed between the outside of the inner tube (22) and the edge of the inlet opening of the eductor (32). [5] Recuperator burner according to claim 1 or 2, characterized by , - that an inner tube (222) with an inner cavity (227) is passed through the heat transfer body (221); and - that the jet pump annular gap (226) and the exhaust gas intake opening (234) are formed in a section of the inner tube (222) located within the heat transfer body (221). [6] Recuperator burner (100) according to one of the preceding claims, characterized bythat the mouth of the jet pump annular gap (26) is positioned within the cross section of the endless exhaust gas intake opening (34) or the closed arrangement of several exhaust gas intake openings. [7] Recuperator burner (100) according to one of the preceding claims, characterized by that the jet pump annular gap (26; 226) and / or the exhaust gas intake opening (34; 234) each have a meandering course. [8] Recuperator burner (100) according to at least one of the preceding claims, characterized by that a further exhaust gas recirculation device (300) is provided with a jet pump which is operated with the mixture of fuel gas, combustion air and the recirculating exhaust gas obtained from the jet pump of the first exhaust gas recirculation device and which is formed downstream of the mixing plane of the fuel gases flowing into the combustion chamber in front of the mouth of the combustion chamber tube (30). [9] Recuperator burner (100) according to claim 8, characterized by that the further exhaust gas recirculation device (300) is arranged in the flow direction upstream of a burner mouth cone (31) of the burner (100) and is arranged with the combustion chamber tube (30') in a common jet pipe (301). [10] Recuperator burner (100) according to claim 8 or 9, characterized by that the further exhaust gas recirculation device (300) comprises a Venturi nozzle module (302) whose inflow opening is arranged behind the burner mouth cone (31). [11] Recuperator burner (100) according to claim 10, characterized by that the further exhaust gas recirculation device (300) comprises at least one segmented flame tube (303) arranged downstream of the Venturi nozzle module (302).

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