Burner head for a premix burner for combusting a gas mixture of hydrogen and air
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- KARL DUNGS
- Filing Date
- 2026-01-13
- Publication Date
- 2026-07-30
Smart Images
Figure EP2026050697_30072026_PF_FP_ABST
Abstract
Description
[0001] Karl Dungs GmbH & Co. KG, January 22, 2025, Karl-Dungs-Platz 1, DNGS P070 WO, 73660 Urbach, Keyword:
[0002] Heat Engine Burner Head H2 - Flame Holder for Hydrogen-Air Flames
[0003] Burner head and premix burner for the combustion of a gas mixture of hydrogen and air
[0004]
[0001] The invention relates to a premix burner and a burner head for this premix burner for the combustion of a gas mixture of a fuel and air, which comprises at least predominantly hydrogen.
[0005]
[0002] Premix burner systems for process heat applications in the low-temperature range are generally known, for example in the food industry, for instance for coffee roasters, bakeries and the like. In these premix burner systems, natural gas or propane gas is conventionally used as fuel.
[0006]
[0003] EP 2 870 409 B1 discloses a burner for burning a fuel / air mixture. The burner has a blower and a burner head. The blower serves to supply the fuel / air mixture to the burner head. The burner head has a metal fiber membrane as a flame holder and a flashback arrestor. The flashback arrestor is arranged upstream of the metal fiber membrane and spaced apart from it. EP 2 641 023 B1 describes a manufacturing process for such a metal fiber membrane.
[0004] Further metal fiber membranes as flame holders are found in EP 2 641 022 B1 and EP 2 856 027 B1. After flowing through the metal fiber membrane, the fuel / air mixture is ignited at the surface of the membrane serving as the combustion side and held there as a stable flame.The metal fiber membrane serves to prevent, on the one hand, the flame from being blown out of the flame holder by the incoming gas mixture and, on the other hand, to prevent the flame from passing through the flame holder upstream towards the mixing unit, which is called flame flashback.
[0007]
[0005] The use of hydrogen as a fuel in such premix burners places special demands on the design of the flame holder, since hydrogen is a very reactive gas. During the combustion of hydrogen, the flame tends to propagate towards the mixing unit, even through relatively small openings in the flame holder. Furthermore, when hydrogen is used as a fuel, the flame burns closer to the flame holder, so that the flame holder is subjected to greater thermal stress during operation with a burning flame than with other fuels. This increases wear during hydrogen operation, as individual metal fibers of the metal fiber membrane can glow and detach from the membrane, thus significantly reducing the service life of the metal fiber membrane.
[0008]
[0006] Furthermore, the metal fiber membrane as a flame holder does not prevent flame flashback. When a flame flashback occurs, the metal fiber membrane can be damaged, so that each flame flashback necessitates maintenance and, if necessary, replacement of the burner head.
[0007] Therefore, the object of the invention is to provide a burner head and a premix burner with which stable and safe combustion of a gas mixture of hydrogen and air is possible, in particular without flame flashback, with the longest possible service life.
[0009]
[0008] This problem is solved with the burner head according to claim 1 and the premix burner according to claim 15:
[0010]
[0009] The burner head according to the invention is designed for a premix burner for the combustion of a gas mixture of hydrogen and air. The burner head according to the invention has an inlet opening, a flame arrestor, an outlet opening and a flame holder.
[0011]
[0010] A flow of the gas mixture can be introduced through the inlet opening into a flow channel formed in the burner head. To generate the flow of the gas mixture, which can be introduced into the burner head of the premix burner through the inlet opening, the premix burner can, for example, have a blower, a mixing unit, and a control unit. The blower can, for example, be designed as a radial or axial blower. The mixing unit can, for example, be configured to add hydrogen gas to an airflow generated by the blower, so that the hydrogen gas and the air mix (completely). The mixing unit is, in particular, arranged on the suction side of the blower. It can be configured to mix the hydrogen into the incoming airflow on the suction side of the blower, for example, with a Venturi mixing system.The blower can thus convey the mixture of air and fuel – namely hydrogen – towards the burner head and simultaneously act as a mixer for the air and fuel. Alternatively, the mixing unit can also be located downstream of the blower and upstream of the burner head. The control unit can be configured to control the blower and the mixing unit, allowing a desired mixing ratio between hydrogen gas and air to be set via the control unit.
[0012]
[0011] The flame arrestor is arranged such that it (completely) occupies the cross-section of the flow channel in the burner head. The flame arrestor can be located in or at the inlet opening or downstream of the inlet opening, but spaced apart from the outlet opening, in the burner head. The flame arrestor is designed to allow the flow of the gas mixture to pass through and to cool and / or slow down a flame front propagating through the flame arrestor.
[0013]
[0012] The flow can be directed from the flow channel of the burner head through the outlet opening downstream to the inlet opening and, in particular, downstream to the flame arrestor into a flame zone. In or on the flame zone, for example, one or more ignition electrodes can be arranged, which are configured to ignite the gas mixture flowing from the outlet opening. A flame monitoring unit can also be arranged in or on the flame zone, which is configured to detect a flame in the flame zone.
[0013] A special feature of the present invention is the flame holder, which is arranged in or on the outlet opening, occupying the cross-section of the flow channel. The flame holder is a rigid, fiber- and wire-free body. Due to the rigid and wire-free design of the flame holder, its service life can be significantly extended during hydrogen operation.The flame holder body is wire-free, which prevents individual metal wires and / or fibers from glowing and gradually detaching from the flame holder's surface during operation of the burner head—while a hydrogen flame burns in the flame zone. The flame holder is a rigid, in particular continuous, body designed to distribute or conduct the heat generated during combustion in all spatial directions—laterally outwards as well as downwards against the flow. For example, if the flame holder body is cylindrical (disc-shaped), the heat can be distributed or conducted in both radial and axial directions. The flame holder body is designed to a predetermined (constant) depth, particularly in the flow direction.The flame holder is specifically designed to allow the flow of the gas mixture to pass through and to cool and / or slow down a flame front spreading through the flame holder, thereby preventing flame flashbacks and improving the safety of the premix burner in hydrogen operation.
[0014]
[0014] Preferably, the flame holder body has an upstream side facing away from the flame zone and an outstream side facing the flame zone, which are fluidically connected to each other via a plurality of channels. It is preferred that the channels in the flame holder body extend (exclusively) in the flow direction from the upstream side to the outstream side.
[0015]
[0015] The flame holder body has, in particular, a (regular) honeycomb structure. The honeycomb structure comprises, in particular, a plurality of identical honeycombs that repeat in a regular pattern. Preferably, the honeycombs of the honeycomb structure adjoin one another, so that adjacent honeycombs are in at least partial positive contact with one another. For example, adjacent honeycombs have common honeycomb walls.
[0016]
[0016] The honeycombs are preferably identically shaped. In a broader sense, a honeycomb is understood to be a cell that encloses a cavity. The cavities of these cells can be circular, triangular, square, pentagonal, hexagonal, or polygonal, and are enclosed by the honeycomb wall. The honeycomb wall extends perpendicular to the cross-section in the axial direction or flow direction. Each of the honeycombs can thus form a channel.
[0017]
[0017] The channels formed by the honeycomb structure in the flame holder body extend, in particular, from an outflow side facing the flame zone to an inflow side of the flame holder body facing away from the flame zone. Each of the channels preferably runs in a straight line from the inflow side to the outflow side. The channels are, in particular, at least substantially parallel to each other and aligned in the direction of flow. Preferably, each of the channels is unbranched. The honeycomb walls can be smooth. Alternatively, the honeycomb walls can also have a certain roughness. The edges of the honeycomb walls on the outflow side of the flame holder—the outflow edges—can be sharp-edged to promote the formation of micro-vortices. Alternatively, the outflow edges can also be rounded. The honeycomb walls are, in particular, formed from (very thin) sheet metal. The sheet metal can, for example, be made of a high-melting-point metal, such as...The sheet thickness is preferably less than 100 µm, preferably less than 60 µm, and particularly preferably less than 50 µm.
[0018]
[0018] Preferably, each of the channels has a predetermined channel width and a predetermined channel length. The channel widths are preferably (significantly) smaller than the channel lengths.
[0019]
[0019] In particular, the channel widths are smaller than the channel lengths by a factor of more than 10, in particular more than 20.
[0020]
[0020] The depth of the flame holder body is preferably (significantly) greater than the channel width, preferably by a factor of 10 or 20 greater than the channel widths, thereby further reducing the risk of flame propagation. The flame holder body enables heat conduction against the flow direction. Due to the (particularly) small channel widths, it is made more difficult for the flame to migrate from the flame zone on the downstream side of the flame holder through the channels to the upstream side, since the heat losses at the channel or honeycomb walls of the flame holder body locally cool the flame as it travels through, and the previously self-sustaining combustion reaction locally extinguishes.
[0021]
[0021] The channels through the flame holder body can each have a channel width that is less than 0.9 mm, preferably less than 0.7 mm, and particularly preferably less than 0.5 mm. The channels can each have a channel length that is greater than 5 mm, preferably greater than 7 mm, and particularly preferably greater than 10 mm.
[0022]
[0022] Preferably, the flame arrestor, which is arranged upstream of the flame holder at a distance, and the flame holder are identical in design. This further increases the safety of the burner head against flame flashbacks.
[0023]
[0023] The flame holder body can be made of a (high-melting-point) metal and / or ceramic. As an alternative to the honeycomb structure, the flame holder body can also be made of another structure, for example, sintered metal spheres.
[0024]
[0024] Preferably, the flame holder body is formed at least substantially cylindrically (disc-shaped) around a central axis. The honeycomb structure can then be arranged, in particular, concentrically or spirally to the central axis of the flame holder body. Alternatively, the flame holder body can also be triangular, rectangular, square, or polygonal. The individual honeycomb structures can also be arranged not concentrically to the central axis, but, for example, in strips arranged one after the other.
[0025] The channels formed in the flame holder body preferably extend exclusively along the direction of flow, but not perpendicular to the direction of flow.
[0025]
[0026] The hydrogen-air gas mixture may contain up to 35 vol.%, in particular up to 30 vol.%, preferably up to 25 vol.%, and most preferably up to 20 vol.%, of another fuel gas. The other fuel gas may be a hydrocarbon-containing gas, for example, a natural gas mixture, a propane gas mixture, and / or a biogas mixture.
[0026]
[0027] The premix burner according to the invention for the combustion of a gas mixture of hydrogen and air has a burner head of the type described above. All features and advantages described with regard to the burner head, in particular with regard to the flame holder, also apply to the premix burner according to the invention.
[0027]
[0028] Further details and advantageous embodiments of the invention will become apparent from the dependent claims, the drawings, or the description. The drawings show:
[0028]
[0029] Figure 1 shows an example of a premix burner;
[0029]
[0030] Figure 2 shows an example of the flame holder in longitudinal section;
[0030]
[0031] Figure 3 shows a detailed top view of the flame holder;
[0032] Figure 4 shows an example of the flame holder in top view;
[0031]
[0033] Figure 5 shows another example of the flame holder; as well as
[0032]
[0034] Figure 6 shows another example of the flame holder in top view.
[0035] Figure 1 schematically illustrates an embodiment of a premix burner 10 according to the invention. The premix burner 10 has a burner head 11 and a blower 12 according to the invention, which are fluidically connected to each other via a connecting channel.
[0033]
[0036] The blower 12 shown in Figure 1 is designed as a radial blower. Alternatively, the blower 12 can also be designed as an axial blower or another type of blower.
[0034]
[0037] The blower 12 is configured to generate an airflow 14. In this embodiment, a hydrogen flow 15 is mixed into the airflow 14 at an intake side 40 of the blower 12 by means of a mixing unit 13. The burner output can be varied by adjusting the speed of the blower 12. Due to the intake-side mixing of the hydrogen upstream of the blower 12, the hydrogen-to-air ratio can remain at least substantially constant, even with varying speeds of the blower 12. At higher speeds, the blower 12 draws in more air from the environment as well as more hydrogen from the hydrogen nozzle, so that the hydrogen-to-air ratio remains at least substantially constant. The airflow 14 and the hydrogen flow 15 are further mixed within the blower 12.
[0035]
[0038] The blower 12 is specifically designed to change the rotational speed of its rotor and thus the flow velocity of the gas mixture 16, and consequently the burner output. The mixing unit is preferably designed to provide a pressure for the hydrogen flow 15 that is at least substantially constant. The ratio between hydrogen and air can be changed, for example, by means of a pressure regulator in the mixing unit 13 and / or by means of a throttle in the hydrogen injection system.
[0036]
[0039] The burner head 11 has an inlet opening 17, a flame arrestor 18, a flame holder 21 and an outlet opening 22. A flow channel 20 is formed between the inlet opening 17 and the outlet opening 22, through which the flow 16 of the gas mixture can be directed.
[0037]
[0040] The inlet opening 17 is configured to allow the gas mixture flow 16 to enter the burner head 11 through it. The flame arrestor 18 can be arranged between the inlet opening 17 and the outlet opening 22 within the burner head 11, or in or on the inlet opening, so that the gas mixture flow 16 passes through the flame arrestor 18. In Figure 1, the flame arrestor 18 is arranged within the burner head 11, occupying the cross-section 19 of the flow channel 20 and spaced apart from the flame holder 21.
[0038]
[0041] Downstream of the flame arrestor 18, the flame holder 21 is arranged in or on the outlet opening 22.
[0039]
[0042] Through the outlet opening 22, the flow 16 from the flow channel 20 of the burner head 11 can be discharged into a flame zone 23.
[0043] At least one ignition electrode 24 is arranged in the flame zone 23, which is configured to ignite the outgoing gas mixture. A flame monitoring unit 25 is also arranged in the flame zone 23. The flame monitoring unit 25 is configured to detect the presence of a flame in the flame zone 23. The flame monitoring unit 25 can, for example, detect the UV emission of a flame located in the flame zone 23. Alternatively, the flame monitoring unit 25 can also be configured as an electrode that is configured to electrically detect the presence of a flame in the flame zone.
[0040]
[0044] The detailed construction of the flame holder is described below with reference to Figure 2. Figure 2 shows a detailed longitudinal section view of the flame holder 21.
[0041]
[0045] The flame holder 21 is a rigid, fiber- and wire-free body 26, which has an outflow side 27 facing the flame zone 23 and an inflow side 28 facing away from the flame zone 23. The flow 16 of the gas mixture impinges on the inflow side 28 of the flame holder 21 at its end face in the flow channel 20.
[0042]
[0046] The flame holder 21 has a plurality of channels that extend from the upstream side 28 through the body 26 to the downstream side 27. The channels 29 are identical in design. The channels 29 in Figure 2 run in a straight line from the upstream side 28 of the body 26 to the downstream side 27 of the body 26. The plurality of channels 29 allows the flame holder to direct the flow 16 of the gas mixture from the upstream side 28 through the flame holder 21 to the downstream side 27 and into the flame zone 23. At the downstream side 27, each of the channels 29 has a downstream edge 30 at its opening. The downstream edges 30 of the channels 29 can be sharp-edged.
[0043]
[0047] Micro vortices 31 can form at the outflow edges 30, which can help to hold a flame produced during the combustion of the gas mixture in the flame zone 23 on the flame holder 21.
[0044]
[0048] The channels 29 shown in Figure 2 have a channel width 32 that is (significantly) smaller than the flame-holding depth 33 of the body 26. In this example, the channel length 34 corresponds to the flame-holding depth 33, since the channels 29 run in a straight line from the upstream side 28 to the downstream side 27.
[0045]
[0049] Figure 2 is merely a schematic illustration. The channel lengths 34 are, for example, at least 3 mm, 4 mm, or 5 mm, but preferably about 10 mm long. The channel widths 32, on the other hand, are significantly smaller than the channel lengths 34. The channel widths 32 are, for example, 0.5 mm, preferably 0.4 mm wide. The ratio between channel length 34 and channel width 32 can be in a range between 7 and 35, preferably between 8 and 30, and particularly preferably between 12.5 and 25.
[0046]
[0050] The flame holder 21 shown in Figure 2 occupies the cross-section 19 of the flow channel 20 and extends in the longitudinal and transverse directions x, y. The flame holder 21 also extends in the flow direction z.
[0051] In the example shown in Figure 1, the flame barrier 18 is identical to the flame holder 21.
[0047]
[0052] Figure 3 shows a detailed view of the flame holder body 26 as a front-end top view. The flame holder body 26 has a honeycomb structure 35. The honeycomb structure 35 consists of regularly arranged honeycombs 36 that are adjacent to and connected with each other.
[0048]
[0053] In the example shown in Figure 3, honeycombs 36 with alternating opposite orientations border each other in the longitudinal direction x. In the example shown, a honeycomb 36 oriented in the transverse direction (the corner points upwards in Figure 3) is thus followed by a honeycomb 36 oriented opposite to the transverse direction y (the corner points downwards in Figure 3).
[0049]
[0054] The honeycomb structure 35 shown in Figure 3 is composed of honeycombs 36, which have a triangular base. Unlike the one shown in Figure 3, the bases of the honeycombs 36 can also be round, oval, square, or polygonal.
[0050]
[0055] In the transverse direction y, in the example shown in Figure 3, the longitudinally x-oriented rows of honeycombs 36, which are always alternately oriented in opposite directions, adjoin one another. The rows of honeycombs 36 are stacked on top of each other. The channels 29 formed by the honeycombs 36 extend in the flow direction z. The honeycomb structure 35 is formed by a plurality of struts 37 with predetermined strut widths 38.
[0056] Figure 4 shows an example of the burner head 11 in a (frontal) top view. In the example shown in Figure 4, the honeycomb structure 35 is arranged linearly (not concentrically) in the longitudinal and transverse directions x, y, so that several rows of honeycombs 36 adjoin each other, in which the individual honeycombs 36 are oriented alternately.
[0051]
[0057] Figure 5 shows another example of the burner head 11 in a (frontal) top view. The flame holder 21 also has a honeycomb structure 35, which—unlike in Figure 4—is arranged concentrically to a central axis 39 of the flame holder 21. In the example shown in Figure 5, the honeycombs 36 are arranged in a ring, with the adjacent honeycombs 36 in each ring alternating their orientation, namely in the radial direction r and against the radial direction r. In contrast to the representation in Figure 5, it is also possible to arrange the honeycombs 36 in a spiral. This has the advantage that the production of the honeycomb structure 35 can be significantly simplified. During production, corrugated sheet metal is covered with a smooth sheet and wound around a central pin, resulting in a spirally oriented honeycomb structure 35.
[0052]
[0058] Figure 6 shows another example of the burner head 11, in which the flame holder 21, unlike in the previous examples, is not disc-shaped (cylindrical) but rectangular, in particular square. The orientation of the honeycomb structure 36 in this example is a linear arrangement as in Figure 4.
[0059] The invention relates to a premix burner 10 and a burner head 11 for this premix burner 10 for the combustion of a gas mixture of fuel and air, which comprises at least predominantly hydrogen. The burner head 11 has an inlet opening 17, a flame arrestor 18, an outlet opening 22, and a flame retainer 21. A flow 16 of the gas mixture can be introduced through the inlet opening 17 into a flow channel 20 formed in the burner head 11. The flame arrestor 18 is arranged such that it (completely) occupies the cross-section 19 of the flow channel 20 in the burner head 11. The flow 16 can be discharged from the flow channel 20 of the burner head 11 through the outlet opening 22 downstream to the inlet opening 17 and, in particular, downstream to the flame arrestor 18 into a flame zone 23.A special feature of the present invention is the flame holder 21, which is arranged in or on the outlet opening 22, occupying the cross-section 19 of the flow channel 20, and is a rigid, fiber- and wire-free body 26. Due to the rigid and wire-free design of the flame holder 21, its service life during hydrogen operation can be significantly extended. Reference numerals.
[0053] 10 Premix burner
[0054] 11 Burner head
[0055] 12 Blower (radial blower)
[0056] 13 Premixing section
[0057] 14 Air current
[0058] 15 Hydrogen flow
[0059] 16 Flow of the gas mixture
[0060] 17 Entrance opening
[0061] 18 Flame barrier
[0062] 19 Cross-section of the flow channel 20 Flow channel of the burner head 21 Flame holder
[0063] 22 Exit opening
[0064] 23 Flame zone
[0065] 24 Ignition electrode
[0066] 25 Flame monitoring unit
[0067] 26 Flame holder bodies
[0068] 27 Outflow side
[0069] 28 Upstream side
[0070] 29 channels
[0071] 30 Egress edge
[0072] 31 microvortices
[0073] 32 channel width
[0074] 33 Body depth
[0075] 34 Channel length
[0076] 35 honeycomb structure
[0077] 36 honeycombs
[0078] 37 bridges
[0079] 38 bridge width
[0080] 39 Central axis
[0081] 40 Intake sideR Radial direction x Longitudinal direction
[0082] y transverse direction
[0083] z Flow direction
Claims
Patent claims:
1. Burner head ( 11 ) for a premix burner ( 10 ) for the combustion of a gas mixture of hydrogen and air, comprising: - an inlet opening (17) through which a flow (16) of the gas mixture can be introduced into a flow channel (20) formed in the burner head (11); - a flame arrestor (18) which is arranged in or on the inlet opening (17) occupying the cross-section (19) of the flow channel (20); - an outlet opening (22) through which the flow (16) of the gas mixture from the flow channel (20) of the burner head (11) can be discharged downstream to the inlet opening (17) into a flame zone (23); and - a flame holder ( 21 ) which is arranged in or on the outlet opening ( 22 ) occupying the cross-section ( 19 ) of the flow channel ( 16 ), wherein the flame holder ( 21 ) is designed as a rigid, fiber- and wire-free body ( 26 ).
2. Burner head ( 11 ) according to claim 1 , characterized in that the body ( 26 ) of the flame holder ( 21 ) has a honeycomb structure ( 35 ).
3. Burner head (11) according to claim 1 or 2, characterized in that the body (26) of the flame holder (21) has an upstream side (28) facing away from the flame zone (23) and an outflow side (30) facing the flame zone (23), which are fluidically connected to each other via a plurality of channels (29).
4. Burner head (11) according to one of the preceding claims, in particular according to claim 3, characterized in that the channels (29) in the body (26) of the flame holder (21) extend in the flow direction (z) from the upstream side (28) to the outflow side (39).
5. Burner head ( 11 ) according to one of the preceding claims, characterized in that each of the channels (29) has a predetermined channel width (32 ) and a predetermined channel length (34 ).
6. Burner head ( 11 ) according to one of the preceding claims, in particular according to claim 5, characterized in that the channel width (32 ) is smaller than the channel lengths (34 ), preferably the channel widths (32 ) are smaller than the channel lengths (34 ) by a factor of more than 10, in particular by more than 20.
7. Burner head ( 11 ) according to one of the preceding claims, characterized in that the channels (29) each have a channel width (32 ) which is less than 0.9 mm, preferably less than 0.7 mm, particularly preferably less than 0.5 mm.
8. Burner head (11) according to one of the preceding claims, characterized in that the channels (29) each have a channel length (34) that is greater than 3 mm, preferably greater than 5 mm, particularly preferably greater than 10 mm.
9. Burner head (11) according to one of the preceding claims, characterized in that the upstream flame arrestor (18) and the flame holder (21) are identical.
10. Burner head ( 11 ) according to one of the preceding claims, characterized in that the flame holder (21 ) is made of metal and / or ceramic .
11. Burner head ( 11 ) according to one of the preceding claims, characterized in that the honeycomb structure (35) is formed by a plurality of adjacent honeycombs (36 ).
12. Burner head ( 11 ) according to one of the preceding claims, characterized in that the body (26) of the flame holder (21 ) is at least substantially cylindrical, forming a central axis (39) defining a central axis, wherein the honeycombs (36) are preferably arranged concentrically or spirally to the central axis (39) of the body (26) of the flame holder (21 ).
13. Burner head ( 11 ) according to one of the preceding claims, characterized in that the channels (29) formed in the body (26) extend exclusively in the direction of the flame holder depth (33) of the body (26).
14. Burner head ( 11 ) according to one of the preceding claims, characterized in that the gas mixture contains a proportion of at most 35 vol. -%, in particular at most 20 vol. -%, of another fuel gas, wherein the fuel gas is or are, for example, a natural gas mixture, a propane gas mixture, and / or a biogas mixture.
15. Premix burner ( 10) for the combustion of a gas mixture of hydrogen and air, comprising a burner head ( 11 ) according to one of the preceding claims .