Combustor head and premix combustor that combusts a gas mixture of hydrogen and air

Abstract

This invention relates to a premixed burner and a burner head for the premixed burner, the premixed burner being used to burn a gas mixture consisting of fuel and air, which at least primarily comprises hydrogen. The burner head has an inlet opening, a flame arrestor, an exit opening, and a flame retainer. Flow of the gas mixture is introduced through the inlet opening into a flow channel constructed in the burner head. The flame arrestor is arranged such that it (completely) occupies the cross-section of the flow channel in the burner head. Flow is discharged from the flow channel of the burner head through the exit opening downstream of the inlet opening and particularly downstream of the flame arrestor into the flame zone. A distinctive feature of this invention is the flame retainer, which is arranged in or thereon in a manner that occupies the cross-section of the flow channel and is a rigid, fiber-free, and wireless body.

Description

Technical Field

[0001] This utility model relates to a premixed burner and a burner head for the premixed burner, the premixed burner being used to burn a gas mixture consisting of fuel and air, which at least primarily comprises hydrogen. Background Technology

[0002] Premixed burner systems are commonly known for use in process heat applications in low-temperature ranges, such as in the food industry, for example, in coffee roasters and bakeries. These premixed burner systems typically use natural gas or propane as fuel.

[0003] EP 2870409 B1 discloses a burner for burning a fuel / air mixture. The burner has a blower and a burner head. The blower supplies the fuel / air mixture to the burner head. The burner head has a metal fiber membrane as a flame retainer and a flame backlash arrestor. The flame backlash arrestor is arranged upstream of and spaced apart from the metal fiber membrane. EP2641023 B1 describes a method for manufacturing such a metal fiber membrane.

[0004] EP 2641022 B1 and EP 2856027 B1 mention additional metal fiber membranes as flame holders. The fuel / air mixture is ignited at the surface of the metal fiber membrane used as the combustion side after flowing through it, and is stabilized there as a flame. The metal fiber membrane serves to prevent the flame from being blown out of the flame holder by the accompanying gas mixture, and also to prevent the flame from penetrating upstream through the flame holder in the direction of the mixing unit; this is known as flame backflash.

[0005] Using hydrogen as fuel in such a premixed burner places special demands on the design of the flame holder because hydrogen is a highly reactive gas. During hydrogen combustion, the flame tends to penetrate the mixing unit even with relatively small openings in the flame holder. Furthermore, when using hydrogen as fuel, the flame burns closer to the flame holder, resulting in a greater heat load on the flame holder during operation with the combustion flame compared to other fuels. This increases wear during hydrogen operation, as the individual metal fibers of the metal fiber membrane may burn and detach from the membrane, thus significantly shortening its lifespan.

[0006] Furthermore, the metal fiber membrane used as a flame retainer cannot prevent flame backflash. When flame backflash occurs, the metal fiber membrane may be damaged, resulting in maintenance and, if necessary, replacement of the burner head each time. Utility Model Content

[0007] Based on this, the objective of this invention is to provide a burner head and a premixed burner that enable stable and safe combustion of a gas mixture consisting of hydrogen and air over the longest possible service life, especially in the absence of flame backlash.

[0008] This task is solved using the burner head and premixed burner:

[0009] The burner head according to this invention is designed for use in a premixed burner for burning a gas mixture consisting of hydrogen and air. The burner head according to this invention has an inlet opening, a flame arrestor, an exit opening, and a flame retainer.

[0010] The flow of the gas mixture can be introduced into a flow channel constructed in the burner head through an inlet opening. To generate the flow of the gas mixture that can be introduced into the burner head of the premixed burner through the inlet opening, the premixed burner can, for example, have a blower, a mixing unit, and a control unit. For example, the blower can be constructed as a radial or axial blower. For example, the mixing unit can be configured to add hydrogen gas to the airflow generated by the blower, thereby causing the hydrogen gas and air to mix (completely) with each other. In particular, the mixing unit is arranged on the suction side of the blower. The mixing unit can be configured to mix hydrogen gas into the suction-flowing airflow on the suction side of the blower, for example using a Venturi mixing system. In this way, the blower can convey the mixture of air and fuel (i.e., hydrogen) in the direction of the burner head and simultaneously act as a mixer for air and fuel. Alternatively, the mixing unit can also be arranged downstream of the blower and upstream of the burner head. The control unit can be configured to operate the blower and the mixing unit, thereby allowing the desired mixing ratio between hydrogen gas and air to be adjusted by means of the control unit.

[0011] The flame arrestor is arranged such that it (completely) occupies the cross-section of the flow passage in the burner head. The flame arrestor may be arranged in or at the inlet opening, or downstream of the inlet opening but spaced apart from the exit opening in the burner head. The flame arrestor is configured to allow the flow of the gas mixture through and to cool and / or slow the flame front propagating through it.

[0012] The flow can be directed from the flow channel of the burner head through the exit opening downstream of the inlet opening, and particularly downstream of the flame arrestor, into the flame zone. An ignition electrode, or multiple ignition electrodes, configured to ignite the gas mixture flowing from the exit opening, can be arranged within or at the flame zone. Furthermore, a flame monitoring unit configured to detect the flame within the flame zone can be arranged within or at the flame zone.

[0013] The distinctive feature of this invention lies in the flame retainer, which is arranged in or outside the opening in a manner that occupies the cross-section of the flow channel. The flame retainer is a rigid, fiber-free, and wire-free body. This rigid and wire-free design significantly extends the service life of the flame retainer during hydrogen operation. The wire-free nature of the flame retainer body prevents individual metal wires and / or fibers from burning and gradually detaching from the surface of the flame retainer during burner head operation (when the hydrogen flame in the flame zone is burning). The flame retainer is a rigid, particularly coherent, body designed to distribute or conduct the heat generated during combustion in all spatial directions (laterally outward and downward against the flow). For example, when the flame retainer body is designed as a cylinder (disc), heat can be distributed or conducted in both the radial and axial directions. In particular, the flame retainer body is constructed at a predetermined (constant) depth in the flow direction. In particular, the flame retainer is configured to allow the flow of the gas mixture through and to cool and / or slow the flame front propagating through the flame arrestor, thereby preventing flame backlash and improving the safety of the premixed burner in hydrogen operation.

[0014] Preferably, the flame holder body has an inflow side facing away from the flame zone and an outflow side facing the flame zone, the inflow side and the outflow side being fluidly connected to each other via a plurality of channels. Preferably, the channels in the flame holder body extend (only) from the inflow side to the outflow side in the flow direction.

[0015] In particular, the flame holder body has a (regular) honeycomb structure. Specifically, the honeycomb structure comprises multiple identical cells that repeat in a regular pattern. Preferably, the cells of the honeycomb structure are adjacent to each other, such that adjacent cells are at least segmentally in form-fitting contact with each other. For example, adjacent cells share a common cell wall.

[0016] Preferably, the honeycomb is formed in the same manner. A honeycomb is broadly understood as a series of individual cells surrounding an empty cavity. These cavities can be circular, triangular, square, pentagonal, hexagonal, or polygonal, and are surrounded by honeycomb walls. The honeycomb walls extend perpendicular to the cross-section in the axial or flow direction. Thus, each cell in the honeycomb can form a channel.

[0017] The honeycomb-formed channels in the flame holder body extend from the outflow side facing the flame zone to the inflow side away from the flame zone. Each channel preferably extends linearly from the inflow side to the outflow side. In particular, the channels are oriented at least substantially parallel to each other in the flow direction. Preferably, each channel is unbranched. The honeycomb walls can be designed to 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 (outflow edges) can be constructed with sharp edges to support the formation of micro-vortices. Alternatively, the outflow edges can also be rounded. The honeycomb walls are constructed, in particular, of (very thin) sheet metal. For example, the sheet metal can be constructed of a high-melting-point metal (e.g., stainless steel). The sheet metal thickness is particularly less than 100 micrometers, preferably less than 60 micrometers, and particularly preferably less than 50 micrometers.

[0018] Preferably, each of the channels has a predetermined channel width and a predetermined channel length. Preferably, the channel width is (significantly) smaller than the channel length.

[0019] In particular, the channel width is less than 1 / 10 of the channel length, and especially less than 1 / 20.

[0020] Preferably, the depth of the flame holder body is significantly greater than the channel width, preferably 10 or 20 times the channel width, thereby further reducing the risk of flame penetration. The flame holder body enables heat conduction against the flow direction. The particularly small channel width makes it difficult for the flame to migrate from the flame zone on the outflow side of the flame holder to the inflow side, because heat loss at the channel walls or honeycomb walls of the flame holder body locally cools the flame during migration, and previously self-sustaining combustion reactions are locally extinguished.

[0021] The channels through the flame holder body may each have the following channel widths: less than 0.9 mm, preferably less than 0.7 mm, and particularly preferably less than 0.5 mm. The channels may each have the following channel lengths: greater than 5 mm, preferably greater than 7 mm, and particularly preferably greater than 10 mm.

[0022] Preferably, the flame arrestor, arranged at a distance upstream of the flame retainer, is constructed identically to the flame retainer. This further enhances the safety of the burner head against flame backlash.

[0023] The flame holder body can be made of (high melting point) metal and / or ceramic. Alternatively, with a honeycomb structure, the flame holder body can also be made of other structures (e.g., sintered metal spheres).

[0024] Preferably, the flame holder body is formed, at least substantially cylindrical (disc-shaped), around a central axis. The honeycomb cells of the honeycomb structure can thus be arranged concentrically or spirally with the central axis of the flame holder body. Alternatively, the flame holder body can also be constructed in triangular, rectangular, square, or polygonal shapes. The individual cells of the honeycomb structure can also be arranged non-concentrically with the central axis, for example, in a strip-like arrangement.

[0025] Preferably, the channel formed in the flame holder body extends only along the flow direction and not laterally.

[0026] The gas mixture consisting of hydrogen and air may be mixed with other fuel gases in proportions of up to 35% by volume, particularly up to 30% by volume, preferably up to 25% by volume, and especially preferably up to 20% by volume. The other fuel gases to be mixed may be hydrocarbon-containing gases, such as natural gas mixtures, propane mixtures, and / or biogas mixtures.

[0027] The premixed burner according to this invention for burning a gas mixture consisting of hydrogen and air has a burner head of the type described above. All the features and advantages described with respect to the burner head, and especially to the flame holder, are equally applicable to the premixed burner according to this invention. Attached Figure Description

[0028] Further details of the advantageous embodiments of this utility model are derived from the dependent claims, drawings, or description. Wherein:

[0029] Figure 1 An example for a premixed burner is shown;

[0030] Figure 2 An example of a flame retainer is shown in longitudinal section;

[0031] Figure 3 A detailed view of the flame holder is shown in top view;

[0032] Figure 4 An example of a flame retainer is shown in top view;

[0033] Figure 5 Another example of a flame retainer is shown; and

[0034] Figure 6 Another example of a flame retainer is shown in a top view. Detailed Implementation

[0035] exist Figure 1The image schematically depicts one embodiment of a premixed burner 10 according to the present invention. The premixed burner 10 has a burner head 11 and a blower 12 according to the present invention, the burner head and the blower being fluidly connected to each other via a connecting channel.

[0036] exist Figure 1 The blower 12 shown is configured as a radial blower. Alternatively, the blower 12 may also be configured as an axial blower or other blowers.

[0037] Blower 12 is configured to generate airflow 14. In this embodiment, hydrogen flow 15 is mixed into airflow 14 at the suction side 40 of blower 12 by means of mixing unit 13. The burner power can be changed by the rotational speed of blower 12. Since hydrogen is mixed on the suction side upstream of blower 12, the ratio of hydrogen to air can remain at least substantially constant even when the rotational speed of blower 12 changes. At higher rotational speeds, blower 12 draws more air from the environment and more hydrogen from the hydrogen nozzle, thereby maintaining the ratio of hydrogen to air at least substantially constant. Airflow 14 and hydrogen flow 15 are further mixed in blower 12.

[0038] In particular, the blower 12 is configured to change the rotational speed of its rotor and thus the flow rate of the gas mixture 16 and thus the burner power. Preferably, the mixing unit is configured to provide at least substantially constant pressure for the hydrogen flow 15. For example, the ratio between hydrogen and air can be changed by means of a pressure regulator in the mixing unit 13 and / or by means of a throttle valve in the hydrogen injection section.

[0039] The burner head 11 has an inlet opening 17, a flame arrester 18, a flame retainer 21, and an exit opening 22. A flow channel 20 is formed between the inlet opening 17 and the exit opening 22, through which the flow 16 of the gas mixture can be guided.

[0040] The inlet opening 17 is configured so that the flow 16 of the gas mixture enters the burner head 11 through the inlet opening 17. A flame arrestor 18 may be arranged within the burner head 11 between the inlet opening 17 and the exit opening 22, or may be arranged within or at the inlet opening, thereby allowing the flow 16 of the gas mixture to pass through the flame arrestor 18. Figure 1 In the burner head 11, the flame arrestor 18 is arranged in a manner that occupies the cross section 19 of the flow channel 20 and is spaced apart from the flame holder 21.

[0041] Downstream of the flame arrester 18, the flame retainer 21 is arranged in or at the exit of the opening 22.

[0042] The flow 16 can be directed from the flow channel 20 of the burner head 11 through the exit opening 22 into the flame zone 23.

[0043] At least one ignition electrode 24 is arranged in the flame zone 23, configured to ignite the outflowing 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. For example, the flame monitoring unit 25 can detect UV radiation from the flame in the flame zone 23. Alternatively, the flame monitoring unit 25 can also be designed as an electrode, configured to electrically detect the presence of a flame in the flame zone.

[0044] The following reference Figure 2 Describe the detailed structure of the flame holder. Figure 2 A detailed view of the flame holder 21 is shown in longitudinal section.

[0045] The flame holder 21 is a rigid, fiber-free and wireless body 26 having an outflow side 27 facing the flame zone 23 and an inflow side 28 away from the flame zone 23. The flow 16 of the gas mixture encounters the inflow side 28 of the flame holder 21 at its end in the flow channel 20.

[0046] The flame holder 21 has multiple channels that extend from the inflow side 28 through the body 26 to the outflow side 27. Channel 29 is designed similarly. Figure 2 The channel 29 extends linearly from the inflow side 28 of the body 26 to the outflow side 27 of the body 26. Due to the multiple channels 29, the flame holder is configured to allow the flow 16 of the gas mixture from the inflow side 28 through the flame holder 11 toward the outflow side 27 into the flame zone 23. At the outflow side 27, each channel 29 has an outflow edge 30 at its inlet. The outflow edges 30 of the channel 29 can be designed to be sharp.

[0047] Micro-vortices 31 can be formed at the outflow edge 30, which can help keep the flame formed during combustion of the gas mixture in the flame zone 23 at the flame holder 21.

[0048] exist Figure 2 The channel 29 shown has a channel width 32, which is configured to be (significantly) smaller than the flame holder depth 33 of the body 26. In this example, the channel length 34 corresponds to the flame holder depth 33, because the channel 29 extends linearly from the inflow side 28 to the outflow side 27.

[0049] Figure 2This is for illustrative purposes only. For example, the channel length 34 is at least 3 mm, 4 mm, or 5 mm, but preferably about 10 mm. The channel width 32 is significantly smaller than the channel length 34. For example, the channel width 32 is 0.5 mm, preferably 0.4 mm. The ratio between the channel length 34 and the channel width 32 can be in the range of 7 to 35, preferably 8 to 30, and particularly preferably 12.5 to 25.

[0050] exist Figure 2 The flame holder 21 shown occupies the cross section 19 of the flow channel 20 and extends in the longitudinal direction x and the transverse direction y. The flame holder 21 also extends in the flow direction z.

[0051] exist Figure 1 In the example shown, the flame arrestor 18 is configured to be the same as the flame retainer 21.

[0052] Figure 3 A detailed view of the flame holder body 26 is shown as an end-side top view. The flame holder body 26 has a honeycomb structure 35. The honeycomb structure 35 consists of regularly arranged cells 36, which are adjacent to each other and joined together.

[0053] exist Figure 3 In the example shown, the cells 36, which are always alternately oriented in opposite directions in the longitudinal direction x, are adjacent to each other. Therefore, in the example shown, the cells 36 oriented in the transverse direction (with corners at...) Figure 3 (Middle finger pointing upwards) follows the honeycomb 36 (corners at) oriented in the opposite lateral direction (y-axis). Figure 3 (Middle finger pointing downwards).

[0054] exist Figure 3 The honeycomb structure 35 shown is constructed from honeycomb 36, which has a triangular base. (The last sentence appears to be incomplete and possibly contains errors.) Figure 3 As shown, the bottom surface of the honeycomb 36 can also be constructed as a circle, an ellipse, a square, or a polygon, depending on the shape.

[0055] exist Figure 3 In the example shown, the arrangement of cells 36 extending in the longitudinal direction x, which are always alternately oriented in opposite directions, is adjacent to each other in the transverse direction y. The arrangement of cells 36 is stacked on top of each other. The channels 29 formed by the cells 36 extend in the flow direction z. The cell structure 35 is formed by a plurality of patches 37 having a predetermined patch width 38.

[0056] Figure 4 An example of the burner head 11 is shown in a top view (end side). Figure 4In the example shown, the cell structure 35 is arranged linearly (non-concentrically) in the longitudinal direction x and the transverse direction y, such that multiple arrangements of cells 36 are adjacent to each other, in which the individual cells 36 are alternately oriented.

[0057] exist Figure 5 Another example of a burner head 11 is depicted in a top view (end-side). The flame retainer 21 also has a honeycomb structure 35, which (compared to...) Figure 4 (Different from the central axis) and arranged concentrically with the central axis 39 of the flame holder 21. Figure 5 In the example shown, the cells 36 are arranged in a ring, wherein, in each ring, the orientations of adjacent cells 36 alternate (i.e., in the radial direction r and against the radial direction r). Figure 5 Unlike the illustration, it is feasible to arrange the honeycomb 36 in a spiral shape. This has the advantage that the manufacturing of the honeycomb structure 35 can be significantly simplified. During manufacturing, corrugated sheet is covered with a smooth sheet and wound around a central pin to form a spirally oriented honeycomb structure 35.

[0058] Figure 6 Another example of the burner head 11 is shown, in which the flame holder 21 differs from the previous example; it is not disc-shaped (cylindrical) but rectangular, and especially square. In this example, the orientation of the honeycomb 36 is as follows: Figure 4 That's a linear arrangement.

[0059] This invention relates to a premixed burner 10 and a burner head 11 for the premixed burner 10, the premixed burner being used to burn a gas mixture consisting of fuel and air, which at least primarily comprises hydrogen. The burner head 11 has an inlet opening 17, a flame arrestor 18, an exit opening 22, and a flame holder 21. A flow 16 of the gas mixture is introduced through the inlet opening 17 into a flow channel 20 constructed 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 exit opening 22 downstream of the inlet opening 17 and particularly downstream of the flame arrestor 18 into the flame zone 23. A distinctive feature of this invention is the flame holder 21, which is arranged in or thereon in the exit opening 22 such that it occupies the cross-section 19 of the flow channel 20, and is a rigid, fiber-free, and wireless body 26. By employing a rigid and wireless design for the flame holder 21, its service life during hydrogen operation can be significantly extended.

[0060] List of reference numerals in the attached diagram:

[0061] 10 Premixed Burner

[0062] 11 Burner Head

[0063] 12 blowers (radial blowers)

[0064] 13 Premixed Section

[0065] 14 airflow

[0066] 15 hydrogen streams

[0067] Flow of 16 gas mixtures

[0068] 17 Enter the opening

[0069] 18 Flame arrestor

[0070] 19 Cross-section of the flow channel

[0071] Flow channel of 20 burner head

[0072] 21 Flame Holder

[0073] 22 Leave the opening

[0074] 23 Flame Zone

[0075] 24 ignition electrodes

[0076] 25 Flame Monitoring Units

[0077] 26 Flame Holder Body

[0078] 27 outflow side

[0079] 28 Inflow side

[0080] 29 channels

[0081] 30 outflow edge

[0082] 31 Micro-vortex

[0083] 32-channel width

[0084] 33 main body depth

[0085] 34-channel length

[0086] 35 honeycomb structure

[0087] 36 honeycomb

[0088] 37 stitches

[0089] 38-inch splice width

[0090] 39 central axis

[0091] 40 suction side

[0092] R radial direction

[0093] x longitudinal direction

[0094] y-direction

[0095] z Flow direction

Claims

1. A burner head (11) for a premixed burner (10), the premixed burner being used to burn a gas mixture consisting of hydrogen and air, the burner head having: - Through the inlet opening (17), the flow (16) of the gas mixture can be introduced into the flow channel (20) constructed in the burner head (11); - A flame arrester (18) is arranged in or at the inlet opening (17) in such a way that it occupies the cross section (19) of the flow channel (20); -The exit opening (22) allows the flow (16) of the gas mixture to be directed from the flow passage (20) of the burner head (11) through the exit opening downstream of the inlet opening (17) into the flame zone (23). as well as - A flame retainer (21), which is arranged in or thereon in a manner that occupies the cross section (19) of the flow channel (16), The flame holder (21) is constructed as a rigid, fiber-free and wireless body (26).

2. The burner head (11) according to claim 1, characterized in that, The main body (26) of the flame holder (21) has a honeycomb structure (35).

3. The burner head (11) according to claim 1 or 2, characterized in that, The body (26) of the flame holder (21) has an inflow side (28) facing away from the flame zone (23) and an outflow side (30) facing the flame zone (23), the inflow side and the outflow side being fluidly connected to each other via a plurality of channels (29).

4. The burner head (11) according to any one of the preceding claims, especially according to claim 3, is characterized in that, The channel (29) in the body (26) of the flame holder (21) extends from the inflow side (28) to the outflow side (39) in the flow direction (z).

5. The burner head (11) according to any 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. The burner head (11) according to any one of the preceding claims, especially according to claim 5, is characterized in that, The channel width (32) is less than the channel length (34), and preferably the channel width (32) is less than 1 / 10, especially less than 1 / 20, of the channel length (34).

7. The burner head (11) according to any one of the preceding claims, characterized in that, Each of the channels (29) has a channel width (32) of less than 0.9 mm, preferably less than 0.7 mm, and particularly preferably less than 0.5 mm.

8. The burner head (11) according to any one of the preceding claims, characterized in that, Each of the channels (29) has a channel length (34) greater than 3 mm, preferably greater than 5 mm, and particularly preferably greater than 10 mm.

9. The burner head (11) according to any one of the preceding claims, characterized in that, The flame arrester (18) and the flame retainer (21) arranged upstream are constructed identically.

10. The burner head (11) according to any one of the preceding claims, characterized in that, The flame holder (21) is made of metal and / or ceramic.

11. The burner head (11) according to any one of the preceding claims, characterized in that, The cellular structure (35) is formed by multiple adjacent cells (36).

12. The burner head (11) according to any one of the preceding claims, characterized in that, The body (26) of the flame holder (21) is constructed at least substantially cylindrically in a manner that defines a central axis (39), wherein the honeycomb (36) is preferably arranged concentrically or spirally with the central axis (39) of the body (26) of the flame holder (21).

13. The burner head (11) according to any one of the preceding claims, characterized in that, The channel (29) formed in the body (26) extends only in the direction of the flame holder depth (33) of the body (26).

14. The burner head (11) according to any one of the preceding claims, characterized in that, The gas mixture contains a share of other fuel gases of up to 35% by volume, particularly up to 20% by volume, wherein the fuel gases are, for example, a mixture of natural gas, a mixture of propane, and / or a mixture of biogas.

15. A premixed burner (10) for burning a gas mixture consisting of hydrogen and air, having a burner head (11) according to any one of the preceding claims.

Images