Heating element and device for heating gases

Abstract

The present invention relates to a heating element (100) for heating gases, comprising a body portion (108) which extends along a conduction direction (L) and is formed from at least one conductor track (10) made of an expanded metal having a plurality of strands (12), and comprising contacting portions (110a, 110b) for connecting to a power source (112), which contacting portions are provided at respective ends of the body portion (108) which are opposite one another relative to the conduction direction (L). The invention further relates to a device for heating gases, comprising at least one such heating element, and to a method for heating gases by means of such a device.

Description

[0001] 222368PDE / MLHHmna 1

[0002] Heating element and device for heating gases

[0003] Description

[0004] The present invention relates to a heating element for heating gases and to a device for heating gases, which comprises at least one such heating element.

[0005] Several scenarios are conceivable in which gases need to be heated on an industrial scale. A non-limiting example is the heating of ammonia, particularly for reforming or cracking. Ammonia, due to its structure and chemical formula NH3, is known to bind large quantities of hydrogen and is relatively easy to handle. In particular, it has a boiling point of only -33 °C and is therefore much easier to liquefy and thus transport or handle than atomic hydrogen. This makes it an ideal carrier medium for transporting large quantities of hydrogen over long distances by ship, a sector that is expected to see significant growth due to the global shift towards renewable energies and the associated need for storage methods, especially for green hydrogen.In this context, ammonia produced using sustainably generated energy, for example in locations with high solar irradiance using photovoltaic systems, can be stored and transported in order to be used as an energy carrier in other locations and / or at other times.

[0006] To break down the ammonia transported in this way back into its atomic components, or to release the hydrogen it contains for further use including energy production, various techniques are known, which include catalysis.222368PDE / MLHHmna 2

[0007] While these processes can be carried out, they always require heating the ammonia. Although the development of novel low-temperature catalysts is underway, temperatures above 500 °C are generally still necessary to efficiently decompose ammonia into molecular hydrogen and nitrogen. Therefore, there is a need for efficient heating devices and methods to heat ammonia appropriately and efficiently. It should be explicitly noted that such heating elements and devices are not limited to the treatment of ammonia; in principle, any gas can be heated with them.

[0008] An example of such an electric heating element is known from US 12,023,643 B1, in which an electrically conductive grid structure produced by a 3D printing process is used as a heating element to heat a corresponding gas by applying an electric current. However, such 3D-printed heating elements are relatively expensive and complex to manufacture, or, due to their manufacturing method, can only be produced in small quantities per printing device and time unit.

[0009] Accordingly, there is a need for an alternative heating element for heating gases that enables simple and cost-effective manufacturing and thus the production of high quantities, while still achieving reliable and energy-efficient heating of the respective gases.

[0010] To solve this problem and to overcome the disadvantages of the prior art discussed above, a novel heating element for heating gases is proposed according to the invention, which comprises a body section extending along a conductor direction, formed from at least one conductor track made of expanded metal with a plurality of webs, and contact sections provided at each opposite end of the body section for connecting to a power source.

[0011] This includes applying a voltage between the two contact sections, which can trigger the flow of a current through the heating element. This, in turn, will lead to the generation of Joule heating and thus to the heating of the heating element due to the finite electrical resistance of at least one conductor.

[0012] According to the invention, the proposed use of expanded metal, which is significantly easier and faster to produce than with 3D printing, allows for the creation of an alternative heating element that is considerably cheaper and easier to manufacture in large quantities while offering comparable heating performance and operational efficiency. It should be noted that expanded metal is essentially a sheet-like or web-shaped metal structure in which shear cuts and plastic stretching create openings at the cut points. These openings lie between the resulting ribs of the expanded metal and thus allow the gas to be heated to flow three-dimensionally through the corresponding section of the heating element. Simultaneously, a sufficiently high heating current can be conducted, and the gas to be heated can be in contact with the ribs over a large area for optimal heating efficiency.

[0013] It should be noted at this point that the direction of the conductor in the body section does not have to be completely straight, but that variants according to the invention are also conceivable in which curved, bent or angled sections are provided, so that corresponding body sections can extend between the contact sections in several dimensions in a substantially freely configurable manner.

[0014] Care must be taken to ensure that no areas with excessively high ohmic resistance to the heating currents occur within the body section, as these could create so-called hotspots. In these areas, temperature spikes would occur due to increased Joule heating, potentially leading to deterioration of the metal material and even burn-through. To prevent the formation of such zones, see 222368PDE / MLHHmna 4

[0015] among other things, the extent of node areas between the webs of the expanded metal and a cross-section thereof, relating to the direction of conduction of the body section, shall each be at least as large as the width and / or the thickness of the webs in a cross-section thereof, wherein the extent of the node areas, relating to the direction of conduction, may preferably be at least 1.8 times, more preferably at least 2 times, more preferably at least 3 times as large as the width and / or the thickness of the webs.

[0016] Due to the manufacturing process, the ribs of the expanded metal can have square, particularly rectangular, cross-sections, and / or the cross-sectional area of ​​the ribs and / or the expansion of the expanded metal over the heating element can vary to create locally different resistance zones. In this way, areas can be created in a controlled manner where, due to increased ohmic resistance, locally elevated temperatures are achieved during operation of the heating element, if this is desired for optimizing the process parameters of the respective heating element. For example, a different temperature of the heating element might be desired in a region where a gas to be heated is just entering the heating element than in downstream regions where the gas to be heated has already been preheated to a certain temperature after passing through part of the heating element.In such a case, the corresponding parameter of the heating element would be varied across the direction of the flow. However, varying corresponding parameters in other directions is also conceivable, for example, to create a temperature gradient between an edge region and a central region of the body section. It should also be noted that the use of square and, in particular, rectangular cross-sections for the expanded metal webs, as also mentioned, can achieve turbulent flow of the gas to be heated and thus improved heat transfer. Furthermore, such a cross-section has a larger surface area relative to its volume than, for example, a circular cross-section, which can also increase the efficiency of heating processes. 222368PDE / MLHHmna 5.

[0017] While it is theoretically possible to create a suitable heating element by appropriately shaping a single conductor track from expanded metal in three dimensions, for example by appropriately rolling or folding it, embodiments are also conceivable in which the body section comprises a plurality of conductor tracks that are interconnected at connection points. In particular, all of the aforementioned conductor tracks can be made of expanded metal and brought into the overall shape of the body section by appropriate shaping of the individual conductor tracks and suitable connections between them.

[0018] Furthermore, in certain embodiments of the invention, such a heating element can comprise differently shaped conductor tracks, in particular smooth and embossed conductor tracks, which are preferably adapted such that they exhibit essentially the same electrical resistance. Accordingly, by matching the electrical resistance of the multiple conductor tracks along the conduction direction of the body section to one another, the formation of local temperature peaks due to differing Joule heating can also be counteracted in this way, if desired.Various measures are conceivable to achieve the appropriate adjustment of the electrical resistances of the individual conductor tracks to one another, for example a variation of mesh sizes, i.e. a reduced mesh width of smooth tracks or a larger mesh width of embossed tracks, a reduction of the width of the nodes of the smooth tracks compared to the embossed tracks, a reduction of the material thickness of smooth tracks, a reduction of the width of the smooth tracks themselves, a reduced web width or even the use of a different material with a higher specific resistance in smooth tracks.

[0019] Furthermore, at least some of the conductor tracks may be embossed and adjacent embossed conductor tracks may each be offset by an substantially half division, and / or the embossed conductor tracks may be substantially geometrically identical.222368PDE / MLHHmna 6

[0020] be designed. In this way, it becomes possible to connect a plurality of embossed conductor tracks to each other in a suitable manner, without local mechanical weak points of the heating element occurring, since sufficiently dimensioned connection areas can be provided in each case.

[0021] Furthermore, in the connection areas already mentioned between adjacent conductor tracks, a material-bonded connection can be provided, in particular a soldering or a welding; however, in principle, form-fit connections or calendering are also possible.

[0022] Although different materials can be used for the expanded metal in heating elements according to the invention, and in particular different materials within the same heating element in different conductor tracks, provided that the corresponding materials have sufficient heat resistance and suitable electrical and mechanical properties, the expanded metal can in particular consist of or comprise a high-alloy stainless steel and / or have a specific electrical resistance of at least 0.8 Q / m*m 2 exhibit such high-alloy stainless steels, which are suitable for the intended application in terms of their thermal, electrical and mechanical properties, are also relatively inexpensive to obtain and easy to process, and exhibit high resistance to corrosion, which is advantageous when heating with corrosive gases and especially ammonia.

[0023] Furthermore, it should be noted that although the body section of the heating element according to the invention can in principle have any external shape and can, for example, be circular-cylindrical, it is also shown that in particularly preferred embodiments the body section can be formed with a rectangular, in particular square, cross-section perpendicular to the direction of the conductor.

[0024] Furthermore, it should be noted that the electrical contact sections mentioned refer to a stretching direction of the expanded metal of 222368PDE / MLHHmna 7

[0025] At least one of the conductor tracks of the body section can be opposite each other, so that in this case the conduction direction will correspond to the extension direction of the respective conductor track. Of course, other orientations of the conductor track are also conceivable; for example, the current direction could also be perpendicular to the extension direction, or several conductor tracks could be combined in a single heating element whose extension directions are oriented differently with respect to the conduction direction.

[0026] Furthermore, it should be noted that in the area of ​​the contact sections, a compression or pinching of at least one conductor track may occur, which, particularly in embodiments with a plurality of conductor tracks, simplifies the contacting of these overall and contributes to a compact size in this area of ​​the corresponding heating element.

[0027] Furthermore, it should be noted that a coating may be provided, at least partially, in the body section of the heating element according to the invention. This coating may preferably comprise nickel, iron, and / or cobalt, which may exhibit catalytic properties for specific applications of the heating element. Alternatively, such coatings may also be incorporated into a housing of a device according to the invention in a different manner, which will be described below.

[0028] Depending on the desired shape of the heating conductor, in certain embodiments the body section can be cut out from a blank in order to give the heating conductor its final shape between the contact sections.

[0029] Furthermore, in heating elements according to the invention, the extension of the body section can meander in two or three dimensions, i.e., the direction of conduction does not have to be completely straight in order to achieve the 222368PDE / MLHHmna 8

[0030] To be able to equip available installation spaces with a suitable heating element in the desired and optimal manner. Especially in such cases, manufacturing by cutting from a blank can be advantageous.

[0031] Such a device according to the invention for heating gases according to a further aspect of the present inventions comprises in particular at least one heating element of the type just described, at least one current source which is connected to the contacting sections of the at least one heating element in order to conduct a current through the heating element, and preferably a housing with a chamber in which one of the heating elements is received and electrically insulated.In this system, a chamber, whose design can be adapted to the shape of the corresponding heating element and which, for example, can have a rectangular or square internal cross-section, forms a flow path for the gas to be heated. The gas must be supplied and discharged in a suitable manner, while three-dimensional flow through the heating element within the chamber is enabled by its design with conductive tracks made of expanded metal. Alternatively, such devices can be operated independently of corresponding housings serving as flow guides in other suitable containers.

[0032] It can be advantageous to form multiple chambers within a single housing, each containing a heating element, where the chambers can form a series or multiple parallel flow paths. In particular, with a series arrangement of the corresponding chambers in a limited installation space, an extended heating path for the gas can be created by repeatedly routing it back and forth through the chambers. The series-connected heating elements can each have different properties and / or operating parameters, for example, they can be operated at different temperatures.

[0033] It should also be noted that the electrically insulating mounting of the heating element can be achieved by means of an insulating support element, in particular an insulating disc, or a honeycomb structure.

[0034] Furthermore, it should be noted that the device according to the invention may also include a catalyst which may be arranged upstream and / or downstream of the at least one heating element in the direction of gas flow and / or may be arranged in the area of ​​the heating element.

[0035] According to a further aspect, the present invention relates to a method for heating gases using a device of the type just described, comprising passing an electric current from the at least one power source through the at least one heating element and passing the gas through the at least one chamber of the housing to heat it. The gas to be heated, which accordingly comes into contact with the at least one heating element of the device according to the invention, can be or contain, in particular, ammonia, methanol, or synthesis gas, thereby giving rise to the advantages and application possibilities described above, and wherein the corresponding gases can, in particular, be produced using renewable energies as storage media without CO2 emissions.

[0036] Further features and advantages of the present invention will become even clearer from the following description of an embodiment thereof, when viewed together with the accompanying figures. These show in detail:

[0037] Figures 1a and 1b schematic representations of a conductor track formed from expanded metal of a heating element according to the invention; 222368PDE / MLHHmna 10

[0038] Figures 2a and 2b show a sectional view and an isometric view of a schematic representation of a heating element according to the invention with a plurality of conductor tracks;

[0039] Figure 3 shows a schematic isometric representation of a device according to the invention for heating gases; and

[0040] Figures 4 to 7 show further variants of heating elements according to the invention.

[0041] Figures 1a and 1b schematically show a conductor 10 of a heating element according to the invention for heating gases, formed from expanded metal, which will be described further below with reference to Figures 2a and 2b. Figures 1a and 1b show that the conductor 10, made of expanded metal produced by locally cutting and stretching a metal sheet, comprises a plurality of webs 12 which, in this example, enclose diamond-shaped meshes 14, which in turn have node areas 16 at their corners.

[0042] The corresponding parameters of the expanded metal can also be seen in Figure 1b; in particular, the mesh width is denoted by MB, the mesh length by ML, the web width by SB, and the web thickness by SD. Furthermore, the node length is denoted by KL, and the stretching direction is indicated by R. In the present application, in which such expanded metal is subjected to an electric current, it is evident that the extent of the node regions 16 must be sufficiently large to prevent local temperature hotspots. In this way, currents supplied by the adjacent webs 12 can be guided through the node regions 16 in such a manner that the local electrical resistance does not lead to an undesirably high temperature increase in the expanded metal at that point.

[0043] Regarding the specific design of a heating element according to the invention, which comprises a plurality of such conductor tracks 10, reference is now made to Figures 2a and 2b, which show such a heating element 100 in a schematic way in a cross-section and an isometric representation, respectively.

[0044] It can be seen that in this specific embodiment, the multiple conductor tracks 10 comprise differently shaped types of conductor tracks, in particular embossed conductor tracks 102, which have a corresponding wave pattern, and smooth conductor tracks 104, which are each provided between two adjacent embossed conductor tracks. The individual conductor tracks 102, 104 are connected to each other in respective connection areas 106, and the entire body section 108 of the heating element 100 formed by the conductor tracks 102, 104 has a square cross-section in one cross-section with respect to its extension direction L.

[0045] Furthermore, it should be noted that contact sections 110a, 110b are provided at the opposite ends of the body section 108 of the heating element 100, in which a corresponding current source 112, shown here only schematically, is connected, so that the direction of extension L corresponds to a direction of the corresponding heating current. In the area of ​​contact sections 110a, 110b, the several conductor tracks 102, 104 were crimped or crimped to simplify their electrical and mechanical contact.

[0046] It should also be noted that additional measures may have been taken in the area of ​​the contact sections 110a, 110b to reduce the electrical resistance in the connection area of ​​the heating element 100 to the power source 112, thereby enabling lower surface temperatures at this position than in the area of ​​the expanded metal webs. For example, additional layers of expanded metal or sheets could be integrated to increase the conductor cross-section, or other measures could be taken.

[0047] Additional material can be added, for example more solder material, an additional clamp could be slid over the relevant contact and / or a different cutout could be used in this contact area and folded in.

[0048] Furthermore, it should be added that various measures may have been taken to prevent local excessive heating of the heating element 100, for example by appropriately increasing the material density in the connection areas 106, which may be produced by soldering or welding, and / or by equalizing the electrical resistances of the embossed and smooth conductor tracks 102, 104, for example by different material thicknesses or mesh sizes of the corresponding expanded metal tracks.

[0049] Furthermore, reference is made to Figure 3, which shows a schematic view of a device 200 according to the invention for heating gases. The device 200 comprises an outer housing 202 in which a total of three gas-tight chambers 204 are defined in respective inner housings, each of which contains one of the heating elements 100 from Figures 2a and 2b and is electrically insulated.

[0050] The device 200 further comprises a current source (not shown) which is connected to the respective contact sections of the individual heating elements 100 and supplies a corresponding heating current to the individual heating elements 100.

[0051] By allowing the gas to be heated to flow through the respective chambers 204 either in a parallel or series manner, while the heating elements 100 are supplied with electric current, heating of the corresponding gas can be achieved, and catalyst agents can also be integrated into the chambers 204 of the heating elements 100 or placed upstream and / or downstream of them, in order not only to heat the corresponding 222368PDE / MLHHmna 13

[0052] not only to induce or promote desired chemical reactions, but also to control gases.

[0053] While in the embodiment shown in Figure 3 only heating elements 100 are used in the manner described above, which extend in a purely linear manner according to the variant shown in Figures 2a and 2b, it should be noted with reference to the further Figures 4 and 5 that corresponding heating elements can also be designed in any other shape and in particular meandering in two or three dimensions in order to make optimal use of the available space.

[0054] Figure 4 shows a further variant of a heating element according to the invention, designated by reference numeral 300, whose body section 308 extends in a meandering pattern in two dimensions between the two contact sections 310a and 310b. Given the shape of the body section 308 of the heating element 300, it is evident that it may preferably have been cut from a previously provided blank, with the free sections between the individual curves of the body section 308 being removed from the blank in particular. Furthermore, it should be noted that the heating element 308 rests on a holder 314, and a second, identical heating element 300b is also indicated, which is accommodated within the holder 314.In this way, a three-dimensional structure is created from the two individually contacted heating elements 300 and 300a, which can be exposed to gas to be heated from all sides, and the holder 314 can also serve as a flow guide element.

[0055] Furthermore, as shown in Figure 5 by means of the third variant of a heating element 400 according to the invention, it is also possible to design the body section 408 directly in a meandering manner in three dimensions and to support it by means of a suitable holder 414, which, in addition to plate-shaped elements, also includes pins extending perpendicularly thereto, so that a space-filling 222368PDE / MLHHmna 14

[0056] A structure is created which only requires a single contact via the contact sections 410a and 410b.

[0057] It should be noted that a corresponding holder can generally be made of silicon nitride, aluminum dioxide, etc. in the form of plates, fibers and / or pins and similar materials, and can therefore correspond to the insulating support element mentioned above.

[0058] Figure 6 further shows an embodiment of a heating element 500 in which the body section 508 extends helically between the two contact sections 510a and 510b and could thus, for example, be arranged around a central axis in a tubular receiving space. A similar arrangement applies to the variant 600 from Figure 7, in which a cylindrical shape is formed by a meandering design of the body section 608 between the contact sections 610a and 61b, which also remains permeable to flow from all sides.

Claims

222368PDE / MLHHmna 15 Claims 1. Heating element (100) for heating gases, comprising: - a body section (108) extending along a conductor direction (L), which is formed from at least one conductor track (10) made of expanded metal with a plurality of webs (12); and - contact sections (110a, 110b) provided at each end of the body section (108) opposite each other with respect to the direction of the conductor (L) for connection to a power source (112).

2. Heating element (100) according to claim 1 , wherein an extent of node regions (16) between the webs (12) of the expanded metal and a cross-section thereof with respect to the direction of conduction (L) are each at least as large as the width (SB) and / or the thickness (SD) of the webs (12) in a cross-section thereof, wherein the extent of the node regions with respect to the direction of conduction (L) is preferably at least 1.8 times, further preferably at least 2 times, further preferably at least 3 times as large as the width (SB) and / or the thickness (SD) of the webs (12).

3. Heating element (100) according to one of the preceding claims, wherein the webs (12) each have square, in particular rectangular, cross-sections and / or wherein the cross-sectional area of ​​the webs (12) and / or the stretching of the expanded metal over the heating element (100) varies in order to generate locally different resistance areas.

4. Heating element (100) according to one of the preceding claims, 222368PDE / MLHHmna 16 wherein the body section (108) comprises a plurality of conductor tracks (102, 104) which are connected to each other in connection areas (106).

5. Heating element (100) according to claim 4, wherein differently shaped types of conductor tracks (102, 104) are included, in particular smooth (104) and embossed (102) conductor tracks, which are preferably adapted such that they have essentially the same electrical resistance.

6. Heating element (100) according to one of claims 4 and 5, wherein at least some of the conductor tracks (102) are embossed and adjacent embossed conductor tracks (102) are each shifted by substantially half a division and / or the embossed conductor tracks (102) are essentially geometrically identical.

7. Heating element (10) according to one of the 4 to 6, wherein in the connection areas (106) there is a material-bonded connection between adjacent conductor tracks (102, 104), in particular a soldering or a welding.

8. Heating element (100) according to one of the preceding claims, wherein the expanded metal consists of or comprises a high-alloy stainless steel and / or has a specific electrical resistance of at least 0.8 Q / m*m 2 exhibits.

9. Heating element (100) according to one of the preceding claims, wherein the body section (108) is formed with a rectangular, in particular square, cross-section perpendicular to the direction of conduction (L).

10. Heating element (100) according to one of the preceding claims, 222368PDE / MLHHmna 17 wherein the contact sections (110a, 110b) are opposite each other with respect to a stretching direction of the expanded metal of at least one of the conductor tracks (102, 104) of the body section (108).

11. Heating element (100) according to one of the preceding claims, wherein in the area of ​​the contact sections (110a, 110b) there is a compression or crushing of the at least one conductor track (102, 104).

12. Heating element (100) according to one of the preceding claims, wherein a coating is provided at least section by section in the area of ​​the body section (108), which preferably comprises nickel, iron and / or cobalt.

13. Heating element (100) according to one of the preceding claims, wherein the body section (108) is cut out from a blank.

14. Heating element (300, 400) according to one of the preceding claims, wherein the extension of the body section (308, 408) meanders in two or three dimensions.

15. Device (200) for heating gases, comprising: - at least one heating element (100) according to one of the preceding claims, and - at least one power source (112) which is connected to the contact sections (110a, 110b) to conduct a current through the at least one heating element (100).

16. Device (200) according to claim 15, further comprising: - a housing (202) with at least one chamber (204) in which one of the heating elements (100) is received and electrically insulated, 222368PDE / MLHHmna 18 wherein at least one chamber (204) forms a flow path for the gas to be heated.

17. Device (200) according to the preceding claim, wherein a plurality of chambers (204) are formed within the housing (202), in which a respective heating element (100) is received, wherein the chambers (204) form a serial or several parallel flow paths.

18. Device (200) according to one of claims 15 to 17, wherein the electrically insulating mounting of the at least one heating element (100) is provided by means of an insulating support element, in particular an insulating disc, or a honeycomb body.

19. Device (200) according to one of claims 15 to 18, further comprising a catalyst which is arranged upstream and / or downstream of the at least one heating element (100) in the direction of gas flow and / or is arranged in the area of ​​the heating element (100).

20. Method for heating gases using a device (200) according to any one of claims 15 to 19, comprising: - Conducting an electric current from the at least one power source (112) through the at least one heating element (100); and - guiding the gas through the at least one chamber (204) of the housing (202).

21. Method according to claim 20, wherein the gas to be heated is or contains ammonia, methanol or synthesis gas.

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