Heating device

Abstract

The invention relates to a heating device (1) comprising at least one heating resistor (3) with a plurality of resistive heating elements configured as plate elements (4).

Description

[Technical Field]

[0001] The present invention relates to a heating device comprising at least one heating resistor comprising a plurality of resistive heating elements.

[0002] Furthermore, the invention relates to a thermal treatment system comprising a treatment chamber for an object to be treated and a heating device arranged at least partially within the thermal treatment system. [Background technology]

[0003] Electric heating of industrial furnaces using resistance heating is well known. To do this, an electric current is passed through a heating element with a corresponding electrical resistance, which releases heat. This often involves the use of rod-shaped heating elements. Some furnace types, such as pusher-type furnaces, require a high energy density. Therefore, gas heating systems are usually preferred for these furnaces. However, due to environmental reasons and the availability of fuel gases, efforts are being made to replace gas heating systems as much as possible. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE INVENTION It is an object of the present invention to provide a means for supplying exothermic energy to a thermal processing system. [Means for solving the problem]

[0005] The object of the invention is achieved with the initially mentioned heating device, in which the resistive heating element is configured as a plate element.

[0006] Furthermore, the object of the present invention is achieved by the above-mentioned heat treatment system, in which the heating device is constructed according to the present invention.

[0007] The advantage of this is that the plate elements can be used to construct a heat generating resistor that offers a relatively low flow resistance to the gas flowing therethrough, i.e., the pressure loss caused by the heat generating resistor can be minimized, which in turn is particularly advantageous for heat treatment systems or furnaces that rely heavily on convection for heat transfer, such as bell-type furnaces.

[0008] According to one embodiment of the present invention, it may be provided that one, some or all of the plate elements have a serpentine course, which allows for a higher heat output while still allowing for a relatively compact design, which also makes it easier to fit the heating device into the installation space of an existing heat treatment system.

[0009] To further improve these effects, it can be provided according to embodiments of the invention that the serpentine course has several bends, and if necessary the parts of the plate element between these bends have parallel courses, which in particular allows for improved space utilization.

[0010] In order to better integrate the heating device or the plate element into the thermal treatment system, it can be provided according to an embodiment of the invention that receiving elements for fastening elements are arranged in some or all of the bends, which allows a compact design of the heating device without the risk of unintentional contact between the plate elements or parts of the plate element, and also allows higher flow velocities in the thermal treatment system.

[0011] According to one embodiment of the present invention, the serpentine course is configured as a double serpentine, which allows for simpler contact of the plate elements in a single area of ​​the heat generating register and allows for an increased heat output per plate element to be achieved.

[0012] According to another embodiment of the invention, the plate elements are bent in the shape of a vane, which means that in addition to the "heat generating" function, the plate elements can also have the function of a flow conduit.

[0013] According to another embodiment of the invention, several beads are arranged on at least some parts of the plate element, which allows the plate element to have an improved stability even with a small thickness, thereby preventing or reducing shaking of the plate element in the flow, which also serves to improve the heat transfer between the flowing medium and the plate element.

[0014] According to a further embodiment of the present invention, a plate element having a plate thickness between 0.5 mm and 5 mm can be provided, thereby further improving the above-mentioned effect of low pressure loss.

[0015] In addition to the aforementioned double meander configuration for extending the heating conductor length, according to another embodiment of the invention, it is also possible for some or all of the plate elements to be electrically connected in series to form heating groups.

[0016] According to one embodiment of the present invention, it can be provided that several plate elements connected in series are arranged one above the other and that electrical insulating elements are arranged between the plate elements. Re-stacking allows for a compact design.

[0017] According to an embodiment of the present invention, the three heating groups can also be electrically combined with each other in a star or delta connection, thereby increasing the total heating output of the heating resistor.

[0018] According to one embodiment of the thermal treatment system, it is provided that the heating device is arranged in the flow path for the gaseous medium, in particular in the flow path for the recirculating air, in order to better transfer the exothermic energy.

[0019] This flow path can also be formed by a guide device with several guide vanes, so that according to a further embodiment of the heat treatment system, it can also have a guide device with several guide vanes, the heating device according to the invention being arranged between several guide vanes, and it is also advantageous if some plate elements of these heating devices are bent in a vane-like manner and thus act like additional guide vanes.

[0020] Another embodiment of the thermal treatment system may further include a gas-operated heating device. The combination of electrical and gas heating allows for a reduction in the NOx content in the exhaust gas during non-optimal stages, such as during holding stages with reduced burner power. The hybrid design of the thermal treatment system allows these stages to be operated with reduced burner power using the heating device according to the present invention, or the gas burner not to be operated during these stages. It is also possible to reduce the total heat output of the gas burner and provide the missing heat output through the heating device. This allows the gas burner to operate in the optimal range for a longer period of time, thereby reducing the NOx level in the exhaust gas.

[0021] According to further embodiments of the heat treatment system, the heat treatment system is configured as a pusher-type furnace, a bell-type furnace or a chamber furnace.

[0022] For a better understanding of the invention, it will be explained in more detail with the aid of the following figures.

[0023] They are shown in simplified diagrammatic representation. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 shows an embodiment of the heating device as seen obliquely. [Figure 2] FIG. 2 shows a plate element of an embodiment of the heating device in an oblique view. [Figure 3] FIG. 3 shows a plate element of a heating device according to a further embodiment. [Figure 4] FIG. 4 shows a plate element of a heating device in another embodiment. [Figure 5] FIG. 5 shows a view of the heating device in the direction of flow of the gas to be heated. [Figure 6] FIG. 6 shows the details of the heating device. [Figure 7] FIG. 7 shows further details of the heating device. [Figure 8] FIG. 8 shows portions of a thermal processing system in one embodiment. [Figure 9] FIG. 9 shows a vertical cross section of the heat treatment system according to the embodiment. [Figure 10] FIG. 10 shows a portion of a thermal processing system according to a further embodiment. [Figure 11] FIG. 11 shows a portion of a thermal processing system in accordance with another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] By way of introduction, it should be noted that in the various described embodiments, identical parts are given the same reference symbols or the same component designations. The disclosure contained throughout the description can be similarly transferred to identical parts having the same reference symbols or the same component designations. Also, location information selected in the description, such as top, bottom, side, etc., refers directly to the described and illustrated figures, and if the location changes, these location information must be transferred to the new location accordingly.

[0026] FIG. 1 shows a heating device 1.

[0027] The heating device 1 can be used, in particular, in electrically heated convection furnaces or to convert furnaces with burner heating into at least partially electrically heated furnaces. The heating device 1 can be used, for example, in so-called fixed furnaces or continuous furnaces, i.e., so-called industrial furnaces. An industrial furnace is defined as a walled space in which heat is supplied to an object, in particular to enable a process to be carried out in or on the object. The object can be a product, such as a sheet or blank, a block, or a raw material, such as metal. This process can be, for example, a specific reaction in, on, or with the object, such as melting the object, a phase transformation, hardening of a metal object, or tempering of the object. This list is merely illustrative and should not be understood as limiting. In general, the heating device 1 can be used in a heat treatment system 2 to thermally treat objects, i.e., at high temperatures, batchwise, or continuously. Some examples of heat treatment systems 2 are shown in Figures 8 to 11.

[0028] Industrial furnaces within the meaning of the invention are in particular furnaces used in metallurgy or in the treatment of inorganic objects or objects made exclusively from inorganic raw materials.

[0029] It is also noted that, purely by way of example, the heating device 1 can be used on objects made of aluminum or aluminum alloys, or generally non-ferrous metals or steel.

[0030] The heating device 1 comprises at least one heating resistor 3. The heating resistor 3 comprises or consists of several resistive heating elements. When an electric current is passed through the heating resistor 3, heat is generated by the electrical resistance. This principle is known per se, so to avoid repetition, reference is made to the relevant state of the art.

[0031] The resistive heating element is configured as a plate element 4 or a metal plate element. Such a plate element 4 is shown in FIG.

[0032] A sheet metal within the meaning of the present invention is a metal product whose width and length are much greater than its thickness. The plate element 4 is therefore understood to be a flat piece of metal material of the same thickness throughout, except for tolerances, and bounded on two opposite sides by flat surfaces extending in relation to the thickness.

[0033] In this respect, it should be mentioned that all or some of the resistive heating elements of the heating device 1 can be of the same construction. This is the preferred embodiment of the heating device 1, but it is also possible within the scope of the present invention for different plate elements 4 to be installed in the heating device 1. They can be located in the same heating device 1 or, in the case of several heating devices 1 in the heat treatment system 2, in different heating devices 1. The differences can be in the plate thickness 5, the current-carrying length, the number of bends, the material, etc., or a combination thereof.

[0034] In the following, only one plate element 4 will be described in more detail. However, the statements in this respect can be applied to further or all plate elements 4 of the heating device 1.

[0035] The plate element 4 in the embodiment shown in FIG. 2 is preferred. However, the plate element 4 can also look completely different. For example, in its simplest form, the plate element 4 can be a straight, flat bar. However, in a preferred embodiment, the plate element 4 has a serpentine course with several bends 6 (also called apex regions) and portions 7 between the bends 6. The number of bends 6 and corresponding portions 7 shown in FIG. 2 is not to be understood as limiting. This particular number may depend, inter alia, on the desired total heat output and / or the installation situation of the heating device 1. For example, the plate element 4 may have 2 to 50 bends 6, in particular 6 to 45, for example 10 to 40 bends 6.

[0036] The portions 7 may extend obliquely relative to one another such that the distance 8 between the portions 7 increases starting from the respective bends 6. However, in a preferred embodiment, the portions 7 of the plate element 4 between the bends 6 may have parallel courses, as shown in Figure 2.

[0037] The distance 8 between the portions 7 may be between 1 mm and 50 mm.

[0038] The width 9 of the portion 7 may be between 2 mm and 100 mm, in particular between 10 mm and 60 mm.

[0039] The plate thickness 5 can be between 0.5 mm and 5 mm, in particular between 1 mm and 2 mm. The plate element 4 is therefore relatively thin and therefore has low flow resistance. Figure 5 shows the heating device 1 in the flow direction (perpendicular to the plane of the paper).

[0040] The total length of the plate element 4 in the direction of current flow can be between 100 mm and 3 m.

[0041] The plate elements 4 can be manufactured by forming a straight blank, or the plate elements 4 can be cast into the desired shape, but preferably the plate elements 4 are cut out from a metal sheet by a cutting process, for example with a laser or a water jet.

[0042] The plate elements 4 comprise or consist of at least one metallic material and can be made, for example, of Kanthal™, Nikrothal™ or Inconel™ alloys.

[0043] The serpentine course of the plate element 4 can also have different configurations, as shown by way of example in Figures 3 and 4. For example, instead of the rounded bends 6, right-angled transitions 10 can be provided between the sections 7, as shown in Figure 3. Furthermore, it can be provided that the serpentine course has, for example, a double serpentine configuration (Figure 4), in which two electrical connection areas of the plate element 4 are arranged next to each other.

[0044] To form the heat generating resistor 3, the plate element 4 can be arranged on a receiving element, such as a frame element 11, as shown by way of example in Figures 1, 5 and 6. In principle, the plate element 4 can be connected to the receiving element or arranged in or on the receiving element in various ways. The receiving element can be provided with, for example, groove-shaped recesses into which the plate element 4 can engage. If necessary, these recesses can be undercut.

[0045] However, in the illustrated embodiment, the plate elements 4 are stacked one on top of the other or suspended next to each other within the frame element 11, depending on the installation position. In one exemplary embodiment, the plate elements 4 can be provided with receiving elements 12 for fastening elements 13 (also called holding elements) of the frame element 11. The receiving elements 12 can be configured as receiving lugs, for example, arranged in the top region of the bends 6, as shown in FIG. 2. Preferably, each bend 6 can be provided with such a receiving element 12, so that the plate elements 4 can be connected to the frame element 11 at each bend 6. For connection or attachment, the frame element 11 can have rod-shaped fastening elements 13, which protrude through openings in the receiving elements 12 of the plate elements 4. In other words, the plate elements 4 can be screwed into the frame element 11, as can be seen, for example, in FIG. 5 or FIG. 6. The rod-shaped fastening elements 13 can be held by end plates 14 of the frame element 11.

[0046] The receiving elements 12 of the plate element 4 can also be configured differently, as can be seen, for example, from FIG.

[0047] Preferably, the receiving element 12 is formed integrally with the remainder of the plate element 4 .

[0048] In order to arrange several plate elements 4 in a stack, insulating elements 15 are provided between the plate elements 4. The insulating elements 15 can be arranged to extend through the receiving element 12, so that the opening of the receiving element 12 can have a correspondingly large configuration. In a preferred embodiment, the insulating elements 15 are sleeve-shaped, so that the fastening elements 13 can be arranged to extend through the insulating elements 15. Thus, not only is electrical insulation between adjacent plate elements achieved via the insulating elements 13, but also electrical insulation with respect to the frame element 11 (or, in general, the receiving element with respect to the plate elements 4) can be achieved.

[0049] The insulating element 15 can consist of a material known as an electrical insulating element 15, with the constraint that it must also withstand the temperatures in the thermal treatment system 2. For this reason, the insulating element 15 is preferably designed as a ceramic element.

[0050] As can be seen from Figures 5 and 6, two structurally different sleeve-shaped insulating elements 15 can be used, which can be inserted into one another, which simplifies the assembly of the heating device 1 and the centering of the plate element 4.

[0051] For the preferred assembly of the heating device 1, the frame elements 11 can be provided in a first stage, but do not yet have an end plate 14 on at least one side. Next, first insulating elements 15 are placed on each fastening element 13. These first insulating elements 15 are supported on one of these end plates 14 and provide electrical insulation for this or these end plates 14. Next, the first plate element 4 is pressed in so that the fastening elements 13 protrude into the receiving elements 12. Centering of this plate element 4 is performed by the second insulating element 15, which has a cylindrical extension that can be received by the first insulating element 15, as best seen in Figure 6. The remainder of the heating resistor 3 is constructed by repeating these steps.

[0052] In principle, the electrical contact between the plate elements 4 can be made on opposite sides of the heating device 1. However, in a preferred embodiment, these connections are arranged on the same side of the heating device 1. In particular, so-called connection lugs 16, 17 can also be provided or arranged on and connected to the plate elements 4. In the case of an electrical connection on only one side, for example, plate elements 4 can be used that are in a double-serpentine configuration.

[0053] According to another embodiment example, it can also be provided that some or all of the plate elements 4 of the heating device 1 are electrically connected in series to form heating groups 18. The embodiment of the heating device 1 shown in Figure 1 has three such heating groups 18. The heating groups 18 can also be arranged on the same frame element 11, separated for example by intermediate plates 19 (see Figure 5).

[0054] To form a series connection of the plate elements 4, metallic current connection elements 19 are provided alternately in the end regions of the plate elements 4 (at the beginning and end of the plate elements 4), thereby conducting current from a plate element 4 in a first plane to a plate element 4 in the next plane. The heating groups 18 are therefore passed by the current in a zigzag pattern.

[0055] The current connection elements 19 are preferably also sleeve-shaped. They may have a cylindrical extension on one or both sides, which can be received by the adjacently arranged insulating element 15. The current connection elements 19 may also have a centering effect for centering the plate element 4.

[0056] 2 with reference to section 7, an embodiment of the heating device 1 may provide that beads 20 are arranged or formed in the plate element 4 at least in each section 7, in particular in all sections 7. The beads 20 may be produced by forming the sections 7. The beads 20 may have a depth of 0.5 mm to 3 mm.

[0057] All plate elements 4 of the heating device 1 can be connected in series. However, to increase the total heat output, according to an exemplary embodiment, the heating device 1 can have three heating groups 18, as shown in FIG. 1. These three heating groups 18 can be electrically connected in a star or delta configuration. Referring to FIG. 7, a star configuration of the three heating groups 18 is shown. Electrical connections 21-23 for the three phases P1, P2, and P3, as well as a star point connection 24, can be seen. These electrical connections 21-23 are then connected to a power supply unit 25 (see FIG. 1), through which power can be supplied to the heating register 3.

[0058] The heat treatment system 2 may have one heating device 1 or several heating devices 1 depending on the required heat output. For example, the heat treatment system 2 may have 1 to 20 heating devices 1.

[0059] As already explained, the heating device 1 is used in a heat treatment system 2 to heat a gaseous medium, such as circulating air, through which energy is then introduced into the object to be heat treated.

[0060] The heat treatment system 2 of the first embodiment is shown in detail in Figure 8. It comprises a treatment chamber 26 that accommodates at least one workpiece. Furthermore, the heat treatment system 2 comprises at least one heating device 1 (preferably several) according to the present invention. The heating device 1 can be arranged inside the treatment chamber 13 and / or outside the treatment chamber 13 and at least partially surround it. The at least one heating device 1 can be arranged at least partially, preferably entirely, within a flow path 27 within a housing 28 of the heat treatment system 2. In the illustrated embodiment, the heat treatment system 2 is a so-called pusher-type furnace.

[0061] The flow path 27 may be completely separated from the process chamber 26 via, for example, a gas baffle 29 .

[0062] The thermal treatment system 2 may also have further components corresponding to the state of the art, which will not be further mentioned in this description, but which a person skilled in the art will arrange in the thermal treatment system 2 accordingly as needed.

[0063] Depending on the heat treatment in the heat treatment system 2, the gaseous medium to be heated can be selected or configured, which is known to those skilled in the art and therefore does not need to be discussed further.

[0064] Generally, the heating device 1 has a power rating of at least 0.5 W / cm 2 , especially 0.5W / cm 2 to 25 W / cm 2 The energy density depends on the flowing medium, in particular the type of medium, the velocity of the medium and the temperature of the flowing medium.

[0065] 9 shows a portion of another embodiment of a heat treatment system 2, which is formed in the shape of a bell-type furnace. As in a pusher-type furnace, or in the heat treatment system 2 in general, a fan 30 or turbine may be provided to circulate the gaseous medium within the treatment chamber 26. The heating device 1 may be disposed in a flow path 27 formed centrally and above the fan 30.

[0066] The heating device 1 or one or more further heating devices 1 can also be arranged in a flow path 27 having a different configuration. For example, Fig. 10 shows a guide device for the medium to be circulated. The guide device has several guide vanes 31, between which the flow paths 27 are configured. The guide vanes 31 have a corresponding bending configuration in order to achieve a corresponding flow pattern.

[0067] Some plate elements 4 of the heating device 1 are arranged between these guide vanes 31 or at least between some of the guide vanes 31. As can be seen from Figure 10, the plate elements 4 are bent in a vane shape. In particular, they at least approximately reproduce the curvature of the guide vanes 31, whereby the plate elements 4 also contribute to the guidance of the flow as well as the heating of the gaseous medium.

[0068] In the embodiment of the heat treatment system 2 shown in Figure 10, the plate elements 4 are arranged upright between several guide vanes 31, so that the serpentine course extends vertically. In contrast, Figure 11 shows that the plate elements 4 can also be arranged horizontally. This Figure 11 also shows that, as already explained, the plate elements 4 can also look or be designed differently from those in Figure 2. Here again, several plate elements 4 can be stacked on top of each other and electrically insulated from each other by insulating elements 15. As already explained, this stack can again be held together by fastening elements 13.

[0069] This embodiment also makes it possible to illustrate the versatility and adaptability of the heating device 1 to a wide variety of conditions in existing thermal processing systems 2 .

[0070] The heating device 1 can be arranged or operated by itself, in groups of several heating devices 1 and / or in hybrid applications with at least one gas burner for heating a gaseous fluid.

[0071] In addition to the illustrated examples, "pusher-type furnace" and "bell-type furnace" are also examples, and the heat treatment system 2 can be a chamber furnace, or generally a furnace system with convection heating, such as a convection furnace for a continuously extending belt or roller hearth furnace.

[0072] It should be noted at this point that these exemplary embodiments show possible exemplary embodiments of the heating device 1 or the thermal treatment system 2, whereby combinations of the individual embodiments are also possible.

[0073] It should finally be pointed out that for the sake of clarity and to allow a better understanding of the structure of the heating device 1 or the thermal treatment system 2, these are not necessarily shown to scale. [Explanation of symbols]

[0074] 1 Heating device 2. Heat Treatment System 3 Heat Resistor 4 Plate elements 5 Plate Thickness 6 Bending section 7 parts 8 distance 9 Width 10 Transition 11 Frame Elements 12 Receptive Elements 13 Fastening Elements 14 End plate 15 Insulating Elements 16 Connection Lag 17 Connection Lag 18 Heating group 19 Current connection elements 20 beads 21 Connection 22 Connection 23 Connection 24 Star point connection 25 Power Supply Unit 26 Processing Room 27 Flow path 28 Housing 29 Gas Baffle 30 fans 31 Guide vane

Claims

1. A heating device (1) comprising at least one heating resistor (3) with a plurality of resistive heating elements, A heating device (1) characterized in that the resistive heating elements are configured as several plate elements (4).

2. 2. Heating device (1) according to claim 1, characterized in that one, some or all of the plate elements (4) have a serpentine course.

3. 3. Heating device (1) according to claim 2, characterized in that the serpentine course has a plurality of bends (6).

4. 4. Heating device (1) according to claim 3, characterized in that the portions (7) of the plate element (4) between the bends (6) have courses parallel to one another.

5. 5. Heating device (1) according to claim 3 or 4, characterized in that receiving elements (12) for fastening elements (13) are arranged in some or all of the bends (6).

6. Heating device (1) according to any one of claims 2 to 5, characterized in that the serpentine course has a double serpentine configuration.

7. 7. Heating device (1) according to any one of claims 1 to 6, characterized in that the plate elements (4) are bent in the shape of wings.

8. 8. Heating device (1) according to any one of claims 1 to 7, characterized in that a plurality of beads (20) are arranged on the plate element (4) at least in a plurality of portions (7).

9. Heating device (1) according to any one of the preceding claims, characterized in that the plate elements (4) have a plate thickness (5) between 0.5 mm and 5 mm.

10. Heating device (1) according to any one of the preceding claims, characterized in that some or all of the plate elements (4) are electrically connected in series to form heating groups (18).

11. 11. The heating device (1) according to any one of claims 1 to 10, characterized in that several plate elements (4) connected in series are arranged one above the other and that electrical insulating elements (15) are arranged between the several plate elements (4).

12. Heating device (1) according to any one of the preceding claims, characterized in that the three heating groups (18) are electrically coupled to one another by star or delta connections.

13. A thermal treatment system (2) comprising a treatment chamber (26) for an object to be treated and a heating device (1) arranged at least partially within the thermal treatment system (2), A heat treatment system (2) characterized in that the heating device (1) is configured as a heating device (1) according to any one of claims 1 to 12.

14. 14. A heat treatment system (2) according to claim 13, characterized in that the heating device (1) is arranged in a flow path (27) for a gaseous medium, in particular in a flow path for recirculated air.

15. The heat treatment system (2) according to claim 13 or 14, characterized in that the heat treatment system (2) further comprises a guide device having several guide vanes (31), and the heating device (1) according to any one of claims 1 to 12 is arranged between the several guide vanes (31).

16. The heat treatment system (2) according to any one of claims 13 to 15, characterized in that the heat treatment system (2) further comprises a gas-operated heating device.

17. The heat treatment system (2) according to any one of claims 13 to 16, characterized in that the heat treatment system (2) is configured as a pusher-type furnace, a bell-type furnace or a chamber furnace.

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