AT526909A1 - Heating device - Google Patents

Abstract

The invention relates to a heating device (1) comprising at least one heating register (3) with several resistance heating elements which are designed as plate elements (4).

Description

with several resistance heating elements.

The invention further relates to a thermal processing system comprising a process chamber for an object to be processed and with a heating device,

which is at least partially arranged in the thermal processing plant.

The electrical heating of industrial furnaces with a resistance heater is well known. For this purpose, electrical current flows through a heating element with a corresponding electrical resistance, releasing heat. Rod-shaped heating elements are very often used for this purpose. For some types of furnaces, such as pusher furnaces, high energy densities are necessary. Gas heating is therefore normally preferred for these furnaces. However, due to environmental reasons and the availability of fuel gas, efforts are being made to use gas heating wherever possible.

to be replaced by other heating systems if possible.

It is the object of the invention to provide a possibility for supplying a thermal

moprocessing plant with heating energy.

The object of the invention is achieved with the heating device mentioned at the beginning.

in which the resistance heating elements are designed as plate elements.

Furthermore, the object of the invention is achieved with the thermopro-

process plant in which the heating device is designed according to the invention.

The advantage here is that the plate elements can be used to build a heating register that imposes a relatively low flow rate on a gas flowing through it.

resistance. This means that the heat generated by the heating register can

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have a high proportion of convection, such as in hood furnaces, etc.

According to an embodiment of the invention, it can be provided that one, several or all plate elements have a meandering course.

This makes it possible to provide a higher heating output, while still allowing a relatively compact design. In addition, it is easier to adapt the heating device to the installation space in a

an existing thermal processing plant.

To further improve these effects, it can be provided according to embodiment variants of the invention that the meandering course has several bends and that, if necessary, sections of the plate elements between the bends have a parallel course. In particular, the latter

This design variant enables improved use of space.

For better integration of the heating device or the plate element into the thermal processing system, according to an embodiment of the invention, it can be provided that receiving elements for fastening elements are arranged in several or all of the bends. This enables a compact design of the heating device without the risk of unintentional contact between sections of a plate element or plate elements. This also allows for higher

Flow velocities in the thermal processing plant are possible.

According to a variant of the invention, it can be provided that the meandering course is designed as a double meander, which allows easier contacting of the plate elements in a single area of the heating register.

ter and also an increase in the heating output per plate element can be achieved.

According to another embodiment of the invention, it can be provided that the plate elements are bent in a shovel shape, whereby the plate elements, in addition to the “heating” function, also have the function of a flow line

can take over.

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ment.

According to a further embodiment of the invention, it can be provided that the plate elements have a plate thickness between 0.5 mm and 5 mm, whereby the above-described effect of the low pressure loss is further

ter can be improved.

In addition to the aforementioned double meander formation for extending the heating conductor length, according to another embodiment of the invention it can also be provided that several or all plate elements are used to form

connection of a heating group are electrically connected in series.

According to an embodiment variant of the invention, it can be provided that the plate elements connected in series are stacked one above the other, with electrical insulating elements being arranged between the plate elements.

are arranged in order. The stacking again enables a compact construction.

According to an embodiment variant of the invention, it can also be provided that three heating groups are electrically combined with one another in a star connection or delta connection, whereby the total heating output of the heating register is increased.

can be increased.

According to a variant of the thermal processing system, for better transmission of the heating energy, it can be provided that the heating device is arranged in a flow channel for a gaseous medium, in particular a circulating air channel.

is arranged.

The flow channel can also be provided with a guide vane with guide vane

blades, so that according to a further design variant of the

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of additional guide vanes.

According to another design variant of the thermal processing system, it can be provided that it also has a gas-operated heating device. The combination of "electric heating" and "gas heating" makes it possible to reduce the NOx content in the exhaust gases during non-optimal phases, such as in holding phases with reduced burner output. With the hybrid design of the thermal processing system, it is possible to operate these phases with reduced burner output using the heating device according to the invention and not to operate the gas burner in these phases. It is also possible to reduce the total heating output of the gas burner and to provide the missing heating output via the heating device. As a result, the gas burner operates in the optimal range over longer phases, which in turn reduces NOx emissions.

proportions of the exhaust gas can be reduced.

According to another design variant of the thermal processing plant,

These are designed as stoRofen, hood furnace or chamber furnace.

For a better understanding of the invention, it is explained in the following

Figures are explained in more detail. They each show in a simplified, schematic representation: Fig. 1 an embodiment of a heating device in an oblique view;

Fig. 2 a variant of a plate element of the heating device

in oblique view;

Fig. 3 shows a further variant of a plate element of the heating device

direction;

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escaping gas;

Fig. 6 shows a detail of a heating device;

Fig. 7 shows a further detail of a heating device;

Fig. 8 shows a section of a variant of a thermal processing plant;

Fig. 9 shows a variant of a thermal processing plant in longitudinal section;

Fig. 10 shows a section of another variant of a thermal

moprocess plant;

Fig. 11 shows a section of another variant of a thermal

moprocess plant.

To begin with, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or identical component designations, whereby the disclosures contained in the entire description can be transferred analogously to identical parts with identical reference symbols or identical component designations. The position information chosen in the description, such as top, bottom, side, etc., also refers to the figure directly described and shown, and these position

information to be transferred to the new position in the event of a position change. A heating device 1 is shown in Fig. 1.

The heating device 1 can be used in particular in electrically heated convection ovens or for converting ovens with burner heating into at least partially electrically heated ovens. The heating device 1 can, for example,

be used in so-called standing ovens or in continuous furnaces, i.e. in

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Process plants 2 are shown in Figs. 8 to 11.

An industrial furnace within the meaning of the invention is in particular a furnace which is used in metallurgy or in the processing of inorganic objects or objects which are manufactured exclusively from inorganic raw materials or

have been used.

Just as an example, it should also be noted that the heating device 1 for objects made of aluminium or an aluminium alloy or generally non-ferrous metals

or made of steel.

The heating device 1 comprises at least one heating register 3. The heating register 3 comprises or consists of several resistance heating elements. Heat is generated in it due to the electrical resistance when electrical current is passed through. Since this principle is known per se, in order to avoid

Repetitions refer to the relevant state of the art.

The resistance heating elements are available as plate elements 4 or sheet elements

Such a plate element 4 is shown in Fig. 2.

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A piece of metallic material confined to a flat surface.

It should be mentioned at this point that all or several of the resistance heating elements of the heating device 1 can be designed in the same way. Although this is the preferred embodiment of the heating device 1, it is possible within the scope of the invention that different plate elements 4 can also be installed in the heating device 1. These can be arranged within the same heating device 1 or, if there are several heating devices 1 in a thermal processing system 2, in different heating devices 1. The difference can be in a plate thickness 5, in a length through which current flows, in the number of bends, in the material, etc., or in combinations thereof.

gen.

In the following, only one plate element 4 is described in more detail. However, the explanations can be applied to other or all plate elements 4 of the heating device 1

be transferred.

The embodiment of the plate element 4 shown in Fig. 2 is a preferred one. However, the plate element 4 can also look completely different. For example, the plate element 4 can be a straight, flat bar in its simplest form. In the preferred embodiment, however, the plate element 4 has a meandering course with bends 6 (also referred to as apex areas) and sections 7 between the bends 6. The number of bends 6 and corresponding sections 7 shown in Fig. 2 is not to be understood as limiting. The specific number can depend on the desired total heating output and/or the installation situation of the heating device 1, among other things. For example, a plate element 4 can have between two and 50, in particular between 6 and 45, for example between ten and 40,

have such bends 6.

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the bends 6 have a parallel course to each other.

The distance 8 between the sections 7 can be between 1 mm and 50 mm.

carry.

A width 9 of the sections 7 can be between 2 mm and 100 mm, in particular

between 10 mm and 60 mm.

The plate thickness 5 can be between 0.5 mm and 5 mm, in particular between 1 mm and 2 mm. The plate elements 4 are thus relatively thin, so that they have a low flow resistance. Reference is made to Fig. 5, which shows the heating device 1 in the flow direction (vertical

to the paper plane).

A total length of a plate element 4 in the direction of current flow can be between

100 mm and 3 m.

The plate element 4 can be produced by appropriate forming of a straight blank. It is also possible for the plate element 4 to be cast in the desired shape. Preferably, however, the plate element 4 is cut out of a sheet metal by means of a separation process, for example

for example with a laser or a water jet.

The plate element 4 comprises or consists of at least one metallic material. For example, it can be made of a Kanthal® alloy, a

Nikrothal® alloy or an Inconel® alloy.

As shown in Fig. 3 and 4, the meandering course of the plate element 4 can also be designed differently. For example,

place of the round bends 6 right-angled transitions 10 between the

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mentes 4 are arranged next to each other.

To form the heating register 3, the plate elements 4 can be arranged in a receiving element, such as a frame element 11, as shown by way of example in Figs. 1, 5 and 6. In principle, the plate elements 4 can be connected to the receiving element in a variety of ways or arranged in or on it. The receiving element can, for example, be provided with groove-shaped recesses into which the plate elements 4 can engage. If necessary, these recesses can be

cuts must be carried out.

In the embodiment shown, however, the plate elements 4 are stacked on top of one another or, depending on the installation position, are suspended in an arrangement next to one another in the frame element 11. For this purpose, the plate elements 4 can, according to one embodiment, be provided with receiving elements 12 for fastening elements 13 (which can also be referred to as holding elements) of the frame element 11. The receiving elements 12 can be designed as receiving lugs which are arranged, for example, in the apex areas of the bends 6, as shown in Fig. 2. In this case, each bend 6 can preferably be provided with such a receiving element 12 so that the plate element 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, wherein these fastening elements 13 protrude through openings in the receiving elements 12 of the plate elements 4. In other words, the plate elements 4 can be threaded onto the frame element 11, as can be seen, for example, from Fig. 5 or Fig. 6. The rod- or bar-shaped fastening

elements 13 can be held by end plates 14 of the frame element 11.

The receiving element 12 of the plate elements 4 can also be designed differently

as can be seen, for example, from Fig. 11.

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Preferably, the receiving elements 12 are integral with the rest of the plate elements

ments 4 trained.

For the stacked arrangement of plate elements 4, insulating elements 15 are provided between the plate elements 4. The insulating elements 15 can be arranged to extend through the receiving elements 12, for which purpose the openings in the receiving elements 12 can be made correspondingly large. In the 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. This means that not only the electrical insulation between adjacent plate elements can be achieved via the insulating elements 13, but also the electrical insulation to the frame element 11 (or generally to the receiving element for the plate elements).

ments 4).

The insulating elements 15 can be made of the materials known for electrical insulating elements 15, with the restriction that these materials must also withstand the temperatures in the thermal processing system 2. For this reason

For this reason, the insulating elements 15 are preferably designed as ceramic elements.

As can be seen from Fig. 5 and Fig. 6, two structurally different, sleeve-shaped insulating elements 15 can be used, which can be inserted into one another. This makes it possible to assemble the heating device 1 and to center

The assembly of the plate elements 4 can be simplified.

For the preferred assembly of the heating device 1, the frame element 11 can be provided in a first step, but this does not yet have an end plate 14 on at least one side. A first insulating element 15 is then placed on each of the fastening elements 13. These first insulating elements 15 are supported on one of the end plates 14 and provide electrical insulation to this/these end plate(s) 14. A first plate element 4 is then pushed on so that the fastening elements 13 protrude through the receiving elements 12. This plate element 4 is centered with

second insulating elements 15, which have a cylindrical extension, the

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can be accommodated by the first insulating elements 15, as can best be seen in Fig. 6. The further construction of the heating register 3 is carried out by

repeating these steps.

In principle, the electrical contacting of the plate elements 4 can take place on opposite sides of the heating device 1. In the preferred embodiment, however, 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 and connected to the plate elements 4. For electrical connection on only one side, for example,

Plate elements 4 designed as double meanders can be used.

According to another embodiment, it can also be provided that several or all plate elements 4 of a heating device 1 are electrically connected in series to form a heating group 18. In the embodiment of the heating device 1 shown in Fig. 1, it has three such heating groups 18. The heating groups 18 can also be mounted on the same frame element 11.

arranged, e.g. separated by intermediate plates 19 (see Fig. 5).

To form the series connection of the plate elements 4, metallic current connection elements 19 are provided alternately (at the beginning and at the end of a plate element 4) in the end regions of the plate elements 4, which

introduces electrical current from a plate element 4 in a first level into a plate element 4 of the following level. The heating group 18 is therefore

Electric current flows through it in a “zig-zag” pattern.

The power connection elements 19 are also preferably sleeve-shaped. They can have cylindrical extensions on one or both sides, which can be accommodated by adjacently arranged insulating elements 15. The power connection elements 19 can also have a centering effect for the

Centering of the plate elements 4.

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As can be seen in Fig. 2 based on a section 7, according to a variant of the heating device 1, it can be provided that beads 20 are arranged or formed in the plate elements 4 at least in individual sections 7, in particular in all sections 7. The beads 20 can be produced by forming the sections 7. The beads 20 can have a depth

which is between 0.5 mm and 3 mm.

All plate elements 4 of a heating device 1 can be connected in series. However, in order to increase the total heating output, according to one embodiment, the heating device 1 can have three heating groups 18, as shown in Fig. 1. These three heating groups 18 can be electrically combined with one another in a star connection or delta connection. Reference is made to Fig. 1, which shows a star connection of the three heating groups 18. Electrical connections 21 to 23 for the three phases P1, P2 and P3 can be seen, as well as a star point connection 24. These electrical connections 21 to 23 are then used to connect to a power supply unit 25 (see Fig. 1), via which the heating register 3 is supplied with power.

can be.

A thermal processing system 2 can have one heating device 1 or several heating devices 1 depending on the required heating power. For example, a

Thermoprocessing plant 2 may have between one and 20 heating devices 1.

As already explained above, the heating device 1 is used in a thermal processing system 2 in order to warm up or heat a gaseous medium, such as circulating air.

then the energy is introduced into the object to be heat treated.

A first variant of the thermal processing plant 2 is shown in detail

shown in Fig. 8. This comprises a process chamber 26 for receiving

at least one object to be processed. Furthermore, the thermal processing system 2 comprises at least one of the heating devices 1 according to the invention (preferably

preferably several). The heating device 1 can be arranged inside the process chamber 13

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and/or outside the process chamber 13 and at least partially surrounding it. The at least one heating device 1 can be arranged in a flow

channel 27 can be arranged at least partially, preferably entirely, within a housing 28 of the thermal processing system 2. In the illustrated embodiment,

In the control variant, the thermal processing plant 2 is a so-called pusher furnace.

The flow channel 27 can be completely separated from the process chamber 26

for example via a gas baffle 29.

The thermal processing system 2 can also have other components that correspond to the state of the art, but which are not mentioned further in this description. The expert will, if necessary, identify them accordingly in the thermal processing system 2.

process plant 2.

Depending on the thermal process in the thermal processing system 2, the gaseous medium to be heated can be selected or composed. This is also

known to the expert, so that further discussion is unnecessary.

In general, the heating device 1 is preferably used in thermal processing systems 2 with an energy density of at least 0.5 W/cm?, in particular between 0.5 W/cm?* and 25 W/cm?®?. The energy density depends on the flowing medium, in particular the type of medium, the speed of the medium

and the temperature of the flowing medium.

Fig. 9 shows a detail of another embodiment of a thermal processing system 2. This is designed in the form of a hood furnace. As with the StoRofen or generally in the thermal processing system 2, a fan 30 or a turbine can be provided with which the gaseous medium is circulated in the process chamber 26. The heating device 1 can be arranged in the central and

be arranged in the flow channel 27 formed above the fan 30.

The heating device 1 or one or more additional heating devices 1

can also be arranged in a different designed flow channel 27. For example, a guide device for a medium to be circulated is shown in Fig. 10. The guide device has guide device blades 31, between

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which flow channels 27 are formed. The guide vanes 31 are designed to be curved accordingly in order to achieve a corresponding flow

course to achieve.

Plate elements 4 of the heating device 1 are now arranged between the guide vanes 31 or between at least some of the guide vanes 31. As can be seen from Fig. 10, the plate elements 4 are designed to be curved in the shape of a blade. In particular, they at least approximately reproduce the curvature of the guide vanes 31, whereby the plate elements 4 also serve to

conduction and not only to the heating of the gaseous medium.

In the variant of the thermal processing system 2 according to Fig. 10, the plate elements 4 are arranged upright between the guide vanes 31, so that the meandering course extends in the vertical direction. In contrast, Fig. 11 shows that the plate elements 4 can also be arranged horizontally. This Fig. 11 also shows, as already explained above, that the plate elements 4 can also look or be designed differently than that in Fig. 2. Here, too, it is possible to stack several plate elements 4 vertically on top of each other and to electrically insulate them from each other with insulating elements 15. The stack can again be held together using fastening elements 13, as already explained above.

was carried out.

This design variant also allows the variability and adaptability of the heating device 1 to a wide variety of conditions in existing

Thermoprocessing systems 2 are illustrated.

The heating device 1 can be used alone, in a group of several heating devices 1 and/or in a hybrid application with at least one gas burner.

ner for heating a gaseous fluid.

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In addition to the examples shown, “pusher furnace” and “hood furnace”, the thermal processing system 2 can also be a chamber furnace or generally preferably a furnace system with convective heating, such as convection furnaces

for continuously running belts or roller hearth furnaces.

The embodiments show possible variants of the heating device 1 or the thermal processing system 2, whereby it should be noted at this point that combinations of the individual variants are also possible.

are.

For the sake of order, it should finally be pointed out that for a better understanding of the structure of the heating device 1 or the thermal processing system 2

these are not necessarily shown to scale.

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Heating device

16

List of reference symbols

31 guide vanes

Thermoprocessing plant

Heating register Plate element Plate thickness Bending Section Distance

Width

Transition frame element

Recording element

Fastener

End plate Insulating element Terminal lug Terminal lug

Heating group

Power connector

Bead Connection Connection

Connection

Star point connection

Power supply unit

Process chamber Flow channel Housing Gas baffle

Fan

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Claims (17)

Patent claims 1. Heating device (1) comprising at least one heating register (3) with several resistance heating elements, characterized in that the resistance The standing heating elements are designed as plate elements (4). 2. Heating device (1) according to claim 1, characterized in that one, several or all plate elements (4) have a meandering course. point out. 3. Heating device (1) according to claim 2, characterized in that the meandering course has several bends (6). 4. Heating device (1) according to claim 3, characterized in that sections (7) of the plate elements (4) between the bends (6) have a respective have a parallel course to each other. 5. Heating device (1) according to claim 3 or 4, characterized in that in several or all of the bends (6) receiving elements (12) for fastening ing elements (13) are arranged. 6. Heating device (1) according to one of claims 2 to 5, characterized in that the meander-shaped course is designed as a double meander is. 7. Heating device (1) according to one of claims 1 to 6, characterized indicates that the plate elements (4) are bent in a shovel shape. 8. Heating device (1) according to one of claims 1 to 7, characterized in that beads (20) are arranged in the plate elements (4) at least in sections (7). A202387411-AT 9. Heating device (1) according to one of claims 1 to 8, 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 one of claims 1 to 9, characterized in that several or all plate elements (4) are arranged to form a Heating group (18) are electrically connected in series. 11. Heating device (1) according to one of claims 1 to 10, characterized in that the series-connected plate elements (4) are arranged stacked one above the other, with electrical Insulating elements (15) are arranged. 12. Heating device (1) according to one of claims 1 to 11, characterized in that three heating groups (18) in a star connection or delta circuit are electrically combined with each other. 13. Thermal processing system (2) comprising a process chamber (26) for an object to be processed and with a heating device (1) which is at least partially arranged in the thermal processing system (2), characterized in that the heating device (1) is designed according to one of claims 1 to 12. 14. Thermoprocessing plant (2) according to claim 13, characterized in that the heating device (1) is arranged in a flow channel (27) for a gaseous medium, in particular a recirculation duct. 15. Thermal processing plant (2) according to claim 13 or 14, characterized in that it further comprises a guide apparatus with guide apparatus blades (31), and that between the guide apparatus blades (31) heating devices (1) are arranged according to one of claims 1 to 12. A202387411-AT 16. Thermoprocessing plant (2) according to one of claims 13 to 15, characterized in that it additionally comprises a gas-operated heating device direction. 17. Thermoprocessing plant (2) according to one of claims 13 to 16, characterized in that it is designed as a pusher furnace, hood furnace or chamber furnace is trained. A202387411-AT