EP3236710B1 - Method and device for thermal processing of solids - Google Patents

Description

The invention relates to a method and an apparatus for the thermal treatment of solids. In particular, the present invention relates to a method and a device for the efficient, directly volume-related thermal treatment of solids by means of radio-frequency energy and controlled with regard to their temperature distribution. This can a. for chemical-free wood protection, drying or decontamination of solids.

Technological background of the invention

The course of many technical processes can be significantly influenced by temperature, since a large number of physical and chemical parameters are more or less temperature-dependent. In the context of construction and renovation, this affects, among other things, the draining of buildings, the discharge of chemicals from building materials or the thermal control of wood pests. In the latter case, reaching a lethal temperature of approx. 55 ° C is an alternative to using toxic chemicals as wood preservatives [ C. Hoyer et al., Chem. Ing. Technik 86 (2014) 1187 ]. The quality of indoor air is becoming increasingly important in living and utility rooms. The use of chemicals is often critical here, making thermal treatment methods more important.

From the multitude of problems in construction, in building renovation and in other areas of application, the application potential of the invention focuses on the treatment of more or less extensive flat materials made of solids which are only accessible from one side or which would be accessible from both sides only with great effort. Material thicknesses of up to 10 cm are particularly preferred. Parquet and other wooden floors, wall paneling and other wall cladding or screed floors may be mentioned here as examples. A need for refurbishment can often be limited to these building structures, so that there is a need for adequate processes for treating relatively thin, extensively expanded solid structures that make it possible, for example wood pests combat thermally or remove water and chemicals from these materials. For an efficient and gentle treatment, it is necessary on the one hand to quickly achieve the most homogeneous possible temperature distributions and on the other hand to control the heating precisely in order to avoid material damage due to local overheating. For sensitive surface coatings such as lacquers or veneers, it is often desirable to keep the surface temperature low, possibly even lower than the volume temperature in the solid matrix. The aim of the present invention is to provide a corresponding method based on direct dielectric heating using high-frequency energy. The device allows a non-invasive treatment, which in particular also enables use options in the area of monument protection and use on art objects.

According to the state of the art, there are a number of methods which enable the material volume to be heated by heat conduction from the surface. Mentioned here are the hot air process, in which the surface is heated by a sweeping air stream, the use of heating plates or heated blankets, or the infrared process, in which the primary energy absorption is also practically limited to the surface. The heat conduction into the interior of the structure to be treated is determined by the parameter specific thermal conductivity, which is often low, especially for dry materials, which leads to long heating times. Basically, the heat flow is stronger, the higher the temperature gradient, i. H. the temperature change per distance, and thus the higher the surface temperature set with the above-mentioned processes. Overheating on the surface is, however, limited for technical reasons, especially since thermal damage to these visible surfaces would be particularly critical. For extensive areas such as parquet floors in representative rooms, most treatment methods require successive treatment. This means that treatment facilities such as heating plates or IR emitters have to be moved according to certain time regimes to cover the entire area. A hot air treatment of the entire area and the rooms, on the other hand, has the disadvantage that high temperatures are harmful to other objects (e.g. paintings) that are often present there.

In order to avoid the disadvantages of inhomogeneous temperature distribution, overheating of the surface and slow passive heating of the interior via thermal conductivity, direct heating methods such as the use of microwaves (MW) [ EP 1 374 676 B1 ] or radio waves (RW) [ DE 20 2010 001 410 U1 ], for which heat generation in the volume of the solid is characteristic. The warming is based on the interaction of the electromagnetic waves used with frequencies mostly in the GHz (for MW) or MHz range (for RW) with polar structures in the solid.

For microwave heating, the reorientation of the water molecule, which is an electrical dipole, is the dominant principle of action in most applications. The interaction of the reorienting water molecule with its environment, which can be described as internal friction, creates heat. For this reason, moist materials can usually be heated well using MW. However, the method is often less suitable for dry materials. The temperature profiles are usually very inhomogeneous for MW heating, which causes local overheating. This is due on the one hand to the low penetration depths of the MW and on the other hand to interference phenomena or the radiation characteristics of the horn antennas used. As a consequence, overheating at various surface positions, which is lower than in conventional methods, is nevertheless significant and often critical.

Although the RW method according to the prior art described leads to significantly more homogeneous temperature profiles, the arrangement of electrodes on both sides with regard to the material to be heated leads to restrictions in the applicability of the method, particularly in the case of structures which are only accessible from one side, as described at the beginning . Further advantages of using RW compared to MW in the context described are the greater flexibility with regard to the materials to be heated and their moisture content as well as the higher energy efficiency through the use of an electronic adaptation network. The aspects mentioned predestine the RW method for use on flat, not too thick structures for the purpose of chemical-free wood protection, drying or decontamination, if the energy can be coupled into the corresponding materials with one-sided accessibility.

It is therefore an object of the present invention to provide a method and a device for the efficient, directly volume-related thermal treatment of solids by means of radio-frequency energy and controlled in terms of their temperature distribution, which take up the advantages of radio-frequency heating and the disadvantages described overcome the prior art and provide an operational device that allows the RW method to be used successfully for the applications mentioned. The remaining technological gap, especially with regard to an adequately realizable electrode arrangement is to be concluded by the present invention. The disadvantages of the prior art are to be overcome and an operational device is to be provided which allows the RW method to be used successfully for the applications mentioned.

From the WO 2016/102972 A2 a device for curling or waving hair, which is also based on the drying effect of radio waves, is known. For treatment or drying, however, the electrodes must also be arranged around the hair from two sides in this device. The document US2015 / 089829 A1 discloses an apparatus according to the preamble of claim 1.

Summary of the invention

According to the invention, these objects are achieved by the independent claims. Preferred embodiments of the invention are contained in the subclaims.

The device according to the invention comprises a binary electrode arrangement which can be arranged on a surface of a solid, each having at least two electrodes (electrode structure) which are electrically insulated from one another, the electrodes preferably being located in a planar plane parallel to the surface of the solid to be treated and the electrode arrangement being at least partially electrically conductive shield is surrounded. The electrode structure is electrically conductively connected to a high-frequency voltage source, which is designed to apply a high-frequency voltage with a frequency between 100 kHz and 50 MHz to the electrode arrangement. The device according to the invention is designed such that a high-frequency electric field is established within a structure (solid) arranged under the device. The device according to the invention comprises a holding device which is designed to enable a translatory movement of the electrode arrangement along the surface of a solid.

It is further preferred that the electrodes are designed as interdigitated comb-like structures, each of the structures having a large number of individual electrodes (fingers) which are connected to one another via a common web. In this case, it is preferred that the longitudinal axes of the individual electrodes run parallel or essentially parallel to one another. It is further preferred that the longitudinal axes of the webs run parallel or essentially parallel to one another.

It is a device for efficient thermal treatment in volume by means of a binary electrode structure arranged on the surface of the structure to be heated, for feeding high-frequency energy into predominantly extensive solid bodies, which have a high-frequency voltage source and the voltages with a frequency in the range generated between 100 kHz and 50 MHz, is electrically conductively connected, and which generates a three-dimensional electric field outside the electrode plane in the solid to be treated, which leads to heating in the volume. Electrodes of one polarity can also be connected in groups, contacting then taking place between the individual electrodes.

Such a binary electrode arrangement is to be understood as a two-part arrangement of individual electrodes to form two electrode groups. The electrodes of the individual groups are each electrically conductively connected to one another, but the two electrode groups of the binary electrode arrangement are electrically insulated from one another. A common main axis can be defined by the mutual position of the individual electrodes of the electrode arrangement. This main axis particularly preferably extends along the longest axis of symmetry of the electrode arrangement.

In particular, the present invention can include a binary, essentially two-dimensional electrode structure that is electrically conductively connected to a high-frequency generator that provides a high-frequency voltage with a frequency in the range between 100 kHz and 50 MHz. A frequency range from 1 MHz to 30 MHz is preferred. Frequencies which are approved for industrial, scientific and medical applications (ISM frequencies) are very particularly preferred. The electrode structure is designed in such a way that the electromagnetic waves are coupled into the structure to be treated in such a way that, compared to conventional methods based solely on heat conduction, a more homogeneous dielectric heating can be recorded, since the heating takes place directly in the volume. In addition, the device preferably contains an electronic matching network which is connected between the HF generator and the electrode system in order to minimize or completely eliminate the HF power reflected to the generator. Electromagnetic shielding, which significantly reduces the radiation of electromagnetic waves from the electrode structure into the room, is also part of preferred embodiments of the device according to the invention. In addition to these basic components, preferred implementations of this device advantageously contain one or more temperature sensors and / or devices for automatic system control via a computer system and / or devices for automatic movement of the device the surface to be treated and / or devices for automatic temperature regulation of the surface.

The idea of the present invention is to achieve temperature profiles by using the device according to the invention with only one-sided accessibility of the solid to be treated, which are more homogeneous in comparison to other methods and thus lead faster to the achievement of the objectives. This usually means that the primary energy input in most materials has a penetration depth of a few centimeters. It is even possible to keep the surface temperature lower than the temperature below the surface in the volume of the solid.

The binary electrode system is advantageously designed in such a way that electrode parts that are grounded in an area of the device (so-called "cold" electrodes) and live electrode parts (so-called "hot" electrodes) alternate (interdigital structure) and thus a high-frequency electromagnetic in the underlying material Field is generated. If the distance between the electrodes is of the same order of magnitude as the width of the electrodes, an electromagnetic field is generated, the distribution of which particularly satisfies the requirements of a sufficiently uniform heating. A particularly preferred and structurally robust embodiment of this binary electrode system is an intermeshing comb structure (double comb structure). The electrode arrangement therefore comprises two intermeshing comb structures. A comb structure is understood to mean a structure in which the individual electrodes of the electrode arrangement are arranged in a comb-like manner as prongs or teeth next to one another along an electrically conductive web. In particular, the web can be aligned parallel to the main axis of the electrode arrangement. The comb structure can be formed on one or two sides, i. H. along the web, the individual electrodes can point along a single web either only in a single direction or in two independent directions. In the two-sided design of the comb, the two directions are preferably within a common plane. An intermeshing comb structure is to be understood as any mutual arrangement of two such comb structures, in which the individual tines of both combs are interlocked with one another without electrical contact.

The field strength maxima at the edges of the electrodes can be reduced by using beveled or rounded electrodes. This change means that the overheating at the edges of the electrodes is significantly reduced without the Effect of coupling into the material is significantly limited. Bending radii or bevels of a few millimeters are sufficient to achieve the desired change. In contrast, semicircular electrodes or electrode parts formed towards the surface are less suitable because the energy coupling would be concentrated too much on the center of the electrode (along the line of contact). The electrode arrangement therefore preferably comprises a surface which can be arranged on the surface of the solid, the edges of the surface facing the surface of the solid being rounded or beveled. In particular, said surface can be the surface which can be arranged on the surface of the solid so that a maximum large surface of the solid is covered by the electrode arrangement. In relation to adjacent surfaces of the electrode arrangement, this surface has edges which can be rounded or beveled. When a high-frequency voltage is applied to the electrode arrangement, an alternating electromagnetic field is generated, the field lines of which usually end perpendicular to the individual surfaces of the contacts. A concentration of the field lines usually occurs at the top. Rounding or chamfering the edges enables a more homogeneous distribution of the field lines in the solid body, since the field strength maxima at the edges of the electrodes can be reduced and at the same time an improved and more homogeneous penetration of the area between the contacts can be achieved. It is further preferred that all edges of the electrodes facing the surface to be treated are rounded or beveled.

The electrodes can be perforated to ensure unhindered removal in the event of drying or chemical discharge from the heated structure and thus to prevent recondensation. The electrode arrangement is therefore preferably perforated at least in partial areas. Individual electrodes of the electrode arrangement can be fully or partially perforated. The perforation can preferably be circular, square, rectangular or hexagonal. Mixed forms are also possible, as are a number of perforation passages of different sizes. In areas of high field line density, a variation in the perforation density and / or type can increase the transportability in favor of a more homogeneous field line distribution. If necessary, a suitable adsorbent can also be located directly on the electrodes, which can bind water or pollutants and thus support the discharge. For organic pollutants, activated carbon beds or activated carbon fleeces can be used, which in an advantageous embodiment are connected directly to the electrodes.

The electrode arrangement according to the invention can be applied to the surface of a solid in order to carry out the method according to the invention and can be moved in translation along the surface of the solid to be treated. This application can take place as a direct contact between the respectively opposite surfaces. A small distance between the respective surfaces is also possible; preferably less than 1 mm, less than 2 mm, less than 5 mm or less than 10 mm. In order to protect the contacts and the surface of the material to be treated from soiling and / or damage during a translational movement of the electrode arrangement, a protective layer can be made, at least in particularly stressed areas, for example from a plastic polymer such as PTFE or PE or also from a textile layer such as felt , be upset. The electrode arrangement therefore preferably comprises a surface which can be arranged on the surface of the solid, the surface being at least partially protected by a protective layer. It is further preferred that the surfaces of the electrodes facing the surface to be treated are coated in such a way that damage to the surface during movement during the treatment is prevented or substantially reduced.

In order to ensure the electromagnetic compatibility of the arrangement, the binary electrode system can preferably be completely or partially enclosed by an electromagnetic shield above the surface to be treated. Solid metal sheets, gauzes or metal-coated plastic foils, for example, are suitable as shielding materials. The electrode arrangement is at least partially surrounded by an electrically conductive shield. It is preferred that the electrodes are surrounded by a shield consisting of an electrically conductive material such as solid sheet metal, gauze or metal-coated foil, so that electromagnetic radiation into the room is significantly reduced or eliminated.

In addition to the spatial characteristics of the electromagnetic field in the material to be heated, a continuous or quasi-continuous translational movement of the electrode arrangement is a possibility from a process engineering point of view to homogenize the heating profiles. This can be done, for example, by a corresponding manual movement of the device along the surface of the solid. However, the device preferably comprises a means for automated translatory movement of the electrode arrangement. This means can be provided, for example, by an appropriately mounted actuator platform. Appropriate control or pre-programming of the movement of at least the electrode arrangement enables homogeneous heating of the solid. The device preferably has a means for translational movement of the electrode arrangement with the periphery, such as shielding over the treated area.

Since the highest field strengths and thus the highest heating rates occur at the edges of the binary electrode structure, it is advantageous to align the structure of the electrodes in such a way that during continuous movement for heating a larger area, if possible, no longer positioning of an edge at one point of the surface to be treated occurs. This procedure will be explained for better illustration of a parquet floor in a rectangular room. In order to treat the entire surface, it makes sense to move a rectangular treatment device parallel to two opposite walls. If the electrode structure is surrounded by a cuboid shield, which is moved parallel to the wall, it would be advantageous to arrange the binary electrode structure at an angle of 45 ° to the limits of the shield and thus to the direction of movement. The electrodes are therefore preferably arranged neither parallel nor perpendicular in relation to the preferred direction of movement, an arrangement of the electrodes at an angle of 45 ° being preferred.

The electrodes of the electrode arrangement are preferably arranged perpendicular to the main axis, the length of the electrodes varying along the electrode arrangement. It is particularly preferred that the length of the electrodes varies linearly along the electrode arrangement. In particular, a device is preferred which has a maximum electrode length in the middle of the electrode arrangement and in which the length of the electrodes adjoining it on both sides decreases linearly towards the outer ends of the electrode arrangement. It is further preferred that the shielding of the electrode arrangement has a square base area, into which the aforementioned embodiment with the electrode length decreasing on both sides can be arranged such that the main axis of the enclosed electrode structure runs through two opposite corner points. Such a device is preferably moved along the sides of the square shield, so that there is an arrangement at an angle of 45 ° to the edges of the shield.

Such a design means that with a continuous movement of the arrangement parallel to the wall, each position on the surface to be treated is only briefly covered by an edge. This would not be the case with a parallel or right-angled arrangement of a comb structure relative to the direction of movement and to the frame. Of course, other geometries of the arrangement according to the invention are also possible, taking into account the boundary conditions mentioned. All of these arrangements have in common that by a essentially two-dimensional, flat electrode arrangement, a three-dimensional electric field is established in the structure to be treated, which enables dielectric heating in the volume through the absorption of energy. The movement of the electrode arrangement and the inherent heat conduction in the solid contribute to a homogenization of the temperature profile, which should be taken into account when choosing the treatment time and intensity (power input density). A pulsed energy input with the utilization of heat conduction in the phases without radio wave application is also a procedural option for homogenizing the temperature distributions in the solid.

Continuous measurement of heating is advantageous for an automated and time-efficient treatment process. Since it is generally not possible to insert sensors into the structure to be treated in the application context, the contactless measurement of the surface temperature between the electrodes by means of optical sensors should be used for control purposes. For this purpose, pyrometric sensors can preferably be integrated into the device. Particularly preferred is the additional integration of a computer system, which regulates the RF power and / or the speed of movement of the device over the structure to be treated on the basis of the measured temperature or a plurality of measured temperatures, in order to avoid overheating of the surface and at the same time by ensuring a minimum temperature to ensure the success of the treatment.

Although the device according to the invention enables the volume to be heated, the depth of penetration of the heating can also be controlled by the design of the electrode structure. This is a great advantage for cases in which the subsurface under the wood structure to be treated is unknown and heating of this part of the building structure is to be minimized.

The device according to the invention preferably comprises a regulating device for regulating the surface temperature of the solid. The control device can comprise a means for determining the surface temperature of the solid. This can be at least one, preferably electronic or optical, sensor that detects the surface temperature. The control device can comprise a means for determining the surface temperature of the solid. The control device can comprise a means for determining the electrical field strength. This can be at least one sensor that detects the electric field strength. The control device can include a means for evaluation and control. This can be, for example, a Act computer system, which is designed to evaluate the measurement signals of the individual means for determining and controlling the entire device. In particular, the means or means for determining the surface temperature and / or the means or means for determining the electric field strength can be connected to the means for evaluation and control for evaluation. Furthermore, the means for translational movement and / or the high-frequency voltage source can be connected to the means for evaluation and control for control purposes. The means for evaluation and control can thus be used to adapt the RF power applied to the arrangement and / or the translational movement profile in dependence on certain variables such that a largely homogeneous processing of the solid is made possible. In this respect, the means for evaluation and control in combination with sensors can enable control and regulation of the thermal treatment of solids. In particular, the RF power applied to the electrodes can be regulated as a function of the measured surface temperature.

It is further preferred that the device comprises at least one means for cooling the surface of the solid which enables cooling of the surface of the dielectrically heated solid. These means for cooling the surface of the solid can also be regulated via the means for evaluation and control. The means for cooling the surface can preferably be a device for air guidance. The device for air guidance can be, for example, an active system in which air is supplied to individual partial areas of the electrode arrangement. The supplied air can be generated locally as an air flow by a large number of fans or can be supplied to the individual partial areas by a corresponding air flow control. The air flow can preferably be generated by a single main fan. The air supplied can also be cooled by a cooling device. A perforation in the electrode structure can also be used to guide the air flow for cooling.

An electronic matching network for reducing the high-frequency power reflected back from the electrode arrangement to the high-frequency voltage source is preferably connected in the electrically conductive connection between the electrode arrangement and the high-frequency voltage source. In particular, an electronic matching network, a so-called matchbox, can be connected between the RF voltage source and the electrode arrangement in such a way that the RF power reflected to the generator is reduced or eliminated.

The method according to the invention is based on the use of the device described above and uses the resulting advantages in the thermal treatment of solids. In particular, the method presented for the thermal treatment of solids comprises, as process steps, the provision of a binary electrode arrangement with at least two electrodes which are electrically insulated from one another, the electrode arrangement being arranged on a surface of a solid, and the application of a high-frequency voltage to the electrode arrangement, an electrical one Alternating field is generated in a solid and the solid heats up in volume by this alternating field. In an advantageous embodiment of the method, the volume is heated without the surface overheating. The method according to the invention is suitable for enabling a controlled and direct heating of the structure to be treated and thereby reliably preventing unwanted overheating of parts of the surface and the volume.

Preferably, the electrode arrangement becomes generally translational, i.e., translucent, along the surface of the solid during use of the device according to the invention. in any direction along said surface. More preferably, however, a translatory movement occurs exclusively in directions that are not parallel to the edges of the electrode arrangement. A translatory movement can preferably be carried out manually by a user of the device or by means of a corresponding means for translatory movement of the electrode arrangement.

In the method according to the invention, the surface temperature of the solid can be controlled by a control device and adjusted as required. Preferably, the control device can cool the surface of the solid at least in sections. The electrode arrangement is preferably moved in a manual or automated translatory manner along the surface of the solid. In a preferred embodiment of the method, the surface is cooled by means of an air stream which is guided through perforations in the electrode system. In a further preferred embodiment of the method, water and / or pollutants are bound in a substance provided which is suitable for the absorption of these substances. In preferred embodiments of the method, drying agents and / or hydrophobic adsorbents such as activated carbon, for example in granular or nonwoven form, are involved.

Brief description of the figures

Figur 1

eine schematische Darstellung einer erfindungsgemäßen Vorrichtung zur thermischen Behandlung von flächig ausgedehnten Feststoffen;

Figur 2

eine schematische Darstellung einer bevorzugten erfindungsgemäßen Elektrodenanordnung nach Fig. 1;

Figur 3

schematische Darstellungen einer weiteren bevorzugten erfindungsgemäßen Vorrichtung zur thermischen Behandlung von flächig ausgedehnten Feststoffen in Aufsicht und in Seitenansicht;

Figur 4

schematische Darstellungen von unterschiedlichen Ausgestaltungen des Querschnitts der Elektroden;

Figuren 5a, 5b

schematische Darstellungen einer Anwendung der erfindungsgemäßen Vorrichtung;

Figur 6

Temperaturprofile für vier unterschiedliche Behandlungsregimes am Beispiel des Feststoffs Holz;

Figur 7

ein Temperaturtiefenprofil für die vier Behandlungsregimes nach Figur 6 mit Angabe der Reichweite für das Erreichen einer Letaltemperatur von 60 °C;

Figur 8

schematische Darstellung einer weiteren erfindungsgemäßen Elektrodenanordnung mit Angabe der Positionen der faseroptischen Temperatursensoren; und

Figur 9

den zeitlichen Verlauf der Temperaturen in 10 mm Tiefe sowie die zeitlichen Verläufe von HF-Leistung und HF-Spannung bei Verwendung der in Figur 8 gezeigten erfindungsgemäßen Vorrichtung.

The invention is explained below in exemplary embodiments with reference to the accompanying drawings. Show it:

Figure 1

a schematic representation of a device according to the invention for the thermal treatment of solid materials extended over a large area;

Figure 2

a schematic representation of a preferred electrode arrangement according to the invention Fig. 1 ;

Figure 3

schematic representations of a further preferred device according to the invention for the thermal treatment of solidly expanded solids in supervision and in side view;

Figure 4

schematic representations of different configurations of the cross section of the electrodes;

Figures 5a, 5b

schematic representations of an application of the device according to the invention;

Figure 6

Temperature profiles for four different treatment regimes using the solid wood as an example;

Figure 7

a temperature depth profile for the four treatment regimes Figure 6 with indication of the range for reaching a lethal temperature of 60 ° C;

Figure 8

schematic representation of a further electrode arrangement according to the invention with details of the positions of the fiber optic temperature sensors; and

Figure 9

the time course of the temperatures at a depth of 10 mm as well as the time courses of RF power and RF voltage when using the in Figure 8 shown device according to the invention.

Detailed description of the invention

Figure 1 shows a schematic representation of a device 100 according to the invention for the thermal treatment of solids 10. The device 100 is shown lying on the surface A of the solid 10, the lateral extent generally being significantly larger than in FIG Fig. 1 specified. In particular, part of the surface A of the solid 10 shown is in direct contact with the underside surface B of the electrode arrangement 20. However, such a direct contact between the electrode arrangement 20 and the surface A of the solid 10 is not absolutely necessary, according to the invention it is sufficient , if the field line course starting from the electrode arrangement 20 leads to a corresponding penetration of the solid 10. The electrode arrangement 20 is surrounded at the top and on the sides by a shield 40. This serves to focus the field line course on the volume of the solid 10 and to significantly reduce the parasitic radiation into the surroundings, ie outside the solid 10. A holding device 42 is shown above the shield 40 as an example. In the present case, this serves to make it easier for a user of the device 100 to handle the device 100 manually. The holding device 42 can be designed, for example, as a clamp holder, wrap-around holder or as a screw or plug-in holder for fastening a telescopic rod head. The holding device 42 can also have a possibility for fixing the electrode arrangement 20 to a means for translatory movement of the electrode arrangement 20. With the aid of a corresponding holding device 42, the electrode arrangement can be moved translationally along the surface A of the solid 10. In particular, the most complete possible successive covering of a coherent surface A of the solid 10 is particularly preferred according to the invention. The corresponding movement profile can be chosen freely, but in the case of manual movement in particular, a zigzag profile completely covering the surface A of the solid 10 is particularly preferred for the translatory movement. According to the invention, a high-frequency alternating electromagnetic field is coupled into the volume of the solid 10. This RF field is preferably generated by a high-frequency voltage source 30. This can be connected to the electrode arrangement 20 via an electrically conductive connection. An electronic matching network 50 is preferably connected to the electrically conductive connection between the electrode arrangement 20 and the high-frequency voltage source 30 in order to reduce the high-frequency power reflected back from the electrode arrangement 20 to the high-frequency voltage source 30. The electrode arrangement 20 shown is two interdigitated comb structures. The teeth of the comb and the connecting crosspiece form the individual electrodes. The first web 26 and the second web 28 also provide conductive electrical connections between the individual ones Teeth of a comb. The high-frequency voltage generated by the high-frequency voltage source 30 is applied to the webs 26, 28 and is therefore also connected to the individual electrodes of the respective comb. According to the invention, a strong electromagnetic alternating field is thus formed between the double combs, the field line course generated thereby preferably penetrating deep into the volume of the solid 10 and leading to heating of the material.

Figure 2 shows a schematic representation of an exemplary electrode arrangement 20 according to the invention Fig. 1 . In particular, the interdigitated comb-like arrangement of the first electrodes 22 and the second electrodes 24 as an interdigital structure becomes clear. The electrodes 22a-22f belonging to the first comb are connected to one another in an electrically conductive manner via the first web 26, the web also acting as an electrode. The electrodes 24a-24f belonging to the second comb are connected to one another in an electrically conductive manner via the second web 28. This also acts as an electrode. Both combs are completely electrically insulated from one another and have no electrically conductive connection to one another. An indirect connection only takes place during operation of the device 100 by connecting both combs to the high-frequency voltage source. The individual electrodes 22, 24 extend along a common main axis X of the electrode arrangement 20, the first web 26 and the second web 28 likewise running parallel to the main axis X of the electrode arrangement 20 in the illustration shown. However, the webs 26, 28 can also be oriented in any other way to the main axis X of the electrode arrangement 20, in particular the electrodes 22, 24 can also be electrically connected to one another without a fixed web structure. For example, the electrodes that belong together can also be connected by means of individual cable connections or soldering. In the case illustrated by way of example, the webs 26 and 28 lie in one plane with the electrodes 22a-22f and 24a-24f. However, it is also possible for these webs to be largely above the plane of the electrodes 22a-22f and 24a-24f. In this case, the webs practically do not themselves act as HF electrodes with respect to the material 10 to be treated.

An essential feature of the present invention is the provision of a device for the most homogeneous thermal treatment of solids. A corresponding degree of homogeneity and uniformity is therefore also particularly preferred when designing an electrode arrangement 20 according to the invention. In particular, the respective geometric distances, dimensions and angles between the individual electrodes 22, 24 should be uniform. In the representation of the Fig. 2 this becomes clear from the fact that here two identical comb structures mesh in such a way that the electrode webs are arranged parallel to each other at the same distance. In particular, the left-hand and right-hand distance of each individual electrode 22, 24 from its two closest neighbors are each the same. The pulse duty factor between the width of the electrodes 22, 24 and the distance between the individual electrodes 22, 24 can be chosen freely. However, a duty cycle is also preferred here, which ensures that the inventive idea of the method is implemented as optimally as possible depending on the high-frequency voltage applied to the electrode arrangement 20 and the respective electrode shape.

Figure 3 shows a schematic representation of the essential components of a further device 100 according to the invention for the thermal treatment of solids 10 in top view (top) and in side view (bottom). An electrode arrangement 20 is shown with two intermeshing comb structures, which are comb structures on two sides, in which the electrodes 22, 24 are located on both sides (in the figure above and below) of the respective webs 26, 28. The electrodes 22, 24 extend as shown along a common main axis X, the webs 26, 28 also running parallel to the main axis X in this embodiment as well. The electrodes 22, 24 of the electrode structure 20 are arranged perpendicular to the main axis X, the length of the electrodes varying along the electrode structure. It should be emphasized that in the arrangement according to Fig. 3 the webs are arranged above the electrode structure and not in one plane with it. In this case, they practically do not act as electrodes with respect to the structure 10 to be heated. The length of the electrodes 22, 24 along the electrode structure 20 varies linearly. In particular, the electrode arrangement 20 has a maximum electrode length in the middle of the electrode structure 20. The length of the electrodes 22, 24 adjoining on both sides decreases linearly towards the outer end of the electrode structure 20. It can be seen from the top view that the shield 40 in the exemplary embodiment shown has a square cross section with respect to the plan view. The electrode arrangement 20 is enclosed diagonally in the base of this square. The square generally follows the position of the shield 40. A translational movement of the electrode arrangement 20 shown preferably takes place along the sides of the square shield 40, therefore in the exemplary embodiment shown there is an angle of 45 ° to the edges of the shield in the arrangement shown 40 before.

Figure 4 shows a schematic representation of different configurations of the cross section of the electrodes 22, 24. The individual electrodes 22, 24 of the electrode arrangement 20 each have an edge area on their underside, ie on the surface B facing the surface A of the solid 10, which is characterized by an edge K. In order to influence the course of the field line during operation of the device 100 according to the invention, the shape of this edge region, in particular that of the edges K, can be modified by rounding (right) or beveling (center), in distinction to a rectangular or angular configuration (left). To protect at least the surface B of the contacts 22, 24 and / or the surface A of the structure 10 to be treated, the contacts 22, 24 can also be provided with a protective layer 60. The protective layer 60 can include, for example, the entire contact 22, 24, only individual contact points or only the surface B of the contacts 22, 24. The latter is shown for illustrative purposes in the illustrated embodiment of a contact 22, 24 with rounded edges K (right). All of these embodiments can also have a perforation which allows the removal of substances from the solid structure 10 to be treated and / or the ventilation of the surface A of the solid structure 10.

Example 1: Modeling the spatial distribution of the energy coupling into the treated structure

Among the many possible variations in use, an example is illustrated in which parallel electrodes or electrode parts with alternating polarity ("hot", ie live, and "cold", ie earthed, electrodes) are used for heating. A shield is arranged above the electrodes, which also extends over the adjacent surface. The "cold" electrodes are electrically conductively connected to the grounded shield and the matchbox housing, while the "hot" electrodes are electrically connected to the electronic matching network or to the voltage source for contacting via a copper strip. The arrangement for a vertical treatment (for example a fragment of a wall paneling) is shown schematically in Fig. 5 shown.

Figure 5 shows schematic representations of an application of the device according to the invention with a surface-bound binary electrode arrangement using the example of a wall to be heated. It shows Fig. 5a the shielding with the underlying, invisible comb structure and Fig. 5b a section through the device according to the invention with a visible comb structure.

If a simulation is based on the fact that the electrodes have a width of 20 mm and the distance between the center of the electrodes is 25 mm, the gap between the electrodes is 5 mm. In the direction of the wall surface, the electrodes were each beveled 5 mm at an angle of 45 °, so that there was an effective electrode distance of 15 mm on the surface, which is also decisive for the field distribution in the material. Using realistic assumptions for the heat propagation in the material, the heat transfer between the material surface and air and using the dielectric and physical parameters for the material wood, the temperature distributions for a 50 mm thick wooden component were determined after certain times of the dielectric energy input.

Four different scenarios were compared: conventional heating with a heating plate, dielectric heating using the device according to the invention using radio wave energy, and the use of both methods in pulse mode (1 min heating, 2 min break). A power of 1 kW was used in all cases.

Figure 6 shows temperature profiles for four different treatment regimes using the solid wood as an example. The four resulting temperature profiles are shown after 3 min, 6 min, 9 min and 15 min. Thereby (a) shows the temperature profile with continuous HF heating, (b) the temperature profile with continuous conventional HF heating, (c) the temperature profile with radio wave heating in pulse mode (1 min power on, then 2 min break) and (d) the temperature profile for conventional heating in pulse mode (times as before).

It becomes clear that the maximum of the heating and the total energy input for the case of the radio wave method are clearly shifted into the volume of the material. For a non-thermally insulated surface, the surface temperature can be reduced compared to the target temperature to be achieved in the volume, for example in order not to damage sensitive coatings. The degree of temperature reduction can be varied by the choice of the insulating surface covering or the setting of the heat removal from the surface, for example by a cooling air flow. Conventional heating using a hot plate (analog results would be achieved with hot air and IR treatment), on the other hand, leads to a high surface temperature, a pronounced decrease in temperature with depth and to a significantly lower heating speed in volume. With a decrease in surface temperature to Protection of sensitive surfaces would further reduce the already slow heating rate of the volume.

For practical use, the situation usually arises that a certain maximum temperature must not be exceeded, but a minimum temperature (e.g. the lethal temperature for pest control) must be reached.

Figure 7 shows a temperature depth profile for the four treatment regimes Fig. 6 . The four methods already mentioned are compared for a situation in which the maximum temperature is limited to 100 ° C. The time is shown at which the limit temperature of 100 ° C was reached for the first time at one location. Since the target temperature according to the process was 60 ° C, the penetration depths up to which this temperature was reached are also marked.

Here, too, the clear advantages of the radio wave method using the device and the method according to the invention with a power of 1 kW used (continuously or in the pulses in pulse mode) can be seen. The penetration depths for the radio wave heating (13 mm or 17 mm, based on reaching the lethal temperature of 60 ° C) were significantly higher than those achieved with conventional heating using a heating plate (or analogously with the hot air or infrared method) (5 mm and 8 mm for continuous and pulse operation). The treatment times required for this were comparable. At the same time, this means that much longer treatment times for conventional heating would be necessary for the same penetration depths if the target temperature was to be consistently reached in a certain volume. It should be noted that in the case described, there was no movement of the device over the surface to be treated. In the case of a mobile application, the effective dwell time of the system at the position would have to be taken into account.

Example 2: Heating of a parquet surface with a double comb structure

For demonstration purposes, a wooden plate with a thickness of 20 mm was used using the in Fig. 8 shown double comb structure heated. Construction elements made of steel were used for the electrodes 22, 24 and the webs 26, 28 in these orienting experiments. The distance between the electrodes 22, 24 was between 20 mm and 25 mm.

An RF generator (working frequency 13.56 MHz, maximum power 3 kW) and an electronic matching network (maximum RF voltage 4 kV) were used.

The surface temperature was measured using an IR camera. Fiber optic temperature sensors were positioned at a depth of 10 mm below the wood surface to enable continuous temperature measurement during the RW treatment. The positions of the sensors relative to the electrode structure (marked with x) are also Fig. 8 refer to.

Figure 9 shows the time course of the temperatures at a depth of 10 mm when using the in Fig. 8 shown device according to the invention and using the method according to the invention. These are the results of a typical heating test using the arrangement according to the invention. It could be demonstrated that a preselected minimum temperature of 60 ° C was reached everywhere in the wood plate at a depth of 10 cm. A maximum temperature of 100 ° C was not exceeded. The surface temperatures were significantly lower, as shown by pictures with an IR camera. Here an average temperature of approx. 75 ° C with a maximum surface temperature of 82 ° C was observed.

It can be assumed that an even better homogeneity of the temperature distribution can be achieved by optimizing the electrode structure and using special test regimes (cf. embodiment 1).

The special test regimes represent the method according to the invention, which, thanks to its flexibility, allows successful treatment of very different practical situations.

Reference list

10th

Solid

20th

Electrode arrangement

22a, 22b, ...

first electrodes

24a, 24b, ...

second electrodes

26

first footbridge

28

second bridge

30th

High frequency voltage source

40

shielding

42

Holding device

50

Fitting network

60

Protective layer

A

Solid surface 10

B

Surfaces of the electrode assembly 20

K

Edges of electrodes 22, 24

X

Major axis of the electrode arrangement 20

Claims (15)

1. A device (100) for the thermal treatment of solids (10), comprising a binary electrode arrangement (20) which can be arranged on a surface (A) of a solid (10), each electrode arrangement having at least two electrodes (22, 24) electrically insulated from one another, the electrode arrangement (20) comprising two intermeshing comb structures, the electrode arrangement being at least partially surrounded by an electrically conductive shield, and the electrode arrangement (20) being electrically conductively connected to a high-frequency voltage source (30) which is configured to apply a high-frequency voltage having a frequency between 100 kHz and 50 MHz to the electrode arrangement (20),
   characterized in that
   a holding device (42) is provided, configured to enable a translatory movement of the electrode arrangement (20) along the surface (A) of a solid (10) .
2. The device (100) according to claim 1, wherein the device (100) comprises a surface (B) which can be arranged on the surface (A) of the solid (10), wherein the edges (K) facing the surface (A) of the solid (10) the surface (B) are rounded or beveled and/or the surface (B) is at least partially protected by a protective layer (60).
3. The device (100) according to any one of the preceding claims, wherein the electrode arrangement (20) is perforated at least in partial regions.
4. The device (100) according to any one of the preceding claims, wherein each of the comb structures comprises a web (26, 28) via which the respective electrodes (22, 22a, 22b, 22c, 22d, 22e, 22f, 24, 24a, 24b, 24c, 24d, 24e, 24f) of the electrode arrangement (20) are electrically connected to one another, wherein the webs (26, 28) run parallel to a main axis (X) of the electrode arrangement (20) and wherein the electrodes (22, 22a, 22b, 22c, 22d, 22e, 22f, 24, 24a, 24b, 24c, 24d, 24e, 24f) are arranged perpendicular to the main axis (X) and the length of the electrodes (22, 24) varies along the electrode arrangement (20).
5. The device (100) according to any one of the preceding claims, further comprising a means for translatory movement of the electrode arrangement (20).
6. The device (100) according to any one of the preceding claims, further comprising a regulation device for regulating the surface temperature of the solid (10).
7. The device (100) according to any one of the preceding claims, wherein the device (100) has an adsorbent for receiving the substances emerging from the solid.
8. The device (100) according to claim 7, wherein the adsorbent directly contacts at least one of the electrodes (22, 24).
9. The device (100) according to any one of the preceding claims, wherein the electrode arrangement (20) has at least one perforation which is configured to guide an air stream for cooling.
10. A method for the thermal treatment of solids (10), comprising the following method steps:

    - providing a device (100) for the thermal treatment of solids (10) according to any one of claims 1 to 9, the electrode arrangement (20) being arranged on a surface (A) of a solid (10), and

    - applying a high-frequency voltage having a frequency between 100 kHz and 50 MHz to the electrode arrangement (20), an alternating electrical field being generated in the solid (10) and the solid (10) being heated by this alternating field.
11. The method according to claim 10, wherein the surface temperature and/or the volume temperature of the solid (10) are regulated by a regulation device (70).
12. The method according to claim 11, wherein the regulation device (70) cools the surface (A) of the solid (10) at least in sections by means of at least one means for cooling the surface (A) of the solid (10) .
13. The method according to any one of the preceding claims 10 to 12, wherein the electrode arrangement (20) is moved generally translationally along the surface (A) of the solid (10) or the translational movement does not take place parallel to edges of the electrode arrangement (20).
14. The method according to any one of the preceding claims 10 to 13, wherein the substances emerging from the treated structure of the solid (10) are bound to an adsorber material.
15. The method according to any one of the preceding claims 10 to 14, wherein the surface of the solid is cooled via an air stream, wherein the air stream is preferably guided via perforations in the electrodes (22, 24) of the electrode arrangement (20).

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