Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/46—Dielectric heating
  • H05B6/54—Electrodes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
  • F26B25/06—Chambers, containers, or receptacles
  • F26B25/08—Parts thereof
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B3/00—Drying solid materials or objects by processes involving the application of heat
  • F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
  • F26B3/34—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects
  • F26B3/347—Electromagnetic heating, e.g. induction heating or heating using microwave energy
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/46—Dielectric heating
  • H05B6/48—Circuits
  • H05B6/50—Circuits for monitoring or control
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/46—Dielectric heating
  • H05B6/60—Arrangements for continuous movement of material
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/46—Dielectric heating
  • H05B6/62—Apparatus for specific applications

Definitions

• the present disclosure relates to a system for drying dielectric products.
• Radio Frequency (RF) heating and drying systems utilize electromagnetic energy to rapidly heat and dry many types of bulk materials, such as dielectric materials, as well as finished products, with excellent speed and efficiency. They require only a fraction of the floorspace of conventional heating technologies, produce no greenhouse gasses, do not require high process temperatures, and provide excellent control of final moisture content and uniformity.
• Highfrequency electric fields can create standing waves in electrodes, resulting in high potentials at certain points and zero potential at some other points. As a result, the electric field strength between electrodes will be different across the electrodes extension, leading to spatially nonuniform heat generation in the object being heated. This can create hotspots in the dielectric product during production.
• Embodiments of the disclosure for instance as claimed in the independent claim, address the above shortcomings in the art in whole or in part. Further embodiments of the system for drying of dielectric products are subject matter of the further claims.
• a system for drying of dielectric products comprising, a first array of first electrodes, wherein the first array is arranged along a first plane, which extends along a first direction and a second direction. Furthermore, the system comprises a second array of second electrodes, wherein the second array is arranged along a second plane, which extends along the first direction and the second direction. The first plane is spaced apart from the second plane along a third direction. Each of the first electrodes is spaced apart from its corresponding second electrode along the third direction, forming a plurality of pairs of the first electrode and the second electrode each. Furthermore, the system comprises a plurality of radio-frequency generators adapted to produce radio frequency signals of specific and adjustable amplitude and preselected frequency, wherein each of the plurality of radio-frequency generators is electrically coupled to one pair of the first electrode and second electrode.
• the system comprises two or more appropriately shaped first electrodes and two or more appropriately shaped second electrodes, which define a treatment area in which the dielectric product to be heated is positioned or through which it passes.
• the first array comprises a plurality of first electrodes.
• the first array is arranged along a first plane, which extends along a first direction and a second direction.
• the first array is for example arranged in the first plane.
• the first array comprises at least two first electrodes.
• the first electrodes are arranged along the first plane and extend substantially in the first plane.
• the first electrodes comprise each a first main surface extending along the first plane and a second main surface extending along the first plane.
• the first and second planes can be planar surfaces but are not limited to planar surfaces.
• the first and second planes can also be curved surfaces along which the arrays are arranged.
• the first, second and third directions can be straight lines, like in a cartesian coordinate system, but they are not limited to straight lines.
• the first, second and third directions can also be curved lines. Therefore, the electrodes can be arranged along these curved surfaces, which are formed by the first and second planes.
• the electrodes can be shaped, such that they extend along curved lines, which are formed by the first and second directions. For example, the electrodes are bend along their lateral extensions.
• the second array comprises a plurality of second electrodes.
• the second array is arranged along a second plane, which extends along a first direction and a second direction.
• the second array is for example arranged in the second plane.
• the second array comprises at least two second electrodes.
• the second electrodes are arranged along the second plane and extend substantially in the second plane.
• the second electrodes comprise each a third main surface extending along the second plane and a fourth main surface extending along the second plane.
• the first, second, third and fourth main surfaces each have a greater extension than the side surfaces of the first electrodes and the second electrodes that are aligned transversely to them.
• the first electrodes and the second electrodes are arranged in such a way, that the second main surfaces face the third main surfaces.
• the first electrodes are for example arranged side by side in the first plane.
• the second electrodes are for example arranged side by side in the second plane.
• the first plane is spaced apart from the second plane along a third direction.
• the third direction is perpendicular to the first plane defined by the first and second directions.
• the first plane and the second plane are for example parallel to each other.
• the distance along the third direction between the first plane and the second plane is variable.
• the planes are inclined towards each other.
• Each of the first electrodes is spaced apart from its corresponding second electrode along the third direction, forming a plurality of pairs of the first electrode and the second electrode each.
• a corresponding electrode is for example defined by a first electrode, which is spaced apart from a second electrode by the shortest distance possible along the third direction.
• Each first electrode has a second electrode as a counterpart.
• the system comprises also three second electrodes, forming three pairs.
• One pair consists of one first electrode and one second electrode.
• the distance along the third direction between the first electrodes and the second electrodes is variable across different electrode pairs.
• the distance along the third direction between the first electrode and the second electrode within an electrode pair is variable.
• the electrodes can be inclined towards each other. This facilitates generating varying degrees of heat between the electrodes.
• the system is not limited to one, two or three pairs of first electrode and second electrode.
• the system comprises a plurality of pairs, for example four pairs, five pairs, ten pairs or twenty pairs or more, depending on the size of the dielectric product to be dried.
• the system comprises a plurality of radio-frequency generators.
• Each of the plurality of radio-frequency generators is electrically coupled to one pair of the first electrode and second electrode. Therefore, for each pair of electrodes, there is provided one radio-frequency generator.
• the radio-frequency generator is adapted to produce radio frequency signals of specific and adjustable amplitude and predefined frequency. The frequency of the signal remains the same during operation of the system.
• the radio-frequency generator creates an alternating electric field between the first electrode and the second electrode.
• the wave nature of electric field becomes significant when electrode sizes are comparable to the wavelength, resulting in spatially nonuniform electric field.
• Using an array of a plurality of electrodes on the same plane mitigates this effect and leads to a more uniform electric field even for larger dielectric products to be dried.
• the dimensions of the dried dielectric product are not limited by the used excitation frequency.
• more electrodes are used to cover the whole area of the dielectric product. The generated heat is distributed more uniformly, which leads to an improved drying process.
• the first electrode and the second electrode of each pair are arranged parallel to each other.
• Each of the first electrode and second electrode pairs basically form a plate capacitor. Between the electrodes the electric field is generated.
• the plurality of radio-frequency generators is interconnected by a phase harmonizing system to ensure the plurality of radio-frequency generators operates in phase harmony.
• One important aspect is to ensure a uniform electric field to obtain a uniform heat distribution in the dielectric product.
• all the radio-frequency generators produce each a radio frequency signal with the same frequency.
• the same frequency includes frequencies, which are substantially the same within tolerances.
• the phase harmonizing system enables coupling of a plurality of radio-frequency generators in such a way that harmonization of the frequencies for each radio-frequency generator is improved.
• the value range of the frequency of the produced radio frequency signal is in the range from 1 MHz to 100 MHz.
• the radio frequency signal has a frequency in the value range between 1 MHz and 100 MHz.
• the greatest dimension of the first electrodes in the first plane and the greatest dimension of the second electrodes in the second plane are each smaller than 300 of the wavelength of the specific radio frequency signal.
• the greatest dimension of one electrode is for example the diagonal in case of a square or rectangular shape or the diameter in case of circular electrodes.
• the associated wavelength is approximately 11 meters in vacuum or air. This means that high and zero electric fields are physically separated by 2.75 meters. Hence, if the dimensions of each electrode are 3.3 m times 3.3 m, the electric field will be reasonably uniform. In this context a reasonably uniform electric field is an electric field, whose field strength is at a maximum at the center of the electrodes and the field strength at the periphery of the electrodes is at least 90% of the maximum electric field strength.
• directly adjacent first electrodes of the first array are spaced apart in the first plane by at least a first distance and directly adjacent second electrodes of the second array are spaced apart in the second plane by at least a second distance.
• the first distance and the second distance have approximately the same size, but they can also differ from each other.
• Each of the first electrodes are spaced apart by at least the first distance and each of the second electrodes are spaced apart by at least the second distance and the second distance, thus the electrodes are far enough spaced apart to avoid short-circuits or electric sparks to pass between the first electrodes and between the second electrodes, respectively.
• the first electrodes are for example spaced apart by the first distance along the first direction and spaced apart along the second direction by a distance greater than the first distance. The different distances between the first electrodes along the first plane facilitate a flexible arrangement of the electrodes and mitigate for example tolerances of the electrode areas.
• the second electrodes are for example spaced apart by the second distance along the first direction and spaced apart along the second direction by a distance greater than the second distance.
• the different distances between the second electrodes along the second plane facilitate a flexible arrangement of the electrodes and mitigate for example tolerances of the electrode areas.
• the space between adjacent first electrodes in the first plane and the space between adjacent second electrodes in the second plane are filled with an insulating material.
• the insulating material further improves avoiding electric sparks to pass between the first electrodes and between the second electrodes.
• the electrodes have a square shape, which extends along the first direction and the second direction.
• the electrodes are not limited to square shapes.
• the electrodes can have also circular shapes or polygonal shapes, like rectangular, triangular, trapezoidal or others. Preferably symmetric shapes are used for producing more uniform electric fields.
• the electrodes are arranged in the arrays along a curved first and/or second plane.
• the combination of differently shaped electrodes can be used to cover the surface of the dielectric product, which can have any shape with non-uniform thickness along the first, second and/or third direction.
• the system is adapted to dry dielectric products with curved surfaces and/or products with varying thickness along the first, second and/or third direction.
• the electrodes are arranged in a N-by-M grid, which extends along the first direction and the second direction.
• N and M are natural numbers, wherein N starts from 1 and M starts from 2. N and M must not be different and can have the same numerical value.
• a plurality of electrodes is used to cover the entire area of the dielectric product.
• the 2 m times 3 m large area of the dielectric product is covered by 70 electrodes on each side.
• first electrodes and the second electrodes comprise recesses for releasing moisture from the dielectric product.
• the greatest dimension of the recesses is smaller than 1% of the wavelength of the specific radio frequency signal.
• edges at the periphery of the electrodes should be avoided.
• the edges at the periphery of the electrodes are therefore rounded.
• the edges of the recesses are rounded.
• first electrodes 100 arranged along the first direction L1 are spaced apart by the distance d1 and the first electrodes arranged along the second direction L2 are spaced apart by a different distance greater than the first distance d1.
• the different distances can compensate for tolerances in the dielectric material 50, which is located between two directly adjacent electrodes 100.
• a plurality of electrodes 100 is used to cover the entire area of the dielectric product 99.
• dielectric products 99 which extend along the first direction L1 and/or the second direction L2 beyond the boundaries of the electrodes 100. In this manner a dielectric product 99 can be dried, whose surface area is larger than the surface area of a single electrode 100.
• the electrodes 100 are square shaped.
• the electrodes 100 are not limited to square shapes.
• the electrodes 100 can have also circular shapes or polygonal shapes, like rectangular, triangular, trapezoidal or others. Preferably symmetric shapes are used for producing more uniform electric fields.
• the first electrodes 100 comprise recesses 40. Alternatively, the recesses 40 are left out and the first electrodes 100 do not comprise any recesses 40.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Microbiology (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Biotechnology (AREA)
• Molecular Biology (AREA)
• Drying Of Solid Materials (AREA)

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Citations (11)

• 2024
  • 2024-02-01 EP EP24155302.3A patent/EP4597014A1/de active Pending
  • 2024-10-29 WO PCT/EP2024/080575 patent/WO2025162607A1/en active Pending

Patent Citations (11)

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