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WO2025125354A1 - Procédé et récipient pour le chauffage électrique d'une masse fondue de verre - Google Patents

Procédé et récipient pour le chauffage électrique d'une masse fondue de verre Download PDF

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Publication number
WO2025125354A1
WO2025125354A1 PCT/EP2024/085728 EP2024085728W WO2025125354A1 WO 2025125354 A1 WO2025125354 A1 WO 2025125354A1 EP 2024085728 W EP2024085728 W EP 2024085728W WO 2025125354 A1 WO2025125354 A1 WO 2025125354A1
Authority
WO
WIPO (PCT)
Prior art keywords
heating
glass melt
electrodes
current
glass
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2024/085728
Other languages
English (en)
Inventor
Moritz Hauf
Michael Hahn
Sebastian Wolf
Günter Weidmann
Oliver Orth
Frank Karetta
Volker Ohmstede
Wolfgang Schmidbauer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Schott AG
Original Assignee
Schott AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from EP23215757.8A external-priority patent/EP4570764A1/fr
Priority claimed from EP23215752.9A external-priority patent/EP4570763A1/fr
Application filed by Schott AG filed Critical Schott AG
Priority to PCT/EP2024/085728 priority Critical patent/WO2025125354A1/fr
Publication of WO2025125354A1 publication Critical patent/WO2025125354A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/02—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating
    • C03B5/027—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating by passing an electric current between electrodes immersed in the glass bath, i.e. by direct resistance heating
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/18—Stirring devices; Homogenisation
    • C03B5/183—Stirring devices; Homogenisation using thermal means, e.g. for creating convection currents
    • C03B5/185—Electric means

Definitions

  • the glassmaker has a number of options for heating a glass melt, e.g. gas burners, electric resistance heating, or inductive heating. As of today, gas is the predominant heat source used in glass melting.
  • the first reason is obviously the requirement to replace the electrodes at certain intervals. This not only increases the operational costs for the facility but also has an impact on the carbon footprint since for the production of the electrodes a considerable amount of energy is required. Depending on the type of metal used, very high temperatures for melting have to be achieved and the further shaping and handling steps again consume energy. Hence, a frequent exchange of the electrodes significantly increases the carbon footprint of the glass production method. In addition to this, the glass production process has to be stopped for maintenance because it is not possible to simply pull single electrodes out of the melting tank for replacement while the facility continues operation.
  • the second reason is the just mentioned glass quality.
  • the dissolved metal of the electrodes may cause severe discolorations of the glass melt in different colors depending on the type of metal and glass composition used. While this may be tolerable to a certain extent for cheaper glass products which are dark colored anyway, it is already intolerable for cheaper glass products which are to be completely colorless or to have a certain defined color. For high-quality expensive glass products, this discoloration is an absolute showstopper which has to be avoided by all means.
  • a contamination of the glass products with metal of the electrodes is also critical where a certain light transmittance, especially in the UV region, is needed.
  • glass products for medical packaging and semiconductor industries have specified limits of metal particles allowed in their products.
  • WO 2020/229559 A1 discloses another glass melting tank with a high proportion of electrical energy for soda-lime glass.
  • the electrodes are described as flow barriers. Further, it is explained that a flow barrier can be created in the glass melting tank by just one row of electrodes. However, again it is not explained how the electrodes are connected and which electrical concepts are behind them. Per principle this concept is only suitable for the soda-lime glasses which have a low melting temperature. Special glasses with their high melting temperatures would require such high current densities that secondary defects would inevitably occur in the glass at the electrodes, which would prevent the achievement of the required glass quality.
  • a further problem which is associated with the present design of the electrical heating systems is that there is no flexibility of local energy input for glasses with different compositions (and thus different electrical conductivity), different refining agents, and different requirements for coloring and refining redox systems.
  • the electrode positions determine the location of the energy input. There is no flexibility to vary the energy input spatially without rebuilding the melting tank or without installing a large number of individual heating circuits and thus a large number of electrodes. Since there are no degrees of freedom in the electrical heating system, it is also not possible to counteract local overheating by process changes. Changing the electrode position in glass melting vessels is only possible with a new construction or modification of the vessel.
  • this disclosure relates to a method for electrically heating a glass melt in a melting vessel comprising at least a first heating circuit and a second heating circuit, each heating circuit comprising a power source and at least two electrodes immersible into the glass melt, by providing an alternating current from the power sources to the electrodes wherein the electrodes of the heating circuits are arranged such that a path of current through the glass melt between the electrodes of the first heating circuit and a path of current through the glass melt between the electrodes of the second heating circuit are partially geometrically overlapping in an overlapping region.
  • a "glass melt” is a volume of a batch of glass raw materials that has a viscosity of less than 10 76 dPas. Such a viscosity can be measured using the fiber elongation method, e.g. as described in DIN ISO 7884-6:1998-02, where the elongation speed of a fiber with a defined diameter is determined with different weights at different temperatures.
  • t is the temperature under consideration.
  • A, B and to are the so-called VFT constants that are specific for each glass composition.
  • the feature of "independently applying a delay At” means that the various inverters can be operated with different time delays applied to the clock signal, i.e. the inverters work with differently timewise modified clock signals by keeping the frequency constant resulting in a different phase angle of the supplied current. It does neither exclude that two or more inverters operate with different timewise modified clock signals in a predetermined relationship nor that two or more inverters operate with identically timewise modified clock signals.
  • a “common controller” as used herein takes on several tasks and/or functions. First of all, the common controller collects some or all measurement data that are generated in some or preferably all heating circuits and optionally other parts of the melting vessel. Secondly, the common controller utilizes the collected measurement data to compare the actual values to the stored or set target values and sends out control signals to the control units such as e.g. thyristor power controllers, inverters and/or delay generators.
  • the control units such as e.g. thyristor power controllers, inverters and/or delay generators.
  • the common controller furthermore comprises or is connected to a clock generator or global clock generating a global clock signal.
  • the global clock acts as a frequency control unit which provides an external time base for all inverters. It is used to provide a global clock signal to the delay generators providing an individual shift of the phase angle of the current provided by each inverter.
  • the global clock is synchronized to the power grid frequency and phase. “A heating circuit using power grid frequency and phase” means that such heating circuit does not comprise a rectification device such as e.g. inverter.
  • All tasks and/or functions of the common controller can be concentrated in a single central common controller device; it is also possible that certain tasks and/or functions of the common controller are handled decentrally by further controllers or specialized devices such as e.g. a delay generator.
  • One or more controlling tasks and/or functions of the common controller can also be executed by qualified workers.
  • the common controller can be a part of a distributed control system (DCS).
  • DCS distributed control system
  • the amplitudes and/or phases at least one electrode of each heating circuit and therefore the power of each inverter is controlled.
  • the amplitudes can also be manipulated individually at each inverter.
  • An “inverter” or “frequency changer” is a power electronic component which converts one alternating current of one frequency and/or phase to an alternating current of another frequency and/or phase, in particular an alternating current the frequency and/or phase of which is different from the frequency and/or phase of the grid.
  • an inverter may comprise of (a) a rectifier transforming alternating current (AC) into DC, followed by (b) an intermediate circuit e.g. comprising a capacitor and (c) an inverted rectifier transforming DC into an alternating current.
  • AC rectifier transforming alternating current
  • an intermediate circuit e.g. comprising a capacitor
  • an inverted rectifier transforming DC into an alternating current Using such
  • a further huge advantage over the prior art is the possibility to modify the local input of electric energy into the glass melt exclusively by modifying the operation settings of the glass melting vessel. While in prior art for this purpose a repositioning of the electrode arrangement is necessary, in the present disclosure a variation of the phase settings of the heating circuits will suffice. As a result, it is possible to change these settings during the glass production process and to flexibly react to effects in the molten glass, to adapt the settings for higher or lower throughputs and/or even to another glass composition.
  • setting the shift in the phase angle of the currents may be affected or effected during operation by varying the delay At.
  • the setup can be adjusted to meet the required flow profile under continued operation.
  • the variation of the delay At during operation may also be used to counteract deviations from the intended distribution of the power density due to inhomogeneities of the batch resulting in locally different conductivities or defects of single electrodes, transformers, or inverters.
  • the delay At may even be varied as a function of time in order to create a time dependent heating profile.
  • this system of the present disclosure can be seen as a complex meshed network.
  • Each inverter can initially feed into the glass melt with different power, current, voltage, and phase. Due to a typical resistivity of the glass melt in a range of from 2 Q cm to 200 Q cm at a temperature of 1,600 °C, the inverters as sources of power are not independent from each other. A change in a parameter at one inverter may cause a change in all other inverters being part of the same network. All inverters are to be operated with the same frequency in the range of from 20 Hz to 25,000 Hz and to have a fixed phase angle relative to each other. These two conditions are achieved by a clock generator in a common controller which provides an external time base for all inverters connected to that common controller.
  • the clock signal may be, but does not have to be, synchronized with the frequency of the power grid.
  • the inverter-based system with a common controller may operate in two different modes.
  • a second mode of operation where a shift in the phase angle of a certain inverter is desired, a respective delay At in the clock signal supplied to it will be applied. This can be done individually and independently from each other for all inverters.
  • the delay in the trigger signals may be implemented either centrally directly within the common controller or decentrally by means of separate delay generators installed between the common controller and the respective inverters. With the delay set to zero, the system works like in the first mode of operation.
  • overlapping heating circuits including a phase shift is fully independent of the current frequency and the choice of power source (transformer-based or inverter-based).
  • the inverters might also be operated at power grid frequency while applying the desired delay for the phase shift with the common controller.
  • higher frequencies may be advantageous for minimizing secondary defects at the electrodes which may occur at the interface between the electrode surface and the glass melt due to a share of direct current and to maximize the achievable power input into the melt. This suppresses secondary defects such as bubble formation and electrode corrosion, especially in glasses with polyvalent ions.
  • the inverter-based electric heating circuits may be operated in a range from about 20 Hz to 25,000 Hz, i.e. , from below the standard line frequency up to the medium frequency range, which allows for the selection of the frequency best suited to the posed melting problem.
  • the current frequency of the alternating current provided by the power sources may be less than 25,000 Hz, less than 15,000 Hz, less than 12,000 Hz, less than 10,000 Hz, less than 7,500 Hz, less than 5,000 Hz, less than 4,500 Hz, less than 4,000 Hz, less than 3,500 Hz, or less than 3,000 Hz.
  • the current frequency of the alternating current provided by the power sources may be less than 3,000 Hz.
  • the current frequency of the alternating current provided by the power sources may be at least 20 Hz, at least 50 Hz, at least 100 Hz, at least 1,000 Hz, at least 1 ,500 Hz, at least 2,000 Hz, or at least 2,500 Hz.
  • a lower limit of 100 Hz ascertains that the electrode corrosion is sufficiently low at the required current density and the formation of bubbles is adequately suppressed.
  • An upper limit of 5,000 Hz ascertains that the power loss due to emission and induction remains at an acceptable level.
  • heating of the glass melt in the melting vessel may be affected by at least 30 % or by at least 50 % or by at least 70 % or by at least 90 % or by 100 % by means of the electrical heating.
  • the disclosed method is particularly suitable for providing a large share of the heating power by means of electricity or even completely dispense with any burners, IR heaters, and the like. This results in a great reduction of the carbon footprint of the produced glass.
  • the present method and melting vessel consider some adaptations for achieving an optimal efficiency.
  • the voltage should be adapted according to the conductivity in the melting vessel and the desired power. This can be done with transformers which are specifically adapted to the frequency of the inverters. Furthermore, the phase angle between the current and the voltage has to be corrected. In an ideal case, current and voltage are in phase. This is the case at the point of origin of the power. Due to unwanted complex resistances (capacitances, inductances) along the current path caused by cable coverings, transformer, etc., current and voltage can no longer be in phase. Due to this phase angle shift, part of the generated electrical power is not released in the glass melt (reactive power).
  • the melting vessel of the present disclosure uses a power factor correction in combination with the transformer for compensating this reactive power. These two adaptations may be implemented at any point between the inverter and the melting vessel. In optional embodiments, these adaptations are implemented in close proximity to the electrodes.
  • the melting vessel may be selected from a melting tank, a fining tank, a conditioning zone, a horizontal flow duct, and a vertical duct.
  • the disclosed method is equally suitable for all of these types of melting vessels.
  • the melting vessel may be any part of a larger melting facility containing a glass melt which may comprise parts such as a melting tank, a refining tank or refining area, or pipes or ducts connecting the same.
  • the ducts may also be made of refractory ceramics. The only prerequisite regarding the melting vessel and its shape and size is that it will allow for the installation of two or more heating circuits, i.e. , there has to be enough space for the electrodes of at least two heating circuits within the vessel.
  • the melting vessel may have a cross-sectional shape of a circle, an oval, or a polygon having 3 to 64 corners.
  • the cross-sectional shape may be a circle or oval, which mainly concerns pipes or ducts, or a polygon having 3 to 64 corners, which is particularly of interest for melting tanks and fining tanks.
  • the polygon may optionally have 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 24, 30, 32, 36, 42, 48, 54, 60, or 64 corners. In certain useful embodiments the polygon has 4, 5, 8, 10, 12, 24, 36, 48, 60, or 64 corners.
  • the common controller may be configured to apply the delay At > 0 ps to each clock signal internally and/or delay generators may be installed in the signal lines connecting the inverters with the common controller.
  • the signal lines of the melting vessel may be a direct or indirect connection by wire or wireless technique.
  • At least one electrode of the at least two electrodes immersible into the glass melt comprised by the first heating circuit may also be comprised by the second heating circuit, and the electrodes of the first and second heating circuits are arranged such that when provided with a current, the path of current through the glass melt between the electrodes of the first heating circuit is identical with the overlapping region with the path of current through the glass melt between the electrodes of the second heating circuit.
  • the two heating circuits have one electrode in common. Consequently, the number of electrodes in the melting vessel will be one less than in the two heating circuits, for example three instead of four for a setup with two heating circuits with two electrodes, each.
  • the heating circuits are then arranged such that the path of current of first heating circuit lies completely within the path of current of second heating circuit so that the overlapping region is identical with the former.
  • inverter technology with pulse width modulation which can be used in the entire frequency range from 50 Hz to 10 kHz and beyond, and which offers the great advantage that the power grid phases are loaded evenly so that there will be no unbalanced power grid load.
  • This uniform power grid load is important for the power grid operators and an essential prerequisite for the stable operation of the power grid. For the energy consumer, the even power grid load is a prerequisite for the cost-effective purchase of electrical energy from the power grid operator.
  • Figure 1 is an electric scheme of a glass melting vessel with a single heating circuit using one pair of electrodes.
  • Figure 2 is an electric scheme of a glass melting vessel with three heating circuits each using one pair of electrodes and a decentralized phase shift.
  • Figure 3 is a top view scheme of a glass melting vessel of an embodiment with two transversal heating circuits.
  • Figure 4 is a scheme of the power density in the glass melting vessel of Figure 3 in different operation modes.
  • Figure 5 is a scheme of the temperature in the glass melting vessel of Figure 3 in different operation modes.
  • Figure 7 is a top view scheme of a glass melting vessel of an embodiment with six heating circuits including different phase shifts.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Glass Melting And Manufacturing (AREA)

Abstract

La présente invention concerne un procédé et un récipient pour le chauffage électrique d'une masse fondue de verre, une excellente qualité de verre étant obtenue au moyen d'un chauffage électrique direct à l'aide de multiples circuits de chauffage à base d'onduleur qui peuvent être ajustés indépendamment en amplitude et éventuellement en angle de phase. En outre, une modification des zones de température à l'intérieur du récipient peut être obtenue sans nécessiter de recâblage ou de repositionnement des électrodes.
PCT/EP2024/085728 2023-12-12 2024-12-11 Procédé et récipient pour le chauffage électrique d'une masse fondue de verre Pending WO2025125354A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2024/085728 WO2025125354A1 (fr) 2023-12-12 2024-12-11 Procédé et récipient pour le chauffage électrique d'une masse fondue de verre

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
EP23215757.8A EP4570764A1 (fr) 2023-12-12 2023-12-12 Procédé et appareil de fabrication d'un produit en verre
EP23215752.9A EP4570763A1 (fr) 2023-12-12 2023-12-12 Procédé et récipient pour le chauffage électrique d'un bain de verre
EP23215752.9 2023-12-12
EP23215757.8 2023-12-12
PCT/EP2024/085728 WO2025125354A1 (fr) 2023-12-12 2024-12-11 Procédé et récipient pour le chauffage électrique d'une masse fondue de verre

Publications (1)

Publication Number Publication Date
WO2025125354A1 true WO2025125354A1 (fr) 2025-06-19

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PCT/EP2024/085728 Pending WO2025125354A1 (fr) 2023-12-12 2024-12-11 Procédé et récipient pour le chauffage électrique d'une masse fondue de verre

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WO (1) WO2025125354A1 (fr)

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3395237A (en) * 1967-05-03 1968-07-30 Harold S. Orton Electric resistance furnace
US3818112A (en) * 1973-04-30 1974-06-18 Corhart Refractories Co Electrical furnace for melting glass
US4211887A (en) 1978-10-25 1980-07-08 Owens-Corning Fiberglas Corporation Electrical furnace, zones balanced with a symmetrically tapped transformer
US4600426A (en) * 1984-10-01 1986-07-15 Ppg Industries, Inc. Metering device for molten glass and the like
CN1721348A (zh) * 2004-07-13 2006-01-18 肖特股份有限公司 浮法玻璃设备的电气接地装置
CZ24918U1 (cs) 2012-09-05 2013-02-11 Vysoká skola chemicko - technologická v Praze Sklářská tavící pec pro kontinuální tavení skel řízenou konvekcí skloviny
US20130279532A1 (en) * 2010-10-14 2013-10-24 Schott Ag Energy efficient high-temperature refining
WO2014036979A1 (fr) 2012-09-05 2014-03-13 Vysoká škola chemicko-technologická v Praze Procédé de fusion du verre continue sous convection contrôlée du bain de verre fondu et four de fusion de verre pour la production de ce dernier
DE202019100870U1 (de) 2018-09-28 2019-02-22 Beteiligungen Sorg Gmbh & Co. Kg Schmelzwanne und Glasschmelzanlage
DE102018122017A1 (de) 2017-09-08 2019-03-14 Glass Service, A.S. Schmelzraum eines kontinuierlichen Glasschmelzofens und Verfahren zum Glasschmelzen in diesem Schmelzraum
WO2020229559A1 (fr) 2019-05-13 2020-11-19 Fives Stein Limited Four de fusion de verre horizontal hybride à grande flexibilité dans l'apport énergétique

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3395237A (en) * 1967-05-03 1968-07-30 Harold S. Orton Electric resistance furnace
US3818112A (en) * 1973-04-30 1974-06-18 Corhart Refractories Co Electrical furnace for melting glass
US4211887A (en) 1978-10-25 1980-07-08 Owens-Corning Fiberglas Corporation Electrical furnace, zones balanced with a symmetrically tapped transformer
US4600426A (en) * 1984-10-01 1986-07-15 Ppg Industries, Inc. Metering device for molten glass and the like
CN1721348A (zh) * 2004-07-13 2006-01-18 肖特股份有限公司 浮法玻璃设备的电气接地装置
US20130279532A1 (en) * 2010-10-14 2013-10-24 Schott Ag Energy efficient high-temperature refining
CZ24918U1 (cs) 2012-09-05 2013-02-11 Vysoká skola chemicko - technologická v Praze Sklářská tavící pec pro kontinuální tavení skel řízenou konvekcí skloviny
WO2014036979A1 (fr) 2012-09-05 2014-03-13 Vysoká škola chemicko-technologická v Praze Procédé de fusion du verre continue sous convection contrôlée du bain de verre fondu et four de fusion de verre pour la production de ce dernier
DE102018122017A1 (de) 2017-09-08 2019-03-14 Glass Service, A.S. Schmelzraum eines kontinuierlichen Glasschmelzofens und Verfahren zum Glasschmelzen in diesem Schmelzraum
DE202019100870U1 (de) 2018-09-28 2019-02-22 Beteiligungen Sorg Gmbh & Co. Kg Schmelzwanne und Glasschmelzanlage
WO2020229559A1 (fr) 2019-05-13 2020-11-19 Fives Stein Limited Four de fusion de verre horizontal hybride à grande flexibilité dans l'apport énergétique

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