EP0732866B1 - Process and equipment for heating an electrically conductive liquid - Google Patents

Process and equipment for heating an electrically conductive liquid Download PDF

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Publication number
EP0732866B1
EP0732866B1 EP96400520A EP96400520A EP0732866B1 EP 0732866 B1 EP0732866 B1 EP 0732866B1 EP 96400520 A EP96400520 A EP 96400520A EP 96400520 A EP96400520 A EP 96400520A EP 0732866 B1 EP0732866 B1 EP 0732866B1
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EP
European Patent Office
Prior art keywords
solenoid
liquid
yoke
heating
electrically conductive
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EP96400520A
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German (de)
French (fr)
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EP0732866A1 (en
Inventor
Jacques Nuns
Philippe Fache
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Electricite de France SA
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Electricite de France SA
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Priority claimed from FR9503054A external-priority patent/FR2731867B1/en
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    • 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
    • H05B6/02—Induction heating
    • H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
    • H05B6/105—Induction heating apparatus, other than furnaces, for specific applications using a susceptor
    • H05B6/108—Induction heating apparatus, other than furnaces, for specific applications using a susceptor for heating a fluid
    • 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
    • H05B6/02—Induction heating
    • H05B6/36—Coil arrangements
    • H05B6/365—Coil arrangements using supplementary conductive or ferromagnetic pieces

Definitions

  • the present invention relates to a method and a electrically heated liquid instrument driver.
  • the invention also applies to heating by Joule effect of metals or non-ferrous metal alloys (aluminum, copper, zinc, bronze ).
  • a channel oven sometimes used to heat non-ferrous metals, it is provided with a magnetic circuit, generally made of sheets magnetic, extending partly inside the crucible containing the molten metal and partly outside.
  • a inductor winding is wound around the magnetic circuit in the outside of the crucible. This winding forms the primary of a transformer whose secondary is formed by a stream of liquid metal around the circuit magnetic.
  • This type of oven causes energy losses significant, like traditional induction ovens, because the inductor is located outside the container containing the material to be heated.
  • the channel i.e.
  • the invention also relates to the heating of glasses that are often quite good conductors electric. It is known to heat glasses by induction in so-called "direct coil” ovens. In such oven, a copper coil placed in the molten glass is powered at very high frequency (several hundred kHz) to generate the eddy current dissipators of heat. A serious disadvantage of these ovens is the risk of dielectric breakdown in the interval between the points of turns, where the electric field is Student. To alleviate this drawback, sometimes a so-called "cold cage” oven in which tubular sectors in copper are placed axially inside the coil, cooling water circulating in these areas. The current flow in the coil induces other currents in the sectors, which generate the eddy currents in the molten glass. If these cold cage ovens limit the risks of dielectric breakdown, they have the disadvantage of have poor returns.
  • An object of the present invention is to provide a process for electrically heating a liquid conductor by Joule effect with good yield.
  • the invention thus provides a heating method of an electrolytic liquid consisting of immersing in said liquid a heating instrument having a circuit solenoid inductor electrically isolated from the liquid, and to supply the inductor circuit in alternating current.
  • the invention is applicable to a liquid with significant electrical conductivity, i.e. to an electrolytic liquid but also to a metal or molten alloy or a molten glass.
  • a method according to the invention thus consists in placing the liquid in a tank in which there is also an inductor circuit comprising a solenoid electrically isolated from the liquid and a cylinder head made of soft magnetic material extending axially inside the solenoid, and to supply the solenoid with alternating current.
  • the invention also provides a heating instrument to immerse in an electrolytic liquid allowing the above process to be carried out in the case of an electrolytic liquid.
  • the instrument according to the invention comprises a solenoid arranged coaxially in an electrically insulating cylindrical tube closed at its lower end, solenoid connection terminals to an AC power supply, and a cylinder head soft magnetic material extending axially inside solenoid.
  • This cylinder head may have, at its end adjacent to the lower end of the tube, a directed rim radially outward from the solenoid, so improve efficiency.
  • the cylinder head is arranged to concentrate in the liquidates the induced magnetic field. We can then use greater depths of skin effect by retaining a excellent energy efficiency, which makes it possible to use a significantly lower frequency supply, therefore more economic.
  • the invention further provides a heating oven of an electrically conductive liquid, comprising a tank to receive said liquid, an electrically solenoid isolated from the liquid, extending inside the tank, a cylinder head extending axially inside the solenoid, and an AC power supply connected to the solenoid.
  • Figure 1 shows a cylindrical tank 10 containing an electrolytic liquid to be heated, typically between the room temperature and a temperature of 100 to 150 ° C, or even higher.
  • An inductor winding constituted here by a solenoid 12
  • the solenoid 12 makes part of a heating instrument further comprising the terminals for connection to generator 14 and isolation means electric between the liquid and the copper of the solenoid and connection terminals.
  • These means of electrical insulation also provide chemical protection for copper vis-à-vis the liquid to be heated. They can be made up by an insulating and anticorrosive coating applied to the solenoid turns or by a cylindrical case double surrounding the solenoid. Such a case can also be arranged to allow the circulation of a cooling of the solenoid turns 12.
  • the liquid to heat is found both around and inside the solenoid 12.
  • the applied alternating current induced in the liquid a magnetic field whose flow lines 16 are represented. Due to the conductivity of the liquid, which is for example between 10 and 100 S / m, this magnetic field generates eddy currents which heat the liquid by Joule effect.
  • the supply frequency is chosen according to the diameter of the solenoid, the diameter of the tank and the electrical conductivity of the liquid, taking into account the fact that the latter generally increases with temperature.
  • the frequency used is inversely proportional to the conductivity of the liquid and squared the desired skin effect depth.
  • an optimal power frequency can be sought by previous tests. If tank 10 is metallic, we choose the frequency so that the walls of the tank 10 are not heated directly, that is to say so that the magnetic field induced on the outside of solenoid 12 remains essentially confined in the liquid. In practice, the power frequency will be often above 50 kHz.
  • FIG. 2 shows a heating instrument allowing the process to be implemented at frequencies lower feed.
  • this instrument comprises a cylinder head 24 and a container tube 26.
  • the tube 26 is made of electrically insulating anti-corrosion material.
  • He has a cylindrical shape which surrounds the solenoid 22 and the cylinder head 24, with a closed lower end 28.
  • the cylinder head 24 is for example made of magnetic sheets arranged in a star for supply frequencies of around 5 kHz or, for higher frequencies (typically 20 kHz) from ferrite bars.
  • She has a generally cylindrical shape coaxial with the solenoid 22 and to the tube 26, with an axial bore 30 making it possible to make circulate coolant from the solenoid and the cylinder head, for example water.
  • the cylinder head 24 may have a rim 32, 34 extending radially outwards, as shown in Figure 4.
  • the cylinder head 24 has a structure capable of concentrating the power transmitted opposite the turns of the solenoid 22.
  • the flow lines bend at an angle important in the bottom edge 32. So when the instrument is immersed vertically in the tank 10 containing the electrolytic liquid to be heated, one can induce a high magnetic field without this field being important at the bottom of the tank. The field is good concentrated in the liquid, even if the depth of the effect of skin is relatively large, i.e. if the power frequency is relatively low.
  • the solenoid can then be supplied at frequencies from 5 kHz only for a transmitted power of several hundred of kW and a conductivity of the liquid of the order of 30 to 50 S / m.
  • Figure 3 illustrates the distribution of field lines magnetic 36 in the example of a power of 237 kW, a frequency of 20 kHz and a conductivity of 37 S / m. To one frequency of 20 kHz, the bottom of the tank is not at all heated. Likewise, the upper edge 34 of the cylinder head limits the extension of the magnetic field above the surface of the liquid.
  • FIG. 4 shows an oven that can be used for heating a conductive liquid to higher temperatures high.
  • the liquid in question can be a metal (or metallic alloy) melted, or a molten glass.
  • the oven comprises a tank 110 made of refractory material.
  • the refractory material from the wall of the tank is placed in a metal casing 111.
  • the tank is covered with a cover 113, provided with an opening 115 for introduction matter (liquid or solid not yet melted) to heat.
  • a pouring spout 117 is provided in the part top of tank 110 to drain the liquid from the tank heated.
  • a solenoid 122 provided with an internal cylinder head 124 is placed inside the tank 110.
  • the solenoid is connected to an alternating current generator 114.
  • a path is provided around the solenoid 122 and cylinder head 124 to allow passage of a coolant, such as water, that does circulate a pump 119.
  • the inductor constituted by the solenoid 122 and its cylinder head 124 is placed in a refractory sheath 126 integrated into the bottom of the tank 110.
  • the sheath 126 electrically insulates and thermally the solenoid 122 and its cylinder head 124 of the liquid.
  • the solenoid is placed vertically towards the middle of the tank, and is dimensioned so that the magnetic field induced is essentially confined in the liquid to be heated.
  • the electrical conductivity is very high (resistivities of the order of 10 to 20.10 -8 ⁇ .m).
  • the cylinder head 124 can then be produced from magnetic sheets, and the solenoid can be supplied at a frequency greater than 100 Hz, typically from 300 to 500 Hz.
  • the refractory materials of the tank 110 and of the sheath 126 are chosen from those usually used in metallurgy (adobe for example).
  • the conductivity is lower (up to 150 to 200 S / m) so that we have to increase the frequency supply for the same heating power.
  • a cylinder head 124 made from bars of ferrite, and supply frequencies higher than 10 kHz, typically around 20 kHz.
  • the materials refractories of the tank 110 and of the sheath 126 can be ceramics such as those usually used in the glass industry.
  • the oven shown in Figure 5 differs from that of Figure 4 in that the refractory sheath 226 containing the solenoid 222 and the cylinder head 224 is suspended from the cover 213 of tank 210 instead of being fixed or integrated to the bottom wall of the tank. It will be understood that many other arrangements of the inductor inside the tank are possible.
  • Figure 6 shows another example of an oven that can in particular be used to galvanize sheets.
  • the solenoid 322, the cylinder head 324 and the refractory sheath 326 are placed near the bottom of the tank 310, with their parallel axis at this background.
  • the sleeve 326 crosses for example the width of the tank as shown. It may then be necessary to subdivide the solenoid 322 into several sections windings supplied separately.
  • the heated liquid being molten zinc, we can, thanks to a conventional arrangement of rollers, scroll a sheet in the interval located between the inductor and the bottom of the tank to apply it a zinc coating.

Abstract

The method involves plunging a heating device in the liquid. The heating device has an inductive circuit (12) electrically insulated from the liquid. The inductive circuit is supplied by an alternative current to induce Foucault currents in the electrolytic liquid. The liquid can be placed in a tank (10) made of electrically conductive material. The inductive circuit may be supplied at a frequency selected in such a way that the induced magnetic field will be confined outside the heating device. The heating device may have a system for cooling the inductive circuit.

Description

La présente invention concerne un procédé et un instrument de chauffage d'un liquide électriquement conducteur.The present invention relates to a method and a electrically heated liquid instrument driver.

Elle concerne notamment le chauffage par effet Joule d'un liquide électrolytique corrosif. Dans un liquide corrosif tel qu'un acide, il n'est guère envisageable de plonger deux électrodes pour faire circuler un courant électrique, car le matériau conducteur des électrodes serait attaqué par l'acide. Un montage de type four à induction, avec des enroulements inducteurs placés autour du récipient contenant le liquide, permettrait un chauffage par effet Joule provoqué par des courants induits dans la cuve, donc sans contact direct entre le liquide et un conducteur. Dans ces conditions, le rendement énergétique serait dégradé par perte supplémentaire dans l'inducteur, même si des culasses externes sont prévues. Les fours à induction sont utilisés pour chauffer des métaux, mais dans le cas d'un électrolyte beaucoup moins conducteur, les fréquences d'alimentation seraient trop élevées. En outre, si le liquide est contenu dans un récipient métallique, c'est essentiellement le récipient qui serait chauffé par induction, et cette chaleur serait ensuite communiquée au liquide. Ceci risquerait de provoquer une altération du revêtement anticorrosif du récipient.It concerns in particular the heating by Joule effect corrosive electrolyte. In a liquid corrosive such as an acid, it is hardly possible to immerse two electrodes to circulate a current electric because the conductive material of the electrodes would attacked by acid. An induction oven type assembly, with inductor windings placed around the container containing the liquid, would allow heating by effect Joule caused by induced currents in the tank, therefore without direct contact between the liquid and a conductor. In these conditions, energy efficiency would be degraded by additional loss in the inductor, even if cylinder heads are planned. Induction ovens are used to heat metals, but in the case of an electrolyte much less conductive, supply frequencies would be too high. Also, if the liquid is contained in a metal container, it's basically the container that would be heated by induction, and this heat would then be communicated to the liquid. This would risk alter the anticorrosive coating of the container.

L'invention s'applique également au chauffage par effet Joule de métaux ou d'alliages métalliques non ferreux (aluminium, cuivre, zinc, bronze...). Dans un four à canal, parfois utilisé pour chauffer des métaux non ferreux, il est prévu un circuit magnétique, généralement en tôles magnétiques, s'étendant en partie à l'intérieur du creuset contenant le métal fondu et en partie à l'extérieur. Un enroulement inducteur est bobiné autour du circuit magnétique dans la partie extérieure au creuset. Cet enroulement forme le primaire d'un transformateur dont le secondaire est constitué par une veine du métal liquide autour du circuit magnétique. Ce type de four provoque des pertes énergétiques non négligeables, comme les fours à induction traditionnels, du fait que l'inducteur est situé à l'extérieur du récipient contenant le matériau à chauffer. En outre, le canal, c'est-à-dire la zone intérieure au creuset située entre le circuit magnétique et la paroi du creuset, où le chauffage est le plus efficace, a tendance à se boucher au cours du fonctionnement du four. Ces fours à canal sont limités en fréquence. Ils sont généralement utilisés à 50 Hz, mais les circuits nécessaires pour équilibrer les trois phases sont alors très encombrants et ils perturbent le réseau.The invention also applies to heating by Joule effect of metals or non-ferrous metal alloys (aluminum, copper, zinc, bronze ...). In a channel oven, sometimes used to heat non-ferrous metals, it is provided with a magnetic circuit, generally made of sheets magnetic, extending partly inside the crucible containing the molten metal and partly outside. A inductor winding is wound around the magnetic circuit in the outside of the crucible. This winding forms the primary of a transformer whose secondary is formed by a stream of liquid metal around the circuit magnetic. This type of oven causes energy losses significant, like traditional induction ovens, because the inductor is located outside the container containing the material to be heated. In addition, the channel, i.e. the area inside the crucible located between the circuit magnetic and the wall of the crucible, where the heating is the more effective, tends to get clogged during oven operation. These channel ovens are limited in frequency. They are generally used at 50 Hz, but circuits needed to balance the three phases are so very bulky and they disrupt the network.

L'invention concerne également le chauffage de verres en fusion qui sont souvent d'assez bons conducteurs électriques. Il est connu de chauffer des verres par induction dans des fours dits "à spire directe". Dans un tel four, une spire de cuivre placée dans le verre fondu est alimentée à très haute fréquence (plusieurs centaines de kHz) pour générer les courants de Foucault dissipateurs de chaleur. Un grave inconvénient de ces fours est le risque de claquage diélectrique dans l'intervalle séparant les points de raccordements de la spire, où le champ électrique est élevé. Pour atténuer cet inconvénient, on utilise parfois un four dit "à cage froide" dans lequel des secteurs tubulaires en cuivré sont placés axialement à l'intérieur de la spire, de l'eau de refroidissement circulant dans ces secteurs. La circulation du courant dans la spire induit d'autres courants dans les secteurs, lesquels génèrent les courants de Foucault dans le verre fondu. Si ces fours à cage froide limitent les risques de claquage diélectrique, ils ont l'inconvénient de présenter des rendements médiocres.The invention also relates to the heating of glasses that are often quite good conductors electric. It is known to heat glasses by induction in so-called "direct coil" ovens. In such oven, a copper coil placed in the molten glass is powered at very high frequency (several hundred kHz) to generate the eddy current dissipators of heat. A serious disadvantage of these ovens is the risk of dielectric breakdown in the interval between the points of turns, where the electric field is Student. To alleviate this drawback, sometimes a so-called "cold cage" oven in which tubular sectors in copper are placed axially inside the coil, cooling water circulating in these areas. The current flow in the coil induces other currents in the sectors, which generate the eddy currents in the molten glass. If these cold cage ovens limit the risks of dielectric breakdown, they have the disadvantage of have poor returns.

Un but de la présente invention est de proposer un procédé permettant de chauffer un liquide électriquement conducteur par effet Joule avec un bon rendement. An object of the present invention is to provide a process for electrically heating a liquid conductor by Joule effect with good yield.

L'invention propose ainsi un procédé de chauffage d'un liquide électrolytique consistant à plonger dans ledit liquide un instrument de chauffage comportant un circuit inducteur solénoïde électriquement isolé du liquide, et à alimenter le circuit inducteur en courant alternatif.The invention thus provides a heating method of an electrolytic liquid consisting of immersing in said liquid a heating instrument having a circuit solenoid inductor electrically isolated from the liquid, and to supply the inductor circuit in alternating current.

Plus généralement, l'invention est applicable à un liquide ayant une conductivité électrique notable, c'est-à-dire à un liquide électrolytique mais également à un métal ou alliage fondu ou encore à un verre en fusion. Un procédé selon l'invention consiste ainsi à placer le liquide dans une cuve dans laquelle se trouve en outre un circuit inducteur comprenant un solénoïde électriquement isolé du liquide et une culasse en matériau magnétique doux s'étendant axialement à l'intérieur du solénoïde, et à alimenter le solénoïde en courant alternatif.More generally, the invention is applicable to a liquid with significant electrical conductivity, i.e. to an electrolytic liquid but also to a metal or molten alloy or a molten glass. A method according to the invention thus consists in placing the liquid in a tank in which there is also an inductor circuit comprising a solenoid electrically isolated from the liquid and a cylinder head made of soft magnetic material extending axially inside the solenoid, and to supply the solenoid with alternating current.

Par un dimensionnement approprié du circuit inducteur et par un réglage de la fréquence d'alimentation, on peut confiner essentiellement dans le liquide le champ magnétique induit à l'extérieur de l'instrument de chauffage. On accède ainsi à d'excellents rendements énergétiques (supérieurs à 90%). On bénéficie en outre des avantages propres au chauffage par induction : faible inertie thermique ; possibilité de réguler finement la puissance et la température ; possibilité de transmettre de fortes puissances.By an appropriate dimensioning of the inductor circuit and by adjusting the power frequency, you can essentially confine the magnetic field to the liquid induced outside the heating instrument. We access thus with excellent energy yields (greater than 90%). There are also advantages specific to heating by induction: low thermal inertia; possibility finely regulate power and temperature; possibility to transmit strong powers.

L'invention propose également un instrument de chauffage pour plonger dans un liquide électrolytique permettant de mettre en oeuvre le procédé ci-dessus dans le cas d'un liquide électrolytique. D'autres types d'instruments seraient néanmoins utilisables. L'instrument selon l'invention comprend un solénoïde disposé coaxialement dans un tube cylindrique électriquement isolant et fermé à son extrémité inférieure, des bornes de raccordement du solénoïde à une alimentation en courant alternatif, et une culasse en matériau magnétique doux s'étendant axialement à l'intérieur du solénoïde. Cette culasse peut présenter, à son extrémité adjacente à l'extrémité inférieure du tube, un rebord dirigé radialement vers l'extérieur du solénoïde, ceci afin d'améliorer l'efficacité.The invention also provides a heating instrument to immerse in an electrolytic liquid allowing the above process to be carried out in the case of an electrolytic liquid. Other types of instruments would nevertheless be usable. The instrument according to the invention comprises a solenoid arranged coaxially in an electrically insulating cylindrical tube closed at its lower end, solenoid connection terminals to an AC power supply, and a cylinder head soft magnetic material extending axially inside solenoid. This cylinder head may have, at its end adjacent to the lower end of the tube, a directed rim radially outward from the solenoid, so improve efficiency.

La culasse est agencée pour concentrer dans le liquide le champ magnétique induit. On peut alors utiliser de plus grandes profondeurs d'effet de peau en conservant un excellent rendement énergétique, ce qui permet d'utiliser une alimentation de fréquence sensiblement plus basse, donc plus économique.The cylinder head is arranged to concentrate in the liquidates the induced magnetic field. We can then use greater depths of skin effect by retaining a excellent energy efficiency, which makes it possible to use a significantly lower frequency supply, therefore more economic.

L'invention propose en outre un four de chauffage d'un liquide électriquement conducteur, comprenant une cuve pour recevoir ledit liquide, un solénoïde électriquement isolé du liquide, s'étendant à l'intérieur de la cuve, une culasse s'étendant axialement à l'intérieur du solénoïde, et une alimentation en courant alternatif reliée au solénoïde.The invention further provides a heating oven of an electrically conductive liquid, comprising a tank to receive said liquid, an electrically solenoid isolated from the liquid, extending inside the tank, a cylinder head extending axially inside the solenoid, and an AC power supply connected to the solenoid.

D'autres particularités et avantages de la présente invention apparaítront dans la description ci-après d'exemples de réalisation préférés mais non limitatifs, en référence aux dessins annexés, dans lesquels :

  • la figure 1 est un schéma illustrant la mise en oeuvre d'un procédé selon l'invention ;
  • la figure 2 est une vue schématique en coupe axiale d'un instrument de chauffage selon l'invention ;
  • la figure 3 est un schéma illustrant la répartition des lignes de flux magnétique dans un liquide chauffé par l'instrument représenté sur la figure 2 ; et
  • les figures 4 à 6 sont des schémas en coupe de trois exemples de four selon l'invention.
Other features and advantages of the present invention will appear in the description below of preferred but nonlimiting exemplary embodiments, with reference to the accompanying drawings, in which:
  • Figure 1 is a diagram illustrating the implementation of a method according to the invention;
  • Figure 2 is a schematic view in axial section of a heating instrument according to the invention;
  • Figure 3 is a diagram illustrating the distribution of magnetic flux lines in a liquid heated by the instrument shown in Figure 2; and
  • Figures 4 to 6 are sectional diagrams of three examples of an oven according to the invention.

La figure 1 montre une cuve cylindrique 10 contenant un liquide électrolytique à chauffer, typiquement entre la température ambiante et une température de 100 à 150°C, voire plus élevée. Un enroulement inducteur, constitué ici par un solénoïde 12, est immergé dans le liquide et alimenté par un générateur de courant alternatif 14. Le solénoïde 12 fait partie d'un instrument de chauffage comportant en outre les bornes de raccordement au générateur 14 et des moyens d'isolation électrique entre le liquide et le cuivre du solénoïde et les bornes de raccordement. Ces moyens d'isolation électrique assurent également la protection chimique du cuivre vis-à-vis du liquide à chauffer. Ils peuvent être constitués par un revêtement isolant et anticorrosif appliqué sur les spires du solénoïde ou encore par un boítier cylindrique double entourant le solénoïde. Un tel boítier peut également être agencé pour permettre la circulation d'un fluide de refroidissement des spires du solénoïde 12.Figure 1 shows a cylindrical tank 10 containing an electrolytic liquid to be heated, typically between the room temperature and a temperature of 100 to 150 ° C, or even higher. An inductor winding, constituted here by a solenoid 12, is immersed in the liquid and supplied by a alternating current generator 14. The solenoid 12 makes part of a heating instrument further comprising the terminals for connection to generator 14 and isolation means electric between the liquid and the copper of the solenoid and connection terminals. These means of electrical insulation also provide chemical protection for copper vis-à-vis the liquid to be heated. They can be made up by an insulating and anticorrosive coating applied to the solenoid turns or by a cylindrical case double surrounding the solenoid. Such a case can also be arranged to allow the circulation of a cooling of the solenoid turns 12.

Dans l'agencement de la figure 1, le liquide à chauffer se trouve à la fois autour et à l'intérieur du solénoïde 12. Le courant alternatif appliqué induit dans le liquide un champ magnétique dont des lignes de flux 16 sont représentées. Du fait de la conductivité du liquide, qui est par exemple comprise entre 10 et 100 S/m, ce champ magnétique génère des courants de Foucault qui chauffent le liquide par effet Joule.In the arrangement of Figure 1, the liquid to heat is found both around and inside the solenoid 12. The applied alternating current induced in the liquid a magnetic field whose flow lines 16 are represented. Due to the conductivity of the liquid, which is for example between 10 and 100 S / m, this magnetic field generates eddy currents which heat the liquid by Joule effect.

La fréquence d'alimentation est choisie en fonction du diamètre du solénoïde, du diamètre de la cuve et de la conductivité électrique du liquide, en tenant compte du fait que cette dernière augmente en général avec la température. En première approximation, la fréquence retenue est inversement proportionnelle à la conductivité du liquide et au carré de la profondeur d'effet de peau désirée. Si nécessaire, une fréquence d'alimentation optimale peut être recherchée par des essais préalables. Si la cuve 10 est métallique, on choisit la fréquence de façon que les parois de la cuve 10 ne soient pas chauffées directement, c'est-à-dire de façon que le champ magnétique induit à l'extérieur du solénoïde 12 reste essentiellement confiné dans le liquide. En pratique, la fréquence d'alimentation sera souvent supérieure à 50 kHz.The supply frequency is chosen according to the diameter of the solenoid, the diameter of the tank and the electrical conductivity of the liquid, taking into account the fact that the latter generally increases with temperature. As a first approximation, the frequency used is inversely proportional to the conductivity of the liquid and squared the desired skin effect depth. Yes necessary, an optimal power frequency can be sought by previous tests. If tank 10 is metallic, we choose the frequency so that the walls of the tank 10 are not heated directly, that is to say so that the magnetic field induced on the outside of solenoid 12 remains essentially confined in the liquid. In practice, the power frequency will be often above 50 kHz.

La figure 2 montre un instrument de chauffage permettant de mettre en oeuvre le procédé à des fréquences d'alimentation plus basses. Outre un solénoïde 22 et ses bornes de raccordement non représentées, cet instrument comporte une culasse 24 et un tube conteneur 26. Le tube 26 est en matériau anti-corrosif électriquement isolant. Il a une forme cylindrique qui entoure le solénoïde 22 et la culasse 24, avec une extrémité inférieure fermée 28. La culasse 24 est par exemple réalisée en tôles magnétiques disposées en étoile pour des fréquences d'alimentation de l'ordre de 5 kHz ou, pour des fréquences plus élevées (typiquement 20 kHz) à partir de barreaux de ferrite. Elle a une forme générale cylindrique coaxiale au solénoïde 22 et au tube 26, avec un alésage axial 30 permettant de faire circuler un fluide de refroidissement du solénoïde et de la culasse, par exemple de l'eau. A chacune des extrémités axiales du solénoïde 22, la culasse 24 peut présenter un rebord 32, 34 s'étendant radialement vers l'extérieur, comme le montre la figure 4.Figure 2 shows a heating instrument allowing the process to be implemented at frequencies lower feed. Besides a solenoid 22 and its connection terminals not shown, this instrument comprises a cylinder head 24 and a container tube 26. The tube 26 is made of electrically insulating anti-corrosion material. He has a cylindrical shape which surrounds the solenoid 22 and the cylinder head 24, with a closed lower end 28. The cylinder head 24 is for example made of magnetic sheets arranged in a star for supply frequencies of around 5 kHz or, for higher frequencies (typically 20 kHz) from ferrite bars. She has a generally cylindrical shape coaxial with the solenoid 22 and to the tube 26, with an axial bore 30 making it possible to make circulate coolant from the solenoid and the cylinder head, for example water. At each end axial of the solenoid 22, the cylinder head 24 may have a rim 32, 34 extending radially outwards, as shown in Figure 4.

La culasse 24 a une structure propre à concentrer la puissance transmise face aux spires du solénoïde 22. En particulier, les lignes de flux se courbent selon un angle important dans le rebord inférieur 32. Ainsi, lorsque l'instrument est plongé verticalement dans la cuve 10 contenant le liquide électrolytique à chauffer, on peut induire un champ magnétique élevé sans que ce champ soit important au niveau du fond de la cuve. Le champ est bien concentré dans le liquide, même si la profondeur de l'effet de peau est relativement importante, c'est-à-dire si la fréquence d'alimentation est relativement basse. Le solénoïde peut alors être alimenté à des fréquences à partir de 5 kHz seulement pour une puissance transmise de plusieurs centaines de kW et une conductivité du liquide de l'ordre de 30 à 50 S/m. La figure 3 illustre la distribution des lignes de champ magnétique 36 dans l'exemple d'une puissance de 237 kW, d'une fréquence de 20 kHz et d'une conductivité de 37 S/m. A une fréquence de 20 kHz, le fond de la cuve n'est pas du tout chauffé. De même, le rebord supérieur 34 de la culasse limite l'extension du champ magnétique au-dessus de la surface du liquide.The cylinder head 24 has a structure capable of concentrating the power transmitted opposite the turns of the solenoid 22. In particular, the flow lines bend at an angle important in the bottom edge 32. So when the instrument is immersed vertically in the tank 10 containing the electrolytic liquid to be heated, one can induce a high magnetic field without this field being important at the bottom of the tank. The field is good concentrated in the liquid, even if the depth of the effect of skin is relatively large, i.e. if the power frequency is relatively low. The solenoid can then be supplied at frequencies from 5 kHz only for a transmitted power of several hundred of kW and a conductivity of the liquid of the order of 30 to 50 S / m. Figure 3 illustrates the distribution of field lines magnetic 36 in the example of a power of 237 kW, a frequency of 20 kHz and a conductivity of 37 S / m. To one frequency of 20 kHz, the bottom of the tank is not at all heated. Likewise, the upper edge 34 of the cylinder head limits the extension of the magnetic field above the surface of the liquid.

On peut bien entendu plonger plusieurs instruments de chauffage dans une même cuve. On prend alors toutefois la précaution de les raccorder de façon que le champ magnétique créé par l'un ne soit pas en opposition de phase avec celui créé par ses voisins.You can of course immerse several instruments heating in the same tank. We then take the take care to connect them so that the magnetic field created by one is not in phase opposition with that created by its neighbors.

La figure 4 montre un four utilisable pour le chauffage d'un liquide conducteur à des températures plus élevées. Le liquide en question peut être un métal (ou alliage métallique) fondu, ou encore un verre en fusion. Le four comporte une cuve 110 en matériau réfractaire. Le matériau réfractaire de la paroi de la cuve est placé dans une enveloppe métallique 111. La cuve est recouverte d'un couvercle 113, pourvu d'une ouverture 115 pour l'introduction de la matière (liquide ou solide non encore fondu) à chauffer. Un bec de coulée 117 est prévu à la partie supérieure de la cuve 110 pour évacuer de la cuve le liquide chauffé.Figure 4 shows an oven that can be used for heating a conductive liquid to higher temperatures high. The liquid in question can be a metal (or metallic alloy) melted, or a molten glass. The oven comprises a tank 110 made of refractory material. The refractory material from the wall of the tank is placed in a metal casing 111. The tank is covered with a cover 113, provided with an opening 115 for introduction matter (liquid or solid not yet melted) to heat. A pouring spout 117 is provided in the part top of tank 110 to drain the liquid from the tank heated.

Un solénoïde 122 pourvu d'une culasse intérieure 124 est placé à l'intérieur de la cuve 110. Le solénoïde est relié à un générateur de courant alternatif 114. Comme dans le cas de la figure 2, un trajet est ménagé autour du solénoïde 122 et de la culasse 124 pour permettre le passage d'un fluide de refroidissement, tel que de l'eau, que fait circuler une pompe 119.A solenoid 122 provided with an internal cylinder head 124 is placed inside the tank 110. The solenoid is connected to an alternating current generator 114. As in in the case of Figure 2, a path is provided around the solenoid 122 and cylinder head 124 to allow passage of a coolant, such as water, that does circulate a pump 119.

Dans l'exemple de réalisation de la figure 4, l'inducteur constitué par le solénoïde 122 et sa culasse 124 est placé dans un fourreau réfractaire 126 intégré au fond de la cuve 110. Le fourreau 126 isole électriquement et thermiquement le solénoïde 122 et sa culasse 124 du liquide. Le solénoïde est placé verticalement vers le milieu de la cuve, et est dimensionné pour que le champ magnétique induit soit essentiellement confiné dans le liquide à chauffer.In the embodiment of Figure 4, the inductor constituted by the solenoid 122 and its cylinder head 124 is placed in a refractory sheath 126 integrated into the bottom of the tank 110. The sheath 126 electrically insulates and thermally the solenoid 122 and its cylinder head 124 of the liquid. The solenoid is placed vertically towards the middle of the tank, and is dimensioned so that the magnetic field induced is essentially confined in the liquid to be heated.

Dans le cas où le liquide à chauffer est un métal non ferreux ou un alliage de métaux non ferreux, la conductivité électrique est très élevée (résistivités de l'ordre de 10 à 20.10-8 Ω.m). La culasse 124 peut alors être réalisée à partir de tôles magnétiques, et le solénoïde peut être alimenté à une fréquence supérieure à 100 Hz, typiquement de 300 à 500 Hz. Les matériaux réfractaires de la cuve 110 et du fourreau 126 sont choisis parmi ceux habituellement utilisés en métallurgie (pisé par exemple).In the case where the liquid to be heated is a non-ferrous metal or an alloy of non-ferrous metals, the electrical conductivity is very high (resistivities of the order of 10 to 20.10 -8 Ω.m). The cylinder head 124 can then be produced from magnetic sheets, and the solenoid can be supplied at a frequency greater than 100 Hz, typically from 300 to 500 Hz. The refractory materials of the tank 110 and of the sheath 126 are chosen from those usually used in metallurgy (adobe for example).

Dans le cas où le liquide à chauffer est un verre en fusion, la conductivité est moins élevée (jusqu'à 150 à 200 S/m) de sorte qu'on est amené à augmenter la fréquence d'alimentation pour une même puissance de chauffage. On utilise alors une culasse 124 réalisée à partir de barreaux de ferrite, et des fréquences d'alimentation supérieures à 10 kHz, typiquement d'environ 20 kHz. Les matériaux réfractaires de la cuve 110 et du fourreau 126 peuvent être des céramiques telles que celles habituellement utilisées dans l'industrie du verre.In the case where the liquid to be heated is a glass in melting, the conductivity is lower (up to 150 to 200 S / m) so that we have to increase the frequency supply for the same heating power. We then uses a cylinder head 124 made from bars of ferrite, and supply frequencies higher than 10 kHz, typically around 20 kHz. The materials refractories of the tank 110 and of the sheath 126 can be ceramics such as those usually used in the glass industry.

Le four représenté sur la figure 5 diffère de celui de la figure 4 en ce que le fourreau réfractaire 226 contenant le solénoïde 222 et la culasse 224 est suspendu au couvercle 213 de la cuve 210 au lieu d'être fixé ou intégré à la paroi du fond de la cuve. On comprendra que de nombreux autres agencements de l'inducteur à l'intérieur de la cuve sont envisageables.The oven shown in Figure 5 differs from that of Figure 4 in that the refractory sheath 226 containing the solenoid 222 and the cylinder head 224 is suspended from the cover 213 of tank 210 instead of being fixed or integrated to the bottom wall of the tank. It will be understood that many other arrangements of the inductor inside the tank are possible.

La figure 6 montre un autre exemple de four pouvant notamment être utilisé pour zinguer des tôles. Le solénoïde 322, la culasse 324 et le fourreau réfractaire 326 sont placés près du fond de la cuve 310, avec leur axe parallèle à ce fond. Le fourreau 326 traverse par exemple la largeur de la cuve comme représenté. Il peut alors être nécessaire de subdiviser le solénoïde 322 en plusieurs tronçons d'enroulement alimentés séparément. Le liquide chauffé étant du zinc fondu, on peut, grâce à un agencement conventionnel de rouleaux, faire défiler une tôle dans l'intervalle situé entre l'inducteur et le fond de la cuve pour lui appliquer un revêtement de zinc.Figure 6 shows another example of an oven that can in particular be used to galvanize sheets. The solenoid 322, the cylinder head 324 and the refractory sheath 326 are placed near the bottom of the tank 310, with their parallel axis at this background. The sleeve 326 crosses for example the width of the tank as shown. It may then be necessary to subdivide the solenoid 322 into several sections windings supplied separately. The heated liquid being molten zinc, we can, thanks to a conventional arrangement of rollers, scroll a sheet in the interval located between the inductor and the bottom of the tank to apply it a zinc coating.

Claims (16)

  1. Method for heating an electrolytic liquid, characterized in that at least one heating instrument including an inducing solenoid circuit (12; 22) which is electrically insulated from the liquid is immersed into the said liquid, and in that alternating current is supplied to the inducing circuit, so as to induce eddy currents within the electrolytic liquid.
  2. Method according to Claim 1, characterized in that, the liquid being placed in a vessel (10) made of electrically conductive material, the inducing circuit is supplied at a frequency selected so as to confine, substantially within the liquid, the magnetic field induced outside the heating instrument.
  3. Method according to Claim 1 or 2, characterized in that the heating instrument includes means for cooling the inducing circuit.
  4. Method according to any one of Claims 1 to 3, characterized in that the heating instrument further includes a yoke (24), made of soft magnetic material, extending axially inside the solenoid, the yoke having, at least one axial end of the solenoid, a rim (32, 34) directed radially towards the outside of the solenoid.
  5. Heating instrument for immersing into an electrolytic liquid, characterized in that it comprises a solenoid (22) arranged coaxially in an electrically insulating cylindrical tube (26) which is closed at its lower end (28), terminals for connecting the solenoid to an alternating current supply (14), and a yoke (24), made of soft magnetic material, extending axially inside the solenoid.
  6. Heating instrument according to Claim 5, characterized in that the yoke has, at its end adjacent to the lower end of the tube, a rim (32) directed radially towards the outside of the solenoid.
  7. Heating instrument according to Claim 6, characterized in that the yoke includes another rim (34), directed radially towards the outside of the solenoid (22), at its end opposite the lower end of the tube (26).
  8. Heating instrument according to any one of Claims 5 to 7, characterized in that the yoke (24) includes an axial bore (30) for the circulation of a cooling fluid.
  9. Method for heating an electrically conductive liquid, characterized in that the said liquid is placed in a vessel (10; 110; 210; 310) in which there is additionally at least one solenoid (22; 122; 222; 322) which is electrically insulated from the liquid, with a yoke (24; 124; 224; 324), made of soft magnetic material, extending axially inside the solenoid, and in that alternating current is supplied to the solenoid.
  10. Method according to Claim 9, characterized in that the said electrically conductive liquid is a molten non-ferrous metal or a molten non-ferrous metal alloy.
  11. Method according to Claim 10, characterized in that the yoke (124; 224; 324) is made of magnetic metal sheets, and in that the supply frequency of the solenoid is greater than 100 Hz.
  12. Method according to Claim 9, characterized in that the said electrically conductive liquid is a molten glass.
  13. Method according to Claim 12, characterized in that the yoke (124; 224; 324) has a ferrite-based composition, and in that the supply frequency of the solenoid is greater than 10 kHz.
  14. Furnace for heating an electrically conductive liquid, characterized in that it comprises a vessel (10; 110; 210; 310) for holding the said liquid, a solenoid (22; 122; 222; 322), which is electrically insulated from the liquid and extends inside the vessel, a yoke (24; 124; 224; 324) extending axially inside the solenoid, and an alternating current supply (14; 114) connected to the solenoid.
  15. Furnace according to Claim 14, characterized in that it furthermore comprises means (119) for cooling the solenoid and the yoke.
  16. Furnace according to Claim 14 or 15, characterized in that the solenoid (322) is placed close to the bottom of the vessel (310), with its axis parallel to the said bottom.
EP96400520A 1995-03-16 1996-03-13 Process and equipment for heating an electrically conductive liquid Expired - Lifetime EP0732866B1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
FR9503054A FR2731867B1 (en) 1995-03-16 1995-03-16 METHOD AND INSTRUMENT FOR HEATING AN ELECTROLYTIC LIQUID
FR9503054 1995-03-16
FR9600737A FR2731868B1 (en) 1995-03-16 1996-01-23 METHOD AND EQUIPMENT FOR HEATING AN ELECTRICALLY CONDUCTIVE LIQUID
FR9600737 1996-01-23

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EP0732866A1 EP0732866A1 (en) 1996-09-18
EP0732866B1 true EP0732866B1 (en) 2002-02-20

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EP96400520A Expired - Lifetime EP0732866B1 (en) 1995-03-16 1996-03-13 Process and equipment for heating an electrically conductive liquid

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EP (1) EP0732866B1 (en)
JP (1) JPH08315971A (en)
AT (1) ATE213582T1 (en)
CA (1) CA2171788A1 (en)
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FR2821647B1 (en) * 2001-03-02 2003-10-24 Robert Lipp OMNIDIRECTIONAL SUBMERSIBLE HYDRAULIC TURBINE WITH PERPENDICULAR AXIS
DE102013211563A1 (en) * 2013-06-19 2014-12-24 Behr-Hella Thermocontrol Gmbh heater

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US1362622A (en) * 1920-04-26 1920-12-21 Gen Electric Electric heater
US3936625A (en) * 1974-03-25 1976-02-03 Pollutant Separation, Inc. Electromagnetic induction heating apparatus
FR2694994B1 (en) * 1992-08-24 1994-11-10 Electricite De France Electric heating device by induction of a fluid.
JP3112137B2 (en) * 1993-07-13 2000-11-27 富士電機株式会社 High frequency electromagnetic induction heater

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DE69619285D1 (en) 2002-03-28
CA2171788A1 (en) 1996-09-17
FR2731868A1 (en) 1996-09-20
FR2731868B1 (en) 1997-06-06
JPH08315971A (en) 1996-11-29
EP0732866A1 (en) 1996-09-18
ATE213582T1 (en) 2002-03-15
DE69619285T2 (en) 2002-11-21

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