EP0070273B1 - Plasma melting furnace - Google Patents

Plasma melting furnace Download PDF

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Publication number
EP0070273B1
EP0070273B1 EP82890100A EP82890100A EP0070273B1 EP 0070273 B1 EP0070273 B1 EP 0070273B1 EP 82890100 A EP82890100 A EP 82890100A EP 82890100 A EP82890100 A EP 82890100A EP 0070273 B1 EP0070273 B1 EP 0070273B1
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EP
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Prior art keywords
plasma
melting furnace
axes
plasma melting
covering cap
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EP82890100A
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German (de)
French (fr)
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EP0070273A1 (en
Inventor
Walter Dipl.-Ing.Dr. Lugscheider
Ernst Ing. Riegler
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Voestalpine AG
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Voestalpine AG
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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
    • H05B7/00—Heating by electric discharge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00—Arrangement of elements for electric heating in or on furnaces
    • F27D11/08—Heating by electric discharge, e.g. arc discharge

Definitions

  • the invention relates to a plasma melting furnace with a furnace body with a vertical axis, a cover, one or more electrodes penetrating the bottom of the furnace body, furthermore with at least three plasma torches, which pass through the essentially cylindrical furnace wall or the cover, are arranged inclined towards the bottom and are oriented vertically Filling openings.
  • Plasma melting furnaces of this type are known, for example from US-A-3 422 206, in which a melting furnace is described in which the plasma torches are arranged in the essentially cylindrical furnace wall.
  • the direct arc plasma formed after the voltage is applied does not radiate in the axial direction of the burner as a linear radiator.
  • the material introduced in batches from above is stored as a conical bed in the furnace; it must not lie over the burners, otherwise short circuits occur.
  • the heat transfer from the arc plasmas to the melting material takes place from above.
  • the melting capacity of such furnaces is low due to the poor heat transfer in this direction.
  • plasma torches according to US-A-4181 504 are also used in a process for the gasification of lumpy, carbon-containing material by pyrolysis, the carbon-containing material being introduced continuously into a cylindrical furnace vessel with a horizontal axis. At the same time, stoichiometric amounts of a reactant from the group of hydrogen, ammonia and water are added.
  • a stove which contains an electrically conductive, refractory material, forms a horizontal plane containing the axis of the furnace vessel.
  • the free furnace chamber in which the plasma arcs burn and in which the gasification reactions take place, has the shape of a half cylinder.
  • the plasma torches are inclined against the horizontal and arranged on a line parallel to the axis of the furnace vessel. If, according to an alternative embodiment, the burners are provided on both sides of a vertical plane through the axis of the furnace vessel, they are offset from one another.
  • the normal projections of all burner axes are parallel to each other.
  • the axes of the feeds for the carbon-containing material are each in a plane running through the normal projection of a plasma torch axis.
  • Each feeder is also divided into two lines with inclined axes. Both the inlets and the lines lie in the vertical plane that goes through the points of impact of the plasma rays on the stove and is perpendicular to the normal projections of the burner axes.
  • a furnace vessel used for gasification according to US-A-4181 504 is not suitable as a melting furnace.
  • the object of the invention is to overcome the disadvantages and difficulties described and to create a plasma melting furnace in which small pieces of iron sponge, light scrap and similar metallic or non-metallic materials can be continuously introduced and at the same time the heat transfer to the melting material and thus the efficiency is improved.
  • the object is achieved in a plasma melting furnace of the type defined in the introduction that for the continuous melting of small pieces of material, such as light scrap and sponge iron, the axes of the filling openings provided in the cover in a plane running through the angular symmetry of the normal projection of the axes of two adjacent plasma torches as well as between two vertical planes, which are each perpendicular to the normal projections of the individual torch axes and one of the two planes is placed on the melt by the points of impact of the direct plasma beams and the second plane is a third of the length of the projection of the direct plasma beams from whose exit from the burners runs parallel to it until they meet.
  • small pieces of material such as light scrap and sponge iron
  • the substantially spherical sponge iron particles or the small-sized materials are fed to the metal bath through the filling openings positioned according to the invention in such a way that their surfaces are exposed to the heat radiation of the direct arc plasma of two adjacent burners during the free fall. During the fall through these zones, in which the radiation fields of adjacent plasma torches overlap, the solid materials are preheated and already partially liquefied. With the high temperatures of the direct arc plasmas of around 20,000 K, the heat transfer to all free-falling particles is very in intensive; This type of heat transfer is particularly effective when melting sponge iron, an iron carrier with high porosity.
  • the cover is expediently hemispherical, which causes good reflection and concentration of the heat radiation on the metal bath. Furthermore, the stone consumption for the lining is lower.
  • the cover is advantageously constructed in two parts, the upper part being detachably connected to the lower part and the plasma torches being guided through the lower part of the cover.
  • the filling openings are preferably provided in the upper part.
  • the upper part has an opening or a connector for the removal of furnace gases.
  • feed pipes which can be fed with small-scale material are arranged above the filling openings by means of a vibration conveyor device, the axes of which are aligned with the vertical axes of the filling openings.
  • 1 shows a vertical section through a plasma melting furnace according to the invention.
  • 2 shows an enlarged schematic horizontal section through the plasma melting furnace in the region of the melt surface, with omission of various design details; the heat radiation fields from two adjacent direct arc plasmas from four plasma burners and the positions of four filling openings are shown.
  • the plasma melting furnace is generally designated 1 in FIG. 1. It has a furnace body 2 for receiving the melt 3. An electrode 4 protrudes into the melt 3 through the bottom of the furnace body 2.
  • 5 is generally used to denote the cover of the furnace, which has an essentially hemispherical shape.
  • the cover 5 is constructed in the embodiment shown from two parts, a detachably attached to the furnace body 2 lower part 6 with four plasma torches 8 inclined at an acute angle to the bottom of the furnace body or to the bath surface 7, which are axially displaceably mounted on a support structure 9 , and an upper part 10 detachably connected to the lower part 6 of the hood 5, which can be lifted off by means of a lifting and swiveling device, not shown, as is customary in plasma and arc furnaces.
  • the plasma torches 8 are ignited and the material introduced is melted down. After a sufficiently large sump of liquid metal has been formed, the continuous supply of small pieces of iron sponge and / or light scrap is started.
  • the furnace gases which arise during the melting process are discharged through an opening provided in the upper part 10 or through a connecting piece 11.
  • the connector 11 can be connected to a suction pipe.
  • the filling openings 12 are either lined heat-resistant, the lining on the outside of the furnace is advantageously expanded in a funnel shape, or they are penetrated by water-cooled jacket tubes of appropriate diameter, which tubes also expediently have a funnel-shaped expansion.
  • four filling openings 12 are provided in the upper part 10. They correspond to feed pipes 13, which in turn lie under openings of a vibrating conveyor trough 14, not shown. The material to be melted is conveyed through this channel, the direction of conveyance is indicated by the arrow 15.
  • the plasma melting furnace is tiltably supported on weighing beams 16 and associated raceways 17 in a known manner; it also has an opening, not shown, for the pouring of melt and possibly slag.
  • the inner boundary of the cylindrical furnace body 2 of the plasma melting furnace 1 is designated by 18.
  • 19 denotes the direct arc plasmas (plasma jets) from the four plasma torches 8 arranged symmetrically with respect to the vertical axis of the plasma melting furnace.
  • a line 20 drawn in broken lines is drawn through the point of impact of one of the direct plasma jets onto the melt perpendicular to the projection of the plasma jet.
  • a length L is assigned to the projection of the plasma jet 19 from its exit from the burner 8 to its point of impact.
  • a second line 21 is drawn parallel to line 20 at a distance of L / 3. Lines 20 and 21 mark the traces of two vertical planes.
  • the point of impact mentioned can be easily determined optically.
  • the field lines 22 of the heat radiation are shown in broken lines, which illustrate the directions of propagation of the heat radiation.
  • the area chosen according to the invention for arranging the vertical axes of the filling openings lies in a plane running through the angular symmetry 24 of the normal projection of the axes of two respectively adjacent plasma torches 8 and between the two vertical planes through lines 20 and 21.
  • the material falling through the filling openings passes directly in zones of concentrated heat radiation, one of which is designated 23.
  • Favorable positions of filling openings leading through the cover 5 or the upper part 10 of a plasma melting furnace according to the invention are indicated by 12 '.
  • the direct arc plasmas are through the supplied materials not disturbed.
  • a plasma melting furnace according to the invention, continuous operation with all embodiments of burners is possible.
  • Alloying elements and / or slag formers such as lime and fluorspar, can of course also be introduced through the filling openings 12 continuously or discontinuously; the number of burners is variable and depends on the type of material to be melted and the capacity of the plasma melting furnace.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Gasification And Melting Of Waste (AREA)
  • Furnace Details (AREA)

Description

Die Erfindung betrifft einen Plasmaschmelzofen mit einem Ofenkörper mit vertikaler Achse, einer Abdeckhaube, einer oder mehreren, den Boden des Ofenkörpers durchsetzenden Elektroden, weiters mit wenigstens drei, die im wesentlichen zylindrische Ofenwand oder die Abdeckhaube durchsetzenden, zum Boden hin geneigt angeordneten Plasmabrennern und vertikal gerichteten Einfüllöffnungen.The invention relates to a plasma melting furnace with a furnace body with a vertical axis, a cover, one or more electrodes penetrating the bottom of the furnace body, furthermore with at least three plasma torches, which pass through the essentially cylindrical furnace wall or the cover, are arranged inclined towards the bottom and are oriented vertically Filling openings.

Plasmaschmelzöfen dieser Art sind bekannt, beispielsweise aus der US-A-3 422 206, in welcher ein Schmelzofen beschrieben ist, bei dem die Plasmabrenner in der im wesentlichen zylindrischen Ofenwand angeordnet sind. Das nach dem Anlegen der Spannung gebildete direkte Bogenplasma strahlt als Linearstrahler nicht in der Achsenrichtung des Brenners. Das von oben chargenweise eingebrachte Material lagert als kegelige Schüttung im Ofen ; es darf nicht über den Brennern zu liegen kommen, da sonst Kurzschlüsse entstehen. Die Wärmeübertragung von den Bogenplasmen auf das Schmelzgut erfolgt von oben her. Die Einschmelzleistung solcher Öfen ist aufgrund des schlechten Wärmeüberganges in dieser Richtung gering.Plasma melting furnaces of this type are known, for example from US-A-3 422 206, in which a melting furnace is described in which the plasma torches are arranged in the essentially cylindrical furnace wall. The direct arc plasma formed after the voltage is applied does not radiate in the axial direction of the burner as a linear radiator. The material introduced in batches from above is stored as a conical bed in the furnace; it must not lie over the burners, otherwise short circuits occur. The heat transfer from the arc plasmas to the melting material takes place from above. The melting capacity of such furnaces is low due to the poor heat transfer in this direction.

Weiters sind aus der DE-A-2 912 843 Plasmabrenner mit ringförmiger Kathode zur Erzeugung eines rotierenden Lichtbogens bekannt, wobei beispielsweise schlackenbildende Mittel mit Hilfe eines Inertgases durch eine zentrale Öffnung eines durch die Ofendecke geführten Brenners gefördert werden können. Dabei ergibt sich der Nachteil, daß durch Feststoffzusätze das Bogenplasma gestört wird.Furthermore, from DE-A-2 912 843, plasma torches with a ring-shaped cathode for producing a rotating arc are known, slag-forming agents, for example, being able to be conveyed with the aid of an inert gas through a central opening of a burner guided through the furnace roof. This has the disadvantage that the arc plasma is disturbed by the addition of solids.

Plasmabrenner werden schließlich nach der US-A-4181 504 auch bei einem Verfahren zur Vergasung von stückigem, kohlenstoffhältigem Material durch Pyrolyse eingesetzt, wobei das. kohlenstoffhältige Material kontinuierlich in ein zylindrisches Ofengefäß mit waagrecht liegender Achse eingebracht wird. Gleichzeitig werden stöchiometrische Mengen eines Reaktanten aus der Gruppe Wasserstoff, Ammoniak und Wasser zugeführt. Ein Herd, welcher ein elektrisch leitendes, feuerfestes Material enthält, bildet eine waagrechte, die Achse des Ofengefäßes enthaltende Ebene. Die freie Ofenkammer, in welcher die Plasmabögen brennen und worin die Vergasungsreaktionen stattfinden, weist die Form eines Halbzylinders auf. Die Plasmabrenner sind gegen die Waagrechte geneigt und auf einer Linie parallel zur Achse des Ofengefäßes angeordnet. Sind die Brenner nach einer alternativen Ausführungsform beiderseits einer durch die Achse des Ofengefäßes gelegten vertikalen Ebene vorgesehen, sind sie gegeneinander versetzt.Finally, plasma torches according to US-A-4181 504 are also used in a process for the gasification of lumpy, carbon-containing material by pyrolysis, the carbon-containing material being introduced continuously into a cylindrical furnace vessel with a horizontal axis. At the same time, stoichiometric amounts of a reactant from the group of hydrogen, ammonia and water are added. A stove, which contains an electrically conductive, refractory material, forms a horizontal plane containing the axis of the furnace vessel. The free furnace chamber, in which the plasma arcs burn and in which the gasification reactions take place, has the shape of a half cylinder. The plasma torches are inclined against the horizontal and arranged on a line parallel to the axis of the furnace vessel. If, according to an alternative embodiment, the burners are provided on both sides of a vertical plane through the axis of the furnace vessel, they are offset from one another.

Die Normalprojektionen aller Brennerachsen sind zueinander parallel. Die Achsen der Zuführungen für das kohlenstoffhältige Material befinden sich jeweils in einer durch die Normalprojektion einer Plasmabrennerachse verlaufenden Ebene. Jede Zuführung teilt sich überdies in zwei Leitungen mit geneigten Achsen. Sowohl die Zuführungen als auch die Leitungen liegen in jener vertikalen Ebene, welche durch die Auftreffstellen der Plasmastrahlen auf den Herd geht und senkrecht zu den Normalprojektionen der Brennerachsen steht. Ein gemäß der US-A-4181 504 zur Vergasung eingesetztes Ofengefäß ist als Schmelzofen nicht geeignet.The normal projections of all burner axes are parallel to each other. The axes of the feeds for the carbon-containing material are each in a plane running through the normal projection of a plasma torch axis. Each feeder is also divided into two lines with inclined axes. Both the inlets and the lines lie in the vertical plane that goes through the points of impact of the plasma rays on the stove and is perpendicular to the normal projections of the burner axes. A furnace vessel used for gasification according to US-A-4181 504 is not suitable as a melting furnace.

Mit den bekannten Plasmaschmelzöfen ist es nicht möglich, kleinstückigen Eisenschwamm, Leichtschrott und ähnliche Materialien kontinuierlich und mit gutem Wirkungsgrad aufzuschmelzen, d. h. eine hohe Schmelzleistung bei gleichzeitig niedrigem Energieverbrauch zu erzielen. Eisenschwamm ist im Vergleich zu kompaktem Eisen schlecht wärmeleitend und nahezu als Isolator zu betrachten ; er schmilzt in einem Bad aus flüssigem Metall schwer auf, wird dabei manchmal auch mit Schlacke überzogen und überhitzt, so daß explosionsartige Siedeverzüge stattfinden können.With the known plasma melting furnaces it is not possible to melt small pieces of iron sponge, light scrap and similar materials continuously and with good efficiency. H. to achieve a high melting capacity with low energy consumption. Compared to compact iron, sponge iron is poorly heat-conducting and can almost be regarded as an insulator; it melts heavily in a bath of liquid metal, sometimes being covered with slag and overheated, so that explosive boiling delays can occur.

Die Erfindung stellt sich die Aufgabe, die geschilderten Nachteile und Schwierigkeiten zu überwinden und einen Plasmaschmelzofen zu schaffen, in welchen man kleinstückigen Eisenschwamm, Leichtschrott und ähnliche metallische oder nichtmetallische Materialien kontinuierlich einbringen kann und gleichzeitig die Wärmeübertragung auf das Schmelzgut und somit der Wirkungsgrad verbessert ist.The object of the invention is to overcome the disadvantages and difficulties described and to create a plasma melting furnace in which small pieces of iron sponge, light scrap and similar metallic or non-metallic materials can be continuously introduced and at the same time the heat transfer to the melting material and thus the efficiency is improved.

Die gestellte Aufgabe wird bei einem Plasmaschmelzofen der eingangs definierten Art dadurch gelöst, daß zum kontinuierlichen Aufschmelzen von kleinstückigem Material, wie Leichtschrott und Eisenschwamm, die Achsen der in der Abdeckhaube vorgesehenen Einfüllöffnungen in einer durch die Winkelsymmetrale der Normalprojektion der Achsen zweier jeweils benachbarter Plasmabrenner verlaufenden Ebene sowie zwischen zwei vertikalen Ebenen, welche jeweils senkrecht auf den Normalprojektionen der einzelnen Brennerachsen stehen und wobei eine der beiden Ebenen durch die Auftreffstellen der direkten Plasmastrahlen auf der Schmelze gelegt ist und die zweite Ebene im Abstand von einem Drittel der Länge der Projektion der direkten Plasmastrahlen von deren Austritt aus den Brennern bis zu ihrer Auftreffstelle parallel dazu verläuft, liegen.The object is achieved in a plasma melting furnace of the type defined in the introduction that for the continuous melting of small pieces of material, such as light scrap and sponge iron, the axes of the filling openings provided in the cover in a plane running through the angular symmetry of the normal projection of the axes of two adjacent plasma torches as well as between two vertical planes, which are each perpendicular to the normal projections of the individual torch axes and one of the two planes is placed on the melt by the points of impact of the direct plasma beams and the second plane is a third of the length of the projection of the direct plasma beams from whose exit from the burners runs parallel to it until they meet.

Die im wesentlichen kugelförmigen Eisenschwammteilchen bzw. die kleinstückigen Materialien werden dem Metallbad durch die erfindungsgemäß positionierten Einfüllöffnungen so zugeführt, daß ihre Oberflächen während des freien Falles der Wärmestrahlung des direkten Bogenplasmas zweier benachbarter Brenner ausgesetzt sind. Während der Fallzeit durch diese Zonen, in denen sich die Strahlungsfelder einander benachbarter Plasmabrenner überschneiden, erfolgt eine Vorwärmung der festen Materialien und bereits deren teilweise Verflüssigung. Bei den hohen Temperaturen der direkten Bogenplasmen von etwa 20 000 K ist die Wärmeübertragung auf alle frei fallenden Teilchen sehr intensiv ; diese Art des Wärmeüberganges ist gerade beim Erschmelzen von Eisenschwamm, einem Eisenträger hoher Porosität, besonders effektiv.The substantially spherical sponge iron particles or the small-sized materials are fed to the metal bath through the filling openings positioned according to the invention in such a way that their surfaces are exposed to the heat radiation of the direct arc plasma of two adjacent burners during the free fall. During the fall through these zones, in which the radiation fields of adjacent plasma torches overlap, the solid materials are preheated and already partially liquefied. With the high temperatures of the direct arc plasmas of around 20,000 K, the heat transfer to all free-falling particles is very in intensive; This type of heat transfer is particularly effective when melting sponge iron, an iron carrier with high porosity.

Die Abdeckhaube ist zweckmäßig halbkugelförmig gestaltet, wodurch gute Reflexion und Konzentration der Wärmestrahlung auf das Metallbad bewirkt wird. Weiters ist der Steinverbrauch für die Auskleidung geringer.The cover is expediently hemispherical, which causes good reflection and concentration of the heat radiation on the metal bath. Furthermore, the stone consumption for the lining is lower.

Vorteilhaft ist die Abdeckhaube zweiteilig ausgebildet, wobei der Oberteil lösbar mit dem Unterteil verbunden ist und wobei die Plasmabrenner durch den Unterteil der Abdeckhaube geführt sind.The cover is advantageously constructed in two parts, the upper part being detachably connected to the lower part and the plasma torches being guided through the lower part of the cover.

Die Einfüllöffnungen sind bei einer solchen Ausbildung des Plasmaschmelzofens vorzugsweise im Oberteil vorgesehen.With such a design of the plasma melting furnace, the filling openings are preferably provided in the upper part.

Nach einer vorteilhaften Ausgestaltung der Erfindung weist das Oberteil eine Öffnung bzw. ein Anschlußstück für die Abfuhr von Ofengasen auf.According to an advantageous embodiment of the invention, the upper part has an opening or a connector for the removal of furnace gases.

Weiters sind bei einem erfindungsgemäßen Plasmaschmelzofen besonders zweckmäßig über den Einfüllöffnungen mittels einer Vibrationsfördereinrichtung mit kleinstückigem Material beschickbare Zufuhrrohre angeordnet, deren Achsen mit den vertikalen Achsen der Einfüllöffnungen fluchten.Furthermore, in a plasma melting furnace according to the invention, feed pipes which can be fed with small-scale material are arranged above the filling openings by means of a vibration conveyor device, the axes of which are aligned with the vertical axes of the filling openings.

Die Erfindung wird anhand eines Ausführungsbeispieles in der Zeichnung näher erläutert.The invention is explained in more detail using an exemplary embodiment in the drawing.

In Fig. 1 ist ein Vertikalschnitt durch einen erfindungsgemäßen Plasmaschmelzofen dargestellt. Fig. 2 stellt einen vergrößerten schematischen Horizontalschnitt durch den Plasmaschmelzofen im Bereich der Schmelzenoberfläche unter Weglassung verschiedener konstruktiver Details dar; die Wärmestrahlungsfelder von zwei benachbarten direkten Bogenplasmen aus vier Plasmabrennern und die Positionen von vier Einfüllöffnungen sind eingezeichnet.1 shows a vertical section through a plasma melting furnace according to the invention. 2 shows an enlarged schematic horizontal section through the plasma melting furnace in the region of the melt surface, with omission of various design details; the heat radiation fields from two adjacent direct arc plasmas from four plasma burners and the positions of four filling openings are shown.

Der Plasmaschmelzofen ist in Fig. 1 allgemein mit 1 bezeichnet. Er weist einen Ofenkörper 2 zur Aufnahme der Schmelze 3 auf. Durch den Boden des Ofenkörpers 2 ragt eine Elektrode 4 in die Schmelze 3. Mit 5 ist allgemein die Abdeckhaube des Ofens, welche im wesentlichen halbkugelförmige Gestalt aufweist, bezeichnet. Die Abdeckhaube 5 ist bei der dargestellten Ausführungsform aus zwei Teilen aufgebaut, einem lösbar auf dem Ofenkörper 2 befestigten Unterteil 6 mit vier in spitzem Winkel zum Boden des Ofenkörpers bzw. zur Badoberfläche 7 hin geneigten Plasmabrennern 8, welche auf einer Stützkonstruktion 9 axial verschiebbar gelagert sind, und einem lösbar mit dem Unterteil 6 der Haube 5 verbundenen Oberteil 10, welcher mittels einer nicht dargestellten Hub- und Schwenkvorrichtung, wie sie bei Plasma- und Lichtbogenöfen gebräuchlich ist, abhebbar ist.The plasma melting furnace is generally designated 1 in FIG. 1. It has a furnace body 2 for receiving the melt 3. An electrode 4 protrudes into the melt 3 through the bottom of the furnace body 2. 5 is generally used to denote the cover of the furnace, which has an essentially hemispherical shape. The cover 5 is constructed in the embodiment shown from two parts, a detachably attached to the furnace body 2 lower part 6 with four plasma torches 8 inclined at an acute angle to the bottom of the furnace body or to the bath surface 7, which are axially displaceably mounted on a support structure 9 , and an upper part 10 detachably connected to the lower part 6 of the hood 5, which can be lifted off by means of a lifting and swiveling device, not shown, as is customary in plasma and arc furnaces.

Nach dem Chargieren werden die Plasmabrenner 8 gezündet und das eingebrachte Material eingeschmolzen. Nach Bildung eines ausreichend großen Sumpfes aus flüssigem Metall wird mit der kontinuierlichen Zufuhr von kleinstückigem Eisenschwamm und/oder Leichtschrott begonnen. Die Ofengase, welche beim Schmelzprozeß entstehen, werden durch eine im Oberteil 10 vorgesehene Öffnung bzw. durch ein Anschlußstück 11 abgeführt. Das Anschlußstück 11 kann mit einem Absaugrohr verbunden sein.After charging, the plasma torches 8 are ignited and the material introduced is melted down. After a sufficiently large sump of liquid metal has been formed, the continuous supply of small pieces of iron sponge and / or light scrap is started. The furnace gases which arise during the melting process are discharged through an opening provided in the upper part 10 or through a connecting piece 11. The connector 11 can be connected to a suction pipe.

Die Einfüllöffnungen 12 sind entweder hitzebeständig ausgekleidet, wobei die Auskleidung an der Außenseite des Ofens vorteilhaft trichterförmig erweitert ist, oder sie werden von wassergekühlten Mantelrohren entsprechenden Durchmessers, welche Rohre zweckmäßig gleichfalls eine trichterförmige Erweiterung aufweisen, durchsetzt. In der dargestellten Ausführungsform sind vier Einfüllöffnungen 12 im Oberteil 10 vorgesehen. Sie korrespondieren mit Zufuhrrohren 13, welche ihrerseits unter nicht dargestellten Öffnungen einer Vibrationsförderrinne 14 liegen. Durch diese Rinne wird das aufzuschmelzende Material gefördert, die Förderrichtung ist durch den Pfeil 15 angedeutet. Der Plasmaschmelzofen ist in bekannter Weise kippbar auf Wiegebalken 16 und zugehörigen Laufbahnen 17 gelagert ; er weist ferner eine nicht dargestellte Öffnung für den Abguß von Schmelze und gegebenenfalls Schlacke auf.The filling openings 12 are either lined heat-resistant, the lining on the outside of the furnace is advantageously expanded in a funnel shape, or they are penetrated by water-cooled jacket tubes of appropriate diameter, which tubes also expediently have a funnel-shaped expansion. In the illustrated embodiment, four filling openings 12 are provided in the upper part 10. They correspond to feed pipes 13, which in turn lie under openings of a vibrating conveyor trough 14, not shown. The material to be melted is conveyed through this channel, the direction of conveyance is indicated by the arrow 15. The plasma melting furnace is tiltably supported on weighing beams 16 and associated raceways 17 in a known manner; it also has an opening, not shown, for the pouring of melt and possibly slag.

In Fig. 2 ist die Innenbegrenzung des zylindrischen Ofenkörpers 2 des Plasmaschmelzofens 1 mit 18 bezeichnet. Mit 19 sind die direkten Bogenplasmen (Plasmastrahlen) aus den vier symmetrisch in bezug auf die senkrechte Achse des Plasmaschmelzofens angeordneten Plasmabrennern 8 bezeichnet. Durch die Auftreffstelle eines der direkten Plasmastrahlen auf die Schmelze ist senkrecht zur Projektion des Plasmastrahles eine strichpunktiert gezeichnete Linie 20 gezogen. Der Projektion des Plasmastrahles 19 von dessen Austritt aus dem Brenner 8 bis zu seiner Auftreffstelle ist eine Länge L zugeordnet. Eine zweite Linie 21 ist parallel zur Linie 20 im Abstand von L/3 eingezeichnet. Die Linien 20 und 21 markieren die Spuren zweier vertikaler Ebenen.2, the inner boundary of the cylindrical furnace body 2 of the plasma melting furnace 1 is designated by 18. 19 denotes the direct arc plasmas (plasma jets) from the four plasma torches 8 arranged symmetrically with respect to the vertical axis of the plasma melting furnace. A line 20 drawn in broken lines is drawn through the point of impact of one of the direct plasma jets onto the melt perpendicular to the projection of the plasma jet. A length L is assigned to the projection of the plasma jet 19 from its exit from the burner 8 to its point of impact. A second line 21 is drawn parallel to line 20 at a distance of L / 3. Lines 20 and 21 mark the traces of two vertical planes.

Die erwähnte Auftreffstelle kann optisch leicht festgestellt werden. Für zwei der insgesamt vier direkten Bogenplasmen 19 sind strichliert die Feldlinien 22 der Wärmestrahlung eingetragen, welche die Ausbreitungsrichtungen der Wärmestrahlung veranschaulichen. Wie ersichtlich, existiert eine Zone 23, in welcher sich die Strahlungsfelder der Plasmastrahlen aus zwei benachbarten Brennern 8 überschneiden. Diese Zone ist durch Schraffur hervorgehoben. Der erfindungsgemäß gewählte Bereich zur Anordnung der vertikalen Achsen der Einfüllöffnungen liegt in einer durch die Winkelsymmetrale 24 der Normalprojektion der Achsen zweier jeweils benachbarter Plasmabrenner 8 verlaufenden Ebene und zwischen den beiden vertikalen Ebenen durch die Linien 20 und 21. Das durch die Einfüllöffnungen fallende Material gelangt direkt in Zonen konzentrierter Wärmestrahlung, deren eine mit 23 bezeichnet ist. Günstige Positionen von durch die Abdeckhaube 5 bzw. den Oberteil 10 eines erfindungsgemäßen Plasmaschmelzofens führenden Einfüllöffnungen sind mit 12' angedeutet.The point of impact mentioned can be easily determined optically. For two of the four direct arc plasmas 19, the field lines 22 of the heat radiation are shown in broken lines, which illustrate the directions of propagation of the heat radiation. As can be seen, there is a zone 23 in which the radiation fields of the plasma beams from two adjacent burners 8 overlap. This zone is highlighted by hatching. The area chosen according to the invention for arranging the vertical axes of the filling openings lies in a plane running through the angular symmetry 24 of the normal projection of the axes of two respectively adjacent plasma torches 8 and between the two vertical planes through lines 20 and 21. The material falling through the filling openings passes directly in zones of concentrated heat radiation, one of which is designated 23. Favorable positions of filling openings leading through the cover 5 or the upper part 10 of a plasma melting furnace according to the invention are indicated by 12 '.

Die direkten Bogenplasmen werden durch die zugeführten Materialien nicht gestört. Mit einem erfindungsgemäßen Plasmaschmelzofen ist ein kontinuierlicher Betrieb mit allen Ausführungsformen von Brennern möglich. Durch die Einfüllöffnungen 12 können selbstverständlich auch Legierungselemente und/oder Schlackenbildner, wie Kalk und Flußspat, kontinuierlich oder diskontinuierlich eingebracht werden ; die Anzahl der Brenner ist variabel und hängt von der Art des zu schmelzenden Materials und dem Fassungsvermögen des Plasmaschmelzofens ab.The direct arc plasmas are through the supplied materials not disturbed. With a plasma melting furnace according to the invention, continuous operation with all embodiments of burners is possible. Alloying elements and / or slag formers, such as lime and fluorspar, can of course also be introduced through the filling openings 12 continuously or discontinuously; the number of burners is variable and depends on the type of material to be melted and the capacity of the plasma melting furnace.

Claims (6)

1. A plasma melting furnace comprising a furnace body (2) having a vertical axis, a covering cap (5), one or more electrodes (4) penetrating the bottom of the furnace body (2), furthermore, at least three plasma burners (8) penetrating the substantially cylindrical furnace wall or the covering cap (5) and arranged so as to be inclined towards the bottom, and vertically directed charging openings (12), characterised in that, for the continuous melting of small-sized material, such as light scrap and iron sponge, the axes of the charging openings (12) provided in the covering cap (5) are located in a plane (24) extending through the angular symmetry of the normal projection of the axes of two neighboring plasma burners (8) as well as between two vertical planes (20, 21) each extending perpendicular to the normal projections of the individual burner axes, one of the two planes (20) being laid through the points of impact of the direct plasma jets (19) on the melt (3) and the second plane (21) extending parallel thereto at a distance of one third of the length (L) of the projections of the direct plasma jets (19) from their emergence from the burners as far as to their points of impact.
2. A plasma melting furnace according to claim 1, characterised in that the covering cap (5) is designed substantially semi-spherical.
3. A plasma melting furnace according to claim 2, characterised in that the covering cap (5) is designed in two parts, the upper part (10) being detachably connected with the lower part (6).
4. A plasma melting furnace according to claim 3, characterised in that the charging openings (12) are provided in the upper part (10).
5. A plasma melting furnace according to any of claims 3 and 4, characterised in that the upper part (10) comprises an opening and a connection piece (11) for discharging furnace gases.
6. A plasma melting furnace according to claims 1 to 5, characterised in that supply tubes (13) to be charged with small-sized material by a vibrating conveying means (14), are arranged above the charging openings (12), whose axes are in alignment with the vertical axes of the charging openings (12).
EP82890100A 1981-07-15 1982-07-08 Plasma melting furnace Expired EP0070273B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT0311681A AT371589B (en) 1981-07-15 1981-07-15 PLASMA MELTING OVEN
AT3116/81 1981-07-15

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EP0070273A1 EP0070273A1 (en) 1983-01-19
EP0070273B1 true EP0070273B1 (en) 1985-10-09

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JP (1) JPS5916197B2 (en)
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IT8409513V0 (en) * 1984-05-08 1984-05-08 Biavaschi Ciapusci Ilde SAFETY ANCHOR WITH LOCKABLE HINGE FOR TIMING BELT TO TIGHTEN THE SKI BOOTS.
AT385520B (en) * 1986-07-22 1988-04-11 Voest Alpine Ag METHOD FOR PRODUCING COPPER AND OVEN FOR CARRYING OUT THE METHOD
JPS63112393U (en) * 1987-01-12 1988-07-19
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JPH04330120A (en) * 1991-03-26 1992-11-18 Kunio Watanabe Sheathing, boundary concrete block, and constructing method therefore
JP2002333285A (en) * 2001-05-10 2002-11-22 Ryoda Sato Melting method using plasma arc and plasma arc melting furnace
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DE3266809D1 (en) 1985-11-14
CA1175874A (en) 1984-10-09
ATA311681A (en) 1982-11-15
JPS5818083A (en) 1983-02-02
AT371589B (en) 1983-07-11
BR8204104A (en) 1983-07-05
US4414673A (en) 1983-11-08
JPS5916197B2 (en) 1984-04-13
EP0070273A1 (en) 1983-01-19

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