Asea Brown Boveri Inc.

Asea Brown Boveri Ag

Concast Standard Ag

Sven-Einar Stenkvist

Erik Alfred Lassander

Goran Grimfjard

Goran Wikstrom

Jan Oelscher

Andreas Loebner

Ante Eterovic

Karl-Hugo Andersson

Walter Bochsler

Gerhard Lempa

In order to avoid damage to the inner walls of the arc furnace (1) and a reduction of the electric power when material (5) to be melted has been partly burned down in an arc furnace (1), additives (10) are fed to the filling opening of a hollow electrode (7) by means of a loose-material conveyor (25) during this critical melting phase. An arc (6) between the hollow electrode (7) and a melt (4) in the arc furnace (1) is thereby shortened. A loose-material container (9) is arranged at the end of the loose-material conveyor (25) at a distance from the electrode and can easily be separated from the hollow electrode (7) in order to permit the tilting of the arc furnace (1) to empty out the melt (4). Problematic waste materials which are to be disposed of, such as for example filter dust, can be added to the additives (10).

Method of operating an arc furnace, and an arc furnace

The furnace vessel for a DC arc furnace has a thermostable wall which preferably consists, in the region situated above the slag line (S), of a plurality of water-cooled wall segments (1) made from steel. These wall segments are fastened to a support structure (13-18). At least one of the wall segments (3) consists of nonmagnetic steel or copper and is preferably arranged on the side of the furnace vessel (5) opposite the power supply device (7). In this way, the influence of the high-current lines which extend below or beside the furnace vessel and cause a deflection of the arc can be compensated. The effect of this nonmagnetic wall segment can be partially or virtually entirely cancelled by a trimming plate (19) which is detachably fastened from the outside to the nonmagnetic wall segment (3), in order in this way to achieve optimum trimming of the deflection of the arc.

Furnace vessel for a DC arc furnace

Method and furnace for treatment of ash

To improve operation, particularly to allow more universal use, in which both liquid and solid crude metal, especially iron can be refined in only one reactor vessel, a reactor vessel (1) is of converter-like design with a relatively large space above a melt (7) and with slag (8) lying above said melt. For the removal of slag (8) via a closable slag channel (18'), the meltdown apparatus can be rotated about a center of rotation (20) through .+-.8.degree.. For the complete removal of the melt (7) via a closable melt channel (17') in the bottom region of the meltdown apparatus, the latter can be rotated about a center of rotation (19) through .+-.30.sup.. A magnetic coil (16) fed with direct current and arranged around the meltdown apparatus (1) serves for the magnetic damping of movements of melt (7) and/or slag (8) inside the meltdown apparatus. In the converter mode, a graphite electrode (5) used in the arc mode is replaced by a gas supply conduit, through which oxygen is then supplied under pressure.

Meltdown apparatus

In order to reduce the power loss of a direct current arc furnace the furnace vessel is only partially cooled in the region situated above the melting zone. A first cooling device is provided on a top edge of the vessel. A second cooling device is provided at the height of a slag line. The region of a vessel wall situated therebetween and facing the interior of the vessel above the slag line consists essentially of refractory material.

Furnace vessel for a direct current arc furnace

A choke coil comprises mutually similar flat bars which are electrically connected at the corners. Each coil winding comprises an integral number of mutually similar flat bars which in each case lie on top of one another on contact areas at the corners so as to overlap over a large area. Insulating plates and/or insulating layers having a size approximately equal to the contact area are provided between two adjacent windings at the corners. The stack formed in this way is held together exclusively by means of a clamping device comprising clamping elements which do not cut or pierce the flat bars. A choke constructed in this manner is simple and economical to manufacture can be cooled well and can be produced in virtually any size.

Choke coil

In a direct-current arc furnace having a bottom contact (3) which has a large area, electromagnetically produced bath agitations are influenced by an electromagnet (9) disposed underneath the vessel bottom (4) such that the natural flow in the melt bath, caused by the current flow in the melt, is reversed in direction. In this way the stability of the bottom electrode (3) is substantially increased. The electromagnet (9) is preferably integrated into the electric supply system of the furnace and serves as a smoothing choke.

Direct-current arc furnace

In direct-current arc furnace the arc is deflected in a direction away from the current supply means (19) through the action of the high-current lines (18) extending under the furnace vessel. This leads to the thermal overloading of a part of the furnace vessel walls. If the high-current lines (18a) are for the major part laid in a plane above the furnace bottom, on or below the furnace platform (20), and are taken downwards to the connection fittings (10) on the furnace bottom only on the side of the furnace vessel (1) opposite the current supply means, the arc will again burn symmetrically.

Direct-current arc furnace plant

A direct current arc furnace has a furnace vessel which is surrounded by a metal shell having at least one electrode connected as a cathode, and at least one bottom contact. The bottom of the furnace consists of a lining layer which possesses electrically conducting bricks or the like, which lining layer lies on a contact plate covering most of the bottom. The contact plate forms the bottom contact connected as the anode and lies on a bottom plate. The bottom plate is equipped with a plurality of connection fittings which pass through openings in the bottom plate and are connected via electric wires to a current supplying device provided next to the furnace. For the internal deflection of the arc, at least one section of the lining layer is composed of a material which possesses a lower electrical conductivity than the lining layer in another section which is circumferentially spaced from the one section so as to form circumferentially spaced zones of varying conductivity.

Direct-current arc furnace having circumferential zones of varying

In a direct-current electric-arc furnace, the bottom contact, that is the hearth electrode, must be insulated from the metallic shell of the furnace vessel by insulating material. For this purpose, the bottom plate carrying the bottom contact essentially forms the bottom of the furnace vessel. This bottom contact, with an insulating material, or a material which is at least a poor electrical conductor, inbetween, rests on a part, projecting radially inward, of the metallic vessel shell.

Direct-current electric-arc furnace

In a direct-current arc furnace having a bottom electrode (2), electromagnetically and/or chemically induced bath agitations are substantially eliminated by an electromagnet (9) arranged under the vessel bottom (7). In this way the stability of the bottom electrode (2) is considerably increased. The electromagnet (9) is preferably integrated into the electrical supply of the furnace and serves as a smoothing choke.

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Brugg, Switzerland

Sven-Einar Stenkvist