Industrial electric heating furnaces – Arc furnace device – Electrode
Patent
1986-05-19
1987-09-08
Envall, Jr., Roy N.
Industrial electric heating furnaces
Arc furnace device
Electrode
H05B 709
Patent
active
046929290
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
This invention relates to a self-braking electrode for electric arc furnaces and the like, particularly suited to the production of metal silicon, ferro-alloys, calcium carbide, phosphorus and the like, said electrode consisting of a cylindrical metal casing, of an electrodic mass contained and guided by said metal casing during its formation, solidification and baking steps, and of a reinforcing and sustaining structure which supports said mass, said structure being such as to allow to obtain the final products, in particular metal silicon, without any significant addition of foreign elements.
As is known, various products of the metallurgical industry, such as for example metal silicon, phosphorus, ferrochrome, ferromanganese, calcium carbide and the like, are obtained by reduction of the corresponding ores in an electric arc furnace. The electrodes for said furnaces may consist of cylindrical coal blocks of proper dimensions, which consume in consequence of oxidation and of the contact with the charge, and which, therefore, by means of suitable devices, are lowered as they get consumed and are then replaced by new electrodes when their dimensions have become, in consequence of the consumption, lesser than the minimum allowable dimensions.
Instead of being made of coal, the electrodes may consist of graphite, which is a more expensive material but exhibits a higher conductivity, a higher mechanical resistance and a higher purity, and therefore permits to obtain products of better quality because more pure.
Another type of electrode which too is utilized in the arc furnaces is the one usually referred to as self-baking electrode. Such electrode consists of a metal cylindrical casing, usually a steel casing, equipped with radial fins in its inside, into which casing the electrodic paste is introduced from the top, such paste being made of a variously ground carbonaceous material and of pitch. The electrodic paste, because of the heating due to the current flow, solidifies and bakes, thus forming an integral body with the outer metal casing to which it is anchored by means of said inner fins which have just the function of supporting the electrodic paste mass. In this case the outer metal casing and the fins consume along with the coal. By this type of electrode, which is less expensive than the one consisting of coal blocks or of graphite blocks, an economic saving is attained, but there is the serious drawback of introducing, into the furnace reaction mass, and therefore into the final product, the metal, usually iron, of which the casing and the fins are made, which, as told hereinbefore, gets consumed together with he electrodic paste during the process. Consequently, this type of electrode cannot be utilized for the production of high-quality and low-purity products (which, as is known, find broader and broader utilizations in several technological fields), such as e.g. metal silicon with a low iron content.
A progress in respect of the conventional self-baking electrode is represented by an electrode, always self-baking, in which, however, the outer metal casing is not bound to and integral with the electrodic mass by means of the fins, but is substantially fixed, while the electrodic mass flows in its inside as it is supported by a rod-shaped steel element not bound to and independent of the outer casing, as is described for example in Italian Pat. No. 606568. By means of this type of electrode it is possible to obtain products of better quality, since only the iron, of which said rod-shaped element is made, consumes along with the electrodic mass and passes into the furnace reaction mass and, consequently, into the final product.
An object of the present invention is that of providing a self-baking electrode for arc furnaces which avoids the introduction of foreign elements, in particular iron, into the furnace charge during the reaction and into the final product, and which permits to obtain products, in particular metal silicon, of high quality and with a low impurity content.
Another
Cavigli Mario
Ferrari Lorenzo
Envall Jr. Roy N.
Kinglor-Ltd
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