Industrial electric heating furnaces – Resistance furnace device – With heating element detail
Patent
1988-10-24
1990-04-10
Envall, Jr., Roy N.
Industrial electric heating furnaces
Resistance furnace device
With heating element detail
373122, 373125, H05B 360
Patent
active
049167146
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an improvement in moveable graphitizing furnaces.
As is well-known, electrodes for arc furnaces are used in ferrous metallurgy and are produced by baking, impregnating and annealing carbon materials. Such electrodes are subjected to a graphitizing process in which a D.C. or alternate current at a very high intensity and a comparatively low voltage, i.e. about 160,000 to 200,000 A and 110 to 220 V, is passed through the electrodes. The current flow causes a very high heating of the electrodes, which reach temperatures on the order of 2,300.degree. C. to 3,000.degree. C., whereupon the structure of the carbon passes from amorphous to crystalline, i.e. the carbon becomes graphite.
The graphitizing process has long been carried out by so-called Acheson furnaces in which the current flows crosswise to the axis of the electrodes. Only in recent times have said furnaces been replaced by graphitizing furnaces in which current is passed along the axis of the electrodes according to the so-called longitudinal graphitizing process in which several electrodes to be graphitized are placed aligned in columns between two poles of graphite. Pressure is exerted on such poles in order to keep ends of electrodes to be graphitized in contact with one another and with the poles. The pressure exerted on the poles has to be steady and elastic in order to keep the contact between the ends of the electrodes during any shrinkage or expansion of the electrode columns during the heating process.
In such furnaces the column of electrodes to be graphitized acts as a conductor through which a current is passed. The column is placed horizontally within a mass of granules of metallurgical or petroleum coke which comprise a bed on which the electrode column rests and a covering above the latter so that the electrodes are "included" or enveloped in said stuffing mass. Complex technical and technological problems develop with such a graphitizing process, in which a current is being passed along the axial direction of the furnaces, because of the provision of the stuffing mass acting as a thermal insulation, and the necessity to avoid keeping the cumbersome, heavy, expensive mechanical and electrical equipment idle during the cooling time. The solutions of these problems are the objects of a number of patents concerning movable graphitizing furnaces provided with wheels such as U.S. Pat. Nos. 1,029,121 to Heroult (class 13/7) and 4,015,068 of Vohler (class 13/7), German Pat. Nos. P2018764.8 and P2316494.5 of Sigri Electrographit GmbH, and U.S. Pat. No. 4,394,766, filed in the PCT as No. PCT/US82/01046, of Great Lakes Carbon Corporation.
The latter patent, although it introduces advanced solutions, does not solve some problems associated with substantial drawbacks. Among other things, it should be noted that the arrangement, transport and filling of the stuffing mass of coke under, about and over the electrodes to be graphitized, as well as the use of a tank formed of an outer, continuous shell of steel with a lining, provides a construction that, besides being very heavy, gives rise to serious problems of thermal expansion.
In addition to such problems, the solution proposed by Great Lakes Carbon Corporation has also the drawback of rendering useless a great number of electrode pressing systems as each furnace is provided with its own self-contained system. Finally, only one column of electrodes at a time can be graphitized by the furnace of Great Lakes.
This invention seeks t avoid the drawbacks of the prior art by providing a highly improved graphitizing furnace which is comparatively light, is provided with equipment of very quick operation for the arrangement, removal and rearrangement of the stuffing mass of coke, and in which the power dispersion in the environment is reduced to a minimum. The furnace has an outer pressing system to which it is quickly connected only during the step in which a current is passed through the electrodes so that such pressing system may be connected to other furnaces during the lon
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Antoni Franco
Celani Lohengrin
Di Fabio Emidio
Genevois Jean L.
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