US2224739A - Continuous electrode and method of supplying current thereto - Google Patents

Description

Dec. 10, 1940. MANFREDINI CONTINUOUS ELECTRODE AND METHOD OF SUPPLYING CURRENT THERETO Filed June 15, 1959 lnven/or Aiforneys Manfredini HF Hm Patented Dec. 10, 1940s A I I r I UNITED STATES PATENT OFFICE CONTINUOUS ELECTRODE AND METHOD OF SUPPLYING CURRENT THEBETO Luigi Manfredini, Milan, Italy, assignor to Bet norske Aktieselskab for Elektrokemisk lndustri, Oslo, Norway Application June 15, 1939, Serial No. 279,378 In Italy June 30, 1938 8 Claims- (Cl. 13-19) The present invention relates to continuous and pulled out and again inserted into the unelectrodes which are baked in the furnace in baked electrode mass. which they are used. The object of the inven- The current supply is then taken over by tion is an arrangement for supply of current to other contact rods placed higher up in 'the 6 such electrodes. In practice certain difficulties electrode. Care must of course be taken that the are encountered in the supply of current to selfdistance from the lower contact rods to the end baking electrodes as the electrodes consist of a of the electrode never becomes so great that a baked and an unbaked part, the latter being material loss of voltage may take place. non-conductive. The electrodes are generally As the lower contact rods are firmly attached surrounded by a metallic casing and the supply to the lower part of the electrode by the coking of current is eflected by means of contacts inof the electrode paste in baking, they are exserted from the outside through the casing and cellently suited for suspension of the electrode. into the baked part of the electrode. When contact rods are changed the suspension These contacts must be removed when on arrangement must be connected with the new 15 account of consumption of the electrode they con-tact rods. But no tension should be exerted 15 too closely approach the melt. Thereafter they on the new contact rods until they are suiil are then again inserted into the upper part of ciently baked into the mass to be able to carry the electrode. In many cases this causes diflithe weight of the electrode. These electrodes culties, for example in the melt-electrolysis of are mostly very big and often weigh 10-15 tons. .20 aluminium where a good closing of the furnace As the upper part is soft considerable dimculis difficult and a great loss or voltage may take ties have previously been met with. It is a great place on account of poor conductivity of the advantage of the present invention that it allows electrode mass where the new contacts are ina simple and safe suspension. serted. Especially with big electrodes it is diiil- When using the above described arrangement cult to distribute the current evenly throughout the outer electrode surface remains nicely smooth 2!! s the electrode by means of contacts which are without projections or holes and may be tightly inserted from the side. Even a small loss of packed when entering the furnace. It is imvoltage is in such process of great economic material to the present invention whether the importance. electrode be provided with a casing of metal According .to the present invention the curor other material as for example carbon or :0

rent is supplied by means of contacts which exgraphite or if no casing is used at all. tend into the electrode parallel with or prac- The practical application of the process may tically parallel with the direction in which the be varied considerably. It is thus possible that electrode is fed into the furnace. In practice the contact rods when tubular may be used for this generally means verticaly or practically vercharging of the furnaces. If this charging is 35 tically. It is important that the contacts do not de continuous it is possibleto av id the occurpass through the electrode casing or the exrence of the so-called "a d e terior cover of the electrode. These contacts Instead of charging through tubular contact are inserted into the unbaked part and gradualrods, openings may of course be used, which are ly reach the baked part of the electrode where formed by withdrawal of contact rods. These 40 the conductivity is satisfactory. The contacts openings or the'tubular contact rods may also may consist of any material having good elecbe used for removalof furnace gas. trical conductivity, preferably metal, and have In the accompanying drawing which forms a any suitable shape. They are mostly used in part hereof I show schematically one embodithe form of rods, solid or tubular, which may be ment of my invention, which'drawing, however, tapered to facilitate extraction, and are hereshould be understood as purely illustrative and after referred to broadly as contact rods. It is not limitative upon the scope of my invention. suitable to make such arrangement that a num- In the drawing:

her of contact rods sumcient for the current Figure l is avertical section of the continuous 60 supply extend into the baked part of the elecelectrode selected for illustrative purposes and trOde While other Contact rods are Placed hig of a furnace in which the electrode is mounted,

up. As the electrode is consumed and the conthe contact rods being shown in full lines;

tact rods extending most deeply into the baked Fig. 2 is a plan of the electrode of Fig. 1; portion approach the melt these may be loosened Fig. 3 is an elevation, partly in vertical crosssection, of the supporting and current supplying means for the electrodes; and s Fig. 4 is a plan of the showing of Fig; 3.

More particularly, an aluminum furnace l is provided with a continuous electrode 2 slidably mounted in a permanent casing I. The electrode is suspended and the current supplied thereto by means of vertical contact rods 4 formed with tapered or conical lower ends. These contact rods are arranged in groups or tiers and extend into the electrode in such a way that the respective groups or tiers are in step formation, as illustrated in three different heights. The contact rods of each group or tier are by means of adjustable clamps I connected with a bus bar 8 which is fastened to a beam comprising one or more channel irons I. The beams I thus constitute the actual suspension means for the electrode. The beams are connected in the usual manner to a hoisting arrangement schematically indicated at H, by means of which the beams can be regulated upwardly and downwardly according to requirement. Generally all of the beams are connected in such a way that they may be worked either separately or together.

The adjustable clamps I (Figs. 3 and 4) are conveniently formed of two main parts 8 and O suitably arranged so that thetwo parts may be separated for opening the clamps and joined together in closed position. The part I adjoins the bus bar 6 and is firmly mounted on the beam I. In the illustration of the middle group or tier in Figs. 1 and 2, wherein two supporting channel irons I are shown, the part 0 of the clamp is replaced by a duplicate of the part 8. Between the two parts of the clamp a copper lining or cylinder I0 (likewise conveniently in two parts) is mounted for transmitting the curcurrent supply again turned on.

rent from the clamp to the electrode 4. The two parts of the clamp may if desired be made of bronze. The copper lining of cylinder Il may if desired be replaced by insulating material when it is desired to insulate the contact rods from the clamp.

when the electrode inuse has been burned rods are loosened,'and the contact rods lifted out by suitable mechanism such as a hydraulic jack. These contact rods are then cleaned and given a smooth surface. Raw electrode paste in proper quantities is filled into the cavities or holes left by the contact rods which have been removed so that when the contact rods thus cleaned and given a smooth surface are arranged in their new upper positions, their lower ends are completely surrounded by raw paste.

and a good contact is provided on the baking of the paste. The contact rods thoroughly cleaned are then lowered into the tops of their previous cavities so that their lower conical ends extend through the upper substantially unbaked portion of the electrode a short distance into the midway partially baked portion of the electrode, as indicated by dotted lines in the electrode at the left of Fig. 1. Their respective clamps are then tightened about them and their This process is repeated for each of the remaining groups or cleaning and polishing their surfaces, where nec- 'the total current must pass through the higher tiers of contact rods, when necessary, as the electrode burns away in use.

When using a good electric paste and baking the contact rods into the electrode as described above, the pull needed to extract steel contact I rods of about 70, mm. diameteris approximately 10-40 tons. To avoid difliculties in extracting the contact rods it has been found desirable to remove them completely from the electrode for x 0 essary by grinding to make them smooth.

In the drawing are shown contact rods in three positions. The vertical distance between these positions should be about 20 cm. Thereby the newly introduced contact rods will be surrounded by a paste which still contains a considerable quantity of tar, the baked part of the electrode being roughly 60-80 cm. high at average conditions. When arranged this way the contact rods of the second position electrically connected in parallel with the contact rods of the lower positions will carry 30-60% of the current of the lower contact rods, 1. e. they contribute appreciably in carrying the electric current.

It is also possible to arrange the contact rods in two positions; making the vertical distance between the two positions about 35 cm; This, no doubt, has considerable advantages but the voltage drop in the electrode will be somewhat higher. It must be decided in each special case which procedure will be preferable, in view of the cost of electric power and other costs.-

During the removal ofone group or tier of contact rods the entire weight and current supply of the electrode must be taken over by. the contact rods of the remaining tier or tiers. When it is necessary to extract the contact rods of the lower position they should be cut oil from the current supply about one day ahead whereby contacts so that the baking of the contact rods higher up into the electrode is carried sufllcient- 1y far before the total weight of the electrode is applied to these contact rods.

As above outlined, the suspension of the electrode when the baking is completed, is so secure that a part of the contact rods suffice to carry the weight of'the electrode. This is taken advantage of in the arrangement shown in the drawing by arranging the contact rods in three groups or tiers each connected with one suspending beam. when one group or tier has to be lifted relative to the electrode, because of the electrode consumption, the electrode is suspended by the other two groups or tiers of contact rods which are in turn lifted afterwards.

The regulation of theelectrode is of course effected by means of a common lifting device which is ordinarily connected with all beams.

To reduce the cross section of the con-tact rods these may advantageously be made partly of iron and partly of copper, for instance using an iron core surrounded by copper or a copper core surrounded by iron.

unbaked portion; means for supplying current 7 to the electrode comprising a plurality of removable contact rods extending lengthwise into the electrode from the top thereof, being parallel one with the other and being positioned in the electrode in line with the direction in which the electrode is fed into the furnace; the lower end of one of said contact rods extending well into the lower baked portion of the electrode, terminatlng at a suitable distance above the lower end thereof and being firmly attached therein and thereto by the coking of the electrode paste in baking; another of the said con-tact rods having its lower end terminating above the lower end of the first named contact rod and being less firmly attached to the electrode; the construction and arrangement being such that as the lower end of the electrode is burned away in use the first named contact rod may be removed and the second named contact rod in becoming more firmly attached to the electrode on continued baking thereof, may take over the current supply function of the first named electrode.

2. An electrode for an electric furnace, baked in the furnace in which it is employed, and comprising a lower baked portion, a midway partially baked portion and an upper substantially unbaked portion; a plurality of removable contact rods extending lengthwise into the electrode from the top thereof for supporting the electrode and supplying the electrode with current, said contact rods being parallel one with the other and being positioned in the electrode in line with the direction in which the electrode is fed into the furnace; the lower end of one of said contact rods extending well into the lower baked portion of the electrode, terminating at a suitable distance above the lower end thereof and being firmly attached therein and thereto by the coking of the electrode paste in baking; a second ofsaid contact rods extending through the midway partially baked portion of the electrode, having its lower end terminating in the lower baked portion of the electrode and above the lower-end of the first named contact rod, and being less firmly attached to the electrode than the first named contact rod; a third of said contact rods extending through the upper substantially unbaked portion of the electrode, having its lower end terminating in the midway partially baked portion of the electrode and above the lower end of the second named contact rod. and being less firmly attached to the electrode than the second named contact rod; the construction and arrangement being such that as the lower end of the electrode is burned away in use, the first named contact rod may be removed and the second and third named contact rods in becoming more firmly attached to the electrode I supplying the electrode with current, said con-- tact rods being parallel one with the other, being positioned in the electrode in line with the direc tion in which the electrode is-fed into the furnace and being arranged in groups or tiers; a common suspension means for the contact rods of each group or tier comprising means for supporting, raising, and lowering the contact rods of each group or tier; a common source of current for the contact rods of each group or tier associated with the respective suspension means therefor; the respective groups or tiers of contact rods being in step formation with the lower ends of the contact rods of one group or tier extending well into the lower baked portion of the electrode, terminating at a suitable distance above the lower end thereof and being firmly attached therein and thereto by the coking of the electrode paste in baking, the lower ends of the contact rods of another group or tier terminating above the lower end of the contact rods of the first named group or tier and being less firmly attached to the electrode; the said suspension and current supplying means for each group or tier of contact rods being so constructed and arranged that the contact rods may be detached therefrom for removal and replacement, whereby the contact rods in the lowest group or tier may be removed on burning away of the lower end of the electrode and new contact rods substituted to constitutes. group or tier of contact rods terminating higher up in the electrode.

4. An electrode for an electric furnace, baked in the furnace in which it is employed, and comprising a lower baked portion, a midway partially baked portion, and an upper substantially unbaked portion; a plurality of removable contact rods extending into the electrode from the top thereof for supporting the electrode and supplying the electrode with current, said contact rods being parallel one with the other, being positioned in the electrode in line with the direction in which the electrode is fed into the furnace and being arranged in groups or tiers; a common suspension means for the contact rods of each group or tier comprising a suitable beam, adjustable clamps carried thereby one for each of the contact rods of the group or tier, the beam being movable to and from the furnace hearth for raising and lowering in unison the contact rods supported thereby and the clamps affording means for individual adjustment, re-

moval, and replacement of the contact common bus bar for the contact rods of each group or tier carried by the respective suspension means therefor, normally energized for supplying current to the contact rods and deenergized for the removal and replacement of the contact rods; the respective groups or tiers of contact rods being in step formation with the lower ends of the contact rods of one group or tier extending into the lower baked portion of the electrode, terminating at a suitable distance above the lower end thereof and being firmly attached therein and thereto by the coking of the electrode paste in baking, the lower ends of the contact rods of another group or tier terminating above the lower end of the contact rods of the first named group or tier and being less firmly attached to the electrode; the said suspension means and bus bar for each group or tier being so constructed and arranged that the contact rods in the lowest group or tier may be removed on burning away of the lower end of the electrode and new contact rods substituted to constitute a group or tier of contact rods terminating 7;

higher up in the electrode.

5. In the operation of an electric furnace equipped with a continuous electrode baked in the furnace and supplied with current by a plurality of normally energized removable contact rods extending into the electrode from the top the other, being rection in which the electrode is fed into the furnace and having their lower ends in step relation, the iowerend of one of said contact rods extending well into the baked portion of the electrode, terminating at a suitable distance above the lower end thereof and being firmly attached therein and'thereto by the coking of the electrode paste, the lower end of another of said contact rods terminating above the lower end of the first named contact rod and being less firmly attached to the electrode, the method which comprises deenergizing' and withdrawing the first named contact rod from the electrode after the second named contact rod on further baking of the electrode has become firmly attached therein and thereto but prior to the burning away of the lower end of the electrode to such extent as to expose the lower end of the first named contact rod, partially filling the cavity formed by the withdrawn contact rod with raw electrode paste, inserting a contact rod into the said cavity and raw electrode paste therein to a depth such that its lower end is positioned a suitable distance above the lower end of the second named contact rod remaining in the electrode, energizing the contact rod so inserted, and repeating the operation as the lower end of the electrode burns away so that in the continuous formation of "the electrode to compensate for the burning away of th lower end thereof, the supply of current to the electrode is continuous and the contactrods supplying the current there to have their lower ends always protected by the lower baked portion of the electrode.

6. In the operation of an electric furnace equipped with a continuous electrode baked in the furnace and supplied with current by a plurality of removable contact rods normally energized andconnected in parallel and having their lower ends tapered, saidcontact rods extending into the electrode from the top thereof, being parallel one with the other, being positioned in the electrode in line with thedirection in which the electrode is fed into the furnace and having theirlower ends in step relation, the lower end of one of said contact rods extending well into the lower baked portion'of the electrode, terminating at a suitable distance above the lower end thereof and being firmly attached therein and thereto by the coking oi the electrode paste in baking, a second of said contact rods having'its lower end terminating above the lower end of the first named contact rod and being less firmly attached to the electrode than the first named contact rod, a third of said contact rods having its lowerend terminatihg .above the lower end of the second named contact rod and being less firmly attached to the electrode than the second named contact rod, the method which comprises deenergizing and withdrawing the first named contact rod from the electrode after the second named contact rod'on further baking of the electrode has become, firmly attached therein and thereto but prior to the burning away of the lower end of the electrode to such extent as to expose the lower end of the first named contact rod; partially filling the cavity formed by the withdrawn contact rod with raw electrode paste; inserting a contact rodinto the said cavity and raw electrode paste therein to such a depth that the lower tapered end of the contact rod is thoroughly embedded in the electrode paste and is positioned a suitable distance above the lower end of the second named contact rod remaining in the electrode; energizing the contact rodso inserted and connecting named contact rods; and repeating the operation as the lower end of the electrode burns away so that in the continuous formation of the electrode to compensate for the. burning away of the lower end thereof, the supply of current to the electrode is continuous and the contact rods supplying the current theretohave their lower ends always protected by the lower baked portion of the electrode.

LUIGI MANFREDINI.

it in parallel with the second and third

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