US2680142A

US2680142A - Electric furnace with horizontally rotating consumable electrode and method and means for replenishing the same

Info

Publication number: US2680142A
Application number: US246431A
Authority: US
Inventors: John O Graybeal
Original assignee: Kaiser Aluminum and Chemical Corp
Current assignee: Kaiser Aluminum and Chemical Corp
Priority date: 1951-09-13
Filing date: 1951-09-13
Publication date: 1954-06-01
Anticipated expiration: 1971-06-01
Also published as: GB721980A; FR1068859A; CH316953A

Description

June 1. 1954 J. o. GRAYBEAL 2,680,142

ELECTRIC FURNACE WITH HORIZONTALLY ROTATING CQNSUMABLE ELECTRODE AND METHOD AND MEANS FOR REPLENISHING THE SAME 2 Sheets-Sheet 1 Filed Sept. 13, 1951 s2 o 2&

INVENTOR. JOHN o. eRAYBEfl/ a ATTORNEY J. O. ELECTRIC FURNACE WITH HORIZONTALLY ROTATING CONSUMABLE ELECTRODE AND METHOD AND MEANS FOR REPLENISHING THE SAME Filed Sept. 15, 1951 2 Sheets-Sheet 2 I4 |,6 I9 I x INVENTOR JOHN O. GRAYBEAL BY 522i ATTORNEY Patented June 1, 1954 ELECTRIC FURNACE WITH HORIZONTALLY ROTATING CONSUMABLE E LE 0 T R O D E AND METHOD AND MEANS FOR REPLEN- ISHING THE SAME John 0. Graybeal, Buckley, Wash, assignor to Kaiser Aluminum & Chemical Corporation, Oakland, Calif., a corporation of Delaware Application September 13, 1951, Serial No. 246,431

26 Slaims.

This invention relates to the electric furnaces employing electrodes of the continuous or selfbaking type, and more particularly relates to improved continuous or self-baking electrodes employed in electric furnaces.

Heretofore, continuous electrodes employed in electric furnaces have been of circular or oblong configuration and arranged so that the lower baked portion of the electrodes acts as ananode for conducting current from the furnace bath by which carbon paste in turn becomes baked during operation of the furnace. According to such prior practice, complex suspension means were required to support the electrode, and in the preferred practice, where contact studs were inserted in the electrode mass, it became necessary :1

to periodically remove the contact studs and replace them at an upper position involving considerable expenditure of time and effort.

It is an object of this invention to present an improved arrangement of continuous or self-bal ing electrodes employed in electric furnaces.

It is a further object of this invention to present an improved type of continuous or selfbaking electrode which eliminates the necessity for insertion and removal of the electrical contact studs in the electrode mass.

It is a still further object of this invention to present an improved type of continuous or selfbaking electrode wherein new electrode surfaces are presented to the furnace bath by rotation of the electrode about a horizontal axis.

It has been found that the electrode mass constituting a continuous or self-baking electrode may be baked about a rotatable conductor and that the portions of the electrode mass which are consumed during operation of the furnace may be replaced by applying carbon paste to the surface of such an electrode which has become partially consumed during operation of the furnace and confining the coated paste so applied to the consumed surface for a time sufiicient to allow heat from the conductor to bake the paste. After the new layer of paste has become baked, it may be reintroduced to the electric furnace bath and such surface of the electrode may again perform the function of carbon anode for further operation of the furnace.

In order to illustrate specific examples of this invention, reference is made to the accompanying drawings which are schematic in character and partly in section, with various details of the furnace which are known to the art omitted for the sake of clarity of illustration.

Figure 1 is a side elevational view of a portion of an electric furnace utilizing continuous electrodes of an exemplary form as contemplated by the present invention. The view of Figure l is taken generally along line l-l of Figure 2 with various parts shown in section.

Figure 2 is a sectional view along line 2-2 of Figure 1 showing the various details of a rotatable continuous electrode as contemplated by the present invention.

Figure 3 is an end elevational cross-section view of an electric furnace utilizing a rotatable continuous electrode, wherein the drive means and the conductor means associated with said rotatable continuous electrode are arranged on the opposite sides of the furnace.

Figure 4 is an end elevational cross-section view of an electric furnace utilizing a rotatable continuous electrode, wherein the conductor means is located adjacent the furnace pot and the drive means located exteriorly thereof.

Referring to the figures, the furnace pot H! has disposed thereover a plurality of rotatable continuous electrode units H, each unit being made up of a rotatable metal conductor 52 having the carbon electrode mass [3 baked thereto. The carbon paste which forms the electrode mass is introduced to a hopper means Hi which is made up of sides 55 and I6, side [5 being arcuately extending downward the side of the rotatable electrode in the direction of rotation as indicated at I! so as to form a retaining or mold portion for the electrode paste as it is baked. Hopper side I6 is mounted as in guideway l8 positioned in hopper end pieces It] so as to allow for radial movement of side it to in turn allow the lower edge 20 of side Iii to act as a scraper against the consumed surface of the electrode 13 as it is introduced into the hopper feed area. Hopper end pieces [9 are extended as are sides I! downwardly in the direction of electrode rotation so that a confining and retaining mold section is formed for the end surfaces of the rotatable electrode l3, as indicated at 2 I. In order to obviate any tendency for the portion of the electrode mass it being baked in contact with mold portion H and adhering thereto and thus prevent rotation ac me of the rotatable electrode, a suitable shield means Such as aluminum foil 22 may be introduced between the electrode mass I3 and the mold portion I'I, if desired. The hopper means I4 are securely mounted about the upper portion of the rotatable electrode I3 as by securing the hopper end pieces to the sides of furnace pot II! as indicated at 23. The centrally located metal conductor portion I2 of the rotatable electrode I I is extended to form shafts 24 at the ends of the 1 electrode which shafts 24 are in turn supported on the sides of the furnace pot I by bearing surfaces 25. The respective conductor shafts 24 are rotatably driven intermittently or continuously by suitable gears 26 locked to the shaft 24 as by key means 21 or as by welding. Gears 26 may be individually driven or may be ganged to a common drive shaft 28 mounting worm gears 30.

Electric contact is made to the metal conductor I2 through shaft 24 by means of a contact disc 3|, the periphery of which is immersed in an electric current conductive liquid 32, such as molten metal which is retained in conductive position as by a container 33 attached to the side of the furnace pot at 34. A suitable connection means 35 is provided for connecting the container 33 to the furnace source of power.

It will be apparent that various modifications and changes of the illustrated form of the invention are possible. For example, although metal conductor I2 is illustrated as being hollow, it is obvious that the conductor construction could be solid as well, depending upon considerations of weight, strength and conductive surface presented. Moreover, the surface of the conductor I2 on which the electrode mass I3 is baked may be roughened or otherwise made irregular in order to promote adherence of the baked electrode mass thereto, if necessary.

It will be further apparent that the arrangement of rotatable continuous electrodes illustrated is susceptible of utilization in furnaces of considerable horizontal dimensions. For example, it is contemplated that a furnace such as is illustrated could be elongated to accommodate a large number, for example, or horizontally arranged rotatable continuous electrodes. In such a furnace utilizing a large number of rotatable continuous electrodes, the electrodes could be arranged parallel to each other or could be arranged radially around the center of an annular furnace pot.

Although as shown in Figure 1 the hopper means I4 is arranged to feed vertically downward to the consumed surface of the rotatable continuous electrode, it will be apparent that the hopper could be arranged further to the right as illustrated in Figure 1, so as to overcome any tendency for the newly introduced electrode paste to flow counter to the direction of electrode rotation, if desired.

It is further contemplated that more or less electrode paste may be introduced to hopper I4 than is shown in Figure 1. Due to the relatively close position of the paste introduced to hopper I4 to the hot conductor I2, in certain instances there may be a tendency for the electrode paste extending radially beyond the mold section I"! to bake and thus impede further rotation of the electrode. In such event, a lesser amount of paste introduction so as to eliminate the radial protuberance of paste in the hopper area would be necessary. It is also contemplated that where it it necessary to increase or decrease the thickness of the layer of electrode paste deposited, the side portion I5 and integral mold portion ll of hopper I l may be made separable from and adjustable with the end portions I9, I!) such that portions I5, I! may be moved outwardly or inwardly with respect to the electrode I I. However, if the baking action is relatively slower, the amount of paste fed to the hopper would be correspondingly less critical so that a larger amount of electrode paste could be maintained in the hopper without adverse effect. With further regard to rotation of the rotatable continuous electrode, it will be obvious that the direction of rotation could be reversed by a reversal of parts of the hopper and mold portions of the electrode unit.

In normal operation of a furnace embodying the present invention, any tendency for one consumable electrode to be consumed faster than the others would be compensated for by virtue of the fact that the decrease in distance of the relatively unconsumed electrodes or portions of electrodes and the melt in the furnace would operate to increase the current density for the relatively unconsumed sections and increase the rate of electrode consumption in such section. Accordingly, during normal operation there is no necessity for individual vertical adjustment of the respective electrode units. However, it will be obvious that such vertical adjustment, either for all the electrodes as a unit or for each electrode individually, may be incorporated in the disclosed arrangement, if desired.

As illustrated in Figures 1 and 2 the drive assembly for rotating the respective continuous electrodes is situated between and on the same end as the contact disc means of the electrode. It will be apparent that the drive means and the contact disc or other similar conductor means may be arranged on the shaft of the conductor on opposite sides of the furnace, as illustrated in Figure 3, or may be arranged so as to place the liquid mass 33 adjacent the furnace pot II! with the rotating drive placed exterior thereof, as illustrated in Figure 4. An arrangement whereby the conductive liquid is placed adjacent the furnace, as illustrated in Figure 4, is particularly advantageous when the conductive liquid is a metal of melting point sufficiently above normal temperature so that additional heat is required to maintain the conducting metal in molten condition, the conductive metal by such arrangement then absorbing the necessary heat from the furnace itself.

Conductive liquids which may be employed to deliver current to the respective contact disc may be mercury, Woods metal, lead, zinc, or any other metal alloy or solution which is liquid at operating temperatures and which is not destroyed during the process of current conduction.

Although the preferred form of the invention adopts a liquid conductive means between the stationary conductor input and the rotary conductor I2, it will be apparent that other types of conductors may be utilized. For example, current conduction to the rotary conductor I2 may be through the rotational drive by use of current conducting greases and bearing members supported on the frame structure of the furnace, or by any other suitable means, the use of which makes possible the delivery of the high amounts of current necessary to the rotary conductor I2 with a minimum of power loss.

The various features and arrangements of rotatablecontinuous electrodes and means-for conducting'current thereto herein disclosedmay be embodied in electric furnaces for use in electrolytic production of aluminum from alumina and'for use in other general smelting operations, the making of steel, the production of calcium carbide, and other similar fields of applications wherein furnaces utilizing self-baking electrodes are employed.

What I claim is:

1. An electrode of theself-baking type comprising a substantially horizontally disposed, elongated, current carrying, rotatable, metallic core member which is surrounded with a layer of non-metallic, consumable electrode material, said layer having an upper unbaked portion and a lower baked portion, and wherein said upper unbaked portion and said lower baked portion-are coextensive over the longitudinal extent of said layer.

2. An electrode of the self-baking type having a lower baked portion and an upper unbaked portion, comprising a substantially horizontally disposed, elongated, metallic coremember which is surrounded with a layer of non-metallic, conductive electrode material, the inner section of said layer being baked onto said core member throughout substantially its entire periphery while the outer section of said layeron the lower portion of the core member is baked on the'inner section and the outer section of the upper portion of the layer is in unbaked condition and is attached to the inner section by cohesion.

3. An electrode of the self-baking type having a lower baked portion and an upper unbaked portion, comprising a horizontally disposed, elongated, rotatable, metallic core member, said core member being coveredwith a layer of nonmetallic electrode material, said layer being entirely in the baked condition on the lower portion ofv said core member while only: the inner section of the layer on the upper portion of said core member is in the baked condition.

4. An electrode of the self-baking type, comprising a substantially horizontally disposed, rotatable, elongated, current-carrying core mem-- ber which is provided with a layer of nonmetallic, consumable, electrode material surrounding said core member, said layer comprising anupper unbaked portion and a lower baked portion, said lower baked portion ofsaid layer to. be progressively fed into contact with a furnace bath by rotation of said core member whereby a substantial portion of that part of the baked layer incontact with the furnace bath is consumed.

5. An electrode of the self-baking type comprising a substantially horizontally disposed, elongated, rotatable, current-carrying core member provided with a layer of consumable electrode material surrounding said core member, said layer comprising a lower baked portion to be fed into contact with a furnace bath by rotation of said core member and therein be substantially consumed and an upper unbaked portion to be baked ontosaicl core member as the membenis rotated.

6. An electrode as in claim 5, wherein said core. member is provided with a rough exterior surface to enhance the attachment of said'unbaked electrode material thereto as it is progressively baked.

"7-; An electrode as in claim wherein said core member is provided with a hollow central 6. portion and the layer of electrode material is co-extensive therewith.

8. An electrode of the self-baking typecomprising a substantially cylindrical, rotatable, current-carrying, substantially horizontally disrposed, metallic core member for rotation in a horizontal plane above a furnace bath, said member being provided with a layer of consumable electrode material covering the major: portion of its length; said layer comprising alowerbaked portion to be fed into the furnace bath by rotation of saidcore member and therein substantially consumed and anupper unbakedportion to be progressively applied to the electrode; to replenish that portion of the layer which is'progressively consumed in the furnace bath during rotation of saidcore member;

9. An electrode as in claim '8 wherein the consumable layer is composed of carbonaceous material.

10. The combination with an electric. furnace of an electrode of the self-bakingtype comprising a substantially cylindrical, rotatable, metallic core member rotating in a horizontal plane over the furnace bath, and a layer of non-metallic, consumable electrode material covering said member along a major portion of its length, said layer comprising an upper unbaked portion and a lower baked portion, said lower portion being in contact with the furnace bath, means for rotatably positioning said electrode over the furnace bath, means for rotatably positioning. said electrode over the furnace bath, means for rotating said electrode, and means for supplying electric current to said core member.

11. The combination according to claim 10 wherein a plurality of such. electrodes are arranged in a horizontal plane over a furance bath.

12. The combination as in claim 10 wherein the current supplying means comprises a con tact disc member which is secured on one end of the core member, a conductive receptacle containing a current conductive liquid, positioned in such manner that the lower peripheral portion of, said disc member is always immersed in i said liquid, and means for connecting said receptacle to a suitable source of power.

13. The combination with an electric furnace of an electrode of the self-baking type comprising a substantially cylindrical, rotatable, current-carrying core member rotating in ahorizontal plane over a furnace bath, and provide ed with a layer of consumable electrode material surrounding said core member, said layer comprising a lower baked portion to be progressively fed into contact with the furnace bath and therein be substantially consumed as the core. member is rotated and an upper unbaked portion to be baked onto said core member as the member is rotated, means for supporting the electrode at its ends over said furnace bath, means for rotating said core member, and means for connecting one end of said core member to a suitable source of power.

14. The combination according to claim. 13 wherein a plurality of such electrodes are ar ranged'in a horizontal plane over the furnace bath.

15. The combination as in claim 13 wherein the metallic core member is hollow in the central portion thereof and has shaft-like projections on each end not covered by consumable electrode material.

16; The combination as in claim 13 and including the provision of a hopper extending above and longitudinally of said electrode tofeed unbaked paste-like electrode material progresslvely down upon the top of said electrode to replenish that portion of the electrode layer which is consumed in the furnace bath during progressive rotation of said core member.

17. The combination with an electric furnace of an electrode of the self-baking type compris ing a substantially cylindrical, rotatable, cur rent-carrying, metallic core member rotating in a horizontal plane over a furnace bath, said member being provided with a layer of consumable electrode material covering the major portion of its length, said layer comprising a lower baked portion to be fed into contact with the furnace bath by rotation of said core member and-therein be substantially consumed and an upper unbaked portion to be progressively applied to the electrode to replenish that portion of the baked layer which is progressively consumed in the furnace bath during rotation of said core member, means for supporting the core member over the furnace bath, means for rotating said core member, means for connecting one end of the core member in conductive fashion with a suitable source of power, and hopper means mounted on said furnace and xtending above and longitudinally of said electrode to feed unbaked electrode paste material progressively down upon the top of said electrode to replenish that portion of the electrode layer which is progressively consumed in the furnace bath during progressive rotation of said cor member, said hopper comprising two longitudinally extending side portions, the lower edge of one side extending downwardly to a point closer to the core member than said other side portion, the lower edge of said other side portion being provided with an arcuate section extending downward about the electrode, and two end portions forming, with said arcuate section, a three-sided mold member for retaining the deposited electrode paste material upon the electrode during the baking thereof.

18. A hopper for feeding electrode paste material down upon an electrode of the self-baking type comprising an elongated, rotatable, metallic core member provided with a layer of electrode material surrounding the central portion of said member, said hoppercomprising two spaced longitudinally extending side portions,

the lower edge of one of the side portions extending downwardly a greater distance than the other side portion, a longitudinally, downwardly extending arcuate portion secured to the lower edge of said other side portion, said arcuate portion to act as a retainer for electrode paste material, which has been deposited upon the electrode, while said paste is baking, and end portions that at least cover that area defined by the ends of said sid portions, said end portions forming with said arcuate portion a three-sided mold for retaining the deposited electrode paste in desired position while it is baking.

19. A hopper as in claim 18 wherein one edge of the end portions is integral with said side portion provided with the downwardly extending arcuate portion and each end portion is pro vided with a downwardly extending slot for reception of the ends of the other longitudinally extending side portion.

20. A hopper as in claim 18 wherein the longitudinally extending side portions converge toward each other at their lower edges and wherein the lower edg of said end portions have a semicircular recess provided therein to be positioned closely adjacent over a predetermined circumferential portion of the rotatable core member.

21. In the method of replenishing the consumable electrode material on an electrode of the self-baking type comprising a substantially cylindrical, rotatable, current-carrying, metallic core member to be rotated in a horizontal plane over an electric furnace bath and being covered along the major portion of its length between the end portions with a layer of consumable electrode material to be progressively fed into contact with a furnace bath, said layer comprising a lower baked portion and an upper unbaked portion, the steps of progressively rotating the electrode which causes the lower baked portion of the electrode layer to be progressively immersed in the furnace bath wherein the major portion of said layer is consumed, simultaneously therewith progressively depositing unbaked electrode paste material upon the electrode surface that has previously passed through the furnace bath to build the consumable electrode layer back up to its original thickness prior to immersion in the furnace bath, and thereafter progressively baking the deposited unbaked electrode paste before such time that the deposited electrode material is fed into the furnace bath.

22. A method according to claim 21 wherein the unbaked electrode paste is deposited upon the electrode along a relatively narrow longitudinally extending zone on the upper side of said rotating electrode.

23. A method according to claim 21 wherein the progressively deposited electrode paste layer is restrained axially and radially until it has been thoroughly baked onto the rotating supporting member.

24. A method according to claim 21 wherein the rotation of the electrode is one of continuous motion.

25. A method according to claim 21 wherein the rotation of the electrode is one of intermittent motion.

26. The combination with an electric furnace of an electrode of the self-baking type comprising a substantially cylindrical, rotatable, currentcarrying core member rotating in a substantially horizontal plane over the furnace bath, and a layer of consumable electrode material surrounding said member, said layer having an upper unbaked portion and a lower baked portion, said lower baked portion being in contact with the furnace bath, means for positioning said electrode above the furnace bath in substantially a horizontal plane, means for rotating said elec trode, said means comprising a disk-shaped gear element which is securely fixed to one end of said core member, and a driving element, said driving element being provided on one end with a suitable worm gear for meshing with said disk-shaped gear element and being provided on the other end with means for rotating said driving element from a suitable source of power, and means for conducting current to said core member.

References Cited in the file of thi patent UNITED STATES PATENTS Number Name Date 826,742 Price July 24, 1906 1,150,021 Favier Aug. 17, 1915 1,169,384 Dwight Jan. 25, 1916 1,441,037 Soderberg Jan. 2, 1923 1,496,232 Klugh June 3, 1924 1,748,780 Marshall Feb. 25, 1930 1,944,521 Migvet et al. Jan. 23, 1934