US2728109A - Method of making cathodic electrodes for electrolysis furnaces - Google Patents

Method of making cathodic electrodes for electrolysis furnaces Download PDF

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Publication number
US2728109A
US2728109A US312104A US31210452A US2728109A US 2728109 A US2728109 A US 2728109A US 312104 A US312104 A US 312104A US 31210452 A US31210452 A US 31210452A US 2728109 A US2728109 A US 2728109A
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cathode
paste
blocks
carbon
electrolysis
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Expired - Lifetime
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US312104A
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English (en)
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Bonnot Maurice
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Societe des Electrodes et Refractaires Savoie SA
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Societe des Electrodes et Refractaires Savoie SA
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
    • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes

Definitions

  • the present invention relates to cathodic electrodes 7 for electrolysis furnaces.
  • aluminum is generally manufactured by electrolysis of alumina, dissolved in a; melt of cryolite. This electrolysis is carried out in special furnaces in which electric current is supplied through carbon electrodes, one of which, the upper electrode, plays the part of an anode, the lower electrode playing the parts both of a cathode and of a refractory container for the electrolysis melt.
  • the anode is frequently obtained from a mixture of carbon grains and dust with a hydrocarbon binder, said mixture being shaped by extrusion, compression or any other method and then fired in special furnaces before being placed in the electrolysis tank. It is also known, however, to use so-called self firing anodes, consisting of a casing, generally made of aluminum sheet, filled with an unfired or crude paste of carbon grains and dust mixed with a hydrocarbon binder; such anodes, placed in working position when crude, are fired in the very furnace in which they are used. This method leads, among other advantages, to the saving of the preliminary firing of the paste forming the anode.
  • cathode plays also the part of a refractory container for the electrolysis melt
  • said cathode must be absolutely tight and, particularly, must offer no crack which could lead to the penetration of the electrolysis melt therein.
  • a cathode may be quite pervious to melted metal and, generally, to the electrolysis melt, even when the permeability of the individual blocks which form it is low, if the blocks are poorly bonded together.
  • the penetration of the melt inside the cathode causes, among other drawbacks, a poor quality of the metal produced and a'rapid destruction of the cathode which makes it necessary to interrupt production prematurely.
  • the voltage drop in the cathode which is difiicult to measure with any accuracy, is of the order of 200 to 250 millivolts. This voltage drop begins to increase after a few months of operation, it then increases rapidly and 'at the time when it is found necessary to put the tank out of working, the said voltage drop generally reaches from 500 to 1000 millivolts, as an average 600 to 700 :millivolts.
  • cathodes are generally made out of previously fired carbon blocks, separated from one another by joints of small dimensions filled with a crude brasque consisting of a mixture of carbon grains and dust with a hydrocarbon binder generally having a low melting point. It is therefore always necessary to perform a previous firing 0f the individual blocks.
  • cathodes by tamping crude brasque over their whole area and thickness, the firing being carried out in the proper furnace in which they are to be used.
  • Such a method involves some difficulties and drawbacks, the main four of which are detailed hereafter.
  • the paste delivered from the mixers is actually at a temperature much higher than that of the melting point of the binder; but it has to be spread in thin layers, over a large area (that of the tank), in a medium which is at room temperature (much below the melting point of the binder).
  • Such operative conditions are favourable to a rapid cooling of the paste.
  • the viscosity of hydrocarbon binders usually employed in the electrode industry doubles when the temperature drops by 7 degrees centigrade. The result is that the viscosity of the paste during the tamping varies from one moment to the next and may become such that the shaping of said paste be practically impossible.
  • pastes usually employed for electrodes, and in which the binders are dry pitches having high melting points (70 C. and above) cannot be used in such conditions; pastes must be used which contain binders with low melting points (4045 C.).
  • Such binders however have the drawback of having a lower, fixed carbon content (coking residue), and, consequently less favourable agglomerating properties.
  • Any shaping process such as extrusion, compression, vibration, tamping, ramming, and the like, creates an orientation of the paste layers or strands, and of the particles which form said paste; the result is that products intended to lead electric current, and manufactured by means of such processes have, a resistance to the flow of current, which is a minimum in the plane of the layers or in the direction of the strands and a maximum in the perpendicular direction.
  • a resistance to the flow of current which is a minimum in the plane of the layers or in the direction of the strands and a maximum in the perpendicular direction.
  • a cathode manufactured by such a method therefore opposes a maximum resistance to thefiow of current which circulates vertically between the anode and cathode, through the bath, which among other drawbacks, increases the voltage drop in the cathode.
  • the improved method according to the present invention comprises forming crude blocks of carbon by shaping, for instance moulding or extruding under pressure, a crude paste consisting of carbon and a hydrocarbon binder while keeping said paste at a uniform degree of viscosity, assembling said blocks to the shape desired for the cathode, binding them together by means of crude brasque joints, and firing the so obtained cathode in the electrolysis furnace proper.
  • hydrocarbon binders For the preparation of individual blocks, all usual hydrocarbon binders may be used, including those having a high melting point, a high fixed carbon content andconsequently a maximum of agglomerating properties.
  • the carbon which is used is not different frorngthat generally used for the manufacturing of electrodes.
  • the blocks are shaped in temperature controlled capacities (moulds, dies, or the like), which are adapted to keep the paste, during the entire shaping operation, at a temperature and consequently at a viscosity which are uniform throughout the mass. Furthermore, the shaping may take place under a very high pressure, which may also be controlled.
  • the blocks or bars thus obtained may be cut and, gen erally speaking, machined in such a manner that they can always be arranged with the desired orientation of the layers or strands of paste and of the particles which form said paste, and particularly with' such an orientation that the said layers and particles are parallel with the direction of the flow of current through the electrolysis tank, in order that the cathode offers a minimum resistance to the flow of such current.
  • the cathode is truly a one piece member.
  • the carbon blocks themselves made in one piece, for instance by extrusion in powerful hydraulic presses, do not have the above men-v tioned lack of homogeneity and, in particular, are not laminated. These combined factors impart to the cathodes according to the invention a substantially longer life than that of known cathodes.
  • Fig. 1 is a perspective view of a plane cathode formed of juxtaposed bars
  • Fig. 2 is a view similar to Figure l of a modified construction made otrt of smaller elements.
  • the cathode shown in Figure 1 is formed of bars 1 having a square section and arranged side by side. Said bars comprise grooves Z for housing current input rods 3. They are united together longitudinally by brasque j nts.
  • the cathode shown in Figure 2 consists of substantially cubical bloclgs 19 arranged checkerboard fashion and connected togetherby brasque joints 11.
  • the first type of embodiment which corresponds to Figure 1 calls for square section bars 1, for instance 500 by 500 mm. having a length of 2,408 meters.
  • a mixture containing 82% of strongly calcined anthracite grains and dust, and 18% of coal tar pitch having a iKramer melting point of 85 C. was kneaded to a paste, Said paste was placedat a temperature of C. in a 6.000 metric tons extrusion press and extruded thereby through a die having a square opening of the size required for the bar.
  • the extruded bars were cut to the desired length of 2.400 meters and machined by planing to form the grooves 2 for the rods 3. After having been fitted with said rods, the bars were arranged horizontally on the bottom of the tank, parallel to one another the direction of their extrusion F is horizontal), said bars being separated laterally from one another by joints 25 mm. wide.
  • brasque was kneaded, consisting of 84% of strongly calcined anthracite fine grains and dust and 16% of a coal tar pitch having a Kramef melting point of 45 C.; this brasque was then introduced into the joints at a temperature of 63 to 70 C., by an exhaustive tamping by means of pneumatic tampcrs. A one piece, crude cathode was thus obtained, offering little resistance to the current flow.
  • the Kramer melting point may be defined as being the temperature at which a drop of mercury, placed on top of a plug of solid pitch, arranged at the bottom of a tube dipping into a liquid which is being heated, goes through said pitch plug when the latter melts due to the heating of the liquid. This test is delicate and the prescribed operating method must be followed very strictly to obtain results capable of duplication.
  • bars prepared in the same conditions as above were cut, on their issuing from the die, into cubes 10, with sides of 500 mm.
  • These cubes were machines, as above mentioned, and positioned in horizontal rows provided with a continuous groove 2, each block being oriented so that the direction of extrusion F ( Figure 2) be vertical.
  • the cubes were separated from one another in all directions, by joints 2 5 mm. wide which were filled with crude brasque obtained and introduced according to the above described method.
  • a method for the manufacture of a one-piece cathode for an electrolysis furnace comprising the steps of preparing unfired carbon blocks by shaping under pressure a paste consisting of comminuted carbon and a hydrocarbon binder While keeping said paste at a uniform degree of viscosity, assembling in said furnace said bloclzs in the shape desired for the cathode and to constitute composition as said blocks and firing the obtained cathode in said electrolysis furnace.
  • unfired carbon blocks are prepared by compressing the paste in molds under high pressure at such a temperature that a uniform viscosity is preserved throughout the mass during the whole compressing operation.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
US312104A 1952-06-06 1952-09-29 Method of making cathodic electrodes for electrolysis furnaces Expired - Lifetime US2728109A (en)

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FR309978X 1952-06-06

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CH (1) CH309978A (fr)
DE (1) DE1034872B (fr)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2937980A (en) * 1956-01-24 1960-05-24 Elektrokemisk As Method of making self-baking continuous electrodes
US3001237A (en) * 1956-12-31 1961-09-26 James D Hedges Method of making carbon articles
US3020220A (en) * 1952-09-09 1962-02-06 Helling Werner Continuous carbon electrode
US3053748A (en) * 1957-06-18 1962-09-11 Pechiney Prod Chimiques Sa Novel type electrode for electrolytic cells
US3107212A (en) * 1960-06-28 1963-10-15 Montedison Spa Method and apparatus for baking and preheating bottoms of electrolytic cells by meansof alternating or direct current
US3275488A (en) * 1960-08-05 1966-09-27 Great Lakes Carbon Corp Fabrication of carbon and graphite bodies
US3489984A (en) * 1966-12-27 1970-01-13 Great Lakes Carbon Corp Electrical connection between electrical conductors such as between a metal bar and a cathode of an aluminum cell
US3787311A (en) * 1970-12-12 1974-01-22 Giulini Gmbh Geb Cathode for the winning of aluminum
USB430385I5 (fr) * 1974-01-03 1975-01-28
US4076610A (en) * 1975-07-10 1978-02-28 Elettrocarbonium S.P.A. Cathode in cells for producing aluminium by electrolysis of smelted salts thereof
US4185055A (en) * 1971-09-24 1980-01-22 Aluminum Pechiney Process for heat-treating carbon blocks
EP0008561A1 (fr) * 1978-08-16 1980-03-05 Aluminium Pechiney Appareillage pour compacter les pâtes carbonées dans les garnissages de fours métallurgiques
FR2566002A1 (fr) * 1984-06-13 1985-12-20 Pechiney Aluminium Bloc cathodique modulaire et cathode a faible chute de tension pour cuves d'electrolyse hall-heroult
US5676807A (en) * 1992-06-12 1997-10-14 Moltech Invent S.A. Carbon containing ramming paste in aluminum production cells
WO1998020188A2 (fr) * 1996-10-18 1998-05-14 Moltech Invent S.A. Appareil et procede destines au traitement d'un revetement de cellule d'une cellule a extraction electrolytique d'aluminium
WO2001078460A1 (fr) * 2000-04-10 2001-10-18 Graphtech Inc. Systeme visant a reduire une variation de temperature pendant la graphitisation longitudinale de corps carbones
DE10164008C1 (de) * 2001-12-28 2003-04-30 Sgl Carbon Ag Graphitierte Kathodenblöcke

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE58956C (de) * SOCIETE ELECTRO-METALLURGIQUE FRANCAISE, Direktor A. MASSE in Paris, 43 Rue St. Georges Verfahren zur Herstellung einer Kohlen-Elektrode aus einzelnen Kohlenplatten
US538289A (en) * 1895-04-30 -charles percy shrewsbury
FR564167A (fr) * 1923-03-21 1923-12-22 Talco E Grafiti Val Chisone So électrode à base de graphite naturel et procédé pour sa fabrication
US1556990A (en) * 1922-10-12 1925-10-13 Albert C Henry Commutator brush
US1734811A (en) * 1925-05-19 1929-11-05 Nat Carbon Co Inc Brush for dynamo-electric machinery
US1899064A (en) * 1926-07-01 1933-02-28 Burgess Lab Inc C F Manufacture of electrodes
US2252277A (en) * 1939-04-20 1941-08-12 James R Tate Molded porous electrical brush and the like
US2378142A (en) * 1943-08-23 1945-06-12 Pour I Ind De I Aluminum Sa Method for making furnaces for the electrolytic production of aluminum
US2403301A (en) * 1942-08-29 1946-07-02 Richon Andre Method for making artificial carbon pieces

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH221732A (de) * 1942-06-02 1942-06-15 Aluminium Ind Ag Verfahren zur Herstellung von Kunstkohlekörpern.

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE58956C (de) * SOCIETE ELECTRO-METALLURGIQUE FRANCAISE, Direktor A. MASSE in Paris, 43 Rue St. Georges Verfahren zur Herstellung einer Kohlen-Elektrode aus einzelnen Kohlenplatten
US538289A (en) * 1895-04-30 -charles percy shrewsbury
US1556990A (en) * 1922-10-12 1925-10-13 Albert C Henry Commutator brush
FR564167A (fr) * 1923-03-21 1923-12-22 Talco E Grafiti Val Chisone So électrode à base de graphite naturel et procédé pour sa fabrication
US1734811A (en) * 1925-05-19 1929-11-05 Nat Carbon Co Inc Brush for dynamo-electric machinery
US1899064A (en) * 1926-07-01 1933-02-28 Burgess Lab Inc C F Manufacture of electrodes
US2252277A (en) * 1939-04-20 1941-08-12 James R Tate Molded porous electrical brush and the like
US2403301A (en) * 1942-08-29 1946-07-02 Richon Andre Method for making artificial carbon pieces
US2378142A (en) * 1943-08-23 1945-06-12 Pour I Ind De I Aluminum Sa Method for making furnaces for the electrolytic production of aluminum

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3020220A (en) * 1952-09-09 1962-02-06 Helling Werner Continuous carbon electrode
US2937980A (en) * 1956-01-24 1960-05-24 Elektrokemisk As Method of making self-baking continuous electrodes
US3001237A (en) * 1956-12-31 1961-09-26 James D Hedges Method of making carbon articles
US3053748A (en) * 1957-06-18 1962-09-11 Pechiney Prod Chimiques Sa Novel type electrode for electrolytic cells
US3107212A (en) * 1960-06-28 1963-10-15 Montedison Spa Method and apparatus for baking and preheating bottoms of electrolytic cells by meansof alternating or direct current
US3275488A (en) * 1960-08-05 1966-09-27 Great Lakes Carbon Corp Fabrication of carbon and graphite bodies
US3489984A (en) * 1966-12-27 1970-01-13 Great Lakes Carbon Corp Electrical connection between electrical conductors such as between a metal bar and a cathode of an aluminum cell
US3787311A (en) * 1970-12-12 1974-01-22 Giulini Gmbh Geb Cathode for the winning of aluminum
US4185055A (en) * 1971-09-24 1980-01-22 Aluminum Pechiney Process for heat-treating carbon blocks
USB430385I5 (fr) * 1974-01-03 1975-01-28
US4001104A (en) * 1974-01-03 1977-01-04 Union Carbide Corporation Cemented collector bar assemblies for aluminum cell carbon bottom block
US4076610A (en) * 1975-07-10 1978-02-28 Elettrocarbonium S.P.A. Cathode in cells for producing aluminium by electrolysis of smelted salts thereof
EP0008561A1 (fr) * 1978-08-16 1980-03-05 Aluminium Pechiney Appareillage pour compacter les pâtes carbonées dans les garnissages de fours métallurgiques
FR2433725A1 (fr) * 1978-08-16 1980-03-14 Pechiney Aluminium Appareillage pour compacter les pates carbonees dans les garnissages de fours metallurgiques
FR2566002A1 (fr) * 1984-06-13 1985-12-20 Pechiney Aluminium Bloc cathodique modulaire et cathode a faible chute de tension pour cuves d'electrolyse hall-heroult
EP0169152A1 (fr) * 1984-06-13 1986-01-22 Aluminium Pechiney Bloc cathodique modulaire et cathode à faible chute de tension pour cuves d'électrolyse hall-héroult
US5676807A (en) * 1992-06-12 1997-10-14 Moltech Invent S.A. Carbon containing ramming paste in aluminum production cells
WO1998020188A2 (fr) * 1996-10-18 1998-05-14 Moltech Invent S.A. Appareil et procede destines au traitement d'un revetement de cellule d'une cellule a extraction electrolytique d'aluminium
WO1998020188A3 (fr) * 1996-10-18 1999-01-07 Moltech Invent Sa Appareil et procede destines au traitement d'un revetement de cellule d'une cellule a extraction electrolytique d'aluminium
WO2001078460A1 (fr) * 2000-04-10 2001-10-18 Graphtech Inc. Systeme visant a reduire une variation de temperature pendant la graphitisation longitudinale de corps carbones
DE10164008C1 (de) * 2001-12-28 2003-04-30 Sgl Carbon Ag Graphitierte Kathodenblöcke

Also Published As

Publication number Publication date
CH309978A (fr) 1955-09-30
DE1034872B (de) 1958-07-24

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