US3730859A - Multicell furnaces for the production of aluminum by electrolysis - Google Patents

Multicell furnaces for the production of aluminum by electrolysis Download PDF

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Publication number
US3730859A
US3730859A US00050050A US3730859DA US3730859A US 3730859 A US3730859 A US 3730859A US 00050050 A US00050050 A US 00050050A US 3730859D A US3730859D A US 3730859DA US 3730859 A US3730859 A US 3730859A
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aluminum
pit
bath
furnace
cathode
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US00050050A
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English (en)
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Varda G De
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Montedison SpA
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Montedison SpA
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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

  • Multicell furnaces having inclined bi-polar electrodes for the production of aluminum by electrolysis have already been described.
  • bi-polar electrodes are made of a carbon material and that they are suspended in a molten fluoride bath (U.S. Pat. 3,178,363, issued Apr. 13, 1965).
  • the molten cryolitic bath is contained in a vat having an outside iron lining, which is lined on its inner surface by a solid and electrically highly insulating material, such as for instance, shaped pieces made of siliconnitride-bonded silicon carbide, or of fused alumina, or of pure cryolite, etc.
  • the molten bath in the various cells, crossed by the electrolytic current, for instance is kept at a temperature of 960 C.
  • the lower layers of the bath, located above the vat bottom but beneath the electrode system are a somewhat lower temperature. The temperature reaches a minimum value in those layers of the bath,
  • the present invention surprisingly, overcoming the foregoing drawbacks, allows very simply and inexpensively, to keep the pit for collecting aluminum at least at a temperature which is slightly above the critical temperature of the bath. Thus incrustation of the pit bottom or even obstruction of the whole pit by bath thickening is avoided.
  • the cryolitic bath may have temperatures ranging between 930 and 980 C. It is well known that the bath transfers heat very poorly from top to bottom. From this point of view, its behavior does not substantially differ from that of water at temperatures ranging between 0 and C. It is indeed known that in a glass test tube full of water and heated only at the top, some particles of ice on the bottom, may at least for some time very well coexist with a layer of boiling water on the top.
  • the calories that keep the furnace at its running temperature are produced almost exclusively in the interelectrodic spaces of the various cells as a consequence of the ohmic resistance that the bath opposes to the flow of the electrolysis current.
  • the carbon electrodes have a much higher heat conductivity than that of the bath and therefore heat propagates easily in. such electrodes in any direction and also toward the bottom. It is known that in multicell furnaces having suspended electrodes, immersed in a cryolitic bath, and having a vat bottom sloping down towards the aluminum pit, such electrodes purposely do not reach the step-shaped vat bottom, in order not to short-circuit the multicell furnace or at least not to increase considerably the by-pass of idle electric current outside the single cells.
  • the present invention overcoming a technical prejudice, consists in constantly keeping the lower end of the terminal cathode (or terminal cathodes) and of no other cathode, permanently immersed in the molten aluminum contained in the underlying pit for collecting aluminum. In such a way, a good heat transfer from the terminal cathode to the metal collected in the pit is secured, the metal, in turn, being an excellent heat conductor toward the neighboring zones of the bath and of the vat bottom, thus dispelling or preventing the formation and floating of dangerous aluminum layers below the suspended carbon electrodes of the multicell furnace.
  • the cathodic current supply connecting bars are reconnected to the bus bar, by means of simple known operations.
  • the figure represents schematically a longitudinal section of a multicell furnace with a stepped bottom in accordance with my invention.
  • a symmetrical-type multicell furnace which comprises eight spaced apart suspended and inclined bi-polar electrodes 5, two terminal anodes 8 and terminal cathode 3.
  • terminal cathode 3 is placed in central position with respect to the other electrodes.
  • terminal electrode is understood to mean such electrodes have either only cathode or only anode active surfaces, whereas bi-polar electrodes possess both anode and cathode active surfaces.
  • Bi-polar electrodes 5, terminal anodes 8 and terminal cathode 3 define ten (five-l-five) cells 7, wherein electrolytic decomposition of alumina takes place.
  • Steps 1 descend from the ends of the furnace towards the central zone of the same, where a single collecting pit 2 is placed for the collecting and the tapping of the molten aluminum produced in the individual cells 7.
  • Cathode 3 is axially perforated so that the introduction of a suitable tapping apparatus (not shown in the figure) through the hole 13 into the collecting pit 2, is possible.
  • terminal cathode 3 extends downwardly well inside collecting pit 2.
  • the usual cathodic voltage drop may be maintained for instance between 0.3 and 0.5 volt.
  • the terminal cathode alone will develop a heating ohmic power of 6-10 kw.
  • the corresponding increase of ohmic calories supplied to the terminal cathode will amount to about further 6-10 kwh.
  • the thermal source located in the terminal cathode is almost doubled.
  • the production of these additional calories is advantageous first of all to the carbon terminal cathode and secondly to the underlying pit for collecting aluminum, such aluminum being in direct and lasting contact with the cathodic carbon electrode, which in its turn is partially immersed in said aluminum.
  • a multicell furnace for producing aluminum by electrolysis of alumina dissolved in molten fluoride baths, such furnace comprising a bath containing vat, lined on its inner surface by a solid and electrically poorly conducting material, and a plurality of internally positioned bi-polar electrodes and terminal monopolar electrodes, such electrodes adopted to be suspended in the bath, inclined and made of a carbonaceous material, such furnace further comprising at least one terminal cathode and a stepped shaped vat bottom sloping down toward at least one pit for collecting the aluminum produced by electrolysis, the improvement which comprises a pit being under said terminal cathode, said terminal cathode being well inside said pit so that when said furnace is in operation a good and permanent contact of the carbonaceous material of said terminal cathode and the aluminum collected in the pit is obtained, whereby a suitable heat transfer from the carbon cathode to the molten aluminum collecting into the pit and to the vat bottom is obtained, and means for switching electric contacts between the carbonaceous material of said terminal ca
  • terminal cathode has a plurality of metallic current sup ply connecting bars and nipples, and at least one of said connecting bars is arranged in such a manner that it may be easily electrically connected with and disconnected from a bus bar.
  • terminal cathode is so shaped as to have at least its bottom part more enlarged than its upper part, said enlarged part of said cathode being so located in said collecting pit as to prevent direct contact of said cathode with the walls and the bottom of said pit.
  • a multicell furnace for producing aluminum by electrolysis of alumina dissolved in molten fluoride baths comprising a bath containing vat, said vat lined on its inner surface by a solid and electrically poorly conducting material, a plurality of internally positioned bipolar electrodes and terminal monopolar electrodes suspended in the bath, said electrodes being inclined and made of a carbon material, said furnace further comprising at least one terminal cathode and a stepped shaped vat bottom sloping down toward at least one pit for collecting the aluminum produced by electrolysis, said pit being located under a terminal cathode in a central position with respect to the bottom of the vat, said terminal cathode extending well inside of said pit whereby a good and lasting contact of the carbon material of the terminal cathode and the molten aluminum collected in the pit is realized during furnace operation, said terminal cathode being provided with a plurality of metallic current supply connecting bars and nipples adoptable for tempoarry disconnection and reconnection whereby, the temperature of
  • a multicell furnace for producing aluminum by electrolysis of alumina dissolved in molten fluoride baths comprising a bath containing vat, said vat being lined on its inner surface by a solid and electrically poorly conductive material, a plurality of internally positioned bipolar electrodes and terminal monopolar electrodes, said electrodes being suspended in the bath, inclined and made of a carbonaceous material, said furnace further comprising a stepped shaped vat bottom sloping down toward at least a pit for collecting the aluminum produced by electrolysis, said pit being located beneath a terminal cathode at the bottom of the vat.
  • GIUSEPPE de VARDA t n P. t a p W d O 8 1 ml m I u m e o C 3 S a S v a O d a G t e C 1 Q E I I n O i C S V. I 10 a e 3 I. n: e 3.10 a

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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)
US00050050A 1969-06-30 1970-06-26 Multicell furnaces for the production of aluminum by electrolysis Expired - Lifetime US3730859A (en)

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IT1896269 1969-06-30

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US3730859A true US3730859A (en) 1973-05-01

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US (1) US3730859A (zh)
JP (1) JPS5020936B1 (zh)
AT (1) AT295874B (zh)
CA (1) CA931910A (zh)
DE (1) DE2032112A1 (zh)
ES (1) ES381239A1 (zh)
FR (1) FR2049201B1 (zh)
GB (1) GB1312378A (zh)
NL (1) NL7009351A (zh)
NO (1) NO125356B (zh)
PL (1) PL80709B1 (zh)
SE (1) SE365823B (zh)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4021317A (en) * 1976-05-10 1977-05-03 Aluminum Company Of America Method of operating an electrolytic cell
US4133728A (en) * 1978-01-26 1979-01-09 E. I. Du Pont De Nemours And Company Electrolytic cell with switching means
US4504366A (en) * 1983-04-26 1985-03-12 Aluminum Company Of America Support member and electrolytic method
US4596637A (en) * 1983-04-26 1986-06-24 Aluminum Company Of America Apparatus and method for electrolysis and float
US4622111A (en) * 1983-04-26 1986-11-11 Aluminum Company Of America Apparatus and method for electrolysis and inclined electrodes
US4664760A (en) * 1983-04-26 1987-05-12 Aluminum Company Of America Electrolytic cell and method of electrolysis using supported electrodes
US4865701A (en) * 1988-08-31 1989-09-12 Beck Theodore R Electrolytic reduction of alumina

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61186489A (ja) * 1985-02-13 1986-08-20 Hiroshi Ishizuka アルカリ金属または土金属の溶融塩化物電解装置

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4021317A (en) * 1976-05-10 1977-05-03 Aluminum Company Of America Method of operating an electrolytic cell
US4133728A (en) * 1978-01-26 1979-01-09 E. I. Du Pont De Nemours And Company Electrolytic cell with switching means
US4504366A (en) * 1983-04-26 1985-03-12 Aluminum Company Of America Support member and electrolytic method
US4596637A (en) * 1983-04-26 1986-06-24 Aluminum Company Of America Apparatus and method for electrolysis and float
US4622111A (en) * 1983-04-26 1986-11-11 Aluminum Company Of America Apparatus and method for electrolysis and inclined electrodes
US4664760A (en) * 1983-04-26 1987-05-12 Aluminum Company Of America Electrolytic cell and method of electrolysis using supported electrodes
US4865701A (en) * 1988-08-31 1989-09-12 Beck Theodore R Electrolytic reduction of alumina

Also Published As

Publication number Publication date
ES381239A1 (es) 1973-04-16
DE2032112A1 (de) 1971-03-25
AT295874B (de) 1972-01-25
JPS5020936B1 (zh) 1975-07-18
GB1312378A (en) 1973-04-04
NO125356B (zh) 1972-08-28
SE365823B (zh) 1974-04-01
CA931910A (en) 1973-08-14
FR2049201B1 (zh) 1974-03-01
PL80709B1 (zh) 1975-08-30
NL7009351A (zh) 1971-01-04
FR2049201A1 (zh) 1971-03-26

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