US3728243A - Electrolytic cell for the production of aluminum - Google Patents

Electrolytic cell for the production of aluminum Download PDF

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Publication number
US3728243A
US3728243A US00174892A US3728243DA US3728243A US 3728243 A US3728243 A US 3728243A US 00174892 A US00174892 A US 00174892A US 3728243D A US3728243D A US 3728243DA US 3728243 A US3728243 A US 3728243A
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United States
Prior art keywords
cell
current
lining
cathode
carbon
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Expired - Lifetime
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US00174892A
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English (en)
Inventor
Hatting W Schmidt
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Alcan Holdings Switzerland AG
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Alusuisse Holdings AG
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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
    • C25C3/16—Electric current supply devices, e.g. bus bars
    • 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

  • FIGS. 1 and 2 of the accompanying drawings are a longitudinal section and a transverse section.
  • a fluoride melt (the electrolyte) is contained in a steel pot in which is a layer of insulation 13 and a carbon lining 11.
  • the insulation 13 is of refractory thermally insulating material.
  • Cathodically precipitated aluminium 14 collects on the bottom 15 of the cell.
  • the surface 16 of the liquid aluminium acts as the cathode.
  • Iron cathode bars 17 are embedded in the bottom of the carbon lining 11 and serve to conduct current from the bottom of the cell to the exterior.
  • Anodes 18 of amorphous carbon dip into the fluoride melt from above so as to conduct the direct current to the electrolyte. They are fixed by rods 19 and clamps 20 to two anode bus bars 21. These together constitute an anode beam.
  • the electrolyte 10 is covered with a crust 22 of solidified melt and on top of this is a layer 23 of alumina.
  • the distance d from the underside 24 of the anode to the upper surface 16 of the aluminium can be varied by raising or lowering of the anode beam 21, 21 with the aid of the lifting mechanisms 25 which are mounted on columns 26.
  • the anodes are consumed on their underside to an extent of about 1.5 to 2 cm. each day, according to the particular construction of the cell.
  • the cathode bars 17 have two tasks. They collect the current from the active part of the carbon bottom beneath the anodes 18 and they conduct it out of the cell. Where they collect the current and are designated by 29, the current intensity in the cathode bar increases on both sides towards the exterior. At 28, outside the active part 27 of the carbon bottom, the cathode bars serve as pure current conductors. From each cell, cathode bus bars 30 conduct the current from terminals at the outer ends of the cathode bars 17, to the anode beam 21, 21 of the following cell.
  • the electrolyte possesses a substantially poorer electric conductivity than the liquid aluminium which is situated on the bottom of the cell.
  • the ratio of the two conductivities is between l0 :1 and 10- 1. If the current withdrawal through the carbon bottom does not locally exactly correspond to the current feed through the anodes into the electrolyte, horizontal current density components must occur in the melt, which are caused by the local difference between feed and withdrawal of the current.
  • the great difference of the electrical conductivties of the two Stratified liquids has the effect, according to the tangent law of electric current dynamics, that a kink occurs in the current lines at the boundary surface between electrolyte and liquid aluminium. The result is that the current lines in the electrolyte, to a first approximation, extend vertically.
  • the horizontal current density components in cooperation with the magnetic induction can cause a force field distribution in the liquid metal which is not free from rotation.
  • the consequence of this is a flow of metal combined with a major doming up of metal, which in turn is caused by current density components induced by this movement of a current conductor in a magnet field. Doming up and movement of metal are detrimental to the electrolytic efficiency (ratio of the quantity of aluminium actually obtained to the quantity theoretically precipitated according to Faraday). If the electrolyte efiiciency falls, the electric energy consumption rises (kWh/kg. Al).
  • j j and i signify the current density components in the metal in the three axial directions and B B and B the corresponding components of the magnetic induction.
  • the component transverse to the cell longitudinal axis may be augmented due to the fact that the cathode area, often on account of an excessively great distance between the outside of the anode and the carbon lining of the side walls, is larger than the anode area.
  • the iron cathode bars outside the active part of the carbon bottom can also take up current, if there they are not sufiiciently electrically insulated from the carbon lining of the walls of the cell.
  • the cross section of the iron cathode bars in the active part of the carbon bottom is too small, a great outward displacement of the electrolytic current takes place in the carbon bottom, likewise generating powerful horizontal current density components.
  • the horizontal distance between the outer lower edges of the anodes and the inner faces of the walls of the steel pot does not exceed '55 to 60 cm. If 20 cm. are deducted for thermal insulation and carbon lining, a horizontal interval of at most 40 cm. remains between the outer lower edge of the anodes and the furnace rim, that is the inner surface of the walls of the carbon lining.
  • the minimum horizontal distance between the outer lower edge of the anodes and the furnace rim is 25 to 30 cm.
  • a second feature is that the thermal resistance of the walls of the insulation 13, between the walls of the carbon lining 11 and the walls of the steel pot 12, lies between 0.5 and and and As a consequence, a solid lateral cryolite crust is formed by removal of heat which reduces the cathodic, currentcollecting aluminium area and effectively limits the lateral current flow into the furnace rim.
  • FIGS. 3 and 4 of the accompanying drawings are a diagrammatic longitudinal section and transverse section of a cell embodying the features of the present invention.
  • the cathode bars have their lower faces flush with the interface of the bottom of the carbon lining and the bottom of the insulation. Thus there is no carbon beneath the bars. Furthermore, outside the active part 27 of the carbon bottom the bars are surrounded with insulation 31. Thus there can be no current flow into the bars outside the active part of the carbon bottom.
  • a fourth feature is to place into the active part of the carbon bottom the largest cathode bar cross-section 29 which is compatible with mechanical strength of the carbon bottom.
  • the ratio of iron to carbon should amount to at least 17:100and at most 20:100. If a smaller iron cross-section is provided, unacceptably high horizontal current density components occur in the liquid aluminium. If, on the other hand, a greater iron cross section is provided, a mechanical weakening of the carbon lining occurs, this weakening being caused by the larger thermal coeflicient of expansion of iron in comparison with that of carbon.
  • an electrolytic cell for the production of aluminium by electrolysis of alumina in a melt comprises a pot body of steel; a layer of thermal and electrical insulation against the inside of the body, a lining of carbon against the inside of the insulation layer; the body, the layer and the lining each consisting of a bottom, two side walls and two end walls; iron cathode bars each having at least a part within the lining and a part passing through a side wall of the insulation layer and through a side wall of wall of the insulation layer and through a side Wall of the body; and anodes arranged to dip into electrolyte in the pot; wherein the horizontal distance between outer lower edges of the anodes and adjacent wall surfaces of the lining does not exceed 40 cm.; and thermal resistance of the walls of the insulation layer is between C h. C.
  • the parts of the cathode bars beneath the side wall of the lining are surrounded by insulation; and the ratio of iron cross section to carbon cross section in any vertical plane from end to end of the cell through the bottom of the lining is between 10:100 and 201100.
  • transverse horizontal current density components are largely suppressed, and longitudinal components are reduced.
  • a plant comprises a plurality of electrolytic cells; each cell including at least one terminal outside the pot on each cathode bar, and an anode beam carrying the anodes, and electrical connecting means comprising a plurality of cathode bus bars each of which connects a respective group of at least one of the cathode bar terminals of one cell to the anode beam of the next cell, the cross sections of the individual bus bars being such that, when an equal current flows through each cathode bar,
  • the voltage drop is the same along each bus bar from the respective bar terminal nearest to the anode beam to a point midway along the anode beam.
  • FIG. 6 shows a resistance substitute circuit diagram calculated from the liquid aluminium of one cell to the middle M of the anode beam of the following cell.
  • R is the proportional bottom resistance for an iron cathode bar, calculated from the liquid aluminium to the outer end of the cathode bar.
  • a first cathode bus bar collects the current from n cathode bar terminals. To the commencement of the anode beam of the following cell, it has the resistance R Analogously a second cathode bus bar with its own resistance R collects the current from n terminals, a third cathode bus bar with its own resistance R the current from n;, terminals and so on. R is the resistance of the anode beam of the following cell, calculated to the middle M. of the anode beam.
  • I is the total cell current.
  • Each cathode bar should conduct the same current 1 No horizontal current density components occur in the longitudinal direction of the cell in the liquid aluminium if the cross sections of the individual bus bars are so chosen that the voltage drop in each cathode bus bar, from the point of feed to the last iron cathode bar (points A, B, C, etc.) to the middle M of the anode beam of the following cell is the same.
  • a current 11 1 flows, in the second bus bar a current 11 1 in the third bus bar a current 11 1 and so on.
  • the calculation must take place as if the current I from the anode beam of the following cell were not tapped continuously but at a point exactly in the middle of the cell (point M).
  • FIG. 5 of the accompanying drawings is a diagrammatic plan of an actual layout. It shows a series of three cells A, B, C.
  • each cell includes three groups D, E, F of iron cathode bars on each side.
  • Each group comprises three iron cathode bars G, H, I and a respective bus bar K.
  • two bus bars K are connected to the left end of the anode beam and one bus bar K to the right end.
  • L denotes the direction of the pot line current.
  • a complete series comprises from a few cells up to 100 or more. At the first cell of the series the invention is only to be applied to the bus bar connection to the second cell. At the end of the series all bus bars are connected together.
  • the number of the iron cathode bars depends on the size of the cell, on the current intensity and on several other factors; for example a 100,000 ampere cell can include between and 20 cathode bars (meaning between 10 and 20 protruding ends on each side; often the cathode bars are divided in the middle of the carbon bottom, that is to say that the two halves are disposed in such a way that they have a common axis but do not touch eah other).
  • the number of bus bars there are many possibilities from one bus bar for each cathode bar to only one bus bar for all cathode bars together on each side.
  • the cells are end to end. They may alternatively be side by side.
  • the anode beam can consist of one or more single anodic bus bars.
  • the anode beam 21 consists of two anodic bus bars.
  • An electrolytic cell for the production of aluminium by electrolysis of alumina in a melt comprising:
  • the body, the layer and the lining each consisting of a bottom, two side walls and two end walls,
  • iron cathode bars each having at least a part within the bottom of the lining, a part beneath a side wall of the lining and a part passing through a side wall of the insulation layer and through a side wall of the body,
  • the thermal resistance of the walls of the insulation layer is between h. C. h. C.
  • the ratio of iron cross section to carbon cross section in any vertical plane from end to end of the cell through the bottom of the lining is between 17:100 and 20:100.
  • a plant comprising a plurality of cells according to claim 1 in series, each cell including at least one terminal outside the pot on each cathode bar, and an anode beam carrying the anodes, and electrical connecting means between each cell and the next in the series, each connecting means comprising a plurality of cathode bus bars each of which connects a respective group of at least one of the cathode bar terminals of one cell to the anode beam of the next cell, the cross sections of the individual bus bars being such that, when an equal current flows through each cathode bar, then the voltage drop is the same along each bus bar from the respective bar terminal nearest to the anode beam to a point midway along the anode beam.

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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)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US00174892A 1970-09-01 1971-08-25 Electrolytic cell for the production of aluminum Expired - Lifetime US3728243A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1310170A CH544812A (de) 1970-09-01 1970-09-01 Zelle für die Gewinnung von Aluminium durch Elektrolyse von Aluminiumoxid im Schmelzfluss

Publications (1)

Publication Number Publication Date
US3728243A true US3728243A (en) 1973-04-17

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US00174892A Expired - Lifetime US3728243A (en) 1970-09-01 1971-08-25 Electrolytic cell for the production of aluminum

Country Status (14)

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US (1) US3728243A (is)
JP (1) JPS5242728B1 (is)
AT (1) AT317566B (is)
AU (1) AU461825B2 (is)
BE (1) BE771941A (is)
CA (1) CA943906A (is)
CH (1) CH544812A (is)
DE (1) DE2143603C3 (is)
FR (1) FR2105173B1 (is)
GB (1) GB1352268A (is)
IS (1) IS881B6 (is)
NL (1) NL7111514A (is)
NO (1) NO128773B (is)
ZA (1) ZA715862B (is)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4217197A (en) * 1979-07-18 1980-08-12 Gewerkschaft Eisenhutte Westfalia Apparatus for removing anode residue from anodes of electrolytic melt baths
US4359377A (en) * 1980-02-01 1982-11-16 Swiss Aluminium Ltd. Busbar arrangement for electrolytic cells
EP1927679A1 (en) * 2006-11-22 2008-06-04 Alcan International Limited Electrolysis cell for the production of aluminium comprising means to reduce the voltage drop
CN102453927A (zh) * 2010-10-19 2012-05-16 沈阳铝镁设计研究院有限公司 一种大幅降低铝电解槽铝液中水平电流的方法
CN102758216A (zh) * 2011-04-29 2012-10-31 沈阳铝镁设计研究院有限公司 一种均化铝电解槽铝液中电流分布的方法
CN104694957A (zh) * 2013-12-05 2015-06-10 高伟 设置有中缝挡料板的铝电解槽

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0016728A1 (de) * 1979-03-23 1980-10-01 Schweizerische Aluminium AG Elektrolysezelle zur Aluminiumherstellung durch Schmelzflusselektrolyse von Aluminiumsalzen
CH643600A5 (de) * 1979-12-05 1984-06-15 Alusuisse Elektrolysezelle zur herstellung von aluminium.
FR2576920B1 (fr) * 1985-02-07 1987-05-15 Pechiney Aluminium Cuve d'electrolyse hall-heroult a barres cathodiques et a calorifugeage dissymetriques

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL104954C (is) * 1954-02-09 1900-01-01
US3372105A (en) * 1962-10-22 1968-03-05 Arthur F. Johnson Aluminum reduction cell and insulation material therefor

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4217197A (en) * 1979-07-18 1980-08-12 Gewerkschaft Eisenhutte Westfalia Apparatus for removing anode residue from anodes of electrolytic melt baths
US4359377A (en) * 1980-02-01 1982-11-16 Swiss Aluminium Ltd. Busbar arrangement for electrolytic cells
EP1927679A1 (en) * 2006-11-22 2008-06-04 Alcan International Limited Electrolysis cell for the production of aluminium comprising means to reduce the voltage drop
US20080135417A1 (en) * 2006-11-22 2008-06-12 Bertrand Allano Electrolysis Cell for the Production of Aluminium Comprising Means to Reduce the Voltage Drop
US8500970B2 (en) 2006-11-22 2013-08-06 Rio Tinto Alcan International Limited Electrolysis cell for the production of aluminum comprising means to reduce the voltage drop
CN102453927A (zh) * 2010-10-19 2012-05-16 沈阳铝镁设计研究院有限公司 一种大幅降低铝电解槽铝液中水平电流的方法
CN102453927B (zh) * 2010-10-19 2013-08-14 沈阳铝镁设计研究院有限公司 一种大幅降低铝电解槽铝液中水平电流的方法
CN102758216A (zh) * 2011-04-29 2012-10-31 沈阳铝镁设计研究院有限公司 一种均化铝电解槽铝液中电流分布的方法
CN102758216B (zh) * 2011-04-29 2015-04-15 沈阳铝镁设计研究院有限公司 一种均化铝电解槽铝液中电流分布的方法
CN104694957A (zh) * 2013-12-05 2015-06-10 高伟 设置有中缝挡料板的铝电解槽

Also Published As

Publication number Publication date
DE2143603A1 (de) 1972-03-09
BE771941A (fr) 1971-12-31
AU461825B2 (en) 1975-06-05
DE2143603B2 (de) 1974-08-22
AT317566B (de) 1974-09-10
DE2143603C3 (de) 1975-04-03
JPS5242728B1 (is) 1977-10-26
CA943906A (en) 1974-03-19
NL7111514A (is) 1972-03-03
GB1352268A (en) 1974-05-08
AU3290471A (en) 1973-03-08
CH544812A (de) 1973-11-30
NO128773B (is) 1974-01-07
ZA715862B (en) 1972-04-26
FR2105173A1 (is) 1972-04-28
FR2105173B1 (is) 1975-02-07
IS2023A7 (is) 1972-03-02
IS881B6 (is) 1974-07-19

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