US3900371A - Method of controlling the thickness of the lateral ledges in a cell for the electrolytic recovery of aluminum - Google Patents

Method of controlling the thickness of the lateral ledges in a cell for the electrolytic recovery of aluminum Download PDF

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Publication number
US3900371A
US3900371A US443099A US44309974A US3900371A US 3900371 A US3900371 A US 3900371A US 443099 A US443099 A US 443099A US 44309974 A US44309974 A US 44309974A US 3900371 A US3900371 A US 3900371A
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United States
Prior art keywords
cell
thickness
electrolyte
lateral ledges
resistance
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Expired - Lifetime
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US443099A
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English (en)
Inventor
Kiranendu B Chaudhuri
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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
    • C25C3/20—Automatic control or regulation of cells

Definitions

  • FIGURE shows a schematic vertical section in the longitudinal direction through part of an electrolysis cell.
  • the steel shell 12 which is lined with a thermal insulation 13 of heat-resisting, heatinsulating material, e.g. chamotte, and with carbon 11, contains the fluoride melt (the electrolyte).
  • the aluminum l4 separated at the cathode lies on the carbon bottom 15 of the cell.
  • the surface 16 of the liquid aluminum constitutes the cathode.
  • iron cathode bars 17 in this case transverse to the longitudinal direction of the cell, which conduct the electrical direct current from the carbon lining ll of the cell laterally outwards.
  • Anodes 18 of amorphous carbon dip from above into the fluoride melt l0, and supply the direct current to the electrolyte. They are firmly connected via conductor rods 19 and by clamps 20 with the anode beam 21.
  • the anode beam can consist of one or more conducting bars.
  • the current flows from the cathode bars 17 of one cell to the anode beam 21 of the following cell through conventional bus bars, not shown. From the anode beam 21 it flows through the conductor rods 19, the anodes 18, the electrolyte 10, the liquid aluminum l4, and the carbon lining 11 to the cathode bars 17.
  • the electrolyte 10 is covered with a crust 22 of solidified melt (frozen electrolyte) and a layer of aluminum oxide 23 lying above it. Cavities 25 occur in operation between electrolyte 10 and the solidified crust 22.
  • the thickness of the ledges 24 determines the horizontal extent of the bath of fluid aluminum 14 and electrolyte 10. With rising temperature, the thickness of the ledges 24 generally decreases. with falling temperature generally increases.
  • the average distance d from the lower faces 26 of the anodes to the upper surface 16 of the liquid aluminum which is also known as the interpolar distance, can be adjusted by lifting or lowering the anode beam 21 with the help of the lifting mechanisms 27, which are mounted on pillars 28. This operates on all the anodes. Each anode can however be adjusted by raising or lowering singly. if the respective clamp 20 is opened, the conductor rod 19 is shifted relatively to the anode beam 21 and finally the clamp 20 is again closed.
  • the anodes are consumed continuously on their lower face by about 1.5 to 2 cms per day (anode burning) according to the type of cell, and simultaneously the level of the liquid aluminum rises by about the same amount because of the separation of aluminum at the cathode.
  • anode When an anode is used up, it must be exchanged for a new one.
  • the cell is so operated in practice that, some days after starting up, the anodes of the cell no longer have the same degree of consumption and therefore after use for several weeks they must be exchanged separately. For this reason one finds anodes of different starting age operating together, as appears from the FIGURE.
  • the horizontal surface which contains the totality of the lower faces of the anodes of a cell, is known as the anode table.
  • the aluminum 14 produced electrolytically which collects on the carbon bottom of the cell, is generally tapped once a day from the cell, e.g. by conventional sucking devices. Generally the level of the liquid aluminum 14 is brought back to an optimum value for each type of cell. This value corresponds to the desired metal level, which. can be the starting level.
  • An important characteristic value in the operation of a cell is its electrical base voltage. This is established empirically for each cell having regard to its age, the condition of the carbon lining 11, the composition of the electrolyte melt 10 as well the cell current intensity and current density. For the establishment of the base voltage regard is also had to the horizontal extent of the cathode surface 16, which is influenced by the thickness of the lateral ledges 24.
  • J R is the ohmic base resistance in ohms, U,, the base voltage in volts, l.65 the back electromotive force in volts and J the instantaneous cell current intensity im amps.
  • the interpolar distance must have an optimum value. If the cell is so operated that the horizontal extent of the cathode surface 16 remains unchanged, then generally the rise in level of the liquid aluminum above the carbon bottom is equal to the burning away of the anodes at their lower faces. The cell is designed so that these conditions are reached.
  • the positions (levels) of the anode beam for instance immediately after a tapping operation and immediately before the next tapping operation, will be the same.
  • the actual interpolar distance is from time to time, e.g., between two tapping operations, larger or smaller than the optimum interpolar distance.
  • the departures are substantially caused by irregular rise in the level of the liquid aluminum above the carbon bottom, by irregular burning away of the anodes at their lower faces, and'by variation in the horizontal extent of the cathode surface 16 as a consequence of alteration of the thickness of the lateral ledges 24.
  • the levels of the anode beam for instance immediately after a tapping operation and immediately before the next tapping operation will be different.
  • the method according to my invention for controlling the thickness of the lateral ledges of frozen electrolyte in a cell for recovery of aluminum by electrolysis of aluminum oxide dissolved in a fluoride melt comprises the following operational steps:
  • the instantaneous ohmic cell resistance is calculated, the instantaneous values over a certain period of time are smoothed and the difference AR between this smoothed cell resistance and the base resis tance established for each cell is calculated;
  • the anode beam is raised or lowered in order to match the existing ohmic resistance with the ohmic base resistance of the cell;
  • the level of the anode beam is read by means of a level indicator (in German Weggeber) and is stored;
  • the difference AB is calculated; for which difference changes of level of the anode beam position due to tapping or addition of metal must be taken into consideration;
  • a working operation mentioned in operational step (a) can be a normal servicing of the cell, an anode effect servicing of the cell, a change of anodes or a tapping of metal.
  • Such a working operation can have a disturbing influence on the determination of the ohmic cell resistance until about one hour after the end of the working operation. In practice it is sufficient to wait half an hour after the end of a working operation before determing the ohmic cell resistances.
  • the regular time intervals mentioned under (a) can lie between 2 seconds and 5 minutes. In practice time intervals of 10 seconds to 1 minute have proved to be advantageous.
  • the periods of time likeweise mentioned under (a) can lie between 1 minute and 1 hour. In practice advantageously periods of 10 minutes are chosen.
  • the instantaneous cell voltage U and the cell direct current intensity J are sampled by a computer and the instantaneous ohmic cell resistance is calculated by a computer according to the equation inxl R,-,, is the instantaneous ohmic cell resistance in ohms, U the instantaneous cell voltage in volts, 1.65 the back electromotive force in volts and J the cell direct current intensity in amps.
  • R,-, are smoothed by a computer over a predetermined period of time, for instance over 10 to 15 minutes, and are compared, for instance every 10 to 15 minutes, with the ohmic base resistance R, of the cell. If the computer notices a difference AR between the smoothed value and the ohmic base resistance R, and if this difference exceeds a limiting value previously given to the computer and stored in it, eg 0.5 microhms, then an order is issued by the computer in accordance with which the anode beam is raised or lowered until the instantaneous ohmic resistance of the cell is substantially equal to the ohmic base resistance of the cell. By this operation the optimum interpolar distance of the cell is reached.
  • the level of the anode beam is read by a computer with the help of a level indicator mounted on the anode beam itself.
  • a level indicator a potentiometer is advantageously used.
  • the level value is stored by the computer.
  • the computer calculates thedifferenbe AB. If between these two determinations of the levels of reached resulting in better current efficiency and lower the anode beam metal has been tapped from the cell,
  • the thickness of the lateral ledges is supposed to have increased. If on the contrary the difference is negative, e.g. AB lO mm, the thickness of the lateral ledges is supposed to have decreased.
  • the advantage of the method according to my invention lies in the fact that disturbing changes of the thickness of the lateral ledges of frozen electrolyte can be avoided. Hereby a more uniform all performance is specific consumption of electrical energy.
  • measuring the instantaneous ohmic resistance of said cell at predetermined regular intervals of time during which measurements there are no anode effects which can substantially affect the measured instantaneous ohmic resistance and during which measurements there are no working operations carried out or have been previously carried out which can substantially affect the measured instantaneous ohmic resistance measuring the average instantaneous ohmic cell resistance from a plurality of the measured instantaneous ohmic cell resistances obtained during a predetermined period of time, measuring the base resistance of the cell, obtaining the difference AR between the average instantaneous ohmic cell resistance and the base resistance;

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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)
  • Battery Electrode And Active Subsutance (AREA)
  • Sealing Battery Cases Or Jackets (AREA)
  • Primary Cells (AREA)
US443099A 1974-01-30 1974-02-15 Method of controlling the thickness of the lateral ledges in a cell for the electrolytic recovery of aluminum Expired - Lifetime US3900371A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH124374A CH592749A5 (no) 1974-01-30 1974-01-30

Publications (1)

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US3900371A true US3900371A (en) 1975-08-19

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US443099A Expired - Lifetime US3900371A (en) 1974-01-30 1974-02-15 Method of controlling the thickness of the lateral ledges in a cell for the electrolytic recovery of aluminum

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US (1) US3900371A (no)
JP (1) JPS547491B2 (no)
AT (1) AT345004B (no)
BE (1) BE824655A (no)
BR (1) BR7500573A (no)
CA (1) CA1013292A (no)
CH (1) CH592749A5 (no)
EG (1) EG11547A (no)
FR (1) FR2259163B1 (no)
GB (1) GB1462332A (no)
IE (1) IE40797B1 (no)
IS (1) IS1043B6 (no)
IT (1) IT1031305B (no)
NL (1) NL7501038A (no)
NO (1) NO143633C (no)
PH (1) PH11296A (no)
SE (1) SE410326B (no)
TR (1) TR18265A (no)
ZA (1) ZA75244B (no)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4333803A (en) * 1980-10-03 1982-06-08 Aluminum Company Of America Method and apparatus for controlling the heat balance in aluminum reduction cells
US4857157A (en) * 1987-04-21 1989-08-15 Aluminium Pechiney Process and apparatus for controlling solid electrolyte additions to electrolytic cells for aluminum production
US5114545A (en) * 1991-06-17 1992-05-19 Reynolds Metals Company Electrolyte chemistry for improved performance in modern industrial alumina reduction cells
US20040168930A1 (en) * 2001-02-28 2004-09-02 Oliver Bonnardel Method for regulating an electrolytic cell
CN106676581A (zh) * 2016-12-27 2017-05-17 甘肃东兴铝业有限公司 一种铝电解槽炉帮厚度优化控制方法

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4685514A (en) * 1985-12-23 1987-08-11 Aluminum Company Of America Planar heat exchange insert and method
US4702312A (en) * 1986-06-19 1987-10-27 Aluminum Company Of America Thin rod packing for heat exchangers
US4705106A (en) * 1986-06-27 1987-11-10 Aluminum Company Of America Wire brush heat exchange insert and method
US4678548A (en) * 1986-07-21 1987-07-07 Aluminum Company Of America Corrosion-resistant support apparatus and method of use for inert electrodes

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1961893A (en) * 1933-07-26 1934-06-05 Hartford Empire Co Automatic level control system
US3812024A (en) * 1972-03-20 1974-05-21 Kaiser Aluminium Chem Corp Control of an aluminum reduction cell

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1961893A (en) * 1933-07-26 1934-06-05 Hartford Empire Co Automatic level control system
US3812024A (en) * 1972-03-20 1974-05-21 Kaiser Aluminium Chem Corp Control of an aluminum reduction cell

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4333803A (en) * 1980-10-03 1982-06-08 Aluminum Company Of America Method and apparatus for controlling the heat balance in aluminum reduction cells
US4857157A (en) * 1987-04-21 1989-08-15 Aluminium Pechiney Process and apparatus for controlling solid electrolyte additions to electrolytic cells for aluminum production
US5114545A (en) * 1991-06-17 1992-05-19 Reynolds Metals Company Electrolyte chemistry for improved performance in modern industrial alumina reduction cells
US20040168930A1 (en) * 2001-02-28 2004-09-02 Oliver Bonnardel Method for regulating an electrolytic cell
US7192511B2 (en) * 2001-02-28 2007-03-20 Aluminum Pechiney Method for regulating an electrolytic cell
CN106676581A (zh) * 2016-12-27 2017-05-17 甘肃东兴铝业有限公司 一种铝电解槽炉帮厚度优化控制方法
CN106676581B (zh) * 2016-12-27 2018-07-20 甘肃东兴铝业有限公司 一种铝电解槽炉帮厚度优化控制方法

Also Published As

Publication number Publication date
DE2503635A1 (de) 1975-07-31
IE40797B1 (en) 1979-08-15
IS2257A7 (is) 1975-07-31
NO143633C (no) 1981-03-18
BE824655A (fr) 1975-05-15
NO750253L (no) 1975-08-25
NO143633B (no) 1980-12-08
AT345004B (de) 1978-08-25
FR2259163A1 (no) 1975-08-22
IE40797L (en) 1975-07-30
ZA75244B (en) 1976-01-28
ATA66775A (de) 1977-12-15
FR2259163B1 (no) 1978-04-21
PH11296A (en) 1977-11-02
CH592749A5 (no) 1977-11-15
JPS547491B2 (no) 1979-04-07
GB1462332A (en) 1977-01-26
JPS50114320A (no) 1975-09-08
AU7772575A (en) 1976-08-05
DE2503635B2 (de) 1976-12-16
EG11547A (en) 1977-12-31
CA1013292A (en) 1977-07-05
IS1043B6 (is) 1980-12-16
IT1031305B (it) 1979-04-30
SE410326B (sv) 1979-10-08
TR18265A (tr) 1976-11-10
BR7500573A (pt) 1975-11-11
SE7500956L (no) 1975-07-31
NL7501038A (nl) 1975-08-01

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