EP0101153A2 - Aluminium-elektrolytische Reduktionszellen - Google Patents

Aluminium-elektrolytische Reduktionszellen Download PDF

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Publication number
EP0101153A2
EP0101153A2 EP83303072A EP83303072A EP0101153A2 EP 0101153 A2 EP0101153 A2 EP 0101153A2 EP 83303072 A EP83303072 A EP 83303072A EP 83303072 A EP83303072 A EP 83303072A EP 0101153 A2 EP0101153 A2 EP 0101153A2
Authority
EP
European Patent Office
Prior art keywords
cell
metal
electrolyte
displacement block
molten
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP83303072A
Other languages
English (en)
French (fr)
Other versions
EP0101153A3 (de
Inventor
Adam Jan Gesing
Thomas James Hudson
David Nelson Mitchell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rio Tinto Alcan International Ltd
Original Assignee
Alcan International Ltd Canada
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alcan International Ltd Canada filed Critical Alcan International Ltd Canada
Publication of EP0101153A2 publication Critical patent/EP0101153A2/de
Publication of EP0101153A3 publication Critical patent/EP0101153A3/de
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/06—Operating or servicing
    • C25C7/08—Separating of deposited metals from the cathode
    • 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
    • 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

  • the present invention relates to monopolar or multipolar electrolytic reduction cells for the production of a molten metal product by electrolysis of a molten electrolyte.
  • the electrolyte is contained within a generally rectangular refractory lined shell and the cell is provided with one or more suspended anodes.
  • the area occupied.by the anode or anodes is a large proportion of the total cell floor area occupied by the electrolyte.
  • the cell cathode is a liquid cathode, constituted by a pool of molten metal on the floor of the cell.
  • the depth of this pool progressively increases during the normal cycle of the cell operation and is reduced at intervals when the cell is tapped.
  • the active faces of the anodes are progressively raised to maintain the nominal value of the anode/cathode distance substantially constant and the level of the molten electrolyte in the-cell rises and falls substantially in step with the rise and fall of the molten metal level in the metal pool.
  • the active cathode surface may be constituted by any of the following means:
  • the product metal may be collected in a collection sump, from which it is conventionally tapped off, usually by siphoning, at extended intervals, for example 24 hour intervals.
  • the metal may be stored among the cathode elements, or below the pedestals.
  • the cell is of the drained cathode type or other similar type, in which there is little or no variation in the level of the active cathode surface at the floor of the cell during normal operation of the cell, there is a relatively large variation in the level of the electrolyte surface, because the electrolyte, displaced by the produced metal, is forced upwardly into the restricted space surrounding the anode or anodes.
  • the method of the present invention relies on varying the space available for liquid (in relation to a datum level) in the cell. This may be achieved by raising or lowering a solid block, which is in contact with the molten cell contents to increase or decrease liquid space in line with increase or decrease of liquid metal during the conventional tapping cycle.
  • One method of carrying out the invention is to arrange for one or more of the cell anodes to be adjustable vertically independently of the remainder of the cell anodes. Just after tapping such anode or anodes are set level with the remaining anodes, but as the cell cycle proceeds such anode or anodes are raised to compensate.for the increase of liquid contents of the cell. The . electric current carried by the raised anodes decreases as a result of the increase in the - anode/cathode distance as compared with that for the remainder of the anodes.
  • the reduction cell comprises insulated side walls 1 and floor 2.
  • The'side walls 1 (and end walls) are protected in the conventional manner by a layer 3 of frozen cell electrolyte.
  • Rows of prebake type anodes 4 are arranged at each side of the cell and project to a predetermined depth in the molten cell electrolyte 7.
  • the drained cathode is formed of titanium diboride or other "hard metal" shapes 13 which are supported on carbonaceous cathode blocks 5 and have-slightly inclined upper surfaces which slope downwardly to a central - trough or sump 6, in which the molten metal product collects and is tapped off periodically.
  • the trough requires to be of such size to accommodate the metal produced in 'a normal metal tapping cycle. Since anodes 4 themselves remain at a fixed position in relation to the cathode blocks 5, the electrolyte displaced from the trough 6 by molten metal rises into the space surrounding the anodes.. In order to limit the extent of the change in electrolyte level (which results in progressive change in the level and shape of the protective freeze layer 3) a vertically movable block 8 dips into the electrolyte and is shaped so that it may descend into the trough 6.
  • the block 8 As metal progressively displaces electrolyte from the trough, - the block 8 is raised to lift an increasing portion of the block out of the electrolyte, thus increasing the spaqe available for liquid electrolyte.
  • This system may be employed to compensate in whole or only in part and thus may be employed to maintain the electrolyte level essentially constant or to allow progressive slight increase in electrolyte level during a normal operating cycle.
  • the trough 6 and co-operating displacement block 8 may be arranged longitudinally of the cell (as shown) or transversely or at one end of the cell (or at both ends for a very large cell).
  • the block 8 is preferably arranged over the sump, but may be at a different location in some instances.
  • the displacement block 8 may be formed of carbon (or be constituted-by one or more anodes as already explained).
  • the displacement block is formed essentially of a frozen body of electrolyte.
  • a series of metal fins 11 are arranged on one or more hollow supports 10, through which a coolant (air or gas) is passed, thus maintaining a solid mass 12 of frozen electrolyte to cover the fins 11.
  • the compensating displacement block is located in the molten electrolyte and is raised or lowered to compensate for the correct change of electrolyte level.
  • the displacement block is located in a vessel outside the electrolysis compartment of the cell.
  • a vessel may be inside or outside the steel shell of the cell.
  • the molten metal collects in a relatively small sump 26 at one end of the cell and this communicates with a separate metal collection chamber 27 via a passage 28.
  • the level of molten metal in the chamber 27 is controlled by a vertically movable block 29, which may be formed of alumina or other refractory, which is not subject to attack by molten aluminium.
  • the block is withdrawn at a rate set by the metal production rate of the cell, which is essentially constant. This maintains a constant metal level in the chamber 27.
  • the drive system for the block 29 may be controlled by a sensor, which continually senses the metal level in the chamber 27. The rate of upward movement of the block 29 may then be automatically adjusted in order to maintain a substantially constant metal level in the chamber 27.
  • the sump 26 may be of small size and be filled with correctly sized balls or fragments of TiB 2 or other hard metal" refractory, which is resistant to attack by molten aluminium and molten cell electrolyte.
  • the cell is provided with a drained cathode structure 35, provided with cathode current collectors (not shown) and conventional overhead anodes 34.
  • Product metal is drawn off at intervals, such as 24-hour intervals, from the chamber 27 by conventional means, such as siphon tapping.
  • the selective filter it is preferred to displace the metal from the chamber 27 through a spout 36 into the collection crucible (not shown) by simply driving the displacement block down to the bottom of the chamber.
  • High resistance to the fluid flow through the selective filter prevents re-entry of any substantial amount of metal back into the electrolysis compartment of the cell. It is preferred to maintain an inert gas cover in the upper part of the chamber 27.
  • the product metal can be drawn off from the collection chamber 27 at much more frequent intervals, for example every.15 minutes.
  • the metal collection chamber can be made comparatively small and can conveniently be fitted within the steel shell of the cell. For example, if a cell which produces 1 to 2 tons of metal per'day is tapped every 15 minutes, the yield is only 10 - 20 kg per tapping. The storage capacity for such yield is easily accommodated in a transfer tube in which the displacement lock travels.
  • Another advantage is that the metal can be tapped into a molten metal pipeline as described in European Specification 68782.
  • the electrical insulation between the cells which are interconnected by the molten metal pipeline can be maintained by activating the displacement blocks in different cells in sequence, so that at any one time only one cell would be being tapped and in electrical contact with the molten metal pipeline.
  • This arrangement can be used as the basis for a completely automatic metal tapping system.
  • Figure 4 shows an alternative system in which the metal collection vessel is placed with its lower end in the sump 26, rather than merely communicating with the sump by means of a passage 28 as shown in Figure 3.
  • a metal transfer spout 36 is placed with its lower end in the sump 26, rather than merely communicating with the sump by means of a passage 28 as shown in Figure 3.
  • a metal transfer spout 36 is placed with its lower end in the sump 26, rather than merely communicating with the sump by means of a passage 28 as shown in Figure 3.
  • a metal transfer spout 36 is placed with its lower end in the sump 26, rather than merely communicating with the sump by means of a passage 28 as shown in Figure 3.
  • a metal transfer spout 36 is placed with its lower end in the sump 26, rather than merely communicating with the sump by means of a passage 28 as shown in Figure 3.
  • a metal transfer spout 36 is placed with its lower end in the sump 26, rather than merely communicating with the sump by means of a passage 28
  • a metal selective filter 25 is provided across an entry point at the bottom of the metal collection vessel. Alternatively, this filter could have been provided in the sump 26.
  • a metal selective filter is not essential, although it is preferred to avoid the risk of entry of electrolyte into the metal collection chamber.
  • Any form of restricted orifice can be used at the entrance 25 to the metal collection chamber to ensure that lowering of the displacement block 29 drives molten metal into the tapping system and not back into the cell.
  • more than one metal collection chamber is used for each cell. Then, if one metal collection chamber accidentally becomes blocked or otherwise ceases to function, it can simply be lifted out of the sump, without the need to interrupt operation of the cell, and replaced after repair.

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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)
  • Medicines Containing Antibodies Or Antigens For Use As Internal Diagnostic Agents (AREA)
  • Medicines That Contain Protein Lipid Enzymes And Other Medicines (AREA)
EP83303072A 1982-06-18 1983-05-27 Aluminium-elektrolytische Reduktionszellen Withdrawn EP0101153A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8217712 1982-06-18
GB8217712 1982-06-18

Publications (2)

Publication Number Publication Date
EP0101153A2 true EP0101153A2 (de) 1984-02-22
EP0101153A3 EP0101153A3 (de) 1984-04-11

Family

ID=10531137

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83303072A Withdrawn EP0101153A3 (de) 1982-06-18 1983-05-27 Aluminium-elektrolytische Reduktionszellen

Country Status (6)

Country Link
EP (1) EP0101153A3 (de)
JP (1) JPS596391A (de)
AU (1) AU1591883A (de)
BR (1) BR8303242A (de)
ES (1) ES523365A0 (de)
NO (1) NO832213L (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5409580A (en) * 1992-07-10 1995-04-25 Alcan International Limited Process and apparatus for melting metals and composites while reducing losses due to oxidation
WO1999041430A1 (en) * 1998-02-11 1999-08-19 Moltech Invent S.A. Distribution of alumina-rich electrolyte in aluminium electrowinning cells
WO2001077414A3 (en) * 2000-04-07 2002-05-02 Alcoa Inc Anode cathode distance adjustment device
US6579438B1 (en) 1998-07-08 2003-06-17 Alcan International Limited Molten salt electrolytic cell having metal reservoir
US20150159286A1 (en) * 2012-05-16 2015-06-11 Lynas Services Pty Ltd Electrolytic cell for production of rare earth metals

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH364988A (de) * 1956-12-27 1962-10-15 Montedison Spa Flüssigkeitshebevorrichtung
FR1457746A (fr) * 1964-09-29 1966-01-24 Reynolds Metals Co Perfectionnements apportés aux moyens de commande pour cuves de réduction
CH643885A5 (de) * 1980-05-14 1984-06-29 Alusuisse Elektrodenanordnung einer schmelzflusselektrolysezelle zur herstellung von aluminium.

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5409580A (en) * 1992-07-10 1995-04-25 Alcan International Limited Process and apparatus for melting metals and composites while reducing losses due to oxidation
WO1999041430A1 (en) * 1998-02-11 1999-08-19 Moltech Invent S.A. Distribution of alumina-rich electrolyte in aluminium electrowinning cells
US6579438B1 (en) 1998-07-08 2003-06-17 Alcan International Limited Molten salt electrolytic cell having metal reservoir
WO2001077414A3 (en) * 2000-04-07 2002-05-02 Alcoa Inc Anode cathode distance adjustment device
US20150159286A1 (en) * 2012-05-16 2015-06-11 Lynas Services Pty Ltd Electrolytic cell for production of rare earth metals

Also Published As

Publication number Publication date
ES8501009A1 (es) 1984-11-01
EP0101153A3 (de) 1984-04-11
AU1591883A (en) 1983-12-22
NO832213L (no) 1983-12-19
ES523365A0 (es) 1984-11-01
JPS596391A (ja) 1984-01-13
BR8303242A (pt) 1984-01-31

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Inventor name: GESING, ADAM JAN

Inventor name: HUDSON, THOMAS JAMES

Inventor name: MITCHELL, DAVID NELSON