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WO2010118465A1 - Support pour anode sans tige - Google Patents

Support pour anode sans tige Download PDF

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Publication number
WO2010118465A1
WO2010118465A1 PCT/AU2010/000414 AU2010000414W WO2010118465A1 WO 2010118465 A1 WO2010118465 A1 WO 2010118465A1 AU 2010000414 W AU2010000414 W AU 2010000414W WO 2010118465 A1 WO2010118465 A1 WO 2010118465A1
Authority
WO
WIPO (PCT)
Prior art keywords
anode
anodes
electrical contact
anode assembly
cassette
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.)
Ceased
Application number
PCT/AU2010/000414
Other languages
English (en)
Inventor
Christopher Peter Jones
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.)
ALUMINIUM SMELTER DEVELOPMENTS Pty Ltd
Original Assignee
ALUMINIUM SMELTER DEVELOPMENTS Pty Ltd
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 ALUMINIUM SMELTER DEVELOPMENTS Pty Ltd filed Critical ALUMINIUM SMELTER DEVELOPMENTS Pty Ltd
Priority to CA2779727A priority Critical patent/CA2779727A1/fr
Publication of WO2010118465A1 publication Critical patent/WO2010118465A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • 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
    • C25C3/12—Anodes
    • C25C3/125—Anodes based on carbon
    • 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

Definitions

  • the present invention relates to the operation of an aluminium reduction cell comprising rodless, or continuous, pre-baked anodes.
  • the invention relates to the means of applying the force required to support the anode(s), and to achieve electrical contact.
  • the state-of-the-art approach to aluminium reduction has relied for some time on a metal rod to support the pre-baked carbon anode in the cell.
  • the rod To support the anode, the rod has stubs that mate with holes in the anode.
  • the connection between the rod and the anode is formed by pouring molten cast iron into the gaps, which solidifies as a thimble in each hole to hold the two together.
  • the electrical circuit of the cell includes the rod, the stubs, the cast iron thimbles, and the anode. While this was undoubtedly an improvement over the previous S ⁇ derberg technology, the pre-baked, rodded anode has drawbacks, including that not all of the anode carbon can be usefully consumed by the reduction process.
  • a protective layer of carbon must be left between the bottom surface of the anode and the thimbles to prevent the cast iron dissolving in the electrolyte and contaminating the aluminium produced by the cell. At some point in the process, the consumed anode or butt must be replaced with a new rodded anode.
  • a modern smelter therefore contains a material reclamation loop which involves anode butts, bath material removed with the butts, rods and cast iron thimbles. The capital and operational costs associated with this material reclamation loop are significant.
  • the rod is clamped to the anode beam.
  • the anode beam is part of the superstructure of the aluminium reduction cell and is part of the electrical circuit.
  • the base of the carbon anode is suspended in the molten bath of electrolyte.
  • the passage of electrical current through the cell consumes carbon and produces aluminium at the cathode.
  • the aluminium produced is added to the liquid metal cathode in the bottom of the pot and the surface of the cathode rises with time.
  • adjustments are made to the height of the anode beam by large jacks. In general the rate of addition of aluminium is slightly faster than the rate of consumption of carbon and there is a small net upwards movement of the anode beam.
  • a normal part of the operating routine is to remove the molten aluminium from the cell by tapping at a frequency between 24 to 48 hours.
  • a crucible is brought to the cell which is fitted with a siphon.
  • the siphon is inserted into the cell and sucks out some of the molten aluminium which reduces the level of aluminium pooled on the cathode.
  • the jacks on the superstructure automatically adjust to maintain the distance between the anode and the cathode. The result is that the carbon anode moves downwards.
  • the net movement of the anode is typically downwards, for example, by about 20 mm/day. This is the rate at which the height of the carbon is reduced.
  • a rodded carbon anode might be typically limited to a service life of, say, 24 days. After this time there is still typically about 50 mm of carbon between the thimble and the bottom of the anode. At this point, the anode and the associated rod are removed from service and replaced by a new anode and rod. The carbon on the removed anode (the butt) is stripped from the rod.
  • the rod is cleaned up and set in a new anode block, and the carbon butt is crushed and recycled within the anode production process.
  • the anode change and butt recycle processes expose production operators to elevated temperatures, dust, fumes and noise.
  • the present requirement to recycle and replace rodded anodes is a wasteful, costly, environmentally undesirable, hazardous, and time consuming process. Consequently, there are several strong incentives to eliminate the processes required when using rodded anodes by developing rodless anode technology that allows complete consumption of anode carbon within the cell.
  • the invention therefore provides a continuous pre-baked or rodless anode assembly for an aluminium smelting cell, comprising one or more pre-baked anodes arranged in a cassette, electrical contact means in physical and electrical contact with the anode(s), and between the anodes in the case of multiple anodes in the cassette, the cassette including clamping force applying means including elongate clamping means and tensioning means, said elongate clamping means transferring tensioning forces applied by said tensioning means as a clamping force to the electrical contact means to hold the one or more anodes in the cassette, and to keep the electrical contact means in electrical contact with the one or more anodes.
  • the anode(s) has opposed faces which are exposed for contact by the electrical contact means.
  • the electrical contact means includes one or more contact plates engaging the opposed faces of the anode
  • the elongate clamping means includes the electrical contact means at the opposed fa ces and elongate clamping means extending between the electrical contact means at the exposed end faces.
  • the use of elongate thin members to hold the anode assembly has the advantage of being a mechanically simple, tension-only device which occupies minimal space in the smelting cell, and which is otherwise able to withstand the environment of the smelting cell.
  • the force applying means can be located above the fume cover of the cell, which in a preferred arrangement is located at a level just above the deck plate of the cell; this thereby reduces the exposure of the force applying means to the aggressive cell environment.
  • the elongate thin members may be strap-like members fonned from a metal resistant to the environment of the electrolytic cell and having the necessary tensile strength to apply tension to the anodes in the array.
  • the use of strap-like members is not essential as the strap-like members may be replaced by cables or any similar long thin member capable of applying tension forces to the anodes in the cassette.
  • the tensioner means may include a tension applying screw means engaging one or more disc springs or another suitable means of maintaining tension such as springs or compressible material suitable for the high temperature operating environment; this ensures that appropriate tension is applied to the strap connected to the tensioner means.
  • the elongate clamping means comprises spaced elongate members connected to each other by means which transfers tensioning forces applied by the tensioner means to the clamping means around the exposed corners of the anode(s) in the cassette.
  • the means for transferring tension forces between adjacent elongate thin members may comprise flexible chain means which may be contained within one or more protective sleeves to protect the chain from the environment of the electrolytic cell.
  • the contact means may comprise conductive plate means attached to a frame which extend up and over the top of each anode.
  • Figure 1 is a simplified sectional plan view through a typical cassette embodying the invention showing the contact means at the ends of and between the anodes and the force applying means in schematic form;
  • Figure 2 is a sectional plan view similar to Figure 1 showing one embodiment of the invention
  • FIG 3 is a detailed view of the tensioner means used in the embodiment of Figure 2, and
  • Figure 4 is a detailed view of the connecting means between adjacent force applying strap means used in the embodiment of Figure 2.
  • each cassette 1 supports anodes 2, 3 and 4, together with end contact plates 5 and 6 and intermediate contact plates 7 which engage opposed faces of the anodes.
  • the array of anodes and contact plates is held together by a force applying means or clamping strap arrangement 9 which includes a tensioner means
  • the strap arrangement 9 and tensioner 10 apply the required tension forces to the end contact plates 5 and 6 to ensure that the anodes 2, 3 and 4 are in electrical contact with the end contact plates 5 and 6 and the intermediate contact plates 7.
  • the force applied is sufficient for this purpose but still allows the anodes to be pushed through the force applying means as the anodes are consumed and new anodes are added to the cassette as described further below.
  • Figures 1 and 2 illustrate a three anode cassette 1 embodying the invention
  • the cassette may support more, or less, than three anodes, including one anode, although ideally, the number of anodes in each cassette should not exceed about six.
  • the embodiment of the invention relates to the force applying means for holding the anode or anodes in the cassette in electrical and physical contact, the manner in which the cassette is supported in an electrolytic cell does not form part of the invention and will not be described in particular detail since any suitable arrangement within the capability of a person skilled in the art may be used while still reaping the benefits of the present invention.
  • the strap arrangement 9 includes a front strap 11, a back strap 12 and end straps or plates, which in the present embodiment, are the end contact plates 5 and 6. If needed, further plates may be added to the contact plates, for example, if the contact plates are defined by narrow strips (not shown) engaging narrow portions of the anodes.
  • the tensioner means 10 which is illustrated in further detail in Figure 3, includes a force applying bolt and nut arrangement 15 mounted in a frame comprising side plates 16 and cross plate 17 through which the bolt arrangement 15 passes, the arrangement being secured by bolts, as illustrated, to the end plate 6.
  • the bolt arrangement 15 is secured by any suitable means to the front strap 11 so that the necessary tension forces may be applied to this strap.
  • a stack of disk springs is positioned between the cross plate 17 and the tension applying nut 18. It will be appreciated that the use of disc springs is not essential as they may be replaced by a suitable coil spring, or some other suitable resilient means.
  • a flexible chain member 19 is secured to the respective strap/plates 11 and 5, and enclosed within a protective sleeve 20, as illustrated in greater detail in Figure 4.
  • a similar chain connector 21 is secured to the other end of the end strap/plate 5 and the back strap 12, the back strap 12 being secured to the plate 6 in any suitable manner, whereby the tension means 10 operates to tension the end plates 5 and 6 and the intermediate plates 7 and the anodes 2, 3 and 4 in the cassette 1, to ensure that electrical contact between the respective anodes and the contact plates is maintained.
  • connection of the tensioner means 10 to the front strap 11 provides access to the tensioner so that the tension forces applied may be adjusted as required. While in the present illustrations the force applying means 9 is located in the lower regions of the anode cassette, it will be appreciated that this mechanism may if desired be located above the fume cover of the electrolytic cell to which the cassette 1 is fitted to isolate the mechanism from the cell environment.
  • the anodes 2, 3 and 4 are periodically incrementally pushed down through the contact plates or pads of the cell by any suitable jacking arrangement (not illustrated).
  • This displacement of the anode block disturbs the electrical contact at the conduction pad as the anode surface slips past the pad.
  • the low resistance connection between the contact pad and the anode surface must be maintained during this disturbance.
  • the low resistance connection is achieved by the softening or melting of aluminium as it enters the contact region as a result of the passage of electrical current through the contact, and by heat transfer to the contact area from the operating cell.
  • the necessary electrical connections to the superstructure of the cell and the means of conducting potline current to the anodes does not form part of the invention and may be achieved in any suitable manner, such as by flexible bus connectors for example.
  • the anodes are supported by contact plates or pads.
  • the anode is supported by the force applying means with the contact pads compressed against its outside faces.
  • the contact pads can comprise a part of the cell conductor.
  • the anode can be pushed downwards through the pads, while the top surface is free for the placement of a replacement anode which is held in position with a suitable glue. In this way, consumption of the anode is continuous and the recycling of butt material is not necessary.
  • the anodes are supported in the cell by the force applying means generating a clamping force in the order of about 50 kN to about 100 kN per cassette.
  • This clamping force is required both to adequately support the block without risk of slippage and to help provide an acceptably low voltage drop across the sliding joint interface.
  • the electrical resistance across the contact surface is dependent upon the contact pressure. Low electrical resistance generally requires large applied stresses. In rodded technology, large applied stresses, of about 5 MPa, are obtained across the electrical contact between the carbon anode and the cast iron thimble because of the differential rates of thermal expansion between cast iron/steel and carbon as the temperature of the assembly is elevated to its operating temperature. Typically, the operating voltage drop across the cast iron thimble is around 120 mV.
  • the aim in rodless anode technology is to at least match this performance.
  • the required compression forces amount to several tens of tonnes.
  • the operation of the cell is not thermally or physically disturbed by the addition of replacement anode carbon.
  • the anode temperature at the working surface remains essentially constant for the life of the cell's operation, eliminating bath freezing on the bottom surfaces of introduced anodes, and cell temperature excursions due to opening the crust, factors which often cause operational problems in pre-bake cells fitted with conventional rodded anodes.
  • fume evolution is not increased during the anode replacement process, unlike with a conventional pre-bake cell, where the hot surface of the electrolyte is exposed to the atmosphere for several minutes on each anode change, resulting in very significant fume evolution to the atmosphere.
  • the anode block does not have a cast-in rod assembly; • No spent anodes (butts) are generated. This means that all of the following manufacturing processes are eliminated. o Anode butt removal and transportation o Anode butt cooling and fume capture o Anode butt cleaning o Anode butt stripping o Anode butt crushing and sizing o Anode butt dust handling and disposal o Anode cover (bath) recycling o Rod repair and cleaning o Cast-iron recycling preparation and handling o Anode rodding (casting)
  • the anode has aluminium at the electrical connection interface for current conduction.
  • the aluminium at the electrical connection interface operates near its melting point at the point of current entry to the anode;
  • Anodes are arranged in cassettes
  • the whole cassette may be removed, the repair made and the cassette reinserted in the cell;
  • the benefits of the rodless anode technology include: Reduced Capital Costs

Landscapes

  • 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)

Abstract

L'invention concerne un ensemble (1) anode précuite ou sans tige pour une cellule de fusion d'aluminium, comprenant une ou plusieurs anode(s) précuite(s) (2, 3, 4) disposées dans une cassette afin de présenter deux faces d'extrémité exposées, des moyens de contact électrique (5, 6, 7) au niveau des faces d'extrémité exposées de la ou des anodes, et entre les anodes dans le cas d'anodes multiples dans la cassette. La cassette comprend des moyens d'application d'une force de serrage comportant des moyens de serrage allongés (9) et des moyens de tension (10), lesdits moyens de serrage allongés transférant les forces de tension appliquées par lesdits moyens de tension comme une force de serrage aux moyens de contact électrique (5, 6, 7) au niveau des faces d'extrémité exposées des anodes, pour maintenir l'anode ou plusieurs anodes dans la cassette, et pour garder les moyens de contact électrique (5, 6, 7) en contact électrique avec l'anode ou plusieurs anodes.
PCT/AU2010/000414 2009-04-16 2010-04-15 Support pour anode sans tige Ceased WO2010118465A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA2779727A CA2779727A1 (fr) 2009-04-16 2010-04-15 Support pour anode sans tige

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US16977109P 2009-04-16 2009-04-16
US61/169,771 2009-04-16

Publications (1)

Publication Number Publication Date
WO2010118465A1 true WO2010118465A1 (fr) 2010-10-21

Family

ID=42982051

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU2010/000414 Ceased WO2010118465A1 (fr) 2009-04-16 2010-04-15 Support pour anode sans tige

Country Status (2)

Country Link
CA (1) CA2779727A1 (fr)
WO (1) WO2010118465A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012021924A1 (fr) * 2010-08-16 2012-02-23 Aluminium Smelter Developments Pty Ltd Cassette d'anodes sans tige

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115747885B (zh) * 2022-09-30 2023-09-01 广元中孚高精铝材有限公司 一种电解槽批量停槽后二次启动方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU673125B2 (en) * 1991-11-07 1996-10-24 Comalco Aluminium Limited Continuous prebaked anode cell
US5665213A (en) * 1991-11-07 1997-09-09 Comalco Aluminium Limited Continuous prebaked anode cell

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU673125B2 (en) * 1991-11-07 1996-10-24 Comalco Aluminium Limited Continuous prebaked anode cell
US5665213A (en) * 1991-11-07 1997-09-09 Comalco Aluminium Limited Continuous prebaked anode cell

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012021924A1 (fr) * 2010-08-16 2012-02-23 Aluminium Smelter Developments Pty Ltd Cassette d'anodes sans tige

Also Published As

Publication number Publication date
CA2779727A1 (fr) 2010-10-21

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