EP0996773A1 - Cellule a cathode drainee pour la production d'aluminium - Google Patents

Cellule a cathode drainee pour la production d'aluminium

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Publication number
EP0996773A1
EP0996773A1 EP98928496A EP98928496A EP0996773A1 EP 0996773 A1 EP0996773 A1 EP 0996773A1 EP 98928496 A EP98928496 A EP 98928496A EP 98928496 A EP98928496 A EP 98928496A EP 0996773 A1 EP0996773 A1 EP 0996773A1
Authority
EP
European Patent Office
Prior art keywords
cell
cathode
aluminium
drained
anode
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.)
Granted
Application number
EP98928496A
Other languages
German (de)
English (en)
Other versions
EP0996773B1 (fr
Inventor
Vittorio De Nora
Jean-Jacques Duruz
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.)
Moltech Invent SA
Original Assignee
Moltech Invent SA
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Filing date
Publication date
Application filed by Moltech Invent SA filed Critical Moltech Invent SA
Publication of EP0996773A1 publication Critical patent/EP0996773A1/fr
Application granted granted Critical
Publication of EP0996773B1 publication Critical patent/EP0996773B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • 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

  • the invention relates to cells for the production of aluminium by the electrolysis of an aluminium compound dissolved in a molten electrolyte, for example alumina dissolved in a molten fluoride-based electrolyte.
  • the invention also concerns a method of producing aluminium in this drained cathode cell .
  • the electrolytic cell trough is typically made of a steel shell provided with an insulating lining of refractory material covered by prebaked anthracite-graphite or all graphite carbon blocks at the cell floor bottom which acts as cathode and to which the negative pole of a direct current source is connected by means of steel conductor bars embedded in the carbon blocks.
  • the side walls are also covered with prebaked anthracite-graphite carbon plates or silicon carbide plates.
  • the anodes are still made of carbonaceous material and must be replaced every few weeks.
  • the operating temperature is still approximately 950°C in order to have a sufficiently high rate of dissolution of alumina which decreases at lower temperatures and to have a higher conductivity of the electrolyte.
  • ACD anode-cathode distance
  • IEG interelectrode gap
  • DSA® noble metal activated titanium metal
  • U.S. Patents 3,400,061 (Lewis et al) and 4,602,990 (Boxall et al) disclose aluminium electrowinning cells with sloped drained cathodes arranged with the cathodes and facing anode surfaces sloping across the cell. In these cells, the molten aluminium flows down the sloping cathodes into a median longitudinal groove along the centre of the cell, or into lateral longitudinal grooves along the cell sides, for collecting the molten aluminium and delivering it to a sump.
  • Patent 4,544,457 (Sane et al ) proposed a drained cathode arrangement in which the surface of a carbon cathode block was covered with a sheath that maintained stagnant aluminium on its surface in order to reduce wear. In this design, the cathode block stands on the cell bottom.
  • U.S. Patent 5,203,971 discloses an aluminium electrowinning cell having a partly refractory and partly carbon based cell lining.
  • the carbon-based part of the cell bottom may be recessed in respect to the refractory part, which assists in reducing movement of the aluminium pool .
  • U.S. Patent 5,368,702 (de Nora) proposed a novel multimonopolar cell having upwardly extending cathodes facing and surrounded by or in-between anodes having a relatively large inwardly-facing active anode surface area.
  • electrolyte circulation was achieved using a tubular anode with suitable openings.
  • WO 96/07773 (de Nora) proposed a new cathode design for a drained cathode, where grooves or recesses were incorporated in the surface of blocks forming the cathode surface in order to channel the drained product aluminium.
  • Aluminium is present in the electrolyte as a suspension of small particles, soluble in small amounts, and reacts with the anode gas which contains mainly CO 2 formed by the reaction of oxygen with carbon. This is facilitated by the fact that the bubbles of C0 2 which form on the anode escape with difficulty from under the anode, through the electrolyte, before the gas is collected and purified to recover fluorides and eliminate other dangerous polluting impurities .
  • the reaction between aluminium and CO 2 which reduces considerably the current efficiency of the process is facilitated by the movement of the electrolyte due to the intermittent escape of big bubbles formed, and by the movement of the aluminium pool maintained on top of the carbon cathode to protect the cathode from chemical corrosion by the formation of aluminium carbide. Such movement of the aluminium pool, due to the electromagnetic forces which become violent when the current distribution is not uniform, additionally leads to erosion of the cathode surface.
  • One object of the present invention is to provide a drained cathode cell for the production of aluminium which has characteristics which make the cell efficient from the point of high current efficiency but also from the point of view of reduced energy consumption.
  • a further object of the invention is to enhance the circulation of electrolyte in a drained cathode cell by using non-carbon oxygen-evolving anodes designed to favour the escape of the anodically-produced gas while promoting circulation of the electrolyte.
  • a yet further object of the invention is to provide a drained cathode cell in which the cell sidewall also acts as an active cathode whereby the cell can operate at low current densities.
  • An even further object of the invention is to implement a drained cathode cell design that can operate without formation of a crust of solidified electrolyte, possibly by operating at high current densities from 1 to 2
  • Another object of the invention is to provide a cell of drained cathode configuration having non-carbon non-consumable anodes of shapes which permit the rapid escape of bubbles when they are still small.
  • Yet another object of the invention is to provide a cell of drained cathode configuration wherein a small inter-electrode distance of several centimeters (typically 3cm or less) can be maintained while reducing contact between the produced aluminium and the anodically-released gases, by avoiding a deep pool of aluminium with waves and by facilitating release of the bubbles of anodically- produced gas .
  • the invention proposes a drained cathode cell for the production of aluminium by the electrolysis of an aluminium compound dissolved in a molten electrolyte, in which the active cathode surfaces are dimensionally stable and have an aluminium-wettable surface and are at a slope, and in which anode surfaces parallel to the cathode surfaces are spaced by a reduced anode-cathode gap and are configured to induce an upward release of the anode gas and an upward circulation of the electrolyte with a downward draining of the aluminium produced.
  • the anode-cathode gap between the sloping anode and cathode surfaces is up to 3 cm, possibly about 2 cm.
  • the entire cell bottom or part of it is at a slope so that the aluminium can be better moved and collected.
  • the slope is such that it is sufficient to ensure an efficient release of bubbles of the anodically- released gas before these bubbles become too big, thereby avoiding or considerably reducing reaction with particles of aluminium.
  • the cell bottom is sloped without moving the center of the cell (i.e. one end is raised, the other end is lowered) .
  • the tapping of the aluminium is made from a storage located inside or outside the cells, at an end of the cell or at the side, or in the middle.
  • the active cathode surface is made dimensionally stable by a slurry-applied coating of aluminium-wettable refractory material which controls the sodium penetration.
  • the cell side wall also acts as an active cathode and is protected by an aluminium-wettable titanium diboride coating, or titanium diboride plates, or a fiber cloth or a porous sheet filled with a titanium diboride slurry, on which aluminium is also formed.
  • the main active cathode surface has a slope. This slope is for example from 5° to 60° to horizontal, preferably from 5° to 45°.
  • the cathode slope is obtained using the cross- section of the cathode blocks, as disclosed in PCT publication WO96/07773 (de Nora) .
  • the cathode slope is obtained by providing a wedge- shaped member ("wedge"), which is solid or is made of vertical plates spaced apart, on a flat cathode bottom, the wedge being made of carbon or of "heavy" materials, i.e. having a specific weight greater than the molten aluminium and cryolite, or incorporating internal ballast, this wedge also being coated with an aluminium-wettable titanium diboride coating, see for example U.S. Patent 5,472,578 (de Nora) .
  • wedge wedge- shaped member
  • the cathode is made of a solid body of titanium- diboride-based material made by consolidating preformed titanium diboride, for example as described in PCT publication WO7/08114 (Sekhar et al) or by micropyretic reaction for example as described in U.S. Patents 5,217,583 and 5,316,718 (both in the name of Sekhar et al) , possibly coated with an aluminium-wettable titanium diboride coating, for example as described in U.S. Patent 5,534,119
  • the anode is a consumable carbon anode.
  • the anode is a non-carbon oxygen evolving anode.
  • the non-carbon oxygen evolving anode comprises an assembly of plates, rods, elongated members such as strips, with a cross-section and spacing so as to favour gas escape, for example rods in so-called "spaghetti" configuration.
  • the non-carbon oxygen evolving anode is a double- faced structure with louvers or other openings in its surface for directing the anodically-produced gas inside the anode structure.
  • the anode has a cross-section to favour escape of the anodically-produced gas and circulation of the electrolyte.
  • the cell side wall is provided with sufficient internal and/or external insulation that the cell operates without formation of a crust of frozen electrolyte.
  • the cell operates at a high current density, from 0.5 to 2 Amp/cm 2 .
  • An aluminium-wettable coating is applied to components of the cell as a slurry containing an "active" powder of aluminium-wettable material (like titanium diboride) , wherein fibers are added to the slurry : a) The fibers are made of electrically-conductive and non-conductive materials such as carbonaceous, metals, carbides, nitrides, borides, alumina etc. b) The active aluminium-wettable powder is titanium diboride and similar materials, preformed or formed in situ. c) The fibers form a woven or non-woven cloth. Further features of the invention are set out in the claims .
  • Fig. 1 is a cross-sectional view through part of a drained cathode aluminium production cell according to the invention
  • Fig. 2 is a plan view of the anode of the cell of Fig. 1;
  • Fig. 3 is a side elevational view of the part of the anode of Fig . 2 ;
  • Fig. 3A is a cross-section along line 3A-3A of Fig. 3;
  • Fig. 4 is a cross-sectional view through part of the drained cathode aluminium production cell of Fig. 1.
  • Fig. 5 is a cross-sectional view through part of another drained cathode aluminium production cell according to the invention.
  • Figs 6, 7 and 8 are longitudinal cross-sectional views through part of three further embodiments of drained cathode cells;
  • Fig. 8A shows a detail of Fig. 8.
  • Fig. 1 shows part of a drained-cathode aluminium production cell comprising a plurality of non-carbon oxygen-evolving anodes 10 suspended over a cathode 30 comprising a cathode mass 32 having inclined cathode surfaces 35 and coated with an aluminium-wettable coating 37, for example a slurry-applied titanium diboride coating according to U.S. Patent 5,316,718 (Sekhar et al) .
  • the cathode mass 32 is advantageously a composite alumina-aluminium-titanium diboride material, for example produced by micropyretic reaction of i ⁇ 2 , B 2 O 3 and Al .
  • Such composite materials exhibit a certain plasticity at the cell operating temperature and have the advantage that they can accommodate for thermal differences during cell start up and operation, while maintaining good conductivity required to effectively operate as cathode mass.
  • the cathode mass 32 can be made of carbonaceous material, for example packed carbon powder, graphitized carbon, or stacked plates or slabs of carbon imbricated with one another and separated by layers of a material that is impermeable to the penetration of molten aluminium.
  • the cathode slope can be obtained using the cross-section of the assembled cathode blocks, the sloping top surface of the assembled cathode blocks forming the active cathode surface, as further described in international patent application WO 96/07773 (de Nora) .
  • the cathode mass 32 is supported in a metal cathode holder shell or plate 31 (see Fig. 4) as disclosed in Applicant's international patent application PCT/IB97/ 00589, to which current is supplied by one or more current collector bars extending through the electric and thermic insulation in the bottom of the cell, or through the sides of the cell.
  • the inclined active cathode surfaces 35 are arranged in a series of parallel rows of approximately triangular cross-section, extending along (or across) the cell. These surfaces 35 are inclined at an angle of for example 30° to 60° to horizontal, for instance about 45°. This slope is such that the produced aluminium drains efficiently, avoiding the production of a suspension of particles of aluminium in the electrolyte 54. Between the adjacent inclined surfaces 35 is a trough 38 into which aluminium from the surfaces 35 can drain. Conveniently, the entire aluminium production cell is at a slope longitudinally, so the aluminium collected in the troughs 38 can drain to one end of the cell where it is collected in a storage inside or outside the cell.
  • the anodes 10 are suspended above the cathode 30 with a series of active inclined anode surfaces on plates 16 facing corresponding inclined cathode surfaces 35 leaving a narrow anode-cathode space, which can be less than 3cm, for example about 2cm.
  • the active parts of the anodes are formed by plates 16 which for example are made of nickel-iron-aluminium or nickel-iron-aluminium-copper with an oxide surface as described in U.S. Patent No. 5,510,008 (de Nora et al) . As shown in Fig. 1, these plates 16 are arranged in facing pairs forming a roof-like configuration.
  • the sloping inner active faces of the anode plates 16 assist in removing the anodically-evolved gases, principally oxygen.
  • the chosen slope - which is the same as that of the cathode surfaces 35, for example about 45° - is such that the bubbles of anodically-released gas are efficiently removed from the active anode surface before the bubbles become too big. The risk of these gas bubbles interacting with any particles of aluminium in the electrolyte 54 is thus reduced or eliminated.
  • Each anode 10 comprises an assembly of metal members that provides an even distribution of electric current to the active anode plates 16.
  • the active anode plates 16 are suspended from transverse plates 18 fixed under a central longitudinal plate 19 by which the anode is suspended from a vertical current lead-in and suspension rod 14, for example of square cross-section.
  • each anode 10 is made up of four pairs of active anode plates 16 held spaced apart and parallel to one another and symmetrically disposed around the current lead-in rod 14. As shown in Fig. 1, each active anode plate 16 is bent more-or-less about its center at about 45°, the opposite plates 16 of each pair being spaced apart from one another with their bent lower ends projecting outwardly, so they fit over the corresponding inclined cathode surfaces 35.
  • pairs of transverse plates 18 which each carry two pairs of the active anode plates 16 are symmetrically disposed about the current lead-in rod 14 so that, overall, the active anode plates 16 are equally distributed about the axis of the current lead- in rod 14.
  • two side-by-side pairs of active anode plates 16 are carried by two transverse plates 18 spaced apart lengthwise along the plates 16/19.
  • the active anode plates 16 have a series of apertures 17 of sufficient height that the level of the molten electrolyte 54 intersects these apertures 17 about mid-way along (as shown in Fig. 1) , allowing for passage of the anodically-released gases and circulation of the electrolyte 54 induced by gas- lift.
  • these apertures 17 are of oblong shape equally spaced apart from one another along the length of the plates 16, but other shapes are possible, for example circular or oval and possibly with unequal spacing.
  • circular apertures 17 are illustrated in the right hand part of Fig. 3.
  • the illustrated active anode plates 16 could be replaced by a series of bent vertical rods , or a grid structure having through- spaces for gas release .
  • Fig . 4 shows part of the drained-cathode aluminium production cell of Fig . 1 , comprising a plurality of non- carbon oxygen-evolving anodes 10 suspended over a cathode 30 comprising a cathode mass 32A, 32B having inclined cathode surfaces 35 and coated with an aluminium-wettable coating 37 , for example a slurry- applied titanium diboride coating according to U . S . Patent 5 , 316 , 718 ( Sekhar et al ) .
  • the lower part 32B of the cathode mass is advantageously a composite alumina-aluminium-titanium diboride material , for example produced by micropyretic reaction of Ti ⁇ 2 , B 2 ⁇ 3 n ⁇ 3- Al .
  • Such composite materials exhibit a certain plasticity at the cell operating temperature and have the advantage that they can accommodate for thermal differences during cell start up and operation, while maintaining good conductivity required to effectively operate as cathode mass.
  • the top part 32A of the cathode mass can be made of carbonaceous material, for example packed carbon powder, graphitized carbon, or stacked plates or slabs of carbon imbricated with one another and separated by layers of a material that is impermeable to the penetration of molten aluminium.
  • the cathode slope can be obtained using the cross-section of the assembled cathode blocks, the sloping top surface of the assembled cathode blocks forming the active cathode surface, as further described in international patent application WO 96/07773 (de Nora) .
  • each carbon block making up the top part 32A of the cathode mass has in its bottom surface two metal current conductors 42 for evenly distributing electric current in the blocks.
  • the top part 32A of the cathode mass is surrounded by a mass of ramming paste 32C which could alternatively be replaced by silicon carbide plates .
  • the lower part 32B of the cathode mass is supported on a metal cathode holder shell or plate 31 as disclosed in Applicant's international patent application PCT/IB97/ 00589, to which current is supplied by one or more current collector bars extending through the electric and thermic insulation 40 in the bottom of the cell, or through the sides of the cell.
  • a horizontal removable insulating cover 60 which rests above the level of the electrolyte 54.
  • This cover 60 is made in sections which are removable individually with the respective anodes 10, optionally leaving gas-release gaps 63 ' around the anode rods 14.
  • the described cell can operate at a current density from 0.5 to 2 Amp/cm 2 of the projected surface area of the active anode plates 16. Due to the slope of the active surfaces of the anode plates 16, for example at about 45°, the bubbles of oxygen generated during electrolysis on these sloping surfaces escape by moving rapidly up, and are released from the top of the active sloping surfaces while the size of the bubbles remains small. This upward escape of the tiny bubbles of oxygen creates a lift in the molten electrolyte 54 adjacent to the inclined anode surfaces. As indicated in Fig.
  • the level of the molten electrolyte 54 intersects the apertures 17 about half-way up, so that anodically-released gas (oxygen) can escape by passing through these apertures 17. Also, the molten electrolyte 54 circulated upwardly by gas lift can pass out through the apertures 17, from where it circulates down outside the inclined surface of the anode plates 16, as indicated by arrow E in Fig . 1.
  • a supply of fresh alumina is periodically fed to the space outside the bottom of the anode-cathode gap, as indicated by arrow A.
  • This fresh alumina is then entrained in the flow of electrolyte 54 into the anode-cathode gap so that the electrolyte 54 in this gap never becomes depleted of alumina during operation.
  • ionic aluminium is converted to metallic aluminium on the aluminium-wettable surface 37 of the inclined cathode surfaces 35. Because of the slope of this cathode surface, for example at about 45°, the aluminium produced drains as a thin film and is collected in the troughs 38.
  • the inclined active surfaces of the anode plates 16 and the inclined active cathode surfaces 35 can be spaced apart with a small anode-cathode gap, less than 3cm and possibly only 2cm, while maintaining a high efficiency of the electrolysis.
  • Fig.5 illustrates part of another cell according to the invention including an anode structure of modified design, the same references being used to designate the same elements as before, or their equivalents, which will not be described again in full.
  • each anode 10 comprising a series of inclined active lower plates 16 suspended by a vertical current lead-in rod 14 via current distribution members 18.
  • the current distribution members 18 are formed by a series of side-by-side inclined metal plates 16 connected by cross-plates, not shown.
  • the active parts of the anodes are formed by the inclined plates 16 which for example are made of nickel-iron-aluminium or nickel-iron-aluminium-copper with an oxide surface as described in U.S. Patent No. 5,510,008 (de Nora et al) .
  • These plates 16 are arranged in facing pairs forming a roof-like configuration.
  • the sloping inner active faces of the anodes 10 assist in removing the anodically-evolved gases, principally oxygen.
  • the illustrated anode 10 has three pairs of inclined plates 16 in roof-like configuration. However, the anode 10 can include any suitable number of these pairs of inclined plates .
  • the plates 16 could be replaced by a series of rods or fingers spaced apart from one another and also inclined. In this case, the anodically-evolved gases can escape between the rods or fingers .
  • the cathode 30 comprises a metal cathode carrier 31 in the form of a shell or dished plate to which current is supplied by current distribution bars 42 which in this case are horizontal and lead through the side of the cell.
  • the current collector bars 42 could be vertical and extend through the bottom of the cell.
  • the inner shell 31 has a flat bottom and inclined side walls 33, and forms an open- topped container for a cathode mass 32 which advantageously is a composite alumina-aluminium-titanium diboride material, for example produced by micropyretic reaction of Ti ⁇ 2 , B 2 O3 and Al and which wraps around the edges of the cathode carrier 32 's inclined side walls 33.
  • an air or gas space (not shown) can be provided between the underside of the cathode carrier shell 31 and the top of the bricks 40, in the spaces left between the horizontal current distribution bars 42 wherein a plurality of additional spacers such as girders are provided.
  • This space under the central flat part of the cathode carrier 31 acts as a thermic insulating space by means of which it is possible to adjust the temperature of the cathode 30 (shell 31 and cathode mass 32) by supplying a heating or cooling gas to the space.
  • the cathode 30 can be heated by passing hot gas through the space.
  • the surface of the cathode mass 32 can be cooled to make the electrolyte
  • the central part of the top of the cathode 32 mass has a flat surface which can be inclined longitudinally along the cell and leads down into a channel or a storage for draining molten aluminium, situated at one end of the cell.
  • a coating 37 of aluminium-wettable material preferably a slurry-applied boride coating as described in U.S. Patent 5,316,718 (Sekhar et al) .
  • a plurality of active cathode bodies 39 having inclined surfaces also coated with the aluminium- wettable coating 37 and which face the inclined faces of the active anode plates or rods 16.
  • each anode 10 resting on the current distribution members 18, it is possible to place a thermic insulating cover (not shown) .
  • a thermic insulating cover (not shown)
  • the inclined active plates or rods 16 of the anode 10 are held with a small spacing above the inclined cathode surface 35.
  • such thermic insulating cover can be held level with or slightly below the top of the cell sidewalls 22 and just above the level of the electrolyte 54.
  • the described cell of Fig. 5 employs inclined non- carbon oxygen-evolving anodes 10 facing a dimensionally- stable drained cathode 30 with inclined aluminium-wettable operative surfaces 35/37, enabling the cell to operate with a narrow anode-cathode gap, say about 3cm or less (particularly because of the improved gas release with the inlined anode-cathode surfaces) , instead of about 4 to 5 cm for conventional cells.
  • This smaller anode-cathode gap means a substantial reduction in the heat produced during electrolysis, leading to a need for extra insulation to prevent freezing of the electrolyte.
  • Figs 6 to 8 show three further embodiments of drained cathode cells with consumable carbon anodes 10 ' .
  • the cathode is made up of a series of carbon blocks 82 of generally rectangular cross- section assembled together side-by-side on a layer of refractory insulating material 40. These carbon blocks 82 are joined by ramming paste or glue. Each carbon block 82 has a centrally-located current collector bar 42 extending transverse to the cell .
  • wedge-shaped carbon bodies 83 On the flat top face of blocks 82 are arranged wedge-shaped carbon bodies 83 having sloping top surfaces 84 inclined at about 5° to horizontal. As illustrated, these top surfaces 84 are oppositely inclined to one another to provide a series of shallow V-shaped recesses forming the active cathode surfaces . These bodies 83 are also joined by ramming paste or glue to the blocks 82, advantageously using a TiB 2 - containing slurry, as described in U.S. Patent N°. 5,320,717 (Sekhar) .
  • the lower active faces of the anodes 10 ' have corresponding V-shaped inclined surfaces facing the inclined active cathode surfaces 84.
  • the anode surfaces have exactly the same angle of inclination as the cathode surfaces, e.g. about 5°.
  • the anode-cathode gap is held at a reduced value, about 3cm or less. This is sufficient to promote efficient removal of the bubbles of anodically- generated gas. This also promotes an upward (and sideward) circulation of the electrolyte 54 in the anode-cathode gap, whereas the produced aluminium is drained to the center of the V-shaped recesses and collected by inclining the cell to one side, where the aluminium is collected.
  • Fig. 7 illustrates a similar design, but where the cathode blocks 82 are of trapezoidal cross-section and have integral inclined surfaces 84, arranged alternately to form the shallow V-shaped recesses.
  • the sloping cathode surfaces 84 are provided by the modified cross- sectional shape of the carbon blocks 82.
  • Fig. 8 illustrates a modification of the drained cathode cell of Fig. 6 wherein the solid cathode wedges 83 are replaced by wedge-shaped members made of a series of side-by-side spaced-apart plates 85 connected by cross-bars 86. As illustrated, each wedge-shaped cathode member is made up of eight vertical plates 85 joined by two crossbars 86. However, any suitable number of plates 85 can be connected by any suitable number of cross-bars 86, of round cross-section or any other suitable cross-section.
  • plates 85 can be made of carbon, in which case they are secured to the cathode blocks 82 or loaded with ballast.
  • the plates 85 can be made of a refractory material, such as alumina, having a specific weight greater than molten aluminium.
  • the entire surface of the wedge-shaped plates 85, or at least their top parts including the sloping surfaces, will be coated with an aluminium-wettable refractory material, preferably slurry-applied TiB 2 .
  • the produced aluminium can drain in the spaces between the plates 85.
  • the height of the lower end of the wedge-shaped plates 85 is such that it is possible to allow a fluctuation of the level of the produced aluminium to facilitate tapping of the aluminium by a batch process.
  • the cell floor is advantageously inclined to promote collection of the aluminium at the side/end of the cell.
  • the cells of Figs 6, 7 and 8 could employ non-carbon oxygen-evolving anodes instead of carbon anodes .

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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)
  • Secondary Cells (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)

Abstract

Cellule à cathode drainée pour la production d'aluminium par électrolyse d'un composé d'aluminium dissous dans un électrolyte fondu, dans laquelle les surfaces (35) de cathode actives ont des dimensions stables et possèdent une surface (37) en pente, mouillable par l'aluminium, qui permet le drainage de l'aluminium produit de la surface de la cathode. Les anodes (10) sont des anodes en carbone ou exemptes de carbone dotées de faces actives (16) faisant face aux surfaces (35) de la cathode, lesdites faces et surfaces étant inclinées jusqu'à environ 60°. L'espace entre les surfaces inclinées des anodes et de la cathode ne dépasse pas 3 cm et est configuré de telle manière qu'une circulation ascendante de l'électrolyte est induite dans ledit espace par les gaz libérés par l'anode. Un bain riche en alumine est introduit dans la partie inférieure de l'espace anode-cathode.
EP98928496A 1997-07-08 1998-07-07 Cellule a cathode drainee pour la production d'aluminium Expired - Lifetime EP0996773B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US89096397A 1997-07-08 1997-07-08
US890963 1997-07-08
PCT/IB1998/001045 WO1999002764A1 (fr) 1997-07-08 1998-07-07 Cellule a cathode drainee pour la production d'aluminium

Publications (2)

Publication Number Publication Date
EP0996773A1 true EP0996773A1 (fr) 2000-05-03
EP0996773B1 EP0996773B1 (fr) 2007-06-20

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EP98928496A Expired - Lifetime EP0996773B1 (fr) 1997-07-08 1998-07-07 Cellule a cathode drainee pour la production d'aluminium

Country Status (6)

Country Link
EP (1) EP0996773B1 (fr)
AU (1) AU8031398A (fr)
CA (1) CA2295495C (fr)
DE (1) DE69837966T2 (fr)
NO (1) NO321787B1 (fr)
WO (1) WO1999002764A1 (fr)

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WO2000063464A1 (fr) * 1999-04-16 2000-10-26 Moltech Invent S.A. Cellule electrolytique pourvue d'un dispositif d'alimentation en alumine ameliore
ES2223587T3 (es) * 1999-10-26 2005-03-01 Moltech Invent S.A. Celda para electrolisis de aluminio, con funcionamiento a baja emperatura.
WO2007105124A2 (fr) * 2006-03-10 2007-09-20 Moltech Invent S.A. Cellule d'extraction electrolytique d'aluminium avec pertes de chaleur réduites
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NO20000095L (no) 2000-03-06
WO1999002764A1 (fr) 1999-01-21
DE69837966T2 (de) 2008-02-28
CA2295495C (fr) 2007-11-20
DE69837966D1 (de) 2007-08-02
CA2295495A1 (fr) 1999-01-21
NO321787B1 (no) 2006-07-03
AU8031398A (en) 1999-02-08
NO20000095D0 (no) 2000-01-07
EP0996773B1 (fr) 2007-06-20

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