Abstract: A cell for the electrowinning of aluminium has a cavity for containing electrolyte (20) and one or more non emerging active anode bodies (5) that are suspended in the electrolyte. The electrolyte's surface (21,21?) has an expanse extending over the cavity and is substantially covered by a self-formed crust (25) of frozen electrolyte. The crust is mechanically reinforced by at least one preformed refractory body (30, 30?,30?). The electrolyte crust is formed against the preformed refractory body and bonded thereto so as to inhibit mechanical failure of the crust and collapse of the crust into the cavity.

Abstract: A cell for the electrowinning of aluminium (50) from alumina dissolved in a molten electrolyte comprises a generally horizontal cell bottom (5), preferably aluminium-wettable, on which a pool of product aluminium (50) is collected from at least one electrically conductive cathodic element (10) having aluminium-wettable cathode surfaces (11). The cathodic element comprises an inclined cathodic wall (10) in the electrolyte (60) above the generally horizontal cell bottom (5). The cathodic wall (10) has an upwardly-oriented inclined face (11) that forms a sloping upper aluminium-wettable drained active cathode surface on which aluminium is produced and drains into the aluminium pool (50), and a downwardly-oriented inclined face (12) which is in contact with the molten electrolyte (60) and which overlies the aluminium pool (50). The aluminium pool (50) covers substantially the entire cell bottom (5) including underneath the cathodic wall (10).

Abstract: A cell for the electrowinning of aluminum (50) from alumina, comprises an inclined plate-like or grid-like open anode structure (25) which has a generally v-shaped configuration in cross-section. The anode structure (25) has a downwardly-oriented sloping electrochemically active surface that is generally v-shaped in cross-section and spaced above an upwardly-oriented corresponding sloping cathode surface (11) by an anode-cathode gap (40) in which alumina dissolved in a circulating electrolyte (60) is electrolysed. The anode structure (25) has a plurality of anode through-passages (45) distributed thereover for an up-flow of alumina-depleted electrolyte (60) from the anode-cathode gap (40).

Abstract: A cell for the electrowinning of aluminium from alumina dissolved in a fluoride-containing molten electrolyte, comprises a non-carbon metal-based anode having an electrically conductive metallic structure. This anode structure comprises an outer part with an electrochemically active anode surface on which, during electrolysis, oxygen is anodically evolved, and which is suspended in the electrolyte substantially parallel to a facing cathode. The anode structure has one or more flow-through openings extending from the active anode surface through the metallic structure, the flow-through opening(s) being arranged for guiding a circulation of electrolyte driven by the fast escape of anodically evolved oxygen. The outer part of the anode comprises a layer that contains predominantly cobalt oxide CoO to enhance the stability of the anode.

Abstract: A slurry comprises suspended aluminum particles in a colloid having dispersed colloidal particles of a metal oxide such as a hydroxide. The metal oxide is reducible by metallic aluminum. The slurry has such a basic pH that dissolution of the aluminum particles in the slurry is inhibited so that when the slurry is subjected to a heat treatment, the undissolved aluminum particles are reactable with the colloidal particles to form an aluminum-based mixture resistant to chemical attack made of aluminum oxide, metal aluminum and the metal of the colloidal particles. The slurry can be used to form an aluminum-based protective coating on a component, in particular of an aluminum electrowinning cell or an apparatus for treating molten aluminum.

Abstract: A cell for the electrowinning of aluminium comprises a metal-based anode (10) containing at least one of nickel, cobalt and iron, for example an anode made from an alloy consisting of 50 to 60 weight % in total of nickel and/or cobalt; 25 to 40 weight % iron; 6 to 12 weight % copper; 0.5 to 2 weight % aluminium and/or niobium; and 0.5 to 1.5 weight % in total of further constituents. The anode (10) may have an applied hematite-based coating and optionally a cerium oxyfluoride-based outermost coating. The cell contains a fluoride-containing molten electrolyte (5) at a temperature below 940° C., in which the anode is immersed and which consists of: 5 to 14 weight % dissolved alumina; 35 to 45 weight % aluminium fluoride; 30 to 45 weight % sodium fluoride; 5 to 20 weight % potassium fluoride; 0 to 5 weight % calcium fluoride; and 0 to 5 weight % in total of one or more further constituents.

Abstract: An anode for electrowinning of aluminium from alumina comprises a cobalt-containing metallic outer part that is covered with an integral oxide layer containing predominantly cobalt oxide CoO. The integral oxide layer can be formed by surface oxidation of cobalt from the metallic outer part before use.

Abstract: A cell for electrowinning a metal, in particular aluminium, from a compound thereof dissolved in an electrolyte (30) comprises an anode (40) and a cathode (10,11) that contact the electrolyte (30), the cathode (10,11) being during use at a cathodic potential for reducing thereon species of the metal to be produced from the dissolved compound. The electrolyte (30) further contains species of at least one element that is liable to contaminate the product metal (20) and that has a cathodic reduction potential which is less negative than the cathodic potential of the metal to be produced. The cell further comprises a collector (50) for removing species of such element (s) from the electrolyte (30).

Abstract: A cell for the electrowinning of aluminium comprises an electrolysis chamber (20) in which alumina is electrolysed to produce aluminium (30) and a collection reservoir (40,40?) in which product aluminium is collected. The electrolysis chamber and the collection reservoir are in liquid communication so that aluminium produced in the electrolysis chamber can flow from the electrolysis chamber into the collection reservoir. The electrolysis chamber contains one or more metal-based anodes (15). Each anode has an active anodic surface (16) spaced above a facing cathodic surface (31) on which aluminium is produced. The cathodic surface is formed on a structural body (12) by a layer made of molten aluminium into which product aluminium is incorporated during operation. The anodic surface and the cathodic surface have a substantially constant operative position.

Abstract: An anode for electrowinning aluminium comprises an electrically conductive substrate that is covered with an applied electrochemically active coating comprising a layer that contains predominantly cobalt oxide CoO. The CoO layer can be connected to the substrate through an oxygen barrier layer, in particular containing copper, nickel, tungsten, molybdenum, tantalum and/or niobium.

Abstract: A cell for the electrowinning of aluminium by the electrolysis from an aluminium compound dissolved in a molten electrolyte (50), comprises: (I) a plurality of non-carbon anodes (10), each anode being suspended in operating in the molten electrolyte by an anode stem (11) that connects the anode (10) to a positive current source; and (II) a thermic insulating cover (60,60?) which covers the electrolyte (50) and through which each anode stem (11) extends from the positive current source to an anode (10). The insulating cover (60,60?) comprises a plurality of movable sections (60) that together cover a substantial part of the electrolyte (50). Each movable section (60) covers a corresponding portion of the electrolyte (50) that is located therebelow and that can be uncovered by moving the corresponding movable section (60).

Abstract: A cell for electrowinning aluminium from alumina, comprises: a metal-based anode having an electrochemically active outer part comprising a layer that contains predominantly cobalt oxide CoO; and a fluoride-containing molten electrolyte in which the active anode surface is immersed. The electrolyte is at a temperature below 950° C., in particular in the range from 910° to 940° C. The electrolyte consists of: 6.5 to 11 weight. % dissolved alumina; 35 to 44 weight % aluminium fluoride; 38 to 46 weight % sodium fluoride; 2 to 15 weight % potassium fluoride; 0 to 5 weight % calcium fluoride; and 0 to 5 weight % in total of one or more further constituents.

Abstract: A ceramic material (20, 20A, 20B, 20C, 20C?, 20D, 20E, 20E1, 20E2, 20E3, 20E4, 20F) comprises a structural mass made of at least one refractory compound selected from refractory borides, aluminides and oxycompounds, and combinations thereof. This structural mass has an open microporosity that is impregnated with colloidal and/or polymeric particles of iron oxide and/or a precursor of iron oxide. These particles promote wetting of the structural mass by molten aluminum and/or form upon heat treatment a sintered barrier against oxygen diffusion through the structural mass. The ceramic material can be used on cathodes (15), carbon or metal-based anodes (5,5,?), sidewalls (16) and other parts (26) of aluminum electrowinning cells, on electrodes (15A) of arc furnaces, and on stirrers (10) or vessels (45) of aluminum purification apparatus.

Abstract: A cell for the electrowinning of aluminium has a cavity for containing electrolyte (20) and one or more non emerging active anode bodies (5) that are suspended in the electrolyte. The electrolyte's surface (21,21?) has an expanse extending over the cavity and is substantially covered by a self-formed crust (25) of frozen electrolyte. The crust is mechanically reinforced by at least one preformed refractory body (30, 30?,30?). The electrolyte crust is formed against the preformed refractory body and bonded thereto so as to inhibit mechanical failure of the crust and collapse of the crust into the cavity.

Abstract: An anode for the electrowinning of aluminium by the electrolysis of alumina in a molten fluoride electrolyte has an electrochemically active integral outside oxide layer obtainable by surface oxidation of a metal alloy which consists of 20 to 60 weight % nickel; 5 to 15 weight % copper; 1.5 to 5 weight % aluminium; 0 to 2 weight % in total of one or more rare earth metals, in particular yttrium; 0 to 2 weight % of further elements, in particular manganese, silicon and carbon; and the balance being iron. The metal alloy of the anode has a copper/nickel weight ratio in the range of 0.1 to 0.5, preferably 0.2 to 0.3.

Abstract: A slurry comprises suspended aluminium particles in a colloid having dispersed colloidal particles of a metal oxide such as a hydroxide. The metal oxide is reducible by metallic aluminium. The slurry has such a basic pH that dissolution of the aluminium particles in the slurry is inhibited so that when the slurry is subjected to a heat treatment, the undissolved aluminium particles are reactable with the colloidal particles to form an aluminium-based mixture resistant to chemical attack made of aluminium oxide, metal aluminium and the metal of the colloidal particles. The slurry can be used to form an aluminium-based protective coating on a component, in particular of an aluminium electrowinning cell or an apparatus for treating molten aluminium.

Abstract: A method of operating an aluminium electrowinning cell that has one or more metal-based anodes (5). The anodes (5) comprise metal-based foraminate anode bodies (10) which are suspended by metal-based anode stems (20) in a molten electrolyte (50) and which are spaced above a cathode (30). The method comprises electrolysing alumina dissolved in the molten electrolyte (50) by passing current via the anode stems (20) and the anode bodies (10) through the electrolyte (50) to the facing cathode (30) whereby aluminium (60) is cathodically produced and gas is anodically evolved. The gas promotes an electrolyte circulation (51) through the foraminate anode bodies (10) which facilitates dissolution of alumina. Each anode (5) has a foraminate anode body (10) suspended by least three anode stems (20) that are spaced apart from one another and distributed around a foraminate stemless central part of the anode body (10).

Abstract: A cell for electrowinning aluminium from alumina, comprises: a metal-based anode having an electrochemically active outer part comprising a layer that contains predominantly cobalt oxide CoO; and a fluoride-containing molten electrolyte in which the active anode surface is immersed. The electrolyte is at a temperature below 950° C., in particular in the range from 910° to 940° C. The electrolyte consists of: 6.5 to 11 weight. % dissolved alumina; 35 to 44 weight % aluminium fluoride; 38 to 46 weight % sodium fluoride; 2 to 15 weight % potassium fluoride; 0 to 5 weight % calcium fluoride; and 0 to 5 weight % in total of one or more further constituents.

Abstract: An anode for electrowinning aluminium comprises an electrically conductive substrate that is covered with an applied electrochemically active coating comprising a layer that contains predominantly cobalt oxide CoO. The CoO layer can be connected to the substrate through an oxygen barrier layer, in particular containing copper, nickel, tungsten, molybdenum, tantalum and/or niobium.

Abstract: A method of forming a dense and crack-free hematite-containing protective layer on a metal-based substrate for use in a high temperature oxidising and/or corrosive environment comprises applying onto the substrate a particle mixture consisting of: 60 to 99 95 weight %, in particular 70 to 95 weight % such as 75 to 85 weight %, of hematite with or without iron metal and/or ferrous oxide; 1 to 25 weight %, in particular 5 8 to 20 weight % such as 8 to 15 weight %, of nitride and/or carbide particles, such as boron nitride, aluminium nitride or zirconium carbide particles; and 0 to 15 weight %, in particular 5 to 15 weight %, of one or more further constituents that consist of at least one metal or metal oxide or a heat-convertible precursor thereof.