Abstract: A process is disclosed for the treatment of an alumina process feedstock prior to transferring the treated feedstock to an alumina process for extracting refined alumina from the treated feedstock. The treatment process includes the following steps: (a) heating the alumina process feedstock to a temperature of 400C. to 650C. by direct contact with combustion gases, and (b) cooling the heated feedstock to a temperature at which it can be handled and fed to the alumina process. The treatment process is characterised by controlling the contact time of the solid alumina process feedstock at temperatures in the above range in step (a) to less than 5 minutes.

Abstract: An electrolytic reduction cell for production of a metal includes an outer steel shell, a layer of insulating material adjacent the outer steel shell and a carbonaceous layer overlaying the insulating material and protecting the insulating material from an electrolytic bath to be contained in the cell. The carbonaceous layer includes at least one carbonaceous cathode block having an upper surface and a lower surface, with a plurality of electrical contact plugs being mounted in electrical contact with the lower surface of the cathode block. A collector plate is in electrical contact with the electrical contact plugs. The electrical contact plugs are distributed over the lower surface of the cathode block such that in operation of the cell, a substantially isopotential surface is achieved at the top surface of the cathode block.

Abstract: A method for modifying the surface of kaolinite or a kindred mineral comprises the step of subjecting the mineral to a water vapor plasma. The modification involves the generation of reactive hydroxyl sites on the surface of the kaolinite. The plasma treatment may be followed by treatment with an appropriate chemical reagent to further modify the surface properties of the mineral.

Abstract: An apparatus for breaking the anode butt (15) and stripping the thimbles (13) from the yoke stubs (12) of an anode. The apparatus includes a support frame (20), a fixed plate assembly (21) secured to the supporting frame (20) and a ram assembly (22) extendible towards the fixed plate assembly (21). The fixed plate assembly (21) comprises a substantially rigid fixed plate (23) having recesses (24a) to receive the yoke (11) and yoke stubs (12). The recesses (24a) are shaped such that the thimbles (13) on the yoke stubs (12) of the anode butt (15) abut against the fixed plate assembly (21) during the extension of the ram assembly (22) to contact and break the anode butt. The fixed plate assembly (21) may be provided with a stub locating mechanism which locates the stubs in position and abuts against the thimbles (13) on the stubs (12) during the extension of the ram assembly (22). The stub locating mechanism also abuts against and is supported by the substantially rigid fixed plate (23).

Abstract: An actuator assembly comprises a piston within an actuating cylinder, and a valve for controlling the flow of actuating fluid to the first side of the piston. When the valve is actuated the flow of fluid to the first side of the piston is stopped and the pressure of the actuating fluid on the piston is sufficient to maintain the piston in a predetermined position along the stroke path. Also disclosed is a method of actuating the crust breaker of a smelter pot using the apparatus described. Fluid leakage through the piston rod sealing assembly is reduced; the volume of compressed air used by the smelter is reduced; and the working life of the actuator is improved.

Abstract: The present invention is concerned with an apparatus for supply of molten metal including a holding furnace pivotable about an axis having a metal chamber for holding molten metal, an outlet for supplying molten metal from said chamber and an inlet well communicating with said metal chamber, said inlet well being positioned on or adjacent the pivot axis of the holding furnace and displaced along the pivot axis from said outlet, a charging means for intermittently supplying a controlled flow of molten metal to the inlet well of the holding furnace, and a control means for varying the degree of pivot of the holding furnace to maintain a predetermined supply of molten metal. Also claimed as a holding furnace for the supply of molten metal, and a method for supplying molten metal using such apparatus.

Abstract: A process for treatment of a solid material containing fluoride and sodium, such as spent potlining from aluminum reduction cells, comprising the following steps: 1) contacting the solid material with recycled caustic liquor and source of calcium in a digestor; 2) passing the mixture to a separating device to separate into liquid and solid fraction; 3) recycling part of the liquid fraction containing caustic concentration of 75-200 g/l, calculated as Na.sub.2 CO.sub.3 to step (1); and 4) recovering concentrated caustic liquor from liquid fraction. The product of the process is a solid residue having low levels of leachable fluoride and a concentrated caustic liquor.

Abstract: A vacuum lifting device that is particularly suitable for lifting refractory slabs used to line aluminum smelting cells incudes suction cups which engage the object to be lifted. A plurality of mechanical supports can be moved so that they extend at least partly underneath the object being lifted when the object is raised from the ground. The mechanical supports can hold the object in case of vacuum failure and improve the safety of the device. An optional automatic override can ensure that the mechanical supports are in the down position in the case of vacuum failure.

Abstract: A method for concentrating a clay slurry by subjecting the slurry to indirect heat exchange within a heat exchanger to elevate the temperature of the slurry while specifically suppressing boiling of the liquid within the heat exchanger. The heated slurry is subsequently subjected to a rapid pressure reduction which causes flash evaporation of part of the liquid. The rapid pressure reduction can occur in a separation vessel.

Abstract: An apparatus (50) for contacting a gas stream (62) with solid particulate material includes two contacting zones (58, 60). Sets of angled blades (54, 56) cause gas flowing through the contacting zones (58, 60) to have a swirling circumferential velocity. Solid particulate material is fed from hopper (70) via line (72) to the upper contacting zone (56), in which the swirling gas flow causes a turbulent band of particles (60) to form. Contact between the gas and the solid occurs in this band of particles. Overflow of particles from band (74) flows down conduits (76, 77) and into lower contacting zone (58). The swirling gas flow in contacting zone (58) causes a turbulent band of particles (78) to be established. The gas stream enters at conduit (62) and travels through the turbulent band of particles (78) in the lower contacting zone (58). The gas then passes through restriction (66), through the turbulent band of particles (74) in upper contacting zone (60) and then leaves the apparatus (50) via outlet (68).

Abstract: Aluminum-based products are disclosed which contain 0.5 to 4.5 wt % lithium and which further contain no more than 1 ppm of each of the alkali metal impurity elements sodium, potassium, rubidium, and cesium. The products are capable of being aged to a peak-aged condition at which they have a grain boundary region substantially free of liquid phase eutectics comprised of sodium and potassium that form embrittlement phases at room temperature, and have a higher fracture toughness than a similar product containing more than 5 ppm in total of the alkali metal impurity elements.

Abstract: A support structure for supporting continuous prebaked anodes in an aluminium smelting cell comprises a pair of side plates (3) and a pair of end plates (4) connected together to form an enclosed superstructure. The supporting structure includes at least one pair of spaced cross-plates (8, 9) that are configured to provide wedging surfaces which act to support an anode (14) therebetween. Electrical current is fed to the anodes via the cross-plates. Respective pairs of cross-plates supporting adjacent anodes may be spaced to define heat exchange passages which can be used to control the temperature of the support structure. A method for operating an aluminium smelting cell at variable amperage by positive and controlled extraction of heat from the cell.

Abstract: A process for removing a carbon dioxide, HF or sulfur dioxide contaminant from an exhaust gas stream containing that contaminant comprising providing a gas stream to a reaction zone, the gas stream entering the reaction zone from underneath and being caused to flow through the reaction zone with components of velocity in substantially upwards and circumferential directions; contacting the gas stream in the reaction zone with particulate material to adsorb the contaminant on the particulate material, wherein the flow of gas in the reaction zone causes a dispersed toroidal bed of particulate material to be formed in the reaction zone; the slip velocity of the gas stream relative to the particulate material in the toroidal bed is greater than 1 m/s; and entraining a fine fraction of the particulate material in the gas stream whereby the fine fraction is removed from the toroidal bed by the gas stream exiting the bed; and separately recovering a coarse fraction of the particulate material from the reaction zone.

Abstract: An electrolytic reduction cell for the production of metal is provided, in which liquid metal is deposited at or adjacent an upper surface of a cathode. The electrolytic reduction cell includes an anode structure and a cathode located beneath the anode structure, wherein an upper portion of the cathode comprises an aggregate of particles sized and shaped such that in operation of the cell liquid metal is present in at least an upper part of the aggregate and a slurry of liquid metal and particles is established, the slurry comprising a substantially uniform dispersion of the particles in a continuous liquid phase of the liquid metal, the slurry having a viscosity sufficiently high such that under operating conditions of the cell the slurry is relatively immobile. Methods for the production of a metal by electrolysis in the electrolytic cell are also provided.

Abstract: Particles of metal alloys and composites have been developed that are particularly suitable for use in producing thixotropic alloys and in the injection molding of such alloys. The particulate material comprises particles of metal alloy or composite, wherein a substantial proportion of the particles is shaped such that the ratio of the length of the largest dimension of a particle to the effective diameter of the particle is in the range of 1.0 to 4.0 and the substantial proportion of particles has a particle size wherein the largest dimension of the particles lies within the range of 0.5 to 5.0 mm. This allows convenient handling of the particles whilst also avoiding binding or clogging of the screw, in the case where a screw extruder is used.

Abstract: A substantially lithium-free aluminum base alloy product having improved combinations of elongation and fracture toughness in an aged condition, the aluminum alloy product comprising at least 0.5 wt. % magnesium; 0.01 to 1 ppm Na; 0.01 to 1 ppm K; less than 0.1 ppm Rb; and less than 0.1 ppm Cs, the remainder comprising aluminum, the amount of Na, K, Rb and Cs measured by GDMS, the product in an aged condition having a grain boundary region substantially free of liquid phase eutectics comprised of Na and K that form embrittlement phases at room temperature; and an increase in fracture toughness compared to an aluminum magnesium alloy having greater amounts of Na, K, Rb and Cs.

Abstract: A process for preparing a high strength magnesium alloy comprising heating a melt comprised of a base metal of magnesium, greater than 0.5% of lithium, and at least one alkali metal impurity selected from the group consisting of sodium, potassium, rubidium and cesium, the total alkali metal present in an amount greater than 5 ppm, to a temperature of about 50.degree. to 200.degree. C. above the melting point of alloy being refined in a vacuum for a sufficient time to reduce the aggregate concentration of alkali metal impurities in the melt to less than about 5 ppm as measured by GDMS.

Abstract: An apparatus for heating or cooling solid suspension slurry. The apparatus comprises a vessel (1) for containing the slurry and a draft means contained within a draft section of a draft tube (2) to circulate and maintain the suspension. Extending substantially the length of cylindrical section (26) of the draft tube below the draft means are plate heat exchangers (7, 21, 23, 25, 27, 29) connected in series. The plate heat exchangers may be recessed into the wall of the draft tube so as not to increase the pressure drop through the draft tube or may be arranged in pairs along the axis of the draft tube so that the proportion of the cross-sectional area of the draft tube occupied by the heat exchangers is minimized.

Abstract: A furnace configuration is disclosed in which the furnace is inductively heated by external insulated coils and a susceptor is placed within the charge of reactants away from the outer surfaces of the charge. Consequently, heat is transferred to the charge and the process approaches completion before the insulation is subjected to high temperatures.

Abstract: A continuous feeder for feeding alumina to an aluminum reduction cell is positioned over a discharge outlet (114) of an alumina hopper. The feeder includes a flow control valve member (140) which is connected to a positioning means (132) by rod (142). The flow control valve member (140) includes a tapered section such that varying the vertical position of member (140) varies the clearance between the member (140) and an outlet orifice, which allows control over the flow rate of alumina from the hopper. The alumina flow control means is preferably mounted within an elongate tubular member (130), which is further mounted inside a housing (120). Housing (120) allows for removal of the flow control means for maintenance without having to first empty the hopper.