Abstract: The invention relates to nonferrous metallurgy, in particular to the electrolytic production of aluminum, namely to the devices for feeding electrolytic cells, and can be used to feed alumina, aluminum fluoride, crushed electrolyte to electrolytic cells for producing aluminum. A device for feeding an electrolytic cell for producing aluminum comprises a hopper, a metering chamber with loading windows located around a perimeter of an upper part of the metering chamber above the hopper base, a valve stem with a pneumatic actuator, an upper locking element rigidly fixed to the valve stem at the upper part of the metering chamber, wherein the upper locking element is positioned between upper and lower edges of loading windows, when the stem is in an upper position, and a lower locking element is mounted on an end of the valve stem.

Abstract: This invention relates to nonferrous metallurgy, in particular to a device and method for electrolyte composition analysis based on differential thermal measurements for aluminum electrolysis control. The device is comprised of a metal body including a reference material and an electrolyte sample receptacle, temperature sensors immersed into the reference material and in an electrolyte sample, a system for registration, data processing, and visualization of obtained results. A method includes immersing a metal body into an electrolyte; filling a receptacles with the molten electrolyte; removing and cooling down the metal body having the filled receptacle above a crust on the molten electrolyte surface; drawing and analyzing differential-thermal curves based on which the liquidus temperature, electrolyte superheating and phase and blend compositions of electrolyte solid samples are determined taking into account all crystallizing phases the content of which in the electrolyte sample is no less than 3 wt %.

Abstract: In one embodiment, a feed system for distributing fluidized feed material, comprises: a distribution unit configured to fluidize feed material; and a control unit fluidly coupled to the distribution unit, wherein the control unit comprises: a chamber configured to hold the feed material provided from the distribution unit; and a feeder unit fluidly coupled to the chamber: and a second gas inlet configured to provide gas to the chamber; and a material discharge pipe fluidly coupled to the chamber and the second gas inlet.

Abstract: A system is provided including an electrolysis cell configured to retain a molten electrolyte bath, the bath including at least one bath component, the electrolysis cell including: a bottom, and a sidewall consisting essentially of the at least one bath component; and a feed material including the least one bath component to the molten electrolyte bath such that the at least one bath component is within 30% of saturation, wherein, via the feed material, the sidewall is stable in the molten electrolyte bath.

Abstract: A system is provided including an electrolysis cell configured to retain a molten electrolyte bath, the bath including at least one bath component, the electrolysis cell including: a bottom, and a sidewall consisting essentially of the at least one bath component; and a feeder system, configured to provide a feed material including the least one bath component to the molten electrolyte bath such that the at least one bath component is within 2% of saturation, wherein, via the feed material, the sidewall is stable in the molten electrolyte bath.

Abstract: A crust breaking device for metal melts includes a pneumatic cylinder having a cylinder housing, a piston, which is axially displaceable within the cylinder housing, and a piston rod, which is fastened to the piston. The piston rod is guided by the cylinder housing and movable between a retracted final position and an extended final position. The device includes an electronic control unit and a valve arrangement, which can be actuated via the electronic control unit and is connected via control lines to front and rear pressure chambers inside the cylinder housing. The device further includes at least one metal plate that is fixedly arranged within the cylinder housing in order to define a final position of the piston or the piston rod. The metal plate and the piston are electrically connected to the control unit such that a contact of the piston with the metal plate closes a circuit.

Abstract: The process involves pouring a smothering powder onto a spent anode placed on a support to cover it, with the aim of limiting fluorinated gas emission by the anode. The support may include a temporary tank, pre-filled with powder and provided with an opening for discharging the powder towards the anode on the support.

Abstract: Pot tending machine for a series of electrolysis cells designed for the production of aluminum by igneous electrolysis including: a) an overhead traveling crane which can be relocated above said electrolysis cells, b) a tool carriage onto which is fixed a service module comprising tools; c) a tapping winch, interdependent of said overhead traveling crane, designed to grasp and position near cell a tapping assembly including a ladle, a tapping tube and a vacuum device; d) a freestanding device able to generate compressed air; characterized in that said compressed air generating device of includes a first compressor, able to provide a flow of compressed air at least equal to the minimum air flow necessary for operations other than tapping, and at least one second compressor mounted in such a way that, when operating simultaneously with said first compressor, the unit provides a flow of compressed air at least equal to the minimum output of air necessary during tapping.

Abstract: A handling device for hoods of an aluminum production cell by fused bath electrolysis, including a positioning device and a hood-gripping device. The positioning device includes a vertical guide device, a mobile support mounted on the guide device so that it can be moved in at least a vertical direction during use, an articulated arm, a first framework mounted on the articulated arm so that it can pivot about a first rotation axis A substantially horizontal during use, a motor to make the first framework pivot about the first rotation axis A, a second framework mounted on the first framework so that it can be moved along the first translation axis B that is substantially horizontal during use, and means of displacing the second framework along the first translation axis B. The hood-gripping system is fixed to the second framework and includes a set of gripping devices designed to grip a set of hoods at a number of fixing points.

Abstract: A process for shutting down an operating electrolytic cell for the production of aluminium is described. The process includes: lowering anodes until a lower portion of the anodes is immersed in an aluminium layer; allowing the aluminium layer and an electrolyte bath to cool down with the lower portion of the anodes immersed in the aluminium layer; determining if the electrolyte bath is solidified, and if the electrolyte bath is solidified, raising the anodes before solidification of the aluminium layer to create a space between the solidified electrolyte bath and the anodes and the aluminium layer.

Abstract: System and method for measuring alumina qualities and communicating the same are disclosed. In one example, a system includes an aluminum electrolysis cell, a feeder configured to supply a feed stock using a feed stream to the aluminum electrolysis cell, and a measurement device in communication with the feed stream, the measurement device adaptable to receive, release, and determine at least one attribute associated with the feed stock.

Abstract: The method of process control is for a Hall-Héroult process of aluminum production from alumina ore in an industrial potline. The method includes measuring an array of sampled potline data including a plurality of cell voltages (V) and a plurality of line amperages (A) at a plurality of time points. The method also includes calculating a predicted voltage (PV) for each cell voltage and line amperage in the array. The method further includes controlling a plurality of alumina ore feed rates and a plurality of pot voltage settings based upon the predicted voltages. The method also includes calculating a plurality of bath temperatures based upon the predicted voltages. The PV variable is preferably used in an automated control environment. The PV variable is also preferably used to monitor cell noise levels, operating temperature, metal pad roll, and oscillatory electrical shorting events.

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: The present invention relates to a method of improving the current efficiency (CE) in an electrolytic aluminum production cell with an electrolytic bath, at least one anode and at least one cathode, and passing current between said anode and said cathode through said bath and feeding an aluminum containing feedstock to the cell. The CE is improved in that the aluminum containing feedstock is prepared in a manner where it contains substantially no humidity or water before it is fed to the cell, where the electrolytic process is carried out at conditions with reduced amount of hydrogen present.

Abstract: Disclosed is a method for the continuous production of aluminum from alumina including a first step of converting alumina (Al2O3) into aluminum sulfide (Al2S3) and a second step of separation of aluminum from aluminum sulfide in a separating reactor. Wherein in the first step in a conversion reactor alumina is dissolved in a molten salt to form a melt and a sulfur containing gas is fed through the melt whereby the sulfur containing gas acts as a reagent to convert at least part of the alumina into aluminum sulfide and at least part of the melt is used in the second step. Further the invention relates to an apparatus for operating the method.

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: This invention relates to a method for controlling additions of powder materials into an electrolytic cell designed for the production of aluminium by fused bath electrolysis. The method according to the invention, which can easily be automated, can be used to maintain monitoring of operation of the feed even during anode effects.

Abstract: A method of controlling an aluminum reduction cell including the following steps: maintaining alumina concentration within preset limits by alternating base, underfeed and overfeed modes; measuring cell voltage and potline amperage; calculating current normalized voltage value and a rate of changing thereof in time; comparing the calculated values of the normalized voltage with preset values thereof and correcting anode-cathode distance when passing from the base mode to the overfeed or underfeed modes; and measuring a number of alumina feed doses in the underfeed mode and overfeed mode over a time period sufficient for the alumina to dissolve.

Abstract: Operations in an electrolytic cell for producing aluminum are controlled by sensing infrared radiation on an outer surface of a cell chamber to determine an actual temperature. When the actual temperature is greater than a target temperature, a crust hole is repaired or the actual rate of addition of aluminum fluoride to the cell is increased. When the actual temperature is less than a target temperature, the actual rate of addition of aluminum fluoride to the cell is reduced.

Abstract: The invention relates to a regulation method for an electrolytic cell for the production of aluminium by means of reduction of alumina dissolved in a molten cryolite bath, wherein a solidified bath ridge is formed on the internal walls of the pot, a quantity B, referred to as the “ridge variation indicator”, which is sensitive to the variation of said solidified bath ridge, is determined and at least one of the setting means of the pot (such as the anode-metal distance) and/or at least one control operation (such as the addition of AlF3) is modified as a function of the value obtained for said indicator. The indicator may be determined from electrical measurements on the pot and/or from measurements of the liquid metal surface area. The method according to the invention makes it possible to regulate an electrolytic cell effectively at currents of up to 500 kA with an electrolyte bath with an AlF3 content greater than 11% and reduce the number of AlF3 content measurements in the bath considerably.

Abstract: Process for early detection of an anode effect in an aluminum production cell based on molten salt electrolysis. The cell comprises at least one anode, at least one cathode and cathode connecting conductors and anode connecting conductors.

Abstract: The invention relates to a regulation method for an electrolytic cell for the production of aluminium by means of reduction of alumina dissolved in a molten cryolite bath and comprises the addition, in the electrolyte bath, during pre-determined time intervals p referred to as “periods”, of a determined quantity Q(p) of aluminium trifluoride (AlF3) determined by the following equation: Q(p)=Qint(p)?Qc1(p)+Qt(p), where Qint(p) is an integral (or “self-adaptive”) term which represents the total actual AlF3 requirements of the cell and which is calculated from a mean Qm(p) of the actual AlF3 supplies made during the last N periods, Qc1 is a compensating term corresponding to the so-called “equivalent” quantity of AlF3 contained in the alumina added to the cell during the period p, and Qt(p) is a corrective term which is a typically increasing function of the difference between the measured bath temperature T(p) and the set-point temperature To.

Abstract: Operations in a cell for electrolytic production of aluminum are controlled by establishing a standard rate of addition of aluminum fluoride to a molten electrolyte covered by a crust; establishing a target temperature for a duct carrying offgas from a chamber containing the molten electrolyte; measuring an actual temperature in the duct; and, in response to the actual temperature measurement in the duct, performing at least one of (1) when the actual temperature is greater than the target temperature, inspecting the crust for a crust hole and then repairing any observed crust hole, and (2) varying an actual rate of addition of aluminum fluoride to the electrolyte by increasing the actual rate above the standard rate when the actual temperature is greater than the target temperature and by reducing the actual rate below the standard rate when the actual temperature is less than the target temperature. Controlling operations in accordance with the invention improves cell energy efficiency.

Abstract: Electrolysis of alumina dissolved in a molten salt electrolyte employing inert anode and cathodes, the anode having a box shape with slots for the cathodes.

Abstract: An improved method is described for adding alumina to a Söderberg or pre-bake type electrolytic cell fed by schedule crust breaking. Instead of adding the full amount of alumina required following each crust breaking, as is traditional, the standard dose of alumina is now split into two smaller doses. Thus, a major proportion, e.g. about 50 to 90% by weight, of the theoretically required alumina to sustain the electrolysis between crust breakings is added following a crust breaking. The electrical resistance of the electrolyte is monitored between crust breakings, and if the resistance begins to rapidly increase indicating the approach of an anode effect, the anodes are activated into a pumping action thereby breaking the crust adjacent the anodes, allowing alumina to flow into the molten electrolyte, and also creating a stirring action within the molten electrolyte. This lowers the resistance such that any anode effect is avoided until the next full crust breaking.

Abstract: An apparatus for the smelting of aluminum includes a melting furnace that is separate from and free of permanent interconnection with an electrolytic cell. The melting furnace is preferably an induction melting furnace that is designed for optimum heating and intermixing of a cryolite electrolyte and alumina, and the electrolytic cell is preferably designed for electrolysis of alumina without regard for heating, mixing or dissolving requirements. Methods for operating the apparatus are also described.

Abstract: A drained-cathode cell for the electrowinning of aluminium comprises one or more anodes (14) suspended over one or more cathodes (16). The or each anode (14) and cathode (16) respectively have a sloped V-shaped active anode surface (22) and parallel sloped inverted V-shaped drained cathode surfaces (18) facing one another and spaced apart by two sloped inter-electrode gaps (20), arranged so the electrolyte circulates upwardly in the sloped inter-electrode gaps (20) assisted by anodically produced gas and then returns from a top part (22′) to a bottom part (22″) of each inter-electrode gap (20) along an electrolyte path (26,27,36,37).

Abstract: A cell for the electrowinning of aluminum using anodes (10) made from a alloy of iron with nickel and/or cobalt is arranged to produce aluminum of low contamination and of commercial high grade quality. The cell comprises a cathode (20) of drained configuration and operates at reduced temperature without formation of a crust or ledge of solidified electrolyte. The cell is thermally insulated using an insulating cover (65,65a,65b,65c) and an insulating sidewall lining (71). The molten electrolyte (30) is substantially saturated with alumina, particularly on the electrochemically active anode surface, and with species of at least one major metal present at the surface of the nickel-iron alloy based anodes (10). The cell is preferably operated at reduced temperature from 730° to 910° C. to limit the solubility of these metal species and consequently the contamination of the product aluminum.

Abstract: A cell of advanced design for the production of aluminium by the electrolysis of an aluminium compound dissolved in a molten electrolyte, has a cathode (30) of drained configuration, and at least one non-carbon anode (10) facing the cathode both covered by the electrolyte (54). The upper part of the cell contains a removable thermic insulating cover (60) placed just above the level of the electrolyte (54). Preferably, the cathode (30) comprises a cathode mass (32) supported by a cathode carrier (31) made of electrically conductive material which serves also for the uniform distribution of electric current to the cathode mass (32) from current feeders (42) which connect the cathode carrier (31) to the negative busbars.

Abstract: An object of the invention is to provide a method for continuously producing electrodeposited copper foil while thiourea-decomposed products remaining in copper electrolyte are removed through activated carbon treatment. Another object is to provide high-resistivity copper foil obtained through the method. The present invention further provides an electrodeposition apparatus including a path for circulating a copper sulfate solution, whereby in said path is provided a filtration means for removal of thiourea-decomposed products remaining in copper electrolyte.

Abstract: A method of maintaining molten salt concentration in a low temperature electrolytic cell used for production of aluminum from alumina dissolved in a molten salt electrolyte contained in a cell free of frozen crust wherein volatile material is vented from the cell and contacted and captured on alumina being added to the cell. The captured volatile material is returned with alumina to cell to maintain the concentration of the molten salt.

Abstract: An electrolytic cell (40) for the electrowinning of aluminium comprises a plurality of anodes (60) immersed in a molten electrolyte (50), each anode (60) having an oxygen-evolving active surface of open structure facing and spaced by an inter-electrode gap from a cathode (70); a thermal insulating cover (45) above the surface (51) of the molten electrolyte (50); and an alumina feed device (10) arranged above the molten electrolyte surface (51) for spraying and/or blowing alumina (55) to an area of the molten electrolyte surface (51), from where the alumina (55) dissolves as it enters the electrolyte (50) and alumina-rich electrolyte flows to the inter-electrode gaps where it is electrolysed to produce oxygen gas on the anodes (60) and aluminium on the cathode (70).

Abstract: A cell for the electrowinning of aluminium comprising one or more anodes (10), each having a metal-based anode substrate, for instance comprising a metal core (11) covered with an metal layer 12, an oxygen barrier layer (13), one or more intermediate layers (14; 14A, 14B) and an iron layer (15). The anode substrate is covered with an electrochemically active transition metal oxide layer, in particular an iron oxide-based outside layer (16) such as a hematite-based layer, which remains dimensionally stable during operation in a cell by maintaining in the electrolyte a sufficient concentration of iron species and dissolved alumina. The cell operating temperature is sufficiently low so species and dissolved alumina.

Abstract: A method of treating an electrolyte for use in the electrolytic reduction of alumina to aluminum employing an anode and a cathode, the alumina dissolved in the electrolyte, the treating improving wetting of the cathode with molten aluminum during electrolysis. The method comprises the steps of providing a molten electrolyte comprised of ALF3 and at least one salt selected from the group consisting of NaF, KF and LiF, and treating the electrolyte by providing therein 0.004 to 0.2 wt. % of a transition metal or transition metal compound for improved wettability of the cathode with molten aluminum during subsequent electrolysis to reduce alumina to aluminum.

Abstract: An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises a molten electrolyte having the following ingredients: (a) AlF3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and (b) about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound may be, for example, a fluoride, oxide, or carbonate. The metal can be nickel, iron, copper, cobalt, or molybdenum. The bath can be employed in a combination that includes a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the bath of the present invention during electrolytic reduction of alumina to aluminum can improve the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode.

Abstract: The present invention provides a method of producing a highly pure aluminum primary base metal having a purity of at least 99.95 wt % (3N5), or a still higher purity close to the 4N that is a purity value of a secondary refined base metal. Alumina, the Si component of which is decreased by acid cleaning, is placed in a Hall-Heroult electrolysis cell as a main raw material. An aqueous solution of sulfuric acid, an aqueous solution of sulfuric acid plus hydrofluoric acid, or the like is used for acid cleaning. In order to remove Si, an acidic aqueous solution heated to at least 40° C. is preferred. Use of deashed coke and/or pitch as a carbon material for anode in addition to the use of acid-cleaned alumina produces a highly pure aluminum primary base metal in which the Si and Fe components are further decreased.

Abstract: A process for repairing a hole in the crust of an electrolytic cell. The hole is repaired by covering it with a receptacle containing solid particles. The receptacle comprises a polymeric material. More preferably, the receptacle comprises a cellulosic material, such as paper, polymer-impregnated paper, or cardboard. A closed paper bag having at least two paper layers and weighing about 15-20 lb. (6.8-9.1 kg) is particularly preferred. When the electrolytic cell produces aluminum by electrolysis of alumina, the solid particles comprise an aluminum compound such as alumina, aluminum fluoride, cryolite, or a mixture of such compounds. Two preferred forms of alumina include smelting grade alumina (SGA) and alumina dust collected by an electrostatic precipitator (ESP dust).

Abstract: A process for electrolyzing Al2O3 to produce aluminum in a low temperature bath containing AlCl3 and an alkali metal chloride. The bath is maintained at a temperature of less than about 300 ° C. Solid aluminum is produced at the cathode in a frozen layer of the alkali metal chloride.

Abstract: An inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode includes a ceramic oxide material preferably made from NiO, Fe2O3 and ZnO. The inert anode composition may comprise the following mole fractions of NiO, Fe2O3 and ZnO: 0.2 to 0.99 NiO; 0.0001 to 0.8 Fe2O3; and 0.0001 to 0.3 ZnO. The inert anode may optionally include other oxides and/or at least one metal phase, such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. The Ni—Fe—Co—O ceramic material exhibits very low solubility in Hall cell baths used to produce aluminum.

Abstract: A non-carbon, metal-based high temperature resistant anode of a cell for the production of aluminum has a highly conductive metal-based substrate coated with one or more electrically conductive adherent intermediate protective layers and an outer layer which is electrically conductive and electrochemically active. The electrochemically active layer contains one or more electrocatalysts fostering the oxidation of oxygen ions as well as fostering the formation of biatomic molecular gaseous oxygen from the monoatomicnascent oxygen obtained by the oxidation of the oxygen ions present at the surface of the anode in order to inhibit ionic and/or monoatomic oxygen penetration. The intermediate layer(s) constitute(s) a substantially impermeable barrier to ionic, monoatomic and/or biatomic gaseous oxygen to prevent attack of the metal-based substrate. The electrocatalyst can be iridium, palladium, platinum, rhodium, ruthenium, silicon, tin, zinc, Mischmetal oxides and metals of the Lanthanide series.

Abstract: The invention relates to a method of producing aluminum in an electrolytic cell, particularly in a drained cell, such cell comprising a cathode (20) and facing anodes (10), each anode (10) being spaced apart in its operative position from the cathode (20) by an anode-cathode reduced distance defining an anode-cathode gap containing the bath being electrolyzed. The method comprises: feeding alumina into the electrolyte where it is dissolved; electrolyzing an alumina-rich bath in the anode-cathode gap; and periodically moving at least one anode (10) in order to intake rich-alumina electrolyte into the anode-cathode gap thereby distributing alumina-rich electrolyte under the entire anode surface.

Abstract: An electrolytic cell (40) for the electrowinning of aluminium comprises a plurality of anodes (60) immersed in a molten electrolyte (50), each anode (60) having an oxygen-evolving active surface of open structure facing and spaced by an inter-electrode gap from a cathode (70); a thermal insulating cover (45) above the surface (51) of the molten electrolyte (50); and an alumina feed device (10) arranged above the molten electrolyte surface (51) for spraying and/or blowing alumina (55) to an area of the molten electrolyte surface (51), from where the alumina (55) dissolves as it enters the electrolyte (50) and alumina-rich electrolyte flows to the inter-electrode gaps where it is electrolysed to produce oxygen gas on the anodes (60) and aluminium on the cathode (70).

Abstract: This method of managing the operation of a plant for the production of aluminium by igneous electrolysis, of the type having a set (2, 3) of two electrolysis tankrooms, each having a series of tanks, the tankrooms being mutually parallel and symmetrical with respect to a central passageway (4) in which the handling of the liquid-aluminium tapping ladle is carried out, consists in carrying out the various handling operations at each of the tanks, necessary for the operation of the plant, in a closed loop, the members (13, 13′, 13″, 13′″, 14, 14′, 14″, 14′″) needed for the operation being moved over all the tanks of the two tankrooms of continuous cycles. The invention also relates to the plant for implementing this method.

Abstract: The smelting of aluminum from alumina in the Hall-Heroult process can be dramatically improved by lowering power consumption and in the use of carbon free anodes by using a feed of positively charged alumina. Laboratory experiments have shown that the apparent solubility and reactivity of alumina in molten fluoride baths is surprisingly increased by altering the negatively charged aluminum hydroxide Al(OH)4− particles, at about pH of nine, to positively charged particles containing Al+++ with a pH of less than two, by using acid solutions. The alumina thus produced is referred to as Al+++ alumina, or positively charged alumina. In particular, sulfuric acid is used to convert aluminum hydroxide using the Bayer process to a family of basic aluminum sulfates, 3Al2O3.4SO3.9H2O, which are dehydrated and calcined to produce Al+++ alumina.

Abstract: A non-carbon, metal-based high temperature resistant anode of a cell for the production of aluminium has a metal-based substrate coated with one or more electrically conductive adherent applied layers, at least one electrically conductive layer being electrochemically active. The electrochemically active layer contains one or more electrocatalysts fostering the oxidation of oxygen ions as well as fostering the formation of biatomic molecular gaseous oxygen to inhibit ionic and/or monoatomic oxygen attack of the metal-based substrate. The electrocatalyst can be iridium, palladium, platinum, rhodium, ruthenium, silicon, tin, zinc, Mischmetal oxides and metals of the Lanthanide series. The applied layer may further comprise electrochemically active constituents from oxides, oxyfluorides, phosphides, carbides, in particular spinels such as ferrites.

Abstract: A pneumatic cylinder for actuating fume extraction valves in fume and heat extraction plants has a piston (2) that may be actuated from both sides with at least one working surface and that can be made to slide by pressurised air in a cylinder (1) with at least one working chamber (4), as well as an energy accumulator with regulating means. The regulating means can be controlled by control means to open or keep open the fume extraction valves. In order to obtain a compact pneumatic cylinder for a fume and heat extraction plant which is easy to install, a storage chamber in which air or pressurised air is stored as compressible pressure medium is provided as energy accumulator. The storage chamber is in communication with a compression surface (7) of the piston (2), at its side opposite to the working surface (7), so that pressure medium may flow between the storage chamber and the compression surface (7).

Abstract: A process for control of the alumina content of the bath in a cell for production of aluminum by electrolysis of alumina dissolved in a molten cryolite-base salt, consisting of alternation of phases of alumina underfeeding and phases of alumina overfeeding compared with a theoretical mean rate of alumina consumption of the cell, the said alternation being a function of values, calculated at the end of each control cycle i of duration T, of the mean resistance R(i) measured at the cell electrode terminals, of the rate of change of this resistance or resistance slope P(i), of the rate of change of the resistance slope or curvature C(i) and of the extrapolated slope PX(i)=P(i)+C(i).times.T, these values being compared respectively with reference values Po, Co and PXo in order to modulate, according to an appropriate control algorithm, the alumina content of the bath in a very narrow concentration range between 1.5 and 3.5%.

Abstract: A process for recovering at least one of CF.sub.4 and C.sub.2 F.sub.6 from a vent gas from an aluminum electrolysis cell. The process includes the steps of:(a) removing inorganic fluorides from a vent gas comprising inorganic fluorides and at least one of CF.sub.4 and C.sub.2 F.sub.6 to obtain a purified vent gas; and(b) contacting the purified vent gas with a membrane at conditions effective to obtain a retentate stream rich in at least one of CF.sub.4 and C.sub.2 F.sub.6, and a permeate stream depleted in at least one of CF.sub.4 and C.sub.2 F.sub.6.

Abstract: A process for changing spent anodes while recovering the majority of the gaseous compounds evolved by the spent anodes and by the bath crust removed from the electrolytic pots during the cooling phase uses an effluent-collection device for electrolytic pots. A device for collecting gaseous effluents from pots for the production of aluminum by igneous electrolysis allows the recovery of the gaseous compounds evolved by the spent anodes and by the crust which they contain during the replacement and cooling of these anodes and this crust. The device preferably includes a degassing and cooling container located at one of the ends of the hooding device of the pots. The container can be made to communicate with the suction produced by the gas collection device.

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: A clutch mechanism, particularly for automatically operated automotive transmissions, for engaging shift ranges of continuously variable transmissions or step-by-step variable transmissions, and having at least two independently axially movable clutch rings with clutch profiles which cooperate with respective corresponding mating clutch rings clutch profiles, a clutch carrier mounted on a transmission element for rotation therewith in a fixed axial position, and having fluid actuated pressure pistons for shifting the movable clutch rings toward the mating rings. The clutch system can be disengaged under load and requires a small construction space. It can be produced at low cost and is almost free from drag losses. Clutch times and clutch travels are short. The shift pressures are very low. In addition, several clutches can be combined into a compact and relatively small clutch assembly.