Abstract: This invention relates to a cathode element for use in a pot of an electrolytic cell intended for production of aluminum. The cathode element comprises a cathode block and a steel connection bar. The connection bar includes at least one metal insert, whose electrical conductivity is greater than the electrical conductivity of the said steel. The presence of an insert according to the invention can simultaneously result in a very large drop in the global cathode voltage and a very strong reduction in the current density at the head of the block.

Abstract: The invention relates to a cooling method of a igneous electrolytic cell for aluminium production wherein heat transfer fluid droplets (or “divided heat transfer fluid”) are produced, preferentially in a confined volume in contact with a specified surface of at least one wall of the shell of the pot of the electrolytic cell, so as to induce the evaporation of all or part of said droplets by contact with said surface and remove the heat from said surface. The invention also relates to a cooling system capable of implementing the cooling method. The invention makes it possible to obtain a high cooling efficiency due to the latent heat of vaporisation of the heat transfer fluid.

Abstract: The present invention relates to a method of pre-heating a pot provided with anodes and cathodes for the production of aluminium by electrolysis, said method including a first step, prior to the pot being supplied with current, during which a layer of a granular conductive material is deposited then crushed between the anodes and the cathodes, characterized in that the granular conductive material is graphite-based and in that the layer of granular conductive material only extends, after crushing, over a part of a lower surface of each anode and takes the form of contact blocks.

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: The invention relates to a process and an installation for the treatment of gaseous effluents produced by at least one electrolytic cell (1) in which the effluents are conveyed by at least one conveyance duct (11) to treatment means (12-19) comprising at least one reactor (12) to extract fluorinated products contained in effluents by reaction with powder alumina (16) and a separation device (13) to separate the alumina output from the reactor (12) from the residual gas fraction and comprising filter means (14). According to the invention, the effluents are cooled before being treated by the injection of droplets of a cooling fluid into the conveyance duct(s) (11) at at least one point (P) located upstream of the reactor (12), and by vaporisation of the said fluid. The invention provides an efficient means of cooling effluents from electrolytic cells without affecting their operation.

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: The present invention relates to a method of pre-heating a pot provided with anodes and cathodes for the production of aluminium by electrolysis, said method including a first step, prior to the pot being supplied with current, during which a layer of a granular conductive material is deposited then crushed between the anodes and the cathodes, characterized in that the granular conductive material is graphite-based and in that the layer of granular conductive material only extends, after crushing, over a part of a lower surface of each anode and takes the form of contact blocks.

Abstract: The invention relates to a cooling method of a igneous electrolytic cell for aluminium production wherein heat transfer fluid droplets (or “divided heat transfer fluid”) are produced, preferentially in a confined volume in contact with a specified surface of at least one wall of the shell of the pot of the electrolytic cell, so as to induce the evaporation of all or part of said droplets by contact with said surface and remove the heat from said surface. The invention also relates to a cooling system capable of implementing the cooling method. The invention makes it possible to obtain a high cooling efficiency due to the latent heat of vaporisation of the heat transfer fluid.

Abstract: This invention relates to a cathode element for use in a pot of an electrolytic cell intended for production of aluminum. The cathode element comprises a cathode block and a steel connection bar. The connection bar includes at least one metal insert, whose electrical conductivity is greater than the electrical conductivity of the said steel. The presence of an insert according to the invention can simultaneously result in a very large drop in the global cathode voltage and a very strong reduction in the current density at the head of the block.

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: 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: The invention concerns a process for shaping, by compacting, carbonaceous blocks formed by a carbonaceous paste based on a carbonaceous aggregate such as coke, anthracite or graphite, and an organic cokable binder such as tar and optional additives. The carbonaceous paste is introduced into a mould in which some of the walls are displaceable with respect to their initial position and there are successively applied to said paste at least one stress .sigma..sub.n along an axis A.sub.n, then at least one stress .sigma..sub.n+1 along an axis A.sub.n+1 which is not coincident with the axis A.sub.n, then at least one stress .sigma..sub.n+2 along an axis A.sub.n+2 which is not coincident with the axis A.sub.n+1, and so forth, repetitively, each stress .sigma..sub.(i) being applied after at least partial suppression of the stress .sigma..sub.(i-1). Use of the process substantially enhances compactness of the carbonaceous blocks.

Abstract: An apparatus for shaping, by compacting, carbonaceous blocks formed by a carbonaceous paste based on a carbonaceous aggregate such as coke, anthracite or graphite, and an organic cokable binder such as tar and optional additives. The carbonaceous paste is introduced into a mould in which some of the walls are displaceable with respect to their initial position and there are successively applied to said paste at least one stress .sigma.n along an axis An, then at least one stress .sigma.n+1 along an axis An+1 which is not coincident with the axis An, then at least one stress .sigma.n+2 along an axis An+2 which is not coincident with the axis An+1, and so forth, repetitively, each stress .sigma.(i) being applied after at least partial suppression of the stress .sigma.(i-1). Use of the apparatus substantially enhances compactness of the carbonaceous blocks.

Abstract: The invention concerns a process and an apparatus for optimizing combustion in a furnace which has open chambers, referred to as a ring furnace, for the baking of carbonaceous blocks, the furnace comprising a plurality of preheating, baking and cooling chambers which are aligned in series, each chamber being formed by the alternating juxtaposition of hollow heating partitions in which the combustion gases circulate and compartments in which the carbonaceous blocks to be baked are stacked, the combustion gases being extracted by a suction pipe connected by delivery tubes to each of the heating partitions of the first natural preheating chamber.

Abstract: The invention relates to a process for relaxing lateral stresses at the end of shaping by compacting of a block constituted by an aggregate and a binder (such as a carbon-containing paste), to which is applied a main monoaxial stress in a rigid mold having a bottom and four side walls. According to the process, at the end of compacting and along the compacting axis, there is maintained a residual stress of between 50 and 2000 kilopascals, and preferably between 100 and 500 kilopascals. At least two of the side walls of the mold are then moved apart by a few millimeters, followed by the elimination of the main stress and the extraction of the molded block. The residual stress is maintained for a period of between 1 and 20 seconds following the moving apart of the walls.

Abstract: The invention relates to an apparatus of the vibrocompactor type for compacting carbonaceous blocks, and which comprises a vibrating table on which a carbonaceous paste is to be disposed, a heavy mass located below the table, and damper means located between the table and the mass for suspending the table above the mass. According to the invention, the damper means comprises inflatable pneumatic cushions. These cushions may be connected in parallel permanently to a source of fluid under a controllable pressure, or alternatively may be connected in parallel during the inflation of the cushions, and then isolated individually or in groups from the source of fluid. The apparatus may also include a means for measuring the pressure in each cushion or in a group of cushions, and a means for signalling the drop in pressure in each cushion or group.

Abstract: The invention relates to a method of regulating the tar content of precooked anodes intended for the production of aluminum by electrolysis, to an optimum level Bm corresponding to the maximum dry density of the anodes, which utilizes measurements on crude anodes emerging from compaction and without awaiting the results of the cooking process. The method comprises the following repeatedly carrying out of the following sequence of steps:(a) forming a carbonaceous paste containing, by weight, an initial tar content Bo %;(b) forming a number n of anodes from the initial carbonaceous paste, and determining mean dry density by measuring their height H and weight P when they emerge from compaction;(c) forming a further carbonaceous paste containing tar content, .gamma.(Bo+x.sub.o) % where x.sub.o is greater or less than zero;(d) forming a number m of anodes from the second carbonaceous paste and determining the mean dry density .gamma.(Bo+x.sub.o) of the m anodes when they emerge from compaction;(e) comparing .

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.