Abstract: The sodium content of aluminum melt is reduced efficiently to within acceptable limits by filtering the primary metal from the electrolytic cell through a loosely packed filter bed of granular material which in part comprises carbon. The treatment is carried out before alloy additions are made, and the temperature of the melt before entering the filter is higher than 780.degree. C.

Abstract: Alkali and alkaline earth metals are removed from light metal melts by causing the melt to flow through a bed consisting of granules of a mechanically resistant and chemically inert carrier particles which have a coating of carbon. A suitable granule is prepared by mixing particles of inert carrier material with a cokable carbonaceous material and heating the mixture in a closed reaction vessel to the carbonaceous material and produce an adherent coating of carbon on the carrier particles of the granulate. The density of the coated granules is greater than 2.5 g/cm.sup.3.

Abstract: Alkali and alkaline earth metals are removed from light metal melts by causing the melt to flow through a bed consisting of granules of a mechanically resistant and chemically inert carrier particles which have a coating of carbon. A suitable granule is prepared by mixing particles of inert carrier material with a cokable carbonaceous material and heating the mixture in a closed reaction vessel to produce an adherent coating of carbon on the carrier particles of the granules. The density of the coated granules is greater than 2.5 g/cm.sup.3.

Abstract: The sodium content of aluminum melt is reduced efficiently to within acceptable limits by filtering the primary metal from the electrolytic cell through a loosely packed filter bed of granular material which in part comprises carbon. The treatment is carried out before alloy additions are made, and the temperature of the melt before entering the filter is higher than 780.degree. C.

Abstract: The invention relates to a device for introduction of gases into reaction vessels containing liquids, especially vessels undergoing thermal stress, in particular filter housings for metal melts, using a gas-permeable body of heat-resistant material, fitting into a metal sleeve anchored in the wall of the reaction vessel. The wall of the reaction vessel consists of three different layers, namely a rigid inner layer of heat-resistant material, a loose intermediate layer of bulk material, and a casing of metal. The metal sleeve extends from the outside into the loose intermediate layer, the rigid inner layer and the gas-permeable inlet body are directly adjacent to one another, and the boundary surface of the gas-permeable inlet body has a permanently applied, thoroughly gas-tight cover of ceramic material.

Abstract: A metal melt is filtered by causing the melt to flow successively into a filter chamber, downwards through the filter chamber, into a riser chamber, upwards through the riser chamber, and out of the riser chamber, and simultaneously introducing a counter-current flow of gas into the filter chamber, while the filter chamber contains a loose bed of granulate, whereas in the riser chamber there is no granulate nor is gas introduced therein.

Abstract: A vessel which, when in use, is subject to thermal stress, and which includes a device for introduction of gas through the wall of the vessel, the device comprising a metal sleeve fastened to the outer face of the wall of the vessel in an adjustable and easily exchangeable manner by a combination of screws and spring washers, and a gas-permeable body of fire-resistant material which is mounted adjustably and exchangeably in the metal sleeve under spring pressure. Either a major portion of the gas-permeable body is formed as a frustum of a cone, which has a short cylindrical portion on its end of larger cross section, or the gas-permeable body consists of two cylindrical portions of different cross section. The spring pressure is exerted by at least one dished spring column consisting of a series of pairs of oppositely oriented dished spring washers.