Abstract: The invention comprises a charging apparatus for melting furnaces, especially for plasma melting furnaces, for the continuous melting of preferably prepared aluminum scrap material.With the help of the proposed solution a controlled and regulated supply of the scrap material along with the prevention of a direct application of the plasma arc or other energy sources directly to the material to be melted, can be accomplished with the simultaneous pre-warming and cleaning of the material to be melted, wherein the metal loss resulting from burning is minimized, the contents of the contaminants within the metallic smelt is reduced and, in addition, an effective environmental protection can be accomplished. This is attained by the provision of an axially movable shaft 4 arranged vertically or tilted in the opening 1 of the furnace and having on the charging side a charging funnel 6 with an exhaust ring nozzle 7.

Abstract: Plasma-arc furnace for continuously melting metals, particularly for melting down recovered light-metal scrap, comprising a trough-shaped melting vessel with a substantially vertical stack thereabove, a feeding device above the stack for feeding in materials to be melted, a sump below the vessel and a charge chute between the vessel and the sump, with at least two plasma-arc burners so arranged that base points of their arcs are within an area of transition from the chute to the sump, a stirring device, removing means for molten metal, and means for scrubbing and cleaning exhausted plasma gas so that the latter can be discharged into the atmosphere.

Abstract: In the process for the preparation of pure aluminum oxide by the steps of hydrochloric acid decomposition of mechanically or thermally activated clay or alumina containing minerals, separating the insoluble residue, removing the iron from the solution, crystallizing the aluminum chloride in the iron-free solution, thermally decomposing the crystallizate to aluminum oxide and recovering the hydrochloric acid from the decomposition gases, the improvement comprising effecting the process by the steps of mechanically pretreating the clay, drying the pretreated clay, thermally or mechanically activating the clay, subjecting the activated clay to circulating leaching, separating the leached material into an SiO.sub.2 containing residue and an AlCl.sub.3 solution, extracting the AlCl.sub.3 solution to an evaporating crystallization and thermally decomposing the crystals to produce .alpha.-Al.sub.2 O.sub.3.