Abstract: The invention relates to an apparatus for the classification of solid materials, preferably that of hard and highly pure materials, comprising a housing provided with an inlet stub, fine fraction outlet stub and a coarse fraction outlet stub as well as vane-crowns. The fluid carrying the material to be separated or classified radially passes through two vane-crowns with the vanes oriented at an angle to the tangent of the vane-crowns. Upon passage through the first vane-crown the separating or classifying chamber is reached whereupon the coarse fraction is separated out and the fluid flows radially through the second vane-crown whereupon the flow becomes axial with the fluid exiting against gravity and the separated material being collected below in a closed storage tank associated with the coarse product outlet stub.

Abstract: The present invention relates to a priming or body paint having active anti-corrosive and surface cleaning effect containing binding material, pigment and optionally solvent, filler and/or additives, characterized in that said pigment, optionally in addition to other known pigments, comprises:(a) 30-70% parts by weight, preferably 40-55% by weight of alumina hydrate (Al/OH/.sub.3),(b) 20-55% by weight of at least of one of atoxic oxides, hydroxides, oxide hydroxides, carbonates or phosphates of amphoteric elements or metals of variable valency possessing less valency than the maximum, in case of aluminum the oxide or hydroxide thereof,(c) 0-50% by weight, preferably 2-15% by weight of calcium and/or magnesium carbonate,and the grain size thereof is <20 .mu.m, preferably 2-10 .mu.m.

Abstract: An air-jet mill provided with pregrinding chambers and inner sizer suitable for fine grinding (below 10 .mu.), for cryogenic grinding and also for surface treatment during grinding of hard, elastic and/or thermoplastic materials.During operation there are no moving components to be exposed to heavy wear, and an inner sizer, forming an integral part of the grinding space, uses the energy left after grinding in the system to enable a sharp sizing or separation of fine fractions.

Abstract: According to the process the grains are led to the surface or ducts of a rotary element farther in than the flange of the rotary element, thus the coarse grains are led to the flange of the rotary element in a counterflow to the sizing medium. In a housing on an impeller deflecting elements are arranged, the carrier medium and the mixture of material to be sized are fed into the housing by medium inlet tubes, and led out by coarse and fine fraction outlet tubes or nozzles, and one inlet disc is arranged above the impeller so that they form an annular assorting space which is divided by deflecting elements into segments, and a passage connected to the inlet tube of the sizing medium is formed between the mantle of the inlet disc and the inner wall of the housing at its upper end, where ducts leading into the assorting space are arranged in the inlet disc farther in than its flange, and which are connected to the carrier medium inlet tube.

Abstract: The invention relates to a process for the reduction of sodium hydroxide losses of the Bayer-cycle by modified causticization of red mud which comprisessubjecting an optionally previously concentrated red mud slurry led off from the red mud washing line by ramification and containing a liquid phase which has a concentration of 5-40 g. caustic Na.sub.2 0/1. caustification by adjusting the lime content expressed as CaO through addition of lime or lime milk to 1-3.2 moles per mole Al.sub.2 O.sub.3, preferably to 2-2.5 moles per mole Al.sub.2 O.sub.3, related to the total Al.sub.2 O.sub.3 content of the slurry;stirring the slurry for 0.3-5 hours at a temperature of 70.degree.-110.degree. C., preferably at 80.degree.-100.degree. C.;adding to the slurry 3-4 moles, preferably 3.2-3.4 moles, of soda related to 1 mole of the originally dissolved Al.sub.2 O.sub.3, and continuing the stirring for 1-4 hours at 80.degree.-100.degree. C., preferably at a temperature of 90.degree.-95.degree. C.

Abstract: An improved process for accelerating the digestion process in the Bayer alumina process is provided which promotes both the goethite-hematite conversion and a more perfect and quick dissolution of the diaspore. The above is achieved by carrying out the digestion in the process of 5-20% by weight calculated on the dry weight of the bauxite of a novel hydrogarnet catalyst.

Abstract: The invention relates to an improved process for the production of alumina according to the Bayer technology, of bauxites containing goethite and especially of boehmitic or diasporic bauxites, for the acceleration of the digestion process, for the transformation of goethite into hematite, for the increase of alumina yield and for the reduction of the caustic soda losses, the essence of which consists in carrying out the digestion in the presence of 2-6% CaO and 0.2-2.0% Mg.sup.++, Fe.sup.++, Mn.sup.++ Co.sup.++ ions based on the weight of the dry bauxite or of compounds or ores containing these ions in the indicated quantities.

Abstract: The present invention provides for an improvement in the Bayer Aluminum manufacturing process wherein the digestion of goethite-containing bauxite is effected in higher yields, at lower temperatures and in a single step by carrying out said digestion in a wet caustic solution containing both calcium oxide and sodium chloride.

Abstract: An improved process for the enrichment of bauxites with unfavorable textures and low qualities via flotation and carried out after selective agglomeration. According to the process of the invention a water-soluble prepolymer of low chain length is added to the slurry as flocculating agent, thereafter the polymerization is started again by heating the slurry and/or adjusting its pH and/or adding a catalyst thus converting the polymer chain fragments adhered onto the gangue with high surface activity into a cross-linked resin, and finally the slurry is subjected to flotation in the presence of a conventional flotation aid.

Abstract: Disclosed is a method for the treatment of the red mud byproduct of the Bayer aluminum process, wherein limestone, hydrated lime or other CaO-containing material is added to the red mud in certain molar proportions to the ingredients of the red mud, then the mixture is further mixed with a reducing agent, and the entire mixture is subjected to a reducing heat treatment during the course of which the mix becomes softened or molten. The iron and the slag are separated from each other while the mix is still molten, or after it has been cooled, and then the Na and Al-content of the slag is extracted with a sodium carbonate solution containing a caustic, or with a sodium carbonate solution and a solution of a caustic in two steps.

Abstract: A method for processing bauxites according to the Bayer technology, with an increased yield in Al.sub.2 O.sub.3 and with decreased caustic soda losses, starting particularly from goethite bauxites of boehmite and/or diaspore type and carrying out the digestion at 180.degree.C to 300.degree.C using an aluminate liquor containing Na.sub.2 O.sub.caustic in a concentration of 80 to 300 g./l. The digestion is carried out in the presence of a calcium compound in an amount corresponding to 2 to 6 % of CaO calculated for the dry weight of bauxite and of a sulfate salt in an amount corresponding to 1.0 to 7.0 g./l. of sulfate ion concentration, whereby the goethite content of the bauxite is converted into hematite. The process provides advantageous conditions for the complete dissolution of the boehmite and diaspore content of bauxite in the vicinity of the equilibrium molar ratio, and enables to recover efficiently the caustic soda losses in the Bayer process itself, requiring no supplementary operation.