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: 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: The invention relates to plant operations for increasing the cycle times of heat exchangers by the digestion of the aluminium oxide content of a slurry according to the Bayer technology, said slurry consisting of bauxite and sodium aluminate liquor, using an equipment in which the material is heated stepwise and in more parallel material streams, then the material streams are combined and further heated, or combined and kept at the same temperature, or after combination further heated and kept at the same temperature, characterized in that a part of the parallel material streams is slurry, another part of same is aqueous sodium hydroxide solution, preferably sodium aluminate liquor containing sodium hydroxide, or water, and the parallel material streams are exchanged in the heat exchangers in a cyclical manner.

Abstract: The invention relates to a method of burning, calcining or sintering fine-grain material in which the burnt material separated from the gas flow is supplied to a residence container from which a part of the material is returned to the burning zone and the remainder of the material is supplied to the cooling zone. Such a method is distinguished by a low heat and energy requirement and by a simple construction of the apparatus and permits ideal adaptation of the burning conditions to the particular material.

Abstract: A self-adjusting powder distributor--which is particularly intended for use with alumina calcination apparatus--comprises a casing with a permeable partition, a plurality of outlets, and means for introducing preheated hydrate above the partition and fluidizing air therebelow. The fluidized hydrate withdraws through outlets of the casing for further treatment or partly as final product. The casing is provided with means by which the amounts and mutual ratios of the withdrawing material can be adjusted according to preselected values by altering the cross-sectional flow area or the level of the outlets.

Abstract: A self-adjusting powder distributor--which is particularly intended for use with alumina calcination apparatus--comprises a casing with a permeable partition, a plurality of outlets, and means for introducing preheated hydrate above the partition and fluidizing air therebelow. The fluidized hydrate withdraws through outlets of the casing for further treatment or partly as final product. The casing is provided with means by which the amounts and mutual ratios of the withdrawing material can be adjusted according to preselected values by altering the cross-sectional flow area or the level of the outlets.

Abstract: In a sediment raking device with a centrally arranged rotated torque tube, radially arranged booms and rake arms between said booms at a lower level a link rod is provided between the rake arms and the torque tube which is connected to the rake arm by a hinge and to the torque tube by a universal joint (FIG. 1).

Abstract: Displacement slurry pump equipped with known piston-rod drive, in which on a piston rod expediently three pistons are arranged at a distance of at least one stroke length, they are a liquid piston moving the auxiliary liquid free of solid matter, and on both sides thereof a slurry piston each moving on one side the slurry, on the other side, however, the auxiliary liquid. The liquid piston fits sealed to the liquid cylinder provided with liquid suction valves, whereas the two slurry pistons fit by slot to the slurry cylinders provided with slurry suction valves and slurry delivery valves. The effective section of the liquid cylinder is larger than the effective section of a slurry cylinder each. The slurry pump may be of single-operation or of double-operation, of one-cylinder or two-cylinder or three-cylinder construction.