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: According to the invention, the grains of the hydrate slurry are separated by sedimentation where the dispersed bubbles of air are removed in course of the presizing, then a supplementary sizing is carried out. Preferably, a liquid free from hydrate grains is fed in to stream against the sinking grains. This liquid is advantageously the spent liquor of the hydrate filter. The apparatus according to the invention consists of a container with conical bottom, a feeding device, a slurry outlet stub and an overflow channel. The inlet stubs of the feeding device, however, are placed off-center and every stub is connected with a presizing equipment. This equipment is composed of a bundle of pipes and/or a pack of plates which are slop placed to geometrical axis: At the upper part of the presizing equipment there is a foam overflow apparatus. The bottom of each presizing equipment is connected with a common cone-frustum type deflector casing. The casing is concentric with the container.

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: An apparatus for separating a slurry into phases containing larger and smaller grains has an upright tank in which a plurality of downwardly extending inlet pipes open at their lower ends between outlets for the coarse and fine phases located at the bottom and top of the tank, respectively. At the lower end of each inlet pipe, an upwardly widening frustoconical cup is provided with a bottom confronting the open end of the inlet pipe to deflect the slurry upwardly and outwardly. Within the cup swirl vanes impart a swirl to the slurry.

Abstract: A method of and apparatus for the mixing of a slurry in a tank having a conical bottom along the axis of the tank, and air-lift pipe is provided which is supplied at its lower end with compressed air to induce an upward flow of the slurry and air mixture through the pipe during start up of a mixing operation. Thus an injection is cut off when steady state is reached and air is injected at an upper level in the pipe located in the upper third of the length thereof but below the upper eighth for continuing mixing operation.

Abstract: The clamping element for the releasable fastening of spatially arranged or parallel bars, tubes and similar objects has a basic body comprising at least one fixing hole and two or three, but in given case several inlet holes for each fixing hole, penetrating the fixing hole, parallel with and/or by-passing each other, and tensioning insert arranged in the fixing holes. The tensioning insert has recesses corresponding to the penetrations and it is formed as to allow its tensioning in axial direction. The basic body is preferably spherical, cylindrical or prismatic.

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: The invention relates to a pressure limiting valve, mainly for hydraulic mine props, which has a working space with an inlet opening connected to a high-pressure space and an outlet opening connected to low-pressure space in the operative position of the valve, a displaceable first valve member engageable with a valve seat within this working space in the shut-off position of the valve, a spring pressing the first valve member to the valve seat and in a given case, a spring sustaining the valve seat, suitably a gas spring and in which according to the invention the first valve member has transfer passages ensuring communication between the inlet opening and the outlet opening in the open position of the valve, as well as second valve member provided with a frustoconical head facing the cover plate and having a stem loosely fitted in a guide bore formed in the first valve member which is formed with an annular axial flange surrounding the head of the second valve member which is concentrically arranged within

Abstract: The invention relates to a new a method for simultaneous recovering vanadium, molybdenum and gallium from alumina factory aluminate liquors. The recovering is carried out in one step by electrolyzing an alumina factory aluminate liquor a temperature exceeding 70.degree. C. with a current density of from 400 to 1200 A/m.sup.2 using a low-melting liquid alloy as a cathode and agitating said alloy mechanically.By using the new process the three precious metals can be recovered simultaneously in one step with good efficiencies without any preliminary treating of the aluminate liquor and without using any auxiliary chemical.

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: The invention relates to a new method of reducing the organic substance content of alum earth production cycle performed according to the Bayer technology. By the method of the invention the majority of the organic substances present in the circulating lye can be removed easily and with only slight losses in sodium content.According to the invention one proceeds so that soda present in the hydrate wash and/or in the soda salt solution is caustified with lime, the solution is evaporated to reach a total sodium oxide concentration of 200 to 400 g/l, the precipitated solid is separated and removed from the system, and the liquid is recycled.

Abstract: The invention concerns a process and an apparatus for measuring the anisotropy value of form changes in normal direction in sheet metals (the r-value). In course of a standard tensile test, the longitudinal change of dimension of the test piece is measured. When a preselected value of change of dimension in longitudinal direction which is characteristic of the material of the test piece, is reacted during the measuring process, the appertaining change of dimension in lateral direction is measured. Thereafter, an r-value is selected from the r-values corresponding to different changes in dimension in lateral direction at a preselected longitudinal change of dimension, which is closest to the one measured at the change of direction in lateral direction. The apparatus comprises comparator and switching units which are connected to signal transmitters converting changes of dimension in longitudinal direction into electric signals.

Abstract: A method of and apparatus for the determination of the standard tensile yield point in which the extension of a test body is monitored, comprises determining in the course of continuous extension within the elastic limit, the ratio of the instantaneous extension and the associated load, storing this ratio and in the course of further continuous extension the ratios of a given residual extension as well as that of the instantaneous extension and the instantaneous load are determined, the stored ratio value is summed with the ratio of the given residual extension and the instantaneous load, and the thus obtained sum is compared with the ratio of the instantaneous load whereby the instantaneous load at which the compared values become substantially equal gives the tensile yield stress at the given residual.

Abstract: The invention relates to a process for preparing alumina being suitable for layer chromatography.The alumina suitable for layer chromatography is prepared in accordance with the invention in such a manner that an aluminium trinydroxyde containing 34 to 37% by weight of bayerite, 3 to 5% by weight of pseudoboehmite and 60 to 62% by weight of amorphous aluminium trihydroxide is heated at 300.degree. C. to 400.degree. C. for 2 to 4 hours.The activated alumina thus produced is snow-white, has a large specific surface and its average grain size is within the range between 8 and 20 .mu.m.The product complies with the requirements of layer chromatographical technique.

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.