Abstract: Methods and apparatus are provided, which separate out at least a portion of fine dust, including fluoride, from recycled alumina. The difference in natural drop velocity and flow properties of fine and coarse particles is used to effect the separation.

Abstract: A method and an apparatus for cleaning flue gases with particulate slaked lime are described. In the method, burnt lime is dry-slaked with water to a moisture content of at least 5% by weight, and the slaked lime is contacted with the flue gases within 1 minute of the slaking. Preferably, the slaked lime is mixed with recirculated powdered lime from the flue gas cleaning before contacting it with the flue gases.

Abstract: A device for mixing particulate material and liquid includes a container, an inlet for the introduction of particulate material into the container, a liquid spraying device for spraying liquid over the particulate material in the container, a disc agitator arranged in the container, and an outlet for discharging material mixed with liquid from the container. A fluidization device is provided to fluidize the particulate material in the container during the mixing operation. The inlet is arranged at one lengthwise side wall of the container, so as to extend along that wall. The outlet is arranged in the other lengthwise side wall, so as to extend along the wall.

Abstract: A fan module for clean room applications, comprising outer, vertical restriction walls (5) with a lower edge part (6) having a planar lower surface (7) as well as an element (9) protruding from the outer edge of the planar lower surface for cooperation with a filter docking module (2) provided in a roof filter frame (4) having a substantially planar upper surface (8) with an extension corresponding to said planar lower surface, whereby said protruding element (9) is designed to overlap part of said filter docking module (2).

Abstract: A method and a cleaning device for the mechanical cleaning of a powder, in particular of primary aluminum oxide, direct the powder against a surface in order to strip particulate impurities adhering to the surface of the powder. The aluminum oxide to be cleaned is introduced into a stripping device having a striking mechanism directing the powder with a speed of 20 to 30 m/s several tens of times per second for a time period of <1 to 10 seconds against impact blades rotating in a direction opposite to the striking mechanism The particles of the cleaned, powder-form aluminum oxide having a size of >10 .mu.m are separated from the cleaned, powder-form aluminum oxide having a size <10 .mu.m and the impurities by an air sifter and/or a cyclone and are fed for smelting electrolysis. The powder-form aluminum oxide having a size <10 .mu.m and the impurities are fed to a waste dump or are further processed as raw material.

Abstract: A ceiling construction comprising a frame built out of longitudinal girders 1 and cross girders 2 connected to the longitudinal girders. Tiles 3 are suspended in fields defined by the frames. Heat-exchanger elements 4 are arranged above the tiles 3. In order to assure that an as good as possible heat transfer between the heat-exchanger elements 4 and the tiles 3 is guaranteed, the tiles are mounted according to the invention on the heat-exchanger elements by means of holding magnets 8.