Abstract: An improved flue gas cooler 10, or bank of coolers 10, handles flue gas G from aluminum reduction cells in an aluminum smelter plant. Each flue gas cooler 10 has a gas inlet chamber 14, a gas outlet chamber 16, and a matrix of gas cooling tubes 18 extending between the inlet chamber and the outlet chamber. Each cooling tube 18 has a bell-shaped inlet end 19 comprising an aerodynamically curved gas-accelerating profile effective to facilitate streamlined flow of flue gas G into the tube. The improved flue gas cooler makes it possible to connect the flue gas cooler to receive flue gas G direct from the aluminum reduction cells without getting clogged by dust and sublimates present in the flue gas.

Abstract: An improved flue gas cooler (10), or bank of coolers (10), handles flue gas G from aluminium reduction cells in an aluminium smelter plant. The or each flue gas cooler (10) has a gas inlet chamber (14), a gas outlet chamber (16), and a matrix of gas cooling tubes (18) extending between the inlet chamber and the outlet chamber. Each cooling tube (18) has a bell-shaped inlet end (19) comprising an aerodynamically curved gas-accelerating profile effective to facilitate streamlined flow of flue gas G into the tube. The improved flue gas cooler makes it possible to connect the flue gas cooler to receive hot raw flue gas G direct from the aluminium reduction cells without getting clogged by dust and sublimates present in the flue gas. Once cooled, the flue gas can be safely passed on to a flue gas cleaning plant of the dry scrubbing type.

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: Process for the separation of fine dust which contains impurities from alumina. The contaminated alumina is firstly subjected to a disintegration step in order to liberate fine dust from the alumina, and then the purified alumina is selectively separated from the fine impurity-containing dust in a separation step.

Abstract: Heat exchanger for gases, comprising a vertical shaft with upward flow of gas between rows of staggered horizontally disposed sets of tubes, downwardly restricted by a gas penetrable bottom (2) and upwardly by the uppermost set of tubes, and over its entire vertical length containing a granular material (7) which is kept in motion by the essentially vertically upward gas stream. The heat exchanger is characterized therein that the ratio between the diagonal free opening a and the horizontal free opening b between the tubes (4) in the set of tubes lies within the range 0.45:1-0.9:1 for controlling and restricting the vertical movement of the grains in the heat exchanger, thereby obtaining an approximately continuous temperature gradient in the gas-grain mixture over the entire height of the heat exchanger.