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The Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide) and was developed by Carl Josef Bayer.Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (Al 2 O 3), the rest being a mixture of silica, various iron oxides, and titanium dioxide. [1]
It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH) 3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(OH)), mixed with the two iron oxides goethite (FeO(OH)) and haematite (Fe 2 O 3), the aluminium clay mineral kaolinite (Al 2 Si 2 O 5 (OH) 4) and small amounts of anatase (TiO ...
Alumina is extracted from the ore bauxite by means of the Bayer process at an alumina refinery. This is an electrolytic process, so an aluminium smelter uses huge amounts of electric power; smelters tend to be located close to large power stations, often hydro-electric ones, in order to hold down costs and reduce the overall carbon footprint ...
The liquid aluminium is removed from the cell via a siphon every 1 to 3 days in order to avoid having to use extremely high temperature valves and pumps. Alumina is added to the cells as the aluminum is removed. Collected aluminium from different cells in a factory is finally melted together to ensure uniform product and made into metal sheets.
Bauxite was discovered in 1821 by Pierre Berthier who named it after a village named Les Beaux where he found it. [6] To obtain the alumina from the bauxite ore, a process was developed that used acid to dissolve aluminium but resulted in a product that contained large amounts of iron and titanium dissolved within which were difficult to remove. [6]
The density of aluminium is 2.70 g/cm 3, about 1/3 that of steel, much lower than other commonly encountered metals, making aluminium parts easily identifiable through their lightness. [28] Aluminium's low density compared to most other metals arises from the fact that its nuclei are much lighter, while difference in the unit cell size does not ...
The first stage is the calcination of the bauxite at 1200 °C with sodium carbonate and coke. The alumina is converted in sodium aluminate. Iron oxide remains unchanged and silica forms a polysilicate. In the second stage sodium hydroxide solution is added, which dissolves the sodium aluminate, leaving the impurities as a solid residue. The ...
This step could be replaced by the Pedersen process -- either result in alumina. Unlike the smelting processes of iron and coal into steel or copper and tin into bronze, which require thermal energy, alumina must be smelted with electrical energy. This is done through the Hall–Héroult process, producing 99.5–99.8% pure aluminum. [2] [7]