Bauxite

Bauxit - Rohstoff zur Aluminiumgewinnung
bauxite - raw material for aluminum production

the bauxite is an aluminum - ore, which predominantly consists 3, boehmite and Diaspor AlOOH, furthermore the Fe-oxides Hämatit and Goethit, the clay mineral Kaolinit and small portions of Anatas TiO 2 of the aluminum minerals hydrargillite aluminium (OH). ItsNames it owes to its first discovery site Les Baux de Provence in Southern France, where it was discovered 1821.

emergence

in the geosciences Lateritbauxite (silicate bauxites) are differentiated from the carbonate bauxites (lime bauxites). The already early discovered carbonate bauxites lie primarily in Europe over carbonate rocks (limes and dolomites), where it by lateritische decomposition clay-enrich storages and/or. Clay-enrich solution arrears developed. Their economic meaning decreased opposite the Lateritbauxiten strongly.

The Lateritbauxite lies in numerous countries of the entire tropical belt. They resulted from lateritische decomposition of completely different silikatischer rocks such as granites, Gneise, basalts, Syenite, clay/tone and Tonschiefer. Opposite Fe-rich Lateritdecken bauxites form with particularly intensive decomposition and increased drainage, which make a dissolution possible of Kaolinit under formation of hydrargillite. In stores the aluminum-richest ranges are frequently under a Fe-richer layer. Contrary to thatAlmost exclusively hydrargillite appears to carbonate bauxites as aluminum mineral.

occurrences and production

the most important producing countries are Australia, Brazil, Guinea and Jamaica, further occurrences are and. A. in India, north China, Russia and Suriname (see table). In Europe finditself the most important dismantling places in Greece, Hungary, France, Romania, Serbia and Montenegro and Spain. In the year 1998 the Weltförderung amounted to approximately 128 million tons. From today's viewpoint economically bauxite occurrences worthy of exploitation and the secured might cover the need of the next 200 years.Bauxite is promoted predominantly in the open mining. Ideally the humushaltigen earth layers in the sense of a lasting, environmentalfair development, set free by the dismantling, are first stored temporarily and used later for the recultivation.


The largest promotion nations (2003)
rank country deliveries
(in millions t)
Country struggled deliveries
(inMillion t)
1 Australia 56,3 11 Guyana 1,8
2 Brazil 20 12 Kazakhstan 1,2
3 Guinea 16,8 13 Ghana 0,7
4 Jamaica 13,4 14 Indonesia 0,6
5 India 10 15 Iran 0,4
6 China 8 16 Hungary 0,3
7 Russian Föd. 5,4 17 Turkey 0,2
8 Suriname 3,5 18 France 0,2
9 Venezuela 2,7 19 Serbia and Montenegro 0,2
10 Greece 2,4 20 Romania 0,1

source: Trade paper - the world in figures (2005)


out approx. 95% of the diminished bauxite are produced aluminum. Small quantities serve the production during favorable compositionof aluminum chemicals, abrasives and fireproof stones. A by-product of the aluminum production is gallium.

The bauxite is heated up in receivers with 150-200 °C in caustic soda solution, whereby aluminium goes as aluminate into solution and is filtered off from the Fe-rich arrears (Rotschlamm) (Bavarian procedures). From the aluminate caustic solutioncausing of fine aluminium hydroxide separates as crystallization germ pure hydrargillite with the cooling and, which is converted by glowing into aluminium 2 O 3. The alumina becomes under additive of Kryolith as fluxing agent with approx. 1000°C melted and in electrolysis - cells with high current consumption toometallic aluminum reduces (resound Héroult process).

literature

Bardossy, G. (1982): Karst of bauxite. Bauxites DEPOSIT on of carbonates of skirt. Elsevier Sci. Publication. 441 S. Bardossy, G. and Aleva G.J.J. (1990): Lateritic of bauxite. Development in Economic Geology 27, Elsevier Sci. Publication., 624 S. ISBN 0-444-98811-4

 

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