Authors:
J. Theodor Wehrli, Y. Jiang
The International Committee for Study of Bauxite, Alumina & Aluminium (ICSOBA), Zhengzhou, China, 25-27 November 2010
Abstract
Aurukun bauxite is a high reactive silica, monohydrate type of bauxite, which contains around 56% Gibbsite, 13% Boehmite and about 10% of total SiO2. Digestion at intermediate to high temperatures is required and silica related caustic soda consumption will be high. As a result, Aurukun bauxite is perceived as being of poor quality and expensive to process, even though that the total available alumina is high at around 45% Al2O3.
Aurukun bauxite also contains significant amounts of quartz and the amount of reactive silica can be reduced significantly by selecting optimum processing conditions. A recent study showed that there are many benefits associated with the high quantity of Desilication Products (DSP) formed during processing, including very rapid liquor desilication. The incorporation of most inorganic liquor impurities into the DSP cage structure, results in pure plant liquors and a high precipitation yield. Consequently, the number and size of precipitation tanks can be reduced, no side stream causticisation or out-salting operation is required, scaling of equipment is minimised and good product quality is expected. Boehmite extraction is also relatively fast with only 5 to 10 minutes residence time required to achieve optimum alumina extraction, favouring tube digestion technology.
As a result, a very simple and robust process design with high liquor productivity is possible. This paper will present details of typical Aurukun bauxite characteristics and issues to be considered for process design.
