Technical Note

Removal of limestone from bauxite by magnetic separation

E.Th. Stamboliadis*, G. Kailis

Mineral Resources Engineering Department, Technical University of Crete, 73100 Chania, Greece


Received 13 November 2002; accepted 15 November 2003



ABSTRACT

Bauxite is the main source for the production of alumina and metal aluminum by the Bayer process. Limestone is an impurity associated to bauxite due to geological and morphological conditions prevailing during its formation. Experimental work has shown that limestone can be easily removed from bauxite using magnetic separation techniques.

Three samples of Greek bauxite were used with different CaCO₃ content, that assayed between 2.5% and 8.5% CaO. The samples were screened to three size fractions 0-5mm, 5-10mm and 10-20mm. The equipment used for the test work was a belt roll magnetic separator and it was possible to produce more than one magnetic products from each fraction by passing the non-magnetics for second or third time. From one pass to the other the roll speed and hence the feed rate was reduced. The results show that limestone can be removed from bauxite. Depending on the feed CaO assay and the specifications of the product it is possible to produce different product qualities leaving the non magnetic fraction as a residue.



Keywords: Limestone; Bauxite; Magnetic separation



* Corresponding author
   E-mail : elistach@mred.tuc.gr