Increasing Extraction Efficiency Using a Closed Grinding Circuit

Votorantim Metais — CBA’s alumina refinery produces 0.9 Mtpa of SGA. Recently the particle size of the rod-ball mill product has suffered an increase of 35% in the +590 μm fraction. This results from higher grinding charge and variation of bauxite blend, with a rise in proportion of higher Work Index bauxite. Additionally, the top entry design digesters favor low residence time, compromising digestion efficiency even further. This increases residue generation with alumina and caustic loss.