Morton, R.A.
The control of calcium and titanium oxide in metallurgical grade alumina is essential for both smelter efficiency and high grade metal production.
High calcium oxide levels adversely affect current efficiencies and alumina solubility in reduction plants while the presence of titanium in aluminium metal will adversely affect the manufacturing quality of the metal particularly its electrical conductivity and the ability to roll the metal to foil.
The control of these impurities is made more difficult when low grade bauxites are processed in low temperature digest plants.
The history of CaO and TiO2 in Worsley sandy alumina is reviewed along with the various control measures taken as both the liquor carbonate and organic carbon levels have varied. The current use of a calcium recycling process is explained along with its effect on product calcium oxide levels and process stability.
