Production of calcium metal by aluminothermic reduction of Egyptian limestone ore

Abstract

Calcium metal was successfully produced from Egyptian limestone ore under vacuum using aluminium as a reducing agent. The aluminothermic reduction process of CaO by aluminium metal was followed up by collected amounts of produced calcium metal. The progress of the reduction process was investigated by the phase analysis of produced reaction residues through X-ray diffraction. The technical parameters affecting the reduction progress were investigated such as reductant stoichiometry, reduction temperature and reduction time. Maximum metallic yield (30%) was obtained by using charge containing 19.4% aluminium powder reduced at 1300°C for 90 min under vacuum (10−3 mbar). The reduction residues composed mainly of unreacted calcium oxide, tri-calcium aluminate (3CaO·Al2O3), mayenite (12CaO·7Al2O3) and traces of calcium aluminide (CaAl4). The probable reaction sequences of the aluminothermic reduction of calcium oxide were also discussed.