An improved lime sinter process to produce ai203 from low-grade al- Containing resources

Abstract

Low-grade bauxites and non-bauxite resources are widely distributed, which are suitable to extract alumina by the lime sinter process. The application of the lime sinter process is restricted by the high consumption of calcium, the large amount of slag and the poor alumina leaching property of clinkers. An improved lime sinter process based on the dry-sintering is proposed by adding Na20-containing compounds to decrease CaO addition and increase alumina leaching property. The molar ratios of CaO to A12o3 and Na2O to A12o3 are 0.6 and 0.4, respectively. Na4Ca3(A102)io as well as trace amounts of CaOAl2O2 and 12CaO7Al2O3 are formed after sintering at 1200°C for 30min in CaO-Al2O2-Na2O system, the alumina leaching efficiency of which is above 90%. The minerals after sintering in CaO-Al2O2-SiO2-Na2O system include Na4Ca3(A1O2)10, 12CaO7Al2O2, 2CaOSiO2 and 2CaOAl2O3SiO2. The leaching efficiency of clinkers increases as the sintering temperature increases to 1300°C.