A Novel Process of Alumina Production from Low-Grade Bauxite Containing Sulfur

Soda-lime sintering process and lime sintering process are the research focus on utilization of low-grade alumina recently. The latter process can realize dry-sintering process and its energy consumption is relatively lower. However, its sintering temperature is up to 1350 °C, which is unfavorable to industrial production. Based on lime sintering method, a novel process of alumina production from low-grade bauxite containing sulfur or fly ash is carried out in this paper. The phase of alumina transforms from 12CaO·7Al2O3 (C12A7) to 4CaO·3Al2O3·SO3 (C4A3S), whose alumina leaching property is better, through decreasing sinter temperature and time and adjusting the content of CaSO4 of the raw materials of lime sintering process. The main phases of the clinker sintered at 1250 °C are C4A3S and silicon dioxide. Its leaching ratio reaches 89% after 10 min reaction, and the conditions of leaching temperature and sodium carbonate’s concentration are lower than that of C12A7.