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.