The study for reduction roasting of laterite residue in the presence of CaF2

Abstract

Lately, an increasing number of companies invested in the hydrometallurgical process of laterite ores. In the meantime, the research on disposal of laterite residue has come under spotlight the sake of environmental protection, economic efficiency, and resource utilization. Consequently, reduction roasting process in the presence of CaF2 is proposed to treat laterite residue efficiently and recover valuable components. The thermodynamic calculation was conducted to study the mechanism of phase transformation and roasting in the presence of CaF2. It is found that CaF2 would react with iron olivine and chromite to release iron and chromium. In addition, the addition of CaF2 avails the reduction, migration, aggregation, and growth of metallic Fe and Cr. The optimal conditions for addition of CaF2 and temperature is 10% and 1200 °C, respectively. The recovery of chromium reached 95.61% at 10% CaF2 addition from 65.86% without CaF2 addition and the metallization reduction of iron increased from 77.2% to 91.87%. The function of CaF2 was further investigated by the microstructure evolution of roasting products.