Nonmolten state metalized reduction of saprolitic laterite ores: Effective extraction and process optimization of nickel and iron

Abstract

Laterite ore is an important raw nickel ore resource, and methods for extracting valuable metals from low-nickel saprolitic laterite has not been fully developed. This paper proposes a technology, called nonmolten state metalized reduction (NSMR), for extracting nickel and iron from saprolitic laterite in a tube furnace. On the basis of the mineralogical study of ores and feasibility analysis of NSMR, the direct metalization behavior of nickel and iron under different influencing factors was systematically studied. Results showed that the recoveries of nickel and iron were only 14.2% and 32.5%, respectively. For the optimization of the reaction process, the effects of additives, predehydration, and regulating mineral composition on the recovery of nickel and iron were investigated, and the results showed that the recoveries of nickel and iron after optimization increased to 94.1% and 87.4%, respectively. The behaviors of nickel and iron before and after optimization were compared and analyzed. Nickel and iron were metalized in situ before optimization but did not migrate or polymerize remarkably. After optimization, most of the nickel–iron solid solution was polymerized and showed a ribbon shape, which is beneficial for magnetic separation. This result confirmed that the optimized process can effectively improve the metalization of nickel and iron. The lower rate of iron recovery as compared with that of nickel recovery was attributed to the different existing states of the two elements in the ore. The newly generated fayalite was the primary reason for the low iron recovery. Meanwhile, a small amount of sporadically embedded ferronickel in the tailings was responsible for the loss of iron and nickel. The proposed innovative technology can realize nonmolten metalized saprolitic laterite ores and effective beneficiation of nickel and iron.