Behavior of Reduction and Growth of Metal in Smelting of Saprolite Ni-ore in a Rotary Kiln for Production of Ferro-nickel Alloy

The sampling of raw materials in the rotary kiln, firing experiment by the experimental kiln, and water quenching experiment have been performed, and the clarification of behavior of the reduction and the growth of metal has been attempted by SEM-EDS. In the amorphous serpentine region, NiO has very high reducibility than FeO. The increase in heating temperature above 1 273 K allows the fine reduced metal to be confined in the silicate, which causes the extraction by the bromine methyl alcoholic solution to be difficult. This allows the degree of reduction to enter apparently the depression region. However, the increase in heating temperature above 1 525 K allows melt to occur, which causes the fine metal to coalesce with each other. Therefore, the degree of reduction leaves the depression region, and approaches the equilibrium values. Low-MgO and high-FeO·NiO silicate is enriched by the fractional crystallization, and thereafter reduction reaction is enhanced. From the result of SEM observation that metals occur from the lower temperature in the low-MgO and high-FeO ore containing much point defect, NiO and FeO in the crystal lattice are reduced via cationic and electronic defect species, the oxygen occurred diffuses toward the crystal surface via vacancies. However, the lack of experimental data of defect chemistry in Ni-ore requires the further investigation. From the fact that the temperature of the melt occurrence coincides with the temperature of metal beginning to grow largely in SEM observation, it is confirmed that the fine metals coalesce with each other via melt to grow.