Grain growth characteristics of metallic iron in the direct reduction of vanadium-bearing titanomagnetite concentrates

The effects of reductants and additives on the grain growth of metallic iron were investigated during the direct reduction of vanadium-bearing titanomagnetite concentrates. It is found that both the particle size and the vanadium content of metallic iron in reduced samples considerably increases as the reduction temperature rises. In comparison with a reduced sample using anthracite or lignite as a reductant,the particle size of metallic iron in a reduced sample using bitumite as a reductant considerably increases. This may be attributed to the high ash content of bitumite. A further study on the mechanism of the grain growth of metallic iron shows that Na₂CO₃ and Na₂SiO₃,with low melting points,decompose the structures of fayalite and hercynite and generate some low-melting-point phases,while SiO₂ react with fayalite and form eutectic mixtures. These substances with low melting points can improve the diffusion of metallic iron in reduced samples and facilitate the grain growth of metallic iron.