钒钛磁铁精矿直接还原过程中金属铁颗粒长大特性

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

通过钒钛磁铁矿精矿直接还原实验,研究了不同还原剂和添加剂对还原过程金属铁颗粒长大的影响.提高还原温度能促进还原产物中金属铁颗粒的长大,金属铁颗粒中V含量也显著增加.与用无烟煤和褐煤还原产物相比,用烟煤还原产物中金属铁颗粒明显长大,这是由烟煤中高灰分含量所引起的.金属铁颗粒长大机理的研究表明:Na2CO3和Na2SiO3的熔点较低,且能破坏铁橄榄石和铁尖晶石的结构,并生成一些低熔点物质,而SiO2能与铁橄榄石形成低共熔混合物.这些低熔点物质都有助于改善金属铁相的扩散,从而促进金属铁颗粒长大.

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.