A novel process of reverse flotation-hydrogen reduction for preparation of high-purity iron powder with superior magnetite concentrate

Abstract

A novel process of reverse flotation-hydrogen reduction for preparation of high-purity iron powder with superior magnetite concentrate was developed. The ultra-pure magnetite concentrate with 72.12 % Fe and 0.19 % SiO2 was obtained by reverse flotation, and the Fe recovery reached 82.3 %. Thermodynamic and kinetic analyses revealed that the reduction ability of H2 was stronger than that of CO at T > 810 °C, and hydrogen reduction was easier to occur than coal-based reduction. The reduction behavior of ultra-pure magnetite concentrate showed that compared with traditional Höganäs process reduction, iron powder with higher purity could be obtain at lower temperature by hydrogen reduction. The whiskers and nodular irons were formed on the surface of magnetite particle during coal-based reduction and hydrogen reduction, respectively. The interparticle bonding caused by nodular irons was weaker than that by whiskers, which was favorable to H2 diffusion. Under the optimal conditions, the high-purity iron powder was obtained by hydrogen reduction, whose Fe grade, MFe content and metallization rate achieved 99.16 %, 97.86 % and 98.69 %, respectively. This iron powder can meet the FHY200 grade in the Chinese industry standard of reduced iron powder for powder metallurgy (YB/T 5308-2011), and it also can be used as iron source to prepare lithium iron phosphate with high purity and good electrochemical performance by coprecipitation method.