Preparation Of High Purity Reduced Iron Powder From High-quality Magnetite Concentrate By Reverse Flotation-hydrogen Reduction Of Low Carbon

China’s high-quality iron ore resources are relatively abundant,mainly used to produce iron concentrate to be used as raw materials for blast furnace ironmaking,which has not been utilized at high value,disguised as a serious waste of valuable high-quality resources.In this paper,a new process of reverse flotation-hydrogen reduction was developed for preparation of high purity reduced iron powder with high-quality magnetite concentrate as raw material,which abandoned the traditional process of coarse reduction in tunnel kiln-fine grinding magnetic separation-hydrogen reduction.The new process not only reduced carbon emission,energy consumption and pollution,but also controled the introduction of impurity elements from the source and improveed the purity of reduced iron powder.In this paper,the magnetic separation and reverse flotation behaviors of high-quality magnetite concentrate were firstly studied comparatively,and the appropriate purification process was recommended.Then,based on the thermodynamics and kinetics of Fe₃O₄ coal-based and hydrogen reduction,the behaviors of coal-based reduction and hydrogen direct reduction of ultra-pure iron concentrate powder were compared,and the influence of their reaction conditions on the reduction were found out.Finally,an exploratory study on the preparation of lithium iron phosphate using high purity iron powder obtained by hydrogen direct reduction as the iron source was carried out.The results of the study showed that for the high-quality magnetite concentrate with 68.38%TFe and 4.99%SiO₂,the reverse flotation purification was more effective,and the ultra-pure iron concentrate with 72.12%TFe and 0.19%SiO₂ could be obtained.At high temperature（>810℃）,the reduction ability of H₂ was higher than that of CO,and the apparent activation energy of hydrogen and coal-based reduction reactions were 41.91k J/mol and 113.31k J/mol,respectively.Using ultra-pure iron concentrate as raw material,the secondary reduced iron powder with TFe,MFe and metallization rate of98.91%,97.43%and 98.50%was obtained by the conventional coal-based combinated hydrogen reduction process,and the high purity reduced iron powder with TFe,MFe and metallization rate of 99.16%,97.86%and 98.69%was obtained by hydrogen direct reduction process at 950℃ for 3h.Compared with coal based reduction,the bonding strength between hydrogen reduction particles was weak,and the gas molecules were easier to diffuse into the reactants,so the hydrogen reduction reaction was easier to carry out.The chemical composition index of hydrogen direct reduction iron powder far exceeded the requirements of MHF200 superior iron powder for powder metallurgy,and the process performance index was close to its requirements.Taking the iron powder as the iron source,lithium iron phosphate powder with high purity and uniform particle size could be prepared by wet combined fire process.Figures 49,Tables 25,References 96.