Enrichment of Fe-Containing Phases and Recovery of Iron and Its Oxides by Magnetic Separation from BOF Slags

摘要

Steel slag normally contains a large amount of iron and its oxides. Therefore, it is a potential renewable resource in case of inadequate iron ore supply. To recover the metals from steel slag, two types of BOF slags were remelted at 1873K. The liquid slags were cooled using four types of cooling conditions, namely, water granulation, splashing, air cooling, and furnace cooling, to investigate the influence of cooling rate on mineral components, especially the enrichment behavior of Fe-containing minerals. Subsequently, wet magnetic separation was conducted to examine the relations between iron recovery ratio and cooling conditions. The results show that the slags under the four cooling conditions mainly contained dicalcium silicate, RO phase, Fe_tO, 2CaO(Fe,Al)_2O_3, and calcium ferrite. However, tricalcium silicate, 12CaO-7Al_2O_3, M-A spinel, and free CaO and MgO were occasionally observed. The amount of glass matrix decreased, the Fe-containing minerals increased, and the minerals more fully crystallized when the cooling rate of the liquid slag was decreased. From granulation to furnace cooling of the slags, the iron content in the recovered concentrate and the iron recovery ratio both increased. This result is in agreement with the findings on phase transformation through SEM analysis.