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

Abstract

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 1873 K. 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, FetO, 2CaO(Fe,Al)2O3, and calcium ferrite. However, tricalcium silicate, 12CaO·7Al2O3, 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.

Crystallization Behavior of Liquid CaO-SiO2-FeO-MnO Slag in Relation to Its Reaction with Moisture

“…In general, the crystallization temperatures of precipitated phases became lower with increasing the cooling rate from 10 K/min to 800 K/min, which is to be expected. A similar trend was reported previously concerning the crystallization behavior of synthetic coal ash slag [33] and BOF slag [34] under different cooling rates. It can be understood that the increasing of cooling rates resulted in larger increase in slag viscosity as temperature was lowered before crystallization commenced enabling a higher degree of undercooling (a lower crystallization temperature).…”

Modification of microstructure of LD slag for recovery of hybrid flux material

“…The rationale put here for the difference in the grade of coarse and fine particles also agrees with few research works conducted on studying the of grindability of steel slag. The work done by Wang et al [25] also found similar results when studying the cementitious property of steel slag powder based on their size. In this study, XRD studies were conducted with fine and coarse fractions of steel slag, and it was observed that coarse particles contained more of RO phase and wustite phase while the finer fractions contained more C3S and C2S.…”

Scenario Analyses for By‐Products Reuse in Integrated Steelmaking Plants by Combining Process Modeling, Simulation, and Optimization Techniques

“…The reactivity with water increases with the application of rapid cooling . Moreover, the slow cooling of BOF slag, promoting the good distribution of crystals, results in a fraction with high iron and low phosphorus content . By controlling the additions under a rapid cooling condition, the extraction of metallic iron can be performed by the carbothermic reduction reaction, and the remaining slag can be used for construction applications .…”