High temperature co-processing of basic oxygen furnace slag and blast furnace slag: Self-pulverization and reduction mechanism

The treatment of basic oxygen furnace (BOF) slag with low energy consumption and high efficiency still presents challenges. In order to achieve the comprehensive utilization of BOF slag, a novel process is developed for co-processing of basic oxygen furnace slag and blast furnace slag. The influence of process parameters on the phase transformation, the reduction mechanism of P and the self-pulverization separation of slag were investigated by combining chemical analysis, XRD, thermodynamic calculations, EPMA and kinetics. The results showed that at BFS/BOF slag mass ratio 3:7, reduction temperature 1600 °C and reduction time 60 min, the iron-containing phase and Ca₂SiO₄-Ca₃(PO₄)₂ in the slag transform into iron alloys and Ca₂SiO₄ phases. P is reduced and enters the reduced iron, eliminating the negative effect of P on the C₂S crystalline transformation. Finally, during the cooling process, Ca₂SiO₄ transforms from β to γ, resulting in volume expansion, and the self-pulverization rate of the slag reached a maximum value of 79.44 %. After sieving, the reduced iron with a grade of 77 % is obtained, which can be recycled as pig iron. This process not only improves the overall efficiency of slag modification, but also contributes to more effective utilization of slag resources.