Research on the mechanism of high-efficient slagging and dephosphorization of bottom-blown limestone powder in converter furnace

The traditional lime slagging steelmaking process suffers from the limitations of high energy consumption and high emissions. The use of blown limestone powder can create local low-temperature zones within the molten pool to enhance the dephosphorization efficiency. Therefore, this study proposes a high-efficiency slagging smelting technology using converter-blown limestone powder. Compared with the traditional lime calcined in a kiln, this technology directly blows 0.18–1.0 mm particle size limestone powder into the melting pool of the converter, and realizes rapid decomposition by using high temperature (the activity degree of 0.44 mm particles reaches 350 mL in 60 s), which eliminates the need for lime calcination and reduces CO 2 emissions from the source. The CO 2 generated from the decomposition can optimize the kinetic conditions of the melt: on the one hand, it can participate in the reaction as an “endogenous oxygen source” to enhance the value of gas recovery; on the other hand, it can enhance the stirring of the melt, which can increase the decarburization rate by 1.68 times at a flow rate of 40 mL/min of CO 2 . Under the process conditions of 1400°C, alkalinity R = 3.5 and FeO content of 20%, the endpoint dephosphorization rate is over 85%, and the initial dephosphorization rate reaches 0.0118%/min, which is significantly higher than that of 0.0098%/min of traditional lime, and the fine-grained CaO enlarges the slag-gold reaction interface, and the foam slag formation ability is better. The simultaneous realization of high-efficiency dephosphorization and CO 2 resource utilization provides a feasible path for green low-carbon steelmaking with both economic and environmental benefits.