Research on Using Limestone for Slagging during BOF Steelmaking Process

This paper introduced the primary research on the method of using limestone instead of lime for slagging during BOF steelmaking. The study showed that the heat is sufficient for limestone to completely replace lime on the condition that the ratio of hot metal to ferrous scrap is adjusted properly. According to thermodynamic calculations, the partial pressure of CO2 at the hot metal surface at the early stage of converter steelmaking is close to 0 and nearly all the CO2 can react with elements in hot metal, producing CO and reducing O-2 consumption. Slag with high oxidizability, high basicity and relatively low temperature can be formed quickly by using limestone, which is advantageous for dephosphorization. Industrial tests showed the endpoint Lp rises with the proportion of lime replaced by limestone increasing. CO2 volume expands by 4000 similar to 30000 times when limestone is heated at extremely high speed in converter, resulting in the fragmentation of some parts of limestone and the increase of the contacting area of limestone and slag. The unreacted core model with surface exfoliated was introduced.