Investigation of the Influence of Slag Basicity on Metal Droplet Dephosphorization

As a part of ongoing work on metal droplet dephosphorization, this study specifically investigated the effect of slag basicity (V ratio) by employing time lapse sampling while monitoring simultaneous decarburization using a constant volume pressure increase technique (CVPI) with X-ray fluoroscopy. The dephosphorization kinetics of droplets with two different initial carbon concentrations (2.51 and 0.007 wt pct), were tracked by quenching and analyzing droplets after different reaction times. The reaction kinetics were further elucidated by combining the decarburization rate of the droplet, measured via CVPI with the bloating behavior of droplet observed in-situ by X-ray fluoroscopy. The results showed that for high carbon droplets the dephosphorization rate increased with increasing slag basicity largely due to the increasing droplet decarburization rate, which enhanced mass transport of phosphorus by CO bubble stirring. Further increasing slag basicity increased the peak decarburization rate, but did not appear to further increase droplet dephosphorization. In low carbon droplets, the dephosphorization rate was also increased with increasing slag basicity because of the higher phosphorus partition ratio and larger mass transfer parameter kA resulting from the faster oxygen transfer in the slag causing an increase in the interfacial area for reaction.