The Influence of Sulfur on Dephosphorization Kinetics Between Bloated Metal Droplets and Slag Containing FeO

The bloating behavior of metal droplets and the dephosphorization behavior of bloated droplets at 1853 K (1580 °C) were investigated using X-ray fluoroscopy coupled with constant volume pressure change measurements and chemical analysis of quenched samples. The effect of sulfur content on dephosphorization kinetics was studied during the decarburization period. The slag foamed during the reaction forming a foamy layer over a dense layer. After a short incubation period, the droplets became bloated due to internal decarburization. The bloated droplets floated from the dense slag into the foamy slag. The behavioral changes are directly related to the effect of sulfur on the incubation time for swelling. The dephosphorization reaction was very fast; droplets with low sulfur contents experienced phosphorus reversion shortly after entering the foamy slag, while those with higher sulfur content took a longer time to swell and went through reversion before they entered the foam. The dephosphorization rate and maximum phosphorus partition were higher at lower CO evolution rates because the dynamic interfacial oxygen potential increased with the decreasing oxygen consumption rate. The rate controlling step for dephosphorization was initially a combination of mass transport in both the metal and the slag. As the iron oxide in the slag was depleted, the rate control shifted to mass transport in slag.