Kinetics of Phosphorus Transfer between Iron Oxide Containing Slag and Molten Iron of High Carbon Concentration under Ar-O₂ Atmosphere

Abstract

In the present report, the results are described of kinetic experiments of phosphorus reaction in a molten CaO-Li₂O-SiO₂-FeO-Fe₂O₃ slag/Fe-4.4%C molten metal/Ar-O₂ gas (P_O2=0-0.2 atm) system. The experimental temperature is 1300°C and the slag-metal bath is stirred by an eccentric alumina stirrer (rotation speed, R=30-300 rpm). From the experimental results, it is found that dephosphorization rate increases with increasing the oxygen partial pressure of the Ar-O₂ gas atmosphere. The change in the stirrer's rotating speed does not affect the dephosphorization rate obviously, while rephosphorization rate increases with increasing the stirring speed. It is also shown that maximum phosphorus concentration ratio, ((%P)/[%P])_max, obtained at the time point when the phosphorus reaction changes from dephosphorization to rephosphorization, increases with the increase in the ratio of ferric iron to total iron of the slag. The ((%P)/[%P])_max ratio decreases with increasing the stirring speed in the range of R>50 rpm. The relation between the experimental conditions and the rate of the phosphorus reaction accompanied by simultaneous slag-metal-gas reactions are interpreted qualitatively in terms of the change in a hypothetical slag-metal interfacial oxygen potential. The experimental results are explained quantitatively by means of a mathematical kinetic model calculations. The model calculation fits the experimental results resonably well.