The nitrogen reaction between carbon saturated Iron and Na₂O-SiO₂ slag: Part II. Kinetics

Abstract

The kinetics of the nitrogen reaction between carbon saturated iron and Na₂O-SiO₂ slags and between Na₂O-SiO₂ slags and an inert gas phase were investigated at 1200 °C. For the nitrogen transfer from the iron alloy to slag, the overall mass transfer coefficient of nitrogen was calculated to be 2.2 × 10⁻⁴ cm/sec. For nitrogen transfer from Na₂O-SiO₂ slag to argon gas, it is shown that the rate controlling process is mass transfer in the slag phase, and the mass transfer coefficient of nitrogen is 9 × 10⁻⁴ cm/sec. Experiments were also conducted to demonstrate nitrogen removal from hot metal by Na₂CO₃ treatment at 1200 °C. In these experiments, 325 grams of Na₂CO₃ was added to the 6.5 kg of Fe-C-N(-Si) alloy. When the metal contained silicon, nitrogen was transferred from the iron alloy to slag after the silicon was oxidized. When the iron alloy contains no silicon, nitrogen removal was faster. In both cases the nitrogen reversion occurred because of the decrease of slag volume and slag basicity. Furthermore, the presence of silicon in the metal retarded nitrogen reversion.