Determination of interfacial reaction rate constant of nitrogen between N₂–CO₂–CO–Ar and molten iron using isotope exchange technique

The application of CO₂ in the steelmaking process has yielded promising results, demonstrating a certain capability for nitrogen removal. To accurately determine the kinetic parameters of nitrogen reactions at the iron melt interface under CO₂ injection conditions, an isotope exchange technique was employed. This technique was used to monitor the evolution of the nitrogen isotopic composition during the reaction between a ²⁸N₂–³⁰N₂–CO₂–CO–Ar gas mixture and an iron melt of controlled composition. The kinetic parameters of nitrogen were subsequently calculated for various CO₂/CO ratios. Furthermore, the dissociation rate determining model was applied to establish the relationship between the interfacial reaction rate constant (k_c) and the activity of surfactive elements (O, C, and S) in molten iron (a_O, a_C, and a_S), expressed as k_\rm c=\dfrac4.35\times10^-6\left(1+14.25a_\rm O+0.25a_\rm C+6.50a_\rm S\right)^2 .