Kinetics of the reaction of C₂H₆, CH₄-CO₂ and CO-CO₂-O₂ gases with liquid iron

The kinetics of several gas-metal reactions relevant to bath smelting have been investigated. The rate of carburization of liguid iron by C₂H₆ gas was measured between 1 400 and 1 600 °C under conditions in which partial pressure of C₂H₆ was in the range of 0.016 to 0.04 atm and sulfur content in the iron was in the range of 0.003 to 0.5 wt%. The experimental results indicate that the rate is controlled by the dissociation of C₂H₆ on the surface of iron and gas phase mass transfer in series. The gas phase mass transfer can be corrected with reasonable accuracy and the chemical rate constants were obtained. The rate was retarded by sulfur in liquid iron and there was evidence of a large residual rate at high sulfur contents. The rate of carburization of pure liquid iron (a_s = 0.01) by CH₄-CO₂ gas mixture was measured at 1 600 °C under conditions at which the rate is controlled by gas phase mass transfer and chemical reaction in series. The gas was 6% CH₄ and up to 2.5% CO₂ in Ar. It was concluded that CH₄ and CO₂ reached the surface of the iron before they reacted with each other and carburization by CH₄ and decarburization by CO₂ occurred independently for the present experimental conditions. The rate of decarburization of carbon saturated liquid iron by CO-CO₂-O₂ gas mixture was measured at 1 600 °C. The partial pressure of O₂ in 90%CO/10%CO₂ gas was in the range of 0 to 0.03 atm and sulfur content in the metal was 0.1 wt%. The measured rate shows that the gases reached the surface of metal before they reacted with each other and decarburization by CO₂ and O₂ proceeded independently at a high gas flow rate (5 l/min), but there may have been some gas phase reaction at lower flow rate (2 l/min).