CO₂ conversion and decarburization kinetics of CO₂ gas and liquid Fe–C alloy at 1873 K

The reactions between CO₂ gas and liquid Fe–C alloy with different initial carbon concentrations at 1873 K were investigated using experimental results, thermodynamic equilibrium, and kinetic analysis. The average CO₂ conversion is greater than 80% when the carbon content ranges from 4.0 to 1.0 wt.%. When the carbon content decreases from 0.5 to 0.1 wt.%, the average CO₂ conversion diminishes from 83.50% to 40.84%. This proves that CO₂ gas and liquid Fe–C alloy reaction does not reach equilibrium under experimental conditions compared with the calculated thermodynamic data. Through the kinetic analysis, it is shown that in the medium- to high-carbon liquid Fe–C alloys, the rate-controlling step involves CO₂ gas mass transfer or mixed rate-controlling of CO₂ gas mass transfer with adsorption and dissociation of CO₂ gas. In contrast, in the low-carbon liquid Fe–C alloy, carbon mass transfer occurs in the molten alloy. The critical carbon content of the rate-controlling step transformation is 0.7937 wt.%.