The Chemical Diffusivity of Oxygen in Liquid Iron Oxide and a Calcium Ferrite

Measurements have been made of the chemical diffusion coefficient of oxygen in liquid iron oxide at temperatures from 1673 to 1888 K and in a calcium ferrite (Fe/Ca = 2.57) at temperatures from 1573 to 1873 K. A gravimetric method was used to measure the oxygen uptake during the oxidation of the melts by oxygen or CO2-CO mixtures. The rate was shown to be con trolled by mass transfer in the liquid melt. The chemical diffusivity of oxygen in liquid iron oxide at oxygen potential between air and oxygen was found to be 4.2 ± 0.3 x 10-3 cm2/s at 1888 K. That in iron oxide at oxidation state close to iron saturation was established to be given by the empirical expression log D = -6220/T + 1.12 for temperatures between 1673 and 1773 K. For the calcium ferrite (Fe/Ca = 2.57) at oxygen potential between air and oxygen, the diffusivity of oxygen was found to be given by log D = -1760/T - 1.31 for temperatures between 1673 and 1873 K.