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

摘要

(1) The chemical diffusivity of oxygen in liquid iron oxide and a calcium ferrite has been determined by directly measuring the oxygen uptake during the oxidation. (2) The chemical diffusivity of oxygen in liquid iron oxide at oxygen partial pressure between 0.21 and 1.0 atm was determined to be 4.2 (+-0.3) x 10~(-3) cm~2/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 = -6500/T + 1.27 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 - 2.31 for temperatures between 1673 and 1873 K. (3) It appears that the chemical diffusivity of oxygen in liquid iron oxide decreased with the oxidation state. The decrease is by approximately 40 pct between iron-saturation and equilibrium with oxygen at 1 atm. The strong dependence found by Mori and Susuki was demonstrated to be the results of the effect of interfacial chemical reaction. (4) The chemical diffusivity of oxygen increased when calcium oxide was added to iron oxide. (5) The measurement of previous studies, which generated the values of chemical diffusivity two orders of magnitude lower than the present results, was demonstrated to be dominated by the interfacial chemical reaction rather than liquid phase diffusion.