Rate of interfacial reaction between molten CaO-SiO2-Al2O3-Fe x O and CO-CO2

Abstract

Measurements of the rates of reduction of iron oxide from molten CaO-SiO2-Al2O3-Fe x O slags by Ar-CO mixtures have been made using a thermogravimetric method. The apparent first-order rate constant, with respect to the partial pressure of CO, of the gas/slag interfacial reaction was deduced from the measured rates, where the effects of the mass transfer in the gas and slag phases were minimized. It was found that the apparent first-order rate constant decreased with the concentration of ‘FeO’ from 100 to 20 wt pct, whereas it remained essentially constant in the range from 5 to 20 wt pct ‘FeO’. At a given iron oxide concentration, the reduction-rate constant increased significantly with an increase in the CaO/SiO2 ratio. For fixed slag compositions, the reduction rate increased slightly with the oxidation state of the slags. When the rate constant is expressed in the form of k=k′(Fe3+/2+)α, the values of α range from 0.15 to 0.25. The effect of temperature in the range from 1673 to 1873 K on the reduction rate of iron oxide in a 40.4CaO-40.4SiO2-14.2Al2O3-5‘FeO’ (wt pct) slag was studied. The calculated activation energy, based on these results, is 165 kJ/mol.