Dissolution of Fe2O3 and FeO Pellets in Bath Smelting Slags.

Abstract

The rate of the dissolution of hematite and wustite pellets in bath smelting type slags was investigated at 1723 K. The rates were measured by the change in their diameter and the rate of gas evolution from the pellet. The diameter of the pellets, as a function of time, was obtained from recorded X-ray radiograph pictures. For unstirred slags it was found that the rate of the dissolution of hematite pellets was faster than that of wustite pellets due to gas evolution from the hematite pellets which increases heat and mass transfer. The rate of the dissolution of wustite and hematite pellets were much faster in slags stirred with argon and, in this case, wustite dissolved faster. The rate of gas evolution during the dissolution of hematite with an inert gas over the slag was also measured by using a mass flowmeter. The rate of gas evolution was also determined under different CO-CO2 gas mixtures by analyzing the off gas with a mass spectrometer. It was found that the amount of oxygen evolved increases with decreasing the CO2/CO ratio. From the experimental results the heat transfer coefficient for the present conditions was estimated. These values were extrapolated to the actual operating conditions of a bath smelter and the melting time and the amount of undissolved pellets at the steady state in the slag were calculated. It was estimated that the pellets melt in less than 10 sec and the fraction of unmelted pellets, in the slag in a typical practice, is less than 1% of the volume of the slag. The rate of production in a bath smelter depends on the amounts of Fe2+ and Fe3+ resulting from the dissolution of the pellets. The present results indicate that for Fe2O3 pellets the rate of iron production will be about 25% less than for FeO.