Variation of the redox conditions and the resultant phase assemblages during iron ore sintering

Abstract

The oxygen potential prevailing during iron ore sintering wasmeasuredwith a zirconia sensor in a series of sinter pot experiments. Thiswas done to get a better indication of the redox conditions during commercial sintering. It was found that the pO2 is appreciably more oxidizing than previously assumed, with a minimum value of ~0.01 atm. It is concluded that this value represents the oxygen potential of the gas phase and it is therefore a mixture of combustion gas and downdraft air. The contents of a quenched sinter pot where the reactions were interrupted with the flame front situated midway through the sinter bed were investigated. X-ray diffraction analysis, using an internal standard to quantify the amorphous slag phase, revealed that at the flame front only magnetite and slag were present. SFCA phases only formed at the top of the bed after the flame front had passed. Thermodynamicmodeling of the phases at equilibriumagree qualitativelywith the phase analysis and explained the extensive presence of magnetite and melt, as well as the formation of calcium ferrite phases during cooling below 1100 °C.