Effect of iron ore particle assimilation on Sinter structure

The properties of the melt generated during sintering determine the structure of the bonding phases formed. Melts that do not undergo reshaping and coalescence solidify into porous structures and this could have an adverse effect on sinter properties. The properties of melts, just prior to solidification, are highly dependent on the chemical composition of the adhering fines layer in granules and the assimilation behaviour of the nuclear particles. In this study, a carefully controlled bench-scale furnace was used to manufacture analogue sinters, which were characterized using optical microscopy and image analysis. Results show that altering the lime, and silica content of the adhering fines changed the structure of the analogue sinters formed because this altered the ability of the melt generated from the adhering fines, or primary melt, to react with iron oxide. The properties of the ore nuclear particles-in particular, porosity-have a significant influence on the proportion assimilated during the sintering period. The assimilation mechanism is different for porous ores because primary melts are highly mobile and readily penetrate into pores. Results also indicate that because of differences in assimilation mechanism, there are benefits in increasing the volume of primary melt (i.e. increased level of fines) when sintering blends containing high levels of porous ores. Maximum sintering temperature was also shown to be important because it influences assimilation rate and the viscosity of melts.