Effect of flux granulometry on the sintering process using thermodynamic analysis

Granulometry of fluxes plays a vital role in melt formation during sintering and ultimately affects sinter quality. This primarily depends on viscosity and chemistry of
melt formed in the process which in turn depends on several parameters such as the
alumina content of iron ore (and therefore base mix), the amount and type of flux added to
the base mix as well as reducing conditions. Limestone and pyroxenite are the two major
fluxes used in sintering. Smaller sized materials (typically less than 1 mm) in the base mix
form the primary melt during sintering and subsequently dissolve the derivatives of iron
along with gangue. Sinter quality is greatly affected by flux granulometery because of
alternation in the local melt chemistry. Despite of various efforts in direct correlating the
sinter quality with melt chemistry, no insights can be provided in improving the process
parameters. Therefore, thermodynamic modelling studies can influence on changes in
flux granulometery on sinter phases, which forms the basis of this work. In this study, the
effect of the <1mm fraction of limestone and pyroxenite on sinter phases was investigated
using thermodynamic analysis. Percentage of -1mm fraction in fluxes, limestone and
pyroxenite, was varied in base mixture to get different local chemistries for bulk chemistry
of sinter. Thermodynamic heating and cooling cycle’s analysis was performed to predict
the final phases in the sinter. Analysed results revealed that with increase of percentage of
-1mm in limestone results in increase of calcium ferrite in sinter with availability of CaO and
magnetite, spinel and silicate phases gets predominant with higher percentage of pyroxenite.
Keywords : Iron ore sintering, Thermodynamic analysis, Granulometry.