Sintering characteristics and kinetics of acidic haematite ore pellets with and without mill scale addition

Abstract

Haematite ore pellets require very high induration temperature (>1573 K) while, magnetite ore pellets require much lower temperature due to the oxidation of magnetite during induration. Mixing of some magnetite in haematite ore can improve the sintering property of pellets during induration. Mill scale is a waste material of steel plant which contains mainly FeO and Fe3O4. It can also be blended in haematite ore pellet mix which can enhance diffusion bonding and recrystallisation bonding and facilitate sintering at the lower temperature like magnetite ore. The extent of improvement in sintering property, sintering mechanism and its kinetics in the presence of mill scale is very imperative to study. In current study, the sintering characteristics of acidic iron ore pellet with 15% mill scale and without mill scale has been studied separately through microstructure observation, apparent porosity measurement and volume change. The volume changes due to heating at varying temperature and time has been measured by mercury displacement method and the data has been exploited for sintering kinetics study, wherein, extent of sintering alpha has a power relation with time. Several kinetics parameters such as time exponent (n), rate constant (k) and activation energies have been estimated for above two pellets and compared. While acidic pellet without mill scale requires 385 k cal mol(-1), acidic pellet with 15% mill scale requires only 310 k cal mol(-1) activation energy.