Estimating effect of chrome ore granulometry on sintered pellet properties

Chromite ore pellets are used for ferrochrome production by the smelting reduction process. The strength and porosity of the sintered pellets play a significant role in smelting reduction. Granulometry of the chromite fines used for pellet production is an imperative enabler which controls the pellet strength and porosity by packing of particles and formation of bonds due to melting of gangues at high temperature sintering. The effect of chromite ore granulometry and sintering process parameters was evaluated to improve the metallurgical performance of pellets in a submerged arc furnace. The drop test, compressive strength and porosity of sintered pellet samples from plant and laboratory tests were evaluated. Mathematical correlations of the pellet properties (strength and porosity), ore granulometry and sintering parameters were determined using Statistica (ver7), statistical software package. It was found that ore granulometry, i.e. particle size, plays a vital role in the pelletisation process by controlling the number of contact points for bond formation and due to different liberation and smelting reduction characteristics of gangue minerals. It was concluded that for Sukinda chromite ores, required pellet properties can be achieved by maximising the 74-37 μm fraction of chromite fines in the charge and sintering at 1000°C.