Effect of pyroxenite and olivine minerals as source of MgO in hematite pellet on improvement of metallurgical properties

Abstract

Pelletization of hematite ore requires high fineness and very high induration temperature (~1325 °C) owing to its poor diffusion bonding unlike magnetite ore. Further, high-alumina hematite pellets show very high reduction degradation index (RDI) during low temperature (500–650 °C) reduction due to their volume expansion and lattice distortion. Noamundi (India) hematite ore contains very high Al2O3 (2.3%) with adverse ratio of alumina to silica (~2) for which, it shows very high RDI. In this work, the acid pellets prepared from Noamundi ore fines of optimum Blaine fineness show good cold crushing strength (CCS). However, it shows very high RDI (77%). In order to reduce RDI, MgO in form of two different gangue-containing fluxes, such as pyroxenite and olivine in varying quantities has been added. The optimum requirement and performance of these fluxes has been examined and compared. Both pyroxenite and olivine fluxed pellets show significant lowering of RDI (26% and 23%, respectively) and improvement of other properties, viz CCS, swelling indices etc with good reducibility (70%–77%). Finally, a good quality acidic hematite pellet was developed from high-alumina ore without using any lime which is very important charge material in combination of basic sinter in blast furnace.