A New Approach of Pelletizing: Use of Low-Grade Ore as a Potential Raw Material

Abstract

For carbon neutrality, the use of sinter should be decreased owing to higher CO₂ emission in the sintering process of the blast furnace operations. This trend might contribute to the increased use of iron ore pellets with lower CO₂ emission in the fabrication process, high reducibility and gas permeability due to higher mechanical strength. The pelletizing process mostly uses high-grade iron ore such as magnetite (Fe₃O₄) as the main raw material, which has been depleted due to the increasing demand for pellet production. The current study attempted to replace magnetite ore with low-grade limonite ore (Fe₂O₃∙nH₂O) at different additional levels (10, 30, 50 and 100 wt%). The augmented limonite content influenced the increase in the porosity of pellets, which resulted from dehydration. The effect of microstructure on the compressive strength of mixed pellets before reduction and the reduction behavior of mixed pellets in a hydrogen atmosphere could be elucidated by porosity and pore size distribution analysis. The integration of limonite with magnetite facilitated the formation of small-sized pores, which in turn resulted in a significantly enhanced microstructure, with the limonite-mixed pellets demonstrating compressive strength comparable to that of magnetite pellets. The goethite phase provided a pathway for hydrogen permeability, and consequently, the reduction degree of limonite-mixed pellets in a H₂ atmosphere amounted to a reduction degree of 80%, which is similar to that of magnetite pellets. The mechanical strength of mixed pellets during reduction suggests their potential to withstand the stack layer in blast furnace operations. These findings could suggest the potential to utilize low-grade iron ore pellet process.

Graphical Abstract

Enhancing blast furnace sustainability via pellet feed optimization