CO2-Free Flux for Sustainable Iron Ore Pelletizing

Abstract

The iron and steel manufacturing sector directly accounts for 7–9% of global CO₂ emissions. Raw material preparation, such as iron ore sintering, pelletizing, and cock making, is the major CO₂ emitter. As climate change becomes a bigger concern, steel manufacturers need to lower CO₂ emissions without hindering efficiency or increasing costs. In recent years, the percentage of iron ore pellets in blast furnaces has increased due to its uniform size, good reducibility, and high tumbler index. Pelletizing is energy-intensive and emits considerable CO₂. Around 20% of CO₂ emissions during pellet making come from fluxes. In the present work, the authors established a novel CO₂-free flux called wollastonite (CaO.SiO₂) for sustainable palletization. Pellets with varying percentages of wollastonite (0–6%) are prepared and tested for chemical, physical, and metallurgical properties. Image analysis through an optical microscope is carried out to quantify the phases of fired pellets. SEM–EDS is performed to evaluate the chemical composition of the melt and slag phases. The results showed that the reducibility index (RI) and swelling index (SI) of pellets decreased with an increase in wollastonite dosage. Pellet strength increases with an increase in wollastonite addition up to 1.2% CaO (2.27% wollastonite), and a decrease in strength is observed thereafter. The increase in strength is attributed to the increase in slag bonds. The decrease in strength beyond 1.2% CaO is mainly because of an increase in low melting eutectics and more magnetite content. Pellets with 2.27% wollastonite to get 1.2% CaO showed good physical and metallurgical properties.

Graphical Abstract