The iron and steel manufacturing sector directly accounts for 7 to 9 percent of global carbon dioxide (CO2) emissions. Raw material preparation — such as iron ore sintering, pelletizing and coke 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 percent of CO2 emissions during pellet making come from fluxes. In the present work, a novel CO2-free flux called wollastonite (CaO.SiO2) for sustainable pelletizing is established. Pellets with varying percentages of wollastonite (0 to 6 percent) were prepared and tested for their chemical, physical and metallurgical properties. Image analysis by an optical microscope was carried out to quantify the phases of fired pellets. SEM-EDS was 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 increased with an increase in wollastonite addition up to 1.2 percent CaO (2.27 percent wollastonite), and a decrease in strength was observed thereafter. The increase in strength is attributed to the increase in slag bonds. The decrease in strength beyond 1.2 percent CaO is mainly due to an increase in low-melting eutectics and more magnetite content. Pellets with 2.27 percent wollastonite to get 1.2 percent CaO showed good physical and metallurgical properties.
Full-text paper:
Mining, Metallurgy & Exploration (2024) 41:1035–1050, https://doi.org/10.1007/s42461-024-00949-9
