Utilization of Cobalt Smelting Slag in Metallurgical Pellets and the Mechanism of Pellet Performance Enhancement

Cobalt smelting slag (cobalt slag) has a complex composition, and its disposal can lead to environmental pollution and resource wastage. Therefore, a novel method for producing metallurgical pellets was proposed using cobalt slag, magnetite, and bentonite as raw materials. The impact of cobalt slag addition on the comprehensive performance of the pellets and the impact on SO₂ emissions in the flue gas during the roasting process was studied. By analyzing the raw materials characteristics and pellet mineral structure, the mechanism for improving pellet performance was elucidated.The results indicate that as the mass fraction of cobalt slag increases from 0 to 2.0%, the green ball drop strength increases from 2.3 times/0.5 m to 13.6 times/0.5 m, and the average compressive strength increases from 11.5 N/mm² to 14.9 N/mm². The addition of cobalt slag significantly improves the comprehensive performance of the pellets. However, the high sulfur content in cobalt slag increases the concentration of SO₂ emission during roasting. Cobalt slag’s strong hydrophilicity plays the role of a binder in pellet feed, and its addition benefits the balling performance of pellet feed. Oxides of iron, calcium, silicon, aluminum, and other elements contained in cobalt slag react during the roasting process of pellets to form low-melting-point calcium ferrite liquid phase. An appropriate amount of liquid phase serves as a liquid-phase bonding agent, making the hematite crystal structure within the pellets more compact, reducing the internal porosity of the pellets, which helps to improve the compressive strength of roasted pellets.This study offers a new approach for the resourceful utilization of cobalt slag within the steelmaking process.