8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

Ore-based steelmaking generates a variety of residues including dusts, sludges, scales and slags. Recycling of these residues within the process or via other applications is essential for sustainable production from both environmental and economic aspects. In blast furnace (BF) ironmaking, the gas-cleaning equipment recovers the particles in the off-gas as BF dust and sludge. Traditionally, the dry dust is recycled via the sinter, but in the case of pellet based BF, recycling methods utilizing cold bonded briquettes and injection have been developed. Depending on the BF operation, the main output of zinc from the BF is more or less via the top gas. Therefore, as the dust is recycled, the sludge has to be dezinced prior to recycling to prevent accumulation of zinc in the BF. Although dezincing and recycling of the low-zinc fraction via sinter have been reported, research towards recycling of the high-zinc fraction of BF sludge within the integrated steelplant is lacking. In the present paper, the high-zinc fraction of tornado-treated BF sludge was incorporated in self-reducing cold-bonded agglomerates. The agglomerates were subjected to smelting reduction experiments aiming to study the feasibility of recycling the in-plant residues to the desulfurization plant. Difficulties in the melt-in of the agglomerates suggested that cold-bonded pellets were more suitable for recycling than cold-bonded briquettes. However, full-scale trials suggested that cold-bonded briquettes can be used to recycle in-plant residues to the desulfurization plant without affecting the desulfurization process and final steel quality.