Abstract
In ore-based steelmaking, blast furnace (BF) dust is generally recycled to the BF via the sinter or cold-bonded briquettes and injection. In order to recycle the BF sludge to the BF, the sludge has to be upgraded, removing zinc. The literature reports cases of recycling the low-zinc fraction of upgraded BF sludge to the BF. However, research towards recycling of the high-zinc fraction of BF sludge within the ore-based steel plant is limited. In the present paper, the high-zinc fraction of tornado-treated BF sludge was incorporated in self-reducing cold-bonded briquettes and pellets. Each type of agglomerate was individually subjected to technical-scale smelting reduction experiments aiming to study the feasibility of recycling in-plant residues to the hot metal (HM) desulfurization (deS) plant. The endothermic reactions within the briquettes decreased the heating and reduction rate leaving the briquettes unreduced and unmelted. The pellets were completely reduced within eight minutes of contact with HM but still showed melt-in problems. Cold-bonded briquettes, without BF sludge, were charged in industrial-scale trials to study the recycling potential to the HM deS plant and basic oxygen furnace (BOF). The trials illustrated a potential for the complete recycling of the high-zinc fraction of BF sludge. However, further studies were identified to be required to verify these results.
Highlights
Ore-based steelmaking generates a variety of residues including dusts, sludges, scales, and slags
As the basic oxygen furnace (BOF) has been recognized as a possible recycling route for in-plant residues, a logical succession is to study the potential of recycling the high-zinc fraction of upgraded blast furnace (BF) sludge using this process
As agglomerates including high carbon-containing BF flue dust have been successfully recycled to the BOF [9,10], the rise of melt-in problems are most likely to be seen when recycling to the hot metal (HM) deS plant
Summary
Ore-based steelmaking generates a variety of residues including dusts, sludges, scales, and slags. As the BOF has been recognized as a possible recycling route for in-plant residues, a logical succession is to study the potential of recycling the high-zinc fraction of upgraded BF sludge using this process. In the present paper, smelting reduction of cold-bonded agglomerates in the form of briquettes and pellets was studied in technical-scale experiments aiming for recycling the high-zinc fraction of upgraded BF sludge in the HM deS plant. The potential for recycling the sludge was studied in industrial-scale trials by charging cold-bonded briquettes, without BF sludge, to the HM deS plant. In order to study the feasibility of improving the recycling capacity while maintaining the high quality of the final steel, the cold-bonded briquettes were charged to the BOF in industrial-scale trials as well. The sulfur pick-up of the crude steel was addressed by producing and characterizing cold-bonded briquettes produced with binders of low-sulfur contents in laboratory-scale
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