Contribution Oral Presentation
Reduction of Sticking Tendency of Iron Ore Pellets by Using Steel By-product as Coating Material
One of the challenges facing steel producers that rely on direct reduction technologies is the sticking tendency of iron ore pellets, which might lead to disrupting operational procedures. In an effort to reduce the sticking tendency of iron ore pellets, suppliers apply inactive coating materials and steel producers apply an additional coating in the form of slurry prior to charging pellets to the furnace.
In this work, the suitability of steel plant’s by-products to be used as a secondary coating material is investigated. In order to determine the optimum coating conditions, their influence on pellets reducibility and sticking index was quantified. The coating condition in question includes dosage amount and slurry concentration of the coating material. Coating amounts were varied in the range of 1-5 kg per ton of ore and slurry concentrations were varied in the range of 5-30% in this study. Thermogravimetric analysis was used to measure the relative reducibility of the pellets under different coating conditions. The reduction conditions were set to simulate reduction temperature and reducing gas composition in Midrex shaft furnace. The samples that exhibited higher reducibility were those at coating condition of:
• 20% slurry conc. & 3.0 Kg /ton iron ore
• 30% slurry conc. & 3.0 Kg /ton iron ore
• 30% slurry conc. & 4.0 Kg /ton iron ore
Sticking index measurements were determined according to ISO 11256 for these samples that showed relatively higher reducibility. Since the samples showed similar sticking index values, an additional optimization analysis in terms of operational cost was carried out. It was concluded that the coating conditions with optimum reducibility and adequate sticking resistance are 3.0 kg per ton of ore and 30% slurry concentration.