Article ID: ISIJINT-2020-251
The abundant refractory titanomagnetite (TTM) provides a cheap alternative source of iron, but this ore contains impurities and is difficult to process to make suitable concentrates for the blast furnace. In this study, reduction roasting of a primary TTM concentrate followed by magnetic separation was investigated to understand the effects of reduction time, coal dosage, and CaF2 addition on the reduction behavior of TTM and growth mechanism of iron particles. The phase composition of reduced samples was characterized by X-ray diffraction. The size distribution of iron particles was quantitatively examined using image analysis. Results showed that CaF2 can help improve the reduction degree and particle size of metallic iron. The metallization degree increased from 85.5% to 89.5% when the CaF2 dosage increased from 0% to 4%, while a minor increase was observed when the CaF2 dosage exceeded 4%. Accordingly, the TTM samples were treated by reduction roasting with 4% CaF2 and 25% coal at 1200°C for 60 min followed by magnetic separation. A magnetic concentrate with an iron content of 91.1% and a recovery of 92.9% was achieved. In addition, the relationship between the size distributions of iron particles and grinding fineness was also studied. The size distribution using data from the diameter of iron particles was found to be close to the actual grinding fineness.