Usage of High-LOI Iron Ore Fines in Pellet Making

Abstract

Loss on ignition (LOI) in the mineral represents the chemically bonded water which can be removed at high temperatures only. High LOI in iron ore fines has an adverse affect during pellet induration process. High-LOI iron ore fines are required for detailed laboratory pelletization studies and are used in pellet making. The received iron ore is martite–goethitic and hematite–goethitic form of ore with high LOI content. The iron ore consists of 57.7% Fe, 6.19% SiO2, 2.69% Al2O3, 8.80% moisture and 8.85% LOI. From thermo-gravimetric analysis, the LOI removal temperature is 280 to 450 °C and time required for complete LOI removal is 10 to 12 min. Detailed laboratory and pilot-scale pelletization studies have been carried out to optimize the induration furnace cycle for utilization of 100% high-LOI iron ore fines as well as optimum utilization of high-LOI iron ore fines in the present pellet plant induration furnace without changing the firing cycle. From laboratory studies, it has been found that for utilization of e 100% high-LOI iron ore fines (7–9%) in pellet making to achieve desired pellet properties, induration firing cycle should be increased from 54 to 62 min (Drying: 2 min, Preheating: 3 min) and increase in firing temperature by 20 °C results in reduction in pellet production by 14.8% and additional raw material consumption is increased by 4.09% for production of 12,000 t/day pellets. From laboratory as well as pilot-scale studies, it has been found that up to 20% FMG ore can be mixed in the pellet ore blend without affecting the properties of the pellet at the present operating conditions of pellet plant. With the increase in green pellet carbon from 1 to 1.2%, there are no improvements in firing temperature 1300 °C.