The Effect of Coke Powder on the Iron Ore Fines Reduction by Carbon Monoxide

Iron ore fines and coke powder are synergistically reduced in a drop-tube reactor. The effects of temperature, CO concentration, and the blending ratio (BR) of coke powder are investigated. The results show that increasing temperature promotes reduction within the range of 800-1200 °C, while CO concentration has a lesser effect. The kinetic mechanism can be explained by a nucleation-and-growth model, and the activation energies for iron ore fines, the mixture with fine coke powder at BR = 0.4, and the mixture with the same particle size coke powder at BR = 0.4 are 19.09 kJ/mol, 50.61 kJ/mol, and 47.80 kJ/mol, respectively. Coke powder causes the outlet CO concentration to be equal to or greater than the inlet CO concentration and the outlet CO₂ concentration decreases. Increasing BR from 0.4 to 0.8 and 0.8 to 1.2 mainly promoted the conversion of Fe₃O₄→FeO and FeO→Fe, respectively. The sticking index reached a minimum of 0.86% when BR = 0.4. However, overall sticking inhibition was more effective when BR = 1.2. The mechanism of sticking inhibition is that the coke powder acts as a physical barrier, reducing the collision and contact probability between the iron ore fines, thereby preventing iron whiskers from entangling or bridging.