Kinetics Calculation of the Non-isothermal Reduction of Pellet

The reduction tests of pellet were carried out from room temperature to 1,373 K in the condition of traditional blast furnace (TBF) and oxygen blast furnace (OBF) by thermogravimeter measurement. The apparent activation energy E, pre-exponential factor A and the controlling steps of reaction were determined by the nonisothermal method of Coats-Redfern. In the condition of TBF, the reduction is controlled by solid diffusion to interfacial chemical reaction at initial stage, and gas diffusion at final stage. In the condition of OBF, the controlling step switched from solid diffusion to gas diffusion + interfacial chemical reaction in the beginning and the interfacial chemical reaction at the late stage. Meanwhile, the transition temperature points of the controlling step were predicted. The transition temperatures are 750 degrees C and 900 degrees C in TBF and 630 degrees C (earlier 120 degrees C than in TBF) and 900 degrees C (after the insulation) in OBF.