Non-isothermal Kinetics of Carbothermic Reduction of Fayalite

Fayalite is one of the major components in many metallurgical slags, such as copper slag and nickel slag, which contains higher iron grade than that in minable iron ores. It is believed that the carbothermal reduction process at high temperature is an effective way to reutilize fayalite-bearing slags. In this paper, the non-isothermal reduction kinetics of fayalite were conducted using a thermogravimetric differential thermal analyzer heated to 1400 °C with different heating rates. The methods of Flynn-Wall-Ozawa and Malek were adapted to handle the kinetic data. The results show that the activation energy increases until the conversion rate is 50% due to the deterioration of kinetic conditions, and then decreases. The average activation energy is 514.20 kJ/mol. When the conversion rate is lower than 50%, the reaction model is the secondary chemical reaction model with the integral form of (1−α)2. Subsequently, with the conversion rate increasing, the model changes to the uniform growth of one-dimensional nucleation with the integral form of lnα.