Carbothermic reduction kinetics of ilmenite concentrates catalyzed by sodium chloride and microwave-absorbing characteristics of reductive products

Abstract

Carbothermic reduction kinetics of ilmenite concentrates catalyzed by sodium chloride and the microwave-absorbing characteristics of the resulting reductive products were investigated; the reduction degree of the reaction was deduced to be $R = {{4(16y + 56x)(\Delta {W_\Sigma} - {f_{A - P}}W)} \over {7(16y + 56x + 112)}}$ . Results show that the activation energy is 112.03 kJ/mol when NaCl is used as catalyst, lowering to 23.11 kJ/mol for the final stage activation energy using sodium silicate as a catalyst. There is a sharp change in the reduction rate constant at temperature ranges of 1,223 K–1,273 K and 1,373 K–1,423 K. Microwave-absorbing characteristics of reductive products were measured by the method of microwave cavity perturbation. It was found that microwave-absorbing characteristics of reductive products obtained at temperatures of 850° C, 1,100° C and 1,150° C show sharp changes. Through X-ray diffraction (XRD) characterization, it was found that the formation of Fe occurs at a temperature of 900° C during the reduction process of ilmenite concentrate. The decrease of FeTiO3 content results in the decrease of microwave-absorbing characteristics, while the increase of Fe content gives rise to the increase of microwave-absorbing characteristics. The decreasing trend is larger than the increasing trend, which is the main reason for the sharp changes in the microwave-absorbing characteristics of reductive products at the temperature range of 850° C to 900° C. When the decreasing trend is smaller than the increasing trend, it becomes the main reason for the sharp changes in microwave-absorbing characteristics of reductive products at the temperature range of 1,100° C to 1,150° C. Kinetics results show that sodium chloride can catalyze the carbothermic reduction of ilmenite, and microwave-absorbing characteristic investigations indicate that microwave heating can be used in the carbothermic reduction of ilmenite.