Microwave-absorbing characteristics of carbothermic reduction products of ilmenite concentrate catalyzed by sodium borate

Abstract

Carbothermic reduction kinetics of ilmenite concentrate catalyzed by sodium borate and microwave-absorbing characteristics of reduction products were investigated. Kinetics results showed that the reaction was controlled by the nuclei formation model, the apparent activation energy was 100.74 kJ/mol, which was lower about 34.40 kJ/mol and 11.29 kJ/mol compared with the final stage activation energy using sodium silicate and sodium chloride as catalysts, respectively. The final reduction degree was 54.95%, 64.14% at temperatures of 1423 K and 1473 K, respectively, higher about 32.21% compared with those results by sodium silicate under the same conditions. The microwave-absorbing characteristics of reduction products were measured by the method of microwave cavity perturbation. The results demonstrated that the microwave absorbing characteristics of reduction products obtained at temperatures of 900 °C, 1100 °C and 1200 °C changed greatly. The formation of Fe occurred at the temperature of 900 °C. The decreasing of FeTiO3 content resulted in the decrease of the microwave absorbing characteristics, while, the increasing of Fe content resulted in the increase of microwave absorbing characteristics. The decrease of FeTiO3 content and the increase of FeTi2 O5 (MgTi2 O5 ) content made the microwave absorbing characteristics decrease, the increase of Fe content made the microwave absorbing characteristics increase. The decreasing trend was larger than the increasing trend, which was the main reason for the great changes of microwave absorbing characteristics of reduction products obtained at the temperature range of 850 °C–900 °C and at the temperature range of 1100 °C–1200 °C.