Carbothermic reduction kinetics of boron-bearing iron concentrate

In order to deeply understand the carbothermic reduction mechanism of boron-bearing iron concentrate,the isothermal reduction of boron-bearing iron concentrate/carbon composite pellets was performed with high purity graphite as a reductant,and was kinetically analyzed by the integration method. The reduction temperature was set as 1000,1050,1100,1150,1200,1250 and 1300℃,and the C/O molar ratio was 1.0. When the reduction degree ranged from 0.1 to 0.8,the reduction temperature had important effect on the apparent activation energy and rate controlling step. If the reduction temperature was not greater than 1100℃,the average apparent activation energy was 202.6 k J·mol^-1,and the rate controlling step was carbon gasification. But if the reduction temperature was higher than 1100℃,the average apparent activation energy was 116.7 k J·mol^-1,and the reduction rate was the mixed control of carbon gasification and Fe O reduction reaction. When the reduction degree was not less than 0.8(reduction temperature 〉1100℃),the reduction might be controlled by carbon diffusion in metallic iron. Carbon gasification is the main rate controlling step for the reduction of the composite pellet due to the intense chemical inhibition effect of boron in the boron-bearing iron concentrate on carbon gasification.