The effect of coal size, iron ore concentrate size, temperature and carbon oxygen mole ratio on the
reduction rate of iron
ore pellets
containing high, middle, low volatile coals as reductant has been investigated in nitrogen at temperature range of 1 223～1 473 K by using a thermal weight loss balance. The
reduction rate of iron ore pellets has been increased with decreasing the coal and iron ore concentrate size, increasing temperature and carbon oxygen mole ratio, but the above mentioned four factors have greater effect on reduction rate for pellets containing low volatile coal. Most of the experimental data can be successfully represented by four well known kinetics equations based on carbon gasification, gas diffusion and phase boundary reaction as rate controlling step and the rate constant can be evaluated, then the activation energy for pellets containing different volatile coals can be calculated by Arrhenius equation. It has been concluded that gas diffusion should be the reduction controlling step of composite pellets as the calculated activation energy based on the assumption that gas diffusion is the rate controlling step, is the greatest. The higher the volatile content of coal is, the easier the pellets is to be reducted because the activation energy for gas diffusion is smaller for composite pellets containing higher volatile coal.