Effect of Residual Volatile Matter on Reduction of Iron Oxide in Semi-charcoal Composite Pellets

Abstract

Japanese cypress was carbonized partly at maximum carbonization temperatures T_{C, max}=823, 1073 and 1273 K in order to obtain semi-charcoal with some residual volatile matter (V.M.). The semi-charcoal obtained at T_{C, max}=823 K retained much V.M., mainly H₂. Then, the semi-charcoal composite pellets have been prepared and reduced at reduction temperature T_R=1073, 1173 and 1273 K in N₂ gas atmosphere. Fractional reduction F (%) after 60 min of the carbon composite pellet using semi-charcoal particle with the size of 63–75 μm at T_{C, max}=823 K was 19% at T_R=1073 K and 40% at T_R=1173 K, and was higher than any other pellets. Fractional reductions F (%) of the semi-charcoal composite pellets at T_{C, max}=823, 1073 and 1273 K were over 90% for 60 min at T_R=1273 K. The reducibility of semi-charcoal composite pellets was did not depend on residual V.M. at T_R=1273 K. On the other hand, fractional reduction F (%) of the semi-charcoal composite pellet at T_{C, max}=1073 K using semi-charcoal with the particle size of 23–35 μm was 38% for 60 min at T_R=1173 K, and was higher than any other pellets using semi-charcoal with the particle sizes of 63–75 and 105–150 μm. As the size of semi-charcoal particle decreased, the reduction of iron oxide was much enhanced at T_R=1173 K.