Reduction Behavior of Iron Oxide in Semi-chacoal Composite Pellets

Abstract

Biomass has a novel advantage, i.e., no CO₂ emissions, because of carbon neutral. We proposed semi-charcoal composite iron oxide pellets in order to decrease reducing agent at blast furnace and CO₂ emissions. Japanese cedar were carbonized partly at maximum carbonization temperatures (T_{C, max} = 823, 1073 and 1273 K) in order to obtain semi-charcoal with residual volatile matter (V.M.). It was found that the semi-charcoal retained much V.M., mainly H₂, at T_{C, max} = 823 K and that the semi-charcoal with some residual V.M. could be prepared by controlling T_{C, max} in the carbonization. Composite pellets using such semi-charcoal have been prepared and reduced at reduction temperature (T_R) in N₂ gas atmosphere. Fractional reductions F(%) of the semi-charcoal composite pellets at T_{C, max} = 823, 1073 and 1273 K were 17 ∼ 24 % for 60 min at T_R = 1073 K. Moreover, fractional reduction F(%) of the semi-charcoal composite pellet at T_{C, max} = 823 K was 62 % for 60 min at T_R = 1173 K and was higher than the pellet at T_{C, max} = 1273 K by about 30 %. When T_{C, max} was lower, namely the pellet had more residual V.M., the reduction of iron oxide was more accelerated at T_R = 1073 and 1173 K. Fractional reductions F(%) of all the semi-charcoal composite pellets were about 100 % for 50 ∼ 60 min at T_R = 1273 K. These reducibility of semi-charcoal composite pellets were higher than those of semi-coal-char composite pellets at T_R = 1273 K.