1982 Volume 68 Issue 10 Pages 1578-1585
The effects of foreign oxides on the oxidation behavior of reduced iron are investigated and the following results are obtained. The oxidation starting temperature of iron reduced from pure hematite and hematite containing Al2O3 or CaO at 800°C are about 430°, 300° and 460°C, respectively. It is found that oxidation of reduced iron apparently stop before being completely oxidized to ferric oxide, when iron reduced from hematite containing a sufficient amount of CaO is oxidized at the temperature higher than 600°C. The higher the oxidation temperature and the lower the water vapor pressure, the lower the oxidation degree. Further, the oxidation degree depends on the content of CaO and shows the minimum at 1.25 mol% CaO. On the other hand, iron reduced from hematite containing Al2O3 is oxidized towards the complete oxidation without the apparent stop of oxidation The porosity of iron reduced from hematite containing CaO and Al2O3 is practically the same and higher than the critical porosity except the case of the extremely low content of CaO. The contraction during oxidation of reduced pellets containing CaO and decrease of pore radius by the oxide built upon the wall of pore are considered to be the cause of the apparent stop of oxidation.