Disintegration of Synthesized Iron Oxides by Reduction at 550°C in 30%CO-N2 Gas Stream

Samples of ternary 80%Fe2O3 CaO-SiO2 systems and 77.6Fe2O3-CaO-SiO2 3%Al2O3 systems were sintered at 1300, 1 350 and 1400°C in air. Their disintegration, caused by the reduction at 550°C for 60min in 30% CO-N2 gas stream, was studied and the following results were obtained.(1) Samples studied contain only granular type hematite, reported as harmless, and yet cracks developed severely through minerals surrounding hematite crystals in some samples especially of the quarternary systems during the reduction, resulting in severe disintegration.(2) The extent of crack development changes depending on the toughness of minerals surrounding hematite crystals and the intercrystal spacings of hematite as well.(3) In the case of samples with low basicity, the toughness of glassy silicate decreases when Al2O3 is added into it or when it crystallizes during the cooling. The intercrystal spacing increases as a result of the increase in size and decrease in number of hematite crystals. In samples being satisfied with both conditions, cracks develop severely resulting in the large disintegration.(4) In the case of samples with high basicity, the intercrystal spacing is so large that the extent of crack development depends mostly on the toughness of minerals surrounding hematite crystals. As the minerals in question increase in size, the toughness decreases resulting in the severe crack development. Al2O3 helps increase amounts of calcium ferrite which increases in size at 1 350°C and over.