Sintering of magnetite pellets under oxidizing, neutral and reducing atmospheres

Iron ore concentrate pellets are now sintered (induration heat hardened) under oxidizing conditions. Pellets produced from magnetite ore concentrate are completely oxidized during sintering to hematite pellets. These pellets then require a blast furnace to reduce the hematite to metallic pig iron. Partially reduced pellets would save energy and fuel during transportation and further reduction. It has been stated in the literature that the most important single factor responsible for the development of strength in fired magnetite pellets containing no additive is the oxidation of the magnetite to hematite and the subsequent recrystallization and grain growth of this constituent. However, experiments shown in this paper reveal that oxidation is not necessary to produce high-strength pellets. Magnetite concentrate pellets developed similar strength when sintered at 1,350°C (2,460°F) under either oxidizing (air) or inert (argon) atmosphere; the pellets sintered under argon remained magnetite. In addition, magnetite concentrate pellets sintered under reducing (CO) atmosphere also remained as magnetite, but required induration temperature of approximately 150°C (300°F) less than pellets sintered under the other atmospheres