Reduction Process of CaO-Fe₂O₃ Binary Calcium Ferrite and Resultant Expansion

Abstract

The reduction process of artificial 2CaO·Fe₂O₃, CaO·Fe₂O₃ and CaO·2Fe₂O₃ by CO-CO₂ mixed gas and the accompanied expansion have been studied in connection with the behaviour during reduction of lime self-fluxing sinter. The main results obtained are as follows :
(1) A scheme of reduction process of CaO·2Fe₂O₃, CaO·Fe₂O₃ and 2CaO·Fe₂O₃ at 800°, 900°, 1 000 °C (solid line) and 550°C (chain line) was found as follows :
(2) At 800°, 900°, and 1 000°C, the expansion (about 0.8%) in the reduction of CaO·2Fe₂O₃ and CaO·Fe₂O₃ occurred up to formation of 2CaO·Fe₂O₃, Ca0·3FeO.Fe₂O₃ and Fe_xO, and the expansion in the case of 2CaO·Fe₂O₃ was only small.
(3) At 550°C, the abrupt expansion (about 4%) in the reduction of CaO·Fe₂O₃ may be caused by formation of metallic iron and carbon deposition incidental to its formation, and that the expansion in the reduction of CaO·2Fe₂O₃ occurred in two steps; the first step expansion (about 0.8%) occurred up to formation of Fe₃O₄ and the second abrupt expansion may be caused by the same reason as in CaO·Fe₂O₃.
(4) At each temperature, the expansion of Fe₂O₃ was the highest and the expansion of calcium ferrite was much less than Fe₂O₃, and the expansion of binary calcium ferrite increased with increasing Fe₂O₃ content in ferrite.