Characterization of Precipitated Carbon by XPS and Its Prevention Mechanism of Sticking during Reduction of Fe₂O₃ Particles in the Fluidized Bed

Abstract

The Fe₂O₃ particles with the diameter between 74 and 150 μm were pre-reduced with CO at 923 K to precipitate the carbon on the surface. Then the particles were reduced by CO at 1173 K in the fluidized bed for examining the efficiency of the precipitated carbon for preventing the sticking. The result showed that the sticking of particles with high metallization ratio could be retarded or prevented by the precipitated carbon. For clarifying the prevention mechanism of the sticking, the carbon in different states was characterized by X-ray Photoelectron Spectroscopy (XPS) and its effects on sticking were discussed. The carbon on the surface was divided into two states, the graphitic carbon and the carbon in Fe₃C. On account of the sticking of Fe₃C at approximately 1054 K and the sticking of the sponge iron at the micron scale, the structural change of the precipitated iron by the carburization and the formation of Fe₃C only retard the sticking. Therefore, the prevention of the sticking at 1173 K was attributed to the graphitic carbon. Due to the formation of metallic iron layer avoiding the consumption of the carbon and the formation of Fe₃C restraining the dissolution of the graphitic carbon, the graphitic carbon accumulated on the surface of the particles, resulted in n_C/n_Fe above 1.0, so that Fe₃C and the metallic iron was coated by the graphitic carbon to block their contact among the particles.