Microstructure of Iron Containing Oxide Particle Obtained by CO Reduction of Wustite Pellets Consisting of MgO or CaO Solid Solution
Katsuhiko TAKAHASHI, Minoru ASADA, Masahiro KAWAKAMI
CO reduction of wustite pellets dissolving MgO or CaO was carried out in order to clarify the effect of solutes on reduction rate and the microstructure of oxide particle that were precipitated in the reduced iron, as well as the morphologies and microstructure of reduced iron phase were observed with X-ray diffraction and microscope. The results are summarized as follows.
The reduction rate of wustite pellets increased with an increase in CaO contents. Although the reduction rate of wustite pellets dissolving MgO also increased, the acceleration effect of MgO was smaller than that of CaO.
The particle size of MgO and CaO were 300-500 nm and 20-40 nm, respectively. They were larger than the particle size obtained by H2 reduction. The total porosity of the reduced pellet increased with an increase in CaO content or MgO content, because the sintering of reduced iron grains was prevented by addition of CaO particle or MgO particle.
The magnesium concentration at the reaction interface in wustite side increased to approximately 5-6 times that of bulk content, and the calcium concentration also increased to about 1.5 times.
From the discussion of mass transfer in wustite, it can be said that the oxide particles size should be depending on the ratio of vacancy diffusion to chemical reaction rate.
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