Nucleation of the Iron Phase and Its Growth during the Reduction of Wustite with H2 or CO
1972 Volume 36 Issue 11 Pages 1093-1100
Details
1972 Volume 36 Issue 11 Pages 1093-1100
The nucleation and growth of the iron phase on wustite during the reduction with H2-N2 or CO-N2 at 650∼850°C and the properties of iron reduced were investigated.
The results obtained are as follows:
(1) The nuclei originated from pores and edges on the wustite surface in the H2-N2 reduction. On the other hand, they originated mostly from edges in the CO-N2 reduction. In either gases an iron nucleus on wustite grew linearly against the reduction time.
(2) The rate of iron growth on wustite was proportional to PH2 in the range of PH2=0∼0.2 atm. The reproducibility of the rate of iron growth in CO-N2 was worse than that of H2-N2 reduction. The rate of iron growth was proportional to PCO in the range of PCO=0∼0.8 atm and kept nearly constant over PCO=0.8 atm.
(3) The apparent activation energy for iron growth on the wustite surface was about 14 kcal/mol in H2 and fluctuated in the range of 16∼32 kcal/mol with CO concentration in CO-N2. The rate of iron growth in H2 was nearly 40 times larger than that of CO at the same partial pressure of reducing gas.
(4) The iron reduced in H2 was very dense at the FeO/Fe interface and the iron growth into the wustite bulk was not appreciable. On the other hand, the iron reduced in CO was porous and the iron growth into the wustite bulk was remarkable.
(5) The rate of iron growth in H2 was controlled by an interfacial reaction at the FeO/Fe/H2-three phase boundary on the wustite surface. At the beginning of CO reduction the iron growth took place at the FeO/Fe interface both on the surface and inside the specimen, because the porous structure of iron and CO2 formed by the reduction of FeO affected the rate of iron growth on wustite. Wide scattering of the data of iron growth in CO reduction may be attributed to the effect of CO2 from the FeO/Fe interface inside the FeO bulk.
