1981 Volume 67 Issue 2 Pages 303-312
Iron oxide pellets being resistant to crushing into pieces on adding onto the iron melt were made from iron oxide powder by pressing and sintering. The melting rate of pellets into iron melt and the reducing rate of pellets by carbon in iron melt were obtained by measuring CO gas evolved. The effects of the kind of iron oxide, oxide additives in pellets, temperature and carbon content of iron melt on the melting rate, and the rate of reduction of solid iron oxides by carbon in iron melt were investigated. The following results were obtained:
(1) The result using heated pellets showed that the heat transfer was not the rate-determining step. The estimated diffusion layer of carbon in iron melt showed that the carbon transfer could be the rate-determining step. Both the carbon transfer and the chemical reaction were estimated to control the melting and reducing of iron oxide.
(2) The relation between the total reduction and the time was linear from about 20% to about 70% of the reduction, where solid iron oxides were reduced by carbon dissolved in iron melt.
(3) The apparent activation energies of melting of pellets into the carbon saturated iron melt were 35 for Fe2O3, 18 and 41 for Fe3O4 above and below 1470°C, and further 44 and 79 kcal/mol for FeO above and below 1470°C, respectively.
(4) The melting rates of Fe2O3, Fe3O4, and FeO pellets into the iron melt at 1570°C were proportional to the 0.57, 0.45, and 0.42 power of the carbon content in iron melt (wt %), respectively. The minimum volume cf CO gas evelved was obtained at about 2% C.