Effect of H₂–H₂O on the Reduction of Olivine Pellets in CO–CO₂ Gas

抄録

Large amounts of injectants are used in the blast furnace (BF) process to reduce coke consumption, but this changes the gas composition in the BF shaft where iron ore reduction takes place. H₂ and H₂O gases change markedly in the gas atmosphere at high injection levels, which makes it important to investigate their effects on the reduction of iron oxides in a CO–CO₂ atmosphere. The gaseous H₂ and H₂O content in the BF shaft atmosphere is approximately 8%. In the present work olivine pellets were reduced in H₂–H₂O–CO–CO₂ and CO–CO₂ atmospheres with equal reducing potentials of H₂ and CO by fixing the H₂/H₂O and CO/CO₂ ratios. No significant differences in the reduction rates of iron oxides were found between the H₂–H₂O–CO–CO₂ and CO–CO₂ atmospheres at high temperatures but at lower temperatures H₂–H₂O–CO–CO₂ had higher reduction rate. Activation energies determined for hematite to magnetite reduction for both gas mixtures indicated better initial stage and later stage reduction in the H₂–H₂O–CO–CO₂ atmosphere. Field Emission Scanning Electron Microscope (FESEM) analysis was carried out on samples, and wüstite relics were found in the inner parts of pellets reduced to iron in the CO–CO₂ gas but not in the samples reduced in the H₂–H₂O–CO–CO₂ gas.