EFFECT OF REDUCING GAS ON THE VOLUME CHANGE DURING REDUCTION OF IRON-OXIDE COMPACTS

Iron oxide compacts fired at 1 373 K for one hour were reduced at 973- 1 373 K using different reducing gases; namely CO, H-2 50%H-2-CO and s imulated reformed natural gas. The reduction course has been followed up by means of recording weight-loss changes as a function of time. Th e structure of the compacts was examined by reflected light microscope whereas the volume change was measured by displacement method. II has been found that both temperature and reducing gas composition have a significant effect on the volume change behaviour during reduction. Th e volume change values of the completely reduced compacts were not wel l representing the volume change behaviour during reduction. The great er swelling was observed for compacts reduced with pure CO giving a ma ximum value of 224% for compacts reduced up to 90% reduction at 1 173 K. Reduction with pure H-2 showed a maximum contraction of 24% for com pacts completely reduced at 1 123 K. The volume change behaviour for c ompacts reduced with gas mixtures was mainly dependant on the relative contents of CO and H-2 in the reducing gas. Mechanisms have been prop osed for the volume change trends for compacts reduced with the differ ent gases and correlated with the microstructure of the reduced compac ts.