Thermodynamic of selective reduction of laterite ore by reducing gases

As the sulfide ore deposits become less economical and environmental viable as a source of nickel, increasing attention is being paid to the laterite ores. But in the pyrometallurgical process of laterite, more efforts should be paid to control the reduction of iron oxide in order to get high nickel-content nickeliferous product. For these reasons, equilibrium condition of iron oxide when laterite ore was selectively reduced by CO2/CO, H2O/H2 and CO2/H2 was studied from the perspective of iron activity with an assumption that the activities of FeO and Fe3O4 equal 1 in this work, and it well accounts for the inescapability of Fe metallization. Activity coefficient of iron in Ni-Fe binary solid alloy was calculated by Miedema model based on the known thermodynamics datum filed. According to Raoult's law, the relationship among the Fe/Ni ratio, reduction temperature and reduction gas composition was calculated when laterite ore was selectively reduced by the three different reduction systems. The calculation result was discussed and also compared with the experimental result. The trend of metal iron content in the reduction product of laterite ore varying with temperature and gas composition was well predicted by the calculation result.