Low-temperature hydrogen reduction of iron oxide by controlling the water potential using a CaH2 drying agent

Abstract

Lowering the reduction temperature of iron oxide is of great significance in applied engineering, but challenging to achieve in a hydrogen tube furnace as the partial pressure of hydrogen is limited to 1 ​atm. In this study CaH2 was used as a drying agent to control the partial pressure of water vapor to lower the reduction potential of iron oxide. By comparing the extent of formation of the reduction product α-Fe in Fe3O4 reduced under hydrogen with and without CaH2 at various temperatures, the presence of CaH2 was shown to lower the temperature required for complete reduction from 400 ​°C to 300 ​°C accompanied by an increase in the H2/H2O ratio of the outlet gas. Thermodynamic calculations indicated that the addition of CaH2 increases the reduction potential, causing a higher production ratio of α-Fe. These findings indicate that CaH2 promotes reduction by efficiently absorbing the water vapor generated during reduction.