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

• Published in: Journal of solid state chemistry 2021-10, Vol.302, p.122441, Article 122441
• Main Authors: Tsuchida, Takayuki, Fukushima, Jun, Tobise, Masahiro, Hayashi, Yamato, Takizawa, Hirotsugu
• Format: Article
• Language: English
• Subjects: CaH2; Hydrogen reduction; Iron oxide; Metal hydride; Thermodynamics; Water potential
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2021.122441

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. [Display omitted] •Hydrogen reduction of magnetite was conducted using CaH2 drying agent.•CaH2 lowered partial pressure of water vapor.•Reduction temperature was lowered by using CaH2.•CaH2 promotes reduction in temperature by absorbing water vapor.