Direct Reduction of Iron Ores by Ammonia: Metallurgical Property, Reduction Kinetics, and Superiority Analysis

Ammonia (NH3) is a carbon-free energy source, making it a highly promising reductant for low-carbon ironmaking production. To achieve stable and efficient production of shaft furnaces, exploring the metallurgical properties, kinetics, and superiority of iron ore reduction in the NH3-based metallurgy process is necessary. This study investigated the reducibility of NH3 by evaluating the reduction index (RI) and the reduction disintegration index (RDI) of iron ores. The kinetics of 40 pct NH3 reduction of iron ore pellets in the temperature range of 700 degrees C-900 degrees C was calculated using the model-free method. Compared with carbon monoxide (CO), NH3 appeared superior for reducing iron ore pellets at 900 degrees C, which can effectively inhibit iron whisker growth. Furthermore, using NH3 as the reductant can improve the reduction disintegration degree of iron ores at 550 degrees C, especially the RDI of sinter. Nitrogen (N2) and argon (Ar) as the carrier gases exhibited negligible effects on the reaction rate and RI of NH3 reduction of iron ore pellets. Increased temperature and NH3 concentration were conducive to accelerating the reduction rate of the iron ore pellets. The apparent activation energy in the later stage of the reaction can reach a peak of 76.7 kJ/mol.