Research on Metallurgical Properties and Dynamics of Lump Ore Reduction under Ammonia Conditions

Employing ammonia (NH₃) as a reducing agent for iron ore has become an emerging research direction. High-temperature thermogravimetric analysis equipment was used to study the reduction degree and isothermal kinetics of NH₃-reduced lump ore (L1) within the temperature range of 800 ℃–950 ℃. Meanwhile, the low-temperature reduction disintegration performance of L1 at 500 ℃ was investigated. Under conditions of 900 ℃ and a 60 % NH₃ concentration, a metallization rate of 98.26 % was achieved. The reduction process produced nitric oxide (NO) concentrations as high as 431 ppm. As the reaction progresses, the NO concentration gradually decreases. At 500 ℃, as the concentration of NH₃ increased, the specific surface area, pore size, and reduction disintegration degree of the reduced sample all increased. Kinetic analysis shows that the diffusion and geometric shrinkage models can well describe the reduction process of lump ores. The activation energy values derived from both model-fitting and model-free approaches for L1 reduction using 60 % NH₃ were determined to be 64.78 kJ/mol and 61.60 kJ/mol, respectively.