Effects of Alkaline Roasting and Reduction Treatment on Gangue Removal from Iron Ore Using a Flow-Type Reactor

The declining quality of global iron ore resources, marked by increasing concentrations of silicon (Si), aluminum (Al), and phosphorus (P), presents significant challenges to the steelmaking industry. The present study investigated the integration of alkaline roasting, a reduction treatment, and alkaline hydrothermal processing as a means of removing gangue components from low-grade iron ore, using a flow-type reactor system. Experiments were conducted using an Ore B specimen containing 67.9% Fe, 1.6% Si, 1.2% Al, and 0.17% P (mass fraction). The goal was to optimize the processing conditions and assess the mineralogical transformations associated with each step. Alkaline roasting, in conjunction with a 5 M NaOH hydrothermal treatment, removed 50% to 80% of Si, Al, and P in the ore with minimal loss of iron. Reduced ore samples subjected to the alkaline hydrothermal treatment exhibited enhanced dephosphorization and a greater degree of gangue removal at lower temperatures, although resistance to leaching increased at higher temperatures due to the formation of stable compounds. A comparison of results obtained using batch and flow-type reactors established that the latter provided a greater extent of gangue removal and improved overall process efficiency. This work provides a basis for the development of energy-efficient, environmentally sustainable technologies for upgrading low-grade iron ores. These techniques could be used to improve the quality of raw materials utilized in steel production, thus contributing to reduced energy consumption, lower CO₂ emissions, and enhanced resource utilization.