Thermodynamics, Kinetics, and Key Parameter Optimization of Manganese Extraction from Steel Slag by Indirect Intensification Process of Chlorination Roasting Method

This study utilized the magnetic separation of steel tailings as raw material, employing ammonium chloride as the chlorinating agent to extract valuable manganese elements from steel slag through chlorination roasting. Initially, the feasibility of manganese extraction from steel slag via chlorination was analyzed based on thermodynamic calculations. Subsequently, single-factor experiments, in conjunction with the Plackett-Burman method, were conducted to investigate the effects of roasting temperature, roasting duration, ammonium chloride dosage (mass ratio of ammonium chloride to steel slag), and steel slag particle size on manganese extraction efficiency. The results indicate that the reactions of MnO with NH₄Cl and HCl(g) exhibit ΔGθ < 0. Under optimized conditions (roasting temperature of 1000 °C, roasting time of 50 min, dosage ratio of ammonium chloride to steel slag of 2.5:1, and steel slag particle size of 75-106 μm), the manganese extraction rate can reach 75.98%. The order of significance for the factors affecting the manganese extraction rate is as follows: temperature > time > steel slag particle size > dosage ratio. The chlorination process for manganese extraction is primarily controlled by surface chemical reaction. Additionally, the formation of CaCl₂ enhances the extraction efficiency of manganese from steel slag.