Puppet Strings of Hydrogen Plasma Reduction of Iron Ores: The Impact of Process Parameters on Plasma Properties and Reduction Kinetics

The reduction effect of plasma in the arc reactor under varying pressure (300–900 mbar), arc current (100–300 A), and electrode-to-sample distances (5–20 mm) was studied utilizing magnetite (Fe$_3$O$_4$) as a model material. Thermodynamic modeling and experimental results revealed that higher pressures improved metallic yield by reducing iron evaporation, achieving up to 89.4 pct reduction at 900 mbar. Kinetic analysis demonstrated rapid magnetite reduction to wüstite within the first 5 minutes and stabilization of metallic iron formation after 15 minutes, with higher currents expediting reduction but increasing energy demand. Plasma characterization via optical emission spectroscopy confirmed the hydrogen utilization efficiency by studying effects of Fe, H, Ar, and Na emissions on plasma behavior and process dynamics, including phenomena like double arcing and contamination from crucible materials. Energetic efficiency peaked at 900 mbar, 200 A, and 10 mm ACD, balancing metal yield and energy consumption.