Hydrogen Direct Reduced Iron Melting in an Electric Arc Furnace: Benefits of In Situ Monitoring

The transition toward environmentally friendly steelmaking using hydrogen direct reduced iron as feed material in electric arc furnaces will eventually require process adjustments due to changes in the pellet properties when compared to, e.g., blast furnace pellets. To this end, the melting of hydrogen direct reduced iron pellets with 68 and 100% reduction degrees and Fe content of 67.24% was investigated in a laboratory-scale electric arc furnace. The presence of iron oxide-rich slag had a significant effect on the arc movement on the melt and an inhibiting effect on iron evaporation. The melting was monitored with video recording and optical emission spectroscopy. The videos were used to monitor the melting behavior, whereas optical emissions revealed iron, gangue elements, and hydrogen from the pellets radiating in the plasma. Furthermore, the flow of the melt is well seen in the videos, as well as the movement of slag droplets on the melt surface. After the experiments, the metal had silica-rich inclusions, whereas slag had mostly penetrated into the crucible. The most notable differences in melting behavior can be attributed to the iron oxide-rich slag, its interaction with the arc and penetration into the crucible, and how it affects the arc movement and heat transfer.