Reaction Mechanisms During Melting of H-DRI Focusing on Slag Formation and the Behavior of Vanadium

The reaction mechanisms during melting of hydrogen direct reduced iron pellets (H-DRI) with different degrees of reduction were studied experimentally at 1773 K to 1873 K at different times (60 to 600 seconds), focusing on the autogenous slag formation. It was found that an autogenous slag is formed inside the pellets prior to the melting of the metal phase. The formation of the autogenous slag started with the melting of FeO, initially located in the center of the iron grains. The liquid FeO flowed into the pore network of the pellet. While flowing, the liquid FeO dissolved parts of the residual oxides, forming an autogenous slag. The slag stayed in the pore network until the iron was molten. Upon melting of the iron, the slag coalesced into spherical droplets. The final state is reached upon the separation of the metal and slag phases by flotation, as a bulk slag was formed on the surface of the liquid iron. In addition, since the iron ore used in this study contains vanadium, the behavior of V was discussed separately based on the experimental observations to build a basis for future studies on V extraction.