Some Aspects of the Melting and Dephosphorization Mechanism of Hydrogen‐DRI

Abstract

To meet the future environmental challenges, hydrogen direct reduced iron (H‐DRI) is expected to constitute the principal material for virgin steel production. For an efficient value chain, knowledge of the melting mechanism and dephosphorization mechanism of H‐DRI is needed. The in situ melting behavior, the melting mechanism, and the dephosphorization mechanism during heating of H‐DRI are investigated experimentally at 1773 and 1873 K. It is found that the melting rate of H‐DRI varies with the reduction degree (91–99.5%), increasing with decreasing reduction degree. An autogenous slag forms during heating and flows through the pores of the H‐DRI, thus increasing its effective thermal conductivity. The fraction of filled pores varies with reduction degree explaining the difference in melting rate. At this stage, the dissolution of apatite is initiated and completed upon melting of the metal phase. A gradual reversion of phosphorus from the autogenous slag to the liquid metal is observed after complete melting. The rate of reversion is discussed based on the properties of the H‐DRI, for example, reduction degree and carbon addition.