Theoretical and Practical Limitations of Hydrogen Steelmaking – A Process Simulation Perspective
The interest in using hydrogen as a reducing agent for steelmaking is growing, but simplistic models often overlook the need for excess hydrogen to fully convert iron oxides. Excess hydrogen and thermal energy in the outlet gases must be recovered if the process is to be energy efficient or sustainable. We present a SysCAD simulation which highlights the key issues and the importance of addressing them for economically viable large-scale hydrogen steelmaking processes.
Presentation by Tanai Marín of SysCAD. First presented at the 62nd Conference of Metallurgists (COM 2023), on Aug 21-24, 2023, in Toronto, Canada: https://com.metsoc.org/
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(Abstract)
An increased interest in reducing emissions from carbon-based processes for steel and other raw materials has driven exploration of other energy and reagent-based alternatives such as the use of hydrogen, in this case as the main reducing agent for steelmaking. In some cases, the analyses are based on overly simplistic models of the hydrogen steelmaking process that assume a stoichiometric supply of pure hydrogen for the intermediate reactions and final reduction reaction, FeO + H2 = Fe + H2O. This latter reaction is however strictly limited by thermodynamic considerations –significant excess hydrogen is necessary to assure full conversion of the iron oxides, and a substantial amount of that hydrogen remains in the outlet gases. This hydrogen, along with the thermal energy contained in the outlet vapor, must be recovered if the process is to be energy efficient or even sustainable. Higher temperatures favour the reduction reactions, but complicate heat recovery and removal of the water vapor by condensation and any remaining water vapor recycled to the shaft inlet will reduce the hydrogen reduction efficiency. We present a SysCAD simulation energy and mass balance model considering thermodynamic equilibrium of the hydrogen steelmaking process which highlights the key issues, both theoretical and practical, that need to be addressed for such processes to be economically viable at the large scales necessary for hydrogen to replace carbon-based fuels in the steelmaking industry. A custom thermodynamic system database for the H2-steelmaking process was developed for this model and used within SysCAD and its Thermodynamic Calculation Engine (TCE) capabilities coupled with the heat and mass balance.