Abstract:

An increased interest from industry, government and academic sectors in reducing carbon-based processes to produce steel and other commodities and raw materials has resulted in exploring other energy and reagent-based alternatives such as de use of hydrogen, in this case as main reducing agent for steelmaking. In some cases, the discussion could erroneously be based on simplistic models of the hydrogen steelmaking process, assuming a supply of pure hydrogen and looking at only the stoichiometry of intermediate and a final reduction reaction FeO + H₂ = Fe+H₂O. This latter reaction is however strictly limited in the thermodynamic sense by equilibrium considerations – so excess hydrogen is necessary to assure full conversion of the iron oxides, and a substantial amount of hydrogen remains in the reaction shaft outlet. This, along with the thermal energy contained in the outlet vapor, must be recovered if the process is to be energy efficient or even sustainable. At higher temperatures, the equilibrium is more favourable, but heat recovery and removal of the water vapor by condensation becomes more difficult 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.

Keywords: Hydrogen Steelmaking, Thermodynamic Modelling, SysCAD, Process Simulation, Gibbs Free Energy Minimization

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Dr. Rod Stephenson