Heat recovery from EAF off-gas for steam generation: analytical exergy study of a sample EAF batch

The high amount of latent and sensible enthalpy discharged from the melting process in an electric arc furnace (EAF) through the off-gas offers high potential for waste heat recovery. Evaporative cooling systems (ECSs) installed at dedusting systems of some EAFs are utilising this waste heat for steam generation and subsequent usage of steam for further applications. Within the following paper, further optimisation approaches of this waste heat recovery are examined comparatively by means of exergetic analysis. Thereby, the focus is on the excessive intake of false air into the dedusting system to ensure a complete CO post-combustion. While a sheer energetic examination of the enthalpy hardly shows any differences, the exergetic calculation confirms the significantly higher amount of generated steam with controlled false air ingress. For the calculated optimal reference case with stoichiometric post-combustion, between 50 and 70% more steam could be produced. Even though a stoichiometric post-combustion cannot be realised for safety reasons, the calculation shows the potential of controlled false air intake for CO post-combustion.