Characterization of steel industry co-products and recycling pathways

The steel industry generates large volumes of fine co-products, whose valorization requires evidence-based process decisions. This study integrates various characterization techniques to translate laboratory data into practical recycling routes for seven co-products of this industrial activity. Our main contribution is a composition-structure-reactivity (CSR) correlation model for KR powder, which defines processability windows, indicating when to prioritize metallurgical return (binder/Fe input), when to opt for cementitious/carbonate routes (alkaline/porous streams), and when to condition use through pretreatments (desalination, dehumidification, ignition loss control). Based on this logic, we present a classified recycling structure that maps property profiles for four priority routes: agglomeration (briquettes/pellets) for Fe/C-rich fractions; thermal routes with selective volatilization of Zn/Pb in zinc-containing dusts; selective hydrometallurgy when speciation requires Zn/Pb removal; and cementitious/accelerated carbonation solutions for alkaline streams (FGD/KR). We also consolidated decision rules through measurable thresholds (Zn, Cl − , moisture/LOI, BET, PSD) and a standardized reporting scheme for comparison between plants and direct use in life cycle assessments (LCA). The results demonstrate high recycling potential, with environmental benefits (e.g., CO 2 capture and utilization in alkaline streams), technical feasibility (internal return, adsorbents, cementitious additions), and attention to operational and regulatory constraints (Zn/Pb/Cl − contents, dust emissions). The work provides a practical guide for route selection, reducing implementation uncertainties and strengthening circularity in the modern steel industry.