Capture lime kiln flue gas CO ₂ through enhanced wet carbonation of steel slag: pilot-scale demonstration and cementitious performance

This study demonstrates pilot-scale enhanced wet carbonation of steel slag for CO2 capture from industrial lime kiln flue gas using a self-aspirating reactor. Laboratory experiments clarified carbonation mechanisms and optimized key process parameters, followed by pilot-scale validation using lime kiln flue gas. Carbonation mainly involved free lime (f-CaO), portlandite (Ca(OH)2), and calcium silicate phases, producing calcite as the dominant product. Slurry pH showed a strong correlation with reaction kinetics and served as a practical indicator for wet carbonation of basic oxygen furnace slag. Under optimized pilot-scale conditions, treatment of flue gas containing ∼20 vol.% CO2 achieved a CO2 uptake of 7.09 wt.% within 15 min, with a capture efficiency of 50–70%. Carbonation effectively eliminated the volume instability associated with free lime in steel slag. Concrete incorporating 30 wt.% carbonated slag exhibited reduced early-age strength but comparable later-age strength.