Feasibility study on carbon capture using stainless-steel slags

This study investigated the carbonation behavior of Cr/Ni-containing stainless-steel slag as a CO₂-reactive material and evaluated its preliminary reuse potential in cement-board specimens. Under the present laboratory-scale conditions, temperature showed the most apparent effect on the TGA-derived carbon capture capacity, followed by carbonation time and particle-size range. In the tube-furnace system, the carbon capture capacity increased from 500 to 750 °C for all particle-size groups, but declined at 800 °C, suggesting that the effective carbonation window was limited by high-temperature deterioration, possibly associated with sintering and partial decarbonation. Reducing the CO₂ concentration from 100% to 20% lowered the capture capacity, while the relatively favorable temperature remained 750 °C. In the fluidized-bed system, steam addition enhanced carbonation more strongly than temperature increase alone, and 20% H₂O/CO₂ showed the highest capacity within the tested steam-content range and reactor configuration. Comparison between the static powder-bed and fluidized-bed systems showed similar final TGA-derived capacities at 500–750 °C, whereas the fluidized bed performed better at 800 °C, likely because particle motion reduced local agglomeration and maintained more effective gas–solid contact. Construction-material screening further indicated that carbonated slag could be incorporated at conservative replacement ratios of 5% and 10%. The 10% specimen showed relatively favorable thermal uniformity and low-frequency sound-insulation response, while both replacement levels satisfied the adopted localized compressive-strength threshold. Overall, this study provides preliminary feasibility evidence for using Cr/Ni-containing stainless-steel slag as a CO₂-reactive and potentially reusable low-replacement construction-material component.