Ex Situ CO₂ capture by carbonation of steelmaking slag coupled with metalworking wastewater in a rotating packed bed

Both basic oxygen furnace (BOF) slag and cold-rolling wastewater (CRW) exhibiting highly alkaline characteristics require stabilization and neutralization prior to utilization and/or final disposal. Using CO₂ from flue gases as the stabilizing and neutralizing agents could also diminish CO₂ emissions. In this investigation, ex situ hot stove gas containing 30 vol% CO₂ in the steelmaking process was captured by accelerated carbonation of BOF slag coupled with CRW in a rotating packed bed (RPB). The developed RPB process exhibits superior results, with significant CO₂ removal efficiency (η) of 96-99% in flue gas achieved within a short reaction time of 1 min at 25 C and 1 atm. Calcite (CaCO₃) was identified as the main product according to XRD and SEM-XEDS observations. In addition, the elimination of lime and Ca(OH)₂ in the BOF slag during carbonation is beneficial to its further use as construction material. Consequently, the developed RPB process could capture the CO₂ from the flue gas, neutralize the CRW, and demonstrate the utilization potential for BOF slag. It was also concluded that carbonation of BOF slag coupled with CRW in an RPB is a viable method for CO₂ capture due to its higher mass transfer rate and CO₂ removal efficiency in a short reaction time.