Chemical-Free Pressure-Swing Carbonation of BlastFurnace Slag for CO₂ Utilization and Sequestration

There is consensus that achieving carbon neutrality will require that CO₂ emissions to decrease. Decreasing unavoidable process-related CO₂ emissions will require that CO₂ be sequestered and utilized. Large amounts of process-related CO₂ are unavoidably released, and large amounts of slag are produced by the iron and steel industries. Mineral carbonation of slag is a CO₂ sequestration and utilization technique that offers promise for decreasing CO₂ emissions and effectively utilizing byproducts. However, the chemicals consumed and waste solutions produced have hindered the development of the mineral carbonation technique. In this study, a chemical-free pressure-swing method for carbonation of blast furnace slag was developed. Ca extraction at high pressures and different slag doses was assessed. CaCO₃ precipitation at low pressure was assessed, and the effects of adding seed crystals and performing pressure-swing carbonation by applying a vacuum were assessed. The idea that there is no need for chemical additions has been confirmed. Precipitated CaCO₃ with a purity of more than 99% was produced, and the maximum CO₂ uptake capacity under ideal scenario was 267.1 (g-CO₂)/(kg-slag). A preliminary assessment was performed, and future research directions were suggested.