Chemical-Free Pressure-Swing Carbonation of Blast Furnace 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.