Co-utilization of CO₂ and calcium silicate-rich slags for Precipitated calcium carbonate production (Part I)

A promising option for long-term storage of CO₂ is to fixate carbon dioxide as carbonates in minerals. Slag from iron and steel works is a potential raw material for carbonation due to its high content of calcium silicates. Carbonation of calcium silicates produces calcium carbonate (CaCO3), which is used as filler and coating materials in paper. Precipitated calcium carbonate (PCC) is currently produced by carbonating burned lime. If calcium silicate-rich slag materials are used instead of limestone for producing PCC, considerable energy savings and carbon dioxide emissions reductions could be achieved. A suitable process utilizing acetic acid for producing calcium carbonates from calcium silicates was identified. The option for fixating carbon dioxide with calcium silicate-rich slag using acetic acid as reaction intermediate and solvent was investigated using process modeling and laboratory-scale batch experiments. Using this process, 0.24 t of CO₂ could theoretically be captured and stored per ton of iron and steel slag products carbonated, while the world-wide CO₂ storage potential was estimated to be 62-83 Mt/a. The experiments showed that the calcium in iron and steel slags easily dissolve in acetic acid.