Preliminary assessment of a method utilizing carbon dioxide and steelmaking slags to produce precipitated calcium carbonate

One of the options that can contribute to the reduction of carbon dioxide emissions for climate change mitigation is the so-called CO₂ sequestration by mineral carbonation, or CO₂ mineral sequestration. Steel manufacturing could benefit from this option by utilizing its own by-products, i.e. steelmaking slags to combine with CO₂. We have recently studied a method, where aqueous solution of ammonium salt (e.g. ammonium acetate, ammonium nitrate and ammonium chloride) is used to extract calcium selectively from the steel converter slag, followed by precipitation of pure calcium carbonate by bubbling CO₂ through the produced solution. The ammonium salt solution is recovered and re-used. The purpose of this research was to determine if the economic potential of the method warrants moving forward to large-scale application. Despite the small solvent losses, the method was found to have economical potential. In addition, it has significant CO₂ emission reduction potential as well. Scaling up the reactor from the small laboratory scale will allow more detailed design for the process to be made followed by a full economical evaluation including all of the important operational and capital investment costs.