Case Study for Utilisation of CO₂ from Flue Gases in PCC Production from Slags

This article presents a techno-economic assessment for producing precipitated calcium carbonate (PCC) from steelmaking slag. The studied case consists of a stainless steel plant generating slag and a paper plant consuming PCC situated at a relatively close distance. The process uses ammonium salts such as ammonium chloride as solvent for extracting calcium from the slag and subsequently precipitating calcium carbonate using lime kiln flue gas. The process was modelled and the investment costs and operational costs estimated. In addition, the environmental footprint of the process was assessed. The results from this work indicates that the process could in its current stage of development be economic for producing calcium carbonate of similar grade as ground calcium carbonate (GCC) used by paper mills. At the same time, the process would avoid 0.3 t CO2 emissions per tonne PCC produced. Although the operational costs for the process were found to be similar to that of a conventional PCC process, the investment is more than twice the cost of a conventional PCC process. The main reason for the high investment costs is that the studied process uses an ammonium salt solution needs to be recovered for reuse and removed from the PCC product, while a conventional PCC process uses only water as a process solution.