Serpentinite Carbonation Process Routes using Ammonium Sulfate and Integration in Industry

Abstract

Vast resources of serpenitinite rock available worldwide are capable of binding CO2 amounts that diminish the capacity of methods based on geological storage of CO2. R&D has been ongoing in Finland for many years on developing large-scale application of process routes for serpentinite carbonation. Several routes have been assessed in the laboratory, in all cases using ammonium salts to extract magnesium from rock followed by carbonation either in a gas/solid reactor at elevated temperatures and pressures or in an aqueous solution at ambient conditions. The choice for either route is motivated by the CO2-producing source, (waste) heat availability, the magnesium (hydro-)carbonate product aimed at, and a preference for energy efficiency or simplicity. Rocks from several locations have been analysed. A special issue is the recovery of the ammonium flux salt, typically from an aqueous solution. As for application, several industry sectors are considered, such as a (natural gas fired) power plant, a lime kiln, or iron- and steelmaking, applying mineral carbonation (MC) to blast furnace top gas. The analysis includes life cycle assessment (LCA). Finally, the use of magnesium (hydro-)carbonates for heat storage is addressed.