Mineral carbonation: Thermal activation of serpentine as flexible component in energy systems

In this article, the thermal activation of serpentine for mineral carbonation using an electrically heated fluidised bed was studied. This process step is combined into a novel process configuration with rapid thermal activation and a thermal energy storage. For the studied serpentinite mine tailings, the thermal activation durations corresponding with desired mineralogical changes were ' 2 min at 700 °C, 4–8 min at 650 °C, 16–75 min at 600 °C and ' 75 min at 550°C, improving reaction kinetics compared to chamber furnace processing at 650°C for 30 min or 750 °C for 15 min. In all fluidised bed experiments, the preferred mineralogical changes corresponded to a dehydroxylation degree of 52–72 % determined with simultaneous thermal analysis. Fourier-transform infrared analyser was used for online determination of the dehydroxylation degree and could be used for process control if the measurement delay was considered better. The mass and energy balances for an industrial-scale thermal activation plant matching 100,000 tCO₂/a storage were calculated. The average electrical power demand was 17.4 MW, of which 22.9 % was recovered from steam and 61.7 % was stored in the thermal energy storage silos. Twelve-hour and 7-day buffering times resulted in silo volumes of 452.5 m³ and 3167 m³ and thermal energy storage capacities of 129.0 MWh and 903.2 MWh, respectively. Further studies should include process parameter optimisation as well as techno-economic and life cycle assessments to holistically improve the concept.