Process modelling and analysis of ikaite production for atmospheric CO2 removal through ocean alkalinity enhancement

The production of ikaite, a metastable calcium carbonate hydrate, offers a promising pathway for atmospheric CO 2 removal through ocean alkalinity enhancement. This study explores the feasibility of ikaite production through a three-step process, involving calcite (CaCO 3 ) dissolution under elevated CO 2 pressure, CO 2 degassing from the calcium carbonate rich solution, and subsequent crystallisation. Here, a mathematical model was developed and validated against experimental data, and the effect of key operational parameters was examined. The calcite loading/dosage, particle size and CO 2 pressure for dissolution, seed loading and particle size for crystallisation, and degassing pressure as critical factors have significant impact on process efficiencies. Under optimal conditions, involving CO 2 pressures of 2 bar for dissolution, 0.01 bar for degassing, and 0.001 bar for crystallisation, with seed loading of 5 kg/m³ and seed particle sizes of 3 μm, the process achieved steady state ikaite production of 1.64 kg/m³ from a calcite feed of 0.83 kg/m³ . This investigation demonstrates the technical viability of ikaite production through CO 2 pressure swing and informs its future development as a potential contributor to climate change mitigation. • Ikaite production process for atmospheric CO 2 removal was designed with pressure swing. • Processes including calcite dissolution with CO 2 , degassing and crystallisation have been modelled. • Key factors influencing ikaite production process have been exploited and analysed. • Results of this work could provide a guidance for production of other minerals.