Mineralisation as a carbon sink for DAC: A case-study for solar thermal process integration

The rising demand for critical minerals entails more greenhouse gas (GHG) emissions and increased generation of tailings and other mining wastes. This study proposes a novel process integrating concentrated solar power (CSP), accelerated mineral carbonation (AMC), and direct air capture (DAC) technologies to reduce such wastes and emissions. A closed-loop Rankine cycle generating 10 MW_e electric power for a hypothetical Australian nickel mine site case-study is simulated in Aspen Plus. High temperature steam is first used in the AMC heat exchanger (AMC-HX) to provide the enthalpy for AMC before expanding in the turbine to produce the design electricity. The turbine's low-enthalpy exit steam is then used in the DAC heat exchanger (DAC-HX) as a final heat sink before condensation and pumping back to the boiler. The boiler's thermal duty is supplied by a solar central receiver system (CRS) complemented by a 10-h thermal energy storage system.

For the nominal CRS design and energy balance, a net of 5.78 MJ heat per kg of carbonated product is calculated, 10 MW_e electricity for mining beneficiation is maintained, while 10.7 MJ per kg of CO₂ produced in DAC is also provisioned. An annual production of 175.7 kt of carbonates is predicted, permanently locking away 92.2 kt of atmospheric CO₂, and reducing diesel consumption by almost 90 %. Such a design integration can bring all power-related CO₂ emissions of this case-study to zero, with a further CO₂ avoidance of 68.55 kt annually to offset non-power related emissions. In addition to verifying the technical and economic feasibility of such a design, a full life cycle assessment relative to business-as-usual is imperative to help in achieving the 2050 net-zero emissions target in the mining sector.