Power Plant CO2 Capture Integrated with Lime-based Direct Air Capture
Power plants equipped with carbon capture and storage (CCS) technologies can reduce the cost of net-zero carbon systems, but the addition of variable renewable energy (VRE) sources like wind and solar can make them difficult to design and operate while limiting their commercial potential. Increased cyclic operation of electricity generators could also reduce capacity factor and efficiency, increase operations and maintenance costs, and potentially increase CO2 emissions. Improving CCS processes and designs could enable a low-cost, net-zero carbon electricity system.
Project Innovation + Advantages:
The Massachusetts Institute of Technology (MIT) will investigate the cost-effective design and operation of a negative carbon emissions power plant concept, invented by 8 Rivers Capital, that combines flue gas CO2 capture with a lime-based direct air capture (DAC) process while not affecting power plant flexibility. First, the power plant flue gas is fed into a calciner, a reactor that breaks down calcium carbonate (CaCO3) into lime and CO2. Next, the CO2-rich gas (>30% CO2) from the calciner is separated to recover high- purity CO2, which can be stored. Last, the lime goes through a novel DAC process that captures additional CO2 from the air in the form of solid CaCO3 that can be sequestered or reused as feed to the calciner. The process can be retrofitted to existing power plants or deployed as part of new low-carbon emissions power plants. The DAC process will continue working even when the power plant is not operating. Preliminary calculations indicate that the system can achieve negative emissions as great as -0.16 tCO2/MWh under baseload operating conditions.
Improvements in the design and processes of CCS-equipped plants in high VRE environments could dramatically reduce the cost of a net-zero carbon system. Benefits include:
Flexible CCS systems can enable the continued use of low-cost domestic fuel for electricity generation and increase the reliability of a deeply decarbonized electricity system.
Flexible CCS systems can achieve high CO2 capture rates from flue gas. Enabling deep turndown of natural-gas fired plants at times of high VRE output will reduce fuel consumption and CO2 emissions.
Flexible CCS systems can reduce the cost of a net-zero carbon electricity system by providing dispatchable power to a high-VRE grid.