Calcium carbonate looping: Carbon capture ready for pre-commercial demonstration
CCL uses limestone-based sorbents and is particularly suited for retrofitting existing power and industrial plants. The technology combines low net efficiency penalties with low CO2 avoidance costs and low environmental impact. The EU-funded SCARLET project addressed the demonstration of the technology at semi-industrial pilot scale and the key challenges of scaling-up the process to larger-scale units. Long-term pilot tests focused on the reactivity of the sorbent under realistic operating conditions to obtain reliable information about the process performance. Conducted with different limestone sorbents, the results showed steady-state absorption rates in the carbonator higher than 90 % and overall CO2 capture rates higher than 95 % under a wide range of parameters. The pilot testing results provide a consistent set of experimental data at semi-industrial scale and valuable operational experience that enables to scale-up the process on a solid foundation. Reliable simulation tools were developed and validated against experimental data from long-term pilot testing at 1 MWth to extend to larger scale and an up-scaled 20 MWth pilot plant was designed with commercialisation in mind. Full-scale application of the CCL process to power, cement and steel plants shows a net efficiency loss in a range of 6-7 %-points (including CO2 compression) for hard coal and lignite fired power plants combined with very competitive CO2 avoidance costs of 20-27 € per tonne CO2 compared to other CO2 capture technologies. Integration of CCL in cement plants is of particular interest since spent sorbent can be directly utilised as raw material for the clinker production leading to significantly lower CO2 avoidance costs than amine scrubbing. Moreover, CO2 released during calcination of raw meal can only be avoided by CO2 capture. Life cycle analyses conclude that the environmental burden of power and industrial plants can be significantly reduced by a CCL retrofit. SCARLET has taken an important step towards maturity and commercialisation of one of the most promising CO2 capture technologies. CCL technology will contribute to the reduction of CO2 emissions from various emission sources, especially energy and industrial applications.
Keywords
Calcium carbonate looping, carbon capture, CO2, power, cement and steel, SCARLET
