Integrated absorption-mineralisation for energy-efficient CO2 sequestration: Reaction mechanism and feasibility of using fly ash as a feedstock

The most critical challenge for the large-scale implementation of amine-based carbon dioxide (CO2) capture is the high energy consumption of absorbent thermal regeneration. To reduce the energy requirement, absorbent thermal regeneration can be replaced by a chemical method that integrates amine scrubbing, chemical regeneration and CO2 mineralisation in one process. However, the mechanisms of the process and the application of industrial waste as feedstocks have not been fully investigated. In the present work, we studied the integrated CO2 absorption-mineralisation process using the benchmark solvent monoethanolamine (MEA) as an amine absorbent and fly ash as a chemical regeneration agent. We investigated the mechanism involved in the mineralisation in detail and studied the performance of MEA in regeneration by mineralisation of calcium oxide (CaO) at various CO2-loadings. The performance stability of MEA was verified in multicycle CO2 absorption-mineralisation experiments. We also investigated the technical feasibility of using fly ash as a feedstock for absorbent regeneration. Our results show that MEA can be regenerated after a carbonation reaction with both calcium oxide and fly ash at 40 °C, and that the CO2 absorbed by MEA is precipitated as calcium carbonate. Compared with traditional thermal regeneration-based CO2 capture, the integrated CO2 absorption-mineralisation process displays a similar cyclic CO2-loading (0.21 mol/mol) but has great advantages in energy reduction and capital cost savings due to the smaller energy requirement of amine regeneration and the limitation of CO2 compression and pipeline transport. This technology has great potential for industrial application, particularly with CaO-containing wastes such as fly ash and carbide slag.