Deactivation of Ca-based sorbents by coal-derived minerals during multicycle CO2 sorption under elevated pressure and temperature

Deactivation of Ca-based sorbents by coal-derived minerals during multicycle CO 2 sorption reactions at elevated temperature and pressure was investigated using a laboratory-scale horizontal-tube reactor. The sorbents tended to undergo a solid-solid reaction with coal-derived ash components such as silicon (Si) and aluminum (Al) during multicycle CO 2 sorption with an intermediate hydration stage. This reaction formed complex inorganics, such as mayenite (Ca 12 Al 14 O 33 ), calcium silicate (Ca 2 SiO 4 ), and spurrite (Ca 5 (SiO 4 ) 2 CO 3 ), and substantially decreased the sorbents' CO 2 sorption ability. Interaction with the coal-derived minerals was significant during the multicycle calcination-carbonation reaction only when the sorbents were subjected to the intermediate hydration treatment. This result suggests that steam enhanced the solid-solid interaction between the minerals and the sorbents at elevated temperature (>873 K) and pressure (6.0 MPa) and that the interaction should be avoided by selecting proper reaction conditions for efficient utilization of the Ca-based sorbents.