Influence of Hydration by Steam/Superheating on the CO2 Capture Performance and Physical Properties of CaO-Based Particles

This paper studied the effect of the cyclic carbonation/calcination reactions and the hydration-based reactivation methods (i.e., hydration by steam and hydration by superheating) on the CO 2 capture performance and physical properties of pelletized CaO-based sorbent particles in a fixed bed reactor. Hydration by superheating consisted of first a steam hydration process in 15 vol % H 2 O at 300 °C and a subsequent superheating process in 100% CO 2 at 550 °C. It was found that during the successive carbonation/calcination cycles, the chemical activity of CaO sorbent particles fell rapidly while their physical properties (i.e., weight loss after rotations and compressive strength) were largely maintained. In addition, both hydration by steam and hydration by superheating were effective in reactivating the chemical activity of CaO-based pellets to nearly the same level. Hydration by steam, however, significantly weakened the physical strength of CaO-based pellets whereas hydration by superheating largely maintained their mechanical properties over 20 cycles. The positive effect of hydration by superheating was ascribed to the carbonation of Ca(OH) 2 during the superheating step at 550 °C.