Deactivation of CaO DFMs for ICCU-RWGS and calcium looping

https://doi.org/10.1016/j.ccst.2021.100001

“We further investigated the influence of regeneration temperature on the performance of CaO. After 50 cycles of ICCU, the regeneration of CaO at 850 °C in H₂ results in a significant reduction of CO₂ capture capacity from 12.45 to 2.12 mmol/g_CaO (Fig. 2a). This is due to the sintering of CaO particles at high regeneration temperature (Valverde et al., 2014) (fig. S17e). In addition, we investigated the kinetic performance for carbonation and H₂ regeneration (Fig. 2b, 2c and 2d). The carbonation rate of rapid adsorption is decreased with the increase of carbonation temperature, while the carbonation time is prolonged. The carbonation kinetics are directly related to the efficiency of industrial applications, represented by the flue gas throughput of per unit of CaO at per unit time. Compared to the carbonation rate, faster regeneration is more correlated to the deactivation of CaO derived from the fast volume shrinkage from CaCO₃ (36.9 cm³/mol) to CaO (16.9 cm³/mol) (Fig. 2c) (Dean et al., 2011).

In addition, regenerating CaO in CO₂ should be responsible for the deactivation of CaO (Dean et al., 2011, Perejon et al., 2016). By changing the regeneration atmosphere from H₂ to CO₂ at 850 °C, we observe rapid deactivation, especially in the initial 30 cycles (fig. S16a). Therefore, the deactivation of CaO can be effective prohibited in H₂ regeneration. More importantly, the regeneration of CaO under H₂ could well retain the characteristics of rapid adsorption of CaO in cycles of carbonation and regeneration (fig. S16b), which is beneficial for practical applications by shortening the carbonation stage. “

Fig. 2. Cyclic carbonation and H₂-regeneration performance of CaO under isothermal (600 °C, 650 °C and 700 °C) and non-isothermal conditions (carbonate at 650 °C and regenerate at 850 °C). (a) Cyclic capacity of CO₂ capture; (b) Comparison of dynamic profiles of 2nd and 50th cycles; (c) Comparison of carbonatation and regeneration rate in cycles;(d) Comparison of carbonatation and regeneration time in cycles. (carbonation rates and times were calculated from the rapid adsorption stage)

Fig. S16. The comparison of regeneration atmosphere (CO₂ or H₂) in non-isothermal ICCU. (a) Comparison of cycle stability of CO₂ capture capacity; (b) Comparison of 2^nd and 50^th cycle on the carbonation kinetics.