Steam reactivation of CaO for carbon capture

The following content is about using steam to activate CaO, aiming to enhance the stability of CaO for carbon capture. They are copied from an open access paper ( It is clear that steam activation is an effective method to enhance the stability of CaO-based sorbents for CO2 capture.

” Our research on spent sorbent reactivation was based on experience with reactivation of sorbent utilized for SO2 retention [4648]. Carbonation, like sulphation, is a gas-solid reaction with solid product formation at the surface of the reactant; therefore, similar limits and methods for reactivation were expected. An important difference is reversibility of carbonation, i.e., the product layer may be easily removed to expose sintered sorbent surface area to hydration. Taking into account the above analysis, sorbent hydration appears to be the most promising method for reactivation. It is based on a simple chemical reaction: CaO + H2O → Ca(OH)2. Considering the hydration technique, hydration by steam was chosen because there is no excess water to be removed, sample drying is not required and there is no loss of sorbent with liquid reactant [15].


“Figure 3. Steam reactivation effect on sorbent activity during carbonation in the TGA [15]. Kelly Rock limestone; 20 cycles (20% CO2, N2 balance, 650 °C, 30 min/100% N2, 850 °C, 30 min); reactivation by steam (saturated steam, 200 °C, 30 min); and carbonation in TGA (15% CO2, N2 balance, 700 °C).”

Typical results for sorbent reactivation tests are presented in Figure 3. It may be seen that spent sorbent had a carbonation degree ∼35%, regardless of particle size. After reactivation, the sorbent had higher activity and final value for the carbonation conversions in the first cycle above ∼75%, regardless of the particle size, which was significantly higher than related values for spent sorbent. “
“The behaviour of reactivated spent sorbent in CO2 capture cycles is shown in Figure 4. It can be seen that carbonation in the initial cycles was higher than for the natural sorbent and reactivated sorbent displayed significantly better conversions at the end of multi-cycle tests. The final result is an average carbonation of ∼70% during 10 cycles with reactivated sorbent. This analysis shows that steam reactivation actually improves sorbent characteristics, and may enable use of the sorbent for prolonged times, or at least until attrition phenomena dominate. This can aid in further development of the process of CO2 separation by CaO-based sorbents.”
Figure 4. Steam reactivation effect on sorbent activity during CO2 cycles in the TGA. Kelly Rock, 0.300–0.425 mm; calcination (100% N2, 850 °C); carbonation (15% CO2, N2 balance, 650 °C).”

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