Steam Hydration Reactivation of CaO-Based Sorbent in Cyclic Carbonation/Calcination for CO2 Capture

The calcium looping process is one of the most promising approaches for CO2 capture, which is based on the cyclic carbonation/calcination reactions of Ca-based sorbent. However, the sorbent suffers from an unavoidable deactivation of CO2 capture capacity and durability during the cyclic CO2 capture process. Separate steam hydration after calcination is valid to regenerate the reactivity of spent sorbent. In this study, the effects of hydration temperature, steam concentration, and hydration frequency on the sorbent reactivity during 10 carbonation/calcination cycles were investigated using a pressurized thermogravimetric analyzer with reagent-grade CaCO3 used as a precursor under atmospheric pressure. The morphology changes of spent sorbent after calcination under various conditions were observed by a scanning electron microscope. The results revealed that the reactivity and durability of the spent sorbent is significantly recovered by separate hydration after calcination. In addition, the enhancement was more pronounced at lower hydration temperatures and higher steam concentrations. Separate hydration after every calcination performed far better than the low-frequency hydration hydrated just once or every 3 cycles. In comparison to other steam reactivation strategies, such as the steam addition during the carbonation and calcination process, separate steam hydration after calcination has shown excellent reactivation performance.