Hydration reactivation of CaO-based sorbent for cyclic calcination- carbonation reactions

Abstract

Cyclic calcination-carbonation (CC) reactions have important applications, such as carbon dioxide (CO2) capture from power plant flue gases and zero emission systems for hydrogen production. A critical challenge is the severe activity loss of CaO-based sorbent with increasing cycle numbers. In present study, A Thermax 500 high pressure thermogravimetric analyzer (PTGA) and the Scanning Electron Microscopy (SEM) technology were used to examine hydration reactivation on CaO-based sorbents. Two hydration methods, liquid hydration and steam hydration, were both investigated. It was found that CaO sorbents calcined under lower CO2 partial pressure lose activity more slowly with cycle number. Both the two hydration methods efficiently improved sorbent activity during cyclic CC reactions. The mean values of activity increase for liquid hydration and steam hydration after 6 cycles were ∼22% and ∼27% respectively. SEM images showed that the hydrated CaO particles both exhibited surface area and porosity more favorable for CO2 diffusion through the CaCO3 product layer. It seemed that hydration frequency could affect sorbent cyclic performance and a relatively high frequency should be beneficial. Moreover, comparison with previous study confirmed that hydration reactivation could be efficient at a wide range of condition. Results of the present study demonstrate that hydration is a promising method to improve long performance of CaO sorbents in cyclic CC reactions, which provide consultations for process designing in flue gases CO2 capture and zero emissions systems.