On the factors affecting the deactivation of limestone under calcium looping conditions: A new comprehensive model

Abstract

Calcium looping is an appealing route for addressing CO2 capture and energy storage challenges. Despite the fast deactivation, limestone is still considered the major candidate sorbent material, due to its high availability and low cost. Herein, the phenomena governing the activity loss of limestone under calcium looping conditions are investigated and a comprehensive model is proposed. The carbonation conversion was found to linearly depend on the CaO porosity before reaction. Sintering of CaO during each calcination stage affects porosity. On the contrary, CaCO3 sintering does not affect the deactivation of the material. Apart from CaO sintering, it was found that structural changes during cycling greatly enhance the loss of activity. In-situ XRD experiments revealed that after each calcination step CaO crystal size increases leading to a gradual loss of porosity and surface area with cycles. The proposed model predicted accurately the deactivation of limestone under various cycling conditions.