Understanding the effect of inert support on the reactivity stabilization for synthetic calcium based sorbents

Abstract

The decay of sorbent reactivity in multiple carbonation/calcination cycles is a critical problem for calcium looping. By introducing inert support materials into CaO particles, the cyclic reactivity of calcium based sorbent could be drastically improved. However, there is a lack of understanding of the interaction between the CaO grain and the support material; thus, much of studies of synthesizing calcium based sorbents are by trial-and-error. In order to understand the possible mechanism of synthetic calcium based sorbent, the widely accepted Zener pinning theory in the field of metallurgy was used here to describe the inhibition of CaO grain sintering due to the addition of inert support. A simple model of CaO grain growth for synthetic calcium-based sorbents was developed to analyze the effect of inert support on the stabilization of cyclic reactivity of CaO. The mechanism of sintering resistant in the synthetic calcium-based sorbents was the pinning force exerted by the dispersed support particles. The inhibition effect of inert support on CaO grain growth is related with the grain migration due to surface energy (γ), support size (r) and volume fraction (f), and the interaction (Finteract) between the support and CaO. The model was validated with the published data and can predict reasonably the experimental results, and the relative importance of some elementary steps was discussed. This study will provide a theoretical understanding for the further development and reactivity improvement of synthetic calcium-based sorbents.