Calcium Looping (Ca-L), most typically carried out in dual interconnected Fluidized Bed (FB) systems, is among the most promising techniques for CO2 capture from combustion flue gases [1]. Recent studies have addressed the effect of steam in influencing the sorbent performance [2,3]. From the analysis of the literature, the role of water vapour in Ca-L cycles is intriguing and not yet fully understood. During calcination, the presence of steam entails two opposite effects: on the one hand, steam is able to speed up sorbent sintering, through the enlargement of the mean pore size with a consequent reduction of active surface area. On the other hand, this enlargement makes pores less vulnerable to plugging during the carbonation stage. The net effect of steam upon calcination depends on the balance between these two counteracting effects. Tests carried out using steam during carbonation have shown that steam can “catalyze” the heterogeneous CaO/CO2 reaction by enhancing gas diffusion in the product layer – in conditions in which this is the rate-limiting stage of the process – through the CaCO3-rich shell of the sorbent particles. This paper aims at contributing to the discussion, presenting the results of an experimental campaign carried out in a lab-scale FB reactor. Tests have been designed so as to compare Ca-L performance without steam (assumed as a reference case), with that observed in the presence of steam in either calcination or carbonation, or in both stages. Experiments with a reference limestone have been performed to characterize CO2 uptake and in-bed particle fragmentation. Moreover, porosimetric and microscopic analyses have been carried out to characterize microstructurale and textural modifications of the limestone. Results highlighted the positive role that the presence of steam can exert in Ca-L processes by enhancing the overall sorbent utilization, and the relevance of steam-induced microstructural changes of the sorbent particles.
The role of steam in calcium looping: the effect on sorbent microstructure and performance / Coppola, Antonio; Montagnaro, Fabio; Scala, Fabrizio; Salatino, Piero. - (2016), pp. 1-1. (Intervento presentato al convegno 4th International Conference on Chemical Looping tenutosi a Nanjing, China nel 26-28 Settembre 2016).
The role of steam in calcium looping: the effect on sorbent microstructure and performance
MONTAGNARO, FABIO;SCALA, FABRIZIO;SALATINO, PIERO
2016
Abstract
Calcium Looping (Ca-L), most typically carried out in dual interconnected Fluidized Bed (FB) systems, is among the most promising techniques for CO2 capture from combustion flue gases [1]. Recent studies have addressed the effect of steam in influencing the sorbent performance [2,3]. From the analysis of the literature, the role of water vapour in Ca-L cycles is intriguing and not yet fully understood. During calcination, the presence of steam entails two opposite effects: on the one hand, steam is able to speed up sorbent sintering, through the enlargement of the mean pore size with a consequent reduction of active surface area. On the other hand, this enlargement makes pores less vulnerable to plugging during the carbonation stage. The net effect of steam upon calcination depends on the balance between these two counteracting effects. Tests carried out using steam during carbonation have shown that steam can “catalyze” the heterogeneous CaO/CO2 reaction by enhancing gas diffusion in the product layer – in conditions in which this is the rate-limiting stage of the process – through the CaCO3-rich shell of the sorbent particles. This paper aims at contributing to the discussion, presenting the results of an experimental campaign carried out in a lab-scale FB reactor. Tests have been designed so as to compare Ca-L performance without steam (assumed as a reference case), with that observed in the presence of steam in either calcination or carbonation, or in both stages. Experiments with a reference limestone have been performed to characterize CO2 uptake and in-bed particle fragmentation. Moreover, porosimetric and microscopic analyses have been carried out to characterize microstructurale and textural modifications of the limestone. Results highlighted the positive role that the presence of steam can exert in Ca-L processes by enhancing the overall sorbent utilization, and the relevance of steam-induced microstructural changes of the sorbent particles.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
