Post-combustion calcium looping process with a highly stable sorbent activity by recarbonation

• Published in: Energy & environmental science 2012, Vol.5 (6), p.7353-7359
• Main Authors: Arias, Borja, Grasa, Gemma S, Alonso, Mónica, Abanades, J. Carlos
• Format: Article
• Language: English
• Subjects: Calciners; Calcium; Carbon dioxide; Carbonates; Carrying capacity; Reactors; Regeneration; Sorbents
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/c2ee03008j

This paper presents a novel sorbent regeneration technique for post-combustion calcium looping CO 2 capture systems. The advantage of this technique is that it can drastically reduce the consumption of limestone in the plant without affecting its efficiency and without the need for additional reagents. The method is based on the re-carbonation of carbonated particles circulating from the carbonator using pure CO 2 obtained from the gas stream generated in the calciner. The aim is to maintain the CO 2 carrying capacity of the sorbent close to optimum values for CaL post-combustion systems (around 0.2). This is achieved by placing a small regeneration reactor between the carbonator and the calciner. This reactor increases slightly the conversion of CaO to carbonate so that it exceeds the so-called maximum CO 2 carrying capacity of the sorbent. This increase compensates for the loss of CO 2 carrying capacity that the solids undergo in the next calcination-carbonation cycle. Two series of experiments carried out in a thermogravimetric analyzer over 100 cycles of carbonation-recarbonation-calcination show that the inclusion of this recarbonation step is responsible for an increase in the residual CO 2 carrying capacity from 0.07 to 0.16. A conceptual design of the resulting capture system shows that a limestone make-up flow designed specifically for a CO 2 capture system can approach zero, when the solid sorbents purged from the CaL system are re-used to desulfurize the flue gas in the existing power plant. This sorbent regeneration technique for post-combustion Ca-looping CO 2 capture systems can drastically reduce the consumption of limestone in the plant.