Self-activation and effect of regeneration conditions in CO2-carbonate looping with CaO-Ca12Al14O33 sorbent

CO2 capture by solid sorbents through uptake-regeneration cycling is a promising option for high temperature removal of CO2 from combustion gases and synthesis/fuel gases. The present study investigates the influence of regeneration atmosphere and temperature on the CO2 uptake capacity during repeated cycling of CaO-based solid sorbents. The sorbents were synthesised to contain 75 and 85% w/w of active phase (CaO) and binder (Ca12Al14O33) and were then subjected to cycling tests with repeated CO2 uptake and release in a thermogravimetric analyser TGA for up to 200 cycles. Test conditions were chosen to test high temperature CO2 capture at 600 degrees C in an atmosphere containing 14 and 25% v/v., CO2 (N-2 balance). Three different regeneration conditions were tested: (a) mild condition: regeneration at 900 degrees C in 14% CO2 or 100% N-2; (b) moderate condition: regeneration at 1000 degrees C in 14% CO2; and (c) severe condition: regeneration at 1000 degrees C in 86% CO2. Hydration of the sorbent during synthesis and prolonged carbonation prior to the cycling tests significantly improved the stability of the uptake capacity. Interestingly, the pretreated 75% w/w CaO synthetic sorbent maintained a good uptake capacity up to the 150th cycle under severe regeneration conditions and even showed continuously increasing CO2 uptake capacity throughout the 150 cycle test with 25% CO2. The 75% w/w CaO sorbent is thus an interesting candidate for future work on high temperature CO2 capture. (C) 2013 Elsevier B.V. All rights reserved.