Investigation on the effect of steam on the sorbent performance for the calcium looping process

In this work the performance of an Italian limestone was investigated to understand the effect of the presence of steam during the Calcium Looping (CaL) process. The investigation was carried out simulating CaL conditions in a lab-scale fluidized bed operated in batch mode alternatively as a calciner and as a carbonator. The operating conditions were 940°C with 70% of CO2 (in volume) and 650°C with 15% of CO2, to simulate the calcination and the carbonation stages, respectively. The percentage of steam (when present) was 10%. The experimental campaign consisted of tests where steam was present only during the calcination stage, only during the carbonation stage, or in both; the results were compared with a dry base case where the steam was not present. During each step the CO2 capture capacity was monitored and at the end of each test the exhaust sorbents were analyzed in terms of their porosimetric features. Finally, results were compared with those obtained in a previous investigation on a different (more reactive) German sorbent in order to correlate the sorbent performance with the microstructural features of the sample.