Enhancement of CaO for CO2 capture in an FBC environment

Experiments have been carried out on three Canadian limestones to determine their ability to remove CO2 in multiple carbonation/calcination cycles. Two systems have been used: a circulating fluidized bed combustor (CFBC) operated in the bubbling FBC mode; and a thermogravimetric analyzer (TGA). The falloff in CO2 capture ability of the limes derived from these limestones was initially in agreement with an empirical correlation, but subsequently the decay in performance was slower. The use of Na2CO3 and NaCl to reactivate the lime and enhance CO2 capture failed to do so in the FBC environment, but in the case of NaCl, produced significant improvements in performance in the TGA after several cycles, while Na2CO3 did not improve performance in either case. The use of 100% CO2 failed totally to reactivate sorbents in the TGA, but did improve performance in the FBC. There is also evidence from surface area measurements that carbonation in 100% CO2 atmospheres influences pore size and surface area in the FBC environment. These results suggest that 100% CO2 atmospheres may provide a possible reactivation method for some limestones and that the use of NaCl and Na2CO3 for this purpose requires further investigation in FBC environment.