Process analysis Of CO2 capture from flue gas using Ca-based carbonation/calcination cycles is presented here. A carbonation/calcination system is composed essentially of two reactors (an absorber and a regenerator) with Ca-based sorbent circulating between the two reactors (assumed here as fluidized beds). CO2 is, therefore, transferred from the absorber to the regenerator. Because of the endothermicity of the calcination reaction, a certain amount of coal is burned with pure oxygen in the regenerator. Detailed mass balance, heat balance and cost of electricity and CO2 mitigation for the carbonation/calcination cycles with three Ca-based sorbents in dual fluidized beds were calculated and analyzed to study the effect of the Ca-based sorbent activity decay on CO2 capture from flue gas. The three sorbents considered were: limestone, dolomite and CaO/Ca12Al14O33 (75/25 wt %) sorbent. All results, including the amount of coal and oxygen required, are presented with respect to the difference in calcium oxide conversion between the absorber and the regenerator, which is an important design parameter. Finally, costs of electricity and CO2 mitigation costs using carbonation/calcination cycles for the three sorbents were estimated. The results indicate that the economics of the carbonation/calcination process compare favorably with competing technologies for capturing CO2. (C) 2008 American Institute of Chemical Engineers.