Effect of steam and CO2 concentration in atmosphere at both calcination and carbonation stages on CO2 capture for calcium-based sorbent was investigated in a twin-bed calcination/carbonation cycle reaction system.Microstructure analysis from electronic scan image and N2 adsorption/desorption was supplemented to understand mechanism affecting carbonation by steam.The results show that steam in atmosphere of both calcination and carbonation stages can enhance CO2 capture performance of sorbents

and the optimal mass percent in these atmospheres is 10% and 5%

respectively.Effect of steam at carbonation stage on CO2 capture was stronger for sorbent modified by alumina cement than for natural limestone.High CO2 partial pressure at calcination stage results in severe sintering

thus low capacity of CO2 capture.Increase of CO2 capture performance can be achieved by using steam in the atmosphere of both calcination and carbonation stages because steam in flue gas can improve micro-porosity of these sorbents.