The microstructure of CaO as CO2 carrier has significant effect on its cyclic calcination/carbonation performance during capturing CO2 from coal combustion.The fractal dimension was proposed as a characteristic parameter for microstructure of CaO.The fractal characteristics of CaO as well as its effect on CO2 capture performance were investigated during cyclic calcination/carbonation reactions.The results showed that the fractal dimension of CaO exhibited a decrease with increasing cycle number

and its pore channel changed from rough and irregular to smooth and regular.The fractal dimension of CaO showed a drop with increasing calcination temperature.The higher the fractal dimension of CaO

the greater the carbonation rate.CaO had a sharp reduction in the fractal dimension during the first 10 min of the carbonation period

and then the fractal dimension changed slowly with time.In the test range of CaO fractal dimension (D) less than 2.61

there was a linear proportional correlation between fractal dimension and cyclic carbonation conversion.And there probably was a critical Dcr

when D＞Dcr

CaO conversion likely declined with further increasing D.