Microstructure Improvement of Modified Calcium-Based Sorbents during Cyclic CO<sub>2</sub> Capture

Abstract

Limestone is modified with acetic acid solution as a CO2sorbent in order to solve the problem that the carbonation conversion of limestone decays sharply with the number of cycles. The results show that the carbonation conversion of modified limestone is much higher than original one, and it still achieves as high as 0.5 after 20 cycles. The mechanism of the carbonation conversion improvement for modified limestone was investigated by means of XRD, SEM and nitrogen adsorption instrument. It indicates that the grain size of CaO from modified limestone is smaller than original one. The acetification restrains the increase of grain size for CaO as the number of cycles increase. Sequentially, the extent of sintering for modified limestone is reduced. The fractal dimension of calcined modified limestone is higher than calcined original one. The inner surface of calcined modified limestone is much rougher and more complicated. The acetification makes limestone produce abundant pores. The surface area and pore volume of calcined modified limestone are far greater than those of calcined original one after the same cycles.