Effect of pre-calcination for modified CaO-based sorbents on multiple carbonation/calcination cycles

Abstract

Abstract In the present work, the effect of pre-calcination on carbonation conversion and cyclic stability of modified CaO-based sorbent was investigated by thermogravimetric analyzer (TGA). The modified CaO-based sorbents with CaAc 2 as precursor were respectively doped with different elements (Mg, Al, Ce, Zr and La). The specific surface area, pore volume and pore size distribution were tested by N 2 isothermal adsorption measurements. The phase compositions of sorbents were characterized by X-ray diffraction (XRD). The results showed that the cyclic stabilities of the sorbents were improved by pre-calcination. The pre-calcination was conducted at 900 °C for 5 h in air by the muffle furnace. With pre-calcination, the cyclic stabilities of sorbents could be as high as 96% after 22 cycles, such as CaO-Al, CaO-Ce and CaO-La. After contact with air, the carbonation conversions of spent sorbents with pre-calcination suddenly increased by about one-sixth due to the change of channel structure by hydration. Both the cyclic stability of sorbent and the durability of reactivation were related to the structural stability of sample, especially the stability of mesopores between 2 nm and 5.5 nm. The present work also provided an easy and low-cost method for reactivating the spent CaO-based sorbents.