Abstract:

In order to improve the CO₂ capture capacity of limestone in the cyclic calcination／carbonation cycles for coalfired power plants, the limestone was modified by the waste wood vinegar. The cyclic CO₂ capture behavior of the modified limestone was investigated in a calcination／carbonation reactor. The carbonation conversion was calculated according to change of the sample in the cyclic reactions, which characterized CO₂ capture capacity of the sample. The phase and the microstructure of the modified limestone were examined by XRD (X-ray diffraction) and SEM (scanning electron microscope) analysis to reveal the reaction mechanism. The results showed that the cyclic carbonation conversion of the limestone was enhanced after the modification treatment. The modified limestone with lower ratio of limestone／waste wood vinegar got, higher carbonation conversion. The optimum ratio of limestone to waste wood vinegar was 20g／400mL. The modified limestone exhibited the highest cyclic carbonation conversion at 700℃. The modified limestone showed higher sintering resistance than the limestone at the high calcination temperature. The carbonation conversion of the modified limestone after 20 cycles achieved 46％ at the optimum reaction conditions, which was 2.9 times higher than that of the limestone. The main composition of the modified limestone was the calcium acetate hydrate. The calcined modified limestone demonstrated better microstructure in the multiple cycles,  compared with the limestone which was suitable for cyclic CO₂ capture.

Key words:  waste wood vinegar, modification, limestone, calcination, carbonation, CO₂ capture