CO_2 capture using fly ash from coal fired power plant and applications of CO_2-captured fly ash as a mineral admixture for concrete

摘要

The utilization of fly ash as a solid sorbent material for CO_2 capture via surface adsorption and carbonation reaction was evaluated as an economically feasible CO_2 reduction technique. The results show that fly ash from a coal fired power plant can capture CO_2 up to 304.7 μmol/g fly ash, consisting of 2.9 and 301.8 μmol/g fly ash via adsorption and carbonation, respectively. The CO_2 adsorption conditions (temperature, pressure, and moisture) can affect CO_2 capture performance of fly ash. The carbonation of CO_2 with free CaO in fly ashes was evaluated and the results indicated that the reaction consumed most of free CaO in fly ash. The fly ashes after CO_2 capture were further used for application as a mineral admixture for concrete. Properties such as water requirement, compressive strength, autoclave expansion, and carbonation depth of mortar and paste specimens using fly ash before and after CO_2 capture were tested and compared with material standards. The results show that the expansion of mortar specimens using fly ash after CO_2 capture was greatly reduced due to the reduction of free CaO content in the fly ash compared to the expansion of specimens using fresh fly ash. There were no significant differences in the water requirement and compressive strength of specimens using fly ash, before and after CO_2 capture process. The results from this study can lead to an alternative CO_2 capture technique with doubtless utilization of fly ash after CO_2 capture as a mineral admixture for concrete.