Study on the composite gravel preparation and the synergistic absorption of CO2 by fly ash of CFB boiler

The cooperative treatment of fly ash and fuel gas of coal-fired plants is a promising way. In this study, circulating fluidized bed fly ash (CFBFA), gypsum, Portland Cement (PC) and water were mixed and pelleted, with carbonation curing by fuel gas to prepare the composite gravel. Experimental results showed that C S H gel and ettringite were the main hydration products and calcite was the main carbonation product. The highest strength of the composite gravel reached 11.11 MPa at 28d which was positively related to the absorption rate of CO 2 , and the CO 2 absorption rate reached 4.789 %. Both hydration and carbonation reactions contributed positively to strength. The carbonation process caused a higher Si 2p binding energy, and the addition of gypsum led to a higher binding energy of Ca 2p. The addition of gypsum increased the porosity and main pore diameter. The porosity and main pore diameter determined the strength of composite gravel. It was observed that gypsum acted as a catalyst to promote the formation of hydration products and carbonation products. This study provided a theoretical support for the preparation of composite gravel which was a substitute for river sand and natural gravel.