CHARACTERISTICS AND SO2 CAPTURE CAPACITIES OF SORBENTS PREPARED FROM PRODUCTS OF SPRAY-DRYING FLUE-GAS DESULFURIZATION

The characteristics and the SO2 capture capacities of sorbents prepared from products of spray-drying flue gas desulfurization (FGD) have been studied. Sorbents were prepared by first slurrying Ca(OH)2 and CaSO3 and/or CaSO4 with and without the addition of fly ash and then drying. Compared to the use of pure Ca(OH)2, the SO2 capture and Ca(OH)2 utilization decreased for sorbents prepared without fly ash and increased for sorbents with fly ash. Flake-like ill-crystallized tobermorites were observed for all the sorbents containing fly ash. In addition, significant amounts of needle-shape Ca4Al2(OH)12SO4 . 6H2O and Ca6Al2 (OH)12(SO4)3 . 26H2O (ettringite) were also observed for the sorbents containing CaSO3 and/or CaSO4. These newly formed compounds dissociated into CaSO3 . 0.5 H2O and inert precursors upon sulfation, and were responsible for the high SO2 capture capacities and Ca(OH)2 utilizations of the sorbents prepared with fly ash.