Study On Properties And Utilization In Additive Of Cement Of Ashes From Fluidized Bed Combustion

Due to lack of effective ways to utilize the fly and bottom ashes of fluidized bed combustion (FBC ashes), it is difficult to use widely the advanced technology of fluidized bed combustion and defulfurization. In this paper, the properties of FBC fly/ bottom ashes are systematically analyzed and coMPared with Pulverized Coal (PC) fly ashes, and a modified method is demonstrated to evaluate the reactivity of FBC ashes. The difference between the reactivity of FBC ashes and that of PC fly ashes are investigated by XRD, SEM. At last, the properties of FBC ashes used as additive of cement are studied.The results show that,(1) FBC ashes are different from PC fly ashes due to the great differences in forming conditions, such as the combustion temperature, desulfurizer and the efficiency of desulfurization. The differences mainly lie in that FBC ashes have special chemical composition and properties of activity, so FBC ashes are special pozzolanic material. (2) The particles of FBC ashes are irregular and loose textured, which are significantly different from those of PC fly ashes that are spherical and coMPact, so the requirement of water consistence of FBC fly ashes is much higher than that of PC fly ash, and the water absorption of FBC bottom ashes is very high. (3) It is for the first time to analyze the polymerization degree of [SiO4] and [AlO6] of FBC ashes by IR,and the results show that the polymerization degree of [SiO4] and [AlO6] of FBC ashes is lower than that of PC fly ashes, especially the former. (4) The current methods for evaluating the reactivity of pozzolanic materials are not suitable for FBC ashes. A modified method is demonstrated which can assess the reactivity really and directly. (5) The reactivity of FBC ashes is higher than that of PC fly ashes for the differences in morphology/granulometry and mineral composition.The studies on the 70% P.O.425 cement-30% FBC ashes-water show, (1) The strength of mortar is higher than that of the 70% P.O.425 cement-30% PC fly ashes-water mortars. SO₃ content in the pastes must be paid attention to. (2) The setting time of 70% P.O.425 cement-30% FBC ashes-water pastes is normal. (3) The soundness of system isn't normal when SO₃ content exceed 3.5% a lot. (4) Soundness of cement is not as steady as PC fly ashes -cement -water pastes. When Fly Ash is mixed into FBC -cement - water pastes, the soundness of cement is improved. (5) If SO3 content don't exceed 3.5%, long-term compressive and bend strength of 70%cement-30% FBC...