Utilization And Some Properties Of Circulating Fluidized Bed Combustion Ashes

Fluidized bed combustion (FBC) technology is advanced because it can meet the demand of environment protection, but the byproducts, namely FBC ashes, are still something new to most people. As a result, the utilization of them and even the further promotion of the technology are seriously hampered. Some properties of FBC ashes such as water absorbing abilities and expansion have seriously affected their application in the cement concrete. Several kinds of FBC ashes are chosen in the paper. The recycle treatment of FBC ashes are mainly studied in the paper. Meanwhile, the ways to reduce the expansion ratio of FBC ashes are mentioned.The particles of FBC ashes are irregular and loose textured, so the water requirement of normal consistency of FBC fly ashes is much higher than that of PC fly ash, and the water absorption of FBC bottom ashes is very high. FBC ashes can be used for stabilization and solidification of sewage sludge. (1) For the bed ash, the appreciate mix proportion to sludge is 2:1.For the fly ash, the mix proportion is 1:1.The pH value of solidification admixture can keep above 11 at the first 7 days. The alkaline environment can guarantee the sterilization effect. At 28d, the pH value is about 9. This can offer the essential condition for the vegetation resumes. (2) At 28d, the strength of solidification admixtures of bed ash and sludge is about 2MPa and fly ash is about 1MPa. The heavy metal leaching properties of stabilized/solidified admixture of FBC ashes and sludge can meet Chinese standard.(3) The addition of twenty percent of lime in the stabilized/solidified admixture can improve the sterilization effect.The pozzolanic reactivity of FBC ash is high and great expansion takes place when it hydrates. Mortars can be produced with FBC ashes. (1) The best proportion of binding material for FBC bed ash is FBC bed ash: PC fly ash: cement is 0.56:0.24:0.2.The appreciate strength and expansion ratio can be got with this mix proportion.(2) The available proportion for FBC fly ash is FBC fly ash: PC fly: and cement is 0.56:0.24:0.2 or 0.8:0:0.2.(3) The strength and dry density can meet Chinese standard JC 890一2001.The addition of 1% CaCl2 or Na2CO3 can reduce the expansion ratio and do little effect on the strength. But it is not desirable to reduce expansion of FBC ashes.