1998 Volume 77 Issue 8 Pages 793-804
Fundamental study was carried out aiming at the development of a large amount of use technology as civil materials of the coal ash from the fluidized-bed combustion boilers. A series of study was done by using coal ash produced from the fluidized-bed combustion boilers of the normal pressure and pressurizing. The properties of coal ash, and the characteristic of the solidified coal ash by steam treatment for the kneading material with water were examined. The main results obtained are sumamarized as follows: (1) The amount of amorphous materials is not influenced by the condition in boiler (pressure, carbon dioxiide concentration and so on) though a solid phase reaction takes place between ash of coal and lime at boiler temperature 850°C, generates more amorphous substances with a lot of CaO contents of the fluidized bed materials.(2) In case the coal ash in the normal pressure and pressurizing is about 1 of CaO/SiO2 mole ratio and about 2.5 CaO/Al2O3 mole ratio, the solidified coal ash is optimized in the amount of the ettringite and C-S-H, and shows the maximum compressive strength.(3) The leached rate of the toxic heavy metals of the solidified coal ash satisfied a solid environmental standard. Moreover, the amount of the toxic heavy metals and the electric conductivity of the leached solution in the solidified coal ash reached lower value than those in the coal ash. Therefore, it is judged that the toxic heavy metals became steadier reactive materials by solidification.