1984 Volume 19 Issue 1 Pages 35-46
A morphological characterization of size-density-classified coal fly ash was carried out. Four types of fly ash from coal-fired power plants and a testing boiler in Japan and the Unites States, 1) white gray sample, 2) black sample, produced from the same coal by the same boiler, 3) high sulfur coal fly ash, and 4) fly ash mixedfired from coal and heavy oil were tested.
Sample was fractionated by three testing sieves (opening: 149, 74, 44μm) and five heavy liquids (1.6, 2.0, 2.4, 2.8, 3.2 g/cm3). The shape and color of particles were observed by a scanning electron microscopy and a transmission optical microscopy, respectively. The composition of particles was analyzed by an energy dispersive X-ray analyzer. The particles in the size-density-fraction were classified into typical shapes and colors.
Black sponge-like particles containing principally carbon are concentrated in the fraction of size >44μm, density 1.6-2.4 g/cm3, nonopaque angular particles containing silicon are in the fraction >74μm, 2.4-2.8 g/cm3, black surface crystallized particles containing iron or calcium are concentrated in the fraction > 3.2 g/cm3. Sample 1 is composed of lower density particles than sample 2 and sponge-like particles are not observed in sample 1. The rate of fraction >3.2 g/cm3 in sample 3 is 5.6% and is more than the rates of same fractions in other samples. The fraction is composed of surface crystallized particles enriched with iron. In sample 4, 10-30% of fraction >44 m, 1.6-2.4 g/cm3 is composed of fragments of spheres, but sponge-like particles are not observed in the sample. The rate of fraction 2.8 g/cm3 in sample 4 is only 0.8%.
Size-density-classification technique is powerful technique for characterizing coal fly ash.
