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Fly ash is one of the residues generated in the combustion of coal. It is generally
captured from the chimneys of coal-fired power plants, and is one of the two types of ash jointly
known as coal ash; the other, bottom ash, is removed from the bottom of coal furnaces.
The combustion of powdered coal in thermal power plants produces fly ash. The high
temperature of burning coal turns the clay minerals present in the coal powder into fused fine
particles mainly comprising aluminium silicate. Fly ash produced thus possesses both ceramic
and pozzolanic properties and is alkaline in nature. The soil type found in and around
Neyveli is acidic in nature. Color of fly ash depends upon its carbon content. Fly ash consists
of large part of solid or hollow spherical (Furr et al., 1987) particles of silica, iron and
alumina, with small portions of thin walled multifaced polyhedrons called
cenospheres (Shanmugasundaram, 1988).
Rathore and Regan (1984) suggested that fly ash is basically a complex mixture of
various solids and semisolids. The main constituents of fly ash are silica, alumina, iron oxide
and calcium oxide. It also comprises mineral mine calcium (Ca), magnesium (Mg), sulphur
(S) and unburnt particles (Thesis and Gardner, 1990). |
