FLY ASH – an overview
FLY ASH – an overview
- It is produced when combustion of solid materials takes place. Fly ash is in the form of a very fine powder and tends to travel long distance in air.
- Thermal power plants based on coal are the largest producers of fly ash.
- Fly ash in thermal power plants is a coal combustion product composed of fine particles that are driven out of the boiler with the flue gases (mixture of gases produced by the burning of fuel). The ash that falls at the bottom of the boiler is called bottom ash.
- In modern coal-fired power plants, fly ash is generally captured by electrostatic precipitators (ESP) or other particle filtration equipments before the flue gases reach the chimneys.
- Together with the bottom ash removed from the bottom of the boiler, the fly ash is known as coal ash.
- Depending upon the source and the type of the coal being burned, the components of fly ash vary considerably, but all the fly ashes include substantial amounts of silicon dioxide (SiO2), aluminium oxide (A12O3) and calcium oxide (CaO). FLY ASH – an overview
- An electrostatic precipitator (ESP) is a filtration device that removes fine particles like dust and smoke from a flowing gas using the force of an induced electrostatic charge that minimally impedes the flow of gases through the unit.
- In contrast to wet scrubbers which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in the form of electricity).
- Uses of fly ash are as follows:
- Fly ash can replace the use of cement by up to 35%.
- Fly ash bricks are light in weight and high in strength and durability.
- It can be used as a filling material in roads, embankments, abandoned mines, etc.
- Fly ash can be used for reclamation of land from water bodies.
- It can also be used in agriculture. It enhances the water-holding capacity of land and thus increases the crop yield.
Policy Measures by MoEFCC
- The MoEFCC, by notification in 2009, made it mandatory to use fly ash in the construction projects such as road construction and filling of low lying areas within 100 km of a thermal power plant. FLY ASH – an overview