Fly Ash

What is Fly Ash?

Ash, as we know is produced whenever combustion of solid materials like coal takes place. Fly ash is one such residue which rises with the gases into the atmosphere. The ash which does not rise is termed as bottom ash. In industrial terminology, fly ash generally refers to ash produced during combustion of coal. Fly ash is generally captured by electrostatic precipitators or other particle filtration equipments before the flue gases reach the chimneys of coal-fired power plants. Fly ash contains large amounts of aluminium silicate along with silicon dioxide (SiO2) and calcium oxide (CaO).

Dangers posed by Fly ash

Fly ash is a very fine powder and tends to travel far in the air. If fly ash is not captured and disposed off properly, it can pollute air and water considerably. When inhaled fly ash causes respiratory problems. Fly ash in the air slowly settles on leaves and crops in fields in areas near to thermal power plants and lowers the plant yield

Indian Scenario

Coal accounts for about 70% of power production in the country. The thermal power plants in India generate an estimated 100 million tonnes of fly ash per annum. The World Bank has already cautioned India that by 2015, disposal of coal ash would require 1000 square kilometres or one square metre of land per person.

Uses of Coal Ash

Despite the enormity of the problem, fly ash has many advantages and can be successfully used to the benefit of society. The following are some of its advantages

  1. Building Construction: Cement can be replaced upto 35% by fly ash thus reducing the cost of construction considerably.
  2. Fly Ash Bricks: Fly ash bricks are light in weight and offer high strength and durability and can be made at construction site also.
  3. Road Construction: Fly ash is a better fill material for road embankments and in concrete roads, fly ash can be used upto 35% of total cement, thus making cost-effective roads.
  4. Land Filling: Fly ash can be used in developing wastelands for their productive use in agriculture, floriculture and forestry.
  5. Mine Filling: Abandoned mines can be filled up with fly ash.
  6. Agriculture: It has been established by agriculture research institutes that fly ash can increase the crop yield by 10% to 50% and it also enhances water holding capacity of the land in use.

Government Action

The Ministry of Environment and Forests vide its notification in 2009, has made it mandatory to use :-

  1. Fly Ash based products in all construction projects, road embankment works and low lying land filling works within 100 kms radius of Thermal Power Station.
  2. Fly Ash in all mine filling activities within 50 kms of Thermal Power Stations.