Fly Ash | 05 Jul 2021

Why in News

National Thermal Power Corporation (NTPC) Limited has invited Expression of Interest (EOI) for sale of fly ash, in its endeavour to achieve 100% utilization of fly ash, from the designated plants of the Middle East and other regions.

• Fly Ash is a byproduct from burning of coal in the thermal power generation.

Key Points

• Fly Ash:
  
  • About:
    
    • It is called fly ash because it is transported from the combustion chamber by exhaust gases.
    • It is collected from the exhaust gases by electrostatic precipitators or bag filters.
      
      • An electrostatic precipitator (ESP) is defined as a filtration device that is used to remove fine particles like smoke and fine dust from the flowing gas.
      • It is the commonly used device for air pollution control.
  • Composition:
    
    • Fly ash includes substantial amounts of silicon dioxide (SiO₂), aluminium oxide (Al2O₃), ferric oxide (Fe2O₃) and calcium oxide (CaO).
  • Properties:
    
    • Resemble Portland cement but is chemically different.
      
      • Portland cement is a binding material in the form of a finely ground powder that is manufactured by burning and grinding a mixture of limestone and clay.
      • Its chemical composition includes calcium silicates, calcium aluminate and calcium aluminoferrite.
    • Exhibit cementitious properties.
      
      • A cementitious material is one that hardens when mixed with water.
  • Uses:
    
    • It is used in concrete and cement products, road base, metal recovery, and mineral filler among others.
  • Harmful Effects:
    
    • Fly ash particles are toxic air pollutants. They can trigger heart disease, cancer, respiratory diseases and stroke.
    • When combined with water they cause leaching of heavy metals in ground water.
    • It also pollutes the soil, and affects the root development system of trees.
• Fly Ash Utilisation:
  
  • NTPC has collaborated with Cement manufacturers around the country to supply Fly Ash.
  • To promote the use of Fly Ash bricks in building construction, NTPC has set up Fly Ash brick manufacturing Plants at its Coal based Thermal Power Plants.
    
    • These bricks are being utilized in Plants as well as township construction activities exclusively.
    • On average, 60 million Fly Ash bricks are being manufactured annually by NTPCs own Fly Ash brick Plants.
  • As per the MoEF&CC directives, NTPC stations must keep at least 20% of total Fly Ash produced in reserve for the issue to Fly Ash brick/blocks/tiles manufacturers and issuing Fly Ash free of cost to them.
    
    • About 9% of the total Fly Ash produced in NTPCs stations, is being utilized by Fly Ash bricks/blocks and tiles manufacturing units annually.
  • During the year 2020-21, almost 15 NTPC stations supplied Fly Ash to various Road projects and Ash utilization crossed by nearly 20 million tonnes.
  • Over the last five years the fly ash utilisation has grown up by 80% in the country.
  • Pradhan Mantri Awas Yojana (Urban) has focused on new construction technologies such as using fly ash bricks that are innovative, and environmentally friendly.
  • Even state governments have come out with their Fly ash utilization policies, e.g. Maharashtra was the first state to adopt the policy.
  • A web portal for monitoring of fly ash generation and utilization and a mobile based application titled “ASHTRACK” has been launched by the Government.
  • GST rates on fly ash and its products have been reduced to 5%.

Source:PIB