(Sample Material) Study Kit on Current Affairs for UPSC Mains Exam: Science and Technology: Fly Ash
(Sample Material) Study Kit on Current Affairs for UPSC Mains Examination
Science and Technology: Fly Ash
Fly ash is one of the naturally-occurring products from the coal combustion process and is a material that is nearly the same as volanic ash.
Fly ash is generally captured by electrostatic precipitators or other particle filtration equipment before the flue gases reach the chimneys of coal-fired power plants.
Depending upon the source and makeup of the coal being burned, the components of fly ash vary considerably, but all fly ash includes substantial amounts of silicon dioxide (SiO2) (both amorphous and crystalline), aluminum oxide (AI2O3) and calcium oxide. (CaO), the main mineral compounds in coal-bearing rock strata.
Considered hazardous, the fly ash consists of the following elements or substances in trace concentrations (up to hundreds ppm): arsenic, beryllium, boron, cadmium, chromium, hexavalent chromium, cobalt, lead, manganese, mercury, molybdenum, selenium, strontium, thallium, and vanadium, along with very small concentrations of dioxins and PAH (Polycyclic Aromatic Hydrocarbon) compounds.
- It is estimated that for every megawatt of coal generated, about 5-6 tonnes of fly ash is produced.
- Fly ash has a proven usefulness as an input in cement manufacturing, road building and house construction.
- About 30-35 per cent of fly ash that gets generated goes into cement manufacture, including Pozzolanic cement mortar and concrete, 12 per cent respectively is used for mine filling and brick making, 11 per cent finds its way into low lying areas and about 3 per cent is utilized for agriculture.
New Avenues of Usage
- Stowing of ash into abandoned coal mines, using fly ash for railway embankments’ and ash- based bituminous roads, flux bonded bricks and Tiles and mine filling.
- In collaboration with IIT-Kanpur, NTPC the largest thermal power, generator of the country had used fly ash for the. manufacture of pre-stressed railway concrete sleepers and development of ash based bituminous roads and flux bonded bricks and tiles at Ramagundam.
- Ash is also being .used in the manufacture of high-density polyethylene (HOPE), products through IIT Delhi.
- Interestingly, fly ash has found its way into agriculture as a soil modifier and source for micro and macro nutrients.
- Various crops have been grown and harvested in varying agro climatic conditions and different soil-crop combinations and successful increase in crop yields have been demonstrated by many agricultural universities.