(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.