Working of Thermal Power Plant
- In pulverized fuel fired plants, the majority of the ash produced is carried out of the furnace with the exhaust gas. Electrostatic precipitators or fabric filters collect this and discharge it into hoppers.
- From the hoppers it is conveniently conveyed by a stream of air to the point of disposal or transport off the site.
- With all solid fuel fired plants, a significant amount of heavier ash, including some clinker, collects in the hopper at the bottom of the furnace.
- This may be sluiced away with a jet of water or dragged away with a mechanical scraper.
- Electrostatic precipitators remove fly ash by electrically charging the dust particles and attracting them to an oppositely charged plate.
- Fabric filters remove the ash by filtering the flue gas through a filter bed established on a woven fabric.Ultimately, ash may be disposed off in a wet or dry state.
- For wet disposal, the ash is mixed with water to form a slurry, which is pumped to a settling pond.
- For dry disposal, the ash Is partially agglomerated by mixing with some water to avoid a dust nuisance and transported by road or rail to a suitable disposal site.
Q. Explain working of each of the following in a thermal power plant. (I) Induced draught, (II) forced draught.
Induced draught : Here a fan called ID fan is provided at the outlet of boiler, that is, just before the chimney. This fan sucks hot gases from the furnace through the superheater, economizer, reheater, and discharges gas into the chimney. This results in the furnace pressure lower than atmosphere and affects the flow of air from outside to the furnace.
Forced draught : In this system, a fan called forced draught fan is installed at the inlet of the boiler. This fan forces the atmospheric air through the boiler furnace and pushes out the hot gases form the furnace through superheater, reheater, economizer and air heater to stacks.
Q. Write any four demerits of a thermal power plant.
Demerits of thermal power plant :
- Operating cost and maintenance cost is very high as compared with hydro plants.
- Coal handling, ash disposal is difficult.
- Pollution due to heat, smoke and is much more.
- Water-requirement to produce steam ash.