Coal-Fired Thermal Generating Plants
ATCO Power operates two major coal-fired thermal generating stations in Alberta: Battle
River and Sheerness. In these thermal power stations, coal is burned to heat water in a boiler and convert it to high-pressure steam. The high-pressure steam is directed into a steam turbine which turns the turbine shaft. This shaft is connected to an electrical generator which produces electricity.
A condenser converts the steam exhausting from the turbine back into water which is reused in the boiler. The condenser contains tubes which have water circulating through them to cool the steam. The water is supplied by a nearby reservoir or river. This
condensing process increases the efficiency of electricity generation.
Coal for the generating stations is often extracted from a nearby coal mine. The mined land is reclaimed, often to a level better than its original state. For example, the Sheerness Generating Station works with the
local mining company to ensure that the mined land is returned to levels of productivity as good or better than existed
previous to mining.
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Coal haulers take the coal to the generating station, where it is crushed
and stockpiled. A conveyor belt carries the
crushed coal from the stockpile to bunkers within the power station. The coal is fed as
required into pulverizers, where it is ground to a fine dust, the consistency of
talcum powder. A fan blows the coal into the boiler’s furnace. Water
flows through tubes that form the walls of the furnace and the intense
heat of the burning coal causes the water inside the tubes to boil.
The boiling water rises into the steam drum at the top of the boiler where
the steam is separated from the water. The steam, at high pressure, is
super-heated to still higher temperatures and then used to turn the steam
turbine and an electricity generator. After leaving the turbine, the steam – now at a lower temperature
and a lower pressure – passes through the condenser, condensing the steam back into water which is pumped back to the boiler to repeat the cycle.
The fine, powdery ash produced when coal is burned is called flyash.
The hot gases and flyash move out of the boiler’s furnace and
into electrostatic precipitators – a series of
electrically-charged metal plates that attract and hold the flyash
particles. The collected flyash is
either sold for use as an additive to concrete or trucked to the mine
site to be used for fill. |
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