A boiler, also referred to as a steam
generator, is a major component in the plant cycle. It is a closed
vessel that efficiently uses heat produced from the combustion of
fuel to convert water to steam.
Efficiency is the most important
characteristic of a boiler since it has a direct bearing on
electricity production. Boilers are classified as either drum-type or
once-through. Major components of boilers include an economizer,
superheaters, reheaters, and spray attemperators.
Economizer.
The economizer is the section of the
boiler tubes where feedwater is first introduced into the boiler and
where flue gas is used to raise the temperature of the water.
Steam Drum (Drum Units Only).
The steam drum separates steam from the
steam/water mixture and keeps the separated steam dry.
Superheaters.
Superheaters are bundles of boiler
tubing located in the ßow path of the hot gases that are created by
the combustion of fuel in the boiler furnace. Heat is transferred
from the combustion gases to the steam in the superheater tubes.
Superheaters are classified as primary
and secondary. Steam passes first through the primary superheater
(located in a relatively cool section of the boiler) after leaving
the steam drum.
There the steam receives a fraction of
its final superheat and then passes through the secondary superheater
for the Reheaters.
Reheaters are bundles of boiler tubes
that are exposed to the combustion gases in the same manner as
superheaters.
Spray Attemperators.
Attemperators, also known as
desuperheaters, are spray nozzles in the boiler tubes between the two
superheaters.
These spray nozzles supply a fine mist
of pure water into the flow path of the steam to prevent tube damage
from overheating. Attemperators are provided for both the superheater
and reheater.
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