Additional heat is added by increasing the
steam temperature through bundle of tubes.
These are Super heaters.
There are two kind of super heaters used
in a boiler. Convection types are placed in the second pass and heat transfer
will be from flue gas by convection.
The exit coils will be placed at the top
of furnace. Heat transfer will be mainly by Radiation. This is the Final super
heaters.
When the tubes are staggered horizontally,
between the two headers, they can be provided with drains. This is known as
drainable super heaters. This arrangement is practiced in oil/gas fired
boilers. In a coal fired boiler, they are placed vertically and known as Platen
super heaters. The condensate in the bottom of each coil shall be made to
evaporate to allow passage for steam. This is achieved by slow firing with vent
open. The starting time will be more in this case before closing vents.
No comments:
Post a Comment