1. ALA Presentation
Elements of Mechanical Engineering (2110006)
SUB : Superheater
En. No : 170120119064
Division : I-1
Branch : Mechanical Engineering
Created by : Prasang Patel Guided by :
Gandhinagar Institute Of
Technology
3. CF
j
Hot gases
Steam Space
s
D
Bottom flue
A
BC Main steam Pipe
Drum
Water Level Headers
A,B,C – Stop valves
S- Steel tubes
CF- Chimney flue
D- Damper
Steam
out
4. Introduce layout of SUPER HEATER
• The figure shows valves A,B and C at top. The valve, A and B control
the passage of steam entering and coming out of superheater
respectively. When valve A and B are open and C is closed, wet steam
pass through superheater and enter the steam main. When valve A
and B are closed and valve C is open, wet steam directly enter the
steam main.
5. Theory:
The steam leaves the water surface and pass into steam space
in boiler drum. Steam formed above the surface f water is always wet,
i.e. it carries some minute droplets of water. If wet steam is all that is
required, the steam is piped directly from the steam space to steam
main.
6. But if superheated steam is required, the wet steam is removed
from the steam space and piped into a “superheater”.
This consists of a long tube or series of tubes which are
suspended across the path of the hot gases from the furnace. As the
wet steam progresses through the tube or tubes, it is gradually dried
out and eventually superheated.
7. A superheater commonly used in Lancashire boiler is shown in Figure.
This superheated consists of two headers and set of superheater tube made of
high quality steel in form of U-tube. Superheater is located in the path of
furnace gases where the temperature of hot gases is not less than 550˚C. The
superheater is located just before the entry of hot gases to bottom flue.
The amount of hot gases passed over the superheated tubes should be in
proportion to the steam passing through tubes and degree of superheat
required. To avoid overheating, some amount of hot gases may be diverted
with the help of the damper. The superheater may be by passed by bringing
the damper in vertical position and thus passing flue gases directly to bottom
flue. The damper may be partially closed to control the degree of superheat
irrespective of steam flow rate.
8. Superheaters in packaged steam generators and HRSGs (Heat
recovery steam generator)-general features.
Packaged steam generators generate up to 300,000 lb/h steam,
while a few gas turbine HRSGs generate even more depending on
the gas turbine size. Steam pressure in cogeneration and combined
cycle plants typically ranges from 150 to 1,500 psig and
temperature from saturation to 1,000°F Seamless alloy steel tubes
are used in superheater construction.
9. Advantages of superheated steam:
1. Superheated steam is at high temperature. So it increases overall
efficiency of steam plant.
2. It reduces steam consumption for same power produced.
3. It reduces condensation losses in pipes and engine cylinder of
steam engine.
4. When superheated steam is supplied to turbine, the steam is drier
at later stages. Driver the steam, lesser the water particles and
turbine blade erosion.
