This document discusses steam generators and feedwater heaters used in thermal and nuclear power plants. It provides definitions of boilers and steam generators, describing their main components like drums, superheaters, and economizers. It compares firetube and watertube boilers, listing advantages and disadvantages of each. The document also describes types of feedwater heaters like open and closed, and their purposes in preheating feedwater to improve thermodynamic efficiency.

1. Dr. S. VIJAYA BHASKAR
PROFESSORINMECHANICALENGINEERING
SREENIDHIINSTITUTEOF SCIENCE& TECHNNOLOGY
GHATKESAR,HYDERABAD,TS, INDIA

2. Steam Generators
- Types, Accessories.
- Feed water heaters
M.Tech. (THERMAL ENGINEERING) I Year – I Semester
THERMAL AND NUCLEAR POWER PLANTS
CODE: 6M111

3.  ‘A closed vessel in which steam is produced
from water by combustion of fuel.’
 A boiler is defined as "a closed vessel in
which water or other liquid is heated, steam
or vapor is generated under pressure for
external use to do mechanical work.“

4.  Water is pumped into the boiler at operating pressure
 Heat of flue gases vaporises water to form steam
 Steam formed is passed into steam space above the water
space
 This steam is always wet. Superheated steam is obtained by
passing wet steam through super-heater, where it is dried
and then superheated
 To increase efficiency, water is passed through an economiser
where its temp. is increased and then it is pumped into the
boiler. This way less heat is required to heat the steam.

5.  ‘A combination of apparatus for producing,
furnishing or recovering heat together with the
apparatus for transferring the heat so made
available to the fluid being heated and
vapourised.’
 Components of a steam generator
◦ Boiler drum
◦ Superheater
◦ Economiser
◦ Air Preheater

6.  Controlled release of heat in the fuel.
 Efficient transfer of heat to the feed water to
produce steam at desired Pressure (P),
Temperature (T) and quality.
 Steam to be supplied from boiler at constant
Pressure by maintaining the steam generation
rate and steam flow rate equal.
 Water must be contained safely.

7. 1. Operating Pressure
2. Steam Generating Rate
3. Quality of steam required
4. Availability of floor space
5. Fuel to be used
6. Nature of the load on the boiler
7. Initial cost
8. Operating and maintenance cost
9. Availability of water
10. Accessibility for repair and inspection

8. 1. Capable of producing maximum amount of steam with
minimum fuel consumption.
2. It should occupy less space and be light in weight.
3. Capable of quick starting and should rapidly meet the
fluctuation in load.
4. Safe in working.
5. Economical and should require very little attention during
operation.
6. All parts should be easily accessible for inspection and
repairs.
7. Components should be transported without difficulty.

9. 8. Installation should be simple.
9. Tubes should not accumulate soot or water deposits and should
be sufficiently strong to allow for wear and corrosion.
10. Water and gas circuits should be such as to allow minimum fluid
velocity for low frictional losses.
11. Should have as less joints as possible to avoid leaks, which may
occur due to expansion and contraction.
12. Velocities should be high for high heat transfer rates with
minimum pressure drop through the system.
13. Should confirm to safety regulations laid down in Boiler Act.

10. HRSH->Heat Recovery Steam Generator

11. 1. Position of flue gases and water
Fire tube, water tube
2. Axis of shell
Horizontal, vertical, inclined
3. Location of furnace
Externally fired, internally fired
4. Method of circulation
Natural, Forced

12. 5. Mobility
Stationary, Portable
6. Usage
Packaged, Unpackaged
7. Pressure
High, Low
8. Tubes
Single, Multi

13. In the fire tube boiler the hot gases are
inside the tubes & the water surrounds
in the tube.
Ex.

14. In the water tube boiler the water is inside
the tube & the hot gases are surround them.

17.  Furnace is located inside the Boiler Drum or shell.
 Hot flue gases are fed through the tubes.
 Tubes are surrounded by water.
 Boiler shell contains water and steam under pressure.
 Tube contains grate.
 Air for combustion of fuel, flowing beneath the grate moves upwards
through the fire bars.
 Superheater tubes placed at exit of the flue gases.
 Used generally for up to 10000 kg/hr and low pressures upto 20 bar

18.  Low initial cost
 Large water content provides safety in
operation, during failure of feed water supply
 Suitable for fluctuating loads
 Low Space occupied

19.  Rate of evaporation is low and reaches operating
pressures slowly
 Suitable only for low capacities.
 Shell size 2.4m, shell thickness 3 cm, stress
considerations limit generation pressure to 20kg/cm2
 Lower efficiency
 Explosion is very dangerous due to large water content
 Transportation is difficult due to large shell size
 Useless for steam power plants due to slow rate of steam
generation
 Difficult design
 Less accessible to repairs

22.  Furnace is outside the drum
 Small parallel tubes contain water connected to
drum with the header
 Gases pass outside tubes containing water
 Flow of water is downward
 Steam returns to drum through uptake header

23. Water Tube Boilers

24.  High pressures and capacity
 Operating temps and pressures reached faster due to smaller water to
steam content
 Hot gases travel at right angles to water flow so heating surfaces are
effective
 Combustion space is larger so complete combustion possible with
better efficiency
 Thermal stresses low as all parts are at uniform temp due to quick
circulation
 Less serious damage compared to others due to lesser water content.
 Furnace area can be altered
 Higher Efficiency
 Suitable for power plant
 Parts easily accessible for cleaning
 Easily transported
 Simple design

25.  High initial cost
 Impure and dirty water not suitable as a small deposit can
cause explosion
 Failure in feed water supply can cause boiler overheat

28.  Shell
 Furnace
 Grate
 Setting
 Foaming
 Scale
 Blowing Off
 Lagging (Insulation outside
boiler shell or steam piping)
 Refractory (Fire proof in side
combustion chamber by fire brick)
 Water flow path
 Steam flow path
 Gas flow path
 Water space
 Steam space
 Water level
 Fittings/mountings
 Accessories

30.  An economizer is a heat exchanger, used for
heating the feed water before it enters the boiler.
 The economizer recovers some of waste heat
of hot flue gases going to chimney.
 It helps in improving the boiler efficiency.
 It is placed in the path of flue gases at the rear
end of the boiler just before air pre-heater.
ECONOMIZER

33.  A steam injector lifts and forces the feed water into
the boiler. It is usually used for vertical and locomotive
boilers and can be accommodated in small space.
 It is less costly. It does not have any moving parts thus
operation is salient.
 It is compact
 Can achieve high thermal efficiency
 Easy of operation

36.  The function of an air pre-heater is similar to
that of an economizer. It recovers some portion of
the waste heat of hot flue gases going to chimney,
and transfers same to the fresh air before it enters
the combustion chamber.
 Due to preheating of air, the furnace temperature
increases. It results in rapid combustion of fuel
with less soot, smoke and ash. The high furnace
temperature can permit low grade fuel with less
atmospheric pollution. The air pre-heater is
placed between economizer and chimney.

41.  It is used to feed the water at a high pressure against
the high pressure of steam already existing inside the
boiler.
 Reciprocating and Rotary pumps

43. STEAM SEPARATOR

45. A feedwater heater is a power plant component
used to pre-heat water delivered to a steam
generating boiler.
In a steam power plant,feed water heaters
allow the feedwater to be brought up to the
saturation temperatur very gradually improves
the thermodynamic efficiency of the
reducing plant operating costs and
also helps to avoid thermal shock
to the boiler metal.

47. Open FeedWater Heater
TYPES OF FEEDWATER HEATERS
Closed FeedWater Heater
 An open heat exchanger is
one in which extracted steam
is allowed to mix with the
feed water.
 This kind of heater will
normally require a feed pump
at both the feed inlet and
outlet since the pressure in
the heater is between the
boiler pressure and the
condenser pressure.
 A deaerator is a special case
of the open feedwater heater
which is specifically designed
to remove non-condensable
gases from the feedwater.
Closed feedwater heaters are
typically shell and tube heat
exchangers where the feedwater
passes throughout the tubes and
is heated by turbine extraction
steam. These do not require
separate pumps before and after
the heater to boost the feedwater
to the pressure of the extracted
steam as with an open heater.
Many power plants incorporate a
number of feedwater heaters and
may use both open and closed
components. Feedwater heaters
are used in both fossil- and
nuclear-fueled power plants.

48. OPEN FEEDWATER HEATERS
 An open heat exchanger is one in which
extracted steam is allowed to mix with the
feedwater.
 This kind of heater will normally require a
feed pump at both the feed inlet and
outlet since the pressure in the heater is
between the boiler pressure and the
condenser pressure.
 A deaerator is a special case of the open
feedwater heater which is specifically
designed to remove non-condensable
gases from the feedwater.

50. CLOSED FEEDWATER HEATERS
Closed feedwater heaters are typically shell and
tube heat exchangers where the feedwater passes
throughout the tubes and is heated by turbine
extraction steam. These do not require separate
pumps before and after the heater to boost the
feedwater to the pressure of the extracted steam
as with an open heater.
Many power plants incorporate a number of
feedwater heaters and may use both open and
closed components. Feedwater heaters are used in
both fossil- and nuclear-fueled power plants.