A PRESENTATION ON
CT Institute of
2. CLASSIFICATION OF STEAM POWER PLANT
3. LAYOUT OF A MODERN STEAM POWER
4. SELECTION OF SITE FOR STEAM POWER
5. COAL HANDLING SYSTEM
6. COMBUSTION SYSTEM
7. ASH HANDLING SYSTEM
9. FEED PUMPS
11. AIR-PREHEATER & SUPERHEATER
INTRODUCTION OF STEAM POWER PLANT
• In india 65% of power is generated by steam or thermal
• A steam power plant converts the chemical energy of the
fuels into mechanical/electrical energy.
CLASSIFICATION OF STEAM POWER PLANTS
The steam power plants may be classified as follows:
2.Industrial power stations or captive power stations
1) Central stations : These stations is meant for general sale to the
customers who wish to purchase it.
2) Industrial power stations : This type of power station is run by a
manufacturing company for its own use & its output is not available
for general sale.
Description about layout of steam power plant
• The layout of a modern steam power plant
comprises of the following four circuits :
1). Coal and Ash handling system
2). Air and gas Circuit
3.) Feed water and Steam flow circuit
4.) Cooling Water circuit
Components of a modern steam power plant:
1. Boiler 2. steam turbine
3. Generator 4. condenser
5. Cooling towers 6. circulating water pump
7. Boiler feed pump 8. wagon tippler
9. Crusher house 10. coal mill
11. Induced draught fans 12. Ash precipitators
13. Boiler chimney 14. Forced draught fans
15. Water treatment plant 16. Control room
17. Switch yard
Essential requirements of steam power plants
2. Minimum capital cost
3. Minimum operating & maintenance cost
4. Capacity to meet peak load effectively
5. Minimum losses of energy in transmission
6. Low cost of energy supplied to the consumers
7. Reserve capacity to meet future demands
8. Simplicity of design
9. Use of automatic equipment
SELECTION OF SITE FOR STEAM POWER STATION
• The following points should be taken into consideration while
selecting the site for a steam power station:
1. Availability of raw material 2. Nature of land
3. Cost of Land 4. Availability of water
5. Transport facilities 6. Ash disposal Facilities
7.Availability of labour 8. Size of the plant
9. Load centre 10. Public problems
11. Future extensions
The combustion equipment is a component of the steam generator. Since
of heat is the combustion of a fuel, a working unit must have, whatever,
equipment is necessary to receive the fuel & air, proportioned to each
other & to the boiler steam demand, mix, ignite, and perform any other
special combustion duties, such as distillation of volatile from coal prior
Basic requirements :
1. Through mixing of fuel & air.
2. Ready & accurate response of rate of fuel feed to load.
3. Practical distillation of volatile components of coal.
4. Adequate control over point formation & accumulation of ASH, when
coal is the fuel.
ASH HANDLING SYSTEM
• Burning of pulverized coal in the furnace results in the generation of
large quantity of ash . This ash constitutes of 80% fly ash and 20%
bottom ash. Fly ash is one of the residues generated in combustion,
and comprises the fine particles that rise with the flue gases.
• A station using low grade fuel has to deal with large quantities of
ash. Handling of ash includes :
1. Its removal from the furnace.
2. Loading on the conveyers and delivery to the fill or dump from
where it can be disposed off by sale or otherwise.
ASH HANDLING CHARACTERISTICS
A good ash handling plant should have the following characteristics :
1. It should have enough capacity to collect the large amount of ash that may be produced in a
2. It should be able to handle hot and wet ash effectively and with good speed.
3. The plant should not cost much.
4. The operation charges should be minimum possible.
5. The operation of the plant should be noiseless as much as possible.
6. The plant should have high rate of handling.
7. The plant should be able to operate effectively under variable load conditions.
8. Commonly used equipment: belt conveyor, Trollies or rails cars etc.
ASH HANDLING EQUIPMENTS:
• The commonly used equipment for ash handling in large & medium
size plants may comprise of:
1. Bucket elevator
2. Bucket conveyor
3. Belt conveyor
4. Pneumatic conveyor
5. Hydraulic sluicing equipment
6. Trollies or rail cars etc.
CLASSIFICATION OF ASH HANDLING SYSTEM :
The modern ash-handling system are mainly classified into four groups :
1). Mechanical Handling system: This system is generally employed for low
capacity power plants using coal as fuel.
2.). Hydraulic system: In this system ash is carried with the flow of water with high
velocity through a channel & finally dumped in the sump.
3). Pneumatic system: This system can handle abrasive ash as well as fine dusty
materials such as fly ash.
4). Steam jet system: In this case steam at sufficiently high velocity is passed
through a pipe & dry solid materials of considerable size are carried along
FLY ASH DISPOSAL SYSTEM
• Burning of pulverized coal in the furnace results
in the generation of large quantity of ash . This
ash constitutes of 80% fly ash and 20% bottom
ash. Fly ash is one of the residues generated in
combustion, and comprises the fine particles that
rise with the flue gases.
Boiler is an apparatus to produce steam.
Thermal energy released by combustion of fuel issued to
make steam at the desired temperature and pressure.
The steam produced is used for:
1). For generating power in steam engines or steam
2). Heating the residential and industrial buildings.
3). Performing certain processes in the sugar mills,
chemical and textile industries.
a). Safety: The boiler should be safe under the operating conditions.
b). Accessibility: the various part of boiler should be accessible for
repair & maintenance.
c). Capacity: Should be capable of supplying Steam according to the
d). Efficiency: Should be able to absorb a maximum amount of heat
produced due to burning of fuel in the furnace.
e). It should be simple in construction.
f). Its initial cost and maintenance cost is low.
g). It should be capable of quick starting and loading.
CLASSIFICATION OF BOILERS
• According to what flows in the TUBE :
a). FIRE TUBE
b). WATER TUBE
Comparison between Fire-tube & water-tube boilers
S no. Particulars Fire tube boilers Water tube boilers
1. Mode of firing Internally fired Externally fired
2. Rate of steam
3. construction Difficult Simple
4. transportation Difficult Simple
5. Treatment of water Not so necessary More necessary
6. Operating pressure Limited to 16 bar Under high pressure as
7. Floor area More floor area Less floor area
8. Shell diameter Large for same power Small same power
9. explosion Less More
10. Risk of bursting lesser More risk
MERITS OF WATER TUBE BOILER OVER FIRE TUBE
a). Generation of steam is much quicker due to small ratio of water content to
steam content . This also helps in reaching the steaming temperature in short
b). Its evaporative capacity is considerably larger and the steam pressure range is
c). Heating surfaces are more effective as the hot gases travel at right angles to the
direction of water flow.
d). The boiler can be easily transported and erected as its different parts can be
e). The combustion efficiency is higher because complete combustion of fuel is
possible as the combustion space is much larger.
f). All parts of the water tube boilers are easily accessible for cleaning, inspecting
TYPES OF FIRE TUBE BOILERS
• There are mainly five types of fire tube boilers :
1). Simple vertical boiler
2). Cochran boiler
3.) Cornish boiler
4). Lancashire boiler
5). Locomotive boilers
1). SIMPLE VERTICAL BOILER
• It consist of a cylindrical shell,
the greater portion of which is
full of water & remaining is
the steam space.
• At the bottom of the fire box is
grate on which fuel is burnt
and the ash from it falls in the
• A simple vertical boiler is self-
contained & can be easily
2). COCHRAN BOILER
• It is one of the best types of
vertical multi-tubular boiler,
and has a number of horizontal
• Cochran boiler consist of a
cylindrical shell with a dome
shaped top where the space is
provided for steam.
3). CORNISH BOILER
It consists of a cylindrical shell
with flat ends through which
passes a smaller flue tube
containing the furnace.
• The products of combustion
pass from the fire grate
forward over the brickwork
bridge to the end of the
4). LANCASHIRE BOILER
• This boiler is reliable, has
simplicity of design, ease of
operation & less operating &
• It is commonly used in sugar-
mills & textile industries
where along with the power
system & steam for the process
work is also needed.
About Locomotive boilers :
• Locomotive boiler is a horizontal fire tube type mobile boiler. The main
requirement of this boiler is that it should produce steam at a very high
rate. Therefore, this boiler requires a large amount of heating surface
and large grate area to burn coal at a rapid rate. In order to provide the
large heating surface area, a large number of fire tubes are setup and
heat transfer rate is increased by creating strong draught by means of
• ADVANTAGE :
a. Large rate of steam generation per square metre of heating surface. To
some extent this is due to the vibration caused by the motion.
b. It is very compact.
c. The pressure of the steam is limited to about 20 bar.
WATER TUBE BOILERS ARE CLASSIFIED AS :
1). Horizontal Straight tube boiler
There are two types of Horizontal straight tube boiler:
a. Longitudinal drum
b. Cross drum
there are three types of cross drum boiler :
1. two drum
2. four drum
3. three drum
2). Bent tube boiler
There are one type of bent tube boiler :
a. Low head three drum
1). Evaporative capacity :
It can be expressed in terms of :
a. kg of steam/hr
b. kg of hour/hr/m2 of heating surface
c. kg of steam/kg of fuel fired
2). Factor of Evaporation
• It is defined as the ratio of the heat received by 1kg of water at the
working conditions to that received by 1 kg of water evaporated from
and at 100 degree.
The feed pump is a pump
which is used to deliver feed
water to the boiler. It is a
desirable that the quantity of
water supplied should be at
least equal to the evaporated
and supplied to the engine.
Two types of pumps which are
commonly used as feed pumps
1. Reciprocating pumps
2. Rotary pumps
• An economiser is a device in
which the waste of heat of the
flue gases is utilised for
heating the feed water.
• Economiser are mainly two
a. Independent type
b. Integral type
• The above figure shows that an independent type vertical tube
economiser. It is also called Green’s economiser.
• It is employed for boilers of medium pressure range upto about 25
• It consists of a large no. of vertical cast iron pipes p which are
connected with two horizontal pipes, one at the top & the other at
overall efficiency of the plant is increased.
AIR PREHEATER & SUPER HEATER
AIR PREHEATER :
The function of the air preheater is to increases the temperature of
air before it enters the furnace. It is generally placed after the
economiser ; so the flue gases pass through the economiser & then
to the air.
• Degree of heating depends upon :
1. type of fuel
2. type of fuel burning equipment
3. rating at which the boiler & furnace are operated
About Air preheater
• There are three types of air
1. Tubular type
2. Plate type
3. Storage type
• This pic shows that a tubular
type air preheater.
• The function of a super heater is to increase the temperature of the
steam above its saturation point.
• Superheated steam has the following advantages:
1 steam consumption of the engine or turbine is reduced.
2. Efficiency of the steam plant is increased.
• There are two types of super heaters:
1. convective super heater
2. Radiant super heater