�ݺ�ߣ

What is economiser?
“A Device , which increases
the temprature of feed
water using waste heat of
flue gases leaving the boiler
through chimney.

Economiser
•construction

•working

•advantages
•disadvantages

Construction of
economisers
Consists of a large numbers of

vertical cast irons (steel water

pipes)
One end of vertical pipe connected

with horizontal pipe A & another
end with B.

Working of
economisers
The feed water enters into economiser

through the bottom pipe A.
Then, it comes into top pipe B through
the vertical pipes.
After that ,it comes into boiler for
further working.

Working of economisers
 The hot flue gases coming from

boiler pass over the vertical tubes of
economiser.
 OBSERVE :
The heat transfer takes place
from flue gases to cold water rising in
vertical tubes of economiser.

Working of economiser
The heated feed water is supplided

to the boiler from STOP VALVE.

Effects of working
The soot of flue gases which gets deposited

on the vertical pipes REDUCES
EFFICIENCY of the economiser.

TO PREVENT SOOT DEPOSIT ,the
scrapers S move up & down by chain and
gears to keep the external surface of the
pipe clean(for better HEAT TRANSFER)

Effects of working
A BLOW OFF COCK VALVE is

provided at back end of vertical
pipes to remove sediments

deposited in the bottom boxes .
A SAFETY VALVE provided at the
end of the pipe A for the safety of

the pipes.

Advantages
Higher feed water temperature tend to

reduce boiler thermal stersses, so life

boiler increased.

of

Economisers utilized waste heat from flue

so fuel consumption of
boiler reduces.
Increased evaporate capacity
gases,

of boiler.

Disadvantages
Economisers placed at passage of

the flow of flue gases , so

pressure drop take place of
flue gases (loss of draught)

Air-preheater: An Essential Element
of Fuel Fired Steam Power Plants

What is air preheater?
A device, which increases the

tempurature of air
before it supply to the
furnance using heat from
flue gases passing through
chimney.

Types of air preheater
Recuperative
type air
preheater

Regenerative
type air
preheater

Recuperative turbulent
type air preheater
•Construction

•Working
•Advantages
•Disadvantages

Construction
installed between
economisers and the chimney .

An air preheater is

It consists of large numbers tubes

which arranged
in the path flue gases
shell .
Inlet air is at lower end .

Baffles are provided inside air preheater .
The soot hoppper is provided at the

bottom .

Working
Hot flue gases enters into tubes from the

top of the shell and leaves from to the
chimney.
The inlet air at R.Tem. Is admitted into
the shell with the help of the fan.
The air passes upward around the tubes
in the opposite direction to the flow of
the hot gases.

Working
Baffles increases the total path length of air
and thus increase heat transfer .
The heated air leaves at the upper end of
the tube bank absorbing heat from the
hot flue gases.
The soot hopper provided at the bottom
is used to collect soot during cleaning
operation of the tubes.

Advantages of air
preheating
Preheated air

increases combustion

rate and then increases steam
generations rate of boiler.
Due to higher temperature of air, furnance
temperature increases, so low grade

coal can be burnt efficiently .

Advantages of air
preheating
Air heated by heat of exhaust gases.

It reduces fuel consumptions .
Therfore thermal efficiency of

boiler increased.

Disadvantages of air
preheating
There are formations of clinkers , on the

grate due to higher combustion
temperature.
Natural draught is not possible with air
pre heater because of temperature of flue
gases is reduced , also pressure drop take
place in the flow of the flue gases.
therfore forced draught is required.

�ݺ�ߣ

Economiser & air preheater

More Related Content

Economiser & air preheater