What is the Economiser in power plants?
It’s the heat exchanger used in Boilers to recover the heat from
exhaust flue gases.
What are the functions of economisers in Boilers?
Functions of economisers:
It recovers the heat from flue gas leaving the boiler, there
by reduces the losses
It helps in raising the feed water temperature, there by
reduces the fuel consumption
It increases the Boiler efficiency
It lowers the power plant operation cost
What are the different types of economisers?
Types of economisers
Pressurized economisers
Non pressurized economisers
Steaming type
Non steaming pipe
What do you mean by steaming type economisers?
Economisers where only sensible heat is added to feed water
What do you mean by non-steaming type economisers?
Economisers where sensible heat and part of latent is added
to feed water
Efficiency Calculations:
ηEco. =
(Economiser outlet feed water temperature Two-Economiser inlet feed water
temperature Twi) X 100 / (Economiser inlet flue gas temperature
Tfi- Economiser inlet feed water temperature Twi)
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Example:
Calculate the economiser effectiveness, whose
feed water inlet & outlet temperatures are 160 Deg C & 240 Deg C
respectively & flue gas inlet & outlet temperatures 390 deg C & 220
deg c respectively.
Solution:
Twi = 160 deg C
Two = 240 deg C
Tfi = 390 deg C
Tfo = 220 deg C
ηEco = (Two-Twi) X 100 / (Tfi-Twi)
ηEco = (240-160 ) X 100 / (390-160)
ηEco= 34%
In an non steaming economiser of efficiency
51%, feed water inlet and outlet temperatures are 105 deg c & 160 deg C
respectively, calculate the flue gas temperature entering the economiser
Solution:
Twi = 105 deg C
Two = 160 deg C
Tfi = 370 deg C
Tfo = ? deg C
ηEco= 51%
ηEco = (Two-Twi) X 100 / (Tfi-Twi)
51= (160-105 ) X 100 / (Tfi-105)
Tfi X 51-105 X51 = 5500
Tfi = 212.8 deg C
A economiser inlet feed water & flue gas
temperature are 125 deg C and 405 deg C respectively, calculate the feed water
leaving the economiser, consider efficiency of economiser 43%
Solution:
Twi = 125 deg C
Two = ? deg C
Tfi = 405 deg C
ηEco= 43%
ηEco = (Two-Twi) X 100 / (Tfi-Twi)
43= (Two-125 ) X 100 / (405-125)
12040 = 100 X Two-12500
Two = 245.4 deg C
For more calculations related to power plant read Powerplant & Calculations
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