AIR PRE HEATER FOR BOILER IN THERMAL POWER PLANT

We have completed our discussion on Steam Generator structural and Pressure part erection

work. Small tips were also provided to construction worker which i think will be useful during

actual erection work. After completing the structural and pressure parts it is time now to discuss

about other main equipment like AIR PRE HEATER.

An Air Pre heater (APH) is a general term to describe any device designed to heat air, before

another process (for example, combustion in a boiler) with the primary objective of 

increasing the thermal efficiency of the process. They may be used alone or to replace a 

recuperative heat system or to replace a steam coil.

Air pre heaters are mainly two types (i) Tubular Airheater  (ii) Ljunstorm rotary air pre heater

bisector or trisector. Tubular air heater is now becoming an obsolete equipment only can be

seen in old and small capacity power house. However use of Ljunstorm air heater is common

to any size of unit. There are advantages and dis advantages for both type of air pre heater in 

use. We will confine our discussion only on Ljunstorm air preheater erection.

The picture above shows the overall construction feature of Ljunstorm air pre heater'

Names of the main parts of the LJUNGSTROM APH are:-

      1)    Expansion block (08)        

2)    Cold centre section (01)

3)    Main pedestal (02) 

4)    Side pedestal (02)

 5)     Guide bearing Assy (01)   

 6)    Support bearing Assy (01)

 7)    Rotor post (01)

 8)    Cold pocket ring (08)

 9)    Hot pocket ring (08) 

10) Hot centre section (01)

11) Cold end tension rings (08)

12) Hot end tension rings (08)

13) Drive pedestal (01)  

14)  Rotor drive unit

15) Guide bearing oil circulation unit

16)  Support bearing oil circulation unit

17) Rotor stoppage alarm sensor

18) Soot blowing system

19) Leakage control system     

20)  Shop assy modules (09)

21)  Semi modules (09) 

22) Gratings (72)

23) Baskets(heating elements)

24) Duct corner Assy (08)

25) Seismic stoppers (08)        

26) Rolled panels/Casings (16)

27) Field insulation 

28) Thermocouple for temperature Measurement.

Picture shows the location of Air preheater in a boiler ( having mills on the side) . PAPH stands

for Primary Air Preheater ( Left and Right) and SAPH stands for Secondary Air Preheater (Left 

and right)

Picture above shows Air Preheaters are in advanced stage of erection including interconnecting duct.

to be continued.

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