Flue gas desulphurisation technics .ppt

Flue gas desulphurisation technics

1. Final Audit :Utilization of Flue Gas Energy
P M V Subbarao
Professor
Mechanical Engineering Department
Minimize Final Exhaust Gas Temperature….
Properly Utilize Enthalpy of Flue Gas….

2. s
1
2
3
4
5
6
2f
2s   
4523
hhmhhm
mreheatsteafmainsteam
 

3. DPNLSH
Platen SHTR
R
H
T
R
LTSH
Economiser
APH ESP ID Fan
drum
Furnace
BCW
pump
Bottom ash
stack
screen
tubes
Thermal Structure of A Boiler Furnace

4. Furnace ater wall absorption
Platen SH
Pendent SH
CSH
Reheater
Combustion LossesC & R losses
Hot Exhaust Gas
losses

5. Sequence of Energy Exchange from Flue Gas to Steam
PLATEN
SH
FLUE GAS
EVAPORATOR
Water Wall
COVECTIVE
LTSH
RH PENDENT
SH

6. Fuel Power
Furnace absorption
Platen SH
Final SH
LTSH
Reheater
Combustion LossesC & R losses
Hot Exhaust Gas
losses
~400
0
C

7. Details of 500 MW(e) Capacity Indian Power Unit
•Main steam Flow rate: 425 kg/s.
•Main Steam Temperature: 540
0
C
•Reheat Steam Flow rate: 38.7 kg/s.
•Air Flow Rate: 577.06 kg/s.
•Coal Flow Rate: 73.8 Kg/s.

8. 500 MW

9. Gas Temperatures
•Platen Super Heater:
•Inlet Temperature: 1236.4
0
C
•Outlet Temperature: 1077
0
C
•Final Super Heater:
•Inlet Temperature: 1077
0
C
•Outlet Temperature: 962.4
0
C
•Reheater:
•Inlet Temperature: 962.4
0
C
•Outlet Temperature: 724.3
0
C
•Low Temperature Super
Heater:
•Inlet Temperature: 724.3
0
C
•Outlet Temperature: 481.3
0
C
Steam Temperatures
•Platen Super Heater:
•Inlet Temperature: 404
0
C
•Outlet Temperature: 475
0
C
•Final Super Heater:
•Inlet Temperature: 475
0
C
•Outlet Temperature: 540
0
C
•Reheater:
•Inlet Temperature: 345
0
C
•Outlet Temperature: 540
0
C
•Low Temperature Super
Heater:
•Inlet Temperature: 359
0
C
•Outlet Temperature: 404
0
C

10. DesignCalculated
1Adiabatic Flame Temp (K)1957 1966
2FEGT (
0
C) 1102 1117
3Platen SH-I Outlet (
0
C) 932 951
4
Platen SH-II Outlet-I outlet
(
0
C) 859 878
5RH 3rd & 2nd outlet (
0
C) 595 604
6RH 1st Stage outlet (
0
C) 510 531
7Economiser outlet (
0
C) 385 398
8APH Outlet (
0
C) 138 151
Flue Gas Temperature At different regions of
Furnace:210 MWe)

11. Steam and Gas Paths

12. Suggested Fluid Velocities
•Flue gas velocities: 10 –18 m/s.
•Steam in super heaters & reheaters: 10 –25 m/s.
•Water Wall circulation : 0.35 –3.5 m/s.

13. 500 MW

14. LMTD for various Devices

15. Surface Area of Heat Exchangers: 500 MW

16. Economizer
•The economizer preheats the feed water by utilizing the residual heat
of the flue gas.
•It reduces the exhaust gas temperature and saves the fuel.
•Modern power plants use steel-tube-type economizers.
•Design Configuration: divided into several sections : 0.6 –0.8 m gap

17. Tube Bank Arrangement

19. Thermal Structure of Economizer
•Out side diameter : 25 –38 mm.
•Tube thinckness: 3 –5 mm
•Transverse spacing : 2.5 –3.0
•Longitudinal spacing : 1.5 –2.0
•The water flow velocity : 600 –800 kg/m
2
s
•The waterside resistance should not exceed 5 –8 %. Of
drum pressure.
•Flue gas velocity : 7 –13 m/s.

20. Thermal Balance in Economizer.
•The energy absorbed by steam
•The convective heat lost by flue gas
•Overall Coefficient of Heat Transfer, U)(
,,, inecoouteco
steam
conabs
hhmQ 
 TUAQ
ecolosscon


,

21. Mean Temperature Difference
•The average temperature difference for parallel flow and counter flow
is expressed as
•It is also called log mean temperature difference
•When t
max/t
min> 1.7, the average temperature may be expressed as:
•Generally, the flow direction of the flue gas is perpendicular to the
axes of tubes.
•If number of bends are more than four, the flow can be treated as
counter or parallel flow.min
max
minmax
log3.2
t
t
tt
t



 2
minmax
tt
t



22. Complex Flow
•Parallel flow and counter flow may simultaneously exist in one section
of an economizer.
•This is called complex flow.

23. •For a given set of inlet and outlet temperatures of the fluids,
•The temperature difference of parallel flow is the greatest,
•The temperature difference of counter flow is the lowest
•And that of complex flow is in between.
•The average temperature difference in a complex flow can be
calculated as:
•When
•Otherwise, the temperature difference is determined by
•The value of K
tdis determined by flow type and the thermal
parameters.  
copa
ttt  5.0 copa
tt  92.0 cotdtKt 

26. Gas Temperatures
•Platen Super Heater:
•Inlet Temperature: 1236.4
0
C
•Outlet Temperature: 1077
0
C
•Final Super Heater:
•Inlet Temperature: 1077
0
C
•Outlet Temperature: 962.4
0
C
•Reheater:
•Inlet Temperature: 962.4
0
C
•Outlet Temperature: 724.3
0
C
•Low Temperature Super Heater:
•Inlet Temperature: 724.3
0
C
•Outlet Temperature: 481.3
0
C
•Economizer:
•Inlet Temperature: 481.3
0
C
•Outlet Temperature: 328.5
0
C
Steam Temperatures
•Platen Super Heater:
•Inlet Temperature: 404
0
C
•Outlet Temperature: 475
0
C
•Final Super Heater:
•Inlet Temperature: 475
0
C
•Outlet Temperature: 540
0
C
•Reheater:
•Inlet Temperature: 345
0
C
•Outlet Temperature: 540
0
C
•Low Temperature Super Heater:
•Inlet Temperature: 359
0
C
•Outlet Temperature: 404
0
C
•Economizer:
•Inlet Temperature: 254
0
C
•Outlet Temperature: 302
0
C

27. Furnace absorption
Platen SH
Pendent SH
CSH
Reheater
Economizer
APH
Combustion LossesC & R losses
Hot Exhaust Gas
losses