It is the Construction of 500 MW Subcritical Boiler. as well as the Steam cycle flow and water cycle flow of a Boiler

1. Construction
of
500 mw boiler
by
Vaibhav G. Paydelwar
( Project Engineer)
Sunil Hi-Tech Engineers
Limited

2. WHAT DO YOU MEAN BY BOILER
?
 Boiler means any closed vessel exceeding 22.75 Ltr. in capacity used
for steam generation under pressure. The first boiler was developed in
1725 and its working pressure was 10 kg/ cm2.
 Boiler can be regarded as a number of interconnected heat
exchangers arranged in such manner that heat available by burning of
fuel is transferred to convert water into steam in most efficient manner.

3. FUNCTION OF BOILER
 To produce the steam at the desired rate at
desired pressure and temperature with use of
resources such as oil, coal & water for generating
the power.

4. Types of Boilers
Natural circulation Boiler :Drum to down comer - to main ring header – to ww tubes
and back -to drum. Due to difference in density of water and steam this
types of circulation takes place.
 Forced circulation (Assisted circulation) Boiler :As per operating pressure of the boiler approaches to
the critical pressure, additional pumps are required to install in down
comers, because at this pressure there is no appreciable density
difference between water and steam to have natural circulation of
water.

5. NEED FOR ASSISTED
CIRCULATION
0.7
Density of Water
0.6
0.5
0.4
Critical
Point
0.3
0.2
0.1
Density of Steam
0
80
100
120
140
160
180
Pressure (Kg/cm2)
200
220
240

6. According to working pressure
Sub critical pressure boiler : when working
pressure of boiler is between 130 to 180 kg/ cm2
critical boiler : when working pressure of boiler
is 225.56 kg/ cm2
Super critical boiler : when working pressure of
boiler is 240.10 kg/ cm2

7. Why to go for higher capacity ?
1’-2’ = Work done in turbine
from P1 – P2
2’-3 = Heat Rejection in
condenser
3-4 = Water pumped to boiler
4-1 = Heat addition in eco and
boiler.

8. SPECIAL FEATURES OF 500MW BOILER
Controlled circulation of feed water in water walls with the
help of 3 Nos. of boiler circulating water pumps installed on
down comers. Rifled bore water wall tubes as against smooth
bore tubes in 210 MW boiler.
 Provision of Orifices for equal distribution of water in water
wall tubes from bottom ring header.
 All down comers are connected to front header of the
bottom ring header.


9. DESIGN FACTOR
For the construction of boiler parts subjected to
pressure and their integral attachment, the designer
takes into account several factors
 Relative Cost
 Mechanical Properties
 Manufacturing Method
 Scaling Resistance
 Maintenance

10. Various parts of Boiler
BOILER IS DIVIDED INTO TWO PASS: FIRST PASS
 SECOND PASS
First pass of the boiler consists of:-
 Furnace water wall.
 Divisional super heater pendent assembly.
 Final Super heater pendent assembly.
 Reheater front pendent assembly. (CRH)
 Reheater rear pendent assembly. (HRH)
 Rear Arch Panel.
 Water Wall screen tubes.

11. Second pass of the boiler consists of: Steam cooled wall.
 Economizer lower bank coils.

Economizer middle bank coils.

Economizer upper bank coils.

LTSH lower bank coils

LTSH upper bank coils

Eco. Hanger tubes.

LTSH terminal tubes.

12. ECONOMISER
 Requirement why ?
 Advantages
•
•
As the economiser recover the heat in the flue gas that leaves the boiler
and transfer to working fluid there will be saving in fuel consumption.
As the feed water is preheated in the economiser and enter the boiler
tube at an elevated temperature( near to saturation temp.) the heat
transfer area required for the evaporation surface required will be
reduce considerably. As the size of boiler also will be reduced.
 Types of Economiser
Steaming
 Non steaming
• Plain tube economiser
• Fin-tube economiser


13. Plain tubes
Direction of Gas Flow
Direction of Gas Flow
Inline Arrangement
Staggered
Arrangement

14. Fin-tube Eonomiser

15. Tube size and spacing


The tubes can be made any length and diameter with 38mm to 52mm
OD. The side spacing and back spacing can be arranged for good
cleaning, absorption of heat and less draught loss. Spacing about 90mm
to 140mm.
It is composed of three banks of 130 parallel tube elements arranged in
horizontal rows in such a manner that each row is in line with the row
above and below.

16. Drum & Drum Internals
 Requirement
Separation of saturated steam from the steam-water mixture produced by
the evaporating tubes
 Mixing feed water from economiser and water separated from steam – water
mixture, and re-circulate through the evaporating tubes.
 Carrying out blow down for reduction of boiler water salt concentration.
 Treatment of Boiler water by chemicals

construction of drum
1
11
111

17. BOILER DRUM:
Construction: Fusion welded
Material specification: SA299
Design pressure: 204.9 kg/cm2
Maximum operating press: 193 kg/cm2
Thickness for straight portion: 195/165 mm
Overall length of drum : 22070 mm
Outside dia. Of Drum : 2138 mm
Internal dia. Of Drum :1778 mm
Elevation of drum centre above ground level: 71.583 meter
No. of distribution headers : 6
No. of cyclonic separator :92
No. of secondary dryers : 92
No. of final dryers : 124
Maximum permissible DT between any two parts of Drum : 50 0C

18. Connection to Boiler Drum

•
•
•
•

•
•
•
•
•
•
•
Main connection
Feed lines
Down comers
Up risers
Super heater supply tubes
Auxiliary connection
Blow down line
Chemical dosing line
Instrumentation tapping
Air vents
Safety valves
Nitrogen filling line
High and low level trips

20. Drum Internals
Feed
header
Anti vortex spider
Steam separator
Steam dryers or scrubbers
C.B.D. line
 E.B.D. line
 chemical dosing line

22. Water Walled Furnace
Requirement
 Advantages






In furnace not only combustion but also heat transfer is taking place
simultaneously.
The maintenance work involved in repairing the firebricks (which is
otherwise necessary) is completely eliminated.
Due to heat transfer in the furnace, temperature of the flue gas leaving
the furnace is reduced to the acceptable level of the superheating
surfaces.
Higher heat loading in the furnace is possible, as heat is being
simultaneously removed by heat transfer, and hence economy in
surfacing.
Providing a Gas tight seal to the combustion chamber to prevent air
infiltration.

23. Water Wall Furnace Constuction

25. Expansion and Sealing
53mm
29mm
58mm
174mm
36mm
330 mm

26. Buckstay and Furnace Guides

27. Superheaters
 Requirement?
By increasing the temperature of the steam, the useful energy that can be
recovered economically increases thus the efficiency of the cycle also as can
be seen in Fig.3.40.
 Superheating of steam eliminates the condensation of steam during
transporting of steam in pipelines and inside the early stages of turbines
which is harmful to the turbine blades and pipe lines.
 Limits the work done by turbine stages to avoid excessive erosion of blades


28. Types of superheater


radiant superheater
convective superheater

29. Relationship in SH Design






The steam temperature desired
The super heater surface area required
The rate of steam flow through the tubes (mass flow)
The material best suited for the super heater tubes
The gas temperature zones where the surfaces are to
be located
The arrangement of surfaces to meet the characteristics
of the fuel to be used with specific reference to the
spacing of tubes

30. Material for SH
ASME CODE
NOMINAL
TEMP.LIMIT 0C
COMPOSITION
SA 213
CARBON STEEL
450
SA 213 T1
C-1/2 Mo.
470
SA 213 T11
11/4 Cr. –1/2 Mo.
550
SA 213 T22
21/4 Cr.-1 Mo.
580
SA 213 T9
9 Cr.-1 Mo.
635
SA 213 TP 304 H
18 Cr.-8 Ni.
705
SA 213 TP 347 H
18 Cr.-10 Ni.
705
SA 213 TP 316 H
16 Cr.-12 Ni.-2 Mo.
705
Description
Tube Size
Material
Radiant Roof Tubes
i.
ii.
Ø 63.5 X 6.3
Ø 57 X 5.6
SA 213, T11
SA 213, T11
wall
i.
ii.
iii.
Ø 63.5 X 6.3
Ø 51 X 5
Ø 76.1 X 10
SA 210, Gr C
SA 210, Gr C
SA 210, Gr C
Steam Cooled front wall
tubes
i.
ii.
iii.
Ø 51 X 5
Ø 63.5 X 6.3
Ø 44.5 X 7.1
SA 210, Gr C
SA 210, Gr C
SA 210, Gr C
Front Wall Hanger Tubes
Ø 51 X 5.0
SA 210, Gr C
Rear Roof Tubes
i.
ii.
SA 210, Gr C
SA 210, Gr C
Steam
tubes
Cooled
Eco and
tubes
Side
LTSH
Support
Ø 51 X 5
Ø 44.5 X 7.1
Ø 47.63 X 8.6
SA 210, Gr C

31. Description
Tube Size
Material
Steam Cooled Side Wall tubes
Ø 51 X 5
SA 210, Gr C
Bifurcate Tubes (Bottom Header)
Ø 51 X 5
SA 210, Gr C
LTSH Horizontal Tubes
i.
ii.
Ø 51 X 5
Ø 51 X 5.6
SA 210, Gr C
SA 210, Gr C
Pendent Coil Tubes
i.
ii.
Ø 51 X 5
Ø 51 X 5.6
SA 213, T11
SA 213, T11
Divisional Panel inlet loose tubes
i.
ii.
Ø 51 X 6
Ø 44.5 X 4.5
SA 210, Gr C
SA 210, Gr C
Divisional Panel Outlet loose tubes
i.
Ø 51 X 6
SA 213, T11
Steam Cooled Spacer
i.
ii.
iii.
iv.
v.
vi.
vii.
Ø 63.5 X 8
Ø 51 X 5.6
Ø 63.5 X 6.5
Ø63.5 X 7.1
Ø 63.5 X 7.1
Ø 51 X 5.0
Ø 51 X 5.0
SA
SA
SA
SA
SA
SA
SA
213,
213,
213,
213,
210,
213,
210,
T11
TP347H
TP347H
T11
Gr C
T11
Gr C

32. Reheater
 Requirement?
Description
Tube Size
Material
Reheater Wall tubes
Ø 60.3 X 4
SA 313, T11
Cross over tubes
Ø 54 X 3.6
SA 213, T11

33. Sr
.
Heating Surface
Type
Area in m2
N
o.
1
Radiant roof, steam cooled wall LTSH
9620
Horizontal and pendent.
2
Super Heater Divisional Panel
1361
3
Final Super heater Platen
1458
4
Reheater radiant wall front and side,
5075
front platen, rear platen.
Total Heating Surface
17514 M2

34. Sr.
Parameters
Rating
No.
1
Super heater system flow
1681 TPH
2
Reheater System Flow
1430.64 TPH
3
Pressure at super heater outlet
179 Kg/cm2
4
Temperature at super heater outlet
540 oC
5
Pressure at reheater inlet
44.88 Kg/cm2 (g)
6
Temperature at reheater inlet
342.7 oC
7
Pressure at reheater outlet
42.68 Kg/cm2 (g)
8
Temperature of reheater outlet
540 oC
9
Feed Water temperature
255 oC
10
Ambient air temperature
28 oC
11
Combustion air temperature secondary
335 oC
12
Fuel Quantity
330 TPH
13
Air Quantity (Total Combustion air)
2030 TPH
14
Temperature of Gas at boiler exit
142 oC
15
Total Heat output of the system
1076 Kcal/Hr

35. BOILER AIR & FLUE GAS TEMPERATURES
PLSH
RH
MAX-134 ºC
FSH
DRUM
758-726 ºC
720 ºC
1020-793 ºC
1135-1020 ºC
LTSH
461 ºC
ECO
11001250
355 ºC
SA-318 ºC
APH
A
B
147 ºC
PA-313 ºC
143 ºC
137 ºC
ESP

36. BOILER WATER & STEAM TEMPERATURE
PLSH
RH
DRUM
FSH
286-349 ºC
520-540 ºC
344-540
426-520 ºC
1300-1400
349-426 ºC
LTSH
243-286 ºC ECO
APH
A
B
ESP

37. M.S
H.
R.
H
C.R.H
500MW BOILER
BCW
Pump
FROM F.R.S
BOTTOM RNG HDR
WW PANELS & 1ST PASS
W.W.
1ST PASS W.W O/L HDRS
ROOF I/L HEADER
2ND
2nd PASS LOWER C-HDRS
PASS UPPER C-HDR
LTSH I/L HEADER
LTSH & O/L HEADER
D.P.I/L HEADER
D.P.O/L HEADER
FINAL S.H.
R.H.HEADER
2ND
ECONOMISER
PASS ROOF O/L HDR(REAR