Presentation on FBC Boilers
Welcome
Fluidized Bed Combustion Systems
By
M.RAJAVEL, SDGM / R&D/PCPS
BHEL, TRICHY -14
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
What is Fluidization ?
Fluidized Bed
FLUIDISED BED BOILER
When
Buoyancy Force
Buoyancy
Force
balances
Gravity Force
Gravity Force
FUEL
AIR
ASH
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Why call it Fluidized Bed ?
Light object Floats ; Heavier ones Sink
(Fixes Fuel Size)
AIR
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
AIR
28th August 2012
Presentation on FBC Boilers
Why call it Fluidized Bed ?
Horizontality Maintained
(Fixes Ash drain mechanism from Bed)
ASH
ASH
ASH
Fixed Bed
Fluidised
Bed
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28th August 2012
Presentation on FBC Boilers
Why call it Fluidized Bed ?
Pressure drop is  Bed Height
(Fixes Fan Power)
Umf
P
B
A
B
A
Flow / Velocity
AIR
AIR
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
What is Fluidization ?
Fixed Bed
STOKER FIRED BOILER
Buoyancy
Force
When
Gravitational Force
ASH
FUEL
Upto
25mm
AIR
is predominant
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Why call it Fluidized Bed ?
FLUIDISED BED BOILER
A Bed of Solid Particles exhibit the
properties of a FLUID namely:
è
Lighter objects float heavier ones sink
è Pressure drop is  Bed Height
è Horizontality maintained
hence termed as Fluidized Bed
FUEL
AIR
ASH
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
How does a Fluidized Bed work ?
The Bed of solid particles have to be retained at that size:
Combustion Temperature has to be well below ash fusion
temperature
FLUIDISED BED BOILER
Heat transfer walls are enclosed
Ash does not fuse - no slagging
Heat transfer by Gas / Particles Convection & Radiation
Fuel size upto 10mm - No PULVERISING
Ash soft amorphous state - less erosion
FUEL AIR
ASH
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
How does a Fluidized Bed work ?
When Fuel is injected into a Fluidized
Bed of solid particles which is heated
to Ignition Temperature of Fuel, it
burns imparting heat to the entire bed
FLUIDISED BED BOILER
Fuel Combustion takes place due to the
heat available in the Bed Ash - millions of
IGNITORS
Fuel of any Quality can be fired
FUEL
AIR
ASH
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
How does a Fluidized Bed work?
Combustion of Solid Fuel leaves
behind Ash. Finer fraction carried by
flue gas, coarser fraction replenishes
the bed solid inventory and excess is
drained out by drain pipes
FLUIDISED BED BOILER
Ash is dry and granular and is easily
handled.
FUEL
AIR
ASH
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Summary of Combustion Technologies
FLUIDIZED
BED
PNEUMATIC
TRANSPORT
PRESSURE
DROP
FIXED
BED
GAS FLOW/VELOCITY
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Presentation on FBC Boilers
Technology Comparison
FLUIDISED – BED FIRING
FBC
STOKER
(FIXED BED)
GAS
PULVERISED FIRING
(ENTRAINED BED)
GAS
GAS
FUEL
FUEL
AIR
AIR
FUEL
AIR ASH
AIR
FUEL
ASH
ASH
Vel
2.3 - 3 m/s
1.2 - 6 m/s
4.6 - 6.1 m/s
Par 
6000 m
300 - 1000 m
50 m
Temp
1600  C
850 C
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
1600  C
28th August 2012
Presentation on FBC Boilers
Advantages of Fluidized Bed
Combustion Boilers
Low combustion temperature- <900 DegC lead to less
Nox emission.
Sulphur present in coal can be recovered in-situ by
adding limestone. SOx emission can be reduced >90%
S + O2  SO2
CaO + SO2 +1/2 (O2) --> CaSO4
Poor quality coal/lignite, coal washery rejects,
containing ash >70%, can be used.
Biomass fuel can be fired either independently or in
combination with fossil fuels.
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28th August 2012
Presentation on FBC Boilers
Advantages of Fluidized Bed
Combustion Boilers
FBC Boilers can be operated in all loads without
sacrificing combustion efficiency.
Fuel of size less than 6 m.m. is used in FBC boilers
and hence need not be pulverised as does in P.F.
Boilers.
No moving grate or burners in FBC boilers.
Ash does not fuse at 900 DegC and hence soot
blowers are not required.
High combustion efficiency of fuel due to higher
residence time and entire surface area of fuel in
contact with air.
•
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28th August 2012
Presentation on FBC Boilers
Stoker fired boiler
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28th August 2012
Presentation on FBC Boilers
Stoker Fired Boilers
Moving Component (Travelling Grate) in the high
temperature Furnace zone
Combustion temperature 1400 - 1600°C; heat transfer in
furnace by Flame Radiation
Fuel Ignited by the already burning Fixed Bed
Fuel Combustion time limited to grate travel length - hence
fuels of poorer quality than design do not burn fully
Due to grate cooling requirements a minimum air quantity
is required - hence excess air is high at part loads
Very low relative movement between Fuel and Air
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Fluidised Bed Combustion
Boilers
Atmospheric pressure
Fluidised Bed
Combustion Boilers
(AFBC)
Pressurised Fluidised Bed
Combustion Boilers
(PFBC)
I
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Presentation on FBC Boilers
Atmospheric Fluidised Bed
Combustion Boilers
Bubbling Fluidised Bed
Combustion Boilers
(BFBC)
Circulating Fluidised Bed
Combustion Boilers
(CFBC)
I
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Presentation on FBC Boilers
FBC Test Facilities
10 t/hr BFBC Prototype Boiler - 1977
BFBC Test Facility-1986
Combustion Test Rig-1979
(90 t/hr Hot water)
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Presentation on FBC Boilers
AFBC Technology Development
1981 : First 12 t/h Commercial Boiler commissioned
1984 : First 10 MW power plant for Washery Rejects
1987 : First 10 MW power plant for Straw
1992 : First 20 MW (100 t/h) power plant for Rejects and Char
2000 : Largest boiler in operation of 180 t/h (45 MW)
2002 : Export of 17 MW Boilers to PT IBR Indonesia
2003 : Largest Boiler (300 t/hr) offered
2006 : Design of 120 MW Boiler ready
2008 : 3x18 MW Order from PT KPP, Indonesia
2009 : 2 X 180 t/hr BFBC Boiler order from JSPL, Angul
66 Boilers Contracted Over 2.5 million operating hours
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Presentation on FBC Boilers
Drum
SHI
Eco
Coal
Bunker
DESH
Air Heater
S H II
Feeder
Main
Steam
EVA
ESP
Ash
Air
Distributor
I D Fan
P A Fan
F D Fan
Schematic of AFBC Boiler
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28th August 2012
Presentation on FBC Boilers
AFBC Components
1
5
10
4
9
2
3
7
8
6
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
1 Steam Drum
2 Bed Superheater
3 Bed Evaporator
4 Convection Superheater
5 Economiser
6 Windbox
7 Air Distributor Plate
8 Hot Air Duct
9 Cold Air Duct
10 Air Preheater
28th August 2012
Presentation on FBC Boilers
Compartment – Unique Operational feature
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Presentation on FBC Boilers
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Presentation on FBC Boilers
Flow Diagram of CFBC Boiler - Separate FBHE
DRUM
Spiess
Valve
SECONDARY AIR
ID Fan
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Presentation on FBC Boilers
CFB Process Advantages
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Presentation on FBC Boilers
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Major Milestone -CFBC Technology Development
1995 : First CFBC boiler of capacity 175 TPH contracted
1995 : Utility size 2x125 Mwe capacity plant order received from
Surat Lignite plant (SLPP)
2003 : RVUNL, Rajasthan -2x125 Mwe plant using high sulphur content
lignite (6%)
2005 : First 2x250 MW CFBC power plant order received from
NLC,Neyveli.
2008 : Export order received from New Calidonia to supply 405 TPH
steam generator
28 CFBC Boilers Contracted .
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Typical Fuel analysis ( Assam Coal)
Proximate
Moisture
Volatile Matter
Ash
Fixed Carbon
HHV
%
%
%
%
kcal/kg
4.50
39.58
3.77
52.15
7792
Ultimate
Carbon
Hydrogen
Sulphur
Nitrogen
Moisture
Ash
Oxygen
%
%
%
%
%
%
%
78.36
5.04
2.57
0.98
4.50
3.77
4.78
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Chemical composition of fuel ash
(Assam Coal) and limestone:
Assam Coal
Lime Stone
Silica (SiO2)
%
56.70
4.90
Aluminium Oxide(Al2O3)
%
15.0
1.20
Iron Oxide (Fe2O3)
%
17.90
1.00
Titanium Oxide (TiO2)
%
0.80
1.00
Calcium Oxide (CaO)
%
1.70
53.70
Magnesium Oxide (MgO)
%
1.60
0.50
Sodium Oxide (Na2O)
%
3.50
1.00
Potassium Oxide (K2O)
%
2.60
0.10
Carbon di Oxide (CO2)
%
-
37.00
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
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Presentation on FBC Boilers
C.
ASH ANALYSIS
Silica (SiO2)
1.
51.08
48.42
52.38
48.15
52.56
(%)
14.83
13.84
15.73
13.66
15.97
(%)
18.60
25.16
15.31
26.14
14.36
1.30
1.04
1.42
0.96
1.49
0.26
0.19
0.32
0.16
0.37
2.04
1.73
2.18
1.68
2.25
(%)
2.
Alumina (Al2O3)
3.
Iron Oxide (Fe2O3)
Titania (TiO2)
4.
(%)
5.
Phosphoric Anhydride(P2O5) (%)
Lime (CaO)
6.
(%)
7.
Magnesia (MgO)
(%)
0.51
0.41
0.65
0.37
0.73
8.
Sulphuric Anhydride(SO3)
(%)
8.82
7.08
9.09
6.81
9.91
(%)
0.16
0.10
0.26
0.10
0.31
(%)
2.41
2.03
2.66
1.97
2.76
Sodium Oxide (Na2O) max
9.
10.
D.
1.
2.
3.
Potassium Oxide
ASH FUSION RANGE (under reducing atmosphere)
Initial Deformation Temp.(IDT) oC
1075
1050
1100
1050
1100
oC
1125
1100
1150
1100
1150
1175
1150
1200
1150
1200
Hemispherical Temp.
FusionTemp.
oC
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28th August 2012
Presentation on FBC Boilers
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28th August 2012
Presentation on FBC Boilers
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Presentation on FBC Boilers
Supercritical 600 MWe CFBC Boiler- Baima, China
 Research on supercritical CFB
was started in 2003. A
demonstration of 600MWe
supercritical CFB was initiating
in 2006 supported by
government.
 The first demonstration in
Baima was approved in 2008,
that shall be commissioned in
2011
Steam T : 571℃/569℃
Steam P : 25.4MPa
Steam Flow: 1900t/h，
Boiler efficiency: 92%
SO2
: <300mg/Nm3，
Nox
: <200mg/Nm3，
Generation efficiency:42%
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Design of 600MWe Supercritical CFB
Boiler ,
Design features:
 Vertical tube design with partial
rifle tube ;
 Mass flow rate is 1400kg/m2s
 6 cyclones with 6 external heat
exchangers (EHEs);
 Bottom ash drained from both two
side walls through roller type ash
cooler;
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Design Feature:
Benson vertical tube water membrane, mass flow 800kg/M2S.
Twin furnace (with total cross section 15x28m2 and 55 m height) divided by
a partition water wall.
Six cyclones with inner diameter 9m.
six external heat exchanger (EHE).
In furnace superheater panels.
The LT SH and LT RH in second pass.
The HT RH , the MT SH located in EHEs.
There are two options for the cyclone selection –steam cooled and insulated.
Water jacketed rotary ash cooler is used bed ash 2011.
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
28th August 2012
Presentation on FBC Boilers
Arrangement of 600MWe supercritical CFB Boiler of
Tsinghua’s Design
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Presentation on FBC Boilers
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Thanks for Your Patient Listening
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