fluidized bed combustion systems by m.rajavel, sdgm / r&d/pcps bhel, trichy -14
DESCRIPTION
Welcome. Fluidized Bed Combustion Systems By M.RAJAVEL, SDGM / R&D/PCPS BHEL, TRICHY -14. What is Fluidization ?. Fluidized Bed. FLUIDISED BED BOILER. When Buoyancy Force balances Gravity Force. Buoyancy Force. Gravity Force. AIR. FUEL. ASH. Why call it Fluidized Bed ?. - PowerPoint PPT PresentationTRANSCRIPT
Bharat Heavy Electricals Limited TIRUCHIRAPALLI
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Fluidized Bed Combustion SystemsBy
M.RAJAVEL, SDGM / R&D/PCPSBHEL, TRICHY -14
Welcome
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What is Fluidization ?
When
Buoyancy Force
balances
Gravity Force
Buoyancy Force
FLUIDISED BED BOILER
Fluidized Bed
FUEL AIR
ASH
Gravity Force
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Light object Floats ; Heavier ones Sink (Fixes Fuel Size)
AIR AIR
Why call it Fluidized Bed ?
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Horizontality Maintained(Fixes Ash drain mechanism from Bed)
Why call it Fluidized Bed ?
ASH
ASHASH
Fixed Bed Fluidised Bed
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AIRAIR
Flow / Velocity
P
A
B A B
Pressure drop is Bed Height(Fixes Fan Power)
Umf
Why call it Fluidized Bed ?
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Presentation on FBC Boilers
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What is Fluidization ?
When
Gravitational Force
is predominant
Buoyancy Force
STOKER FIRED BOILER
Fixed Bed
FUEL
AIR
ASH
Upto 25mm
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Why call it Fluidized Bed ?
FLUIDISED BED BOILER
FUEL AIR
A Bed of Solid Particles exhibit the
properties of a FLUID namely: Lighter objects float heavier ones sink
Pressure drop is Bed Height
Horizontality maintained
hence termed as Fluidized Bed
ASH
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How does a Fluidized Bed work ?
FLUIDISED BED BOILER
FUEL AIR
The Bed of solid particles have to be retained at that size:
Combustion Temperature has to be well below ash fusion temperature
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
ASH
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How does a Fluidized Bed work ?
FLUIDISED BED BOILER
FUEL AIR
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 bedFuel Combustion takes place due to the heat available in the Bed Ash - millions of
IGNITORS
Fuel of any Quality can be fired
ASH
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FLUIDISED BED BOILER
FUEL AIR
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
Ash is dry and granular and is easily handled.
How does a Fluidized Bed work?
ASH
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Summary of Combustion Technologies
GAS FLOW/VELOCITY
PR
ES
SU
RE
D
RO
P
FIXED BED
FLUIDIZED BED
PNEUMATIC TRANSPORT
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Technology Comparison
2.3 - 3 m/s 1.2 - 6 m/s 4.6 - 6.1 m/sVel
6000 m 300 - 1000 m 50 mPar
FUEL FUEL
STOKER
(FIXED BED)
FLUIDISED – BED FIRING FBC
PULVERISED FIRING
(ENTRAINED BED)
AIR ASHASH ASH
FUELFUEL
AIRAIR
AIR
GAS GAS
GAS
Temp 1600 C 850 C 1600 C
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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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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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Stoker fired boiler
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Stoker Fired Boilers
Moving Component (Travelling Grate) in the high temperature Furnace zoneCombustion temperature 1400 - 1600°C; heat transfer in furnace by Flame RadiationFuel Ignited by the already burning Fixed BedFuel Combustion time limited to grate travel length - hence fuels of poorer quality than design do not burn fullyDue to grate cooling requirements a minimum air quantity is required - hence excess air is high at part loadsVery low relative movement between Fuel and Air
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Fluidised Bed Combustion Boilers
Atmospheric pressure Fluidised Bed Combustion Boilers (AFBC)
Pressurised Fluidised Bed Combustion Boilers (PFBC)
I
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Atmospheric Fluidised Bed Combustion Boilers
Bubbling Fluidised Bed Combustion Boilers (BFBC)
Circulating Fluidised Bed Combustion Boilers (CFBC)
I
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10 t/hr BFBC Prototype Boiler - 1977
FBC Test FacilitiesFBC Test Facilities
Combustion Test Rig-1979
BFBC Test Facility-1986
(90 t/hr Hot water)
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AFBC Technology DevelopmentAFBC 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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CoalBunker
Feeder
P A Fan
E S P
Air Heater
EcoS H I
S H II EVA
Drum
Schematic of AFBC Boiler
I D Fan
AirDistributor
F D Fan
MainSteam Ash
DESH
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AFBC ComponentsAFBC Components
1 Steam Drum2 Bed Superheater3 Bed Evaporator4 Convection Superheater5 Economiser6 Windbox7 Air Distributor Plate8 Hot Air Duct9 Cold Air Duct10 Air Preheater
1
23
4
5
6
78
9
10
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Compartment – Unique Operational feature Compartment – Unique Operational feature
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Flow Diagram of CFBC Boiler - Separate FBHE
ID Fan
SpiessValve
DRUM
SECONDARY AIR
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CFB Process Advantages
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Major Milestone -CFBC Technology DevelopmentMajor 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 .
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Proximate
Moisture % 4.50Volatile Matter % 39.58Ash % 3.77Fixed Carbon % 52.15HHV kcal/kg 7792
Ultimate
Carbon % 78.36Hydrogen % 5.04Sulphur % 2.57Nitrogen % 0.98Moisture % 4.50Ash % 3.77Oxygen % 4.78
Typical Fuel analysis ( Assam Coal)
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Assam Coal Lime StoneSilica (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 53.70Magnesium Oxide (MgO) % 1.60 0.50Sodium Oxide (Na2O) % 3.50 1.00
Potassium Oxide (K2O) % 2.60 0.10
Carbon di Oxide (CO2) % - 37.00
Chemical composition of fuel ash (Assam Coal) and limestone:
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C. ASH ANALYSIS
1.Silica (SiO2)
(%)51.08 48.42 52.38 48.15 52.56
2. Alumina (Al2O3) (%) 14.83 13.84 15.73 13.66 15.97
3. Iron Oxide (Fe2O3) (%) 18.60 25.16 15.31 26.14 14.36
4.Titania (TiO2)
(%)1.30 1.04 1.42 0.96 1.49
5. Phosphoric Anhydride(P2O5) (%) 0.26 0.19 0.32 0.16 0.37
6. Lime (CaO) (%) 2.04 1.73 2.18 1.68 2.25
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
9. Sodium Oxide (Na2O) max (%) 0.16 0.10 0.26 0.10 0.31
10. Potassium Oxide (%) 2.41 2.03 2.66 1.97 2.76
D. ASH FUSION RANGE (under reducing atmosphere)
1. Initial Deformation Temp.(IDT) oC 1075 1050 1100 1050 1100
2. Hemispherical Temp. oC 1125 1100 1150 1100 1150
3. FusionTemp. oC 1175 1150 1200 1150 1200
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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 : 25.4MPaSteam Flow: 1900t/h,Boiler efficiency: 92%SO2 : <300mg/Nm3,Nox : <200mg/Nm3,Generation efficiency:42%
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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;
Design of 600MWe Supercritical CFB Boiler ,
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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.
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Arrangement of 600MWe supercritical CFB Boiler of Tsinghua’s Design
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