Download - CFB Presentation and Power Plant Overview
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1. Introduction
2. Principle of CFB boiler
3. Combustion in CFB
4. CFB main components&equipments
4.1 Feed water system
4.2 Superheater system
4.3 Chemical feeding system
4.4 Combustion Air system4.5 Fuel system
4.6 Flue gas system
4.7 Ash system
4.8 Make up sand and limestone system
BASIC of CFB boiler
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Basic component
Steam
Steam Outlet
Make up water
Condenser
Turbine
FW tank
P
G
CW out
CW in
Boiler
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Cogeneration (Cogen)
Steam
Steam Outlet
Make up water
Condenser
Turbine
FW tank
P
G
CW out
CW in
Boiler
Lowpressure
use inprocess
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Solid fuel
combustion boiler
Stokersboiler
Pulverized fuelCombustion boiler
Fluidized bedboiler
Bubbling BedCirculating
Fluidized Bed
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Stokers boiler
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Pulverized fuel Combustion boiler
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Basic components of CFB
Steam
WaterSteam Drum
Downcomer
Fuel Limestone
Steam Outlet
Super Heater
Economizer
Feed Water Inlet
Ash Cooler
Loop Seal
Bottom Ash
To Ash Silo
Fly Ash
Primary Air Fan
Secondary Air Fan
InducedDraftFan
Dust CollectorHot
Cyclone
Air Heater
Water Wall
Exhaust Gas
FluidizedBed
CombustionChamber
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FUEL &S O R B E N T
G AS
AIR AS H
FUEL &S O R B E N T
G AS
AIR AS H
AIR
PULVERIZED F IR ING
FUELA IR
G A S
ASH
BFB C FB
FLUIDIZED -BED F IR ING
FUEL
G AS
AIR A SH
GRATE F IR ING
(F IXE D B ED ) (E N TR AIN ED B ED )
Velocity 2.5-3 m/s 4.5-9 m/s 1.2-3 m/s 4.5-6.7 m/s
Furnace Temp. 1090-1370C 1200-1540C 815-930C 815-930C
2. CFB principle
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3. Combustion in CFB
Requirement for combustion;
1) the presence of a fuel (a combustible material)
2) enough oxygen to support combustion and
3) enough heat to bring the fuel to its ignition temperature
and keep it there.
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TimeTime to complete the combustion process
TurbulenceTurbulence provides more effective mixing of fuel and air, causes even heat
distribution and fills the entire combustor volume;
TemperatureTemperature of the combustor atmosphere must be kept above ignition
temperature. Preheating incoming combustion air increases temperature ofthe furnace atmosphere. Ignition temperatures and combustion temperatures
vary with fuel type and preparation.
The three "T"s of combustion, all necessary for goodcombustion
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4. CFB main component & equipments
4.1 Feed water system
4.2 Superheater system
4.3 Chemical feeding system4.4 Combustion Air system
4.5 Fuel system
4.6 Flue gas system
4.7 Ash system
4.8 Make up sand & limestone system
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4.1 Feed water system (1)
- Provide water to boiler corresponding toboiler load
- Water feed at appropriate quantity, pressureand temperature
- Feed water quality take cared by watertreatment plant
- Chemical dosing system control boiler waterquality
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NATURAL CIRCULATION (DRUM)
SUPERHEATER
EVAPORATOR
ECONOMIZER
FEED WATER PUMP
HEAT
4.1 Feed water system (2)
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4.2 Superheater system
- Sat. steam generated from furnace and separatorflow trough steam drum to crossover duct, backpass casing then SH coils
- SH coils arrangement depend on boiler design
- SH temperature controlled by desuperheater
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4.3 Chemical feeding system
- Purpose is to maintain boiler water/steamquality
- Na3PO4dos just before economizer
- Ammoniaand Hydrazinedos at feed watertank
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4.4 Combustion air system
- Main combustion air are Primaryand Secondaryair
- Primary airwork as bed fluidized air, maincombustion air and cooling for wall screw
- Secondary airfulfill combustion (control excess
air)
Boiler body
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4.5 Fuel system
- For CFB, coal is main fuel
- Amount of sludge limited by bed temperature
Anthracite
Bituminus
Sub bituminus
Lignite
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4.6 Fuel gas system
- Flue gas + ash are products of combustion
- Transfer heat to water wall
- Along flue gas path, refractory liningwill protect water wallfrom erosion and overheat
- Furnace pressure controlled by ID fan(Induced Draft fan)
- To maximize efficiency, combustion air heated at air-preheater.
- Finally, before stack, dust in flue gas was collected at ESP(Electrostatic precipitator)
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4.7 Ash handling system (1)
- Heavy solid particle accumulated at bed area is Bottom Ash
- Light particle fly away with flue gas is Fly Ash
- Bottom ash drained out from boiler via water cooled bottomash screw
- Part of fly ash transfer out at back pass hopper, then the verysmall fly ash will be collected at dust collector (ESP)
- In some design, fly ash will be reused by fly ash recalculating
sys.
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4.8 Make up sand and Limestone
- Purpose of make up sand feeding is to:
1. Maintain Bed pressure
2. Sand work as heat transfer material
- Purpose of limestone feeding is to:
1. Capture SO2
Less erosion
2. Maintain bed pressure ( same as sand but more gentle)
Heat + CaCO3 CaO + CO2
CaO + SO2
+ O2
CaSO4
+ Heat
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