1. CFBC BOILER

2. Presentation on basics of CFBC BOILER

3. What is CFBC?
• It stands for Circulating Fluidized Bed Combustion.
• Fuel particles are suspended in a hot , bubbly fluidy
bed of ash ( containing sand / limestone) through
which nozzles of air are provided for combustion.
• Operating at high flue gas velocities 4 to 7 m/sec.
• Used for low capacity of plant 100 MW , 200MW .
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4. Why CFBC ?
• Fast and intimate mining of gas and solids promotes rapid
heat transfer and chemical reaction within the bed.
• Fuel burnt in these boilers include coal , washery rejects ,
rice husk , wood chips and other agricultural wastes at
high efficiency .
• These boilers are burnt at 850 – 900 degree C.
• These boilers uses crushed coal 3-6 mm of size, so no
pulverize is required.
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5. Basic Flow Diagram Of CFBC
Boiler
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6. Plant Overview
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7. Parts Of CFBC Boiler
• FLUIDIZED BED
• CIRCULATION
• BED MATERIAL
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8. Fluidized Bed
 At bottom of the boiler furnace there is a bed inert material
 Air supply is from under the bed at high pressure . This lift the bed
material and coal particles . Then the coal combination takes place
This is fluidized bed.
 Combustion air is supplied in CFBC boiler at 2 levels
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9. •60% at bottom of combustor at high pressure to fluidized bed.
40% in freeboard to complete combustion.
•SA fan – preheating combustion air
•PA fan – preheating fluidized air

10. Circulation
• Fine particles of partly burned coal ,ash and bed material are
carried along with the flue gases to the upper areas of furnace
and then to cyclone.
• In cyclone heavy particles separate from the gases due to
centrifugal force and falls on the cyclone hoppers .
• This returns to the furnace for re-circulation. So the thermal
efficiency of plant increase.
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11. FBHE Fluidized bed heat exchanger
• It is 4 rooms structure containing –
 1 Evaporator
 2 Super heater A
 3 Super heater B
 4 Re heater
• Elimination of heat transfer bundle in combustor.
• Very low carbon in ash and limestone consumption.
• Better fuel flexibility due to provision for adjusting heat
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12. Features of CFBC
• Taller boiler structure
• Coal is crushed to a size of 3-6 mm of size depending on the rank of coal
• The fluidizing velocity in circulating beds ranges from 4-7 m/sec
• Combustion efficiency is 99.5%
• Combustion takes place at 850-900 degree c.
• There are no steam generators tubes immersed in the bed.
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13. Advantages
• High Efficiency
• Combustion efficiency 95%
• Overall operating efficiency 88%
• Fuel flexibility
• Ability to burn low grade fuel
• Pollution control
• Sox formation is minimized by adding limestone
• low combustion temperature eliminates Nox formation.
• Easier ash removal – no clinker formation.
• Simple operation , quick start up
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14. Advantages cont…
• No slag in furnace – no soot blowing
• High reliability and low maintenance cost .
• Auxiliary power reduction by eliminating the flue gas
de sulphurisation FGD .
• Can use different types of solids fuels.
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15. THANK
YOU