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 CFBC DESIGN

COMPARISION

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Comparison with other Design

Parameter Lurgi-

Lenges ( A)

U- Beam (B) CVL

(C)

1.Solid

particleseparation

External

uncooled Hotcyclone

In furnace &

external – UBeam( many

rows)

External water

cooled hotcyclone.

2. Solid

separatorconstruction

Uncooled, Hot,

Mechanical typelarge cyclone

with 300-350

mm thick

refractory lined

Uncooled, “u”

beams banksuspended from

top, inside the

flue gas path,

outlet of

combustor

Water cooled

membrane type, mechanical

construction

with 25-50 mm

refractory

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Comparison with other Design

Parameter Lurgi-

Lenges ( A)

U- Beam (B) CVL

(C)3.Expansion

of Solid

particle

separator

Hot cyclone-

moves upward.,

Combustor movesdownwards &

requires very

large special

expansion joint -

Critical

In furnace &

external – U

Beam. No issue

External water

cooled hot

cyclone.- Bothcombustor &

Cyclone moves

downward

together- no issue

4.Supports forseparator

Bottomsupported

Suspendedfrom top of

extended wall. 

Lot many

opening on the

roof.

Top supported

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Comparison with other Design

Parameter Lurgi-

Lenges ( A)

U- Beam (B) CVL

(C)

5.Solid

particle

separator – 

efficiency

High Relatively less

than Hot cyclone.

It largely depends

on “recirculation

effect” at “U”beam

lower part

High

6. Solid

recirculationlocation

Bottom of

combustor. Butportion of solids

are cooled in

the FBHEs

Recirculation is

falling at the high

elevation in the

combustor. 

Sufficient time is

not given for

combustion of

particles which are

reentering

 All collected

solids particlesare entering in

the lower

portion of

combustor&

have more time

in combustor

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Comparison with other Design

Parameter Lurgi-

Lenges ( A)

U- Beam (B) CVL

(C)

5.Solid

particle

separator – shape

retaining

Hot cyclone-

maintenance on

the refractory

U Beams may

undergo erosion &

possibility to gettwisted leading to

out of position and

gas leaning

affecting ash

collection

efficiency. Needsinspection

Water cooled hot

cyclone rugged

construction beingalmost circular.

Small refractory

touch-ups.

6. Location of

separator

External to

combustor

In furnace

combustor

beams uncooled

may face

erosion .

External to

combustor

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Comparison with other Design

Parameter Lurgi-

Lenges ( A)

U- Beam (B) CVL

(C)

7. Success of CFB

process

High Relatively less

than Hot cyclone

due to collectioneffiency.

High

8. Dust loading

at second pass

1.0 More than 1.7

as the ESP first

hopper ash isre-injected into

the combustor

1.0

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Design superiority

• Due to above listed differences CVL CFB

design is superior to U- Beam.

• Our reference list is the testimony for the

design superiority in such a short span of

introduction.

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Lurgi

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 Additional re-injection

is done.

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CFBC DESIGN WITH COLD CYCLONE

•  UPPER FURNACE / HORIZONTAL PASS IS PACKED WITH

HTS (SUPER HEATER, EVAPORATOR & ECONOMISER

TOP BANK)

•  HIGH CONCENTRTAED SOLIDS PAASING OVER ABOVE

HEAT TRANSFER SURFACES

• THE LIFE OF HEAT TRANSFER SECTION (HTS) IS INFERIOR

TO HOT CYCLONE

• THE VELOCITY IN THIS DESIGN IS LOWER THAN

VELOCITY FOLLOWED FOR CFB TECHNOLOGY

• COLD CYCLONE IS OPERATING AROUND 450° C GAS

TEMPERATURE. THE COLLECTION EFFICIENCY IS

INFERIOR TO HOT CYCLONE OPERATING AROUND 850 TO

900 °C

• AS THE COLD CYCLONE IS BOTTOM SUPPORTED & THE

RETURN LEG TO THE CUMBOSTOR IS AT 45O ° C, THERE IS

A DIFFERENTIAL THERMAL EXPANSION BETWEEN

COMBUSTOR & CYCLONE / RETURN LEG

• MORE UNBURNT CARBON LOSS DUE TO REDUCED

COLLECTION EFFICIENCY ( COLLECTION EFFICIENCY WILL

BE SLIGHTLY BETTER THAN BUBBLING BED DESIGN)

• THE LIFE OF HTS CONSIDERING HIGH ASH % IN INDIAN COAL

IS EXPECTED TO BE LOW.

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Typical CFBC Boiler  

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WATER COOLED HOT CYCLONE