Circulating fluidized bed boiler (cfb boiler) how does it work and its principle

1. BASIC DESIGN OF
CIRCULATING FLUIDIZED BED
BOILER
8 FEBRUARY 2012
Pichai Chaibamrung
Asset Optimization Engineer
Reliability Maintenance Asset Optimization Section
Energy Division
Thai Kraft Paper Industry Co.,Ltd.

2. By Chakraphong Phurngyai :: Engineer, TKIC
Biography
Name :Pichai Chaibamrung
Education
2009-2011, Ms.c, Thai-German Graduate School of Engineering
2002-2006, B.E, Kasetsart Univesity
Work Experience
Jul 11- present : Asset Optimization Engineer, TKIC
May 11- Jun 11 : Sr. Mechanical Design Engineer, Poyry Energy
Sep 06-May 09 : Engineer, Energy Department, TKIC
Email: [email protected], [email protected]

3. By Chakraphong Phurngyai :: Engineer, TKIC
Content
1. Introduction to CFB
2. Hydrodynamic of CFB
3. Combustion in CFB
4. Heat Transfer in CFB
5. Basic design of CFB
6. Cyclone Separator

4. By Chakraphong Phurngyai :: Engineer, TKIC
Objective
•To understand the typical arrangement in CFB
•To understand the basic hydrodynamic of CFB
•To understand the basic combustion in CFB
•To understand the basic heat transfer in CFB
•To understand basic design of CFB
•To understand theory of cyclone separator

5. By Chakraphong Phurngyai :: Engineer, TKIC
1. Introduction to CFB
1.1 Development of CFB
1.2 Typical equipment of CFB
1.3 Advantage of CFB

6. By Chakraphong Phurngyai :: Engineer, TKIC
1.1 Development of CFB
•1921, Fritz Winkler, Germany, Coal Gasification
•1938, Waren Lewis and Edwin Gilliland, USA, Fluid Catalytic
Cracking, Fast Fluidized Bed
•1960, Douglas Elliott, England, Coal Combustion, BFB
•1960s, Ahlstrom Group, Finland, First commercial CFB boiler, 15
MW
th
, Peat

7. By Chakraphong Phurngyai :: Engineer, TKIC
1.2 Typical Arrangement of CFB Boiler
•CFB Loop
- Furnace or Riser
- Gas – Solid Separation (Cyclone)
- Solid Recycle System (Loop Seal)
•Convective or Back-Pass
- Superheater
- Reheater
- Economizer
- Air Heater

8. By Chakraphong Phurngyai :: Engineer, TKIC
1.2 Typical Arrangement of CFB Boiler

9. By Chakraphong Phurngyai :: Engineer, TKIC
1.2 Typical Arrangement of CFB Boiler

10. By Chakraphong Phurngyai :: Engineer, TKIC
1.2 Typical Arrangement of CFB Boiler
•Air System
- Primary air fan (PA. Fan)
- Secondary air fan (SA. Fan)
- Loop seal air fan or Blower

11. By Chakraphong Phurngyai :: Engineer, TKIC
1.2 Typical Arrangement of CFB Boiler
•Flue Gas Stream
- Induced draft fan (ID. Fan)

12. By Chakraphong Phurngyai :: Engineer, TKIC
1.2 Typical Arrangement of CFB Boiler
•Solid Stream
- Fuel Bunker
- Bed Bunker
- Sorbent Bunker
- Bottom ash Bunker
- Fly ash Bunker
Feed
Drain

13. By Chakraphong Phurngyai :: Engineer, TKIC
1.2 Typical Arrangement of CFB Boiler
•Water- Steam Circuit
- Economizer
- Steam drum
- Evaporator
- Superheater

14. By Chakraphong Phurngyai :: Engineer, TKIC
1.3 Advantage of CFB Boiler
•Fuel Flexibility

15. By Chakraphong Phurngyai :: Engineer, TKIC
1.3 Advantage of CFB Boiler
•High Combustion Efficiency
- Good solid mixing
- Low unburned loss by cyclone, fly ash recirculation
- Long combustion zone
•In situ sulfur removal
•Low nitrogen oxide emission

16. By Chakraphong Phurngyai :: Engineer, TKIC
1.3 Advantage of CFB Boiler
•In Situ Sulfur Removal
Calcination
Sulfation

17. By Chakraphong Phurngyai :: Engineer, TKIC
1.3 Advantage of CFB Boiler
•Low Nitrogen Oxide Emissions

18. By Chakraphong Phurngyai :: Engineer, TKIC
2. Hydrodynamic in CFB
2.1 Regimes of Fluidization
2.2 Fast Fluidized Bed
2.3 Hydrodynamic Regimes in CFB
2.4 Hydrodynamic Structure of Fast Beds

19. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Fluidization is defined as the operation through which fine solid are
transformed into a fluid like state through contact with a gas or
liquid.

20. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Particle Classification
<130
<180
<250
<600
Foster
Size (micron)
<590<25025%
>420>100100%
<840<45050%
75%
100%
Distribution
<1190<550
<1680<1000
PB#15HGB

21. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Particle Classification

22. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Comparison of Principal Gas-Solid Contacting Processes

23. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Packed Bed
The pressure drop per unit height of a packed beds of a uniformly
size particles is correlated as (Ergun,1952)
Where U is gas flow rate per unit cross section of the bed called
Superficial Gas Velocity

24. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Bubbling Fluidization Beds
Minimum fluidization velocity is velocity where the fluid drag is
equal to a particle’s weight less its buoyancy.

25. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Bubbling Fluidization Beds
For B and D particle, the bubble is started when superficial gas is
higher than minimum fluidization velocity
But for group A particle the bubble is started when superficial
velocity is higher than minimum bubbling velocity

26. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Turbulent Beds
when the superficial is continually increased through a bubbling
fluidization bed, the bed start expanding, then the new regime
called turbulent bed is started.

27. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization

28. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Terminal Velocity
Terminal velocity is the particle velocity when the
forces acting on particle is equilibrium

29. By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Regimes of Fluidization
•Freeboard and Furnace Height
- considered for design heating-surface area
- considered for design furnace height
- to minimize unburned carbon in bubbling bed
the freeboard heights should be exceed or closed
to the transport disengaging heights

30. By Chakraphong Phurngyai :: Engineer, TKIC
2.2 Fast Fluidization
•Definition

31. By Chakraphong Phurngyai :: Engineer, TKIC
2.2 Fast Fluidization
•Characteristics of Fast Beds
- non-uniform suspension of slender particle agglomerates or
clusters moving up and down in a dilute
- excellent mixing are major characteristic
- low feed rate, particles are uniformly dispersed in gas stream
- high feed rate, particles enter the wake of the other, fluid drag
on the leading particle decrease, fall under the gravity until it
drops on to trailing particle

32. By Chakraphong Phurngyai :: Engineer, TKIC
2.3 Hydrodynamic regimes in a CFB
Lower Furnace below SA:
Turbulent or bubbling
fluidized bed
Furnace Upper SA:
Fast Fluidized Bed
Cyclone Separator :
Swirl Flow
Return leg and lift leg :
Pack bed and Bubbling Bed
Back Pass:
Pneumatic Transport

33. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Axial Voidage Profile
Bed Density Profile of 135 MWe CFB Boiler (Zhang et al., 2005)
Secondary air is fed

34. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Velocity Profile in Fast Fluidized Bed

35. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Velocity Profile in Fast Fluidized Bed

36. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Particle Distribution Profile in Fast Fluidized Bed

37. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Particle Distribution Profile in Fast Fluidized Bed

38. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Particle Distribution Profile in Fast Fluidized Bed
Effect of SA injection on particle
distribution by M.Koksal and
F.Hamdullahpur (2004). The
experimental CFB is pilot scale CFB.
There are three orientations of SA
injection; radial, tangential, and mixed

39. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Particle Distribution Profile in Fast Fluidized Bed
No SA, the suspension
density is proportional
l to solid circulation rate
With SA 20% of PA,
the solid particle is hold up
when compare to no SA
Increasing SA to 40%
does not significant on
suspension density above
SA injection point
but the low zone is
denser than low SA ratio
Increasing solid circulation
rate effect to both
lower and upper zone
of SA injection point
which both zone is
denser than low
solid circulation rate

40. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Effects of Circulation Rate on Voidage Profile
higher solid recirculation rate

41. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Effects of Circulation Rate on Voidage Profile
higher solid recirculation rate
Pressure drop across the L-valve is
proportional to solid recirculation rate

42. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Effect of Particle Size on Suspension Density Profile
- Fine particle - - > higher suspension density
- Higher suspension density - - > higher heat transfer
- Higher suspension density - - > lower bed temperature

43. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Effect of Bed Inventory on Suspension Density Profile

44. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Core-Annulus Model
- the furnace may be spilt into two zones : core and annulus
Core
-Velocity is above superficial velocity
-Solid move upward
Annulus
-Velocity is low to negative
-Solids move downward
core
annulus

45. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Core-Annulus Model
core
annulus

46. By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrodynamic Structure of Fast Beds
•Core Annulus Model
- the up-and-down movement solids in the core and annulus sets
up an internal circulation
- the uniform bed temperature is a direct result of internal
circulation

47. By Chakraphong Phurngyai :: Engineer, TKIC
3. Combustion in CFB
3.1 Stage of Combustion
3.2 Factor Affecting Combustion Efficiency
3.3 Combustion in CFB
3.4 Biomass Combustion

48. By Chakraphong Phurngyai :: Engineer, TKIC
3.1 Stage of Combustion
•A particle of solid fuel injected into an FB undergoes the following
sequence of events:
- Heating and drying
- Devolatilization and volatile combustion
- Swelling and primary fragmentation (for some types of coal)
- Combustion of char with secondary fragmentation and attrition

49. By Chakraphong Phurngyai :: Engineer, TKIC
3.1 Stages of Combustion
•Heating and Drying
- Combustible materials constitutes around 0.5-5.0% by weight
of total solids in combustor
- Rate of heating 100 °C/sec – 1000 °C/sec
- Heat transfer to a fuel particle (Halder 1989)

50. By Chakraphong Phurngyai :: Engineer, TKIC
3.1 Stages of Combustion
•Devolatilization and volatile combustion
- first steady release 500-600 C
- second release 800-1000C
- slowest species is CO (Keairns et al., 1984)
- 3 mm coal take 14 sec to devolatilze
at 850 C (Basu and Fraser, 1991)

51. By Chakraphong Phurngyai :: Engineer, TKIC
3.1 Stages of Combustion
•Char Combustion
2 step of char combustion
1. transportation of oxygen to carbon surface
2. Reaction of carbon with oxygen on the carbon surface
3 regimes of char combustion
- Regime I: mass transfer is higher than kinetic rate
- Regime II: mass transfer is comparable to kinetic rate
- Regime III: mass transfer is very slow compared to kinetic rate

52. By Chakraphong Phurngyai :: Engineer, TKIC
3.1 Stage of Combustion
•Communition Phenomena During Combustion
Volatile release cause the
particle swell
Volatile release in non-porous
particle cause the high
internal pressure result in
break a coal particle into
fragmentation
Char burn under regime I, II,
the pores increases in size à
weak bridge connection of
carbon until it can’t withstand
the hydrodynamic force. It will
fragment again call “
secondary fragmentation”
Attrition, Fine particles from
coarse particles through
mechanical contract like
abrasion with other particles
Char burn under regime I
which is mass transfer is
higher than kinetic trasfer.
The sudden collapse or other
type of second fragmentation
call percolative fragmentation
occurs

53. By Chakraphong Phurngyai :: Engineer, TKIC
3.2 Factor Affecting Combustion Efficiency
•Fuel Characteristics
the lower ratio of FC/VM result in higher combustion efficiency
(Makansi, 1990), (Yoshioka and Ikeda,1990), (Oka, 2004) but the
improper mixing could result in lower combustion efficiency due to
prompting escape of volatile gas from furnace.

54. By Chakraphong Phurngyai :: Engineer, TKIC
3.2 Factor Affecting Combustion Efficiency
•Operating condition (Bed Temperature)
- higher combustion temperature --- > high combustion efficiency
High combustion temperature result in high
oxidation reaction, then burn out time
decrease. So the combustion efficiency
increase.
Limit of Bed temp
-Sulfur capture
-Bed melting
-Water tube failure

55. By Chakraphong Phurngyai :: Engineer, TKIC
3.2 Factor Affecting Combustion Efficiency
•Fuel Characteristic (Particle size)
-The effect of this particle size is not
clear
-Fine particle, low burn out time but the
probability to be dispersed from cyclone
the high
-Coarse size, need long time to burn out.
-Both increases and decreases are
possible when particle size decrease

56. By Chakraphong Phurngyai :: Engineer, TKIC
3.2 Factor Affecting Combustion Efficiency
•Operating condition (superficial velocity)
- high fluidizing velocity decrease combustion efficiency because
Increasing probability of small char particle be elutriated from
circulation loop
- low fluidizing velocity cause defluidization, hot spot and sintering

57. By Chakraphong Phurngyai :: Engineer, TKIC
3.2 Factor Affecting Combustion Efficiency
•Operating condition (excess air)
- combustion efficiency improve which excess air < 20%
Excess air >20% less
significant improve
combustion efficiency.
Combustion loss
decrease
significantly
when excess air
< 20%.

58. By Chakraphong Phurngyai :: Engineer, TKIC
3.2 Factor Affecting Combustion Efficiency
•Operating Condition
The highest loss of combustion result from elutriation of char
particle from circulation loop. Especially, low reactive coal size
smaller than 1 mm it can not achieve complete combustion
efficiency with out fly ash recirculation system.
However, the significant efficiency improve is in range 0.0-2.0 fly
ash recirculation ratio.

59. By Chakraphong Phurngyai :: Engineer, TKIC
3.3 Combustion in CFB Boiler
•Lower Zone Properties
- This zone is fluidized by primary air constituting about 40-80% of
total air.
- This zone receives fresh coal from coal feeder and unburned
coal from cyclone though return valve
- Oxygen deficient zone, lined with refractory to protect corrosion
- Denser than upper zone

60. By Chakraphong Phurngyai :: Engineer, TKIC
3.3 Combustion in CFB Boiler
•Upper Zone Properties
- Secondary is added at interface between lower and upper zone
- Oxygen-rich zone
- Most of char combustion occurs
- Char particle could make many trips around the furnace before
they are finally entrained out through the top of furnace

61. By Chakraphong Phurngyai :: Engineer, TKIC
3.3 Combustion in CFB Boiler
•Cyclone Zone Properties
- Normally, the combustion is small when compare to in furnace
- Some boiler may experience the strong combustion in this zone
which can be observe by rising temperature in the cyclone exit
and loop seal

62. By Chakraphong Phurngyai :: Engineer, TKIC
3.4 Biomass Combustion
•Fuel Characteristics
- high volatile content (60-80%)
- high alkali content àsintering, slagging, and fouling
- high chlorine content àcorrosion

63. By Chakraphong Phurngyai :: Engineer, TKIC
3.4 Biomass Combustion
•Agglomeration
SiO2 melts at 1450 C
Eutectic Mixture melts at 874 C
Sintering tendency of fuel is indicated by the following
(Hulkkonen et al., 2003)

64. By Chakraphong Phurngyai :: Engineer, TKIC
3.4 Biomass Combustion
•Options for Avoiding the Agglomeration Problem
- Use of additives
- china clay, dolomite, kaolin soil
- Preprocessing of fuels
- water leaching
- Use of alternative bed materials
- dolomite, magnesite, and alumina
- Reduction in bed temperature

65. By Chakraphong Phurngyai :: Engineer, TKIC
3.4 Biomass Combustion
•Agglomeration

66. By Chakraphong Phurngyai :: Engineer, TKIC
3.4 Biomass Combustion
•Fouling
- is sticky deposition of ash due to evaporation of alkali salt
- result in low heat transfer to tube

67. By Chakraphong Phurngyai :: Engineer, TKIC
August 2010August 2010
PB#11 : Fouling Problem (7 Aug 2010)
3.Front water wall
- Add refractory 2 m.
(Height) above kick-out
2.Right water wall
- Change new
tubes (4 Tubes)
5.Roof water wall
-Change new tubes (4 Tubes)
-Overlay tube
-More erosion rate
1.5 mm/2.5 months
4. Screen tube & SH#3
- ¾º Slag ·Õèà¡ÒШíҹǹÁÒ¡
1.Front water wall upper
opening inlet
-Overlay tube (26Tubes)
-Replace refractory
May 2010 Aug 2010

68. By Chakraphong Phurngyai :: Engineer, TKIC
PB11 Fouling
May2010
6 months
Aug2010
2 months
Oct2010
2 months
Severe problem in Superheat tube fouling
•Waste reject fuel (Hi Chloride content)
•Only PB11 has this problems
•this problems also found on PB15 (SD
for Cleaning every 3 months)

69. By Chakraphong Phurngyai :: Engineer, TKIC
3.4 Biomass Combustion
•Corrosion Potential in Biomass Firing
- hot corrosion
- chlorine reacts with alkali metal àfrom low temperature melting
alkali chlorides
- reduce heat transfer and causing high temperature corrosion

70. By Chakraphong Phurngyai :: Engineer, TKIC
Foster Wheeler experience
Wood/Forest Residual
Straw,Rice husk
Waste Reject

71. By Chakraphong Phurngyai :: Engineer, TKIC
3.5 Performance Modeling
•Performance of Combustion
- Unburned carbon loss
- Distribution and mixing of volatiles, char and oxygen along the
height and cross section of furnace
- Flue gas composition at the exit of the cyclone separator
(NOx,SOx)
- Heat release and absoption pattern in the furnace
- Solid waste generation

72. By Chakraphong Phurngyai :: Engineer, TKIC
4. Heat Transfer in CFB
4.1 Gas to Particle Heat Transfer
4.2 Heat Transfer in CFB

73. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Mechanism of Heat Transfer
In a CFB boiler, fine solid particles
agglomerate and form clusters or
stand in a continuum of generally
up-flowing gas containing sparsely
dispersed solids. The continuum is
called the dispersed phase, while
the agglomerates are called the
cluster phase.
The heat transfer to furnace wall
occurs through conduction from
particle clusters, convection from
dispersed phase, and radiation
from both phase.

74. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Effect of Suspension Density and particle size
Heat transfer coefficient is proportional to the square root of suspension density

75. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Effect of Fluidization Velocity
No effect from fluidization velocity when leave the suspension density constant

76. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Effect of Fluidization Velocity

77. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Effect of Fluidization Velocity

78. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Effect of Vertical Length of Heat Transfer Surface

79. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Effect of Bed Temperature

80. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Heat Flux on 300 MW CFB Boiler (Z. Man, et. al)

81. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Heat transfer to the walls of commercial-size
Low suspension density low heat
transfer to the wall.

82. By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Heat Transfer in CFB Boiler
•Circumferential Distribution of Heat Transfer Coefficient

83. By Chakraphong Phurngyai :: Engineer, TKIC
5 Design of CFB Boiler
•5.1 Design and Required Data
•5.2 Combustion Calculation
•5.3 Heat and Mass Balance
•5.4 Furnace Design
•5.5 Heat Absorption

84. By Chakraphong Phurngyai :: Engineer, TKIC
5.1 Design and Required Data
•The design and required data normally will be specify by owner or
client. The basic design data and required data are;
Design Data :
-Fuel ultimate analysis -Weather condition
-Feed water quality -Feed water properties
Required Data :
-Main steam properties -Flue gas temperature
-Flue gas emission -Boiler efficiency

85. By Chakraphong Phurngyai :: Engineer, TKIC
5.2 Combustion Calculation
•Base on the design and required data the following data can be
calculated in this stage :
- Fuel flow rate - Combustion air flow rate
- Fan capacity - Fuel and ash handling capacity
- Sorbent flow rate

86. By Chakraphong Phurngyai :: Engineer, TKIC
5.3 Heat and Mass Balance
•Heat Balance
Fuel and
sorbent
Unburned in
bottom ash
Feed water
Combustion air
Main steam
Blow down
Flue gas
Moisture in fuel
and sorbent
Unburned in fly ash
Moisture in
combustion air
Radiation
Heat input
Heat output

87. By Chakraphong Phurngyai :: Engineer, TKIC
5.3 Heat and Mass Balance
•Mass Balance
Fuel and
sorbent
bottom ash
Solid Flue gas
Moisture in fuel
and sorbent
fly ash
Mass input
Make up
bed material
bottom ash
Fuel and
sorbent
Make up
bed material
Solid in Flue gas
fly ash
Mass output

88. By Chakraphong Phurngyai :: Engineer, TKIC
5.4 Furnace Design
•The furnace design include:
1.Furnace cross section
2.Furnace height
3.Furnace opening
1. Furnace cross section
Criteria
- moisture in fuel
- ash in fuel
- fluidization velocity
- SA penetration
- maintain fluidization in lower
zone at part load

89. By Chakraphong Phurngyai :: Engineer, TKIC
5.4 Furnace Design
2. Furnace height
Criteria
- Heating surface
- Residual time for sulfur capture
3. Furnace opening
Criteria
- Fuel feed ports
- Sorbent feed ports
- Bed drain ports
- Furnace exit section

90. By Chakraphong Phurngyai :: Engineer, TKIC
6. Cyclone Separator
•6.1 Theory
•6.2 Critical size of particle

91. By Chakraphong Phurngyai :: Engineer, TKIC
6.1 Theory
•The centrifugal force on the particle entering the cyclone is
•The drag force on the particle can be written as
•Under steady state drag force = centrifugal force

92. By Chakraphong Phurngyai :: Engineer, TKIC
6.1 Theory
•Vr can be considered as index of cyclone efficiency, from above
equation the cyclone efficiency will increase for :
- Higher entry velocity
- Large size of solid
- Higher density of particle
- Small radius of cyclone
- Higher value of viscosity of gas

93. By Chakraphong Phurngyai :: Engineer, TKIC
6.2 Critical size of particle
•The particle with a diameter larger than theoretical cut-sizeof
cyclone will be collected or trapped by cyclone while the small
size will be entrained or leave a cyclone
•Actual operation, the cut-off size diameter will be defined as d50
that mean 50% of the particle which have a diameter more than
d50 will be collected or captured.

94. By Chakraphong Phurngyai :: Engineer, TKIC
6.2 Critical size of particle
Effective number
Ideal and operation efficiency

95. By Chakraphong Phurngyai :: Engineer, TKIC
References
•Prabir Basu , Combustion and gasification in fluidized bed, 2006
•Fluidized bed combustion, Simeon N. Oka, 2004
•Nan Zh., et al, 3D CFD simulation of hydrodynamics of a 150 MWe circulating fluidized bed
boiler, Chemical Engineering Journal, 162, 2010, 821-828
•Zhang M., et al, Heat Flux profile of the furnace wall of 300 MWe CFB Boiler, powder
technology, 203, 2010, 548-554
•Foster Wheeler, TKIC refresh training, 2008
•M. Koksal and F. Humdullahper , Gas Mixing in circulating fluidized beds with secondary air
injection, Chemical engineering research and design, 82 (8A), 2004, 979-992

96. By Chakraphong Phurngyai :: Engineer, TKIC
THANK YOU FOR YOUR ATTENTION