This document provides an overview of circulating fluidized bed boilers. It begins with biographical information about the author Pichai Chaibamrung, followed by an outline of the content to be covered. The content sections include introductions to circulating fluidized bed design, hydrodynamics, combustion, heat transfer, and cyclone separators. Key points are made about fluidization regimes, characteristics of fast fluidized beds, stages of combustion, and factors impacting combustion efficiency.
This material provides the basic of design, operation and maintenance so that you can use this as guide line to operation, to inspect your boiler. Hope this will be benefit you.
This material provides the basic of design, operation and maintenance so that you can use this as guide line to operation, to inspect your boiler. Hope this will be benefit you.
The presentation details about the Boiler Operation specifically while lightup of boiler and loading of boiler. the course participants discuss in details about the operations carried in their respective power stations
The presentation deals with the most complex and fundamental process in a CFBC boiler. i.e., Combustion. Provides an insight into the various features in a CFBC boilers which are incorporated to enhance cpmbustion.
Boiler purge is the basic process of resetting boiler before lightup. This presentation explains the logic, schematics & working of purge procedure. For enhanced knowledge of this topic, I can be reached at tahoorkhn03@gmail.com.
The Presentation discusses the Air-Heater Performance Indices and the Boiler Performance calculation. One can Calculate the air ingress in the air-heater and the boiler and losses incurred thereby. The presentation also describes in details about the boiler efficiency and its calculation.
Recognize numerous types of heat exchangers, and classify them.
Develop an awareness of fouling on surfaces, and determine the overall heat transfer coefficient for a heat exchanger.
Perform a general energy analysis on heat exchangers.
Obtain a relation for the logarithmic mean temperature difference for use in the LMTD method, and modify it for different types of heat exchangers using the correction factor.
Develop relations for effectiveness, and analyze heat exchangers when outlet temperatures are not known using the effectiveness-NTU method.
Know the primary considerations in the selection of heat exchangers.
The presentation details about the Boiler Operation specifically while lightup of boiler and loading of boiler. the course participants discuss in details about the operations carried in their respective power stations
The presentation deals with the most complex and fundamental process in a CFBC boiler. i.e., Combustion. Provides an insight into the various features in a CFBC boilers which are incorporated to enhance cpmbustion.
Boiler purge is the basic process of resetting boiler before lightup. This presentation explains the logic, schematics & working of purge procedure. For enhanced knowledge of this topic, I can be reached at tahoorkhn03@gmail.com.
The Presentation discusses the Air-Heater Performance Indices and the Boiler Performance calculation. One can Calculate the air ingress in the air-heater and the boiler and losses incurred thereby. The presentation also describes in details about the boiler efficiency and its calculation.
Recognize numerous types of heat exchangers, and classify them.
Develop an awareness of fouling on surfaces, and determine the overall heat transfer coefficient for a heat exchanger.
Perform a general energy analysis on heat exchangers.
Obtain a relation for the logarithmic mean temperature difference for use in the LMTD method, and modify it for different types of heat exchangers using the correction factor.
Develop relations for effectiveness, and analyze heat exchangers when outlet temperatures are not known using the effectiveness-NTU method.
Know the primary considerations in the selection of heat exchangers.
Heat of combustion & bayers theory sem 5MAYURI SOMPURA
organic chemistery ,heat of combustion ,bayers strain theory ,bayers strain theory for cyclobutane ,bayers strain theory for cyclopenatne ,ring size ,energy ,stability ,application of bomb calorimeter ,torsional strain ,angular strain
It gives information about Advanced Vapor Compression Cycles: Trans-critical cycle and their types, Ejector refrigeration cycle and their types. Presentation of cycle on P-h and T-s chart.
In this paper two case studies are presented, which are relevant to boiler operating and design engineers. One is a vibration problems experienced in CFBC boilers and other is about a repeated BFP failure in a power plant.
Omae2018 77032 improved-energy_method_on_helical_buckling_of_tubing-rev1Lixin Gong
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Casing and tubing buckling
Lubinski's Error in old energy method
Onset and Post buckling behavior of PIP Helical Buckling
Updated equations of critical helical buckling forces
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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. 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: ty_giuly@hotmail.com, pichacha@scg.co.th
By Chakraphong Phurngyai :: Engineer, TKIC
3. 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
By Chakraphong Phurngyai :: Engineer, TKIC
4. 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
By Chakraphong Phurngyai :: Engineer, TKIC
5. 1. Introduction to CFB
1.1 Development of CFB
1.2 Typical equipment of CFB
1.3 Advantage of CFB
By Chakraphong Phurngyai :: Engineer, TKIC
6. 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
MWth, Peat
By Chakraphong Phurngyai :: Engineer, TKIC
7. 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
By Chakraphong Phurngyai :: Engineer, TKIC
10. 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
By Chakraphong Phurngyai :: Engineer, TKIC
11. 1.2 Typical Arrangement of CFB Boiler
• Flue Gas Stream
- Induced draft fan (ID. Fan)
By Chakraphong Phurngyai :: Engineer, TKIC
14. 1.3 Advantage of CFB Boiler
• Fuel Flexibility
By Chakraphong Phurngyai :: Engineer, TKIC
15. 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
By Chakraphong Phurngyai :: Engineer, TKIC
16. 1.3 Advantage of CFB Boiler
• In Situ Sulfur Removal
Calcination
Sulfation
By Chakraphong Phurngyai :: Engineer, TKIC
17. 1.3 Advantage of CFB Boiler
• Low Nitrogen Oxide Emissions
By Chakraphong Phurngyai :: Engineer, TKIC
18. 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
By Chakraphong Phurngyai :: Engineer, TKIC
19. 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.
By Chakraphong Phurngyai :: Engineer, TKIC
21. 2.1 Regimes of Fluidization
• Particle Classification
By Chakraphong Phurngyai :: Engineer, TKIC
22. 2.1 Regimes of Fluidization
• Comparison of Principal Gas-Solid Contacting Processes
By Chakraphong Phurngyai :: Engineer, TKIC
23. 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
By Chakraphong Phurngyai :: Engineer, TKIC
24. 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.
By Chakraphong Phurngyai :: Engineer, TKIC
25. 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
By Chakraphong Phurngyai :: Engineer, TKIC
26. 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.
By Chakraphong Phurngyai :: Engineer, TKIC
27. 2.1 Regimes of Fluidization
By Chakraphong Phurngyai :: Engineer, TKIC
28. 2.1 Regimes of Fluidization
• Terminal Velocity
Terminal velocity is the particle velocity when the
forces acting on particle is equilibrium
By Chakraphong Phurngyai :: Engineer, TKIC
29. 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
By Chakraphong Phurngyai :: Engineer, TKIC
31. 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
By Chakraphong Phurngyai :: Engineer, TKIC
32. 2.3 Hydrodynamic regimes in a CFB
Cyclone Separator :
Swirl Flow
Back Pass:
Pneumatic Transport
Furnace Upper SA:
Fast Fluidized Bed
Lower Furnace below SA:
Turbulent or bubbling
fluidized bed
Return leg and lift leg :
Pack bed and Bubbling Bed
By Chakraphong Phurngyai :: Engineer, TKIC
33. 2.4 Hydrodynamic Structure of Fast Beds
• Axial Voidage Profile
Secondary air is fed
Bed Density Profile of 135 MWe CFB Boiler (Zhang et al., 2005)
By Chakraphong Phurngyai :: Engineer, TKIC
34. 2.4 Hydrodynamic Structure of Fast Beds
• Velocity Profile in Fast Fluidized Bed
By Chakraphong Phurngyai :: Engineer, TKIC
35. 2.4 Hydrodynamic Structure of Fast Beds
• Velocity Profile in Fast Fluidized Bed
By Chakraphong Phurngyai :: Engineer, TKIC
36. 2.4 Hydrodynamic Structure of Fast Beds
• Particle Distribution Profile in Fast Fluidized Bed
By Chakraphong Phurngyai :: Engineer, TKIC
37. 2.4 Hydrodynamic Structure of Fast Beds
• Particle Distribution Profile in Fast Fluidized Bed
By Chakraphong Phurngyai :: Engineer, TKIC
38. 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
By Chakraphong Phurngyai :: Engineer, TKIC
39. 2.4 Hydrodynamic Structure of Fast Beds
• Particle Distribution Profile in Fast Fluidized Bed
Increasing solid circulation
Increasing SA to 40%
rate effect to both
does not significant on
lower and upper zone
suspension density above
of SA injection point
SA injection point
which both zone is
but the low zone is
denser than low
denser than low SA ratio
solid circulation rate
No SA, the suspension With SA 20% of PA,
density is proportional the solid particle is hold up
l to solid circulation rate when compare to no SA
By Chakraphong Phurngyai :: Engineer, TKIC
40. 2.4 Hydrodynamic Structure of Fast Beds
• Effects of Circulation Rate on Voidage Profile
higher solid recirculation rate
By Chakraphong Phurngyai :: Engineer, TKIC
41. 2.4 Hydrodynamic Structure of Fast Beds
• Effects of Circulation Rate on Voidage Profile
Pressure drop across the L-valve is
proportional to solid recirculation rate
higher solid recirculation rate
By Chakraphong Phurngyai :: Engineer, TKIC
42. 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
By Chakraphong Phurngyai :: Engineer, TKIC
43. 2.4 Hydrodynamic Structure of Fast Beds
• Effect of Bed Inventory on Suspension Density Profile
By Chakraphong Phurngyai :: Engineer, TKIC
44. 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 core
- Solid move upward
Annulus
- Velocity is low to negative annulus
- Solids move downward
By Chakraphong Phurngyai :: Engineer, TKIC
45. 2.4 Hydrodynamic Structure of Fast Beds
• Core-Annulus Model
core
annulus
By Chakraphong Phurngyai :: Engineer, TKIC
46. 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
By Chakraphong Phurngyai :: Engineer, TKIC
47. 3. Combustion in CFB
3.1 Stage of Combustion
3.2 Factor Affecting Combustion Efficiency
3.3 Combustion in CFB
3.4 Biomass Combustion
By Chakraphong Phurngyai :: Engineer, TKIC
48. 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
By Chakraphong Phurngyai :: Engineer, TKIC
49. 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)
By Chakraphong Phurngyai :: Engineer, TKIC
50. 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)
By Chakraphong Phurngyai :: Engineer, TKIC
51. 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
By Chakraphong Phurngyai :: Engineer, TKIC
52. 3.1 Stage of Combustion
• Communition Phenomena During Combustion
Attrition, Fine particles from
coarse particles through
mechanical contract like
Volatile release in non-porous abrasion with other particles
particle cause the high
internal pressure result in
break a coal particle into
fragmentation
Char burn under regime I
which is mass transfer is
higher than kinetic trasfer.
The sudden collapse or other
Volatile release cause the type of second fragmentation
particle swell call percolative fragmentation
occurs
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”
By Chakraphong Phurngyai :: Engineer, TKIC
53. 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.
By Chakraphong Phurngyai :: Engineer, TKIC
54. 3.2 Factor Affecting Combustion Efficiency
• Operating condition (Bed Temperature)
- higher combustion temperature --- > high combustion efficiency
Limit of Bed temp
-Sulfur capture
-Bed melting
-Water tube failure
High combustion temperature result in high
oxidation reaction, then burn out time
decrease. So the combustion efficiency
increase.
By Chakraphong Phurngyai :: Engineer, TKIC
55. 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
By Chakraphong Phurngyai :: Engineer, TKIC
56. 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
By Chakraphong Phurngyai :: Engineer, TKIC
57. 3.2 Factor Affecting Combustion Efficiency
• Operating condition (excess air)
- combustion efficiency improve which excess air < 20%
Combustion loss
decrease
significantly
when excess air
< 20%. Excess air >20% less
significant improve
combustion efficiency.
By Chakraphong Phurngyai :: Engineer, TKIC
58. 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.
By Chakraphong Phurngyai :: Engineer, TKIC
59. 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
By Chakraphong Phurngyai :: Engineer, TKIC
60. 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
By Chakraphong Phurngyai :: Engineer, TKIC
61. 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
By Chakraphong Phurngyai :: Engineer, TKIC
62. 3.4 Biomass Combustion
• Fuel Characteristics
- high volatile content (60-80%)
- high alkali content à sintering, slagging, and fouling
- high chlorine content à corrosion
By Chakraphong Phurngyai :: Engineer, TKIC
63. 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)
By Chakraphong Phurngyai :: Engineer, TKIC
64. 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
By Chakraphong Phurngyai :: Engineer, TKIC
66. 3.4 Biomass Combustion
• Fouling
- is sticky deposition of ash due to evaporation of alkali salt
- result in low heat transfer to tube
By Chakraphong Phurngyai :: Engineer, TKIC
67. PB#11 : Fouling Problem (7 Aug 2010) August 2010
1.Front water wall upper
opening inlet 4. Screen tube & SH#3
- Overlay tube (26Tubes) - Slag
- Replace refractory
2.Right water wall
- Change new
tubes (4 Tubes)
May 2010 Aug 2010
5.Roof water wall
-Change new tubes (4 Tubes)
- Overlay tube
- More erosion rate
1.5 mm/2.5 months
3.Front water wall
- Add refractory 2 m.
(Height) above kick-out
By Chakraphong Phurngyai :: Engineer, TKIC
68. PB11 Fouling
May2010 Aug2010 Oct2010
6 months 2 months 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)
By Chakraphong Phurngyai :: Engineer, TKIC
69. 3.4 Biomass Combustion
• Corrosion Potential in Biomass Firing
- hot corrosion
- chlorine reacts with alkali metal à from low temperature melting
alkali chlorides
- reduce heat transfer and causing high temperature corrosion
By Chakraphong Phurngyai :: Engineer, TKIC
71. 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
By Chakraphong Phurngyai :: Engineer, TKIC
72. 4. Heat Transfer in CFB
4.1 Gas to Particle Heat Transfer
4.2 Heat Transfer in CFB
By Chakraphong Phurngyai :: Engineer, TKIC
73. 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.
By Chakraphong Phurngyai :: Engineer, TKIC
74. 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
By Chakraphong Phurngyai :: Engineer, TKIC
75. 4.1 Heat Transfer in CFB Boiler
• Effect of Fluidization Velocity
No effect from fluidization velocity when leave the suspension density constant
By Chakraphong Phurngyai :: Engineer, TKIC
76. 4.1 Heat Transfer in CFB Boiler
• Effect of Fluidization Velocity
By Chakraphong Phurngyai :: Engineer, TKIC
77. 4.1 Heat Transfer in CFB Boiler
• Effect of Fluidization Velocity
By Chakraphong Phurngyai :: Engineer, TKIC
78. 4.1 Heat Transfer in CFB Boiler
• Effect of Vertical Length of Heat Transfer Surface
By Chakraphong Phurngyai :: Engineer, TKIC
79. 4.1 Heat Transfer in CFB Boiler
• Effect of Bed Temperature
By Chakraphong Phurngyai :: Engineer, TKIC
80. 4.1 Heat Transfer in CFB Boiler
• Heat Flux on 300 MW CFB Boiler (Z. Man, et. al)
By Chakraphong Phurngyai :: Engineer, TKIC
81. 4.1 Heat Transfer in CFB Boiler
• Heat transfer to the walls of commercial-size
Low suspension density low heat
transfer to the wall.
By Chakraphong Phurngyai :: Engineer, TKIC
82. 4.1 Heat Transfer in CFB Boiler
• Circumferential Distribution of Heat Transfer Coefficient
By Chakraphong Phurngyai :: Engineer, TKIC
83. 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
By Chakraphong Phurngyai :: Engineer, TKIC
84. 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
By Chakraphong Phurngyai :: Engineer, TKIC
85. 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
By Chakraphong Phurngyai :: Engineer, TKIC
86. 5.3 Heat and Mass Balance
Heat input
• Heat Balance Main steam
Heat output
Radiation
Feed water
Blow down
Flue gas
Moisture in fuel Unburned in fly ash
and sorbent
Fuel and
sorbent
Combustion air
Unburned in Moisture in
bottom ash combustion air
By Chakraphong Phurngyai :: Engineer, TKIC
87. 5.3 Heat and Mass Balance
Mass input
• Mass Balance
Mass output
Solid Flue in Flue gas
Solid gas
Make up
bed material
Fuel and
sorbent
Moisture in fuel fly ash
and sorbent
Fuel and
sorbent
Make up
bed material
fly ash
bottom ash
bottom ash
By Chakraphong Phurngyai :: Engineer, TKIC
88. 5.4 Furnace Design
• The furnace design include: 1. Furnace cross section
1. Furnace cross section Criteria
2. Furnace height - moisture in fuel
3. Furnace opening - ash in fuel
- fluidization velocity
- SA penetration
- maintain fluidization in lower
zone at part load
By Chakraphong Phurngyai :: Engineer, TKIC
90. 6. Cyclone Separator
• 6.1 Theory
• 6.2 Critical size of particle
By Chakraphong Phurngyai :: Engineer, TKIC
91. 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
By Chakraphong Phurngyai :: Engineer, TKIC
92. 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
By Chakraphong Phurngyai :: Engineer, TKIC
93. 6.2 Critical size of particle
• The particle with a diameter larger than theoretical cut-size of
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.
By Chakraphong Phurngyai :: Engineer, TKIC
94. 6.2 Critical size of particle
Effective number
Ideal and operation efficiency
By Chakraphong Phurngyai :: Engineer, TKIC
95. 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
By Chakraphong Phurngyai :: Engineer, TKIC
96. THANK YOU FOR YOUR ATTENTION
By Chakraphong Phurngyai :: Engineer, TKIC