Transcript
Biography Name :Pichai Chaibamrung
BASIC DESIGN OF CIRCULATING FLUIDIZED BED BOILE BO ILER R 8 FEBRUARY 2012 201 2
Pichai Chaibamrung Asset Optimization Engineer
Reliab ili ility ty Maintenanc e As Ass set Op timiz timization ation Sec tion Energy Division
Education 2009-201 2009-2011, 1, Ms.c, Ms.c, Thai-Ge Thai-Ge rman Grad uate Sc hoo l of Enginee ring 2002-2006, 2002-2006, B.E, Kaset Kaset sart Unive Unive sity
Work Experienc Experienc e Jul 11- p resent resent : Asset Op tim ization Engine er, TKIC KIC Ma y 11- Jun 11 : Sr. Me c hanic al Design Design Engine Engine er, Poyry Poyry Energy Sep 06-Ma y 09 : Eng ine er, Energ Energ y Dep a rtme nt, TKIC KIC Ema il:
[email protected] , picha cha@ cha@s scg .co.th
Tha i Kraft Kraft Pap er Ind ustry Co.,Ltd. By ChakraphongPhurngyai:: Engineer, TKIC
Content
Objective
1. Introdu ctio n to C FB 2. Hydrodynam Hydrodynam ic o f CFB 3. Com bustion in CFB CFB 4. Hea t Transfer in C FB 5. Ba Ba sic d esign o f CFB CFB 6. Cyc lone Sep Sep arator
By Chakraphong Phurngyai :: Engineer, TKIC
• • • • • •
To und erstand erstand the typ ical arrangeme nt in CFB CFB To und erstand erstand the b asic asic hyd rodynamic of CFB To und ersta ersta nd the b asic asic c om bustion in CFB To und ersta ersta nd t he b asic asic h ea t tran sfer in CFB CFB To und ersta ersta nd b asic de sign of C FB To und erstand erstand theory of cyc lone sep sep arator
By ChakraphongPhurngyai:: Engineer, TKIC
1. Introduction to CFB 1.1 Developm ent of C FB 1.2 Typ ica l eq uipme nt of C FB 1.3 Adv anta ge of C FB
By Chakraphong Phurngyai :: Engineer, TKIC
1.2 Typ ic al A rrang em ent of CFB CFB Boiler •
CFB Loop - Furnace or Ris Riser er - Gas –Solid –Solid Sep aration (Cyclone) - Solid Recyc le Sys System tem (Loo (Loo p Seal) Seal)
•
Conve ctive or Back-Pas Back-Pass s - Superheater uperheater - Reheater - Econo mizer mizer - Air Heater
By Chakraphong Phurngyai :: Engineer, TKIC
1.1 Development of CFB • 1921, 1921, Fri Fritz tz Winkler, Winkler, Ge rmany, C oa l Ga sificat ion • 1938, 1938, Waren Lew is and Edw in Gilliland Gilliland , U US SA, Fluid Fluid Ca talytic Cra c king , Fast Fluidized Fluidized Bed • 1960, 1960, Doug las Elliott lliott , Engla Engla nd , Co al Com bustion, BF BFB • 1960s 1960s, Ahlstrom Ahlstrom Group , Finland, Finland, Firs First co mme rcial CFB CFB boiler, 15 MW th , Pea Pea t
By ChakraphongPhurngyai:: Engineer, TKIC
1.2 Typ ic al A rrang em ent o f CFB CFB Boiler
By ChakraphongPhurngyai:: Engineer, TKIC
1.2 Typ ic al A rrang em ent of CFB CFB Boiler
1.2 Typ ic al A rrang em ent o f CFB CFB Boiler • Air System - Prima Prima ry air fan (PA. Fan) - Sec ond ary air fan (SA. Fan) - Loop sea l air fan fan or Blower Blower
By Chakraphong Phurngyai :: Engineer, TKIC
1.2 Typ ic al A rrang em ent of CFB CFB Boiler •
Flue G as Strea Strea m - Induc Induc ed draft fan (ID. (ID. Fan)
By ChakraphongPhurngyai:: Engineer, TKIC
1.2 Typ ic al A rrang em ent o f CFB CFB Boiler • Solid Stre am - Fuel Bunker Bunker - Bed Bunker Bunker - Sorbent Bunker unker
Feed
Drain
- Bottom ash ash Bunker Bunker - Fly a sh Bunker
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
1.2 Typ ic al A rrang em ent of CFB CFB Boiler •
Water- Steam Circuit Circuit - Econo mizer mizer - Steam d rum rum - Eva porator - Superheater uperheater
1.3 Ad va nta ge of CFB CFB Boiler • Fuel Flexibility
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
1.3 Ad va ntag e o f CFB CFB Boile r •
• •
High Combustion Efficiency - Goo d solid solid mixing mixing - Low unburned unburned loss loss by cyc lone, fly ash ash recirculation - Long c omb ustion ustion zone zone In situ sulfur removal Low nitrog nitrog en o xide xide em iss ission
1.3 Ad va nta ge of CFB CFB Boiler • In Situ Sulfur Rem Rem ov al
Calcination
Sulfation
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
1.3 Ad va ntag e o f CFB CFB Boile r •
Low Nitroge n Oxide Emiss Emissions
2. Hydrod ynam ic in CFB CFB 2.1 Regimes of Fluidization 2.2 Fast Fast Fluidized Bed 2.3 H Hyd yd rodyna mic Reg imes in CFB CFB 2.4 Hydrod ynam ic Struct Struct ure of Fast Fast Bed Bed s
By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Reg ime s of Fluidizatio Fluidizatio n •
Fluidizatio luidizatio n is de fined a s the o pe ration throug h whic h fine solid solid a re transformed transformed into into a fluid like like state state through c onta ct w ith a ga s or liquid.
By ChakraphongPhurngyai:: Engineer, TKIC
2.1 Re gim es of Fluidizatio n • Particle Cla ssificatio n
Distribution
HGB
PB#15
100%
<600
<1000
<1680
75%
<250
<550
<1190
50%
<180
<450
<840
25%
<130
<250
<590
>100
>420
100%
By Chakraphong Phurngyai :: Engineer, TKIC
Size (mic ron) Foster
By ChakraphongPhurngyai:: Engineer, TKIC
2.1 Reg ime s of Fluidizatio Fluidizatio n •
Partic Partic le Cla ssific ific atio n
By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Reg ime s of Fluidizatio Fluidizatio n •
Pac ked Bed The p ress ressure ure d rop p er unit height of a pac ked bed s of a uniformly uniformly size ize p artic les is c orrela ted as (Ergun (Ergun ,1952)
2.1 Re gim es of Fluidizatio n • Com pa rison of Princip Princip al Ga s-Solid Co nta cting Proc Proc esses
By ChakraphongPhurngyai:: Engineer, TKIC
2.1 Re gim es of Fluidizatio n • Bubbling Fluidization Beds Minimum Minimum fluidiz fluidization ation veloc ity isveloc ity where the fluid fluid d rag is eq ual to a particle’s weight less less its buoya ncy.
Where U is ga s flow rate p er unit cross sec tion o f the b ed ca lled Superficial Gas Velocity
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
2.1 Reg ime s of Fluidizatio Fluidizatio n •
Bubbling Fluidization Fluidization Bed s For B and D p article, the b ubb le is started when superficial ga sis higher than minimum fluidiz fluidization ation ve locity But for group A pa rticle t he b ubb le is started when superficial velocity is higher g her than minimum minimum bubb ling velocity
By Chakraphong Phurngyai :: Engineer, TKIC
2.1 Reg ime s of Fluidizatio Fluidizatio n
2.1 Re gim es of Fluidizatio n • Turbulent Beds whe n the superficial is co ntinually increased increased through a bubb ling fluidization fluidization bed , the bed sta rt expand ing, then the new regime ca lled turbulent bed is started.
By ChakraphongPhurngyai:: Engineer, TKIC
2.1 Re gim es of Fluidizatio n • Termina l Veloc ity
Terminal veloc ity is is the particle velocity when the forces acting o n particle is equilibrium
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
2.1 Reg ime s of Fluidizatio Fluidizatio n •
Freeboa rd and Furnace Height - co nsidered nsidered for design design heat ing-surfac urfac e a rea - co nsidered nsidered for design design furnac furnac e height - to minimiz minimize unburned ca rbon in bubb ling bed the freebo ard heights should be exceed or closed closed to the t ransport ransport disengaging heights
By Chakraphong Phurngyai :: Engineer, TKIC
2.2 Fa Fa st Fluid Fluid izatio n •
Cha rac te ristics istics of Fast Fast Beds - non-uniform non-uniform suspe nsion nsion o f slende slende r pa rticle ag glomerates or clusters clusters moving up and dow n in a dilute - excellent mixing mixing are m ajor charac teristic - low feed rate, pa rticles rticles are are uniformly dispers dispersed ed in gas stream stream - high feed rate, particles enter the wa ke of the othe r, fluid fluid drag on the lea ding particle de crea se, fall under the g ravity until until it drop s on to trailing trailing pa rticle rticle
2.2 Fa Fa st Fluid Fluid izatio n •
Definition
By ChakraphongPhurngyai:: Engineer, TKIC
2.3 2.3 Hydrod Hydrod yna mic regim es in a CFB 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
By ChakraphongPhurngyai:: Engineer, TKIC
2.4 Hydrod yna m ic Structure Structure o f Fast Fast Bed Bed s •
Axial Axial Voidag e Profile rofile
Secondary air is fed
2.4 Hydrod yna mic Struc ture of Fast Fast Bed Bed s • Velo cit y Profile Profile in Fast Fast Fluidized Fluidized Bed
Bed Density Profi le of 135 MWe CFB Boiler (Zhang et al., 2005) 2005)
By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrod yna m ic Structure Structure o f Fast Fast Bed Bed s •
Velo cit y Profile Profile in Fast Fluidized Fluidized Bed
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
2.4 Hydrod yna mic Struc ture of Fast Fast Bed Bed s • Partic le Distrib Distrib utio n Profile Profile in Fast Fluid ized ized Bed
By ChakraphongPhurngyai:: Engineer, TKIC
2.4 Hydrod yna m ic Structure Structure o f Fast Fast Bed Bed s •
Partic le Distrib Distrib utio n Profile Profile in Fast Fluid ized ized Bed
2.4 Hydrod yna mic Struc ture of Fast Fast Bed Bed s • Partic le Distrib Distrib utio n Profile Profile in Fast Fluid ized ized Bed Effect of SA injection on particle distribution distribution by M.Koksal 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
By ChakraphongPhurngyai:: Engineer, TKIC
2.4 Hydrod yna m ic Structure Structure o f Fast Fast Bed Bed s •
Partic le Distrib Distrib utio n Profile Profile in Fast Fluid ized ized Bed Increasing SA to 40% does not significant on suspension density above SA injection point but the low zone is denser than low SA ratio
2.4 Hydrod yna mic Struc ture of Fast Fast Bed Bed s • Effects of Circulation Rate Rate on Voida ge Profile rofile
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
No SA, the suspension density is proporti onal l to solid circulation rate
By Chakraphong Phurngyai :: Engineer, TKIC
With SA 20%of PA, the solid particle is hold up when compare to no SA
higher solid recirculation rate
By ChakraphongPhurngyai:: Engineer, TKIC
2.4 Hydrod yna m ic Structure Structure o f Fast Fast Bed Bed s •
Effects of Circulation Rate Rate on Vo idage Profile rofile
2.4 Hydrod yna mic Struc ture of Fast Fast Bed Bed s • Effec t o f Partic le Size Size on Suspe nsion Den sity Profile - Fine pa rticle rticle - - > higher sus suspensi pension on d ensity ensity - Higher Higher sus suspension pension d ensity ensity - - > higher heat transfer transfer - Higher Higher sus suspensi pension on d ensity ensity - - > lower bed te mp erature
Pressure drop across the L-valve is proportional to solid recirculation rate
higher solid recirculation rate
By Chakraphong Phurngyai :: Engineer, TKIC
2.4 Hydrod yna m ic Structure Structure o f Fast Fast Bed Bed s •
Effec t o f Bed Inve Inve nto ry on Suspe uspe nsion nsion Density Density Profile
By ChakraphongPhurngyai:: Engineer, TKIC
2.4 Hydrod yna mic Struc ture of Fast Fast Bed Bed s • Core-Annulus Core-Annulus Mod el - the furnace m ay be spilt spilt into two zones : core and a nnulus Core - Velocity is above superficial velocity - Solid move upw ard Annulus - Velocity is low to nega tive - Solids mov e d ow nward
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
core
annulus
2.4 Hydrod yna m ic Structure Structure o f Fast Fast Bed Bed s •
Core-Annulus Core-Annulus Mod el
2.4 Hydrod yna mic Struc ture of Fast Fast Bed Bed s • Core Annulus Mod el - the up -and-dow n movem ent solids solids in the co re and a nnulussets up an internal circulation - the uniform bed tem perature is a d irect irect resul resultt of internal circulation
core
annulus
By Chakraphong Phurngyai :: Engineer, TKIC
3. Com bustion in CFB CFB 3.1 Stag e of C omb ustion 3.2 Fac tor Affec ting Comb ustion Efficiency Efficiency 3.3 Comb ustion ustion in C FB 3.4 Biom om ass Co mb ustion ustion
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
3.1 Stage of Combustion • A pa rticle of solid solid fuel injec injec ted into into an FB FB unde unde rgoes the following following seq uence o f events: - Heating and drying drying - Devolatil Devolatiliz ization ation and volatile volatile com bustion bustion - Swelling and p rima rima ry fragmentat ion (for some t ypes of coa l) - Com bustion bustion of cha r with sec sec ond ary fragmentat fragmentat ion and attrition attrition
By ChakraphongPhurngyai:: Engineer, TKIC
3.1 Stag e s of Co m bustion •
Heating and Drying Drying - Com bustible mate rials rials c onstitute onstitute s around 0.5-5.0 0.5-5.0% % by we ight of t ota l solids solids in com bustor bustor - Rate o f heating 100 100 °C/ sec – 1000 1000 °C/ sec - Heat transfer transfer to a fuel particle (Halder 1989) 1989)
3.1 Stag es of Com bustion • Devolatiliz Devolatilization and volatile com bustion bustion - first stead y relea se 500-600 500-600 C - sec ond release 800-1 800-1000 000C C - slowe st spec ies is CO (Kea irnse irnse t a l., 1984) 1984) - 3 mm coa l ta ke 14 sec to dev olatilze at 850 C (Basu and Fraser, 1991) 1991)
By Chakraphong Phurngyai :: Engineer, TKIC
3.1 Stag e s of Co m bustion •
Char Com bustion bustion 2 step of cha r comb ustion ustion 1. trans transpo po rtation of oxyge n to ca rbo n s sur urfac fac e 2. Rea ction o f carbo n with oxygen on the ca rbon surf surfac ac e 3 regime regime s of c har com bustion bustion - Reg ime I: mass transfer is is highe r than kinetic rate - Reg ime II: II: mass transfer is c om pa rable to kinetic rate - Reg ime III: III: ma ss transfer is is ve ry slow slow co mp ared t o kinetic rate
By ChakraphongPhurngyai:: Engineer, TKIC
3.1 Stage of Combustion • Comm unition unition Phenome na During During Combustion Combustion
Volatile release in non-porous particle cause the high internal pressure result in break a coal particle int o fragmentation
Attrition, Fine particlesf rom Attrition, coarse particlesthrough mechanical contract like abrasion with other particles
Char burn un der regime I which ismasstransfer i s higher than kinetic trasfer. The sudden collapse or other type of second fragment ation call percolativefr agmentation occurs
Volatile release cause the particle swell
Char burn under regime I, II, the poresincreases in size weak bridge connection of carbon until it can’t withstand the hydrodynamic force. It will fragment again call “ secondary fragmentati on on”” By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
3.2 3.2 Fac Fac tor Affecting Com bustion bustion Eff Efficienc icienc y •
Fuel Characteristics the low er ratio of FC/ FC/ VM result result in higher com bustion bustion efficiency (Ma kansi, kansi, 1990), 1990), (Yoshi (Yoshioka oka and Iked Iked a,1990), (Oka, 2004) 2004) b ut the improper mixing mixing c ould result esult in lower com bustion bustion efficiency d ue to prompting e sca pe o f volatile volatile ga s from furnac furnac e.
3.2 3.2 Fac Fac tor Affec ting Co mb ustion ustion Eff Efficienc icienc y • Ope rating co ndition (Bed (Bed Tempe rature) rature) - higher com bustion bustion tempe rature rature ----- > high high com bustion bustion efficienc efficienc y
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
By ChakraphongPhurngyai:: Engineer, TKIC
3.2 3.2 Fac Fac tor Affecting Com bustion bustion Eff Efficienc icienc y •
Fuel Cha ract eristic eristic (Particle size) ize)
3.2 3.2 Fac Fac tor Affec ting Co mb ustion ustion Eff Efficienc icienc y •
Operating condition (superficial velocity) - high fluidiz fluidizing ing velocity d ecrease com bustion bustion efficiency efficiency bec ause ause Increasing Increasing p robab ility ility of small small cha r pa rticle c le b e elutriated from circulation loop
-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 incr eases and decreases are possible when particle size decrease
- low fluidizing fluidizing velocity c ause de fluidization, fluidization, hot spo spo t and sintering ng
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
3.2 3.2 Fac Fac tor Affecting Com bustion bustion Eff Efficienc icienc y •
Operating co ndition (exce ss air) - co mb ustion ustion efficiency improve w hich excess air < 20% 20% Combustion loss decrease significa ntly when excess air < 20%.
3.3 Com b ustion ustion in CFB CFB Boiler Boiler Low er Zone Prop erties - This zone is fluidized fluidized by primary air c onstituting a bo ut 40-80% 40-80% of tota l air. air. - This zone receives fres fresh h co al from c oa l feede r and unburned coal from cyclone though return valve - Oxygen de ficient zone, zone, lined lined w ith refracto refracto ry to p rotect c orrosi orrosion on - Denser Denser than upp er zone zone
By Chakraphong Phurngyai :: Engineer, TKIC
• Operating C ondition ondition The hig hest loss loss of c om bustion result result from from elutriation o f cha r pa rticle from c irculation irculation loop . Es Espec ially, ially, low rea ctive co al siz size e sma ller ller than 1 mm it ca n not achieve c omp lete com bustion bustion efficiency with o ut fly a sh recirculation system. However, the significant efficiency improve is in range 0.0-2.0 fly ash ash rec irculation irculation ratio.
Exc ess air >20% le ss significa ignifica nt improve co mb ustion efficienc efficienc y.
By Chakraphong Phurngyai :: Engineer, TKIC
•
3.2 3.2 Fac Fac tor Affec ting Co mb ustion ustion Eff Efficienc icienc y
By ChakraphongPhurngyai:: Engineer, TKIC
3.3 Com b ustion ustion in CFB CFB Boile r • Upp er Zone Zone Prop Prop erties - Seco ndary isadd ed at interface interface between lower and upper zone zone - Oxygen-rich Oxygen-rich zone zone - Most Most o f char com bustion bustion occurs - Char particle could ma ke many trips trips around the furnace be fore they are finally finally entrained o ut through through the t op o f furnace furnace
By ChakraphongPhurngyai:: Engineer, TKIC
3.3 Com b ustion ustion in CFB CFB Boiler Boiler •
Cyc lone Zone Prop Prop erties - Normally, Normally, the c omb ustion ustion is sma ll w hen co mp are to in furnac furnac e - Some boiler may e xperience xperience the strong c omb ustion ustion in this zone which c an be ob serve by rising temp erature in in the c yclone exit and loop seal seal
By Chakraphong Phurngyai :: Engineer, TKIC
3.4 Biom ass Com bu stion •
Agglomeration SiO2 m elt s at 1450 C Eutec tic M ixture ixture m elts at 874 C
Sintering intering te ndenc y of fuel is indicate d by the following following (Hulkkonen (Hulkkonen et a l., 2003) 2003)
By Chakraphong Phurngyai :: Engineer, TKIC
3.4 Biom Biom ass Com bustion • Fuel Characteristics - high volatile c ontent (60-80 (60-80% %) - high high alkali content à sintering, slagging, and fouling - high high c hlorine hlorine content à c orrosion orrosion
By ChakraphongPhurngyai:: Engineer, TKIC
3.4 Biom Biom ass Com bustion • Opt ions for Avoiding the Agg lomeration Problem Problem - Use of add itives itives - china c lay, dolomite, kaolin soil soil - Preprocessing o f fuels - wat er leaching - Use of alternative bed mat erials erials - dolomite, magnesi magnesite, and alumina alumina - Reduction in bed temperature temperature
By ChakraphongPhurngyai:: Engineer, TKIC
3.4 Biom ass Com bu stion •
3.4 Biom Biom ass Com bustion
Agglomeration
• Fouling - is sticky de position position of a sh d ue to eva poration of alkali salt - result result in low heat transfer transfer to tube
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
August 2010
PB#11 : Fouling Problem Problem ( 7 Aug 2010) 1.Front water wall upper openinginlet - Overlay t ube (26Tubes) - Replace refractory
PB11 Fouling
4. Screen tube & SH#3 -
Slag
May2010 6 months
Aug2010 2 months
Oct2010 2 months
2.Right water wall - Change new tubes (4 Tubes) M ay 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
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 ChakraphongPhurngyai:: Engineer, TKIC
3.4 Biom ass Com bu stion •
Co rrosion rrosion Pot ent ial in Bioma ss Firing - hot co rros rrosion ion - chlorine rea rea cts with alkali alkali metal à from from low temp erature erature melting alkali chlorides - reduc e heat transfer transfer and ca using using high tempe rature rature c orros orrosion ion
Foster Wheeler experience
Wood/Forest Residual
Straw,Rice Straw,Rice husk
Waste Reject
By Chakraphong Phurngyai :: Engineer, TKIC
3.5 3.5 P Performanc erformanc e M ode ling •
Performa erforma nce of Com bustion bustion - Unburned c arbon loss loss - Distribution tribution and mixing mixing of vo latiles latiles,, char and oxygen along the height a nd cross cross sec tion of furnac e - Flue gas com po sition ition at the exit exit of the cyc lone sepa sepa rato r (NOx,SOx) - Heat release elease a nd ab soption pattern in the the furnace furnace - Solid wa ste ge neration
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
4. Hea t Tra Tra nsfer in C FB 4.1 Gas to Particle Particle Hea t Transfer ransfer 4.2 Hea t Transfer in C FB
By ChakraphongPhurngyai:: Engineer, TKIC
4.1 Hea t Tra Tra nsfer in C FB Boile oi le r •
Me c hanism of Heat Trans Transfer fer
4.1 Hea Hea t Tra Tra nsfer in CFB Boile oi le r • Effec t o f Sus Suspe pe nsion nsion De nsity nsity a nd pa rticle size size
In a CFB boiler, fine solid particles agglom erate and form c lustersor stand in a continuum of generally up-flowing g as conta ining ining sparsely sparsely d ispe rsed rsed solids. ds. The c ont inuum is ca lled the d ispersed spersed p hase, while the ag glomerates are are c alled the cluster phase. The he at transfer to furnace w all occurs through conduc tion from from particle c lus lusters ters,, co nvec tion from from dispersed phase, and radiation from fr om b oth pha se. Heat transfer transfer coefficient is pr oportional to the square root of suspension density
By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Hea t Tra Tra nsfer in C FB Boile oi le r •
Effec t of Fluidization Fluidization Veloc ity
By ChakraphongPhurngyai:: Engineer, TKIC
4.1 Hea Hea t Tra Tra nsfer in CFB Boile oi le r • Effec t of Fluidization Fluidization Veloc ity
No effect from fluidization velocity when leave the suspension density constant
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
4.1 Hea t Tra Tra nsfer in C FB Boile oi le r •
Effec t of Fluidization Fluidization Veloc ity
By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Hea t Tra Tra nsfer in C FB Boile oi le r •
Effec t of Bed Tem Tem pe rature
By Chakraphong Phurngyai :: Engineer, TKIC
4.1 Hea Hea t Tra Tra nsfer in CFB Boile oi le r • Effec t o f Vertica l Leng Leng th o f Heat Transfer ransfer Surfac Surfac e
By ChakraphongPhurngyai:: Engineer, TKIC
4.1 Hea Hea t Tra Tra nsfer in CFB Boile oi le r • Hea t Flux Flux on 300 M W CFB CFB Boile r (Z. (Z. Ma n, et . al)
By ChakraphongPhurngyai:: Engineer, TKIC
4.1 Hea t Tra Tra nsfer in C FB Boile oi le r •
Heat t ransfer ransfer to the w alls of c omm ercia l-size ize
4.1 Hea Hea t Tra Tra nsfer in CFB Boile oi le r • Circum ferentia l Distribution o f Heat Trans Transfer fer Co effic ient
Low suspension density low heat transfer to the wall.
By Chakraphong Phurngyai :: Engineer, TKIC
5 Design o f CFB CFB Boile r • • • • •
5.1 Design and Required Data 5.2 5.2 Com bustion bustion Ca lculation 5.3 Heat and Mass Balance 5.4 Furnac e Design Design 5.5 Heat Absorption
By ChakraphongPhurngyai:: Engineer, TKIC
5.1 Design and Required Data • The d esign esign and required required dat a norma lly lly will be spec spec ify ify by owner or client. The ba sic d esign esign dat a a nd required dat a a re; Design Design Data : - Fuel ultimat e a nalysis - Weather c ondition ondition - Feed w ater quality - Feed w ater properties Required Data : - Main steam steam prope rties - Flue ga s em iss ission
By Chakraphong Phurngyai :: Engineer, TKIC
- Flue gas temperature - Boiler efficienc y
By ChakraphongPhurngyai:: Engineer, TKIC
5.2 5.2 Comb ustion ustion Calc ulation •
5.3 Heat and Mass Balance
Base on the design and required data the following data can be ca lculated in this this stag e : - Fu Fue l flo w ra ra t e - C o m bu bustio n a ir flo w ra ra t e - Fa Fa n c ap ap ac ac itit y - Fu Fue l an an d as a sh ha nd lilin g ca c a pa pa c it y - Sorbent flow flow rate
• Heat Balance
Heat input Main steam Heat output Radiation
Feed water Blow down
Flue gas
Moisture in fuel and sorbent
Unburned in fly ash
Fuel and sorbent
Combustion air
Unburned in bottom ash
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
5.3 Heat and Mass Balance •
Moisture in combustion air
5.4 Furnac Furnac e Design Design Mass input
Ma ss Bala Bala nce
Mass output
• The furnace d esign include: 1. Furnace cross section
1. Furnac e cross sec tion Criteria
2. Furnace height 3. Furnace opening
- fluidiz fluidization ation velocity - SA pene tration tration
SolidSolid Flue in gas Flue gas
Make up bed material
- mo isture isture in fuel - ash ash in fuel
- maintain fluidization in lowe r zone a t part load
Fuel and sorbent
Moisture in fuel and sorbent
fly ash
Fuel and sorbent Make up bed material
fly ash bottom ash bottom ash By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
5.4 Furnac Furnac e Design Design 2. Furnace height Criteria
6. Cyc lone Sep Sep arator 3. Furnace opening Criteria
- Heating surface surface - Residual esidual time for sulfur sulfur cap ture
-
Fuel feed ports Sorbent feed ports Bed d rain ports Furnace e xit sectio n
By Chakraphong Phurngyai :: Engineer, TKIC
6.1 The The o ry •
The ce ntrifugal ntrifugal force o n the p article entering entering the c yclone is
•
The drag fo rce on the p article can b e written as
•
Under stea stea dy state d rag force = cent rifugal force
By Chakraphong Phurngyai :: Engineer, TKIC
• 6.1 The ory • 6.2 Critic Critic al siz size e o f p article
By ChakraphongPhurngyai:: Engineer, TKIC
6.1 The The o ry
• Vr can be considered considered as index index of cyc lone lone e fficiency, fficiency, from from above eq uation the c yclone effic iency will increas increase e for : - Higher Higher entry velocity - Large size ize o f solid solid - Higher Higher de nsity nsity of particle - Sma ll rad rad ius of cyc lone - Higher Higher value of viscosity viscosity of gas
By ChakraphongPhurngyai:: Engineer, TKIC
6.2 Critical size of particle •
6.2 Critical size of particle
The pa rticle with a d iameter larger than theoretical cut-size of cyclone will be c ollected ollected or trapped trapped by c yclone while while the small size ize will be ent rained rained or leave a cyc lone Effective number
•
Actua l ope ration, ration, the c ut-off size ize d iameter will be defined as d50 that me an 50% of the pa rticle rticle whic h have a d iameter more than d50 will be c ollected ollected or cap tured. tured.
Ideal and operation efficiency
By Chakraphong Phurngyai :: Engineer, TKIC
By ChakraphongPhurngyai:: Engineer, TKIC
References • • • • • •
Prab Prab ir Basu , Combustion and g asifica ca tion in fluidized b ed , 2006 Fluidized bed c om bustion, Simeon Simeon N. Oka , 2004 2004 Nan Zh., Zh., et al, 3D CFD simulation simulation of hydrodyna micsof a 150 MWe circulating fluidized b ed bo iler, er, Chem ica l Engine ering Journa l, 162, 2010, 821-828 Zhang M., et a l, Heat Heat Flux profile le of the furnace wall of 300 MWe CFB CFB Boiler, powder tec hnolog y, 203, 2010, 2010, 548-554 548-554 Foster Whe eler, TKIC ref resh tra ining, 2008 M. Koks Koksal and F. Humdullahper , Gas Mixi xing ng in circulating fluidized dized be dsw ith second ary air injection , Chemic al engine ering researc h and d esign, gn, 82 (8A), (8A), 2004, 979-992 979-992
By Chakraphong Phurngyai :: Engineer, TKIC
THANK HA NK YOU YO U FOR YOUR YO UR A TTENTIO NTIO N
By ChakraphongPhurngyai:: Engineer, TKIC
