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Circulating Fluidized Bed Boiler Technology
A competitive option for CO capture through oxyfuel combustion?A competitive option for CO2 capture through oxyfuel combustion?
tIEA 1st Oxyfuel Combustion Conference, Cottbus, 9 September 2009
Nicklas Simonsson Vattenfall Research & Development ABNicklas Simonsson, Vattenfall Research & Development ABTimo Eriksson, Foster Wheeler Energia OyMinish Shah, Praxair Inc.
© Vattenfall AB
Outline
1. Air CFB boiler technology– Development trends– Current state of the art– Main principles and benefits
2. Hamburg CHP oxyfuel CFB conceptual design study– Objective– Design basis– Design basis– ASU and CO2 processing unit– Boiler design
T h i l lt– Techno-economical results
3. Summary and conclusions
© Vattenfall AB 2
Air CFB Technology – Development trendsgy p
• Traditionally CFB boilers characterised by
– Small unit sizes– Low/moderate steam data
Unit Capacity (MWe)
500
600
800 800 MWeUnit Capacity (MWe)
500
600
800 800 MWe
– Mainly used in applications with difficult to use fuels and biomass
• Significant scale up of unit 300
400 Lagisza
JEA300
400 Lagisza
JEA g psize and increase of steam data during last decade
• Today CFB technology must be considered a competitive0
100
200
Pilot Plant Oriental Chem
Turow 1
VaskiluodonNova ScotiaTri-State
General Motors0
100
200
Pilot Plant Oriental Chem
Turow 1
VaskiluodonNova ScotiaTri-State
General Motors be considered a competitive option also for large-scale utility applications
01970 1975 1980 1985 1990 1995 2000 2005 2010
Start-Up Year
01970 1975 1980 1985 1990 1995 2000 2005 2010
Start-Up Year
Source: Foster Wheeler
© Vattenfall AB 3
Source: Foster Wheeler
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Air CFB Technology – Current state of the artgy
Foster Wheeler Lagisza CFB unitFoster Wheeler Lagisza CFB unit
• Worlds largest and first supercritical CFB boiler• Handed over to customer in Poland in June 2009
460 MW
Th F t Wh l L i CFB b il f t l
• 460 MWe gross• 275bar/560°C/580°C• 290°C feed water temperature• >43% net efficiency
© Vattenfall AB 4
The Foster Wheeler Lagisza CFB boiler – from conceptual design to existing plant
43% net efficiency
Air CFB Technology – Principles and benefitsgy p
• Combustion of fuel in a high bed inventory consisting of a mixture of fuel, ashes and sorbent (limestone). Bed suspended or fluidised through air entering the bottom of furnace
Solid recirculation
Source: Foster Wheeler
© Vattenfall AB 5
Hamburg OxyCFB CHP conceptual design studyg y p g y
Objective:• To evaluate the competitiveness and possibilities p p
of CFB technology in oxyfuel applications
Study performed in close cooperation with:F t Wh l (b il d i )• Foster Wheeler (boiler design)
• Praxair (ASU and CO2 compression)
Design basis:Design basis:• Hamburg site conditions• Bituminous coal (LHV 25.1 MJ/kg)• 500 MWe grosse• 0-400 MWDH (output and temperature levels
varying during the year)• Both air and oxyfuel cases investigated
CO t t >90%
The Tiefstack CHP plant – one of several units delivering district heating to the the city of Hamburg The Hamburg district heating network
© Vattenfall AB 6
• CO2 capture rate >90% Hamburg. The Hamburg district heating network consist of over 770 km pipelines.
Hamburg OxyCFB CHP conceptual design study
Included activities:
g y p g y
• Conceptual boiler design, performance, cost and layouts for air and oxyfuel
• ASU and CPU design, performance, cost and layoutslayouts
• Flue gas cleaning options• ASU O2 purity sensitivity and optimisation study
D t il d ll l t H&MB l l ti• Detailed overall plant H&MB calculations• Overall plant heat integration optimisation• Plant Layout• Economical evaluations• Risk assessment
Fl h t f th H&MB l l ti ( b )
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Flow sheet from the H&MB calculations (above) and the resulting OxyCFB plant layout.
ASU and CO2 compression and purification unit designsdesigns• Unit designs based on Praxair’s state of the art
• Air separation unit– Dual trains with total capacity 7088 TPD O2 (contained)
@ 1.3 bar and 172°C– Optimisation study – 97%-vol O2 purity selectedOptimisation study 97% vol O2 purity selected– Low temperature heat recovery to DH network
• CO2 processing unit– Single train (with two parallel compression units) with
total capacity of 7860 TPD CO2 contained (inlet flue gas CO2 concentration ~85%-vol)
– CO2 capture rate 93.3%– CO2 product quality 96.1%-vol. @ 110 bar and 30°C– Low temperature heat recovery to DH network and
heat integration for vent gas expansion– No provisions for SOX and NOX removal – although
© Vattenfall AB 8
No provisions for SOX and NOX removal although pursued by Praxair for future developments
Air- and oxyfuel CFB boiler designy g
• Existing 460 MWe,gross Lagisza boiler design used as starting pointstarting point
– Low mass flux BENSON once-through technology with vertical furnace tubes
– Sliding pressure operation
• Steam data – representative for given time frame– Steam data: 600°C/620°C /290 bar– Feed water temp: 300°C
• Assumptions OxyCFB design (compared to AirCFB)– HP steam flow kept constant – Furnace velocities similar as in air firing– Same flue gas excess O2 content (3.6%-vol, dry)– Oxidant O2 so that adiabatic combustion temperature does
not exceed that of air firing– Same Ca/S ratio
© Vattenfall AB 9
– Air ingress 1% of flue gas flow
OxyCFB process flow diagram – flue gas sidey p g g
Vent gasesBypass eco
LP B
To stack
Boiler
DryingCompression
Conden-
serGas cleaning
Secondary RG preheater
Boiler eco
LP eco B
HRC
CO2
Fuel
H2O and soluble impurities
gas
Intrex
Recycle gases
RG preheater
HRS
AirASU
TransportStorage
Fluidizing gasPreheatersMixing
ASU
N2
Oxygen(97% O2)Mixing
Steam
Air
© Vattenfall AB 10
Overall plant technical & economical key datap yAirCFB
CondensAirCFB
DH*OxyCFB Condens
OxyCFB DH*
Fuel input [MW] 1052 1052 1047 1047
Economical assumptions
• Yearly operating time: 7500h• Rate of interest: 6%(real)
Gross Power [MWe] 506 469 516 482
Net Power [MWe] 472 435 381 347
District heating [MWth] - 269 - 269
Net efficiency [%] 44.9 41.4 36.4 33.2
( )• Plant life: 25 years• Coal price: 6.6 €/MWh (incl.
transport & handling) (IEA WEO 2007)
• District heating credit: 25 €/MWh (EU b d NG i 8 €/MWh)
Total efficiency [%] - 67.0 - 59.9
Specific invest. [€/kWe net] 1621 1703 2952 3096
COE [€/MWhe] 39.8 28.1 65.6 52.7
(EU border NG price + 8 €/MWh) (NG=17 €/MWh IEA WEO 2007)
• Investments on Q3 2008 level and uncertainty of +/-30%
• No cost for CO2 transport and storage included[ e]
CO2 avoid. cost [€/ton CO2] - - 37.9 33.4storage included
• DH can significantly improve plant economics
*Yearly average values due to varying DH output and temperature levels.
• Slightly higher COE and CO2 avoid. cost compared to PF cases on equal basis. However:– Uncertainties in investment costs between studies– Not considered that CFB cases potentially could utilise lower quality fuels more cost effective
CFB ld ll b titi b th ith d ith t CO t !
© Vattenfall AB 11
CFB could very well be competitive – both with and without CO2 capture!
Hamburg OxyCFB study – Summaryg y y y• Established air CFB advantages also valid for
OxyCFB– Fuel flexibility (Hard coal Lignite Biomass)Fuel flexibility (Hard coal, Lignite, Biomass)– Possibility to use low grade/less expensive fuels– SOX and NOX reduction without secondary
measuresSi l f l f di
Solidrecirculation
SolidrecirculationREACTOR REACTOR
CFB CFB
– Simple fuel feeding system
• Additional potential advantages in oxyfuel operation
Solidflow inSolid
Solidflow
Solidflow
flow in
– High O2 concentration designs – turbulent bed and heat exchanger arrangements provide good means of equalising temperature levels
– Flexi-BurnTM – Easier to enable same boiler to be a) Internal circulation b) External circulation
flowout out
Fluidizingair flow
Fluidizingair flow
operated with both air and oxyfuel firing– No fuel pulverising – no need for primary recycle
flow– Furnace at overpressure – easier to minimise air
The INTegrated Recycle heat EXchanger (INTREXTM) - an additional advantage in oxyfuel operation in terms of combustion temperature control
© Vattenfall AB 12
Furnace at overpressure easier to minimise air ingress
control.
INTREXTM and Flexi-BurnTM are trademarks of Foster Wheeler AG
Hamburg OxyCFB study – Summary
Disadvantages/issues:B il i l d ili ti li htl l l t ffi i
g y y y
• Boiler island auxiliary consumption – slightly lower plant efficiency• Limestone consumption• Ash flows and disposal issues• Erosion of reactor walls – although rare in new CFB designsErosion of reactor walls although rare in new CFB designs
Uncertainties, risks and development needs:• So far only small scale OxyCFB test rigs (< 100 kW)So far only small scale OxyCFB test rigs (< 100 kW)• Further validation in pilot and demo scale necessary (as for PF Oxyfuel)• Uncertainties related to:
– Ultra-supercritical steam data (> 600ºC) in both air and Oxyfuel operation– In-bed SO2 capture in Oxyfuel operation– Combustion control systems– Heat transfer in Oxyfuel operation
© Vattenfall AB 13
Vattenfall will continue to follow development of oxyfuel CFB technology closely!
Thank you!
For further information please contact:
Nicklas Simonsson
Vattenfall Research & Development AB
tel.: +46 (0)8 739 5561
© Vattenfall AB
Back-up
© Vattenfall AB
OxyCFB DH profiles efficiency distributiony p yElectrical and total efficiences in the operating profiles
80,0Yearly
67,966,1
61,158,860,0
70,0
Yearly average
29 731,7 33,4
35,4 35,633,2
49,8
35,640,0
50,0
ficie
ncy
[%]
29,7
10 0
20,0
30,0Eff
0,0
10,0
Profile 1 400MW DH
Profile 2 360MW DH
Profile 3 290MW DH
Profile 4 150MW DH
Profile 5 0MWDH cond.
Yearly average 269 MW DH
El t i l t ffi T t l ffi
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Electrical net efficency Total efficency
Efficiency summaryy y
• Efficiency penalty condensing
Efficiency summary - condensing and DH operation
90,0CondensingDH yearly condensing
operation:– 8.5 %-points
• Efficiency penalty67,070,0
80,0
Condensing operation
DH -yearly average
• Efficiency penalty district heating operation:
– 8.2 %-points41,4
44,9
36 4
58,8
40,0
50,0
60,0
cien
cy [%
]
p
• Efficiency penalty lower in district heating operation
33,236,4
20,0
30,0
,
Effi
due to better possibilities for low temperature heat integration
0,0
10,0
AirCFB with DH OxyCFB with DH AirCFB condensing OxyCFB condensing
El t i l t ffi T t l ffi
© Vattenfall AB 17
integrationElectrical net efficency Total efficency
ASU oxygen purity optimisation studyyg p y p yImpact of ASU O2 purity
CO2 avoidance cost CO2 capture cost CO2 capture rate
37,00 100
%]
32,00
O2
cost
[€/to
n] 95
capt
ure
rate
[%
CO2 capture rate
27,00CO
90
CO
2 c
22,0095% 97% 99,5%
Oxygen purity [%]
85
© Vattenfall AB 18
