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Effect of pressure on chemical
looping combustion of coal with an iron ore based oxygen carrierQilei
Song*,
Rui Xiao,
Shuai Zhang,
Wenguang Zheng,
Yichao Yang , Laihong ShenThermal Engineering Research Institute
School of Energy and EnvironmentSoutheast University, Nanjing 210096, China
[email protected] ; [email protected] ; [email protected]* Presenter and Current address:
Department of Chemical Engineering & BiotechnologyUniversity of Cambridge
CB2 3RA [email protected]
IFPLyon, France, 1719, March, 2010
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Contents CLC at Southeast University, Nanjing, China
Experiments design
Pressurized steam coal gasification
Effect of pressure on CLC with iron ore
Long cycle performance at typical pressures
Conclusion
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Roadmap (CLC)
Development of Oxygen carriers
Commercialization
Reactivity test with, TGA, FzD
Reactivity test with solid fuels
Performance in large reactor
Performance in pilot scale reactor
Technology Theory
Industrial demonstration
Science of Chemistry & Materials
Kinetics study, thermodynamics
Coal gasification,reaction kinetics
Reactor design and modelling
Scale up and optimization
Scale up
Concept
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Chemical looping at Southeast University
Nanjing, China Laboratory scale reactorTGA, PTGA, fixed bed, fluidized bed, Dual connected fluidized bed (gasifier + CLC), Pressurized fluidized/fixed bed,
Larger scale and pilot scale reactor1kWth CLC combustor10kWth CLC combustor10kWth Chemical looping Hydrogen100 kWth Pressurized CLC Combustor
Publications: 20
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Chemical looping at Southeast University,
Nanjing, China Oxygen carrier developmentNiO/NiAl 2O4, coprecipitation, coal, deactivation
Low cost materialsNonmetal oxide: CaSO4/CaS , powder, anhydrite particleIron oxide, sinteredIron ore, Calcined, from Australia, Brazil, China, etc,
IlmeniteIron oxide scale from steel industryIron Nickel ore
Publications: 14
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Low cost Calcium based CaSO4/CaS cycle
A. Abad et al. Fuel 86 (2007) 10211035
Effect of CaSO4/CH4 Ratio on Equilibrium Composition
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
10
20
30
40
50
60
70
80
90
100
0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.201E-4
1E-3
0.01
0.1
1
10
(b)
CO 2CO
H2
F r a c
t i o n
( m o
l , % )
CaSO 4/CH 4 molar ratio
(a)
CH 4
900o
C
CaSO 4/CH 4 molar ratio
H2O
F r a c
t i o n
( m o
l , % )
CO
H2
H2S
SO 2
COS
S 2
Sulphur release??Song et al, Energy Fuels 2008 , 22 (6), 3661-3672. http://dx.doi.org/10.1021/ef800275aSong et al, Ind. Eng. Chem. Res. 2008 , 47 (21), 8148-8159. http://dx.doi.org/10.1021/ie8007264Song et al, Korean. J. Chem. Eng. 2009 , 26 (2), 592-602. http://dx.doi.org/10.1007/s11814-009-0101-2Song et al, Energy Convers. Manage 2008 , 49 (11), 3178-3187. http://dx.doi.org/10.1016/j.enconman.2008.05.020
Song et al, Ind. Eng. Chem. Res. 2008 , 47 (13), 4349-4357. http://dx.doi.org/10.1021/ie800117aShen et al, Combust. Flame. 2008, 154(3), 489-506. http://dx.doi.org/10.1016/j.combustflame.2008.04.017
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Chemical looping at Southeast University,
Nanjing, China Numerical modelling and scale upSystem simulation: Aspen PlusMultiphase CFD modelling of Pressurized coal gasifierMultiphase CFD modelling of fuel reactor
Multiphase CFD
modelling of
air
reactor
Multiphase CFD modelling of interconnected fluidized beds
Shen, et al, Science in China Series E: Technological Sc, 2007 Xiang et al, Energy Fuels, 2008 Deng, et al, Energy Fuels, 2008
Deng et al, Int. J. Greenhouse Gas Control 2009
Publications: 8
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Major Challenges of coal fueled CLC Low operating temperature (~1000 oC)
Difficult to couple with advanced power generation system
Low efficiency
compared
with
traditional
combustion
Slow gasification rate, limiting stepPressurized Chemical Looping Combustion
Combined Cycle (PCLCCC) may be a solution. Higher coal combustion efficiency
Potential higher system efficiency for power generation, steam turbine + gas turbine
Lower cost of CO2 capture Wolf, J. et al, Fuel 2005
Garcia-Labiano et al, Energy Fuels 2006 Anthony, Ind. Eng. Chem. Res. 47 (6) (2008) 1747-1754.
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Pressurized CLCCC Existing established technologies
Pressurized Fluidized Bed Combustion Combined CycleR&D at Southeast University ~30 years
1MWt PFBC test facility (SEU-PFBC)15 MWe PFBC-CC pilot power plant
2MWt pressurized spout-fluid bed coal gasifier for2G PFBC-CC
References:
CFB technologySasol Gasification technologyFCC unit
M. Y. Zhang, in: Proceedings of the 12th International Conference on Fluidized Bed Combustion, 1993 Xiao, et al, Fuel 86 (10 11) (2007) 1631-1640.
J. C. van Dyk; et al, Int. J. Coal Geol. 65 (3-4) (2006) 243-253. Minchener, Fuel 84 (17) (2005) 2222-2235.
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Pressurized CLCCCDeveloping Chemical looping Technology
R&D at Southeast University, ~7 years
1 kWth Chemical-looping combustor 10 kWth Chemical-looping combustor 0.1 MWth PCLC combustor
References:10 kWth coal fueled CLC reactor in Chalmers, Sweden
50 kWth pressurized CLC combustor, KIER10 kWth CLC combustor, ICB/CSIC150 kWth CLC, VUTAlstom, TOTAL, IFP, etc.
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10 kWth Coal fueled CLC Combustor
Lyngfelt, et al., 2008 Shen, et al., 2009
Chalmers, Sweden Southeast, China
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Pressurized CLCCombined Cycle
Xiao et al, Energy Fuels, 2010, 24 (2), 14491463. http://dx.doi.org/10.1021/ef901070cMajor issue: Circulation of materials between two reactors, ref FCC
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Development of Oxygen Carrier Cost of Oxygen carrier
Deactivation by sulfur containing gases Thermal sintering
Inevitable Loss with coal ash, Environmental problem
Solutions 1: Reasonable cost, high stability materials
Synthetic high reactivity particles, NiO/NiAl2O4
Solutions 2: Low cost materials
Natural metal oxide, i.e. ilmenite (FeTiO3Fe2TiO5) Calcium based sulfate sulfide (CaSO4/CaS) cycle. Sulfur? Oxide scales (residual materials) from steel industry.
Leion, H. et al. Int. J. Greenhouse Gas Control 2008Chuang et al. Combust. Flame 2008
Song et al. Energy Fuels 2008
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Purpose Coal fueled PCLCCC system (Concept) Effect of Pressure on steam coal gasification Effect of Pressure on CLC of coal with iron ore Long term performance of oxygen carrier under
typical pressures
Application of Lowcost iron ore based oxygen carrier in Pressurized CLC
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Reactions StepsNormal coal fueled CLC concept (In situ gasification in the presence of oxygen carrier)(1) Coal pyrolysis and gasification:
Coal > Char + Pyrolysis gases and volatilesChar+H 2O+CO2 CO + H2 + CO2
(2) Oxidation of gases with oxygen carrier3Fe 2O3+H2=2Fe 3O4+H2O
3Fe 2O3+CO=2Fe3O4+CO2
(3) Regeneration of oxygen carrier: Air reactor4 Fe3O4 + O2= 6 Fe2O3
Fuelreactor
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Experimental setup
coal feeding unit, water/gas feeding and steam generator units, reactor, temperature control unit, back pressure regulator, steam cooler, filters, and gas analysis system.
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Materials
Proximate and Ultimate Analyses of Coal Samples
26.990.911.161.744.1664.7625.8742.8629.871.4XuzhouQ HSadNadO ad aH adC adAshFCadVadMad
Heatvalue
(MJ/kg)ultimate analysis (ad, wt%)
proximate analysis (ad,wt%)
sample
Chemical Analysis of the Natural Iron Ore Samples (CVRD, Brazil)
2.010.040.010.88004.1890.75Received
0000.910.000.004.3194.79Calcined
IgPSAl2O3MgOCaOSiO2Fe2O3Iron ore
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Operating Condition
1000 mL/min (S.D.)Oxidation gas flow rate
5% O2/N 2Oxidation1000 mL/mininert gas flow rateN2Inert gas1000 mL/min (S.D.)Total gas flow rate
87% H2O/N 2Gasification gas0.4 gFuel mass0.125 0.180 mmCoal particle sizeXuzhou Bituminous Coal, ChinaFuel
30 mmheight40 gMass0.09 0.125 mmOxygen carrier particle size 970
C
Reaction temperature0.1MPa 0.6MPaPressureCalcined CVRD iron ore, BrazilOxygen carrierOperation ParametersSpecies
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Characterization analysis
Received
Calcined1100 oC 6h, air
Phase:Hematite(Fe2O3)
Quartz (SiO2)
0 10 20 30 40 50 60 70 80 900
1000
20003000
4000
50000
2000
4000
6000
8000
Fresh, as received
B
B A
A
A
A A A A
A A
A
A A A
CD
C
2 (degree)
Calcined at 1100 oC, 6h
B AB B
B
A A A A A A
A
A A
A A
I n t e n s i
t y ( c o u n
t s )
A: Hematite, Fe2O
3
B: Quartz,. SiO2
C: Dolomite, CaMg(CO3)
2
D: Goethite, FeO(OH)
A
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Steam Coal Gasification Over Quartz
0.1 MPa 0.5 MPa
CO2 and H2 (Excess steam)Unsteady flow: pulse pump & pressure fluctuationPeaks emerge later at higher pressure 1>5 min
0 10 20 30 40 50 60 70 80 900
2
4
6
8
10
12
14
16
18
20
22
24
0 2 4 6 8 100
4
812
16
20
C o n c e n
t r a
t i o n
( % )
Time (min)
CO CO 2
CH 4 H2
C o n c e n
t r a t i o n
( % )
Time (min)
0 10 20 30 40 50 60 70 80 900
2
4
68
10
12
14
1618
20
22
0 2 4 6 8 100
4
812
16
20
C o n c e n
t r a
t i o n
( % )
Time (min)
CO CO 2 CH
4 H2
C o n c e n
t r a t i o n
( % )
Time (min)
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Gas Composition (dry basis)
Coal: Chinese Xuzhou coalMass: 0.4 g, 0.125 0.180 mmGasification agent: 87% H2O/N 2Flow rate:1000 mL/minT: 970 degrees
1.Thermodynamics
2. Kinetics:Higher [H
2O]
Diffusion within micropore
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Chemical looping combustion with iron ore
0.1 MPa reduction Oxidation
High CO2 obtained Volatiles: residence time short, not completely burnedCO release at later reduction period
Some CO2 release during oxidation
0 10 20 30 40 50 60 70 80 900
2
46
8
10
12
14
16
18
20
22
24
26
C o n c e n
t r a
t i o n
( % )
Time (min)
CO CO
2
CH4
H2
0 5 10 15 20 25 30 35 400
1
2
3
4
5
C o n c e n
t r a
t i o n
( % )
Time (min)
CO
CO 2 O
2
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0.5 MPa reduction and oxidation
Lower CH 4 and CO, higher CO 2 in later periodMore CO 2 release during oxidation
Pressure enhance unburned char combustion
0 10 20 30 40 50 60 70 80 90
02468
1012141618202224
26283032
C o n c e n
t r a
t i o n
( % )
Time (min)
CO CO
2
CH 4 H2
0 5 10 15 20 25 30 35 400
1
2
3
4
5
C o
n c e n
t r a
t i o n
( % )
Time (min)
CO CO 2 O
2
Chemical looping combustion with iron ore
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Gas composition and CO2 yield
CO2 increases from ~80% to ~92%CO decreases from 15% to ~5%CH4 fairly change but decrease at higher pressureH2 negligible and not detected at higher pressures
CO2 yield
0.1 0.2 0.3 0.4 0.5 0.60
10
20
30
40
5060
70
80
90
100
G a s c o m p o s i
t i o n (
V o
l . % )
Pressure (MPa)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.70
10
20
30
40
5060
70
80
90
100
Gasification over Quartz sand
C O
2 C a p
t u r e y i e
l d ( % )
Pressure (MPa)
Reduction of Iron ore
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Effect of Pressure on Carbon Conversion
Carbon Conversion is low: need long residence timeLower than gasification: Thermodynamics
Pressure suppresses pyrolysisbut enhance char gasification
dXc/dt~XcXc
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.70
10
2030
40
50
60
70
80
90
100
C a r b o n
C o n v e r s
i o n ( %
)
Pressure (MPa)
Gasification over Quartz Reduction period Oxidation period Total
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00.00
0.05
0.10
0.15
0.20
0.25
0.1 MPa
0.3 MPa 0.4 MPa 0.6 MPa
C a r b o n
c o n v e r s
i o n r a
t e r C
( 1 / m i n )
Carbon conversion XC
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Char Gasification over oxygen carrier:
apparent kinetics
OH2
OH1
C
C
2
2
1
1
1
pk
pk dt
dX
X r C
+=
=
0.0 0.1 0.2 0.3 0.4 0.5 0.60.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
A p p a r e n
t g a s i
f i c a
t i o n r a
t e r
C ( 1 / m i n )
Partial pressure of steam pH2O (MPa)
Experimental Model prediction
A simple Langmuir Hinshelwood model excluding the effect of product inhibition provided a reasonable illustration of the effect of pressure on carbon conversion rate.However, excessive steam partial pressure results in negative effect.
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Effect of pressure on oxygen carrier Conversion
Oxidation reflects the extent of previous reductionIncreasing pressure, reduction conversion higher!Higher pressure has negative detrimental effect,
Thermodynamics: pressure of products (CO 2, H 2O) increase
0 10 20 30 40
0.980
0.982
0.984
0.986
0.988
0.990
0.992
0.994
0.996
0.998
1.000
1.002N2
M a s s - b a s e
d c o n v e r s
i o n
Time (min)
0.1 MPa 0.2 MPa 0.3 MPa 0.4 MPa 0.5 MPa 0.6 MPa
5% O 2/N2, 1000 mL/min
(a) 0.1 0.2 0.3 0.4 0.5 0.60.000.050.100.15
0.200.250.300.350.400.450.500.550.600.650.700.750.80
X
( - )
Pressure (MPa)
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0.1 MPa 0.5 MPaPurer CO 2 after 10 cycles
Activation during the redox cyclesNo appreciable deactivation
Effect of pressure on gas composition
long cycles
0 2 4 6 8 10 12 14 16 18 200
10
20
30
40
50
60
70
80
90
100
A c u m u l a
t i v e g a s c o m p o s i
t i o n
( v o
l . % )
Number of cycles
CO
CO 2 CH 4 H2
(a)0 2 4 6 8 10 12 14 16 18 20
0
20
40
60
80
100
A c u m u
l a t i v e g a s c o m p o s
i t i o n
( v o
l . % )
Number of cycles
CO CO
2
CH 4 H
2
(b)
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Effect of pressure on oxygen carrier Conversion:
Cyclic performance
0 2 4 6 8 10 12 14 16 18 200.0
0.2
0.4
0.6
0.8
1.0
OC conversion at 0.1 MPa OC conversion at 0.5 MPa
V a r i a t i o n o
f O C c o n v e r s
i o n
X ( -
)
Number of Cycles
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XRD analysis
0.1 MPa 0.5 MPa
H: hematite, M: magnetite, Q: Quartz, C: CaSi, possible
Activation with cyclesNo evident formation between iron and coal ash
0 10 20 30 40 50 60 70 80 90
Q HHH
H
HQHH
H Q
H
H H H
H
HH
H
M
2 de ree
(a) Calcined
MH
Q Q
HM
M
H
HM
Q
H
H
M
M H
M
(b) 0.1MPa-5red
C
HMHM MHMQ
H
Q
Q
H MH
QM
(c) 0.1MPa-10red
Q
QC
HMH
MHM
H
HM
H
M
M
(e) 0.1MPa-20red
(d) 0.1MPa-15red
H MQM C H
Q
Q H
H HQ
Q MM
H
MMH
Q
0 10 20 30 40 50 60 70 80 90
Q
Q HHH
H
HQHH
H Q
H
H H H
H
H H
H
M
2 (degree)
(a) Calcined
MQQ
CMH
Q
MM M
H
HM
Q
H
H
M
M
H
M
(b) 0.5MPa-5red
M MQ
C
M
H
MHM MHM
Q
H
Q
Q
H MH
MM
(c) 0.5MPa-10red
Q
MMQ Q
C
QH
MH
MHM
H
H MH
M
M
(e) 0.5MPa-20red
(d) 0.5MPa-15red
M MQ
CM
QH
H H
Q
H M MH
M
MHQ
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SEM Atmospheric Pressure
5red 10red 15red 20red
Particles maintain structureMore small grains formed after 10 cyclesSlight cracking after 20 cycles
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SEM Elevated pressure of 0.5 MPa
5red 10red 15red 20red
Particles maintain structure Activation after 5 cyclesSlight sintering and cracking after 20 cycles
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Pore size distribution
Maintain mesopore structureMore porous with cyclesSlight sintering at elevated pressure
1 10 100 10000.0
1.0x10 -52.0x10 -53.0x10 -54.0x10 -55.0x10 -56.0x10 -57.0x10 -58.0x10 -59.0x10 -51.0x10 -41.1x10 -4
P o r e
V o
l u m e
d V / d D
( c m
3 / g n m
)
Pore Diameter dP (nm)
Calcined 0.1MPa-5red 0.1MPa-10red 0.1MPa-15red 0.1MPa-20red
(a)
1 10 100 10000.0
1.0x10-5
2.0x10 -53.0x10 -54.0x10 -55.0x10 -56.0x10 -5
7.0x10 -58.0x10 -59.0x10 -51.0x10 -41.1x10 -4
P o r e
V o
l u m e
d V / d D
( c m
3 / g n m
)
Pore Diameter d P (nm)
Calcined 0.5MPa-5red 0.5MPa-10red 0.5MPa-15red 0.5MPa-20red
(b)
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ConclusionHigh CO2 Concentration could be obtained at relative high pressures;
The elevated pressure suppresses the pyrolysis of volatiles while it interestingly
enhances coal char gasification and reduction with iron ore in steam;
Excessive steam partial pressure may have a detrimental effect on the coal
gasification and the reduction of oxygen carrier by gasification gases;
Oxygen carrier maintains mesoporous structure after cycles; Crystalline Phases
do not change, no appreciable interaction of iron ore and coal ash;
Reactivity increased with cycles and stabilized after 510 cycles; No significant
deactivation within 20 cycles; Iron ore based oxygen carriers is promising
Limited experiments shows High temperature, high pressure CLC is promising
Accepted by Combust ion & Flame, Energy & Fuels
Xiao et al, Combusti on Flame, in press, http://dx.doi.org/10.1016/j.combustflame.2010.01.007Xiao et al, Energy Fuels, 2010, 24 (2), 14491463. http://dx.doi.org/10.1021/ef901070c
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Further work at SoutheastHigher pressures (20 30 atm) in PTGA
Longterm cycles of reduction and oxidation (50 100 cycles)
Modification of iron ore to reactive particles with active additives and inert support
Test of other low cost oxygen carriers, e.g. ilmenite
Sulfur and ash interaction with oxygen carriers
Kinetics study at elevated pressures
Multiphase CFD modelling of CLC process
Design of Novel CLC Reactors , 100 kWth PCLC combustor under
construction.
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CLC at Combustion groupUniversity of Cambridge
Dr. John Dennis
Dr. Stuart ScottTypical research topics related to Chemical looping:
Chemical looping combustion of solid fuels
Chemical looping Hydrogen from coal with steam iron process
Zero Emission Coal Alliance (ZECA) for H2 production and CO2
capture, Calcium looping sorbents
Kinetics and modelling of Chemical looping process
Multiphase DEM
CFD
modelling
of
Chemical
looping
process
A k l dg t
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Acknowledgements
National Natural Science Foundation of China (Grant Nos. 50606006, 90610016)
HighTech Research and Development Program of China (2009AA05Z312 )
National Basic Research Development Program of China (2010CB732206) Prof. Laihong Shen, SEU
Prof. Rui Xiao, SEU
Dr. John Dennis, University of Cambridge Dr. Henrik Leion, Chalmers University of Technology
Dr. H. J. Ryu, KIER
Many other researchers who have helped and are helping us on CLC.
China Scholarship Council
Conference Grant from Queens College and Shell Fund
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Thank you for your attention! Questions?
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