ceria based electrolyte and magnesia refractories
TRANSCRIPT
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Advantages of IT - SOFC Faster start-up and operating response. Developers are aiming
at a start-up time of less than 10 minutes for some applications. A wider and cheaper range of materials can be used to construct
the device.
Increased material durability.
Increased product robustness.
And importantly, reduced overall cost.
Electro lyte For Intermediate Temperature mus t
ful l f ield this characterist ics
High density
High ionic conductivity
Gas tightness
Oxygen vacancy must be high
Interm ediate temperature of
500-800C
Gadol in ium dop ed Cer ia
(Ce0.8Gd0.2O1.9 - CG20)
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Spray Pyrolysis Ceria doped Gadol inia Electrolyte
In recent years, the spray pyrolysis synthesis
technique has been used widely for the preparation
of solid oxide fuel cell (SOFC) electrolyte thin films.
Advanteges:
Spray-pyrolyzed thin films also offer good film
quality and low processing costs;
Large area covering and easy to be implemented atlarge scale production.
Methods of Deposition
Vacuum evaporation Electrostatic assisted
vapor deposition
Sputtering Metal organic chemical
vapor deposition [MOCVD]
Colloidal deposition Electrochemical vapor
deposition [EVD]
Sol-Gel Laser deposition
Electrophoretic deposition Spray pyrolysis
Spray pyrolysis was adapted for the deposition of CG20
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As-prepared powder
Oxidiser
Ce(NO3)3 (aq) 0.5M
Gd(NO3)3 (aq) 0.25M
Fuel (reducing
agent)
Alanine (s)
Annealing
500C, 3h
CG20 powder
Precursor
Vaporization of water
Combustion of the reaction mixture
Uniaxial pressing 150 MPa
Thermal treatment
1400C, 4h
CG20 ceramics
DTA/
TG
XRD
SEM
XRD
SEM
XRD
SEM
Obtaining of Ce0.8Gd0.2O2- powder byCombustion Method
The XRD analysis of CG20 as-prepared powders show the
direct formation of gadolinium
doped ceria with an average
crystallite dimension of 20 nm
10 20 30 40 50 60 70
0
500
1000
1500
2000
2500
3000
D = 20 nm
Intensity
(a.u.
)
2(CuK
Ce0.8Gd0.2O2-
as-prepared powder
XRD analysis of CG20 as-prepared powder
SEM ima es of the as- re ared owderDTA curve for alanine recursor
20 30 40 50 60 70 80
0
1000
2000
3000
4000
a=5.4296 A
Ce0.8Gd0.2O2-
500C, 3h
Intensity(
a.u
.)
2(CuK
D = 21 nm
XRD analysis of CG20 annealed powder
SEM images obtained for the annealed powder
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The ceramic body of CG20
CG20
Apparent density
[g/cm3]
Relative density
[%]
Absorption
[%]
Open porosity
[%]
6.45 89.00 0.74 5.97
10 20 30 40 50 60 70 80
0
1000
2000
3000
4000
5000
(420)
(331)
(400)(222)
(311)
(220)
(200)
Intensity
(a.u.
)
1400C, 4h
Ce0.8Gd0.2O2-
2(CuK
(110)
a=5.418 A
SEM micro graphs s how a ceramic w ith sintered grains o f nanometer sizequasiuni form in size and shape and no sign i f icant grain grow th
l d
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XRD
SEMAs-deposed film
Oxidiser
Ce(NO3)3 (aq) 0.5M
Gd(NO3)3 (aq) 0.25M
Fuel (reducing
agent)
Alanine (s)
Thermal treatment
1300C, 4h
Spraying
8, 12 and 16 layers
Vaporization to 1M and 2M
Combustion on the support
XRD
SE
M
The flow chart of CG20 films deposition
Airbrush
Setup for deposition
CG20 films by spray
pyrolysis
CG20 layers deposition
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SEM images and EDX spectra for
GS2, 15 seconds
SEM images for GS2. Transversal cut
of the deposed layer
SEM images and EDX spectra for
GS3, 20 seconds
Deposition of CG20 on Glass supports
10 20 30 40 50 60 70
0
200
400
600
800
(400)(222)
(311)(220)
(200)
(110)Ce0.8Gd0.2O2-
2(CuK
Inte
nsity
(a.u.
)
film on glass substrate
XRD patterns of CG20 deposed onglass
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Number of supports Numbers of layers
2 ZrO2 supports 8 layers
2 ZrO2 supports 12 layers2 ZrO2 supports 16 layers
Conditions: P = 2 atm, T = 3000C, t = 5 second spraying (for one layer) and 30 second break
SEM images for
sample obtained
from 8 layers,
concentration of
1M, as-deposed
Deposition of CG20 on ZrO2 supports
SEM images for
sample obtained
from 8 layers,
concentration of 1M,
thermal treatment at
13000C, 4h.
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SEM images for sample obtained from 8 layers, concentration of 2M,
thermal treatment at 13000C, 4h.
Deposition of CG20 on ZrO2 supports
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SEM images for
sample obtained
from 12 layers,
concentration of
1M, as-deposed at
3000
C
SEM images for
sample obtained
from 12 layers,
concentration of
1M, thermal
treatment at
13000C, 4h.
Deposition of CG20 on ZrO2 supports
SEM images for
sample obtained
from 12 layers,
concentration of 1M,
thermal treatment at
13000
C, 4h.
SEM images for
sample obtainedfrom 12 layers,
concentration of
2M, thermal
treatment at
13000C, 4h.
SEM images for
sample obtained from
16 layers,
concentration of 1M,
thermal treatment at
13000
C, 4h.
SEM images for
sample obtained from16 layers,
concentration of 2M,
thermal treatment at
13000C, 4h.
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SEM of transversal cut of the sample obtained from 16 layers,
2M concentration
Deposition of CG20 on ZrO2 supports
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Conclusions
Combustion method simple way to directly obtain CeGd20An annealing treatment at 500C, 3h is necessary to obtain cubic single
phase.
The nanometric powder pressed to form dens ceramic bodies(1400C, 4h).
By the spray pyrolysis method uniform, compact, dense, cracks freeand adherent CG20 layers was deposed on glass and zirconia supports
respectively, with a thickness up to of 3.5 m.By a post-deposition thermal treatment at 1300C, 4h the morphology
of the layer has been improved showing sintered nanometer size
particles.
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Magnesia Refractories
high refractorinessdue to high melting point
2800C;
good powder density - 3.58 g/cm3;has a thermal conductivity - 0.07 [W/m*deg];
grain size ranging from 100-200 m
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Sizing the kiln
]0,013479[m4)-8400(100*0.138
100*15*0,2Vc 3
2,56[m]h*B
VcLc
4)(100*ta*G
100*t*PVc
/h]0,171163[m15*2,56T*LS
0
200
400
600
800
1000
12001400
1600
0 100 200 300 400 500 600 700 800 900 1000
Temperature
Time
1000C/1h
1400C/4h
1000C/1h
500C/3h
Capacity of production: 2t/year
Products which are treated in the kiln: SOFC electrolyte thin layer
Raw materials: ZrO2 products, treated with CeOs thin layer
Time burning cycle: 15h
l
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}High temperature refractories
Heat loss
Fire Brick Light insulators
Magnesia Brick
MgO powder
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Kiln section
MaterialThickness
(m)
Temperature
zone [C]
Thermal
conductivity
[W/m*deg]Length [mm]
0.142636
zone 1 Firebrick 0.09 25-500 0.7+64*10
Light brick 0.08 0.1+14.5*10
0.793057
zone 2 Firebrick 0.07 500-1000
Light brick 0.1 0.1+14.5*10
1.084035
zone 3 Magnesia brick 0.1 1000-1400 6.2+268*10
MgO - powder 0.12 0.07
Light brick 0.1 0.1+14.5*10
0.285272
zone 4 Magnesia brick 0.07 1400-1000 6.2+268*10
MgO - powder 0.08 0.07
Light brick 0.08 0.1+14.5*10
0.242651
zone 5 Firebrick 0.09 1000-70 0.7+64*10
Light brick 0.08 0.1+14.5*10
Kiln section
MaterialThickness
(m)
Temperature
zone [C]
Thermal
conductivity
[W/m*deg]Length [mm]
0.142636
zone 1 Firebrick 0.08 25-500 0.7+64*10
Light brick 0.06 0.1+14.5*10
0.793057
zone 2 Firebrick 0.07 500-1000
Light brick 0.1 0.1+14.5*10
1.084035
zone 3 Magnesia brick 0.11 1000-1400 6.2+268*10
MgO - powder 0.12 0.07
Light brick 0.09 0.1+14.5*10
0.285272
zone 4 Magnesia brick 0.08 1400-1000 6.2+268*10
MgO - powder 0.09 0.07
Light brick 0.08 0.1+14.5*10
0.242651
zone 5 Firebrick 0.07 1000-70 0.7+64*10
Light brick 0.08 0.1+14.5*10
Temp.
interval
[0C]c
Avg.
temp
.
[0C]
Length of
the zones
[m]
Vertical walls Heat loss Ceiling Heat loss
Total heat
loss
[kJ/kg]Area
[m2]
k
[W/m2*grd
]
(pi-a)
[deg][kW] [kJ/kg]
Area
[m2]
k
[W/m2*
deg]
(pi-a)
[deg][kW] [kJ/kg]
25-500 262.5 0.142636 0.001997 0.964091 242.5 0.0004686
7.085232
0.000998
0.98517 242.5 0.000239
3.61368 10.698912
500-1000 750 0.793057 0.011103 0.827533 730 0.006707101.409
8
0.00555
1
0.84301
5730
0.00341
6
51.6499
2153.05976
1000-
14001200 1.084035 0.015176 0.354719 1160 0.006245 94.4244
0.00758
8
0.35667
91160
0.00351
553.1468 147.5712
1400-
10001200 0.285272 0.003994 0.489439 1160 0.002267
34.2770
4
0.00199
7
0.49317
81160
0.00114
2
17.2670
451.54408
1000-70 535 0.242651 0.003397 0.982833 495 0.001615 24.41880.00169
9
0.99802
6495
0.00083
9
12.6856
837.10448
Heat loss calculation throughthe walls
Heat loss calculation throughthe ceiling
Total heat loss by walls and ceiling
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Sensitive Heat
Temperature
interval
[C]
Sensitiv heat of the
material
[kJ/kg]
Losses in the
enviroment
[kJ/kg]
Heat
accumulated in
the plate
support
[kJ/kg]
Total stage
[kJ/kg]
Total
cumulative
[kJ/kg]
25-500 77.88 10.6989 449.332 537.9009 537.9009
500 81.055 153.059 81.055 618.9559
500-1000 91.865 147.571 485.8 730.724 1349.6799
1000 172.92 172.92 1522.5999
1000-1400 85.6 537.8 770.971 2293.5079
1400 256.52 258.52 2552.0909
1400-1000 -50.54 51.544 -537.8 -536.796 -1480.372
1000-70 -87.39 37.104 -893.29 -943.576 -943.576
0
619
1523
2552
-1480,37
-943,57
0
200
400
600
800
1000
1200
1400
1600
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Temperature[oC]
Specific energy consumption [kJ/kg]
Q- DIAGRAM
q - Diagram
Temperature interval` MaterialThermal process
[kJ/kg]
Necessary heat
[kJ/kg]
Heating Q = m*c*T
250C-5000C
ZrO2: 0.145*(0.594*500-
0.45*25)41.43375
77.88393CeO2:0.074*(500*1.02678-
25*0.8328)36.45018
5000C soaking time ZrO2 43.065 81.05586Oxide formation CeO2 37.99086
Heating ZrO2 49.391.86554
5000C-10000C CeO2 42.56554564
10000Csoaking time ZrO2 92.365
172.9214The sinterisation process initialize and the
networks finalizeCeO2 80.5564
Heating
10000C-14000C ZrO2 50.54785.6082
CeO2 35.0612
14000Csoaking time ZrO2 142.912258.5296
The sinterisation process finalize CeO2 115.6176
Cooling
14000C-10000C ZrO2 -50.547 -50.547
Cooling
10000
C-700
C
ZrO2
-87.3915
-87.3915
Process description of the productduring the heat treatment
Al2O3 support
Temperature interval
[oC]
Thermal process
[kJ/kg]
250C-5000C 449.3224
5000C-10000C 485.8019
10000C-14000C 537.8069
14000C-10000C -537.8069
10000C-700C -893.2921
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Electric heaters
44
12
)100
(*
*100prod
n
T
C
Q
con
conS*
T
Q necessary [W] Cn
[W/m2*K4]
Tprod
[K]
12 Area Tcon
[K]
136 5.77 773 0.54 0.01997 871
335 5.77 1273 0.54 0.11103 1285
561 5.77 1673 0.54 0.15176 1679
The superficial temperature of the heater Tcon
eN
NZ
Number of heaters per sectionsZones Number of heaters
First zone 2
Second zone 4
Third zone 8
Terminal shapeSelecting the heaters type
The one that we need
for the first and secondzone
The one that we need
for the third zone