Ceria Based Electrolyte and Magnesia Refractories

8/14/2019 Ceria Based Electrolyte and Magnesia Refractories

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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.



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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.


SEM images for

sample obtained

from 12 layers,



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,



13000

C, 4h.

SEM images for

sample obtained from16 layers,



13000C, 4h.


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SEM of transversal cut of the sample obtained from 16 layers,

2M concentration



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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



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



Light brick 0.09 0.1+14.5*10

0.285272



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

Date post:	30-May-2018
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Ceria Based Electrolyte and Magnesia Refractories

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