CFD SIMULATION OF FUEL REACTOR IN CHEMICAL LOOPING COMBUSTION

Presented by : Mr. Ratikorn Sornumpol

Advisor : Assoc. Prof. Dr. Pornpote PiumsomboonCo.-Advisor : Asst. Prof. Dr. Benjapon Chalermsinsuwan

Department of Chemical Technology

Chulalongkorn UniversityMHMK202 , July 13 ,2014

DEFENSE THESIS

2

Contents

INTRODUCTION

Part I Cold flow modelExperiment I

Results & discussion IConclusion I

Part II Hot flow modelExperiment II

Result & discussion IIConclusion II

2

Chemical looping combustion principles

A new process for oxidising fuels using metal oxides as oxygen carriers transporting oxygen from combustion air to fuel

no mixing of combustion air and fuel, combustion products (CO2 and H2O) not diluted by N2

Highly exothermal reactions in air reactor

Fuel reactor is exothermic/endothermic depending on fuel and oxygen carrier

INTRODUCTION

Fig 1. Chemial looping combustion

Air reaction system: 4M + 2O2 → 4MO Fuel reaction system: 4MO + CH4 → 4M + CO2 + 2H2O

3

Problems• There are less data to construct an industrial scale chemical looping reactor. • There is less work being investigated effect of operating condition on hydrodynamic behavior and rate of reduction reaction in fuel reactor.

• The key parameter to enhance rate of conversion is mixing index but there hasn’t none of work to investigate it .

• The parameter are not comprehensive and need to do systematic statistical study .

4Fig 2. Bubbling fluidized bed reactor

INTRODUCTION

To develop numerical model of bubbling

fluidized bed fuel reactor

To analyze effect of operating condition on hydrodynamic behavior and rate of reaction in bubbling fluidized bed

reactor

OBJECTIVES

5

Part I Bubbling fluidized bed

Experiments

1.2 Grid Independency and Steady state test

1.3 effect of operating parameter

on mixing index

1,900 cells 7,500 cells 30,000 cells Steady state test

Particle diameter Initial static bed height Particle density Fluidizing velocity

1.1 Validated mathematical model

2.2 Grid Independency and Steady state test

2.3 effect of operating parameter

on mixing index

1,900 cells 7,500 cells 30,000 cells Steady state

test

Analysis of variance of S.D. of solid volume fraction in axial direction

Analysis of variance of S.D. of solid volume fraction in radial direction

Main effect and interaction effect

Linear regression and Surface contour plot

2.1 Validated mathematical model

Results and discussion

Conclusions

3.1 Effect of operating parameter on mixing index in axial direction

3.2 Effect of operating parameter on mixing index in radial direction

Experiment Part I

AirDensity 1.225 kg/m3

Viscosity 1.8×10-5 kg/ms

Nickel oxide (NiO)Density 2,500 kg/m3

Diameter 530 micron

Model-2D geometry-Unsteady state-Eulerian 2 phase-Kinetic theory of granular flow

Fig 3. Schematic diagram of bubbling fluidized bed reactor Jung et al. (2012)

0.155 m

0.20 m

Outflow

Velocity inlet = 0.59 m/s

0.40m

Wall

- Particle-wall restitution coefficient =1

Particle-particle

-Particle-particle restitution coefficient =0.99

- Specularity coefficient = 0.6

Experiment part I : Grid independency test and Steady state test

Fig 4. Grid independency test

1,900 cells 7,500 cells 30,000 cells

38x50

75x100

150x200

Experiment Part I : Effect of operating parameter on mixing index

Particle densityLow : 1300kg/m3

High : 2350 kg/m3Particle diameterLow : 200 µmHigh : 600 µmGeldart group

B

Fluidization velocityLow : 1.5 UmfHigh : 1.75 Umf

Bubbling regime

Ratio of initial static bed height to diameter column Low : 0.5DHigh : 0.75D

10

Result & Discussions Part I : Validated mathematical model

Fig 5. Axial particle velocity in radial direction and granular temperature at height 0.14 m

Fig 6. Instantaneous axial and lateral particle velocity at height 0.14 m between 20 – 28 sec

11

Result & Discussions Part I : Grid Independency and Steady state test

Fig 7. Averaged solid volume fraction in radial direction at height 0.14 m

Fig 8. Absolute pressure along height of bubbling fluidized bed reactor

To select 75 x100

To calculate averaged S.D. solid volume fraction in 5 - 20 sec.

Standard deviation of solid volume fraction

MixingHow to evaluate mixing index ??

How to measure distribution of particle in vessel ??

To calculate standard deviation (S) of samples

221 )(....)(

1XXXX

nS n

S = Standard deviation X = A sample value = An average of sample valuen = Number of samplesX

12

13

Result & Discussions Part I : Summary result of standard deviation of solid volume fraction in radial and

axial directions

Treatment A(micron) B(m) C(kg/m3) D(m/s)SD axial direction

SD radial direction

1 200 0.50D 1300 1.5Umf 0.1844 4.29E-05a 600 0.50D 1300 1.5Umf 0.1774 4.51E-04b 200 0.75D 1300 1.5Umf 0.2449 1.17E-03ab 600 0.75D 1300 1.5Umf 0.2334 1.01E-03c 200 0.50D 2350 1.5Umf 0.1846 4.66E-03ac 600 0.50D 2350 1.5Umf 0.1701 5.72E-04bc 200 0.75D 2350 1.5Umf 0.2464 3.94E-03abc 600 0.75D 2350 1.5Umf 0.2235 3.40E-03d 200 0.50D 1300 1.75Umf 0.1800 8.35E-04ad 600 0.50D 1300 1.75Umf 0.1687 3.04E-04bd 200 0.75D 1300 1.75Umf 0.2377 2.17E-03abd 600 0.75D 1300 1.75Umf 0.2223 2.29E-03cd 200 0.50D 2350 1.75Umf 0.1817 1.96E-03acd 600 0.50D 2350 1.75Umf 0.1594 1.67E-03bcd 200 0.75D 2350 1.75Umf 0.2400 6.42E-03abcd 600 0.75D 2350 1.75Umf 0.2072 3.69E-03

14

Result & Discussions Part I : Analysis of variance of S.D. of solid volume fraction in axial direction

Table 1 :The analysis of variance for standard deviation of solid volume fraction in axial direction .

Source

Sum of

Squares DF

MeanSquare

FValue

Prob > F

Model

0.014411836 10

0.001441184

1272.4279

< 0.0001

A0.001185

081 10.0011850

811046.31

33<

0.0001

B0.012605

676 10.0126056

7611129.6

11<

0.0001

C8.05506E-05 1

8.05506E-05

71.11853 0.0004

D0.000286

456 10.0002864

56252.913

03<

0.0001

AB4.72656E-05 1

4.72656E-05

41.731045 0.0013

AC0.000139

831 10.0001398

31123.457

12 0.0001

AD4.19256E-05 1

4.19256E-05

37.016334 0.0017

BD1.27806E-05 1

1.27806E-05

11.284075 0.0201

ABC6.63063E-06 1

6.63063E-06

5.8542104 0.0602

ACD5.64063E-06 1

5.64063E-06

4.9801346 0.0760

Residual

5.66313E-06 5

1.13263E-06

Cor Total

0.014417499 15

 Y1 = 0.2 - 0.008356 XA + 0.028XB - 0.001994XC – 0.004481XD – 0.001469XAXB – 0.003206 XAXC – 0.001369

XAXDRegression model

R-Squared 0.9996Adj R-Squared 0.9988

15

Result & Discussions Part I : Main effect and interaction effect on mixing index in axial direction

Fig 9 . The effect of main parameter on standard deviation in axial

direction

Fig 10 . The effect of interaction effect on standard deviation in

axial direction

AB , AC , AD ,BD

16

Result & Discussions Part I : Surface contour plot on mixing index in axial direction

-1-0.5

00.5

1

-1

-0.5

0

0.5

1

0.16

0.18

0.2

0.22

0.24

Sta

ndard

devia

tion o

f solid v

olu

me f

raction in a

xia

l direction

Particle diameterInitial bed height

Fig 11. Response surface of AC

Fig 12 . Response surface of AB

Fig 13. Response surface of AD

Fig 14. Response surface of BD

Fluidization velocity

Initial static bed height

Particle diameterParticle diameter Particle density

Particle diameter-1

-0.50

0.51

-1

-0.5

0

0.5

10.16

0.18

0.2

0.22

0.24

Sta

ndard

devia

tion o

f solid v

olu

me f

raction in a

xia

l direction

Initial static bedheightFluidization velocityFluidization velocityInitial static bed height

17

Conclusion Part I : Bubbling fluidized bed reactor in batch reactor

( Mixing index in axial direction)

For axial direction , All main parameters had the significant effect on mixing in axial direction.

Increasing velocity and particle diameter shall be increased mixing index because increasing of gas velocity caused gross internal circulation that induce particle circulate around bubble .

Optimum condition of properties of nickel oxide is particle density 2,350 kg/m3 and particle diameter 600 micron for good mixing in axial direction .

18

Result & Discussions Part I : Analysis of variance of S.D. of solid volume fraction in radial direction

Table 2 :The analysis of variance for standard deviation of solid volume fraction in radial direction .

 Y2 = 0.002162 - 0.0004882 XA + 0.0008497XB + 0.001127XC – 0.0004678XAXC + 0.000375XBXD – 0.0004504 XAXBXCXD

Regression model

R-Squared 0.9877Adj R-Squared 0.9387

Source

Sum ofSquare

s DFMean

SquareF

ValueProb >

F

Model4.85662

E-05 124.04719

E-0620.14070

8 0.0153

A3.81313

E-06 13.81313

E-0618.97596

3 0.0224

B1.15517

E-05 11.15517

E-05 57.48658 0.0048

C2.03381

E-05 12.03381

E-05101.2118

6 0.0021

D1.04709

E-06 11.04709

E-065.210823

6 0.1067

AC3.50167

E-06 13.50167

E-0617.42596

6 0.0250

AD5.62757

E-08 15.62757

E-080.280054

5 0.6333

BC8.01428

E-07 18.01428

E-073.988283

7 0.1397

BD2.25518

E-06 12.25518

E-0611.22283

2 0.0441

ABC6.56769

E-08 16.56769

E-080.326839

2 0.6076

ABD1.4214E

-06 11.4214E

-067.073560

8 0.0764

BCD4.68232

E-07 14.68232

E-072.330145

2 0.2243

ABCD3.24639

E-06 13.24639

E-0616.15558

7 0.0277

Residual

6.02837E-07 3

2.00946E-07

Cor Total

4.91691E-05 15

19

Result & Discussions Part I : Main effect and interaction effect on mixing index in radial

direction

Fig 15 . The effect of main parameter on standard deviation in radial direction

Fig 16 . The effect of interaction effect on standard deviation in

radial direction

AC , BD

20

Result & Discussions Part I : Surface contour plot on mixing index in radial direction

Fig 17. Response surface of AC

Fig 18. Response surface of BD

Particle diameterParticle density Fluidization

velocityInitial bed height

21

Conclusion Part I : Bubbling fluidized bed reactor in batch reactor

( Mixing index in radial direction)

For radial direction , Three parameters (Particle diameter , Initial bed height and Particle density had the significant effect on mixing in radial direction.

Increasing particle diameter will be increased mixing index but initial bed height and particle density will bed decreased mixing index.

In real case , I suggest that focused on axial direction more than radial direction significantly because of S.D in radial direction had a very little value comparable S.D. in axial direction. For optimum condition in experiment , we will select particle size 600 micron and particle density 2350 kg/m3

Part II Fuel reactor in chemical looping combustion

Experiments

2.2 Grid Independency and Steady state test

2.3effect of operating parameter on mixing

index

8,334 cells 17,732 cells 35,979 cells Steady state test

Particle diameter Initial static bed height Syngas temperature Fluidizing velocity

2.1 Validated mathematical model

1.2 Grid Independency and Steady state test

1.3 effect of operating parameter

on mixing index

8,334 cells 17,732 cells 35,979 cells Steady state

test

Analysis of variance of CO conversion

Analysis of variance of H2 conversion

Main effect and interaction effect

Linear regression and Surface contour plot

1.1 Validated mathematical model

Results and discussion

Conclusions

Effect of operating parameter on carbon monoxide conversion

Effect of operating parameter on hydrogen conversion

Experiment Part II

AirDensity 1.225 kg/m3

Viscosity 1.81×10-5 kg/ms

Nickel oxide (NiO)Density 2,600 kg/m3

Diameter 150 micron

Model-2D geometry-Unsteady state-Eulerian 2 phase-Kinetic theory of granular flow

Fig 19. Schematic diagram of Interconnected circulating fluidized bed reactor Johansson et al.(2003)

Dimension of CFBH1 = 1.9 mD1 = 0.19 mH2 = 0.5 mD2 = 0.19 mH3 = 0.15 mD3 = 0.14 m

H2

D1

D2

D3

Fluidizing velocity - ug,ao = 1.1 m/sec- ug,po = 0.087 m/sec- ug,fo = 0.19 m/sec

Initial bed height (In case solid inventory 9 Kg)- Air reactor = 4.9 kg (15cm) - Fuel reactor = 3.2 kg (10cm)- Pot seal = 0.9 kg (3cm)

- Particle-wall restitution coefficient =1

-Particle-particle restitution coefficient =0.99

- Specularity coefficient = 0.6

H1

Experiment part II : Grid independency test

Fig 20 . Grid independency test

8,334 cells 17,332 cells 35,979 cells

Experiment Part II : Effect of operating parameter on rate of reaction

Fuel reactor(Varied Gas velocity)Syngas CO 44.5 mol %H2 22.22 mol %CO2 11.11 mol% H2O 22.22 mol%

Air reactor(Fixed Gas velocity 1.73 m/s)AirN2 78 mol% O2 22 mol%

Pot seal(Fixed Gas velocity 0.087 m/s)N2 N2 100 mol%

molkJH

gOHsNisNiOgH

r /1.2

)()()()(

1

22

molkJH

gCOsNisNiOgCO

r /3.43

)()()()(

2

2

molkJH

sNiOsNigO

r /479

)(2)(2)(

2

2

222 )()()( HgCOgOHgCO

Experiment Part II : Effect of operating parameter on rate of reaction

Particle diameterLow : 150 µmHigh : 175 µmGeldart group B

Fluidization velocityLow : 1.25 UmfHigh : 1.5 Umf

Bubbling regime

Ratio of initial static bed height to diameter column Low : 0.75DHigh : 1.0D

Syngas temperatureLow : 773 KHigh : 873 K

27

Result & Discussions Part II : Validated mathematical model

Fig 21. Pressure drop along height of air reactor and fuel reactor

28

Result & Discussions Part II : Grid Independency and Steady state test

Fig 22. Absolute pressure along height of air reactor

Fig 23. Gas temperature at exit of fuel reactor of case c and b

To select 17732 cell for solving problem

To calculate averaged syngas conversion in 25 - 35 sec.

29

Result & Discussions Part II : Summary result of Syngas conversion

Case

Particle

diameter(micr

on)

Initial bed

height

Syngas

temperature

(K)

Fluidization

velocity(m/s)

Conversion of carbon

monoxide(-)

Conversion of hydrogen

(-)

1 150 0.750D 7731.25U

mf82.719 82.19466

2 175 0.750D 7731.25U

mf83.5181 82.98708

3 150 1.0D 7731.25U

mf94.483 89.534

4 175 1.0D 7731.25U

mf86.811 86.3587

5 150 0.750D 8731.25U

mf97.620 97.6089

6 175 0.750D 8731.25U

mf94.89417 94.78449

7 150 1.0D 8731.25U

mf88.15304 87.97684

8 175 1.0D 8731.25U

mf92.613 92.37386

9 150 0.75D 773 1.5Umf 94.632 94.5106810 175 0.750D 773 1.5Umf 96.093 95.874193411 150 1.0D 773 1.5Umf 92.8520 92.7663812 175 1.0D 773 1.5Umf 71.3488 70.8960813 150 1.0D 873 1.5Umf 95.1873 95.0841814 175 0.750D 873 1.5Umf 78.4516 77.7703115 150 1.0D 873 1.5Umf 93.0507 92.6686716 175 1.0D 873 1.5Umf 65.1346 52.07539

30

Result & Discussions Part II : Analysis of variance of carbon monoxide

Table 3 :The analysis of variance for carbon monoxide conversion.

 Y3 = 87.97274 – 4.636453 XA – 2.41691 XB – 2.12881 XD – 2.21435XAXB – 3.72216XAXD – 2.83048 XBXD – 3.05326 XCXD– 2.0537XAXBXD + 2.076XAXCXD+ 2.367XBXCXD

Regression model

Sum of Mean F

Source Squares DF

Square Value Prob > F

Model 1257.8 10125.7

87.83 0.0174

A 300.38 1300.3

818.7 0.0075

B 85.07 1 85.07 5.3 0.0697

D 230.54 1230.5

414.35 0.0128

AB 76.28 1 76.28 4.75 0.0812

AD 217.93 1217.9

313.57 0.0142

BD 75.15 1 75.15 4.68 0.0829CD 82.03 1 82.03 5.11 0.0734

ABD 65.47 1 65.47 4.08 0.0995ACD 70.9 1 70.9 4.41 0.0897BCD 87.34 1 87.34 5.44 0.0671

Residual

80.32 5 16.06

Cor Total

1338.12 15

R-Squared0.9662

Adj R-Squared0.8199

31

Result & Discussions Part II : Main effect and interaction effect on carbon monoxide conversion

Fig 24 . The effect of main parameter on carbon monoxide conversion

Fig 25. The effect of interaction effect on

carbon monoxide conversion

AD

32

Result & Discussions Part II : Surface contour plot on carbon monoxide conversion

Fig 26 . Response surface of AD

33

Conclusion Part II : Fuel reactor in chemical looping combustion

( Conversion of carbon monoxide )

Particle diameter and fluidization velocity has a significant effect on carbon monoxide conversion

Decreasing particle diameter and fluidization velocity will be improved carbon monoxide conversion .

For maximizing conversion of carbon monoxide conversion is selected particle diameter 150 micron and 1.25 times of minimum fluidization velocity

34

Result & Discussions Part II : Analysis of variance of hydrogen

Sum of Mean FSource Squares DF Square Value Prob > F

Model1970.6

611 179.15 6.65 0.0411

A 395.45 1 395.45 14.67 0.0186B 194.92 1 194.92 7.23 0.0547D 112.85 1 112.85 4.19 0.1102

AB 118.7 1 118.7 4.4 0.1038AD 373.3 1 373.3 13.85 0.0204BC 37.4 1 37.4 1.39 0.3041BD 181.04 1 181.04 6.72 0.0606CD 287.29 1 287.29 10.66 0.0309

ABD 152.82 1 152.82 5.67 0.0759ACD 108.55 1 108.55 4.03 0.1152

ABCD 8.34 1 8.34 0.31 0.6076Residual 107.81 4 26.95

Table 4 :The analysis of variance for hydrogen conversion.

 Y4 = 86.59153 – 4.59151 XA – 3.51029 XB – 2.63579 XD – 2.70372XAXB – 4.85023XAXD – 1.50855 XBXc – 3.3438 XBXD – 4.2574 XCXD – 2.5847XAXBXD - 2.58474XAXCXD - 0.70217XAXBXCXD

Regression model

R-Squared0.9461

Adj R-Squared0.8055

35

Result & Discussions Part II : Main effect and interaction effect on hydrogen conversion

Fig 27. The effect of main parameter on hydrogen conversion

Fig 28. The effect of interaction effect on hydrogen conversion

AD ,CD

36

Result & Discussions Part II : Surface contour plot on carbon monoxide conversion

Fig 26 . Response surface of AD