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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