Effect of operating parameters in fuel reactor of chemical looping combustion

using computational fluid dynamic simulation

Presented by : Mr. Ratikorn Sornumpol

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

Department of Chemical Technology

Chulalongkorn University

MHMK202 , February 26 ,2014

PREDEFENSE

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Contents

INTRODUCTION

EXPERIMENTALS

RESULTS & DISCUSSION

CONCLUSIONS

ON GOING WORKS

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3Fig 1 CO2 emission from energy use continue to rise

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INTRODUCTION

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 2 Chemial looping combustion

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

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INTRODUCTIONAdvantage of fluidization process

•To base on the energy consumption analysis, it has been found that a fluidized bed mixer offers the most efficient and economical process compared to other mixers.

• High, uniform mass and heat transfer rate

Disadvantage of fluidization process

•High electrical energy needed

•Expensive supplied air systemWhat factor have a significant effects on mixing in

gas-solid ? 5

Problem• 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 .

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PROBLEMS

To develop numerical model of bubbling fluidized bed fuel

reactor

To analyze effect of operating condition on hydrodynamic behavior and reduction reaction

in fuel reactor

OBJECTIVES

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INTRODUCTION

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

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To create 2-D fuel reactor geometry by using Gambit 2.2.30 To simulate cold flow

model by ANSYS fluent and validate model from

literature of Loha,C. et.alTo build experimental

design and analyze data by using ANOVA

EXPERIMENTAL

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EXPERIMENTALTo simulate cold flow

model by ANSYS fluent

Select Euler-Euler modelDescription value

Particle density 2500 kg/m3Gas density 1.225kg/m3

Mean particle diameter 530 μmRestitution coefficient 0.99

Numerical scheme QUICKSuperficial gas velocity 0.587 m/s

Bed width 0.155 mBed height 0.4 m

Static bed height 0.2mGrid interval spacing 0.005m

Inlet boundary conditions Velocity

Outlet boundary conditions OutfllowTime steps 0.0001

Drag model Gidaspow

Table1 . Set up parameters in numerical model

0.155 m

0.20 m

Outflow

Velocity inlet

To create 2-D fuel reactor geometry by using Gambit

2.2.30

0.40m

Wall

Particle-wall restitution coefficient =0.95

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EXPERIMENTALTo validate model from literature of

Jung. et.al

To build experimental

design and analyze data by using

ANOVA

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RESULT &DISSCUSSIONSGrid independence

study38x50

75x100

150x200

Model validation

Fig 3. Comparison of numerical result and experimental data

Fig 4. Grid independency test

Medium mesh was selected to compute 2D-Cartesian bubbling fluidized bed.

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RESULT &DISSCUSSIONSTime Independency test

2 k Factorial design

The standard deviation of solid volume fraction in axial direction and radial direction is selected to response

parameter.

Fig 5 . Time independency test for overall pressure drop

Table2 . Level of factor parameter in 2 K factorial design

221 )(....)(

1XXXX

nS n

VariableSymb

ol Level    Low(-1) High(+1)

Particle diameter A 200 600Aspect ratio of Initial static bed/Diameter

column B 0.5 0.75

Particle density C 1300 2350

Excess fluidization velocity D 1.5Umf 1.75Umf

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RESULT &DISSCUSSIONSTable 3: 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

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RESULT &DISSCUSSIONSEffect of operating conditions on S.D. of solid volume fraction in axial direction

Table 4 :The analysis of variance for standard deviation of solid volume fraction in axial direction.

Source Sum of squares DF Mean square F-Value Prob> F

A 1.18E-03 1 1.18E-03 65.32 < 0.0001

B 0.013 1 0.013 694.97 < 0.0001

D 2.89E-04 1 2.89E-04 15.93 0.0021

AC 1.40E-04 1 1.40E-04 7.73 0.0179

Residual 1.99E-04 11 1.81E-05

Total 0.014 15

In axial direction ,Increasing particle size and fluidization velocity have reduced standard deviation of solid volume fraction in radial direction.

Fig 6 . The effect of different factors on standard deviation in axial direction

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RESULT &DISSCUSSIONSEffect of operating conditions on S.D. of solid volume fraction in radial direction

Table 5: The analysis of variance for standard deviation of solid volume fraction in radial direction.Source Sum of squares DF Mean square F-value Prob> F

A 3.39E-06 1 3.39E-06 55.7442837 0.0175B 1.08E-05 1 1.08E-05 177.299219 0.0056C 1.93E-05 1 1.93E-05 317.520296 0.0031D 1.29E-06 1 1.29E-06 21.1394989 0.0442AB 1.70E-07 1 1.70E-07 2.78668632 0.2370AC 3.09E-06 1 3.09E-06 50.7408562 0.0191BC 6.15E-07 1 6.15E-07 10.1083398 0.0863BD 2.61E-06 1 2.61E-06 42.9032912 0.0225ABC 1.35E-07 1 1.35E-07 2.21574994 0.2750ABD 1.71E-06 1 1.71E-06 28.0415009 0.0339ACD 2.05E-07 1 2.05E-07 3.36772321 0.2079BCD 6.32E-07 1 6.32E-07 10.3912584 0.0843ABCD 3.66E-06 1 3.66E-06 60.1186358 0.0162

Residual 1.22E-07 2 6.09E-08    Total 4.77E-05 15

Fig 7 . The effect of different factors on standard deviation in radial direction

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RESULT &DISSCUSSIONSEffect of operating condition on flow pattern

“ac”

“acd”

Fig 8. Solid volume fraction contours and solid flux vector for ac and acd at 15 sec.

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CONCLUSIONS Three main parameters had the significant effect on mixing in axial direction and all main parameters had the significant effect on mixing in radial direction.

For axial direction , increasing velocity and particle diameter shall be decreased mixing index because increasing of gas velocity caused gross internal circulation .

For radial direction , increasing particle diameter will be decreased mixing index.

From the contour of solid volume fraction at 15 s, adjusting operating parameters to high level such as particle size, particle density and fluidization velocity , the “acd “ case have the lowest S.D. in axial and radial direction .

The mechanism of mixing in bubbling fluidized bed can bed described that the bubble were then generated and coalesced to form larger bubble. It is commonly recognized that solids mixing in a fluidized bed is mainly caused by the movement of bubbles.

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On going works

-To determine kinetic data from literature and simulate hot flow model

- To analyze effect of operating condition on reduction reaction in fuel reactor

ACKNOWLEDGMENT

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THANK YOU FOR YOUR KIND ATTENTION

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Time Independence test

To select 15-25 sec for averaged calculation

0 5 10 15 20 25 30 350

500

1000

1500

2000

2500

3000

3500

6250cell

Time(sec)

Overa

ll_p

ressu

re_d

rop

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101000 102000 103000 1040000

0.5

1

1.5

2

Absolute pressure_in_axial direction at_Time averged 15-25sec

6500cell13500cell27500cell

Absolute_pressure

Heig

ht

of

air

reacto

rGrid Independence test

To select 13500cell for simulation

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0 0.05 0.1 0.15 0.2 0.25 0.30

0.5

1

1.5

2

Time_averaged_solid_volume_fraction_in_axial_direction

Numerical_3D(Paper)6250cell13500cell27000cell

Solid volume fraction

Heig

ht

of

reacto

rValidation model