Simulation of biomass gasification with Euler ...

Simulation of biomass gasification with Euler-Lagrangian method :

reactor scale to particle scale

Tao ChenFluid Dynamics Division

Workshop 16 March

Contents

1. Fluidized bed gasification2. Single particle pyrolysis

Background

3. Single particle combustion4. Char particle gasification

Workshop 16 March

Background

1. Fluidized bed gasification

pp g c p

dm m

dt= + +

vf f g

pp p

dIdt

= Tw 4T

(T T ) (G 4 T ) Q4

p p pp p p g p p p

d e Am c hA

dts= - + - +

CFD-DEM modeling

( ) ( ) ,g g g g g p mSte r e r¶

+Ñ× =¶

u

( ) ( ) ( ) ,g g g g g g g g eff g g p momp Ste r e r e e r¶

+Ñ× = -Ñ +Ñ× + +¶

u u u gt

( ) ( ) ( ) ,( )g g g g g g eff s h p h radE E p h S S Ste r e r e a¶

+Ñ× + =Ñ× Ñ + + +¶

u

( ) ( ) ( ) , i ig g i g g g i g g eff i p Y YY Y D Y S Ste r e r e r¶

+Ñ× =Ñ× Ñ + +¶

u

Reaction A E nC+0.5O2=CO 3.0e+4 1.49e+8 0C+CO2=2CO 4.02e+7 2.48e+8 0C+H2O=CO+H2 1.21e+8 2.48e+8 0CO+0.5O2=CO2 2.2e+12 1.67e+8 0H2+0.5O2=H2O 6.8e+15 1.68e+8 0CH4+0.5O2=CO+2H2 3.0e+8 1.26e+8 -1CO+H2O=CO2+H2 2.75e+10 8.38e+7 0CH4+H2O=CO+3H2 4.4e+11 1.68e+8 0

Reaction mechanism:


1. Fluidized bed pyrolysis

Reaction RateCELL→CELLA k=4×1013exp(-45000a/RT)CELLA→0.45C2H4O2+0.2C2H2O2+0.1CH3CHO+

0.25HMFU+0.3C2H5CHO+0.15CH3OH+0.4CH2O+0.31CO+0.41CO2+0.05H2+0.83H2O+0.02HCOOH+0.2G{CH4}+0.05G{H2}+0.61Char

k=2×106exp(-19100/RT)

CELLA→LVG k=4Texp(-10000/RT)CELL→5H2O+6Char k=6.5×107exp(-31000/RT)

Cellulose pyrolysis kinetics

Reaction RateHCE→0.58HCE1+0.42HCE2 k=1×1010exp(-31000/RT)HCE1→0.025H2O+0.5CO2+0.025HCOOH+0.5CO+0.8CH2O+0.125C2H5OH+0.1CH3OH+0.25C2H4+0.125G{H2}+0.275G{CO2}+0.4G{COH2}+0.45G{CH3OH}+0.325G{CH4}+0.875Char

k=1.2×109exp(-30000/RT)

HCE1→0.25H2O+0.8CO2+0.05HCOOH+0.1CO+0.15G{CO}+0.15G{CO2}+0.2G{H2}+0.3CH2O+1.2G{COH2}+0.375G{C2H4}+0.625G{CH4}+0.875Char

k=0.15Texp(-8000/RT)

HCE1→Xylan k=3Texp(-11000/RT)HCE2→0.2H2O+0.175CO+0.275CO2+0.5CH2O+0.1C2H5OH+0.2C2H4O2+0.025HCOOH+0.25G{CH4}+0.3G{CH3OH}+0.275G{C2H4}+0.4G{CO2}+0.925G{COH2}+Char

k=5×109exp(-33000/RT)


Hemicellulose pyrolysis kinetics

1. Fluidized bed pyrolysisLignin pyrolysis kinetics

Reaction RateLIG-C→0.35LIGcc+0.1pCoumaryl+0.08Phenol+0.41C2H4+H2O+0.7G{COH2}+0.3CH2O+0.32CO+0.495G{CH4}+5.735Char

k=1.33×1015exp(-48500/RT)

LIG-H→LIGOH+0.5C2H5CHO+0.5C2H4+0.25C2H4O2 k=6.7×1012exp(-37500/RT)

LIG-O→LIGOH+CO2 k=3.3×108exp(-25500/RT)

LIGCC→0.3pCoumaryl+0.2Phenol+0.35C3H4O2+0.7H2O+0.65G{CH4}+0.6G{C2H4}+G{COH2}+0.4CO+0.4G{CO}+6.75Char

k=1.67×106xp(-31500/RT)

LIGOH→LIG+0.9H2O+0.1CH4+0.6CH3OH+0.1G{H2}+0.3G{CH3OH}+0.05CO2+0.55CO+0.6G{CO}+0.05HCOOH+0.85G{COH2}+0.35G{CH4}+0.2G{C2H4}+4.15Char

k=1×108exp(-30000/RT)

LIG→0.7C11H12O4+0.3ANISOLE+0.3CO+0.3G{CO}+0.3CH3CHO k=4Texp(-12000/RT)LIG→0.95H2O+0.2CH2O+0.4CH3OH+CO+0.2CH4+0.05HCOOH+0.45G{CO}+0.5G{COH2}+0.4G{CH4}+0.65G{C2H4}+0.2CH3CHO+0.2C2H5CHO+5.5Char

k=4×108exp(-30000/RT)

LIG→0.6H2O+0.4CO+0.2CH4+0.4CH2O+0.2G{CO}+0.4G{CH4}+0.5G{C2H4}+0.4G{CH3OH}+2G{COH2}+6Char

k=8.3×1012exp(-8000/RT)


Secondary tar decompositionReaction RateHMFU→3CO+1.5C2H4 k=4.28×104exp(-25704/RT)C2H5CHO→0.5CO2+0.5H2+1.25C2H4 k=4.28×104exp(-25704/RT)pCoumaryl →CO2+2.5C2H4+3Char k=4.28×104exp(-25704/RT)Phenol →0.5CO2+1.5C2H4+2.5Char k=4.28×104exp(-25704/RT)XYLOSE→2CO2+H2+1.5C2H4 k=4.28×104exp(-25704/RT)LVG→2.5CO2+1.5H2+1.75C2H4 k=4.28×104exp(-25704/RT)HAA→2CO+2H2 k=4.28×104exp(-25704/RT)Glyoxal→2CO+H2 k=4.28×104exp(-25704/RT)Lumped Phenol→2CO2+3C2H4+3Char k=4.28×104exp(-25704/RT)

1. Fluidized bed pyrolysisParameter Value

Reactor geometry (m) 0.072×0.65×0.00085wall temperature (°C) 500inlet gas temperature (°C) 463inlet gas flow rate (g/s) 0.05

Sand particle shape spherediameter (μm) 850density (kg/m3) 2650

Biomassparticle

shape spherediameter (μm) 850material mixture of pine and

sprucedensity (kg/m3) 600feeding rate (g/s) 0.00835

Resolution grid 20×130×1time step (s) 1.0e-5


9s 9.1s 9.2s 9.3s 9.4s 9.5s 9.6s

2. Single particle pyrolysisindex of the ratio of the heat transferresistances inside of and at the surface of a body

lintra-particle temperature gradientlunsynchronized conversion inside the particlelstructure change during pyrolysis

ldp=10~100 mm

2. Single particle pyrolysis

( ) ( ) ( )444

s ss s s g s s

T e Sc T hS T T G T Qt

r k s¢¶ ¢=Ñ Ñ + - + - +

¶

( ) ( ) ,g g g g g p mSte r e r¶

+Ñ× =¶

u

( ) ( ) ( ) ,g g g g g g g g eff g g p momp Ste r e r e e r¶

+Ñ× = -Ñ +Ñ× + +¶

u u u gt

( ) ( ) ( ) ,( )g g g g g g eff s h p h radE E p h S S Ste r e r e a¶

+Ñ× + =Ñ× Ñ + + +¶

u

( ) ( ) ( ) , i ig g i g g g i g g eff i p Y YY Y D Y S Ste r e r e r¶

+Ñ× =Ñ× Ñ + +¶

u

001 (1 )t

t sg g

s

mm

e e= - -

2. Single particle pyrolysisLow temperature pyrolysis

2. Single particle pyrolysisHigh temperature pyrolysis

9.5d mm=

1276wallT K=

1050airT K=

Air

3. Single particle combustion

Heterogeneous reactions

C + 0.5 O2 = CO

C + CO2 = 2 CO

C + H2O = CO + H2

Homogeneous reactions

H2 + 0.5O2 = H2O

CO + 0.5O2 = CO2

C6H6.2O0.2 + 2.9O2 = 6CO + 3.1H2

T Y_CO2


10 s 20 s 30 s

40 s 50 s 60 s

70 s 80 s 90 s


4. Char particle gasification

Airx

y

in 1069 KT =

in 3.3 m/sV =

600 KT =

600 KT =

pressure outlet

dp

Parameter Valuer (kg/m3) 1154.5e0 (-) 0.286

dp (mm) 5.2S0′ (m2/m3) 3.11×107

Ψ (-) 2.28mash/m0 0.14

cs (J/(kg K)) 1100 + 0.6·Ts


Parameter Value

r (kg/m3) 1040.3

e0 (-) 0.385

S0′ (m2/ m3) 8.09×108

Ψ (-) 10.0

dp (mm) 2.2

mash/m0 0.11

Tin (K) 1675

Vin (m/s) 0.05

Steam gasification


Steam&N2

xy

in 1000 KT =

in 1.0m/sV =

1000 KT =

1000 KT =

pressure outlet

Parameter Value

r (kg/m3) 1154.5

e0 (-) 0.286

S0′ (m2/m3) 3.11×107

Ψ (-) 2.28

mash/m0 0.14

Gasification condition：d = 5 mm, Vin = 1.0 m/s, Tin = 1000 K, YO2 = 0, YH2O = 60%


5 s 10 s 20 s

30 s 40 s 50 s


10 s 30 s

50 s 70 s


10 s 30 s

Without Stefan flow effect

5. Conclusions

p Biomass gasification is a multiscale problem.Particle scale detailed pyrolysis behaviorshould be taken into account: temperaturegradient, Stefan flow effect, et al.

p Gasification mechanism should captureproduct variation with the change of operatingconditions. Global mechanism is too rough toachieve this goal.

Simulation of biomass gasification with Euler ...

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