Simulation of Biomass Gasification in

Circulating Fluidized Bed Reactor by Aspen

Plus

09/02/2013 1

T. S. Pinho, A. M. Ribeiro, L. M. S. Silva

Departamento de Engenharia Química, CIETI, Instituto Superior de Engenharia do Porto (ISEP), Rua Dr. AntónioBernardino de Almeida, 431, 4200-072 Porto – Portugal

+351 228340500; email: lms@isep.ipp.pt

Tips to be Covered

Goals

Background & Justification

Model featuresModel features

Simulation

Results & Conclusions

09/02/2013 2

Goals

Implement a kinetic model for biomass gasification

Simulate in Aspen Plus

Validate with experimental data Validate with experimental data

09/02/2013 3

Background & justification

Biomass is 4th largest source of energy

Potential of 220 Gtons(oven-dry) ⇔ ~4500 EJ

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Mobilization of ~5% ⇒225 EJ (~5 Gtoe)

50% total primary energy demand at present

Physical & Chemical properties

of biomass

Type Almond shells

Status As-received Dry-ash-free (DAF)

Moisture (wt%) 7.90 ―

Ash (wt%) 1.16 ―

Volatile matter (wt%) 72.45 79.67Volatile matter (wt%) 72.45 79.67

Carbon (wt%) 46.65 51.30

Hydrogen (wt%) 5.55 6.10

Oxygen (wt%) 38.74 42.60

LHV (kJ·kg-1) 18350 ―

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S. Rapagnà, N. Jand, A. Kiennemann, P. U. Foscolo, Biomass Bioenerg. 19 (2000) pp. 187-197

Flowsheet for biomass

gasification

Biomass pyrolysis

Volatiles combustion

Char gasification

Solid residence time &

gasifier height

O2 amount

09/02/2013 6

Char stoichiometric

coeffcients

H2O amount

... And two user-defined Fortran

blocks

Pyrolysis yield

pressure correctionGas-solid

reaction model

PRESCORR

GASIFIER

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PRESCORR

( )P.)atm(Yield)P(Yield 066011 −⋅=

31

2

1

1

11111

−−==

⋅=

−+⋅

+

−=−

pyrolysisparticle

core

nfilmash

ashsfilm

*ii

iC

X

X

R

RY

kkYkYkk

PPr

ε

DAF char yield prediction

Biomass→Char + CO+H2+H2O+CO2+CH4+CxHy+tar

09/02/2013 8

Adapted from: D. Neves, H. Thunman, A. Matos, L. Tarelho, A. Gómez-Barea

Prog. Energ. Combust. 37 (2011) pp. 611-630

DAF char yield prediction

Cells in yellowyellow refer to empirical correlations function of temperature

T(ºC)= 700.00 YC,tar YC,CxHy YC,CH4 YC,CO YC,CO2 0.00 0.00 Ytar,F YC,F-YC,ch.Ych,F

YC,F= 51.3% YO,tar 0.00 0.00 YO,CO YO,CO2 YO,H2O 0.00 YCxHy,F YO,F-YO,ch.Ych,F

YH,F= 6.1% YH,tar YH,CxHy YH,CH4 0.00 0.00 YH,H2O YH,H2 YCH4,F YH,F-YH,ch.Ych,F

YO,F= 42.6% 0.00 0.00 0.00 −Ω1 0.00 0.00 1.00 YCO,F 0

Ychar,F= 13.0% 0.00 0.00 -1.00 0.15 0.00 0.00 0.00 YCO2,F 2.18E-04

LHVg LHVcxhy LHVch4 LHVco 0.00 LHVg LHVh2 YH2O,F(ΣYj,F-

Ych,F.ΣYj,ch).LHVg

Ultimate analysis

09/02/2013 9

D. Neves, H. Thunman, A. Matos, L. Tarelho, A. Gómez-Barea, Prog. Energ. Combust. 37 (2011)

pp. 611-630

0.00 0.00 0.00 0.00 0.00 0.00 1.00 YH2,F Ω2

⇓⇓⇓⇓ ⇓⇓⇓⇓ ⇓⇓⇓⇓

LHVg(MJ/kg)= 11.060 0.61 0.86 0.75 0.40 0.27 0.00 0.00 46.42% 0.398474

YC,ch= 88.1% 0.33 0.00 0.00 0.57 0.36 0.89 0.00 1.06% 0.413067

YO,ch= 10.0% 0.07 0.14 0.25 0.00 0.00 0.11 1.00 1.64% 0.059111

YH,ch= 1.5% 0.00 0.00 0.00 -0.03 0.00 0.00 1.00 11.41% 0

Yash,ch= 9.8% 0.00 0.00 -1.00 0.15 0.00 0.00 0.00 18.21% 0.000218

11.06 47.15 49.92 10.11 0.00 11.06 119.49 14.64% 9.629412

0.00 0.00 0.00 0.00 0.00 0.00 1.00 0.33% 0.003348

Ultimate analysis

Typical gasification reactions

(1) H2+½O2→H2O

100% conversion(2) CO+½O2→CO2

(3) CH4+2O2→CO2+2H2O

Volatile combustion

Gasification

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(4) C+1/φO2→2(1-1/φ)CO+(2/φ-1)CO2 φ depends on particle diameter

(5) C+H2O↔CO+H2

Gas-solid reactions(6) C+CO2→2CO

(7) C+2H2↔CH4

(8) CH4+H2O↔CO+3H2 Steam reforming of CH4

(9) CO+H2O↔CO2+H2 Water-gas shift reaction

...And their kinetics

rC-i

(4)

(5)

( )112 −−− satmgcmk film ( )atmPP *ii − eqK

p

.

dP

T

T

..

⋅

751

1800264

2920 φ

−Te

17967

8710

( )112 −−− satmgcmks

2OP

.

dP

T

⋅

−750

3

200010

−Te

21060

247 eq

COHOH K

PPP 2

2−

T..

e 81

3026064417 −

Gas-solid

(6)

(7)

09/02/2013 11

pdP ⋅e247 eqK e

p

.

dP

T.

⋅

× −750

4

200010457

−Te

21060

2472COP

p

.

dP

T.

⋅

× −750

3

200010331

−Te.

17921

120 eq

CHH K

PP 4

2− T.e. 81

184006101215 −×

Source: C. –Y. Wen, T. –Z. Chaung, Ind. Eng. Chem. Process Des. Dev., 18 (1979) pp. 684-695

...And their kinetics

Reaction Reaction rate Unit

(1) mol·m-3·s-1

(2) mol·m-3·s-1

(3) mol·m-3·s-1

.0525014

homogeneous

22

4

3158

109769510838 OH

T.

.

CCe. ⋅⋅××−

24

5

3158

10304911105523 OCH

T.

.

CCe. ⋅⋅××−

2

4

3158

109769

930 OCOT.

.

CCe. ⋅⋅×−

⋅− CC 330000

eqK

(8) mol·m-3·s-1

(9) mol·s-1·g-1ash

09/02/2013 12

−= T

..

eq eK0525014

137133

Sources: C. –Y. Wen, T. –Z. Chaung, Ind. Eng. Chem. Process Des. Dev., 18 (1979) pp. 684-695

K. –F. Cen, H. –J. Ni, Z. –Y. Luo, J. –H. Yan, Y. Chi, M. –X. Fang, X. –T. Li, L. –M. Cheng,

“Theory, design and operation of circulating fluidized bed boilers”,

Beijing: Chinese Electric Power Press, 1998.

⋅⋅

−−

OHeq

HCOCH

T.

CK

CCCe

2

2

4

3

9871

30000

312

( )

−+−

−

⋅

⋅−×

T.T.

P.

*COCO

e

Pxx.

9871

277605553918

25050410545

+−=

⋅=

=

T..

eq

OHeq

HCO*CO

COCO

eK

PPK

PPx

PPx

817234

68933

2

22

Residence time of char

& gasifier diameter (GASIFCAL)

09/02/2013 13

Results

0%

10%

20%

30%

40%

50%

60%

CO H2 CO2 CH4

Dry

ga

s co

mp

osi

tio

n %

vo

l.

Component

SBR=0.5Simulation

Literature

0%

10%

20%

30%

40%

50%

60%

CO H2 CO2 CH4

Dry

ga

s co

mp

osi

tio

n %

vo

l.

SBR=0.7Simulation

Literature

09/02/2013 14

Component Component

0%

10%

20%

30%

40%

50%

60%

CO H2 CO2 CH4

Dry

ga

s co

mp

osi

tio

n %

vo

l.

Component

SBR=1.0Simulation

Literature

ER=0

Tpyrolysis=700 ºC

Tgasification=820 ºC

Results

0%

5%

10%

15%

20%

25%

30%

680 730 780 830

CO

mo

le f

ract

ion

(%

dry

ba

sis)

Tgasification (ºC)

Simulation

Literature

0%

10%

20%

30%

40%

50%

60%

690 710 730 750 770 790 810 830

H2

mo

le f

ract

ion

(%

dry

ba

sis)

Tgasification (ºC)

Simulation

Literature

ER=0

SBR=1

09/02/2013 15

Tgasification (ºC) Tgasification (ºC)

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

690 710 730 750 770 790 810 830

CO

2m

ole

fra

ctio

n (

% d

ry b

asi

s)

Tgasification (ºC)

Simulation

Literature

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

690 710 730 750 770 790 810 830

CH

4m

ole

fra

ctio

n (

% d

ry b

asi

s)

Tgasification (ºC)

Simulation

Literature

Results

20%

30%

40%

50%

60%

Dry

ga

s co

mp

osi

tio

n %

vo

l.

Simulation

Literature

09/02/2013 16

0%

10%

20%

CO H2 CO2 CH4

Dry

ga

s co

mp

osi

tio

n %

vo

l.

Component

Data from: M. Siedlecki, W. De Jong, Biomass Bioenerg. 35 (2011) pp. S40-S62

ER=0.26

SBR=1.4

Tpyrolysis=700 ºC

Tgasification=820 ºC

Conclusions

Devolatilization & pyrolysis yields can be well

estimated by the work of Neves et al.

ASPEN simulation predicts moderately H2 and CH4

content of syngas but fails on CO and CO2.2

The trend of the composition with temperature is

correctly simulated.

09/02/2013 17

Thank you for your attention

Tiago Pinho and Luís Silva

+info:

1030759@isep.ipp.pt

lms@isep.ipp.pt

09/02/2013 18