SUWIC, Sheffield University

SUPERGEN - WORK PACKAGE 3

MATHEMATICAL MODELLING WORKSHOP

14 Tuesday March 2006

University of Sheffield

Mathematical Modelling of Biomass Pyrolysis and Mathematical Modelling of Biomass Pyrolysis and Mathematical Modelling of Biomass Pyrolysis and Mathematical Modelling of Biomass Pyrolysis and Gasification in LabGasification in LabGasification in LabGasification in Lab----scale Packedscale Packedscale Packedscale Packed----bed Systemsbed Systemsbed Systemsbed Systems

SUWIC SuperGen Research Team: Dr Yao Bin Yang, Dr Changkook Ryu, Dr David Poole, Paul Gilbert, Adela Khor,

Professor VidaProfessor VidaProfessor VidaProfessor Vida SharifiSharifiSharifiSharifi, Professor Jim Professor Jim Professor Jim Professor Jim SwithenbankSwithenbankSwithenbankSwithenbank

Pyrolysis of WoodPyrolysis of WoodPyrolysis of WoodPyrolysis of Wood

Data Logger/ PC

Furnace Controller

Liquid Traps

Condensers

Nitrogen

Pyrolyser

Reactor:

Inner diameter: 12 cm

Height: 32.5cm

Wood Samples:

cubes 20x20mm, 200g

Gas purge: Nitrogen: 2l/min

Heating rate: 10oC/min.

Pyrolysis of Wood

Two types of model used:

two-stage parallel reaction model (Janse et al. [23] and Blasi [24] )

to predict final product yield

Pyrolysis of Wood

FG modelFG modelFG modelFG model to predict product compositionsTable 4. Kinetic parameters and precursor pool size (yields) for main species for wood pellets in the FG model (after Jong et al. [3])

1.2050018,4005.2×10111-CH2O

0.3970021,0302.3×10112-CH3OH

0.4080017,8005.2×10111-CH3OH

0.280025,9302.8×10121-C2H4

3850020,5005.2×10111-tar

0.1210030,7003.1×10121-H2*

0.6210027,7003.1×10123-CH4

0.680022,5006.5×10112-CH4

0.0580019,2006.5×10111-CH4

3.0250026,0004.4×10122-H2O

11.94120019,9005.2×10111-H2O

1.80330035,9302.8×10123-CO

3.05320026,3006.5×10122-CO

1.9050020,3005.2×10111-CO

0.9090024,8302.8×10123-CO2

3.1050020,5005.2×10112-CO2

0.9590018,3005.2×10111-CO2

Yield per

precurs

or pool

wt% (daf)

σ/R (K)E/R (K)A (s-1)

Precursor pool

identifier

per evolved

species

* * * * Assumed in this work

The FurnaceThe FurnaceThe FurnaceThe Furnace

Pyrolysis of Wood

0

100

200

300

400

500

600

700

0 1000 2000 3000 4000 5000 6000

Time, sec

Te

mp

era

ture

, °C

8

10

12

14

16

18

1000 1500 2000 2500 3000 3500

Time, secL

ocal h

eati

ng

rate

, ºC

/min

0.85

0.76

0.61

0.47

0.33

0

0 (measured)

r /r 0 =

0.85

0.76

0.61

0.47

0.33

0

Programmed wall T

Measured T at the centre

Predicted T at the centre

Temperature profile Local heating rate profile

Pyrolysis of Wood

10

20

30

40

50

300 400 500 600 700 800

Final temperature, ºC

Yie

ld, w

t%

Tar

Gas

Char

Comparison between model prediction and experiments for the yields of final products

0

20

40

60

80

100

120

0 1000 2000 3000 4000 5000

Time, sec

M/M

0x100%

TGA

test

Packed-bed

pyrolyser

(predicted)

Pyrolysis of Wood

Packed-bed compared to TGA test

Pyrolysis of Wood

-2

0

2

4

6

8

10

12

14

16

18

100 200 300 400 500 600 700

Temperature, ºC

Ga

s c

om

po

sit

ion

, v

ol %

CO2

CO

CH4

H2

C2H4

CO2 CO

CH4

H2

C2H4

Wood

0

2

4

6

8

10

12

14

16

1000 2000 3000 4000 5000

Time, secG

as c

om

po

sit

ion

, vo

l %

-10

0

10

20

30

40

50

1000 1500 2000 2500 3000 3500 4000 4500 5000

Temperature, ºC

CO2

CO

CH4

H2

C2H6C2H4

70 160 250 340 430 520 610 700 700

FG model FG model FG model FG model MeasurementMeasurementMeasurementMeasurement

Gas compositionsGas compositionsGas compositionsGas compositions

Pyrolysis of Wood

Some preliminary conclusions from the pyrolysis modelling

�Secondary reactions (tar cracking) becomes important for real (large-scale) system, different from TGA data; Modelling experiences with different biomass or its derived fuels show different tar cracking abilities, suspected to related to mineral content in the fuel.

�FG model requires refining and improvements, especially the ability to predict the final product yields. FG-biomass model newly developed at Advanced Fuel Research, USA, will be tested and assessed.

�Thanks Miss N Anh Phan for carrying out the wood pyrolysis tests

Conceptual Modelling Study on Conceptual Modelling Study on Conceptual Modelling Study on Conceptual Modelling Study on Pyrolysis Tube with Emphasis on Pyrolysis Tube with Emphasis on Pyrolysis Tube with Emphasis on Pyrolysis Tube with Emphasis on

Tar CrackingTar CrackingTar CrackingTar Cracking

Pyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar Cracking

Nitrogen

Biomass feed

GasesTar

Char

Heated wall 500∘C - 800∘C

Pyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingThe ModelThe ModelThe ModelThe Model

BiomassBiomassBiomassBiomass

GasesGasesGasesGases

TarTarTarTar

CharCharCharChar

GasesGasesGasesGases

CharCharCharChar

kkkk1111

kkkk2222

kkkk3333

kkkk4444

kkkk5555

KKKKiiii =A=A=A=Aiiii exp(exp(exp(exp(----EEEEiiii/RT) (i=1,2,3,4,5)/RT) (i=1,2,3,4,5)/RT) (i=1,2,3,4,5)/RT) (i=1,2,3,4,5)

Pyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar Cracking

0

20

40

60

80

100

120

140

160

180

200

0 100 200 300 400 500 600 700

Tube length, mm

mass %

-200

0

200

400

600

800

1000

Tem

pera

ture

, K

Solid TGas T

Fixed carbon

Volatile matterMoisture

Hot char layer

Wall at 700oC

Pyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar Cracking

0

10

20

30

40

50

0 100 200 300 400 500 600 700

Tube length, mm

Vo

l %

CO

CO2

H2O

Wall at 700oC

Tar

CH4

H2

Pyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar CrackingPyrolysis Tube & Tar Cracking

0.4% (4000ppm) 7.1%800oC

1.07%18.0%700oC

15.8%25.7%600oC

33.5%36.4%500oC

Tube Length

800mm

Tube-length

500mm

Wall Temperature

Tar concentration (Tar concentration (Tar concentration (Tar concentration (volvolvolvol%)%)%)%)at tube exitat tube exitat tube exitat tube exit

Pyrolysis and Gasification

�Hot char layer can reduce tar significantly in the pyrolysis process;

�Further cracking of tar can be achieved by steam gasification, to 1/8 of that from pyrolysis with nitrogen;

�Problem with tube steam gasification – char gasification rate is too low

to match the pyrolysis rate and an additional/separate char gasifierreactor is required.

SubSubSubSub----ConclusionsConclusionsConclusionsConclusions

THANKS