gasification of woody biomass at the pilot-scale...overview of usda-forest service gasification...

Gasification of Woody Biomass at the Pilot-Scale

Thomas ElderLeslie H. Groom

USDA-Forest ServiceSouthern Research Station

Gasifier work

• 25 kW downdraft gasifierwas acquired from Community Power Corporation

• Located at the Winn District Ranger Station on the Kistachie National Forest

• July 2008-Delivery

• October 2008-Comissioning

Frontiers in Biorefining, St. Simons Island, October 22, 2010

Cooperative Projects

• The system is an integrated– Gasifier

– Spark ignited engine

– Electrical generator rated at 25 kW

• National Forest System – Functional Energy

• Southern Research Station – Feedstock Effect

• Forest Health Protection – Demonstration Projects

• Unique location


Overview of USDA-Forest Service Gasification Project

• Located at Winn Ranger District Office



• Feedstock (to date) has been southern pine and mixed hardwood chips

• Chips are loaded into two drying bins that hold ~500 pounds of dry chips each



• The chips are sorted to size

• An auger transports the chips into the gasifier



• The reaction is initiated with a resistance heater

• The gasifier is open to the atmosphere

• It has several heated zones with temperatures in the range of 600-900°C

• At these temperatures, and in an oxygen starved environment, the wood is converted into producer gas


Gasifier dimensions and zones




• Grate at the bottom of the gasifier


• The gas is exits the gasifier at ~ 500°C and is cooled in a tube and shell heat exchanger to ~110°C

• The heat exchanger requires periodic maintainence



• Next the gas is filtered to remove particulates



• The composition is monitored in real-time with an infrared gas analyzer

– O2

– CO

– CO2

– CH4

– H2



• The cleaned and cooled gas goes to a conventional, spark-ignited, internal combustion engine

• The engine runs only on the producer gas

• This powers a generator capable of producing 25kW of electricity



• The electricity generated is adequate to power the Winn Ranger District Office building, with the excess returned to the utility grid.


Control Panel (one of them,anyway)


Initial Research Runs

• Feedstock– Pine chips (MC ~12%)– Mixed hardwood chips (~50% oak, 25% elm, hickory, 25% sweetgum, maple, beech) (MC~13%)

• Flowrate– 70 scmh (heat exchanger issues)– 62 scmh– 55 scmh– 40 scmh (char, pressure issues)

• Typical run– ~5 hours total– ~1 hour from cold start to operating temperatures– ~ 1 hour at operating temperature to stabilize– Report data for last 3 hours of the run

• Results– Temperature profiles– Gas composition/efficiency


Wood consumption

• Hourly consumption increases with gas flow rate

• Hardwood consumption is higher than pine


15

17

19

21

23

25

27

29

31

33

40 50 60 70

Kgh

-1

Flow rate (Nm3h-1)

feedstock consumption

pine

hardwood

Results-temperature profiles

0

100

200

300

400

500

600

700

800

900

1000

0 1 2 3 4 5 6

tem

pe

ratu

re (

°C)

run time (hours)

Hardwoods 40 scmh

level 1

level 2

level 3

level 4

level 5

grate


Results-gas composition

0

5

10

15

20

25

0 1 2 3 4 5 6

gas

com

po

siti

on

(%

)

run time (hours)

hardwoods 40 scmh

CO

CO2

"CH4"

H2


Results: Flow rate/feedstockTemperatures at Level 1

300

350

400

450

500

550

600

650

700

40 45 50 55 60 65 70

°C

flow rate (Nm3h-1)

level 1

pine

hardwood



720

740

760

780

800

820

840

860

40 45 50 55 60 65 70

°C

Flow rate (Nm3h-1)

level 2

pine

hardwood



820

830

840

850

860

870

880

890

900

910

920

40 45 50 55 60 65 70

°C

flow rate(Nm3h-1)

level 3

pine

hardwood



820

830

840

850

860

870

880

890

900

910

40 45 50 55 60 65 70

°C

Flow rate (Nm3h-1)

level 4

pine

hardwood



835

840

845

850

855

860

865

870

875

880

885

40 45 50 55 60 65 70

°C

Flow rate (Nm3h-1)

level 5

pine

hardwood


Results: Flow rate/feedstockTemperatures at grate

600

620

640

660

680

700

720

740

40 45 50 55 60 65 70

°C

Flow rate (Nm3h-1)

grate

pine

harwood


Results-Temperatures

• Temperatures for hardwoods are generally lower than for softwoods

• Temperature may increase slightly with flow rate



19

19.5

20

20.5

21

21.5

22

22.5

23

0 1 2 3

CO

%

time (hours)

pine

hardwoods

10.5

11

11.5

12

12.5

13

13.5

14

0 1 2 3

CO

2 %

time (hours)

pine

hardwoods

2.5

3

3.5

4

4.5

5

5.5

6

0 1 2 3

CH

4%

time (hours)

pine

hardwoods

17.5

18

18.5

19

19.5

20

20.5

0 1 2 3

H2

%

time (hours)

pine

hardwoods

Results: Flow rate/feedstockCO %

20

20.2

20.4

20.6

20.8

21

21.2

21.4

40 45 50 55 60 65 70

% v

/v

Flow rate (Nm3h-1)

CO

pine

hardwood


Results: Flow rate/feedstockCO2 %

11.6

11.8

12

12.2

12.4

12.6

12.8

13

13.2

40 45 50 55 60 65 70

% v

/v

Flow rate (Nm3h-1)

CO2

pine

hardwood


Results: Flow rate/feedstockCH4 %

3

3.2

3.4

3.6

3.8

4

4.2

40 45 50 55 60 65 70

% v

/v

Flow rate (Nm3h-1)

CH4

pine

hardwood


Results: Flow rate/feedstockH2 %


18.4

18.5

18.6

18.7

18.8

18.9

19

19.1

19.2

19.3

19.4

40 45 50 55 60 65 70

% v

/v

Flow rate (Nm3h-1)

H2

pine

hardwood

Energy content

5.75

5.8

5.85

5.9

5.95

6

6.05

6.1

40 45 50 55 60 65 70

MJm

-3

Flow rate (Nm3h-1)

Energy content

pine

hardwood


Efficiency

0.68

0.69

0.7

0.71

0.72

0.73

0.74

0.75

0.76

0.77

40 45 50 55 60 65 70

Flow rate (Nm3h-1)

efficiency

pine

hardwood


Gas composition and quality

• Composition varies over a fairly small range• Hardwoods generally produce less CO, more CO2

and H2

• H2 inversely related to temperature at level 5• “Methane” decreases with flow rate for

softwoods, levels off for hardwoods• Gas quality (as measured by heat of combustion)

– Decreases with flow rate for softwoods, levels off for hardwoods

• Efficiency increases with flow rate


Next Studies-Feedstocks

• FACE sites

– Chips from Rhinelander have begun to arrive

• Impact of silviculture

– SRS-University of Arkansas-Monticello

• High Extractive Slash Pine


CO

55 SCMH

feedstock

pine hardwoods poplar clean pine whole tree pine

% C

O

16

18

20

22

24

26

CO2

55 SCMH

feedstock


% C

O2

8

9

10

11

12

13

14

CH4

55 SCMH

feedstock


% C

H4

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

H2

55 SCMH

feedstock


% H

2

15

16

17

18

19

20

Next Studies-Processes

• GTL

– FT(?)

– Mixed alcohols?

– DME

• CHP


gasification of woody biomass at the pilot-scale...overview of usda-forest service gasification...

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