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Transcript of A Comparison of Batch, Stop- Flow-Stop, and Flowthrough Pretreatments of Corn Stover Chaogang Liu,...
A Comparison of Batch, Stop-Flow-Stop, and Flowthrough Pretreatments of Corn Stover
Chaogang Liu, Charles E. WymanThayer School of Engineering
Dartmouth CollegeHanover, New Hampshire 03755
2003 AIChE Annual Meeting San Francisco, CA November 20, 2003
Biomass Refining CAFI
USDA IFAFS Project Overview
• Multi-institutional effort funded by USDA Initiative for Future Agriculture and Food Systems (IFAFS) Program to develop comparative information on cellulosic biomass pretreatment by leading options with common source of cellulosic biomass– Aqueous ammonia recycle pretreatment - YY Lee, Auburn
University– Water only and dilute acid hydrolysis by co-current and
flowthrough systems - Charles Wyman, Dartmouth College– Ammonia fiber explosion - Bruce Dale, Michigan State University– Controlled pH pretreatment - Mike Ladisch, Purdue University– Lime pretreatment - Mark Holtzapple, Texas A&M University– Logistical support and economic analysis - Rick Elander/Tim
Eggeman, NREL
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Flowthrough (FT) Pretreatment• Based on early work by Bobleter, Antal• Flows just hot water or very dilute acid solution
through stationary biomass• Removes large fraction of hemicellulose and lignin • Separates sugars from reactor, reducing time for
decomposition • Achieves high cellulose digestibility• Uses less chemicals than co-current process• Provides a less corrosive environment • However, high amounts of water are needed,
increasing energy for pretreatment and recovery
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How are FT and Batch Different?
Batch FT
Xylose yield <~90% ~100%
Lignin removal <10% >50%
Digestion yield <~90% ~100% (by SSF) Digestion time 7 days ~2 days (by SSF)
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Questions
• Why is FT so much different from batch?
• How can FT configuration make this difference?
• Can we combine the favorable features of FT and batch?
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Objectives of This Study
• Evaluate effects of flow rate, temperature, and acid concentration on solubilization of hemicellulose and lignin in a flowthrough reactor
• Particularly focus on developing detailed time profiles of the fate of major biomass components and closing material balances
• Seek to understand mechanism responsible for much different behavior of batch and FT to develop advanced systems that can combine the best features of each while overcoming their limitations
• Evaluate the behavior of a novel approach called stop-flow-stop (SFS) and compare its performance with that for batch and FT
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Corn Stover Composition• NREL supplied corn stover to all project participants
(source: BioMass AgriProducts, Harlan IA)• Stover washed and dried in small commercial operation,
knife milled to pass ¼ inch round screen
Glucan 36.1 %
Xylan 21.4 %
Arabinan 3.5 %
Mannan 1.8 %
Galactan 2.5 %
Lignin 17.2 %
Protein 4.0 %
Acetyl 3.2 %
Ash 7.1 %
Uronic Acid 3.6 %
Non-structural Sugars 1.2 %
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Schematic of FT System
Back Regulator
Sand Bath
Valve-1
P
Cold WaterR
eact
or
T1
HPLC
Pump
Wateror
DiluteAcid
TC
Valve-2
Sample
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Flowthrough Reactors
Gasket filters ( Average pore size, 5 μm )
Internal volume : 37.8 mL
Biomass loading: ~6.5 g
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Internal volume : 3.8 mL
Biomass loading: ~0.5 g
Small reactor Big reactor
Effect of Flow Rate and Temperature on Residual Xylose for Compressed Water
1
10
100
0 8 16 24 32 40 48 56 64
Time, minutes
% o
f p
ote
nti
al x
ylo
se
180C,0mL/min
180C,1mL/min
180C,10mL/min
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Effect of Flow Rate and Temperature on Residual Xylose for Compressed Water
1
10
100
0 8 16 24 32 40 48 56 64
Time, minutes
% o
f p
ote
nti
al x
ylo
se
180C,0mL/min
180C,1mL/min
180C,10mL/min
200C,0mL/min
200C,1mL/min
200C,10mL/min
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Effect of Flow Rate and Temperature on Residual Xylose for Compressed Water
1
10
100
0 8 16 24 32 40 48 56 64
Time, minutes
% o
f p
ote
nti
al x
ylo
se
180C,0mL/min180C,1mL/min180C,10mL/min200C,0mL/min200C,1mL/min200C,10mL/min220C,0mL/min220C,1mL/min220C,10mL/min
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Total Xylose Yield for 0.05wt% Sulfuric Acid Pretreatment at 180oC
0
20
40
60
80
100
0 4 8 12 16Time, minutes
% o
f po
ten
tial t
ota
l xyl
ose
0 mL/min
1 mL/min10 mL/min
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Change in Lignin Removal with Flow Rate for Water Only and Very Dilute
Acid at 180oC after 16 minutes
0
10
20
30
40
50
60
flow rate,0mL/min
flow rate,1mL/min
flow rate,10mL/min
% o
f o
rig
inal
Kla
son
lig
nin
hot water only
0.05wt% sulfuric acid
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Solubilized Xylan Vs Lignin Removal for Compressed Water Pretreatment
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80
Lignin removal (% of the original Klason lignin)
So
lub
ilize
d x
ylan
(%
of
po
ten
tial
xyl
ose
)
180C, 0mL/min
180C, 10mL/min
200C, 0mL/min
200C, 10mL/min
220C, 0mL/min
220C, 10mL/min
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Possible Pathway for Hemicellulose Hydrolysis
H OL O’L OS M D
H: Hemicellulose
OL : Undissolved long-chain oligomers
O’L: Dissolved long-chain oligomers
OS : Dissolved short-chain oligomers
M : Monomers
D : Degradation products
Mass transfer control
Reaction control
Reaction control
Reaction control
Reaction control
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Reaction control
Mass Balance for FT Pretreatment with Compressed Hot Water at 15 FPU
FL reactorTreatedSolids
Hydrolysis
Enzyme @15FPU/g of glucan, 72h
Water
Corn Stover
ResidualSolids
Hydrolyzate
Fermentation
43.4 lb34.3 lb glucan
0.4 lb xylan
100 lb(dry basis)
36.1 lb glucan21.4 lb xylan
36.7 lb glucose0.31 lb xylose
4.45 gal ethanol
7.2 lbDissolved mass
96.5% glucan to glucose, 68.2% xylan to xylose at 15 FPU/ g of glucan97% overall glucan and xylan conversion92% theoretical ethanol yield from glucose + xylose96.3% overall mass balance closure (total dissolved mass+residual solids + G + X)
52.1 lb22.2 lb xylose oligomers1.2 1b xylose monomer
2.1 lb glucose
1.81 gal ethanol
2.64 gal ethanol
Mass Balance For FT Pretreatment with Very Dilute Acid at 15 FPU
FL reactorTreatedSolids
Hydrolysis
Enzyme@15FPU/g of glucan, 72h
0.05wt %wt H2SO4
Corn Stover
ResidualSolids
Hydrolyzate
Fermentation
46.6 lb33.2 lb glucan0.43 lb xylan
100 lb(dry basis)
36.1 lb glucan21.4 lb xylan
36.1 lb glucose0.39 lb xylose
13.4 lbDissolved mass
4.50 gal ethanol
97.8% glucan to glucose, 80% xylan to xylose at 15FPU/g of glucan97.5% overall glucan and xylan conversion92% theoretical ethanol yield from glucose + xylose 98.1% overall mass balance closure (total dissolved mass+residual solids + G + X)
48.2 lb21.5 lb xylose oligomers1.5 Ib xylose monomer
3.2 lb glucose
1.91 gal ethanol
2.59 gal ethanol
Liquid Fraction Concentrations Over 4 Minute Intervals for FT with
Compressed Water at 200oC
0
5
10
15
20
25
30
35
0 1 2 3 4 5 6Fraction numbers
Co
nce
ntr
atio
n,
g/L
overall sugars
other substances
total dissolved mass
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Sugar Concentrations in Liquid Fraction Over 4 Minute Intervals for FT Pretreatment with
0.05wt% Acid at 190oC
0
5
10
15
20
25
30
0 1 2 3 4 5 6
Fractions
Xyl
ose
co
nc,
g/L monomeric xylose
xylose oligomers
total xylose
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Stop-Flow-Stop (SFS) Test Modes
0
10
0 4 8 12 16 20 24
Time, minutes
Flo
w r
ate
, m
L/m
in
SFS 1
0
10
0 4 8 12 16 20 24
Time, minutes
Flo
w r
ate
, m
L/m
in
SFS 2
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Total Xylose Fate for Batch, FT, and SFS Runs with Water at 200oC
0102030405060708090
100
Batch
, 20m
inute
s
Batch
, 24 m
inute
s
FT, 24m
inute
s
SFS1, 24
min
utes
SFS2, 24
min
utes
%, o
f or
igin
al t
otal
xyl
ose
residual xylose in solids
total xylose in hydrolyzate
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Residual Xylan for Batch, FT, and SFS Runs with 0.05wt% Acid at 180oC
0
20
40
60
80
100
0 4 8 12 16Time, minutes
% o
f o
rig
inal
to
tal x
ylan
batchFT, 10 mL/minSFS1SFS2
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Concentration of Xylose in Hydrolyzate for Pretreatment with Compressed Hot Water at 200oC
02468
10121416
batch
, 20 m
inutes
batch
, 24 m
inutes
FT, 24 m
inutes
SFS1, 24
min
utes
SFS2, 24
min
utes
Con
cent
rati
on, g
/L monomeroligomers
Note: 60, 50, and 40mL of wash water were used for batch, SFS1, and SFS2, respectively.
Hydrolyzate Sugar Concentration for Pretreatment of Corn Stover with
Hot Water at 200oC
Modes
Hydrolyzate
Volume
mL
Xylose monomer
g/L
Xylose
Oligomers
g/L
Total
Xylose
g/L
Total xylose
Yield
%
Batch,
20 minutes
60 0.6 10.7 11.3 46.6
Batch,
24 minutes
60 0.1 2.8 2.9 12.1
FT, 10 mL/min 240 0.4 5.4 5.8 96.2
SFS 1 90 1.2 12.3 13.5 83.5
SFS 2 120 0.8 10.0 10.8 88.6
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Note: 60, 50, and 40mL of wash water were used for batch, SFS1, and SFS2, respectively.
Lignin Removal for Batch, FT, and SFS Runs with Water at 200oC
010203040506070
Batch
, 20 m
inutes
Batch
, 24 m
inutes
FT, 24 m
inute
s
SFS1, 24
min
utes
SFS2, 24
min
utes
% o
f or
igin
al K
laso
n l
ign
in
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Lignin Removal for Batch, FT, and SFS Runs with 0.05wt% Acid
at 180oC after 16 minutes
0
10
20
30
40
50
60
Batch FT SFS1 SFS2
% o
f or
igin
al K
laso
n li
gnin
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Cellulose Digestibility for Batch, FT, and SFS Pretreatment (15 FPU/ gram cellulose, 72 h)
7880828486889092949698
%
of
theo
reti
cal
yie
ld
Water, 200oC 0.05wt% acid, 190oC
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Comparison of Batch, FT, and SFS with Hot Water at 200oC
Total xylose
yield, %
Total xylose
conc, g/ L
Lignin removal,
%
Cellulose digestibility
, %
Batch ~ 46 ~ 11 ~ 10 ~ 85
FT ~ 96 ~ 6 ~ 55 ~ 95
SFS 83~ 88 10 - 13 40 - 45 88 ~ 90
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Summary• Flow rate acts somewhat like temperature and acid in effect on
solubilization of hemicellulose and lignin• Increase in xylan removal with flow rate is inconsistent with
traditional first order kinetic models, suggesting that other factors like mass transfer may also play an important role in hemicellulose hydrolysis, especially in the early reaction times
• Compared with batch, FT can significantly increase the yields of hemicellulose sugars, lignin removal, and cellulose digestibility, but the hydrolyzate is very dilute
• SFS can significantly reduce the amount of water consumption while realizing good hemicellulose sugar yields and cellulose digestibility
• In the future, we will optimize the SFS operation and investigate mechanisms responsible for the better performance of FT and SFS so that we can develop a more effective process.
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Acknowledgments
The United States Department of Agriculture Initiative for Future Agricultural and Food Systems Program through Contract 00-52104-9663 for funding our research
The United States Department of Energy Office of the Biomass Program and the National Renewable Energy Laboratory
Our partners from Auburn, Michigan State, Purdue, and Texas A&M Universities and the National Renewable Energy Laboratory
The National Institute of Standards and Technology through award 60NANB1D0064 for funds for some equipment used
The Thayer School of Engineering at Dartmouth College
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Questions?
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