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Amber Broch, S. Kent Hoekman, Curt Robbins DesertResearch Institute
Chuck Coronella Univ. of Nevada, Reno
Larry Felix, Wei Yan Gas Technology Institute
Pacific West Biomass Conference
January 16-18, 2012
San Francisco, CA
Renewable Solid Fuels via HydrothermalCarbonization HTC) of Cellulosic Biomass
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Background and Introduction Lignocellulosic biomass is a promising feedstock for
production of heat, chemicals, fuels, and electrical power
Diverse biomass sources:o Woods, agricultural wastes, grasses, other
Large diversity of biomass sizes, shapes, compositions, and
other parameters creates difficulty in:o Handling, transporting, and storing different materials
o Feeding different materials into a single thermal conversionunit
2
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Purpose of Biomass Pre-Treatment
Three main objectives1. Homogenize feedstocks
o Reduce handling difficulties
o Convert multiple materials into a single feedstock
2. Increase energy densityo Reduce the oxygen content of raw biomass
o Higher energy density reduces transportation andhandling costs
3. Improve storage stability logisticso Address seasonality of some feedstocks
o Improve suitability for co-firing with coal
Overall goal:
Convert biomass into a solid biochar that resembles low-grade coal3
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Biomass Thermal Pre-Treatment
Processes
Two processes are of particular interest
1. Torrefaction
Mild form of pyrolysis
Dry conditions, low O2 levels
Produces gases and solid char
2. Hydrothermal Carbonization (HTC)
Also known as wet torrefaction,
hydrothermal pretreament (HTP), hot
pressurized water (HPW) treatment, and
others.
Produces gases, liquids, and solid char
Pressure
Vessel
155-295oC
Solid
Biomass
H2O
Recovered
Solid
(Bio-char)
Condensed
Liquid
Non-
condensable
gases
To gasifier/ pyrolyzer
For energy/ fuels
HTC Process
4
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HTC Laboratory Set-Up 2-Liter Stirred Parr Pressure Vessel
Parr
Reactor
Motor
Ice Bath
He
Tedlar
Bag
Dilute
Gases
Mass Flow
Meter
Mass Flow
Controller
T
T
P
T
Relative Humidity
Instrument
1. Biomass & H2O
are heated to
temperature and
held for set time
2. Bomb is cooled
in an ice bath
3. Gases are collected in a Tedlar bag by
sparging Helium through the reactor
E-11
Solid
Liquid
4. Reactor is opened and
contents are weighed,
rinsed and separated
by vacuum filtration
He (purging & diluting)
Heated Pretreated gas
Products
Gases Liquids HTC Char
5
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HTC Feedstocks and Lab Processes
Treatment of Different Feedstocks:o Woody Feedstocks:
Loblolly Pine
Tahoe Mix (White Fir/ Jeffery Pine)
Pinyon/ Juniper
o Herbaceous Feedstocks: Rice Hulls
Corn Stover
Sugar Cane Bagasse
Process Conditions:
o Temperature: 155-295C
o Hold Time at Temperature: 5 - 60 min
o Water/ Biomass Ratio: 4 - 15
o Feedstock Size: ~ in.
Raw Loblolly
255 C for 30
min
215C for 30
min
175 C for 30
min
6
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Laboratory Analyses of Products
MeasurementsGases
Volume (flow
measurements)
Composition - GC
Liquids
Total Organic Carbon
Organic Acids (IC)
Carbohydrates (HPLC)
Non-volatile mass
pH
Solids and Feedstocks C,H,N,S,O
Energy Content(calorimetry)
Moisture Content Acetone Extractables
Volatiles, Fixed Carbon,Ash
Mass Balance
Carbon Balance
Energy Densification
Pelletization Characteristics
7
Determination
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Method Development
GC Method for Gaseous Products
8
2 column method provides identification of H2, CO, CO2,CH4, Ethane, Ethene, Acetylene, Propene.
The dominant gaseous product is CO2, with a small amount
and CO. Typically, no other identified species are measured
GC Conditions:Column 1:
6-ft. x 1/8 in. Molecular Sieve 13X
90C isothermal
Column 2:
6-ft. x 1/8 in. Silica Gel 40 C isothermal for 9 min.; then
increase 15C/min to 200C (5-min.
hold)
Sample loop: 1.0 mL
Carrier gas: He (11.0 mL/min.)
Detector: TCD 105 15 20
H2
COCH4
Ethane
CO2
Ethene
Acetylene
Propene
O2
N2
CO
CO2
HTC of Loblolly Pine @ 255
Calibration Gas Mixture
Retention Time, min.
0
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Method Development-
HPLC Method for Water Soluble Products
9
Developed to quantify 5-HMF and Furfural in liquids
Simultaneous detection with other sugars
Suc
rose-Trehalose
Glucose-Pinitol
G
alactose,Xylose,Mannose
Fr
uctose,Inositol,Arabinose
Le
voglucosan F
urfural
Erythritol
Mann
itol,Glycerol
Arabitol
HPLC Chromatogram of HTC Liquid from Loblolly Pine at 255C.
HPLC Conditions: Waters Alliance 2695 with
Waters 2414 Refractive Index
(RI) detector
Waters Sugar-Pak TM column
(6.5 x 300 mm)
Isocratic elution with water at
0.4 mL/min Column temp: 60C
Detector temp: 50C
Other methods described in
Hoekman, S.K., A. Broch, and C. Robbins, 2011: Hydrothermal Carbonization (HTC) of
Lignocellulosic Biomass. Energy Fuels, 25 (4), pp 18021810
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Effect of Temperature on Mass Recovery
10
Percentageofstartingdryfeedstock
Tahoe Mix Loblolly Pine Pinyon/ Juiper
Corn Stover Rice Hulls Sugar Cane Bagasse
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
'215* 235 255 275
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
215 235 255 275
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
215 235 255 275
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
215 235 255 275
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
215 235 255 275
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
215 235 255 275
Set Temperature of Reaction
Solid CharH2O Solubles(non-volatiles, acetic and
formic acids, 5-HMF and
furfural)
Gases
Balance is primarily water
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Effect of Temperature on Energy
Content of HTC-Char
11
Energy content of HTC char increases above temperatures around 200C
Feedstock
Replicate experiments
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Effect of Temperature on Atomic O/C
Ratio of HTC Char
12HTC treatment of both woods and grasses results in similar Atomic O/C ratios above temperatures
around 250 C
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Effect of Temperature on Sugar Recovery
13
Maximum sugar recovery in the liquids occurs around 215-235C
Sugar composition changes after ~200C
Percentageofstartin
gdryfeedstock
Set Temperature of Reaction
Percentageofstart
ingdryfeedstock
Tahoe Mix Loblolly Pinyon/ Juniper
Corn Stover Rice Hulls Sugarcane Bagasse
0%
1%
2%
3%
4%
5%
6%
7%
8%
9%
175 215 235 255 275
0%
1%
2%
3%
4%
5%
6%
7%
8%
9%
175 215 235 255 275
0%
1%
2%
3%
4%
5%
6%
7%
8%
9%
175 215 235 255 275
0%
1%
2%
3%
4%
5%
6%
7%
8%
9%
175 215 235 255 275
0%
1%
2%
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5%
6%
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8%
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175 215 235 255 275
0%
1%
2%
3%
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5%
6%
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8%
9%
175 215 235 255 275
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Effect of Temperature on Organic Acids
14
Percentageofstart
ingdryfeedstock
Set Temperature of Reaction
Tahoe Mix Loblolly Pinyon/ Juniper
Corn Stover Rice Hulls Sugarcane Bagasse
0%
2%
4%
6%
8%
10%
12%
215 235 255 2750%
2%
4%
6%
8%
10%
12%
215 235 255 2750%
2%
4%
6%
8%
10%
12%
215 235 255 275
0%
2%
4%
6%
8%
10%
12%
215 235 255 275
0%
2%
4%
6%
8%
10%
12%
215 235 255 275
0%
2%
4%
6%
8%
10%
12%
215 235 255 275
Recovery of organic acids in the liquid increases with increasing reaction temperature
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Pelletization of HTC Char
15
Pelletization helps improve storage,transportation and handling of biomassfeedstocks.
Compare pelletization behavior of rawbiomass, torrefied biomass and HTC Char
Pellet Production:o 15 MT hydraulic press with heated die (set
at 7.5 MT and 140C)
o 13 mm diameter with L/D ratio of 0.6 to0.75.
o 30 second hold time
Pellet Characterization Testso Fuel value
o Abrasion
o Hydrophobicity
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Pellet Behavior Comparison
Pellet Density Hydrophobicity
16
Mass and energy density of
HTC-char pellets increase with
increasing treatment
temperature. HTC-Char has higher mass and
energy density than raw
feedstock or torrefied char.
Pellets are immersed in water.
Raw feedstock pellet begins todisintegrate immediately.
Torrefied pellet crumbles afterremoval from water
HTC-Char pellet maintainsintegrity for weeks.
Raw Feedstock HTC Char Torrefied
Time: 0 min (no water)
Time: 1 min in water
Time: 2 hrs, removed from water
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Conclusion
17
HTC process is an effective way to increase the value of biomassfeedstocks
o Energy density of many feedstocks increased by ~ 40%
o Can be applied to wide variety of biomass types
Two-Step pre-treatment process could be of greater value:
o Low temp (~200oC) for maximum sugar recovery
o High temp (~250-275oC) for maximum biochar energy
Pelletization further enhances the value of HTC-char
o Easily forms stable pellets having very high energy density
Ancillary benefits being investigated:
o Co-firing with coal looks attractive
o Use of biochar for soils improvement and carbon sequestration
o Possible uses of water-soluble products
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Acknowledgements
18
o DOE funding sources DE-FG36-01GO11082
EE-0000272
o Keri Noack- Laboratory Work
o Stephanie Salke, Anna Cunningham- Laboratory Analyses
o Hoekman, S.K., Broch, A., Robbins, C., 2011. Hydrothermal Carbonization (HTC) of
Lignocellulosic Biomass. Energy & Fuels 25, 1802-1810.
o Acharjee, T.C., Coronella, C.J., Vsquez, V.R., 2011. Effect of Thermal Pretreatment on
Equilibrium Moisture Content of Lignocellulosic Biomass. Bioresource Technology102,
4849-4854.
o Yan, W., Hastings, J.T., Acharjee, T.C., Coronella, C.J., Vsquez, V.R., 2010. Mass and
Energy Balances of Wet Torrefaction of Lignocellulosic Biomass. Energy & Fuels 24, 4738-
4742.
o Yan, W., Acharjee, T.C., Coronella, C.J., Vsquez, V.R., 2009. Thermal Pretreatment of
Lignocellulosic Biomass. Environmental Progress & Sustainable Energy28 (3), 435-440.
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