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1
Algae Under Pressure and in Hot Water – Hydrothermal Pathways to
Renewable Fuels
Phillip E. Savage
University of Michigan Chemical Engineering Dept.
2
Energy Usage Trends
society transitions to new energy sources when it improves life - not because of scarcity
3
Why Liquid Fuels from Biomass?
~ 15 TW ~ 450 quads
courtesy A. Yokochi - Oregon State Univ
Biomass is recently stored solar energy - renewable energy
We need liquid fuels for transportation.
We can grow enough biomass to meet this need.
Biofuels are renewable - live off the sun in real time.
4
Can algae be a better biofuel feedstock?
Major issues with terrestrial crops: Expensive Food/Feed vs. fuel Require lots of land,
water, and fertilizer Less efficient at
photosynthesis Indirect land use
change Chisti Y. Biodiesel from microalgae. Biotechnol Adv 2007;25(3):294-306.
4
Crop Oil Yield (L ha-1 y-1) Soybean 450 Camelina 560 Sunflower 955 Rapeseed 1,190 Jatropha 1,890 Oil Palm 5,950 Microalgae 3,800-50,800
5
Microalgae Aquatic biomass (lots of water) Can have very high oil content
along with protein and polysaccharide No food vs. fuel competition Water provides structural support (no lignin) High biomass growth rates
~ 5000 gal/acre/yr (~ 10X relative to terrestrial biomass)
Can grow in salt water (reduce fresh water needed) Industrial ecology possibilities - co-locate with water treatment and coal-fired power plants
6
Algae need much less land than conventional energy crops!
Land Area to Replace 50% of Petroleum Distillates
Adapted from Bryan, et al. (2008)
7
8
Standard approach is dewatering, drying, lipid extraction (e.g., with hexane), and oil processing to make biodiesel or “green” diesel
$$$$, requires organic solvents, acids, bases
Let’s use a potentially greener approach!
Biofuel from Microalgae
9
Overview Develop biofuel processes that use wet algae paste avoid drying minimal dewatering no lipid extraction
Feedstock flexible high-lipid algae not required useful for other wet biomass
Hydrothermal approach - Use high-temperature liquid water to convert biomass into fuels mimic nature break down biomacromolecules in algae
HydrothermalProcess
wet biomass fuel product
10
Introduction to High-Temperature Water (HTW)
HTW: Liquid H2O at 200 – 350oC (TC = 374oC)
Properties of HTW different from room-temperature water
• Lower dielectric constant
• Fewer and less persistent H-bonds
Increased solubility of organic compounds
• Higher KW = (H+)(OH–) enhanced acid catalysis 0
20
40
60
80
100
0 200 400
T (oC)
Die
lect
ric C
onst
ant
-14
-13
-12
-11
0 100 200 300 400
T (oC)
log
K w0.0001
0.0010
0.0100
0.1000
25 75 125 175 225 275Temperature (oC)
Ben
zene
mol
e fr
acti
on
11
Hydrothermal Routes from Wet Algae to Biofuels
Wet Biomass (algae)
Crude Bio-oil Hydrocarbon Fuel or Oil
Liquefaction Upgrade
Fatty Solids
Crude Biodiesel
Hydrocarbon Fuel Deoxygenation
~ 350 °C
CH4, H2 Processes that work with wet biomass (its natural state) and avoid organic solvents could be less costly, more energy efficient, and more environmentally sustainable.
US Patent: 2012/0079760A1
US Patent: 2012/0055077A1
Savage, Science, 2012
12
http://www.igb.fraunhofer.de/WWW/Presse/Jahr/2000/en/PI_Algae.en.html
OIL
Hydrothermal Liquefaction
(HTL)
Microalgae Growth
aqueous by-product
liquid fuel
CO2
H2O
Hydrothermal Catalytic
Processing
bio-oil components
Recover energy & nutrients in aqueous stream – essential for energy-positive & sustainable process
Microalgae HTL Process
Energy Recovery
Energy Recovery
N, P recycling
13
Hydrothermal Liquefaction of Microalgae
Hydrothermal Liquefaction
wet algal biomass Crude bio-oil
Brown, Duan, Savage, Energy & Fuels, 2010 Valdez, Dickinson, Savage, Energy & Fuels, 2011 Duan, Savage, Ind. Eng. Chem. Res., 2011 Valdez et al., Biomass & Bioenergy, 2012 Valdez & Savage, Algal Research, 2013
14
Experimental Procedure
14
HTL Products
Aqueous Phase
Biocrude (Organic Phase)
Light Biocrude
Heavy Biocrude
Solids
250°C 300°C
350°C
400°C
0
5
10
15
20
25
30
100 200 300 400 500
Pres
sure
(MPa
)
Temperature (°C)
Liquid Water
Water Vapor
15
Elemental Analysis of Bio-Crude
Temp. (°C) C H O N S Dry Algae 43.3 6.0 25.1 6.4 0.53
200 74.6 10.8 11.8 2.4 0.44 300 75.2 10.3 9.8 4.3 0.79 400 76.7 10.3 8.7 3.6 0.91
Crude Oil2 83-87 10-14 0.1-1.5 0.1-2.0 0.5-6.0
• O decreased with temp. • S increased with temp.
2Data from h6p://en.ci9zendium.org/wiki/Petroleum
From Brown, Duan, & Savage., Energy & Fuels. 2010
Nannochloropsis sp.
16
0 15 30 45 60 75 900
10
20
30
40
50 Total Biocrude
yield
(wt %
)
time (min)
Biocrude Yields (wt%) from Isothermal HTL
Valdez et al., Biomass & Bioenergy, 2012
50 – 80% energy recovery in biocrude
17
Total Ion Chromatogram of Bio-Crude O
OH
O
OH
HO O
OH
HN
C16 fatty acids
350 °C, 60 min
18
C & N distributions at 20 min
Light Biocrude
Heavy Biocrude
Water-soluble
Products
Solids Gas
Light Biocrude
Heavy Biocrude Water-
soluble Products
Solids
Light Biocrude
Heavy Biocrude
Water-soluble
Products
Solids Light
Biocrude
Heavy Biocrude
Water-soluble
Products
Solids Gas
Light Biocrude
Heavy Biocrude
Water-soluble
Products
Solids
Light Biocrude
Heavy Biocrude Water-
soluble Products
Solids
C
N
250°C 350°C 400°C
19
0 30 60 900
10
20
30
40
50
60
70
80250ºC
Yie
ld (w
t %)
time (min)
SOLAPPLBCHBCGAS
0 30 60 900
10
20
30
40
50
60
70
80300ºC
Yie
ld (w
t %)
time (min)
SOLAPPLBCHBCGAS
0 30 60 900
10
20
30
40
50
60
70
80350ºC
Yie
ld (w
t %)
time (min)
SOLAPPLBCHBCGAS
0 30 60 900
10
20
30
40
50
60
70
80400ºC
Yie
ld (w
t %)
time (min)
SOLAPPLBCHBCGAS
19
Solids Aqueous-phase Products
Light Biocrude
Heavy Biocrude Gas
P. Valdez, et al., Hydrothermal Liquefaction of Nannochloropsis sp.: Systematic study of process variables and analysis of the product fractions, Biomass and Bioenergy, (2012)
Reaction Network?
Heavy Biocrude
Solids Light Biocrude
1
2
3
Gas
Aqueous-phase Products
20
Reactions of Intermediate Products
4mL Swagelok
Reactor
200mL Induction-heated
Parr Reactor
Light Biocrude
Heavy Biocrude
Solids
Aqueous-phase Products
+ Gas
350°C, 40min 15 wt % slurry
350°C, 10-40min 5 wt % loading
Product Workup
21
Heavy Biocrude
Solids Light Biocrude
1
2
3
6
Gas
Aqueous-phase Products
5
4
Reaction of Aqueous-phase Products • Aqueous-phase produces Light and Heavy Biocrudes and relatively large amounts of CO2 (~3 wt %)
0 10 20 30 400
10
20
30
40
50 Reaction of Solids
yiel
d (w
t %)
time (min)(a)
0 10 20 30 400
20
40
60
80
100
120Reaction of Aqueous�phase Products
yiel
d (w
t %)
time (min)(b)
0 10 20 30 400
20
40
60
80
100 Reaction of Light Biocrude
yiel
d (w
t %)
time (min)(c)
0 10 20 30 400
20
40
60
80
100 Reaction of Heavy Biocrude
yiel
d (w
t %)
time (min)(d)
Solids
Aqueous-phase Products
Light Biocrude Heavy Biocrude
Gas
T = 350°C
Valdez & Savage, Algal Research, under review
22
Heavy Biocrude
Solids Light Biocrude
1
2
3
6
Gas
Aqueous-phase Products
5 8
7 4
Reaction of Light Biocrude • Light Biocrude produces Aqueous-phase and Heavy Biocrude
22
0 10 20 30 400
10
20
30
40
50 Reaction of Solids
yie
ld (
wt
%)
time (min)(a)
0 10 20 30 400
20
40
60
80
100
120Reaction of Aqueous�phase Products
yie
ld (
wt
%)
time (min)(b)
0 10 20 30 400
20
40
60
80
100 Reaction of Light Biocrude
yie
ld (
wt
%)
time (min)(c)
0 10 20 30 400
20
40
60
80
100 Reaction of Heavy Biocrude
yie
ld (
wt
%)
time (min)(d)
Solids
Aqueous-phase Products
Light Biocrude
Heavy Biocrude
Gas
T = 350°C
Valdez & Savage, Algal Research, under review
23
Reaction of Heavy Biocrude • Heavy Biocrude produces Aqueous-phase products, Light Biocrude
and H2, C1, and C2 gases
23
Heavy Biocrude
Solids Light Biocrude
1
2
3
6
Gas
9
Aqueous-phase Products
5 8
11
7 4
10
0 10 20 30 400
20
40
60
80
100 Reaction of Solids
yie
ld (
wt
%)
time (min)(a)
0 10 20 30 400
20
40
60
80
100
120Reaction of Aqueous�phase Products
yie
ld (
wt
%)
time (min)(b)
0 10 20 30 400
20
40
60
80
100 Reaction of Light Biocrude
yie
ld (
wt
%)
time (min)(c)
0 10 20 30 400
20
40
60
80
100 Reaction of Heavy Biocrude
yie
ld (
wt
%)
time (min)(d)
Solids
Aqueous-phase Products
Light Biocrude
Heavy Biocrude
Gas
T = 350°C
Valdez & Savage, Algal Research, under review
24
Building a Kinetics Model
• Write & solve governing equations – xi = mass fraction of each product – 1st order kinetics
• Estimate rate constants by minimizing objective function
• Used MATLAB, Constrained, non-linear multivariable function
24
dxidt
= ν ijk j xij∑
i∑
Objective Function = xiexp. − xi
calc.( )2
i∑
Heavy Biocrude
Solids Light Biocrude
1
2
3
6
Gas
9
Aqueous-phase Products
5 8
11
7 4
10
25
Model & Exptl. Results for HTL
25
0 30 60 900
10
20
30
40
50
60
70
80250ºC
yiel
d (w
t %)
time (min)0 30 60 90
0
10
20
30
40
50
60
70
80300ºC
yiel
d (w
t %)
time (min)
0 30 60 900
10
20
30
40
50
60
70
80350ºC
yiel
d (w
t %)
time (min)0 30 60 90
0
10
20
30
40
50
60
70
80400ºC
yiel
d (w
t %)
time (min)
Solids Aqueous-phase Products
Light Biocrude
Heavy Biocrude
Gas
Aqueous-phase Products
Gas
Aqueous-phase Products
Light Biocrude
Heavy Biocrude
Light Biocrude
Heavy Biocrude
Solids
Aqueous-phase Products
Light Biocrude
Heavy Biocrude
Solids
Gas
Solids
Gas
Solids
26
Model Predictions
26 Valdez & Savage, Algal Research, 2013
300 350 400 450 500 5500
10
20
30
40
50
temperature (ºC)
bioc
rude
yie
ld (w
t %)
Biocrude Yield Prediction
Brown et al.3
Faeth et al.18
Li & Savage19
Biocrude yields from liquefaction of Nannochloropsis sp. at 60 min
Gas yields from hydrotherrmal treatment of Nannochloropsis sp. at 60 min
0 20 40 60 800
15
30
45
60
75
90Guan et al.
gas
yiel
d (w
t %)
time (min)
27
Model Predictions
27 Valdez & Savage, Algal Research, 2013
High temp, short time gives highest biocrude yields Rapidly heat to high temperature “Fast” liquefaction
28
Fast Hydrothermal Liquefaction • Nannochloropsis sp. • 1.5 mL stainless steel batch reactors • Thermocouple dummy reactors • Setpoint temperatures 300-600°C • Reaction times 1, 3, 5 min • Quench in cold water
28
29
Temperature Profile
176 °C
283 °C 297 °C 297 °C
565 °C 593 °C
0
100
200
300
400
500
600
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
Tem
pera
ture
(°C
)
Time (minutes)
300°C Setpoint Temperature
600°C Setpoint Temperature
30
Total Biocrude Yield (wt.%)
13 ± 7
38 ± 0.5 44 ± 1 66 ± 11
14 ± 4 10 ± 3
0
100
200
300
400
500
600
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
Tem
pera
ture
(°C
)
Time (minutes)
300°C Setpoint Temperature
600°C Setpoint Temperature
Uncertainty given is standard deviation
31
Total Biocrude Yields - 1 minute
31
0 10 20 30 40 50 60 70 80
25 300 350 400 450 500 550 600
Bioc
rude
Yiel
d (w
t.% d
.a.f.)
Setpoint Temperature (°C)
Faeth, Valdez & Savage, Energy & Fuels, 2013
32
Reaction Ordinate • Severity index that combines effects of time and
temperature1
32
• Used previously with wood pulping • Numerical integration using experimental temperature
trajectory
1 T. Rogalinski, T. Ingram, and G. Brunner, e Journal of Supercritical Fluids, 2008, 47, 54–63.
33
Total Biocrude Yield with R0
33
0 10 20 30 40 50 60 70 80 90
0 2 4 6 8 10 12 14 16
Bioc
urde
Yiel
d (w
t.% d
.a.f.)
Log(R0)
Fast HTL
Unreacted Algae
Faeth, Valdez & Savage, Energy & Fuels, 2013
34 34
0 10 20 30 40 50 60 70 80 90
0 2 4 6 8 10 12 14 16
Bioc
urde
Yiel
d (w
t.% d
.a.f.)
Log(R0)
Fast HTL Conv HTL
Conv. HTL Data from Valdez et al., Biomass and Bioenergy, 2012
Unreacted Algae
Total Biocrude Yield with R0
35
Biocrude O/C, N/C Ratios
35
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20
0 2 4 6 8 10 12
Atom
ic Ra
tio
Log(R0)
Fast HTL O/C Conv HTL O/C Fast HTL N/C Conv HTL N/C
Algae N/C = 0.145
O/C
N/C
Algae O/C = 0.353
Faeth, Valdez & Savage, Energy & Fuels, 2013
36
Model Compound Approach • Chemical details likely to be obscured starting with algae directly
36
Ester Triglycerides
Proteins
Chlorophyll
Carbohydrates
Amino Acid
Phytol Bio-oil
Algae
Specific How do model compounds react individually and interact with each other in HTW?
Sugars
37
Phenylalanine Ethyl Oleate Protein Lipids
37
38
Phenylalanine Reaction Pathway
38
[Changi et al., ChemSUSChem (2012)]
39
Ethyl Oleate Hydrolysis
• Sigmoidal shape - autocatalysis
• Adding oleic acid increases conversion
• Catalysis by product (oleic acid) confirmed
Moles Oleic Acid Moles Ethyl Oleate
Conversion (240˚C, 30 minutes)
0 0.07 ± 0.03 0.25 0.27 ± 0.07 0.5 0.41 ± 0.05 1 0.61 ± 0.09
[Changi et al., Ind.Eng.Chem.Res. (2011)]
Effect of Added Oleic Acid
39
40
Phenylalanine + Ethyl Oleate
40
41
• Phenylethylamine (primary product) yield decreases with added ester
• Styrene, 2-phenylethanol (2° products) yields increase with added ester
41
Reactions enhanced in presence of ester
Effect of Adding Ethyl Oleate
[Changi et al., ChemSUSChem (2012)]
42
Effect of Adding Phenylalanine • Formation of new products - oleic acid amides, phenylacetaldehyde
42
0
0.005
0.01
0.015
0.02
0.025
0.0 0.2 1.0 5.0
Mol
ar Y
ield
of P
heny
lace
tald
ehyd
e
Ethyl Oleate : Phenylalanine
At 350 °C and 10 min
[Changi et al., ChemSUSChem (2012)]
43
Reaction Network for Binary System
43 [Changi et al., ChemSUSChem (2012)]
44
Reaction Network for Binary System
44
Increased Rates
[Changi et al., ChemSUSChem (2012)]
45
Parity Plot for Binary System
45
46
Insights to Chemistry of Algae Liquefaction
• Oligomerization in amino acid system at high temperatures
– Decreases quality of bio-oil
– Use hydrogenation strategy to prevent oligomers
• Binary mixtures of amino acids and esters form amides
– Decreases yield of fatty acid components in bio-oil
– Adds nitrogen to crude bio-oil
– Rates of individual reactions increase
46
47
Summary • Hydrothermal Liquefaction (HTL) converts wet
biomass into crude bio-oil • Reaction network for HTL of algae established
– Reaction modeling, reactor engineering
• Fast HTL produces biocrude in higher yield and shorter time than conventional HTL – 66 wt.% yield in 1 min.
• Reaction ordinate unifies results from conventional and fast HTL
• Model compounds provide insights into HTL chemistry
48
• Peter Valdez, Julia Faeth, Shujauddin Changi • NSF – EFRI – 0937992 • EPA, NSF Graduate Fellowships • College of Engineering – University of Michigan • Rackham Graduate School – University of Michigan
Acknowledgements
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