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ORNL is managed by UT-Battelle
for the US Department of Energy
Materials Selection
For Biomass
Thermochemical
Liquefaction (And
Gasification)
James Keiser, Michael Brady,
Samuel Lewis, Sr, Raynella
Connatser and Donovan Leonard
Oak Ridge National Laboratory
Oak Ridge, Tennessee
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Outline
• Background on Oak Ridge National
Laboratory (ORNL)
• Description of biomass thermochemical
processing methods
• Characterization and laboratory corrosion
studies of bio-oils
• Examination of components exposed in
biomass liquefaction systems
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Oak Ridge National Laboratory Opened During The Manhattan Project
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ORNL Is The Department Of Energy’s Largest Science And Energy Laboratory
$1.65B budget
World’s most intense
neutronsource
4,400employees
World-class research reactor
3,000researchguests annually
$500M modernization
investment
Nation’s largest
materials research portfolio
Most powerful open
scientific computing
facility
Nation’s most diverse
energy portfolio
Managing billion-dollar U.S. ITER
project
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Background On Thermochemical Processing Of Biomass
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Biomass Thermochemical Processing Methods Can Create Corrosive Environments
Current corrosion studies at ORNL are concentrated on the interaction of structural materials with bio-
oils from biomass liquefaction
Process Temperature
Range
Primary
products
Torrefaction 200-320°C Solid, gas
Liquefaction 250-600°C Liquid, gas, solid
Gasification >600°C Gas, liquid
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Biomass And Biomass Derived Fuels Offer Benefits But Bring Issues
• Reduce net production of greenhouse gases
through relatively rapid regrowth of biomass
• Reduce consumption of imported petroleum by
displacement of petroleum derived products
• Because of the significant oxygen content of
biomass, bio-oils derived from biomass have an
oxygen content as high as 40% and the bio-oil is
very acidic
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Laboratory Characterization And Corrosion Studies With Bio-Oils
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Acidic Nature Of Bio-Oils Necessitates Characterization Of Their Acid Content
And Their Corrosivity
• Bio-oils are chemically characterized
- Acidity of oil is determined using modified versions of ASTM D664
- Concentration of organic acids is determined using capillary electrophoresis (ORNL) and/or ion chromatography (ISU)
• Corrosion tests are conducted
- Corrosion resistance of 5 common structural alloys is determined
- Test temperature is usually 50°C, test duration is 1,000 h, and one set of samples is immersed in the bio-oil while one set is held above the surface of the bio-oil
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Organic Acids In Bio-Oils Can Be Characterized Using Various Methods
• ASTM D664 analysis method was modified to better extract the water soluble organic acids
• Changes include use of a high sonic energy aqueous extraction technique and a hydrophilic titration solvent
• Capillary electrophoresis is used for separation of the organic acids; electrospray mass spectrometry is used to structurally characterize the separated components (ORNL)
• Gas chromatography with mass spectrometric detection in the electro-ionization sampling mode is also used for organic acid identification (ISU)
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Analysis Techniques Include Modified And Developed Approaches To Address Polarity
And Oxygenation LevelBorrow from energy industry, develop new approaches to accommodating polarity & oxygenation
– ModTAN: ASTM D664 with intense extraction and hydrophilic titration solvent
– Acidified organic GC-MS/basified anion CE, CE-MS: chromatographies tailored to phase miscibility
– Aldehyde/ketone LC-MS: derivitization to enhance detection of oxygenates
– TDP-GC-MS: direct sampling of corrosive organic fractions and deposits thermal gradient & finally pyrolyzing environment
ModTAN CE CE-MS LC-MS GC-MS TDP-GC-MS
Acetic&formic acid MW acids Ald/Ket Smaller HCs larger HCs, chars
Decreasing polarity, oxygenation
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• Advanced sampling of CE effluent for MS structures will give additional species information
• “Unknown” organic acid species accessible directly from pre-separated capillary effluent containing aqueous fractions or extracts
07282010008.d: EIC 363.0 -All MS
07282010008.d: BPC 229.0 -All MS0.0
0.5
1.0
1.5
5x10
Intens.
0
2
4
6
4x10
Intens.
0 5 10 15 20 25 30 Time [min]
59.5137.4
166.2 183.2 199.2 213.3
227.3
241.3
255.3
265.2283.3
293.2
309.2 325.2 341.1353.2 367.4 398.3
-MS, 19.0min #946
0
20
40
60
80
100
Intens.
[%]
50 100 150 200 250 300 350 m/z
CE-MSOfPolycarboxylicAroma cAcids&Aroma cAnhydrides
naphthaleneanhydride
naphthalenetetracarboxylicacid
Higher Molecular Weight Organic Compounds Can Be Structurally Characterized
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Significant Concentrations Of Formic And Acetic Acids Make Bio-Oils Very Acidic
Source ORNL modified
Total Acid Number
ORNL Capillary
Electrophoresis
Biomass Type
mg KOH/g oil extracted Formate % Acetate %
NREL 86 0.24 0.19 Oak
U of Massachusetts 108 0.78 4.07 Mixed hardwood
VTT 66 0.65 0.78 Pine sawdust
Anonymous 68 1.88 7.17
USDA 58.5 0.75 4.53 Switchgrass
PNNL (stabilized) 51.9 1.66 4.51
Iowa State 129.1 1.91 8.20 Corn stover-organic*
Iowa State 79.3 0.49 9.37 Corn stover-aqueous
Iowa State 146.7 0.75 5.86 Red oak-organic*
Iowa State 97.9 0.44 11.44 Red oak-aqueous
* Average of fractions 3 and 4
Petroleum refiners want a crude oil with TAN ≤0.5
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Laboratory Corrosion Studies Are Used To Assess The Corrosivity Of Bio-Oils
• Samples of five structural alloys are exposed to bio-oil and to bio-oil vapors
• Corrosion coupons and stress corrosion U-bend samples are immersed and exposed in the vapor phase of each environment
• Exposure temperature is 50°C unless oils are “stabilized” to minimize polymerization
• Samples are examined after the first 250 hour exposure, after an additional 250 hours and again after another 500 hours for a total of 1,000 hours
• Stabilized bio-oils and/or oils with significantly reduced oxygen content can be tested in autoclaves at higher temperatures
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Many Materials Exhibit Unacceptable or Marginal Corrosion Rates (mm/y)
Time (hr) Carbon Steel 2¼ Cr – 1 Mo 409 Stainless 304L
Stainless
316L
Stainless
USDA bio-oil derived from switch grass after 500 hours
Above 0.23 0.36 <0.01 <0.01 <0.01
Immersed 0.62 1.44 0.82 <0.01 <0.01
VTT pyrolysis oil derived from pine sawdust after 500 hours
Above 0.60 0.85 0.14 <0.01 <0.01
Immersed 2.93 4.09 0.35 <0.01 <0.01
Mix of fractions #3 and #4 ISU bio-oil derived from corn stover after 1,000 hours
Above 1.16 1.57 0.15 <0.01 <0.01
Immersed 2.10 3.75 1.20 <0.01 <0.01
Aqueous fraction #5 derived from ISU corn stover after 1,000 hours
Above 1.21 1.44 0.03 <0.01 <0.01
Immersed 1.28 1.81 0.67 <0.01 <0.01
Based on assumption that >0.25 mm/y (0.010 inches/y) is unacceptable and 0.10-0.25 mm/y (0.004-0.010 inches/y) is marginally acceptable
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At 50°C, Corrosion Studies Show• As produced bio-oils are very corrosive to common structural
materials (carbon steel, 2¼Cr-1Mo steel and 409 stainless steel)
because of the significant carboxylic acid content
• As-produced bio-oils are not corrosive to 300 series stainless steels
like 304L and 316L
• Reduction of oxygen content to ≤ 3.3% results in no corrosion of the
low alloy materials even at elevated temperature – based on
additional ORNL autoclave tests
• However, these laboratory corrosion studies only serve as a
screening test since biomass liquefaction will be done at higher
temperatures and pressures
• Since exposure in actual operating systems is at much higher
temperatures and pressures, ORNL is providing samples for
exposure in operating systems and examining components and
samples exposed for extended times in operating systems
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Sample And Component Examination And Characterization
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Laboratory Corrosion Studies Are Complemented With Higher Temperature
And Pressure Field Exposures
Five stainless steel rings evaluated
after exposure in a biomass reactor
Cyclone used in a biomass
gasification/pyrolysis system was
examined after extended service
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Sample Exposures In The Iowa State Fluidized Bed Pyrolysis Unit Are On-Going
Ten samples (six different alloys) are currently being exposed in the freeboard portion of Iowa State University’s fluidized bed pyrolyzer
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ORNL “Spool Pieces”, Pipe Sections Of Various Alloys, Are Exposed In Operating
Biomass Liquefaction Systems
• These spool pieces were fabricated at ORNL and provided to
organizations for installation in high temperature areas of operating
biomass liquefaction systems
• The piece on the left contains sections of four different stainless steel
type alloys while the component on the right contains sections of six
different stainless steel type alloys
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Replaced Pipe From ISU System Was Destructively Examined
• Microstructures show preferential internal attack (shallow, wedge shaped oxide intrusions)
• The replacement spool piece provided by ORNL is still in the system where it is accumulating exposure time
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Preferential Internal Oxidation Has Been Observed On Many 316L/H Samples
5 mm
Surface
Scale
Metal
a)
20 mm
SurfaceScale
Metal
b)
20 mm
Surface
Scale
Metal
c)
20 mm
Surface
Scale
Metal
d)
20 mm
Surface
Scale
Metal
f)
5 mm
Scale
Metal
e)
Exposure times are estimated as 100-200 hr for a & c and 600-100 hr for b & d.
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Preferential Oxidation Observed On Pyrolyzer Component With Longer Exposure Time
Efforts are on-going to expose samples and/or get pyrolyzer components
with longer exposure times to better assess this type of oxidation
Cr-Fe Rich Oxide
Metal
Inner Surface of Tube
Fe-Cr Rich Oxide
Internal Attack
Cr-Fe-Si-Mo Rich Oxide
Metal
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Another Set Of Samples Was Examined After Exposure To Different
Operating Conditions
• Alloys exposed included 304L, 316L and 310 stainless steels along with the higher nickel content Alloy 825
• Samples were exposed less than 100 hours
• Limited amounts of oxides were formed on surfaces of the 300 series stainless steels
• Minor amounts of sulfur, potassium, phosphorus and calcium were detected in the scales, but no chlorine
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Alloy 825 Reacted More Extensively Than The 300 Series Stainless Alloys
304L Fe-(18-20)Cr-(8-12)Ni
wt.% base
310 Fe-(25-28)Cr-(20-22)Ni
wt.% base
316L Fe-(16-18)Cr-(10-12Ni)
-(2-3)Mo wt.% base
825 Ni-22+Fe-(19-23)Cr-
(2.5-3.3)Mo wt.% base
Surface
Metal Oxide
Oxide
Ni-S
10 mm
10 mm 10 mm
20 mm
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A 316L Stainless Steel Tube That Cracked After Exposure To Off-Normal Operating
Conditions Was Examined
100 mm
Outer Surface
Inner Surface
1
2
The electron microprobe was used to determine the elemental distribution in the crack and in the surface around the crack
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Significant Concentrations Of S And Cl Were Found In the Crack
10 mm
Cracks
Metal
Fe Cr Mo
O S Cl
Relative intensity increases from black to blue to green to yellow to red to white
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Biomass Gasification Creates Unique Environments That Can Be Very Corrosive
• The high temperature Chemrec black liquor gasification process brings molten salts into contact with refractories at 900-1000°C
• Refractories were identified and/or developed that have sufficient resistance to the sodium compounds
• The TRI black liquor/municipal waste gasification process creates a syngas with a high carbon activity around metallic tubes at 600-800°C
• Alloys have been identified that have greatly improved resistance to carburization
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Biomass Gasification Creates Unique Environments That Can Be Very Corrosive
• The Nexterra wood gasification process produces a syngas that contains tars and low molecular weight carboxylic acids
• Higher chromium alloys are available that resist corrosion by formic and acetic acids at temperatures of interest
• Several of these systems have metallic shells that are cool enough for condensation of chloride-containing moisture and/or formic and acetic acids
• Alloys are available that are resistant to chloride cracking as well as attack by formic and acetic acids
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Summary• All as-produced bio-oils showed significant levels of acidity
and concentrations of formic and acetic acids
• Corrosion tests at 50°C showed the bio-oils were corrosive
to carbon steel, 2¼ Cr – 1 Mo steel and 409 stainless steel
• Examination of samples and components exposed at higher
temperatures in operating systems indicate a potential for:
- preferential internal oxidation of 300 series stainless steels
- more severe corrosion of high nickel alloys when exposed
in sulfidizing environments
- cracking of 300 series stainless steels in off-normal, poorly
controlled environments
• Biomass gasification can produce corrosive environments,
but materials solutions have been/can be identified
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Thanks for your attention!
I’ll try to answer any questions you might have.
Funding for this work was provided by the U.S. Department of Energy, Bioenergy
Technologies Office (BETO)
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