corrosion studies with biomass-derived fluids

11/12/2014

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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


• 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


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


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


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


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


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


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


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


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


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)

corrosion studies with biomass-derived fluids

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