Corrosion Issues Associated With Thermochemical Production Of Biofuels

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1 Corrosion Issues Associated With Thermochemical Production Of Biofuels James R Keiser, Michael P Brady, Samuel A Lewis, Sr and Raynella M Connatser Oak Ridge National Laboratory

2 Studies Have Been Conducted To Assess And Address Corrosion In Many Systems For Thermochemical Processing Of Biomass Gasification of biomass derived liquids in paper mills Steam reforming of biomass derived liquids in paper mills Fast pyrolysis of various types of biomass Production of biomass-derived liquids by other processes such as hydrothermal liquefaction and hydropyrolysis

3 There Are Materials Issues In Gasification Of Biomass In gasification of a paper mill s black liquor waste stream at ~950 C, the sodium carbonate/sodium oxide reacted with the alumina refractories to form sodium aluminate causing rapid degradation of the refractories - Refractories have been identified that give satisfactory life In steam reforming of black liquor at ~600 C, the reducing environment in the fluidized bed led to carburization of the pulsed heater tubes - More resistant alloys have been identified Wear and corrosion issues have been observed in wood gasifiers currently being used at ORNL - Design improvements appear to address problems

4 Liquefaction/Pyrolysis Of Biomass Presents Materials Challenges Fast pyrolysis produces an oil containing significant amounts of oxygen much of which is in the form of water and carboxylic acids Hydrothermal liquefaction of biomass produces an oil with lower oxygen content (<20%), but the oil has higher viscosity and the process requires severe processing conditions C and 2,500-3,000 psi Hyropyrolysis of biomass utilizes hydrogen gas at a lower pressure but higher temperature to make a product with lower oxygen content

5 ORNL Is Conducting Corrosion Studies In Biomass-Derived Liquids For Several Projects Oil from fast pyrolysis of various types of biomass Bio-oil and the aqueous phase from hydrothermal liquefaction Bio-oil and the aqueous phase from hydropyrolysis Bio-oil produced by catalysis of lignocellulosic sugars Treated pyrolysis oil blended with home heating oil Bio-oil before and after hydrotreating in an ebullated bed reactor Bio-oil blended with petroleum and processed in a fluid catalytic cracker

6 ORNL Corrosion Studies Involve Several Tasks Chemical characterization of bio-oil (see poster #26 by Lewis and Connatser) and development of new analysis techniques Laboratory corrosion studies at 50 C in as-produced oil and the aqueous fraction Laboratory corrosion studies in autoclaves at temperatures up to 350 C in treated oil and the aqueous fraction Exposure of ORNL-provided samples in components of operating systems Destructive examination of components removed from operating bio-oil production systems

7 Measuring Of Biofuel Upgrade Products & Corrosive Species With Direct, Polarity-Matched Analytical Approaches Bio-oils, particularly pyrolysis oils, contain increased acids (threatens implementation) and organic oxygenate levels (compromises fuel blendability) Unique physical phases & varied hydrophilicity of pyrolysis liquids pose challenges to traditional analytical methods Challenge: To develop quantitative and qualitative speciation data that elucidates paths to corrosion and indicates mechanisms of catalytic upgrading

8 Addressing Full Range of Bio-Oil Constituents Modified Total Acid Number (ModTAN) & Capillary Electrophoresis (CE) chemical speciation in an aqueous context allows fast screening of bio-oils for acid content & material degradation routes CE-Mass Spectrometry (MS) allows structural study of unknown larger organic acids Acidic, non-polar solvent Gas Chromatography (GC)-MS offer neutral-molecule confirmation of species identification in the base approach. Thermal desorption (TD) GC-MS provides more efficient bio-oil analysis method by permitting direct analysis of samples. Pyrolysis (P) GC-MS brings insights into deposit composition, indicating a large component of bio-oil species & very little true char. ModTAN CE CE-MS LC-MS GC-MS TDP-GC-MS Acetic&formic acid MW acids Ald/Ket Smaller HCs larger HCs, chars Continuum of bio-oil analysis: decreasing polarity, oxygenation

9 ph Titrations & Separations Reveal Acid Species UV Abs (A. U.) Typical titration curve generated during calculation of ModTAN value. formic unk org acids A. U. A. U CE: Percentage Unknown Organic Acids: 46.5% Vol Titrant (μl) acetic Time (min) Time (min) Unique physical phases & varied hydrophilicity of pyrolysis liquids pose challenges to traditional analytical methods of calculating acidity (TAN). Solution: ModTAN Previous methods of organic oxygenate speciation (non-titrated GC-MS, LC-MS) suffer from low and/or biased detection sensitivity due to extraction inefficiencies. Solution: CE & TD/P-GC-MS

10 Thermal Desorption/Pyrolysis GC-MS Reduces Sample Bias Corn Corn%Stover% Organic Organic% Extraction Extrac4on% Labels match middle panel Due to the over-sampling of lighter plant oils when conventional solventextraction GC-MS methods Corn Stover Corn%Stover% Thermo Thermo% Consequences if heavy oils are analytically under-represented: Disposal of energetically valuable residuals along with inorganic char Underestimation of corrosivity of low-% sludge deposits on infrastructure materials Corn%Stover%Pyro% Corn Stover Pyro

11 Laboratory Corrosion Studies Provide Means To Assess Corrosivity Of Bio-Oils Initial corrosion tests are conducted at 50 C since this represents the highest temperature at which bio-oil would likely be stored or transported Five alloys used for structural applications that provide a range of corrosion resistance are included in each test Two types of samples are tested coupons to assess general corrosion and U-bend samples to determine the likelihood of stress corrosion cracking One set of samples is immersed in the bio-oil and one set is suspended above the surface of the oil Aqueous fractions and bio-oils that are stable at higher temperature are tested in autoclaves

12 Laboratory Corrosion Tests Provide Data On Corrosion At 50 C Carbon Steel 2¼Cr- 1Mo 409 SS 304L SS 316L SS As-produced pyrolysis oil X X X OK OK Stabilized pyrolysis oil Hydrotreated pyrolysis oil (Oxygen ~3.3%) Hydrotreated pyrolysis oil (Oxygen ~1.3%) X X OK OK OK OK OK OK OK OK OK OK OK OK OK Aqueous fraction from biomass liquefaction X X OK OK OK X = Corrosion rate calculated from exposed samples 0.25 mm/yr OK = Corrosion rate calculated from exposed samples < 0.25 mm/yr

13 To Assess Corrosion During Production And Processing, Autoclave Tests And Field Studies Are Important Test Components Laboratory tests are conducted with a limited volume of bio-oil, so corrodent depletion is always a concern Field exposures in bench-scale and demonstration systems are often for limited duration and conditions are frequently changed Field exposures include exposure of corrosion samples we provide as well as examination of components vessels, transfer lines, fittings, etc. that have been exposed for an extended time to a process environment

14 Stainless Steel Transfer Line On A Biomass Pyrolysis System Showed Surface Degradation After Limited Service Corrosion product ID Surface Tube wall

15 A Stainless Steel Fitting Exposed To Off- Normal Conditions Showed Cracking Stainless steel fitting was exposed to abnormally high levels of sulfur and chlorine Extensive cracking was observed and sulfur and chlorine were identified in the cracks Although these conditions should not normally be encountered, this shows maintaining control of the environment can be critical Metal Cracking

16 A Stainless Steel Reactor Vessel Exposed A Limited Time Showed Degradation Vessel was used for treatment of bio-oil under conditions that are proprietary Inside surface of vessel showed evidence of interaction with the process environment Metal Metal

17 Summary Analytical techniques specifically suitable for biomass derived oils are being developed and utilized to characterize the biooils Laboratory corrosion studies have demonstrated that untreated bio-oils are highly corrosive to carbon steel and 2¼Cr-1Mo steel Bio-oils treated to remove the oxygen compounds, particularly the carboxylic acids, are not corrosive to these alloys even at higher temperatures and pressures Field exposures show more studies are needed for evaluation of higher alloys in the more severe environments associated with production and processing of bio-oils Our goal is not to allow materials problems to prevent commercialization of any biomass processing technologies

18 Funds for the research described in this presentation were provided by the Bioenergy Technologies Office of the U.S. Department of Energy Thank you for your interest in this presentation! I will try to answer any questions you might have.