Outline. Background on Oak Ridge National Laboratory (ORNL) Description of biomass thermochemical processing methods

Transcription

1 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 ORNL is managed by UT-Battelle for the US Department of Energy 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 2 Presentation_name 1

2 Oak Ridge National Laboratory Opened During The Manhattan Project 3 Presentation_name ORNL Is The Department Of Energy s Largest Science And Energy Laboratory $1.65B budget 4,400 employees 3,000 research guests annually $500M modernization investment Most World s powerful open most intense scientific neutron computing source facility World-class research reactor Nation s largest materials research portfolio Nation s most diverse energy portfolio Managing billion-dollar U.S. ITER project 4 Presentation_name 2

3 Background On Thermochemical Processing Of Biomass 5 Presentation_name Biomass Thermochemical Processing Methods Can Create Corrosive Environments Process Temperature Range Primary products Torrefaction C Solid, gas Liquefaction C Liquid, gas, solid Gasification >600 C Gas, liquid Current corrosion studies at ORNL are concentrated on the interaction of structural materials with biooils from biomass liquefaction 6 Presentation_name 3

4 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 7 Presentation_name Laboratory Characterization And Corrosion Studies With Bio-Oils 8 Presentation_name 4

5 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 9 Presentation_name 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) 10 Presentation_name 5

6 Analysis Techniques Include Modified And Developed Approaches To Address Polarity And Oxygenation Level Borrow 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 11 Presentation_name Decreasing polarity, oxygenation Higher Molecular Weight Organic Compounds Can Be Structurally Characterized Advanced sampling of CE effluent for MS structures will give additional species information Unknown organic acid species accessible directly from preseparated capillary effluent containing aqueous fractions or extracts Intens. x CE-MS Of Polycarboxylic Aroma c Acids & Aroma c Anhydrides d: EIC All MS naphthalene anhydride 0.5 Intens. 0.0 x d: BPC All MS naphthalene tetracarboxylic acid Presentation_name Time [min] 6

7 Significant Concentrations Of Formic And Acetic Acids Make Bio-Oils Very Acidic Source ORNL modified Total Acid Number ORNL Capillary Electrophoresis mg KOH/g oil extracted Formate % Acetate % Biomass Type NREL Oak U of Massachusetts Mixed hardwood VTT Pine sawdust Anonymous USDA Switchgrass PNNL (stabilized) Iowa State Corn stover-organic* Iowa State Corn stover-aqueous Iowa State Red oak-organic* Iowa State Red oak-aqueous * Average of fractions 3 and 4 13 Presentation_name 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 14 Presentation_name 7

8 15 Presentation_name Many Materials Exhibit Unacceptable or Marginal Corrosion Rates (mm/y) Time (hr) Carbon Steel 2¼ Cr 1 Mo 409 Stainless 304L Stainless USDA bio-oil derived from switch grass after 500 hours 316L Stainless Above <0.01 <0.01 <0.01 Immersed <0.01 <0.01 VTT pyrolysis oil derived from pine sawdust after 500 hours Above <0.01 <0.01 Immersed <0.01 <0.01 Mix of fractions #3 and #4 ISU bio-oil derived from corn stover after 1,000 hours Above <0.01 <0.01 Immersed <0.01 <0.01 Aqueous fraction #5 derived from ISU corn stover after 1,000 hours Above <0.01 <0.01 Immersed <0.01 <0.01 Based on assumption that >0.25 mm/y (0.010 inches/y) is unacceptable and mm/y ( inches/y) is marginally acceptable 16 Presentation_name 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 8

9 Sample And Component Examination And Characterization 17 Presentation_name 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 18 Presentation_name 9

10 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 19 Presentation_name 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 20 Presentation_name 10

11 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 21 Presentation_name Preferential Internal Oxidation Has Been Observed On Many 316L/H Samples Surface Scale a) Surface Scale b) Surface Scale c) 5 mm 20 mm 20 mm Surface Scale d) Scale e) Surface Scale f) 20 mm 5 mm 20 mm Exposure times are estimated as hr for a & c and hr for b & d. 22 Presentation_name 11

12 Preferential Oxidation Observed On Pyrolyzer Component With Longer Exposure Time Cr-Fe Rich Oxide Internal Attack Cr-Fe-Si-Mo Rich Oxide Inner Surface of Tube Fe-Cr Rich Oxide Efforts are on-going to expose samples and/or get pyrolyzer components with longer exposure times to better assess this type of oxidation 23 Presentation_name 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 24 Presentation_name 12

13 Alloy 825 Reacted More Extensively Than The 300 Series Stainless Alloys Surface 304L Fe-(18-20)Cr-(8-12)Ni wt.% base Oxide 316L Fe-(16-18)Cr-(10-12Ni) -(2-3)Mo wt.% base 10 mm 10 mm Ni-S Oxide 310 Fe-(25-28)Cr-(20-22)Ni wt.% base 10 mm 20 mm 825 Ni-22 + Fe-(19-23)Cr- ( )Mo wt.% base 25 Presentation_name A 316L Stainless Steel Tube That Cracked After Exposure To Off-Normal Operating Conditions Was Examined Outer Surface 1 Inner Surface mm The electron microprobe was used to determine the elemental distribution in the crack and in the surface around the crack 26 Presentation_name 13

14 Significant Concentrations Of S And Cl Were Found In the Crack Fe Cr Mo O S Cl Cracks 10 mm Relative intensity increases from black to blue to green to yellow to red to white 27 Presentation_name 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 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 C Alloys have been identified that have greatly improved resistance to carburization 28 Presentation_name 14

15 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 chloridecontaining 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 29 Presentation_name 30 Presentation_name 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 15

16 Funding for this work was provided by the U.S. Department of Energy, Bioenergy Technologies Office (BETO) Thanks for your attention! I ll try to answer any questions you might have. 31 Presentation_name 16