fundamental challenges to materials integrity in
TRANSCRIPT
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Clive R. Clayton and Devinder Mahajan
Institute of Gas Innovation and Technology Department of Materials Science and Chemical Engineering
Stony Brook University
AEC 2018New York, NY
March 26-28, 2018
Fundamental Challenges to Materials Integrity in Biodigester Environments
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Future of Digesters to Manage Food and Farm Waste
• New York state will ban food waste from landfills in the next decade.• In California, the state is making big investment digesters. In 2017-18
alone, $99 million is available from the California Department of Food and Agriculture (Cdfa) to industry-led projects for installation of digesters.
• In October, I-GIT organized a National Grid sponsored workshop in Syracuse to identify key challenges to biogas production in digesters.
• Digester technology will be key to economical production of renewable gas (RNG).
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Sulphate Reducing Bacteria (SRB) Induced Corrosion of 304ss Screen and Tank Weldment
• Biodigesters expose constructionalloys to a complex organic/biologicalenvironment that can lead tocorrosion and costly down time formaintenance.
• Most alloys are designed for Inorganicexposure and little is still knownabout the effect of organiccompounds on corrosion.
Source: Microbiologically Influenced Corrosion Ed: G Kobrinp202 NACE Int. 1993
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Factors Contributing to Corrosion in Biodigesters: Microbial Influenced Corrosion
Biofilm formation creating differential aeration cells and modifying passive films and alloy surface composition
Organic Acids activating iron dissolution by chelation and delaying Active-Passive Transition
Ubiquitous Sulphate Reducing Bacteria (SRB) generating hydrogen sulphide which forms sulphides with elements needed for passive film formation
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Biofilm Formation
Source M. Ozcan et al J Oral Rehabilitation 30 ( 2003) 290
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Corrosion of Substrate: Cathodic Activity at Sloughed Region of Biofilm Driving Under-film Anodic Dissolution ( Differential Aeration Cell)
Source: De Gruyter Online
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XPS In Vacuo and XANES (Synchrotron) Data
Source A.J Francis et al Env. Sci. and Tech. Vol 28, 4, 636 (1994)
• Data show good agreement for microbe speciation studies
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Biofilm Protein Component Attachment via Protein Sulphur to MoO42-Adsorbed on 304 ss Surface
Reduction of Surface Molybdate to Mo5+ is possibly induced by the Sulphur containing residual proteins in the Exopolymer of Delaya (Pseudomonas) Marina
Molybdate is a powerful pitting inhibitor!
Mo5+
Source: G. Chen et. al. Corrosion Vol 52, No 12 (1996) p 891
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Polarization analysis of Stainless Steel: Factors Affecting Corrosion characteristics in a Test Solution
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Example of Prior Exposure to Organic Acid Showing Anodic Activation
Preexisting protective oxide film appears to be stripped by exposure to Lactic Acid by chelation. Similar results were found for citric and oxalic acids
Source: Glenn French MS Thesis Stony Brook University ( 1998)
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SRB Generate multiple Sulphur compounds which are corrosive. H2S most aggressive to stainless steels and degrades concrete.
Mechanism for Generation of Multiple Sulphur Species
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XPS of SRB (Desulfovibrio sp.) Biomass Following Injection of Metal Additions in Solution (components of 317 ss)
Corresponding Sulphides observed on 304 SS on exposure to SRB
Source: C.R.Clayton ECASIA 97 Eds I.Olefjord et al. p21 Wiley (1997)
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SRB (Desulfovibrio sp.) Environment Reacts with 304ss to Inhibit Passive Formation in Test Electrolyte (deaerated 0.1 M HCl)
Reactions of with Stainless Steel in Digester Environments
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SRB Influence on 317 ss Corrosion Resistance
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Concluding Remarks
• Fundamental understanding of organic corrosion mechanisms can improve materials selection and corrosion prevention strategies for digester equipment.
• The understanding can lead to better corrosion resistant design of digesters.
• Collaboration between Materials Scientists and Chemical Engineers will be crucial for a successful outcome.