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    Presentation 2b Whittaker

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    moorthymtps_54120305
    The condenser tubes in a glass-lined heat exchanger tank have experienced frequent corrosion failures over many years. Previous tube materials like 316L stainless steel and alloy C-276 failed within two years. The current zirconium 702 tubes fail within 18 months. Biological growth in the condenser is believed to cause corrosion through a mechanism where iron-oxidizing bacteria concentrate chloride and ferric ions under biofilms, creating a pitting environment for the zirconium tubes. Analysis found the bacteria sphaerotilus, known to oxidize iron, in the biological growth. Laboratory experiments simulating the conditions reproduced the corrosion. Low flow allowing biological growth is a key factor in the frequent condenser tube failures

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    Presentation 2b Whittaker

    Uploaded by

    moorthymtps_54120305
    6 views27 pages
    The condenser tubes in a glass-lined heat exchanger tank have experienced frequent corrosion failures over many years. Previous tube materials like 316L stainless steel and alloy C-276 failed within two years. The current zirconium 702 tubes fail within 18 months. Biological growth in the condenser is believed to cause corrosion through a mechanism where iron-oxidizing bacteria concentrate chloride and ferric ions under biofilms, creating a pitting environment for the zirconium tubes. Analysis found the bacteria sphaerotilus, known to oxidize iron, in the biological growth. Laboratory experiments simulating the conditions reproduced the corrosion. Low flow allowing biological growth is a key factor in the frequent condenser tube failures

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    The condenser tubes in a glass-lined heat exchanger tank have experienced frequent corrosion failures over many years. Previous tube materials like 316L stainless steel and alloy C-276 failed within two years. The current zirconium 702 tubes fail within 18 months. Biological growth in the condenser is believed to cause corrosion through a mechanism where iron-oxidizing bacteria concentrate chloride and ferric ions under biofilms, creating a pitting environment for the zirconium tubes. Analysis found the bacteria sphaerotilus, known to oxidize iron, in the biological growth. Laboratory experiments simulating the conditions reproduced the corrosion. Low flow allowing biological growth is a key factor in the frequent condenser tube failures

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    6 views27 pages

    Presentation 2b Whittaker

    Uploaded by

    moorthymtps_54120305
    The condenser tubes in a glass-lined heat exchanger tank have experienced frequent corrosion failures over many years. Previous tube materials like 316L stainless steel and alloy C-276 failed within two years. The current zirconium 702 tubes fail within 18 months. Biological growth in the condenser is believed to cause corrosion through a mechanism where iron-oxidizing bacteria concentrate chloride and ferric ions under biofilms, creating a pitting environment for the zirconium tubes. Analysis found the bacteria sphaerotilus, known to oxidize iron, in the biological growth. Laboratory experiments simulating the conditions reproduced the corrosion. Low flow allowing biological growth is a key factor in the frequent condenser tube failures

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
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    of 27

    Biologically Induced

    Corrosion of Zirconium
    702 Heat Exchanger
    Tubes
    Gary Whittaker, PE

    Eastman operates a proprietary


    process utilizing a glass lined
    tank to process an organic stream
    containing a small amount of
    mineral acid.
    The condenser on top of the GLT
    has been plagued by corrosion
    problems since it was added to
    the system many years ago.

    GLT Condenser Layout


    vapor out
    filtered water out
    condenser
    filtered water in

    Vapor out

    process in
    GLT

    heat in
    sludge out

    History
    Process was designed without a
    condenser
    First condenser was 316L, failed
    quickly
    Second condenser was alloy
    C-276, failed in two years
    Current condenser is Zirconium
    702, fails in 18 months

    Alloy C-276 Tubesheet

    Zr 702 Tubesheet

    Zr 702 Tubesheet

    Eddy Current Results

    Window in shell pre-cleaning

    Window in shell post-cleaning

    Proposed Corrosion Mechanism


    1. Low flow rates through the condenser shell
    allow biological infestation to occur.
    2. Iron oxidizing bacteria present in the biomass oxidize ferrous ion (Fe+2) in the water to
    ferric ion (Fe+3), a strong oxidizer.
    3. Chloride Ion (Cl-) is attracted to the biomass to maintain charge balance.
    4. Chloride ion combined with a strong
    oxidizing agent is known to pit zirconium.

    River Water Chemistry

    Iron 0.03 mg/L


    Chloride 9.5 mg/L

    Bio Analysis
    Samples of the bio-mass were
    collected by the plant micro-biologist
    Analysis showed the presence of

    filamentous bacterium called


    sphaerotilus, a well-known
    ferrous oxidizer
    Identity was confirmed by both a
    staining method and genetic analysis

    Sphaerotilus collected from the


    condenser.

    Sphaerotilus from literature

    Laboratory Simulation
    Bio-mass samples were collected
    and placed in a jar with fresh river
    water
    After several weeks exposure
    samples were taken to measure iron
    and chloride levels in the bio-mass

    Simulation Results
    Chloride 1100 ppm
    Iron 4000 to 12000 ppm

    Zirconium oxide nodules were found


    in the pits.
    Zirconium chloride complexes are
    the primary corrosion product of
    ferric chloride pitting
    The complexes are hydrolyzed to
    zirconium oxide forming nodules

    Conclusions
    1. Zr 702 performs better than alloy C-276 in this
    mix of hot organic and mineral acids.

    2. Biological films composed of iron oxidizing


    sphaerotilus form on the shell side of the
    exchanger.
    3. Biologically produced ferric ion combines with
    chloride in the river water to produce a strong
    pitting environment under the bio-mass.
    4. Low flow through the condenser shell promotes
    bio-mass formation and pitting of the tubes.

    Questions?

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