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Steam Cycle Chemistry in Air-Cooled Condensers · Steam Cycle Chemistry in Air-Cooled Condensers...

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Steam Cycle Chemistry in Air-Cooled Condensers NV Energy ACC User’s Group * November 12-13, 2009 Andrew Howell * Xcel Energy
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  • Steam Cycle Chemistryin Air-Cooled Condensers

    NV Energy ACC Users Group * November 12-13, 2009 Andrew Howell * Xcel Energy

  • Steam Cycle Chemistry Goal for ACC:minimize corrosion of carbon steel

    Resulting in:

    minimal particulate transport (iron oxide) minimal through-wall leaks

  • Consequences of particulate transport

  • steam generating tube chemical cleans steam generating tube failures frequent filter element replacement

    (if condensate filter) resin contamination / difficult regeneration

    (if condensate polisher)

    Consequences of particulate transport

  • Rapid loading of condensate filters

  • Rapid loading of condensate polishers

  • Air inleakage:

    potential vacuum deterioration (air binding)

    increased steam cycle contamination with oxygen and carbon dioxide

    rapid loading of anion resin (if polisher)

    Consequences of through-wall leaks

  • early condensate steam / condensate velocity vacuum conditions

    Iron Corrosion: contributing issues

  • Early Condensate Environment(steam cycle pH ~9)

    NH3

    NH3NH3

    NH3

    NH3

    CO2

    CO2

    Condensate: pH ~8

    Vacuum

    NH3NH3

    NH3NH3 NH3

    CO2CO2

    Condensate: pH ~9

    Vacuum

  • Steam / Condensate Velocity:laminar flow in pipe (velocity vectors)

  • Steam / Condensate Velocity:turbulent flow (velocity vectors)

  • Flow

  • Flow

  • Mechanism of metal loss:2-phase flow-accelerated corrosion

    (???)

  • Chemistry optimization:Elevate pH in early condensate.

  • Early Condensate Environment:increased ammonia feed (pH ~10)

    NH3

    NH3NH3

    NH3

    NH3

    CO2

    CO2

    Condensate: pH ~9

    Vacuum

    NH3NH3

    NH3NH3 NH3

    CO2CO2

    Condensate: pH ~10

    Vacuum

    NH3

    NH3

    NH3

    NH3

    NH3

    NH3

    NH3

    NH3

    NH3

    NH3

    NH3 NH3

    NH3 NH3

    NH3

    NH3

    NH3

    NH3

    NH3

  • -- or feed alternative less-volatile chemical (e.g. amine)

    [ decomposition byproducts may generate concerns in some systems ]

  • alternative material to carbon steel low-alloy or stainless steel inserts / coatings depends on mechanism confirmation

    design to minimize overall velocity and turbulence

    Other resolution options for iron corrosion:

  • ACC impact depends on unit type & design:

    combined cycle more tolerant of particles and air ingress high pH operation typically simple

    once-through supercritical low tolerance for particles impact of leaks on polisher impact of high pH operation on polisher

  • combustion turbine-

    generator

    combustion chamber

    heat recovery steam generator

    turbine-generator

    steam

    condenser

    Combined Cycle Power Plant

    drums

    blowdown

  • Combined Cycle Power Plants

    steam drums / blowdown for some contaminant removal

    frequent operation in cycling mode no polisher or filter typically included

  • condenser

    hotwell

    boiler

    HPturbine

    IPturbine

    LP turbine

    DA LP heatersHP heaters

    econ

    SH

    RH

    crossover

    condensatepump

    boilerfeed pump

    attemperationsteam

    steam

    Supercritical Once-through Power Plant

    polisher

  • Supercritical Once-through Power Plants

    superior water quality required (polisher and condensate filter)

    high pH and air inleakage impacts polisher performance and costs

    normally in baseload operation mode

  • ACC Design & Construction: Chemistry Impacts

    weld debris and fluoride contamination

  • Weld flux debris

  • ACC Design & Construction: Chemistry Impacts

    weld debris and fluoride contamination iron oxides / miscellaneous crud

  • Iron oxides / miscellaneous construction crud

  • ACC Design & Construction: Chemistry Impacts

    weld debris and fluoride contamination iron oxides / miscellaneous crud improper galvanic tube coating

  • Improper Galvanic Tube Coating

  • ACC Design & Construction: Chemistry Impacts

    weld debris and fluoride contamination iron oxides / miscellaneous crud improper galvanic tube coating cleanup for initial unit startup

  • Initial Operation: System Cleanup

  • Initial Operation: System Cleanup

  • Initial Operation: System Cleanup

  • Initial Operation: System Cleanup

  • Initial Operation: System Cleanup

  • Initial Operation: System Cleanup

  • ACC Design & Construction: Chemistry Impacts

    weld debris and fluoride contamination iron oxides / miscellaneous crud improper galvanic tube coating cleanup for initial unit startup upper duct access for future inspections

  • Ideal Upper Duct Access

  • Non-Ideal Upper Duct Access

  • ACC Design & Construction: Chemistry Impacts

    weld debris and fluoride contamination iron oxides / miscellaneous crud improper galvanic tube coating cleanup for initial unit startup upper duct access for future inspections condensate deaerator

  • Condensate Deaerator

  • Condensate Deaerator

  • ACC Design & Construction: Chemistry Impacts

    weld debris and fluoride contamination iron oxides / miscellaneous crud improper galvanic tube coating cleanup for initial unit startup upper duct access for future inspections condensate deaerator upper duct isolation

  • Upper Duct Isolation

  • Upper Duct Isolation

  • Guidelines for Off-Line Inspection of Air Cooled Condensers

    - document through the PowerPlant & Environmental Chemistry

    research subcommittee of ASME

    Air-Cooled Condenser Interest Group- email communications & discussions

  • Conclusions

    Steam Cycle Chemistry is an important factor to be considered in the design and operation of power plants with air-cooled condensers.

    Steam Cycle Chemistryin Air-Cooled CondensersSteam Cycle Chemistry Goal for ACC:minimize corrosion of carbon steelConsequences of particulate transportSlide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Combined Cycle Power PlantsSlide Number 22Supercritical Once-through Power PlantsACC Design & Construction: Chemistry ImpactsWeld flux debrisACC Design & Construction: Chemistry ImpactsIron oxides / miscellaneous construction crudACC Design & Construction: Chemistry ImpactsImproper Galvanic Tube CoatingACC Design & Construction: Chemistry ImpactsInitial Operation: System CleanupInitial Operation: System CleanupInitial Operation: System CleanupInitial Operation: System CleanupInitial Operation: System CleanupInitial Operation: System CleanupACC Design & Construction: Chemistry ImpactsIdeal Upper Duct AccessNon-Ideal Upper Duct AccessACC Design & Construction: Chemistry ImpactsCondensate DeaeratorCondensate DeaeratorACC Design & Construction: Chemistry ImpactsUpper Duct IsolationUpper Duct IsolationGuidelines for Off-Line Inspection of Air Cooled Condensers- document through the PowerPlant & Environmental Chemistry research subcommittee of ASMEAir-Cooled Condenser Interest Group- email communications & discussionsConclusions


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