Workshop Grouping

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    Thailand Power Workshop Grouping

    Bangkok office

    29 & 30-Mar-2012

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    Executive Summary

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    Boiler System: Found the problem of Hydrogen damage issue. The root-cause was

    come from condenser in-leakage issue from cooling part.

    Solution

    Review the chemical treatment program to effective control corrosionin system with Nalcos product.

    Implement @T ORP on BFW to monitor the .

    Cooling System:

    High chloride issue in cooling system anytime.

    Induce to face the stress corrosion cracking (SCC) on SS304condenser tube.

    Solution

    Review the chemical treatment program to effective microbial and alsocontrol chloride in system with Nalcos product.

    Implement 3DTRASAR for cooling system.

    Implement the condenser performance monitoring to ensure thetreatment program.

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    General Information

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    June 2011:Condenser in-leakage issue

    Nov 2011:Low pH in BFW

    Dec 2011:T/A to fix the condenser

    Jan 2012:Normal run

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    Problem analysis forBoiler system

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    Speed

    Governor

    Variable Loading

    HP Steam

    Turbine

    ValveShaft speed

    Generator

    Low pressure

    steam

    Hot

    well

    To boiler as feed water

    Cooling tower

    (Operating range 40-50 MW)

    Condensate Return

    DEAERATOR

    HP Boiler LP Boiler

    LP Steam

    MB(Demin

    MU)

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    Boiler System

    1 unit CFB Boiler

    HP = 70 bar, 130 tons/hrConsisting of Economizer, Boiler, Superheater #1 and #2Deaerator

    2 bar, 115-118 C, DO

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    Important Issue

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    Boiler System

    The plant experience with 2 (two) tube failures in December 2011.The failures were occurred in the water wall tubes about 5 m above theburner as showing in the picture below

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    Hydrogen Damage

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    The main problem with this failure is

    that it gets spread across the waterwall tubes in totally an unpredictableway. Hence to find out the regionsaffected in the water wall bycondenser leakage, exhaustive specialprobe ultrasonic testing is required.

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    Characteristics of Hydrogen Damage, Caustic Gouging andAcid Phosphate Corrosion

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    Determine the root cause

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    Major Root Cause Influence Confirmation Remark

    Influence of excessive deposits Yes Deposit in steam drum (Boilerinspection May & Sep 2011)

    Heavy deposition in sampling tube(Sep 2011)

    Flow disruption: deposits, DNB,bend/sharp changes in tube direction,

    locally high heat transfer, etc.

    Yes Flow disruption only influence bydeposition

    Influence of acidic contamination Yes pH of boiler drop to ~8.5 on May2011

    Condenser leak-minor but occurredover an extend period

    Yes pH of boiler dropped to ~8.4

    Hardness in condensate went upto >0.5 ppm

    Chloride concentration in HP

    evap. went up >10 ppm

    Water treatment plant up set leading tolow pH condition

    No

    Error in chemical cleaning process No No chemical cleaning conducted in2011

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    BFW data trend

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    8

    8.2

    8.4

    8.6

    8.89

    9.2

    11/2/2011

    11/4/2011

    11/6/2011

    11/8/2011

    1

    1/10/2011

    1

    1/12/2011

    1

    1/14/2011

    1

    1/16/2011

    1

    1/18/2011

    1

    1/20/2011

    1

    1/22/2011

    1

    1/24/2011

    1

    1/26/2011

    1

    1/28/2011

    1

    1/30/2011

    pH 8.5-9.2

    pH 8.5-9.2

    7.37.47.57.67.77.87.98.08.1

    8.2

    Conductivity

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    Solution for Boiler system

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    Immediate Solution

    Isolate the condenser and plug all the leaking tubesand tubes with high depth wastage. Ensure there is nocooling water in-leakage by checking condensatequality (cation conductivity, hardness, chloride; etc)

    Selective tube sampling for deposit measurement.Inspection using fiber optic (boroscope) can provideuseful information

    Tube replacement for all tubing with hydrogen damage

    and/or significant wall loss be replaced Check the efficacy of chemical cleaning

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    Long Term Solution

    Chemical cleaning

    Proper chemical cleaning method/procedure

    Prevent condenser in-leakage by improving integrity ofsurface condenser

    Install on-line instrumentation to improve condenserleakage detection capability and cycle chemistry control

    On-line cationic conductivity @CPD and outlet DA

    DO meter @CPD and outlet DA

    @Temp. ORP @ CPD/Inlet DEA and Outlet DA (optional)

    Develop specific cycle chemistry targets, action levels andshutdown policies to maintain good HRSG cleanliness.

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    Problem analysis forCooling system

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    Open Cooling Water

    RR = 6,000 M3/hr, HV = 1,000 M35 cell cross flow cooling tower with high efficiency fillTemperature Supply: 34 0CTemperature Return: 42 0C

    Pipe: carbon steelCondenser

    DT cooling water (design) = 8 0CTubes: SS 304Tubes Sheet: CS with epoxy coating

    Lube Oil CoolersServed by open cooling water systemTubes: Cu:Ni = 90:10Tubes Sheet: CS with epoxy coating

    Air CoolersServed by open cooling water systemTubes: Cu:Ni = 90:10Sheet: carbon steel coated with epoxy

    Make-up water : clarified water

    Source: river waterPretreatment: clarifier filter raw water tankcooling tower

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    Important Issue

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    Cooling Water System

    There were condenser tube leak event occurred in the surface condenser in year 2011. The tubefailure occurred on June 2011, 5 tubes were cracked and leaked cause very high conductivity ofcondensate and low pH of boiler water (

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    Nalco 3DTRASAR Optimizer

    The cooling water quality at 6 cycle with no NaOCl

    were not aggressive for Stainless 304

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    When we run simulation program with NaOCl to control FRC0.2-0.5 ppm.

    Higher chloride in cooling water will increase potential for stainlesscorrosion

    From above snapshot we found there are issue of SS-304 corrosion thatmay be the root cause for this issue that make the penalty from unplanshutdown for 2 day around (3Bahtx20kwx1000x24hrx2day = 2.88 MB/time)

    Nalco 3DTRASAR Optimizer

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    Water Quality MU vs CW

    Trend of Make up & cooling water quality seem stable, so the problem may behidden such as- not matching treatment program,- not matching control target

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    Solution for Cooling system

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    To prevent stainless corrosion in condenser and H2 damage in Boiler tubeWe recommend follow.-

    1. Replace the oxidizing biocide form chloride to bromine base2. Replace treatment program

    3. Use automation system control feeding system to increase systemreliability

    4. Replace treatment program for more reliability5. Use automation system to monitor and control feeding system in Boiler

    system

    SOLUTION

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    1. Replace the oxidizing biocide form chloride to bromine base

    To prevent SS-304 corrosion, we recommend to use stabilize bromine foroxidizing biocide that will not increase chloride in water.

    SOLUTION

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    NALCO TREATMENT

    SOLUTION

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    Nalco 3DTRASAR Optimizer

    With Nalco solution, we can run cooling system at 7 cyclewithout SS-304 corrosion or scale from Calcium Phosphate

    All field aregreen

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    Summary of Commercial part

    C i l

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    Commercial part

    Units Price per Unit

    Kg/Year 6.00

    Kg/Year 165.00

    Kg/Year 155.00

    Kg/Year 198.00

    Kg/Year 113.00Kg/Year 246.00

    Kg/Year 81.00

    Total Cont/Year

    Total Treatment Costs 932,912.0

    3,639,709.7

    Internal Treatment BT-3000 4 Continuous Feed 5,616.0 454,896.0

    Boiler System

    Oxygen Scavenger Eliminox 0.5 Continuous Feed 562.0 63,506.0Condensate Treatment N-356 1.5 Continuous Feed 1,685.0 414,510.0

    Product Category or

    Control Parame ter

    Scale Inhibitor

    pH

    Cycles of Concentration

    Cooling System

    TRASARMild Steel Corrosion Inhibitor

    Oxidizing Biocide

    Product Number or

    Additive

    3DT104

    H2SO4

    Control Method

    Tag Polymer

    Dosage or

    Control Set

    Point

    7.0 3D Scale Control

    31

    7.6

    0 Timer Control

    253DT129

    ST-70 1,717,567.0

    3,245

    2,649

    8,675

    Annual Cost

    410,643.8

    43,138.1

    Annual Usage

    7,190Automatic

    535,448.8

    2,706,797.7Total Treatment Costs

    1) Chemical 303,309.14 Bht/m

    2) Equipment rental

    -3DTRASAR for CW + 4 pump + Solenoid valve 15,000 Bht/m-3DTfB (CONTROLLER & NCSM) 33,600 Bht/m

    Total Treatment Cost 351,909 Bht/m4,222,909 Bht/Y

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    Commercial part

    3DTRASAR Value Package

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    Workshop grouping

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