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    Introduction To Cooling Water Treatment

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    somani
    This document discusses cooling water treatment. It introduces important water parameters for cooling water like pH, hardness, chlorides and dissolved gases. It describes types of cooling water systems and problems they face like corrosion, scaling, fouling and microbial growth. Factors affecting these problems and methods to control them using inhibitors, dispersants and chemical treatment programs are explained.

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    Introduction To Cooling Water Treatment

    Uploaded by

    somani
    40 views40 pages
    This document discusses cooling water treatment. It introduces important water parameters for cooling water like pH, hardness, chlorides and dissolved gases. It describes types of cooling water systems and problems they face like corrosion, scaling, fouling and microbial growth. Factors affecting these problems and methods to control them using inhibitors, dispersants and chemical treatment programs are explained.

    Original Description:

    Cooling Water Treatment

    Original Title

    Cooling Water Treatment

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    This document discusses cooling water treatment. It introduces important water parameters for cooling water like pH, hardness, chlorides and dissolved gases. It describes types of cooling water systems and problems they face like corrosion, scaling, fouling and microbial growth. Factors affecting these problems and methods to control them using inhibitors, dispersants and chemical treatment programs are explained.

    Copyright:

    © All Rights Reserved
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    40 views40 pages

    Introduction To Cooling Water Treatment

    Uploaded by

    somani
    This document discusses cooling water treatment. It introduces important water parameters for cooling water like pH, hardness, chlorides and dissolved gases. It describes types of cooling water systems and problems they face like corrosion, scaling, fouling and microbial growth. Factors affecting these problems and methods to control them using inhibitors, dispersants and chemical treatment programs are explained.

    Copyright:

    © All Rights Reserved
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    of 40

    Introduction to

    COOLING WATER TREATMENT


    Important Water Parameters

    pH
    Hardness
    Chlorides
    Silica
    Metal ions
    Turbidity
    Conductivity / TDS
    Alkalinity
    Phosphates
    Oil & Organics
    Dissolved gases
    Indices commonly used

    Langelier Saturation Index (LSI)

    Ryznar Stability Index (RSI)

    Puckorius – Practical Scaling Index (PSI)

    Larson & Skold index (LI)


    Cooling Water Systems – Types:

    Once Through systems

    Closed Systems

    Open Recirculatory Systems


    Open Recirculatory System
    Evaporation Return Header

    Drift

    HE
    S
    S
    Makeup HE
    F

    Basin / Sump
    Blowdown

    Basin Drain
    Cooling Water Systems - Problems
    Corrosion

    Scaling Fouling

    Microbial Growth
    CORROSION
    CORROSION

    Corrosion is an electrochemical

    phenomenon

    by which a metal reverts to its natural

    state.
    CORROSION CELL
    O O
    OH

    Fe OH

    Oxidizes O O
    OH

    Fe OH

    OH
    OH-
    Fe++ OH- O O
    Fe2O3
    e-
    RUSTFe e-
    Anode Cathode
    CORROSION FACTORS AFFECTING
    REQUIRES CORROSION

    pH
    Anode
    Oxygen & Dissolved gases
    Cathode Dissolved & Suspended solids

    Electrolyte Velocity

    Temperature
    Electron flow
    Microbial Growth
    EFFECT OF pH ON CORROSION RATE
    CORROSION
    RATE

    4 10
    pH
    SCALING
    What happens when water

    Evaporates…………….
    + -
    + - + -

    + - + -
    + - + -
    + - + -
    + - + -
    + - + -
    + - + - + -
    + - + - + -
    + - + - + -
    SCALING :

    Precipitation of the water soluble


    salts once their saturation levels are
    exceeded.
    Common Scales

    Calcium Carbonate

    Calcium Sulphate

    Silicate

    Magnesium salts

    Calcium orthophosphate

    Iron salts
    Factors affecting Scaling:

    • pH
    • Temperature
    • Alkalinity
    • Solubility
    • Velocity
    MINERAL SCALES
    Temperature - Major Impact on Solubility

    SOLUBILITY

    TEMPERATURE
    EFFECT OF SCALE ON HEAT TRANSFER
    % Reduction in U-Coefficient
    100
    SiO2
    90
    80 Clay (Kaolin)
    70
    60 CaSO4
    50
    40 CaCO3
    30
    20
    10 Al2 O3
    0
    0.001 0.010 0.100
    Scale Thickness (inches)
    FOULING
    FOULING:

    Air Borne Water Borne

    Under deposit
    corrosion

    Choking of tubes > Microbial growth


    Blockage of water passage Induces Scaling
    & Corrosion
    Common Foulants

    Dirt and Silt

    Sand

    Corrosion Products

    Natural organics

    Microbial matter
    Factors Affecting Fouling:

    Suspended solids
    Turbidity
    Temperature
    Velocity
    Oils
    Microbial Slime
    Corrosion products
    CORROSION INHIBITION
    Corrosion Inhibition

    Gen. Inh
    Cathodic Inh Anodic Inh

    Cathode No Electron Migration Anode


    MAIN CORROSION INHIBITORS

    Orthophosphates
    Organophosphonates
    Polyphosphates
    Nitrites / Nitrates
    Silicates
    Zinc
    Molybdates
    Azoles

    USE INHIBITORS SYNERGESTICALLY


    PRETREAT & PASSIVATE
    SCALE & FOULING
    CONTROL
    SCALING & FOULING CONTROL

    Limit Cycles of Concentration

    Soften the Makeup water

    Acid feed to maintain pH

    Higher velocities

    Use Chemical Inhibitors


    Scale Control Mechanism

    Threshold inhibition

    Crystal Distortion
    Crystal Modification

    R
    R P O
    R
    P O
    O O P O
    O O
    O O
    COMMON ANTISCALANTS

    Organophosphonates

    Polyphosphates

    Low molecular weight anionic polymers


    DISPERSION
    - - - -
    -

    scale scale
    scale
    scale
    DISPERSION

    Repulsion
    scale scale

    Dispersants adsorb onto particles. This


    creates highly charged surfaces, which repel
    each other.
    Polymers – Main Functions

    Particulate matter dispersion

    Inorganic phosphate control

    Iron fouling control

    Crystal modifications

    Scale control
    MICROBIAL CONTROL
    CHEMICAL TREATMENT PROGRAMMES
    Program Targets:

    Corrosion Control : < 2 mpy : Long eqpmt.life


    Scale Control : < 15mg/dm2/day:Efficient heat tfr
    TVC : <1,00,000 org./ml : min.slime,biofilm
    SRB : < 25/100ml : No pitting
    NRB : Min.causing no pH drop:No alkali addition
    COC : highest possible : Water & Ecological
    conservation
    Sustained & efficient operations for long
    duration

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