nalco cooling tower presentation

Nalco CompanyCooling Water Presentation 6-24-04

Stress Management for Cooling Systems

TVWD Cooling Tower TVWD Cooling Tower Seminar and WorkshopSeminar and Workshop

November 29, 2005November 29, 2005

AgendaAgenda

IntroductionIntroductionFundamentals of Cooling WaterFundamentals of Cooling WaterCooling System Problems (Stresses)Cooling System Problems (Stresses)Treatment ProgramsTreatment ProgramsThe Engineering ApproachThe Engineering ApproachMicrobiological Control and Microbiological Control and MonitoringMonitoringStress ManagementStress Management

The purpose of cooling The purpose of cooling systems is to transfer systems is to transfer heat from one substance heat from one substance to anotherto anotherThe substance that The substance that gives up its heat is gives up its heat is ““cooledcooled””The substance that The substance that receives the heat is the receives the heat is the ““coolantcoolant””

THE COOLING PROCESS

Open Recirculating SystemsOpen Recirculating Systems

Open recirculating systems are open to the atmosphere Open recirculating systems are open to the atmosphere at the tower. As the water flows over the tower, heat at the tower. As the water flows over the tower, heat picked up by the process is released by evaporation. picked up by the process is released by evaporation.

The cooling water then returns to the heat exchangers The cooling water then returns to the heat exchangers to pick up more heat.to pick up more heat.

Open Recirculating SystemOpen Recirculating SystemMakeupWater

Pump

Blowdown

EXAMPLESSpray PondsCooling TowersEvaporative Condensers

CHARACTERISTICSAvg. Temp. Change: 20-30°F [11.1-16.7°C]Amount of Water Used: Moderate

Heat Exchanger

Cooling Tower


Heat TransferHeat TransferProcess in which heat Process in which heat is transferred from is transferred from one substance to one substance to another.another.

EvaporationEvaporationProcess by which Process by which the hot cooling the hot cooling water releases its water releases its heat to the heat to the atmosphere so atmosphere so that it can return that it can return cool water back to cool water back to the heat the heat exchangersexchangers


A cooling tower provides two conditions A cooling tower provides two conditions that enhance the evaporation process...that enhance the evaporation process...

Break water into tiny droplets, thus Break water into tiny droplets, thus providing more escape routes for water providing more escape routes for water molecules to evaporate.molecules to evaporate.Fans provide rapid flow of air through Fans provide rapid flow of air through the tower which removes evaporated the tower which removes evaporated water molecules and allows even more to water molecules and allows even more to escape.escape.

Why Use Water for Cooling?Why Use Water for Cooling?

Plentiful; Readily Available; CheapPlentiful; Readily Available; CheapEasily Handled: Easily Handled: PumpablePumpableCan carry large amounts of heatCan carry large amounts of heatDoes not expand/contract much at Does not expand/contract much at normally encountered temperaturesnormally encountered temperaturesDoes not decomposeDoes not decompose

Why Use Water for Cooling?Why Use Water for Cooling?

Specific Heat: Measure of how well Specific Heat: Measure of how well a substance absorbs heata substance absorbs heatWater can absorb more heat than Water can absorb more heat than virtually any other substance that virtually any other substance that would be considered for industrial would be considered for industrial coolingcoolingMinor increases in temperatureMinor increases in temperatureMinimal environmental impactMinimal environmental impact

Why IsnWhy Isn’’t Water Perfect for t Water Perfect for Cooling?Cooling?

Dissolves everything it touches: Dissolves everything it touches: Metal; earth; stone; gassesMetal; earth; stone; gassesUnique dissolving ability has earned Unique dissolving ability has earned water the title...water the title...

Two Sources of WaterTwo Sources of WaterSurface WaterSurface Water

Low in dissolved solidsLow in dissolved solidsHigh in suspended solidsHigh in suspended solidsQuality changes quickly with seasons & weatherQuality changes quickly with seasons & weather

Ground WaterGround WaterHigh in dissolved solidsHigh in dissolved solidsLow in suspended solidsLow in suspended solidsHigh in iron & manganeseHigh in iron & manganeseLow in oxygen, may contain sulfide gasLow in oxygen, may contain sulfide gasRelatively constant quality & temperatureRelatively constant quality & temperature

What Chemical Properties of What Chemical Properties of Water Are Important?Water Are Important?

Important Properties of WaterImportant Properties of Water

1. Conductivity1. Conductivity2. Hardness2. Hardness3. Alkalinity3. Alkalinity4. pH4. pH5. Silica 5. Silica 6. Other impurities6. Other impurities

---- Iron, Manganese,Iron, Manganese,Chlorides, Phosphate, etc.Chlorides, Phosphate, etc.

EvaporationEvaporation

Each 10Each 10°°F [6F [6°°C] drop in temperature results C] drop in temperature results in an avg. 0.85% evaporation of in an avg. 0.85% evaporation of

recirculated cooling waterrecirculated cooling waterER = (RR)*(dT/10)*(.0085)ER = (RR)*(dT/10)*(.0085)

WhereWhere::ER: Evaporation Rate [gpm]ER: Evaporation Rate [gpm]RR:RR: Recirculation Rate [gpm]Recirculation Rate [gpm]dT:dT: Temp drop across tower [DegF]Temp drop across tower [DegF]

Concentration of Dissolved Concentration of Dissolved SolidsSolids

Only pure water can evaporateOnly pure water can evaporate–– Excluding volatile chemicals Excluding volatile chemicals

like bleachlike bleachNo dissolved solids leave the No dissolved solids leave the liquid waterliquid waterIf there are no other water If there are no other water losses from the system, the losses from the system, the evaporation process causes an evaporation process causes an increase in the concentration increase in the concentration of dissolved solids in the of dissolved solids in the recirculating cooling water.recirculating cooling water.

6

1

32

54

ConstantEvaporation

Concentration of Dissolved Concentration of Dissolved SolidsSolids

Mineral scale will form if the Mineral scale will form if the dissolved solids concentration in the dissolved solids concentration in the cooling water becomes too highcooling water becomes too highSupersaturationSupersaturation

Impact of Blowdown onImpact of Blowdown onConcentration RatioConcentration Ratio

Blowdown:Blowdown:Deliberate Deliberate discharge of discharge of water to prevent water to prevent the dissolved the dissolved solids from solids from getting to highgetting to high

6

1

32

54

Constant Evaporation

6

32

54

Constant Evaporation

1

WithZeroBlowdown

With Continuous BlowdownMaintaining 4 Cycles

Makeup WaterMakeup Water

Amount of water Amount of water required to required to replace water lost replace water lost by evaporation by evaporation and blowdownand blowdown

Evaporation

Makeup

Blowdown

Makeup = Evaporation +

Blowdown

Concentration RatioConcentration Ratio

CR = Make-up Flow

Blowdown Flow

MU = Evaporation xCR

(CR – 1)

COMMON COOLINGCOMMON COOLINGSYSTEM PROBLEMSSYSTEM PROBLEMS

CORROSION

MICROBIO

FOULINGSCAL

E

Cooling System ProblemsCooling System Problems

Left unchecked these Left unchecked these problems causeproblems cause

Loss of heat transferLoss of heat transferReduced equipment Reduced equipment lifelifeEquipment failuresEquipment failuresLost productionLost productionLost profitsLost profitsIncreased Increased maintenance costsmaintenance costsPlant shutdownPlant shutdown

MINERAL SCALEMINERAL SCALE

Mineral ScaleMineral Scale

Cooling Water contains many Cooling Water contains many different minerals different minerals ---- normally these normally these minerals are dissolved in the waterminerals are dissolved in the waterUnder certain conditions minerals Under certain conditions minerals can come out of solution and form can come out of solution and form into hard, dense crystals called into hard, dense crystals called SCALESCALE

Scaled Heat Exchanger Tubes


Common ScalesCommon ScalesCalcium CarbonateCalcium CarbonateMagnesium SilicateMagnesium SilicateCalcium PhosphateCalcium PhosphateCalcium SulfateCalcium SulfateIron OxideIron OxideIron PhosphateIron PhosphateOthers...Others...

CaPO4

CaCO3


The Following Factors AffectThe Following Factors AffectScale Formation...Scale Formation...

Mineral ConcentrationMineral ConcentrationWater TemperatureWater TemperatureWater pHWater pHSuspended SolidsSuspended SolidsWater Flow VelocityWater Flow Velocity


Scale usually forms in hot areas of Scale usually forms in hot areas of cooling systemscooling systemsReduces heat transfer efficiencyReduces heat transfer efficiencyMechanical/Chemical cleaningMechanical/Chemical cleaningUnder deposit corrosion (pitting)Under deposit corrosion (pitting)Plant shutdownPlant shutdownEquipment replacementEquipment replacement

Preventing Mineral ScalePreventing Mineral Scale

Limit concentration of scale forming Limit concentration of scale forming minerals: Blowdown, clarify/filter MUminerals: Blowdown, clarify/filter MUFeed acid to reduce pH & alkalinity: Feed acid to reduce pH & alkalinity: Reduces scaling Reduces scaling ---- increases corrosionincreases corrosionMechanical design changes: Increase HX Mechanical design changes: Increase HX water velocity, water velocity, backflushbackflush, air rumble , air rumble Apply chemical scale inhibitorsApply chemical scale inhibitors

Mineral ScaleMineral ScaleThree Classifications Of ScaleThree Classifications Of Scale

Inhibiting Chemicals AreInhibiting Chemicals Are……

Crystal ModifiersCrystal Modifiers–– Prevent scale from Prevent scale from ““laying downlaying down””

SequestrantsSequestrants–– Prevent scale from agglomeratingPrevent scale from agglomerating

DispersantsDispersants–– Affect mineral charge so that scale Affect mineral charge so that scale

formers repel each otherformers repel each other

Normal OperationsNormal Operations

Parameters 7.6 7.9 8.1 8.4 8.7 8.9 9.2Calcite 0.4 1.3 3.9 10.9 29 68 96 pHTricalcium Phosphate 1 1 1 1 1 1 1 Temp 120Magnesium Silicate 0.1 0.3 1 3.2 10 28 72 PO4 2Silica 0.6 0.6 0.55 0.53 0.5 0.44 0.36 Cycles 8

Comments:

Parameters 6 7 8 9 10 11 12Calcite 6 6.5 7 7.4 7.7 8 8.3 pH 8.3Tricalcium Phosphate 1 1 1 1 1 1 1 Temp 120Magnesium Silicate 1.3 1.6 2.1 2.5 3 3.5 0.8 PO4 2Silica 0.4 0.5 0.55 0.6 0.7 0.75 0.8 Cycles

Constants

Impact of pHConstants

Impact of Cycles

PGE Beaver Condenser Scale AnalysisPGE Beaver Condenser Scale Analysis

Calcium Carbonate ScaleCalcium Carbonate Scale

High Silica, Minimum BlowdownHigh Silica, Minimum Blowdown

Parameters 7.6 7.9 8.1 8.4 8.7 8.9 9.2Calcite 0.67 1.9 5.5 15 38 89 187 pHTricalcium Phosphate 1 1 1 1 1 11 1 Temp 120Magnesium Silicate 0.2 0.8 2.8 9 28 81 203 PO4 2Silica 1.08 1.07 1.05 1 0.9 0.8 0.7 Cycles 15

Comments: 15 cycles, 230 PPM Silica

Parameters 7.6 7.9 8.1 8.4 8.7 8.9 9.2Calcite 0.4 1 3 9 24 60 136 pHTricalcium Phosphate 1 1 1 1 1 11 1 Temp 80Magnesium Silicate 0.1 0.1 0.3 1.1 3.6 11 31 PO4 2Silica 1.8 1.8 1.8 1.78 1.73 1.64 1.5 Cycles 15

Comments: 15 cycles, 230 PPM Silica

Impact of pH and High SilicaConstants

Impact of pH and High SilicaConstants

CORROSIONCORROSION

CORROSIONCORROSION

Corrosion is the mechanism by which metals Corrosion is the mechanism by which metals are reverted back toare reverted back to

their their naturalnatural ““oxidizedoxidized”” statestate

Battery AnalogyBattery AnalogyAnodeAnodeCathodeCathodeElectrical CircuitElectrical CircuitMetal lost at anodeMetal lost at anode

CorrosionCorrosion

e -

Electrolyte

Ano

de

Cat

hode

Simplified Corrosion CellSimplified Corrosion Cell

Fe 2+

CATHODE

ANODE

O2

OH-

e-

STEP 1

STEP 2

STEP 3

STEP 4

Water withDissolvedMinerals

Base Metal

O2

e-e- e-

Four Step Corrosion ModelFour Step Corrosion Model

Step 1Step 1: At the anode, pure iron begins to break : At the anode, pure iron begins to break down in contact with the cooling water. This down in contact with the cooling water. This step leaves behind electrons.step leaves behind electrons.Step 2Step 2: Electrons travel through the metal to the : Electrons travel through the metal to the cathode.cathode.Step 3Step 3: At the cathode, a chemical reaction : At the cathode, a chemical reaction occurs between the electrons and oxygen carried occurs between the electrons and oxygen carried by the cooling water. This reaction forms by the cooling water. This reaction forms hydroxide.hydroxide.Step 4Step 4: Dissolved minerals in the cooling water : Dissolved minerals in the cooling water complete the electrochemical circuit back to the complete the electrochemical circuit back to the anode.anode.

Factors Influencing CorrosionFactors Influencing Corrosion

pHpHTemperatureTemperatureDissolved SolidsDissolved SolidsSystem DepositsSystem DepositsWater VelocityWater VelocityMicrobiological GrowthMicrobiological Growth

100

10

05 6 7 8 9 10

Cor

rosi

on R

ate,

Rel

ativ

e U

nits

pH

Corrosion Vs. pHCorrosion Vs. pH

Corrosion Vs. TemperatureCorrosion Vs. Temperature

Corrosion Rate

Tem

pera

ture

In general, for every 18°F in water temperature, chemical reaction rates double.

Other Causes of CorrosionOther Causes of Corrosion

System DepositsSystem Deposits•• Anodic pitting sites develop under depositsAnodic pitting sites develop under deposits

Water VelocityWater Velocity•• Too low = depositsToo low = deposits•• Too high = ErosionToo high = Erosion

Microbiological GrowthMicrobiological Growth•• Deposits; Produce corrosive byDeposits; Produce corrosive by--productsproducts

Types of CorrosionTypes of Corrosion

All cooling system metallurgy experiences some All cooling system metallurgy experiences some degree of corrosion. The objective is to control degree of corrosion. The objective is to control the corrosion well enough to maximize the life the corrosion well enough to maximize the life

expectancy of the system...expectancy of the system...

1. General Corrosion1. General Corrosion2. Localized Pitting Corrosion2. Localized Pitting Corrosion3. Galvanic Corrosion3. Galvanic Corrosion

Base Metal

General Etch Uniform Attack

Water

Original

Thickness

General CorrosionGeneral Corrosion

Preferred situationPreferred situationTake a small Take a small amount of metal amount of metal evenly throughout evenly throughout the systemthe systemAnode very largeAnode very large

Base Metal

Localized Pitting Attack

WaterOriginal

Thickness

Pitting CorrosionPitting Corrosion

Metal removed at Metal removed at same rate but from a same rate but from a much smaller areamuch smaller areaAnode very smallAnode very smallOften occurs under Often occurs under deposits or weak deposits or weak pointspointsLeads to rapid metal Leads to rapid metal failurefailure

Galvanic CorrosionGalvanic CorrosionActive End

Passive End

MagnesiumGalvanized SteelMild SteelCast Iron18-8 Stainless Steel Type 304 (Active)18-12-3 Stainless Type 316 (Active)Lead TinMuntz SteelNickel (Active)76-Ni-16 Cr-7 Fe Alloy (Active)BrassCopper70:30 Cupro Nickel67-Ni-33 Cu Alloy (Monel)Titanium18-8 Stainless Steel Typ 304 (Passive)18-12-3 Stainless Steel Type 316 (Passive)GraphiteGoldPlatinum

Occurs when two Occurs when two different metals different metals are in the same are in the same systemsystemMore reactive More reactive metal will corrode metal will corrode in presence of less in presence of less reactive metalreactive metalPotential for Potential for galvanic corrosion galvanic corrosion increases with increases with increasing distance increasing distance on charton chart

Affects of CorrosionAffects of Corrosion

Destroys cooling system metalDestroys cooling system metalCorrosion product deposits in heat exchangersCorrosion product deposits in heat exchangersHeat transfer efficiency is reduced by depositsHeat transfer efficiency is reduced by depositsLeaks in equipment developLeaks in equipment developProcess side and water side contamination Process side and water side contamination occursoccursWater usage increasesWater usage increasesMaintenance and cleaning frequency increasesMaintenance and cleaning frequency increasesEquipment must be repaired and/or repairedEquipment must be repaired and/or repairedUnscheduled shutdown of plantUnscheduled shutdown of plant

Methods To Control CorrosionMethods To Control Corrosion

Use corrosion resistant alloys: $Use corrosion resistant alloys: $Adjust (increase) system pH: ScaleAdjust (increase) system pH: ScaleApply protective coatings: IntegrityApply protective coatings: IntegrityUse Use ““sacrificial anodessacrificial anodes””: Zn/Mg: Zn/MgApply chemical corrosionApply chemical corrosioninhibitorsinhibitors

Anodic Corrosion InhibitorsAnodic Corrosion Inhibitors

Stop corrosion Stop corrosion cell by blocking cell by blocking the anodic sitethe anodic siteSevere localized Severe localized pitting attack can pitting attack can occur at an occur at an unprotected unprotected anodic sites if anodic sites if insufficient insufficient inhibitor is inhibitor is presentpresent

Anodic InhibitorsAnodic InhibitorsChromatesChromatesNitritesNitritesOrthophosphatesOrthophosphatesSilicatesSilicatesMolybdatesMolybdates

Cathodic Corrosion InhibitorsCathodic Corrosion Inhibitors

Stop corrosion cell Stop corrosion cell by blocking the by blocking the electrochemical electrochemical reaction at the reaction at the cathodecathodeCorrosion rate is Corrosion rate is reduced in direct reduced in direct proportion to the proportion to the reduction in the size reduction in the size of the cathodic area.of the cathodic area.

Cathodic InhibitorsCathodic InhibitorsBicarbonatesBicarbonatesPolyphosphatesPolyphosphatesPolysilicatesPolysilicatesZincZincPSOPSO

General Corrosion InhibitorsGeneral Corrosion Inhibitors

Protect metal by Protect metal by filming all filming all surfaces whether surfaces whether they are anodic or they are anodic or cathodiccathodic

General InhibitorsGeneral InhibitorsSoluble OilsSoluble OilsTolyltriazolesTolyltriazolesBenzotriazolesBenzotriazoles

Nalco Corrosion MonitorNalco Corrosion Monitor

Linear Polarization Resistance (LPR)Linear Polarization Resistance (LPR)Effective in Low Conductivity Waters Effective in Low Conductivity Waters ––Soft Water, CondensateSoft Water, CondensateProbes and Tips are one unitProbes and Tips are one unitBattery PoweredBattery PoweredInternal Data Logger Internal Data Logger –– PDA/Computer PDA/Computer Down LoadDown LoadInexpensiveInexpensive

Unit 2 NCM 100 Data

0.00

0.50

1.00

1.50

2.00

2.50

4-Sep 6-Sep 8-Sep 10-Sep 12-Sep 14-Sep 16-Sep 18-Sep 20-Sep

Date

M P

Y

Start Trial

Chlorine Shock Normal Operations

Startup

Unit 2 Circ Water Corrosion Rates

9/6/03 to 9/17/03

Unit Shutdown

FOULINGFOULING

FoulingFouling

FOULING is the accumulation of solid FOULING is the accumulation of solid material, other than scale, in a way that material, other than scale, in a way that hampers the operation of equipment or hampers the operation of equipment or

contributes to its deteriorationcontributes to its deterioration

Common FoulantsCommon FoulantsSuspended SolidsSuspended Solids

Silt, Sand, Mud and IronSilt, Sand, Mud and IronDirt & DustDirt & DustProcess contaminants, e.g. OilsProcess contaminants, e.g. OilsCorrosion ProductsCorrosion ProductsMicrobio growthMicrobio growthCarryover (clarifier/lime softener)Carryover (clarifier/lime softener)

Water CharacteristicsWater CharacteristicsWater TemperatureWater TemperatureWater Flow VelocityWater Flow VelocityMicrobio GrowthMicrobio GrowthCorrosionCorrosionProcess LeaksProcess Leaks

Factors Influencing FoulingFactors Influencing Fouling

Affects of FoulingAffects of Fouling

Foulants form deposits in hot and/or low Foulants form deposits in hot and/or low flow areas of cooling systemsflow areas of cooling systemsShellShell--side heat exchangers are the most side heat exchangers are the most vulnerable to foulingvulnerable to foulingDeposits ideal for localized pitting Deposits ideal for localized pitting corrosioncorrosionCorrosive bacteria thrive under depositsCorrosive bacteria thrive under depositsMetal failure resultsMetal failure results

Economic Impact of FoulingEconomic Impact of Fouling

Decreased plant efficiencyDecreased plant efficiencyReduction in productivityReduction in productivityProduction schedule delaysProduction schedule delaysIncreased downtime for maintenanceIncreased downtime for maintenanceCost of equipment repair or replacementCost of equipment repair or replacementReduced effectiveness ofReduced effectiveness ofchemical inhibitorschemical inhibitors

FoulingFouling

Three Levels Of Attack Can Be Three Levels Of Attack Can Be Employed To Address The Effects Employed To Address The Effects

Of Fouling...Of Fouling...

1. Prevention1. Prevention2. Reduction2. Reduction3. Ongoing Control3. Ongoing Control

Preventing FoulingPreventing Fouling

PreventionPreventionGood control of makeup qualityGood control of makeup qualityGood control of corrosion, scale, & microbioGood control of corrosion, scale, & microbio

ReductionReductionIncrease blowdownIncrease blowdownSidestream filterSidestream filter

Ongoing ControlOngoing ControlBackflushing, Air rumbling, Clean tower basinBackflushing, Air rumbling, Clean tower basinChemical treatmentChemical treatment

Preventing FoulingPreventing Fouling

PreventionPreventionHigh Efficiency Multimedia FiltersHigh Efficiency Multimedia Filters–– Capable of 80% removal of 0.5 micronCapable of 80% removal of 0.5 micron–– Typical multimedia depth filters capable of Typical multimedia depth filters capable of

80% removal only down to 10 micron80% removal only down to 10 micron–– Most (greater than 90%) of particles found in Most (greater than 90%) of particles found in

a cooling tower are less than 10 microna cooling tower are less than 10 micron

Do not overlook Do not overlook sidestream sidestream filtration and filtration and choose wisely!choose wisely!

FoulingFoulingChemical TreatmentChemical Treatment

Charge Charge ReinforcersReinforcers–– Anionic polymers increase strength of Anionic polymers increase strength of

charge already present on suspended charge already present on suspended solidssolids

–– Keep particles small enough so they Keep particles small enough so they do not settle outdo not settle out

Wetting AgentsWetting Agents–– SurfactantsSurfactants–– Penetrate existing depositsPenetrate existing deposits–– Wash away from metal surfacesWash away from metal surfaces

MICROBIOLOGICALMICROBIOLOGICALGROWTHGROWTH

Microbiological GrowthMicrobiological Growth

Water treatment is Water treatment is about managing about managing three fouling three fouling processes...processes...CorrosionCorrosionScaleScaleMicrobioMicrobio

The microbial fouling The microbial fouling process is...process is...

The most complexThe most complexThe least understoodThe least understoodThe hardest to The hardest to measure and monitormeasure and monitorControlled using the Controlled using the least desirable, most least desirable, most expensive, & expensive, & potentially hazardous potentially hazardous productsproducts


Three Kinds Of Troublesome Three Kinds Of Troublesome Microorganisms In Cooling Water...Microorganisms In Cooling Water...

1. Bacteria1. Bacteria2. Algae2. Algae3. Fungi/Mold/Yeast3. Fungi/Mold/Yeast

BacteriaBacteria

Sears Tower

Bacteria extremely Bacteria extremely smallsmallCompared to a Compared to a human, a bacteria is human, a bacteria is like a grain of sand to like a grain of sand to the Sears Towerthe Sears TowerSize allows many Size allows many (millions) to fit into a (millions) to fit into a small volume of small volume of water...water...

BacteriaBacteria

There are as many There are as many bacteria in 12 oz. of bacteria in 12 oz. of cooling water as cooling water as there are people there are people living in the United living in the United StatesStatesThere are 40,000 There are 40,000 times as many times as many bacteria in a 50,000 bacteria in a 50,000 gallon cooling gallon cooling system as there are system as there are people in the world!people in the world!

12oz.Cooling Water

40,000 X50MGAL

Cooling System

BacteriaBacteria

Types of BacteriaTypes of Bacteria1. Slime Forming1. Slime Forming2. Anaerobic Corrosive2. Anaerobic Corrosive3. Iron Depositing3. Iron Depositing4. Nitrifying4. Nitrifying5. Denitrifying5. Denitrifying

BacteriaBacteria

Slime Formers

Iron DepositingAnaerobic

Typical Rods

BacteriaBacteria

Produce acidic waste that lowers pH andProduce acidic waste that lowers pH andcauses corrosioncauses corrosionProduce large volumes of iron deposits Produce large volumes of iron deposits that foulthat foulProduce acids from ammonia that Produce acids from ammonia that increase corrosion & lower pHincrease corrosion & lower pHForm sticky slime masses that foul & Form sticky slime masses that foul & cause reduced heat transfercause reduced heat transfer

Two Classifications of BacteriaTwo Classifications of Bacteria

PlanktonicPlanktonic::FreeFree--floating bacteria in bulk waterfloating bacteria in bulk water

SessileSessile::Bacteria attached to surfacesBacteria attached to surfacesOver 95% of bacteria in a cooling system Over 95% of bacteria in a cooling system are sessile and live in BIOFILMSare sessile and live in BIOFILMS

BiofilmsBiofilms

Contribute to all Contribute to all cooling water cooling water problemsproblemsUnderdeposit Underdeposit corrosioncorrosionTrap silt & debris Trap silt & debris which foul heat which foul heat exchangers and exchangers and tower filltower fillProvide nucleation Provide nucleation sites for scale sites for scale formationformation Biofilm Formation

FLOW

ThermalFoulant Conductivity

CaCO3 1.3-1.7CaSO4 1.3CaPO4 1.5MgPO4 1.3Fe Oxide 1.7Biofilm 0.4

P P

Common biofilms are 4 times more insulating than CaCO3 scale!

BiofilmsBiofilms

More insulating More insulating than most than most common scales common scales Reduce heat Reduce heat transfer efficiencytransfer efficiencyIncrease dP across Increase dP across heat exchangers & heat exchangers & reduce flowreduce flowHealth risks Health risks (legionella)(legionella)

AlgaeAlgae

Require sunlight to growRequire sunlight to growFound on tower decks & exposed areasFound on tower decks & exposed areasForm Form ““algae matsalgae mats””Plug distribution holes on tower decksPlug distribution holes on tower decksPlug screens/foul equipmentPlug screens/foul equipmentConsume oxidantsConsume oxidantsProvide food for other organismsProvide food for other organisms

FungiFungi

Use carbon in Use carbon in wood fibers for wood fibers for foodfoodDestroy tower Destroy tower lumber by either lumber by either surface or internal surface or internal rotting (deep rot) rotting (deep rot) Loss of structural Loss of structural integrity of towerintegrity of tower

Factors Affecting Growth of Factors Affecting Growth of MicroorganismsMicroorganisms

Microorganism Sources: Air or Makeup Microorganism Sources: Air or Makeup waterwater

Cooling systems provide the ideal Cooling systems provide the ideal environment for microbiological growth environment for microbiological growth –– Nutrients: Ammonia, oil, organic Nutrients: Ammonia, oil, organic

contaminantscontaminants–– Temperature: 70Temperature: 70--140140°°F acceptableF acceptable–– pH: 6.0 pH: 6.0 -- 9.0 ideal9.0 ideal–– Location: Light/No LightLocation: Light/No Light–– Atmosphere: Aerobic/AnaerobicAtmosphere: Aerobic/Anaerobic

Controlling Microbiological Controlling Microbiological GrowthGrowth

Water QualityWater Quality–– Eliminate organic contaminants (food)Eliminate organic contaminants (food)–– No food = No bugsNo food = No bugs

»» Bugs are Bugs are carniverous carniverous –– A forest feeds A forest feeds itselfitself

System Design ConsiderationsSystem Design Considerations–– Clean tower and sumps, cover decksClean tower and sumps, cover decks

Chemical Treatment with BiocidesChemical Treatment with Biocides


Chemical Treatment With BiocidesChemical Treatment With Biocides

Oxidizing BiocidesOxidizing BiocidesNonNon--oxidizing Biocidesoxidizing BiocidesBiodispersantsBiodispersants

What About Dipslides?What About Dipslides?

Simple, quick, and inexpensive.

However, only gives bacteria levels from the bulk water.

There is more to this picture!

Monitoring Tools for Monitoring Tools for Planktonic Microorganisms Planktonic Microorganisms

-- DipslidesDipslidesDipslides only measure selected Dipslides only measure selected aerobic planktonic microorganismsaerobic planktonic microorganisms

Total aerobic bacterial counts Total aerobic bacterial counts determined from dipslides are useful determined from dipslides are useful for tracking for tracking trendstrends

Aerobic Plate CountsAerobic Plate Counts

Microbiological MonitoringMicrobiological Monitoring

Sessile Monitoring

Tracide, ATP

Bio Box

DIVERSITYDIVERSITYof different kinds….

the state of being unlike or different

refers to the KINDS of microorganisms present

Differential Microbiological Differential Microbiological Analysis (DMA)Analysis (DMA)

Testing designed to differentiate the microbiological content within a system.

From: Analysis No. MB 207310 ABC Plant Date Sampled 9/ 9/97 Date Received 9/10/97 Date Completed 9/15/97 Sample Marked: Date Printed 9/15/97 Cooler Outlet

>>> Microbiological Evaluation <<<

PHYSICAL APPEARANCE Liquid with Floc

TOTAL AEROBIC BACTERIA 4,000 Enterobacter <100 Pigmented <100 Mucoids <100 Pseudomonas <100

Spores <10

TOTAL ANAEROBIC BACTERIA Sulfate Reducers 2

Clostridia <10

TOTAL FUNGI Yeasts <10 Molds 20

IRON-DEPOSITING Gallionella None Sphaerotilus None

ALGAE Filamentous None Nonfilamentous None

OTHER ORGANISMS None

Lab Comments: All counts express colony forming units per ml.

Microscopic examination: few crystals and very few diatoms.

The goal in microbial fouling control ...

is almost never to “sterilize” the system, but rather,

...it is to MANAGE the fouling control process to a level that causes no operational problems

How do I measure How do I measure biofilms?biofilms?

Sessile monitoring is an Sessile monitoring is an integral part of the microbial integral part of the microbial

monitoring programmonitoring program

Planktonic results have a weak Planktonic results have a weak correlation to the sessile populationcorrelation to the sessile population

The sessile population, or biofilms, are The sessile population, or biofilms, are the true microbial control targetthe true microbial control target

Surface Microbial Surface Microbial Monitoring Test Kit Monitoring Test Kit

Surface Microbial Monitoring Test KitSurface Microbial Monitoring Test Kit–– Applied Services C0243Applied Services C0243–– SBIO is test codeSBIO is test codeKit contains supplies necessary to Kit contains supplies necessary to sample a surfacesample a surfaceMeasures microorganisms on surfaces, Measures microorganisms on surfaces, i.e., sessile populationi.e., sessile population

Monitoring Tools for Monitoring Tools for Sessile MicroorganismsSessile Microorganisms

Sessile MonitoringSessile MonitoringSwab

Coupon

SterileBuffer

BioBox Surface MicrobialTest Kit

Bio BoxBio Box

Visual indicatorVisual indicator

Removable Slides Removable Slides for Microscopic for Microscopic AnalysisAnalysis

• Planktonic counts don’t often correlate with sessile counts.

• Use microbial types, numbers, and locations as clues to current conditions, trends, and improvements.

• Be creative with sample point locations, timing with cleanup events, etc.. to provide powerful diagnostic information.

• Establish criteria for success

BioManageBioManageTMTM Best PracticesBest PracticesRecognizing The ProblemRecognizing The Problem

THANK YOU THANK YOU --

Any questions on Any questions on any topics we any topics we covered?covered?

Every system Every system …… under under stressstress

High Stress Causes:High Stress Causes:–– ScaleScale–– CorrosionCorrosion–– FoulingFouling

Low Stress CausesLow Stress Causes–– High water costsHigh water costs–– High energy costsHigh energy costs–– High chemical costsHigh chemical costs

Stress: varies by system Stress: varies by system operationoperation

High temperaturesHigh temperaturesLong holding time indices (Long holding time indices (HTIHTI’’ss))Biological/Organic contaminationBiological/Organic contamination–– Size, type and diversity of bioSize, type and diversity of bio--

populationspopulations

Low flow ratesLow flow ratesHigh oxidant concentrationsHigh oxidant concentrationsWater chemistryWater chemistry

Stress: varies by system Stress: varies by system designdesign

Erratic feed systemsErratic feed systemsProblematic equipmentProblematic equipment–– Blowdown valves, makeBlowdown valves, make--up up

systems, etc.systems, etc.

Monitoring problemsMonitoring problems–– How does the rest of your facility How does the rest of your facility

work?work?

System design limitationsSystem design limitationsSystem locationSystem location

Stress: varies by industryStress: varies by industry

Capacity limitationsCapacity limitationsAggressive water Aggressive water chemistrychemistry

Variable water Variable water chemistrychemistry

NutrientNutrient--rich rich environmentsenvironments

Regulatory NeedsRegulatory NeedsRegulatory NeedsRegulatory Needs

System System ContaminationContamination

Long Long HTIHTI’’ssEquipment often idle Equipment often idle for long periodsfor long periods

Food & BeverageFood & BeverageInstitutionalInstitutionalSemiconductorSemiconductor

Stress: varies by locationStress: varies by location

Texas City, TX

Morris, IL

San Diego, CA

El Segundo, CA

Houston, TX

Westchester, IL

Sandy, UT

Beaumont, TX

Phoenix, AZ

Rahway, NJ

Naperville, IL

Tiger Bay, FL

Sioux City, IAMartinez, CA

Variab

le Wate

r

Chemist

ry

Low Hardness

Low Alkalinity

High HardnessHigh Alkalinity

High TemperaturesVariable Water Chemistry

Critical SystemsVariable Water Chemistry

High water costGray water use

Environmental ConcernsHigh Bio-Activity

Minneapolis, MN

Texas City, TX

Morris, IL

San Diego, CA

El Segundo, CA

Houston, TX

Westchester, IL

Sandy, UT

Beaumont, TX

Phoenix, AZ

Rahway, NJ

Naperville, IL

Tiger Bay, FL

Sioux City, IAMartinez, CA

Variab

le Wate

r

Chemist

ry

Low Hardness

Low Alkalinity

High HardnessHigh Alkalinity

High TemperaturesVariable Water Chemistry

Critical SystemsVariable Water Chemistry

High water costGray water use

Environmental ConcernsHigh Bio-Activity

Minneapolis, MN

Stress: constantly varyingStress: constantly varying……

Control Based on System Stress

-

10

20

30

40

50

60

70

80

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89

Time (each interval = 4 hours)

Con

cent

ratio

n (p

pm)

Active Concentration (ppm)Treatment Concentration (ppm)

As system stress varies, 3D TRASAR adjusts dosage to compensate. At times of high stress, more inhibitor is fed. When stress decreases, less inhibitor is fed.

High Stress!Low Stress!

Stress: unpredictableStress: unpredictable

3D TRASAR Optimizes System Stress

-

200

400

600

800

1,000

1,200

1,400

1,600

1,800

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61

Time (Each Division = 4 hours)

Con

duct

ivity

3D TRASAR detects low stress and increases conductivity to minimize operating cost.

3D TRASAR detects high stress and decreases conductivity to prevent operational problems.

3D TRASAR detects low stress and increases the conductivity to minimize operating cost.

In this case, a bleach feed system failed. When the system was repaired at 10:50 PM, high concentrations of bleach were fed into the system, increasing system stress. 3D TRASAR detected the stress and decreased the conductivity to prevent an operational problem.

Stress: undiscoveredStress: undiscovered

-

100

200

300

400

500

600

700

800

900

1,000

Time (each division = 1 day)

OR

P (m

V)

-

0.5

1.0

1.5

2.0

2.5

3.0

Cop

per C

orro

sion

Rat

e (m

py)

ORP Copper

Before 3D Bio-Control, ORP-based control was erratic and copper corrosion rates were high.

After 3D Bio-Control was implemented, ORP levels were reduced, variability was reduced and copper corrosion rates improved.

3D Bio-Control Started

Stress: many sourcesStress: many sources

Average Daily Nalco Bio-Index

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

1-Ju

n

2-Ju

n

3-Ju

n

4-Ju

n

5-Ju

n

6-Ju

n

7-Ju

n

8-Ju

n

9-Ju

n

10-J

un

11-J

un

12-J

un

13-J

un

14-J

un

15-J

un

16-J

un

17-J

un

18-J

un

19-J

un

20-J

un

21-J

un

22-J

un

23-J

un

24-J

un

25-J

un

26-J

un

27-J

un

28-J

un

29-J

un

30-J

un

Date

Nal

co B

io-In

dex

Monday

Monday

Monday

Monday

Monday

Bio-activity stresses cooling systems.

Bringing idle equipment online increases system

stress.

Stress: requires dynamic Stress: requires dynamic responseresponse

June 16Nalco Bio-Index and Pump On Time

(5)

-

5

10

15

20

25

30

35

0:00 3:00 5:40 8:40 11:40 15:00 18:20 21:28

Time (Hours:Minutes)

Nal

co B

io-In

dex

-

1

2

3

4

5

Pum

p O

n (m

inut

es)

Pump On (minutes) Nalco Bio-Index

Nalco Bio-Index Set-Point

3D TRASAR detects a change in the bio-population and starts applying more oxidizing biocide to compensate.

When 3D TRASAR detects a change in the rate of bio-population increase, it responds by feeding less biocide, controlling the bio-population, but preventing a biocide overdose.

Stress: intermittentStress: intermittent

3.0

4.0

5.0

6.0

7.0

8.0

9.0

12:00 AM 12:00 PM 12:00 AM 12:00 PM 12:00 AM 12:00 PMDate/Time

pH

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Mild

Ste

el C

orro

sion

Rat

e (m

py)

pH MS Corrosion Rate

7:17 PM: acid upset causes pH to drop.

11:24 PM, pH returns to normal

In spite of extremely low pH, corrosion rate is unaffected.

Stress: interrelated causesStress: interrelated causes

1.80

1.85

1.90

1.95

2.00

2.05

2.10

2.15

2.20

2.25

2.30

Date (Each Division = 10 days)

Exch

ange

r Effi

cien

cy

Average Silica = 8 ppm


Prior to 3D TRASAR control, phosphate upsets put stress on the system which caused significant fouling. In this case, the overfeed caused a 14% efficiency loss.


Stress: interrelated causesStress: interrelated causes

1.80

1.85

1.90

1.95

2.00

2.05

2.10

2.15

2.20

2.25

2.30

Date (Each Division = 10 days)

Effic

ienc

y Fa

ctor


4


4

4Average Silica = 7 ppm

Even with a significant phosphate overfeed, efficiency loss due to fouling was only 3%.

Stress: unique to every Stress: unique to every systemsystem

Stress: highly visibleStress: highly visible

Manage

Stress

Grow Revenue

Control Costs

Reduce Cost of Capital

Manage Risks

Improve Cash Flow

improve product quality

extend time between turnarounds

reduce maintenance

decrease chemical usageavoid

equipment purchase

reduce legal exposure

reduce operating liability

minimize onsite inventory

fixed contract pricing

increase throughput

decrease energy usage

decrease water usage

extend equipment life

avoid EH&S fines

avoid unplanned expenses

improve operator efficiency

Stress: highly visibleStress: highly visible

nalco cooling tower presentation

Documents

hot cooling water

substance heat

use water

cool water

water flows

break water

evaporated water molecules

purpose of cooling systems