The Effect of Copolymer and Iron on the Fouling Characteristics of Cooling Tower Water Containing Corrosion Inhibitors

AN ABSTRACT OF THE THESIS OF

Abdullah A. Abu-Al-Saud for the degree of Doctor of

Philosophy in Chemical Engineering, presented on August

15, 1988.

Title: The Effect of Copolymer and Iron on the Fouling

Characteristics of Cooling Tower Water Containing

Corrosion Inhibitors. Redacted for Privacy Abstract approved: Dr. James G. Knudsen

Various antifoulant treatment programs and the considerations necessary for the effective use of such programs were examined.

Two different groups of tests, with and without iron contamination, have been carried out on the effectiveness of several of the state-of-the-art copolymers (PA, HEDP, AA/HPA, AA/MA, SS/MA and AA/SA) in the inhibition of the fouling of high hardness cooling tower water containing phosphate corrosion inhibitors

(polyphosphates and orthophosphates). The tests were conducted on metal surfaces (SS, CS,

Adm, and Cu/Ni), using simulated cooling water in a specially designed cooling tower system.

For each group of tests at various pH values (6.5,

7.5 and 8.5), the effects of flow velocity (3.0, 5.5, 8.0 ft/sec) and heat transfer surface temperature (130, 145,

160°F) on thefouling characteristics of cooling tower water havebeen investigated. During the course of each test, the water quality was kept constant.

For the iron tests, the effects of iron presence

(2, 3 and 4 ppm Fe) on the fouling characteristics of the cooling tower water havebeen investigated and discussed for three different situations:

1. High hardness cooling tower water and iron.

2. High hardness cooling tower water, iron and

phosphate corrosion inhibitors.

3. High hardness cooling tower water, iron,

phosphate corrosion inhibitors and copolymers.

When fouling occurred, measurements were made of the fouling thermal resistance as a function of time.

Four different fouling curves were obtained, linear, concave upward, asymptotic and sawtooth curves.

The fouling data obtained were correlated with the

Heat Transfer Research, Inc. (HTRI) model and fouling predictive equations and charts were developed.

For the two groups of tests, the effectiveness of each copolymer has been evaluated and the threshold values of surface temperature, flow velocity and pH have been identified. The Effect of Copolymer and Iron on the Fouling Characteristics of Cooling Tower Water Containing Corrosion Inhibitors

Abdullah A. Abu-Al-Saud

A THESIS

submitted to

Oregon State University

in partial fulfillment of the requirements for the degree of

Doctor of Philosophy

Completed August 15, 1988

Commencement June 1989 APPROVED: Redacted for Privacy ProfesIgor* Chemical Enginering Department in charge of major( Redacted for Privacy

Chairman of'CiAeolcal Engineering Department

Redacted for Privacy

Dean of Gr ate Schol

Date thesis is presented August 15, 1988

Typed by K. Abu-Al-Saud for Abdullah A. Abu-Al-Saud ACKNOWLEDGEMENT

My special thanks goes to my professor, Dr. James G.

Knudsen, for his advice and encouragement. I would also like to thank Professor Charles E. Wicks for his concern and assistance.

I am particularly grateful to my friends Khalid Al-

Qusami and Hani Redha for their help. My deepest thanks and love are for my wife for without her, this work would not have come to life. This thesis is dedicated to my mother, my wife, my daughter and my sisters and their families. TABLE OF CONTENTS

PAGE:

I. INTRODUCTION 1

II. GENERAL REVIEW AND LITERATURE SURVEY 4

Heat Transfer Equations 4

Fouling Types 5

Fouling Mechanism 8

Important Parameters 10

Predictive Methods 12

Chemical Treatments 18

III.EXPERIMENTAL EQUIPMENT 27

Heat Exchanger System 29

Test Sections 29

Cooling Tower System 33

Data Acquisition System 35

IV. EXPERIMENTAL PROCEDURES 36

Experimental Program 36

Procedure 39

V. CALCULATION PROCEDURES 45

Calculation of FoulingResistance 45

Error Estimation 49 Calculation of Inner Wall Shear Stress 53

Fitting the Fouling Curves 55

VI. RESULTS AND DISCUSSION 57

General Data 58

Results Presentation and Data Treatment 59

Tests Without Iron 60

Iron Tests 73

Deposit Composition 99

Types of Fouling Resistance Time Curves Obtained 100

Analysis of the Fouling Data 103

Data Reduction and Discussion 111

Discussion of Model Constants E, a and b 125

Scale Strength 132

Fouling as a Function of Time and Asymptotic Fouling Resistance 133

Conditions Showing Insignificant Fouling 140

VII. APPLICATION OF RESULTS 143

Model Correlational Equations 143

Threshold Values 162

Application to other Geometries 162

VIII.CONCLUSIONS 164

BIBLIOGRAPHY 171 APPENDICES PAGE

AppendixA Nomenclature 178

AppendixB Calibration Equations 183

AppendixC Chemical Analysis Procedure 185

AppendixD Sample Calculations 187

AppendixE Summary of Test Results 190

AppendixF Fouling Resistance Time Curves 213

AppendixG Composite Plots of Selected Runs 244

AppendixH Deposit Compositions 282

Appendix I Nonlinear Regression 285

AppendixJ Average Cooling Tower Water Quality 310

AppendixK Average System Flowrates 316

AppendixL Plots of Correlational Curves 320

AppendixM Solubility Information 353 LIST OF FIGURES

FIGURE PAGE

III-1. Schematic Flow Diagram of Experimental Equipment 28

111-2. Annular Geometry of Test Section 30

IV-1. Water Conditioning System 40

V-1. Cross Section of Clean and Fouled Test Section 46

VI-1A. Fouling Resistance Time Curves 101

VI-1. Normalized -In Od vs Velocity 104

VI-2. Error Plot of Deposition Rate 119

VI-3. Error Plot of Time Constant 124

VI-4. Error Plot of Fouling Resistance 136

VI-5. Curves of Constant R'*', on Grid of Velocity vs Surface Temperature 146

VI-6. Curves of Constant Surface Temperature on Grid of Rte. vs Velocity 154 LIST OF TABLES

TABLE PAGE

III-1. Heat Transfer Research, Inc. Rods Specification 32

IV-1. Constituents of the City Water and System Water 37

IV-2. Additives Used in Each Group of Tests 38

IV-3. Typical Volumes and Flowrates 43

VI-1. Regression Analysis 106 VI-2. Constants to be Used in Equations (6-5), (6-12) and (6-13) 116

VI-3. Comparison of Experimental Values vs Model Equations for Od, Ac and R4*-1, 137

VI-4. Threshold Value for Various Additives 141 THE EFFECT OF COPOLYMER AND IRON ON THE FOULING CHARACTERISTICS OF COOLING TOWER WATER CONTAINING CORROSION INHIBITORS

I INTRODUCTION

This study is part of an on-going experimental

program under way at Oregon State University on the fouling characteristics of cooling-tower water.

Fouling is defined as the formationof deposits on

heat exchanger surfaces which impede the transfer of heat and increase the resistance to fluid flow.

Cooling-tower water is utilized as a medium for heat

rejection to the surroundings via heat-exchange equipment.

Untreated open recirculating cooling-tower water may

contain significant concentrations of scale-forming ions,

such as Ca-1-, Mg4-°, PO..- and SiOa- which

can form inverse solubility salts at high temperature. These salts may deposit on the hot heat-transfer surface.

Control of pH and the use of scale inhibitors are the common methods by which fouling of cooling tower water can

be reduced or, in the best case, prevented. As pH

decreases, thesolubility of many scale forming salts

increases and the deposition rate is significantly

reduced. The pH is usually reduced to the range of 6.5

and 7.0 by the addition of sulfuric acid to the cooling

water system. Under these conditions, however, the cooling water is slightly corrosive to the material in the 2 system, therefore corrosion treatment is necessary. Non- toxic phosphate corrosion inhibitors are now being used to meet environmental requirements. However, all of the phosphate-containing treatment programs suffer one major draw back; the phosphate level used must be very stringently controlled. Too much phosphate causes uncontrolled precipitation of calciumphosphate salts, while too little does not provide the corrosion protection required. To alleviate this problem, corrosion inhibitors are commonly used in conjunction with antifoulants.

The objective of this investigation is to study the effects of state-of-the-art copolymers as antifoulants on the fouling characteristics of cooling-tower water containing phosphate corrosion inhibitors with and without iron contamination. Corrosion inhibitors used in this study are orthophosphate and polyphosphate. Antifoulants used are polyacrylates, phosphonates (HEDP), acrylic acid/hydroxypropyl acrylate (AA/HPA), acrylic acid/sulfuric acid (AA/SA), sulfonated styrene/maleic anhydride (SS/MA) and acrylic acid/maleic anhydride

(AA/MA).

The amount of deposit on a heat-transfer surface is measured in terms of the thermal resistance of the deposit. Generally, if the thermal resistance is less than 0.0001 ft° hr °F/Btu, the amount of fouling is tolerable, and the heat exchanger operates essentially as 3 a clean heat exchanger.

The most important parameters that effect the fouling process are surface temperature and the surface condition of the heated surface, fluid bulk temperature, flow velocity/shear stress and water quality. A correlation, among the important parameters that affect and control fouling, which will reliably predict fouling resistance or determine conditions under which fouling would not occur would be most useful to the designer and operator of heat exchange equipment. 4

II GENERAL REVIEW AND LITERATURE SURVEY

Heat Transfer Eauations

The effect of fouling in terms of fouling resistance on thedesign of heat transfer equipment is expressed in the fundamental equation for the overall heat transfer coefficient Ur, on the outside of the surface as

1 = 1 AQ 1 + Ara + Rw (2-1) U0 hr.) Ai hi Ai

Where: U = overall heat transfer coefficient h = convective heat transfer coefficient A = surface area Re = thermal resistance of deposit and subscript:

0 = outside i = inside w = wall

The convective heat transfer coefficients, hi and h0, and the thermal resistance of the wall can be determined with reasonable accuracy using well established techniques and correlations.

Accurate general methods for predicting the fouling resistance, which is often a major or even the dominating term in the equation, have not been developed for two reasons. First, fouling varies with time which makes it difficult to justify the assumption of a steady state. 5

Second, the fouling resistancedepends on the thermal

conductivity of the deposit.

Since the fouling resistance often approaches an equilibrium value, the heat exchanger designer selects the

values for fouling resistance from some tabulated values

or from experience based on sources which often do not

have any relevance to the actual operating conditions.

This is unacceptable, as the fouling resistance may be

controlling, and can be the most important factor in the

sizing of the heat exchange equipment. This can result in

the heat exchange equipment operating below normal efficiency or result in the over design of the heat

exchanger. Thus, there is substantial incentive to

develop correlations which will reliably predict fouling

resistances or determine conditions under which fouling would not occur.

Foulina Types

The mechanism of fouling for cooling tower water can

vary according to the source and quality (hardness, pH,

suspended solid, treatment type, etc...) of the particular

water under consideration.

The primary types of fouling occurring in cooling

tower water system are precipitation fouling of inverse solubility salts, sedimentation, corrosion of the heat 6 transfer surface and biological growth.

Precipitation Fouling Precipitation fouling involves the crystallization of dissolved species from solution onto the heat-transfer surface. Precipitation fouling occurs when process conditions lead to supersaturation of the dissolved inorganic salts having inverse solubility with temperature at the heat-transfer surface. Common inverse solubility salts include CaCO:.1, CaS0,, Mg(OH)e and Cae(P0...)e.

Normally there is a time interval between the start-up of a clean heat exchanger and the first detectionof a decrease in the heat transfer due to fouling. During this time delay or initiation period, negligible fouling deposition is observed and conditions that promote subsequent fouling are established. Among these are establishment of a temperature, concentration or velocity gradient, formation of crystal nucleation sites, or formation of a sticky film on the heat exchanger surface.

At a certain point in fouling process, the nucleation sites become so numerous they combine together and the fouling increases rapidly. Precipitation fouling has been reviewed by Hasson (11).

Particulate Fouling Particulate fouling is defined as the accumulation of 7 particles such as sand, dust, clay, etc., suspended in the cooling tower water onto heat-transfer surface. It is frequently superimposed on crystallization fouling process. In a few cases, the deposition occurs as a result of gravity, in which case the process is referred to as sedimentation. This type of fouling was reviewed by

Gudmundsson (9).

Corrosion Fouling

Corrosion fouling involves an electrochemical reaction of the heat exchanger surface, producing reaction products and roughening of the heat transfer surface.

This may both inhibit heat transfer and promote fouling by other mechanisms. This type of fouling was reviewed by

Somerscales (30).

Biological Fouling

Warm heat exchanger surfaces can provide suitable environments for bacteria, algae and fungi, which can form layers which significantly decrease the rate of heat transfer. This biofouling is usually prevented in cooling towers by adding chlorine or other biocides. A review of biofouling is by Characklis (3).

Of the above fouling types, precipitation fouling is 8 the most significant in the fouling of cooling tower water.

Fouling Mechanism

The overall fouling process can be viewed as consisting of five subprocesses:

Initiation

An induction period of a certain time duration is normally present during which conditions that promote subsequent fouling are established. Among these are establishment of a temperature, concentration, or velocity gradient, formation of crystal nucleation sites or formation of a sticky film on the heat exchanger surface. In some cases, an initial enhancement in heat transfer may actually occur because the rough initial deposit may act as a turbulator to break up the viscous sublayer. For more detail see Characklis (2).

Transport To The Surface

The transport mechanisms which are very important for cooling tower water are: 9

* Diffusiophoresis: A concentration gradient acts as driving force.(1)

* Turbulent diffusion: particles become entrained in eddies of turbulent boundary layers and are swept toward the surface.

Attachment

Some of the factors that are thought to contribute to foulant adhesion are van der waals forces, electrostatic forces, thesurface tension of the absorbed surface film and external force field. (1)

Transformation

Once the deposit is formed, transformation, i.e. physical or chemical changes, or aging, may occur. (1)

Removal

Removal or re-entrainment of the deposit may begin as soon as an initial layer is deposited. Removal may occur as a result of spallation where material is detached in a

large mass or as a result of erosionwhere material is detached in a particulate form or as a result of dissolution where material is detached in ionic form, Somerscales (30). 10

Important Parameters

The fouling process of cooling tower water appears to be most affected by flow velocity/shear stress, surface temperature, water quality and the condition of the heated surface, Watkinson (35).

Velocity Effects

Velocity affects the fouling process with respect to both deposition and removal. Velocity influences mass diffusion-controlled deposition processes through convective mass transfer to the surface. The effect of velocity on the removal process is generally correlated in terms of wall shear stress and deposit mechanical strength. (26)

Temperature Effects

In cooling water systems, the temperature of the surface is higher than the bulk fluid temperature. In such cases, the inorganic substances that are inverse solubility salts may deposit on the high temperature surface. The crystallizationrate of inverse solubility salts is exponentially related to the inverse of the surface temperature in the form of an Arrhenius type of relationship which is characteristic of a chemical reaction. For constant heat flux operation the 11 temperature at the tube surface-scale interface increases as fouling proceeds and this temperature which increases within the deposit plays a vital role in the aging of the deposit. The aging processproduces changes in the crystal structure which effects the strength of the deposit and thereby the removal rate of the deposit. Bulk temperature has an effect on the saturation concentration of the salts in solution and on the rate of crystallization. Thus, the rate of development of fouling resistance generally increases with temperature.

Surface conditions

A rough surface provides numerous nucleation sites which help in initiating the deposition process. Thus, a smooth surface will have correspondingly a longer induction period. In many instances it has been found that once the clean surface is wholly covered by the deposit then the ensuing fouling process is not in any way determined by the tube material or the surface conditions.

Water Quality

In cooling water systems, water quality is a key factor in fouling problems that might occur. Salts with inverse solubility may lead to scaling. Suspended solids may settle out on the heat transfer surface. In general pH and the concentration of different mineral salts 12 components have been used to characterize water chemistry.

These quantities can be related to fouling tendencies of water. (27)

Predictive Methods

Recent attempts to mathematically model the fouling processes have been based on the following general material balance.

dR, = 0, (2-2) de

Where: = fouling resistance = X,/k, e = time = deposition rate 0, = removal rate X, = instantaneous fouling film thickness kg = thermal conductivity of fouling deposit

The deposition rate function depends upon the mechanism of fouling, the surface temperature, the flow conditions, and the water quality. The removal rate function depends upon the strength of the crystalline structure and the shear stress resulting from the flow of the fluid over the deposit layer. When the removal rate increases with the fouling layer thickness due to the deteriorating stability of the deposit, the deposition and removal rate ultimately become equal resulting in a constant asymptotic fouling resistance value. The basic 13 problem infouling research is to determine those parameters which affect deposition and removal rate and to develop predictive correlations to account for these effects. The following authors CSantoso (29), Suitor

(22), Story (31), Roy (28), Lahm (19) and Taborek et al

(32)] give summaries of the fouling models that exist in the literature as follows:

Kern-Seaton Model (13,14)

This model was the first model to account for simultaneous deposition and removal rates. The model predicts an asymptotic fouling resistance and was derived to obtain curves which could describe fouling data obtained by Katz (14). The deposition rate was assumed to be constant, and the removal rate was assumed to be proportional to the shear stress and to the instantaneous thickness of the deposit layer. Kern and Seaton (15,16) proposed the following model for the material balance

Equation:

dXf = K1C1W KeTX,, (2-3) de

Where: K,C1W = deposition rate = removal rate K1,1liquid = shear stress = instantaneous fouling film thickness 14

Upon dividing Equation (2-3) by the thermal

conductivity of the deposit K, and integrating, R., becomes

= Rw*,C1 exp(-e/e,)] (2-4)

With: 1=0* = K1C1W (2-5) KeK,T

and 09,= 1 KT (2-6)

Where: IR"m'r = the asymptotic fouling resistance, or fouling factor, it is attained when the deposit and removal rates are equal.

= time constant.

Equation (2-4) shows that R., will approach F2', as

time becomes large.

Watkinson-Epstein Model

Watkinson-Epstein (36) postulated that the deposition rate isproportional to the product of the mass flux normal to the surface and the sticking probability. The sticking probability is proportional to the adhesive force and inversely proportional to the hydrodynamic forces at the interface, and theremoval rate is similar to Kern-

Seaton's model. 15

00 = K'Js and = km(C, C.)

Where:

K' = proportionality constant s = sticking probability = mass flux Km = convective mass transfer coefficient C. = concentration of foulant at the interface C,, = concentration of foulant in the bulk

Watkinson-Epstein obtained experimental data for sour gas oil and compared the data against the fouling model proposed by Kern and Seaton (15,16). It was found that the asymptotic fouling resistance was inversely proportional to the mass flow rate squared, incontrast to the mass flow rate to the first power in the Kern model

Equation (2-4). They also found that the initial fouling rate was inversely proportional to the mass flow rate and dependent exponentially on the initial wall temperature.

In the Kern-Seaton model, the initial fouling rate, which is a product of R*1,. and 1/0, given in Equations (2-4) and

(2-5), is directly proportional to the mass flow rate to the first power and independent of the wall temperature.

HTRI Model

Taborek, et al (33), in a very comprehensive work on cooling tower water, used the Kern-Seatonconcept of deposition and removal to postulate a fouling model that 16 also considered water chemistry and its effect on the fouling resistance. The deposition term is a function of the scale surface temperature in an Arrhenius-type crystallization reaction term and water chemistry parameter. Also included is a velocity function for the deposition rate.

00 = CiFs'Or" expE-E/Rs,T.] (2-9)

Where:

Ct,n = constant = deposition velocity functions = water quality term which is a function of LSI E = activation energy of deposit reaction 1=4 = gas constant T. = absolute temperature of the scale surface

The removal term is presented as a function of the wall shear stress, the scale thickness and scale bonding strength of the deposit

0, = CaTX, (2-10) Y

Where:

= constant Y = scale strength term 17

Combining Equations (2-9) and (2-10) and substituting into Equation (2-2), an expression for the fouling rate is obtained

dRor = C1F-Qh expC-E/R T.] CeTK.f.R.r. (2-11) de

For n=1, integrating Equation (2-9) results in an expression for the fouling resistance as a function of time

Rr = Km exp(-E/R, T.)(1 exp(-K..e) (2-12)

Where:

K = CiFsI2-1 = CaPKr/Y

After a very large time, the asymptotic fouling resistance, R*.r is given by:

R41', = Ka exp(-E/R T.) (2-13)

writing Equation (2-12) in terms of R4'.,

Rr= R4*.rE1 exp(-e/e,)] (2-14) where

= 1 (2-15) K4 CeTKr 18

Chemical Treatments

The most commonly used medium for removing heat in industrial processes is water from open recirculating cooling tower systems. Corrosion is one of the most costly problemsencountered in cooling towers. It causes two major problems: equipment failure and loss of heat transfer efficiency. The corrosion process can be prevented, or at least, reduced by adding corrosion inhibitors.

One of the most successful non-chromate treatments for corrosion inhibition has been phosphate combinations. The problem with phosphate based treatments is the formation of phosphates salts that precipitate on the heat transfer surfaces. Thus cooling tower water is chemically treated to prevent corrosion and or fouling.

Corrosion Inhibitors Corrosion is an electrochemical process, arising from the existence of areas called anodes, where electrons are lost by metal, and other areas called cathodes, where electrons are accepted. Thus agents that control corrosion have been classified according to the mechanism of their action as anodic or cathodic inhibitors.

The corrosion inhibition process is best summarized as one or more of three general mechanisms (26). In the first, the inhibitor molecule is adsorped on the metal 19 surface by the process of chemisorption, forming a thin protective film either by itself or in conjunction with metallic ions.

In the second, some inhibitors, however, merely cause a metal to form its own protective film of metal oxides. In the third, the inhibitor reacts with a potentially corrosive substance in the water.

Anodic inhibitors passivate the metal by shifting its oxidation potential at the anode several tenths of a volt in the noble, less positive, direction and slowing the corrosion reaction. A protective, invisible, film is formed along the anode that may eventually cover the entire metal surface and prevent corrosion.

Cathodic inhibitors suppress the reduction of oxygen at the cathode by the electrons of the corrosion current.

In contrast to the anodic inhibitors they often form a visible film along the cathode surface, which polarizes the metal by restricting the access of dissolved oxygen to the metal substrate. The film also prevents depolariza- tion by blocking hydrogen evolution sites.

In actual plant operation, usually two or more corrosion inhibitors are blended to utilize the advantages of each and to minimize their respective limitations.

Frequently anodic and cathodic inhibitors are combined to give better total metal protection. In this way the plant corrosion control program can be significantly improved. 20

Orthophosphates

An orthophosphate ion (23,26) behaves as a weak

anodic inhibitor by forming a loose film on the surface of

the metal. This film is not tenacious and is sensitive to changes in pH. Protection by orthophosphates is meager and uncertain at best. Thus for these reasons and for the danger of calciumphosphate sludge formation, orthor- phosphates are rarely used alone for corrosion control.

Polyphosphates

Polyphosphates are cathodic inhibitors. Their

inhibition mechanism and their behavior is (23,26) as follows: polyphosphates form a durable polarizing film on

the cathodic surface of most metals. The molecule adsorps or bonds with calcium ions to form colloidal particles.

These positively charged particles bond tightly to the metal surface and form a protective film.

At high temperatures and low or high pH, polyphosphates revert to orthophosphate. This reversion process is a major problem associated with use of polyphosphates, since orthophosphates are a weak anodic inhibitor which cannot provide thecorrosion protection of polyphosphate. Also, orthophosphates can react with other components in the cooling water and form inverse solubility salts which precipitate on heat transfer surfaces. 21

A draw back of polyphosphates is their nutrient potential for algal growth when they revert to orthophosphates.

Dissolved metal ions in the waterwill have positive and negative effect on the polyphosphate inhibition process. A positive effect of dissolved iron in the water is the strengthening of the protective film through the inclusion of iron. The negative effect is that iron can complex polyphosphate, thereby rendering it useless as an inhibitor. Recent technology has substantially minimized the limitation of polyphosphate by blending with other materials.

Antifoulants

Antifoulants are used alone or in combination in order to properly control fouling. Fouling in an actual cooling tower is an extremely complex phenomenon, thus an understanding of individual foulants and their control is important. Foulants can be calcium compounds, iron oxide, microbiological suspended solids and process contamination. Antifoulants can be polymeric or nonpolymeric

(polyphosphate) in nature. Polymeric anti-foulants prevent fouling by two processes. First by acting as scale inhibitors of inverse solubility salts, and second, by dispersing the suspended particles in the cooling 22

water. Types and mechanisms of fouling inhibitors are reviewed by (23,26).

Scale Inhibition

Precipitated salts of calcium and magnesium often

form dense scales and sludges which are difficult to remove. In addition, they are very effective heat

insulators. CaC0a, CaS0,, CaSI0a, MgSI0a, Caa(PO4)a and

MgP0,,. particles are ome of the most prevalent scale

forming compounds in cooling water systems.

The co-polymers inhibit the scale formation of these

compounds by adsorping to the surface of their crystals and disturb their lattice structure and normal growth

patterns, thereby preventing them from growing into larger particles. The inclusion of a relatively large irregular-

ly shaped polymer in the scale lattice tends to produce particles that are amorphous in nature and relatively non-

adherent thus preventing the deposition of a dense uniformly-structured crystalline mass on the metal

surface. In theory these crystals can develop internal stresses which increase as the crystal grows, with the

result that the deposit breaks away from the metal surface. 23

Dispersants

Dispersants are polymers which control particles by

increasing the charge on the particle surface by imparting

a like charge to them and to the heat transfer surface,

thereby keeping the particle repelled and suspended.

There are cationic polymers and anionic polymers,

which act as dispersants. Cationic polymers ionize in water to become positively charged. Anionic polymers

ionize in water to become negatively charged. For this reason, polymers are oftenly referred to as polyelectro-

lytes. Because of fouling material, other than the water- borne salts found in cooling water already has a slightly

negative surface charge. It is economically sound to add anionic polymers to the water. These increase the

negative surface charge and keep particles separated.

Dispersants work on water and air-borne foulants such as

mud, clay, sand, silt and dirt.

Polyphosphates Polyphosphates are chelating agents. They alter the

crystal structure and producedeformed crystals that

prevents the growth ofnormal calcite crystal that leads

to scaling. Chelants are sequestrants that depend upon

stoichiometric reactionsbetween themselves and deposit

components. A sequestrant is an agent which prevents an ion from exhibiting its normal properties by complexing 24 with it below stoichiometric levels. Polyphosphates have been used to control iron and hardness salts for a number of years. Polyphosphates have little effect on the precipitation of calcium sulfate. In recirculating cooling systems, polyphosphates are more often used to control corrosion.

Polyacrylates

Polyacrylates are polymers which have been used as scale control agents and also for the control of suspended matter as a dispersant agent. Polyacrylates adsorp on to the crystal structures of scale forming materials, and thus limits crystal growth and ultimately scale formation.

Polyacrylates, like, other polymers act as dispersants by impairing like charges to the surfaces of the particles thus keeping them in suspension.

Phosphonates

Phosphonates do not hydrolyze as easily as polyphosphates. For this reason they are better deposit-control- agents than polyphosphates, whereas polyphosphates are superior corrosion inhibitors. The mechanism of scale inhibition is the same as that of polyphosphates. One phosphonate class is hydroxyetheyidene-1,1 diphosphonate

(HEDP). 25 Copolymers

Copolymers are being used as dispersants and scale

inhibitors in cooling water systems. Copolymers are formed when different monomers are used in the polymeriza- tion reaction, thus utilizing the advantages of each monomer and minimizing their respective limitations. Four state-of-the-art copolymers are being investigated in this study.

SS/MA

Sulfonated styrene/maleic anhydride copolymer (SS/MA) prevents the formation and deposition of scale and sludge and in particular calcium phosphate. SS/MA is a highly charged anionic polyelectrolyte that is chemically and thermally stable.

AA/SA

Acrylic acid/sulfuric acid copolymer (AA/SA) is a threshold inhibitor which inhibits crystal growth by introducing an impurity into the lattice of a growing crystal. AA/SA is particularly effective for controlling the precipitation of calcium phosphate. The AA/SA copolymer is a dispersant for suspended materials such as silt and metal oxide. 26

AA/HPA

Acrylic acid/hydroxypropyl acrylate copolymer

(AA/HPA) is an organic scale inhibitor particularly for

calcium phosphate. It is also a dispersant agent for particulate matter such as clay and iron oxide.

AA/MA

Acrylic acid/maleic anhydride copolymer (AA/MA), like

the above three copolymers, acts as a scale inhibitor and dispersant. 27

III EXPERIMENTAL EQUIPMENT

The equipment used for this study has evolved over a

period of several years. Several earlier studies (4, 9,

21, and 24) and recent studies (19, 28, 29) have described earlier and recent versions of the system. The differences among these studies is the minor paraphrasing of

their description of the system. To avoid further paraphrasing in this study, the most recent study of

Santoso's (29) description is presented with minor modification as it applies to this study.

The equipment was designed to simulate the operating conditions of a commercial cooling tower system. A schematic flow sheet of the complete system is shown in

Figure III-1. It consists of three main parts: the heat exchanger system, test sections and the cooling tower system. To eliminate the effect of corrosion on the fouling characteristics as much as possible, non-corrosive materials are used throughout the cooling tower system.

Piping was primarily of polyvinylchloride (PVC) or chlorinated polyvinylchloride (CPVC), stainless steel and

glass. 28

AIR ( 1101ratiE TER AN r

TENPERATuRE RENEGE

WEB SLOWDOWN AND SAMPLE

RI LEVEL CONISOL CVO VAC vAL RE

1 TES SECTIONS

STORAGE Tam

LOW WATER NEU* CONTROL VALVE NOT WATER PUMP CAICuLIstlas Pula. 0 WATERR

Figure III-1: Schematic Flow Diagram of Experimental Equipment 29

Heat Exchanger System

In order to maintain a constant bulk temperature of

the water being tested a heat exchanger system was

employed. The heat exchanger system is a closed loop

circulating system. City water, heated to 120 130°F in

a 40 gallon domestic electric water heater is pumped to

the shell side of countercurrent shell and tube heat

exchanger. The cooling water to be tested is heated in

the tube side of the heat exhanger. The heat exchanger

has 19 stainless steel tubes with 1/2 in OD, 16 BWG wall,

and a length of 7 feet. A temperature controller regu-

lates theheated water flow rate to the heat exchanger to

maintain a constant water bulk temperature in the test

system.

Test Sections

After the cooling water is heated in the heat

exchanger, it flows through the test sections. A test

section of annular geometry is shown in Figure 111-2. The

heater rod has anoutside diameter of .42 inches and is heated electrically over a length of 4 inches. Four

chromel-constantan thermocouples are embedded in the heater wall to record the wall temperature as deposit

accumulates on the rod surface. They are located on the 30

. 16 in .

Outer Class Tube

0--.Scale Formed on Inner Core Flow /Heater Surface t .42 in

Wall Resistance Thermocouple/ Heater

Figure 111-2: Annular Geometry of Test Section 31 same cross-sectional plane 90° apart from each other. The outer glass tube has an inside diameter of .75 inches and the overall length of the test section is 16 inches. The test sections are mounted in Portable Fouling Research

Units (PRFU) provided by Heat Transfer Research, Inc.,

(HTRI).

The test fluid flows through the annular section between the heater rod and the glass tube. Fouling occurs on the outside of the heated portion of the inner tube.

Conditions such as flow rate and surface temperature of the heated sectioncan be set easily to the desired level by making appropriate adjustments in the flow rate of the water to be tested and the power input to the heater. 32

TABLE III-1

HTRI Heater Rod Specifications

ID MATERIALOUTSIDE HEATED k/x (Btu/hrft°F) NUMBER DIAMETERSECTION (THERMOCOUPLES) LENGTH A B C D (in) (in)

240 SS 0.42 3.95 6,531 3,876 7,156 11,996

120 CuNi 0.4215 3.90 48,543 22,882 9,348 11,930

115 Adm 0.4225 3.9 37,881 34,961 70,095 32,499

238 SS 0.422 3.90 -- 52,730 14,836 --

239 SS 0.421 3.80 25,369 8,228 8,164 10,148

Note: k = Thermal resistance of rod. x = Distance of thermocouple below surface of the rod. SS = Stainless steel (316L). Adm = Admiralty. CuNi = Copper-Nickel (90/10) 33 Heater rods and specifications such as dimensions and

thermal resistances of the tube wall are provided by HTRI.

These values of each rod used in the investigation are summarized in Table III-1.

Cooling Tower System

The cooling tower system consists of three major

parts: the spray cooling tower, the cooling tower sump and the blowdown unit. The total volume of cooling tower water in the system is about 260 liters. Cooling water is circulated through the system, absorbing heat in the heat exchanger and in the test sections and then is cooled in the spray cooling tower.

Spray Cooling Tower

The spray cooling tower is a cylindrical empty column

2 feet in diameter, 20 feet high. It is mounted con- centrical above the cooling tower sump. After water flows

through the test sections, it flows to the top of the cooling tower where it is sprayed through spray nozzles and falls through the tower. An induction fan at the top of the cooling tower draws air up through the tower and out the top. 34

Cooling Tower Sump

The cooling tower sump is a reinforced plastic

cylindrical tank 4 feet high, 34 inches in diameter, with

1/8 inches thick wall. Water from the cooling tower spray

is returned to the cooling tower sump to be recirculated.

Fortified city water was supplied to the cooling

tower sump from the make-up tank through a level control

valve to make up for evaporation and discharge losses.

Other additives to the system were added directly to the

cooling tower sump by means of metering pumps. Sulfuric

acid (.05N) flows by gravity through a solenoid valve which was activated by pH controller.

Blow Down Unit

As the cooling tower water evaporates, the concentra-

tion of the mineral constituents increases due to the

input of fortified citywater and other additives being

fed continuously to make up for the evaporative losses.

In order to maintain a constant cooling tower water

quality (mineral content), blowdown was withdrawn from the bottom of the cooling tower sump. A metering pump was

used to control the rate of blowdown from the system, and

the discharge was collected in the calibrated blowdown

storage tank. 35

Data Acquisition System

Two data acquisition systems were utilized. The first system was a Digitec 1000 Datalogger. This equipment was capable of scanning the system sensors (temperature, flow, power, pH, conductivity and corrosion rate) at desired intervals (one minute to five hours) and print out the results in millivolts on a paper tape.

The second system was a Hewlett-Packard HP85 micro- computer for data acquisition. With this combination, it was possible to scan the system at any desired time during a test. Flows, temperatures, heat fluxes, fouling resistances, pH, conductivity and corrosivity could be printed out after each scan. At the end of a test all data were tabulated and plots of velocity, surface temperature, fouling resistance, pH, conductivity and corrosion rate as a function of time were produced by the computer. 36

IV EXPERIMENTAL PROCEDURES

Experimental Proaram

The purpose of this study is to determine the effectiveness of state-of-the-art copolymers as fouling inhibitors with, and without iron contamination and using phosphates as corrosion inhibitors. Several parameters which significantlyaffect fouling will be investigated.

Three different velocities (3, 5.5 and B ft/sec) and surface temperatures (130, 145 and 160°F) will be covered. The three major water chemistry parameters are pH, corrosion inhibitor additives and fouling inhibitors additives. The effect of the material of the heated surface will be studied.

The main constituents of the city water and additives free system water are shown in Table IV-1. Runs 302 to

407 are without iron addition.

These will be referred to as non-iron tests.

Beginning with run 408, iron will be added to the system through a metering pump. Thesewill be referred to as iron tests. The addition of the iron will be accomplished by adding the required amount of ferrous sulfate heptahydrate (Fe S(14.7 Ha0) to the system.

For the duration of the investigation, phosphate corrosion inhibitors as orthophosphates and polyphosphates will be used. Table IV-2 shows the additives that will be used in each group of tests. 37

Table IV-1. Constituents of the City Water and AdditiveFree System Water

System Water Constituent City Water Average Values

Specific conductance, micrombo 100 1700 Sulfate, ppm SO... 10 800 Chloride, ppm Cl 10 40 Total hardness, ppm CaCOm -- 1000 Calcium hardness, ppm CaCO 27 660 Magnesium hardness, ppm CaCOm -- 340 Copper, ppm Cu -- 0.1 Iron, ppm Fe -- 0.1 Sodium, ppm Na -- 60 Zinc, ppm Zn 0.9 Chromate, ppm Cr0.. 1.0 Total phosphate, ppm PO.. 0.2 Silica, ppm SiOe 20 35 Suspended Solids, mg/1 10 38

Table IV-2. Additives Used in Each Group of Tests.

Additives

Run Nos. None HEDP PA PP OP AA/HPA AA/MA SS/MA AA/SA Fe

302-307 2-4 2-4 4-5 5-6 308-313 4-5 5-6 -- 314 -323 -- 4-5 5-6 10 324-332 10 10 333-335 10 -- 336 -338 -- 4-5 5-6 339 -341 -- 4-5 5-6 10 342 -344 -- 4-5 5-6 10 -- 345 -347 -- 4-5 5-6 10 348-365 -- 4-5 5-6 10 -- 366 -371 -- 4-5 5-6 10 372-374 -- 4-5 5-6 375 -380 -- 4-5 5-6 10 381-383 -- 4-55-6 384 -395 -- 4-5 5-6 10 396-401 -- 4-5 5-6 10 402 -407 -- 4-5 5-6 10 -- 408 -413 -- 4-5 5-6 2 414-419 -- 4-5 5-6 4 420-429 2-4 -- 4-5 5-6 4 430-435 -- 4-5 5-6 10 4 436-438 439 -450 3 451-461 -- 4-5 5-6 3 462-469 10 -- 4-5 5-6 3 numbers represent ppm

HEDP - 1-Hydroxyethylidene-1, 1-diphosphonic acid (Monsanto 2010)

PA - Polyacrylate (Goodrich K732)

PP - Polyphosphate added as Na2P20,

OP - Orthophosphate added as Na3P0,.

AA/HPA - Acrylic acid/hydroxypropyl acrylate

AA/MA - Acrylic acid/maleic anhydride

SS/MA- Sulfonated styrene/maleic anhydride

AA/SA - Acrylic acid/sulfonic acid

Fe - Iron added as FeSO. 7H20 39

Procedure

SYSTEM TO OBTAIN DESIRED WATER QUALITY

The system to obtain desired water quality was described by previous studies. The following description is adapted from the following studies (17, 29) with minor modification as it applies to this study.

The local city water contains about 20 ppm of calcium hardness and about an equal amount of silica. It is therefore, necessary to fortify the city water with calcium and magnesium to obtain the compositions shown in

Table IV-1.

The complete water conditioning system is shown in

Figure IV-1. City water (float controlled) and saturated calcium and magnesium sulfatesolution (provided by a metering pump) flow into the well agitated make-up tank.

The saturated calcium sulfate solution (fortifying solution) is prepared by mixing city water with powdered native calcium sulfate from Fisher Scientific. The required amount of magnesiumsulfate is also added into the fortifying solution.

The mixture from the make-up tank flows through a float controlled valve to the cooling tower sump. The water to be tested was pumped through the cooling tower system by the circulation pump. The bulk water temperature was adjusted to the desired set point. The circula- 140

CITY WATER

H 1101 ORROSIO OLUTI INHIBITOR EVEL CONTROL SATURATED METERING MAKE-UP. PUMP tly9:4.iCMS; SOLENOID VALVE TANK SOLUTION

I U A:3I METERING PUMP

PH ONTRO L VEL CONTROL WATER CONDITIONING SYSTEM COOLING CIRCULATION L . TOWER PUMP TO FOULING TEST UNIT TO DRAIN SUMP 0 SLOWDOWN TANK

METERING PUMP

Figure IV-1: Water Conditioning System 41 tion of water was continued until the hardness and silica concentrations increased to the desired level, after which the blowdown was withdrawn from the cooling tower sump by a metering pump to maintain the desired water quality.

Other materials were added directly to the cooling tower sump. Phosphate corrosion inhibitor of appropriate composition was added at a constant rate to the sump through a metering pump. Antifoulant additives (whenever used) were added directly to the cooling tower sump by means of a metering pump. Iron as ferrous sulfate heptahydrate Fe SO4-7H0 was also added directly to the sump through a metering pump.

The pH was controlled at the desired level by the addition of sulfuric acid (.05N) or sodium hydroxide, as needed, which flowed by gravity through a solenoid control valve which was activated by a pH controller.

RUN INITIATION

After the desired water quality for a particular run was obtained, the heater rods were fitted into the test sections. Then flow rate and surface temperature were set to the desired values by making appropriate adjustments in the flow rate and the power input to the heaters.

The Hewlett Packard 3540 data logger and the Digitec

1000 data logger were activated. The Digitec 1000 data logger was set to record every two hours throughout run 42 duration. The Hewlett Packard 3540 data logger was set to record ten readings at two minute intervals for calibration purposes, then it was set to record at six hour intervals for the remainder of the test.

PROCESS MONITORING

The systemwater was analyzed everyday for hardness, silica, sulfate, chloride and level of additives. Samples were takenat the beginning and at the end of each set of runs and were sent to Betz laboratories for complete analysis.

Corrosion, conductivity and pH were measured by on- line instruments and recorded by the data logger.

The amount of flow from blowdown, fortifying solution, city water and additives were recorded daily.

Evaporation rates were calculated from daily flow-rate measurements. Typical flow rates and volumes are given in

Table IV-3.

The blowdown rate is adjusted so that the Holding

Time Index (HTI) in the system is about 24 hours. The HTI is the time required for the concentration of a constituent in the system to be reduced by 50% without addition of that constituent to the system. Variation in environmental conditions in the laboratory brought about fluctuation in the evaporation and city water rate. The fluctuation was not serious because the mineral content of 43 the city water is small compared to the amount of minerals in the cooling tower water. The flowrateof the fortifying solution could be adjusted manually to maintain a constant water composition.

Table IV-3 Typical volumes and flowrates.

Volume in the system 260 1 Evaporation 100 200 1/day City water 200 300 1/day Blow down 175 1/day Saturated CaSO. solution 50 90 1/day Inhibitor solution 2 3 1/day

Flow rates and power levels were monitored daily and adjusted manually whenever they were found to deviate from their original set values.

A volume of 20 ml commercial chlorine bleach was added daily directly into the cooling tower sump and 70 ml

Was added to the make-up water tank for control of biological growth.

RUN TERMINATION

Generally runs were terminated when the fouling resistance reached a constant value or when essentially no fouling was observed (i.e. the measured fouling resistance was less than .0002 hr fte °F/Btu after about 150 hour duration). In many instances, runs were terminated while the fouling resistance was still increasing. Usually, in 44

these runs, sufficient data were obtained, so that the correlational methods used were applicable and it was

apparent that the ultimate asymptotic fouling resistance would not be acceptable in an operating heat exchanger. When runs were terminated, the heater power and water flow

in the test sections were turned off, the heater rods were removed from the test sections and the deposit, if any, was scraped off from the rod. After it was thoroughly

dry, the sample was sent to the DuPont Company for chemical analysis, and then the heater rods were cleaned

using a standard procedure and reused. 45

V CALCULATION PROCEDURES

Calculation of Fouling Resistance

The method of calculation of the fouling resistance is presented in the experimental procedure and the data acquisition system manuals. All previous fouling studies that used the cooling tower system used in this study, included the method of calculation of the fouling resistance (19, 29, 31). To avoid repetition and paraphrasing, the following was adapted from Santoso (29).

The method of calculation of the fouling resistance is based on the quantities defined in Figure V-1. During a test, flow rate in the test section, bulk temperature and heater power remained essentially constant. Under these conditions the temperature at the liquid/solid interface (Ts) is assumed to remain constant.

The wall temperature, Tw, was calculated from the wall thermocouple temperature, Tc, and the thermal conductance k/x between thermocoupleand the heater wall by the Equation:

Tw = Tc Q/AH (5-1) k/x where

Q/AH = heat flux, Btu/hr ft2 Figure V-1: Cross Section of Clean and Fouled Test Section 47

At constant heat flux and constant velocity, the difference between the surface temperature, Ts and the bulk temperature, Tb is constant. The surface temperature

is determined as follows.

Ts Tb = 0/AN (5-2) h where

h = heat transfer coefficient, which must be calculated.

The local bulk water temperature is calculated with the Equation:

Tb = Q + Tin (5-3) 8.0208 (r)(c,) (w,) where

= heater power consumption, Btu/hr = water density, lbm/ft:1 P = water heat capacity, Btu/lbm °F Wf = volumetric flowrate, gpm Tin = inlet water temperature, °F

8.0208 is the multiplication factor to convert gpm to ft'3/hr.

Clean Condition (beginning of the run)

Tsc, = Tw = Tc Q/AH (5-4) k/x where

subscript = denotes the clean condition

Thus the heat transfer coefficient for a clean rod, 48 h,, is calculated from Equation (5-2) using Ts, found in

Equation (5-4):

h, = Q/AH (5-5) Ts, Tb

It is related to the flow velocity by Equation:

h, = K Vm (5-6)

where

K = proportionality constant

m= .7 if V>4 ft/sec or .93 otherwise

= clean condition

When a run is started, 10 scans of the data sensors are made at 2 minute intervals, from which an average value of K is calculated.

Kavg = ( E hi/Vim) / 10 (5-7)

The value of Kavg computed above remains constant provided the assumption of constant bulk temperature holds.

Fouled Condition:

For a given velocity,

h = Kavg Vm (5-8) 49

The surface temperature for the fouled condition Ts,

can now be determined from Equation (5-2):

Ts =Q/AH + Tb (5-9) h

and finally, the fouling resistance Rf can be calculated

by Equation:

Rf = ( Tc Ts ) 1 (5-10) Q/AH k/x

The calculations were carried out by a Hewlett

Packard 85 computer in conjunction with an HP 3054

Data logger.

Error Estimation:

This is an estimate of the possible error in the

measured value of the fouling resistance.

The relative error in the heat flux can be calculated

from Equation:

d(Q/AH) = dQ .±. dDROD ± dL (5-11) (Q/AH) Q DROD L where

Q = heater power consumption DROD = outside diameter of clean heater rod L = heated length section

and

dQ = dQmv (5-12) Q Qmv 50

The heat flux and bulk temperature are relatively constant during a run.

Using Equation (5-2)1 the relative error of Tc and Tin can be calculated by the following equation:

.949 dTmv , Tmv < -1.0 dT = (Tmv + 5.02) (5-13) T

.8765 dTmv Tmv ?. -1.0 - (Tmv + 4.72)

The relative error of the bulk temperature is calculated from Equation (5-3):

dTb = Zt dQ ± Z. dWF ± ZtZ2 WFTin dTin (5-14) Tb Q WF Q Tin where

Zt = Q (5-15) Q + ZE. Tin WF

Ze = 8.0208 (r)(Cp) (5-16)

and from Equation (5-3):

dWF = dWmv (5-17) WF (Wmv 4) 51

Clean Condition

From Equation (5-4):

dTsc Tsc

(k/x)Tc dTc ± (Q/AH) d(Q/AH) ± (Q/AH) d(k/x) (5-18) Za Tc Za Q/AH Za8 (k/x) where

Za = (k/x) Tc Q/AH (5-19)

and from Equation (5-15):

dhc = d(Q/AH) -± Ts, dTs ± Tb dTb (5-20) he Q/AH Tsc-Tb Tsc Tsc-Tb Tb

Fouled Condition:

The relative error in surface temperature is obtained by differentiating Equation (5-9).

dTs = (Q/AH) d(Q/AH) t Q/AH dh ± hTb dTb (5-21) Ts Z4 Q/AH 24 h Z, Tb where

Z, = Q/AH + hTb (5-22)

Since the flow velocity also remains essentially constant throughout the run: 52

dh = dhc (5-23) h he

Finally, from Equation (5-10) the relative error of the fouling resistance is:

dRf = (k/x) Tc dTc ± (k/x) Ts dTs ± (k/x)(Tc-Ts)

2, Tc Z,, Ts ;t5

d(Q/AH) ± Q/AH d(k/x) (5-24) Q/AH 2, k/x where

2, = (k/x)(Tc-Ts) Q/AH (5-25)

Setting appropriate errors to each measured variable:

dTmv = ± .005 millivolts dD2 = ± .0005 millivolts dQ = ± .005 millivolts dL = ± .005 millivolts d(k/x) = ± 50 millivolts d(Wmv) = ± .005 millivolts the numerical values of the maximum relative error of the surface temperature and fouling resistance can be calculated from Equations (5-21) and (5-24).

The maximum experimental error in absolute value of the measured fouling assistance is ±15%. Within a run, the precision is much less than this as indicated by fouling resistance time plot in Appendix F. Several earlier studies (19, 29, 31) present a sample of calculation for fouling resistance and error estimation. 53

Calculation of the Inner Wall Shear Stressfor Flowing Water

Properties of water (50 I T I 200°F)

= viscosity, ibm /ft sec

(242/3600) (5-26) + 8078.4]-'5 +f) 2.1482 120

where

r = (T+459.72) 281.615 (5-27) 1.8

T = temperature, °F

= density, lbm/ft = 63.45 .0156T = kinematic viscosity, ft2/sec =

Flow rate/velocity

GPM = flowrate, gallon/minute

V = velocity, ft/sec

The fluid properties are evaluated at the bulk

temperature of the fouling fluids.

Smooth Annular Ducts

dp = I.D. of outer tube, inches

di = O.D. of inner tube, inches

V = velocity, ft/sec = (.4085) GPM / (d12-di2) 54

Re = Reynolds number

= ( 4 rpl ) V (5-28) (12)(a) where

4 r, = de2 dmax2 , inches (5-29) d,

dmax2 = ( d,2 - di2 ) inches (5-30)

in( de°Vd17'2 )

f = friction factor = .079 Re Re > 4,000 (5-31)

Te = shear stress on outer wall, lbf/ft

f 1V2 (5-32) 2g,

Ti = shear stress on inner wall, ibf /ft2

= Te ( de/di ) ( dmax2 d12 ) (5-33) d.2 dmax2 55

Smooth Tubes

d = ID of tube, inches V** = water velocity, ft/sec

Re = Reynolds number = (d/12) v r /

f = friction factor

= .079 (Re--a."5)* (Re > 5000)

= wall shear stress, lbf/ft2

= fr V2 /2 g,

= 32.17 lbm ft/lbf sect combining all relationships

= .0395 H:._:777. (5-35) g, (d/12)-2:5

* If the tube wall has a known roughness, a friction factor equation that also includes roughness should be used.

** If water flow in tube is known in terms of gallons per minute (GPM), then the velocity (ft/sec) is V = 4(GPM) / C(60)(7.48)(u)(d/12)2]

Fitting The Fouling Curves

From the model developed by Heat Transfer Research,

Inc. (HTRI), it was expected that the most of fouling resistance vs time curves could be represented by

Equation:

Rf = RP (1 exp / (5-35) 56

The above equation assumes that fouling begins as soon as the test begins. However, on many of the runs in this study, an induction period or dead time of a certain duration was observed during which negligible fouling deposition occurred. Therefore, it was necessary to modify the above equation to include the induction period as follows

= El exp (-(e (31)/(31,)] (5-36)

where e, is the induction period or dead time.

In order to solve for the constant 1=i4"r. and 0,, it was necessary to use a nonlinear regression since Equation

(5-35) cannot be linearized. A summary of the method of nonlinear regression analysis is given in Appendix I. 57 VI. RESULTS AND DISCUSSION

In order to understand the fouling process and how to control it, the fouling must be related to time, water quality, liquid flow rates, heat transfer surface temperature and the condition of the heat transfer surface.

Relations of this type could be used to design heat transfer equipment subject to fouling, and to formulate operating and cleaning schedules for heat transfer equipment.

It is clear from the literature on fouling that it is a broad and expanding subject. Thus the researcher on fouling must be content to work toward narrow and well defined objectives if progress is to be made toward finding better means of dealing with fouling problems.

In order to properly control fouling, an understanding of individual foulants and their control is required.

For cooling tower water containing phosphate corrosion inhibitors several state of the art copolymer are current- ly manufactured to mitigate calcium phosphate deposition.

The task of the fouling researcher is then to test their effectiveness in preventing fouling under various conditions of water quality, flow rates and heat transfer surface temperature and how they will affect the fouling characteristics of the cooling tower water fouling. 58

Hopkins (13), who studied how ferric oxide fouls heat transfer surface in a 304 stainless steel tube, recom- mended his use of crevice corrosion to explain his fouling data.

Taborek (32), believes that the progress in fouling research requires the systematic collection of data on a wide variety of fouling systems and the subjection of such data to the variouspredictive fouling models in the literature.

In an attempt to shed light, or if possible, to answer some of thesequestions in the area of cooling tower water fouling, it was decided to examine the fouling behavior of high hardness cooling tower water with and without iron as a contaminant.

General Data

The experimental data for all the tests conducted in this study are available at the Department of Chemical

Engineering, Oregon State University, (Contact: J.G.

Knudsen). These data (for each run) are daily cooling tower water chemical analysis and flow rates. Tables of fouling resistance as a function of time, pH, surface temperature, flow velocity, corrosivity, heat flux and ambient temperature along with summary statistics of these values are also available at the Department of Chemical 59

Engineering, Oregon State University. However, tables showing average and standard deviation values of cooling tower water analysis and flow rates are given in Appen- dices J and K, respectively. In an earlier study, Herbig

(12) solubility data werecompiled and saturation curves were constructed for the cooling tower water. These data along with solubility data for iron systems are given and discussed in Appendix M.

Results Presentation and Data Treatment

A summary of all runs are presented in a format shown in Table E-1 in Appendix E. This table showsrun number, run duration, run condition (velocity, surface temperature, pH), additives, the asymptotic or final fouling resistance value and heater rod surface material.

Time plots of fouling resistance along with time plots of velocity, temperature and water quality (pH, conductivity and corrosivity) is another way of presenting the data, (See Appendix F). For each run, these plots allow one to determine if variations of any of these parameters during the run has an effect on the fouling resistance.

The final fouling resistance at run termination is presented in Appendix E, in a series of three dimensional figures, Figures E-1 through E-16. These figures are 60 pictorial representations of all runs grouped according to the cooling water with same additives. For a given constant water quality, the three major parameters of interest are water velocity in the test section, surface temperature of the heated section and the pH of the water in the system, these parameters areshown on the figure.

The cell of this matrix shows the final fouling resistance, the heater rod material type and the run number.

The results displayed in these figures show (in a qualitative manner) the effect of velocity, surface temperature and pH on the fouling characteristics of a given water.

The threshold values for each fouling inhibitor under

which fouling would not occur (R .f.. < 0.0001 hr ft2 °F Btu) are presented in Table VI-6.

Composite plots were constructed to show qualitative- ly the affect of various parameters on the fouling. These figures are given in Appendix G.

Throughout the subsequent sections where data are discussed and analyzed, a reference is made to the appendices and figures mentioned in this section.

Tests Without Iron:

The objectives of the proposed research without iron contamination were as follows: 61

1. To determine the effect of various state of the art antifoulants in reducing or eliminating calcium phosphate fouling of cooling tower water containing phosphate corrosion inhibitors under various conditions of pH, flow velocity and surface temperatures.

2. It was suspected that some antifoulants are a source of or increase fouling tendency. Thus one objective of this investigation was to determine and identify those antifoulants and the conditions at which they increase the fouling tendency.

3. In addition to information this study provides about the characteristics of the cooling tower water fouling, the data, when correlated, will allow prediction of fouling behavior under similar conditions.

A total of 107 tests were conducted to investigate the three objectives listed above. The following sections discuss and describe these tests.

Run Description and Discussion

1. No additive (runs 436-438)

The results of this additive combination are shown in

Figure E-1.

These runswere essentially blank runs in which no additive whatsoever was added to the high hardness water (Table IV-1) used in this study. 62

The effect of velocity on the fouling resistance for

runs 436 (5.5 ft/sec), 437 (8 ft/sec) and 438 (3 ft/sec)

is shown in Figure G-1. The effect of velocity shown in

Figure G-1 is consistent in that higher velocity produces

less fouling.

These runs were at 160°F and pH of 7.5. While the

rate of fouling for the additive-free water was not high, there is no indication in Figure G-1 that an asymptotic

fouling resistance has been attained. After a long time

unacceptable levels of fouling would probably occur

particularly at the two lower levels of velocity (5.5 and

3.0 ft/sec).

2. Additive: 4-5 ppm PP, 5-6 ppm OP, 2-4 ppm HEDP, 2-4 ppm PA (runs 302 through 307).

The results of this additive combination are shown in

Figure E-2.

All runs for thiswater were at 3 ft/sec and a pH

value of 7.0. Runs 302 through 304 were at 145°F and comparison of these runs is given in Figure G-2. Runs

305-307 were at 160°F and comparison of these runs is given in Figure G-3. Considerable fouling occurred with

this additive. Therefore, the use of HEDP in combination with polyacrylate do not appear to be effective in

reducing the deposition tendency of water containing polyphosphate and orthophosphatecorrosion inhibitors. The material of the heater used in these runs has little 63 effect, carbon steel shows somewhat higher scaling than stainless steel and copper/nickel at 145°F but somewhat lower at 160°F.

3. Additives: 4-5 ppm PP, 5-6 ppm OP (runs 308-313, 336- 338, 372-374 and 381-383). The results of this additive combination are shown in

Figure E-3.

With this additive, runs 372-374 at 160°F and 6.5 pH, copolymer AA/MA was being flushed from the system.

Composite plots comparing runs 311, 313 both at 160°F and

6.5 pH (Figure G-4) and runs 336-338 at 160°F and 7.5 pH

(Figure G-5) show the effect of velocity and in general agree with the fact that a higher velocity produces less fouling. The composite plot comparing (Figure G-6), run

309 and 310 both at 145°F shows the effect of increasing pH from 7.0 to 7.5. Figure G-7 compares runs 313 with stainless steel heater rod and run 372 with Admiralty heater rod both at identical conditions. The results are comparable and agree within the experimental error of the measurement. At 6.5 pH and 130°F, insignificant fouling occurred for this additive.

4. Additive: 10 ppm OP (runs 333-335).

The results of this additive combination are shown in

Figure E -4. 64

With this additive, minimal fouling was observed at

velocities higher than 3 ft/sec. As expected, higher

fouling occurred at 3 ft/sec and was increasing quite

rapidly. The effect of velocity for this additive is

shown in Figure G-e. Runs were at 6.5 pH and 160°F.

5. Additive: 10 ppm OP, 10 ppm AA/HPA (runs 324-332).

The results of this additive combination are shown in

Figure E-5.

With this additive, all runs were at 160°F. Runs

324-326, runs 327-329 and runs 330-331 were at pH 6.5, 7.5

and 8.2 respectively. For all tests, it appears that

negligible fouling would occur at the threepH levels

investigated. The values of fouling resistance at pH 7.5 and 8.2 would seem to indicate that this additive combina-

tion is effective in reducing the tendency of fouling.

Figure E-5 shows the fouling resistance values for the

runs of this additive.

6. Additive: 4-5 ppm PP, 5-6 ppm OP, 10 ppm AA/HPA (runs 314-324 and 348-365).

The results of this additive combination are shown in

Figure E-6.

Four levels of pH; 8.1, 8.5, 7.5 and 6.5, were

investigated for this additive combination. At these pH levels, the copolymer AA/HPA was effective in reducing the

fouling tendency of the phosphate. At a pH level of 7.5, 65 very little fouling was observed. Higher but insignificant fouling resistance at 160°F occurred for pH levels of 6.5 and 8.5 compared to those at pH of 7.5.

This could be due to the higher phosphate level for the runs in which the pH levels were 6.5 (24 PP, 80 OP) and

8.5. The effect of pH for this additive is shown in

Figure G-9. Figure G-9 shows that the trend with respect to pH is consistent in the sense that lower pH produces less fouling. Figure G-10 shows the effect of pH at 8.5 and velocity for runs 348-350. The pH dropped for runs

348-350 at 200 hours and significant fouling occurred.

This could be due to the pH decrease, since much of the suspended calcium phosphate dissolved. Hence, as pH was brought to the desired value, rapid fouling occurred. Low fouling occurred at pH 7.5 at 160°F for runs 351-353.

Figure G-11 shows the effect of velocity for these runs.

This figure also shows that with 5.5 ft/sec higher fouling occurred for no explainable reason compared to the runs at e and 3 ft/sec which unexplainably differ little from each other. Very little fouling occurred at pH 7.5 and 130°F for runs 316 and 317. Figure G-12 shows the effect of velocity for runs 316 and 317. The effect of velocity for runs 354-356 is shown in Figure G-13. The curve for 3 ft/sec in this figure agrees quite well with that obtained for run 314 shown in Figure G-14. Figure G-15 also shows consistent behavior with respect to velocity for runs 66

357-359. A sudden increase in fouling resistance started to occur at about 125 hours. See Figure G-15 and time plots for these runs in Appendix F. This sudden increase in fouling resistance is not apparent except that at this time pH started increasing slowly reaching a value close to 9.0 at the end of the runs. Conductivity decreased slowly during this period of increasing pH. Had the sudden increase in the fouling resistance not occurred, it appears that the asymptotic fouling resistance would be in the range 0.0001 to 0.0003 hr ft °F/Htu. The fouling resistance for runs 363-365, pH of 6.5 and 160°F,was increasing slowly at run termination. The runs were terminated because of the abnormally high phosphate levels, (24 ppm PP, 80 ppm OP). The effect of velocity for these runs is shown in Figure G-16.

Figure G-17 shows the effect of surface temperature for runs 320 and 321. Figures G-18 and G-19 show consistent behavior with respect to surface temperature for runs

356-359 and 353 and 362 respectively. In general less fouling was observed at lower surface temperature

(130°F); the amount of fouling was very small. Figure G-

72 shows the effect of pH and surface temperature for runs

317 and 323. 67

7. Additive: 4-5 ppm PP, 5-6 ppm OP, 10 ppm AA/MA (runs 339-341, 366-371, 396-401).

The results of this additive combination are shown in

Figure E-7.

With this additive, threepH levels were investigated; 6.5, 7.5 and 8.5. Composite plots in Figure G-20 for runs 339-341 at 160°F and pH is 7.5, Figure G-21 for runs 366-368 at 160°F and pH is 6.5 and Figure G-22 for runs 368-371 at 130°F and pH of 6.5 show the effect of velocity and temperature. For all three conditions, significant fouling occurred although at a lower rate of the higher velocity as would be expected. Consistent behavior with respect to surface temperature is shown in

Figure G-22 for runs 368 at pH 6.5 and 160°F and run 371 at pH 6.5 and 130°F. Runs 368 and 371 both were at 3 ft/sec.

Significant fouling was obtained for this additive at a pH of 6.5 at phosphate levels about two times those employed at a pH level of 7.5. In all cases of different combinations of surface temperatures and flow velocities at pH's of 6.5 and 7.5, fouling was increasing rapidly, showing little tendency to approach an asymptote.

For this additive, runs 396-398 at 160°F and 399-401 at 130°F were at a pH of B.5. The effect of velocity for runs 396-398and runs 399-401 areshown in Figures G-23 and G-24 respectively. This effect is consistent with the results obtained at pH's of 6.5 and 7.5. The irregulari- 68 ties shown in Figure G-24 were caused by a power failure at about 300 hours. While the equipment was idle, the pH decreased and much of the suspended calcium phosphate dissolved. Hence, when the equipment was restarted, rapid fouling occurred with subsequent sloughing of the deposit as pH was brought to 8.5. The effect of surface temperature at pH of 8.5 is shown in Figure G-25. This figure shows that at 8 ft/sec the effect of surface temperature is consistent with the results obtained for pH's of 6.5 and 7.5 for 8 ft/sec. However, in Figure G-26 (runs 398-

401) and for 3 ft/sec, surface temperature appears to have little effect. This is probably due to the presence of considerable suspended solids of calcium phosphate in the bulk stream at a pH of 8.5. Also, the higher average phosphate content for run401 at 130°F could have caused the fouling resistance to be higher than expected.

For all tests, acrylic acid/maleic anhydride (AA/MA) copolymer was not effective in mitigating the precipitation of calcium phosphate.

8. Additive: 4-5 ppm PP, 5-6 ppm OP, 10 ppm SS/MA (runs 342-344, 375-380, 402-407). The results of this additive combination are shown in

Figure E -8.

For different combinations of surface temperatures and flow velocities, three pH levels; 8.5, 7.5 and 6.5 69 were investigated. For pH of 6.5, Figures G-27 and G-28 show the effect of velocity and surface temperature respectively. Values of fouling resistance at pH's of 6.5 and 7.5 show in Figure E-8 show that this additive fouled somewhat more at pH of 6.5 than that at pH of 7.5. This is probably due to higher phosphate levels at pH of 6.5

(50% higher) than that at pH of 7.5.

Figure G-27 (runs 375-377) shows that the curves of

5.5 ft/sec and 8.0 ft/sec are nearly coincident. This is probably due to higher phosphate levels experienced at pH of 6.5. Figure 6-28 also shows the effect of surface temperature for runs 377 and 380 both at 3.0 ft/sec and a pH of 6.5. There was virtually no deposition at a surface temperature of 130°F.

For a pH of 8.5, runs 402-407, the effect of velocity at 160°F is shown in Figure G-29. For runs 402-407, although the asymptotic fouling resistance for both 3.0 ft/sec and 5.5 ft/sec appear to ultimately approach each other, the results are consistent with preview results of the velocity effect. The effect of velocity for runs 405-

407 and at 130°F is given in Figure G-30. Figure G-30 inexplicably shows the fouling resistance at 5.5 ft/sec to be greater than that at 3.0 ft/sec.

The effect of surface temperature is shown in Figure

G-31 (8 ft/sec) and Figure G-32 (3 ft/sec). 70

At the conditions investigated for this additive, the amount of fouling was very small over the range of velocities covered, indicating that sulfonated styrene/ maleic anhydride (SS/MA) is an effective copolymer in reducing the fouling tendency of polyphosphate/orthophosphate inhibitors.

9. Additives: 4-5 ppm PP, 5-6 ppm OP, 10 ppm AA/SA (runs 345-347, 384-389, 390-395).

The results of this additive combination are shown in

Figure E-9.

With this additive, three pH levels 6.5, 7.5 and 8.5 were investigated. Figure E-9 shows the results for all the runs with 10 ppm active acrylic acid/sulfuric acid

(AA/SA) copolymer. Virtually no fouling was observed at the conditions of the tests. This copolymer appeared to be very effective in preventing fouling by the polyphosphate/orthophosphate corrosion inhibitor. The effect of velocity and temperature and pH is shown in Figures G-33 to G-37, respectively.

This additive showed somewhat higher fouling at the high surface temperature (160°F) at both pH at 6.5 and 8.5 than that at pH of 7.5. At the pH levels of 6.5 and 8.5, the orthophosphate (OP) level was 50 to 75% greater than at 7.5. Figure G-33 for runs 384-386 at pH of 6.5 shows that the fouling to be increasing at a constant rate but 71 does show some tendency to level off at a value in the

0.0005 hr ft °F/Btu range.

For no explainable reason, there is insignificant velocity effect shown in Figure G-33. In Figure G-34 for runs 390-392, pH of 8.5, the fouling appeared to level out at about 0.0001 hr ft °F/Btu at about 40 hours. However, during this period pH was very erratic dropping to below

7.0 and then increasing before stabilizing at about 60 hours. At 40 hours a sudden increase in fouling occurred probably due to thebehavior of the pH. The asymptotic fouling resistance, even after the sudden increase, is still not exceedingly high, 0.0002 to 0.0006 hr ft °F/Btu.

For no apparent reason, the asymptotic fouling resistance for 5.5 ft/sec is significantly lower than that for 3.0 ft/sec, a result that is not consistent with previous results.

A consistent behavior with respect to surface temperature is shown in Figures G-35 and G-36 for runs

386, 389 and runs 392, 395, respectively. Virtually no fouling was observed at the surface temperature at 130°F.

The effect of pH is shown in Figure G-37 for runs 386 (pH of 6.5) and 392 (pH of 8.5). It appears that lower fouling occurs at pH of 6.5 but results are inconclusive because of the effect of erratic pH values during run 392. 72

Effectiveness of Copolymers in Reducing the Fouling Tendency of Phosphate Corrosion Inhibitors

For pH of 8.5, four different copolymers were compared in figures G-38 (8.0 ft/sec, 160°F), G-39 ft/sec,

160°F), G-40 (8.0 ft/sec, 130°F) and G-41 (3.0(3.ft/sec,

130°F). In all cases, AA/MA was not an effective copolymer in reducing calciumphosphate deposition. AA/HPA and AA/SA were both very effective at a surface temperature of

160°F. At 130°F surface temperatureAA/SA was very effective and slightly more effective than AA/HPA. AA/SA and AA/HPAare compared in figure G-68. AA/SA appeared as if it would be effective if variation in the pH during Run

392 (Appendix F) had not occurred. AA/HPA (Run 356) is reasonably effective showing a probable asymptotic fouling resistance of 0.0004 hrft2di°F/Htu. Generally, SS/MA is only moderately effective, except at 8.0 ft/sec and 130°F it is about as ineffective as AA/MA.

For pH of 7.5, Figures G-66 for runs 314, 338, 344 and 347, all at 3 ft/sec, and G-67 for runs 315. 340. 343 and 348, all at 8.0 ft/sec, compare the effectiveness of various copolymers in reducing calciumphosphate deposition. In the case of the copolymer AA/HPA, SS/MA and

AA/SA fouling was effectively reduced by their presence and in all cases acceptablefouling experienced. The copolymer, AA/MA had no effectiveness reducing fouling tendency. In fact, a greater fouling rate and ultimately higher final fouling resistance was experienced with this 73 copolymer presence than when it was absent (Runs

337,338). For pH of 6.5, the effectiveness of the copolymers in reducing the calcium phosphate deposit is shown in G-65, for runs 311, 365, 368, 377 and 386. For this and at the extreme conditions of 3.0 ft/sec velocity 160°F surface temperature, AA/HPA and AA/SA were very effective. SS/MA was reasonably effective giving asymptotic fouling resistance about 70% of those when no copolymer was used.

Copolymer AA/MA was ineffective.

Iron Tests:

The objectives of the proposed research with iron as a contaminant were as follows:

1. To determine the effects of total iron concentration, the type of iron (ferric or ferrous, particle or colloidal) on the fouling characteristics of cooling tower water.

2. To determinehow well various antifoulants will reduce or eliminate iron fouling for various flow velocities and surface temperatures.

3. To determine how well the fouling data from such a system fits predictive models. 74

A total of 62 tests were conducted to test the effects of the presence of iron. These can be divided into several categories.

1. Runs on high hardness cooling tower water to determine the influence of iron concentrationon the amount of fouling. Also to determine the influence of flow velocity and surface temperature on the fouling characteristics of the cooling tower water when iron is present.

2. Runs to determine the influence of iron on the characteristics of the cooling tower water containing phosphate corrosion inhibitors.

3. Runs to determine the effectiveness of antifoulants in reducing or eliminating the deposition of iron.

4. Runs to test the validity of some of the various hypothesis made concerning the iron fouling.

Table E-1 and Figures E-1 through E-16 show the operating and water quality condition for all runs. For runs for which fouling occurred, the fouling data was fitted to Equation (5-35). Results are given in Table

VI-1. 75

Run Description and Discussion

1. Additive: 4-5 ppm PP, 5-6 ppm OP, 2 ppm Fe (runs 408- 413).

Six runs with this additive are shown in Figure E-10.

These runs were the beginning of an extensive investigation of the effect of the presence of iron in the cooling tower water. The runs with iron consisted of the addition of soluble iron (FeS0.4-7Hp1(3) directly to the cooling tower sump at a rate to maintain a given total iron content in the water.

For the six runs shown in Figure E-10, total iron content was maintained at a nominal 2 ppm in the cooling tower water. For these runs, the solution in the iron supply vessel showed some precipitation of brownish iron oxide.

The pH of the cooling tower water was maintained at

7.5. The effect of velocity is shown in Figure G-42

(160°F). For these conditions, the effect of velocity is consistent with previous observations. Considerable fouling occurred at all velocities and sloughing of the deposit occurred at all velocities. The effect of velocity shown in Figure G-43 (130°F) indicates an inconsistency. Run 412 (8.0 ft/sec, Cu/Ni) shows more fouling than either of the other runs, run 413(3.0 ft/sec,

SS) and run 411 (5.5 ft/sec, SS). A possible explanation to this inconsistency is the following: For this additive combination (Run 412, 8.0 ft/sec, Cu/Ni), the Cu/Ni rod 76 surface corroded and the corrosion products on the rod surface served to immobilize the deposit materials at the wall and thus reduced the removal effect of velocity.

2. Additive: 4-5 ppm PP, 5-6 ppm OP, 4 ppm Fe (runs 414- 419).

With this additive, threeruns (runs 414-416) at

160°F and three runs (417-419) at 130°F are shown in

Figure E-11. The level of total iron in the system was maintained at a nominal 4 ppm. The effect of velocity for runs 414-416 at 160°F is shown in FigureG-44 and the results are consistent with previous observations with respect to the effect of velocity, although initially velocity appeared to have little effect. For these runs in this section and subsequent sections, a small amount of sulfuric acid was added to the vessel containing the ferrous sulfate solution in order to clarify it and dissolve the precipitate that was present during runs 408-

413 (2 ppm total iron).

The nominal level of phosphate corrosion inhibitor was 4-5 ppm polyphosphate and 5-6 ppm orthophosphate.

While it was attempted to maintain these levels for runs

417-419, some deviations occurred. Generally the total phosphate ranged between 10 and 14 ppm.

Negligible fouling was observed for this additive at the low surface temperature of 130°F. Figure G-45 shows 77 the effect of velocity and the results are consistent with previous observations. Figure G-46 compares runs 415 and 418 at 8 ft/sec and

Figure G-47 compares runs 416 and 419 at 3 ft/sec, showing the effect of surface temperature, despite the somewhat higher level of iron in runs 415 and 416 (3.7% versus

3.0%, in runs 418 and 419). The effect of surface temperature appears to be consistent with the results of previous observations. For run 415, the rapid increase in fouling isdue to a decrease in pH due to adding the iron solution at a high rate to increase iron content. As the pH was brought back to the desired level of 7.5, a more reasonable fouling resistance was obtained.

3. Additive: 4-5 ppm PP, 5-6 ppm OP, 4 ppmFe, 2-4 ppm HEDP (runs 420-429).

This was a series of tests to determine the effectiveness of low levels of HEDP in reducing fouling by iron and phosphate corrosion inhibitors. The results are shown in Figure E-12.

In Figure G-48 for runs 420 (5.5 ft/sec), 421 (8.0 ft/sec) and 422 (3.0ft/sec), the effect of velocity is shown at pH of 7.0 and surface temperature of 160°F. The effect of velocity is consistent with previous results.

That is, very low fouling occurs at 8.0 ft/sec and considerable fouling occurs at 3.0 ft/sec. A number of duplicate runs were made with this 78 additive and the results are shown in Figure G-49. For runs 422-426 (at pH of 7.5, velocity of 3.0 ft/sec and surface temperature T,.. of 130°F), fair agreement is obtained between the various runs if the sloughing of deposits for runs 424, 425 and 426 is neglected. This sloughing occurred early in the course of the runs.

Sloughing is not predictable and is highly dependent on the nature of the deposit and the nature of the heater surface.

Some of the differences observed betweenruns may be due to the variation of phosphate content during the runs.

For runs 422, 423 and 424 (which agree well with each other neglecting the early sloughing of the deposit of runs 424), the total phosphate content of thewater was

11-13 ppm with a standard deviation of about 4.6.

However, for runs 425 and 426 the total phosphate was about the same but the standard deviation was only about

2.2.

The conclusion is that only fair reproducibility of results is obtained among the series of runs shown in

Figure G-49. But this may be due to the fluctuation of the phosphate content of the water during the runs.

Figure G-50 shows the effect of surface temperature for this additive in which run 422 (160°F) is compared with run 429 (130°F). Virtually no fouling is observed at 79 the low surface temperature while significant fouling is observed at the high surface temperature.

4. Additive: 4-5 ppm PP, 5-6 ppm OP, 4 ppm Fe, 10 ppm AA/MA (runs 430-435).

Results for this additive are shown in Figure E-13.

This was a series of runs to determine the effectiveness of the copolymer AA/MA (acrylic acid/maleic anhydride) in minimizing the fouling of water containing .phosphate corrosion inhibitors and iron. In agreement with previous results with AA/MA without iron discussed previously, it is seen that AA/MA is not effective at minimizing fouling and in fact appears to enhance fouling.

The effect of velocity is shown in Figure G-51 in which runs 430 (5.5 ft/sec), 431 (8.0 ft/sec) and 432 (3.0 ft/sec) are compared at surface temperature of 160°F. The effect of velocity is consistent with previous results if the sloughing of the deposit for all the runs is neglected. Considerable sloughing occurred at each velocity.

The effect of surface temperature is virtually negligible for this additive, as indicated by Figure E-13 and Figure G-52 in which run 431 (160°F) are compared at

8.0 ft/sec. However, if the sloughing of the deposit for run 431 is neglected, the resulting fouling would have been somewhat greater for the higher surface temperature run. 80

The effectiveness of HEDP and AA/MA is shown in

Figure G-53, in which run 414 (no additive), run 420 (2-4 ppm HEDP), and run 430 (10 ppm AA/MA) are compared. The ineffectiveness of AA/MA is evident. HEDP may have some slight effect in reducing fouling since run 414 (no additive) contained an average of 3.7 ppm total iron while run 420 (2-4 ppm HEDP) contained 2.8 ppm of iron and yet the fouling for both runs is nearly the same.

5. Additive: 3 ppm Fe (runs 439-450).

Results for this additive, which consisted of 3.0 ppm

Fe, is shown in Figure E-14.

The effect of velocity, shown in Figure G-54 for runs

439 (5.5 ft/sec), 440 (8.0 ft/sec) and 441 (3.0 ft/sec) is consistent with previous results. Comparing Figure G-54 with Figure G-1 shows the dramatic effect of the presence of iron in water. For example, at 3.0 ft/sec, the fouling resistance for run 438 (no Fe) was about 2.0E-4 hr ft2

°F/Btu at 280 hours while at the same run duration for run

441, the fouling resistance was about 8.0E-4 hr ft2

°F/Btu. Figure G-55 compares three identical runs at 5.5 ft/sec at T. of 160°F in which the water contained 3.0 ppm of total iron. Good agreement is shown between runs 439 and 448. Run 445 shows a significantly higher fouling resistance after about 80 hours. At this time, a power failure occurred. When the equipment was idle the pH 81 dropped lower than 7.5. When the systemwas restarted, the fouling rate was much higher than for runs 439 and

448. Similarly, Figure G-56 compares three identical runs at 3.0 ft/sec and T,. of 160°F. These runs compare very well with each other. However, the effect of the power failure at 80 hours for run 447 is evident. As the equipment was restarted considerable sloughing occurred.

Had this sloughing not occurred, the resulting fouling for run 447 would have been greater than for runs 441 and 450 in agreement with the results shown in Figure G-55 for runs 439, 445 and 448.

6. Additive: 4-5 ppm PP, 5-6 ppm OP, 3 ppm Fe (runs 451- 461).

Results for this additive are shown in Figure E-15.

Figure 39 shows the effect of velocity in which runs 451

(5.5 ft/sec), 452 (8.0 ft/sec) and 453 (3.0 ft/sec) are compared at Ts of 160°F. At the end of the runs the effect of velocity is consistent with previous results.

All runs showed a rapid increase in fouling resistance early in the runs. Inspection of the water analyses showed that, initially, thewater contained about 12 ppm of total iron. As the runs proceeded, the iron content of the water was gradually reduced to about 3.0 ppm. The average iron level for the runs is 4.9 ppm with a standard deviation of 3.2. It is interesting to note that as the iron content is reduced the deposits are sloughed off and 82 the fouling resistance attains an apparent constant value considerably below the maximum value which was attained early in the runs.

Figure G-58compares 3 identical runs at 3.0 ft/sec and Ts of 160°F. All runs appear to converge to ap- proximately the same fouling resistance (even run 453, in which the water initially had a very high iron content and very high fouling was observed early in the run).

Figure G-1 (no additive), G-54 (3 Fe), and G-57 (4-5

PP, 5-6 OP, 3 Fe) canbe compared to show the effect of additives. For example, at a velocity of 3 ft/sec and Ts of 160°F and at a run duration of 180 hours, the fouling resistance for run 438 (no additive) (Figure G-1) is 1.0

E-4 hr ft' °F/Btu, for run 441 (3.0 Fe) (Figure G-54) is

3.0 E-4 hr ft 22°F/Btu, and for run 453 (4-5 PP, 5-6 OP, 3

Fe) (FigureG-1) is 11.0 E-4 hr °F/Btu. Increased fouling occurs when iron is present in the water and even more fouling occurs when iron is present along with phosphate corrosion inhibitors. The fouling effects of the iron and the phosphates appear to be additive as discussed below.

These three runs complete the investigation of the effect of the presence of ironalong with the phosphate

inhibitor at a surface temperature of 130°F. The results are shown in Figure E-15R and plotted in Figure G-59 which shows the effect of velocity. Very low fouling is 83 observed for this combinationof additives under these conditions. Figure G-59 shows that the effect of velocity is consistent with previous results with fouling increasing as the velocity decreases. The average orthophosphate level was somewhat greater than 10 ppm and average iron level was 4 ppm. Even under these conditions the fouling appears to be insignificant at the three velocities investigated.

7. Additive: 4-5 ppm PP, 5-6 ppm OP, 3 ppmFe, 10 ppm HEDP (runs 462-469).

This series of runs was designed to investigate the effect of the presence of HEDP along with the iron and the phosphate corrosion inhibitor. The results are shown in

Figure E-16 and the effect of velocity is shown in Figures

G-60 (160°F), G-61 (130°F) and G-62 (160°F). Runs 464SS and 469SS are duplicates as are runs 462SS and 468SS.

Significant fouling is observed in Figures G-60 through G-62 even at the low surface temperature of 130°F

Figure G-61. The results indicate that HEDP is not effective in inhibiting calcium phosphate and iron deposition and it even appears to enhance the fouling.

The effect of velocity shown in Figures G-61 through

G-62 is consistent with previous results with fouling increasing as velocity decreases. The effect of velocity is not as significant as would be expected from previous results indicating that the deposit is probably quite hard 84 and quite adherent to the heater surface so that the removal rate is lower than would be expected with a soft deposit. At 130°F surface temperature (Figure G-61) the effect of velocity is almost negligible in the range 3.0 to 5.5 ft/sec.

The effect of surface temperature for this additive combination is shown in Figure G-63 (8.0 ft/sec) and

Figure G-64 (3.0 ft/sec). The effect of surface temperature is consistent with previous results with fouling increasing as surface temperature increases. At 8.0 ft/sec, however, the effect of surface temperature is not large but at 3 ft/sec the surface temperature has a large effect with the fouling at 130°F being about one half of that at 160°F.

The average concentration of additives for these sets of runs is fairly uniform although the average iron level is somewhat low; 1 ppm for runs 462 through 467 and 2 ppm for runs 468 and 469. Average orthophosphate level ranged from 6.7 to B.4 ppm and polyphosphate ranged from 3.1 to

4.4 ppm.

Effect of Iron in the Presence of Phosphate Corrosion Inhibitors at a pH of 7.5

The effect of the presence of iron in the cooling tower water containing corrosion inhibitors is shown in Figures G-69 (8.0 ft/sec), G-70 (5.5 ft/sec) and G-71 (3.0 ft/sec). In all runs which are compared in these figures, 85 the phosphate level was nearly the same and the major difference was the iron content.

In Figure G-69, for runs 337 (no iron), 409 (1.9 ppm

Fe) and 415 (3.7 ppm Fe), slightly higher fouling is observed for run 409compared to run 337. However, run

415 shows very little fouling even though the water contained 3.7 ppm Fe. One reason for this low fouling may have been due to the nature of the deposit which at the high velocity of 8.0 ft/sec was more easily removed than the deposits from runs 337 and 409.

In Figure G-70 for runs 336 (no iron), 408 (1.9 ppm

Fe), 414 (3.7 ppm Fe), 454 (3.5 ppmFe) and 457 (3.9 ppm

Fe) slightly higher fouling is observed for runs (except for run 414) containing 3.5 to 3.9 ppm Fe compared to run

336 for which no iron was present. Runs 454 and 457 (3.5 to 3.9 ppm Fe) compare quitewell with each other. It appears, on the average, that asymptotic fouling resistance for these runs would be 15 to 25 percent greater than when no iron is present. In this set of comparisons,

Run 408 (1.9 ppm Fe) showed higher fouling than Run 336

(no iron). This is consistent with the result obtained at

8.0 ft/sec. The fouling for Run 414 (3.7 ppm Fe) is considerably lower than that for runs 454 and 457 which contain the same amount of iron. This was also true for

Run 415 (compared to Run 337). Again, this may be due to the type of deposit formed in runs 414 and 415. 86

The comparison at 3.0 ft/sec is shown in Figure G-71.

Again, the water containing 1.9 ppm Fe (Run 410) shows the highest fouling. The fouling for water containing 3.5 to

3.9 ppm Fe (runs 416, 456, 458) is lower than the fouling for Run 410 but somewhat higher than the fouling for water containing no iron (Run 338).

Figure G-59 shows the effect of velocity at 130°F. Although average orthophosphate level was somewhat greater than 10 ppm and average iron level was 4 ppm, the fouling appeared to be insignificant at the three velocities investigated because of the low surface temperature of the heater.

In summary, it appears that the presence of iron (3.5 to 3.9 ppm Fe) causes somewhat higher fouling (15 to 25 percent above that for water containing no iron). Water containing 3.5 to 3.9 ppm Fe showed lower fouling than water containing 1.9 ppm Fe, possibly due to the nature of the deposits formed with the higher iron content water.

The high fouling for the low levels of iron (1.0 ppm Fe) could also have been due to the presence of precipitate in the iron solution supply tank. From theabove discussion it was concluded that the fouling effects of the iron and the phosphates appear to additive. 87

Effectiveness of HEDP Copolymer in Reducing the Deposition of Iron

Water containing phosphate corrosion inhibitors and iron was investigated with 10 ppm HEDP additive. The effectiveness of this additive in inhibiting deposition is shown in Figure G-74 (3.0 ft/sec, 160°F) and Figure G-76

(5.5 ft/sec, 160°F). In all cases, the presence of HEDP appears to enhance the fouling rather than inhibit it.

Effect of Iron on theDistribution of Deposit on the Heater Rod Surface

In the Run Description section (Iron test section, additive no. 5), the effect ofoperational parameters of flow velocity and surface temperature was discussed. The discussion showed that the effect of flow velocity and surface temperature is consistent with previous results obtained for high hardness cooling tower water with and without phosphate corrosion inhibitors, i.e. higher velocities tend to reduce the fouling, and lower surface temperatures tends to reduce the fouling.

In this section the nature of the deposit (its composition and distribution over the heater rod) is discussed. A total of 11 runs, starting with runs 439, were conducted during the course of this investigation containing only high hardness water and 3 ppm iron. Iron was maintained in solution by the addition of sulfuric acid to the iron solution tank. 88

For Runs 439 (5.5 ft/sec, 160°F) and 441 (3 ft/sec,

160°F) (both with stainless steel heater rods), the deposit was a gelatinous film of ferric hydroxide which had a tan color. The gelatinous deposit was over the heated area only. Since Runs 436-438 showed that high hardness cooling tower water without phosphate corrosion inhibitor at a pH of 7.5 is not in scaling condition, it is speculated that fouling was only due to the iron presence. There was no deposit on the non-heated areas of the heater rod. This led to the speculation that heat transfer plays a major role in the formation and bonding of the iron film to heater rod surfaces. To explain this, it was postulated that if the mass transfer alone caused the formation and the bonding of the deposit film, then there would be a fouling film all over the heater rod surface, heated and nonheated areas.

To verify this postulation, Runs 439 and 441 were repeated (Runs 445 and 447). The results supported the postulate in that a gelatinous tan colored film of ferric hydroxide was obtained again only on the heated area of the heater rod. To further support the postulate, Runs

439 and 441 were again repeated (Runs 442 and 444), but this time the surface temperature was different (Ts of

130°F) while Runs 439, 441, 445 and 447 have Is of 160°F.

The results of Runs 442 and 444 showed no deposit on the heater rod. This indicates again that mass transfer alone 89 cannot form a deposit of iron film and that heat transfer at a surface temperature of 130°F does not cause iron particulate to bond to the heater rod surface. This suggests that a threshold energy level was needed before this gelatinous film could form. This behavior is explained later in this chapter through the help of coagulation theory. Some properties of Fe(OH);, are presented here to help explain the formation of the gelatinous film on the heated area. When hydrated ferric hydroxide coalesces, it forms a gelatinous material. This material has the power of absorbing large quantities of water when heated in solution. This explains the presence of the gelatinous film only on the heated area of the heater rod surface. The hot surface helps Fe(OH), to absorb largequantities of water and thus coagulation takes place and large flecks of red-brown gelatinous

Fe(OH)a form and deposit on the hot surface. The hot surface causes Fe(OH), to grow by helping the colloidal particles to aggregate and thus the deposit forms.

Runs 440, 443 and 446 (CuNi heater rod, 8 ft/sec and

160°F) showed a very interesting behavior of iron deposition process. In Run 440 the deposit was particulate in nature, depositing only on the non-heated area of the heater rod in contrast to Runs 439 and 441 (which were run for thesame run duration and same water quality simul- taneously with Run 440) with stainless steel rods where 90

deposits of gelatinous film of ferric hydroxide formed only on the heated area of the heater rod. The color of the deposit was mainly brown, suspected to be the color of a mixture of particles of iron oxide and ferric hydroxide, with some particles having a pale bluish color (olive green color) suspected to be copper corrosion. Table H-1

shows appreciable amount of copper present in the deposit along with iron, silica and aluminum. The presence of an

appreciable amount of copper and the presence of manganese for the first time in the deposit was found only for those runs where iron waspresent in the cooling tower water.

The visual observation and the constant presence of copper

and manganese in the deposit collected from the surface of the copper/nickel rod support the conclusion that copper corrosion is taking place in the copper/nickel rod since

there is no other source of copper and manganese except

from copper oxide forming on the surface of the heater rod. To further investigate the particle deposition process on the Cu\Ni heater rod, Run 440 was repeated (Run

443). The same behavior was observed in this repeat run

(Run 443). In this run, no deposit was observed on the heated area and only a deposit of particles was present on

the non-heated region. From these two runs, 440 and 443,

it was possible to postulate:

a. The copper/nickel surface corrosion by playing the role as a substrate has the ability in absence of heat 91 to bond physically with iron particles with a force enough to resist the shear forces.

b. The rough surface of copper/nickel rod (which had been in use for a very long time) played a role in trapping the particles and then by agglomeration, the particles grew in size.

c. On the heated area of the heater rod, the heat exerted a retarding force for the particles, and the speculation here is that a thermophoresis process is occurring.

To investigate postulates a, b and c, a third test under the same conditions as Runs440 and 443 was conducted (Run 446). A new copper/nickel rod was used in this run. The result of this run was consistent with runs

440 and 443 which suggests that the roughness of the surface probably did not play a major role and that the surface corrosion was the major factor in forming the particle deposit.

With respects to part c above, it is speculated that heat transfer acted as a retarding force which forced the particles away from the heated surface, or by weakening the bonding force and thus shear forces were able to remove the particles as they reached or formed on the surface or by the thermophoresis process (i.e. material migrates from the hot surface back to the liquid bulk which is cooler than the surface). Where there was no 92 heat transfer, the mass transfer process was able to transport the particulate material to thesurface and the particles bonded to the surface. This indicates that a shear force of 8 ft/sec alone is not strong enough to prevent deposit at the non-heated area.

Hopkins (13), in his work on the fouling of a stainless steel tube by Fep...073, used the crevice corrosion phenomenon to explain the fouling mechanism of Fep0,,, on the stainless steel tube. Hopkins, in his conclusion of his work, recommends that his use of crevice corrosion to explain his data be tested by more work on iron fouling.

Since the fouled surface of the copper/nickel rod in this investigation was found to be in a corrodedcondition, it is of interest to use Hopkins postulate in explaining the deposition mechanism on copper/nickel rods. The fundamen- tals of crevice corrosion are described by Fontana and

Greene (7). Briefly, the principlerequirements for crevice corrosion of material in aqueous media are a metal surface partially shrouded by a non-conductor (i.e. a spotty FeO da deposit), creating a stagnant crevice which acts as anode:

M + ne- (M = Fe, Cu, Cr, and Ni)

a relatively large cathodic area (i.e. the unfouled portions of the tube) at which: 93

Oe + 2He0 + 4e- 40H-

and trace amounts of an aggressive ion such as the chloride ion (as used in this study to prevent biofouling), which serves to transport and precipitate the metallic ion as a corrosion product (rather than allowing it to form a protective oxide film);

M"4- ncl- + nHa0 M(OH), +

with the HCl-f'- promoting further attack.

Hopkins (13), stated that corrosion products on the surface serve to bind the red hematite deposits more firmly to the wall and using crevice corrosion phenomenon he postulated that the initial spotty fouling triggers further fouling by the crevice corrosion process. The stabilization of the initially loose deposit structure by the corrosion products serves to suppress the release mechanism. From the discussion above, and from the discussion earlier about the nature of the deposit and the corrosion of the copper/nickel rod, it appears that the behavior of the iron particles depositionprocess on copper/nickel surface is in agreement with Hopkins' use of crevicecorrosion process and postulation. However, to further investigate this assumption, more tests designed specifically for this purpose is needed, since the above 94 discussion was based only on visual observation of the presence of particles. The possibility of the presence of very small particles on the copper/nickel heated surface need also be checked by closer examination of the surface.

Deposit Distribution on the Heater Rod Surface in the Presence of Iron and Phosphate Corrosion Inhibitors at pH of 7.5

The effect of iron when phosphate corrosion inhibitors were present was discussed earlier (Effect of

Iron in the Presence of Phosphate Corrosion Inhibitors at a pH of 7.5 Section) in terms of the thermal fouling resistance values, it was found on the average that asymptotic fouling would be 15 to 25 percent greater than when no iron was present. The results for copper/nickel rod obtained in Runs 452 and 455 for this additive combination wereconsistent with the previous results obtained for high hardness and iron water. Thus the postulates and explanations given in the previous section is further supported by the observation of the deposit nature and distribution in these runs. Although phosphate corrosion inhibitors are present in these runs, a layer of copper corrosion was observed in both Runs 452 and 455 on the nonheated area. Two layers were observed on the nonheated area; the first layer was bluish-green in color and on top of it a second layer of a large number of brown colored particles. With this additive, all runs, includ- 95 ing runs with copper/nickel rods, had a tan, wet layer of a powdery-like deposit on the heated area of the heater rod. The composition of the deposit of Runs 452 and 455 is given in Table H-1. When the runs were terminated and the heater rods were removed from test sections for cleaning and deposit collection, and after the tan colored, wet-powdery deposit was dried, the deposit became very loose and started to fall off the surface of the heater rod and a second layer which was of a white color suspected to be mainly of calcium phosphate appeared.

This second layer had to be removed mechanically from the heater surface. The tightness and compactnessof this second layer is consistent with all previous results and observation of the nature of calciumphosphate deposit.

The above observations permit the following speculations:

1. In the case of copper/nickel rod, the phosphate corrosion inhibitors were not able to prevent copper corrosion fromoccurring when iron was present. This is perhaps due to either the behavior of the corrosion inhibitor in this condition or due to the concentration of the inhibitors used. Thus further experimentation is required.

2. In the case of the heated area, deposition occurred for all runs, the above discussion (Effect of

Iron in the Presence of Phosphate Corrosion Inhibitors at a pH of 7.5 Section and additive number 6 in Run Descrip- 96 tion and Discussion Section) showed the effect of the presence of iron on the fouling characteristics of the cooling tower water is additive, i e layer of inverse solubility salts with a particulate layer of iron product of ferric hydroxide on top of it.

Deposit Distribution on theHeater Rod Surface in the Presence of AA/MA, HEDP, Iron and Phosphate Corrosion Inhibitor

Effectiveness of HEDP copolymer with this additive combination inreducing iron deposition was discussed in an earlier section of this chapter. With this copolymer, a heavy precipitation of deposition material was experienced for all flow velocities, surface temperatures, heater surface materials and HEDP levels. The deposit covered the rods on heated and non-heated areaswith an apparent thicker layer of deposit on the heated area. The deposit also covered all the glass tubes that house the heater rodsand the flow meters to a point it was impossible to permit visual observation of the deposit. The deposit in this case was also powdery innature with a faint tan color indicating formation and deposition of particulate ferric hydroxide. The deposit was easily removed from the surface of the heater rod. It was very difficult, almost impossible to maintain 3 ppm iron in the cooling water when HEDP was present. 97

Towards the end of Runs 468 and 469, the addition of

HEDP copolymer was terminated and the iron concentration

went up to the desired level of 3 ppm. This indicates

that HEDP acts as an agglomerating agent instead of acting

as an inhibitor in this case.

Runs 430-435 were conducted to test the effectiveness

of AA/MA in preventing iron deposition. Runs 430-432 were at 160°F and 433-435 were at 130°F. At both temperatures

the deposit was a gelatinousfilm of ferric hydroxide covering the heated area of all rods stainless steel and copper/nickel alike. For the copper/nickel rod (Run 434) only a brown color and greenish particles were found to cover the non-heated area. Deposit collected from the surface of copper/nickel rod (Run 434, Table H-1) showed a significant amount of copper which indicated copper/nickel rod surface corrosion.

Effect of the Material of the Heater Surface

The results presented herein generally support the conclusion that the material of the heater surface has

little effect on the fouling. Figure G-2for runs 302

(SS), 303 (CS) and 304 (CuNi) indicate that before the deposit sloughed off the heater, carbon steel showed somewhat higher fouling with stainless steel and copper/nickel about equal. After the deposit sloughed off, all three surfaces fouled at the same rate. Figure G-3 98 for runs 305 (SS), 306 (CS) and 307 (CuNi) shows good agreement with little difference between stainless steel and copper/nickel and erratic behavior on the carbon steel. For carbon steel, if sloughing had not occurred at about 75 hours, it would also not have been very different from the other two surfaces. Figure G-7 for runs 313 (SS) and 372 (Adm) shows good agreement between the two materials.

Reproducibility of Results

Several duplicate runs were made. The comparison between duplicate runs is shown in Figures G-73 through

G-74. Figures G-73and G-75 compare runs in which the additives are only phosphate and iron. In Figure G-73

(8.0 ft/sec, 130°F) there is relatively good agreement between the runs (Runs 418 and 460) and generally the fouling is very low. The somewhat higher fouling shown by

Run 460 could be due to a slightly higher phosphate content of the water (14.9 versus 12.1 ppm) and slightly higher iron content (4.0 versus 3.0 ppm). The same observations apply to Figure G-75 (3.0 ft/sec, 130°F) but in each case the fouling is very low.

Figure G-76 (5.5 ft/sec, 160°F) compares Runs 462 and

468. For these runs the water contained 10 ppm HEDP in addition to the phosphate and the iron. Both phosphate 99 and iron levels are comparable and good agreement is observed between the two runs. Figure G-74 (3.0 ft/sec, 160°F) compares Runs 464 and

469 in which the water contained 10 ppm HEDP in addition to the phosphate and the iron. Good agreement is observed between the two runs up to about 100 hours. The fluctuation of pH for Run 469 and the slightly high iron content of the water (2.0 versus 1.0 ppm) may explain the deviation between the two runs beyond 100 hours.

Deposit Composition

For additive combinations for which deposit occurred, the deposit was collected and analyzed. With the exception of the presence of very minor constituents, the deposit was mainly calcium phosphate. When iron was added to the cooling tower water, iron was also present in the deposit as a major constituent along with calcium phosphate components.

Chemical analysis of the deposits is shown in

Appendix H, Table H-1. This table shows the run number, the condition of water quality for which the deposit occurred and the percentage of the constituent of the deposit. Table H-1 (Deposit Composition Table) and Table VI-1 (lists run number and Rwr) can be used to match the deposit and its thermal resistance. 100

Types of Fouling Resistance Time Curves Obtained

The fouling curves could be assigned to four distinct categories; asymptotic, linear, concave upward and

(occasionally) a sawtoothed curve. A sawtooth curve was obtained when the deposit gradually built up, suddenly sloughed off the heater rod surface and then built up to the same, or higher, level before it sloughed off again.

Linear and concave upward curves were observed only for a few runs with linear curves occurring more frequently.

In Table VI-1, runs which have such curves are identified and the fouling-time curve for each run is given in Appendix F. In Figure VI-1A, the types of the fouling resistance-time curves obtained in this study are shown. Curve A represents a linear fouling behavior;

Curve B represents a concaveupward fouling behavior;

Curve C represents an asymptotic fouling behavior and

Curve D represents a sawtooth fouling behavior.

It was observed during the course of the investigation that runs for which a linear fouling behavior was obtained, the deposit was hard and difficult to remove from the surface of the heater rod, indicating strong adhesion to the heater surface. Linear fouling curves result when deposition rate is constant and there is no removal or the difference between the deposition rate and removal rate is constant. Runs which exhibited concave 101

Figure VI-1A: Fouling Resistar:eTime-Curves 102 upward curve behavior suggests that the deposition rate increases or the removal rate decreases with time.

Taborek et al (32), reported that this casewas not experimentally observed and it is most undesirable. The deposit for the concave upward fouling behavior was also hard and difficult to remove from the heater rod surface, suggesting strong bonding of the deposit to the heater surface wall and between the deposit constituent. Curve C shows an asymptotic curve which is a common characteristic of cooling tower water fouling. Curve C was the most frequent type of fouling curve obtained in this study. It illustrates fouling behavior as described by Kern and

Seaton (15) and thus it can be fitted to Equation (5-36):

Rw = RN-,E1 exp(-(e ed)/e.)] (5-36)

The deposit showing the asymptotic fouling behavior was a soft deposit that was easy to remove from the heater rod surface. Frequently the deposit falls off the heater surface upon drying. In this case of asymptotic fouling, the assumption is that the removal rate increases with the thickness of the deposit layer, indicating that shear strength of the deposit is decreasing or other mechanisms deteriorating the stability of the deposit layer is taking place. In this case, deposition rate and removal rate ultimately become equal resulting in an asymptotic form of 103 the fouling resistance-time curve. It is also possible that asymptotic behavior may result from the deposition rate decreasing with increasing deposit thickness to the point where essentially no deposition occurs.

Figure VI-1A also shows a delay time, to. This delay or dead time was reported frequently in the literature of fouling. Table VI-1 list the dead time that was obtained for various runs in this study. It was observed during this period that an enhancement ofheat transfer occurred due to increases roughness of the surface as nucleus formation proceeds.

Analysis of the Fouling Data

A nonlinear regression analysis was used to fit the data of the runs shown in Table VI-1 to Equation (5-36). The regression analysis was performed to obtain e,, e, and

Rw'r of Equation (5-36). In some cases it was necessary to fix the dead time e, so negative values of Rf would not result from the regression.

For the runs which had a negative fouling resistance value at the beginning of the run, the abscissa was shifted before performing the regression analysis.

For runs in which the deposit sloughed off, only a portion of the fouling curve was fitted to Equation 104

(1/C-7) Normalized = 0.2704 -;421

2.5 Standard Error = .0284 0

,1483

.F/5 2 o' -1/429 8342 / 8455

34$11

4.1 U

z 1.5 S. . ,Nc.. ..., N , .P.28 4 C ... v.N. / . . I R451 ^P54 r e x-, 0 e #s? 0 ' . ".., N i K1 , , \ / t5y i + .0 e - -(- < ' .48 / 0 <2 . RA + .6 e . u. ek"" c>C's / c,,,

R-Squared = 0.805 8.5

Correlation Coefficient= 0.897-

t I 1 t

2 4 6 8 18 Velocity (ft/sec) Figure VI-1 Normalized -in 0,vs Velocity 105

(5-36). In some of these runs the fouling value before and after sloughing was about the same.

In some cases the fouling resistance-time curves had an increasing deposition rate and data for these runs was not fitted to Equation (5-36). Since this equation is good only for constant deposition rate. The fouling resistance-time curve in this case is concave upward.

No regression analysis was performed for most runs that had a fouling resistance value of Rm.,- 0.0001 ft2hr°F/Btu. Runs that were analyzed are shown in Table

VI-1.

For some of the runs, the fouling resistance-time curves were very close to linear. These runs were fitted using simple linear regression to obtain the slope of the

line which represent the deposition rate. Hence only 0,

is reported. In Table VI-1 values of ec e,, R",, deposition rate

(03 = R',- /e,) and R2 (The coefficient determination) are given for each run. Table VI-1 also show, for each run, foot notes about the conditions under which regression was or was not performed.

Values of ELI, ems,, R"-, and 0,1 were then used to

correlate the data of the HTRI model. AppendixI contains a summary of the method ofnon-linear regression used in

this study. 106

TABLE VI-1 Regression Analysis

DEAD TIME ASYMPTOTICDEPOSITION COEFFICIENT RUN TIME CONSTANT FOULING RATE OF NUMBER HOUR HOUR DETERMINATION Ad e. R;x104 Od R2

302 40.33 81.62 6.63 8.13E-6 .92 303 0.0 50.06 8.11 1.62E-5 .85 304 0.0 31.09 7.14 2.30E-5 .51 305 3.27 128.80 11.10 8.62E-6 1.00 306 43.66 410.78 9.03 2.20E-6 .93 307 0.0 116.06 11.94 1.03E-5 1.00 308 * * * * * (7) 309 0.0 6.01 2.08 3.45E-5 .59 310 0.0 195.10 23.12 1.19E-5 .97 311 0.0 158.82 16.19 1.02E-5 .97 312 60.0 21.72 .26 1.22E-6 .64 313 0.0 108.30 6.19 5.72E-6 .95 314 10.0 77.82 4.57 5.87E-6 .98 315 14.03 126.28 2.07 1.64E-6 1.00 316 * * 0.38 * * (4) 317 * * 0.05 * * (4) 318 * * * * * (5) 319 * * * * * (5) 320 5.39 43.23 0.81 1.88E-6 .96 321 * * 0.23 * * (4) 322 0.0 839.23 14.11 1.68E-6 .70 323 0.0 4.35E10 4.32E8 9.92E-7 .98 324 * * 0.71 * * (4) 325 0.0 1.37E7 4.68E4 3.41E-7 .89 326 0.0 383.74 5.43 1.42E-6 .99 327 50.86 12.44 1.70 1.36E-5 .95 328 50.69 10.99 1.02 9.25E-6 .94 329 33.75 26.84 1.88 7.00E-6 .90 330 5.0 65.32 1.23 1.89E-6 .93 331 0.0 26.50 1.14 4.29E-6 .96 332 5.83 27.91 .73 2.61E-6 .95 333 40.09 217.65 1.15 5.30E-7 .83 334 4.28 140.58 .e0 5.67E-7 .96 335 0.0 170.53 1.84 1.08E-6 .91 107 TABLE VI-1 (cont.) Regression Analysis

DEAD TIME ASYMPTOTICDEPOSITION COEFFICIENT RUN TIME CONSTANTFOULING RATE OF NUMBER HOUR HOUR DETERMINATION e. e. Rsx104 Od IR°

336 0.0 40.11 6.58 1.64E-5 .95 337 0.0 29.99 5.37 1.79E-5 .91 338 0.0 31.61 7.11 2.25E-5 .93 339 0.0 156.49 15.81 1.01E-5 1.00 340 0.0 213.09 15.36 7.21E-6 1.00 341 0.0 77.89 16.10 2.07E-5 .99 342 84.0 47.44 .36 7.57E-7 .69 343 7.0 55.24 .44 8.00E-7 .91 344 0.0 36.72 1.48 4.02E-6 .95 345 * * * * * (6) 346 * * * * * (6) 347 * * * * * (6) 348 18.36 63.67 5.64 8.86E-6 .98 349 1.14 91.21 4.47 4.90E-6 .97 350 0.0 54.35 4.78 8.79E-6 .96 351 1.66 33.80 3.03 8.97E-6 .98 352 1.66 22.33 1.94 8.70E-6 .98 353 1.66 25.92 1.B4 7.11E-6 .93 354 0.0 21.38 3.71 1.74E-5 .99 355 0.0 14.42 1.58 1.10E-5 .94 356 0.0 11.45 3.96 3.35E-5 .9B 357 24.68 36.47 2.14 5.68E-6 .97 35B 2.68 260.71 3.46 1.33E-6 .94 359 11.65 100.59 4.03 4.01E-6 .98 360 * * 0.10 * * (4) 361 * * 0.14 * * (4) 362 2.44 46.50 .70 1.50E-6 .91 363 14.75 216.07 3.41 1.58E-6 .95 364 0.0 146.14 2.44 1.67E-6 .95 365 0.0 68.08 2.15 3.16E-6 .98 366 0.0 23.87 12.22 5.12E-5 .92 367 0.0 13.32 10.73 8.05E-5 .96 368 0.0 20.02 14.16 7.07E-5 .94 369 0.0 75.28 2.61 3.47E-6 .96 370 15.2 22.09 3.53 1.60E-5 .98 371 16.33 23.95 4.58 1.91E-5 .98 108 TABLE VI-1 (cont.) Regression Analysis

DEAD TIME ASYMPTOTICDEPOSITION COEFFICIENT RUN TIME CONSTANT FOULING RATE OF NUMBER HOUR HOUR DETERMINATION e., Ac. R;x10' * FS a FM

372 0.0 54.70 3.00 5.48E-6 .98 373 .93 8.52 1.36 1.59E-5 .81 374 .93 27.14 6.63 2.44E-5 .97 375 11.93 106.05 4.95 4.66E-6 1.00 376 3.92 73.46 3.77 5.14E-6 1.00 377 2.91 85.47 8.22 9.62E-6 .99 378 * * 0.24 * * (4) 379 * * 0.02 * * (4) 380 * * 0.20 * * (4) 381 * * .25 * * (4) 382 * * .15 * * (4) 383 * * .57 * * (4) 384 * * 3.61 1.92E-6 * (4) 385 10.66 392.94 8.30 2.11E-6 .94 386 * * 3.10 1.68E-6 * (1) 387 2.6 58.47 .66 1.13E-6 .72 388 0.0 264.70 1.30 4.90E-7 .79 389 9.0 413.50 2.06 4.98E-7 .78 390 11.43 11.17 .85 7.61E-6 .80 391 6.4 13.66 1.0 7.32E-6 .90 392 1.4 36.45 2.29 6.30E-6 .93 393 * * .23 * * (4) 394 * * .19 * * (4) 395 * * .12 * * (4) 396 2.45 412.05 32.55 7.90E-6 1.00 397 2.45 398.23 25.71 6.46E-6 1.00 398 1.42 99.04 17.61 1.79E-5 1.00 399 6.21 450.34 23.12 5.14E-6 .99 400 6.21 427.20 10.85 2.54E-6 .98 401 1.21 276.15 31.27 1.13E-5 1.00 402 4.68 53.86 10.92 2.03E-5 .98 403 8.68 92.06 7.64 8.30E-6 .99 404 .68 27.97 9.79 3.50E-5 .99 109 TABLE VI-1 (cont.) Regression Analysis

DEAD TIME ASYMPTOTICDEPOSITION COEFFICIENT RUN TIME CONSTANT FOULING RATE OF NUMBER HOUR HOUR DETERMINATION e. Ac. RSx10' * Oe Re

405 16.38 157.70 14.40 9.13E-6 .96 406 9.11 1113.69 32.57 2.92E-6 .95 407 11.11 84.94 12.95 1.53E-5 .98 408 0.0 415.44 39.03 9.39E-6 .89 409 0.0 92.06 12.72 1.38E-5 .77 410 1.4 170.55 26.59 1.56E-5 .86 411 40.87 165.44 B.06 4.87E-6 .94 412 42.87 215.69 24.86 1.15E-5 .98 413 46.87 317.98 26.57 8.36E-6 .98 414 1.23 26.12 4.32 1.65E-5 .97 415 1.23 9.75 1.37 1.40E-5 .83 416 4.23 31.00 10.17 3.28E-5 .99 417 0.0 21.62 .59 2.73E-6 .55 418 0.0 18.57 .32 1.73E-6 .42 419 * * .27 * * (4) 420 .96 60.41 5.71 2.45E-6 .95 421 0.0 57.78 3.72 1.44E-6 .92 422 0.0 85.98 8.99 1.05E-5 .98 423 2.31 76.54 16.62 2.16E-5 .94 424 15.31 70.91 23.87 3.37E-5 .97 425 .62 80.43 21.72 2.70E-5 .84 426 * * 2.16 * * (7) 427 1.23 1.65 .63 3.83E-5 .87 428 * * .44 * * (1,4)

429 * * _ .17 * * (4) 430 4.33 11.94 3.20 2.68E-5 .93 (8,3) 431 4.33 239.66 20.01 8.35E-6 .99 (8,3) 432 1.33 31.17 6.87 2.21E-5 .99 (8,3) 433 1.1 64.98 6.18 9.52E-6 .99 434 1.1 190.05 9.69 5.10E-6 .99 435 * * 10.14 6.73E-6 97.88 (2,10) 436 * * .89 * 41.47 (1,4) 437 * * .33 * 88.14 (1,4) 110 TABLE VI-1 (cont.) Regression Analysis

DEAD TIME ASYMPTOTICDEPOSITION COEFFICIENT RUN TIME CONSTANT FOULING RATE OF NUMBER HOUR HOUR DETERMINATION ed e. R;x104 Od Ft°

438 0.0 4.92 .45 9.17E-6 .77 439 * * 2.44 * * (2,10) 440 0.0 250.47 .77 3.08E-7 .84 441 78.12 189.22 12.15 6.42E-6 .96 442 * * .74 * * (1,4) 443 0.0 60.65 .49 8.05E-7 .76 444 0.0 799.59 4.75 5.94E-7 .82 445 89.17 1231.76 34.63 2.81E-6 1.00 446 1.95 80.52 3.02 3.76E-6 .98 447 45.85 52.10 6.69 1.29E-5 .95 448 160.24 589.06 16.70 2.84E-6 .98 (8) 449 21.41 54.54 11.97 2.20E-5 .97 (3,8) 451 .81 32.27 18.70 5.80E-5 1.00 (3) 452 .8 19.26 18.26 9.48E-5 .97 (3) 453 .76 24.27 22.56 9.30E-5 1.00 (3) 454 5.50 94.97 10.06 1.06E-5 .97 455 20.63 25.05 7.89 3.15E-5 1.00 456 6.73 89.47 12.27 1.37E-5 .97 457 30.8 153.45 17.23 1.12E-5 .96 458 64.0 88.63 16.67 1.89E-5 .98 459 0.0 177.99 2.09 1.17E-6 .84 460 0.0 56.77 .73 1.29E-6 .85 461 1.46 3248.28 39.07 1.20E-6 .95 462 1.49 210.43 16.62 7.90E-6 1.00 463 * * 7.3 .03 .99 (1) 464 1.46 119.97 15.08 1.26E-5 1.00 465 2.67 1755.76 56.44 3.21E-6 1.00 466 .67 1200.16 29.68 2.47E-6 1.00 467 0.0 353.44 15.32 4.33E-6 .99 468 .82 216.82 17.69 8.16E-6 .99 469 .82 254.53 27.19 1.07E-5 1.00

Note: (1) Fouling increased linearly with time. (2) Fouling curve concave upward. (3) Fouling sloughed off during run. (4) Insignificant fouling R. 1 0.0001 ftE hr F°/Btu. (5) Computer problem. (6) Fouling value less than zero. (7) Rod Problem. (8) Power failure. (10) Final fouling value. 111

Data Reduction and Discussion

HTRI Model

The HTRI model is used to correlate the fouling data obtained in this study. This model was discussed in

Chapter II and a summary is given here.

The HTRI model is a semi-theoretical model whereby the fouling resistance-time curves can be predicted in the form of an initial fouling rate and an asymptotic fouling resistance. Taborek, et al.(32) discuss this model in length.

This model is based on the fundamental material balance Equation:

dR.r. = 00 0, (2-2) de where

= fouling resistance

e = time

Od = deposition rate

0, = removal rate

The deposition and removal rates are represented by the following relationships:

0,1 = C1F,AlvlexpC-E/R,J1 (2-9) 112

0, = CETX-F/Y (2-10)

Determination of HTRI Model Correlation Constant from Data

Determination of the constants and functions of the model equations was discussed in great detail by Taborek, et al (32). In the present study, the method of determination is adapted for the use of modern computers. From the data, experimental sets were selected in such group- ings as to isolate single effects and to allow determination of the functions required for solution of Equations

(2-9) and (2-10).

Deposition Rate

The initial rate, 00, of deposition can be obtained by differentiating and evaluating the derivative of the equationof fouling (5-35) at e =

= exp-(e-e0)/e,:=1 (5-35)

= dR = (6-1) de e=.9,

and ta,:, andthus 93,:i can bedetermined from fittingthe experimentaldatatoEquation (5-35). Values of ec,er., and 00 are givenin Table VI-1. 113

By maintaining a constant water quality, On becomes constant and Equation (2-9) reduces to the form of

Equation (6-2):

00 = C3 F, exp(-E/RT.) (6-2)

where:

Cn = constant which includes On

F, = velocity function

E = activation energy of reaction

R, = gas constant

T. = absolute surface temperature

The experimentally obtained value of 0. along with the operational parameters of velocity and surface temperature can now be used to determine the velocity function, the constant C,, and the activation energy E of

Equation (6-2).

The Velocity Function, F,

Sets of data with the same water quality and surface temperature and their corresponding deposition rate 0. were selected for correlation. 0. was plotted against velocity to fit Equation: 114

In =ln Ce, V/C-7 (6-3)

These plots are shown in Appendix L. Normalizing these plots by plotting ln(0,/Ce,) against velocity (Figure

VI-1), the average slope of 0.2704 is obtained with average standard deviation of 0.03.

Thus the velocity function F, is of the form of:

F, = exp(-0.2704V) (6-4)

Equation (6-4) shows that F, is a decreasing function of velocity. Since 93,1is directly proportional to F, in

Equation (6-2), increasing velocity will have the effect of decreasing 0,1. Taborek et al (32) reported the following velocity function for cooling tower water:

F, = exp(-1/3 V)

Santoso (29) obtained the following velocity function for the cooling tower water:

F = exp(-.352V)

The velocity functionsobtained in this study and those reported by Santoso and Taborek et al are in reasonable agreement. 115

The Activation Energy Constant, E.

Rewriting Equation (6-2) with the F_ as determined previously:

ln(56,7F) = 1nCa E/R,T. (6-5)

where:

T. = absolute temperature

and selecting sets of data each with the same water quality, ln(0,1/F.,)is plotted versus (1/T11) to determine the constant Ca and the constant E for each of the fifteen water qualities considered. These plots are shown in

Appendix L. The values of Ca and E are tabulated in Table

VI-2. Values of Ca and E show that Ca and E depend on water quality. These values also show a great dependency of Ca on water quality compared to that of E. The results also indicate that the value of E has an affect on the value of Ca. Higher or lower value of E will result in higher or lower Ca, respectively. This effect of E on Ca is also an indication of water quality effect on Ca.

No general pattern was observed between pH and E.

Waters with iron contamination have lower E when additive(s) such as HEDP is present. This was expected since these additive(s) provide more heterogeneous nucleation. A considerable variation of the activation energy E was 116

TABLE V1-2

Constants to be used in equations(6-5), (6-12), (6-13)

(RI; s 1.987 Btu /lbmole R) 130 1 Ts S 160F .08 1 + S .43 lbf/fta a =(a +1) 1.75 a s (a/1.75) - 1

WATERADDITIVESpH C. E C. a a b Btu/lbmol hr II (PPM) ft2F/Btu

4-5 PP 7.3062E3 1.341E-19-11.66-7.665.645 1 5-6 OP 7.0 7.976E-3 2-4 PA 2-4 HEDP 1.838 .0529.016 2 4-5 PP 7.52.534E8 3.511E4 4.040E-63 5-6 OP - 4-5 PP 7.816E-7 0.315-.8203.244 3 5-6 OP 8.1 4.323E7 3.539E4 10 AA/HPA

4-5 PP 0.698-.601-2.907 4 5-6 OP 8.5 2.542E10 4.109E4 2.207E7 10 AA /HPA

4, .- 4-5 OP 0.068-.961-3.396 5 5-6 PP 7.5 2.285E13 4.944E4 1.751E2 10 AA/MA

4-5 OP 3.474E2 2.128 .216 .089 6 5-6 PP 8.5 3.834E-1 1.138E4 10 AA/MA

.. -.4 4-5 PP 2.625 .5 -4.0 7 5-6 OP 8.5 3.238E3 2.158E4 1.186E11 10 SS/MA

4-5 PP 3.579E-2 2.471 .412 1.903 8 5-6 OP 6.5 4.098E3 2.416E4 10 SA/MA

4-5 PP 1.958 0.726-.585 .732 9 5-6 OP 7.5 1.118E1 1.551E4 2 Fe

4-5 PP 3.941E-3 1.483 -.152 6.628 10 5-6 OP 7.5 4.394E17 6.156E4 4 Fe 117

TABLE VI-2 CONTINUED

Constants to be used in equations (6-6), (6-11),(6-13)

(Rq = 1.987 Eltu/lbmole R) 130S Ts 1160F .08 1 7 1 .43 lbf/ft2 a = (a +1) 1.75 a = (a/1.75) - 1

WATERADDITIVESpH Ca E C4 a a b * (PPM) ft2F/Btu Btu/Ibmol hr

4-5 PP 11 5-6 OP 7.5 1.265E18 6.331E4 1.223E-3 1.349-.229 2.064 4 Fe 2-4 HEDP

4-5 PP 12 5-6 OP 7.5 3.121E2 1.852E4 2.541E-4 0.233-.867 1.867 4 Fe 10 AA/MA

13 3 Fe 7.5 4.303E15 5.778E4 6.433E-13 1.972 .127 6.628

4-5 PP 14 5-6 OP 7.5 4.859E31 9.975E4 4.168E25 -.123-1.07-11.298 3 Fe

4-5 PP 15 5-6 OP 7.5 2.296E3 2.237E4 5.081E4 1.461-.165-1.581 3 Fe 10 HEDP 118 found among the fifteenwaters considered in this study.

E values ranged from 9.975E4 to 7.306E3.

As was found by Santoso (29), no particular pattern was observed in this study with respect to pH or the type of additive used. It therefore appears, at least for present, the individual values of C:.3 and E should be used with the specific additive combination for which they were obtained.

With the functions of Equation (6-2) determined above, it can now be used to calculate the deposition rate

0, with measured values of velocity and surface temperature for each water quality considered in this study.

The deposition rate values obtained from the model

Equation (6-2) are plotted against the experimentally obtained deposition rate values Figure VI-2, while some scattering of data can be expected from the inherent complexity of fouling, thecorrelation between deposition rate values predicted by Equation (6-2) and those obtained experimentally appear quite sound. The average standard deviation of the ratio (experimental values over model values) is 58%.

Removal Rate

In chapter II, Equations (2-10) and (2-15) show that the removal rate and the time constant are inversely proportional to each other: Figure VI-2 Error Plot of 00

15.2

14.2

13.2

12.2

11.2

10.2

9.2

8.2

8.4 9.4 10.4 11.4 12.4 13.4 14.4 15.4 -1n(950), Predicted by Model Equation

00 : ft2 hr °F/Btu 120

R. = R-*,(1-exp(-0/0)) (2-14)

0, =CTX.F (2-10)

e, = Y (2-15) Ce7K-r-

Equation (2-15) shows that the removal rate is a function of the time constant 19,. Equation (2-14) has a slope of 1 at 8=0:

dCR,(8)/R"'] = (e-"-""cr,"-o= 1 (6-6) d(e/e,) (3=0

This implies that if the initial rate of deposition

were to be maintained, R, would reach its asymptotic value R4*',in one time constant It also implies that the smaller the value of the time constant e, the higher the value of the initial deposition rate. Thus the time constant can be defined as the time required for R, to reach its asymptotic value R-me, if there would be no removal rate.

Equation (2-14) also shows that with presence of removal rate the value of R. reaches 63.2% of its final value R'r when the time elapsed is equal to one time constant, 8,. Consequently, we have: 121

Time elapsed 28, 3e, 4e, R,(e) as h of its asymptotic value R4, 86.5 95 98

Thus, after four time constants, e, the R.1 value has essentially reached its asymptotic value.

With the removal rate function determined from fitting the experimental fouling time data to Equation

(5-35) by non-linear regression as described in Appendix

I, the experimentally obtained value of A, can now be used to determine a functional relationship as given in

Equation (2-15):

e, (2-15) CeTKI,

Based on the argument given by Taborek et al (32), the characterizing function of the deposit structure Y is assumed to be a primary and increasing function with flow velocity. Thus:

Y a V4w with a>0

Knudsen suggests(17, No.1), that shear stress and not velocity is the more fundamental parameter in removal rate. Also correlating the removal rate data with shear stress will allow the results to be used for other geometries by matching their corresponding shear stresses. For HTRI test sections with water flowing at bulk tem- 122 perature of 115°F, the fluid shear stress is given by the following equations:

(1b-r/ftE") = 1.1159 x (6-7)

where:

V = ft/sec.

A description of themethod ofcalculation of shear stress for the HTRI test section is given in Appendix D.

Although the effect of temperature on the strength of the deposit and thus the removal process is known, the way in which the temperature effect takes place is not known.

However, several postulations are found in the literature.

Santoso (29), stated that fouling studies to date, including HTRI model, havenot quantified the effect of temperature on the removal process. As temperature of the deposit increases, the strength of the deposit should be affected and thereby also the removal rate. Thus in this study the Santoso (29) method of including temperature term in the removal equation is adapted. It is assumed that the deposit structure Y is a function of both surface temperature and velocity:

Y a khm (6-8) 123 where

T.1 = surface temperature in °F

To make the surface temperature a correlated variable, it is expressed as an exponential function with power b. The removal rate function (2-14) can now be expressed as:

er = C, with a = (a/1.75) 1 (6-9)

Coefficient C, includes theproportionality constant of Equation (6 -8) and the quantities CaKF of Equation (2-

14). Cel

With experimental values of err., velocity and surface temperature, the quantities of C,, a and b were determined using multiple linear regression analysis. This was done for each of the fifteen waters considered. The values of

a and b appear to be dependent on the water quality, their values do not show a specific pattern or correlation with pH.

In Figure VI-3 the experimentally obtained values of

Eic are plotted against the values of e, obtained by the model Equation (6-9). The average standard deviation of the ratio (experimental values over themodel values) is

67%. Figure VI-3 ErrorPlot of O. 7.2

6.2

5.2

4.2

U 3.2

2.2

1.2

1.5 2.5 3.5 4.5 5.5 6.5 7 ln(O.), Predicted by Model Equation

: hours 125

Discussion of Model Constants E, a and b

Activation Energy, E The activation energy E values tabulated in Table VI-

2 are discussed in this section. At a pH of 8.5, water 4,

6 and 7 show that the smallest activation energy value is obtained for water 6. This result is consistent with the findings discussed in earlier sections about the ineffectiveness of AA/MA copolymer in inhibiting fouling. Since smaller activation energy implies that deposit materials would not have difficulty to form. This leads to the speculation that AA/MA copolymer helps promote heterogeneous nucleation and thus less energy is needed for crystallization of fouling constituents.

Water 5 at a pH of 7.5 has a higher E value than water 6 at pH of 8.5 (both waters have the same additive combination). This is also consistent in that higher pH values leads to lower solubility, and thus particulates and colloids will settle on the heat transfer surface providing secondary nucleation sites which promote a heterogeneous nucleation and thus less energy is required for crystallization. Water 5 and 12 have the same pH of

7.5 and the same additive combination with the exception of the presence of 4 ppm Fe in water 12. These two waters show clearly that the presence of iron in the water reduced the activation energy drastically from 4.94E4 to 126

1.85E4. This is also consistent in that the presence of solid and contaminant material in the water will help and promote heterogeneous nucleation.

By comparing water 9,10 and 14 all at pH of 7.5, the following is observed: although water 9 has less iron than water 10 and 14 it has a very small E value compared to that of water 10 and 14. This result is contradictory in that more contaminant promotes more heterogeneous nucleation and thus less energy is needed for crystallization. To explain this contradiction, the conditions at which tests of each water wereconducted were examined.

It was found that for water 9 no acid was added to the iron solution tank and that the iron tank contained a brown colored solution with a layer of ferrous hydroxide precipitate on the bottom. Thus for water 9, a mixture of

Ferrous hydroxide solution and particles was added to the system. This addition of particles and ferrous hydroxide promoted more heterogeneous nucleation resulting in a lower energy of activation. For water 10 and 14 sulfuric acid was added to the iron solution tank to maintain the iron in solution as it was added to the system. In this case no iron particles were present in the iron tank and no particles were added to the cooling water from the iron solution tank. Thus colloidal ferric hydroxide formed in the system. Hence, waters 10 and 14 did not have as much iron particles as water 9 and this resulted in a higher 127 value of E.

Iron has more than one oxidation state and the most stable is oxidation state +3. This suggests that Fe(II) can be oxidized to Fe(III) without great difficulty. In acidic solution with the presence of oxygen at 1 atm pressure, Fe(II) compounds are readily oxidized to

Fe(III).

4Fee'(..,0) + OE: (0)+ 4W(^0) + 2H20

But even at lower partial pressures of oxygen, as in the atmosphere, and less acidic media, the above reaction may still be spontaneous.

In aqueous solution, Fe(II) is pale green and Fe(III) is colorless. Fe(III) ion hydrolyzed to Fe(OH)a in solution. Further evidence for the hydrolysis reaction comes from the fact that aqueous solutions of Fe(III) are acidic.

Comparison of waters 2,10 and 14 all at a pH of 7.5 shows that higher activation energy is obtained when iron is added to the phosphate containing water (water 9 is not included in the comparisonfor the reasons discussed in the previous paragraph). This is in contradiction with the fact that the presence of contaminant reduces the activation energy values. Thus more experimentation is needed in order to check the reproducibility of the E values. It is also evident from comparing waters 12 and 128

15, both at a pH of 7.5, that when antifoulant copolymers at 10 ppm concentration were added (to phosphate water with iron contamination i.e. water 10 and 14), E values were reduced significantly. A possible explanation is that, first, iron deposit on the heater rod surface provides secondary nucleation sites thus promoting heterogeneous nucleation which requires less energy and thus smaller activation energy. Secondly, HEDP and AA/MA, by adsorping on to the crystal structures, play the role of being impurities and inhibit the growth ofa homogeneous crystals by homogeneous crystallization. Thus the heterogeneous crystallization dominates, which requires a smaller activation energy than homogeneous crystallization. Activation energy of water 13 represents the energy required for Fe(OH)a colloids to agglomerate. This process is explained through the help of the coagulation theory.

When two colloids come in close proximity there are two forces acting on them. The electrostatic potential created by a "halo" of counter ions surrounding each colloidal particle reacts to repel the other particles, thus preventing contact. The second force, an attraction force (van der waals force), supports contact. This force decreases more rapidly with distance than the electrostatic potential, but is stronger at close distance. The 129

net force of these two forces as they relate to one

colloid is repulsive at greater distances and becomes

attractive only after passing through a maximum net

repulsive force, called the energy barrier, at some

distance between colloids. Once the force becomes

attractive, an agglomeration of the particles takes place.

A means of overcoming the energy barrier must be

available before agglomeration of particles can occur.

Brownian movement, the random movement of smaller colloids because of molecular bombardment which results from the

energy provided by heat transfer, may produce enough

momentum for particles to overcome the energy barrier and

thus collide.

In this study then, E in its arrhenius-type expres-

sion represents the energy that colloids must possess before agglomeration can take place and thus the forming

of larger colloidal particulates which bond to the heat

transfer surface. Parkins (25) who studied the formation

of surface films in pressurized reactors systems, included

E in an Arrhenius-type expression in his deposition rate

expression. In Parkins' work E was defined as the energy

required for chemical linkage.

Since water qualities and additives used in this

study are different from those used by Santoso (29) a one

to one comparison of activation energy is not possible. However, comparing E ranges may shed light on the extent 130 of the range of E value for cooling tower water fouling for the purpose of generalization. The range of E values obtained in this study. is 9.98E4 (water 14) to 7.31E3

(water 1). The values obtained by Santoso (29) ranged from 2.09E5 (20 ppm Cr0,.., 4 ppm Zn, 3 ppm HEDP and pH of

8.0) to 1.44E4 (20 ppm CrOL., 4 ppm Zn, 200 ppm suspended solids and a pH of 7.5). It appears that activation energy ranges are comparable. In Santoso's study, the highest activation energy value is about twice asmuch as the value obtained in this study. Likewise, the lowest activation energy values is about twice as much as the value obtained in this study. If water number 1 is excluded, then a much more comparable range would be obtained between the two studies. This range would be 9.98E4 (water 14) to 1.14E4 (water 6) compared to the same range of Santoso's which is discussed above.

Constants a and b The positive values of parameter a (with exception of water 1) tabulated in Table VI-2 indicate that the scale strength factor is an increasing function of velocity.

This result supports the concept on which HTRI Model was based i.e. the strength of the deposit structure is directly proportional to the flow velocity.

With respect to the parameter b, a discussion of the effect of surface temperature on the scale strength is 131 necessary. The postulation is that some deposits (which were observed in this study also) appear to break down at higher temperatures. That is, as the temperature within the deposit (which is represented by the surface tempera-

ture in this study) increases, a structural change takes place within the deposit and the deposit may easily slough off after it reaches a certain thickness. The scale strength of this type of deposit is a decreasing function of surface temperature and the value of b is negative. The growth of deposits with negative values of b, could be much easier controlled by fluid shear stress. Even low shear stress will probably be effective in removal of deposit, (Santoso (29)).

Positive values of b suggest that a solid encrusta-

tion may result as temperature within the deposit increases. Surface temperature is used here as pseudo temperature to characterize the temperature changes within

the layer of the deposit. Values of the b parameter

tabulated in table VI-2 show that the presence of the copolymer additives such as AA/HPA, AA/MA etc. have a very

strong effect on the b values. This is indicated by considering water no. 2 with no copolymer additive. Water

no. 2 has b value of 29.016 which indicates that a higher

surface temperature will result in a stronger deposit structure, while all other waters have either a negative b

value or smaller positive values of b ranging from 0.089 132 to 6.268. As postulated above, negative values of b will result in a weaker deposit structure with higher surface temperature.

During the discussion of E for water 13,it was indicated that heat transfer was acting as a source of energy required for the occurrence of agglomeration, thus the effect of the surface temperature is one of promoting agglomeration. This effect of temperature is also indicated by the positive value of b for water 13. A positive value of b indicates that higher surface temperature will produce more adhesive and coherent deposit film.

Scale Strength

On the assumption of constant thermal conductivity of the deposit layer Kr, Equation (2-15) shows that the time constant 19, is directly proportional to the ratio of the deposit structural strength function Y to the fluid shear stress, T as:

e. = (2-15) CETK/.. also

(9, a Y/T since

Y a T.1 ' (6-8) 133

then

ecr: T a VA% (6-11)

Thus, 0,T or equivalently Y is an indicator of the

sensitivity of the deposit to velocity and surface

temperature. The effect of flow velocity and deposit

surface temperature was discussed earlier. Plots of 01,,T versus surface temperature and velocity for each water quality are given in Appendix L. These figures indicate

that strength of deposit Y is an increasing function of flow velocity which indicates that for the same deposit, higher velocity tends to produce a deposit of higher strength by making the deposit more compact and tight.

Velocity also has a removal function through shear stress forces. It was found that deposits of similar composition could have different shear strength depending on the water quality for which deposits took place.

Fouling as a Function of Time and Asymptotic Fouling Resistance, R4*,,

With all functional relationships determined from

experimental data as shown in the previous sections in

this chapter, Equations (6-2) and (6-12) can now be used

to predict the deposition rate 0, and the removal rate 0,.

= Czi,F exp-(E/RT..) (6-2) 134

(6-12) C41-''T.1"

By substituting Equations (6-2) and (6-12) into

Equation (2-2) and integrating, fouling resistance, R./r as a function of time is obtained

exp(-E/Rc,T.,)E1-exp(-e/C.,TT..1)3 (6-13)

where

= absolute surface temperature

= surface temperature in °F

or in terms of the time constant

R-r=CmF,e,exp(-E/R,,,T.)C1-exp(-19/ec:)] (6-14)

To obtain the asymptotic fouling value R*1-, Equation

(6-14) after a long time becomes:

Wig = e. exp(-2/R,J..) (6-15) with

ec = ce. T (6-9) and

Fs, = exp(-0.2704v) (6-4)

or, in terms of shear stress: 135

Fv = exp(-3.522 T-71'1.7) (6-16)

Equation (6-15) is now a predictivemodel equation for the asymptotic fouling resistance for each water quality considered in this study. As found by Santoso

(29),it has not been possible in this study to develop a correlation, so that a single set of parameters could apply to all water qualities considered in this study.

Thus the values of the parameters Ca, C4, a, b and E which are tabulated in Table VI-2, have to be used with their corresponding water qualities. The use of these parameters are also limited to a wall shear stress of 0.08 'r

0.43 lb-e/ft2 and surface temperature of 130°F Ti,.

160°F. In Figure VI-4, the experimentally obtained asymptotic fouling resistance is plotted against the values predicted by the model Equation (6-15). The average deviation of the ratio (experimental values over those of the model Equation (6-15)) is 48%.

A comparison of the experimental values and those values obtained from the model equations for deposition rate 00, time constant e. asymptotic fouling resistance R4`1, is given in Table VI-3. Figure VI-4 Error Plotof R.* 10.5

OJ 9.5

9.5

7.5

6.5

3.5

5.4 6.4 7.4 9.4 9.4 10.4

-1n(Rr"), Predicted by Model Equation

R,' : ft2 hr °F/Btu 137

Table VI-3 Comparisons of Experimental Valuesvs Model Equations for 16,i,49.9 and Rt

Water Run 1d I. Ratio 0. 0. Ratio (R,)E +4 (R0E+4Ratio No. No. Exp. Predict. Exp. Predict. Exp. Predict. Eq. 6-2 Eq. 6-9 Eq. 6-15

302 8.128E-068.128E-06 1.000 81.620 81.810 0.998 6.634 6.6500.998 303 1.620E-05 8.128E-06 1.993 50.060 49.950 1.002 8.109 4.060 1.997

1 304 2.296E-05 8.129E -06 2.825 31.090 77.530 0.401 7.138 6.302 1.133 305 8.620E-06 9.416E-06 0.915 128.790 124.170 1.037 11.102 11.692 0.950 306 2.199E-06 9.416E-06 0.234 410.780 135.140 3.040 9.031 12.725 0.710 307 1.029E-05 9.416E-06 1.093 116.060 120.380 0.964 11.936 11.335 1.053

338 2.250E-05 4.722E-05 0.476 31.610 31.610 1.000 7.112 14.927 0.476 2 336 1.640E-05 2.402E-05 0.683 40.110 40.110 1.000 6.576 9.6350.683 337 1.790E-05 1.222E-05 1.465 29.990 29.990 1.000 5.370 3.664 1.466

353 7.110E-066.428E-06 1.106 80.920 91.205 0.887 5.754 5.862 0.982 314 5.870E-06 6.428E-06 0.913 77.810 91.205 0.853 4.565 5.8620.779

3 351 8.970E-06 3.270E-06 2.743 33.800 38.230 0.884 3.033 1.2502.426 320 1.880E-06 3.270E-06 0.575 43.230 38.230 1.131 0.811 1.240 0.654 362 1.500E-06 1.492E-06 1.005 46.500 46.550 0.999 0.697 0.694 1.004

354 1.740E-05 1.877E-050.927 21.380 21.380 1.000 3.712 4.013 0.925 355 1.100E-059.550E-06 1.152 14.420 14.420 1.000 1.582 1.377 1.149 359 4.010E-066.769E-06 0.592 100.590 73.940 1.360 4.032 5.0050.806

4 350 8.790E-06 6.769E-06 1.299 54.350 73.940 0.735 4.775 5.005 0.954 357 5.880E-063.443E-06 1.708 36.470 39.100 0.933 2.143 1.346 1.592 348 8.860E-06 3.443E-06 2.573 30.670 39.1000.784 2.716 1.346 2.018 349 4.900E-06 1.751E-06 2.798 91.210 122.130 0.747 4.472 2.139 2.091

366 5.120E-054.320E-05 1.185 23.870 24.5300.973 12.219 10.600 1.153 5 371 1.910E-05 1.150E-05 1.661 23.950 37.568 0.638 4.578 4.320 1.060 369 3.470E-065.850E-060.593 75.280 49.650 1.516 2.613 2.904 0.900

396 7.900E-068.541E-060.925 412.050 394.320 1.045 32.54633.3240.977 397 6.460E-06 4.299E-06 1.503 398.230 454.400 0.876 25.714 19.534 1.316

6 401 1.130E-05 1.039E-05 1.088 276.150 307.720 0.897 31.169 31.965 0.975 399 5.130E-06 5.283E-06 0.971 450.340 387.070 1.163 23.123 20.452 1.131 400 2.540E-06 2.688E -06 0.945 427.200446.040 0.958 10.846 11.989 0.905

404 3.500E-05 3.555E-05 0.985 27.970 42.836 0.653 9.792 15.228 0.643 402 2.030E-05 1.808E-05 1.123 53.860 61.224 0.880 10.924 11.072 0.987 7 403 8.300E-069.199E-060.902 92.060 92.030 1.000 7.638 8.466 0.902 407 1.520E-05 1.459E-05 1.042 84.940 84.923 1.000 12.952 12.390 1.045 405 9.130E-06 7.421E-06 1.230 157.700 157.737 1.000 14.399 11.706 1.230 138

Table VI-3 (cont.) Comparisons of ExperimentalValues vs Model Equations for ps.,, eandRf

Ratio (R0E+4 (R0E+4Ratio Water Run 0, 0, Ratio 0. 0. Exp. Predict. No. No. Exp. Predict. Exp. Predict. Eq. 6-2 Eq. 6-9 Eq. 6-15

8.299 5.620 1.477 385 2.110E-06 1.430E-06 1.476 392.940 392.941 1.000 1.562 2.058 5.397 0.381 8 389 4.980E-072.039E-06 0.244 413.500 264.700 0.658 0.606 1.086 387 1.130E-06 1.037E-06 1.090 58.470 58.470 1.000 1.296 1.397 0.928 388 4.900E-07 5.276E-07 0.929 264.700 264.700 1.000

32.991 0.806 410 1.560E-05 1.697E-050.919 170.550 194.440 0.877 26.593 39.02831.342 1.245 408 9.390E-068.632E-06 1.088 415.440 363.100 1.144 12.720 5.8372.179 9 409 1.380E-05 4.391E-06 3.143 92.060 132.930 0.693 27.9060.952 413 8.360E-06 8.947E-060.934 317.980 311.900 1.019 26.572 7.629 1.057 411 4.870E-06 4.455E-06 1.093 165.440 167.610 0.987 8.063

11.999 0.848 416 3.280E-05 3.889E-050.843 31.000 30.850 1.005 10.171 4.319 5.193 0.832 10 414 1.650E-05 1.978E-05 0.834 26.120 26.850 0.973 2.3900.573 415 1.400E-05 1.006E-05 1.392 9.750 23.7500.411 1.370 0.339 1.743 417 2.730E-06 1.560E-06 1.750 21.620 21.7200.995 0.591

20.667 0.804 462 7.900E-06 2.708E-050.292 210.430 76.3102.758 16.618 1.009 425 2.700E-05 2.708E-050.997 80.430 79.500 1.012 21.721 21.531 20.645 1.156 424 3.370E-05 2.708E-05 1.244 70.910 76.230 0.930 23.867 0.998 16.617 20.7780.800 11 423 2.160E-05 2.708E-05 0.798 76.540 76.720 21.986 0.409 422 1.050E-05 2.708E-05 0.388 85.980 81.180 1.059 8.992 8.467 0.674 420 2.450E-06 1.378E-05 0.178 60.410 61.4600.983 5.707 3.684 1.010 421 1.440E-06 7.007E-06 0.206 57.780 52.570 1.099 3.719

0.543 432 2.200E-05 4.121E-050.534 31.170 30.731 1.014 6.872 12.663 2.570 1.244 430 2.680E-05 2.096E-05 1.279 11.940 12.255 0.974 3.197 1.000 20.000 25.5550.783 12 431 8.350E-06 1.066E-05 0.783 239.660239.600 0.975 433 9.520E-06 9.726E-060.979 64.980 64.980 1.000 6.184 6.344 434 5.100E-06 4.966E-06 1.027 190.050 190.050 1.000 9.685 9.348 1.036

0.738 449 2.190E-058.160E-06 2.684 54.540 198.830 0.274 11.972 16.224 0.453 447 1.280E-05 8.160E-06 1.569 52.100 181.110 0.288 6.693 14.778 15.440 0.787 13 441 6.420E-06 8.160E-060.787 189.220 189.220 1.000 12.150 0.955 446 3.750E-06 2.111E-06 1.776 120.520 224.130 0.538 4.520 4.732 1.459 440 3.080E-06 2.111E-06 1.459 250.570 250.570 1.000 7.714 5.288 139

Table VI-3 (cont.) Comparisons of Experimental Values vs Model Equations for Ocip 0., and RI,

Ratio Water Run id 1. Ratio O. O. Ratio 111,1E+41110E+4 No. No. Exp. Predict. Exp. Predict. Exp. Predict. Eq. 6-2 Eq. 6-9 Eq. 6-15

457 1.120E-05 7.531E-05 0.149 153.450 26.520 5.786 17.232 19.973 0.863 454 1.060E-05 7.531E-05 0.141 94.960 26.520 3.581 10.058 19.973 0.504 451 5.790E-05 7.531E-05 0.769 32.270 26.520 1.217 18.699 19.973 0.936 5.023 1.570 14 455 3.150E-053.831E-05 0.822 25.050 13.110 1.911 7.886 452 9.480E-05 3.831E-05 2.475 19.270 13.110 1.470 18.259 5.023 3.635 459 1.170E-06 1.227E-06 0.954 177.990 276.940 0.643 2.087 3.398 0.614 460 1.290E-06 6.242E-07 2.067 56.770 136.900 0.415 0.733 0.8540.858

469 1.070E-05 1.705E-050.628 254.530 254.530 1.000 27.200 44.5500.611 0.955 15 468 8.160E-068.672E-06 0.941 216.820213.600 1.015 17.688 18.523 462 7.900E-068.672E-06 0.911 210.430 213.600 0.985 16.620 18.523 0.897 467 4.330E-06 6.770E-060.640 353.440 353.440 1.000 15.320 23.929 0.640

STD (n) 0.661 0.739 0.504

Average 1.139 1.106 1.055

X Deviation 58.000 66.800 47.800 140

Conditions Showing Insignificant Fouling

Threshold values of pH, flow velocity, shear stress and surface temperature for various additive combinations are shown in Table VI-4. Under these conditions the asymptotic fouling resistance is expected to be less than or equal to 0.0001 ft2 hr °F/Btu. R4*r 10.0001 ft2 hr

°F/Btu is the threshold value for fouling resistance used in this study. Other basis for establishing a threshold may be used. The threshold values shown in Table VI-4 were inferred from the matrix Figures E-1 to E-16 in Appendix E and from Table VI-1 where many runs for various additive combinations show fouling resistance value less than or equal to 0.0001 hr ft2 °F/Btu. The shear stress in Table VI-4 was calculated fromEquation (6-7) for the

HTRI test section with water flowing at bulk temperature of 115 °F. 141

TABLE VI-4

Threshold Values For Various Additives

THRESHOLD VALUE FOR FOULING

ADDITIVES VELOCITY SHEAR STRESS SURFACE pH ft/sec lbf/ft2 TEMPERATURE Eq. (6-7) °F

NONIRON TEST

1. NO ADDITIVE 17.5 I 3.0 I .076 1 160

2. 4-5 ppm PP, 5-6 ppm OP, * * * * 2-4 ppm HEDP, 2-4 ppm PA

3. 4-5 ppm PP, 5-6 ppm OP 16.5 2 3.0 I .076 1130

4. 10 ppm OP 16.5 >5.5 >.220 1160

5. 10 ppm OP, 10 ppm AA/HPA 17.5 >5.5 > .220 1 160 16.5 >3.0 >.076 1 160 18.2 I8.0 I .425 1 160

6. 4-5 ppm PP, 5-6 ppm OP 1 7.5 I 3.0 I .076 1 145 10 ppm AA/HPA 16.5 I 3.0 I .076 1 160

7. 4-5 ppm PP, 5-6 ppm OP * * * * 10 ppm AA/MA 8. 4-5 ppm PP, 5-6 ppm OP 1 7.5 I 5.5 I .220 1 160 10 ppm SS/MA 1 6.5 I 3.0 I .076 i 130

9. 4-5 ppm PP, 5-6 ppm OP i7.5 I 3.0 I .076 1 160 10 ppm AA/SA 16.5 t 5.5 I .220 1 130 1 8.5 I 5.5 2 .220 1 160

* Not found in ranges investigated (asymptotic fouling resistance was always greater than .0001 hr ft2 °F/Btu). 142

TABLE VI-4 CONTINUED

Threshold Values For Various Additives

THRESHOLD VALUE FOR FOULING

ADDITIVES VELOCITYSHEAR STRESS SURFACE pH ft/sec lbf/ft2 TEMPERATURE Eq. (6-7) °F

IRON TEST

1. 4-5 ppm PP, 5-6 ppm OP * * * * 2 ppm Fe

2. 4-5 ppm PP, 5-6 ppm OP .1 7.5 >8.0 > .426 <160 4 ppm Fe 17.5 1 3.0 1 .076 1 130

3. 4-5 ppm PP, 5-6 ppm OP 17.5 1 3.0 1 .076 1 130 4 ppm Fe, 2-4 ppm HEDP

4. 4-5 ppm PP, 5-6 ppm OP * * * * 4 ppm Fe, 10 ppm AA/MA

5. 3 ppm Fe 17.5 15.5 1 .220 1 130

6. 4-5 ppm PP, 5-6 ppm OP 1 7.5 18.0 1 .425 1130 3 ppm Fe

7. 4-5 ppm PP, 5-6 ppm OP * * * * 3 ppm Fe, 10 ppm HEDP

* Not found in ranges investigated (asymptotic fouling resistance was always greater than .0001 hr ft2 °F/Btu). 143

VII. APPLICATION OF RESULTS

Model Correlational Equations

The model equations developed in Chapter VI. may be used in several ways. Apparent uses of the relations would be:

1. The prediction of e. thus knowing the time, the fouling value, R.f, would need to reach 98% of Rw.r.

2. The prediction of the effect of shear stress forces, and thus, the flow velocity effect, and the prediction of the effect of the surface temperature.

3. The fouling resistance as a function of time.

4. The prediction of the asymptotic fouling resistance, Rif

The prediction of the deposition rate, psci, and removal rate, 96,.

In summary, the model equations are:

a. The time constants, 8,

9c, = Cw T, Tih3 (7-1)

b. The flow velocity function, F.

= exp (-3.522 T'"-" ') (7-2) 144

c. The Asymptotic Fouling Resistance, R*,

R41-, = Ca F, erx Cexp (-E/R,,T,)] (7-3)

d. The fouling resistance as a function of time, R,

R,= CaF49,Cexp(-E/R,,T.)]C1-exp(-e/8.)] (7-4)

or in terms of R'",- and A,

R, (0) = Raw Cl exp (-09/0)] (7-5)

where

19 = time constant, hours

7 = shear stress, lb /ft2

Ti.. = heater absolute surface temperature, °R

T..i= heater surface temperature, °F

Ca = ft2 °F/Btu

C, = hours

E = deposit activated energy, Btu/lbmol

Rg = gas constant, 1.987 Btu/lbmol °R

Rf = fouling resistance, ft2 hr °F/Btu

R-m-r= asymptotic fouling resistance, ft2 hr °F/Btu

As was stated in Chapter VI., values of Ca, C,, a, b and E which are tabulated in Table VI-2 are unique for each additive combination, flow velocity (shear stress of

0.08 1 7 0.43 lbf/ft2) and surface temperature (130 T.

160°F) for which they were derived. 145

Threshold Curves For a given water quality, equations (7-1), (7-2) and

(7-3) could be used to construct contours of the asymptotic fouling resistance, R41.., as a function of flow velocity and heater surface temperature. Figures VI-5

(a-o) are threshold curves for the 15 water quality modeled in this study. The threshold values of R', shown in these Figures are 0.0001, 0.0002 and 0.0003 ft2 hr

°F/Btu. Other threshold values of R* could be used as basis of the threshold curves. For a given additive, these curves permit thedetermination of the operational parameters (flowvelocity/shear stress and heat transfer surface temperature) under which a certain asymptotic fouling resistance, WF, would be maintained.

Charts to Predict R*1.- With surface temperature (or velocity) held constant at various values, Equations (7-1), (7-2) and (7-3), may be used to construct plots of R'f as a function of velocity (or surface temperature). Figures VI-6a through

VI-6o are plots of FR."-r as a function of velocity at three levels of surface temperature (130°F, 145°F and 160°F) for the 15 water quality studied. These plots permit the determination of the condition of velocity for each level of surface temperature at which a particular R', value will occur. 1146

WATER i 1

4.5

. Datafor thiswater was availableonlyat 3 ft/sec

4.25

3.25

148 ne 168 178 HS 199 Surface Temperature (°F) Figure VI-5a Contour of Asyptotic Fouling vs Velocity and Surface Temperature

WATER *2

I I 25

f=1E-4

29 Mml -4

VIM

I . I t , I

145 1:1 155 168 165 178 175 Surface Temperature( °F) Figure VI-5b Contour of Asyptotic Fouling vs Velocity and Surface Temperature 1147 HATER #3

18 u w 8

4) 4- - 6

4.)

a 4

188 128 148 1b8 188 288 Surface Temperature (°F) Figure VI-5c Contour of Asyptotic Fouling vs Velocity and SurfaceTemperature

HATER #4

4) 4- 6

198 118 128 138 148 158 ua 178 Surface Temperature (°F) Figure VI-5d Contour of Asyptotic Fouling vs Velocity and Surface Temperature 148 WATER #5

4., U ° 4

118 130 158 178 198 Surface Temperature (°F) Figure VI-5e Contour of Asyptotic Fouling vs Velocity and Surface Temperature

WATER *6

U N 15

HO 128 148 168 1E0 288 Surface Temperature (°F) Figure VI-5f Contour of Asyptotic Fouling vs Velocity and Surface Temperature 1149

WATER 1 7

188 US 148 168 188 288 Surface Temperature (°F) Figure VI-5g Contour of Asyptotic Fouling vs Velocity and Surface Temperature

WATER $8

129 138 148 158 168 178 188 Surface Temperature (°F) Figure VI-5h Contour ofAsyptotic Fouling vs Velocity and Surface Temperature 150

WiTa .9

SI 185 128 135 158 165 188 195 218 Surface Temperature (°F) Figure VI-5i Contour of Asyptotic Fouling vs Velocity and Surface Temperature

WATS I 18

138 148 158 168 DO 198 Surface Temperature (°F) Figure VI-5j Contour of Asyptotic Fouling vs Velocity and Surface Temperature 151

WATER t 11

16 u

.6, 12

4.)

....I U 0

13 122 14 ng 199 199 SurfaceTemperature(°F) Figure VI-5k Contour of Asyptotic Fouling vs Velocity and Surface Temperature

WATER t 12

118 138 158 ry 198 218 Surface Temperature (°F) Figure VI-51 Contour of AsyptoticFouling vs Velocity and Surface Temperature 152

16118 13

138 148 158 168 178 188 1% 288 Surface Temperature (°F) Figure VI-5m Contour of AsyptoticFouling vs Velocity and Surface Temperature

NITER 814

18 aui

4- - 8

118 128 138 148 158 168 178 188 Surface Temperature (°F) Figure VI-5n Contour of Asyptotic Fouling vs Velocity and Surface Temperature 153

MIER #15

N HS 128 148 168 lES Surface Temperature (°F) Figure VI-5o Contour of Asyptotic Fouling vs Velocity and SurfaceTemperature 1514

WATER 111

178 Data for this water was available only

153

136

119 s 182 4-4

n es

68 LL

L.- 51

cs' 34 4- 17

cc 8

2 2.75 3.5 4.25 5 Velocity(ft/sec) Figure VI-6a Curves of Constant Surface Temperature vs Asymptotic Fouling Resistance and Velocity

WATER #2

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6b Curves of Constant Surface Temperature vs Asymptotic Fouling Resistance and Velocity 155

WATER # 3

2 3 4 5 6 7 8 Velocity(ft/sec) Figure VI-6c Curves of ConstantSurface Temperature vs Asymptotic FoulingResistance and Velocity

WATER 4

t 28

16 co

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6d Curves of Constant Surface Temperature vs Asymptotic Fouling Resistance and Velocity 156

RATER # 5

188

4 89

-P co

L .c48

11- cr

2 3 4 5 6 8 9 Velocity(ft/sec) Figure VI-6e Curves of Constant Surface Temperature vs Asymptotic Fouling Resistance and Velocity

RATS # 6

4 59

n48

4- ?a

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6f Curves of Constant Surface Temperature vs Asymptotic Fouling Resistanceand Velocity 157

WATS I 7

19.3

17.3

oa 15.3

13.3

11.3

9.3

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6g Curves of Constant Surface Temperature vs lAsymptotic Fouling Resistanceand Velocity

WATER #8

4.) °q6

L 1: 4

* 2 k.

tic

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6h Curves of Constant Surface Temperature vs Asymptotic Fouling Resistance and Velocity 158

41TER # 9

188

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6i Curves of Constant Surface Temperature vs Asymptotic Fouling Resistance and Velocity

WITS #10

t 12 is -4 *

4.)9 co r6L

4.., 14-

*4-3 cr

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6j Curves of Constant Surface Temperature vs Asymptotic Fouling Resistance andVelocity 159

it TER t 11

25 4

-; 28 4.) co

15 .0

4') 18 4-

Ce 5

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6k Curves of Constant Surface Temperature vs Asymptotic Fouling Resistance and Velocity

WATER t 12

16 4 si *

12 4->

4.> 4-

z 4 %- rr

2 3 4 5 6 7 8 Velocity(tt/sec) Figure VI-61 Curvesof Constant SurfaceTemperature Velocity vs AsymptoticFouling Resistance and 160 DATER I 13

4 * 2

1L ' L t4 6 4-

* 4- 3

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6m Curves of Constant SurfaceTemperature vs Asymptotic FoulingResistance and Velocity

WATER 014

1 200

168

L r

138E

8 I .

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6n Curves of ConstantSurface Temperature vs Asymptotic FoulingResistance and Velocity 161

MIER t 15

n cm

L 3

* 18

2 3 4 5 6 7 8 9 Velocity(ft/sec) Figure VI-6o Curves of Constant Surface Temperature vs Asymptotic Fouling Resistance and Velocity 162

Fouling Resistance-Time Curves

Once the time constant A, and the asymptotic fouling resistance R*1, are determined from Equations (7-1) and (7-

3) respectively, Equation (7-5) may be used to develop fouling resistance-time curves. These plots will help in plant-shutdown scheduling.

Threshold Values

Table VI-4 may be used to select additive combinations along with threshold values of flow velocity (shear stress), heater surface temperature and pH at which the asymptotic fouling resistance. R", is not expected to exceed a threshold value of 0.0001 ft2 hr °F/Btu.

Application to Other Geometries

In order to use the results of this study for flow of a given water in other geometries (annular flow was used in this study), the wall shear stress of the flow in other 163 geometries would be matched to those of this study. For example, to obtain a velocity in smooth tube that results

in comparable shear stress to those used in this study,

Equation (5-34) should be used.

Consider water flowing in 1 in I.D. smooth tube at a bulk temperature of 100°F then

I = 61.9 lbm/ft74

H = 4.6 x 10-4 lbm/ft sec

Thus, to determine flow velocity in the smooth tube required to give wall shear stress of 0.425 lb /ft2 (0.425

lbf/ft2 corresponds to flow velocity of 8 ft/sec in HTRI annular test section used in this study), Equation (5-34) is used 0.425 = (0.0395) C(4.6)(10-4)]°- (61.9)5 (32.17)(1/12) from which

V = 10.13 ft/sec

thus, flow velocity of 10.13 ft/sec in a smooth tube will give a shear stress of 0.425 113/ft2.

Several numerical examples showing some of the application of such results and equations obtained in this study in the design and operation of heat transfer equipment are given in an earlier study by Santoso (29). 164

VIII. CONCLUSIONS

In the previous chapters, the fouling data for a variety of additives were presented and discussed. Data was also correlated according to the HTRI model. The following are conclusions:

1. The tests showed that it is possible to minimize the effect of fouling that result from adding phosphate corrosion inhibitors by maintaining appropriate levels of certain controlling parameters of copolymer additives, heater surface temperature, flow velocity and pH.

2. The operational parameters of pH, flow velocity and surface temperature were found to significantly influence the fouling characteristic of all additive combinations considered in this study. However, it was always the case that high flow velocity (8ft/sec), low

surface temperature (130°F) and low pH (6.0 to 7.5 ) are conditions at which virtually no deposition occurred for all additive combination considered in this study with exception of those additive combinations that had AA/MA copolymer.

3. Various copolymers were tested in this study with respect to their effectiveness in reducing the fouling 165

tendency of phosphate corrosion inhibitors. Some were found to be considerably more effective than others.

For pH of 8.5, AA/MA copolymer was not an effective copolymer in reducing calcium phosphate deposition.

AA/HPA and AA/SA copolymers were both very effective at surface temperature of 160°F. At surface temperature of

130°F AA/SA was very effective and slightly more effective

than AA/HPA. SS/MA copolymer was only moderately effec-

tive except at 8.0 ft/sec and 130°F where it was effec-

tive. Otherwise SS/MA was about as ineffective as AA/MA.

For pH of 7.5, copolymers AA/HPA, SS/MA, and AA/SA were effective in reducing the fouling of phosphate

corrosion inhibitors . In all cases fouling was reduced by their presence and acceptable fouling was experienced.

The copolymer AA/MA had no effectiveness in reducing fouling tendency; in fact, a greater fouling rate and

ultimately higher final fouling resistance was experienced with this copolymer presence than when it was absent.

For pH of 6.5, the effectiveness of the copolymers in reducing the calcium phosphate deposition was very good.

At the extreme conditions of 3.0 ft/sec flow velocity and

160°F surface temperature, AA/HPA and AA/SA copolymers

were effective; SS/MA was reasonably effective giving an

asymptotic fouling resistance about 70% of that when no

copolymer was used. Copolymer AA/MA was ineffective. 166

4. The effect of iron in the presence of phosphate corrosion inhibitors was studied with respect to its effect on the fouling characteristic of the cooling tower water. It appears that the presence of iron (3.5 to 3.9 ppm Fe) causes somewhat higher fouling (15 to 25 percent above that for water containing no iron). Water containing 3.5 to 3.9 ppm Fe showed lower fouling than water containing 1.9 ppm Fe, possibly due to the nature of the deposits formed with higher iron content water. With respect to the fouling characteristic of the cooling tower water containing iron and phosphate corrosion inhibitors, the effect of iron and phosphate appears to be additive and the fouling-time curve, for when no iron is present, is not altered in any way.

5. The effectivenessof HEDP copolymer in reducing the deposition of iron was investigated in this study. In all cases, the presence of HEDP copolymer appears to enhance the fouling.

6. Fouling of cooling tower water containing phosphate corrosion inhibitors with and without iron present was investigated on four different heater surface materials, stainless steel (SS), carbon steel (CS), admiralty brass and 90/10 copper nickel. Virtually no difference was observed in either the fouling rate or 167 fouling resistance of the deposit formed on these surfaces.

7. Several duplicate runs were made and good reducibility of the data can be obtained when identical conditions are maintained between the duplicate runs.

Fluctuations in pH and differences in phosphate and iron content of the water can cause disagreement between duplicate runs.

B. For the phosphate inhibitors, the major constituent of the deposit was calcium phosphate. When iron was present in the water, it was also present in the deposit.

9. Various additive combinations and conditions showed insignificant fouling. For these additive combinations and conditions, threshold values and conditions of water quality, surface temperature and flow velocity

(shear stress) were established.

10. Fouling values, when fouling occurred, were obtained under very well defined condition of water quality, heat transfer surface temperature, flow velocity

(shear stress). These values can be used by heat exchange equipment designers and operators, Tables VI-1, VI-3. 168

11. The fouling data for a variety of additive combinations were correlated according to the HTRI model.

The resulting correlation has provided parameters which are specific for each water considered in Table VI-2.

Threshold curves for the asymptotic fouling resistance were produced using HTRI model correlations. These curves, along with HTRI equations, can be used by the designers and operators of the heat exchange equipment.

The designers can use them to predict thefouling values that they can use in their designs; the operators can use them to follow the progression of the fouling. It will also help plant shut-down scheduling. Given the heat transfer surface temperature, flow velocity (shear stress should be used in all relations developed in this study), fouling resistance as a function of time, the asymptotic fouling resistance and the time constant can be calculated for each of the fifteen water considered or similar waters. Also for a specific water, condition of flow velocity, surface temperature can be calculated for a specific additive combination.

12. Correlating the removal rate function with the heat transfer surface temperature gave a good agreement with HTRI model and gave support to Santoso (29) qualitative assumption of the effect of temperature on removal rate. 169

13. The presenceof additives in the water affects

the deposit strength dependency on surface temperature.

Adding copolymer to the cooling tower water reduced the

value of the exponent b to which the surface temperature

is raised. The b value reduced from 29 for no additive to

a value in the range of 0.08 to 6 or negative value with

additives.

14. It was possible to use HTRI model to correlate

the data for the additive combination which contained only

iron and no phosphate corrosion inhibitor. In fact the fouling characteristic of the cooling tower water was in

no way different from water having no iron present. The deposit in this case was a gelatinous film of ferric hydroxide. Due to the presence of water in this gelatinous film, a high fouling resistance was experienced.

15. The presence of various antifoulants did not alter in any way the fouling characteristics of the cooling tower water. The fouling resistance time-curve still follows an asymptotic fouling curve of constant deposition rate. The presence of these antifoulants made the strength of the deposit structure weaker, thus it was easily sloughed off by the shear forces. Also it was possible, because of the weak deposit, to operate at relatively high 170 surface temperature (160°F) and high pH of 7.5 without experiencing a large fouling resistance values. 171

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18. Knudsen, J.G. et al. "Fouling Characteristics of

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Inhibitors". Proceedings of the 1987 ASME JSME

Thermal Engineering Joint Conference. Vol.3. pp 109-

115, (1987).

19. Lahm, L. "Effect of Water Quality and Surface

Temperature on the Scaling Characteristics of Cooling

Tower Water". M.S. Thesis, Oregon State University,

(1982).

20. Lahm, L. and Knudson, J.G. "Precipitation Fouling of

Cooling Water". Heat exchangers, theory and practice. Taborek, J., Hewitt, G.F. and Afgan, N., eds. Hemi-

sphere, New York. pp 863-869, (1983).

21. Lee, S.H. "Deposition Characteristics of Magnesium Silicate and Calcium Carbonate in Cooling Tower

Water". M.S., Oregon State University, (1979).

22. Marner, W.J., Ritter, R.B. and Suitor, J.W. "The History and Status of Research in Fouling of Heat

Exchangers in Cooling Water Service". Canadian Journal of Chemical Engineering, vol. 55, pp. 374-380

(1977). 175

23. McCoy, J.W. "The. Chemical Treatment of Cooling

Water". Chemical Publishing Company, New York,

(1976).

24. Morse, R.W. "Alkalinity Effects on the Scaling of

Simulated Cooling Tower Water". M.S. Thesis, Oregon

State University, (1979).

25. Parkins, W.E. "Surface Film Formation in Reactor Sys tems", Proc Tripartite Cont Transport Materials Pres-

surized-water Nucl Systems, Chalk River, Feb 28-

March 1,1961, edited by G.B. Vaysour, AECL-1265, June

(1961).

26. "Principles of Industrial Water Treatment" 2nd

edition. Drew Chemical Corporation. Boonton, New

Jersey, (1978).

27. Ralston, P.H. "Inhibiting Water Formed Deposits With

Threshold Compositions". Materials protection and

performance, 11, No.6, 39 June (1972).

28. Roy, B.B. "Fouling Characteristics of Cooling Tower

Water pH Effect". M.S. Thesis, Oregon State Univer

sity, (1982). 176

29. Santoso, E. "Fouling Characteristics of Cooling Tower

Water Containing Corrosion Inhibitors". Ph.D. Thesis,

Oregon State University, (1987).

30. Somerscales, E.F.C. "Corrosion Fouling". Fouling of heat exchange equipment, eds. J.M. Chenoweth and

M. Impagliazzo. American Society of Mechanical

Engineers, New York, New York, pp 17-27, (1981).

31. Story, M.K. "Surface Temperature Effects on Fouling

Characteristics of Cooling Tower Water". M.S. Thesis,

Oregon State University, (1975).

32. Taborek, J. et al. "Fouling: The Major Unsolved

Problem in Heat Transfer". Chemical Engineering

Progress, vol. 68, part 1, pp 54-67, (February 1972)

and part 2, vol. 68, pp 69 -78, (July 1972).

33. Taborek, J. et al. "Predictive Methods For Fouling

Behavior". Chemical Engineering Progress, vol.68,

No.7, July (1972).

34. Troup D.H. and Richardson, J.A. "Scale Nucleation on

Heat Transfer Surface and Its Prevention". Chemical

Engineering Commun. vol.2, pp 167-180, (1978). 177

35. Watkinson, A.P. "Water Quality Effects on Fouling From Hard Waters". Heat exchangers, theory and

practice. Taborek, J., Hewitt, G.F. and Afgan, N.,

eds. Hemisphere, New York, pp 853-861, (1983).

36. Watkinson, A.P. and Epstein, N. "Fouling in a Gas Oil

Heat Ex-changer". Chemical Engineering Symposium

Series, Vol.65, (1969).

37. Woerner I.E. and Boyer D.R. "Impact of Select

Polymers on Calcium Phosphate Inhibition".

Paper No. 314 presented at Corrosion 84, April 2-6,

1984, sponsored by National Association of Corrosion

Engineers, Houston, Texas, 77218. APPENDICES 178

APPENDIX A

NOMENCLATURE 179

A Surface area, ft2

AA Area of flow in an annulus, ft2

AH Area of heated cross-section, ft2 b Exponent in Equation (6-11)

Constants

C1 Foulant concentration, lbmole/ft'3

Cp Heat capacity of water, Btu/lbm °F d Tube diameter, in

Outside diameter of an annuli, in de Inner diameter of an annuli, in

DIGLAS Inside diameter of glass tube, in

DROD Outside diameter of heater rod, in

E Energy of deposition, Btu/blmol f Local friction coefficient, lbf/ft2

Fv Velocity dependent

32.17 ibm ft/lbf sect h Convective heat transfer coefficient

K,Ka..K.. Proportionality constants k Thermal conductivity of rod material, Btu/hr ft °F

K1 Fouling deposition rate, ft2 °F/Btu

K, Constant in fouling removal rate term, hr kf Thermal conductivity fouling deposit, Btu/hr ft°F

L Length of heated section of rod, in

M Mass flow rate, ibm /hr 180 m Empirical constant n Exponent on water quality function

Q Rate of power supply, Btu/hr

Qmv Power transducer reading, millivolts r2 Correlation coefficient

R Heat transfer resistance, ft2 hr °F/Btu

Re Reynolds number

Rf Fouling resistance, ft2 hr °F/Btu

Rfi Fouling resistance of point, ft2 hr °F/Btu

(Rf)F Final fouling resistance, ft2 hr °F/Btu

R*, Asymptotic fouling resistance, ft2 hr °F/Btu

Rg Universal gas constant, Btu/lbmol °R

SS Sum of squares deviations

Temperature, °F

Tb Local bulk water temperature, °F

Tc Wall thermocouple temperature, °F

Tin Inlet bulk water temperature, °F

Tmv Temperature, millivolts

Ts Temperature of fouling deposit surface, °F

Tw Temperature of wall, °F

U Overall heat transfer coefficient, Btu/hr ft2

Fluid velocity, ft/sec

W Mass flow rate, lbm/hr

WF Volumetric flowrate, gpm

Wmv Flow transducer, millivolts xf Instantaneous fouling deposit thickness, in 181

x/k Thermal resistance of tube wall, ft2 hr °F/Btu

ZI..ZM Variables defined in section V 182

SUBSCRIPTS avg Average value

c Clean condition f Fouled condition

i Inside of tube o Outside of tube my Millivolts reading

GREEK LETTER a Exponent in Equation (6-11)

Time, hr ec Time constant, hr ed Time at beginning of test when the fouling rate is essentially zero, hr ei Time at point, hr

P Viscosity, lbm/ft sec

Density,lbm/ft

T Fluid shear stress at wall, lbg/ft2

Od Deposition rate, ft2 °F/Btu

Or Removal rate, ft2 °F/Btu

Deposit strength factor

Water quality function 183

APPENDIX B

CALIBRATION EQUATIONS 184

WATTMETER TRANSDUCER

Q = 341.3 x Qmv (8-1)

where

Q = heater power consumption, Btu/hr

Qmv = wattmeter transducer reading, miilivolts

THERMOCOUPLES: CHROMEL CONSTANTANT (TYPE E)

T = 32.583( Tcm + 5.02 Tcm, < -1.0 (8-2)

T = 38.529( Tc, + 4.72 )-r-3Th'5 Tc, 1 -1.0

where

T = temperature, °F

Tcm, = thermocouple output, millivolt

ROTAMETERS

WF = Flowcal (Wmv-4) (B-3)

where

WF = volumetricl flowrate, gpm

Flowcal = constant, characteristics of flow transducer

Wmv = millivolt reading of flow transducer 195

APPENDIX C

CHEMICAL ANALYSIS PROCEDURES 186

A sample of the cooling tower water was analyied daily for total hardness, calcium hardness, magnesium hardness, magnesium hardness, sulfate (S0,,), chloride

(C1), silica (Si), orthophosphate (OP), polyphosphate (PP) and iron when iron was present.

The procedure, chemical reagents, equipment and daily analysis values for the chemical analysis of the cooling tower are available at chemical engineering department,

Oregon State University, Corvallis Oregon. The daily analysis of these constituents for each run is given in

Appendix J. 187

APPENDIX D

SAMPLE CALCULATIONS lee

In Chapter V., the method of calculation of fouling resistance for clean and fouled condition and the method of error estimation of fouling resistance for fouled and clean conditions were given. These methods are a part of the data acquisition and estimationsoftware used to monitor and read thevarious system parameters in this study. Several earlier studies present a sample of calculation for fouling resistance and error estimation. Some of these studies are (19, 28, 29).

SHEAR STRESS CALCULATION

d =DIGLAS

=.750 in

d, =DROD

=.420 in

=61.66 lbm/ft74

from Equation(5-30):

dmax2 = (.7502 .4202) .383 in In (.7502 .4202)

from Equation (5-29):

= (.7502 .3332) / .750 = .306 in 189 from equation (5-28)

Re = (.306)(V) (61.66) = (3.987)(10.1) V (12) (1.42 / 3600)

(.076) C(3.987) (101) V 3-.7-45

(9.564)(10-'3) V_.

fromequation (5-32)

= (9.564)(10-'3) (61.66)(v2) (2) (32.2)

= (9.157) (10 -1)V1.7' andequation (5-33)

TI = (9.157) (10 -4)Vi '7L5 (.750 /.420)(.333-.4022) .7502-.333

=(1.116) (10 17)W--7,5

TI (1bf/ft2) = (1.116) (10-2) V' °'' , V = ft/sec 190

APPENDIX E

SUMMARY OF TEST RESULTS 191

A summary of runs 302 through 469 is given in Table

E-1 and Figure E-1 through E-16.

Table E-1 shows run numbers, run duration, heater surface material, final or asymptotic fouling values and run condition (pH, velocity, heater surface temperature and additives). Figure E-1 through E-16 are matrix figures which show run numbers, heater surface material, final or asymptotic fouling resistance and the additive combination used.

These parameters are given as a function of surface temperature, flow velocity and pH. The symbols, CS, Ad,

CuNi and SS refer to carbon steel, admiralty, 90\10 copper/nickel and stainless steel. TABLEE-1. 192 SUMMARYOT RUNS mmmammommilommomm

1 DURATION VELOCITY T S Rfla4 AVERAGE ADDITIVES 1 1 RUN (hours) (fthsc) ( 7) (*) CALCIUM pH (Inv) 1

1 HARDNESS 1

! (ppm) 1

I 1 1302(5.5.) 335.6 3,0 145 5.5 1041 7.0 1,2,8,91 1303(c.s.) 335.6 3.0 145 9.0 1041 7.0 1,2,8,91 1104(cu-N-1) 115.6 3.0 145 7.8 1041 7.0 1.2.8.9! 1305(S.S.) 262.7 3.0 160 9.7 1051.7 7.0 1,2,8,91 t306(c.s.) 262.7 3.0 160 3.6 '1051.7 7.0 1.2,8,91 1107(cu-Ni) 262.7 1.0 160 10-6 1051-7 7.0 1.2.8.0! 008(5.5.) 5.5 145 (Rod Problem) 7.0 1,2 !309(C.S.) 167 5.5 145 2,8 962 7.0 1.2 310(C.S.) 506.3 5.5 145 20.4 927.7 7.5 1,2 n11(Adm.) 188 3.0 160 1o.6 676.2 6.5 1,2 :11Tdm.) 146 5.5 160 (Rod Problem) 6.5 1..2 n13 Acim. 194 5.5 160 5,8 682.1 6.5 1.2 1314(Adm.) 167 3.0 160 4.1 671.2 7.5 1,2,3 1115(Cu-N1) 167 8.0 160 1.4 671.2 7.5 1.2.1 016(Adm.) 164 3.^ 130 0.9 645.9 7.5 1,2,3 1317(Cu-N1) 164 8,(' 110 0 645.9 7.5 1.2.1 018(Adm.) r319(0u-M1) (Computer Problem) r320(Adm.) 162 5.5 160 0.9 650 7.5 1.2.3 0 21(Cu-Ni) 162 5.5 145 0.5 550 7.5 1,2,1 022(Adm.) 210 3.0 160 3.0 619.6 8.1 1.2.3 . 323(Cu -Ni) 210 1.0 160 1.9 619.6 8.1 1.2.1 024(S.S.) 167 5.5 160 0.8 592.5 6.5 3,4 025(Cu-Ni) 167 8.0 160 0.6 592.5 6.5 3,4 (326(Adm.) 167 3.0 160 1.2 592.5 6.5 3.4 327(S.S.) 167 5.5 160 1.6 634.2 7.5 3,4 52S(Cu-Ni) 8.0 167 16o 1.1 634.2 7.5 3,4 029(A4m.) 167 3.0 160 1.9 634.2 7.5 3,4 030(s.s.) 167 5.5 160 1.3 660 8.2 3,4 931(cu-Ni) 167 8.0 160 1.2 660 8.2 3,4 832(A4m.) 167 1.0 160 0.9 660 8.2 3,4 933(s.5.) 165 5.5 160 0.6 670.4 6.5 4 534(Cu-N1) 165 8.0 160 0.6 670.4 6.5 4 93 (Adm.) 145 3.0 160 1.2 670.4 6.5 4 836(S.S.) 163 5.5 160 7.1 626.3 7.5 1,2 937(Cu-Ni) 163 8.o 160 6.1 626.3. 7.5 1,2 918(Adm.) 163 1.0 160 7.8 626.3 7.5 1.2 939(S.S.) 165 5.5 160 10.7 622.4 7.5 t,.,5 340(Cu-Ni) 165 -.8,0 .160 8.4 622.4 7.5 1,2,5 341(Adm.) 165 1.0 160 14.3 622.4 7.5 1.2.5 t

IIIIMIMMISMOMIMMIMMOMMEIMMMMUIMMOMMOMINIMIMMIMMIMMOMMUIMIIIIMMUM ===== SAMMIIMPIIM MOWS

(*) : (ft **2) * hr *V / btu PF 4 -5.ppm (**) 1 v 6 : SS /MA 10 ppm 2 : OP 5-6 ppm 7 : SA/AA 10 ppm 3: A /HPA 10 ppm 8 : EDP 2 -4.ppm 4 : OP 10 ppm 9 : FA 2-4 ppm 5 : AA/MA 10 can TABLEE-1 CONTINUED 193 SUMMARY 0? RUNS MOOMMIIIIMIWOM

1 DURATIONVELOCITY T S RfxE4 AVERAGE ADDITIVES

(hours) (ft/see) ( 7) (*) CALCIUM pa i t RUNHARDNESS 1 (PP2) 1

1342(5.5.) -167 5:5 160 0.41 609.8 7.5 1,2,6 1 143(0u-Ni) 167 8.0 160 0.45 609.8 7.5 1,2,6 1 1144(Adru.) 167 3.0 160. 1.53 '609.8 7.5 1,2,6 13450.S.) 168 5.5 160 0.15 612.6 7.5 1,2,7 8.0 160 1146(Cu-Ni) 168 0.18 612.6 7.5 1,;:7 1 1147(Adm.) 168 3.0 160 0.19 612.6 7.5 1,2,7 ! I 1

I. 1 I 1 I 1

1 1

1 1 I 1 I 1 1 1 1 1 1 1 ! 1 1 1 - I .1 : 1

I 1 I I

I 1

1 1 I. I I I I

pOIDOWOMPUROMMINIMMMWMOMPOOMOIMMIOMMIOMONimmglimmem MiMMIWOMMOMMIRMINSMOIMMO

(*) (ft ** '2) * hr * 8 / btu (**) 1 : PP 4-5 prat 6: SS/MA 10 ppm 2 : OP 5-6 ppm 7: SA/AA 10 pfom 3 : AA/HPA 10 ppm 8 : HErF 2-4 ppm 4 : op to ppm 9 : PA 10 ppm 5 : AA /MA 10 ppm if if" Ea G) t) Ea C4 Ca EJ E4 ta (J(,) Ea Ca Ea (a 114 E4 Ca Ca (4 C4 (4 G) El E4 Ca(4 Ea Ca Ca Ca (4 Ca Ca G) G) Ca L4 Ca (J LJ La L4 Ca La (4 Ca G) 7U uP up u0 up OD CD OD OD 00 OD CD 100 cD co .4 .4 .4 .4 .4 .4 .4 .4 .4 .4 onoN om cm cm cm cm cm om (.4 0 (01 0 4t C: LA 4. La 44Pa046 00 Om EA 4. G4 r- C) uD OD Om E4 4= C4 r- C) uD OD .4 Om LA 4= W 44 t. 0 OD .4 Om LA 4, La ta ... 0 ND co GI 44

OD .0 40 GO

6.'014--.. o 0 et t" t' 6.". 4) N) 1.11 r. i-. 0-* 44 ha h) r. r- r- r- WW Ca r. .-- r. 4. 41 4. (4 WW I I 4- 4= 4: ta G) G) Ea Ea ta uD u) 0) 4, 4, 4, ON Cn 06 t. t. 6... uD 0 uD alEn al En r. cm G) GI Gi 4- 4- 4- h) h) h) 4, 4, 4, ha hi h) -4 -4 *...4 it r- r- r.. OD OD 03 G3 G) G) 0 0 0 03 CO CO NJ ha Fa .4. 4. 4- 4. 44 4. .4-4 ....4 uD . u) ca Ea G) -4 ...4 ,4 En Om cn uD u) u) cn E4 ii >13 13 2013 13 164 ., 3 3 s. W 1 4 LJ CO CA G4 0) C4 IJ CO CA W CD CA W CO CA G3 %4 LA EJ co EA 14 CD CA EJ:4 LA G) ' CA GI CO LA 4) CO CA G) 4 LA G) ..1 !A EJ ,4 CR 4) 03 LA W 3, 1 CA 1c) C) 4. C) C) 4. C) C) LA 0 0 4, C) 0 L4 C) 60 4. 0 6... E4 0 (3 4 C> r et t. 3- uD 14 C) , EA CD C) (A CD C) 4. C) 0 4. Ci uD 4. C) u) LA 40 4, CD rel C) NJ N) C) 14 %4 C) EJ t. C) 60 s4 0 G4 4) 0 (A s4 0 6." 44 0 LA ,4 0*4 uD C) .1 h) C) al G4 0 60 CO () 0 La C> (0 4- CS C) CD Ci C) C) x "; II -c 0 I II 403* M O x (3 I s0 M Is)WWWW00WWWWN*0 t,) 4) E4 cm cn es) 1K) Is) L4 cn CP Ga EJ 4.4 E) Ca Ca14-.N.-.i41-..1-.NOWWW00000000000OMON00 Om Cn cn CM Cn EnCa (4 44 01 01 En CP In EA G) Gi Gj ha ha ha cal 01 EA cm 01 cn 1.) G4.0 N) N1 -'1 7D t.. C> In 41 GI EJ L4 6-. 04 EA 0 G4 W LA ,4 4, ,4 4, 0) ..4 t. '4 LJ G4 ()%1 G) 4) LA 0 6.. '4 .4 L4 s4 OD t. 4) 0 LA 14 ,4 C4 C) CA (0 r. 0 C 11 :r ', t) Em 0 LJ 4, ,4 G4 En n) cn E) LA t. 4) CD t. 0 4, LA ',4 4) CO '4 6... Cn 3- IV 4) C) L4 44 (3 W CO G3 (3 4, t. h) EJ 4) LA EA ND .4 ,4 4) ON N4 4, wit) I. et CT EU et * ri. "-' IP. 9.0 II.. 0-0 .- 73 0 M1 C IF00041.1L4000WWW000000MW4.Mr-NCAWK)M....t.h),-..-0430014.44.r-Wr-NWO-4G) .406040e .0o .Ooreiwoo. 4. .6000001bOoomoomosOe.o40.e.ome Ga 0 1,.. ''' N) IS) 61) CP CP EA Cn t. t..01 L4 t. 4) 4) 0 4) 60 14 C) 4, L4 4, 0 "4 Z 0 CA CD ha 0 LA CA cn .-. t- up o EJ Ps) *4 ON uD 0 o-. OD 03 CO m 03 hi U) (.4 OD h) 03 I.) r- CO 0 cn 6-- .4 LA EA (3 h) 4. Oh CO 4, C> u) I.) G)ta (3 4, C) 0 6.. 60 u) h) 41 0 0) 4, 6. t" h) ,1 0) G4 03 EA 4 0 %./ %.0 :ri I " (1 Cm ULL' " '4 .4 *4 ,4 .4 ,4 03 CO CO CO 03 (0 .4 *4 cm 01 cn LA (A EA 4. 4. 4. 4. 4. 4. 0 0 uD CA LA LA (11 LA CA C4 CAIA 4 -4 .4 cn on en 01 0+ cn ha h) N3 CP Cft cn G) Ca c) C) C) C> Om on cn V V V LAUD s4 *4 .4cn on 04 4= 4- h) h) h) ha h) h) Co 03 OD cA LA c4 CA LA CA 0000 CO 03 OD uD u) u0 CO CO OD L4 EA LA C) C> C4 LA LA E4 h) h3 CO CO CO hi h) 4. 4, 4, En 01 cn u) uD CO CO OD CO CD CO CP 01 CD Pa P.. r>mo >w OICOCO4+.4.4.000 ,4 ,4 V C> 0 0 C) 0 LA EA EA 43 C) uD uD 0010101101D1D000O0303CDCO0004.4. 4- u0 LP 0 CO CO CD CO CD 0001CPUIUIO1011n01 01 01 01 01 0 01 01 en CP C0 CD en al En Cn cn en en en"4 "4 ,4 OD Co OD CD CO 0) ,4 "4 o.4 CO 0) co 0 am3m . mm>> L4 EA LA L4 E4 LA (A LA LA CA LA EA L4 L4 EA L4 14 L4 EA CA LA CA L4 EA LA CA LA EA CA LA L4 LA CA L4EA LA LA LA EA LA L4 LA L4 EA LA (A L4

P 4 30. U) 'NO .10 .0 .10 01 01 AD. 1.0 .111 .111 .110 .0 .10 .10 .0 01 .0 .0 OD 14 N.) ha ha h) I.) ha Is) ha h) h) h) h) h) ha h) N4 N3 N3 NJ NJ N3 N4 NJ NJ NJ N4 Ea N4 NJ N3 NJ NJ NJ N4 N3 NJ N) N) N4 NJ N4 NJ N3 N4 N3 NJ t4 I hi-I m 01 N .0 .0 .0 NS Vs .0 gm .10 .0 10 N (71 En m CO CP 01 01 Cn ol En En 4 .4 LA LA EA C4 EA E4 ,4 "4 "4 4. 4. 4. 4= 4- 4. 1.4 Ea G) Ea E) Ca Ca 6) A Ea E) Ca E) La Ea Ea Ea Ea Ea 4: PI OD r C 195

TABLE E-1 CONTINUED SUMMARY OF RUNS 1396-416)

AVERAGE 11 I: RUNDURATION VELOCITY .T S. RNE4CALCIUM pHADDITIVES!) S (hours) (ft/sec) F) (*) HARDNESS ( 11 ft ( ppm ) 11

:1 1. 1. 396 532:43 5.50 159.65 16.18 827.3 8.5 1,2,5 11

:: 397 532.43 8.00 160.16 . 18.60 927.38.5 1,2,5 '! II 398 532.43 3.00 159.85 21.11 827.38.5 1,2,5 11 :1 399 378.21 5.53 130.91 13.39 677.3'8.5 1,2,5 11 11 400 378.21 3.07 132.64 6.33 677.38.5 1,2,5 il 401 378.21 3.00 131.74 24.51 677.38.5 1,2,5 Ii II 402 114.68 5.50 158.60 8.68 831.0 8.5. 2,3,5 :1 II 403 114.68 8.01 160.66 4.85 831.0 8.S .2,3,5 II Ii 404 114.68 3.00 159.20 8.97 831.0 8.5 2,3,5 II 405 220.11 5.49 128.53 9.88 840.0 8.5 2.3,5 ::

II 406 220.11 . 8.01 127.15 5.56 840.08.5 2.3,5 II 407 220.11 3.00 128.54 11.36 840.0 8.5 2,3,5 II 408 252.4 5.50 158.58 5.60 840.08.5 2,5,7 :1 II 409 252.4 8.01 161.50 5.14 840.0 8.5 2,5,7 II II 410 252.4 3.00 160.26 14.62 840.08.5 2,5,7 II II 411 226.87 .5.50 128.82 5.84 840.07.5 2,5,7 II II 412 226.87 8.01 130.18 14.00 840.0 7.5 2,5,7 11 II 413 226.87 3.00 128.32 11.60 840.07.5 2,5,? I! II 414 112.2 5.50 159.04 4.01 639.0 7.5 2,5,e !! II 415 112.2 8.00 160.15 1.46 639.0 7.5 2,5.8 11 11 416 112.2 3.00 158.63 10.05 639.0 7.5 2.5,8 11 1$

(ft , 2) hr F / btu

1 : 10 ppm AA/MA . 1: - 5 ppm Poly-phosphate 3: 10 PPM 56/MA 4 4 - S ppm Ortho-phosphate 5: 5 - 6 ppm Ortho-phosphate: 6: 2 - 4 HEOP

7 1 2 opm iron 8 4 ppm Iron 196

TABLE E -1 CONTINUED SUMMARY OF RUNS (417-458)

AVERA1E RUN DURATION VELOCITY T S RfxE4 CALCIUM pHADDITIVES (**) It (hours) Aft/sec) ( F) (*) HARDNESS (PPm)

417 168 5.50 132.50 0.71 754.0 7.6 2,3,5 418 168 8.00 132.10 0.31 754.0 7.6 2,3,5 419 168 3.00 130.20 0.27 754.0 7.6 2,3,5 420 232 5.50 159.40 4.20 645.0 7.5 2,3,4,5 421 232 8.00 160.80 1.90 645.0 7.5 2,3,4,5 422 232 3.00 161.40 11.00 645.0 7.5 2,3,4,5 423 167 3.00 158.80 11.50 538.0 7.4 2,3,4,5 424 167 3.00 158.50 5.60 538.0 7.4 2,3,4,5 425 166 3.00 159.50 5.60 622.0 7.6 2,3,4,5 426 166 3.00 162.50 2.20 622.0 7.6 2,3,4,5 427 164 5.50 130.10 0.70 -623.0 7.6 2,3,4,5 428 164 8.00 131.50 0.40 623.0 7.6 2,3,4,5 429 164 3.00 132.10 0.20 623.0 7.6 2,3,4,5 430 257 5.50 160.30 5.50 603.0 7.4 1,2,3,5 431 257 8.00 159.70 5.20 603.0 7.4 1,2,3,5 432 257 3.00 160.10 2.10 603.0 7.4 1,2,3,5 433 161 5.50 127.10 3.70 600.0 7.4 1,2,3,5 434 161 8.00 129.20 4.70 600.0 7.4 1,2,3,5 435 161 3.00 127.20 10.10 600.0 7.4 1,2,3,5 436 263 5.50 159.80 0.90 745.0 7.5 NONE 437 263 8.00 159.60 1.80 745.0 7.5 NONE 438 263 3.00 158.10 2.10 745.0 7.5 NONE 439 301 5.50 159.10 2.40 710.0 7.5 6 440 301 8.00 162.60 0.60 710.0 7.5 6 441 301 3.00 161.20 8.00 '710.0 7.5 6 442 192 5.50 130.30 0.40 666.0 7.5 6 443 192 8.00 131.10 0.20. 666.0 7.5 6 444 192 3.00 130.40 0.70 666.0 7.5 6 445 305 5.50 159.10 5.50 703.0 7.6 6 446 305 8.00 161.00 3.20 703.0 7.6 6 447 305 3.00 160.50 6.90 703.0 7.6 6 448 303 5.50 158.10 3.50 736.0 7.6 6

449 303 3.00 160.10 9.20' ' 736.0 7.6 6 450 303 3.00 159.40 9.90 736.0 7.6 6 451 177 5.50 160.30 6.20 -'657.0 7.6 2,3,6 452 177 8.00 160.30 4.10 657.0 7.6 2,3,6 453 177 3.00 160.00 11.00 657.0 7.6 2,3,6 454 257 5.50 160.40 9.60 720.0 7.6 2,3,6 455 NOTE: HEATERFAILED 720.0 7.6 2,3,6 456 257 3.00 160.50 12.00 720.0 7.6 2,3,6 457 205 5.50 158.30 9.78 712.0 7.6 2,3,6 458 205 3.00 129.53 13.00 712.0 .7.6 2,3,6

(*) : (ft ** 2) * hr * F / btu (**) 1 : 10 ppm AA/MA 4 : 2 - 4 ppm HEDP

2 : 4 - 5ppm polyphosphate 5 : 4 ppm Fe

3 : 5 - 6ppm orthophosphate 6 : 3 ppm Fe 197

No Additive

ArAdr Ar0 ZCJ

436S:.9 5.5/ Air Airr \ 2.0

438SS 3.0 \5) pH = 7.5 A PI J((' 130 145 160 TEMPERATURE - F

# FOULING. RESISTANCE STILL INCREASING AT END.OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN

FIGURE E -1 RESULTS WITH WATER CONTAINING NO ADDITIVES 198

4-5 PP 5-6 OP 2-4 HEIM CONDITIONS 2-4 PA

pH 145 f6 TEMPERATURE - FOULING RESISTANCE STILL INCREASING AT END OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN

FIGURE E-2 (5 PP 6 OP)

130 145 I TEMPERATURE - F # FOULING RESISTANCE STILL INCREASING AT END OF RUN 3(-. DEPOSIT PERIODICALLY REMOVED DURING RUN FIGURE E-3 RESULTS FOR PHOSPHATE CORROSION INHIBITOR WITH NO COPOLYMER ADDED 200

CONDITIONS 10 OP

130 f45 160 TEMPERATURE - F # FOULING RESISTANCE STILLINCREASING AT END OF RUN * DEPOSIT PERIODICALLY REMOVEDDURING RUN FIGURE E-4 201

CONDITIONS 10 OP 10 AA/NPA

pH. 130 145 160 TEMPERATURE - F # FOULING RESISTANCE STILLINCREASING AT END OF RUN DEPOSIT PERIODICALLY REMOVED DURINGRUN FIGURE E-5 pH

(24 PP 80 OP)

TEMPERATURE - F # FOULING RESISTANCE STILL INCREASING AT END OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN FIGURE E-6 RESULTS FOR PHOSPHATE CORROSION INHIBITOR WITH 10 PPM AA/HPA rOPOLYMER ADDED 203

6.6 PP, 5.9 OP 5.5 PP, 4.3 OP

130 145 160 TEMPERATURE - F RESU:TS WITH COPOLYMER AA/MA

(6 PP 6 OP)

(7 PP 10 OP) (ti PP 1G(5i) . 11.-5 370CuNI 67Cu N 8.0 2.4 14.2 369SS 366SS 5.5 5.0 .16.5 pH 6.5 71Adm 68Adrris 3.0 I30 .145 ..reo---_ RESULTS FOR PHOSPHATE CORROSION INHIBITOR WITH 10 PPM AA/MA COPOLYMER ADDED TEMPERATURE - F FOULING .RESISTANCE STILL INCREASING AT END OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN FIGURE E-7 204

4.7 PP.3.3 OP 6.9PP.S S OP

130 145 160 TEMPERATURE - F RESULTS WITH COPOLYMER SS/MA

TEMPERATURE - F 'At FOULING. RESISTANCE STILL INCREASING. AT END OF.RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN

RESULTS FOR PHOSPHATE CORROSION INHIBITOR WITH 10 PPM SS/MA COPOLYMER ADDED FIGURE E-B 205

(6 PP 8 OP) (9 PP 9 OP)

0.2 394CuNi 8.0 0.2 5.7 393SS Vss 5 0,1 4.3 3.0 pH 85 95AdmAgii11111111"r392Adm 130 145. 160 C7 PP 5 OP)

NH 130 145

130 . 145

TEMPERATURE F # FOULING. RESISTANCE STILL INCREASING AT END OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN

FIGURE E 9

RESULTS FOR PHOSPHATE CORROSION INHIBITOR WITH 10 PPM AA/SA COPOLYMER ADDED 206

5.8 PP, 5.3 OP, 1.9 Fe 9.2 PP, 8.2 OP. 1.9 Fe

130 145 160 TEMPERATURE - F

# FOULING RESISTANCE STILL INCREASING AT END OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN

FIGURE EI0 RESULTS WITH 2 PPM TOTAL IRON 207

5.8 PP, 6.8 OP, 3.7Fe

AWAVAIVO eC)

Arlilass 5 5 rArAsio.i 7.5 p 3.0 \5(> 130 145r160 TEMPERATURE- F RESULTS WITH 4 PPM TOTAL IRON

2.3 PP, 9.8 OP. 3.0 Fe ACIPIrdr0 co

417SS 5.5

0 419SS 3.06) pH = 7.5 .3ArAir 130 145 160 TEMPERATURE F RESULTS WITH PHOSPHATE AND 3PPM IRON FOULING.RESISTANCE STILL INCREASING AT END. OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN

FIGURE E-11 208

2.6 PP 8.6 OP, 2.9 Fe 4.3 PP, 8.1 OP,2 8/re

Ar 5.5 3.0

Ar, 2.8 PP. 11.7 OP, 2.7 Fe AAirA.Alr 8.( ArArAr.5 ArldrA3.0 1 2.8 PP, 9.0 OP, 2 6 Fe AidrAr 8 0sec, 2,2 ArAr 5.5./\'1/4 3.00 4<(> Ardiffe130 145 160r TEMPERATURE - F # FOULING RESISTANCE STILL INCREASING AT END OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN FIGURE E-12 RESULTS WITH PHOSPHATE, IRON AND HEDP 209

2.1 PP, 9.4 OP, 4.5Fe 4.0 PP. 10.2 OP, 2.8 Fe

Adir5.2 431CN 8.0 ec'

430S:.5 5.5 /\r° Ar10.1AWAVAir CNC) pH 7.5 435SS 3..0 130 145 160 TEMPERATURE- F

# FOULING RESISTANCE STILL INCREASING AT END. OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN FIGURE E-13 RESULTS WITH PHOSPHATE, IRON AND AA/MA . 210

3.7 Fe 2.9Fe

AdridrAr0 eCi Addrier 3.5 448SS 5 * 9.9 \°650s Arar4: 3.0 130 145 160 TEMPERATURE- F # FOULING RESISTANCE STILL INCREASING AT END OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN

FIGURE E-14 RESULTS WITH 3PPM IRON AS THE ONLY ADDITIVE 211

5.9 PP, 8.6 OP, 4.9 Fe

4.1 452CN 8.0 $ 6.2 451SS 5.5

11.0

453SS 3.0 pH 7.5 130 145 160 4.9 PP, 7.4 OP, 3.9 Fe

0.8 11 Heater Fail 460CN 455CN 8.0

1.4# 9.6 459SS 454SS 5.5 b 12.0

461:0# 456SS pH 7.5 3.0 130 145 160 5.5 PP, 8.4 OP, 3.5 Fe

ec' Arld Mir\go Ar Air457S:0.5 5 5 3.0FitC pH 7.5 Ar ArAr 130 145 160 TEMPERATURE- F # FOULING. RESISTANCE STILL INCREASING AT END.OF RUN * DEPOSIT PERIODICALLY REMOVED DURING.RUNI

FIGURE E-15 RESULTS WITH PHOSPHATE AND 3PPM IRON 212

4.4 PP, 6.7 OP. 1.0 Fe 3.1 PP, 8.4 OF, 1.0 Fe

7.0 7.5 # 466CN 463CN 8.0

9.2 11.5 # 46555 462S5 5.5 9.4 13.2# 7.5 pH 467SS 46455 3.0 130 145 160 4.1 PP, 8.3 OP. 2.0 Fe

8.0 el."

13.6 468SS 5.5

19.9 C.f 7.5 pH 469SS 3.0 () 130 145 160 TEMPERATURE F

# FOULING RESISTANCE STILL INCREASING AT END OF RUN * DEPOSIT PERIODICALLY REMOVED DURING RUN

FIGURE E -16

RESULTS WITH 4-5 PPM POLYPHOSPHATE. 5-6 PPM ORTHOPHOSPHATE.3 PPM TOTAL IRON. 10 PPM HELP 213 APPENDIX F

FOULING RESISTANCE TIME CURVES 214 These plots are in sequence for Run 302 through 469.

These plots include fouling resistance-time curves along with plots of pH, conductivity, corrosivity, surface temperature and velocity as a function of time. These plots allowone to see if variation of any of these parameters affect the fouling resistance. a VELOCITY SURFACE TEM, (f) 4+- - -0- 41.00110CORM-RATE 21 4 1 .,4 VELOCITY fffff o SURFACE 1EAF (F) o o o FO.CONO.CORR-RATE w a v . " MI 0 10.4 t T I0. .,.,. 1v. 1 a 1 1 s C 304 i". JO '3410.n;2U .,/ 1 u i2 3 1 4 4 0 RI 4 10-4 _.?1t -t. I. VELOCIly ( .... a - SURFACE TIN? (F) N- a 10S 2 ;26 k. ;20 \ } .11 1 0 JO ; 411305 a 401 SURFACE 11111. (F) SURFACE TEMP (F) w 111 PN.CORO.CRR-RAZE v .4 RI 1 10.4w t .4 VELOCITY oooo a FN.CONO,COMR-RAZE .4 u v ; w 3200 100 ; 14 0 i2 30 ) ;100 .9 ;2O 300 3 4 11 4RO3 0 Y 4ELACI1V 10r) ea SUOFACS TEAS (F) , PA.C00.C011-0014 a of 04 4 1 5 10.4 . - . : 444444 II If. : : : E ...... a 41.0000.C0 -1.11 1 S 14 . . 5 . 1. I.' w.T t T. " 1 0. 100 100 .1 ;200 100 it" ) i2.i.10 i C1'200 ;204 1 i1 34 S:20 30 30 ; 100 .1I3110 :71 140 480 44 40. 40 4.. 11V 4444444 14A IF) . 44444//4 1f.41 : SUOVACS 100 4F! : : A.COM.000-00111 fo Of 14 :114 1 ,,,,, 100 IM 140 .4,600,0 A A ;300 t300 MO 11 :300 tw o I1*14 is*3 300 %ODMO 300 4444444 111112 (F4 141.01.0.20110-11011 111 S 10., 44444 Ca 141 11,4 NoCIM0.C.0 -01.141 Of S 10.4 P. . 0 I: ill il ...1 . . -. a 4 4 % tIN ow I O OOO 44 .. -4 100 i i ..... 11141 "t i .100 I. .100 . } t . .1' tf. 10 42.01 is..A ill jail.i o :204 1 wiled ... :... a 7; le. 144 it.. 454350 400300 400MI 4111114 40 Cis 4003 ; $$$$$$$ ISM' 111 a On:0:0;(6.1.1:8111: 01 I 60.4 - t* T.* VELOCITY OOOOO C SU! CCC AC[ (5) PM. COMO. COOP-WM 7 RI 1.4 i 114 . TOO I. . 411,i1 T.t T. SOO 1 ..1 OS it ...TO* II _.10 iii lo ... A 1 1 i A f A 1 * ISO 71pee %ilea ; t itOS i ISO " 1 100 T*4 JO ° 3410 Is 30 NIS JOS 44 480 48 0 400 4 400 FFFFF CE TEMP ti T 10.4 VELOCITY 1pa I: i . ''s 1 ....COMO CORR-MATE 4 1 1 :t m 1 1111 I TY CCCCC 4 CC ! OO CIL 1St! 45 . a . . w PM COMO. coom-eAva . a . a " ._ - 1 el e 10.4 . - t . t is 104 iv 1 1 SO* I I 104 1 1 I 100 O ( iswim 110* ) I I i IGO a'.. I A ,ISO* I I ;. JO* S) i S:ZO ii gas. it.. 5 TOO 100 O ' 100 3 is 40* 400 404 00 00

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Wil 04 It 141! 41 . * PO. 411 C411-46.4 44 .4 .1 - t ?..4-1_.s_. "1 1 a ; I ; N. I I a 00 2 , .DWI 34111 lee i.. 00 Ibibe r\>CD 40 44 CIO \ se 4I.4111I 000 oo L. 411. t-14 .1 OO OOO .14! 41111. I I 414.2. bi ; : t 7.1 40 u. i. 40 44 440 " rim 00000 ; .11 UK. -1.-70-+-:2:-. MN /00-14 OOOOOO 411.11 ...as ...-. . I " . 0 . i i I. t . i- 1 5. % 0 " ; z_. iI. a I. ). I 1- 1444 SO . 444 S ,.I t i !".`": oo o 06 I It! I , - --.4- II I 11 1.:111 , vi ,...... I...16. .:117.....-V: . -a. A 41 1.114 4. 1 14 I a. 3 i. 1 1. II 0 1" t 242

44414 0. 441 44, o. 443

v t

0(44 .NV444

FIRS 3ar4.31 rt. 4 fly. 4VA 044

1344,

flair

11,44 4, 441 .1 Own 0,443

3 I Mn.4w", 2 .111111 t tttttt

444 644 IM 1

3 3

3344 041004. 14304 111140 041

f sT : Tt411 4:1141.113 3344 4444441

4440 44 Sim 4431

A3440 .444 144 : 111441 4:44642 rut 000 4/4 4444 144

Tin444414 142 4410.10, 243

Ow ..!

...... ' it' .." 11...W.."' I

1111 rt. rt.

..;Wt. rt ti : sr

.44 rt.C... 1

Min 4? .10 .. .:. NI 1...... ' .I .1: t .3. t i

MI6 .404%. it,.,i,,,,,'1 IMO 11, ur 44.1 44 -

:It.: 244 APPENDIX G

COMPOSITE PLOTS OF SELECTED RUNS 2145

COMPOSITE PLOT # RUN 436,437,438

2.1 7.5 pH LS 160 f 43655 - 5.5 ft/see 1.8 437C1 - 1.0 ft /..o 1.7 61153 - 3.0 ft /..e LO No Additive 1.0 1 1.4

1.3 Ira L2 6 LI d Pm° 1 rD 0.9 Pm ki; ; M 0.7 0 R 0.8 O MO 4'44' 14 0.4 O M3 1 !ems 0 o.0.2 /t 0.1 0 "r. 0.1 O 44 so 120 180 200 240 280

T1112 (HOUR) U RUN439 + RUN 437 o RUN439

FIG,OE G-I Effect of Velocity.

COMPOSITE PLOT RUN , :502,303,304

Conditizes: Material - 302 SS 303 CS 2 4-5 -?? 5-6 - C? 304 CuNt -rt 2-4- EE? *rte 7 ,I4\ 2-4 - ?A J 4C. 3.0 - f:/sec / 145 - '7 /0' 4.-4k

04°1111\ fr.44 A *4' 4 a rem I 44 f44 Peaer42 A 3 EJ WI.64 3 .110 md

i I 1 i i a Al 24 174 110 704 744 780 370

nAJOICU 2.15 CI f !=7 + I.303 4 f 394 FTGURL U-2 Effect of material. 246

COUPOSITE PLOT RUN # 305,306,307

11 Conditions: 4-5 - PP 10 5-6 - OP 2-4 - REDP ea4. 1 2-4 - PA 2tr° a 3.0 - ft/sec 160 - eter2r 7.0 - w yea ,wo Material - 305 SS 306 CS 5 307 Cutai 4

7 40 ee 120 100 700 74 nmE01Cdr* a r 3aa lOS 0 it 3a, FIGURE 3 Effect of aaterial.

atIPOSTE PLOT RUN 311,312,313

HEATER FAILED DATA NOT VALID

a 20 4 110 Oa 100 1 10 140 100 1 la 100 Ins.; mzu a f 311 f 312 al 313 1, GUnE G -4 Effectof velocity. 247

C0/4PCIGITE FLCIT RUN 41* 176%337,313

*I, ..2,41ff A.A' 7, W..0, 4.4 II-41 ....--r."4--r , o- a- -, ...0.- ( 3 4--,-7e-

o.' Conditions: 4-5 - PP 5-6 - OP 160 - .17 6.5 - pH 2 Material and Velocity 7 - 336 SS, 5.5 ft/sec 337CuHL, 8ft /sec 338 Ads, 3 ft/sec

a .4a BO BO 120 120 40 400

ps", 0 f338 .137 0 33a FIGURE G -5 Effect of material and velocity.

COMPOSITE PLOT RUN # 309,310

Conditions: - PP 5-6 - OP 5.5 - ft /sec 145 - 'T Material - CS pH - 309,7.0 310, 7.5

7 700 400 100

WMC41111 0 11. 2011 + ala FIGURE G-6 Effect of 01. 248

COPAPOSilE PLOT RUN # 313 do 372

as Condition.: 4-5 - PP 5-6 - OP 5.5 - ft/soc 3 160 - °I 6.5 - p0 Rue 313 SS (6 PP. 5 OP) ZS Rua 372 Ads (5 PP, 6 OP)

1.5 **I /4 0b

mm 0.3 ;111

0 0

-0. 0 22 40 105 T1MC 0/xml 0 ssrltAsrist: + An.51.5.5.5r,SCC FIGURE G 7 Duplicate rune without copolymer.

C01.1PCISITE PLOT RUN # 333,314,135

Conditions: 10 OP 1 A 160 7.5 pH Material and Velocity 6 0.2 333 SS, 5.5 ft/see :4 LL 0.3 2 334 CuHI, 8 ft/see CI 335 Mm, 3 ft/see OA .0" lW '2 0.3 d 4 -1r el a.+ d

0.3 * 1 el

2 0.2

a., I 0 SO.1.

0.1

-0.2 I- TI 120 140 130 0 20 40 BO 00 100

T11.f.:14+:1.1r:1 f 335 O IP 333 334 FLGLJF)E C 0 Effect of velocity and material. 249

COMPOSITE PLOT RtJNL33.7 4 5511 333 45

Condition.; 4-5 6 - OP as 3 - ft/sec 10 -AS/HP4 160 - Material - Ado Run 353 - 7.3p8(6PP,10 OP) Run 356 - 8.5pa(5PP,6 OP) Run 365 - 6.5p6(24PT,80 OP)

1.3

0.5

22 47 67 ro 107 122 142 71.4C (ffxrt) thirr3r/747.3 mor.sr/5.3.3 S ieirri3172.2.3 rIG4RE G-9 Effect of

COMPOSITE PLOT 1013 RUN #346-357 14 Condition,: 4-3 - PP (9 PP, 10 Fr) 26.-.6122256mmac131336' IS 5-6 - OP 10 - AAMPA 12 130 - 8.5 - p11 11 Run 348 SS 5.5 ft/... Run 349 Curti - 8 ft/sec 10 Run 330 Ada - 3 ft /nec f."4"rerewdra..**.'"...fra**'6**4°4°.

S 2

10,7 200 ZOO 402

7111[ R) o rvasr/3 4. CuSlartS 0 Arn3173 P.M FIGURE G-10 Effect of velocity

COMPOSITE PLOT RUN # 351 -353

1.11

1.5 4-5 - PP 1.4 Conditions: (' PT,100P) 4-5 - 011, 1.1 10 - A5/87A 130 °T 8.3 - pa Lou 351 53 - 5.3 ft /new Run 332 Curti - 8 ft/stn Run 333 Ado 3 ft/.en

SOO 400 107 200

7714E!i-rx.r.) 6 A*Tzrfz. 0 .7.7413T/7. caiisr/s riGurq: C-11 Effect of velocity. 250

GO ISPOSITE PLOT RUN # 316,317

Conditions: 4-5 - PP 5-6 - OP 10 - AA/HPA 3 07 130 - 7.5 - pH

1 0- .6

; as I ii; 0- .4

0.2

Material and Velocity - 316 Adm, 3 ft/sec 317 CuNI,8 ft/sec

I I I I 11111 71 44 55 is 100 120 144 144 144.4040omp j. 3111 .4 14 217 FIGURE G 12 Effect of velocity and material.

COMPOSITE PLOT RUN # 364-356

v. 4

SS .

A tooditioneo 6-5 - PP (3 PP. 6 OP) 3 3-6 - OP 10 AA/EPA 160 Z3 . 7.5 pa Rue 356 SS 5.3 ft/mec Rum 355 CuMi - 4 ft/sec 2 Rum 356 Ade - 3 ftfeec

LS . a

0.4

o , O O eo ao 100 120 140 'MC (1104.10 =4...viz *C4NiSr/S Adev4311 F CURE G -13 Effectof velocity. 251

COMPOSITE PLOT RUN # 314,315

4.3 Connitiona: 4-5 - PP 5-6 - OP 10 - AA/HPA 160 - 'T 7.5 - pH Material and Velocity 314 Adm, 3 ft/sec 315 CuNi, 8 ft/sec

0.3

70 Y SO BO 100 170 140 100

7114411011133 0 f 3,4 * f 315 EttnOt of velocity and material. F I GunE G- 11+

COMPOSITE PLOT RUN # 357::59

4-5 - R 13 4 Cognitions' rr or% 5-6 OP + 7 10 - AA/IPA. 130 - °7 8.3 pa 6 Sun 357 SS - 5.5 it/sec 195Pgr 3 Run 358 Celli . 8 ft /nee a Sun 359 Ade - 3 It /see a1 1!"

U 3

O 42 so 110 150 100 140 150 320 WC 0471JT3 a SAWS 4. cANArts 4AneSP/3 'fleet of velocity. pp. polyacrylace. FIGURE 0-15' 252

COMPOSITE PLOT RUN j .36.3-365

Cooditioes: 6-5 (24 PP, 40 Of) 5-6 - Of 10 - AA/RPA 160 - 6.5 - pH Rua 363 SS - 5.5 ft/see Run 364 CuNi - a ft/see Run 365 Ado - 3 fc/see

77."t

2D eo aD 100

nmci,efout) o sss.ar/s 4 o.,eiarfs a Men5r/-7. FicuRe Gto Zffeet of velocity.

COMPOSITE PLOT RUN it 320,371

Conditions: 4-5 - PP 5-6 - OP 10 - AA/HPA 5.5 - ft/sec 7.3 - pH

2 Material andTemperature 320 Ada, 160'1, 321 Cumi, 145*F

0.1

I O 31 40 ev aO t00 *31 1402 IOO AWNCOMM f. 320 +/321 FIGURE G-17 Effect of temperatureand material. 253

COMPOSITE PLOT MUSS # 354 4 338

1/2"1"aaeaszaa.a.a

Conditions; 4-5 - PP 5-6 - OP 10 - kAiHPA 3 - ft/sac 2 8.5 - pi Material - Ado Run 356 - 160'T (5 PP,6 OP) Run 359 130°? (5 PP, 4 OP)

O 43 80 120 160 200 240 243 320 MAC(NOtR) amn,2r/.-2,5.5,1scr + Azn3rtsisJ2n7 F110.1RE G-113 Effect of surface temperature.

COMPOSTTE PLOT

MUMS 1 8,65 4 361 14 Cooditiooas 4-5 . PP 2.2 5-6 - OP 3 - ft/sec 2 10 - AA/EPA 7.3 OB 1.11 Material - Adm Ruo 333 160°P (6 P7,10 OP) LIS Rum 362 .4 130°7 (6 PP, 14 OP)

1.4

1.1

0.4 a 0.6

0.4 3 0.1

0 00 100 110 140 Timc frau!) 0 adro3fits..7.3,16Cf .1. Ammar/7475,ur FIGURE G-10 Ilffect of aortae. temperature.. 254

COMPOSITE PLOT RUN # 33q,340,341

14 Conditions: 4-5 - PP 5-6 - OP 13 10 - AA/MA 3 13 160 - 7.5 - pH 11 'U7 to

se a 7 A'

1G 6 r4' o- g a a' e- Material and Velocity a e. 4 r' cr - 339 SS, 5.5 ft/sec ArD4-- 340 Curti,8 ft/sec E 3 4.- }s° 4 .er ..p. 341 Mm, 3 ft/sec 3 IJ...... *4--

0 0, , , :a 40 00 40 100 120 140 164

14,8414.2UPS) 331 e 344 o p 341

F ICURE G-ENI Effect of material and velocity.

COMPOSITE PLOT RUN # 366-368

17 16 + 13 14 13 12

Cooditioest 4-3 - PT (11 PP. 14 OP) 5-6 - OP 10 - AA/MA 160 - °7 6.5 - p8 C 4 Rue 366 SS - 5.5 Pt/sec 2 3 Rue 367 Curti - 6 ft/4ec 7 Rum 368 Ade - 3 ft /see

O 22 40 00 PA 100 120 140 160 144

711.4C (1121.11) o waer/s 4aeeeris Mer.5115

r10URE 0-21 Ilffect of velocity. 255

=ZAPCG)TE PLOT

RV G # .U1.11 4371 17 It 13 14

11 Condition's 4 -5 - PP 3-6 - OP 10 3 - ft/sec 10 - AA/MA 6.5 - pH a Material Ads Run 366 - 160°7 (11 PP, 14 OP) Run 371 - 130°7 (7 PP, 11 OP)

1 I 1 I 1 1 1 1 I I I I O 25 42 o aa too 110 140 150

11/4C (M31Ue) + Ci mrar/Scs,1 oar 04n3F/G0.3.140( FIGURE G-22 Effect of 'efface temperature.

COMPOSITE PLOT RUN # 399,400,401

26 8.3 PH 24 130 10 AA/MA 399 - 5.5 ft/sec 22 400 - 8.0 ft/sec 401 - 3.0 ft/sec 20 ( 7 PP .6 OP ) 18

16 rs 12

2 6

O 4 6. 2

2 0 100 200 300 400

TIME (HOUR) O f399 + I 400 /401 FIGURE 0-23 FECT OE VELOCITY 256

COMPOSITE PLOT RUN # 396.397,398

26 8.5 PR 24 160 F 10 AA/MA 396 - 5.5 rt/soc 22 397 - 8.0 ft/.ec 398 - 3.0 ft/.4c 20 ( 5 PP . 4 OP ) W I IS 16

(4! 12

a z a 0 O 4

0 2

TIME (HOUR) 0 396 # 397 o #398 FIGURE G-24 EFFECT OF VELOCITY

COMPOSITE PLOT RUN # 397.400

19 18 8.3 PH 8.0 ft/sec 17 10 AA/MA 2 16 397 - 160 1' (3 PP. 4 OP) 400 130 (7 PP. 6 OP) 15 t 14 F13

( 12

U 10

9 a e 7 O 0 3 3 WO 4 3 2

0 100 200 300 400

TIME (HOUR) O # 397 + # 400 FIGURE 0-25 EFFECT OF SURFACE TEMPERATURE 257

COMPOSITE PLOT RUN # 398,401

7.20

7; 12 rA 10 8 . 5 PH CC 3.0 ft /see 0 10 66/MA 398 - 160 F (3 PP. 4 OP) 401 - 130 F (7 PP. 6 OP) 0

0 100 200 300 400

TIME (HOUR) O # 398 + # 401 FIGURE G-26 EFFECT OF SURFACE TEMPERATURE

COMPOSITE PLOT RUN # 375-377

4 -5.- FP Coaditiones (9 rP, 11 OP) 5-6 OF 2 10 85 /MA 160 °7 7.3 - pa Run 375 SS - 3.5 ft/see Run 376 Cali - 8 tt/eec Run 377 Ad= - 3 ft/see 0

I I 1 1 O X1 67 80 100 120 140 160 180 100 ruc(motic) O =.66ritz + cworts a A*63r/s FIGURE U-27 Effect of velocity. 258

COMPCSTE PLOT MUG f 97 I 360 7

4 - Condition.: 6-5 - PP 5-6 - OP 3 3 - ft / sec 10 - SS/MA 6.5 - pa 2 Ma [41.141 - Ads, S. 377 - 16007( S PP, 11 OP) Rua 380 - 13007 (6 pp,10 op)

1 I 4 0 20 40 W 00 100 120 140 160 160 200

311.40 (FC1t.R) O .4r3111"3.6.3,180r .44m3/17.0.5.1.32' FIGURE G-28 Effect of surface saeperacure.

COMPOSITE PLOT RUN # 402.403,404

3 8.5 PH 160 F 2 10 SS/MA 402 - 5.3 ft/sec 403 - 8.0 ft/aec 404 - 3.0 ft/aec

C 7 PP . S OP )

0 20 40 eo 80 100 120" TIACHOURS) 402 # 403 0 # 404

FIGURE G-29 EFFECT OF VELOCITY 259

COMPOSITE PLOT RUN # 405,406,407 to

8.5 PH 9 - 130 F 10 SS/MA 8 405 - 5.5 ft/sec 406 - 8.0 ft/sec 407 - 3.0 ft/sec 7- ( 5 PP , 3 OP )

-2 1 0 40 ao 120 160 200 240 TMCHOURS) 0 # 405 p 406 # 407 FIGURE 0-50 EFFECT OF VELOCITY

COMPOSITE PLOT RUN # 405,406

8.5 PH 8.0 ft/sec

1 10 AA/MA 403 - 160 F (7 PP. 5 OP) 406 - 130 F (5 PP. 3 OP)

0 40 ao 120 150 200 240 MME(HOURS) 0 0 403 + 0 406 FIGURE G-31 EFFECT OF SURFACE TEMPERATURE 260

COMPOSITE PLOT RUN # 404.407

4 8.5 PH 3.0 ft/sec 3 10 AA/MA 606 - 160 F (7 PP.5 OP) 407 - 130 2 F (3 PP. 3 OP)

2 0 40 80 120 180 200 240 TMO(HOURS)

O 404 4. 41 407 FIGURE G-32 EFFECT OF SURFACE TEMPERATURE

COMPOSITE PLOT RUN # 384--386

Conditions: 4-5 - PP (7 PP, S OP) 5-6 - OP 10 - SA/AA 160 - °7 6.5 - pH two 384 SS - 5.5 ft/see Run 385 Curti - 6 ft/see Ruo 366 Ad. - 3 ft/see 13 t 2

I.0

100 O 27 40 W 100 120 Iva 160 ISO 0104.1t, 0r:-.5..irtZ Cbbsr/s amfrzr/s Effect of velocity. FIGURE 0-30 261

COMPOSITE PLOT RUN # 330-392

44(0 P.13 10

3 .4

Conditioos4 4-5 - PP (9 PP. 9 OP) 5-6 OP 10 - SA/AA 160 - °T Sue 390 SS - 5.5 ft /see O $.5 pa. Rue 391 CuMi - 6 ft/see tun 391 Ann - 3 ft/sec

( 160 102 140 5 O eo 120 1MC 05:kr4 PM o7-.5rts CuNA(7.1 Parr.ST/S FIGURE S-1 /Sect of velocity. COMPOSITE PLOT

RUNS 91.393 5 3411

Conditional 4-5 - PP 5 -6 - OF 3 - ft/eme 10 SA/AA 6.5 - 91 Material - Ada Sun 386 4, 160°7 (7 PT. 9 OP) Sum 30 130°7 (5 11,4 3 OP)

j 1

iiiiiiii i 1 120 140 110 100 200 O 10 100

0109.01) movarAr.5.15co. (41143r/S60,113Or FLOURS5-31 Effect of surface temperance.

COMPOSITE PLOT MUAS# 305 3

5-6 - OT 3 - tt/oes 3 10 - SA/A $.5 - pi Material - Ai Sum 392 - 160°7 (9 T74 9 OP) Eec 303 130°7 (7 FP, $ OP)

120 140 2 00 o to* nom: (tom) 41443f,1.13,1 Arep.57/3(141(1110T FIGURE G-?-6 Effect GI 'affect temperature. 262

COMPOSnE PLOT

letkiS WA 6 393

Conditioast 4-5 - PP 5-6 - OP 3 - ft/see --;,-*. 10 - SA/AA O Iso - °7 Material - Ada Run 386 - 6.5 p8 (7 PP, 9 OP) Rum 392 - 8.5 pH (9 PP, 9 OP)

I I I I 1 i i I I 1 i 1 t I T8 40 80 80 100 120 140 160 160 200 TAIL (KAP) 0 umarisesaiscr + AdmIrts,ao.iscr FIGURE G-37 111448 of oa

COMPOSITE PLOT RUN # 355,391,397.403

12 II

,k1*.

;" 8.5 PH 0.6 8.0 ft/sec

355 61 AA/HPA(5PP. 6OP) 6 391- AA/SA (9PP. 9OP) 397- AA/MA (5PP. 4OP) a 3 403- 5S /MA (7PP. 5 OP) 04 1.2# 7 3 D 2 .6,362113600C'seeiseGa 20.01' AA/ HPA

0 40 ao 120 160 200 240 260 320

TAE(HOUR) CI #355 # 391 o # 397 a p 403 FIGURE G-38 COMPARISON OF COPOLYMERS 263

COMPOSITE PLOT RUN # 356,392,398,404

21 20 PH 1.0ft/sec 19 .40F 156- AA/HPA PP. 6OP) 18 (5 4 :92- AA/SA(9PP.9 17 OP) :38- AA/MA(5PP.4 OP) -24- SS/MA 216 (7PP. 3OP) ,AN N.15 Nils"a*. 14 t erer# T 13 er t_ 12 .0 6- 11 96 U 10 t,4 6 ,2S/ MA 9 .se, 8 - 94 ZZ7 - 6 - Z 5 _ AA4 7 iI 42.:Swea8619ie14esEit9 le-. OD 4 AA/HPA 2 -

0 I I I 1 I 0 40 80 120 160 200 240 280 320

TIME (HOUR) 11 0 3b8 4 # 392 6 0 398 a #404 FIGUREG-39 COMPARISON OF COPOLYMERS

COMPOSITE PLOT RUN # 358,394,400,406

Nikgre4444'.412k6 114 S A r401

4 0 AA/HP A o . lb.., o ammo 4 ,, ralaseas2 321 1741 6 t..' IEIG61 3 #ffl 058GO

ha I.I_0343 4,A4 10 Ma' A 2 O 8.5 PH 4.0 8.0 ft /see . 130 F A 4-441ate 358 - AA/HPA (5 PP. 4 OP) a -.14.4 :If5 394 - AA/SA 1 A .,,, 04 3, (7 PP.8OP) at...00a 400 - AA/MA(7 PP. 6 OP) 406 - 55/116(5 PP. 3 OP) A7: ANSA loft- . A. re--4. 0.44-1-4-4 ++ 0 1- I

0 40 80 120 160 200 240 260 320 TINE(HOUR) U 0 356 + 0 394 O # 400 A 4 406 FIGURE 0-46 COMPARISON OF COPOLYMERS 264

COMPOSITE PLOT RUN # 359,395,401.407

26 8.5PH 24 3.0It/see 130P 359- AA/HPA(5 22 PP. 4OP) 9-0 395- AA/SA (7PP. 8OP) O 3 20 401- AA/MA (7PP. 6OP) 407- SS/MA (5PP. 3OP) N le t 4, T16 4, 94'44 14 .." 11112

10 w5 a aaa AA/HPA 4 *4 efeeireogra.=iiaw*aa°EassialisisseBiseeo O 6 Ayr seltiNer&tera 4 a 0 I- BB 2 : AgtalvaeGeGa 66 0 41E..10 ' AA/SA 2 0 40 80 120 160 200 240 280 320

MME (HOUR) #359 + 1 395 o i 401 A # 407 FIGURE G-4I COMPARISON OF COPOLYMERS

COMPOSITE PLOT RUN # 408,409.410

24 7.3 PH 160 F 22 - 2 Fe 408 - 5.5 ft/mme I 20 409 - 8.0 ft/see 410 - 3.0 ft/soc C IS ( 6 PP .5 OP )

eg 16

70 12

H10 Al ta X 3 0 z 3 0 4 2 n

0 I I I I 0 40 DO 120 160 200 240 nw(louRs) U # 406 .1 409 0 # 410 FIGUREG-42 EFFECT OF VELOCITY 265

COMPOSITE PLOT RUN # 411-413

2 ppmIRON 14 7.5 PH 13 130 F 2 Fe 411 - 5.5 ft/sec 412 - 8.0 ft/sec 413 - 3.0 ft/sec

( 6 PP . S OP )

5 us 4

0 1 40 80 120 160 200 240

TIME(HOUR) 0 SS 5.5F/S CuN1a F/S 33 3 P/8

FIGURE G-43 EFFECT OF VELOCITY

COMPOSITE PLOT RUN #414-416 160 F . 7.5 PH 4 PPM IRON 11 7.5 PH 160 F 10 4 F. 414 - 5.5 ft/sec 9 415 - 8.0 ft/sec J 416 - 3.0 ft/sec ( 6 PP 6 OP ) S

( 5

3 0 M41 2 0

0 W 0 1

TIME (HOUR) S.S.(5.5F/5) CuNI(8.0F/S) 5.5.(3.0/S) FIGURE G-44 EFFECT OF VELOCITY 266

COMOSITE PLOT RUN # 417,418,419

0.8 0.7 0.8 a 0.0 0.4 r,0 0.3

-0.3 -0.4 11; -0.0 -0.0 - 0.7 a -o.e 7.5 pH 130 -0.0 41799 - 5.5ft/440 416CN - e.0 ft /..o O -1 41999 - 3.0 ft /..o -1.1 2.3 PP. 6.6 OP, 3.0 4, - 1.8 O 20 40 ea ea 100 120 140 100 TOIE (HOUR) a RUN 417 RUN 418 oRUN 411

FIGURE G-45 Meet of Velocity.

COMPOSITE PLOT RUN # 415,418

5 4 7.5 pH 2.8 .0 ftleee 415CM - 160r 41tION -130 2.4

1, 2 A A Le 5.6 PP, 6.4 OP, 3.7 51. re 1.8 19-22, 0-13( H-5 n. .5 . gra 14 1.4 0 15( 1.1

OA X 0.0 0 2.2 PP. 9.6 OP. 3.0 re 8 OA 1-t 5 01 111111 TIII 0 Eft 40 80 SO 100 120 140 100 TrIO(HOURO) + 418

FIGURE 0-46 Effectof SurfaceTemp 267

COMPOSITE PLOT RUN # 418,419

4 I3 Et. laa 0 13" 5. 7 a ol \ s v.b'a.ts

M 7 ,.8To a s 4 at Id A 4 U Oti

3 7.5 pH 3.0 ft/sec ; 41638 - 160 F X 61953 - 130 X Ab, 2 3 2 -1 2 2.2 PP, 9.8 OP, 3.0 Fe -6 O 20 40 00 80 100 120 140 100

TIII2(101725) 0 419 + 419

FIGURE G -47 Effect 0( $0110,0 Temperature.

COMPOSITE PLOT RUN # 420,421,422

12 7.5 pH 160 F 62055 - 5.5 ft/moo 421CH - 1.0 ft/aeo 62235 - 3.0 ft/seo 6.3 PP. 1.1 OP. 2.8 Fo

I I I I I 0 40 so 120 100 200 240

7110020UR0) 0 420 + 421 0 422

FIGURE G-412 Effect of Velocity. 266

COMPOSITE PLOT# RUN 422,423,424, 425.420 12 + 7.5 pH 0 II 130 F 3.0 ft /..O 10 611 00 27e2r1r RC 0421 01.. 9 4 aeoa, ri, 1. oales3 - 05430 02 7- 0 y ,,,1 V. $61% I - C'17. A 1 7 1 5- + 1-5 so ii 41' 4 - 41 4pi' er4r)i 3 . ; , f, 71, , V ' l.4' 2 1.6 , 41 0 1)21 3 1 zra-e'ar 1 4,4 & .2,- / h. 1 re' 4 rr 04.444-0e. %.611* 0 0 . 0 6, ' i e--4V- ,.002 J4 '.1X 4'.*44;*)1-4( %6 99.

I 5(

0 , 1 5 40IIIIIII60 120 100 100 140 TIME(HOUR) O R( 422 RUN o RUN 424 A RUN 420 it RUN 420

.'IGURE G-49 Opeporlsoo of Identical Tests.

COMPOSITE PLOT # RUN 422,429

is 7.3 pH 11 3.0 ft /..o 62203 - 160 F 10 42953 - 130F t F. 4 9 1-5 1. °17. Eta% H VI. %. I 4.1 MHO I rilai'taa3 o 2205

!... 7 I° 1 A a(

O f : 4 d N 0( 3 -1 O 21 1 2 2 -1 n 1 i O 2.6 PP. 6.6 OP, 2.6 14 9. 0

SO 120 100 200 140 TIME (HOUR) 0 RUN '422 + RUN 42.0

FIGURE 0-50 Effect of Surfs. Tee,* 269

COMPOSITE PLOT # RUN 420,431,432

7.3 316 160 r /t It'l 43033 - 3.3 ft/see 431021 - CO ft/sea ;I 4 4)233 - 1.0 ft/see ) 10.2 OP. 2.6 re TA iy .,- 1 .,941k. yr'4k.44.4"1 11% r # 1 4 i \ , R 24 L ! ? .'

4 uil .#' t 7i i i , k I

1; r# t '9'4 \ I 7 '1 'a9ta , Xi rseavizi la4\st tPi 4tic.,-4-4/' 0

0 40 O 0 120 100 240 (1001) 0 RUN 432 + RUN 431 0 RUN 430

FIGURE G-31 Lffect et

COMPOSITE PLOT # RUN 431,434

10 7.3 PR .0 ft/see oriN If 43101 - 140 r 43401 - 130 r 910(21 il

,. I Lill ,s 0... ,i.0-

i° .° ell ,. co' yid4'. ...4?.ii. .e.

O 40 120 100 200 240 TOUI (HOUR) nsum 431 + RUN 434

csouRa 13-72 21fect el Sedate Dempermrs. 270

COMPOSITE PLOT # RUN 414,420,430

19 -r 7.3ON 3.3 ft/.ea * 5 0 160 61633 - No Additive ti 42033 -2 -6 11300 42033 - 10 4A/MA 6 e. 4 .. 4 4 7 .7' voiog2. 4+ 44. a,,,,,, Lit' .6-1 5 : 4 0'm 0Q 4 PI 4..* 41 4 14.° 9°+ I-. ..,11 .o r. 0/. 3 -I /. m r* %. , I. jerk....4.1.-0-11 to/ 13 o / e1 a ci3 1 C70

-1 40 00 120 140 TUB (1101113) Il RUN 114 + RUN 420 0 RUN 430

FIGURE 0-53 Meet el Various Additives.

COMPOSITE PLOT # RUN 441,440,439

7.3 pa 160 r 83133 - S.3 ft/se 66004 - S.0 ft/we 64113 - 3.0 Et/se 3.0 F.

1 ISO 100 100 240 T1I11 WOE a RUN441 +NUN 440 0 NUN 4111

FIGURE 0 -54 Iliad of V.14.4167. 271

COMPOSITE PLOT # RUN 439,445,448

7.3 pH 3.5 ft/4664 160 F 511 13

h I

N fivirertigIviva:

1 0 40 I llllllllll144 140 so 840 100 310 TU11 (HOUND) O RUN 433 + RUN 440 pal440

FlGUPI G-55 Compacisea el Identical Testi.

COMPOSITE PLOT # RUN 441,447,450

7.5 6,41 lo 3.0 tt/1661 140 P4.11 :11 i44 V IN - T or %NW "

40 7 I ari144 pta0,ei 4,0 - a. ltfir 44

3- ; 0,111 4 7j Li 1 rigeorela° "

44 N 1113 1M WA 140 VA T1111 (1010) O BUN 441 +1011 441 RUN 440

FIGURE CP.54 el Identical lllll . 272

COMPOSITE PLOT # RUN 01,452,453

7.1 p41 160 45I5S- 5.5Et/see 852CM- 1.0ft/660 45330- 3.0tthese 2.8 PP. 9.6 OP. 6.27 14 *, 13

11 0 10

I.. o ; 7 -

O s

P - 0

I 1111111.11111 a la 40 M 00 100 120 140 100 ISO full (50015) 3 RUN 451 + RUN 452 0 RUN 443

F1GUNO G-37 5ffeec et Velocity.

COMPOSITE PLOT # RUN 453,456,458

1P 10 7.1 pit 3.0 rtimme 17 160 r 1111 SS

10 11.1 PP, 0.6 OP, 4.11 re 14 11-61-8-49-06. 13 131.1"6-9-0'111 4-* Is 4/Es.

, /0 44 8PP.-, 7 0 t It. s ho 2 41.1. s 4 1r Jf iis. a 1

1 Ar"

OS 40 00 SO 105 NO 140 ISO ISO TWO (4OM) 3RUN 453 RUN 430 4 RUN 405

F I GUM! 0-35 Comparlims et losecleal Tests. 273

COMPOSITE PLOT RUN # 459,460,461

kuu451:4:3 2 17774r- 1.9 3.5IT=L,./3.7 1.8 4-5 PP 1.7 'II 1 F. 1.6 1.3 o u. 16 1.4 s ol. u. 1.3 Fir (51' 1.2 P.111 410.'14 1.1 u. 1;0 1 % ry u. 4-5 PP 0.9 S-o vP 0.6 44 JP. 0.7 0.6 ,5 03 I.d ek/sw,..1 1/4.0 I. 1577 0.4 OP. 4-5 PP "' 1°. 5-h op 03 0,11 F6 0.2 0.1 0 I I IIIIIIIIIII O 20 40 60 80 100 120 140 160 160

11ME(1 ours) 0 459 + 460 0 461 F10Ul:K0 -59 EFFECTOf VELOCITY

COMPOSITR PLOT RUN # 462,463,464

14 kun 464143 13 - 3.5 Fl/mieu ltlil 4-5 PP 12 - 5-h OP IF. 73' 11 - lo HEW O io Roo 4..1 chi 9 i.III1

a - 4-5 PP 5-6 of, 7 F. lu 116P

km. 4, 3 o.o to

4 Oho lo 0 4-5 PP 3 0 F. II. 2 III HEW - 0 I I I 0 40 60 120 160 200 240 nmeOlows)

0462 + 463 .5 464 'mune 0 -or Erre= or moan, 2714

COMPOSITE PLOT RUN # 465,466,467

t0 Pun 4o5S:7 9 - l 5.5 tt/see. 170 F 4, 4-5 PI' 1U¢. , 8 6. 5- s 01. 92. 1 )7,7 iv mlply it 7 OV kuo I .70,21.12:1 7.S 00 6 VV. E 4-5 Pr 3-I 1,09 6.1 °V , ita 0E0P 4 ' F0.10 7.5'Ai W 3 170 F 0 4-5 PP Z 2 3 3 1 FE 0 LO 11UP 16 I

-1 -1. 7-1-1 O rrrI 40 80 120 160 200 240 280 320

TIME(hours) 0 463 466 0 467 F /Gupg 3-01 rFTZCZ 07 VELOCITY

COMPOSITE PLOT RUN # 468,469

20 41.11.43 19 5 . 5 FP: 1u I, 18 -5 PP 17 5-11 F. Ilb111.:1,P kom 4.s4 7.5 01 1211/2s, F 4 -5 PP 511 Fe tontun

O 3 833 4 2

0 0 200 300 400

1111E(hours) O468 + 469 FrouPC uncr 07VELOCITY 275

COMPOSITE PLOT RUN # 463,466

ku 46) CU

a.0 I t 7 It., V 4-5 PP 2 5 -e VP I Fr lu IILVP kuu 41..14 F u. /s., 4 8 11 F 4-5 PP 5., UP 4 Fr LIIIKVP in a 3

0 3 2 3

0 O 40 80 120 160 200 240 280 320

TIME(haws) O 463 466 FIGURE 6443 EFFECTorSURFACE TEXPERATURE

COMPOSITE PLOT RUN # 464,467

77s. ).0 It/sec 11.1. F 4.5 PP 5-t. 14. 3 F* to HEDP r7rarRI*. ...111.1 ).0 it/sec 4.5 VP 5-4 UP FE 1U UEDP

O 40 60 120 160 200 240 260 320 MACOteurs) O 464 + 467 FIGUREGr64 EFFECT OF SURFACE TEMPERATURE 276 =MK:SITE PLOT PUN # .311 & 365&368 .77 4 ZI MR LAPre , tier AdmoRwl 17 C000litisuo g4-5 PP I S" 5-4 . OF 13 - 3.0 - frieee + ISO -°F lme311 me 4441.cime (6 Pf, 6 OP) 14- 11 4.3 - pa lee 363 - 10 Ak/RPA (34 OP, 60 PP) ; 13 - Isterial - Ad. lux 361 -4,10AA/MA(11 PP, 14 OP) Im34/P110 34/MA (I FP, 11 11 0P) Imo 344 10 14/AA (777, 5OP) 11 . 10- I. 1 - t 4- 7 i 4 a vs 4 ' : 4 : I :1 E 1 o

1 100 110 140 ISO 160 107 TeX Ovu') 0 44/31 =,1144 4 4411.44 ei/VIPA FIGURE C 62 Sneer of copolymer.

COMPOSITE PLDT RUN 9 314,33E1,341 344.347 Conditions:4:37 PP 5-6- OP 3.0 - ft/eso 3 160 - 7.3 - pH cochlear - 314, AA/111,4 Material - Ade 338, None 341, AA/MA 344, SUM 347,56/6A

3 - 4- 2 3-

20 al 00 80 Sae 120 141 180 murocum 0 if314 t * A t 344 X t 347 FIGURE G-66 StIect oecopolymer.

COMPOSITE PLOT RUN 313,337,340 744.7M Comditlomes4-5 - PP 5-4 OP 1.0 ft/see 160 'V 7.3 - pa Muer/41 - Cedl

Copolymer - 315, AA/RVA 337, None 340, 44/./i4 343, 13 /MA 348,SA/AA

FIGURE 0-67 Effect of copolymer. 277

COMPOSME PLOT RUN# 356 & 392 1.31,11a160r 3

4.3

2.3

3 C666141646) 4-5 FP t 23 5-6- or 3 ft/464

Zu 160 -°7 2 . 8.5 - 0 Macerial - 46. 1.3 Ima 356 - 10 44/11PA (5 PP, 6 OP) Rua I119 - 10 34/4A (9 PP, 9 OP)

0.3

0 1 1 I 1 1 0 23 oo so so 'Co 120 140 MC (11311e) C /ans.4f/C.KAPA osmulf,Atas FIGURE 0-68 Mesa at 0684170.r.

COMPOSITE PLOT RUN # 337,409,415

16 7.3pH 15 8.0ft/s00 14 160

11. 13

D 0 12 C 11 10

011. * 14 a os 7 b., OP 601 837

.c a

-4 )3 2 615-5. PP. 6.4 OP. 3.7 Fe

30 120 160 200 240 71LE( hours ) 0337 +409 0 415

TOURS 0-67 Effect of tree5.4Psosesce of neophaco 278

COMPOSITE PLOT RUN # 336(SS),408(SS)

414(55),454(ss).457(ss) 19 10 - 7.3 pH 5.8 ft/sea 17 1n0 F e 16 - e o .+ 13-, 4 .. 14 - o 13 44 12 I. I 11 e - 4. .., 10 - 4xxXx. ^X,. 0.3.9I° 9 - .1' .0)VC 4'5:4596.. AA'I"'t 444164 A .44A- A.44-1A 7 .0460,0 -.. ..1:I. " 6I.Et.cr, 7 oft 6 deitsidel la,h. o di P16 F3' I a. 5 - a X 334 .3 4.aa ..xr i 4 --l ' + + ++ e- 3.7 Val 3 X 41% - 5.8 PP. 6.4 OP, ''..f V 2 - X -t4' 'A X . 3PP,6.OP. 3.5 Pe 1 tr

O 40 80 ; 120 160 200 240

TIME(heurs) II 326(55) + 414(55) 0408(55) D 45,(55) X 437(55) FIGURE6-71Meet of Iron La Prosaism of Phosphate Corrosion Inhibitor.

COMPOSITE PLOT RUN # 338(SS),410(SS) 416(55).456(35).458(55) 24 7.3 pH t 22 3.0 ft/en 160 l 4 . 20 + t + . *4t C + la V' r 4 3 No + + .1. 1.- 16 dl. * + O 14 - OP 4141.0::: 41:4,.0. G 1 4,4 S' . 4,..:4. 12 AN aA ... 40+ 6. 110 WP.* t. -4 ,t,:4- ...is& A a °:.th:r4r0P.1/4.**394:E. +. .514. .,e,gol°-h, pP.' 4 . .41.1.4 4,4,....' 41. 455 8 4, 4. A.,, Ai 4 4 ..0.1, ...}11°-;:ala2rak13311 a C di6aWailki:"4 O X z 4 Ale X . 3

32le a

2 O 40 ao 120 160 200 240

711.1E(hours) n 338(55) 410(55) . 4 416(51) 456(55) 458(55)

13-71 Meet of tree La Province of Phosphate Inhibitor. 279

CO IA PO S11E PLOT RUN dr 317723

Condit/ow 4-5 PP 5-4 - OP 10 - AA /83A 5.0 - fehoec Matarlal CuNi plI and ****** Curs 317,7.3.130'3 323,5.1.140'F

-1.I Is of in 138 1411 IY 1111 8.:(87113 a 313 F181-01 G-72 tlfeet .( came rrrrrr and pg.

COMPOSITE PLOT RUN # 418,460

0.8 Run f73-741--- 9.0 Itisoc 1:30 F 0.7 4-5 PP S-6 OP 3 Fe 2 0.6 Run 41.11114 7.5 141 u. 8.0 rt:s., t 130 F 0.5 4-5 PP S-4 oP 1 Fe id 0.4 0

60.3 0 z 0.2 7

0.1

0 PI 1 1 1 1 1 1 1 0 20 40 60 BO 100 120 140 160 180

4.71ME4(heoeurs) n 418 FIGURE 0-73 COMPARISON OF IDEUTICAL RUNS 280

COMPOSITE PLOT RUN # 464,469

TO Run 4fte5:: 19 tL/men 160F 16 4-s PI. 17 5-e .)1:. 3 I 3 Fe co G 10 HEM-

9 a 7 6 5 4 a 2

0 0 100 200 300 400 1114(hours) O 464 + 469 FIGURE 0-7 COMPARISON OF IDENTICAL RUNS

COMOSITE PLOT RUN # 419,461

2 Run 4L9SC 1.8 3.0 ft/sou 130 1.6 -5 PP 5-6 OP 02' 1.4 3 3 Fe 10' 1.2 T7rar-Run 61LIU 1 3.0 ft/440. 130 F . 0.8 4-5 PP 5-4 OP 0.6 3 FE 0.4 15 2.3 PP. LP OP. 3.0 Fe

11a 0.2 0 5 (71 -0.2 RI 0.4 0 3Z 0.6 8 -1 1.2 -- 20 40 60 80 loo 120 140 160 180 lUghows) O 461 419 FIGURE 0-75COMPARISON OFIDENTICALRUNS COMPOSITE PLOT RUN # 462,468

14 Run 46233 773-7 13 5.5 FL/sec 160 F 4-5 PP 12 5-6 op 3 Fe 11 10 HFDP Run 4651:1:2 10 1.5 5.5 Ft/se. 9 160 F 4-5 PP 8 5-6 OP 3 Fe 10 HEDP 7

0 100 200 300

TIL4E(hours) CI 462 + 468 FIGURE G-76COMPARISON OF IDENTICAL RUNS 282 APPENDIX H

DEPOSIT COMPOSITION 263

TABLE: H-1 CHEMICAL ANALYSIS OF DEPOSIT COMPOSITIONS (values ratioed to P)

RUN # P Ca Si Mg Na/Zn Zn Fe Al S Cl K Na Cu

338 1 1.01 .169 .120 .063 .030 .244 .100 .115.080.074

341 1 1.14 .106 .121 .036 .026 .061 .073

348 1 1.08 .126 .143 .059 .024 .079 .076

349 1 1.08 .124 .123 .071 .029 .076 .081.062

350 1 1.03 .138.148 .069 .026 .089 .092.067

351 1 1.08 .182 .122 .087 .047 .042 .104 .069 352 1 1.20 .146 .102 .070 .063 .047 .079 .079 .079 353 1 1.11 .227 .128 .090 .046 .051 .118 .087.087 .066 354 1 1.18 .127 .134 .045 .025 .074

355 1 1.11 .120 .133 .062 .026 .081

356 1 1.13 .137 .145 .045 .021 .085 .085.075 .065 357 1 .98 .175 .134 .050 .020 .034 .110 .069 .080 358 1 1.03 .164 .150 .054 .023 .034 .104 .067 359 1 1.11 .204 .135 .053 .023 .042 .129 .078 .054 366 1 .29 .203 .074 .061 .026 .191 .478 .075 367 1 .32 .164 .069 .061 .037 .210 .448 .079 368 1 .30 .230 .081 .058 .035 .218 .489 .075 .045 375 1 .46 .313.100 .069 .033 .309 .356 .127.093.094 .057 376 1 .44 .242 .094 .075 .035 .279 .327 .115.088.082 .041 377 1 .45 .299 .102 .086 .030 .206 .383 .111.087.088 .080 .0306 390 1 .99 .163 .152 .047 .047 .106 .100.081 .102 .0307 391 1 .93 .159 .150 .055 .042 .113 .103.089 .0453 392 1 .95 .185 .182 .056 .061 .123 .121.097 .102

396 1 1.39 .386 .292 .032 .046 .134 .139.102 .081

397 1 1.60 .379 .270 .034 .125 .147.092 .069 .104 .0320 398 1 1.35 .390 .262 .048 .055 .139 .139.099 .041 399 1 1.13 .127 .146 .081 .077.069

400 1 .97 .134 .158 .086 .074.063 .043 .051 401 1 1.11 .154 .153 .104 .094.076

402 1 1.22 .215 .182 .050 .142 .175.101 .084 .050 403 1 1.15 .172 .171 .043 .108 .143

404 1 1.55 .347 .220 .061 .149 .197.098

405 1 1.05 .171 .143 .114 .132.077

406 1 1.13 .146 .126 .090 .125.073 .050 407 1 1.02 .210 .150 .036 .130 .134.072

408 1 1.66 .079 .046 .091 .173

409 1 1.44 .091 .041 .089 .101 .157

410 1 1.66 .155.086 .047 .106 .178

411 1 1.08 .192.104 .053 .206 .100

412 1 .91 .186.130 .047 .231 .111 .113

413 1 .95 .174 .122 .045 .188 .099 .315 418 1 .63 .348 .077 .476 .228 .227

420 1 .86 .211 .121 .052 .337 .128 .128 421 1 .74 .222 .103 .049 .470 .127 .111

422 1 1.11 .223 .116 .078 .490 .104 .114 2814

TABLE: H-1 CONTINUED CHEMICAL ANALYSIS OF DEPOSIT COMPOSITIONS (values ratioed to P)

RUN 1 P Ca Si Mg Na/Zn Zn Fe Al S Cl K Na Cu

423 1 1.08 .265 .128 .059 .367 .132 .113 .106

424 1 1.07 .234 .116 .063 .366 .118 .108

428 1 .56 .290 .129 .072 .447 .189 .160 .383

433 1 .91 .314 .169 .0681.005 .199 .282 .220.162

434 1 .82 .252 .135 .062 .678 .179 .369 .228.139 .206

435 1 .82 .266 .173 .053 .566 .171 .286 .161 .095

*440C 1 .58 1.294 .1831.591 .527 .402 .325.318 .638

441 1 1.72 1.461 .329 .3651.604 .502 .642 .401.366 .418

446 1 .91 5.129 .639 .7791.8411.456 .870 .930

*446C 1 .63 2.228 .2371.969 .693 .625 .469 1.195

*447 1 1.53 3.507 .608 .5843.9871.0131.432 .861.859 .689 .389

451 1 1.21 .197 .144 .049 .142 .122 .137 .089

452 1 1.32 .210 .124 .052 .205 .117 .154 .091 .079

452C 1 .67 .352 .123 .073 .636 .186 .147 .129 .169

453 1 1.45 .226 .108 .060 .238 .124 .168 .075

454 1 .93 .199 .132 .104 .213 .116 .120 .034

455 1 .91 .215 .138 .099 .243 .123 .128 .059

455C 1 .60 .313 .127 .075 .529 .190 .151 .137 .215

456 1 .89 .202.142 .085 .200 .120 .095 .134

457 1 .97 .201 .146 .104 .278

458 1 .86 .219 .132 .095 .293 .131 .123

462 1 .73 .192 .121 .055 .323 .123

462 1 .61 .228 .128 .037 .360 .143 .132

463 1 .70 .205 .113 .057 .392

463C 1 .67 .218 .119 .039 .401 .137 .117

464 1 .76 .211 .129 .062 .349

464C 1 .70 .231 .112 .043 .532 .138

465 1 .58 .193 .095 .048 .675 .121

465C 1 .54 .200 .107 .038 .555 .127 .112

466 1 .51 .210 .107 .036 .542 .128

466C 1 .51 .212 .101 .541 .131

467 1 .56 .204 .102 .042 .607

467C 1 .59 .207 .102 .043 .653 .131

468 1 1.07 .216 .104 .040 .445 .130 .139 .108

469 1 1.19 .192 .098 .038 .463 .126 .164

C: non-heated area of heater rod surface.

*440C: Mn = 0.254 *446C: Mn = 0.375 *447 : Cr = 0.948 285 APPENDIX I

NONLINEAR REGRESSION 286 The nonlinear regressionprocedure obtains least squares estimates of the parameters in a nonlinear regression model. Since analytical solution is not available in this case, the procedure uses a search algorithm in an attempt to determine the estimates which minimyze the residual sum of squares.

The following nonlinear relation was used to fit the experimental data.

R.r(e) = R*f C1 exp(-(9 Oci) / e,] (5-35)

In fitting the runs data er, was treated as variable to be found along with R*f and ee,.. However, when the result of the regression produced a negative fouling resistance value, 61, was fixed at a value that gives the best coefficient of determination. In this appendix plot of the result of the regression is shown for runs302 through 469 in sequence. Examina- tion of these plots should be done with conjunction of

Table VI-1.

The algorithm used for the nonlinear regression was developed by Marquardt (1963), and is a compromise between using a straight linearizationmethod and the method of steepest descent. I" 1 300 . 300 2E7 3 I I. 250 250 Isirlir . 200 200 305 T- I 1 (HOUR) 307 3113 #RUN I 150 MIN 150 HOUR) RUN tted t It 100 TI #RUN 100 TIMI( 11.'Actual ftI 50 . . mow 1 I 50 10 4 10 i 0 12 10 J' ( A 82 : h 6 7 4 2 0 A 04 t A 2 8 7 6 B 4 2 0 A 04 0 250 220 190 302 364 306 160 HOUR) RUN 3641114 #RUN MK REM 130 TI 3 r a 30 4 t 2 3 2 )I 1 0 04 70100 it'll liver" _R 9

A it I 1111 t 11111 J04.1 A. al it I ,, iiiiiilli 111111111111W. A. 4,40,4 TTT1T11 T1 TTTIF rp-T rrrilTTTnZ t a

t ittt 1;1 nt:i=t Ai ....44S..,4044 A. ....~.^44,044 corn 1rV 1111111 1 1111111v I .... M. NOV.--1,404 1_11,c, e e . .-400,00 4040 T vl 1 1111 -r 11-1-1T-1-1 1 11111111111_ 24 '" I I I IIIIIII FI r a1.! . 23 em 1 1 1 -.41041.1 1 1 I I J1111111 1 ..tv A. om,...4.00(4 i 1111 1 11110 I I I 1 I IL 1 1 1 1 2 i I 1 1 9 8 99 9 R p a R as. ,08-40040 1 1 1 1 1 1 1 1 1 1 1 1 1 d ... ..4M 0. w...... s*4,40<0 4 4 j 0 1-T-11 T-T1 r oil 1 I 1 I I 1 1 f 1 1 1 1 99 gI 9* a 111 1 11111111111 1 111 4. . I 7" 0 40(10, AIL ...... -.4,404 ITTTTITTI -FT TT I TTI-t-TTI-r-ri rrn 9 aR Ir a a 111111111! 111111111I 111111111 0a e d d -lerO<41 a fe .16 ...4... 4,10 a9 99 a R a2 a 1 111 111 11 111111111 111 1 111 e 0 1111 1 13_11 I 1111 11111.111.11 0 0 0 .. 1"400,4 4 o 4 a- 400,.1 4 a I AS. 0 0 AM4. .16 S,S11.2 -.44o(*. a a

-III IIIIII WI 1111tI 111111111 MIL AS. 0.....0.1.7.AA040 a .46 111111111111111 8H 6 A I A 4 ft M 40.0.0 1 3 m. 'III 1111 1111 O ° _

A a

1 1 1 1 f 1 1 1 1 1 1 1 ft ...... M.*. M aft. ...Af t. Was 4,04 /. 1111 4 I ft ft ...,aftm-ICK s . >0 t 4- w.is ...---ve vo wr wa s .....-. O ..aups 4.>014*--qe us vs uP I I 1.0.. I I P 1 1 1 8 ...... ti . A 6 *5'OP* vs 10,0.4^ O 0 Y 41, 01.11-c1 . ....v.-. 1 1 1 1 1 1 1 1 1 8 . 1 1 1 1 1 1 1 1 1 1 1 1 1 V 66 11111111111111 1 1 1 1111111 1 111 296

MIin

0 a) In iS 110 71111040,1

r I

0 40 10 133 140 0 40 TIP1114wel

RUN B 372 RUN N 373 ( 1.6 (2.5 I a t t - Pitted A A 2 2 2 1.2 ual . h h r 5 0.8 B

)0.4 * 0.5 0 0 A A I II I 1 1 I 1_IIIII I I 4 0 4 0 20 40 60 80 100 20 40 60 80 100 TIME( Hour) TIME( Hour) 297

RUM it 374 BUN 0 375 8

0 4 0 100 0 20 40 60 80 40 80 120 160 200 TIM Hour) TIM Hour)

RIM I 376 RUN # 377

40 80 120 160 200 40 80 TIM! (Hour) 120 160 200 TIM Hour)

BUN # 383 RIM I 38? ( 4 0.8 . . . t t A A - Ti tted . 2 2 3 0.6 S Actual

/2 B 0.4

) 0.2

A A 4 0 4 0 0 40 80 120 160 200 O 30 60 90 120 150 TIM How) TIM Hour) 298

MN I 388 BUM! I 389 ( (0.8 0.8 ! ' ' ! t - t A - Fitted A 2 2 0.6 2 actual 0.6 11.

0.4 0.4 B t ) 0.2 )0.2 -it - * 1 0 0 A A 0 I t . 1- I. 4 sail 4 0 0 30 60 93 120 153 0 30 60 90 120 150 TIM Hour) TIM Hour)

BUN 390 RUN II 391 i (0.8 ! ! 111-, r 7 -' ! i 4 t ' ...... w Tittod ... A 4 1 ' 'As a: 2 O. 8 . : peon/ 0.6 - h h - .,,,,,,.#.#- r 0.6 - 7 I / - s. . / 0.4 B 0.4 . t . . . I . ) 0.2 *1 , 0.2 -- . 1 0 0 A A 4 0 4 0 11 15 19 23 27 31 35 0 5 10 15 20 25 30 TIMIttiour) TIM14our)

RUN II 392 RUN 11 396 (13 (1.5 . 7 !111!111 I . 1 I 1- '' . ! " '! "! " t .."" fitted - il Fitted A -. 2 1.2 -yr paioal .. im.i<8 2 12 '2' Acta/

h . , . h 0.9 - 9 aw 7 . - I . . -4 // . . B 0. 6 , ../ 6 Agir t 2 - U u - it - ) -1 * 0.3 *.* , - *: 3- . . . "ii - X o _dr . . A - - A . 1 ....1 ....i.,,. Agi 11 4 0 40 1111,11 Al 12111 1 11 0 10 20 30 40 0 40 90 120 160 200240 TIM Hour) TIM HOUR) 299

RUN II 397 RUN R 398 (16 12 T -' I'1'''! '''''I'' t t A ,4,4i 2 4 ''g :Actual 12 h 8 - . : 6- J /7 8 . B tir - t u4- . u ) . ) 4 i2 0 414 A : -, A 40 ar.i...1.1...1.1i..- 4o 0 40 80 120 160 200 240 0 40 80 120 160 200 240

71M1( HOUR) TIME( HOUR)

RUN t 399 RUN 0 400 (15 c 9 it t A "" Fitted A 2 2 12 e- r Aotaal 6

awl 9 14 6 11 )2 3 0 0 A A 40 4 0 0 100 200 300 400 0 100 200 400 TIP M Hour) TIP ( How)

RUN II 401 RUN 11 402 c 25 (10 t t A A 2 33 28

13 6

B /0 4

*5 2 0 6 A A 40 40 0 100 200 300 400 0 20 40 60 80 100 120 TIM( Hour) TIM( Hour) 3 0 C

RUN 1 403 RUN II404. (6 (10 t t A A5 2 2 8 h 4 6 7 3 B 4 u 2 2 1 i 1 0 0 A A 4 0 40 120 40 60 80 0 20 40 60 80 100 0 20 100 120 TIM Hour) TIM Hour)

RUN 1 405 RUN 1 406 (12 t 7 tted . A10 2 2 Actual h 8 . .

1. 10. 6 B 4

A ".V.;11.11Ita 1111,till."' 4 0 240 80 0 40 90 120 160 200 120 160 200 240 TIMM Hour) TD 1Y Hour)

RUH 0 407 RUN 408 (20 (12 7 7 1 a t t - lined A A10 0000077 o 2 2 -Actual . 2 16 h h 8 o - . . 4 r - . 12 7 - IF /6 -. / Bt t u4 . u ) .. ) * ' *4 2 1 4/3 : 0 A 4 0 0 40 80 120 160 200 240 40 80 120 160 200 240 TIM( Hour) TI MIK Hour) 301

RUN # 410 RUN 4 409 ( 24 ( 16 t t A20 A 212 2 16

T 8 / 12 B 8

) 4 4 0 0 A A 4 0 4 0 0 50 100 150 200 253 0 40 83 120 160 200 240 TIPS( Hour) TIteHour)

RUN #411 RUN 6 4i2 16

A 2 12 h r

Ir 8 B t *4 0 A 40 40 80 120 160 203 240 0 40 80 120 160 200 240 TIM( Hour) TI MR Hour)

RUN II 413 RUN # 414 (12 T t Ti tted A10 7 2

/ 6 B 4

I 2 0 A 4 0 0 40 80 120 160 200 240 20 40 60 93 100 120 TIME Hour) TIPS( Hour) 302

RUN 6 415 RUN 416 12 I t t A 1.5 A 10 2 2 h 1.2 8

0.9 6 B B 4 u 0.6 : . i 0.3 1 2 0 0 A A 4 0 II 11111 111.1111111111111" 40 0 20 40 60 80 100 0 20 40 60 80 100 120 120 TIME( Hour) TIME( Hour)

RUN 4/7 RUN II 418 0.8 ..I . .i..I.. 1 , . !. 1 o3 t .2 2 2 A - : It tted . "., 2 .41 Actual .... 2 0.4 0.6 I _.,...A.,...--- _... r- ...... h. - 3 r O. 3 70.4 . 7 / . : . / . 2 0 2 if . t 0 re . '4 ti ) O.2 . ) * 0.1 0 0 A A 4 0 I.r..),. 4 0 0 30 60 90 120 150 180 0 30 60 90 120130 180 'filet HOUR) TIM NOM

BUN B 420 RUN II 421 (1.6 t A 2 1.2

/I00.8 B t ) 0.4

0 A 4 0 40 90 120 160 200 240 0 40 80 120 160 200 240 TIM HOUR) TIME HOUR) a)E

Nna#

oz Ot 09 06 OOT CET 0 Ok ce CET 09T OX OIE WION MilliMOH

1#111#Set )t NI )e'T ft*littlitIlitit/tifit 1 P111411 T ro J 11 z 9'O n ;1'0 T 2'0

0 0 T; 6T Ez Ts ;E 6E 0 OT OE OE OP cc 09 LI)34(MOH LiairanoN

9 6 ET ST 0 oe OF 09 OOT

061014 MILLatriOli 304

RIM 6 431 RUN I 432 (1.6 ( 4 t t A A 2 2 1.2 3 h

0.8 2 3 t 0.4 * 0 0 A A 4 0 40 0 4 8 t2 16 20 ?A 0 4 8 12 16 20 24 TI MM HOUR) TIMICHOUR)

RUN II 433 BUN II 434 (5 t A 2 4 rh 3 to

A 4 0 0 20 40 60 80 100120 33 60 90 120 150 180 TIMM HOUR) TIMUHOUR)

RUN 8 438 RUN I 440 (0.6 (0.6 t t S 0.5 rittail A 0.5 .Autual 2 h 0.4 h 0.4 / 0.3 / 0.3 B B u 0.2 u 0.2 s 0.1 0.1 A A 4 0 4 0 0 10 20 30 40 50 60 0 100 200 300 400 TIMMMI(HOUR) TI MI( HOUR) 03E I. 1 09T 006 1I 1, 0ES OE 09Z 11. I I 006 tit T (MOH Sit (MOH Lit 1. # 1 MOH 8WTI MILL OR )>l NM I 00Z 08 8ma 4LL 111 I SILL OBT I TAPall 0714.3t3 ... OOT OP OPT 1I.II . I I1 9'0 '0; Z'0 0T'T 0 0 0 a Z T V 0 OOT )8 a 9 t 1 n ( 0 0 !.; t 00E t OSZ I 89T I11 I OOP IV 006 OR (an NT (MOH VI Itt 00Z oa )SILL 9tt it 111 -00e MOH INMI 09T SILL $OT # LL OZT EL I ponli Tenpu II 00; I III t Ili" a Z vQ 0 09

tins#811 NMI611

EI E9 E8 COT

LL)51(18108

N111# )9T

/ 8 ... . 1 . n - 1 . ( I - 4 . . Ai V 10Vi 3 V I ow.V I V I I 0 OE OP 09 06 0 OOT ooz ooe OOP )SILLMOH v.csnoilmi

tins11s Nna#

OT OE OE OP OG 09 or Qv os AMU(MOH) LL)1WWEN 150 180 200 150 133 166 120 455 90 HOUR) 457 439 ME 132 HOUR) 11 90 HOUR) RUN* 3060 TI RUN* 98 1711( RUN 60 T1Mt( 0 3064 030 ( t A 2 6 4 )2 0 A 04 12 A 10 2 9 6 B 4 2 04 ( 1.5 A 1.22 0.9 0.6 0.3 6 A 04 300 t 300 t 210 250 I 250 t 180 454 200 Mill" 200 t 150 HOW 11456 150 HOUR). 458 150 HOUR) RUMI 100 171,11X RUN flied 100 TIMI( IRUM 120 TIM( 50 .Ti 50 90 10 A a 6 4 2 0 0 12 10 8 6 4 2 :s 0 0 15 12 9 6 3 0 60 ( t 2 t *4 8 A 4 ( t 2 h 7 * 0 A 4 ( t A 2 t 1 0 A 4 RUN 460 RUN 6 461 ( 2 t t A A 2 0.8 1.6 h 0.6 1.2.

B 0.4 0.8

* 0.2 * 0.4 0 0 A A 4 0 4 0 0 30 60 90 120 150 180 0 30 60 90 120 150 190 TIME HOUR) TIPS( HOUR)

RUN 0 462 RUN #463 i ta....1."1".1."1".1"... (9 . F t :... Fi tted t A0 1 ais0a$'4- 2 : I -Actual . 2 .- h 9 h - A. r - . - r / 6 . i / a . . a t . . t u4 . u ) - - )2 . 0 2 . .. A 4 vAir. iiAit ',Ilia tall. tiiii 4 0 0 40 90 120160 300240 0 40 80 120 160 200 240 TIM( HOUR) TIM( HOUR)

RUN It 464 RUN I 463 (15 ( 10_. I I I 111111 a 1 g II . 111. tF A A .i"''''7 itted 2 12 2 9 7 i . Aertaai h - 9 6

6 4 u . ) - 3 2 1 1 - .4 0 0 A A ' 40 40 I"'.A....1....1.,..1....i...." 0 40 80 120 160 200 240 0 50 100 150 200 250 300 TIM MTh TIM HOUR) 3 C

RUN II 466 RUN B 467 1 ( 1 I II I III! 11 I Ili r ill I t A A 26 a

7 1 4 B t t

0 0 A A 4 0 r7I I. I II II. kl.61,..1 I 4 0 50 100 150 200 250 300 50 100 150 200 250 300

TI MK HOUR) TI MU HOUR)

RUM i 468 RUN f 469 24

t A20 2 h 16

5 12 B 8

A 40 100 200 300 400 0 100 200 300 400 TI NIX HOUR) TI Hawn 310

APPENDIX 3

AVERAGE COOLING TOWER WATER QUALITY 1

TABLE J-1 AvERAGE COOLING TONGA PATER QUALITY

@@@

.: Nun s : Total 1 Ca : Mop !Sulfate : Poly : Ortho : Silca :

: :: : Mire. : Nord. 1 Hard. I. as : Phospt Phospt .

Average is CaCOS as CaCO3 :asCaCOS 1 SO4 1 as PO4 1 as PO4 : S:1102 : P M

Std. Dov : pp. : pp. : ppo : pp. I POI : PP@ r poi

. lo2..4 . . : . . . . : :Average I 1567.5 I 1041 : 526.5 1 .1450 4.12 I 5.81 : 33.8 : 7.0 : : : 0.81 . ::Std. DIY. : 54.6 : 20.1: 51.8 1 50 0.72 1.89:

; : . 1:15-7 : . . . . - : . .

:Average : 1552 1051.7: 470.4 : 1460 3.91

: : : : 70:?:2 : :std. DIY. : 69.8 : 75.0: 67.1 : 44.7 0.775 3.5eg

. . . . :: ;08-9 : : . . .

:tdvdr4q. : 1386.6 : 962 : 424.4 I 1273.3 : 5.96 1 4.75 : 34.5 : 6.96

:Std. ppv. : 145.7 : 124.61 142.8 : 87.3 : 1.764 0.61 1 0.71 : 0.09 :

1 3in ......

::Aytraqo I 1 . 4.57 1 i : : 1439.5 : 927.71 511.8 1500 3.49 37.3 7.51 : 1 ::Std. Dv*. 1 227.8 1 155.0: 111.9 : 44.7 1.56 I 1.29 : 2.34: 0.04 :

. . . . . I : I. . . . :1 311-2 :

''Average 1 : 1 : : 1071.2 .676.2: 394.8 1066.7 : 6.29 6.21 36 : 6.52 :

ltd. Duo. 1 32.9 : 24.1: 14,8 1 57.7 : 2.0 : 0.80 : 1.4 : 0.04 :

.. 317 . . : : . . .

: :Average : 1101.9 1 682.1 : 419.7 : 1025 : 5.8 . 5.22 1 36 : 6.54

::std. Opy. : 45.9 : 23.8: 29.3 : 28.9 : 0.47 : 0.38 : 1 : 0.05 :

;

. . 314-5 . . . : : : ::Aytrage 1085.1 : 413:9 1042.5 1 : 671.2: 6.49 : 5.01 : 31 : 7.50 :

::Std. Div. . 54.0 : 22.1: 49.1 : 105.3 : 1.41 : 0.66 : 2.; : --

: : :: : : : : : :

. . 3t6-7 : ......

: IP44.6 I :Average 645.9: 398.7 : 966.7 : 5.99 : 5.3 : 29.5 : 7.50 14.4 1 10.8: 9.9 1 28.9 1 :std. Oev. 0.84 : 1.30 : 0.70:

: :

! 320-1 . . . : . : .

. ::Ayprape : 1043.8 : 650 : 393.8 1 950 . 6.24 : 3.43 : 34.3 1 7.47

:Std. 04Y. : 15.3 : 13.1 1 9.? : 24.5 1 0.50 : 0.30 : 4.041 0.08 :

: 1

. . : :: 322 -3 . . . . .

::Aytrage . ! 998.6 1 619.6! 378.9 : 880 4.10 4.58 : 35.7 : 8.09 ::Std. DIY. : ' . ' 22.3 18.7 10 1.21 2115.4 °al 14.52 13422s. _lam

TABLE J -1 CONTINUED AwETASE COOLING TOWER MATER OUALITT

: : : Poly : Oetho : StlIca It u n : Total 1 Ca : No Sulfate

: : ' H Hard. : Hard. : Hied. : at PlictiOt Poosot

. : : as PO/ : ; P :: Average :as CaCOS as CaC:: as CaCO3 : SO4 as PO4 S:I02

Std. 01.. : pps r pp. : ppe 1 PP/ PP/ Pfle : PP/

! . :: 324-6 1 . .

:..897.5 : ---- : 9.45 : 36.5 : 6.45 : 1111v,e191 : 943.8 : 592.5 331.3 : 1.1 2.12 : 0.05 : ::Std. Dey. 27.8 : 15.7 : 16.7 : 33.0

. :: 327-9 ...... : : 4 : : 7.50 ::everage ! 1002.3 1 634.2 367.5 952 9.24 ''' 37.5

1 : : 1.25 : 0.70: 0.1 : ::Std. Dev. 71.3 1 45.3 : 31.1 114.1.

. :1 330-2 . . !

: : :fleetest/. : 1051.4 r 660 )9) 982.5 : ---- : 8.1 : 37 : 8.18

2.2 0.05 : ::Std. 0.v. 25.0 : 19.1 : 20.3 : 53.8 : 1 1.4 :

:: 333-5 . . . . : : - -- : 9.4 36.5 : 6.52 ::Avgragg : 1110.2 : 67m.4 : 435 : 1096.7 : : : 1.0 0.71 0.04 ::Std. Oev. ' 15.5 : 6.77 1 1,1.4 r 95 : ----

. : :: 336-8** ; . .

: ; 36 ; 7.',5 ..4vgrupp : 1031.R.1. 626.3 : 405.6 : 900 4.3 r 4.66 : ... 43.9 : .- : : 0.71 1.41 : Std. Dee. 26.7 : 20.9 : 1.3

....: 1 t - -: ; : .: 319-41 : : . : : : 622.4 : 383.4 : 890 5.76 6.1 ::Average : 1^07.8 : : : 23.4 58.9 0.32 0.34 342:332 70.:1 1:Std. Dee. 11.3 : 13.0 1 1 : :

:: : 1 : 342-4 :

t 830 : :. 6.i : 30.7 :; Average I 10t3.2 : 609.8.I 4034 5.76 7.52 : 1 1:Std. Dee. 1 42.2 : 34.2 : 24.6 1 14.1 : 1.24 0.75 : 4.16 0.04 ::-.... ------:...... : ... : - ..... : : : . :: 345 .7

: : ::Average : t014.6 : 612.6 : 402 1 A68 1. 3,28 : 6.8 32.2 : 7.40 . ::Std. Div. t 37.9 : 41.0 : 20.6 : 39.6 :. .1.42 A 1.4 2.39 : --. TABLE J-1 CONTINUED AVERAGE 020LI&G-TOWER WATER QUALITY

...... 0...m...... m..mgmw.m...... www.mnium...... =m5....m...... 1 I Mg :Sulfatipl Poly I:Rund 1 Total Ca Ortho 181lical I: ------1 Hard. I Hard. 1 Hard. I. as :Phospt Phospt1 as IPH1 II Avrag las CaCO3 is CaCJO:as CaC01 SO4 ias PO4 as PO41 S102 1 ppm ppm 11 Std. Dv I ppm : ppm I 1 I PPre ppm I ppm II: 1-1-----1-----1 1...-----:-:1 ----1 I 1 . 1:348-349-330 1 . I : t 1:Avirrag 11,033.58 1651.92 1399.23 :804.72 1 8.07 10.47 :26.67 18.09 : I : :Std. Nov. : 63.01 I 41.75 I 28.24I 59.27I 9.49 10.27 1.50 10.56 1-----I . I 1------1 1-1 1 . 11351 -3.52 -333 1 1 1 1 I IlAverags 11,146.92 1756.35 1383.65 :336.15 1 5.93 9.9628.50 17.33 I

I 1:Std. 0ey. 1 221.03 :138.06 1 77.32 1213.32 5.83 1.66 3.07 10.02 1 11 I t I 1------t t-----1

1 : :1334-335-336 1 1 t . 1 : 11Avrac 1 894.00 1388.00 1306.00 :732.00 I 4.69 6.2826.40 18.39

: I : :Std. Dv. I 30.89 1 43.89 1 47.05I 34.29 1.40 1.51 0.49 10.42

I 1 I -----1 II 1 1 I . :1357-338-339 I 1 1 . 1 1 . 1 1 4.34 I 11Avarag I 909.53 1528.71 1329.33 :710.91 5.26 27.32 18.60 I:Std. Dv. 1 123.91 1166.30 I51.45 1106.81I 0.54 1 0.51 1.54 10.04 11 1 I I I 1 I I -----I 1 11360-261-362 1 1 : I . I i 1 IlAviorag 1 902.50 1529.83 1255.83 1716.67 1 5.90 t 13.8030.33 17.50 1 : : :Std. Ov. I 68.28 1214.50 t 31.28 1 62.36 : 4.40 1 4.83 1.23 :0.08 I 1 11 1 1 1 I t-----1

1 1 : 1 ::363 -364-363 I 1 1 I 11Avarag 11,303.13 1946.88 13136.25 1870.00 123.78 1 80.3233.17 16.38 : 1 I:Std. Dv. I 57.21 1 67.48 1104.66 : 86.02 121.51 16.99 6.49 10.25

1 1------I ------I--..--:

1:366-367-368 I 1 I 1 1 1. 1 1 1 1Av.prag I 816.50 1464.55 1451.95 1514.50 110.60 13.95 126.67 16.47 l 1 11Std. 0v. I 431.59 1188.71 :194.70 1202.95 1 6.90 4.52 I 3.31 10.06 1...-----1-----1 11 It...------1 1 I I I I . :1369-370-371 1 I I . 1Averavo 912.50 1472.92 1456.25 1314.84 1 6.50 i 10.29 128.50 :6.52 1

I 1:Std. Nov. 1 167.57 1 28.08 1145.20 1 33.47 1 5.48 1 4.17 1 3.50 10.20 ------1 1 1 1 1 1

I I . :1372-373-374 1 . I I : 11Avarag 912.00 :558.00 1354.00 1601.67 1 5.15 5.56 :29.50 16.46 1 1 1:Std. Dv. I 109.16 1110.39 1 72.62 173.07 1 2.77 2.47 1 4.50 :0.05

1 1--_---1..----: 1 i

I 1 . 11375-376.-377 I 1 : . 1 1 11Avarag 1 993.731672.50321.25 1737.50 1 7.88 11.4830.00 16.47 ::Std. Dv. 57.40 I 66.76 29.50 1 49.18 1 5.24 3.43 I 3.56 10.07 I ...... MOIMMIOMMIBMIMMAIMMMMUMMWMMISO.1

11378-379-380 I 1 11Avarag 11,082.50 1765.00317.50 1760.00 1 5.88 9.62 130.33 16.52 1 : 11Std. Dy.' 1 80.97 164.81 23.38.1 64.42 3.61 2.09 1 3.33 :0.04 11 I i 1 I-1 1:381-382-383 1 1 1 1 1:Avarag 11,115.00 1800.00315.00 :785.00 1 4.20 8.80 :30.00 16.30 : 1 3.02 I : :Std. Ov. 1 30.82 118.71 21.21 : 5.00 1.72 2.00 :0.00 $ 11 I 1 1 I:384-.385-386 I 1 1 1 ItAvsvag 11,138.37 1835.71302.86 1802.001 6.57 8.99 30.17 16.51

i 2.52 ::Std. Dye. I 56.04 167.90 39.631 38.68 2.91 1.93 10.03 11 I I 1 1 1 1 11387-388-389 I I 1 11Avirrags :1,161.00 1768.00393.00 1767.50 1 5.26 7.32 27.75 16.50 1 I 1.37 I 11Std. Ov. 1 141.22 1 83.39 60.30 1 37.00 2.04 0.25 10.00 11 1 I 1 11390-391-392 : 1 1:Avarag 11,063.00 1729.38333.63 :806.00 9.14 8.81. 29.33 18.51 : I 1.87 10.02 I : :Std. Day. 1 97.21 :105.52 56.09 t 73.10 4.22 3.79 1 11 1 1 11393-394-395 : 1 8.07. 129.33 18.50 1 IlAv.erag 11,092.50 1768.75323.75 :832.50 1 6.57 t 1.99 1.51 I 1.89 10.00 1:Std. Dv. I 53.68 1 60.89 45.09 I 78.54 1-----: I ..1.1.11111. 7 4

TAEiLE CONTINUED AVEZAGE COOLING TOWER WATER QUALITY

tn XXXXXXXXXXXXX 31=11222211

11 Run I Total 1 Ca 1 No I Sulfate 1 Poly Ortho I Silica I 1

Ii --- IHard. I Hard. I Hard. i as 1 Phospt Phospt i as 1 P H TOTAL : SOLUBLE 11 Average as CaCO3 as CaC:3 In CaCO3 1 SO4 I as PO4 as PO4 1 Si02 1 IRON 1 IRON

11 I 1 Std. Dev I pps pps 1 PIN POI 1 pp. ppe 1 pps

11396-397-398 1 1 1

1:Average 11,120.38 821.:1 1 293.08 i 848.46 1 5.49 4.28 1 27.62 I 8.50

11Std. Dev. I 66.66 77.13 1 43.48 i 69.71 1 2.38 1.66 1 0.84 I 0.00

11399-400-401 I 1 1

I:Average 11,032.12 677.11 1 354.81 1 728.08 1 6.73 5.91 I 24.04 1 8.50

11Std. Bev. 1 52.26 43.17 1 44.55 I 38.56 1 3.65 3.90 1 2.22 1 0.00

11 1 1 1

11402-403-404 1 1 1:Average 11,284.00 831.001 443.00 952.00 1 6.88 i 5.48 1 26.00 1 8.50

11Std. Dev. 1 40.91 29.71 1 28.21 81.40 1 2.65 t 2.25 1 0.00 1 0.00

11 1 i------1 1 1

11405-406-401 I 1 1

1lAverage 11,263.75 1 840.00 1 423.75 987.50 1 4.70 1 3.33 I 29.88 1 8.50 1

11Std. Der. 1 43.57 t 43.:1 I 38.79 92.70 1 1.69 I 0.63 I 1.36 1 0.00

11 1 1 1 1

11408-401-410 I 1 1 1 I 1 1 1

IlAverage 11.308.57 I 831.06 1 470.71 1 975.00 1 9.19 8.21 I 20.83 1 7.46 I 1.94 I 0

11Std. Div. I 108.32 I 4931 1 69.15 I 32.79 1 5.19 3.95 1 6.14 I 0.04 I 0.14 I 0 __ - -1 ------: ----- _ -1 -1 1 I---_____

I 1 I- 1 1 1 11411-412-413 1 1:Average 11,140.00 1 730.00 1 410.00 I 913.33 I 5.76 5.30 1 26.33 I 7.50 i 1.9 I 0

IIStd. Div. I 21.31 I 23.43 1 31.62 I 53.75 1 1.98 0.99 I 1.70 1 0.00 t 0.13 1 0 ----- I ------I------1: - -1 :------: ------I 1 1

11414-415-416 I 1

I:Average I 960.00 1 639.00 1 321.00 1 714.00 1 5.82 6.40 1 22.00 1 7.51 3.14 1 0

IIStd. Dev. 1 50.20 1 42.00 1 66.80 1 37.20 I 1.14 1.16 1 3.83 1 0.05 0.17 t 0 TABLE J -1 CONTINUED' COMM TOYER YAM QUALITY

1111111114111111111111181SOSSOISSS111111111118111114111.8111111 111

111va 11 Total 1 C. I Ng Ilullite :Pell I arta' !Silica!: '

1: 1 !lard. 1 Ilard. t Mud. 1 as 1 Pbospt : hasp' 1 as 1 P M : TOTAL 1

t 11 Average *las CaCO3 las atCO3asCaCO3 1 604:1 as PO4 1 as PO4 1 8102 1 : 110A . II Std. Dev 1 pp. 1 pp. : ppo 1 ppil 1 1114 : pp/ 1 KO. 1 I -...:-..-:--...:-.----;-.....:-...----: :: -1- -1-: . 1:417-411 1 1 1 1 1 t 1 1

::Average 11,225.13 1 753.67 1 470.42 1123.33 1 2.261 1.71 1 22.57: 7.61 1 3.04 :

1151d. Bev. 1 167.43 1 76.54 1 11.71 1 125.41 1 1.81 1 2.64 1 3.77 10.03 1 1.15 1

: .... :-...... 1 ...... : 1: 1 : : : . . 1:420-422 : : 1 1 ' : . ' 1

1:Average :1,076.00 1 645.00 1 431.00 1722.00 : 4.33 1 1.10 1 22.83 1 7.45 1 2.71 1

1:Std. Dev. 1 125.12 1 10.00 1 61.51 1 55.01 1 1.84 : 2.77 I 1.47 1 0.15 1 .75 :

1:423-424 1 . 1 . 1 . I ,

::Average 1 890.13 1 538.13 : 360,00 1635.00 1 2.79 1 11.66 1 21.51 1 7.40 1 2.61 1

11St4. Div. 1 102.50 1 11.12 1 91.50 1 81.96 1 1.201 3.34 1 1.13 : 0.33 1 0.59 :

:: : : : : 1- 1 : 1

1:422-426 1 . . : 1 1 : .

::Average : 977.08 1 622.50 1 352.12 : 766.67 : 2.80 : 8.95 1 18.53 17.55 a 2.62

1:Std. 2ev. : 61.29 : 20:68 : 41.83: 55.87 : 0.85 : 1.43 : 0.36 : 0.03 : 0.45

11 : 1 : 1 : : : : . 1:427-421 : : . . : : . .

1:Average 11,008.93 1622.86 1 379.57 1 732.14 : 2.64 : 1.61 1 21.44 : 7.36 1 2.89

1:Std. Der. 1 83.71 I 35.21: 43.24 ; 61.63 1 1.03 1 1.28 : 3.04 : 0.07 1 0.47 :

. . . . 1:430-432 : : : . .

::Average : 170.10 :103.00 1 367.30 1 725.00 1 3.97: 10.11 1 18.33: 7.43 1 2.75 1.40 : 4.68 1 0.17 : 0.67 1 1:Std. Dtv. : 68.14 1 41.40 1 31.12 1 60.01 1 1.26 :

: : 1 . 1 1 1 :1423-435 : . . . 1 16.40 1 7.43 1 4.43 1 : :Average 1 191.17 1600.13 1381.17 1 172.01 1 2.11 1 1.43 1 11Std. lit. 1 45.60 1 41.27 1 33.02 1 31.62 1 1.011 2.61 ! 3.01 10.08 1 0.71 t

: 1 1 1

. t 1:436-438 .1 1 1 1 la 1 . 11Average 11,073.33 1745.00 1 322.78 1 632.00 1 NO : NO 1 34.67 1 7.30 : NO

1 1 3.06 10.00 1 11514. 1ov. 1 11.72 1 47.43 1 12.77 I 112.56 1 .

1...... _: -....: : : : 1-1 I 1 ::

! 1 : ! 11431-441 1 : 1 : I 1 11Aversge 11,073.501701.601341.50 I 744.30 I NO 1 NO I 21.251 7.41 1 2.16 1 11111. lov. I 105.31 1 14.14 1 13.00 I 31.35 I I I 2.43 I0.01 1 0.64 1

:--: : : : ' 1 11 I 1 :

t 1 1 I I' I 1:442-444 1 t .1 1 . 11Avorage :1,040.131663.131 425.001745.00.1 NO I NO I 24.20 1 7.50: 3.72:

I : 1.10 I 0.03 1 0.64 I ::.....-:-.1-1--1-4--1...... --:-:-...... 11311. II,. I 75.31 I 63.67 $ 36.11 1 76.11 I :----:

1 8 1 I 1 1:445-447 1 I I : I I:Average 11,071.331 703.33 I 375.00:727.71 I NO ! NO : 22.40I 1.311 3.071 : 0.11 I0.03 : 0.3 : 11311. lov. I 44.63 I 27.50 I 41.75 I 1.23 I I

1...... 1--: I 1 1 ------: :-: 1 :: t I 1 : : 1 :1441-450 I 1 1 . 1 24.00 I 2.94 ! Ilheroge 11,115.36 1 733.56 1 371.44 I741.01 1 NO I NO I 7.63 I I. 1.16.: 11114. 1e,. I 115.111 54.171 13.421 137.131 I 2.13: 0.061 :1-...... :-...... 1-0.-.....1....--.1--:...... :-..r.....:-...:---;

: I I ; 11431-453 1 I .1 1 I 21.67 17.62 1 4.11 I 11Averoge. 11,022.16 I657.14 I363.71 1 714.21 1 3.16 : 1.63 1 11111. Ilv.1 71.47 I 46.11 1 61.17 1 72.77 1 1.71 : 0.70 1 4.13 10.06 : 3.23 1 1-.....-4...... 1-.1-:-..-1-4...-....g...... :-...... l...... ---.1 1 : 11454-456 1 I' .1 I : 1I ; 7.31 1 %Ami3o 1 -110.11 1;720.51 1311.11 I .716.77 1 4.11 I 7.43 : 21.40 1 3.94 I 0.04 1 1.77 1 :1114. lov. 77.12 : :43.00 I 31.51 1 44.72: 1.14 I 1.64 1 3.71 :

I 1 1 : 1 . 1437-431 : . I I 1 24.67 :7.62 : 3.51 1 1:Average 11,111.40 I 712.00:317.50 :105.01 1 5.33 I 1.44: 1.03 : 1.51 I 0.01 1 1.03 1 'I' Ito.: 21.11 I 23.61 t 37.71 1' 10.41 I 1.10 : 4,...... t...... :...... p...... :...... !...... 1 --- : ------:------1------1 316 APPENDIX K

AVERAGE SYSTEM FLOWRATES TADLE1 K-1 AVERAGE FLOW-RATES (LITERS/DAY)

., RUN I :AVG : 1 I EVAPORA- CITY BLOW I FORTIFY : INNISI- 1: :STD DEV : TION 1 WATER I I DOWN SOLUTION I TOR 1

302-4 I AVG I 184.4 1 254.2 175.2 : 103.9 I 3.46

I I STD DEV 6.6 9.8 2.2 8.2 : 1.0

:I 305 -7 r AVG T 195.5 269.9 180.6 : 10373 2:§K----: :

1 STD 0EV 24.7 23.7 4.6 : 5.2 : 0.71 I

: AU T 2,670 ; 283:f I65.9

STD DEV 28.4 : 33.3 8.3 I 5.9 : 1.42

T-4Vg i77.6 1 261.^ 164.0 81:9 : 2.W :

STD DEv 28.9 : 42.7 2.0 : 26.7 : 0.91

I. 1 311-2 AVG g0.5 : 277.6 fWa ;a:7

: STD DEv 11.5 ; 11.6 6.1 : 8.1 : 0.81 Ave 1r3 196 73 287:3 168:7 : 6973 : 3.17- :

1 STD DEV 1 8.7 t 12.1 12.9 : 1.0 : 0.68

AVG rR4.7 168:9 : 6C.0

I : 1/I2 DEv 10.6 10.4 ] 3.6 : 2.2 0.69 :

169.4 61.8 : 3.82 1 I Ave : 271,6 175.2 .4 L in_m_i_ 7_7___1 7.6 _j__ 1.9 _j__ 0.9 _L_ 0.50_:

125-1 I : : : t : Ave -1;0:3-- -ZSI:b-- -10:3- : --b1:3-- :-3:58-- Lata_m_l_ 7.3__l_ 8.6_J__ 2.4_j__ 1.3 _L_0.78 __: II --172=3 : Ave : -133:1 : -2167,-- : 768:3" : --bIrr- !'Tar-

: : STD DEv 8,0 : 2,0 1 2,1 1 .1,2 : 2,01____:

: 1 : :1-----5f4=s AVG 194.4 296.1 : 173.6 : 63.3 : 3..69 VI 6.6 _j_ 6.0 _j LAIR-ZELL 3.8_I_ 7.2 L__0.61 ..._:

327=9 1 An : 77178- . "268;6- : -T597a- . 64.2 -7--Cab--

. 16.7 : 16.0 . 3,1 : 1.3 0.47 -----170-:2 1"-ii28-1E21-7761-1---1-f,73--1---75:;--r---ary----4727-----:

STD DEV 1 8.0 : 17.2 : 2.1 : 118 I__0.36:

111-3 : Ave 1 169.8 : M.9 : IZZ -r br.3-- T5:45 7

I STD DEV : 5.3 1 20.2 10.9 : 0.4 1 0.32 1

;'t---- 11;:a : AVG : 185 : -2757 : 155.5 : -3257---1 -373 ----7

1 UTD DEV : 7.4 I 11.0 1 9.7 1.6 : 0.27 :

: 17977 ; 2817- 1 : 625:7 : :11:----33,;:ar I AVG -17172 9.83 -`'

: 10.6 : 1 : : I ST2 Sp : 8.3 4.6 1.6 0.32

: T69.9 : : Ii----342:4I I AVG :78275- -M:8 6573---T--5712----1

j smssy j__7.3 : 15.6 : 10.1 : 6.3 : 0.39

1 : 267.1 : 172.8 ----143 :7 I AvG 1Zs.2 ;371 5:a7 ---1

:1 j_m_sl3rj_ 6.1 1 7.3 . , 0.9 : 5.0 1 0.42

TABLE : K-1 Continued AVERAGE FLOW -RATES (LITERS/DAY) ii... ..30.

I: RUN * :AVG :EvAPORI CITY I BLOWIFORTIF:INHIBI:

1: 1sTDDEV TION :WATER : DOWNISOLUTIITOR

1: 348-349-350:AVG :156.6 1260.41172.2 62.7 1 2.2 1

STD DEV 6.4 1 11.4 1 2.6 5.1 I 1.5

351-352-353:AVG 1169.5 1271.2:164.2 56.8 : 2.4 :

: STD DEV 18.7 : 32.1 : 29.0 4.8 1 1.3 :

254-355-356:AVG 1166.7 :273.61165.4 55.0 I 3.1

: STD DEV 25.7 : 31.7 1 11.3 2.5 0.3 1

357-358,-359:AVG :174.2 1270.8':157.3 1 57.5 I 2.9 1

1: STD DEV 24.0 1 33.8 21.9 I 4.8 : 1.0 :

II 360 - 361 -262:AVG :156.6 1271.4:184.3 65.4 1 0.0 :

I STD DEV 27.6 28.4 1 11.2 0.9 1 0.0 I

:1 363-364-3651AVG 1175.2 1274.9:173.6 65.6 1 0.0 1

1 STD DEV : 13.8 : 13.9 I 4.9 1.1 1 0.0

:1 366- 367 -3681AVG :152.5 1269.61166.1 40.1. 0.5 :

: STD DEV 18.6 I 13.3 : 8.3 8.4 I 1.2 I

1 369-370-3711AVG :114.2 1251.71172.5 30.9 I 1.8

1 STD DEV 1 24.6 1 25.8 : 5.7 6.4 : 1.6 1

!I 372-373-374:AVG :128.3 1260.11175.2 50.1 1 1.0 :

; STD DEV 1 28.4 1 44.8 1 1.3 7.0 : 1.4 :

11 375-376-377:AVG :143.6 :264.4:174.1 1 48.3 I 2.0 1

11 : STD DEV 1 3.6 : 7.1 1 2.8 I 8.6 I 1.6 1

II378-379-380:AVG 1121.6 A245.8:174.9 53.9 I 2.7 1

1 STD DEV 1 17.0 1 17.2 I 2.3 1 8.0 I 1.1 :

!I381-182-3831AVG :139.8 1259.8:173.9 1 49.4 I 0.0 1

1 II I STD DEV 1 5.8 1 6.4 I 0.1 1 0.3 1 0.0

384-385-366:AVG :135.6 1254.2:174.3 50.'8 I 1.1 1

1 I I I STD DEV 1 6.6 1 6.8 1 1.6 2.2 1.4

1: 387-388-389:AVG :126.0 :247.61183.3 1 56.2 1 2.2 I

I 1 1 STD DEV I 9.4 1 15.9 I 8.1 1 4.4 1.6

1: 390-391-392:'AVG :133.3 :248.2:171.0 46.8 I 3.0 :

I : II I STD DEV : 29.7 1 34.1 : 8.2 11.6 0.5

1: 393 - 394 -3951AVG :107.1 :213.8:172.8 1 57.8 1 1.8 I

: : 1.5 1: 1 STD DEV 1 7.0 1 5.6 1.1 7.2 TABLE ; K-1 Continued AVERAGE FLOW-RATES (LITERS/DAY)

======.======79MIO=M=MM.WW.71,M===.=.17,======.76======.====...

I! RUN # :AVG IEVAPORI CITY I BLOWIFORTIFIINHIBII

:STD DEV 1 TION :WATER 1 DOWNISOLUTI1 TOR 1 1I m398-397-398 I Ave 1129.81231.41170.6 1 60.4 1 2.5 1

I STD DEV I 6.1 t 7.9 I 2.6 1 6.6 I 0.6 :

:1399-400-401 1 AVG 1108.61214.81172.9 : 58.9 1 3.0 I

11 1 STD DEV : 10.3 : 12.0 : 3.8 I 3.9 1 0.3 1

11402-403-404 I AVG 1146.01233.61170.5 I 75.1 1 2.9 I

11 : STD DEV 1 40.1 1 43.9 1 3.9 1 0.7 1 0.3

11405-406-407 1 AVG 1168.21257.2:168.6 1 71.8 1 3.0 1

1 STD DEV 1 27.7 1 32.8 1 4.0 1 5.1 1 0.2 1

11408-409-410 I AVG 1143.81218.91168.3 1 70.0 1 2.7 I

11 1 STD DEV 21.0 1 44.7 1 12.3 1 9.9 I 0.9 1

11411-412-413 1 AVG 1135.11241.41169.9 1 55.3 1 3.2 1 if it 1 STD DEV 1 9.9 1 15.6 1 7.3 1 4.0 I 0.2 1

11414-415-416 : AUG 1152.11262.01171.2 1 53.8 1 6.0 1

I STD DEV I 23.9 1 20.4 1 8.7 1 2.5 1 0.3 1

I f TABLE : K-1 Cont inued AVERAGE FLOW-RATES (LITERS/DAY)

: RUN 1 IAVG :VAPOR: CITY : BLOW :FORTIF:INHIBITOR :INHIBITOR:IRON 1

:STD DEV : 'ION :WATER : DOWN 1SOLUTI:PHOSPHATE :COPOLYMER! :

:417-19 : AVG 1146.7 :248.6 1173.1 63.6 : 0.0 1 014.01 :

: STD DEV 12.4 : 21.8 : 7.9 : 13.8 : 0.0 : 011.02 :

:420-22 AVG :151.5 :260.8 :170.8 : 48.7 : 1.8 : 3.08:3.38 :

: STD DEV 1 8.6 : 10.2 1 9.6 1 10.3 1 1.8 1 1.06:0.62 :

:423-24 I AVG : 48.0 :152.3 :173.9 : 58.1 0.6 : 3.33:3.24 1

: STD DEV : 11.8 1 7.1 : 6.2 : 7.1 : 1.4 0.23:0.31 1

:425-26 1 AVG : 59.2 :170.3 :176.4 55.4 : 0.0 : 3.29:3.38 :

: STD DEV : 15.1 : 15.0 : 1.3 1 5.7 : 0.0 I 0.21:0.64 1

:427-29 1 AV6 :152.2 :257.5 :174.7 : 54.3 : 0.0 : 2.93:2.78

: STD DEV 1 15.3: 26.1 : 1.4 1 1.7 : 0.0 : 1.37:0.21

:430-32 : AVG 90.3 :195.0 :170.0 : 53.8 ; 2.4 : 2.85;4.58 1

1 STD DEV : 47.1 : 44.5: 8.5 1 3.0 I 1.5 : 2.5411.45 1

:433-35 1 AVG :167.3 :267.5 :167.9 : 55.1 : 1.0 I 3.11:6.53 :

: STD DEV : 5.2 : 6.0 : 4.5 : 4.9 : 1.6 : 0.4:0.97 :

:436-38 : AVG :154.4 :269.4 :171.0 : 61.6 : NO : NO 1 NO 1

a a a I STD DEV 1 5.8 I 10.5 1 2.0 1 7.7

:439-41 I AVG :198.9 :294.3 :170.4 : 66.8 I NO NO 1 4.6 :

1 STD DEV : 10.3 : 15.7 1 8.5 1 6.2 : :0.77 :

:442 -44 : AVG 1155.5 1250.7 :168.4 : 65.6 NO NO 13.99

STD DEV 30.3: 23.7: 6.5 : 4.5 1 :0.43

:445-47 1 AVG :136.2 :237.6 :173.7 1 63.9 : NO NO :3.41 1

: STD DEV : :9.5 : 22.1 1 11.4 : 3.5 1 10.81 :

:448-50 : AVG :112.8 :213.1 :168.2 : 60.7 I NO a NO :3.95 :

a : STD DEV : 21.7 : 25.0 1 6.6 1 8.8 : 10.79 :

:451-53 : AVG 11E2.6 :248.4 :168.0 1 62.0 ; 2.3 : NO :4.27 :

1 STD DEV : 30.1 : 26.9 1 11.6 1 7.8 : 1.1 : :2.37

1 1454-56 AVG 1164.5 1265.2 :185.1 1 75.4 1 1.1 : NO :4.46 :

1 STD DEV : 10.1 1 20.0 : 16.5 I 5.1 : 0.2 : :0.89 :

:457-59 1 AVG : 68.2 :164.8 :175.6 1 7.8 1.7 NO 12.83

: STD BEV : 27.5 I 28.8 : 15.6 1 1.4 : 0.9 : :0.79 I 320 APPENDIX L

PLOTS OF CORRELATIONAL CURVES

Figures M-1(a-h) Correlational of -1n0d vs velocity at a

constant surface temperature for 8 sets of different

water qualities.

Figures M-2(a-q) Correlation of ln(ed /Fv) vs

C1/(Ts+460)] C109) for the 17 different water

qualities observed in Table VI-2.

Figures M-3(a-q) Curves of Constant Velocity on Grid of

Time Constant vs Surface Temperature for the 17

different water qualities observed in Table VI-2.

Figures M-4(a-q) Curves of Constant Velocity on Grid of

(Time constant x shear stress) vs Surface Temperature

for the 17 different water qualities observed in

Table VI-2. 321 PLOTS OF CORRELATIONAL CURVES

Figures L-1(a-h) Correlational of -ln0d vs Velocity at a

constant surface temperature for 8 sets of different

water qualities. i 22

16 C6. 11.447 C7 = .25436

R- SOARED = .8298 14.6 Correlation coeficient = 8.911

13.2

18.4

2 5.2 6.8 8.4 18 Figure L la MOCITY(Ftiec)

14 C4 = 9.62133

C7 = 8.22365

R- SQUAW = 0.9867 13 Correlation Coefficient = 0.991E

2 3.6 5.2 6.8 8.4 18 Figure Llb 1,110CITY(ftilec) 14

2 3.6 5.2 6.8 8.4 18

Figure L lc VELOCITY(Ft/Sec)

I 16 COLNAU V=0.2990 11-9M8321999 14.6 Urrelationftefided=0.99%

18.4

2 3.6 5.2 6.8 8.4 18 Figure L 1d VaJX11Y(Ft6Set) 3 2 4

. I I I 3 C6 = 11.7428

C7 = 9.322895

18 R-911110 = 8.7241

Correlation Coefficient = 8.851

R342 14 a a

R343

12 R344

2 3.6 5.2 6.8 8.4 18

Figure L le YEICCITY(Ft/Sec)

14 C6 = 9.33751

C7 = 8.287554

13 R-SQURRO = 8.981

Correlation Coefficient = 8.99

Z 11

2 3.6 5.2 6.8 8.4 18

Figure Llf YELOCI1Nt/Sec) 16 Cb= 18.833

C7 = 0.34883

R- SOARED = 8.959 14.6 Correlation Coefficeint = 8.977

R421 MIN A R421

R462

18.4

9 2.

2 3.6 5.2 6.8 8.4 18

Figure Llg tELOCITY(Ft/Sec)

. V V 14 C6 = 8.61839

C7 = 1.21661

13 R-SQL/RE1 = 8.9946

Correlation Coefficient = 8.997

z 11

8 I. AL

2 3.6 5.2 6.8 8.4 18

Figure Llh tELOCITY(Ft/Sec) 326 PLOTS OF CORRELATIONAL CURVES

Figures L-2(a-o) Correlation of ln(ed /Fv) vs

C1/(Ts+460)3 C10:3) for the 15 different water qualities observed in Table VI-2. 327

WATER I 1 " I " 13 C3 2 7.9768657E-83

E/R8 = 3.67782E+83

R- Squared = 8.48

LL Ik H 8385 R382

8387

I A_

161 162 163 164 165 166

(X 1E-5) Figure L-2a (1/(Ts + 468))

MITER # 2

. I " " 1r 12 C3=2.5337977E88

E/Rg = 1.76699E04

11 R- Squared = 0.5326

R318 18 RIM 3 IL

9 8337

6 I. 1 111 . I . . . I . I

161 162 163 164 165 166

(X 1E-5) Figure L-2b E1 /(Ts + 468)) WATER t3

12.6

12.2

4 11.8

11.4

161 163 165 167 169 171 Figure L-2c Was + 468)] (X 1E-5)

MATER t 4

11.7

11.2

318.7 b.

V z J ma

9.7

9.2

161 163 165 167 169 171

1E-5) Figure L-2d El/(Ts +468)1 29

MIS # 5

11.3

18.8

18.3 3 U.

13 9.8 z J 9.3

8.8

8.3

161 163 165 167 169 171

Figure L-2e t1/(Ts + 468)] (X 1E-5)

WATER #6

10.9

18.7

18.3

18.1

161 165 167 169 171 (X 1E-5) Figure L-2f [1/(Ts + 46e)] MATER 7

18.8

10.5

318.2

-I 9.9

9.6

9.3

161 163 165 167 169 171 (X 1E-5) Figure L-2g (1 /(Ts + 468)]

NITER t 8

14.5

V 11.5

8.5

161 163 165 167 169 171 (X 1E-5) Figure L 2h [1/(1's + 468)] 3 31

WATER 19

18.8

318.6 IL

18.4

18.2

161 163 165 167 169 171 Figure L-21 Was + 468)] (X 1E-5)

WATER $ 18

12 114 C3 = 4.394859E17 = 3.8983234

11.5 R-Squartd = 9.9754

18.5

9.5 P414

9 $415 . i . I . i

161 163 165 167 169 171 Figure L 2j IlATs + 468)] AC 1E-5) "1,-, 2

MITER # 11

12.4

11.9

11.4

3 U. 4. 18.9

18.4

9.9

9.4

161 163 165 167 169 171 (X 1E-5) Figure L-2k I1 /(Ts +468)]

WATER # 12

11.2

9.8 3 U. St 9.6 1/, z

9.4

9.2

161 163 165 167 169 171

(X 1E-5) Figure L-21 El/(Ts + 468)l WATER $13

VA 163 165 167 (X 1E-5) Figure L-2m Was + 4601

liMERS 14

13.1

12.1

9.1

8.1

7.1

161 US 165 167 169 171 tX 1E-i) Figure L-2n E1/(Is + 4601 HATER # 15 . I I 11.6 C3 = 2.2957388E83 FA67 E'Rg c 1.1262E84

R- Squared = 8.8631

11.2 F.465

P469 iW3

18.4

it462 11468

18 . I I

161 163 165 167 169 171

Figure L-2o Was + 4E8)] (X 1E-5) 335 PLOTS OF CORRELATIONAL CURVES

Figures L-3(a-o) Curves of Constant Velocity onGrid of

Time Constant vs Surface Temperature for the 15

different water qualities observed in Table VI-2. WATER t 1

188 . 05

IRight Axis is For 5.5 ft/sec only * Data far this water was available 158 * only at 3 ft/sec . 94 1%

0 0 z 129 V .83 u

4, 90 C C

4, .821 C C 0 O 68 U

E . 81 ; 38

128 138 148 158 168 178

Figure L 3a Surface Teeperature ( F)

WATER 1 2

688

L 450 0 V

3110 C 0

CM U

158

148 146 152 158 164 178 Figure L-3b Surface Imperative ( F) 179 179 168 160 158 F) 158 F) 3 Teueerature( 4II Imperatore( IIITER HATER 148 Surafce 149 Surface 138 L3c 138 L3d 129 248 288 168 129 48 Figure 188 159 51 60 38 Figure t. 0 5 0 0 C 4' C 0 ;- 8 11 C. j 0 5in 0 C 4' 0 C 0 178 179 168 160 5 158 F) 158 (F) NITER Tesperature 6 ( WATER # Twenty* t 149 Surface 148 Surface 138 L3e 138 L3f 128 128 199 a 0 U 0 0 68C 0 0 U48 E 29 8 Figure 1:1 g 6 U 0 Figure MATER t 7

Eel

L608 3 0 V a C

C 0 U 280

DA 08 148 158 168 179 Figure L-3g Surface Telperature ( F)

A L 3 0 V

0 4; a C I C 0 U

E 10114.yv is

168 178 13 139 148 158 Figure L 3h Surtace Ttiperthre (F) 4 170 179 168 168 158 (F) III HO 9 Tespelture 4WATER #WATER 148 Surface HO 9.0aceUvrabire(F) 138 up L-3i L-3j NO 120 880 600 400 298 Figure 38 27 24 21 18 15 Figure ; 5 0 0 4 C 0 1' C 0 0 0 E ; 8 A 4: O ; 341

MATER # 11

406

L343 z 0

2E* C a 4,

C 0 U

189

128 138 148 158 168 179 Figure L-3k Surface Temperature ( F)

MATER 11 12

L388 0 6 U 0 4; ZS C a

C 0 U

128 138 MO 156 168 179 Figure L-31 9.11qUeTewerdwe(D 342 170 178 168 168 13 158 (F) 14 159 (F) IiITER0 Teoperature WATER# Teoperature 148 Surface 148 Surface 139 us L-3m L-3n Figure 120 Figure 1208 1888 MS MS 200 1888 888 688 El 8 L 0 o a O C li 0 C 0 E 0 6 40 C 4+ a 9 I g2 WATER I 15

0 6 1688

1208

488

129 138 148 158 168 179 Figure L 3o Surface Imperatore ( F) 3144 PLOTS OF CORRELATIONAL CURVES

Figures L-4(a-o) Curves of Constant Velocity on Grid of

(Time Constant x Shear Stress) vs Surface Temperature

for the 15 different water qualities observed in

Table VI-2. WATER 1 1

( 9 P \ ' I'

O L6 V

13 138 148 193 168 Figure L 4a Surface Teeeerature

WATER t2

141

195

t4, q. uH 0 6 35

149 146 152 158 164 Figure L-4b SeaceTemegure(F) MATER 1 3

188

128 138 148 158 168 178 Figure L 4c Surface Teeperature ( F)

NITER 14

46 14 0

129 138 HO MS 168 170 Figure L-4d SerfaceTemwatwe(D MATER

129 138 148 150 168 178 Figure L-4e Surface Teweratare < f)

WATER #6

128 138 148 12 168 178 Figure L-4f Surface TemperatureF) -4C

MATER i 7

128 136 148 158 168 178

Figure L-4g Surface Temperature ( F)

MATER 8

130 148 159 168 178 Figure L-4h Surface Taunter. ( F) HATER 84

488

300

189

128 138 148 159 168 178

Figure L-4i Surhce Temperature(F)

NATO i 19

148 130 168 178 Figure L-4j SorfueTempffgwe(F) MATS 0 11

150

128

1 ,( 98 I)+ I+ ua 0 L 68 5

128 138 148 158 168 179

Figure L 4k Surface Temperature ( F)

HATER 112

168

128

129 138 148 158 168 178 Figure L-41 Surfacetwerahre(F) MITER i 13 188) I V I V II If I 1, V IF 1r I 18 8 ft /sec

40 P+ 9.9 u z 6

3 5.5 ft/sec 3 ft/sec

128 138 148 158 168 178

Figure L 4m Surface Temperature ( F)

NITER # 14

128

189

138

o 48

13 138 148 150 168 178 Figure L 4n Surface Temperature ( F) 138 140 158 168 178 Figure L 4o Surface Toperatuer (F) 353

APPENDIX M

SOLUBILITY INFORMATION 354 As a guide to cooling tower water treatment, McCoy

(23) calculates the solubility of the scaling compounds at standard conditions, then suggests that concentrations be held lower than thecalculated saturation values. Using only the hydrogen phosphate complexes and the solubility product of Ca29(P0,)e, he calculates the saturation concentration of Caa(PO4),.

Herbig (12), collected solubility data for the cooling tower constituents. Using these data he generated saturation curves for different potential precipitant. An example of such curves is Figure M-1.

Table M-1 lists the solubility products constant at threedifferent temperatures (130, 145, 160°F) for the cooling water constituents. This table is adapted from Herbig (12) with the iron solubility products constants calculated during the course of this investigation.

Humphris( ) reported information on the solubility of calcium phosphate in a cooling tower and an equation was derived from these data for predicting cooling water conditions. Figure M-2 is a nomogram produced from the derived equation. I I 1 1 E ill 1 i 1 i lit 1-

WIN

/MO pH

10. 100. Calcium Hardness, CaH as ppmCaCO3

Figure M-1saturation Curves of Calcium and Orthophosphate in Solution with Respect to Calcium Phosphate 356

TABLE M-1

Equilibrium Equations LOG K VALUES

130°F 145°F 160°F

1. CMq0H"] EH-4-1 = Kl -11.29 -11.12 -10.96 Eilcr']

2. EMaS0.. ag) = K2 2.59 2.67 2.74 [Mcf"Har-]

3. EW] LOH] = K. -13.15 -12.95 -12.78

4. CMcIP0,-;) = K9 3.40 3.40 3.40 Ellg"][POi.?-]

5. EMc-30,.. ag] = K. 1.8 1.8 1.8 CMg4'3CHP0-]

6. ECaeJCP0-P'' = K;5 -31.24 -32.33 -33.59 ECa;.4(P0,..)p]n

7. EF-1-4-1CHF.P0,+1 = K. -2.30 -2.36 -2.41 EHaP0,,7

8. CH.HHPO4-3 = K, -7.19 -7.20 -7.23 EH,P0,,1

9. CH~3CP04-3 =KEG -11.90 -11.78 -11.65 [HP0°' ]

10.[CaP0...1 = K. 6.66 6.71 6.76 CCe'"-]CP0:4-3

11.ECaHPO4 aci] = K,0 3.23 3.68 4.21 CCe-'3CHP057,-]

12. CCat-1,-.P07,3 = K11 .72 .8 .92 tCaP4-3E1-1,.P07 357

13.CCaS0,..aq] = K12 2.42 2.47 2.51 CCe"-]CSO4-7

14.CFeP0,,.2H0].[W] =Kizi 16.04 16.137 16.23 CFe:1-1-][HPO-7CH20]E?

15.CFeP0.4].CW1 =K1.4 16.63 16.804 16.97 EFe'."'±][HP0F4-7

16.CFePO,.2HE.0] = 24.13 24.290 24.44 CFe'4'7CPUR.-7CHE.,0]

17.CFePO42H20] = 28.15 28.189 28.22 EFe-3'') EPOP.-][HF.0]

18.CFeP0,..,]. =K 28.74 28.86 28.96 EFe.9-1-7CPOil-]

19.[FeP0,..).EH =Kla 9.493 9.68 9.86 CFe'][H,P0..1]

20.EFe(OH)33.EW-3-3 =Kl., -2.13 -1.80 -1.48 EFe"43EHE.03°

* Brackets indicate activities. TOTAL TOTAL CALCIUM PHOSPHATE mg/1 (Ca Co3) pH mg/1(Na 3 PO4) 1000 6.6 100 950 - 95 9007t-- 6 . 7 E 90 850 E- 85 800 6 . 8 80 = 175 750 5. 9 700 70 7.0 650 55 600 = 7.1 60 550E- 7.2 F: 55 =._ 500 f--7.3 50 7. 4 -- 45 450 7.5 7. 6 400 40 7. 7 7. 8 350 7. 9 35 8.0 8.1 300 8.2 --- 30

250 25

Figure M-2 Precipitation Nomogram