Paper No.

494

COIRROSIONC)LThe NACE International Annual Conference and Exposition

UPDATEOF OZONE USE IN COOLING TOWERS

PAUL R. PUCKORIUSPuckorius & Associates, Inc.

PO BOX 2440Evergreen, CO 80437-2440

ROBERT T. HESSPuckorius &Associates, Inc.

PO BOX2440Evergreen, CC)80439

ABSTRACT

Ozone use in cooling towers has continued, but at a much lower rate of expansion than five(5) years ago. The reasons for this reduction are primarily due to a better understanding of theozone performance requirements. Ozone is not a complete treatment in most cases and islimited due to high costs for installation. Specific case histories are reviewed along with updatedguidelines for ozone applications and economic evaluation.

INTRODUCTION

Ozone has been reported to be a complete treetment for cooling tower systems for scale,corrosion, and biological control. These claims often are not verified. When investigated, thoseapplications that appear to provide complete treatm:nt actually involve the presence ofchemicals or water reactions not directly caused by ozone but indirectly related.

Ozone applications have been analyzed in detail which show ozone as a goodmicrobiological, with some major limitations; yet an excellent Legionella bacteria control agent.Scale inhibition is unpredictable and often ineffective. Corrosion inhibitor on mild steel isprimarily related to high pH and alkalinity, not ozone. Substantial increase in copper corrosionand copper plating on mild steel and galvanized ste:l, with greatly increased corrosion andpitting is common.

It has bee noted that many ozone applications wwe initiated in chemically treated coolingwater systems that had previously unacceptable results which certainly is a driving force to tryany alternate technologies.

These reports included early ozone use as well ~s recent ozone use. This inconsistencyprompted detailed, independent evaluations of numerous ozone applications. The results ofthese evaluations have contributed to the development of guidelines for end users whenconsidering ozone use.

CopyrightICl996 byNACE International.Requestsforpermissionto publishthismanuscriptin any form, in part or in whole must be made in writing to NACEInternational, Conferences Division, PO. Box 218340, Houston, Texas 77218-8340. The material presented and the views expressed in thispaper are solely those of the author(s) and are not necessarily endorsed by the Association. Printed in the U.S.A.

A number of ozone applications during the last 2 years have been discontinued due to highcosts, ineffective performance, and excessive maintenance. This trend is due to initial overemphasis of benefits that proved to be misleading or erroneous. Details of some of thesediscontinued ozone applications are provided within this report.

We have also evaluated a number of succe!$sfulapplications of ozone in cooling watersystems. Their successes have contributed to the development of the guidelines as to whereand how ozclne can be applied effectively. Details of some of these continuing ozoneapplications are provided within this report.

COOLING SYSTEM CRITERIA/ CONCERNS WITH OZONE

As a basis for evaluating the use of ozone, it is extremely important to understand coolingwater systems. The basic water cooling tower systems (Figure 1), can vary extensively indesign, operation, and occurrence of contaminants when utilized in different industries. Thesevariations are critical in predicting the performance and cost effectiveness of ozone (as well asother chemicals) in protecting water cooling tower systems. Specific criteria to be considered inpredicting ozone effectiveness are:

a) Ozone demand due to organic andjor oxidizable inorganic reducing agents entering thewater cooling tower system from the makeup water, air, and/or process contamination;

b) The time to circulate water through the entire cooling system; that value obtained bydividing the system volume by pumpin~ rate. Ozone is less effective if greater than 10minutes.

c) Hide-outareas for bio-mass such as in water-on-the-shell-side heat exchangers, withincooling tower film fill, deep basins, and periodically stagnant equipment.

d) Corrosion of copper (if over 0.2 mpy) and mild steel (if over 1.0 mpy) with no pittingattack nor copper plating on steel or galvanizing.

e) Water temperatures (over 100F(380C)]which willquickly deactivate ozone.

Specific objectives for successful ozone use are:l No loss of heat exchange due to deposition.l No fmicrobiologicalgrowths, including Legionella.l Zero voluntary discharge.l Greater cycles than with chemical treatment.l Decreased water usage.l Recluced costs vs. conventional chemical treatment.l Reduced labor.l Eliminate chemical handling.l Achieve low maintenance.

COOLING TOWER SYSTEMS/ OPERATIONS/ DESIGN

Cooling tower systems differ for each major industry relative to design and operatingcharacteristics. These differences must be understood when evaluating ozone as well as othertreatment programs. These industry specific criteria apply when ozone is the onlytreatmentutilized. Hclwever,they may not apply when ozone is used with other compatible chemical

494/2

treatments. Thefollowing criteria are based on ozone use in North American cooling systemsand may not apply to industries throughout the world since success has occurred in Australia,Japan, and Europe.

HVACor Air Conditioning SystemsHVACor air conditioning systems (Figure 2) are perhaps the best suited for successful ozone

use with this design. They seldom have major atmospheric, makeup water or processcontaminaticln that consumes ozone. The time per cycle usually is less than 10 minutes, due toa small system capacity to recirculation rate ratio. Temperatures seldom exceed 100F(380C).

The design shown in Figure 2 illustrates the }-WACsystems that can have one or several airconditioning (condensers) and they all have water on tube-side water (WTS) cooling, which ismuch easier to keep clean than water on shell-s de exchangers. The materials of constructionare heat exchanger (condenser) tubing of copper or copper alloy that can tolerate 0.5 to 1.0 mpy(roils per year) and perhaps higher, and mild steel piping that can tolerate 5 mpy corrosion rates.These systems are relatively easy to treat for biomass. Ozone can be effective, but may notalways be cost effective.

There are two (2) additional design considerations in HVACsystems that are deterrent toozone (and chemical treatment) use. The first i:; the utilization of waterside enhanced coppercondenser tubes and cooling tower film fill. The enhanced copper tubes have grooves or shallowfins that require outstanding cleanliness and corrosion protection for satisfactory life-expectancy.The cooling tower fill,when film-fillis utilized, also must be kept clean of deposits to maintaindesign evaporation and heat rejection.

The seccmd design consideration for HVACcooling tower systems that willadversely impacton ozone effectiveness is when heat-pumps or small chillers are used. This results in piping oflong lengths (and much greater time per cycle) for the cooling water passing from the coolingtower to the heat pumps in each office, condo, or store within a large complex and returning tothe cooling tower. With these designs, ozone is usually ineffective.

Oil Refineries and Chemical PlantsThese (Figure 3) are generally poor candidates for ozone use as a stand-alone treatment.

This is due to high ozone demand created by olganicsand inorganic entering these systemsthat oflen cannot be satisfied by the ozone generating equipment. The time per cycle is often 20minutes or more due to complex systems and deep basins. The water temperatures oftenexceed 130F (54C). Both of these factors cause a rapid loss of ozone and the inability tomaintain effective ozone residuals without mult injection locations.

These cooling tower systems often have many heat exchangers, often with water on the shellside (WSS), and many use mild steel tubes that require very good corrosion protection with ratesof 0.5 mpy (orless corrosion and ~ pitting. Ths is attainable with standard chemical treatmentprograms and not with ozone.

Utility Fossil StationsThese (Figure 4) also are considered relatively poor candidates for effective ozone alone

use, but for different reasons. They can have moderate to high organic loading due to use ofuntreated raw makeup water that can contain relatively high organic loading, high suspendedsolids, and bioorganisms. These plants generally have a very long time per cycle, often in

49413

excess of 30 minutes. This is due to their large capacity versus the circulation rate. The watertemperatures are usually mild (1OOF(38C)or less) but can exceed 120F (49C). Generallythese conditions can result in very high or excessive and uneconomical ozone use, unlesschemicals such as bromide ion is present or added for improved bio-control.

UtilityNuclear Power StationsUtilitynuclear power stations (Figure 5) are also considered poor candidates for ozone alone

use for many of the same reasons as the fossil fuel stations. Yet, this depends upon the specificsite cooling water system design. Ifthe service water and condenser water are combined, ozoneuse is ineffective and not practical due to the presence of redundant safety-related service waterequipment that have little or no water flow during normal operation. This prevents ozone fromentering and effectively treating the system at cost effective dosages.

Steel MillsSteel mills (Figure 6) also are often generally very poor candidates for ozone alone use

since they are often quite similar to refinery/chelmical plant design/operation. They generallyutilize poor quality makeup water and encounter considerable atmospheric and processcontamination from dirt, dust, iron oxide, and sulfurous gases that cause an excess ozonedemand. These cooling tower systems generally are also very complex with jacketed cooling(water on shell side), multiple heat exchangers, long time per cycle due to large system volumeswith relatively low circulating rates, and water temperatures commonly exceeding 120F{490C).These are excess ozone consumers and thus prevent the effective use of ozone. Should theybe absent, ozone could be effective.

Light Manufacturing Industry Cooling SystemsThese often are similar to the HVACcooling systems (Figure 2) and can be good candidates

for ozone use. Ifdesign is more like refinery chemical plants, then there is excess ozonedemand or rapid ozone loss, these criteria would reduce the potential for successful ozone use.

A summary of ozone use versus industries is given in Table 1.

OZONE CONSUMERS

Ozone is not usually cost-effective when makeup water chemical oxygen demand (COD)levels are high (above 20 mg/1). This is due to easily ozone oxidizable organics. Ozone is such arapid reactant, that biomass hid-outin some heat exchangers may not be reached andcontrolled.

Another predictable ozone properly is temperature degradation. It is known that ozone isdestroyed more rapidly as the water temperature increases. A temperature of 130F (54C)causes rapid destruction. Recent evaluations of case histories indicate that even temperaturesof 100F(380C) are considered to be excessive and result in rapid ozone destruction.

Cooling Tower Contaminants/Sources/Ozone Consumers

- Makeup water - orgarlics/bio-organisms/ammonia/iron/manganeselswlfideslnitrites

- Atmospheric - organics/ammoniakxdfideskwlfurdioxide/bioorganisms

494/4

- System - oils/organics/iron/copper/galvanizing/plastics/filter media/wood and woodpreservatives

CASE HISTORY & OZONE RESULTS

Any water treatment performance evaluations must include sufficiently detailed techniques toprovide accLlrate, consistent data. They must include testing for corrosion, deposition, biological,and water quality as well as knowledge of the system metallurgy, operating characteristics, anddesign. AISCIacceptable system protection for each parameter must be established such ascorrosion rates, amount of deposition, etc. Certainly economic evaluations willdetermine therelativebenefitsandacceptanceofozoneversusalternatetreatmentprograms.

The followingcase histories provide effective detailed evaluations of ozone use in severalcooling water systems.

CASE HISTORY#1

System SpecificsThis HVACsystem provides a maximum design of 3000 tons (1) of refrigeration which serves

comfort and computer cooling requirements. It includes four cooling towers, two with 1000 Tcapacity each, and two with 500T each. The cooling towers operate as one system, with 2000 Tbeing the normal operating load and the remaining 1000 T as backup (see Figure 7).

Water vclume of the system is approximately 10,000 gallons. The water recirculation rate atmaximum normal operation is 6000 gpm. Thus, time per cycle is 1.66 minutes; very short. Insummer, the cooling towers receive maximum water temperature at 110F(440C) maximum andcool to 90F(320C), a 20F(-140C)At at top heat load. The system operates year round. Winterwater temperature, due to free cooling, is 45 to 50F(7 to 10C). Makeup is a very lowhardness and low alkalinity potable city water. I_hesource is clarified river water (see Table 11).

The reciprocating refrigeration machine condensers are fabricated with smooth copper tubes,mild steel tube sheets, and mild steel water boxes. Water is through tubes. The circulating linesare mild steel. Two cooling towers are wood with PVC film fill and two are fiberglass withceramic fill.

Prior to the use of ozone, the previous treatment was a conventional cooling towerformulation consisting of: a scale inhibitor (HEDP), a mild steel corrosion inhibitor (zinc), acopper corrosion inhibitor (TTA)and a dispersant (polyacrylate); with no pH control. The pH fellbetween 8.0 and 9.0 at 3-6 cycles (COC). Both a hydantoin (bromine release agent) and a non-oxidizing biocide (DBNPA)were used for microloiologicalcontrol.

The chemical treatment was monitored for one year, to obtain a base of performance beforethe ozone program was put into operation. Control of chemical feed and COC was erratic due tofluctuating c~peration and inadequate chemical teed equipment. The maximum number of COCobserved was six, as recommended by the supplier. Water treatment costs were about US$17,600 per year. Results were considered to be not good. They showed higher than desired

494{!5

(less than 3 mpy) mild steel corrosion rates of 6 to 9 mpy, with pitting and local attack; and onlyfair copper corrosion rates of 0.2 to 0.4 mpy (desired was 0.2 or less); also, some scale andmicrobiological deposits were occurring).

The ozone generator was of the corona discharge type, capable of producing 28 pounds ofozone per day from dry air. Normal ozone load was 35 to 40 percent of generator capacity. Theozone-air mixture was fed through diffusers in a six foot deep sump. Off-gas was drawn into thetower and expelled by the fans.

Corrosion MmitoringOnce be{iun, the ozone feed rate settled into providing a residual of 0.18 mg/1at the sump

pump. COC ranged initiallyfrom 6 to 8 (see Ta!oleIi). Corrosion rates in roils per year (mpy)over the first 15 months, as measured on 30 and 60 day coupons were:

MildSteel QQM2!2! 316 Stainless4.5 1.26 0.022.3 1.064,2 0.69 304 Stainless3.1 0.39 0.054.5 0.86 0.083.2 0.81 0.021.5 0,391.31.8 Admiralty Galvanized Steel2.2 0.26 0.262.2 0.603.1 0.354.44.5 90:10 Cu:Ni

0.10

While the corrosion rate values for mild steel coupons are not too alarming, the couponappearance was. Pits on all mild steel coupons during the 15 months that the system wasmonitored were too numerous to count. In many of the pits, a copper color could be seen, andcopper was confirmed by scanning electron microscope with X-ray probe. In some areas notpitted, the steel surface was copper plated. In some instances, the copper remained on the steeleven after slcid cleaning.

Copper and copper alloy coupons were often covered with a dark brown adherent coating.This was fir%assumed to be a patina similar to one that forms on weathered MonelTMmetal, andwhich might offer some corrosion protection. However, when immersed in acid for cleaning, ared precipitate formed from the brown coating which deposited as a powdery film on the coupon.Most of the film could be removed with a nylon brush. What remained gave all the copper andcopper alloy coupons darker appearance than a new coupon of the same material, and 9enerallydarker than-a coupon used in a chemically trea~ed closed system.

It was also observed that much of the metal loss on copper and copper alloyunder the coupon holder or the inert washer andior in the stamped numerals.

494/6

coupons was

Since crevice (or under-deposit) corrosion often is due to differential oxygen cells, ozonebeing a stronger oxidant than oxygen was likely to create a more potent differential oxidant cell.To study this possibility, a set of coupons was doubled up on the same holder: two mild steelcoupons, copper coupled with an Admiralty brass coupon, and 304 coupled with 316 stainless.Also a rubber band was wrapped tightly around two mild steel coupons to determine if excesscorrosion was occurring in crevices. The mild steel coupons were upstream of the copper andthe copper upstream of the stainless. Allwere left in the system for 82 days.

The two mild steel coupons had faced each other to form the crevice. Most of the corrosionwas where the edges touched. The corrosion rates for these two coupons were 4.4 and 4.5 mpy,higher than the average of the previous coupons.

The copper and Admiralty coupons bolted together to form a crevice, showed somediscoloration and a mild general etch. Corrosion rates were 0.39 and 0.35 mpy respectively.Mildsteel coupons from the ozone-treated system were red due to precipitated copper.

The results show that ozone is corrosive to copper and its alloys, and the dissolved coppercan then plate out on steel and set up a galvanic corrosion cell.

The stainless steel coupons were clean, and had excellent protection. Corrosion rates were0.02 mpy.

No indications of scale formation were observed anywhere in the system. Dirtywhiteparticles, like sand, were found in the tower basin. These analyzed as calcium carbonate,calcium silicate and silica. The water quality (Table Ii) shows that loss of calcium, silica, andalkalinity is occurring compared to the chloride Ie\rels.

There were no biological deposits in the system but the towers had some algae on areas thatare wet intermittently. The water was always crystal clear.

Results were considered acceptable with still a concern over the copper corrosion.

The cost ofelectricity for the operation of the air compressor and the ozone generator wasUS $2,066 for twelve months of operation.

CASE HISTORY #2

System SpecificsThis cooling system provides air conditioning on a college campus. It consists of two(2) 900

ton absorption refrigeration machines, of which only one is in use at a time. Condenser tubematerial is 95:5 copper/nickel. Tube sheets and water boxes are steel and all circulating pipingand valves are steel. Circulating pump housings are cast iron; impellers are bronze. Water isthrough tubes.

There are three 300 T cross-flow galvanized steel towers with stainless steel basins. Thethree basins are connected to a common suction (supply) header. The return water isproportioned to both ends of the three towers. System volume is estimated at 4,000 gallons.

4947

Maximum load is 900 T; circulation rate 2700 gpm. Thus, time per cycle is 1.5 minutes.Each tower has a capacity of 900 gpm. Cooling tcwer has film fillhoneycombed PVC; fanblades are aluminum. Desi~n AT~F) is 16, but can range from 14 to 23 in service. Maximumtemperatures were 95F (35 C).

The towers and the circulating piping are only two years old and were started up on ozone.However, the two absorption machines are nine years old. There was no previous treatment asthe chillers were originally on once-through river water. The condenser tubing was acid cleanedprior to ozone use.

The ozone generator has a capacity of six(6) pounds per day of ozone. At a circulation rateof 2700 gpm and fullgenerator capacity, the maximum dosage of ozone would be 0.185 mg/1,assuming complete dissolution. However, the povveron the generator was generally only 50percent of capacity. The dosage was therefore est[mated to be 0.09 to 0.10 mg/1of ozone,although this high a residual was never found. Oz.cmewas monitored for four (4) months andshowed less than 0.07 mg/1. The makeup water quality and system water quality is provided inTable Ill. This data shows COC of 4-18 depending upon the water ingredients.

MicriobioMonitoringTotal bacteria counts (dipslides) were 104to 1CIScolonies per ml; however, the water was

sparkling clear and there were no slime or algae deposits on any equipment.

Corrosion MonitoringCorrosion was monitored with coupons and a linear polarization corrosion rate monitor.

Corrosion rates in mpy over this period were:

MildSteel6.355.8624,154.387.077.22

Galvanized Steel4.98

Copper0.270.180.340.190.21

Admiralty0.350.51

304 Stainless 90:10 Cu/Ni0.08 0.13

316 Stainless 95:5 Cu/Ni0.10 0.13

The mild steel coupons looked very much like those in Case History #1. There was a deepgeneral etch throughout the surface of the coupon, almost a gouging effect. The corrosionmonitor reading was constant throughout the test at about 6 mpy and did not show the wideswings that the coupons showed.

494!8

Copper coupons had the same dark brown coa:ingas in Case #1, which released metalliccopper when cleaned with acid.

Copper/nickel coupons had lower corrosion rates than the average of copper coupons andAdmiralty. 304 and 316 stainless steel rates were excellent, Aluminum did very poorly; as didgalvanized steel.

The highest ozone reading obtained in the tower basins was 0.07 mg/1,with an average ofabout 0.05 mg/1. There was probably not enough contact time in this system for properdissolution. Return water on top of the towers generally contained zero ozone. It is interesting tonote that while this installation is operating at less than half the ozone residual as Case #1, theyare experiencing the same copper plating and pitting of mild steel. The water quality (Table Ill)shows that silica and some calcium is being lost based on chloride concentration.

Particles found in the basins analyzed as calcium carbonate, calcium silicate and corrosionproducts(iron and copper oxides). However, some scale in the cooling tower fillwas found withequipment (chiller) inspection showing only a thin coating of scale.

Treatment operations costs with ozone are calculated at US $3,000 for nine(9) months (fourmonths for the AC season, five months for computer cooling).

ADDITIONAL CASE HISTORIES

There have been additional case histories that have been reported earlier that have shownvery good corrosion control when ozone has been used alone. Investigation showed that variousinorganic mild steel corrosion inhibitors were present due to the ozone. One case history showedhigh nitrates (over 100 mg/1)due to inadequate drying of air. Another showed zinc levels above3 mg/1as a result of galvanized steel corrosion. inorganic, ozone compatible chemicals, such asmolybdates, phosphates, even chromates have been used for improved mild steel corrosioncontrol.

Several case histories have reported bromide addition with ozone to improve biologicalcontrol and the persistence of oxidant (bromine not ozone) in cooling tower systems.

CONCLUSIONS

These, and additional case histories have led us to the following conclusions for ozone use:

1. Ozone has effectively controlled the growth of biological organisms.2. Scale did not occur on heat exchange su[faces, even at higher cycles of

concentration than was possible on the same water with chemical treatment.3. Water analyses show that silica is lost mcwethan any other mineral.4. Calcium carbonate and calcium silicate precipitates occurred in the tower basin. Scale

also clccurred on tower filland in hot heat exchangers.5. Total alkalinity decreases due to decomposition and/or precipitation as carbonate.6. Chloride and sulfates cycle up linearly.7. Magnesium hardness is not removed and concentrates similar to chlorides and sulfates.8. Ozone treated cooling tower water is crystal clear.

9. Ozone residuals decrease rapidly from the injection point, are often zero at the return tothe tower and always lost through the cooling tower fill.

10. Ozone has caused high copper corrosion I-ates with copper plating on mild steelcoupons.

11. Ozone can cause high mild steel corrosion and pitting.12. Crevice and under-deposit corrosion is ac~elerated with ozone.

Ozone clearly is a bio-control chemical, if it can reach all areas of the cooling tower system.Corrosion of copper alloys is often excessive, while mild steel shows pitting and occasional highrates. Scale has occurred at higher temperatures but also in HVACsystems. Ozone is totallyunpredictable for scale control. Scale can be conirolled by water softening. Ozone applicationsrequire much Imorestudy to determine how it can be used most cost-effectively without creatingother serious problems. However, ozone does appear to offer some major advantages overstandard chemical treatments, principally better microbiological control. Cost effectiveness issite specific and should utilize the economic evaluation guidelines presented in an earlier paper.

Ozone use in cooling tower systems usually can be predictable depending upon the specificindustry conditions found. Ozone is not a panacea as a stand-alone treatment in most cases,but can be under the right conditions. Ozone use with compatible chemical treatments is morecommon toda!yversus earlier ozone-alone applications. The chemicals most often utilized arebromides, to produce bromine for improved bio-;ontrol; phosphates, molybdates, and zinc saltsfor improved corrosion control; resistant polymers for scale control (or use of softened or reverseosmosis makeup water), Ozone applicability depends upon specific criteria that must beevaluated prior to its consideration or use. (Table IV). Acceptable corrosion performance may besimilar to standard chemical treatments. (Table VI It is extremely critical to have adequatemonitoring toclls in place to evaluate its performance. They should provide results rapidly,before system damage occurs and include all effective monitoring parameters as shown in TableV!. Ozone has a place today in cooling tower sys[em protection, and likelywillhave a greaterconsideration as well as use when a better understanding of its mechanisms is developed andwhen a uniform method is used to evaluate its co:st effectiveness.

GUIDELINESFOR OZONE USE

The followingguidelines for ozone use are based on the case histories that have beenanalyzed and evaluated. These guidelines are sysitem specific:

l Ozone as a standalone treatment is dependent upon waterquality, system design, and operation. It is not applicable in manycooling tower systems.

l Ozone is not effective with high c~rganicloading.l Ozone is generally ineffective or unpredictable as to scale control or as a scale

control agent or inhibitor.l Ozone causes copper alloy corrosion and often mild steel pitting.l Ozone may not be effective for bio-control throughout entire

cooling system.

49410

REFERENCES

M.F. Humphrey and R.F. French, Cooling Tower WaterConditioning Study, Jet Propulsion Lab.Publication 79-104, 15 Dec. 1979, JPL, Pasadena, California.

Baldwin, L.L.et al, The Investigation and Applicaiion of Ozone for Cooling Water Treatment,IWC-85-36.

W.K. McGrane, Ozone and Reverse Osmosis, Cclrrosion 93, Paper 483,

P.A. Burda, et al, Performance and Mechanisms of Cooling Tower Treatment by Ozone,Corrosion 93, !Paper488

D. MillerFielclTesting of Cooling Tower and Hea: Exchanger Performance Before and AfterInstallation of an Ozone Water Treatment System, Reports ##161-90.18,461-91.4, PG&E,Technical and Ecological Services, Sept. 1990.

R.C. Schwartz, Field Study - Ozonation of HVACRecirculating Water,IWC-92-53.

D.J. Tierney, EiS. Feeney, R.A. Mott, Performance Evaluation of Ozone Cooling WaterTreatment at t(ennedy Space Center:, IWC-95-46.

P.R. Puckorius, Dileep Thatte, Economics of Ozone Application in Cooling Water Systems,NACE, Corrosion 94, Paper 472.

Puckorius, P.R.; J. Maxey Brooke, Ozone For Cc~olingTower Systems - Is It a Panacea?,NACEAnnual Conference, March 1991.

R.G. Rice, J.F. Wilkes, BiocidalAspects of Ozone for Cooling Water Treatment- ProbableImpacts of Bromide IonCTI 92, Tech Paper TP-92-07.

R.T. Hess, D. Puckorius, P.R. Puckorius, Polymws in Cooling Water, Industrial WaterTreatment, March 1992.

R.G. Rice, Byproducts of Ozonation Formed During Treatment of Water, Corrosion 93, Paper479.

494111

TA%LE 1. APPLICABILITY OF C)ZONE veins INDUSTRY

Industyv

HVAC

Oil RefineriesL

Chemical Plants

Utilities - Fossil

Utilities - Nuclear

Steel Mills

Light ManufacturingJ?

Ozone Applicability

Good

Very Poor

Vew Poor

Poor

Vem Poor

Poor

Good

494/1 3

. .._--L_-l __ ....-.-1-.. ..__ 1-..... .---- .-1-------- L ------------ _.-.~.-~-_.__ -.-._

-------CASE HISTORY#2 - DURING INITIALOZONE USE:y:7=-----TA~T7;---~--------7---T

---j ------ -- --------- -------- --------- --+-----------..._ ._ ___ . . ___ ....___

- :p~r:=:-----

.-.---....

. 1I - ~==----

_-

ParameterE

I 1- --------.

:i : g;~;:n::

_

. . .-

l.. ._. _ _______ . ______

--1----------- -------- ---- .N;A- ---~ -:---- -------- ----------..-.-.__.I,__: ------ ::-_-:_T::-.:I:_. - ___ ;,_.._. ___

--.-:_.l:_

:;a$:,=:~=;:;:::+::~::]_j;::.

-1-44- -------- -N[A- ------- -------- -------

E::?F:~;$~:~$:~::

~

~ , __ ---32 .. .. _________._____..ioo

. l-_._._-.. ._-. ---- ..- ______ _ ~:g _ . .-. ---- ~TA..... .. .... -- .-..-.. ,.Nitrate as NOS__._~J_--_____

Trace

1

_. ...

Iron, Ferrous---,_---- O!:.._.

- t: l-----~---=f

...

.-. +._. ..> . ---

:: !Q~~.lrX2!2 .~....

;;~~{+=: f+:i:;l;:i-==E:;-

Copper, total, in solut

&Zs~i;

_ ---,::----;:j:,~;:z~:~=~;=~;=-:-

;Z:::~j:----[~3=-l=-l~~~~~~

...--.-+. ..-.-. --------- -------- ___ _____

--:!=!----[-------=-..--. - 1.. --._-\-.._--._. _ .. . . . ... . . .. ... .. .... . .~ _-__--:

49L/14

1.

2.

3.

4.

Ieiu l-i-. Iv

COOLING TOWER SYSTEMS

CRITERIA DETRIMENTAL TO

Ozone Consumers

ECONOMICAL OZONE USE

u Makeup water organics/iron/manganese/ammonia/bio-organisms

n Atmospheric organics/amrnonia/sulf ides/sulfur dioxide

- Process/organics/ammonia/sulfides

Retention Time: Time/Cycle = Capacity/Recirculating Rate

u Over ten (1 O) minutes

Large Water Use

D Over 1 million gallons per day

Temperature

- Over 11 OF

49415

TABL.E VACCEPTABLE CORROSION RATES (MPY)

Heat Exchanger Tubes NAS 0.5 MPY or less

Heat Exchanger Tubes (: u 0.2 MPY or less

Heat Exchanger Tubes sa 0.2 MPY or less

Lines MS 3-5MPY

All Cases -- no pitting

MPY = roils per year; MS = mild steel;CU = copper alloy; SS = Stainless Steel

494/16

TABLE VIEFFECTIVE MONITORING OF OZONE

EFECTIVENES:S REQUIRES:

. Detailed Water Analyses

. Rapid Corrosion Monitoring

. Deposition Monitoring

. Bio-Monitoring

. Ozone & ORP Analyses in SpecificLocations of System

. Equipment Inspection

494/1 7

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