A Technical Paper:

Oxistop CoatingsFor Boiler Tube Maintenance

Prepared for the:

INTERNATIONAL CONFERENCEOn Advances in Condition and Remaining Life

Assessment for Fossil Power Plants

October 16 – 18, 2006Louisville, Kentucky

T. E. BATTON - PRESIDENT

OXISTOP, LLC, 6331 MARKET STREET, BOARDMAN, OHIO USA 44512

Technical Paper:Oxistop CoatingsFor Boiler TubeMaintenance

Prepared for the:

INTERNATIONAL CONFERENCE:On Advances in Condition and RemainingLife Assessment for Fossil Power Plants

October 16 – 18, 2006Louisville, Kentucky

The authorsTim E. BattonPresident and Senior Managing Partner

Al BraceyDirector of Materials and Installation

6331 Market StreetBoardman, Ohio USA 44512

Electronic accessThis technical paper, and other Oxistoparchives are available for download atwww.oxistop.com.

IntroductionOXISTOP, LLC, an Ohio based LimitedLiability Company, is the sole distributorand applicator of the Oxistop line of ceramiccoatings developed specifically for the fossilfuel power generation and traditionalrefractory markets. Both markets currentlyexperience failure and high maintenancecosts related to maintaining key componentsof production.

Power generated from fossil fuel combustionrelies on boiler tube integrity. Boiler tubefailure can be related to the destructivenature of slag, oxidation, corrosion, erosionand abrasion. These issues are becomingincreasingly important due to the worldwidedemand for more power and operationalcontrols related to emissions regulations.

At a fraction of the cost of currentalternatives, the Oxistop line of coatingmaterials has been proven to stop orminimize the damage caused by thesedestructive conditions. As an added benefitof utilizing these materials, boiler tubescoated with Oxistop coatings will maintainoptimum heat transfer into boiler waterwall tubes by replacing the iron oxideprotective (and insulating) layer and residuebuild-up that occurs when boiler tubes aresubjected to high heat and coal combustionwith a ceramic based protective barrier.This protective barrier will resist slagbuildup that will also decrease heat transferthrough the boiler tube.

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© 2006, OXISTOP, LLC, 6331 MARKET STREET, BOARDMAN, OHIO USA 44512,WWW.OXISTOP.COM. © 2006, PARKSDESIGN (LAYOUT AND DESIGN)

History and useOxistop, LLC was formed in the spring of2004 by a number of partners with extensivepower generation maintenance problemsolving experience. The company is theexclusive distributor and installer of Oxistopcoatings and to date, over 30,000 Sq. Ft. ofour coating has been installed nationwide.

As a result of successful early trialapplications and high interest in theindustry in cost effective solutions tomaintenance issues pertaining to boilerreliability, many repeat orders have resultedfrom over sixty (60) initial applications intwenty-three (23) different states.

The ability of Oxistop high temperaturemetal coatings to reduce both slag andresidue buildup, stop corrosion and oxidationand resist fly ash erosion and abrasion hasled our client base to evaluate benefitregarding issues in the following areas:

•BURNERS AND OVER FIRED AIRPORTS —SLAG AND CORROSION.

•REFRACTORY DOORS AND BURNERREFRACTORY — SLAG

•ECONOMIZER TUBES – CORROSION AND EROSION

•TUBE SHIELDS AND DUCT SUPPORTS – CORROSION ANDEROSION

•NOSE AND SLOPE AREAS – CORROSION AND SLAG

•WATERWALL AREAS – CORROSION, SLAG ANDHEAT TRANSFER

•SUPERHEAT AND REHEAT TUBES – FOULING ANDHEAT TRANSFER

To date, the types of coals and operationshave had little affect on the success incoating material performance. Whether itis eastern or foreign coals, 100% PowderRiver Basin (PRB) or any blend combination,the materials perform equally well.This is not to say that Oxistop coatingscannot be “tailor made” to meet specificcustomer needs.

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TOTAL: 31,083 (PSF)

(20.4%)

(16.8%)

(7.5%)

(2.8%)

(32.4%)

(13.1%)

(3.8%)

(2.4%)

(0.9%)

WATERWALL

BURNER

OF AIR PORT

SLOPE

PENDANT

REFRAC

PLATEN

ECONOM

TEST COUPONS

Oxistop Coating Analysis(Per Square Foot)

(32.4%)WATERWALLTOTAL: 10,081 (PSF)

(20.4%)BURNERTOTAL: 6,328 (PSF)

(16.8%)AIR PORTTOTAL: 5,225 (PSF)

(13.1%)SLOPETOTAL: 4,076 (PSF)

(7.5%)PENDANTTOTAL: 2,334 (PSF)

(3.8%)REFRACTOTAL: 1,179 (PSF)

(2.8%)PLATENTOTAL: 859 (PSF)

(2.4%)ECONOMTOTAL: 729 (PSF)

(0.9%)TEST COUPONSTOTAL: 272 (PSF)

Advantages of oxistopcoatings on metalThe advantages of Oxistop coatingscompared to other coatings are a history ofproven performance in the circulatingfluidized bed boiler (CFB) industry for overfifteen (15) years. This material wasenhanced and refined for specificapplications in the mainstream pulverizedcoal market in October of 2004. Comparedto metallic coatings such as thermal sprayor weld overlay, the advantages include notaltering the integrity of the tube itself,thereby preventing or hindering futurerepair work to the tubes as the thermalspray and overlay process will. Stress is notput on the tubes as with an overlay process;in fact Oxistop coatings will improve heatdistribution. Oxistop coatings can beremoved by grit blasting or grinding ifrequired. Whereas thermal spray andoverlay will reduce heat transfer, Oxistopcoatings will enhance this process.

Oxistop Coatings Will:•Reduce the oxidation of metals at high temperatures.

•Improve the temperature uniformity of boilerwaterwall tubes.

•Reduce the abrasive wear of fly ash on boiler tubes.

•Reduce the buildup of combustion by-products inpulverized coal burning boilers.

•Improve heat transfer into boiler waterwall tubes.

•Demonstrate excellent corrosion and acid resistance athigh temperatures.

Oxistop coatings are installed 3 to 6 Milsthick and will not crack due to expansionand contraction of the metal substrate.They can be used in conjunction withthermal spray technology, which will providea cost effective package and act as a sealerfor specific and severe applications wherethe attributes of both, in combination, arean advantage.

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10,011

2,242

19,045

29,678

0

5000

10000

15000

20000

25000

30000

EROSIONTOTAL

HEAT TRANSFERTOTAL:

SLAG TOTAL

CORROSION TOTAL

Issues Addressed:

(48.7%)SLAG TOTAL:29,678 (PSF)

(31.2%)CORROSION TOTAL:19,045 (PSF)

(16.4%)HEAT TRANSFERTOTAL: 10,011 (PSF)

(3.7%)EROSION TOTAL:2,242 (PSF)

Oxistop Coating Analysis(Per Square Foot)

Case studiesAlthough boiler runs between plannedoutages of 12–36 months make evaluationof oxistop coating trials time consuming, anumber of repeat applications have beenseen based on favorable observations andmeasurable data. Examples are as follows:

Case study number one

In June of 2004, the first trial of OxistopMC-19-GR coating was installed in a 100MW boiler burning eastern bituminous coal.A waterwall test area of approximately 120square feet and two (2) burners of a sixteen-burner wall were selected to evaluate slag-shedding capabilities of the coating. Row

“B” burners were identified and coated aseyebrow slagging was heaviest a that level.Economizer tubes were also coated toeliminate corrosion occurrence between tubeshields and the tubes.

After one year of boiler operation, the coatedburners developed no eyebrows and were

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Based on successful trial on MC-19-GR after one year, entireburner wall coated. Note refractory (gray) coating.

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slag free. During a planned outage in Juneof 2005 the coating material was found to bein-tack and continues to be in operation andperforming into year three. As a result of thisperformance, the entire burner wall wascoated (16 burners) and has continued toprovide to date slag shedding benefits, inaddition to corrosion and erosion wearprotection. Oxistop a GY-30 RefractoryCoating was utilized to provide a slag sheddingprotective barrier to the burner refractory.Also coated were additional waterwall areas,for slagging and corrosion, and the undersideof the upper slope to eliminate clinker buildup.

Case study number two

Oxistop, Year Two:A Case StudyIn April of 2006, Oxistop installed MC-19-GR coating on a 192 MW boiler burning100% PRB coal. Oxistop prepared by gritblast and coated less than half of the maincombustion area and most of the radiantzone of the reheat furnace from below theburners to above the overfired air ports.This totaled a little over 5,500 square feet.The application was comfortably completedin the time allotted.�

After approximately twelve days of base lineinformation compiled in March, thepreliminary data verified that the applicationof Oxistop coating enhanced heat transferin the coated area resulting in an increasein boiler steam output of 5-7 MW. The FEGT(Furnace Exit Gas Temperature) hasdecreased by 75 degrees. All this has beenaccomplished burning slightly less coal. Thewaterwall tubes are cleaner and protected

Slag shedding off burner wall coated withOxistop MC-19-GR

from fly ash erosion, corrosion, slag, andwater cannon damage.� Payback for the costof the Oxistop coating application was 24days. Continual monitoring verifies heattransfer data indicating power outputincrease remaining constant after more thanfive months on-line as a result of the Oxistopcoating application.

The Owner states the following:�

1) The water cannon usage in this areais significantly lower.

�

2) The cordial thermocouple rateof delta-t is notably slower and,more significantly, stabilizes at alower number.

�

3) The furnace exit gas temperaturesof the reheat box are belowhistorical data.

�

4)� High temp RH and low temp SHthermocouples are belowhistorical data.

�

5) Decrease in air heater outlet gastemperature.

�

6) Lower fuel usage eliminating overfiring to make steaming rate.

�

7) Maximum megawatt output isincreased to198 Mega Watts, with slightly lesscoal burned.

A subsequent application of 5,520 squarefeet is scheduled for installation in thesuperheat boiler in the fall of 2006 basedon impressive results of the spring trial.Similar benefits are anticipated.

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45’

REHEAT FURNACE – 192 MW BOILER

45’

Refractory coating applicationsUtilized primarily around burners andrefractory lined manway doors, OxistopGY-30 is a 3,000°F coating material designedto give refractory substrates similar slagshedding characteristics to the Oxistopmetal coating.

Recently, Oxistop has developed a systemusing an unique refractory material thatchemically sets without heat and allows theOxistop GY-30 coating to remain completelybonded after initial refractory curing. Thisis important during outages where time isof the essence and a “one step” package isrequired to address refractory repairs aswell as the slag protection being sought.As a result of packaging the coating withthis impressive material, GY-30 saleshave accelerated.

LimitationsOxistop MC-19-GR is a high temperature,corrosion resistant material that is usedon waterwall and related tube apparatus,such as superheat and reheat tubes wherethe range of steam temperatures are notlimiting factors.

It had been used in conjunction with theCFB power industry, beginning inapproximately 1990, to minimize fly asherosion, which approximates a lowgrade sandblasting affect. When the erosionresistance limits of the ceramic coating arereached, thermal spray technology has beenused as a base and packaged with ceramiccoating to attain excellent results.

The non-catalytic nature of Oxistop coatingsprovides a protective barrier that preventsthe reaction of combustion by-productadherence to boiler tubes. Upper slope areasand wing-wall tubes are some areas thathave demonstrated the limits to Oxistopcoatings in overcoming slag accumulationdue to boiler design issues. On low angleupper slopes, gravity and gas flow patternscan overcome the advantages of this non-catalytic feature and allow for slag to remaina problem. Some wing wall designs thathave small gaps between the tubes whensurrounded by combustion by-product gasflow streams, allow for slag to bond to itselfbetween the coated tubes to create the basefor clinker formation. Coating of these tubes,in this case has shown to have little effecton clinker formation.

Even with these observed limitations, slagresistance of Oxistop coatings has beenreadily demonstrated around burners, overfired airports, on waterwalls, superheat andreheat platen and pendant tubes and theundersides of slope areas. Corrosion, tubewastage and erosion continue to beminimized and in many cases, eliminatedby the coating. However, in that thesematerials rely on an initial heat curing forbonding and strengths, care must be givenwhen the practice of washing downscaffolding after an outage is used. Afterair-drying and before the heat set the coatingwill revert back to a wetted state if exposedto water. After initial heat curing the coatingbecomes resistant to all acids, salts, solvents,water, and alkalies.

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Soot blower type, velocity and particulatepickup during operation, all are mitigatingfactors regarding eventual wearing ofOxistop coating around soot blowers.Although defining the limits of ceramiccoating are inconclusive and ongoing inregards to durability in these areas, thermalspray coating is a proven solution tothis problem when combined with theOxistop coating.

Given the range and severity of maintenanceissues regarding tube integrity and boilerreliability—overlay technology has, and willremain an option for restoring lost tube wallthickness. Oxistop coatings have beenintroduced to the power industry to expandthe range of options for tube maintenancepractices with additional benefits, includingcost effectiveness.

ConclusionAt a cost of approximately one tenth of weldoverlay, the industry interest continues toclimb regarding both the Oxistop brand ofmetal and refractory coatings. While notmarketed or seen as a cure-all, Oxistopcoatings do provide proven alternatives andoptions to current practices pertaining tohigh cost maintenance as well as boilerreliability issues. Oxistop coatings are userfriendly due to the fact that they are non-toxic, air drying and quickly applied. Curingof the material is accomplished during boilerstart-up with no holds or separate heatingrequirements. Consequently, other repairwork in the boiler may continue during theinstallation process. Expanded use of Oxistopcoatings will reduce maintenance costs andincrease boiler efficiency and reliability over

time. Durability has been demonstrated ininitial Oxistop coating trials, beginning in2004. Each subsequent application hasshown staying power, in many casesoutage-to-outage, and continued effectiveperformance to date.

*ADDITIONAL PICTURES, PRODUCT INFORMATION ANDUSE CAN BE OBTAINED BY ACCESSING THE OXISTOPWEBSITE AT OXISTOP.COM. REFERENCE ARE AVAILABLEUPON REQUEST.

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The authorsTim E. BattonPresident and Senior Managing Partner

Al BraceyDirector of Materials and Installation

6331 Market StreetBoardman, Ohio USA 44512

Electronic accessThis technical paper, and other Oxistoparchives are available for download atwww.oxistop.com.

© 2006, OXISTOP, LLC, 6331 MARKET STREET, BOARDMAN, OHIO USA 44512,WWW.OXISTOP.COM. © 2006, PARKSDESIGN (LAYOUT AND DESIGN)