TDF-042 - Tire Derived Fuel, An Environmentally Friendly Resource

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T A G .RESOURCE RECOVERY

TIRE DERIVED FUEL:

AN ENVIRONMENTALLY FRIENDLY RESOURCE

Presented by

Terry Gray

T.A.G. Resource Recovery

Presented at

Rubber Recycling Symposium

in conjunction with the

74th Annual Meeting of the Rubber Association of Canada

Toronto, Ontario

March 3, 1994

18038 RADWORTHY DRIVE * SUITE ! 0 ' OUSTON,M 77084 PHO NE: (713) 463-7552



TIRE DERIVED FUEL:

AN ENVIRONMENTALLY FRIENDLY RESOURCE

PERSPECTIVE

Modern man has slowly awakened to the limitations of hisglobal resources and environment. We are recognizing theimportance of conserving natural resources through optimum

utilization, including minimizing and reusing resources containedin materials previously considered to be "wastes". We are alsorecognizing that our air and aquatic environments have limitedabilities to absorb abuse. In an ideal world, we would endlessly

recover and reuse all resources - and we would do so withoutdetrimental impact upon our environment.

Although most of us agree with this ideal objective, we havesignificant differences of opinion about practical compromisesrequired in today's real world. Some are unwilling to support anysteps other than one giant step into the ideal scenario for fearthat interim compromises will prevent achievement of the ultimateobjective. Others recognize the value of resources conservedthrough interim steps and believe that these steps contribute tothe evolution of even greater conservation gains.

This debate has impacted virtually all "waste" materials,

including scrap tires. Tires represent a significant resource.Ideally, a tire's polymerized rubber mixture would be perpetuallyreused. However, today's applications for this material arecapable of consuming only about 10% of the waste tires generatedannually in North America. These markets are growing, but even themost optimistic projections show markets for less than 40% in 5years.

Should the remainder of this resource be squandered throughlandfilling? Should it become a public liability and health hazardthrough stockpiling in hopes that market limitations willmiraculously disappear sometime in the future? Or should it beutilized as an energy resource on an interim basis until higher

value uses are developed? Since no one consciously wants to wastea potentially valuable resource, the answer should depend solelyupon its compatibility with our environment. Avoiding unnecessaryconsumption of natural resources through alternative use of wastetires is a worthwhile objective if it can be done without acounter-balancing negative impact on our environment. As a result,it is appropriate to examine the chemical characteristics of tires

and their historical environmental experience as an energyresource.



CHEMICAL CHARACTERISTICS OF SCRAP TIRES

The chemical characteristics of any energy resource impact itsenvironmental acceptability. Tires are a hydrocarbon-based

material derived from oil and gas. Some inorganic materials areadded to enhance reactions or performance properties. Tires havea heat content of 14,000 to 15,5 00 Btu/pound, depending on the typeof tire and degree of wire removal. By comparison, importedeastern coal that would be displaced by use of tires in Ontariotypically contains 11,500 to 13,000 Btu/pound.

The composition of tires and coal vary depending on type andsource. However, Exhibit 1 provides representative proximate andultimate (elemental) analyses of tires (with and without bead wire)and a bituminous eastern coal similar to that commonly importedinto Ontario.

A comparison of the proximate analyses indicates that tiresoffer efficiency advantages versus coal. For instance, tiresgenerally have a lower moisture content than coal. Since theenergy required to heat and vaporize inherent water is generallynon-recoverable in the energy conversion process, lower moisturecontent can translate into higher energy utilization efficiency.The lower ash content of TDF without wire offers a similaradvantage. Atire's higher volatile-to-fixed carbon ratio enhancesits ability to combust rapidly and completely. Based on proximateanalysis, tires compare favorably to coal as an energy source.

Based on ultimate analysis, tires offer some additionaladvantages. Their lower sulfur content (especially in terms of

pounds/million Btu) offers the potential advantage of decreasingSox emissions compared to many eastern coals. Their lower carbon-to-hydrogen ratio can theoretically reduce carbon dioxidegeneration since hydrogen converts to water in the combustionprocess. Lower inherent nitrogen content could marginally decreaseNOx emissions. The chlorine content of tires is higher than thisspecific example, but it is comparable to many coals.

Elemental ash analysis provided i n Exhibit 2 indicates thattires generally contain metal concentrations comparable to , orlower than, coal with one notable exception. Zinc oxide is addedto tires as part of the rubber vulcanization process at levelsapproaching 1.0 - 1.5% by weight. Therefore, zinc levels in tiresare much higher than coal. As a result, applications using tiresas an energy resource must be able to control zinc emissions toavoid a negative environmental impact.

From a chemical standpoint, tires offer both environmentaladvantages and disadvantages versus coal. Therefore, tires must beused in applications that utilize their advantages and properlycontrol their disadvantages for them to provide a valuable andenvironmentally-friendly energy resource.



EXHIBIT 1COMPARATIVE CHEMICAL CHARACTERISTICS

CHARACTERISTIC

MOISTURE

ASH

VOLATILE

FIXED CARBON

TIRESW/WIRE

--t TOTAL 1 1 0 0 . 0 0 1 0 0 . 0 0 1 0 0 . 0 0

CHARACTERISTIC

CARBON

HYDROGEN

NITROGEN

SULFUR

ASH

CHLORINE

MOISTURE

OXYGEN (DIFF)

TOTAL

COALTIRESW/WIRE

TDFW/O WIRE

7 2 . 2 5

6 . 7 4

0 . 3 6

1 . 2 3

8 . 7 4

0 . 0 9

1 . 0 2

9 . 6 7

1 0 0 . 0 0

Source: Babcock and Wilcox

3



EXHIBIT 2

ELEMENTAL ASH ANALYSIS (% , OXIDE FORM)

ELEMENT (OXIDE)

ALUMINUM

CALCIUM

IRON

MAGNESIUM

PHOSPHORUS

POTASSIUM

TITANIUM

SILICONE

SODIUM

SULFUR

ZINC

METAL

TOTAL

TIRESCOAL I W/WIRE

TDFW/O WIRE

NOTE: ALL OTHER ELEMENTS LESS THAN 0.10%

SOURCE: BABCOCK AND WILCOX



HISTORICAL ENVIRONMENTAL PERFORMANCE

Backcrround

Scrap tires have been utilized as a supplemental energy sourcein Japan, Europe and the United States since the 1970s. Theexperience base has increased significantly during the last 10years as tires have been recognized as an acceptable fuel for somecombustion processes. Applications using scrap tires havebroadened to include cement kilns, industrial boilers,traditionally-conservative utilities and dedicated electricalgeneration facilities. The following discussion provides examplesof demonstrated environmental performance for major applications.

Pulp and Paper Industry

The pulp and paper industry combusts bark and waste wood instoker-fired boilers to provide steam and power required forprocessing operations. Wood is combusted on moving grates thatalso transport residual ash from the boiler. Coal, oil or gas canbe fired into the boiler above the grate to enhance combustion andmaintain operating temperatures, especially when wood moisturecontent is high.

This application utilizes tire derived fuel (TDF) obtained by

processing scrap tires into uniform, flowable chips generally about2 inches by 2 inches in size. Bead wire is often removedmagnetically to avoid fouling of grates and ash handling systems.TDF can be introduced separately or as an integral part of the woodmixture with relatively simple, inexpensive metering systems.TDF'S high volatile component enhances combustion of wood on thegrate and improves fuel efficiency, especially when the wood iswet.

The environmental impact associated with use of TDF in thisapplication is dependent upon characteristics of the displacedfossil fuel and system environmental control equipment. The twopredominant factors controlling environmental acceptability are SOX

and particulate (zinc oxide) emissions. SOX emissions may decreaseif TDF displaces coal with ahigher sulfur content. Alternatively,Sox can be controlled by scrubbers present in some systems,especially if the scrubbers operate at a neutral or basic pH.Particulate emissions can be controlled by electrostaticprecipitators (ESPs) or baghouses. In general, the mostenvironmental 1 acceptable applications occur when coal isdisplaced in systems with baghouses or ESPs.



Based on review of available information, more than 10 U.S.paper mills are currently using significant quantities of TDF incompliance with applicable regulations, with others undergoing

testing. The Champion facility in Bucksport, Maine has been one ofthe largest users of TDF since 1990. Their boiler is capable ofconsuming up to 3.5 tons of TDF per hour (14.5% by heat input) toproduce almost 500,000 pounds of steam per hour. In fact, somewaste tires now exported from Ontario are reportedly processed foruse at this mill.

Exhibit 3 provides environmental data associated withperformance testing conducted at this site in 1989. A baselinetest was conducted using their normal mixture of gas, bark, coaland sludge. TDF was then substituted for coal at levelsrepresenting 6.3%, 10.3%, and 14.5% of heat input. At the maximumTDF level, NOx, SOX and total hydrocarbon emissions remainedvirtually unchanged, while particulate matter increased 6%. Amongthe metals, beryllium and chromium decreased, lead remained belowdetection limits and cadmium increased. Zinc increasedsignificantly percentage-wise, but total quantities remainedacceptable. Overall particulate emissions remained well withinacceptable limits.

Performance data has also confirmed environmentalacceptability of TDF in similar paper mills and industrial boilersin at least Oregon, Washington, California, Illinois, Georgia andSouth Carolina. Several of these states are recognized for theirenvironmental sensitivity and rigorous regulatory enforcement.However, these applications must be carefully screened to definefacilities capable of using TDF within environmentally acceptablelimits. Only a small percentage of industrial boilers have therequired combination of system design and fuel usage conducive toappropriate TDF usage.

Public Utility Boilers

Canada and the United States have executed agreements designedto reduce the impact of acid rain through mandatory reductions inSox emissions. Major coal-fired utilities using midwestern andeastern coals are under intense pressure to achieve mandatoryreductions at minimal cost to their customers. They are faced withpurchasing expensive low-sulfur coal or making substantial capitalinvestments in additional air pollution control equipment. As adirect result, conservative utilities have begun to recognize the

potential value of TDF as an alternative fuel with a lower sulfurcontent than local coal. Use of TDF offers an opportunity toconcurrently reduce both SOX emissions and fuel costs, whileproviding a partial solution to historical scrap tire disposal andstockpiling problems.



EXHIBIT 3

COMPARATIVE EMISSIONS FROM

CHAMPION INTERNATIONAL MILL AT BUCKSPORT, MA INE

(EXPRESSED AS LB/MM BTU)

CRITERIA BASELINE

NOx

SOX

PARTICULATE

TOTAL HYDRO.

BERYLLIUM

CADMIUM

CHROMIUM

LEAD

ZINC

14%.% TDF(BY HEAT)

PERCENTCHANGE



Over one million whole tires are being utilized annually atOhio Edison's wet bottom boiler in Toronto, Ohio. The company hasconducted comprehensive environmental tests at incremental tire

utilization rates up to 20% of heat input, as summarized in Exhibit4. In this case, SOX emissions increased slightly compared to thecoal being used at the time, but NOx and particulate decreasedsignificantly. Analysis of bottom ash transport water showed noincrease in dissolved or total metals. The facility operates infull compliance with applicable regulations

TDF is also being used in cyclone boilers with rapidlyincreasing interest. Pulverized coal is introduced tangentiallyinto a large cylindrical chamber and combusted, with ash fallinginto a wet collection system at the bottom. TDF must generallymeet stringent size restrictions (1 inch by 1 inch or less) toallow complete combustion in suspension. This size also enhances

TDF movement through coal handling systems.

Otter Tail Power Company has been using up to 30,000 tons ofTDF per year at its plant in Big Stone, South Dakota. Usage couldpotentially reach 100,000 tons/year if high-quality TDF can beobtained at cost-effective pricing. TDF has reportedly proven toenhance combustion control and efficiency when added to theirprimary low-Btu lignite fuel. The facility operates in compliancewith all applicable regulations, but detailed data was notavailable.

Wisconsin Power and Light has conducted extensive tests usingTDF as a supplemental fuel in its cyclone boiler at Beloit. The

system has an ESP for particulate control. Comparative criteriapollutant data is also provided in Exhibit 4. Particulate, SOX,hydrochloric acid and hydrofluoric acid concentrations decreasedwith use of 7% TDF. However, NOx, CO and hydrocarbons increased,but remained within applicable permit limits. WP&L has constructedits own TDF processing facility based on economics and supplyconsiderations, but the purchased system has had difficultyachieving production expectations.

In addition to these examples, TVA and Illinois Power haveconducted extensive trials in their cyclone boilers, and at least5 other utilities have tested TDF in various boiler designs andfuel mixtures. Tires have even been used as a primary fuel in

dedicated, specially designed power boilers in California andConnecticut using 5 million and 10 million tires per year,respectively. After some initial difficulties associated withscale up of this technology, these facilities have reportedlyoperated in compliance with strict new-source performance criteria.



EXHIBIT 4

COMPARATIVE EMISSIONS FROM A CYCLONE BOILER

WISCONSIN POWER AND LIGHT

COMPARATIVE EMISSIONS FROM A WET BOTTOM POWER BOILER

OHIO EDISON'S TORONTO, OHIO FACILITY

(EXPRESSED AS LBS/MM BTU)

CRITERIA

CRITERIA

SOX

NOx

PARTIC.

LEAD

PARTICULATE( LB/MMBTU

SOX ( LBIMMBTU)

NOx (LB/MMBTU)

CO (LB/HR)

HYDROCARBONS

(LB/HR)

HCL (LB/HR)

HF (LB/HR)

BASELINE

BASELINE

5.30

0.601

0.0631

0.0963 E-3

7% TDF CHANGE % )

10% TIRES

5.71

0.436

0 .0564

0.0963 E-3

20% TIRES

5.34

0.387

0.0453

0.0912 E-3



Cement Kilns

Scrap tires have been used as a supplemental fuel in cementkilns in Europe and Japan since the 1970s and currently representa rapidly growing application in North America. Only CalvarasCement in California consumed waste tires 7 - 8 years ago, but morethan 10 kilns currently use whole tires or TDF as a supplementalenergy source. Many others are conducting performance teststargeted at future use.

Previous presentations have covered details of cementmanufacture and kiln operation. However, some factors impactingcurrent interest in scrap tires as a supplemental energy sourcedeserve mention:

Losistics-

Kilns are typically located near market populationcenters with large waste tire quantities and difficult tiredisposal problems, providing efficient logistics.

Energy Intensity - Kilns are energy intensive, allowing consumptionof 500,000 - 1,500,000 million tires/year/kiln. Fossil fuelsavings can provide a competitive economic advantage.

Rigorous Combustion Conditions - A unique combination of hightemperatures, long residence times and turbulent air flow promotecomplete combustion of organic compounds contained in tires.

Inherent SOX Control - Limestone used in cement manufacture is

commonly used in APC systems to absorb SOX, providing inherent SOXcontrol.

Ash Utilization - Ash resulting from tire combustion becomes anintegral component of the cement product, displacing purchasednatural resources and eliminating ash disposal requirements.

Broad Applicability - Demonstrated technology allows use of tiresin older long kilns, as well as newer preheater and precalcinertypes.

Although these factors encourage use of tires as asupplemental fuel in kilns, demonstrated performance is a critical

consideration in establishing environmental acceptability of thisapplication. Extensive environmental data has been generated fora variety of kiln configurations and fuel displacements. Timelimitations preclude discussion of all available data, but severalexamples should be included.

Exhibit 5 provides comparative data resulting fromcomprehensive tests conducted by Florida Crushed Stone. TDFrepresenting 14% energy displacement was introduced into the riser



SUMMARY

Scrap tires can be an environmentally-friendly alternativeenergy resource when used in appropriate applications. Energyutilization is an important component of successful scrap tiremanagement programs within the U.S., allowing this resource to beused rather than wasted. Tires have also been accepted as anenvironmentally-viable alternative fuel in cement kilns in westernCanada, resulting in substantial conservation of non-renewablefossil fuels. When the demonstrated performance of tires as anenergy resource is objectively evaluated, many jurisdictions haveconcluded that our environment is better served by recognizing thevalue of this resource rather than wasting it while waiting forideal solutions.



section of their preheater kiln. Particulate and SOX emissionsdeclined with TDF use. Volatile organics increased but semi-volatile organics decreased by an even greatermargin, resulting ina net reduction in organic emissions. Changes in metal

concentrations were nominal. Comprehensive testing of dioxins andfurans showed a net reduction of over 50% with TDF use. FloridaCrushed Stone is currently using approximately 1,000,000 scraptires per year as an alternative energy source in full compliancewith all applicable regulations.

Performance results for Ashgrove Cement's kiln in Durkee,Oregon are provided in Exhibit 6. Emissions of particulate, SOX,chlorides and all heavy metals declined or remained constant.Total hydrocarbons increased about lo%, but polynuclear aromaticsdeclined about 10%. This plant's performance is accepted in one ofthe most environmentally-sensitive states in the U.S.

Within Canada, use of tires as a supplemental fuel in cementkilns has been accepted by some provinces as an environmentallyacceptable and appropriate use of this resource based on testingperformance. Tillbury Cement completed TDF trials at theirfacility in Delta, British Columbia during September-October, 1990.Tillbury's kiln is equipped with a 4-stage suspension preheater,planetary coolers, and an electrostatic precipitator. All fuel isnormally introduced at the firing end of the kiln, but TDF wasadded between the preheater and kiln sections to provide about 7%

of the kiln's energy requirement. Two tests were conducted foreach of the baseline and TDF usage trials. Testing results areprovided in Exhibit 7. Particulate and HC1 emissions decreasedsignificantly. SOX and NOx emissions increased but remained within

acceptable levels. There were no material increases in metals.

In addition to Tillbury's experience, LaFarge has alsocompleted testing to allow use of tires at its Richmond, BC kiln.Within Alberta, Inland Cement (Edmonton) and LaFarge (Exshaw) havecompleted environmental testing. Inland's performance has beendetermined to be acceptable by Alberta Environment. Inland and theAlberta Tire Recycling Management Board have executed an agreementthat will allow Inland's use of scrap tires as an integralcomponent of Alberta's rapidly-evolving tire management program.LaFarge's application is currently under review by the Ministry.



EXHIBIT 5

CRITERIA

Particulate

SO2 Emissions

Volatile Organics

ENVIRONMENTAL PERFORMANCE DATATDF INTRODUCTION INTO RISER SECTION

OF PREHEATER KILN AT FLORIDA CRUSHED STONE

AcetoneBenzeneTolueneChl oromethaneOthers

Total

Semi-volatile

Organics ((216-C18)

Metals

A umi numArsenicBariumCadmiumChromiumCobaltCopperIronLead

MagnesiumMercuryMolybdenumNickelSeleniumSilverTitaniumVanadiumZinc

UNITS

grains/dscf

pounds/hour

ppm @ 10% 02

pounds/hour

pounds/hour

BASELINE

0.0104

56.80

96.4

595.15

0.02

0.08

0.01

(0.01

(0.03

0.15

5.01

6.86

<O .004

0.02

(0.005

0.02

0. 05

0.03

1.39

0.13

0.500.04

0.02

(0.02

(0.004

(0 .OO9

0.22

(0.02

3.12

14% TDP

0.0103

52.21

118.5

551.30

0.02

0.15

0.20

0.03

0.04

0.44

0.90

8.13

(0.004

0.02

(0.005

0.01

(0. 002

0.03

1.30

0.04

0.550.01

0.02

(0.02

(0. 004

(0.009

0.26

<0.02

1.68



EXHIBIT 5 - CONTINUED

CRITERIA

ENVIRONMENTAL PERFORMANCE DATA

TDF INTRODUCTION INTO RISER SECTIONOF PREHEATER KILN AT FLORIDA CRUSHED STONE

DIOXINS

2378-tetra12378-penta123478-hexa123789-hexa123678-hexa1234678-heptaoctaother tetraother pentaother hexaother hepta

subtotal

FURANS

2378-tetra12378-penta23478-penta23478-hexa123678-hexa234678-hexa123789-hexa234678-hepta234789-heptaocta

other tetraother pentaother hexaother hepta

EQUIV.TOXICITYFACTOR

AVG EMISSION RATE(10 E-6 LB/HR)

COAL 14%TDF

subtotal

TOTAL (10E-6 lb/hr)

EQUIV 2378-TETRADIOXIN EMISSIONS(10 E-6 LB/HR)COAL 14%TDF

. .



EXHIBIT 6

ENVIRONMENTAL PERFORMANCE DATATDF INTRODUCTION INTO RISER SECTIONOF PREHEATER KILN AT ASHGROVE CEMENT

CRITERIA UNITS

Particulate lbs/hr

Sulfur dioxide lbs/hr

Chlorides lbs/hr

Total hydrocarbons lbs/hr

Polynuclear aromatic lbs/hrhydrocarbons (PNA)

Naphthalene,Dibenzofuran,Phenanthrene

Heavy metals microgramsArsenicCadmiumChromiumNickelZincCopperLeadIronBariumVanadium

PERMITBASELINE 9-10% TDF LIMIT

5 . 2 7 4.83 18.0

(1.5 (1.2 6.3

0.268 0.197 NA

3.0 3.3 NA

0.0058 0 .0053 NA



EXHIBIT 7

CRITERIA(MG/DSCF)

Particulate

NOx as NO2

02 (vol % dry)

C02 (vol % dry)

Metals

Class ILead

AntimonyCopperManganeseVanadiumZinc

Class I1ArsenicChromiumCobaltNickelSeleniumTellurium

Class I11ThalliumCadmiumMercury

ENVIRONMENTAL PERFORMANCE DATATDF USAGE AT TILLBURY CEMENT

INORGANIC EMISSIONS

BASELINE 7% TDF USE

TEST 1 TEST 2 AVERAGE TEST 1 TEST 2 AVERAGE

NOTE: < denotes lower than sensitivity of the analytical procedurefor the specific conditions

16

TDF-042 - Tire Derived Fuel, An Environmentally Friendly Resource

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