Scrap Tire Pyrolysis

Pyrolysis is the process of thermal degradation of a substance into smaller, less complex molecules. Many processes exist to thermally depolymerize tires to salable products. Almost any organic substance can be decomposed this way, including rice hulls, polyester fabric, nut shells, coal and heavy crude oil. Pyrolysis is also known as destructive distillation, thermal depolymerization, thermal cracking, coking, and carbonization.

Pyrolysis produces three principal products - pyrolytic gas, oil, and char. Char is a fine particulate composed of carbon black, ash, and other inorganic materials, such as zinc oxide, carbonates, and silicates. Other by-products of pyrolysis may include steel (from steel-belted radial tires), rayon, cotton, or nylon fibers from tire cords, depending on the type of tire used.

Each product and by-product is marketable. The gas has a heat value from 170 to 2,375 Btu/ft3 (natural gas averages 1000 Btu/ft3) . The light oils can be sold for gasoline additives to enhance octane, and the heavy oils can be used as a replacement for number six fuel oil. The char can substitute for some carbon black applications, although quality and consistency is a significant impediment.

Conrad Industries operates a pyrolysis unit in Centralia, Washington. The unit is manufactured by Kleenair Products Company of Portland, Oregon, and licensed to Conrad. The plant began operation in March 1986, and currently has 10 employees. The unit is operated one shift per day, 5 days per week, 52 weeks per year. Conrad has five additional units planned around the United States, using four different feedstocks.1

The pyrolysis unit in Centralia converts 100 tires per hour (about one ton, assuming each tire weighs 20 pounds) to 600 pounds of carbon black, 90 gallons of oil, and 30 therms (8000 ft3) of vapor gas. In addition to tire rubber, Conrad's unit has been used to pyrolyze substances as diverse as rice hulls, nut shells, biomass (including wood, paper, and compost), and plastics (including polyester, polyethylene, and propylene).1

Thia chapter discusses a "generic" pyrolysis process in detail and describes some of the significant variations. An analysis of the environmental impact and financial viability is also be presented.

8.1 PROCESS DESCRIPTION

The actual pyrolysis process is the result of heating long-chain polymers in the absence of oxygen. The heat causes the molecules to vibrate. The higher the temperature, the more rapid the vibration. At temperatures above 237*C (460*F), the vibration causes the weaker bonds in the molecules to snap, creating new, shorter molecules. These new molecules have lower molecular weights than the parent molecules. Long exposure to high temperature will eventually cause all of the organic molecules to break down, leaving the char residue. The quality and quantity of these three pyrolytic products, oil, gas, and char, depend upon the reactor temperature and reactor design.2 Table 8-1 shows the effect of reactor temperature on the product mix. Conrad Industries generates gas, oil, and char in approximately equal proportions.1

Nearly all of the processes used for tire pyrolysis have the same basic unit operation, with variations in the reactor design. First, this chapter describes the basic process

Table 8-1. Approximate Product Distribution as a Function of Pyrolysis Reactor Temperature for Reductive Process Category3

Reactor Temp, *C (•F)

Gas, %

Oil, %

Char, %

500 (932)

6

42

52

600 (1112)

10

50

40

700 (1292)

15

47

38

800 (1472)

31

40

29

using a "black box," or generic reactor as shown in Figure 8-1. Specific types of reactors are described later in the chapter.

8.1.1 Materials Handling

The only raw material required for most tire pyrolysis processes is scrap tires. Some processors purchase and use whole tires, while others chip whole tires into two inch pieces, or purchase the tires already chipped. Conrad uses a local tire chipper to shred whole tires to a 2-inch size, wire-in, for their use. The tire chipper, who works on Conrad property, receives a tipping fee for collecting the tires, and provides the TDF to Conrad free of charge. Conrad has had no problem with reliability of their TDF source.1

If whole tires are used, they are usually added manually to the reactor. If the processor is using chipped tires, the chips are stored in a chip silo (see Figure 8-1, Item 1), and are fed from the silo into the reactor using a vibratory feeder or a screw conveyor to achieve a controllable and known feed rate. The feed passes through an air lock system consisting of two valves or a rotary star valve. From the air lock, the feed enters the pyrolysis reactor (Item 2).

8.1.2 Generic Reactor Description

In the reactor, the chips are heated to pyrolysis temperature, and the tire chips begin to break down. Reactors are operated from 237 to 1000'C (460 to 1830'F), with the maximum oil yield occurring at 450*C (840'F).1 Conrad's reactor, which is a cylindrical-shaped furnace chamber with two reaction tubes or retorts, is operated between 900 and 1,000'F.1

TOP CNp Mo

nm rynw^wB

Ouanah Tower

Recycled Hu 01

HwvyOI

(PorOMdOwPwcm)

Pyro-gaa Burner

Char

Pyro-gaa Burner

Figure 8-1. Generic Pyrolysis Process

Because of high reactor temperatures, the hydrocarbon volatiles vaporize immediately, and are vented from the reactor to a quench tower (Item 3), where they are sprayed with cooled, recycled, heavy oil, and the larger molecules (molecules containing eight carbon atoms (C8) or more) are condensed. The condensate leaves from the bottom of the quench tower and is collected in the heavy oil receiver (Item 4). Compounds that are not condensed (i.e., light oil, C3-C7) in the quench tower enter a non-contact condenser that uses cold water. The light oils, C3 to C7, are condensed and collected in the light oil receiver (Item 6) .

Although pyrolytic oil contains significant quantities of benzene and toluene that have high value in the pure form, removal of these compounds from the pyrolytic oil requires expensive fractional distillation equipment. Pyrolysis operators have been reluctant to make the capital investment in distillation equipment because the risk is too high and the return on investment is too low. As a result, the pyrolytic oil must be sold as a replacement for Number Six (low priced grade) fuel oil. The oils generated at Conrad's Centralia facility contain a maximum of 1.5 percent sulfur, and have a potential market as blender oils for commercial fuel.1

The gas remaining after oil recovery, called pyrolytic gas, or pyro-gas, is typically composed of paraffins and olefins with carbon numbers from one to five. Depending on the process, the heat value of the gas can range from 170 to 2,375 Btu per cubic foot, and averages 835 Btu per cubic foot.4 (Natural gas averages around 1000 Btu per cubic foot.) Most processes use the pyrolytic gas as fuel to heat the reactor. Any surplus gas can be flared or used to replace natural gas as boiler fuel. Emissions from burning pyro-gas would be similar to those from burning natural gas or low sulfur coal.

Part of the gas generated at Conrad's Centralia facility is used as fuel for the plant pyrolysis unit. The remaining gas currently is burnt in a outside flare. Currently, about 3.5 MHBtu's are burnt in the flare as excess; Conrad staff hope to have a commercial market for the excess gas in the future.1

Char is the solid product from the pyrolysis reactor. Char represents about 37 percent, by weight, of the total products from the process.4 Pyrolysis char has limited marketability due to unfavorable characteristics. First, the char contains as much as 10 to 15 percent ash, which adversely affects its reinforcing properties in new tire manufacturing. Also, the char's particle size is too large to permit it to qualify as high quality carbon black.4 Third, the char from the reactor is contaminated with steel wire, and rayon, cotton, and nylon fibers. Fibers can be removed mechanically, however, and the steel wire can be removed using a magnet. The carbon black from Conrad's Centralia facility averages less than 0.75 percent sulfur, and can be sold for uses such as copier toner, plastics products, rubber goods (hosing, mats), and paint.1

Most pyrolysis projects make some attempt to reduce the ash content and to upgrade the product char to a material comparable with commercial carbon black. Steam activation, pulverizing, screening, acid leaching, benzene extraction, filtering, and other processes have been used to upgrade char, but with questionable results. Pulverizing, screening, and conveying will create fugitive particulate emissions. Steam activation, extraction, leaching and filtering generate VOC fugitive emissions. Even upgraded char, however, cannot compete with virgin carbon black, or even with carbon black made from substoichometric combustion of hazardous organic wastes.

8.2 SPECIFIC REACTOR TYPES

Although there are hundreds of tire pyrolysis processes, they all can be categorized as either oxidative or reductive. Table 8-2 contains a list of manufacturers of oxidative and reductive processes with capacities, operating temperatures, and product mixes.

The oxidative process is not precisely "pyrolysis" because it injects oxygen or air into the reactor.5 The strict definition of pyrolysis is the thermal degradation of material in the absence of oxygen. The oxidative process is included here, because the elements of the process and the unit operations are identical to pure pyrolysis. In the oxidative process, thermal degradation still occurs, but the oxygen reacts with degradation products causing partial combustion. This partial combustion is called "sub-stoichiometric combustion", because there is insufficient oxygen for complete combustion. Heat from the combustion causes additional thermal degradation of the remaining scrap tires. Gases produced by the partial combustion include carbon monoxide, carbon dioxide, hydrogen, and sulfur dioxide, which are not produced in the reductive process.

Steam injection is a variation of oxidative combustion because the predominant reactions involve cracking hydrocarbons to form carbon monoxide, carbon dioxide, and hydrogen. Because the gas products are not consumed as in the substoichiometric process, the steam injection process produces more combustible gas products than the oxidative process. In addition to the heat required to heat the reactor and contents, tne steam injection process requires an external source of heat to produce the steam.

Table 8-2. Manufacturers of Pyrolysis Units and Operating Conditions w o o

Table 8-2. Manufacturers of Pyrolysis Units and Operating Conditions

Process Hm*

Capecity tpd

Reaction Tenp, *C

Yields as

a percent of Tiras

Oil, X

Chsr

, X Gas, X

Oulnlyn

120

600

62

16

11

0

Nippon Zeon

26.S

449-500

56

31

3

10

Sunotoao

S

704

54.7

31.7

9.5

4.1

Tosco

IS

510

52

29

11

4

MWTItt»

Kobe

26.S

500

41

33

7

5

HVU

fl.6

677

22

47

17

10

Herko/Klener

238

600

47

30

17

6

ERftG

3

871

38

30

28

4

C«rb Oll t Gil

60

600

45

33

13

9

Nippon 0 t F

27

500

49

36

10

5

Inten Company

100

496

52

35

7

4

iutrieb

6

427

35

38

20

5

Cerb-OII

112

1010

43

34

18

6

ïokohwa

8.2

500

53

33

n/a

n/a

OnthwM

30

400

21

20

51

7

Tyrolysis

165

534

45

39

0

16

Bergbau

1.3

923

5

35

20

10

DDP

25

722

27

39

12

The reductive process is the more traditional process for tire pyrolysis. This process excludes all sources of oxygen and relies on the reactor heat alone to decompose the tires. Some processors pressurize the reactor with an inert gas such as nitrogen to prevent air from leaking into the reactor, while some inject hydrogen to react with the sulfur present in the rubber in the tires to form hydrogen sulfide. Hydrogen sulfide can be recovered and sold as a by-product.

As mentioned earlier, a number of different types of reactors have been tried in tire pyrolysis. Almost any vessel that can be sealed can be used as a pyrolysis reactor. Reactor design has a significant effect on the quality of char produced, due to a uniform temperature gradient, and the abrasion of the particles with one another. Some of the reactor types that have been used are:

• sealed box rotary kiln

• traveling grate kiln fluidized bed

Below, different reactor designs are discussed in order of increasing technical complexity, and thus, increasing cost. Char quality also improves through the list, but none produce a quality char comparable to carbon black in most applications, even after upgrade.

8.2.1 Sealed Box

The sealed box is the simplest but most labor intensive process. In this process, whole tires are stacked manually in a steel cylinder equipped with airtight heads on each end. Heat is added either externally or directly inside the reactor until the reactor reaches the desired pyrolysis temperature. The reactor is then held at that temperature for several hours. Next the reactor is cooled, opened, and manually cleaned to remove char, wire, and fabric. It is then reloaded, and the process is repeated. This process requires a minimum of three reactors to provide a constant source of gas to fire a boiler.

8.2.2 Rotary Kiln

The rotary kiln is simple in concept, but difficult to operate in practice. The rotary kiln is a refractory lined, steel cylinder mounted horizontally on trunions and riding rings. It is pitched slightly toward the discharge end to facilitate material flow through the kiln. The kiln is fed from the high end and can be fed either whole tires or TDF chips. It can be fired internally or heated externally. One of the biggest operating problems is sealing the inside of the kiln against leaks. Kilns are usually operated with a slight negative pressure (induced draft). Almost all kilns leak to some degree, and these leaks cause outside air to enter the reactor, which results in ignition of the product gases. Rotary seals are provided at the inlet and discharge ends of the kiln, but sealing an eight to ten foot rotating cylinder is extremely difficult.

8.2.3 Screw Kiln

Thé screw kiln is a stationary steel cylinder equipped with a rotating screw device that moves the material through the cylinder. Screw kiln cylinders are often much smaller in diameter than rotary kilns. The normal feed is chipped tires with the wire removed. (Exposed wire causes feed and handling problems.) The primary advantage of using its screw kiln reactor is that its screw shaft is much smaller, and therefore easier to seal, than the large cylinder of the rotating kiln. The main disadvantage of the use of the screw kiln is the mechanical problems associated with a screw moving inside an extremely-hot, erosive environment.

8.2.4 Traveling Grate Kiln

The traveling grate kiln is a fixed vessel equipped with a chain-link type grate that moves continuously from the feed end to the discharge end. The kiln can be heated directly or indirectly. Tires or TDF are fed through an air lock onto the feed end of the grate. As the grate moves, the tires are degraded. The char is discharged at the end of the bed into a collection hopper, and the grate is recycled back to the feed end of the kiln. Mechanical problems exist with the traveling grate kiln because equipment must operate in a high temperature, erosive environment.

8.2.5 Fluidized Bed

The fluidized bed reactor is a vertical steel vessel to which TDF is fed through a side port. A fluidized bed of TDF is maintained with hot air. The abrasive action of the fluidized particles erode the char from the TDF, reducing the tire material to small pieces. As the TDF decomposes, ash and char are swept out of the reactor with the fluidizing air. The biggest disadvantages of a fluidized bed system are the need to remove entrained solids from the vapors, and the need to maintain the hot, fluidizing gas. The two main advantages are the good solids mixing and uniform solids temperature profile in the fluidized bed. These two advantages produce the finest grade char of any of the pyrolysis processes.

8.2.6 Other Reactors

Other reactors and processes include the hot oil bath, molten salt bath, microwave, and plasma. These processes have been researched on laboratory and some cases pilot plant scale. None have proven commercially successful.

8.3 ENVIRONMENTAL IMPACTS

Pyrolysis units are expected to have minimal air pollution impacts because most of the pyro-gas generated in the pyrolysis process is burned as fuel in the process. During burning, the organic compounds are destroyed. Assuming complete combustion, the decomposition products are water, carbon dioxide, carbon monoxide, sulfur dioxide and nitrogen oxides.

Conrad's Centralia plant has no pollution control equipment except for the outside flare for the excess gas. No continuous emissions monitoring systems are used. No local regulations apply to the facility, although an annual inspection is conducted on site by regulatory agencies. Plant personnel conduct weekly leak checks for gases from pipes, valves, and flanges. Few air emissions result from operation of this equipment. Air pollution control equipment is not even necessary to meet state standards.1

An emissions test of the pyro-gas was conducted at Conrad on December 18, 1986, while pyrolyzing TDF. Measurements included particulate, metals, volatile and semi-volatile organic compounds, sulfur dioxide (S02), nitrogen oxides (NOx) , carbon dioxide (C02) , oxygen (02) , and carbon monoxide (CO),1 The test results are presented in Table 8-3. Note that these emission estimates do not reflect atmospheric emissions.

8.3.1 Particulate Emissions

As seen in Table 8-3, particulate emissions in the pyro-gas were estimated to be emitted at a rate of 0.0001 lbs per MMBtu.1

Table 8-3. Emission Estimates from Pyrolysis Facility,

Conrad Industries1'*

Concentration

Emission Rate" (Iba per WBtu)

Concentration

Emission Rate" (Iba per WBtu)

Particulate

2,500

1 X 10*4

Plaaaa Hetala

Aluairaji

1.51

6.7 X 10'8

Chroaiua

0.82

3.7 X 10-«

Iron

9.89

43.9 X 10'8

Nagneaiua

0.45

2.0 X 10'8

Manganese

0.09

0.4 X 10*8

Mercury

0.05

0.2 X 10"8

Nickel

2.95

13.1 X 10*8

Potaaaiua

1.84

8.2 X 10-8

Sod i us

18.62

82.7 X 10-8

Zinc

0.65

2.9 X 10-8

Seal-Volatile Organic Coapounds

Bia-(2-ethy-haxyOphthalate

10.2

45.3 X 10*8

Butyl Benzyl-phthalate

1.7

7.5 X 10-8

01-n-butyl-phthalata

0.9

4.0 X 10*8

Naphthalene

2.87

12.7 X 10-8

Phenol

1.4

6.2 X 10'8

Volatile Organic Conpounds

Benzene

20.2

c

Ethylbenzene

24.1

c

Toluene

30.8

c

Xylenes

16.2

c

Sulfur Dioxide

310,500

7.7 X 10"2

Nitrogen Oxides

Nitrogen Oxides

210,000

Theaa eanaaion eatisatea reflect the coaposition of the pyro-gas, tiiich is either burned in the process as fuel or (for the excess pyro-gas) vented to the facility's flare. These estimates do not reflect atanspheric emissions.

These eaiission rates were calculated by taking the average concentrations reported for the coapotnd and sultiplying it by the average flow rate for the test runs. An energy input value of 31 WfBtu was used to calculate Iba/HMBtu.

Flow rates were not reported. Thus, pounds of eariaaiona per hour could not be calculated.

Quantitative estimates of fugitive emissions were not available. Fugitive emissions of particulate occur during the handling and processing of char. Char contains carbon black, sulfur, zinc oxide, clay fillers, calcium and magnesium carbonates and silicates, all of which produce PUjq emissions. Operations such as screening, grinding, and processing cause PM10 emissions and could be controlled with dust collectors and a baghouse.

8.3.2 VOC Emissions

The major source of VOC emissions is from fugitive sources. VOC fugitive emissions occur from leaks due to worn or loose packing around pump shafts and valve stems, from loose pipe connections (flanges), compressors, storage tanks, and open drains. The composition of the fugitive emissions is a combination of "pure" pyro-gas and non-condensed light oils. Table 8-4 presents the composition of "pure" pyro-gas.2 The primary constituents of pyro-gas are hydrogen, methane, ethane, propane, and propylene. These five constituents account for over 98 percent of the pyro-gas composition.

In practice, pyro-gas will always contain some non-condensed light oils. Table 8-5 gives the composition of the light oil condensed from pyro-gas at 0*C (32*F).4 Listed among the components are toluene, benzene, hexane, styrene, and xylene. Emissions of benzene, ethylbenzene, toluene, and xylene were measured in the stack test at Conrad Industries. Flow rates for the tests measuring these compounds were not reported; thus, emission rates (lbs/MMBtu) could not be estimated.

No references to fugitive emissions from the pyrolysis process could be found in the literature. To estimate the order-of-magnitude emissions from this process, a model plant was assumed. Based on a Department of Energy study, the most economical plant size is 100 tons per day (2000 tires per day) .4 This size would make the plant roughly equal to one hundredth the size of the model refinery listed in AP-42.6 TCible 8-6 gives one hundredth of the fugitive emissions from the refinery, the number units in the process, and the daily emissions from each source. Based on these assumptions, a typical pyrolysis plant would emit about 50 kilograms of VOC's per day (about 100 pounds per day), or 18.7 megagrams per year (21 tons per year total).

Fugitive VOC emissions can be significantly reduced by specifying components (e.g., pumps, valves, and compressors) specifically designed to minimize fugitive emissions. Fugitive VOC emissions can also be reduced by training operators and mechanics in ways to reduce fugitive emissions, good supervision, and good maintenance practices.

8.3.3 Other Emissions

Semi-volatiles, S02, and NOx were also measured in the pyro-gas. The majority of the semi-volatile compounds detected were phthalates. The methods used to detect the semi-volatiles (gas chromatography/mass spectrometry analysis using dry sorbent resins) could have been the source of the phthalates, because these methods can give rise to phthalate contamination.1

8.4 OTHER ENVIRONMENTAL AND ENERGY IMPACTS

If markets for char cannot be developed, the char becomes a major solid waste problem. Analysis of char from the pyrolysis of scrap tires does not indicate a problem with hazardous materials.4 However if it must be disposed of in a landfill, the char should be collected in plastic bags and shipped and disposed of in steel drums to prevent additional fugitive emissions during transportation and disposal.

Table 8-4. Chromatographic Analysis of Pyrolytic Gas from Shredded Automobile Tires with Bead Wire In2

Constituent

Volume Percent

Hydrogen

47.83

Methane

29.62

Ethane

18.52

Propane

5.70

Propylene

8.82

Isobutylene

0.73

Isobutane

0.34

Butane

0.23

Butene-1

0.14

trans-Butene-2

0.07

iso-butene-2

trace

Pentane

ND*

1,3-Butadiene

ND * not detected

Table 8-5. Chromatographic analysis of light oil condensed from pyrolytic gas at 0*C using shredded tires with bead vire4

Constituent Volume Percent

Toluene

11.

.05

Benzene

8.

.83

1-Hexene

5.

.85

Hexane

4.

.07

8-Methyl-8-Butene

3.

.55

trans & cis-8-Hexene

3.

.42

Styrene

3.

.03

Ethyl Benzene

3.

.33

Xylene

4.

.18

3,3-Dimethyl-l-Butene

1.

.11

8-Methyl Butane

1.

.04

2,8-Dimethyl Butane

1.

,04

8-Methyl-l,3-Butadiene

1.

.85

Cyclopentane

1.

,48

Other

46.

,17

NOTE: These light oils comprise only about 2 percent of the total pyrolytic gas volume.

Table 8-6. Estimated fugitive VOC emissions from a "generic" pyrolysis plant6'*

Fugitive

Emissions

Source

No. of Sources in Process

VOC kg/day

Emissions lb/day

Pipe Flanges

47

2.72

6

Valves

12

30.84

68

Pump Seals

4

5.90

13

Compressors

1

5.00

11

Pressure Relief Valves

1

2.27

5

Open Drains

7

4.54

10

TOTAL

51.27

113

* Based on one hundredth the size of the refinery (value x 0.01).

In addition, depending on the feedstock, some non-flammable by-products result, such as fiberglass, or scrap steel. Conrad hopes to generate a market for the fiberglass as a filler material, although it is landfilled currently. The scrap steel can be sold to a scrap dealer.1

If non-contact, water cooled condensers are used, water pollution problems should be minimal. Except for cooling, the only other source of water contamination is water used in washing the plant floors and equipment. Oil spills may occur, and should be isolated, contained and cleaned up without contaminating the waste water.

Most processors like to maintain at least a 30 day stock pile of raw materials as protection against market fluctuations, transportation problems or work stoppages. The pile must be maintained properly. If the pile is not "live storage" (first in, first out), the pile could pose a potential health hazard due to rodent and insect infestations. The potential of a tire pile fire is always a possibility, and fire fighting equipment and access to the pile is important.

8.5 COST CONSIDERATIONS

During the past ten years, no less than 34 major pyrolysis projects have been proposed, designed, patented, licensed, or built (see Table 8-2). Only one or two are operational today, arguably, none on a commercial basis. Technically, tire pyrolysis is feasible; but financially, it is very questionable. This section reviews some of the highlights of the financial analysis of the process and products.

The economics of the pyrolysis business are extremely complex. First, an investment of over $10 million is required to construct a 100 ton per day plant.4 Second, the business has many important variables, none of which are fixed or easily predictable. For example, the yield of the pyrolytic oil can vary from 82 to 171 gallons per ton of tires fed into the process. The selling price of pyrolytic oil can vary from 36 to 95 cents per gallon, depending on the composition and quality. Other products of the pyrolysis process have similar potential variations. Because of this, economic analyses require many assumptions.

In 1983, the U.S. Department of Energy evaluated the economic viability of tire pyrolysis and published its findings in a report entitled Scran Tires; A Resource and Technology Evaluation of Tire Pvrolvsis and Other Selected Alternative Technologies.2 Their "Economic Results" stated in part:

"Economic Results. An analysis of each project using the preceding economic parameters and computer program was performed. The results showed negative cash flows for each project. Using the accelerated capital recovery system (ACRS) still showed negative cash flows for each project. The reason for these negative cash flows is that tire pyrolysis is only economic with unique situational variables. There are a number of questions about product quality, product price, and feed stock cost which tend to lend a vagueness to the economic analysis..."

The DOE report evaluated the sensitivity of the model results to changes in selected variables such as capital investment, labor, utilities, and product prices. In this analysis, all but one of the variables were held constant and the selected variable was evaluated from minus 20 percent of the assumed value to plus 20 percent, in 10 percent increments. The two variables with the largest impact on profitability were the tire tipping fees (fees paid for the disposal of scrap tires — an income for tire acquisition cost), and selling price of the products. Table 8-7 summarizes the tipping fees and product selling prices

Table 8-7. Tire Acquisition.Prices and Selling Prices of Products Required to Produce a 20 Percent Return-on-equity for Five Tire Pyrolysis Units2 (dollars)

Material

ERRG

Foster-

Garb

Kobe

Kutrieb

Wheeler

Oil

Tipping fee"

0.75

0.04

0.16

1.03

0.11

Oil"

8.13

0.60

0.77

8.15

0.77

Char®

0.10

0.06

0.07

0.33

0.06

Steeld

121

13

35

68

39

• Tipping fee, credit received for tire disposal,$/tire b Selling price of pyrolytic oil, $/gallon c Selling price of char, $/pound d Selling price of scrap steel, $/ton required to produce a 20 percent Return-on-Equity (ROE) for five pyrolysis processes modeled in the report. The analysis assumes all of the pyro-gas generated is consumed as fuel in the process.

Higher tire tipping fee could enhance tire pyrolysis economics. The business can be made financially successful if the tipping fees to the process operator range from $1.00 to $8.00. Currently, several states charge a tire disposal fee of a dollar or more at the time of purchase. Most of the fees, however, pay to administer the program, pay the tire collector, the distributor, the tire processor, and the end user of the scrap tires. The end user frequently collects only 15 to 20 cents per tire. As a comparison for Table 8-7, in the 2nd quarter of 1991, crude oil sold for about $20 per barrel ($0.47 a gallon), high quality carbon black sold for $0.28 per pound, and scrap steel sold for approximately $25 per ton.

8.6 CONCLUSIONS

Air pollution implications of pyrolysis are minimal with correct design and operation. VOC's in the gas can leak from pump seals, pipe flanges, valve stems, drains, and compressors. Particulate matter is generated from handling and processing the char. Emissions data from pyrolysis units are minimal, because many plants operate for short periods of time, and often only at pilot scale level.

Tire pyrolysis operations are currently small scale. Large scale operations would not be economically feasible at present. Economically, pyrolysis is a marginal venture. Unless area tire disposal costs are high, on-site energy savings can be realized, tax advantages are present, and higher value products (such as benzene and toluene) can be made.

8.7 REFERENCES

1. Memorandum from Clark, C., Pacific Environmental Services, Inc., (PES) to Michelitsch, D., EPA/ESD/CTC. September 28, 1991. Site Visit — Conrad Industries.

2. Dodds, J., W.F. Domenico, D.R. Evans, W. Fish, P.L. Lassahnn, and W.J. Toth. SCRAP TIRES: A Resource and Technology Evaluation of Tire Pyrolysis and Other Selected Alternate Technologies. U.S Department of Energy. November, 1983.

3. Schulman, B.L., P.A. White. Pyrolysis of Scrap Tires Using the Tosco II Process. American Chemical Society 0-8418-0434 9/78/47-076-274. September, 1978.

4. Wolfson, D.E., J.G. Beckman, J.G. Walters, and D.J. Bennett. Destructive Distillation of Scran Tires U.S. Department of Interior, Bureau of Mines. Report No. 7302. April 1973.

5. Foster Wheeler Power Products, Ltd. Corporate Report; Tvrolvsis—Tvre Pvrolvsis Plant.

6. U.S. Environmental Protection Agency. Compilation of Air Pollutant Emission Factors. Fourth Edition, AP-42, p. 9.1-13.

Guide to Alternative Fuels

Guide to Alternative Fuels

Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.

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