&EPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/3-91-024
December 1991
Air
Burning Tires for Fuel
and Tire Pyrolysis:
Air Implications
control
technology center
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EPA-450/3-91-024
BURNING TIRES FOR FUEL AND TIRE PYROLYSIS:
AIR IMPLICATIONS
CONTROL TECHNOLOGY CENTER
Sponsored by
Emission Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Air and Energy Engineering Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
December 1991
-------
EPA-450/3-91-07-
December 1991 •
Burning Tires for Fuel and Tire Pyrolysis:
Air Implications
by
G. Clark, K. Meardon, and D. RusseU
Pacific Environmental Services, Inc.
3708 Mayfair Street, Suite 202
Durham, NC 27707
EPA Prime Contract 68D00124
Work Assignment 16
Project Manager
Deborah Michelitsch
Control Technology Center (CTC)
Emission Standards Division
Office of Air Quah'ty Planning and Standards (OAQPS)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Prepared for
Control Technology Center
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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ACKNOWLEDGEMENTS
This report on air emissions from the burning of tires
as fuel and from tire pyrolysis was prepared for Ms. D.
Michelitsch of EPA's Control Technology Center (CTC) by C.
Clark, K. Meardon, and D. Russell of Pacific Environmental
Services, Inc. (PES), Durham, NC. The authors would like to
thank the many contributors to this report who supplied the
necessary information to make this report possible. These
include Mr. W. Siemering of Calaveras Cement Company; Mr. W,
Conrad of Conrad Industries; Mr. S. Hoard and Mr. N. Stiren
of Holnam, Inc.; Ms. D. Muller Crispin of the Oregon State
Scrap Tire Program; Mr. E. Ellery and Mr. R. Graulich of
Oxford Energy Corporation; Mr. S. Miller of Smurfit
Newsprint; Mr. 6. Reeves of the Stanislaus County Air
Pollution Control District; Mr. W. Holewinski and Mr. W.
Hutchinson of Wisconsin Power and Light; and Mr. P Koziar of
the Wisconsin Waste Tire Program.
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PREFACE
•
This project was funded by EPA's Control Technology
Center (CTC) and prepared by Pacific Environmental Services,
Inc. (PES).
The CTC was established by EPA's Office of Research and
Development (ORD) and Office of Air Quality Planning and
Standards (OAQPS) to provide technical assistance to State,
local, and private air pollution control agencies. Three
levels of assistance can be accessed through CTC. First, a
CTC Hotline has been established to provide telephone
assistance on matters relating to air pollution control
technologies. Second, more in-depth engineering assistance
can be provided when appropriate. Third, the CTC can
provide technical guidance through publication of technical
documents, development of personal computer software, and
presentation of workshops on control technologies.
The technical guidance projects, such as this one,
focus on topics of national or regional interest and are
identified through contact with State and local agencies or
private organizations. Sufficient interest in the disposal
of scrap tires through their use as a fuel warranted
development of a technical document on air emissions from
the burning of tires for fuel and from tire pyrolysis. This
document briefly discusses various industries that use tires
either primary or supplemental fuel. In addition, this
document discusses the pyrolysis of tires. This document
serves as a reference source for those seeking further
information.
iii
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DISCLAIMER
This report has been reviewed by the Control Technology
Center (CTC) established by the Office of Research and
Development CORD) and Office of Air Quality Planning and
Standards (OAQPS) of the U.S. Environmental Protection
Agency (EPA), and has been approved for publication.
Approval does not signify that the comments necessarily
reflect the views and policies of the U.S. EPA nor does
mention of trade names or commercial products constitute
endorsement or recommendation for use.
IV
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TABLE OF CONTENTS
List of Tables ...................... viii
List of Figures ..... ................. x
EXECUTIVE SUMMARY ..................... ES-1
1. Introduction ..................... 1-1
1.1 Waste Tire Generation and Disposal ....... 1-2
1.2 Waste Tires As Fuel ............... 1-3
1.2.1 Waste Tire Characteristics and
Composition ............... 1-5
1.2.2 Waste Tire and TDF Cost Considerations . . 1-5
1.2.3 Air Pollution Emissions Issues ...... 1-10
1.3 Markets For Tires As Fuel ............ 1-11
1.4 State Waste Tire Disposal Programs ....... 1-12
1.5 Methodology ............. . ..... 1-17
1.6 References . . '. ................ 1
2 . Overview of Process Units Burning Tires For Fuel . . . 2-1
2.1 Kilns ...................... 2-2
2.2 Boilers . . . . ................. 2-2
2.2.1 Pulverized Coal Boilers ......... 2-4
2.2.2 Cyclone Boilers ............. 2-5
2.2.3 Stoker Boilers .............. 2-6
2.2.4 Fluidized Bed Boilers .......... 2-11
2.3 References ................... 2-17
3. Dedicated Tires-to-Energy Facilities ......... 3-1
3.1 Industry Description .............. 3-1
3.2 Process Description ............... 3-3
3.2.1 General- Operation ............ 3-4
3.2.2 Operational Difficulties ......... 3-6
3.3 Emissions, Control Techniques and Effectiveness . 3-8
3.3.1 Emissions ................ 3-3
3.3.2 Control Techniques . .' .......... 3-10
3.3.3 Permit Conditions and Issues ....... 3-16
3.4 Other Environmental and Energy Impacts ..... 3-17
3.5 Cost Considerations ............... 3-18
3.6 Conclusions . . . ................ 3-20
3.7 References • ............. ...... 3-21
4.0 Tire and TDF Use in Portland Cement Kilns ...... 4-1
4.1 Industry Description .............. 4-4
4.2 Process Description ............... 4-9
4.2.1 Mixing and Grinding ........... 4-9
4.2.2 Calcination ............... 4-12
4.2.3 Preheaters and Precalciners ....... 4-12
4.2.4 Finished Cement Grinding ......... 4-14
4.2.5 Tires as Fuel in the Kiln ........ 4-18
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TABLE OF CONTENTS (Continued)
Pace
4.3 Emissions, Control Techniques and
their Effectiveness T~r[
4.4 Other Environmental and Energy Impacts I TS
4.5 Cost Considerations J~"
4.6 Conclusions " **
4.7 References 4~'3/
5.0 TDF as Fuel in Waste Wood Boilers at Pulp and
Paper Mills j!"^
5.1 Industry Description ~~j:
5.2 Process Description 5~5
5.3 Emissions, Control Techniques and
their Effectiveness 5~8
5.3.1 Emissions 5"8
5.3.2 Control Techniques 5-22
5.4 Other Environmental and Energy Impacts 5-25
5.5 Cost Considerations 5-25
5.6 Conclusions 5-26
5.7 References 5-27
6.0 Tires and TDF as Supplemental Fuel In
Electric Utility Boilers 6-1
6.1 Industry Description 6-1
6.2 Process Description 6-1
6.2.1 Materials Handling 6-4
6.2.2 Combustion 6-6
6.3 Emissions, Control Techniques and their
Effectiveness 6-8
6.3.1 Particulate Emissions 6-8
6.3.2 S02 Emissions 6-14
6.3.3 NOX Emissions 6-16
6.3.4 CO Emissions 6-16
6.3.5 Trace Metal Emissions 6-16
6.3.6 Other Air Emissions Information 6-16
6.3.7 Control Equipment Issues 6-20
6.4 Other Environmental arid Energy Impacts 6-23
6.5 Cost Considerations 6-23
6.6 Conclusions . 6-23
6.7 References 6-26
7.0 Use of TDF as a Supplemental Fuel at Other
Industrial Facilities 7-1
7.1 Description of Industries 7-1
7.2 Process Description 7-4
7.3 Emissions, Control Techniques and their
Effectiveness 7-5
7.4 Other Environmental and Energy Impacts 7-5
7.5 Cost Considerations 7-5
7.6 Conclusions 7_3
7.7 References 7_9
vi
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TABLE OF CONTENTS (Continued)
Page
8.0 Scrap Tire Pyrolysis 8-1
8.1 Process Description 8-2
8.1.1 Materials Handling 8-4
8.1.2 Generic Reactor Description . 8-4
8.2 Specific Reactor Types 8-8
8.2.1 Sealed Box 8-10
8.2.2 Rotary Kiln 8-11
8.2.3 Screw Kiln 8-11
8.2.4 Traveling Grate Kiln 8-12
8.2.5 Fluidized Bed 8-12
8.2.6 Other Reactors 8-12
8.3 Environmental Impacts 8-13
8.3.1 Particulate Emissions 8-13
8.3.2 VOC Emissions 8-15
8.3.3 Other Emissions * . . . 8-16
8.4 Other Environmental and Energy Impacts 8-16
8.5 Cost Considerations . 8-20
8.6 Conclusions 8-23
8.7 References 8-25
APPENDIX A State Contacts for Waste Tire Programs
VII
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LIST OF TABLES
Table ES-1-
Table 1-1.
Table 1-2.
Table 1-3.
Table 1-4.
Table 1-5.
Table 1-6.
Table 2-1.
Table 3^1.
Table 3-2.
Table 3-3.
Table 3-4.
Table 4-1.
Table 4-2.
Table 4-3.
Table 4-4.
Table 4-5.
Table 5-1.
Table 5-2.
Table 5-3.
Table 5-4.
Comparison of criteria pollutants from
electric generating plant
Scrap tire generation
Comparative fuel analysis, by weight
Comparative composition and fuel
value of various tire types . . , .
Market barriers to TOP use ....
Waste tire disposal laws in the U.S.
States without laws or regulations
for waste tire disposal
Page
ESr4
1-4
1-6
1-6
1-13
1-14
Emission test results of three pilot
FBC boilers burning supplemental TDF
. . . 1-16
. . . 2-15
Permitted emission levels at
The Modesto Energy Project, Westley, CA. . . 3-9
Permitted emission limits for each
boiler, Exeter Energy Project, Sterling,
CT . . . . : 3-9
Criteria pollutant and metals emissions,
by year, The Modesto Energy Project . . . . 3-11
Organic compound emissions, by year,
The Modesto Energy Project 3-12
Portland cement facilities that have been,
or are, burning TDF or whole tires 4-5
Effect of burning 9 to 10 percent TDF in
a gas and oil co-fired dry process, rotary
cement kiln controlled by an ESP 4-20
Effect of burning TDF on HAP emissions
from Holnam/Ideal Cement, Seattle, WA . . . 4-29
Effect of burning 15 percent TDF in a
gas-fired rotary lime kiln 4-30
Emissions estimates for Calaveras' cement
kiln stack while burning 20 percent
TDF 4-32
Pulp and paper mills with experience burning
TDF in waste wood boilers 5-3
Emission of PNA's and metals from
Port Townsend Paper and Crown Zellerbach
Corporation 5-9
Summary of particulate tests on two
hog-fuel boilers at Smurfit Newsprint,
Newberg, OR . 5-10
Summary of non-particulate testing on
the #10 boiler at Smurfit Newsprint,
Newberg, OR 5-11
Vlll
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Page
Table 5-5. Summary of tests on 3 hog-fuel boilers
at Package Corp. of America 5-12
Table 5-6. Emissions burning TDF and waste wood
Dow Corning Corporation, Midland, MI .... 5-13
Table 5-7. Summary of tests on hog-fuel boiler at
Champion International Corp., Sartell, MN . 5-14
Table 6-1. Electric utilities with TDF experience
as a supplemental fuel 6-2
Table 6-2. Air emission test data for Wisconsin
Power and Light 6-9
Table 6-3. Emission results at Ohio Edison 6-10
Table 6-4. Summary of emission rates burning 2* TDF
at Illinois Power, Baldwin Generation
Station 6-11
Table 6-5. Summary of emission rates from testing
at United Power Association, Elk River,
MN . . . . 6-11
Table 6-6. Summary of emissions from a wood-fired
utility boiler cofiring TDF 6-12
Table 6-7. Comparison of heavy metal content of slag
at baseline and 5% TDF at Wisconsin Power
and Light 6-24
Table 7-1. Other industrial boilers with TDF
experience 7-2
Table 7-2. Summary of emissions at Monsanto, Sauget,
IL . . . 7-7
Table 7-3. Summary of air emissions test data while
burning TDF at Saginaw Steering and Gear . . 7-7
Table 8-1. Approximate product distribution as a
function of pyrolysis reactor temperature
for reductive process category 8-3
Table 8-2. Manufacturers of pyrolysis units and
operating conditions 8-9
Table 8-3. Emission estimates from pyrolysis facility,
Conrad Industries 8-14
Table 8-4. Chromatographic analysis of pyrolytic gas
from shredded automobile tires with bead
wire in • 8-17
Table 8-5. Chromatographic analysis of light oil
condensed from pyrolytic gas at 0*F
using shredded tires with bead wire .... 8-18
Table 8-6. Estimated fugitive VOC emissions from
a "generic" pyrolysis plant 8-19
Table 8-7. Tire acquisition prices and selling prices
of products required to produce a 20
percent retum-on-equity for five tire
pyrolysis units 8-22
ix
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LIST OF FIGURES
Page
Figure 1-1. Trace metal levels in whole waste tires
compared to bituminous coal 1-7
Figure 2-1. Typical cyclone coal burner . 2-7
Figure 2-2. Typical mechanical feeder on a spreader
stoker 2-9
Figure 2-3. Typical fluidized bed boiler 2-12
Figure 3-1. Oxford Energy Process Flow Sheet 3-5
Figure 4-1. Fuel Use at cement kilns 4-3
Figure 4-2. Typical wet process material handling
during Portland Cement manufacture 4-10
Figure 4-3. Typical dry process material handling
during Portland Cement manufacture 4-11
Figure 4-4. Typical clinker production process
during Portland Cement manufacture 4-13
Figure 4-5. Four-stage suspension preheater with
a precalciner at a Portland Cement plant . . 4-15
Figure 4-6. Traveling grate preheater system at a
• Portland Cement plant 4-16
Figure 4-7. Finish mill grinding and shipping
during Portland Cement manufacture 4-17
Figure 4-8. Effect of burning TDF on criteria
pollutants emissions from Holnam/Ideal
Cement, Seattle, WA 4-23
Figure 4-9. Percent change in emissions of metals
when burning TOF at Holnam/Ideal Cement,
Seattle, WA 4-24
Figure 4-10. Percent change in VOC emissions when
burning TDF at Holnam/Ideal Cement,
Seattle, WA 4-25
Figure 4-11. Percent change in emissions when burning
15% TDF in a gas-fired rotary lime kiln
controlled by a venturi scrubber 4-31
Figure 5-1. Smurfit Newsprint Process Flows 5-7
Figure 5-2. Percent change of particulate emissions
over baseline (0% TDF) in wood waste
boilers burning TDF 5-17
Figure 5-3. Particulate emission rates from hog-fuel
boilers burning TDF supplementally 5-18
Figure 5-4. Change in emission rate of SO2 over
baseline (0% TDF) at varied TDF input
rates for hog-fuel boilers : 5-19
Figure 5-5. Change in emission rate of NOX over baseline
(0% TDF) at varied TDF input rates for
hog-fuel boilers 5-19
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LIST OF FIGURES (Concluded)
Page
Figure 5-6. Change in emission rate of CO over
baseline (0% TDF) at varied TDF input
rates for hog-fuel boilers 5-20
Figure 5-7. Change in zinc emission rates when burning
TDF at six pulp and paper plants 5-21
Figure 5-8. Percent change in metals emissions at five
mills burning TDF 5-23
Figure 5-9. Percent change in emissions of PNA's at
three paper mills burning TDF 5-24
Figure 6-1. Particulate emissions while burning TDF
or whole tires at coal-fired electric
utilities 6-13
Figure 6-2. SC>2 emissions while burning TDF or tires
at coal-fired electric utilities 6-15
Figure 6-3. NOj emissions while burning TDF or tires
at coal-fired electric utilities 6-17
Figure 6-4. Trace metal emissions rates when burning
waste tires compared to coal ........ 6-18
Figure 6-5. Trace metal emission rate changes when
burning waste tires compared to coal .... 6-19
Figure 6-6. Dioxin and furan emission rates when
burning waste tires compared to coal .... 6-21
Figure 6-7. Dioxin and furan emission rate changes
when burning waste tires compared to coal . 6-22
Figure 7-1.
Summary of percent change in SO2, NOX,
and particulate emissions at Monsanto
Chemicals and Saginaw Gear
Figure 8-1. Generic Pyrolysis Process
7-6
8-5
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EXECUTIVE SUMMARY
This report presents data and analysis concerning burning
tires and tire-derived .fuel (TDF) in process and power
equipment in the United States. There is significant
interest being expressed by several industries concerning
the use of tires and TDF for fuel. This has caused an
increase in requests for information from local agencies and
for permit applications. Previously, there has not been a
central publication on the effects of burning tires or TDF
for fuel. The purpose of this report is to summarize data
on the effect of burning tires or TDF on atmospheric
emissions, emissions control techniques, control
efficiencies, and economics.
Scrap tires present unusual disposal problems. The very
characteristics that make them desirable as tires, long life
and durability, makes disposal almost impossible. The fact
that tires are thermal-set polymers means that they cannot
be melted and separated into their chemical components.
Tires are also virtually immune to biological degradation.
Landfilling scrap tires is unacceptable for several reasons,
not the least of which is the fact that they tend to rise
to, and break through the surface liner.
Recycling scrap tires into useful products such as floor
mats, sandal soles, and fish barriers, have very limited
demand and at best could assemble only a small fraction of
the available scrap tires.
This investigation found four industries that were using
tires and TDF for fuel. Also investigated was the thermal
degradation of tire and TDF (pyrolysis) into salable
products. These industries were:
ES-l
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• Electric utilities that use TDF and whole tires as
supplemental feed in power generation. One company
was using whole tires as its sole source of fuel in
power generation.
• Cement manufacturing companies use tires and TDF to
supplement their primary fuel for firing cement
kilns. Some of the companies were using tire or TDF
directly in the kiln, some were using tires or TDF
in the precalciner (prior to the kiln proper), and
one company was using tires or TDF in both
processes.
• Pulp and paper companies use tires or TDF as
supplemental fuel in their waste-wood products
boilers.
• Other industries use TDF in utility and process
boilers as supplemental fuel.
TECHNICAL APPROACH
•
The approach used to collect and analyze data on burning
tires and TDF is presented in this section.
Sources of Information
Initially, a detailed literature search was conducted to
identify industries and companies with experience burning
tires or TDF for fuel, emissions from the process, and
emission controls and their effectiveness. A data base was
created including all companies with experience burning
tires or TDF, by industry and location. The U.S. EPA
Regional Office for each plant location burning tires or TDF
was contacted for specific emissions information. The State
and local air pollution control agencies were also contacted
for emissions data from plants testing or using tires or TDF
for fuel.
Based on the information obtained from these sources
selected companies from each industry were contacted by
telephone to determine if they were still burning tires or
ES-2
-------
TDF, if they had data on emissions while burning tires or
TDF, and their future plans concerning tires or TDF as fueJ .
Data obtained from the plants were compiled and analyzed.
Based on this analysis, five companies were selected for
site visits. Information on tires or TDF use, feed
equipment modifications necessary to facilitate the burning
of tires or TDF, operating problems created by using tires
or TDF, operating advantages with using tires or TDF, and
cost benefits of using tires or TDF was also gathered.
Further information was obtained on emissions while burning
•tires or TDF, baseline emissions (emissions when tires or
TDF are not being burned), emission controls in use,
modifications to controls necessary to facilitate tire or "
TDF burning, and efficiency of emission controls.
Data obtained from the site visits were analyzed and
detailed trip reports were written and reviewed by each
affected company to verify technical data and remove
confidential business information. The data from the trip
reports, along with data from the literature search and air
pollution control agencies, were compiled, summarized, and
analyzed. These data were used as the basis of this report.
RESULTS
The primary area of interest of this investigation was the
effect of burning tires or TDF on the emissions from the
process. Other areas of concerns were the emission control
devices, changes to controls necessary to facilitate burning
tires or TDF, and the economics of burning tires or TDF.
Effect on Emission
The effect of burning tires or TDF on emissions varies
substantially based on the industry and the type of emission
ES-3
-------
controls installed. No emissions data were obtained during
this investigation on tires or TDF for a process in which
the emissions were uncontrolled. The effects of burning
tires or TDF on SOT lesions, by industry, are presented here.
Electric Utilities
Of all the emissions test data received from plants
generating electric power using tires or TDF, the company
reporting the lowest levels of emissions was Oxford Energy's
Modesto, CA, plant. This plant's fuel was 100 percent
whole, scrap tires, yst its ©missions were several orders-
of-magnitude lower than the other electric utilities (see
Table ES-1).
The effect of burning tires on coal-burning utilities varied
by pollutant. Particulates generally decreased as the
percent of TDF in tha fuel increased. This occurred in all
but one series of tests. The sulfur oxides increased in
some tests with Increased TDF use, decreased in some tests,
and stayed about the same in one series. The nitrogen
oxides generally decreased with the increase use of tires or
TDF; some by as much as 50 percent. In one series of tests,
the nitrogen oxides increased 15 percent.
Cement Manufacturing
The effect of a fuel change to burning tires on emissions in
cement kilns appears rainor. Particulates increased slightly
from 0.10 to 0.12 pounds per million Btu (20 percent)
comparing baseline (zero TDF in the fuel) to 14 percent TDF.
Both sulfur oxides and nitrogen oxides decreased (40 percent
and 26 percent, respectively) in this range of TDF in the
fuel. Carbon monoxide, however, increased 33 percent. The
effect of burning tires or TDF in kilns on VOC's and HAP's
appears to be positive (a significant reduction in most
ES-4
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Table ES-1.
Comparison of Criteria Pollutants from Electric
Generating Plants
Power Plant
Oxford Energy
100X Tires
UP A. Elk River
ftasellne (OX TDF)
5X TDF
10X TDF
UPSL. Beloit
Baseline. OX TDF
7X TDF
Ohio Ediaon
Baseline
5X TDF
10X TDF
15X TDF
20X TDF
Northern Statea
Baseline
7X TDF
lUinoia Power'
2X TDF
Particulates
Ib/MMBtu
0.000022
0.21
0.015
0.009
0.52
0.14
0.063
0.0717
0.0564
0.0815
0.0453
0.083
0.310
0.17
Sulfur
Oxides
lb/MM8tu
0.000014
1.41
1.80
1.53
1.14
0.87
5.30
5.73
5.71
5.47
5.34
.
0.021
0.074
5.78
Nitrogen
Oxides
Ib/MMBtu
0.000098
0.78
0.58
0.30
0.79
0.91
0.601
0.510
0.436
0.443
0.387
0.19
0.125
NT
Carbon Monoxide
Ib/MMBtU
0.000072
NT
NT
NT
1.52
7.26
NT
NT
NT
NT
NT
NT
NT
NT
NT • Not tested or data not available.
ES-5
-------
cases). Notable exceptions are tetrachloroethane (up over
20 times the baseline rates) and 1,1,1-trichloroethane (up 5
times the baseline rates).
Pulp and Paper Mills
The effect of burning tires or TDF in waste-wood (hog fuel)
boilers in pulp and paper mills was generally unfavorable on
the emissions. Particulates increased in every series of
tests when the TDF percentage was increased. The reason for
this is probably due to the type of emissions control
devices used on hog fuel boilers: venturi scrubbers. The
effectiveness of venturi scrubbers decreases as the particle
size in the emission decrease. Zinc oxide is used in the
manufacture of tires, and is present in significant
quantities in scrap tires. Zinc oxide has a relatively low
vaporization temperature and is vaporized when tires are
burned. When zinc oxide vapors condense, they form sub
micro-sized particles that are too small to be removed with
a venturi scrubber. This is verified by comparing the zinc
• •
emissions in hog-fuel boilers to baseline. Zinc emissions
increased in most cases 300 percent (and in one case, almost
50 times the base line emission rate). The effect of
burning tires on other pollutants was mixed, and distinctive
trends could not be determined.
Other Industries
During the investigation, TDF trials and emission test data
were obtained from industries not listed above. Most of the
processes were burning TDF in a plant's utility steam or
process boiler. One test, at Dow Chemical, involved burning
TDF in a waste-wood boiler and is discussed in Chapter 5,
TDF as fuel in Waste Wood Boilers at Pulp and Paper Mills.
Another plant in this category, Boise-Cascade, was burning
ES-6
-------
TDF in a lime kiln, and is included in Chapter 4, Tire and
TDF Use in Portland Cement Kilns.
Of the remaining "other" category, only two supplied test
data. The results are so mixed that.no trends or
conclusions could be drawn.
Pyrolvsis
There are essentially no process emissions from pyrolysis
units. The primary sources of emissions are fugitive
sources (for particulate emissions) and equipment leaks (for
VOC emissions). The fugitive particulate emissions come
from handling, crushing, screening, and packaging the char
by-product from the process. There is nothing meritorious
about these emissions and they can be handled using standard
dust control practices, canopy hoods for dust collection,
and a baghouse for particulate removed. The dust generated
does not appear to be hazardous.
The VOC emissions occur from leaks around from valve stems,
pump shafts, worn packings, and pipe joints. Fugitive VOC
emissions can be minimized with proper design and specifying
seal-less pumps and valves, and with good preventive
maintenance.
Emission Control Devices
All plants that tested and/or used TDF used the control
devices already installed at the facility except Oxford
Energy, who designed their control equipment specifically
for controlling emissions from burning tires. Most plants
have not modified their control equipment to facilitate
burning tires or TDF. An exception was Smurfit, a pulp and
paper mill. Smurfit was replacing their venturi scrubber
ES-7
-------
with an ESP to improve particulate removal and to increase
the amount of TDF they are permitted to burn.
Whether burning tires or TDF improves or deteriorates
emissions appears to depend on the control devices
installed. ESP's seem to work the best for controlling
emissions while burning tires or TDF. It is believed that
the zinc content actually helps the ESP perform better, and
this improved performance is seen in reduced emissions.
Fabric filters (baghouses) also seem to be well suited for
the control of emissions while burning tires or TDF.
However, venturi scrubbers do not perform well when the
process is burning tires or TDF. As noted earlier, the
efficiency of venturi scrubbers decreases as particle size
decreases and emissions from tires and TDF contain
pollutants that are too small to be removed by venturi
scrubbers.
Cost Indications
Some companies have tested burning tire or TDF in their fuel
at the request of State agencies, but most are motivated by
the possibility of lowering their operating costs. The
savings resulting from replacing some of the primary fuel
with tires or TDF is very site specific. Factors that
affect the potential savings include the availability of
scrap tires, local processing costs to make TDF,
transportation cost, inventory and handling costs, and
governmental incentives. Other major factors are the
availability of primary fuel, transportation cost of primary
fuels, and availability and cost of other alternative fuel.
There are other considerations in using tires or TDF that
are not cost related, but could affect profitability. These
include the stabilizing effect of using a high-energy, low-
moisture fuel, and the possibility of reduced criteria
ES-8
-------
pollutants emissions. The latter could result in the
consumption of lower grade (and, therefore, lower cost) fuel
and still meet emission limits.
Conclusion
With the proper emission controls, burning tires for their
fuel energy can be an environmentally sound method of
disposing of a difficult waste. It can also be financially
advantageous and can improve the operating characteristic of
a rtumber of processes.
ES-9
-------
1. INTRODUCTION
Air pollution control agency personnel have an increasing
need for technical information describing the air pollution
implications of several methods of waste or scrap tire
disposal. Environmental concern for tire disposal has
historically focused on the solid and hazardous waste issues
involved. Further, much information has already been
written describing the comparative merits of disposal
alternatives such as recycling,, pyrolysis, and burning for
fuel, in minimizing scrap tires and maximizing recycle
markets. Air quality issues resulting from waste tire
disposal issues, however, have not been as well documented.
The U.S. Environmental Protection Agency's Control
Technology Center recognizes the need for data describing
the air quality impacts of two of these disposal options ~
the controlled burning of tires to recover its fuel value
and pyrolysis for fuel and carbon black. The purpose of
this report is to summarize available air emissions and
control data and information on tire pyrolysis and burning
tires for fuel.
This report describes air pollution issues by source
category. Chapter 2 contains an overview describing the
types of process units primarily burning tires. Chapter 3
describes dedicated tire-to-energy facilities. Portland
Cement plants with experience burning tires are covered in
Chapter 4. Chapter 5 summarizes the experience of pulp and
paper plants in burning chipped tires as a supplemental
fuel. Electric utilities burning tires as a supplemental
fuel are described in Chapter 6. Chapter 7 includes any
other industrial facilities with experience burning rubber.
Last, Chapter 8 contains information on tire pyrolysis.
1-1
-------
1.1 WASTE TIRE GENERATION AND DISPOSAL
Waste tires are generated in the United States at an
estimated rate of approximately 240 million tires
(approximately 2.4 million tons) per year.1'2 These
estimates do not include tires that are retreaded or reused
second-hand; retreading and reuse are considered to extend
the life of a tire before it is scrapped.
Of the 240 million, between 170 and 204 million waste tires
generated annually are estimated to be landfiiled or
stockpiled.1-2 Tires pose a unique landfill problem, not
only because of their large numbers, but also because the
materials used to ensure their durability and safety also
make their disposal difficult. For example, whole tires do
not compact well, and actually "rise" through a landfill
mass to the surface as the dirt surrounding them compacts.1
Further, when stored in the open (either in a landfill or in
a tire stockpile), tire piles provide breeding grounds for
insects such as mosquitoes and rodents. One mosquito, the
Asian Tiger Mosquito, is slowly migrating across the
country, and is of particular concern, because it can carry
dangerous diseases such as encephalitis. Tires retain heat
and provide many pockets of still, shallow water that are
ideal for mosquito breeding. Open tire piles also can
ignite easily, creating toxic smoke and fumes, and are
difficult to extinguish. The resulting sludge creates a
serious ground water pollution problem.
Approximately 8 to 11 percent of the scrap tires generated
annually (approximately 192,000 to 264,000 tons/year) are
estimated to be burned for fuel.1'2 Section 1.2 below
discusses the advantage and disadvantages of tires as fuel.
Disposal options other than landfilling, stockpiling, or
burning account for approximately 5 to 16 percent of the
1-2
-------
tires generated.1'2 These options include manufacture of
fabricated products such as car moldings; reclaiming of the
rubber; manufacture of asphalt rubber for road binding
material, sealcoat, or asphalt paving aggregate; formation
of underwater reefs or highway barriers; and tire export.1'2
Table 1-1 provides additional detail on the estimated number
of tires for various recycle and energy recovery options.
Altogether, the existing stockpile inventory on a national
scale is estimated to be approximately 2 billion tires (20
million tons).1'2
1.2 WASTE TIRES AS FUEL
Tires can be burned whole, or can be 'shredded or chipped
before burning. Tires that are shredded into pieces are
called Tire-Derived-Fuel, or TDF. TDF that is very small
(i.e., less than 1/4" diameter) is sometimes called crumb
rubber. Crumb rubber can be burned or can be fabricated
into other .rubber products. TDF that results from tire
recapping operations is called rubber buffings, and is made
up of small one-half inch slivers. Material handling
capabilities of facilities burning whole tires must be able
to accommodate a fuel that is large, heat intensive, and
contains a significant amount of metal. Burning TDF also
requires material handling creativity, but TDF is more
readily adaptable to the material handling and combustion
capabilities of many fuel-burning sources. TDF can be
•
shredded to sizes as small as 1-inch square.
•
Radial wire is the mat of steel placed under the tread to
enhance tread strength and durability. Bead wire consists
of many strands of high tensile strength steel that provide
strength and reinforcement to the tire side walls. Radial
and bead wires can account for as much as 10 percent of the
total weight of a tire.3 The remainder of the weight of the
tire is about 60 percent rubber, and 30 percent fiber.
1-3
-------
Table 1-1. Scrap Tire Generation
(millions of tires per year)
EPA,
Markets for Scrap
Tire Study1
Scrap Tire
Management
Council,
19902
Total Scrap Tires
Generated
242
240
Landfill/
Stockpile
Energy Recovery
Fabricated
Products
Reclaim Rubber
Asphalt Rubber
Reefs/Barriers
Tire Exports .
Retread6
Reuse6
187.8
25.9
11.1
2.9
2.0
p.3'
12
33.5
10
170.4
19.2
2.4
4.8
0.2
4.8
- 204.0
- 26.4
-12.0
-12.0
1.2
- 4.8
- 9.6
12
0
1 Includes use for playground equipment and erosion
control.
b Retreaded tires and reused tires are not considered
"scrap" tires. Thus, although the number of tires
retreaded or reused are reported here for completeness,
they are not included in the estimates of total scrap
tires generated.
1-4
-------
1.2.1 ffaste Tire Characteristics and Composition
Tires are a good fuel for several reasons. Tires contain
about 15/000 Btu's per pound (about 300,000 Btu's per tire).
Coal heating values range from 6,000 to 13,500 Btu's per
pound. Further, they are compact, have a consistent
composition, and contain a low moisture content. Also, many
components of tires, such as sulfur and nitrogen, compare
favorably to coal in percent makeup. Table 1-2 compares
composition of tires to that of midwest coal.4 Table 1-3
compares composition of various types of tires.5 Most trace
metal levels in tires are equivalent to the levels in coal;
zinc and cobalt are higher in tires.6 Figure 1-1 shows
trace metal level of whole tires compared to bituminous
coal.6
On the other hand, the size of whole tires requires the
ability to feed large fuel to a burner, and their strength
makes them difficult to cut into more manageably sized
pieces of fuel. Also, chlorine, ash, and volatiles are
present in higher quantities in tires and TDF than in most
coals. Further, the metal contained in tires, in the form
of the radial wire and bead, wire can be a problem in many
fuel applications. For example, loose or molten wire can
clog ash exit or grate combustion openings in boilers.
1.2.2 Waste Tire and TDF Cost Considerations
Sources desiring to burn tires may obtain them in several
ways. Whole tires can be obtained from two basic sources.
First, tires can come from the "flow"; that is, from retail
businesses collecting old tires on a daily basis. This
includes tire .manufacturers, tire retail stores, and tire
collectors, sometimes called tire jockeys. Tire jockeys
cull the tires they collect for those that can be reused or
retreaded, and then sell the remainder. Second, tires can
1-5
-------
Table 1-2. Comparative Fuel Analysis, by Weight
Fuel
TOF
Ctarlfler
Sludoe
Coal
Wood Uaate
Teat 1
Teat 2
Teat 3
Test 4
Table
Tire Stock
Flberglaa*
belt
Stect belted
Nylon
Polyester
Kevlar Belted
Carton
83.57
4.36
73.92
30.96
28.29
25.67
24.71
Heating
Value
Hydrogen Oxygen Nitrogen Sulfur Aaft Moiature
7.09 2.17 0.24 1.23 4.78
0.49 2.17 0.47 0.26 3.16
4.8S 6.41 1.76 1.59 6.23
3.16 23.33 0.13 0.04 1.31
2.37 20.95 0.13 0.03 1.49
2.54 19.17 0.12 0.03 1.11
2.44 18.46 0.12 0.02 1.13
1-3 . Comparative Composition and Fuel
of Various Tire Types5
Heating
Value
(Btu/lb)
13,974
11,478
14,908
14,752
16,870
Components, UtX
C M, 0, M, S
75.8 6.62 4.39 0.2 1.29
64.2 5.00 4.40 0.1 0.91
78.9 6.97 5.42 <0.1 1.51
83.5 7.08 1.72 <0.1 1.20
86.5 7.35 2.11 <0.1 1.49
0.62
88.69
5.24
41.05
46.73
51.36
53.12
Value
Ash
11.7
25.2
7.2
6.5
Btu/lb
15,500
924
13,346
5,225
4,676
4,031
4,233
F1
<0.02
<0.02
<0.02
<0.02
1-6
-------
I
-4
100000
B 10000
o.
§
3
1
0>
a
o
•-3
i
o
U
1000
100
10
o.i
0.01-=
0.001
WP&LDaia
Oxford Energy Data
I 3
I
1
o
•as!
51 '5 t
«
•S
o
I 1
e
1
U
4>
U
3
E
3
C
U
2
U E
^ S
o •§
E E .S
3 2 H
•§
• c
o
K
u
a
NOTE:
Figure 1-1. Trace metal levels in whole waste tires
compared to bituminous coal.5
Tick mark* Indicate measured waste tire metal concentrations. Bar shows the range in trace MUl concentrations Measured i»
bltinfnou* coal .
-------
come from existing piles, in which the tires are often old
and very dirty. TDF must be purchased from a tire-shredder,
or shredded on-site using purchased or leased equipment.
Energy required to produce smaller sizes of rubber pieces
increases exponentially.7 For example, about 40 Btu's are
required to produce one pound of 6-inch TDF, while 750 Btu's
are required to produce a pound of 1-inch TDF.7 From a
general cost perspective, 2-inch TDF, wire-in TDF, can cost
as little as $20/ton, whereas crumb rubber (wire-free, from
20-30 mesh) averages $160/ton.7 Capital costs, of course,
vary according to capacity. A shredder that can chip 100
tires/hr into 2-inch TDF costs about $50,000; larger
machines (1000 tires/hr capacity) can cost $500,000.7
Haulers may be paid from $0.35 to $5.00 to dispose of whole
tires.1 In general, the cost to landfill whole tires is
double the cost to landfill mixed municipal solid waste.
The rate charged for landfilling whole tires depends on the
quantity of tires being landfilled and the region of the
country- For small quantities, landfill fees range from $2
to $5 per truck tire.1 One survey in Illinois found that,
in 1990, Chicago-area landfills charged an average of $2.98
to landfill each passenger tire.7 For large quantities,
tipping fees range from $35 to $100 per ton for whole tires.
In some instances, a landfill's bad experience with whole
scrap tires have led to a ban on the tires.
Shredding companies charge from $19 to $75 per ton to form
TDF.1 Many States and municipalities allow landfilling of
shredded tires, but not whole tires. In States where
landfill space is at a premium, and tire tipping fees are
high, landfilling shredded tires can result in a
considerable savings over disposing of the tires whole.1
1-8
-------
One TDF supplier has found that pulp and paper mills are the
most profitable (i.e., purchase the most expensive type of
TDF) type of customer, followed by cement plants and utility
boilers.8 Pulp and paper mills pay a higher price for TDF
for several reasons. First, the pulp and paper mills demand
a higher quality of shredded tire; that is, tires that are
clean and have all the metal removed.8 Second, they do not
have the fuel-buying power that a utility might have; thus,
tires provide a proportionally larger economic incentive for
them.8 One pulp and paper mill was paying approximately $39
and $43/ton for TDF in 1990 and in part of 1991,
respectively.9
Cement manufacture is a power-intensive process, which
allows cement companies to buy fuel in bulk and obtain the
fuel at a somewhat lower price. Also, kiln feed mechanisms
are easily modified, to accept alternate fuels. Further,
because temperatures in a kiln reach 2700*F, kilns can burn
poorer quality coal than pulp and paper mills or even
utilities, and can easily tolerate a wide variety of waste
products.10 In addition, kilns can accommodate the lower
priced TDF (wire-in TDF and even whole tires). These
factors make the economics of supplying TDF to cement
manufacturers less favorable than for pulp and paper
mills.10 One cement manufacturer is paying approximarely
$30/ton for TDF.11
Utilities have the least economic incentive to use tires.8
Often, power plants that use TDF only substitute up to 5
percent of their total energy requirements with TDF.
Utilities must buy better quality coal (i.e., higher heat
value and lower ash) than cement plants, but have
significant bulk fuel-buying power. They are not usually
interested in TDF unless the price is $1 per million Btu's
(MMBtu's) ($30-$31 per ton) or less.8 The use of petroleum
coke has recently been increasing in the utility industry,
1-9
-------
partially in response to the reduced demand for coke in the
depressed steel industry.10 Coke often costs from $0.50 to
$0.75/MMBtu ($14 to $21 per ton), which is difficult for TDF
to match in many regions.10
Regional economics of TDF are paramount. Electric Power
Research Institute (EPRI) created a computer model of TDF
use in a cyclone-fired boiler. The model included an
economic analysis of alternative fuel firings to account for
the fact that, if boiler efficiency decreases, the company
would need to purchase power to replace power lost by the
boiler derating.12 These costs are called "busbar power
costs".12 Even considering the decrease in the net heat
rate caused by TDF use, the model found that TDF provided
overall savings in levelized busbar power costs relative to
100 percent coal-firing.12
1.2.3 Air Pollution Emissions Issues
The principal concern when using tires for fuel is the
effect on emissions. Pollutants of particular concern
include criteria pollutants, particulates, metals, and
unburned organics.
Particulate emissions may increase if combustion is not
complete. As seen in Tables 1-2 and 1-3, sulfur emissions
may decrease if the tires or TDF replace higher sulfur coal,
but may increase if tires or TDF replace wood waste
containing little sulfur. NOX emissions, likewise, may
increase or decrease based on the relative nitrogen content
of the fuel. Also, NOX emissions may increase if additional
excess air enters the combustion system to facilitate the
feed of the tires or TDF.
Heavy metal content varies in tires and TDF relative to coal
as shown in Figure l-l. in particular, zinc, which is added
1-10
-------
to tires during rubber compounding to control the rate of
vulcanization, has the potential to increase from an
emissions standpoint.13
Organics, especially polynuclear aromatic hydrocarbons, were
measured at a number of facilities. Dioxin and furan
formation are also of concern because of their toxic nature.
The two main process units burning TDF and tires are kilns
and boilers. Kilns are usually controlled by electrostatic
precipitators (ESP's) or fabric filters. Boilers are
usually controlled by venturi scrubbers or ESP's, although
some are uncontrolled.
A recent EPA report characterized the emissions from the
simulated open burning of scrap tires under experimental
conditions.14 The report identified several pollutants of
potentially significant health concern from uncontrolled
scrap tire fires, including benzo(a)pyrene, benzene, lead,
zinc, and numerous aromatic organic compounds.14
Environmental concerns identified by the report included
leaching of metals present in the ash to groundwater systems
and localized problems resulting from high SO2 emissions.
1.3 MARKETS FOR TIRES AS FUEL
Applications that can burn whole tires include a few cement
kilns, large dedicated tires-for-fuel boilers, and some
experimental applications in utility boilers. Applications
that can use TDF include most cement kilns, many thermal
decomposition units, boilers at pulp and paper plants,
utility plants, and other industrial facilities.
As described in more detail in subsequent chapters, the
desirability of tires or TDF varies among each industry.
Often that advantage is regionally specific, because the
1-11
-------
incremental benefit of tires is tied to regionally
comparative fuel prices.
The U.S. Environmental Protection Agency's Office of Solid
Waste recently produced a report entitled "Markets for Scrap
Tires", which summarizes the barriers to development of TDF
markets for dedicated tire-to-energy facilities, other
utility facilities, the cement industry, the pulp and paper
industry, and pyrolysis facilities. Table 1-4 summarizes
the reported barriers.
1.4 STATE WASTE TIRE DISPOSAL PROGRAMS
As of January 1991, 33 States had laws or regulations
pertaining to disposal of waste tires. Other States
introduced waste tire measures in their respective 1991
State legislatures. Nine States remain with no legislation
passed or pending.15
Table 1-5 shows the status of waste tire disposal laws for
States with laws, and summarizes some features of the
measures.15 Table 1-6 lists States with laws or regulations
proposed and those with no planned laws or regulations.
Many States have provided funding for reasons such as
developing scrap tire recycling industries and administering
disposal programs. Funds also are dedicated to increasing
tire or TDF market incentives by methods such as allowing
price preferences when purchasing recycled and recyclable
goods, or to give priority status to businesses proposing to
expand use of tire derived material. Table 1-5 also lists
which regulations cover storage, processing, or
transportation of tires.15
Of the 33 States with either laws or regulations in place,
over half (18) include market incentives for tire use such
as a monetary rebate, grant, loan, or funds for testing.
1-12
-------
Table 1-4. Market Barriers to TDF Use1
Industry
Economic Barriers
Hon-economic barriers
Dedicated Tirt- to-
1. Cost of air pollution
equipment.
1. Siting.
P o*er Industry
1. Lou utility buy-back rstes for 1.
electricity in many regions of
the U.S.
2. Low tipping fee in many
regions.
Siting.
Cement 1. Handling and feeding capital 1.
costs.
2. Low cost of alternate fuels.
3. Expense and downtime in
environmental permitting
process.
Delay in environmental
permitting procedures.
Pulp and Paper Mills 1. Wire-free TDF is expensive. 1.
2. Handling costs. 2.
3. Low alternate fuel cost. 3.
Wire in TDF can plug
hog fuel boilers.
Wire can limit ash
market.
Higher PM emissions
than for hog-fuel
alone.
Use of new fuel often
requires reopening of
environmental permits.
Pyrolysis Facilities
1. Capital and operating costs.
2. High cost for upgrading char
by-products.
Upgrading char needs
to be commercially
denonstrated on •
sustained basis.
1-13
-------
Table 1-5. Waste Tire Disposal Laws in the U.S.15
January 1991
State Regulatory
Coverage
AZ P
CA S,P
CO S.P
CT S
FL S.P.H
U S.P.H
IN S
IA
KS S.P.H
mr s
LA C
ME S,P.
N (draft)
MD S.P.M
Ml S.P.H
MM S.P.H
MO S.H
Funding Source Market Incentives Landfill
Restrictions
2X tales tax on bans whole tires
retail «ale
».25/tlre disposal grants
fee
Si/tire retell KID grants tires auat be cut
•ales '
$. SO/vehlcle title grants/loans
penal t fees/tire grants tires oust be cut
storage sites
bans whole tires
S. SO/tire retail grants tires aust be cut
sales
Si/tire retail tires nust be cut
•ales
tires suit be cut
Si/tire disposal
fee
State budget
appropriations
S.SO/vehicte title grants
fee
(^/vehicle title grants bans whole and
transfer cut tires
$. SO/ tire retail funds/testing ban* whole tires
Air Emissions delated Contents
Report fro* Integrated waste Management Fund due
12/1/91 on feasibility of tire use In ceawnt
kilns, pulp and paper, and other operations.
Funding 5 TOF teat burnt In 1991; IL paya 90X of
teat cost (Reference 7). Lou Interest loan* to
fuel user* to retrofit or laprov* equipment.
Funding 5 TOF test burn* In 1991 pay* 90X of test
cost (Reference 7). Lou Interest loan* to fuel
users to retrofit or Improve equipment.
Waste tire abatement report recoonend* use of TOF
•t the 3 State Universities.
sales
ret«*I
-------
Table 1-5. (Concluded)
I
M
HI
State Regulatory .
Coverafle"
NC S.P.H
MH S
OH
OK S,P
OR S,P,H
Rl S,P
SO S.P
TN
TX
UT
VA
VT
UA S.P.H
Ul S.P.H
WV
WY
funding Source Market Incentive* Landfill Air Emission* Related Cements
Restrictions
tX tales tax on new funds county tire tires must be cut
tires collection
toun graduated
vehicle
registration fee
tires must be cut
Si/tire surcharge grants tires mst be cut
new tire sales
Si/tire disposal S.OI/lb tires must be cut
tax on rvew tire
sales
S. SO/tire tax on Law bant tires as • source of fuel within State,
new tire sales within 30 siile of any reservoir watershed, and
bans tire export outside State as a fuel source.
tires aust be cut Open burning banned except In area* with
populations under 5,000.
bans whote tires
bans whole tires
graduated tax per S20/ton
tire size
S. 50/tire disposal funds/testing Several State subsidized testa of TDF and whole
fee on new tire tires.
sales
fl/vehicle grants
registration
S2/tire per vehicle *20/ton tires must be cut Tires have been burned at 4 facilities In Ul.
title fee
' S • Storage regulations
P • Processor regulations
H • Hauler regulations
-------
Table 1-6. States Without Laws or Regulations for Waste Tire Disposal15
January 1991
i
M
Ok
State
AK
M
HS
NV
sc
Al
OE
CA
Status legislative Comments Air (Missions ••(•ted Cements
Proposed
Proposed
Proposed
Proposed NV also has environmental conservation law tilth
section thst regulates tire transportation.
Proposed
Hone Solid waste Management plan under development
None No legislation
None 1990 Comprehensive Solid Watte Management plan has
no stated tire disposal requirements.
HI None Draft statewide solid waste nanagenent plan does
not addresa tires.
Honolulu County plans • scrap tlra •anagesjent progrs
that would provide for tire shredding for sale to
Honolulu Power.
10
NV
NJ
NO
PA
None
None
None
None
None
Proposed bill to require State solid waste
planning encourages general recycling.
Solid waste plan before legislature does not
attrition tires.
1987 Recycling Act has tire recycling incentives,
but no restrictions.
No legislation.
Two waste tire bills Introduced in last years;
neither resulted In legislation. No plans for
1992.
S • Storage regulations
P • Processor regulations
H • Hauler regulations
-------
The law in one State, Rhode Island, bans tire burning as a
source of fuel within the State and within 30 miles of
reservoir watershed.15 Furthermore, it bans tires exported
from the state to be burned as fuel.15 South Dakota
regulations, on the other hand,-permit open burning in areas
with populations under 5000.1S
1.5 METHODOLOGY
First, a literature search was conducted to gather
information on pyrolysis and burning tires for fuel and to
identify companies using tires or TDF in their process.
Information was gathered on emissions, control techniques
required, control technique effectiveness, and control
equipment cost.
Second, information was gathered through contacts with EPA
Regional, State, and local air pollution control agencies.
Copies of emission test results were requested and analyzed
to determine the effect of burning tires either as the sole
fuel or as a supplemental fuel. Permit applications and
permits were reviewed to determine the processes using
tires, the control techniques used, the limits set, and the
permit conditions under which the permits were approved.
Trade associations provided information on companies burning
tires, and other available information.
Third, site visits were planned to facilities burning tires
or •TDF. Six companies, one from each major industry group
using tires for fuel or pyrolysis, were selected for site
visits. The facilities visited included the following:
• An electrical generating plant using tires as its
only source of fuel
• An electrical generating plant using tires to
supplement their primary fuel
1-17
-------
• A cement manufacturer using tires to supplement its
primary fuel in a vet process cement kiln
• A cement manufacturer using tires to supplement its
primary fuel in a dry process cement kiln
• A paper mill using tires to supplement their fuel in
a waste heat boiler
• A pyrolysis plant thermally decomposing tires into
products.
In addition, a facility that shredded whole tires into TDF
was visited. At each site, information was collected on the
processes using tires, modifications necessary to
accommodate tire use, control equipment in use, effect of
tire use on emissions, control equipment effectiveness, cost
of process and control equipment changes, changes in
personnel or resource needs, and benefits of tire use.
Problems using tires, and tire supply issues, such as
source, quality, and reliability, were also discussed.
1-18
-------
1.6 REFERENCES
1. U.S. Environmental Protection Agency, Office of Solid
Waste. Markets for Scrap Tires. EPA/530-SW-90-074B.
September 1991.
2. Scrap Tire Management Council. Scrap Tire Use/Disposal
Study. September 11, 1990. p. 1-4
3. Murphy, M.L. Fluidized Bed Combustion of Rubber Chips:
Demonstration of the Technical and Environmental
Feasibility. Energy Biomass Wastes. 11:371-380.
1988.
4. Jones, R.M., J.M. Kennedy, Jr., and N.L. Heberer.
Supplementary Firing of Tire-Derived Fuel (TDF) in a
Combination Fuel Boiler. TAPPI Journal. May 1990.
5. Pope, K.M. Tires to Energy in a Fluidized Bed
Combustion System. Presented at EPRI Conference:
Waste Tires as a Utility Fuel. San Jose, CA. January
28, 1991.
6. Wisconsin Power and Light. The Operational and
Environmental Feasibility of utilizing Tires as a
Supplemental Fuel in a Coal-Fired Utility Boiler
Preliminary Report. State of Wisconsin. 1990 Waste
Tire Management and Recovery Program.
7. Berger, C., Illinois Scrap Tire Management.Study
Summary. Illinois Department of Energy and Natural
Resources. Presented at the EPRI Conference: Waste
Tires as a Utility Fuel. San Jose, CA. January 28,
1991.
8. 'Memorandum from Clark, C., Pacific Environmental
Services, Inc. (PES),"to Michelitsch, D., EPA/ESD/CTC.
October 2, 1991. Site Visit — Waste Recovery, Inc.
9. Memorandum from Clark, C., PES, to Michelitsch, D.,
EPA/ESD/CTC. October 2, 1991. Site Visit — Smurfit
Newsprint Corp.
10. Schwartz, J.W., Jr. Engineering for Success in the TDF
Market. Presented at the Recycling Research
Institute's Scrap Tire Processing and Recycling
Seminar, "West Palm Beach, FL. April 27, 1989-
11. Memorandum from Clark, C., PES, to Michelitsch, D.,
EPA/ESD/CTC. October 28, 1991. Site Visit —
Calaveras Cement Company.
1-19
-------
12. McGowin, C.R. Alternate Fuel Co-Firing with Coal in
Utility Boilers. Presented at the EPRI Conference:
Waste Tires as a Utility Fuel. San Jose, CA. January
28, 1991.
13. Gaglia, N., R. Lundquist, R. Benfield, and J. Fair.
Design of a 470,000 Ib/hr Coal/Tire-Fired Circulating
Fluidized Bed Boiler for United Development Group.
Presented at EPRI Conference: Waste Fuels in Utility
Boilers. San Jose, CA. January 28, 1991.
14. U.S. Environmental Protection Agency: ORD:AEERL:CRB.
Characterization of Emissions from the Simulated Open
Burning of Scrap Tires. EPA-600/2-89-054. October
1989.
15. Recycling Research Institute. Third Annual Legislative
Update. The Scrap Tire News. Vol. 5, No. 1. January
1991.
1-20
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2. OVERVIEW OF PROCESS UNITS BURNING TIRES FOR FUEL
Controlled burning of tires or TDF for fuel value occurs
most frequently in two types of process units - kilns and
boilers. This chapter will describe the general process
operation of cement kilns and boilers. The various types of
boiler configurations will be described with attention to
the implications for burning tires or TDF. Kilns in two
industries have burned tires or TDF supplementally - lime
manufacturing and, more commonly, cement manufacturing.
Currently, in the U.S., a few boilers operate by burning
solely whole tires or TDF, all in the electric utility
industry. These are discussed in chapter 3, Dedicated
Tires-to-Energy Facilities. Chapter 4, Tire and TDF Use in
Portland Cement Kilns, discusses in more detail the use of
TDF in lime and cement kilns.
Most often, boilers burn tires or TDF as a supplemental fuel
for either coal, gas, refuse-derived-fuel (RDF), or wood
waste. The two industries where supplemental use of TDF is
most prevalent are electric utilities, where the primary
fuel is most often coal, and pulp and paper mills, where the
primary fuel is most often wood waste, also known as hog
fuel. These industries are discussed further in Chapter 5,
TDF Use in Waste Wood Boilers, and Chapter 6, Tires as
Supplemental Fuel in Electric Utility Boilers.
Finally, several other industrial processes have tested or
used TDF as a supplemental boiler fuel to coal or RDF.
These include plants that manufacture chemicals, glass,
grain, steering and gear manufacturing, and tractors. These
other industrial processes are grouped together, and are
discussed in Chapter 7, Supplemental TDF Use in Other Boiler
Applications.
2-1
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2.1 KILNS
Rotary portland cement kilns can use TDF or whole tires as
supplemental fuel. Kilns are large cylinders that tilt
slightly downward to one end and rotate slowly, so that feed
materials travel to the far end by gravity.1 Fuel is
generally fired at the lower end, so that the hot gases rise
upward through the kiln, passing countercurrent to the
descending raw feed material.1 As feed travels down the
kiln, water is evaporated, and a chemical reaction occurs by
which the feed changes to a rock-like substance called
clinker. Clinker is cooled after exiting the kiln, and then
ground with gypsum to make cement.1 Under normal operation,
no solid waste such as ash or slag exits the kiln; all raw
feed and fuel components are incorporated into the clinker.
Even if the kiln is upset, the out-of-specification clinker
that results can often be reground and recycled to the kiln.
Details of the cement process and environmental impacts are
presented in Chapter 4.
When whole tires are used as supplemental fuel in cement
manufacture, they generally enter the process at the upper
feed end of the kiln. Depending on the specific process
flow at a facility, TDF can be added at the feed end, at the
lower (firing) end, or in a raw feed preheater/precalciner
that is lo'cated before the raw feed entrance. These options
are described in more detail in Chapter 4, Tire and TDF Use
in Portland Cement Kilns.
2.2 BOILERS
The type of boiler configuration and firing method
significantly affect the success of burning tires or TDF.
This section serves to summarize the implications of burning
TDF in several boiler configurations most common in the
industry at this time.
2-2
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Coal fuel in boilers is primarily combusted by suspension
firing or by grate firing. Boiler configurations that
combust fuel in suspension include the fluidized bed and the
cyclone types. Combustion occurs primarily on the grate in
underfed stoker boilers. Combustion happens both in
suspension and on the grates in spreader stoker type
boilers, depending on the fuel size and the grate type,
i.e., traveling, reciprocating, or chain.
TDF is difficult to burn in suspension because of its size
and weight. Some industrial experience exists burning TDF
in pulverized, cyclone, and spreader/stoker boilers. One
utility tested whole tires in a pulverized boiler.
Recently, much interest and some TDF testing has focused on
TDF use in fluidized bed boilers, where fuel is suspended in
a hot bed of inert material.
Metal contained in tires can cause operational difficulties.
If whole tires or TDF, wire-in, is used, the wire must be
removed from the grate or bed. Wire that becomes trapped on
the grate can become molten and plug grate holes vital to
incoming combustion air.2 Small pieces of radial mat-type
wire can form "bird-nest" shaped accumulations that block
conveyor joints, slag exit points, and augers.2 Further,
facilities selling the slag that results from combustion may
need to separate the metal from the slag to maintain a
salable product. One facility quenches their slag into
small beads, which they sell. Because buyers could not
tolerate the heavy sharp bead wire, the company installed a
magnetic separator to remove the wire. Other facilities
have decided that wire-free TDF is mandatory.3-4
Zinc content of the tires may be an issue, also. Boilers
that combust fuel in suspension typically maintain a higher
chamber temperature (2000*F) than those that combust on a
grate (1600-1650'F). At 2000'F, zinc compounds from the TDF
2-3
-------
may be fairly volatile.5 Zinc oxide crystals could condense
onto the slag or ash surface in cooler areas, in which case
the zinc could leach later from a landfill and cause the
groundwater to exceed health standards.5 Zinc, however,
could also be trapped in the glassy melt, from which it
would not be leachable.9
The following sections describe each boiler type and
summarize its operation with and without TDF.
2.2.1 Pulverized Coal Boilers
In a pulverized boiler, the coal is ground to the
consistency of talcum powder in a mill, and then entrained
in an air stream that is fed through the burners to the
boiler combustion chamber.6 Firing, therefore, occurs in
suspension. Pulverized boilers can be wet-bottom, which
means that coals with low ash fusion temperatures are used,
and molten ash is drained from the bottom of the furnace, or
can be dry bottom, which means that coals with high ash
fusion temperatures are used, and dry ash removal techniques
can occur.6
The ash fusion temperature is the temperature the ash
particles begin to melt and agglomerate; fused ash causes
plugging of the holes in the grate, and can cause
significant damage to the boiler. Therefore, a higher ash
fusion temperature means fewer ash problems. However, the
iron content in TDF tends to lower the fusion temperature of
the ash. In some cases, therefore, a higher quality coal
with a higher fusion temperature may be required to
counteract the effect of the TDF.
Because pulverized coal boilers are designed to burn fuel in
•
suspension, small TDF are typically used.7 TDF is often a
maximum of 1-inch in diameter, but can be as small as 1/4-
2-4
-------
inch.7 Even so, pulverized coal boilers must often be
modified with a bottom dump grate, so that the TDF that
falls to the bottom can combust.7 One utility is testing
whole tires in a pulverized coal boiler.8 This is described
in more detail in Chapter 6.
The Electrical Power Research Institute (EPRI) created a
computer model to evaluate co-firing three alternate fuels
with coal in a 50 MW pulverized unit, retrofitted to
accommodate feeding of the alternate fuels.7 The
particulate emissions from the boiler were assumed to be
controlled by an ESP. The model assumed that TDF were 1-
inch maximum in size, wire-free, and that the percent TDF
varied from 0 to 100 percent. The boiler was assumed to
require modification of receiving, storage, and pneumatic
transport equipment, and installation of a bottom dump grate
to ensure complete combustion of larger pieces.7 The
results showed that TDF, co-fired with coal, does not
.significantly affect boiler performance.7 Boiler efficiency
did decrease and net heat rate did increase with increased
percent TDF, because the higher excess air that was required
more than offset benefits of higher heat and lower moisture
of the TDF as compared to coal.7 Although EPRI did model
TDF input up to 100 percent, the paper noted that, in
reality, 20 percent TDF might be the limit in most boiler
configurations because of boiler limitations on fuel or
performance.7
2.2.2 Cyclone Boilers
Cyclone boilers, like wet-bottom pulverized coal units, burn
low ash fusion temperature coal, but the coal is crushed so
that 95 percent is smaller than 1/4 inch.9 The coal is fed
tangentially to the cyclone burners, which are mounted
horizontally on the outside of the boiler and are
cylindrical in shape.9 A typical cyclone burner is shown in
2-5
-------
Figure 2-I.10 Small coal particles are burned in
suspension, but larger particles are forced against the
outer wall. The resulting slag is mostly liquid because of
the high radiant temperature and low fusion temperature, and
is drained from the bottom of the furnace through a tap.6
Cyclone furnaces are most common in utility and large
industrial applications.
Because most of the ash is removed as molten slag, addition
of a bottom grate is not necessary.7 However, small TDF is
required, because much of the combustion must occur in
suspension.7 TDF that is too large to combust completely
can get carried over into the boiler or dust collection
system, and cause blockage problems.9 Therefore, particle
size may inversely determine the amount of TDF that can be
used in a cyclone boiler.11 Three cyclone-fired boilers at
utilities have burned 1" x 1" TDF in test operation, one at
the 2 percent, one at the 5 percent, and one at up to a 10
percent level.3«9«12 one pulp and paper mill plans the use of
TDF in a cyclone-fired hog-fuel boiler.13
2.2.3 Stoker Boilers
In stoker boilers, fuel is either dropped or rammed onto a
grate. Stoker boilers are identified by the type of feed
mechanism and the type of grate. Feed may be by spreader,
overfeed, or underfeed. Grates may be travelling,
reciprocating, chain, or dump type.
Approximately 12 stoker boilers are burning TDF
supplementally on a commercial basis, all in the pulp and
paper industry (see Chapter 5). One industrial stoker
boiler at a tractor factory is testing TDF use. Five of
these 13 are underfeed stokers, and 8 are spreader stokers.
Of the spreader stoked boilers, 2 are reciprocating grates,
2 are travelling grates, and 4 are of unknown grate type.
2-6
-------
Igniter
Coal
nozzle
Figure 2-1. Typical cyclone coal burner.
10
2-7
-------
2.2.3.1 Spreader Stoker Boilers. The large majority of
boilers used to combust waste wood, or hog-fuel, are of the
spreader stoker type. The term "spreader" refers to the
type of fuel feeder used. A typical mechanical feeder on a
spreader stoker is illustrated in Figure 2-2. A spreader
stoker feeder imparts energy to a stream of crushed coal
being fed to the furnace.6 Fuel drops from a hopper through
a slot onto a flipping mechanism, often a wheel.2 Material
hitting the wheel is propelled onto the grate.2 Because
size of the fuel pieces affects how far the piece is thrown
by the wheel (larger pieces are propelled further than
smaller pieces), uniform coverage of the grate by the fuel
occurs.12 Some combustion occurs in suspension, and some
occurs on the grate. This type of combustion produces ash
that retains significant carbon content, and flyash
reinjection is common.
Spreader stoker boilers can have traveling grates,
reciprocating grates, or dump grates.6 A traveling grate
travels toward the feeder, and fuel on the grate is burned
with air coming through the grate. Large fuel pieces fall
quickly to the grate. Mid-sized pieces fall more slowly and
often land on top of larger pieces. The fines are caught in
the air up-draft, and are burned while suspended in air.
Ash is dumped at the end of the hearth, and is collected in
an ash pit below the grate.6 A reciprocating, or vibrating,
grate is comprised of bars that resemble a series of steps
sloping downward that move back and forth, pushing the
burning material through the boiler. This provides air flow
above and below the hearth. Ash and other materials may
fall through the grate to hoppers or be dropped in hoppers
at the end of the grate. Reciprocating and traveling grates
are continuously cleaned of ash. A dump grate does not have
continuously moving parts, and simply dumps ash at
intermittent intervals to a hopper. All these grates must
maintain a constant covering of ash or fuel, because exposed
2-8
-------
Deflector plate
with tuyeres
Reciprocating
feed plate
Revolving
rotor
Figure 2-2. Typical mechanical feeder
on a spreader stoker.10
2-9
-------
grate metal can be damaged by direct contact with the heat.4
Therefore, proper fuel sizing is imperative so that good
distribution of coal and ash on the grate results. Cooling
from the combustion air passing through the grate protects
the grate as does the insulating effect of the coal/ash
layer on top.6
To burn TDF successfully in a spreader/stoker furnace, the
particle size of the chipped tires must be slightly smaller
than the largest coal or wood size permitted so that the TDF
falls on top of a layer of primary fuel. Theoretically, a
bed of large fuel pieces is created on the grate, covered
with a layer of mixed TDF and smaller fuel pieces. If TDF
is in direct contact with the grate, oils from the rubber
would flow into the grate openings, carbonize, and plug the
grate. The size of TDF can be 2 to 4 inches in diameter.
2.2.3.2 Overfeed Stoker Boilers. Coal combusted in
overfeed stoker boilers is fed from above onto a traveling
or chain grate, and burns on the fuel bed as it progresses
through the furnace. Ash falls into a pit at the rear of
the stoker.6 The same TDF issues apply as were mentioned
under spreader stoker boilers.
2.2.3.3 Underfeed Stoker Boilers. In underfeed boilers,
fuel is pushed by rams or screw conveyors from underneath
the grate into the furnace through a channel, or retort, and
spills out of the channel onto the grate to feed the fuel
bed. As the fuel is pushed further from the center channel,
it combusts, and ash falls over the peripheral sides of the
grate into shallow pits.6 Some underfeed stokers have only
one retort, but double retorts exist with side ash dump, as
do multiple retort units with rear ash discharge. Heat loss
and maintenance costs are higher for this type of stoker.
2-10
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2.2.4 Fluidized Bed Boilers
A fluidized bed combustion system (FBC) is one that has a
high temperature (1500'F to 1600*F) inert material, such as
sand, ash, or limestone, occupying the bottom of the
chamber.14 Figure 2-3 illustrates a typical fluidized bed
boiler. Limestone, either as primary bed material, or as an
addition, provides the additional advantage of SO2
scrubbing.14*15 The advantage of fluidized bed combustion
over the other 3 boiler types is that the fluidization of
the inert bed material allows fuels with higher moisture and
ash content to be burned, and still yield nearly complete
combustion. Further, SOX control is easily and efficiently
accomplished. The bed material is fluidized by one of two
methods as described below.
In a bubbling FBC, incoming combustion air enters the
chamber through nozzles located a couple of feet below the
surface of the bed, producing a violent boiling action.14
Fuel is pneumatically injected into the chamber and is
suspended by this action.14 Combustion occurs partially in
suspension and partially in the bed. The bed material
continually scrubs the outside layer of ash from the fuel,
exposing fresh combustible material for burning.14 Dense
materials, like rocks and metal sink to the bottom of the
sand, where a line-bed changeout system continually pulls
this bottom layer out.14 The removed material is cooled,
magnets pull out the metal, and screens retain rocks or
other tramp debris. Bed material is then returned to the
combustor.14
In a circulating FBC system, the bed is fluidized by air
passing through a wall-mounted distributor.15 Combustion
occurs in the same way as in the bubbling FBC. Bed material
is gravity fed down into the bed.15 Fuel is fed into the
2-11
-------
Overbed
coal feed
Underbed
coal feed
Limestone
Flue gas
Steam
Underbed coal feed
Feedwater
Figure 2-3. Typical fluidized bed boiler.
10
2-12
-------
combustion chamber by an air-swept spout.15 The bed
material, containing fuel and ash, is then circulated
through a cyclone, where the lighter bed material and
unspent fuel are separated from the heavier ash, metal, and
other tramp material, and are recirculated back to the
bed.15
Wire removal from the fluidized bed in both systems has been
a design challenge. Hire can compose up to 10 percent of a
tire's weight.16 This wire does not change physical form in
a fluidized bed boiler, and accumulates, inhibiting or even
eliminating fluidization in the bed.16 Poor air/fuel
distribution results, eventually causing the system to shut
down.16
One FBC currently operating in Japan uses a revolving-type
fluidized bed that allows relatively large tire chunks (up
to 10 inches) to be fed to the chamber.4 The central
portion of this bed is more fluidized than the outer
portions, so solids flow to the center, where fuel is
injected.4 Deflectors above the outer bed area "lap" waves
of material back to the center.4 An air distributor directs
non-combustibles to drain chutes on each side of the bed.4
The amount of fluidizing air and overfire air is
automatically proportioned by optical devices that measure
furnace luminosity.4
•
One utility unsuccessfully tested TDF in a circulating FBC
boiler .that had been retrofitted from a spreader/stoker
design.4 Problems involved wire clogging the boiler grate
openings and ash drawdown, and overload of the particulate
control device. Two other FBC boilers are in the planning
stages, both at utilities, and both are designed for
supplemental TDF use. One is a circulating FBC design, and
one is a bubbling design.14-15
2-13
-------
Three pilot tests burning TDF have been performed on FBC
boilers, one of a bubbling FBC boiler, and two of
circulating FBC boilers. First, Energy Products of Idaho,
Inc. (EPI), tested a pilot 3 f t x 3 ft. bubbling bed FBC.
The test was in response to problems resulting from TDF
burning in a FBC boiler retrofitted from a spreader/stoker
design, and located at a Wisconsin power plant.16 Problems
during the commercial test indicated that better tramp metal
removal was necessary, combustion was not adequate, and that
the particulate control device, an electrified filter bed,
was not commensurate with the ash levels generated.16
Because the utility test showed that the tramp material exit
from the bed, a perforated "draw-down" cone, became clogged,
EPI designed an on-line bed changeout system, which
continually pulls the bottom layer of sand and wire out of
the bed, cleanses it, and returns it.14 Emission results of
the pilot test burning 100 percent tires are shown in Table
2-1.u
A second pilot test has been performed by Pyropower, Inc.,
in preparation for construction of a 52 MW, 468,000 Ib/hr
circulating bed FBC in Niagara Falls', NY, for United
Development Group.5 Design is for the plant to burn up to
20 percent TDF, wire-free.5 The pilot test was run on a 0.6
MW plant using from 16 to 50 percent TDF, wire-in, on a
weight basis.5 The test experienced problems with uneven
tire feed and wire accumulation at ash discharge points.
Lime was added to the bed to reduce sulfur emissions.16
Calcium to sulfur ratio was about 1.7 to 2.0, and resulted
•in 90 percent sulfur capture.5 Emissions of the pilot test
are summarized in Table 2-1.5
Third, a pilot test was performed by Foster-Wheeler
Development Corp., in preparation for the construction of a
2-14
-------
Table 2-1.
Emission test results of three Pilot FBC boilers
burning supplemental TOP5'14'15
EM, bubbling bed FBC
100X TOP*
Pyropotter, circulating
ted FBC
16-50X TDF
Foster-Wheeler
circulating bed FBC
20X TDF, wire-in
PM NO,
222 ppa,
"P^
0.21 -0.33
Ib/MWtu
0.146
ib/mstu
$0, VOC
630 pp., ND4
Wpprf
0.25-0.36
Ib/MNitu6
»
0.486
Ib/MMBtu
HCl CO
0 30 pp.
0*
0.1-0.3
Ib/MMBtu
0.116
Ib/MMBtu
* Fuel consumption and aass flow rate were not available; therefore, pounds per Billion Btu's could
not be determined.
With aoaonia spray for (to, reduction.
* With UM injected into bed for SO, reduction.
4 Not detected.
2-15
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20 MW, 200,000 lb/hr circulating bed FBC in Manitowoc, WI,
for Manitowoc Public Utility.15 The plant will be designed
to accommodate coal, petroleum coke, and limited amounts of
municipal waste water sludge, refuse-derived-fuel, and TDF,
wire-in. The pilot test burned 20 percent (by weight), 2-
inch, wire-in TDF.15 Two parallel baghouses controlled the
pilot unit.15 Emission results of the pilot test are
summarized in Table 2-1.15
2-16
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2.3 REFERENCES
1. U.S. Environmental Protection Agency. Office of Air
Quality Planning and Standards. Portland Cement Plants
~ Background Information for Proposed Revisions to
Standards. EPA-450/3-85-003a. May 1985.
2. Schwartz, J.W., Jr. Engineering for Success in the TDF
Market. Presented at the Recycling Research
Institute's Scrap Tire Processing and Recycling
Seminar, West Palm Beach, FL. April 27, 1989.
3. Schreurs, S.T. Tire-Derived Fuel and Lignite Co-Firing
Test in a Cyclone-Fired Utility Boiler. Presented at
EPRI Conference: Waste Fuels in Utility Boilers. San
Jose, CA. January 28, 1991.
4. Howe, W.C. Fluidized Bed Combustion Experience with
Waste Tires and Other Alternate Fuels. Presented at
EPRI Conference: Waste Tires as A Utility Fuel. San
Jose, CA. January 28, 1991.
5. Gaglia, N., R. Lundguist, R. Benfield, and J. Fair.
Design of a 470,000 Ib/hr Coal/Tire-Fired Circulating
Fluidized Bed Boiler for United Development Group.
Presented at EPRI Conference: Waste Fuels in Utility
Boilers. San Jose, CA. January 28, 1991.
6. U.S. Environmental Protection Agency. Compilation of
Air Pollution Emission Factors, Fourth Edition, AP-42.
7. McGowin, C.R. Alternate Fuel Co-Firing with Coal in
Utility Boilers. Presented at the EPRI Conference:
Waste Tires as a Utility Fuel. San Jose, CA. January
28, 1991.
8. Horvath, M. Whole Tire and Coal CoFiring Test in a
Pulverized Coal-Fired Boiler. Presented at EPRI
Conference: Waste Fuels in Utility Boilers. San Jose,
CA. January 28, 1991.
9. Stopek, D.J., A.K. Millis, J.A. Stumbaugh, and D.J.
Diewald. Testing of Tire-Derived Fuel at a 560 MW
Cyclone Boiler. Presented at the EPRI Conference:
Waste Tires as a Utility Fuel. San Jose, CA. January
28, 1991.
10. U.S. Environmental Protection Agency. APTI Course
SI:428A, Introduction to Boiler Operation. Self-
Instructional Guidebook. EPA-450/2-84-010. December
1984.
2-17
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11. Granger, John E. Fuel Characterization of
coal/Shredded Tire Blends. Presented at EPRI
Conference: Waste Fuels in Utility Boilers. San Jose,
CA. January 28, 1991.
12. Hutchinson, W., 6. Eirschele, and R. Newell.
Experience with Tire-Derived Fuel in a cyclone-Fired
Utility Boiler. Presented at EPRI Conference: Waste
Fuels in Utility Boilers. San Jose, CA. January 28,
1991.
13. Telecon. Clark, C., Pacific Environmental Services,
Inc. (PES), with Bosar, L., Fort Howard Corporation,
Green Bay, WI. February 27, 1991. TDF used at Fort
Howard.
14. Pope, Kent M. Tires to Energy in a Fluidized Bed
Combustion System. Presented at EPRI Conference: Waste
Fuels in Utility Boilers. San Jose, CA. January 28,
1991.
15. Phalen, J., A.S. Libal, and T. Taylor. Manitowoc
Coal/Tire Chip-Cofired Circulating Fluidized Bed
Combustion Project. Presented at EPRI Conference:
Waste Fuels in Utility Boilers. San Jose, CA. -January
28, 1991.
16. Murphy, M.'L. "Fluidized Bed Combustion of Rubber Tire
Chips: Demonstration of the Technical and Environmental
Feasibility." Energy Biomass Wastes. 1988 11:371-380
2-18
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3. DEDICATED TIRES-TO-ENERGY FACILITIES
Most facilities that burn tires or TDF use the rubber to
supplement a primary fuel such as coal, gas, or waste wood.
One company, however, the Oxford Energy Company, is
operating two electric power plants using tires as the only
fuel, and is planning several more.
3.1 INDUSTRY DESCRIPTION
Two dedicated tires-to-energy facilities, are currently
operational in the United States: the Modesto Energy
Project in Westley, California, and the Exter Energy Company
in Sterling Connecticut. The Modesto Energy Project is a
subsidiary of The Oxford Energy Company (Oxford Energy),
which.was founded in 1985, and is the only commercially
operating electric power plant using only tires for fuel.
The plant, which cost about $40 million to build, has a
potential generating capacity of 15.4 megawatts (MW) of
electricity per year and an actual capacity of 14.5 MW.1 It
was designed specifically to burn whole scrap tires as its
sole fuel. Although tire-derived fuels have been tried on a
smaller scale elsewhere in the world, the Modesto Energy
Project is apparently the first to operate successfully on a
large scale.2
The location of the Modesto Energy Project is directly
adjacent to the country's largest tire pile, which contained
at its maximum, somewhere between 30 and 40 million-tires.
The tires in this pile are piled up to 40 feet high, and
initially covered a canyon 1/4 mile wide for about a mile in
distance.1
The technology used for the Modesto Energy Project was
developed and licensed by the German company Gummi-Mayer in
the late 1970's. The prototype facility on which Modesto
3-1
-------
was based has been operating successfully since 1973, but
is only generating about 1 to 2 MW. Oxford Energy has
exclusive licensing rights for the technology for the entire
United States.4
In August 1991, Oxford Energy began start-up operations of
another dedicated tires-to-energy electric power plant,
called The Exeter Energy Company. Exeter, located in
Sterling, Connecticut, is a $100 million, 30 MW facility,
which is twice as large as the Modesto Energy Project.1
When commercial operation begins, power will be sold to
Connecticut Light and Power.5 No tire pile exists near the
Connecticut site, and Exter Energy Company uses a tire
collection system. A tire sorting center will be located in
Plainfield, Connecticut. The boilers can combust both whole
and shredded tires.6 An anticipated 10 million tires per
year will be used.1 The facility is anticipated to produce
a greater cash flow than the Modesto Energy Project because
all tires will come from the "flow", generating greater tire
tipping fees; the fuel feed system is less complicated (no
420-foot incline is needed); and the same size workforce is
used in generating twice the amount of electricity.1
Oxford Energy has also announced plans to build the Erie
Energy Project, to be located in Lackawanna, New York. . This
facility is a 30 MW, 10 million tire/yr, plant that is in
the last stages of planning for construction. The plant is
planned to be constructed in an Economic Development Zone,
which gives tax benefits to the company. Power sales will
be to New York State Electric and Gas. Construction is
•
anticipated to begin by the late 1991, with operation
beginning in 1993. The plant will not be required to obtain
a PSD permit, and a draft air permit and draft EIS have been
submitted.1
3-2
-------
A fourth facility, the Moapa Energy Project, is planned for
construction in Moapa, Nevada, about 50 miles northeast of
Las Vegas. The plant would require 15 million tires per
year to generate 49 MW per hour, and would sell power to
Nevada Power. The environmental impact statement and air
emissions permits for this facility have been accepted, and
public hearings are upcoming. Construction may begin in
1992, with operation commencing in 1993.1
3.2 PROCESS DESCRIPTION
This section of the report describes the process used at the
Modesto Energy Project.
Tires for the boilers are obtained from the adjacent tire
pile and from the community. Altogether, about 4.5 million
tires per year are burned! The Modesto Energy Project is
required to obtain about half of these tires from the
existing tire pile, and is permitted to acquire about half
of its fuel from the community (referred to as the "flow").
For example, 2.6 of the 4.8 million tires burned in 1990 at
the facility were from the "flow." This arrangement exists
to balance the need to reduce the size of the hazardous tire
pile with the desire of the company to obtain the most
economical source possible of tires. Oxford Energy
currently (1991) pays about $0.25 per tire for tires from
the tire pile, but receives money for each tire acquired
from the flow. The size of the tire pile will be decreased
until a tire reserve remains of about 4 million tires.1
Modesto has created a subsidiary, Oxford Tire and Recycle,
to collect and transport tires from tire dealers. The
company sorts the tires to remove good used tires for resale
for recapping or retreading. The remaining scrap tires
(approximately 80 percent) are fed whole to the boilers.1
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3.2.1 General Operation
The facility consists of two whole-tire boilers that
together generate 125,000 pounds per hour of 930 psig
steam.6 The output steam of the .80-foot high boilers
combines to drive a 15.4 MW General Electric steam turbine
generator. Figure 3-1 provides a schematic of the process
flow at Oxford.
Tires acquired from the "flow" are stored in a specially
designated area near the existing tire pile. The tires are
fed into a hopper located adjacent to the tire pile. An
automated tire feed system singulates tires (spaces them
individually) up to 800 tires per hour, to a conveyor belt
traveling 420 feet up a hill to the power plant. Tire feed
rate averages 350 to 400 tires per hour to each boiler:1
The boilers and feed system can accommodate tires made of
rubber, fiberglass, polyester, and nylon, and as large as 4
feet in diameter. Tires larger than four feet must be
chipped or used in other ways. Assuming each tire weighs
about 20 pounds, total weight of the tires fed to each
boiler is about 7,000 to 8,000 Ibs per hour. (Total energy
input is estimated to be 190 million (MM) Btu's.1) Tires
are weighed by automated scales and information is fed to
the computer to facilitate appropriate tire feed to the
boilers. Tires are fed onto the grate in the combustion
chamber located at. the bottom of one of the two 80-foot high
boilers. The 430 square-foot reciprocating stoker grates
are composed of several thousand steel bars made of a
stainless steel alloy to prevent slag from adhering to the
metal.1 This prevents plugging of the air distribution
system by viscous liquids resulting from tire combustion.
The grate configuration allows air flow above and below the
tires, which aids -in complete combustion. The bars resemble
a series of steps sloping downward that move back and forth,
3-4
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Loader
Feed
Hdpper
Stack
n
Thermal Denox
_Sulfur,
Removal
o (x
Feed Conveyor 4
Grate Furnace
Fabric Filter
7 Baghous*
WVVV L
Bottom
Ash
Ry Ash Gypsum
Figure 3-1. Oxford Energy Process Flow Sheet.
3-5
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pushing the burning tires through the boiler. Essentially
all of the slag and ash is moved along the reciprocating
grates. At the end of the grates, the slag and ash fall
into a water quench on a submerged conveyor, which then
transports the ash and clay to storage hoppers,1 for sale as
by-products.3
Although tires begin to ignite at about 600*F, the boilers
are operated above 2000'F to ensure complete combustion of
organic compounds emitted by the burning tires.2 The heat
generated by the burning of the tires rises into the
radiation chamber, which is constructed of refractory
brickwork.6 This heat causes water contained in pipes in
the refractory to turn to steam. The high-pressures steam
is forced through a turbine, causing it to spin. The
turbine is linked to a generator that generates power, which
is then sold to the Pacific Gas and Electric Company. After
passing through the turbine, the steam is condensed to water
in a cooling system, and is recycled to the boiler to be
reheated.2
To meet emissions limits, the Modesto Project had to install
state-of-the-art emission control devices. Detailed
descriptions of all air pollution control equipment is
contained in Section 3.3.
3.2.2 Operational Difficulties
Oxford Energy has had to make significant modifications to
the Modesto Energy Project to operate successfully. Because
power is being sold to a utility (California Edison), power
generation must be consistent. If tire feed problems
prevent enough fuel from being combusted to maintain
consistent power generation, gas-firing of the boilers is
used to maintain power. This is an expensive solution.
Therefore, successful and reliable tire feed is imperative.
3-6
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Inconsistent tire feed also yields variable temperatures In
the boiler, and the plant experienced some operational
problems that resulted from temperature fluctuations.
Therefore, the plant had to make modifications to the
facility to ensure consistent power generation.
The prototype facility on which Modesto was based uses
manual tire feed.6 Modesto personnel felt it necessary to
automate the tire feed system. The initial system, however,
did not deliver a consistent feed of tires to the furnaces.
The one weigh station, located near the tire pile, could not
make allowances for the variability in size and type of tire
entering the conveyor apparatus.6 Inconsistent power
generation resulted.
Tire handling also provided another challenge. Because the
tires are whole, timing of their entrance to the boilers is
critical to ensure a steady Btu input to the boilers.
During rain, mud and sand from the tires acquired from the
pile would accumulate on the conveyor belt. The length and
steepness of this conveyor caused tires to slide off the
belt.1
Another initial problem encountered was several grate bars
popped out of place, exiting at the end of the inclined
floor of the boiler. Engineers determined that the
fluctuations in steam load and on/off cycling of the furnace
were allowing ash and slag to be wedged in the spaces
between bars and to lift the bars out of place.6
To enhance consistent tire feed, four tire weigh scales were
installed where tires are fed into the two combustion
chambers. Each furnace is fed by two weigh scales. The
goal of the new system is to feed 80 to 90 pounds of tires
in a batch to maintain the desired heat input to the
system.6 The new system has allowed consistent boiler
3-7
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operation. At the same time, the new system has minimized
the grate problem. The speed of tire delivery overall was
increased.6 Finally, a special belt washing system was
installed to solve the problem of tire slippage on the
conveyor. The belt washing system is now used in particular
before a rain storm.1
Another problem initially encountered was the disintegration
of the refractory brick initially installed in the boilers.
This was caused by the high boiler temperatures. The
refractory was removed, and Modesto has experimented with
two different solutions, one in each boiler. In Boiler No.
1, the 3-foot thick refractory was replaced with a high
thermal conductivity brick that transmits the heat to the
boiler skin. This facilitates cooling of the inner boiler
walls, causing slag to solidify on the inner refractory as a
protective layer. This has increased the fuel need for this
boiler, but is still a satisfactory solution. For boiler
No. 2, a different approach was used. In this case, the
water walls, which initially ran down the boiler sides to a
level about 20-feet above the grates, were extended down to
grate level. Water walls (tubes filled with water) generate
steam and deliver it to the drum. The economizer preheats
the feed water. This approach has protected the new
refractory very well.1
Problems with the air pollution control equipment also had
to be addressed. These are discussed in Section 3.3.
3.3 EMISSIONS, CONTROL TECHNIQUES AND THEIR EFFECTIVENESS
3.3.1 Emissions
Pollutant emission levels for criteria pollutants as listed
in the permit for the Modesto facility are summarized in
Table 3-1. Annual compliance tests are required and have
3-8
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Table 3-1. Permitted Emission Levels
The Modesto Energy Project,
Westley, CA7
Pollutant
CO
NOX
PM
sox
HC
Ibs/day
346.4
500.0
113.0
250.0
148.4
Note: Based on 700 tires per hour, 300,000 Btu's per tire,
and 24 hours per day, these permitted emission levels
are equivalent to: 0.069 Ibs/MMBtu for CO; 0.099
Ibs/MMBtu for NOx; 0.022 Ibs/MMBtu for PM; 0.050
Ibs/MMBtu for SO ; and 0.029 Ibs/MMBtu for HC.
Table 3-2. Permitted Emission Limits for Each Boiler
Exeter Energy Project, Sterling, CT
Pollutant gr/dscf Ib/MMBtu
PM10 0.0150
S02 • 0.1090
NOX 0.1200
CO 0.1670
VOC 0.0300
3-9
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been conducted on the facility since 1987. Table 3-2
contains permitted limits for the Exeter Energy Project in
Sterling, CT. Table 3-3 contains a summary of test data for
criteria pollutants and metals for Modesto in 1988 and 1990.
Table 3-4 shows organic compound emissions from Modesto.
Testing of emissions from Modesto has been frequent.
Comparison of these emissions to baseline (no TDF use) is
not appropriate, but they can be compared to coal-fired
utility emissions on a Ib/MMBtu basis. Such a comparison is
provided in the Chapter 6, which covers utility boilers, in
Figures 6-1 through 6-4.
3.3.2 Control Techniques
Three air pollution control systems are used at the Modesto
Project. These systems are used in series to control NOX,
particulate matter, and SOX. An Exxon thermal de-NOx system
is uesd to control NOX emissions; a fabric filter is used to
control particulate matter; and a wet scrubber is used to
control SOX emissions. The following paragraphs describe
these three air pollution control systems and any
operational problems associated with their use.
3.3.2.1 De-NOx System. At the Modesto Energy Project, N0x
is reduced by use of a selective non-catalytic ammonia
injection system manufactured by Exxon, which is designed to
operate at the top of the combustion chamber. Rising gases
are injected with a fine spray composed of compressed air
and 20 pounds per hour of anhydrous ammonia per boiler. The
NOX is converted to inert nitrogen gas and water. Each
boiler has two injection zones, each of which operates at
300 scf/hr of air flow. Design efficiency is 35 percent,
and plant engineers estimate actual efficiency varies
between 25 and 35 percent.1
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Table 3-3. Criteria Pollutant and Metals emissions,
by year, The Modesto Energy Project5-8
Pollutant
Criteria
CO
P*
HC
Metals
Lead
Caokiua
Chrcaiua (total)
Mercury
Arsenic
Zinc
ChroaiuB
(hexavalent)
Copper
Manganese
Mickel
Tin
Aluvinua
Iron
Beryllium
Liarit 1988
Ib/day Ib/day
346.4 247.8
500.0 384.3
113.0 31.2
250.0 127
148.4 0.646
0.026
0.0018
0.0011
<0. 00003
0.0026
7.75
0.015
0.023
0.28
0.62
October 9-11.
1990*
Ib/day
311.5
424.6
93.12
61.9s
0.006*
0.016
0.020
0.003
0.00
0.623
0.0
0.032*
0.007
0.027*
0.018
0.101*
0.316*
0.00
October 9-11, 1990
Ib/ailUon Btu
7.2 x 10"5
9.8 x 10'J
2.2 x 10"5
1.4 x 10"*
1.3 x 10-*
3.7 x 10"*
4.7 x 10"*
6.7 x 10'7
0.00
1.4 x 10"4
0.0
7.5 x 10-*
1.6 x 10"**
6.3 x 10"*1
4.2 x 10"*
2.3. x 10'*
7.3 x ID'5*
0.00
* Aswjwd 24 hr/day operation
* Aa sulfur trioxidc; sulfur dioxide not reported
* WOL or trip blank showed significant nwasurement.
3-11
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Table 3-4. Organic Compound Emissions by year,
Energy Project5-8
The Modesto
Pollutant Liait 1988
Ib/dey lb/day
MCI «22.3
Dioxin and Furan 4.2 X 1
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Initially, NOX emissions were problematic, but now seem to
be under control. First, the amount of ammonia needed was
discovered to be less than originally thought.1 Although
tests performed in early 1988 showed a 3--day NOX average
that was below the permitted level of 500 Ib/day, Modesto
was forced to use previously purchased offsets.3
Initially, much breakthrough of unreacted ammonia (ammonia
"slip") from the boilers into the wet scrubber occurred,
causing emissions to exceed the ammonia limit on some runs.3
Reduced ammonia levels stopped the breakthrough, and NOX
emission levels were still within required limits.
Second, mixing of the flue gas and reagent had to be
improved. Reduction efficiency is limited primarily by
amount of mixing within the chamber; increased mixing aids
in contact between reagent and pollutant, and stabilizes the
air temperature, further optimizing the reaction.
Therefore, negative pressure was decreased to reduce tramp
air. Also, the operational reciprocating compressor was
replaced by a centrifugal rotary screw type compressor.
Further, ash build up on the boiler superheater tubes was a
problem, impeding heat transfer to cool down the flue gas.
This problem was resolved by using acoustics to cause the
ash to fall off the superheater and economizer tubes. This
allowed lower fuel consumption, resulting in decreased NOX
emissions.1
NOX reduction at. the Exeter Energy facility is planned to be
somewhat different than that at Modesto. Specifically, urea
will be sprayed into the combustion chamber instead of
ammonia. The advantages of using urea are numerous: urea is
more efficient, not hazardous, less corrosive, and easier to
handle. In addition, urea is a liquid, so compressed gas is
not needed. Disadvantages of urea, however, include the
extreme sensitivity of the system to urea concentration. At
low urea concentrations (less than 50 percent), rampant
3-13
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biological growth occurs, which plugs the lines. At urea
concentrations over 50 percent, the urea itself can plug
lines. Further developments may include the use of ammoniua
hydroxide. The initial installation cost of using urea may
be comparable to, or even less than, using ammonia. Since
the urea itself is less expensive than ammonia, the cost per
ton of NOX removed using urea is likely to be less. This
type of system was not fully developed when the Modesto
plant was under construction, and the cost to retrofit the
existing plant is not economical.1
3.3.2.2 Fabric Filter. After exiting the boiler chambers
and the de-NOx system, exhaust gases pass through a large
fabric filter. A fabric filter was chosen over an
electrostatic precipitator (ESP), because a fabric filter
was believed to provide a higher particulate reduction
efficiency, and because this fabric filter design was BACT.1
The fabric filter uses Gore-Tex* bags to avoid problems with
sticky particulates or acid sprays.6 The acid spray results
from the temperature controlling spray system located
upstream of the fabric filter to protect against temperature
excursions and to agglomerate the ash for easier removal.6
Staff at the Modesto Energy Project believe this particular
baghouse was somewhat oversized, because the emissions from
the plant were of such concern during permitting and
construction.1 Modesto personnel are required to keep 25
percent of the bag requirement as spares on site.1
Dust from the fabric filter collection system has tended to
accumulate on the sides of the hopper in a problematic
manner. Noting the success of acoustics on the boiler ash
that collected on the superheater and economizer tubes,
plant personnel successfully transferred that technology to
the fabric filter hoppers; periodic sonic blasts now
maintain clean hopper sides.1
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3.3.2.3 Scrubber. After exiting the fabric filter, exhaust
gases pass to a wet scrubber manufactured by General
Electric (GE) Environmental Services for SOX removal. The
system uses a lime mist to remove sulfur compounds,
producing gypsum. The lime is purchased as calcium oxide in
pebble form, and is slaked to form a calcium hydroxide
solution (11 percent by weight) used at a rate of 5,000
gallons per day. Exhaust gases enter the scrubber at a
temperature of about 375*F and exit at a temperature of
about 125*F. The gas is reheated to about iso*F before
exiting the stack. About 3 to 5 million BTU per hour are
required to operate the scrubber system.1 The gypsum is
sold as an agricultural supplement.2
Personnel at Modesto noted many problems that have had to be
overcome to operate the scrubber system successfully.
First, GE installed a vacuum type technology to remove
scrubber sludge. This system was undersized and could not
handle the sludge volume. A larger vacuum pump system has
been ordered. Second, personnel have experimented with
moving the lime injection location from the top of the
scrubber to the bottom. Adding lime near the bottom
encourages better mixing and a quicker response in
increasing the pH. This has resulted in a more consistent
SOX emissions rate. However, a permanent injection system
for the bottom of the scrubber has not been designed yet.
Third, because the spray nozzles were plugging continuously,
a filter grate was installed before the recycle pumps in the
system. Fourth, the two mist eliminators are problematic.
The vendor installed small hooks on the mist eliminator to
increase the efficiency from 11 feet per second (fps) of gas
to 21 fps. However, the gypsum gets caught on the hook,
filling it up, reducing the efficiency to the normal 11 fps,
and allowing gypsum carryover from the unit. Maintenance
personnel must clean the hooks about every 3 months to
minimize gypsum carryover. Last, the closed loop heat
3-15
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exchange system was initially made of carbon steel and
corroded. It has been replaced with a stainless steel
system using turbine extraction.1
3.3.3 permit Conditions and Issues
The Modesto Energy Project is overseen locally by the
Stanislaus County, California, Department of Environmental
Resources, Air Pollution Control District (APCD). The
Modesto Energy Project has numerous permit conditions the
facility must meet. Limits are set for all criteria
pollutants (see Table 3-1) and ammonia. In addition, the
plant must not exceed 20 percent opacity. The Modesto
Energy Project must perform an annual source test. On-site
inspections are performed weekly. The plant operates and
maintains continuous emissions monitoring systems for NOX/
SOX, CO, CO2, O2, and opacity, and the resulting data are
submitted to Stanislaus County on a weekly basis. Both
boilers are required to use Best Available Control
Technology (BACT). Under California Law A2588, the Air
Toxics "Hot Spots" Information and Assessment Act of 1987,
the plant must report emissions of 24 hazardous air
pollutants including such pollutants as dioxins, PCB's
formaldehyde, arsenic, hexavalent chromium, mercry, iron,
nickel, lead, and zin.1 The most recent stack test results
are presented earlier in Tables 3-3 and 3-4.
Other selected permit requirements are listed below.7
1. Modesto must report emissions of SOX, NOX, and CO on
a Ib/day basis from midnight to midnight; a summary
of these data shall be provided weekly to the APCD.
2. Ammonia breakthrough of the exhaust shall not
exceed 50 ppmv, except for the first 2 hours of
start-up and the last hour of shutdown.
3. Trace metals, dioxin and furan emissions shall not
exceed the estimated emission levels as listed in
the Modesto Energy Company's District approved risk
3-16
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assessment. If these levels are exceeded, explicit
procedures for performance of new risk assessment
and curtailment of operations are set forth.
4. Gross electrical output shall not exceed 14.4 MW,
averaged over 24 hours.
5. The exhaust stack must be equipped with CEMS for
opacity, NOX, S02, CO, O2, and volume flow rates.
6. If control equipment failure occurs, tire input is
to be immediately curtailed, and furnace
temperature is to be maintained at 1800'F until all
tires in the incinerator are combusted. Auxiliary
burners must be used, if necessary, to maintain the
minimum temperature.
Plant personnel state that, three times in the past, they
have shut down all or part of the plant rather than exceed
their permitted NOX levels. In 1988, one boiler was shut
down on one occasion, and the whole plant was shut down on
another occasion when NOX limits might have otherwise been
exceeded. Since that time, no shut downs have occurred for
that reason. Most recently, a shut-down occurred to avoid a
NOX exceedance in October of 1991.1
3.4 OTHER ENVIRONMENTAL AND ENERGY IMPACTS
Other environmental impacts include solid waste (slag, dust,
etc.) and water. The facility recycles all solid wastes
generated as described below.
Byproducts of the boilers (slag) and of the pollution
control devices are almost wholly recycled. The boiler
generates about 24 tons per day of slag, which has a high
steel content from the metal in the tires, mainly radial and
bead wiring. Oxford has an agreement to sell the slag to a
cement company at a cost of $10/ton. However,
transportation to the cement company has proven a problem;
estimated costs are higher than the sales price. Currently,
Modesto is negotiating a more cost-effective hauling
3-17
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arrangement where a trucking company would backhaul the slag
to the Nevada cement plant in trucks emptied in the Westley
area that would otherwise be returning empty. The slag
provides some of the iron content required of raw materials
in the cement production process.1
The particulate matter collected from the fabric filter has
a high zinc oxide content, and is sold to a metal refiner to
recover the zinc. The fabric filter generates dust at a
rate of 18 bags/day,each bag weighing approximately 1300
pounds. Zinc content of the bag ranges from 25 to 40
percent. The bags are sold on a sliding scale price range,
depending on the zinc content of the bag. The rate is based
on a zinc cost of about $20/ton. Budgeted revenues last
year for fabric filter dust were $174,000.1
•
The gypsum produced by the alkali scrubber is sold as an
agricultural supplement or soil conditioner to California
farmers. It is generated at a rate of 10 tons/day and sold
for $5 per ton.1
The facility's original waste water treatment and
evaporation system was too small to handle the required
volume, and some wastewater had to be treated offsite.9
One of the initial requirements made of the Modesto Project
was installation of a comprehensive fire system. The large
and unwieldy tire pile was surrounded by an. underground
sprinkler system and fire hydrants. Further, tire removal
from the pile follows a carefully drafted plan to result in
•
optimal fire lanes among the tires.1
3.5 COST CONSIDERATIONS
As noted earlier, the company must pay the landowner (who
also owns the tire pile) a varying amount, approximately $27
3-18
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per ton (about $0.25 for each tire removed) at the present
time, but Modesto receives money for each tire acquired from
the "flow".1
The Modesto Energy Project is designated as a "qualifying
facility" under PURPA, the Public Utilities Regulatory
Policies Act of 1978. This act makes companies eligible for
long-term power sales agreements with public utilities. The
projects are exempt from the rate of return regulations that
plants must use that burn conventional fuels. Further, the
California Alternative Energy Law guarantees long-term
revenues to companies burning waste or renewable energies at
a rate equal to wholesale cost of power plus the avoided
cost of power. (Avoided cost means the cost for a utility
burning conventional fuels to add the amount of potential
power being provided by the alternative fuel user.)
Effectively, this yields a very attractive power cost for
the power producer coupled with a long-term (15-year)
promise that the utility will'buy at that rate. In
California, that rate is about $0.08 per kilowatt-hour in
the current contract. Although the power contract
guarantees the revenue stream, the plant must guarantee
output. Therefore, whenever tire feed became a problem
power had to be generated using gas, which hurt
profitability.1
The Modesto Energy Project has sustained overall financial
losses since the plant commenced construction. A local
California newspaper reported that, in 1987, the Company
posted a loss of $678,502. In 1988, the loss had grown to
$2.1 million, although the company's revenues for 1988 had
increased from $1.5 million to $7.9 million. The article
reports net income of $1 million for the first 9 months of
1989.10
3-19
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As the plant worked out operational problems, the power
generated had to be consistent, because the long-term power
contract requires dependable power for sale. Therefore,
when tire-feed was a problem, the company had to keep the
boilers operating using natural gas, at considerable company
expense.
3.6 CONCLUSIONS
The generation of electricity at dedicated tire-to-energy
facilities appears to be very promising from both an air
pollution and a financial perspective.
Oxford experienced difficulties at first with several of
their emission control devices. These difficulties have
been overcome. Based on Oxford Energy's experiences,
controlled emissions from their Modesto Energy Project
compare extremely favorably to controlled emissions from
electric utility plants powered by traditional fuels. Most
emission rates (Ibs/MMBtu) at Oxford are below those at
other electric generating plants burning traditional fuels.
"Dedicated tire-to-energy facilities must be able to supply
consistent power generation to the utility. Thus, it is
extremely important that a consistent source of tires be in
place. A tire acquisition system must be developed for
each plant.
As with any new venture, Oxford has had a number of
operational difficulties that have affected the financial
viability of their original facility. These difficulties
appear to have been overcome, and with new, larger
facilities, dedicated tire-to-energy plants appear to have a
very good financial outlook.
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3.7 REFERENCES
1. Memorandum from Clark, C., and K. Meardon, Pacific
Environmental Services, Inc., (PES), to Michelitsch,
D., EPA/ESD/CTC. November 19, 1991. Site Visit—
Modesto Energy Project, The Oxford Energy Company.
2. Sekscienski, G. Meltdown for a Tough One. EPA
Journal. Office of Communications and Public Affairs.
15:6. November/December 1989.
3. U.S. Environmental Protection Agency. Markets for
Scrap Tires. EPA/530-SW-90-074B. September 1991.
4. Alternate Sources of Energy. Volume 90, April 1987.
p. 43.
5. Ohio Air Quality Development Authority. Air Emissions
Associated with the Combustion of Scrap Tires for
Energy Recovery. Prepared by: Malcolm Pirnie, Inc.
May 1991.
6. Oxford Meets Performance Goals Firing Whole Tires.
Power. October, 1988. pp. 24, 28.
7. Stanislaus County Department of Environmental Resources
Air Pollution Control District. Permit for Modesto
Energy Company. Issued 3/9/88. Permit No. 4-025.
8. The Almega Corporation. Source test data for Modesto
Energy Project, Westley, CA. The Oxford Energy
Company. October 9-10, 1990.
9. "Tires, Tires Everywhere...Oxford Energy Offers a
Solution," Environmental Manager. 1(4) November 1989.
10. Phillips, D. "Out to Confound the Skeptics". The
Press Democrat. Santa Rosa, California. January 7,
1990. pp. E1,E6.
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4. TIRE AND TDF USE IN PORTLAND CEMENT KILNS
The portland cement production process is extremely energy
intensive (from 4 to 6 million Btu's (MMBtu's) are required
to make a ton of product); therefore, alternative and cost-
effective fuel options are of great interest. Waste tires
have been tried as a supplemental fuel in veil over 30
cement kilns and in at least one rotary lime manufacturing
kiln. Currently, tires are in use, either on a trial or
permanent basis, in 11 cement kilns and one lime kiln.
A cement kiln provides an environment conducive to the use
•
of many fuel substances, such as tires, not normally
included in the fuel mix. Specifically, the very hot, long,
inclined rotary kiln provides temperatures up to 2700"F,
long residence time, and a scrubbing action on kiln
materials that allows a kiln to accommodate and destroy many
problem organic substances. Also, the rock-like "clinker"
formed in the kiln can often incorporate the resulting ash
residue with no decrease in product quality. Tires are a
compact fuel, with very low moisture. Tires have some iron
and zinc content, both desirable materials in the raw
material mix for cement manufacturing. Further, the
materials handling operations already in place at many
cement plants require only minimal modification to
accommodate TDF feed. For these reasons, cement kilns are
one of the most common methods by which energy in waste
tires is recovered.
Cement plants attract favorable power rates because the
process is so energy intensive; TDF cost per Btu is thus
less of a savings. Second, cement kilns can accommodate
many alternate fuels,1 such that regional availability and
price for these may affect the marginal savings of TDF. For
example, on the Southeast Gulf coast, petroleum coke is
4-1
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often less expensive than TOP. Whole tires are cheaper than
TDF, but feeding and handling equipment for whole tires is
expensive.1
Other alternative fuels of interest to the industry have
included organic hazardous waste (e.g., solvents), waste
oil, and wood chips. In 1990, seven cement plants reported
to the Portland Cement Association (PCA) that their primary
fuel included waste; three reported using a combination of
coal and waste as primary fuel.2 The type of waste was not
specified and, therefore, the number burning tires or TDF
specifically could not be determined. The PCA reported that
31 plants utilized waste fuel as an alternate fuel in 1990.2
The. number of kilns reporting use of waste fuels is 40
percent higher in 1990 than in 1989.2 There is no record of
waste fuel being burned in cement kilns at all in 1972.3
Overall, the number of cement plants with kilns fired by
fuels other than coal, natural gas, or oil, has risen from
2.2 percent in 1983 to 15.2 percent in 1990. Figure 4-1
i
graphs this change.
This chapter describes the use of whole tires and TDF in the
cement industry in five sections. First, an industry
description is provided. Second, the cement production
process is described, including traditional fuel use and use
of both whole tires and TDF as supplemental fuel. Third,
air pollution implications are discussed in detail,
including emissions, control techniques, and control
effectiveness. Fourth, other environmental and energy
impacts are evaluated. Last, cost considerations of tire
use are described.
4-2
-------
80
a 60
-------
4.1 INDUSTRY DESCRIPTION
As of the Summer of 1991, 112 cement plants were operational
in the United States.2 Annual U.S. production of clinker in
1990 was approximately 81 million tons per year. Using an
average of 5 MMBtu's per ton of clinker produced, some
400 x 1012 Btu's are required nationally by the industry
each year. One source estimated that, theoretically, if all
waste tires went to the cement industry, waste tires could
provide approximately 11 percent of the fuel requirements
for the cement industry.*
Many industry-wide changes over the last decade have
dramatically affected fuel use and efficiency in the cement
industry. First, a trend toward more prevalent use of the
dry process 'of cement manufacture rather than the wet
process continues. New technology in conjunction with fuel
savings provided by the dry process have made it the process
of choice. In fact, no new wet process kilns have been
built in over 15 years.2 Second, over the last decade, many
plants have converted their kilns to coal firing because of
coal's cost effectiveness in comparison to oil and gas.
Although both of these trends have had a considerable effect
on fuel efficiency and cost in the industry, use of
supplemental fuels, such as waste tires, continues to be of
high interest to the industry. All fuels are purchased,
however, based on regional prices.
Table 4-1 provides a list of cement facilities in the United
States that have been reported to be burning tires or to
have burned tires in the past. Test data on air emissions
while burning tires were obtained for three cement
facilities and one lime plant. These facilities comprised
both wet and dry process plants, and plants that burned
whole tires and TDF. A summary of this test data is
presented in this report in section 4.3 below.
4-4
-------
Table 4-1. Portland Cement Facilities that have been,
or are, Burning TDF or Whole Tires
COMPANY AND LOCATION
KILNS DESCRIPTION*
TDf OR TIRE EXPERIENCE
AIR EMISSIONS
TEST DATA
COMMENTS/REFERENCES
Allentown
(LeHIgh Portland
Cement CO.)
Allentown, PA
Ash Grovt Cement Co.
Uest Plant
Durkee, OR
llu* Circle, Inc.
Atlanta, CA
•ox Crow Cesjent Co.,
•OK Crow Plant
Midlothian, TX
Celeveraa Ceewnt Co.
Redding, CA
California Portland
Cement
(Arliana Portland)
Rlillto, AZ
California Portland
Cement
Mojave. CA
Centex
Illinois Cement Co.
LaSaile, IL
Essroc Materials, Inc.
Naiareth, PA
2 dry kilns; coal/coke
fired
Dry/1980; PM; ESP;
natural gas/oil co-
flra; one four-stag*
preheater; 500,000 tpy.
2 dry kilns; coal/coke
fired
1 dry kiln; PH/PC;
coal-fired; baghouse;
310,000 tpy
1 kiln; PH/PC; FF; coat
fired, 650.000 tpy
4-dry kilns; 1 with
PH/PC; coal-fired; 2
kilns Inactive In 1990.
Current use; burned sine* 6/90,
2"x2"; fed pnetmtlcally into feed
end of kiln; penal t ted to burn up
to 10X TDF; currently running BX
Past use
Past use; 2"x6" TDF; 10-12X TDF
Current use; burned since 1985,
2"x2" TDF, wire-free now; whole by
•Id-1991; about 20X itu; 65 tons
TDF per day (6,000 tires); TDF Into
riser duct just above kiln feed
housing
Past use; 2"x2" 10X of energy fro*
TDF; TDF since 1986
Extensive
testing for PM,
SO,, awtals,
HC; showed no
significant
Increase
References 2 and 5
References 2, 6, and 7
Reference* 2 and 5
CEMS only; test References 2, S. and 7
burn planned
soon
1 dry kiln; PH/PC; FF; 2.5Hx 2.5"; 30X TDF of total fuel
coal-fired; 3,250 tpd
Ves; emission
not signifi-
cantly differ-
ent than burn-
ing coal
No
Ho
1 dry kiln; PH; FF;
coal fired.
1 planned dry kiln; PC;
to be corseted 1991
Test use; anticipate 4/91 test bum Applied for
test burn
peralt; plant
4/91 test burn.
Test bum In
November
Use peralt Modification fro» local
agency. References 1, 2. 7, and 0
References 1 end 2
References 2,5, end 7
Completed penalt application; pit
April 1991 teat burn.
References 2 and 9
Reference! 2, S, and 7
-------
Table 4-1. (Continued)
COMPANY AND LOCATION KILNS DESCRIPTION*
TDF OR TIRE EXPERIENCE
AIR EMISSIONS
TEST DATA
COMMENTS/REFERENCES
Florlde Crushed Stone 1 dry kiln; PH; FF; ;
Co. coal fired
Rrookvllle, fi
Giant Resource
Recovery
Nerleyvllle. SC
Glfford Kill
Co. Nerleyvllle, SC
(now HIM Circle)
Nolne«/ldeel Ceaent
Dundee, Ml
4 wet Kline; ESP; coel
fired
t dry kiln; PH; ff;
coel fired
2 wet kllne; coel/coke-
ffred
Pett use; fed TDF Into preheeter; Incomplete
•topped beceuse of preheeter
plugging problem; In*tell Ing whole
tire feeder; Test dete (10/90) not
vet Id. but tested for PM, SO,,
VOCs, furane, dloxlns. Betels.
Pest uee; whole tlrei; VOL of No
energy from TOF during teetlng; In
process of asking *odifIcetlone to
(ratalI feed equipment.
2"x2"
References 2 and 10
References 2 and S
Referencee 2 end 11
Reference* 2 and S
HolneeVldeet Ceewnt
Seettle. UA
Koseoe Ceaent Co.
Kosnoedele, KY
La Ferge Corp.,
lei cones Plant
New Braunfele, TX
1 wet kiln; ESP;
coeI/coke fired
1 dry kiln; PH; FF;
coel fired, 2,160 tpd
1 dry kiln; PH/PC
Current uee; 2" wire-free; test
penalt ie for up to 25X; first used
TDF In 1906; discontinued because
TDF not price competitive with
coel; reinstated TDF use In 1990;
20X of energy Is froa TDF.
Pest use; shredded TDF
Current test use; 2" wire-free.
Used TDF experimentally for 2 yrs;
completed trials for emission
testing; permit being Issued to
Unit TOF to 25X of energy used;
planning to test VOC, PAH's,
PCOD/PCCB.
Yes; using OX,
lit, and UX
TDF; conplete
data for PM,
SOJ. NO,, heavy
swtals, PNA's,
and VOC'e.
res (PM, SO,,
CO, HC, HCI)
planned
References 2, 9. 12, and 13
References 2, 5, and 7
Investigating tire burning on corporate
level. References 2, 5, and 7
-------
Table 4-1. (Continued)
CONPAHV AND LOCATION
KILNS DESCRIPTION*
TDF OR TIRE EXPERIENCE
AIR EMISSIONS
TEST DATA
COMMENTS/REFERENCES
lone Star Cement, Cap*
Glrardeu, HO
Medusa Concrete
Cllnchfletd. GA
1 Met Kiln Inactive In
1990; 1 dry kiln u/PH;
FF; coal fired.
Test burn coon Reference 7
Reference* 2 end S
Medusa Cement
Charlevolx, Nl
Monarch Cement
Co.
Hunfcoldt. KS
River Cement Co.,
Seine Plant
Featua, MO
RMC Lone Star
Davenport, CA
Roanoke Cement Co.
Cloverdale Plant
Roanoke, VA
Southdown, Inc.
Southwestern Portland
Cement Co.
Vlctorvllte, CA
Southdown, Inc.
Southwestern Portland
Cement Co.
Falrborn, OH
1 dry kiln; PH/PC;
coat-fired
3 dry kllna; 2 with PH;
FF; coal/coke
2 dry kllna; FF; coal
fired.
1 dry kiln; PH/PC; ESP;
coal fired
S dry kllna; 1 with PH;
coal fired; TOF planned
In kiln with PH
2 dry kllna, 1 with
PH/PC; FF; coal fired.
1 dry kiln; PH FF; coal
fired.
Current u*e
Teat u*e; planning me of whole
tires, beginning with 4X and
Increasing to 20X tires; tires from
retailers «nd naybe from dumps.
Current use; test permit; use not
continuous; whole and shredded; TDF
added at precalciner; whole added
Into feed end of kiln by double
gate method.
Past permitted use; Whole 36"; 10-
1SX; use was successful and are
renewing alternate fuels permit;
tires were slid, not rolled. Into
feed end of kiln.
Yea, winter
1991; tires at
20X
CEMS; new test
data
CEHS; new
emissions testa
have been done
References 2 and 5
References 2 end 5
References 2 and 5
References 2 and U
Have spent $320,000 for equipment and
testing; will be paid a disposal fee
for taking tire*, and perhape a atate
subsidy based on $0.50 tax on new
tires; currently permitting.
References 2 and IS
Test permit; final permit pending CEMS
data analysis. Whole into kiln feed
end; TDF Into preheater at precalciner.
References 2, 7. and 16
Tire burning stopped until renew permit
to burn whole tire*; public opposition
to solvent-derived fuels; working their
copy through the permit process
Reference* 2, 7, 16. and 17
-------
Table 4-1. (Continued)
CONPAHr AND LOCATION
KIINS DESCRIPTION*
TOF OB TIRE EXPERIENCE
AIR EMISSIONS
TEST DATA
COMMENTS/REFERENCES
fouthdoun, Inc.
(Southwestern)
lyons, CO
St. Nary1* Peerless
Ceewnt
Detroit, Ml
Manufacture
1 dry kiln; PH/PC; ff;
gaa, co«I, waste oil;
1.400 tpd
1 wet kiln; coel-fired
Current use; J"x3" TOF; dropped on
to feed shelf by screw conveyor;
1/2 ton/hr 8 5X; torn feeding
problems; plugging of rubber shred*
to hopper If threds have belt* and
beadi.
Referencea 2. 5. 7. and
Referencea 2 and 5
•olaa Cascade
Uallula, UA
1 rotary Haw kiln; TDF up to 1SX
freed by gaa, oil. and
tires; venturl acrubber
controlled.
fee; 5/64;
baseline gsa
fired; TDF 15X
with gaa;
Matured PAH 'a
and swtala
UM Manufacturing rotary kiln.
Reference 10
* PN • Preheater, PC • Precalcfner, ESP • electrostatic precipltator, FF • fabric filter
-------
4.2 PROCESS DESCRIPTION
In the portland cement manufacturing process, three steps
occur. First, raw materials are crushed and mixed. The raw
materials are powdered limestone, alumina, iron, and silica.
Second, the raw materials are fed to an inclined rotary kiln
in which they are heated to at least 2700'F. A rock-like
substance called clinker is formed, which exits the kiln and
is cooled. Third, the cooled clinker is finely crushed, and
about 5 percent gypsum is added to produce finished cement.
Details of the process are explained below.
4.2.1 Mixing and Grinding
Cement may be made via a wet or a dry process. In the wet
process, water is added to the mill while grinding raw
materials to form a slurry before entering the kiln. Much
of the fuel must be used to evaporate this water from the
feed. In the dry process, raw materials are also ground
finely in a mill, but no water is added and the feed enters
the kiln in a dry state. Therefore, much less fuel is
needed in the kiln. Many older kilns use the wet process;
in the past, wet grinding and mixing technologies, provided
more uniform and consistent material mixing, resulting in a
higher guality clinker. Dry process technologies have
improved, however, to the point that all of the new kilns
since 1975 use the dry process. Figure 4-2 diagrams typical
wet process material handling, and Figure 4-3 shows typical
dry process material handling. Fuel type, or use of tires,
does not affect this part of the operations, except that
tire use may allow less iron to be added from raw materials.
Usually, without an iron supplement, raw materials would
contain about 2 percent iron; cement requires about 3 to 3.5
percent iron. Metal in tires is mostly steel and iron. One
cement plant estimated that, in one test using whole tires,
iron content was raised 0.1 percent by the tires.16
4-9
-------
CRUSHED RAW
MATERIALS
FROM STOCKPILE
i
H
O
WATER
CORRECTING
TANKS
SLURRY
BASIN
MAWMATERIAIS -*•
ARE PROPORTIONED
RAW UATtRIAlt
Ulll
Figure 4-2.
Typical wet process.material handling during
Portland Cement manufacture.3
-------
CRUSHED RAW
MATERIALS FROM
STOCKPILE
HAW MATERIALS -» U )
ARC PROPORTIONED
HAW MATERIALS
MILL
TO
PAEHEATEH
DRV MIXING AND
BLENDING SILOS
GROUND HAW
MATERIAL STORAGE
Figure 4-3,
Typical dry process material handling during
Portland Cement manufacture,3
-------
4.2.2 Calcination
As stated in Chapter 2, cement kilns incline slightly toward
the discharge end and rotate slowly. Feed materials slowly
progress to the exit of the kiln by gravity. The majority
of the fuel is burned at the discharge end of the kiln, so
that the hot gases pass countercurrent to the descending raw
feed material. Wet process kilns are typically over 500
feet long, and evaporation of water from the feed occurs in
the first 20 to 25 feet of the kiln. Dry process kilns can
be 20 to 25 percent shorter than wet process kilns because
little or no residence time is needed to evaporate water
from the feed and the feed heats faster. After evaporation,
the temperature of the feed material increases to about
2700'F during passage through the kiln, and several physical
and chemical changes occur. The water of hydration in the
clay is driven off, the magnesium carbonate calcinates to
MgO and C02, the calcium carbonate calcinates to CaO and
CO2, and, finally, the lime and clay oxides combine at the
firing end of the kiln to form clinker. Figure 4-4 provides
a schematic drawing of the typical clinker production
process. Section 4.2.6 below discusses the various methods
by which tires and TDF are being added to supplement kiln
fuel.
4.2.3 Preheaters and Precalciners
Dry process cement production facilities often have several
other types of manufacturing equipment designed to increase
fuel efficiency. First, many dry process kilns add a
preheater to the feed end of the kiln to begin heating of
the feed prior to its entrance to the kiln. Two main types
of preheaters exist, the suspension preheater and the
traveling grate preheater; both use hot, exiting kiln air to
facilitate a more efficient heat transfer to the feed than
could occur in the feed end of the kiln itself.1 This
4-12
-------
EXHAUST STACK
1
CONTROL
DEVICE
PRIMARY AIR
AND FUEL
MATERIAL FLOW-
RAW
FEED
MATERIAL
SECONDARY
AIR
COOLER
CLINKER
OUTLET
Figure 4-4.
r production process during
Cement manufa3
manufacture.
-------
addition decreases the amount of fuel needed to form one ton
of clinker. Compared to a wet process kiln, a dry process
kiln with a preheater system can use 50 percent less fuel.
The second development to increase fuel efficiency in a dry
process kiln is a precalciner. For this system, a vessel
called a flash precalciner is located between the preheater
and the kiln, and is fueled by a separate burner. A
discussion of tire use to supplement precalciner fuel is
discussed in section 4.2.6 below.
Figure 4-5 shows a four-stage suspension preheater with a
precalciner. Feed is blown from stage to stage by the
rising countercurrent air, reaching the precalciner after
Stage 3 and before being blown into Stage 4. Figure 4-6
shows a traveling grate preheater. About 95 percent of the
calcining of the feed occurs in the precalciner. The
calciner may use preheated air either from the kiln or the
clinker cooler. Precalciners allow several operating
advantages. Because calcination is rapid, adjustment to the
calcination rate can be made quickly to yield uniform feed
calcination. A kiln with a precalciner is shorter, because
less distance is needed for calcination. Also, production
capacity can be increased over a kiln of identical diameter
without a precalciner, because the shorter kiln can be
rotated at a higher rate while still maintaining proper
operating characteristics of feed residence time and bed
depth.
4.2.4 Finished Cement Grinding
Calcined clinker is ground in ball mills, mixed with gypsum,
and shipped in bags or bulk. Figure 4-7 depicts finish mill
grinding and cement shipping. The type of fuel used to make
clinker does not affect these operations.
4-14
-------
FEED (FROM 3RD STflGEI
FUEL (COflL. CBS. OIL. ETC. I
OXYGEN (COOLER. KILN. BTHOSPHEREI
PRODUCT (TO 4TH STflCEl
FLASH PRECALCINER
KILN :;
:::
i
i
•umc*
r^~-
'f-
J 1
X _ I
COOLtH
--•- VtHI
CLIMCCN
Figure 4-5. Four-stage suspension preheater with a precalciner
at a Portland Cement plant.3
-------
i
H
Ok
PELLETIZER
PAN
TO COLLECTION
DEVICE
TRAVELING GRATE
Figure 4-6. Traveling grate preheater system at a
Portland Cement plant.3
-------
AIR
CLASSIFIER
CEMENT
COLLECTOR
I
M
•J
PACKAGING TRUCK
MACHINE
Figure 4-7. Finish mill grinding and shipping during
Portland Cement manufacture.3
-------
4.2.5 Tires as Fuel in the Kiln
Tires or TDF can be used to supplement the kiln fuel and/or
the precalciner fuel. When TDF is added to the kiln fuel
mix, it is often added at the burner (lower) end of the
kiln, near, but not mixed with, the coal feed. At one plant
(Holnam/Ideal) , TDF is fed in above the coal flame.19 This
arrangement permits the chips to be blown further into the
kiln and causes the chips to fall through the coal flame to
produce much better combustion. In most cases, TDF is added
at the feed end (high end) of the kiln. Several kilns have
added whole tires at the feed end of the kiln so that
burning occurs as the tires move down the kiln; this method
is common in Europe.4 However, many kilns in the U.S.,
particularly wet process kilns, have chains hanging down in
the feed end of the kiln to enhance heat exchange. Such
equipment forms a barrier to everything but finely ground
materials, and precludes use of whole tires at the feed end.
Kilns with preheaters provide the best environment for
adding TDF or tires at the feed end, because significant
preheating of the dry feed has occurred before the feed
contacts the tire chips.
Tires have occasionally been used to supplement the primary
precalciner fuel (usually coal), with mixed results.
Florida Crushed Stone in Brookville, Florida, was feeding
TDF into the preheater, but had to discontinue use because
of plugging of the preheater (most likely due to oil
condensate from the incomplete combustion of the tire
chips). The company is in the process of installing a whole
tire feeder with weight-belt, computer, variable rate belt,
and triple gate chute to feed tires into the kiln.10
Southwestern Portland Cement in Victorville, California, not
only adds TDF successfully to the preheater, but •
concurrently supplements the primary kiln fuel by mixing
4-18
-------
whole tires in the kiln feed.16 Tire chips are added in the
preheater, at the pyroclone (precalciner) unit, right after
the tertiary air duct that brings hot air from the clinker
cooler.16 The chips burn cpiickly and go up the air stream
into the preheater. Concurrently, whole tires are
introduced into the feed end of the kiln with a double gate
method. First, the tire is fed upright into a downward
chute that slopes 30 to 40 degrees, so that it rolls down
and stops at the second gate. The first gate closes and the
second gate opens. The tire then rolls across the feed
shelf and into the kiln. The double gate method reduces
excess air. introduction to and heat loss from the kiln.16
Using both kinds of tires concurrently helps maximize the
percent of fuel provided by tires. . Whole tire use reduces
coal used at the firing end of the kiln, but too many whole
tires would provide too much heat in the kiln feed end. The
TDF replaces coal used in the precalciner, but would not be
used in the kiln, because they are more expensive than the
whole tires.16
4.3 EMISSIONS, CONTROL TECHNIQUES AND THEIR EFFECTIVENESS
Testing results from three cement facilities and one lime
kiln were evaluated for this report. The four facilities
are: Ash Grove Cement, Durkee, Oregon; Holnam/Ideal Cement,
Seattle, Washington; Calaveras Cement, Redding, California;
and Boise Cascade Lime, Wallula, Washington.
Testing performed at Ash Grove Cement in Durkee, Oregon, on
October 18 to 20, 1989, evaluated criteria pollutants,
aliphatic and aromatic compounds, metals, and specifically
examined chloride emissions to assess the possibility of
dioxin formation.20 Ash Grove's normal fuel is a mixture of
gas and coal. As seen in Table 4-2, emissions of chloride
were lower burning some TDF than with normal kiln firing,
and; therefore, the Oregon Department of Environmental
4-19
-------
Table 4-2. Effect of Burning 9 to 10 percent TDF in a Gas
and Oil Co-fired Dry Process, Rotary Cement Kiln
Controlled by an ESP20
Ash Grove Cement, Durkee, Oregon
Pollutant -
Particulate, Ib/MMBtu
SO2, Ib/MMBtu
CO, ppm
Aliphatic compounds,
Ib/MMBtu
Nickel, ng
Cadmium, ng
Chromium, pg
Lead, /ig
Zinc, ng
Arsenic, /ig
Chloride, Ib/hr
Copper, /ig
Iron , ng
Baseline,
0* TDF
0.969
0.276
0.049
0.0011
30
3.0
30
DL'
35
0.2
0.268
37
400
9-10% TDF
0.888
0.221
0.036
0.0009
DL'
2.0
DL'
DL'
35
0.2
0.197
13
200
Percent
Change
-8
-20
-27
-18
NAb
-33
NAb
NAb
0
0
-26
-65
-50
' Below detection limit (DL).
NA
not applicable
4-20
-------
Quality (DEQ) found that the use of TDF as a supplemental
fuel at Ash Grove did not enhance the potential for dioxin
formation.20 The same report described screening tests
performed for 17 specific polynuclear aromatic hydro'carbons
(PAH's). Only three PAH's were detected (naphthalene,
dibenzofuran, and phenanthrene) and each were detected in
all eight samples. However, the highest levels of these
compounds were detected while firing normal fuel (gas and
coal), not when burning TDF.20
Testing at Ash Grove also examined total hydrocarbons,
vaporous heavy metals, and approximately 115 other PAH's.
Emission testing for total hydrocarbons showed results
similar when burning TDF and under conditions when TDF was
not burned. Since there are no permit limitations on total
hydrocarbons, these were not addressed further in the
report. For the ten metals tested, emissions during the
tire chip burning were equal to or less than emissions when
tire chips were not being burned. The report states that
there is no evidence that the emission concentrations found
for any of the 10 metals warrant concern. Finally, the
screening of the other PAH's did not identify any other
compounds of significance. For all PAH's, none of the
compounds detected are listed as human carcinogens or
possible human carcinogens.20 The Oregon DEQ is requiring
Ash Grove in Durkee to conduct a one-year ambient monitoring
program for particulate emissions.20
In October, 1990, testing at Holnam/Ideal Cement, in
Seattle, Washington, was performed at baseline (100 percent
coal-fired), 11 percent TDF, and 14 percent TDF.12 Holnam
is a wet process cement plant. The kiln emissions are
controlled with an ESP. Particulate, SO2, NOX, VOC, and
semi-volatile organic compound emissions decreased
significantly from baseline for both 11 and 14 percent TDF
use rates. CO emissions increased 30 and 36 percent,
4-21
-------
respectively, for the 11 and 14 percent tests. Several -
metals were tested, including cadmium, chromium, copper,
leak, and zinc. These also exhibited decreased emissions
with the exception of chromium emissions during the 11
percent TDF test, which showed increased emissions.
Figure 4-8 graphs criteria pollutant emissions for each TDF
level tested at Holnam's kiln.12 The percent change in
emissions of metals at Holnam is shown in Figure 4-9, and
the percent change of VOC emissions is shown in Figure
4-10.12 Table 4-3 summarizes the results of hazardous air
pollutant (HAP) emission testing performed at Holnam.12
One lime manufacturing plant, Boise Cascade, in Wallula,
Washington, burns 15 percent TDF supplementally to natural
gas in their rotary kiln.18 Testing was performed in 1986
for metals and organics only. Most significant were the
dramatic increases in zinc, chromium, and barium emissions
when burning TDF during the test.18 The kiln emissions are
controlled by a venturi scrubber, which would not be
effective for collecting small metallic particles like zinc
oxide. (The collection efficiency of venturi scrubbers
decreases as particle size decreases.) Table 4-4 lists
results of this test, and Figure 4-11 graphs the percent
change in emissions of metals and organics from this kiln.18
Because of the extensive reuse of combustion air in the
process at Calaveras1 facility, the fabric filter exhaust is
the only point of emissions for the kiln, clinker cooler,
and raw mill. Exhaust gases from the fabric filter are
monitored continuously for carbon monoxide, nitrogen oxides,
and hydrocarbons. Calaveras has tested toxic pollutants
while burning 20 percent TDF. Table 4-5 summarizes these
test results, giving emission factors for metals, hazardous
air pollutants, polyaromatic hydrocarbons, dioxins and
4-22
-------
i
10
u
2.5 -
2 -
1 -
0.5 -
0
2.73
•
• . 2.43
2.57 ^
~~B ~:i:*-.r-
234 ""-•'". Z02
" * • * "™~**""*-». m^m
--... -f|
"•--.._
"""••-•
1.62
- . 0.35 0.36
°f A A
A - mt ^
A 0.11 0.12
rf1 n n
M U LJ
Partlculate
SO2
• .. .
NOx
mm
UM
CO
±- _
0% 11%
Percent TDF In Fuel
Note: A we! process coal fired cement kiln controlled by an ESP.
14%
Figure 4-8. Effect of burning TDF on criteria pollutant emiSBions from
Holnam/Ideal Cement, Seattle, WA,12
-------
-100%
-50%
+50%
+100%
Cadmium
Chromium
Copper
Lead
Zinc
-31
84
Note: (1) Wei-process, coal-fired, cement kiln controlled by an ESP.
(2) Arsenic was also measured and was below detectable limits
In all samples.
11%TDF
14%TDF
Figure 4-9. Percent change in emissions of metals when burning TDF
at Holnam/Ideal Cement, Seattle, WA.12
-------
-100%
-50%
+50%
+100%
i
M
W
Total VOC
Acetone
Benzene
Toluene
Xyfenes,
Total
-82
96
Note: (1) Wet-process, coal-fired cement kiln controlled by an ESP.
(2) Carbon tetrachloride was measured also. Emissions Increased from
0 gm/day at baseline to 0.81 gm/day and 6.6 gm/day at 11% and
14%, respectively.
11%TDF
14%TDF
Figure 4-10. Percent change in VOC emissions when burning TDF
at Holnam/Ideal Cement, Seattle, WA-.12
-------
-100%
-50%
+50%
+100%
i
M
01
Methyl
Bromide
1,3-
Butadlene
Methyl
Ethyl
Ketone
Carbon
Disulflde
Chloro-
benzene
-82
+37
Note: (1) Wet-process, coal fired cement kiln controlled by an ESP,
(2) Carbon tetrachlortde was measured also. Emissions Increased from
0 gm/day at baseline to 0.81 gm/day and 6.6 gm/day at 11% and
14, respectively.
11%TDF
14%TDF
Figure 4-10. Percent change in VOC emissions when burning TDF
at Holnam/Ideal Cement, Seattle, WA.
12
(Continued)
-------
-100%
-50%
+50%
+100%
Ethyl
Chloride
Methyl
Chloride
Dlchloro-
Methane
Ethyl
Benzene
Styrene
Note: (1) Wet-process, coal fired cement kiln controlled by an ESP.
(2) Carbon tetrachlorlde was measured also. Emissions Increased from
0 gm/day at baseline to 0 81 gm/day and 6.6 gm/day at 11% and 14%,
respectively.
11%TDF
14%TDF
Figure 4-10. Percent change in VOC emissions when burning TDF
at Holnam/Ideal Cement, Seattle, WA.12 (Continued)
-------
-50%
+400%
+800%
+1200% +1600% +2000%
M
00
Tetra
Chlor-
ethene
1,1,1
Trlchloro-
ethane
Trlchloro-
flouro-
methana
Trlchloro-
triflouro-
ethane
Vinyl
Chloride
+1857
Note: Carbon tetrachlorlde was measured also.
Emissions Increased from 0 am/day at baseline
to 0.81 gm/day and 6.6 gm/day at 11% and 14%,
respectively.
11%TDF
Figure 4-10. Percent change in VOC emissions when burning TDF
at Holnam/Ideal Cement, Seattle, WA.12
(Concluded)
-------
Table 4-3. Effect of Burning TDF on HAP Emissions
from Holnam/Ideal Cement, Seattle, WA12>*
Pollutant
Acanaphthene
Acanaphthylene
Anthracene
Ienzo
-------
Table 4-4.
Effect of Burning 15 Percent TDF in a
Gas-fired Rotary Lime Kiln
Boise Cascade, Wallula, WA18-*
Pollutant
100% Gas-
Fired
lbxlO'*/MMBtu
85% Gas, 15%
TDF
lbx!0'6/MMBtu
Change
Organicsb
Anthracene
Phenanthrene
Fluoranthene
Pyrene
Benzo(a)-
Anthracene
Chrysene
Benzo(b)Fluor-
anthene
Benzo (k) Fluor-
anthene
Metals
3.7
51.9
8.6
6.6
1.1
1.1
0.8
0.3
1.8
29.1
8.8
6.2
1.1
1.1
0.8
0.4
-51
-44
+2
-6
0
0
+33
Arsenic
Copper
Zinc
Iron
Nickel
Chromium
Cadmium
Lead
Vanadium
Barium
1.9
3.2
28.8
231.7
5.6
83.3
1.4
4.1
5.7
24.9
3.5
2.9
427.7
168.3
3.5
318.6
1.3
2.8
3.8
52.1
+84
-9
+1,385
-27
-38
+282
-7
-31
-33
+ 109
' Kiln emissions are controlled by a variable throat venturi
scrubber, 27-29 in. H,0.ia
b Also measured, but not detected with or without (TDF) were
naphthalene, acenaphthalene, benzo(a)pyrene,
dibenzo(a,h)anthracene, benzo(g,h,ijperylene, and
indeno(1,2,3-cd)pyrene.
4-30
-------
ORGANtCS
+20%
+40%
NlckeJ
Chromium
Cadmium
METALS
-200%
Zinc
+200% +400% +600% +800% +1,000% +1,200% + 1,400%'
Note: Also measured, but not detected with or without TDF, were naphthalene,
ecenaphthaiene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(ghi)perylene,
end Indeno (1,2,3-cd)pyrene.
Figure 4-11. Percent change in emissions when burning 15%
TDF in a gas-fired rotary line Jciln controlled
by a venturi scrubber.18
4-31
-------
Table 4-5. Emissions Estimates for Calaveras Cement Kiln
Stack While Burning Twenty (20) Percent TDF21
Compound
Metals
Arsenic
Beryllium
Cadmium
Chromium
(hex)
Copper
Lead
Manganese
Mercury
Nickel
Selenium
Zinc
Formaldehyde
Benzene
Dioxins/Furans
PAH's (total)
Phenols
Chlorobenzenes
Radionuclides
Crystalline
Silica
Toluene
Xylene (p + m)
Xylene (o)
Actealdehyde
PCS
Emission Factor
grams/ton
clinker grams/MMBtu
3.63 x 10'3
5.33 x 10**
6.63 X 10'3
3.00 X 10'4
6.20 X 10*3
1.88 X 10*2
4.96 x 10'2
4.33 x 10'2
8.52 X 10'2
2.12 X 10-2
3.79
2.98
0.17
4.2 x 10-7
2.9 X 10*1
6.8 X 10'2
2.8 X 10-3
7.5 X ID'7
4.5 X 10'1
3.80 X 10'2
1.85 X 10'2
1.85 X 10*2
1.86
5.0 x 10'*
Emission
Rate
(Ibs/hr)
7.4 x 10'*
1.1 x 10-*
1.4 x 10'3
6.2 x 10-5
1.3 x 10'3
3.9 x 10'3
1.0 x 10'2
8.9 x 10'3
1.7 x 10'2
4.3 X 10'3
7.8 x 10"1
1.8
1.0 X 10*1
2.5 X 10'7
1.8 X 10'1
4.0 X 10"2
1.7 X 10'2
4.5 X 10'7 .
9.2 X 10'2
2.3 X ID'2
1.1 X 10'2
1.1 X 10'2
1.1
3.0 X 10'*
4-32
-------
Table 4-5. (Concluded)
Emission Factor
Compound grams/ton
clinker
Hydrogen
flouride 0.04
Hydrogen
chloride 1.25
Vinyl chloride
Methylene
chloride
Chloroform
1,2-
dichloroethane
1,1,1-
trichloroetuiane
1,2-
dibromoethane
Trichloro
ethylene
Tetrachloro-
ethylene
Particulate 18.22
grams/MMBtu
5.61
7.55
4.25
3.54
8.21
1.87
4.70
5.93
X 10'4
X 10'*
X 10'*
X 10'4
X 10**
X 10'3
X 10'*
X 10'4
Emission
Rate
(Ibs/hr)
8.2
2.5
3.4
4.6
2.5
2.1
5.0
1.0
2.8
3.5
X 10'3
X 10'1
X 10'*
X 10'4
X 10'4
X ID'4
X 10'4
X 10"3
X 10'4
X 10'4
3.7
4-33
-------
r
furans, and particulates. Testing did not include baseline
(without TDF in the fuel) conditions.21
As seen in Table 4-5, particulate emissions were found to be
emitted at a rate of 0.04 Ib/ton clinker. In 1981,
particulate emissions from the kiln, clinker cooler, and raw
Bill were estimated to be 0.027 Ib/ton clinker burning only
coal. When the raw mill was bypassed (i.e., kiln and cooler
dust were not recycled), emissions from the kiln and cooler
were estimated to be 0.051 Ib/ton clinker.21
Test results using CEMS at Southwestern Portland Cement in
Victorville, California, showed no increase in particulates,
a decrease in NOx, and an increase in CO.16
4.4 OTHER ENVIRONMENTAL AND ENERGY IMPACTS
No information was found that indicated other environmental
impacts for the cement industry as a result of using whole
tires or TDF. Often, cement dust is ducted back into the
kiln, except in cases where the alkali content of the dust
would cause a problem for the quality of the finished
cement. In those cases, the dust from the fabric filter or
ESP is landfilled. This situation does not change with tire
use. At Holnam, plant personnel have experimented with
briquetting ESP dust.19
Permit conditions were found in several cases that limited
the storage and transportation of tires on plant
premises,and that mandated safety and emergency procedures
and precautions because of the fire hazards.
In one case, the State has limited a cement plant to the
sources of its tires. Gifford-Hill in Harleyville, S.C.,
has a permit condition that the tires must come from a tire
dealer, not a landfill or an outside storage facility. This
4-34
-------
condition was added because the State has had problems with
tires contaminated with garbage or were infested with
mosquitoes.11
4.5 COST CONSIDERATIONS
Use of tires or TDF is economical only in relation to other
supplemental or waste fuels in the industry on a regional
basis. The kilns most likely to burn TDF are those with
preheaters because the introduction of tires into the kiln
is more easily accomplished through the preheater (i.e., it
is more difficult to feed tires into kilns without a
preheater).
Calaveras, which burns approximately 60 tons per day,
purchases 2-inch wire-in TDF for approximately $30 per ton.
On a dollar per Btu basis, this is approximately one-half
the cost of coal. Calaveras will be installing a whole tire
feed system, which will cost about $400,000. (In this
system, whole tires will be fed by a conveyor into the
exhaust of the kiln.) A tipping fee of between $0.50 and
$1.00 per tire for whole tires will be charged by Calaveras.
Once the whole tire system is in place, Calaveras estimates
that the tire fuel will cost one-tenth or less the cost of
coal on a Btu basis.21
At another cement manufacturer, Holnam/Ideal, TDF costs are
34 percent of their coal costs on a dollar per Btu basis.
Fuel costs at Holnam/Ideal are approximately 19 percent of
their production costs. Of this 19 percent, coal accounts
for 50 percent of the cost; coke, 35 percent; and TDF, 15
percent.19
4-35
-------
4.6 CONCLUSIONS
The long residence time and high operating temperatures of
cement kilns provide an ideal environment to burn tires as
supplemental fuel. Results of several tests conducted on
cement kilns while burning tires or TDF indicate the
emissions are not adversely affected, but in many cases
improve when burning tire.
Costs associated with modifying feed equipment to burn TDF
in cement kilns is minor in most cases. Cost savings in
fuel cost can be 70 to 90 percent of the cost of the primary
fuel, depending on location and governmental incentives.
Overall, burning tires or TDF in cement kilns appear to be
an economically satisfactory and environmentally sound way
of not only disposing scrap tires, but also reclaiming their
fuel value.
4-36
-------
4.7 REFERENCES
1. U.S. Environmental Protection Agency. Market for Scran
Tires. EPA/530-SW-90-074B. September 1991.
2. Portland Cement Association, U.S. and Canadian Portland
Cement Industry: Plant Information Summary. December
31, 1990.
3. U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards. Portland Cement
Plants—Background Information for Proposed Revisions
to Standards. EPA-450/3-85-003a. Hay 1985.
4. Scrap Tire Fuel for Cement Kilns. Exchange Meeting
Summary. Sponsored by U.S. Department of Energy,
Office of Industrial Programs. October 2, 1984.
Chicago, Illinois. CONF-8410167
5. Ohio Air Quality Development Authority. Air Emissions
Associated with the Combustion of Scrap Tires for
Energy Recovery. Prepared by: Malcolm Pirnie, Inc.
May 1991.
6. Telecon. Russell, D., Pacific Environmental Services,
Inc., (PES) with Hale, C., Ash Grove Cement Co. March
1, 1991. Ash Grove's TDF experience.
7. Memorandum from Clark, C., PES, to Michelitsch, D.,
EPA/ESD/CTC. Summary of Meeting with Scrap Tire
Management Council. October 29, 1991.
8. Telecon. Clark, C., PES, with Siemering, W., Calaveras
Cement. February 20, 1991. Calaveras' TDF experience.
9. Telecon. Clark, C., PES, with Justice, A., Illinois
Department of Energy and Natural Resources. February
19, 1991. TDF use in Illinois.
10. Telecon. Russell, D., PES, with Lauer, C., Florida
Crushed Stone, Brookville, Florida. March 15, 1991.
TDF experience.
11. Telecon. Russell, D., PES, with Bunn, L., South
Carolina Department of Health and Environmental
Control. February 14, 1991. South Carolina TDF
experience.
12. Amtest. State of Washington, Department of Ecology.
Rubber Tire Chip Trial Burn. Holnam Incorporated
Industries. Stack Testing and Chemical Analysis.
October 15-19, 1990.
4-37
-------
13. Telecon. Clark, C., PES, with Hoard, S., Holnam/Ideal
Cement, Inc., Seattle, Oregon. March 5, 1991. TDF
experience.
14. Telecon. Russell, D., PES, with Allan, G., California
Air Resources Board. February 14, 1991. Facilities
burning tires or TDF in California.
15. Campbell, Tom. "Cement Maker Plans to Use Tires as
Fuel in Botetourt Kiln." Article in Richmond Times
Dispatch. June 6, 1991. p. E-6.
16. Telecon. Clark, C., PES, with Mclver, D., Southdown,
Southwestern Portland Cement. February 28, 1991.
Southdown's TDF experience.
17. Telecon. Clark, C., PES, with Hilkins, T., Ohio EPA,
Air Division. February 28, 1991. TDF use in Ohio.
18. Source Test for Boise Cascade Lime Manufacturing
Facility, Walluloa, WA. Prepared for Washington
Department of Ecology. Test Date: May 20, 1986.
19. Memorandum from Clark, C., PES, to Michelitsch, D.,
EPA/ESD/CTC. October 28, 1991. Site Visit —
Calaveras Cement Company.
20. Oregon Department of Environmental Quality. Air
Contaminant Discharge Permit Application Review Report.
Permit Number: 01-0029. Applicaton No.: 12326. Ash
Grove Cement West, Inc., Durkee, OR. March 1990.
21. Memorandum from Clark, C., PES, to Michelitsch, D.,
EPA/ESD/CTC. November 8, 1991. Site Visit — Holnam,
Inc./Ideal Cement.
4-38
-------
5. TDF AS FUEL IN WASTE WOOD BOILERS AT
PULP AND PAPER MILLS
Pulp mills generate large amounts of waste wood products,
such as bark and contaminated wood residues, in the process
of making wood chips for the pulp digester. Also, many
paper companies operate saw mills adjacent to the wood yard
to maximize resources; these mills generate waste wood
slabs, logs, trimmings, pellets, shavings, saw dust, etc.,
that can be a solid waste disposal problem.1 Heating value
of these waste wood ranges from about 7,925 to 9,010 Btu's
per pound of fuel, on a dry basis. Tires, as mentioned
earlier, generate 15,000 Btu's per pound. Bark is the most
common component of waste wood in the pulp and paper
industry.1
Many mills burn this wood waste in boilers to obtain heat
energy for process steam, and to alleviate possible solid
waste disposal problems. These waste wood boilers are known
as "hog-fuel" boilers. A base load of supplemental fuel of
some kind is required in hog-fuel boilers, because the
significant variations of the size, moisture content, and
heating value of the wood waste may not allow consistent
boiler performance. Supplemental fuel facilitates uniform
boiler combustion, and ensures that a minimum amount of
power is generated regardless of the fuel value of the wood
waste at any one time.
Operators traditionally use coal, gas, or oil, whichever is
the cheapest fuel in their area, as the supplemental fuel.
For the past 15 years, however, some paper mills have used
TDF commercially or on a test basis in hog-fuel boilers.2
The consistent Btu value and low moisture content of TDF in
combination with its low cost in comparison to other
supplemental fuels make TDF an especially attractive
alternative fuel in this industry.
5-1
-------
The economic value added by the use of TDF varies by
location, and, thus, TDF is not universally the most
economical fuel for use in pulp and paper mill hog fuel
boilers.
5.1 INDUSTRY DESCRIPTION
As of the Summer of 1991, at least 10 pulp and paper
companies are adding tire-derived-fuel (TDF) to their hog
fuel boilers as an alternative supplemental fuel. In
addition to boilers at pulp and paper plants, one boiler at
a silicon manufacturing facility burns TDF supplementally
with their primary fuel of waste wood chips. Information
and emissions data from this boiler have been included with
this section. Table 5-1 contains a list of pulp and paper
mills that have burned TDF commercially, or have tested TDF
in the past.
The most common type of boiler configuration to burn hog-
fuel is the spreader stoker type, although some overfeed
stokers also exist. Spreader stoker boilers can burn fuel
with high moisture content, are relatively easy to operate,
and have relatively high thermal efficiency. Overfeed
stoked boilers have lower particulate emissions relative to
spreader stoker boilers because less combustion occurs in
suspension.13
In recent years, environmental concerns over water quality
have led to installation of waste water treatment plants at
pulp and paper mills. The underflow from the primary
clarifier has generated another solid waste disposal
problem. To solve this problem, some mills are feeding
clarifier sludge to hog fuel boilers. The high moisture
content of the sludc in conjunction with its low Btu
content creates more difficult operating conditions for the
furnace. Comparative composition of TDF, coal, wood waste,
5-2
-------
Table 5-1.
Pulp and Paper Mills with Experience Burning TOP
in Waste Wood Boilers
Company and Location
Augusta Newsprint
TOP Use
Current
Air Emissions Test Data
Unknown
•olltr(a) Description
CoaeMnts/Referencee
Augusta, GA
Chaqplon International
lucksport, ME
Chwplon International
(artel(, MN
Crown Zellerbech
Port Angeles, UA
Oou Corning Corporation
Midland, Ml
Fort Howard Corporation
• I neon, GA
Fort Howard Corporation
Green lay, Wl
Georgia-Pacific Paper
Cedar Springe, GA
Georgia-Pacific
Toledo, 0*
Shredded; 2" or
less, wire free;
2.5 tons/hr
(permitted up to
3.5 ton»/hr)
Past
Current TDF or oil
used with wood;
Current
Current
Current
3X;
2"x2" and 1«x1»;
30 tons tire/1000
tons coal per day
Current
"; 5X
Unknown
Tea; HO,, awtala, non-
nethene organlca; tests
were done with coal at 80t
level both for baseline and
TDF test. TDF at 1.5X, and
rest wood chips.
Tee, PHA's, awtels
Yes; PM, PM,0, SO,, MO,,
ratals
Ho; None required
Yes; Test regularly for
partfculate; alao have
tested for NO, and SO]
4 boilers; 3 burn oil only. 4th
burns aultifuele at 500,000
Ibs/hr.
Oil boiler converted to burn hog
fuel; venturl scrubber
279.000 Ib/hr, ESP
Past
Plant has 6 boilers totali
3 underfeed type that use 2"«2"
TDF; 2 spreader-stoker type that
use t"x1" TDF; 1 cyclone fed with
no TDF use now, but use planned.
•oiler Is spreader/stoker
traveling grate type; generate*
500,000 (be steam/hr at 880 pelg
and 900'F. TDF Is fed on the
bark conveyor.
Plant had swny violation*, even
when not burning tires. Given up
on tire burning currently
Reference 3
Reference 3
Reference 3
Silicon production
facility; TDF need In
wood chip boiler.
Reference 3
Produce recycled paper;
coal other base load
fuel. Reference* 3 and
4
Used to to Greet
Southern Paper; have
burned TDF for several
years; penaltted for
100 tpd TDF. but
average 60 tpd; coal
other base load fuel.
References 4 and 6
Reference 6
-------
Table 5-1. (Concluded)
Coapany and location
TOF U*e
Air Enl**lon* T»»t Data
Rollard) Description
nta/Referancee
Inland-to
ROM. GA
Pap«r
Current
10 X TOF
boiler*
In 2 of
Yet; opacity, partfcutate.
•nd MO,.
Packaging Corp. of
America.
Tomahawk. Ul
Currant
Ul
Port Townaend Papar
Port Townaend, UA
ROM Kraft Pulp and
Papar Mill
ROM, GA
Saurflt Ntwaprlnt
Newburg, OR
Sonoco Products Co.
Heruvllle. SC
Ulltaawtta Industrie*
Albany, OR
Currant; uaually
3-6X of fual U
oil or TDF
Currant
IX
2"x2»
Yea; taata performed for
criteria, haiardoua, and
toxic pollutant*. Including
ratal* and dloxln/furan;
testing dona on an overall
facility b**l*. with alt
boiler* vented together,
•one not burning tire*.
Ye*; Participate*, PNA'*.
heavy awtal*
Unknown
Ye*; boiler t 10.
partlculate, VOC
Currant
2X
2"x4" TOF
Ye*
Plant hat 4 boiler* totali 2 burn
coal only; 2 burn hog fual and
about 10X (itu ba»U) TOF. Both
hog fual boiler* are Coabuitlon
Engineering boiler* rated at
165.000 Ib* •t*aa)/hr with
vibrating *tok*r grata*. 344 ft1
In *lt*. All 4 boiler* are
vented together and controlltd by
tultlcyctone* and one ESP. TDF
fed fro*) a hopper with a variable
tpeed *crau outflog, and ara
added to the bark atraaai.
Three traveling grata
•preeder/ttoker type boilers; all
vent to comon duct, then
•eparate to two ESP'* and itacka.
1977; 200.000 Ib/hr; vanturl
acrubber
Two boiler* ualng TOF; f9
•preeder/atoker, 145.000 tb/hr.
fixed grata*, vanturl acrubbar; •
10 *pr*ader/*tokar. 300.000 Ib/hr
traveling grata, venturl acrubbar
Ju*t replaced with ESP 4/91
Control by wet tcrubbar; *tokar
fed type hog fual boiler. Feed
I* done with a hoewaade hopper
and fe«d conveyor. TDF I* Mixed
with the hog fuel after the hog
fuel exit* • dryer.
Have been burning TDF
for 3 year*; did obtain
panalt aiodlfIcatlon.
Reference* 2. 3, and 7
Formerly Owen*
IlllnoU. Nakooaa, and
fiaorgla Pacific;
produce* corrugated
paper Material*.
Reference 8
Reference 3
Reference 3
Hop* to Incraaae
percent TDF I tail t efter
ISP operational.
Reference* 3 and 9
Reference 3
Reference* 3, 10, 11,
and 12
-------
and clarifier sludge were provided in the introduction in
Table 1-2 and is reprinted here.
Table 1-2. Comparative Fuel Analysis, by Weight3
Fwl
TDF
Clarffler
Sludge
Coal
Wood Waste
TMt 1
Test 2
Test 3
T**t 4
Component
(percent)
Carbon
83.87
4.86
73.92
30.98
28.29
25.67
24.71
Hydrogen
7.09
0.49
4.85
3.16
2.37
2.54
2.44
Oxygen
2.17
2.17
6.41
23.33
20.95
19.17
18.46
Nitrogen
0.24
0.47
1.76
0.13
0.13
0.12
0.12
Sulfur
1.23
0.26
1.59
0.04
0.03
0.03
0.02
Aah
4.78
3.16
6.23
1.31
1.49
1.11
1.13
Mofature
0.62
88.69
5.24
41.05
46.73
51.36
53.12
Heat i no
Value
Btu/lb
15,500
924
13,346
5,225
4,676
4,031
4.233
5.2 PROCESS DESCRIPTION
Most waste heat boilers are fairly small, ranging from
100,000 to 200,000 pound of steam per hour (100 to 200
MMBtu's per hour). Overall feed rate of hog fuel averages
about 84 tons per hour. The maximum rate of, TDF is between
10 and 15 percent of the total Btu's required. The reason
for this is that one of the main uses of the hog fuel boiler
is to burn hog fuel. Ten to 15 percent TDF is all that is
needed to accomplish this.
Varied boiler firing configurations are found in hog fuel
boiler applications, including dutch oven, fuel cell,
spreader stoker with traveling or vibrating grates, and
cyclone stoker types. As stated previously, the spreader
stoker is the most widely used of these configurations.
Spreader/stoker boilers in the pulp and paper industry often
have an air swept spout added to the front of the boiler to
feed bark down on top of the coal.u Wood is puffed at one-
5-5
-------
second intervals through the spout so it falls onto the coal
base on the grate. The air swept spout can also blow TDF
sized up to about 3" x 2", without any additional capital
equipment expenditure. However, to retrofit an existing
spreader/stoker boiler with an air swept spout to
accommodate TDF fuel is not economically feasible.1*
Alternatively, in the waste heat boiler, bark, wood waste,
and sludge are conveyed to an overhead, live-bottom bin.
This fuel is then introduced to the boiler furnace by an air
jet, which casts the fuel out over the stoker grate in a
thin, even layer.1 The advantage of this type of boiler
configuration is that it has a fast response to load
changes, has improved combustion control, and can be
operated with a variety of fuels.1
If coal is the primary base load fuel, it is typically
pulverized and fed to separate pneumatic systems that feed
individual burners. TDF, when used, is usually fed via a
variable-rate weigh belt or variable-speed screw conveyor to
the bark conveyor feeding the overhead bin. This
configuration permits effective mixing of TDF, bark, wood
waste, and sludge.
Figure 5-1 is a schematic diagram of the process flow
through Smurfit Newsprint's two hog-fuel boilers. Wood
sludge, waste wood chips, and bark are fed into the two
boilers. TDF is added as a supplemental fuel, and is
currently limited by an air permit to 1 percent of the
boiler fuel. Exhaust from the combustion chamber of the
boilers exits through multicyclone systems and scrubbers,
which collect ash from the exhaust streams.15
5-6
-------
TDF
TDF
Clarified
Water
Overflow
Sludge
Figure 5-1. Smurfit Newsprint Process Flows15
5-7
-------
5.3 EMISSIONS, CONTROL TECHNIQUES AND THEIR EFFECTIVENESS
5.3.1 Emissions
This report examined six sets of test data from waste wood
boilers at pulp and paper mills (and one at a silicon
manufacturing plant). Of the six, control at one is
unknown, two are controlled by venturi scrubber, two by
ESP's, and one by both a scrubber and an ESP. The State of
Washington tested two of these facilities: Port Townsend
Paper and Crown Zellerbach Corporation. Table 5-2 presents
the particulate, heavy metals, and polynuclear hydrocarbons
(PNA) emissions data from these test. Both of these plants
use venturi scrubbers for emissions control. Smurfit
Newsprint has performed several tests over the last 3 years.
Particulate results at Smurfit are summarized in Table 5-3.
Results of testing on other criteria pollutants and heavy
metals are contained in Table 5-4. Packaging Corporation of
America (formerly Nekoosa Packaging) tested criteria
pollutants, metals, PCB's, and dioxins and furans at
baseline and about 1.5 percent TDF- These results are
summarized in Table 5-5. Champion International in Sartell,
Minnesota, tested particulate, SOX, metals, and semi-
volatile organics, although the results of the organics
testing while burning TDF were lost in a laboratory
accident. Results of this test are found in Table 5-6. Dow
Corning, a silicon manufacturing facility, burns TDF in
their wood chip boiler, and has performed air emissions
testing for particulates, S02, NOX/ and metals. These data
are summarized in Table 5-7. The following paragraphs
summarize the test results by pollutant for each plant.
Figures are provided that graph the emissions change as TDF
percent increased.
Fuel use varied significantly during the six tests evaluated
here. Three burned 100 percent wood waste for baseline, and
5-8
-------
Table 5-2. Emission of PNA's and Metals from Port Townsend
Paper and Crown Zellerbach Corporation16'17*2*
(Venturi Scrubber Controlled)
Port Tounaend Paper (2/25/86) Crown Zellerbach Corp. (6/10/86)
pn|i,,»«r WMU Wood * 5* OH Vaete Wood * 7X TDF Wat t« Wood * 12X Oil Waitt Wood * 2X TDF * 1W Oil
Ib/hr
Ptrtlculate 46.2
Mttili
Araenlc
larlue
Cadmlue 0.009
Chroalue 0.01
Copper
Iron
Lead 0.1
Nickel 0.1
Vanadlua 0.2
Zinc 3.1
Anthracene 0.03
Phenanthrene 0.1
Fluoranthane
Pyrene
•enio(b)F luorenthene
•enxo( k ) F 1 uor anthene
•enio( a ) F I uoranthene
Chryaene
TOTAL PHA'a
IbxIO4/
KMBtu Ib/hr
63.8
NA
257.4
42.8 0.007
54.9 0.01
2.415.6
1.999.8
603.9 0.03
689.0 0.01
902.9 0.001
14,790.6 48.8
9.9 0.01
419.8 0.2
459.4
249.5
0.6
0.6
1.6
3.2
0.3
HHStu Ib/hr
11.0
NA
350.5
31.3
34.9
2.296.8
2.574.0
132.3
59.0
8.9
249.480.0 0.5
26.7
772.2
235.6
380.2
1.2
0.6
2.2
2.4
IbxIO4/
MHBtu
3.3
11.3
2.9
0.5
30.7
263.1
64.0
3.5
3.0
2.455.0
1.0
45.3
37.4
47.8
2.3
0.7
0.0
0.0
Ib/hr MHBtu
15.4
6.28
29.1
5.8
3.5
40.0
377.8
72.4
3.6
7.5
3.1 16.381.4
0.6
16.7
14.2
21.7
0.0
0.0
0.0
0.0
0.02
-------
Table 5-3. Summary of Particulate Tests on Two Hog-fuel
Boilers at Smurfit Newsprint, Newberg, OR10'1*'*""0
19 Boiler - Particulate1
Date
3/13/87
1/29/87
3/6/87
2/9/87
TDF, %
0.0
1.0
1.5
1.8
PM Emissions,
Ib/hr
315'
73
162.0
>140.6
' Controlled by venturi scrubber
110 Boiler - Particulate1
Date
5/28/87
5/28/87
5/28/87
11/14/87
8/14/90
% TDF
0
1
1.5
1
1
PM
Ib/hr
26.8
45.6
57.2
30.5
26.0
Emissions
tons/yr*
117
200
251
134
114
• Controlled by venturi scrubber
b Assumes 8,760 h/yr
5-10
-------
Table 5-4. Summary of Non-particulate Testing on the
110 Boiler at Smurfit Newsprint, Newberg, OR18-19-20'25
110 Boiler - Other Pollutants'
Pollutant
Criteria
VOC6
NO/
so2d
CO*
Barium
Cadmium
Chromium
Copper
Iron
Lead
Zinc
Titanium
Date
5/28/87
5/28/87
5/28/87
11/14/89
8/14/90
11/14/89
8/14/90
11/14/89
8/14/90
11/14/89
8/14/90
11/14/89
11/14/89
11/14/89
11/14/89
11/14/89
11/14/89
11/14/89
11/14/89
% TDF
0
1
1.5
1.0
1.0
1.0%
1.0%
1.0%
1.0%
1.0%
1.0%
1.0%
1.0%
1.0%
1.0%
1.0%
1.0%
1.0%
1.0%
Ib/hr
25.1
8.0
69.9
1.2
1.0
82.8
33.4
4.8
ND
94.9
146
0.000
0.017
0.006
0.020
0.260
0.037
3.82
0.000
ton/yr
110
35.1
306
5.3
4.4
36.3
146
21
ND
417
639
-
-
-
-
-
-
-
-
• Controlled by venturi scrubber
b VOC limit is 189 TPY
c NOX limit is 2,850 TPY
d SO2 limit is 250 TPY
• CO limit is 570 TPY
5-11
-------
Table 5-5. Summary of Tests on 3 Hog-fuel Boilers at
Package Corp. of America (formerly Nekoosa)2
November 7, 1989
Pollutant
Particulate
NOX
CO
S02
Chromium VI
Metals
Arsenic
Cadmium
Lead
Nickel
Zinc
Mercury
Chloride
Benzene
0% TDF
19.0
114.36
111.09
180.67
0.0129
0.003
<0.0023
0.019
<0.008
0.715
0.0005
0.96
<5.57xlO'2
1-2% TDF
lb/hr
20.7
107.06
147.23
268.00
0.036
0.003
<.0023
0.018
<0.008
0.851
0.0006
1.82
6.65X10'2
% Change
+9
-6
+33
+48
+179
0
DL§
-5
DL«
+19
+20
+90
+20
NOTE: All three boilers are ducted to common duct and then
to two ESP's.
' Below detection limit (DL) .
5-12
-------
Table 5-6. Emissions Burning TOP and Haste Hood
Dow Corning Corporation, Midland, MI22'*
March 9-29, 1989
m
i
H
Ul
Pollutant
Participate
Cadilua
Total
Chronlua
Zinc
••rytlliW
NO.'
«Q,'
ot
Ib/hr
4.29
0.00049
0.00128
0.0634
NO
-
-
ror
Ib/HNBtu
0.0122
1.39x104
3.64K10"*
1.8x10^
NO
0.1S3
0.026
5X TDF
Ib/hr Ib/WBtu
7.53 0.0205
-
.
-
-
0.162
0.028
X Change
468
N/T
N/T
N/T
N/T
+6
+8
10X TOF
Ib/hr Ib/WBtu
11.22 0.0305k
-
.
-
-
0.133
0.037
X Change
*150
N/T
N/T
N/T
N/T
-13
»<2
15X TOF
Ib/hr
38.10
0.0028
0.0019
11.32
NO
-
»
Ib/MNBtU
0.1130k
8.21u104
S.S7JC10-*
0.03
NO
0.081
0.059
X Change
*826
+491
*53
•16,567
NO
-47
*127
* Controllad fay ESP.
k (Million IfMite of 0.035 Ib/MMBtu at 12 percent CO,.
' Ho ll«lt for Borylllua Maa 7.3 K 10J (b/hr.
* NO, Million* ll«lt It 0.7 Ib/MNBtu.
* $0j 11*1t Is 0.8 Ib/NNBtu.
N/T • Not Tetted.
NO • Not Detected.
-------
Table 5-7. Summary of Tests on Hog-fuel Boiler at
Champion International Corp., Sartell, MN
March 12-16, 1990*
Particulate
so,
Cadmium
Chromium
Lead
Mercury
Zinc
0%b
Ib/hr
19.7
266
0.0025
0.048
0.050
0.00038
0.23
4% TDF*
Ib/hr
24.3
277
0.0018
0.0046
0.036
0.00008
3.43
% Change
+23
+4
-28
-90
-28
+111
+1,391
• Semivolatile organic samples at 4% TDF were lost in a lab
accident; thus, baseline results are not included here.
b Baseline - 82% coal, 13% bark, 5% sludge, 0% TDF-
c TDF - 80% coal, 12% Bark, 4% sludge, 4% TDF.
5-14
-------
supplemented with TDF for secondary tests (Smurfit,
Packaging Corporation of America, and Dow Corning Corp.)
The other three varied the primary and supplemental fuels
dramatically. Port Townsend burned waste wood plus 5
percent oil for baseline, and waste wood plus 7 percent TDF
for the rubber test.19
Crown Zellerbach burned waste wood and 12 percent oil for
baseline, and waste wood with 11 percent oil and 2 percent
TDF for the rubber test.16 Champion International burned 82
percent coal, 13 percent bark and 5 percent sludge for
baseline, and for the TDF test, burned 80 percent coal, 12
percent bark, 4 percent sludge, and 4 percent TDF.23
One additional source conducted a test on performance at a
waste-wood boiler burning TDF that included results on steam
generated and boiler efficiency using the heat-loss method
for varied fuel mixes.2 Although the test summary notes
that emissions testing was done, the results were not
obtained. Nevertheless, one of the conclusions of the test
report was that TDF had no environmental disadvantages when
compared with the supplemental coal used during the tests.2
5.3.1.1 Particulate Emissions. Particulate emissions
increased in all six emission tests reported here. Percent
TDF varied from 0 to 15 percent. A comparison of percent
change in particulate emissions over baseline is given in
Figure 5-2. An emission rate comparison is found in Figure
5-3.
One paper mill, Inland-Rome, in Rome, GA, ran four tests
burning varying amounts of wood waste, TDF, biological
sludge from the plants secondary effluent treatment system,
and coal.2 One TDF test was run at 7 percent TDF and 93
percent wood waste; particulate emissions were similar to
baseline.2 Another test was run with 12.8 percent TDF, 12.1
5-15
-------
percent sludge, and 75.1 percent wood waste; particulate
increased slightly over baseline in this test, but did not
exceed permitted levels.2 The test boiler at this facility
shares the ESP and stack with three other power boilers
(also burning wood waste and/or pulverized coal and TDF);
therefore, the incremental increase due solely to the change
in fuel mix at the test boiler could not be determined.2
5.3.1.2 Sulfur Dioxide Emissions. Sulfur dioxide emissions
also increased somewhat in all tests. Figure 5-4 shows
emission rate changes for SO2.
5.3.1.3 Nitrogen Oxides Emissions. The nitrogen oxides
(NOX) in Dow-Corning's emissions decreased about 50 percent
between their highest and lowest burning rates. Packaging
Corp. of America's results show a 5 percent drop in NOX.
Smurfit and Champion did not test for nitrogen oxides. A
summary of nitrogen oxides tests is given in Figure 5-5.
5.3.1.4 Carbon Monoxide Emissions. Emissions of carbon
monoxide increased in the one data set comparing baseline to
data with TDF. This comparison is graphed in Figure 5-6.
5.3.1.5 Heavy Metals and Polvnuclear Aromatics (PNA). Zinc
emissions are frequently mentioned as an element that could
increase significantly when burning TDF, because of the zinc
content of the rubber. Because zinc oxide has a small
particle size, sources controlled by scrubbers have
particular concern that the zinc oxide will escape the
control device. ESP's, on the other hand, would be well
suited to pick up a small metallic particulate. Zinc was
measured at all six plants evaluated here. Data on zinc
emissions show that in all five data sets where comparison
to baseline levels was available, zinc emission rates did
increase,often dramatically- Figure 5-7 graphs zinc
5-16
-------
800
CA
C
O
'in
tn
1 600
UJ
O)
§
.C
O
o^ 200
-
—
—
—
498 *«
1 7%TDF| 1 2%TDf|
A B
470
1%TDF
C
+113
15% TDF
C
1.0% TDF
48 f
D
Plant
478
6% TDF
E
4182
10% TDF
E
4788
18% TDF
4% TDF
423 j
1 1
E F
KEY
A-Fort Touraand; ••••(In* Included SX oil; scrubber controlled
•-Crown Zttlerbsch; ••••line Included 12X oil; TDF t«it Included 11X oil; Scrubber controlled
C-Smrflt netMprint - scrubber controlled.
0-Pecklng Corp of America; ESP controlled.
E-Dou Corning; ESP controlled.
F-Champion; Bxellne - 82X coel, 13X bark, 5X sludge; TOF Included BOX coat, 12X berk. 4X sludge.
Figure 5-2. Percent change of particulate emissions over baseline (0% TDF) in
wood waste boilers burning TDF.
-------
ui
I
60 -
7% 10%
Dow-Coming
ESPcortrotod
PortTownsend
WoodwMt* + 5% ol;
•cnibbw cortrotod.
Crown ZaDarback
„ in ... ... .
.......... LJ
BaMln* Inducted 12% oi;
TDF (Mt (nduitod 2» TOP
.
oontroDvd.
Srnuffit
WoochvMU + 1.5* TDF;
•cfubb«r coriioiud.
Packaging Corp of Amarica
ESPoortrolad
Champlocj
13% bvtc. 5% tludo*; TDF
IM! - B0% co«t
4%«kJdg*.4%TDi:.
15%
Figure 5-3. Particulate emission rates from hog-fuel boilers
burning TDF supplementally.
-------
1
200
150
s
50
0
o%
SmrltPlart
—-©- —
1%
%TDF
Packaging Cap o> America
1.5%
4%
Figure 5-4. Change in emission rate of SO, over
baseline (0% TDF) at varied TDF input
rates for hog-fuel boilers.
120
100
so
60
£
6 40
20
0
11408
82.8
o
33.4
O
107.06
%TDF
Qmurtl NMMprtnl Pirtiaginq Corp of Annrto
1.5%
Figure 5-5. Change in emission rate for NOX over
baseline (0% TDF) at varied TDF input
rates for hog-fuel boilers.
5-19
-------
147.23
111.08
0%
OmurttPtant
0
1%
%TDF
1.5%
Figure 5-6. Change in emission rate of CO over
baseline (0% TDF) at varied TDF input
rates for hog-fuel boilers.
5-20
-------
Ul
I
M
u
50
40
w
Q 30
"8
£
20
10
I
.08 .23 M.
I
I
?
.72
0%
I
3.1
382
.85
1% 1.5%
%TDF
G
31
2%
48.8
Port
Towrw«nd [
(Scrubb«i)|
343
4%
11.32
Dow Coming
Port Townsend
Crown Zellerbach
EZ3
Champion
Packaging Corp
of America
Smurfit
7% 15%
Figure 5-7, Change In zinc emission rates when burning TDF at six pulp
and paper plants.
-------
emission rates and denotes whether control at each facility
is by scrubber or ESP.
Washington State tested two (Port Townsend and Crown
Zellerbach) waste heat boilers controlled by venturi
scrubbers for PNA's, both at baseline (no TDF) and while
burning TDF.24 Crown Zellerbach found emissions of zinc to
be seven times higher when tires were burned, and emissions
of arsenic, chromium, cadmium, and barium to increase loo
percent.16 Port Townsend found zinc concentrations
increased almost 17 times when burning tires, but other
metals had decreases or smaller increases.17 The high zinc
increase at Port Townsend may be attributable to the higher
tire input percentage, whereas the higher emissions of other
metals at Crown Zellerbach may be because of the 11 percent
Btu input provided by oil.16-17 Figure 5-8 shows percent
change in metals emissions other than zinc for both
Washington paper facilities. Zinc emissions were shown in
Figure 5-7.
Emissions of all PNA's from Crown Zellerbach decreased,
while those from Port Townsend varied.16-17 Figure 5-9
compares percent change of specific PNA's from the two
companies.
5.3.2 Control Techniques
Of the seven plants where the control device was known,
three controlled emissions with venturi scrubbers, three
controlled emissions using ESP's, and one controlled
emissions with one scrubber and one new ESP on two separate
boilers. In total, 13 boilers were located at these seven
plants. Four of the individual boilers were known to be
controlled by venturi scrubbers, and nine were known to be
controlled by ESP.
5-22
-------
O)
I
K>
Ut
-100%
+200%
+400%
+600%
Arsenic
Copper
Iron
Nickel
Chromium
Cadmium
Lead
Vanadium
Barium
Mercury
V/////A +93
T
•40
+30
+28.7
+43.7
91.4
V//////7/////////////////////////////////////////A
T
+829.2
i'j"; •'"!.;,•!• i V{'i; •,; •;':' \''.'!'' ''jCiil *<7i
Port TowrtMnd
7%TDF
Crown Z*H«rfoach
2%TDF
Packaging Corp of America
1.5XTDF
Oow Coming
15%TDF
Champion
4%TDF
Figure 5-8. Percent change in metals emissions at five mills burning TDF,
-------
Ul
I
-100% -50%
+50% +100% +150% +200%
Anthracene
Phenanthrene
Flouranthene
Pyrene
Benzo(b)Flouranthene
Benzo(K) Flouranthene
Benzo(a)Flouranthene
Chrysene
Benzene
- -1001//////////////////,
4-170
+100
+38
H20
Port Townsend
7%TDF
Crown Zellerbach
2%TDF
Packaging Corp of America
Figure 5-9. Percent change in emissions of PNA's at three paper mills burning TDF.
-------
5.4 OTHER ENVIRONMENTAL AND ENERGY IMPACTS
A positive result of TDF use in waste wood boilers is that
facilities are able to burn sludge and waste wood more
successfully, decreasing the likelihood of solid waste
disposal problems. Results from a series of waste wood
boiler performance tests using ASME codes concluded that use
of TDF supplementally in hog-fuel boilers enhances
combustion of wood waste, and enables disposal of biological
sludge in conjunction with wood waste without necessitating
use of other fossil fuels such as coal.2 No applicable
environmental limits were exceeded during these tests.2
As noted earlier, use of TDF by Smurfit is currently limited
to 1 percent of the boiler fuel (by weight) by their air
permit. Smurfit hopes to increase the percent TDF burned to
5 percent when an ESP is brought on-line to control their
larger boiler. Smurfit personnel believe that the use of
the ESP may increase the zinc content of the ash, thereby
affecting its quality. This increase in zinc is expected
because the ESP will pick up the fine zinc oxide particles
with much more efficiency than the scrubber. In addition,
an increase in TDF burned will increase zinc levels.15
5.5 COST CONSIDERATIONS
Economically, the advantages of TDF can be very site-
specific. Primary, or base load, fuel costs vary
significantly, as does the delivered cost of TDF. TDF
supplies a consistent and dry Btu input to boilers. This is
an important advantage because the wood wastes typically fed
to the hog-fuel boilers have a high and variable moisture
content, which makes hog-fuel boiler operation a challenge.
Availability of TDF is a problem at some mills. The costs
of TDF to a pulp and paper mill is affected by whether there
is a tipping (tire disposal) fee or State rebate incentives
5-25
-------
that provide revenue to offset TDF costs. For example,
Smurfit paid between $39 and $43 per ton in 1990 and part of
1991, respectively, for their TDF. A rebate program lowered
the respective costs to approximately $21 and $23 per ton of
TDF, for an equivalent rebate of $18 and $20 per ton.15
5.6 CONCLUSIONS
Burning tires or TDF in a waste-wood boiler improves the
performance of the boiler system. The high energy and low
moisture content of TDF help stabilize boiler operations and
overcome some of the operating problems caused by fuel with
low heat content, variable heat content, and high moisture
content.
Unfortunately, using TDF in hog-fuel boilers appears to
deteriorate emissions quality'. In every set of data,
particulates in the emissions increased with a corresponding
increase of TDF usage. The other criteria pollutants also
increased in most cases, but not as consistently as.
particulates.
Cost considerations are site-specific and depend on the
availability, cost, and transportation of alternative
supplemental fuels.
5-26
-------
5.7 REFERENCES
1. U.S. Environmental Protection Agency Compilation of air
Pollution Emission Factors, Fourth Edition, AP-42.
p. 1.6-1.
2. Jones, R.M., M. Kennedy, Jr., and N.O. Heberer
"Supplemental Firing of Tire-derived Fuel (TDF) in a
Combination Fuel Boiler." TAPPI Journal. May 1990
pp.107-113.
3. Ohio Air Quality Development Authority. Air Emissions
Associated with the Combustion of Scrap Tires for
Energy Recovery. Prepared by: Malcolm Pirnie, Inc.
May 1991.
4. Telecon. Clark, C., Pacific Environmental Services,
Inc. (PES), with Bosar, L., Fort Howard Corporation.
February 27, 1991. TDF experience.
5. Telecon. Russell, D., PES, with Thorpe, L., Georgia-
Pacific Paper Co., March 1, 1991. TDF experience.
6. Telecon. Clark, C., PES, with Fuller, B., Oregon
Department of Air. February 28, 1991. TDF use in
State.
7. Telecon. Clark, C., PES, with Jones, B., Inland-Rome
Paper Co., March 6, 1991. TDF experience.
8. Telecon. Clark, C., PES, with Koziar, P., Wisconsin
Waste Tire Program. February 20, 1990. TDF use in
State.
9. Telecon. Clark, C., PES, with Miller, S., Smurfit
Newsprint. February 27, 1991. TDF experience.
10. Telecon. Clark, C., Pacific Environmental Services,
Inc. (PES), with Crispin, D.M., Oregon Department of
Environmental Quality Hazardous and Solid Waste
Division. February 27, 1991. TDF use in State.
11. Telecon. Clark, C., PES, with Wickwire, L., Willamette
Industries. March 5,1991. TDF experience.
12. Memorandum from Clark, C., PES, to Michelitsch, D.,
EPA/ESD/CTC. Summary of Meeting with Scrap Tire
Management Council. October 29, 1991.
13. U.S. Environmental Protection Agency. Nonfossil Fuel
Fired Boilers — Background Information. EPA-450/3-82-
007. March 1982.
5-27
-------
14. Schwartz, J.W., Jr. Engineering for Success in the TDF
Market. Presented at Recycling Search Institute Scrap
Tire Processing and Recycling Seminar. West Palm
Beach, FL., April 27, 1989.
15. Memorandum from Clark, C., PES, to Michelitsch, D.,
EPA/ESD/CTC. October 28, 1991. Site Visit — Smurfit
Newsprint.
16. Washington State Department of Ecology. Polynuclear.
Aromatic Hydrocarbons and Metals Emitted from the
Burning of Tires at Crown Zellerbach, Port Angeles,
Washington, June 10 and 11, 1986. Source Test 86-10a.
17. Washington State Department of Environmental Source
Test Summary of Emissions to Atmosphere from Port
Townsend Paper Co., Port Townsend, Washington. February
25 and March 5, 1986. Report No. 86-01.
18. Horizon Engineering. Particulate emissions test report
on Smurfit Newsprint's 19 Hogged Fuel-Fired Boiler.
Tire Chip Supplement Trials at Newberg, Oregon.
January-March, 1987.
19. Horizon Engineering. Stack Emission Test Report.
Smurfit Newsprint's No. 10 Hogged Fuel Fired Boiler.
Tire Chip Supplement Trials. Newberg, Oregon. May-
July 1987.
20. Horizon Engineering. Stack Emission Test Report.
Smurfit Newsprint's No. 10 Hogged Fuel Fired Boiler.
Fiber-Based-Fuel Trials and Annual Tests. Newberg,
Oregon. November 14-17, 1989.
21. Clean Air Engineering. Report on Diagnostic Testing.
Performed at Nekoosa Packaging Tomahawk Mill. Units
7,8, and 10. Tomahawk, Wisconsin. CAE Project No.
4842/2. November 7,1989.
22. EDI Engineering and Science. Report of Tire Chip Test
Burn. Performed for Dow Corning, Midland Michigan, on
the Wood Fired Boiler. March 9-29, 1989.
23. Pace Incorporated. Results of the March 12-16, 1990
TDF Trial burn Testing on the Unit 3 Stack at the
Champion International Corporation Facility Located in
Sartell, Minnesota.
24. Drabek, J., and J. Willenberg. Measurement of
Polynuclear Aromatic Hydrocarbons and Metals from
Burning Tire Chips for Supplementary Fuel. State of
Washington Department of Ecology. Presented at 1987
TAPPI Environmental Conference. Portland,Oregon.
April 26-29, 1987. 12 pp.
5-28
-------
25. Horizon Engineering. Stack Emission Test Report.
Smurfit Newsprint No. 10. Hog Fuel Fired Boiler.
Annual Compliance Tests. Newberg, Oregon. August 14,
1991.
5-29
-------
6. TIRES AND TDF AS SUPPLEMENTAL FUEL
IN ELECTRIC UTILITY BOILERS
This section discusses electric utility plants that use
whole tires or TDF supplementally to produce power in
boilers. Facilities that combust 100 percent tires to
produce power were discussed in Chapter 3, Dedicated Tires-
to-Energy Facilities.
6.1 INDUSTRY DESCRIPTION
As described in Chapter 2, many boiler configurations have
been tested and commercially operated burning whole tires or
TDF on a supplemental basis. In the utility industry, coal-
firing boilers are primarily of the pulverized coal
configuration.
As of the Summer of 1991, at least nine boilers at seven
plants were burning, or planning to burn, whole tires or TDF
on either a test or commercial basis. Currently, one
pulverized coal boiler at a utility plant is testing use of
whole tires. Three cyclone-fired boilers at utilities are
currently testing TDF use. One utility currently operates
two underfed stoker boilers that use TDF on a commercial
basis. One utility tested TDF unsuccessfully in a fluidized
bed combustion (FBC) boiler that was a retrofitted spreader
stoker design, and two utilities are currently constructing
new FBC boilers to accommodate TDF use. Table 6-1 lists
these plants and summarizes information about their TDF
experience, boiler configuration, and air emissions testing.
6.2 PROCESS DESCRIPTION
Boilers at electric power plants use fuel to generate power
for municipalities and industry. The heat generated by the
6-1
-------
Table 6-1.
Electric Utilities with TDF Experience
as a Supplemental Fuel
COMPANY AND LOCATION
TOF USE
AIR EMISSIONS TEST
DATA
BOILER(S) DESCRIPTION
COMMENTS/
REFERENCES
Illinois Power
Baldwin Generating
Station
Baldwin, IL
Manltowoc Public Utility
Manltowoc, Ul
O\
Northern States Power
French Ialand, Ul
Ohio Edlaon Company
Toronto, OH
Teat baaI a; 3/91 moat
recent teat. 1"x1"; 2X
during teat burn; 100 tpd
TDF; add TOF at coal
reclaim prior to banner
ail I la; alao eventually
want to teat adding TDF
after hammer ail 11 and
adding varloua slzee TDF.
Current use; <10X; 2"x2"
wire-free; ailx with coal
using • proportioning belt
feeder; can't use In cold
weather because tire pile
freeiea
Test In 1982; Unsuccess-
ful; electrified filter
bed for PM Inadequate
because metal in tires
shorted out device; also
heat level In boiler too
high.
2 tests 1990; Whole tires
up to 20X Itu content;
tires burned down to
residual metal within IB-
foot drop to boiler bed
Yes; 3/91 test burn on
Unit No. 1; tested PM,
SOj. beryl 11 in.
cadmium, lead, total
chronlcm, and zinc; 2X
TDF during test.
No
Yes
Test In May 1990;
tires dropped In at 5
different rates
equating to 0, 5, 10,
IS, and 20 percent
tires aa fuel. All
partlculate and SO]
llMlts were net.
2 twin cyclone fired boilers, universal
pressure, balanced draft, turbine rated
560 MU; output capacity of 4,199,000 Ib/hr
steaai at 2620 palg and lOOS'F; borne
Illinois coal; controlled by western
Precipitation ESP, dealgn gaa volume of
1.730.000 ftVmln with 99X efficiency; 600
ft atack.
Rebuilding two 90,000 Ib/hr underfed
stoker/spreader boilers for TDF when tire
pile thaws; have 80,000 Ib/hr coal-fired
stoker/spreader, and 1 coal-fired 150,000
boiler; coal la <1X sulfur. Also have 1
new 200,000 Ib/hr circulating fluldlzed
bed, plan to burn tone TDF here too. PIC
has listestone sorbent for SOj reduction.
150.000 Ib/hr steaai capacity bubbling
fluldlzed bed; retrofitted froja
spreader/stoker design; primary fuel Is
wood waste.
Pulverized coal-fed, front-fired, wet
bottom, noncontiguous tap. Tires dropped
into boiler.
Nave temporary
test burn penal t;
References 1-5
References 6 and 7
Reference* 8 and 9
Ohio EPA end USEPA
have approved
permits allowing
tire Input up to a
20X Itu level.
References 2, 10,
11, 12, and 13
-------
Table 6-1 (Continued)
COMPANY AND LOCATION
TDF USE
AIR EMISSIONS TEST
DATA
BOILER(S) DESCRIPTION
COMMENTS/
REFERENCES
Otter Tall Power Co.
Big Stone city, SO
Traverse City Light i
Power
Traversa City, HI
.United Development Group
Southern Electric Intl.
Niagara Falls, NT
United Power Association
Elk River, MN
Wisconsin Power t Light
Rock River Gen. Station
Belolt, Ul
Testing since 10/89;
current use Is 2Mx2" wire
free at 10X; no metering
system, TDF is dumped into
the coal handling systeM
as It Is received; one
supply problem Is wet TDF
chips freeze to rail cars
and are difficult to
remove.
Under construction;
designed for up to <20X
TDF, wire-free. Commer-
cial operation will begin
on coal only. Test TDF
after atable on coal
2 1979 tests: 1 test at
OX, 5X. and 10X TDF, wire-
free, 2", polyester type
tires, emissions testing
done; 1 test with 2"-
6-TOF, wire-in, rates from
5X to 65X, no air testing
done.
Test program since 6/69;
have tested crutt> at 10%
with no problems; 1"x1"
TDF tested up to 7X level
wire-In
No
Unknown
No
Yea; first teat only;
tested for PM. SO,,
NO,, Cl, and HjS04.
Yea; 7X TDF; measured
PM, SOj, SO,, CO, org-
anlcs, NCI, HF. trace
metals, dioxln, and
furan, PCB's, and POMs
440 MU, 3.250.000 Ib/yr cyclone-fired
boiler; 3000'F; lignite la primary fuel;
468,000 Ib/hr, 52 MU, circulating
fluldlzed bed. Bed augmented by limestone
for SO] control. Pulse-Jet FF planned,
alr-to-cloth ratio of 3.88.
3 boilers; TDF teated In 2 stoker-fired
with traveling grata, 135,000 Ib/hr, 12
MU; Also have 1 pulverized coal, 235,000
Ib/hr, 25 MU, no TDF testing; all designed
for coal, 2 also natural gas.
2 boilers; both cyclone-fired 75 MU.
525,000 Ib/hr; each has ESP.
Would bum higher
percentage, but
arc limited by TDF
supply.
References 2 and
14
Reference 15
Reference 16
All 3 boilera vent
to one FF. Plant
waiting for
economical and
adequate supply of
TDF before
Initiating
commercial
operation.
Reference 17
References 2. 14,
18, 19, and 20
Note 1: Teat data are available for NY State Gas and Electric, Balnbrldge Plant, ffnghamton, NY, and for Northern Indiana Power, South Bend, IN.
Reference 13.
Note 2: Illinois has modified their regulations so that no permit modification Is needed for permit holders wanting to burn tires or TOF up to the
20X level. The State must be notified of the fuel change, however. Reference 13.
-------
burning of the tires rises into the radiation chamber. In
this chamber, the heat causes water contained in pipes in
the refractory brick wall to turn to steam. The high-
pressures steam is forced through a turbine, causing it to
spin. The turbine is linked to a generator that generates
power. After passing through the turbine, the steam is
condensed to water in a cooling system, and returned to the
boiler to be reheated.
This section summarizes the experience of electric utility
facilities that have tested TDF or tires, or that are using
them in commercial operation. This section will describe
the technical operation and modifications needed to
accommodate TDF or tire use. The air emissions data and
other environmental information will be described in
sections 6.3 and 6.4 of this chapter respectively.
6.2.1 Materials Handling
Materials handling provides the first challenge to burning
TDF in a utility boiler. TDF must be correctly sized so as
to "fit" in fuel conveyors, and must be well-mixed, to
ensure proper combustion.
Two plants have tried conveying TDF to the boiler through
coal crushing equipment. At Illinois Power and Light,
mixing of the coal and the TDF has to occur at the front of
the conveying system, because the remainder of the system is
closed.5 Thus, TDF must be able to go through the hammer
mills at this time.5 In the future, the company would like
to test having the TDF bypass the mill, because although the
TDF caused no operational mill problems, the TDF size did
not decrease appreciably.1
Wisconsin Power and Light (WP&L) experienced several
problems conveying the TDF through the existing coal
6-4
-------
blending facility.18 First, the crushers did not
significantly reduce the size of the TDF. Second, the
crusher has magnetic separators to remove large ferrous
metal pieces that can damage the coal crushers. These
magnets pulled the small crumb rubber from the conveyor.
Therefore, to use TDF the magnet had to be turned off, which
was unsafe and could cause damage to the crusher.
Subsequently, Wisconsin Power and Light added an additional
coal yard conveyor to safely blend TDF with coal downstream
from the coal crushing equipment.18
Other companies have tried various methods of mixing fuel
and TDF either on conveyors, or in storage. Otter Tail
Power did not modify its existing lignite handling, feeding
and burning equipment to burn TDF. Initially, TDF was fed
into an auxiliary conveyor and mixed with lignite after the
crusher house. The mixture then entered the boiler building
on a single conveyor. In more recent tests, however, the
TDF was pushed into a rotary car dumper and conveyed to live
storage, where natural mixing with the lignite occurs.21
United Power used a coal/TDF blending system in which TDF
was blended with coal at the reclaim hoppers. A variable
speed conveyor belt was used to control the mixture during
fuel reclaim.17 This system worked well for the low (up to
10 percent) TDF fuel blends, but problems were experienced
in the tests using up to 65 percent TDF. Specifically, the
material plugged up the fuel conveying system at the reclaim
hoppers and at the coal scales.17 Further, the larger
pieces of TDF segregated to the outside areas of the fuel
storage bunkers, resulting in a non-uniform fuel blend that
plugged the inlet to the stokers, and resulted in uneven
fuel distribution on the furnace grates.
Wisconsin Power and Light has also experienced the problem
of plugging of the coal feeders by oversized TDF; a plugged
6-5
-------
feeder must be manually dismantled and unplugged, causing
several hours of unit derating. The company is working with
suppliers to achieve more consistent and accurate TDF feed
size.18
Two of the utility boilers reported here used 1-inch TDF,
one at the 2 percent level and one at the 7 percent level.
Three have used 2-inch TDF up to the 10 percent level. One
has burned whole tires up to 20 percent of their Btu
requirement.
Flyash and slag handling systems also require consideration,
and sometimes modification. At Wisconsin Power and Light,
the slag is sold to a buyer that can not tolerate wire
content. Therefore, a magnetic separator is required to
remove small pieces of steel wire that become incorporated
into the slag during combustion.18
At United Power Association, ash was unaffected by TDF use
at the 10 percent level.17 However, when TDF provided as
much as 65 percent, by weight, of the fuel mix, a dust
control problem with the ash resulted as it was conveyed
from the ash storage silo to the ash storage pit. The ash
appeared to be significantly finer and more resistant to
wetting, and use of wetting agents had to be increased.
6.2.2 Combustion
Generally, TDF contribution to combustion is a positive one.
TDF provides an economic fuel with a constant Btu content
and low moisture.
One boiler utilizing TDF on a continual test basis, Otter
Tail Power, burns lignite as a primary fuel.21 Because
lignite has a relatively low Btu content (6200 Btu/lb), TDF
offers improved flame stability to their operation.12
6-6
-------
However, in initial tests burning 1-inch TDF at the 25
percent level, at Otter Tail, a significant amount of the
rubber carried beyond the radiant section of the boiler.21
The facility now does not exceed 10 percent levels of TDF
input.
Wisconsin Power and Light also found that if larger TDF were
burned, the oversize pieces were swept out the bottom of the
boiler with the slag. Some carry over is acceptable,
because some combustion does occur in the furnace behind the
cyclone. Even if partially burned TDF does exit the boiler,
WP&L personnel state that it is quickly extinguished in the
slag tank and removed by screening. Nevertheless, WP&L
limits TDF size to 1-inch, wire-in. No operational or
equipment changes to the boiler were necessary for WP&L to
utilize TDF as a supplemental fuel.18
Ohio Edison made modifications to its boiler so that whole
tires could be added to the boiler at varying feed rates.
The rate of addition of whole tires was chosen to result in
TDF percentage in the fuel corresponding to baseline (0
percent),5, 10, 15, and 20 percent.12
United Power Association reported very even boiler operation
including longer, hotter flames during their initial tests
of up to 10 percent TDF. A higher smoke generation rate was
reported when burning TDF, but the fabric filter operated
successfully (although more frequent cleaning was required
due to increased pressure drop over the system). United
Power conducted another test, burning up to 65 percent TDF,
by weight, although no emissions tests were run. The boiler
had no operational problems combusting the TDF up to 50
percent TDF. In fact, this high TDF fuel blend showed a
significant combustion advantage in starting up the boilers,
because the rubber ignited at a lower temperature than the
subbituminous coal. However, at TDF levels from 50 to 65
6-7
-------
percent, the grates did not always maintain an adequate
layer of ash to prevent overheating damage, and the fuel
tended to seal the grate combustion holes, causing
incomplete combustion.17
6.3 EMISSIONS, CONTROL TECHNIQUES AND THEIR EFFECTIVENESS
Air emissions testing data from five facilities were
evaluated for this report. The results are summarized here,
by pollutant. The most extensive testing was performed by
WP&L, who tested criteria pollutants, heavy metals, dioxins
and furans, and other organic compounds. Table 6-2
summarizes test data for all criteria pollutants at WP&L.18
Ohio Edison tested particulate, S02, NOX , and lead;
emissions results from this whole tire test are provided in
Table 6-3.12 Illinois Power tested PM, metals, and S02;
their emissions data are summarized in Table 6-4.* In 1979,
United Power Association performed two TDF tests at their
Minnesota facility, and conducted air emissions tests during
the first test burn for particulate, NOX, S02, sulfuric
acid, and chloride.17 These emission results are summarized
in Table 6-5.17 Northern States Power tested TDF in their
wood-fired utility boiler in 1982, without much success.9
Their emissions data are summarized in Table 6-6.9
Comparisons of the data from these plants are provided in
the pollutant specific discussions that follow; the Northern
States Power data are not included with graphical summaries
of the other four facilities, because its boiler is wood
fired, while the other four co-fire the TDF with coal.
6.3.1 Particulate Emissions
Three of the five data sets show that particulate emissions
decreased overall with increased TDF loading. A fourth
company, Illinois Power, did not provide baseline data by
which to compare emissions. Figure 6-1 compares the
6-8
-------
Table 6-2. Air Emission Test Data for Wisconsin
Power And Light18
Pollutant
Particulate Matter,
Ib/MBTU
Sulfur Dioxide, Ib/MBtu
Nitrogen Oxides , Ib/MBtu
Carbon Monoxide, Ib/hr
Hydrocarbons (as CH-) ,
Ib/hr
HC1, Ib/hr
HF, Ib/hr
100%
Coal
0.52
1.14
0.79
1.52
5.16
25.77
1.86
7% TDF
0.14
0.87
0.91
7.26
10.27
19.89
1.34
Change
(%)
-73
-24
+16
+377
+99
-23
-28
6-9
-------
Table 6-3.
Emission Results at Ohio Edison12
(Ib/MMBtu)
Tire Feed
Rat*
Particular*
MO,
Lead
Day 1
OX Tir*t
Run 1
Run 2
Run 3
Average
None
0.0764
0.0370
0.0760
0.0631
4.71
5.15
6.03
5.30
0.761
0.598
O.U5
0.601
0.0000938
0.0000931
0.000102
0.0000963
Day 2
5X Tires
Run 1
Run 2
Run 3
Average
1 tire p«r
34 seconds
0.0472
0.0959
0.0719
0.0717
5.44
5.83
5.93
5.73
0.391
0.547
0.593
0.510
0.0000973
0.0000997
0.000101
0.0000993
Day 3 Run 1
10X Tire* Run 2
Run 3
Average
1 tire per
17 seconds
0.0414
0.0692
0.0385
0.0564
5.62
5.76
5.74
5.71
0.324
0.478
0.504
0.436
0.0000977
0.0000966
0.0000947
0.0000963
Day 4 Run 1
15X Tire* Run 2
Run 3
Average
1 tire per
11.3 seconds
0.0781
0.0776
0.0889
0.0815
4.85
5.80
5.75
5.47
0.342
0.455
0.531
0.443
0.0000931
0.0000986
0.0000982
0.0000966
Day 5 Run 1
20X tires Run 2
Run 3
Average
1 tire per
8.5 seconds
0.0377
0.0380
0.0603
0.0453
5.03
5.38
5.60
5.34
0.313
0.407
0.440
0.387
0.0000881
0.0000934
0.0000921
0.0000912
On day 4 (15X TOP), tire feed supply problem resulted in several interruptions of tire supply to
the boiler.
6-10
-------
Table 6-4. Summary of Emission Rates Burning 2% TDF
at Illinois Power, Baldwin Generation Station*
March 21, 1991
Pollutant
PM (ESP inlet)
PM (ESP outlet)
soz
Beryllium
Cadmium
Total Chromium
Lead
Zinc (filter catch
only)
Ib/hr PPM
17,926.93
922.7
2,396
0.00966
0.02387
0.56249
0.08095
0.00484
Ib/MMBtU
3.438
0.1722
5.28
Table 6-5. Summary of Emission Rates from Testing
at United Power Association, Elk River, MN17
May, 1979
Pollutant
Participate
SOj
MO,
HjSO,
Chloride
(•* CI-) inlet to
fabric filter
OX
Ib/hr
5.49
380
202
4.0
8.1
TDF
lb/
MMBtu
0.021
1.41
0.78
0.015
0.029
5X
Ib/hr
3.55
454
144
3.6
7.2
TDF
lb/
MMBtu
0.015
1.80
0.58
0.014
0.029
10X
Ib/hr
2.61
430
90
3.3
7.7
TDF
lb/
MMBtu
0.009
t.53
0.30
0.012
0.027
6-11
-------
Table 6-6.
Summary of Emissions from a Wood-fired
Utility Boiler Cofiring TDF
Northern States Power Co.9
French Island, WI
November, 1982
Pollutant
Particulars
»i
MO,
CO
Aldehydes
Benzene
Phenols
PolyaroMtic
hydrocarbons
100X Wood-Wast* 9% lubber Buffing* 7X
ppi (dry) Ib/tWBtu ppa (dry)
0.083
7 0.020
90 0.19
2300 • 2700
66.6 • H
18
61
150
Ib/IMBtu ppi (dry)
0.25'
50
48
2200
12
25
U
170
TDF
Ib/HMBtu
0.31'
0.074
0.125
-
-
•
-
-
Exceeds Wisconsin liait of 0.15 Ib/MtBtu
6-12
-------
U>
5
.50
-40
c -30
g
tn
E .20
UJ
o>
| .10
o
t
cd ft_
Q. .05
.52
O
x
0%
X
X
(Wisconsin Power ft Ughfl
.1772
.008
2%
5% 7% 10%
%TDFInFuel
15%
-A
i_
20%
100%
Ohio Edison
....-A--
Unlted Power Assoc. Illinois Power Wisconsin Power & Light
Modesto Energy Project
(100% Tires)
Figure 6-1. Particulate emissions while burning TDF or whole tires at
coal-fired electric utilities.
Not*: On day * (15X TOF) Ohio Edison experienced tire feed supply problem that resulted In several Interruptions of tlr* supply to the
boiler.
-------
particulate emission rates for these four companies by TDF
level. The fifth company, Northern States Power, had
significant operational problems with their particulate
control device during their test.9 Their particulate data
are not included in Figure 6-1 for this reason, and also
because the boilers primary fuel is wood waste, not coal.9
Wisconsin Power and Light reported that, when burning
certain high-sulfur coals, opacity from their ESP's
increased by about 1.5 percent for each 1 percent
incremental increase in the TDF blend rate.18
Ohio Edison reported that the higher emission rates at lower
tire feed rates may be related to the non-uniform Btu supply
associated with slower whole tire feed rates. To achieve a
5 percent TDF rate, on a Btu basis, whole tires were added
one per 34 seconds. Tires were added every 8.5 seconds to
result in a 20 percent TDF input. As Btu supply from tires
approached a uniform and fairly constant feed rate during
their tests, operating conditions appeared to stabilize and
emission rates to decline. On day 4 of the test (15
percent), for example, tire feed problems caused interrupted
tire supply, and the report states that data from that day
support the view that uniform tire feed results in lowered
emissions.12
6.3.2 SO.. Emissions
As shown in Figure 6-2, S02 emission results showed variable
emission rates over different TDF levels at different
facilities. Variations in the sulfur level of the primary
coal fuel could account for some of these inconsistent
results.
6-14
-------
Ot
1
en
S
5
w
c
o
tn
ut
CM
CO
b
5
4
3
2
1
0
C
A -A "
.. 8-73 • 571 A- *
A— • Q (innote Power) 547 ^ (Onto Edison)
6.30 5:28 B84
-
-
-
1.80
Ml " 16S
_ B (UnHed Power A*aodakon)
0— . . xr
. '-14 ~ O (WbeonshPow«r4UghO -_ •
(100% Tires)
Figure 6-2. SO2 emissions while burning TDF or tires at coal-fired
electric utilities.
Not*: On day ^ (1SX TDF) Ohio Edison experienced tire feed supply problems that resulted In several interruption* of tire supply to the
boiler.
-------
6.3.3 NO Emissions
Two tests showed decreased NOX emissions, and one, WP&L
showed increased NOX emissions. Figure 6-3 graphs these
emission data. The levels emitted at WP&L were still only
60 percent of the facilities' emission limit.18 WP&L
personnel theorize that the emissions increase is due to
higher flame temperatures in the cyclone caused by the TDF
and a subsequent increase in thermal nitrogen oxide
formation.18 Cyclone boilers tend to have high NOX
emissions because of high flame temperature, relative to
other boiler configurations, even when burning coal.
6.3.4 CO Emissions
Data from WP&L were the only information to compare CO
emission rates over varied TDF levels. WP&L found that CO
increased, indicating that additional excess air may be
required when utilizing TDF, but levels were still less than
50 percent of the permitted level.18
6.3.5 Trace Metal Emissions
WP&L provides the only data showing trace metal concen-
trations in flue gas. Changes in trace metal emissions
during testing at WP&L were reported to be small and
statistically insignificant.18 Figure 6-4 shows trace metal
emission rate comparisons for WP&L. Figure 6-5 shows change
in rate for trace metals at WP&L.
6.3.6 Other Air Emissions Information
Ohio Edison reported emissions of lead during their test;
lead remained relatively constant throughout the tests from
0 percent to 20 percent TDF.12 WP&L reported that HC1 and
6-16
-------
l.U
B .75
CD
5
2
25
m~ •*
tn
g 0.5
w
'c
u]
X
i -2s
Ok
1
M
0
1
.01
.Q (Wisconsin Power ft UghQ
.70 ^
-S'7'
.76 •-.......
_» ' •-.. .58
.601 '"• -....
""*"""•••--. ""**••-
^ -•:->-v-.t
"\" A
""-•-..... .436
'''-•...
V~
-• A-...
443 A (OMoEdtoon)
.387
• (UnkedPowscAssoo.)
.30
1 1 1 1
D% 2% 5% 7% 10%
% TDF In Fuel (a)
Ohio Edison United Power Assoc. Wlnsconsln Power & Light
A • -
-------
Ot
I
M
00
| CoalATire Blend
0.01
0.008
0.006
0.004 --
0.002--
Figure 6-4. Trace metal emission rates when burning waste tires
compared to coal.18
Note: Tick mark indicates average emission rate; bar shows +/-2 standard deviation
range in data. Bars are truncated at zero.
-------
20
10
a
o
1
E
-20 L
02
O.I
-0.1
0.2
0.004
I
Emission Increase
«. I
I
Emission Decrease
0.002
-0.002 -
-0.004 L
E E E
339
.5 'fa "0
3 -a
CQ
U
c -a E ^
§ g .2 5
E C E °
•& ** o *~)
u
o
U
E "5
3 •*
C (M
U *-v
•o *-•
S t
s
.2
c
i
"aJ
E E
.2 .2
c -a
Figure 6-5. Trace metal emission rate changes when burning
waste tires compared to coal. a
Note: Positive change indicates an emission increase when burning tires blended with
coal as compared to coal only. Tick mark (»•) indicates average measured
change; bar shows +/~2 standard deviation range in data. Tick mark (•«)
indicates estimated emission change based on fuel analyses.
-------
HF emissions were reduced.18 Reasons for this reduction
were unknown.18 WP&L reported that dioxin and furan
emission rates were small, and the change over baseline in
all cases was statistically insignificant.9 Figure 6-6
graphs emission rates of several dioxin and furan compounds
at WP&L and Figure 6-7 graphs the change in emission rate
for dioxin and furan compounds. Polycyclic organic matter
and PCB's were measured at WP&L, but were not detected
during any test runs.18
6.3.7 Control Equipment Issues
Weekend shutdown maintenance at WP&L has shown some unusual
deposits on the ESP plates and wires, but the deposits are
soft and easily removed.18
United Power Association experienced good fabric filter
operation when burning up to 10 percent TDF. However, when
the facility tested TDF levels up to 65 percent, operation
of the fabric filter was of primary concern. The ash from
the rubber was significantly more difficult to cleanoff the
bags than the coal ash. The resultant ash build up on the
bags caused an increased pressure drop across the system
from 3" to 6". Personnel operated the cleaning cycle
continuously, and operated both reverse air fans for the
duration of the test, which improved the situation.17
The Northern States Power facility experienced significant
operational problems with their electrolysed pebble bed
scrubber during tests burning from 7 to 9 percent TDF (mixed
with woodwaste) in a retrofitted fluidized combustion bed
boiler. The electrostatic voltage dropped to near zero on
several occasions; on others, the collection efficiency
declined continually. Several reasons for this are
suggested. First, the ash during the test was more cohesive
6-20
-------
I
M
i.uxiu •
8A« 1 A-8
.0x10
1
£>
~* £ A 1 A-8
£ 6.0x10
^^
2 ;
a
o -
"?2 A A— fl A-O
$ 4.0x10
w ;
2A» 1 A-8
.0x10
_ *&
u,
8
H
oo
'•^
^i
1:-'
• • !;
i i
Q £ C
Q g c
(— t ^
f^f\
K 3 "
rf H i
k.
1
%
>
i
3 U
3
C ••
I ;
i
~|:::|
<«
L,
J
^L,
r«
L!
|
•H
c
t
t
t
%
11
^
>
J
i!l-
1 1
1 § (
^
3
0
-4
«^ ]^
Ii
i i
3 Q 8
n Q c
J U^i
5 H g
^
oo *s
K§-
f"lU
«s
2
o
l.OxlO6
8.0x10
6.0x10
7
7
4.0x10
2.0x10'-
| Coal/Tire Blend
Coal Only
—
J <
{
-^ •<-
' "i
Tetrachloro-
dibenzo Dioxins
Tetrachloro-
dibenzo Furans
I,
Total PeCDD
1
Total HxCDF
Figure 6-6. Dioxin and furan emission rates when burning waste tires
compared to coal.18
Note: Tick mark indicates average emission rate; bar shows +/-2 standard deviation
range in data. Bars are truncated at zero.
-------
1.0x10
5.0x10
oT
0*
,2
g
-5.0x10
1 .
1 •
i.uxiu"-
Emission Increase
1
1
5/\_. * ]r\-7
.UXll)
_|_
-J.UXIU
Emission Decrease
1 1
I 1
-i.uxiu -
ft s S g S g 6 g §| || gg Q g
yfiyuyySU <->3 IS -Is fl 8
*"" " oi 2 £-0.0 OH" 35 -git U _«
K•) indicates average change; bar
show +/-2 standard deviation range in data.
-------
than the ash generated from waste wood alone. This ash
hindered the flow of the scrubber media and increased
microbridging in the annulus, allowing more unscrubbed
particulate matter to penetrate the scrubber. Further, the
ash burden to the scrubber was 50 percent higher than
normal, overloading the scrubber. Last, the high carbon
content of the ash, together with the high ash loading,
caused the electrostatic grid current to rise to a point
that the scrubber control circuit dropped the grid voltage.9
6.4 OTHER ENVIRONMENTAL AND ENERGY IMPACTS
Slag leachate tests performed at WF&L showed no changes as a
result of burning TDF.18 Table 6-7 shows a summary of
results of metals analysis on the slag at WP&L.
6.5 COST CONSIDERATIONS
One company, WP&L, purchases TDF at a cost of $20 to $30 per
ton delivered. On an energy basis, this is $0.67 to $1.00
per MMBtu.22 The State of Wisconsin has an incentive
program that reimburses WP&L for disposing of scrap tires
originating in Wisconsin. The reimbursement rate is $0.20
per tire, or about $20 per ton, based on an average tire
weight of 20 pounds per tire. With this incentive, the cost
of TDF to WP&L is between zero and $0.33/MMBtu. The cost of
coal, delivered, to WP&L ranges from $1.80 and
$2.00/MMBtu.22
6.6 CONCLUSIONS
Based on the experience and the emissions data from power
plants burning tire or TDF, the use of tires and TDF as
supplemental fuel is viable. In many cases, the quality of
the emissions actually improves with increased use of tires
or TDF as supplemental fuel.
6-23
-------
Table 6-7. Comparison of the Heavy Metal Content
of Slag at Baseline and 5% TDF at
Wisconsin Power And Light18
Trace Metal
Arsenic
Barium
Boron
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Mercury
Nickel
Selenium
Silver
Sulfate
Zinc
Total Dissolved Solids
100% Coal,
ng/1
0.004
<0.01"
<0.1
<0.01
4.78
<0.02
<0.02
<0.02
0.004
<0.002
<0.02
<0.002
<0.01
<5
<0.01
28
5% TDF,
ag/1
<0.002
0.01
<0.1
<0.0002
2.89
0.0004
<0.02
0.06
<0.003
0.0002
<0.02
<0.002
<0.01
<5
0.02
40
Change,
%
>-50
DL'
DL'
DL'
-40
DL'
DL'
>200
>25
DL*
DL'
DL1
DL'
DL'
>100
+43
• Below detection limit (DL).
6-24
-------
Because electric utilities use so much primary fuel, they
obtain the best prices for the fuel and transportation. As
a result, the differential savings, per million Btu's, are
less than other industries. On the other hand, the benefits
of using tires or TDF on creating stable operating
conditions in the boiler may be more important than the
differential cost savings for the overall profitability.
6-25
-------
r r
6.7 REFERENCES
1. Telecon. C. Clark, Pacific Environmental Services,
Inc., (PES), with Stopek, D., Illinois Power Co. Marc*
7, 1991. TDF use at Illinois Power
2. Telecon. C. Clark, PES, with McGowin, C., Electric
Power Research Institute. February 15, 1991. TDF
experience at utility oilers.
3. Telecon. D. Russell, PES, with Purseglove, P.,
Illinois EPA. February 14, 1991. TDF experience of
Illinois facilities.
4. Burns & McDonnell. Tire-Derived-Fuel Emissions Test
Report for Illinois Power Co. at their Baldwin Station
Unit 1. March 1991.
5. Stopek, D.J., A.K. Millis, J.A. Stumbaugh, and D.J.
Diewald. Testing of Tire-Derived Fuel at a 560 MW
Cyclone Boiler. Presented at the EPRI Conference:
Waste Tires as a Utility Fuel. San Jose, CA. January
28, 1991.
6. Telecon. D. Russell, PES, with Gulash, T., Manitowoc
Public Utility. February 25, 1991. Experience with
TDF at Manitowoc.
7. Phalen, J., A.S. Libal, and T. Taylor. Manitowoc
Coal/Tire Chip-Cofired Circulating Fluidized Bed
Combustion Project. Presented at EPRI Conference:
Waste Fuels in Utility Boilers. San Jose, CA. January
28, 1991.
8. Howe, W.C. Fluidized Bed Combustion Experience with
Waste Tires and Other Alternate Fuels. Presented at
EPRI Conference: Waste Tires as A Utility Fuel. San
Jose, CA. January 28, 1991.
9. Northern States Power Co. Alternative Fuel Firing in
Atmosphere Fluidized-Bed Combustion Boiler. EPRI CS-
4023. Final Report. June 1985.
10. Telecon. C. Clark, PES, with Justice, A., Illinois
Department of Energy and Natural Resources. February
14, 1991. Tire recovery program at Illinois.
11. Telecon. D. Russell, PES, with Horvaf, M., Ohio
Edison. February 26, 1991. Experience with tires-for-
fuel.
6-26
-------
12. Horvath, M. Whole Tire and Coal CoFiring Test in a
Pulverized Coal-Fired Boiler. Presented at EPRI
Conference: Waste Fuels in Utility Boilers. San Jose,
CA. January 28, 1991.
13. Memorandum from Clark, C., PES, to Michelitsch, D.,
EPA/ESD/CTC. Summary of Meeting with Scrap Tire
Management Council. October 29, 1991.
14. Telecon. D. Russell, PES, with Rolfes, M., Otter Tail
Power. February 25, 1991. TDF experience.
15. Ohio Air Quality Development Authority. Air Emissions
Associated with the Combustion of Scrap Tires for
Energy Recovery. Prepared by: Malcolm Pirnie, Inc.
May 1991.
16. Gaglia, N., R. Lundguist, R. Benfield, and J. Fair.
Design of a 470,000 Ib/hr Coal/Tire-Fired Circulating
Fluidized Bed Boiler for United Development Group.
Presented at EPRI Conference: Waste Fuels in Utility
Boilers. San Jose, CA. January 28, 1991.
17. O'Brien, M.V., and W.C. Hanson, United Power
Association, Elk River, MN. Shredded Tires for
Electric Generation. Presented at APCA. Atlanta, GA.
June 19-24, 1983.
18. Wisconsin Power and Light Company. The Operational and
Environmental Feasibility of Utilizing Waste Tires as a
Supplemental Fuel in a Coal-Fired Utility Boiler.
Preliminary Report. State of Wisconsin, 1990. Waste
Tire Management and Recovery Program.
19. Telecon. C. Clark, PES, with Eirschele, G., Wisconsin
Power and Light. February 20, 1991. TDF experience.
20. Hutchinson, W., G. Eirschele, and R. Newell.
Experience with Tire-Derived Fuel in a Cyclone-Fired
Utility Boiler. Presented at EPRI Conference: Waste
Fuels in Utility Boilers. San Jose, CA. January 28,
1991.
21. Schreurs, S.T. Tire-Derived Fuel and Lignite Co-Firing
Test in a Cyclone-Fired Utility Boiler. Presented at
EPRI Conference: Waste Fuels in Utility Boilers. San
Jose, CA. January 28, 1991.
22. Memorandum from Russell, D., PES, to Michelitsch, D.,
EPA/ESD/CTC. November 8, 1991. Site Visit —
Wisconsin Power and Light Company.
6-27
-------
f
r
7. USE OF TDF AS A SUPPLEMENTAL FUEL AT OTHER
INDUSTRIAL FACILITIES
Several coal-fired boilers at industrial manufacturing
facilities have reported using TDF as a supplemental fuel on
a commercial or test basis. Further, TDF has been
considered as a secondary fuel at several boilers firing
biomass or refuse-derived fuel (RDF). This chapter
summarizes information obtained on some of these facilities.
Note that data from a boiler burning TDF at a silicon
manufacturing facility, Dow Corning in Midland, Michigan,
are reported in Chapter 5 with waste wood boilers, because
the primary fuel for this boiler is wood chips. Further,
data on TDF use at Boise Cascade, an "other" manufacturing
facility, are included in Chapter 4 with cement
manufacturing, because the rotary kiln used to manufacture
lime is similar to the rotary cement kilns.
7.1 DESCRIPTION OF INDUSTRIES
As of the Summer of 1991, at least eight industrial
facilities have used TDF commercially or have tested TDF.
These facilities are listed in Table 7-1. Only one,
Firestone Tire Manufacturing in Decatur, IL, is known to be
using TDF currently on an on-going basis.2 Two, Hannah
Nickel in Oregon, and Firestone Tire Manufacturing in Des
Moines, Iowa, are no longer burning tires. Hannah Nickel
closed, and, although it has reopened under new ownership,
the facility has no plans to burn tires.3 The boiler at
Firestone in Iowa was shut down, because it could not meet
particulate limits burning the very large agricultural tires
manufactured at the plant.2
At Les Schwab Tires in Oregon, the small package steam
generator uses 25 tires per hour. It has been in operation
7-1
-------
Table 7-1. Other Industrial Boilers with TDF Experience
COMPANY AND LOCATION
TDF USE
AIR EMISSIONS TEST DATA
•OILER(S) DESCRIPTION
COMMENTS/REFEREHCES
Archer Daniel* Midland
Decatur, IL
Caterpillar Tractor
IL
Firestone Tire
D«« Molnee, IA
FlrMton* Tire
Oecetur, IL
Current; long-tens test
basis; (natal I Ing th«lr own
shredder on-slte
I
kJ
Hannah Nickel
OR
Past; could burn 100 tpd;
20,000 Ib/hr; 500,000
tlraa/hr; burned large
agrle. tlraa I other uaata.
Currant; can burn 100 tpd;
22,000 Ib/hr; 500,000
tlraa/yr; passenger tlras;
burns 251 by Might
passenger tires * other
rubber acraps; rest Is wood,
paper, also.; 80X of Itu
COOKS from tires.
Past
Lea Schwab Tires
Prlnevllle, Ot
Monsanto Conpany
Sauget, IL
Current; 25 whole tlrea par
hour; both passenger and
light truck tires
Test bests; 20% TDF, wire-
In, 2" x 2-
Test burning may occur In
April 1991; IL EPA granted
Company a long tarn penalt;
doing testing and tire-burning
on their own;
ir 1991
Test planned for
Exceeded opacity Halt; needed
febrlc filter, but decided not
econ. feasible.
Neesurea part(cutatea, CO and
COj only; opacity
Unknown
Unknown
Yes; test 12X90 boiler M;
tested PM, SO,, HO,, CO, M,
NCI, total organ!cs, Betels,
dloxln; TDF blended with coal.
Spreader stoker boiler
sMklng process eteaa)
1983 pulsating floor
furnace.
1984 puteat Ing floor
furnace; hydraulic re*
pushes weste from charging
hopper Into prle*ry coab.
charter with etepped
hearth; water cooled wall*
In chatter; pulses of air
•hake the fuel charge and
•owe It down hearth;
typical run I* 7 to 17
day*.
At on* tlM. burned tire*
for 2-3 year* In nickel
calclnera.
Saul I steaai generator
Spreader stoker Traveling
grate boiler; ESP
controlled
6reln processing plant.
Reference 1
Reference 1
Shut down 1987 for
exceeding opacity Halt.
Reference 2
Penal t Halt* riuaber of
operating hour*; can
burn 100X tire*.
References 2 and 3
Primary nickel plant
producing nickel swtal;
abandoned tire burning
and closed plant; new
owner ha* opened plant,
but ha* no plans to burn
tire*. Reference 4
Retreader. Reference 2
Chaalcal* plant.
References J and 6
-------
Table 7-1. (Concluded)
COMPANY AND LOCATION
TDF USE
AIR EMISSIONS TEST DATA
BOILER(S) DESCRIPTION
COMMENTS/REFERENCES
Saglnaw Division, CMC
Saglnaw, Michigan
Test basis; SX TDf
YM; tested bolter §6 In 11/83
for PH. SO]. NO,. at 0 end 10X
TDF; tested *2 In 3/08 for PM,
SO,, SO,. NO,, et 0 end SX TDF;
tested n In 1/89 for PM at 0,
10. 15. end 20X TDF.
tZ spreader stoker
traveling grate. SO,000
Ib/hr; controlled by
•ultlclone.
Steering and gear
facility. References 7.
8. and 9
I
tJ
Hornets »nd RefuM-Perjyed fuel FicMltUi
Akron Recycle Energy
SystM
Akron. OH
RDF plant(s),
NMM unknown
SC
Refuse-derIved-fuel
poyer plant
Nane unknown
OH
• loataes burner
Name unknotn
M£
Unknown
Unknown
Ves; perforaed 24 br test to
get penaltted; CEMS
•wasureaMnts only; on 3rd
shift exceedances occurred,
and no pemlt approved.
Company wants to try again.
Has capability to burn tires Unknown
Refuse-derived-fuel
power plant.
Reference 10
Problea* In State In
past burning TDF In REF
boilers; none occurring
now. Reference 11
Refuse-derived-fuel
power plant.
Reference 10
Currently being
paneltted by Maine DEP.
Reference 12
-------
since 1987 with moderate success. Whole tires are
automatically fed into the unit, which burns tires at 2000'F
and produces 100 psig process steam.2
Four facilities are currently testing tires, as shown in
Table 7-1. Three are testing on an occasional basis, but
Archer Daniels Midland (ADM), a grain processing plant in
Decatur, Illinois, has been granted a long-term test permit
by the Ohio EPA.1 Little information was gathered regarding
boiler configuration or pollution control devices in use at
these facilities.
Four plants are reported to have considered burning TDF
supplementally in boilers with a primary fuel of biomass or
refuse-derived fuel. These plants are listed in Table 7-1.
Two RDF fired power plants are attempting to obtain permits
to burn tires.10 One biomass burner in Maine is reportedly
in the permit process, and has been designed with the
capability of burning tires.12 Personnel at the State Air
Pollution Agency in South Carolina indicated that several
municipalities had tried, unsuccessfully, in the past to
burn TDF in their RDF incinerators.11 No information was
obtained on boiler configuration or air pollution control
equipment.
7.2 PROCESS DESCRIPTION
Descriptive information of equipment or process flow was
obtained for only one facility. The Firestone Tire
Manufacturing facility in Decatur, Illinois, operates a
pulsating floor boiler. A hydraulic ram stokes the chamber,
which has a stepped grate. Pulses of air shake the fuel
charge, and move it down the hearth.2 The boiler burns
tires and other waste on a batch basis; a typical run lasts
from 7 to 17 days.2
7-4
-------
7.3 EMISSIONS, CONTROL TECHNIQUES AND THEIR EFFECTIVENESS
Emission test data were evaluated for two facilities:
Monsanto Company in Sauget, Illinois, and Saginav Steering
and Gear, in Saginav, Michigan. Figure 7-1 summarizes
percent change in particulate, SO2, and NOX emissions at
these two facilities.
Test results for Monsanto are summarized in Table 7-2.
Testing in 1990 measured criteria pollutants, HC1 and HF
while burning 100 percent coal, and while burning coal and
20 percent TDF. Emissions of all pollutants decreased,
except CO and S02. The increase in CO does not appear
significant given the negligible emission rate of CO in both
tests.5
Three sets of tests have occurred at Saginaw Steering and
Gear. The first, in 1983, measured particulate, SO2 and
NOX, in Boiler #6.7 All three pollutants increased at 10
percent TDF compared to baseline.7 In 1988, boiler 12 was
tested for particulate, SO2, S03, at baseline and 5 percent
TDF. Particulate, S03, and NOX increased, while S02
decreased.9 In 1989, particulate emissions from boiler 12
were tested given this time at four TDF levels: 0, 10, 15,
and 20 percent.8 Particulate emissions rose throughout the
series.8 Table 7-3 summarizes all these data.
7.4 OTHER ENVIRONMENTAL AND ENERGY IMPACTS
No information on other environmental and energy issues was
obtained for these sources.
7.5 COST CONSIDERATIONS
No information on cost considerations was obtained for these
sources.
7-5
-------
-50
-0 +
+ 50
+ 100
+ 150
+200
(Snglnaw f 2, 5% TDF)
+ 15
Monsanta
20%TDF
Saglnaw #6
10%TDF
Saginaw #2
5%TDF
Saglnaw #2
10%TDF
Saglnaw #2
15%TDF
Saglnaw #2
20%TDF
Figure 7-1. Summary of percent change in SO,, NOK, and particulate
emiasions at Monsanto Chemicals and Saginaw Gear'-7'8'9
-------
Table 7-2. Summary of Emissions at Monsanto
Sauget, IL5
December 18-19, 1990
Particulate
CO
VOC
S02
NO,
HC1
HF
Metals
Dioxin
100% Coal
Ib/hr
3.60
0.38
1.04
83.0
34.7
13.5
0.93
Test
80% Coal,
20% TDF %
Ib/hr
1.79
0.53
0.73
109.0
24.3
9.59
0.84
Data Not Available
Change
-50
+40
-30
+31
-30
-29
-10
Yet
Table 7-3. Summary of Air Emissions Test Data While Burning
TDF at Saginaw Steering and Gear7'8-9-*
Saginaw, MI
Date
Moveotoer
2-3, 1983
March 22-
24, 1988
January
23-26,
1989
ftoiltr Pollutant
Mo.
6 Particulate
SO:
"Pi
2 Particulate
SOj
5°:
"0,
2 Particulate
MMllne
1001 Coal
Ib/hr
28.34
106.75
81.98
6.93
(0.2656
Ib/MHBtu)
34.7
6.11
4.06
4.42
5X TDF
Ib/hr
7.02
(0.2628
Ib/MMBtu)
40.2
2.35
8.59
1« TDF
Ib/hr
76.99
161.34
84.42
5.09
15X TDF 20X TDF
Ib/hr Ib/hr
11.40 11.72
* TDF burned supplementally with coal.
7-7
-------
7.6 CONCLUSIONS
The results of burning TDF as supplemental fuel at other
industrial facilities are inconsistent and incomplete.
Because of this, no conclusions can be made as to the
effects of burning TDF in other industrial facilities.
7-8
-------
r
r
7.7 REFERENCES
1. Telecon. Clark, C., Pacific Environmental Services,
Inc. (PES), with Justice, A., Illinois Department of
Energy and Natural Resources. February 19, 1991.
Illinois TOF testing plans.
2. U.S. Environmental Protection Agency. Markets for
Scrap Tires. EPA/530-SW-90-074B. September 1991.
3. Ohio Air Quality Development Authority. Air Emissions
Associated with the Combustion of Scrap Tires for
Energy Recovery. Prepared by: Malcolm Pirnie, Inc.
May 1991.
4. Telecon. Clark, C., PES, with Fuller, B., Oregon
Department of Air. February 28, 1991. Oregon TDF
experience.
5. The Almega Corporation. Boiler Emissions and
Efficiency Testing TDF/Coal Mixed Fuel Project.
Prepared for Monsanto Company, Sauget, IL. December 18
and 19, 1990.
6. Telecon. Russell, D., PES, with Purseglove, P.,
Illinois EPA. February 14,1991. TDF experience in
Illinois.
7. A.H. Environment, Inc. Report to Saginaw Steering and
Gear, CMC. Boiler #6. .November 2, 3, 1983.
8. Affiliated Environmental Services, Inc. Report to
Saginaw Div/GMC on Stack Particulate Samples Collected
on Boiler |2 At General Motors Steering Gear, Saginaw,
MI. February 10, 1990.
9. Swanson Environmental, Inc. Air Emission Study Plant £2
Powerhouse, Boilers #1 and #2. Prepared for Saginaw
Division, CMC, Saginaw, Michigan. March 22-24, 1988.
10. Telecon. Clark, C., PES, with Hilkins, T., Ohio EPA,
Air Division. February 28, 1991. TDF Use in Ohio.
11. Telecon. D. Russell, PES, with L. Bunn, South Carolina
Department of Health and Environmental Control.
February 14, 1991. TDF experience in SC.
12. Telecon. D. Russell, PES, with L. Hamjian, U.S.
Environmental Protection Agency. Region I. February
15, 1991. Facilities burning TDF in Region I.
7-9
-------
r
r
8. 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
•hells, 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.'
8-1
-------
r
r
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
This 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
8-2
-------
Table 8-1. Approximate Product Distribution
as a Function of Pyrolysis Reactor
Temperature for Reductive Process
Category3
Reactor Temp,
CF)
Gas, %
Oil, %
Char, %
500 (932)
600 (1112)
700 (1292)
800 (1472)
6
10
15
31
42
50
47
40
52
40
38
29
8-3
-------
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 nost 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
8-4
-------
Figure 8-1. Generic Pyrolysis Process
8-5
-------
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
8-6
-------
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 MMBtu'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
8-7
-------
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, the steam injection process requires
an external source of heat to produce the steam.
8-8
-------
Table 8-2. Manufacturers of Pyrolysis Units and Operating Conditions
Proc«M NMM
OXIPATIVEt
Qulnlyn
Nippon Zeon
Sumotooo
Toico
REDUCTIVE;
K<*»
09 KW
\O H*rko/Kltn«r
ERRG
C«rb Oil C CM
Nippon 0 ft F
lnt«n Company
rutrltb
Carb-OII
YokohMW
OruihMM
Tyrolytlt
••rpbau
ORP
Cipaclty
tpd
120
26. 5
S
15
26.5
B. 6
230
5
60
27
100
6
112
8.2
30
165
1.3
25
•tactlon
Te«pf 'C
600
449-500
704
510
500
677
600
871
600
500
496
427
1010
500
400
534
923
722
Oil, X
62
56
54.7
52
41
22
47
M
45
49
52
35
43
53
21
45
5
27
Vlttcte •• • ptrcwrt of
Char, X
16
31
31.7
29
33
47
30
30
33
36
35
38
34
33
20
39
35
39
TlrM
CM, X
11
3
9.5
11
7
17
17
28
13
10
7
20
18
n/«
51
0
20
12
Iron, X
0
10
4.1
4
S
10
6
4
9
5
4
5
6
n/»
7
16
10
0
-------
The reductive process is the more traditional process for
tire pyrolysis. This process excludes all sources of oxygei
and relies on the reactor heat alone to decompose the tires
Some processors pressurize the reactor with an inert gas
•uch as nitrogen to prevent air from leaking into the
reactor, while some inject hydrogen to react with the sulfuj
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
• screw 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
8-10
-------
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
The 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.
8-11
-------
f r
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
•nd 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.
8-12
-------
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 Ibs per
MMBtu.1
8-13
-------
r
r
Table 8-3. Emission Estimates from Pyrolysis Facilj
Conrad Industries1 •'
"articulate
•laaam Metals
Altai HUB
Chromium
Iron
Magnesium
Manganese
Mercury
•Icxel
Potassium
Sodium
Zinc
Semi-Volatile Organic Compounds
•is-<2-ethy-
hexyDphthalate
•utyl ienxyl-
phthalate
Dt-n-butyl-
phthelate
Naphthalene
Phenol
Volatile Organic Compounds
tenzene
Ethyl benzene
Toluene
Xylenes
Sulfur Dioxide
Nitrogen Oxides
Concentration
(M/aT)
2.500
1.31
0.82
9.89
0.45
0.09
0.05
2.95
1.84
18.62
0.65
10.2
1.7
0.9
2.87
1.4
20.2
24.1
30.8
16.2
310,500
210,000
Eaiuion «»ttb
(Iba per IWBtu)
1 x 10'*
6.7 x 10"8
3.7 x 10'8
43.9 x 10"8
2.0 x 10~8
0.4 x 10"8
0.2 x 10'8
13.1 x 10"8
8.2 x 10'8
82.7 x 10"8
2.9 x 10'8
45.3 x 10"8
7.5 x 10'8
4.0 x 10"8
12.7 x 10'8
6.2 x 10"8
c
c
c
c
7.7 x 10"2
9.7 x 10"3
* These earisaion eatiavtea reflect the coMpoaition of the pyro*gaa, Uiich ia either burned in tl
process as fuel or (for the excess pyro-gas) vented to the facility's flare. These estimates
not reflect atmospheric emissions.
These emission rates were calculated by taking the average concentrations reported for the
conpound and Multiplying it by the average flow rate for the test runs. An energy input value
of 31 MHBtu was used to calculate Ibs/MMBtu.
c Flow rates were not reported. Thus, pounds of emissions per hour could not be calculated.
8-14
-------
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
EM,,, emissions. Operations such as screening, grinding, and
processing cause Pit,,, 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 (Ibs/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.
8-15
-------
the most economical plant size is 100 tons per day (2000
tires per day) .* This size would make the plant roughly
equal to one hundredth the size of the model refinery listed
in AP-42.6 Table 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.* 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.
8-16
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Table 8-4. Chromatographic Analysis of Pyrolytic
Gas from Shredded Automobile
Tires with Bead Wire In2
Constituent
Volume Percent
Hydrogen
Methane
Ethane
Propane
Propylene
Isobutylene
Isobutane
Butane
Butene-1
trans-Butene-2
iso-butene-2
Pentane
1,3-Butadiene
47.83
29.62
18.52
5.70
8.82
0.73
0.34
0.23
0.14
0.07
trace
ND*
NO1
ND
not detected
8-17
-------
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.
8-18
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Table 8-6. . Estimated fugitive VOC emissions from
a "generic" pyrolysis plant6-'
Fugitive
Emissions
Source
Pipe Flanges
Valves
Pump Seals
Compressors
Pressure Re-
lief Valves
Open Drains
TOTAL
No. of
Sources in
Process
47
12
4
1
1
7
VOC
kg/day
2.72
30.84
5.90
5.00
2.27
4.54
51.27
Emissions
Ib/day
6
68
13
11
5
10
113
Based on one hundredth the size of the refinery (value x
0.01).
8-19
-------
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
•crap 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
8-20
-------
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 Scrap Tires: A Resource and
Technology Evaluation of Tire Pyrolvsis 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
shoved 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
8-21
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Table 8-7. Tire Acquisition.Prices and Selling
Prices of Products Required to Produce a
20 Percent Retum-on-equity for Five Tire
Pyrolysis Units2
(dollars)
Material
Tipping fee*
Oilb
Char*
Steel*
ERRG
0.75
8.13
0.10
121
Foster-
Wheeler
0.04
0.60
0.06
13.
Garb
Oil
0.16
0.77
0.07
35
Kobe
1.03
8.15
0.33
68
KutrJ
0.1
0.7
0.0
39
• Tipping fee, credit received for tire disposal,$/tire
6 Selling price of pyrolytic oil, $/gallon
c Selling price of char, $/pound
d Selling price of scrap steel, $/ton
8-22
-------
required to produce a 20 percent Retum-on-Eguity (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 Bade 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
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r r
higher value products (such as benzene and toluene) can be
Bade.
8-24
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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. D.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 Scrap Tires U.S.
Department of Interior, Bureau of Mines. Report No.
7302. April 1973.
5. Foster Wheeler Power Products, Ltd. Corporate Report;
Tyrolysis—Tvre Pvrolvsis Plant.
6. U.S. Environmental Protection Agency. Compilation of
Air Pollutant Emission Factors. Fourth Edition, AP-42,
p. 9.1-13.
8-25
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r
r
APPENDIX A
STATE CONTACTS FOR WASTE
TIRE PROGRAMS
(Reprinted from U.S. Environmental Protection Agency,
Markets for Scrap Tir0?, EPA-530-SW-90-074B,
September 1991)
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ALABAMA
Jack Honeycut
Alabama Department of Environmental Management
Solid Waste Section
1751 Congressman W.L. Dickinson Drive
Montgomery, Alabama 36130
Telephone: 205-271-7761
ALASKA
Glen Miller
Alaska Department of Environmental Conservation
P.O. Box O
Juneau, Alaska 99811-1800
Telephone: 907-465-2671
ARIZONA
Barry Abbott
Ari2ona Department of Environmental Quality
Office of Solid Waste Programs
2005 North Central
Phoenix, Arizona 85004
Telephone: 602-257-2176
ARKANSAS
Tom Boston
Arkansas Department of Pollution Control and Ecology
Solid Waste Division
P.O. Box 9583
Little Rock, Arkansas 72209
Telephone: 501-570-2858
CALIFORNIA
Bob Boughton
California Waste Management Board
1020 Ninth Street, Suite 300
Sacramento, California 95814
Telephone: 916-322-2674
A-3
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COLORADO
Pamela Harley
Colorado Department of Health
Hazardous Materials and Waste Management Division
4210 East llth Avenue
Denver, Colorado 80220
Telephone: 303-331-4875
CONNECTICUT
David Nash
Connecticut Department of Environmental Protection
Solid Waste Management Division
165 Capital Avenue
Hartford, Connecticut 06106
Telephone: 203-566-5847
DELAWARE
Richard Folmsbee
Delaware Department of Natural Resources and
Environmental Control
Division of Air and Waste Management
P.O. Box 1401
Dover, Delaware 19903
Telephone: 302-739-3820
DISTRICT OF COLUMBIA
Joe O'Donnel
Recycling Department
2750 South Capitol St. SW
Washington, DC 20032
Telephone: 202-767-8512.
FLORIDA
Bill Parker
Department of Environmental Regulation
Office of Solid Waste - Twin Towers Office Building
2600 Blair Stone Road
Tallahassee, Florida 32399-2400
Telephone: 904-922-6104
A-4
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GEORGIA
Charles Evans
Georgia Department of Natural Resources
Industrial and Hazardous Waste Management Program
3420 Norman Berry Drive • 7th Floor
Hapeville, Georgia 30354
Telephone: 404-656-2836
HAWAII
Al Durg
Department of Health and Environmental Quality
Solid and Hazardous Waste
5 Waterfront Plaza • Suite 250
Honolulu, Hawaii 96813
Telephone: 808-543-8243
IDAHO
Jerome Jankowski
Department of Health and Welfare
Division of Environmental Quality
Hazardous Materials Bureau
1410 North Hilton
Boise, Idaho 83706
Telephone: 208-334-5879
ILLINOIS
Chris Burger
Dept. of Environment and Natural Resources
325 West Adams • Room 300
Springfield, Illinois 62704-1892
Telephone: 217-524-5454
INDIANA
Timothy Holtz
Department of Environmental Management
Solid and Hazardous Waste Management
105 South Meridian Street
Indianapolis, Indiana 46225
Telephone: 317-232-7155
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IOWA
Teresa Hay
Iowa Department of Natural Resources
Waste Management Authority
900 East Grand Avenue
Henry A, Wallace Building
Do Moines, Iowa 50319-0034
Telephone: 515-281-8941
KANSAS
Ashok Sunderraj
Kansas Department of Health and Environment
Bureau of Waste Management
Forbes Field
Topeka, Kansas 66620
Telephone: 913-296-1595
KENTUCKY
Charles Peters
Department of Environmental Protection
Division of Waste Management
18 Reilly Road
Frankfort, Kentucky 40601
Telephone: 502-564-6716
Randy Johann
Kenruckian Regional Planning and Development
11520 Commonwealth Drive
Louisville, Kentucky 40299
Telephone: 502-266-6084
LOUISIANA
Butch Stegall
Louisiana Department of Environmental Quality
Office of Solid and Hazardous Waste
P.O. Box 44066
Baton Rouge, Louisiana 70804-4066
Telephone: 504-342-9445
A-6
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MAINE
General: Cliff Eliason; Enforcement: Terry McCovern
Department of Environmental Protection
Bureau of Solid Waste and Management
State House, Station 17
Augusta, Maine 04333
Telephone: 207-582-8740
Jody Harris
Recycling: Maine Waste Management Agency
Office of Waste Recycling & Reduction
State House Station No. 154
Augusta, Maine 04333
Telephone: 207-289-5300
MARYLAND
Muhamud Masood
Department of the Environment
Hazardous and Solid Waste Management Administration
2500 Broening Highway, Building 40
Baltimore, Maryland 21224
Telephone: 301-631-3315
MASSACHUSETTS
Jim Roberts
Department of Environmental Quality
Division of Solid Waste
1 Winter Street, 4th Floor
Boston, Massachusetts 02108
Telephone: 617-292-5964
MICHIGAN
Kyle Cruse
Department of Natural Resources
Resource Recovery Section
P.O. Box 30241
Lansing, Michigan 48909
Telephone: 517-373-4738
A-7
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MINNESOTA
Tom Newman
Pollution Control Specialist
Minnesota Pollution Control Agency
Waste Tire Management Unit
520 Lafayette Road
St Paul, Minnesota 55155
Telephone: 612-296-7170
MISSISSIPPI
Bill Lee
Department of Environmental Quality
Office of Pollution Control
Division of Solid Waste Management
P.O. Box 10385
Jackson, Mississippi 39209
Telephone: 601-961-5171
MISSOURI
Jim Hull
Department of Natural Resources
Waste Management Program
P.O. Box 176
Jefferson City, Missouri 65102
Telephone: 314-751-3176
MONTANA
Tony Grover
Department of Health and Environmental Sciences
Solid and Hazardous Waste Bureau
Room B-201, Cogswell Building
Helena, Montana 59620
Telephone: 406-444-2821
A-8
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NEBRASKA
Dannie Dearing
Department of Environmental Control
Land Quality Division
P.O. Box 98922
Lincoln, Nebraska 68509-8922
Telephone: 402-471-4210
NEVADA
John West
Division of Environmental Protection
Bureau of Waste Management
123 West Nye Lane - Capitol Complex
Carson City, Nevada 89710
Telephone: 702-687-5872
NEW HAMPSHIRE
William Evans
New Hampshire Department of Environmental Services
Waste Management Division
6 Hazen Drive
Concord, New Hampshire 03301
Telephone: 603-271-3713
NEW JERSEY
Joe Carpenter
Recycling Division
Department of Environmental Protection
Division of Solid Waste Management
850 Bear Tavern Road, CN 414
Trenton, New Jersey 08625-0414
Telephone: 609-530-4001
NEW MEXICO
Marilyn G. Brown
Health and Environmental Department -
Solid and Hazardous Waste Management Program
1190 St Francis Drive
Santa Fe, New Mexico 87503
Telephone: 505-827-2892
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NEW YORK
Ben Pierson
Division of Solid Waste
Department of Environmental Conservation
50 Wolf Road
Albany, New York 12233
Telephone: 518-457-7337
NORTH CAROLINA
Jim Coffey, De« Eggers (technical assistance)
Department of Environment, Health, and Natural Resources
Solid Waste Management Division, Solid Waste Section
P.O. Box 27687
Raleigh, North Carolina 27611-7687
Telephone: 919-733-0692
NORTH DAKOTA
Steve Tillotson
State Department of Health
Division of Waste Management
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OREGON
Deanna Mueller-Crispin
Department of Environmental Quality
Hazardous & Solid Waste Division
811 SW Sixth
Portland, Oregon 97204
Telephone: 503-229-5808
PENNSYLVANIA
JayOrt
Department of Environmental Resources
Bureau of Waste Management
P.O. Box 2063, Fulton Building
Hanisburg, Pennsylvania 17105-2063
Telephone: 717-787-1749
RHODE ISLAND
Victor Bell
Office of Environmental Coordination
83 Park Street
Providence, Rhode Island 02903
Telephone: 401-277-3434
Adam Marks
Central Landfill
65 Shun Pike
Johnson, Rhode Island 02919
Telephone: 401-942-1430
SOUTH CAROLINA
John Ohlandt
Charleston County Health Department
334 Calhoun Street
Charleston, South Carolina 29401
Telephone: 803-724-5970
A-ll
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SOLTTH DAKOTA
Terry Keller
Department of Water and Natural Resources
Office of Solid Waste
Room 222, Foss Building
523 East Capital
Pierre, South Dakota 57501
Telephone: 605-773-3153
TENNESSEE
Frank Victory
Department of Health and Environment
Division of Solid Waste Management
Customs House, 4th Floor
701 Broadway
Nashville, Tennessee 37247-3530
Telephone: 615-741-3424
TEXAS
LD. Hancock
Department of Health
Permits & Registration Division
Division of Solid Waste Management
1100 West 49th Street
Austin, Texas 78756-3199
Telephone: 512-458-7271
Donald O'Connor
Texas State Department of Highways and
Public Transportation
Materials and Testing Division
125 East llth Street
Austin, Texas 78701
Telephone: 512-465-7352
A-12
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UTAH
Dorothy Adams
Salt Lake City County Health Department
Sanitation & Safety Bureau
610 South 200 East
Salt Lake City, Utah 84111
Telephone: 801-534-4526
VERMONT
Eldon Morrison
Agency of Natural Resources
Department of Environmental Conservation
Waste Management Division
103 South Main Street, Laundry Building
Waterbury, Vermont 05676
Telephone: 802-244-7831
VIRGINIA
R. Allan Lassiter, Jr.
Division of Recycling
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WEST VIRGINIA
Paul Benedun
Department of Natural Resources
Division of Waste Management
1456 Hansford Street
Charleston, West Virginia 25301
Telephone: 304-348-6350
WISCONSIN
Paul Koziar
Department of Natural Resources
Bureau of Solid & Hazardous Waste Management
101 South Webster Street
Madison, Wisconsin 53707
Telephone: 608-267-9388
WYOMING
Timothy Link
Department of Environmental Quality
Solid Waste Management Program
122 West 25th Street
Herschler Building, 4th Floor
Cheyenne, Wyoming 82002
Telephone: 307-777-7752
A-14
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TECHNICAL REPORT DATA
(fltate md Inttnictiont on the rtvtnt btfort completing)
REPORT NO.
3. RECIPIENTS ACCESSION NO.
«. TITLE ANO SUBTITLE
Burning Tires for Fuel and Tire Pyrolysis:
Air Implications
S. REPORT DATE
1QQ1
*. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Charlotte Clark, Kenneth Meardon, Dexter Russell
. PERFORMING ORGANIZATION REPORT NO.
I. PERFORMING ORGANIZATION NAME ANO ADDRESS
Pacific Environmental Services
3708 Mayfair Street, Suite 202
Durham, North Carolina 27707
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68D00124, WA116
12. SPONSORING AGENCY NAME ANO ADDRESS
U.S. Environmental Protection Agency (MD-13)
Emission Standards Division
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
13. TYPE OP REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
If. SUPPLEMENTARY NOTES
ESD Work Assignment Manager: Deborah Michelitsch, MD-13, 919-541-5437
1«. ABSTRACT
This document was developed in response to increasing inquiries into the environmenta'
impacts of burning waste tires in process equipment. The document provides informa-
tion on the use of whole, scrap tires and tire-derived-fuel (TDF) as combustion fuel
and on the pyrolysis of scrap tires. The use of whole tires and TDF as a primary fuel
is discussed for dedicated tire-to-energy facilities. The use of whole tires and TDF
as a supplemental fuel is discussed for cement manufacturing plants, electric
utilities, pulp and paper mills, and other industrial processes. The focus of the
document is on the impact of burning whole tires and TDF on air emissions. Test data
are presented and, in most instances, compared with emissions under baseline
conditions (no tires or TDF in the fuel). The control devices used in these
industries are discussed and, where possible, their effectiveness in controlling
emissions from the burning of whole tires or TDF is described. In addition, this
report provides information on the processes themselves that use whole tires or TDF,
the modifications to the processes that allowed the use of whole tires or TDF, and
the operational experiences of several facilities using whole tires or TDF. The
economic feasibility of using whole tires and TDF for the surveyed industries is
discussed. Finally, contacts for State waste tire programs are presented.
17.
KEY WORDS ANO DOCUMENT ANALYSIS
DESCRIPTORS
b.lOENTIFIERS/OPEN ENDED TERMS
c. COSATi Field/Group
Air pollution
Boilers
Combustion
Cement kilns
Electric utilities
Pyrolysis
Pulp and paper mills
Scrap tires
Tire-derived-fuel
Waste tires
1S. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (Till! Report I
21. NO. Or PA
228
20. SECURITY CLASS iTIni pagn
22. PRICE
EPA
2220-1 (*•». 4-77) »*Kviou« COITION is OMOLCTC
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