c/EPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-80-007a
July 1980
Research and Development
Processing
Equipment for
Resource Recovery
Systems
Volume I.
State of the Art
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. ‘Special’ Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution-sources to meet environmental quality standards.
This document is available to the public through the National Technical orma-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-80-007a
July 1980
PROCESSING EQUIPMENT FOR RESOURCE RECOVERY SYSTEMS
Volume I. State of the Art
by
David Bendersky
Daniel R. Keyes
Marvin Luttrell
Mary Simister
Denis Viseck
Midwest Research Institute
Kansas City, Missouri 64110
Contract No. 68-03-2387
Project Officer
Donald A. Oberacker
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views and
policies of the U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or recommendation
for use.
During the course of this research, some manufacturers who were contacted
regarding their processing equipment requested that their names not be used or
that their names not be directly associated with particular pieces of equipment.
it t order to honor these requests and maintain consistency, information from
manufacturers’ literature and generalized replicas of drawings of equipment are
not sourced.
ii
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FOREWORD
The Environmental Protection Agency was created because of
increasing public and government concern about the dangers of pollution to the
health and welfare of the American people. Noxious air, foul water, and
spoiled land are tragic testimony to the deterioration of our natural
environment. The complexity of that environment and the interplay between its
components require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its impact, searching
for solutions. The Municipal Environmental Research Laboratory develops new
and improved technology and systems for the prevention, treatment, and
management of wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for the preservation and treatment
of public drinking water supplies, and to minimize the adverse economic,
social, health, and aesthetic effects of pollution. This publication is one
of the products of that research; a most vital communications link between
the researcher and the user community.
This report presents the results of a study of equipment and systems
for processing municipal solid wastes into energy related products. The
study was divided into three phases. The first phase, reported herin, was
devoted to a study of the state of the art and formulation of research needs.
The second phase, was devoted to field tests of magnetic separators, air
classifier and air emissions. The third phase was involved with field tests
of shredders.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
iii
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TABLE OF CONTENTS
Page
Disclaimer. . . . . . . . . • • • • • * • • • ii
Foreword
Abstract . . . . . . iv
Figures ix
Tables xii
Acknowledgements. . . . . . . . . . . . . . . . . . . . . . xiii
Section 1 — Introduction. . . . . . . . 1
Section 2 — Methodology and Preliminary Results 3
3
LiteratureSearch . . . . . . 3
Systems Survey . . . . . . . . . . . . . . . . . . . . 4
Equipment Survey . . . . , . . . . . . . 11
SiteVisits 15
Discussions With System Designers. . . . 15
Discussions With Equipment Manufacturers . . . . . . . 15
SectIon 3 — State of the Art, . . . . . . . . . . . . . . . 17
Waste-to—Energy Processing Systems . . 17
Amnes,Iowa 18
Baltimore, Maryland 20
Baltimore County, Maryland. . . 21
South Charleston, West Virginia . . . . . . . . . 22
Chicago, Illinois 25
East Bridgewater, Massachusetts 26
El Cajon, California 26
Milwaukee, Wisconsin 28
Washington, D. C. . . . . . . . . . . 31
Palmer Township, Pennsylvania . . . . 31
Pompano Beach, Florida 33
Riverside, California 34
St. Louis, Missouri 36
Southgate, California 38
vii
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TABLE OF CONTENTS (continued)
Page
Processing Equipment 38
Shredders 39
Magnetic Separators. . . 47
Air Classifiers. . . . 52
Screens 59
Dryers 66
Densifiers 70
ReceivingFacilitles 73
Conveyors. . . 75
Storage Retrieval Bins . . . 78
Dust Controls 86
Electrical Controls. . . . . . . . 92
Fire and Explosion Controls. 94
Economics 102
Section 4 — Research Needs 104
Introduction. . . 104
Ceneral Research Needs 107
Shredder Research Needs 112
Magnetic Separator Needs 118
Air Classifier Research Needs . . . . 119
Screen Research Needs . . . 122
Dryer Research Needs 126
Densifier Research Needs . . . . 130
Conveyor Research Needs . . . . 132
Storage and Retrieval Research Needs. 125
Receiving Facility Research Needs . . . . . . 136
Equipment Control Research Needs. . . 138
Fire and Explosion Research Needs 141
Economic Research Needs 149
Appendices 154
A — References 154
B — Contacts 168
C — Equipment Specifications . . 177
D — Equipment Installations . 188
viii
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FIGURES
Number
1 Fuel/feedstock processing systems at 14 plants. . . . . . . . . . 12
2 Flow diagram of Ames, Iowa plant . . . 19
3 Baltimoreplantflowdiagram . . . . . 21
4 Flow diagram of the BaltinKre County, Maryland facility . . . . . 23
5 Flow diagram (South) charleston pyrolysis facility. . . . . . . . 24
6 Flow diagram of Chicago facility 25
7 Flow diagram of East Bridgewater plant. . . . . . . . . . . . . . 27
8 Flow diagram of El Cajon facility . . . . . . . . . . . . . . . 29
9 Flow diagram of Milwaukee plant . . . . . . . . . 30
10 Flow diagram of NCRR facility . . . . . 32
11 Flow diagram of Palmer Township facility. . . . . . . . . . . . . 33
12 Flow diagramof Pompano Beach facility . . . . 35
13 Flow diagram of Riverside facility • • • 36
14 Processing flow diagram—St. Louis (demonstration plant) . . . . . 37
15 Flow diagram of Southgate facility. . . . . . . . 38
16 Horizontal shaft hammermill • 40
17 Vertical shaft hammermill . . . . . . . . . . 41
18 Cross—section of a roller grinder . . . . . . . . . . . . . . . . 42
ix
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FIGURES (continued)
26
27
28
29
30
31
32
33
34
35
36
37
38
straight air classifier.
zigzag air classifier
vibrating air classifier
rotary air classifier
tub air classifier
Page
43
43
44
48
49
50
50
53
53
53
55
55
60
61
62
63
67
69
• 70
71
Number
19 Disc—mill shredder
20 Ball mill
21 Knife shredder
22 Principle of magnetic separation (belt type).
23 Principle of “hockey stick” belt magnet
24 Principle of single drum magnetic separator
25 Principle of dual—drum magnetic separator
Principle of
Principle of
Principle of
Principle of
Principle of
Gyrating screen
Reciprocating vibrating screens .
Rotary (trommel) screen
Disc screen
Rotary dryer
Fluid—bed solid waste dryer . . .
Pellet mill (roller and die section).
Compactor
x
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FIGURES (continued)
Number Page
39 Layout of a solid waste receiving facility with floor pad
receiving area. 74
40 Layout of a receiving facility with receiving pit . . . . . . . . 74
41 Push—pit receiving facility 75
42 Conical “sweep bucket” bin 79
43 Two discharge methods used with silos . . . . . . . . . . . . . . 80
44 Inverted bin with dual travelling screw discharge . . 81
45 Flow problems encountered in MSW storage and retrieval. 82
46 Invertedbinwithrollers • 83
47 Rectangular bin with screws and doffing rolls . . . . . . . . . . 84
48 Bin with vertical and horizontal discharge screws 85
49 Principle of a cyclone separator 87
50 Circularbaghouse ................. 88
51 Rectangular baghouse. . . . . . . . 89
52 Wet scrubber dust collector . 90
53 Baltimore County, Maryland, control panel . . . . . . 93
xi
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TABLES
Number Page
1 Waste—to—energy systems (with processing) 6
2 Additional systems surveyed • 9
3 Waste—to—energy systems (with processing) scheduled to be
operational by 1978 10
4 Processing equipment used in waste—to—energy systems 13
5 Types of processing equipment used or planned at 14 waste—to—energy
systems 14
6 Shredder types used in waste—to—energY systems 46
7 Magnetic separators types used at waste—to—energy systems. . . . 51
8 Air classifier types used in waste processing systems 57
9 Types of screens at waste processing plants 64
10 Types of densifiers used at waste—to—energy systems 72
11 Types of conveyorsusedat waste—to—energy systems 77
12 Types of storage and retrieval bins at waste—to—energy systems . 85
13 Dust controls at waste—to—energy systems 91
14 List of research needs, by category 105
xii
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ACKNOWLEDGEMENTS
The study was conducted by Midwest Research Institute (MRI) for the
U. S. Environmental Protection Agency (EPA), Municipal Environmental Research
Laboratory, located in Cincinnati, Ohio. The EPA Project Officer was
Donald A. Oberacker.
The MRI Project Director was David Bendersky. Other MRI personnel
who contributed to this study were Dan Keyes, Robert Levesque, Marvin Luttrell,
Doug Fiscus, Bruce Simister, Mary Simister, Carl Clark, John LaShelle,
Carol Green, Charles Brown, Tek Sutikno, Einile Baladi, Charles Roinine and
Cal Bolze.
We gratefully acknowledge the cooperation of the many municipal
officials who provided information on their plans and experience with waste
processing plants, and the extensive technical data and commentary provided
by system designers and represerititives of equipment supply companies.
xiii
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SECTION 1
INTRODUCTION
The combined need for new energy sources and better waste disposal
techniques in the U. S. has stimulated considerable interest and activity in
the recovery of energy and other resource from municipal solid waste (MSW).
A variety of energy recovery systems have been designed which produce waste—
derived fuels in solid, liquid or gaseous forms. Processed MSW may be used
directly as a solid fuel in power plants boilers and other industrial heaters,
or as a feedstock for pyrolysis and other systems which convert the processed
MSW into liquid or gaseous fuels. The raw waste is processed through
various combinations of equipment which usually include one or more of the
following unit operations: shredding, magnetic separation, air classification,
screening, drying, and densification. In addition to these unit operations,
these systems usually also Include, receiving facilities, conveyors, dust
collectors, cyclone separators, electrical controls, storage and retrieval
bins, and other ancillary equipment.
Much of the equipment presently being used for waste—to--energy
systems was not originally designed for use on municipal solid waste, which
is a difficult material to handle and process. Some characteristics that
make MSW difficult to handle and process are: (1) it is a mixture of many
different materials and shapes; (2) the moisture content can vary
considerably; (3) it does not flow well; (4) it contains abrasives; (5) it
is putrescible; and (6) It tends to compact in storage. Thus far, operating
experience, tests and evaluations of waste—to—energy systems have been
insufficient to provide a firm basis for optimum design, selection and
operation of processing equipment for these systems.
In light of the situation, the U. S. Environmental Protection
Agency contracted with Midwest Research Institute to conduct research, tests
and evaluations of alternative processing equipment and systems for converting
municipal solid waste into a solid fuel for feedstock for liquid/gaseous
fuel conversion systems. The project was intended to stimulate and advance
the technology of waste—to—energy systems by providing information useful to
equipment manufacturers, system designers and system operators
Phase I of the study, reported herein, was concerned with (1) a
study of the present state of the art of equipment used to process MSW into
1
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energy—related products,* and (2) the identification of areas which require
additional research to improve the state of the art. Phase I was conducted
during the period March through Devember 1976, with some updating in the
summer of 1978.
Phases II and III were devoted to in—plant tests and evaluation of
processing equipment, aimed at satisfying some of the research needs.
* Only equipment which affects the energy—related product streams were
included in this study; equipment used to process only the non—energy
streams, such as metals and glass recovery, were not included in this
study.
2
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SECTION 2
METHODOLOGY AND PRELIMINARY RESULTS
The methodology used to establish the state of the art of waste—
to—energy systems and associated processing equipment, and to identify the
research needs included: (1) a search of the relevant literature, 2) a
survey of present and planned waste—to—energy systems, (3) compilation of
available date on associated processing equipment, (4) visits to plant
sites, and (5) discussions with system designers and equipment manufacturers.
LITERATURE SEARCH
The purpose of the literature search was to assemble and review
available literature relating to the processing of municipal solid waste
into fuel or fuel feedstock. The literature consisted of two major
components:
1. General literature, including technical reports, journal
articles, conference proceedings, books and other reference materials
pertaining to waste—to—energy systems, processing operations, and general
equipment data; and
2. Manufacturers’ literature regarding specific types of processing
equipment.
The general literature provided a basis for formulating an initial
assessement of the state of the art waste processing technology and for
preparing a preliminary list of municipal waste—to—energy systems; it was
also utilized as the core of a project library used as a source of
references throughout the course of the project. The manufacturers’
literature served as a base for the development of equipment data, which is
presented in a later section of this report.
The first step in the assembly of relevant literature was a
comprehensive review of MRI’s existing Solid Waste Library. This library,
which houses hundreds of documents relating to solid waste management and
resource recovery, was surveyed; and pertinent documents were transferred
from the general library to a special project library. Selected Texas A & M
3
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literature files were also surveyed for relevant documents, and such documents
not already in the NRI library were made available to the project library.
Additionally, EPA’s bibliography “Solid Waste Management-Available Information
Materials, as well as other bibliographies containing solid waste, resource
recovery or energy—related documents, were surveyed for materials pertinent
to the project; these documents were then ordered. Furthermore, the EPA
Project Officer was instrumental in locating and sending a number of pertinent
references. Upon receipt, each reference was reviewed to assure its relevance
prior to its incorporation into the library. A listing of the references
accumulated and reviewed is contained in Appendix Al.
The manufacturers’ literature file contains literature from 64
manufacturers of shredders, magnetic separators, air classifiers, screens,
driers, storage bins, conveyors and miscellaneous equipment. A listing of
companies which manufacture waste processing equipment is given in Appendix
A2.
SYSTEMS SURVEY
In addition to the literature review, a survey of all known existing
and planned waste—to—energy systems throughout the United States was conducted.*
The criteria for systems included in the survey were: (1) that the system
produce an energy product, and (2) that the system utilize processing
equipment to convert the waste Into a fuel or fuel feedstock.
During the course of the literature review, a preliminary list of
existing and planned systems was developed. This preliminary list was
composed of 90 systems, including municipal facilities, county and regional
systems, and pilot plants or demonstration projects.
Contacts were made with representatives of each of these 90 systems
to obtain up—to-date Information on the system. Initial contacts were made
by telephone whenever possible. Followup contacts and communication with
those individuals who could not be reached by telephone were conducted by
written correspondence. After describing the purpose of the project, MRI
staff requirested the following information from each system representative.
1. The type of energy product being or to be produced, if any;
2. The plant capacity;
3. The type of processing operations employed, if any;
4. The designer of the processing system;
* The survey of waste—to—energy systems was conducted during the summer of 1976.
4
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5. When and where the system is now, or is planned to be operational;
and
6. Whether or not the system will be available for tests.
Additionally, technical reports and economic evaluations were
requested when the representatives indicated such materials to be available.
Upon completion of all telephone contacts and receipt of written
replies, systems data were then tabluated for each of the systems.
The breakdown of these systems Is as follows:
54 systems met the criteria of producing an energy product and
utilizing processing equipment
12 systems for which no final decision had been made as to the type
of technology to be employed
7 systems not utilizing energy recovery
6 systems did not respond to telephone or wirtten Inquiries
4 systems do not use processing operations
2 systems were no longer operational
2 systems were duplicates of other systems in the survey (listed
under two different names)
1 system was a test facility, to be superseded by a large—scale
facility included in the 54 systems meeting project criteria
1 system was only an experimental plant
1 system for which correspondence was returned, indicating “no
such address”
90 systems — total
Table 1 is a listing of the 54 systems meeting the basic project
criteria (i.e., producing an energy—related product and utilizing processing
equipment). For each system, the type of energy product to be produced,
the system designer, and the anticipated operational date are included.
Table 2 lists the additional 36 systems surveyed and their status.
From the 54 systems in Table 1, a furhter selection process was
undertaken to determine those which were expected to be operational by
January 1978. This date was chosen as the time frame necessary for
implementation of field tests during the present contract period. Fourteen
systems were found to meet this final criterion; these are listed in
Table 3.
5
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TABLE 1. WASTE—TO-ENERGY SYSTEMS (WITH PROCESSING)
—, ._
Name/Location of Anticipated
System Energy Product System Designer Operational Date
1. Akron, Ohio Steam Glaus, Pyle, Schamer, December 1979
Burns and Dehaven
2. Albany, New York RDF* Smith and Mahoney Spring 1980
3. Ames, Iowa RDF HDR In operation
4. Baltimore Steam Monsanto Under repair
Maryland
5. Baltimore County, RDF Teledyne In operation
Mary land
6. Bridgeport, RDF CEA, Occidental Early 1979
Connecticut
7. Capital District RDF Homer and Shifrin Not available
New York
8. Central Contra Pyrolysis gas Brown and Caidwell 1979
Costa County,
California
9. Charleston, Pyrolysis gas Union Carbide In operation
West Virginia
10. Chemung County RDF Americology Not available
New York
11. Chicago, Illinois RDF Parsons—Consoer Mid—1978
12. Columbus., Ohio Steam Jeffrey Manufac— 1980
turing Company
13. Dade County, RDF Black—Clawson 1980
Florida
14. Dallas, Texas RDF HDR January 1979
15. Detroit, Michigan Steam Being negotiated Not available
16. Duluth, Minnesota RDF Conoer, Townsend Janaury 1979
And Associates
17. East Bridgewater, RDF CEA December 1976
Massachusetts
18. El Cajon, Pyrolysis Occidental Partial operation
California liquid fuel
19. Erie County, RDF Homer and Shifrin March 1978
New York
20. Essex County, RDF Unknown Not available
New Jersey
21. Fairmont, RDF Joseph Edeskuty Not available
* Shredded refuse derived fuel.
6
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TABLE 1. (continued)
Name/Location of Anticipated
System Energy Product System Designer Operational Date
22. Hackensack, RDF Burns and Rowe Not available
New Jersey
23. Haverhill, Steam VOP—Martin 1980
Massachusetts
24. Hempstead, Steam Black Clawson April 1978
New York
25. Hennepin County, RDF HDR—feasibility study Not yet
Minnesota determined
26. Honolulu, Hawaii Probably gas Sunn, Low, Tom & Hara Not available
27. Irvine, California Pyrolysis gas Barber—Colman Not available
(test facility)
28. Knoxville, RDF Black—Clawson 1980
Tennessee
29. Lane County, RDF Allis—Chalmers Summer 1978
Oregon
30. Menlo Park, Electricity Combustion Power Under
California Company development
31. Middlesex County, Steam or gas Roy F. Weston 1980 to 1981
New Jersey
32. Milwaukee, RDF Americology Partially
Wisconsin operational
33. Monroe County, RDF Raytheon Late 1978
New Jersey
34. Montgomery County, RDF Bonnett, Fleming July 1979
Maryland Corddry and
Carpenter
35. Montgomery County, RDF Unknown Not available
Ohio
36. Mt. Vernon, Pyrolysis gas Union Carbide Not available
New York
37. New York, RDF Homer and Shifrin 1980
New York
38. Outagami County, RDF Allis—Chalmers December 1978
Wisconsin
39. Palmer Township, Fuel Pellets Elo and Rhodes 1978
Pennsylvania
40. Pompano Beach, Methane Waste Management, May 1978
Florida Incorporated
7
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TABLE 1. (concluded)
Name/Location of Anticipated
System Energy Product System Designer Operational Date
41. Portland, Oregon RDF Not yet determined 1980
42. Riverside, Pyrolysis gas Pyrolysis Systems, Spring 1977
California Incorporated
43. St. Louis, RDF Homer and Shifrin Inactive
Missouri
44. San Antonio, RDF Unknown 1979
Texas
45. Sanitary District Pyrolysis Unknown Not available
No. 1, Lawrence,
New York
46. Santa Rosa, RDF Lumberman and Sira Not available
California
47. Scranton, RDF Metcalf and Eddy 1979
Pennsylvania
48. Southgate, Pyrolysis Etnerprise Company In operation
California (test
facility)
49. Springfield, RDF HDR 1979
Illinois
50. Tampa Bay, Probably HDR Not available
Florida pyrolysis
51. Toledo, Ohio RDF Samborn, Steketee, Late 1978
Otis and Evans
52. Washington, D. C. RDF NCRR In operation
(test
facility)
53. Winchester RDF Malcolm Pirnie, Not available
County, New York Incorporated
54. Wilmington, RDF Unknown 1980
Delaware
8
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TABLE 2. ADDITIONAL SYSTEMS SURVEYED
Ansonia, Connecticut
Beverly, Massachusetts
Chatauqua County, New York
Cuyahoga Valley, Ohio
Evanston, Illinois
Ft. Wayne, Indiana
Franklin, Ohio
Greensboro, North Carolina
Hamilton, Ontario
Hammond, Indiana
Hartford, Connecticut
Housatonic Valley, Connecticut
Jacksonville, Florida
Lancaster, California
LaVerne, California
Lawrence, Massachusetts
Los Gatos, California
Lyndhurst, New Jersey
Madison, Wisconsin
Memphis, Tennessee
Minneapolis, Minnesota
New Britain, Connecticut
New Jersey, Central
Norwalk, Connecticut
Oakland, California
Oakland County, Michigan
Peoria, Illinois
Philadelphia, Pennsylvania
Red Lion, Pennsylvania
Richmond, Virginia
Saugus, Massachusetts
Seattle, Washington
Springfield, Missouri
Staten Island, New York
Union County, New Jersey
Upland, California
Status
No decision
No response
No decision
No preprocessing
No response
No longer operational
No energy recovery
No decision
No preprocessing
No energy recovery
No decision
No decision
No response
No longer operational
Test facility
No decision
Experimental plant
Same as Hackensack, New Jersey
No decision
No response
No energy recovery
No decision
No preprocessing
No decision
Resource recovery not part of
present plan
No decision
No response
No decision
No response
No decision
No preprocessing
No energy recovery
No energy recovery
Same as New York, New York
No energy recovery
Correspondence returned——no such
address
Name
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
9
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TABLE 3. WASTE-TO—ENERGy SYSTEMS (WITH PROCESSING) SCHEDULED
TO BE OPERATIONAL BY 1978
1. Ames, Iowa
2. Baltimore, Mary-
land
3. Baltimore County,
Maryland
4. Charleston, West
Virginia
5. Chicago, Illinois
6. East Bridgewater,
Massachusetts
7. El Cajon, Cali-
forni a
8. Milwaukee,
Wisconsin
9. Palmer Township,
Pennsylvania
10. Pompano Beach,
Florida
11. St. Louis,
Missouri
12. Riverside,
California
13. Southgate,
California
14._Washington, D.C.
In operation since 1975
Being redesigned
Partly operational.
since 1976
In operation since
1974
Shakedown
In operation since
1976
Shakedown
Shakedown
Shakedown
Start up 1978
In active
Unknown
50 Unknown
30 Experimental plant
Capacity
(Tons Per
Location Energy Product Day) Status
RDF 360
Pyrolysis (steam) 900
RDF 455
Pyrolysis (gas) 182
RDF 900
Eco-Fuel II 220
Pyrolysis (oil) 180
RDF 900
RDF 135
Methane 45-90
RDF 270
Pyrolysis (gas) 300
Pyrolysis (oil)
RDF and Pellets
10
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EQUIPMENT SURVEY
Based on the information compiled in the systems survey, a
comprehensive investigation of the processing equipment used at each of the
systems expected to be operational by 1978 was undertaken. The equipment
survey was concentrated on these systems because of their potential availability
for tests within the present project period. Some data were also gathered on
the MSW processing systems and equipment which are potentially applicable for
waste—to—energy systems.
The initial taks in the equipment survey was to construct a f low—
chart of the processing equipment used at each of the waste—to—energy systems
under consideration. This task was accomplished by using the Information
collected in the systems survey. Only those pieces of processing equipment
which directly affect the energy product (fuel or fuel feedstock) stream were
included in the chart, shown in Figure 1. From this chart, a list of
processing equipment which are within the scope of this project was compiled.
This list, shown in Tables 4 and 5, includes all the major types of equipment
and variations within each type.
The next task was to determine what data should be collected for
each piece of equipment. To accomplish this task, the literature collected
during the literature search, including the manufacturers’ literature, was
culled for information pertaining to processing equipment specifications and
performance. Additionally, information gained in discussions with system
designers, plant site visits and from NRI project consultants was used in
the design of data sheets.
The equipment data sheets incorporated three major sections: (1)
specifications, (2) performance data, and (3) costs. The specifications
section include detailed items which are pertinent to the general type of
equipment and items which deal with each specific piece of equipment being
used or planned for waste—to—energy systems. The performance section relates
only to data on the performance of the equipment on NSW. The cost section
includes capital, operating, and maintenance costs, also as they relate to
performance on MSW.
11
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PV OLY5IS u JIO
ii L—I I
C ’. I n - - H
R ...i. nq
M(Th ANL
a...,,, SI.. __________ j________ I_ “
P S acsi l.iq t i I
Figure 1. Fuel/feedstock processing systems at 14 plants.
12
-------
TABLE 4. PROCESSING EQUIPMENT USED IN WASTE-TO-ENERGY SYSTEMS
1. Receiving facilities
a. Scales
b. Building
c. Loaders
d. Ancillary equipment
2. Conveyors
a. Flight
b. Belt
c. Vibratory
d. Pneumatic
3. Shredders
a. Hammermills - vertical, horizontal
b. Grinders - roller, disc-mill
c. Flail mill
d. Wet Pulp
e. Ball mill
f. Knife mill
4. Magnetic Separators
a. Belt type
b. Drum type
5. Air Classifiers
a. Straight
b. Zigzag
c. Vibrating
d. Drum
e. Concentric
6. Screens
a. Trommel
b. Vibrating-reciprocating and gyrating
c. Disc
7. Dryers
a. Drum-type
b. Fluid-bed
8. I ensifiers
a. Pelletizers
b. Briquetters
c. Cubers
d. Extruders
a. Compactors
9. Storage and Retrieval Systems
10. Electrical Control Systems
11. Dust Control Systems
a. Cyclones
b. Baghouses
12. Fire and Explosion Control Systems
13
-------
TABLE 5
TYPES OF PROCESSING EQUIPMENT USED OR PLANNED AT 14 WASTE—TO—ENERGY SYSTEMS
Prinary Magnetic
leceining Shreddtr Separator
Teledn A.ani000 Sings
Scales Pulverizer
Mad l 60—90
Painbeak. i.f&ep Hans-
Ding.
Storage
Pelletinet Ms oso Gthv4i Conveycro
-— Atlas Rader. PSI. Rex—
nord, Phyfran,
P eivflgid
Monsanto Atlas Jeffrey Hans—
lecturing
Reonord
—— Griffin —— Iron Hustler
Etoi000-
outsit
—- Ta unton
Lonatian
A.en, loan
5.ltDaete. NArylond
Haltioure Cn ,snty.
Haryl e.sd
s .eIeatan. WAtt
Vit ini .
ie$e, Illinni.
Last NAtdgtec,
NA.saoHe..tt .
*1 CaJan. California
Riiks • Vt ,neouin
Palour TnsblP.
p sySe i a
P eao Isa. Florida
tjes,.id.. California
St. Losia. Miosenri
Sosth$sta. cal i fornIa
U. hiniten. DC.
..LI .ble.
Seal,, factoring
Hodel 994
Tol.do N. skn ..n
00.10. Teacen
Ts,hiba,
1,000 liP
Cat 950 Hell C any
Toledo Model 42D
Sc ,1. 5
Willisen
lb NA
lb Mont Inns
mIner-
lean Hodel
60-90
U k Will l
If. Nb
l b HeLL C aOY
osallen Pit— ——
Pee C,.-
caper. NAy-
tree
S II 1110 Crn dlnc
Pt Model 14-60
3 ii F-1
1 II 3850
1 Ca.. V ’lA
Fo .t ’s,d
3 fIHeil
407Nb
C.ap. Rtar
PA lecerpriso
44 X 60
IA WiLlt.nn.
Model 180
— — Carter-Day
-- Carter—Day
NA
Che.ical Alt Srcond ary
Cl.vsiil i _Screen C enattov Shredder
—. Radec 130 -— -- - - Aentitan
Puloerteor
Model 60-90
—- N atIonal —— — . flail 8165 -—
Reaeurre
Recovery
Dire. — . -- -- -. - -
iRE/P
and SE 565
s/s 26425
—- -- Triple/S — - . Hell HT6S Carbornedon
Vibnolo-
trietOr
NA HA -- -- Reran 522A -- --
Ir t oend let
Triple S
Stearns - - occidental Guarantee Rater 522A Hel oitiOae S
—— —. A.erLnolOgy — — -— HeLl 8165 Hail
NA - - NA - - NA - - If.
NA — - Triple!S —— -— — — Genendlgr
Vtbrnlo-
trieter
-- nader Site A la —-
—. — — Triple/S —— C , ebontlce — - H ,1
Vibtole— reset
critter
Allen
sicS Ho
and Iron
Aserican
Sheet
Natal
3W. Greer, ten—
nerd, Sy.iena
end Engineering fWnufacturtug
NA
Hayfran Reanord
6 ,e o to od
NA
NA
Carrier Hoyt ran
-- NA NA
I SA HA IA
NA NA
—— MA Pyrolysia
Spet
Control
04
tts.nte
Fisher -
Controls
Adec—Coapulee
Teledyne
inion Cashier
NA
C IA Cleveland
Controls
Procon (UOP)
NA
Rio end eRodes
PA
HA
Minns,poli l
Hones,.el 1
Col en
Allen—5r.dle
NA
-— NA Miller— Continental. 1 . 4cr, Stephon.
Hoff t Ad On
- - - - —. Enterprise ISyf ran
California—- NA
‘ l let
Co eny
-------
The data forms were completed to the extent possible by MRI, using
the general manufacturer’s literature and the systems literature. They were
then sent to the respective manufactueres for verification of information and
completion of the forms. When possible, this information was also sought from
plant/design personnel.
SITE VISITS
Project personnel vistied seven waste—to—energY plant sites to
obtain first—hand jnformation. The plants visited were at Ames, Iowa; El Cajon,
California; Washington, D, C.; Baltimore, Maryland; Cockeysvllle, Maryland;
Charleston, West Virginia; Chicago, Illinois; and St. Louis, Missouri.
Attempts were made to visit plants in East Bridgewater, Massachusetts, and
Milwaukee, Wisconsin, but because these plants were under construction,
visits were not permitted.
DISCUSSIONS WITH SYSTEM DESIGNERS
Personal discussionS were held with representatives of ten orga-
nizations which have designed waste—to—energy systems. The purpose of these
discussions was to obtain firsthand information concerning the procedures
presently being used to design and select processing systems and equipment
for waste-to—energy systems.
The organizations contacted included Homer and Shifrin, Inc.,
designers of the St. Louis EPA demonstration plant; Monsanto Enviro—Chem
Systems, Inc., designers of the Baltimore pyrolysis plant; Henningson,
Durham and Richardson, designers of the Ames, Iowa plant; Ralph M. Persons,
designers of the Chicago RDF plant; Occidental Research Corporation,
developers and designers of the El Cajon pyrolysis plant; Enterprise
Company, designers of the pyrolysis plant at Southgate, California; Teledyne
National, designers of the Baltimore County RDF plant, Combustion Equipment
Associates, developers and designers of the East Bridgewater, Connecticut,
Eco—Fuel plant; and Elo and Rhodes, designers of the Palmer Township,
Pennsylvania, system, and NCRR, designers of the Washington, D. C., arid
New Orleans facilities. The individuals contacted at these organizations
are listed in Appendix B.
DISCUSSIONS WITH EQUIPMENT MANUFACTURERS
Personal discussions were held with representatives of 16 orga-
nizations which manufacture and/or distribute equipment for use in waste—
to—energy systems. The purpose of these discussions was to obtain firsthand
15
-------
information on the characteristics of their equipment, the performance of their
equipment on MSW, and areas which require additional research.
The organizations included the Gruendler Crusher and Pulverizer
Company (shredders and tromxnels), Williams Patent Crusher and Pulverizer
Company (Shredders, conveyors and air classifiers), American Pulverizer
Company (shredders), the Hail Company (shredders, dryers, and stationary
packers), Dings Company (m netic separators), W. D. Patterson (distributors of
screens, baghouse filters, air classifiers, vibrating feeders, shredders and
control devices), Rexuord Company (conveyors), Beloit—Jones (secondary
shredders), Fenwal, Inc. (explosion controls), Stearns Magnetics, Inc.
(magnetic separators), Carter—Day Company (filters, control systems),
Triple S. Dynamics Systems (air classifiers), National Resource Recovery
Corporation (air classifiers), Rader Systems (air classifiers, screens).
The individuals contacted at these organizations are listed In Appendix B.
16
-------
SECTION 3
STATE OF THE ART
This section describes the state of the art of waste—to—energy
processing in terms of fourteen systems and the equipment comprising those
systems. The information presented reflects a diversity of equipment designs,
system configurations and overall approaches to the process of refining MSW
into energy products. The experience encountered with the equipment and
systems is reported, and those areas where substantial data are lacking are
introducted as a prelude to the subsequent section on research needs.
WASTE—TO-ENERGY PROCESSING SYSTEMS
As discussed in the previous section, 14 systems were identified
which meet the project criteria of producing an energy—related product and
utilizing processing equipment, and which were expected to be operational by
January 1978. In describing each of these systems, the following information
is presented:
General information includes such data as system tape, designer,
operational date and capacity.
Processing system describes the various operations employed to
produce the energy product and other resources.
Performance problems involves experience relating to the system in
general, either during actual operations or preliminary tesing, with emphasis
on problems with preprocessing equipment.
Potential as test site examines the factors of accessibility to the
facility, scale of the system, and other variables which could affect the
viability of testing at each site.
17
-------
Ames, Iowa
The Ames, Iowa facility, operational since November 1975, produces
a refuse—derived fuel product for use in the adjacent Ames Municipal Electric
Service Power plant. Ferrous metals and aluminum are also recovered from the
MSW. Designed by Henningson, Durham and Richardson, Inc., of Omaha, Nebraska,
the facility has a capacity of 45.4 metric tons per hour and is operated
about 8 hours per day.
The entire system is housed in one building, with the receiving
section walled off from the processing section. The plant receives mostly
residential and industrial waste. Demolition materials, automobiiles,
liquids and contaminated or hazardous wastes are not accepted. Additionally,
items such as appliances and tires are removed from the waste stream prior to
processing.
The processing plant has 30.5 meter by 48.8 meter fully-enclosed
receiving and storage facility. Upon entering the facility, the trucks
containing the raw refuse are weighed, after which they dump their contents onto
the receiving floor. A front—end loader pushes the raw refuse onto a conveyor,
which carries the material directly to the primary shredder. Intial shredding
reduces the refuse to a maximum of about the 15 centimeter size.
After primary shredding, the refuse is subjected to magnetic
separation for removal of ferrous metals, and then to a secondary shredding
operation, which further reduces the particles to a monimal 2.54 centimeter
size. The shredded refuse is then fed into a surge bin and then into an
air classifier at a controlled rate. The light fraction leaving the air
classifier .goes into a cyclone separator which segregates the refuse from the
airstream. The combustibles are then pneumatically conveyed, first to a
storage bin and ultimately into the power plan boilers.
A flow diagram of the processing operations is shown in Figure 2.
The refuse—derived fuel is primarily used in the largest of the
three boilers in the power plant. Four refuse fuel conveyor pipelines
are connected to this boiler; however, normally, only two of the four lines
are operated on diagonally opposite corners, with the other two for backup.
The refuse fuel represents about 12 percent of the total fuel input to the
boiler at maximum level; after a 5—year operation, it is anticipated that the
percentage will be increased to 20 percent.
18
-------
Row Refute
Ipp ng FLoe.
Source: Funk, 1976.
A ,
Aluminum Non—Fen’aun Reject
Storage Storage Storage
Electricity
Out
Auhi
Figure 2. Flow diagram of Ames, Iowa plant.
-------
Some unanticipated problem areas have been encountered in the
operation of the plant: (1) dust accumulation, which creates a housekeeping
problem as well as potential fire, explosion and health hazards; (2) jammIng
in the storage bin due to streching of the sweep bucket chain; (3) plugging
of the pneumatic conveyors; (4) spillage of the MSW at the air classifier
entrance; and (5) appreciably less throughput of the secondary shredder than
originally anticipated.
Some testing and evaluation of the Ames facility is currently being
conducted by a group from Iowa State University.* Although additional
testing is possible, there is a potential problem relating to the layout of
some of the unit operations, which inhibits access to input and output
streams.
Baltimore, Maryland
The City of Baltimore facility was designed to convert refuse to
steam through a gas pyrolysis system developed by the Monsanto Company in
St. Louis. The facility was to operate at a capacity of 90.7 metric tons per
hour, about 10 hours per day. The initial operation ran from January to
September 1975, after which the plant was closed to correct several unexpected
problems. Following completion of the modifications, operation was resumed,
but technical problems have continued.
Raw refuse is dumped from the packer trucks into a large receiving
bin and they conveyed to one of two horizontal shredders. The shredding
operation produces a product with a nomimal 10.2 centimeter shred size, which
is then conveyed to the storage bin. The shredded refuse is removed from the
bin by means of rotating buckets which deposit the portioned product onto
a signie outfeed belt. This in turn feeds the waste into the pyrolysis kiln.
The kiln itself is 5.8 meters in diameter and about 30.5 meters
long. It rotates at about two revolutions per minute and is lined with
refractory material to keep the heat within the kiln and to protect the metal
shell. The high heat necessayr to pyrolyze the waste is supplied by a portion
of the waste itself and by a supplemental fuel (No. 2 heating oil). Steam is
produced through the combustion of the resultant pyrolysis gases In an
afterburner which creates the heat necessary to operate two waste—heat
boilers. The steam Is piped to an existing Baltimore Gas and Electric
steam distribution system which heats and cools downtown buildings.
A flow diagram of the system appears in Figure 3.
* The Ames tests are being jointly funded by the EPA and ERDA.
20
-------
Ra mfeeder
Clean Air to
Atmosphere
Residuals
Figure 3. Baltimore plant flow diagram.
The Baltimore system has experienced several significa t problems,
which caused shutdowns: (1) the residue from the kiln has had a tendency to
slag, Indicating that the glass particles In the refuse are being nietled by the
high temperatures in the kiln; (2) additionally, the high pyrolysis
temperatures have caused failures of the kiln’s refactory lining; and (3) there
have been excessive particulates in the exhaust gases, which the system’s
wet scrubbers have not been able to remove. The installation of electrostatic
precipitators, should alleviate the last problem. Since these problems were
not encountered In the pilot plant and therefore not anticipated at full—
scale operation, numerous modifications in the design have been necessary.
Two additional problems were encountered relative to processing:
(1) an explosion occured in one of the shredders during operation, causing
damage to the shredder itself as well as to the building; (2) feed problems
have been experienced in removal of the shredded waste from the storage bin.
problems.
The plant is not available for tests because of operational
Baltimore County, Maryland
The Baltimore County facility is located in Cockeysville, Maryland.
Designed by Teledyne National, the system produces refusè—derviced fuel to
be used in bark furnace, cement kiln, and possibly other applications, and
also recovers ferrous metals. It has a capacity of 90.7 metric tons per
hour and currently processes approximately 455 metric tons per day.
Gas
Scrubbei
Afterburner
Stack
Receiving
Storage
Source: Sussman, 1975. Metal
21
-------
The facility utilizes receiving pits rather than a signie receiving
room. Trucks back into the individual pits and dump the waste, which Is
subsequently pushed onto a conveyor belt by hydraulic rams. The refuse Is
then conveyed directly into one of two horizontal shredders, under the control
of an operator who regulates material flow from an elevated control room.
The control system Is a computerized design by Teledyne. The shredders
reduce the waste to a maximum 7.6 to 10.2 centimeter shred size.
The shredded refuse is conveyed to a belt magnet for removal of
ferrous metal, after which it is fed Into two air classifiers In series.
The first separates the MSW into a combustible fraction and a heavy fraction
(metals, glass, etc.). The second classifier separates the combustible fraction
Into two grades of RDF fuels.* Finally, the light fraction is compacted and
transported to the user sites. A trommel screen and other equipment have
recently been added for removal of glass and aluminum from the heavy fraction.
A bag house is used to clean up airborne discharges from the shredders and
air classifiers.
A flow diagram of the system appears in Figure 4.
Baltimore County encountered some back pressure problems In the air
classifiers, caused by the cyclone separators. Teledyne designed special
rotary airlocks to correct this problem. The RDF system is operational at the
present time, and the RDF has been used as fuel for process heat at a paper
manufacturing plant.
The Baltimore County facility has been used as a test site for this
proj ect • **
South Charleston, West Virginia
Designed and operated by the Union Carbide Company, the South
Charleston facility converts refuse into a gas by means of a patented
pyrolysis process called the PUROX system. The facility has a capacity of
181.8 metric tons per day, and is normally operated 24 hours per day. The
plant has been operatiolial since 1974.
The South Charleston facility has a separate storage building where
the waste is intlally dumped and stacked by a front—end loader. The loader
then picks up the stored waste and Is weighed on a platform scale, after which
it dumps the refuse onto a conveyor leading to the shredder. Prior to enter-
ing the shredder, the waste is subjected to manual sorting to remove tires and
other materials which could cause stalling or jamming of the shredder.
* The second air classifier is not normally used.
** Tests conducted at the Baltimore County plant are reported in Volume II.
22
-------
Source: McKewen, 1976.
Figure 4. Flow diagram of the Baltimore County, Maryland, facility.
-------
The vertical shredder produces a nominal 7.6 centimeter shred size.
Following this initial refinement, the refuse is then fed under a drum
magnet to remove the ferrous metals, and then conveyed to a feed hopper at
the top of the vertical pyrolysis reactor. The material is fed into the top
of the reactor by two 14—inch hydraulic rams and passes into the lower zone of
the reactor. Oxygen is simultaneously fed into the reactor at a ratio of
about 20 percent by weight of the refuse. Noncombustibles are metled at the
25000 temperature of the lower zone, to produce a fine—grain slag (about 17
percent by weight of the input waste).
The gasses generated in the reactor are cleaned by water spray and
an electrostatic precipitator and are currently being burned for disposal.
The gas heating value is about 13,034.5 kilojoules per cubic meter.
A flow diagram of the South Charleston system appears In Figure 5.
The main problem concerning processing reported by Union Carbide
representatives relates to the magnetic separation system. A considerable
amount of paper and plastic is being picked up along with the ferrous
fraction. This is a single drum magnet located 90 degrees to the shredder
take—off conveyor. The system operators recognize that this magnet installation
Is not designed for best efficiency.
The emphasis at the South Charleston facility is on the pyrolysis
system rather than the initial processing operations; It is a pilot plant.
As a result, the expenditure of resources on the processing equipment has
been limited; however, Union Carbide indicated that they probably would be
willing to cooperate in a front—end testing program.
Condensate
(To Wait. Water
Tr.otin.nt Plant)
Ferrous Metal
Source: Parkhurst, 1976.
Figure 5. Flow diagram (South) Charleston pyrolysis facility.
Municipal
Houi.hold
Mogn.t lc
Fuel Product
Oxyijen
Combustion Zon.
Wcjt r Quench
-
24
-------
Chicago, Illinois
The Chicago facility was designed as a joint venture by the
Ralph M. Parsons Company of Pasadena, California, and Consoer—Townsend and
Associates of Chicago. It is an RDF system which also recovers ferrous
metals, designed to operate at a capacity of 145 metric tons per hour
(900 metric tones per day). The plant is currently in the shakedown phase.
The facility has a double—line processing system, fed by two
apron conveyors linking the common receiving room to the primary horizontal
haminermills. After primary shredding, shred size is specified to be
95 percent 20.3 centimeters or less. Following primary shredding, the
material Is conveyed to an air classifier, and the light fraction is
subjected to secondary shredding, specified as 95 percent 3.8 centimeters
or less.
The shredded light fraction is then pneumatically conveyed to two
storage silos at the power generating plant, owned by Commonwealth Edison,
where it Is fired as a supplementary fuel. Dust control is provided by
dust hoods and a vacuum system which remove the dust fromthe plant, directing
it through a baghouse filter prior to discharge into the atmosphere. Fire
protection devices are also Incorporated into the plant design.
A flow diagram of the Chicago RDF system appears in Figure 6.
Figure 6. Flow diagram of Chicago facility.
The Chicago facility was originally scheduled to begin operations
In laste 1976, but problems with the secondary shredders resulted In
postponement of startup. The plan is presently in partial operation due to
problems with the secondary shredder and air classifier.
Ilp .n Fko,
C . .. Sh,.dd., A CI ...4fl.. M
F.H F..d C,w
I -I
F. .,.
N .. Ot* M..i.
& se.. . . I
LO LO -
Source: Chicago—summary of solid waste disposal systems study.
25
-------
The Chicago plant will be tested under a separate EPA test program
presently being negotiated.
East Bridgewater, Massachusetts
The East Bridgewater plant produces a proprietary finely shredded
refuse—derived fuel product called Eco—Fuel II. Designed by Combusion
Equipment Associates, Inc., in conjuction with the Arthur D. Little firm,
the East Bridgewater plant began production in December 1976. In addition
to the production of Eco—Fuel II, the facility recovers ferrous metals. It
has a capacity of 22.7 metric tons per hour based on 24 hours per day.
As shown in Figure 7, the processing system begins with a primary
shredding process which utilizes a flail—mill type of shredder. Following
shredding, the refuse is conveyed to a magnetic separator and then screened
and classified into three fractions: an oversized fraction, which is recycled
through the primary shredder; a fine fraction composed mainly of glass and
dirt; and a shredded MSW fraction. The shredded portion is chemically
treated by a process which helps to reduce it to a fine particle size but
does not change its chemical composition. Finally, the product is passed
through a ball mill for actual size reduction, and then screened and air
classified to create the Eco—Fuel II.
The East Bridgewaterplant has been previously operational, first in
the incineration of MSW and then for the production of a coarse—shredded
RDF product called Eco—Fuel I. Problems with the present system have included
general problems with the control system, because of its sophistication and
complexity. An explosion occurred in the plant, resulting in the death of an
employee.
It would appear unlikely that EPA—sponsored tests could be done at
the East Bridgewater plant. The system operators feel that testing would
interfere with normal operations; however, they might be interested in having
tests done at their Carter—Day test facilities in Minneapolis, Minnesota.
El Cajon, California
The El Cajon facility, designed by Occidental Research Corporation,
utilizes a pyrolysis system to convert MSW into a liquid fuel product. The
processing plang will have a capacity of 181.8 metric tons per day. Currently,
the processing equipment is being tested; the plant is partially operational.
26
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MSW 100%
Primary
Shredding
Magnetic
Screening
Screening
Chemical
Treatment
Screenin j
Air
C làssi fication
Heat Steel
Treatment Boil Mill
Inert Residue Eco_Fu. ITM 2 Ferrous Metals
8—12% 52—56% 6—8%
Source: Combustion Equipment Associates, Inc. and Arthur D. Little, Inc.
Figure 7. Flow diagram of East Bridgewater plant.
27
-------
El Cajon receives only residential and commercial waste, which are
dumped onto the receiving building following weighing of the trucks. A
front—end loader then pushes the MSW onto a depressed flight conveyor; the
conveyor speed is controlled by the control room operator.
As shown in Figure 8, the initial processing step is shredding,
which is performed by a horizontal shredder with 7.6 centimeters by 12.7
centimeters grate opening . The large grate size was employed to handle
large or hard pieces of refuse in the shredder. From the shredder, the
refuse is transported via pan conveyor to a belt conveyor equipped with a
belt magnet for ferrous removal. The belt conveyor then carries the MSW into
a center—post rotating conveyor and deposits it in the main storage room.
From there it is transported into a small storage bin. The MSW is discharged
from the small bin by a linked—chain conveyor; a set of rotating blades fluff
the waste before it moves onto the belt conveyor leading to the 10—stage
zig—zag air classifier. The light fractions from the air classifier are then
conveyed to a rotating drier which is heated by gases from the pyrolysis reactor
reactor. Finally, the dried waste is screened to remove the fines and is
reshredded to produce a fine fluff necessary for the pyrolysis unit. All
equipment which generates dust is equipped with a baghouse filter system.
Front end equipment is being tested. Initial problems have been
encountered concerning (1) the proper speed for the belt conveyors and (2)
jamming of waste around the head pulley of the conveyors.
This plant is being tested under a separate EPA—OSWNP contract.
Any additional tests would have to be integrated with the present test plans.
Milwaukee, Wisconsin
Owned, designed and operated by Americology, a division of American
Can Company, the Milwaukee plant started operation in 1977. When full
operational, the facility will have a capacity of 136.4 metric tons per hour
and is expected to operate 8 hours per day. It will produce RDF, as well as
recover ferrous metals, aluminum and glassy aggregate. The RDF will be used
to fire boilers in the Oak Creek plant of Wisconsin Electric Power Company.
The flow diagram of the processing system is shown in Figure 9.
As indicated, paper is hand—sorted from the incoming refuse prior to
shredding. After leaving the primary shredder, the material is air—
classified, and the light fraction processed through the secondary shredder.
Finally, the material will be transported into a storage bin, discharged
into trucks and hauled to the power plant. Some equipment changes are
presently being made, primarily the additiona of magnetic separators and
services to provide a cleaner fuel product.
28
-------
Figure 8. Flow diagram of El Cajon facility.
Source: Levy, 1975.
-------
I Secondary
Shredd.
Air
Claui her
Primary
Shredder
r d-Sortrng
for Paper
0
x..i L d
paper/Fiber
4 .e -,
Source: AmericologY
Figure 9.
Flow diagram of Milwaukee plant
-------
Accessibility to the Milwaukee plant for testing purposes is somewhat
doubtful. Ainericology, under contract to dispose of Milwaukee’s solid waste,
Is reluctant to permit tests of the plant by an outside organization at this
time. However, Americology representatives have indicated willingness to
discuss the possibility at a later date.
Washington, D. C .
This Is a pilot plant test facility which can operate at a
capacity of 22.7 metric tons per hour. In addition to the production of
RDF and pellets, the facility has been used to recover ferrous metals,
aluminum, and glass. It has been operational since 1972 under the management
of the National Center for Resource Recovery.
The processing system incorporates a shredder, which discharges
into a vibrating air classifier. The light fraction from the air classifier
goes into a cyclone separator or segregation of RDF from the air stream.
Finally, the RDF is pneumatically conveyed into the incinerator pit. NCRR
has recently installed a secondary shredder and a pelletizer to extrude the
light fraction into pellets. A flow diagram of the system appears In Figure
10.
The NCRR system has experienced some problems with the air
classifier; however, details have not been published.
Since the NCRR system is a testing facility, it is a potential site
for tests requiring cortrolled operating conditions.
Palmer Township, Pennsylvania
The Palmer facility, is designed to process MSW to produce a
pelletized RDF product for use in cement kilns. The plant, which is a joint
interest of the Palmer Township Board of Supervisors and the local cement
industry, is designed to Elo and Rhodes Consulting Engineers of Easton,
Pennsylvania. In addition to the production of fuel, the facility will
recover ferrous metals, aluminum and glass. It is designed to operate at a
capacity of 18.2 metric tons per hour.
As shown in Figure 11, the refuse is initially dumped into a
receiving pit, from which it is conveyed into a totally enclosed system
designed to avoid dust and odor. The refuse is first ground in a primary
shredder into a nominal 7.6 centimeter shred size. A magnetic drum removes
the ferrour metals, and the refuse stream is then processed through two air
separators. The first removes the lighter materials which then pass into a
31
-------
LEGEND:
I. Dumping Floor
2. Main Conveyor
3. Shredder
4. Vibrolutrialor (Air Classifier)
5. Duct (Carrying Li 9 ht Iroctiors to Cyclone)
6 Air Classifier induced Droft Blower
7. Cyclone
8. #otary Air Lock Feeder
9. Pheumatic Conveyor Blower
10. Heavy Fraction Conveyor
Ii. Primary Magnet
12. Conveyor (For Non-Magnetic Material)
13. Magnetic Head Pulley Scavenger
14. Plus Two—inch,Mlnus Four_inch.HeaVY Fraction
(Feed to Eddy Current Separator)
15. Ovenize Mat,riol Bin
16. Separator B.ject Bin
17. Eddy Current Separator
18. Separator R. SC$ Sin
A. Product Light Fraction to Incinerator Pit
B. Product Heavy Fraction
C. Product ,cov.red Magnetic Metok
D. Product t.cov.red Magneflc Metok
F. Product MInus Two—inch Heavy Fraction
(for Glrns tecovery)
F. Product Pecovered Aluminum
Source: Alter and Natof, 1976.
Figure 10. Flow diagram of NCRR facility.
-------
FOR RE-SHREDDING
‘IRON RECYCLE
Figure 11. Flow diagram of Palmer Township facility.
ROADS
air separators for further segregation and into a cyclone for separation of
the RDF fraction from the airstream. The material is then passed through a
secondary shredder. At this stage, the fraction is less than 2.54 centimeters
in size. A second and final air separation takes out residual glass and
rubble. Following screening, a light fraction is densified to form the
compacted fuel pellets, which are then collected in a storage bin and held
until they are transported to the kilns.
There are several reservations about using Palmer Township as a
test site: (1) the facility will operate at a relatively small scale, and
(2) i has been difficuti to obtain information about the facility from
local officials, making it difficult to evaluate the potential of this plant
for tests.
Pompano Beach, Florida
The Pompano Beach plant, dedicated in May 1978 is a “proof of
process” system funded by the Department of Energy (DOE). The facility is
TO CEMENT PLANT
FOR FUEL
ALUMINUM AND
NON- FERROUS
FOR RECYCLE
Source: Elo and Rhodes, 1976.
33
-------
designed to produce a methane—rich gas by anaerobic digestion of MSW coupled
with sewage sludge. Additionally, ferrous metals and paper can be recovered.
The plant will have an initial capacity of 1.9 to 3.8 metric tons per hour
and is expected to operate 24 hours per day.
Processing of the MSW first involves primary shredding and magnetic
separation, both of which will take place in the “shredding facility.” The
stream will then be conveyed to the “processing facility,” where it will pass
through a storage and retrieval system, a troinmel, a secondary shredder, and
an air classifier. Following processing, the stream will be conveyed into the
digestor system. A how diagram of the system appears in Figure 12.
DOE has indicated that the Pompano Beach facility will be made
available to EPA for environeinntal testing, and data will also be collected
on process parameters.
Riverside, California
Designed by Pyrolysis Systems, Inc. andowned by the City of
Riverside, California, the facility will initially serve as a pilot plant to
demonstrate process feasibility. The process, called the X—50 Pyrolysis
System, will produce a low Btu gas which will be converted in the plant to
electrical energy by internal combustion engine driven generators. The
system has been developed for installation in combinations of 45.4 metric
tons per day modules, with capacities ranging from 45.4 to 454.5 metric
tons per day. The first—phase Riverside plant will have a capacity of 1.9
metric tons per hour, and will operate 24 hours per day; in the planned
second phase, capacity will be increased to 11.4 metric tons per hour, also
based on a 24—hou operation.
As shown, in Figure 13, the only refinement process to be utilized in
the system is shredding. Ancillary operations include the receiving facility,
a unique live—bottom inverted storage bin designed to prevent bridging of
the MSW, conveyors and a simple control system. Following retrieval from the
storage bin, the MSW is pyrolyzed at a temperature of 15000 F., and surplus
pyrolytic gases are converted into electricity by a natural gas internal
combustion engine/generator.
The pilot plant at Riverside is the first test facility for the X—50
process. The designers have patents on some of the devices and equipment but
no viable performance data are available.
Full scale testing at Riverside does not seem feasible at this time,
since this is the first pilto plant and it is a small—scale facility. Given
the usualy problems encountered in intlal process testing, it would appear
unlikely that the facility would ye available to test the processing equipment.
34
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Heat
Source: Energy Research and Development Administration (ERDA)
Figure 12. Flow diagram of Pompano Beach facility.
Shredder
Separator
Dj 9 ester
H 2 S
Co 2
-------
Shcodd ing Arcu
Figure 13. Flow diagram of Riverside facility.
St. Louis, Missouri
The St. Louis facility described here in the demonstration facility
which was operational from 1972—1976 (part—time operation). The demonstration
facility has a capacity of 32 metric tons per hour. It produces RDF and
recovers ferrous metals. The system designer is Homer and Shifrin of
St. Louis, The plant is presently inactive.
The St. Louis demonstration facility utilizes only primary shredding,
followed by air classification. Magnetic separation takes place after air
classification on the heavy fraction only, and does not therefore affect the
energy product. The light fraction is passed through a cyclone separator,
conveyed to a storage bin and then transported to the Union Electric power
plant for use as a supplementary fuel in the boilers. A flow diagram of the
system appears in Figure 14.
The St. Louis plant was designed primarily to demonstrate the
feasibility of processing MSW into a supplementary fuel for power plant
boilers. As a first generation plant, it has also been used to collect
initial experience on the operation of a waste—to—energy stystem. Some of
111
M.roI Sund Curbon
1 L )
Isch lco
c [ 1
Generc.$or
CLID
Source: Pyrolysis Systems, Inc.
36
-------
B.lt Conveyor
Surg. Bin
Source: MRI, 1975
Figure 14. Processing flow diagram—St. Louis (demonstration plant).
the important findings relative to processing equipment were (1) an air
classifier is effective in removing the nonburnables from the MSW, (2)
there is considerable wear of the haminermill hammers, (3) there is
Considerable wear at the bends in pneumatic conveyors, (4) the enunission
from the air classifier contains a considerable amount of particulates, (5)
there are high levels of noise in and around the processing plant, and (6)
there have been fires in the control room, hammerinili. feed belt and
Storage bins.
R.c.u.d
Conv.yor
Vibratory
Conveyor
Nugg.tiz.r
Magnetic Separator
Magnetic M.tals Truck
Light FracHon Storag. Bin
Conveyor
Cyclone S.parator
Conveyor
SelF—Unloading Truck
Stationary Packer
37
-------
The St. Louis demonstration pland has been used by MRI (under a
separate contract) to evaluate pollution aspects (bacteria and virus)
of the waste—to—energy process. The plant may be available to conduct
other tests which may be appropriate for this plant. However, this is a
first generation plant, lacking many of the refinements of new plants, so
that data collected at this plant many not be representative of the latest stat
ate of the art
Southgate, California
The Southgage facility utilizes a pyrolysis system to extract fuel
oil and gas from MSW. The pyrolysis concept was originially developed by
Due Engineering Company of Irvine, California, who subsequently sold the
manufacturing and marketing rights to the Enterprise Company of Santa Ana,
California. Enterprise has incorporated its own processing equipment Into the
pyrolysis process. Capacity at Southgate is 45.5 metric tons per day.
Following thorouth testing and evaluation, the plant is to be shipped to
New York (to a client whose name is confidential).
The refuse shredded In a double—shaft horizontal hammermill
designed by Enterprise specifically for processing MSW; however, the shredder
has only been tested on small quantities of waste to date. Following
shredding, the MSW is conveyed directly to the pyrolysis reactor. A flow
diagram appears in Figure 15.
PROCESSING EQUIPMENT
Waste—to—energy processing equipment performs a series of refinement
operations, which transform the MSW into fuel or fuel feedstock. In the
following two sections of the report, the processing equipment used in waste—
to—energy systems Is divided into (1) unit equipment, and (2) supplementary
equipment. Unit equipment is defined as equipment which changes the
character of the waste stream. Unit equipment includes shredders, magnetic
Source: Enterprise Company
Figure 15. Flow diagram of Southgate facility.
38
-------
separators, air classifiers, screens, dryers and densifiers. Supplementary
q 4pment is defined as equipment which aids in the processing of MSW but
does not change the character of the waste stream. Supplementary equipment
includes receiving facilities, conveyors, storage and retrieval bins,
electrical controls, dust controls, and fire and explosion controls. Within
each category of equipment there are various types; e.g., the category
“shredder” incorporates vertical hammermills, horizontal hammermills, ring
mills, grinders, flail mills, and ball mills.
Althrough the unit equipment and supplementary equipment are
discussed separately, it Is Important to remember that various combinations
of these pieces of equipment make up a processing system. There is an
important interrelationship between the various pieces of equipment in the
system, with each piece directly affecting the performance of the others, as
well as the entire system.
The state of the art of processing equipment for waste—to-energy
systems will be discussed in the following manner:
1. Description of the function of each unit operation and
supplementary operation;
2. Enumeration of the types of equipment for each unit operation
and supplementary operation, and a description of the technical aspects of
each type of equipment; and
3. A comparison of the different types of equipment and experience
with this equipment on MSW.
Summary tables of data received from equipment manufacturers are
provided in Appendix C.
Shredders
Function : Shredders are machines used to reduce the size of raw
MSW. Shredding the raw MSW has the following desirable effects in waste—to—
energy systems: (1) the waste is made more homogenous, (2) the volume is
reduced, (3) separation of the noncombustibles from the combustibles Is made
easier, and (4) waste—derived fuel or feedstock Is sized so that it can
readily burn In power plant boilers or be converted into liquids or gases in
pyrolysis reactors.
Primary shredders are used to initially reduce the Incoming raw MSW;
secondary shredders are used to further reduce the size of the output prod-
uct from the primary shredder. All of the waste—to—energy systems investigated
in this study use a prijary shredder, and most use a secondary shredder.
39
-------
Description : The most common type of shredder presently used both
as a primary and secondary shredder, for waste—to—energy systems is the
hammermill. A haimnermill consists of a central rotor with hammers prvoted
to the rotor circumference. The rotor and hammers are enclosed in a heavy—
duty housing. The housing may be lined with hard metal members, and some have
stationary breaker plates or cutter bars mounted Inside the housing. The in-
coming waste is reduced in size by being beaten and torn by the rotating ham-
mers.
There are two basic types of hammermills—--the horizontal shaft type
and the vertical shaft type. In the first type, shown in Figure 16, the rotor
shaft Is mounted In a horizontal position and Is supported on both ends with
bearings. Input is from the tope and the material flows through the machine
by gravity perpendicular to the shaft and exits out the bottom. Most hori-
zontal hammerinills have a curved grate placed across the outlet under the
swinging hammers. The material is pounded by the hammers until it is small
enough to pass through the grate openings. The size of the output material
in horizontal type hammermills is therefore controlled primarily by the size
of the opernings in the grate. _______
Breaker
Bar
G
Input
nveyor
Grate Bar5
Output Conveyor
• • .1.
.‘ • S •. •• V’•• *.
..•I ’ • _ A .. .
FIgure 16. Horizontal shaft haminerrnill.
40
-------
Vertical shaft hammermills, shown in Figure 17, have the rotor shaft
mounted in the vertical position. The lower shaft bearing is a thrust type
to support the weight of the shaft. The input material enters at the top and
flows by gravity parallel to the shaft axis. The upper section of the outer
housing is cone—shaped and tapers down to a throat section and into a straight
cylinder section. The upper hammers start the reduction process as the mate-
rial drops downward towards the throat section. Once the material passes the
throat section, it is further reduced by the action of the lower hammers and
the breaker bars on the inner housing walls. The final shredded product is
swept horizontally Out through the discharge chute at the bottom. Material
entering the shredder which cannot be reduced is automatically rejected
through a chute in the upper section of the machine.
Conical
Pre —breaking
Section
Figure 17. Vertical shaft hainmermill.
Two types of grinders are being used as secondary shredders in waste—
to—energy systems — roller grinders and disc—mill grinders . In both grind-
ers the shafts are vertical. In the roller grinder, shown in Figure 18, a
set of geat—like rollers are mounted around the periphery of the rotor. The
inner surface of the tapered housing is ribbed. The income material is in-
troduced into the upper part of the machine and is first exposed to a set
of breaker bars which breaks up large objects. The material then enters the
Space between the rotor and the housing. The action of the rolling gears and
the tapered outer ribs progressively reduces the size of the material as it
drops down to the exit. 41
Rejection
Section
N
p
Grinding
Section
Exit
Section
-------
Figure 18. Cross—section of a roller grinder
The disc mill grinder, shown in Figure 19, is used to produce a very
fine grind of MSW. The material is ground between two large discs——one sta-
tionary and the other rotated by the vertical shaft. Each disc has teen on
its active surfaces. The income material enters through an opening in the
center of the upper stationary disc, and is impelled by centrifugal force
between the two discs, where it is ground and exits through an outlet at the
circumfrence of the housing.
The flail mill is being used as a primary shredder in at least one
waste—to—energy system. The shredding is done by mult:iple linked arms or
chains mounted on opposed rotors. The incomeing waste is passed between the
two sets of rotating flails and is thereby reduced in size. Since flail mills
pass all imput materials quickly without repeated impacts, wear and energy
requirements are lower than in other types of shredders. However, the degree
of shreddings is usually less that other shredders.
The ball mill is being used as a secondary shredder at one waste—
to—energy plant. Ball mills, as shown in Figure 20, have a cylindrical shell,
rotating on a horizontal shaft, and are charged with a grinding medium such as
42
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Inlet Impeller
OUTI.ET
Fan Blad.s
INLET Motor Shaft Stationary Head
7/ Skim!
Stationary
— Shredder Plates
Rotating
________ Shredder Plates
Rotor
Lu ricotion
Water Drain
Drive Motor
Lubrication
Lower B.oring
Gage
Figure 19. Disc—mill shredder.
She I I
Trunnion
Feed
Inlet
Drive Gear
Product
Outlet
Figure 20. Ball mill.
43
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steel balls. The size reduction is effected by tumbling of the balls on the
material. Both batch and continuous ball mills are available. In batch—type
mills, openings are provided through which the grinding medium and the pro-
cess material can be loaded and discharged. In continuous—type mills, mate-
rial is fed and discharged through hollow trunnions at opposite ends of the
mill.
A recent European development is the knife—type shredder, shown in
Figure 21. It has two shafts which rotate in opposite directions (towards the
center of the machine). The “knives t ’ are attached to the shafts in an
alternating, complementary configuration, with little space between the
knives. Each shaft is driven by a separate hydraulic motor at slow variable
speeds (0 to 40 revolutions per minute). The hydraulic motors are driven by
an electric motor and high pressure pump. The electric motor runs at a constant
speed in a constant direction; all variations in speed and direction of the
shafts are accomplished through the use of hydraulic fluids. Shredding is
accomplished through the following process: (1) the MSW enters the top of the
shredder, (2) it is directed to the center of the turning shafts, (3) is torn
apart by the knives as they rotate in opposite directions, and (4) the shredded
waste is discharged from the bottom. Other features available In this type
of shredder are hydraulic rams for force feeding and an ejection system for
unshreddables. The knife—type shredder has a blockage control system; where
too much resistance is met, the machine automatically reverses, releases
the jammed articles(s) and goes forward.
Knife Shaft
Motor
Top View
Sideview of Knife
Figure 21. Knife shredder.
44
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Experience : A survey 183 shows that there were over 50 installations
of solid waste shredders in the United States (listed in Appendix D i), They
are being used to process a variety of solid wastes including municipal,
industrial, commercial, oversize bulky wastes, institutional, wood, incinerator
residue, paper, sewage , railroad drainage and plastics. The shredded waste
is being used for landfill, incineration, energy recovery, pyrolysis, Eer—
rous separation, baling, and composting.
All of the waste—to—energy systems presently in operation or expected
to be operational by 1978• have at least one shredder in the system. The types
of shredders being used in these systems are given in Table 6. Details of :ii
shredders being used or planned in these systems are given in Appendix C,
Although a considerable number of shredders have been installed in the last
few years, there is as yet comparatively little published data on the
performance of shredders on IISW,
Performance data for some shredders operating on NSW have been
reported by Trezek el al, 193 Ruf, 163 Reinhardt et al., 151 Shannon et at ., 171
and analyzed by Anath et al. 13
Trezek’s study 193 was conducted with a comparatively small (9.1
metric tons per hour) horizontal haminermill, under controlled laboratory
conditions. The effects of moisture content, feed rate and rotor speeds on
size distribution and energy consumption were investigated. The data show
that increasing the moisture content and decreasing the speed produces a
coarser product. The energy consumption was found to be a parabolic function
of the moisture content and feed rate.
Ruf 163 reported shredding data collected at Gainesville, Florida,
experimental composting plant. The main objective of the project was to
determine maintenance requirements, equipment reliability and costs. Data
were collected on a primary shredder (horizontal—shaft harnmerinill, with a
capacity of 27.3 metric tons per hour) and a secondary shredder (horizontal
haminerinill with a capacity of 18.2 metric tons per hour). Bulky material
was removed prior to primary grinding, and ferrour metal was removed after
the first shredder, prior to secondary grinding. The principle operating
problem reported was plugging of the shredders, due to material jamming
between the rotor and the housing, causing the machine to brake to a halt.
Problems with dust, flying objects and noise were also encountered. The
dust contained a. considerable number of broad grouping of microorganisms,
and the atmosphere in the vicinity of the shredder was found to be a potential
hazard to the health of exposed personnel. Capital and operating costs were
reported but not considered to be representative because the plant was
operated only a portion of the day, administrative and supervisory Costs were
not included, and many modifications were made during the data collection
period.
45
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TABLE 6. SHREDDER TYPES USED iN WASTE—TO--ENERGY SYSTEMS
System
Shredder Type
Ames, Iowa
Baltimore, Maryland
Baltimore County, Maryland
Charleston, West Virginia
Chicago, Illinois
East Bridgewater, Massachusetts
El Cajon, California
Milwaukee, Wisconsin
Palmer Township, Pennsylvania
Pompano Beach, Florida
Riverside, California
St. Louis, Missouri
Southgate, California
Washington, D.C.
Horizontal hammermill (P,S)
Horizontal hazmnermill (P)
Horizontal hammermill (P)
Vertical hainmermill (P)
Horizontal haminermill (P)
Roller mill (s)
Flail mill (s)
Ball mill Cs)
Horizontal hammerntill (P)
Disc mill (s)
Horizontal harnmerrnill (P)
Vertical (5)
Unknown (P)
Unknown (s)
Vertical hammermill (P)
Horizontal hammermill (s)
Unknown (P)
Horizontal hammermill (P)
Horizontal haxnmerrnill (P)
Horizontal hanmtermill (P)
Vertical hairintermill (s)
P = Primary shredder.
S = Secondary shredder.
Reinhardt and Ham 151 reported on their study of shredded MSW at
Madison, Wisconsin, which was initiated in 1966. Two shredders, a 10 metric
tons per hour horizontal shaft hatnmertnill and a 136 metric tons per hour
vertical shaft hammermill, were evaluated under similar conditions. The
study showed that the energy consumption per ton of waste processed was less
for the vertical shaft haminermill than for the horizontal—shaft haimnerinill.
Some operational problenis were encountered with the vertical shaft unit,
including internal jamming, explosions, and trouble with the radial and
thrust bearings on the main shaft.
Hammer wear is the major maintenance problem in the shredding of MSW.
As the hammers wear, their effectiveness in shredding the waste decreases,
due to blunting the hammer tips and increased clearence between hanuners and
the housing and/or grates. When the hammers become worn they must be retipped.
After a number of retippings the entire hammer must be replaced. Some
manufactureres of hanimerinills offer reversible—action hammer rotors, so that
both sides of the hammers can be utilized before retipping, which increases
the amount of waste that can be processed before shutdown for repair of the
hammers. 46
-------
Savage and Trezek’ 64 measured hammer and grate bar wear in a hori-
zontal hammermjll. Both hard-faced and nonhard-faced hammers were used in
the study. Also, hard-surface welding material and base hammer material were
analyzed for their resistance to wear. It was found that (1) impact plays
an insignificant role compared to abrasive forces; (2) the incoming waste
should be fed uniformly across the rotor width to avoid localized hanniier wear;
(3) hard-faced hammers wear less than nonhard-.faced hammers; and (4) a reduc-
tion in hammer wear occurred at reduced rotor speed.
There is comparatively little definitive data on the wear of the shred-
ders in full-scale corrmercial plants. Furthermore, standard procedures for
measuring and evaluating wear are not being used in the industry. Each plant
operator decides on the schedule to be followed in retipping worn hammers.
Some operators retip the hammers every day, others every week, and some do
not retip at all, but simply change the hammers when they become badly worn.
The optimum procedures for retipping hammers based on performance and eco-
nomics have not been established.
gnetic Separators
Function : Magnetic separators are used to remove magnetic material, pri-
marily ferrous metals, from the mixed municipal solid waste. There are two
important reasons for removing the ferrous metals in waste—to—energy systems;
(1) to increase the heat content of the refuse derived fuel or feedstorck;
and (2) to recover a saleable product. There is approximately 8 percent fer—
fous metal In the incoming MSW (Smith, 1976), 78 so that its removal increases
the heating value of the recovered fuel or feedstock about 900 kilojoules
per kilogram. Futhermore, the removal of the metal reduces wear on subse-
quent processing and handling equipment and also reduces the amount of ash
when the fuel is burned.
There are presently four markets for ferrous metal recovered from MSW:
steel manufacture, detinning, copper mining, and ferroalioy production. A
list of solid waste processing facilities which recover or plan to recover
ferrous metals from MSW is given in Appendix D—2.
In all the waste—to—energy systems expected to be operational by 1978, the
MSW is shredded prior to magnetic separation. In most systems the magnetic
separator is located after the primary shredder. In some cases an air
classifier is used to remove the efr’rous metals from the shredded MSW along
with other heavy materials and a magnetic separator is used to separate the
ferrous metals from the heavy fraction.
Description: There are two basic types of magnetic separators used for
MSW—.-the belt—type and the drum—type.
47
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The principle of a simple belt—type magnetic separator is shown in Figure
22. The separator is usually positioned over the discharge end of the MSW
feed belt, as shown, The attraction of the magnet lifts the ferrous metal
out of the MSW, and the belt on the magnetic separator conveys the metal along
the magnet until it reaches the end of the magnetic field and drops into a
receiving bin. A more complex belt—type magnetic separator, devioped spe-
cifically for MSW is shown in Figure 23. This design was developed to
overcome the problems of entrapment of pieces of paper and plastic along
with the ferrous metal. This new design consists of three separate magnets
arranged in a “V ’ 1 shape, and hence referred to as the “hockey stick” design.
A rubber belt conveys the material from one magnet to the next; the first
magnet picks up the matérial from the mixed MSW. The material picked up
by the first magnet Is conveyed around the bend of the “V” to the second
magnet. The polarity of the second magnet Is reversed from the first magnet.
Passage around the bend and the reversal of polarity between magnets agitates
the adhering material and tends to release trapped nonmagnetics. After
passing over the second magnet, the material is momentarily released as it
passes over an air—gap between the second and third magnets. When an
attrachted tin can or other magnetic material reaches the air gat it falls
away, releasing the can and belt. The forward motion of the can carries it
frito the field of the last magnet, and It is pulled back up to the blet and
conveyed to the discharge area. The released nonniagnetic material is not
affected by the last magnetic field and falls away.
Belt
Mixed Wastes ( 7F
Metals
Feed Belt Non—Ferrous —o
Wastes 0
_______ : : : :
Figure 22. Principle of magnetic separation (belt type).
48
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Path of Attracted Steel
Path of Loose Nonmagrietics
Figure 23. Principle of “hockey stick” belt magnet.
The principle of a single drum—type magnetic separator is shown in Fig-
ure 24. The drum is preferable positioned over the head pulley of the belt
carrying the mixed MSW. A stationarY magnet is located inside the revolving
drum shell. The ferrous metal in the MSW is picked up by the magnet and is
conveyed around the drum circumfreflCe until it passes the magnetic field
and is discharged. The single drum magnet tends to entrap pelces of paper
arid plastics, just as the simple belt magnet does. To minimize this problem,
two drum magnets, with an intermediate belt conveyor are recommended as
Shown in Figure 25. The first drum is suspended above the end of the MSW feed
Conveyor and rotates in the direction of the material flow. The ferrous mate—
rial is picked up and tossed forward to the intermediate belt conveyor. Most
of the nonmagnetic materials falls to a take—away conveyor located below the
first drum. The second drum, which can be smaller than the first because of
less material flow, is positioned over the discharge end of the intermediate
Conveyor, and rotates in a direction opposite to the material flow to avoid
bridging or jamming. The ferrous metal is carried over the top of the
drum and released on a conveyor or bin on the far side.
Experience : There is as yet relatively little recorded experience with
magnetic separators operating on MSW. A prominent manufacturer of magnetic
Separators lists 24 solid waste magnet installations, with the earliest In
stalled in 1973. The five ste—to--energy systems, listed in Table 7, use
magnetic separators which affect the energy product. One of the first magnetic
separators used In a waste—to—energy system was the St. Louis demonstration
Plant in 1972 (parkhurst, 1976). The belt magnet unit was initially located
after the shredder However, after an air classifier was added to the system,
Recovered Steel
49
-------
the magnetic separator was relocated to the heavy fraction stream from the
air classifier. Therefore, in this system, the amount of magnetic metal
(and other nonburnables) in the P.DF was not affected by the magnetic separator
but by the air classifier.
Magnetic Drum
Ferrous Metal
Non—Magnetic Material
Figure 24. Principle of single drum magnetic separator.
Revolving Drums
Figure 25. Principle of dual—drum magnetic separatcu ,
Stationary
Magnet
Inside Revolving
Drum Shell
Shredder
Ferrous
Conveyor
0
0I
50
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TABLE 7. MAGNETIC SEPARATOR TYPES USED AT WASTE—TO—ENERGY SYSTEMS-
System Magnet Type
Ames, Iowa Belt
Baltimore County, Maryland Belt
Charleston, West Virginia Drum
East Bridgewater, Massachusetts Belt
El Cajon, California Drum
List includes only those systems in which the magnetic separator
affects the energy product stream.
Data on magnetic separators at the Ames plant show that the amount of
ferrous metal recovered during a 3—month period was 5.4, 5.9, and 6.6 percent,
respectively. 60 However, the efficienty of the recovery based on the amount
of ferrous metal in the raw MSW, and the purity of the recoverd metal frac-
tions were not reported.
The separation of magnetic metals has been performed at the East
Bridgewater plant, using a magnetic pulley and a suspended belt magnetic
separator. The only available information on the performance is that the
recovery rate is 6.8 percent and “this separator produces a magnetic fraction
that is adequately cleaned for the current market”. ’ 9
Although magnetic separators have been used for numerous industrial ap-
plications, their use on MSW presents some unusual problems. The amount of
ferrous metals in MSW is relatively high as compared with tramp metal removal
requirements from other industrial products. There is a tendency for nonmag-
netic materials, such as paper and plastic, to be entrapped with the ferrous
metal, thereby reducing the purity of the recovered metal product. Further-
more, the sharp edges on the ferrous metal tend to make the life of rubber
belts very short. Few people in the solid waste industry have expert knowl-
edge about magnetic separation equipment. Even fewer are knowledgeable about
magnetic theory as it applies to the separation of shredded NSW.
Until recently the designers of MSW processing plants had to use con-
ventional magnets, which were designed for unrelated industries. These mag-
nets were in the form of magnetic pulleys, magnetic drums or suspended box
magnets. They did not work well on shredded MSW because of the above unique
conditions. A design was needed for extraction and cleaning of a continuous
flow of fast moving steel buried in a comparatively deep burden of nonhomo-
51
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genous material. The challenge was approached in several ways by magnet de-
signers. The two principal designs recently developed specifically for MSW
are the dual drum design and the “hockey stick” belt magnets, described ear-
lier. There is as yet insuff:icient experience with either of these new mag-
nets to properly evaluate their performance and economics on shredded MSW.
Preliminary data indicate that they perform better than the early designs,
but more data are required before definitive conclustions can be drawn.
Air CiassLfiers
Function-—Air classifiers are used in waste—to—energy processing lines
to segregate the MSW stream into two fractions. One fraction consists of light
materials (paper, plastic, wood, dust, etc.); the other fraction is composed
of heavy materials (metals, glass, etc.). Air classification concentrates
the combustibles into the light fraction as a fuel product. Also, the metals
and glass can be separated from the heavy fraction and sold in secondary mar-
kets. Generally, the air classifier is placed after the magnetic separator
and before the secondary shredder.
Description——Air classifiers separate MSW relative to the particle size
and density. All of the classifiers use one of two types of air transport
to aid in the separation. A positive pressure air transport system has the
effect of pushing the MSW through the system. This is accomplished by attach-
ing a blower to the system and creating a higher pressure within the system
relative to the external environemtn. The other method, a negative pressure
air transport system, pulls the MSW. An exhaust fan is placed at the end of
the system,creating a. lower pressure within the system (the same effect as
a vacuum) .
There are five types of air classifiers: straight, zigzag, vibrating,
rotary drum and concentric tube.
MSW enters the straight air classifier, illustrated in Figure 26, at
the mid—section of a long, thin, vertical chamber. An airlock is used for
feeding, to aid in maintaining a controlled, metered flow of MSW, and prevents
any change in internal pressure which would adversely effect the performance
of the airflow. This type of air classifier uses an upward (negative) airflow
through the vertical chamger to effect separation. The separation occurs
because the light fraction follows the airflow upward and the heavy fraction
falls to the bottom.
MSW is fed into zig—zag classifiers, shown in Figure 27, at the mid-
section of the housing. There are step—like structures above and below the
inlet wfthin the housing. These classifiers use gravitational force and the
impact upon the sides of the classifier to minimize entrapped “lights.” The
separation is effectec by an upward negative airflow. The shape of the struc-
ture creates a swirling—air effect which enhances the separation. “Lights”
follow the airstream up and “heavies” fall.
52
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In Feed
Rotary Air Lock
Air
Lights
Heavies
Figure 2b. Principle of straight air classifier.
\
\
Rotary Air Lock
___ —— Air
_________ Heavies
Lights
Figure 27. Principle of zigzag air classifier.
53
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Vibrating air classifiers, illustrated in Figure 28, combine the gravita-..
tional, stratifying effect of vibration and the density classification intro-
duced by an airflow. The NSW is fed into the classifying chamber where it
remains in contact with a gradula sloping surface which vibrates along a 20—
40 degree axis. Air comes through the inlet, “heavy” discharge chute, and
the fluidizing air grids. The light infraction, moved to the top by vibration,
is carried by the airstrearn around the U—shaped curve and discharged upwards
while the heavy fraction is discharged at the bottom. 80
Lights Discharge
Heavies Discharge
Light Fraction
Heavy Fraction
Air
Figure 28. principle of vibrating air classifier.
The rotary air classifie , shown in Figure 29, has a drum which
is installed at an angle. The MSW is fed into the lower end of the drum
by a conveyor. The drum rotates, allowing entrapped light particles to
separate from the heavy fraction. A negative airflow is used to pull the
light fraction the length of the drum; the heavy fraction falls to the lover
end of the drum and out a discharge chute. The light fraction enters a
plenum where the air velocity decreases and the light fraction drops. Dust
follows the reduded airflow up the plenum. 69
In the concentric_tub e air classifier, shown in Figure 30, the MSW enters
at the top of the inner cylinder and hits a cone—shaped object used to agitate
and loosen the waste. The MSW then enters the outside cylinder where there
is an upward airflow. The light fraction follows the airstream, upward and
the heavy fraction drops.
\
\ — Vibrating
54
-------
Figure 29.
4
Air Flow
Conveyor
Heavy Discharge
Principle of rotary air classifier.
1
_____Air
Lights
_________ Heavies
Outer Wall
Figure 30. Principle of tube air classifier.
£
_________ Heavies
Dust
____ —— Lights
Plenum
Screw Discharge
1
55
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Air classification systems usually include some type of feeder, a fan
(with motor) and a cyclone separator, which is used to segregate the light
fraction from the airstream. Most systems use a negative airflow and rotary
airlocks (with motors), and some systems also use air filtering equipment
for dust collection.
Experie : Table 8 lists the types of air classifiers used in present
waste processing systems. Tests have been run on the straight air classi-
fier at st. Louis, with the findings as follows: 54
1. Over a period of 1 year an average of 80.6 percent of the raw refuse
was separated Into the light fraction.
2. The composition of the raw MSW and the light fraction was as follows:
Raw MSW Light Fraction Percent of Initial
( Percent by wt) ( Percent by wt) — Raw MSW
Paper 54.1 62.8 93.5
Plastic 4.5 7.8 86.0
Wood 3.2 2.7 67.9
Glass 4.2 2.9 557
Magnetic MetalS 6.2 0.2 2.6
Other MetalS 0.6 0.39 523
Organics 5.8 0.8 52.8
MiscellaneOus 21.4 22.4 84.4
3. The results of five particulate emission tests showed an average of
0.74 kilogramS per megagram.
4. There were significant bacteria and virus counts in the emissions.
At Ames, the moisture content of the MSW has had a negative effect on
the classifier’s performance. To counteract this, the airflow was adjusted
accordingtY Also, MSW entering the separation chamber was being thrown hori-
zontally with more force than originally intended. This was corrected by in-
stalling a baffle to divert the material downward.
55
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TABLE 8. AIR CLASSIFIER TYPES USED IN WASTE PROCESSING SYSTEMS
System Location Type of Air Classifier
Ames, Iowa Straight
Baltimore County, Maryland Concentric Tubes
Chicago, Illinois Vibrating
El Cajon, California Zigzag
Milwaukee, Wisconsin Zigzag
Pompano Beach, Florida Vibrating
St. Louis, Missouri Straight
Washington, D.C. Vibrating
Houston, Texas Rotary
New Orleans, Louisiana Vibrating
A vibrating air classifier has been installed and tested at Washington,
D.C., and vibrating air classifiers were installed at Chicago, Illinois, Pom-
pano Beach Florida, and New Orleans, Louisiana. The tests at Washington, D.C.
had several procedural inadequacies and were therefore not published. Manu-
facturers of this type of classifier claim the following: 80
1. There is less entrapment.
2. Airflow need is less.
3. Retention time of particles in the separator is greater.
4. There is less sensitivity to particle size, and separation is more
dependent on specific gravity.
Zigzag air classifiers have been tested In the laboratory at limited
scale by several firms. Stanford Research Institute conducted tests to de-
termine the usefulness of air classifiers in the solid waste field. 2 ’ The
tests using MSW were not useful for the purposes of this discussion because
the emphasis was on the separation of individual components (e.g., paper,
plastic, or metals) rather than on the effect of the process on the fuel
fraction.
57
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The El Cajon, California, and Milwaukee, Wisconsin, systems have zigzag
classifiers. At El Cajon, some problems have been experienced. The problems
involve the relationship of the airflow and classifier shape, which can cause
vortex currents. If the airflow is too great, the vortex effect will be too
great and separation will be impeded. The same result occurs if the airflow
is insufficient. Steps were taken to select the proper airflow relative to the
configuration of the classifier. No data are available at this time from El
Cajon or Milwaukee.
A concentric—tube type air classifier is being used at Baltimore County,
Maryland. There is a proprietary mechanism in this classifier which breaks
up chunks of MSW to improve the separation efficiency. This installation has
encountered problems due to back pressure from the cyclone.
A rotary drum air classifier was installed in Houston, Texas, and tests have
been conducted on a pilot unit. The tests encompassed effects of feed rate, drum
incline, air velocity, revolutions per minute of drum, and MSW characteris—
tics. 69
The manufacturers of rotary drum classifiers claim:
1. The classifier works best on MSW with a shred size of 10 to 30.5 centi—
meters.
2. Better separation is obtained with lower air velocities.
3. MSW remains in the separation zone for a longer period of time.
4. Rotating action eliminates entrapment.
5. There is less efficiency reduction due to feed surges.
6. When finer (than 10 to 30.5 centimeters) fuel stock is necessary,
secondary shredders will have to be installed after the air classifiers.
Generally, there are several performance questions which are common to
all air classifiers and which have not been adequately tested and reported
to date:
• Optimum airflow and air velocity.
Methods to eliminate unburnables from light fraction.
Methods to eliminate entrapment of lights with heavies.
Full scale performance data.
58
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Screens
Function : Screens are used to allow a system operator to extract material
within a particular size range from the NSW stream. Screens represent a type
of separation equipment, segregating the MSW by particle size only instead of
by density and particle size as the air classifier does. The position of a
screen in the process line varies tremendously; it could be the first piece
of equipment or be installed after the shredders or air classifier. For ex—
ample, a screen may be used to eliminate comparatively large particles (glass,
metals, etc.), before size reduction takes place, or it may be used to remove
fine material after primary and/or secondary shredding.
Description: There are three types of screens that may be used in MSW—
to—energy systems: Vibrating, rotary, and disc,
Vibrating screens are divided into gyrating and reciprocating . The separa-
tion accomplished through the use of screens is based on particle size. The
screens are equlped with openings of a certain size which allow particles
smaller than the opening to pass through. The motion serves three purposes:
(1) it allows more particles to come in contact with the screen surface; (2)
it minimizes entrapment of small particles; and (3) it aids in moving the
solid waste down the screen. The screens are generally set at an an le so
gravity can also assist in moving the MSW the length of the screen. 87
Gyrating screens , illustrated in figure 31, are equipped with a motor
at one end of the screen housing. The opposite end can pivot but does not
add any additional motion. The rotor has counterbalancing weights which cre—
ate an easy horizontal side—to—side motion.’ 87
Reciprocating screens can be vibrated two ways. In all cases the motion
is caused by a rotor, counterweight system. (1) The action can be along an
angle of 20 degrees to 45 degrees, as shown in Figure 32a. This type of motion
causes the entire housing, which is suspended on springs, to move along the
angle, and the particles leave the screen surface. Then the particles land,
and the housing returns to the original position, thereby moving the parti-
cles forward. (2) The action is a rocking motion, end—to—end, in which the
screen Is on an incline and the housing Is on springs. As illustrated in Fig-
ure 32b, the housing deps at one end while rising at the other in an alter-
nate fashion, creating the rocking action. Both of these actions occur under
much higher speeds that gyrating screens. Generally, the screen surfaces in
all vibrating screeners are made of nylon or wire mesh.
The rotary (trommel) screen, illustrated In Figure 33, looks like a long
metal cylinder with holes punched in it. There is a motor at one end which
rotates the drum. The length and diameter of the drum have a direct relation-
ship to the efficiency of the trommel. The longer the drum, the longer the
59
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MSW will remain in contact with the screen. And, the greater the diameter,
the more effective the trommel will be in breaking up large objects, such
as trash bags. Also, the rate of rotation plays a role in the trammel’s sep—
aration efficiency.
Rotor.
Housing
— -‘
Bouncing Ball Screen Cleaner
Figure 31. Gyrating screen.
Bed
Screen
A disc screen, as illustrated in Figure 34, has a series of discs at—
tached to small—diameter cylinders in parallel configuration. The discs from
each alternating cyliner complement each other, and as the cylinders rotate,
objects of small size pass through the length of the screen.
Action of Material on Screen Surface
60
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Counterweights
End View—Rocking Type
(b)
Screen
Spring
Direction of Action
Figure 32. ReciprocatIng vibrating screens.
Direction of
Housing
Side View— Horizontal Vibrating Type
(a)
Screen
Spring
61
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c5 00000 p(JU
)QQQQQ 0 00
0000 00 00
00000000000
000 0000000 0 0O0 0000 00 00C
(
D000 000 0000
0000rQ000 000 000000000 OO
000 0L-OOO0O00O00OOOO0OQ- C
) Qp 0O0i p0C000O0OOOOOO J
Side View
Screen Surface
Figure 33. Rotary (trommel) screen.
)
C
C
D
)
D
)l
Motor
End View
62
-------
U
I
-
r—
Top View
Figure 34. DIsc screen.
63
Side View
Cy’inders Discs
SI
-------
Experience : Table 9 lists the types of screens used at various waste
processing plants. Vibrating screens have previously been used extensively
in the food processing industry. Their application in MSW processing is for
fine screening, with screen openings as small as 0.0035 centimeters. This
variety of screen can have several layers of screen surfaces to separate the
MSW into several particle size groupings. F{owever, the reciprocating motion
is very jerky and the MSW actually leaves the screen surface, which could
create housekeeping problems and less efficient separation. The screen wear
is significant, and there is a large amount of associated vibration affect-
ing the structure and other connected equipment. 187
TABLE 9. TYPES OF SCREENS AT WASTE PROCESSING PLANTS
Location Type of Screen
East Bridgewater, Massachusetts Trormitel and gyrating
El Cajon, California Gyrating
Washington, D.C. Trommel
Houston, Texas Tromrnel
New Orleans, Louisiana Trotiuiiel
Toronto, Canada Trommel
Pompano Beach, Florida Trommel.
Ames, Iowa Trommel
El Cajon, California Trommel
Palmer Township, Pensylvannia Trommel
In gyrating motion screens, the material never leaves the surface of
the screen, so that the retention time is longer and separation is Improved.
As the material travels down the gyrating screen its path changes, thereby
increasing particle agitation and improving separation efficiency. The bed
in this type of screen is thin, increasing the chances of the particle passing
through the screen.’ 87
64
-------
Gyrating screens often come equipped with bouncing balls to prevent
blockage of the scrEen. Manufacturers have made laboratory tests with this
type of screen using MSW, but the results have not been made available. A
gyrating screen is installed at El Cajon, California, and at East Bridgewater
Massachusetts. However, to date there has been no performance data from these
installations.
Rotary (trommel) screens have been used in the mineral industry for many
years for coarse screening. Trominels have been installed or planned at East
Bridgewater, Massachusetts; Palmer Township, Pennsylvania; Pompano Beach,
Florida; and New Orleans, Louisiana. Several installations also use trommels
in their nonferrous metals recovery systems (e.g., Ames, Iowa and El Cajon).
NCRR, TVA, Continental Can, Vista Chemical Company, and Warren Springs
Lab (in England) have been investigating the use of trommels as a first sep-
aration operation prior to shredding (called pretrommeling). NCRR, in its
tests on the trommel screen 212 used a 2.7 metric diameter, 3 meter long trommel
with adjustable slope of 0 to 7 degrees, 10.2 centimeter square openings in
wire cloth (75 percent of surface is open) and 10 lifters (implements along the
inside of the trommel which increase the retention time). They report the fol-
lowing findings:
1. An increase to 14 lifters increase capacity significantly.
2. From 12 trials of materials passing through the trammel, the mean
was:
a. 64 percent of magnetic metals in MSW pass through trommel.
b. 75 percent aluminum metals in MSW pass through trommel.
c. 96.6 percent glass in MSW pass through trommel.
3. The neces•aary retention time is 25 to 30 seconds.
4. The capacity was 13.6 megagrams per hour.
5. Blinding was not a problem, but cloth was caught by the wire screen-
ing.
6. Nearly all garbage bags were opened.
7. A 55 to 64 megagrams per hour unit should:
a. Be 12.2 meters long
65
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b. Use punch plate instead of wire screen
C. Have 12.1 centimeter diameter holes, and
d. Use a 3.2 meter diameter drum.
8. Cost savings for a system using pretrornmeling are estimated to be 8.5
percent.
Some feel pretrommeling is desireable because the recoverables are in
a better form for marketing, the wear on downstream equipment should be less,
and energy consumption should be decreased. More testing and data are needed
to substantiate the claims.
Disc screens have been used in the forest products industry to separate
ice chunks from wood chips. Tests have been conducted for the separation of
glass, having a nominal size of 15.2 centimeters and less, from shredded waste.
Results were favorable although actual data were not disclosed. Shredded over-
sized bulky waste was also tested (including mattresses) and no disruption
of operations occurred. The manufacturers suggest that disc screens by used
after primary shredding and before secondary shredding. To date, this type
of screen is not known to have been installed at any MSW processing plant.
Function: In waste—to—energy systems, dryers are primarily used to reudce
the moisture content of the MSW, thereby increasing its Btu value. Moisture
reduction abs results in imporved storability, possibly imporved air classi-
fication, a d possibly reduction of bacteria and virus. Generally, the dryer
is Installed just before or just after the air classifier.
p !o ——There are two types of dryers used In waste—to—energy sys-
tems: rotary dryers and fluid—bed dryers.
A rotaty drying system, shown in Figure 35, includes (1) a blower to
circulate the heat, and effect the MSW evacuation, (2) a combustion chamger
to generate the heat using RDF, (3) a rotary drum which has a variable speed
motor, and (4) a cyclone separator which separates the MSW from the alrstream.
The MSE inlet Is located directly in front of the rotary drum. The waste and
hot airstream flow through the drum in multipe stages, generally passing
the length of the drum three times before exiting to the cyclone separator.
The drum rotates constantly, agitating the waste and permitting greater sur-
face area to be exposed to the heat.
66
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To Cyclone
blower
Chamber
Drier
Motor
Figure 35. Rotary dryer
-------
A fluid—bed dryer , as depicted in Figure 36, consists of a jet heat source
which furnishes hot gas, and a bed material to which the heat is transferred.
The agitation, caused by energy waves set up by the jet heat source, increases
the heat trasnfer to the bed. The bed heats the drier chamber and the 14 5W
enters the chamber at the side. Also, a blower is used to transport the heat
and the MSW, and a cyclone is used to separate the MSW from the airstream.
Experience : The El Cajon, California processing plant has a rotary dryer,
and other designers are investigating the possibilities of using a dryer in
their respective systems. The idea behind drying Is to reduce the amount of
unburnables (i.e., water) in the MSW product. To justify the incorporation
of drying in the system, the cost of the equipment must be balanced by the eco-
nomic value of the end product. Some manufacturers feel that the only way to
make dryers attractive Is to make sure that the combustion chambers are fired
by the RDF, thus reducing energy costs.
It is possible that the drying process can kill bacteria and virus, but
there are no data to support this theory.
Performance data on two rotary dryers and a fluidized—bed dryer are pre-
sented in the following table. The two rotary dryers are (1) a 12.2 meter
long by 3 meters diameter dryer used at El Cajori, California, and (2) a 4.6
meter long by 20.3 centimeter diameter rotary dryer used in a 1972 test. 64
A fluldized—bed dryer was also tested during the 1972 research.
Rotary Rotary Fluidized
12.2 siX 4.6m X 20.3cm Bed
Feed rate (Mg/hr) 6.7 0.05 0.45
Inlet T (°c) 107 201 146
Outlet T 6 62 6 --
Heat consumptiOn (kj/tng) 1.24 x 10 1.27 x 10 --
Moisture level (7 ) 3.5 5 35
As shown in the table, there is a temperature advantage (146°c to 201 0C)
for the fluidized bed dryer compared to the second rotary dryer. This is due
to the more efficient heat transfer through the bed medium.
There are several questions concerning dryer performance Ofl HSW which
shauld be research.
1. Can the dryers kill harmful bacteria and virus in MSW?
2. Does drying improve the efficiency of air classjfjcatjon?
3. What are the emissions from the dryers?
4. What are the costs and benefits of installing a dryer?
68
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Exhaust
‘0
Propane
Dried
Sotid Waste
Solid Waste Feed
Bed Material
(Date Pits)
Drive Mechan,sm
Figure 36. Fluid—bed solid waste dryer.
-------
Densifiers
Funuction : The basic purpose for the densifier is a MSW—to—energY system is
to enchance the storability and/or transportability of the fuel. Also, these is
an increase in energy value per unit volume. Densifiers are located at the end
of the process line, before the storage and retrieval system. Densification
allows more MSW fuel (by weight) to be stored in the same volume.
Description : There are five pieces of equipment which can be used to
densify MSW: pelletizerS, briquetters, cubetters, extruderS, and compactors.
Each piece of equipment mentioned applies force to reduce comparatively large
volumes of MSW into smaller volumes.
PelletizerS , shown in Figure 37, are constructed in a cylindrical
shape. The cylinder has holes in it to act as a die. The MSW is fed into the
chamber, usually using a screw feeder, and two rotating rollers within the
cylinder force the material through the die. Blades surrounding the exter-
ior of the die—cylinder are used to cut the pellets to size.
Figure 37. Pellet mill (roller and die section).
70
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A briquette is formed by forcing the material into a mold. Generally,
this is accomplished by passing the MSW between two rollers, on which
individual molds of various sizes are mounted.
For cubing , the MSW Is forced through square dies by rollers
Extruding is the process of feeding the MSW Into a cylinder of substan-
tial size, then forcing the waste through a cylinder of much small size,
resulting In a long tube of MSW being discharged from the cylinder.
Compactors are used primarily to compress RDF Into transport trucks.
The RDF is fed into a large chamber, the chamger feed—door Is closed securely;
a rain In the end of the chamber moves forward via hydraulic motors and com-
pacts the refuse into a fraction of its original volume. A compactor is 11—
lustrated in Figure 38.
Feed
Ram
—
Exit Door
Hydraulic Motor
Figure 38. Compactor.
Experience: Table 10 lists types of densifiers used at present and plan-
ned waste— 9—energy systems. NCRR has done some preliminary studies on densi—
fIcation. 1 ’ They looked at pelletizing, briquetting, cubing and extrusion.
Two other firms have investigated pelletizing. 47
71
-------
TABLE 10. TYPES OF DENSIFIERS USED AT WASTE—TO-ENERGY SYSTEMS
Location Type
Baltimore County, Maryland
Compactor
and pellet mill.
Chicago, Illinois
Compactor
Milwaukee, Wisconsin
Compactor
St. Louis, Missouri
Compactor
Washington, D.C.
Pellet mU
1
Some sources indicate that densification of MSW cannot be accomplishec
without the us of binders. However, at least one firm has successfully made
pellets wihout a binder by controlling temperature and pressure. A pelletizer
has the effect of a grinder in two ways: (1) the roller and die are in con-
tact, and wear against each other, and (2) the mill reduces the particle size.
Therefore, steps must be taken to minimize the size reduction of the MSW and
the resulting wear on the pellet mill.
The following table shows some limited data on pellets made by Elo and
Rhodes 47 by an industrial firm that preferred not to have its name used.
Elo and Rhodes Industrial
Pellet 1 Pellet 2
Size 6 mm x 25.4 mm Variable
Density 481.2 kg/ms — —
Kilojoule/kilogram 15,319 18,103
Percent of moisture —— 6
Percent of ash 18.2
Percent of non
combustibles in ash 99.6
Btu/kilogram of ash 66
There is interest in briquetting as a future densifying process, but
there are some problems. The low density of MSW makes briquetting difficult.
It will probably be necessary to use a binder and have a compara j small
shred size (under 6 millimeters). However, this adds a great deal of ex-
pense. Due to feeding problems of MSW through briquetters, the capital costs—
to—capacity ratio is quite high. It would be necessary to increase capacity
(cost remaining the same) to make briquetting attractive.
72
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There are many questions to be answered concerning densification, which
include:
1. Need for binders.
2. Particle size requirements.
3. Composition effects.
4. Moisture effects.
5. Storability and transportability.
6. Costs versus benefit.
Compactors are installed at St. Louis, Missouri, Baltimore County,
Maryland, and Milwaukee, Wisconsin. They were installed to improve transpor-
tability of processed RDF to the boilers where it is to be used. No perfor-
mance data are available.
Receiving Facilities
Function: The purposes of receiving facilities at resource recovery plants
is to: (1) receive the raw MSW from the packer trucks or other delivery ye—
hides. (2), temporarily store the MSW, (3) remove undesirable materials, and
(4) feed the MSW into the processing system.
Description: The incoming delivery trucks with their loads of MSW are
weighed on platform scales, which are usually built into the outside road-
way or the floor of the receiving building. The scale platform may be large
enough to accomodate the entire truck, or each axel may be weighed separately
and totaled. The tare (empty weight) of the truck is subtracted from the total
weight to obtain the net weight of the MSW. The weight data are recorded
either manually or automatically, depending on the sophistication of the
scale.
After being weighted, the truck is drived to the receiving area where
the waste is dumped. The MSW receiving area may be either the floor of the
building or large pits into which the waste is dumped. In most plants, con-
ventional rubber—tired wheel loaders are used to push the waste from the main
pile into the feed conveyor which is rece—sed into the floor of the receiv-
ing area. In one plant, the receiving pits are equipped with hydraulic rams
which push the waste onto the conveyors. Prior to feeding the MSW onto the
Conveyor, any materials which cannot be processed are manually removed. Typ-
ical layouts of receiving facilitys are shown in Figures 39,40, and 41.
73
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Figure 39. Layout of a solid waste receiving
facility with floor pad receiving area.
Truck Entrance
Feed
Conveyor
System
Elevati r g
Conveyor
Figure 40.
Recessed Conveyor
=
=
Receiving
Pit
-
Trucks
-
-
Discharge
Conveyor
Layout of a receiving facility with receiving pit.
Receiving Pad
Truck Entrance
Trench with Conveyor
Feeder in Bcotom
Elevating Conveyor
Shredder
I I I I I I I I I
74
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scu esr f
Figure 41.
Push—pit receiving facility.
Experience : There have been many years of experience in weighing refuse
trucks, associated with landfills and incinerators. As a consequence there
are no known significant problems with truck scales for waste—to—energy sys-
tems. The system designer and user need only decide on the type and special
features desired, elected a reliable manufacturer, and see that the unit is
properly installed, operated, and maintained.
There are some important unanswered questions about the receiving area.
It is presently not known whether it is best to use: (1) receiving pads or
pits, and (2) wheel loaders or hydraulic rams. Alos, the optimum design of
the receiving area and building from the standpoint of efficient truck traf —
fic, air pollution, and noise levels has not been well established.
Conveyors
Functiofl ConveyOrs are used as a transportation system between unit
operations. They do not add to the refinement process but allow refinement
to be accomplished in a smooth, continuous process line.
I
75
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Description : There are four basic types of conveyors used in MSW plants:
belt, flight, vibrating, and pneumatic.
Belt conveyors are constructed of several piys of various materials (rub-
ber, nylon) similar to a tire. Idler rollers are used to guide the belt. The
idlers can be set at an angle to create a trough. Due to the high revolutions
per minute ratings of motors used to drive conveyors, speed reduction equip-
ment must be supplies. The motor drive is connected to a pulley which actu-
ally moves the belt using the forces of friction and the torque created by
the motor.
There are several varieties of conveyors which can be included under
the heading of flight conveyors , which is a general category including those
conveyors which have “pocket” implements (e. g. buckets, pans, etc.). Pan
(apron) conveyors, are frequently used as initial feeder in MSW proces—
sing operations. The pans overlap to prevent leakage. Leakage can also be
prevented by using a piano hinge conveyor. Flight conveyors are made of steel
and the drive mechanism is generally a chain and sprocket.
Vibrating conveyors operate on a stroke principle similar to reciprocat-
ing vibrating screens, described earlier. The stroke action can range from
a fraction of an inch to several inches. The force acts on an angle (20 degrees
to 45 degrees) relative to the horizontal plane. The material actually leaves
the surface and lands at a forward point. This type of conveyor is often
used to accomplish even feeding into a piece of equipment (e.g., air classifier).
Pneumatic conveyors run on the same negative/positive pressure principles
as air classifiers, described earlier. Negative pressure pneumatic conveyors
are often used to transport RDF to storage bins and boilers. Negative systems
are usually best suited for transporting materials from multiple sites to
one site, with a rotary airlock necessary to accomplish discharge. Positive
pre—sure systems are usually utilized to transport from one locale to multiple
locales. Negative airflow systems have fewer leakage problems, since all the
leakds are inward. It is easier to unload trucks with a vacuum System and
when the air—to—particle ratio is greater. Air transport Systems need strict
velocity and airflow controls. Also, they consume more energy than mechanical
conveyors 65,205
Experience : In assessing experience with conveyors, several points must
be carefully considered:
1. Cleanliness
2. Metering capabilities
3. Jamming
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4. Effects of MSW characteristics
Table ii lists the types of conveyors used in waste—to--energy systems.
TABLE 11. TYPES OF CONVEYORS USED AT WASTE-TO-ENERGY-SySTEMS
Ames, Iowa Flight, pneumatic, vibrating
Baltimore, Maryland Flight
Baltimore County, Maryland Flight, belt
Charleston, West Virginia Belt
Chicago, illinois Flight, belt, pneumatic
El Cajon, California Flight, belt
Milwaukee, Wisconsin Apron
Riverside, California Vibrating, belt
St. Louis, Missouri Belt, vibrating, flight
Southgate, California Belt, flight
Washington, D.C. Pneumatic, belt
Pneumatic conveyors are used at St. Louis, Missouri; Ames, Iowa; and at
Chicago, Illinois. At Ames, pluggage has occurred due to the moisture content
and matting characteristics of MSW. The plugs were removed using “sewer jets.”
Also, the conveyor liners have worn out at the elbows; the worn areas become
rough and catch light material as it passes. These liners are being replaced
with more resistant material which retains its smooth surface longer. Addi-
tionally, the airflow had to be increased due to uneven feeding into the trans—
port system.
Flight conveyors are used for transporting raw or shredded MSW. They are
used at Ames, Iowa; Baltimore, Maryland; Chicago, Illinois; El Cajon,
California; and Milwaukee, Wisconsin. As mentioned before, cleanliness can be
accomplished with Z—pan, piano hinge, or overlapping pan constructions. Some
MSW can still spill over the sides, but flight conveyors can be built fairly
wide, with skirts and dribble pans. The flights have a high degree of impact
resistance, fire will not damage them, and maintenance is negligible.
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Either inboard or outboard rollers can be used. Outboard rollers allow
the weight to be distributed over a greater area and thereby permit larger
loads to be conveyed. Maintenance is also easier. The rollers generally wear
out faster than the chain and, with outboard rollers, the roller can be re-
placed without removing the chain.
Jamming of flight conveyors has been experienced at several facilities.
Often the disruption was caused by problems with a down—line piece of equip-
ment (e.g., rejects from the shredder). In systems where two angles are needed,
manufacturers have found it better to use two conveyors. The first should have
the lesser angle. The second (steeper angle) should be run at a higher speed.
This relieves the jatmuing effect caused by material slippage when one conveyor
is used. Problems of under powering have also caused slippage and jamming.
Manufacturers are specifying greater power requirements to solve this problem.
Manufacturers state that angles up to 40 degrees can be used without creating
a slippage problem, if flights are installed.
Belt conveyors are used for shredded material at Chicago, Illinois; Ames,
Iowa; Riverside, California; and St. Louis, Missouri. Belt Conveyors have
a cleanliness problem. Slide—backs occur on inclines and the idlers cause
unwanted agitation and spillage problems. Skirts and dribble pans can be in-
stalled to help the situation. Belt conveyors are prone to damage from im-
pacts of objects falling on the belt.
Vibrating conveyors are frequently used for transporting MSW between unit
operations. They even—out the.material and, for this reason, are used often for
feeding unit operations (i.e., shredders and air classifiers). The vibration
can cause structural problems along the process line, as well as housekeeping
problems. Designers are having some problems in accurately sizing vibrating
conveyors, for MSW.
Storage and Retrieval Bins
Function : Storage and retrieval bin8 allow a waste—to—energy plant to
process large quantities of fuel and then allow the fuel to be transported
when needed. Using such a system, RDF can be processed in a single 8—hour
shift and burned for electrical generation on a 24—hour basis.
Description : Construction and design differences In storage and retrieval
bins involve the shape of the structure and the method of discharge.
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A conical “sweeD bucket” bin 18 depicted in Figure 42. The RDF enters at the
top and falls to the bin floor. The waste is transported to the bin via a
pneumatic conveyor (with cyclone separator) or a flight conveyor. This in-
take operation is the same for most of the storage systems discussed. A “sweep
bucket” arrang nent is used for retrieval purposes. The end of the chain of
buckets is attached to a powered ring. This allows the buckets to rotate about
the pile of RDF. The buckets at the end n igrate toward the center., fill and
drag the waste through a discharge chute Onto a conveyor. The speed of the
chain is adjustable to allow control over the feed rate. The RDF is usually
pneumatically transported to the next operation.
Figure 42. Conical “sweep bucket” bin.
Two other types of discharge systems could be paired with a conical-
shaped bin or cylindrical silo. They both use screws. The first (Figure 43a)
has the screw running the diameter of a suspended silo. The screw pivots at
one end and follows a rail which is in an arc configuration on the opposite
end. The waste exits from the end where the screw pitch is greatest. The sec-
ond (Figure 43b) has the screw attached to a post in the center. The other
end is connected to a motor which rims along a track at the outer perimeter.
Discharge is from an opening at the center of the bin.
Sad. V w
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Track
Conveyor
Figure 43. Two discharge methods used with silos.
(a)
(b)
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An inverted bin , shown in Figure 44, consists of inward sloping walls
(4 degrees to 7 degrees), with the bottom of the bin wider than the top. This
design is to help prevent bridging (see Figure 45a) of the MSW. There are
three types of retrieval mechanisms that have been used with this type of
bin: (1) a series of parallel feed screws with variable pitch and speed, (2)
a pair of feed screws which rotate in the opposite direction and travel the
length of the bin on an exterior track (Figure 44), and (3) a series of rol-
lers which run on individual motors, enabling the operator to vary the speed
of each roller (Figure 46). The discharge with the screws is at the end with
the greater pitch; for the rollers, it is through the bin bottom.
A ‘ doffing roll” bin is shown in Figure 47. The screws located in the
upper portion of the bin are used to even the pile of MSW as it enters. A
drag chain system in the bin floor is used to push the RDF into a group of
rotating teeth. The speed of the drag chain can be manipulated to control
the evacuation rate. The teeth have a fluffing effect making the waste more
uniform and more easily transported.
S r.w
S . v;.w
Figure 44. Inverted bin with dual travelling screw discharge.
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Air Pocket
MSW “Dead Spot”
Constant Pitch Screw
Figure 45. Flow problems encountered in MSW storage and retrieval.
(a)
Flowing MSW
(b)
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L
iop View
— —
Figure 46. Inverted bin with rollers
A
Motors
83
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I
lop View
7
1
/
/
Figure 47. Rectangular bin with screws and doffing rolls.
Screw
Doffing Rolls
Side View
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The live—center bin, shown in Figure 48, is constructed so the width
at the bottom is much smaller than at the top. There are a series of verti-
cal screws used to even—out the incoming RDF and to keep it loose. Two
screws in the bottom are used for discharge. The speed can be regulated to
control the rate of discharge.
Bin with vertical and horizontal discharge screws.
Experience: Table 12 lists the types of storage and retrieval systems
in use or planned.
TABLE 12. TYPES OF STORAGE AND RETRIEVAL BINS AT WASTE-TO-ENERGY SYSTEMS
Location
Bin Type
Discharge Type
Ames, Iowa
Conical
Sweep-bucket
Baltimore, Maryland
Conical
Sweep-bucket
Chicago, Illinois
Conical
Sweep-bucket
El Cajon, California
Rectangular
Scews and doffing
rolls
Riverside, California
Inverted
Rolls
St. Louis, Missouri
Inverted
Dual screws
side Vew
Figure 48.
End View
-------
At St. Louis, Missouri, an inverted bin with screw discharge was used.
Results have been termed as satisfactory. Some bridging occurred, but it was
not considered significant. The walls at the bottom of the bin started bulg-
ing, due to the “avalanche” effect of the collapsing MSW. The problem was
corrected by adding stiffeners to the outer wall surfaces. Also, the origi-
nal motor was not large enough, and the screws were unable to turn, due to
the high frictional forces of the material. A larger torque motor solved
this problem. 54
Riverside, California, plans to use an inverted bin with roller bottom
discharge. The designer claims that all the bin structure is useful storage
space; controlled feeding is easily accomplished; the inward sloping walls
prevent bridging; the power usage is minimal; and the motors used supply
greater torque action. Presently, no performance data are available.
The “doffing roller” bin is used at El Cajon, California, as a small
(1—hour) storage bin. However, performance data are not yet available on
this type of bin.
Manufacturers of the vertical/horizontal screw bin claim that this mech-
anism will prevent bridging, will even and mix the contents of the bin, and
that no concrete foundation is necessary. The vertical screws must rotate
when the bin is being charged or discharged. However, no performance data are
available l44
The pitch of the screw in all screw discharge mechanisms has a direct
effect on a discharge performance. Using a constant—pitched screw, “dead”
spots (Figure 45b) will occur. There will be a freer flow using variable—
pitched screws. 9 °
There Is a need for more data concerning bridging, compaction, even/con-
trollable retrieval, moisture effects for MSW storage and retrieval bins.
Dust Controls
Function : The function of a dust control system is to minimize the re-
lease into the atmosphere of dust created by MSW processing. Dust comes from
two basic sources: the raw MSW itself (ash, fines, fibrous material, etc.) and
the dry refinement processes (shredding, air classification, etc.).
DescriptiO Three types of equipment are used in waste—to—energy plants
for dust control: cyclone separators, bag—houses, and wet systems.
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Figure 49 depicts a ç lone separator and its internal actions. The dust—
laden air enters near the top of the inverted cone vessel. The air spirals
down the vessel and returns to the outlet (at the top) in the reverse manner.
This creates centrifugal forces which power the particles to the outside of
the vessel. Gravity then causes the dust to fall. The particular cyclone shown
has a “stack” to deflect any dust remaining in the outlet airstream. Cyclone
efficiency is dependent on airflow, velocity, pressure, the diameter and the
length of the cone.
Stack
— — - C eon Air
— Dirty Air
Figure 49.
Principle of a cyclone separator.
are a series of cloth filters aligned in a housing. The struc-
ture may be either circular, as shown in Figure 50, or rectangular, as shown
in Figure 51. The dust laden air enters the housing near the bottom, where
heavy particles fall out immediately. The air then flows upward and passes
through the filter bags, with dust adhering to the outsides of the stream
jetted in the reverse direction through the bags. The air—to—cloth ratio has
a significant effect on the efficiencY of the device. Both cyclones and bag—
houses are operated by negative or positive—pressure air transport systems.
One type of wet du co ol is a scrubber dust collector, which is il-
lustrated in Figure 52. The dust—laden air enters at the top portion of a
long cylinder. The inlet is tapered, with an adjustable device to control
Dust
87
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Cleaning Mechanism
Exit
D sr Laden Ar
______ Air
- Dust
Figure 50. Circular Baghouse.
88
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Pump Far Bag
C’eaning
a-Dust
Dust Fafling
Rotary Ar Lock
Figure 51. Rectangular Baghouse
89
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Irde
Mechansm
—— C eon Air
Dtjst
Dirty Water Discharge
Figure 52. Wet scrubber dust collector.
90
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air velocity, located at the end. Liquid is injected near the top of the
vessel in a fine mist, which collects the dust particles. The dust—laden mist
and the air are forced to the outer portions of the vessel by a rotating mech-
anism which creates a centrifugal air pattern within the cylinder. At the
bottom of the cylinder, a concentric tube extends several centimerts into
the vessel. The air leaves via the inner tube and the dusty water leaves by
the outer cylinder. Another MSW wet dust control is to moisten the waste suf-
ficiently to prevent a dust problem; e.g., by inserting water sprays in the
harnmermill.
Exper1ence Table 13 lists the types of dust control systems at the var —
ious waste—to—energy facilities. The St. Louis, Missouri, pilot plan is an
outdoor operation, and the dust problem has not been obvious. However, it
has been found that there is a significant amount of particulate emissions
from the processing equipment. At Ames, Iowa, the system is housed in a build-
ing, and the dust problem is significant.
TABLE 13. DUST CONTROLS AT WASTE-TO-ENERGY SYSTEMS
Location Type
Baltimore, Maryland Cyclones
Baltimore County, Maryland Baghouse
Chicago, Illinois Bag filter
East Bridgewater, Massachusetts Bag filter
El Cajon, California Wet system
Pompano Beach, Florida Cyclones and
Bag-house
St. Louis, Missouri Cyclones
2ai.mer Townshij , Pennsylvania Closed system
Bag—houses are used at the Baltimore County, Chicago, and East Bridgewater
plants. East Bridgewater has the bag—house connected to all unit operations,
and the plant is equipped with a grounding rod to prevent any adverse effects
from static charges. All of these bag houses use reverse airstreams to allow
cleaning of the bags without shutting down the entire system. Presently, how-
ever, there is no performance data available.
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Bag filters are reported to have a high efficiency, although there are
no supporting data available for MSW. It is known that the efficiency is af-
fected by the shape of the bag. The top—load type of bag—house reduces main-
tenance time involved in changing damaged bags, while side—door types do not
allow total accessibility to the bags.
The wet—jet dust control concept may be effective but ti requires a dry-
ing system to insure that the energy value of the fuel is not adversely af-
fected. Water sprays might also have adverse effects on the equipment (e.g.,
corrosion) and its function (e.g., separation efficiency in an air classifier)
El Cajon uses such a system, employing water sprays over the primary shredder
discharge conveyor. Data on the efficiency of these wet dust control systems
are not available. To date, no waste—to—energy system has installed a wet
scribber on the processing equipment.
Electrical Controls
Function : Electrical controls refer to the electrical system through
which the various pieces of equipment——shredders, conveyors, etc.——are con-
trolled.
Description : Thus far, the information obtained concerning electrical
controls is sketchy and Incomplete. More detailed information must be col-
lected before specific data on electrical control systems at municipal solid
waste—to—tnergy plants can be developed.
Discussions with MSW plant designers indicate that the electrical control
systems are custom designed installations for each plant and vary widely in
degree of sophistication. Those designers who have taken a minimal approach
rely on simple, more manual types of instrumentation and control. Other plants,
such as Baltimore County, Maryland, have highly automated control systems.
Closed circuit television is used in some instances to monitor operations
that are not readily accessible or are dangerous for personnel. Two-way ra-
dio communication systems are also being utilized. At some plants, visual
monitoring of the refuse flow is done from a glass-enclosed control booth
where the operator has a good view of the unloading activities and other parts
of the plant.
Baltimore County, Maryland , has a control system which uses a computer
for testing and control functions. The system was developed by the plant designer.
Data from various pieces of equipment (e.g., weight from scales, amps from
shredders) are fed into the computer; such data can be recalled from the data
banks at any time. The computer system has built—in safety ranges for various
parameters for the different pieces of equipment. If trouble arises, the “fault”
indicator light on the control panel will indicate the particular piece of
equipment which is malfunctioning. The computer will also activate shutdown
procedures.
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00 L 0 D. p ii 0 0 --
______ 0’
E II 0 2
0 0 0 LI Dth0
00000000 ____
SI ..4d ., po
LLL L ‘ ) ____ ___
Flu. Akno G ppI . Cn... f0p .. .ien . f W I., I,c.I .. s .. .,
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LE6U O [ J t3 LiIØ.t ( ) .‘ ... D. .w Id
Figure 53. Baltimore County, Maryland, control panel.
At the Charleston, West Virginia , plant a minimal approach has been taken
in regard to controls and instrumentation. Also, there have been numerous ad-
ditions and modifications to the original electrical equipment. Most of the
monitoring devices consist of rather simple, direct visual read—out informa-
tion.
A small control panel, shown in Figure 53, is in front of each operator
and rotates with the booth. The upper portion of the panel has indicator
lights showing the operational condition of the equipment listed. The lower
left portion has the push pit controls; the bottom center and bottom left
are controls for the input conveyor and shredder. These two pieces of equip-
ment can be controlled manually or automatically. A key lock can be activated
so the system is not mistakenly started (e.g., during repairs). The center
of the panel has indicator lights for fire and operating mode, buttons to
activate emergency equipment, and buttons to start and stop the grappling
crane. This crane, used to remove unshreddables from the input stream, is
controlled by the operators (via levers on the side of the control panel)
the transfer bridge controllers in the receiving area. The rest of the plant
is monitored by closed circuit television. 16
rt 4 k
_____ I I I .1 1 j I I I
a___ _____ ____ ______
a
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At El Cajon , the front—end equipment is in the receiving building. The
operator watches the receiving floor, shredder, and storage area from an air—
conditioned, glass—enclosed cubical located above the floor level. From this
control booth, the operator can control the conveyors and the shredder. The
operator also has a read—out on his control panel from the scale where in-
coming trucks are weighed. The operator signals the driver to proceed or to
stay at the scale area until he is released to go into the plant.
There are three separate motor control centers at the El Cajon installa-
tion. The primary shredder operates on 2.300 volts There is a separate motor
control center for the shredder. This motor control center, specified as “NEMA
Class E-2 Medium voltage,” is in a separate prefabricated metal building void
of any combustible gas. Except for the primary shredder and one gas compressor
operating in 2,300 volts, most of the rest of the plant operates on 400 volts.
The designer of the City of Baltimore, Maryland , installation considers
much of the information on the control system proprietary. The electrical
control system is their own design. Closed circuit television cameras are
used to monitor some operations, like shredders and other areas that are dan-
gerous and not readily accessible.
The various trouble indicators in the control system include:
•Indicators to tell whether a shaft is turning.
•Motor amperage regulators.
•Level indicators of various kinds.
•Pressure indicators that measure vacuum or pressure to activate relays.
The primary speed is controlled by the amperage on the primary shredder.
The designer’s opinion is that the amperage controller “feels” the refuse
stream better than the operator can. The operator has an override, and if
there is a problem he can manually effect a stop.
Fire and Explosion Protection
Background : MRI has learned of several incidents of explosions and fires
in municipal solid waste plants. In addition, all of the shredder manufacturers
contacted had expressed concern over the possibility of explosions occurring
when mixed municipal waste enters the shredder.
The research conducted to date indicates that fires in the shredding
phase of the system are the rule rather than the exception. The existence
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Also, the larger pieces qf metal, which stay in the shredder longer,
sometimes become red hot. When the hot metal falls into the shredded mate-
rial, a smoldering type of fire can easily develop. One opinion expressed
by a plant designer was that the small smoldering type of fire is usually
handled best by simply locating the source of fire, pulling It out and spray-
ing it with a water hose.
An additional consideration in regard to fire hazard is that many of
the conveyors are of rubber construction. There have been instances of con-
veyor belts catching fire. There have also been reports of fires in other
areas besides the shredder area; e.g., in the motor starter control rooms.
Solid waste shredding plants are vulnerable to explosions because of
the presence in the refuse stream of such items as gasoline cans, propane
tanks, dynamite, TNT, gunpowder, and live ordinance. Another possible source
of shredder explosions is hybrid dust/gas mixtures.
In assessing explosions and explosion protection, it is important to
differentiate between deflagrations and detonations. The overpressurization
in a deflagration occurs over a time interval on the order of 0.1 to 1.0 sec-
onds in a typical-sized shredder--the burning takes place at a flame speed
below the velocity of sound. The local overpressurization in a detonation
occurs instantaneously via shockwave--the burning takes place at a flame speed
above the velocity of sound in the unburned medium.
Most protective measures, discussed later in this section, are effec-
tive for deflagrations but cannot provide much protection for detonations.
The major protection measures for detonations are blast-resistant construc-
tion and the isolation of personnel and expensive equipment.
The exact conditions under which a dust explosion will occur in a ref-
use shredder are apparently not known. However, when dust particles are small
enough to be classified as powder (particle size less than 1 millimeter),
a spark, hot spot, or other ignition source can ignite the dust cloud. Dust
explosion hazard appears to be minimal for those shredders that are deliver-
ing a product of at least a few centimeters in size.
Although the risk factor appears low for dust explosions in the shredder
itself, dust does represent a hazard in other parts of the plant. Dust/shred-
ded refuse fires have occurred on conveyors and in dry, dust-collecting de-
vices where the fine particles are separated from the coarser particles. Also,
dust explosions would be more likely in size reduction operations where a
fine powder refuse-derived fuel is being produced.
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Hybrid mixtures should be considered particularly hazardous. When combusti-
ble dust and flammable gas or vapor are present at the same time in the shred-
der they can be explosive. Unfortunately, even small quantities of gas can
combine with an accumulation of fine, combustible dust to form an explosible,
hybrid mixture.
Description: The following fire and explosion measures and damage con—
trol techniques are being employed, either singly or in various combinations,
at waste—to—energy plants:
1. Manual screening and segretation of incoming refuse.
2. Isolation of personnel (especially near shredder).
3. Barricades or blast mats near the shredder (to protect personnel and
valuable equipment from penetration by fragments from explosions.)
4. Explosion venting.
5. Continuous water spray (in the shredder)
6. Automatic water sprinklers for conveyors.
7. Automatic water sprinklers for building.
8. Water hoses.
9. Explosion suppression systems.
10. Fire suppression systems.
11. Dust control systems.
In addition to the above measures, the following have been suggested as
some additional protection techniques.
1. In plants where the control room is close to the shredder, high—
strength glass or plastic (>3 psig fracture pressure) in control room windows.
2. An emergency water spray system which would inject water into the
shredder before ignition, which would be activated by a flammable gas detec-
tor installed in the shredder.
3. If steam is generated at the plant, the steam can be injected into
the shredder instead of a water spray.
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4. Dry powder extinguishing agents, such as those presently utilized
in suppression systems in Germany.
Some of these protection meansures are described in the following sec-
tions.
Screening and Segregation of Incoming Refuse : Some plant designers stress
maximum front-end separation to divert hazardous materials. The presorting
of incoming municipal waste is handled in several ways. In some cases, the
individuals making pickups on the route are instructed not to load anything
onto the truck that appears to be a dangerous material. Generally, when trucks
arrive at the plant, they dump onto an unloading floor. The man operating
the front-end loader is instructed to look for and segregate any hazardous
items. The operator in the control room, through visual inspection of the
incoming material on the conveyor as it moves to the shredder, also tries
to sort out hazardous items.
However, due to the wide assortment of hazardous items and the large
shredding stream capacities involved, it is virtually impossible to completely
eliminate all hazardous material from entering the shredders.
Explosion Venting : Explosion venting refers to vent doors, blow off
hatches, rupture discs, etc., on the equipment or building containing the
explosion. The basic principle of explosion venting is that the maximum pres-
sure developed in a deflagration can be reduced if the gases are allowed to
escape from the confining structure before the combustion process is complete.
To be effective, the vent area and its location in respect to the ignition
source must be designed to allow the gases to escape before damaging pressure
develops. In addition, the ducting used to channel the gases out of the build-
ing must be designed to prevent the recompression of gases on the way out.
Large discrepancies exist between the venting recommendations of the
various designers and manufacturers. There is a need for explosion venting
tests so that more accurate guidelines can be developed for equipment as com-
plicated in shape and content as a refuse shredder.
Continuous Water Spray in Shredder : A continuous water spray is used
in some refuse and automobile shredders to control dust. A fine water spray
or mist has also been found to provide explosion protection. The water vapor
in the shredder serves as an inerting agent. A vapor concentration of about
30 volume percent or higher will extinguish or prevent a methane-air flame.
In addition the suspended water droplets are effective as a quenching medium
for flame. Small, closely-spaced drops are more effective than large droplets
in quenching flame.
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However, the use of continuous water spray in the shredder has several
undesirable side—effects. When water is absorbed by the Shredded refuse, mag-
netic separation of ferrous metals is more difficult; the combustion eff 1—
ciency and heating value of the shredded refuse Is lowered; and water can
cause corrosion in the shredder.
Explosion Suppression System : Explosion suppression systems are report-
edly effective for gas and dust explosions. These systems operate on the prein—
ise that there is a delayed (measured in milliseconds) betweei ignition and
the build up of destructive pressure. If a suitable extinguishing agent is
injected quickly enough after ignition, the explosion can be prevented.
Several different types of explosion detection devices, including ultra-
violet, infrared, thermal and pressure, can be used to activate the suppre—
sion system. In practice, these detection devices activate extinguishing agents
(which are stored in pressurized containers) through explosive discharge.
Explosion suppression system extinguishing agents most commonly used in
the United States are the halogenated hydrocarbons (halons). Chemical ex-
tinguishing powders such as ammonium phosphate and sodium bicarbonate are
favored in Germany.
Although experience with explosion suppression has been limited at MSW
plants, the number of damaging explosions in automobile fragmentizers has
reportedly been reduced considerable after installing and properly maintain-
ing suppression systems.
Explosion suppression systems have reportedly been installed at several
MSW Installalons, including the following:
Baltimore (City), Maryland
Baltimore County, Maryland
Elmira, New York
Milwaukee, Wisconsin
East Chicago, Illinois
City of Hempstead, New York
Experieflç The Factory Mutual Research Corporation (FRMC) of Norwood
Massachusetts, published the resu of a survey they conducted to sess
refuse shredder explosion hazard.
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Data acquired in the survey were from MSW processing plants where ref-
use was shredded for fuel preparation, materials recovery, incineration, or
landfill. Included in the survey were the three most common types of refuse
shredders; horizontal-shaft harnmermills, vertical hanimermills and grinders.
The FMRC survey revealed that refuse shredder explosions are a widespread
problem at municipal solid waste shredding plants--of the 45 MSW shredding
plants included in the survey, 34 (or 76 percent) have experienced at least
one explosion. A total of 97 explosions were documented in which some damage
occurred, or which required special explosion protection measures to avoid
damage. One plant experienced 14 explosions in a 3-year period.
The conclusions reached by FMRC as a result of their survey include the
following:
I. Shredder explosions are numerous, but the damage and injury potential
is usually limited, due to the structural integrity of the shredder.
2. Only 3 of the 97 explosions documented resulted in personal injury
and those three involved personnel in the immediate vicinity of the shred-
der.
3. Only five of the reported explosions resulted in more than $25,000
property damage or caused the shredder to be shut down for more than a week.
Plant damage was usually to peripheral equipment such as conveyors or ducts,
which are not as sturdy as shredders.
4. Of the 41 expLosions surveyed where a probable cause could be identi-
fied, 30 incidents (73 percent) were caused by common flammable gases ,or va-
pors--gasoline, propane, paint, thinner. Commercial or military explosives
such as dynamite or gunpowder were responsible for 11 (27 percent) of the
explosions. Combustible dust and hybrid dust/gas mixtures were possible sources
of some of the other explosions.
5. Protection measures that can reduce the frequency and severity of
explosions include: manual screening of incoming refuse; continuous water
spray within the shredder (effective against flammable vapor and dust explo-
sions as well as fires); explosion venting, when properly designed; pressure-
activated explosion suppression systems using Halon 1011 agent, when pressure
transducers are carefully maintained to prevent dirt accumulation; and dry
powder extinguishing agent (effective against dust explosions).
6. Explosion venting in most of the existing shredders is inefficient.
Vents on shredders are often too small, and too remote from the ignition loca-
tion or too heavy to relieve overpressure. Vent ducts for venting gas out
of the shredder building are often missing or not adequate to prevent recoin-
pression of the gases. Some plants have modified their vents after the first
explosions in order to improve the venting configurations.
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The following summarizes the information collected on fire and explo-
sion experiences and protection provided in the processing areas at waste—
to—energy plants.
The Ames, Iowa plant has experiences one shredder explosion and one fire
to date. The explosion, caused by shortgun shells, was very small and damage
was minimal. The first was started by gasoline; again damage was not appre-
ciable. A water spray system and venting are the two preventive measures in-
stalled.
Since staring operation, the Baltimore, Maryland , plant has experiences
one shredder explosion, one conveyor fire, and one fire in the storage bin.
The shredder explosion appeared to be a detonation type of explosion and could
have been caused by dynamite. No one was hurt, but a day’s work was lost due
to repairs needed on the ducts and housing. The conveyor fire was quenched
by the sprinkler system and there was no damage. The storage bin fire started
spontaneously and the fire department was called to extinguish the fire.
The following protection methods and equipment are employed at the Bal-
timore City plant, according to information furnished by the designer. There
is a sprinkler system in the receiving building and sprinkler systems for
all conveyors. A “dry” system is used——water lines are dry to prevent freez-
ing in winter. Should a fire occur, sensors would activate springlers to im-
mediately flood the entire system with water. Each of the two shredders are
housed in individual buildings so that an explosion In one shredder will not
effect the other shredder. Personnel are not allowed in these buildings when
the shredders are operating. Both shredders have explosion supppressjon systems
and relief ducts. The roof is vented to help eliminate dust.
The Eco_Fuel®II produced at the East Bridgewater, Massachusetts , plant
holds the potential for explosion problems due to its fine dust—like char-
acter. However, specific data on explosions at this plant are not available.
East Bridgewater has a completely sprinkled building (water). Much of
the quipment has explosion relief doors. There is a dust control system with
pick up points on all the major equipment that generate dust, and there is
also a vacuum cleaning system for maintenance. The filters are located out-
side the building, and the equipment and filter bags are grounded to control
build—up of static electricity.
The designer advised that the 1,000 horsepower shredder at the El Cajon
plant will not have an explosiOnSuPPressiofl system due to the high cost.
There will be an opportunity to segregate such things as oxygen bottles and
gasoline cans prior to shredding.
The shredder has an explosion relief in the top of the shredder housing and the
feed housing. Just above the shredder housing is an explosion panel through
the roof of the building. 100
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Normal fire protection, including hose reels, is provided for the smol-
dering type of fire. Due to the speed of the conveyor, the operator would
not have time to extinguish a fire on the conveyor. The material moves rap-
idly and is deposited onto the storage pile before the operator could use
water to quell the fire while it is on the conveyor. In this instance, should
the material start to smolder in the storage pile, the storage pile would
by sprayed with a fire hose.
Emergency water sprays operated automatically by temperature control,
are provided in the dryer and in the cyclone that collects the dried organic
material. Explosion relief is provided in the cyclone duct work in the event
of a dust explosion.
The building construction complies with the National Fire Underwriters
Building Code.
At the Palmer Township plant, there is a large explosion relief chamber
in the primary shredder, according to the designer. A deluge sprinkler sys-
tem in the shredder is a National Board of Fire Underwriters system that has
been adapted for this use. There are two ways to activate it--manually from
the control booth or by a temperature-activated device within the shredder.
The building has a sprinkler system. Dust is not a problem, according
to the designer, since this is a “closed system.” A pneumatic system is used
to move the material after it leaves the primary shredder. The system is to-
tally enclosed, with the air being recirculated, so no air will be exhausted.
As discussed in the systems section, the shredder facility at Pompano
Beach, Florida , has been in operation for several years. This facility will
be used in the methane conversion system. Therefore, the explosion and two
fires experienced at the facility are of interest. The shredder explosion
caused little damage to the shredder (the shredder is vented), but caused
the destruction of 30.5 meters of conveyor. The fire was quenched with por-
table fire extinguishers. The cause of the explosion was determined to be
some paint thinner cans. Small munitions have reportedly gone through the
shredder with no effect.
Two conveyor fires were caused by (1) sparks from welding equipment and
(2) the motor overheating. The sprinker system was not effective in extin—
quishing these fires; a regular waterhose has been installed to correct this
problem. 215
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The St. Louis, Missouri, plant had a shredder explosion and several
fires. The explosion was at the shredder feeder; the cause was not deter-
mined. The only damage was that the windows of the control room were shat-
tered. Four fires included: (1) an overheated electric motor which caused
extensive damage due to a mistakenly closed sprinkler valve, (2) an air
classifier fan, (3) a conveyor belt fire, and (4) a fire in the metal re-
jects chute from the shredder. The last three fires caused little damage,
but had to be quenched with hand fire extinguishers because the fires were
too small to trigger the sprinkler system. 215
ECONOMICS
The data for the study of the economics of processing equipment for
waste—to—energy systems were collected by methods similar to those used for
the preceding state—of—the—art discussions. First, a literature search was
conducted of all available reports and documents dealing with waste—to—energy
systems. This search was followed by contacts with equipment manufacturers,
personnel at the processing facilities and system designers.
The literature search provided little, if any, meaningful information
for comparative economic evaluation. The accounting practices and reporting
categories varied widely, making it nearly impossible to assemble costs for
comparison purposes. Moreover, the cost information that was presented was
in terms of overall systems costs, rather than individual equipment costs.
For example, the total size of the crew needed to operate a particular facil-
ity was frequently given, but with no indication as to the percent of the
crew’s time devoted to an individual piece of equipment.
The cost data presented for many of the systems were often preliminary
engineering estimates, leading to questions of the validity of the data and
the’ resultant comparative analyses. The weaknesses of these preliminary es-
timates are exemplified by two cases. The first of these is the scale of the
facility. Frequently, the costs, for example, of a 45.4 metric tons per day
demonstration plant are merely extrapolated forward for a 1,818.2 metric tons
per day conwaercial plant. Clearly, this sort of estimation procedure is in-
adequate in an area where economies of scale are undeveloped, and the econo-
mics as a whole have not been investigated. Similarly, many of the existing
facilities, although full-scale operations, are operating considerably below
capacity. The result is that the fixed elements of the Cost are distributed
over a smaller amount of municipal solid waste, distorting the true economic
picture.
The responses by manufacturers to questions Concetnjng economics further
expressed the lack of good economic data on MSW processing equipment. In gen-
eral, the information obtained from manufacturers was limited to capital costs,
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equipment, all major operating and maintenance costs, quality of the product,
and the relationships to other equipment in the system. All of these vari-
ables relate to total overall cost of the system, but the relationship is
particularly significant for the latter two——quality of output and relation-
ship to other equipment. Two examples of this relationship are: does shred-
ding of MSW to a relatively small size significantly reduce the operation time
and wear on other equipment, thus lowering the total operating cost of the
system? 21 2) will the addition of pretromnieling reduce the total cost of the
system.
The need to develop reliable information for all of these economic var —
iables is basic for any type of meaningful comparison or evaluations of equip-
ment. Likewise, knowledge of the trade—offs between technical performance and
cost of the various equipment is an essential input in the development of a
waste—to—energy system. These needs were echoed by virtually all of the manu-
facturers and designers contacted in this phase of the study, indicating that
the state of the art of economics relating to MSW processing equipment is pres-
ently properly developed.
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SECTION 4
RESEARCH NEEDS
INTRODUCTION
The preceeding section on the state of the art of waste—to—energy process-
ing has not only described the developments in the industry to date, but has
also pointed out, both directly and indirectly, those areas where further re-
search is needed. The deliniatiOn of those needs, based upon an understanding
of the state of the art, has been a significant focus of this study.
Each of the research needs presented is discussed in the following
format: (1) a background review, which summarizes the state of the art relevant
to the specific item; (2) a statement of the jectiy ( 2 to be met in address-
ing the research need; and (3) a suggested pproach or approaches to address
the research need.
In developing this section of the report, no attempt has been made to
establish priorities for addressing the research needs, and the order of presen-
tation is not intended to suggest relative importance. The needs are categorized
for ease of reference, into: (1) general research needs; (2) research needs
relative to particular types of equipment; (3) fire and explosion protection
and (4) economic research needs. A listing of specific needs by these
categories is presented in Table 14.
Some of these research needs have been undertaken in Phase II of this
contract and other EPA sponsored contracts, as noted. However, many of
these research needs remain.
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TABLE 14. LIST OF RESEARCR NEEDS, BY CATEGORY
General
1. Determine Optimal Arrangements(s) of Unit Processing Equipment.
2. Study Emissions from Processing Equipment.
3. Determine pertinent MSW Characteristics.
4. Evaluate Potentially Applicable Equipment.
Shredders
5. Compare the Performance of Various Types of Shredders.
6. Determine Maintenance Requirements of MSW Shredders.
7. Determine Optimal }Iammer Design(s) for MSW Hammermills.
8. Establish Shred Size Requirements.
9. Evaluate the Cost Effectiveness of Signie Versus Multiple Shredders.
Magnetic Separato S
10. Compare Performance of Filet and Drum Magnets.
Air Classifiers
U. Determine the Optimal Operating Conditions for Air Classifiers.
12. Cornpare the Performance of Difference Types of Air Classifiers.
Screens
13. Compare the Performance of Coarse Screens.
14. Compare the Performance of Fine Screens.
15. Determine the Effects of Pretroinmeling.
Dryers
16. Determine the Effect of Drying on Bacteria and Virus.
17. Evaluate the Effect of Drying on Efficiency of Air Classification.
18. Evaluate the Effect of Drying on the Storability of RDF.
19. Evaluate the Effect of Drying on the Cornbusion Characteristics of RDF.
Densifiers
20. Determine the Optimal Operating Conditions for Dengifiers.
21. Determine the Specifications for Densif led RDF.
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TMLE 14, (continued)
Conveyo rs
22. Determine the Optimal Operating Conditions for Vibrating and Pneumatic
Conveyors.
23. Compare the Performance of ConveyorS.
24. Compare the Air Transport Systems.
Storage and Retrieval
25. Compare the Performance of Various Storage and Retrieval Systems.
Receiving Facilities
26. Evaluate Receiving Facilities.
27. Evaluate MSW Segregation Prior to Processing.
Controls
28. Characterize Present Control Systems
29. Determine the Effectiveness of Present Control Systems.
Fire Explosion and Protection
30. Study the Incidence of Fires in MSW Processing Plants.
31. Determine Fire Resistance Characteristics of MSW Processing
Equipment.
32. Determine the Effectiveness of Fire Protection Systems in
MSW Plants.
33. Study the Incidence of Explosions in MSW Plants.
34. Determine the Effectiveness of Explosion Protection Systems in
MSW Plants.
35. Evaluate Spillage and Dust Controls.
Economics
36. Develop Effective Accounting Method(s).
37. EstabliSh Capital Costs of Processing Equipment.
38. Determine Economic Life of Processing Equipment.
39. Determine Equipment Operating and Maintenance Costs.
40. Perform Cost Effectiveness Analysis!
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GENERAL RESEARCH NEEDS
Research Need No. 1 — Determine Optimal Arrangement (s)
of Unit Processing Equipment
Background
There is considerable variation in the arrangement of the unit process-
ing equipment (shredders, magnetic separators, air classifiers, etc.) in the
present and planned waste—to—energy processing systems. To some extent the
individual unit equipment and its arrangement depend on the particular fuel
or fuel feedstock product being produced. However, even where the same pro-
duct is produced, there are presently variations in the processing equipment
and its arrangement. For example, both the Ames, Iowa, plant and the Chicago,
Illinois, plant produce the same product——RDF for use as supplementary fuel.
Although both systems start with a primary shredder, from there on the se-
quence of operations is different. In the Ames plant the sequence of operations
after primary shredding are magnetic Separation, secondary shredding, and air
classification, whereas in the Chicago plant, the operations after primary
shredding are air classification and secondary shredding. Even greater differ-
ences in the arrangement of unit equipment exist in the various plants prepar-
ing fuel feedstocks. It is apparent that a study of optimal arrangement(s) of
unit processing equipment is required.
Objective
The purpose of this research is to determine the effect of various ar—
angement(s) of unit processing equipment for producing refuse—derived fuels
or feedstocks.
Approach
The first step is to determine the rationale used by the system designers
to establish the present unit equipment arrangements at the various facilities.
Preliminary discussions with representative system designers indicate that In
most cases there were good reasons for the selections and arrangements. How-
ever, in some cases,the selection was based primarily on the fact that similar
equipment in similar arrangement was used at another plant(s). Even where
individual reasoning had been used; in most cases the proof of these judgements
has yet to be established on the basis of actual plant performance and cost
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data are required. Field test data should be collected on different systems
which are producing the same product, such as RDF. The data should include:
(1) the amount of product produced versus the amount of MSW processed; (2)
the quality of the product, including the shred size distribution, the amount
of nonburnables, the heat content, and the moisture content; (3) the total energy
consumed by the system; and (4) production costs.
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Research Need No. 2 — Study Emissions from MSW Processing Equipment*
Background
There Is a lack of data on the emissions from MSW processing plants. The
only reported data on waste—to—energy processing plants are some tests conducted
at the St. Louis demonstraction plant. These tests showed that there was a
significant amount of particulate emissions from the air classifier discharge,
and there were comparatively high noise levels in the plant (Shannon, et al.,
May 1975). Additional tests were conduted at the St. Louis Plant to determine
the amount and types of bacteria and virus in the air emissions from the plant.
Tests conducted on a MSW compost plant showed “extremely high and potentially
dangerous concentrations” of particulates emitted from the shredding operation
(Ruf, 1974).
It is apparent that additional waste processing equipment tests are re-
quired. Also the microorganism content of. waste—derived fuels and fuel feed—
stocks should be investigated to determine whether special handling of these
products is required.
Objective
The objective of this research is to collect and analyze the emissions
from waste processing plants. An allied objective Is to investigate the micro-
organism content of refuse—derived fuels and feedstocks.
Approach
Tests should be conducted at representative waste processing plants to
collect data necessary to evaluate the effluents (air, water, solid, and noise)
from these plants. The program should include: (1) a study of emissions from
unit equipment; (2) evaluation of the influence of operating parameters on
emissions; (3) evaluation of emission control techniques; (4) a thorough analy-
sis of the environmental impacts of waste—to—energy plants. The effluents should
be analyzed for composition; trace elements; particulate loading and size; bac-
teria and virus content; BOD, COD, ph, and leachates. In addition, samples of
the MSW stream should be taken throughout the systems and analyzed for poten-
tially hazardous materials Including bacteria and virus.
* This research need has been partially fulfilled under EPA Contract Nos.
68—02—2166 and 68—13—2387.
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Research Need No. 3 — Determine Pertinent MSW Characteristics
Background
To properly select and operate equipment to process NSW into a fuel or
feedstock, it is necessary L;o know the characteristics of the MSW. Although
some studies of the composition of MSW have been made, a number of characters-
istics which are important to processing are not known.
Some of the characteristics of the waste which are important from the stand-
point of processing equipment are bulk density, composition, moisture content,
size distribution, flow characteristics, component densities, abrasives, mirco—
organisms, compaction, and storage characteristics.
Objective
The purpose of this research is to determine the characteristics of MSW
which are important from the standpoint of processing equipment.
App roach
First, a complete list of the characteristics of MSW that are important
trom a processing standpoint should be formulated. Then representative samples of
NSW should be taken throughout the entire process stream, before and after each
process, and analyzed for each characteristic. Data should be taken at various
locations around the country, and over the four seasons of the year. A suE f i-
cient number of samples should be taken so that the results are statistically
reliable.
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Research Need No. 4 — Evaluate Potentially Applicable Processing Equipment
Background
There is a tendency in any industry, including the comparatively new re-
source recovery industry, to use the same or similar equipment used In a pre-
vious plant(s). It Is natural and logical in designing a new plant to specify
a piece of equipment that has been used successfully in a previous plant. How-
ever, this tends to minimize the use of new equipment or equipment not pre-
viously used in the industry, which may be superior to those normally used.
A considerable amount of equipment has not yet been evaluated for waste—
to—energy systems. For example, the 1976 Thomas Register lists 115 manufactures
of shredders, 403 manufactures of belt conveyors, 99 manufactures of flight
conveyors, and 117 manufactures of pneumatic conveyors. Relatively, only a
small number of potentially applicable equipment has been evaluated for waste—
processing systems to date. Furthermore, new equipment, such as the knife
shredder and discs screens, have been developed which should be evaluated for
MSW applications.
Objective
To evaluate processing equipment which may be applicable to resource re-
covery systems, which have not yet been evaluated.
Approach
The first step in this research should be to survey equipment which may
be applicable to waste-to-energy systems and which has not yet been evaluated.
A list of the most promising equipment should then be formulated and arrange-
ments made to test this equipment.
New equipment should first be tested in an MSW test facility. Facilities
to test MSW processing equipment exist in Washington, D.C. (NCRR), Berkeley,
California (University of California), and Toronto, Canada. If the Initial
tests are promising the equipment should be evaluated in appropriate full—
scale resource recovery systems.
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SHREDDER RESEARCH NEEDS
Research Need No. 5 — Compare Performance of Various
Types of Shredders
Background
A variety of shredders are being used in waste processing systems, includ-
ing horizontal and vertical shaft hammermills, flail mills, ball mills, ring
grinders, and disc grinders. In many cases, different types of shredders are
being used for the same purpose. It is not clear whether one type is superior
to another for processing MSW. The advantage, disadvantages and limitations
of each type of shredder have not yet been firmly established. In—plant opera-
tional data are required which will show the performance characteristics of
each type of shredder operating under similar conditions, so that shredder
selection can be based on direct comparisons.
Obj ective
To provide comparative performance data on various types of shredders.
Approach
The types of shredders to be investigated should include horizontal hammer—
mills, vertical hammermills, flail mills, ball mills, ring grinders, and disc
grinders. The shredders should be evaluated for both primary and/or secondary
shredding of MSW. The operating conditions should be as similar as possible
so that the results can be compared. The data to be collected should include:
(1) amount of energy required per ton of waste shredded; (2) production rates;
(3) size analysis of the shredded waste; (4) noise levels near the shredder;
(5) weat characteristics; (6) capital and operating costs; (7) downtime and
reasons for stoppages; (8) fires and explosions; (9) dust and spillage; and
(10) ancillary equipment requirements.
The tests should be conducted at full—scale MSW plants operating under
normal conditions. The various types of shredders presently installed or
planned in waste—to—energy systems are given in Table 6, Section 3. It would
be useful to collect data from as many of these and other plants shredding MSW
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(listed In appendix D l) as possible to provide a significant data base from
which firm conclusions can be drawn,
* This research need is presently being partially fulfilled under EPA Con—
tract No. 68—02—2586.
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Research Need No. 6 — Determine Maintenance Requirements of MSW Shredders*
Background
The maintenance of shredders used to process MSW is a serious problem.
Experience has shown that the internal parts of hanirnermills, particularly the
hammers, wear rapidly when processing MSW. In many cases the hammers must be
retipped every day. Other parts, such as the breaker plates and grates, also
are subject to wear. The exact cause(s) of shredder wear has (have) not been
fully investigated, although it is known that MSW contains highly abrasive ma-
terials such as glass, hard metals and dirt, which adversely affect shredder
components.
Retipping the hammers by welding is a common practice. However, the opti-
mum procedures for retipping, including the proper time to retip, the best
welding material, manual versus automatic welding, and the optimum time to
repace the entire hammer have not beenfirmly established. Furthermore, the
proper procedures for maintenance of othe r types of MSW shredders have also
riot been established.
Objective
The objective of this research is to establish the proper maintenance
procedure for hammermills and other types of shredders used for MSW.
App roach
The proper maintenance procedures for shredders should be established on
the basis of experience in full scale MSW processing plants. The maintenance
procedures employed at representative plants should be recorded along with the
performance of the equipment. These data should be analyzed to determine the
effects of various procedures on shredder performance and costs. In particu-
lar, data should be collected on the procedures and materials used in retipping
haminermills, replacement of complete hammers, maintenance of other hammermull
parts, and the maintenance of other types of shredders.
The various types of shredders presently installed or planned in waste—
to—energy systems are given in Table 6, Section 3. It would be useful to
collect data from as many of these plants and other plants shredding MSW
(Appendix Dl) as possible to provide a significant data base upon which firm
conclusions can be drawn.
* This research need is being partially fulfilled under EPA Contract No.
68—03—2589.
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Research Need No. 7 — Determine Optimal Hammer Design(s) for MSW Hanunermills*
Background
There are a variety of hammer designs used in hammermills, The shape of
the hammers can be blunt-edged, sharp-edged, round-edged, multiple-edged, bell—
shaped, double-edged or four-edged and other variations. Furthermore, the nurn—
ber and arrangement of the hammers on the rotors can be varied. There is little
or no published Information on the advantages and/or disadvantages of various
hammer designs for shredding MSW. Some small-scale laboratory work has been
done, but no full—scale field test data have been reported.
Obj ective
The objective of this research is to provide field test data showing the
effect of various hammer designs on hammermill performance.
Approach
At least one horizontal—shaft hammermjll and one vertical—shaft hammer—
mill in a waste processing plant should be equipped with a variety of hammer
designs, and the effects of each design on MSW shredder performance should be
determined. The hammer designs should include various shapes, numbers of ham-
mers and arrangements of hammers on the rotor. The shredder performance to be
determined should include the shred size, throughput capacity, energy require-
ments, hammer wear, and other pertinent observations.
* This research need is being partially fulfilled under EPA Contract No.
68—03—2589.
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Research Need No. 8 — Establish Shred Size Requirements
Background
One of the most important specifications for an MSW shredder is the re-
quired output particle size. The required output particle size is dependent
upon the application of the waste—derived fuel or fuel feedstock. At the
present time, shred size requirements vary from about 10 centimeters for some
pyrolysis reactors down to 0.15 millimeter for “Eco—Fuel.” The nominal
particle size for suspension firing of RDF is about 2.5 centimeter. However,
the optimal shred size for the various applications has not been firmly estab-
lished. Furthermore, the effects of gradations within the “nominal” particle
size are as yet unknown.
Obj ective
The purpose of this research is to establish the optimum particle sizes
for the various applications of waste—derived fuel and fuel feedstock.
Approach
The first task that should be undertaken is to determine what tests have
been conducted to date to establish the particle size requirements for the
various applications of waste—derived fuels and fuel feedstocks. The major
developers and users of the products and otherinterested organizations* should
be contacted for this information. After this information is gathered, a
test program should be implemented to provide needed data. Tests should be
conducted using a controlled variety of particle sizes in each application to
establish the optimum particle size(s) for each. The applications should
include suspension—fired boilers, front—f irec boilers, pyrolysis reactors,
methane generators, pellets, briquettes, and other possible applications of
waste—derived fuels and fuel feedstock.
Potential tests sites include installations which presently use or plan to
use refuse—derived fuel or fuel feedstock. These installations include the
Baltimore County, Maryland, plant; the Ames, Iowa, Power Plant; the Commonwealth
plant; the Pompano Beach, Florida, methane plant.
* ASTM is presently studying MSW fuel specifications.
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Research Need No. 9 — Evaluate the Cost of Effectiveness of Single
Versus Multiple Shredders
Background
The first RDF demonstration plant (St. Louis) used a single shredder to
reduce the raw MSW to a nominal 3.8 centimeter shred size. Most of the newer
RDF plants are using two shredders to produce approximately the same shred
size. The rationale for using multiple shredders is that the amount of wear
on each shredder will be decreased, thereby reducing overall operating costs.
This has yet to be proven and reported.
Objective
The purpose of this research is to determine the performance and cost—
effectiveness of single versus multiple shredders.
Approach
Performance and cost data should be collected at MSW processing plants
using single and multiple shredders. Performance data should include shred
size, distribution, throughput, wear rates, and energy consumption. The
cost data should include amortized capital, operating and maintenance costs.
The collected data should be analyzed to determine whether multiple shredders
are superior to single shredders, and, if so, under what conditions.
Potential tests sites for single and multiple shredder tests are listed
in Table 6 and Appendix Dl.
* This research need is being partially fulfilled under EPA Contract No.
68—03—2589.
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MAGNETIC SEPARATOR NEEDS
Research Need No. 10 — Compare Performance of Belt and Drum Magnets*
Background
Two principal types of magnets are being used to separate ferrous metals
from MSW: the belt—type magnet and the drum—type magent. There are a variety
of designs within each category. Early designs have not worked well because
of unique problems encountered with MSW. As a consequence, both belt and drum-.
type magnets have recently been redesigned specifically for MSW. As yet, there
is insufficient field data available to evaluate the performance of these
redesigned magnets. Furthermore, the relative advantages and disadvantages of
belt magnets and drum magnets for MSW have not been established.
Obj ective
To evaluate the performance of recently developed magnetic separators and
compare the results of belt and drum types.
Approach
Field tests should be conducted on the “hockey stick” type belt magnets
and the dual—drum magnets to determine their performance on recovery of ferrous
metals from shredded MSW. The tests of both magnet types should be conducted
under similar conditions so that the results can be compared. The data to be
collected should include: (1)percentageof ferrous metal recoverd based upon
the original amount in the shredded MSW: (2) amount of nonferrous metal
contained in the ferrous metal fraction (3) amount of energy required to
operate the magnet; (4) maIntenance required, and (5) costs. Care should be
taken to set up and operate the magnetic separators so that optimum recovery
from each magnet is achieved. The conditions fround for optimum performance
for each magnet should be reported.
MSW plants using belt and drum type magnets are listed In Appendix D-2.
* This research need has been partially fulfilled under EPA Contract No.
68—03—2387.
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AIR CLASSIFIER RESEARCH NEEDS
Research Need No. 11 — Determine the Optimal Operating Conditions for
Air Classiflers
Background
Air classifiers are used in waste—to—energy systems to separate the MSW
into two fractions: a light fraction, made up principally of combustibles,
and a heavy fraction, containing primarily metals and glass. Operating per-
sonnel have complained that there is a lack of information concerning optimal
operating conditions for air classifier. This can result in unstaisfactory
amounts of glass, metal, etc., in the light fraction, and entrapment of
combustibles in the heavy fraction.
Objective
The objective is to determine the optimal operating conditions for MSW
air classifiers.
Approach
The types of air classifiers that should be researched are: zig—zag,
straight, vibrating, rotary, and concentric tube.* The operating parameters
to be investigated can be divided into two groups: those parameters common
to all types of air classifiers and those parameters which are different for
each type. The common parameters are: (1) airflow rate; (2) air velocity;
(3) feed rate; (4) MSW characteristics; (5) position of equipment in the process
line; and (6) costs. The unique parameters for vibrating classifiers are
the storke and revolutions per minute associated with the vibrating motion;
for the rotary classifier the unique parameters are the slope and revolution
per minute of the rotating drum.
The performance factors to determine optitnality for all the types of
air classifiers are: (1) energy consumed, (2) emissions, (3) weat,
(4) throughput, (5) characteristics of the “light” fraction and the “heavy”
fraction, and (6) operating and maintenance Costs.
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The best conditions for conducting this test are to have a full—scale
operation where it is possible to adjust the operating parameters at will.
NCRR, in Washington, D. C., is one such facility. Information may also be
obtained through tests at the following commerican plants with the corresponding
type of air classifiers (in parenthesis): Chicago, Illinois (vibrating),
Pompano Beach, Florida (vibrating), Houston, Texas (rotary), Baltimore
County, Maryland* (concentric tube), El Cajon, California (zig—zag),
Milwaukee, Wisconsin (zig—zag), and Ames, Iowa (straight).
* Tests of a concentric tube air classifier at the Baltimore County,
Maryland RDF plant have been conducted under EPA Contract No. 68—03—2387.
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Research Need No. 12 — Compare Different Types of Air Classifiers
Background
There are five major varieties of air classifiers in use or planned to be
used in waste—to—energy systems: zig—zag, straight, vibrating, rotary, and
concentric. The relative performance of each type has not yet been
established. However, several users have been unsatisfied with the performance
to date of various types. This has stimulated the design of new air classifiers
such as the rotary and concentric—bute types.
Obj ective
The objective is to compare the performance of various types of air
classifiers under the same conditions.
Approach
The types of air classifiers that should be investigated under this
research need are: zig—zag, vibrating, straight, rotary, and concentric—tube.
The tests should be conducted under “normal” operating conditions, i.e., similar
conditions for each type of air classifier, to Insure valid comparison.
The data to be collected for performance comparison purposes are: (1)
energy consumption, (2) emIssions, (3) equipment wear, (4) capacity, (5) MSW
output characteristics, and (6) operating and maintenance costs. The final
evaluation will be in terms of cost effectiveness (the trade—off between
costs and technical performance).
This research should be conducted at commercial plants. The plant
should be full—scale, and operated under “normal” conditions. For a list
of potential test sites refer to Research Need No. 11.
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SCREEN RESEARCH NEEDS
Research Need No. 13 — Compare Coarse Screens
Background
Trommels (rotary) and disc screens are coarse screens. The disc screen
is very new, and little data on its performance on MSW have been compiled.
The trommel screen has been tested on MSW by NCRR, TVA, Vista Chemical Company
and others.
It would be of interest to determine what screen is best suited for what
particular job (e.g., pretrommeling, nonferrous recovery). If they are suited
to do the same job, it is valuable to determine the comparative cost—effective-
ness. Data are not presently available to answer these q estions.
Obj ective
The objective of this research is to compare the performance of coarse
screens on MSW.
Approach
The types of corase screens to be research are troimnels and disc screens.
The tests should be conducted under normal plant operating conditions.
The performance data that should be collected are: (1) energy consumed,
(2) the characteristics of the captured fraction and through fraction, (3)
the throughput, (4) equipment wear, and (5) operating and maintenance costs.
A further delineation of the material characteristics are: size distribution,
moisture content, percent glass, percent ferrous metals, percent nonferrous
metals, percent wood, and percent paper. Equipment wear can be determined
through maintenance costs, and decrease in thickness of the screen. The final
evaluation criteria will be cost—effectiveness.
The tests should be conducted at a full—scale, full operational facility
under similar conditions. The following sites have the types of screen shown
in parenthesis: East Bridgewater, Massachusetts (tronunel); Pompano Beach,
Florida (trommel; Houston, Texas (trammel; New Orleans, Louisiana (trominel);
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and Palmer Township, Pennsylvania (tronimel). There are no known installations
using or planning to use a disc screen.
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Research Need No. 14 — Compare Fine Screens
Background
Generally, vibrating screens are used for fine screening purposes. The
two vibrating screens under investigation for use in MSW—to—energy systems for
fine screening are reciprocating and gyrating screens. These two actions have
specific effects on the separation efficiency of the screen: (1) the motion
determines the time the particles are in contact with the screen (retention
time), (2) the regularity or irregularity of the motion affects efficiency,
and (3) the motion can affect wear.
Presently, gyrating screens are in use at waste—to—energy plants;
reciprocating screens toour knowledge, are not. There have been no tests or
studies reported that address the question of efficiency, or cost—effectiveness
of fine screening
Obj ective
The objective of this research is to compare the performance of fine
screens.
Approach
The approach to be used is conducting this research is identical to the
approach given in Research Need No. 13.
The research should be conducted at a full—scale plant under normal plant
operating conditions. Gyrating screens are used at El Cajon, California, and
East Bridgewater, Massachusetts. There are no known MSW—to—energy facilities
presently using reciprocating screens.
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Research Need No. 15 — Determine the Effects of Pretrommeling
Pretrommeling for MSW processing plants has attracted interest due to the
following anticipated effects: (1) less wear on the shredders, (2) improved
separation in air classifiers, (3) improved form of recoverables for the pur-
pose of selling to secondary markets, and (4) decrease in overall system cost.
There have been some tests conducted to assess some of the operating char-
acteristics of rotary screens.* However, sufficient data to support the use of
pretromineling for waste—to—energy systems have not yet been established.
Obj ective
To quantitively determine the effects of pretrommeling on waste—to—energy
systems.
Approach
The research should be conducted using a trommel under predetermined opti-
mal operating conditions. A minimum process line’ consisting of a trornmel, shred-
der, and air classifier with the necessary ancillary equipment is needed. The
following data should be obtained: (I) capital Costs for the trornmel, shredder,
and air classifier; (2) the amount of wear on the shredder and associated operat-
ing and maintenance costs without pretromrneling; (3) efficiency of the air clas-
sifier and associated operating and maintenance Costs without pretrommeling;
(4) the characteristics of recoverables from the “heavy” fraction of the air
classifier without pretrommeling; (5) the amount of wear on the shredder and
operating and maintenance costs with pretrommeling; (6) the efficiency of the
air classifier and operating and maintenance costs with pretrommeling; and
(7) the characteristics of the recoverables from the trommel and air classifier.
The wear on the shredder will be indicated by hammer weight loss. The ef-
ficiency of the air classifiers will be indicated by the percentage of metals,
glass, etc., In the combustible fraction and the percentage of combustibles In
the heavy fraction. The characteristics of the recoverables from the trommel
and the heavy fraction of the air classifier which should be measured are:
percentage composition by weight of glass, ferrous metals, nonferrous metals,
paper, plastic, wood, etc.; and the size distribution for each category.
* Tests of a rotating screen as a pretronunel have recently been conducted
by NCRR at the New Orleans, Louisiana, processing plant under an EPA
contract.
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DRYER RESEARCH NEEDS
Research Need No. 16 — Evaluate the Effect of Dryers on the Efficiency
of Air Classification
Background
Some plant operators, and RDF users are not satisfied with the separation
efficiency of air classifiers. In particular, they find unacceptable amounts
of metals, glass, etc., in the light fraction. Some of the causes of poor
air classification performance may be associated with high moisture content
of MSW. The removal or reduction of this moisture through a drying system may
improve the air classification process. However, data are not available to
support this contention.
Obj ective
The objective is to determine whether the use of a dryer will improve
the separation efficiency of MSW air classifiers.
Approach
Tests should be conducted on two process lines with the following minimal
equipment; one with a shredder, dryer and air classifier and the other with
a shredder and air classifier. The two lines should be identical except for
the addition of a dryer in one process line.
The data that should be collected are (1) the amount of noncombustibles
in the light fraction, and the amount of combustibles in the heavy fraction
for the stream without a dryer, and (2) determination of the same information
for the process line with the dryer. This research can be extended to
determine the relationship of the heat in the dryer to the moisture reduction
and the efficiency of the air classifier.
The trade—offs between improved product quality and the increased costs
associated with using a dryer should be taken into account in the final
evaluation.
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Research Need No. 17 — Evaluate the Effect of Drying on the Combustion
Chpracteristics of RDF
Background
The moisture content of MSW reduces the effectiveness of RDF as a fuel,
absorbing energy in the combustion process. It has been shown that the mois-
ture in NSW can be significantly reduced, or eliminated, by installing a
dryer in the process line. However, therearepresentlY no data available to
show the effect of moisture reduction on the combustion characteristics of
RDF.
Objective
The objective of this research is to determine the relationship between
drying and the combustion characteristics of RDF.
Approach
The research should be conducted under normal operating conditions using
a process line without a dryer and a system with a dryer (all other parameters
being equal). The data that should be collected are: (1) the percent of mois-
ture in the RDF, (2) the energy value of the RDF, and (3) the energy consumed
by the dryer. The operating parameters of the dryer should be changed to deter-
mine their effect on the above data.
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Research Need No. 18 — Evaluate the Effect of Drying on the Storability
of RDF
Background
There are concerns about the storability of RDF. There are indications
that stored RDF presents a fire hazard, is odorous, and has poor flow charac-
teristics. These factors reduce the amount of time RDF can be stored. The
storage problem of RDF may be caused, at least in part, by the moisture of
MSW.
Theoretically, the removal of the mositure from the MSW should improve
or eliminate some of the storage problems of RDF. However, data are not pre-
sently available to support this theory.
Obj ective
The objective of this research is to determine if drying MSW has any posi-
tive effects on the storability of RDF.
Approach
This research should be conducted under normal operating conditions using
a minimum process line of a shredder, dryer and a long-term storage and re-
trieval system. The RUF should be stored for various time periods. The follow-
ing data should be determined, first without a dryer and then with a dryer:
(1) percent of moisture in the RDF, (2) amount and type of gases in the stor-
age bin, (3) the temperature of the RDF in the storage bin, and (4) the f low—
ability of the MSW.
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Research Need No. 19 — Determine the Effect of Dryers on Bacteria and Virus
Background
Preliminary tests indicate that there may be significant amounts of
particulates in the emissions from equipment processing MSW. Additional re-
search on the bacteria and virus in these emissions is being conducted.
Although there is presently no data to substantiate the relationship be-
tween the bacteria and virus population and the use of a dryer, equipment manu
facturers believe that including a dryer in the system could eliminate all
or part of the bacteria/virus from the product and the emissions.
Obj ective
The objective is to determine whether bacteria and virus in MSW are re-
duced by passing the waste through a dryer.
Approach
A rotary drum dryer, the Only type presently in use at waste-to-energy
systems, should be tested under normal operating conditions. The following
data should be collected: (1) the bacteria and virus types and counts in the
MSW stream and emissions prior to drying; and (2) the bacteria and virus types
and Counts in the NSW and emissions after drying.
The study can be extended to test the effect of temperature changes on
data Item (2). Associated energy consumption, operating costs and maintenance
costs should be evaluated.
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DENSIFIER RESEARCH NEEDS
Research Need No. 20 — Determine the Optimal Operating Conditions for
Densifiers
Background
The two types of densifiers presently of greatest interest for waste—to--
energy systems are pellet mills and bdquetters. There is interest in densi—
fying RDF because it may: (.1) increase storability, (2) enhance transportabil-
ity, and (3) increase adaptability for certain applications.
Insufficient data on optimum operating conditions for MSW densifiers are
presently available. *
Obj ective
To determine the optimal operating conditions for pellet mills and bri—
quetters.
Approach
The operating parameters should, be varied to determine their effect on
the performance of the densifier(s). The operating parameters are Identical
for both pelitiziers and briquetters: (1) the flow rate, (2) the size distri-
bution of the particles, (3) use or nonuse of a binder; and (4) the composi-
tion of the MSW (percent paper, plastic, wood, and moisture).
The optimal operating conditions can be determined by changing the above
parameters and observing the resulting effects on the following performance
factors: (1) energy consumption, (2) capacity, (3) operating and maintenance
costs, (4) the size and shape of the product, (5) the density of the product,
and (6) equipment wear.
A pellet mill has been installed at NCRR, Washington, D.C., and Baltimore
County, Maryland. Briquetters have not been installed nor are they presently
planned for installation at any known facility. It is possible that this re-
search can be conducted at equipment manufacturing sites.
* NCRR and Teledyne National recently conducted research on pellet mills at
the Washington, D.C., and the Baltimore County waste processing plants,
respectively.
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Research Need No. 21 — Determine the Specifications for Densified RDF
Background
Due to the increasing national Interest in using coal burning—boilers,
one of the chief advantages to densifying RDF Is to adapt It for use In such
boilers. Fuel In varying sizes and densities Is necessary for effective fir-
ing of various types of boilers (e.g., stoker—fired boilers). Presently, there
is no information available on the best sizes and densities for densjffed RDF
for such applications.
Objective
To determine the specifications for densi fled RDF.
Approach
Pellets and briquettes of varying sizes and densities should be produced;
the heating value of each should be determined through calorimetric (ASTM stan-
dard) laboratory tests; then, the densifled RDF should be tested in the boil-
ers. The data should be evaluated, for the purpose of find the best size
and density of densified RDF.
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CONVEYOR RESEARCH NEEDS
Research Need No. 22 — Determine the Optimal Operating Conditions for
Vibrating and Pneumatic Conveyors
Background
There has been extensive research conducted by designers and manufacturers
on the best operating conditions for belt and flight conveyors. However, re-
search has not been found which shows the best operating conditions for
vibrating or pneumatic conveyors for MSW. Users have encountered wear and
plugging problems with penumatic conveyors, and designers have had problems
with correct sizing of vibrating conveyors. Therefore, data on the optimal
operating conditions of these two types of conveyors of MSW are needed.
Objective
To determine the optimal operating conditions of vibrating and pneumatic
conveyors for transporting MSW products.
Approach
The conveyors should be tested under various operating conditions; deter-
mination of optimal conditions should then be made by comparing the operating
parameters with the resultant performance.
The following are some operating parameters for vibrating conveyors: (1)
pan width, (2) angle of incline, (3) stroke, (4) angle of the stroke, (5) cycles
per minute, and (6) the MSW characteristics (e.g., particle size distribution,
composition, and moisture content). The operating parameters for pneumatic
conveyors are: (1) airflow rate, (2) air velocity, (3) pressure, (4) the pipe
diameter, (5) the number of bends, (6) the angle(s) of the conveyor, and (7)
the HSW characteristics.
The performance factors which should be used to determine optimum operat-
ing conditions for both types of conveyors are: (1) energy consumption, (2)
throughput, (3) leakage or spillage, (4) wear, and (5) operating and maintenance
costs. The following additional factors should be used for pneumatic conveyors:
(1) the resultant moisture content of MSW, and (2) the amount of pluggage.
The research should be conducted at full—scale facilities. The following
facilities have pneumatic conveyors: Ames, Iowa; and Chicago, Illinois. Vi-
brating conveyors are in use at Ames, Iowa.
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i esearch Need No. 23 — Compare the Performance of Conveyors
Background
Both belt and flight conveyors are used to transport raw or shredded sw
in waste—to —energy systems. Users cannot agree on the advantages of disadvan-
tages of each type of conveyor. Data are needed to determine the advantages
of each type of conveyor for specific MSW transport tasks.
Obj ective
To compare the performance of belt conveyors and flight conveyors for
MSW.
Approach
Test should be conducted under normal operating conditions. It is
necessary to maintain identical operating parameters (e.g., MSW characteristics)
for both conveyors. The performance data that should be collected are: (1)
energy consumed, (2) throughput, (3) operating and maintenance costs, (4)
wear, (5) spillage from the conveyors, (6) potential damage due to fire, and
(7) damage due to impacts. The final evaluation should be a cost—effectiveness
analysis for each conveyor type.
The test site(s) should be a full—scale plant operating under normal
conditions. The operating parameters must be similar if multiple sites are
selected. The following sites use belt conveyors: Baltimore County, Maryland,
South Charleston, West Virginia; Chicago, Illinois; and El Cajon, California.
Flight (apron) conveyors are used at Ain s, Iowa, Baltimore, Maryland;
Baltimore County Maryland; Chicago, Illinois; El Cajon, California and
Milwaukee, Wisconsin.
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Research Need No. 24 — Compare Pneumatic Transport Systems
Background
There are two types of pneumatic transport systems: negative pressure and
positive pressure. Negative pressure systems are generally considered better
when transporting material from several locations to one, and positive air
systems are considered better for accomplishing the transfer of material from
one location to several.
Pneumatic conveyors for MSW have encountered some problems, such as plug-
gage, leakage and wear. Presently, there are no data available to show which
type of air transport system is most effective for transporting MSW.
Objective
To study and compare the performance of negative air and positive pressure
transport systems for MSW.
Approach
The tests should be conducted under predetermined optimal operating con-
ditions. The data that should be collected are: (1) amount of leakage or spil-
lage, (2) amount of pluggage, (3) drying effect, (4) energy consumption, (5)
capacity of the system, (6) wear, and (7) the operating and maintenance costs.
The data should be evaluated in terms of cost-effectiveness.
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STORAGE AND RETRIEVAL RESEARCH NEEDS
Research Need No. 25 — Compare the Perfo nce of Storage and Retrieval
Svste
Background
There are a variety of storage and retrieval systems available for waste-
to—energy plants. Presently, data are not available to compare the performance
of the various storage and retrieval systems.
Storage and retrieval system users have encountered several problem areas:
(1) nonuniform discharge, (2) bridging and “deadspots”, (3) minimal amount of
useful storage area, (4) excessive energy consumption, and (5) minimum storage
time due to odor, fire hazards, and packing.
Objective
To compare the performance of different storage and retrieval systems
for RDF.
App roach
The storage and retrieval systems that should be evaluated are: (1) a
conical bin with sweep bucket retrieval, (2) an inverted bin with screw dis-
charge, (3) an inverted bin with roller discharge, (4) a rectangular bin with
doffing rolls and screws, and (5) a bin with vertical and horizontal screw
discharge.
The following data should be collected: (1) the controllability and uni-
formity of discharge; (2) the amount of bridging; (3) the occurrence of “dead
spots;” (4) storage bin feed—in rate; (5) the ratio of useful storage area
to the area of the entire bin; (6) the energy consumed; (7) the operating,
maintenance, and capital costs; and (8) the concentration of gases within the
bin.
The following is a list of waste processing facilities with their corre-
sponding types of storage and retrieval systems: Ames, Iowa (conical, with
sweep buckets); Baltimore, Maryland (conical with sweep bucket); Chicago,
Illinois (conical, with sweep buckets); El Cajon, California (rectangular,
with doffing rolls) and St. Louis, Missouri (inverted, with screws).
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RECEIVING FACILITIES RESEARCH NEEDS
Research Need No. 26 — Evaluate Receiving Facilities
Background
Receiving facilities play an important role in waste processing plants,
yet little has been reported on the performance of these facilities. The prin-
cipal functions of receiving facilities are to: (1) weigh the incoming MSW
delivery trucks, (2) provide facilities to receive and temporarily store the
MSW, (3) remove undesirable material from the MSW, and (4) feed the MSW into
the processing system. There are various designs and layouts of receiving
facilities being used; the scales may be outdoors or indoors; the truck weights
may be recorded manually or automatically; the truck traffic patterns are dif-
ferent; the loads may be dumped on the floor or into pits; techniques for re-
moval of undesirables vary; and the method for moving the NSW from the storage
area to the feed conveyor may be by pusher trucks or hydraulic rams. In spite
of their importance and the significant variations in design, there has been
no reported systematic evaluation of MSW receiving facilities.
Obj ective
The purpose of this research is to evaluate the performance of receiving
facilities in waste processing plants. The various types of receiving facili-
ties being used should be evaluated and the results compared.
Approach
The evaluation of receiving facilities should include: (1) the time re-
quired for the delivery trucks to be weighed, dump their loads, and depart
from the plant; (2) the number of trucks that can be accommodated per shift;
(3) difficulties experienced by the truck drivers within the plant; (4) the
accuracy of the weighing process; (5) the ability to remove undesirable mater-
ial from the waste pile; (6) the cost effectiveness of total—truck versus single
axle scales; (7) the effectiveness of receiving pads versus pits; (8) the ad-
vantages and disadvantages of wheel loaders versus hydraulic ram loaders; (9)
environmental pollution within the receiving building; and (10) effects of
receiving facility layout on performance and costs.
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Research Need No. 27 — Evaluate NSW Segregation Prior to Processing .
Background
There Is almost an unlimited variety of objects which may appear in MSW
which should be removed prior to processing in a waste-to-energy plant. Bulky
objects, such as discarded refrigerators, mattresses, motor blocks and tires,
are usually too large or dense to be accommodated by the primary shredder.
Some objects are undesirable because they can cause fires or explosions in
the shredders. Included in the latter category are comercial and military
explosives, and a variety of flammable liquids, gases, and dust.
The problem is how to identify and remove undesirable objects prior to
processing. Large, bulky wastes are readily Identifiable, and in many (but
not all) cities, these are collected and disposed of separately. It is the
small, dense, flaninable or explosive objects that present a major problem be-
cause they cannot be easily identified. Various techniques are being tried
to identify and remove these undesirable objects, with only moderate success.
Some plants have instructed the trash collectors to avoid putting any suspic-
ious objects in the refuse trucks. However, in most cases It is left to the
operators of the front-end loader and the shredder feed belt to visually iden-
tify and remove any undesirable objects prior to entry into the primary shred-
der. The lack of effectiveness of the present procedures is affirmed in a re-
cent survey of MSW shredding plants covering nearly 100 explosions in MSW pro-
cessing plants. Although it is probably impossible to identify and remove all
undesirable objects from MSW, it is desirable to conduct additional research
in this area in an attempt to improve the present situation.
Obj ective
The objective of this research is to develop effective methOds that will
identify and remove undesirable objects from MSW prior to processing.
Approach
The first step is to study the present techniques for identification and
removal of undesirable objects to determine which is most effective. The next
step is to conceive and evaluate tehniques which will improve the effectiveness
of segregation prior to processing.
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EQUIPMENT CONTROL RESEARCH NEEDS
Research Need No. 28 — Characterize Equipment Control Systems in Waste
Processing Plants
Background
The controls addressed here refer to the electrical system through which
the various pieces of processing equipment are operated and controlled. The
electrical control system ties all of the separate pieces of equipment together
into a complete processing entity.
Literature searches have revealed very little information regarding elec-
trical control systems at MSW plants. The information obtained from direct con-
tact with plant designers is sketchy and Incomplete.
Obj ective
The objective of this research is to characterize the electrical control
systems at present and planned resource recovery plants.
Approach
As’a first step, a data form covering resource recovery plant control
systems should be designed. The data foruz8 should then be mailed to the de-
signers of each of the MSW systems being studied. Each plant designer would
be asked to complete the data form and return it, plus any available wiring
and/or block diagrams on the system.
It will probably be necessary, in some cases, to visit plants personally
to obtain complete control system data, wiring diagrams, block diagrams, etc.
In these instances, photographs should be taken (assuming permission is granted)
of the operator’s control booth, control console, push button panels, control
room and other control panels and equipment.
The completed control system data forms, photographs and wiring and block
diagrams will represent a data base from which the characteristics of prepro-
cessing systems at present resource recovery plants can be analyzed and com-
pared.
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Research Need No. 29 — Determine the Effectivenssof Equipment Control Systems
A t Waste Processing Plants
Background
Preliminary discussions with system designers indicate that the electri-
cal control systems are custom..’designed for each plant, and vary widely in
degree of sophistication from plant to plant. Some designers have taken a mini-
mal approach, relying on simple, manual instrumentation and control, while
others favor highly automated control systems.
Obj ective
The primary objective of this research is to establish the differences in
effectiveness of control systems at waste processing plants. The research should
attempt to answer the following questions:
1. Under what circumstances does the simple, manually—operated control
system seem to be more effective than the more sophisticated, automated con-
trol system?
2. Under what set of circumstances is an automated control system, rather
than a manual control system, necessary?
3. Compare the simple, manual control to a more automatic control sys-
tem; what is the difference in number of personnel required to operate the
plant?
4. When does a control system become “too automatic”—-so complicated that
the cost-effectiveness is reduced?
5. From the standpoint of safety, what are the advantages and disadvan-
tages of the various control systems?
6. What are the general guidelines and minimum requirements that need to
be satisfied when installing electrical controls for the processing area in
resource recovery plants?
Approach
As a first step, the completed control system data forms, photographs,
wiring diagrams, block diagrams, etc., obtained in Research Need No. 28,
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should be analyzed and information compiled for later use. Field surveys would
then be run to evaluate the advantages and disadvantages of different types
of control systems.
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FIRE ANI) EXPLOSION RESEARCH NEEDS
Research Need No. 30 — Study the Incidence of Fires in Waste Processing Plants
Background
The number of fires which have occurred at MSW processing facilities indi-
cates that the fire hazard Is significant. A major factor contributing to this
hazard is the heterogeneous and combustable nature of mixed municipal waste.
Objective
The objectives of this research are to answer the following questions
regarding fires at NSW plants: (1) in what area of the plant have most fires
occurred? (2) what were the causes of these fires? (3) what was the amount of
damage resulting in each of the fires? (4) what injuries resulted from the
fires? (5) what was the downtime resulting from the fires; and (6) how were
the fires extinguished?
Approach
A basic method would be to gather detailed data relative to the above
questions from MSW plants that have experienced fires. As a first step, a
data form for compiling the desired Information should be designed. These
data forms, after being completed, would make up a basic Fire Experience
Data Bank for later interpretation and analysis.
It Is anticipated that several methods would be used in gathering the
data and completing the data forms including: (1) literature searches; (2)
data from system designers and operators, and insurance companies; (3) tele—
phone contacts; and (4) visits to MSW plants.
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Research Need No. 31 — Determine Fire Resistance Characteristics of Waste
Processing Equipment
Background
Preliminary research has uncovered several instances of fires in municipal
solid waste processing plants which were started and/or spread because of the
flammability of some of the equipment components. There have been cases of
rubber conveyor belts catching fire, and other cases of equipment components
starting the fire.
Obj ective
The purpose of this research would be to determine which of the
equipment components in the processing portion of resource recovery plants
would be candidates for replacement by fire—resistant components and what
uther fireproofing techniques should be employed. The research would address
the following:
1. Which of the processing equipment and supplementary equipment
if flarmnable; i.e., could start a fire or add to the spread of a fire?
2. Are there fire—resistant materials and/or equipment than can
replace identified fire hazards?
3. What other fireproofing procedures would be advantageous?
Approach
As a first task in this study, the “Fire Experience Data Bank” developed
in Research Need No. 30 should be analyzed to determine which pieces of
equipment or components of MSW systems have been responsible for the fires
that have already occurred. The second task would involve on—site
inspections of waste processing facilities. Insurance company specialists,
personnel with the National Fire Protection Association and other interested
organiations may be asked to assist in this task. The last task would entail
contracting and obtaining recommendations from various equipment component
manufacturers.
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Research Need No. 32 — Determine the Effectiveness of Fire Protection Systems
in Waste Processing Plants
Background
The research conducted to date indicates that the probability of fire
in NSW plants is high. Apparently, most of the fires originate in the shredder
area, but there have also been reports of fires in other areas including con-
veyor lines, control rooms, and storage bins.
Obj ective
The objective of this research is to study the experience of waste pro-
cessing plants that have experienced fires to determine which fire protection
systems have been effective and which were ineffective In preventing or ex-
tinguishing fires.
Approach
The first task would be to analyze the information regarding past fires
at MSW plants, utilizing the Fire Experience Data Bank developed in Research
Need No. 30, and make additional contacts as necessary. The second task would
be to determine which fire protection measures have been effective for: (1)
preventing fires, and (2) controlling and/or extinguishing fires after they
start.
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Research Need No. 33 — Study the Incidence of Explosions in Waste Proc ess tnp
Plants
Background
Waste processing plants are vulnerable to explosions because of the
heterogeneous nature of mixed municipal refuse. The explosion hazards
include such items as gasoline and solvent containers, propane tanks,
ammunition, gunpowder, dynamite, TNT, and occassionally even live ordinance.
Combustible dust, flammable gases and hybrid dust/gas mixtures are also
possible explosion sources in waste processing plants.
Obj ective
The purpose of the research is to answer the following questions: (1) in
what area of the plant have most explosions occurred? (2) what were the causes
of these explosions? (3) what was the amount of damage resulting in each of
the explosions? (4) what injuries resulted from the explosions? (5) what was
the downtime resulting from the explosions; and (6) what changes or modifica-
tions were made to guard against a similar occurrence in the future?
Approach
As a first step, a data form for compiling the desired information should
be designed. One data form would be completed for each explosion researched.
These data forms, after being completed, would form a basic Explosion Exper-
ience Data Bank for later interpretation and analysis.
It is anticipated that several methods would be used to gather the data
including: (1) literature searches; (2) mailing data forms, along with an ex-
planatory letter, to system designers and operators and other data sources;
(3) telephone contacts; (4) personal visits to NSW processing facilities;
and (5) working with insurance companies to develop information from their
files.
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Research Need No. 34 — Determine the Effectiveness of Explosion Protection
Systems in Waste Processing Plants
Background
Municipal solid waste processing plants are vulnerable to explosions be-
cause of the heterogeneous nature of mixed municipal refuse. The explosion
hazards include such items as gasoline and solvent containers, propane tanks,
ammunition, gunpowder, dynamite, TNT, and occassionaily even live ordinance.
Combustible dust, flammable gases and hybrid dust/gas mixtures are also pos-
sible explosion sources. Other industries, such as automobile shredding have
gained experience which may also be applicable to processing MSW.
Obj ective
The objective of this research is to answer the following:
1. What venting configurations, water spray systems, suppression systems,
and other preventative measures have proved most successful in other indus-
tries?
2. Which of the techniques employed in the automobile scrap and other
industries are adaptable to municipal solid waste systems?
3. What modifications in explosion protection systems have been made at
MSW shredder installations that have already experienced explosions. Which
protection measures have proved effective?
4. What surveillance and screening methods are most effective for eliminat-
ing hazardous materials from the refuse fed into the shredder?
5. Can the experiences in Germany with dry powder extinguishing agents
help us in MSW explosion problems in the U.S.?
6. What is the incidence of explosive vapor concetitration in shredders?
7. How effective is a shredder water spray system for explosion protec-
tion?
8. What is the feasibility of an emergency water spray system in shred-
ders that would be activated before ignition, as soon as a high-f laninable gas
or vapor concentration is detected?
9. What venting configurations for different types of shredders are most
effective?
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10. Which halon explosion suppression system is most effective for the
different types of shredders?
Approach
The research would consist basically of data gathering through the follow-
ing:
1. Contact with automobile fragmentizer operators, fragmentizer equipment
manufacturers, insurance companies, and others. Methods employed in collecting
the data would include mailing data forms, telephone contact, and personal
visits. Preferably, the researchers should build a file of photographs to sup-
plement the other data.
2. Survey existing refuse shredder operators who have experienced explo-
sions at their plants.
3. Experiment with different techniques, including both manual and auto-
matic, for screening and sorting out hazardous materials before they enter
the shredder to determine which techniques are most effective.
4. Investigate the explosion tests that have been conducted in Germany
with dry powder extinguishing agents. Field test the effectiveness of these
dry agents.
5. Monitor flammable gas concentrations in operating shredders to deter-
mine incidence of occurrence.
6. Conduct shredder explosion tests with and without a water spray system.
7. Using the experience and information gained from tests described in 5
and 6 above, design and test the effectiveness of an emergency water spray sys-
tem that is activated as soon as a high—flammable gas or vapor concentration is
detected (before ignition).
8. Conduct shredder explosion tests to learn more about:
• Structural integrity of shredders; and
• Venting configurations that are most effective for different shred-
ders.
9. Test the effectiveness of shredder explosion suppression systems to
determine designs that work best for the different types of shredders. The
effects of agent concentration and container location should be included in
these tests. Also, the effects of dirt accumulation in the pressure transducers
146
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and techniques for eliminating the dirt accumulation problem should be
investigated.
147
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Research Need No. 35 — Evaluate Spillage and Dust Controls
Background
Spillage and dust are generated throughout MSW processing plants. Dumping
the raw MSW from the delivery trucks, moving the MSW onto the feed conveyor,
conveying the MSW, shredding the MSW, air classification and almost every other
step in the process cause spillage and dust to be liberated from the waste
stream. Uncontrolled spillage and dust are undesirable because of potential
health hazards to plant personnel, fire and explosions, and general house-
keeping. Some attempts have been made to control spillage and dust in MSW pro-
cessing plants. Some of the more recent waste-to-energy plants have included
dust collection systems, but their effectiveness has not yet been tested. At-
tempts have been made to minimize spillage by installing enclosures around the
processing equipment, but complete control of spillage has yet to be achieved.
Objective
To evaluate present spillage and dust control systems in waste-to-energy
plants, and determine which systems are most effective.
Approach
Tests should be conducted in resource recovery plants equipped with the
latest techniques for spillage and dust control. The amount of spillage and
dust collected throughout the plant should be measured and recorded daily over
a period of about 1 week at each plant. The type of control system should be
described any any operating problems reocrded. For caomparison, tests should
also be conducted in a plant which is not equipped with such controls. Reco—
mendations for possible improvements in either the design or operation of the
control systems should be made.
Waste—to—energy plants equipped with spillage and/or dust controls in-
clude the Chicago, Illinois, plant; and Baltimore County, Maryland,* plant.
A potential test site for a plant not equipped with dust control is the Ames
Iowa, plant
* Preliminary tests of the dust control system at the Baltimore County plant
were recently conducted under EPA Contract No. 68—03—2387.
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ECONOMIC RESEARCH NEEDS
Research Need No. 36 — Develop Effective Accounting Method(s )
Background
One of the major deficiencies in studies of the economics of MSW processes
is the lack of standard accounting practices to facilitate the comparison of
economic data. Standardization, however, Is not sufficient in Itself. The
inputs to the accounting system must be easily collected; and the output should
be in a form that is useful for the type of analysis that is required.
The need to develop an effective accounting system is apparent in many of
the preceding research needs. However, Its use is not limited to these areas.
Both existing and future waste processing facilities will require the information
that can be derived from this system. Existing facilities will need this
information to monitor performance, to determine optimal equipment replacement
schedules and to evaluate new equipment developments. Future recovery
facilities will need the information in the selection of equipment and for
determing financial requirments.
Obj ective
To develop an accounting system for waste processing plants that Is
consistent, provides useful information, and is easy to maintain.
Approach
The approach that should be taken in devioping an effective accounting
system Is two—fold. First is the formulation of a conceptually valid system.
The second, accomplished simultaneously, is ananalysisof accounting systems
currently being used at the various recovery facilities. This step possibly
could be expanded to include other industries with similar characteristics——
large capital costs, and relatively undeveloped. Examples of such
industries Include solar reactors, nuclear power plants, etc.
The evaluation criteria to be used in both steps of this apprach are:
(1) timeliness of Information; (2) usefulness of information; (3) ease of
maintenance; and (4) consistency.
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Research Need No. 37 — Compare Capital Cost of Processing Equipment
Background
Capital cost is the first variable required in making any type of compari-
son of various equipment through cost—effectiveness. Moreover, capital cost
includes more that just equipment cost. Labor for installatior , a major adapta-
tions to plant or equipment required for implementation in a particular system,
other installation costs, term of debt instrument (if any), cost of capital,
and the cost of the required square footage of the plant are examples of the
other types of cost that should be included in capital costs.
Objective
To identify the true capital cost of resource recovery processing equip-
ment.
Approach
The first step in establishing the capital cost of a particular piece of
equipment is to identify all segments of the cost. Next, data must be collected
on these identified costs. It is necessary to develop a mechanism to collect
these data. This mechanism may be taken from the standard accounting system sug-
gested In the preceding research need.
A value analysis should then be performed on each piece of equipment of
interest so that realistic comparisons can be made within each class of equip-
ment, such as shredders, air—classifiers, and conveyors.
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Research Need No. 38 — Determine Economic Life of Processing Equipment
Background
“Economic life” may be defined as that point in time when replacement of
a given piece of equipment becomes more cost-effective than additional repair.
The importance of economic life is implicit in any capital budgeting decision.
Likewise, working capital requirements are directly tied to the useful life
of a piece of equipment as is its cost—effectiveness. Because much of the
equipment used in recovery facilities is totally new, and others, such as
shredders,have such limited experience on MSW, any attempt to extrapolate
economic life from current data would be severely deficient.
Objective
To determine the economic life of processing equipment In resource re-
covery systems.
Approach
Two different approaches are described accompanied with a brief statement
of their advantages and disadvantages.
The first approach utilizes information on economic life and the asso-
ciated cost curves for a particular piece of equipment as used in other areas.
From these data a probable economic life and cost curve can be estimated. There
are two major weaknesses with this approach. First, there is no reason to be-
lieve, for example, that the way a shredder reacts in the grain industry has
any relationship to the way it reacts on NSW. Second, this analysis is limited
to oniy a few equipments, since many have been developed specifically for HSW
and, therefore, have no histories from which to draw comparisons.
Another approach to determine economic life is toobserve the equipment
over a long period of time, perhaps as much as 20 years, During this observa-
tion period it will be necessary to collect data on all maintenance costs and
their timing. In addition, for any operating costs that increase over the life
of the equipment (for reasons other than inflation) data will also have to be
collected. From these data (and the capital cost data discussed in Research
Need No. 37) a capital budgeting model can be developed to identify the eco-
nomic life. Although this approach is considerably more accurate than the first
approach, there is a problem with the great amount of time that is required.
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Research Need No. 39 — Determine Equipment Operating and Maintenance Costs
Background
The operating and maintenance costs are extremely important variables
in the economic analysis of MSW processing equipment. Experience at some f a—
cilities has shown that these costs fluctuate widely and can mean the differ-
ence between financial success and failure. Unfortunately, these costs are
presently misunderstood and undeveloped.
Objective
To identify the operating and maintenance costs associated with MSW pro-
cessing equipment.
Approach
For each class of equipment to be studied, a comprehensive list of operat-
ing and maintenance costs should be developed. These costs include labor, energy,
other utilities, repairs (Including frequency), etc. On—site data collection
and detailed analysis will be required.
It is paramount that an effective accounting system, such as described
earlier, be used for collection of these data to insure reliability. Careful
attention must be paid to detect variations in the costs due to changing para-
meters, such as the effect of other equipment In the system, throughput, and
quality of the product.
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Research Need No. 40 — Perform Cost—Effectivensss Analysis
Background
As municipalities and other organizations concerned with the funding of
resource recovery facilities become more demanding in terms of justifying ex-
penditures, cost—effectiveness analysis will become increasingly important.
It can be used, for example, to investigate the trade—off s between costs and
technical performance——a key to identifying optimal systems.
Obj ective
To perform cost—effectiveness analysis of MSW processing equipment.
Approach
The approach used in this analysis should combine economic data and tech-
nical performance data to formulate the following relationships:
C. = £ (K , Q, 0 1 M 1 , E.)
where C = cost_effectiveness of equipment type i
= capital cost of equipment I
= economic life of equipment i
E. relationship to other equipment j in the system
Q = quality of the product
0 M = operating and maintenance cost of equipment i
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APPENDIX A
REFERENCES
APPENDIX A-i
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85. Horsier and Shifrin, Inc. Energy Recovery From Waste: A Municipal-Utility
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158
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86. Institute of Scrap Iron and Steel. Governments’ Role in Resource Recovery.
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37. lowaManufacturing Co. Model 11028 Rotary Drum Air Classifier System. Form
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88. It Still Looks Like This Fall For the Milwaukee Resource Recovery Plant.
Resource Recovery and Energy Review, January/February 1976.
89. Jackson, F. R. Recycling and Reclaiming of Municipal Solid Wastes. Noyes
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90. Jenike and Johanson, Inc. Storage and Flow of 5Oljd . No. SF5 — i, North
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92. Kelley, K. N. Hard-Facing Shredder Components. Waste Age, July 1976.
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96. Koppe rs Cu • I1I. El iL Storage file Let I ug Concep I for H dI og RDF. bu I • No.
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159
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160
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135. National Solid Waste Manufacturers Institute. Industrial and Oversized
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161
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143. Proceedings of 1976 National Waste Processing Conference. Boston,
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141+. Proceedings of the 1976 National Waste Processing Conference. Supplement -
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145. The Public Gets the Facts. Solid Waste Management, April 1976.
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152. Reinhardt, 3. J., and R. K. Ham. Solid Waste’Milling and Disposal on Land
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j53. Reinhardt, J. J., and R. K. Ham. Solid Waste Milling and Disposal on Land
Without Cover. Volume 2. Data Condensations. NTIS-PB—234 931. u.s.
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154. Resource Recovery Techno.33y for Urban Decisiontnakers. Urban Technology
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155. Resource Recovery: The ‘Pision and the Verities. Phoenix Quarterly.
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156. Resource Sciences, Inc. Proposal: Solid Waste Disposal and Electrical
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157. RexnOrd, Inc. Rex Apron Convcyors and Feeders. Brochure. Milwaukee,
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158. Rexnord, Inc. Solid Waste Handling ConveyOrs. Brochure No. 325-1071.
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159. Rexnord, Inc. Conveyor Division. Rex-Rated Apron Feeders. Bulletin No.
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160. Ruhner, C. R. Domestic Solid Waste and Household Characteristics. Waste
Age, April 1976.
16].. Rogers, L i. V., and S. J. Mitte. Solid Waste Shredding and Shredder
Selection. Environmental Protection Publication SW.1.40, U.S. Environmental
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162. Rotex, Inc. RoteX Screeners. Catalog No. 806. Cincinnati, Ohio.
162
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163. Ruf, J. A. Refuse Shredders at EPA’s Gainesville, Florida, Experimental
Composting Plant. Wasie Age, May/June 1974. pp. 58—66.
164. Savage, C., and C. J. Trezek. On Grinder Wear in Refuse Commi.nution,
Compost Science, September/October 1974.
165. Schrag, M. P. Combined Firing AppLications Study, Special Interim Report:
Needed Testing and Evaluation of Equipment and Processes in the Use of
Refuse as a Supplementary Fuel. Midwest Research Institute, Kansas City,
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166. SchuLz, H. W. A Pollution—Free System for the Economic Utilization of
Municipal Solid Waste for the City of New York: I. Thermal Oxidation
Processes. Columbia University in the City of New York, April 15, 1973.
167. SchwegLer, R. E. List of Reviewed Energy and Resource Recovery Projects.
Waste Age.
168. Schweiger, R. C. Power from Waste. Power, February 1975.
169. Seldman, 1. N. High Technology Recycling; Costly and Stilt Wasteful.
Compost Science, March/April, l 7A.
170. Selecting Air Qualit7 Monitoring instrumentation. Equipment News, June
1976.
171. Shannon, L. .1., C C a I . Test and Evaluation Program for St. Louis——Union
Electric Ref’ .ise P.mel Project. dv s Research Institute Proposal, Kansas
City, Missouri, January 75
172. Shannon, L. J., D. E. Fiscus, and P. C. Corman. St. Louis Refuse Processing
Plant: Equipment, Facility, and Environmental Evaluations. EPA—650/2—75—
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173. Shilepsky, A. Resource Recovery Plant Implementation: Guides for Municipal
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174. Shilepsky, A., and R. A. Lowe. Resource Recovery Plant Implementation:
Guides for Municipal Officials—-Planning and Overview. SW-157.t, U.S.
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175. Shredders and Pulverizers. In: 1976 Sanitation Industry Yearbook, P. Wulff,
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176. Shredding/Resource Recovery Saves Land and Money in Beaufort. Waste Age,
September, 1976.
177. Smith, F. A. Comparative Estimates of Postconsumer Solid Waste. Sw—148,
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178. Smith, F. A. Quantity and Composition of Postconsumer Solid Waste: Material
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1976.
179. smith, F. A. Resource Recovery Plant Cost Estimates: A Comparative Evalua-
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163
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181. Solid Waste Shredders. The American City and County. June 1976.
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183. Solid Waste Shredding: Continued Growth in Waste Processing. Waste Age,
July 1976. op. 3-.—40.
184. Solid Wastes, Caothermai Provide Alternative Power Sources. Professional
Engineers, Move nber 1974.
185. Sprout-Waidron, Division of Koppers Co., Inc. Live Center Bins for In-
dustrial/MunicipaJ. SolId Waste. Spec. Theet No. 6051. Muncy, Pennsylvania.
186. Stanton, StockwelliHenningSOfl, Durha.n and Richardson, Inc. Southern
California Urban Resource Recovery rroject, Volume 1: Executive Sunenary.
Los Angeles, California, February 1 76.
187. Sullivan, 3. F. Screening Technology Handbook. Triple/S Dynamics
Systems, Inc., Dallas, Texas, 1975.
188. Sullivan, P. N., and H. V. Makar. Quality of Products from Bureau of
Hines Resource Recovery Systems and SuitabiLity for Recycling. In: Proceed-
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189. Sussman, 0. B. Baltimore Demonstrates Gas Pyrolysis; Resource Recovery
from Solid Waste. Environmental Protection Publication SW—75d.j. U.S.
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190. Sutterfield, C. V. Refuse as a Supplementary Fuel for Power Plants--November
1973 through March 1974; Interim Progress Report. Environmental Protection
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191. Titlow, S. L. What Every Public Official Should Know About Resource Re-
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192. Train, R. E. Win the War on Waste. Presented at Third National Congress
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Study. Waste Age, July 1975.
194. Triple/S Dynamics Systems, Inc. Applications-Rotascreen. Brochure. Dallas,
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195. Tunnah, B. C., A. Hakki, and R. J. Leonard. Where the Boilers Are: A Sur-
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196. U.S. Environmental Protection Agency. Supplement No. 5 for Compilation of
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164
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199. U.S. Environmental Protec jon Agency, Office of Solid Waste Management Pro—
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200. U.S. Environmental Protection Agency, Office of Solid Waste Management Pro-
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201. U.S. Environmental Protection Agency, Office of Solid Waste Management Pro-
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202. Ward Industries, Inc. Fdjl—Safe Motion Control Switch. Bull. No. W-4 ..
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203. Warren Spring t.ahorritory. The ew Prospectors. Department of Industry and
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204. Watson Engineers, Inc. Evaluation of Belt and Pneumatic Conveyers in the
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Kansas, 1976.
205. Watson Engineers, Inc. Storage and Retrieval Bins. Report No, 76—MO1.9—7—020,
Overland Park, Kansas, 1?76.
206. Witteon, R. T. Urban Refuse: Mew Source for Energy and Steel. Professional
Engineer, November 1974.
207. Wilson, D. C. Innovation in the Technology of Recycling and Barriers to Its
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208. Wilson, P. 0., et al. Design Considerations for a Pilot Process for Refuse.
Massachusetts Institute of Technology, May 1973.
209. ¶Jinkler, P. F. An Infrared Spectral Sensor for Refuse Sorting. U.S. Environ-
mental Protection Agency, 1974. 81 pp.
210. Wittner, P. Who Cares? Agencies Study Solid Waste Plan Results. Daily
Tribune, March 24, 1976.
211. Wogrolty, E. C. Briquotting of Waste for Solid Fuel. Laboratory for Plastics
Engineering—tQ , Vienna, Austria,
212. woodruff; IC. L. Preprocessing of Municipal Solid Waste for Resource Recovery
with a Troernel. AIME Transactions, September 1976.
165
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APPENDIX A-2
MANUFACTURERS’ OF WASTE PROCESSING EQUIPMENT
Air Classifiers
Mac Equipment Company
Triple/S Dynamics
Americology
Combustion Power Company
Occidental Research and Development
Rader
Conveyors
Aerodyne Machinery Corporation
American Baler Company
Baletnaster
Freeman Balers
Hammermills, Inc.
Mayfran
Prab Conveyors, Inc.
Rexoord
Sullivan Equipment Company
Goodyear (conveyor belts)
Jeffrey Manufacturing Company
Cyclone Separators
F isher-Kiosterman
Carter-Day
Dryers
N. E. C.
Guaranty Performance
Fire/Explosion Control Systems
Fenwal
Magnetic Separators
Dings Magnetic Group
Eriez Magnetics
Freeman Balers
Stearns agnetics, Inc.
166
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Shredders/Pulverizers
American Pulverizer Company
3eloit Jones
Betna Engineering
Demon Manufacturing Company
Detroit Stoker Company
Eidal Metal Processor (mfd. by Carborundum)
Gruendlar Crusher and Pulverizer
Hamniermills, Inc.
HaZeInag
The Eeil Company
Jeffrey Manufacturing Company
Frances and John S. Lame Limited
Montgomery Industries Enternational
Newell xanufacturing Company
Pennsylvania Crusher Corporation
Rescor, Inc.
Saturn Manufacturing, Inc.
Tracor Marksman
Williams Patent Crusher Pulverizer
Enterprise Company
Storage Bins
American Sheet Metal, Inc.
Atlas Systems
Sprout-Waidron
Mille r-I offt
Screens
Rotex Screeners
Radar
Gruendler
Triple/S Dynamics
Filters (Baghous. )
Griffin Environment Company
Carter-Day
Mac Equipment Company
Total Systems
Allis-Chalmers wcs International
Browning-Ferris Whee labra tor-Frye
Torrax Fairfield Engineering Company
tracor Marksman
167
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APPENDIX B
CONTACTS
1. U. S. Environmental Protection Agency
Albert Klee, Chief
Processing Branch
EPA — Municipal Environmental Research
Laboratory (MERL)
Cincinnati, Ohio
John 0. Burckle
Project Officer
EPA-MERL
Cincinnati, Ohio
Robert Lowe
Steve Levy
Frank A. Smith
Yvonne Garbe
David Sussinan
EPA — Office of Solid Waste
Management Programs
Washington, D. C.
2. Consultants
Francis W. Hoim, Professor
Texas A & M University
College of Engineering
College Station, Texas
Jack J. Rollins, President
Watson Engineers, Inc.
8112 Newton
Overland Park, Kansas
JohnRuf
Burns and McDonnell
4600 East 63rd Street
Kansas City, Missouri
168
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CONTACTS (continued)
Bruce W. Simister
Equipment Consultant
207 East 66th Street
Kansas City, Missouri
3. System Designers
E. D. Stewart, Manager
Solid Waste Systems
Monsanto Enviro—Chern Systems, Inc.
St. Louis, Missouri
F. E. Wisely
Homer and Shifrin
St. Louis, Missouri
Dave Kiumb
Union Electric Company
St. Louis, Missouri
Harvey Funk, Assistant Vice President
William J. Hazell, Environmental Engineer
Richard R. Bell, Environmental Engineer
Russell Menke, Environmental Engineer
Jim Bierman, Mechanical Engineer
Henningson, Durham and Richardson
Omaha, Nebraska
Robert E. Mitchell
B. Milton Wilson
The Ralph M. Parsons Company
100 West Walnut Street
Pasadena, California
George Mallan, Director
Peter Ware, Plant Site Manager
George G. Gale, Engineering Project Manager
Occidental Research Corporation
1855 Carrion Road
La Verne, California 91750
169
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CONTACTS (continued)
John Mathews
Lynn R. Niendorf
J. R. Rivero
Union Carbide Corporation
Tanawonda, New York
Harvey Alter, Director of Research Programs
J. Berral
National Center for Resource Recovery
1211 Connecticut Avenue, N. W.
Washington, D. C. 20036
Ken Rogers
Kutty Menon
Richard Valonino
Combustion Equipment Associates
555 Madison Avenue
New York, New York
Ted Sjoberg
Stanley P. Lawler, Mooij
Ame ri cob gy
American Can Company
Greenwich, Connecticut
Heikki R. Ebo
Ebo & Rhodes, Consulting Engineers
East on, Pennsylvania
James A. Welty, President
Pyrolysis Systems, Inc.
3964 — 17th Street
Riverside, California
Peter Vardey
Waste Management, Inc.
900 Jorie Boulevard
Oak Brook, Illinois
Hal Gordy
Teledyne National
Monterey, California
170
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CONTACTS (continued)
4. Municipal and Regional Representatives
C. Malik, Department of Public Works
Richard V. Rodice, Project Engineer
William C. Ryder, Chief Engineer
City of Chicago
Chicago, Illinois.
Richard P. Chaste, Director
Connecticut Resource Recovery Authority
60 Washington Street
Hartford, Connecticut
E. Zulver, Project Director
City of Baltimore
Baltimore, Maryland
Edward Bales
Tennessee Valley Authority
Knoxville, Tennessee
Nathaniel Albee
Palmer Township, Pennsylvania
Arnold Chantland
Public Works Director
Ames, Iowa
Heikkl R. Elo
Elo & Rhodes, Consulting Engineers
Eas ton, Pennsylvania
5. Equipment Manufacturers
Wendell Patterson Screen, Dust Collectors
W. D. Patterson Company (distributor)
1319 Swift
North Kansas City, Missouri 64116
Andrew Livingston, President Dryers
Guaranty Performance
P. 0. Box 748
Independence, Kansas 67301
171
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CONTACTS (continued)
A. E. Gedaudas — Separation Sales Magnetic Separators
Eriez Magnetics
Ashbury Road at Airport
Erie, Pennsylvania 16512
Craig D. Blair, Eidal Markets Manager Grinders
Carborundum Company
Solid Waste Conversion Division
P. 0. Box 1497
Hagerstown, Maryland 21740
Dr. Clark Grinders
Beloit—Jones
401 South Street
Dalton, Massachusetts
Don Graverman, Vice President Sales Shredders
American Pulverizer
5540 West Park Avenue
St. Louis, Missouri 63110
T. A. Johnstone Storage and Retrieval Bins
American Sheet Metal, Inc.
Box 9
Tulatin, Oregon 97062
Henry G. Liseicki, Industry/Product Manager Conveyors
Rexnor d
P. 0. Box 2022
Milwaukee, Wis cons in
William A. Wilmot, Director of Solid Waste Conveyors
Conveyors Systems Division
Myf ran, Inc.
P. 0. Box 43038
Cleveland, Ohio 43038
J. Mike Meek Conveyors
SEMCO
P. 0. Box 7634—T
Houston, Texas 77007
172
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CONTA S (continued)
M. J. Gilberto, Manager Conveyors
Stephens —Adamson, Inc.
275 Rldeway Avenue
Aurora, Illinois 60507
Jim Ireland Conveyors
Fairfield Engineering Company
346 Chicago Avenue
Marion, Ohio 43302
William S. Hopkins Shredders
Tractor Marksman, Inc.
6500 Tractor Lane
Austin, Texas 78721
D. G. Morgan, General Manager Magentic Separators
Stearns Magnetics, Inc.
6001 South General Avenue
Cuday, Wisconsin 53310
Frank G. Hamilson Air Classifiers
Rader Systems, Inc.
2400 Poplar Avenue
Suite 312
Memphis, Tennessee 38112
Harold B. Mackenzie Air Classifiers
National Resource Recovery Corporation
330 Naperville Road
Wheaton, Illinois 60187
Rodgers H. Hill Air Classifiers
Triple/S Dynamics, Inc.
103]. South Haskel Avenue
Dallas, Texas 75223
Mike Heaman Cyclone Separators
Fisher—KiOS terinan
2901 Magazine Street
P. 0. Box 11190
Station H
Louisville, Kentucky 40211
173
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CONTACTS (continued)
W. B. Hickman, Principal Engineer Storage and Retrieval
Executive Vice President
Atlas Systems Corporation
East 6416 Main Avenue
P. 0. Box 496
Parkwater Station
Spokane, Washington 99211
M. S. Peterson, Product Manager Shredders
Jfffrey Manufacturing Division
Dresser Industries
P. 0. Box 1879
Columbus, Ohio 43216
Don Kaminsky, Manager Shredders, Compactors,
Hell Company Dryers
3000 West Montana Street
P. 0. Box 593
Milwaukee, Wisconsin 53201
Harry J. Skelton, Vice President Shredders, Trommels
Gruendler Crusher and Pulverizer Company
2915 North Market Street
St. Louis, Missouri 63105
John Kossakoskl, Marketing Coordinator Shredders
Ralph French, Engineering
Enterprise Company
616 South Santa Fe
Santa Anna, CalIfornia 92705
Harold Groves
Williams Patent Crusher and Pulverizer Company Shredders, Conveyors
2701—2723 North Broadway
St. Louis, Missouri 63102
K. WI. Schueler Magnetic Separators
Dings Company — Magnetic Group
4740 West Electric Avenue
Milwaukee, Wisconsin 53219
174
-------
CONTACTS (continued)
K. N. Ugargol Dust Collectors, Air
CEA—Carter --DaY Transport
500 — 73rd Avenue
N. E. Minneapolis, Minnesota 55432
N. Patterson Air Classifiers
Raytheon Service Company
12 Second Avenue
Burlington, Massachusetts
L. 0. Snyder Air Classifiers, Dust
Mac Equipment, Inc. Collector
6420 Underwood Avenue
Omaha, Nebraska 68132
K. R. Sterrett, Principal Engineer Storage and Retrieval
Spro ut—Waidron
Metal Products Division
Koppers Company
Nuncy, Pennsylvania 17756
Eugene N. A. Baikoff, President Shredders
Jacques Rossat
Bema Engineering Company
4 Chemin de Roseneck
Lousanne, Switzerland
Murray D. MeMabon Electrical Controls
R. G. DiCenzo
Westinghouse Electric Corporation
1215 West 12th Street
Kansas City, Missouri 64101
Mr. Andrea J. Martin Explosion/Fire Protection
Systems Engineer
Protection Systems Division
Fenwal, Inc.
DiviSiOfl of Walter Kidde Company
Ashland, Massachusetts
175
-------
CONTACTS (continued)
Ronald E. House Explosion/Fire Protection
Safety, Inc.
St. Louis, Missouri
Pat Ertz Explosion/Fire Protection
Safety, Inc.
2500 South Mill STreet
Kansas City, Missouri
176
-------
APPENDIX C
EQUIPMENT SPECIFICATIONS
Table C—i
EQUIPMENT DATA - SHREDDERS
H nnn.1ACt, ,rn. r An. Icerfeer lit! I In n. vii IIai WI iliinnP Cruen ’i l.r in! frey
Node I 60-90 690 7119 6,100 84-60 994
Il ortoontel Ilo r l oonp i l I Ioti o nt n . l Itor leo ot.t flotteontit I lont eoot*t
I I,.w,oer,t li II .nnocr.nf 8 IIn..n.rn.ttl IIo . r nti l I16nnonnntI I
Rev rNth Ie No No No 7 . . NA No
l4oI I .t (fr$) 47,671 46,954 6 1,364 6 1,344 ‘ .3 ,713 70,455
VnltNAe(voit n 4,160 NA 1$ NA NA i i ’ .
1 1, 1.6 Co,,t oI Wat.r Npr .y NA NA NA NA
Pt .rtop Yin. .,
O3npty ( . .n’C ” lA$) IN NA 1 16 8 . NA N’.
lit NA I I ’ . NA NA I A !
Il.,e.dovo yin.. muIr.) 15-70 NA NA NA NA NA
IIi . . .n ,r
N.t.rINI W..r.nI !ni “ I ! ’ NnnRn , ,onn. Ninjø ,.. .. Il .tf l, ld NA
Met. , . . .,
W.i 9 ht I’..) 37.2 11. 1 11 8. NA 95 NA
No.6ev 40 32 32 40 30 3 !)
NIrnpa NA NA NA 6.11 IloubI. Fired hoot Cieo .
VelocIty (.1.) 71.6 HA IA! NA 10 . NA
Rnp l ic.lInI. Yen Ye. 7.i yen Ye. Yen
Tipp ibi. 34 1 Y n n 700 YiP You Y r.
fl.n ,eer Co .r.t. of Grit. Poll P,.Il Y . .li Pull NA Foil
1 0. 5 6cr Pli.t.
Net.rl.i 1640/1050 C .rbo ,i Hm. ,ginon N .n l i p n o u. $ 5 .9 5.... 114
Stv.t
A ,ljuotnl ,ln N O Ye. 116 y . I SA NA
linvernibi. N .. Yen NA TSP NA NA
Ant.
lie. (en.) 22.9 n. 22.9 I V . NA NA 7.6
(7.6 • I ) , ?)
WolilIt (bt) 2.3 (391.7) NA NA NA 89 NA
Thtcko.ni (C..) 20.3 NA NA NA NA NA
A4J.unt .Int. Ms NA 11’. NA NA I ii
Motor
up 1,000 1,000 1,000 1,000 NA t ,000
1 1 1 $ 7 60 500 720 900 900 NA
tn,tO r
Ot iNAt .r (.) I.S NA NA PA IA I A !
Np..9 (.1.) 57.6 NA MA NA NA I V .
InertIa (bp.-n . ) 19N.5 NA NA NA NA 6635.6
Nonn.i C.p,0(ty (N 9 /l.r) 30.3-40.8 116 HA Ill NA NA
risk Cep .ctty (116/he) 45.4 12.7 N I . 72.7 32 23
C.pit.l Coot ($) NA NA I A ! NA 1 16 P 16
Pno .rr (6w) NA MA 1,026 NA
1nar y Coun . t, .ed NA N ’ . IA! I V . HA
( 6 . 1/ 14 *)
NA 1101 avn.IlnbI .r not 1 Ic .abIn.
177
-------
TABLE C—i (concluded)
Manvmaot,Iror Carhoroocl’,m o,’Iott toil lot Iraror liarhaman o p E l
Model I 0 ( 10 Sl,ro.Iov’,ror 020 - - AGO 92 g
Type Ring fish vertical Vertical liorleontel Verti cal
(in.,..)’ rest it liaea..O net ii llaaaaera.t I I liaaaaer.al II
Rovoralklo NA N O Ye a Von Mon tee
Wo lgist ( Apt 6g b ? S i lO 10,000 9545.6 60,909 70 136, 9
Voltage (vol lv) 1 14 400 ‘ ,6 0/3 46013 120/4, 1643 115/4,66
Duet Control NO 96 116 116 Raghoaso ag, Pno.aaatto
Ate
Startop Tino
r.v.pty (eor.o..IeI 1 16 1 , 1 1 5111 5 -10 50 5— 10
lousiest (niuutoe) 56 NA 745 116 5 N A
Rivobown Tier (ml v.t,’n) 96 2 6 4 25 29.25
iiuamt’r
l lnter l n l 1 16 11 6 260 lOGO MR S Macroman Steel 1163
Wolgist (Isp) 29 116 6 ,5 Oariahio 11.3 79 an s I 9.65
Monio’r 6 ( 1 2 34 164 26 46
Shape 116 NA tot Inog.. lit ThIn Rnotaogular pi p Roetang l,lar
voloelty (n /u) 36.5 MA 60.6 69.6 719 9 69.5
R e ylnoo nh lt #6 116 Moe Ste Yea Yea
T ippuh l . #6 116 Moe You Sea O ne
(bonnet Cover-ego of Grate 66 06 116 116 11 10’ NA
Nroakor Liar-au
Macoctal IsA NA lit PI G UI -SO -S NA
Ad$oatahlo 96 166 146 (4.6 No NA
Rovor,lklo 116 1 16 1 16 116 Sea NA
( (rato
Mine (on) NA 06 NA at 10.2 n IS.? NA
WeIg ht (kg) NA NA 746 NA 1 16 NA
31,Irhnraa (on) NA l It 716 NA 20.3 NA
Adl,.etahbo NA NO NA 46 16. NA
toe
III ’ 1,51 )0 7 0,osrs l 200 250 1,0 4 9 0 I 000
R It I NA 1,700-1,700 1,115 1,175 9 4 10 600
M,,tor
Oln.eofnr ( c i I . ) NA I I NA 70.3 116
Spoo.l (n/a) 9,2 06 (9.6 60.6 71.90 #9,3
martin (kg—n 2 ) 5200.5 NA 110.3 110.) 66 NA
Nones ,! Cupnotty (14 1 1 /1st) NA NA 73.6 1 16 5 4 , 5 37.1
‘oak Capeolty (Mg/kr) 72.1 NA 2? ? 66 913 ,9 311.7
Cep ttal Poet ($2 N O NA 70,000 70,000 NA NA
i’,neor (Isv) ft NA 160 (06 560 NA
georgy macrood 06 1 16 MA NA 60,366 #6
( 1 13/ Fig)
178
-------
TABLE C-2
EQUIPMENT DATA— MAGNETIC SEPARATORS
Manufacturer Sterns Eriez Dings Din s
Model 30-A SR 60 in. SUMS 48 in. SUMS
Type Belt Drum Belt Belt
Weight (kg) 2,268 9,979 5,454.5 6,364
Voltage 230/460/3/60 NA 120/575 230/460
3 amps 60 Hz
Separator
Width (in) 1.4 1.8 1.5 1.2
Speed (m/s) 1.5 NA 79.3 30.5122
Magnet
Size (cm) 76 x 86 x 59 width NA NA
60
Weight (kg) 1,164 NA NA NA
Type Electromagnet Permanent Electromagnet Electromagnet
and Elec-
tromagnet
Power (kw) 2.75 7.2 15 14.3
Normal Capacity 24 NA 54.5 NA
Peak (Mg/hr) 45 45 90.9 45
( Fe 95 90-95 95+ 95+ -
Energy Consumed 36.5 KJIMg 10 HP 848 V..J/Mg 5 HP
Capital Cost ($) 6,614 22,000 35,000 23,000
Source: Equipment manufacturers.
179
-------
TABLE C-3
EQUIPMENT DATA — AIR CLASSIFIERS
Manufacturer Raytheon TripLcIS Radar NRRC
Model 1102B Vibrolutrator 130 2 Classifiers
Type Rotary Drum Vibrating Straight Concentric
Voltage 230/460 NA NA
Dimenc ions
Length (in) 17.9 NA 7.6 9.1, 4.6
Width (in) 6.9 NA 2.6 2.1, 1.5
Height (in) 12.8 MA NA NA
Ancillary
Equipment Airlock Blower Airlock Cyclone
Blower Cyclone Blower Blower
Conveyor Separator Conveyor Airlock
Dust Collector Airlock Cyclone
Separator
Airflow (m 3 /sec) NA 9.4 18.9-23.6 NA
Velocity (m/sec) 1.5—4.1 MA NA NA
Motor
HP 6/15,7.5,75, 3/250,30,25 25,200 2/200
2,10,150
RPM NA NA 1,750—1,780 NA
Normal Capacity NA NA 28 NA
(Mg/hr)
Peak Capacity 32-36 72.7 45 68.2
(Mg/hr)
Capital Cost ($) NA NA 114,934 NA
Source: Equipment Manufacturers.
180
-------
TABLE C—4
EQUIPMENT DATA - SCREENS
Maaufact’ rer Rotex Radar Triple/S
Model 522A 55 Rota Screen
Type VibraC1n Disc Rotary
Dimensions
Length (m) 5.4 4.8 12.2
Width (m) 2.2 1.7 3.2
Height (m) 1.4 1.1 NA
Weight (kg) 3,032 NA NA
Incline (degrees) 4 0 0-7
Motion Gyrating NA Rotating
Motor
HP 7.3 2/7.5 125
RPM 1,200 MA NA
Screen Openings 6.35 an and -2.5 cm 114 mm
1.0 ann
Screen Size
Length Cm) 3.7 NA MA
Width (m) 1.5 NA NA
Thickness (sin) NA NA 19
Motion RPM 211 MA NA
Diameter (cm) 8.9 NA NA
Norm Capacity (Mg/br) 5.45 NA NA
Peak Capacity MA NA 56.8
(Mg/br)
Capital Cost Cs) NA NA 160,000
Source: Equipment manufacturers.
181
-------
TABLE C-5
EQUIPMENT DATA - DRYER
Manufacturer Guaranty Performance
Model 1,005-400
Type Rotary Suspension
Dirnens ions
Length 12.2 in
Diameter 3.0 rn
Weight 19,318 kg
Voltage 460 v/3/60 Hz
Airflow 10.4 m 3 /sec
Velocity 22.9 rn/sec
Fire Protect Waterspray
Dust Control None
Ancillary Equipment 20 liP Motor, Airlock,
Rock Trap, Cyclone
Norm Capacity 6.7 Mg/hr
Peak Capacity 6.8 Mg/hr
Percent Moisture Reduced 3.5
Energy Consumed 1.24 x io6 < Mg
Capital Costs $176,000
Source: Equipment manufacturer.
182
-------
TABLE C—6
EQUIPMENT DATA - DENSIFIER
Manufacturer Heil
Model HTP-l,000
Type Compactor
Diinens ions
Length 9.1 m
Width 2.4 m
Height 3 m
Weight 15,909 kg
Voltage 460/230
Cylinder Pressure 141 kg/cm 2
Stroke 38 sec
Volume 2.8
Norm Capacity 45_55 Mg/hr
Peak Capacity 136 Mg/hr
Capital Cost $35,000-$40,000
Source: Equipment manufacturer.
183
-------
TABLE C-7
EQUIPMENT DATA - STORAGE AND RETRIEVAL BINS
Manufacturer Miller Hoht American Sheet Atlas Sprout Waldron
Metal
Model Type “H ” DRB-6 LC-50
Type Twin Screw Doffing Roll Bin Sweet Bucket Live Center Bin
Traversing
Unloader
Dimensions
Length (c i) 18.3 11.4 25.8 (Base 7.3
Diameter)
Width (m) 5.8 2 21.9 (Bin 3.5
Sheet
Base Diameter)
Height (rn) 10 5.9 6.1 (Deck 9.3
Diame cer)
Voltage 460 NA 480 NA
Power (kw) 112 NA NA MA
Motor
HP 150,1/2 NA 40,7.5 24
RPM NA NA NA NA
Discharge 2 Screws/ 4 Screws Sweep 6 Vertical
Variable Bucket Screws
Pitch through
center
Mechanism Traverse 8 doffing rolls 4 Conveyors 2 Horizantal
drive screws at
bottom
Storage Capacity 850 34 (5.7 Mg) 2,727
( ) (142 Mg) (455 Mg) j25 (it Mg)
Discharge Rate 55 Variable Variable variable
(Mg/hr)
Capital Cost ($) 74,540 NA 687,000 NA
Source: Equipment manufacturers.
184
-------
TABLE C—8
EQUIPMENT DATA - CONVEYORS
Manufa turer Senico i S i Mayfran B e x o oNi Staph
)jQdel 9315z Style “A 1IV C 84 x 2 .45 x
13.2.5 x 10 j n
pi . , atic p tjc Pnemnat ic Z-Pan Apr ofl Vibrating
Voltage 4,160 NA NA 460 NA NA
Pressure (kg/ITI’) 24-34 3,168 2,464 NA NA 3-60 x 230/463
Air lou (a 3 /sec) 5.7 3.8 1.1 NA NA NA
Velocity (m/sac 35.1 NA 36.6 NA NA NA
Width (diameter) 4.4 cm 35.6 cs O,3 cm 2 .08 a Flight 2.4 a Uight NA
Motor lIP GO OO 60 7.5 , . 0 NA NA
L ngt li N.; NA NA 22.9 c n Flight 30.5 cm Flight NA
Ocpth NA NA NA 15.2 c Flight 15.2 cm FlIght NA
lncli e (degrecs) NA NA NA NA 0-2 1 ) NA
speed (ca/aec) NA NA NA 9.1-15.2 0-20.3 NA
ho! ler
inboard/Outboard NA NA NA Inboard Outboard NA
Stress (cm-kg) NA NA NA 8 ,250 104,650 NA
Diameter (cm) NA NA MA 10.16 12.1 NA
Thickness (cm) NA NA NA 3.65 7.14 NA
Table Width (a) NA NA NA NA NA 2.1
Thickness (cm) NA NA NA NA NA 0.95
Incline (degrees) NA NA NA NA s dec1in
Strol e (cm) NA NA NA NA NA 2.54
NAtion NA NA NA NA NA 30 ’ -438 cpa
Motor lIP NA NA NA NA NA 20
aP I4 NA NA NA NA NA 1,200
Idler Pulleys Incline NA NA NA NA NA NA
Spac log MA NA NA NA NA NA
Normal Capacity 45 NA 3.6 NA NA 40.8
(Mgi tnt)
Peak Capacity 72.7 41 9.1 45.4 54.4
(Mg/hr)
Capital Costs ($5 MA NA NA 21,600
Source: Equipmnant Manutacturers.
-------
TABLE 08 (continued)
nasufacturer Stephens — Carrier— Fairfield Continental Iron Hustler true Hustler
Adamaun Mexnard
Model nit 90 305 s 72 Mckee 60 inches 60 inches inclined trnegh Pins hinge
15.8 * 25 NP
‘rjps vibrating Vibrating Belt Belt Belt flight
voltage 3-60 x 230/460 HA NA NA 1*0/460 440
Present NA NA NA NA MA NA
Airf law NA NA NA NA NA 3M
Vslecity (rn/eec) NA NA NA NA NA NA
Width (diaeeterflm) NA NA 1.5 1.5 1.5 2.1
P$ototHP NA NA NA NA NA 20
langth(a) NA NA NA NA NA 5.2
Mpth(m) NA NA NA NA N A 1.2
pa I nt l ins (degrees) NA NA 22 20 34
Spad (cm/sac) N A pa 76.2 109 NA NA
toilers NA NA NA NA
inward/Outboard NA NA NA NA NA NA
Stress NA MA NA NA NA NA
uLaaetsr (cm ) NA NA NA NA NA NA
Thickness (cm) NA NA NA NA NA pa
Table Width (a) 2.3 1.8 NA NA NA NA
Thickness (cm) 0.95 NA NA NA NA NA
Incline (d.grees) 5 declIne 1 decline NA NA NA NA
Stroke (cm) 2.34 NA NA NA NA NA
N otion NV 4 CM NA NA NA NA NA
Not orN ? 2.5 13 NA 15 20 pa
RP M 1200 NA 20 ’ NA NA
141cr Pulleys Incline NA NA NA 35 35 NA
(degrees)
Spacing (a) NA NA 1.5 NA NA
Normal Capacity 40.8 NA NA 54.5 54.5
Gig/br)
Peak Capacity 54.4 45 55 NA 90.9 90.9
Glg/hr)
capital costa (5) 25,300 NA NA NA NA 35,000
-------
TABLE C—9
EQUIPMENT DATA - BAGHOUSES
Manufacturer Griffin carter-Day Griffin Griffin
Model JA 1200D 144RJ120 JA48OS D-1296
Type Reverse Jet Reverse Reverse Reverse Jet
Height (rn) 4.7 9.8 4.7 8.8
Length (in) 12.8 NA 7.3 12.2
Width in) 3.3 4.3 1.7 4.7
No. bags 1,200 144 480 1,296
Cloth Area (m 2 ) 997 355.5 398.8 1,077
No. Modules 10 1 4 1
Airflow (m 3 /sec) 30.4 9 12.4 47.2
Cost MA NA NA $89,000
Source: Equipment manufacturers.
-------
APPENDIX D
EQUIPMENT INSTALLATIONS
TABLE D- 1
SHREDDER INSTALLATIONS
Shredder Type Manufacturers
Type & ot Rated capacity Use ol
Location Start-up Quantity waste (tons per hour) Products Status
ALASKA
1976 I vertical municipal 5 TPH tanc lf ill operarion i
CALIFORNIA
Lp AngeIes 97$ I vertical rnurnci pal IS TPl landfill pilot protect
en Diego 976 I horizontal municipal 35 TPH pyrolyws pilot protect
COLØRADO
Alamosa P972 I vertical municipal IS TPM l ndfilI operational
1975 2 vertical municipal 20 TPH la ,dfill lw/ferrous operational
sep ar ation l
1974 I vertical municipal 5 IPH landfill operation I
CONNFCTICUT
Ansonla 1974 I horizontal 08W 30 IPH ferrous recovery operationa 1
8. incineration
DELAWARE
New CIstle 972 2 horizontal municipal 50 TPII fertou recovery operational
County primaries (prim aries i & landfill
2 hOritontal
secondaries
FLORIDA
rpvard County 970 2 horizontal municipal 75 TPt ferrous recovery operational
& 36W & landfIll
Ft. lauderdale 1973 I horizontal municipal 60 IPH incir’erati on operarionai
&OBW
rnpano Beach 1972 vertical municipal IS TPH landfill operational
1978 I vertical municipal 60 TPH l ndfilI 8
codisposal teems operational
GLORGIA
ftid ita 1970 I horizontal municipal 60 TN - i bate Landfill operationai
ekalb 1973 2 vertical rnuniciral 50 TT’I -l landfill operational
ILL INOiS
Ch lcaaa 1970 I horizontal OBW 25 TPH Iand D( p amlon al
Chicago 1970 2 horirOnral municipal 75 TPH each ene y recovery starr-up
pdmaries & 08W
2 vertical municipal 60 IPI-4 each
secondaries
INDIANA
east Chicago 977 I horIzontal 08W 25 TPH ir iciner fion operational
lOW A
Ames 975 2 horizontal municipal 50 IPH each j rgy recovery operational
I ortwntal
primary
I h riz* ntal
secondary
Source: Wacte Age, July 1978
188
-------
TABLE 1)— 1 (contInued)
KANSAS
McPherson 975 I vertical municIpal IS IPII landfill operatIor i al
KENTUCKY
Louisville 962 I horizontal 08W 20 TPI4 incineration operatIon tl
LOUISIANA
New Orleans 1976 I vertical municIpal 60 TI’H resource recovery Start-up
& landfill
1 horIzontal 08W 60 TPH
Vermiillori Parish 978 I horizontal municipal 40 7PM landfill starr-up
MAINE
Lewiston 1977 I vertical munIcipal 30 TPH ferrous recovery operational
8 08W & landfIll
MARYLAND
Sal(tmore 1975 2 horIzontal municIpal 50 7PM each pyrolysis pilot project
Coc8.eysvllle 1975 2 horIzontal municipal 70 TI’ l4 each resource recovery operational
& landfill
MASSACHUSETTS
Hotlssron 1974 I horizontal municipal 40 1PM Ferrous recovery operational
8 05W & landfill
MVS OURI
St LouIs 1969 I horizontal 08W 30 T H Incineration operational
MONTANA
Great FaIls 1973 2 vertIcal municIpal 20 TPI ferrous recovery ope!ational
IS TPH & landfill
NU 1RASKA
Omana 1976 I horizontal municipal 50 TPH ferrous recovery operatIonal
& 08W & bale landfill
IJEW ERSEY
Moitmouth 1975 2 vertical municipal 40 7PM each ferrous recovery Operational
& landfill
NEW YORK
Elmira 1973 2 horizontal municIpal 40 7PM each landfill operational
8 08W
NORTH CAROLINA
C,uilferd County 1973 I vertical municipal SO 7PM landfill Operatlor tal
& 08W
OHIO
Columbus 975 3 horizontal munidpai 60 TPH each ferrous recovery operational
& 08W & landfill
Wiilou hby 1Q73 2 vertical municIpal 12 1PM each landfIll operationai
OREGON
La crande 1978 I vertical municIpal 20 IPH ferrous recovery
& landfill operati onal
Lane County 1977 2 horizontal municIpal 65 ‘TI’H (primary) landfIll operational
I horizontal 45 Tl’14 (secondary)
primary
I horizontal
secondary
189
-------
TABLE D—1 (concluded)
PENNSYLVANIA
Harrisburg 1Q70 I horizontal 08W 25 TPH iflClrt Ct atlofl O pef atlonal
Charleston 974 3 vertical municIpal 75 TPH ferrous recovery operational
& 08W & landfill
GeorgetOwn
County 974 I vertical municipal 20 Tt’H ferrous recovery operational
& landfill
Beaufort 1975 vertical municipal 20 TPH ferrous recovery operational
landfill
Williamsburg
County 1973 I vertical municipal 20 Tl’H landfill operational
SOUTH DAKOTA
Aberdeen 1975 I vertical municipal 20 TPH seperation operational
& landfill
TEXAS
Houston I 965 1 horIzontal municipal 40 TPH resource recovery operational
Odessa 974 I horizontal municipal 50 TPH ferrous recovery & operational
soil enrichment
Texarkana 977 I horizontal industrial 20 TPH ferrous recovery operational
8. landfIll
VIRGINIA
Norfolk 1975 I horizontal municipal 30 TPH incineration operational
& 08W
WASHINGTON
Cowlitz County 1976 I horizontal municipal 50 Yl’M landfill operational
Seattle 1978 I vertical industrial 20 TPH landfill operational
Tacoma 1971 I horizontal 08W 40 TPH landfill operational
WISCONSIN
Appleton 1974 2 horizontal municIpal IS T H each ferrous recovery operational
& landfill
M4cllson 1967 I horizontal municipal 10 T! H landfill w/ferrous operational
I vertic .4l IS TPH separation
Milwaukee 1976 2 horizontal municipal 15 TrH each energy recovery 8 operational
2vertical pe.sflredded 60 TN each ferrous separation
municipal
CANADA
edmonton. 1970 2 vertical municipal ZS TN each landfill operational
Alberta
Hamilton. 1Q72 3 vertical municipal 45 TN each ferrous recovery operational
Ontario 8. IncIneratIon
St. Catharines, 970 2 vertical municipal 30 TN each landfill operational
Ontario
Toronto. 1975 I horizontal municipal 20 TN ferrous recovery operational
Ontario & landfIll
Regina, 1973 I horizontal municipal 25 iPH landf Ill operational
Saskatchewan
190
-------
TABLE D—2
SOLID WASTE ‘1AGNET INSTALLATiONS
Belt Msgt ets
Resource Recovery Facility Aberdeen, SD
Division of Browning-Ferrous
9225 Lawudale City of St. Catherines
Houston, TX Ontario, C&nada
Resource Recovery Corporation Envirogetics, Inc.
Division of Browning-Ferrous 1600 16th Street
Hollieton, MA Roboken, NJ
c/n l4&T Prod, of Canada Ltd. Nei l - Venezue la
do . Ran. Solid Waste South America
Reduction Unit
Kenoca Avenue, Hamilton Texas Sanitary Landfill
Ontario, Canada 117 iurch Lane
Cockeysvil.le, ) 21030
Lambao& s-Lane
Wilmington, DE Ministry of the Environment
Experimental
Solid Waste Reduction Plant North York, Toronto
15th Street and River Road Canada
Great Falls, M l ’
Pleasant Grove, TJT
M&T cheaicals, Inc.
7000 Kapkowski Road Lehigh County .Authority
Elizabeth, NJ 07201 Allentown, PA
City of Ames Milwaukee, WI
Ames, Iowa (2 units)
City of Toronto
Company of Omedaga
Shredder Plant Canterbury City Council
Town of Saline, N? Canterbury, Australia
Zupan Enterprises M&T Products of Canada
Pueblo, Colorado Hamilton, Ontario
Canada
Aerobic Destructor
Fayettevill., AK Municipal Service,
Old Northport Road
Swtthtown, NY
Sources Equipment Manufactures.
191
-------
TABLE D—2 (concluded)
Drum Magnets
Cowlitz County, Washington
City of Harrisburg, Pennsylvania
City of Baltimore, Maryland
Refuse Energy System Company
Saugus, Massachusetts
Gulf Contracting Company
Brevard County, Florida
Cass County Reclamation
Peculiar, Missouri
Beaumont Birch Company
Baltimore, Maryland
Dnion Carbide Corporation
Linde Division
South Charleston, West Virginia
Special Magnets
City of Appleton, Wisconsin
Jersey City, New Jersey
Reynoldr Aluminum Company
City of Franklin, Ohio
U.S. Bureau of Mines Raw Refuse Plant
Edmonston, Maryland
Garrett Research
Levern, California
National Center for Resource Recovery
City of Washington, D.C.
192
-------
TECHNICAL REPORT DATA
(
Please read 1ns c dons on the revera e before completing)
1. REPORT NO.
2.
3. RECIPIENT’S ACCESSION NO.
EPA—600/2—80—007a
4. TITLE AND SUBTITLE
5. REPORT DATE
PROCESSING EQUIPMENT FOR RESOURCE RECOVERY SYSTEMS
Volume I. State of the Art
July 1980 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR S
8, PERFORMING ORGANIZATION REPORT NO.
David Bendersky, Daniel R.
Keyes, Marvin Luttrell,
MRI PROJECT NO. 4213—D
Mary Sixnister and Denis Viseck
9. PERFORMING ORGANIZATION NAME A
NO ADDRESS
10. PROGRAM ELEMENT NO. COS — Waste
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 64110
as—Fuels, Task 5.1 1NE624E624D1
11. CONTRACTJGRANT
68—03—2387
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Municipal Environmental Research Laboratory——Cin.,OH
Office of Research and Development
Final, Volume I of III
14. SPONSORING AGENCY CODE
U.S. Environmental Protecti
Cincinnati, Ohio 45268
on Agency
EPA/600/ 14
15. SUPPLEMENTARY NOTES
See also Volume II (EPA—600
/2—80—007b) and Volume III (EPA—600/2--80—007c)
Project Officer: Donald A.
Oberacker 513/684—7881
‘lb. A l MP. l
The purpose of this project was to study processing equipment and systems to convert
municipal solid waste (MSW) into a fuel or a fuel feedstock. The first phase was to
review the present state of the art and identify the research needs required to
advance the technology of waste—to—energy systems. Test plans were then formulated
and field tests conducted to meet some of the research needs. The study is intended to
provide information useful In the design, selection and operation of fuel and feedstock
preparation equipment for existing and future waste—to—energy systems.
Volume I presents the results of the first phase of the project and covers two principal
subjects: (1) the present state of the art, and (2) the additional research needs con-
cerning processing equipment for waste—to—energy systems. A major part of the first
phase was conducted in the period March through December 1975.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDEN11F IERS/OPEN ENDED TERMS
C. COSATI Field/Group
materials recovery
refuse
refuse disposal
processing
shredders
magnetic separators
research
solid waste
air classifiers
13B
68
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS IThirReporti
Unclassified
21. NO. OF PAGES
207
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Po,m 2220—1 (Ray. 4—77)
193
U.S. GOVERNMENT PRINTING OFFICE: 1980—65716510019
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