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 ------- 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. ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- t f - — h sh . .d. r—1 J _______ A,.., I. h . .i I Moq .ti C , M d. S.ga M , ______ Sh.. .. L M h1 1P,i ,m,y iii I J I Sh .dd. .j ______ . 5rMq..#e { .i in. L. _ .i” ”v (j ’ u ..i... WI,. S . Mø. NC* Li ’— ”v ________ H 1-H Th .dd_1__ [ . J___Ei ‘c’o’- __________ I I ‘‘ I Cl . . fl r _ J Aj. I_ . j— ’’ i_iF i , H S q. H_______ T .w.Wip. _________ OL JS G 5 3.ipims... M d. LJ ”’ L_ 4 i N V .. ______ I Sh SI k , $. ..p._ C’. PV OLY5IS u JIO ii L—I I C ’. I n - - H R ...i. nq M(Th ANL a...,,, SI.. __________ j________ I_ “ P S acsi l.iq t i I Figure 1. Fuel/feedstock processing systems at 14 plants. 12 ------- TABLE 4. PROCESSING EQUIPMENT USED IN WASTE-TO-ENERGY SYSTEMS 1. Receiving facilities a. Scales b. Building c. Loaders d. Ancillary equipment 2. Conveyors a. Flight b. Belt c. Vibratory d. Pneumatic 3. Shredders a. Hammermills - vertical, horizontal b. Grinders - roller, disc-mill c. Flail mill d. Wet Pulp e. Ball mill f. Knife mill 4. Magnetic Separators a. Belt type b. Drum type 5. Air Classifiers a. Straight b. Zigzag c. Vibrating d. Drum e. Concentric 6. Screens a. Trommel b. Vibrating-reciprocating and gyrating c. Disc 7. Dryers a. Drum-type b. Fluid-bed 8. I ensifiers a. Pelletizers b. Briquetters c. Cubers d. Extruders a. Compactors 9. Storage and Retrieval Systems 10. Electrical Control Systems 11. Dust Control Systems a. Cyclones b. Baghouses 12. Fire and Explosion Control Systems 13 ------- TABLE 5 TYPES OF PROCESSING EQUIPMENT USED OR PLANNED AT 14 WASTE—TO—ENERGY SYSTEMS Prinary Magnetic leceining Shreddtr Separator Teledn A.ani000 Sings Scales Pulverizer Mad l 60—90 Painbeak. i.f&ep Hans- Ding. Storage Pelletinet Ms oso Gthv4i Conveycro -— Atlas Rader. PSI. Rex— nord, Phyfran, P eivflgid Monsanto Atlas Jeffrey Hans— lecturing Reonord —— Griffin —— Iron Hustler Etoi000- outsit —- Ta unton Lonatian A.en, loan 5.ltDaete. NArylond Haltioure Cn ,snty. Haryl e.sd s .eIeatan. WAtt Vit ini . ie$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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 76 ------- 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. 77 ------- 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. 78 ------- 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 79 ------- Track Conveyor Figure 43. Two discharge methods used with silos. (a) (b) 80 ------- 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. 81 ------- Air Pocket MSW “Dead Spot” Constant Pitch Screw Figure 45. Flow problems encountered in MSW storage and retrieval. (a) Flowing MSW (b) 82 ------- L iop View — — Figure 46. Inverted bin with rollers A Motors 83 ------- I lop View 7 1 / / Figure 47. Rectangular bin with screws and doffing rolls. Screw Doffing Rolls Side View 84 ------- 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. 86 ------- 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 ------- Cleaning Mechanism Exit D sr Laden Ar ______ Air - Dust Figure 50. Circular Baghouse. 88 ------- Pump Far Bag C’eaning a-Dust Dust Fafling Rotary Ar Lock Figure 51. Rectangular Baghouse 89 ------- Irde Mechansm —— C eon Air Dtjst Dirty Water Discharge Figure 52. Wet scrubber dust collector. 90 ------- 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. 91 ------- 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. 92 ------- 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 .. ., 0 ®®100 ®@ (i’) $$.p j A. Moo .o O OH C nv. o. fo w®.o. Sp..d Pii 2 A .p Ib...I (iJ 1 —” (.)ø ..1 W ‘ °P St.,. 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 93 ------- 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 94 ------- 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. 95 ------- 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. 96 ------- 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. 97 ------- 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. 98 ------- 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. 99 ------- 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 ------- 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. 215 101 ------- 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, 102 ------- 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. 103 ------- 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. 104 ------- 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. 105 ------- 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! 106 ------- 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 107 ------- 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. 108 ------- 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. 109 ------- 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. 110 ------- 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. 111 ------- 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 112 ------- (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. 113 ------- 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. 114 ------- 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. 115 ------- 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. 116 ------- 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. 117 ------- 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. 118 ------- 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. 119 ------- 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. 120 ------- 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. 121 ------- 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); 122 ------- and Palmer Township, Pennsylvania (tronimel). There are no known installations using or planning to use a disc screen. 123 ------- 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. 124 ------- 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. 125 ------- 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. 126 ------- 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. 127 ------- 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. 128 ------- 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. 129 ------- 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. 130 ------- 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. 131 ------- 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. 132 ------- 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. 133 ------- 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. 134 ------- 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). 135 ------- 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. 136 ------- 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. 137 ------- 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. 138 ------- 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, 139 ------- 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. 140 ------- 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. 141 ------- 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. 142 ------- 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. 143 ------- 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. 144 ------- 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? 145 ------- 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 ------- and techniques for eliminating the dirt accumulation problem should be investigated. 147 ------- 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. 148 ------- 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. 149 ------- 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. 150 ------- 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. 151 ------- 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. 152 ------- 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 153 ------- APPENDIX A REFERENCES APPENDIX A-i BIBLIOGRAPHY 1. Aleshin, E., ed. Proceedings of the Fifth Mineral Waste Utilization Sym- posium. U.S. Bureau of Mines and III Research Institute, April 1976. 2. Alter, H.) and W. R. Reeves. Specifications for Materials Recovered from Municipal Refuse. EPA-670/2-75-034, U.S. Environmental Protection Agency, May 1975. 3. Altar, H., C. Ingle, and S. a. Kaiser. Chemical Analyses of the Organic Portions of Household Refuse; the Effect of Certain Elements on Incinera- tion and Resource Recovery. Reprinted from Solid Wastes Management, December 1974. 4. Alter, H., S. Natof, and L. C. Elayden. Pilot Studies Processing MSW and Recovery of Aluminum Using an Eddy Current Separator. In; Fifth Mineral Waste Utilization Symposium. Chicago, April 13—14, 1976. 5. Alter, H., S. L. Natof, K. 1.. Woodruff, W. L. Freyberger, and E. L. Michaels. Classification and Concentration of Municipal Solid Waste. In Proceedings of the Fourth Mineral Waste Utilization Symposium, May 1974. 6. Alvarez, R. J. Study of Conversion of Solid Waste to Energy in North America. Hofstra University, Hempstead, New York, 1976. 7. American Sheet Metal, Inc. American Sheet Metal’s Doffing Roll Metering Bin. Bull. No. DRB—76. Tulatin, Oregon. 8. Ames, Iowa (City of), The Engineering Research Institute of Iowa State University, ERDA Ames L.ab, and Midwest Research Institute. Evaluation of Ames Solid Wastes Resources--An Energy Recovery System: Quarterly Report No. 2, September 7, 1976. 9. Ames, Iowa (City of), The Engineering Research Institute of Iowa State University, ERDA Ames Lab, and Midwest Research Institute. Evaluation Program for the Ames, Iowa Refuse Fuel Project: Work Plan. Prepared for the U.S. Environmental Protection Agency, Cincinnati, Ohio. 10. Ananth, K. P., and J. Shum. Fine Shredding of Municipal Solid Waste. EPA—600/2-76—208, U.S. Environmental Protection Agency, Washington, D.C., July 1q76. 59 pp. 11. Ananth, K. P., and J. Shun. Fine Shredding Study Report No. 3, October 1 to October 31, 1975. Midwest Research Institute, Kansas City, Missouri, 1975. 154 ------- 12. Artanth, K. P., and H.. Schrag. Fine Shredding Study——work Plan. Midwest Research Institute, Kansas City, Missou j, 1975. 13. knanth, K. P., at al. Fine Shredding Study-—Draft of rask Report. Midwest Research Institute, Kansas City, Missouri, January 1976. 14. AreIla, D. C. Recovering resources from solid waste using wet-processing; EPA ’s Franklin, Ohio, demonstration project. Environment L Protection Publication SW—47d. U.S. Government Printing 0ffic , Washington, D.C. 1 1974. 26 pp. 15. Atlas Systems Corp. Typical Service and Instruction Manual Based on installation at the City of Ames, Iowa. Spokane, Washington. 16. Baltimore County: The Newest Kid on the Block. Solid Wastes Management/ RRJ, September 1976. pp. 36-40. 17. Bechtel Corp. Fuels from Municipal Refuse for utilities, NTIS—PE-242 413. Electric Power Research Institute, March 1975. 18. Bettham, C. B., and J. Diebold. Conversion of Soj 4 Waste to Fuels. NWC— TP-5197. Waval Weapons Center, China Lake, California, January 1976. 30 pp. 19. Beningson, P.. Ii ., K. .1. Rogers, T. .1. Latnb, and R. H. Nadkarrti. Produc- tion of Eco—Fuel-Il from Municipal Solid Waste--CEA/AjuL Process. Combus- tion Equipment Associates, Inc., and Arthur 0. Little, inc., New York. 20. Bodner, R. M. Dutchess County, N.Y. Hoves Tovards Pyrolysis. Waste Age, September 1976. 21. Boettcher, R. A. Air classification of solid wastes; performance of ex- perimental units and potential applications of solid waste reclamation. Environmental Protection Publication SW-3O . U.S. Government Printing Office, Washington, D.C., 1972. 73 pp. 22. Bro ssaud, A. Indirect Energy Savings Generated by Urban Refuse Recovery. In: Fifth Mineral Waste Utilization Symposium, Chicago, IllinoIs, April 1976. 23. Burns and McDonnell Engineering Co. Generation of Electrical Energy from Municipal Rcfusc and Waatcwater Sludge. No. 75—048—4. Kansas City, Missouri, 1976. 24. Carleon, 0., D. Spencer, and H. Christenson. Monroe County Resource Re.. covery Project. Raytheon Service Co., Burlington, Massachusetts, 1976. 25. CEACarter-DayCo. Dust and Air Pollution Control Systems. Brochure. Minneapolis, Minnesota. 26. CEAcarter-DayCo. Dual—Clone Dust Separators. Bull. No. D-543. Minneapolis, Minnesota. CEA Carter-Day Co. Industrial Dust Filters. Bull. No. RS-2. Minneapolis Minnesota. 28 Chantland, A. 0., and H. Funk. Ames, Iowa Opens Recovery System: Refuse Derived Fuel to be Used by City. Reprint from Waste Age, October l9 . 29 Cheremisinoff, P. N., and R. A. Young. Control of Pine Particulate Air Pollutants; Equipment Update Report. Pollution Engineering, Aaiguet 1976. 1.55 ------- 30 Chisainore, G. C., and R. H. R. Higgin. Ontario Resource Recovery Program. Province of Ontario, Canada. Toronto, 1976. 31. CiminO, J. A. Health and safety in the solid waste industry. American Journal of Public Health, 65 (1), January 1975. pp. 38—46. 32. City of Chicago. Suxunary of Solid Waste Disposal Systems Study. Chicago, Illinois, 1972. 33. Cohen, H., and C. Parrish. Densified Refuse-Derived Fuel...A Further Appli- cation of Waste. NCRR Bull. VI, No. 1. National Center for Resource Re- covery, Inc., Washington, D.C., Winter 1976. 34. Courcittee of Tin Mill Products Producers. Progress Report on Recycling. American Iron and Steel Institute, Washington, D.C. 35. Coninittee of Tin Mill Products Producers. Suninary Report of Solid Waste Processing Facilities. American Iron and Steel Institute, Washington, D.C., 1976. 36. Constant, P. C., Jr., H. C. Sharp, and G. W. Scheil. Collaborative Test of the Continuous Col.orimecric Method for Measurement of Nitrogen Dioxide in Ambient Air. Midwest Research Institute, February 1975. 37. Conversion of Refuse to Energy-Conference Papers. First International Conference and Technical Exhibition, Montreu. c-Switzerlirnd, November 1975. 38. Conveyor Equipment Manufacturers Association. Belt Conveyors For Bulk Materials. Cahners Publishing Co., Boston, 1966. 39. Copeland, J. 0., and F. A. Collins. An Investigation of the Best Systems of Emission Reduction for Fossil Fuel-—Municipal Refuse Fired Steam Generator Units. U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, August 1975. o. Cunisings, J. P. Final Report on the Class & Nonferrous Heta Recovery Sub- system, Franklin, Ohio. In: Fifth Mineral Waste Utilization Sympositen, Chicago, April. 1976. 41. Cutler, H. Scrap Processers and Resource Recovery.. .The Need for Expanded Markets. Institute of Scrap Iron and Steel, 1975. 42. Davis, S. M. Maintenance of Solid Waste Shredders. Waste Age, July 1975. 43. Dia’, L. F., L. Riley, G. Savage, and 0. J. Trezek. Health Aspect Considara- dons Associated with Resource Recovery. Compost Science, September 1976. 44. Dille, E. K., 0. L. Kiumb, and C. V. Sutterfield. Recycling Solid Wastefor Utility Fuel and Recovery of Other Resources. Edison Electric Institute Bulletin, January/February 1974. 45. Earley, 0. E., et al., ed. Energy and the Environment, Proceedings of the Second National Conference. College Corner, Ohio, American Institute of Chemical Engineers, Dayton, Ohio, November 1975. 46. The East Hamilton Solid Waste Reduction Unit-—SWARU. Waste Age, 1976. 47. Elo, H. K., and F. a. Rhodes. Solid Waste Fuel Pellets Provide Fuel Supplement. Pollution Engineering, February 1976. pp. 32-33. 48. Energy Alternatives: A Comparative Analysis. The Science and Public Policy Program, University of Oklahoma, May 1975. 156 ------- 49. Energy Recovery from Solid W aste: Volume I. Sunenary Report, Volume II. Technical Report. HASA/ASEE Systems Design Institute, September 1974. SO. Fan, 0. On the Air Classified Light Fraction of Shredded Municipal Solid Waste. I. Composition arid Physical Characteristics. Resource Recovery and Conservation, 1, 1975. 51. Fernandes, J. H. Energy Conservation and the Potential Role of Waste. Presented at United States/Japan Energy Conservation Seminar, San Antonio, Texas, February 1974. 52. Fifth Mineral Waste Utilization Symposium, List of Attendees and Speakers. U.S. Bureau of Mines and lIT Research Institute, Chicago, Illinois, April 1976. 53. Fifth Mineral Waste Utilization Symposium, Program. U.S. Bureau of Mines and lIT Research Institute, Chicago, illinois, April 13—14, 1976. 54. Fiscus, 0., P. Gorman, and L. Shannon. St. Louis Refuse Plant; Equipment Facility and Environmental Evaluation. EPA65O1275..044. U.S. Environmental Protection Agency, May 1975. 55. Fiscus, 0. E., et al. Test Program to Determine Optimum Sampling Pro- cedure and Documentation and Development of Optimum Laboratory Analysis Procedures for Refuse Derived Fuel. Proposal submitted to the Environ- mental Protection Agency for Midwest Research Institute, August 1975. 56. Fisher—Kiosterman, Inc. Wet Dust Collectors. Bull. No. 220w. Louisville, Kentucky. 57. 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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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- |