Solid Waste Processing. a State-Of-The-Art Report on Unit Operations and Processes. INSTITUTION Environmental Health Service (DHEW/PHS), Rockville, Md

DOCUMENT RESUME

ED 092 345 SE 017 240 AUTHOR Engdahl, Richard B. TITLE Solid Waste Processing. A State-of-the-Art Report on Unit Operations and Processes. INSTITUTION Environmental Health Service (DHEW/PHS), Rockville, Md. Bureau of Solid Waste Management. REPORT NO PHS-1856; SW-4c PUB DATE 69 NOTE 78p. AVAILABLE FROM Superintendent of Documents, U. S. Government Printing Office, Washington, D. C. 20402 ($0.75, paper cover)

EDRS PRICE MF-$0.75 HC-$4.20 PLUS POSTAGE DESCRIPTORS *Ecology; Environmental Research; *Management Systems; Recycling; Resource Materials; Sanitation; *State of the Art Reviews; Surveys; *Waste Disposal; Wastes IDENTIFIERS *Solid Waste Management ABSTRACT The importance and intricacy of the solid wastes disposal problem and the need to deal with it effectively and econowically led to the state-of-the-art survey covered by this report. The material presented here was compiled to be used by those in government and private industry who must make or implement decisions concerning the processing of solid wastes and the recovery and utilization of the wastes that are salvageable. The survey involved a detailed review of the pertinent technical and trade literature, personal interviews with individuals knowledgeable in appropriate fields, and questionnaires sent to the state health departments. For convenience, the report is divided into two major parts: Unit Operations and Processes and Major Waste Categories. The first part of the report is divided into six sections: Densification and Size Reduction, Separation, Sanitary Landfill and Open Dumping, Incineration, Chemical Processing, and Recovery and Utilization. This first part of the report also includes various regulations concerning solid waste disposal, discussion being based on responses to the questionnaires sent to the state health departments. The second part of the report, arranged alphabetically, covers all the major categories considered. The report concludes with a bibliography, which relates to both parts of the report. (JP) U.S. DE PARTMENTOF HEALTH, EDUCATIONS WELFARE NATIONAL INSTITUTE OF EDUCATION THIS DOCUMENT HAS BEEN REPRO DUCEO EXACTLY AS RECEIVED FROM THE PERSON OR ORGANIZATION ORIGIN ATING IT. POINTS OF VIEW OR OPINIONS STATED DO NOT NECESSARILY REPRE SENT IOOFF1CiAL NATIONAL INSTITUTE OF SOLID EDUCATION POSITION OR POLICY WASTE PROCESSING state-of-the-art reportonunit operations and processes I IOLID WASTE PROCESSING

(.1 0, chi state-of-the-art report w onunit operations andprocesses I/ This report (SW-4c) was prepared for the Bureau of SolidWaste Management by RICHARD B. ENGDAHL and staff of the Battelle Memorial Institute, Columbus Laboratories under Contract No. PH 86-66-160

U.S DEPARTMENT OF HEALTH, EDUCATION,AND WELFARE Public Health Service Consumer Protection and Environmental Health Service ENVIRONMENTAL CONTROL ADMINISTRATION Bureau of Solid Waste Management 1969 Foreword

UNDER authority of the Solid Waste Disposal Act (Public Law 89-272) the Department of Health, Education, and Welfare has assumed major responsibilities for improving solid waste management practices in the United States. These responsibilities include conduct of research and demonstra- tions for developing or improving solid waste handling and disposal methods. The Bureau of Solid Waste Management has sponsored the present study to provide a comprehensive reference to currently available solid waste unit operations and processes. Information is offered on the reliability of processes, performance data, economic factors, and range of commercially available equipment as an aid to researchers and those now engaged in solid waste management.

RT',..1-TARD D. VAUGHAN, Director, Bureau of Solid Waste Management. Contents PAGE INTRODUCI ION 1 Unit Operations and Processes DENSIFICATION AND SIZE REDUCTION 3 Preparation for sanitary landfill 4 Densification Size reduction Preparation for incineration 8 Densificatian Size reduction Preparation for composting 9 Hammerraills Flail mills Vertical-axis rasps Drum rasps Roller crushers Pulpers Preparation for salvage 10 SEPARATION 11 Processes incidental to separation 11 Size reduction Sizing Fluid-solid separation Sorting 13 Hand sorting Mechanical sorting Washing and scrubbing 13 Gravity separation 13 Heavy-media separation Jigging Table separation Spiral separation Magnetic separation 14 Electrostatic separation 16 Flotation 15 SANITARY LANDFILL AND OPEN DUMPING 16 Types of solid wastes dumped 16 INCINERATION 18 General characteristics of the incineration process 16 Kinds 01 furnaces 17 Industrial incineration 17 Capital costs 18 Operating costs 19 Waste-heat recovery 21 Heat available Methods of heat recovery Applications for recovered heat Performance of heat-recovery systems Economic incentive for heat recovery CHEMICAL PROCESSING 22 Hydrolysis 22 Combustion (incineration) 23 Extraction 23 Pyrolysis 23 Carbonization 23 Oxidation (chemical) 23 Sintering 23 Precipitation, gelling, and crystallization 23 Psie Calcination 23 Melting 23 Electrolysis and electrodialysis 2( Combination and addition 24 Evaporation 24 ton exchange 24 Miscellaneous processes 24 RECOVERY AND UTILIZATION 24 The scrap metals industry 24 Quantities of scrap returned to industry Kinds of nonferrous scrap metals and materials Prices of scrap metals Sources of scrap metals Marketing scrap metals Preparation of scrap metals 28 Production of marketable metals from scrap materials 29 Melting Melting and refining Smelting and refining Distillation Hydrometallurecal processes Regulations Concerning Solid Waste Dis- posal Based on August 1966 Survey_____ 31

Major Waste Categories 33

Bibliography 69 Figures 1 Densification data, refuse at Chandler, Arizona, test station (1954) _ 5 2Compaction data, treatment of British refuse (1963) 6 3 Compaction ratio versus percent reduction in volume 7 4Typical size-reduction flow sheet 12 5The reclamation of municipal refuse by the SACS process 26 6Depithing of bagasse 37 7Processing of U.S.Steel basic open-hearth slag at Wylam, Alabama 50 8The deinking of secondary Paper fiber by screening 54 Tables 1 Classes of chemicals used in flotation 15 2 Principal components of a municipal incinerator and costs 18 3 First cost distribution for parts of an incinerator installation 18 4Capital investment in equipment for fly -ash collection at the South Charleston, West Virginia, powerplant 19 5Comparative costs of two types of incinerators in New York City 19 6Operating costs for municipal incinerators in six U.S. cities 20 7 Annual costs of operating electrostatic precipitators at the South Charleston, West Virginia, powerplant 20 8The commercial treatment of industrial and municipal solid wastes 25 9Nonferrous scrap recovered in the United States in 1964 . _ ___ 27 10Partial list of precious metal scrap 27 11 Scrap metal quotations for August 16, 1966 28 12The production and utilization of blast-furnace slag In 1957 49 13Typical formulations used with flotation machines 63 SOLID WASTE PROCESSING A state-of-the-art report on unit operations and processes

ANY KINDS of solid wastesconsiderable, cross-referencing Is ex- from a wide variety of sourcestensive to eliminate repetition. The must e processed daily for disposalfirst part of the report is divided Into in the United States. The greatsix sections: Densification and Size diversity in physical farm and chem-Reduction, Separation, Sanitary ical content of the thousands of tonsLandfill and Open Dumping, Incin- of solid wastes produced makes iteration, Chemical Processing,and extremely difficult to obtain an over- Recovery and Utilization. This first all view of the disposal problem. Add-part of the report also includes var- ing to the complexity of the situation,iousregulationsconcerningsolid various industries and municipalities, waste disposal, discussion being based influenced by a wide range of geo-on responses to the questionnaires graphical, technical, and historicalsent to the State health departments. considerations, employ many differentThe second part of the report, ar- methods of treatment and combina-ranged alphabetically, covers all the tions of equipment. Intimately asso-major waste categories considered. ciated with the disposal of wastes,The report concludes with a bibliog- moreover, is a problem of equal sig-raphy, which relates to both parts of nificance: the conservation of thethe report. nation's natural resources. The importance and intricacy ofACKNOWLEDGMENTS the solid wastes disposal problem and the need to deal with it effectively Many people in government and in- and economically led to the state-of- dustry cooperated with the Battelle the-art survey covered by this report.survey team and contributed valuable The material presented here was com-information from their varied experi- piled to be used by those in govern-ences for this compilation. Their as- ment and private industry who mustsistance is gratefully acknowledged. make or implement decisions con- The survey team, whose activities were cerning the processing of solid wastescoordinated by Richard B. Engdahl, and the recovery and utilization of included the following: David E. Bear- the wastes that are salvageable. Theint and Hobart A. Cressdensification survey involved a detailed review ofand size reduction; Edward A. Beidler, the pertinenttechnical and tradeMary R. Fulmer, and George F. Sach- literature, personal interviews withselincineratlon,sanitarylandfill, and open dumping, and chemical re- individuals knowledgeable in appro-duction processes; John R. Burke and priate fields, and questionnaires sentRaymond W. Schatzphysical sepa- to the State health departments. ration; and Howard C. Renken, John Forconvenience,thereports isR. Burke, and Raymond W. Schatz divided into two major parts: Unit recovery and utilization. Editing and Operations and Processes and Majorreviewwereprovider.byDolores Waste Categories. Because overlap is Landreman. Unit operations andprocesses

WHETHER one or a sequence of unit Size-reduction equipment. divides operations is required for solid wastematerials and reduces their individual processing depends on many factors,or particle sizes. "Comminution" is chief of which is the nature of thea general term often applied to size- solid waste. In this survey, considera-reduction processes. Some of the tion of metallic wastes was limitedmore familiar examples of size-reduc- primarily to nonferrous materials, betion equipment are rock crushers, cause iron and steel scrap processing hourmills,anddomesticsink- isalreadyreceivingconsiderable mounted garbage grinders. attention from both Industrial and Densificationandsize-reduction government organizations; automo-equipment Is readily available in a bile salvaging therefore, is not cov-wide range of types and capacities ered in the section on densificationfrom many manufacturers. While and size redaction. There are, how- mu.:11 of this equipment was designed ever, many other waste disposal proc-to handle materials other than solid esses that require densification andwastes, most manufacturers are ready size reduction. Consequently, this sub- to modify existing equipment or to ject is discussed first. aid in the design and development of newequipmentforsolidwaste DENSIFICATION AND SIZE disposal. REDUCTIONS Densification 'andsize-reduction equipment has been applied to most Densification and size reduction aremethodsofsolidwastedisposal. two unit processes employing equip-Sanitary landfill operations employ ment widely different in function, per- various machines to increase the formance, and character. compaction and reduce the bulk vol- Densificationequipmentsignifi- ume of the refuse. Size-reduction cantly increases the weight of ma-equipment has been used In Prance terial occupying a given volume. Aon sanitary landfills for years and scrap-metal baling press Is an excel-has recently been tried in North lent example. Densification or com-America.Size-reductionequipment pacting equipment is not to be con- has been used to reduce oversize and fused with pelletizing, or briquetting. bulky wastes for incinerators. Shred- types of equipment. Pelletizing equip-ding the entire feed to the conven- ment functions in a particle-size- tional Incinerator has been tried, but enlargment capacity by agglomeratingapparently with little success. Com- material and usually does not produceposting operations make extensive a significant reduction of the bulk useofsize-reductionequipment; volume. however, most United States composting plants have been of the pilot Thehighlydevelopedsecondary- or demonstration type; hence, full- materials industry is not discussed, norscale and long-term operating experi- is equipment to provide densification endence with such equipment has been size reduction of waterborne solid wastes.lacking. Disposal by salvage has ac- 4 SOLID WASTE PROCESSING countedforanextremelysmall landfill. Some of the types to be dis- duced. A review of some of the vari- percentage of solid wastes. While cussed, such as packer-type collectionous types available from United States densification and size-reduction trucks, could also be discussed in con-manufacturers can be found in Ref- equipment has been employed innection with incineration or otheruse Collection Practice." A more re- salvage, applications have been few. methods of disposal. However, sincecent review appears in Machine De- An exception to thisis found inlandfill is the most common methodsign." These trucks normally carry England and Scotland, where directof disposal, they are included here. 10- to 30-cubic-yard bodies on a salvageofsolid wastes has been Densification. As human popula-standard heavy-duty truck chassis. intensively practiced. tions grow, suitable sanitary landfillAn exception to the practice of using In general, details on equipment areas become more difficult to locatea standard heavy-duty truck chassis were not found In the literature. Per-and more expensive. One obvious al-is the Wesco Jet, a packer truck de- formance data, if mentioned, were ternative is to make maximum use ofsigned specifically for refuse collec- usually limited to the horsepower rat-available areas by reducing the bulktion. Depending on the character of ing of the driving motor, a rotor speed,of the solid wastes. In most sanitarythe refuse, packer-type trucks can re- or perhaps the average size of thelandfills, crawler or rubber-tired bull-duce the material to as little as one- comminuted material. Reliability was dozers have been used to work thethird its original loose volume." Prices rarely mentioned. Economic factorsfills. Depending on the character offorcompletepacker-typetrucks were usually limitedto estimatedthe refuse, these machines can ef- ranged from $18,000 to over $30,000." operating or maintenance costs. Capi-fect a compaction ratio of about 3 to European collection vehicles were tal costs were not discussed to any 1. A machine designed specifically forreviewed by Rogus in Part II of an great extent in the literature surveyed. sanitary landfill work has becomearticle in Public Works.'" Four com- If more details are required, it will beavailable." This is a 25-ton com-paction systems are shown and de- necessary to initiate a more extensivepactor-dozeremploying lugged orscribed. One system employs two- program of correspondence and visitsgear-tooth-like wheels. The claim hasstage compaction with a reciprocating to manufacturers, operating sites, and been made that it quickly reducesram followed by a swiveled compres- consulting firms. packing crates and other large debris. sion plate that moves the refuse into Pertinent information on manufac-It was reported that twice as muchthe truck body. Two of the systems turers of densification equipment canrefuse can be placed in a given areause helical screws to compact and be found in Thomas Register of Amer- without increasing the depth of fill asmove the refuse into the truck body. ican Manufacturers' under the head- was formerly possible when a crawlerThe fourth system is quite unique in ings "Presses" and "Balers." Another tractor was used for compaction. that the truck body is a cylindrical source is The Waste Trade Directory.' Anotherlandfill-compactionde-drum fitted with an internal two-lead Oiz,e-reduction equipment is widelyvice is a ballasted-drum type withworm welded to the inner walls. The used and is particularly important inlugs;it is pulled behind a dozer."drum rotates at 3 to 4 rpm, crushing, the mineral and chemical process in-It also vibrates to improve compac-compressing, and advancing the ref- dustries. Because of this broad inter-tion. A gasoline engine carried on theuse toward the front of the drum. est, many articles were found dealing frame of the compactor supplies the As landfills are moved to more with the various aspects of size reduc- energy of vibration. distant sites, it becomes more eco- tion. Various types of size-reduction Few references were found in thenomical to employ central collection equipment are reviewed in the Chem-literature relative to compaction de-stations. At these stations, local col- ical Engineers Handbookand Thevices at sites of solid waste genera-lection trucks dump the refuse into EncytopediaofChemicalProcesstion. A British publication mentionedlarge-capacity transfer semitrailers Equipment' A review article by Sterna lever-operated unit intended tofor hauling to the landfill site." Local also contains a list of manufacturerscrush empty food, oil, or paint cans."'trucks dump the refuse into a hopper, and the types of equipment .each sup- A somewhat different unit, apparentlywhere it is hydraulically compacted plies."' Other sources for manufac-of United States manufacture, wasand pushed into the transfer trailer. turers of size-reduction equipment aresaid to crush tin cans, glass bottles, Rogus mentioned a similar type of Thomas Register and the Mechanicaland plastic bottles and jugs.'" The Engineers' centralized collection station used in Catalog' None ofthecrushing occurred between continu-Europe." This appears to be the same equipment mentioned in these refer-ous belts running at 100 feet persystem described in somewhat more ences was designed specifically forminute. solid waste disposal. detail in an English article'" This Vacuum-type leaf collectors seemsystem is based on a 7-foot-diameter PREPARATION FOR SANITARY to be increasingly common. The highby 21-foot-long compaction cylinder LANDFILL velocities at which the leaves enterfitted with a hydraulic ram. A 75- the collection box result in a signifi-horsepower electric motor powers the Most solid wastes have been dis-cant amount of compaction. An article hydraulic system. Refuse is loaded posed of in landfills. In fact, otherin Public Works described a 30-horse-from the top through a hatch closed disposal methods produce their ownPower "Giant Vac" leaf loader thatby a sliding door. When the compac- solid wastes that ultimately must finduses a 14-cubic-yard plywood collec-tor cylinder is full, the end is opened their way to a landfill of one typetion box fittedto a 13-foot-longand the refuseis pushed into a or another. Landfills have always beendump-body chassis." The cost was matching circular container mounted required and from all indications thisgiven at $2,800, which included $300on a transfer truck, will not change in the near future. for labor. A recent development in solid waste Following is a discussion covering Compacting of solid wastes at thecompaction is a unique machine de- the types of densification and size-re-point of collection has been practicedsigned by the D and J Press Com- duction equipment that have beenin the United States since 1950 whenpany."' ". "' The machine is 60 feet used when disposal is to a sanitarypacker-type refuse trucks were intro-long by 23 feet wide and it weighs Preparation for sanitary landfill5

500

1,1 1000

A 500 400 -0. 350'- 250-+

Kt 40 60 80 r applVed Load ,psi FIGURE 1. Densification data. Refuse at Chandler, Arizona, test station, 1954,

75 tons. Mounted on the machine arebeen reduced from 105 per week tounique machine in some detail. a wheel trencher and conveyor sys-only 10 per week. An interesting feature of the Brit- tem, a tamper, a dozer blade, and a An unsuccessful attempt at com-ish report is a plot of percent reduc- four-stage hydraulic press. Refuse ispacting refuse was made in Los An-tion in volume versus compressive dumped onto a side apron, whichgeles County, California, where com- pressure for refuse of three initial transfers it to the compaction presses.pactingand balingofmunicipaldensities. These data are referenced The refuse is extruded from the ma-refuse was Wed.'''. "°Compressorsto the Institute of Public Cleansing chine via a 36- x 36-inch chute intoand balers used were not entirelyand the work of W. A. Lewis.'" When a self-dug trench that can be up tosatisfactory and the bulldozers at thethe Chandler, Arizona, data are re- 8112 feet deep. Fill dirt is placed overlandfill sites had difficulty moving theplotted to a percent reduction in vol- the compressed refuse and tamped.bales around. Some work has alsoume basis, rather than density, they It was reported that the machine canbeen done at the United States Pub-differ from the British data (Figure handle large items such as old re-lic Health Service Test Station at2). The curves for the 170- and 243 - frigerators and furniture. Compaction Chandler, Arizona, on compressionpounds- per -cubic -yard British refuse ratio was reported to vary betweenand baling of municipal refuse. Thebegins to flatten out with approxi- 10 to 1 and 20 to 1. Two 450-horse-only published information found onmately a 70 percent reduction in vol- power diesel engines supply the power this latter operation is a density-ume at pressure of 6 to 8 pounds per under the control of two operators.versus-applied-loadcurve(Figuresquare inch. The comparable 250 - Cost effectiveness and reliability ap-1)." pounds- per -cubic -yard Chandler ref- parently remain to be determined. This curve appears to be in con-use curve has a very different shape In a refuse compaction project at flict with British data in a report de-and a 70 percent reduction in volume the King County Sanitary Operations,scribing a machine for compactingis not achieved until the pressures are Seattle,Washington, the objectiverefuse in barges.u° For hundreds of3 to 4 times those required with the was to produce s solid that wouldyears London has been reclaimingBritish refuse. No doubt differences neither decay nor emit harmful gasesareas by disposing of refuse in low- inrefuse composition caused this when used in a landfill. A proposedlyingwastelands along the lowervariance. high-pressUre (200-psi)compactionreaches of the Thames. Barges have The curves charted from the Brit- Process was expected to reduce solidbeen used to transport refuse fromish data indicate where the point of wastes to one-tenth of the originalLondon wharves and to disposal sites.diminishing returns is located with volume. The low density of the refuse reach-respect to the applied pressure. The A glass-wool and shingle manufac-ing the barges made for uneconomi-British article concludes that pres- turer in the United States was re-callightloads. To improvethesures much over 6 to 8 pounds per ported as using a transfer stationsituation,anoverheadfoot-typesquare inch would be wasteful and compactor," With use of the compac-compacting machine was developeduneconomical, since higher compres- tor, trailer runs from the plant to theand installed at Walbrook Wharf.sion pressures would result in only disposal site were reported to haveThe Britishreportdescribesthissmall increase4 in the percent reduc- 6 SOLID WASTE PROCESSING

80 170 lb/yd3 70

E 60 , Chandler ,Arizo no Data, 250 lb/yd3 .5, 50

z40 cr t 30

L 5 10 15 20 25 Compressive Force, psi FIGURE 2. Compaction data. Treatment of British refuse, 1963. tion in volume. While this analysisPuts the compaction ratio at 10, orduction of solid wastes for disposal applies to barges where total weight300 percent above that obtainable by sanitary landfill. Some applications that can be carried by a barge is lim-with a 70 percent reduction in volume.are rather unusual, at least compared ited, It does not hold for landfills, If the objective, then, is a reason- with ordinary United States practice, where a much greater unit loadingabletradeoffbetween compactionThe more unusual methods will be can be supported. For example, when ratio and overall compactor costs, itdiscussed first. compaction ratio is plotted againstmight be approached on the basis of Upon first consideration, grinding percent reduction in volume (Figurea plot of compaction ratio versus ap- municipal refuse before it is disposed 3), this Is not a straight-line func-plied compressive pressure. The pointof to a landfill might seem a needless tion, Most important is the increaseof diminishing returns will then beand expensive proposition, It is not an in the slope of the curve with increasewhere the slope of this curve "kneesunknown practice, however. A short in the percent reduction in volume.over" and becomes very nearly paral- article by Meyer briefly outlines the Thus, at the higher values of percentlel to the pressure axis. Heil - Gondard solid wastes reduction reduction in volume, small increases Since extensive compaction-ratiosystem based on a grinder developed result in very large gains in the com-versus applied-pressure data did hotin France.!°` The unique claim for paction ratio. For example, if col-appear to exist, it is recommendedthis hammermill type grinder is that lected refuse receives a 70 percentthat they be accumulated. Such datait will reject items that cannot be reduction in volume, the compactionwould be of great value to users andeasily reduced. This is achieved first ratio is 3.33. Gaining another 10 per-designers of refuse compaction equip-by hammer rotation that is opposite cent in the percent reduction in vol-ment. It would also be interesting toin direction to that in conventional ume raises compactionto5.0,a know how refuse might respond whenhammermilis and second by a rather 50 pereent gain over a compaction the applied load is released. tall vertical discharge chute built over ratio of 3.33. Another 10 percent gain Size reduction. Few published ac-the top of the mill. Ungrindable mat- to 90 percent reduction in volumecounts were available on the size re-ter is said to be batted up into the Preparation for sanitary landfill 7

20 VI = Initial volume Vf c.Final volume

1 I I 20 40 60 80 100 V;Vf Percent Reduction in Volume(PRV), x100 Vi

PRV CR 1 .1 ) CR 0% 1.00 10 Ili 20 1. 30 12543 40 1.67 502.00 602.50 CR 703.33 PRV 80 5.0 90 10.0 100 9520.0 100% 0

FIGURE 3. Compaction ratio versus percent reduction in opium!. 8 SOLID WASTE PROCESSING chute, where it is collected. Grindingfor final disposal. An 80-percent re- bustibles, grinding for greater uni- and sorting would therefore be ac- duction in volume, or 5 to 1 compac-formity, drying to bring moisture complished in one operation. Milledtion ratio, was reported as typical. content below 10 percent, and, finally, refuse with an original density of 375 Grinders were available from 18 toextruding a 2- to 3-inch-diameter bri- pounds per cubic yard has had its12 inches hi diameter with screenquette. Calorifie value was reported to densityincreasedtoabout1,050 openings from % to % inch in di-be in the range of 8,000 to 10,000 Btu pounds per cubic yard, for a compac-ameter. Separators are available toper pound. One drawback seemed to tion ratio of about 2.8 to 1. The milled remove metal, wood, plastics, glass,be that 6 tons of normal domestic refuse was claimed to be less attrac-and other nonpulpable materials."refuse produce 1 ton briquettes and tive to Pests. Where feed material was uncontami-the remaining 5 tons had to be dis- This system was reported in use atnated paper, the resulting uniformposed of by other means. a number of French landfills and at apulp was being reused by some paper Metal recovery from incinerator large landfill at Montreal. The city ofmills, by manufacturers of roofingresidue is a common practice. In Madison, Wisconsin, recently receivedpaper, and as paper mache for packingEurope, some plants bale this for sub- a demonstration grant to test theand decorative items. sequent sale. In the U.S. literature this Gondard process. Rogus mentions that Two applications of the syatemaspect of densifisation was barely some French farmers have been ap-have been described in the literature,mentioned. plying screened, shredded, and pul-one in a new bank building,' where Size reduction. With a few excep- verized refuse to their farmlands for thesystemhandlesdining-roomtions, the present application of size- many years."' wastes, and the other at the Anaheimreduction equipment to municipal Another rather unusual size-re-(California)Stadium."' The_ la,tterincinerators has been limited to the duction process was described in Engi-application is a $50,000 installationreduction of bulky or oversized items neering.'"Relatively simple, it consistsdesigned to reduce the 13,000 poundsin the United States as well as in Eu- of a large rotating pulverizer drumof trash that. accumulate during arope. Shredding of the entire feed has; into which refuse and water are intro-typical ball game. Nominal capacitybeen tried and was apparently in very duced. On the drum inside wall are of this unit is 2,000 pounds per hour.limited use recently. Its use has been fixed plates that elevate the refuse Brush chippers represent anotheradvocated for future incinerator ap- through a fixed crushing cone as it is type of on-site solid waste size-reduc-plications by Meyer."' forced farther along the drum. Thetion equipment that has been coming Bulky or oversized refuse is the cont. addition of water (up to 40 percent)into wider use. These brush chippersbustible solid waste that cannot, for helps fibrous materials, like paper, toare smaller versions of large woodseveral practical reasons, be directly break down. The resulting producthogs, which are simply hammermillscharged to conventional municipal in- has a peat-like appearance and iswith knife-like hammers. They werecinerators. This waste may be too no longer dusty or offensive. Densityavailable from many manufacturers.large for direct charging, it may burn increase is about 2.8 to 1, working with Reduction in volume is about 80 per-too slowly, or it may contain noncom- a feed density of about 288 poundscent. Chippers can be unit-towed be-bustible portions that interfere with per cubic yard. Process time in thehind a truck " or mounted with athe incinerator grates or residue-dis- drum is about 1 hour. packer on a truck chassis."' charge system. TYPical examples are The pulverizer described above is Paperboard-box shredders are yetconstruction and demolition wastes, made by Vickers Seerdrtun Limited,another method for reducing bulkfurniture, mattresses, and tree stumps. Surrey, England, and a plant is involume at the site of solid waste gen- A hatnmermill installation at the operation at Wheatley, Oxfordshire,eration. Although box shredders haveGansvoort Street Incinerator in New England. This particular drum is 8been rather common and the equip-York City was described in 1961." feet in diameter by 29 feet in lengthment has been readily available, noA test run indicated that it would re- and rotates at 11.5 rpm. Nominal ca- technical literature was found on theduce demolition wastes(primarily pacity rating is 45 tons per day (TPD),subject, although general advertisingwooden beams) . Nothing further was although a continuous 7yz tons perpamphlets were available. found in the literature, however, and hour (TPR) throughput is possible, it was learned from other sources that ft is housed in a temporary 18- by PREPARATION FOR INCINERATION the mill was soon taken out of service, 30-foot builsing, has a 50-kw power Theliteraturedescribesappli- A more recent news item indicates requirement, and is operated by twocations of both densification andthat the problem of satisfactorily re- men. The plant is designed to besize-reduction equipment to incinera- ducing bulky solid wastes still remains moveable to a new site. The Britishtors although the majority of theseto be solved!' The news item also men- article quoted present "all-up costs"applicationsinvolvesize-reductiontioned that the New York City Sani- at $1.40 per long ton, which they saidequipment. tation and Air Pollution Control De- could conceivably drop to $0.84 per Densification. Densification equip-partments were working together to long ton with further development. ment is not normally associated withevaluate the use of shredders for re- A slurry-type waste disposal systemthe incineration of solid wastes, Theducing oversize burnable wastes. using size reduction has been de-only description approaching a densi- Rogus, in articles on European inscribed that combines a grinder, afication process was found in Rogus'cinerators, stated that most of the slurry-transfer system, and a waterreview on Western European practice,incinerators investigated also handled extractor." 112, 4". " Paper and foodin which the making of briquetteslarge, oversize materials.""." These wastes are wet-ground to a pulp andfrom refuse was mentioned."' Experi-materials were segregated and moved the resulting slurry is pumped to anmental work has been done in Eng-by crane to specially designed impact extractor where the water is removedland and Switzerland, and more wascrushersormultiple-typeshears. and recirculated to the grinder. Thebeing Planned. The process involvedAfter being reduced, the material was semidry pulp is discharged to a cansorting the refuse to remove noncom-chuted to the common receiving pit Preparation for composting9 for processing with the normal refuse.success in the past. On the basis ofreduction equipment for composting Fichtner, Maurer, and Muller re-the two articles referenced above, itwill be discussed in six broad cate- ported that a Hazemag impact crusherappears that hammermills have beengories: hammermills, flail mills, ver- was in use at the Stuttgart incinera-unable to handle unsegregated refusetical-axis rasps, drum rasps,roll tion plant to reduce bulky incomingat an acceptable level of reliability crushers, and pulpers. refuse," The article did not discussand maintenance." *" Hammermills. Hammermi Ils repre- the crusher further. sent the broadest category and cover Kaiser proposed the burning of bulky PREPARATION FOR COMPOSTING alltypesofhigh-speed crushers, items on a refractory floor in a special Densification equipment is not nor-grinders, chippers, or shredders that bulk-refuse furnace, thus eliminatingmally associated with composting.employ pivoted or fixed hammers or the need for hammermills, which haveThere is mention in the literature ofcutters. These machines usually have sometimes operated with cnly indif-pelletizing compost; however, this ac-a simple horizontal rotor, but twin ferent results."' " tually functions as a particle-size-en-rotors and a vertical rotor orientation A wood chipper in use at a Fitch-largement process. Baling of salvagewere also available. However, the burg, Massachusetts, incinerator inmaterials, such as paper, cardboard,literature provided very few details. 19555" was used to reduce Christmasand metals, has been practiced at Part of the United States Public trees, banana stalks, and demolition some compost plants. Health Service research project Ini- wood wastes. Prior to use of the chip- Withrespecttosize-reductiontiated in 1953 at Chandler, Arizona, per, tree sap had caused prate prob-equipment,compostingoperationswas the development, construction, lems by sticking and jamming the me-have represented what is perhaps theand operation of a 10-tons-per-week chanical components. most extensive application of such (TPW) experimentalcomposting Although shredding of the entireequipment in the field of solid wasteplant" During the operation of this refuse feed to an incinerator has notdisposal. A size-reduction operation ispilot facility, substantial information been common practice, it was tried in required at one point or another Inwas reportedly gathered on the cost the early 1950's at the Betts Avenuevirtually all of the many types ofof refuse grinding, but further details Incinerator in New York City.", "' composting processes. were not gien in the project report, Four hammermills, each having a 30- The amount of size reduction prac- and attempts to obtain more informa- TPH nominal capacity, were designed ticed during composting operationstion were unsuccessful. into the plant. The shredding opera-can vary, depending on the type of A 1956 report of the American So- tion was admittedly experimental. composting process and the intendedciety of Civil Engineers presents cost The objective was to provide operat-use of the resulting product. A fewinformation on 12 different compost ing data and experience that wouldoperations compost the refuse in themethods." The pilot-plant operation determine whether a more homogen-"as-collected" condition, with no sizeat San Diego which is described was eous feed justifiedthe additionalreduction at all. Other processes re-on a rather small scale, Initial pile operating, maintenance, and capitalquire same size reduction of the in-weights running between 5,340 and costs associated with the shreddingcoming material, sometimes in a slow- 8,340 pounds. According to the report, equipment. It is interesting to notemoving rasping machine. Still otherthe cost figures do not include the ex- that shredders were not incorporatedcomposting processes require average pense of supervision, plant invest- in subsequent New York City incin- particle sizes below an inch. This re- ment, and other overhead, but do erator plants for treating the entire quirement has often been met by two- reflect the expense of grinding, clean- feed to the incinerator. stage grinding in hammermills. If the up, power, turning, wetting, fly con- Meyer, describing the Heil-Clon-final product is to be acceptable fortrol, additive materials, and screen- dard hammermill, mentioned the firsthome gardening and horticulturaling when utilized. Operating costs commercial installation of this mill inpurposes, it must be of uniform char- ranged from $1.56 per ton for an an incinerator would be made by aacter and free of rocks, glass shards,unground, no-additive, compost to a French firm in St. Quentin." A Swisslarge metal fragments, and other un-high of $20.48 per ton for a coarse Incinerator was also described indesirable, potentially injurious com- grind with a straw additive. The aver- which the refuse was milled, sewageponents. Screening, ballistic separa- age cost was $12.79 per ton. When sludges were added, ',rut the wet mix-tion, and final reduction in a roll grinding was employed, its costs ac- ture dried and then burned. The heatcrusher or hammermill usually ac- counted for 30 to over 60 percent of for drying was derived from the pre-complish this before the compost is the total cost per ton. The size-reduc- viously dried refuse-sludge fuel mix-bagged fordistribution and sale.tion unit was simply identified as a ture. Other uses for compost usually do notgarbage grinder and no further in- Meyer and Leibman each claimedrequire such stringent control on the formation was supplied. greatly improved incinerator opera-character of the product, so that a re- A full-scale operation involving the tion and savings on cost and size ofduced degree of size reduction or none Dano process was initiated in 1956 at other components from the use of at all, Is employed. Sacramento." The picked refuse, be- shredders.'", Explosive hazards As far as the size - reduction processfore entering the Dano blostabilizer from containers of volatile liquids andis concerned, all composting plants indrum, was ground in a 25-ton Penn- aerosal cans were eliminated. Also,the United States appear to differsylvania hammermill. The mill was feed rates to the incinerator could befrom each other, even others of theconsidered oversized for the job, and more uniform' and easier to control,same type,possibly because mostbreakdowns were reported as being but no published data were found onplants are demonstration or pilotinfrequent. Major maintenance con- these effects. projects. Rarely do two plants use the sisted of removing, resurfacing, and The use of size-reduction equip-same size-reduction equipment, in the replacing the hammers. This took 3 ment in shredding the entire feed forsame manner, and on the same type of to 4 hours to accomplish and was done an incinerator has not been a greatsolid waste. In view of this, size- every 3 months. Another hammermill 10 SOLID WASTE PROCESSING reduced the compost leaving the bio-design, were moved into position bytype. Only one reference to its use stabilizer. This plant was shut down in simple rotation. This unit was de-was found in the literature." This 1963. signed specifically for the reductionarticle briefly describes a smooth, A 1983 review of European cora- of municipal solid wastes when shockdouble-roll crusher in use at Almelo, Dc+ting equipment mentions hammer- loads and abrasion predominate. Thein The Netherlands. It was reported mills and rasping machine§ as the two flail reducer was used at two points inthat this crusher was used to reduce types of refuse grinders used in Eu- the composting processon the in-glass shards and other brittle mate- rope' Most ofthe haramermiliscoming refuse and during a regrindrials in mature compost before it were of the single-rotor, swing-ham- midway through the digestion phase.leaves the plant. mer, high-speed type. Some recent Vertical-axisrasps. Another ap- Pulpers. A final type of size-reduc- hanunermills, however, have employedproach to reducing operation andtion unit employed with composting tworotorsrunningatdifferentmaintenance costs of solid waste sizeoperations is the unique pulper in use speedsfor example 1,500 and 3,000reduction is to use the rasping ma at Altoona, Pennsylvania," This wet Min" chine. The vertical-axis rasp was de-PulPer consists of a 6-foot-diameter Another 1983 review covers a verti- veloped in The Netherlands."'" Itsteel bowl with a rotatable steel plate cal-shaft hanunermill develoPed byconsists of a vertical axle carryingmounted in the bottom. During opera- TolleinacheCompostingSystems, eight horizontal arms hinged to ro-tion, the bowl is first partially filled Limited, London, England.b1" Whiletate upward. The axle rotates atwith water, which is followed by the any size Is possible, the one described about 15 to 25 rpm, sweeping the armssolid material to be composted. The Is a 150-horsepower unit rated at 12over the upper bottom, or grindingsteel plate rotates at 650 rpm and in 5 TPH, The unit features mobility andfloor, of the unit. The grinding floorminutes produces a slurry containing ballistic separation of ungrindables. is made up of alternate plate sectionsabout 5 percent solids. The slurry is Maintenance was reported to be less containingeitherperforationsorthen discharged through a screen to than $0.26 per ton of refuse processed.welded extensions. The material toa screw-type dewatering press where The van Maanen system of com-be reduced is dropped into the unitthe moisture content is reduced to 75 posting makes no attempt at size re- where the rotating arms move it intoto 80 percent. A second press follows, duction until decomposition is com-contact with the protruding raspingwhich reduces the moisture content plete."'Raw, incomingrefuseis pins. The material that is suflicientlYto 60 to 80 percent. The pulp is then sprinkled with water and placed in reduced then drops through the holesdischarged to the digester. windrows. In 2 or 3 months, the wind- in the following plate. rows are turned, and in 4 to 8 months Rasping units are about 16 feet in PREPARATION POR SALVAGE the compost is mature. It is thendiameter by about 7 feet in height. The last method of solid waste dis- screened, sorted, and finally passedCapacities are in the 5- to 15-TPHposal to be considered in this section through a hammermill. This economi- range, depending primarily on theof the report is disposal by salvage. cal system of composting was in usesize of the holes in the perforatedFor the purposes of this study, salvage in The Netherlands, where the com-plates. Compared to a hamrnermM,is intended to cover the applications post was applied to amble farmlanda rasping unit has a higher first costof densification and size-reduction to maintain and improve the physicaland is larger. The advantages of aequipment to the direct recovery, characteristics of the soil. The articlerasp are in reduced power require-processing, and use of materials taken mentions harnmermIlls but does notments and much less maintenance. from nonferrous, mixed solid wastes, go into any further details. Drum rasps. Another type of rasp-such as those collected by municipali- TheHell-Oondardharrunerrnill ing unit is the drum type. In theties. This discussion does not cover the mentioned previously has also beenUnited States, this has been devel-wide range of equipment in everyday applied to composting, In Haarlem, oped in the form of a unit known asuse in the existing and already highly Holland, a plant used such a mill,"a palvemtor."..". 251, I" This is a 8-developed automobile scrap and sec- as did several in Spain." The Span-foot-diameter by18-foot-longin-ondary- materials industries. ish installations were at Pamplonaclined drum covered on the inside The literature survey indicated that (60 TPD), Zaragoza(120TPD),wall with triangular steel plates. Thisdisposal of solid wastes by salvage was Cadiz (40 to 50 TPD), and Madridunit has been used to tear open bags,limited. This was particularly true in (200 TPD) . Several others were being break up large agglomerations, andNorth America, and, with two excep- built or were being Planned. Themix the incoming refuse before it istions, It seemed as limited in Western Gondard hammermills are rated in sent to the flail-type htunmermills. Europe Only three articles were found the 10- to 14-TPH range and reduce The Dano grinder, Egsetor unit, iswith more than passing mention to the refuse to a nominal size of abouta drum-type rasp."' In addition to in-salvage as a means of solid waste dis- an inch. ternal rasping bars, this unit has aposal. Several of the articles found on See also: Zircaloy. screen within the outer drum. Mate-composting do mention that salvage Flail mint, A tomposting systemrialfalling through the screen isoperations were being, or could be, under development for a number ofPassed to the grinders or directly toapplied to the system. None, however, years in the United States makes usecompost piles. It rotates at 12 rpmoffered details describing existing or offlail-typeslze-reductionequip- and was reported to require about 8proposed densification or size-reduc- ment.", "'"''' "I This is a horizon-kw per ton of refuse. The Dano bio-tion equipment. tal, single-rotor unit with a studdedstabilizer also has a mechanical rasp- In the United States, large-scale shell and hammers attached to theingactiononmaterialmovingdisposal of municipal-type solid wastes rotor by means of chains. Replace-through the rotating drum. by salvage seemed to be limited to the ments of hammers and chains were Roll crushers. A crusher that seemedunique system existing in Los Angeles, report.ed to be relatively easy, while to have bad limited application toCalifornia. An article on this subject new shell studs, due to the uniquecomposting operations is the rollerappeared in a 1963 lame of Compost Processes incidental to separation11 Science!" Prior to 1957, residents of Rogus' series of articles on Westernspecific gravity; magnetics susceptibil- Los Angeles separatedtheirsolid Europeanpractices.Rogus stated ity;electrical conductivity;radio- wastes into garbage, combustible re-that, with the exceptions of Englandactivity; and decrepitation. fuse, and noncombustible refuse. The and Scotland, direct salvaging was In many instances it is possible to garbage was fed to swine and the com- not practiced extensively in Westernchange physical properties by such bustibles were burned in backyardEurope. He went on to point out thatmeans as chemical alteration of sur- incinerators. The resulting incineratorEnglish sail age plants did employface characteristics, drying to im- residue was mixed in with the non-highly developed and enlelent ma-prove electrical conductivity, oxida- combustibles, which were collectedchinery, including presses and baling tion to affect magnetic properties, and and disposed of through the salvagemachines. More extensive informa-application of vacuum to porous ma- industry. Since 1957 and the passingtion was not given. Bogus concludedterials to change specific gravity. The of air pollution laws, Los Angeles nothat the trend was away from sal- unit proceeses that are described in longer permits backyard incineration.vaging because of the effects of highthe following Paragraphs are:(1) Garbage not ground and flushed tolabor costs, modern technology, andProcesses incidental to separation, in- sewers was being put in with com-development of synthetic materials.eluding size reduction (crushing and bustibles and disposed of to municipal He further reasoned that new endgrinding), sizing (screening and clas- incinerators or landfills. Noncom-uses would have to be found fordilation), and fiuid-solid separation bustlbles were still being separated salvageablematerialbeforethis (thickening,filtration, dust collec- and disposed of by a contractor. method of disposal could be con-tion); (2) sorting; (3) washing and The prime material salvaged fromsidered competitive." scrubbing; (4) gravity concentration; Los Angeles' noncombustible refuse See also: Recovery and Utilization; (5) magnetic separation; (6) electri- was tin cans; although scrap iron, cast Individual Waste Types. cal separation; (7) flotation. iron, and nonferrous metals were also SEPARATION See also: Diamond Grinding Wheel removed. The cans were being used Dust; Refractory; Wastepaper, in a process that precipitated copper Physical methodsofseparation from leaching solutions at co*.per- may be applied to solid wastes by PROCESSES INCIDENTAL TO SEP- refining operati:ns. After magneticutilizing existing or induced differ- ARATION separation and processing to removeences in the physical properties of the extraneous materials (food wastes,materials being separated, The sePa- Size reduction. Before separation labels, paint, etc.), the tin cans wereration may result in the productioncan be accomplished, the materials to shreddedinto"premt". The canof a useful product or in easier dis-be separated must be liberated and shredder was described as a special posal of one or more fractions of thesufficiently reduced in size for appli- one developed to provide an ideal waste. cation of separation techniques. Btu, productfortheprecipitationof The materials defined assolid reduction and sizing, consequently, copper.Furtherdetailsonthe waste, "garbage, refuse, and othermay play an important part in most shredder were not given. discarded solid materials", have notseparation processes. Because the ma- Apparently, the only other large-been subject to separation treatmentterials that constitute solid wastes scale direct salvaging operation inother than the simplest type such asmay range from the hard-rock types North America was an installationhandsorting, because until recentlyto vegetable, fibrous, and even fleshy outsideMontreal,Canada." Thethere has been no need for separationtypes, a wide range of crushing and prime purpose of this plant was set-to permit easier disposal. It is quitegrinding equipment is required. In ually bulk reduction of municipal probable that with Increased empha-one instance, equipment peculiar to solid wastes, not salvage. The refusesis on this subject, more of the avail-the mineral industry may be quite moved from the receiving pits to hop- able techniques will find application.satisfactory, yet in another instance pers and from there to conveyor belts, A few cost data are presented here,the same machinery might be un- where it passed through a sortingbut they should be used only as ausable, For treating some materials, room. Apparently, all sorting was doneguide because costs may vary mark-new equipment might have to be de- by hand labor, the workers droppingedly in different applications of thesigned, as has recently been the case the Salvageable material into collec-same process. In addition, availablefor the processing of automobile tion boxes via chutes. Salable material cost data are at least several yearsbodies. In general, it might be con- was taken to one of two baling presses. old, and with the changing economiccluded that with the various types of It was reported that when salvag-picture can no longer be consideredcrushing and grinding equiPment ing was in operation, bulk was reducedfirm. available, units can be procured for by 40 percent and weight by 25 per- A large number of companies man-almost any type of size-reduction cent, based on the incoming refuse. ufacture various designs of the equip- operation. All material not salvaged Passed toment described. A typical reference If the material to be treated is hard one of two Cionde.rd harnmermills"source to manufacturers is the Miningand abrasive yet will fracture under impact or can be abraded, equipment From the mills, the refuse went to aGuidebook, which is published yearly!used in the mineral industry, such stationary packer which loaded 35-Similar guidebooks are published byas jaw and gyratory crushers, rolls, cubic- yard containers. These were, inthe trade journals that serve the vari-ball and rod mills, and hanunermills, turn, picked up by a special truck andous industries. is applicable. For materials that de- hauled to a landfill. Maintenance costs The major differences in physicalform under pressure, knife-blade or on the hturunerrailla were estimated toproperties by which solid wastes maycutting-type hammermills, shredders, be less than $0.57 per ton, with ham-be separated are as follows: color,chippers, etc., are applicable. mers being replaeed every 1,000 tons.luster; size; shape; tenacity, brittle- If extremely fine grinding is re- Salvage as a disposal method inness, or friability; structure and frac-quired, Particularly for materials uti- European countries was discussed Inture, texture; surface characteristics;lization rather than liberation, such 338-244--70---3 12 SOLID WASTE PROCESSING Feed

Size Reduction$

Sizing Oversize

Finished Product FIGURE 4. Typical size-reduction flow sheet.

devices as vibratory ball mills anda typical size-reduction-sizing flow Consequently, in a classifier closed- fluid-energy mills are available. sheet (Figure 4). circuit grinding operation, it is not High-speed agitators or macerators A combination of size reduction and unusual to find a concentration of may be utilized in some operations.sizing may also constitute a unit sep- higher specific-gravity material in the In the utilization of waste paper, foraration process when one or more offiner size fractions of the classifier example, liberation of ink from news- the constituents grinds more easilyproduct. print is done in a Hydrapulper, athan another, thus producing a fin- Particle shape affects sizing, Acicu- high-speed agitator manufactured byished coarse fraction and a finishedlar (needle-like) and platy materials the Black Clawson Company. A sim-fine fraction. The treatment of alu-are much more difficult to size than ilar machine is the Wet Pulper man-minum dross is an example of this. equidimensional particles. ufactured by The French Oil MillTheslagcomponentbreaksup Probably one of the most significant Company. readily, whereas the malleable alu- advances in screening has been the in- The use of several different types ofminum does not. After crushing andtroduction of the sieve bend. This is a crushing and grinding equipment isscreening, a coarse oversize, high instationary, concave screen made up quite common. This has led to thealuminum, and afineundersize, of wedge wire bar screen at right development of such terms as primaryhigh in slag, are produced. angles to the material flow. Because or coarse crushing, secondary or in- Sizing may be done either wet orof the angle at which the material termediate crushing, fine crushing, dry with screens or classifiers. Screenscontacts the screen, a wider screen and grinding, the distinctions between may be either stationary or moving,opening can be used for a given size the operations being purely arbitrary.fiat or inclined. Screen movementof separation. This increases the com- What may be a line-crushing unit in may be brought about by shaking, ro-mercial field of applitation down to as one treatment may be a coarse-tation, or vibration. Screen openingsfine as 100 mesh for high capacity crushing unit in another. may vary from several inches or more per unit of screen area and minimizes Size-reduction equipment is usuallyin the coarse grizzly screens, the screen blinding, the filling of screen openings quite massive. It is generally avail- being constructed of railroad rails, toby particles of the same size. able in unit sizes varying from lab- fine screens with openings 0.0015 inch The greatest improvement in classi- oratory devices to mammoth unitsin diameter (400 mesh), or boltingfication has probably been the intro- that require several-thousand-horse-cloths with even finer openings. Theduction of the cyclone, both wet and power motors to operate. openings may be round, square, rec-dry. The crushing surfaces are usuallytangular, or slotted. Round, fiat, and Sizing is a relatively simple and in- replaceable,thus, thelifeof thewedge-shaped wires may be used. expensive operation. Horsepower re- equipment is long. A 30- or 40-year Classification generally takes thequirements have beer. low. Screen life for, well-designed and well-con-Place of screening in the fine-sizecloth replacement has been the major structed units is not unusual. ranges. Wet classifiers of the helical-maintenanceiteminscreening, The cost of size reduction in thespiral type, the rake type, or the cy- whereasinclassificationwear of coarse sizes is lowa few cents perclone type are very common, Airflights or spirals has been the major ton, whereas in fine grinding it mayclassificationlikewise employs cy-cost item. Rubber, ceramic, or other run from $0.50 to $1.00 per ton. Theclones or mechanically driven cen-linings keep maintenance low in cy- primary cost item is power, mainte-trifugal separators clones or centrifugal separators. nance being next. Labor cost is usual- The mechanism of sizing by set eens See also: Bagasse: Brewing, Dis- ly low unless the operation requiresis dependent simply on particle size tilling, Fermenting Wastes; attendance to permit uniform feeding.versus size of opening, whereas in Wastepaper; Wood Wastes; Zir- Sizing.In many operations sizingclassification, settling rates determine caloy. isconcurrent with sizereduction. the size of the separation. Settling Fluid-solidseparation.Inmost The function of sizing is to limit therates are a function of size, shape, andprocesses of physical separation of size of materials going to the next specific gravity. Of two particles of the materials, some method must be em- unit processeither further crushingsame size and shape, the one with theployed for the removal of a solid trac- or separationas may be seen from higher specific gravity will settle first. tion from a fluid medium. Gravity separation 13 For liquid-solidseparation, suchequipment being associated with the Mechanicalsorting.Mechanical devices as thickeners, filters, centri- waste-paper-salvage industry. sorters utilizing color or radioactivity fuges, cyclones, classifiers, and even Hand sorting. Hand sorting of ma- have recently been introduced. Color screens have commonly been used for terial is probably the oldest unit proc-difference or radioactivity is detected this purpose. Crude liquid-solid sepa-ess of physical separation. To a de-by a sensing device, which In turn ration can be effected by stationarygree, sorting operations are performedtriggers an air blast that blows the drainage on a sloping floor or in tanksin virtually every manufacturing in- sensed particle out of the mainstream or bins with provision for liquid re-dustry, if for no other reason than toof fall. At Eldorado, Canada, uranium moval at the bottom. reject imperfect items. ore larger than 3 inches is sorted. A Gaseous-solidseparations(dust The material to be sorted must have demonstration run in South Africa collection) may be accomplished inareadilydistinguishablepropertytreated between 25 and 50 tons per settling chambers, baffle-type crliec-such as color, luster, shape, size, gen- hour. tors, centrifugal collectors (cyclones) , app:arance, or radioactivity. It See also: Wastepaper. mechanical -type collectors, gas filters, should be the minor constituent and bag houses, spray washers, and elec-of such size and weight that it can WASHING AND SCRUBBING trical precipitators. readily be moved. Washing and scrubbing techniques In many of these devices, separa- In some basic industries such ashave been employed to remove minor, tion of the fluid and solid is simplymining, hand sorting has been elim- fineconstituents fromthe main a matter of settling by means ofinated because of the increasing cost coarse bulk of a material. If hand thickeners,settlingchambers, bagof labor, and, to a lesser degree, the sorting is to be employed, removal of houses, etc. In other devices, such asdevelopment of mechanical methods. these fines may be advantageous in filters, the fluidof the fluid-solid Much of the solid waste generatedremoving surface dirt. Washing and stream is forced through a membrane by an urban population could be handscrubbing can be used if a fine frac- (filter cloth) that retains the solids sorted at its source to minimize subse- tion is worthless or if it would create on its surface. quent disposal problems. (This hasa problem in subsequent separation Thickening followed by filtr,tionbeen done in Los Angeles for many processes. Clay, for example, is read- has probably been the most commonyears.) Separation of household and ily removed by washing, Clay left with procedure used in liquid-solid sepa- similar waste into such categories asan ore is troublesome in crushing and ration. With solids that filter reason-paper, glass, metal (cans, etc.), andgrinding, screening, and various sepa- ably well, vacuum filters of either the garbage, would impose no particular ration processes, particularly flota- drum or the leaf type can be used.problem on the individual householdtion. A trommel screen equipped with For more difficult filtration problems,and would be done at no cost to thespray nozzles is a good washing device, pressure filtration in plate and frameoverall waste-disposal program. TheThe tumbling of the material as the or pressure-tank-type units can besorted items could then be channelled screen rotates exerts a scrubbing ef- employed. In vacuum filtration, theto their proper disposal point (e.g.,fect. For heavy-duty work where pressure differential has been limitedreuse, incineration). more scrubbing is required, the log - to atmospheric pressure (14,5 psi at Hand sorting of contractors' con-washer type of equipment Is employed. sea level), whereas with pressure fil-struction waste into its various com- See also.' Pickle Liquor. ters, pressures of 50 to 60 psi have not ponents should facilitate waste dis- been unusual. posal without adding a significant GRAVITY SEPARATION The cost of vacuum filtration hascost to construction. varied widely, $0.10 to $0.20 per ton A very effective method of hand Gravity separation or concentration being the average. Thickening costssorting is to use a picking belt aboutis based on differences in specific have been very low, as in the cost of24 inches wide if there are sortersgravity and sizes of materials. In- dewatering by screening, cycloning,only on one side, or 36 to 48 inchescluded are jigging, tabling, spiraling, and similar methods. wide if there are sorters on both sides.and heavy-media separation, Two The cost of electrostatic precipita- Sorters are usually about 5 feet apart.particles of the same size but of e"- tion may vary from as little as $0.02A belt speed of 30 to 40 feet per min-ferent specific gravity can ke. to as much as $0.30 per 100,000 cubicute has been the average. Chutes orrated, as can two particles of the feet of gas treated, depending on thebelts below the picking belt are pro-same specific gravity but of different solids content, the solids size, and thevided to handle the picked fraction.size. Inasmuch as proper combina- efficiency of removal required, The material on the belt should betions of specific gravitatnd size will Drying may be required in some in- clean, not more than one unit deep,result in a large particle of low spe- stances to reduce the moisture con-and wellilluminated. Benches orcific gravity that reacts to applied tent to an acceptable figure. Rotary .forces in the same fashion as a small tables can also be used, particularlyparticle of high specific gravity, sizing kilns and spray driers have been twowhere deposition of a uniform layerprior to separation is desirable for commonly used types. Heated floors on a belt is not feasible, as in the casemaximum effectiveness. Heavy-media and vertical towers have also beenof wastepaper-type materials. Pick- separation is an exception to the fore- employed. The primary cost in dryinging rates vary widely from severalgoing statement in that, regardless of has been that of fuel, and the fuelhundred pounds per hour for light,size, specific gravity is the only prop- requirements are virtually a directbulky material to as much as 10 tonserty that has an effect. function of the moisture content. for dense rock types. At a labor cost See also: Animal-Product Residues; of $1.00 per hour, this corresponds to SORTING Wood Wastes; Zinc. a cost range from $0.10 to $7.00 per Heave-media separation.Various Both hand sorting and mechanicalton. solutions or pulps with different spe- sorting have been employed, with See also: Refractory; Tin; Waste-cific gravities are available. If a ma- much ofthemechanicalsortingpaper. terial is immersed in ot.e of these 11SOLID WASTE PROCESSING solutions or pulps, it will float or sink,is waved up and down in a containerbles have been replaced by spirals. depending on its own speciflc gravityof v ater, it will be found that after Forlow-specific-gravitymaterials, and the specific gravity of the solutionsufficientmovementthehighet-tablet with porous decks have been or pulp. Thus. if a mixture of sand ofspecific-gravitymaterialswillbeavailable. Air blown through the deck sp gr 2.65 and hematite (Pe,04) of spconcentrated at the bottom of theacts as the fluid medium for separa- gr 5.0 is immersed in a pulp composedbasket. This Is Jigging. In commercialtion. of ferro-silicon and water (sp gr 3.0), practice, a water-solid mixture is The standard Wililey table is about the sand will float and the hematitepaised through a trough or box hav- 17 Y2 feet tong and 6 feet wide, requires will sink, thus effecting a separation.ing a perforated bottom. Water is11/2 to 2 horsepower, and has a ca- Although various heavy liquids such alternately forced up through the Pacity of 15 to 150 tons of material per as carbon tetrachloride (sp gr 1,67),bed and then drawn back down by 24 hour& acetylene tetrabromide (sp gr 2.95),means of a plunger, This action Spiral separation. The Humphreys and thallotts formate-malonate (spopens up the bed of material, movingSpiral is a gravity concentrating de- gr 4.2) among others, have been avail- the lower specific-gravity particlesvice for the treatment of sand-size able, their costs and the problems offarther than the higher. Since thematerial, It consists of a cast-iron recovering them havelimited their usebed compacts on the reverse stroke,trough of curved cross section wound to laboratory experimentation. In op-the heavier particles move fartherin a spiral with 2-foot outside diam- erating plants, heavy media havethan the light particles. As the mate-eter. The trough contains five or six found rather wide application. Therial passes through the trough or box,complete turns, depending on use. Pulp or heavy medium consists of athis action is repeated a number ofThe feed,in the form of pulp is intro- mixture of water and fine solids, usu-times at a rate of several hundredduced at the head of the spiral. The ally sand, galena, magnetite, or fer-strokes per minute, thus stratifyingheavy material remains in the bottom rosilicon. Choice of the solid and thethe material so that it can be sepa-of the trough and isdischarged ratio of solids to water in the Pali)rated as it leaves the jigs. The pul-through ports spaced along the bot- determines the specific gravity of thesating movement can be obtained bytom. The lighter material rides up on heavy media. Sand has normally been mechanical plunger action or by air,the side of the trough and is dis- used for low-specific-gravity media,the latter having been the one mostcharged at the end of the spiral. Wash magnetite and galena for intermedi-used. water may be added along the spiral ate-specific-gravity media and ferro- Material as coarse 'as several inchesto assist in the separation. silicon for high-specific-gravity me-down to about 10 mesh can usually be Spirals take up little space, have no dia. Maximum specific gravities ob- successfully treated on jigs. Generally moving Parts, and are extremely easy tainable have been about 3,2 to 3.4speaking,water requirementsareto operate, Capacities with ores have with ferrosilicon. Use of sand mediahigh for jigging operations. Skilledranged from about 1.0 to 0.5 tons per would normally be restricted to thelabor and close attention has been hour, treatmentofcoarse,low-specific- called for in good Jigging operations. gravity materials, the sand being re- Table separation. Tables are bed- MAGNETIC SEPARATION covered from the separated fractions typegravity-separationmachines If a mixture contains some Parts by washing and screening, When ga-used in the treatment of sand-sizethat are affected by a magnetic field, lena is used, the galena is recovered bymaterials. The more common tablesmagnetic separation may be possible. flotation. Magnetite and ferrosiliconhave been rectangular, the feed beingProbably the simplest illustration of can be recovered by magnetic meth- introduced as a slurry at one end ofmagnetic separation is the common ods. The upper size limit of materialthe narrow side of the table. A re-use of a magnet head pulley on a belt treatable by heavy-media proceduresciprocating motion is imparted to theto remove cans or tramp iron. The has been about 2 inches, the lowertable. This motion Is normally a slownonmagnetic fraction falls vertically, limit about 66 mesh. forward stroke followed by a quick re-whereas the magnetic material clings Various types of vessels have been turn. Under this action, heavier par-to the belt under the influence of the used in heavy-media separation, theticles move forward a greater distance magnet and drops from the belt at a most popular being cones, classifiers,than light particles. At the same timedifferent location. and drums for particle sizes coarserwash water is applied across the ta- Magnetic separations can be made than about Y4 inch, and cyclones forble at right angles to the directiondry or wet and with either low or high deslimed feed Y4 inch x 85 mesh. of movement. The wash water exertsmagnetic intensity. The majority of Capacities of heavy-media unitsa greater influence on the lighter par-magnetic separation have used low- have varied widely, depending on the ticles, causing them to move acrossintensity separators (5,000 gauss) in size of the material, specific gravities, the table at a greater rate than theremoving most ferrous alloys. High- and the closeness of the cut desired.heavier ones. The combination ofintensity separators (20,000 gauss) A 4-foot-diameter cone processing 1112 stroke and water results in a partiallymay be employed in the treatment o1 x %-inch iron ore has treated 40 tonsdiagonal particle movement, with theweakly magnetic matzials such as per hour. heavier particles discharging at thehematite and manganese ores. Treatment cost probably would notend of the table and the lighter ones There are a variety of different types exceed $0.50 per ton on coarser ma-over the side. The deck may be riffledof separators, the belt, induced-roll, terials. Loss of the flotation mediato aid in the separation. The rifflesand drum being the most common. and labor, together with the media- Provide a place for the fine, heavy ma- The magnetic field may be produced recovery system, would account forterial to avoid the action of the washby electromagnets or permanent mag- Most of this cost. water coming across the table. Spacenets. The latter are becoming more Jigging. If a mixture of materialsrequirements are high, and the shak-POPLIN' because they require no elec- of different specific gravities is placeding action requires substantial foun-trical equipment. in a wire-mesh basket and the basketdations. To a considerable extent, ta- Pretreatment may be employed to Sanitary landfill and open dumping 15 TABLE I CLASSES OF ORMOLU USED IN FLOTATION Clusificatton Function Typical chemicals Prothers Stabilize troth Pine oil, cresylio acid, alcohol. Collectors Make particles hydrophobic.Xanthates, dithlophos- phates, soaps, f4e1 oil, amines. Depressors Make particles hydrophilic..NON, various inorganic salts. pH modifiers Change pH to intensify ef-Acids and alkalies. fect of other reagents.

convert a nonmagnetic material to aparticles. The alt bubbles catty the The number of cells required for magnetic one. Hematite, which is non-particles to the surface and form aany particular operation is a function magnetic, can be converted to mag-stabilized foam. that can be scrapedof the quantity of materials to be netic artificial magnetite by a reduc-off. The unwanted minerals remainPzocessed, the percent solids of the tion roast. in the pulp. In addition to alteringPulp, and the length of flotation time. See also: Aluminum; Refractory; surface properties to make certain The cost of flotation has varied Slag; Zircaloy. substances more floatable, it is pos-from $0.60 to several dollars per ton, sibleto use various chemicals todepending on reagent consumption ELECTROSTATIC SEPARATION reduce floats b fifty. and the complexity of the treatment Some materials are conductors of The surface characteristics of ma-Process. Skilled operators have usu- electricity, others are not. If a mix-terials can be classified as either hy- ally been required, but one operator ture of conductors and nonconduc- drophobic or hydrophilic. In flotation, can ordinarily look after a number of tors is fed onto a grounded, moving these Properties can be altered as de- banks of cells. roll and charged by means of an elec-sired. The hydrophobic particles at- Flotation has been one of the most trode, the nonconductors acquire atach themselves to the air bubblesefficient and widely applicable sePa- charge and are pinned to the roll,and float, whi'e the hydrophilic par-ration processes in use. Theoretically, which they adhere to until brushedticles remain in the pulp. Alterationit can be applied to any mixture of off, The conductors, on the otherof a surface may result from the re-Particles that are essentially liberated hand, do not acquire a charge andaction or adsorption of flotation-and small enough to be lifted by air thus discharge from the roll in ac-reagent molecules, Flotation reagentsor gas bubbles. Particles ranging in cordance with their normal trajectorythat produce hydrophobic surfacessize from 20 mesh down to about 5 as determined by their mass and theare composed of long-chain moleculesmicrons are responsive to flotation speed of the roll. This method of sepa- that resemble mhtche.s, the heads ofseparation techniques. ration makes use of the so-calledwhich represent the end that reacts See also: Wastepaper. pinning effect. A lifting effect canwith the particle. The other end is also be obtained, thus altering the hydroPhobic. SANITARY LANDFILL AND discharge paths of the particles. The chemicals that have been used OPEN DUMPING The same separation effect can bein flotation may be grouped into sev- obtained by dropping the materialeral classes according to their pin- Probably the most widely used between oppositely charged plates.notary function. Some of the more im- methods for final disposition of solid The path of tall is affected in accord- portant are shown in Table 1. wastes have been sanitary landfill and ance with the electrical conductivity The process is carried out in a flo- open dumping. These have generally of the materials. tation machine or cell, which is sim- cost less than other disposal methods The applicationofelectrostaticply a box that contains an agitatorwhile not creating the acute pollution separation has been limited to the for keeping the solids in suspension.problem that has oftenoccurred range of about 20 to 100 mesh. ForAn agitator may provide the air forwhen solids have been discharged di- maximum effectiveness, the particlethe air bubbles ty aspiration, or airrectly to waterways or to the atmos- bed on the drum or in free fall canMay be added under low pressure di- phere. However, Interest has been be a single layer thick. This naturallyrectly beneath the agitator, Pulp flowsgrowing in methods of disposal other limits capacity. Equipment cost hasby gravity from one cell to the next.than on the land for several reasons: been relatively high because of theCells vary from 16 by 16 inches in (1) Land disposal requires large tracts auxiliary power facilities required, cross section by 18 inches in depthof land. Many communities and in- (214 cubic feet) to 58 x 56 x 58 inchesdustries can no longer obtain the FLOTATION (100 cubic feet). The smaller celllarge areas needed. The ever-increas- Flotation may be defined as awould require approximately Y2 horse- ing quantity of waste makes this an physiochemical method of concen- power; the larger 10 horsepower. urgent problem in some areas; (2) trating finely divided material. Specif- In addition to the individual cell- water pollutinn may result when sur- ically, the process involves chemicaltype construction, other flotation ma- faceor groundwater leachesthe treatment of surfaces in a pulp tochines are like long, deep troughs withwastes dumped on spoil areas. Even create conditions favorable for thea number of agitators positioned uni- waste materials that are innocuous in attachment of air bubbles to selectedformly throughout their lengths. themselves often form injurious prod- 16 SOLID WASTE PROCESSING ucts upon degradation; (3) air pollu- wastes(Georgia,Minnesota) ;ba-are spread in open fields where they tion may result from degradation of gasse(Hawaii) ;potato-processingare later disked in. Meat-processing dumped andimpropertlycovered wastes(Idaho);canningwastesplants in Nebraska dump grease slur- wastes, either when particles of waste(Idaho); meat-processing andries in open pits. become airborne or when combustible slaughterhouse wastes (Idaho, Min- wastes ignite to produce mixtures ofnesota, Nebraska) ; lumbering wastesINCINERATION particulate and gaseous matter; (4) (Idaho,Minnesota) ;rubberwastes The incineration of municipal ref- increased industrial activity results (RhodeIsland) ;plasticswastes use has been treated in detail in not only in the generation of a greater(RhodeIsland) ; textile wastes Municipal Refuse Disposal but a brief quantity of wastes, but also in a (RhodeIsland);chemicalwastesreview of some of that information is greater variety of wastes. Thus, the (Minnesota,RhodeIsland) ;oils given here so that ea integrated dis- burden imposed on the land, air, and(Rhode Island); buffing wastes andcussion can be presented. For details, water resources is increasing in mag-leather scraps from tanneries (Newthe original work should be con- nitude and complexity; (5) certainHampshire) ;sawdust and shavingssulted." Part of the experience mu- resources, such as copper, zinc, andfromsawmillsandwoodworking nicipalities have had with waste in- lead, are nonrenewable. These mate- plants (Minnesota, New Hampshire,cineration can be applied to incinera- rials are squandered when wastes North Carolina) ; scrap from shoe fac-tion of some industrial wastes. containing them are indiscriminatelytories (New Hampshire) ;brickyard dumped in spoil areas; and (6) openwastes(New Hampshire) ;wastesGENERAL CHARACTERISTICS OF dump areas are scenic blights andfrom the investment casting process THE INCINERATION PROCESS have an adverse effect on land values. (New Hampshire) ; coal-washing fines While a properly operated sanitary (Ohio) ;fly ash from power plants The complexity of an incineration landfill can greatly limit these ad-and ashes from various other indus-plant increases with its capacity and verse effects, especially (2), (3), andtries (Minnesota, Ohio) ;precipitatesthe existing air-pollution standards. (8), development of alternative dis-from treatment ofmetal-finishingSome general characteristics of the Posal methods or salvage techniqueswastes (Minnesota, Ohio, Pennsyl-incineration process are:(1) when is a desired goal, because in densely vania) ;coal refuse (Pennsylvania) ;well operated it disposes of the health populated areas, space for sanitaryand limesludgefrom beet-sugarproblems associated with refuse ac- landfills is decreasing. processing (Minnesota). cumulation and reduces waste volume As a consequence of these trends A report from Rhode Island titled, at least 60 percent (more frequently the United States Congress enactedRefuse Disposal in Rhode Island,80 to 85 percent) in a central plant Public Law 89-272, which authorizedProbably the best source of informa- with minimum nuisance;(2)it is research and development into Un-tion on disposal of industrial solid adaptable over a wide range of equip- provedmethodsforsolidwastewastes, stated that: "Officially or re-ment capacities, such as from small disposal. liably, there is little known about thedomestic incinerators to large central- disposal of bOustrial wastes. Cer-ized municipal incinerators with ca- TYPES OF SOLID WASTES DUMPED pacity of 1,000 tons per day or more; OR BURIED tain general }, formetion is available that may eV some ideas on the quan- (3) it can handle the mixture of gar- In the questionnaire sent to thetities, typa.21 and expected problemsbage and rubbish which results from State health departments as part of involved ear ect of solid wastesthe currently favored single-collection thissurvey,information was re- disposal 47 Data on the quantities ofmethod; and (4) the passive charac- quested concerning the kinds and ex- solid wptes product. I by industries Inter of the clinker produced in prop- tent of disposal problems created by Island were presented, buterly operated furnaces considerably solidindustrialwastesgenerated sin the units were not clear, theaids its ultimate disposal. within the State. In the case of 10dati are omitted from the present re- Incineration costs reported by Re- States, the reply was that no inven-Poft. Knowing the number of menu-im in 1955 showed a decline of from tory Is made of solid wastes. The re-fOturing employees in each of these $4.78 per ton in older New York City maining 19 States were in a position idustries, and assuming that costs of plants to $2.60 per ton in a new plant, to give some information as to typesdisposal average $8.00 a ton, It wasand $2.39 per ton cost for a new Ro- of industrial solid wastes disposed ofcalculated "that Rhode Island indus- chester, New York, plant.'" by dumping or burial. No State lex-, try may expend $750,000 to $1,000,000 Gilbertson and Black quoteda cept Rhode Island) kept que.ntitati Per year for solid waste disposal."'charge to homeowners in the Wash- records, although two States (0444- In a report of a study made in theington suburban sanitary district of gia and Montana) estimated that/theSan Francisco Bay area, It is recom-$36 per year for refuse service, and waste from mining was about s reral mended that there be detailed report- state that at least 85 percent of the thousand tons per day. ing of solid waste production by in- total cost of providing refuse service Examples of industrial soliwastesdustries." is spent on collection.'" Assuming an disposed of on or in the grnd are: In addition to describing kinds ofannual load of 2.6 tons of refuse per papermill residues from wte treat-wastes, some States also respondedhousehold and an incineration cost ment (Alabama, Georgia,innesota,with Information on t:te methods ofof about $3.00 per ton, the incineration Ohio, Pennsylvania) ;radioactivesolids disposal. It was reporad that process might cost an average of $7.50 wastes (Alaska, South D;ikota); heavyin Georgia sludges and muds from per household. Making some allowance machinery (Alaska) ; /Mining wastesWining, quarrying, metal finishing,for present cost of landfill (assumed (Alaska,Arizona,Npeorgia,Idaho, and papermaking are normally im-at $1.00 per ton), complete conver- Minnesota, Montana, Nevada) ; sea-pounded in low areas for sedimenta-sion to incineration might raise the foodprocessing !wastes(Alaska) ; tion with the sedimentation basinsGilbertson and Black figure by ap- metal refining weste.s (Arizona, Min- being abandoned when they are filled.proximately 15 percent. nesota,Nevadiy,Ohio) ;quarrying In Nebraska, slaughterhouse wastes The furnace, as either a single or

Jr Industrial incinerationI a multiple unit, is essential to all in-(2) the single- or multiple-cell, rec- cineration plants. A secondary cham-tangular, batch-feed type. This may ber provides space for the completebe a refractory-lined or water- coo'ed combustion of unburned furnace gasfurnace with a charging door in the and elimination of odors from stackmiddle or near the back of the ceiling gas and for the destruction of theof each cell. It is equipped with either organic content of any solias carriedfixed or moving grates set level or in- by it. This secondary chamber mayclined; and (3) the continuous-feed be integral with the furnace. type. The major mechanical differ- A gas cooler usually precedes theence between this and the batch -teed solids separator, since available sepa- types is obvious from the names: ref- rators have not operated at tempera- use is fed into one in batches; into the tures usual for exit gases from theother continuously. Ashes are also re- secondary chamber. moved continuously, and an air seal It was repotted that Dorr-Oliveris maintained with the furnace con- supplied a system using high-speedtinuously. The inclined, rotating-kiln centrifugal dewatering teamed with type is essentially the same as the con- thermaloxidationinafluidizedtinuous-feed type, except that it has (sand)bed reactortoincineratea refractory-lined, slowly revolving sludge'" cylindrical kiln that is used in the Fly-ash emission is determined byfinal burning stage. plant design and operating conditions. In the continuous-feed types of Schwarz described measures to befurnaces, the grates are the traveling taken by incineration plants to con-type, inclined, flat, or a combination; trol air pollution. Fly ash increasesthe furnaces require a minimum of with burning rate, air rate, or agita-manual stoking. tion.'" Some idea of particle size and Usually, all three types of furnaces analysis was given in Municipal Ref-are lined with refractories and insu- use Disposal." The fallout that oc-lating brick. curred in an area around an incinera- Various designs are shown in the tion plant hiParis,France, wasliterature. These include cross-section reported by Chovin." drawings " of the furnaces of the Cal- Dry collection of fly ash includes theumet incineration plant in Chicago, use of refractor baffles, low-velocitythe Northwest plant in Philadelphia, subsidence chambers, and multicy-a modern continuous-feed-type in- clone centrifugal separators. But suchcineration plant, the Volund rotat- methods have been hardly adequate toing-kiln incinerator, a continuous- meet the fly-ash limitations recom-feed grate, the Saint-Ouen (France) mended by the American Society ofplant" and the Fort Lauderdale in- Mechanical Engineers (see commentscinerator." of Ellsworth and Engdahl) .1" Electro- static dust precipitators, as have been INDUSTRIAL INCINERATION used in Europe, have been discussed Ti e use of incinerators for disposal by Bump." of solid industrial wastes appeared to Wet collection employs either water be very limited. Fourteen States re- sprays or impingement on a wet sur-sponding to the survey questionnaire face. Results by various methods havereported that the kind and amount of been reported by Fife and Boyer'' andindustrialsolidwastes incinerated by Vickerson." T were unknown. California reported Arizona, Arkansas, Colorado, Kansas, The nature of incinerator slags hasthat there was little incineration be- Kentucky, Maine,Missouri,Montana, cause of air-pollution regulations and New York, North Carolina, Pennsylvania, been discussed by Herbert'" and Texas, Washington, Wyoming. Regis " economics. The only industry in that State which carried on extensive KINDS OF FURNACES burning was agriculture, which was Michaels listed three types of refuseexempt from air-pollution laws. Idaho furnaces' ": (1) The single - chamber, reported that although no industries cylindrical, batch-feed type. This is aincinerated wastes, many of them did refractory-linedfurnacechargedburn wastes prior to dumping. through a door in the upper part of Solid industrial wastes reported as the furnace. Refuse Is dropped intobeing incinerated were sawmill and the furnace periodically and stoked tolumber-industrywastes,corncobs, the periphery manually or mechan-bagasses, packing material, and textile ically by a rotating cone with ex-rejects. "Tepee" type burners were tended rabble arms. The dumpingoften used to burn sawdust and corn- grates are located around the periph-cobs In tour States. t Bagasse was tNebraska, New Hampshire, South Da- ery and are operated whenever the ac-incinerated for fuel in Hawaiian sugar kota, Utah. cumulation of ash warrants removal; Kraft pulp mill la one Mate 18 SOLID WASTE PROCESSING dried and burned its sludge in bark-sueparticularly since the adminis- burning boilers. Georgia's mills weretration that builds the plant may not also considering this method of dis-have to operate it. This explanation posal. In that State, most industriesaccounts in part for the wide range maintained burning areas where dry,in capital costs of various plants as combustible solids such as packingfrom $1,000 to $5,000 per ton of ca- material and textile rejects were in-pacity. This approach tends to reduce cinerated, and some industries main-the premium on good operability and tained regular incinerators for this design. purpose. A chemical industry had Construction costs were described adopted incineration on an experi- in Municipal Refuse Disposals: "Most mental basis in Minnesota. incinerator plants cost from $3,000 to Only Tennessee reported that many $4,000 per ton of rated 24-hour ca- industries in the State incineratedpacity to build and equip. Buildings solid wastes. Incineration of woodaccount for from 40 to 78 per cent of wastes was reported to be fairlytotal costs (an average of 68 per cent common in the lumber industry infurnaces and appurtenances account TABLE 2 Minnesota. for from 18 to 24 (sic] per cent of thersINCIPAL COMPONENTS OF A MINIMAL The general overall approach tototal (the average 35 per cent); and INCINERATOR AND COSTS so industrial incineration is presented the chimney accounts for from 4.5 to in two papers,' " and design cri-11 per cent (the average '7 per cent). Illustrative teria are reviewed in several.""' "Construction costs adjusted to 1957 nth oostiton Thermodynamic calculations re-levels reported for 21 incinerators ofratod quirespecific information on thebuilt since 1949 (16 since 1954) had acity amounts of combustibles, their den- a median of $3,650 per ton of capacity. (dollars) sity, moisture, and calorific values,This compares to a median cost for availability of carbon, hydrogen, oxy- 1946 of $2,000 a ton, or an increaseScales, scale house, entrances gen, etc. Their abrasive and corrosive of approximately 82 per cent in 11 andexits,maneuvering action on grates, refractories, andYears. General construction costs for yard, dumping rail,and enclosing wall $100 other materials must be considered. the same period increased approxi- Storage bin 200 Practically no information of this sort mately 100 per cent "' Crane. 226 was available for some of the newer Construction costs for New YorkOutsides flues and fly-ash- special wastes, for example, variousincinerators have been separated by removal facilities 400 syntheticsandchemicals."The the following functions: architectural Chimneys 300 heatingvaluesofvariousfuel and structural; mechanical; electri- Miscellaneous items, such as materials together with the heatingcal; heating; ventilating; plumbing; drains, piling, and wood- and miscellaneous (Table 2), bogs 76 values of various wastes have been Furnaces 1,200 reported." "I Greeley estimated that about 40 perInside flues 85 Incineration provides an effectivecent of the cost of an incinerator was Building and enclosures 1,416 method to remove combustible mate-for furnaces and appurtenances, and rials from scrap metals. It has beenabove 60 percent for building, chim- Total 4,000 widely used to burn the insulationney, approaches, and storage bin"' from copper wire and cable. The prac- (Table 2). Greeley also estimated the tice of burning pilesof insulated relative costs for parts of the instal- wire in open fields formerly was wide-lation (Table 3). sPread, but has become rather lim- Michaels tabulated incinerator con- ited. According to Lipsett the adop- struction costs for 25 incinerators'" tion of plastic for insulation andData were given on the location; ca- stringent pollution regulations have pacity;yearcompleted;material introduced serious difficulties in re-burned; type of grate; number of fur- TABLE 3 moving Insulation from wire." He naces; capacity of each furnace; com- FIRST COST DISTRIBUTION FOR PARTS OF AN stated In 1963 that fortunes have beenbustion chamber volume; type of 1NOINSICATO1 INSTALLATION spent on facilities to remove the new dust-collection system; number, insulating compounds from the wire, Approx. but that most of the installations wereheight, and diameter of stacks; type Part ireate ofwallconstructioninfurnace, portenrater not entirely satisfactory in the abate- total ment of the smoke nuisance. chamber, and flue; waste-heat utili- See also: Chemical Wastes; Paint;zation; plant operation; and cost of plant. Scales, yard, storage bin, Petroleum Residues; Pulp and and outside appurtenances- 11.0 Paper. Coal-fired powerplant experience Building and cranes 37.0 provides a guide to possible first costs Furnaces, combustion cham- CAPITAL COSTS of incinerator collection. The capital bers, flues, and appur- Michaels noted that municipalitiesinvestment in equipment bus-tailed at tenances 35.0 tend t6 have a different view of capi- Relatively simple fly-ash- the South Charleston, West Virginia, removal facilities 7.0 tal costs than private enterprises."'Powerplant of the Union Carbide Cor- Chimney 10.0 A municipality attempts to keep capi- poration for the collection of fly ash, tal charges low to minimise the fi-has been given by Magnus.'' Costs Total 100.0 nancing requiredusually a bond is- were given for both electrostatic and °por11tl:7i costa19 bafile-type collectors as well as the 1983 costs for replacing this equipment, the steam-generating rates of the equipment, and the costs of the equipment on a cost-per-pound-of- steam basis (Table 4), Magnus states that the cost of mechanical collectors andelectrostaticprecipitatorsis roughly $0.15 and $0.55 per pound of powerhouse steam-generating capacity, respectively. OPERATING COSTS Michaels noted difficulties in com- TABLE 4 paring operating costs between vari- CAPITAL INVESTMENT IN EQUIPMENT FOR FLY-ASH COLLECTION AT THE ous plants. "Determining typical op- SOUTH CHARLESTON, WEST VIRGINIA, POWERPLANT trt erating costs is rather difficult because Capital some municipalities include the cost cost of removing residue; others exclude t Total Replacement Steam potPeutd maintenance costs, etc. However, a Collection equir meat installed cost (I) ot plant containing an average amount cost (I) rate (Ib(lur) deem of mechanization, operating on a 24 ee hr a day basis, and having a mini- hPour mum capacity of 300 tons/day, if effi clently run, should cost betweenI/2 (1) Precipitators (Boilers 9 through 13) and 1 man-hour/ton to operate. Ob- (1947) 270,711 628,000410,000 1.B9 viously, the type of material handled, (2) Mechanicalseparators(Boilers9 i.e., mixed refuse, garbage, rubbish, through 13) (1937) 69,346 174,000 etc., the degree of mechanization, the(3) Precipitators(Boilers14 and15) air pollution and other health stand- (1942) 79,084 205,000300,000 0.68 ards to be met, and the housekeeping (4) Precipitator (Boiler 16) (1945) 35,236 81,800150,000 0.66 (5) Precipitators(Boilers17 and18) standards all have a bearing upon the (1944) 74,974 178,000300,000 0.59 ultimate operating costs. The cus- (6) Precipitator and mechanical separator tomer should be aware of these fac- (Boiler 25) (1954) 104,804 135,600289,000 0.47 tors and should be able to advise the (7) Mechanical separators (Boilers 30 and consulting engineer of the 3tandards 31) (1961-64) 43,648 43,646300,000 0.14 he requires."'" Rogus reported overall operating Total 687,853 1,346,946 costs. "In 1953, landfill cost was $2.26/ ton while the average incineration 1963 equipment snd labor coat index.1.0. cost of 12 plants was $4.78. However, the new Oansevoort Incinerator has averaged only $2.50 /ton. A new plant at Rochester, New York, is reported to have a basic operating cot of only $2.39/ton including the cost of operating a stack-gas washer. The initial cost of the plant was $1,373,728. TABLE 5 Hence, it appears that incinerator op- COMPARATIVE COSTS OF TWO TYPES OF INCINERATORS IN NEW YORt CITY (165 COSTS) erating costs are becoming competi- Coal the tivewithlandfillcosts and Manually principal remaining problem isto Cod item Mechanised stoked continuous typo batch type assure their clean operation."'" (average for I) (iterate A higher plant cost can provide a tor 4) lower operating cost" (Table 5). Providing for 24-hour furnace op-Total construction coats per ton per day of capacity eration has been shown to be desir- (including engineering but exclusive of land) $6,600.00 $3,750.00 able by comparison of the daily aver- 5. 65 7. 50 age operational costs, in dollars per Total operating coats per ton of refuse destroyed ton of furnace, for 1-, 2-, and 3-shift Operating less residue disposal 2. 40 4. 20 operations." But collection on an 8- Maintenance and repair 1. 05 1.06 hour -per -day basis necessitates buffer Administration and supervision. 0. 60 0.66 Pension 0.60 0.90 storage capacity the size of which Fuel and utilities 0. 05 0. 05 should provide for variations in the Amortization 0. 95 0.96 foreseeable future in amount and character of the incoming refuse. Two plants bale since been onstructed elsewhere for 95,900 per tos per day.

33S-24 4 4 20 SOLID WASTE PROCESSING Recommended store` ge capacity rangessize and its operating cost. Grab TABLE 6 were between 12 and 36 hours of bucketcranematerialhandling OPERATING COSTS FOR MUNICIPAL INCIN- plant capacity." A 1000-TPD Newequipment is more suitable for bulky ERATORS IN SIX U.S. CITIES York City plant design provided 1 tonobjects than a conveyor system ac- of liquid-level pit capacity per ton Cost per Lou cording to Wiehrmanreos City of refuse per day of plant capatity. One ton of Some indication of operating costs processed liquid-level pit capacity was consid-of electrostatic precipitators Is pro- ered equivalent to 6 cubic) yards ofvided from power plants. The total Philadelphia $4.24 truck-compacted refuse. cost of collecting fly ash at the South Washington, D.0b 2. 28 Storage and handlingfacilitiesCharleston Union Carbide coal-fired Detroit 4. SO should provide for handling objects atplant with eight electrostatic precipi- Milwaukee 8. 49 least 80 inches square according totators was reported as $31,500 perNew York Car 5. 55 Wiehrmann."' Year with a breakdown of this costLos Angeles. 3. 18 It was pointed out that operatingand operating costs on a unit basis costs also varied widely, depending on Costs ate for one plant in each city in 10$0, wept (Table '1). Seven of the precipitators for New York, where the cost is the MS average for the type of refuse burned and thewere equipped with 25-kva double- three Mints. bDoes not Include amortisation °tots. thoroughness of the burning, the de- halfwavemechanicalrectification Cost computed on baste of tons burned (amount gree of sanitation controls exercised,units, while the precipitator of Boiler charged minus residue). the type of incinerator plant and the25 was supplied with a vacuum-tube extent of its mechanization, the wagerectifier (a 75-kv 25-kva full-wave scale and amount of fringe benefits,Kenotron unit). and the productivity of labor and ef- The costs of constructing and op- ficiency of management." Operatingerating air pollution control equip- costs for six cities were comparedment as required to meet various (Table 6). municipal incinerator stack emission Maintenanceandrepairswerelimits were reviewed by Fife and commented on "The modern incin-Boyer'" Rogus has reported foreign eration plant is dirty, dusty, odor costs for Western Europe,'" The total Producing, and requires more thancosts of on-site domestic incineration normal routine care to even approachhave been estimated by Engdahi and a power plant in spit-and-polish ap- Hein to be higher than for municipal pearance and trouble-free operation.disposal."' "An annual budget for maintenance Certain economy in plant cost re- and repairs approximating 5 percentsults from the use of a dust separator, of the total capital costs of the plantsince higher gas velocities then be- usually is relequate, particularly ifcome permissible in the preceding the plant is well designed and constructed; ifit was properly tested, adjusted, and broken In; and If it Is always kept in good condition. Main- tenance and repairs can be expected to cost between 10 percent and 15 Percent of the total cost of operation, depending on the size and type of plant. Approximately half the cost TABLE 7 will be for labor and the other half ANPUAL COSTS OF OPERATING ELECTROSTATIC PRECIPITATORS AT THE SOUTH CHARLESTON, for materials. WIRT VIRGINIA, POWIR PLANT01 "Routine maintenance is preven- Total annual Annual coat ofAnneals:cal ot tive.Weekly inspections,cleaning, Cost Item cost of all mechanical taciturn units rectification tube (unit and greasing, removal of clinkers and (unit baste) slag, minor repairs to easily accessible basis) parts of the plant and machinery, Operating labor 812,400 $1 , 558 81,559 and less frequent inspections and re- Electric power 7,876 1,880 895 pairs to hard-to-get-at parts of the Water 1,002 127 127 plant will help prevent major dam- Repair labor 9,027 2.723 s 134 age and emergencies. b 425 Is 855 "In addition to routine maintenance Repair material 1,198 118 210 and repairs, major repairs are needed Total 31,500 4,629 3,779 occasionally; reconstruction and modernization of furnaces, cranes, and Vectors: other parts of the plant are needed Number of units: 7 with mechanical rectification, 1 with vacuuratube retie, less frequently; and a complete over- tication. haul and modernization of the plant tabor, 84.45 per hr (hourly rate plus fringe benefits). is necessary perhaps every 25 years Power, $6.00 per mkwh. or so." " Water, $160 per rnmg. Refuse storage to afford 24-hour Daily13111/Ittbtahlb00. operation minimizes the Installation bSemis:to zu) created Waste-heat recovery21 parts of the plant which operate atthem. Useful heat is required for gen-a function of steam temperature; that high temperatures 'wed therefore areeration of process steam or electricis, if steam temperatures can be held of more costly const .Letton, Usuallypower'" Usually, this has been donebelow 1,000°F., little or no tube attack an efficient collection device is neededin conventionally designed boilers andshould occur. to reduce the amount of suspendedfurnaces, with perhaps specialized An alternative method of heat re- particulate solids in the stack gas toequipment installed only for conveying covery is to have an air-heater type the desired air pollution limit. and feeding the combustible materialof heat exchanger following the in- Several references concerning theinto the combustion chamber.""""cinerator chamber. Again, this might use of afterburners to combat theSimilarly, the recovery of useful heatbe very inefficient because excess air smoke from incinerators appear in thefrom the incineration of mixed solidwould be needed to cool the flame to literature."'" Houston stated thatmunicipal wastes and sewage sludgeprotect the refractory walls of the burning was the best nicthod for re-has been practiced extensively in Eu-incinerator, and the temperatures of moving insulatiOn from copper wire, rope,"' ", 1" but not in the Unitedthe gas-to-air heat exchanger metal but that this required incinerationStates because of the generally un-would have to be held to moderate with proper smoke controls. He addedfavorable fuel economics for waste- levelsto give reasonable heat-ex- that probably the cheapest way toheat recovery`" If in addition to what- changer life. All of these methods control smoke would be by burningever fuel saving is possible, however,must be designed to cope with ex- the insulation with an afterburner, asome value were placed on ease of tremely dusty gas probably involving secondary combustion chamber main-handling of a refuse disposal prob-someadhesion;t the dust to the tained at 1,800* to 2,200° F. by burn-lem and on environmental quality (airtubes. ing oil or gas. Purity and land beautification), heat Applications for recovered heat. If HoUston also claimed that if after-recovery from thecombustion ofthe waste heat is recovered as steam, burners were well designed and weremunicipal waste could be made moreit can be utilized for turbine drives operated properly, the matter releasedattractive. The outcome of each analy- for the auxiliary equipment on the to the atmosphere would be reducedsis will depend on specific local con- plant, such as. blowers and pumps. to a light haze. He estimated that theditions and standards of environmen-Alternatively, the turbine can drive bare, direct cost of the smallest prac-tal quality. In many locations waste-an electric generator for the gener- tical incinerator unit and the cheapestheat recovery may not seem justifiedation of electric power for internal method of smoke control would be be- for many years."' use In the plant or for sale. If the tween $11,000 and $14,500. That esti- Heat available. The long-term trendPlant is located adjacent to a popu- mate was published in May 1957."7 has been for the cellulose content oflated area, the steam can be used for Salvage and sorting have not beenmunicipal solid waste to increase with district heating or for industrial proc- considered rewarding beyond the im-decreasing moisture; hence, the heatessing. A plant has been installed for provement they have afforded in han-value from combustion of the wastecombination of seawater distillation dling and in the uniformity of teedhas been rising. In the United States,with incineration.'" Instead of steam, and the combustibility of the refuse.it was estimated to be about 5,000the heat can also be recovered in the Similar benefits result from grinding,Btu per pound, with the likelihood form of hot water, which can bo used but some sorting is usually required tothat by 1980 it would have reachedfor heating the premises or for sale protect the grinders. 5,500 Btu per pound. This trend willin the neighboring area'" This has While it may be advantageous to probably have some effect on increas- been done extensively in Denmark. remove metal, large objects, and non-ingthefeasibilityofwaste-heat Performance of heat-recovery sys- combustibles from refuse in prepara- recovery.'" tems. The amount of steam generated tionforchargingitintothe Methods of heat recovery. The sim- Per pound of refuse burned depends incinerator, experience in the Unitedplest method of waste-heat recoveryon many factors.'1'. "' The most effi- States has indicated that salvagefrom municipal incineration has beencient generation has been in water- operations and reduction processesthe incorporation of a waste-heattube-wall boilers operating with low have generally not been profitable. boiler immediately following the in-excess air without interruption for 24 The appearance of new productscinerator for the regeneration of hothours a day. In general, to achieve such as plastic packaging materials inwater or steam. One disadvantage ofsatisfactory heat generation, it has refuse, and therefore in the furnacesuch a system has been that the re-been necessary to provide auxiliary feed, can produce certain gaseous de- fractory-lined furnace would be un-fuel to maintain constant generation compositionproductsnecessitatingable to withstand the temperaturebecause of the varying moisture con- stack-gas treatment. The require-generated by stoichiometric combus-tent of the refuse and the varying ments for such treatment would betion of the waste; hence, the chambersupply of refuse. difficult to predict. must be cooled by dilution of the com- In general, thereliability of a Designs and performance of equip-bustion gases with excess air. Thewater-walled waste-heat boiler will ment for the control of air pollutionlogical alternative to this less efficientbe highest of all, unless tube temper- system is the construction of an inte-atures are carried so high that corro- from municipalIncineratorshave sion is a problem, been discussed in detail by Jens andgral boiler, the furnace lining being Economic incentive for heat re- Rehm." formed by steel tubes to provide acovery. The value of the heat recov- water-cooledincineratorchamber. ered will be determined by the cost WASTE-HEAT RECOVERY This has been demonstrated to beof using competitive fossil fuels and highly successful In many installations upon the load factor that needs to be A few combustible industrial wastesin Europe. One difficulty has been with maintained for the particular use in- generated in manufacturing proc-boiler-tube corrosion duo to sulfatestended. A major economic) advantage esses have normally been used as fuelor chlorides on the fire side of theto the recovery of heat, particularly by the organizations that generate tubes. This attack has appeared to bewhere environmental quality is con- 22 SOLID WASVE PROCESSING sidered important, has been the vol- Ideally, the techniques used for dis-and the cost of operation has also ume effect of the extraction a heat posal of solid wastes should; (I) Pro- been significant. As long as justifica- trona exhaust gases In the furnace duce revenue or at least cost thetion for chernical processing of waste and the use of less excess air because producer little or nothing; (2) con-is based solely on the ability to sell Of the completely water-cooled fur-sume most of the material; (3) be ofthe products above fixed and operat- nace, Both of thesefactors havea nonseasonal nature; (4) produce aning costs, there is little chance that greatly reduced the volume of dustyend product that contributes somethese processes will be adopted. If gases to be cleaned, and hence havebeneficial results to the economy ofpoor public relations are engendered reduced first costs, operatieg costs,the country; (5) not result in pollu-by pollution or unsightly conditions, and maintenance costs of suitable tion of the environment. chemicalrecoveryprocesses may dust-collecting equipment. Selection of techniques for Inclu- nevertheless become necessary. sion in this study, however, was not The chemical processes described in CHEMICAL PROCESSING ordinarily limited by these criteria.the literature are reviewed here briefly Processes that consume very smallin the order of the frequency of their Chemical processing of solid wastes.-amounts of waste-10 percent or lessappearance in the literature, The lit- for recovery of usable materials endwere excluded, on the other hand,erature on acidification, chlorination, energy is inherently one of the mostas offering no appreciable reduction of appealing approaches to the disposal condensation, dehydration, dilution, problem. In practice, however, suchthe solid-wastes problem. displacement, dissolution, hydrogena- processing has often proved costly. In Although this has been essentiallytion,neutralization,nitrogenation, addition to the many articles cited, a study of the waste problem in thepolymerization, reduction, and vapor- this survey of published Information United States, techniques for chemi-ization of solid industrial wastes was onchemkelprocessingcovered cal reduction of solid wastes describedfound to be very scanty. No reference Chemical ii,t)stracts, Engineering In- in the foreign literature are coveredto commercial applications of any of dex, and Industrial Arts Index for theeven though It is recognized that onethese processes was found. More de- of the basic problems of effective dis-tailed discussions will be found in the period 1950 to 1966. Public Healthposal is economics and that economics"Major Waste Categories" section of Service Publication No. 91, Bibliog- are different for every area of thethis report. raphy Series No. 4, Supplement E, en- world. A number of articles and pat- titled Re /use Collection and Disposalents are considered, although evidence HYDROLYSIS 1960-1961, was reviewed also. Twenty-nine processes of interest of industrial practice was lacking, be- Hydrolysis provides a means for were identified. The list includes somecause air, land, and water pollutionutilizingagriculturalresidues and Processes that are 'physical rathercontrol and conservation of resourceswood wastes. Its potential application than chemical to insure that this sec- are becoming more urgent all the time. is worldwide. Glucose is obtained by tion of the report covers all "non -In the future these may alter thehydrolysis of the cellulose portion of mechanical" processes: acidification; economics of some solid waste dis-plants. Hydrolysis of the hemicellu- alcoholysis;calcination;carboniza- posal processes. In some cases, theloses in plants yields pentoses, which tion; chlorination; combination andprocesses decribed in the literatureupon dehydration form furfural, an addition; combustion (incineration) ; may not have survived because of eco-important raw material for plastics. condensation;dehydration,dews- nomic or other conditions. Neverthe- The lignin remaining after recovery tering, and drying,dilution;dis- less, knowledge of their temporaryof these hydrolysis products is a po- placement; dissolution; distillation; demonstration or use may be helpfultentially valuable chemical raw ma- electrolysis and electrodialysis; evap- in similar circumstances. terial. Lignin can also be hydrolyzed. oration; extraction; hydrogenation; The literature reviewed showed thatWhen plant residues are used for hydrolysis; ion exchange; melting; although chemical processing of somemanufacture of paper, board, and neutralization; nitrogenation; nitra-solid wastes for salvage and recoveryrayon, it is the lignin that is hydro- tion, is technically feasible, there has been and arnmornation;oxidation limited interest in these processes notlyzed to alcohols and acids in order (chemical) ; polymerization; precipi- to recover cellulose fibers from the tation, crystallization, and gelling; only because of problems of economics Pyrolysis; reduction; sintering; va-and marketing, but also because ofwaste. At least one plant in the United porization and gasification. impuritiesandnonuniformityofStates has hydrolyzed lumber and Two Main groups of chemical proc-quantity and composition of the wastePulp-mill leftovers to obtain glucose. esses can be distinguished, the deter-material. A number of sulfite mills have pro- mination depending upon whether It was apparent from the literatureduced alcohol with yeast from the entirely new products are obtained inand from correspondence with Stateglucose formed in pulping process. the course of treatment or whetherhealth departments that there haveThis is justifiable as a means of re- not been many commercial applica-ducing stream pollution. A review of only a recovery of existing raw ma- tions of chemical processes for treat- terials takes place. The classificationing solid industrial wastes. A few in-hydrolysis equipment has been made differentiates between the manufac- dustrieshaveincineratedsolids. by Taubln.11° ture of new products and reclamationMany more have burned wastes In See also: Agricultural Wastes; Ani- processes. The latter are cyclic proc- open dumps. The most common mal-Product Residues; Bagasse; esses. Waste products in the true sense method of disposal has been to ac- Brewing,Distilling Fermenting do not occur. The term is commonlycumulate solid wastes in spoil areas. Wastes; Food-Processing Wastes; used, and is used in this study evenThis choke has been dictated by eco- FruitWastes; Germanium; though at the present time many ma-nomics. Land disposal has nearly al- Leather Fabricating and Tannery terials are or could be recycled in-ways been selected as the cheapest Wastes; Plastic; Pulp and Paper stead of simply being processed asmethod. Most chemical processes re- Wastes; Tex ti I e s;Vegetable wastes. quire a substantial capital investment, Wastes; Wood Wastes. Melting 23 COMBUSTION (INCINERATION) See also: Brewing, Distilling, Fer- Combustion or incineration has ap- menting Wastes; Food- Processing peared to offer the most hope for Wastes;PetroleumResidues; implementation in the near future. Rice; Textiles; Wood Wastes. It has the advantage of providing the ultimate in volume reduction, and OXIDATION (CHEMICAL)t frequently it is the most practical way Chemical oxidation of organic waste to treat toxic substances. Althoughmaterials yields a variety of products, chemical recovery is possible in somebut there has not been much com- cases(e.g.,recoveryofchemicals mercial application of this process. from black liquor for sulfate pulping),Some use has been made of bagasse heat is generally the only salvageableand sawdust as reducing materials in by-product.Airpollutioncontrolmetallurgical operations. Measures may limit this practice In See also: Bagasse; Carbides; Chem- some areas or call for advanced de- icalWastes;Food-Processing sign and process control. Wastes; Inorganic Wastes; Pulp See also: Animal-Product Residues; andPaper; Rubber; Wood Asbestos; Ash, Cinders, Flue Dust, Wastes. Ply Ash; Bagasse; Brewing, Dis- SINTERING tilling, Fermenting Wastes; Brick Plant Wastes; Chemical Wastes; Sintering has been pi acticed for re- Coal Refuse; Electroplating Resi-covery of metals and for converting dues; Gypsum; Molasses; Organicwastes to a form usable in building Wastes; Paint; Pulp and Paper;materials, particularly for utilization Petroleum Residues; Photograph-of slag and fly ash. ic Paper; Plastic; Rubber; Sulfur; See also: Aluminum; Ash, Cinders, Wood Wastes; Yttrium. Flue Dust, Fly Ash; Bauxite Resi- due; Coal Refuse; Cobalt; Inor- EXTRACTION ganic Residues. Extractionof constituents from waste solids by means of solvents hasPRECIPITATION,GELLING, AND been an important means of obtaining CRYSTALLIZATION salable chemicals and metals. How- Precipitation, gelling, and crystalli- ever, the high cost of most solvents has zation have limited application for limited the commercial value of manyprocessing solids industrial wastes. of these recovery processes. Some metals (e.g., silver) have been See also: Agricultural Wastes; Ala-recovered by precipitation. rniurn; Animal-Product Residues; See also: Animal-Product Residues; Brewing, Distilling, Fermenting Copper; Fish; Fruit Wastes; Gyp- Wastes; Coffee; Fish;Fruit sum; Leather Fabricating and Wastes; Glass; Manganese; Nuts; Tannery Wastes; Pickle Liquor; Pickle Liquor; Plastic; Poppy; Pulp and Paper; Titanium. Pulp and Paper; Sisal; Titanium; Vanadium;VegetableWastes; CALCINATION Zinc. Calcination has had fairly wide- PYROLYSIS spread application for the recovery of Pyrolysisof carbonaceous wastecalcium compounds, such as lime and materials leads to recovery of a num-gypsum, from sludges. A continuous ber of by-products, the most impor- ealciner which reduces aqueous waste concentrates to anhydrous melts has tant of which is charcoal. Pyrolysisbeen described by Hlttman."' has been practiced on a commercial See also: Acetylene Wastes; Asbes- scale In the United States. The atom- tos; Calcium; Coal; Pickle Liq- ized-suspension technique isuseful uor; Pulp and Paper; Slag; Ti- for pyrolyzing sludges. tanium. See also: Animal-Product Residues; The terms pyrolysis and carbonization Fruit Wastes; Leather Fabricat- MELTING arenotentirelyinterchangeable, al ing and Tannery Wastes; Petro- though carbonization may be considered Melting residues to recover metals asaspecialcaseofpyrolysisin leumResidues;Plastic;Pulpsuch as copper, iron, zinc, and lead which volatiles are cooled sufficiently and Paper; Rubber; Vegetable has been practiced. Silicon-containing rapidly to prevent further decomposition Wastes; Wood Wastes. wastes have also been melted for by- (cracking). product recovery. CARBONIZATION' See also: Animal-Product Residues; Carbonization of carbonaceous Ash, Cinders, Flue Dust Ply Ash; This term referstooxidation by wastes has been practiced to obtain BrickPlant chemically combined oxygen, such as Waste;Copper; contained in FINO,, etc. It thus activated carbon. It has been carried Glass: Lead; Pulp and Paper; differs from combustion. which Involves out on a commercial scale. Plastic; Titanium. oxidation with free oxygen, 24 SOLID 'WASTE PROCESSING ELECTROLYSIS AND ELECTRO- DIALYSIS Electrolysis and electrodialysis can be used to recover iron and acid from spent pickling solutions and to recover chemicals from spent sulfite pulping liquor. A pilot plant has been in operation for treating sulfite waste in this manner. RECOVERY AM) UTILIZATION See also: Beryllium; Manganese; The disposal of solid waste mate- Pickle Liquor; Pulp and Paper; riels frequently involves their direct Titanium. ultimatedisposal.However, some COMBINATION AND ADDITION types of solid warts have been processed for the recovery of valuable Combination and addition reactions constituents prior to the ultimate dis- are steps in the production of di- posal of the remaining material. Such methyl sulfide and sulfoxIde from the wastes have usually been processed to lignin in kraft black liquor. This has recover or produce any one or more been used on a commercial basis. of the following types of products: See also: Calcium; Pulp and Paper. (I) Products that are recycled to the EVAPORATION operation from which the waste material originated; (21 Products that Evaporation has been used to re- serve as raw materials for manufac- coversalablesolidsfromwaste turing operations; and (3) Products liquors. Steep water, whey, and beet that are utilized directly. Pulp have been evaporated and used The scope of the commercial appli- for feed. Copperas has been recovered cation of physical beneRciation unit from pickle liquor by evaporation. processes to the treatment of such Lignosulfonates have been produced wastes is indicated in Table 8. by evaporation of sulfite liquors. Fur low and gollinger have described See also: Brewing, Distilling, Fer- a proposed system for the disposal of menting Wastes; Pickle Liquor; municipal garbage and refuse that Pulp and Paper; Starch. features the recovery of nonferrous ION EXCHANGE scrap, ferrous scrap, aluminum scrap, Dissolution glass, plastics, rubber, rags, and paper Ion exchange can be used for the by hand sorting and magnetic sepa- recovery of chemicals from the solu- See: Leather Fabricating and Tan-ration."' A diagram of the plant is ble-base (sodium, magnesium, am- nery Wastes; Plastic; Pulp andshown in Figure 5. monium) pulping liquors. Paper. Roughly 20 percent of the waste See also: Ash, Cinders, Flue Dust,Distillation tonnage processed would be removed Fly Ash; Pulp and Paper. in the salvage section by hand sorting. See: Chemical Wastes; Food-Proc-Four successive selection conveyors MISCELLANEOUS PROCESSES essing Wastes; Fruit Wastes, Pe- Acidification troleum Residues; Plastic; Pulp and Paper. See: Ash, Cinders, Flue Dust, Fly Ash; Wood Wastes. Hydrogenation Moho !yes See: Pulp and Paper. See: Plastic. Neutralization Chiorination See: Chemical Wastes; Pickle Liq- uor. See: Carbonaceous Shales; Fruit Wastes. Nitrogetudion, nitration, and ammoniation Condensation See: Bagasse; Carbonaceous Shales; See: Plastic; Wood Wastes. Plastic. Dehydration, dmeatering, and drying Polymerization See: Coal; Food-Processing Wastes; See: Bagasse; Paint; Plastic. Pulp and Paper; Wood Wastes. Reduction Dilution See: Copper; Lead. See: Chemical Wastes. Vaporization and Gasification Displacement See: Ash, Cinders, Flue Dust, Fly See: Calcium; Pickle Liquor. Ash. The scrap metals industry 26

would be employed in this section forthe refuse stream by a magnetic headthe 1966 edition of Metal Statistics.' It the salvage of various solid materials.pully located at the discharge end ofillustrates the geographical distribu- Cardboard, newsprint, kraft paper, the third selection conveyor. The finaltion of firms and the kinds of scrap and mixed paper would be shreddedstep in the reclamation of solids froze..materials with which those firms deal. and baled after being hand sortedthe waste stream would involve theSeveral of the companies listed also from thefirstselection conveyor.hand sorting of aluminum cans andoperated mines, smelters, and refin- Rags, glass,plastics, miscellaneouscontainers from the fourth selectioneries internationally, and some had nonferrous metals, and rubber wouldconveyor. The remaining waste wouldmore than one plant in the United be hand sorted from the second selec-then be processed through the prepa-States for the treatment of nonfer- tion conveyor Into large salvage con-ration, digestion, and finishing steps,rous scrap metals. A number of for- tainers located on both sides of thewhich are in experimental stages. eign buyers are included in the list. conveyor. Light ferrous metals and The Waste Trade Directory contains tin cans would be removed from theTHE SCRAP METALS INDUSTRY a complete list of scrap-metal proces- delivery end of the second selection The reclamation and utilization ofsors arrarited geographically and ac- conveyor and from the third selectionnonferrous scrap metals is an old and well established industry engaged incording to kinds of metals processed' conveyor by magnetic belt separators.a multimillion-dollar business annu- The major conclusions drawn from The separator of each of these selec-ally. Thousands of dealers, smelters,the study of nonferrous scrap are tion conveyors would be equipped with and refiners have been strategically (1) The large number of dealers a strong electromagnet and a beltlocated throughout the United States and processors for gathering, prepar- oriented at right angles to the direc-to collect and process scrap metalsing, smelting, refining, and market- tion of refuse movement. Heavy fer-and metal-bearing products. A partial ing scrap metals assures much com- rous metals would be removed fromlist of such companies Is presented in petition and consequently promotes TABLE 8 TEE COMMERCIAL TREATMENT OF INDUSTRIAL AND MUNICIPAL SOLID WASTES Solid waste Waste-producin lndnatrp Wssteprocessilig indualry Waste-separation process Xecovered tutu/ prod acts Garbage and refuse__ Residential, commercial, Municipalities Hand sorting, magnetic Nonferrous scrap, and industrial separation. ferrous scrap, assemblages. glass, plastics, rubber, rags, paper. Waste wood Pulp Paper Gravity separation (by Wood, bark. heavy media). Bark Pulp Fertilizer Screening Sized bark. Bagasse Sugar Paper. Screening Bagasse fiber, pith. Wastepaper Residential, commercial, Paper Nand sorting, gravity Paper fiber. and industrial separation (by assemblages. cyclones), mechanical sorting, screening, magnetic separation, flotation. Grinding wastes Tool Gravity separation (by Diamonds. heavy liquids), flotation. Fly ash Electric power Electric power Magnetic separation, sir Ferropozzolan, puri- classification, screening. fied pozzolan. Slag Steel Steel Magnetic separation, Sized slag. screening. Foundry wastes Foundry Foundry Magnetic separation, Molding sand, metals, screening, gravity alloys. separation (by shaking tables), air classification. Nonferrous metal Atomic power, electric Atomic power, Magnetic separation, Alloys, metals. scrap. power, automobile. electric power, screening. automobile. Nonferrous metal Smelting Smelting Screening, gravity repo- Metals. residues. ration (by Jigs and shaking tables), air classification, heavy- media separation. 28 SOLID WASTE PROCESSING

Gatbage Wood, and refuse trees,Cie.

Shredder

Receiving Pit

Metering Gate,

lioaftttous Hand Sorting metals

Plastics

Rubber a

a Tin cant end light fertous metals

Heavy fenous metals

Aluminum cans and CORrlinera Water. liquid organic wastes, or sewage sludge Impact Plaii GrinderI Primary Digester I Impact Flail Grindert Secondety Neste

Crude compost

Landfill 4 Coarse compost and Disposal telect item

pine compost

{Bagging Machine

Ragged compost

FIGURE 15. The reclamation of munichxd refuse by the SACSprocess. The scrap metals industry27 efficiency in reclamation and utiliza- Precious metals have been recov- tion. ered from a variety of materials, in- (2) Because of the efficiency of the cluding photographic film and solu- industry, large tonnages of new scraptions. Parry presented the list of such metals generated in manufacturingmaterials in an article published in operations by major companies are1962 (Table 10).' transferred to secondary processors to Recoveryofthelesscommon produce marketable metals. metals has also been important in- (3) The operations to produce mar- dustrially as evidenced by literature ketable metals are complex, and theydescribing plants and operations. TABLE 9 require special skills, expensive fa- See also: Nonferrous Scrap; Pre- NONFERROUS SCRAP RECOVERED IN THE cilities,andknowledgeofmetalcious Metals. UNITED STATES IN 19841 marketing. They must be conducted Prices of scrap metals. Four cate- inreasonablylargescaletobe gories of nonferrous scrap materials Weight Type of map recovered, competitive. have been particularly important be- Ihoustode (4) The recovery and refining op-cause of the large tonnages involved. atone erations are much simpler and henceScrap aluminum, copper, lead, and less expensive when different types of zinc have been sufficiently importantAluminum 652.0 materials are treated separately in-industrially' to warrant daily publi- Antimony: stead of as mixtures. cation of prices for the more common Antimonial lead 22. 3 Quantities of scrap returned to in-types of scrap containing those met- Secondary smelters.... 20.8 dustry. The United States Bureau of Primary smelters 0. 3 als. Table 11 lists the scrap-metal Coper, alloyed and unalloyed Mines compiles and publishes statis-prices for August 16, 1966, given in 73 to 90% as much as tics regarding the recovery in theAmerican Metal Market. It illustrates domestic mine output, United States of the major nonfer- the price differentials for the various 1915-84) 1093.0 rous scrap metals. These data -naytypes of copper, lead, zinc, and alu- Secondary lead 641.8 be found in Minerals Yearbook.' The Magnesium alloys 10. 0 Bureau of Mines, as well as the indus- minum scrap. Mercury (76 -lb flasks) 0.9 try in general, has differentiated be- Sources of scrap metals. Most of Nickel 23.0 tween "primary" and "secondary"the nonferrous scrap metals returned Tin 23.5 production of metals. "Primary" pro-to industry have been obtained from duction derives metals from ores andindustrial plants that generally have concentrates, while "secondary" pro-not processed their scrap metals for duction derives them from scrap met- reuse,Plants that generate large TABLE 10 als and industrial by-products. Theamounts of scrap metals may have term "new scrap" has been used tocontracts with wholesale dealers for PARTIAL LIST OF PRECIOUS METAL SCRAP 14 designatecuttings,turnings,and the collection of those metals. The re- Type of scrap other waste materials generated dur- mainder of scrap metals has been ing the fabrication of equipment and brought to dealers by collectors fromTurnings, chips, shavings. merchandise. "Old scrap" refers to sources such as small shops and mu-Silver on steel bearings. parts of obsolete equipment and tonicipal refuse collection. The dis-Silver steel turnings. piping, wire, and other materials re-mantling of obsolete machinery and Grindings. claimedindismantlingbuildings, Blanking scrap, stampings, strip, and ships, and the like. buildings has also provided a source. The Minerals Yearbook for 1964, Examples of the reclamation ofPowder mixtures. Volume 1, contains information re-scrap metals on a large. scale by aScreen scrap. major manufacturer and on a modestSolder scrap. garding the activities of secondary Brazing alloy scrap. producers of metals and the tonnagesscale by a municipality have been de-Contact alloy scrap. of products. The data in Table 9 werescribed in recent publications. AnSilver on steel, tungsten, and molyb- abstracted from that publication toarticleof January 1988 described denum scrap. show the magnitude of the second-equipment used tocollect150,000 Bimetal scrap. Silver-paint waste, wipe rags, paper, ary-metals industry. pounds daily of aluminum chips from and cans. Kinds of nonferrous scrap metalsprofiling operations." Problems re- Old batteries. and materials. The referenced datasulting from the accumulation of Plating solutions. on the quantities of industrial scrapscrap aluminum at the source were Precipitates, sludges and sediments. metals showed a number of classifica- Coated copper wire and racks. eliminated by Installing at each pro-Filter pads. tions for the materials processed andfiler a Torbit separator to gather theAnode ends. the products obtained. Actually, therecontinual now of metal particles. TheTank scrapings. are many more classifications of non- publication stated that the sale valueElectrolytic silver. ferrous scrap metals. The Nationalof the scrap aluminum was increasedHypo solutions. X-ray film. Association of Secondary Material In- noticeably by the chip-ccIlecthig sys-Coated plastics, ceramics, glass, mica, dustries, Inc., has issued Circular NFLtem because contamination of the quarts, etc. 68, "Standard Classification for Non-product was prevented by conUnuousChemicals. perrous Scrap Metals", which con-removal of the chips from the pro- Mirror solutions (WO. tains standard classifications for 119 tilers. Platinum-bearing material. types of nonferrous scrap metals." Sanders has furnished InformationGold on molybdenum or tungsten wire. 838-244TO--3 28 SOLID WASTE PROCESSING

TABLE it SCRAP METAL QUOTATIONS FOR AUGUST 14, 1064-CARLOAD LOTS DELIVERED TO BUYER'S WORKS

Wholesale Wholesale buying price, buying price, Type cf scrap metal cent,' (or Type of scrap metal cents (or dollars, where dollars, where indicated) indicated) REFINERS' COPPER SCRAP b SMELTERS' SCRAP ZINC Copper: New zinc clippings 10. 50-11. 00 No. 1 44. 00Old zinc (clean) 8. 00-8. 76 39.00Old die cast (clean basis) 7. 50 -5.00 Light 85. 60Die-cast slab (92% minimum) 10. 15-11.20 Refinery brass* 32. 00Dross galvanizing 10. 75-12.00 Dross; continuous mill 9. 80-11.00 BRASS-INGOT MAKERS' SCRAP b Zinc skimmings i Up to S. 76 East Midwest SMELTERS' SCRAP ALUMINUM Copper: No. 1 44. 00 44. 00Aluminum clippings: No. 2 39.00 39. 00 3003 s3 16. 00-10.60 Light 35. 60 38. 00 8161'' 18.00 -16.50 No. 1 composition solids 37.00-37. 6038. 00-38. 50 110025 16. 00-18.60 Composition borings, turnings._ 36.00-30. 6036. 00-35. 50 6062 613 16. 00-16.50 Radiators , 26.00-26. 60 28. 00 2014 145 15. 00-16.60 Yellow brass: 20171" 1b. 00-16.50 Solids 25. 00 24. 00 2024 240 16.00 -16.60 Turnings. 21. 00 21. 00 7075 7°3 13, 00-13. BO Aluminum clippings (mixed) 14. 60-15.50 SMELTERS' SCRAP LEAD Old aluminum cast, including clean crankcases, pistons 19. 00-13.00 Battery plates: Smelting charge per ton Aluminum borings and turnings, clean dry (East) _dollars._ d 70.00-76.00 basis, less than 1% zinc, 1% iron content__ 12. 50-13.50 Clean, heavy soft lead cents.. 12. 75-13. 00 Cable lead: Lead content do_ 12. 75-13. 00 Copper content _do_..- b U. 60

Source:" Anter9.an Metal gulag," August 17,19/8. 1160.00-01.50 Chiftp, hued on 14.0 costs In St. Lolls. b Leas 630.00 handling charge, For Sty copper content guaranteed in eicsen of DO% f Buis sample.

concerning the collection of scrap bydivision of the City of Memphis. PREPARATION OF SCRAP METALS the Light, Oas, and Water Division of See also: Slag. Nonferrous scrap materialsfre- the City of Memphis." He emphasized Marketing scrap metals. Scrap met-quently require treatments to prepare the importance to profitable salvagea's have been sold by dealers to whole- them for melting, smelting, and refin- operations of the conversion of scrapsalers and to smelters. The value ofing operations. Turnings, borings, and into forms that bring the highestthe scrap and whether a specific kindPunchings of new metals may be sub- prices. In 1983, scrap brass from lightof scrap will be sent to a primary or ajected to magnetic separation to re- bulbs and other sources were sold tosecondary smelter depend on themove iron or steel fragments. In some dealers for $3,600. Coils of insulatedproximity of the smelters, togetherInstances, degreasing has been prat- copper wire, lengths of lead-coveredwith other considerations. The mostticed to overcome the adherence of the cable, and leaded copper connectorsimportant factor is the compositionferrous contaminants to the turnings were heated to destroy the insulationof the scrap in desirable metals andand borings, Stripping machines or and. to separate lead from copper byundesirable metals or foreign mate-manual methods have been used to melting the lead below the meltingrials. The composition influences theremove lead sheathing and insulation point of copper. About 87,000 poundsexpenses for transPorting,sorting,from electrical cables. Materials that of lead and 262,000 pounds of coppersampling, preliminary treating, smelt-are not entirely metallic, such as were salvaged in 1963 by the utilitying, and refining. sweepings, drosses, ashes, and slags, Production of marketable metals from scrap materials29 may be ground to liberate metallicniques and equipment to identify, sort,bringing scrap metals into salable prills, drippings, and grindings. Theprocess, and package scrap is a vital forms has been to melt them and then liberated metallic particles can thenphase of the business, according tocast them into convenient shapes for be recovered by physical methods ofKobrin. One sorting technique he de- handling industrially. This can be separation based on differences inscribed was based on the marked ef- done with metallic scrap that, has been specificgravity or other physicalfect of certain impurities on the hard-sorted and otherwise prepared so that properties. nessoftitanium.Hence,Kobrinthe metal or alloy will be of a market- If the source of a particular lot ofstated, Brinell hardness tests can be able composition. scrap metal is known, the lot can ueused to segregate various grades of The terms "melting" and "smelt- sold without analysis. Mixed materials titanium scrap. ing" are frequently used interchange- 'of uncertain origin must be sampled An example of the use of grinding ably. However, simple alteration from 4, and analyzed to provide a basis for to free scrap metal from glass is givena solid to a liquid, usually by heating, 4210yment. These operations add to thein another article by Sanders on theis considered "melting". "Smelting" expense of the transactions, but theysalvage shop of the Light, Oas, andrefers to melting or fusing, and is can be minimized or avoided by care-Water Division of the City of Mena-usually applied to ores, with accom- ful segregation or sorting of scrapPhis." He described the use of a ro-panying chemical changes to sepa- metals. tary drum crusher, which treatedrate metals or compounds of metals Scrap metals acquired by dealers 89,000 light bulbs in 1 year. The grind- from other constituents of the ores have been sorted piece by piece bying drum was filled with light bulbsor charge materials. In general, how- workmen who have attained greatand several chunks of scrap iron. Ro- ever, plants that produce secondary skill in identifying the many types oftation of the drum ground the glassmetals by furnacing operations are metals and alloys encountered. Thefree from the metallic ends. called smelters. The nonferrous -scrap sorting process has frequently been Bulky materials (e.g., wire, turn-industry employs various kinds of repeated at the smelting plant. Theings, thin plates, sheets, and radi-conventional equipment for melting, surest and simplest means for Iden-ators) have been baled by compression depending on the properties and the tifying scrap is by knowledge of itsin hydraulic presses to facilitate han-quantities of the materials to be use or origin. Thus, plumbing fixtures,dling and charging the materials tomelted. copper wire, automobile radiators, andfurnaces. Compaction of small pieces Indirectly Fired Kettles and Cruci- lead battery plates are easily distin-also promotes heat transfer in thebles. Heated kettles or pots can be guished, even by only slightly expe-furnaces and minimizes lossesof used to melt magnesium, zinc, and the rienced people. metals by oxidation and by entrain-so-called white metals (alloys of tin Less obvious metallic articles mayment of metal particles in slags. Inor of lead), because these materials be subjected to tests depending oncontrast to the requirements for mas- melt at relatively low temperatures. specific physical and chemical prop-sive charge materials in furnacingKettles for this purpose have been erties of metals and alloys. Pieces mayprocesses, chemical methods require made inessentiallyhemispherical be tested with a magnet to helpthe large surface areas of particulateshapes from cast iron or welded steel. identify steel with nonferrous coat- materials for the most efficient reac-They are mounted in refractory fur- ings and certain bronze and nickeltion. Therefore, in contrast to balingnaces in such a manner that their alloys. Filing and drilling are used toor briquetting of fine particles, it maycontents are exposed to view and so determine the relative hardness ofbe advantageous to grind or shred ma- that fuel oil or gas can be burned in pieces, and the freshly exposed sur-terials when chemical processes arethe space under the kettles. Kettles faces of metals may be noted for color employed. have been available in sizes to hold and texture as an aid in classification. It frequently is necessary to expel any desired tonnage up to 100 tons or A number of spot tests with chemicalsmoisture from scrap metals simply to more. have been developed for rapidly iden- guard against explosions upon contact The same method of indirect heat- tifying metals or alloys. 'These testswith hot materials in the furnaces.ing has also been employed on a much make use of characteristic colors,Conventionaldryers,fireddirectly smaller scale to melt gold, silver, or gassing, or formation of precipitateswith the most readily available fuel,alloys of the precious metals. For this when reagents are dropped on metallichave been used, purpose, a ceramic crucible of per- surfaces. Well-equipped laboratories haps 25-pound capacity is used infor chemical analyses are adjuncts toPRODUCTION OF MARKETABLE stead of a metallic kettle because the some scrap-handling plants. They are METALS FROM SCRAP MATE- temperature required to melt the pre- used to identify and analyze scrap for RIALS cious metals is too high for use of Iron purposes of classification as well as or steel vessels. Crucibles of larger for the control of smelting and alloy- The production of metals as mar-sizes are used widely in the scrap - ing processes. ketable ingots, bars, pellets, or othermetal industry to melt alloys of COP- Kobrin has discussed the influenceshapes and forms from scrap mate-per, lead, zinc, aluminum, and other of identifying and segregating typesrials is discussed here according tometals. of scrap on the profitability of sec-the major unit operations employed. Equipment to melt metals in cruci- ondary-metals recovery?' He claimedThe operations vary from simplybles has been manufactured by a that dealers were being confrontedmelting scrap metal in a heated vesselnumber of companies, The heat may with greater amounts of such ma-preparatory to pouring the moltenbe supplied by burning fuels or by the terials as beryllium-copPer, Inconel,product into molds to form appropri- consumptionofelectricalenergy. titanium, and precious metals. Whenate solid shapes, to complex combi- Some of this equipment has been de- scrap is properly segregated, it cannations of hydrometallurgical andsigned to permit tilting of the crucible be directed back to specific mills.pyrometallurgical procedures. or the entire furnace to pour the Therefore. developing special tech- Melting. The simplest operation formolten metal. High-frequency induc- 30 SOLID WASTE PROCESSING tlon furnaces belong in this category.try has been used almost exclusivelyproducts that require smelting and They have been used extensively for for the primary smelting of copper,refining. Salsbury et al. presented data melting precious metals that areand the open-hearth furnaces usedthat can be used to survey available treated in relatively small amounts. for steelmaking can be classified asmarkets and to make preliminary esti- Ordinarily, little or no obnoxiousreverberatory furnaces. Reverberatorymates of the return to be expected smoke or fume is produced from the furnaces can be designed and erected, kinds of melting equipment described from an ore."' in sizes to suit various needs, by e Reverberatory types offurnaces above. The reason for thisin the caselarge number of engineering and con- may be used for smelting and refining. of melting kettlesis that the melting struction firms. The capacities ofBlast furnaces also are employed for is conducted at temperatures too lowfurnaces used in the secondary-met-smelting nonferrous scrap materials. to volatilize metals or their compoundsals industry have ranged from as lit- See also: Aluminum. and that the gaseous products of com- tle as 1 ton to about 150 tons. Blast Furnaces. Blast furnaces con- bustion do not come In contact with See also: Aluminum; Copper; Lead.sistofverticalshafts. They are the charge material. The usual small Rotary Furnaces, A rotary furnacecharged at the top with a mixture of scale ofoperation with Indirectlyconsists of a refractory lining in a steelmetal-bearing materials, fluxes, and heated crucibles generally does notshell that resembles a cylindricalro-coke. The coke is burned in air sup- produce much fume or smoke. tary kiln. Magnesite brick Is the usualplied through tuyeres placed near the Melting and refining. In the ma-refractory lining material. The steel bottom of the shaft. A crucible and jority of cases, scrap metals requirecylinder is surrounded by riding rings, tap holes are positioned below the some refining after melting, evenwhich run on steel rollers mounted on tuyeres. The crucible serves as a reser- though the scrap was carefully sortedpiers. Burners are attached at the end*lir for the molten materials, which and prepared for melting. The refiningof the furnace, and an opening is pro- descend through the Incandescent treatment may consist of simply skim-vided in the side of the cylinder.coke at the tuyere level. The molten ming dross and slag from the surfaceChargematerialsareintroducedproducts are removed periodically of the molten bath, or it may involvethrough the opening. Slag and metalthrough the tap holes. successive treatments with reagentsare skimmed or drained by rotating Oxygen enrichment of the air sup- to remove one contaminant after an-the furnace to bring the opening toplied in blast-furnace smelting of other. Severaltypesof internallyany desired level. Rotary furnaces arescrap materials has been adopted and fired furnaces have customarily beencommonly supplied by companies en-substantial benefits have been claimed applied for the melting and refining of gaged in the erection of smeltingfrom this practice when applied to .:,crap metals. equipment. The capacities of singlecharges of battery plates and lead The reverberatory types of furnace,units may be from about 1 to 50 tons. drosses. stationary and rotary, produce the Rotary furnaces operate in the same Blast furnaces can be erected in a major portions of secondary metals.manner as reverberatory furnaces,variety of sizes, and the smaller sizes It has been estimated that most of the that is, by internal combustion of fuelcan be obtained as complete units brass and bronze ingots consumed byin the space above the charge mate-ready to install on foundations, A industry originated from the treat-rial. Some metallurgists favor rotarysomewhat typical furnace, which has ment of scrap materials in reverbera-furnaces over stationary reverberatorybeen described in the literature, meas- tory-type furnaces. Large amounts offurnaces because heat transfer andures 6 feet by 3 feet by 10 feet deep. aluminum, lead, and zinc metals andcoalescense of twills of metal are pro-That furnace is water jacketed and alloys have also been produced withmoted by the ability to mix the chargehas six tuyeres on each long side of such furnaces. by rotating the furnace. Rotation ofthe furnace. The water-jacketed type Reverberatory Furnaces. A rever- the furnace also enables the opera-of construction has been most com- beratory furnace is a rectangular en- tor to pour the molten contentsmon. it has the advantage that a shell closure, usually lined with magnesiteconveniently, of solidified slag forms on the water- brick, with openings hi the sides or Smelting and refining. Smelting in-jacketed walls of the shaft to take the the roof for receiving charge mate-volves chemical changes in conjunc-place of refractories. The crucibles of riats, Skimming doors are Installed intion with melting or fusing of mate-blast furnaces have ordinarily been the side valLs of the furnace to removerials. The chemical changes generallyformed of basic refrattories. slag or dross, and tap-holes extendconsist of reduction or dissociation of An article published In the Engi- through the refractories at severaloxides or other compounds to form neering and Mining Journal de-scribes levels above the furnace bottom formetals, and the formation of slags.advantages for an unusual method of skimming slag and for draining theOrdinarily, it has not been possible toconstructing ablast molten metal product. Burners for themake the chemical reactions so selec- furnacefor combustion of oil or gas are insertedtive that only one metal Is produced in smelting copper scrap." It states that through one end of the furnace andsmelting. Consequently, it has gen-the capacity for smelting a copper a flue for exhausting the products oferally been necessary to refine thescrap was increased frorn 35 to 100 combustion is provided at the oppo-metallic products from smelting op-TPD of charge material. At the same site end. The heat from the combus-erations to obtain separate marketabletime, coke consumption droPPed from tion is transferred directly to themetals. 25 to 10 percent of the charge. These charge by radiation and conduction. Schedules for purchasing ores andbenefits resulted from inverting the "Reverberatory" refers to the rever-concentrates have been developed and bosh of a blast furnace; that is, from beration or radiation of heat from theare widely used, especially by the com- increasing rather than decreasing the roof of the furnace onto the chargepanies engaged in the primary smelt-cross-sectional area of the furnace or bath in the furnace. The rever- ing of copper, lead, and zinc. Although shaft at the tuyere line. The lowest beratory type of furnace which hassuch schedules are intended for oresgrades of scrap, consisting of irony probably been the one most commonly and concentrates, they may be in-brass, sweepings, ashes, skimmings, used in the secondary-metal indus- formative to producers of nonmetallicresidues, radiators, wire, grindings, Regulations concerning solid waste disposal91 Powders, cuttings, chips, and clad ma- ers has been screened to yield dustMost of the zinc oxide produced by terials, were smelted in this furnace. containing 96 percent metallic zincslag fuming plants has been trans- Blowers to supply the air blast andwith 96 percent of it as minus 325-ported to electrolytic zinc plants for Pumps to furnish the cooling watermesh particles. recovery of the zinc as metallic zinc. may be of the positive-displacement Retort Furnaces. Retort furnaces Hydrometallurgicalprocesses. A or the centrifugal types. Ladles andhave been used to produce zinc metalnumber of hydrometallurgical proc- slag pots are heeded to receive and to from zinc dross, zinc die castings, newesses Involving operations such as dis- convey the molten slag and metaland old zinc scrap, and similar typessolution, precipitation, cementation, products. The gaseous Products fromof scrap that contain mostly zinc.filtration, and electrodeposition have the tops o: blast furnaces have con-Lower grades of materials and non-been employed in the recovery and tained too much fume to be expelled metallicmaterialsarepreferablyutilization of metals from scrap ma- directly to the atmosphere; hence, theprocessed at primary smelters. Re-terials. In many cases the methods top gas has been passed through bagtort furnaces have been employed toare combinations of familiar steps houses or scrubbing plants. separate the* more vahrble metalscommonly used in separations for The use of blast furnances for sec-such as zinc, cadmium, and mercury, chemical analysis. The combinations, ondary smelting has been confinedfrom silver. however, may be very complex, and mostly to the treatment of materials Slag Fuming. The process known asthey must be varied to suit the specific containing lead or copper, The rela-"slag fuming" is a form of distilla-properties of the materials to be tionship between reverberatory fur-tion because it utilizes the high vaportreated and the types of products de- naces and blast furnaces in the smelt- pressure of metallic zinc at elevatedsired. And in turn, the equipment for ing of battery plates and lead drossestemperature. Initially, it was appliedconducting the operations must be were discussed in connection with theto recover zinc as zinc oxide fromsuited to those needs and to the re- uses of reverberatory furnaces. Blastmolten slag while slags were beingagents and other conditions of the furnaces have generally been em-produced. The process was also usedoperations. ployed for smelting the poorer gradesto reclaim zinc from slags rejected to See also: Copper; Germanium; Pre- of copper-bearing scrap because thewaste dumps before the fuming proc- ciousMetals;PyriteCinder; Process can reduce copper from itsess was invented. It depends on the Uranium; Yttrium; Zinc. oxides and it can produce copperreduction of the zinc compounds in relatively free from contaminants.slag by reaction, either directly or in. The product from a copper blastdirectly, with carbon injected into the furnace, called black copper, how- molten slag. ever, contains small but objectionable Pulverized coal suspended in air is amounts of antimony, bismuth, tin,blown into the molten slag contained lead, zinc, and nickel. Such materialin a rectangular furnace of water-REGULATIONS CONCERNING requires electrolytic refining. jacketed construction. The mixture of SOLID WASTE DISPOSAL See also: Copper; Slag. coal and air is introduced through Distillation. Distillation has beentuyeres placed near the bottom of the (Based on August 1966 Survey) employed to reclaim metals having low furnace. The method causes violent boiling points from scrap materials.turbulence of the slag bath. The coal Several types of furnace have been innot only provides for reduction of the In the August 1968 survey of the general use, but their essential fea-zinc, but also for generation of heat.State health departments, informa- tures are similar. The larger furnaces,The coal requirement has been abouttion was requested concerning regu- for the distillation of scrap zinc, have20 percent of the weight of the slag;lations covering the disposal of solid been refractory-lined chambers sur-about 2 hours of blowing time haswastes. Information contained in the rounding bottle-shaped retorts madebeen required to eliminate the zincfollowing paragraphs was supplied. ofmoldedrefractorymaterials.from a batch of slag. Slag quarried In most States, the municipalities Either gas or oil has been burned infrom old dumps can be charged withor counties have the authority to op- the furnaces to supply heat throughmolten slag from smelting furnaces.erate and control solid-waste activi- the walls of the retorts. Retorts usu-The ratio of cold slag to molten slagties. Ten States did not have any ally hold about 4,000 pounds of scrapand the ratio of coal to air has beenlegal authority in the matter of solid which may be charged as solid orcontrolled to maintain the tempera-waste disposal, private or municipal. molten metal. ture in the furnace at about 2,200° P.The legal authority reported by 13t Distilled zinc may be condensed to The mixture of zinc vapor and car-States was based on general health or a molten form or to zinc dust. A con-bide monoxide expelled from the slagnuisance laws and on water and air denser consisting of a steel shell linedbath is oxidized in the space above.pollution control laws. In Minnesota with refractory has been used for pro-Then the gaseous mixture containingand Texas permits must be obtained ducing molten zinc. It is attached tozinc oxide passes through coolers and from the water pollution control board the retort and protrudes from thebag filters. The product from the bagwhen areas adjacent to waters of the furnace. The usual dimensions of afilters has normally contained aboutstate are used as waste disposal areas. condenser are about 8-foot length70 percent of zinc and about 8 percentIt was pointed out that in Montana and 3-foot diameter. The product isof lead. It is densified, and most of themuds and sludges from mining are not withdrawn through a tap hole in thelead is expelled by heating in rotary Condenser and cast into slabs forkilns at about 2,300° P. with additions Arizona, Colorado, Georgia, Hawaii, marketing. of about 2 percent of fine coke. This Kansas, Maine, Missouri, Nevada, Wash- Unlined steel condensers have beentreatment increases the density of the ington, Wyoming. used to produce zinc dust. They may ?Alabama, Alaska, Arkansas, California, zinc oxide from about 40 to 185 pounds Idaho, Minnesota, New Hampshire, North be 8 feet long, 7 feet wide, and 14 feet per cubic foot and provides a product Carolina, Ohio, Pennsylvania, Tennessee, tall. The product from such condens- containing about 1 percent of lead. Texas, Utah. 32 SOLID WASTE PROCESSING a health hazard, so industries are leftufacturing insecticides. Samples weredemand (sop), and both ammoniac& to themselves to work out disposalcollected in test wells adjacent to the and nitrate nitrogen. In addition, methods. burial area(Tennessee). Observa-samples were analyzed for organic Depending on the situation, thesetional wells have also been required content by chromatography. safeguards may be required in orderbefore a permit was issued for an in- Current activities reported by states to obtain a permit in Minnesota: (1) dustrial waste disposal area (Texas) .responding to the questionnaire in- Diking around the site (assuming theTests have also been made for radio-cluded the following: dike is sound) ;(2) diversion or con- active contamination of a well (Utah). The Arkansas State Pollution Con- tainment of surface drainage;(3) Water contamination, of course, istrol Commission was designated the sealing of previous soil or rock forma-of special interest. The survey of State State agency for reviewing solid waste tions;(4)covering of dumped orhealth departments revealed that agrant applications. No staff had as stored material to minimize erosionnumber of solid industrial wastes haveyet been obtained. and control drainage and storm-water contaminated State waters: (1) For- In California a statewide inventory percolation;(5) regular supervisionest industry and lumbering wastes, was being made of sources, quantities, and control of operations; and (8) such as sawdust, bark, drainage frommethods of disposal, etc., of all types provision of an alternate site disposal. log ponds, and slabs (Alaska, Idaho.of solid wastes. The following were listed as beingMinnesota, South Dakota) ; (2) runoff In Idsto a planning grant had been subject to regulation because they arefrom mining wastes subsequent toobtained to study the solid waste prob- potentially deleterious or detrimental leaching(Arizona,Nevada); (3) lem, including solid industrial wastes. topublichealth:slaughterhouses,mining wastes (Georgia, Idaho, Min-Also in Idaho, a regulation providing rendering works, glue works, deposi-nesota, South Dakota, Texas) ;(4) for State authority for control of ref: tories of dead animals, tanneries,pulp and papersludge(Georgia,use disposal had been proposed. wool-washing establishments, paperPennsylvania) ; (6)sulfurfrom In Rhode Island in July 1986 a solid mills, by-product coke ovens, dyestockpiles (Minnesota) ;(8) calcium waste disposal program was estab- works, oil refineries, dairies, cream-hydroxide from the manufacture oflished in the Division of Environ- eries, cheese factories, milk stationsacetylene gas (Georgia) ;(7) potato-mental Health. One of the main ob- (Pennsylvania, Montana)and theprocessing wastes, such as culls, andjectives of the new Program was to burning of cotton-gin wastes (Texas).other potato wastes (Idaho); (8) ani-determine the adequacy or inadequacy Only six States had specific legis-mal carcasses (Idaho);(9)Meat-of existing solid waste disposal prac- lation providing authority for thepacking and rendering wastestices and the need for additional regu- State health departments to conduct(Texas); (10) metal refining wasteslations for the enforcement of an a program for the control of the stor- (Nevada) ; (11) metalfinishing acceptable statewide solids disposal age, collection, and disposal of solidwaste sludges (Pennsylvania); andprogram. No full-time personnel were wastes(Montana,Nebraska, New(12) feed lot wastes (Texas). working with industries or munici- York, Oregon, South Dakota, Texas). In Texas, to prevent water contami- palities to help them with solid waste In Texas this authority is specific fornation by feed lot wastes, facilities problems. refuse deposited within 300 yards ofwere required that would retain all In Maine, the Division of Sanitary a public highway. In Idaho legislationrunoff generated by a 2-inch rain from Engineering was gathering data with of this type has been proposed. a waste disposal area. which to develop a statewide compre- No routine testing was reported by In response to a question concern-hensive plan for solid waste disposal. any State for the detection of con-ing the tests made to determine theMunicipal solid waste disposal was tamination of water by solid wastesstability of solidindustrial wastesbeing studied. Solid industrial wastes deposited in spoil areas. It was indi-deposited in a spoil area It was re-might be studied at a later date. cated that normally routine streamvealed that generally the tests used A bill to give the Ohio State Health surveys show whether pollution is oc- to determine whether surface water orDepartment authoritytoregulate curring. If problems develop, the testsgroundwater is being contaminated bysolid wastes was scheduled for Intro- in Minnesota were generally highlysolid industrial waste deposited induction into the next session of the specialized, as required by the naturespoil areas depend upon the naturelegiela lure. Ohio had obtained a grant of the problem. One State reportedof the material deposited. Tests usedunder the Solid Waste Act (P.Ii. 89- that tests were run in the vicinity ofin Texas include color, turbidity, dis-272) for a survey of and statewide a spoil area used by an industry man- solved oxygen, biochemical oxygenplanning for solid waste disposal. Major Waste Categories

Acetylene Wastes Lime Agricultural Wastes Magnesium Aluminum Manganese Animal-Product Residues Mica Antimony Mineral Wool Asbestos Molasses Ash, Cinders, Flue Dust, Fly Ash Molybdenum Asphalt Municipal Wastes Bagasse Nonferrous Scrap Bauxite Residue Nuts Beryllium Nylon Bismuth Organic Wastes Brass Paint Brewing, Distilling, Fermenting Paper Wastes Petroleum Residues Brick Plant Waste Photographic Paper Bronze Pickle Liquor Cadmium Plastic Calcium Poppy Carbides Pottery Wastes Carbonaceous Shales Predous Metals Chemical Wastes Pulp and Paper Chromium Pyrite Cinders and Tailings Cinders Refractory Coal Refrigerators Cobalt Rice Coffee Rubber Coke-Oven Gas Sal Skimmings Copper Sand Seafood Cotton Shingles Dairy Wastes Sisal Diamond Grinding Wheel Dust Slag Distilling Wastes Sodium Electroplating Residues Starch Fermenting Wastes Stone Spans Fish Sugar Beets Flue Dust Sugar Cane Fluorine Sulfur Fly Ash Tantalum Food-Processing Wastes Tetratthyllead Foundry Wastes Textiles Fruit Wastes Tin Furniture Titanium Germanium Tobacco Glass Tungsten Glass Wool Uranium Gypsum Vanadium Hemp Vegetable Wastes Hydrogen Fluoride Wastepaper Inorganic Residues Wood Wastes Iron Wool Lead YttriuM Leather Fabricating and Tannery Zinc Wastes Zircaloy Leaves Zirconium

33 34 SOLID WASTE PROCESSING ACETYLENE WASTES capronitrile, and caprolactam for thebenefit of refining. This has meant Acetylene wastes have been cal-synthesis of Perlon, Furan as thethat the scrap could not contain ex- cined and carbide made from the re- starting material for P31Yarnictc, poly- cessive contaminants. Alloying metals covered lime. One plant was reportedurethane, alkyd and Buna-type resins, may be added, however, to bring the as having a capacity of 330 TPD.'" and rubber has been discussed." Stepscomposition of the product to specifi- for the preparation of nylon from fur-cations, or the contaminants may be AGRICULTURAL WASTES fural are given by Voss "' Use of plantdiluted to acceptable levels by addi- See also:Animal-Product Resi-residues in the manufacture of plas- tions of purer metals or alloys. dues; Bagasse; Food-Processing tics has been reviewed."1' See also: Recovery and Utilization; Wastes;FruitWastes;Nuts; Alkaline digestion of the stems of Reference 233. Slag;SugarBeets;Vegetablerye and reed softens tissues to improve Wastes; Wood Wastes; Refer-assimilaloility by ruminant animals. ALUMINUM TURNINGS ences 18, 21, 46, 47,103,156,252, Morken presented a comprehensive 279, 285, 300,308,315,331,341,ALUMINUM discussion of problems connected with 367, 395, 406,437,460,473,486, See also: Recovery and Utilization; the preliminary treatment of oily 490. Reference 148. aluminum turnings." The turnings or chips considered were produced at the EXTRACTION SMELTER RESIDUES rate of about 20,000 pounds per day by Carotene has been extracted from Residues from aluminum smeltingmachining operations in an automo- certain leaf meals for use as a feedoperations (drosses) are treated bybile plant. They contained about 21 supPlement." a crushing-grinding-screening-classi-Pe cent of liquids present as oil and fication operation for the recovery of w ter. About 0.30 percent ot uncom- HYDROLYSIS the contained metallic aluminum.b ed Iron, evidently abraded from The Soviet Union hydrolytic Indus-This aluminum is in the form of prills,cu ting tools, was present as very fine try has produced large quantities ofshot, large spill splatters, etc., and isPa tees adhering to the oily alutni- ethyl alcohol, 2-furaldehyde, carbonintimately mixed with or coated bynuchips. It was imperative to re- dioxide, acetic, acid, activated char-slag. The aluminum metal, being mal- move the iron because the reclaimed coal coal, vanillin, trioxyglutaric acidleable, resists crushing or grinding,aluminum was to be used for pistons. and glucose from wood and agricul-whereas the slag is very fragile and Morken wrote that magnetic aePa- tural residues."' The products and by-breaks up easily. Consequently, this ration appeared to be the best method products of agrarian residues werewaste material is amenable to a dif-for removing the iron, but that this surveyed in 1956 by Wilder and Hir-ferential crushing-grinding operationwould require dried chips. The most zel"' and in 1952 by Goethe Is."' Ausing screens orairclassification economical and satisfactory procedure continuous process for hydrolysis ofequipment to effect the separation. for drying oily chips appeared to be wood and agricultural wastes was de- Hamtaermills are normally used forby use of a rotary kiln, directly fired scribed by Desforges In 1952.1" disintegration. Ball mills have been with gas. The method in which heat The nature of reaction productsemployed, but they tend to beat small input was controlled to vaporize rather from hydrolysis of celluloeic wastesparticles of slag into the malleable than burn the oil minimized oxidation WO described by Heinemann 114 Thealuminum. Any of the usual vibrating of the aluminum but caused much waste materials from hydrolysis canor shaking-type screens are suitable,smoke. It was believed that, in addi- be used as a humectant in agricul-as well as the normal type of airtionto the smoke nuisance, the ture "' and as fertilizer.'" classifiers. The waste or dross treatedmethod of heating presented a severe The hemicelluloses that occur In as-will contain some 20 to 30 percentexplosion hazard. A number of experi- sociation with cellulose have beenmetallic aluminum, The product for ments were conducted to remove oil by used for large-scale production of fur-return to furnaces should containmeans other than heating. None of fural. They are hydrolyzed by sulfuricfrom au to 70 percent aluminum.the experiments was satisfactory, ac- acid, which then dehydrates the liber-Dusting is a problem in that up tocording to Morken. ated pentoses to form furfural. Corn10 percent of the feed may eventually Eventually, Morton and his asso- stalks, flax wastes, sunflower stalks,be dust. In addition, because of theciates returned to thermal removal fruit seeds or pits, bagasse. Peach gum, friable nature of the slag, about 50of the oil. It was learned that the nut shells, reeds, olive husks, andpercent of the feed may finally be adrum-type dryer could be used without corn cobs are examples of residuesrelatively fine-size fraction (minus 20 nuisance or hazard, provided the that Scan be hydrolyzed to producemesh), which Is not considered treat- furfurai.a. a, fo. P. as. Ia. SO, 16.9. m, 324,1110. amount of oil on the chips was held MIL BO, 1144. Ilk 4$4 able because of the fine dissemination reasonably constant. A process was of the aluminum in the slag. developed in which centrifugal sePa- The swelling rate of plant waste and The beneflelatIon process is simplerators were used to remove oil to a its influence on the yield of furfuraland reliable. It is relatively inexpen- content of 2.1 to 2.3 percent. This was has been reported'" Acetic acid as asive, but no specific cost data weredone by flushing the chips in a by-product of furfural production hasavailable. The recovered aluminum iscentrifuging basket with cold water been reported."' The residue from fur-generally melted in reverberatory-and then admitting 90-psi steam for fural,production horn sal bark, areca,type furnaces, cast into pigs, and sold about 2 minutes. (palm) nut husks, and coconut shells,to consumers of metallic aluminum. Theflow ofaluminumchips has been used as a filler for phenolic It has not been feasible to remove through the reclaiming facilities was plastics," natural can be readily con- metallic contaminants, except magne- described by Morken as follows. The verted to furan, tetrahydrofuran, hex-sium, from molten aluminum scrapincoming utly chips were received in amethylenediamine, and adipic acidmaterials. Therefore, the producers ofskid boxes, which were dumped into for the synthesis of nylon; or to di-aluminum ingots from scrap have had a conveyor system containing mag- chlorobutane, adiponitrile, B -aminoto make salable products withoutnetic separators to remove tramp Ash, cinders, flue dust, fly ash35 iron. The conveyor depositedthe aluraintint recovered was eventually treated with steam In the absence of chips in a surge hopper, which fedmelted, cast into ingots, and recycledoxygen. The proteins and fats ob- two centrifugal separators. After cen- to the foundry. The quantity of alu- tainedwereseparatedandthe trifuging, the chips were conveyed minum recycled was sufficient to pro-purificationcompleted by vacuum pneumatically to the drum wryer.vide about 60 percent of the metal re-distillation."' The dryer discharged into a bucketquired by the foundry for piston conveyor, which fed a double-deckmanufacture, PYROLYSIS vibrating screen. This screen removed Chapman has described how the Fuels and solvents can be manufac- particles less than 30 mesh in sizeDuke Power Company of Charlotte, tured by pyrolysSs of waste products because it was considered uneconomi- North Carolina, employed magneticfrom the fat and vegetable -oil in- cal to recover this fine material. Theseparation to recover aluminum metal dustries."' screen oversize was discharged ontofrom strands of steel and aluminumANTIMONY a magnetic separator from whence wire." See: Lead, the cleaned chips were conveyed to See also: Separation. melting furnaces. ASBESTOS Evidently, considerable thought and SINTERING See: Plastic; Reference 284. experimentation was required to de- Fe-Si-Al-Ti alloys were produced vise the successful process for thefrom red mud from aluminum oxide CALCINATION preparation of aluminum scrap out- preparation in an arc furnace,'" Silica refractories are obtained by lined in the foregoing paragraph. It calciningasbestos waste and raw is interesting that the solution came ANIMAL-PRODUCT RESIDUESmagnesite." from the judicious selection of a INCINERATION Prosier combination of well-known Several industries including soap, Asbestos wastes plus clay and bind- types of equipment and machinery. leather,glue,gelatin, and animalers are cast in plastic and fired to See also: Separation. feed manufacture, have been based on meatpacking waste products. Bio-produce porous ceramics.'" REVERBERATORY FURNACES chemicals have also been producedASH, CINDERS, FLUE DUST, Reverberatory furnaces have been from packinghouse residues. Freezing FLY ASH Preferredformeltingaluminum these wastes has largely overcome scrap. Ordinarily a layer of flux hasshipping and storage problems. Fly ash has been described as a been used to protect the surface of EXTRACTION finely divided, powdery, man-made the molten aluminum from oxidation. pozzolan composed ofspheres of The flux may consist of sodium chlo- Biochemicals extracted from pack-amorphous silica and alumina"' Ac- ride, potassium chloride, and cryolite. ing house materialsinclude hor-cording to Russel, 8.25 million tons of Calcium chloride and sodium fluoridemones, vitamins, enzymes, liver prod- it were produced in the United States also might be used. Chlorine gas mayucts, bile acids, sterols, feed supple- in 1956 by pulverized-coal-fired boil- be bubbled through the molten bath ments,andglandularproducts.ers.'" He further indicated that the to combine with magnesium if it isGlands and organs have been col- annual domestic production of fly ash necessary to eliminate that element, lected and preserved by freezing untilhas been increasing since 1953 and Nitrogen is introduced as a refiningshipment lots accumulated.'" Curing,could go as high as 16.8 million tons , agent to expel dross and oxides fromevaporation, and extraction are in-Per Year. Chemicals contained in coal the metallic baths of aluminum. volved in coverting the collagen toash include: cobalt, nickel, molybde- See also: Recovery and Utilization.hide trimmings, tannery fleshings,num, chromium, vanadium, tin, zinc, ete., to gelatin and glue. Tallow haslead, arsenic, gold, platinum, pal- DRYING been produced by extraction of tank- ladium, silver, beryllium, gallium, lan- age.'" A rathercommonpreparatory thanum,silicon,aluminum,iron, manganese,magnesium, calcium, treatment is simple drying, It fre- HYDROLYSIS quently is necessary to expel moisture phosphorus, sodium, and potassium. from scrap metals to guard against Hydrolyzates of materials of ani- Approximately 1 grant of gold per explosions from contact with hot ma- mal origin such as feathers, fish meal,ton is found in coal ash, but this is terials in furnaces. Conventional dry-meat, and fish residue can be usednot an economic source because the ers, which are fired directly with theas animal feed ingredients."' Thechemical processing problems involved Twitchell method has commonly been in recovery are extremely complex. most available fuel. are used for dry-used to obtain fatty acids and glycer-The problems of enrichment and iso- ing scrap materials. ine from fats by hydrolysis. A plantlation of the separate chemicals have EXTRACTION near Chicago has been reported tonot been solved successfully. process 100 million pounds of fats and Dumping is the easiest and most Furnace wastes from the manufac- oils per year by this method.!" economical way of disposing of fly ture of aluminum are extracted to re- ash, but even dumping costs $1.00 per cover fluorine, sodium, and aluminum MECHANICAL SEPARATION ton or $16 million per year, most of compounds.'"'" Inedible slaughterhouse materialsthis to the utility companies. have been passed through a grinding Industry has found that not only is MAGNETIC SEPARATION machine to a heating device, a cook-the disposal of fly ash expensive, but Morken also described how theing vessel, and a centrifuge to recoverthe areas available for its disposal are piston foundry of the Chrysler Cor-fat, meat, and bone scrap.'" becoming scarce. Fly-ash disposal is poration recovered aluminum metal a particularly annoying problem of from oily aluminum turnings by mag- MELTING major importanceto the electric netic separation and screening.''' The Bones have been autoclaved andPower plants that burn pulverized 36 SOLID WASTE PROCESSING Coal, since it is not uncommon for aerator could correct a sub-normal ACIDIFICATION single utility system to produce ascollector performance". much as a million tons of fly ash per Magnus described the collection of The adsorption capacityoffly year. The electric-powerindustryfly ash at the South Charleston, Westash" and brown coal ash "" Is in- realizes that the solution to this prob- Virginia, power plant of the Chemicals creased by treating these ashes with lem lies in the large-scale utilizationDivision of the Union Carbide Cor-hydrochloric acid, of the ash. poration." The fly ash produced by INCINERATION Most of the Ry ash not disposed ofthe coal-fired boilers of this plant was by landfilling has been utilized di-collected by electrostatic precipitators By burning a mixture of coal ash rectly without being processed. Theat the rate of 328.000 pounds per day.with lime and sand, a binding ma- following are some of the ways inAbout 36,850 pounds of fly ash wereterial can be obtained that is similar which fly ash has been utilized; (1) Inreleased daily to the etmosphere byto portland cement."' portland cement; (2) in mass struc- the precipitators. ION EXCHANGE tural concrete; (3) in masonry cinder The problem of maintaining high and concrete building blocks; (4) incollection efficiencies developed soon Of three mediaion-exchange res- lightweight aggregate; (5) as a road-after the precipitators had been in-ins, cindets, and light asheslight base choking material for highwaystalled at the plant. The gas flow rateashes are reported as giving the best construction; (6) as a filler for bitu-eventually proved to be the criticalremoval of phenol from phenolic minous mix; (7) as a filler material infactor that had affected the achieve- wastes. They decolorize the wastes as roofing and putty; (8) as a soil con-ment of the desired collection effi- ditioner: (9) as a soil stabilizer; (10) ciency, It was also found that changes MELTING In oil-well grouting; (11) as a sandin the characteristics of the coal substitute in sand blasting; (12) as aburned by the plant had a direct effect Coal ashes, limestone, coal, and metal-polishing agent and mild abra-upon the operation of the precipita-Fe C, have been melted to form sive; and (13) as a filtering medium. tors. The plant has, however, been able 2FeSi02. The calcium aluminate slag Recent research to improve knowlto achieve precipitator collection e has then been leached. The residue, edge of the characteristics and prop-flciencies ranging from 93.2 to 5..7after the addition of limestone, can erties of fly ash has been described bypercent. be used in the manufacture of iron Snyder."'. cement." See also: Incineration; Inorganic TREATMENT SINTERING Residues; Reference 506. A process for the recovery of ferro- Fly ash from a Long Island power pozzolan and a fine purified pozzolanstation has been sintered and used as COLLECTION from fly ash by magnetic separation,lightweight aggregate in cement."" air classification, and screening hasGermany also had a plant for mak- Katz stated that the various types ofbeen described in Potter.ift Fly ashing products from fly ash." Blast fur- cyclone collectors are suitable for thewas treated in a Roto-Flux magneticnace flue dust has been sintered and collection of particles that are usuallyseparator by sieves, air separators, areturned to the blast furnaces for larger than from 5 to 10 microns inbattery of magnetized coils, and asmelting." projected-area diameter." Such col-conveyor belt to produce magnetic lectors have been applied in series with ferropozzolan, coarse purified poz- VAPORIZATION the electrostatic precipitator, especial- zolan, and fine purified pozzolan. The Flue dusts from the production of ly where large particles of carbon orseparator could process 10 tons of flycopper, zinc, and manganese have grit predominate in the effluent gases. ash per hour to produce a ferropoz-been processed for the recovery of The installation of a cyclone im-zolan containing from 50 to 70 per-arsenic and bismuth. In this process mediately following the electrostaticcent of the iron oxide content of thethe dust is roasted, and the arsenic precipitator would improve the over-original ash. Ferropozzolan has beengiven off as a fume is condensed." all collection efficiency of a systememployed as a heavy-medium ma- troubled by the severe reentrainmentterial in heavy-medium separationsASPHALT of highly conductive ash that agglom-and as a constituent of ferral cement See: Reference 308. erates upon passing throughthefor the manufacture of special dense precipitator. mortars and concretes. The chiefBAGASSE Katz indicated that the effectiveProduct of the separation is purified Bagasse is the fibrous residue that collection of fly ash by electrostaticpozzolan, a high-strength productremains after the sugar juice has been precipitation depends primarily uponthat is offered on the market on apressed from sugar cane. It consists the electrical power input to the pre-certified quality-controlled basis. Theof about 30 percent pith, 10 percent cipitator. The optimum power char-Roto-Flux separator requireslittle water-soluble materials, and 60 per- acteristics of theprecipitator arespace and costs about $15,000. cent good-quality fibers that range determined by the electrical resistiv- in length from 1.5 to 1.7 mm. These ity of the fly ash. This in turn is de- DISPOSAL WITH SEWAGE SLUDGE fibers are normally pulped following pendent upon the sulfur content of the Investigation of the possibility oftheir separation from the nonfibrous coal burned in the plant, the tempera-disposing of fly ash with sewagePith cells, dirt, finely divided bagasse ture of the effluent gas, and the car- fibers, and weeds. sludge has shown that the material Bagasse is separated into fractions bonaceous content of the fly ash. He will dry to a nondusting mass requir-for applications that range from use stated that, "it is conceivable that bying less disposal space than when theas feedstuff to use as a raw material altering the coal burned, flue gas tem-two are disposed of separately. Fly forhigh grade - paper processing. perature, or the particle size distribu-ash can also enhance the filtration ofWhen utilization schemes are not tion of the pulverizers, the plant op- sludge. feasible, residues can often be burned Bauxite residue37 Sugar mill bagasse

Magnetic Separator Sow Tramp iron

Depithing Mill Pith to sugar mill boilers

To pulp Depithed mill bagasse

Baler

Baled bagasse to storage FIGURE 6. Depithing of bagasse,

to recover their fuel value. Charcoaltion (Figure 8). Tramp iron entering generated at between 100 and 160 Psi. and activated carbon can also be ob- the depithing station with the bagasseOven-dry bagasse has a calorific value tained from many of these materials.is first removed by a magnetic separa- of about 8,200 Btu per pound. Bagasse Bagasse has frequently been burnedtor. Most of the pith is then sepa-with 50 percent moisture has a gross as a fuel to produce steam required byrated from the bagasse fiber in aheating value of about 4,400 Btu per the sugar mill for both power andHorkel depithing mill. In this mill, the pound. An average of 1.2 tons of ba- processing. However, the pulp and pa-bagasse is first shredded by hammer- gasse (moisture-free basis)is proper industry has found that bagassemills and then screened into separateduced for each ton of cane sugar fibers are quite suitable for the pro-fractions of pith and fiber. The sepa- output?", wv. duction of insulation board, particle board, and almost any type of paper,ration is not a clean one, for the fiber NITRATION ranging from bleached fine-qualitystill contains about one-third of the Nitrolignin is obtained from bagasse writing and printtng papers to un-pith initially charged to the mill. Aby nitration and digestion of the bleached wrapping papers and news- portionofthedepithedfiberisproduct."' print. The first pulp and paper millshipped directly to the pulp mill for to utilize bagasse as a raw materialsubsequent wet depithing and pulping OXIDATION has been in operation for over 20with dilute caustic soda, while the re- A mixture of bagasse and coke is years. The construction of other mills maining fiber is usually baled andused in the reduction of nickeliferous was impeded for a time, however, bystored for fut'tre use. The pith sepa-serpentine." various technical difficulties. The de-rated by the Horkel mill Is returned velopment of new techniques about 10to the sugar mill, where it is burned POLYMERIZATION years ago was soon followed by the in the boilers as fuel. It is either trans- A plastic molding material called construction of over 30 bagasse pulpferred to the boilers by conveyors andValite has been produced by polymer- mills throughout the world. bucket elevators or by blowers and izing aldehyde and ketone products of An annotated bibliography prepared bagasse with phenol,' by West describes the utilization ofcyclones. The bagasse and the de- bagasse for paper, board, plastics, and pithed fiber are removed through the SCREENING depithing station with conveyors. chemicals'" Bagasse utilization has The recovery of fiber from bagasse been summarized In three papers."- "1. HYDROLYSIS by screening has been mentioned by Martinez in connection with the utili- See also: References 18, 22, 24, 42, Pulp for viscose rayon is producedzation of bagasse for the manufac- 55,78, 88, 92,107,155,198-201,by hydrolysis of bagasse. ture of paper by the pulp and paper 212,214,253,254,288,271,283, Seealso:AgriculturalWastes;industry."' 290,299.301,302,325,401,411, Vegetable Wastes; Reference 275. 443,486,488,539. BAUXITE RESIDUE INCINERATION A mixture of bauxite residue and DEFITHING Whole bagasse is normally burnedfuel that has been pelletized and sin- Bagasse fiber is usually prepared at 45 to 50 percent moisture in boilerstered has been used as lightweight for paper pulping in a depithing sta-having special furnaces. Steam isaggregate."' 38 SOLID WASTE PROCESSING BERYLLIUM SCREENING CARBONACEOUS SHALES An electrolytic refining process is Spent grains after fermentation are Humic fertilizer has been obtained used to prod:we beryllium from scrap almost universally removed on finefrom carbonaceous shales by nitra- atBerylliumMetals & Chemical screens and are processed for use astion and chlorination."' Corporation.'" cattle food. Eight to 10 pounds of this BISMUTH material can be recovered per bushel CHEMICAL WASTES of grain processed. This by-product is Chemicalmanufacturingplants See: Lead. an essential part of the industry'sproduce solid wastes that are extreme- BRASS overall economy. ly varied in nature. Many toxic chem- See: Copper; Foundry Wastes; Ref- icals (e.g., phenol) can be destroyed erence 390. BRICK PLANT WASTE by incineration. Occasionally, solid wastes from chemical plants can be INCINERATION utilized in some fashion, e.g., use of BREWING, DISTILLING, FER- Brick-plant waste has been burnedwaste tar from alcohol preparation for MENTING WASTES and exploded and used as building a bitumen-type binder. The brewing, distilling, and fermen- material"' See also: Inorganic Residues. tation industries are concerned with MELTING CHEMICAL OXIDATION the production of alcoholic beverages, A bitumen-type binder has been pharmaceuticals, and a limited num- Scrap brick, slag, and other indus-produced by oxidation of the waste ber of organic chemicals. The princi-trial wastes can be melted and usedtar from the preparation of synthetic pal solid waste from distilleries isto produce mineral wool."' '°' alcohol." stillage, the residual grain mash from distillation columns. In 1984, 630,000BRONZE DILUTION tons were utilized. This material is re- Effluent residues from conversion covered almost completely by the in- See: Copper. of paraffins into fatty acids can be dustry for animal feed or for conver- diluted and used as a base for foundry sion to chemical products. It has been CADMIUM binder." reported that 85 percent of the stil- See: Reference 249. lage is recovered as dried feeds, 14 DISTILLATION percent as wet feed, and only 1 per- CALCIUM Most solvents can be reclaimed by cent is lost. See also: Lead. "" Light oil and solvent Some chemicals have been recov- can be obtained by distillation of spent eredfromfermentationbroths. COMBINATION AND ADDITION straw oil from coke production.°° Among them are d-lactone and 1-lac- Calcium sulfate sludge formed in INCINERATION tone following calcium pantothenate the course of various manufacturing Poisonous sediments and solutions production, vitamins and amino acidsprocesses (e.g., from the working ofcontaining phenols, waste oils, and from fermentation wastes, bacitracinpotash salts, from the neutralizationthe like can be destroyed by oil- and amino acids from distillers' solu- with lime of the sulfuric acid spin- gasificationburnerswithspecial bles, tartaric acid from wine residues,ning solutions of the rayon industrY,iniectors, even when the moisture con- nicotinic acid from vitamin wastes,and in the manufacture of phosphorictent is high or fluctuating.'" Solid and glycerol from alcohol stillage. acid from phosphates) can be simul-cyanide has been incinerated using See also: Food-Processing Wastes; taneously utilized with the ammonia- waste solvent as fuel."' The incinera- Molasses. cal liquors of cokeries and carbon di-tion of solid wastes from tank-car oxideto produce ammonium sul-cleaning has been described. " CARBONIZATION fate."' The ash of distillers' dried solubles Dow has a $2.25 million incineration has growth-stimulation properties ac- CALCINATION plant that handles 81 million Btu/hr cording to Dannenburg" of liquid wastes and 60 million Btu per Modern (1949) methods for recal-hour of solid wastes. Materials dis- EVAPORATION cluing waste calcium carbonate haveposed of include 400,000 gallons per Brewery wastes have been eva-been surveyed by Knibbs and Gee."' month of liquid still residues, washes, porated and the residue used as feed."' DISPLACEMENT slurries,andothercontaminated EXTRACTION liquid products, 1700 drums and other Silicon carbide has been preparedcontainers of semiliquid and solid Tartrates, tannins, vitamin P-likeby extracting the calcium hydroxidewastes per month; 17,000 cubic yards compounds, potash, acetic acid, andfrom the furnace sediment formedper month of other refuse, including other compounds have been produced during the manufacture of calciumlarge amounts of plastics.'" from winery wastes."' Proteins arecarbide, mixing the remainder with Lederle has incineratedrubbish, extracted from brewery residues and carbon, and heating the mixture in angarbage, and valueless by-products converted to plastics.'" electric furnace."" from plant operations and sludges HYDROLYSIS CARBIDES from sewage and waste-treatment op- Hydrolyzates from distillery sludge erations. Iron, glass, and other non- are sources of edible protein, deficient Tungsten and cobalt have been re- combustibles have been removed by only in tryptophan and methionine."'covered from scrap sintered carbides.hand sorting."' The metals are oxidized with sodium Industrial wastes have been incin- INCINERATION nitrite as the first step in the recovery erated at the Badische Anilin-Soda Potash has been recovered by in-process." Fabrik plant. " cineration of fermentation wastes."' See also: Lead. At Kodak Park, trash, waste sol- Reverberatory furnaces 39 vents, oils, and various solid and liquid as a building material.". 2" The manu- and generators. The residual Iron can chemicals have been burned in an in-facture of light concrete aggregate bythen be consumed in iron or steel einera tor."' the suction sintering process has been making. Three wastes that have been in-described..' 6 Rubble, slag sand, boiler cinerated even though auxiliary fuelash, coal dump heat, fly ash, and clay MELTING is required for their combustion are acan be utilized in this manner."' Sin- A process has been developed to carbon waste slurry, a highly coloredtered coal refuse can also be reworkedproduce steel from copper slag. The TNT waste, and a gas containing hy- to fibers, yarn, or wool." The indus-slag piles at Anaconda, Montana, and drogen sulfide." trial significance of the elements inCiarkdale, Arizona, have amounted to 40 and 30 million tons, respectively. NEUTRALIZATION coal ash have been described by Headlee."2 About 3 tons of stag are required to Tailings in the production of hy- produce 1 ton of steel." Three plants drofluoric acid can be dry neutralizedCOBALT were being erected to recover iron with calcium carbonate and used as Wastes of cobalt xanthate contain-from copper slag. It was also planned an additive to control the setting ofing cobalt, copper, and zinc have been to recover copper from the slag. "'' ea cements." sintered to recover these metals"''' PRECIPITATION CHROMIUM See also: Lead; Pyrite Cinders and Copper has been recovered from Tailings; Zinc; Reference 61. Heating sludges containing chro- copper-bearing waste solutions by ntitun above 200° C. causes the chro-COFFEE precipitation on iron." mium to convert to the poisonous Coffee grounds have been extract- REVERBERATORY FURNACES chromate form.'" ed to obtain oils, fats, waxes, and Reverberatory furnaces are used for resins." melting, refining, and alloying cop- CINDERS per, brass, and bronze scrap metals. See: Ash, Cinders, Flue Dust andCOKE-OVEN GAS The intent in processing these types Fly Ash;Pyrite Cinders and See: Pickle Liquor. of scrap is to sort the types so that Tailings. marketable copper or alloys of cop- COPPER per can be produced with a minimum COAL See also: Recovery and Utilization;of refining, a minimum loss of alloy- See also: Lime; Reference 331. Cobalt; Inorganic Residues; ing metals, and a maximum utiliza- Lead; Pyrite Cinders and Tail-tion of alloying metals from scrap CALCINATION ings; Zinc; References 32, 66, 426. sources. Preparatory operations, such The carbonaceous pyrite In the resi- as magnetic separation, drying, and due from calcining wastes from grad- BLAST FURNACES baling frequently are required prior ing of coal can be used to produce sul- The blast furnace has been used to furnace treatments. furic acid." Calcined wastes from coalfor melting copper scrap, the copper A charge of coPper-bearing scrap is mines can be used in the preparationafterwards being refined in adjacentfirst melted and then stirred and sam- of cement." reverberatory furnaces." pled for chemical analysis. The chem- icalanalysis dictates the refining DEHYDRATION CHEMICAL REDUCTION steps, which normally consist of flux- Charcoalofhighdiscoloration Slags from copper smelters haveing, oxidation, and slagging. Suitable power can be obtained from lignitebeen reprocessed into building ma-mixtures of limestone, silica, and iron by dehydration with sulfuric acid." terials by blowing air and carbonoxides are added as fluxes to combine dioxide through the slag in the elec-with oxides of metals so that those INCINERATION tric furnace and feeding lime and aoxides may be removed from the fur- Coalwasheryrefusehas beensolid reducing agent onto the surfacenace. In fact, oxidation of contami- burned and used in the manufactureof the slag." nating metals is induced by blowing ofconcrete.". "I Carbon sludge air through iron pipes into the melt. from partial oxidation of fuel is dis- HYDROMETALLURCICAL PROCESS. It is frequently necessary to sample posed of by spraying it into a furnace ING and analyze the metal again after the for burning." fluxing and refining operations. And A process for producing copper tub- finally,if the product is brass or MECHANICAL SEPARATION ing from scrap copper by a three-stepbronze, additions of zinc, tin, or other procedure is described in Iron Ape.'"alloying metals may be made to bring There has been increased interestThe copper scrap is leached in am4the product to specifications. in reclaiming fine coals from coalmonium carbonate withaeration. The slag from an operation of this processing waste waters. Both flota-After purification,the solutionis kind is skimmed into pots and allowed tion techniques and use of cyclonestreated at 325 F with hydrogen in to solidify. The slag generally contains and centrifuges appear to have meritan autoclave to precipitate copper for this purpose, enough copper to warrant reworking. powder. The powder is filtered fromThis might be done by smelting it in a SINTERING the solution and dried in an inertblast furnace. Alternatively, the slag atmosphere, after which it is screened from a reverberatory furnace might Disposal of tailings from coal proc-to yield closely controlled particlebe crushed to liberate shots of metal essing is made easier by installingsizes for extrusion into copper tubing. from the mass of earthy material. The shaft furnaces in which dewatered Similar techniques for dissolution in shots may be recovered by screening material is dried and partially sin-ammonium salts have been employedor by other physical methods. The tered." The sinter can be crushed,to reclaim copper from copper-cladfinal residual slag may or may not mixed with Portland cement, and usedsteel and items such as small motorscontain suMclent copper or other 40 SOLID WASTE PROCESSING metal compounds to lustily smelting The collection of diamond grinding- FOOD-PROCESSING WASTES to reduce those compounds to metalswheel dust from the tool-grinding op- incident to their recovery. erations of the Tungsten Carbide Tool, The annual production of agricul- Incorporated, of Detroit, Michigan,tural residues in the United States is SMELTING has been briefly described in SteelPsomething like three times the coun- Some copper and copper-base scrap Diamond dust has been collected attry's annual consumption offood. has been smelted in primary smeltersthis plant in compact, illterless cen-Agriculture residues are generated in for the purpose of reclaiming onlytrifugal collectors that weigh only 65large amounts throughout the world the copper. With this type of smelt- pounds each. These units were mount- (e.g., the quantity of only one waste ing, most or all of the alloying metalsed on the walls of the plant, but theybagasseproduced In the world each such as zinc and tin, are wasted. Oncan also be installed on machinery,year amounts to about 300 million the contrary, the brass and bronze suspended from the ceiling, or placedtons). Many of these wastes can be ingot makers who treat scrap ma-on tables that occupy little more thanutilized as raw materials for produc- terials have endeavored to retain all2 square feet of floor space. Each unittion of chemicals and plastics, as cat- of the valuable alloying metals, as well Is priced under $200no more thantle feed and mulch, and for manu- as the copper, from the scrap becausethe cost of the average diamondfacture of paper, board, and rayon. bronze scrap ordinarily Is purchasedgrinding wheel. Almost one-fifth ofThe Bureau of Agriculture and In- on the basis of the copper and tinthe coot of a grinding wheel can bedustrial Chemistry of the Department contents of the scrap. saved by the recovery of diamondsof Agriculture has been investigating Reclamation of all of the metals infrom the grinding dust. methods for utilizing these residues copper-base alloys ts an apparent ad- (since 1935. A major deterrent to the vantage in favor of secondary smelt- DISTILLING WASTES construction of processing plants is the fact that much of this industry is ers. That advantage can be realized See: Brewing, Distilling, Ferment- best if the scrap materials are sorted seasonal. Installations designed on into types that can be trade directly ing Wastes; Molasses. the basis of peak loads would remain into saleable grades of ingots. If theELECTROPLATING RESIDUES idle much of the year. scrap material contains undesirable See also: Animal-Product Residues; contaminants, expensive refining op- Metals are recoverable from some Bagasse;Fruit Wastes;Rice; erations are required, or the contami- electroplating residues, but recovery Vegetable Wastes; Sanitary. nants must be diluted to tolerableprocesses have rarely been applied un- Landfilland Open Dumping; limits by blending with purer alloys less the waste contained precious met- References 112, 292. or metals. In cases in which the con- als. Metal sludge from the treatment taminants are large or difficult to re-of electroplating wastes has been CARBONIZATION move, it might be most economicalcombined with a variety of combus- Many carbonaceous waste materials to treat the scrap in a primary smelt- tible wastes (fly ash, coal dust, painthave been used for the manufacture er, where copper can be traced fromsludge, oil, and grease) and burnedof activated carbon. The properties of large proportions of iron, sulfur, andin an incinerator on conical inclined,the finished product depend on the many other metals or compounds. rotating grate containing perfora-waste carbonized. Decolorizing acti- A means for reclaiming metals from tions for the passage of ashes andvated carbons have usually been em- starters and generators from obsolete clinker!". "4 ployed as powders. Sawdust and lignin automobiles is to charge the parts to produce carbons of this kind. Vapor FERMENTING WASTES adsorbent carbons are usually in the steel-making furnaces to obtain cop- form of hard granules and are gen- per-bearing steel. Starters and gen- See: Brewing, Distilling, Ferment- erally produced from coconut shells erators have also been treated in cop- ing Wastes. and fruit pits (e.g., plum and apricot per smelters to remove the iron as kernels). Carbonization proceeds at slag while the copper is collected asFISH temperatures that are high enough to molten metal. Gelatinisprepared fromfish remove most of the volatile cor.stitU- wastes!' Fish wastes are hydrolyzedents but not high enough to crack the COTTON and the product is used in the manu-evolved gases."' Use of chemicalim- Citric and matte acids are extractedfactureofcosmeticointments."'pregnating agents causes carboniza- from cotton-production wastes!" Prawn-shell wastes have been ex-tion to proceed under conditions that See also: Reference 73. tracted with acetone, decalcified, andPrevent the deposition of hydrocar- refiuxedwithcausticto produce bons on the carbon surface.414 DAIRY WASTES chitin!" Carbonization of residues from alco- See: Food-Processing Wastes. hol, beer, and sugar factories and of See also: Animal-Product Residues. acorn husks is carried out to obtain DIAMOND GRINDING WHEELFLUE DUST activated carbon! Sawdust, from var- DUST ious woods and peanut, cottonseed, See: Ash, Cinders, Flue Dust, Flyand rice hulls are impregnated with Many grinding wastes contain fine Ash. industrial diamonds used l grinding ZnCia or CaO and carbonized. The FLUORINE Product is used for bleaching cotton- operations. Although diamonds can seed oil!" be recovered by several methods, in- See: Reference 123. eluding acid leaching, separation in DEHYDRATION, DEWr1TERING, heavy liquids, and flotation, the pro-FLY ASH DRYING cedures which have been used are See: Ash, Cinders, Flue Dust, Fly Charcoalofhighdiscoloration proprietary and closely guarded Ash. Power can be obtainer, iro.n various 0/ass 41 wastes(cottonseed and sunflower-netic pulley, It is usually recycled tobe used as food for ruminants and fer- seed hulls, corn husks, straw, sawdust, the foundry, while tramp iron is soldtilizer for plants." and lignite) by dehydration with sul- as scrap, Vibrating screens are fre- CHLORINATION furic acid." Pear, apple, potato, beet, quently employed for the recovery of whey,andotherfood-processing molding sand from metal-sand mix- Chlorination of ttie terpene frac- wastes have been dried and used fortures. The cleaned sand is reused ontion of orange oil from orange peel stock feed.", al". '6' The high water con- the foundry molding floor, while theproduces a material useful as an in tent has restricted the use of food-separated metallic pieces and core processing wastes for many uses. Im- butts are subsequently treated for theDISTILLATION proved dehydration techniques are recovery of the various metals they Products of the distillation of apri- needed. Industries most likely to becontain. Metals and alloys are oftencot kernels are benzaidehyde, benzoic customers for dehydrated food wastes recovered from these and the non-acid, and hYdrogen cyanide. The resi- that can be transported at low costmetallic waste materials by means ofdue is fed to animals.'" are the animal feed, chemical, and screens, shaking tables, ball mills, Jaw fertilizer industries!". * crushers, and magnetic pulleys. The EXTRACTION metal concentrate produced from the Various by-products such as pectin, DISTILLATION beneflciation of these wastes is eitherseed oils, limonene. peel oils, glyco- Furfural has been obtained from recycled to the foundry for melting orsides and vitamin P (citrin) are ex- various food processing residues byshipped to a secondary smelter. tracted from citrus wastes.'" 1* Pectin distillation with hydrochloric acid. The recovery of clean foundry sandand melte acid are extracted from ap- Methods of improving the yield havefrom waste-containing, burned clay,ple wastes. A plasticizer has been been described." carbonaceousmaterial, andsilicamade from the refuse from production flour by means of magnetic separa-of Chinese citron." HYDROLYSIS tion, screening, end air classification GELLING The cellulose in plant residues ishas been described by Zimnawoda." A process for producing dried pulp readily saccharifled and fermented.After the waste molding sand has beenfor cattle feed from peelings, cores, Sugars obtained in this manner haveprepared by magnetic separation andand trimmings wasted in canning of been used as feed to fermentation screening, it is pneumatically scrubbed pears involves treatment of the waste plants producing ethanol, methanol,against the cone-shaped target ofto form a calcium pectate gel. The acetone, butanol, and fusel oil, as well a dry pneumatic scrubber. Coatings ofsediment fromthistreatmentis as protein, and yeast for cattle feed.dehydrated clay and burned carbonpressed and dried and sold as cattle The residue is a reasonably pure lig- are removed from the sand grains by feed. " . nosulfonhe acidsolution. However, attrition and separated from them by starch has generally been a cheapermeans of air entrainment and subse- HYDROLYSIS raw material for glucose than cellu- quent dust collection. Pectin is produced by hydrolysis of lose. The application of this same dry dried peel of citrus fruits" The prod- pneumatic scrubber to the reclama- ucts of hydrolyzing the protein in ap- OXIDATION tion of foundry sand at the Superior ple seeds have been described." Grape The Zimmerman process, which in-Foundry, Incorporated, of Cleveland,wastes can be hydrolyzed to recover volves wet oxidation of wastes underOhio, has been described bysugars and other chemicals." pressure with partial recovery of fuelBarczak." PYROLYSIS value, is applicable to some food- Puryear and Wile have mentioned Processing wastes." the use of magnetic separation and Peach pita are charred and made screening in their description of ainto charcoal briquets."' FOUNDRY WASTES thermal process employed by theFURNITURE Foundry wastes have often beenLynchburgFoundry Companyof See: Sanitary Landfill and Open treated for the recovery of materials Lynchburg, Virginia, for the recoveryDumping; References 35, 530, 555. that can be recycled to the foundryof molding sand from waste con- operation. Foundry sand, metals, andtaining a resin binder and a carbonGERMANIUM alloys have commonly been recovered residue." An automated process for reclaim- from various types of foundry wastes Herrmann has described the appli-ing high-grade germanium from scrap by means of magnetic separation,cation of magnetic separation andhas beendescribed.'" Germanium screening, gravity separation, and air screening to the preparation of a simi-chloride has been Isolated by hydroly- classification. Recovered metals and lar waste prior to the reclamation ofsis from wastes from the manufacture alloys not recycled within the foundry sand by another thermal process em- of diodes and transistors." can be sold as scrap. ployed at the Dearborn, Michigan, See also: Lead; Nonferrous Scrap; St. John has described the generalspecialty foundry of the Ford MotorZinc. application of magnetic separation, Company." screening, and gravity separation to See also: Inorganic Residues; Sep-GLASS the recovery of brass, foundry mould- aration; Recovery and Utiliza- The Bassichis Company in Cleve- ing sand, and metals from those tion; Slag; Specific metals. land has since 1900 been processing wastes commonly generated in brassFRUIT WASTES and marketing powdered glass in var- foundries. 'Thesewastesinclude ious mesh sizes and types and is the brass turnings, wet foundry sand, and See also: Food-Processing Wastes;largest in its field. Conventional proc- Metal-bearing nonmetallic material References 58, 437. essing machinery, adapted to this par- such as skimmings, skulls, slags, ashes, AMMONIATION ticular materiel/ and need has been and refractories. Brass is usually re- Dried, limed citrus pulp when am-used. Sources of scrap glass for proc- covered with a centrifuge and a mag-moniated and treated with acid canessing have been altered drastically by 12 SOLID WASTE PROCESSING many factors including two major In the mining and mineral indus-to produce pure lead and pure anti- trends, one technologic, the other eco- tries, recovery of materials Is rarelymony as separate products. In either nomic: (a) the trend from bottles to feasible. case, the antimony as well as the lead cans and paper cartons, (b) the elim- All pyrometallurgical processes is returned to industry. This is im- ination by higher labor costs of theproduce slags. Blast-furnace slag isportant because both the antimony praetice of salvaging broken glassproduced In greatest quantity. Theand the lead content generally are from general refuse. As a result, someamount of slag is about equal to thepaid for in purchasing scrap battery industries that could use cracked bot- amount of pig iron produced. All stags lead. tles as a raw material have had tocontain a certain proportion of the turn to other materials because themetal produced or refined, but re- CHEMICAL RED al cmaN supply of scrap bottles Is too small and covery is not practiced to any extent. Lead waste fromelectrodesof undependable. Thus, an economicThere are several mechanical uses forstorage batteries containing lead sul- method for segregating scrap bottlesslags. They are used as aggregates,fide has been molded with carbide from municipal refuse would find arail ballast, housing-project founda-sludge and water and chemically ready market. Dark glasses have been tions, and gravel for roadmaking and red uced." manufactured from industrial polish-railway building, and In practically MELTING ing waste and construction glass."' all circumstances where gravel or Lead has also been reclaimed from See also: Recovery and Utilization; crushed stone could be used. A serious various solid wastes by melting.'". "' Reference 148. drawback to many slags is their tend- REVERBERATORY FURNACES EXTRACTION ency to dust or disintegrate during the course of time. Chemical uses of Lead is recovered from a variety of Rare-earth elements in wastes from slags, include their use as cement,. fer- materials. by. use of. reverberatory grinding optical glasses can be almosttilizer, and slag wool. furnaces. Battery plates, which con- completelyextractedbycomplex Three kinds of sludge are produced stitute the largest source of scrap lead, chemical procedures for experimentalin the steel industry: flue dust, millusually are smelted in blast furnaces use." scale, and neutralized pickle liquor.to produce antimonial lead. That MELTING About 1 billion gallons of pickle liquor Product may be made into soft lead Most glass manufacturers remeltare generated in the United States (free from antimony) in a reverbera- for reuse the scrap glass resultingeach year. This amount of Weide liq-tory furnace or in a kettle. Battery from their own processes if the scrap uor contains 250,000 tons of iron. Theplates also are melted In a reverbera- has not become contaminated withtotal amount of solids in spent, neu-tory furnaces directlyto produce other materials along the way. tralized,pickleliquor amountsto antimonial lead. A variety of lead al- about 2 million tons each year. Theloys from scrap pipe, coffins, bear- GLASS WOOL neutralized slurry remains plastic forings, and roofing also are melted in See: Sanitary Landfill and Openan almost infinite time. Pickle liquorkettles or reverberatory furnaces. The Dumping; Reference 439. can be processed for recovery of ironlead from most of its scrap materials and iron compounds and acid. Thesecan be refined to products equal to GYPSUM processes are becoming more wide- the refined lead from primary smelt- See also: References 189, 190, 209, spread as time goes on. The neutral-ers. In fact. the refining steps, soften- 356. ized sludge can be used as a construc-ing (removing antimony), decopper- CRYSTALLIZATION tion material. Flue-dust sludgeis izing, dezincing, and debismuthizing When powderedwastegypsum generally filtered, sintered, and re-may be the same in secondary plants from the pottery industry is heatedturned to the blast furnace. Theas in printery smelters. withaluminumsulfatesolution,average furnace produces about 1,000 Reverberatory furnaces also are large crystals of gypsum are obtained.tons of dust a day. The scale re- employedtosmeltvariouslead The properties of the calcined crystalsmoved in rolling mills is deposited indrosses,especiallythose obtained have been given." a scale pit and is usually charged tofrom the refining of scrap lead in kettles. And reverberatory furnaces in DEHYDRATION the furnace. It amounts to about 60 tons per day for a rolling operation, turn produce slags and drosses that Gypsum plaster has been manufac- are smelted best in blast furnaces. A tured from waste-gypsum molds byIRON rather complex relationship exists be- autoclaving. See: Copper; Foundry Wastes; In- tween the melting, smelting, and re- HEMP organic Residues, Pickle Liquor; fining of the many types of lead scrap See: Reference 14. Pyrite Cinders and Tailings. and the equipement used for the operations. HYDROGEN FLUORIDE LEAD See also: Tetraethyllead; Waste Re- Slag from the manufacture of hy- LEATHER FABRICATING AND drogen fluoride has been washed, covery and Utilization. TANNERY WASTES elutriated, crushed, and stirred with Lead scrap can be made into the Leather wastes have been processed sulfates or chlorides to form purevarious grades of pure lead or into tomanufactureglue,carburizing crystals of calcium sulfate." lead alloys by secondary smelters. This agents, and fertilizer. Tannery wastes is possible because the usual impuri-have been used to produce feed. Fer- INORGANIC RESIDUES ties in lead scrap can be removed tilizers have been produce from waste See also: Ash, Cinders, Flue Dust,readily. Hence, lead battery platesleather." Fly Ash; Foundry Wastes; Picklemay be smelted to produce antlmoni- LiqUor; Slag; Specific inorganiccal lead for the manufacture of new DISSOLUTION residues; Reference 403. batteries, or the lead may be refined Constituents of glue have been re- Nylon 43 Covered from leather wastes by vari- MOLYBDENUM arately. This makes careful sorting ous dissolution processes."' I'. " See: Reference 145. advantageous. Various operations, In- cluding sorting, drying, degreasing, in- HYDROLYSIS MUNICIPAL WASTES Collagen-containing wastes of the cinerating, and baling, are used in the leather industry have been treated by Only one chemical method, incin- preparation of scrap metals for smelt- hydrolysis to produce an artificialeration, has been practiced for theing and refining. leather" Albuminold hYdrelYzetea disposal of municipal wastes. It em- The actual production of market- prepared from leather wastes can beploys oxidation of the waste withable metals from scrap materials in- used in cosmetic preparations." Pro- free air at elevated temperatures. A volves. five major processes: melting, tein-containing skin, bones, and other variant of this process, so- called "wetmelting and refining, smelting and re- tannery refuse can be hydrolyzed tooxidation," has been practiced to afining, distillation, and hydrometal- produce a food product. limited extent in recent years, with/logical processes. at least one application to sewage Ample facilities and processes exist PRECIPITATION sludge." In the process,, the sludge is for producing useful metals from Chromates can be recovered fromoxidized to destruction by pumping a metallic scrap. This makes it possible tanning wastes by precipitation'" water suspension of it and air into for small amounts of scrap from scat- a pressure vessel; both are maintained PYROLYSIS tered sources to be brought to straW- for some time at elevated pressure gically located centers. The scrap can Waste leather or wool can be auto-and temperature. be processed economically at those claved and the residue used as fer- See also: Incineration; Referencecenters because the volume of ma- tilizer." Leather trimmings can be 183. terial can be sufficiently large for the converted into a carburizing agent by purpose, heating in a muffle furnace and then NONFERROUS SCRAP mixing with calcium carbonate.' See also: Recovery and Utilization; Precious metals are recovered from Foundry Wastes; Inorganic Resi- LEAVES a great variety of industrial waste dues;Precious Metals;PYrite materials. Examples of annual recov- Cinders and Tailings; See: Sanitary Landfill and Openeries of nonferrous metals during 1984 Specifics Dumping; Reference 91. nonferrousmetals;Reference areover one-half million tons of 148. aluminum, slightly more than one LIME NUTS Waste from lime works has beenmillion tons of copper, and 120,000 mixed with coal wastes, formed intoounces of platinum-group metals. The Extraction of cashew-kernel rejec- shapes, combined with solid fuel, and less common metals, such as germa-tions gives a bland yellow oil. The burned to a clinker." Various lime nium, zirconium, and yttrium are alsoresidue can be used in the manufac- wastes are used in the liming of pod- reclaimed from scrap metals. ture of chocolate or as feed." zolic soils." Some time sludge is also The term "secondary", when used Destructive distillation of the hulls dried for in connection with metals, does notof groundnuts yields gas, acetic acid, andused acid-waste refer to quality. It refers to metalsmethanol, and charcoal."' neu tra tion produced from scrap or waste ma- Seealso:StoneSPails:Sugar Seealso:AgriculturalWastes; Beets; References 57, 234. terials to distinguish them from "pri- Food-ProcessingWastes;Ref- mary" metals, which are produced erence 463. MAGNESIUM from ores and et.ncentrates of ores. NYLON Hydrochloric acid has been used toTwo other designations are used in leach iron and aluminum from thethe secondary-metal industry; name- Nylon fibers can be recovered from solid wastes from magnesium pro- ly, "new scrap" and "old scrap ". The waste nylon by destroying the non- duction'" scrap generated as turnings, punch- nylon portion of the waste with See also: Aluminum. tugs, trimmings, damaged parts, andacid." Waste nylon has good ion-ex- the like, by fabricators of machinery change properties." Chemical treat- MANGANESE and equipment is called new scrap.ment of Nylon-6 waste has been re- Metallic manganese has been ob-Metals salvaged from obsolete ma- viewedbyDibaandVarseek." tained by electrolysis of a solution of chinery, buildings, or ships is termedNylon-6 wastes have been depolymer- manganese obtained by extracting aold scrap. ized to 6- caprolactani by alkaline de- mixture of manganese containing Most manufacturers prefer to sendpolymerization at elevated tempera- slags and pyrolusite. their scrap metals to plants estab- turesor by hydrolysis." Nylon-8 lished for the processing of such ma- waste can be dissolved under pressure MICA terials. Consequently, the source ofin alcohol, particularly ethyl alcohol; Mica has been recovered in sheets much of the secondary metals is man- the polymer will precipitate in the after chemical processing of wastes ufacturing plants. The other sourcesform of fine particles when the solu- from mica mines. are the scrap metals brought to dealers by collectors from small shops,tion Is cooled." It can be dried and MINERAL WOOL municipal refuse, obsolete machinery, reused. Polyamide (nylon) wastes can See: References 105, 346. and dismantled buildings, be dissolved and repreelpitated; the A great deal of sorting and proc-Precipitate can be rewied to produce MOLASSES essing of scrap materials may be re-nylon."' " Waste nylon -6 can be Potassium salts have been recov-quired preparatory to the productiontreated with an alkaline solution to ered by incineration of wastes fromof marketable metals. The smeltingprecipitate impurities. After the rub- molasses." and refining of metals Is much sim- bery precipitate Is filtered off, capro- See also: Brewing, Distilling, Fer-pler and less expensive if relativelylaetarn can be isolated front the so- menting Wastes. Pure types of metals are treated sep-lution." 44 SOLID WASTE PROCESSING Seealso: AgriculturalWastes; emulsions from the chemical treat- CRYSTALLIZATION Plastic; References 304, 307, 371, ment of oil. Petroleum residues are Waste pickle liquor has been regen- 414. usually disposed of by incineration after removal of most of the oil anderated using high-acid (18%) baths. ORGANIC WASTES water from these residues. The spent bath is evaporated, seeded, Manyorganicindustrialwaste and acidified and the ferrous sulfate sludges can be burned with little or removed by crystallization. The acid CARBONIZATION supernatant can be reused!" no auxiliary fuel after they have been Activated carbon has been produced partially dewatered by filtration, cen- DISPLACEMENT trifugation, or screening. By use ofby burningthe sludges from oil multiple hearth incinceration (where refineries." In the Ruthner process, sulfuric heat economy is relatively high) even acid and iron oxide are recovered liquid sludges can be burned. An ap- DISTILLATION from spent pickling liquor by convert- paratus for purifying industrial efflu- Distillation of petroleum residuesing ferrous sulfate to ferrous chloride ents and utilizing organic matter foryields a material that is a plasticizerand sulfuric acid by reacting it with fuelIsdescribed."Carbonaceous and agglutinant." hydrochloric acid. The ferrous chlo- waste materials can be destructively ride precipitate is roasted to reclaim distilled in a retort. Condensible ma- INCINERATION hydrochloric acid, and the ferrous terials are removed from the vapor, Petroleum sludges are usually dis-oxide is returned to the blast fur- and the remainder is returned to the posed of by incineration after as muchnace. A demonstration recovery plant retort. The solid can be used forof the oil is recovered as possible.based on this process was operated at charcoal!" The simultaneous carboni-These sludges may be viscous liquidsthe Niles, Ohio, plant of Republic zation and sulfonation of organicor semisolids containing water, freeSteel Corporation. Seven major steel wastes produces a granular carbonacid or alkali, and other chemicals.companies shared the cost of the Possessing ion-exchange properties."' The calorific value on a dry basis is $400,000 program.". See also: Agricultural Wastes; Ani- 10,000 to 15,000 Btu per pound. Effi- ELECTROLYSIS AND ELECTRO- mal-ProductResidues;Food- cient heat recovery is not possible DIALYSIS Processing Wastes; Fruit Wastes; withoutcarefullydesignedequip- Vegetable Wastes; Specific or- ment.'" Thermal disposal methods are Iron and sulfuric acid can be re- ganicwastes;References395, recommended for disposal of sludgecovered from pickle liquor by electrol- 396. from leaded-gasoline tanks." ysis'"''' Iron is depOsited on the The coke residue from petroleum cathode and sulfuric acid is recovered PAINT refining has generally been burnedin the anode solution by electrodial- The solid material demanding ulti- with coal for heat recovery, but it canysis of spent pickling solutions. The mate disposal by paint users is thebe burned alone in a specially de-capital cost of a plant treating 1,720 Paint-waste sludgeremoved fromsigned furnace. The sulfur contentgallons per hour of pickle liquor (10 holding pits in spray booths. This may introduce corrosion or sulfur di-TPD iron) was reported as about $2.5 waste is in the form of a sticky massoxide problems. The high vanadiummillion. Operating cost was reported with the consistency of modelling content of the ash can also cause cor- as $3,070 per day, and credits came clay. rosion." The economics of using thisto $1,593 per day!" coke as fuel have been reported." INCINERATION The oily sludges from treatment ofEVAPORATION Paint sludge has been burned in pit waste emulsions have been incinerated Ferrous sulfate can be recovered incinerators." 3C4 Air pollution from by flame incinerators and fluidized-from pickle liquor by evaporation!" .here installations may be a problem bed techniques" Sodium sulfate can also be recovered If the solids content of the sludge is by evaporation." high. PHOTOGRAPHIC PAPER EXTRACTION POLYMERIZATION Silver and gelatin-free paper can berecoveredwhenphotographic Iron in spent pickle liquor can be A method which has been consid-paper wastes are treated with cal-complexed and extracted. The iron is ered for disposal of paint waste iscium oxide and alum in a beater."recovered by adding lime to the ex- Polymerization by heating to a tem-Silver can also be recovered fromtract. Acid can also be reclaimed in perature and for a time equivalent tophotographic wastes by burning thethe process." practice in curing paint." wastes under controlled conditions NEUTRALIZATION PAPER and recovering the silver from the ash by smelting.", "I." Metallurgicalsludgecontaining See: Photographic Paper; Pulp and See also: Chemical Wastes; Plastic; calcium oxide and magnesium oxide Paper; Wastepaper. References 293, 362. can be used to neutralize spent pickle PETROLEUM RESIDUES liquor." Petroleum residues include tankPICKLE LIQUOR SCRUBBING bottom sludges from storage tanks See also: Inorganic Residues. Iron oxide and ammonium sulfate and cracking,Polymerization, and are produced when coke-oven gas is similar processes; coke from equip- CALCINATION scrubbed with spent pickle liquor."' ment tubes and towers; oil emulsions The ferrous sulfate by-product of and oily waste waters from cracking pickle-liquorregenerative processesPLASTIC and distillation and similar processes; can be roasted to produce sulfur diox- Many waste plastics can be proc- and acid sludges, caustic sludges, andide suitable for sulfuric acid'" essed for reuse. Most thermosetting Preciouit metals45 plastics, however, defeat attempts atfrom waste nylon-6, including6- described by Tobola." Polyamide large-scale utilization and are notcaprolactam: sulfuric acid, hydro- wastes have been mixed with mono- even suitable as fuel because the de-chloric acid, formic acid, calciummers and autoclaved to produce a composition(ignition)temperaturechloride and methyl alcohol, watercopolymer."' is high and the flame is not self-under pressure, and alcohols under sustaining. One or two varieties havePressure. After extraction, the poly- PYROLYSIS been used as fertilizer and some, when mer is recovered by precipitation.' Synthetic resins can be cracked in ground line:may be useful as filters.Extraction of organic components tovacua by direct contact with melted Preliminary experiments have beenregenerate asbestos from plastic prod- metals." made to obtain usable materials fromucts was not successful.'" bakelite scrap by means of acetyla- POPPY tion, methylatlon, halogenation, sul- HYDROLYSIS Morpnine is extracted from poppy teflon, or nitration.'" Polyethylene terephtha:ate wastewastes!" See also: Recovery and Utilization;has been subjected to complete alka- Agricultural Wastes; Nylon; Ref- line destruction, aqueous hydrolysis,POTTERY WASTES erences 148, 331. andmethanolysisbeforereuse.' See: Gypsum. Waste nylon has been hydrolyzed to ALCOHOLYSIS recover raw materials.'01 "7 Polyester PRECIOUS METALS Lacquer resins can be preparedurethane can be treated by hydrolysis Scrap that contains precious metals from the waste products of poly-with steam and the recovered mate-may be worth processing. A checklist ethylene terephthalate by their alco-rial blended with new material."of precious-metal scrap has been pre- holysis with glycerol." Cellulose filmCellulose acetate wastes or cellulosesented by Perry.'" wastes can be treated by transesteri-2,5-diacetate obtained by hydrolysis Gold, silver, and the platinum- fication. The products can be usedof photographic film can be treatedgroup metals have been reclaimed in the preparation of thermoplastic with epoxy resins, the resultant mix-from a great variety of industrial materials. turebeingcrushed,ground, and wastematerials.Combinations of granulated before reuse."' Recovery CONDENSATION melting and chemical treatments have of the polymer in waste Nylon -8 can been applied to separate and to refine Waste polyethylene glycol has beenba accomplished by hydrolysis." Syn- the metals. Dissolution and precipi- heated with ethylene glycol and thethetic, resins that contaminate waste - tation have been practiced to separate mixture polycondensed. The product papers can be removed by the previous metals from base metals can be molded." Spinnable polyethyl- hydrolysis."' or from catalyst carriers and to con- ene terephthalate can be obtained centrate the precious metals into from fiber waste by a condensation INCINERATION small bulk. The great value of the process."' For a very large number of chemi- metals permits the use of very cor- cal and plastic wastes the degree of rosive reagents because small units of DISSOLUTION burnability, decomposability, corro-expensive equipment can be em- Cellulose-ester film scrap has been siveness, and hazard is unknown."ployed. Glass-lined vessels, glass pipe treated with caustic and ferrous sul-The liquid residue from burning scraplines, and glandless pumps have been fate,dissolvedin dichloromethanepolyurethane can be returned to theused extensively. Earthenware, rub- and methanol, and centrifuged tonormal foaming process without de-ber-lined steel, and stainless steel produce a clear solution that can becreasing the quality of the final prod- have also been used for digestors, reused." Waste synthetic polymersuct,'" Rigidpolyurethane-foamfilter presses, and cementation vessels. which have been recovered by dissolu- particles have been heated to giveSome typical methods are decribed tion processes include acrylic, vinyl,rigid products useful in place of woodbriefly in the following paragraph. and polyester resins!' Panels and tile.° Polyesters have been Nitric acid or sulfuric acid can be recovered from scrap polyurethane byused to "part", that is, to selectively DISTILLATION burning in air." The pit incineratordissolve, silver from gold in alloys that Polymethacrylic resin waste prod-has been used to incinerate nylonare preponderantly silver. The silver ucts can be chemically treated and wastes" Excess activated sludge fromcan be recovered from solution by distilledto recover methyl meth-treatment of nylon-plant wastes hascementation with copper. Finally, the acryl ate." been mixed with equal parts of com-separated gold and silver can be re- bustible waste and incinerated.!' As-fined by electrolysis or other means EXTRACTION bestos in waste plastics has been re- and cast into bars for delivery. Polyurethane scrap can be ex-generated by burning away the or- In the treatment of the platinum tracted with an alkaline solvent toganic matter."' group of metals, solutions containing remove a portion of the waste Poly- the major portion of the gold, plati- urethane, which, after chemical proc- MELTING num, and palladium as chlorides can essing, can be reused." Several waste Polyethylene terephthalate in waste be prepared by digestion with aqua synthetic polymers can be dissolvedfibers has been melted, and the meltregia. This treatment leaves a residue without apparent chemical changecondensed and extracted to recoverof the less soluble metals, iridium, and than reused after the solvent andwinnable polyethyleneterephthal- rhodium, ruthenium, and osmium. impurities are distilled oft". 44 Capro-ate." Polymer of nylon-8 waste has Gold can be recovered from the solu- lactam can be recovered from super-recovered by melting."' tion by reduction with ferrous chloride PolyaMide wastes by heating, dissolv- and filtration. Atnmonium chloride ing, treating with activated carbon, POLYMERIZATION can be added to the filtrate to precipi- and filtering." Several solvents can Methodsforprocessingplastic tate ammonium chloroplatinate. The be used in the recovery of polymer wastes for repolyrnerlzaUon have beenPrecipitate can be filtered and calcined 46 SOLID WASTE PROCESSING to produce platinum sponge. Palla-the United States have concentrated DISSOLUTION dium can be precipitated as dichloro-sulfite waste liquor to 50 percent sol- Wastepaper ingredients (e.g ink) diamminepalladium;Da Ila diu rn ids and sold it ,ts such or as a powder are dissolved by cooking the paper in sponge can be obtained by calcinationproduced by spray drying. The prod- a mixture of chemicals, principally of the filtered precipitate. uct modified for particular applica- caustic soda; the fiber residue is suit- The original residue of iridium,tions can be sold as a binder or aable for reuse."' rhodium,ruthenium, and osmiumdispersing agent. A small amount has can be fused with alkaline and oxi-been sold in the form of metal com- DISTILLATION dizing fluxes. The fused mass can beplexes for agricultural applications. Tall oil from black liquor can be dissolved in water and distilled to Chemicals have beenrecovered redistilled and sold as such or sent separate ruthenium and osmium asfrom the sludges at some plants. The to a fractionation operation where volatile oxides. These metals can beOntario Paper Company has proc- rosin and fatty acids are recovered." Precipitated as complex salts in theessed sludge for recovery of 4,800Methanol is recovered try distillation manner described for platinum andpounds per day of vanillin, 2,400of evaporated black-liquer solids fol- the precipitates calcined to metallicpounds per day of calcium oxalate,lowing treatment with barium hy- sponges. The residue from the distil- 2,400 pound.s per day of lignin, anddroxide."' Pine oil is separated from lation would contain iridium and rho- 120,000 pounds per day of sodium sul- sulfate turpentine by fractional dis- dium. It can be treated to precipitatefate. tillation. Between 0.2 and 2 gallona complex ammonium compounds sepa- See also: Recovery and Utilization;of pine oil are produced per ton Of rately, and those precipitates can Wastepaper; References 68, 148. pulp. The turpentine is recovered by also be calcined to yield metallic decantation from the condensed re- sponges of the iridium and rhodium. CALCINATION lief gases from kraft digestion at the The separate sponge metals can be A fluidized-bed reactor can be usedrate of 1 to 6 gal/ton of pulp,'" Tur- converted to solid ingots or other suit- to calcine lime mud from recaustizingpentine and rosin are distilled from able shapes by melting and castingoperations at paper mills. The limepine gum and stumps. or by sintering, forging, and rolling, can be reused. The reactor capacity See also: Recovery and Utilization;of a mill using this process was re- ELECTROLYSIS AND ELECT! 0- Ash, Cinders, Flue Dust, Ash Fly; portedas45'TPD.'". ""Calcined DIALYSIS Electroplating Residues; Nonfer- deinking mill sludge can be used for Spent sulfite liquor is being treated rous Scrap; Photographic Paper; filler and in the manufacture of build-on a pilot-plant scale by electrodialy- Specific metals; References 389, ing materials!' sis to recover pulping liquor, produce 391. COMBINATION AND ADDITION lignosulfonicacids,andseparate lower molecular-weight organics. The PULP AND PAPER Dimethyl sulfide can be producedplant is being operated by the Sulfite The solid wastes generated by pulpfrom graft liquor. The process consistsPulp Manufacturers' Research League and paper mills are mostly in the formof adding sulfur to the liquor, heat- in Appleton, Wisconsin.'" of sludges. The amount of solids dis- ing, and flashing off crude &methyl By electrolyzing fibrous waste sus- charged from a mill varies from aboutsulfide, which is then condensed andpended in a sodium chloride solution, 20 to 160 pounds of solids per ton of purified by extraction and distillation.the fibrous material is simultaneously paper produced. About 70 million tons About 60 pounds of dimethyl sulfidedigested and bleached.' of pulp are produced in the world per have been produced per ton of kraft year. Waste solids from this industrypulp. A smaller amount of methyl EVAPORATION amount to something like 3.5 million mercaptan can be produced and iso- Lignosulfonates are produced by tons per year. The solids content oflated. Several plants have been in op- evaporation of sulfite liquors to 50 per- the sludges may be as low as 0.75 per- eration.One produced5millioncent solids in a seif-descaling evapo- cent or as high as 10 percent. Thepounds per year of dimethyl sul-rator. It is an advantage to convert sludges from pulp-mill effluents are w". E." Pressure heating kraft li- the calcium lignosulfonates to the composed primarily of cellulose andquor with additional sodium sulfidesoluble sodium form by ion exchange inert filler materials. They also canand sodium hydroxide yields ether-prior to evaporation'" contain starch, rosin, casein, inks, andsoluble degradation' products (up to other organics together withgrit. 50 percent or more of the organic sub- EXTRACTION wood, wire, rags, and other miscel- stances) plus methyl sulfide, acetic Acetic and formic acids have been laneous trash. The sludge from aand formic acids, and a reactive de- recovered from the waste liquors white-water recovery system is almostmethylated lignin (yielding pyrocate-from neutralsulfitesemichemical entirely cellulose fibers. chol and its homologues, usable inpulping by an extraction process. Final disposal of sludge has usuallyplastics of the bakelite type) .'The a* 'Is Tannins have been extracted been on the land. It has generally beencellulose In paper wastes reacts withfrom the bark of trees including the two principal pulp trees in the Pacific disposed of in the liquid state, butmethanolic hydrogen chloride to pro-Northwest, Douglas fir and western more and more plants are using someduce methyl gluceside, which can behemlock. In addition, hemlock bark form of dewatering equipment so itused to make polyethers for urethanehas been extracted for phenolic acids. can be handled in the semisolid form.foam. Starch can be used as a rawArabogatactan has been extracted Sludge-burning methods such as thematerial for polyethers!" from western larch by the lumber di- Zimmerman and Atomized Suspen- DEWATERINC vision of one of the large paper corn- sion techniques have seemed to be nanies. Several other complex wood promising methods for further de- The problems of dewatering paper- extractives can be produced from creasing the sludge volume, millsludges have been described.wastes. The possible isolation of wax A number of paper companies in 112, 96t, e4 from Douglas fir bark has been in- Pyrolysis47 vestigated. Methods have been foundcombustion has been presented in recently proposed approach has been forextracting xylose from hard-graph form by Blesser," theuseof atomized-suspension woods.'" The sludge precipitated by The Zimmerman process, which em-radiant pyrolysis for the incineration treating an alcohol plant effluent with ploys the principle of wet combus-of sulfite liquors. The capital invest- lime has been leached with soda ash.tion, has been used for combustion ofment for evaporation and incinera- The calcium carbonate residue haspaperbillsludges andliquiddis- tion for a 250-TPD plant has been been reused in the process. Vanillin, posal." ". 6°, "1 Wet-combustion eco- reported as $5.2 million and rate of re- lignin, calcium, oxalate, and sodiumnomics are almost independent of the turn as 16 percent." Sulfur ha; been sulfate have been recovered from thedry-solids content of the waste. This recovered from the gas during com- leaching solution. The raw materialprocess is installed at the A/S Bore- bustion and reused."°. us A fluidoed- for an alcohol plant was the effluentgaard mill at Sarpborg, Norway. In- bed system has been used to recover from the pulp mill." stallation costs for a unit to burn 200chemicals, such as sodium sulfite and Asphalt-coated paper, when treatedtons per day of dry solids have beensoda ash, In the Container-Copeland withcertainsolvents,hasbeenreportedto be inexcess of$11 process" claimed upon solvent evaporation to contain the asphalt in microscopic The atomized - suspension technique ION EXCHANGE particulate form, permitting its use aswas developed by the Pulp and Paper The Pritchard-Praxon and Abiperm an ingredient in pulping operations." Research Institute of Canada forprocesses are examples of ion-ex- Bitumen-containing wastepapers canburning sludges. In this process, afterchange recovery systems for sodium-, be utilized in the papermaking proc-some heating and thickening by ex-magnesium-, calcium-, or ammon- ess after extraction with acid."' haust gases, sludge is injected throughium-based liquors." The capital in- The ash from the incineration ofnozzles or other atomizing devicesvestments for ion-exchange systems spent cooking liquor from the kraftinto a heated chamber, where it isfor 100-200-, and 300-TPD plants process can be leached and the ex-burned at atmospheric pressure.".". havebeenreportedas$767,000, tract causticized to recover COWLES Al Ilk 661 $1,163,000, and $1,511,000,respect- and sulfide chemicals used in the Burned sludges have been used asively. Rates of return have been re- process."' filter material for rubber and asphaltported at 9.0, 12.4, 14.7, in the same tile." Pelletized sludge subjected toorder."' HYDROGENATION high temperatures has been used as a Phenolic materials can be produced lightweight concrete. It might also be OXIDATION by hydrogenation of lignin in paper-usedtomanufacturelightweight Meso-tartaric acid can be obtained mill wastes." Sugars in sulfite-wastebrick." A mixture of sugar-factoryby oxidizing cellulose with nitrogen liquors can be hydrogenated to alco-muds, papermill sludge, and clay yields tetroxide and then hydrolyzing with hols. Tharp has, however, been no eco- portland cement when It is burned."'hydrochloric Materials con- nomical means ofseparatingthe Experimental incineration of paper-taining lignosulfonic acid can be oxi- sugars from the other waste solids." mill sludges has been described.". dized in alkaline medium to obtain HYDROLYSIS Black liquor from sulfate pulpingvanillin, acetovanillin, lignin, and cal- has nearly always been evaporatedcium oxalate.'" Many attempts have been made to and incinerated. The liquor is brought profitably utilize the vast quantitiesto 50 percent solids in multiple-ef- PRECIPITATION of waste lignin from pulping proc-fect evaporators and is further evap- In the Howard process, various por- esses and wood hydrolysis. Recovered orated to 65 percent solids in direct-tions of the sulfite pulp wastes are lignin can be used in the preparation contact evaporators. This is then fedseparated by fractional precipitation. of synthetic resins." The character-to the recovery furnace where the One portion Is burned to provide heat, 'sties of lignin have been described. organics decompose, carbon is burnedand the residue is processed to re- ". "." The sugars produced by hy-away, and the inorganics melt andcover chemicals. Other fractions con- drolysis in the sulfite-pulping process are reduced. Caustic soda, sodium sul- tain materials useful as raw materials are converted to alcohol and yeast'" fide, and soda ash are recovered fromfor the manufacture of plastics and A kraft mill with a capacity of more the smelt."' Lignin can be recovered than 1,400 TPD uses shavings and Acid calcium sulfiteliquorhasfrom kraft liquor by precipitation of sawdust to produce pulp."' often been evaporated and inciner- the lignin with acid. The lignin so ob- ated as an antipollution measure.tained can be processed into useful INCINERATION Steam is produced as a by -product. chemicals. " The burning of papermill sludgeScaling is a particular problem in (solids obtained from the so-calledthese evaporators. The capital in- PYROLYSIS white water from paper machines) vestment for evaporation and incin- Practically all vanillin has been has been limited in the United States.eration for a 200-TPD plant has been produced by the alkaline pyrolysis of The economics of the process is de-reported to be $1.5 million, with a lignin sulfonic acid from sulfite-waste liquor. The yields are low, between 8.0 pendent on the moisture content andnegative return on investment." and 12.0 percent based on the lignin the Btu content of the sludge. The In the case of magnesium-based sulfonic acid, and an elaborate extrac- Btu content per pound of sludgecooking liquors, the evaporated liq- tion and purification process is re- volatiles is on the order of 8,000.uor Is burned in a recovery furnace.quired to produce a pure product. In The heat needed to volatilize a poundSulfur dioxide is then recovered byNorth America, about 1.6million of water ranges from 1,900 to 3,500wet scrubbing, and magnesium oxidepounds of vanillin are produced per Btu. Data on the degree of dewater-by dry scrubbing, for recycle. Bothyear and sold at about $3.00 per ing required of sludges of various vol- ammonium- and sodium-based liq- pound. Most of the vanillin has been atile contents to support their own uors may be treated in this fashion. A used for flavoring, a small amount be- 48 SOLID WASTE PROCESSING Ingconvertedtootherflavoring weak acideffluent from the gasRICE agents and medicinal derivatives.". "'scrubber. The cracking of lignin gives a Copper is removed from the leach The adsorption properties of car- source of chemical raw material com- liquor by cementation with scrap iron. bonized rice hulls and rice stalks have parable to coal-tar production." Cel-The product is sent to a copper smel- been evaluated."' lulose heated in a vacuum to relatively ter for refining and marketing. If See also: Food-Processing Wastes. high temperatures produces IA -anhy- cadmium, thallium, and indium are droglucose, which can in turn bepresent in the decopperized liquor,RUBBER polymerized. Its trimethyl ether, when they are precipitated by comentatlon See also: Reference 303. treatedwithsodiuminliquid with zinc dust. Cobalt is removed by ammonia, produces phenol in yieldsoxidizing with chlorine and precipita- INCINERATION that have been reported at over 50ting with zinc hydroxide. The filtered Use of a two-combustion-chamber percent." Activated charcoal is pro-precipitateiscalcined to produceincinerator incorporating burners in duced by pyrolysis of black-liquorcobalt oxide for sates. Zinc is precipi- both chambers to Insure complete effluents."' tated as zinc hydroxide by use of lime. combustion reportedly solves the odor The precipitate is thickened, filtered,and smoke problem of Incinerating SMELTING dried, and finally calcined to producerubber wastes." A packaged unit There are several processes for re-material suitable for reduction by thecomplete with afterburner is mar- covering heat and chemicals fromelectrolytic process. keted and used for incineration of sulfite wastes by evaporation followed Iron oxide can be recovered from rubber waste."° by smelting. Among these are the In-pyrite tailing by heating the tailings stitute process, the Mead process, theto 2,000 F. The liquid ferrous sulfide OXIDATION Sivo la process, the Storm Kopparberg can be granulated and roasted to give Ozonization treatment of rubber process, the Western Precipitationiron oxide and sulfur dioxide. Sub- waste with hydrogen peroxide yields (Bradley) process, the Sulfox processlimed lead, zinc, and sulfur vapor can a material useful in polymerization."° and the A. D. Little process. Thebe condensed and separated." Pyrite capital investment for smelting for awastes can be purified by extraction PYROLYSIS 200-pound-per-day plant ranges fromand reused.' Under proper conditions of pyrol- $2.45 million to $3.32 million, depend- See also: Coal Refuse. ysis, waste rubber yields materials ing on the process used.' REFRACTORY that are useful as solvents, plasticizers,andsurface-activeagents. PYRITE CINDERS AND TAIL. The W. E. Piechaty Company ofThermal cracking of waste rubber INGS Cleveland has developed a nearlyyields a mixture of maleio acid and A number of nonferrous metals canautomated process for reclaiming re-oil which is useful as a plasticizer. be recovered from cinder, which is the fractory material from nearby steelPyrolysis of waste rubber yields a residue, essentially iron oxide, from mills. In steel manufacture, refractory fraction that can be used in the pro- burning pyrite for the manufacture oflinings in furnaces and ladles areduction of surface active agents."' sulfuric acid. Cinders, in some circum- eroded by the process so that at leastScrap rubber can be destructively dis- stances, are valuable as sources of iron50 percent of the refractory is lost in tilled leaving an ash residue."' " Dis- for making iron and steel. In manythe slag, When the remaining refrac- tillation of scrap rubber results in a cases, however, cinders contain smalltory is too thin for proper contain-light fraction suitable for a varnish but objectionable amounts of nonfer- ment, the furnace or vessel is shutsolvent and a residue that can be rous metals. Hence cinders can bedown, and the deteriorated refractoryused as a filler." processed to recover nonferrous metals is removed and replaced by the new while beneflciating the iron product.refractory. The discarded material isSAL SKIMMINGS The kinds and amounts of recoverable removed from the mill and is proc- Sal skimming are spent flux re- nonferrous metals in cinder dependessed in the following manner: (1) moved from the surface of galvanizing on the composition of the pyrite thatmagnetic removal of all irons;(2) baths on which fluxes are used. They is burned in forming the product. One screening of all fine particles eitherare a mixture of metallic zinc, zinc author has stated that a mixture ofgood or bad; (3) hand sorting to type oxide, and some of the zinc ammoni- residues from pyrite produced inand quality; and (4) crushing andum chloride of the original flux. Sal European countries contained over 50 screening for a marketable refractory skimmings are the least desirable and elements. Most of those elements wereproduct. hence tne least valuable of the wastes present in such minute amounts that The high costs of automation, the from galvanizing operations. They are recovery was not feasible. industry's label of "salvage or used", poorly suited to the distillation and Copper, cobalt, and zinc have beenand the lack of trained supervision in electrolytic processes for reclaiming recovered from cinders containing less this field have combined to place a zinc becau.Af their chloride content. than 1 or 2 percent of any one of these tremendous limitation on expansionFor that reason, most of the sal skim- elements. The usual procedure is to mings produced in the United States roast the cinder, mixed with about 10of this reclaming system into other(over 25,000 tons annually) are treat- Percent of common salt, at aboutareas. ed chemically. 1,100 P in multiple-hearth furnaces. See also: Foundry Wastes; Refer- One method is to leach the sal The gas from the roasting furnaces is ence 118. skimmings with murlatic acid and to scrubbed with water, and the resultant REFRIGERATORS remove the insolubles, which include liquor is used to leach the calcine heavy metals formed by cementation Produced. The roasting operation ren- See: Sanitary Landfill and Open with the metallic zinc. A liquor con- ders the desired metals soluable in the Dumping; References 35, 530, 555. sisting of about 46 percent zinc chlor- Magnetic separation, screening grinding49 TABLE 12 THE PRODUCTION AND UTILIZATION OF BLASTFURNACR SLAG IN 1657 oil)

sus We Ms;processed trtilisstton (short tons)

Screened 25, 414, 327 92% used as railroadballast,aggregate in air-cooled portland-cementconcreteconstruction,all types of bituminous construction, and miscellaneous highway and airport construction. Unscreened 2, 168, 678 61% used as aggregate in highway and airport air-cooled construction. Granulated 4, 318, 485 43% used as raw material in manufacture of hydraulic cement; 45% used in constructing base and insulating courses for highways and also as road fill; and 12% used in concrete- block manufacture and in agricultural and miscellaneous uses. Expanded 2, 941, 660Bulk used in manufacture of lightweight concrete blocks.

ide and 4 percent ammonium chloride nace slag; its use has been largely ex-In 1939 there were 600,000 tons of is produced. Ammonia is added and perimental in nature. Chemical andblast-furnace slag alone used for this zinc ammonium chloride is crystal- Engineering News stated in 1959 that purpose.' "" *" lized from the resulting solution. That from 18 to 20 million short tons of product is sold for galvanizing flux. open-hearth slag were being produced-INCINERATION annually by the steel industry.'" Of Refractoryceramicshavebeen SAM) this amount, United States Steel alone made by burning slag'" See: References 34, 187, 360, 503.produced 6 million short tons, but processed less than half of it for MAGNETIC SEPARATION, SCREEN- SEAFOOD marketing. ING, GRINDING See: Fish. Most of the blast-furnace slag pro- Open-hearthandblast-furnace duced has been utilized in the manner slags have commonly been prepared SHINGLES indicated in Table 12. It has also been for various markets by magnetic sepa- See: Sanitary Landfill and Open employed: (1) in glass for the manu-ration and screening, Magnetic sep- Dumping. facture of amber bottles; (2) In fiber-aration has usually been employed for glass manufacture; (3) As a condi-the recovery of tramp-iron, scrap and SISAL tioner for oyster beds; and (4) As aprimary ferrous metal. Screening has Waxisextractedfromsisal conditioner for cranberry bogs. often been used to size the slag itself wastes." Open-hearth slag has not beeninto fractions suitable for various uses. utilized as extensively as blast-furnace Trauffer has described the process SLAG slag, but it has been used: (1) As anemployed at one Detroit plant for Large quantities of various types of agricultural liming material and fer-treating 110 tons per hour of blast- slags have been processed and mar- tilizer; (2) as a soil supplement andfurnace slag by means of magnetic keted by industry for a variety of uses. conditioner; (3) as railroad ballast;separation and screening to produce According to Chemical and Engineer- (4) as highway chips; (5) as a sealingeight fractions of sized slag." And ing News in 1959, from 30 to 35 for highway surfaces; (8) as highway Peck has described a similar but million short tons of ferrous blast- fill; (7) as an aggregate for the manu-smaller operation which produces six furnace slag were being producedfacture of bituminous concrete; (8) sizes of screened blast-furnace slag annually by the steel industry foras a sand-blasting grit; and (9) asat a rate that varies from 300 to 350 eventualreuse.'"Pit and Quarry a source of trace elements. tons per hour.'" The sizing of both stated that 35 million tons of blast- The slag produced during the manu- blast-furnace and open-hearth slag at furnace slag valued at $52 millionfacture of elemental phosphorus hasa single plant has been described by were produced in1957.8" Approxi- been utilized: (1) As a mad-base ma-Utley.'" Rock Products briefly men- mately 72 percent of this slag was terial; (2) In septic-tank drain fields; tioned how one plant sized phorphorus processed by methods involving the slag at the rate of 700 tons per day," separation of solid particles. Accord- (3) as a drainage stone in sewer lines; Trauffer 4" has also described the ing to Blast Furnace and Steel Plant, and (4) as a rooting aggregate. production of sized agricultural slag slagprocessorsrecovered409,259 See also: Recovery and Utilization; from basic open-hearth slag by means short tons of iron from blast-furnace Foundry Wastes; Inorganic Resi- of magnetic separation and screening. slag in 1956." In 1981 a British blast- dues; References 184, 403, 550. The Birmingham Slag Division of furnace slag plant was turning out the Vulcan Materials Company at Products for varied uses." CALCINATION Wylam, Alabama, has processed basic Open-hearth slag has not been Slags have been calcined to produceopen-hearth slag produced at Bir- utilized as extensively as blast-fur- cement, three types being produced.mingham and stockpiled at Wylam 50 SOLID WASTE PROCESSING

Basic enhearth sla

15-Tcn :er I

124 x 14' But Grizzly

24* x 40" Syntron Vibrating Feeder

30" x 60' Belt Conveyor

4' x 6' Tyler Single-Deck Iron To Iron 2" Scalping Scteen stockpile

*2"

10' x 40' Good Roads law Crusher With 13/4' Set

24- x 75' Belt Conveyor

Dings Magnetic Iron Head Pulley t Standard Steel Sctew I. Dust Rotary Diyer (6' x 32') Conveyoe

I Link-Belt Bucket Elevator

Rotary Cooler (6' x 40')

Dustractor Dusuacroe Link-Belt Bucket Elevator Multicyclone Multicyclone B Dust Collector Dust Collector 4' Symons Short Head Cone Crusher With SA" Set Air Dust Altt Whirlex Whlrlex ,F717cket Elevator Digs Wet Separator Wet Separator Lon Mug etic Steel Bin Head put ey

20" x 30' Synuon Vibrating Feeder Sludge to Gardner. settling Denver Pond Blower 24" Belt Conveyor

3 Two 10' x 12' Mine & Smelter Marcy 800 -Tot Ball Mill With 3/4' Duch uge Grate Storage Wog 'Rabbit ear" 15% -100 mesh Belt Conveyor

Bucket Elevator I 10' Link -Belt Elevator 4 Allis- Chalmers A erovi be .20- SingleDeck 20meah t-2r40;n - mesh--11" SateenS (5' x 10) stag slag

FIGURE 7, Processing of U.S. Steel Deist open-hearth slag at Wylam, Alabama. Titanium51 by the United States Steel Corpora-two after the spalls are exhausted. See also: Recovery and Utilization; tion. Slag ranging in size up to 12- But the unpredictable availability of Cotton; Reference 333. to 15-inch chunks has been treatedsuch byproducts and the sporadic in this plant at the rate of 60 tonslosses it causes is a serious problem CARBONIZATION per hour by the process illustrated into the prime manufacturer. The con- Thevegetable-fibercontentof Figure 7. Large pieces of slag heldstantthreat of such competitionwoolen rags has been treated with up by the bar grizzly are aledged serves as a depressant on stone prices. gaseous HCI and the carbonized fibers through it to the vibrating feeder. Similarly, a large captive stone pro- are removed, after which the material Each of the Dustractor dust-collect-ducer, typified by the lime, steel,is reused." ing systems employed has a capacity alumina, alkali, and other industries, of 28,000 cubic feet per minute. The processes stone primarily for its own EXTRACTION Marcy ball-mill grinds an average ofuse as kiln feed, flux stone, raw ma- Wool and linen waste, Jute waste, 60 tons of slag per hour to at least '75 terial, etc. The cost of producing thisand rayon waste have been extracted percent minus 100 mesh. It has a fl-stone is absorbed by the end product.with an organic solvent to recover inch manganese steel lining and isTherefore, the sizes that cannot be wool grease." charged with 60 tons of United Statesconsumed are regarded as waste. Any HYDROLYSIS Steel high-carbon-steel grinding ballsmonetary return from the sale of such ranging in diameter from 1 to 4stone is applied to reducing the over- Hydrolysis with hydrochloric acid of inches. The belt conveyor employedall cost of the end product. Convert-cotton linters yields sugar." Cotton to recycle the pins 20-mesh slag ising such stone to marketable productslinters mixed with sulfuric acid make equipped with a Dings magnetic headenables the captive plant to sell at aan adhasivi) paste." Carding wastes Pulley, which removes any remaininglower price than the prime stone pro- have been processed by hydrolysis to iron and any undersize grinding ballsducer can. Often such stone is notProduce cigarette paper.Furfural that may pass through the mill grate.merchandised, but is sold or "dumped" has been obtained by hydrolysis of The entire mill circuit is connected toat unreasonably low prices. Subse- linen and flax wastes."4." Rayon- a 10,000-cubic-foot-per-minute Pang- quently, prices of such by-productsPulp-mill rejects have been digested born bag-type dust collection, which may be raised to a reasonable level,and heated and formed into fiber- discharges to the screw conveyor thatbut meanwhile, dumping has a dam- board." reclaims processed slag from the stor- aging effect upon competition. InTIN age silos. This processed slag has been many areas, by-product stone deter- During World War II tin cans were sold at USS Basic Slag for use as amines the price for all similar prime collected for the purpose of recover- soil conditioner. stone. ing the tin. Collection of the cans was SUGAR BEETS costly, and processes for tin recovery SODIUM were not successful. However, this in See: Reference 123. Lime sludge from beet sugar millsno way detracted from the success of has been reburned in a fluidized-bedthe initial hand-sorting operations STARCH reactor and recycled to the process." Lime sludges from beet-sugar millsperformed at the source. Gluten, the principal by-product ofcan be used as fertilizer for low-pH See also: Recovery and Utilization. the starch industry, can be obtained TITANIUM by evaporating steep water. It is used A processing method employed to for feed.'" SUGAR CANE prepare titanium chips for marketing See: Bagasse. has been described in an article ap- STONE SPALLS pearing in Steel."' The article states Boynton has pointed out that InSULFUR that turnings of titanium that arrive most limestone-processing operations Sulfur-refining wastes have beenat the plant, In lots ranging from a there are large tonnages of atone sizes burned in a fluidized bed." few hundred pounds to many tons, that cannot be used or sold, at least are usually contaminated with other without further processing and classi-TANTALUM alloys and with cutting oils. Each lot fication." These "spalls" may accumu- See: Reference 145. must beidentifiedandcrushed. late to the extent that they consti- Trained workers hand-sort the pieces tute a storage problem. Since the costTETRAETHYLLEAD and us;; a series of chemical and elec- of producing such waste stone has Sludges resulting from the manu- trothermal tests to determine alloy already been absorbed, the waste mayfacture of tetraethyllead are preparedtYPes and metal contents. After the have no value, or even a negative for recovery of lead in the furnace by chips are identified and crushed, they value. Through research and re- compressing and pelletizing them un- are thoroughly cleaned in a vibrating processing,itis often possible toder pressure.' degreaser to remove all traces of cut- obtain salable products from such ting oil, greases, and fines. Other con- wastes by grinding and screening atTEXTILES taminating metal particles, such as low cost, often at costs appreciably The major categories of solid textiletool bits, are removed by special mag- lower than costs of other producerswastes have included cotton and cot- netic equipment as the chips are con- manufacturing the same gradation aston linters, woolen scrap and rags, veyed to an electronic checker, where a prime product. The market maywoolen nods, scraps from silk, hemp, they are visually tweeted before then become sated, and prices badlyflax, rayon, and other synthetic ma-packaging. The production of zirco- depressed, and the prime producerterials. These are recovered and re-nium, tungsten alloys, molybdenum, may lose both volume and profit. Suchprocessed to yieldlanolin,sugar, columbium and tantalum from scrap by-product-stone sources may be onlypaper, furfural, fiberboard, and ad-is covered in the Steel article. temporary, disappearing in a year or hesives. In Iron Age a new furnace that Per- 52 SOLID WASTE PROCESSING mits recovery of titanium scrap isextracted from lima-bean pods andmanufacturers, etc., and (4) cuttings described.°" corn cobs."' Protoplasts can be ex-from box and bag manufacturers. CALCINATION tracted from leafy wastes as chloro- The contamination of such paper Pure gypsum can be obtained byphyll derivatives for industrial andwith polystyrenes and polyethylenes, calcining waste sludge from TIO,pharmaceutical use."' asphalt papers, carbon paper, and manufacture.'" HYDROLYSIS plastic-coated paper has presented difficulties and no means were found ELECTROLYSIS The sugar in green-pea hulls can be hydrolyzed under pressure in sul-reported for their economic separa- The production of high-purity ti-furic acid and Torula utilis grown ontion. However, Kobor has described tanium by electrolysis from scrap hasthe sugars produced.'" Torula utilisa means of removing synthetic resin been discussed."' can also be grown on hydrolyzates ofcontaminants by hydrolysis.'" EXTRACTION reed grass refuse.'" Butanol and ace- Since the market value of waste- Titanium oxide can be recoveredtone are produced from sugars frompaper products has varied widely, the from solid wastes from titanium pro-corn cobs and other vegetable waste collection and treatment of it has been duction by teaching and chlorinatingproducts'" The hydrolyzates of saw-somewhat risky. The approproximate to oxidize dust, sunflower wastes, cereal straw,prices paid per ton in November 1966 and the hulls, grits, and other wastesfor various types of reusable waste- MELTING of barley and millet milling have been paper products were as follows: over- Waste sand from titanium mineralfermented to produce yeast."' 1", "'issue news, $25; No. 1 news, $18; old processing can be made into a re-Plant residues have been subjected tocorrugated, $22; white ledger, $50; fractory by Melting it with bauxite in hydrolysis to obtain cellulose for use books, $20; and manila tab cards, $85. a resistance-arc furnace."' in the manufacture of paper andSorting increases the value of waste- RECRYSTALLIZATION board. Agricultural residues," ". "e 4"paper products, but it is expensive. tobacco wastes,'". '1" From one half to 7 man-hours are The gypsum obtaned by neutraliz- banana stems, required to sort a ton of such material. ing the waste acid from 7103 manu-areca stalks,'"corn stalks," juteConsiderable quantities of wastepa- factured with limestone can be cal- sticks,"".414the woody part of hemp,"per have been collected by charitable cined and then recrystallized. Theespartograss,'1°straw,'" and bagasse 14,0J, 23, Ss.13. SS,05, 114-0, 107,10,171,103- organizations and fed back into the properties of recrystallized gypsum 101, 06. 03, 96$, 90, t11, 190, un, 90, 401, 491,03, paper industry; this paper is hand have been given."' VI, "a have all been used for this purpose.sorted at the home level, However, TOBACCO A continuous process has been devel- when this material has been mixed See: Reference 230. oped to prepare pulp from plant resi-with oti,er trash and hauled to a cen- dues."' Plastic can be obtained fromtral disposal point, its segregation and TUNGSTEN reuse has been virtually impossible. plant wastes by hydrolysis." Charitable groups utilizing volun- See: References 61, 145, PYROLYSIS teer labor have been about the only URANIUM Fuels and solvents have been manu- organizations that can afford to col- Jasmy reported on a process for re- factured by pyrolysis of waste prod-lect newspapers, magazines, etc., from covering uranium from unirradiateducts from the fat and vegetable-oilprivate homes. Wastepaper dealers, fuel-element scrap."' Techniques wereindustries' " on the other hand, have been able to describedfordissolving uranium-WASTEPAPER profitably handle overissue news, con- stainless steel in nitric acid, uranium- tainers, cuttings, etc. from manufac- zirconium alloy in hydrofluoric and The reuse of wastepaper products isturers, since the cost incurred in their nitric acids, and uranium-aluminuma growing industry. Much effort is cur- disposal is often included in that of alloy in sIditun hydroxide and sodium rently devoted to improving practicestheir production. Contaminants must nitrate. The scrap is received as bil- and cutting costs not only by the vari-first be sorted from any waste ground- lets, turnings, strips, and fines. Ura-ous individual companies, but also bywood or pulp paper products destined nium has been recovered from the so-the research activities of the organiza-for use in the manufacture of the best lutions of dibutyl carbitol extraction,tions to which the companies belong,quality paper. The reuse of wastepa- with 99.9 percent overall efilciency.among which are the Boxboard Re- per hais been comparatively common The uranium can be stripped fromsearch and Developments Association,in Europe where pulp wood has been the carbitol with nitric acid to yieldthe Waste Paper Institute, and the in short supply and where paper prod- Pure uranyl nitrate. Technical Association of the Pulp and ucts of a relatively low grade are See also: Separation, Paper Industry. Wastepaper that can be reused en-utilized. VANADIUM compasses almost every type of paper It is probable that almost every box- Vanadium is recovered from themanufactured. According to the Wasteboard plant(2,300 in the United production of aluminum oxide by ex- Paper Institute, some 40 grades areStates) uses waste in one form or an- traction."' recognized. Most of these grades refer,other, the majority employing only mechanical disintegration. It has been VEGETABLE WASTES however, to paper types that can be classified as(1) mixed paper, kraftestimated that more than 30 plants See also: Agricultural Wastes; Ba- wrapping, old corrugated containers, employ deinktng operations with an gasse; Food-Processing Wastes; annual capacity over 500,000 tons. References 103, 331, 513. etc., from industrial concerns, department stores, etc., (2) old newspapers See also: References 16, 397. EXTRACTION and magazines collected from private JUNK REMOVAL Pectin can be extracted from potato homes or over-issues from publishers, Since few paper mills sort their pulp 10° Hemicellulose esters have been (3)waste from printers, envelopewastepaper before it is deinked, the Screening53 stock that many of them treat for fiber reclamation is often contaminated with waste materials other than ink. The removal of these contaminants frequently involves the removal of miscellaneous waste materials such TABLE 13 as dirt, cellophane, wet-strength pa- TYPICAL FORMULATIONS USED WITS FLOTATION MACHINES per, adhesive tape, binding cement, heat-seal label scraps, rubber bands, I II paper clips, staples, plastics, baling wire, rags, string, gummed tapes, and 0,8% triton X-100 1.5% NaO2.2 pins. Material such as this must be2.0% tripolyphosphate 3.78% Na23iO3. 1.7% soft soap._ _ _ 3.0% soap. eliminated from the pulped paper fiber 1.3% CaCl2 CaC12 to produce equivalent CaCO3- before deinking to protect the paper- hardness of 215 ppm. making equipment and to insure the Cook in Hydrapulper SO min at 120 F____ Cook in Hydrapulper 30 min at 120 F. proper quality and uniformity of theFloat 3-5 min at 0.8% consistency Float 3 -b min at 0.8% consistency. finished paper product. Junk removal isoften achieved by screening, centrifugal separation, magnetic separation, or mechanical sorting. The Junk encountered in mostscribed as a form of mechanicalwith chemicals the pulp is treated in wastepaper is of such a variety thatsorting. flotation machines, and the contam- both screening and cycioning are re- See also: Separation. inants removed as a froth or scum. quired to remove it, While the removal Two typical formulations are shown of junk from pulped paper is fre- DEINKING quently employed in conjunction with in Table 13. detnking operations, it is not consid- If separation of ink and dirt from Recent developments have indicated ered an inherent part of the deink-paper is required, screening or flota-that polystyrene and polyethylene tion Is usually done of ter the waste has materials may also be removed by ing process itself. been mechanically hydrapulped withflotation. Brown refers to the removal of for-chemicals to free contaminants from The cost for flotation machines for eign matter from pulped fiber bythe fibers. Chemicals commonly used a 50- to 100-ton-per-day plant would means of screening, magnetic separa- be approximately $50,000 to $75,000, tion,and centrifugalseparation.wto loosen ink are sodium silicate, so- Large pieces of such material can bedium peroxide, soda ash, soap, deter- depending on the time of float. Only removed by perforated plates if theygents, and phosphates. Hydrapulpingone operator would be required per are not broken up during the pulpingIs normally done at 120° to 180° F. forshift. The primary cost item in proc- an hour or more. Consistencies may beessing is that of chemicals and may of the fiber, Metallic objects of ironas low as 4 percent or as high as 25be from $10 to $15 per ton of paper. such as paper clips and staples are Labor, maintenance, and power should frequentlyremovedbymagneticpercent, depending upon the system employed. not exceed $1.00 per ton. A fiber re- separators. After hydrapulping and cooking, covery of 90 percent may be expected. Mc Kele has described several pieces the pulp, at less than 1 percent con- After the impurities are separated, of equipment that are utilized in thesistency, is passed over various types bleaching may be used to whiten the removal of junk from pulped waste-of screens to remove coarse impuri- stock before it is prepared for use by paper." The ragger and bucket ele-ties, and probably through cyclone- further washing and thickening. vator or junk remover are commonlytype devices for removal of heavy dirt See also: Separation. employed to clean the pulped fiberend metallics. The pulp is then ready produced by the Hydrapulper. Thesefor deinking by either flotation or MECHANICAL DISINTEGRATION devices operate efficiently with mini- Another method of wastepaper proc- screening (washing). essing is simple mechanical disinte- mum fiber loss when treating Hydra- In the screening-washing type ofgration in an agitator, such as the pulper consistencies that range fromcleaning, the operation Is performedHydrapulper manufactured by the 1.5 to 2.5 percent. In this consistencyon multistage washing cylinders cov-Black Clawson Company, until the range, the ragger and junk removerered with wire of about 85 mesh. Cop-fiber has been beaten up to the de- are most efficient in the removal ofious amounts of wash water are re-sired fineness. A similar machine is balingwire,rags,string, gummedquired to remove the carbon, fillers, the Wet Pulper, manufactured by the tapes, wet-strength papers, etc., andetc. Fiber recovery of 85 percent may French Oil Mill Company, Material bottle caps, wood, beer cans, glass,be anticipated with a chemical cost ofso processed can be utilized as a filler nuts and bolts, etc., respectively. The$10 to $15 per ton. Generally speaking, inthemanufacture of boxboard, ragger consists of a double-serratedthe higher the chemical consumption, matches, and other low-grade prod- sheave with an adjustable, weightedthe brighter the recovered stock. ucts where color and/or specks are wheel that holds the rag or rope in See also: Reference 324. not objectionable and where bulk is place. Power is supplied to the device the primary requirement. by a small, variable-speed motor thatFLOTATION See also: Separation. governs the rate at which the rope is Flotation may also be used to re- SCREENING withdrawn from the Hydrapulper tub.move the contaminants from waste- Klftinau has described the process The action involved in the separationpaper treated in secondary reclama- utilized by the Bergstrom Paper Com- of materials by the ragger can be de-tion systems. After proper preparationpany of Neenah, Wisconsin, for the 54 SOLID WASTE PROCESSING Wastepaper

Continuous Pulper

Centriffter Rejects to sewer

Rejects Jonsson Jonsson Screen Screen

Supraton Fiberizer Fiber

Rejects to Jonsson sewer Screen

Fiber to washing system FIGURE 8. The deinking of secondary paper fiber by screening.

deinking of secondary paper fiber byproduced by the three screens Is sub- applicationofvarioustypesof screening."' The process, illustratedsequently transferred to the pulp-screens to the cleaning of waste in Figure 8, has been employed pri-washing system,whiletherejectpaper in deinking systems.'" Screens marily for drinking pulped secondary material is discharged to sewers. have been employed in these systems paper fiber, but contaminants such In thisoperation,thefiberizer primarily to remove nonferrous ma- as plastic and rubber can also betreats a pulp consistency of slightly terials of low specific gravity. eliminated. The entire stock of pulpedunder 3 percent at a throughput of Multistage screening systems have paper is first passed over only two 12 tons per day of stock, a flow ratebeen employed by many mills in an Jonsson screens at a flow rate aboveequivalent to about 7 percent of theeffort to derive the maximum benefit that of their normal screening capac-total. The fiberizer utilized has beenfrom their fine screens. The coarse ity. This is done to assure a high ratesupplied with a 75-horsepower motor,screens utilized in these systems must of reject flow to the subsequent de- but used only 25 horsepower at a rate have large holes and a high capacity fibering operation. The fiber bundlesof 2,1 horsepower-day per ton. ThisPer unit to remove large particles. and ink of the reject pulp are thenfiberizer was unique in that it facili- The vibrating-deck screen has been broken up in a deftbering machinetates the screening of extraneousmost commonly used for this pur- known as a Supraton fiberizer. Amaterial, such as rubber and plastic, pose, but flat screens, rotary-type third Jonsson screen is finally em-from the paper fiber by permittingscreens, and pressure screens can be ployed to separate the reject mate- them to pass unchanged through the employed as well. rial from the clean paper fiber of thedellbering operation. Most of the fine screens in use have defiberized pulp. The cleaned stock Lehman has considered the general beendesignedtouse fine-slotted Condensation55 plaits, The types most frequently en-stage installation involving the dilu-as a binder, a dispersant, an emulsion countered are the flat screen and thetion and recirculation of fiber pulpstabilizer, and a sequestrant. rotary-vibratory screen. Fine screensbetween stages. The rejects from the The hemicellulose or polyeaccharide with round holes have, however,primarycyclones usuallycontainportion of the wood is readily hydro- proved to be much better. Pressuregood, usable fibers that can subse- lyzed into simple sugars. In the sulfite screens and centrifugal screens are quently be recovered in second, third, process, about 300 to 400 pounds of types of round-holed screens thator fourth stages. Small cyclones op-hemicellulose have been converted into should be strongly considered in anyerate according to the following prin- sugar for each ton of sulfite pulp pro- new or revised screen layout. Verticalciples as given by Fahlgren'"': (1) duced. Although processes for utilizing pressure screens have come close toThe smaller the cyclone diameter, thethese sugars are technically feasible, being the ideal fine screens, as theymore efficient the removal of specksthe economics have been unfavorable. operate in a closed system that is bothand fine dirt particles; (2) the largerStudies in Canada have shown that clean and quiet. the diameter, the longer the Olivethe minimum economical size fora Rated or tailing screens have beenthat can be removed; (3) the higherplant to produce alcohol wouldpro- employed in the multistage systemsthe efficiency of speck removal, the duce 1% times the national consump- because fine screens do not functionhigher the concentration of short fi- tion of alcohol. Fbdder yeasts andor- efficiently without rejecting good fiber bers;(4) for the smaller diameterganic chemicals such as furfural are with waste material. Flat and vibrat-units, consistency of 0.5 percent isimportant products of sugars from ing-deck screens are the only typesmost effective;for larger diameterhemiceliuloses, and the market for of screens capable of achieving theunits, 0.7 percent is considered eco- these materials could grow. clean separation of fiber and fiber-nomical and efficient; (6) secondary Sawmill wastes can be utilized by free waste. and following stages should operatethe pulp industrY to a large extent. See also: Separation. at lower consistencies than the pri- Several mills in Canada have formed mary stage; (6) reject rate is con- cooperatives and purchased the equip- CYCLONES trolled by the back pressure and thement needed to bark and chip wood The general application of cyclonessize of the reject opening; and (7) wastes to make them suitable for pulp- to systems involved in the deinkingthe back pressure should be kept con- ing. Waste bark and mill waste have of secondary paper fiber has been re-the back pressure should be kept also been sent to companies that make viewed by Fahlgren." Cyclones em-constantformaximumcleaning wallboard and roofing felts. ployed in the pulp and paper industry efficiency. The proximity of a healthy petro- have ranged in size from 3 to 48 The size and number of cycloneschemical industry on this continent inches in diameter, and in throughputrequired for a given operation may be has kept the pace of chemical utiliza- from less than 20 to as much as 6,000determined by the character of the tion of forest products consider ably gallonsperminuterespectively. furnish, the character and amount ofbehind that of the Scandinavian Large-volume cyclones have largelyforeign particles to be removed, andcountries, since many wood chemicals replaced the space-consuming rifilerthe volume of the stock to be handled. are competitive with petroleum chem- for the removal of dirt from pulpedA high-capacity, high-efficiency, pri- icals. Experimental work is being done paperfiber.Separationsachievedmary cyclone can be used for the rein this country to make a lignin-type with them have been far superior tomoval of low- and medium-specific- plastic from wood waste. that achieved by the rifer, at bothgravity materials (such as glass and See also: References 202, 438, 442, high and low stock consistencies. sand), which often pass through the 456. Large cyclones are usually em-perforations of the Hydrapulper with ployed after pulping and prior to the stock flow, This device is equipped ACIDIFICATION screening for the removal of junk suchwith conical ceramic inserts that have A pasty coal igniter has been pre- as bottle caps, paper clips, tramp iron,proven to last longer than those ofpared by treating a mixture of peat, rocks, and coarse sand. The following alloy steel. sawdust, and cellulose wastes with types of cyclones are suitable for the See also: Separation. removal of such material: (1) large- acid and wetting the product with WOOD WASTES sulfur in gasoline."' Cellulose, oxalic volume cyclones operating at rela- acid, acetic acid, vanillin, tannin, etc., tively low consistencies,(2)large- Wood wastes start in the forest volume cyclones capable of handlingwhere only about 81 percent of theare recovered from wood and vegetable high-consistency stocks, and (3) rel- tree is removed as sawlog, in thewaste in an apparatus specially de- atively low-volume cyclones capablelumber mills where 16 percent issigned for continuous recirculation of of operating at consistencies as highwasted as sawdust and 34 percent as nitric acid through the waste."' as63 2 percent air dry. slabs and edging, and in the paper CARBONIZATION The smaller cyclones, ranging in mills where about 50 percent of the The activity of carbons from saw- diameter from 3 to 12 inches, havelog is discharged in waste effluents ordust in relation to the activation proc- been widely employed for the removal isdisposed of by burning. Wood of shiver and specks from low-densitywastes can be processed to recover a ess has been described."' "' Dry distil- stocks. Installations of these cyclones lation of sawdust was reported to yield varietyof by-products, but theseactivated carbon of high grade."' have been either single or multistage, processes have been applied to only theprimaryunitsoftenbeing a mall extent. CONDENSATION equipped with a secondary unit. These Lignin, the main noncelluloslo con- Lignocelluloslo wastes nave been units are efficient dirt removers andstituent of wood, can be processed tocondensed with sulfur compounds and operate with a minimum loss of fiber. obtain valuable chemicals, such asdigested with water at high tempera- The maximum cleaning efficiency has pure lignin and dimethyl sulfide. Itture to produce plastic material suita- been provided, however, by a multi-can also be utilized without processing ble for pressing into boardsP 56 SOLID WASTE PROCESSING DEHYDRATION the nitrogen content!" Mellitic acidwaste products!".The separation is Charcoalofhighdiscolorationand other polycarboxylic acids can bebased upon the inducement of a grav- power can be obtained from sawdustobtained by nitric acid oxidation ofity differential between the wood and by dehydration with sulfuric acid." sawdust." Sawdust has been added to the bark. After the bark has been EXTRACTION kilns to reduce iron in the productionfreed from the wood with a chipper, of ferronickel from nickel ores." Oxi-the mixture is immersed in water and Extractives, the noncellulosic por-dation of lignin waste and sawdusta vacuum is applied. Entrained air is tion of wood extractable by neutralwith either phenol nitrate or coppereasily withdrawn from the continuous solvents, include a number of poten-oxide yields vanillin!".'" and interconnected passages of the tially valuable organic chemicals. An wood but not from the collapsed pas- adhesive thatiscold-setting and SCREENING waterproof has been called one of the The application of screening to thesages of the bark. The release of the most promising extract products. sizing of bark was mentioned by Piercevacuum causes water to enter the vas- Wood wastes can be extracted withand Sproul' in their description of acular passages of the wood formerly gasoline 133 and methyl alcohol "to ob- process involving the conversion ofoccupied by air, The heavy combina- tain rosin. bark to plant food.TM' The productiontion of wood and water quickly sinks of plant food and soll-amendmentaway from the lighter combination of GRAVITY SEPARATION products from southern pine bark bybark and air that remains at the water The application of gravity separa-the Green life Products Division of The surface. Wood recoveries of over 90 tion to the recovery of waste woodChesapeake Corporation of Virginia percent are usually achieved in wood- Produced in the pulp and paper indus-was the first commercial application bark separations such as this. try has been described by Wesner."."of this process (United States Patent The Vac-Sink process was first em ployed on a commercial scale' at the HYDROLYSIS 2, 881,066) . In the process, bark is first ground and then screened intoSavannah, Georgia, mill of the Union The conversion of wood cellulose tovarious size fractions. Selected sizesag-Camp Paper Corporation. This fermentable sugars has been the sub- plant can process waste wood ata ca- ject of numerous investigations." ". fractions are subsequently steamed atpacity equivalent to 100,000 cords of t12. 1 i,SS" -SW. 240,/FS,IFS. WS, $21. MI, CC IA a temperature above 170° F. and Im- wood per year. The wood recovered by " Yeast containing 25 percent fatpregnated while hot with solutions ofthe plant can subsequently be DIU- has been grown in these sugars!" Al-various nutrients, After the bark hasessed to make paper, the bark being cohol has been distilled from the fer-been impregnated, itIs dried and utilized as a fuel. Cost data and Infor- mented wood sugars?",White winebagged. Information concerning proc- mation concerning the equipment em- can be obtained by refiuxing sawdustess costs and equipment has not beenployed in the plant have not been with sulfuric acid'"" The glucose ob- available. available. tained from lumber and pulp-mill See also: Separation. See also: Agricultural Wastes; Pulp leftovers can be concerted to levulinic PYROLYSIS and Paper; Sanitary Landfill and acid and formic acid.'" Wood as a Dry distillation of sawdust and wood Open Dumping. chemical raw material has been dis-wastes yields activated carbon of high cussed by Wenzel." Furfural is an im-grade together with methanol, aceticWOOL portant product of wood hydrolysis.acid, acetone and wood tar as by- See: Textiles; Reference 421. "'. 223' 3$7. $3°' 422 Many authors report products!". 4'4 high temperature and on the use of wood wastes in the man- catalytic cracking during pyrolysis ofYTTRIUM ufacture of paper board.'", a". "*. sawdust produces an equirnolar mix- Provow and Fisher published a pa- "' 1". "". " "I The influence of barkture of hydrogen and carbon mon-per describing a process tor reclaim- on the properties of pulp has been de- oxide'" The heat values of the fueling yttrium scrap by chemical pro- scribedJ6'.'1° gas obtained have been given.'" Saw-cedures."' According to these authors, See afro: References 104, 328. dust can be decomposed in a fluidizedyttrium can be recovered from wastes INCINERATION bed" "". "8 Thermal decomposition of by burning the wastes and dissolving Wood residue has been incineratedwood In aqueous medium under pres-the residue in nitric acid. The Impu- in tepee waste burners with some de-sure resulted in larger amounts of rities can be removed by precipitation, gree of air pollutionlow enough tochemicals than destructive distilla-the yttrium then being precipitated be acceptable In some areas." Woodtion."' After recovery of products ob- with oxalic acid. waste has been used for fuel in a largetained by heating sawdust soaked in Provow and Fisher have also dewater tube boiler!'" The products ofkerosene at temperatures below 275° scribed a low-cost process that uses combustion of wood wastes can beF., the temperature is raised, the kero- readily available chemical reagents sene Is distilled, and the residue isand equipment to reclaim yttrium used to produce ammonia'' used as a fuel.'" While the pyrolysis See also: References 354, 533. of wood to produce acetic acid and from scrap in the form of small pieces, OXIDATION turnings, and saw filings."' The scrap methanol was in past years a substan- is converted to crude oxide by ignition. Oxidation and hydrolysis undertial industry, it has largely been sup-One-hundred-pound batches of the pressure followed by hydrogenationplanted by synthetic methods. How- has appeared to be a possibility for theever, recently about 20 million poundsminus 80-mesh oxide are dissolved in preparationofvariouspetroleumof acetic acid a year and 14 million50 percent nitric acid. The resulting chemicals from wood wastes and agri-pounds of methanol a year was beingsolution is purified by hydrolysis of cultural residues.'" produced by the old process'" zirconium, iron, aluminum, and tita- Fertilizer can be Prepared from saw- nium. Then potassium ferrocyantde is dust or wood chips by first oxidizing VAC-SINK PROCESS added to precipitate copper and nickel. the material with nitrogen dioxide The Vac-Sink Process was developedThe yttrium is precipitated as oxa- and then adding ammonia to Increasefor recovery of the wood fraction from late with oxalic acid, after which the Zirconium57/5$ filtered and washed precipitate is ig- and from 60 to 80 percent of the con- moved and reclaimed germanium, nited to produce the oxide, The chem- denser zinc, This concentrate cancopper, and cobalt. ical costs of a large-scale operationeventually be recycled to the retorts. The purified zinc sulfate liquor was were reported as $0.67 per pound ofHeavy-medium separation has beenelectrolyzed in the conventional man- Yttrium oxide. applied in one plant to recover me-ner with anodes of lead alloy and See also: Nonferrous Scrap. tallic zinc from electrothermic zincaluminum cathodes. The deposition residues. of zinc was accompanied by the for- ZINC See also: Separation. mationofsulfuricacidinthe See also: Lead; Pyrite Cinders and so-called "spent electrolyte". That Tailings; Sal Skimmings. HYDROMETALLURGICAL acid liquor was used to leach more PROCESSING ftme. The zinc sheets deposited by EXTRACTION Zinc metal has been produced from electrolysis were stripped from the Weak hydrochloric acid has been zinc oxide in retort or electrolytic re- cathodes, washed and melted. The used to leach zinc from waste mate- duction plants operated mainly formolten zinc was cast into slabs of rials.." Cadmium is extracted fromthe production of primary zinc. The"Special High Grade" quality. the residue of zinc refining with sul- preferred method for reduction of furic acid. The acid solution is elec-zinc oxide has been the electroly-ZIRCALOY trolyzed to recover cadmium.' tic process. The procedure in one Rubin and Gessner have described plant treating zinc oxide fume alonethe use of magnetic separation and GRAVITY SEPARATION has been as described below. screening in the recovery of Zircaloy Phillips briefly mentioned the ap- The fume contained about '17 per- scrap at atomic -power facilities!" plication of gravity separation to the cent zinc, about 1 percent each of leadChips produced during the machin- recovery of zinc from contaminatedand iron, and less than 0.1 percenting of hot-rolled Zircaloy strip are crusts of zinc and zinc oxide in zinc- each of germanium, cobalt, and cop- first crushed in a hamniermill. The smelting operations!" These crustsper. It was ground in airswept ballcrushed material is then conveyed form onthefireclaycondensersmills to about 70 percent minus 325 over strong magnets to remove mag- utilized in the reduction of zinc in mesh and leached batchwise with thenetic contaminants and isfinally horizontal retorts. The spent con- sulfuric acid in spent electrolyte from sized on a 20-mesh screen to elimi- densers have usually been crushed tothe deposition process. The resultingnatefineparticles.The cleaned producemetal-bearing neutral liquor of zinc sulfate wasZircaloy is subsequently melted into refractoryfiltered to remove iron and lead, andingots for later reuse. Particles which have subsequentlythe filtrate purified. Purification was been treated in jigs and on shaking accomplished by stirring copper sul-ZIRCONIUM tables to produce a concentrate con-fate, arsenious oxide, and zinc dust See: Nonferrous Scrap; Reference taining from 60 to 70 percent zincInto the liquor. That treatment re- 145. Bibliography

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Timokhin, N. A., et at. [Artificial gian Patent 611,412, 1961. posala mountainous Prob- leatherforshoeuppers.) 465. VereinigteGlanzstoff-Fabriken lem. Electric Light and Power, U.S.S.R. Patent 153,059. Sub- A.-0.Spinnable polyethyl- 32 (5) :90-3, May 1954. mitted Apr. 28, 1956. Published ene terephthalate) from fiber 477.Wenzl, IL P. J. [Wood as a chem- 1963. waste. British Patent 892,437, ical raw material.)Holzfor- 451. Tobola, S. [Problems of techno- 1962. schung, 10, 129-43, 1956, logical wastes in chemical in- 466. Veres, T. [Extractionofthe 478.Wesner, A. L. Vac-Sink. Pulp and dustry.]Chemik,18,121-4, vanadium content of bauxite Paper, 36, 61-5, Aug. 20, 1962. Apr. 4, 1965. during the production of alu- 479.Wesner, A. L. Vac-Sink goes com- 452. Tompkins, V.Truck-mounted mina by the Bayer process.) mercial. Pulp and Paper, 36, chipper-container.American Acta T echn c a Academiae 59-61, Sept. 3, 1962. City, 79, 18, Dec. 1964. ScientiarumHungaricae,41 480.West, C, J. The Utilization of 453. Touriuiztuni, A. [The activity of (3- 4):259 -68, 1962. Sugar Cane Bagasse for Paper, carbons in relation to the ac-487. Vickerson, 0. L. Fly ash control Board, Plastics and Chemicals. tivation process.] Seito Gijutsu equipment for industrial in- Sugar Research Foundation, Kenkyukaishi, 2, 87-97, 1953. cinerators.InProceedings, Technological Report, Series 454. Trauffer,W.E.Birmingham 1966 National Incinerator Con- 120.8, 200, 1952. Slag's new plant makes MS ference, American Society of 481.Mut owski, S. [Utilization of in- basicagriculturalslagfor MechanicalEngineers, New dustrial wastes in chemical southeastern market. Pit and York, May 1-4, 1086, p. 241-5. processes.)Chemik, 8,9-12, Quarry. 57, 144-8, May 1965. 468. VIlliere,A. The experimental 1955. 455. Trauffer, W. E. Levy's new slag hydrolytic plant at Sorgues, 482.Wiehrmann, K. Waste disposal plantinDetroit.Pitand France. In Proceedings, 4th methodsscope and limita- Quarry, 54 : 135-43, Jan. 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(The manufacture of dark recover diamond dust. Steel, 484. Wilder, C. J,, and R. W. Hirzel, glasses from industrial polish- 144, 70, Mar. 9, 1959. Food processingwastes utili- ing waste and construction 515. . Chemical recovery quells zation and disposal. In Pro- glass.]BelorusskilPolitekh- a pollution threat. Chemical ceedings Annual Pacific North- nicheskiiInstitut,Sbornik Engineering, 72 (20) :90-1, west Industrial Waste Confer- Nauchnykh Rabot, 63, 75-85, Sept. 27, 1965. ence, 7, 53-6, 1956. 1958. 518. . Chip collection system. 485. Wiley, J.S. Some specialized500. Zimmer, H. J. Apparatus for pu- Compressed Air Magazine, 71 equipment used in European rifying industrial end domestic 15, Jan. 1966. compost systems. Compost Sci- effluents and utilizing organic 517. . Chipper rescues inciner- ence, 4 (1) :7-10, Spring 1963. solid matter for generation of ator. American City, 70, 183, 486. Williams, A. E. Straw and ba- energy. British Patent 937,051, Nov. 1955. gasse as papermaking materi- 1963, 518. . Clippers counter Cleo de- als. FibresNatural and Syn- 501. Zimmerman, F. J. New waste dis- bris. American City, 80, 36, Feb. thetic, 15, 219-22, 1954. posal process. Chemical Engi- 487, Wilson, F. D. Bagasse as a fuel 1965. neering, 65, 117-20, Aug. 25, 519. . Commercial - Industrial for steam generation. Sugar 1958. Journal, 17 (2) :15, 18-20, 1954, incineration.GasAge,123 502. Zimmerman, F. J., and D. G. Did- (11) :49-51, May 28,1959. 488. Won, Y. (Production of Furfural dams. The Zimmerman process 620. from Bagasse.] Report of the and its applications in the pulp .ComPacting refusein Taiwan Sugar Experiment Sta- and paper industry, TAPPI, barges saves costs. Engineer- tion (Taiwan), '1, 164-71, 1951. Journal of the Technical Asso- big, 196 (5078) :138-9, Aug. 2, 489. Woodruff, P. H., and A. W. Wene. ciation of the Pulp and Paper 1963. General overall approach to Industry, 43 (6) :710-5, Aug. 521. . Composting gets a try- industrial incineration. In Pro- 1960. out American City, 80, 99-192, ceedings, 1966 National Incin-503. Zimnawoda, H. W. Sand recla- Apr. 1965. erator Conference, American mation can save, you money. 522. . Con Ed turns waste into Societyof Mechanical En- Foundry, 93(6) :62-6, June wealth atfly ash sintering gineers, New York, May 1-4, 1965. Plant. Rock Products, 68, 81 -2, 1966. p. 219-25. 504. Zinina, M. A. (Production of Oct. 1965. 490. Woodward, F. N. Industrial util- food-grade ethyl alcohol and 523. . CF's success story in bio- ization of agricultural wastes. Methanol conforming to GOST chemical& Canadian Chemical Chemistry and industry, (35) 2222-54.] Girdoliznaya t Le- Processing, 45 (12) :42-4, Dec. 844-8, Aug. 30, 1952. sokhimicheskaya Pronisyhlen- 1961. 491. Wulf, R. (Combustion of sludge nost, 18, 19, 1965. 624. . Deinking of Waste Paper. with oil gasification burners.]505. Zurmuhlen, F.H. 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Pulp from Engineering News, 41 (12) :25, pulp liquor. Chemical and En- Sawdust.Ringyo Shikensho Mar. 25. 1963. gineering News, 40(46) :52-3, Kenkyu Hokoku, Bulletin No.509. --. Blast furnace for melting Nov. 12, 1962. 63, 59-68, 1952. copper scrap. Engineer, 213528. . Experience of industrial 495. Yudkevich, Y. D., et at. (Thermal (5529) :100, Jan. 12, 1982. bagasse pulping. World's contact processing of wood 510. (Blast furnace for melt- Paper Trade Review, 142, 1954. waste.]Trudy Vsesoyuznogo ing copper scrap.] Metalturgia, 529. Experimental incinera- Nauchno- Issledovatel' skogo 70, 235, Nov. 1964. tion of Paper Mill Sludges. Institute Pererabotkl t Ispol' 511, Blast furnace slag output National Council for Stream zovaniya Topliva, 13, 162 -70, hits 35,000,000 tons in 1957. Pit Improvement, Technical Bul- 1964. and Quarry, 51, 128, Aug. 1958. letin No. 130, 1960. 498. Zalesov, Y. P. (Paste.] -U.S.S.R.512 ----. The bonus value in a va-530. . Ferrouscancrusher. Patent 104,602, 1957. nillin plant. Canadian Chemi- Machinery (LOndon), 102, 497. Zedet, E. (New process for the cal Processing, 45 (9) :48-50, 1221, May 29,1963. hydrolysis of cellulose.) Chlmie 59, Sept. 1961. 531. . Flyashyieldsgood et Industrie(Parts), 81(3) :513. . Carotene concentrates profit.Power,106(2) :79 -81, 370-5, Mar. 1959. from vegetable leaf wastes. In- Feb. 1962. 498. Zelenka, S. (Utilization of potato dustrial and Engineering532. . Germanium scrapre- starch factory waste products.) Chemistry,36(11) :1057 -61, claimed new way. Sleet, 147, Stdrke, 10, 264-62, 1058. Nov. 1944. 91, Aug. 15, 1060. 72SOLID WASTE PROCESSING 533. . Harnmermill grinds lum- ing: waste disposal poses di- saves landfill space. American ber for incineration. American verse problems. Modern Sani- City, 80, 92-3, Nov. 1985. City, 76(1) :22, Oct. 1961. tation and Building Mainte- 555. . Sanitary fill supermech- 534. . HC1 regenerates waste nance, 18, 14-5, Feb. 1966, anized. American City, 80, 20, pickle liquor. Chemical Engi-545. . Natural gas incinerator; Dec. 1965. neering, 63(2) :132-4, Feb. installation inrestaurant, 556. . Sawdust gets up off the 1956. Hagerstown, Maryland. Mod- floor. Industrial and Engineer- 535. . How BMS will turn tail- ern Sanitation and Building ing Chemistry, 52, Sup. 38A, ingsintoprofit.Canadian Maintenance, 18, 13, Feb. 1966. Jan. 1960. Chemical Processing, 49(11) :546. . Newdevelopmentsin 657. . Scrap: new hope for ti- 71-3, Nov. 1665. 'composting equipment. Com- tanium.IronAge,178,42, 636. . How the Inverted-Bosh post Science, 4(2) :15 -20, Sum- Dec. 20, 1956. blast furnace increases scrap mer 1963. 558. . Sintering profit from a smelting capacity. Engineering547. . New furnace permits re- waste disposal problem. Mining Journal, 158, 100, Aug. covery of reactive metal scrap. Chemical Engineering, 71 (18) 1957. Iron Age, 185, 108, June 23, 34, Aug. 31, 1964. 537. . Incinerator gobbles up 1960. 559. 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141111116$ OffItt SOLID WASTE REGIONAL REPRESENTATIVES (U.S. Department of Health, Education, and Welfare Regional Divisions)

REGION I REGION V Room 1401B-8 Room 712 John Fitzgerald Kennedy Federal New Post Office Building Building 433 West Van Buren Street Government Center Chicago, III. 60607 Boston, Mass. 02203 REGION VI 601 East 12th Street REGION II Kansas City, Mo. 64106 Room 834 H REGION VII Federal Office Building Room 1612 26 Government Plaza 1114 Commerce Building New York, N.Y. 10007 Dallas, Tex. 75202 REGION III REGION VIII 220 7th Street NE. 9017 Federal Office Building Charlottesville, Va. 22901 19th & Stout Streets Denver, Colo. 80202 REGION IV REGION IX Room 404 Federal Office Building 50 Seventh Street NE. 50 Fulton Street Atlanta, Ga. 30323 San Francisco, Calif. 94102 1n U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE Public Health Service Consumer Protection and Environmental Health Service Environmental Control Administration

Public Health Service Publication No. 1856