- Email: [email protected]
Recycling of metals
Conserborion
Printed
& Recycling,
in Great
‘id.
1C, No.
!, pp.
G36i -3658/87 SJ.XT Pergamon Joutnais
1 - 13, i987
Britain.
.CG ‘Ad.
Room 816, Bureau oJ^Mnes, 2401 East Street, NW Washington DC 20246, W.S.A.
are the first two steps recycling. Scrap can be &issified revert, or run aram (b) prompt irldu§PriaS; and (c) ~ost~on.s~~~r or obsolete. ~nr~~ase~ scrap consists of the last tw egsries. Sin.ce home scrap is recycled within the p nt where it is generated and re~~~ir~sno tional processing priorto scrap will be discussed. Prompt industri crap is usua8ly new clean processing
of scrap
egsries:(a)
home,
aterid generated during an in st~~~~~~~gof a~t~~.~~~il~ fenders) scrap is usuaily sdd by the generat n come from a mce scrap comes from a va ient use. The primary roles of the scrap processor are to collect, accumulate, sorts e, market and distribute scrap. S ding is done foil as shearing, baBing or er of activities, s tisn may invoQve any of a nu
Ferrous upplied a slowly increasing portion of the iron CQ~s~rne~in the U.S.A. between 1 s scrap has been used t 81 (Table I>* Almost all of for copper cementation (a cast iron. Small ~~~~~t§ have ucrion @f ferroalloys. errors scrap is usually i~e~t~~i~~ an sorsed according to source or prior use, As ferrons with nonferrous scrap, stainless tee1 and specialty alky scrap, iqaes are economic. ashen mixe scrap is received, it is sold 8s an s of the ultimate cons
Artick published in Encyclopedia
~JMateriab
Scieiace and E&zeering
(Pergzmon
Press, 1986).
2
Percentage of Year
gl__l____~_m__/__l,_~~-
-976 971 - 978 979 -980 ‘981
Consumption (kt) _,” 37 39 37 42 36 37
590 e40 860 680 590 460
total ferrous
~~-Y-_I
consumption
3: 34 36 35 33 35
Shears i-educe aige ~3ieeesof scrap (e.g_ sthuceurai ~~~b~~s~ to a dimension s1uita3~emoi:~~ii2.i
charging, usually I- 1.5 m long. Automobiles pressed into logs also are sheared. Two types cd shear are used: guillotine and alligator shexs. The guillotine shear is the larger of the two, mx&ing of a movable he is b~~~a~~~~~l~~ force t a s~at~~~~r~anvil. The scrap to k cut rests on and protru nd the anvil. Alligae ararsfunction 1ike giant s~ksm-s: except onajr the upper part is movable. e, light-gauge scrap is ~~~~~~~t~~baled or briquetted, Exam s of this type of material sheet remaining after a stampin or punching ~~~~~t~Q~~a turnings (meta:. removed in a ~~~~~i~~~goperation). In ad ition, entire ~~t~~~b~~es an a~~~~a~ce§are sometimes 3alers consist of hydraulic ~y~~~~~~s that compress the scrap by ~~s~~~~git against fixed walRsof I cube. Steel briquetters have a pajir sf rotating drums wit31 a series of cavities aromd the The scrap (e.g. turnings) assw.mes drum into which the scrap is compresse and ~~~~~§~o~s of t cavities. rs are used mostly r ~~e~~r~~g light scrap (e.g automobiles and large home appEiances). They consist of a series of steel b~~~e~s mounted OE rotating drum. The “aammers pass by a series o car, ~~~$~~~~e~or other scrap between the i-sized chunks. Magnetic separation remxes the l?ammers causes it to be qu ic materials such as glass, ru ~‘errous metal from ~~~fer~~~s metals and no3 snd dirt. The resukting ferrous product has the advantages of increased p xmsistency, handling, tra~~~~r~~t~~~ and besting ~b~~~~~~~~st~cs~ En 1 estimated 200 automobile shredders operating in the USA wit a capacity nf more thzn 13 Mt 3er year. The fcxrous fraction of ~~~~~~~a~sdid waste presents a unique case, This naterid &maybe 33L.jdirectly to steel mills for blending with ot etinner, or to a scrap y:ocesssr. The cans must be cleaned of paper scrap processor ~priasrts ~~t~~~i~g~ The deti H - NaNO, solution. This proces also removes any Serrous scrap has cmxsiderably Increase value, and the tin Can be recovered fro dectrolysis.
RECYCLING &ower
purity
nmnhole covers.
a
OF MET.%LS
usuaaly 1,c restricted to a~~~~~~t~~~swith less strongest chemicai aA y s~e~~f~~~ti~~s. These include the ~~~~f~~t~~e of reinforcing bars and igh-purity scrap can be used to make any grade of steel QP cast iron.
scrap
ications are that Cwpper-bearing scrap materiaks are among the ddest used by man, an these nnateriais were recycled by the earliest civilizations. Extensiv continued up to the present time, when copper-bearing scrap accou copper raw materials in 19’79and 4980 (Table 2). Depeding on the meIting technique employed, using scrap to prsduce copper requires only 3 - 4007aof the energy needed to produce pure copper from ore. ~~~~e~-be~~~~g scrap is divided into a number of grades. N0.l co, er scrap fixgusa be unalloyed, as it is used directly to make wirebars. No.2 copper scrap is refined e~e~t~~~~t~~~~~~ and therefore may contain smne impurities, though a copper content of at least 94 - 96% is refinery; its copper content nosmdiy required. Light copper also ass625through an e~e~t~Q~yt~~ must exceed 92%. Refinery-grade brass must contain at least 41.3% co material generally contains less than 40% copper. These last two in a blast furnace and blown in a converter prior to ekctrolyti ~Q~~er-bea~i~g scrap can be used by tube mills, refieers, brass spesiahty csmparies. The end-use determines the preparation of the s ot refine e~e~t~~~~~c~~~y, metallic ~~~t~~~~~t~o~ of scr mvever, small amounts may be ~~~e~t~~?~e~ epending on the user’s ability to fire refine. efiners can produce ap must first be c copper scrap, but No. 2 and light cop ekctrsiy:ically before it can be used for this purpose. rass mills usually use No. 1 copper and brass scrap in their melts in ~~~b~nat~Q~ with pure copper. The composition of brass scrap must be known and kept within narrow limits so as to keep ingot rass vxt made fmn the scrap wi pply aI4oys of known, fixed ety of copper-bearing scrap. chemicals, electraplating, castings (bst and steehmaking ~ D Brompt industrial ~~~~er-bea~~~g scra which accounts for $0 - 70% of r or exanqde, scrap tu~m~~g$ generated by a variety of i~~~st~~a~operation machar!es amour,t to up to 65% of the UK&Sinclude stam drawing rejects, die shavings and short ostcoarsumer scrap mc rail, e~e~t~~~~~s~power utility and defense ips; and in spent sheU casings. ateria!‘s color, spectrosco chemicai analysis, or, in some cases, mag required for the first three methods. Togethe past use, the cob of a clean surface may be ali that is needed to a se~~~~~~t~tat~~~ analysis of an alloy, but this informatios is &en sufficient for sorting Spot testing iavolves obs or lack thereof, between vari
processor.
Traditisnal
ues is used to ~~e~~re ~~~~e~-be~~~~~scra processes include shearing to the size required
by the sustcme:,
?
1. 3. ‘Lka,‘LAi.% am
13. NESS
‘xiqueetmg m crus&ing 3i”chsn and ~~~h~~~i~b~materials “,e.g. Eurnjlngs and 3ormgs], ~!nagnck 3eparation to remove iron, cleaning and One new technique is ~h’~~~~~g of copper -wire scrap. Large, stiff pieces sf WYR d~a: Tresheared prior to chopping. Bales tf wire must broke2 do~wnand are usuaily cut up with an &gator shear. The major steps t I-I consist sf choppifig in three sta es, with magm3is separaticm to remove ferrous ~~~tarn~~a~its fo’cowing the first stage and sizing f~~~~~~~~the second stage. The third stage handles ~~~~~berate~wire from the air sepa ion process which 5Alows sizing. Both the coarse and ~~t~r~~e~~atesize fractions are psocesse y air separation to x-educe four fractions: (a> clean metal, (b) liberate metal with some insulation ~~~ta~~~~~i~~~ :c> unliberated wire, and (d) clean insulation. Shredded automobiles also yield ~~~~er-b~ar~~g scrap. Following magnetic recovery of the Cerrous metals, the ~~~f~rro~s rejects can be processe ber of techrkpes. The n be removed by air separation and n, and/or heavy media copper-bearing metals can then be ban e a~~~~~~rn and zinc are goated in a heavy medium. Cryogenics (i.e. cooling scrap to t I-es as 1ow as - 1 copper from items such as small m iS, ~ra~sf~rmer5i gener When exposed to these very low tern become brittle, whereas copper remai ble. Therefore, crus after cooling will allow relatively large pieces of copper to be separa materials by screening.
RECYCLIivG
5
OF METALS
is needed,
If more i~fQr~ati0~
a
spec&ro§cope
ot testsare used te determine whether the alby
es of ahmkm-n
are often are
wirechopping,
fiveother
processes
for recoverin
she owever,
airclassification
dings (a mixture
of some metal
of with
m shredded for ~a~d~i~g in the scrapyard. For every tonne of shredded steel about 1.5 kg of a~~~i~~~ is recovered. With the mm disused antsmobiles,
can be used
to flcat the aluminu
and
e by hand pickiglg or in a sweat furnace.
zincfrom the
other petals.
Final
Scrap a~~~~~~~ cans come from
SOUPCeS excee are three learels scales,
magnetic sorters a
~~~~ci~a~ solid waste.
mm
that the particles will melt into
large enough
w in the furnace; and (cl ted from the sweated
sweazing -urnace.
mnsistsof a refr
bsx with a 3Poping floor arm meBte64and then rum d5wn % hearth QP collection c mmt be manual8y raked a St flow off Ihe is e hearth. Manual raking is necessary if a rotary arth furnace healed direcily, wit a, or indirectly, with a ceramic-lined, stainless steel tube rotat in a te~~erat~r~es at their lower (d -:otary furnaces are inclined, with weep “lawn the hearth th passes over the weep Drsss recovery is e 3e~arati5~ of me&aKz sroduced whenev a~~~in~~~ The ksn t, which aepenas dirt, spentfluxes and ent isnin anaafter that was taken to prevent %. When the al~~~~~~ contentis suf iross may be sent wever, the majcsri qua1 ~ro~QrtiQ~§ xc mikd and scr or sold to the steel industry for use as ~“urnaceand the rxm-lpound. Wrought ahminum scra sufficient purity can be sdd imarysmeEterwhere dramatic ifficrease ir: conomics are the primary in l:t is used TV make n OS. 5ais practice since t fliith a c;apac.ity sf 73 kh. per year would cost a cm 2% million U.S. :onstructiom of the same sizeplant pro wing can stock fromcan scrap ~.fj- 20 mihn 1J.S. dollars ~~~~~~~h ad ition,recyclist a~n~in~~ 3 .>Yoof the energy nee ed to rmdace new metal. Most secondary alurni and cast scrap (i.e. an i a~~~i~u~castings. In some ca3es ad&km. Scrap (e.g. from wire c~o~~~~g~ can of p vises for al~~~~u~ horn wire c~~~~~~~ inclu mintsand coatings. It
se itslawest
point.The a~~~i~~~ in t to the tap hole and into an ingotmold
L
RECYCLING OF METALS Table 5. Major
Yew industrial Old die-cast X-cast Aircraft
and uses of zirc scrap rriarerials
Sources
Type of scrap Fragmentized
sources
die-cast c&cast
skimmicgs foxing dies
Zinc skimmings Sal-ammoniac skimming:; Zinc dross (top) Zinc dross (bottom) Brass ingoi makers fume New zinc, painted, oxidized, ccrroded Old zinc, painted, oxidized, corroded Prime die casters dross Remelt die-cast (blocks)
7
nonmagnetic portion of crushed automobiles and appliznces rejected castings from die cast operacrons old, oxidized and contaminated accumulators, mostly from automobile wrecking ashes, drorses from melting die-cast scrap forming dies from aircraft and automobile industry hot-dip galvanizing kettles hot-dip galvanizing kettles top of continuous galvanizing kettles bottom of continuous and hot-dip galvanizing kettles baghouse collectors printing pi&s, battery casings, addressograph plates, punchings from rolled zinc roofing, boat anodes, jar tops, spent plating anodes die-casters kettle (high metallic skim) sweating iron-containing and fragmented die cast
User
.--
die-cast alloy disti!lation distillation distillation chemicals die-cast alloy distillation distillation chemicals compounds chemicals (fluxes) distillation distillation
(fluxes) agricultural
chemicals (agriculturai compounds) remelt zinc brass ingot makers gaivaci& remelt zinc distillation
die-cast alioy distillation distillation
Zinc is ~~c~v~~e~ primarily as allay scrap, whit may contain zinc, copper, a&minum, or also recovered from sk~rnrni~~~~ as the major constituent. Zinc major sources and uses of zinc scr maeerials are presented in Table 5. in the form of skimmings, dresses e largest single source of scrap zi xes. These zin~-~o~t~i~~~g wastes are sold rpctly to recyclers. Zinc castings ~The avai&y of fr~gme~tiz~~ di 70s as a result of tremendous expansion of aueomobiie redding. However, owing to the smaller amount of zinc used in the au”iomobiia ew years as a result of increased use of plastics , future zinc recoveffy from e shredding is expected to diminish considerably. rn@bii@S The major role of the essor is in the recovery af zinc from shredd ad. ~~~~ia~~e§. If this is recovered by mechanical means (e.g, fi and/or a number of pr~sblems are created for the ~~~~~rner. If the scree~-iing)rather than. b zinc content of this metering is too low, operation ecycling furnaces is inefficient, ~e~~~t~~~in higher production costs. Excessive aiumi finely divided ziric in the scrap is aunt of §k~rnrn~~g~and therefore the loss o zinc. The recovery of ZixBE: decreased by the of glass, rubber, ~~~errn~~~~by ag between the scrap ssor and the consumer.
Tahe ,1Il--.^,..i.“,.,~iI~~
3.
e. 3.
.Lx~=LA:u ma 13. \,ESS
2.s.
conscmption
Yea1 ,,~“____“,^j_~~=.~~~~:“_ 1976 : 977 1978 :979 l9SO 1981
of magnesium
~oe?s~umption 01 7 7 9 8 a0 7
8 El 9 9 12 4
570 825 225 900 175 044
*Not including magnesium in aluminnm-based Gum used to make aiumirx~m-based alloys
structures snd as
3
scavemger
f5r
scrap 6 -P*.w.--__ Percentage of total magnesium consumption
allay scrap or magne-
s-uxur:I? ~~a§t-~mrmace +on destined
,~~~~~ct~~n.Except when us 301 need to be closely cant purposes, composition xmtain no more than nickel. Therefore, scrap processm esium scrap. Removal ecause magnesium and alumim f these two metals, or
nickel, with some dioys limited to
~gme§i~~-b~~~i~g wastes, such iow prices offered by magnesinm smelters for them.
Percentage of total lead consumption
Year 1976 1977 :978 1379 twl l981
^or onnna;y
659 7% 769 801 676 441
49 53 54 59 63 55
;Lee,
9
RECYCLINGOF MET’~LS
c~~~~ct~r§ of the battery section, from eve the top of the battery, including the posts be battery Is hit against a striker bar to rest of the case and the plates. The remainder a?-es, separatsrs, and acid to fall into a co “lere it is neutralized with lime or ammoni posts and conneclors are separated from the cru more recent concept in processing scrap batteries is to bre battery plates from the casing, followed by heavy me ~~~~~~t~the grid metal from the paste. An alternative m the acid, then charging the entire battery to the s bough about 60 - 65’70of the iead used in batt of the lead used in solder, 25% of the n other products. For ex onsumed by the cable industry and 30% of t is lower rec~c~~~grate is used in very small quantities bo has an average life of 40 years. a large piece of machinery, Virtually all lead scrap is s finds its principal use in the ~rQd~c~i~~ of new batteries, e used to produce other all 7. NIeKEL
ALL
together because of the irn~~rta~~e of nickel, nickeH alloys and stainless are f~~~arne~t~~ly different. Scrap nickel alloys can be used in stainless steel ver, because of the high iron content, stainl s steel scrap cannot be use material for making nickel alloys. Table 8 presents la on the rate of nickel ret IaYickelatloys are usually classified as follows: erallsys possess high strength at high temperatures. A typical ap oys, is In gas turbine engines, ys, such as the Inconels, dustrial scrap is generate content can vary from 20 to aerospace industry in the for d sprues. A major source of obsolete scrap is jet aircraft engines. gh-aickel aIloys and heating alloys are used in c~rr~s~~~- or sxi ications. Nickel contents vary from 28 to iOO%70. metal forming and fabrication. covered as deplete anodes from e~ectrQ~Iati~g~‘This re nickel available for recyclin Table 8. U.S. consumption
Year 1976 I977 1978 1979 1980 1981
Consumption (kt) 47.4 45.8 40.1 52.1 44.8 41.4
of nickel scrap ~~rc~~tage of total nickel consumption 22 23 16 25 22 27
Stainkss steel abys are classified Rnkothree brsad categoraesr 200, 300 and ~400series. As tine 400 series contains only chmnium it will not be treated. The 3 0 series contains a ~~~~Q~i~~an ther elements such as niobium and ~~~y~~e~~~ may also be ?eesent. Appkations of XI@ ies staidess steels are found in kitchen utensils, hospital ~~~i~~e~t~ chemical plants an e aerospace industry. In the 2.00 series, 5 - 10% ~~~~~~~§~ is a to the alloy to promote the f~~~~t~~~ of austenite. emuse nickel serves the same ~Function, the nickel content ‘The users of superalloys a e~~f~~ati~~sfor these dioys, and so r&able segregation and identifk ion of his type 0-f alloy scrap is essenti 0 its recyclirlg and The source or fm e scrap is often a good indisati of its iclentity* ha dition, four relatively simple res (nxignetic testing, spark t g, chemical spot X-ray ~~arese~~~~~ can be use e~t~fi~at~~~= Ef more relia ~.~f~r~atiQ~ or a gua~~~t~~~ e~~~~s~t~~ for chemical ana?ysis 1 gnet test is conducted with a s s it is used to separate pproximate o’r ir_itial
/or sizing. Turnings are usually cm
st~~~~ess-steel scrap is handled. in
e or hammer mifl crusher and
so
:;
RECYCLING OF METALS
the tonnage and degree of recycling of titanium from 19’76to 298%_ ome scrap in the form of cro pings, co3ars aEd turnings. out 86551of total ingot weight ends up as prompt ~~~~~~~~a~ scra restrichio n cor;tamination, only about 35% of total ingot weig melting furnace. The remainder is used for alloying in the st exported, or is lost as grinding and other wastes. A small amount of obsolete scrap, m.ostiy from aircraft maintenance, is also recycled. Tabfe
9 presents
data
OII
Note that 5% of total ingot weight becomes
Table 9. U.S.consumption of titanium scrap*
Year
Consumption, 0)
Percentage of total titanium consumption+
1976 1977 1978 1979 1980 1981
8 360 9 890 11 190 12 700 13 990 I3 420
41 40 38 37 36 34
*Excludes titanium scrap used as an alloying addition. tTotzl consumption includes cmly scrap and sponge; pigment is excluded
scrap must meet very strict standards
for purity,
especial& for aerospace
, because there is very little refining ac.tisn during melting. ~ontam~~a~ts that
cessing include surface oxides res king from exposure to high temperatrares carbons from metalworking ~~bri~a~ts and pieces of cutting tool bits jusually Chips are crushed in a ~ammermi~l to im ing and subsequent briquetbing. The
s are subjected to min
addling and their packin is ther s~~ve~~-va~o~ any foreign metal piece
recessing by the scrap pr -ray s~e~t~os~o~y, segregat ) descales the titaniu surface with nitri
his section col’ers gold, silver and platinumy 1980, when the price of prec al bearing materials have been o scrap is put into a concen siate refinery where it is converted into pure ry sources. ~o~s~rn~tio~ of gold, silver an es 10, 11 and 12, respectively. recious metals are obtaine from a variety of secon fr
ith the exception of
wb~~b silver is recovered.
R. 5. ‘CA.3L.G
and :-ii, YmS
r’abie LO. ‘J.S. consumption
of goId scrap
Consumption Year ----LIBII-.~I_I_~l-~I 1976 i917 1978 1979 1980 I981
Year
_
hi 33 32 43 52 41 49
___I 250 380 090 150 990 460
Consumption 01
__‘____
-1970 1971 1978 1979 1980 !981
3 3 2 2 3 2
216 101 436 410 697 605
Percentage of total goid consumption 23 21 29 35 68 51
Percentage of total siher consumption 60 65 49 49 95 72
.-- ~____l__;.~~
(kg)
ercentage of total piatinum consump:ion
6 704 6 077 6 007 9 620 SO 305 22 182
13 12 11 11 15 12
‘ConscAmption Year ____rr__---~.l__;~,1976 1977 1978 x979 1980 1981
-._
RECYCLING
OF METALS
13
ea”.alytic ~~nve~t~~§ are rern~v~~ from junked cars and then sold for furrher rocessor opens the stainless steel conta:!ners and removes the platinu nina balls or ~~~~y~~rnb that co titute t8;e catalyst. The staintess sree! is sol producer and the catalyst is so to a ~~e~~~~s~~et~~§refiner spec
I. 2. 3. 4. 5. 6. 3.
H. Aher, Toward a national policy for secondary material symposium on resource recovery and environmental issues of industrial solid wastes. Resotlrces and Conservation. Elsevie:, Amsterdam (19%2). Arthur D. Little Inc., Proposed Industrial Recovered Materials Utiiization Targets for the Metals and Metals Prodt~ts Industry. U.S. Department of Energy, Washington, DC (1979). attelie Columbus Laboratories, A Study to Identify Opportunities for Increased Solid Waste Utiiizatiotr: 1~ Generai; II. Metds. National Technical Information Service, Springfield, Virginia (1977). Battelle Columbus Laboratories, Identification of Opportunitiesfor Increased Recycling ofFerrous Solid ;iWaste. National Technical Information Service, Springfield, Virginia (L972). F, V. Carilio, M H. Hibpshman, and R. D. Rosenkranz, Recovery of Secondary Copper and Zinc i.n fhe United States. U,S. Bureau of Mines, Washington, DC (1974). P. Fine, H. W. Rasher, and S. Wakesberg, (eds), Operations :n the Nonferrow Scrap Metai Industry Today. National Association of Recycling Industries, New York (1973) C. L. Kusik and C. B. Kenehan, Energy Use Patte~ns~or~~eta~Recycli~g. US Bureau of Mines, Wastington, DC
(1978). %. G. W. Rheimers, S. A. Rholl, and A. B. Dahlby, Density separations of nonferrous scrap metals with magnetic fhtids, P~Qc. 5th Mineral Waste Utilization Symposium. U.S. Bureau of Mines, Washington, DC (1976). 9. Do L. Siebert, Impact of Technoiogy on the Commercial Secondary Aluminum Industry. U.S. Bureau of Mines, 10. M. 4. Spendlove, Methods for Producing Secondary Copper. U.S. Bureau of Mines, Washington, DC (1961). 11. U.S. Bureau of Mines, Minerals Yearbook. U.S. Bureau of Mines. Wasb~~~ton~ DC (19801. urea” of Mines, Mineral Co~modjty Summaries. U.S. Bureau of M&es,‘Washingtdn, DC (1981). 12. 13. U.S. National Association of Recycling Industries, Recycledlead in the United States: a Study of Current .Wm-ket Trends and Projections. U.S. National Association of Recycling Industries, New York (1975). 14. U.S. b!ational Association of Recycling Industries, Recycling of Nickel Alloys and Stainless Steel Scra_D. U.S.
~at~o~a~ Association of Recychng Industries, New York (1977). 15. U.S. National Association of Recycling Industries, Wire and Cable Chopping and Recovery of Metals Jrom Shredder Operutions. US National Association of Recycling Industries, New York (1977). 96. U.S. Nationai Association of Recycling Industries, Recycling of Zinc. U.S. National Association of Recycling Industries, New York (197%). 17. U.S. National Association of Recycling Industries, liecy&ing Precious Metals. U.S. National Association of Recycfing Industries, New York (1979). 1%. U.S. rational Association of Recycling Industries, Recycling Copper and Brass. U.S. National Association of Recychng Industries, New York (1980). 19. U.S. National Association of Recycling Industries, ~e~ycl~~~~6~~i~~~. U.S. National Association of Recycilng ~~~~st~~es~New York (1981). 20. U.S. National Association of Recycling Industries, Recycled ~et~~$ in the 1980s. U.S. National Association of ustries, New York (19%2).
Printed
& Recycling,
in Great
‘id.
1C, No.
!, pp.
G36i -3658/87 SJ.XT Pergamon Joutnais
1 - 13, i987
Britain.
.CG ‘Ad.
Room 816, Bureau oJ^Mnes, 2401 East Street, NW Washington DC 20246, W.S.A.
are the first two steps recycling. Scrap can be &issified revert, or run aram (b) prompt irldu§PriaS; and (c) ~ost~on.s~~~r or obsolete. ~nr~~ase~ scrap consists of the last tw egsries. Sin.ce home scrap is recycled within the p nt where it is generated and re~~~ir~sno tional processing priorto scrap will be discussed. Prompt industri crap is usua8ly new clean processing
of scrap
egsries:(a)
home,
aterid generated during an in st~~~~~~~gof a~t~~.~~~il~ fenders) scrap is usuaily sdd by the generat n come from a mce scrap comes from a va ient use. The primary roles of the scrap processor are to collect, accumulate, sorts e, market and distribute scrap. S ding is done foil as shearing, baBing or er of activities, s tisn may invoQve any of a nu
Ferrous upplied a slowly increasing portion of the iron CQ~s~rne~in the U.S.A. between 1 s scrap has been used t 81 (Table I>* Almost all of for copper cementation (a cast iron. Small ~~~~~t§ have ucrion @f ferroalloys. errors scrap is usually i~e~t~~i~~ an sorsed according to source or prior use, As ferrons with nonferrous scrap, stainless tee1 and specialty alky scrap, iqaes are economic. ashen mixe scrap is received, it is sold 8s an s of the ultimate cons
Artick published in Encyclopedia
~JMateriab
Scieiace and E&zeering
(Pergzmon
Press, 1986).
2
Percentage of Year
gl__l____~_m__/__l,_~~-
-976 971 - 978 979 -980 ‘981
Consumption (kt) _,” 37 39 37 42 36 37
590 e40 860 680 590 460
total ferrous
~~-Y-_I
consumption
3: 34 36 35 33 35
Shears i-educe aige ~3ieeesof scrap (e.g_ sthuceurai ~~~b~~s~ to a dimension s1uita3~emoi:~~ii2.i
charging, usually I- 1.5 m long. Automobiles pressed into logs also are sheared. Two types cd shear are used: guillotine and alligator shexs. The guillotine shear is the larger of the two, mx&ing of a movable he is b~~~a~~~~~l~~ force t a s~at~~~~r~anvil. The scrap to k cut rests on and protru nd the anvil. Alligae ararsfunction 1ike giant s~ksm-s: except onajr the upper part is movable. e, light-gauge scrap is ~~~~~~~t~~baled or briquetted, Exam s of this type of material sheet remaining after a stampin or punching ~~~~~t~Q~~a turnings (meta:. removed in a ~~~~~i~~~goperation). In ad ition, entire ~~t~~~b~~es an a~~~~a~ce§are sometimes 3alers consist of hydraulic ~y~~~~~~s that compress the scrap by ~~s~~~~git against fixed walRsof I cube. Steel briquetters have a pajir sf rotating drums wit31 a series of cavities aromd the The scrap (e.g. turnings) assw.mes drum into which the scrap is compresse and ~~~~~§~o~s of t cavities. rs are used mostly r ~~e~~r~~g light scrap (e.g automobiles and large home appEiances). They consist of a series of steel b~~~e~s mounted OE rotating drum. The “aammers pass by a series o car, ~~~$~~~~e~or other scrap between the i-sized chunks. Magnetic separation remxes the l?ammers causes it to be qu ic materials such as glass, ru ~‘errous metal from ~~~fer~~~s metals and no3 snd dirt. The resukting ferrous product has the advantages of increased p xmsistency, handling, tra~~~~r~~t~~~ and besting ~b~~~~~~~~st~cs~ En 1 estimated 200 automobile shredders operating in the USA wit a capacity nf more thzn 13 Mt 3er year. The fcxrous fraction of ~~~~~~~a~sdid waste presents a unique case, This naterid &maybe 33L.jdirectly to steel mills for blending with ot etinner, or to a scrap y:ocesssr. The cans must be cleaned of paper scrap processor ~priasrts ~~t~~~i~g~ The deti H - NaNO, solution. This proces also removes any Serrous scrap has cmxsiderably Increase value, and the tin Can be recovered fro dectrolysis.
RECYCLING &ower
purity
nmnhole covers.
a
OF MET.%LS
usuaaly 1,c restricted to a~~~~~~t~~~swith less strongest chemicai aA y s~e~~f~~~ti~~s. These include the ~~~~f~~t~~e of reinforcing bars and igh-purity scrap can be used to make any grade of steel QP cast iron.
scrap
ications are that Cwpper-bearing scrap materiaks are among the ddest used by man, an these nnateriais were recycled by the earliest civilizations. Extensiv continued up to the present time, when copper-bearing scrap accou copper raw materials in 19’79and 4980 (Table 2). Depeding on the meIting technique employed, using scrap to prsduce copper requires only 3 - 4007aof the energy needed to produce pure copper from ore. ~~~~e~-be~~~~g scrap is divided into a number of grades. N0.l co, er scrap fixgusa be unalloyed, as it is used directly to make wirebars. No.2 copper scrap is refined e~e~t~~~~t~~~~~~ and therefore may contain smne impurities, though a copper content of at least 94 - 96% is refinery; its copper content nosmdiy required. Light copper also ass625through an e~e~t~Q~yt~~ must exceed 92%. Refinery-grade brass must contain at least 41.3% co material generally contains less than 40% copper. These last two in a blast furnace and blown in a converter prior to ekctrolyti ~Q~~er-bea~i~g scrap can be used by tube mills, refieers, brass spesiahty csmparies. The end-use determines the preparation of the s ot refine e~e~t~~~~~c~~~y, metallic ~~~t~~~~~t~o~ of scr mvever, small amounts may be ~~~e~t~~?~e~ epending on the user’s ability to fire refine. efiners can produce ap must first be c copper scrap, but No. 2 and light cop ekctrsiy:ically before it can be used for this purpose. rass mills usually use No. 1 copper and brass scrap in their melts in ~~~b~nat~Q~ with pure copper. The composition of brass scrap must be known and kept within narrow limits so as to keep ingot rass vxt made fmn the scrap wi pply aI4oys of known, fixed ety of copper-bearing scrap. chemicals, electraplating, castings (bst and steehmaking ~ D Brompt industrial ~~~~er-bea~~~g scra which accounts for $0 - 70% of r or exanqde, scrap tu~m~~g$ generated by a variety of i~~~st~~a~operation machar!es amour,t to up to 65% of the UK&Sinclude stam drawing rejects, die shavings and short ostcoarsumer scrap mc rail, e~e~t~~~~~s~power utility and defense ips; and in spent sheU casings. ateria!‘s color, spectrosco chemicai analysis, or, in some cases, mag required for the first three methods. Togethe past use, the cob of a clean surface may be ali that is needed to a se~~~~~~t~tat~~~ analysis of an alloy, but this informatios is &en sufficient for sorting Spot testing iavolves obs or lack thereof, between vari
processor.
Traditisnal
ues is used to ~~e~~re ~~~~e~-be~~~~~scra processes include shearing to the size required
by the sustcme:,
?
1. 3. ‘Lka,‘LAi.% am
13. NESS
‘xiqueetmg m crus&ing 3i”chsn and ~~~h~~~i~b~materials “,e.g. Eurnjlngs and 3ormgs], ~!nagnck 3eparation to remove iron, cleaning and One new technique is ~h’~~~~~g of copper -wire scrap. Large, stiff pieces sf WYR d~a: Tresheared prior to chopping. Bales tf wire must broke2 do~wnand are usuaily cut up with an &gator shear. The major steps t I-I consist sf choppifig in three sta es, with magm3is separaticm to remove ferrous ~~~tarn~~a~its fo’cowing the first stage and sizing f~~~~~~~~the second stage. The third stage handles ~~~~~berate~wire from the air sepa ion process which 5Alows sizing. Both the coarse and ~~t~r~~e~~atesize fractions are psocesse y air separation to x-educe four fractions: (a> clean metal, (b) liberate metal with some insulation ~~~ta~~~~~i~~~ :c> unliberated wire, and (d) clean insulation. Shredded automobiles also yield ~~~~er-b~ar~~g scrap. Following magnetic recovery of the Cerrous metals, the ~~~f~rro~s rejects can be processe ber of techrkpes. The n be removed by air separation and n, and/or heavy media copper-bearing metals can then be ban e a~~~~~~rn and zinc are goated in a heavy medium. Cryogenics (i.e. cooling scrap to t I-es as 1ow as - 1 copper from items such as small m iS, ~ra~sf~rmer5i gener When exposed to these very low tern become brittle, whereas copper remai ble. Therefore, crus after cooling will allow relatively large pieces of copper to be separa materials by screening.
RECYCLIivG
5
OF METALS
is needed,
If more i~fQr~ati0~
a
spec&ro§cope
ot testsare used te determine whether the alby
es of ahmkm-n
are often are
wirechopping,
fiveother
processes
for recoverin
she owever,
airclassification
dings (a mixture
of some metal
of with
m shredded for ~a~d~i~g in the scrapyard. For every tonne of shredded steel about 1.5 kg of a~~~i~~~ is recovered. With the mm disused antsmobiles,
can be used
to flcat the aluminu
and
e by hand pickiglg or in a sweat furnace.
zincfrom the
other petals.
Final
Scrap a~~~~~~~ cans come from
SOUPCeS excee are three learels scales,
magnetic sorters a
~~~~ci~a~ solid waste.
mm
that the particles will melt into
large enough
w in the furnace; and (cl ted from the sweated
sweazing -urnace.
mnsistsof a refr
bsx with a 3Poping floor arm meBte64and then rum d5wn % hearth QP collection c mmt be manual8y raked a St flow off Ihe is e hearth. Manual raking is necessary if a rotary arth furnace healed direcily, wit a, or indirectly, with a ceramic-lined, stainless steel tube rotat in a te~~erat~r~es at their lower (d -:otary furnaces are inclined, with weep “lawn the hearth th passes over the weep Drsss recovery is e 3e~arati5~ of me&aKz sroduced whenev a~~~in~~~ The ksn t, which aepenas dirt, spentfluxes and ent isnin anaafter that was taken to prevent %. When the al~~~~~~ contentis suf iross may be sent wever, the majcsri qua1 ~ro~QrtiQ~§ xc mikd and scr or sold to the steel industry for use as ~“urnaceand the rxm-lpound. Wrought ahminum scra sufficient purity can be sdd imarysmeEterwhere dramatic ifficrease ir: conomics are the primary in l:t is used TV make n OS. 5ais practice since t fliith a c;apac.ity sf 73 kh. per year would cost a cm 2% million U.S. :onstructiom of the same sizeplant pro wing can stock fromcan scrap ~.fj- 20 mihn 1J.S. dollars ~~~~~~~h ad ition,recyclist a~n~in~~ 3 .>Yoof the energy nee ed to rmdace new metal. Most secondary alurni and cast scrap (i.e. an i a~~~i~u~castings. In some ca3es ad&km. Scrap (e.g. from wire c~o~~~~g~ can of p vises for al~~~~u~ horn wire c~~~~~~~ inclu mintsand coatings. It
se itslawest
point.The a~~~i~~~ in t to the tap hole and into an ingotmold
L
RECYCLING OF METALS Table 5. Major
Yew industrial Old die-cast X-cast Aircraft
and uses of zirc scrap rriarerials
Sources
Type of scrap Fragmentized
sources
die-cast c&cast
skimmicgs foxing dies
Zinc skimmings Sal-ammoniac skimming:; Zinc dross (top) Zinc dross (bottom) Brass ingoi makers fume New zinc, painted, oxidized, ccrroded Old zinc, painted, oxidized, corroded Prime die casters dross Remelt die-cast (blocks)
7
nonmagnetic portion of crushed automobiles and appliznces rejected castings from die cast operacrons old, oxidized and contaminated accumulators, mostly from automobile wrecking ashes, drorses from melting die-cast scrap forming dies from aircraft and automobile industry hot-dip galvanizing kettles hot-dip galvanizing kettles top of continuous galvanizing kettles bottom of continuous and hot-dip galvanizing kettles baghouse collectors printing pi&s, battery casings, addressograph plates, punchings from rolled zinc roofing, boat anodes, jar tops, spent plating anodes die-casters kettle (high metallic skim) sweating iron-containing and fragmented die cast
User
.--
die-cast alloy disti!lation distillation distillation chemicals die-cast alloy distillation distillation chemicals compounds chemicals (fluxes) distillation distillation
(fluxes) agricultural
chemicals (agriculturai compounds) remelt zinc brass ingot makers gaivaci& remelt zinc distillation
die-cast alioy distillation distillation
Zinc is ~~c~v~~e~ primarily as allay scrap, whit may contain zinc, copper, a&minum, or also recovered from sk~rnrni~~~~ as the major constituent. Zinc major sources and uses of zinc scr maeerials are presented in Table 5. in the form of skimmings, dresses e largest single source of scrap zi xes. These zin~-~o~t~i~~~g wastes are sold rpctly to recyclers. Zinc castings ~The avai&y of fr~gme~tiz~~ di 70s as a result of tremendous expansion of aueomobiie redding. However, owing to the smaller amount of zinc used in the au”iomobiia ew years as a result of increased use of plastics , future zinc recoveffy from e shredding is expected to diminish considerably. rn@bii@S The major role of the essor is in the recovery af zinc from shredd ad. ~~~~ia~~e§. If this is recovered by mechanical means (e.g, fi and/or a number of pr~sblems are created for the ~~~~~rner. If the scree~-iing)rather than. b zinc content of this metering is too low, operation ecycling furnaces is inefficient, ~e~~~t~~~in higher production costs. Excessive aiumi finely divided ziric in the scrap is aunt of §k~rnrn~~g~and therefore the loss o zinc. The recovery of ZixBE: decreased by the of glass, rubber, ~~~errn~~~~by ag between the scrap ssor and the consumer.
Tahe ,1Il--.^,..i.“,.,~iI~~
3.
e. 3.
.Lx~=LA:u ma 13. \,ESS
2.s.
conscmption
Yea1 ,,~“____“,^j_~~=.~~~~:“_ 1976 : 977 1978 :979 l9SO 1981
of magnesium
~oe?s~umption 01 7 7 9 8 a0 7
8 El 9 9 12 4
570 825 225 900 175 044
*Not including magnesium in aluminnm-based Gum used to make aiumirx~m-based alloys
structures snd as
3
scavemger
f5r
scrap 6 -P*.w.--__ Percentage of total magnesium consumption
allay scrap or magne-
s-uxur:I? ~~a§t-~mrmace +on destined
,~~~~~ct~~n.Except when us 301 need to be closely cant purposes, composition xmtain no more than nickel. Therefore, scrap processm esium scrap. Removal ecause magnesium and alumim f these two metals, or
nickel, with some dioys limited to
~gme§i~~-b~~~i~g wastes, such iow prices offered by magnesinm smelters for them.
Percentage of total lead consumption
Year 1976 1977 :978 1379 twl l981
^or onnna;y
659 7% 769 801 676 441
49 53 54 59 63 55
;Lee,
9
RECYCLINGOF MET’~LS
c~~~~ct~r§ of the battery section, from eve the top of the battery, including the posts be battery Is hit against a striker bar to rest of the case and the plates. The remainder a?-es, separatsrs, and acid to fall into a co “lere it is neutralized with lime or ammoni posts and conneclors are separated from the cru more recent concept in processing scrap batteries is to bre battery plates from the casing, followed by heavy me ~~~~~~t~the grid metal from the paste. An alternative m the acid, then charging the entire battery to the s bough about 60 - 65’70of the iead used in batt of the lead used in solder, 25% of the n other products. For ex onsumed by the cable industry and 30% of t is lower rec~c~~~grate is used in very small quantities bo has an average life of 40 years. a large piece of machinery, Virtually all lead scrap is s finds its principal use in the ~rQd~c~i~~ of new batteries, e used to produce other all 7. NIeKEL
ALL
together because of the irn~~rta~~e of nickel, nickeH alloys and stainless are f~~~arne~t~~ly different. Scrap nickel alloys can be used in stainless steel ver, because of the high iron content, stainl s steel scrap cannot be use material for making nickel alloys. Table 8 presents la on the rate of nickel ret IaYickelatloys are usually classified as follows: erallsys possess high strength at high temperatures. A typical ap oys, is In gas turbine engines, ys, such as the Inconels, dustrial scrap is generate content can vary from 20 to aerospace industry in the for d sprues. A major source of obsolete scrap is jet aircraft engines. gh-aickel aIloys and heating alloys are used in c~rr~s~~~- or sxi ications. Nickel contents vary from 28 to iOO%70. metal forming and fabrication. covered as deplete anodes from e~ectrQ~Iati~g~‘This re nickel available for recyclin Table 8. U.S. consumption
Year 1976 I977 1978 1979 1980 1981
Consumption (kt) 47.4 45.8 40.1 52.1 44.8 41.4
of nickel scrap ~~rc~~tage of total nickel consumption 22 23 16 25 22 27
Stainkss steel abys are classified Rnkothree brsad categoraesr 200, 300 and ~400series. As tine 400 series contains only chmnium it will not be treated. The 3 0 series contains a ~~~~Q~i~~an ther elements such as niobium and ~~~y~~e~~~ may also be ?eesent. Appkations of XI@ ies staidess steels are found in kitchen utensils, hospital ~~~i~~e~t~ chemical plants an e aerospace industry. In the 2.00 series, 5 - 10% ~~~~~~~§~ is a to the alloy to promote the f~~~~t~~~ of austenite. emuse nickel serves the same ~Function, the nickel content ‘The users of superalloys a e~~f~~ati~~sfor these dioys, and so r&able segregation and identifk ion of his type 0-f alloy scrap is essenti 0 its recyclirlg and The source or fm e scrap is often a good indisati of its iclentity* ha dition, four relatively simple res (nxignetic testing, spark t g, chemical spot X-ray ~~arese~~~~~ can be use e~t~fi~at~~~= Ef more relia ~.~f~r~atiQ~ or a gua~~~t~~~ e~~~~s~t~~ for chemical ana?ysis 1 gnet test is conducted with a s s it is used to separate pproximate o’r ir_itial
/or sizing. Turnings are usually cm
st~~~~ess-steel scrap is handled. in
e or hammer mifl crusher and
so
:;
RECYCLING OF METALS
the tonnage and degree of recycling of titanium from 19’76to 298%_ ome scrap in the form of cro pings, co3ars aEd turnings. out 86551of total ingot weight ends up as prompt ~~~~~~~~a~ scra restrichio n cor;tamination, only about 35% of total ingot weig melting furnace. The remainder is used for alloying in the st exported, or is lost as grinding and other wastes. A small amount of obsolete scrap, m.ostiy from aircraft maintenance, is also recycled. Tabfe
9 presents
data
OII
Note that 5% of total ingot weight becomes
Table 9. U.S.consumption of titanium scrap*
Year
Consumption, 0)
Percentage of total titanium consumption+
1976 1977 1978 1979 1980 1981
8 360 9 890 11 190 12 700 13 990 I3 420
41 40 38 37 36 34
*Excludes titanium scrap used as an alloying addition. tTotzl consumption includes cmly scrap and sponge; pigment is excluded
scrap must meet very strict standards
for purity,
especial& for aerospace
, because there is very little refining ac.tisn during melting. ~ontam~~a~ts that
cessing include surface oxides res king from exposure to high temperatrares carbons from metalworking ~~bri~a~ts and pieces of cutting tool bits jusually Chips are crushed in a ~ammermi~l to im ing and subsequent briquetbing. The
s are subjected to min
addling and their packin is ther s~~ve~~-va~o~ any foreign metal piece
recessing by the scrap pr -ray s~e~t~os~o~y, segregat ) descales the titaniu surface with nitri
his section col’ers gold, silver and platinumy 1980, when the price of prec al bearing materials have been o scrap is put into a concen siate refinery where it is converted into pure ry sources. ~o~s~rn~tio~ of gold, silver an es 10, 11 and 12, respectively. recious metals are obtaine from a variety of secon fr
ith the exception of
wb~~b silver is recovered.
R. 5. ‘CA.3L.G
and :-ii, YmS
r’abie LO. ‘J.S. consumption
of goId scrap
Consumption Year ----LIBII-.~I_I_~l-~I 1976 i917 1978 1979 1980 I981
Year
_
hi 33 32 43 52 41 49
___I 250 380 090 150 990 460
Consumption 01
__‘____
-1970 1971 1978 1979 1980 !981
3 3 2 2 3 2
216 101 436 410 697 605
Percentage of total goid consumption 23 21 29 35 68 51
Percentage of total siher consumption 60 65 49 49 95 72
.-- ~____l__;.~~
(kg)
ercentage of total piatinum consump:ion
6 704 6 077 6 007 9 620 SO 305 22 182
13 12 11 11 15 12
‘ConscAmption Year ____rr__---~.l__;~,1976 1977 1978 x979 1980 1981
-._
RECYCLING
OF METALS
13
ea”.alytic ~~nve~t~~§ are rern~v~~ from junked cars and then sold for furrher rocessor opens the stainless steel conta:!ners and removes the platinu nina balls or ~~~~y~~rnb that co titute t8;e catalyst. The staintess sree! is sol producer and the catalyst is so to a ~~e~~~~s~~et~~§refiner spec
I. 2. 3. 4. 5. 6. 3.
H. Aher, Toward a national policy for secondary material symposium on resource recovery and environmental issues of industrial solid wastes. Resotlrces and Conservation. Elsevie:, Amsterdam (19%2). Arthur D. Little Inc., Proposed Industrial Recovered Materials Utiiization Targets for the Metals and Metals Prodt~ts Industry. U.S. Department of Energy, Washington, DC (1979). attelie Columbus Laboratories, A Study to Identify Opportunities for Increased Solid Waste Utiiizatiotr: 1~ Generai; II. Metds. National Technical Information Service, Springfield, Virginia (1977). Battelle Columbus Laboratories, Identification of Opportunitiesfor Increased Recycling ofFerrous Solid ;iWaste. National Technical Information Service, Springfield, Virginia (L972). F, V. Carilio, M H. Hibpshman, and R. D. Rosenkranz, Recovery of Secondary Copper and Zinc i.n fhe United States. U,S. Bureau of Mines, Washington, DC (1974). P. Fine, H. W. Rasher, and S. Wakesberg, (eds), Operations :n the Nonferrow Scrap Metai Industry Today. National Association of Recycling Industries, New York (1973) C. L. Kusik and C. B. Kenehan, Energy Use Patte~ns~or~~eta~Recycli~g. US Bureau of Mines, Wastington, DC
(1978). %. G. W. Rheimers, S. A. Rholl, and A. B. Dahlby, Density separations of nonferrous scrap metals with magnetic fhtids, P~Qc. 5th Mineral Waste Utilization Symposium. U.S. Bureau of Mines, Washington, DC (1976). 9. Do L. Siebert, Impact of Technoiogy on the Commercial Secondary Aluminum Industry. U.S. Bureau of Mines, 10. M. 4. Spendlove, Methods for Producing Secondary Copper. U.S. Bureau of Mines, Washington, DC (1961). 11. U.S. Bureau of Mines, Minerals Yearbook. U.S. Bureau of Mines. Wasb~~~ton~ DC (19801. urea” of Mines, Mineral Co~modjty Summaries. U.S. Bureau of M&es,‘Washingtdn, DC (1981). 12. 13. U.S. National Association of Recycling Industries, Recycledlead in the United States: a Study of Current .Wm-ket Trends and Projections. U.S. National Association of Recycling Industries, New York (1975). 14. U.S. b!ational Association of Recycling Industries, Recycling of Nickel Alloys and Stainless Steel Scra_D. U.S.
~at~o~a~ Association of Recychng Industries, New York (1977). 15. U.S. National Association of Recycling Industries, Wire and Cable Chopping and Recovery of Metals Jrom Shredder Operutions. US National Association of Recycling Industries, New York (1977). 96. U.S. Nationai Association of Recycling Industries, Recycling of Zinc. U.S. National Association of Recycling Industries, New York (197%). 17. U.S. National Association of Recycling Industries, liecy&ing Precious Metals. U.S. National Association of Recycfing Industries, New York (1979). 1%. U.S. rational Association of Recycling Industries, Recycling Copper and Brass. U.S. National Association of Recychng Industries, New York (1980). 19. U.S. National Association of Recycling Industries, ~e~ycl~~~~6~~i~~~. U.S. National Association of Recycilng ~~~~st~~es~New York (1981). 20. U.S. National Association of Recycling Industries, Recycled ~et~~$ in the 1980s. U.S. National Association of ustries, New York (19%2).