ISIJ International, Vol. 37 (1997), No. 3, pp. 198-206

Review

Necessity of Scrap Reclamation Technologies

Conditions of Technical Developmentand Present

Katsuhiko NORO.Mitsugu TAKEUCH11)and YoshimasaMIZUKAM12)

Nippon Steel Corporation and NewSteelmaking Process Forum, Otemachi. Chiyoda-ku, Tokyo, IO0-71 Japan.

1) Nippon Steel Corporation and NewSteelmaking Process Forum, Shintomi, Futtsu, Chiba-ken, 293 Japan.2) TheJapan Researchand DevelopmentCenter for Meta]s, Environment- Friendly Steelmaking Process Division, Toranomon,Minato-ku. Tokyo, I05 Japan.

(Received on July 22. 1996; accepted in final form on November12. 1996)

"NewSteelmaking Process Forum"wasinaugurated in 1991 for the purpose of developing an innovative

process capable of contributing to global environmental protection. such as the effective utilization of iron

resource and the reduction of carbon dioxide generation, by recycling the total volume of scrap. This paperoutlines the Forum's activities.

The contents of tramp elements, copper and tin, of waste scrap were predicted to increase to I .5 timesand I .2 times the present values in 201 O. Even if the largest possible amountof waste scrap is recycledwithin the al]owable ranges of steel product composition values. 150-300 million tons of waste scrap will

be heaped up in Japan. Therefore, copper and tin removal technologies were developed. For the massimpurity (copper), the technology to crush scrap at low temperature at the time of pretreatment and thetechnology to automatically discriminate and separate impurity-attached scrap were developed. For thesurface layer impurity (tin), the technology to remove it by oxidation in a high-temperature oxidizing

atmosphere at the time of preheating and melting and the technology to remove it by evaporation in aweakly oxidizing atmosphereweredeveloped. For zinc, the technology to removeit from dust in an externally

heated kiln wasdeveloped.

KEYWORDS:scrap; reclamation, copper; tin; zinc, preheating; melt.

1. Introduction

Domestic accumulation of steel, a material close to

our daily life, is estimated to have reached a billion tonsalready. This is the world's second largest after 3.3 billion

tons of the United States. Japan stands third after the

United States and Germanyin steel accumulation perheadof population and first with Germanyin accumula-tion density per unit area of land, which is about 10

times that of the United States,1) Together with such anenormousincrease in steel accumulation, the occurrenceof waste scrap is also increasing because steel products

are incessantly scrapped after their service life ends.It is commonknowledge that iron and steel scrap is

recycled and reused. Since the process for steelmaking byremelting scrap doesnot needreduction energy, its energyconsumption is one-third to one-sixth that of the processfor steelmaking from iron ore, and its generation ofcarbon dioxide is also smaller in proportion to energyconsumption. Thus the maximumutilization of scrap is

desirable for global environmental protection. Recently,

however, the quality of scrap as steelmaking rawmaterialhas greatly worsened, making it difficult to recycle scrap.If this condition is left as it is, even the serious situationthat unrecyclable scrap is heapedup throughout the landwill be anticipated.

Toprevent the arrival of such a situation, it is necessaryto develop an innovative process capable of contributing

to global environmental protection, such as the effective

utilization of iron resources and the reduction of carbondioxide generation, by recycling the total volumeof scrap.

To this end the "NewSteelmaking Process Forum"to beengagedin the development of such a process under aneight-year program beginning in 1991 was inauguratedat The Japan Research and Development Center for

Metals (JRCM).This paper reports on the outline of the

Forum's activities.

2. Research and DevelopmentStructure of NewSteel-

making Process Forum

Figure I shows the schedule of technical develop-ment.12) The research and development of the NewSteelmaking Process Forumare conducted as part ofthe project related to global environmental industrial

technology research and development of NewEnergyand Industrial Technology DevelopmentOrganization

(NEDO).Regarding the "comprehensive basic research"

section of the research and development, (1) the in-

vestigation of the future trend of scrap, (2) the research

and evaluation for scrap reclamation/melting technolo-gies and (3) the evaluation of an integrated process and

C 1997 ISIJ 198

ISIJ Internationa], Vol. 37 (1997), No. 3

Item of Research 1991 1992 1993 1994 Igg5 199s 1997 1998

(1 )Comprehensive Basi c Research

Investi9aticn of the future trend of scrap

I FResearch and eval uaticn for scrap n lrecl amaticn/mel ting techniques t n

e aEval uaticn of an integrated process and r 1list~ng of pending tasks i

m Ev

(2)Research of a reclamation process and E ascrap metal v l

a UStudy on the tramp element removal l atechniques using solid phase processing u t

a iStudy on the tramp element removal t otechniques using liquid phase processing i n

oStudy of the systematization n

(3)Research of a preheating and melting process

(4)Research of a total system eval uation

Fig. l. Schedule oftechnical development.

listing of pending tasks were selected as the subjects for

studies to be entrusted to Research Institute of Innova-tive Technology for the Earth (RITE) by NEDO,andthe targets and policies of the studies in the latter halfof the research to be started in 1995 were clarified byl994.

Also, the "research of a reclamation process for scrapmetal", the "research of a preheating and melting proc-ess" and the "research of a total system evaluation"

are nowbeing conducted as joint and entrusted studies

of NEDOand JRCM.Thesestudies are participated in

by 12 companies consisting of six Japanese integratedsteelmakers, five Japanese electric-furnace steelmakersand one foreign company.

'

3. Study of the Future Trend of Scrap

3. l. Prediction of Steel Accumulation Volumeand SteelDiscard Volume

Scrap is roughly classified into homescrap, marketscrap and imported scrap. Market scrap is classified

further into process scrap which occurs in customers steel

fabrication processes and obsolete scrap which occurswhenproducts for which steel is used are discarded aftertheir service life ends. Figure 2shows the change in thegeneration of scrap.10) Thehomescrap volume and the

process scrap volume have remained approximately 12million tons/year and 7million tons/year in recent yearsdue to the leveling off of steel production and the im-

provement of steel manufacturing processes representedby continuous casting. What is estimated to increaselargely in the future is the volumeof obsolete scrap whicheven at present accounts for 50 o/o of the total volumeof

scrap.Figure 3showsthe balance betweenscrap supply and

199

demand,madetaken from the statistics by JISF. In 1990,for instance, about 99 million tons of steel wasproducedin Japan. As 30 million tons wasexported directly andindirectly, the remaining 69 million tons wasnewly addedto the cumulative steel stock. Onthe other hand, steel

discarded in that year was 26 million tons. Therefore,the net increase in the cumulative steel stock wasabout40 million tons. Figure 4showsthe relation between thecumulative steel stock and amount of obsolete scrapgenerated. 11) If this trend continues, the cumulative steel

stock is estimated to reach about 1800 million tons in

2010. According to the past statistics, however, the ob-solete scrap occurs at a rate of about 2.70/, each yearto the cumulative steel stock. If this trend remains un-changed, 45 million tons or nearly double the presentwill be discarded in 2010.2) This accounts for about 80 olo

of the total scrap volume occurring in that year.

3.2. Factors WorseningScrap Quality and Prediction ofFuture Scrap Quality

Of waste scrap 80 o/o is an accumulation of variouskinds of steel materials discarded from the construction,machinery and automotive areas.

Therefore, it is not easy to find out the chemicalcomposition of scrap, and fact-finding is not sufficiently

conducted, neither. Table I shows the standards whichhave been enacted by Non-Integrated Steel Producers,and are used at present for scrap acceptance inspection.

Scrap is classified mainly by shape into "heavy scrap","shredded scrap" and "pressed scrap". It was con-ventionally recognized that heavy scrap Hl and H2,which mainly. originate from plates and sections, con-tained relat, ively little impurities becauseplates and sec-tions particularly have been products of blast furnacesand basic oxygen furnaces. However, in these product

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~

70, ooo

60, ooo

50, ooo

40, ooo

30, oOo

20, ooo

1o, ooo

o

Import scrapObsolete scrapProcess scrapHomescrap

80 81 82 83 ' 84 * 85 ' 86 ' 87 ' 88 ' 89 ' 90 ' 91

Fiscal yearFig. 2. Changein the generation of scrap in Japan.

92 ' 95 2000 2005 2010

lron ore

Blast furnace-Converter

Castings

3OOO

Direct export15,000

Indirect export15,200

Cumulativesteel stock1,000,000

Fig. 3. Balance between iron and steel output and scrap supply in Japan in 1990 (1 OOOt).

1,100

co 1,000

co

E!loo

li5

~2

o>i2DE:D

ooc:)

oE

900

800

700

600

500

400

300

200

100

O

Amountof cumulativesteel stock

Ratio of obsolete scrap generated tocumulative steel stock (1ine of 2,7%)

rf•Fd•Yrv ~

Amountof obsolete scrapgenerated

Fig. 4.

110

100

90

80

70

60

50

40

30

20

lO

O

cocoE

~)(D

o(D

cQ,

o)CLaoc,

(D

o~)oocDoE

1955 65 67 69 71 73 75 77 79 81 83 85 87 89 1991

Relation betw~encumulative steel stock and amountof obsolete scrap generated.

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Table 1. Purchase specification of the market scrap.

Species Grade Class Specification and others

ObsoIete Heavy scrap HS ~;6mmThickplate, Shaped steel,

Bar, etc.,

scra p H1 ~6mmThick pl ate, Shaped steel,

Bar, etc.,

H2 3-6mmStoel plate, Round bar, heavy machine scrap

H8 1-3mmThinplato 8nd others

shredded scrap A Car bodies

B Zn coated plate and etc.,

c Sn coated plate

Pressod scr8p A Car bodies

B Zn coated plate and etc.,

c Sn coated plate

Process Newplate BusheIingscrap BundIe

Steel turnings Continued or fragnlented

Table 2. Chemical compositions of tramp elements of typ-ical market scrap in Japan.

Chemioal compositions af ter mel ti ng (%)

Category of market scrapCu Sn Ni cr Zn

car shredded scrap o.23 0.052 0,069 o. 123 (o .050)

a,

~Q,~~oc,,

J:l

o

Heavy scrap o.234 O,017 o.

070 o. 130 (o. 210)'~a'

o+'o'

!':~

Can scrap o,050 o. 128 o,

032 0,061 (o .oo)

Factory bundle o,027 o.

002 o,020 0.031 (o .70)

Homescrap o,021 0.01 o,050 o.

030 (o ,ol )Pig i ron scrap 0.01 o,

002 0.02 0.02 (o. 002)

' Before ~elting

1OO%

90Xt~~~: 80%e'

'~ 70X~u)

~ 60%=a'

cO~ 50%

~v 40X~oo

30%~"~ 20%

1OX

O%

DNonmetalliccomponents

EINon Ferrous

l~Special steel

IComnonsteel andcast i ron

~Surface coatedsteel sheets

RHigh tension steel

areas also, the ratio of electric-furnace steel is graduallyincreasing, and the above classification does not alwaysrefiect the actual quality of scrap.

Table 2 shows the analytical values of "tramp ele-

ments", such as copper and tin, contained in steel scrap,which values were obtained as a result of a special melt-

ing experiment.3) As seen from this table, the values of

copper and tin in scrap are one figure higher than thosein pig iron produced from ore.

The conceivable factors behind the recent gradualdeterioration of obsolete scrap are as follows;

(1) To meet the consumerrequirements for higherefficiency, higher grade and lower cost, consumption ofthe nonferrous material (copper) of electric machineryparts has increased. Also, due to the size reduction ofthe parts, the separation of copper from steel has becomedifficult,

(2) As the consumption ratios of nonmetallic mate-rials such as plastics and rubber have increased, that

of steel has decreased correspondingly.(3) To improve the functions of steel materials, con-

sumption of alloying elements-added steels, coated steels

and clad steels has increased.

(4) Dueto the scrapping and recycling of these steel

materials, tramp elements have circulated and accumu-lated.

Figure 5showsthe componentratios of the raw mate-

201

1973 1980 1986 1992 year

Fig. 5. Componentsratio of raw materials of standard-sized

passenger cars.

rials of standard-sized passenger cars as an example.4)

As seen from the figure, the ratios of steel materials aregradually decreasing, but amongthemthe ratio of coatedsteels alone is rapidly increasing. Also, the ratios of non-ferrous metals and nonmetallic m~terials are increasing,

since waste of complicated mate'rials composition like

scrapped cars is nowadaysshredded into pieces andmagnetically separated into steel, nonferrous metals andnonmetallic materials, not all impurities are mixed in

obsolete scrap. However,nonmetallic materials auxiliary

to the magnetic material; steel, such as motor core, wireharness and electronic substrata are mixed as impurities

at high ratios in obsolete scrap.Thus, due to the increase of tramp elements in obsolete

scrap, the copper and tin contents of products manu-factured from electric-furnace steel have increased tovalues about one figure higher than those of productsmanufactured from hot metal and goodscrap like homescrap, as shownin Table 3.9) The forms of existence ofimpurities in obsolete scrap are roughly classified asshownin Table 4. Copper is present as a massimpurity,

and tin as a surface layer impurity. Of the variousimpurities, tramp elements such as copper and tin arevery difficult to removeby the current oxidation refining

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ISIJ lnternational. Vol. 37 (1997), No. 3

process, once they are mixed in steel. If these trampelements remain in steel, the quality and material char-acteristics of the steel deteriorate. At the electric-furnaceplant, therefore, tramp elements are diluted to suit theintended use of the steel by blending good scrap like

high-purity homescrap or process scrap and pig ironwith obsolete scrap according to the allowable amountsof the tramp elements. In the present Japanese manu-facture of steel products, there is the established segrega-tion of niche, as it were, that steel for bars and shaped

Tabte 3. Contents of cu and Sn by raw material used.

Rawmateri al s Products Cu(%) Sn(%)

used

Market Shapes o. 20-0.35 o. ol 0-0

.020

scrapBars o. 25-0

.50 o. ol 5-0

.025

Special stee~ o. 08-0.13 o. 004-0

.ol 1

Pi9 i ron Ordi nary o, 02-0. 03 o. ool -o.003

and home grade

serap

steel for which control of impurities is relatively loose is

madefrom scrap in electric furnaces, while steel for sheetsfor which impurity control is strict is madefrom iron

ore in blast furnaces and basic oxygen furnaces, andscrap supply and demandare balanced.

However,as the occurrence of obsolete scrap increases

as mentioned above the segregation of niche becomesdifficult, and the necessity arises of using obsolete scrapalso for steel for which impurity control is strict. Also,the concentration of tramp elements is expected to prog-ress further, since steel products manufactured usingobsolete scrap are scrapped year after year. Figure 6shows the estimated trends of copper and tin contentsof obsolete scrap.13) In 2015, the tramp element contentsof obsolete scrap are predicted to increase to 1.2l.5times the present values. The increase in consumption ofthe nonferrous material (copper) of electric machineryparts and the increase in the mixing of copper in obsolete

scrap due to the size reduction of the parts are difficult

to calculate and, therefore, not taken into considerationfor this prediction. If these factors are taken into ac-count, the copper content of obsolete scrap will becomestill higher.

Table 4. Modeof existence of impurities.

Cl assi f~cati on Modeof existence of impuriries Concrete examples(typical metals)

(DMass impurrties Nonferrous metals each having a certain mass Motors(iron and copper)and coexisting w~th iron. Automotive engine blocks

(iron and alum~num)

@Impurities in surface layer Impurities existing as thin nonferrous meta~lic Galvanized sheet(iron and z~nc)phase in surface layer of iron Tinplate(iron and tin)

CAlloy impurtties Elements intentionally added to steel asalloying components to improve performance of

Corrosion-resisting steel (~ron and copper)Stainless steel

steel product. (i ron ,ni ckel

,chromi um,mol ybdenum)

o.03

~;~ 0,02

cl)

l~oc:o

+''!'

+'=CDo=o 0.01o

o,oo

l bar steel scrap

• shaped steel scrap

A heavy scrap (h~gh grade)

- MaxMi n

.;'J'Lt:

I"'dl'

- -,,'S'I"'

1'A ;'

...

,,,r"~"'1F~~'L'I

l985 1990

0.5

0.4

~e

~ 0.3~o~;

~~'~ 0.2o

(S

o. 1

o

It-

'I~$.

•JL -

I.lr'

t'F'I"'1""'1'1itt'

.*J•'~.

.*JL*

'.,;:;*

*_.~**

Fig.

_LJP,1'1".Si"-jl"t ~A • ' I'

1995 2000 2005 2010 2015 2020 l985 I990 I995 2000 2005 2010Fi scal year Fiscal year

6. Simulation of copper and tin concentration for obsolete scrap in futures.

2015 z020

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Q)- 450-u)J~c:'o o 400co+'::'

c c: 350::'osh~ 300o-~'u~ 250

OCL~"T' 200c"L~~ 150

'- o~' ~' nn'~' a)

Ivv

::'o t;

E~ a'uO

::J:]e)o o

Based on the assumption that the content ofimputies in scrap will increase by I .5 times

over the current level in 2020

Based on theassumption that scrap

quality wi~l remain unchangedat the current level

"

Fig. 7.

3.3. Prediction of the Volumeof Unrecyclable Scrap andReclamation Targets

Figure 714) showsthe results of prediction of the future

volume of unrecyclable scrap assuming that the steel

production of 100 million tons/year is maintained by the

current scrap melting process, which mustdependon thedilution methodbecauseno effective meansfor removingtramp elements, such as copper and tin, is available, andalso that the largest possible volume of obsolete scrapcontinues to be recycled within the allowable ranges ofthe composition values of steel products, Unrecyclableobsolete scrap will begin to be actualized in about 2000,and 155-300 million tons of such obsolete scrap will beheaped up throughout the land in 2015. This is anenormousvolumeequal to I OO0-2OOOtimes the volumeof Tokyo Dome.

Therefore, the ratios of removal of tramp elementsfrom scrap necessary for preventing the occurrence andaccumulation of unrecyclable scrap were estimated, asshownin Fig. 815) As a result, it has becomeclear thattechnologies capable to remove copper and tin about55 o/, and about 30 o/, in average must be developed byabout 2010.

4. Present Conditions of Scrap Reclamation Technolo-gies

4.1. Reclamation Technologies

Manystudied were conducted in the past on technol-ogies for removing tramp elements from iron and steel

scrap. Regarding the details, the lron and Steel Institute

of Japanpublished a report on the results of studies madeby the "Research Group Engagedin the Study of theSeparation of Circulative Elements".5) In the Forum'sproject, therefore, the study is pursued mainly on thetechnologies to reclamation those tramp elements in

scrap which are difficult to removeby ordinary oxida-tion refining and which exist in large amounts, that is,

copper and tin. The concept of reclamation and the

present conditions of the development of reclamationtechnologies are described below.

4.1.1. CopperReclamation TechnologyCopper exists both as a mass impurity (attached to

steel) and as an alloy system. For the mass impurity,shredder treatment is already commercialized. In this

treatment, scrap is crushed into pieces by the rotaryhammer,and steel is separated from nonferrous metals

or nonmetallic materials by magnetic or wind separation

- o- - ~;~Results of prediction of the future volume of unrecyclable scrap.

203

'~ 7n)t luI~L

60..:'~L 50

o~',d 40L,g 30-:'~20Lacg 10Lo1'>0

o

Lo o o L,,r)o) o 1- '-ea) e e eo1- c\a c\a c\t'\l

Fig. 8. Ratios of removal of tramp elements from scrap neces-

sary for preventing the occurrence and accumulationof unrecyclable scrap.

and recovered. This is an efficient treating method forlarge volumes of scrap. However, after scrap pieces aremagnetically separated, copper attached to steel is mixedin the steel because the shredders in actual use are notsufficient to completely liberate steel from nonferrousmetals or nonmetallic materials. Particularly, as con-sumption of the nonferrous material of electric machin-ery parts increases, andas the size of the parts is reduced,the mixing of copper in obsolete scrap increases further.

Although the mixing of copper maybe decreased byrepeated crushing and careful magnetic separation, it

is not economical. In order to solve this problem, twotechnologies were developed in this project. Oneis low-temperature crushing, and the other is automatic discrim-inative separation.6) Low-temperature crushing is thetechnology to cool scrap below transition temperatureof steel by liquid nitrogen and crush it to a size of aboutlO mm.This technology can crush scrap and liberate steel

from not only copper but also other nonferrous metalsand nonmetallic materials, allowing complete separationby the magnetic separator. As a result of a test on actualscrapped cars, the copper content of scrap showedthe

prospect of decreasing to below 0.06 olo.

Automatic discriminative separation is technology al-

ready applied to the separation of emptybottles of clearly

different colors. In, the case of steel scrap, however, there

are peculiar difficulties. For instance, copper is delicately

different in color from iron rust. Scrap is irregular in

shape. Separation should be madeas speedy as high-speed conveyance. In this project, the technology to

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ISIJ International, Voi. 37 (1997). No. 3

r~7~~~lMonitor

Scraps entry hopper

Guide

Trackin si nal

CameraRGBvideo signal

OLights

Real•time imageprocessor Terminal

O-Belt-conveyor

Switching-gate(using air cylinder)

~I~l9. Automatncdiscnmmatrve separatron system

Switching- gatecontroller

Fig.

discriminate copper-attached scrap by analyzing the three

elements of light, hue, chromaand lightness, by high-speed image processing was developed, and discrimina-tive separation wasmadepossible at a conveyancespeedof 100m/min. Figure 9showsthe automatic discrimina-tive separation system. It is fairly difficult to economically

remove alloyed copper. Generally, copper is higher in

vapor pressure than iron and allows evaporative separa-tion in principle, but the evaporation velocity is verylow. To improve the evaporation velocity, therefore,

the technology is being developed to accelerate the de-carburization reaction by top blowing weakly oxidizing

powderon liquid steel containing copper under reduced

pressure and increase the boundary area of evaporationby the COgas generated as a result of the decarburiza-tion reaction.7)

4,1.2. Tin Reclamation TechnologyMost of the tin is mixed in scrap as a surface layer

attachment. The technology to treat waste tinplate oc-curring in the can-making stage by alkali electrolysis

and separate tin to recover it is already commercialized.Although pretreatment, such as the removal of surfacelacquering is necessary for used cans, it is possible to

regenerate tin of usedcans as well by the sametechnology

as that used for treating waste tin plate in the can-makingstage.

However,whensuch technology is adopted for generalsteel scrap, the economic effect of tin recovery is lost

because the tin content of scrap is one figure lower thanthe copper content. In this project, therefore, treatmentprocesses for tin recovery were developed as part of thegeneral scrap recycling process.

Oneis the process of heating scrap at high temperaturein an oxidizing atmosphere. As the surface tin is oxidizedand its toughness is reduced by this treatment, the oxide

can be detached by mechanical impact. Whentinplate

and plates as impact-giving material were put into the

rotary kiln, heated at 950'C and rotated, 50 o/o of the tin

was removed. From the industrial viewpoint, how thetinplate and impact-giving material should be mixed andhowthe detached material should be separated withoutcooling the scrap are the future questions to be solved.

Another is the process of heating scrap in a weaklyoxidizing atmosphere and evaporating tin as tin sulfide

or tin oxide to separate tin. Whentinplate was heated

in the cupola and behavior of tin was observed, mostpart of the tin was found to have shifted away to dustand a detinning ratio of 95 o/o Wasobtained.

Furthermore, the process of removing alloyed tin bydecarburizing scrap in a vacuumin the sameway asremoval of copper and the process of removing alloyedtin by decarburizing scrap in the presence of sulfur arealso under development.

4. I .3. Zinc Reclamation TechnologyZinc, which shifts awayto dust at the time of melting

scrap by EAFanddoesnot remain in steel, has no adverseinfluence on steel like copper or tin, it maybe said thatthe problem about zinc is the problem of dust. TheWaeltz's process is mainly used at present for dusttreatment. This process, however, assumes large-scale

treatment and requires the transportation of dust to adistant place. Therefore, howto treat the residue whichoccurs in a great volume at one place after recoveringzinc is the problem to be solved. In this project, therefore,efforts are being madeto develop the technology toincrease the zinc content of dust and also the technologyto economically recover zinc from dust on site.

The slag components, CaOand Si02, exist in dusttogether with zinc, and they decrease the zinc content ofdust. If these slag componentsin dust are allowed toshift to slag whenthe dust is recycled into the meltingfurnace, the dust amountcan be reduced and the zinc

content of the dust can be increased. Dust is chargedinto the furnace in the form of pellets or briquettes with

scrap or injected into the furnace in the form of powder.Thebasic operational factors having the slag componentsin dust caught by slag are being studied.

In the Waeltz's process, the reduction temperature is

high and the reaction velocity is low because zinc is

reduced by coal. Therefore, this process requires the useof a large equipment to ensure economics. In this project,

on the other hand, dust wasreduced by COGequivalentcontaining 50 o/o hydrogen using the externally heatedkiln, and a zinc removal ratio of 90 o/o Wasobtained by0.5-1 .5 htreatment even at a relatively low temperatureof 950'C.8) As this process does not need to use re-fractories, a lightweight, small-scale equipment can beused. Figure 10 showsthe removal ratio aims of copper,tin and zinc from obsolete scrap.

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RawHaterial

Obsolete ScrapJunked car Building and Civ~~

Cn,Sn Cu

,Zn

PackageSn

Process scrap

Zn, Sn

Scrap preparat ian

Cryogenic process

95olade-Cu

Identi f~cati onand separation

9O'/.de-Cu

Removal

at solid

5O%

of Sn

statede-Sn

MeIt ing Removal of Cu

at ~iquid state

Scrap preheatin9 Rwmoval of Sn

5O-9O%~

Mel ti ng

Treatment of Zn

containin9 dust

9O'/.recovery

Fig. lO. Basic process flow on the removal of copper, tin and zinc from scrap.

Cryogenicshreddi ng ,separation

Coldmediun

Preheating : Clean off gasHeat furnace :

LNG exchange

-~>High efficientflue gas ductcollection system

Oxygen

: Block C : Coal or coke Pre~3ating_ ____>-J

El ectri ci ty • fu rnace

: Removal of inclusion

: under vacuum

Flue gas, Scrap, Dust treatment

j Liquid metalVacuumtrearment Melting furnace (de-Zn)(Electricity, fossil fuel )

Fig. 11. Total system evaluation research and its relation with other fundamental researches.

: Block A(Fundamenta~ researches completed) :

Rawmateri al Indenti fi cati on

scrap and separationRawmaterial

(scrap) -->• Heavy•Shredded cars•New plate scrap(No,bundleand No separation):(Oe-Zn)• Turni ngs :de-1 ubricated•Domestic scrap

4.2. Reclamation Technologies as a Total System

The reclamation technologies described above mustbe composedas a system which can be accomplishedsimultaneously with energy reduction technology andenvironmental protection technology. Also, whether theresults achieved in this project can be industrialized as

a total system or whether part of the results can beincorporated into existing processes should be evaluatedfrom both technical and economical aspects.

Therefore, the "research of a total system evaluation"which serves to finish the whole research was startedthis year. Figure 11 showsa conceptual diagram of theresearch of a total system evaluation. Theobject of this

205

: Block B(Total system evaluation research) :: ;...P.r~~~.a.t.i~~.t.M~,;.i.~q.t.f],~_.~~s.;r~a.t.~~~t...; :

F~ow route for flue 9as :- Scrap :

Dust flow :---->

study is to utilize scrap after reclamation by developpedtechnologies. The study is expected to be conducted on"Block B", which is the optimumpreheating andmelting

system, with due consideration given to environmentalprotection, such as control of exhaust gas, and usingl0-15tons/hour test equipment. Regarding the equip-

ment, the melting furnace is planned to permit the useof both electricity and fossil fuel, while the horizontal

and vertical preheating furnaces are planned to permitboth single and tandemoperations. Also, the possibility

of the commercialization of the total system of scrapreclamation technologies, preheating and melting tech-

nology and environmental protection technology is ex-

C 1997 ISIJ

ISIJ International, Vol. 37 (1997). No. 3

pected to be evaluated by simulation based on the studyresults achieved.

5. Conclusion

Of the activities of the "New Steelmaking ProcessForum", the development of reclamation technologieshas been mainly described above, but steel recycling

cannot be pursued smoothly only by reclamation tech-nologies. It is most necessary to enhancesocial recogni-tion of the importance of scrap recovery and recycling

and improve the social structure so that scrap in thediscarding and collecting stages is sufficiently sorted as

a social system. Furthermore, easily recyclable machinedesign and steel composition design capable to facilitate

the removal of tramp elements are considered to becomeimportant technologies to support scrap recycling.

If the total volume of scrap to occur in the future

can be maderecyclable by the development of thesetechnologies, not only will iron resources be effectively

utilized but also the carbon dioxide reduction in 2010 is

estimated to reach 2.20/0 of Japan's total emission ofcarbon dioxide. In order to achieve such magnificenteffects, the establishment of the basis and the earliest

possible spread of the technologies as economically ap-plicable technologies are eagerly desired.

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2) Tetugen Annual Report, JFRMA,Tokyo, (1995), 114.

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