Recycling of Ferrous Scrap from Incinerator Residue

in Iron and Steel Making

E. J. OSTROWSKI National Steel Corp.

Weirton, West Virginia

ABSTRACT

Ferrous scrap from incinerator residue from four sources has been evaluated for potential use in iron and steel making. These evaluations consisted of 42 induction furnace melts, nine laboratory electric furnace melts and a blast furnace test. The studies were conducted at the National Steel Research Center and the Great Lakes Steel Division of National Steel. Relationships were es­tablished for residuals such as tin, copper and nickel. The residuals in the ingots produced from the electric furnace heats confirmed the expected levels determined through statistical analysis.

The ingot residuals varied with the source of inciner­ator residue scrap. The bulk density of scrap varied. The yield loss due to the oxidized and lightweight nature of some of the scrap samples was high. These losses can be minimized by controlling the carbon level of the bath and by compaction of the scrap. The higher density scrap showed good yield and could be melted readily.

The data obtained on the chemistry of the scrap from incinerator residue were used to show effects on hot metal quality if the scrap was used in a blast furnace. A blast furnace test confirmed the limits of use in iron mak­ing. The scrap residuals will have the same effect on steel making since the hot metal is used to produce the steel. The low density of the scrap presents some handling problems at the blast furnace which can be corrected by compaction of the scrap into briquettes.

INTRODUCTION

Recycling in the steel industry is not new. Of the six million cars junked annually, 80 to 88 percen t are re-

87

cycled. Inplant iron units such as blast furnace dust, mill scale and basic oxygen furnace dust are recycled into a usable product through the sintering operations. Blast furnace slag is recycled into road building and as aggre­gate in concrete. Steel making slags are reprocessed to recover metallics and to use the slags as the media in sta­bilized road beds. Waste gases from processes are con­verted to useful energy to continue the cycle in iron and steel making. More recently, the industry has embarked on another facet of recycling i.e., the recycling of ferrous metallics from the solid waste stream. Of particular inter­est is the recycling of ferrous scrap from incinerator residue.

Recycling can be accomplished provided that it is technically and economically feasible. To establish this feasibility, considerable research effort has been ex­pended by the National Steel Corp. to determine the limits of acceptability of ferrous scrap from incinerator residue in iron and steel making. Evaluation tests have been conducted on numerous samples of incinerator res­idue ferrous scrap obtained from various geographical areas. Following these evaluations, a demonstration test was made in a 3000 ton blast furnace at the Great Lakes Steel Division showing the feasibility of true recycling of ferrous metallics from the incinerator residue stream.

LABORATORY STUDIES

The laboratory studies consisted of determining the chemical compostion of the scrap, its bulk densi ty and its potential metallic yield. Where possible, reasons were established for changes in yield. Additional effort was directed toward developing ideas or improvements in scrap suitability. A total of 42 induction furnace

melts and nine electric furnace heats were made in the laboratory facilities at the National Steel Research Center. The established practice for the test work in­volved melting under protective atmospheres to avoid yield losses through oxidation. Sampling and weighing techniques were refined to minimize errors and assure high degrees of accuracy. All data were subjected to computer statistical analysis so that confidence limits could be established. The confidence limits are required to project use limits of the scrap as dictated by the final product specification.

Fig. 1 I ncinerator residue scrap from source A.

INCINERATOR RESIDUE SCRAP PROPERTIES

Fig. I illustrates a composite sample of incinerator residue ferrous scrap from source A while Fig. 2 illus­trates scrap from source B. Comparison of the bulk den­sity of the scrap from various sources is given in Table I. It is apparent that scrap B has a higher bulk density than any of the others and, if available, would be an ideal ma­terial from the physical standpoint for recycling in iron and steel making.

The chemical composition of the scrap from various sources is shown in Table 2. Included are the statistical analyses of the data as well as the expected yield from the scrap. It is apparent that there is a broad range in the

Fig. 2 Incinerator residue scrap from source B.

TABLE I BULK DENSITY DATA FOR INCINERATOR RESIDUE SCRAP

Source A B C D

Bulk Density - Lb/Ft3 (Average) 26.27 76.74 22.71 25.28

Standard Devi ation 10 2.96 10.90 4.05 2.68 20 5.93 21.80 8.10 5.36

Bulk Dens i ty - Lb/Ft3 (Maximum) 32.70 107.70 29.90 29.90 Bulk Dens i ty - Lb/Ft3 (Minimum) 22.00 56.00 16.70 22.70

95% Confi dence Level - Lb/Ft3

Lower Limi t 24.52 73.58 14.44 23.04 Upper Limi t 28.02 79.90 30.99 27.52

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TABLE 2 STATISTICAL ANALYSIS OF CHEMICAL ANALYSIS DATA AND RECOVERIES INCINERATOR RESIDUE SCRAP INDUCTION FURNACE MELTS

(Percent)

Source A 95 Percent

Devi at i on Confidence Interval Mean Minimum Maximum ± 10 ± 20 Lower Upper

--

C .0199 .001 .060 .020 .040 .0081 .0318 S .0323 .0140 .0420 .0075 .0150 .0279 .0368 Mn .013 .002 .020 .0131 .0262 .0053 .0208

P .0338 .010 .178 .0482 .0965 .0053 .0623

Sn .1647 . 112 .216 .0288 .0577 .1476 • 1817

cu .4369 .036 1.058 .3121 .6242 .2524 .6213 Cr .0092 .020 .040 .0159 .0319 .0001 .0187

Ni .0998 .012 • 196 .0581 . 1162 .0654 .1341

Mo .0150 .002 .030 .0098 .0196 .0092 .0208

Pb .1038 .056 . 154 .0304 .0608 .0858 .1217

Yield 98. 11 95.5 100.0 1.3307 2.6615 97.323 98.895

Source B 95 Percent

Deviation Confidence Interval Mean Minimum Maximum ± 10 ± 20 Lower Upper

C 0.417 0.220 0.600 o. 138 0.276 0.335 0.499 S 0.040 0.022 0.062 0.010 0.020 0.034 0.046 Mn 0.296 0.180 0.420 0.059 o. 118 0.260 0.331 P 0.032 0.022 0.042 0.007 0.014 0.028 0.036 Sn 0.080 0.062 O. 102 0.010 0.020 0.074 0.086 Cu 0.214 0.146 0.319 0.058 o. 116 0.179 0.249 Cr o. 120 0.046 0.231 0.056 O. 112 0.087 0.154 Ni o. 108 0.040 0.322 0.089 0.178 0.055 O. 161

Mo 0.014 0.006 0.042 0.009 0.018 0.008 0.019 Pb 0.050 0.038 0.066 0.008 0.016 0.045 0.055

Yield 97.24 93.60 98.91 1.505 3.009 96.275 98.210

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TABLE 2 STATISTICAL ANALYSIS OF CHEMICAL ANALYSIS DATA AND RECOVERIES INCINERATOR RESIDUE SCRAP INDUCTION FURNACE MELTS (CONTI NUED)

(Percent)

Source C 95 Percent

Devi ati on Confidence Interval Mean Minimum Maximum ± 10' ± 20' Lower Ueeer

C .032 .010 .050 .010 .020 .026 .038 S .056 .017 .074 .015 .030 .048 .064 Mn .012 .010 .030 .006 .012 .009 .015 P .061 .039 .094 .018 .036 .051 .022 Sn .135 .094 .177 .026 .052 • 121 • 150 Cu .424 .219 .967 .226 .452 .299 .548 Cr .044 .001 .235 .057 • 114 .012 .075 Ni .066 .019 .091 .019 .038 .056 .077 Mo .026 .016 .040 .007 .014 .022 .030 Al .001 .001 .005 .001 .002 .001 .002 Pb .032 .013 .059 .014 .028 .024 .040 Zn .029 .011 .068 .015 .030 .020 .038 Ti .003 .001 .005 .001 .002 .001 .003

Yiel d 81. 11 68.00 92.46 5.98 11.96 77.80 84.80

Source D 95 Percent

Devi at i on Confidence Interval Mean Minimum Maximum ± 10' ± 20' Lower Ueeer

C .055 .040 .080 .019 .038 .024 .085 S .084 .075 .089 .006 .012 .074 .094 Mn .006 .001 .020 .009 .019 .009 .021 P .022 .019 .024 .. ooi .004 .018 .025 Sn • 138 .109 .164 .026 .052 .096 • ·179 Cu .213 • 142 .313 .072 • 144 .098 .328 Cr .044 .001 .0930 .050 .100 .035 · 123 Ni .053 .041 .079 .018 .036 .023 .081 Mo .014 .007 .024 .007 .015 .002 .025 Al .008 .001 .017 .008 .016 .005 .020 Pb .048 .023 .057 .017 .033 .021 .074 Zn .029 .016 .038 .009 .018 .014 .043 Ti .002 .001 .005 .002 .004 .001 .005

Yie l d 89.22 87.15 92.38 2.24 4.47 85.67 92.78

90

chemical composition of the scrap from the different sources. The yield varies for each scrap. It was noted that scrap C contained unusual amoun ts of dirt and slag. On the average, this as received material contained 16 percent nonmagnetic materials which resulted in the poor metal­lic yield.

ELECTRIC FURNACE TESTS

Incinerator residue ferrous scrap from sources A and B was melted in the laboratory electric arc furnace. Fig. 3 illustrates the charging of the scrap to the furnace. Fig. 4 illustrates a normal heat in progress with no change in emission around the furnace electrode. Fig. 5 illustrates the slight change in emission around the furnace elec­trodes when charging the incinerator residue scrap. The emission results from the reaction of oxide coating on the scrap and some oxidation of the metallics due to this low density.

Table 3 is a tabulation of the results from the heats made with the source A scrap while Table 4 lists the re­sults for the source B scrap. It is apparent that the yield

Fig. 3 Charging incinerator scrap.

Fig. 4 Normal furnace operations with no fume visible.

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from the source B scrap is considerably higher than the source A scrap due primarily to the higher bulk density of the source B scrap.

BLAST FURNACE TEST

For the blast furnace test, the source D scrap was used. A total of 75,000 Ib of this scrap was charged to the D blast furnace at the Great Lakes Steel Division of the National Steel Corp. Fig. 6 shows the D blast furnace. The furnace is capable of producing 3000 net tons/day of iron for conversion to steel in the basic oxygen fur­naces. The burden charged to the furnace consists of pel­lets, sinter, coke and fluxstone. The furnace operates with blast temperatures of 1700 F and blowing rates of 120,000 cfm.

The incinerator residue scrap was delivered by a bot­tom hopper railroad car. Some difficulty was encountered in discharging of the scrap into the bins feeding the charg­ing system of the furnace. The light weight na ture of the scrap caused it to match-stick and rat-hole. The short term solution to the problem was to charge the scrap as

a composite with the sinter used in the charge. Charging of the scrap was at a rate of 50 lb/ton of hot metal This required that the total charging time last for 12 h on this furnace. The selection of this rate was based on limiting the increase in residuals of the hot metal expected from the scrap. A sampling program of the hot metal, slag and dust from the furnace was conducted prior to, during and after the test to determine any changes that may have resulted from the use of this scrap.

The dust catcher was emptied at regular intervals to determine if any of the light weight scrap was carried over by the ascending gases. At no time was there any evidence of carry over. This can be credited to the mode of charging which permitted the scrap to be covered by the dense layer of sinter before entering the furnace. Table 5 shows the chemical composition of the hot metal produced on this furnace. This table identifies the con­ditions that existed at each cast. It is apparen t that there was an increase in the copper con ten t of the hot metal midway in the test. This change was expected based on the amount of copper present in the incinerator residue scrap. Table 6 is a tabulation of the slag analysis for the

Fig. 5 Melting conditions during charging of incinerator

residue scrap.

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Fig. 6 Great Lake-D-Blast Furnace.

.05 SCRAP SOURCES- A B C A 0 C . 04

t-Z LIJ (,) 0: LIJ a.. I .03

0: LIJ a.. 0.. 0 BO (,)

-l <[ t-LIJ ::IE t-�

SCRAP - LB/NTHM

Fig. 7 Expected hot metal copper residual using incinerator

residue scrap from various sources.

93

.04 SCRAP SOURCES-A B C 0

_03 .... Z ..... (,) c:: ..... d-

I

z .02

i= ...J � W ::IE .... .01 O :z:

SCRAP - LB/NTHM

Fig. 8 Expected hot metal tin residual using incinerator residue

scrap from various sources.

B

TABLE 3 SUMMARY OF RESULTS - ELECTRI C ARC FURNACE MELTING TESTS O N INCINERATOR RES I DUE SCRAP

Source A

Test No. 2 3 4 5*

Incinerator Scrap Used - Lb 422 300 300 400 400

Total Heat Weight - Lb 1122 1000 1200 1300 1330

Y i e I d - Pe rcen t 71.8 61.5 61. I 74.0 92.4

Residuals - Final Percent Cu .093 .233 .164 .158 .173 Sn .063 .047 .046 .052 .073 Ni .031 .037 .031 .032 .021 S .015 .016 .017 .017 .015 P .004 .004 .007 .008 .004 Pb .016 .012 .005 .005 <.001

Slag - Percent FeD 50.90 46.42 37.62 30.26 33.45 F:e 40.18 38.17 36.31 30.34 32.32 Si02 7.92 8.72 11.50 12.12 10.07 AI203 2.02 I. 78 2.98 4.09 3.13 CaO 22.18 26.98 22.29 29.89 30.22 MgO 2.78 2.43 5.19 3.58 4.85 MnO I. 79 I. 74 2.47 3.50 3.33 P205 0.10 0.10 0.10 0.10 0.10 S 0.055 0.060 0.038 0.055 0.065

* Simulated BOP Heat

TABLE 4 SUMMARY OF RESULTS - ELECTRI C ARC FURNACE MELTING TESTS O N INCINERATOR RES I DUE SCRAP

Source B

Test No. 6 7 8 9

Incinerator Scrap Used - Lb 374 374 491 560

Total Heat Weight - Lb 1374 1374 1191 1360

Yield - Percent 94.3 94.4 99.5 95.2

Residuals - Final Pe rcent Cu .112 .099 .125 .114 Sn .018 .020 .025 .025 Ni .049 .056 .060 .058 S .015 .016 .016 .017 P .009 .012 .007 .009 Pb .003 .003 .003 .002

Slag - Percent FeD 18.01 24.57 19.68 21.99 Fe 18.80 26.80 22.00 30.70 Si02 13.95 12.40 12 .• 05 10.62 AI203 3.55 3.95 4.56 5.08 CaD 44.50 36.27 39.90 30.27 MgO 10.11 9.03 10.45 14.33 MnO 3.36 2.98 4.07 4.00 P205 0.502 0.296 0.433 0.243 S 0.102 0.064 0.088 0.050

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TABLE 5 HOT HETAL ANALYSIS, INCINERATOR RESIDUE SOURCE 0 FERROUS SCRAP TEST, GREAT LAKES 0 BLAST FURNACE

( Percent )

Cast Weight Cast

Cast Time Tons No. C Hn

8: 30 AM 341 11992 4.36 1.00 II :55 AM* 551 11993 4.57 0.98 3:15 PH 453 11994 4.69 1.00 6:50 PH** 480 11995 4.54 0.91

10:20 PH 441 11996 4.54 0.83 I: 10 AM 287 11997 4.35 0.90 4: 30 AM*** 455 11998 4.64 1.00 7: 10 AM 428 11999 4.66 0.82

* Begin Charge Scrap ** First Cast To Show Effects Of Scrap ***

.020

� .015 w o

ffi 0-

f

...J

� .010 S! z

...J <t I-W

::E .005 b :r:

Last Cast To Show Effects Of Scrap

SCRAP SOURCES - A B C D

50 100 SCRAP - LB/NTHM

150

Fig. 9 Expected hot metal nickel residual using incinerator

residue scrap from various sources.

Si

0.95 0.45 0.39 0.52 0.72 1.10 1. 18 0.72

200

test period. There was no change in either the slag or dust composition from normal operations.

DISCUSSION

Laboratory tests on the feasibility of using incinerator residue 'Scrap in iron and steel making provided the basic information needed to conduct a blast furnace test in which this form of scrap replaces iron ore. The blast fur­nace tests confirmed that residuals such as copper and tin will limit the use of the scrap to a level which will not exceed the product specification. The amount of copper, tin and nickel present varies in the scrap depend­ing on its source. Fig. 7 illustrates the change in hot

� P Cu Ni Cr Ho Sn Ti

.028 .137 .009 .005· .027 .010 .004 .020 .029 .152 .009 <.005 .022 .010 .005 .015 .026 .119 .010 .005 .024 .008 .004 .016 .033 .106 .007 <.005 .018 .010 .006 .010 .027 .119 .008 <.005 .016 .009 .005 .013 .029 .133 .012 <.005 .018 .009 .004 .017 .032 .129 .009 .005 .020 .009 .006 .023 .040 .122 .009 .005 .021 .007 .006 .019

95

Fig. 10 Illustration of compacted incinerator residue ferrous

scrap.

metal copper content using increasing quantities of scrap from different sources in the blast furnace. The band en­compasses the range as derived from plotting the mean values of all scraps evaluated. Fig. 8 illustrates the change in the expected tin level and Fig. 9 shows the change in the nickel level. Any of these residuals present in the hot metal from other sources would be additive. These res­iduals will raise the ingot residual level by the amount of hot metal used and its conversion efficiency in the steel making operation.

Use of the incinerator residue scrap in the blast fur­nace will displace some form of iron ore whether this be sinter or pellets or coarse ore. The amount displaced is based on the Fe content of the ore versus the Fe content of the scrap. At a 65 percent Fe content of the ore and a

95 percent Fe in the scrap, the 50 lb of scrap replaced about 70 lb of ore.

The light weight nature of this form of scrap and its difficult handling present the blast furnace operator with many problems. It taxes his ability to keep the furnace full and to move the materials through his handling sys­tem. The D blast furnace requires about 13,500,000 lb of material to be charged each day. This volume of ma­terial must be in constant motion and cannot be a spo­radic delivery. The use of miscellaneous rna terial such as this scrap must therefore flow as readily as the other ma­terials and must possess a density approaching the ma­terial it displaces. The blast furnace operator will require that the scrap be compacted into briquettes, blocks, bales or balls. The compacted mass must not exceed a dimen­sion greater than 6 in. on any side. A pillow shaped bri­quette 1-3/4 x 1-3/4 x 5 in. would be acceptable or a spherical shape 4 in. in diameter or a compacted cylinder as shown in Fig. 10. The cylinders illustrated in this fig­ure are laboratory tests conducted on source C scrap. The scrap volume was reduced from 10 in. in a 4 in. cylinder to 1 in. in the compacted version. Any form of compaction must maintain its integrity throughout its journey from the source to the final charging to the blast furnace.

CONCLUSIONS

From the extensive studies made on the recycling of incinerator residue ferrous scrap at the National Steel Research Center and the blast furnace tests at the Great Lakes Steel Division of the National Steel Corp., the following conclusions can be made.

(1) The results of the studies show that incinerator residue scrap can be used in iron and steelmaking. Total

consumption will depend on product chemistry specifi­cations as dictated by the residuals copper, tin and nickel.

(2) Incinerator residue scrap has a low bulk density. It must be compacted into a suitable size and shape for use in iron and steel making.

(3) The scrap must be clean to permit high metallic yield. Nonmagnetics must be completely removed.

(4) The blast furnace provides a new means for re­cycling of metallics from the solid waste stream.

(5) The chemical composition of the scrap varies from source to source depending on the geographical area and the system used to reclaim the scrap.

ACKNOWLEDGEMENTS

The author gratefully acknowledges the cooperation and assistance of many people at the Research Center in conducting the laboratory tests. Appreciation is ex­pressed to the Great Lakes Steel personnel who were most cooperative in conducting the blast furnace tests.

REFERENCES

[1) R. S. Hatfield and G. A. Stinson, "Recycling the Steel

in Cans," Testimony before the Subcommittee on Air and Water

Pollution of the Senate Committee on Public Works, March 13,

1970.

(2) P.1. Koros et.al., "The Utilization of Bundled Auto

Scrap and Its Relation to Sheet Quality," AISI Regional Meet­

ing, Nov. 12, 1966. (3) E. 1. Ostrowski, "Use of Ferrous Scrap from Municipal

Solid Waste Incinerators in Steel Making, AIME Environmental

Quality Conference, Washington, D. C., June 7-9,1971.

(4) E. J. Ostrowski, "Recycling of Tin Free Steel Cans, Tin

Cans and Scrap from Municipal Incinerator Residue," AISI 79th

General Meeting, New York, N. Y., May 26,1971.

TABLE 6 SLAG ANALYS IS, INCINERATOR RESI DUE SOURCE o FERROUS SCRAP TEST, GREAT LAKES 0 B LAST FURNACE

(Percent)

Cast No. Time S i02 AI203 CaO � HnO � Basicity Rema rks

11992 S:30 AH 37. IS 10.30 3S,60 9.�0 o. 7� I. 3� 1.01

11993 II : 55 AI1 37. IS 10.10 3S.70 9.80 0.S6 1. �3 1.03 Scrap Charging Begun

1199� 3: 15 PH 36.67 9. �O 39.30 9.50 0.96 1.35 1.06

11995 6: 50 PH 38.04 9.40 39.10 9.00 0.98 1. 31 1.0 I First Cast To Show Scrap Effect

11996 10: 20 PH 37.18 9.70 3S. �o 8.70 0.6� 1.47 I. 00 Scrap Charging Ended

11997 I: 10 AI1 35.98 10.20 39.10 8.90 0.37 1.67 1. 04

11998 4: 30 AI1 36.32 9.70 38.90 S.So 0.45 1. 57 1.04 Last Cast To Show Scrap Effect

11999 7: 10 AI1 37.53 10: 30 3S.70 9: 40 0.50 50 1.01

96