Producing Low Copper Shred for Steel Mills

Author: Mike Shattuck, Recycling Market Manager

Sheet steel mills use a blend of pig iron, DRI, and pre-consumer scrap (bushing). Typically, only about 25% of lower-cost shredded scrap is used in the blend, with the remaining 75% a mix of the higher-cost pig iron, DRI, and pre-consumer scrap.

With the higher cost combined with the limited availability of these commodities, using a higher percentage of low copper shredded scrap allows steel mills to reduce the cost per ton of steel produced.

Process

In a scrap yard, the Shred1 Ballistic Separator follows the primary scrap drums and shredder, just before a picking station. Shredded material is accelerated up to 1,000 fpm in the Shred1. A magnetic element at the separator's end attracts more magnetic steel pieces, dropping them behind a splitter. This material constitutes the low copper stream (#1), making up about 75% of the material. This material is then conveyed to the stacking conveyor without further action needed.  The copper content of this fraction is typically between 0.16%-.020% copper.

The less magnetic material is influenced more by the belt speed's ballistics than by the magnet's attraction. It is directed over a splitter, discharged from the Shred1, and conveyed to a polishing drum. This material, termed copper concentrate, comprises the remaining 25% of the feed.

The #2 material is presented to a magnetic drum with a reduced magnetic field or a polishing drum. This drum is set to “cherry pick” the best ferrous of the #2, which is liberated from any copper-bearing materials. This material, typically making up 10%-15% of the #2 fraction, is blended back to the #1 stream and sold as low copper shred. This increases recovery of the low copper shred.

The #2 material after the polishing drum is presented to a picking station where copper-bearing materials and any nonferrous material are ready for manual picking. This material can be sold to mills that do not require a low copper product or sent for further processing to advance the liberation of copper from steel.

Testing

Material was collected from multiple scrap yards and processed under a Gamma Tech analyzer to verify copper content of the feed material. With over 1,000 tons of material, the average copper content was .29%. 

The Shred1 was configured for a 75/25 split of material, with 75% designated as #1 (low copper) and the remaining 25% as #2 (copper concentrate). After processing 1,000 tons on the Shred1 Ballistic Separator, the #1 fraction underwent assay analysis, revealing a copper content of 0.16%.

The #2 shred underwent polishing drum treatment, recovering an additional 10%. Assay analysis showed a copper content recovery of 0.18%. This shred can be blended into the #1 material without compromising its copper content, enhancing overall recovery.

Unrecovered #2 material at the polishing drum was directed to a picking station, where manual removal of copper-bearing and nonferrous materials occurs. With only 15% of the infeed directed to the picking station, fewer pickers are needed. This reduced feed enables quicker and more efficient work, as the material burden is lighter, and copper-bearing materials are easier to identify. Typical copper picking in a yard ranges from 5-7 lbs. per ton of shred, but with the Shred1, this typically rises to 12-14 lbs. per ton.

Conclusion

By installing a Shred1 Ballistic Separator and a polishing drum, scrap yards can provide premium low copper shredded scrap to steel mills while reducing labor and increasing copper pickings. In many instances, the lower copper scrap commands a premium of more than $40 per ton.