The scrap metal recycling industry refines unprocessed obsolete and prompt scrap into commodity grade material. Obsolete scrap collected from scrap metal dealers, auto salvage facilities, and industrial manufacturers are typically sent to large scale recycling facilities for processing. Once at the recycling facility, the scrap metal is screened for radiation, loaded onto an infeed conveyor, and shredded into fist-sized pieces.
The scrap metal must then be separated into ferrous, non-ferrous, and non-metallic materials. This process requires the scrap metal to be shredded into small pieces, so it can be efficiently and completely separated. Oversized scrap—scrap that is too large to shred—is sized and sorted manually. The Institute for Scrap Recycling Industries (ISRI) has developed standard specifications for scrap commodities to help buyers and sellers value processed metal scrap accurately.
Ferrous metal alloys contain iron. Common ferrous alloys include steel, malleable iron, and gray iron. Iron has magnetic properties, so magnetic attraction is commonly used to identify ferrous alloys. Ferrous scrap is usually separated from non-ferrous material using an electromagnet.
Ferrous scrap is widely used in steelworks and in cast iron and cast steel products made by foundries. According to a steel recovery and recycling rate report, iron and steel account for approximately 90% of the mass of all metals consumed in the United States and globally. The high consumption rate of steel makes it economically feasible to be recycled. As a result, steel is the most recycled material worldwide.
Any metal that does not contain iron is referred to as non-ferrous. Non-ferrous alloys, such as copper based alloys, are non-magnetic and corrosion resistant. They are also heavier than non-metallic metals—an important factor for the separation process. A powerful vacuum or cyclone can effectively suck small, non-metallic pieces away, while leaving non-ferrous alloys in place. Any problematic pieces that are not correctly separated by the magnetic drum or cyclone are recovered at a human-operated “hand-pick” line. At that point, ferrous metals are compacted and shipped to steel mills and foundries, and the remaining material goes on to the non-ferrous separation process.
Non-ferrous separation makes use of eddy currents, induction sorting, and additional hand-picking to sort out various alloys with a focus on aluminum and copper. Some non-ferrous metals, often referred to as “specialty metals,” are rarely recycled because they are typically used in tiny amounts or complicated applications such as computer chips. Their value and relative volume does not justify the cost required for separating and recycling.
Any non-metallic material left over at the end of the separation process is sent to the landfill. The metal recycling industry is working to find new ways to efficiently separate and use more of these materials to reduce waste.
Post time: Oct-09-2021