increasing amounts of copper in steel scrap has until now, proved a real challenge for steel mills. A breakthrough in sensor-based sorting presents a solution to this problem, as Tom Jansen, sales engineer and metals expert for
TITECH in the Middle East, explains.The worldwide market for ferrous scrap, which is the key raw material used by electric arc furnaces (EAFs) for steel production, is growing as virgin resources become more scarce and command a higher premium. In 2010, more than 55% of steel produced in the European Union used steel scrap as its raw material. In the Middle East, 17 million tonnes of crude steel was produced in 2010 from electric arc furnaces and the region is predicted to generate 5% of the global EAF-based steel production by 2020. Ferrous scrap comprises iron and steel and is recovered from a wide variety of sources.
Bulky ferrous scrap is derived from demolished buildings in the form of rebar and structural beams, or infrastructure such as old railway tracks. In this article, we are specifically concerned with the ferrous steel scrap from municipal and domestic sources, including old cars and household appliances. The issue with steel scrap from WEEE and ELV sources in particular is that it rarely occurs in a pure form: it is usually combined with a number of other materials including plastics, textiles and other metals. Increasing levels of copper metal in recovered ferrous scrap are becoming a real
|problem and could threaten the current buoyant market for secondary steel. Steel smelters simply do not want copper contamination in their infeed material. Copper contamination: Meatballs The main contributors to the copper contamination are the so-called ‘meatballs’; electric motors, coils, chokes etc., which usually consist of a steel shell with copper windings inside. These meatballs are increasingly found in many consumer goods, appliances and cars. After shredding and sorting by magnet, they usually end up in the ferrous fraction, where they are a real headache for shredding operators who are trying to turn recovered steel
into a marketable product. Most shredder operators currently rely on manual sorters, or hand-pickers, to remove the meatballs or similar items from their downstream material. But this is not an ideal solution for a number of reasons. However skilled they are, hand-pickers simply cannot keep pace with a large shredding operation and deliver consistent quality and purity 24/7. In addition, it can be very difficult to distinguish copper from the fast-moving ferrous
Doing the sums
Essentially, the presence of copper is a double financial whammy for the shredding companies. First and foremost, having a high level of copper in the infeed material seriously reduces the quality of the shred that is sold. An untreated infeed can contain almost twice as much copper as the market will tolerate for smelting. Secondly, although copper is a contaminant in the ferrous stream, it actually commands a significantly higher market value. Clean copper can be worth 15 times more per tonne than ferrous scrap. It would therefore make huge financial sense to remove and isolate the copper from the ferrous fraction at lowest process cost. As an example, let’s say that a shredder can process 250,000 tonnes per annum. This would typically contain around 100 tonnes of copper. If that copper can be separated successfully, then 100 tonnes represents an additional annual income of around $400,000 at current prices. In addition, by cleaning up the ferrous materials stream, the shredder operator should command a better price because the ferrous scrap is now much purer than before. In addition to the financial benefits, there are environmental impacts to consider.
Recycling just one tonne of steel saves one and a half tonnes of iron and half a tonne of coal. It also reduces water consumption during the production process by 40%1. Anything that could adversely affect steel recycling rates and thereby increase use of virgin resources would therefore have significant enviromental impacts. The incentives to find a solution to copper contamination are therefore clear.
Finding a solution
TITECH has applied all its knowledge and expertise of sensor-based materials sorting to the issue of copper contamination in ferrous scrap. It has arrived at a solution that can deliver a reliable and cost-effective method of reducing
|contamination and presenting the copper as a lucrative additional materials stream. The answer is a sensor based sorting system that uses Energy Dispersive X-Ray Fluorescence (EDXRF) spectrometric equipment to accurately target copper in the ferrous scrap fraction. This is
rather a long name for such an elegant solution, but essentially this system uses the atomic makeup of the materials it is scanning to distinguish one metal from another. It is therefore not fooled by outward appearance or the thickness of components passing under it. Part of
TITECH’s x-tract family of sensor based sorters, the system offers rapid sensing speed, a high degree of measurement accuracy and the ability to sort by material chemistry. It is capable of yielding up to 98% purity on both the steel and copper fractions.
The system is available in a range of different sizes and so can be matched to the scale of the shredding operation. Depending on throughput levels, it can offer a potential payback time of less than a year. In addition to generating the additional clean copper revenue stream and guaranteeing a ferrous fraction of consistently higher purity, the system brings significant savings on reduced manpower and higher throughput.
The secondary metals sector is facing new challenges as world resources become more scarce and recovered materials become more viable. Copper contamination had the potential to become a major issue for ferrous scrap processors. However, the application of modern, automated techniques has presented shredder operators with a simple, effective solution that not only reduces contamination levels in ferrous scrap - thereby increasing its value - but also presents the opportunity to add new and valuable materials stream to their repertoire.