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Scrap – sorted

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Tomra’s LOD for high-purity scrap Tomra has developed a technology – laser object detection (LOD) – that complements its existing automated scrap sorting systems to deliver even higher quality scrap feeds.

Existing electromagnetic sorting technology to identify metals in a mixed-material input stream – such as that coming from an auto-shredder – sometimes allows undesirable scrap material through because its metal content is physically connected to pieces of plastic or rubber. A screw or other metal fastener attached to a piece of shredded plastic or a metal hose-clip attached to a rubber tube are two examples. Similarly, residual pieces of glass or wood also sometimes pass through.

Tomra’s new laser object detection (LOD) add-on module uses a laser scanning across the width of a mixed-scrap-carrying conveyor belt to identify the position of non-metallics in order to eject them from a metals stream and deliver a cleaner scrap product. In other words, LOD provides a ‘negative’ metal sort by ejecting non-metallics to provide a clean-up of metals.

In particular, black polymers that passed through before the application of LOD can now be ‘seen’ in 3D by a sorting system deploying the technology. For example, in combination with Tomra’s Finder equipment – an EM3 electromagnetic metal sensor plus near-infrared (NIR) technology – LOD can be used to upgrade metal ‘concentrate’ (such as zurik) from auto-shredders after an initial sorting step. It can be
used to create a stainless steel ‘concentrate’ by the detection and ejection of plastics, printed circuit boards and insulated copper wire (ICW) from stainless steel. 

The LOD module can be added on to the same platform as the company’s other existing sorting equipment, well clear of the material to be sorted passing beneath it. It bolts on to the Finder platform and can adapt to sorting circuits 42.2in (1,200 mm), 70.9in (1,800 mm) or 94in (2,400 mm) wide.

Eric Thurston, sales manager metals-recycling at Tomra Sorting Inc, USA, says that company tests have shown that the technology can enable zorba and zurik to meet the 99% purity requirement now needed for metal concentrates exported to China. “In the USA, widely used Finder technology was already delivering the 90-95% purity requirement previously required, but when those percentages were increased, we saw that LOD was perfect for those products,” he said.

Objects like printed circuit boards have a different height and physical profile to other pieces of scrap around them, which is what the LOD system can detect, Thurston explained.

While Tomra sees the value of LOD in the US as being a means to purify metal scrap destined for export, Thurston also points out that it has value in the US domestic market – potentially to upgrade a portion of a stream of zorba to the quality required for twitch, for example. The recent tariffs applied on steel and aluminium imports to the US by President Trump are expected to see increased domestic production in the US and, in turn, increased consumption of domestic scrap arisings.

Growing volumes of electronic scrap are a further potential application, noted Thurston, where the separation of wire and circuit boards from black plastics by LOD would add value to the sorted scrap products.

Recycling superconductors

When a hospital magnetic resonance imaging (MRI) scanner comes to the end of its useful life, there is a variety of metals in its components to be recycled. Among these are copper and titanium-niobium superconducting wires that are used to generate the strong magnetic field needed for MRI equipment to function.

Finland’s Kuusakoski Recycling has developed a new approach to extracting the copper, titanium and niobium, but first the complex structure of the scanner needs to be dismantled. 

The company explains that the superconducting coil at the core of MRI scanners is cooled with helium. It comprises multi-layered metal chambers and is cast in resin. While other MRI scanner components are removed and reused where possible, the whole coil inside the resin block has usually been dismantled by flame cutting – a dirty, smoke-inducing process that is said to recover relatively impure copper.
In Kuusakoski’s new approach, just the outermost structures of the coil casing need to be dismantled with flame cuttting. The coil and resin inside the machine are dealt with in a pyrolysis furnace in a process that separates the coil’s copper wire. 

The very fine superconducting niobium-titanium conductors that have been rolled inside a copper wrap are also recovered. “Niobium-titanium cannot be separated from copper with mechanical methods or by melting,” noted Arsi Saukkola, R&D manager, precious metals, Kuusakoski Oy, in a company statement. “That is why we developed an electrochemical method,” he explained, which he said produces very pure electrolytic copper and niobium-titanium wire. “The test production phase was a success, and now we are ready for actual production according to market demand,” he added.

Contacted by Metal Market Magazine, Saukkola declined to give further details of the electrolytic process beyond saying that “The chemistry is quite traditional” and that “The cathodes are made of stainless steel.” He estimated that there are about 100 MRI scanners in use in Finland, Sweden and Estonia, and that 5-10 of those are replaced annually by newer, more powerful MRI units.

While some older units might sometimes see re-use elsewhere, often old scanners are cut into pieces on site for quick removal and prompt installation of the latest equipment.

As 2010 US government data (CDC, National Center for Health Statistics) indicated, in 2007 there were 500 MRI units in the UK public health sector. If just 5% of those units were to be recycled in 2018, there would be at least 25 machines to process, and probably rather more if the private sector and veterinary units in the UK were to be taken into account as well. The 2007 figure listed for MRI units in the USA was 7,810, implying a potential approximate figure of nearly 400 of those units that might be recycled in 2018.

Saukkola told Metal Market Magazine that a typical MRI scanner contains about 400 kg of copper and 50-100 kg of niobium-titanium alloy. Other metals in an MRI scanner are stainless steel, glass-fiber armored copper, but mostly aluminium. “Those are recycled using quite ordinary methods (torch cutting, shear cutting, hammer milling and shredding),” he added.

Kuusakoski Recycling picks up old equipment from hospitals in Finland, Sweden and Estonia, and recycles the materials. It also has scrap treatment plants in Sheffield, UK, and in Sittingbourne, UK, through a joint venture company. It is also active in Plainfield, Illinois, USA.
“Those plants are able to cut whole MRI scanners into recyclable pieces or to buy the superconductive coil from other recyclers,” said Saukkola. He added that Kuusakoski is negotiating with some superconductive wire manufacturers to treat their residues in the same electrolytic process.

Although MRI equipment is the most common application for superconducting wire, “basically, this system could be used in recycling of any superconductive wire with the same structure,”
he explained.

Metso mid-range shears Recognizing that not every scrap processing business has the throughput volume or need to warrant purchase of Metso’s large, heavy-duty, Lindemann PowerCut ™ or Etacut™ shears, the international scrap equipment provider supplies its N-Series™ product line, including the Metso N-Series Inclined Shear (NIS), which is a gravity-fed shear with full automatic operation and the Metso clamshell shear/baler/logger (NCS). 

“We listened to our customer base and responded with several design choices at competitive prices for these markets,” says Keith Carroll, vice-president, Americas, Metso Metal Recycling in San Antonio, Texas.

The Metso NIS incline shears are available with shearing forces of 660, 880, 1,100 and 1,375 tons (615-1,250 tonnes). They can be used to cut multiple materials and are designed to process long pieces of material and bulky scrap as well as typical scrap found at all processing yards. Production capacities range from 16 tons to 55 tons per hour (15-50 tonnes per hour). 

A self-contained unit, the NIS is a gravity-fed shear with an inclined feed chute that has a ‘live’ floor to assist material movement towards the hydraulic shear. While side clamps compress incoming material laterally to a suitable width for cutting, a stepped stamper compresses it vertically to densify it before shearing. Discharged cut material is held by a retention flap before removal and controls the adjustable cutting length set by the machine’s operator.

The NCS clamshell shear/baler/logger are available with shearing forces of 678, 880 and 1100 tons (615, 800 and 1000 tonnes). Production capacities range from 15 to 44 tons per hour (13-40 tonnes per hour). The Metso NCS provides the processors with the ability to either shear, bale or log subject to their market demands.

A self-contained unit the NCS offers a dual clamshell chargebox design for improved trapping and folding of scrap. Both the NIS and the NCS shear frames share several of the critical design features that are also found in the Lindemann premium shear line.

Metso NIS and NCS Shear products are sold, warranted and serviced by Metso. Carroll says that a total of ten N-Series units have been sold already – half of which are or will be installed in the US.

Compact Redwave XRF/C can save scrap costs The X-ray fluorescence sorting technology developed by Redwave (XRF/C) in Austria enables detection of the elemental composition of mixed metals passed through it. The combination of XRF and camera technology in a compact “free-fall” or “chute” design – rather than scanning on a belt – sees input material separated into two streams, which are collected by conveyor and, if necessary, separated further by automated sorting into different metal fractions.

The combination of a camera and XRF sensors with controls using advanced software algorithms enables desirable and undesirable elements to be identified as well as the percentage of each element included in the material. This enables, for example, the sorting of copper from brass, or zinc from stainless steel. It also means that alloys can be separated from each other, such as specific grades of stainless steels – a process that can add value by as much as €250 ($300) per tonne, Redwave notes.

Most of the zorba produced in Europe and the US is exported to China as mixed aluminium and a separate mixed heavy-metal fraction. As more zorba is expected to stay within Western countries where it arises, sensor-based sorting to separate mixed heavy metals and to sort the mixed aluminium fraction will be increasingly needed. XRF-sensor-based technology enables further sorting of zorba and twitch.

3-way-sorting of zorba

An XRF-machine can sort aluminium alloys based on their zinc and/or copper content. Zorba, for example, can be sorted into three different aluminium categories: a low-zinc, low-copper fraction compatible with semi-prime foundry alloys such as 356.1; a high-copper, high-zinc fraction compatible with regular die casting alloys, such as Din 226 in Europe (or A380 in the US); and a fraction with medium contents of zinc and copper compatible with piston alloys. 

By sorting zorba with this three-way-sorting strategy, an aluminium stream (low-copper, low-zinc) compatible with some wrought alloys can be obtained. This stream has a zinc and copper level of around 0.05-0.25 %, with silicon at around 0.4-1.2%. It can be used in several 6xxx series alloys and lowers the cost for automotive sheet significantly. This means that automotive sheet, a product often made of primary aluminium at present, can be produced using scrap aluminium. Such zorba scrap is already available in volumes of around 4 million tonnes per year – the sum of North American and European output – and is helping to increase the average aluminium content of vehicles, notes Redwave. 

In addition to separating light from heavy metals, such as the aluminium in zorba, XRF machines can also further separate the aluminium stream into various fractions. This strategy is not limited to the copper and zinc explained in the three-way sorting of zorba. Other elements, such as iron and manganese, can be used. The same applies for the heavy metal fraction, which makes up a certain percentage in zorba. XRF can further separate heavy metals into packages of copper, brass, stainless steel, zinc etc. These fractions are of a high quality and can be used directly in smelters, notes Redwave. In addition to that the technology can also be used to separate PCBs (printed circuit boards) from zorba, twitch or any other fraction. Also, within an alloys group XRF can be used for a more detailed sorting – for example stainless steel can be separated in 304 and 316.

Free-fall advantages

Redwave says that its compact free-fall design offers advantages compared with a belt-type machine, especially when it comes to heterogeneous and 3D material such as metal scrap. While with XRF or X-ray transmission belt-type machines the material needs to be screened in several streams (usually five size fractions), the requirement for free-fall design is only one screening step between 10 and 180 mm, but achieving efficiencies and purities in the mid- to high-90s. The capacity per metre of sorting width is up to 10 tonnes per hour for zorba and twitch. The largest Redwave XRF/C with sorting width of 1.4 metres is able to sort zorba and twitch with a capacity of 15 tonnes per hour. 

What makes the free-fall design special is the combination of object recognition and chemical analysis together with the advanced software algorithm. It is not only possible to qualify the material in terms of elements present, the algorithm also calculates a so-called “intensity per pixel ratio”, which is basically the percentage content of the element. This makes it possible not only to sort alloy groups from each other, but to also to sort within the same alloy group by looking at the same element at different concentrations.

Other applications

Old cast metal can also be sorted with XRF technology. In Europe, the amount of old cast metal is quite high as the engine is usually taken out before shredding a car and is treated separately. The sorting approach is determined by the quality and composition requirements of the final product. This can be from a simple separation of copper and brass from heavy metals, to separating individual brass and bronze, or various types of stainless from each other.

For the copper industry, instead of buying the highest scrap grade, for instance birch or cliff could be purchased as a cheaper source of copper and sorted with XRF to remove any undesirable elements or alloys for copper production, such as brass, nickel or silver. 

Secondary aluminium
Secondary alloy producers and recyclers can take advantage of XRF technology by installing the equipment on their own sites. They can buy zorba and adopt a sorting logic based on their production, material mix and needs. Depending on market conditions, they can, for instance, optimize their own operation by buying more zorba and doing less sorting, or by buying less zorba and doing more aluminium sorting of their own. By buying zorba and processing it, the output can replace some of the most expensive grades of scrap – potentially saving €200 per tonne, according to Redwave.



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