Acing the chemistry test

Pure aluminum may be an element on the periodic table, but the auto components, factory stampings, building products and other forms of aluminum scrap handled by recyclers consist of a wide assortment of alloyed materials.

Prompt scrap, straight from the factory, tends to have a higher value in part because it is likely to consist of the same aluminum alloy in each collected bin, which makes finding a proper home for such material easier to accomplish.

But the scrap coming across peddler scales and flowing out of auto shredder downstream systems faces one or more sorting steps, providing technology vendors with an opportunity to help recyclers widen their profit margins.

Initial analysis

Bench-top and hand-held analyzers have long been an important companion to nonferrous scrap buyers, whether to properly value incoming scrap or to ensure it is directed with like alloys.

On its website, Westford, Massachusetts-based Hitachi High-Tech Analytical Science (which includes the former Oxford Instruments Industrial Analysis division), says among its hand-held analyzers, “the Vulcan Expert, using LIBS (laser-induced breakdown spectroscopy) technology, is the best choice as this handheld has been calibrated for the task” of alloy identification.

Japan-based Rigaku Corp. points to its Holyoke, Massachusetts-based customer Sullivan Metals as having “discovered LIBS technology” in 2015, when it began using a Rigaku KT-100 model for aluminum and light element analysis.

A case study prepared by Rigaku, which has a North American office in Wilmington, Massachusetts, quotes Brian Powell, a vice president with Sullivan Metals, as saying, “We have been very impressed with Rigaku’s LIBS capabilities of separating 6061 alloys from 5052, which can be very difficult to process so quickly.”

He adds that the tool “allowed us to sort specific alloys out so we’re not making a mixed package.” That, in turn, allowed Sullivan Metals to upgrade the way it prepared aluminum alloyed material, increasing its profitability.

Billerica, Massachusetts-based Bruker describes hand-held LIBS analysis as an “emerging” technology that “shows promising capabilities for alloy analysis, especially in alloys containing low atomic number elements,” including aluminum, magnesium, lithium, silicon and beryllium.

The company says its EOS 500 HH-LIBS model provides analysis of light alloy metals in 3 to 5 seconds, based on “laser excitation of a metal sample, followed by quantitative analysis of the light generated in the [resulting] plume.”

A document on identifying aluminum scrap alloys from Waltham, Massachusetts-based Thermo Fisher Scientific (which includes the Niton brand) states, “The addition of scrap into the aluminum production line represents a major challenge for the industry and creates a considerable opportunity for handheld X-ray fluorescence (XRF).”

Japan-based Olympus Corp., with its North American office in Center Valley, Pennsylvania, is another provider of analyzers offering XRF options. The company says its Delta analyzer line, which includes a hand-held model, has a “range of light alloy [identification] capabilities [that] continues to expand.” The firm says the Delta line’s “outstanding magnesium sensitivity enables [recyclers] to confidently sort aluminum alloys once relegated to OES (optical emission spectrometry) systems.”

Bulking up

Beyond determining specific alloys and chemistries from one sample piece, recyclers and technology providers also are pursuing automated solutions that can identify and separate aluminum scrap in bulk based on its chemistry.

TSI ChemLogix, based in Shoreview, Minnesota, which also offers hand-held analyzers, recently has introduced its ChemLine automatic scrap sorting system, designed to sort magnesium from aluminum, wrought aluminum from cast aluminum or 5000-series aluminum alloys from 6000-series alloys.

The company displayed its ChemLine Aluminum Scrap Sorting System at ISRI2018, the convention in Las Vegas hosted by the Washington-based Institute of Scrap Recycling Industries in April.

TSI says its patented in-line process uses a LIBS sensor to sort aluminum alloys at a rate of up to 5 tons per hour, including the sorting of downstream aluminum pieces from auto shredders. The firm says its LIBS sensors can analyze the elemental concentration of each scrap piece by measuring copper, iron, magnesium, silicon, manganese and zinc levels.

“Sorting occurs based on the actual concentrations” of those elements, TSI says. “The system’s high-speed, high-powered laser burns through contamination and coatings.”

“Previously, LIBS technology had shown promise in research applications as a potential tool for automatic scrap metal sorting. TSI has turned that promise into a reality,” says Todd Hardwick, global marketing manager at TSI ChemLogix. “With an industrial sorting system based on the ChemLine sensor, this new LIBS reality will allow customers to sort aluminum alloys automatically. This advancement will benefit the scrap industry as they adapt to the large increase in aluminum usage that is occurring in the automotive and aerospace markets today.”

Norway-based Tomra, whose Tomra Sorting Solutions business unit is based in Germany and has sales and distribution channels in North America, also is deploying LIBS technology to sort aluminum.

In a presentation for the October 2017 Tomra Leads event, held in Koblenz, Germany, the company’s Frank van de Winkel noted that eddy current sensors, heavy media separation and X-ray technology had all moved automated metals sorting forward. But, he added, LIBS was the next step needed to “detect different aluminum alloys down to the aluminum wrought alloy groups (1000 and 2000 series) and perhaps even to separate single alloys.”

Van de Winkel said in a static laser system, material needs to have a clean surface and be presented in clear view (with no overlapping) before it can be analyzed and ejected for sorting. However, in a dynamic laser system being developed by Tomra, a combination of three-dimensional object analysis and dynamic (moving) laser scanning can allow material to be introduced “randomly” at a pace of 3 meters (9.8 feet) per second.

Tomra says it foresees applications in separating not only the 1000- and 2000-series wrought alloy groups but also in separating 5000-series from 6000-series alloys, making “bulk sorting of material possible” with no need to present a single line of unobstructed pieces to the system.

Germany-based Steinert, with U.S. offices in Walton, Kentucky, introduced an automated aluminum scrap sorting system in 2016. The company’s LSS (laser sorting system) uses LIBS technology in a manner that has the auto body panel stamping process in mind.

At the time the LSS was introduced, Steinert Business Development Manager Karl Hoffmann said it was “targeted at companies that process new scrap or production [scrap] from aluminum stamping facilities—at companies that need to separate 5000- and 6000-series alloys, so that recycled aluminum can be used [at] the same stages of the value-creation process.”

Erie, Pennsylvania-based Eriez is working with the University of Utah and the U.S. Department of Defense Advanced Research Projects Agency (DARPA) on its aluminum sorting R&D. That combined research has led to electrodynamic sorting (EDX) technology designed “to rapidly sort scrap metal for recycling.”

The research partners say the EDX technology “is similar to traditional eddy current separators in that it uses time-varying magnetic fields to sort scrap; but, instead of mechanically rotating a fixed drum of permanent magnets, EDX uses a fixed array of stationary electromagnets.” The DARPA website continues, “Without the limitation of moving parts, it can achieve far higher frequencies of magnetic excitation and recover far smaller particles of scrap metal.”

EDX testing has shown it can sort nonferrous metals by conductivity and by density in a way that is “expected to be cost-effective to operate, with operating costs as low as $1 to $2 per ton for energy and labor.” In 2017, the University of Utah team spun out a new company, EDX Magnetics LLC, to commercialize the technology.

Research being conducted by technology vendors around the world probably will continue to change the way recyclers handle and sort aluminum scrap, with new products likely at successive ISRI conventions.

The author is senior editor of Recycling Today and can be contacted via email at btaylor@gie.net.