Equipment Focus: Downstream Separation

Dec 10, 2019, 19:59 PM
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November/December 2019

By Ken McEntee

Feature Graphics 300 x 2006During the past two years, actual and anticipated restrictions on scrap metal imports into China have driven processors to seek ways to produce the best quality material possible. It’s a buyer’s market, and with Chinese demand declining—and possibly stopping in the future—plenty of material is available to U.S. metal scrap consumers. “With the China situation the way it is, domestic buyers have their choice of metals, and they want material that is furnace-ready,” says a sales manager for metals recycling at a Norwegian equipment maker with a U.S. office in North Carolina. “Suppliers know that they have to up their game to produce material with furnace-ready purity, and our customers are pushing us to give them the tools that allow them to create those purities.”

The scrap market manager for a German equipment maker with a U.S. office in Kentucky agrees. “One of the biggest problems we have as an industry is that when China turns off its flow of materials, everybody is now sitting with unsold inventories that don’t move but have significant value,” he says. “As good as India and Malaysia have been at picking up some of the slack, there is just not the same demand for the volume, and [there] probably never will be. So a big reason that companies are looking to install better sorting equipment is to maintain access to markets. It’s necessary to make a more refined product to hit the global commodity trade.”

To fill that need, several equipment manufacturers and sellers interviewed for this article say they expect to introduce exciting new products in the new year. “We will have more exciting metal [sorting] products available in 2020 for optimizing throughput and purity for nonferrous applications,” the sales manager says. Even now, these equipment sellers say, recyclers can upgrade their equipment to improve performance all along the sorting line, from the powerful magnets that pull ferrous metal out of shredded scrap, to eddy-current separators that remove nonferrous metal from the shredder residue, to the optical and sensor sorters that can identify and segregate various metals and alloys with increasing accuracy.

“We have been implementing a variety of solutions to help our customers navigate today’s new business conditions,” says a nonferrous business development manager at a New York-based seller of shredders and downstream separation plants. “Investments in nonferrous recovery operations, such as upgrading with new technology, adding pre- and post-processing systems, or even investing in new plant designs, help operators achieve increased tons per hour and product purity,” he says.

Anecdotally, recyclers confirm that they have stepped up their game. Thanks to improved downstream sorting, OmniSource (Fort Wayne, Ind.) landfills less than 1% of the metal that enters its auto shredder residue plant in Toledo, Ohio, says John Marks, plant manager. Upstate Shredding (Owego, N.Y.) just finished a two-year, $9 million upgrade of its Owego facility in October. The upgrade includes a new media plant with equipment from several manufacturers. CEO Adam Weitsman says Upstate designed the plant to give the company more control over its end product. “We have always had a sorting plant here to make Zorba,” Weitsman says, referring to the ReMA specification for shredded nonferrous scrap that’s mostly aluminum. “This plant will allow us to separate our own Zorba, and also separate the heavy metals into a marketable copper product, stainless product, etc. It gives us more control over our product and reduces our dependency on export.” The goal, he says, is to produce an “end product that, without exception, can be sold at all times and meet the specifications of the mill we’re selling to.”

After the magnet

Eddy-current separators, which remove nonferrous metals from nonmetallic residue, were the first major downstream processing innovation after magnets. Perhaps because this is an older technology, it’s an underestimated area of sorting optimization, says the CEO of a German equipment manufacturer with its U.S. headquarters in Georgia. Many eddy-current separators in use today are outdated, he says. Zurik—the ReMA specification for shredded nonferrous sensor-sorted scrap that’s mostly stainless steel—generally contains up to 10% Zorba, he points out. This costs processors money because they typically can sell Zorba for a higher price than Zurik. “The Zorba content [of Zurik] should be 1-2%,” he says. “Eddy currents should be able to achieve that on [auto shredder residue] under 0.5 millimeters. Every shredding operation should test its Zurik on the share of Zorba, then should look for better eddy currents if necessary.”

Some companies sell a magnetic separation pulley and conveyor system that can recover low-grade, weakly magnetic stainless steel from the nonferrous stream, whether from electronics processing, wire-chopping lines, or auto shredding. The machine is typically used to refine Zurik, or it’s used on “a stainless steel package where there is some contamination that needs to be removed,” says a brand manager for a Michigan-based equipment manufacturer. A manufacturer of similar equipment positions it as a less-expensive alternative to sensor sorting.

The ability to better separate stainless steel provides operational as well as market advantages, the Michigan brand manager says. “In this industry, downtime is the biggest contributor to loss of revenue,” he says. “Stainless is very hard to shred, and it can create havoc when it goes into a shredder or a granulator for wire [chopping]. Commercial wire sometimes has a stainless jacket around it; what the stainless steel separator is able to do is to pull that stainless out before it goes to the granulator. So now, instead of changing the granulator blades once every two to three hours, you can get exponentially more time out of your blades before you have to shut down for maintenance.”

He explains how it works: “The unit utilizes a strong magnet at the front end of the conveyor—very similar to how an eddy current works—but it doesn’t throw anything off the end of the conveyor. Instead, it retains it and pulls the magnetic stainless steel behind a chute, and then [it] segregates the product so anything that is nonreactive falls off the front.”

Even though “in its pure form, 300-grade stainless steel has virtually no magnetic potential,” the brand manager explains that “after it has been cold-worked or shredded, the potential increases to the point where it can be held by a very strong magnet. As many of the other grades of stainless steel possess magnetic potential in their natural state, they, too, are susceptible to magnetic attraction.”

Advances in magnetic materials are what made this technology possible, the brand manager adds. “Eddy currents, for example, used to use N42, which is a neodymium magnet designated a 42 grade,” with the number an indicator of the strength of the magnetic pull. “Now we’re in N52, which is a couple of progressions higher than where we were 10 years ago, when rare earth [magnets] started to come into the market. The way we have the circuit engineered, we have a very strong magnetic field right along the face of the magnet, and we have had a lot of success in pulling the stainless out.”

X-ray vision

“Going back five to 10 years, the eddy-current separator was typically near the end of the sorting line, and that was the last touch you had at the material,” says the Michigan brand manager. Auto shredding facilities would sell that mixed nonferrous product overseas or to specialized processing facilities that would use heavy media or electrostatic separation to further recover metals from nonmetallic residue and separate elements and alloys. Newer downstream separation technologies that operate in line with or adjacent to the shredder put more of that separation—and potentially more profit—in the shredders’ hands. The newer technologies encompass near-infrared spectroscopy, X-ray transmission, X-ray fluorescence, optical sortation for color, size, and shape, and more—with some equipment using more than one technology at a time.

XRT and XRF are complementary technologies, the Kentucky-based scrap market manager says. “XRF, which [provides] elemental analysis of material composition, is very good technology, but it can struggle when evaluating light elements such as aluminum and magnesium,” he says. “Both of the materials are nearly ‘invisible’ to the XRF energies released.” Also, because XRF analyzes the surface of the material that’s facing the sensor, “this can lead to misclassifications due to how the material is presented to the scanner.” XRF works best on the heavy metal fraction to produce individual commodities or groups, he says. For example, it can separate copper-bearing metals from other nonferrous metals, like zinc and stainless, in one pass. Then, in a second pass, it can separate that concentrated copper fraction into copper, brass, and printed circuit boards.

XRT, on the other hand, looks completely through the material to evaluate its atomic density. “While this technology does not give a true elemental evaluation of the material, it does show a more complete picture of the materials composition,” he says. “This is good for [pieces] that may be a compound of two different materials, such as an aluminum radiator with copper piping hidden behind the fins. Without looking completely through the material, these compounds may be missed.”

His company recommends the use of both XRT and XRF—and more than one of each—to maximize value. “Depending on a number of factors, [a facility could use] as few as one XRT and one XRF, or multiple, depending on how much volume is required to be processed and how many individual commodities the producer wants to make,” he says.

After an ECS or sensor sorter produces Zorba, one or more XRT machines can separate free heavy metals, high-alloy aluminum (those with high proportions of copper and zinc), and light metals as follows, he explains: First, the XRT separates Zorba into aluminum and heavy metal fractions; second, it separates the aluminum stream into cast and sheet aluminum; third, it processes either aluminum stream again to remove free magnesium to make Twitch—the ReMA specification for shredded, separated aluminum scrap that contains no more than 1% free zinc, magnesium, or iron.

When making Twitch, XRT is less expensive, offers higher throughput, and delivers the highest purity product to the aluminum consumers, he says. His company recently announced its XRT separator can reduce free magnesium in the scrap aluminum stream up to 92%—an advancement it can retrofit on its XRT machines sold since 2016. The system can extract the free magnesium separately or put it in the cast aluminum fraction, he says.

The Norwegian company says its newest XRT sorter has a more sensitive, higher resolution camera that can separate pieces of shredded scrap that are between 5 and 40 millimeters in diameter—“half the size of what was previously sortable,” the sales manager for metals recycling says—resulting in purity levels of 98% to 99%. This company uses dual-line sensor technology to separate aluminum from heavy metals, create Twitch, or separate cast from sheet aluminum. “We have been getting more interest from people who want to get to that level of the cast and the lot, particularly with the amount of aluminum that is available these days,” he says.

A look at LIBS

The Georgia-based CEO asserts that laser-induced breakdown spectroscopy separation is one step beyond XRT and XRF, calling it the most innovative new sorting equipment on the market today. LIBS uses lasers to separate nonferrous metals based on their chemistry. His company’s LIBS sorter can provide in-line or standalone separation of up to 15 different metals and alloys in one pass, including separation of cast and wrought aluminum. It can separate pieces ranging from 1 to 6 inches in diameter at a rate of 2 to 3 tons per hour. “It opens up completely new markets for processors because they can move away from mixed products to quality products that can be supplied directly to nonferrous smelters,” he says. “This equipment … is the logical next step for any processor after the traditional sensor sorters. It is the only sorter which really analyzes each piece and achieves 100% clean products. The software allows a completely customized adjustment of the settings to meet the needs of the market or a particular customer.”

Other manufacturers are testing and launching LIBS-based automated scrap sorters as well. A Minnesota-based manufacturer of LIBS handheld scrap analyzers recently partnered with a Texas-based automation firm to test automated LIBS separation in 2018. The test successfully separated aluminum from magnesium and separated wrought and cast aluminum at the rate of 5 tons an hour, achieving 98% purity, they report. One company says its LIBS-based sorter, now operating in Europe, can achieve 99.9% accuracy sorting aluminum scrap into different alloys.

Return on investment

Equipment sellers’ order books indicate that interest in advanced downstream sorting technologies is strong. “The early adopters have already had this equipment for three or four years, and we are now getting to more mainstream acceptance of the refining technology,” the Kentucky-based scrap market manager says. Market-ready advancements in AI and robotics are probably a few years down the road, he adds.

Most vendors declined to discuss prices of their newest sorting equipment. Optical and sensor-based sorting systems generally were in the $300,000 to $600,000 range, depending on the technology and the bells and whistles added on. Return on investment for sorting technologies can range from as little as six months to two years, these representatives say.

For Upstate Shredding, the move to advanced downstream separation was not entirely smooth. Some of the equipment it installed failed to perform as expected and had to be replaced. “During testing, it didn’t make a product that was profitable or marketable,” Weitsman says. “We had to go back to the drawing board numerous times. Those are some expensive lessons when experimenting with new, untested technology.

“It’s tough in our industry because the R&D is so much smaller than in some other industries, so a lot of newer technologies required a leap of faith,” he says. “We wanted to be the first one out and be ahead of other people with the technology, but in my quest to be the first one out, I’ve gotten kicked in the face a couple times.” Some vendors offer testing facilities where yards can send a sample of their scrap to see how the equipment performs before they commit to an equipment purchase.

After making the investment, the key to keeping sorting equipment working at optimum performance is routine maintenance and daily inspections of conveyor belts and other parts, says OmniSource’s Marks. “You want to take care of small problems before they get big,” he says. “Simple housekeeping—like keeping floors and the working environment clean—is one of the most important things you can do.”

Ken McEntee is editor and publisher of The Paper Stock Report and a freelance writer based in Strongsville, Ohio.

Magnets, lasers, X-rays, and optical sensors might be the trick to produce cleaner metal streams.

  • 2019
  • Nov_Dec

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