The increased sophistication of sensor sorting equipment, which began as a way to supplement traditional methods of processing auto shredder output, might qualify it for a more central role with shreds.
"The X-rays now are actually perceptive enough to remove the zinc from aluminum. They also separate sheet and tube from die cast aluminum," according to Dennis Ciccotelli, southeast regional manager at Steinert US LLC, Erlanger, Ky., which sells sensor devices made by its parent company in Germany. The more-common color-based sensors can't handle those distinctions, he said.
"I believe that one day sensor sorting will replace heavy media" that distinguish metals by their density, Ciccotelli said. "It will be much easier to control and maintain."
Even now, some heavy media operators are reducing the strain on their equipment by using sensors ahead of the intake. Diverting irrelevant shards holds down the proportion of unwanted material entering the density sort, Ciccotelli said, adding that he views density sorting that uses sand flow as a more resilient technology than the traditional liquid-based heavy media. "Sand flow is a more manageable process. It handles small tonnage rates but it's more environmentally capable and you can contain it," he said. "But you still have to clean that media, and the media is expensive."
Sensor sorting had problems of scale a few years back, but these have been dealt with, Ciccotelli said. "For a while we were really unsure how many tons an hour we could do with a given system. Could we maintain somewhere between 5 and 10 tonnes an hour and get the high-purity rating of a sand-flow process? At between 5 and 10 tonnes, we now can get purities that sand flow and heavy media can get. It isn't 2 tonnes an hour any more."
Ciccotelli said that Ferrous Processing & Trading Co., Detroit, has been planning the installation of recently acquired XSS X-ray sensor sorting equipment that could perform the same tasks as its existing sand-flow facility.
Eddy current technology, though around a long time, has itself been advancing, he said. Coordinating it with magnets can be effective in sorting aerospace materials. "With the right magnetic matrix and with an adjustable rotor to match with the eddy current, high-frequency eddy current can make very subtle separation of materials," Ciccotelli said, recalling one buyer of aerospace surplus who was faced with a goulash of fasteners. "He was separating titanium from aluminum from stainless using eddy currents." The installation also deployed magnetized sheets with a neodymium-iron-boron mixture.
Steinert US has recently been giving increased attention to metals recovery from the garbage stream. "One of our very first sensor sorters in the waste end is in Iowa. The Ames County plant has an eddy current and a sensor sorter on one of the lines they used to pick (by hand). This is material that has not been shredded," Ciccotelli said.
At competitor Wendt Corp., Tonawanda, N.Y., business development manager Mark Ridall said sensor technology has matured. The issue is tailoring it to niches that can use it profitably.
"From a metallics point of view, you have all the equipment available to you today that you need to recover almost every piece of metallic existing in shredder residue. The next things that will have to come out are glass and plastics," Ridall said. "Nobody's choosing to do glass because there's no market for it. I can spend a million dollars for equipment to be a nice guy, but I'm not going to get any revenue generated by it. Plastics, on the other hand, you'll see getting removed (from auto shredder residue) within 12 to 18 months. There's the beginnings of a marketplace to trade that material."
One hurdle is uncertainty as to whether certain sorts of plastics will pass muster with environmental regulators as a manufacturing material. Ridall expects high-density polyethylene to be the highest-priority plastic in shredder residue. However, matching requirements will be tricky. "I'm sure what's being manufactured in Asia has a different polymer base than what's being manufactured here or in Europe," he said.
"The entire industry is waiting to see what is learned from the facility in the United Kingdom," Ridall said, referring to a facility of California technology developer MBA Polymers Inc. and British scrapyard group European Metal Recycling Ltd. (EMR). With MBA and EMR expecting start-up in the third quarter of this year, feedback is unlikely until mid-2011. "Once there are some published data with reliable results we all can digest, then we'll see some movement," Ridall said.
The economic slump was unkind to narrowly delineated sensor sorts of shredder scrap.
"When the markets fell apart (in late 2008), nonferrous markets fell through the floor. There was no value in producing anything more than zorba (mixed shredder nonferrous) and zurik (a stainless-dominated mixture)," he said. "Even those were down to 20, 25 cents a pound with little movement. Eighteen months later, copper is back to over $3 a pound so you've got more and more people beginning to focus again on creating higher-quality zorba and higher-quality zurik packages. I think we are beginning to see a return of stability to the markets. I think more and more folks will be turning on that advanced separation equipment, because you'll see a differential. It will be worth their while to 'scalp' copper (from brasses) or to produce a higher-quality aluminum or to break down a heavy metals package into individual metallics."
At major scrapyard chains, "the equipment will do what they ask of it. They'll make choices on their process, based on what the end commodity needs to be—for the highest return or to sell most easily," he said.
By Ridall's chronology, the scrap industry's first use of sensors for shredder output in around 2000 was to retrieve stainless steel from the eddy current waste stream. After magnets have done their work, nearly all shredders have eddy current systems to separate nonferrous metals from dirt. Eddy currents also provide the option of creating an adequate segregation of aluminum from other metals. However, stainless steel is inert to the electrical eddy current and lands in the waste stream.
At the turn of the century, stainless steel was a pricing standout in a largely dismal period for nonferrous, Ridall said. That provided an opening for marketing some of the early sensors. "The recoverable metallics (when sensors monitor eddy current waste) typically are going to run between 3 and 5 percent," he said. "That is not counting insulated copper wire, which could be another 3 or 4 percent."
The Institute of Scrap Recycling Industries (ISRI), in categorizing aluminum, assumes that aluminum shredder scrap emerges either from sortation by eddy current (producing tweak) or by selective flotation based on density (twitch). Sensor-delineated aluminum has no pedigree yet.
"I think in time heavy media will become extinct," Ridall said. "At that point, ISRI will potentially need to create a new classification."